JPH08115004A - Fixing device - Google Patents

Abstract

PURPOSE: To enhance heat conduction efficiency from a heating body to a recording material by constituting the surface shape of the vertical cross section of an opposed part to a pressure member in a heating body to be along the surface of the pressure member. CONSTITUTION: The shape of the vertical cross section of the part opposed to a pressure roller 44 in the heating body 43 is constituted to be along the surface of the roller 44. Thus, press-contact force of the roller 44 and the heating body 43 in a press-contact area A is made nearly uniform. The shape of the vertical cross section of the part opposed to an adhesive film 51 in the heating body 43 is constituted to be protruded to the film 51 side with specified curvature. Thus, the press-contact force of the film 51 and the heating body 43 in the press-contact area A is made nearly uniform. In any case, the press- contact force of a recording material sheet to the heating body 43 and the fixing film 40 is made nearly uniform in a fixing nip.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording material carrying a visible image (hereinafter referred to as a toner image) to be heat-fixed, adhered to a heating body via a film, and the recording medium from the heating body via the film. The present invention relates to a film heating type fixing device that applies heat energy to a recording material to heat and fix a toner image, and more specifically, to an improvement for efficient use of heat energy in this type of film heating type fixing device. is there.

This film heating type fixing device is used for electrophotography, electrostatic recording, magnetic recording, etc. in image forming apparatuses such as copying machines, laser beam printers, facsimiles, microfilm reader printers, image display devices. Using a toner made of a heat-meltable resin or the like by an appropriate image forming process means, a method directly on the surface of a recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet, printing paper, etc.) as an image carrier or The toner image formed by the indirect (transfer) method can be used for heat fixing processing as a permanently fixed image on the surface of the recording material.

[0003]

2. Description of the Related Art Conventionally, as a heating type fixing device used in the above-mentioned image forming apparatus, a heating roller maintained at a predetermined temperature, and a pressure roller having an elastic layer and being in pressure contact with the heating roller. A fixing device of a heat roller fixing system is widely used in which a recording material on which a toner image is formed is held and conveyed and heated. However, this heat roller fixing type fixing device requires a time until the temperature rises to a predetermined temperature (time for which the image forming operation is prohibited), that is, a so-called wait time, and a certain amount of heat capacity is required, so that a relatively large amount of electric power is required. In addition, since the temperature of the rotating roller is high, a heat-resistant special bearing is required, and it is dangerous because the roller is in direct contact with the hand, and a protective member is required.The recording material wraps around depending on the roller fixing temperature and curvature. There was a defect that it could cause jamming.

Therefore, a film heating type fixing device has been attracting attention as a heating type fixing device which does not have the above-mentioned drawbacks, and research and development for practical use thereof have been advanced.
The film heating type fixing device includes a thin heat-resistant film (sheet), a moving driving means for the film, a heating element fixedly supported on one side of the film and the other side of the film. And a pressing member which is disposed so as to face the heating body and makes the toner image bearing surface of the recording material to be image-fixed adhere to the heating body via the film, and the film is used at least when the image fixing is performed. Is formed by pressing the heating member and the pressing member while sandwiching the running moving film by traveling at the same speed in the forward direction as the recording material to be image-fixed which is conveyed and introduced between the film and the pressing member. The toner image bearing surface of the recording material is heated by the heating body through the film by passing through the fixing nip portion to apply thermal energy to the toner image to soften and melt the toner, and then the film Release recording material Let, or in which the toner is to separate the film and the recording material after cooling and solidifying (see FIG. 4).

As the heating element, a horizontally elongated heat-resistant, insulating, low-heat-capacity heater substrate having a widthwise direction of the film is in a linear or strip shape along the length of the film contact surface side. A low-heat-capacity energization heating resistor (heating element) is used for the heating element, and the heating element generates heat by supplying power between both ends of the heating element, and the heater substrate is also heated. The entire body rapidly rises in temperature, and the heat of the heating body is applied to the recording material via the film. The temperature control of the heating element is performed by a temperature sensor provided on the heating element, a microcomputer of the image forming apparatus main body, and a heating element driving (energizing heat generation) circuit, and the temperature is controlled to a predetermined fixable temperature. Although the heating element is at a high temperature, the film is driven to move on the heating element at a predetermined speed at least when the heating element generates heat, so local thermal deformation of the film does not occur and stable image fixing is performed. Is executed.

Such a film heating type fixing device is characterized by a short wait time and the like, and is a fixing device that meets the demands of the times. Further, since the size of the heating element is smaller than that of the conventional heating roller system, and the thin heat-resistant film (sheet) has a low heat capacity, efficient heat can be used and power consumption can be reduced.

In the film heating type fixing device, as a pressing member for forming a fixing nip portion between the fixing film and a heating body, a pressing member having a rubber layer having a good releasability such as silicon rubber is used. In the case of using a roller, the pressure roller is considerably radiated with heat during the waiting time of the apparatus, so that the rise to the predetermined fixing temperature in the fixing nip portion is delayed. In order to solve this rising delay, a film member is also used as the pressing member, and the film member is wound and stretched between the traveling drive unit and the driven unit so that the fixing nip portion moves in the same direction and at the same speed as the fixing film. Some have been proposed to drive the vehicle (see FIG. 7). According to this, even in the image forming apparatus in which the image forming operation of the image forming apparatus is speeded up and the time for the recording material to rush from the image forming section to the fixing section is further shortened, the temperature of the fixing nip portion is extremely high. Since the temperature is raised to a predetermined fixing temperature in a short time, it is said that there is no need to perform the so-called standby temperature control in which the temperature of the heating body is raised in advance, energy saving can be realized, and in-machine temperature rise can be prevented.

[0008]

However, according to the research conducted by the present inventors, in the film heating type fixing device, a specific pressure contact force distribution between the heating member and the recording material causes The transfer efficiency of the heat energy from the heating element to the recording material during the passage through the fixing nip portion is different, and there is room for improvement from this point in the conventionally proposed film heating type fixing device. It turned out.

For example, as shown in FIG. 2 (a), film heating is performed by pressing a pressure roller 44 as a pressure member with a fixing film 40 as a heat resistant sheet sandwiched between the flat lower surface of a heating body 43. FIG.
As can be seen from the distribution of the pressure contact force between the heating body 43 and the pressure roller 43 in the pressure contact area A shown in the lower part of the mechanism diagram in (a), the fixing film 40 is provided in the area A.
The pressure contact force at both ends in the traveling direction is smaller than the pressure contact force at the central portion in the same direction, and the pressure contact force in the area A becomes uneven. The larger the pressure contact force, the better the adhesion of the heating element 43, the fixing film 40, and the recording material introduced between the fixing film 40 and the pressure contact roller 44, and the thermal energy from the heating element 43 to the recording material is increased. Transmission efficiency is high. Therefore, in the fixing device shown in the figure, the efficiency of heat energy transfer is relatively good in the central portion, but the efficiency is remarkably poor in the both end portions, and the low transfer efficiency at the both end portions passes through the pressure contact area A. As a whole, the heat energy transfer efficiency to the recording material is deteriorated. In order to increase the efficiency of transfer of thermal energy to the recording material while passing through the pressure contact area A with the structure of the heating element 43 shown in the drawing, the pressure contact force between the heating element 43 and the pressure roller 44 should be increased. Is possible,
This method has a limit because the pressure contact force peak at the central portion in the traveling direction becomes too large and the strength deterioration of the fixing film 40 is accelerated.

As shown in FIG. 2 (b), instead of the pressure roller 44 of FIG. 2 (a) as a pressure member, it is wound between two support rollers (not shown) as film members. Stretched endless belt-like adhesive film 51
Also in the film heating type fixing device using the above, when the lower surface of the heating body 43 is flat, the heating body 43 is in close contact with the heating body 43 in the pressure contact area A shown in the lower part of the mechanism diagram portion in FIG. 2B. As can be seen from the distribution of the pressure contact force with the film 51, in the region A, the pressure contact force is generated only at both ends in the running direction of the fixing film 40, and the pressure contact force is hardly generated at the center part in the same direction. The pressure contact force in A is extremely uneven, and the insufficient pressure contact force at the central portion deteriorates the heat energy transfer efficiency to the recording material as a whole while passing through the pressure contact region A. Also in this case, it is possible to increase the pressure contact force between the heating element 43 and the heating element 43 by causing the heating element 43 to bite into the expanded portion of the adhesive film 51 to increase the tension of the film. Is too large and causes problems such as accelerated deterioration of strength of the fixing film 40 and the adhesion film 51.

The present invention has been made in view of the above background, and an object of the present invention is to provide a film heating system capable of increasing the heat transfer efficiency from the heating body to the recording material as compared with the conventional method. It is to provide a fixing device.

[0012]

[Means for Solving the Problems]

 (Plan to copy claims)

[0013]

In the fixing device according to the present invention, the surface shape of the heating member facing the pressing member forming the fixing nip portion by the pressure applied to the heating member is a shape along the surface of the pressing member. As a result, the pressure contact force between the pressure member and the heating member in the fixing nip becomes substantially uniform, and the pressure contact between the heating member and the heat-resistant sheet of the recording material influences the heat energy transfer efficiency from the heating member to the recording material. The force is also almost uniform in the fixing nip. Therefore, by setting the pressure contact force between the pressure member and the heating body, it is possible to obtain the desired heat energy transfer efficiency without deteriorating the strength of the heat resistant sheet at the local pressure contact force peak in the fixing nip. .

Particularly, in the fixing device of claim 2, in which the rotatable pressure roller having an elastic layer is used as the pressure member, in the fixing device of claim 1, it is more than just above the center of rotation of the pressure roller. By arranging the heating element with the center of the heat generation region of the heating element shifted on the swelling and deforming side of the pressure roller due to the pressure contact rotation with the heating element, heat generation of the heating element immediately above the rotation center of the pressure roller. The heat-generating region matches the pressure-contact region between the deformed pressure roller surface and the heating body better than in the case where the region center is located. Therefore, as compared with the case where the center of the heat generating area of the heating body is located immediately above the center of rotation of the pressure roller, the recording material can be pressed against the heat generating area of the heating body while sandwiching the heat resistant sheet. it can.

In the fixing device according to the third aspect, the heating member and the belt member, which are arranged so as to bite into the stretched portion between the supporting rollers of the belt member as the pressing member, are pressed against each other by the tension of the belt member. And a fixing nip portion is formed. Further, since the surface shape of the heating member in the vertical cross section of the belt member facing portion is a shape projecting to the belt member side with a predetermined curvature, the pressure contact force between the two members in the fixing nip becomes substantially uniform, and the heating member moves to the recording material. The pressure contact force of the recording material with respect to the heating body and the heat-resistant sheet, which influences the heat energy transfer efficiency to the heat transfer sheet, is almost uniform in the fixing nip. Therefore, the desired heat energy transfer efficiency can be obtained without setting the strength of the heat-resistant sheet at the local pressure contact peak in the fixing nip by setting the amount of biting of the heating element into the belt member extension. You can

Particularly, in the fixing device according to the fourth aspect, the heat-resistant sheet has a surface shape in which the amount of biting into the expanded portion in the press-contact region between the belt member and the heating body with the heat-resistant sheet sandwiched therebetween. Since the shape is asymmetrical about the center of the running direction, the difference in the tension between the belt member portions before and after the pressure contact area is different from that of the heating member of each belt member portion in the pressure contact area. The influence on the distribution of the pressure contact force can be offset by the difference in the bite amount. Therefore, the pressure contact force in the pressure contact region can be made uniform as compared with the case where the bite amount is symmetrical about the center.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a fixing device in an electrophotographic image forming apparatus will be described below. First, an outline of an example of an electrophotographic image forming apparatus that can use the fixing device according to the embodiment will be described with reference to FIG. In FIG. 3, in this image forming apparatus, the original 11 is placed on the fixed original glass 10 and the required copying conditions are set, and then the copy start key is pressed. Is driven to rotate at a predetermined peripheral speed. Further, the light source 13, the reflector 14 and the first mirror 1
5 moves along the lower surface of the platen glass 10 from the home position on the left side of the glass to the right side of the glass at a predetermined speed V, and the second mirror 16 and the third mirror 17 move V / 2 in the same direction.
By moving forward at the speed of, the downward document surface of the document on the platen glass 10 is illuminated and scanned from the left side to the right side, and the reflected light of the illumination scanning light on the document surface is fixed to the imaging lens 18 and the fixed fourth to fourth.
6 Rotating photosensitive drum 1 via mirrors 19, 20, 21
Imaging exposure (slit exposure) is performed on the two surfaces.

Prior to this exposure, the surface of the rotary photosensitive drum 12 is uniformly charged to a predetermined positive or negative potential by the primary charger 22, and the charged surface is subjected to the above-mentioned exposure. Then, an electrostatic latent image having a pattern corresponding to the original image is sequentially formed on the surface of the drum 12. Photoconductor drum 1
The electrostatic latent images formed on the two surfaces are developed by the developing roller 24 of the developing device 23 to form a toner image. On the other hand, a transfer material sheet P as a recording material is fed by a sheet feeding means (not shown), is introduced into a transfer portion between the drum 12 and the transfer charger 26 at a predetermined timing through a guide 25, and is transferred to the transfer corona. By receiving the toner, the toner image on the drum 12 is sequentially transferred onto the surface of the transfer material sheet while being in contact with the drum 12.

The transfer material sheet that has passed through the transfer section is sequentially separated from the surface of the drum 12 by separation means (not shown) (for example, a separation belt arranged at the end of the drum 12), and the charge removal needle 27 removes the back charges. Then, the toner image is fixed by being introduced into the fixing device 30 by the conveying unit 28 and the guide 29, and is discharged outside the apparatus as an image formed product. After the transfer, the surface of the drum 12 is cleaned by a cleaning blade 32 of a cleaning device 31 to remove stains such as residual toner, and is repeatedly used for image formation. When the moving optical member that has moved forward moves to a predetermined forward movement end point, it is returned to the initial home position and returns to the initial home position, and waits until the next copy cycle.

Next, a fixing device according to an embodiment of the present invention will be described. The fixing device according to the present embodiment is obtained by changing the shape of the heating body 50 in the conventionally known film heating type fixing device shown in FIGS.
A conventionally known film heating type fixing device shown in FIGS. 4 and 5 will be described. 4 (a) is a side view thereof, and FIG.
4B is an explanatory diagram of a layer structure of the fixing film 40 of the identification fixing device, and FIG. 4B is a rear view of the identification fixing device. FIG.
In (a), an endless belt-shaped fixing film 4
0 is a driving roller 41 on the left side and a driven roller 42 on the right side.
And a low-heat-capacity linear heating body (hereinafter referred to as a heating body) 43 as a heating body arranged below both rollers 41 and 42, and wound around three members. The driven roller 42
Also serves as a tension roller for the fixing film 40,
The fixing film 40 has a predetermined peripheral speed in the clockwise direction as the driving roller 41 is driven to rotate in the clockwise direction, that is, the same peripheral speed as the conveying speed of the recording material sheet P carrying the toner image conveyed from the image forming portion side on the upper surface. Wrinkles and meanders, with speed
It is driven to rotate without any speed delay. The drive roller 4
The offset prevention liquid application roller 41a is arranged so as to be in contact with the surface of the fixing film 40 wound around 1.

A pressure roller 44 as a pressure member is arranged so as to face the lower surface of the heating body 43 with the lower stretched portion of the fixing film 40 interposed therebetween. This pressure roller 4
The shaft 4 has a rubber elastic layer 46 having a good releasability, such as a shaft 45 silicon rubber, and the total pressure is, for example, 4 to 7 by a biasing means (not shown).
It is pressed against the heating element 43 with a contact pressure of Kg.
Then, the recording material sheet P rotates about the axis in the counterclockwise direction, which is the forward direction in the conveying direction.

The heating element 43 is a linear heating element having a low heat capacity and having a longitudinal direction in a direction crossing the plane moving direction of the fixing film 40 (the width direction of the film). 48), a temperature detecting element 49, etc., and is fixedly supported by being attached and held to the heater support 50. The heater support 50 has heat insulating properties, high heat resistance, and rigidity for heat-supporting the heating body 43 with respect to the fixing device and the image forming apparatus. For example, polyphenylene sulfide (PPS), polyamide imide (PAI), polyimide (PI). ), Polyether ether ketone (PE
EK), a high heat resistant resin such as a liquid crystal polymer, or a composite material of these resins and ceramics, metal, glass or the like. The heater substrate 47 is a member having heat resistance, insulation, and low heat capacity, and has a thickness of 1.0 mm, a width of 16 mm, and the like.
This is an alumina substrate with a length of 340 mm. The heating element 48 has an electric resistance material such as silver-palladium (Ag / Pd) or TA ₂ N having a thickness of approximately about the center of the lower surface (facing the fixing film 40) of the heater substrate 47 along the length. 1
0μm, width 1-3mm coated by screen printing,
A heat-resistant glass 60 as a surface protective layer is further formed thereon with a thickness of about 10 μm.
It is coated. The temperature detecting element 49 is, for example, Pt which is provided by coating the upper surface of the heater substrate (the surface opposite to the surface on which the heating element is provided) substantially in the center with screen printing or the like.
It is a resistance thermometer with low heat capacity such as a film. Alternatively, as the temperature detecting element 49, a thermistor or the like having a low heat capacity may be arranged in contact with the heater substrate 47.

In the case of the heating element 43 of the present example, the heating element 48 having a linear or strip shape is energized from both ends in the longitudinal direction to cause the heating element to generate heat over substantially the entire length. Power is AC
It is 100 V, and the energization power is controlled by controlling the phase angle to be energized by an energization control circuit (not shown) including a triac according to the detected temperature of the temperature detecting element 49.

The fixing film 40 has heat resistance, releasability,
A single layer or composite layer film having a layer thickness of 100 μm or less, preferably 40 μm or less, which has durability, can be used. FIG. 4B shows a cross section of the fixing film 40 having a two-layer structure. In this example, the heat-resistant layer 50 as a base layer (base film) of the fixing film and the outer surface of the heat-resistant layer 50 (facing the toner image). Release layer 5 laminated on the side surface)
It consists of one. The heat-resistant layer 50 is made of, for example, polyimide, polyetheretherketone (PEEK), polyethersulfone (PES), polyetherimide (PE).
I), polyparapanic acid (PPA), and other high heat-resistant resin films, and metals such as Ni, SUS, and Al.
Those with excellent heat resistance can be used. The release layer 51 is made of, for example, polytetrafluoroethylene (PTFE), PFA.
Fluorine resin such as or FEP, silicon resin, etc. are preferable (PTFE in this example). The surface resistance value of the fixing film 40 can also be lowered by a method of mixing a conductive material such as carbon black, graphite or conductive whiskers in the release layer 51. This prevents the toner contact surface of the fixing film 40 from being charged. The release layer 51 is laminated on the heat-resistant layer 50 by adhesive lamination of the release layer film, electrostatic coating (coating) of the release layer material, vapor deposition, and C.
It can be performed by stacking by a film forming technique such as VD, or by coextrusion of a heat-resistant layer material and a release layer material to form a two-layer film.

As shown in FIG. 5, the width L ₁ of the fixing film 40 is wider than the width L ₂ of the heating element 48, and the width L _{3 of the} pressure roller is larger than the width L ₁ of the fixing film 40. short. The width L ₄ of the coating roller 41a is shorter than that of the fixing film.

In the above arrangement, the image forming apparatus performs an image forming operation in response to the image forming start signal and the fixing device 3
The recording material sheet P carrying the toner image on the upper surface conveyed to 0 is guided by the guide 29 and fixed to the fixing film 40 at the pressure contact portion (hereinafter referred to as the fixing nip portion) between the heating body 43 and the pressure roller 44. Between the pressure roller 44 and the pressure roller 44, and the toner image surface comes into close contact with the lower surface of the fixing film 40 which is rotated at the same speed as the conveyance speed of the recording material sheet P in the same direction to cause surface misalignment, wrinkling, or deviation. Without passing through the fixing film 40, the fixing film 40 passes through the mutual pressure contact portion between the heating body 43 and the pressure roller 44 while receiving a sandwiching pressure. (Hereinafter, margin)

Since the heating element 43 is electrically heated at a predetermined timing by the image formation start signal, the toner image is heated in the fixing nip portion and becomes a softened / melted image.
The fixing film 40 is turned at a steep angle (the bending angle θ is about 45 °) at the discharge-side edge portion (curvature radius is about 2 mm) 50a of the heater support 50 having a large curvature.
Therefore, the recording material sheet P conveyed through the fixing nip portion while being overlapped with the fixing film 40 is curvature-separated from the fixing film 40 at the discharge-side edge portion 50a and is discharged to the discharge tray. By the time the paper is ejected, the toner is sufficiently cooled and solidified and is in a state of being completely fixed on the recording material sheet P (toner image Tc).

Further, in this embodiment, the heat capacity of the heating element 48 and the heater substrate 47 of the heating element 43 is small, and these are adiabatically supported by the heater support 47.
Since the surface temperature of the heating element 43 in the fixing nip portion is raised to a sufficiently high temperature with respect to the melting point of the toner (or the fixing temperature of the recording material sheet P) in a short time, the heating element 43 is raised in advance. (So-called standby temperature control)
Energy saving can be realized and temperature rise inside the machine can be prevented.

In the above-described conventionally known fixing device, the surface of the heating member 43 facing the pressure roller 44, specifically, the heat-resistant glass 60 has a flat plate shape.
Similar to the above-described fixing device as shown in FIG. 2A, for example, the heating body 43 and the pressure roller 43 in the pressure contact area A are provided.
And the distribution of the pressure contact force with the recording medium is not uniform, and the heat energy transfer efficiency to the recording material is poor as a whole while passing through the pressure contact area A. Simply increasing the pressure contact force between the heating body 43 and the pressure roller 44 is sufficient. Attempting to obtain heat energy transfer efficiency may accelerate the deterioration of strength of the fixing film 40.

Therefore, in the present embodiment, the heating element 43
In order to increase the efficiency of heat transfer from the recording material sheet to the recording material sheet as compared with the conventional case, as shown in FIG. 1A, a portion of the heating element 43 facing the pressure roller 44, specifically, the heat resistant glass 60.
The vertical cross-sectional shape of the heater support body 50 and its surroundings is configured to be along the surface of the pressure roller 44. Thereby, for example, like the pressure contact force distribution between the heating body 43 and the adhesion film 51 in the pressure contact area A shown below the mechanical diagram portion in FIG. The pressure contact force of can be made almost uniform. As a result, the pressure contact force of the recording material sheet to the heating body 43 and the fixing film 40, which influences the heat energy transfer efficiency from the heating body to the recording material, becomes substantially uniform in the fixing nip. Therefore, by setting the pressure contact force between the pressure member and the heating body, it is possible to obtain the desired heat energy transfer efficiency without deteriorating the strength of the heat resistant sheet at the local pressure contact force peak in the fixing nip. .

Here, in the fixing device of FIG. 4, the pressure roller 46 having the rubber elastic layer 46 is attached to the fixing film 4.
When the surface of the fixing film 40 is rotationally driven so as to move in the forward direction of 0, or when the fixing film 40 is driven (rotated), the portion 44a on the entrance side of the fixing nip portion swells as shown in FIG. 6A. Transform to do. As a result, FIG.
Like the pressure contact force distribution between the heating body 43 and the adhesive film 51 in the pressure contact area A shown in the lower part of the mechanical diagram in (a), the pressure contact force between the pressure roller 44 and the heating body 43 is a predetermined pressure. The above range shifts to the approach side. Therefore, if it is left as it is, it is planned as a portion that mainly emits heat energy to the recording material sheet side of the heating body 43.
The heat-resistant glass 60 as the heat generation region and the pressure contact region A are displaced from each other, and the heat energy transfer efficiency is reduced. In order to prevent the heat energy transfer efficiency from being lowered due to the uneven bulging deformation of the pressure roller 44, as shown in FIG. 6B, the heating body 43 is arranged so as to be shifted toward the bulging deformation side. It is desirable to do. According to this, as shown in FIG. 6B, the heat-resistant glass 60 can be matched with the range in which the pressure contact force between the pressure roller 44 and the heating body 43 is equal to or higher than the predetermined pressure. Note that, unlike the example of FIG.
When the pressure roller 44 is rotatably supported and is rotated by the fixing film 40 that is driven to run, the bulging deformation occurs at the fixing nip portion outlet side. Therefore, in this case, it is desirable to dispose the heating body 43 in a shifted manner on the outlet side of the fixing nip portion, which is the bulging deformation side.

[Embodiment 2] Next, a fixing device according to another embodiment of the present invention will be described. The fixing device according to the present embodiment is the fixing device of the conventionally known film heating type shown in FIG. 7 in which the shape of the heating element 50 is changed. Therefore, first, the conventionally known film heating type fixing device shown in FIG. The device will be described. FIG. 7A is a side view thereof, and FIG. 7B is an explanatory view of a layer structure of an adhesion film 51 as a pressing member of the identification fixing device. In FIG. 7A, in this fixing device, instead of the pressure roller as a pressure member,
It differs from the fixing device of FIG. 4 only in that the endless belt-shaped contact film 51 is used, and other points are basically the same as those of the fixing device of FIG. Therefore, the same members as those shown in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted. In this fixing device, the adhesion film 51 as a pressing member is wound and stretched between a driving roller 52 and a driven roller 53 so as to face the lower surface of the heating body with the lower stretched portion of the fixing film 40 interposed therebetween. Is provided. Both rollers 52, 53
The heating body 43 is located substantially in the center of the upper portion of the adhesion film 51 between them, and the adhesion film 51 receives tension from the edge portion 50b on the fixing inlet side of the heater support 50 of the heating body 43, so that the heating body Fixing film 40 between 43
The adhesion film 51 is in close contact with the fixing film 40 with the sheet sandwiched therebetween to form a fixing nip portion. Then, the adhesion film 51 is rotationally driven in the fixing nip portion in the same direction as the fixing film 40 at the same speed.

The adhesion film 51 is the fixing film 40.
The same characteristics as above are required. That is, heat resistance, releasability,
Characteristics such as durability are required. Generally, a single layer or a composite film having a thickness of 5 mm or less, preferably 100 μm or less can be used. FIG. 7B shows a cross section of the adhesive film 51 having a two-layer structure. In this example, the heat-resistant layer 54 as a base layer (base film) of the adhesive film 51 and the outer surface of the heat-resistant layer (facing the toner image). Release surface 55 laminated on the side surface). The heat-resistant layer 54 is also required to have sufficient strength because it is stretched by winding. For example, polyimide, polyetheretherketone (PEEK), polyethersulfone (PES), polyetherimide (P).
Highly heat resistant resin films such as EI) and polyparapanic acid (PPA) and metals such as Ni, SUS and Al having excellent strength and heat resistance can be used. The release layer 55 is a rubber layer formed by coating a base layer, for example, a silicon rubber thin layer or an acrylic rubber thin layer. Also, like the fixing film 40, polytetrafluoroethylene (PTF
E), fluororesins such as PFA and FEP, and silicone resins are preferable. In the case of a single layer structure, only the base layer is provided except for the release layer 55.

In the above-described structure, the recording material sheet P carrying the toner image on the upper surface is conveyed to the fixing device by the image forming operation of the image forming apparatus in response to the image forming start signal.
Is guided by the guide 29, at the pressure contact portion (fixing nip portion) between the heating body 43 and the contact film 51 as the pressure member,
Enter between the fixing film 40 and the adhesion film 51,
The toner image surface is brought into close contact with the lower surface of the fixing film 40 by being sandwiched between the fixing film 40 and the contact film 51 that are rotated in the same direction at the same speed as the recording material sheet P is conveyed, and surface deviation, wrinkling, It passes through the fixing nip portion without any deviation.

Here, the driving roller 52 and the driven roller 53
Adhesion film 51 wound around and stretched between
As described above, the tension is applied from the fixing inlet side edge portion 50a of the heater support 50. At the entrance side to the fixing nip portion, the upper crown of the driven roller 53 around which the adhesive film 51 is wound is above the fixing nip portion, so that the recording material sheet P is fixed at a predetermined angle θ ₁ from above to below. Plunge into the nip. The adhesion film 51 on the side that conveys the recording material sheet P has a driving roller 52.
And the driven roller 53 and the heater support inlet side edge portion 5
Due to the positional relationship of the three points of 0b, tension acts in the fixing nip portion in the direction of bringing the recording material sheet P into close contact with the heating body 43. The recording material sheet P is brought into close contact with the heating body 43 via the fixing film 40 by the contact film 51.

Since the heating element 43 is electrically heated at a predetermined timing by the image formation start signal, the toner image on the recording material sheet P introduced into the fixing nip portion is heated via the fixing film 40 in the fixing nip. Softening
It becomes a fusion image. The fixing film 40 has an inlet-side edge portion 50b and an outlet-side edge portion 50a of the heater support 50 which are both provided with a curvature in order to enhance the transportability of the recording material sheet P.
Of these, the discharge side edge portion 50a having a relatively large curvature
At a radius of curvature of about 2 mm, the traveling direction turns at a steep angle (the bending angle θ is about 45 °). Therefore, the recording material sheet P conveyed through the fixing nip portion while being overlapped with the fixing film 40 is curvature-separated from the fixing film 40 at the discharge-side edge portion 50a, and is discharged to the discharge tray. By the time the paper is ejected, the toner is sufficiently cooled and solidified and is in a state of being completely fixed on the recording material sheet P (toner image Tc).

In this fixing device, the contact film 51 presses the recording material sheet P against the heating body 43 at the fixing nip portion using the pressing roller 44 as a pressing member.
The basic effect of the fixing device is the same. However, the contact film 51 has a much smaller heat capacity than the pressure roller 44. Therefore, the adhesion film 51 from the heating body 43
Very little heat is taken away, and the temperature rises rapidly at the fixing nip. That is, the temperature rising property at the fixing nip portion is very good. When the pressure roller 44 is used (in the case of the apparatus of FIG. 4), the melting point temperature of the toner is reached in half the time to reach the melting point temperature of the toner. In particular, in the fixing nip portion, only the fixing film 40, the recording material sheet P, and the contact film 51 absorb heat, so that heat can be efficiently supplied to the toner.

As described above, in the fixing device shown in FIG. 7, the fixing nip portion is heated to a temperature sufficiently high with respect to the melting point of the toner (or the fixing temperature of the recording material sheet P) in a short time (quick start property). It is not necessary to raise the temperature of the heating body 43 in advance (so-called standby temperature adjustment), and it is possible to sufficiently cope with a high-speed image forming apparatus, energy saving can be realized, and the temperature rise inside the apparatus can be prevented.

However, in the above-described conventionally known fixing device, the surface shape of the heating member 43 facing the pressure roller 44, specifically, the heat-resistant glass 60 has a flat plate shape. Similar to the fixing device as shown in FIG. 2 (b), the pressure contact force distribution between the heating body 43 and the adhesive film 51 in the pressure contact region A is non-uniform, and
The heat energy transfer efficiency to the recording material during passing through the sheet is poor, and if the pressure contact force between the heating body 43 and the adhesive film 51 is simply increased to obtain sufficient heat energy transfer efficiency, the strength of the fixing film 40 deteriorates. There is a risk of hastening it.

Therefore, in the present embodiment, the heating element 43
In order to increase the efficiency of heat transfer from the recording material sheet to the recording material sheet as compared with the conventional one, as shown in FIG. 1B, the contact film 51 in the heating body 43 arranged so as to bite into the spread portion of the contact film 51. Facing part, specifically heat-resistant glass 6
The vertical cross-sectional shape of 0 and the heater support 50 portion around 0 is formed in a shape protruding toward the adhesion film 51 side with a predetermined curvature. Thereby, for example, like the pressure contact force distribution between the heating body 43 and the adhesion film 51 in the pressure contact area A shown below the mechanical diagram portion in FIG. 1B, the adhesion film 51 and the heating body 43 are separated from each other. The pressure contact force was almost uniform. Therefore, the pressure contact force of the recording material sheet with respect to the heating body 43 and the fixing film 40, which influences the heat energy transfer efficiency from the heating body to the recording material, becomes substantially uniform in the fixing nip. Therefore, by setting the amount of biting of the heating body 43 with respect to the adhesive film 51, it is possible to obtain a desired heat energy transfer efficiency without deteriorating the strength of the heat resistant sheet at the local pressure contact force peak in the fixing nip. .

Here, in the fixing device shown in FIG. 7, the contact area A of the contact film 51, which is wound around the driving roller 52 and the driven roller 53 and driven to rotate, is pressed against the heating body 43.
The amount of tension differs between the front and back. Therefore, if the lower surface shape of the heating element 43 is symmetrical with respect to the center in the recording material sheet conveying direction, and the amount of biting into each part of the adhesive film 51 is also symmetrical, the shape shown in FIG. Like the pressure contact force distribution between the heating body 43 and the contact film 51 in the pressure contact area A shown below the mechanical diagram portion, the heater 4 in each part of the contact film 51 in the pressure contact area A is shown.
The distribution of the pressure contact force with 3 becomes non-uniform. As a result, if this condition is left as it is, a sufficient pressure contact force cannot be obtained in the entire width of the heat-resistant glass 60 as the heat generation region in the recording material sheet conveyance direction, and the heat energy transfer efficiency may decrease. In order to prevent such a decrease in heat energy transmission efficiency, as shown in FIG.
It is desirable that the shape is asymmetrical about the center of the traveling direction, and the influence of the difference in the magnitude of the tension on the press contact force is canceled by the difference in the bite amount.

In the fixing device using the adhesive film 51 as the pressing member in FIG. 7, the adhesive film 51 is used.
Since there is a sheet material conveying force in the above, the conveying portion (conveying belt device) 28 and the guide 29 of the image forming apparatus of FIG.
Instead, by disposing the driven roller 53 of the contact film 51 near the charge removal needle 27, the contact film 51 is extended to the vicinity of the charge removal needle 27, and the recording material sheet P exiting the transfer portion is extended. It is also possible to utilize the part of the adhesive film 51 as the transporting means and transport it to the fixing nip portion of the fixing device. According to this, the cost can be reduced because the transport unit 28, the fixing inlet guide 29, and the like are unnecessary. Further, since the recording material sheet P is carried on the adhesion film 51 and then rushes into the fixing nip portion, the recording material sheet P is satisfactorily conveyed to the fixing portion, and wrinkles, skewing, etc. can be prevented. There are merits.

Further, the contact film 51 may be further extended to function as a transfer belt. In this case, a transfer corona is provided on the inner surface of the transfer belt and on the rear surface of the transfer portion, and the toner image on the photosensitive drum 12 is transferred to the recording material sheet P.
Transfer to. According to this, since the transport unit 28, the fixing entrance guide 29, etc. are not required, the cost can be reduced, the separation of the recording material sheet P is good (paper is not selected), and the adhesion film 51 is provided.
There is an advantage that the recording material sheet P and the adhesion film 51 are strongly attracted to each other due to the charge of the reverse polarity of the toner on the back surface, and the offset of the toner to the fixing film 40 during fixing is very small.

[0044]

According to the invention of claim 1, by setting the pressure contact force between the pressure member and the heating body, the strength of the heat resistant sheet is not deteriorated at the local pressure contact force peak in the fixing nip. Since the desired heat energy transfer efficiency from the heating body to the recording material can be obtained, the heat energy transfer efficiency can be improved as compared with the conventional film heating type fixing device without shortening the life of the heat resistant sheet. Can be increased. Therefore, without shortening the life of the heat-resistant sheet, compared to the conventional film heating type fixing device, the fixing nip portion quickly rises to a predetermined fixing temperature to shorten the wait time and reduce the power consumption. Can be reduced.

Particularly, according to the fixing device of the second aspect, in the case where the heating member is arranged such that the center of the heat generation region of the heating member is located immediately above the rotation center of the rotatable pressure roller having the elastic layer as the pressure member. As compared with the above, since the heat generation area can be matched to the pressure contact area between the deformed pressure roller surface and the heating element, the recording material can be pressed against the heat generation area of the heating element with the heat-resistant sheet interposed therebetween. The weight time can be further shortened and the power consumption can be further reduced as compared with the case where the center of the heat generation region of the heating body is located immediately above the center of rotation of the pressure roller.

According to the fixing device of the third aspect, by setting the amount of biting of the heating body into the belt member extending portion as the pressing member, the heat-resistant sheet of the heat-resistant sheet at the local peak of the pressure contact force in the fixing nip can be obtained. Since the desired heat energy transfer efficiency can be obtained without deterioration in strength, the heat energy transfer efficiency can be improved as compared with the conventional film heating type fixing device without shortening the life of the heat resistant sheet. be able to. Therefore, without shortening the life of the heat-resistant sheet, compared to the conventional film heating type fixing device, the fixing nip portion quickly rises to a predetermined fixing temperature to shorten the wait time and reduce the power consumption. Can be reduced.

In particular, according to the fixing device of the fourth aspect, the pressure contact force of each part of the belt member with the heating body in the pressure contact area between the belt member and the heating body with the heat-resistant sheet interposed therebetween is Since the amount of biting of the heating element into the expanded portion inside can be made more uniform than in the case where it is symmetrical about the center of the heat resistant sheet running direction, the weight time can be further shortened and power consumption can be further reduced. Can be reduced.

[Brief description of drawings]

FIG. 1A is an explanatory diagram of a fixing device according to an embodiment.
FIG. 6B is an explanatory diagram of a fixing device according to another embodiment.

2A and 2B are explanatory views of a fixing device according to a conventional example.

FIG. 3 is a side view showing a schematic configuration of an image forming apparatus according to an example.

FIG. 4A is a side view of a conventionally known fixing device. (B)
Is a partial sectional view of the identification attachment device.

FIG. 5 is a rear view of the identification fixing device.

6A and 6B are explanatory views of the fixing device according to the embodiment.

FIG. 7A is a side view of another conventionally known fixing device.
(B) is a partial sectional view of the identification attachment device.

FIGS. 8A and 8B are explanatory views of a fixing device according to an embodiment.

[Explanation of symbols]

 40 Fixing Film 44 Pressure Roller 43 Pressure Body 57 Adhesive Film P Recording Material Sheet

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[Procedure amendment]

[Submission date] May 2, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

[0012]

A fixing device according to claim 1 is
A heat-resistant sheet that is driven to travel, a heating body and a pressing member that press-contact each other with the heat-resistant sheet sandwiched therebetween, and are formed by pressing the heating body and the pressing member with the heat-resistant sheet sandwiched. A recording material carrying an unfixed visible image is introduced between the heat-resistant sheet in the fixing nip portion and the pressure member, and the heat-resistant sheet is moved from the heating body by moving through the fixing nip portion together with the heat-resistant sheet running. In a fixing device for applying thermal energy to a recording material to heat and fix a visible image through the fixing member, a member whose surface shape in a vertical cross section has a predetermined curvature is used as the pressing member, and the pressing member in the heating body is used. It is characterized in that the surface shape in the vertical cross section of the facing portion is formed in a shape along the surface of the pressing member. The fixing device according to claim 2 uses a rotatable pressure roller having an elastic layer as the pressure member, and in the fixing device according to claim 1, the fixing device is rotated while sandwiching the heat-resistant sheet in pressure contact with the heating body. The surface of the pressure roller that deforms so as to bulge mainly in one of the upstream side and the downstream side of the pressure roller rotation center in the running direction of the heat resistant sheet, and the heating body. The swelling of the pressure roller from directly above the center of rotation of the pressure roller so that the predetermined heat generation area of the pressure roller facing portion of the heating body more closely matches the pressure contact area sandwiching the heat resistant sheet. The heating element is characterized in that the center of the heat generation region is shifted to the deformation side and the heating element is arranged. The fixing device according to claim 3 includes a heat-resistant sheet that is driven to run, a heating body and a pressing member that press-contact each other with the heat-resistant sheet interposed therebetween, and the heating body and the pressing member sandwich the heat-resistant sheet. A recording material carrying an unfixed visible image is introduced between the heat-resistant sheet in the fixing nip portion formed by pressurizing and the pressure member, and the recording material carrying the unfixed visible image is moved through the fixing nip portion together with the heat-resistant sheet. In a fixing device that heats and fixes a visible image by applying heat energy from a heating body to a recording material via a heat resistant sheet, a belt member wound around a plurality of support rollers is used as the pressing member. The heating element is arranged so as to bite into the stretched portion of the belt member between the plurality of support rollers to apply tension to the belt member,
In addition, the surface shape of the heating member in the vertical cross section of the belt member facing portion is configured to project to the belt member side with a predetermined curvature. A fixing device according to a fourth aspect is the fixing device according to the third aspect, in which a pressure contact force between each of the belt member portions and the heating body in a pressure contact area between the belt member and the heating body sandwiching the heat resistant sheet is: In order to make the surface shape more uniform in the pressure contact area, the surface shape is configured such that the amount of bite into the expanded portion in the pressure contact area is asymmetrical around the center in the running direction of the heat resistant sheet. It is a feature.

Claims (4)

[Claims] 1. A heat-resistant sheet that is driven to run, and a heating body and a pressing member that are in pressure contact with each other with the heat-resistant sheet sandwiched therebetween, and the heating body and the pressing member are sandwiched by sandwiching the heat-resistant sheet. By introducing a recording material carrying an unfixed visible image between the heat-resistant sheet of the fixing nip portion formed by pressure and the pressure member, the heating material is moved by passing through the fixing nip portion together with the heat-resistant sheet running. In the fixing device for applying thermal energy to the recording material through the heat resistant sheet to heat and fix the visible image, a member whose surface shape in a vertical cross section has a predetermined curvature is used as the pressing member, and the heating member is used. 2. A fixing device, wherein the surface shape in the vertical cross section of the pressing member facing portion in is formed into a shape along the surface of the pressing member. 2. The fixing device according to claim 1, wherein a rotatable pressure roller having an elastic layer is used as the pressure member, wherein the heat-resistant sheet is sandwiched and rotated while being in pressure contact with the heating body. The heat resistance of the heating body and the surface of the pressure roller that deforms so as to bulge mainly to either one of the upstream side and the downstream side immediately above the center of rotation of the pressure roller in the running direction of the heat resistant sheet. The bulging deformation side of the pressure roller is located right above the center of rotation of the pressure roller so that a predetermined heat generation area of the pressure roller facing portion of the heating body more closely matches the pressure contact area sandwiching the sheet. The heating element is arranged such that the center of the heat generation region is shifted.
Fixing device. 3. A heat-resistant sheet that is driven to run, and a heating body and a pressing member that are in pressure contact with each other with the heat-resistant sheet sandwiched therebetween, and the heating body and the pressing member are sandwiched by sandwiching the heat-resistant sheet. By introducing a recording material carrying an unfixed visible image between the heat-resistant sheet of the fixing nip portion formed by pressure and the pressure member, the heating material is moved by passing through the fixing nip portion together with the heat-resistant sheet running. In a fixing device that applies heat energy to a recording material through a heat-resistant sheet to heat and fix a visible image, a belt member wound around a plurality of support rollers is used as the pressing member, and the plurality of support rollers are used. The heating member is arranged so as to give tension to the belt member by digging into the stretched portion of the belt member between the rollers, and the surface shape in a vertical cross section of the belt member facing portion of the heating member is defined by the belt. Element A fixing device characterized in that the fixing device is configured to project to a side with a predetermined curvature. 4. The pressure contact area between the heating member and each part of the belt member in the pressure contact area between the belt member and the heating body sandwiching the heat resistant sheet is more uniform in the pressure contact area. The fixing device according to claim 3, wherein the surface shape is configured such that the amount of bite into the expanded portion in the pressure contact region is asymmetrical about the center in the running direction of the heat resistant sheet.