JP2002099168A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform excellent fixation which is free of cooling unevenness by using a fixing device in which a recording sheet (P) to be fixed is peeled off after cooling the sheet with a cooling means (5) while making it abut against an end less belt (3) by uniformly and stably cooling the endless belt traveling from a heat roll (1) to a peeling roll (2) and the recording sheet (P) being an object of fixation carried while abutting against the belt. SOLUTION: A cooling structure (5) is so arranged that the bending angle (α) at the position where the endless belt (3) is bent when leaving a pressing cooling surface (5a) of the cooling structure (5) after the belt (3) has made a contact with the cooling surface (5a) is >0 deg. and <=7 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing a toner image formed in an image forming apparatus such as a printer or a copying machine using an electrophotographic method on a recording sheet.
In particular, the present invention relates to a fixing device of a system in which a recording sheet to be fixed is heated and pressurized, then cooled by a cooling unit in a state of being in contact with an endless belt, and then separated.

[0002]

2. Description of the Related Art In recent years, as a fixing device used in an image forming apparatus using an electrophotographic system, a fixing roller is stretched at least over a heating roll and a peeling roll which is disposed at an interval between the heating roll and rotates. Endless belt, a pressurizing roll that presses the endless belt against a heating roll, and a cooling structure that cools by contacting the inner peripheral surface of the belt from the heating roll of the endless belt to the peeling roll to heat the endless belt. The recording sheet carrying the toner image is rotated while being rotated in the direction in which the roll, the cooling structure, and the peeling roll pass in this order, and the pressure contact area (nip portion) between the endless belt stretched over the heating roll and the pressure roll. In a state where the cooling structure is in contact with the endless belt, the cooling structure passes through the portion where the cooling structure comes into contact with the endless belt, and is transported to a portion where the cooling structure is placed on a peeling roll to be peeled off. The fixing device has been proposed the method to fix the over images on a recording sheet (e.g., JP-A-4-21
No. 6580, Japanese Unexamined Patent Publication No. 5-72926).

Among them, the fixing device described in Japanese Patent Application Laid-Open No. Hei 4-216580 uses an air-cooling type cooling roll disposed as a cooling structure on the inner peripheral surface of an endless belt so as to be able to contact and separate therefrom. Also, in the fixing device described in Japanese Patent Application Laid-Open No. 5-72926, a large number of air circulation holes are formed on the contact surface of the endless belt with the inner peripheral surface as a cooling structure. An air-cooled box is applied (see FIG. 2 etc.). In any of such fixing devices, the recording sheet carrying the toner image is heated and pressurized, and then cooled by a cooling roll or an air-cooling box in a state where the recording sheet is in contact with the endless belt, and then separated from the endless belt. Thus, fixing is performed.

[0004]

However, in a fixing apparatus of the type in which a recording sheet to be fixed is heated and pressed and then cooled and peeled in a state in which the recording sheet is brought into contact with an endless belt, the following method is used. One issue is how to perform the cooling uniformly and stably.

That is, in the fixing device to which the cooling roll is applied, since the cooling roll is simply brought into contact with the endless belt, the endless belt is deformed due to wrinkles or wavy deformation generated in the endless belt. There is a portion that does not sufficiently contact with the cooling roll and is not cooled. As a result, the toner image on the recording sheet after heating and pressing is not cooled uniformly, which may cause unevenness in image quality.

In the fixing device to which the air-cooling box is applied, the air-cooling box is pressed against the endless belt, so that the contact with the endless belt is impaired by the large number of air circulation holes. Although it is possible to cool the endless belt evenly, it is possible to record after heat and pressure if the air cooling box is pressed too much against the endless belt and the belt is bent greatly. The sheet is easily peeled off from the endless belt portion pressed by the air-cooling box, or the sheet is easily peeled off from the endless belt even when leaving the pressed endless belt portion, as a result,
Also, the toner image on the recording sheet after the heating and pressurization is not cooled uniformly, and there is a possibility that the image quality failure due to such cooling unevenness may occur. In addition, such cooling unevenness is caused by arranging an endless belt with an air-cooling box in contact with the outer peripheral surface side of the endless belt on the opposite side of the endless belt of the air-cooling box as exemplified in the publication. In the case of the configuration, although it is prevented to some extent, there is always a state in which the recording sheet is easily peeled off the belt depending on the pressing amount of the air cooling box on the side that cools the inner peripheral surface of the belt, which causes uneven cooling. There is a risk.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and an object thereof is to cool a recording sheet to be fixed by a cooling unit in a state in which the recording sheet is brought into contact with an endless belt as described above. As a fixing device of a system that separates the belt from the endless belt, a cooling unit that performs cooling while pressing from the inner circumferential surface of the endless belt is conveyed in a state of contact with the endless belt from the heating roll to the peeling roll and the belt. Cool the recording sheet to be fixed uniformly and stably,
An object of the present invention is to provide a fixing device capable of performing good fixing without cooling unevenness.

[0008]

As shown in FIG. 1, a fixing device according to the present invention, which can achieve the above object, has a heating roll (1) and a heating roll (1) provided at an interval. A peeling roll (2), an endless belt (3) that is at least stretched over the peeling roll (2) and the heating roll (2), and rotates and runs. A pressure roll (4) pressed against the roll (1);
Disposed on the inner peripheral surface side (3a) of the endless belt (3);
Press-cooling for cooling while pressing the inner circumferential surface portion of the endless belt (3) from the heating roll (1) to the peeling roll (2) toward the belt outer circumferential surface (3b). And a cooling structure (5) having a surface (5a). The endless belt (3) passes through the heating roll (1), the cooling structure (5), and the peeling roll (2) in this order. The recording sheet (P) carrying the toner image (T) while rotating in the direction (A) is moved between the endless belt (3) and the pressure roll (4), which are stretched over the heating roll (1). Of the cooling structure (5) in contact with the pressing and cooling surface (5a) of the cooling structure (5) in a state of contact with the endless belt (3). 2) The toner is transported to the part where the A fixing device for fixing an image to a recording sheet, wherein the cooling structure (5) is used until the endless belt (3) comes into contact with and separates from a pressing cooling surface (5a) of the cooling structure (5). The bending angle (α) of the portion bent between the two is set to be in the range of 0 ° <α ≦ 7 °. One-dot chain line K in the figure
Indicates a state in which the endless belt (3) is not pressed by the cooling structure (5) and is naturally stretched between the heating roll (1) and the peeling roll (2). It is regarded as a straight line in contact with the top of the roll surface of both the heating roll (1) and the peeling roll (2).

Here, the cooling structure (5) cools while pressing a fixing belt heated at the time of fixing (actually, the recording sheet (P) to be fixed is fixed with an endless belt interposed therebetween. Any structure having a pressure cooling surface (5a) for cooling can be applied. For example, if the entire form is roughly classified, it is arranged to rotate. Examples include a roll type or a belt type, and a fixed type. As the cooling method, a method using a cooling medium (a method of circulating water, a refrigerant, or the like) such as an air cooling method can be applied. As a preferable cooling structure (5), for example, a heat dissipating member is brought into contact with the endless belt from the viewpoint that a large contact area with the inner peripheral surface of the endless belt can be secured, cooling efficiency is improved, and the configuration is simple. At the same time, the heat radiation member is air-cooled. Pressing and cooling surface (5
About a), it is desirable that it is a smooth surface from a viewpoint of ensuring adhesiveness with an endless belt.

The bending angle (α) may be one or plural depending on the form of the cooling structure (5) and the form of the press cooling surface (5a). Even in the case where the endless belt (3) comes into contact with the pressing / cooling surface (5a), a natural tension between the heating roll 1 and the peeling roll 2 of the endless belt (3) (by the pressing / cooling surface) This is the angle formed by the endless belt (3) with respect to the state line when no pressure is applied. The state line referred to here is the same as the one-dot chain line K shown in FIG.

FIG. 2 shows a typical example of the bending angle α due to the difference in the form of the cooling structure and the pressing cooling surface. FIG. 5A illustrates the bending angle α when the cooling structure (5) is in the form of a rotating roll or when the pressing and cooling surface (5a) is a cylindrical curved surface.
1, S2 is the first or last contact point of the endless belt with the pressing cooling surface, O is the center point of the roll or cylindrical curved surface, and θ is the wrap angle of the endless belt. 2 are all the same as the one-dot chain line K in FIG. 1, and are shown as being translated to the position where the endless belt (3) intersects with the portion that first contacts the press cooling surface. is there. FIG. 2B illustrates a bending angle α in a case where the cooling structure (5) is a fixedly arranged member and the pressing cooling surface (5a) is a flat surface. Further, FIG. 2c shows a member to which the cooling structure (5) is fixedly arranged, the pressing cooling surface (5a) being partly curved and partly flat when the endless belt 3 is bent. Bending angles α1 to α4
M1 to M2 in the figure indicate curved portions of the press cooling surfaces (5a) (note that the portions of the press cooling surfaces 5a not indicated by M1 and the like indicate flat portions).
Incidentally, in the case of the cooling structure 5 (pressing cooling surface 5a) shown in the upper part of FIG. 2c, the endless belt (3) is not bent at the contact point S1, but is bent at the contact point S2 for the first time.

When the bending angle α is 0 ° or less, the non-contact portion where the pressing and cooling surface of the cooling structure does not press the endless belt and the endless belt does not contact the pressing and cooling surface easily occurs. And uneven cooling is likely to occur. On the other hand, when the angle exceeds 7 °, the recording sheet to be fixed is not fixed until the endless belt comes into contact with and separates from the pressing cooling surface of the cooling structure (due to the effect of the sheet's own weight and the strength of the waist). The endless belt is easily peeled off, and uniform and sufficient cooling cannot be performed.

According to the fixing device of the present invention, the cooling structure for cooling while pressing the endless belt is bent until the endless belt comes into contact with and separates from the pressing cooling surface of the cooling structure. Is arranged such that the bending angle (α) of the portion to be fixed is within the above specific range, the recording sheet to be fixed is fixed to the endless belt portion (the cooling structure) pressed by the pressing cooling surface of the cooling structure. Between the belt and the belt, the paper is conveyed in a state of being in close contact with the belt without peeling off from the belt. As a result, the recording sheet to be fixed is uniformly and stably cooled in a state in which the recording sheet is in close contact with the endless belt after heating and pressing.

In the fixing device, the cooling structure (5) has a bending angle (β) at a position where the endless belt (3) separates from the pressing cooling surface (5a) of the cooling structure while being bent. Is preferably set to be in the range of 0 ° <β ≦ 22 °.

The bending angle (β) is, as exemplified in the upper part of FIGS. 2B and 2C, a configuration in which the endless belt (3) is separated from the pressing cooling surface (5a) of the cooling structure in a bent state. This is the angle condition required when the angle is set. For this reason, as illustrated in the lower part of FIG. 2C, this is irrelevant when the endless belt (3) is configured to be linearly separated from the pressing cooling surface (5a) without being bent.
Incidentally, for the endless belt (3) in such a linearly separated configuration, β = 0 ° if the bending angle (β) is indicated. Therefore, this bending angle (β)
Is an angle indicating the bending state when the endless belt (3) leaves the press-cooling surface (5a) after it has passed. More specifically, for example, as illustrated in FIG. 2B, the pressing cooling surface (5a) before the endless belt (3) separates is parallel to the state line K of the natural tension of the endless belt (3). In some cases, the angle formed by the endless belt (3) with respect to the state line K, and the pressing cooling surface (5a) immediately before the endless belt (3) leaves as shown in the upper part of FIG. When the belt (3) is not in a state parallel to the state line K of the natural tension (for example, when the belt (3) is inclined or curved), the pressing cooling surface (5
The angle formed by the endless belt (3) with respect to the tangent line or extension line (J) at the part where the endless belt of (a) separates.

In the case of the bending angle (β), the recording sheet to be fixed is conveyed without being peeled off from the endless belt separated from the pressing cooling surface of the cooling structure without peeling off. Will be done. Thus, the recording sheet to be fixed is sufficiently cooled in a state in which the recording sheet is in close contact with the endless belt until the recording sheet is peeled at a peeling point where the peeling roll is located.

Further, in the fixing device, the pressing cooling surface (5a) of the cooling structure (5) is in the belt rotation direction (A).
Is preferably a curved surface having a curvature with respect to. In this case, the curvature is appropriately selected mainly in consideration of securing the adhesion of the endless belt to the press cooling surface. In the case of such a configuration, the endless belt comes into sufficient contact with the pressing and cooling surface of the cooling structure in a more intimate state. This ensures that the recording sheet to be fixed is cooled by the cooling structure via the endless belt that comes into contact with the pressurized cooling surface having the curved surface.

Further, in each of the fixing devices as described above, the endless belt (3) is connected to the outer peripheral surface of the belt (3).
It is preferable to dispose a pressing rotating body (6) for pressing the cooling structure (5) against the pressing cooling surface (5a) from b).
Such a pressing and rotating body may be of a roll type,
Alternatively, there is a belt type in which an endless belt is rotatably wrapped around a support roll. In such a configuration, the endless belt comes into contact with the pressing cooling surface with a higher contact pressure due to the pressing of the pressing rotating body, and more reliably and uniformly. Thereby, the cooling efficiency of the endless belt and the recording sheet by the cooling structure is further improved, and the cooling unevenness is reduced.

In this fixing device, the position where the endless belt (3) of the pressing rotary body (6) is pressed is at least the endless belt (3) on the pressing cooling surface (5a) of the cooling structure (5). Is preferably within a region (E) of 30 mm inward from the first contact portion. In such a configuration, the non-contact portion, which is likely to occur immediately after the endless belt comes into contact with the pressing cooling surface, is securely pressed down from the outer peripheral surface side of the belt by the pressing rotating body and disappears, and the endless belt is pressed and cooled. The surface is more securely adhered.

Further, in the fixing device, a portion of the pressing rotary member (6) that comes into contact with the endless belt (3) is preferably formed of a synthetic resin foam. As the synthetic resin foam, for example, a foam (for example, a sponge-like form) made of a synthetic resin such as polyurethane or styrene is used.
In the case of such a configuration, even if the pressing and rotating body is heated by the endless belt that is heated by being wound around the heating roll, the synthetic resin foam does not store heat due to the heat insulating action,
As a result, the cooling action of the cooling structure is not hindered by the pressed rotating body that has been heated.

Further, it is preferable that the pressing force of the pressing and rotating body (6) in the fixing device is set to 700 gf or less.
With such a configuration, the rotation of the endless belt and the conveyance of the recording sheet due to the pressing of the pressing and rotating body are smoothly performed without being hindered.

Further, the pressing rotary member (6) in the fixing device can swing around a position on the upstream side in the belt rotation direction from a position where the rotary member (6) presses the endless belt (3). It is good to constitute so that it may be supported by a support frame. In such a configuration, since the pressing and rotating body can swing so as to be separated from the endless belt toward the side that opens the front in the transport direction of the recording sheet, after the recording sheet to be fixed is introduced into the fixing device, Even if a paper jam occurs,
Since the pressing and rotating body swings toward the above side due to the paper jammed recording sheet, the paper jammed recording sheet is easily discharged without staying in the apparatus.

The fixing device of the present invention can be used as a fixing device of a multi-color or single-color image forming apparatus using an electrophotographic system, and can be used for forming a multi-color or single-color image formed with a fixing device. You may make it use it, connecting with an apparatus. Particularly in the latter case, for example, after the first fixing is performed by the fixing device on the image forming apparatus side, the second fixing is performed by the fixing device of the present invention connected to the image forming apparatus, Alternatively, it is possible to perform only fixing by the fixing device of the present invention without performing fixing by the fixing device on the image forming apparatus side.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] FIGS.
3 shows a main part of the fixing device according to the first embodiment of the present invention. FIG. 3 is a perspective view thereof, FIG. 4 is a schematic sectional view taken along line IV-IV of FIG. 3, and FIG. FIG. 6 is a schematic bottom view taken along line V of FIG.

The fixing device according to the first embodiment includes a heating roll 10, a peeling roll 20, an endless belt 30.
, The pressure roll 40 and the cooling structure 50 constitute the main part thereof. In the figure, the symbol P is a recording sheet,
T indicates a toner image.

The heating roll 10 includes a roll main body having a coating layer 12 formed on a cylindrical roll core 11 made of aluminum, stainless steel or the like, and a heating halogen disposed in the internal space of the roll core 11. And a lamp 13. The coating layer 12 is made of, for example, an elastic layer made of silicone rubber or the like and having a thickness of about 0.5 to 5 mm, and a fluororesin (PFA or the like) formed on the surface of the elastic layer.
It is formed of a surface layer having a thickness of about several μm to several tens μm. The heating roll 10 is rotatably supported by a support frame (not shown) and is driven to rotate in a predetermined direction (A) by a known rotation driving unit. In addition, this heating roll 1
0 is heated to a predetermined fixing heating temperature (for example, 120 to 180 ° C.) by the heating halogen lamp 13,
In addition, the heating operation of the halogen lamp 13 is feedback-controlled based on information detected by a temperature sensor (not shown) that measures the temperature of the surface of the heating roll, and is maintained at a predetermined fixing heating temperature.

The peeling roll 20 includes an endless belt 30.
Is a roll for urging the recording sheet P to be fixed, which is conveyed in contact with the belt 30, by being stretched while being bent at a predetermined curvature, for example, aluminum, SUS (stainless steel). ) And the like. The peeling roll 20 is rotatably supported by a support frame (not shown) and is elastically urged in a direction in which tension is applied to the endless belt 30 by a known tension applying mechanism such as a spring. It has become so.

As shown in FIG. 8, the endless belt 30 has a belt substrate 31 having a thickness of about 30 to 200 μm and a thickness formed on the outer peripheral surface side of the substrate 31 having a thickness of 10 to 200 μm.
And a degree of elastic release layer 32. Of these, the belt base material 31 is formed using a heat-resistant resin such as polyimide or polyamide, or a metal material such as nickel or aluminum. The elastic release layer 32 is formed of silicone rubber, fluorine rubber, or the like. It is desirable that the outer peripheral surface of the endless belt 30 (specifically, the surface of the elastic release layer 32) be as smooth as possible (a surface close to a mirror surface). This endless belt 30 is
And the heating roll 10
Is driven to rotate in the direction of arrow A in the figure.

The pressure roll 40 is provided so as to press the endless belt 30 against the heating roll 10.
For example, it has the same layer structure as the roll body of the heating roll 10 described above. In addition, similarly to the heating roll 10, a heating halogen lamp 13 may be provided on the pressure roll 40 as necessary to add a heating function.
The pressure roll 40 is rotatably supported by a support frame (not shown) and has a predetermined pressure (5
It is supported by a known pressure mechanism (not shown) so as to be urged in the pressing direction at 0 to 200 kgf). Also,
Due to the pressure contact of the pressure roll 40, a pressure contact portion (N) having a predetermined width is formed between the roll 40 and the endless belt 30 spanning the heating roll 10 (FIGS. 4 and 6).

The cooling structure 50 includes a heat radiating member 51 for cooling while pressing the inner circumferential surface of the endless belt 30 from the heating roll 10 to the peeling roll 20 toward the outer circumferential surface of the belt. And an air cooling mechanism 52 for supplying air to the heat radiating member 51 for air cooling.

As shown in FIG. 4 and FIG. 7, the heat radiating member 51 includes a plurality of heat radiating fins 51a.
And a heat sink made of aluminum or the like formed in a state of being arranged in parallel along the width direction (direction perpendicular to the running direction A) of the endless belt 3.
0 is formed as a press-cooling (heat-absorbing) surface 51b that presses the inner peripheral surface. This pressing cooling surface 51b is
Its cross-sectional shape is substantially rectangular, and its entire surface is formed of a smooth flat surface. On the other hand, the air cooling mechanism 52 is configured as shown in FIGS.
As shown in FIG. 5, the blower fan 53 and the intake fan 54
And a ventilation duct 55 communicating from the blower fan 53 to the intake fan 54 through the heat radiation member 51. In this cooling structure 50, for example, the recording sheet P to be fixed is subjected to any necessary conditions (passing time).
The heat radiation member 51 depends on how many times
And the air cooling efficiency of the air cooling mechanism 52 are appropriately set. The air cooling operation (operation of the fans 53 and 54) by the cooling structure 50 is set so as to be performed during a series of fixing operations after the heating roll 10 is heated to a predetermined fixing temperature. I have.

As shown in FIG. 7, the cooling structure 50 of this fixing device has a bending angle of a portion where the endless belt 30 is bent until it comes into contact with the pressing cooling surface 51b of the cooling structure and separates. (That is, in this embodiment, the bending angle of the endless belt after coming into contact with the corner of the pressing cooling surface 51b on the belt entry side) is set to about 5 ° C. In addition, the cooling structure 50 has a bending angle at a position where the endless belt 30 is separated from the pressing cooling surface 51b of the cooling structure in a bent state (that is, in this embodiment, the angle of the pressing cooling surface 51b on the belt separation side). (The bending angle of the endless belt after contact with the portion) β is set to about 15 °. Such a heat radiating member 51 is disposed so as to be fixedly supported on a support frame (not shown) via the ventilation duct 55 so that the bending angles α and β satisfy the above numerical conditions. .

In this fixing device, a recording sheet P carrying a toner image T formed by a color image forming apparatus such as a color printer using an electrophotographic method is an object to be fixed. For this reason, in this fixing device, a belt transport (not shown) for transporting the recording sheet P carrying the toner image T so as to be introduced into the pressure contact area N between the endless belt 30 and the pressure roll 40 is provided. A sheet conveying means such as a device is provided. In addition, the fixing device transfers the recording sheet P, which is peeled from the endless belt 30 when the endless belt 30 reaches the peeling roll 20, to a storage tray or another post-processing device outside the fixing device. Discharge means such as a discharge roll pair (not shown) for discharging is provided.

Further, the recording sheet P to be fixed by the fixing device is not particularly limited as long as it is a recording medium applicable to an image forming apparatus. From the viewpoint of obtaining the image of FIG.
As shown in FIG. 1, a laminate in which a transparent resin layer 120 mainly containing a thermoplastic resin is formed on a base material 100 is used. Examples of the substrate 100 include plain paper for image formation, coated paper, and photographic paper. Examples of the thermoplastic resin constituting the transparent resin layer 120 include a polyethylene resin and a styrene-acrylate resin. Further, it is preferable that the transparent resin layer 120 has such a thickness that the toner image T is embedded by being melted by heating and pressing at the time of fixing.

Next, the operation of this fixing device will be described with reference to FIG.
This will be described with reference to FIG.

First, when the timing of the fixing operation comes, the heating roll 10 starts rotating to rotate the endless belt 30 in the direction of arrow A, and the heating halogen lamp 13 generates heat by energizing to heat the heating roll 10. The heating is performed to a predetermined fixing temperature to be maintained. At this time, the pressure roll 40 starts to rotate following the rotation of the heating roll 10 via the endless belt 30. In addition, the cooling mechanism 52 (the fans 53 and 54) of the cooling structure 50 starts operating after the heating roll 10 is heated to a predetermined fixing temperature and before the fixing operation is started.

Thus, the pressure contact area N between the fixing belt 30 and the pressure roll 40 is heated to a predetermined fixing temperature, and the endless belt 30 is heated by the heat radiating member 51 of the cooling structure 50. When passing through the pressed portion, the cooling device is forcibly cooled by the heat radiation action.

Subsequently, as shown in FIG. 10A, the recording sheet P (FIG. 10A) on which the toner image T formed according to the image information is transferred to the fixing device in such a state as shown in FIG. 11a) is fed into the pressure contact area N between the fixing belt 30 and the pressure roll 40 by a paper transport device (not shown). Thus, the recording sheet P is heated and pressurized and melted in the press contact area N, and is embedded in the (transparent resin layer 120) of the recording sheet P (FIG. 11B). Then, even after passing through the pressure contact area N, the recording sheet P is conveyed in the direction of arrow A with the rotation of the belt 30 in a state of contacting (adhering) to the outer peripheral surface of the endless belt 30.

Next, as shown in FIG. 10B, the recording sheet P to be fixed, which is conveyed in contact with the endless belt 30, is pressed against the cooling surface 5 of the heat radiating member 51 of the cooling structure 50.
The belt is conveyed so as to pass through the belt portion (cooling region) pressed by 1b while being in contact with the endless belt 30, and is cooled by the heat dissipating action of the heat dissipating member 51 during the passage. That is, while the recording sheet P and the toner image T heated in the pressure contact area N pass through the cooling area, the retained heat is transmitted to the heat radiating member 51 via the endless belt 30 and is radiated (FIG. 11c). Moreover, the heat radiation at this time is performed efficiently because the heat radiation member 51 is air-cooled by the air-cooling mechanism 52. As a result, the toner image T and the recording sheet P (the transparent resin layer 120) are cooled by the heat radiation in a state where the toner image T is embedded in the recording sheet P (the transparent resin layer 120). Almost set.

The recording sheet P that has passed through the cooling area is
As shown in FIG. 10C, the recording sheet is conveyed to the peeling roll 20 in a state of being in contact with the endless belt 30. Because of the inconsistency between the endless belt portion and the endless belt portion extending over the peeling roll 20, the film is naturally peeled off. Thus, the fixing is completed. The recording sheet P peeled from the endless belt 30 is sent to a storage tray or the like by a discharge unit (not shown).

When the fixing by the fixing device is normally performed, the cooling in the cooling area is performed uniformly without unevenness, and as a result, as shown in FIG.
(The transparent resin layer 120) is fixed in such a manner as to be uniformly embedded therein, and the surface of the sheet (the surface of the transparent resin layer 120) after the fixing is smoothed following the smooth surface of the endless belt 30. It is fixed so as to be in a state excellent in properties. That is, the image on the recording sheet P after the fixing is obtained as a high-quality image similar to a photographic image with less irregular reflection of light due to surface irregularities and high glossiness.

FIG. 12 shows a recording apparatus in which the endless belt 30 is conveyed by the endless belt 30 before and after the cooling area where the endless belt 30 passes through the pressing cooling surface 51b of the heat radiating member 51 of the cooling structure 50 in the fixing device. Sheet P
3 shows the result (solid line) of the measurement of the temperature state of FIG.
This temperature measurement is performed when the endless belt is rotated and driven at a constant speed with a thermocouple (one) attached to a portion of the recording sheet P corresponding to the widthwise central portion of the endless belt 30 (that is, the fixing device). The temperature was measured when the entire apparatus was operated under the same conditions as the actual fixing operation, and the temperature was shown. In FIG.
When the pressing cooling surface 51b is simply brought into contact with the endless belt 30 (that is, the bending angles α and β are both “0 °”).
), The result (dotted line) of the temperature state similarly measured is also shown.

The main structure of the fixing device and the structure of the recording sheet used in this test were as follows. Regarding the heating roll 10 and the pressure roll 40,
The roll base materials 11 and 41 have an outer diameter of 44 mm and a thickness of 3 mm.
3 mm thick silicone rubber (JIS-A hardness: 40 degrees) for the elastic layer in the aluminum cylindrical roll and the coating layers 12 and 42, and 3 μm for the surface release layer in the coating layer.
m PFA tube. As for the endless belt 30, the belt base material 31 was a 168 mm long belt made of a thermosetting polyimide film having a thickness of 80 μm, and the elastic release layer 32 was a 3 μm thick PFA coating layer made of PFA. The width of the pressure contact area (N) between the endless belt 30 and the pressure roll 40 was 85 mm, the pressure was 5 kg / cm ² , and the fixing speed (rotation driving speed of the heating roll) was 30 mm / s. On the other hand, as the recording sheet P, a substrate 100 made of coated paper having a basis weight of 180 gsm and a transparent resin layer 120 made of a polyester resin coat layer was used. Also,
As the toner constituting the toner image, a styrene acrylic spherical toner containing wax (average particle size: 5 μm) was used.

From the results shown in FIG. 12, the cooling structure 5
0 cooling surface 51b of heat radiating member 51
It can be seen that when a predetermined amount of pressure is applied (solid line), the temperature is substantially uniformly cooled and temperature unevenness is greatly improved as compared with a case where it is simply brought into contact (dotted line). This is because the pressing cooling surface 51b serving as a cooling area and the endless belt 30
A slight air layer interposed between the endless belt 30 and the pressurized cooling surface 51b is pushed out by the pressing of the pressing cooling surface 51b.
This is because the heat transfer coefficient from the recording sheet P to the heat radiating member 51 via the endless belt 30 was stabilized due to the increase in the adhesive force with respect to b. In addition, the pressing cooling surface 5
Even when the endless belt 1b is pressed against the endless belt 30, there is slight temperature unevenness mainly because the endless belt 30 and the pressing cooling surface 51b at the time of entering the cooling area have any part described above. Such a small air layer sometimes exists, and the cooling effect differs between when the air layer exists and when it does not exist, resulting in temperature unevenness (cooling unevenness). Such temperature unevenness is measured. The result is reflected in the value.

If the recording sheet P is not uniformly and stably cooled while passing through the cooling area, as shown in FIG. 2), the toner image Ta is not maintained in the embedded state due to the cooling temperature unevenness, but floats so that a small step D is generated between the toner image Ta and the surface of the recording sheet P. More likely to be done. Tb in the figure indicates a toner image that has been well cooled and fixed. Further, due to the cooling unevenness described above, the recording sheet P (the transparent resin layer 120) and the toner T are not sufficiently cooled, and their tackiness remains.
When peeled off from the endless belt 30, the surface portion of the transparent resin layer 120 or the like, which is not sufficiently cooled, becomes slightly fuzzy, and as a result, glossiness is impaired.

In this fixing device, the cooling region is formed by pressing the pressing cooling surface 51b of the heat radiating member 51 of the cooling structure 50 against the endless belt 30, and the pressing amount of the pressing cooling surface 51b is determined. If the size is increased, the recording sheet P to be fixed is likely to be peeled off from the endless belt 30 during the conveyance, so that uniform and stable cooling tends to be impossible. Then, the present inventors used the fixing device and the recording sheet P having the above-described configuration to separate the recording sheet P and press the cooling surface 5 of the heat radiation member 51.
The relationship with the amount of pressing of 1b was examined. The amount of pressing was examined using a bending angle at a portion where the endless belt 30 is bent by being pressed by the pressing cooling surface 51b as an index.

That is, as shown in FIG. 14A, the bending angle α of the belt at the portion where the endless belt 30 is bent in contact with the heat radiating member 51 (the end portion 51b on the belt entry side) changes the amount of pressing of the heat radiating member 51. An experiment was conducted to examine the recording sheet P peeling off from the endless belt 30 when the bending angle α was increased. As a result, when the bending angle α exceeds “7 °”, (at least the leading end of) the recording sheet P conveyed in close contact with the endless belt 30 as illustrated in FIG. Immediately after passing through the side end 51b, the endless belt 30 could not follow the bent running state and came off.

Similarly, as illustrated in FIG. 14B,
The bending angle β of the belt at a portion where the endless belt 30 is bent away from the heat radiating member 51 (the end portion 51c on the side away from the belt) is gradually changed by changing the pressing amount of the heat radiating member 51, and the bending angle α is At this point, an experiment was conducted to determine whether the recording sheet P was peeled off from the endless belt 30. As a result, when the bending angle β exceeds “22 °”, the recording sheet P conveyed in close contact with the endless belt 30 to pass through the cooling area as illustrated in FIG.
Immediately after passing through at least the end 51c of the heat radiating member 51 on the side away from the belt, (at least the leading end) could not follow the bent running state of the endless belt 30 and came off.

From the above experimental results, in this fixing device, in order to prevent the recording sheet P from peeling off at the point where the endless belt 30 enters the cooling area pressed by the pressing cooling surface 51b of the heat radiating member 51. It has been found that at least the bending angle α needs to be within the range of 0 <α ≦ 7 °. Further, in order to prevent the endless belt 30 from peeling off at the point where it has passed through the zero attachment area, it is necessary that the bending angle β is further set in the range of 0 <β ≦ 22 °. found.

Incidentally, in the fixing device according to this embodiment, the bending angles α and β
° and about 15 °, the recording sheet P conveyed in close contact with the endless belt 30 did not peel off at the entry point or the separation point of the cooling area. This prevents the recording sheet P from being peeled off by the endless belt 30 before and after the cooling area and in the course of being conveyed while passing through the area, thereby preventing the occurrence of poor cooling and uneven cooling. As a result, the above-described fixing failure (see FIG. 13) due to cooling failure or cooling unevenness does not occur.

[Second Embodiment] FIG. 15 shows a main part of a fixing device according to a second embodiment of the present invention. In the fixing device according to this embodiment, the heat radiating member 51 of the cooling structure 50 is attached to the endless belt 30 from the outer peripheral surface side of the belt.
Roll 60 for pressing against the pressing cooling surface 51b
The fixing device has the same configuration as that of the fixing device according to the first embodiment except that the fixing device is provided.

As shown in FIG. 16, the pressing roll 60 has a roll core 61 made of a metal material or a synthetic resin and an elastic layer 62 made of a synthetic resin foam (for example, urethane sponge) formed on a roll core 61. It has a structure of about 5 to 30 mm, and is formed so that its roll length (width) is longer (wider) than the width of the endless belt 30 as shown in FIG. Also, this pressing roll 60
As shown in FIGS. 15 and 16, the belt 60 is rotated in the belt rotation direction A more than the position M where the endless belt 30 of the roll 60 is pressed.
Arrows G and H with the support shaft 65a at the upstream position as a fulcrum
It is rotatably attached to a support arm 65 that swings in the direction. Reference numeral 68 in the drawing denotes a tension spring 66 whose one end is fixed to a support frame (not shown) and whose other end is locked in the middle of the support arm 65. The tension spring 68 urges the support arm 65 and thus the pressing roll 60 in a direction G in which the endless belt 30 is pressed with a predetermined pressure. The pressing force of the pressing roll 60 is set to be about 700 gf.

Further, the pressing roll 60 presses the endless belt 30 at least at the heat radiating member 51.
Of the pressing and cooling surface 51b, the endless belt 30 is disposed within a region E from the portion where the endless belt 30 comes into contact first to 30 mm inside. This is because, as shown in FIG. 18, in the area E, immediately after the endless belt 30 comes into contact with the pressing cooling surface 51b, a non-contact portion (dotted line) that does not come into contact with the pressing cooling surface due to wrinkling of the belt itself or generation of an air layer. Part drawn with)
This is because the non-contact portion is one of the causes of the cooling unevenness, and it is necessary to effectively and surely eliminate the non-contact portion. In this embodiment, the pressing roll 60 is set to be pressed at a position about 10 mm inside the pressing roll 60.

In the fixing device provided with such a pressing roll 60, basically the same fixing as that of the fixing device according to the first embodiment can be performed. An effect can be obtained.

That is, by the pressing of the pressing roll 60,
The endless belt 30 comes into contact with the pressing cooling surface 51b with a higher contact pressure, and thus the cooling efficiency of the cooling structure 50 for the endless belt 30 and the recording sheet P is further increased. In addition, since the pressing of the pressing roll 60 is performed in the area E, a non-contact portion which is likely to be generated when the endless belt 30 enters the pressing cooling surface 51a is eliminated, and the endless belt 30 is moved to the pressing cooling surface 51a. Contact more reliably and uniformly,
Cooling unevenness due to the non-contact portion of the endless belt 30 is reduced. As a result, in this fixing device, since the recording sheet P to be fixed is cooled more uniformly and stably, it is possible to perform fixing in which a high-quality image with more gloss and smoothness is obtained.

FIG. 19 shows that in the fixing device, the endless belt 30 is cooled by the cooling structure 5 in the presence of the pressing roll 60.
7 shows the results (solid lines) of measuring the temperature state of the recording sheet P conveyed by the endless belt 30 before and after the cooling region passing through the pressing cooling surface 51b of the heat radiating member 51 and at the passage time. This temperature measurement is performed in the same manner as in the case where the temperature state is measured in the first embodiment (FIG. 12). In the same figure, for comparison, the pressing cooling surface 5 of the heat radiating member 51 is not provided without the pressing roll 60.
The same measurement result (dotted line) is also shown for the temperature state when 1b is simply brought into contact with the endless belt 30. Further, this test was performed using a recording sheet P and a fixing device having the same configuration as that used in the test of the first embodiment except that the pressing roll 60 was provided. From the results shown in this figure, when the pressing roller 60 is provided and the endless belt 30 is pressed against the pressing cooling surface 51b of the heat radiating member 51 of the cooling structure 50 (solid line), it is uniformly cooled without temperature unevenness. You can see that.

In addition, the endless belt 30 of the pressing roll 60
Is formed by the elastic layer 61 made of a synthetic resin foam, the endless belt 30 does not accumulate heat even when the pressing roll 60 is heated. To prevent the cooling action of the cooling structure 50 from being hindered. In addition, since the pressing force of the pressing roll 60 is set to the above-described low value, the rotation of the endless bell 30 due to the pressing of the pressing roll 60 and the conveyance of the recording sheet P are smoothly performed without being hindered. The pressing force of the pressing roll 60 that provides such an operation and effect has been examined and examined, and it has been found that it is sufficient to set the pressing force to 700 gf or less regardless of the hardness of the elastic layer 62 of the pressing roll 60.

Further, since the pressing roll 60 is supported by the supporting arm 65 which swings in the above state,
Since the pressing roll 60 can swing so as to be separated from the endless belt 30 on the side (arrow H direction) where the front of the recording sheet P in the transport direction A is opened, as shown in FIG. Even if a paper jam occurs after being introduced into the fixing device, since the pressing roll 60 swings in the direction of the arrow H due to the jammed recording sheet Px, the jammed recording sheet Px is discharged without remaining in the apparatus. It is easy to be.

[Other Embodiments] In the first and second embodiments, the pressing and cooling surface 51b of the heat radiating member 51 in the cooling structure 50 is replaced with the endless belt 30 as illustrated in FIG.
More preferably, the curved surface has a curvature (R) with respect to the rotation direction A. The curvature (R) is determined by the pressing cooling surface 51b.
It depends on other conditions such as the size of
９００900 mm can be set. It is needless to say that the heat radiating member 51 having the curved press cooling surface also needs to be disposed so that the bending angle α is within the above-described specific range. With this configuration, the adhesion of the endless belt 30 to the pressing and cooling surface 51b is improved as compared with the case of the flat surface according to the first embodiment.
As a result, the efficiency of cooling the recording sheet by the cooling structure 50 via the endless belt 30 that comes into contact with the curved pressing cooling surface 51b is improved, and the occurrence of the cooling unevenness is further reduced.

In Embodiments 1 and 2, FIG.
2, the heating roll 10 and the peeling roll 2
Alternatively, a third belt support roll 25 may be provided in addition to 0 to stretch the endless belt 30. In this case, the peeling roll 20 can be configured as a driven roll that is fixedly provided without having a tension function, and the third belt support roll 25 can be configured as a tension roll. Further, the third belt support roll 25
It is also possible to add a meandering prevention function that corrects by displacing (tilting) the end of the roll (its bearing) in the vertical direction or the like according to the meandering state of the endless belt 30.

Further, in the first and second embodiments, as illustrated in FIG. 22, the cooling structure 50 is connected to the endless belt 3.
You may comprise so that it may contact and separate from 0. Similarly, the pressing roll 60 according to the second embodiment may be configured to be provided so as to be able to contact and separate from the endless belt 30. In each case, the cooling structure 50
And the pressing roll 60 are displaceably supported by a known displacement mechanism (such as a cam mechanism), and the cooling structure 50 and the like are separated from the endless belt 30 at the time of non-operation. What is necessary is just to comprise so that the cooling structure 50 etc. may be contacted and pressed against the endless belt 30 at the time of being conveyed to this side.

In the fixing devices according to the first and second embodiments, if necessary, the recording sheet P can be separated from the endless belt 30 wrapped around the separation roll 20 as an auxiliary member for surely separating the recording sheet P. A pawl mechanism may be provided, or a cleaning device or the like for removing extraneous matter adhering to the outer peripheral surface of the endless belt 30 may be provided. In addition, in the fixing devices according to the first and second embodiments, the case where the heating roll 10 is rotationally driven to rotate and drive the endless belt 30 in the predetermined direction A is illustrated. Roll 20 and pressure roll 4
The endless belt 30 may be configured to be rotated and driven in a predetermined direction A by rotating the endless belt 30, or the endless belt 30 may be configured to be rotated and driven directly by a dedicated driving unit.

Further, in the second embodiment, instead of the pressing roll 60, a pressing belt 66 that is rotatably run around a plurality of supporting rolls 67 as illustrated in FIG.
May be provided as a pressing and rotating body that presses the endless belt 30. In this case, the support roll 67 may have the same roll structure as the pressing roll 60. The length L of the pressing belt 66 in the belt rotation direction A for pressing the endless belt 30 (that is, the length substantially corresponding to the separation distance of the support roll 67) L is the belt rotation of the pressing cooling surface 51b as shown in the figure. Not limited to the same length as the direction A,
The length may be shorter or longer than the length of the press cooling surface 51b. Regardless of the length relationship, the pressing cooling surface 5 of the endless belt 30 by the pressing belt 66
1b can be improved, and as a result, the cooling effect of the cooling structure 50 can be improved.

[0064]

As described above, according to the fixing device of the present invention, the endless belt heading from the heating roll to the peeling roll and the belt by the cooling means for cooling while pressing from the inner peripheral surface of the endless belt. The recording sheet to be fixed, which is conveyed in a state of contact with the sheet, is uniformly and stably cooled, and good fixing without cooling unevenness can be performed.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating a main configuration of a fixing device of the present invention.

FIG. 2 is an explanatory diagram showing a typical example of a bending angle α (β).

FIG. 3 is a schematic perspective view showing a main part of the fixing device according to the first embodiment.

FIG. 4 is a schematic sectional view taken along the line IV-IV in FIG. 3;

FIG. 5 is a schematic sectional view taken along the line VV of FIG. 3;

FIG. 6 is a schematic bottom view of the fixing device of FIG. 3;

FIG. 7 is a main part explanatory view showing the configuration of the cooling structure and the bending angles α and β of the endless belt with respect to the pressing cooling surface in the first embodiment.

FIG. 8 is a schematic sectional view showing the configuration of an endless belt.

FIG. 9 is a schematic cross-sectional view illustrating a configuration of a recording sheet.

FIG. 10 is a schematic diagram showing main process states of a fixing operation.

FIG. 11 is a schematic diagram illustrating a process of fixing a toner image to a recording sheet.

FIG. 12 is a graph showing a result of measuring a temperature state of a recording sheet when the cooling structure is disposed on the endless belt by pressing and when the cooling structure is disposed on the endless belt;

FIG. 13 is an explanatory diagram illustrating a state of fixing failure when cooling unevenness (defective) occurs.

FIG. 14 is an explanatory diagram showing the relationship between the bending angles α and β of the endless belt with respect to the pressing cooling surface and the peeling phenomenon of the recording sheet.

FIG. 15 is a schematic sectional view showing a main part of a fixing device according to a second embodiment.

FIG. 16 is an enlarged explanatory view showing a configuration of a pressing roll.

FIG. 17 is a schematic bottom view showing a pressing position of a pressing roll.

FIG. 18 is a schematic explanatory view showing a non-contact portion generated when the pressing cooling surface of the endless belt enters.

FIG. 19 is a graph showing a result of measuring a temperature state of a recording sheet mainly with or without a pressing roll.

FIG. 20 is a schematic explanatory view showing the function and effect of the supporting structure of the pressing roll.

FIG. 21 is an explanatory view of a main part showing another configuration example (in the case of a curved surface having a curvature) of the pressing cooling surface in the cooling structure.

FIG. 22 is a main part schematic diagram illustrating another configuration example of the fixing device according to the invention.

FIG. 23 is a schematic diagram of a main part showing a configuration example in which a pressing belt is provided.

[Explanation of symbols]

1, 10: heating roll, 2, 20: peeling roll, 3,
30 ... Endless belt, 4,40 ... Pressing roll, 5,50 ...
Cooling structure, 5a, 51b: pressing cooling surface, 6: pressing rotating body, 60: pressing roll (pressing and rotating body), 66: pressing belt (pressing and rotating body), 65: supporting arm (supporting frame), A: endless Belt rotation direction, P ... Recording sheet, T
... Toner image, N: pressure contact area, α, β: bending angle, E: area up to 30 mm inside.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Motoki Noya 430 Green Tech Nakai-cho, Ashigamikami-gun, Kanagawa Prefecture, Fuji Xerox Co., Ltd. F-term (reference) 2H033 BA10 BA11 BA12 BA15 BA20 BA21 BA29 CA26

Claims (8)

[Claims] 1. A heating roll, a peeling roll disposed at an interval from the heating roll, an endless belt that is at least stretched between the peeling roll and the heating roll, and that rotates and runs; A pressure roll that presses the belt against the heating roll, and a belt inner peripheral surface portion of the endless belt that is disposed on the inner peripheral surface side of the endless belt and that extends from the heating roll to the peeling roll in the endless belt. A cooling structure having a pressing cooling surface that cools while pressing in the direction of the belt outer peripheral surface side, and rotates and travels in a direction in which the endless belt passes in the order of the heating roll, the cooling structure, and the peeling roll. And a recording sheet carrying a toner image is introduced into a pressure contact area between the endless belt and the pressure roll over the heating roll, and is brought into contact with the endless belt. A fixing device for fixing the toner image to a recording sheet by passing the portion of the cooling structure where the pressing cooling surface comes into contact and transporting and peeling the portion to the portion wound on the peeling roll; The body is disposed such that a bending angle (α) of a portion where the endless belt is bent until it comes into contact with and separates from the pressing cooling surface of the cooling structure is in the range of 0 ° <α ≦ 7 °. A fixing device. 2. The fixing device according to claim 1, wherein the cooling structure has a bending angle (β) of 0 ° at a position where the endless belt separates in a state where the endless belt is bent from a pressing cooling surface of the cooling structure. A fixing device, wherein the fixing device is disposed so as to be in a range of <β ≦ 22 °. 3. The fixing device according to claim 1, wherein the pressing cooling surface of the cooling structure is a curved surface having a curvature in a belt rotation direction. 4. The fixing device according to claim 1, further comprising a pressing rotary member configured to press the endless belt from a belt outer peripheral surface side to a pressing cooling surface of the cooling structure. A fixing device. 5. The device according to claim 4, wherein a position of pressing the endless belt of the pressing rotating body is at least 30 mm inward from a portion where the endless belt first contacts on a pressing cooling surface of the cooling structure. A fixing device, wherein 6. The fixing device according to claim 4, wherein a portion of the pressing and rotating body that contacts the endless belt is formed of a synthetic resin foam. 7. The fixing device according to claim 4, wherein the pressing force of the pressing and rotating body is set to 700 gf or less. 8. The fixing device according to claim 4, wherein the pressing and rotating body is pivotally movable about a position on the upstream side in the belt rotation direction from a position where the rotating body presses the endless belt. A fixing device characterized by being supported.