JP2000259024A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the fixing ratio, to increase the substantial printing speed, and to improve the durability of a fixing device. SOLUTION: This fixing device is provided with a heating roller 11, and a pipe 22 supported in freely rotatably, while being held in contact with the heating roller 11 disposed so as to be freely deformably, and moreover a pressure body 21 disposed in the pipe 22, having a pressurizing surface S1, and pressing means energizing the pressure body 21 toward the heating roller 11, for generating the pressurizing force. The radius of curvature of the pressurizing surface S1 is set corresponding to the radius of curvature of the heating roller 11. Since the time when recording medium is held in contact with the heating roller 11 becomes long, a quantity of heat transmitted from the heating roller 11 to the recording medium can be increased, therefore the fixing ratio can be raised.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic recording apparatus, the surface of a photosensitive drum is uniformly and uniformly controlled by a charging device.
It is uniformly charged, and is exposed by an exposure device to form an electrostatic latent image. Then, the electrostatic latent image is developed into a toner image by a developing device, and the toner image is transferred to a printing medium as a recording medium by a transfer device and fixed by a fixing device.

FIG. 2 is a schematic view of a conventional fixing device.

In FIG. 1, reference numeral 11 denotes a heating roller, and reference numeral 12 denotes a heating element provided in the heating roller 11 as a heating means such as a halogen lamp. The heating roller 11 has a resin coating layer 11b made of a fluororesin or the like having heat resistance and releasability on an aluminum pipe 11a.
Formed by coating. Reference numeral 13 denotes a pressure roller. The pressure roller 13 is formed by coating a heat-resistant rubber roller 13b on a shaft 13a. A pressure spring 14 is disposed between both ends of the shaft 13a and the main body 16 of the fixing device. The pressure spring 14 presses the pressure roller 13 against the heating roller 11 by a predetermined urging force.

Then, a driving means (not shown) is driven to rotate the heating roller 11 and the pressure roller 13 in the directions of the arrows, respectively, so that the print medium 15 on which the toner image has been transferred in advance is rotated by a registration roller (not shown). Is transported along with the pressure roller 13 and
The heat roller 11 and the pressure roller 13 are guided by the frictional force generated between the pressure roller 13 and the fixing unit P1 in contact with the heating roller 11, and pass through the fixing unit P1. At this time, heat is transmitted from the heating roller 11 to the print medium 15, and the toner image on the print medium 15 is heated, pressed, melted, and fixed on the print medium 15.

[0006]

However, in the above-mentioned conventional fixing device, the heating element 12 is moved from the printing medium 15 to the printing medium 15.
The heat is transmitted to the fixing unit P1. However, as the speed of the electrophotographic recording apparatus is increased, the contact time between the print medium 15 and the heating roller 11 is reduced, and the heat is transferred from the heating roller 11 to the print medium 15. The amount of heat generated is reduced, and the fixing rate is reduced.

Therefore, it is conceivable to increase the amount of heat transmitted from the heating roller 11 to the printing medium 15 by increasing the set temperature of the heating roller 11. The warm-up time from when the power of the apparatus is turned on until the temperature of the heating roller 11 reaches the set temperature becomes longer, and the actual printing speed becomes lower. Further, since each bearing portion of the heating roller 11 and the pressure roller 13 and each component around the bearing portion are formed of a resin material, if the set temperature is increased, the heat retained by the fixing device is reduced. The amount increases, and each bearing portion and each component are deformed, worn, or melted, thereby lowering the durability of the fixing device.

Further, by increasing the contact area between the printing medium 15 and the heating roller 11, the heating roller 11
It is conceivable to increase the amount of heat transmitted from the heating roller 11 to the print medium 15, but if the contact area is increased, the outer diameters of the heating roller 11 and the pressure roller 13 need to be increased. The heat capacity of the pressure roller 13 increases. Therefore, not only does the amount of heat required to raise the temperature of the heating roller 11 and the pressure roller 13 increase, but also much heat is transmitted from the heating roller 11 to the pressure roller 13 and released. The warm-up time becomes longer, and the actual printing speed becomes lower.

The heating roller 11 and the pressure roller 13
It is conceivable to increase the pressing force of the pressure roller 13 in order to increase the contact area without increasing the outer diameter of the roller, but in this case, the reaction force received by the pressure roller 13 increases, and Roller 11 and pressure roller 13
Only the contact area at both ends in the axial direction of
The contact area at the center cannot be increased.

Accordingly, since the contact area varies depending on the position of the heating roller 11 and the pressure roller 13 in the axial direction, the amount of heat transmitted from the heating roller 11 to the printing medium 15 varies, and the fixing rate varies. Would.
Further, in each of the positions, the frictional force generated between the heating roller 11 and the pressure roller 13 and the printing medium 15 is different, and the feed amount of the printing medium 15 is different. Would.

The present invention solves the problems of the above-mentioned conventional fixing device, can increase the fixing rate, can substantially increase the printing speed, and can improve the durability. It is another object of the present invention to provide a fixing device capable of preventing the occurrence of wrinkles or the like in a recording medium without causing a variation in a fixing rate.

[0012]

For this purpose, in the fixing device of the present invention, a heating roller rotatably supported, and a heating roller rotatably supported in contact with the heating roller and being deformably disposed. A pressurized body provided in the pipe and having a pressurizing surface facing the heating roller, and a pressurizing body for urging the pressurizing body toward the heating roller to generate a pressing force. Force means.

The radius of curvature of the pressure surface is set in accordance with the radius of curvature of the heating roller.

In another fixing device of the present invention, a heating roller, a pressure member disposed opposite to the heating roller, and a pressure member for urging the pressure member toward the heating roller, And holding means for holding the heating roller.

The holding means has a groove for guiding the pressurizing member and directing the pressing force toward the center of rotation of the heating roller.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a fixing device according to a first embodiment of the present invention, FIG. 3 is a longitudinal sectional view of a main part of the fixing device according to the first embodiment of the present invention, and FIG. First
FIG. 5 is a diagram illustrating a driving system of a fixing device according to the embodiment.

In FIG. 1, reference numeral 11 denotes a heating roller rotatably supported, and reference numeral 12 denotes a heating element provided in the heating roller 11 as heating means such as a halogen lamp. The heating roller 11 is made of a metal 11 having a high thermal conductivity, for example, an aluminum pipe 11a, and a resin coating layer 11b made of a fluorine resin or the like having heat resistance and release properties.
Formed by coating. Reference numeral 21 denotes a pressing body as a pressing means. The pressing body 21 is formed of a material having high rigidity and heat resistance, for example, a composite material made of glass filler and PPS resin. They are arranged facing each other. A surface of the pressing body 21 facing the heating roller 11, that is, a pressing surface S1
Consists of an arc-shaped concave surface having a radius of curvature substantially equal to the radius of curvature of the heating roller 11. In this case, the radius of curvature of the pressing surface S1 is set corresponding to the radius of curvature of the heating roller 11.

The heating roller 11 and the pressing body 21
A pipe 22 surrounding the pressure body 21 and having a length substantially equal to that of the pressure body 21 and made of silicone rubber having elasticity and heat resistance is disposed between the pressure body 21 and the pressure body 21. The pipe 22
Are rotatably supported in contact with the heating roller 11 and are disposed so as to be freely deformable. Therefore, the pressure body 2
1 is made to face the heating roller 11 in the pipe 22. A pressing spring 25 as an urging means is provided between a bracket 21b formed at both ends of the pressing body 21 (only one of them is shown in FIGS. 1 and 3) and the main body 16 of the fixing device. The pressurizing spring 25 urges the pressurizing member 21 toward the heating roller 11 to generate a predetermined pressing force, and heats the pressing member 21 via the pipe 22 by the pressing force. Press against roller 11. Reference numeral 21a is an edge formed on the upstream side and the downstream side of the pressing surface S1 in the transport direction of the printing medium 15 as a recording medium.

A sprocket 23 is fixed to one end of the heating roller 11 so as to be concentric with the heating roller 11. At one end of the pipe 22, a sprocket wheel 24 is disposed concentrically with the pipe 22, and the sprocket 23 and the sprocket wheel 24 are engaged with each other. Therefore, the sprocket 2
3 has teeth 23a and sprocket wheel 24 has holes 24a.
Are respectively formed.

Therefore, when the driving means (not shown) is driven to rotate the heating roller 11 in the direction of arrow A, the rotation of the heating roller 11 is transmitted to the pipe 22 via the sprocket 23 and the sprocket wheel 24,
The pipe 22 is rotated in the direction of arrow B. The peripheral speed of the heating roller 11 and the peripheral speed of the pipe 22 are made equal. In the present embodiment, the sprocket 23
The transmission of the heating roller 11 is transmitted to the pipe 22 by the transmission means including the sprocket wheel 24 and the transmission means. However, other transmission means such as a gear train and a belt may be used.

The heating roller 11 and the pipe 2
2 are rotated in the directions of arrows A and B, respectively. When the print medium 15 on which the toner image is transferred in advance is conveyed with the rotation of a registration roller (not shown) and hits the pipe 22, the print medium 15 is generated between the print medium 15 and the pipe 22 Due to the frictional force, the heating roller 11 and the pipe 22 are guided to the fixing portion P2 in contact with the heating roller 11, and pass through the fixing portion P2. At this time,
Heat is transmitted from the heating roller 11 to the print medium 15,
The toner image on the print medium 15 is heated, pressed, melted, and fixed on the print medium 15.

As described above, the pressing surface S1 is
1, the contact time between the printing medium 15 and the heating roller 11 is increased even when the speed of the electrophotographic recording apparatus is increased. The amount of heat transferred to the medium 15 can be increased, and the fixing rate can be increased.

Since it is not necessary to increase the set temperature of the heating roller 11, the warm-up time from when the power of the electrophotographic recording apparatus is turned on until the temperature of the heating roller 11 reaches the set temperature is shortened. And a substantial printing speed can be increased. Further, since the amount of heat held by the fixing device is reduced, each bearing portion of the heating roller 11 and the pressing body 21 and each component around the bearing portion are deformed, worn, or melted. And the durability of the fixing device can be improved.

Further, the contact area between the printing medium 15 and the heating roller 11 can be increased without increasing the outer diameter of the heating roller 11 and the size of the pressing member 21. 21 can have a small heat capacity. Therefore, not only can the amount of heat required to raise the temperature of the heating roller 11 and the pressing body 21 be reduced, but also much heat is not transmitted from the heating roller 11 to the pressing body 21. Therefore, the warm-up time can be shortened, and the substantial printing speed can be increased.

Further, the contact area can be increased without increasing the pressing force of the pressing body 21, so that the reaction force received by the pressing body 21 can be reduced. Therefore, not only can the contact area at both ends in the axial direction of the heating roller 11 and the pressing body 21 be increased, but also the contact area at the center can be increased.

As a result, the heating roller 11 and the pressing body 21
Since the contact area is equal at each position in the axial direction, the amount of heat transmitted from the heating roller 11 to the print medium 15 is equal, and the fixing rate does not vary. In each of the positions, the heating roller 11
In addition, the frictional force generated between the pipe 22 and the print medium 15 becomes equal, and the feed amount of the print medium 15 becomes equal, so that it is possible to prevent the print medium 15 from wrinkling.

Further, since the set temperature of the heating roller 11 can be lowered, the conveying speed of the printing medium 15 is not restricted by the thermal limitation. Therefore, the printing speed can be increased accordingly.

Next, a description will be given of the results of an experiment in which fixing was performed by the fixing device having the above-described configuration.

FIG. 5 is a comparison diagram of the characteristics of the fixing device. In the figure, the horizontal axis represents the set temperature, and the vertical axis represents the fixing rate. In the drawing, a solid line L1 indicates the characteristics of the fixing device of the present invention, and a broken line L2 indicates the characteristics of the conventional fixing device.

In this case, the outer diameter of the heating roller 11 (FIG. 1) is set to 20 mm, and the outer diameter of the pipe 22 is set to 24 mm.
And the pressing force is set to 13.5 [g / mm].
The conveying speed of No. 5 was set to 25.4 [mm / sec], and the width of the pressing body 21 (the distance between both edges 21 a) in the conveying direction of the printing medium 15 was set to 5 [mm]. Then, using the set temperature of the heating roller 11 as a parameter, the fixing rate when the heating roller 11 was heated at each set temperature was measured.

After affixing the adhesive tape to the print sample on which the solid black printing was performed under a certain pressure, the adhesive tape was peeled off, and the print density before the adhesive tape was adhered was removed. The ratio between the print density and the print density after peeling off the adhesive tape was calculated, and the ratio was measured as the fixing rate.

For reference, the outer diameter of the heating roller 11 is set to 20 mm, and the outer diameter of the pressure roller 13 is set to 24 mm.
[Mm], the pressing force is set to 13.5 [g / mm], and the conveyance speed of the print medium 15 is set to 25.4 [mm / sec]. The rate was also measured.

As shown in the figure, the fixing rate was 90 [%].
In this case, the set temperature of the fixing device of the present invention can be lowered by 30 ° C. from the set temperature of the conventional fixing device. This is due to the difference in the contact area between the print medium 15 and the heating roller 11.

The width of contact between the printing medium 15 and the heating roller 11 with the same pressure (13.5 g / mm) between the fixing device of the present invention and the conventional fixing device, ie, the contact width When the width was measured, in the fixing device of the present invention, the contact width was equal to the width of the pressing body 21 and was 5 [mm], whereas in the conventional fixing device, the contact width was 2 [mm]. mm]. This is because in the conventional fixing device, the rubber roller 13b (see FIG. 2) is connected to the shaft 13a.
This is because it is fixed to and has little flexibility. That is, the contact width depends on the elastic deformation of the pressure roller 13 in the direction in which the pressure is applied.

On the other hand, in the fixing device of the present invention, since the pipe 22 has flexibility,
When the pressing force is applied, the pipe 22 itself deforms following the pressing surface S1 of the pressing body 21. Therefore,
The contact area can be adjusted by changing the shape of the pressing surface S1.

In the present embodiment, the pressing surface S1 is an arc-shaped concave surface having a radius of curvature substantially equal to the radius of curvature of the heating roller 11, but the pressing surface is made flat or convex. be able to. In this case, the radius of curvature of the pressing surface is made larger than the radius of curvature of the conventional pressing roller 13 or larger than the radius of curvature of the heating roller 11.

Next, the reason why the width of the pressing body 21 is set to 5 [mm] will be described.

FIG. 6 is a diagram showing the relationship between the nip width and the fixing rate in the fixing device. In the figure, the horizontal axis represents the nip width, and the vertical axis represents the fixing rate.

In this case, in the fixing section P2 (FIG. 1),
The width of the contact between the heating roller 11 and the pipe 22 is called the nip width. As shown in the figure, when the nip width is equal to or less than a predetermined value, the fixing rate increases as the nip width increases, but when the nip width is larger than the predetermined value, the fixing rate becomes constant. In the case of the fixing device of the present invention used in FIG. 5, the fixing rate became constant when the nip width became larger than 5 [mm].

By the way, as the contact area between the heating roller 11 and the pipe 22 increases, the heating roller 11 and the pipe 2
2, the load applied to the driving means of the heating roller 11 increases.

Therefore, in the present embodiment, the width of the pressing body 21 is set so that the fixing rate can be sufficiently increased and the load applied to the driving means of the heating roller 11 can be sufficiently reduced. It was set to 5 [mm].

The rotation of the heating roller 11 is
In a fixing device that does not use a transmission means including a sprocket 23 (FIG. 4) and a sprocket wheel 24 and rotates the pipe 22 in a continuous rotation, the smaller the contact area, the smaller the pipe 22 is. Rotates smoothly.

By the way, in this embodiment, the pipe 22 is rotated by using the transmission means consisting of the sprocket 23 and the sprocket wheel 24. However, the shape of the sprocket 23, the sprocket 23
If the pitch of each tooth 23a, the pitch of each hole 24a of the sprocket wheel 24, and the like vary, a difference occurs between the peripheral speed of the heating roller 11 and the peripheral speed of the pipe 22.

The printing medium 15 contacts the heating roller 11 on the front surface side on which an image is formed, contacts the pipe 22 on the back surface side, and contacts the printing medium 15 with the heating roller 11.
Between the print medium 15 and the pipe 2
2 is conveyed by the frictional force generated between them. Therefore, if a difference occurs between the peripheral speed of the heating roller 11 and the peripheral speed of the pipe 22, the front and back surfaces of the print medium 15 are fed at different speeds. Will occur.

Therefore, a description will be given of a second embodiment in which the occurrence of jams, wrinkles, etc. in the print medium 15 can be prevented. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol.

FIG. 7 is a view for explaining the conveying force of the print medium according to the second embodiment of the present invention.

As shown in the drawing, the conveying force for conveying the print medium 15 as a recording medium is F, the friction coefficient between the print medium 15 and the heating roller 11 is μ1, and the pipe 22 is The coefficient of friction between the print medium 15 and the pipe 22 is set to μ3, and the coefficient of friction between the print medium 15 and the pipe 22 is set to μ3.
Assuming that the pressure applied by the pressurizing member 21 is N and the load applied to the edge 21a when the pipe 22 rotates is N1, the following formula is satisfied.

That is, by rotating the heating roller 11,
In order to generate the transport force F by the frictional force generated between the print medium 15 and the heating roller 11, it is necessary to satisfy the following equation: F = μ1 · N

Since the transport force F needs to be larger than the resistance applied to the print medium 15, it is necessary to satisfy the following equation: F> μ2 · N + N1.

Therefore, when the friction coefficients μ1, μ2, pressure N, and load N1 are set so as to satisfy the following expression μ1 · N> μ2 · N + N1 (where μ1 <μ2 <μ3). The print medium 15 can be transported by the transport force F.

The surface of the heating roller 11 is coated with a resin coating layer 11b (FIG. 1) made of a fluororesin or the like so as to improve the releasability and prevent the toner of the toner image from adhering. The friction coefficient μ
1 is small.

Therefore, even if the coefficient of friction μ1 is small, at least one of the inner peripheral surface of the pipe 22 and the outer peripheral surface of the pressurizing body 21 must satisfy
A process for reducing the friction coefficient μ2 is performed, and in the present embodiment, the inner peripheral surface of the pipe 22 is
At least a portion in contact with the pressing body 21 is covered with a metal film 30 (not shown) by an electroforming method or the like.

Therefore, when the heating roller 11 is rotated, the pipe 22 can be rotated continuously, and the print medium 15 can be stably conveyed. Since the difference between the peripheral speed of the heating roller 11 and the peripheral speed of the pipe 22 can be made extremely small, the front surface and the back surface of the print medium 15 are sent at the same speed. As a result, it is possible to prevent the print medium 15 from being jammed or wrinkled.

Since the pipe 22 is rotated by the continuous rotation, the sprocket 23 (FIG. 4) and the sprocket wheel 24 are located between the heating roller 11 and the pipe 22.
There is no need to provide a transmission means consisting of Therefore,
The size of the fixing device can be reduced, the number of components of the fixing device can be reduced, and the assemblability can be improved.

Incidentally, a heat-resistant lubricating oil may be applied as the above treatment.

Next, a third embodiment of the present invention will be described. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol.

FIG. 8 is a cross-sectional view of a fixing device according to a third embodiment of the present invention.

In this case, the outer peripheral surface of the pressing body 21
At least a portion in contact with the pipe 22, that is, the pressing surface S1, is coated with a resin coating layer 41 made of a fluorine resin or the like as a process for reducing the friction coefficient μ2. Therefore, the friction coefficient μ2 can be made sufficiently small.

In the first to third embodiments, since the edge 21a of the pressurizing member 21 abuts on the pipe 22, the resistance against the conveying force F increases.

FIG. 9 is a diagram for explaining the resistance to the conveying force.

In the figure, reference numeral 21 denotes a pressing body, and both edges 21a of the pressing body 21 have an acute edge structure. Therefore, the pipe 22 is deformed into a shape substantially equal to the curved surface of the pressing surface S1 (FIG. 8), and is bent at a predetermined angle at both edges 21a.

When the heating roller 11 and the pipe 22 rotate in the directions of the arrows as the printing medium 15 as the recording medium is conveyed, a load N1 is applied to the pipe 22 by the both edges 21a. Moreover, the pipe 22
Is flexible, when the heating roller 11 starts rotating, the pipe 22 is pulled in the fixing unit P2 in the circumferential direction of the heating roller 11 and is deformed as indicated by oblique lines.

Here, the point at which the pipe 21 comes into contact with the edge 21a on the upstream side of the pressurizing surface S1 in the conveying direction of the print medium 15 is defined as P3. Is defined as θ1, the angle θ1 is determined while the heating roller 11 is rotating.
Become smaller. The load N1 increases as the angle θ1 decreases.

When the load N1 increases, the resistance against the conveying force F increases, so that the pipe 22 cannot rotate stably in a continuous rotation, and the print medium 15 cannot be smoothly conveyed.

Therefore, a fourth embodiment of the present invention will be described in which the load N1 is reduced, the resistance to the conveying force F is reduced, and the pipe 22 can be rotated stably in a continuous rotation. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol.

FIG. 10 is a cross-sectional view of a fixing device according to a fourth embodiment of the present invention.

In this case, both edges 45 a, 4
An R surface, that is, an arc-shaped curved surface is formed on 5b. Therefore, even when the pipe 22 is deformed into a shape substantially equal to the curved surface of the pressing surface S1 in the fixing portion P2, it is curved at the both edges 45a and 45b with a predetermined radius of curvature.

Then, the printing medium 15 as a recording medium
The heating roller 11 and the pipe 22 along with the conveyance of FIG.
Respectively rotate in the direction of the arrow, the pipe 22 is smoothly slid along the curved surfaces of the both edges 45a, 45b, so that the load N1 applied to the pipe 22 by the both edges 45a, 45b is increased. Becomes smaller. The point at which the pipe 22 contacts the edge 45a on the upstream side of the pressurizing surface S1 in the transport direction of the print medium 15 is defined as P4. Is θ2, the angle θ2 is
While the heating roller 11 is rotating, it becomes smaller but larger than the angle θ1 (FIG. 9). Therefore, the load N1 does not become particularly large.

As a result, the resistance to the transport force F (FIG. 8) can be reduced, so that the pipe 22 can be rotated stably in a continuous rotation, and the print medium 15 can be transported smoothly.

The load N1 applied to the pipe 22 by the edge 45a on the upstream side of the pressing surface S1 in the transport direction of the printing medium 15 is applied to the edge 4 on the downstream side of the pressing surface S1.
Since the load 5b is larger than the load N1 applied to the pipe 22, an arc-shaped curved surface can be formed only at the edge 45a.

Next, a fifth embodiment of the present invention will be described. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol.

FIG. 11 is a cross-sectional view showing an installation state of a fixing device according to a fifth embodiment of the present invention, and FIG. 12 is a longitudinal section showing an installation state of the fixing device according to the fifth embodiment of the present invention. FIG. 13 is a cross-sectional view of a fixing device according to a fifth embodiment of the present invention.

In the figure, 11 is a heating roller, 12 is a heating element as a heating means, 22 is a pipe, 47 is a pressing body as a pressing means, 51 is a main chassis, and 52 is a main chassis 51 with screws 54. The fixed fixing device frame 53 is fixed to the fixing device frame 52,
It is a holder as holding means for holding the heating roller 11.

The pressurizing body 47 has a metal shaft 60 for increasing rigidity, and bearings 59 (only one of them is provided at both ends of the shaft 60 in FIGS. 11 and 12). Shown). In order to set the direction in which the pressing body 47 is pressed against the heating roller 11, a groove 51a is formed in the main chassis 51.
Is formed, and the bearing 59 is guided along the groove 51a. Further, the pressing member 47 is urged toward the heating roller 11 to generate a predetermined pressing force.
A pressure spring 25 as an urging means is provided between the main chassis 9 and the main chassis 51.

The surface of the pressing body 47 facing the heating roller 11, that is, the pressing surface S2 is formed by an arc-shaped concave surface having a radius of curvature substantially equal to the radius of curvature of the heating roller 11. Also, adjacent to the pressing surface S2, an arc-shaped curved surface S having a large radius of curvature is provided upstream and downstream of the pressing surface S2 in the transport direction of the print medium 15.
3, curved portions 47a and 47b having S4 are formed, respectively.

Therefore, even if the pipe 22 is deformed into a shape substantially equal to the curved surface of the pressing surface S2 in the fixing portion P6, it will be curved with a large radius of curvature along the curved portions 47a and 47b, and will not bend at all.

Then, the printing medium 15 as a recording medium
The heating roller 11 and the pipe 22 along with the conveyance of FIG.
Is rotated in the direction of the arrow, the pipe 22 slides very smoothly along the curved surfaces S3 and S4, so that the load N1 applied to the pipe 22 by the curved portions 47a and 47b can be eliminated.

The direction in which the pressing body 47 is pressed against the heating roller 11 is set according to the direction of the groove 51a. The heating roller 11 is fixed to a fixing device frame 52 via a holder 53, and the fixing device frame 52 is fixed to the main chassis 51 by screws 54.

Therefore, the heating roller 11, the main chassis 51, the groove 51a, the fixing device frame 52, the holder 5
3 and the like, the accuracy of each element is low, the groove 51a and the fixing device frame 52
When the backlash occurs between the holder 53 and the fixing device frame 52 or between the components, the pressing force of the pressing body 47 is generated accurately toward the rotation center of the heating roller 11. Can not be done. In this case, the pressing surface S2 cannot be brought into sufficient contact with the heating roller 11, so that the contact area cannot be made sufficiently large, and the fixing rate decreases.

Therefore, a sixth embodiment of the present invention will be described in which the pressing force of the pressing body 47 can be accurately generated toward the center of rotation of the heating roller 11. In addition, about what has the structure same as 5th Embodiment, the description is abbreviate | omitted by attaching | subjecting the same code | symbol.

FIG. 14 is a cross-sectional view showing an installation state of a fixing device according to a sixth embodiment of the present invention, and FIG. 15 is a longitudinal section showing an installation state of the fixing device according to the sixth embodiment of the present invention. FIG.

In the figure, 11 is a heating roller, 22 is a pipe, 25 is a pressing spring as urging means, 47 is a pressing body as pressing means, 71 is a main chassis, 52
Is a fixing device frame fixed to the main chassis 71 by screws 54, 73 is fixed to the fixing device frame 52, and the heating roller 11, the pipe 22, and the pressure
Reference numeral 56 denotes a holder as a holding means for holding the spring 7, and a spring seat formed on the main chassis 71.

The pressurizing member 47 has a metal shaft 60 for increasing the rigidity, and bearings 59 (only one of them is provided at both ends of the shaft 60 in FIGS. 14 and 15). Shown). A groove 73a is formed in the holder 73 in order to direct the pressing force to the center of rotation of the heating roller 11.
The bearing 59 is guided along a. In order to generate the pressing force by the pressing body 47, a bearing 59 is required.
A pressure spring 25 is disposed between the main chassis 71 and the pressure spring 25.

As described above, since the heating roller 11, the pipe 22, and the pressing body 47 are held by the holder 73, and the bearing 59 is guided by the groove 73a, the positional relationship between the heating roller 11 and the pressing body 47 is Determined by nature. As a result, the pressing force of the pressing body 47 can be generated accurately toward the rotation center of the heating roller 11. Then, the pressing surface S2 (FIG. 13) can be brought into sufficient contact with the heating roller 11 and the contact area can be made sufficiently large, so that the fixing rate can be increased.

Next, a seventh embodiment of the present invention will be described. In addition, about what has the same structure as 6th Embodiment, the description is abbreviate | omitted by attaching the same code | symbol.

FIG. 16 is a cross-sectional view showing an installation state of a fixing device according to a seventh embodiment of the present invention, and FIG. 17 is a longitudinal section showing an installation state of the fixing device according to the seventh embodiment of the present invention. FIG. 18 is a perspective view of a pressurizing unit according to a seventh embodiment of the present invention.

In the figure, 81 is a main chassis, 83
Is a pressing unit fixed to the fixing device frame 52. The pressing unit 83 has a holding unit 83a as holding means for holding the heating roller 11 at both ends, and a pressurizing unit connecting the holding units 83a. Pressing body 8 as pressure means
3b, and each of the holding portions 83a and the pressing body 83b are
It is integrally formed of a composite material including a heat-resistant glass filler and a PPS resin. Reference numerals 84 denote bushes inserted at both ends of the heating roller 11.

A hole 91 having an oval shape for holding the heating roller 11 is formed in each of the holding portions 83a, and the pressure 91 is formed on an extension of the main axis (longitudinal axis) of the hole 91. A body 83b is provided. The pressing surface S5 of the pressing member 83b is formed as an arc-shaped concave surface having a radius of curvature substantially equal to the radius of curvature of the heating roller 11. The pressurizing body 83b
Is provided with a metal shaft 85 to increase rigidity.

A groove 93 is formed in the holding portion 83a in order to direct the pressing force to the center of rotation of the heating roller 11, and the shaft 85 is guided along the groove 93. Further, a tension spring 86 as an urging means is stretched between the bush 84 and the shaft 85 in order to generate a pressing force by the pressing body 83b. Therefore, the heating roller 11 is guided toward the pressing body 83 b through the hole 91.

In this case, since the pressing body unit 83 is integrally formed, the pressing body 83b can be easily disposed on an extension of the main shaft of the hole 91. Therefore,
The pressing member 83 is attached to the heating roller 11 held in the hole 91.
b is pressed, and the pressing force can be generated accurately toward the rotation center of the heating roller 11. Then, the pressing surface S5 can be sufficiently brought into contact with the heating roller 11 and the contact area can be made sufficiently large, so that the fixing rate can be increased.

The present invention is not limited to the above embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0093]

As described above in detail, according to the present invention, in the fixing device, a heating roller rotatably supported, a rotatable support in contact with the heating roller, and a deformation roller are provided. A freely disposed pipe, a pressurized body disposed in the pipe, and having a pressurizing surface facing the heating roller, and urging the pressurizing body toward the heating roller,
Biasing means for generating a pressing force.

The radius of curvature of the pressing surface is set in accordance with the radius of curvature of the heating roller.

In this case, since the pressing surface has a radius of curvature set corresponding to the radius of curvature of the heating roller, even if the speed of the electrophotographic recording apparatus is increased, the contact time between the recording medium and the heating roller is long. That is, the amount of heat transmitted from the heating roller to the recording medium can be increased, and the fixing rate can be increased.

Since it is not necessary to increase the set temperature of the heating roller, the warm-up time from when the power of the electrophotographic recording apparatus is turned on to when the temperature of the heating roller reaches the set temperature can be shortened. , The actual printing speed can be increased. Further, since the amount of heat held by the fixing device is reduced, each bearing portion of the heating roller and the pressurizing member and each component around the bearing portion may be deformed, worn, or melted. As a result, the durability of the fixing device can be improved.

Since the contact area between the recording medium and the heating roller can be increased without increasing the outer diameter of the heating roller and the size of the pressing body, the heat capacity of the heating roller and the pressing body can be reduced. be able to. Therefore, not only the amount of heat required to raise the temperature of the heating roller and the pressing body can be reduced, but also much heat is released from the heating roller to the pressing body without being transmitted. Therefore, the warm-up time can be shortened, and the substantial printing speed can be increased.

Also, without increasing the pressure,
Since the contact area between the recording medium and the heating roller can be increased, the reaction force applied to the pressing body can be reduced. Therefore, not only can the contact area at both ends in the axial direction of the heating roller and the pressing body be increased, but also the contact area at the center can be increased.

As a result, the contact area becomes equal at each position of the heating roller and the pressing body in the axial direction, so that the amount of heat transmitted from the heating roller to the recording medium becomes equal, and the fixing rate varies. Disappears. Further, at each of the positions, the frictional force generated between the heating roller and the pressing body and the recording medium becomes equal, and the feeding amount of the recording medium becomes equal. can do.

Further, since the set temperature of the heating roller can be lowered, the conveying speed of the recording medium is not restricted by the thermal limitation. Therefore, the printing speed can be increased accordingly.

In another fixing device according to the present invention, a heating roller, a pressing member disposed opposite to the heating roller, and a pressing member for urging the pressing member toward the heating roller, And holding means for holding the heating roller.

The holding means has a groove for guiding the pressurizing member and directing the pressing force to the center of rotation of the heating roller.

In this case, the holding means is provided with a groove for guiding the pressing body and directing the pressing force to the rotation center of the heating roller, so that the pressing surface of the pressing body sufficiently contacts the heating roller. Can be in contact. Therefore, the contact area can be made sufficiently large, and the fixing rate can be increased.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a fixing device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a conventional fixing device.

FIG. 3 is a longitudinal sectional view of a main part of the fixing device according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a drive system of the fixing device according to the first embodiment of the present invention.

FIG. 5 is a comparison diagram of characteristics of a fixing device.

FIG. 6 is a diagram illustrating a relationship between a nip width and a fixing rate in the fixing device.

FIG. 7 is a diagram for explaining a conveyance force of a print medium according to a second embodiment of the present invention.

FIG. 8 is a cross-sectional view of a fixing device according to a third embodiment of the present invention.

FIG. 9 is a diagram illustrating resistance to a conveying force.

FIG. 10 is a cross-sectional view of a fixing device according to a fourth embodiment of the present invention.

FIG. 11 is a cross-sectional view illustrating an installation state of a fixing device according to a fifth embodiment of the present invention.

FIG. 12 is a vertical cross-sectional view of a main part showing an installation state of a fixing device according to a fifth embodiment of the present invention.

FIG. 13 is a cross-sectional view of a fixing device according to a fifth embodiment of the present invention.

FIG. 14 is a cross-sectional view illustrating an installation state of a fixing device according to a sixth embodiment of the present invention.

FIG. 15 is a vertical cross-sectional view of a main part showing an installation state of a fixing device according to a sixth embodiment of the present invention.

FIG. 16 is a cross-sectional view illustrating an installation state of a fixing device according to a seventh embodiment of the present invention.

FIG. 17 is a vertical cross-sectional view of a main part showing an installation state of a fixing device according to a seventh embodiment of the present invention.

FIG. 18 is a perspective view of a pressurizing unit according to a seventh embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Heat roller 15 Print medium 21, 45, 47, 83b Pressing body 21a, 45a, 45b Edge 22 Pipe 25 Pressing spring 47a, 47b Curved part 51a, 73a, 93 Groove 53, 73 Holder 83a Holder 86 Tension spring S1, S2 Pressing surface S3, S4 Curved surface

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koichi Matsuzaki 4-11-11 Shibaura, Minato-ku, Tokyo F-term in the offshore company data (reference) 2H033 AA23 BB03 BB04 BB14 BB29 BB30 BB33 BB34

Claims (7)

[Claims] (A) a heating roller rotatably supported; (b) a pipe rotatably supported and deformably arranged in contact with the heating roller; A pressurizing member disposed in a pipe and having a pressurizing surface facing the heating roller; and (d) urging means for urging the pressing body toward the heating roller to generate a pressing force. (E) the fixing device, wherein the radius of curvature of the pressing surface is set in accordance with the radius of curvature of the heating roller. 2. A friction coefficient between a recording medium and a heating roller is set to μ1, a friction coefficient between a pipe and a pressing body is set to μ2, the pressure is set to N, and a pressure is applied when the pipe rotates. 2. The fixing device according to claim 1, wherein, when a load applied to an edge of the body is N1, μ1 · N> μ2 · N + N1. 3. The fixing device according to claim 2, wherein at least one of an inner peripheral surface of the pipe and an outer peripheral surface of the pressure body is subjected to a process for reducing a friction coefficient μ2. 4. The fixing device according to claim 1, wherein at least one of both edges of the pressure body is curved. 5. The fixing device according to claim 1, wherein a curved portion having a curved surface is formed on each of an upstream side and a downstream side of the pressurizing surface in a recording medium conveyance direction. 6. A heating roller, (b) a pressing body disposed opposite to the heating roller, and (c) a pressing body against the heating roller to apply pressure. (D) holding means for holding the heating roller, and (e) the holding means for guiding the pressurized body and applying a pressing force to the rotation center of the heating roller. A fixing device comprising a groove for directing. 7. The fixing device according to claim 6, wherein the holding unit and the pressing body are formed integrally.