JP2002214953A - Fixing device - Google Patents

Abstract

An object of the present invention is to reduce the heat capacity of a heated section, shorten the warm-up time, and improve the sheet separation at a fixing section. SOLUTION: The fixing device according to the present invention comprises an endless belt for fixing, a fixing roller comprising an elastic member for pressing the endless belt against a recording material, and a fixing roller between the recording material and the fixing roller facing the fixing roller. Backup roller, a guide member that guides the traveling path of the endless belt that runs between the fixing roller and the backup roller, and a heating unit that heats the endless belt. The heating unit contacts the endless belt in a non-contact manner. This is a configuration in which heating is performed directly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic system used for a copying machine, a printer, or the like, or an image forming apparatus for forming an image using a toner similar to the electrophotographic system, for fixing a toner image on a recording material by heating. And a fixing device.

[0002]

2. Description of the Related Art As a fixing method most often used in an electrophotographic method, a recording material is interposed between a pair of heat rollers while rotating while applying an appropriate pressure between the heat rollers. There is a heat roller method in which the toner image is melted and the toner image is fixed on the recording material. On the other hand, in recent years, demands for power saving and shortening of warm-up time have been increasing, and development of a fixing device adapted to image colorization has been desired.
Various types of fixing devices have been proposed and put into practical use.

FIG. 6 shows an example of a conventional fixing device using an endless belt suitable for fixing a color image.

In FIG. 6, reference numeral 73 denotes a heating roller having a halogen lamp 75 as a heat source therein, reference numeral 72 denotes a fixing roller, reference numeral 77 denotes a pressure roller, and fixing belt 71 forms a silicone rubber layer on a nickel belt base material. And is hung between the fixing roller 72 and the heating roller 73. The heating roller is made of an aluminum tube, and both ends of the shaft are pressed against the fixing roller by a tension spring 74 to apply tension to the fixing belt 71, thereby stabilizing the running of the fixing belt and improving the close contact between the heating roller and the fixing belt. , The heat transfer from the heating roller to the fixing belt is improved. 79 is a paper guide for improving the introduction of the recording paper to the fixing position. Pressure roller 7
Reference numeral 7 denotes a pressing spring 83 which presses against a fixing roller 72 via a fixing belt 71 in order to secure a fixing nip and perform fixing well. When starting the fuser with the above configuration,
The halogen roller 75 is turned on simultaneously with the rotation of the pressure roller 77 and the fixing roller 72 in the direction of the arrow. The fixing belt is fed along with the rotation of the fixing roller and the pressure roller, and the heating roller is driven to rotate. Halogen lamp 75
Is absorbed by the heating roller 73, and the heat of the heated heating roller raises the temperature of the fixing belt 71, and is also transmitted to the pressing roller 77 and the fixing roller 72. When the temperature of the entire belt reaches a predetermined temperature and the temperature of the fixing belt 71 reaches 170 ° C., the fixing is enabled, and the recording sheet 80 is inserted into the fixing section and passes through the fixing nip.
Settled on top. Reference numeral 82 denotes a release material applying roller for maintaining good releasability between the fixing belt 71 and the toner image.

[0005]

In the above-mentioned conventional fixing device, the heat capacity of the heating roller 73 is large and it takes time for the fixing belt to heat up to a temperature at which fixing can be started, so that the warm-up time cannot be shortened. Further, even if the diameter of the heating roller is reduced in order to reduce the heat capacity of the heating roller 73 or the thickness of the heating roller is reduced, the bending strength of the roller is weakened, and there is a limit. SUMMARY OF THE INVENTION It is an object of the present invention to reduce the heat capacity of a heated portion in a fixing device using an endless belt, shorten the warm-up time, and improve the sheet separation property in the fixing portion.

[0006]

In order to achieve the above object, a fixing device according to the present invention comprises a fixing endless belt, a fixing roller comprising an elastic member for pressing the endless belt against a recording material, and a recording device opposed to the fixing roller. A backup roller that sandwiches the material and the endless belt between the fixing roller, a guide member that guides a traveling path of the endless belt that travels while being sandwiched between the fixing roller and the backup roller, and a heating unit that heats the endless belt,
The heating means is configured to directly heat the endless belt in a non-contact manner.

In addition, no tension is applied to the endless belt between the guide member and the fixing roller, or a weak tension is applied to a common tangent line between the guide member and the fixing roller so that the endless belt does not follow the endless belt. .

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the structure of the present invention, there is no heating roller for heating the fixing belt, and the fixing belt is directly heated in a non-contact manner. Up time can be reduced.
In addition, since the fixing belt is not heated via the heating roller, the responsiveness is good. Further, since the guide member only roughly defines the traveling path of the fixing belt, it does not come into close contact with the fixing belt, so that heat is not easily transmitted to the guide member and loss is small.
Further, since little tension is applied to the fixing belt between the guide member and the fixing roller, a guide member having a small bending strength can be used, and the heat capacity of the guide member can be reduced. Further, by using the fixing roller as a non-rotating fixed pad, the heat capacity can be further reduced, and the warm-up time can be shortened.

[0009]

(Embodiment 1) FIG. 1 shows a fixing device according to a first embodiment of the present invention.
Is a rotatable fixing roller having a foamed silicone rubber layer formed on a mandrel; 3 is a rotatable pressure roller having a silicone rubber layer formed on a mandrel; Pressed to the side. Reference numeral 5 denotes a halogen lamp for heating, and reference numeral 4 denotes a guide member that defines a traveling path of the belt. The fixing belt 1 has a three-layer structure. 1a
Is a belt substrate of polyimide or nickel having a thickness of about 30 to 70 μm, and its inner surface is blackened so as to easily absorb the light of the lamp. 1b has a thickness of 100 to 30
The silicone rubber layer of 0 μm, 1c is a fluororesin layer of 30 μm formed on the surface in order to ensure releasability and durability to the toner.

When the fixing device starts operating, the fixing roller 2
The fixing belt 1 sandwiched between the roller and the pressure roller 3 starts rotating continuously in the direction of the arrow following the rotation of the roller (in the direction of the arrow). At the same time, the halogen lamp 5 is turned on to irradiate the inner surface of the fixing belt 1 and the radiant heat is absorbed by the fixing belt 1 to increase the temperature. When the fixing belt 1 reaches a predetermined fixing temperature, the recording paper 9 carrying the toner image is inserted into the fixing portion sandwiched between the fixing roller 2 and the pressure roller 3, and the recording paper 9 sequentially passes through the fixing nip in the direction of the arrow. Then, the toner image is fixed on the recording paper 9.

The traveling path of the fixing belt 1 is roughly determined by a guide member 4 shown in FIG. The guide member 4 is formed of a heat-resistant resin, and its tip protrudes in a comb-like shape. This is because the light of the halogen lamp 5 is applied to the fixing belt 1 as directly as possible. Further, a portion of the guide member 4 which directly receives the light of the halogen lamp has a reflecting surface, so that the energy of the lamp is efficiently irradiated to the fixing belt 1. The surface of the guide member 4 that contacts the fixing belt 1 is preferably provided with a thin rib or the like so as to minimize the contact area.

FIG. 3 is an enlarged view of the fixing unit. In the pressing portion (nip portion) of the pressing roller 3, the fixing belt 1 and the recording paper 9 are made of rubber foam and have high flexibility because the fixing roller 2 is formed of rubber. Deformed to imitate the side. (A foamed silicone rubber layer having a rubber hardness of 25 degrees and a thickness of 1.5 mm was used for the pressure roller 3 and a thickness of 4 mm for the fixing roller 2.) Therefore, after the recording paper 9 passed through the fixing nip portion, the pressure roller 3 was used. It is configured to be discharged following the side and easily peeled off from the fixing belt 1. This is an effective configuration for fixing a color image in which the amount of toner is large and the toner needs to be dissolved well. When the recording paper 9 is not discharged in the direction of the pressure roller 3, the fixing belt and the recording paper can be naturally separated. And the trouble that the recording paper is wound around the fixing belt easily occurs. As described above, particularly in the fixing of a color image, the discharge direction of the recording paper 9 at the fixing nip is an important requirement for the separation of the recording paper. In order to realize this, silicone rubber is used for the fixing roller 1. Since a toner image cannot be directly fixed by a member having good heat insulating properties, a fixing belt is used in combination with a fixing belt as a heating member for recording paper. However, in the conventional configuration as shown in FIG. 6, the heat capacity of the heating roller required for heating the fixing belt is large, and the fixing belt is heated after the heating roller is heated. It takes time to heat up.
In the configuration of this embodiment, the halogen lamp 5 directly heats the inner surface of the fixing belt 1 and has no heating roller, so that the temperature of the fixing belt can be raised instantaneously. The guide member 4 for regulating the running of the fixing belt 1 only needs to be partially in contact with the fixing belt 1 and does not need to be in close contact with the front surface, and a material having a low thermal conductivity can be used. Does not hinder the climb. Therefore, the warm-up time of the fixing device can be greatly reduced.

In this embodiment, the halogen lamp 5 is used as the heating means. However, it is also possible to use an electromagnetic induction heating method (in this case, a fixing belt base material is used as a heating material) or the like. A configuration in which the belt 1 is heated is preferable.
When a method of transferring heat by contact is used, the adhesion between the heating means and the fixing belt is required, and a contact pressure for the adhesion is required, and therefore, the strength of the contacting member is required, and as a result, the heat capacity of the member is reduced. It goes into a vicious cycle of growing.
In addition, if the tension is not applied to the fixing belt, it is difficult for the fixing member to adhere to the heating member. Therefore, a conventional configuration in which the fixing belt is stretched by applying tension between the rotating rollers as shown in FIG.

In this embodiment, the fixing belt 1 is provided with the fluororesin layer 1c. However, it is not always necessary to provide the fluororesin layer 1c, and the surface layer may be a silicone rubber layer. Further, a mechanism for applying silicone oil to the belt surface may be provided to improve the releasability from the toner. Further, the guide member 4 has the configuration shown in FIG. 2, but this is not limited to this configuration, and any guide member that roughly regulates the shape of the fixing belt 1 without giving tension to the fixing belt 1 is provided. good.

(Embodiment 2) FIG. 4 shows a second embodiment.
In FIG. 4, a fixing belt 1, a fixing roller 2, a pressure roller 3, and a halogen lamp 5 are all the same as in the first embodiment, and the difference from the first embodiment is the configuration of the guide member. Second
The guide member of this embodiment comprises two guide rollers 11 rotatably mounted. The guide roller 11 is provided at a position for guiding the fixing belt 1 to such an extent that the shape of the fixing belt 1 is slightly deformed into a vertically long elliptical shape, and rotates as the fixing belt 1 rotates. The guide roller 11 is a small-diameter metal roller having a diameter of about 5 mm. It is more preferable that the surface of the guide roller 11 is processed to reduce the contact area with the fixing belt 1 (for example, a groove is formed on the circumference) or coated with a heat insulating material. When tension is applied between the rollers and the fixing belt 1 is pulled as in the conventional example, the guide roller 11 bends and the running of the fixing belt does not work well, and the diameter must be increased in order to prevent the warp from occurring. The configuration of the present invention does not pull the fixing belt along the tangent line between the guide rollers as in the related art, but merely regulates the traveling path of the fixing belt 1, so that a large force is not applied to the guide rollers.
It can be a small diameter roller. 12 is a reflecting plate for reflecting light from the halogen lamp 5, and 13 is the fixing belt 1.
Is a guide plate provided so as not to come into contact with the reflection plate when it moves sideways. Note that the guide roller 11 does not necessarily need to be rotated.

(Embodiment 3) FIG. 5 shows a third embodiment.
5, the fixing belt 1, the halogen lamp 5, and the pressure roller 3 are the same as those in the first and second embodiments. Example 3
Is different from those of the first and second embodiments. Example 3
A portion facing the pressure roller 3 across the fixing belt 1 is formed of a fixing pad 20. The fixing pad 20 is made of a foamed silicone rubber layer provided on the bottom of the guide member 22 and its surface is covered with a fluorine resin film 23 of about 50 μm to make it easy to slide with the fixing belt 1. The recording paper 9 is fed by friction with the pressure roller 3, and the fixing belt 1 is rotated by the frictional force with the recording paper 9 and the frictional force with the pressure roller 3 outside the paper width while sliding on the fixing pad 20. According to this configuration, the heat capacity of a portion requiring heating can be further reduced as compared with the configuration using the fixing roller 2, and the warm-up time can be reduced.

[0017]

According to the constitution of the present invention, there is no heating roller for heating the fixing belt, and the fixing belt is directly heated in a non-contact manner, so that there is no waste and the heat capacity of the member to be heated can be reduced as much as possible. Can be shortened. Also,
Since the fixing belt is not heated via the heating roller, the responsiveness is good.

Further, since the guide member only roughly defines the traveling path of the fixing belt, it does not come into close contact with the fixing belt, heat is not easily transmitted to the guide member, and loss is small.
Further, the fixing belt is given only a tension that does not follow the common tangent of both the fixing roller and the guide member. That is, since the fixing belt is hardly subjected to tension between the guide member and the fixing roller, the bending strength of the guide member is increased. Can be used, and the heat capacity of the guide member can also be reduced. Further, by using the fixing roller as a non-rotating fixed pad, the heat capacity can be further reduced, and the warm-up time can be shortened.

[Brief description of the drawings]

FIG. 1 is a sectional configuration diagram of a fixing device as a first embodiment of the present invention.

FIG. 2 is a perspective view of a guide member according to the first embodiment.

FIG. 3 is an enlarged view of a fixing unit according to the first embodiment.

FIG. 4 is a sectional configuration diagram of a fixing device according to a second embodiment of the present invention.

FIG. 5 is a sectional configuration diagram of a fixing device according to a third embodiment of the present invention.

FIG. 6 is a configuration diagram of a conventional fixing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing belt 2 Fixing roller 3 Pressure roller 4 Guide member 5 Halogen lamp 11 Guide roller 20 Fixing pad

Claims (7)

[Claims] An endless fixing belt, a fixing roller made of an elastic member for pressing the fixing belt against a recording material, and a recording material and the fixing belt opposed to the fixing roller are sandwiched between the fixing roller. A pressure roller, a guide member that regulates a traveling path of the fixing belt that travels between the fixing roller and the pressure roller, and a heating unit that directly heats the fixing belt in a non-contact manner; and A fixing device comprising a material in which the hardness of the elastic body of the fixing roller is lower than the hardness of the pressure roller. 2. The fixing device according to claim 1, wherein the guide member comprises a fixed member that does not rotate. 3. The fixing device according to claim 2, wherein the heating unit is a lamp, and the heating unit is disposed in a space surrounded by the guide member and the fixing belt. 4. The fixing device according to claim 1, wherein the guide means is a small-diameter roller, and there is no means for applying tension to the fixing belt. 5. The fixing device according to claim 1, wherein the surface of the fixing roller is formed of a foamed rubber layer. 6. The fixing device according to claim 1, wherein a tension is applied to the fixing belt such that the fixing belt does not follow a common tangent of both the fixing roller and the guide member. 7. The fixing device according to claim 1, wherein the fixing roller is a non-rotating pressure pad.