JPH082686Y2 - Fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a fixing device provided in an image forming apparatus provided in a copying machine or the like and for fixing an image formed on a sheet.

[Conventional technology]

In an image forming apparatus such as a copying machine or a printer, a fixing device is provided on the downstream side of the image forming unit in the sheet conveying direction in order to fix the toner image on the sheet. The fixing device has a heating roller having a heater therein, and a pressure mechanism constituted by a belt or a roller and brought into pressure contact with the heating roller. Then, the toner image on the surface of the sheet passing between the heating roller and the pressure mechanism is heat-fused to fix the toner image.

In the fixing device, an offset preventing liquid is applied to the surface of the heating roller so that the toner image is not transferred to the side of the heating roller when the sheet passes between the heating roller and the pressure mechanism. ing. In order to apply this offset prevention liquid, an offset prevention liquid application roller (hereinafter referred to as an application roller) is provided. This coating roller is configured such that an offset prevention liquid is enclosed in a cylindrical body having a plurality of holes on its outer peripheral surface, and felt having good heat resistance is wound around the outer periphery of the cylindrical body. Then, the coating roller comes into contact with the heating roller while rotating, and the offset prevention liquid sealed inside oozes out from the felt during the rotation and is coated on the heating roller.

For example, when performing full-color copying, it is necessary to use a low viscosity (several hundred centistokes) anti-offset liquid to enhance the anti-offset effect. When such an anti-offset liquid having a particularly low viscosity is used, heat is transferred from the portion in contact with the heating roller during standby when the fixing process is not performed, and the viscosity of the anti-offset liquid is increased more than necessary. It may fall down and the anti-offset liquid may flow out along the heating roller. When the offset prevention liquid flows out, there arises a problem that the first copy image is contaminated with the offset prevention liquid and the consumption amount of the offset prevention liquid increases.

In order to solve such a problem and to make the supply amount of the offset prevention liquid uniform, a fixing device as disclosed in JP-A-62-164076 has been proposed. In this fixing device, a roller for applying the offset prevention liquid is configured to be capable of coming into contact with and separating from a heating roller, for example, and detecting the fixing temperature and the time during which the applying roller is in contact with the heating roller, Control is performed such that the offset prevention liquid application roller is brought into contact with or separated from the heating roller in accordance with the detection result of 1.

[Problems to be solved by the device]

In the conventional fixing device as described above, the oil applying roller is configured to be able to contact and separate from the heating roller. Therefore, except for the fixing process, by separating the applying roller from the heating roller, It is possible to prevent the offset prevention liquid from flowing out. However, in this apparatus, since the coating roller is moved by using the solenoid valve, a drive source for that is required. In addition, the movement control is complicated, which may cause a malfunction.

The purpose of this invention is to eliminate the need for a special drive source for moving the coating roller, and without performing complicated control.
An object of the present invention is to provide a fixing device capable of preventing the offset prevention liquid from flowing out from the coating roller.

[Means for solving the problem]

The fixing device according to the present invention comprises a pair of circulation mechanism, offset prevention liquid application roller, biasing member and self-centering mechanism. The pair of circulation mechanisms includes a heating roller having a heater therein and a pressure mechanism press-contacted to the heating roller, and is a mechanism for fixing an image formed on a sheet passing between them. is there. The offset prevention liquid application roller is arranged so as to be able to take an alignment position in contact with the heating roller and an eccentric position away from the heating roller, and applies the offset prevention liquid to the heating roller. The biasing member biases the offset prevention liquid application roller toward the eccentric position side. The self-aligning mechanism receives the drive force of the circulation mechanism, and automatically aligns the offset prevention liquid application roller when the drive force is transmitted.

[Action]

In this invention, when the circulation mechanism is stopped, the heating roller is urged by the urging member to be positioned at an eccentric position apart from the heating roller. Therefore, the offset prevention liquid enclosed in the offset prevention liquid application roller is
It is prevented from being heated by the heating roller. As a result, the viscosity of the prevention liquid does not decrease more than necessary, and the outflow of the offset prevention liquid can be suppressed.

When the circulation mechanism starts operating, the driving force is transmitted from the circulation mechanism to the self-aligning mechanism. At this time, the automatic alignment mechanism automatically aligns the offset prevention liquid application roller, so that the offset prevention liquid application roller comes into contact with the heating roller.

As described above, the offset prevention liquid application roller is separated from the heating roller by the eccentricity of the biasing member,
The contact is performed by an automatic centering mechanism using a driving force. Therefore, a special drive source for moving the coating roller is unnecessary, and it is not necessary to perform complicated movement control. Moreover, the structure is simpler.

〔Example〕

FIG. 3 shows a copying machine using a fixing device according to an embodiment of the present invention.

In FIG. 3, a manuscript table 2 is fixed to the upper surface of the copying machine main body 1, and a manuscript holder 3 is mounted on the manuscript table 2 so as to be openable and closable. On the right side of the main body of the copying machine 1,
Paper cassettes 4 and 5 are detachably attached. On the left side of the copying machine main body 1 in the drawing, a paper discharge tray 6 for discharging the paper of the copying agent is mounted.

Inside the copying machine main body 1, an exposure device 7 for reading a document is provided on the upper side thereof. The exposure device 7 is composed of a light source, a mirror and the like. Also,
A photoconductor drum 8 on the surface of which an electrostatic latent image is formed is arranged in the center of the copying machine body 1. Around the photosensitive drum 8, a charging device 9, a developing device 10, a transfer device 11, a paper separating device 12, and a cleaning device 13 are sequentially arranged.

A paper feed / transport path 14 for feeding paper is provided between the paper feed cassettes 4 and 5 and the image forming unit constituted by the photosensitive drum 8. Further, between the image forming unit and the paper discharge tray 6, a paper discharge conveyance path 15, a fixing device 16 for fixing the transfer image on the paper, and a discharge roller 17 are arranged.

As shown in FIG. 1, the fixing device 16 has a heating roller 20 inside which a heater (not shown) is arranged, and a pressure roller 21 arranged below the heating roller 20. .
These rollers 20 and 21 are pressed against each other and are rotatably supported by the housing (not shown) of the fixing device 16. A fixing gear 22 is fixed to one end of a roller shaft of the heating roller 20. The fixing gear 22 is connected to a drive system (not shown) by a gear mechanism or the like. An application roller 23 for applying the offset prevention liquid to the heating roller 20 is arranged above the heating roller 20. The coating roller 23 portion is shown in an exploded manner in FIG. As shown in FIG. 4, the coating roller 23 has a cylindrical body 24 having a plurality of holes 24a, and the cylindrical body 24 is filled with silicone oil 25 as an offset preventing liquid. A felt 26 is provided on the outer peripheral surface of the cylindrical body 24 for exuding the offset prevention liquid 25 from the hole 24a.

The roller shaft 27 of the coating roller 23 is rotatably supported by a bearing 30 as shown in the sectional view of FIG. bearing
An engaging portion 30a is formed on a part of the outer periphery of 30. The lower end of the spring 31 is locked to the locking portion 30a, and the bearing 30
Is always urged upward by the spring 31. Spring 31
The upper end of is fixed to the housing of the fixing device 16.
As shown in FIG. 1, a part of the coating roller shaft 27 is
A large-diameter portion 28 is provided, and four blade members 29 (29a to 29a for automatic alignment) 29 (29a to 2) are provided on the outer periphery of the large-diameter portion 28 at equal intervals in the circumferential direction.
9d) is provided. The base end sides of the blade members 29a to 29d are rotatably mounted on the large diameter portion 28 of the coating roller shaft 27. The large diameter portion 28 of the coating roller shaft 27 and the blade members 29a to 29d on the outer periphery of the large diameter portion 28 are fitted into the coating roller gear 33. Here, when the coating roller shaft 27 and the bearing 30 are about to rotate relative to each other or when they are rotating relative to each other, a predetermined frictional force is applied in a direction opposite to the rotation direction of the coating roller gear 33. Is to occur.

The application roller gear 33 is formed in a ring shape, and a support portion 33a is integrally formed on a side wall of the application roller gear 33 side. As shown in FIG. 2, the support portion 33a is rotatably supported by a frame member 34 provided in the housing of the fixing device via a bush. A gear unit that meshes with the fixing gear 22 is provided on the outer periphery of the application roller gear 33. Further, on the inner wall surface, as shown in FIG. 1, locking portions 32 are formed at four positions at equal intervals. This locking part
The reference numeral 32 projects toward the center and has a substantially triangular shape. Then, when the applying roller gear 33 is rotated by the fixing gear 22, the tips of the blade members 29a to 29d can be locked to the locking portions 32, respectively.

 Next, the operation will be described.

When the fixing process operation is not performed, the driving force is not transmitted to the fixing gear 22, and the heating roller 20 and the pressure roller 21 are stopped. In this state, the bearing
30 is pulled upward by the force of F1 by the spring 31, and the coating roller gear 33 is stopped.
The force F2 for rotating the blade members 29a to 29d by 32 is 0, and F1> F2 = 0. Therefore, the application roller shaft 27, that is, the application roller 23 is, as shown in FIG.
The blade members 29a to 29d are positioned eccentrically from the center of the blade 33 in the direction in which the blade members 29a to 29d are prone to fall (direction of FIG. 5A).
As a result, the coating roller 23 separates from the heating roller 20,
A gap h is created between them.

In such a state, the heat from the heating roller 20 side is not transferred to the coating roller 23 side, so that the viscosity of the offset prevention liquid 25 contained in the coating roller 23 is prevented from lowering more than necessary. This prevents the offset prevention liquid 25 from flowing out to the heating roller 20 side.

Further, when the fixing process is started, the driving force from the drive system (not shown) is transmitted to the fixing gear 22,
The rotation of 22 is transmitted to the application roller gear 33. At this time,
A frictional force F2 is generated between the coating roller shaft 27 and the bearing 30 in the direction opposite to the rotation direction of the coating roller gear 33 due to friction. Due to the frictional resistance F2, even when the coating roller gear 33 starts rotating, the coating roller shaft 27 is temporarily stopped.
Therefore, the blade member 29a that was in contact with the locking portion 32 on the inner peripheral surface of the application roller gear 33 is rotated outward. As a result, the application roller shaft 27 is moved toward the center of the application roller gear 33. Due to this movement, the tip portions of the other blade members 29b to 29d are engaged with the corresponding locking portions 32.
And the blade members 29a to 29d are rotated outward by the same force. By such an operation, the coating roller shaft 27 is automatically positioned at the center of the coating roller gear 33. This state is shown in FIG. Of course, the frictional drag force F2, that is, the force to rotate the blade members 29a to 29d outward is larger than the biasing force F1 of the spring 31.

In this way, when the applying roller shaft 27, that is, the applying roller 23 is automatically aligned, the applying roller 23 is heated by the heating roller 20.
Contact the outer peripheral surface of. This allows the cylindrical body of the coating roller
Anti-offset liquid 25 through holes 24a of 24 and felt 26
Permeates the outer peripheral surface and is applied to the heating roller 20.

When the fixing process is completed and the gears 22 and 33 are stopped, the force F2 for rotating the blade members 29a to 29d of the coating roller shaft 27 outward is zero. At this time, when the coating roller shaft 27 stops, a static friction force acts between the coating roller shaft 27 and the bearing 30, and the roller shaft 27 does not easily rotate. However, as described above, in the state where the force F2 for rotating each of the blade members 29a to 29d outward is 0, the force F1 for pulling the bearing 30 of the spring 31 upward becomes stronger,
Further, since no slippage occurs between the application roller shaft 27 and the bearing 30 due to friction, for example, the blade member 29a falls toward the shaft center side, and the application roller shaft 27 is eccentric in the direction A of FIG. As a result, the coating roller 23 moves upward and the heating roller 20
Move away from

As described above, in this embodiment, the application roller 23 is separated from the heating roller 20 except during the fixing process, so that the offset preventing liquid can be prevented from flowing out. Further, at the start of the fixing process, the driving force for rotating the heating roller 20 is used to move the coating roller 23 to the heating roller.
Since it is brought into contact with 20, there is no need for a special drive source for moving the coating roller 23, and no complicated control is required.

[Other Examples]

(B) In the above-described embodiment, the case where the fixing device of the present invention is applied to a copying machine has been described, but it goes without saying that it can be used in other facsimiles, printers and the like.

(C) In the above embodiment, the case where the pressure roller 21 is provided as the pressure mechanism has been described, but the present invention can be similarly applied to a pressure mechanism using a belt or the like.

[Effect of device]

As described above, in the present invention, the offset prevention liquid application roller is separated from the heating roller by the eccentricity of the biasing member,
The contact is performed by an automatic centering mechanism using a driving force. Therefore, a special drive source for moving the coating roller is unnecessary, and it is not necessary to perform complicated movement control. Moreover, the structure is simpler.

[Brief description of drawings]

FIG. 1 is a partially exploded perspective view of a fixing device according to an embodiment of the present invention, FIG. 2 is a partial sectional side view of a coating roller moving mechanism of the fixing device, and FIG. 3 is a fixing device according to an embodiment of the present invention. FIG. 4 is a schematic sectional view of a copying machine in which the apparatus is adopted, FIG. 4 is a sectional view of an application roller of the fixing device, and FIGS. 5 and 6 show an application roller moving mechanism for explaining the operation of the embodiment. It is a front view. 16 ... Fixing device, 20 ... Heating roller, 21 ... Pressure roller, 23 ...
Coating roller, 25 ... Offset prevention liquid, 29a to 29d ... Blade member, 30 ... Bearing, 31 ... Spring, 32 ... Locking member, 33 ... Coating roller gear.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-54-69444 (JP, A) JP-A-53-129048 (JP, A) JP-A-51-58348 (JP, A) JP-A-54- 39643 (JP, A) JP 52-92729 (JP, A) JP 52-33738 (JP, A) JP 51-58349 (JP, A) JP 49-72539 (JP, A) 62-123670 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A pair of circulations for fixing an image formed on a sheet passing between them, comprising a heating roller having a heater therein and a pressure mechanism press-contacted to the heating roller. A mechanism, an offset prevention liquid application roller for applying an offset prevention liquid to the heating roller, which is arranged so as to have an alignment position in contact with the heating roller and an eccentric position away from the heating roller, and the offset prevention liquid. A biasing member that biases the coating roller toward the eccentric position, and a driving force of the circulation mechanism are transmitted, and an automatic alignment mechanism that automatically aligns the offset prevention liquid coating roller when the driving force is transmitted. And a fixing device.