JP2007212907A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow a holding member not to be deformed with push force by a pressure roller even when the holding member smaller and thinner than conventional is used in a film heating type fixing device. <P>SOLUTION: A plate-like reinforcing member 14 is substantially vertically attached to the reverse side to a sliding and contacting face of the holding member 12 in a longitudinal direction. Stress strain is suppressed by a difference between linear thermal expansion coefficients of the holding member 12 and the reinforcing member 14, and the reinforcing member 14 is preferably supported by support pieces 122a, 122b formed by cutting and raising a part of the holding member 12 from a viewpoint of suppressing heat transfer from the holding member 12 to the reinforcing member 14. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixing device mounted on an image forming apparatus such as a printer, a facsimile machine, and a copying machine, and more particularly to a so-called film heating type fixing device.

  In image forming apparatuses such as printers, facsimiles, and copiers, a heat roller type fixing device has been widely used so far to fuse and fix a toner image on a sheet to the sheet. This heat roller type fixing device presses a heating roller containing a linear halogen heater and a pressure roller having an elastic layer, and passes the paper through the nip portion of both rollers, whereby a toner image on the paper is obtained. Is fixed to the paper by heating and pressing.

  Although this heat roller type fixing device can cope with image formation from low speed to high speed, since the heat capacity of the heating roller and pressure roller is large, the heating time from the power ON or standby state to a predetermined temperature (warming up time) is sufficient. For a long time, improvements were required from the viewpoint of energy saving.

Thus, a so-called film heating type fixing device has been proposed in which a seamless film is heated from the back by a heater. In this film heating type fixing device, normally, it is not necessary to energize the heater, and it is only necessary to energize only during the fixing process. Therefore, the warm-up time is shorter and the energy can be saved as compared with the heat roller type.
JP 2004-62053 A JP 2004-94146 A

  In the film heating type fixing device, further energy saving is desired in recent years. For this purpose, it is conceivable to make the holding member pressed against the pressure roller and the film small and thin.

  However, if the holding member is simply made small and thin, the holding member may be deformed by the pressing force of the pressure roller, and the film may be skewed or wrinkled.

  The present invention has been made in view of such a conventional problem, and an object of the present invention is to use a pressure roller in a film heating type fixing device even when a smaller and thinner holding member is used. This is to prevent the holding member from being deformed by the pressing force.

  Another object of the present invention is to improve the thermal efficiency of the fixing device, to save energy, and at the same time to prevent the skew and wrinkles of the film.

  The fixing device of the present invention that achieves the above object includes a rotatable film configured in a cylindrical shape, a heat source that radiates radiant heat provided inside the film, and a sliding contact surface that is in sliding contact with the inner peripheral surface of the film. And a pressing member that presses the sliding contact surface of the holding member through a film, and a plate-like reinforcing member is provided substantially perpendicular to the longitudinal direction on the side surface opposite to the sliding contact surface of the holding member. It is attached.

  Here, from the viewpoint of suppressing stress strain due to the difference in linear thermal expansion coefficient between the holding member and the reinforcing member, and suppressing heat transfer from the holding member to the reinforcing member, a support piece formed by cutting and raising a part of the holding member It is preferable to support the reinforcing member.

In the fixing device of the present invention, since the plate-like reinforcing member is attached to the side surface opposite to the sliding contact surface of the holding member substantially perpendicularly to the longitudinal direction, the pressure member can be used even when the holding member is small and thin. It will not be deformed by the pressing force of. Thereby, the skew of the film and the generation of wrinkles are also prevented.

  Here, if the reinforcing member is supported by a support piece formed by cutting and raising a part of the holding member, stress strain due to a difference in linear thermal expansion coefficient between the holding member and the reinforcing member can be suppressed. Further, heat transfer from the holding member to the reinforcing member can be suppressed, and the thermal efficiency can be improved.

  Hereinafter, the fixing device according to the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments.

  FIG. 1 is a schematic view showing an embodiment of a fixing device according to the present invention. The fixing device shown in FIG. 1 has a cylindrical film 11 that is rotatable, a linear halogen lamp (heat source) 13 that is inserted substantially through the center of the film 11, and a cross section that is in sliding contact with the inner peripheral surface of the film 11. A substantially “U” -shaped holding member 12, a plate-like reinforcing member 14 attached to the approximate center of the inner surface of the holding member 12 in the longitudinal direction, and a pressure roller that presses the holding member 12 through the film 11. (Pressurizing member) 2. The pressure roller 2 is formed by forming an elastic layer 22 such as silicone rubber on the outer periphery of a metal core 21 and further forming a release layer (not shown) such as a fluororesin on the outer periphery if necessary. The metal core 21 is biased in the direction of the holding member 12 by a support member 31 whose one end is rotatably supported by a shaft 30 and whose other end is biased clockwise by a spring 32. As a result, the pressure roller 2 is brought into pressure contact with the holding member 12 via the film 11 to form a nip portion.

  The pressure roller 2 is rotated counterclockwise by a motor (not shown), whereby the film 11 that is in pressure contact with the nip portion is driven clockwise. The paper P guided to the nip portion by the guide 4 is nipped and conveyed in the nip portion, and at the same time, heated and pressurized to melt and fix the toner image on the paper P.

  In the holding member 12, a lower surface (sliding contact surface) 121 (shown in FIG. 3) having a substantially “U” cross section is in sliding contact with the inner peripheral surface of the film 11 and forms a nip portion together with the pressure roller 2. Here, a plate-like reinforcing member 14 is attached in the longitudinal direction at a substantially central portion of the region on the holding member side that receives the pressing force from the pressure roller 2. The reinforcing member 14 effectively prevents the holding member 12 from being deformed by the pressing force of the pressure roller 2. For example, even when the thickness of the holding member 12 is reduced from 2 mm so far to about 0.1 mm, the deformation of the holding member 12 can be sufficiently prevented by attaching the reinforcing member 14 having a thickness of about 2 mm. FIG. 2 shows the results of an experiment conducted by the present inventors.

  FIG. 2 is a plot of the nip pressure at each position in the longitudinal direction of the holding member 12, where the vertical axis is the nip pressure and the horizontal axis is the longitudinal position of the holding member 12. When the reinforcing member 14 was attached to the holding member 12, the nip pressure at each position in the longitudinal direction of the holding member 12 was within a range of approximately 50 ± 10 g. On the other hand, when the reinforcing member 14 was not attached to the holding member 12, the nip pressure of the holding member 12 was about 60g at both ends in the longitudinal direction, about 20g at the center, and the nip pressure was low at the center in the longitudinal direction. . This is because the holding member 12 is bent by the pressing force of the pressure roller 2 and the nip pressure at the central portion is lowered.

  The reinforcing member 14 may be formed integrally with the holding member 12 or may be attached after being manufactured as a separate body. The latter is desirable from the viewpoint of manufacturability. When the reinforcing member 14 is manufactured separately and attached to the holding member 12, a conventionally known method such as welding or adhesion can be used as the attachment method. However, when all of the contact surfaces of the reinforcing member 14 and the holding member 12 are joined, although the joining strength is improved, heat conduction increases from the holding member 12 to the reinforcing member 14, and the holding member 12 and the reinforcing member 14 are integrated to heat capacity. Becomes larger. This is not desirable from the viewpoint of improving the thermal efficiency of the fixing device and saving energy.

  Therefore, it is desirable to reduce the bonding area between the holding member 12 and the reinforcing member 14 within a range in which the strength of the holding member 12 is not significantly reduced. For example, as shown in FIG. 3, after the sliding contact surface 121 of the holding member 12 is cut into a “U” shape, the support pieces 122a and 122b are alternately formed in the longitudinal direction by being raised inward. The reinforcing member 14 may be fitted between the support pieces 122a and 122b. As a result, while the holding member 12 and the reinforcing member 14 are firmly joined, a microscopic air layer is interposed at the joint portion between the two members, and heat conduction from the holding member 12 to the reinforcing member 14 is kept low. It becomes like this. As a result, an increase in heat capacity due to the attachment of the reinforcing member 14 to the holding member 12 is suppressed to a small level.

  FIG. 4 shows another example in which the slidable contact surface 121 of the holding member 12 is cut and raised to form the support pieces 122a and 122b. In the holding member 12 shown in this figure, “U” -shaped linear holes are formed on the slidable contact surface 121 so as to face each other, and then the support members 122a and 122b are formed facing each other. The distance between the support pieces 122a and 122b is substantially the same as the thickness of the reinforcing member 14. The reinforcing member 14 is attached to the holding member 12 by inserting the reinforcing member 14 between the support pieces 122a and 122b. Even in such an attachment method, as described above, while the holding member 12 and the reinforcing member 14 are firmly joined, heat conduction from the holding member 12 to the reinforcing member 14 is suppressed to a low level, and the reinforcing member 14 is held in place. The increase in the heat capacity due to the attachment to 12 can be kept small.

  Of course, in order to increase the mounting strength in the above embodiment, a fixing means such as bonding with an adhesive or welding may be used in combination.

  The thickness and length of the reinforcing member 14 are not particularly limited, and may be determined as appropriate based on the pressing force from the pressure roller 2. Considering a reduction in heat capacity of the reinforcing member 14, it is preferable to make it as thin and short as possible. Further, the reinforcing member 14 may be provided with a plurality of holes to further reduce the heat capacity of the reinforcing member 14. Examples of the material of the reinforcing member 14 include metals such as stainless steel, iron, aluminum, copper, and magnesium.

  Further, it is desirable that the surface of the reinforcing member 14 to which the radiant light from the halogen lamp 13 hits reflects the radiant light as white or metallic color. This is because heating the film 11 with the radiant light reflected by the reinforcing member 14 increases the thermal efficiency and shortens the warm-up time, rather than heating the reinforced member 14 with the radiant light.

  Examples of the material of the holding member 12 used in the present invention include metals such as stainless steel, iron, aluminum, copper, and magnesium, similarly to the reinforcing member 14. A hole may be formed in the holding member 12 from the viewpoint of low heat capacity and thermal efficiency. In this case, the hole is formed by pressing or the like. Further, since the holding member 12 is in sliding contact with the inner peripheral surface of the film, it is recommended that a lubricant such as silicone grease be applied to the sliding contact surface 121 of the holding member 12. By applying the lubricant, the rotational torque of the film 11 can be reduced and wear can be suppressed.

  It is desirable that the inner surface of the holding member 12 to which the radiant light from the halogen lamp 13 hits reflects the radiant light as white or metallic color. Rather than indirectly heating the film 11 through the holding member 12, such as heating the holding member 12 with radiant light and heating the film 11 with the heated holding member 12, the reflected light reflected by the holding member 12 This is because the heating of the film 11 directly by the method has higher heating efficiency and higher heating speed.

  Examples of the film 11 used in the present invention include a two-layer structure having a base layer 11a and a release layer 11b as shown in FIG. In this film 11, the base layer side is in sliding contact with the holding member 12, and the release layer side is in contact with the paper P. The base layer 11a is preferably made of a material having excellent heat resistance and sliding contact resistance, and examples thereof include heat resistant resins such as polyimide, polyamideimide, and aramid; and metal materials such as stainless steel, nickel, aluminum, and copper. On the other hand, examples of the material for the release layer 11b include fluorine resins such as PTFE and PFA. An infrared absorbing material is dispersed and mixed in the release layer 11b. Thereby, radiation light (infrared light) can be efficiently absorbed. Examples of the infrared absorbing material include carbon black, graphite, and iron oxide. Among these, when carbon black is dispersed and mixed, the surface resistance of the film 11 is lowered, frictional charging of the film 11 is suppressed, and toner on the paper can be prevented from adhering to the film 11. Of course, an elastic layer may be provided between the base layer 11a and the release layer 11b if necessary.

1 is a schematic diagram illustrating an example of a fixing device according to the present invention. It is a figure which shows the change of the nip pressure of the longitudinal direction by the presence or absence of a reinforcement member. It is a perspective view which shows the example of attachment to the holding member of a reinforcement member. It is a perspective view which shows the other example of attachment to the holding member of a reinforcement member. It is sectional drawing which shows an example of the film used by this invention.

Explanation of symbols

2 Pressure roller (pressure member)
P Paper 11 Film 11a Base layer 11b Release layer 12 Holding member 13 Halogen lamp (heat source)
14 Reinforcing member 21 Core metal 22 Elastic layer 31 Support member 32 Spring 121 Sliding surface

Claims (2)

A rotatable film configured in a cylindrical shape, a heat source that radiates radiant heat provided inside the film, a holding member having a sliding contact surface that is in sliding contact with the inner peripheral surface of the film, and a sliding contact surface of the holding member In a fixing device including a pressure member pressed against the film through a film,
A fixing device, wherein a plate-like reinforcing member is attached to a side surface opposite to the sliding contact surface of the holding member substantially perpendicular to the longitudinal direction.   The fixing device according to claim 1, wherein the reinforcing member is supported by a support piece formed by cutting and raising a part of the holding member.