JP2008170630A - Image fixing unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which can prevent the heating member from breaking by eliminating the warping of the reinforcing member and holding member inside it. <P>SOLUTION: The heating member has, inside it, a holding means including a holding section formed along the nip made by the heating member and a pressing member pressing each other, and a reinforcement section to push the holding section toward the pressing member, and a heater to heat the holder and the heating member without contacting them. When turning the pressing member, the pressure of the pressing member to the nip is applied turning downstream the pressing position of the facing reinforcement section in the turning direction of the heating member. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fixing device of an image forming apparatus such as a copying machine or a facsimile.

In an image forming apparatus such as a copying machine or a facsimile, a toner image formed on the surface of a photosensitive drum is transferred onto a transfer sheet, and the toner is fixed onto the transfer sheet by a fixing device. The fixing device includes a heating roller configured to include a heating member that heats and melts the toner on the transfer paper, and a pressure member that presses and contacts the heating member to fix and transfer the toner onto the transfer paper. A fixing device is common.
In such a fixing device, in order to reduce power consumption, an on-demand method is employed in which it is not necessary to preheat the fixing device during standby.

In this on-demand type fixing device, a fixing mechanism is important for reducing the heat capacity. For example, Patent Document 1 discloses an on-demand fixing device in which a heating member is provided with a support member (holding means) together with a radiation light source, and the holding means is pressed against a pressure member via a film. Yes. The holding means is composed of a U-shaped metal member formed by a bottom surface portion that forms a fixing nip and a side plate portion that suppresses film deflection and has sufficient strength against pressure applied by a pressure roller. ing. The supporting member is pressed to fix the toner image.
Further, in the heating device (fixing device) described in Patent Document 2, the holding member (holding means) is configured by two members, a first support portion and a second support portion serving as a nip forming portion. It is disclosed.

  In the fixing device configured as described above, the strength of the holding means provided inside the heating member is required to hold the pressure at the nip portion by the pressure member. If the volume of the holding means is increased in order to ensure this strength, the heat capacity of the holding means increases accordingly. As a result, there is a problem that the amount of heat that should be given to the heating member is taken away by the holding means. On the other hand, what comprises a holding means with the combination of the holding member of a thin structure, and the reinforcement member which reinforces an intensity | strength is proposed.

  However, even a combination of a thin-walled holding member and a reinforcing member that reinforces the strength has the following problems. In this configuration, since the reinforcing member and the holding member bend in the rotation direction when the pressure member is driven to rotate, the belt as the heating member is damaged by the reinforcing member and the holding member. FIG. 3 is a schematic diagram showing a configuration of a conventional fixing device (100). 4 is a cross-sectional view of the fixing device shown in FIG. 3 taken along the line AA. In the conventional fixing device (100), when the pressure roller (300) is driven to rotate and the heating belt (200) is rotated, the reinforcing member (500b) and the holding member (500a) are rotated as shown in FIG. As shown in FIG. Then, the bent reinforcing member (500b) and the holding member (500a) break the heating belt (200).

JP 2004-94146 A JP 2004-62053 A

  The present invention has been made to solve the above-described problems of the prior art, and provides a fixing device capable of eliminating the deflection of the reinforcing member and the holding member and preventing the heating member from being damaged. Is.

  According to a first aspect of the present invention, there is provided the fixing device in which the rotatable heating member and the rotatable pressure member are brought into pressure contact with each other and conveyed with the transfer paper interposed therebetween to fix the toner on the transfer paper. A holding means having a holding portion along a nip portion formed by press-contacting the heating member and the pressure member, and a reinforcing portion that presses the holding portion in the direction of the pressure member. A heating source that heats the heating member in a non-contact manner with the holding unit and the heating member, and the pressure applied from the pressure member to the nip portion is opposite when the pressure member is rotated. The present invention relates to a fixing device, wherein the fixing member is added to a rotating downstream side of the heating member with respect to a pressing position of the reinforcing portion.

  According to the first aspect of the present invention, the heating member includes a holding means having a holding portion and a reinforcing portion along the nip portion on the inner side thereof, and a non-contact heating source, and driving rotation of the pressure member. At this time, the pressing force from the pressure member to the nip portion is applied to the rotation downstream side of the heating member with respect to the pressing position of the reinforcing portion of the holding means opposed to the pressing force. Although it tries to bend to the upstream side of the rotation by pressure, the reinforcing part and the holding part try to bend to the downstream side of the rotation by the rotation of the pressure member and the heating member, so that both act on each other and the deflection cancels out. . Therefore, since the holding means does not bend, the holding means does not damage the heating member.

Hereinafter, a preferred embodiment of a fixing device according to the present invention will be described with reference to the drawings.
FIG. 1 is a left side view illustrating a configuration example of an embodiment of a fixing device according to the present invention.
The fixing device (1) according to the present invention includes a heating belt (2) that heats and melts the toner (23) on the transfer paper (22), and the transfer paper (22) that is pressed against the heating belt (2). A pressure roller (3) for conveying and fixing the toner (23) on the transfer paper (22). The heating belt (2) is a heating member, and the pressure roller (3) is a pressure member.

  The heating belt (2) includes a holding means (5) for pressing the heating belt (2) and the pressure roller (3) with an appropriate nip width, and two heating units for heating the heating belt (2). Source (4).

  The holding means (5) is provided along the inner surface of the heating belt (2) corresponding to the nip width of the nip portion (7) formed by the heating belt (2) being pressed against the pressure roller (3). The holding member (5a) and the reinforcing member (5b) joined and integrated at substantially right angles to the upper surface of the holding member (5a). The holding member (5a) is a holding portion along the nip portion, and the reinforcing member (5b) is a reinforcing portion that presses the holding member (5a) in the direction of the pressing member.

  The reinforcing member (5b) is a rectangular plate-like member disposed between the two cylindrical heating sources (4) in a non-contact manner. The reinforcing member (5b) is disposed so that its width (short side) direction is substantially vertical, and the heating source (4) is not interlocked with the movement of the heating belt (2) or the holding means (5) by a fixing member (not shown). Therefore, the reinforcing member (5b) can move upward without contacting the heating source (4).

  The reinforcing member (5b) is not particularly limited as long as the urging force by a pressing member (not shown) that presses the reinforcing member (5b) can be reliably transmitted to the holding member (5a). Can be illustrated. In addition, although the rectangular plate-shaped member was demonstrated as an example as a reinforcement member (5b), it is not restricted to this.

  The holding member (5a) only needs to be able to form an appropriate nip portion (7) by receiving the pressing force from the reinforcing member (5b), and is preferably somewhat elastic. A phosphor bronze plate can be exemplified.

  The pressure roller (3) is driven at a predetermined speed by a driving device (not shown), conveys the transfer paper (22), and also drives the heating belt (2). In the fixing device (1) of the present embodiment, the pressure roller (3) is shifted to the downstream side with respect to the heating belt (2). With this configuration, the pressure applied from the pressure roller (3) to the nip portion (7) is applied to a position downstream of the pressing position of the opposing reinforcing member (5b). The nip portion (7) formed by the pressure contact between the heating belt (2) and the pressure roller (3) is also shifted.

  For example, in the case of the fixing device (1) having a width of the nip portion (7) of about 7 mm, the pressure applied to the pressure roller (3) is about 1.5 mm downstream from the pressing position of the reinforcing member (5b). Will join the position.

  The pressure roller (3) includes a pressure elastic body (11) for applying pressure. The pressure elastic body (11) includes a pressure lever (11a), a pressure spring (11b), and a pressure fulcrum (11c). As the pressurizing spring (11b), an elastic body other than the illustrated coiled spring can be used. The pressure lever (11a) is biased by the biasing force of the pressure spring (11b) with the pressure fulcrum (11c) as a base point. The pressure elastic body (11) generates a pressing force that pressurizes the pressure roller (3) upward, and the transfer paper (22) is interposed between the pressure roller (3) and the heating belt (2). The toner can be fixed by sandwiching the toner.

  Further, as shown in FIG. 1, the fixing device (1) includes an insertion guide (24) for introducing the transfer paper (22) onto which the toner (23) is transferred into the nip portion (7). With the insertion guide (24), the transfer paper (22) is conveyed from the right side to the left side in FIG.

In the present embodiment, the pressure roller (3) is shown as an example of the pressure member, but a pressure belt can also be used, and similar effects can be achieved.
The pressure roller (3), the pressure belt, and the heating belt (2) are not particularly limited in thickness and material, and can be configured with a conventionally known thickness and material.

  In the illustrated example, the heating source (4) is provided with two heat sources that generate radiant heat. However, the heating source (4) is not necessarily limited to this. For example, the heating source (4) is for heating the air in the heating belt (2). It is possible even if it exists.

  Here, the characteristic configuration of the fixing device (1) of the present embodiment will be specifically described with reference to FIG. FIG. 2 is a cross-sectional view of the fixing device shown in FIG. 1 taken along the line BB. FIG. 2A is a diagram showing a state before driving rotation, and FIG. 2B is a diagram showing a state after driving rotation.

  As shown in FIG. 1, in this embodiment, the nip portion (7) formed by the heating belt (2) and the pressure roller (3) being in pressure contact with each other by shifting the pressure roller (3) to the downstream side of the rotation. ) Position is shifted.

  Before driving and rotating the pressure roller (3), as shown in FIG. 2 (a), the reinforcing member (5b) and the holding member (5a) are arranged at the inner center of the heating belt (2). It is stationary.

  In the present embodiment, as described above, the nip portion (7) between the heating belt (2) and the pressure roller (3) is shifted to reinforce the pressure applied to the pressure roller (3). The member (5b) is added while being shifted downstream of the pressing position. Thereby, a reinforcement member (5b) and a holding member (5a) can be bent to the rotation upstream side. By doing so, the deflection to the downstream side due to the rotation of the heating belt (2) and the pressure roller (3) is canceled out.

  Therefore, in this embodiment, when the pressure roller (3) is driven and rotated, the reinforcing member (5b) and the holding member (5a) are not bent in the nip portion (7) as shown in FIG. Press in good condition.

  Thus, since the reinforcing member (5b) and the holding member (5a) are not bent even during the driving rotation of the pressure roller (3) and the heating belt (2), the reinforcing member (5b) and the holding member ( 5a) does not damage the heating belt (2).

  The present invention is preferably used in a fixing device that fixes toner on transfer paper by a pressure roller and a heating belt.

FIG. 3 is a left side view illustrating a configuration example of an embodiment of a fixing device according to the present invention. FIG. 2A is a diagram showing a state before driving rotation, and FIG. 2B is a diagram showing a state after driving rotation. FIG. 10 is a schematic diagram illustrating a configuration of a conventional fixing device. FIG. 4 is a cross-sectional view of the fixing device shown in FIG. 3 cut along a line AA.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing device 2 Heating belt 3 Pressure roller 4 Heating source 5 Holding means 5a Holding member 5b Reinforcing member 7 Nip part

Claims (1)

In a fixing device in which a rotatable heating member and a rotatable pressure member are pressed against each other and conveyed with the transfer paper interposed therebetween, and the toner on the transfer paper is fixed.
The heating member includes a holding portion along a nip portion formed by press-contacting the heating member and the pressure member, and a reinforcing portion that presses the holding portion in the direction of the pressure member. A holding means, and a heating source for heating the heating member in a non-contact manner with the holding means and the heating member,
A fixing force in which the pressing force from the pressing member to the nip portion is applied to the rotating downstream side of the heating member with respect to the pressing position of the opposing reinforcing portion when the pressing member rotates. apparatus.

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