JP2008170882A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which can prevent the heating member from breaking by eliminating warps of the reinforcing member and holding member in it. <P>SOLUTION: The heating member has, inside it, a holding means consisting of a holder along the nip formed by the heating member and the presser pressing each other and a reinforcing part pushing the holder toward the presser while supporting both ends in the length direction of the heating member, and a heater to heat this holding means and the heater without touching. The reinforcing part consists of two bimetal layers, one of which at turning downstream the heating member has a thermal expansion coefficient smaller than the turning upstream layer. <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. Since the holding member and the reinforcing member have such a thin structure, the reinforcing member and the holding member bend in the rotation direction when the pressure member is driven to rotate, and the belt serving as the heating member is damaged by the reinforcing member and the holding member. Occurs. This will be described with reference to the drawings. FIG. 4 is a schematic diagram illustrating a configuration of a conventional fixing device (100). FIG. 5 is a cross-sectional view taken along the line AA of the fixing device shown in FIG. As shown in both figures, the conventional fixing device (100) includes a heating belt (200) and a pressure roller (300), and a holding member (500a) and a reinforcing member (500b) each having a thin structure are provided inside the heating belt. Provided. As shown in FIG. 5, both ends of the reinforcing member (500b) are supported by the pressing member (600). In the fixing device (100), when the pressure roller (300) is driven to rotate and the heating belt (200) is rotated, the pressing member (600) is supported by the reinforcing member (500b) along with the rotation. The part which is not present, especially the part located in the center in the length direction of the heating belt (200) bends in the rotation downstream direction as shown in FIG. 5 together with the holding member (500a). 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. Has a holding part along the nip formed by press-contacting the heating member and the pressure member, and the holding part in a state where both ends in the length direction of the heating member are supported. A holding means comprising a reinforcing portion that presses in the direction of the pressure member; and a heating source that heats the heating member in a non-contact manner with the holding means and the heating member, wherein the reinforcing portion is a bimetallic two-layer structure The fixing device is characterized in that, of the two layers, the layer facing the rotation downstream side of the heating member has a smaller thermal expansion coefficient than the layer facing the rotation upstream side of the heating member. About.

  According to the first aspect of the present invention, the heating member presses the holding portion in the direction of the pressure member in a state where the holding portion along the nip portion and the both end portions in the length direction of the heating member are supported on the inner side. A holding means including a reinforcing portion to be formed and a non-contact heating source are provided, and the reinforcing portion has a bimetal two-layer structure. Of those forming the two layers, the layer facing the downstream side of the rotation of the heating member has a smaller coefficient of thermal expansion than the layer on the upstream side of the rotation of the heating member. The layer facing the upstream side is larger in thermal expansion than the layer facing the rotation downstream side, and is the central portion of the reinforcing portion, that is, the central portion in the length direction of the heating member, and is not supported. It bends to the rotation upstream side of a heating member centering on a part. On the other hand, when the heating member rotates, inside the heating member, the portions other than the two unsupported ends of the reinforcing portion, in particular, the portion located at the center in the length direction of the heating member is the holding portion. At the same time, since it tries to bend to the downstream side of the rotation, both deflections interact with each other and cancel each other. As a result, the holding means does not substantially bend and 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 (1) according to the present invention.
The fixing device (1) according to this embodiment includes a heating belt (2) for heating and melting the toner (23) on the transfer paper (22), and the transfer paper (22) in pressure contact with the heating belt (2). A pressure roller (3) for nipping and 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 pressure roller (3).

  The reinforcing member (5b) is a rectangular plate-like member disposed between the two cylindrical heating sources (4) in a non-contact manner with both ends in the long side direction being not shown in the figure. It is supported by the member. The reinforcing member (5b) is arranged in the heating belt (2) so that the width (short side) direction thereof is substantially vertical, and the heating source (4) is heated by the fixing member (not shown). Further, the reinforcing member (5b) can be moved upward without contacting the heating source (4) because it is fixed so as not to be interlocked with the movement of the holding means (5).

  The configuration of the reinforcing member (5b) will be described with reference to FIG. FIG. 2 is a schematic view showing the structure of the reinforcing member (5b) according to the present embodiment. FIG. 2 (a) shows the reinforcing member (5b) before the driving rotation of the heating belt (2), and FIG. 2 (b) shows the reinforcing member (5b) after the driving rotation of the heating belt (2). The reinforcing member (5b) is made of a bimetal having a two-layer structure in which two metal plates having different thermal expansion coefficients are bonded together. The coefficient of thermal expansion indicates the rate at which the length / volume of an object expands with an increase in temperature per 1 K (° C.). Each layer of the reinforcing member (5b) of the present embodiment includes a low expansion layer (60b) having a small thermal expansion coefficient and a high expansion layer (70b) having a large thermal expansion coefficient. The low expansion layer (60b) is a heating belt ( It faces the downstream side of 2), and the high expansion layer (70b) faces the upstream side of the rotation. When the reinforcing member (5b) is heated by the heating source (4) after the driving rotation of the heating belt (2), the high expansion layer (70b) expands more than the low expansion layer (60b), and FIG. As shown in b), the reinforcing member (5b) bends downward particularly in the central part in the long side direction. 2A and 2B, the upper part of the reinforcing member 5b is the downstream side of the heating belt 2 and the lower side is the upstream side of the heating belt 2.

Here, the specific material of the reinforcing member (5b) of this embodiment comprised with a bimetal is demonstrated. Table 1 below shows the thermal expansion coefficient for each material. According to Table 1, the thermal expansion coefficient of aluminum is 23.0 (× 10 ⁻⁶ / ° C.), the thermal expansion coefficient of magnesium is 25.6 (× 10 ⁻⁶ / ° C.), The coefficient of thermal expansion is large compared to stainless steel, nickel, iron, copper and titanium. Therefore, aluminum or magnesium can be used for the high expansion layer (70b). For example, the combinations shown in Table 2 below can be cited as combinations of the low expansion layer (60b) and the high expansion layer (70b).

  Table 2 shows combinations of the low expansion layer (60b) and the high expansion layer (70b) of the reinforcing member (5b) according to the present embodiment. In Table 2, a combination in which the rotating downstream side of the heating belt (2) is made of stainless steel and the rotating upstream side is made of aluminum (Example 1), a rotating downstream side is made of iron, and a rotating upstream side is made of magnesium (Example 2). ) And a combination (example 3) in which the rotation downstream side is made of titanium and the rotation upstream side is made of aluminum. By using the bimetal by such a combination for the reinforcing member (5b), the reinforcing member (5b) can be deflected to the upstream side of the rotation of the heating belt (2) when heated. In addition, in the above, although the rectangular plate-shaped member was demonstrated as an example as a reinforcement member (5b), it is not restricted to this.

  Furthermore, as the holding member (5a) of the present embodiment, an appropriate nip portion (7) can be formed by receiving the pressing force from the reinforcing member (5b), and it is preferable that the holding member (5a) is somewhat elastic. Examples thereof include a spring-like stainless steel plate and a phosphor bronze plate.

  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).

  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.

  Further, the state of the reinforcing member (5b) and the holding member (5a) before and after driving rotation of the fixing device (1) according to the present embodiment will be specifically described with reference to FIG. FIG. 3 is a cross-sectional view of the fixing device shown in FIG. 1 cut along the line BB. FIG. 3A is a diagram illustrating a state before the driving rotation of the heating belt (2), and FIG. 3B is a diagram illustrating a state after the driving rotation. As shown in both figures, both ends of the reinforcing member (5b) are supported by the pressing member (6). In FIG. 3A, the heating source (4) does not heat the reinforcing member (5b), and the reinforcing member (5b) and the holding member (5a) are stationary at the inner center of the heating belt (2). Yes.

  On the other hand, in FIG.3 (b), since the heating source (4) is heating the reinforcement member (5b), the center part of the reinforcement member (5b), ie, the length of a heating belt (2), is heated. It bends to the upstream side of rotation around the center of the direction. On the other hand, due to the rotation of the heating belt (2), the portions other than both ends supported by the pressing member (6) of the reinforcing member (5b), particularly the central portion, rotate downstream together with the holding member (5a). Try to sway to the side. As a result, the deflections cancel each other out. Therefore, as shown in the figure, the reinforcing member (5b) and the holding member (5a) do not bend in any direction, and the inner center of the heating belt (2) is the same as before the driving rotation. Placed in.

  As described above, in the present embodiment, the reinforcing member (5b) has a bimetal structure, so that even when the pressure roller (3) is driven and rotated, as shown in FIG. 3 (b), the reinforcing member (5b) and The holding member (5a) is pressed in a good state at the nip portion (7) without being bent.

  Thus, since the holding means (5) composed of the reinforcing member (5b) and the holding member (5a) does not bend, the holding means (5) 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. It is the schematic which shows the structure of the reinforcement member which concerns on this embodiment. FIG. 2 is a cross-sectional view of the fixing device shown in FIG. 1 cut along a BB cutting plane line. FIG. 10 is a schematic diagram illustrating a configuration of a conventional fixing device. FIG. 5 is a cross-sectional view taken along the line AA of the fixing device shown in FIG. 4.

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 6 Pressing member 7 Nip part 60b Low expansion layer 70b High expansion layer

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 is held in a state where a holding portion along a nip portion formed by press-contacting the heating member and the pressure member and both ends in the length direction of the heating member are supported on the inner side. A holding means comprising a reinforcing portion that presses the portion in the direction of the pressure member, and a heating source that heats the heating member in a non-contact manner with the holding means and the heating member,
The reinforcing portion has a bimetal two-layer structure, and the layer facing the rotation downstream side of the heating member of the two layers has a smaller thermal expansion coefficient than the layer facing the rotation upstream side of the heating member. A fixing device having a structure.

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