JP2005043840A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent heat conducted from a fixing roller to a pressure roller from being diffused through a bearing for a pressure roller. <P>SOLUTION: The fixing device 10 has the fixing roller 11 incorporating a heating source and a pressure roller 12 made to be in press-contact with the fixing roller, and the pressure roller has a cylindrical core bar 12a, a bearing member 15 arranged in the core bar and turnably supporting the core bar on a shaft member 16 extended in the shaft direction of the core bar, and a heat resistant heat insulating member 14 disposed between the outer peripheral surface of the bearing member and the inner peripheral surface of the core bar. The heat resistant heat insulating member is formed of a material having a higher thermal expansion coefficient than that of the core bar and the bearing member. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fixing device that is used in an image forming apparatus such as a copying machine, a printer, or a facsimile machine, and fixes a toner image on a recording medium.

  Generally, a fixing device used in an image forming apparatus is provided with a heating roller and a pressure roller, and a toner image on a recording medium is thermally fixed by the heating roller and the pressure roller. In the apparatus, a heater is built in the heating roller, and the toner image is fixed by passing a recording medium between the heating roller and a pressure roller that presses the heating roller.

  By the way, bosses are formed at both ends of the heating roller, and bearings are provided on the bosses, and the heating roller is rotatably supported by the fixing device casing via the bearings. Driven at speed. During fixing, the heating roller is maintained at a high temperature by a heater. In order to maintain the heating roller at a high temperature, it is particularly necessary to prevent heat from being dissipated through the bearing.

  For this reason, for example, a heat-resistant heat-insulating bush is provided between the bearing provided on the boss portion of the fixing roller (heating roller) and the frame body supporting the bearing, and the radial cross section of the heat-resistant heat-insulating bush is L-shaped. As shown in the figure, the outer side of the inner circle of the heat-resistant heat-insulating bush is fitted with the frame, and the inner side of the inner circle is fitted with the bearing so that the heat of the fixing roller is prevented from leaking to the frame through the bearing. (See Patent Document 1).

Further, there is a mechanism in which bearings are provided on the bosses at both ends of the heating roller via heat insulating members, and a mechanism for prohibiting the sliding in the rotation direction with respect to the bosses of the heat insulating members is provided (see Patent Document 2).
Japanese Patent Laid-Open No. 5-80669 (paragraph (0010), FIG. 2) Japanese Patent Laid-Open No. 10-3223 (paragraph (0013) to paragraph (0015), FIGS. 2 and 3)

  As described above, in the conventional fixing device, in order to prevent heat from being dissipated from the heating roller to the fixing device housing or the like via the bearing, a heat insulating member is disposed on the boss portion. The heating roller is in contact with the pressure roller, and when heat is transmitted from the heating roller to the pressure roller side, a bearing (pressure roller bearing) that rotatably supports the pressure roller on the shaft member is provided. It cannot be ignored that the heat escapes.

  That is, in the pressure roller, bearings are press-fitted into both ends of the cylindrical metal core, and the shaft member is inserted into the bearing to rotatably support the pressure roller, and the shaft member is heated at both ends thereof. Pressing to the side. For this reason, the heat from the heating roller passes through the metal core and reaches the bearing and the shaft member, and the heat capacity of the pressure roller is increased accordingly.

  On the other hand, as described above, in the pressure roller, the bearing is press-fitted into both ends of the cylindrical metal core, the shaft member is inserted into the bearing, and the shaft member is pressed toward the heating roller at both ends. Therefore, there exists a subject that it is difficult to arrange | position a heat insulation member like patent document 1 or 2. FIG.

  In addition, in high-speed copiers and the like, it is necessary to increase the nip width between the heating roller and the pressure roller in order to ensure the fixing performance. However, if the nip width is widened, the heating roller and the pressure are inevitably increased. As a result, the amount of heat that moves from the heating roller side to the pressure roller side increases, and the heat from the heating roller escapes from the bearing and shaft member through the cored bar. End up. As a result, not only the so-called warm-up time is lengthened, but the temperature is lowered during continuous printing (copying).

  And in order to prevent the temperature drop at the time of continuous copying as described above, increasing the heat accumulation amount in the heating roller by increasing the thickness of the core of the heating roller further increases the warm-up time. Will end up.

  An object of the present invention is to provide a fixing device capable of preventing heat conducted from a heating roller to a pressure roller from being dissipated through a pressure roller bearing.

  According to the present invention, a fixing roller having a built-in heat source and a pressure roller pressed against the fixing roller are provided, and a toner image on a recording medium is recorded on the recording medium by the fixing roller and the pressure roller. In the fixing device for fixing to a medium, the pressure roller rotatably supports the cored bar on a cylindrical cored bar and a shaft member disposed in the cored bar and extending in the axial direction of the cored bar. A bearing member; and a heat resistant heat insulating member disposed between an outer peripheral surface of the bearing member and an inner peripheral surface of the core metal, wherein the heat resistant heat insulating member is a heat of the core metal and the bearing member. A fixing device characterized by being formed of a material having a thermal expansion coefficient higher than the expansion coefficient can be obtained.

  For example, the heat-resistant heat insulating member is a resin having a heat resistance higher than a fixing temperature, the heat-resistant heat insulating member is cylindrical, and the outer peripheral surface of the heat-resistant heat insulating member is the outer periphery of the bearing member. It is positioned between the surface and the inner peripheral surface of the cored bar.

  In the present invention, it is preferable that the heat-resistant heat insulating members are respectively disposed at both ends of the core metal, and the heat-resistant heat insulating members form notches extending in the axial direction of the core metal.

  Furthermore, the heat-resistant heat insulating member has a restricting portion that restricts movement of the bearing member in the axial direction of the metal core, and the restricting portion is, for example, a shaft of the metal core of the heat-resistant heat insulating member. The flange body is formed at the inner end in the direction and protrudes inward in the radial direction.

  Moreover, in this invention, it has the rotation prevention mechanism which prevents the relative rotation with respect to the said core metal of the said heat resistant heat insulation member around the axial direction of the said metal core, This rotation prevention mechanism is the said core, for example A groove formed on the outer peripheral surface of the gold and extending in the axial direction from the axial end; and a locking body formed on the outer peripheral surface of the heat-resistant heat insulating member and extending in the axial direction from the outer end in the axial direction and projecting radially outward. And the locking body is inserted into the groove.

  In the fixing device of the present invention, the heat-resistant heat insulating member is disposed between the outer peripheral surface of the bearing member that rotatably supports the pressure roller on the shaft member and the inner peripheral surface of the core metal of the pressure roller. It is possible to prevent heat conducted from the roller (heating roller) to the pressure roller from being dissipated through the bearing member. As a result, the thickness of the core metal of the fixing roller can be reduced, the warm-up time can be shortened, and the balance of the fixing roller surface temperature distribution can be improved.

  In addition, since the heat-resistant heat insulating member is formed of a material having a thermal expansion coefficient higher than that of the cored bar and the bearing member, the heat-resistant heat insulating member is heated by the heat of the fixing roller during fixing. Since it expand | swells greatly, the adhesiveness of a metal core and a bearing member and a heat-resistant heat insulation member will become very favorable, and will be in the same level as press-fit.

  Further, in the fixing device according to the present invention, the heat-resistant heat insulating members are disposed at both ends of the cored bar, and the heat-resistant heat-insulated member is formed with a notch extending in the axial direction of the cored bar. When the member and the bearing member are mounted on the cored bar, a process such as press fitting is not necessary.

  The fixing device includes a fixing roller having a built-in heating source and a pressure roller pressed against the fixing roller. The toner image on the recording medium is fixed to the recording medium by the fixing roller and the pressure roller. The The pressure roller includes a cylindrical cored bar, and an elastic layer is formed on the outer peripheral surface of the cored bar. A bearing member is disposed in the cored bar, and the cored bar is rotatably supported by a shaft member extending in the axial direction of the cored bar by the bearing member. A heat-resistant heat insulating member is disposed between the outer peripheral surface of the bearing member and the inner peripheral surface of the core metal, and the heat-resistant heat insulating member is a material having a thermal expansion coefficient higher than that of the core metal and the bearing member. Formed with.

  This heat-resistant heat insulating member is a resin having heat resistance higher than the fixing temperature, the heat-resistant heat insulating member is cylindrical, and the outer peripheral surface of the heat-resistant heat insulating member is the outer peripheral surface of the bearing member and the inner peripheral surface of the cored bar. Positioned between the faces. And a heat-resistant heat insulation member is each arrange | positioned at the both ends of a metal core, and the notch extended in the axial direction of a metal core is formed. A flange body projecting radially inward is formed at the axially inner end of the core of the heat-resistant heat insulating member, and this flange body prevents the bearing member from moving inward of the core.

  A groove extending in the axial direction from the axial end is formed on the outer peripheral surface of the core metal, and a locking body extending in the axial direction from the outer end in the axial direction is formed on the outer peripheral surface of the heat-resistant heat insulating member. Then, the locking body is inserted into the groove, and thereby, the relative rotation around the axial direction of the heat-resistant heat insulating member with respect to the cored bar is prevented.

  Embodiments of the present invention will be described below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this example are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.

  FIG. 1 is a side view showing an example of a fixing device according to the present invention. The illustrated fixing device 10 is used in an image forming apparatus to fix a toner image transferred onto a recording paper (recording medium). Used. The fixing device 10 includes a heating roller (fixing roller) 11 having a built-in heater (heating source: not shown), and a pressure roller 12 is pressed against the fixing roller 11.

  Referring also to FIG. 2, the fixing roller 11 has a cylindrical cored bar (for example, aluminum) 11a, and bosses 11b are formed at both ends of the cored bar 11a. The bossed part 11b is a bearing 11c. And is rotatably supported by the fixing device housing (support) 13 and is controlled to rotate at a predetermined rotational speed by a drive source (not shown). A heat-resistant release material 11d is formed on the surface of the metal core 11a with a uniform thickness, and a bearing 11c is attached to the boss portion 11b via a heat insulating material, for example.

  On the other hand, the pressure roller 12 has a cylindrical cored bar (for example, aluminum) 12a, and the outer peripheral surface of the cored bar 12a has a uniform thickness, leaving a little axial end. An elastic body layer 12b is formed. A substantially cylindrical bush (heat-resistant heat insulating member) 14 is inserted into both ends of the core metal 12a, and the outer peripheral surface of the bush 14 is in contact with the inner peripheral surface of the core metal 12a.

  Bearings (iron: bearings for pressure rollers) 15 are disposed in the bushes 14, and shaft members 16 are inserted between the bearings 15 so that the cored bar 12 a is rotatably supported with respect to the shaft members 16. ing.

  As shown in FIG. 1, both end portions (only one end portion is shown in FIG. 1) of the shaft member 16 are supported by a shaft support frame member 17, and the shaft support support member 17 is attached. A biasing member (a tension spring member) 18 is biased upward in FIG. 1, whereby the shaft member 16 is pushed upward, and the pressure roller 12 presses the fixing roller 11.

  Referring to FIG. 2 again, the above-described bush 14 is made of, for example, a heat insulating resin and has a heat resistance of at least a fixing temperature (for example, about 200 ° C.), and heat of the core metal 12 a and the bearing 15. It has a higher thermal expansion coefficient than the expansion coefficient.

  Referring also to FIGS. 3A to 3D, the first flange portion 14a formed along the outer peripheral end and extending radially outward is formed on one end side (the axially outer end in FIG. 2) of the bush 14. Is formed. Further, a second flange portion (flange body) 14b is formed on the other end side (the axially inner end in FIG. 2) of the bush 14 along the outer peripheral end and extending radially inward.

  As shown in FIGS. 3B and 3C, a notch 14c extending in the axial direction is formed on the outer peripheral surface of the bush 14, and the bush 14 is inserted into the cored bar 12a (FIG. 1) by the notch 14c. The outer periphery of the bush 14 is shortened by the amount of the notch 14c, and the outer peripheral surface of the bush 14 presses the inner peripheral surface of the core metal 12a by the restoring force of the bush 14. It closely contacts the inner peripheral surface of 12a.

  The bearing 15 (see FIG. 3D) is inserted into one end side of the bush 14 (the side where the first flange portion 14a is formed) until it abuts against the second flange portion 14b, and is disposed in the bush 14. The The second flange portion 14b prevents the bearing 15 from moving inward in the axial direction. The outer diameter of the bearing 15 is approximately the same as or slightly smaller than the inner diameter of the bush 14, and as a result, the bearing 15 can be inserted into the bush 14 very easily.

  The bush 14 is inserted into the cored bar 12a from the other end side (the side where the second flange part 14b is formed) until the first flanged part 14a contacts the side end of the cored bar 12a (first flanged part). 14a defines the amount of insertion of the bush 14 into the cored bar 12a). Thereby, the outer diameter of the bush 14 is slightly larger than the inner diameter of the core metal 12a. When the bush 14 is inserted into the core metal 12a, the bush 14 is pushed by the core metal 12a in the direction in which the notch 14c is closed, and the bush 14 is easily 14 can be inserted into the cored bar 12a.

  4 (a) is a side view showing a part of the pressure roller 12, and FIG. 4 (b) is a side sectional view showing a part of the pressure roller 12, as shown in FIGS. 4 (a) and 4 (b). Thus, the core metal 12a is formed with a groove 21 extending in the axial direction from the outer end thereof. On the other hand, as shown in FIG. 3A, the bush 14 has one end side (the first flange portion 14a has a first flange portion 14a). A locking piece 22 is formed which extends along the outer peripheral surface in the axial direction from the formed side) and protrudes outward in the radial direction. As described above, when the bush 14 is inserted into the cored bar 12a, The locking piece 22 is inserted into the groove 21 described above, thereby preventing the rotation of the bush 14 around the axis relative to the cored bar 12a.

  As shown in FIG. 2, when the bush 14 and the bearing 15 are mounted on the cored bar 12a, the axially outer end of the bushing 14 is positioned at a position that substantially coincides with the extension line of the axially outer end of the release material 11d. It is done. As a result, the axially outer end of the elastic body layer 12b is positioned more inside than the axially outer end of the release material 11d.

  As shown in FIG. 2, the axial length of the release material 11d of the fixing roller 11 is longer than the maximum recording paper (for example, A3 size), and the length indicated by the alternate long and short dash line is A3 size recording paper. Then, the length of the elastic layer 12b is also longer than that of the A3 size recording sheet. That is, the interval indicated by the alternate long and short dash line is a path through which the A3 size recording sheet passes. Further, the outer end face in the axial direction of the bearing 15 is positioned at a position substantially coincident with the extension line of the outer end in the axial direction of the elastic layer 12b.

  When fixing is performed using the above-described fixing device, if the fixing roller 11 is heated, heat is conducted from the fixing roller 11 to the pressure roller 12 side, but the bush 14 is a heat-resistant heat insulating material. Therefore, the heat conduction to the bearing 15 is extremely small, and the heat escape to the shaft member 16 through the bearing 15 is extremely small.

  Moreover, as described above, since the thermal expansion coefficient of the bush 14 is higher than the thermal expansion coefficient of the core metal 12a and the bearing 15, the bush 14 is in close contact with the core metal 12a and the bearing 15 due to the expansion of the bush 14, and press-fitted. It will be almost the same state as.

  As described above, when the bush 14 and the bearing 15 are mounted on the cored bar 12a, it is not necessary to perform a process such as press-fitting. However, when fixing is performed (that is, when the fixing roller 11 is heated), substantially. Therefore, the relationship between the core 12a, the bush 14 and the bearing 15 can be maintained well.

  Now, PPS resin is used as the material of the bush 14, the diameter of the shaft member 16 is φ10 mm, the diameter of the pressure roller 12 is 40 mm, the thickness of the core metal 12a is 1 mm, the elastic layer (non-conductive silicon rubber layer with PFA) Fixing was performed using a conductive PFA coat layer as the release material 11d, with the thickness of the layer formed) being 5 mm, the diameter of the fixing roller 11 being 55 mm, the thickness of the cored bar 11a being 1 mm, This example is hereinafter referred to as an experimental example).

  For comparison, fixing was performed using a bearing 15 that was press-fitted into the core metal 12a without using the bush 14 (hereinafter, this example is referred to as Comparative Example 1. In Comparative Example 1, other parts are used. Is the same as the experimental example).

  Further, in Comparative Example 1, fixing was performed with the thickness of the cored bar 11a of the fixing roller 11 being 5.5 mm (hereinafter, this example is referred to as Comparative Example 2. In Comparative Example 2, the other portions are the same. The same as in Comparative Example 1). In both the experimental row and Comparative Examples 1 and 2, the fixing device was mounted on a digital copying machine at a roller peripheral speed of 388 mm / sec, and the surface temperature of the fixing roller was measured. The result is shown in FIG.

  In FIG. 5, the solid line indicates an experimental example, the broken line indicates Comparative Example 1, and the alternate long and short dash line indicates Comparative Example 2. Further, in FIG. 5, the vertical axis represents the fixing roller surface temperature (temperature (° C.)), and the horizontal axis represents the measurement point. The fixing roller 11 and the pressure roller 12 extend from the front side (front side) to the rear side (rear side) of the copying machine. The central position of the fixing roller 11 in the axial direction is the center, and 150 mm from the center to the front side. The surface temperature of the fixing roller 11 was measured at a position up to 150 mm from the center to the rear side, and the surface temperature was measured when the control temperature was reached.

  As can be easily understood from FIG. 5, in the experimental example, it is understood that the variation in the surface temperature of the fixing roller is extremely small, and the temperature difference between the central portion and the front and rear sides is small. In other words, in the experimental example, the balance in the axial direction of the fixing roller surface temperature was little lost and good fixing could be performed.

  This means that when heat is conducted from the fixing roller 11 to the pressure roller 12, the heat that escapes to the shaft member 16 via the bearing 15 by the bush 14 is extremely reduced, and as a result, the axial change in the surface temperature of the fixing roller is reduced. It means you can do less.

  On the other hand, in Comparative Example 1, the surface temperature difference between the central portion of the fixing roller 11 and the front side and the rear side is extremely large (the axial balance of the fixing roller surface temperature is greatly lost), and the fixing performance is deteriorated. Similarly, in Comparative Example 2, although the balance in the axial direction of the fixing roller surface temperature is not much larger than that in Comparative Example 1, the balance is more greatly disrupted than in the experimental example, and the fixing performance is affected to some extent.

  In Comparative Example 2, although the thickness of the core metal 11a is made thicker than that in Comparative Example 1, the balance of the fixing roller surface temperature in the axial direction is less disrupted, but the thickness of the core metal 12a must be increased. Not only does this increase the cost, but the weight also increases.

  In the experimental example, although the core bar 11a is thinner than the comparative example 2, the balance in the axial direction of the fixing roller surface temperature is very little, and as a result, cost reduction and weight reduction can be achieved.

  Further, in the above experimental example and comparative examples 1 and 2, the center position in the axial direction of the fixing roller 11 is the central position, the position 150 mm from the center to the front side is the front position, and the position 150 mm from the center to the rear side is the rear position. As the position, the time required to reach the control temperature at each of these three points was measured. The result is shown in FIG.

  In FIG. 6, the vertical axis represents temperature (° C.) and the horizontal axis represents time (sec). (1) is the temperature change at the center position in the experimental example and the comparative example 1, (2) is the temperature change at the front position in the comparison row 1, (3) is the temperature change at the rear position in the comparative example 1, (4) Is the temperature change at the front position in the experimental example, (5) is the temperature change at the rear position in the experimental example, (6) is the temperature change at the central position in the comparative example 2, and (7) is the temperature change at the front position in the comparative row 2. , (8) are temperature changes at the rear position in Comparative Example 2.

  As can be easily understood from FIG. 6, in the experimental example and the comparative example 1, there is almost no difference in the time to reach the control temperature (that is, the warm-up time), but at the front position and the rear position, However, the warm-up time is slightly shorter than in Comparative Example 1. Moreover, about the comparative example 2, it turns out that warm-up time is long.

  In this way, in the experimental example, the thickness of the cored bar 11a is thin, and the heat that escapes to the shaft member 16 via the bearing 15 by the bushing 14 is extremely small. Therefore, especially in the front position and the rear position, Becomes shorter.

  As described above, the experimental example is superior to the comparative examples 1 and 2 in terms of the balance of the fixing roller surface temperature and the warm-up time, and the thickness of the cored bar 11a can be reduced.

  In the above-described embodiment, the PPS resin is used as the bush (heat-resistant heat insulating member) 14. For example, instead of the PPS resin, a polyamideimide (PAI) resin or a polyethylketone (PEK) resin is used. Also good. Furthermore, the thickness of the bush 14 is at least about the same as the thickness of the core metal 12a of the pressure roller 12 in consideration of durability and heat insulation. When the thickness of the core metal 12a is 1 mm, The thickness of the bush 14 is 1 mm to 5 mm.

  In the fixing device, a heat-resistant heat insulating member is disposed between the outer peripheral surface of the pressure roller bearing and the inner peripheral surface of the core member of the pressure roller so that the heat-resistant heat insulating member is thermally expanded between the metal core and the bearing. Because it is made of a material having a thermal expansion coefficient higher than the rate of heat, the heat conducted from the fixing roller to the pressure roller when used in an image forming apparatus such as a copying machine, printer, or facsimile machine is heat-resistant The member can be prevented from escaping to the bearing side, the warm-up time of the fixing device can be shortened, and the surface temperature distribution of the fixing roller can be kept in a well-balanced manner, which can be applied to good fixing.

FIG. 2 is a side view illustrating an example of a fixing device according to the present invention. FIG. 3 is a diagram illustrating a fixing roller and a pressure roller, with the pressure roller partially broken. It is a figure which shows an example of the bush and bearing used by this invention, (a) is the figure which looked at the bush from the side, (b) is the figure which looked at the bush from the axial direction outer side, (c) is the side of the bush Sectional drawing, (d) is a side sectional view of the bearing. It is a figure which shows an example of the pressure roller by this invention, (a) is the figure which shows the part from the side, (b) is the partial sectional view of the part. FIG. 7 is a diagram illustrating measurement results of fixing roller surface temperature distributions of an example of a fixing device according to the present invention and a comparative example. It is a figure which shows the warm-up time of an example of the fixing device according to the present invention and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Fixing roller 11d Release material 12 Pressure roller 11a, 12a Core metal 11b Boss part 13 Fixing device housing | casing (support body)
12b Elastic layer 14 Bush (heat-resistant heat insulating member)
11c, 15 Bearing 16 Shaft member 17 Shaft support frame member 18 Biasing members 14a, 14b Flange portion 14c Notch 21 Groove 22 Locking piece

Claims (9)

A fixing roller having a built-in heat source; and a pressure roller pressed against the fixing roller, the toner image on the recording medium being fixed to the recording medium by the fixing roller and the pressure roller. In the fixing device,
The pressure roller includes a cylindrical cored bar, a bearing member disposed in the cored bar and rotatably supported on a shaft member extending in the axial direction of the cored bar, and an outer peripheral surface of the bearing member. A heat-resistant heat insulating member disposed between the inner peripheral surface of the cored bar,
The fixing device according to claim 1, wherein the heat resistant heat insulating member is formed of a material having a thermal expansion coefficient higher than that of the core metal and the bearing member.   The fixing device according to claim 1, wherein the heat-resistant heat insulating member is a resin having heat resistance higher than a fixing temperature.   The heat-resistant heat insulating member has a cylindrical shape, and an outer peripheral surface of the heat-resistant heat insulating member is positioned between an outer peripheral surface of the bearing member and an inner peripheral surface of the core metal. Or the fixing device according to 2.   The fixing device according to claim 3, wherein the heat-resistant heat insulating members are respectively disposed at both ends of the cored bar.   The fixing device according to claim 4, wherein the heat-resistant heat insulating member has a notch extending in an axial direction of the cored bar.   The fixing device according to claim 4, wherein the heat-resistant heat insulating member includes a restricting portion that restricts movement of the bearing member in the axial direction of the cored bar.   The fixing device according to claim 6, wherein the restricting portion is a flange body that is formed at an axially inner end of the core metal of the heat resistant heat insulating member and protrudes radially inward.   The fixing device according to claim 4, further comprising an anti-rotation mechanism that prevents relative rotation of the heat-resistant heat insulating member with respect to the core around the core of the core. The rotation prevention mechanism is formed on the outer peripheral surface of the cored bar and extends in the axial direction from the axial end portion, and is formed on the outer peripheral surface of the heat-resistant heat insulating member and extends in the axial direction from the axial outer end and radially outward. A protruding locking body,
The fixing device according to claim 8, wherein the locking body is inserted into the groove portion.

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