JP2006126421A - Roller unit and fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roller unit in which a wire rod is prevented from being pulled out and its wind pitch will not vary. <P>SOLUTION: The metal core 124 of a fixing roller 10 has, in its hollow part, the wire rod 12 inserted extending in the lengthwise direction (in the direction of the arrow L) of the metal core 124 and having a length almost equal to that of the metal core 124. A pair of annular parts 14 are formed at both ends of the wire rod 12 in the lengthwise direction of the metal core 124 so as to press the internal wall face of both the ends of the metal core in the lengthwise direction. Each of the annular part 14 comprises a plurality of annuli 14a which are in close contact with each other. The annular parts 14 are formed only at both the longitudinal ends of the metal core 124. The pair of annular parts 14 at both the ends are connected to each other by a connecting part 16, extending in the direction of the arrow L in contact with the internal wall face of the metal core 124. The linear member 12 is formed by suitably bending one wire rod. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a roller unit that conveys a recording medium while being held between other rollers, and a fixing device using the roller unit.

  2. Description of the Related Art As an output device for a computer or workstation, an electrophotographic image forming apparatus that forms an image on a recording medium using a powder developer (toner) is known. In such an image forming apparatus, for example, an image bearing member such as a photosensitive drum is irradiated with light carrying image information (for example, laser light) to form an electrostatic latent image, and a developing roller is applied to the electrostatic latent image. The toner is supplied to form a developed image, and the developed image is transferred to a recording medium using a transfer roller or the like to form a transferred image (developed image). The recording medium on which the transfer image is formed is conveyed to a fixing device, and the transfer image is fixed on the recording medium in the fixing device. The fixing device is usually provided with a fixing roller having a built-in heater and a pressure roller in pressure contact with the fixing roller. When the transfer image is fixed on the recording medium, the transfer image is heated and pressed at a predetermined fixing temperature while the recording medium is nipped and conveyed by the fixing roller and the pressure roller. The transfer image is fixed on the recording medium by this heating and pressurization. The recording medium on which the transferred image is fixed is discharged while being sandwiched between discharge rollers or the like.

  The fixing device will be described with reference to FIG.

  FIG. 14 is a schematic diagram illustrating a schematic configuration of a conventional fixing device.

  The fixing device 100 is for making a toner (image) 102 a permanent visible image on a recording medium 104 such as recording paper. The recording medium 104 conveyed in the direction of arrow A by a conveyance unit (not shown) is guided by the fixing inlet guide 106 and enters the nip portion 108 between the fixing roller 120 and the pressure roller 130.

  The fixing roller 120 is for heating and melting the toner 102. The thermistor 140 is in contact with the outer peripheral surface (front surface) of the fixing roller 120, and the thermistor 140 is configured to measure the temperature of the outer peripheral surface of the fixing roller 120. Further, the fixing roller 120 incorporates a heat source (a heating element) such as a halogen heater 122. A controller (not shown) controls the halogen heater 122 based on the outer peripheral surface temperature measured by the thermistor 140, whereby the outer peripheral surface temperature of the fixing roller 120 is maintained at a predetermined fixing temperature.

  As the fixing roller 120, for example, an outer peripheral surface of a cored bar 124 made of, for example, an iron or aluminum pipe is coated with a fluororesin layer 126 having good releasability. The fixing roller 120 is rotated in the direction of arrow B by a drive source (not shown).

  The pressure roller 130 is for pressing the recording medium 104 against the fixing roller 120 with a predetermined pressure. As the pressure roller 130, for example, an outer peripheral surface of a metal core 132, for example, covered with an elastic body layer 134 such as silicone rubber or fluororubber with a predetermined thickness is generally used. While pressing the pressure roller 130 against the fixing roller 120 with a predetermined pressure and rotating it in the direction of arrow C, a load for fixing the toner 102 to the recording medium 104 is applied.

  When the recording medium 104 enters the nip portion 108 (ie, is sandwiched by the nip portion 108), the toner 102 on the recording medium 104 is melted at the fixing temperature and the melted toner 102 is loaded with the load. The recording medium 104 is pressed and fixed to the recording medium 104. The recording medium 104 on which the toner 102 is fixed is separated from the fixing roller 120 by a separation claw 142 and reaches a paper discharge roller (not shown), and is discharged out of the apparatus by the paper discharge roller.

  The above-described fixing roller 120 is required to rise quickly from the viewpoint of shortening the waiting time. For this reason, there is an image forming apparatus in which the time (rise time) from when the image forming apparatus main body is completely cooled to when the main switch is turned on and when the first copy is discharged is 30 seconds or less. This rise time is getting shorter year by year.

  Further, from the viewpoint of energy saving, it is required to reduce power consumption for warming the fixing device as much as possible in a standby state in which the main switch of the image forming apparatus main body is turned on. For this reason, in the above standby state, it is necessary to completely turn off the heater of the fixing device. Thus, when the heater of the fixing device is completely turned off in the standby state, in order to bring the surface of the fixing roller to a predetermined temperature almost at the same time when the heater is turned on, the thickness of the fixing roller is reduced and the heat capacity is reduced. It needs to be small. For this reason, a fixing roller made of a thin aluminum alloy having a good thermal conductivity is often used.

  In order to shorten the above-described rise time, the thickness of the fixing roller 120 made of aluminum has recently been reduced to about 0.8 mm. When the thickness of the fixing roller 120 is further reduced, the fixing is performed when the recording medium 104 is sandwiched between the fixing roller 120 and the pressure roller 130 (nip portion 108) and the developed image is fixed with heat and pressure. The roller 120 may be deformed.

  In order to solve the above problems, a technique has been proposed in which a helical coil spring is inserted into the fixing roller 120 to reinforce the fixing roller 120 (see, for example, Patent Document 1).

  This technique will be described with reference to FIGS.

  FIG. 15 is a cross-sectional view showing the fixing roller into which the coil spring is inserted. FIG. 16 is a schematic view showing a coil spring that has come out of the core metal. FIG. 17 is a cross-sectional view showing a cored bar on which a stopper is formed. FIG. 18 is a cross-sectional view showing a coil spring with a varying winding pitch. In these drawings, the same components as those shown in FIG. 14 are denoted by the same reference numerals.

  As shown in FIG. 15, a coil spring 150 wound spirally is inserted into the inner space of the cored bar 124. The coil spring 150 extends in the longitudinal direction of the cored bar 124 and contacts the inner peripheral surface of the cored bar 124 to press the inner peripheral surface. Since the cored bar 124 is very thin, the pressing force received by the outer peripheral surface of the fixing roller 120 also affects the coil spring 150. For this reason, when the fixing roller 120 starts to rotate and the pressure roller 130 starts to rotate, the pressed fixing roller 120 and the coil spring 150 begin to move slightly in the longitudinal direction thereof. In this case, the movement of the fixing roller 120 is suppressed by a roller stopper (not shown). However, since the coil spring 150 is only inserted into the fixing roller 120, the coil spring 150 gradually moves in the direction of the arrow D to move the core. It begins to escape from the gold 124 (see FIG. 16). When the fixing roller 120 and the pressure roller 130 continue to rotate, the coil spring 150 falls off the core metal 124.

Therefore, as shown in FIG. 17, a technique has been proposed in which stoppers 124 a are formed at both ends in the longitudinal direction of the cored bar 124 so that the coil spring 150 does not come out of the cored bar 124.
JP-A-10-116675

  However, in the technique shown in FIG. 17, the coil spring 150 does not come out of the core metal 124, but as shown in FIG. 18, the coil spring 150 may move inside the core metal 124 and the winding pitch may vary. . When the winding pitch of the coil spring 150 varies in this way, the strength for reinforcing the core metal 124 varies in the longitudinal direction of the core metal 124 and the nip pressure changes, so that the recording medium is skewed. Further, since the heat capacity is larger in the “dense” part of the winding pitch than in the “sparse” part, the change in the entire surface temperature of the fixing roller 120 is not uniform. As a result, inconveniences such as poor fixing and temperature control become difficult.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a roller unit in which a wire does not come out and the winding pitch does not vary, and a fixing device incorporating the roller unit.

In order to achieve the above object, the roller unit of the present invention comprises:
(1) a hollow cylindrical roller;
(2) The hollow portion of the cylindrical roller extends in the longitudinal direction and is approximately the same length as the cylindrical roller, and the inner wall surfaces of both ends in the longitudinal direction of the cylindrical roller are pressed outward. And a wire rod formed with a pair of annular portions on both ends,
(3) The pair of both-end annular portions are respectively
(3-1) A pitch angle formed by an orthogonal direction perpendicular to the longitudinal direction of the cylindrical roller and the diameter direction of the both end annular portions is α, and the inner wall surface of the cylindrical roller and the inner ends of the both end annular portions are When the coefficient of dynamic friction with the part in contact with the wall surface is μv and the coefficient of correction of the coefficient of dynamic friction is ξ,
(3-2) α <tan ⁻¹ (μv) or α <tan ⁻¹ (ξμv) is satisfied.

here,
(4) In the wire, an intermediate annular part having the same shape as the annular part at both ends may be formed between the pair of annular parts at both ends.

Also,
(5) The wire is formed with a plurality of connecting portions extending in the longitudinal direction of the cylindrical roller, which connect adjacent ones of the both-end annular portion and the intermediate annular portion,
(6) Each of the plurality of connection portions may be formed at different positions in the circumferential direction of the cylindrical roller.

further,
(7) The connecting portion may be separated from the inner wall surface of the cylindrical roller.

Furthermore,
(8) The wire has a coefficient of thermal expansion greater than that of the cylindrical roller, and
(9) The outer diameter of the annular portions at both ends may be smaller than the inner diameter of the cylindrical roller.

Furthermore,
(10) The wire has a coefficient of thermal expansion greater than that of the cylindrical roller, and
(11) The outer diameters of the both end annular portions and the intermediate annular portion may be smaller than the inner diameter of the cylindrical roller.

Furthermore,
(12) The wire may be composed of a plurality of divided partial wires.

Furthermore,
(13) Each of the annular portions at both ends may be formed by a plurality of rings in close contact with each other.

Furthermore,
(14) The both-end annular portion and the intermediate annular portion may be formed by close contact of a plurality of rings.

Furthermore,
(15) The pitch angle of the annular portions at both ends may be approximately 0 degrees.

Furthermore,
(16) The pitch angle of both the annular portions at both ends and the intermediate annular portion may be approximately 0 degrees.

In order to achieve the above object, a fixing device of the present invention includes a fixing roller having a heat source disposed therein and a pressure roller pressed against the fixing roller, and performs recording between the fixing roller and the pressure roller. In a fixing device for conveying an image while pinching the medium and fixing an image on the recording medium,
(17) The cylindrical roller described above is used as the fixing roller.

  Here, the pitch angle of the present invention will be described with reference to FIGS.

  10A and 10B schematically show the pressing force that the fixing roller receives from the pressure roller during operation of the conventional fixing device. FIG. 10A is a front view, and FIG. 10B is a side view. FIG. 11 is a schematic diagram showing the deformation of the outer peripheral wall of the fixing roller when the strength of the fixing roller is lowered. 12 is a cross-sectional view showing the fixing roller of FIG. FIG. 13 is a schematic diagram showing the stress that the coil spring receives from the fixing roller when the pressure roller rotates.

  Normally, the pressure roller 130 (see FIG. 14) or the fixing roller 120 is manufactured in an inverted crown shape. For this reason, when the fixing roller 120 is pressed by the pressure roller 130, the applied pressure f slightly changes from both longitudinal ends of the fixing roller 120 to the center. However, in the nip portion 108 (see FIG. 14), it is considered that a load (pressing force f) having a substantially equal distribution is applied to the fixing roller 120 from the pressure roller 130.

  During the operation of the fixing device, the fixing roller 120 and the coil spring 150 receive radiant heat from the heater 122 (see FIG. 14) built in the fixing roller 120, so that their rigidity is reduced to some extent. Since the fixing roller 120 is thin, due to the reduction in rigidity, as shown in FIGS. 11 and 12, in the vicinity of the portion where the coil spring 150 is in contact with the inner peripheral surface of the fixing roller 120. A slightly projecting deformation 120a occurs. Such a deformation 120 a is spirally generated on the entire circumference of the fixing roller 120. Therefore, the direction of the stress (acting force) that the coil spring 150 receives from the fixing roller 120 with the rotation of the fixing roller 120 and the pressure roller 130 is regulated to some extent in the pitch angle direction of the coil spring 150. Further, since the coil spring 150 is not fixed inside the fixing roller 120, when the pressing roller 130 presses the fixing roller 120 and the coil spring 150 is bent (deformed), the fixing roller 120 and the coil A gap is formed between the spring 150 and the spring 150. When the gap is generated as described above, the diameter of the coil spring 150 is repeatedly reduced and enlarged in accordance with the rotation of the fixing roller 120, and the coil spring 150 freely rotates inside the fixing roller 120. . As a result, the coil spring 150 moves inside the fixing roller 120 due to the influence of the acting force accompanying the rotation of the pressure roller 130.

  During this movement, the fixing roller 120 deforms (bends) due to the radiant heat received from the heater 122, so that the inner peripheral wall of the fixing roller 120 and the coil spring 150 form a screw pair. For this reason, the coil spring 150 moves in the longitudinal direction depending on the winding direction of the coil spring 150 like a screw motion inside the fixing roller 120.

  The force (acting force) that the coil spring 150 receives from the fixing roller 120 when the pressure roller 130 rotates will be described. In FIG. 13, it is shown that the acting force is acting only on one point of the coil spring 150 that is in contact with the inner wall surface of the fixing roller 120 (supporting portion). The entire circumference of the spring 150 is acting.

  First, the force acting on the entire circumference of the support portion corresponding to one turn of the coil spring 150 is examined. As shown in FIG. 13, the force Fx in the rotation axis direction of the fixing roller 120 acting on the coil spring 150 by the pressing force from the pressure roller 130 is

Fx = F · sin α (1)
It becomes. Here, Fx is an acting force in the direction of the rotation axis of the fixing roller 120, and F is an acting force acting on the support portion of the coil spring 150 from the inner wall surface of the fixing roller 120. Α is a pitch angle of the coil spring 150. The frictional force Ff represented by the equation (2) acts in the direction that prevents the coil spring 150 from moving with respect to the acting force represented by Fx. Note that Fy is an acting force in a direction orthogonal to the rotation axis direction of the fixing roller 120.

Ff = μs · F · cos α (2)
Or

      F′f = μv · F · cos α

(3)
Here, μs is a static friction coefficient indicating the magnitude of the static friction force acting on the inner wall surface of the fixing roller 120 and the support portion. μv is a dynamic friction force coefficient represented by Coulomb friction force and viscous friction force. In general, μs> μv, the static frictional force acts at the moment when the coil spring 150 moves inside the fixing roller 120, and the dynamic frictional force is when the coil spring 150 moves inside the fixing roller 120. Works. Therefore, from the equations (1), (2), (3)
The condition for preventing the coil spring 150 from moving inside the fixing roller 120 is expressed by Equation (4).

F'f> Fx (4)
Therefore, the pitch angle α of the coil spring 150 that satisfies Expression (4) is expressed by Expression (5).

α <tan ⁻¹ (μv) (5)

  Here, one turn of the coil spring 150 was examined. However, as described above, it is considered that the fixing roller 120 receives a load having a distribution almost equal to the longitudinal direction of the coil spring 150 with respect to the pressing force from the pressure roller 130. It receives a pressing force evenly at any position. This condition is established as a condition that the entire coil spring 150 does not move. Therefore, by forming the pitch angle α of the coil spring 150 so as to satisfy the condition of the formula (5), the coil spring 150 does not move inside the fixing roller 120.

  As can be seen from the above, the movement of the coil spring 150 does not depend on the force acting on the support portion of the coil spring 150, and the friction acting between the support portion of the coil spring 150 and the inner wall surface of the fixing roller 120. Depends on the coefficient.

  Strictly speaking, the pressing force by the pressure roller 130 becomes maximum at the nip portion 108. However, this pressing force causes the coil spring 150 inside the fixing roller 120 to be deformed (bent) with respect to the pressing direction, and the diameter of the coil spring 150 becomes gentler toward the portion where the relative angle forms 90 degrees with respect to the pressing direction. Expand to. That is, the entire shape of the coil spring 150 becomes an elliptical shape by the pressing force from the pressure roller 130. At this time, the deformation amount (deflection amount) in the nip portion 108 is different from the deflection amount at a portion where the relative angle forms 90 degrees with respect to the pressing direction. As a result, the support portion of the coil spring 150 does not necessarily receive a uniform frictional force on the entire circumference. Therefore, an equation (6) in which the pitch angle α is corrected by adding an empirical correction coefficient ξ to the friction coefficient of the friction force acting on the coil spring 150.

α <tan ⁻¹ (ξμv) Equation (6)
May be used.

  In the present invention, a wire formed so as to have a pitch angle α satisfying the condition of Expression (5) or Expression (6) is inserted into, for example, a fixing roller (an example of a cylindrical roller in the present invention). The rigidity of the fixing roller is ensured without moving the wire.

  In the roller unit of the present invention, when an external force is applied to the cylindrical roller from the outside, both ends in the longitudinal direction of the cylindrical roller are pressed outward by the annular portions at both ends, so that both ends in the longitudinal direction are hardly deformed. Therefore, fatigue failure of the cylindrical roller can be prevented. Moreover, since both-ends annular part satisfy | fills said numerical formula, this both-ends annular part does not move to the longitudinal direction of a cylindrical roller. Therefore, the wire rod does not come out of the cylindrical roller, and is not offset inside the cylindrical roller.

  Here, when the intermediate annular portion having the same shape as the both-end annular portions is formed between the pair of both-end annular portions, the intermediate annular portion outside the inner wall surface of the cylindrical roller. The cylindrical roller is hardly deformed even if an external force is applied to the cylindrical roller from the outside.

  Further, the wire is formed with a plurality of connecting portions extending in the longitudinal direction of the cylindrical roller for connecting adjacent ones of the both end annular portions and the intermediate annular portion, and the plurality of connections. When each part is formed at a position different from each other in the circumferential direction of the cylindrical roller, when the cylindrical roller is heated from the inside, the plurality of connection parts are arranged on the circumference of the cylindrical roller. Since they are formed at positions different from each other in the direction, the peripheral wall of the cylindrical roller is uniformly heated, and temperature spots do not occur.

  Further, when the connecting portion is separated from the inner wall surface of the cylindrical roller, the connecting portion is separated from the inner wall surface of the cylindrical roller, so that a uniform external force is applied to the cylindrical roller from the outside. When this occurs, the cylindrical roller is uniformly deformed at the connecting portion.

  Furthermore, the wire has a coefficient of thermal expansion greater than that of the cylindrical roller, and an outer diameter of the annular portion at both ends is smaller than an inner diameter of the cylindrical roller. In this case, it is easy to insert the wire into the hollow portion of the cylindrical roller. Further, when the cylindrical roller is heated, the wire is also heated. At this time, the annular portions at both ends of the wire press the inner wall surface of the cylindrical roller outward. As a result, the cylindrical roller is reinforced by the wire.

  Furthermore, the thermal expansion coefficient of the wire is larger than that of the cylindrical roller, and the outer diameters of the both-end annular part and the intermediate annular part are larger than the inner diameter of the cylindrical roller. Is also small, it is easy to insert the wire into the hollow portion of the cylindrical roller. Further, when the cylindrical roller is heated, the wire is also heated. At this time, the both-end annular portion and the intermediate annular portion of the wire press the inner wall surface of the cylindrical roller to the outside. As a result, the cylindrical roller is reinforced by the wire.

  Furthermore, when the said wire is comprised from the divided | segmented some partial wire, since a partial wire becomes small, it is easy to manufacture.

  Furthermore, each of the annular portions at both ends can further reinforce the cylindrical roller when a plurality of rings are in close contact with each other.

  Furthermore, when the both ends annular portion and the intermediate annular portion are formed by close contact of a plurality of rings, the cylindrical roller can be further reinforced.

  Furthermore, when the pitch angle of the annular portions at both ends is approximately 0 degrees, it is possible to more reliably prevent the wire from moving in the hollow portion of the cylindrical roller.

  Furthermore, when the pitch angles of both the end annular portions and the intermediate annular portion are substantially 0 degrees, it is possible to more reliably prevent the wire from moving in the hollow portion of the cylindrical roller.

  Further, according to the fixing device of the present invention, not only the fixing roller is reinforced by the wire, but also the wire does not move in the longitudinal direction of the cylindrical roller, so that temperature fluctuations of the fixing roller are prevented and fixing performance is improved. To do.

  Embodiments of the present invention will be described with reference to the drawings.

  A roller unit according to a first embodiment of the present invention will be described with reference to FIG.

  FIG. 1 is a cross-sectional view illustrating a first embodiment of the roller unit. In this figure, the same components as those shown in FIG. 15 are denoted by the same reference numerals. Here, a fixing roller will be described as an example of the roller unit.

  The hollow portion of the cored bar 124 (an example of the cylindrical roller in the present invention) of the fixing roller 10 extends in the longitudinal direction of the cored bar 124 (in the direction of arrow L) and is approximately the same length as the length of the cored bar 124. The wire 12 is inserted and arranged. A pair of both end annular portions 14 that press the inner wall surfaces of both ends in the longitudinal direction outward are formed at both ends in the longitudinal direction of the cored bar 124 of the wire 12. Each annular portion 14 is composed of a plurality of rings 14a (also referred to as rings, here two rings are shown) that are in close contact with each other. Both end annular portions 14 are formed only at both ends in the longitudinal direction of the cored bar 124. Further, the pair of annular portions 14 at both ends are connected by a connecting portion 16 that contacts the inner wall surface of the core metal 124 and extends in the direction of arrow L. The wire 12 is formed by appropriately bending a single wire.

  The pitch angle formed by the orthogonal direction (arrow Y direction) orthogonal to the longitudinal direction of the metal core 124 (arrow Y direction) and the diameter direction of both end annular portions 14 is α, and the inner wall surface of the core metal 124 and both end annular portions 14 When the coefficient of dynamic friction with the part in contact with the inner wall surface is μv and the coefficient of correction of this coefficient of dynamic friction is ξ,

α <tan ⁻¹ (μv) or α <tan ⁻¹ (ξμv) is satisfied. Here, the pitch angle α is set to 0 degree.

  When the pressing force of the pressure roller 130 (see FIG. 15) acts on the fixing roller 10, both ends in the longitudinal direction of the cored bar 124 are pressed outward by the annular portions 14 at both ends. do not do. Therefore, fatigue failure of the cored bar 124 can be prevented. Moreover, since the pitch angle α of the annular portions 14 at both ends satisfies the above formula, the annular portions 14 at both ends do not move in the longitudinal direction of the cored bar 124. Therefore, the wire 12 does not come out of the cored bar 124 and is not offset inside the cored bar 124.

  A second embodiment of the roller unit of the present invention will be described with reference to FIGS.

  FIG. 2 is a perspective view showing Example 2 of the roller unit. FIG. 3 is a perspective view showing an example of a wire. FIG. 4 is a partial cutaway view showing a part of the core bar broken away. FIG. 5 is a longitudinal sectional view of FIG. In these drawings, the same components as those shown in FIG. 15 are denoted by the same reference numerals. Here, a fixing roller will be described as an example of the roller unit.

  The hollow portion of the cored bar 124 (an example of the cylindrical roller in the present invention) of the fixing roller 20 extends in the longitudinal direction of the cored bar 124 (in the direction of arrow L) and is substantially the same length as the length of the cored bar 124. The wire 22 is inserted and arranged. A pair of both-end annular portions 24 that press the inner wall surfaces of both ends in the longitudinal direction outward are formed at both ends in the longitudinal direction of the cored bar 124 of the wire 22. Further, in the wire rod 22, an intermediate annular portion 26 having the same shape and the same size as the both-end annular portions 24 is formed between the pair of both-end annular portions 24. The pair of annular portions 24 at both ends and the intermediate annular portion 26 are connected by a connecting portion 28 that contacts the inner wall surface of the cored bar 124 and extends in the direction of arrow L. The wire 22 is formed by appropriately bending a single wire.

  Each of the annular portions 24 at both ends includes a plurality of rings (also referred to as rings, here two rings are shown) 24a in close contact with each other. Both end annular portions 24 are formed only at both ends in the longitudinal direction of the cored bar 124. One intermediate annular portion 26 is composed of a plurality of rings (also referred to as rings, here two rings are shown) 26a that are in close contact with each other. Although three intermediate annular portions 26 are shown here, two or four or more intermediate annular portions 26 may be formed.

  The pitch angle formed by the orthogonal direction (arrow Y direction) orthogonal to the longitudinal direction (arrow L direction) of the core metal 124 and the diameter direction (arrow D direction) of the both-end annular part 24 and the intermediate annular part 26 is α, and the metal core When the dynamic friction force coefficient between the inner wall surface of 124 and the annular contact portion 24 (and the intermediate annular portion 26) in contact with the inner wall surface is μv and the correction coefficient of the dynamic friction coefficient is ξ,

α <tan ⁻¹ (μv) or α <tan ⁻¹ (ξμv) is satisfied. Here, the pitch angle α is set to 0 degree.

  When the pressing force of the pressure roller 130 (see FIG. 15) acts on the fixing roller 20, both ends in the longitudinal direction of the cored bar 124 are pressed outward by the annular portions 24 at both ends. do not do. Further, since the intermediate annular portion 26 reinforces the intermediate portion in the longitudinal direction of the cored bar 124, the intermediate portion is not deformed. Therefore, fatigue failure and deformation of the cored bar 124 can be prevented. Moreover, since the pitch angle α of the annular portions 24 at both ends satisfies the above mathematical formula, the annular portions 24 at both ends do not move in the longitudinal direction of the cored bar 124. Therefore, the wire 22 does not come out of the cored bar 124 and is not offset inside the cored bar 124.

  A third embodiment of the roller unit of the present invention will be described with reference to FIG.

  FIG. 6 is a longitudinal sectional view showing Example 3 of the roller unit. In this figure, the same components as those shown in FIG. 15 are denoted by the same reference numerals. Here, a fixing roller will be described as an example of the roller unit.

  In the hollow portion of the cored bar 124 of the fixing roller 30 (which is an example of the cylindrical roller in the present invention), four partial wires 32, 34, 36, 38 extending in the longitudinal direction of the cored bar 124 (arrow L direction). Is inserted and placed. The length of each partial wire rod 32, 34, 36, 38 is about a quarter of the length of the cored bar 124. Therefore, the total length of the four partial wire rods 32, 34, 36 and 38 is substantially the same as the length of the cored bar 124. The partial wire 32 and the partial wire 38 have the same shape and the same size, but are disposed in opposite directions in the hollow portion of the cored bar 124. The partial wire 34 and the partial wire 36 have the same shape and the same size.

  Two annular portions 32a and 32a are formed in close contact with one end portion in the longitudinal direction of the partial wire rod 32, and one annular portion 32b is formed at the other end portion in the longitudinal direction. The annular portion 32 a and the annular portion 32 b are connected by a connection portion 32 c that extends in the arrow L direction and contacts the inner wall surface of the cored bar 124. Similarly to the partial wire 32, the partial wire 38 is also formed with one annular portion 38a at one end in the longitudinal direction and two annular portions 38b and 38b in close contact with the other end in the longitudinal direction. Has been. The annular portion 38a and the annular portion 38b are connected by a connection portion 38c that extends in the direction of arrow L and contacts the inner wall surface of the cored bar 124.

  In addition, annular portions 34 a and 34 b are formed one by one at both ends in the longitudinal direction of the partial wire 34. The annular portions 34 a and 34 b are connected by a connection portion 34 c that extends in the arrow L direction and contacts the inner wall surface of the cored bar 124. Similarly to the partial wire 34, the partial wire 36 is also formed with annular portions 36 a and 36 b at both ends in the longitudinal direction. The annular portions 36 a and 36 b extend in the direction of the arrow L and The connection part 36c which contacted the wall surface is connected. Therefore, the state in which the four partial wires 32, 34, 36, and 38 are inserted and arranged in the hollow portion of the cored bar 124 is very similar to the wire 22 shown in FIG.

  When the four partial wires 32, 34, 36, and 38 arranged in the hollow portion of the cored bar 124 are viewed as a whole, the inner wall surfaces of both ends in the longitudinal direction are pressed outward at both ends in the longitudinal direction of the cored bar 124. A pair of annular portions 32a and 38b at both ends are formed. Further, in the four partial wire rods 32, 34, 36, and 38, intermediate annular portions 32b and 34a (36a and 34b) (38a and 36b) having the same shape and the same size as the annular portions 32a and 38b at both ends are paired annularly at both ends. It is formed between the parts 32a and 38b.

  The pitch angle formed by the orthogonal direction (arrow Y direction) orthogonal to the longitudinal direction (arrow L direction) of the cored bar 124 and the diameter direction of each annular portion 32a, 32b, 34a, 34b, 36a, 36b, 38a, 38b is α And the coefficient of dynamic friction between the inner wall surface of the cored bar 124 and each annular portion 32a, 32b, 34a, 34b, 36a, 36b, 38a, 38b that contacts the inner wall surface is μv, and the correction coefficient for this dynamic friction coefficient Is ξ,

α <tan ⁻¹ (μv) or α <tan ⁻¹ (ξμv) is satisfied. Here, the pitch angle α is set to 0 degree.

  When the pressing force of the pressure roller 130 (see FIG. 15) is applied to the fixing roller 30, both ends in the longitudinal direction of the core metal 124 are pressed outward by the both end annular portions 32a and 38b. Almost no deformation. Further, since the intermediate annular portions 32b, 34a, 34b, 36a, 36b, and 38a reinforce the longitudinal intermediate portion of the core metal 124, the intermediate portion is not deformed. Therefore, fatigue failure and deformation of the cored bar 124 can be prevented. Moreover, since the pitch angle α of each annular portion 32a, 32b, 34a, 34b, 36a, 36b, 38a, 38b satisfies the above mathematical formula, these annular portions do not move in the longitudinal direction of the cored bar 124. Therefore, the partial wire rods 32, 34, 36, and 38 do not come out of the cored bar 124 and are not offset inside the cored bar 124. Moreover, since each partial wire 32,34,36,38 is short, while being able to improve the precision on formation processing, it can insert in the metal core 124 more easily. Note that the strength of the fixing roller 30 can be increased by increasing the number of partial wires.

  Embodiment 4 of the roller unit of the present invention will be described with reference to FIG.

  FIG. 7 is a longitudinal sectional view showing Example 4 of the roller unit. In this figure, the same components as those shown in FIG. 15 are denoted by the same reference numerals. Here, a fixing roller will be described as an example of the roller unit.

  In the hollow portion of the cored bar 124 of the fixing roller 40 (which is an example of the cylindrical roller according to the present invention), four partial wire rods 41, 42, 43, 44 extending in the longitudinal direction (arrow L direction) of the cored bar 124. Is inserted and placed. The length of each partial wire rod 41, 42, 43, 44 is about a quarter of the length of the cored bar 124. Therefore, the total length of the four partial wires 41, 42, 43, 44 is substantially the same as the length of the cored bar 124. Each partial wire 41, 42, 43, 44 has the same shape and the same size. In the cored bar 124, the partial wire rods 41 and 43 are arranged in the same direction, and the partial wire rods 42 and 44 are arranged in a direction opposite to this direction.

  One annular portion 41a, 41b is formed at each longitudinal end of the partial wire 41, and one annular portion 41c is formed between the pair of annular portions 41a, 41b. The annular portion 41 a and the annular portion 41 c are connected by a connection portion 41 d that extends in the direction of arrow L and contacts the inner wall surface of the cored bar 124. Similarly, the annular portion 41 c and the annular portion 41 b are connected by a connecting portion 41 d that extends in the direction of arrow L and contacts the inner wall surface of the cored bar 124.

  One annular portion 42a, 42b is formed at each longitudinal end of the partial wire 42, and one annular portion 42c is formed between the pair of annular portions 42a, 42b. The annular portion 42a and the annular portion 42c are connected by a connecting portion 42d that extends in the direction of arrow L and contacts the inner wall surface of the cored bar 124. Similarly, the annular portion 42c and the annular portion 42b are connected by a connection portion 42d that extends in the direction of arrow L and contacts the inner wall surface of the cored bar 124. The connecting portion 41d and the connecting portion 42d are disposed at positions that are 180 degrees apart in the outer peripheral direction of the cored bar 124.

  One annular portion 43a, 43b is formed at each longitudinal end of the partial wire 43, and one annular portion 43c is formed between the pair of annular portions 43a, 43b. The annular portion 43a and the annular portion 43c are connected by a connecting portion 43d that extends in the direction of arrow L and contacts the inner wall surface of the cored bar 124. Similarly, the annular portion 43c and the annular portion 43b are connected by a connecting portion 43d that extends in the arrow L direction and contacts the inner wall surface of the cored bar 124.

  One annular portion 44a, 44b is formed at each longitudinal end of the partial wire 44, and one annular portion 44c is formed between the pair of annular portions 44a, 44b. The annular portion 44a and the annular portion 44c are connected by a connecting portion 44d that extends in the direction of arrow L and contacts the inner wall surface of the cored bar 124. Similarly, the annular portion 44c and the annular portion 44b are connected by a connection portion 44d that extends in the arrow L direction and contacts the inner wall surface of the cored bar 124. The connecting portion 44d and the connecting portion 43d are arranged at positions separated by 180 degrees in the outer peripheral direction of the cored bar 124. Further, as described above, the connecting portion 41d and the connecting portion 42d are also arranged at positions 180 degrees apart in the outer peripheral direction of the cored bar 124, so that the inner wall surface is relatively uniform due to the radiant heat from the heater 122 (see FIG. 14). Is heated. As a result, the outer peripheral surface and the peripheral wall of the fixing roller 40 are uniformly heated and cooled, so that temperature spots do not occur.

  When the four partial wires 41, 42, 43, 44 arranged in the hollow portion of the core metal 124 are viewed as a whole, the inner wall surfaces of both ends in the longitudinal direction are pressed outward at both ends in the longitudinal direction of the core metal 124. A pair of annular portions 41a and 44b at both ends are formed. Further, in the four partial wire rods 41, 42, 43, and 44, intermediate annular portions 41c, 41b, 42a, 42c, 42b, 43a, 43c, 43b, 44a, and 44c having the same shape and the same size as the both-end annular portions 41a and 44b. Is formed between the pair of annular portions 41a and 44b at both ends.

  The orthogonal direction (arrow Y direction) orthogonal to the longitudinal direction (arrow L direction) of the cored bar 124 and the annular portions 41a, 41c, 41b, 42a, 42c, 42b, 43a, 43c, 43b, 44a, 44c, 44b The pitch angle formed by the diameter direction is α, and the inner wall surface of the cored bar 124 and the inner wall surface of the annular portions 41a, 41c, 41b, 42a, 42c, 42b, 43a, 43c, 43b, 44a, 44c, 44b are contacted. When the dynamic friction force coefficient with the part to be used is μv and the correction coefficient of this dynamic friction coefficient is ξ,

α <tan ⁻¹ (μv) or α <tan ⁻¹ (ξμv) is satisfied. Here, the pitch angle α is set to 0 degree.

  When the pressing force of the pressure roller 130 (see FIG. 15) is applied to the fixing roller 40, both ends in the longitudinal direction of the core metal 124 are pressed outward by the annular portions 41a and 44b at both ends. Almost no deformation. Further, since the intermediate annular portions 41c, 41b, 42a, 42c, 42b, 43a, 43c, 43b, 44a, 44c reinforce the longitudinal intermediate portion of the cored bar 124, the intermediate portion is not deformed. Therefore, fatigue failure and deformation of the cored bar 124 can be prevented. In addition, since the pitch angle α of each of the annular portions 41a, 41c, 41b, 42a, 42c, 42b, 43a, 43c, 43b, 44a, 44c, 44b satisfies the above formula, these annular portions are the longitudinal lengths of the cored bar 124. Does not move in the direction. Therefore, the partial wire rods 41, 42, 43, 44 do not come out of the cored bar 124 and are not offset inside the cored bar 124. Moreover, since each partial wire 41, 42, 43, 44 is short, it can improve the precision in forming and can be inserted into the core metal 124 more easily. Note that the strength of the fixing roller 40 can be increased by increasing the number of partial wires.

  With reference to FIG. 8, Example 5 of the roller unit of the present invention will be described.

  FIG. 8 is a longitudinal sectional view showing Example 5 of the roller unit. In this figure, the same components as those shown in FIG. 15 are denoted by the same reference numerals. Here, a fixing roller will be described as an example of the roller unit.

  In the hollow portion of the cored bar 124 (an example of the cylindrical roller in the present invention) of the fixing roller 50, four partial wire rods 51, 52, 53, 54 extending in the longitudinal direction (arrow L direction) of the cored bar 124. Is inserted and placed. The length of each partial wire 51, 52, 53, 54 is about a quarter of the length of the cored bar 124. Therefore, the total length of the four partial wires 51, 52, 53, 54 is substantially the same as the length of the cored bar 124. Each partial wire 51, 52, 53, 54 has the same shape and the same size. Inside the cored bar 124, the partial wire rods 51, 52, 53, 54 are arranged in different directions.

  Annular portions 51a and 51b are respectively formed at both ends in the longitudinal direction of the partial wire 51, and the annular portions 51a and 51b extend in the direction of the arrow L and are connected to the inner wall surface of the core metal 124. 51c is connected.

  One annular portion 52a, 52b is formed at each of both ends in the longitudinal direction of the partial wire 52, and the annular portion 52a and the annular portion 52b extend in the direction of the arrow L and contact the inner wall surface of the core metal 124. 52c is connected.

  One annular portion 53a, 53b is formed at each of both ends in the longitudinal direction of the partial wire 53, and the annular portion 53a and the annular portion 53b extend in the direction of the arrow L and contact the inner wall surface of the cored bar 124. 53c is connected.

  Annular portions 54a and 54b are respectively formed at both ends in the longitudinal direction of the partial wire 54. The annular portion 54a and the annular portion 54b extend in the direction of arrow L and are connected to the inner wall surface of the core metal 124. 54c is connected.

  The four connection portions 51c, 52c, 53c, and 54c are arranged at positions that are 90 degrees apart from each other in the outer circumferential direction of the cored bar 124. For this reason, the inner wall surface is heated relatively uniformly by the radiant heat from the heater 122 (see FIG. 14). As a result, the outer peripheral surface and the peripheral wall of the fixing roller 50 are uniformly heated and cooled, so that temperature spots do not occur.

  When the four partial wires 51, 52, 53, 54 arranged in the hollow portion of the cored bar 124 are viewed as a whole, the inner wall surfaces of both ends in the longitudinal direction are pressed outward at both ends in the longitudinal direction of the cored bar 124. A pair of annular portions 51a and 54b at both ends are formed. Further, in the four partial wire rods 51, 52, 53, 54, intermediate annular portions 51b, 52a, 52b, 53a, 53b, 54a having the same shape and the same size as the annular portions 51a, 54b at both ends are paired with the annular portions 51a at both ends. , 54b.

  A pitch angle formed by an orthogonal direction (arrow Y direction) orthogonal to the longitudinal direction (arrow L direction) of the cored bar 124 and the diameter direction of each annular portion 51a, 51b, 52a, 52b, 53a, 53b, 54a, 54b. α is set, and μv is a dynamic friction force coefficient between the inner wall surface of the cored bar 124 and each annular portion 51a, 51b, 52a, 52b, 53a, 53b, 54a, 54b, and the portion contacting the inner wall surface. When the coefficient is ξ,

α <tan ⁻¹ (μv) or α <tan ⁻¹ (ξμv) is satisfied. Here, the pitch angle α is set to 0 degree.

  When the pressing force of the pressure roller 130 (see FIG. 15) is applied to the fixing roller 50, both ends in the longitudinal direction of the core metal 124 are pressed outward by the annular portions 51a and 54b at both ends. Almost no deformation. Further, since the intermediate annular portions 51b, 52a, 52b, 53a, 53b, 54a reinforce the intermediate portion in the longitudinal direction of the core metal 124, the intermediate portion is not deformed. Therefore, fatigue failure and deformation of the cored bar 124 can be prevented. In addition, since the pitch angle α of each of the annular portions 51a, 51b, 52a, 52b, 53a, 53b, 54a, 54b satisfies the above mathematical formula, these annular portions do not move in the longitudinal direction of the cored bar 124. Therefore, the partial wires 51, 52, 53, 54 do not come out of the cored bar 124 and are not offset inside the cored bar 124. Moreover, since each partial wire 51,52,53,54 is short, it can improve the precision in forming and can be inserted into the metal core 124 more easily. Note that the strength of the fixing roller 50 can be increased by increasing the number of partial wires.

  With reference to FIG. 9, Example 6 of the roller unit of this invention is demonstrated.

  FIG. 9 is a longitudinal sectional view showing Example 6 of the roller unit. In these drawings, the same components as those shown in FIG. 15 are denoted by the same reference numerals. Here, a fixing roller will be described as an example of the roller unit.

  The hollow portion of the cored bar 124 (an example of the cylindrical roller in the present invention) of the fixing roller 60 extends in the longitudinal direction of the cored bar 124 (in the direction of the arrow L) and is approximately the same length as the length of the cored bar 124. The wire 62 is inserted and arranged. A pair of both-end annular portions 64 that press the inner wall surfaces of both ends in the longitudinal direction outward are formed at both ends in the longitudinal direction of the cored bar 124 of the wire 62. Further, in the wire 62, an intermediate annular portion 66 having the same shape and the same size as the both end annular portions 64 is formed between the pair of both end annular portions 64. The pair of annular portions 64 at both ends and the intermediate annular portion 66 are connected to each other by a connecting portion 68 that extends away from (in contact with) the inner wall surface 124a of the core metal 124 in the arrow L direction. Since the connecting portion 68 is not in contact with the inner wall surface 124 a of the fixing roller 60, the nip pressure does not change when the pressure roller 130 (see FIG. 14) presses the fixing roller 60 during fixing temperature adjustment. As a result, it is possible to reduce the adverse effect on the image caused by the change in the nip pressure. The wire 62 is formed by appropriately bending a single wire.

  Each of the annular portions 64 at both ends includes a plurality of rings (also referred to as rings, here two rings are shown) 64a that are in close contact with each other. Both end annular portions 64 are formed only at both ends in the longitudinal direction of the cored bar 124. In addition, one intermediate annular portion 66 includes a plurality of rings (also referred to as rings, here two rings are shown) 66a that are in close contact with each other. Although three intermediate annular portions 66 are shown here, two or four or more intermediate annular portions 26 may be formed.

  The pitch angle formed by the orthogonal direction (arrow Y direction) orthogonal to the longitudinal direction (arrow L direction) of the core metal 124 and the diameter direction of both end annular portions 64 and the intermediate annular portion 66 is α, and the inner wall surface 124a of the core metal 124 is shown. And the dynamic friction force coefficient between the both ends annular portion 64 (and the intermediate annular portion 66) in contact with the inner wall surface is μv, and the correction coefficient of the dynamic friction coefficient is ξ,

α <tan ⁻¹ (μv) or α <tan ⁻¹ (ξμv) is satisfied. Here, the pitch angle α is set to 0 degree.

  When the pressing force of the pressure roller 130 (see FIG. 15) acts on the fixing roller 60, both ends in the longitudinal direction of the cored bar 124 are pressed outward by the annular portions 64 at both ends, so that both ends in the longitudinal direction are almost deformed. do not do. Further, since the intermediate annular portion 66 reinforces the intermediate portion in the longitudinal direction of the core metal 124, the intermediate portion is not deformed. Therefore, fatigue failure and deformation of the cored bar 124 can be prevented. Further, since the pitch angle α between the both-end annular portion 64 and the intermediate annular portion 66 satisfies the above mathematical formula, the both-end annular portion 64 and the intermediate annular portion 66 do not move in the longitudinal direction of the cored bar 124. Therefore, the wire 62 does not come out of the cored bar 124 and is not offset inside the cored bar 124.

  In the above-described first to sixth embodiments, the both-end annular portion 24 and the like of the wire 22 and the intermediate annular portion 26 and the like always press the inner wall surface 124a of the cored bar 124 at a normal temperature and a high temperature. Instead of such a wire 22, in Example 7, the thermal expansion coefficient is larger than the thermal expansion coefficient of the cored bar 124, and the outer diameters of the both-end annular part 24 and the intermediate annular part 26 are the cores. A wire rod smaller than the inner diameter of the gold 124 was used. When such a wire is used, it is easy to insert the wire into the hollow portion of the cored bar 124. Further, when the cored bar 124 is heated, the wire is also heated and expands, so that the both ends annular part 24 and the intermediate annular part 26 etc. of the wire press the inner wall surface of the cored bar 124 outward. As a result, the cored bar 124 is reinforced by the wire.

  In each of the above-described embodiments, the shape of both ends of the wire may be either open end or closed end. Further, the moving direction varies depending on the winding direction of the wire inserted into the cored bar 124, but in each of the above embodiments, the pitch angle is set to be approximately 0 degrees or small enough to prevent the wire from moving inside. Either winding direction is acceptable. Further, since the strength of reinforcing the inside of the fixing roller varies depending on the number of turns of the annular portion, the strength of reinforcement can be adjusted by changing the number of turns. In addition, the operation | work which assembles each wire to the inside of a roller can be performed by inserting, twisting in the direction which the diameter of a wire reduces using a jig | tool.

It is sectional drawing which shows Example 1 of a roller unit. It is a perspective view which shows Example 2 of a roller unit. It is a perspective view which shows an example of a wire. It is a fragmentary broken view which fractures | ruptures a part of core metal and shows the inside. It is a longitudinal cross-sectional view of FIG. It is a longitudinal cross-sectional view which shows Example 3 of a roller unit. It is a longitudinal cross-sectional view which shows Example 4 of a roller unit. It is a longitudinal cross-sectional view which shows Example 5 of a roller unit. It is a longitudinal cross-sectional view which shows Example 6 of a roller unit. FIG. 2 schematically shows a pressing force that a fixing roller receives from a pressure roller during operation of a conventional fixing device, wherein (a) is a front view and (b) is a side view. FIG. 6 is a schematic diagram illustrating deformation of an outer peripheral wall of the fixing roller when the strength of the fixing roller is reduced. FIG. 12 is a cross-sectional view showing the fixing roller of FIG. 11. It is a schematic diagram showing the stress that the coil spring receives from the fixing roller when the pressure roller rotates. FIG. 10 is a schematic diagram illustrating a schematic configuration of a conventional fixing device. It is sectional drawing which shows the fixing roller in which the coil spring was inserted. It is a schematic diagram which shows the coil spring which came out of the metal core. It is sectional drawing which shows the metal core in which the stopper was formed. It is sectional drawing which shows the coil spring from which the winding pitch fluctuated.

Explanation of symbols

10, 20, 30, 40, 50, 60 Fixing rollers 12, 22 Wire rods 14, 24, 64 End annular portions 26, 66 Intermediate annular portions 32, 34, 36, 38, 41, 42, 43, 44, 51, 52 53, 54 Partial wire 32a, 32a, 34a, 34b, 36a, 36b, 38a, 38b, 41a, 41c, 41b, 42a, 42c, 42b, 43a, 43c, 43b, 44a, 44c, 44b, 51a, 51b, 52a, 52b, 53a, 53b, 54a, 54b Annulus 16, 28, 32c, 34c, 36c, 38c, 41d, 42d, 43d, 44d, 51c, 52c, 53c, 54c, 68 Connection 124 Core metal 124a Core metal Inner wall

Claims (12)

A hollow cylindrical roller;
A pair of hollow portions of the cylindrical roller that extends in the longitudinal direction and has substantially the same length as the cylindrical roller, and that presses the inner wall surfaces of both ends in the longitudinal direction of the cylindrical roller to the outside. It is provided with a wire rod in which both end annular portions are formed,
The pair of both-end annular portions are respectively
A portion in contact with the inner wall surface of the inner wall surface of the cylindrical roller and the both end annular portions, where α is a pitch angle formed by an orthogonal direction orthogonal to the longitudinal direction of the cylindrical roller and the diameter direction of the both end annular portions. And the dynamic friction force coefficient of ν is μv and the correction coefficient of the dynamic friction coefficient is ξ,
A roller unit characterized by satisfying α <tan ⁻¹ (μv) or α <tan ⁻¹ (ξμv). The wire is
The roller unit according to claim 1, wherein an intermediate annular portion having the same shape as the both-end annular portions is formed between the pair of both-end annular portions. The wire is
A plurality of connecting portions extending in the longitudinal direction of the cylindrical roller are formed to connect adjacent ones of the both-end annular portion and the intermediate annular portion,
Each of these multiple connections is
The roller unit according to claim 2, wherein the roller units are formed at different positions in the circumferential direction of the cylindrical roller. The connecting portion is
The roller unit according to claim 3, wherein the roller unit is separated from an inner wall surface of the cylindrical roller. The wire has a coefficient of thermal expansion greater than that of the cylindrical roller, and
The roller unit according to claim 1, wherein an outer diameter of the annular portion at both ends is smaller than an inner diameter of the cylindrical roller. The wire has a coefficient of thermal expansion greater than that of the cylindrical roller, and
5. The roller unit according to claim 2, wherein an outer diameter of each of the both end annular portions and the intermediate annular portion is smaller than an inner diameter of the cylindrical roller. The wire is
The roller unit according to any one of claims 1 to 6, wherein the roller unit is composed of a plurality of divided partial wires. The roller unit according to any one of claims 1 to 7, wherein each of the annular portions at both ends includes a plurality of rings in close contact with each other. The roller unit according to any one of claims 1 to 7, wherein the both-end annular portion and the intermediate annular portion are formed by closely attaching a plurality of rings. The cylindrical roller according to claim 1, wherein the pitch angle of the annular portions at both ends is approximately 0 degrees. The cylindrical roller according to any one of claims 2 to 9, wherein the pitch angle of both the end annular portion and the intermediate annular portion is substantially 0 degree. A fixing roller having a heat source disposed therein and a pressure roller pressed against the fixing roller are provided, and the recording medium is conveyed between the fixing roller and the pressure roller to convey an image on the recording medium. In the fixing device for fixing,
12. A fixing device using the cylindrical roller according to claim 1 as the fixing roller.

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