Patent Description:
<CIT>discloses an induction heating roller configured to heat yarns. The induction heating roller includes: a hollow roller main body; and a coil provided radially inward of the roller main body. As an alternating current flows through the coil, eddy currents are induced in the roller main body due to electromagnetic induction, and the roller main body is heated by Joule heating (that is, heat is generated in the roller main body by induction heating). The induction heating roller is supported in a cantilever manner so that yarns can be easily wound onto the roller.

Induction heating rollers each generally has difficulty in obtaining equal distribution of the surface temperature of the roller main body in its axial direction because heat generation therein is less likely to be equal in the axial direction and because heat is more likely to be dissipated at axial end portions of the roller main body to the outside. To deal with this, an induction heating roller described in <CIT>includes a jacket chamber filled with a heating medium in a gas-liquid two-phase state, and the jacket chamber is provided in a roller main body so as to extend in an axial direction of the roller. As the jacket chamber functions as a heat pipe, the inequality in the distribution of the surface temperature of the roller main body in the axial direction is improved.

Other examples of the prior art can be seen in documents <CIT>, <CIT> and <CIT>.

To provide such a jacket chamber in a roller main body, however, it is necessary to increase the thickness of the roller main body in its radial direction. This increases the heat capacity of the roller main body, which worsens the heating efficiency of the roller main body. In view of the above, the present inventors conceived an idea of providing a cylindrical heat equalizing member having a heat conductivity higher than that of the roller main body, in contact with an inner circumferential surface of the roller main body. This facilitates equalization in the distribution of the surface temperature of the roller main body because the heat equalizing member functions as a heat pipe. Furthermore, it is possible to efficiently heat the roller main body because the thickness of the roller main body is smaller and therefore the increase in the heat capacity is smaller.

Now, reference is made to a case in which the heat equalizing member is applied to an induction heating roller supported in a cantilever manner, as described in <CIT>. In this case, the heat equalizing member is inserted into a space radially inside the roller main body through an opening of the roller main body, which is provided at its base-end-side portion in the axial direction ("axial base end portion"). Furthermore, a ring-like fixing member (hereinafter referred to as a "fixing ring") for fixing the roller main body and the heat equalizing member to each other is attached to the axial base end portion of the roller main body, for example. The fixing ring is arranged to extend further radially inward relative to the heat equalizing member in order to firmly fix the heat equalizing member provided radially inward of the roller main body.

As described above, at the axial end portions of the roller main body, it is more likely that heat is dissipated to the outside to cause a surface temperature drop. In view of the above, the present inventors used carbon steel, which is a ferromagnetic material, as a material of the fixing ring, based on the following grounds: the present inventors used such a fixing ring in order to improve the distribution of the surface temperature of the roller main body by facilitating the flow of magnetic flux through the fixing ring to facilitate the generation of eddy currents, thereby to increase the amount of heat generation at the base end portion of the roller main body. However, when this configuration was actually tested with a heater turned on, excessive heat was generated in the fixing ring and the temperature at the base end portion of the roller main body rose higher than that of its axially central portion, disadvantageously. That is, the present inventors found that: in the above configuration, magnetic flux excessively passed through the fixing ring extending further radially inward (toward the coil) relative to the roller main body, to induce eddy currents excessively, and therefore excessive heat was generated in the fixing ring.

An object of the present invention is to mitigate heat generation in a fixing ring provided to an induction heating roller.

In a first aspect of the present invention, an induction heating roller includes: a rotatable roller unit; and a heater including a coil provided radially inward of the roller unit. The roller unit includes: a roller main body including a cylindrical heating target configured to be heated by induction heating due to magnetic flux passing in an axial direction of the roller unit, the magnetic flux being generated by electric current flowing through the coil; a heat equalizing unit including a heat equalizing member which is in contact with an inner circumferential surface of the heating target, the heat equalizing member extending in the axial direction, and having a heat conductivity higher at least than that of the inner circumferential surface of the heating target; a fixing ring provided so as to be in contact with a first-side end portion of the heating target which is on a first side in the axial direction and with a first-side end portion of the heat equalizing unit which is on the first side in the axial direction, the fixing ring fixing the roller main body and the heat equalizing unit to each other; and a first magnetic member provided between the heating target and the coil in the radial direction, the first magnetic member being provided on the first side relative to a center of the heating target in the axial direction and on a second side opposite to the first side relative to the fixing ring in the axial direction.

In this aspect of the present invention, the fixing ring is provided so as to be in contact with the first-side end portion of the heating target and with the first-side end portion of the heat equalizing unit in the axial direction of the roller unit (hereinafter, simply referred to as an "axial direction"), and the fixing ring fixes the roller main body and the heat equalizing unit to each other. At least a part of the fixing ring is, in general, positioned closer to the coil than the heating target and the heat equalizing unit in the radial direction. Magnetic flux tends to, in nature, concentratedly flow into the shortest path, through which magnetic flux readily passes, among paths for magnetic flux, and therefore in the above configuration, magnetic flux is more likely to flow into the fixing ring. This increases the possibility that heat is generated in the fixing ring due to induction heating.

To deal with this, in the above aspect of the present invention, the first magnetic member is provided radially inward of the heating target, and is provided on the first side relative to the axial center of the heating target in the axial direction and on the second side relative to the fixing ring in the axial direction. Thus, appropriately disposing the first magnetic member makes it possible to form a new path through which magnetic flux more readily passes than a path extending via the fixing ring. Due to this, as compared to the case in which no first magnetic member is provided, the amount of magnetic flux passing through the fixing ring can be reduced, leading to reduction of eddy currents generated in the fixing ring. Accordingly, it is possible to mitigate heat generation in the fixing ring provided to the induction heating roller.

In a second aspect of the invention, the induction heating roller of the first aspect is arranged such that the heat equalizing member has a relative permeability lower than that of the fixing ring.

In the above configuration in which the heat equalizing member has the lower relative permeability, magnetic flux is less likely to pass through the heat equalizing member, and this increases the likelihood that the magnetic flux concentratedly flows into the fixing ring. Even in this configuration, because the new path through which magnetic flux readily passes is created by the first magnetic member in the above aspect, it is possible to effectively decrease the amount of magnetic flux passing through the fixing ring.

In a third aspect of the invention, the induction heating roller of the first or second aspect is arranged such that the first magnetic member is provided so as to correspond to a whole circumference of the fixing ring in a circumferential direction of the fixing ring.

In this aspect, the inflow of magnetic flux into the fixing ring is further reduced as compared to the case in which the first magnetic member is provided only partially with respect to the circumferential direction of the fixing ring.

In a fourth aspect of the invention, the induction heating roller of any of the first to third aspects is arranged such that the first magnetic member is in contact with the inner circumferential surface of the heating target.

If the flow of magnetic flux is disturbed between the first magnetic member and the heating target, there is a possibility that the magnetic flux detours to flow into the fixing ring. As compared to the case in which the first magnetic member is not in contact with the heating target (i.e., the case in which there is a gap between the first magnetic member and the heating target), the above arrangement facilitates the flow of magnetic flux between the first magnetic member and the heating target, and therefore it is possible to reduce the amount of magnetic flux detouring to flow into the fixing ring.

In a fifth aspect of the invention, the induction heating roller of any of the first to fourth aspects is arranged such that the first magnetic member is in contact with the heat equalizing member.

As magnetic flux passes through the first magnetic member, the first magnetic member is also heated by induction heating. Because the first magnetic member is in contact with the heat equalizing member in this aspect, heat generated in the first magnetic member is transmitted to the heating target via the heat equalizing member. This makes it possible to efficiently heat the heating target.

In a sixth aspect of the invention, the induction heating roller of any of the first to fifth aspects is arranged such that there is a gap between the first magnetic member and the fixing ring in the axial direction.

In the above aspect, as compared to the case in which there is no gap between the first magnetic member and the fixing ring (i.e., the case in which the first magnetic member is in contact with the fixing ring), it is possible to reduce the transmission of heat, generated by eddy currents flowing in the first magnetic member, toward the fixing ring. This makes a temperature rise in the fixing ring smaller. Furthermore, due to the presence of the gap, magnetic flux is less likely to flow toward the fixing ring.

In a seventh aspect of the invention, the induction heating roller of any of the first to sixth aspects is arranged such that the first magnetic member is a pressing member provided side by side on the first side of the heat equalizing member in the axial direction and configured to press the heat equalizing member; and the heat equalizing unit further comprises a biasing member provided between the pressing member and the fixing ring in the axial direction and configured to bias the pressing member toward the second side in the axial direction.

In the above aspect, the pressing member is biased in the axial direction, and by the biased pressing member, the heat equalizing member is pressed in the axial direction. This makes it possible to firmly fix the heat equalizing member in the axial direction. Furthermore, because the pressing member is provided to function as the first magnetic member, an increase in cost is smaller as compared to the case in which the first magnetic member and the pressing member are provided as different members.

In an eighth aspect of the invention, the induction heating roller of any of the first to seventh aspects is arranged such that the heater includes a second magnetic member provided radially outward of the coil, the second magnetic member being provided so as to be opposed to the first magnetic member in the radial direction.

In this aspect, the heater is provided with the second magnetic member. This makes it possible to form a path through which magnetic flux readily passes along the second magnetic member. This facilitates the flow of magnetic flux between the first and second magnetic members opposed to each other in the radial direction when the magnetic flux flows between the heater provided radially inside and the roller unit provided radially outside. Accordingly, it is possible to reliably reduce the amount of magnetic flux passing through the fixing ring.

In a ninth aspect of the invention, the induction heating roller of the eighth aspect is arranged such that the second magnetic member is structured by a plurality of parts arranged in the circumferential direction of the fixing ring.

In this aspect, the flow of the magnetic flux between the first magnetic member and the second magnetic member is further facilitated, as compared to the case in which the second magnetic member is provided to cover only a limited area with respect to the circumferential direction of the fixing ring.

In a tenth aspect of the invention, the induction heating roller of the eighth or ninth aspect is arranged such that: the heater includes a third magnetic member provided adjacent to an end portion of the coil on the first side in the axial direction, the third magnetic member extending further radially outward relative to the coil; and the second magnetic member is provided in contact with the third magnetic member.

In this aspect, magnetic flux generated by currents flowing through the coil is intentionally guided by the third magnetic member to the second magnetic member. Thus, the magnetic flux are reliably introduced into the second magnetic member.

In an eleventh aspect of the invention, the induction heating roller of any of the first to tenth aspects is arranged such that the fixing ring has a relative permeability lower than that of the first magnetic member.

In this aspect, the fixing ring has the lower relative permeability, and this makes it less likely that magnetic flux passes through the fixing ring, and therefore eddy currents are less likely to flow in the fixing ring. This makes the heat generation in the fixing ring further smaller.

In a twelfth aspect of the present invention, an induction heating roller includes: a rotatable roller unit; and a heater including a coil provided radially inward of the roller unit. The roller unit includes: a roller main body including a cylindrical heating target configured to be heated by induction heating due to magnetic flux passing in an axial direction of the roller unit, the magnetic flux being generated by electric current flowing through the coil; a heat equalizing unit including a heat equalizing member which is in contact with an inner circumferential surface of the heating target, the heat equalizing member extending in the axial direction and having a heat conductivity higher at least than that of the inner circumferential surface of the heating target; and a fixing ring provided so as to be in contact with a first-side end portion of the heating target which is on a first side in the axial direction and with a first-side end portion of the heat equalizing unit which is on the first side in the axial direction, the fixing ring fixing the roller main body and the heat equalizing unit to each other. The fixing ring includes a high resistive portion provided at a part of the fixing ring with respect to its circumferential direction and configured to decrease eddy currents flowing in the circumferential direction.

In this aspect, as same as in the first aspect, the fixing ring is arranged to extend further radially inward relative to the heating target and the heat equalizing unit, which increases the likelihood of inflow of magnetic flux into the fixing ring. This may cause a problem that the magnetic flux passing through the fixing ring induces eddy currents whirling in the circumferential direction of the fixing ring, to cause great heat generation in the fixing ring. To deal with this, in this aspect, the high resistive portion is provided at a part of the fixing ring in the circumferential direction, and the high resistive portion decreases the eddy currents flowing in the circumferential direction of the fixing ring. Accordingly, it is possible to mitigate heat generation in the fixing ring provided to the induction heating roller.

In a thirteenth aspect of the invention, the induction heating roller of the twelfth aspect is arranged such that the high resistive portion has a cross-sectional area, which is orthogonal to the circumferential direction, smaller than that of a portion of the fixing ring other than the high resistive portion.

In this aspect, because the cross-sectional area of the high resistive portion orthogonal to the circumferential direction is smaller, the electric resistance in the circumferential direction is higher at the high resistive portion. The high electric resistance in the circumferential direction of the fixing ring makes it possible to reduce the eddy currents.

In a fourteenth aspect of the invention, the induction heating roller of the thirteenth aspect is arranged such that: the high resistive portion has a hole to make the cross-sectional area of the high resistive portion smaller than that of the portion other than the high resistive portion.

In this aspect, the high resistive portion with a smaller cross-sectional area is easily provided just by boring a hole at a part of the fixing ring.

In a fifteenth aspect of the invention, the induction heating roller of the fourteenth aspect is arranged such that the hole is filled with an insulator.

Providing a hollow hole at a part of the fixing ring in the circumferential direction may decrease the strength of the fixing ring at the high resistive portion. In this aspect, the insulator filling the hole mitigates such a decrease in strength of the fixing ring.

In a sixteenth aspect of the invention, the induction heating roller of the twelfth aspect is arranged such that: the fixing ring includes a plurality of ring pieces which are separable in the circumferential direction; the ring pieces are connected to each other via insulators; and portions of the fixing ring in which the insulators are respectively provided in the circumferential direction function as the high resistive portion.

In this aspect, due to the insulators interposed between the plurality of ring pieces, it is possible to reliably reduce the eddy currents from flowing while whirling in the circumferential direction of the fixing ring.

In a seventeenth aspect of the invention, the induction heating roller of any of the first to sixteenth aspects is arranged such that: the roller main body is supported in a cantilever manner; and the fixing ring is provided, in the axial direction, at a base end portion of the heating target, which is the first-side end portion of the heating target.

In the roller main body supported in a cantilever manner, a portion of the base end portion of the roller main body which is exposed to outside air is smaller than that of its leading end portion. Therefore, heat is less likely to be dissipated at the base end portion. For this reason, when heat is generated in the fixing ring provided to the base end portion of the heating target, the generated heat tends to be transmitted toward the leading end side of the heating target before being dissipated to the outside. The above tendency is more likely to cause a temperature gradient, in which the temperature is higher at the base end side in the axial direction of the heating target while the temperature is lower at the leading end side, resulting in the problem of poor distribution of temperature on the surface of the heating target. In this aspect, by mitigating the heat generation in the fixing ring provided to the base end portion of the heating target, the above-described temperature gradient is moderated, leading to improvement in the distribution of the temperature on the surface of the base end portion of the heating target.

In an eighteenth aspect, a spun yarn drawing device includes the induction heating roller recited in any one of the first to seventeenth aspects, and the apparatus is arranged such that a plurality of yarns are wound onto an outer circumferential surface of the induction heating roller in a lined-up manner in the axial direction.

In this aspect, it is possible to equalize the distribution of temperature of the roller surface, and to efficiently raise the temperature of the roller surface. This stabilizes the quality of the yarns wound onto the induction heating roller, to enable production of high-quality yarns.

The following describes a first embodiment of the present invention with reference to <FIG>.

First of all, with reference to <FIG>, a description is given of the structure of a spun yarn take-up machine <NUM> including induction heating rollers <NUM> of the first embodiment. <FIG> is a front view of the spun yarn take-up machine <NUM>. The description below is given on the premise that the up-down direction, front-back direction, and left-right direction shown in <FIG> are respectively the up-down direction, front-back direction, and left-right direction relative to the spun yarn take-up machine <NUM>. The spun yarn take-up machine <NUM> is configured so that yarns Y spun out from a spinning apparatus <NUM> are drawn in a spun yarn drawing device <NUM> and the drawn yarns Y are wound up in a yarn winding apparatus <NUM>.

The spinning apparatus <NUM> is configured to produce yarns Y by continuously spinning out molten polymer such as nylon and polyester. To the yarns Y spun out from the spinning apparatus <NUM>, oil is applied at an oil guide <NUM>. The yarns Y are then sent to the spun yarn drawing device <NUM> via a guide roller <NUM>.

The spun yarn drawing device <NUM> is an apparatus for drawing the yarns Y and is provided below the spinning apparatus <NUM>. The spun yarn drawing device <NUM> includes godet rollers <NUM> to <NUM> housed in a thermal insulation box <NUM>. The godet rollers <NUM> to <NUM> are configured to be driven and rotated by respective motors. Each of the godet rollers <NUM> to <NUM> is the induction heating roller <NUM> heated by induction heating using a coil. Yarns Y are wound onto an outer circumferential surface of each of the godet rollers <NUM> to <NUM>. The thermal insulation box <NUM> has, at a lower portion of its right side surface, an inlet 12a through which yarns Y are introduced into the thermal insulation box <NUM>. The thermal insulation box <NUM> further has, at an upper portion of its right side surface, an outlet 12b through which yarns Y go out of the thermal insulation box <NUM>. Yarns Y are wound onto each of the godet rollers <NUM> to <NUM>, in order from the lowermost godet roller <NUM>, at a winding angle smaller than <NUM> degrees.

The lower three godet rollers <NUM> to <NUM> are preheating rollers configured to preliminarily heat yarns Y before drawing them. The roller surface temperature of each of these rollers is arranged to be equal to or higher than the glass transition temperature of the yarns Y (e.g., on the order of <NUM> to <NUM> degrees centigrade). The upper two godet rollers <NUM> and <NUM> are conditioning rollers configured to thermally set the drawn yarns Y. The surface temperature of each of these rollers is arranged to be higher than the surface temperatures of the lower three godet rollers <NUM> to <NUM> (e.g., on the order of <NUM> to <NUM> degrees centigrade). Furthermore, the yarn feeding speeds of the upper two godet rollers <NUM> and <NUM> are higher than those of the lower three godet rollers <NUM> to <NUM>.

The yarns Y introduced into the thermal insulation box <NUM> through the inlet 12a are, at first, preliminarily heated to a drawable temperature while being transferred by the godet rollers <NUM> to <NUM>. The preliminarily heated yarns Y are drawn due to the difference in yarn feeding speed between the godet roller <NUM> and the godet roller <NUM>. The yarns Y are then further heated to a higher temperature while being transferred by the godet rollers <NUM> and <NUM>, with the result that the drawn yarns Y are thermally set. The yarns Y having been drawn in this way go out from the thermal insulation box <NUM> through the outlet 12b.

The yarns Y drawn by the spun yarn drawing device <NUM> are sent to the yarn winding apparatus <NUM> via a guide roller <NUM>. The yarn winding apparatus <NUM> is an apparatus for winding the yarns Y and is provided below the spun yarn drawing device <NUM>. The yarn winding apparatus <NUM> includes a bobbin holder <NUM>, a contact roller <NUM>, and the like. The bobbin holder <NUM> has a cylindrical shape extending in the front-back direction, and is driven and rotated by a motor, which is not illustrated. Bobbins B arranged side by side in an axial direction of the bobbin holder <NUM> are attached to the bobbin holder <NUM>. The yarn winding apparatus <NUM> is configured to wind yarns Y onto the bobbins B at the same time by rotating the bobbin holder <NUM>, to produce packages P. The contact roller <NUM> is configured to come into contact with the surfaces of the packages P to adjust the shape of each package P by applying a predetermined contact pressure to each package P.

Next, the structure of each of the induction heating rollers <NUM>, which are used as the godet rollers <NUM> to <NUM>, will be described with reference to <FIG> and <FIG>. <FIG> is a cross section of each induction heating roller <NUM>. <FIG> is a perspective view of a heat equalizing unit <NUM> and the like, which will be described later. <FIG> is a diagram showing a heat equalizing member <NUM> pressed by a pressing member <NUM>. A roller main body <NUM> of the induction heating roller <NUM> is supported in a cantilever manner by a motor <NUM> configured to rotate and drive the roller main body <NUM>. Hereinafter, a direction in which the roller main body <NUM> extends (i.e., a left-right direction on the sheet of <FIG>) is referred to as an "axial direction" or "axially". In the present embodiment, the axial direction of the roller main body <NUM> is identical with an axial direction of a roller unit <NUM> (which will be described later) and to an axial direction of a heat equalizing unit <NUM> (which will be described later). Relative to the roller main body <NUM>, a side closer to the motor <NUM> in the axial direction is referred to as a "base end side" (a first side in the present invention). A side opposite from the base end side is referred to as a "leading end side" (a second side in the present invention). Furthermore, a radial direction of the roller main body <NUM> may be simply referred to as a "radial direction" or "radially". Still further, a circumferential direction of the roller main body <NUM> may be simply referred to as a "circumferential direction".

The induction heating roller <NUM> includes: the rotatable roller unit <NUM>; and a heater <NUM> provided radially inward of the roller unit <NUM>. The induction heating roller <NUM> is configured to raise the temperature of an outer circumferential surface of the roller unit <NUM> by induction heating caused by a coil <NUM> provided in the heater <NUM>, and thereby to heat yarns Y wound onto the roller unit <NUM>. The roller unit <NUM> is rotated and driven by the motor <NUM>. The heater <NUM> is fixed to a heater supporting portion (not illustrated) attached to the motor <NUM>. That is, the roller unit <NUM> is configured to be rotatable but the heater <NUM> is configured to be non-rotatable.

To begin with, the roller unit <NUM> will be described. The roller unit <NUM> includes: the roller main body <NUM>; the heat equalizing unit <NUM>; and a fixing ring <NUM>. The roller main body <NUM> is a cylindrical member and is configured to be rotated and driven by the motor <NUM>. The heat equalizing unit <NUM> is provided radially inward of the roller main body <NUM> and radially outward of the coil <NUM>. The heat equalizing unit <NUM> is provided to equalize the temperature distribution on the roller main body <NUM> in the axial direction. The fixing ring <NUM> is attached to an axial base end portion (a base end portion in the axial direction) of the roller main body <NUM>. The fixing ring <NUM> fixes the roller main body <NUM> and the heat equalizing unit <NUM> to each other. Hereinafter, details of each of the components will be described.

The roller main body <NUM> is, for example, made of carbon steel, which is magnetic and conductive material. The roller main body <NUM> includes: an outer cylindrical portion <NUM> (a heating target in the present invention) with a cylindrical shape, which is provided radially outward of the coil <NUM> and extends in the axial direction; a cylindrical core portion <NUM> provided radially inward of the coil <NUM>; and an end face portion <NUM> connecting a leading end portion of the outer cylindrical portion <NUM> to a leading end portion of the core portion <NUM>. The roller main body <NUM> has an open end on the base end side. The outer cylindrical portion <NUM>, the core portion <NUM>, and the end face portion <NUM> are, for example, unitarily formed as a single member. Alternatively, at least two of the outer cylindrical portion <NUM>, the core portion <NUM>, and the end face portion <NUM> may be respectively formed by components different from each other. For example, the following configuration is possible: the outer cylindrical portion <NUM> is formed by a first component; and the core portion <NUM> and the end face portion <NUM> are formed by a second component. In this case, the first component and the second component are fixed to each other, for example, by welding, or fixed by a fixing member such as screws or the like. Note that the whole of the roller main body <NUM> does not have to be made of one material (for example, of carbon steel mentioned above). That is, as long as the outer cylindrical portion <NUM> and the end face portion <NUM> are made of magnetic and conductive material, the rest of the roller main body <NUM> may be made of another material. The core portion <NUM> does not have to be made of magnetic material. Yarns Y are wound onto an outer circumferential surface 34a of the outer cylindrical portion <NUM>. The length of the outer circumferential surface 34a in the axial direction is, for example, <NUM>. The heat equalizing unit <NUM> is in contact with an inner circumferential surface 34b of the outer cylindrical portion <NUM>. The core portion <NUM> has a shaft inserting hole 35a in which a drive shaft <NUM> of the motor <NUM> is inserted. The drive shaft <NUM> is fitted in the shaft inserting hole 35a, and thereby the roller main body <NUM> is fixed to the drive shaft <NUM>. This allows the roller main body <NUM> to be supported in a cantilever manner by the motor <NUM> and to be rotatable with the drive shaft <NUM>. The end face portion <NUM> has, at its radially outer end portion, a contact surface 36a with which a leading end portion of the heat equalizing member <NUM> is in contact. The contact surface 36a is a tapered surface, which is sloped so that its thickness in the axial direction decreases toward radially outside.

The heat equalizing unit <NUM> includes: the heat equalizing member <NUM>, the pressing member <NUM>, and springs <NUM> (a biasing member in the present invention). The heat equalizing member <NUM> is used to equalize the distribution of the surface temperature of the outer cylindrical portion <NUM> of the roller main body <NUM> in the axial direction. The heat equalizing member <NUM> is a cylindrical member provided radially inward of the outer cylindrical portion <NUM> of the roller main body <NUM> and radially outward of the coil <NUM>. The heat equalizing member <NUM> is pressed by the pressing member <NUM> and by the springs <NUM> toward the leading end side in the axial direction and radially outward, and due to this, the heat equalizing member <NUM> is fixed to the roller main body <NUM> (the details thereof will be described later.

The heat equalizing member <NUM> is a cylindrical member extending in the axial direction, and is, for example, made of C/C composite material (carbon fiber reinforced-carbon matrix-composite material), which is a composite material of carbon fiber reinforcement in a matrix of graphite. The heat equalizing member <NUM> has a heat conductivity higher than that of the roller main body <NUM> made of carbon steel (at least higher than that of the inner circumferential surface 34b of the outer cylindrical portion <NUM>). Due to its higher heat conductivity, the heat equalizing member <NUM> has a function of equalizing the temperature distribution on the outer cylindrical portion <NUM> in the axial direction. For example, the heat conductivity of carbon steel is <NUM> W/mk, while the heat conductivity of C/C composite material in the axial direction is <NUM> W/mk. Furthermore, the heat equalizing member <NUM> has a relative permeability lower than that of the roller main body <NUM>. For example, the relative permeability of carbon steel is <NUM> to <NUM>, while the relative permeability of C/C composite material is approximately <NUM>.

The heat equalizing member <NUM> is in contact with the inner circumferential surface 34b of the outer cylindrical portion <NUM> of the roller main body <NUM>. Now an area of the outer circumferential surface 34a of the outer cylindrical portion <NUM> with respect to the axial direction, onto which yarns Y are wound, is defined as a wound region R. The heat equalizing member <NUM> is provided to cover the wound region R with respect to the axial direction. Furthermore, the heat equalizing member <NUM> is structured by a plurality of heat equalizing pieces <NUM> separable with respect to the circumferential direction (see <FIG>). A base-end-side end face 44a and a leading-end-side end surface 44b of each heat equalizing piece <NUM> are tapered. To be more specific, the end face 44a is arranged so that its radially outer edge is on the base end side relative to its radially inner edge, in the axial direction. The end surface 44b is arranged so that its radially outer edge is on the leading end side relative to its radially inner edge, in the axial direction. The end surface 44b is shaped to match with the contact surface 36a of the end face portion <NUM> of the roller main body <NUM>.

The pressing member <NUM> is biased by the springs <NUM>, and thereby to press the heat equalizing member <NUM> toward the leading end side in the axial direction and outward in the radial direction. The pressing member <NUM> is a ring-like member (see <FIG>), and its outer diameter and inner diameter are substantially equal to those of the heat equalizing member <NUM>, respectively. A leading-end-side end face 42a of the pressing member <NUM> is a tapered pressing surface arranged so that its radially inner edge is on the leading end side in the axial direction relative to its radially outer edge. That is, the end face 42a is designed to match with the surface formed by the above-described base-end-side end faces 44a of the heat equalizing pieces <NUM>. Each spring <NUM> is in a gap <NUM> between the pressing member <NUM> and the fixing ring <NUM> in the axial direction. A base end portion and a leading end portion of the spring <NUM> are in contact with the fixing ring <NUM> and the pressing member <NUM>, respectively, and the spring <NUM> is compressed in the axial direction. Due to this, each spring <NUM> biases, with its restoring force, the pressing member <NUM> toward the leading end side in the axial direction. Because the pressing member <NUM> is biased by the springs <NUM>, the heat equalizing member <NUM> is pressed toward the leading end side in the axial direction (see an arrow in the left-right direction on the sheet of <FIG>). Simultaneously, due to the tapered end face 42a, the heat equalizing member <NUM> is pressed also outward in the radial direction (see arrows in the up-down direction on the sheet of <FIG>). As a result, outer circumferential surfaces 44c of the heat equalizing pieces <NUM> are reliably brought into contact with the inner circumferential surface 34b of the outer cylindrical portion <NUM> of the roller main body <NUM>. It should be noted that the number of springs <NUM> is not particularly limited. Instead of the one or more springs <NUM>, a rubber elastic member or the like may be used as a biasing member biasing the pressing member <NUM>.

The fixing ring <NUM> is a ring-like member provided at an axial base end portion of the outer cylindrical portion <NUM> of the roller main body <NUM>. The fixing ring <NUM> is, for example, made of carbon steel as same as the roller main body <NUM>. That is, the relative permeability of the above-described heat equalizing member <NUM> is lower than the relative permeability of the fixing ring <NUM>. The fixing ring <NUM> extends further radially outward relative to the outer cylindrical portion <NUM> of the roller main body <NUM>, and extends further radially inward relative to the heat equalizing unit <NUM>. A radially inner end portion of the fixing ring <NUM> is closer to the coil <NUM> than the outer cylindrical portion <NUM> and than the heat equalizing unit <NUM> in the radial direction. That is, the distance between the fixing ring <NUM> and the coil <NUM> in the radial direction is shorter than the distance between the heat equalizing unit <NUM> and the coil <NUM> in the radial direction. The fixing ring <NUM> is provided in contact with the axial base end portion of the roller main body <NUM> and with an axial base end portion of the heat equalizing unit <NUM>. Specifically, as shown in <FIG>, the fixing ring <NUM> has a surrounding portion 33a. The surrounding portion 33a is shaped so as to surround a part of the roller main body <NUM> and a part of the heat equalizing unit <NUM> with respect to three sides thereof, i.e., the radially outer side, the radially inner side, and the base end side in the axial direction. Thus, the base end portion of the outer cylindrical portion <NUM> of the roller main body <NUM> and a base end portion of the pressing member <NUM> are surrounded, with the result that the roller main body <NUM> and the heat equalizing unit <NUM> are fixed. Furthermore, the fixing ring <NUM> has a recessed portion 33b to accommodate the springs <NUM>. The recessed portion 33b provides the gap <NUM> between the pressing member <NUM> and the fixing ring <NUM> in the axial direction.

The following describes the heater <NUM>. The heater <NUM> includes: a bobbin member <NUM>, the coil <NUM>, and a flange <NUM>. In the heater <NUM>, the coil <NUM> is wound around the bobbin member <NUM> extending in the axial direction. An axial base end portion of the bobbin member <NUM> is attached to the flange <NUM>.

The bobbin member <NUM> is a cylindrical member provided radially inward of the outer cylindrical portion <NUM> of the roller main body <NUM> and radially outward of the core portion <NUM>. The bobbin member <NUM> is, for example, made of carbon steel as same as the roller main body <NUM>. The coil <NUM> is wound around an outer periphery of the bobbin member <NUM>.

The coil <NUM> is used to heat the roller main body <NUM> by induction heating. The coil <NUM>, which is wound around the bobbin member <NUM>, is provided inward of the outer cylindrical portion <NUM> of the roller main body <NUM> and outward of the core portion <NUM>. As an alternating voltage is applied to the coil <NUM>, an alternating current flows through the coil <NUM>, to generate an alternating magnetic field.

The flange <NUM> is a disc-like member. The flange <NUM> has, at its radially central portion, a through hole 53a so that the flange <NUM> and the drive shaft <NUM> of the motor <NUM> do not interfere with each other. The flange <NUM> is, for example, made of carbon steel as same as the roller main body <NUM>. The flange <NUM> is provided at an axial base end portion of the heater <NUM>. The axial base end portion of the bobbin member <NUM> is attached to the flange <NUM>. The flange <NUM> is fixed to the heater supporting portion (not shown) of the motor <NUM>. The flange <NUM> extends further radially outward relative to the coil <NUM>. A radially outer end portion of the flange <NUM> is positioned on the base end side in the axial direction relative to the fixing ring <NUM> of the roller unit <NUM>, so as to cover the fixing ring <NUM>. There is a gap between the flange <NUM> and the fixing ring <NUM>, to prevent interference between the flange <NUM> of the heater <NUM> configured not to rotate and the fixing ring <NUM> of the roller unit <NUM> configured to rotate.

As an alternating voltage is applied to the coil <NUM> in each induction heating roller <NUM>, an alternating current flows through the coil <NUM>, to generate an alternating magnetic field, and magnetic flux passes through the outer cylindrical portion <NUM> of the roller main body <NUM> in the axial direction. This induces eddy currents flowing in the roller main body <NUM> in the circumferential direction, and the outer cylindrical portion <NUM> is heated by Joule heating. The induction heating rollers <NUM> each generally has difficulty in obtaining equal distribution of the surface temperature of the roller main body <NUM> because heat generation therein is less likely to be equal in the axial direction and because the heat is more likely to be dissipated at the axial end portions of the roller main body <NUM> to the outside. For this reason, the heat equalizing member <NUM> is used to equalize the distribution of temperature on the outer cylindrical portion <NUM> in the axial direction. As described above, the heat equalizing member <NUM> has a lower relative permeability. Therefore, the magnetic flux is less likely to pass through the heat equalizing member <NUM>, and heat is less likely to be generated in the heat equalizing member <NUM>.

As described above, at the axial end portions of the roller main body <NUM>, it is more likely that heat is dissipated to the outside, to cause a surface temperature drop. In view of the above, the present inventors used carbon steel, which is a ferromagnetic material, as a material of the fixing ring <NUM> in order to improve the distribution of the surface temperature of the roller main body by facilitating the flow of magnetic flux through the fixing ring <NUM> to facilitate the generation of eddy currents, thereby to increase the amount of heat generation at the base end portion of the roller main body <NUM>. Magnetic flux tends to, in nature, concentratedly flow through the shortest path, through which magnetic flux readily passes, among paths for magnetic flux. Because of this, the present inventors selected at first SUS (Steel Use Stainless), which is a non-magnetic material, as a material of the pressing member <NUM> so that magnetic flux passes through the fixing ring <NUM> rather than through the pressing member <NUM>. However, when this configuration was actually tested with the heater <NUM> turned on, excessive heat was generated in the fixing ring <NUM> and the temperature at the base end portion of the roller main body <NUM> rose higher than that of its axially central portion, disadvantageously.

The above-described problem will be schematically described with reference to <FIG>. In the induction heating roller <NUM>, a path <NUM> through which magnetic flux readily passes is formed by the members made of ferromagnetic carbon steel. (It should be noted that arrows are depicted just to improve visibility. The direction of the magnetic flux changes when the direction of the current flowing through the coil <NUM> changes. ) To be more specific, the path <NUM> extends through the bobbin member <NUM>, the flange <NUM>, the fixing ring <NUM>, the outer cylindrical portion <NUM> of the roller main body <NUM>, and the end face portion <NUM>. Because magnetic flux tends to, in nature, pass near a surface of a ferromagnetic material ("skin effect"), the path <NUM> is formed so as to pass on or near the surfaces of the above-described members.

If the magnetic flux concentratedly flows through the path <NUM>, eddy currents are excessively induced in the fixing ring <NUM>, leading to a large amount of heat generation in the fixing ring <NUM>. In particular, magnetic flux passing through the fixing ring <NUM> in the axial direction induces eddy currents whirling in the circumferential direction of the fixing ring <NUM>. This makes the heat generation more significant. Furthermore, the fixing ring <NUM> is provided at the base end portion of the roller unit <NUM> supported in a cantilever manner, and a portion of the fixing ring <NUM> which faces the outside is smaller than that of a leading end portion of the roller unit <NUM>. Therefore, the heat is less likely to be dissipated from the fixing ring <NUM>. For this reason, the heat generated in the fixing ring <NUM> is more likely to be transmitted toward a leading-end-side portion of the outer cylindrical portion <NUM> of the roller main body <NUM> before it is dissipated to the outside. The present inventors considered that this tends to cause a temperature gradient, in which the higher temperatures are observed at a base-end-side portion of the outer cylindrical portion <NUM> while lower temperatures are observed at the leading-end-side portion thereof, resulting in the problem of poor distribution of temperature on the outer circumferential surface 34a of the outer cylindrical portion <NUM>.

To mitigate heat generation in the fixing ring <NUM>, each induction heating roller <NUM> has the below-described configuration. Specifically, a description will be given, referring back to <FIG> and <FIG>.

In the first embodiment, each induction heating roller <NUM> has the following configuration so as to provide another path through which magnetic flux readily passes, which is different from the above-described path <NUM> (see <FIG>). First of all, the pressing member <NUM> provided to press the heat equalizing member <NUM> is made of carbon steel, which is a ferromagnetic material, as same as the roller main body <NUM> and the like. Hereinbelow, the pressing member <NUM> is referred to as a first magnetic member <NUM>. In other words, the pressing member <NUM> is used as the first magnetic member <NUM>. As shown in <FIG>, the first magnetic member <NUM> is provided between the outer cylindrical portion <NUM> of the roller main body <NUM> and the coil <NUM> in the radial direction, and is provided on the base end side relative to the center of the outer cylindrical portion <NUM> in the axial direction and on the leading end side relative to the fixing ring <NUM>. The first magnetic member <NUM> is in contact with the inner circumferential surface 34b of the outer cylindrical portion <NUM> and in contact with the heat equalizing member <NUM>. There is the gap <NUM> between the first magnetic member <NUM> and the fixing ring <NUM> in the axial direction. It is preferable that the first magnetic member <NUM> is provided so as to correspond to the whole circumference in the circumferential direction, as shown in <FIG>, for example. However, the present invention is not limited to this. For example, the first magnetic member <NUM> may be structured by parts separable in the circumferential direction and arranged with spaces interposed between them.

The heater <NUM> includes a second magnetic member <NUM>. The second magnetic member <NUM> is made of carbon steel, as same as the first magnetic member <NUM>. As shown in <FIG>, the second magnetic member <NUM> is provided radially outward of the coil <NUM>, and is provided so as to be opposed to the first magnetic member <NUM> in the radial direction. The second magnetic member <NUM> is attached to the flange <NUM> (a third magnetic member of the present invention), and is in contact with the flange <NUM>. The second magnetic member <NUM> is provided so that the second magnetic member <NUM> and the first magnetic member <NUM>, which is provided to the rotating roller unit <NUM>, do not interfere with each other. It is preferable that, as shown in <FIG>, for example, the second magnetic member <NUM> is structured by parts arranged in the circumferential direction with spaces interposed between them. However, the present invention is not limited to this.

In each induction heating roller having the above-described configuration, a new path through which magnetic flux readily passes is formed by the first magnetic member <NUM> and the second magnetic member <NUM>. This will be schematically described with reference to <FIG>.

As shown in <FIG>, a path <NUM> (see a bold line in <FIG>) through which magnetic flux readily passes is formed aside from the path <NUM> by the first magnetic member <NUM> and the second magnetic member <NUM>. To be more specific, the path <NUM> passes through the bobbin member <NUM>, the flange <NUM>, the second magnetic member <NUM>, a part of the fixing ring <NUM>, the first magnetic member <NUM>, and the outer cylindrical portion <NUM>, and the end face portion <NUM> of the roller main body <NUM>. Now, among the paths through which magnetic flux can pass, reference is made in particular to paths formed in the roller unit <NUM>. Of these, the path passing through the first magnetic member <NUM> (see the path <NUM>) is shorter than the path passing through the base end portion of the roller main body <NUM> and through the fixing ring <NUM> (see the path <NUM>). Due to this, magnetic flux is more readily to pass through the path <NUM> than the path <NUM>, and this reduces the amount of magnetic flux passing through the fixing ring <NUM>. This reduces generation of eddy currents in the fixing ring <NUM>.

In the above-described configuration, the inflow of magnetic flux toward the fixing ring <NUM> is further reduced due to the following two reasons. The first reason is that the first magnetic member <NUM> is in contact with the inner circumferential surface 34b of the outer cylindrical portion <NUM>. This facilitates the flow of magnetic flux between the first magnetic member <NUM> and the outer cylindrical portion <NUM>, and this decreases the possibility that the magnetic flux detours to flow into the fixing ring <NUM>. The second reason is that there is the gap <NUM> between the first magnetic member <NUM> and the fixing ring <NUM> in the axial direction. This decreases the possibility that the magnetic flux passing through the first magnetic member <NUM> flows into the fixing ring <NUM>.

Because the magnetic flux passes through the first magnetic member <NUM>, the first magnetic member <NUM> is also heated by induction heating. As described above, the first magnetic member <NUM> is in contact with the inner circumferential surface 34b of the outer cylindrical portion <NUM> and in contact with the heat equalizing member <NUM>. Due to this, heat generated in the first magnetic member <NUM> is directly transmitted to the outer cylindrical portion <NUM>, or is transmitted to the outer cylindrical portion <NUM> via the heat equalizing member <NUM>. Consequently, the outer cylindrical portion <NUM> is efficiently heated.

With reference to <FIG>, the following describes a change in distribution of temperature on the outer circumferential surface 34a of the outer cylindrical portion <NUM> of the roller main body <NUM> in the axial direction, due to the presence or absence of the first magnetic member <NUM> and the second magnetic member <NUM>. The present inventors observed the distribution of the temperature on the outer circumferential surface 34a in the axial direction for two cases with and without the first and second magnetic members <NUM> and <NUM>, for comparison. (For the case without the magnetic members, the pressing member <NUM> is made of non-magnetic material, and no second magnetic member <NUM> is provided. ) In both cases, the temperature at a center of the outer circumferential surface 34a in the axial direction was set to <NUM> degrees centigrade. Furthermore, the operation speed (circumferential speed) of the roller unit <NUM> was set to <NUM>/min. Under these conditions, comparison was made for the distribution of the temperature on the outer circumferential surface 34a in the axial direction, between the case in which the first magnetic member <NUM> and the second magnetic member <NUM> are provided ("Example") and the case in which these magnetic members are not provided ("Comparative Example").

The result of the comparison is shown in <FIG>. The horizontal axis represents the distance of a point on the outer circumferential surface 34a from a leading end of the roller main body <NUM>. That is, the smaller the distance is, the closer the point is to the leading end of the roller main body <NUM>. The larger the distance is, the closer the point is to a base end of the roller main body <NUM>. As described above, the length of the outer circumferential surface 34a in the axial direction is <NUM>. The vertical axis represents the difference in the surface temperature from the temperature at the center of the outer circumferential surface 34a in the axial direction (hereinafter "axially central portion"), that is, at the point at the above distance of <NUM>. In Comparative Example (see a broken line in <FIG>), the larger the distance from the leading end of the roller main body <NUM> is (that is, the closer the point is to the fixing ring <NUM> on the base end side), the higher the surface temperature is. At some points, there were observed <NUM> degrees centigrade or more differences from the surface temperature at the axially central portion. Meanwhile, in Example (see a solid line in <FIG>), it was observed that the temperatures at the axial base end portion of the outer circumferential surface 34a were somewhat lower than the temperature at the axially central portion. Furthermore, the difference in the surface temperature between the axial base end portion and the axially central portion of the outer circumferential surface 34a was within <NUM> degrees centigrade at every point. Thus, the temperature gradient at the axial base end portion of the outer circumferential surface 34a has been improved. It was confirmed that the heat generation in the fixing ring <NUM> was reduced by providing the first magnetic member <NUM> and the second magnetic member <NUM> thereby to form the path <NUM> (see <FIG>) through which magnetic flux more readily passes than the path <NUM>.

As described above, the first magnetic member <NUM> is provided radially inward of the outer cylindrical portion <NUM>, and is provided on the base end side relative to the axial center of the outer cylindrical portion <NUM> in the axial direction and on the leading end side relative to the fixing ring <NUM> in the axial direction. Thus, appropriately disposing the first magnetic member <NUM> makes it possible to form the new path <NUM> through which magnetic flux more readily passes than the path <NUM> extending via the fixing ring <NUM>. Due to this, as compared to the case in which no first magnetic member <NUM> is provided, the amount of magnetic flux passing through the fixing ring <NUM> can be reduced, leading to reduction of eddy currents generated in the fixing ring <NUM>. In this way, it is possible to mitigate heat generation in the fixing ring <NUM> provided to the induction heating roller <NUM>.

Furthermore, in the configuration in which: the heat equalizing member <NUM> has a low relative permeability; and this increases the likelihood of concentrated inflow of magnetic flux into the fixing ring <NUM>, it is possible to effectively decrease the amount of magnetic flux passing through the fixing ring <NUM> by forming the path <NUM>, through which magnetic flux readily passes, by the first magnetic member <NUM>.

Furthermore, in the configuration in which the first magnetic member <NUM> is provided so as to correspond to the whole circumference in the circumferential direction, it is possible to further reduce the inflow of magnetic flux into the fixing ring <NUM>, as compared to the case in which the first magnetic member <NUM> is provided only partially with respect to the circumferential direction.

Furthermore, the first magnetic member <NUM> is in contact with the inner circumferential surface 34b of the outer cylindrical portion <NUM>. As compared to the case in which there is a gap between the first magnetic member <NUM> and the outer cylindrical portion <NUM>, the above arrangement facilitates the flow of magnetic flux between the first magnetic member <NUM> and the outer cylindrical portion <NUM>, and therefore it is possible to reduce the amount of magnetic flux detouring to flow into the fixing ring <NUM>.

Furthermore, the first magnetic member <NUM> is in contact with the heat equalizing member <NUM>. This allows heat generated in the first magnetic member <NUM> by induction heating to be transmitted to the outer cylindrical portion <NUM> via the heat equalizing member <NUM>. This makes it possible to efficiently heat the outer cylindrical portion <NUM>.

Furthermore, there is the gap <NUM> between the first magnetic member <NUM> and the fixing ring <NUM>. Due to this, as compared to the case in which the first magnetic member <NUM> is in contact with the fixing ring <NUM>, it is possible to reduce the transmission of heat, generated by eddy currents flowing in the first magnetic member <NUM>, toward the fixing ring <NUM>. This makes a temperature rise in the fixing ring <NUM> smaller. Furthermore, due to the presence of the gap <NUM>, magnetic flux is less likely to flow toward the fixing ring <NUM>.

Furthermore, the pressing member <NUM> (the first magnetic member <NUM>) is biased in the axial direction and thereby the heat equalizing member <NUM> is pressed by the pressing member <NUM>. This allows the heat equalizing member <NUM> to be firmly fixed in the axial direction. Furthermore, because the pressing member <NUM> is provided to function as the first magnetic member <NUM>, an increase in cost is smaller as compared to the case in which the first magnetic member <NUM> and the pressing member <NUM> are provided as different members.

Furthermore, because the second magnetic member <NUM> is provided to the heater <NUM>, a path through which magnetic flux readily passes can be formed along the second magnetic member <NUM>. This facilitates the flow of magnetic flux between the first magnetic member <NUM> and the second magnetic member <NUM> opposed to each other in the radial direction when the magnetic flux flows between the heater <NUM> provided radially inside and the roller unit <NUM> provided radially outside. Accordingly, it is possible to reliably reduce the amount of magnetic flux passing through the fixing ring <NUM>.

Furthermore, in the configuration in which the second magnetic member <NUM> is structured by parts arranged in the circumferential direction, the flow of the magnetic flux between the first magnetic member <NUM> and the second magnetic member <NUM> is further facilitated, as compared to the case in which the second magnetic member <NUM> is provided to cover only a limited area with respect to the circumferential direction.

Furthermore, generated magnetic flux is intentionally guided by the flange <NUM> functioning as the third magnetic member to the second magnetic member <NUM>. This allows the magnetic flux to be reliably introduced into the second magnetic member <NUM>.

Furthermore, in the configuration in which the roller main body <NUM> is supported in a cantilever manner, heat generation in the fixing ring <NUM> provided to the base end portion is mitigated, thereby to moderate the above-described temperature gradient, leading to improvement in the distribution of the temperature on the axial base end portion of the outer circumferential surface 34a of the outer cylindrical portion <NUM>.

Furthermore, in the spun yarn drawing device <NUM> including the above-described induction heating rollers <NUM>, it is possible to equalize the distribution of temperature on roller surfaces, and to efficiently raise the temperature on the roller surfaces. This stabilizes the quality of yarns Y wound onto the induction heating rollers <NUM>, to enable production of high-quality yarns.

The following will describe modifications of the first embodiment. Components which are equivalent to or the same as those in the first embodiment are given the same reference numerals, and the descriptions thereof are not repeated, if appropriate.

The following describes a second embodiment of the present invention with reference to <FIG>, <FIG>. Components which are equivalent to or the same as those in the first embodiment are given the same reference numerals, and the descriptions thereof are not repeated, if appropriate.

<FIG> is a cross section of an induction heating roller <NUM> of the second embodiment of the present invention. <FIG> shows a fixing ring <NUM>, viewed from the base end side in the axial direction. The fixing ring <NUM> will be described later. <FIG> is a cross section taken along VIII(b)-VIII(b) in <FIG>.

The induction heating roller <NUM> of the second embodiment of the present invention includes a roller <NUM> and a heater <NUM>. The roller <NUM> includes: the roller main body <NUM> including the outer cylindrical portion <NUM>; the heat equalizing unit <NUM> including the heat equalizing member <NUM>; and the fixing ring <NUM> made of carbon steel. The roller main body <NUM> is supported in a cantilever manner.

Now, a description will be given of differences between the induction heating roller <NUM> and the induction heating roller <NUM> of the first embodiment. The pressing member <NUM> of the roller <NUM> is made of non-magnetic material such as SUS. That is, the first magnetic member <NUM> is not provided. Furthermore, the second magnetic member <NUM> is not provided to the heater <NUM>.

Due to the above-described arrangement, in the induction heating roller <NUM>, a path <NUM> (see a bold line) passing through the fixing ring <NUM> made of carbon steel is formed as a path through which magnetic flux readily passes. If excessive eddy currents flow in the circumferential direction of the fixing ring <NUM> due to the magnetic flux passing through the fixing ring <NUM>, excessive heat may be generated in the fixing ring <NUM>. For this reason, the fixing ring <NUM> has the following configurations in order to mitigate heat generation in the fixing ring <NUM> by reducing eddy currents.

As shown in <FIG>, the fixing ring <NUM> has high resistive portions <NUM>. Each high resistive portion <NUM> is a portion of the fixing ring <NUM> in the circumferential direction. The high resistive portion <NUM> has an electric resistance higher than that of other portion in the circumferential direction. In <FIG>, two high resistive portions <NUM> are provided. The high resistive portions <NUM> are portions of a ring main body <NUM> made of conductive material, which portions respectively have holes <NUM> with respect to the circumferential direction. Each hole <NUM> is, for example, a hole bored through the ring main body <NUM> in the axial direction and shaped like a slit extending in the radial direction (see <FIG>). Because of this, the cross-sectional area of each high resistive portion <NUM> (strictly speaking, the cross-sectional area of each portion of the conductive ring main body <NUM>) orthogonal to the circumferential direction is smaller than that of the portion other than the high resistive portions <NUM>. This makes the electric resistance at the high resistive portions <NUM> in the circumferential direction higher than that at the portion other than the high resistive portions <NUM>. The high resistive portions <NUM> therefore decrease the eddy currents flowing in the circumferential direction, to mitigate heat generation in the fixing ring <NUM>. Each hole <NUM> is filled with an insulator <NUM>. By filling the holes <NUM> with the insulators <NUM>, a decrease in strength of high resistive portions <NUM> is mitigated. The insulator <NUM> is made of synthetic resin, for example, and is firmly attached to an inner circumferential surface 75a of the corresponding hole <NUM>.

The shape and the like of each hole <NUM> is not particularly limited, as long as it reduces the cross-sectional area of the high resistive portions <NUM>. For example, each hole <NUM> may be a round hole, instead of the slit-shaped hole. Furthermore, each hole <NUM> does not have to be bored through the ring main body <NUM> in the axial direction. It may be bored through the ring main body <NUM> in the radial direction, for example. Still further, each hole <NUM> does not have to be a through hole bored through the ring main body <NUM>. Moreover, the number of the holes <NUM> is not limited to two. Furthermore, each high resistive portion <NUM> may have a notch or the like, instead of the hole <NUM>.

As described above, the fixing ring <NUM> is provided with the high resistive portions <NUM>. Due to this, eddy currents flowing in the circumferential direction of the fixing ring <NUM> are reduced by the high resistive portions <NUM>, and this makes it possible to mitigate heat generation in the fixing ring <NUM> provided to the induction heating roller <NUM>.

Furthermore, because the cross-sectional area of each high resistive portion <NUM> orthogonal to the circumferential direction is smaller, the electric resistance in the circumferential direction is higher at the high resistive portion <NUM>. The high electric resistance in the circumferential direction of the fixing ring <NUM> reduces the eddy currents flowing therein.

Furthermore, the one or more high resistive portions <NUM> each having a smaller cross-sectional area can be easily provided just by boring the hole(s) <NUM> in the ring main body <NUM> of the fixing ring <NUM>.

Furthermore, the insulator filling each hole <NUM> mitigates the decrease in strength of the fixing ring <NUM>.

Claim 1:
An induction heating roller (<NUM>) comprising:
a rotatable roller unit (<NUM>); and
a heater (<NUM>) including a coil (<NUM>) provided radially inward of the roller unit (<NUM>),
the roller unit (<NUM>) comprising:
a roller main body (<NUM>) including a cylindrical heating target (<NUM>) configured to be heated by induction heating due to magnetic flux passing in an axial direction of the roller unit (<NUM>), the magnetic flux being generated by electric current flowing through the coil (<NUM>);
a heat equalizing unit (<NUM>) including a heat equalizing member (<NUM>) which is in contact with an inner circumferential surface (34b) of the heating target (<NUM>), the heat equalizing member (<NUM>) extending in the axial direction and having a heat conductivity higher at least than that of the inner circumferential surface (34b) of the heating target (<NUM>); characterized by
a fixing ring (<NUM>) provided so as to be in contact with a first-side end portion of the heating target (<NUM>) which is on a first side in the axial direction and with a first-side end portion of the heat equalizing unit (<NUM>) which is on the first side in the axial direction, the fixing ring (<NUM>) fixing the roller main body (<NUM>) and the heat equalizing unit (<NUM>) to each other; and
by a first magnetic member (<NUM>) provided between the heating target (<NUM>) and the coil (<NUM>) in the radial direction, the first magnetic member (<NUM>) being provided on the first side relative to a center of the heating target (<NUM>) in the axial direction and on a second side opposite to the first side relative to the fixing ring (<NUM>) in the axial direction.