Patent Publication Number: US-10779364-B2

Title: Induction heated roll apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an induction heated roll apparatus. 
     Background Art 
     An induction heated roll apparatus is used in, for example, a continuous heat treatment process of continuous materials, for example, sheet materials or web materials, such as plastic films, papers, fabrics, non-woven fabrics, synthetic fibers, and metal foils, as well as wire rods (yarn materials). The induction heated roll apparatus includes an induction heating mechanism disposed inside a roll body that rotates. The induction heating mechanism causes a circumferential wall part of the roll body to generate heat by an induced current. 
     Recently, there has been a demand for making a change to a heating temperature by the roll body in a short time in association with a change in, for example, continuous material type. After termination of the heat treatment process, an operator needs to stay at a site unless the temperature of the roll body lowers to a certain temperature or below from the viewpoint of safety and sanitation. It is thus necessary to cool the roll body in a short time as much as possible. 
     Examples of roll apparatuses designed to cool the roll body include an air cooling type one disclosed in Patent Document 1 which is designed to cool the roll body by supplying air to a clearance part between the roll body and the induction heating mechanism. Specifically, this roll apparatus includes an air supply pipe coupled to one end of the roll body, and an air exhaust pipe coupled to an opposite end of the roll body. A blower for supplying air to the clearance part is coupled to the air supply pipe. 
     With the above configuration, however, air is simply supplied from one end portion of the roll body by the blower, and the air warmed in the clearance part is not positively exhausted at the other end portion side of the roll body. This may lead to the problem of uneven cooling in the roll body. 
     Although a method for water cooling the roll body by supplying water and mist into the interior of the roll body has also been conceived, the cost of installing a water supply circuit is expensive. Upon occurrence of a water leak or the like, dielectric breakdown may lead to an accident. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: Japanese Unexamined Patent Publication No. 2010-17943 
     SUMMARY OF THE INVENTION 
     Problems to Be Solved By the Invention 
     Accordingly, the present invention has been made to solve the above issues, and has for its main object to make it possible to uniformly cool the roll body and/or the induction heating mechanism by gas. 
     Means of Solving the Problems 
     Specifically, an induction heated roll apparatus of the present invention includes a roll body, an induction heating mechanism, and a cooling mechanism. The roll body has a hollow part. The induction heating mechanism is disposed in the hollow part and designed to cause the roll body to be subjected to induction heating. The cooling mechanism is designed to cool the roll body and/or the induction heating mechanism by generating a gas flow in a clearance part between the roll body and the induction heating mechanism. The cooling mechanism includes a suction port, an exhaust port, and a suction mechanism. The suction port is disposed on one axial end side of the roll body and designed to communicate with the clearance part. The exhaust port is disposed on an opposite axial end side of the roll body and designed to communicate with the clearance part. The suction mechanism is coupled to the exhaust port and designed to suck gas in the clearance part from the exhaust port. 
     With the above configuration, an external gas is sucked from the suction port disposed on the one axial end side of the roll body, and the external gas flows through the clearance part between the roll body and the induction heating mechanism by coupling the suction mechanism to the exhaust port disposed on the opposite axial end side of the roll body, and then sucking the gas from the exhaust port. Here, the clearance between the roll body and the induction heating mechanism has an approximately cylindrical shape, and the external gas sucked from the suction port flows uniformly in the circumferential direction, thus making it possible to uniformly cool the roll body and/or the induction heating mechanism. Here, since the gas warmed by flowing through the clearance part is actively sucked by the suction port and exhausted, the roll body and/or the induction heating mechanism can be cooled more evenly. Additionally, a circumferential structure of the roll body intended for obtaining a main effect of uniformly cooling the roll body needs only to dispose the suction mechanism on the opposite axial end side of the roll body, thereby avoiding complication of the circumferential structure of the roll body. 
     Besides the above, the high-temperature gas may be exhausted to an appropriate place, such as outdoors, so that no high-temperature gas is exhausted into the installation space for the roll body by, for example, disposing an exhaust duct in the suction mechanism. This not only prevents the high-temperature gas from threatening the safety of an operator, but also prevents adverse effects on the continuous heat treatment process of a continuous material. 
     The roll body includes a cylindrical shaped shell part having a pair of axial ends, and a pair of journal parts respectively coupled to both axial ends of the shell part. The gas flowing through the clearance part preferably flows at a uniform flow velocity in the circumferential direction in order to obtain the effect of cooling the roll body or the like and circumferential temperature uniformity of the roll body. 
     For this purpose, a plurality of the suction ports are preferably disposed at the journal part on the one axial end side. By disposing the plurality of suction ports, it is possible to ensure mechanical strength of the journal parts and also uniformly suck the gas in the circumferential direction of the clearance part while reducing suction resistance. 
     In order to make the gas flow velocity in the clearance part more uniform in the circumferential direction, the suction ports are preferably disposed at equal intervals in the circumferential direction at the journal part on the one axial end side. 
     Entry of foreign matter into the roll body from the suction port can cause, for example, the problem that the induction coil of the induction heating mechanism is broken. In order to suitably solve the problem, the suction port is preferably provided with a filter for removing foreign matter in the gas to be sucked. An aperture ratio (or opening) is variously settable according to dust that can occur around the roll body. When the filter has a small aperture ratio, the suction resistance may increase. Therefore, suction performance of the suction mechanism needs to be enhanced to obtain a desired flow velocity by way of, for example, using a high-pressure suction device. 
     The exhaust port is disposed on the roll body side and is therefore rotated, whereas the suction mechanism is disposed on a stationary side and is therefore not rotated. As a specific embodiment for sucking the gas in the clearance part from the exhaust port being rotated, it is conceivable that the suction mechanism includes a stationary body disposed on the stationary side so as to cover the exhaust port, and a suction device coupled to the stationary body and designed to suck the gas in the clearance part from the exhaust port. Here, the stationary body may be a component dedicated to the suction mechanism. When the roll body is provided with a rotary transformer for a temperature detection device, the stationary body may be a stator housing to hold a stator of the rotary transformer or may be formed integrally with the stator housing. 
     In the configuration that the roll body includes a pair of axial ends and a pair of drive shafts respectively disposed at both axial ends, it is conceivable to dispose the exhaust port on an outer circumferential surface of the drive shaft on the opposite axial end side in order to increase a contact area between the gas flowing through the clearance part and an inner surface of the shell part of the roll body as much as possible. In this configuration, it is conceivable to dispose the stationary body on the drive shaft so as to cover the exhaust port by interposing therebetween two bearings disposed so as to hold the exhaust port therebetween. 
     The induction heating mechanism includes an induction coil and a support shaft to support the induction coil. The support shaft is supported from the inside of the roll body with a bearing interposed therebetween. If the bearing is subjected to high temperature, grease deterioration is accelerated, and damage may occur early. The damage to the bearing becomes a factor of corotation of the induction coil and the roll body, and there is a risk of a serious electrical accident. 
     In order to suitably solve the above problem by eliminating the bearing that can be subjected to the high temperature gas on the exhaust side, one axial end of the support shaft is preferably supported on the roll body with a bearing interposed therebetween, and an opposite axial end of the support shaft is preferably supported on a member disposed on a stationary side (for example, a support shaft block). 
     In this configuration, it is necessary to dispose a rotary seal in order that no external gas is sucked from a clearance between the drive shaft of the journal part and the support shaft in the roll body on the opposite axial end side. 
     In the configuration that the support shaft is supported through a bearing on each of both axial end sides of the roll body, the bearing disposed on the opposite axial end side of the roll body is preferably disposed axially further outside than the exhaust port. 
     With this configuration, the bearing on the opposite axial end side is located axially further outside than the exhaust port, and it is therefore possible to prevent the bearing from being positively subjected to the high-temperature gas, and the lifetime of the bearing is less likely to become shorter. It is also possible to prevent the external gas from being sucked from the bearing, and also prevent the bearing from reaching high temperatures by increasing ventilation resistance in such a manner that a shielding structure, such as a shielding plate, is disposed between the bearing on the opposite axial end side and the exhaust port. 
     In order to simplify the structure of the opposite axial end side of the roll body, the stationary body is preferably designed to support the opposite axial end side of the support shaft. 
     In order to simplify the structure of the suction mechanism, the suction device is preferably integrally disposed on the stationary body with no piping interposed therebetween. 
     It is conceivable to employ, as the suction device, electric ones, such as a motor fan and a blower. Meanwhile, when a compressed gas source exists at an installation location of the induction heated roll apparatus in a factory or the like, it is possible to use, as the suction device, a gas flow amplifier designed to suck the gas from the exhaust port by being supplied with a compressed gas from the compressed gas source. 
     When the induction heated roll apparatus is installed in an atmosphere containing a corrosive gas and a combustible gas, a serious accident may occur due to the fact that the corrosive gas or the combustible gas is sucked into the roll body. In order to suitably solve this problem, the induction heated roll apparatus preferably further includes a supply mechanism designed to supply the gas to the suction port. The supply mechanism preferably includes supply piping to supply the gas to the suction port, and a joint member to connect the supply piping and the suction port. 
     The gas exhausted from the exhaust port by the suction device has a high temperature, and the high-temperature gas is then exhausted outside. This may induce the problem of thermal effects on the surrounding environment. It is therefore preferable to further include a circulating passage designed to permit communication between the suction port and the exhaust port outside of the roll body so as to return the gas sucked from the exhaust port by the suction device to the suction port, and a heat exchanger disposed in the circulating passage and designed to cool the gas. This configuration contributes to reducing the influence of suction and exhaust. 
     The cooling of the roll body or the like is intended to, for example, quickly lower the temperature to a safe temperature after termination of an operation, quickly lower the temperature when changing settings to a lower operating temperature in association with a change in production type, or quickly lower the temperature when replacing with another roll body having a different function. In these cases, no load operation is basically carried out. 
     Meanwhile, a load (heat treated object) to be taken into the roll body has a high temperature. Accordingly, due to heat input from the load to the roll body, the temperature of the roll body may gradually increase even when an electrical input is discontinued. In such a case, there is a temperature control method for stably controlling the temperature at a predetermined temperature by carrying out heat extraction slightly exceeding the heat input of the load, and then inputting induction heating, which corresponds to an excess thereof. This type of operation needs cooling during the load operation, thus necessitating temperature uniformity in the axial direction of the roll body during the cooling. Therefore, the roll body preferably includes a jacket chamber enclosing a two-phase gas-liquid heating medium therein and extending in the axial direction. 
     An amount of heat needed for cooling and time needed for cooling in the roll body bear a proportionate relationship to a flow velocity, namely, flow rate of the gas. In other words, when the flow rate of the gas in the clearance part is increased, the amount of heat needed for cooling is increased to reduce the time needed for cooling. However, during the load operation, the necessary amount of cooling differs depending on the amount of heat of load and operation conditions. Accordingly, the cooling mechanism is preferably designed to adjust the flow rate of the gas flowing through the clearance part. This configuration makes it possible to efficiently adjust to a predetermined temperature of the roll body. 
     The gas flows along the outer circumferential surface of the induction coil in the induction heating mechanism by the cooling mechanism, and thus insulation deterioration can occur due to entry of moisture or a contaminant. Therefore, the outer circumferential surface of the induction coil of the induction heating mechanism is preferably coated with an insulating varnish, such as a polyimide-based, silicone-based, or epoxy-based one. A selectable insulating varnish is one which is durable against a maximum temperature that the induction coil reaches. 
     Contact between the induction heating mechanism and the roll body may induce a ground fault, thus necessitating a certain clearance therebetween. In order to improve the cooling effect by reducing the clearance part between the roll body and the induction heating mechanism so as to increase the flow velocity of air flow, an insulating pipe being smaller than an inner circumferential diameter of the roll body is preferably secured to an outer circumference of the induction heating mechanism, and the clearance part is preferably formed between the roll body and the insulating pipe. Even when the insulating pipe and the roll body come in contact with each other, the contact is less likely to cause a serious accident because the insulating pipe is thus disposed. 
     When moisture is attached to the inner surface of the roll body, rust can occur, thus leading to insulation deterioration. Therefore, the inner surface of the roll body is preferably coated with an antirust material (for example, hard chromium plating, nickel plating, or an antirust paint, such as Stainless Coat (product name)). 
     In order to increase the cooling effect by increasing a heat transfer area of the inner surface of the roll body, a rugged structure is preferably formed on the inner surface of the roll body. Because the inner surface of the roll body serves as a heat generation part due to induction heating, the inner surface is preferably made into a regular shape in the circumferential and axial directions from the viewpoint of equalizing the amount of heat generation. 
     Effects of the Invention 
     With the present invention thus configured, it is possible to uniformly cool the roll body and/or the induction heating mechanism by the gas. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view schematically illustrating a configuration of an induction heated roll apparatus in a first embodiment; 
         FIG. 2  is a sectional view taken along line A-A of  FIG. 1 , illustrating a configuration of a suction port in the first embodiment; 
         FIG. 3  is a sectional view taken along line B-B of  FIG. 1 , illustrating a configuration of an exhaust port in the first embodiment; 
         FIG. 4  is a sectional view illustrating a configuration of an opposite axial end side of a roll body in the first embodiment; 
         FIG. 5  is a graph indicating temperature drop characteristics of the roll body due to a difference in air volume; 
         FIG. 6  is a sectional view illustrating a configuration of an opposite axial end side of a roll body in a second embodiment; 
         FIG. 7  is a sectional view illustrating a configuration of an opposite axial end side of a roll body in a third embodiment; 
         FIG. 8  is a sectional view schematically illustrating one modification of a suction mechanism; 
         FIG. 9  is a sectional view schematically illustrating another modification of the suction mechanism; 
         FIG. 10  is a sectional view schematically illustrating still another modification of the suction mechanism; 
         FIG. 11  is a sectional view schematically illustrating one modification of a suction port; 
         FIG. 12  is a sectional view schematically illustrating another modification of the suction port; 
         FIG. 13  is a sectional view schematically illustrating still another modification of the suction port; 
         FIG. 14  is a sectional view schematically illustrating yet another modification of the suction port; 
         FIG. 15  is a sectional view schematically illustrating a supply mechanism in an induction heated roll apparatus in a modified embodiment; 
         FIG. 16  is a diagram schematically illustrating a configuration of the induction heated roll apparatus in the modified embodiment; 
         FIG. 17  is a sectional view illustrating one configuration of a roll body in the modified embodiment; and 
         FIG. 18  is a sectional view illustrating another configuration of the roll body in the modified embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     First Embodiment 
     An induction heated roll apparatus  100  in a first embodiment is intended to be used in, for example, a continuous heat treatment process of a continuous material, for example, sheet materials or web materials, such as plastic films, papers, fabrics, unwoven fabrics, and metal foils, as well as wire rods (yarn materials). 
     Specifically, as illustrated in  FIG. 1 , the induction heated roll apparatus  100  includes a hollow cylindrical roll body  2  being rotatably supported, and an induction heating mechanism  3  disposed in a stationary state within a hollow part of the roll body  2 . 
     The roll body  2  includes a shell part  21  having a cylindrical shape, and a pair of journal parts  22  respectively disposed on both ends of the shell part  21 . Each of the journal parts  22  includes a flange portion  221  to cover an end opening of the shell part  21 , and a hollow drive shaft  222  formed integrally with the flange portion  221 . The drive shafts  222  are respectively rotatably supported on blocks  51  and  52  with bearings  41  and  42 , such as rolling bearings, interposed therebetween. The roll body  2  is designed to be rotated by a driving force applied from the outside by a rotation drive mechanism, such as a motor (not illustrated). 
     The shell part  21  of the roll body  2  is provided with a plurality of jacket chambers  21 A that extend in a longitudinal direction (axial direction) and enclose a two-phase gas-liquid heating medium therein. The jacket chambers  21 A are spaced apart from each other, for example, at equal intervals, in the entire circumferential direction. A surface temperature of the shell part  21  is made uniform by latent heat transfer of the two-phase gas-liquid heating medium enclosed within the jacket chambers  21 A. 
     The induction heating mechanism  3  includes a cylindrical iron core  31  having a cylindrical shape, an induction coil  32  being wound on an outer circumferential surface of the cylindrical iron core  31 , and support shafts  331  and  332  each supporting the cylindrical iron core  31  and the induction coil  32 . The support shafts  331  and  332  are respectively disposed on both ends of the cylindrical iron core  31 . The support shafts  331  and  332  are individually inserted into the drive shaft  222  and are respectively rotatably supported on the drive shaft  222  with bearings  61  and  62 , such as rolling bearings, interposed therebetween. Thus, the induction heating mechanism  3  is held in a stationary state with respect to the roll body  2  in the inside of the roll body  2  being rotated. A lead wire L 1  is coupled to the induction coil  32 , and an AC power source (not illustrated) for applying an AC voltage is coupled to the lead wire L 1  with a power regulating apparatus (not illustrated) interposed therebetween. 
     With the induction heating mechanism  3 , an alternating magnetic flux occurs upon application of the AC voltage to the induction coil  32 , and the alternating magnetic flux passes through the shell part  21  of the roll body  2 . An induced current occurs in the shell part  21  due to the passage of the alternating magnetic flux, and the shell part  21  generates Joule heat by the induced current. 
     The induction heated roll apparatus  100  of the present embodiment includes a cooling mechanism  7  that cools the roll body  2  and the induction heating mechanism  3  by generating a gas flow in a clearance part X 1  between the roll body  2  and the induction heating mechanism  3 . The gas that is a cooling medium in the present embodiment is air that is atmospheric gas in an installation space of the roll body  2 . Alternatively, the gas may be nitrogen gas or the like by changing the atmospheric gas into, for example, nitrogen gas or the like. 
     As illustrated in  FIG. 1 , the cooling mechanism  7  is designed to cool the roll body  2  and the induction heating mechanism  3  by introducing an external gas of the roll body  2  from one end in an axial direction of the clearance part X 1  having an approximately cylindrical shape formed between the roll body  2  and the induction heating mechanism  3 , while discharging the external gas from an opposite end in the axial direction of the clearance part X 1  to the outside. As used herein, the axial direction is a crosswise direction on a paper surface as indicated by arrows in  FIG. 1 . 
     Specifically, the cooling mechanism  7  includes a suction port  71 , an exhaust port  72 , and a suction mechanism  73 . The suction port  71  is disposed on one axial end side of the roll body  2  and communicated with the clearance part X 1 . The exhaust port  72  is disposed on the opposite axial end side of the roll body  2  and communicated with the clearance part X 1 . The suction mechanism  73  is coupled to the exhaust port  72  and designed to suck the gas in the clearance part X 1  from the exhaust port  72 . 
     As illustrated in  FIG. 2 , a plurality of the suction ports  71  are disposed on a flange portion  221  in the journal part  22  on the one axial end side. The suction ports  71  are disposed, for example, at equal intervals, in a circumferential direction at the flange portion  22  on the one axial end side. Each of the suction ports  71  is composed of a through hole formed along an axial direction of the flange portion  221 . An opening shape of the suction ports  71  in the present embodiment is a circular shape. Besides this, the opening shape may have different shapes, such as an elongated circular shape, an oval shape, a rectangular shape, and a polygonal shape. The suction port  71  is provided with a filter  8  for removing foreign matter in the gas to be sucked. Although the filter  8  in the present embodiment is an integrated one which closes the suction ports  71 , the filter  8  may be disposed on each of the suction ports  71 . 
     As illustrated in  FIG. 3 , a plurality of the exhaust ports  72  are disposed on an outer circumferential surface of the drive shaft  222  in the journal part  22  on the opposite axial end side. The exhaust ports  72  are disposed, for example, at equal intervals, in the circumferential direction in the drive shaft  222  on the opposite axial end side. Each of the exhaust ports  72  is composed of a through hole formed along a radial direction on a circumferential side wall of the drive shaft  222 . An opening shape of the exhaust ports  72  in the present embodiment is a circular shape. Besides this, the opening shape may have different shapes, such as an elongated circular shape, an oval shape, a rectangular shape, and a polygonal shape. A bearing  62  is disposed axially further outside than the exhaust ports  72  in the drive shaft  222  on the opposite axial end side. 
     As particularly illustrated in  FIG. 4 , the suction mechanism  73  includes a cover body  731  that is a stationary body disposed so as to cover the exhaust ports  72  on the stationary side, and a suction device  732  coupled to the cover body  731  and designed to suck the gas in the clearance X 1  from the exhaust ports  72 . The cover body  731  and the suction device  732  are coupled to each other by connecting piping (connecting duct)  733  in the present embodiment. 
     The cover body  731  has an approximately cylindrical shape and is disposed outside the outer circumferential surface of the drive shaft  222  having the exhaust ports  72  formed therein. An inner circumferential surface of the cover body  731  and the outer circumferential surface of the drive shaft  222  form an exhaust space X 2  for outwardly exhausting the gas exhausted from the exhaust ports  72 . The cover body  731  is provided with a connection port P 1  designed to connect the connecting duct  733 , and the exhaust space X 2  is communicated with the connection port P 1 . The cover body  731  is disposed through two bearings  91  and  92  on the drive shaft  222  so as to cover the exhaust ports  72 . The bearings  91  and  92  are disposed so as to axially hold the exhaust ports  72  therebetween. The cover body  731  is disposed axially further outside than the block  52  in the drive shaft  222 . The cover body  731  is secured to the stationary side so as not to rotate together with the drive shaft  222 . 
     A rotary transformer  10  is disposed axially outside the drive shaft  222  provided with the cover body  731 . The rotary transformer  10  transmits a detection signal of a temperature sensor T 1  (refer to  FIG. 1 ) to detect a temperature of the shell part  21  of the roll body  2 , to a controller on the stationary side. The rotary transformer  10  includes a rotor  101  disposed on the drive shaft  222  of the journal part  22 , and a stator  102  disposed around the rotor  101 . The stator  102  is disposed in a stator housing  103  having a cylindrical shape. 
     The suction device  732  is designed to suck the gas in the clearance part X 1  from the connection port P 1  of the cover body  731  with the exhaust space X 2  interposed therebetween. The suction device  732  is, for example, a motor fan, a blower, or a suction pump. The suction device  732  is disposed on the stationary side. An exhaust duct (not illustrated) is coupled to the exhaust port P 2  of the suction device  732 . The exhaust port P 2  in the exhaust duct is disposed in, for example, an external space (for example, outdoors) being different from the installation space of the induction heated roll apparatus  100 . The suction device  732  may be disposed in the external space, and the suction device  732  disposed in the external space and the connection port P 1  of the cover body  731  may be coupled to each other by the connecting duct  733 . The suction device  732  is designed so that a suction force is changeable by changing, for example, the number of revolutions. This makes it possible to adjust a flow rate of the gas flowing through the clearance part X 1 . Alternatively, a flow rate adjustment mechanism, such as a flow rate adjustment valve, may be disposed in the connecting duct. 
     When suction is started by the suction device  732  in the above configuration, the gas in the clearance part X 1  is sucked from the exhaust port  72 , and external gas around the roll body  2  is sucked from the suction ports  71  into the clearance part X 1 . The gas sucked from the suction ports  71  flows through the interior of the clearance part X 1  and is then exhausted from the exhaust ports  72 . Because the bearing  62  is located axially further outside than the exhaust ports  72 , most of the high-temperature gas is exhausted from the exhaust ports  72  before coming into contact with the bearing  62 , thus making it possible to prevent the bearing  62  from being positively subjected to the high-temperature gas. 
     A shielding structure  11 , such as a shielding plate, is disposed between the bearing  62  and the exhaust ports  72  on the opposite axial end side. The shielding structure  11  makes it difficult for the high-temperature gas to come into contact with the bearing  62  on the opposite axial end side. It is also possible to prevent the external gas from being sucked from the bearing  62  because ventilation resistance on the bearing  62  side is increased. 
     Similarly, a shielding structure  12 , such as a shield plate, is disposed inside the bearings  91  and  92  disposed between the cover body  731  and the drive shaft  222 . The shielding structure  12  makes it difficult for the high-temperature gas to come into contact with the bearings  91  and  92 . It is also possible to prevent the external gas from being sucked from the bearings  91  and  92 . 
     Furthermore, in the present embodiment, the following treatments are applied to portions with which the external gas sucked from the suction ports  71  comes into contact. That is, an outer circumferential surface of an induction coil  32  with which the external gas comes into contact is coated with a heat-resistant insulating varnish, such as a polyimide-based, silicone-based, or epoxy-based one. Specifically, the heat-resistant insulating varnish is applied to the outer circumferential surface of the induction coil  32 . An inner surface of the roll body  2  with which the external gas comes into contact is coated with a heat-resistant material. Specifically, a heat-resistant paint or an antirust paint is applied to, or a plating process for antirust is applied to the inner surface of the roll body  2 . 
     Effect of First Embodiment 
     With the induction heated roll apparatus  100  thus configured, the suction mechanism  73  is coupled to the exhaust ports  72  disposed on the opposite axial end side of the roll body  2 . By sucking the gas from the exhaust ports  72 , the external gas is sucked from the suction ports  71  disposed on the one axial end side of the roll body  2  and flows through the clearance part X 1  between the roll body  2  and the induction heating mechanism  3 . Here, the clearance part X 1  between the roll body  2  and the induction heating mechanism  3  has the approximately cylindrical shape, so that the external gas sucked from the suction ports  71  flows uniformly in the circumferential direction. It is therefore possible to uniformly cool the roll body  2  and the induction heating mechanism  3 . Here, since the gas warmed by flowing through the clearance part X 1  is actively sucked by the suction port  73  and exhausted, the roll body  2  and/or the induction heating mechanism  3  can be cooled more evenly. Additionally, the circumferential structure of the roll body  2  for the purpose of obtaining the major effect of uniformly cooling the roll body  2  needs only to dispose the suction mechanism  73  on the opposite axial end side of the roll body  2 . Hence, the configuration around the roll body  2  does not become complicated. 
     Besides the above, with the present embodiment, the high-temperature gas is exhausted to an appropriate place, such as outdoors, so that no high-temperature gas is exhausted into the installation space of the roll body  2 , by disposing the exhaust duct in the suction mechanism  73 . This not only prevents the high-temperature gas from threatening the safety of the operator, but also prevents adverse effects on the continuous heat treatment process of the continuous material. 
     Meanwhile, an investigation was conducted on temperature drop characteristics of the roll body due to a difference in air volume (a flow rate of air exhausted from the exhaust ports, namely, a flow velocity of the air in the clearance part X 1 ). The roll body has a diameter of 250 mm and an axial length of 1400 mm. An ambient temperature was 20° C., and a cooling start temperature of the roll body was 200° C. A surface temperature of the roll body was measured when the roll body was cooled in a state in which the number of revolutions of the roll body was set to 90 rpm. Time elapsed until the surface temperature of the roll body was lowered to 30° C. was measured by setting the air volume to 7 m 3 /min, 4 m 3 /min, 1 m 3 /min, and natural cooling (0 m 3 /min). 
     The results are presented in  FIG. 5 . Although the natural cooling needs 420 minutes or more, the cooling time decreases with increasing the air volume, and the cooling time is less than 60 minutes when the air volume is 7 m 3 /min, as presented in  FIG. 5 . 
     A load having a higher temperature than a necessary operating temperature may enter the roll body  2  (heated roll). Therefore, a roll temperature may increase even when an electric input is discontinued. In this case, it is difficult to make high-precision temperature control only by cooling due to the gas flow. Hence, there is a method of precisely controlling to a desired temperature by carrying out heat extraction slightly exceeding the heat input of the load, and then inputting only an amount of heat corresponding to an excess thereof by induction heating. The heat control by cooling under flow volume adjustment as described above is effective for making this control. 
     Even during cooling, the uniformity of temperature distribution in the shell part  21  of the roll body  2  is extremely important when the load operation is being carried out. The shell part  21  of the roll body  2  includes the jacket chambers  21 A enclosing the two-phase gas-liquid heating medium therein. It is therefore possible to improve temperature uniformity in the axial direction of the shell part  21  of the roll body  2  during the cooling operation. 
     Moreover, the suction ports  71  are disposed at the journal part  22  on the axial one end side. It is therefore possible to ensure mechanical strength of the journal part  22  and also uniformly suck the gas in the circumferential direction of the clearance part X 1  while reducing suction resistance. 
     Second Embodiment 
     An induction heated roll apparatus in a second embodiment is described below. Members identical or corresponding to those in the first embodiment are identified by the same reference numerals. 
     The induction heated roll apparatus  100  of the second embodiment is mainly different from the first embodiment in support form of support shafts  331  and  332  of an induction heating mechanism  3 . 
     Specifically, in the induction heated roll apparatus  100 , as illustrated in  FIG. 6 , the support shaft  331  on one axial end side is rotatably supported on a drive shaft  222  on the one axial end side with a bearing  61 , such as a rolling bearing, interposed therebetween. The support shaft  332  on the opposite axial end side extends outward from the drive shaft  222  on the opposite axial end side and is secured to a member (support shaft block)  13  disposed on a stationary side. 
     When suction is carried out from exhaust ports  72  by a suction mechanism  73  in the above configuration, not only the gas in a clearance part X 1  between a roll body  2  and the induction heating mechanism  3  is sucked, but also the external gas may be sucked from a clearance between the drive shaft  222  and the support shaft  332  on the opposite axial end side, and from a rotary transformer  10 . Therefore, a rotary seal  14  is disposed between an inner circumferential surface of the drive shaft  22  and an outer circumferential surface of the support shaft  332  in the present embodiment. Alternatively, the rotary seal  14  may be disposed between an inner circumferential surface of the stator housing  103  of the rotary transformer  10  and an outer circumferential surface of the drive shaft  222 . 
     When suction is started by a suction device  732  in the above configuration, the gas in the clearance part X 1  is sucked from exhaust ports  72 , and the gas around the roll body  2  is sucked from suction ports  71  into the clearance part X 1 . On this occasion, because the rotary seal  14  is disposed closer to the opposite axial end side than the exhaust ports  72 , it is possible to prevent the external gas from being sucked from the opposite axial end side. The gas sucked from the suction ports  71  flows through the interior of the clearance part X 1  and is then exhausted from the exhaust ports  72 . Because any bearing (the bearing  62  in the foregoing embodiment) is not disposed on the opposite axial end side in the interior of the roll body  2 , no high-temperature gas comes into contact with the bearing. 
     Effect of Second Embodiment 
     In addition to the effect of the first embodiment, the induction heated roll apparatus  100  thus configured produces the following effect. That is, the support shaft  332  on the opposite axial end side is supported on a block  13  on the stationary side. Therefore, the bearing that can be subjected to the high-temperature gas is eliminated to prevent damage to the bearing due to the high-temperature gas, thereby preventing corotation of an induction coil  32  and the roll body  2 . 
     Third Embodiment 
     An induction heated roll apparatus in a third embodiment is described below. Members identical or corresponding to those in the first and second embodiments are identified by the same reference numerals. 
     As illustrated in  FIG. 7 , the induction heated roll apparatus  100  of the third embodiment is different from the second embodiment in that at least a cover body  731  and a stator housing  103  of a rotary transformer  10  are integrally formed together.  FIG. 7  illustrates an embodiment in which a support shaft block  13  is also integrally formed in addition to the cover body  731  and the stator housing  103 . 
     Specifically, in the induction heated roll apparatus  100 , the cover body  731 , the stator housing  103 , and the support shaft block  13  are made of a common cylindrical member  15  that is a stationary body. A side circumferential wall of the cylindrical member  15  is disposed on a drive shaft  222  with two bearings  91  and  92  interposed therebetween. Space between the two bearings  91  and  92  serves as an exhaust space X 2 . A connection port P 1  designed to connect a suction device  732  is disposed between the two bearings  91  and  92  on the side circumferential wall. A stator  102  of a rotary transformer  10  is disposed at a position opposed to a rotor  101  of the rotary transformer  10  on an inner circumferential surface of the side circumferential wall. A support shaft  332  extends through a bottom wall of the cylindrical member  15 , and the support shaft  332  is secured to the bottom wall. “Bottom” here refers to the ends of a closed cylindrical shape. The cylindrical member  15  is secured to a stationary side by a member (not illustrated). The member on the stationary side is designed to prevent rotation of the cylindrical member  15  and axially slidably support the roll body  2  and the like in order to allow their thermal elongation. 
     Effect of Third Embodiment 
     In addition to the effects of the first and second embodiments, the induction heated roll apparatus  100  thus configured is capable of simplifying the configuration on the opposite axial end side of the roll body  2  and decreasing the number of components because the cover body  731 , the stator housing  103 , and the support shaft block  13  are made of the common cylindrical member  15 . 
     Other Modified Embodiments 
     The present invention is not limited to the foregoing embodiments. 
     For example, as illustrated in  FIG. 8 , the suction device  732  may be directly attached to the connection port P 1  of the cover body  731  (or the cylindrical member  15 ) without interposing the connection duct therebetween. 
     In this case, a gas flow amplifier designed to receive a compressed gas from a compressed gas source and suck the gas from an exhaust port may be used as the suction device  732 . With this configuration, there is no need to separately prepare, for example, a ventilator or a blower when the compressed gas source exists at an installation location of the induction heated roll apparatus  100  in a factory or the like. 
     Although the cover body  731 , the stator housing  103 , and the support shaft block  13  are integrally formed together in the third embodiment, just the cover body  731  and the stator housing  103  may be integrally formed together. In this case, the support shaft  332  on the opposite axial end side is supported by the support shaft block  13 . In the configuration of the first embodiment, the cover body  731  and the stator housing  103  may be integrally formed together. 
     When the cover body  731  and the stator housing  103  or the like are integrally formed together, the connection port P 1  may be disposed axially further outside (a bottom wall side) than the stator  102  of the rotary transformer  10  in the common cylindrical member  15  as illustrated in  FIGS. 9 and 10 .  FIG. 9  illustrates a configuration that the support shaft  332  is supported by the support shaft block  13 .  FIG. 10  illustrates a configuration that the support shaft  332  is supported by the cylindrical member  15 . Here, the exhaust ports  72  are composed of an annular space formed between the drive shaft  222  (or the rotor  101 ) and the support shaft  332  on the opposite axial end side. 
     In the configuration in  FIG. 9 , the external gas may be sucked from an opening of the cylindrical member  15 , namely, the space between the rotor  101  and the stator  102 . Therefore, a rotary seal  16  is preferably disposed closer to the opening than the stator  102  on the side circumferential wall of the cylindrical member  15 . In both configurations in  FIGS. 9 and 10 , a through hole  15   h  designed to communicate with the outside is formed between the stator  102  and the rotary seal  16  or the bearing  9  on the side circumferential wall of the cylindrical member  15 . An appropriate flow rate of gas is designed to be sucked from the through hole  15   h  so that the rotor  101  and the stator  102  are cooled to make them less likely to deteriorate. In  FIG. 10 , the bearing  9  is preferably provided with a shielding structure, such as a shielding plate, in order to prevent suction of the external gas from the bearing  9 . 
     In each of the foregoing embodiments, the exhaust ports  72  are disposed on the outer circumferential surface of the drive shaft  222  of the journal part  22 . The exhaust ports  72  may be disposed on the flange part  221  of the journal part  22  as in the case with the suction ports  71  in the foregoing embodiments. In this case, an annular cover body  731  is disposed so as to oppose to the flange part  221 . 
     In each of the foregoing embodiments, the suction ports  71  are disposed at the flange part  221  of the journal part  22  on the one axial end side. Besides this, a variety of changes can be made if it is a position at which it is possible to supply the gas to one axial end side of the clearance part X 1 . 
     For example, as illustrated in  FIG. 11 , the support shaft  331  on the one axial end side may be supported on a block  17  disposed outside the roll body  2 , and an annular space formed between the drive shaft  222  and the support shaft  331  on the one axial end side may be used as the suction port  71 . Alternatively, the suction port  71  may be used together with a suction port disposed at another position. When a filter is attached to the suction portion  71 , the filter needs to be disposed between a rotary part (the drive shaft  222 ) and a nonrotary part (the support shaft  331 ). Therefore, a clearance between an inner circumferential surface of the filter and an outer circumferential surface of the support shaft  331  needs not to exceed an allowable foreign matter size. 
     Alternatively, as illustrated in  FIG. 12 , an internal flow channel R 1  may be coaxially formed inside the support shaft  331  and around the shaft, and the internal flow channel R 1  may be branched radially on the induction coil  32  side of the support shaft  331  so as to be opened in the outer circumferential surface of the support shaft  331 . In this case, the opening of the internal flow channel R 1  in an axial end surface of the support shaft  331  serves as the suction port  71 . The suction port  71  may be used together with a suction port disposed at another position. 
     Still alternatively, as illustrated in  FIG. 13 , a through hole H 1  may be formed along an axial direction on the side circumferential wall of the drive shaft  222  on one axial end side. Preferably, a plurality of the through holes H 1  are formed at equal intervals in a circumferential direction on the side circumferential wall. In this case, openings of the through holes H 1  on an axial end surface of the drive shaft  222  serve as suction ports  71 . The suction ports  71  may be used together with a suction port disposed at another position. 
     Moreover, as illustrated in  FIG. 14 , a through hole H 2  may be formed along a radial direction on the side circumferential wall of the drive shaft  222  on one axial end side. Here, the through hole H 2  is formed axially further inside than a bearing  61  on the one axial end side. In this case, a radially outside opening of the through hole H 2  serves as a suction port  71 . The suction port  71  may be used together with a suction port disposed at another position as needed. 
     When the induction heated roll apparatus  100  is installed in a harmful atmosphere containing a corrosive gas and a combustible gas, the induction heated roll apparatus  100  may further include a supply mechanism  18  designed to supply gas to the suction port  71  as illustrated in  FIG. 15 . This configuration is capable of eliminating the probability of causing a serious accident to happen due to the fact that the corrosive gas or the combustible gas is sucked into the roll body  2 . The gas supplied may be an inert gas, such as nitrogen gas, besides air. Alternatively, air containing a mist may be supplied. 
     It is conceivable to configure the supply mechanism  18  so as to include supply piping  181  to supply the gas to the suction port  71 , and a joint member  182  to connect the supply piping  181  and the suction port  71 . The supply piping  181  is coupled to a connection port P 3  disposed in the joint member  182 . In the configuration in  FIG. 15 , the suction port  71  is disposed on the outer circumferential surface of the drive shaft  222 , and a gas introduction port  181   a  of the supply piping  181  is disposed in an atmosphere separated from the harmful atmosphere by a wall W. 
     The joint member  182  has an approximately cylindrical shape disposed outside the outer circumferential surface of the drive shaft  222  provided with the suction port  71 . An inner circumferential surface of the joint member  182  and the outer circumferential surface of the drive shaft  222  form an introduction space X 3  designed to introduce the gas into the suction port  71 . The joint member  182  is provided with a connection port P 3  designed to connect the supply piping  181 , and the introduction space X 3  is communicated with the connection port P 3 . The joint member  182  is disposed on the drive shaft  222  so as to cover the suction port  71  by interposing therebetween two bearings  191  and  192  disposed so as to hold the suction port  71  therebetween in the axial direction. The joint member  182  is secured to the stationary side so as not to rotate together with the drive shaft  222 . The bearing  61  and the bearings  191  and  192  are preferably provided with a shielding structure, such as a shielding plate, in order to avoid suction of the gas in the harmful atmosphere. 
     Alternatively, the induction heated roll apparatus  100  may further include a circulating passage CP and a heat exchanger HE as illustrated in  FIG. 16 . The circulating passage CP is designed to permit communication between the suction port  71  and the exhaust port  72  outside of the roll body  2  so as to return the gas sucked from the exhaust port  72  by the suction device  732  to the suction port  71 . The heat exchanger HE is disposed in the circulating passage CP and designed to cool the gas. 
     The circulating passage CP illustrated in  FIG. 16  includes the suction mechanism  73  of the foregoing embodiment, and a connecting piping (connecting duct) CP 1  to connect the exhaust port P 2  in the suction mechanism  732  and the suction port  71  in the suction device  732 . The connecting piping CP 1  and the suction port  71  are coupled to each other by a cover body CP 2  having the same structure as the cover body  731  used in a connection structure for the exhaust port  72  and the suction mechanism  73 . The configuration having the above circulating passage CP is capable of reducing the influences of suction and exhaust. 
     Further, in the induction heated roll apparatus  100 , an insulating pipe  34  being smaller than inner circumferential diameter of the roll body  2  may be secured to the outer circumference of the induction heating mechanism  3 , and the clearance part X 1  may be formed between the roll body  2  and the insulating pipe  34  as illustrated in  FIG. 17 . The insulating pipe is disposed so as to cover the entirety of the induction coil  32  of the induction heating mechanism  3 . The insulating pipe  34  is disposed separately from the induction coil  32  in an outer diameter direction. The clearance part X 1  between the roll body  2  and the induction heating mechanism  3  can be reduced to increase a flow velocity of an air flow by the insulating pipe  34 , thus improving cooling effect. If the insulating pipe  34  and the roll body  2  come in contact with each other, a serious accident is less likely to occur. 
     Furthermore, as illustrated in  FIG. 18 , a rugged structure  2 Z is preferably formed on an inner surface of the roll body  2  in order that a heat transfer area on the inner surface of the roll body  2  is increased to enhance the cooling effect. Although the rugged structure  2 Z is formed by forming recesses on the inner surface of the roll body  2  in  FIG. 18 , the rugged structure  2 Z may be formed by forming protrusions on the inner surface. Because the inner surface of the roll body  2  serves as a heat generation part due to induction heating, the inner surface is preferably made into a regular shape in the circumferential and axial directions from the viewpoint of equalizing the amount of heat generation. 
     Although the cover body  731  and the cylindrical member  15  in the foregoing embodiments have the cylindrical shape, both may have, besides the cylindrical shape, any polygonal cylindrical shape, such as a rectangular cylinder, as long as it covers the outer circumference of the drive shaft  222 . 
     Besides the above, it will be understood that the present invention is not limited to the foregoing embodiments, and various modifications may be made without departing from the spirit and scope of the present invention. 
     DESCRIPTION OF THE REFERENCE CHARACTERS 
     
         
           100  induction heated roll apparatus 
           2  roll body 
           21  shell part 
           21 A jacket chamber 
           22  journal part 
           222  drive shaft 
           3  induction heating mechanism 
           31  induction coil 
           331 ,  332  support shaft 
         X 1  clearance part 
           7  cooling mechanism 
           71  suction port 
           8  filter 
           72  exhaust port 
           73  suction mechanism 
           731  cover body (stationary body) 
           732  suction device 
           61 ,  62  bearing 
           91 ,  92  bearing 
           13  block (support shaft block) 
           15  cylindrical member (stationary body) 
           18  supply mechanism 
           181  supply piping 
           182  joint member