JP2008181051A - Fixing device and image forming apparatus equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a great temperature difference from occurring in an exciting coil even with a configuration of introducing cooled air from only one end part side of a heating roller to cool the exciting coil stored inside the heating roller. <P>SOLUTION: A fixing device is provided with a pipe like core material 34 extending in an axial direction of the heating roller with an exciting coil 32 on its outer periphery. A plurality of ventilation holes 41 for having cool air circulating inside from one end part 38 side to another end part 39 side come into contact with the exciting coil is opened at a peripheral wall of the core material 34 in the axial direction at prescribed spacings. The plurality of ventilation holes is provided so that opened area on the another end part 39 side is greater when compared to the one end part 38 side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, the exciting coil that generates heat by the electromagnetic induction action is housed in the heating roller, and is cooled by the cooling air introduced from one end side of the heating roller by the blowing means. The present invention relates to a fixing device and an image forming apparatus including the same.

  In an image forming apparatus (such as a printer, a facsimile machine, a copying machine, and a multi-function machine) that forms an image on recording paper by an electrophotographic process, unfixed toner transferred from the photosensitive member onto the recording paper is recorded by heat and pressure. There is provided a fixing device for fixing the toner. In this fixing device, in recent years, an electromagnetic induction heating method in which a heating medium such as a heating roller is heated by Joule heat generated by an eddy current generated by electromagnetic induction has attracted attention from the viewpoint of energy saving.

  In such an electromagnetic induction heating type fixing device, in addition to a configuration in which an induction heating unit including an exciting coil, a magnetic core, and a holding member thereof is disposed opposite to the outer peripheral side of the heating roller, from the viewpoint of space saving, The structure which accommodated the induction heating unit in the inside of a heating roller is employ | adopted.

However, in such an encapsulated induction heating unit, the temperature of the exciting coil is increased by the radiant heat of the heating roller and the heat generated by the heating roller. In order to avoid the exciting coil from being cooled to an abnormally high temperature state, a technique is known in which cooling air is introduced into the heating roller by a fan to cool the exciting coil (Patent Document 1). To 3).
Japanese Patent No. 3497444 JP 2000-29336 A JP 2003-186323 A

  However, in the above-described conventional technique, in the configuration in which the cooling air is introduced only from one end side of the heating roller by the fan, the temperature of the cooling air gradually increases toward the downstream side, and the wind pressure applied to the exciting coil is also increased. Therefore, the cooling capacity is greatly reduced on the downstream side compared to the upstream side. For this reason, if the air volume is set based on the temperature of the downstream exciting coil that becomes high, the temperature of the upstream exciting coil decreases more than necessary and the heating efficiency of the heating roller decreases. There arises a problem that the temperature unevenness in the direction occurs.

  On the other hand, in the configuration in which cooling air is introduced from both sides of the heating roller, an axial temperature difference is less likely to occur in the exciting coil. However, when the shape of the end of the heating roller is asymmetric, the flow of cooling air This causes a problem that it is difficult to set the balance on both sides. Moreover, since it is necessary to provide two fans or to connect one fan and both ends with a long duct, there arises a problem that the manufacturing cost is increased and noise is increased.

  The present invention has been devised to solve such problems of the prior art, and its main object is to cool one of the heating rollers in order to cool the exciting coil housed inside the heating roller. An object of the present invention is to provide a fixing device configured to prevent a large temperature difference from occurring in an exciting coil and an image forming apparatus provided with the same even when cooling air is introduced only from the end side of the coil.

  In the present invention, an exciting coil that generates heat by an electromagnetic induction action is housed inside the heating roller, and is cooled by cooling air introduced from one end side of the heating roller by a blower. In the fixing device configured as described above, the heating roller has a pipe-shaped core member that extends in the axial direction and the excitation coil is provided on the outer periphery, and one end of the core member is provided on the peripheral wall of the core member. A plurality of ventilation holes are formed at predetermined intervals in the axial direction for applying cooling air flowing through the interior from the part side toward the other end side to the excitation coil. It is set as the structure provided so that it might become a large opening area in the other edge part side compared with the edge part side.

  According to the present invention, when cooling air is introduced from one end side, the air flow hole on the other end side located on the downstream side becomes larger, so that the amount of cooling air hitting the exciting coil increases and excitation is performed. Since heat dissipation of the coil is promoted, it is possible to improve the problem that the cooling capacity is lower than that of one end side on the upstream side, and to prevent a large temperature difference from occurring in the exciting coil. The exciting coil can be cooled to an appropriate temperature state without causing thermal damage to the exciting coil and without deteriorating the heating efficiency of the heating roller, thereby suppressing temperature unevenness in the axial direction of the heating roller. A great effect can be obtained in realizing high-quality and stable fixing processing.

  According to a first aspect of the present invention for solving the above-described problems, an exciting coil for generating heat from the heating roller by electromagnetic induction is housed inside the heating roller, and at one end of the heating roller by a blowing means. In the fixing device that is cooled by the cooling air introduced from the side, the fixing device includes a pipe-shaped core member that extends in the axial direction of the heating roller and has the excitation coil provided on the outer periphery thereof. A plurality of ventilation holes are provided in the peripheral wall at a predetermined interval in the axial direction for applying cooling air that circulates in the interior from one end side to the other end side of the core member to the exciting coil. The plurality of ventilation holes are provided so as to have a larger opening area on the other end side than on the one end side.

  According to this, when cooling air is introduced from one end side, on the other end side located on the downstream side, the ventilation hole becomes large, so that the air volume of the cooling air hitting the exciting coil increases and the excitation coil Since heat dissipation is promoted, it is possible to improve the problem that the cooling capacity is low as compared with the one end side on the upstream side, and to prevent a large temperature difference from occurring in the exciting coil.

  According to a second aspect of the present invention for solving the above problems, a magnetic core is provided on the outer periphery of the core member, and a through hole is formed in a peripheral wall portion of the core member corresponding to the magnetic core, The cooling air flowing through the inside of the core material is directly applied to the magnetic core.

  According to this, the exciting coil is cooled by the cooling air passing through the ventilation hole, and at the same time, the magnetic core is cooled by the cooling air flowing through the inside of the core material without passing through the core material. Can be increased.

  3rd invention made | formed in order to solve the said subject is set as the structure by which the said several ventilation hole was provided so that it might become a small opening area in a center part compared with one edge part side.

  According to this, since the cooling capacity at the center portion is lower than that at one end side, the temperature of the heating roller is compared with that at one end side by continuously passing a small size recording paper. When the temperature is lowered at the center, it can be avoided that the exciting coil is excessively cooled at the center and the heating efficiency of the heating roller is deteriorated, thereby suppressing temperature unevenness in the axial direction of the heating roller. Can do.

  4th invention made | formed in order to solve the said subject, The arrangement | positioning area | region of the said excitation coil in the said core material is divided into three area | regions of 1st, 2nd, and 3 from one edge part side, The second region in the central part where the ventilation holes are provided with an opening area smaller than the first region on one end side is set to a width corresponding to the recording medium of the minimum size.

  In this case, since a large temperature difference occurs between the end portion and the central portion during continuous paper feeding, the minimum size recording medium that defines the width of the second region in the central portion is a paper feed cassette or paper feed. What is necessary is just to make it the minimum size (usually postcard size) of the recording media that can be continuously fed from the tray (manual feed tray).

  In a fifth aspect of the present invention made to solve the above problems, the core material is formed of a non-metallic material that is non-magnetic and non-conductive.

  According to this, since it is possible to avoid the core material itself from generating heat due to the electromagnetic induction action, the power loss can be reduced. In addition, although the non-metallic material is inferior in thermal conductivity as compared with the metallic material, it does not generate heat due to the electromagnetic induction action, and as a result, the effect of preventing the temperature rise is substantially the same as that of the metallic material.

  In this case, the core material is made of a high-strength synthetic resin material, particularly PPS (poly phenylene sulfide) or liquid crystal polymer, which has high heat resistance and can obtain high rigidity capable of stably holding the exciting coil. Is preferred.

  According to a sixth aspect of the present invention for solving the above-described problems, a plurality of the exciting coils are arranged in the axial direction along the axial direction, and at the same axial position corresponding to each of the plurality of exciting coils. A plurality of magnetic cores are provided on the core material in the circumferential direction, and the ventilation holes are provided at positions between the magnetic cores arranged in the circumferential direction.

  According to this, since the magnetic core is provided in each of the plurality of exciting coils arranged in the axial direction, the length of the magnetic flux passing through the heating roller is shortened, so that the oscillation control in the high frequency power source is facilitated. And by providing a ventilation hole in the position between the several magnetic body cores spaced apart in the circumferential direction, it cools by applying cooling air to each of the plurality of exciting coils without being obstructed by the magnetic body core be able to.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a copying machine to which the present invention is applied. The copying machine (image forming apparatus) includes an original reading unit 1 that reads an image of an original, an image forming unit 2 that forms an image of the original read here on a recording paper (recording medium) with toner, and a recording here. A recording unit having a fixing unit (fixing device) 3 for fixing a toner image formed on the paper. The recording sheet is supplied from the paper supply unit 4 to the image forming unit 2, and the fixing unit 3 completes the fixing process. Is discharged to the paper discharge unit 5.

  In the image forming unit 2, the photosensitive drum 12 uniformly charged by the charging roller 11 is irradiated with laser light from the laser scanning unit 13 to form an electrostatic latent image on the image forming surface of the photosensitive drum 12. After that, the toner in the developing unit 14 is supplied to the photosensitive drum 12 through the developing roller 15 to develop the electrostatic latent image on the image forming surface, and the toner image formed thereby is transferred. The image is transferred onto the recording paper by the roller 16.

  FIG. 2 is a cross-sectional view showing a main part of the fixing unit 3 shown in FIG. The fixing unit 3 includes a heating roller 21 that thermally melts the toner image on the recording paper (recording medium) S, and a pressure roller 22 that is urged in a direction to come into pressure contact with the heating roller 21 by a spring (not shown). The recording paper S is fed into the nip portion between the heating roller 21 and the pressure roller 22, and the toner on the recording paper S is fixed to the recording paper S by the action of heat and pressure.

  The heating roller 21 has a hollow cylindrical roller body 23 made of a magnetic shunt alloy such as iron-nickel alloy, and an electromagnetic induction heating unit 24 is accommodated in the roller body 23. The electromagnetic induction heating unit 24 is driven by a high frequency power source 25, and the roller body 23 generates heat by a high frequency magnetic field generated by the exciting coil 32. The periphery of the electromagnetic induction heating unit 24 is covered with an insulating pipe 26. A release layer (not shown) made of a fluororesin or the like is formed on the surface of the roller body 23.

  The pressure roller 22 includes a metal core 28 made of an aluminum alloy material and an elastic layer 29 made of a sponge material such as foamed silicone rubber formed around the metal core 28.

  FIG. 3 is a cross-sectional view of the heating roller 21 shown in FIG. 2 in the axial direction. The electromagnetic induction heating unit 24 accommodated in the heating roller 21 includes a plurality of exciting coils 32 arranged in series in the axial direction, and a magnetic core assembly 33 individually provided in the plurality of exciting coils 32. And a core member (coil holder) 34 extending in the axial direction to hold the exciting coil 32 and the magnetic core assembly 33.

  The exciting coil 32 is formed coaxially with the heating roller 21 by a conducting wire (Litz wire) 35 wound around the center line of the heating roller 21. Each of the exciting coils 32 is provided with two magnetic core assemblies 33 at the same axial position and symmetrical positions with the center line of the heating roller 21 as the center. One exciting coil 32 is formed by winding a conducting wire 35 around the core assembly 33.

  The pair of magnetic core assemblies 33 corresponding to one excitation coil 32 is centered on the center line of the heating roller 21 with respect to the magnetic core assemblies 33 corresponding to the excitation coils 32 adjacent in the axial direction. Thus, they are provided at an arrangement angle shifted by 90 degrees in the circumferential direction.

  The core member 34 is formed in a pipe shape having a square cross section so as to conform to the arrangement form of the magnetic core assembly 33, and the cooling air generated by the fan (air blowing means) 36 is passed through the duct 37 to the core. The exciting coil 32 is cooled by being introduced into the core member 34 from one end 38 of the member 34.

  The core material 34 is made of a non-magnetic material that is non-magnetic and non-conductive, and the non-metal material has high heat resistance and high rigidity capable of stably holding the exciting coil. A high-strength synthetic resin material that can be used, such as PPS (poly phenylene sulfide) or a liquid crystal polymer, is suitable.

  If the core material 34 is made of a non-magnetic and non-conductive synthetic resin material in this way, the core material 34 itself can be prevented from generating heat due to electromagnetic induction, thereby reducing power loss. Can do. Further, although the synthetic resin material is inferior in thermal conductivity to the metal material, it does not generate heat due to the electromagnetic induction action, and as a result, the effect of preventing the temperature rise is substantially the same as that of the metal material.

  4 is a perspective view showing the electromagnetic induction heating unit 24 shown in FIG. 3, in which the excitation coil 32 is cut. On the peripheral wall of the core member 34, a plurality of ventilation holes 41 are provided at predetermined intervals in the axial direction for applying cooling air from the fan 36 to the excitation coil 32.

  The ventilation hole 41 is provided at a position between two magnetic core assemblies 33 that are spaced apart from each other in the circumferential direction corresponding to one excitation coil 32. That is, of the first to fourth flat plate portions 34a to 34d constituting the peripheral wall of the core member 34, the second is provided at the place where the magnetic core assembly 33 is attached to the first and third flat plate portions 34a and 34c. The first and third flat plate portions 34a, 34a, 34d are provided in the fourth flat plate portions 34b, 34d, and the magnetic core assembly 33 is attached to the second, fourth flat plate portions 34b, 34d. A ventilation hole 41 is opened at 34 c, and the excitation coil 32 is provided outside the ventilation hole 41 so as to cover it.

  Thus, the cooling air introduced into the core member 34 from the inlet 43 on the one end portion 38 side by the fan 36 flows through the inside of the core member 34, and the outlet port 44 on the other end portion 39 side. And the exciting coil 32 is cooled by being discharged from the plurality of ventilation holes 41.

  The ventilation holes 41 are provided so as to have different opening areas depending on the position in the axial direction. Here, the region where the exciting coil 32 is disposed in the core material 34 is divided into three regions 46, 47, 48 of the first, second, and third regions from one end 38 side, and the same region 46, 47. The plurality of ventilation holes 41 in 48 are provided with the same opening area, and the ventilation holes 41 in the third region 48 on the other end 39 side (downstream side) The opening area is larger than the ventilation hole 41 in the first region 46 on the 38th side (upstream side).

  As a result, in the third region 48 on the other end 39 side, the ventilation hole 41 becomes larger, so that the flow rate of the cooling air hitting the excitation coil 32 is increased and the heat dissipation of the excitation coil 32 is promoted. As compared with the first region 46, it is possible to improve the problem that the cooling capacity is lowered in the third region 48 on the downstream side.

  Furthermore, the ventilation hole 41 in the 2nd area | region 47 of the axial center part is provided here with an opening area smaller than the 1st area | region 46 by the side of one edge part 38. FIG. Thereby, the cooling capacity in the central portion is lower than that on the one end portion 38 side. The second area 47 in the center is set to a width corresponding to the paper width of a minimum size recording paper (usually postcard) that can be continuously fed from a paper feeding tray (manual feed tray) or a paper feeding cassette (not shown). Yes.

  When small-size recording paper is continuously fed, the central portion of the heating roller 21 is maintained at a predetermined fixing temperature by temperature control, whereas the end portions 38 and 39 on the side of the end 38/39 outside the recording paper width are maintained. In the region, since there is no heat radiation due to contact with the recording paper, the temperature gradually rises as the number of sheets passing increases and becomes higher than the central portion, and the exciting coil 32 is also radiated by the radiant heat from the heating roller 21. The end portions 38 and 39 are in a higher temperature state than the center portion.

  In this way, when the temperature of the exciting coil 32 becomes higher at the end portions 38 and 39 than at the central portion due to continuous passing of small-size recording paper, cooling is performed at the end portions 38 and 39 and the central portion. If the capacity is equal, the central exciting coil 32 is excessively cooled and the heating efficiency of the central part is deteriorated, but as described above, the ventilation hole 41 is made smaller than the one end 38 side in the central part, By setting the cooling capacity in the central portion lower than that of the one end portion 38 side, overcooling of the exciting coil 32 in the central portion can be avoided.

  Thereby, it is possible to prevent a large temperature difference from occurring in the plurality of exciting coils 32 arranged in the axial direction, and there is a possibility that all the exciting coils 32 may be appropriately damaged, that is, thermally damaged. The temperature unevenness in the axial direction of the heating roller 21 can be suppressed by cooling to a temperature state that does not exceed the upper limit temperature and does not fall below the lower limit temperature that may deteriorate the heating efficiency.

  FIG. 5 is a cross-sectional view showing in detail a main part of the heating roller 21 shown in FIG. The magnetic core assembly 33 includes a magnetic core 51 and a core holder 52 that holds the magnetic core 51 and is fixed to the core member 34. The magnetic core 51 is formed of a ferromagnetic material such as ferrite, protrudes from the base 51 a extending inside the exciting coil 32 to the outside of the exciting coil 32, and the tip is the inner peripheral surface of the heating roller 21. The protrusion part 51b which adjoins to is provided.

  The magnetic flux generated by the exciting coil 32 is guided by the magnetic core 51 and proceeds in a substantially radial direction from the front end surface of the protruding portion 51 b and enters in a direction substantially orthogonal to the inner peripheral surface of the roller body 23. At this time, since the tip of the projecting portion 51b serving as a magnetic pole in the magnetic core 51 is close to the inner peripheral surface of the heating roller 21, the distance through which the magnetic flux passes through the air having low permeability is shortened. In this case, the magnetic flux density is increased and the heat generation efficiency is improved.

  A through hole 54 is formed in the peripheral wall portion of the core member 34 on which the magnetic core assembly 33 is provided, and cooling air flowing through the core member 34 directly hits the magnetic core 51. As a result, the exciting coil 32 is cooled by the cooling air discharged from the ventilation holes 41, and at the same time, the magnetic core 51 is cooled by the cooling air flowing through the core material 34 without passing through the core material 34. The cooling effect can be further enhanced.

  The core holder 52 has a box shape in which the attachment surface side with respect to the core material 34 is opened so as not to disturb the contact between the magnetic core 51 and the cooling air, and is formed on the peripheral wall of the core material 34 at both ends in the axial direction. An elastic locking piece 57 that elastically engages with the mounting hole 56 is provided, and the base 51 a of the magnetic core 51 is fixed in a state of entering the through hole 54.

  In the heating roller 21, a heat generation area is formed around the axial center position of the magnetic core 51, and the heating roller 21 rotates around the stationary electromagnetic induction heating unit 24, thereby generating heat on the heating roller 21. The area moves and the heating roller 21 is heated uniformly in the circumferential direction. In particular, since a plurality of magnetic cores 51 are arranged at equal intervals in the circumferential direction at the same axial position, the rotation of the heating roller 21 is started and then the state of the temperature distribution in the circumferential direction is made uniform. Since the magnetic core 51 is arranged so as to partially overlap with the magnetic core 51 adjacent in the axial direction at different arrangement angles, the magnetic body 51 can be shortened. Since the heat generation area formed corresponding to the core 51 is formed without any gap in the axial direction, the temperature distribution in the axial direction can be made uniform.

  FIG. 6 is a perspective view showing another example of the electromagnetic induction heating unit according to the present invention. In the electromagnetic induction heating unit 61, a plurality of ventilation holes 63 are formed in the peripheral wall of the core member 62 as in the above example. In particular, here, the region where the exciting coil 32 is disposed in the core member 62 is The first, second, and third regions 64 to 66 are partitioned, and the second region 65 in the center is not provided with a vent hole. The second area 65 at the center is set to a width corresponding to the paper width of the minimum size recording paper (for example, postcard).

  The plurality of ventilation holes 63 in the same region 64/65 are provided with the same opening area, and the ventilation hole 63 in the third region 66 on the other end 69 side (downstream side) It is provided with a larger opening area than the ventilation hole 63 in the first region 64 on one end 68 side (upstream side).

  In this configuration, compared with the above example, the cooling capacity at the center can be set much lower, and when a small-size recording sheet is continuously passed, This is suitable when a large temperature difference occurs between the central part.

  FIG. 7 is a perspective view showing another example of the electromagnetic induction heating unit according to the present invention. In this electromagnetic induction heating unit 71, a plurality of ventilation holes 73 are formed in the peripheral wall of the core material 72 as in the above example. In particular, here, the region where the exciting coil 32 is disposed in the core material 72 is The first and second regions 74 and 75 are divided into two equal parts in the axial direction, and a plurality of ventilation holes 73 in the same region 74 and 75 are provided with the same opening area. The vent hole 73 in the second region 75 on the other end 79 side (downstream side) has a larger opening area than the vent hole 73 in the first region 74 on the one end portion 78 side (upstream side). Is provided.

  FIG. 8 is a perspective view showing another example of the electromagnetic induction heating unit according to the present invention. In this electromagnetic induction heating unit 81, a plurality of ventilation holes 83 are formed in the peripheral wall of the core member 82, as in the above example. In particular, here, the plurality of ventilation holes 83 are provided on the one end 88 side. The opening area is gradually increased from the (upstream side) toward the other end 89 (downstream side).

  The configuration shown in FIGS. 7 and 8 is different from the examples shown in FIGS. 4 and 6, and the end side and the center of the heating roller 21 generated when a small-size recording paper is continuously fed. This is suitable when there is no need to consider the temperature difference between the parts. The configuration shown in FIG. 8 is suitable when the cooling capacity needs to be set finely according to the position in the axial direction.

  In the above example, a pair of magnetic core assemblies are provided for each excitation coil, and the core material is formed in a square cross section so as to conform to the arrangement of the magnetic core assemblies. However, a configuration in which three or more magnetic core assemblies are provided for one excitation coil is also possible.

  In this case, around the core material, a plurality of magnetic core assemblies are arranged at equal intervals in the circumferential direction at the same axial position, and a mounting angle with the adjacent magnetic core assemblies in the axial direction is predetermined in the circumferential direction. For example, the angle is set to be 60 degrees in the case of three and 45 degrees in the case of four, and the core is a polygon having an even number of sides such as a hexagon and an octagon so as to conform to the arrangement of the magnetic core assembly. It is formed in a cross section of shape.

  In this way, increasing the number of magnetic cores arranged in the circumferential direction at the same axial position is convenient for making the temperature distribution in the circumferential direction uniform, and the heating roller 21 starts rotating. It is possible to further shorten the time from the transition to the state where the temperature distribution in the circumferential direction becomes uniform.

  In the above example, the configuration in which the pressure roller is brought into pressure contact with the heating roller in which the induction heating unit is accommodated and the recording paper is passed through the nip formed between the two is described. In order to improve the characteristics, the present invention can be similarly applied to a configuration using a heating belt having a heat capacity smaller than that of the roller. In this case, an endless belt-shaped heating belt is wound around the heating roller and the fixing roller in which the induction heating unit is accommodated, and a pressure roller disposed opposite to the fixing roller and a portion where the heating belt is wound around the fixing roller. By passing the recording paper between them, the toner on the recording paper is fixed to the recording paper by the action of heat and pressure.

  The fixing device and the image forming apparatus including the fixing device according to the present invention may be configured such that cooling air is introduced only from one end side of the heating roller in order to cool the excitation coil accommodated in the heating roller. The exciting coil that has the effect of preventing a large temperature difference from being generated in the exciting coil and that heats the heating roller by electromagnetic induction is housed inside the heating roller and heated by the blowing means. It is useful as a fixing device that is cooled by cooling air introduced from one end side of the roller and an image forming apparatus including the fixing device, such as a printer, a facsimile machine, a copying machine, and a multifunction machine.

Schematic sectional view showing a schematic configuration of a copying machine to which the present invention is applied Sectional drawing which shows the principal part of the fixing | fixed part shown in FIG. A sectional view in the axial direction of the heating roller shown in FIG. The perspective view which shows the electromagnetic induction heating unit shown in FIG. Sectional drawing which shows the principal part of the heating roller shown in FIG. 3 in detail The perspective view which shows another example of the electromagnetic induction heating unit by this invention The perspective view which shows another example of the electromagnetic induction heating unit by this invention The perspective view which shows another example of the electromagnetic induction heating unit by this invention

Explanation of symbols

3 Fixing part (fixing device)
DESCRIPTION OF SYMBOLS 21 Heating roller 23 Roller main body 24 * 61 * 71 * 81 Electromagnetic induction heating unit 32 Excitation coil 33 Magnetic body core assembly 34 * 62 * 72 * 82 Core material 36 Fan (blowing means)
38, 68, 78, 88 One end 39, 69, 79, 89 The other end 41, 63, 73, 83 Ventilation hole 51 Magnetic core 54 Through hole

Claims (7)

An exciting coil that heats the heating roller by electromagnetic induction is housed in the heating roller, and is fixed by cooling air introduced from one end side of the heating roller by a blowing means. A device,
The heating roller has a pipe-shaped core member that extends in the axial direction and the excitation coil is provided on the outer periphery. On the peripheral wall of the core member, from one end side of the core member to the other end portion A plurality of ventilation holes are formed at predetermined intervals in the axial direction to apply cooling air flowing through the interior toward the exciting coil, and the plurality of ventilation holes are compared to one end side. And a fixing device provided with a large opening area on the other end side.   A magnetic core is provided on an outer periphery of the core material, and a through hole is formed in a peripheral wall portion of the core material corresponding to the magnetic core, and cooling air flowing through the core material is supplied to the magnetic core. The fixing device according to claim 1, wherein the fixing device is directly applied.   The fixing device according to claim 1, wherein the plurality of ventilation holes are provided so as to have a small opening area at a central portion as compared with one end portion side.   The region where the exciting coil is disposed in the core material is divided into three regions of first, second, and third from one end side, and the ventilation hole is formed from the first region on one end side. The fixing device according to claim 3, wherein the second region in the central portion provided with a small opening area is set to a width corresponding to a recording medium of a minimum size.   The fixing device according to claim 1, wherein the core member is made of a non-metallic material that is non-magnetic and non-conductive.   A plurality of the exciting coils are arranged in the axial direction along the axial direction, and a plurality of magnetic cores are provided in the circumferential direction at the same axial position corresponding to each of the plurality of exciting coils. The fixing device according to claim 1, wherein the ventilation holes are provided at positions between the plurality of magnetic cores arranged in the circumferential direction.   An image forming apparatus comprising the fixing device according to claim 1.

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