WO1999000712A1 - Fixing apparatus - Google Patents

Abstract

A fixing apparatus capable of attaining the preheating of a recording medium more effectively and the increase of a transfer speed of the recording medium, which is provided with a fixing roller (22) and a pressure roller (24) urged against the fixing roller (22) so that the pressure roller (24) rolls in contact therewith, and adapted to fix an unfixed toner on a sheet (S) by passing the sheet (S) supporting the unfixed toner on an upper surface thereof through the contact-rolling portions of the fixing roller (22) and pressure roller (24) in one direction. The apparatus is characterized by being provided with a first heating means (26) provided in a position spaced from the fixing roller (22), heat transfer means (28, 32) for receiving heat from the first heating means (26) and heating the sheet (S) passing through the contact-rolling portions, and preheating and transfer means (30, 34) positioned on the upstream side, with respect to the mentioned one direction, of the pressure roller (24), heated with the heat transmitted from the first heating means (26) via the heat transfer means (28, 32), for preheating the portion of the sheet (S) which is about to pass through the contact-rolling portions, from a rear surface thereof which does not support the unfixed toner thereon, and transferring the sheet (S) to the contact-rolling portions.

Description

 Specification

Technical field

 The present invention relates to a fixing device used for melting and pressing unfixed toner on a recording medium and fixing the toner on the recording medium, and particularly to a fixing device for an electronic image forming apparatus. Background art

 Conventionally, in a fixing device for an electronic image forming apparatus, instead of the conventional heat roller fixing method, for example, as shown in FIG. 13 as a technique described in JP-A-6-318001, A fixing belt B is stretched between the fixing roller R1 and the heating roller R3, and a pressure roller R2 that presses the fixing roller R1 from below through the fixing belt B is provided. A technology combining the preheating of the recording medium D has been developed.

 By preheating the recording medium D, the temperature of the nip portion between the pressure roller R2 and the fixing belt B can be set low. By using the fixing belt B having a small heat capacity, the recording medium The temperature of the fixing belt B can be rapidly cooled when D passes through the nip portion. In addition, this cooling can increase the cohesive force of the toner separated from the fixing belt B at the exit of the nip portion, and the increased cohesive force increases the releasability of the fixing velvet B and the toner, Even without oil or only a small amount of oil applied, a clear fixed image without offset can be obtained. As described above, the belt fixing system provides a fixing device in which the problems of both the releasability and the oil application, which cannot be solved by the conventional heating roller system, are solved at once.

Here, the configuration of the conventional belt fixing type fixing device shown in FIG. 13 is schematically shown. To explain, the fixing roller R1, the pressure roller R2, and the heating and tension roller R3 are provided, and the fixing roller B is stretched between the fixing roller R1 and the heating and tension roller R3. Have been. An oil application roller R 4 is disposed above the fixing belt B, and a guide plate G is disposed below the fixing belt B with a gap therebetween. The space between the lower portion of the fixing belt B and the guide plate G defines a preheating passage for the recording medium D.

 On the other hand, a heating source H is provided inside the heating and tension roller R3, and a heating source may be additionally provided inside the fixing roller R1 and the pressure roller R2. In order to control the temperature of the fixing belt B, a thermistor S is provided in contact with the non-sheet passing portion of the fixing belt B.

 However, in the belt-fixing type fixing device having the above-mentioned configuration having the above-described configuration, if the transport speed of the recording medium D is increased to increase the number of processed sheets per unit time (for example, per minute). However, the amount of heat generated by the heating source H has to be increased, and the nip width at the nip has to be increased.

 On the other hand, from the viewpoint of preheating the recording medium D, the guide plate G itself rises in temperature by receiving heat radiation (radiant heat) from the fixing belt B, and is in a state of heating the recording medium D from the lower surface. The effect of preheating by this is expected. However, the heating of the guide plate G is a phenomenon only in the initial stage when the recording medium D starts to be conveyed to the guide plate G. When the recording medium D starts to pass over the guide plate G, the recording medium D itself is heated. As a result, the heat from the guide plate G is taken off, and the radiant heat from the fixing belt B is cut off, so that the continuous preheating of the recording medium D by the guide plate G cannot be expected.

Further, in order to enhance the preheating effect of the recording medium D by the fixing belt B, the gap between the guide plate G and the lower portion of the fixing belt B is narrowed, and the recording medium D passing over the guide plate G is It is conceivable to approach the lower part. However, if the recording medium D is too close to the lower portion of the fixing belt B, the recording medium on which the toner image is formed The upper surface of the body D may be rubbed against the lower part of the fixing belt B, and the toner image may be disturbed, and a certain gap is required.

 Furthermore, since the guide plate G is arranged in a fixed state, the recording medium D conveyed in a state of sliding (frictional contact) thereon acts as a load during conveyance. That is, when the transport speed of the recording medium D is increased as described above, the transport load acts strongly as an adverse effect, particularly from the viewpoint of achieving a favorable transport state.

 SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a fixing device capable of more effectively achieving preheating of a recording medium and achieving an increase in the conveying speed of the recording medium. It is to provide.

 It is another object of the present invention to provide a fixing device which can eliminate the possibility that a toner image is disturbed by rubbing against a fixing belt while a recording medium is being preheated.

 Another object of the present invention is to provide a fixing device capable of achieving a reliable transport state by minimizing the transport load while the recording medium is being preheated. is there. Disclosure of the invention

In order to solve the above-described problems and achieve the object, a fixing device according to the present invention includes a fixing roller, and a pressure roller that is urged to be in rolling contact with the fixing roller. The fixing device fixes the unfixed toner on the sheet by passing the sheet carried by the fixing roller and the pressure roller along the rolling contact portion in one direction. A first heat generating means disposed apart from the roller, a heat transfer means for receiving heat transfer from the first heat generating means and heating the sheet passing through the rolling contact portion; and The roller is located upstream with respect to the one direction with respect to the one direction, and receives heat from the first heat generating means via the heat transmitting means to apply heat. A preheating means for preheating the heated sheet before passing through the transfer portion from a back surface on which the unfixed toner is not carried, and for conveying the sheet toward the transfer portion; It is characterized by doing.

 In addition, the present invention is characterized in that the heat transfer means has a predetermined heat capacity, the heating roller being disposed apart from the fixing roller, and being endlessly bridged between the heating roller and the fixing roller. A first heat transfer belt for transferring the heat of the heat generating means to the fixing roller, wherein the conveying / preheating means includes: a supporting roller disposed upstream with respect to the one direction of the pressing roller; A second heat transfer belt having a predetermined heat capacity is provided between the support roller and the pressure roller.

 Further, according to the present invention, the second heat transfer belt conveys the sheet toward the rolling contact portion as the second heat transfer belt travels, and receives heat from the pressure roller to be heated. The heat is dissipated and the sheet is preheated from the back. Further, the present invention is configured to further include a second heat generating means for heating the second heat transfer belt.

 Further, the present invention is configured such that the first heating means is built in the heating roller.

 Further, the present invention is configured such that the first heating means includes a halogen lamp.

 Further, the present invention is configured such that the first heating means includes a planar heating element attached to an inner peripheral surface of the heating roller.

 Further, the present invention is configured such that the first heat generating means is provided outside the heating roller in a state of facing the first heat transfer belt.

 Further, the present invention is configured such that the first heating means includes a sheet heating element attached to an outer peripheral surface of the heating roller.

Also, the present invention is characterized in that the first heat generating means heats the first heat transfer belt by induction heating. It is configured so as to be an induction heating means for generating heat.

 Also, the present invention provides the first heat transfer device, wherein the induction heating means is located between the fixing roller and the heating roller, and the first heat transfer belt is located upstream of the rolling contact portion with respect to a traveling direction of the first heat transfer belt. The heat transfer belt is configured so as to be induction heated.

 Further, the present invention is configured such that the first heat transfer belt is formed including an endless metal base material and a release layer coated on an outer peripheral surface of the metal base material. Have been.

 Further, the present invention is configured such that the metal base is formed from a nickel electrode belt.

 Further, the present invention is configured such that the first heat generating means includes a halogen lamp disposed opposite to the first heat transfer belt.

 Further, the present invention is configured such that the second heat generating means is built in the pressure roller.

 Further, the present invention is configured such that the second heat generating means is built in the support roller.

 Further, the present invention is configured such that the first heat generating means is arranged to be spaced upstream from the fixing roller in the one direction.

 Further, the present invention is configured such that the first heat generating unit is disposed apart from the fixing roller along a direction intersecting the one direction.

 Further, the present invention is configured such that the first heat generating means is disposed on a side opposite to a side on which the pressure roller is in rolling contact with the fixing roller and is separated from the fixing roller. .

Further, according to the present invention, the heating roller is disposed within a preheating influence range in which heat radiated from the first heat transfer belt can preheat the sheet before passing through the fixing unit. It is configured as follows. Further, according to the present invention, the heating roller is disposed outside a preheating influence range in which heat radiated from the first heat transfer belt can preheat the sheet before passing through the fixing unit. It is configured as follows.

 Further, the present invention provides a method as described above, wherein the sheet conveyed on the second heat transfer belt between the first heat transfer belt and the second heat transfer belt is the first sheet before the rolling contact portion. The heat transfer belt is configured to be separated so as not to contact the heat transfer belt.

 Further, the present invention is configured such that the first heat transfer belt is disposed at a position outside a region where the sheet conveyed on the second heat transfer belt may pass. ing.

 Further, the present invention further includes a driving means for rotatingly driving the pressure roller, wherein the first heat transfer belt is frictionally engaged with the pressure roller via the second heat transfer bellows. Thus, the fixing roller is driven to run, and the fixing roller is configured to be rotationally driven by the rotation of the pressure roller via the first heat transfer velvet.

 Further, the present invention is configured such that the first heat transfer belt is formed including an endless base material and a release layer coated on an outer peripheral surface of the base material. Further, the present invention is configured such that the endless base material is made of metal.

 Further, the present invention is configured such that the metal base is formed from a nickel electrode belt.

 Further, the present invention is configured such that the endless base material is made of a synthetic resin.

 Further, the present invention is configured such that the synthetic resin base material is formed from a polyimide resin belt.

Further, the present invention is configured such that the second heat transfer belt is formed including an endless base material and a release layer coated on the outer peripheral surface of the base material. Further, the present invention is configured such that the endless base material is made of a synthetic resin.

 Further, the present invention is configured such that the synthetic resin base material is formed from a polyimide resin belt.

 Further, the present invention is configured such that the second heat transfer belt includes an endless base material, and a surface layer formed on a peripheral surface of the base material and formed of a chargeable material. I have.

 In addition, the present invention provides a charging unit that is disposed to face the second heat transfer belt, charges the second heat transfer belt, and attracts the sheet to the second heat transfer belt. It is configured to further include. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a front view showing a configuration of an embodiment of a fixing device according to the present invention, and FIG. 2 is a front view showing a state where a collar is attached to a heating roller provided in the fixing device shown in FIG. ,

 FIG. 3 is a side view showing the configuration of the oil application roller provided in the fixing device shown in FIG.

 FIG. 4 is a front view showing a first modification of the fixing device having the configuration of the embodiment shown in FIG.

 FIG. 5 is a front view showing a second modification of the fixing device having the configuration of the embodiment shown in FIG.

 FIG. 6 is a front view showing a third modification of the fixing device having the configuration of the embodiment shown in FIG.

FIG. 7 is a front sectional view showing the configuration of another embodiment of the fixing device according to the present invention, and FIG. 8 is a diagram showing a rolling contact state between a fixing roller and a pressure roller in the fixing device shown in FIG. And FIG. 9 is a front view showing the configuration of the driving mechanism in the fixing device shown in FIG.

 FIG. 10 is a diagram showing a configuration angle in an experimental example conducted for examining an allowable range of an arrangement position of a heating roller with respect to a fixing roller in the fixing device shown in FIG. 7, and FIG. FIG. 6 is a front view showing a configuration of a first modified example of a first heating unit provided in the fixing device according to the first embodiment,

 FIG. 11B is a front view showing a second modified example of the first heating means provided in the fixing device according to the present invention,

 FIG. 11C is a front view showing a third modified example of the first heating means provided in the fixing device according to the present invention,

 FIG. 11D is a front view showing the configuration of a fourth modified example of the first heating means provided in the fixing device according to the present invention,

 FIG. 12A is a front view showing a configuration of a first modified example of the second heating means provided in the fixing device according to the present invention,

 FIG. 12B is a front view showing a configuration of a second modified example of the second heating means provided in the fixing device according to the present invention,

 FIG. 13 is a front view schematically showing a configuration of a fixing device according to the related art. BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, a configuration of an embodiment of a fixing device according to the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, a description will be given of a case where the fixing device is applied to an electronic copying apparatus using zeography as an electronic image forming apparatus. It is needless to say that the present invention is not limited to this and can be applied to an electronic facsimile machine, an electronic printer, and the like.

(Schematic description of fixing device 10) First, as shown in FIG. 1, the fixing device 10 of this embodiment includes a housing 12 as a housing structure, which is fixed to a frame of an electronic image forming apparatus (not shown). A base 14 directly fixed on the device frame, a pair of left and right main mounting stays 16 fixedly mounted on the base 14 and an upper part of both main mounting stays 16 Top plate 18 connected to each other and this base

On the upper side of the main mounting stay 16 on the right side in the figure (that is, upstream in the transport direction of the recording paper (hereinafter, referred to as unfixed sheet S) on which the unfixed toner as a recording medium is carried on the upper surface). And a sub-mounting stay 20 movably mounted along the conveying direction of the unfixed sheet S in a state where the sheet S stands upright.

 Here, the left direction indicated by the arrow in the figure is defined as a transport direction as one direction in which the unfixed sheet S is transported. That is, the above-mentioned main mounting stay 16 and sub-mounting stay 20 are located on the left and right sides of the unfixed sheet S conveyed along one direction, and extend respectively along this one direction. It is arranged in.

 Further, the fixing device 10 is configured as a roller, and includes a fixing roller 22 that is rotatably supported around its own central axis by two main mounting stays 16 and a fixing roller that is fixed to both main mounting stays 16. A pressure roller 24 supported below the roller 22 so as to be able to move in a substantially vertical direction while being capable of being pressed against the roller 22 and rotatably supported around its own central axis; 6, is disposed upstream of the fixing roller 22 with respect to the conveying direction of the unfixed sheet S, is mounted so as to be movable along the conveying direction, and is supported rotatably around its own central axis. A heating / tension roller (hereinafter simply referred to as a heating roller) 28 with a built-in heat source 26 such as a halogen lamp inside, and both sub-mounting stays 20 are rotatable around their own central axis. The support rollers 30 supported by Ete is configured.

Further, the fixing device 10 has, as a belt configuration, an endless fixing belt (first heat transfer belt) 32 wound around a fixing roller 22 and a heating roller 28, and a pressure roller 24. Of the endless wound between the roller and the support roller 30 Noreto (second heat transfer belt) 34. Here, a space between the two belts 32 and 34 is defined as a preheating passage P through which the unfixed sheet S is conveyed while being preheated by the two belts 32 and 34.

 Further, the fixing device 10 keeps the tension of the fixing belt 32 constant, applies silicone oil to the outer surface of the fixing belt 32, and

The oil application roller 36 for cleaning the outer surface of 2 and the heating port roller 28 are biased in the direction away from the fixing roller 22 to cooperate with the oil application roller 6 on the fixing belt 32. A pressure lever 40 for biasing the pressure roller 24 to the fixing roller 22 by biasing the pressure roller 24 to a direction close to the fixing roller 22 and a tension lever 38 for applying a predetermined tension. And further provided.

 In the fixing device 10 having such a schematic configuration, the unfixed sheet S conveyed thereon is conveyed in accordance with the conveyance / preheating belt 34 traveling counterclockwise in the drawing. The belt is conveyed toward the rolling contact point (the nip) between the belt 32 and the conveying / preheating belt 34, and is passed through the two belts 32, 34 while being pressed against each other. The fixing member is set so as to be thermocompressed and fixed on the sheet.

 {Description of fusing roller 2 2}

 The above-described fixing roller 22 has a core metal part 22 A rotatably supported via a bearing in a circular first support hole 16 A formed in the main mounting stay 16. And a roller main body 22B around which the fixing belt 32 is wound, the roller outer diameter being set to 20 mm. . Here, in this embodiment, the core part 22 A is formed of an iron shaft having a diameter of 12 mm, and the mouthpiece body 22 B is formed on the outer periphery of the core part 22 A with a thickness of 4 mm. It is made of silicone rubber heat-resistant elastic body (specifically, silicone rubber sponge; product with a hardness of 30C).

A first driven gear 42 is coaxially fixed to one end of the cored bar 22 A. The first driven gear 42 has a drive mechanism (not shown in detail) Drive A gear 44 is engaged, and a driving force from a driving mechanism is transmitted to the first driven gear 42 via the driving gear 44, so that the fixing roller 22 is driven to rotate. ing.

 (Description of pressure roller 24)

 The above-described pressure roller 24 is formed on the main mounting stay 16 and rotatably supports, via a bearing, a second shaft hole 16 B having a long hole shape extending substantially vertically. At the same time, a core 24 A supported movably along the extending direction of the core 24 A is coaxially disposed around the outer periphery of the core 24 A, and a conveying / preheating belt 34 is wound therearound. The roller body 24 B is configured to be turned, and the outer diameter of the roller is set to 2 O mm. Here, in this embodiment, the core 24 A is formed of an iron shaft having a diameter of 14 mm, and the roller body 24 B is attached to the outer periphery of the core 24 A with a thickness of 3 mm. The silicone rubber heat-resistant elastic body (specifically, a silicone rubber harder than the fixing roller 22 described above; a product with a JISA hardness of 40 degrees) is formed.

 Note that a second driven gear 46 is coaxially fixed to one end of the cored bar portion 24 A, and the second driven gear 46 is combined with the first driven gear 42 described above. The driving force from this is transmitted to the second driven gear 46 via the first driven gear 42, and the pressure roller 24 is moved in the opposite direction to the fixing roller 22. Further, it is configured to be driven to rotate at the same speed.

 Here, in the fixing device 10, the sheet feeding speed of the unfixed sheet S is set to 10 mm / sec to 500 mm / sec, and the gap of the preheating space P is set to 0.5 mm to 20 mm. The pre-heating time, which passes only the distance connecting the centers of the fixing roller 22 and the heating roller 28 to each other, is set so as to satisfy the condition of 0.1 to 4 seconds. Settings are specified.

 (Explanation of heating roller 28)

In the heating roller 28 described above, as a heat source 26, in this embodiment, a halogen lamp of 600 W in which the light distribution at both ends is set to be 50% larger than the center is provided. Provided. In this embodiment, the heating roller 28 is made of an aluminum pipe core having a diameter of 2 Omm and a thickness of 1.75 mm and anodized. At both ends, as shown in FIG. A collar 48 made of ether ether ketone (PEEK) 24 mm in diameter is fixed to prevent the fixing belt 32 from meandering and offset.

 {Description of support roller 30}

 The support roller 30 is rotatably supported by the sub-mounting stay 20 in a state in which the support roller 30 is located on the right side in the drawing of the heating roller 28 in other words, in other words, in a state of being located on the upstream side in the conveying direction of the unfixed sheet. I have. That is, the support roller 30 is formed on the sub-mounting stay 20, and is rotatably supported via a bearing in a long groove 50 extending along a substantially obliquely upward direction. A metal core 3 OA supported movably along the direction, and a roller body 3 OB that is coaxially arranged around the metal core 3 OA and around which the conveying / preheating velvet 34 is wound. It is configured. Here, in this embodiment, the core metal part 3 OA is formed from a 14 mm-diameter iron shaft, and the roller body 30 B is a silicone body attached to the outer circumference of the core metal part 3 OA with a thickness of 3 mm. The pressure roller 24 is formed substantially in the same manner as the pressure roller 24 from a heat-resistant elastic body made of rubber. The support roller 30 is mounted in a fixed state at an arbitrary position of the long groove 50 via a mounting mechanism described later.

 (Explanation of fixing belt 32 and conveyance · Preheating belt 34)

The fixing belt 32 described above has a heat capacity per square cm of the fixing belt 32 of 0.002 cal Z ° C to 0. 025 ca 1 /. Those of C are preferred. For this reason, in this embodiment, the fixing belt 32 has an inner diameter of 50 mm, an endless belt body made of nickel electrode or the like having a thickness of 40 im, and an outer peripheral surface of the belt body having a thickness of 150 / m. And a heat-resistant elastic release layer of silicone rubber attached thereto. On the other hand, the conveyance pre-heating belt 34 is formed of an endless belt made of silicone rubber. In the standby state, heat is released from the fixing belt 32 and heat is transferred from the nip portion with the fixing belt 32. On the other hand, during the fixing operation, the unfixed sheet is conveyed.While being conveyed on the preheating belt 34, the unfixed sheet receives the heat transfer from the nip portion described above, and While the paper is passing through the nip portion, heat is received from the fixing belt 32 and each is heated to preheat unfixed toner from the lower surface.

 The conveying / preheating belt 34 is frictionally charged in a state of being in contact with the fixing belt 32 as described above, and its charge amount is 1 to 5 KV (the charge amount in an idling state for 30 seconds). Although measurement results have been obtained, the unfixed sheet S conveyed here is brought into close contact with the surface of the preheating belt 34 due to the triboelectric charging of the conveyance and preheating belt 34, and this conveyance · As the preheating belt 34 travels, it is conveyed toward the part where it comes into contact with the fixing belt 32 (the nip). As described above, the unfixed sheet S is conveyed in a state in which the unfixed sheet S is conveyed in a state in which the unfixed sheet S is brought into close contact with the surface of the preheated velvet 34. That is, the temperature non-uniformity of the unfixed sheet S is minimized. As described above, the uniformity of the temperature of the unfixed sheet S is ensured based on the triboelectric charge amount of the conveying / preheating belt 34, so that the above-described “good” image generation in the solid image is obtained. The results have been obtained.

 Here, the transporting / preheating belt 34 is not limited to the silicone rubber as described above, and may be configured such that only the surface layer is formed of conductive rubber. In this case, the idling state for 30 seconds is provided. Of the unfixed sheet S based on the triboelectric charge of the conveying and preheating belt 34 in the same manner as described above. As a result, a test result of “good” regarding the occurrence of image unevenness in the solid image described above has been obtained.

(Explanation of mechanism for applying tension to fixing belt 32) As a mechanism for applying tension to the fixing belt 32 described above, the fixing device 10 includes the oil application roller 36 and the tension lever 38 described above. As shown in FIG. 3, the oil application roller 36 includes a main shaft 36A rotatably supported via a bearing (not shown) on the main mounting stay 16 and an outer periphery of the main shaft 36A. The heat-resistant paper layer 36 B impregnated with silicone oil is configured so that the support shaft 36 A is formed of an iron shaft having a diameter of 8 mm in this embodiment. 6B is formed so as to have a roller outer diameter of 14 mm in a state in which 10 porous fluororesin films 36C are mounted on the outer periphery thereof.

 On the other hand, a tension lever 38 as a member constituting a mechanism for applying tension to the fixing belt 32 has its lower end pivotally supported by a main mounting stay 16 and its upper end being a tension spring. It is connected to one end of the main mounting stay 16 through 52. By the urging force of the tension spring 52, the tension lever 38 is rotationally urged so as to abut against the outer periphery of the heating roller 28 with a predetermined pressure contact force F2 at an intermediate portion thereof.

 That is, the heating roller 28 is biased in a direction away from the fixing roller 22 by the urging force of the tension spring 52 via the tension lever 38, whereby the heating roller 28 and the fixing roller 2 are displaced. The fixing benolet 32, which is wrapped around the endless 2, is tensioned to a predetermined tension with its upper part regulated by the oil application roller 36. As a result, the fixing belt 32 is driven to run in an endless manner in a stable state without slipping or loosening with the rotation of the fixing roller 22.

 {Description of the mechanism for applying tension to the conveyor and preheating belt 34}

As a mechanism for imparting tension to the above-described conveying / preheating belt 34, the fixing device 10 is provided with a sub-attaching stay 20 to the base 14 as described above, although not shown in detail. Movable mechanism that supports movably along the direction, Secondary mounting A fixing mechanism for fixing the stay 20 to the base 14 at an arbitrary position. Here, the conveying and preheating belt 34 is wound between the pressure roller 24 attached to the main attachment stay 16 and the support roller 30 attached to the sub attachment stay 20, and The mounting stay 20 is deviated in a direction away from the main mounting stay 16, and is conveyed between the rollers 24, 30 .The secondary mounting is performed while the preheating belt 34 is tensioned to a predetermined tension. By fixing the stay 20 to the base 14, a predetermined tension is applied to the conveying / preheating belt 34. As a result, the conveyance preheating belt 34 is driven to travel in an endless manner in a stable state with no slippage or loosening due to the rotation of the pressure roller 24.

 {Fixing and transporting 'Description of the pressure contact mechanism of the preheating belts 32, 34)

 Next, a description will be given of a pressing mechanism 54 for pressing the two belts 32 and 34 at a position where they are wound around the fixing roller 22 and the pressing roller 24 with a predetermined pressing force. The press-contact mechanism 54 is pivotally supported at one end by a main mounting stay 16 via a support shaft 56, and abuts from below on the metal core portion 24 A of the pressure roller 24 at an intermediate portion. A pressure lever 40 that can be connected, and a pressure spring 58 whose lower end is connected to the other end of the pressure lever 40 and whose upper end is connected to the upper part of the main mounting stay 16 are provided. It is configured. Due to the urging force of the pressure spring 58, the pressure lever 40 comes into contact with the outer periphery of the core 24A of the pressure roller 24 at the intermediate portion thereof with a predetermined pressing force F1. The fixing roller 22 and the pressure roller 24 are pressed against each other by the predetermined pressure. That is, the two belts 32 and 34 come into rolling contact with each other with a predetermined nip width at the respective winding positions around the fixing roller 2 and the pressure roller 24.

Here, in this embodiment, the fixing position of the fixing roller 22 and the pressing roller 24 is such that a line connecting the center positions of the fixing roller 22 and the pressing roller 24 is clockwise from a perpendicular passing through the center position of the fixing roller 22. Is set to be inclined by a predetermined acute angle. As a result, the nip position of both belts 32, 34 (that is, the center position of the nip width described above) is The position is defined so as to be slightly shifted forward (in other words, leftward in the drawing) along the conveyance direction of the unfixed sheet S slightly below the position immediately below the center position of the fixing roller 22. .

 {Description of the arrangement of both belts 3 2 and 3 4)

 On the other hand, in this embodiment, the fixing positional relationship between the fixing roller 22 and the heating roller 28 is such that the lower side of the fixing belt 32 wound around the rollers 22 and 28 is in a substantially horizontal state. The vehicle is set to run leftward in the figure. The mounting position relationship between the pressure roller 24 and the support roller 30 is such that the distance between the conveying / preheating belt 34 wound around both rollers 24 and 30 and the fixing benolet 32 is Immediately below the heating roller 28, it is set so as to be in a range of about 5 to 20 mm. That is, the upper side of the conveyance preheating belt 34 is set obliquely with respect to the horizontal lower side of the fixing velvet 32 so that the upper side of the preheating belt 34 is inclined upward with respect to the above-mentioned two positions. ing.

That is, a lower side of the fixing belt 3 2, the upper side of the conveyance and preheating Bell Bok ^{3 4,} and defines a so-called wedge-shaped transfer space that an apex Knitting flop position, in this way, The unfixed sheet S is reliably brought to the nip position between the two belts 3 2 and 3 4 as the conveying / preheating belt 34 travels, where it is pressed against the predetermined pressing force F 1, and The unfixed toner is fixed on the sheet in a state where the toner is preheated by receiving the preheating from both the nozzles 32 and 34.

 {Description of the thermistor}

Further, the fixing device 10 includes a thermistor 60 for controlling the temperature of the fixing belt 32. In this embodiment, the thermistor 60 is, as shown in the figure, a non-sheet passing portion of the fixing belt 32, that is, the fixing velvet 32 directly wound around the heating roller 28. It is configured so that it can contact the right part in the figure and detect the surface temperature of the part. That is, the thermistor 60 is electrically connected to a control unit (not shown), and the temperature of the fixing belt 32 is connected to the control unit. It is configured to convey information.

 (Explanation of fixing operation in fixing device 10)

 The fixing operation on the unfixed sheet S in the fixing device 10 configured as described above will be described below.

 First, in a process device of an electronic image forming apparatus (not shown), the time required for the unfixed sheet S to be conveyed to the fixing device 10 of this embodiment (that is, during idling), the drive gear of the drive mechanism (not shown) is used. When the first and second driven gears 42 and 46, which are successively coupled to the first and second driven gears 44 and 46, are rotated in opposite directions, the fixing roller 22 and the pressure roller 24 are rotated. They will be driven to rotate in opposite directions. Then, as the rollers 22 and 24 rotate, the fixing belt 32 and the conveying / preheating belt 34 respectively wound around the rollers 22 and 24 are driven to run in opposite directions.

 As a result, the fixing belt 32 is heated by the heat source 26, and the conveyance preheating belt 34 is formed through the heat release from the heated fixing belt 32 and the pressing force F1. Heat is received by contact heat transfer between the fixing belt 32 and the fixing belt 32 via the nip portion, and the fixing belt 32 is heated.

 From the idling state where both belts 32 and 34 are heated in this way, when a process device (not shown) is started to execute a predetermined image forming process and unfixed toner is carried on the sheet, The sheet on which the unfixed toner is carried, that is, the unfixed sheet S, is conveyed to a position above the conveying / preheating belt 34 of the fixing device 10 by a conveying mechanism (not shown), and conveyed. Based on the amount, it will be placed in close contact with it. As a result, the unfixed sheet S is thereafter continuously transported toward the nip portion between the transport / preheating belt 34 and the fixing belt 32 as the transport / preheating belt 34 travels. Become.

In the course of being conveyed toward the nip portion as the preheating belt 34 travels, the unfixed sheet S receives heat from the fixing belt 32 and The unfixed toner is preheated, and the unfixed sheet S itself is preheated from the lower surface by receiving the contact heat transfer from the conveying / preheating belt 34. In this way, when the leading edge of the unfixed sheet S is brought to the nip, the unfixed toner carried on the sheet is brought into a sufficiently heated state.

 In other words, the unfixed toner preheated (preheated) as described above is pressed by the nip portion and passes therethrough, so that it is thermally fused and fixed on the sheet. The amount of heat applied to the unfixed sheet S when passing through the sheet is small because the unfixed sheet S has already been preheated up to here. Therefore, according to this embodiment, it is possible to lower the lower limit temperature of the fixing temperature required in the nip portion, whereby it is possible to reduce the amount of heat generated in the heat source 26, There is an advantage that the running cost can be reduced.

 On the other hand, since there is room for applying heat in the nip, even if the conveying speed of the unfixed sheet S is increased, it is possible to secure the minimum necessary fixing temperature. There is an advantage that it is possible to increase the number of fixing processes per unit, that is, to achieve a higher process speed.

 As described above, while the unfixed sheet S is being conveyed by the conveying / preheating belt 34, the unfixed sheet S is conveyed to the preheating belt 34 based on the charge amount. It is conveyed in a state of being in close contact with the sheet. Therefore, the amount of heat transferred by the contact from the conveying / preheating belt 34 spreads evenly over the unfixed sheet S, and the heat fixation state is minimized. (Image forming state) is achieved.

Further, the unfixed sheet S is conveyed in a state in which the unfixed sheet S is brought into close contact with the preheating belt 34, so that the above-described gap in the preheating space P is set as small as possible (specifically, the conveyance, The distance between the preheated velvet 34 and the fixing belt 32 is set so as to be in a range of about 5 to 2 O mm immediately below the heating roller 28. You. ), The size of the apparatus can be reduced, and the heat from the fixing belt 32 can be more effectively received by the unfixed sheet S. The amount of heat transfer can be reduced more efficiently. During continuous operation, that is, in an operation state in which the unfixed sheet S is sequentially conveyed to the fixing device 10, the heat of the fixing belt 32 is dissipated by the conveyed unfixed sheet S, and the heat of the conveyance belt However, there is always a predetermined interval between two consecutive unfixed sheets S, and between these intervals, the fixing belt 3 2 In this way, a state of direct contact with the conveying / preheating belt 34 is achieved. That is, in the state of direct contact at the nip portion, the heat is directly transferred from the fixing belt 32 to the conveyance belt 34 to the preheating belt 34, whereby the temperature of the conveyance * preheating Benoret 34 reaches the required temperature. Upon heating, the preheating effect can be maintained.

 (Description of Example)

 Next, a measurement result (Example 1) when the conveying speed of the unfixed sheet S is used as a parameter when the fixing operation is actually performed using the fixing device 10 having the configuration shown in FIG. As shown in FIG. 13, the conventional configuration (that is, the unfixed sheet is fixed) described in a prior application published by the same applicant as the present applicant (Japanese Patent Application Laid-Open No. Hei 6-318001). The measurement results (comparative example) when the fixing operation is performed using the fixing device having the configuration of being conveyed on the guide plate) will be described below.

 {Study on retention}

First, the control temperature in the thermistor 60 was set to 160 degrees, the nip width was set to 4 to 5 mm, and the idling state was set to 30 seconds, and the unfixed sheet passing test was performed. The fixability was measured. Table 1 shows the measurement results. table 1

Here, the guide plate temperature shown in the comparative example in Table 1 is the position indicated by the symbol “X” on the guide plate G in FIG. 13, that is, at the approximate middle point in the length along the transport direction of the guide plate G. The temperature of the transfer / preheating belt 34 shown in the example is determined by the temperature of the transfer / preheating wound around the support roller 30 as indicated by the symbol “Y” in FIG. The figure shows the measurement results of the temperature at the position where the belt 34 is fed out toward the nip portion, in other words, at the position where the conveying / preheating belt 34 starts to separate from the support roller 30.

 On the other hand, in Table 1, the symbol “〇” indicating the fixability measurement evaluation indicates that the fixability is good, and the symbol “△” indicates that the fixability is at the full limit for judging good. The symbol “X” indicates that the fixability is poor and a cold offset is occurring.

As is clear from Table 1, when the transport speed of the unfixed sheet S is increased in the comparative example (prior art), the temperature of the guide plate G is increased due to the heat radiation from the fixing belt Β according to the increase. However, the rise in temperature is not enough to increase the transport speed, and as a result, the fixing property gradually deteriorates, and it is understood that the transport speed of the unfixed sheet has an upper limit. On the other hand, in this embodiment, the transporting / preheating belt 34 is sufficiently heated by receiving heat radiation and heat transfer from the fixing belt 32, and the unfixed sheet S is transferred to the transporting / preheating belt 34. The temperature at the position indicated by the symbol “Y” at which contact starts is maintained sufficiently high, and the lower surface of the unfixed sheet S can be sufficiently heated. As a result, the fixing temperature at the nip portion can be lowered. Therefore, even if the conveying speed of the unfixed sheet S is increased, it is possible to achieve a sufficient fixing temperature commensurate with that.In other words, according to the configuration of this embodiment, the unfixed sheet S Even if the transport speed of S is increased, the effect that the fixing operation can be reliably performed is achieved.

 {Consider transportability)

In the above-described paper passing test of the unfixed sheet, the transportability was measured. Table 2 shows the measurement results.

t

Transfer speed Comparative example (conventional technology) This embodiment

 Paper type 45 kg 55 kg 68 kg 45 kg 55 kg 68 k

 50 mm / sec (10 sheets // 4 'min) 0/10 0/1 0 0/10 0/1 0 0/10 0/10

 100 mm / sec (20 sheets ZA4 min) 1/1 0 0/1 0 0/1 0 0/1 0 0/10 0/10

 1 50 mm / sec (30 sheets / A4min) 2/10 1/1 0 0/1 0 0/1 0 0/10 0/10

200 mm / sec (40 sheets 4 minutes) 3/10 2/1 0 1/1 0 0/1 0 0/10 0/10

In Table 2, the data shown in the comparative examples were tested for transportability in a state in which the unfixed sheet was forcibly brought into close contact with the guide plate G by sucking air from below the guide plate G. The data in the present embodiment and the comparative example are represented by fractions, where the denominator indicates the number of sheets passed and the numerator indicates the number of jammed sheets in the number of sheets passed. As is evident from Table 2, in the comparative example, as the transport speed was increased, the probability of jamming became higher, and the transportability was deteriorated. On the other hand, in the present embodiment, the unfixed sheet S force conveyed to the fixing device 10 and adsorbed on the preheating belt 34 by a conveying mechanism (not shown) is used for the conveyance and preheating belt 34. As it travels, it is conveyed toward the nip, so that the contact with the guide plate functions as frictional resistance and does not act as so-called conveyance resistance as in the past, and a good unfixed sheet The effect that the S transport state is achieved is also achieved.

 {Description of modified example)

 It is needless to say that the present invention is not limited to the configuration of the embodiment described above, and can be variously modified without departing from the gist of the present invention.

 For example, in the above-described embodiment, the case where the fixing device 10 is applied to an electronic copying machine has been described. However, the present invention is not limited to such an application, and an electronic facsimile device, an electronic facsimile It goes without saying that the present invention can be applied to an electronic image forming apparatus such as a printer.

 Hereinafter, various modifications will be described with reference to the drawings. In the following description, the same parts as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

 {Explanation of the first modified example)

As shown in FIG. 4, the fixing device 1 OA according to the first modified example has a heating roller 28 with a built-in heating source 26 as well as a pressure roller 24 as in the case of the above-described embodiment. An auxiliary heating source 62 is built in the metal core part 24 A, and an auxiliary thermistor 64 is provided to control the temperature of the conveying and preheating belt 34 heated by the auxiliary heating source 62. I have. This auxiliary heating source 62 is formed similarly to the above-mentioned heating source 26. The rubber forming the roller body 24 B of the pressure roller 24 is formed of heat-resistant rubber.

On the other hand, in the first modified example, the auxiliary thermistor 64 is directly wound around the non-sheet passing portion of the transport / preheating belt 34, that is, the pressure roller 24, as shown in the drawing. It is configured such that it contacts the lower part in the figure of the transporting / preheating belt 34 and can detect the surface temperature of the lower part. That is, the auxiliary thermistor 64 is electrically connected to a control unit (not shown) together with the thermistor ⁶⁰ described above, and is configured to transmit temperature information of the transport / preheating belt 34 to the control unit. .

 By configuring the first modified example in this manner, the conveying / preheating belt 34 can be more reliably heated, and the unfixed sheet S can be surely preheated from the lower surface. As a result, the conveyance speed of the unfixed sheet S can be more effectively improved, and the fixing processing speed can be increased.

 説明 Explanation of the second modification)

 As shown in FIG. 5, a fixing device 10 according to a second modification includes a heating roller 26 in addition to a heating source 26 as in the case of the above-described embodiment, and a supporting roller 3. A second auxiliary heating source 66 is incorporated in the core metal part 3 OA of 0, and a second auxiliary heating source 66 is controlled by the auxiliary heating source 66 in order to control the temperature of the preheating belt 34. An auxiliary thermistor 68 is provided. The auxiliary heating source 66 is formed in the same manner as the heating source 26 described above. The rubber forming the roller body 30B of the support roller 30 is formed of heat-resistant rubber.

On the other hand, in the second modified example, the second auxiliary thermistor 68 is directly connected to the non-sheet passing portion of the transporting / preheating belt 34, that is, the support roller 30, as shown in the drawing. It is configured so that it can contact the right side portion in the drawing of the transported / preheated belt 34 to be wound and detect the surface temperature thereof. That is, this second auxiliary The thermistor 68 is electrically connected to a control unit (not shown) together with the thermistor 60 described above, and is configured to transmit temperature information of the conveying / preheating belt 34 to the control unit.

 By configuring the second modification in this way, the transport / preheating velvet 34 can be more reliably heated, and the unfixed sheet S can be reliably preheated from the lower surface. As a result, the conveyance speed of the unfixed sheet S can be more effectively improved, and the fixing processing speed can be increased.

 {Explanation of the third modified example}

 As shown in FIG. 6, a fixing device 10C according to a third modification is a charging device that forcibly charges the conveying / preheating belt 34 in a state where it is added to the configuration of the above-described embodiment.

70. In the third modification, the charger 70 is constituted by a corona charger.

 As described above, in the third modified example, by providing the charger 70, it is possible to reliably charge the transport / preheating belt 34, and the transport / preheating belt 34 has not been determined yet. It is configured so that the unfixed sheet S adsorbed on the unfixed sheet S can be conveyed toward the nip portion by reliably adsorbing the adhered sheet S and carrying the preheating belt 34 along with the traveling.

 Further, in the third modification, the unfixed sheet S is attracted and adhered to the surface of the conveying / preheating belt 34 based on the above-mentioned charged state. As a result, even if the unfixed sheet S is conveyed in a curled state on the conveying / preheating belt 34, the unfixed sheet S curled based on the charge amount described above is conveyed on the preheating belt 34. It will be adsorbed in a state in which it is in close contact with. Therefore, while the unfixed sheet S is being preheated in the preheating passage P, there is a possibility that the unfixed toner image on the unfixed sheet S rubs against the fixing belt 32 and the toner image is disturbed. Will be eliminated.

Even if the unfixed sheet S is curled as described above, the conveyance Since the preheating passage P is adsorbed in a state of being in close contact with the heat belt 34, the height of the preheating passage P can be set as low as possible, thereby reducing the overall height of the fixing device 10C, The size can be reduced.

 Further, in the configuration of the above-described embodiment, the transport direction of the unfixed sheet S has been described to be substantially the horizontal direction, that is, the heating roller 28 is located on the side of the fixing roller 22. Although described as being disposed, the present invention is not limited to such a configuration, and although not shown, the conveying direction of the unfixed sheet S is set to the vertical direction, May be disposed below the fixing roller 22. In particular, in the latter configuration, that is, in the vertical configuration in which the transport direction is the vertical direction, the unfixed sheet S needs to be securely brought into close contact with the transport and preheating belt 34, so the charging shown in the third modified example described above is performed. In the configuration including the container 70, the effect can be particularly exhibited. Further, in the above-described embodiment, the force described so as to dispose the heating roller 28 on the side of the fixing roller 22 (that is, on the upstream side along the conveying direction of the unfixed sheet S) is described. Without being limited to such a configuration, the fixing roller 22 may be disposed above the fixing roller 22.

 {Description of other embodiments)

 In the above-described embodiment, the heating roller 28 is disposed on the side of the fixing roller 22 (that is, on the upstream side along the conveying direction of the unfixed sheet S). In other words, the heating roller 28 is configured so that the unfixed sheet S passing through the preheating passage P is fixed to the fixing belt so that the space between the fixing belt 32 and the guide plate 30 functions as a preheating passage P. Although described as being within the preheating influence range preheated by the heat radiated from 32, the present invention is not limited to such a configuration, and may be applied to the pressure roller 24 of the fixing roller 22. The heat roller 28 may be disposed so as to be located relatively above, in other words, the heat roller 28 may be located outside the preheating influence range.

In the following, another configuration adopting a configuration in which the heating roller 28 is disposed above the fixing roller 22 (ie, so as to be separated in a direction intersecting the conveyance direction of the unfixed sheet) is adopted. The configuration of the fixing device 10D according to the embodiment will be described in detail below with reference to FIGS. 7 to 10 of the accompanying drawings. The same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

 {Outline description of fixing device 10}

 First, as shown in FIG. 7, the fixing device 10D of this embodiment has a housing 12 as a housing structure, similarly to the above-described embodiment, and the housing 12 is provided with a device frame. A base 14 directly fixed on the upper side, side plates (main mounting stays) 16 standing upright from the left and right side edges of the base 14, and a secondary mounting stay 2 similar to the above-described embodiment. 0, an upper cover part 7 2 attached to the side plate 16 so as to cover a substantially upper right part in the drawing, and a left cover part 7 attached to the side plate 16 so as to cover a substantially left part thereof. 4 and have.

 Here, the upper cover part 7 2 is fixedly attached to the side plate 16, and at the upper right part thereof, a swing lever 76 is located on the right side in FIG. It is pivotally supported so that the left side in the figure is open around 8 turns. On the other hand, the left cover part 74 is swingably attached to the side plate 16 so that the upper part is opened around the second support shaft 80 located at the lower part.

 Further, the fixing device 10D has a roller configuration that includes a fixing roller 22 rotatably supported on a side plate 16 around a fixed axis, and a substantially lower portion of the fixing roller 22 (specifically, an obliquely lower portion). A pressure roller 24 supported rotatably on the side plate 16 around a fixed axis set in parallel with the fixed axis of the fixing roller 22, Attached to the swing lever 76 in a state of being located substantially above (specifically, obliquely above), and supported rotatably around its own central axis, a heat source 26 such as a halogen lamp is internally provided. It has a built-in heating roller 28 and a supporting roller 30 rotatably supported on both sub-mounting stays 20 around its own central axis.

Further, the fixing device 10D has a fixing roller 22 and a heating port as a belt configuration. Preheating of an endless belt wound endlessly around a fixing belt (heat transfer belt) 32 wound around a roller 8 and a pressure roller 24 and a supporting roller 30 similarly to the above-described embodiment. · It is configured to include the transport belt 34.

 Here, although the details will be described later, the fixing roller 22 is formed of an elastic roller, while the pressing roller 24 is formed of a roller having a higher hardness than the fixing roller 22. On the other hand, as shown in FIG. 8, the distance D between the rotational centers O 1 and O 2 of the fixing roller 22 and the pressure roller 24 is, as shown in FIG. It is set slightly smaller than the sum of the radii of R 2 of 4 (R 1 + R 2). As a result, in the mutual contact portion (nip portion) of the fixing roller 22 and the pressure roller 24, the two contact each other with a predetermined pressure contact force P1, whereby the fixing roller 2 2 will be brought into a concave state at the rolling contact part. That is, a sufficient nip width is secured.

 In addition, the fixing device 10D applies silicone oil to the outer surface of the fixing belt 32, and the oil applying roller 36 for cleaning the outer surface of the fixing belt 32 is orthogonal to the fixing belt 32. The first coil spring 82 for applying a predetermined tension to the fixing belt 32 and the heating roller 28 are urged in a direction away from the fixing roller 22 so that the first coil panel Further, a second coil spring 84 for applying a predetermined tension to the fixing belt 32 in cooperation with the fixing belt 32 is further provided.

 On the other hand, on the upper portion of the left cover portion 74 described above, a sheet (hereinafter referred to as a “fixed sheet”) that has passed through the rolling contact portion and has been fixed with unfixed toner by thermocompression bonding with the fixing roller 22 and the pressure roller 24. In this embodiment, the paper discharge passage 86 is configured to discharge the fixed sheet upward in a substantially upright state. Is set to

The lower discharge roller 88 is rotatably supported by the left force bar portion 74 while being positioned between the paper discharge passage 86 and the rolling contact portion. , To be described later With the driving force from the moving mechanism 90, it is driven to rotate at a speed equal to or higher than that of the pressure roller 24 (for example, a rotation speed set 5% faster than the speed of the pressure port 24). It is configured as follows. The lower discharge roller 88 is in rolling contact with the lower discharge roller 88 obliquely from above, while the upper discharge roller 92 is in rolling contact with the lower discharge roller 88 via a panel panel 94 with a predetermined elastic force. The position of the upper discharge roller 92 and the lower discharge roller 8

The line connecting the center positions of the sheet 8 and the sheet 8 is set to be substantially orthogonal to the sheet ejection path of the fixed sheet.

 In the fixing device 10D having such a schematic configuration, the unfixed sheet S conveyed onto the preheating / conveyance belt 34 by a conveyance mechanism (not shown) is transferred to the lower surface where the unfixed toner is not adhered. The preheating ′ is contacted and supported by the transport belt 34, and the preheating ′ is the rolling contact between the fixing roller 2 and the pressure roller 24 around which the fixing belt 32 is wound with the endless running of the transport belt 34. It is set so that the toner is heat-pressed and fixed on the sheet by being guided toward the nip (nip portion) and being inserted in a state where the two 22 and 24 are pressed against each other. ing.

 {Description of fusing roller 2 2}

 The above-mentioned fixing roller 22 is provided coaxially around the outer periphery of the cored bar 22 A, which is rotatably supported by a side plate 16 via a bearing (not shown). And a roller body 22B around which the fixing belt 32 is wound. The roller outer diameter is set to 38.5 mm in this embodiment. Here, in this embodiment, the core part 22 A is formed of an iron shaft having a diameter of 25 mm, and the roller body 22 B is provided with a thickness of 6.75 mm on the outer periphery of the core part 22 A. Silicone rubber heat-resistant elastic body (specifically, silicone rubber sponge with ASKER C hardness of 35 degrees) is formed as an elastic roller.

As shown in FIG. 9, a first driven gear 96 is coaxially mounted on a shaft disposed at one end of the cored bar 22A, and a one-way clutch 98, which will be described in detail later, is mounted on the shaft. The first driven gear 96 has a driving mechanism 9 described in detail later. The transmission gear 100 forming a part of 0 is engaged. In this manner, the driving force from the driving mechanism 90 is transmitted to the first driven gear 96 through the transmission gear 100 as a rotational force in the clockwise direction in the figure, and is transmitted through the one-way clutch 98. The rotational force is transmitted to the fixing roller 22.

 {Description of pressure roller 24}

 The above-mentioned pressure roller 24 is provided coaxially around the outer periphery of the core 24 A, which is rotatably supported on the side plate 16 via a bearing (not shown). And a roller body 24B, and the roller outer diameter is set to 35 mm. Here, in this embodiment, the core 24 A is formed of an iron shaft having a diameter of 32 mm, and the roller body 24 B has a thickness of 1.5 mm on the outer periphery of the core 24 A. It is formed as a hard roller from a heat-resistant silicone rubber elastic body (specifically, silicone rubber having a JISA hardness of 15 degrees that is harder than the fixing roller 22 described above). The outer periphery of the roller body 24B is covered with a 50 / m-thick fluorine resin tube.

 As shown in FIG. 9, a shaft provided at one end of the cored bar 24 A has a second driven gear 102 fixed coaxially thereto. 2 is combined with the above-described first driven gear 96, and a driving force from this is transmitted to the second driven gear 102 via the first driven gear 96, and the The roller 24 is configured to be rotationally driven along the counterclockwise direction opposite to the fixing roller 22.

Here, in this embodiment, as a main drive for conveying the unfixed sheet, a preheating-conveying belt 34 is wound and a pressure roller 24 for endlessly running the belt is set. The gear ratio of the first and second driven gears 96 and 102 is set so that the peripheral speed of the fixing roller 22 does not become faster than the peripheral speed of the pressure roller 24 even during thermal expansion. Have been. That is, when the fixing roller 22 is rotated by the second driven gear 102, the rotation speed is determined by the frictional force between the fixing roller 32 and the pressure roller 24 via the preheating and conveying belt 34. Slightly slower than the rotation speed when rotating together It is set as follows.

 On the other hand, in this embodiment, the pressure roller 24 is not located immediately below the fixing roller 22, but rather in the conveying direction of the unfixed sheet rather than immediately below the fixing roller 22. When a perpendicular line passing through the center point of the fixing roller 22 is used as a base line, the base line and a line passing through both center points of the fixing roller 22 and the pressing roller 24 are provided. It is placed on the stake so that the angle between the minute and the minute is a predetermined acute angle. The line segment defining the center point of the pressure roller 24 is set so as to be substantially perpendicular to the conveying direction of the unfixed sheet.

 (Description of one-way clutch 98)

 Here, the one-way clutch 98 is connected to the first driven gear 9 of the fixing roller 22.

6, relative rotation in the clockwise direction in the figure is permitted, but the relative rotation in the counterclockwise direction in the figure is locked, in other words, both are integrally rotated. Specifically, in the cold state, the fixing belt 32 frictionally engages with the pressure roller 24, and the fixing roller 22 frictionally engages with the fixing belt 32, and is pressed by the press roller 4. When the fixing roller 22 and the fixing belt 32 are driven (rotated), the peripheral speed of the fixing roller 22 rotating clockwise in the drawing becomes the same as the peripheral speed of the pressure roller 24, Although the speed is slightly higher than the peripheral speed of the driven gear 96, this speed difference is absorbed by the one-way clutch 98.

 Note that the heat generated by the heating roller 28 heats the fixing roller 22 via the fixing belt 32 and enters a warm-up state, and the outer diameter of the fixing roller 22 increases due to thermal expansion, so that the peripheral speed of the fixing roller 22 increases. Is set so that it does not become faster than the peripheral speed of the pressure roller 24 even if the speed becomes faster, so even in this case, this speed difference is reliably absorbed by the one-way latch 98. .

On the other hand, since such a one-way clutch 98 is provided, the following effects are additionally achieved. That is, if such a one-way clutch 98 is not provided, as an unfixed sheet, for example, coated paper When the glossy paper with such a surface is conveyed by the conveyance belt 34, the preheating occurs. Slip occurs between the unfixed sheet on the conveyance belt 34 and the fixing belt 32, and the pressure is applied. The driving force of the roller 24 is not transmitted to the fixing belt 32 and the fixing roller 22, and a situation occurs in which these are not driven (rotated). If such a situation occurs, the unfixed sheet may stop at the transfer portion and cause a jam, or even if the unfixed sheet on the unfixed sheet can pass through the transfer portion, The image is disturbed by being rubbed by the stopped fixing belt 32.

 However, in this embodiment, since the one-way clutch 98 is provided between the fixing roller 22 and the first driven gear 96, the driving force of the pressure roller 24 is temporarily transmitted to the fixing belt 32. If the peripheral speed of the fixing roller 22 starts to become slower than the peripheral speed of the first driven gear 96, the first driven gear 96 turns clockwise in FIG. It will be driven to rotate. In this way, the unfixed sheet can be reliably passed through the transfer portion, effectively preventing the possibility of jamming, and the image of the unfixed toner when passing through the transfer portion. Disturbance is suppressed.

 {Description of Fixing Benoret 3 2}

 In this embodiment, the fixing belt 32 described above has an endless belt body made of polyimide having an inner diameter of 60 mm and a thickness of 1 OO / xm, and a thickness of 20 mm on the outer peripheral surface of the belt body. And a heat-resistant elastic release layer of silicone rubber coated with 0 μπι.

 The fixing belt 32 is not limited to being formed of polyimide and silicone rubber, but may be an endless velvet body such as a nickel electrode as in the above-described embodiment. A heat-elastic release layer of silicone rubber coated on the outer peripheral surface of the belt body.

 {Description of mechanism for applying tension to fixing belt 32}

As described above, in this embodiment, tension is applied to the fixing belt 32. The first coil panel 82 that applies a predetermined tension to the fixing belt 32 and the heating roller 28 are fixed by pressing the oil application roller 36 in a state perpendicular to the fixing belt 32 as a mechanism. There is provided a second coil spring 84 that urges the fixing belt 32 in cooperation with the first coil panel 82 to urge the roller 22 away from the roller 22.

 Here, the first coil spring 82 is attached to the left cover part 74 so as to urge the casing 104, which rotatably supports the oil application roller 36, toward the fixing venolet 32. Installed. That is, the casing 104 is supported by the guide ribs 106 attached to the side plate 16 so as to be able to freely contact and separate from the fixing belt 32. In this way, when the left cover part 74 is opened to the left in the figure, the first coil spring 82 pressing the casing 104 is removed from the casing 104, and the oil The pressing state of the applying roller 36 against the fixing belt 32 is released. Further, when the left cover part 74 is rotated rightward in the drawing and closed, the first coil spring 82 presses the casing 104 with the pressing force P2, and the oil application roller 36 is fixed. The belt 32 is pressed with a predetermined tension.

 On the other hand, the second coil spring 84 is interposed between the left end of the swing lever 76 in the figure and the side plate 16 so that the swing lever 76 rotates clockwise in the figure. In other words, the heating roller 28 supported by the swing lever 76 is mounted so as to be pressed by the third pressing force P3 in a direction away from the fixing roller 22. As a result, a predetermined tension is applied to the fixing belt 32.

 That is, the heating roller 28 is biased in a direction away from the fixing roller 22 by the biasing force of the second coil spring 84 via the swing lever 76, whereby the heating roller 28 and the fixing roller The fixing belt 3 2, which has been wrapped around the endless, is tensioned to a predetermined tension.

 As described above, the operation of the first and second coil springs 82, 84 causes the fixing belt 3

2 is frictionally engaged with the pressure roller 24 and rotates together therewith. In accordance with the entrainment, the fixing roller 22 is driven by the fixing belt 32 in a stable state with no slip or looseness.

 {Description of drive mechanism 90)

 As shown in FIG. 9, the drive mechanism 90 for rotationally driving the pressure roller 24 and the like described above is driven by the electronic copying apparatus when the fixing apparatus 10D is mounted on the electronic copying apparatus. A transmission gear 100, which is connected to an output gear GE connected to a power source via a gear train (not shown), and is rotationally driven by receiving a driving force from the output gear GE; A first driven gear 96 connected to the fixing roller 22 via the clutch 98, and a second driven gear always engaged with the first driven gear and coaxially fixed to the pressure roller 24. Driven gear 102.

 The drive mechanism 90 further includes an idle gear 108 that is always engaged with the transmission gear 100 described above. The idle gear 108 is coaxially fixed to the lower discharge roller 88. The third driven gear 110 is always engaged, and is configured to rotationally drive the lower discharge roller 88 at a speed equal to or higher than the rotation of the pressure roller 24.

 {Other configurations)

 Between the peeling claw 111 for peeling off the fixed sheet adhered to the outer peripheral surface of the fixingless roller 24 of this embodiment, and the lower discharge roller 88 and the upper discharge roller 92 described above ( And a paper ejection sensor 114 that detects that the leading end of the fixed sheet has been conveyed to the transfer portion.

Also, in order to control the temperature of the heat source 26 built in the heating roller 28, the fixing roller 32 and the thermistor 60 that detects the temperature of the fixing belt 32 wound around the outer peripheral surface of the heating roller 28 are used. 2nd thermistor 1 16 for detecting the temperature of the outer peripheral surface of the portion of the fixing belt 3 2 wrapped around the outer periphery of 2 and 3rd thermistor 1 1 8 for detecting the temperature of the outer peripheral surface of the pressure roller 24 Although not shown, a control circuit for controlling heat generation of the heat source 26 based on the detection results from the first to third thermistors 60, 116, 118 is further provided. . Explanation of the arrangement of the heat roller 28

 As described above, in this embodiment, the heating roller 28 is disposed substantially above the fixing roller 22, whereby the heating roller 28 is wound around an endless between the heating roller 28 and the fixing roller 22. The unfixed sheet conveyed on the preheating / conveying belt 34 is separated from the fixing belt 32 and the preheating-conveying belt 34 so as not to contact the fixing belt 32. In other words, this means that the fixing belt 32 is disposed at a position outside an area where an unfixed sheet conveyed on the preheating-conveying belt 34 may pass. I have.

 By arranging the heating roller 28 above the fixing roller 22 in this manner, the unfixed sheet being transported is carried on the upper surface of the sheet regardless of the curved posture (curl state) of the sheet. The unfixed toner is reliably prevented from coming into contact with the fixing belt 32, and the rolling contact portion between the fixing roller 22 and the pressure roller 24 without disturbing the unfixed toner (that is, the pre-heating of the fixing roller 32 and preheating) (The point of contact with the conveyor belt 34) and fix it.

 (Description of configuration angle of heating roller 28)

 In the fixing device 1 OD having the above-described configuration, a special effect can be achieved by disposing the heating roller 28 substantially above the fixing roller 22 as described above. Here, as shown in FIG. 10, in order to clearly define the range of “approximately above”, an experimental example in which the configuration angle of the heating roller 28 was variously changed and the optimum range was determined will be described. I do.

First, in this experimental example, a vertical line passing through the center point of the fixing roller 22 is defined as a base line B, and the base line B and a line segment L connecting both center points of the fixing roller 22 and the heating roller 28 are defined. When the constituent angle is defined as 0, the position of the heating roller 28 is changed so that the constituent angle 0 is 90 ° to 180 °, and the fixing roller 22 and the pressure roller are changed. The frequency of occurrence of rubbing of the image at the entrance of the transfer portion with 24, and the frequency of occurrence of the abnormality at the exit of the transfer portion were measured for single-sided copying and double-sided copying, respectively. Here, for the soil having a constituent angle of 0, the value measured in the counterclockwise direction from the base line B was defined as “10”, and the value measured in the clockwise direction from the base line B was defined as “1”. Therefore, the heating roller 28 at + 180 ° and the heating roller 28 at 180 ° indicate the same position, and +105. The heating roller 28 located at 255 ° and the heating roller 28 located at 255 ° indicate the same position. On the other hand, the abnormality at the exit of the transfer contact portion in this embodiment means occurrence of an offset or occurrence of a jam at the exit of the transfer contact portion.

 The measurement conditions are as follows.

 That is, the nip width at the transfer contact portion was set to 8 mni, and the pressing force P1 for this was set to 24 kgf / one side. On the other hand, the temperature of the portion of the fixing belt 32 wound around the fixing roller 22 was set to 160 ° C., and the surface temperature of the pressure roller 24 was set to 140 ° C. Further, the conveying speed of the unfixed sheet was set to 180 mmZsec, and the pressure roller 24 was driven to rotate in synchronization with the conveyance speed. And, as the toner, Fuji Xerox's A color toner is used,

 [01 50]

 Thus, the configuration angle 0 is 90. , 1 05. , 1 20. , 150 °, 180. , One 150 °, one 120 °, one 105. , — 90. And measured under the above-mentioned measurement conditions.

Table 3 shows the measurement results.

Table 3

\ Different one-sided Coby Double-sided copy Evaluation structure \ Normal

 Image \ At the exit of the transfer section at the entrance of the transfer section Angle at the exit of the transfer section at the entrance of the transfer section \ Frequency of abnormalities in image rubbing frequency Frequency of abnormalities in image rubbing frequency \

 90. 3/5 0/5 5/5 0/5 X

105 ° 0/5 0/5 1/5 0/5 Δ

120 ° 0/5 0/5 0/5 0/5 〇

150 ° 0/5 0/5 0/5 0/5 〇

± 180 ° 0/5 0/5 0/5 0/5 〇

— 150 ° 0/5 0/5 0/5 0/5 〇

— 120 ° 0/5 0/5 0/5 0/5 O

-105 ° 0/5 2/5 0/5 3/5 X 90. 0/5 5/5 0/5 5/5 X

As is clear from Table 3, when the constituent angle 0 is larger than 105 ° and smaller than 110 °, that is, when the constituent angle Θ is measured only in the counterclockwise direction, When the angle is within the range of 105 ° to 255 °, there is no occurrence of image rubbing at the entrance of the transfer contact portion and no abnormality at the exit of the transfer contact portion, and good fixing is achieved. The action was found to be running. On the other hand, if the constituent angle 0 is less than 105 °, either the image rubs at the entrance of the transfer part or the abnormality at the exit of the transfer part occurs, and good fixing operation is not performed. There was found.

 As described in detail above, in this embodiment, the heating roller 28 is disposed substantially above the fixing roller 22, and specifically, the heating roller 28 is positioned at the center of the heating roller 28 and the fixing roller 22. With the line connecting the center points of the fixing roller 22 and the pressure roller 24 as the base line B, the angle measured from the base line B is about 10 5 And a fixing belt 32 wound endlessly between the heating roller 28 and the fixing roller 22, and a pressure roller 24. The unheated sheet conveyed on the preheated 'conveying belt 34' does not contact the fixing belt 32 between the preheated 'conveying belt 34' wound around the endless belt and the supporting roller 30. Will be separated. In other words, this means that the fixing belt 32 is disposed at a position outside a region where the unfixed sheet conveyed on the preheating / conveying belt 34 may pass. .

As a result, according to this embodiment, unlike the case of the above-described embodiment, the effect of the preheating from the heat transfer belt 32 cannot be expected, but the preheating is performed on the unfixed sheet that is being conveyed on the conveying belt 34. No matter what kind of bending posture (curl state) is caused by the preheating of the preheating from the lower surface of the conveyor belt 34 and the slack caused by the jumping up or the difference in the conveying speed from the transfer unit, etc. The unfixed toner carried on the upper surface of the sheet is reliably prevented from coming into contact with the fixing belt 32, and the rolling contact portion between the fixing roller 22 and the pressure roller 24 without disturbing the unfixed toner. In other words, it is possible to guide the fixing belt 32 and the preheating section to the rolling contact portion between the transport belt 34 and fix the toner reliably. Become.

 In this embodiment, the upper fixing roller 22 is formed from an elastic roller, and the lower pressure roller 24 is formed so as to have a higher on-roller hardness than the elastic roller. As compared with the conventional configuration in which the fixing roller is formed of a hard roller, the shape of the two nips can easily achieve the state of being recessed downward and the state of being recessed upward. As a result, according to this embodiment, a force in the direction in which the fixed sheet is separated from the fixing belt 32 is obtained from the nip shape itself at the rolling contact portion, and the surface on the side in contact with the fixing belt 32 is obtained. Even if the toner is carried on the fixing belt 32, the amount of oil applied by the oil applying roller 36 for preventing offset to the fixing belt 32 can be suppressed to a very small amount, and the oil The fixing operation without the offset and the jam is achieved.

 Further, in this embodiment, a material having a small heat capacity is adopted as the fixing belt 32 as a heat transfer belt, and the wrapping angle of the fixing belt 32 around the heating roller 28 is large. This means that the fixing belt 32 is in close contact with 28. In addition, before the unfixed sheet S is brought to the rolling contact portion, the unfixed sheet S is preheated from the lower surface by the preheating conveyor belt 34. As a result, according to this embodiment, even if the unfixed sheet S is rotated at a high speed, that is, even if the number of sheets passed per unit time is a large Temperature can be reliably maintained.

Further, in this embodiment, the heat source is not built in the fixing roller 22 formed as an elastic roller, and the heat source 28 is disposed at a position separated from the fixing roller 22. 26, the thickness of the silicone rubber heat-resistant elastic body 22B of the fixing roller 22 can be sufficiently increased. As a result, according to this embodiment, The nip width in the portion can be made sufficiently wide while maintaining the fixing roller 22 at a small diameter. In this embodiment, a one-way clutch 98 is interposed between the first driven gear 96 and the fixing roller 22 so that the main drive for sheet conveyance (that is, the sheet The pressure roller 24 is set instead of the fixing roller 22 as the drive roller that regulates the conveyance speed of the roller. For this reason, even if the fixing roller 22 is heated during the fixing operation and, as a result, the outer diameter of the fixing roller 22 is thermally expanded due to thermal expansion, the sheet conveying speed is regulated by the fixing roller 22. Since the sheet is not conveyed, this thermal expansion does not change the conveying speed of the sheet, so that the sheet can always be kept constant. As a result, according to this embodiment, the linear velocity can be kept constant, and it is possible to reliably prevent rubbing of the transferred image.

 {Description of Modifications of Other Embodiments]

 In the other embodiments described above, the unfixed sheet is described as being conveyed to the fixing device 1OD from the lateral direction. However, the present invention is not limited to such a configuration, and the unfixed sheet is not limited to such a configuration. May be configured to be conveyed vertically, for example, from bottom to top. In this case, the pressure roller 24 is disposed not on the side but below the fixing roller 22, while the heating roller 28 is disposed on the pressure roller 24 of the fixing roller 22. It goes without saying that it will be arranged on the side opposite to the side of the sword.

 Further, in the other embodiments described above, the third thermistor 118 for detecting the temperature of the outer peripheral surface of the pressure roller 24 has been described, but this can be omitted. Needless to say.

 In the other embodiments described above, the heat source 26 is described as being constituted by a halogen lamp disposed inside the heating roller 28, but the present invention is not limited to such a configuration. Instead, as shown in FIG. 11A as a first modified example, it may be constituted by a sheet heater 26 A attached in a state of being closely attached to the inner peripheral surface of the heating roller 28. .

Further, the heat source 26 is not limited to the configuration built in the heating roller 28, As shown in FIG. 11B as a second modified example, a state where the heating roller 28 is disposed outside the heating roller 28, specifically, a surface state where the heating roller 28 is attached in close contact with the outer peripheral surface of the heating roller 28 The heater 26B may be used.

 Further, in the configuration in which the heat source 26 is disposed outside the heating roller 28 in this manner, as shown as a third modification in FIG. 11C, the fixing belt 32 is directly heated by the induction heating. An induction heating mechanism 120 may be provided, and as shown as a fourth modified example in FIG. 11D, the heating device is disposed to face the outer peripheral surface of the fixing belt 32, It is configured to have a halogen lamp 122 that directly heats it and a reflector 124 that collects (condenses) heat from the halogen lamp 122 toward the fixing belt 32. May be.

 In the third and fourth modified examples shown in FIG. 11C and FIG. 11D, the positions of the induction heating mechanism 120 and the halogen lamp 122 The fixing belt 32 is disposed between the roller 8 and the fixing belt 32 so as to heat a portion of the fixing belt 32 located on the upstream side of the rolling contact portion in the running direction of the fixing belt 32. In the third modification shown in FIG. 11C, the fixing belt 32 cannot use a synthetic resin such as polyimide as a base material. It goes without saying that the belt is made of metal such as a belt.

 In the above-described embodiment and the other embodiments, the preheating / conveying belt 34 is configured such that the heat from the heat source 26 is transferred to the transfer portion via the fixing belt 32 and heated. As described above, the present invention is not limited to such a configuration.

As shown as a first modified example of the second heat generating means, it may be configured such that it is disposed as an auxiliary heat source 1 26 inside the pressure roller 24. In this case, unlike the other embodiments described above, it goes without saying that the third thermistor 118 for detecting the temperature of the outer peripheral surface of the pressure roller 24 is an essential component.

 As shown in FIG. 12B as a second modification of the second heating means,

The auxiliary heat source 1 26 may be arranged inside 30. Although not shown, it goes without saying that auxiliary heat sources may be provided in the pressure roller 24 and the support port roller 30, respectively. Industrial applicability

 As described in detail above, according to the present invention, there is provided a fixing device capable of more effectively achieving preheating of a recording medium and achieving an increase in the conveying speed of the recording medium. Further, according to the present invention, there is provided a fixing device which can eliminate the possibility that the toner image is disturbed by rubbing against the fixing belt while the recording medium is being preheated. Further, according to the present invention, there is provided a fixing device capable of minimizing the conveyance load of the recording medium while the recording medium is being preheated and achieving a reliable conveyance state. . Thus, the fixing device according to the present invention is suitable for use in an image forming apparatus such as an electronic copying apparatus, an electronic printer apparatus, and an electronic facsimile apparatus.

Claims

The scope of the claims

1. A fixing roller, and a pressure roller which is urged so as to be in rolling contact with the fixing roller, wherein a sheet having unfixed toner carried on a surface thereof contacts a rolling contact portion between the fixing roller and the pressure roller. In a fixing device for fixing the unfixed toner on the sheet by passing along the one direction,

 First heat generating means disposed apart from the fixing roller,

 Heat transfer means for receiving the heat transfer from the first heat generating means and heating the sheet passing through the rolling contact portion;

 The sheet which is located upstream of the pressure roller in the one direction, is heated by receiving heat transfer from the first heat generating unit via the heat transfer unit, and is heated before passing through the rolling contact portion. And a preheating / transporting means for preheating the sheet from the back surface on which the unfixed toner is not carried, and transporting the sheet toward the rolling contact portion.

 2. The heat transfer means is provided with a heating roller disposed apart from the fixing roller, and is endlessly stretched between the heating roller and the fixing roller, and has a predetermined heat capacity. A first heat transfer belt for transferring heat of the heat generating means to the fixing roller,

 The conveying / preheating means is endlessly bridged between a support roller disposed upstream of the pressure roller in the one direction and the support roller and the pressure roller, and has a predetermined heat capacity. 2. The fixing device according to claim 1, further comprising a second heat transfer belt having the fixing device.

3. The second heat transfer belt conveys the sheet toward the rolling contact portion in accordance with the traveling thereof, and receives heat from the pressure roller to be heated and radiated. 3.The fixing device according to claim 2, wherein the sheet is preheated from the back side.

4. The fixing device according to claim 2, further comprising a second heat generating means for heating the second heat transfer belt.

 5. The fixing device according to claim 2, wherein the first heat generating unit is built in the heating roller.

 6. The fixing device according to claim 5, wherein the first heat generating means includes a halogen lamp.

 7. The fixing device according to claim 5, wherein the first heat generating means includes a planar heat generating body attached to an inner peripheral surface of the heating roller.

 8. The fixing device according to claim 2, wherein the first heat generating means is disposed outside the heating roller so as to face the first heat transfer belt.

9. The fixing device according to claim 8, wherein the first heating means includes a planar heating element attached to an outer peripheral surface of the heating roller.

 10. The fixing device according to claim 8, wherein said first heat generating means is an induction heating means for generating heat by induction heating of said first heat transfer belt.

11. The induction heating means is located between the fixing roller and the heating roller, and is located on the upstream side of the rolling contact portion with respect to a traveling direction of the first heat transfer belt. 10. The fixing device according to claim 10, wherein the fixing device is provided so as to induction heat the transmission portion.

 12. The first heat transfer belt is formed including an endless metal base material and a release layer coated on an outer peripheral surface of the metal base material. 21. The fixing device according to claim 11, wherein:

 13. The fixing device according to claim 12, wherein the metal base is formed from a nickel electrode belt.

 14. The fixing device according to claim 8, wherein the first heat generating means includes a halogen lamp disposed to face the first heat transfer belt.

15. The second heat generating means is incorporated in the pressure roller. The fixing device according to claim 4, wherein

 16. The fixing device according to claim 4, wherein the second heat generating means is incorporated in the support roller.

 17. The fixing device according to claim 1, wherein the first heat generating unit is disposed at a position upstream of the fixing roller in the one direction.

18. The fixing device according to claim 1, wherein the first heat generating means is disposed apart from the fixing roller along a direction intersecting the one direction.

19. The first heat generating means is disposed on a side opposite to a side on which the pressure roller is in rolling contact with the fixing roller and is separated from the fixing roller. Item 2. The fixing device according to item 2.

 20. The heating roller is disposed within a preheating influence range where heat radiated from the first heat transfer belt can preheat the sheet before passing through the fixing portion. 3. The fixing device according to claim 2, wherein:

 21. The heating roller is disposed outside a preheating influence range in which heat radiated from the first heat transfer belt can preheat the sheet before passing through the fixing portion. 3. The fixing device according to claim 2, wherein:

 22. Between the first heat transfer belt and the second heat transfer belt, the sheet conveyed on the second heat transfer belt is provided with the first heat transfer belt before the rolling contact portion. 3. The fixing device according to claim 2, wherein the fixing device is separated so as not to contact the transmission belt.

23. The first heat transfer belt, wherein the first heat transfer belt is disposed at a position outside a region where the sheet conveyed on the second heat transfer belt may pass. 3. The fixing device according to claim 2, wherein:

 24. The apparatus further comprises driving means for driving the pressure roller to rotate.

The first heat transfer belt passes through the pressure roller and the second heat transfer belt. By frictional engagement, it is driven to travel,

 3. The fixing device according to claim 2, wherein the fixing roller is driven to rotate by the rotation of the pressure roller via the first heat transfer belt. The fixing device according to claim 2, wherein the first heat transfer belt is formed including an endless base material and a release layer coated on an outer peripheral surface of the base material. apparatus.

 26. The fixing device according to claim 25, wherein the endless substrate is made of metal.

 27. The fixing device according to claim 26, wherein the metal base is formed from a nickel electrode belt.

 28. The fixing device according to claim 25, wherein said endless base material is made of a synthetic resin.

 29. The fixing device according to claim 28, wherein the synthetic resin base material is formed from a polyimide resin belt.

 30. The second heat transfer belt, comprising: an endless base material; and a release layer coated on an outer peripheral surface of the base material. Item 7. The fixing device according to Item 1.

 31. The fixing device according to claim 30, wherein the endless base material is made of a synthetic resin.

 32. The fixing device according to claim 31, wherein the base made of a synthetic resin is formed from a belt made of a polyimide resin.

 33. The claim, wherein the second heat transfer belt comprises an endless base material, and a surface layer formed on the outer peripheral surface of the base material and formed of a chargeable material. 3. The fixing device according to item 2, wherein

3 4 · The second heat transfer bell is disposed so as to face the second heat transfer belt. 34. The fixing device according to claim 33, further comprising a charging unit that charges the sheet and adsorbs the sheet to the second heat transfer belt.