JPH11344883A - Fixing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more effectively realize the preheating of a recording medium by providing a heat generating means for preheating a sheet which is being carried by heating a belt-carrying means. SOLUTION: This fixing equipment 10 is constituted of a fixing roll 28 which is pivotally supported around a fixed axial line on a side plate 16, a pressure roll 30 supported on the side plate 16 around a fixed axial line set in parallel with the fixed axial line of the roll 28 in a state where it rolls in contact with the roll 28 nearly under the roll 28, and a heating roll 34 attached to a rocking lever 22 in a state where it is positioned nearly above the roll 28, supported around the center axial line of its own and incorporating a heat generating source for fixing 32 such as a halogen lamp. Furthermore, the equipment 10 is provided with a fixing belt 36 which is wound endlessly over the rolls 28 and 34. The belt 36 is heated by the heat generating source 32, and a carrying belt 76 is heated by a heat generating source for preheating 78, and the unfixed sheet S is preheated by contact heat transmission from the carrying belt 76.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] 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.

[0002]

2. Description of the Related Art Conventionally, in a fixing device for an electronic image forming apparatus, instead of a conventional heating roll fixing method, for example, as shown in FIG. 10 as a technique described in JP-A-6-318001, a fixing roll is used. R1 and heating roll R3
And a pressure roller R2 pressing the fixing roller R1 from below through the fixing belt B.
A technique has been developed in which the recording medium D is preheated by a belt fixing method provided with.

[0003] By preheating the recording medium D, the temperature of the nip portion between the pressure roll R2 and the fixing belt B can be set low, and by using the fixing belt B having a small heat capacity, the recording medium D can be used. At the time of passing through the nip portion, the temperature of the fixing belt B can be rapidly cooled. Further, this cooling causes the fixing belt B at the exit of the nip portion to move.
The cohesive force of the toner to be separated from the toner can be increased. Due to the increase of the cohesive force, the releasability of the toner from the fixing belt B and the toner can be enhanced, so that even if no oil is applied or only a small amount of oil is applied, there is no clear and clear. Thus, a stable fixed image 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 roll system, are solved at once.

Here, the structure of a conventional belt-fixing type fixing device shown in FIG. 10 will be schematically described. The fixing device includes a fixing roll R1, a pressure roll R2, and a heating / tension roll R3. A fixing belt B is stretched between R1 and the heating and tension roll R3.
An oil application roll R4 is disposed above the fixing belt B, and a guide plate G is disposed below the fixing belt B with a gap. A preheating passage for the recording medium D is defined from the space between the lower portion of the fixing belt B and the guide plate G.

On the other hand, a heating source H is provided inside the heating and tension roll R3, and a heating source may be additionally provided inside the fixing roll R1 and the pressure roll 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.

[0006]

However, in the conventional fixing device having the above-described structure, the space between the fixing belt B and the guide plate G is defined as the preheating passage for the recording medium D as described above. Therefore, when the recording medium D carrying the unfixed toner image on the upper surface is conveyed over the guide plate G, for example, the paper has a curl habit or the recording medium D is being conveyed during the conveyance. If the recording medium D is jumped up or sagged due to a difference in conveyance speed from the transfer unit, the recording medium D is lifted in a partially curved state, and the lifted portion touches the fixing belt B from below. It has been pointed out that the unfixed toner image carried here may be disturbed to cause image defects, and improvement is demanded.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and a main object of the present invention is to achieve more effective preheating of a recording medium so as to increase the transport speed of the recording medium. It is an object of the present invention to provide a fixing device that can perform the fixing.

It is another object of the present invention to provide a fixing device capable of eliminating 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 reducing a conveyance load of a recording medium as much as possible while a recording medium is being preheated, thereby achieving a reliable conveyance state. That is.

[0010]

Means for Solving the Problems The above-mentioned problems are solved,
In order to achieve the object, a fixing device according to the present invention includes a fixing roll and a pressure roll that is urged to be in rolling contact with the fixing roll. A fixing device for fixing the unfixed toner on the sheet by passing a sheet carried on the surface along a contact portion of the fixing roll and the pressure roll in one direction. A heating roll, which is disposed adjacent to the side opposite to the side on which the pressure roll is disposed and in which a heating means is disposed, and which is endlessly wound around the heating roll and the fixing roll. A heat transfer belt that receives heat transfer from the heat generating means and heats unfixed toner on the sheet passing through the rolling contact portion;
An upstream side of the pressure roll with respect to the one direction, a belt transporting means disposed independently of the pressure roll, comprising a transport belt running endlessly. And a belt conveying means for supporting the lower surface of the sheet before passing the sheet, and conveying the sheet toward the rolling contact portion by endless running of the conveying belt, and heating the belt conveying means, thereby A heating means for preheating the sheet being conveyed.

According to a second aspect of the present invention, in the fixing device, the heat generating means heats the transport belt.

According to a third aspect of the present invention, in the fixing device, the belt conveying means includes a pair of rolls around which the conveying belt is wound endlessly, and the heat generating means includes at least one of the rollers. It is characterized by being built in a roll.

According to a fourth aspect of the present invention, in the fixing device, between the heat transfer belt and the conveyance belt, the sheet conveyed on the conveyance belt is located before the rolling contact portion. The heat transfer belt is spaced apart from the heat transfer belt.

According to a fifth aspect of the present invention, in the fixing device, the heat transfer belt is located at a position outside an area where the sheet conveyed on the conveyance belt may pass. It is characterized by being arranged in.

According to a sixth aspect of the present invention, in the fixing device, the heat transfer belt includes an endless base material formed of a heat transfer material and an outer peripheral surface of the base material. And a release layer formed.

According to a seventh aspect of the present invention, in the fixing device, the endless substrate is made of metal.

According to the fixing device of the present invention, the endless base member is formed of a nickel electroformed belt.

According to a ninth aspect of the present invention, in the fixing device, the endless substrate is made of a synthetic resin.

Further, according to the fixing device of the present invention, the endless substrate is formed of a polyimide resin.

According to a ninth aspect of the present invention, in the fixing device according to the ninth aspect, the transport belt is formed of an endless base material and a chargeable material which is coated on an outer peripheral surface of the base material. And a surface layer provided.

Further, according to the tenth aspect of the present invention, the fixing device is provided so as to face the transport belt, and includes charging means for charging the transport belt and adsorbing the sheet. It is further characterized by comprising:

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of an embodiment of a fixing device according to the present invention will be described below in detail with reference to the accompanying drawings.

{Schematic Description of Fixing Device 10} First, as shown in FIG. 1, the fixing device 10 of this embodiment has an electronic image forming apparatus (not shown) as a housing structure, for example,
The apparatus includes a housing 12 fixed to a frame of the electronic copying apparatus. The housing 12 includes a bottom plate 14 fixed directly on the apparatus frame, side plates 16 erected from left and right side edges of the bottom plate 14, respectively. The upper cover 1 attached to the side plate 16 so as to cover a substantially upper right portion in the drawing.
8 and a left cover portion 20 attached to the side plate 16 so as to cover a substantially left portion thereof.

Here, the upper cover part 18 is fixedly attached to the side plate 16, and at the upper right part thereof,
The swing lever 22 is swingably supported so that the left side in the figure is opened around the first support shaft 24 located on the right side in the figure. On the other hand, the left cover part 20
Is swingably attached to the side plate 16 such that the upper part is opened around the support shaft 26.

Further, the fixing device 10 has a roll configuration in which a fixing roll 28 is rotatably supported on the side plate 16 so as to be rotatable around a fixed axis, and substantially below (specifically, obliquely below) the fixing roll 28. A pressure roll 30 rotatably supported by the side plate 16 around a fixed axis set in parallel with the fixing axis of the fixing roll 28 in a state of being in contact with the roller, and substantially above the fixing roll 28 (specifically, Is attached to the swinging lever 22 in a state of being positioned obliquely upward, is rotatably supported around its own central axis, and includes a heating roll 34 having a fixing heat source 32 such as a halogen lamp built therein. It is provided with. Further, the fixing device 10
The image forming apparatus further includes a fixing belt (heat transfer belt) 36 wound endlessly over the fixing roll 28 and the heating roll 34.

Here, although the details will be described later, the fixing roll 2
Reference numeral 8 denotes an elastic roll, while the pressing roll 30 includes a roll having a higher on-roll hardness than the elastic roll. On the other hand, the fixing roll 28 and the pressure roll 30
As shown in FIG. 2, the distance D between the center of rotation and the radius R1 of the fixing roll 28 and the sum of the radii R2 of the pressing roll 30 (R1 + R2) are set to be slightly smaller but shorter. As a result, at the mutual rolling contact portion (nip portion) of the fixing roll 28 and the pressing roll 30, the two roll contact each other with a predetermined pressure contact force P 1.
8 will be brought into a concave state at the rolling contact portion. That is, a sufficient nip width is secured.

The fixing device 10 includes a fixing belt 3
6, a silicone oil is applied to the outer surface of the fixing belt 36, and the oil applying roll 38 for cleaning the outer surface of the fixing belt 36 is pressed against the fixing belt 36 in a state of being orthogonal thereto. 3
First coil spring 4 for applying predetermined tension to 6
0, and a second coil spring 42 that urges the heating roll 34 in a direction away from the fixing roll 28 and cooperates with the first coil spring 40 to apply a predetermined tension to the fixing belt 36. I have.

The lower right portion of the upper cover 18 in the drawing is largely opened, and a sheet S on which unfixed toner is carried on the upper surface (hereinafter simply referred to as an unfixed sheet).
However, an inlet port 44 that is taken into the housing 12 along one direction (transport direction) indicated by an arrow in the figure is defined. The entrance port 44 is provided with a belt transport mechanism 46 for transporting the unfixed sheet S carried out from the side of the electronic copying apparatus toward a contact portion between the fixing roll 28 and the pressure roll 30. ing. This belt transport mechanism 46
Will be described in detail later.

On the other hand, the fixing roll 28 and the pressing roll 30
Thus, a sheet discharge path 48 for discharging a sheet on which the unfixed toner is fixed by thermocompression (hereinafter, referred to as a fixed sheet) is formed. In this embodiment, the sheet discharge path 48 The fixed sheet is set to be discharged upward in a substantially upright state.

A lower discharge roll 50 is rotatably supported by the left cover 20 in a state positioned between the discharge passage 48 and the rolling contact portion. The lower discharge roll 50 is described later. A configuration is adopted in which the driving force from the driving mechanism 52 is obtained and the rotation is performed at a speed equal to or higher than that of the pressure roll 30 (for example, a rotation speed set 5% faster than the speed of the pressure roll 30). Have been. The lower discharge roll 50 includes
The upper paper discharge roll 54 is in contact with the upper discharge roll 54 with a predetermined elastic force via the leaf spring 56 in a state of rolling contact from obliquely above. The position of the upper discharge roll 54 is set such that a line connecting the center positions of the upper discharge roll 54 and the lower discharge roll 50 is substantially orthogonal to the discharge path of the fixed sheet. Have been.

In the fixing device 10 having the above-described structure, the unfixed sheet S carried out from the electronic copying apparatus is brought into contact with and supported on the belt transport mechanism 46 with the lower surface on which the unfixed toner is not adhered. And the fixing belt 3
6 is guided toward a rolling contact portion (nip portion) between the fixing roll 28 and the pressure roll 30 around which the toner 6 is wound, and the toner is thermocompression-bonded by being inserted in a state where the two rolls 28 and 30 are pressed against each other. And is fixed on the sheet.

{Description of Fixing Roll 28} The fixing roll 28 described above includes a core 28A rotatably supported on a side plate 16 via a bearing (not shown), and a core 28A.
A roll body 28B is provided coaxially around the outer periphery of A and has a fixing belt 36 wound thereon. The outer diameter of the roll is set to 38.0 mm in this embodiment. Here, in this embodiment, the core part 28A has a diameter of 25 m.
m, formed from an iron shaft, and the roll body 28B
It is formed as a soft roll from a silicone rubber heat-resistant elastic body (specifically, silicone rubber having a JIS A hardness of 18 degrees) attached to the outer periphery of the cored bar 28A with a thickness of 6.5 mm.

A first driven gear 58 is coaxially mounted on a shaft disposed at one end of the cored bar 28A via a one-way clutch 60 which will be described in detail later. A transmission gear 62 that constitutes a part of the drive mechanism 52, which will be described in detail later, meshes with the one driven gear 58. In this manner, the driving force from the driving mechanism 52 is transmitted to the first driven gear 58 via the transmission gear 62 as a clockwise rotational force in the drawing, and the one-way clutch 60
The rotational force is transmitted to the fixing roll 28 via the fixing roller 28.

{Description of the Pressure Roll 30} The pressure roll 30 described above includes a core 30A rotatably supported on the side plate 16 via a bearing (not shown), and a core 30A.
A and a roll main body 30B coaxially arranged on the outer periphery of A, and the outer diameter of the roll is set to 35 mm.
Here, in this embodiment, the core 30A has a diameter of 3 mm.
Roll body 30B formed from a 2mm iron shaft
Is formed from a silicone rubber heat-resistant elastic body (specifically, a silicone rubber having a JIS A hardness of 20 degrees, which is harder than the above-described fixing roll 28) and is attached to the outer periphery of the cored bar 30A with a thickness of 1.5 mm. Have been. The outer periphery of the roll body 30B is covered with a 50 μm-thick fluororesin tube.

The shaft provided at one end of the cored bar 30A has a second driven gear 64 coaxially fixed thereto. The second driven gear 64 is connected to the first driven gear 64 described above. Gear 58
The driving force from this is transmitted to the second driven gear 64 via the first driven gear 58, and the pressing roll 30 moves in the counterclockwise direction opposite to the fixing roll 28. It is configured to be driven to rotate.

In this embodiment, the pressure roller 30 is set as the main drive for conveying the unfixed sheet, and the peripheral speed of the fixing roller 28 is increased even when the fixing roller 28 is thermally expanded. The gear ratio of the first and second driven gears 58 and 64 is set so that the peripheral speed of the roll 30 does not become faster. That is, the fixing roller 28 is connected to the second driven gear 6
The rotation speed at the time of rotation by 4 is set to be slightly lower than the rotation speed at the time of rotation by frictionally engaging with the pressure roll 30 via the fixing belt 36.

On the other hand, in this embodiment, the pressure roll 30 is not located immediately below the fixing roll 28, but rather in the conveying direction of the unfixed sheet rather than immediately below the fixing roll 28. It is arranged at a position deviated by
When a perpendicular line passing through the center point of the fixing roll 28 is used as a base line, a position where an angle formed by this base line and a line segment passing through both center points of the fixing roll 28 and the pressure roll 30 is a predetermined acute angle It is arranged in. In addition, this pressure roll 30
Is set so as to be substantially perpendicular to the conveying direction of the unfixed sheet.

{Description of One-Way Clutch 60} The one-way clutch 60 described above is
8 is allowed to rotate relative to the first driven gear 58 in the clockwise direction in the figure, but the relative rotation in the counterclockwise direction in the figure is locked, in other words, both rotate integrally. Is configured. Specifically, in the cold state, that is, the fixing belt 36 frictionally engages with the pressure roll 30 and
In a state in which the fixing roller 28 frictionally engages with the fixing belt 36 and the fixing roller 28 and the fixing belt 36 are driven (rotated) by the pressure roller 30, the peripheral speed of the fixing roller 28 rotating clockwise in FIG. The peripheral speed of the first driven gear 58 is slightly higher than the peripheral speed of the first driven gear 58, but this speed difference is absorbed by the one-way clutch 60.

The fixing roll 36 is heated by the heat of the heating roll 34 via the fixing belt 36 to be in a warm-up state, and the outer diameter of the fixing roll 36 increases due to thermal expansion, so that the peripheral speed of the fixing roll 36 increases. Even so, the speed difference is set so as not to be faster than the peripheral speed of the pressure roll 30, so even in this case, the speed difference is reliably absorbed by the one-way clutch 60.

On the other hand, such a one-way clutch 60
Is provided, the following effects are additionally achieved. That is, if such a one-way clutch 60 is not provided, when a glossy sheet such as a coated paper is conveyed to the transfer portion as an unfixed sheet, the unfixed sheet is fixed to the unfixed sheet. Slip occurs between the fixing belt 36 and the belt 36, and the driving force of the pressure roller 30 is not transmitted to the fixing belt 36 and the fixing roller 28, so that the driven roller 30 is not driven (rotated). When such a situation occurs, the unfixed sheet stops at the transfer portion and jams, or even if the unfixed sheet can pass through the transfer portion, the unfixed toner on the unfixed sheet is stopped. Is rubbed by the fixing belt 36, and the image is disturbed.

However, in this embodiment, the one-way clutch 60 is connected to the fixing roll 28 and the first driven gear 58.
Therefore, even if the driving force of the pressure roller 30 is not transmitted to the fixing belt 36, the peripheral speed of the fixing roller 28 is lower than the peripheral speed of the first driven gear 58. At the time when it starts to be late, the first driven gear 58 is driven to rotate clockwise in the drawing.
In this way, the unfixed sheet is reliably passed through the contact portion, and the risk of jamming is effectively prevented, and the unfixed toner image is disturbed when passing through the contact portion. Is suppressed.

{Description of Heating Roll 34} Inside the heating roll 34, as the heat source 32 for fixing, in this embodiment, an 800 W halogen lamp whose light distribution at both ends is set to be 50% larger than the center. Is provided.
The heating roll 34 has a diameter of 3 in this embodiment.
It is a 0 mm, 3.5 mm thick aluminum pipe core coated with a 20 μm thick PTFE coating layer. The bearings at both ends are made of heat-resistant resin made of polyetheretherketone (PEEK) with a diameter of 30 mm. Color 66
Are press-fitted, thereby preventing the fixing belt 36 from meandering and offset.

{Description of Fixing Belt 36} The fixing belt 36 described above is designed so that the unfixed toner on the unfixed sheet S is preheated to the fixing temperature by heat radiation and fixed without giving an excessive amount of heat. 36 has a heat capacity per square cm of 0.002 cal / ° C to 0.025 c
al / ° C. are preferred. For this reason, in this embodiment, the fixing belt 36 has an inner diameter of 60 m.
m, an endless belt body made of polyimide having a thickness of 100 μm, and a heat-resistant elastic release layer of silicone rubber coated on the outer peripheral surface of the belt body with a thickness of 200 μm.

The fixing belt 36 is not limited to being formed of polyimide and silicone rubber. For example, an endless belt body made of, for example, 40 μm nickel electroformed, and an outer peripheral surface of the belt body are used. And a heat-resistant elastic release layer of silicone rubber coated with a thickness of 200 μm.

{Description of Oil Application Roll 38} The fixing device 10 is provided with an oil application roll 38 for applying a small amount of release oil on the outer peripheral surface of the fixing belt 36. The oil application roll 38 is
A support shaft 38A rotatably supported in an axial fixed state,
A heat-resistant paper layer 38B impregnated with silicone oil is provided on the outer periphery of the support shaft 38A.
Is formed from an iron shaft having a diameter of 8 mm in this embodiment.
It is formed so as to have a roller outer diameter of 22 mm in diameter with the porous fluororesin film 38C of μm mounted. By configuring the oil application roll 38 in this manner, it is possible to apply a small amount of stable oil to the outer peripheral surface of the fixing belt 36.

The dirt (toner and the like) adhering to the outer peripheral surface of the fixing belt 36 is transferred to and adhered to the outer peripheral surface of the oil application roll 38. Because of this,
A cleaning brush is in contact with the outer peripheral surface of the oil application roll 38, and the oil application roll 38 is always in contact with the cleaning brush.
Is cleaned to remove dirt attached thereto.

{Description of Mechanism for Applying Tension to Fixing Belt 36} As described above, in this embodiment, the oil application roll 38 is orthogonal to the fixing belt 36 as a mechanism for applying tension to the fixing belt 36. A first coil spring 40 for applying a predetermined tension to the fixing belt 36 by pressing in a state, and urging the heating roll 34 in a direction away from the fixing roll 28 to fix the fixing belt in cooperation with the first coil spring 40. A second coil spring for applying a predetermined tension to the belt;

Here, the first coil spring 40 has a casing 68 that rotatably supports the oil application roll 38.
Is attached to the left cover 20 so as to urge the fixing belt 36 toward the fixing belt 36. That is, the casing 68
The guide rib 70 attached to the side plate 16 supports the fixing belt 36 so as to be able to freely contact and separate from the fixing belt 36. Thus, when the left cover part 20 is opened to the left in the figure,
The first coil spring 40 pressing the casing 68 is removed from the casing 68, whereby the pressing state of the oil application roll 38 against the fixing belt 36 is released. Further, when the left cover portion 20 is rotated rightward in the drawing and closed, the first coil spring 40 presses the casing 68 with the pressing force P2, and the oil application roll 38 applies a predetermined tension to the fixing belt 36. Will be pressed.

On the other hand, the second coil spring 42 is interposed between the left end of the swing lever 22 in the figure and the side plate 16, and in other words, rotates the swing lever 22 clockwise in the figure. Then, the heating roll 3 supported by the swing lever 22
4 is a third pressing force P in a direction away from the fixing roll 28.
3 so as to press it. As a result, a predetermined tension is applied to the fixing belt 36.

That is, the heating roll 34 is biased in a direction away from the fixing roll 28 via the swing lever 22 by the urging force of the second coil spring 42, whereby the heating roll 34 and the fixing roll 28 The fixing belt 36 stretched endlessly is tensioned to a predetermined tension.

As described above, the first and second coil springs 4
Due to the action of the fixing belt 36, the fixing belt 36 frictionally engages with the pressure roller 30 and rotates, and the fixing roller 28 slips with respect to the fixing belt 36 according to the rotation of the fixing belt 36. It is driven in a stable state without slack.

<< Description of Belt Transport Mechanism 46 >> In the present embodiment, the belt transport mechanism 46 described above is arranged such that the pressure roll 3 is located upstream with respect to the transport direction of the pressure roll 30.
0, a drive roll 72 located downstream in the transport direction, a driven roll 74 located upstream in the transport direction, and a transport wound endlessly around both rolls 72, 74. A belt 76 and a heating source 78 for preheating, such as a halogen lamp, built in the driven roll 74 for heating the transport belt 76 are provided. The drive roll 74 is driven to rotate in a counterclockwise direction in the figure by a drive mechanism 52 described later, and the unfixed sheet S brought on the transport belt 76 is moved in the direction shown by the arrow in the figure. It is configured to be conveyed toward a rolling contact portion between the fixing roll 28 and the pressure roll 30.

Here, the arrangement height position of the two rolls 72 and 74 is defined so that the drive roll 72 is higher than the driven roll 74. That is, the transport belt 76 wound around both rolls 72 and 74 is attached so as to incline diagonally upward and leftward in the figure so that the height thereof increases as it enters the housing 12. On the other hand, the introduction-side end of the transport belt 76, that is, the lower right end in the figure, is disposed in the electronic copying apparatus adjacent to the entrance port 44 on the right side in the figure. The lead-out end, that is, the upper left end in the figure, is positioned so as to face a rolling contact portion (nip portion) between the fixing roll 28 and the pressure roll 30.

{Description of the Conveying Belt 76} On the other hand, the conveying belt 76 is formed of an endless belt made of silicone rubber. During the fixing operation, the conveying belt 76 is heated by receiving heat from the heat source 78 for preheating and is not fixed. It is set so that the toner is preheated from the lower surface. This preheating heat source 78
Is configured to heat the transport belt 76 wound around the support roll 40 containing the preheating heat source 78 at the time of heat generation.

The transport belt 76 is frictionally charged between the drive roller 72 and the driven roller 74 in the endless running state as described above, and the charge amount is 1 to 5K.
V (the amount of charge in the idling state for 30 seconds) was obtained, but the unfixed sheet S conveyed here was transferred due to the frictional charging of the conveyor belt 76.
Is brought into close contact with the surface of the transport belt 76, and is transported toward the rolling contact portion (nip portion) between the fixing roll 28 and the pressure roll 30 as the transport belt 76 travels. As described above, the unfixed sheet S is
6, the heat transfer from the conveyor belt 76 to the unfixed sheet S is performed uniformly, and the temperature unevenness of the unfixed sheet S is
It will be suppressed as much as possible. Thus, the transport belt 76
Since the uniformity of the temperature of the unfixed sheet S is ensured on the basis of the triboelectric charge amount, a test result of “good” regarding the occurrence of image unevenness in the solid image described above has been obtained.

Here, the transport belt 76 is not limited to the silicone rubber as described above, and may have a configuration in which only the surface layer is formed of conductive rubber.
The charge amount in the idling state for 30 seconds is 500
A measurement result of V to 1 KV is obtained, and the uniformity of the temperature of the unfixed sheet S is ensured in the same manner as described above based on the triboelectric charge amount of the transport belt 76, so that the solid image in the above-described solid image is obtained. A test result of “good” regarding the occurrence of image unevenness has been obtained.

{Description of Driving Mechanism 52} As shown in FIG. 3, the driving mechanism 52 for rotatingly driving the pressure roll 30, the driving roll 72, and the like has the fixing device 10 mounted on an electronic copying apparatus as shown in FIG. In this state, the transmission gear 62 meshes with an output gear GE connected to a drive source of the electronic copying apparatus via a gear train (not shown), and is driven to rotate by receiving a driving force therefrom. The fixing roll 28 is always engaged with the fixing roll 28 via the one-way clutch 60.
, And a second driven gear 64 which is always meshed with the first driven gear and is coaxially fixed to the pressure roll 30.

The drive mechanism 52 further includes a first idle gear 80 that always meshes with the transmission gear 62 described above.
The third driven gear 82, which is coaxially fixed to zero, is always engaged with the third driven gear 82, and is configured to rotate the lower discharge roll 50 at a speed equal to or higher than the rotation of the pressure roll 30.

Further, the driving mechanism 52 further includes a second idle gear 84 that always meshes with the second driven gear 64, and the second idle gear 84 is coaxially fixed to the driving roll 72. The driven gear 86 is always meshed with the driven gear 86, and the driving roll 72 is driven to rotate at a rotation speed lower than the rotation speed of the pressure roll 30.

{Other Configurations} Fixing Device 1 of this Embodiment
In addition to the above-described configuration, reference numeral 0 denotes a peeling claw 88 for peeling off the fixed sheet adhered to the outer peripheral surface of the pressure roll 30, as shown in FIG. A paper ejection sensor 90 is provided for detecting that the leading end of the fixed sheet has been conveyed between the paper roll 54 (the rolling contact portion).

In order to control the temperature of the fixing heat source 32 built in the heating roll 34 and the preheating heat source 78 built in the driven roll 74, the fixing belt 36 wound around the outer peripheral surface of the heating roll 34 is controlled. First to detect the temperature of the part
And a second thermistor 92 for detecting the temperature of the outer peripheral surface of the portion of the fixing belt 36 wound around the outer periphery of the fixing roll 28.
, A third thermistor 96 for detecting the temperature of the outer peripheral surface of the pressure roll 30, and a fourth thermistor 98 for detecting the temperature of the outer peripheral surface of the portion of the conveyor belt 76 wound around the outer periphery of the driven roll 74. And, as shown in FIG.
These first to fourth thermistors 92, 94, 96, 9
And a control circuit 100 for controlling the heat generation of the heat source 32 based on the detection result from the control unit 8. The control circuit 100 controls the heat generation state of the fixing heat source 32 via the first heater driver 102 and the second heater driver 1
The heat generation state of the preheating heat source 78 is controlled via each of the heat sources.

{Description of Arrangement Above Heating Roll 34} As described above, in this embodiment, the heating roll 34 is disposed substantially above the fixing roll 28, and thus the heating roll 34 and the fixing roll 28, the guide plate 44 is separated from the fixing belt 36 wound endlessly so that the unfixed sheet conveyed on the guide plate 44 does not contact the fixing belt 36. . In other words, the fixing belt 36 is
This means that the unfixed sheet conveyed above is disposed at a position outside a region where the unfixed sheet may pass.

As described above, the heating roll 34 is connected to the fixing roll 2
8 above, no matter how the unfixed sheet in the middle of conveyance is in a curved posture (curled state),
The unfixed toner carried on the upper surface of the sheet is reliably prevented from coming into contact with the fixing belt 36, and the unfixed toner is guided to the rolling contact portion between the fixing roll 28 and the pressure roll 30 without disturbing the unfixed toner. Can be fixed.

{Description of Configuration Angle of Heating Roll 34} In the fixing device 10 having the above-described configuration, the heating roller 34 is disposed substantially above the fixing roll 28 as described above, thereby achieving a specific effect. Can be done.
Here, in order to clearly define the range “approximately above”, as shown in FIG. 5, an experimental example will be described in which the configuration angle of the heating roll 34 is variously changed and the optimum range is obtained.

First, in this experimental example, a perpendicular passing through the center point of the fixing roll 28 is defined as a base line B.
Is defined as θ, and the line segment L connecting the center points of the fixing roll 28 and the heating roll 34 is defined as θ, the position of the heating roll 34 is changed, and the configuration angle θ becomes 90 ° or more.
At 180 °, the frequency of occurrence of image rubbing at the entrance of the transfer part between the fixing roll 28 and the pressure roll 30 and the frequency of occurrence of abnormalities at the exit of the transfer part are determined during single-sided copying. And at the time of double-sided copying, respectively.

Here, ± of the constituent angle θ is defined as “+” when the value is measured counterclockwise from the base line B, and “−” is defined as the value measured clockwise from the base line B in the figure. Therefore, +1
The heating roll 34 at 80 ° and the heating roll 34 at −180 ° indicate the same position.
The heating roll 34 at 105 ° and the heating roll 34 at −255 ° indicate the same position. on the other hand,
In this embodiment, the abnormality at the outlet of the transfer portion means occurrence of an offset or occurrence of a jam at the outlet of the transfer portion.

The measuring conditions are as follows.

That is, the nip width at the rolling contact portion was set at 8 mm, and the pressing force P1 for this was set at 24 kgf / one side. On the other hand, the temperature of the portion of the fixing belt 36 wound around the fixing roll 28 was set to 160 ° C., and the surface temperature of the pressure roll 30 was set to 140 ° C. Further, the conveyance speed of the unfixed sheet was set to 180 mm / sec, and the pressure roll 30 was driven to rotate in synchronization with the conveyance speed. As the toner, A color toner manufactured by Fuji Xerox Co., Ltd. was used, and as a sheet, plain paper of 64 g / m2 was adopted.

Thus, the constituent angle θ is set to 90 °, 1
05 °, 120 °, 150 °, 180 °, -150 °,
Divided into nine types of -120 °, -105 °, -90 °
The measurement was performed under the measurement conditions described above.

Table 1 shows the measurement results.

[0071]

[Table 1]

As is clear from Table 1, when the constituent angle θ is larger than 105 ° and smaller than −105 °, that is, when the constituent angle θ is measured only in the counterclockwise direction, When the angle is within the range of from 255 ° to 255 °, there is no occurrence of image rubbing at the entrance of the transfer part and no occurrence of abnormality at the exit of the transfer part, and a good fixing operation is performed. It has been found. On the other hand, when the constituent angle θ is 10
When the angle is 5 ° or less, it was found that either an image rubbing at the entrance of the transfer part or an abnormality at the exit of the transfer part occurred, and good fixing operation was not performed.

As described in detail above, in this embodiment, the heating roll 34 is disposed substantially above the fixing roll 28, and more specifically, the heating roll 34 is positioned at the center of the heating roll 34 and the center of the fixing roll 28. The line segment L connecting the point is the fixing roll 2
In a state where a line segment connecting the center points of the pressure roller 8 and the pressure roll 30 to each other is set as a base line B, the angle measured from the base line B is about 105
The fixing plate 36 is disposed at a position within the range of about 255 degrees to about 255 degrees, so that the fixing plate 36 wound endlessly between the heating roll 34 and the fixing roll 28 and the guide plate 44 The unfixed sheet conveyed on 44 is separated so as not to contact the fixing belt 36. In other words, the fixing belt 36 is
This means that the unfixed sheet conveyed above is disposed at a position outside a region where the unfixed sheet may pass.

As a result, according to this embodiment, regardless of the curved posture (curl state) of the unfixed sheet in the middle of conveyance due to jumping up or sagging due to a difference in conveyance speed from the transfer section, etc. The unfixed toner carried on the upper surface of the sheet is reliably prevented from coming into contact with the fixing belt 36, and the unfixed toner is fixed without disturbing the unfixed toner.
To the rolling contact portion between the pressure roller 30 and the pressure roll 30, and it can be reliably fixed.

{Description of Fixing Operation in Fixing Device 10}
Next, the fixing operation on the unfixed sheet S in the fixing device 10 configured as described above will be described.

First, in the process equipment (not shown) of the electronic image forming apparatus, the output gear GE is driven to rotate during the time until the unfixed sheet S is conveyed to the fixing device 10 of this embodiment (ie, idling time). Then, the transmission gear 62, the first driven gear 58, and the second driven gear 64, which are sequentially meshed with the fixing roller 28 and the second driven gear 64, are sequentially driven to rotate in opposite directions, so that the fixing roll 28 and the pressure roll 30 move in opposite directions. It will be driven to rotate. And
With the rotation of the two rolls 28 and 30, the fixing belt 36 wound around the fixing roll 28 and the heating roll 34 is driven to run clockwise in the drawing. on the other hand,
The fourth driven gear 86 meshing with the second driven gear 64 via the second idle gear 84 is driven to rotate in the same direction as the second driven gear 74, so that the driving roll 72 is turned in the opposite direction in the figure. The transport belt 76 is driven to rotate clockwise, and as a result, the transport belt 76 is driven to run counterclockwise in the drawing.

Here, the fixing belt 36 is a heat source 3 for fixing.
2, and the transport belt 76 is heated by the preheating heat source 78, respectively.

From the idling state in which both belts 36 and 76 are heated as described above, 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 carrying the unfixed toner, that is, the unfixed sheet S is transported by a transport mechanism (not shown) to the transport belt 76 of the fixing device 10.
The sheet is conveyed to the upper side, and is placed in close contact with the conveying belt 76 based on the above-mentioned charge amount. As a result, the unfixed sheet S is thereafter continuously conveyed toward the nip portion between the fixing roll 28 and the pressure roll 30 as the conveyance belt 76 travels.

In the course of being conveyed toward the nip portion as the conveyance belt 76 travels, the unfixed sheet S receives contact heat transfer from the conveyance belt 76,
The unfixed sheet S itself is preheated from the lower surface.
In this way, when the leading end of the unfixed sheet S is brought to the nip, the unfixed toner carried on the sheet is brought into a sufficiently heated state.

That is, the unfixed toner heated to the fixing temperature as described above passes therethrough while being pressed against the nip portion, whereby the unfused toner is thermally fused and fixed on the sheet. The amount of heat applied to the unfixed sheet S when passing through the section is small since the unfixed sheet S has already been preheated up to this point.
Therefore, according to this embodiment, it is possible to lower the lower limit temperature of the fixing temperature required in the nip portion,
Thereby, there is an advantage that the life of each roll can be extended, and therefore, the running cost can be reduced. In addition, it is possible to reduce the amount of heat generated by the heat source 36, thereby making it possible to reduce the running cost.

On the other hand, if the amount of heat applied in the nip portion is constant, it is possible to secure the minimum necessary fixing temperature even if the conveying speed of the unfixed sheet S is increased. Thereby, there is an advantage that it is possible to increase the number of fixing processes per minute, that is, to increase the process speed.

As described above, while the unfixed sheet S is being conveyed by the conveyor belt 76, the unfixed sheet S adheres to the conveyor belt 76 based on the charge amount. It will be transported in a state. Therefore, the amount of heat transferred from the conveyor belt 76 by contact spreads uniformly to the unfixed sheet S, and a good fixing state (a good image forming state without image unevenness) in a state where heating unevenness is eliminated as much as possible. Is achieved.

In this embodiment, the upper fixing roll 28 is formed of a soft roll, and the lower pressure roll 30 is formed of a hard roll. As compared with the conventional configuration in which the roll is formed from a hard roll, it is possible to easily achieve the state in which the roller is recessed downward from the state in which it is recessed downward. As a result, according to this embodiment, a force in the direction in which the fixed sheet is separated from the fixing belt 36 is obtained from the nip shape itself at the rolling contact portion, and the toner is carried on the surface in contact with the fixing belt 36. Even if the fixing has been performed, the amount of oil applied by the oil application roll 38 for preventing offset to the fixing belt 36 can be suppressed to a very small amount, and even if oilless, fixing to the fixing belt 36 side without offset or jamming is performed. Action will be achieved.

In this embodiment, the upper fixing roll 28 is formed from an elastic roll, and the lower pressing roll 30 is formed from a roll having a higher on-roll hardness than the fixing roll 28. As compared with the case where both are formed from hard rolls, the nip direction in the rolling contact portion can easily achieve a state of being convex upward from substantially horizontal. As a result, according to the present embodiment, the amount of oil applied by the offset oil application roll 38 can be suppressed to a very small amount, and a fixing operation without offset and jam can be achieved even without oil.

Further, in this embodiment, a material having a small heat capacity is adopted as the fixing belt 36 as the heat transfer belt, and the winding angle of the fixing belt 36 around the heating roll 34 is large. This means that the fixing belt 36 is in close contact. As a result, according to this embodiment, even if the sheets are fed at a high speed, that is, even if the number of sheets passed per unit time is a large number, it is necessary for the fixing operation at the transfer contact portion between the fixing roll 28 and the pressure roll 30 The temperature can be reliably maintained.

In this embodiment, the heat source is not built in the fixing roll 28 which is an elastic roll, but the heat source 32 is built in the heating roll 34 disposed at a position separated from the fixing roll 28. As a result, the thickness of the silicone rubber heat-resistant elastic body 28B of the fixing roll 28 can be made sufficiently large. As a result, according to this embodiment, the nip width at the rolling contact portion is reduced by the fixing roll 28. Can be made sufficiently wide while maintaining a small diameter.

In this embodiment, the one-way clutch 60 is interposed between the first driven gear 58 and the fixing roll 28, so that the main drive for sheet conveyance (that is, the sheet conveyance speed) is performed. , A pressure roll 30 is set instead of the fixing roll 28. For this reason, for example, the fixing roll 28 is heated during the fixing operation, and as a result, the fixing roll 28 is heated by thermal expansion.
Even if the outer diameter of the sheet expands thermally, the sheet conveying speed is not regulated by the fixing roll 28, so that the sheet conveying speed does not change due to the thermal expansion, and the sheet can always be kept constant. become. As a result, according to the present embodiment, it is possible to maintain the linear velocity constant and reliably prevent transfer deviation, image rubbing, and the like.

[0088]

[Explanation of Modifications] It is needless to say that the present invention is not limited to the configuration of the above-described embodiment, but 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 apparatus 10 is applied to an electronic copying apparatus has been described. However, the present invention is not limited to such an application, and an electronic facsimile apparatus, It goes without saying that the present invention can be applied to an electronic image forming apparatus such as an electronic printer.

Further, in the above-described embodiment, the unfixed sheet is described as being conveyed to the fixing device 10 from the lateral direction. However, the present invention is not limited to such a configuration, and the unfixed sheet may be conveyed. The sheet may be configured to be conveyed in a vertical direction, for example, from bottom to top.

Further, in the above-described embodiment, the preheating heat source 78 has been described as being disposed inside the driven roll 74. However, the present invention is not limited to such a configuration, and FIG. As a first modified example, in the fixing device 10A, the preheating heat source 78 is connected to the driving roll 72.
It may be arranged inside.

Further, as shown in FIG. 7 as a second modification, in the fixing device 10B, the heat source for preheating 78 may be arranged on both the driven roll 74 and the driving roll 72.

Further, in the above-described embodiment, the transport belt 76 is frictionally charged, and the unfixed sheet S is brought into close contact with the transport belt 76 based on the charged electrical charge. The present invention is not limited to this configuration, and may be configured as shown in FIG. 8 as a third modification. That is, the fixing device 10C according to the third modification example
A charger 106 for forcibly charging the transport belt 76 is provided in addition to the configuration of the embodiment described above.
In the third modification, the charger 106 is formed of a corona charger.

As described above, in the third modified example, the provision of the charger 106 makes it possible to reliably charge the transport belt 76, and to reliably transfer the unfixed sheet S transported to the transport belt 76. And the unfixed sheet S adsorbed by the conveyance belt 76 as it travels.
Is transported toward the nip portion.

Further, in the third modified example, the unfixed sheet S is transferred to the transport belt 7 based on the above-described charged state.
6 is adsorbed in a state of being in close contact with the surface. As a result, even if the unfixed sheet S is conveyed onto the conveyance belt 76 in a curled state, the unfixed sheet S curled on the basis of the charge amount described above is attracted and adhered to the conveyance belt 76. Will be. Accordingly, while the unfixed sheet S is being preheated in the preheating passage P, the possibility that the unfixed toner image on the unfixed sheet S rubs against the fixing belt 42 and the toner image is disturbed is reliably eliminated. Will be.

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. However, the present invention is not limited to such a configuration. Although not shown, the unfixed sheet S
May be disposed in the vertical direction, that is, the pressure roll 30 may be disposed on the side of the fixing roll 28. In particular, in the vertical configuration in which the transport direction is the vertical direction, the unfixed sheet S needs to be surely adhered to the transport belt 76. Therefore, the configuration having the charger 106 according to the third modification described above is particularly advantageous. Can be demonstrated.

Further, in the configuration of the above-described embodiment, the heat source 32 for fixing is provided to heat the contact portions of the fixing roll 28 and the pressure roll 30 with each other. The present invention is not limited to such a configuration, and may be configured as shown in FIG. 9 as a fourth modification. That is, the fixing device 10 according to the fourth modification example
In D, an auxiliary heat source 108 is provided in the core metal 30A of the pressure roll 30 to heat the outer periphery of the pressure roll 30 so that the heating temperature in the transfer contact portion is reduced by the heat source for fixing. It is configured to raise the temperature together with 32.

By configuring the fixing device 10D according to the fourth modification as described above, it is possible to further increase the fixing temperature at the rolling contact portion as compared with the above-described embodiment. In addition, it is possible to set the transport speed of the unfixed sheet S to a higher speed.

[0099]

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 increasing the conveying speed of the recording medium. Will be.

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, while the recording medium is being preheated, the transport load of the recording medium is reduced as much as possible.
A fixing device capable of achieving a reliable transport state is provided.

[0102]

[Brief description of the drawings]

FIG. 1 is a front sectional view showing a configuration of an embodiment of a fixing device according to the present invention.

FIG. 2 is a diagram illustrating a state of rolling contact between a fixing roll and a pressure roll.

FIG. 3 is a front view showing a configuration of a driving mechanism.

FIG. 4 is a block diagram showing a configuration of a control system for executing temperature control of a heat source.

FIG. 5 is a diagram illustrating a configuration angle in an experimental example performed to check an allowable range of an arrangement position of a heating roll with respect to a fixing roll.

FIG. 6 is a front view showing a configuration of a first modified example of the fixing device according to the present invention.

FIG. 7 is a front view showing the configuration of a second modification of the fixing device according to the present invention.

FIG. 8 is a front view showing the configuration of a third modification of the fixing device according to the present invention.

FIG. 9 is a front view showing a configuration of a fourth modified example of the fixing device according to the present invention.

FIG. 10 is a front view schematically showing a configuration of a conventional fixing device.

[Explanation of symbols]

 10 (10A; 10B; 10C; 10D) Fixing device 12 Housing 14 Bottom plate 16 Side plate 18 Upper cover 20 Left cover 22 Swing lever 24 First support shaft 26 Second support shaft 28 Fixing roll 28A Core 28B Roll body 30 Pressure roll 30A Core part 30B Roll body 32 Heat source for fixing 34 Heating roll 36 Fixing belt 38 Oil application roll 40 First coil spring 42 Second coil spring 44 Inlet port 46 Belt transport mechanism 48 Paper discharge path 50 Lower discharge roll 52 Drive mechanism 54 Upper discharge roll 56 Leaf spring 58 First driven gear 60 One-way clutch 62 Transmission gear 64 Second driven gear 66 Collar 68 Casing 70 Guide rib 72 Drive roll 74 Follower roll 76 Transport belt 78 Preheating Heat source 80 first eye Lug gear 82 Third driven gear 84 Second idle gear 86 Fourth driven gear 88 Peeling claw 90 Discharge sensor 92 First thermistor 94 Second thermistor 96 Third thermistor 98 Fourth thermistor 100 Control circuit 102 First heater driver 104 Second heater driver 106 Charger 108 Auxiliary heat source GE Output gear S Unfixed sheet

Claims (12)

[Claims] An image forming apparatus comprising: a fixing roll; and a pressure roll which is urged to be in rolling contact with the fixing roll, wherein a sheet having unfixed toner carried on a surface thereof is rotated by the fixing roll and the pressure roll. By passing the contact along one direction,
In a fixing device for fixing the unfixed toner on the sheet, the fixing roll is disposed adjacent to a side opposite to a side on which the pressure roll is disposed, and a heating unit is disposed inside. A heat transfer belt that is endlessly wound around the heating roll and the fixing roll, receives heat from the heating unit, and heats the unfixed toner on the sheet passing through the transfer unit. An upstream side with respect to the one direction of the pressure roll, a belt conveying means disposed independently of the pressure roll, comprising a conveyance belt that runs endlessly, and the upper surface of the conveyance belt A belt conveying means for supporting the lower surface of the sheet before passing through the contact portion and conveying the sheet toward the contact portion by endless running of the conveying belt; and heating the belt conveying means. And a heating means for preheating the sheet being conveyed thereby. 2. The fixing device according to claim 1, wherein said heat generating means heats said transport belt. 3. The belt conveyor according to claim 2, wherein the conveyor belt has a pair of rolls around which the conveyor belt is wound endlessly, and wherein the heat generator is incorporated in at least one of the rolls. Fixing device. 4. The apparatus according to claim 1, wherein a gap between the heat transfer belt and the transport belt is
The fixing device according to claim 2, wherein the sheet conveyed on the conveyance belt is separated from the heat transfer belt before the rolling contact portion so as not to contact the heat transfer belt. 5. The heat transfer belt according to claim 2, wherein the heat transfer belt is disposed at a position outside an area where the sheet conveyed on the conveyance belt may pass. Fixing device. 6. The heat transfer belt according to claim 1, wherein the heat transfer belt includes an endless base material formed of a heat transfer material, and a release layer coated on an outer peripheral surface of the base material. The fixing device according to claim 1. 7. The fixing device according to claim 6, wherein the endless substrate is made of metal. 8. The fixing device according to claim 7, wherein the endless base member is formed from a nickel electroformed belt. 9. The fixing device according to claim 6, wherein the endless substrate is made of a synthetic resin. 10. The fixing device according to claim 9, wherein said endless substrate is formed of a polyimide resin. 11. The transport belt according to claim 1, wherein the transport belt includes 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 claim 1. 12. The fixing device according to claim 11, further comprising a charging unit disposed to face the transport belt, charging the transport belt and adsorbing the sheet.