JPH1124485A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the degree of freedom in the design of a driving mechanism for the traveling drive of a fixing belt by disposing a driving roll on the upstream side of a fixing roll and endlessly extending the fixing belt for preheating unfixed toner between the fixing roll and the driving roll. SOLUTION: This fixing device is constituted to provide the fixing roll 22, a pressure roll 24 and a roll 28 used for heating and driving which is arranged on the upstream side of the fixing roll 22, in the carrying direction of an unfixed sheet S and provided to be movable in this carrying direction and further incorporates a heat generating source 26 such as a halogen lamp and, etc., inside. Further, the endless fixing belt 32 is wound on the fixing roll 22 and the roll 28 used for heating and driving. At this time, the gap between the fixing belt 32 and a guide plate 34 is prescribed as a preheating path P on which the unfixed sheet S is preheated/carried by the fixing belt 32. The unfixed sheet S on the guide plate 34 is carried toward the rolling contact part, of the fixing belt 32 and the pressure roll 24, to fix toner on the sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device which is used for fixing an unfixed toner on a recording medium by fusing and pressing the recording medium, for example, in an electronic image forming apparatus.

[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 belt fixing type fixing device having the above-described structure, the driving roller for driving the fixing belt B to travel is a roller rotatable around a fixed axis. Is preferably rotated, and from this viewpoint, the pressure roll R2
Is configured to rotationally drive the fixing roll R1 to which the roller rolls. As described above, when the driving roll for driving the fixing belt B to travel is limited to only the fixing roll R1, for example, a design constraint is imposed on a transmission path of a driving force, an installation position of a driving source, and the like, and design freedom is increased. The degree may be impaired. For this reason, there is a demand for a driving mode that further improves the degree of freedom in design.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to further improve the degree of freedom in design when designing a driving mechanism for driving a fixing belt to travel. It is an object of the present invention to provide a fixing device that can perform the fixing.

[0008]

Means for Solving the Problems The above-mentioned problems are solved,
In order to achieve the object, according to the first aspect of the present invention, a fixing device includes a fixing roll, a pressure roll that is urged to be in rolling contact with the fixing roll, and an unfixed toner on the surface. In the conveying direction in which the carried sheet is conveyed, the driving roll disposed upstream of the fixing roll, and the fixing roll and the driving roll are endlessly wrapped around and receive heat transfer from a heat source. A fixing belt that preheats unfixed toner on the sheet before passing through a rolling contact portion between the fixing roll and the pressure roll; and a driving unit that rotationally drives the driving roll. And

Further, according to a second aspect of the present invention, in the fixing device, the heat source is built in the driving roll.

According to a third aspect of the present invention, in the fixing device, the driving roll is mounted so as to be movable at least along the transport direction.

According to a fourth aspect of the present invention, the fixing device further comprises an urging means for urging the driving roll in a direction away from the fixing roll.

According to a fifth aspect of the present invention, in the fixing device, the driving unit includes a driving gear fixed coaxially to the driving roll and a transmission gear meshed with the driving gear. The drive gear is characterized in that it can turn around the transmission gear while maintaining the meshing state with the transmission gear.

According to a sixth aspect of the present invention, in the fixing device according to the sixth aspect, the transmission gear is rotatably supported around a predetermined fixed axis, and the driving gear has a base end formed with the base. It is characterized in that it is rotatably supported at the tip of a turning arm that is rotatably supported around a fixed axis.

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

Further, according to the fixing device of the present invention, the base material is formed of a metal belt.

According to a ninth aspect of the present invention, the fixing device is characterized in that the substrate is formed of a nickel electroformed belt.

According to a tenth aspect of the present invention, the fixing device is characterized in that the base material is formed of a resin belt.

Further, according to the eleventh aspect, the fixing device according to the present invention is characterized in that the base material is formed of a polyimide resin.

[0019]

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

First, as shown in FIG. 1, a fixing device (hereinafter, simply referred to as a fixing device) 10 for an electronic image forming apparatus according to this embodiment has a housing structure as shown in FIG. And a housing 12 fixed to the frame of the electronic image forming apparatus, the base 1 being directly fixed on the apparatus frame.
4, a pair of left and right mounting stays 16 fixedly mounted on the base 14 and a top plate portion 18 for connecting the upper portions of the both mounting stays 16 to each other.

Here, the left direction indicated by the arrow in the figure is defined as the transport direction in which the unfixed sheet S is transported.
That is, the mounting stays 16 described above are located on both left and right sides of the unfixed sheet S conveyed in the conveying direction, and are disposed so as to extend along the conveying direction.

The fixing device 10 has a roll configuration in which a fixing roll 22 is rotatably supported on both mounting stays 16 so as to be rotatable around its own central axis. The non-fixed sheet S is conveyed in a direction in which the unfixed sheet S is transported in a state in which the non-fixed sheet S can be moved along the vertical direction in a state capable of being pressed against the roller and is rotatably supported around its own central axis. And is mounted on the upstream side of the fixing roll 22 so as to be movable along the transport direction and supported rotatably around its own central axis, and has a built-in heat source 26 such as a halogen lamp therein. And a heating and driving roll 28.

Further, the fixing device 10 includes a fixing roll 2
2 and an endless fixing belt 32 wound around the heating and driving roll 28, and an unfixed sheet disposed below the fixing belt 32 and conveyed from the image forming mechanism via a conveying mechanism (not shown). The guide plate 34 guides S toward a contact portion (nip portion) between the fixing belt 32 and the pressure roll 24. Here, a space between the fixing belt 32 and the guide plate 34 is defined as a preheating passage P through which the unfixed sheet S is conveyed while being preheated by the fixing belt 32.

The fixing device 10 includes a fixing belt 3
2, a silicone oil is applied to the outer surface of the fixing belt 32, an oil application roll 36 for cleaning the outer surface of the fixing belt 32, and the heating and driving roll 28 are fixed to the fixing roll 32. The pressing lever 24 is biased in a direction away from the fixing roller 22 by biasing the fixing belt 32 in a direction away from the fixing roller 22 in cooperation with the oil application roll 36. A pressure lever 40 for pressing the pressure roll 24 against the fixing roll 22 is further provided.

In the fixing device 10 having such a schematic configuration, the unfixed sheet S conveyed on the guide plate 34 is further conveyed toward the rolling contact portion between the fixing belt 32 and the pressure roll 24. It is set so that the toner is thermocompressed and fixed on the sheet by being inserted in a state where the transfer contact portion is pressed.

{Description of Fixing Roll 22} The above-described fixing roll 22 is a core metal part 22A rotatably supported via a bearing in a circular first support hole 16A formed in the mounting stay 16 via a bearing. And a roll main body 22B disposed coaxially around the cored bar 22A and around which the fixing belt 32 is wound, and the outer diameter of the roll is set to 20 mm. Here, in this embodiment, the core metal part 2
2A is formed of an iron shaft having a diameter of 12 mm, and the roll body 22B is formed of a heat-resistant silicone rubber body having a thickness of 4 mm attached to the outer periphery of the cored bar 22A (specifically, a silicone rubber having an Asker C hardness of 30 degrees). Rubber sponge).

{Description of the Pressure Roll 24} The pressure roll 24 described above is formed on the mounting stay 16 and extends through the second shaft hole 16B in the form of a long hole extending substantially in the vertical direction via a bearing. A metal shaft portion 24A rotatably supported by a shaft and supported movably along an extending direction thereof;
A roll main body 24B is provided coaxially around the outer periphery of the cored bar 24A, and the outer diameter of the roll is set to 20 mm. Here, in this embodiment, the core metal part 2
4A is formed from an iron shaft having a diameter of 14 mm, and the roll main body 24B is made of a silicone rubber heat-resistant elastic body attached to the outer periphery of the cored bar 24A with a thickness of 3 mm (specifically, harder than the fixing roll 22 described above). Of JIS A hardness of 40 degrees silicone rubber).

Here, in the fixing device 10, the sheet passing speed of the unfixed sheet S is set to 10 mm / sec to 500 mm / sec.
Seconds, the gap of the preheating space P is set to 0.5 mm to 20 m.
m, and the pre-heating time that passes only the distance connecting the centers of the fixing roll 22 and the heating / driving roll 28 to each other so as to satisfy the condition of 0.1 second to 4 seconds. Is set.

{Description of Heating and Driving Roll 28} Inside the heating and driving roll 28 described above, as a heat source 26,
In this embodiment, the light distribution at both ends is 50% from the center.
A large set 600 W halogen lamp is provided. In this embodiment, the heating and driving roll 28 is made of an aluminum pipe core having a diameter of 20 mm and a wall thickness of 1.75 mm, which is anodized.
The spindle 28A is coaxially fixed. As shown in FIG. 2, a collar 30 made of a heat-resistant resin, polyetheretherketone (PEEK), having a diameter of 24 mm is fixed to both support shafts 28A. The meandering and offset of the fixing belt 32 are prevented.

On the other hand, in this embodiment, the heating and driving roll 28 is configured to function as a driving roll. That is, the driven gear 42 is coaxially fixed to one support shaft 28 </ b> A of the heating and driving roll 28. Although not shown in detail, the driven gear 42 includes a driving gear 44 (that is, a driving force transmission mechanism (not shown) for transmitting a driving force from a driving source (not shown)) constituting a driving mechanism (that is, driving means). The driving gear 44), which is received and rotationally driven via the driving gear 44, meshes with each other. The driving force from the driving mechanism is transmitted to the driven gear 42 via the driving gear 44, and the heating and driving roll 28 is rotationally driven. It is configured as follows.

More specifically, as shown in FIG.
4 is rotatably supported by a support shaft 46 fixed to the mounting stay 16. One end (a base end) of a turning arm 48 is pivotally supported on the support shaft 46 so as to be turnable.
At the other end (tip) of the turning arm 48, the above-mentioned support shaft 28A of the heating and driving roll 28 is rotatably supported. Here, the driven gear 42 and the drive gear 44 are formed with the same module, and mesh with each other. As a result, the driven gear 42 is driven to rotate by the rotation of the driving gear 44, and can be turned around the driving gear 44 while the driving force transmission state is maintained.

The mounting stay 16 described above includes:
The guide shaft 5 for inserting the support shaft portion 28A of the heating and driving roll 28 and guiding the turning operation thereof (that is, guiding the guide shaft movably at least along the transport direction).
0 is formed. Therefore, in this embodiment, the guide groove 50 is formed around the support shaft 46 and the support shaft 4.
It is formed in an arc shape having a radius equal to the distance between the shaft 6 and the spindle 28A.

A hard alumite layer is formed on the outer peripheral surface of the heating / driving roll 28. This allows
When the heating / driving roll 28 is rotationally driven, the outer peripheral surface of the heating / driving roll 28 and the inner peripheral surface of the fixing belt 32 frictionally engage with each other via a hard alumite layer. The rotation is reliably transmitted to the fixing belt 32, so that the fixing belt 32 is favorably driven to run.

{Description of Fixing Belt 32} The fixing belt 32 has a heat capacity per 1 cm 2 of the fixing belt 32 so that the unfixed toner on the unfixed sheet S can be preheated and fixed by heat radiation. 0.002 cal / ° C ~
Those having 0.025 cal / ° C are preferred. For this reason, in this embodiment, the fixing belt 32 has an inner diameter of 50 mm and a thickness of 40 μm, an endless belt body such as nickel electroformed, and a thickness of 15 mm on the outer peripheral surface of the belt body.
And a heat-resistant elastic release layer of silicone rubber attached at 0 μm.

{Description of Oil Application Roll 36} The fixing device 10 is provided with an oil application roll 36 for applying a small amount of release oil on the outer peripheral surface of the fixing belt 32. As shown in FIG. 4, the oil application roll 36 includes a support shaft 36A rotatably supported by a mounting stay 16 via a bearing (not shown), and a support shaft 36A.
A heat resistant paper layer 36 in which the outer periphery of A is impregnated with silicone oil
B, the support shaft 36A is formed of an iron shaft having a diameter of 8 mm in this embodiment, and the heat-resistant paper layer 36B is provided with a 100 μm porous fluororesin film 36C mounted on the outer periphery thereof. The diameter of the
It is formed to have a roller outer diameter of 4 mm.

By configuring the oil application roll 36 as described above, it is possible to apply a small amount of stable oil to the outer peripheral surface of the fixing belt 32.

The configuration for applying oil is as follows.
In addition to the configuration of the oil application roll 36 described above, FIG.
As shown in (1), a donor roll 37 for applying and cleaning oil to a fixing belt 32 having a heat-resistant elastic layer of silicone rubber or the like provided on a metal core, and a cleaning provided with synthetic leather or the like on the metal core. Fixing belt and oil by three rolls combining a roll 39 and a nonwoven fabric impregnated with silicone oil on a metal core, or an oil application roll 41 provided with a layer of nonwoven fabric and a layer of synthetic leather An application / cleaning mechanism can also be employed.

{Description of Mechanism for Applying Tension to Fixing Belt 32} On the other hand, as a mechanism for applying tension to the fixing belt 32, the fixing device 10 includes a tension lever 38, as shown in FIG. . The lower end of the tension lever 38 is pivotally supported by the mounting stay 16 so as to be swingable, and the upper end thereof is connected to the tension spring 5.
2 is connected to one end of the mounting stay 16. By the urging force of the tension spring 52, the tension lever 38 is rotationally urged such that the tension lever 38 comes into contact with the outer periphery of the heating and driving roll 28 at a predetermined pressure contact force F2 at an intermediate portion thereof.

That is, the heating / driving roll 28 is biased in the direction away from the fixing roll 22 along the above-described guide groove 50 by the urging force of the tension spring 52 via the tension lever 38, whereby the heating The fixing belt 32, which is endlessly stretched between the dual-purpose driving roll 28 and the fixing roll 22, is tensioned to a predetermined tension while its upper portion is regulated by the oil application roll 36. . As a result, the fixing belt 32 rotates with the rotation of the heating and driving roll 28,
The vehicle is driven endlessly in a stable state with no slip or looseness.

{Description of Pressing Mechanism of Fixing Belt 32 and Pressure Roll 24} Next, the fixing belt 32 and the pressure roll 24
A description will be given of a pressing mechanism 54 for pressing the fixing belt 32 and the fixing belt 32 at a position where the fixing belt 32 is wound around the fixing roll 22 with a predetermined pressing force. The pressure contact mechanism 54 is pivotally supported at one end by a mounting shaft 16 via a support shaft 56, and is capable of abutting against the core 24 A of the pressure roll 24 from below. The lower end is connected to the other end of the pressure lever 40, and the upper end is attached to the
And a pressurizing spring 58 connected to the upper part. By 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 roll 24 with a predetermined pressure contact force F1, and as a result, the fixing belt 28 wound around the fixing roll 22 and the pressure roll 24
Means that they come into pressure contact with each other with this predetermined pressure contact force.
That is, the fixing belt 32 and the pressure roll 24 come into contact with each other at a predetermined nip width.

In this embodiment, the fixing position of the fixing roll 22 and the pressure roll 24 is predetermined clockwise from a perpendicular line lowered from the center of the fixing roll 22 to the fixing belt 32. Is set to be inclined by the angle of Thus, the nip position between the fixing belt 32 and the pressure roll 24 (that is, the center position of the nip width described above) is slightly smaller in the transport direction of the unfixed sheet S than immediately below the center position of the fixing roll 22. Along the front (to the left in the figure).

{Description of Guide Plate 34} This fixing device 10
Is provided with a guide plate 34 for guiding the unfixed sheet S conveyed by a conveying mechanism (not shown) toward a rolling contact portion between the fixing belt 32 and the pressure roll 22. As shown in FIG. 6, the guide plate 34 is located at a central position M where a perpendicular line is lowered from an intermediate point between the axes of the heating and driving roll 28 and the fixing roll 22, and the upper surface of the guide plate 34 and the lower portion of the fixing belt 32 Is set so that the gap L1 is 3 mm. In this embodiment, the distance L3 between the axes of the heating and driving roll 28 and the fixing roll 22 is 47 mm,
The distance L2 between the perpendicular from the center of the fixing roll 22 and the above-described center position M is set to 23.5 mm.

As shown in FIG. 7, the guide plate 34
A release treatment layer 62 made of a fluororesin such as PTFE (polytetrafluoroethylene) is provided on the surface. As shown in FIGS. 1 and 6, the guide plate 34 is grounded so as not to disturb the unfixed image. Instead of grounding, a guide brush, a varistor element, a diode, or the like may be used.

On the other hand, the lower side of the fixing belt 32 wound around the fixing roll 22 and the heating / driving roll 28 is set so as to run leftward in the drawing in a substantially horizontal state. The distance between the fixing belt 32 and the fixing belt 32 is about 5 to 20 mm just below the heating and driving roll 28.
Is set to be within the range. That is, the guide plate 3
Reference numeral 4 is set obliquely with respect to the horizontal lower side of the fixing belt 32 so as to head in an upwardly inclined state with respect to the nip position described above.

That is, the lower side of the fixing belt 32 and the guide plate 34 define a so-called wedge-shaped conveyance space having the nip position at the apex.
Is reliably brought to the nip position between the fixing belt 32 and the pressure roll 24 by being conveyed on the guide plate 34, where it is pressed against the fixing belt 32 based on a predetermined pressing force F 1, and Since the unfixed toner is heated in advance by receiving the heat radiation, the unfixed toner is thermally fixed on the sheet.

{Description of Thermistor} 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 belt 32 directly wound around the heating and driving roll 28, It is configured to be able to contact the part and detect its surface temperature. That is, the thermistor 60 is electrically connected to a control unit (not shown) and configured to transmit temperature information of the fixing belt 32 to the control unit.

{Explanation of Experimental Example When Angle θ and the Like are Changed} As shown in FIGS. 8 and 9, the fixing device 10 having the above-described configuration is configured such that the center point of the fixing roll 22 is C1, and the center point is C1.
The intersection point between the perpendicular line lowered from and the winding position of the fixing belt 32 is C2, the center point of the pressure roll 24 is C3, and the angle between the straight lines C1 and C2 and the straight lines C2 and C3 is defined as θ. In this case, when the position of the pressure roll 24 is changed, θ
Is 90 to 180 degrees (in FIG. 8, θ
Are 90 degrees and 175 degrees, respectively. ), The paper passing speed is 70 mm / sec,
The fixing pressure is set to 20 kgf, the surface temperature of the fixing belt 32 is set to 160 ° C., and the hardness and angle θ between the fixing roll 22 and the pressure roll 24 are changed.

Then, when 55 kg paper was used as the experimental example 1, and 68 kg paper was used as the experimental example 2,
In the case where an OHP film is used as the experimental example 3 and whether the unfixed image is transferred with the toner for Minolta CF-70 on three types of test papers, whether image distortion, gloss unevenness, etc. occur. Was tested. In these tests, when five sheets were passed and no gloss unevenness of the image occurred on all five sheets, ○ when even one of the images showed uneven gloss, Δ the gloss of the image on all five sheets X if unevenness occurs, and even one fixing belt 3
When the test paper is wrapped around 2, the results of those tests are shown in Tables 1 to 3, respectively, in a state where ▲ is displayed.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

[Table 3]

In Experimental Example 1 shown in Table 1 described above, the angle θ
When the angle θ is larger than 140 degrees, it is understood that unevenness in glossiness of an image is likely to occur gradually when the angle θ is larger than 140 degrees. You. When the angle θ is 110 degrees or less, the sheet often winds around the fixing belt 32. When the angle θ is 100 degrees or 90 degrees, the entire sheet winds around the fixing belt 32 and the image quality is good. Was unable to make a judgment. When the rubber hardness of the fixing roll 22 is higher than the rubber hardness of the pressure roll 24 and the difference between the two is large, it has been found that the probability of occurrence of poor gloss of the image is high.

In Experimental Example 2 shown in Table 2, the angle θ was 175
And 180 degrees, good images were obtained without the occurrence of gloss unevenness in the images. Angle θ is 175 degrees, 180
When the fixing roller 22 has a rubber hardness of 60 degrees, gloss unevenness of the image occurs, and when the angle θ is 180 degrees, the fixing roller 22 and the pressing roller 24 are not affected by the glossiness. When the fixing roller 22 had a rubber hardness of 60 degrees, gloss unevenness of the image always occurred.

In Experimental Example 3 shown in Table 3, almost the same experimental results as in Experimental Example 2 described above were obtained.

Therefore, it was found from the above-mentioned experimental examples 1 to 3 that the angle θ is preferably 125 to 160 degrees. Thus, the heating roll 28 is fixed to the fixing belt 32.
Even if it functions as a driving roll for driving the fixing belt, it is possible to drive the fixing belt 32 satisfactorily and to find the optimum fixing state by changing the angle θ. Therefore, since the fixing belt 32 can be driven to travel by the heating and driving roll 28 in this manner, when designing a driving mechanism for driving the fixing belt 32 to travel, the degree of freedom in design can be further improved. Becomes possible.

<< Description of Other Embodiments >> It goes without saying 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, only the heating and driving roll 28 is set so as to be movable at least along the transport direction. However, the present invention is not limited to such a configuration, and the driven gear A driving gear 44 meshed with the heating and driving roll 28 having the fixed 42 and the driven gear 42
May be rotatably mounted on the sub-frame, and the sub-frame may be movably mounted on the mounting stay 16. In this case, the driving gear 44
The endless belt (or endless chain) is used as a member for transmitting the driving force to the subframe, and the tensioning mechanism is applied to the endless transmission member so that the subframe can be moved in a straight line parallel to the transport direction. It is also possible to support.

[0058]

As described above in detail, according to the present invention, there is provided a fixing device capable of further improving the degree of freedom in designing a driving mechanism for driving the fixing belt to travel. Will be.

[0059]

[Brief description of the drawings]

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

FIG. 2 is a side view showing a heating and driving roll used in the fixing device shown in FIG.

FIG. 3 is a front view showing the mounting configuration of the heating and driving roll shown in FIG. 2;

FIG. 4 is a front view showing the configuration of an oil application roll used in the fixing device shown in FIG. 1;

FIG. 5 shows a fixing belt for applying oil to the fixing belt, which is different from the configuration of the oil application roll shown in FIG.
FIG. 3 is a front view illustrating a configuration of an oil application / cleaning mechanism.

FIG. 6 is a front view showing a positional relationship between the guide plate and the fixing belt shown in FIG.

FIG. 7 is a front view showing the configuration of the guide plate shown in FIG.

FIG. 8 is a front view showing a positional relationship between a fixing roll and a pressure roll.

FIG. 9 is an enlarged front view showing a state near a nip portion in FIG. 8;

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

[Explanation of symbols]

 Reference Signs List 10 Fixing device 12 Housing 14 Base 16 Mounting stay 16A First support hole 16B Second support hole 18 Top plate 22 Fixing roll 22A Core portion 22B Roll body 24 Pressure roll 24A Core portion 24B Roll body 26 Heating source 28 Heating and driving roll 28A Support shaft 30 Collar 32 Fixing belt 34 Guide plate 36 Oil application roll 37 Donor roll 38 Tension lever 39 Cleaning roll 40 Pressing lever 41 Oil application roll 42 Follower gear 44 Drive gear 46 Support shaft 48 Swivel arm 50 Long groove 52 Tension spring 54 Pressure contact mechanism 56 Support shaft 58 Pressure spring 60 Thermistor 62 Release treatment layer F1 Fixing portion pressing force F2 Tension portion pressing force P Preheating passage S Unfixed sheet

Claims (11)

[Claims] An image forming apparatus comprising: a fixing roll; a pressure roll which is urged to come into contact with the fixing roll; and an upstream of the fixing roll with respect to a conveyance direction in which a sheet having unfixed toner carried on the surface is conveyed. And a driving roll disposed on the side, and endlessly wrapped around the fixing roll and the driving roll, receive heat transfer from a heat source, and pass through a rolling contact portion between the fixing roll and the pressure roll. A fixing device, comprising: a fixing belt that preheats unfixed toner on the previous sheet; and a driving unit that rotationally drives the driving roll. 2. The fixing device according to claim 1, wherein the heat source is built in the driving roll. 3. The fixing device according to claim 1, wherein the drive roll is mounted so as to be movable at least along the transport direction. 4. The fixing device according to claim 3, further comprising: urging means for urging the driving roll in a direction away from the fixing roll. 5. The drive means includes a drive gear fixed coaxially to the drive roll, and a transmission gear meshing with the drive gear, wherein the drive gear is configured to surround a periphery of the transmission gear with the drive gear. The fixing device according to claim 3, wherein the fixing device is capable of turning while maintaining the meshing state. 6. The transmission gear is rotatably supported around a predetermined fixed axis, and the drive gear is provided at a distal end of a turning arm whose base end is rotatably supported around the fixed axis. The fixing device according to claim 5, wherein the fixing device is rotatably supported. 7. The fixing belt according to claim 1, wherein the fixing belt includes an endless base member formed of a heat transfer material and a release layer coated on an outer peripheral surface of the base member. The fixing device according to claim 1. 8. The fixing device according to claim 7, wherein said base material is formed of a metal belt. 9. The fixing device according to claim 8, wherein said base material is formed of a nickel electroformed belt. 10. The fixing device according to claim 7, wherein said base material is formed of a resin belt. 11. The fixing device according to claim 10, wherein said base material is formed of a polyimide resin.