JPH11258938A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of prolonging the life of the whole device by extending the service life of a fixing belt, in making the fixing belt possible to stably perform endless run. SOLUTION: This fixing device, provided with a heating roll 28 pivotally supported in freely rotationally around a shaft fixed on a housing 12, incorporating a heat generating source 26, a locking blade 18 pivotally supported in freely lockingly on the housing 12, the fixing roll 22 pivotally supported in freely rotationally around the shaft line fixed on the locking blade 18, the pressure roll 24 pivotally supported in freely rotationally around the shaft line fixed on the locking blade 18, while mounted so as to be held in rotary contact with the fixing roll 22, the heat transmitting belt 32 endlessly extended around the heating roll 28 and the fixing roll 22, transmitting the heat to the rotary contact part between the fixing roll 22 and the pressure roller 24 on receiving the heat transmission from the heat generating source 26, and a coil spring 62 applying specific tension to the transmitting belt 32, is allowed to let unfixed toner so as to be fixed on a sheet S, in consequence that the sheet carrying the unfixed toner on its surface is allowed to pass through the rotary contact part.

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. A fixing belt B is stretched between R1 and a heating roll R3, and a recording medium D is preheated by a belt fixing method in which a pressure roll R2 that presses the fixing roll R1 from below through the fixing belt B is provided. Technologies that combine these have been developed.

[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 fixing device of a belt fixing type shown in FIG. 7 will be schematically described. The fixing device includes a fixing roll R1, a pressure roll R2, and a heating and 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 P 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.

Here, in the fixing device of the conventional configuration having the above-described configuration, tension is applied to the fixing belt B so that the fixing belt B is kept taut in order to make the fixing belt B run endlessly in a stable state. However, conventionally, in order to apply tension to the fixing belt B, the heating roll is also used as the tension roll, and the heating and tension roll R3 is defined. To the heating roll R
3 was urged by a spring so as to be separated from the fixing roll R1. Further, in order to prevent the fixing belt B from shifting and falling off during the endless running, resin rings C for stopping the fixing are attached to both ends of the heating and tension roll R3.

[0007]

In the above-described fixing device using the endless belt of the conventional construction, the heating roller R3 is used to apply tension to the fixing belt B and maintain the fixing belt B at a predetermined tension. The rotation axis is movable without being fixed. Therefore, on the contrary, there is a possibility that the fixing belt B flaps during the endless running, and a situation where the fixing belt B does not stably wind around the outer circumference of the heating roll R3 may occur. Thus, the fixing belt B is heated by the heating roll R3.
The fixing belt B must be
, The edge of the fixing belt B comes into sliding contact with the resin ring C for preventing the deviation.

As a result, an overload is applied to the edge of the fixing belt B, causing abrasion and breakage. When the edge of the fixing belt B is worn or damaged in this way, the life of the fixing belt B is shortened, and the life of the fixing device is shortened, and the reliability of the entire fixing device is reduced. And a solution was requested.

The present invention has been made in view of the above circumstances, and a main object of the present invention is to stably and endlessly drive a fixing belt to prolong the life of the fixing belt, thereby increasing the life of the entire apparatus. An object of the present invention is to provide a fixing device that can be lengthened.

Another object of the present invention is to stably and endlessly drive the fixing belt to reduce wear and tear of the fixing belt.
An object of the present invention is to provide a fixing device capable of suppressing breakage and improving the reliability of the entire apparatus.

[0011]

Means for Solving the Problems The above-mentioned problems are solved,
According to a first aspect of the present invention, there is provided a fixing device including a housing, a heating roller rotatably supported by the housing so as to be rotatable around a fixed axis, and including a heating unit. A swinging member pivotally supported by the housing, a fixing roll pivotally supported by the swinging member about a fixed axis, and a rotatable member about the fixed axis by the swinging member. A pressure roll that is rotatably supported and is attached to the fixing roll so as to be in contact with the fixing roll, and is endlessly wrapped around the heating roll and the fixing roll. A heat transfer belt that transfers heat to a contact portion between the heat transfer belt and the pressure roll, and a tension applying unit that applies a predetermined tension to the pre-heat transfer belt. Passes through the contact area By, is characterized in that to fix the unfixed toner on the sheet.

According to a second aspect of the present invention, in the fixing device according to the second aspect, the tension applying means biases the swinging member in a direction in which the fixing roll is separated from the heating roll. It is characterized by comprising means.

According to a third aspect of the present invention, in the fixing device, the urging means includes an elastic member stretched between the swing member and the housing. And

Further, according to the fourth aspect of the present invention, the fixing device further comprises an oil applying means for applying oil to the heat transfer belt.

According to a fifth aspect of the present invention, in the fixing device according to the fifth aspect, the oil applying means includes: a donor roll that rolls on the heat transfer belt at a predetermined rolling angle; An oil supply roll that rolls and contacts the roll and supplies oil thereto is provided.

According to a sixth aspect of the present invention, in the fixing device, the donor roll is supported by the housing so as to be rotatable around a fixed axis.

Further, according to the seventh aspect of the present invention, the fixing device further comprises a driving means for driving the donor roll to rotate.

The fixing device according to the present invention may further include a drive unit for rotating the pressure roll, wherein the heat transfer belt is in friction with the pressure roll. The fixing roll is driven to run by the combination, and the fixing roll is rotationally driven by the rotation of the pressure roll via the heat transfer belt.

According to a ninth aspect of the present invention, in the fixing device according to the ninth aspect, the driving unit rotationally drives the fixing roll at a peripheral speed lower than that of the pressure roll. .

According to a tenth aspect of the present invention, in the fixing device, the fixing roll includes a driven gear mounted coaxially with the fixing roll, and the driving unit meshes with the driven gear. A driving gear, a one-way clutch is interposed between the driven gear and the fixing roll,
The one-way clutch is characterized in that rotation of the fixing roll is faster than that of the driven gear, and that rotation of the fixing roll later than the driven gear is prohibited.

Further, according to the eleventh aspect of the present invention, the fixing device is characterized in that the driving means rotationally drives the donor roll.

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

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

According to a fourteenth aspect of the present invention, the fixing device is characterized in that the endless substrate is formed of a polyimide resin.

According to a fifteenth aspect of the present invention, in the fixing device according to the fifteenth aspect, the fixing roll includes a cored bar and an elastic member disposed around the cored bar with a predetermined thickness. And a layer.

[0026] In the fixing device according to the present invention, according to claim 16, the pressure roll is formed of a roll having an outer periphery that is harder than the on-roll hardness of the elastic layer. And

According to the fixing device of the present invention, the distance between the rotation axis of the pressure roll and the rotation axis of the fixing roll is determined by the radius of the pressure roll and the radius of the pressure roll. It is characterized in that it is set shorter than the sum of the radii of the fixing roll.

Further, according to the invention, the fixing device according to the present invention is arranged such that a fixing roll, a pressure roll which rolls on the fixing roll with a predetermined nip width, and a distance from the fixing roll. Provided, a heating roll having a heat source disposed therein, a heat transfer belt having a predetermined heat capacity, endlessly wound between the fixing roll and the heating roll, and an unfixed toner on the surface. Guide means for guiding the carried sheet so that its leading end first abuts against the outer peripheral surface of the pressure roll, and then passes through the rolling contact portion of the fixing roll and the pressure roll in one direction. Wherein the unfixed toner is fixed on the sheet by passing through the rolling contact portion.

[0029]

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.

{General Description of Fixing Apparatus 10} As shown in FIG. 1, the fixing apparatus 10 of this embodiment has a housing structure, which is mounted on an electronic image forming apparatus (not shown), for example, a frame of an electronic copying apparatus. It has a housing 12 to be fixed. The housing 12 includes a base 14 directly fixed on the apparatus frame, a pair of left and right side plates 16 fixedly mounted on the base 14, and a swing axis common to both side plates 16. A swing plate 18 is provided as a pair of left and right swing members pivotally supported around 18A.

Here, the left direction indicated by the arrow in the figure is defined as a transport direction as one direction in which the unfixed sheet S is transported. That is, the above-mentioned side plates 16 are located on both left and right sides of the unfixed sheet S conveyed in one direction,
It stands up in a state of extending along the one direction.
The unfixed toner image is set so as to be conveyed while being formed on the upper surface of the unfixed sheet S.

On the other hand, the fixing device 10 has a roll configuration in which a fixing roll 22 is rotatably supported by the rocking plates 18 about a rotation axis at a fixed position, and a rocking roller is rotated about a rotation axis at a fixed position. A pressure roll 24 rotatably supported by the plate 18 and mounted below the fixing roll 22 so as to be rolled in pressure contact with the fixing roll 22; and a rotatable shaft rotatably mounted on both side plates 16 about a rotation axis at a fixed position. The fixing roll 22 includes a heat source 26 such as a halogen lamp, and a heating roll 28 disposed upstream of the fixing roll 22 along the one direction. That is, in this embodiment,
The three rolls 22, 24, 28 are each rotatably supported around a fixed rotation axis.

Here, although the details will be described later, the fixing roll 2
2 is composed of an elastic roll, while the pressure roll 24 is composed of a roll having an outer periphery having a higher on-roll hardness than the elastic roll. On the other hand, the distance D between the rotation centers of the fixing roll 22 and the pressing roll 24 is slightly smaller than the sum (R1 + R2) of the radius R1 of the fixing roll 22 and the radius R2 of the pressing roll 24, as shown in FIG. Is set to be short (that is, D <R1 + R2). As a result, at the mutual rolling contact portion (nip portion) of the fixing roll 22 and the pressing roll 24, the two roll contact each other with a predetermined pressure contact force P1, whereby the fixing roll 22 is depressed at the rolling contact portion. Will be brought to the state. That is, a sufficient nip width is secured.

Further, the fixing device 10 supports the lower surface of the conveyed unfixed sheet S (that is, the surface on which the unfixed toner image is not formed) and also fixes the fixing roll 2.
The fixing device further includes a guide plate 30 that guides the roller 2 and the pressure roll 24 toward each other's rolling contact portion, and an endless fixing belt 32 that is wound around the fixing roll 22 and the heating roll 28. Here, between the guide plate 30 and the fixing belt 32, the unfixed sheet S is
2 is defined as a preheating passage P that is conveyed while being preheated from both upper and lower surfaces.

The fixing device 10 includes a fixing belt 3
An oil application / cleaning mechanism 34 for applying silicone oil to the outer surface of the fixing belt 32 and cleaning the outer surface of the fixing belt 32 is further provided.

In the fixing device 10 having such a schematic configuration, the unfixed sheet S conveyed onto the guide plate 30 by the conveyance mechanism (not shown) is moved downward by the guide plate 30 to which the unfixed toner is not adhered. 30 and is guided toward a rolling contact portion (nip portion) between the fixing belt 32 and the pressure roll 24, and is inserted in a state where the two are pressed against each other. The toner is thermocompressed and fixed on the sheet.

{Description of Fixing Roll 22} The above-described fixing roll 22 includes a core metal part 22A that is rotatably supported on a swing plate 18 that is swingably attached to the side plate 16 via a bearing (not shown). The roll body 2 is disposed coaxially around the cored bar 22A and around which the fixing belt 32 is wound.
2B, and the roll outer diameter is set to 30 mm in this embodiment. Here, in this embodiment, the core 22A is formed of an iron shaft having a diameter of 20 mm, and the roll body 22B is a silicone rubber heat-resistant elastic body (specifically, 5 mm thick) attached to the outer periphery of the core 22A. Is made of silicone rubber sponge having an Asker C hardness of 35 degrees.

A first driven gear 38, which constitutes a part of a drive mechanism 36, which will be described in detail later, is coaxially mounted on a shaft disposed at one end of the cored bar 22 A of the fixing roll 22. The first driven gear 36 is attached via a one-way clutch 40 described in detail later.
A second driven gear 42 fixed coaxially to the end of the fourth gear 4 is always meshed. In this manner, the second driven gear 4
The pressure roller 24 is directly rotated in the counterclockwise direction in FIG. Further, the fixing roller 22 can be rotationally driven clockwise in the drawing by the driving force transmitted from the second transmission gear 42 to the first transmission gear 38 and further transmitted via the one-way clutch 40. The state has been made.

{Description of Pressure Roll 24} The pressure roll 24 described above is composed of a core 24A rotatably supported on a swinging plate 18 via a bearing (not shown), and a core 2A.
And a roll main body 24B disposed coaxially around the outer periphery of the roll 4A, and the outer diameter of the roll is set to 30 mm. Here, in this embodiment, the core metal part 24A is formed of an iron shaft having a diameter of 28 mm,
4B is a silicone rubber heat-resistant elastic body attached to the outer periphery of the cored bar portion 24A with a thickness of 1 mm (specifically, JI having a hardness on a roll harder than the above-described fixing roll 22).
(Silicone rubber having an SA hardness of 40 degrees). In addition, a layer thickness 25
The fluororesin layer is coated at μm.

The shaft provided at one end of the metal core 24A has the above-mentioned second driven gear 42 coaxially fixed thereto, and the second driven gear 42 has the above-mentioned first driven gear 42 attached thereto. Of the driven gear 38 are engaged with each other. The swing axis 18A of the swing plate 18 is set to be coaxial with the rotation axis of the pressure roll 24. Thereby, for example, the rocking plate 1
Even if the shaft 8 swings about the swing axis 18A, the first driven gear 38 fixed to the fixing roller 22 supported by the swing plate 18 does not engage with the second driven gear 42 at all. , The driving force is reliably transmitted from the second driven gear 42 to the first driven gear 38.

As described above, in this embodiment, the pressure roller 24 is set as the main drive for transporting the unfixed sheet, and the fixing roller 22 keeps the peripheral speed even when it is thermally expanded. The gear ratio of the first and second driven gears 38 and 42 is set so that the rotation speed does not become faster than the peripheral speed of the pressure roll 24. That is, the fixing roll 22 is
The rotation speed when rotated by the driven gear 42 is set to be slightly lower than the rotation speed when rotated by frictional engagement with the pressure roller 24 via the fixing belt 32. .

On the other hand, in this embodiment, the pressure roll 24 is not located immediately below the fixing roll 22 but is located in the conveying direction of the unfixed sheet rather than immediately below the fixing roll 22. It is arranged at a position deviated by
When a perpendicular line passing through the center point of the fixing roll 22 is used as a base line, a position at which an angle formed by this base line and a line segment passing through both center points of the fixing roll 22 and the pressing roll 24 becomes a predetermined acute angle. It is arranged in. Note that this pressure roll 24
Is set so as to be substantially perpendicular to the conveying direction of the unfixed sheet.

{Description of One-Way Clutch 38} Here, the one-way clutch 40 described above
2 allows the first driven gear 38 to rotate in the clockwise direction in the drawing, but locks the relative rotation in the counterclockwise direction in the drawing, in other words, rotates the two together. Is configured. Specifically, in a cold state, that is, the fixing belt 32 frictionally engages with the pressure roll 24,
In a state in which the fixing roller 22 is frictionally engaged with the fixing belt 32 and the fixing roller 22 and the fixing belt 32 are driven (rotated) by the pressure roller 24, the peripheral speed of the fixing roller 22 rotating clockwise in the drawing is: The speed is equal to the peripheral speed of the pressure roll 24 and is slightly higher than the peripheral speed of the first driven gear 38, but this speed difference is absorbed by the one-way clutch 40.

The fixing roll 36 is heated via the fixing belt 32 by the heat generated by the heating roll 28 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 24. Therefore, even in this case, the speed difference is reliably absorbed by the one-way clutch 40.

On the other hand, such a one-way clutch 40
Is interposed between the first driven gear 38 and the fixing roll 22, the following effects are additionally achieved. That is, if such a one-way clutch 40 is not provided, when a glossy sheet such as a coated paper is conveyed as an unfixed sheet to the rolling contact portion, the unfixed sheet is fixed to the unfixed sheet. Slippage occurs between the fixing belt 32 and the belt 32, and the driving force of the pressure roller 24 is not transmitted to the fixing belt 32 and the fixing roller 22.
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 32, and the image is disturbed.

However, in this embodiment, the one-way clutch 40 is connected to the fixing roll 22 and the first driven gear 38.
Therefore, even if the driving force of the pressure roller 24 is not transmitted to the fixing belt 32, the peripheral speed of the fixing roller 22 is lower than the peripheral speed of the first driven gear 38. At the time when it starts to be late, the first driven gear 38 is driven to rotate clockwise in the drawing.
In this manner, the unfixed sheet is reliably passed through the contact portion, and the risk of jamming is effectively prevented. At the same time, the unfixed toner image when passing through the contact portion is disturbed. Will be suppressed.

<< Description of Heat Roll 28 >> In the above-described heat roll 28, in this embodiment, a halogen lamp of 800 W in which the light distribution at both ends is set to be 50% larger than the center is provided as the heat source 26. Have been. The heating roll 28 has a diameter of 30 mm in this embodiment.
Then, the thickness of aluminum pipe core of 3.5mm, thickness 20μ
m coated with a PTFE coating layer. The bearings at both ends are made of heat-resistant resin polyetheretherketone (PEEK) made of a 34 mm diameter collar (ring).
6, the fixing belt 32 is prevented from meandering or offset.

<< Description of Fixing Belt 32 >> The fixing belt 32 described above is used to preheat the unfixed toner on the unfixed sheet S to a fixing temperature by heat radiation and to fix the toner without applying an excessive amount of heat. 32 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 32 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 150 μm.

The fixing belt 32 is not limited to being formed of polyimide and silicone rubber. For example, an endless belt body such as a 40 μm nickel electroformed belt and an outer peripheral surface of the belt body may be used. 150μm thick
And a heat-resistant elastic release layer made of silicone rubber coated with a silicone rubber.

{Description of Oil Applying / Cleaning Mechanism 34} The fixing device 10 has an outer peripheral surface of the fixing belt 32
An oil application / cleaning mechanism 34 for applying a very small amount of release oil is provided. The oil applying / cleaning mechanism 34 includes a donor roll 48 that contacts the outer peripheral surface of the fixing belt 32 at a predetermined contact angle, and an oil supply roll 50 that contacts the donor roll 48. Here, the donor roll 48 is rotatably supported by the side plate 16 around a rotation axis at a fixed position, and is connected so as to be rotationally driven by the drive mechanism 40 described above. That is, a third driven gear 52 is coaxially fixed to a shaft portion (not shown) of the donor roll 48. The third driven gear 52 will be described in detail later. A gear 42 and two idle gears 54, 5
6 are engaged.

On the other hand, the oil supply roll 50 is
A support shaft 50A rotatably supported by a bracket 20 slidably mounted on the support shaft 50, and a heat-resistant paper layer 50B impregnated with silicone oil on the outer periphery of the support shaft 50A. In this embodiment, the shaft 50A is formed of an iron shaft having a diameter of 8 mm, and the heat-resistant paper layer 50B has a roll outer diameter of 22 mm in a state where a porous fluororesin film 50C of 100 μm is mounted on the outer periphery thereof. Is formed. Further, the oil supply roll 50 is elastically rolled in contact with the donor roll 48 with a predetermined urging force by a first coil spring 60 interposed between the side plate 16 and the bracket 20.
By configuring the oil supply roll 50 in this way, it is possible to stably apply a small amount of oil to the outer peripheral surface of the fixing belt 32 via the donor roll 48.

The outer peripheral surface of the donor roll 48 includes
Dirt (toner and the like) adhering to the outer peripheral surface of the fixing belt 32 is transferred and adheres, and is contaminated. Therefore, the cleaning brush 5 is provided on the outer peripheral surface of the donor roll 48.
8 is in contact, and the outer peripheral surface of the donor roll 48 is constantly cleaned to remove dirt attached thereto.

{Description of Mechanism for Applying Tension to Fixing Belt 32} On the other hand, in order to allow the fixing belt 32 to run endlessly without flapping and to be stably wound around the heating roll 28, A tension applying mechanism for applying tension is provided. In this embodiment, the tension applying mechanism moves the above-described rocking plate 18 in a direction in which the fixing roll 22 attached thereto is separated from the heating roll 28 (specifically,
A second coil spring 62 is provided as an elastic member that urges to swing (to the left in the figure). Here, the second coil spring 62 is
It is stretched between 6 and the rocking plate 18.

As described above, since the swinging plate 18 is entirely swung to the left in the drawing to apply a predetermined tension to the fixing belt 32, the fixing belt 32 is wound around. One or both of the fixing roll 22 and the heating roll 28, which are movable,
There is no need to urge the two members apart from each other via an elastic member such as a spring. In other words, as described above, the fixing roll 22 and the heating roll 2
8 can be arranged with the respective rotation axes fixed.

As a result, according to this embodiment, the fixing belt 32 is wrapped around the fixing roll 22 and the heating roll 28 rotating around the fixed axis endlessly. In a stable state, it is wound around the heating roll 28 in particular. In this manner, particularly when the fixing belt 32 is wound around the heating roll 28, the contact of the edge of the fixing belt 32 with the collar 46 attached to the heating roll 28 is suppressed, and the conventional fixing belt 32 is prevented from contacting. Wear and damage due to contact are prevented. Therefore, the shortening of the service life due to the wear and damage of the fixing belt 32 as in the related art is reliably prevented, and the service life is extended.

{Description of Drive Mechanism 40} On the other hand, the drive mechanism 36 for rotating and driving the pressure roll 24 and the like described above
As shown in FIG. 3, in a state where the fixing device 10 is mounted on the electronic copying apparatus, the fixing apparatus 10 is detachably engaged with an output gear GE connected to a drive source of the electronic copying apparatus via a gear train (not shown). A transmission gear 44 that meshes with the transmission gear 44 and is driven to rotate by receiving a driving force from the transmission gear 44; a second driven gear 42 that constantly meshes with the transmission gear 44 and is coaxially fixed to the pressure roll 24; And a first driven gear 38 connected to the fixing roll 22 via the one-way clutch 40 described above.

The drive mechanism 36 is connected to the second
Idle gears 5 that always mesh with the driven gear 42
4 and 56, and these idle gears 54 and 56
Is the third coaxially fixed to the donor roll 48 described above.
, And is configured to rotationally drive the donor roll 48. More specifically, the first idle gear 54 always meshes with the second driven gear 42, the second idle gear 56 has a small diameter portion 56 </ b> A constantly meshed with the first idle gear 54, and a third driven gear 56. A large-diameter portion 56B that always meshes with the gear 52 is provided coaxially and fixed to each other. In this way, the donor roll 48
The fixing belt 32 is driven to rotate in the clockwise direction in the drawing, which is the same as the running direction, so that the fixing belt 3 can achieve the oil application and cleaning effects without slipping.

{Other Configurations} A first thermistor for detecting the temperature of the portion of the fixing belt 32 wound around the outer peripheral surface of the heating roll 28 for controlling the temperature of the heat source 26 incorporated in the heating roll 28. 64, a second thermistor 66 for detecting the temperature of the outer peripheral surface of the pressure roll 24, and a third thermistor 68 for detecting the temperature of the outer peripheral surface of the fixing roll 22. 3 based on the detection results from the thermistors 64, 66, 68.
And a control circuit for controlling heat generation.

[0059]

[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 the 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.

In the above-described embodiment, the unfixed sheet has been 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. In this case, the pressure roll 24 is not under the fixing roll 22,
Needless to say, the heating roll 28 is disposed on the side of the fixing roll 22 opposite to the side on which the pressure roll 24 is disposed. .

In the embodiment described above, the heat source 26 is described as being disposed inside the heating roll 28. However, the present invention is not limited to such a configuration, and the first modification As an example, as shown in FIG. 4, an auxiliary heat source 70 may be further provided inside the pressure roll 24. In the following description, the same parts as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

In the above-described embodiment, the heating roller 28 is disposed on the side of the fixing roller 22, and has an endless fixing belt 32 wound around the fixing roller 22 and the heating roller 28. An unfixed sheet S is defined as a preheating passage P through which the unfixed sheet S is conveyed while being preheated from both upper and lower surfaces by the guide plate 30 and the fixing belt 32. It has been described that the unfixed sheet is preheated before being nipped by the rolling contact portion to increase the fixing efficiency. However, the present invention is not limited to such a configuration, and the second embodiment shown in FIG.
As shown in the modification, the heating roll 28 may be arranged above the fixing roll 22.

In the case of the second modification, the above-mentioned preheating effect cannot be expected, but by disposing the fixing roll 22 on the side of the heating roll 28, the unfixed sheet on the way of conveyance can be obtained. As a result, the effect that the unfixed toner image touches the fixing belt 32 to disturb the image is surely eliminated.

In the second modification, basically, only the arrangement position of the heating roll 28 with respect to the fixing roll 22 is different from that of the above-described embodiment, and the description of the same parts is omitted. Only the different parts will be briefly described below.

That is, in the second modification, the configuration of the oil application / cleaning mechanism 34 is slightly different from that of the above-described embodiment, and the above-described two-roller provided with the donor roll 48 and the oil supply roll 50 is provided. Unlike the configuration of the embodiment, a configuration including one roll of only the oil application / cleaning roll 48 'is adopted.

On the other hand, in the second modification, the position of the swing center 18A of the swing plate 18 is not changed, and the swing plate 1
8 is a swing center 18 which is the same as the center axis of the pressure roll 24.
It is swingable around A, and is swingably biased to the side in the figure by the second coil spring 62. Thus, the fixing belt 32 is fixed to the oil application / cleaning roll 4 constituting the oil application / cleaning mechanism 34.
8 'is elastically brought into contact with 8', whereby a predetermined tension is generated.

By configuring the second modification as described above, the configuration of the drive mechanism 36 for rotating and driving the pressure roll 24 and the like is similar to that of the above-described embodiment described with reference to FIG. Configuration is sufficient.

In the second modification, the pivot axis 18A of the pivot plate 18 is set in the same manner as in the above-described embodiment.
Although described as being coaxial with the rotation center of the pressure roll 24, the present invention is not limited to such a configuration, and as shown in FIG. May be configured to be coaxial with the rotation center of the transmission gear 44 disposed on the side of the transmission gear 44 so as to always mesh with the transmission gear 44. With such a configuration, the swing plate 18 can swing freely around the swing axis 18A in the vertical direction in the figure, and swings downward as shown in the drawing of the second coil spring 62. By mounting the plate 18 so as to urge it, a predetermined tension can be reliably applied to the fixing belt 32.

[0070]

As described above in detail, according to the present invention, the fixing belt can be stably driven endlessly, the life of the fixing belt can be prolonged, and the life of the entire apparatus can be prolonged. A fixing device will be provided.

Further, according to the present invention, there is provided a fixing device capable of stably running the fixing belt endlessly, suppressing wear and breakage of the fixing belt, and improving the reliability of the entire apparatus. Will be.

[0072]

[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 front sectional view showing a configuration of a first modification of the fixing device according to the present invention.

FIG. 5 is a front sectional view showing the configuration of a second modification of the fixing device according to the present invention.

FIG. 6 is a cross-sectional view schematically showing a configuration of a third modified example of the fixing device according to the present invention, centering on a driving mechanism.

FIG. 7 is a front view schematically showing a configuration of a conventional fixing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Fixing apparatus 12 Housing 14 Base 16 Side plate 18 Oscillating plate 18A Oscillating axis 20 Bracket 22 Fixing roll 22A Core part 22B Roll body 24 Pressure roll 24A Core part 24B Roll body 26 Heat source 28 Heating roll 30 Guide plate 32 fixing belt 34 oil application / cleaning mechanism 36 drive mechanism 38 first driven gear 40 one-way clutch 42 second driven gear 44 transmission gear 46 collar 48 donor roll 48 'oil application / cleaning roll 50 oil supply roll 50A spindle 50B Heat resistant paper layer 50C Resin film 52 Third driven gear 54 Idle gear 56 (56A, 56B) Idle gear 58 Cleaning brush 60 First coil spring 62 Second coil spring 64 First thermistor 6 second thermistor 68 third thermistor 70 auxiliary heat source

Claims (18)

[Claims] A housing rotatably supported by the housing so as to be rotatable around a fixed axis;
A heating roll having a built-in heating means, a swing member pivotally supported by the housing, a fixing roll pivotally supported by the swing member about a fixed axis, and a swing member A pressure roll, which is rotatably supported around a fixed axis and is attached to the fixing roll so as to be in contact with the fixing roll, is endlessly wound around the heating roll and the fixing roll, and is A heat transfer belt that transfers heat to a contact portion between the fixing roll and the pressure roll by receiving the heat transfer, and a tension applying unit that applies a predetermined tension to the pre-heat transfer belt. A fixing device for fixing the unfixed toner on the sheet by passing the sheet having the surface carried thereon through the rolling contact portion. 2. The fixing device according to claim 1, wherein the tension applying unit includes an urging unit that urges the swinging member in a direction in which the fixing roll is separated from the heating roll. 3. The fixing device according to claim 2, wherein said urging means includes an elastic member stretched between said swing member and said housing. 4. The fixing device according to claim 1, further comprising oil applying means for applying oil to said heat transfer belt. 5. The oil applying means includes: a donor roll which rolls on the heat transfer belt at a predetermined rolling angle, and an oil supply roll which rolls on the donor roll and supplies oil thereto. The fixing device according to claim 4, wherein: 6. The fixing device according to claim 5, wherein the donor roll is rotatably supported by the housing so as to be rotatable around a fixed axis. 7. The fixing device according to claim 6, further comprising a driving unit that rotationally drives the donor roll. 8. The heat transfer belt further includes a driving unit that rotationally drives the pressure roll, wherein the heat transfer belt is driven to travel by frictionally engaging with the pressure roll, and the fixing roll is driven by the heat transfer belt. The fixing device according to claim 1, wherein the fixing device is driven to rotate by the rotation of the pressure roll via a belt. 9. The fixing device according to claim 8, wherein the driving unit drives the fixing roll to rotate at a lower peripheral speed than the pressure roll. 10. The fixing roll includes a driven gear mounted coaxially with the fixing roll, the driving unit includes a driving gear meshing with the driven gear, and between the driven gear and the fixing roll: A one-way clutch is interposed, and the one-way clutch permits rotation of the fixing roll faster than the driven gear, and prohibits rotation of the fixing roll slower than the driven gear. Item 10. The fixing device according to item 8. 11. The fixing device according to claim 8, wherein the driving unit drives the donor roll to rotate. 12. 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. 13. The endless base member is formed from a nickel electroformed belt.
3. The fixing device according to 2. 14. The fixing device according to claim 12, wherein said endless base material is formed of a polyimide resin. 15. The fixing roll according to claim 1, wherein the fixing roll comprises a cored bar, and an elastic layer disposed on the outer periphery of the cored bar with a predetermined thickness. 3. The fixing device according to claim 1. 16. The fixing device according to claim 15, wherein the pressure roll is formed of a roll having an outer periphery harder than the on-roll hardness of the elastic layer. 17. The distance between the rotation axis of the pressure roll and the rotation axis of the fixing roll is set shorter than the sum of the radius of the pressure roll and the radius of the fixing roll. The fixing device according to claim 1. 18. A fixing roll, a pressurizing roll which rolls in contact with the fixing roll at a predetermined nip width, a heating roll which is disposed separately from the fixing roll and has a heat source disposed therein, A heat transfer belt having a predetermined heat capacity and endlessly stretched between a fixing roll and the heating roll, and a sheet on which unfixed toner is carried on the surface, first, the leading end of which is the outer periphery of the pressure roll And a guide means for guiding the fixing roll and the pressure roll so as to pass along the rolling contact portion in one direction. A fixing device for fixing toner on the sheet.