JPH11344884A - Fixing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing equipment which prevents degradation in fixing capabil ity, even if the speed at which an unfixed sheet is carried, that is the speed at which the paper passes through, is increased. SOLUTION: This fixing equipment 10 has a fixing roller 28 and a pressure roll 30 which rotates in contact with the fixing roller 28 at specific pressure, and it fixes unfixed toner onto a sheet S by making the sheet S with the unfixed toner held on its surface pass in one direction through the rotating contact part of the fixing roller 28 and pressure roller 30. In this case, the device is equipped with a heating roll 34 which is disposed next to the fixing roller 28 and opposite to the side where the pressure roller 30 is disposed, and which has a heating means 32 disposed inside. The equipment is also equipped with a heat transmission belt 36, which is stretched endlessly between the heating roll 34 and fixing roll 28, receives heat transmitted from the heating means 32, and heats the unfixed toner on the sheet S passing through the rotating contact part. The device is further equipped with a controller which exerts standby control for keeping the surface of the heating roller 34 within a specific temperature-range during standby and paper passage control for keeping the surface of the fixing roller 28 within a specific temperature range at the start of paper passage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for use in a copier, a printer, a facsimile, etc., for fusing and pressing unfixed toner on a recording medium and fixing the toner on the recording medium.

[0002]

2. Description of the Related Art In a recent fixing device for an electrophotographic apparatus, as shown in FIG. 14, a fixing roll R1 and a heating and tension roll (hereinafter simply referred to as a "heating roll").
A technique has been developed that combines a belt fixing method in which a fixing belt B is stretched between R3 and a pressing roll R2 that presses from below through the fixing belt B, and preheating of the recording medium D. Thereby, the temperature of the nip portion can be set low by preheating, and by using the fixing belt B having a small heat capacity, the temperature of the fixing belt B is rapidly cooled when passing through the nip portion, and the fixing belt B is separated from the fixing belt B at the exit of the nip portion. By increasing the cohesive force of the toner, the releasability between the fixing belt B and the toner is enhanced, and a clear fixed image with no offset can be obtained even when no oil is applied or only a small amount of oil is applied. This device is known as a fixing device that solves the problems of releasability and oil application that could not be solved by the heating roll system.

The configuration of this conventional fixing device will be briefly described below. The fixing device includes a fixing roll R1, a pressure roll R2 disposed immediately below the fixing roll R1, and a side of the fixing roll R1 (an upstream side along a recording medium conveyance direction).
And a heating roll R3 disposed in the fixing roll R1.
A fixing belt B is stretched between the heating roller R3 and the heating roller R3.

An oil application roll R4 is provided above the fixing belt B. A guide plate G as a recording medium support is provided below the fixing belt B with a gap, and a heating path P for the recording medium is formed between the fixing bell and the lower part of the B and the guide plate G. I have.

The fixing belt B obtains a desired tension when the heating roll R3 is pressed by the pressing lever U in a direction to separate the fixing belt R1 from the fixing roll R1, and slips or loosens when driven by the fixing roll R1. It is possible to make stable rotation without any trouble.

[0006] Inside the heating roll R3, a heating heater H is provided as a heating source. A thermistor S is provided for measuring the surface temperature of the heating and tension roll R3. When the temperature is measured in the contact state, the thermistor S is not preferably brought into contact with the paper passing area of the fixing belt B. Therefore, the thermistor S is brought into contact with the non-paper passing area of the fixing belt B.

In the conventional fixing device having the above-described configuration, the heating roll R3 is controlled by a control (not shown) based on the temperature measured from the thermistor S during the fixing operation.
Is controlled so that the surface temperature of the heater H becomes the set temperature.

According to the above-described method of controlling the heater H, the temperature of the fixing belt B on the fixing roll R1 changes according to the rotation time of the fixing belt R, and is not constant during the sheet passing. If the time is short, the fixing roll R
In order to increase the temperature of the fixing belt B on the fixing roller R1, the set temperature of the heating roll R3 is increased, and the temperature of the fixing belt B on the fixing roll R1 is controlled so as to always enter the fixable region. There is a need.

However, during full-color continuous copying or the like, the rotation time of the fixing belt B becomes longer, so that the temperature of the fixing belt B on the fixing roll R1 rises, that is, the temperature at the exit of the nip increases. The temperature characteristics are as shown in FIG.

In FIG. 15, the horizontal axis represents the fixing belt B.
The vertical axis indicates the temperature of the fixing belt B on each roll. First, a description will be given of a temperature characteristic when the heat release amount of the heater H is controlled such that the temperature of the fixing belt B on the heating roll R3 becomes the set temperature T2. In this case, the wavy line W1 indicated by a solid line in the upper part of FIG. 15 indicates the temperature of the fixing belt B on the heating roll R3. On the other hand, a lower characteristic curve C1 indicates a change in the temperature of the fixing belt B on the fixing roll R1.

After the waiting time, as the rotation time of the fixing belt B increases, the temperature of the fixing belt B on the fixing roll R1 increases. When the temperature of the fixing belt B on the fixing roll R1 exceeds the fixing upper limit temperature T1, the possibility of occurrence of an offset or a jam of thin paper increases. If the temperature of the fixing belt B on the fixing roll R1 is lower than the fixing lower limit temperature T1 'indicated by the broken line in FIG. 2, problems such as low-temperature offset and unfixed areas of toner occur. Therefore, the temperature of the fixing belt B on the fixing roll R1 is determined by the fixing upper limit temperature T1 and the fixing lower limit temperature T1 '.
Is a normal state.

As a countermeasure, as shown in FIG. 15, when the temperature of the fixing belt B on the fixing roll R1 is the highest, the temperature of the fixing belt B on the heating roll R3 is set to be equal to or lower than the fixing upper limit temperature T1. When the temperature is set to T2 '(the characteristics in this case are indicated by broken lines W2 and C2), the offset,
Although the occurrence of jam of thin paper can be prevented, the temperature of the fixing belt B on the fixing roll R1 becomes lower than the fixing lower limit temperature T1 '.
, It takes a longer time to reach, and the copy speed decreases from Ts to Ts'.

On the other hand, when the fixing operation of the recording medium is completed,
The conveyance operation of the recording medium is interrupted, and accordingly, the running operation of the fixing belt B is also stopped, and the heat generation operation of the heater H in the heating roll R3 is also stopped, so that a standby state is set. With the setting of the standby state, the surface temperature of the fixing roller R1 together with the fixing belt B decreases. As a result, when the standby state is continued for a long time, the fixing belt B and the fixing roll R1 are completely cooled, and when the fixing operation is restarted from the cooled state, the fixing roll R1 is cooled to a fixing-possible temperature. It takes time to heat, forcing the operator to wait for a long time, and there is a need for improvement.

For this reason, although not shown, the fixing roll R
Further, an auxiliary thermistor for measuring the surface temperature of the heating roll R3, which is the measurement result of the thermistor S, until the surface temperature of the fixing roll R1 rises to near the feasible fixing temperature as shown in FIG. When the surface temperature of the fixing roll R1 exceeds the vicinity of the fixable temperature, the amount of heat radiation of the heater H is controlled based on the surface temperature of the fixing roll R1, which is the measurement result of the auxiliary thermistor. To control the heat radiation amount of the heater H,
So-called priority control has been proposed. By executing this priority control, it is possible to shorten the time for heating the fixing roll R1 from the standby state to the fixing temperature while preventing the occurrence of the offset or the jam of the thin paper, which has been pointed out previously. Desired effect can be obtained.

[0015]

Here, in an electronic image forming apparatus such as an electronic copying apparatus or an electronic printer to which the fixing device is mounted, recently, particularly, the sheet conveying speed (that is, the sheet passing speed per unit time). (The number of sheets) is extremely increased (increased), and so-called high-speed apparatus is required. To make the fixing device correspond to such a high speed, the traveling speed of the fixing belt B must be increased. This means that the amount of heat transmitted by the fixing belt B per unit time is reduced.

On the other hand, as described above, the arrangement position of the thermistor S is defined so as to come into contact with the non-sheet passing portion of the fixing belt B wound around the heating roll R3. For this reason, at the time of continuous paper passing, the sheet does not contact the non-paper passing portion, so that heat is not released, and heat is stored here,
As a result, the measured temperature of the thermistor S increases, and FIG.
The temperature will be raised to a state beyond the control switching point shown in FIG. Then, in the continuous paper-passing state, since the heat radiation amount of the heater H is controlled based on the surface temperature of the fixing roll R1 which is the measurement result of the auxiliary thermistor, the control switching point in the priority control has been exceeded. Means that the heat radiation amount of the heater H is controlled based on the surface temperature of the heating roll R3 which is the measurement result of the thermistor H.

As a result, while the heat radiation amount of the heater H is kept constant based on the measurement result of the thermistor H, the heat of the fixing roll R1 is absorbed in a large amount by the sheet which is continuously fed at a high speed. The surface temperature of the fixing roll R1 gradually decreases as shown in FIG. In this way, since the priority control is performed, the surface temperature of the fixing roll R1 gradually decreases in the continuous paper passing state at a high speed, and a situation occurs in which the fixing property is not ensured. Is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a fixing device in which the fixing property does not deteriorate even if the conveying speed of an unfixed sheet, that is, the paper passing speed increases. It is to provide.

Another object of the present invention is to provide an image processing apparatus which is capable of increasing the conveying speed of an unfixed sheet, that is, even if the sheet passing speed is increased.
An object of the present invention is to provide a fixing device capable of substantially maintaining the surface temperature of a fixing roll at the fixing temperature.

[0020]

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 fixing roll, and a pressure roll that is in contact with the fixing roll at a predetermined pressure. The fixing device fixes the unfixed toner onto the sheet by passing the sheet carried by the fixing roll and the pressure roll along the rolling contact portion of the fixing 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 from the heat generating means and heats the unfixed toner on the sheet that passes through the transfer portion; and a standby state that maintains the surface temperature of the heating roll in a predetermined temperature range in a standby state. Running state control, with the sheet passing operation start, it is characterized by comprising a control means for performing a paper passing state control to maintain the temperature of the fixing roll surface a predetermined temperature range.

According to a second aspect of the present invention, there is provided a fixing device including a fixing roll, and a pressure roll which is in contact with the fixing roll at a predetermined pressure. In a fixing device for fixing the unfixed toner on the sheet by passing the carried sheet along a rolling contact portion of the fixing roll and the pressure roll along one direction, the fixing device includes a fixing roller, 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 wrapped around the heating roll and the fixing roll; A heat transfer belt that receives the heat transfer from the means and heats the unfixed toner on the sheet that passes through the rolling contact portion; a determination unit that determines whether the standby state or the paper passing state; and the determination unit is in the standby state. Determined In this case, a standby state control for maintaining the surface temperature of the heating roll in a predetermined temperature range is executed, and when it is determined that the sheet is in the paper passing state, the sheet passing state in which the temperature of the fixing roll is maintained in the surface predetermined temperature range. And control means for executing control.

According to a third aspect of the present invention, in the fixing device according to the third aspect, the discriminating unit determines that the sheet is being passed when the sheet passing command is received, and the sheet passing command is not received. It is characterized in that the state is determined to be a standby state.

In the fixing device according to the present invention, according to the fourth aspect, the control means includes a first detecting means for detecting a surface temperature of the heating roll, and a first detecting means for detecting a surface temperature of the fixing roll. And a second detecting means for detecting,
In the standby state control, the heating unit is controlled based on a detection result of the first detection unit. In the sheet passing state control, the heating unit is controlled based on a detection result of the second detection unit. It is characterized by controlling.

According to a fifth aspect of the present invention, in the fixing device according to the fifth aspect of the present invention, there is provided a fixing device comprising:
And a third detecting means for detecting the surface temperature of the pressure roll.

According to a sixth aspect of the present invention, in the fixing device according to the sixth aspect, in the standby state control, the control unit is configured to perform a control based on a detection result of the third detection unit.
It is characterized in that the second heating means is controlled.

[0026]

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 device (not shown) as a housing structure, for example,
The housing includes a housing 12 fixed to a frame of the electronic printer. The housing 12 includes a bottom plate 14 directly fixed on the apparatus frame, side plates 16 rising from right and left side edges of the bottom plate 14, and 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, The heating roll 34 is attached to the swing lever 22 in a state where the heating roll 34 is positioned obliquely upward, and is rotatably supported around its own central axis.

The fixing device 10 includes a heating roll 3
4, a first lamp such as a halogen lamp.
And a heat source 32 disposed inside the pressure roll 30.
For example, it further includes a second heat source 33 such as a halogen lamp, and a fixing belt (heat transfer belt) 36 wound around endlessly over the fixing roll 28 and the heating roll 34.

Here, although the details will be described later, the fixing roll 2
Numeral 8 is composed of an elastic roll, while pressure roll 30 is composed of 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 centers of rotation is slightly smaller than the sum of the radius R1 of the fixing roll 28 and the radius of the pressing roll 30R2 (R1 + R2). As a result, in the 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, whereby the fixing roll 28 is pressed.
Is brought into a state depressed 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 figure is bent inward, and is positioned below the bent piece, and is separated from the bent plate by a large amount. It is fixed to. From between the upper cover portion 18 and the guide plate 44, a sheet (hereinafter, simply referred to as an unfixed sheet) carrying unfixed toner on the upper surface is moved in one direction (conveying direction) indicated by an arrow in the drawing. An inlet port 46 is defined along the interior of the housing 12.

Here, the guide plate 44 is attached in a state of being inclined obliquely upward and leftward in the figure so that the height thereof increases as it enters the housing 12. On the other hand, the leading end of the guide plate 44, that is, the lower right end in the drawing, is an endless sheet transport end disposed in the electronic printer and adjacent to the entrance port 46 on the right side in the drawing. The guide plate 44 is positioned so as to face the outlet end of the belt EB. Part)
Is positioned so as to face the.

The leading end of the unfixed sheet conveyed along the direction (conveying direction) indicated by an arrow in the drawing toward the fixing device 10 through the endless belt EB first contacts the guide plate 44. , And is guided so as to be conveyed obliquely upward. As a result, the unfixed sheet guided by the guide plate 44 is guided to a rolling contact portion between the fixing roll 28 and the pressure roll 30.

On the other hand, the fixing roll 28 and the pressure 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 portion 20 in a state between the discharge path 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 such a schematic configuration, the unfixed sheet S conveyed onto the guide plate 44 via the endless belt EB by the conveying mechanism.
The lower surface where no unfixed toner is attached
The fixing belt 36 is guided toward a rolling contact portion (nip portion) between the fixing roll 28 and the pressure roll 30 around which the fixing belt 36 is wound, and is pressed between the two 28 and 30. It is set so that the unfixed toner is thermocompressed and fixed on the sheet by being inserted.

{Description of Fixing Roll 28} The above-described fixing roll 28 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 of a silicone rubber heat-resistant elastic body (specifically, silicone rubber having a JIS A hardness of 15 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 Pressure Roll 30} As described above, the pressure roll 30 incorporating the second heat source 33 is a core metal part rotatably supported on the side plate 16 via a bearing (not shown). 30A and a roll main body 30B coaxially disposed on the outer periphery of the cored bar 30A, and the outer diameter of the roll is set to 35 mm. Here, in this embodiment, the core 30A is formed of an iron shaft having a diameter of 32 mm, and the roll body 30B is
A silicone rubber heat-resistant elastic body (specifically, the fixing roll 28
JIS A hardness of 20 degrees and silicone rubber). The outer periphery of the roll body 30B is covered with a 50 μm-thick fluororesin tube.

A 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 allows the fixing roller 28 to rotate relative to the first driven gear 58 in the clockwise direction in the figure, but in the counterclockwise direction in the figure. It is configured such that the relative rotation is locked, in other words, both rotate integrally. Specifically, in the cold state, that is, the fixing belt 36 frictionally engages with the pressure roller 30, and the fixing roller 28 frictionally engages with the fixing belt 36, and the fixing roller 28 and the fixing roller 28 are pressed by the pressure roller 30. When the fixing belt 36 is driven (rotated), the peripheral speed of the fixing roll 28 rotating clockwise in the drawing is the same as the peripheral speed of the pressure roll 30, and is lower than the peripheral speed of the first driven gear 58. This speed difference will be absorbed by the one-way clutch 60, although it will be made slightly faster.

The fixing roll 36 is heated via the fixing belt 36 by the heat generated by the heating roll 34 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 >> In this embodiment, the heating roll 34 having the above-described first heat source 32 has a thickness of 30 mm in diameter and a thickness of 3.5 mm in thickness of an aluminum pipe core. The bearings at both ends are coated with a 20 μm PTFE coating layer and have a diameter of 34 m made of heat-resistant resin made of polyetheretherketone (PEEK).
The m collar 66 is press-fitted, thereby preventing the fixing belt 36 from meandering and offset.

The first heat source 32 is built in the heating roll 34. In this embodiment, as shown in FIG. 3, the first heat source 32 has a large size. And a short halogen lamp 32B for a small-sized sheet are provided side by side. Here, in this embodiment, a large-sized sheet is a sheet of A4 size in the horizontal direction, A3 size in the vertical direction, B5 size in the horizontal direction, B4 size in the vertical direction, and the like. , B5 size in the vertical direction, A4 size in the vertical direction, and postcard size in any direction.

That is, in this embodiment, the long halogen lamp 32A is set to have a length capable of covering 297 mm, which is the short side of A3. 210m which is short side
m is set to a length that can cover m.
In addition, in each of the halogen lamps 32A and 32B, the light distribution at both ends is set to be 30 to 50% larger than the center.

<< Description of Fixing Belt 36 >> The above-described fixing belt 36 preheats the unfixed toner on the unfixed sheet S to a fixing temperature by radiating heat and fixes the unfixed toner without applying 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 roll outer diameter of 22 mm in diameter in a state where the porous fluororesin film 38C of μm is 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.

Incidentally, dirt (toner and the like) adhering to the outer peripheral surface of the fixing belt 36 is transferred and adhered to the outer peripheral surface of the oil application roll 38 to be soiled. 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, as a mechanism for applying tension to the fixing belt 36, the oil application roll 38 is orthogonal 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 is 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 Drive Mechanism 52} As shown in FIG. 4, the drive mechanism 52 for rotationally driving the pressure roll 30 and the like is provided with the fixing device 10 mounted on an electronic printer, as shown in FIG. A transmission gear 62 meshes with an output gear GE connected to a drive source on the printer side via a gear train (not shown), and is rotationally driven by receiving a driving force from the output gear GE.
And a first driven gear 58 which is always meshed with the transmission gear 62 and connected to the fixing roll 28 via the one-way clutch 60, and is always meshed with the first driven gear and A second driven gear 64 fixed coaxially.

The drive mechanism 52 further includes an idle gear 72 that always meshes with the transmission gear 62 described above.
The idle gear 72 always meshes with a third driven gear 74 coaxially fixed to the lower discharge roll 50, and drives the lower discharge roll 50 to rotate at a speed equal to or higher than the rotation of the pressure roll 30. It is configured to be.

{Other Configurations} Fixing Device 1 of this Embodiment
In addition to the above-described configuration, reference numeral 0 denotes a peeling claw 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 78 is provided to detect that the leading end of the fixed sheet has been conveyed between the paper roll 54 (the rolling contact portion).

{Structure of Control System} On the other hand, the fixing device 10 controls the drive of the above-described drive mechanism 52, and also includes the first heat source 32 built in the heating roll 34 and the pressure roll 30. As shown in FIG. 5, a control device 86 is provided for controlling the heat generation of the second heat source 33.
The control device 86 includes a non-sheet passing portion (that is, a portion of the fixing belt 36 where the unfixed sheet S does not contact) of the fixing belt 36 wound around the outer peripheral surface of the heating roll 34 for the above-described heat generation control. ) (Hereinafter, simply referred to as a heating roll temperature).
And a fixing belt 36 wound around the outer periphery of the fixing roll 28.
A second thermistor 82 for detecting the temperature (hereinafter, simply referred to as a fixing roll temperature) Tf of the outer peripheral surface of the sheet passing portion (that is, the portion of the fixing belt with which the unfixed sheet S contacts).
Third thermistor 84 that detects the temperature of the outer peripheral surface of pressure roller 30 (hereinafter, simply referred to as pressure roller temperature) Tp.
Are connected, and the first to third thermistors 80 and 8 are connected.
The first and second heat sources 32 and 33 are configured to control the heat generation based on the detection results Th, Tf and Tp from the light sources 2 and 84.

The control device 86 controls the large-sized halogen lamp 3 of the first heat source 32 via the first heater driver 88A in accordance with a control procedure described in detail later.
2A, the halogen lamp 32B for the small size of the first heat source 32 via the second heater driver 88B, and the halogen lamp for the second heat source 33 via the third heater driver 88C. Are respectively controlled.

{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. 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 structure, 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. 6, 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 in the counterclockwise direction from the base line B, and “−” is defined as the value measured in the clockwise direction in the figure from the base line B. 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 to 8 mm, and the pressing force P1 for this was set to 24 kgf / one side. On the other hand, the temperature of the portion of the fixing belt 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.

[0075]

[Table 1]

As is apparent 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.

{Description of Heat Generation Control Method by Control Device 86} Next, a heat generation control method (control procedure) of the first and second heat sources 32 and 33 in the control device 86, which is a feature of the present invention, will be described. This will be described with reference to the flowcharts in FIGS.

This control device 86 is not shown, but
CPU controlling overall control and RO with built-in program
M, a RAM in which threshold values and set values are stored in advance, an interface circuit for transmitting information to and from a control device of an electronic printer to which the fixing device 10 is attached, various I / O circuits,
/ O port and the like. In a state where a paper passing command is not received from the electronic printer, a standby state is defined, a predetermined standby state control procedure is executed, and a paper passing command is issued from the electronic printer. In this state, the paper passing state is defined as long as the paper passing command is not terminated, and a predetermined paper passing state control procedure is executed.

That is, basically, in the rotation standby state, the control device 86 sets the heating roll temperature to the first set value (set temperature) T1 based on the detection result Th of the first thermistor 80. In addition to controlling the heat generation of the first heat source 32, the second heat source 33 is controlled based on the detection result Tp of the third thermistor 84 so that the pressure roll temperature becomes the second set value (set temperature) T2. On the other hand, in the sheet passing state, the first heat source 32 is controlled to generate heat so that the fixing roll temperature becomes the third set value (set temperature) T3 based on the detection result of the second thermistor 82. It is configured to be.

The control device 86 is provided with the first heat source 3
The second large-sized halogen lamp 32B of the first heat source 32 is connected to the second large-sized halogen lamp 32B via the first heater driver 88A.
B, and the halogen lamp constituting the second heat source 33 is connected via the third heater driver 88C.
Each heat generation state (that is, heat generation amount) is configured to be controlled.

In the sheet passing state, the controller 86 determines the size of the conveyed sheet based on the sheet passing information. While energizing only the large-sized halogen lamp 32A among the built-in first heat sources 32,
The second heat source 33 built in the pressure roll 30 is controlled to generate heat in the same manner as in the standby state. On the other hand, when it is determined that the first heat source 32 has a small size, Is configured to supply current only to the halogen lamp 32B.

Hereinafter, a control procedure in the above-described control device 86 will be described in detail with reference to flowcharts of FIGS.

{Description of Main Routine of Control Procedure in Control Unit 86} First, as shown in FIG.
6 executes a predetermined initialization operation when a power supply (not shown) is turned on, and thereafter executes a standby state control for heat generation control of the first and second heat sources 32 and 33 (step S1).
0). The standby state control operation will be described later in detail with reference to FIG.

The standby state control in step S10 is executed until a paper-passing command is issued from the electronic printer to which the fixing device 10 is attached (step S1).
2) When a sheet passing command is received, each drive unit of the drive mechanism 52 is activated to perform drive control in accordance with a predetermined drive control procedure (step S14), and the first and second sources 3 are driven.
The paper passing state control for the heat generation control of steps 2 and 33 is executed (step S16). Note that the drive control procedure has nothing to do with the present invention, and a description thereof will be omitted, and the sheet passing state control operation will be described in detail with reference to FIG.

The paper passing state control in step S16 is executed as long as the paper passing command is received, and when it is detected that the paper passing command is completed (step S18), the driving of each drive unit in the drive mechanism 52 is performed. Is stopped, and the process returns to step S10 to execute the standby state control.

In this way, the control device 86 executes a basic heat generation control operation of the first and second heat sources 32 and 33.

{Description of Control Procedure of Standby State Control} Next,
The control procedure of the standby state control in step S10 described above will be described in detail as a subroutine with reference to FIG.

When this standby state control is started, first,
The heating roll temperature Th is detected via the first thermistor 80 (Step S10A), and the detected temperature Th is set to the first temperature.
It is determined whether the temperature is higher than the set temperature T1 (step S10B). If NO is determined in step S10B, that is, if the detected temperature Th is equal to the first set temperature T
If it is determined that the temperature is not more than 1, the heating roll temperature has not yet reached the target first set temperature T1, so the first heat source 3 built in the heating roll 34
2, only the large-size halogen lamp 32A is energized to generate heat (step S10C).

On the other hand, if it is determined YES in step S10B described above, that is, if it is determined that the detected temperature Th is higher than the first set temperature T1, the heating roll temperature which is already the target is set. Since the temperature has exceeded the set temperature T1, the power supply to the first heat source 32 built in the heating roll 34 is stopped (step S10D), and the heat generation of the large-size halogen lamp 32A is stopped.

After the heat generation to the first heat source 32 built in the heating roll 34 is thus controlled, this time,
The pressure roll temperature Tp is detected via the third thermistor 84 (step S10E).
It is determined whether the temperature is higher than the set temperature T2 (step S10F). If NO is determined in this step S10F, that is, if the detected temperature Tp is equal to the second set temperature T
If it is determined that the temperature is equal to or lower than 2, since the pressure roll temperature has not yet reached the target second set temperature T2, the second heat source 3 built in the pressure roll 30
The halogen lamp No. 3 is energized to generate heat (step S10G).

On the other hand, if it is determined YES in step S10E, that is, if it is determined that the detected temperature Tp is higher than the second set temperature T2, the pressure roll temperature has already become the target. Since the temperature has exceeded the second set temperature T2, the power supply to the second heat source 33 built in the pressure roll 30 is stopped (step S10H), and the heat generation of the halogen lamp is stopped.

As described above, after the heat generation control of the second heat source 33 built in the pressure roll 30 is executed based on the temperature of the heating roll, this control procedure is terminated, and the process returns to the original main routine. .

{Description of control procedure of paper passing state control}
The control procedure of the sheet passing state control in step S16 will be described in detail as a subroutine with reference to FIG.

When the paper passing state control is started, first,
It is determined whether or not the size of the unfixed sheet conveyed (that is, passed) from the electronic printer is a small size (step S16A). If NO is determined in this step S16A, that is, if it is determined that the size of the conveyed sheet is a large size, of the first heat source 32 built in the heating roll 34, Only the halogen lamp 32A for the size is energized (step S16B). Then, the heat generation state of the second heat source 32 built in the pressure roll 30 is controlled (Step S).
16C). Here, in this step S16C,
The same heat generation control operation as the heat generation control of the second heat source 32 executed in steps S10E to 10H in the standby state control described above is executed as a subroutine.

On the other hand, YES in step S16A described above
Is determined, that is, when it is determined that the conveyed sheet size is small, the heating roll 3
4, only the small-sized halogen lamp 32B out of the first heat sources 32 built in the power supply 4 (step S4).
16D).

After the control operation according to the size of the conveyed sheet is executed, the second thermistor 82
, The fixing roll temperature Tf is detected (step S1).
6F), it is determined whether or not the detected temperature Tf is higher than the third set temperature T3 (step S16G). If NO is determined in this step S16G, that is,
If it is determined that the detected temperature Tf is equal to or lower than the third set temperature T3, the fixing roll temperature has not yet reached the target third set temperature T3. The first heat source 32 is energized to generate heat according to the size of the sheet (step S16).
H).

On the other hand, if it is determined YES in step S16G described above, that is, if it is determined that the detected temperature Tf is higher than the third set temperature T3, the fixing roll temperature already at the target is determined. Since the temperature has exceeded the set temperature T3 of 3, the power supply to the first heat source 32 built in the heating roll 34 is stopped (step S16I), and the heat generation of the halogen lamp is stopped.

As described above, after the heat generation control of the first heat source 32 built in the heating roll 34 is executed based on the fixing roll temperature, this control procedure is terminated, and the process returns to the original main routine.

As described in detail above, since the control procedure in the control device 86 is configured, the heating roll 34 is activated when the driving mechanism 52 is activated upon receipt of a sheet passing command.
The first heat source 32 incorporated in the heating roller 34 has a surface temperature Th of the heating roll 34, which is a measurement result of the first thermistor 80.
From the standby state control in which the temperature is controlled to the first set temperature T1 on the basis of the surface temperature Tf of the fixing roll 28, which is the measurement result of the second thermistor 82, to control the temperature to the third set temperature T3. The sheet passing state control operation is switched to the current sheet passing state control, and the sheet passing state control operation is continued as long as the sheet passing command is issued.

As a result, according to this embodiment, in the sheet passing state, the measurement target is not changed in accordance with the detection result of the first thermistor 80 as in the related art,
The first heat source 32 is controlled based on the fixing roll temperature. As a result, the sheet passing speed increases, and the sheet frequently passes through the nip portion, so that a large amount of heat is generated from the fixing roll 28. Even if deprived, the first heat source 3
2 is controlled to generate heat, and the calorie of the deprived portion is supplied (transmitted) from the heating roll 34 to the fixing roll 28 via the fixing belt 36, as shown in FIG.
At all times, the fuser roll temperature will be substantially maintained at the fuseable temperature. In this manner, even in a high-speed paper passing state, the fixing property is ensured, and a good fixing operation is performed.

Further, in this embodiment, since the second heat source 33 is incorporated in the pressure roll 30 constituting one of the nip portions, a sufficient amount of heat for heating the unfixed sheet S is supplied. As a result, even if the traveling speed of the fixing belt 36 is increased, a sufficient amount of heat can be supplied to the nip portion. In this way, it is possible to sufficiently cope with an increase in the paper passing speed.

Here, the second pressure is applied to the pressure roll 30 as described above.
In the configuration in which the heat source 33 of
The size of the sheet is determined, and when it is determined that the sheet is of a small size, the power supply to the second heat source 33 is stopped so that the second heat source 33 does not generate heat. As a result, an increase in the temperature of the non-sheet passing portion of the heating roll 34 provided with the first thermistor 80 is effectively suppressed. As a result, according to this embodiment, the temperature of the first heat source 32 built in the heating roll 34 is controlled by the second thermistor 82 that detects the surface temperature of the fixing roll 28 during the paper passing state.
Even if it is performed based on the measurement result of
A good and safe heat generation state is achieved without abnormally increasing the surface temperature of No. 4.

In this embodiment, the first heat source 32 built in the heating roll 34 includes a large-size halogen lamp 32A and a small-size halogen lamp 3A.
In the standby state and the sheet passing state of the large size sheet, the halogen lamp 32A for the large size is energized to generate heat only, and in the sheet passing state of the small size sheet, the halogen lamp 32A for the small size is supplied. The halogen lamp 32B is configured to be energized to generate heat only. As a result, according to this embodiment, the heating roll 3
The fixing operation is executed in a more stable state by suppressing an abnormal increase in the surface temperature of No. 4.

Further, in this embodiment, the control device 8
6 performs the standby temperature control operation described above,
Even if the standby time extends for a long time, the rising time from the standby time can be shortened, and the effect of shortening the standby time required until the start of the fixing operation can be obtained.

Further, in this embodiment, the heating roll 34 is disposed substantially above the fixing roll 28, and specifically,
A line L connecting the center point of the heating roll 34 and the center point of the fixing roll 28 is formed by the fixing roll 28 and the pressing roll 3.
In the state where the line segment connecting the center points with 0 is the base line B,
The heating roll 34 is disposed at a position where the angle measured from the base line B is in a range of about 105 degrees to about 255 degrees.
Between the fixing belt 36 and the guide plate 44 wound endlessly between the fixing plate 28 and the fixing roll 28.
The unfixed sheet conveyed above is separated so as not to contact the fixing belt 36. In other words, this means that the fixing belt 36 is disposed at a position outside an area where the unfixed sheet conveyed on the guide plate 44 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 the 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.

In this embodiment, the fixing roll 28 is formed from an elastic roll, and the pressure roll 30 is formed so as to have a higher on-roll hardness than the fixing roll. Therefore, according to this embodiment, even if the sizes of the fixing roll 28 and the pressure roll 30 are reduced, the nip width at the rolling contact portion between them can be sufficiently ensured,
As a result, it is possible to achieve a reduction in the size of the fixing device and an increase in the sheet conveying speed, and it is possible to provide a fixing device particularly suitable for a color printer.

Further, in this embodiment, the upper fixing roll 28 is formed from an elastic roll, and the lower pressure roll 30 is formed with a higher on-roll hardness than the fixing roll 28. The shape of the nip at the rolling contact portion is easier to change from a state in which the fixing roller is formed downward to a state in which the fixing roller is formed from a roll having a higher on-roll hardness than the elastic roll of the present invention. Can be achieved. 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.

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 configured as a soft roll, but the heat source 32 is built in the heating roll 34 disposed at a position separated from the fixing roll 28. I decided to
The thickness of the silicone rubber heat-resistant elastic body 28B of the fixing roll 28 can be made sufficiently thick. As a result, according to this embodiment, the nip width at the rolling contact portion can be reduced while maintaining the fixing roll 28 at a small diameter. , Can be taken sufficiently wide.

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.

[0112]

[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 device 10 is applied to an electronic printer has been described. However, the present invention is not limited to such an application, and the electronic facsimile device, the electronic facsimile Needless to say, the present invention can be applied to an electronic image forming apparatus such as a copy machine.

Further, in the above-described embodiment, the description has been made such that the unfixed sheet is 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 30 is not below the fixing roll 28,
Needless to say, the heating roll 34 is arranged on the side of the fixing roll 28 opposite to the side on which the pressure roll 30 is arranged. .

In the above-described embodiment, the temperature of the belt on each roll is measured and used for controlling the heater. However, the surface temperature of each roll is directly measured,
It can also be used to control the heating source 32 (33).

In the above-described embodiment, the heat generation control (that is, the energization control) of the second heat source 33 built in the pressure roll 30 is controlled by the third thermistor 84 as shown in FIG. Temperature Tp of the pressure roll 30 detected through the
Has been described to be executed based on the detection result, but the present invention is not limited to such a configuration / procedure,
As a first modified example, a first method for measuring the surface temperature Th of the heating roll 34 without using the third thermistor 84 is described.
The heat generation control of the second heat source 33 may be executed based on the detection result of the thermistor 80 described above and the detection result of the second thermistor 82 that measures the surface temperature Tf of the fixing roll 28.

The control procedure according to the first modification will be described below with reference to FIGS. 11 and 12. The same parts (same procedure) as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

That is, in the standby state control, as shown in FIG. 11, the first thermistor 80 is turned on in step S10A.
When it is determined that the surface temperature Th is lower than a predetermined first set temperature T1 based on the surface temperature Th of the heating roll 34 detected through the Second heat source 3 built in roll 30
3 to generate heat (step S10G),
When it is determined that the surface temperature Th is higher than the predetermined first set temperature T1, the power supply to the second heat source 33 is stopped and the second heat source 33 is controlled so as not to generate heat.

As described above, in the standby state control in the first modification, steps S10E and S10F shown in FIG. 8 are omitted, and the third thermistor 84 for detecting the surface temperature of the pressure roll 30 is provided. Will be omitted. As a result, the control procedure is simplified, and the third
The thermistor 84 becomes unnecessary, and the cost can be reduced due to the reduction in the number of parts. In addition, since the thermistor that comes into contact with the outer peripheral surface of the pressure roll 30 is omitted, the possibility that the outer peripheral surface of the pressure roll 30 is damaged by the thermistor is reliably eliminated, and a longer life based on this is achieved. become.

On the other hand, in the sheet passing state control, as shown in FIG. 12, the second thermistor 82 is set in step S16G.
The surface temperature Tf of the fixing roll 28 detected through
When it is determined that the temperature is lower than the third predetermined temperature, the heater with a built-in heating roll, that is, the first heat source 32 built in the heating roll 34 is energized to generate heat (step S16H). Along with the heater with built-in pressure roll,
That is, control is performed so that the second heat source 33 built in the pressure roll 30 is energized to generate heat (step S16J).

In step S16G, the fixing roll 28
If it is determined that the surface temperature Tf is higher than the third predetermined temperature, the power supply to the first heat source 32 is stopped to prevent the first heat source 32 from generating heat (step S16I).
The power supply to the second heat source 33 is also stopped so as not to generate heat (step S16K).

As described above, the surface temperature T of the fixing roll 28
By performing the energization control of the second heat source 33 in accordance with f, the temperature in the nip portion can be more reliably controlled, and the fixing property can be improved.

In the first modified example described above,
In the standby state control, the first and second heat sources 32, 33
The first thermistor 80 for detecting the surface temperature Th of the heating roll 34 is used to control the temperature of the heating roll 34. However, in the paper passing state control, the first thermistor 80 is not used at all and the fixing roll 28 The first and second heat sources 32 and 33 are controlled via a second thermistor 82 for detecting the surface temperature Tf of the first and second heat sources. For this reason, as shown in FIG. 13 as a second modification, the first thermistor 8
0 can be configured to be used as a sensor for detecting a temperature abnormality in the sheet passing control state.

That is, as shown in FIG. 13, in a control circuit for controlling the first heat source 32 by the control device 86, an emergency cutoff switch 90 is interposed in series with the first heat source 32. Have been. Further, the second thermistor 82 for detecting the surface temperature Tf of the fixing roll 28 is connected to the control device 86 via the fixing roll rotation control device 94A, and detects the surface temperature Th of the heating roll 34. The first thermistor 80 is connected to a control device 86 via a heating roll standby control device 94B.
Here, the fixing roll rotation control device 94A and the heating roll standby control device 94B are alternatively connected to the control device 86 via a first switch 92.

On the other hand, a heating roll rotation abnormality control device 94C is connected to the first thermistor 80, and the control device 94B and the heating roll standby time control device 94B are selectively connected via a second switch 96. Is connected to the first thermistor 80. It should be noted that the heating roll rotation abnormality control device 94
When C detects a heating abnormality during the rotation of the heating roll 34,
The switch 90 is configured to be turned off via the relay 98.

In the circuit configuration of the second modified example, in the standby state, the first and second changeover switches 92 and 96 are switched as shown by broken lines, and the control device 86 operates in the standby state. In state control, the first
Based on the detection result from the thermistor 80, the heat generation of the first and second heat sources 32 and 33 is controlled. On the other hand, in the sheet passing state, the first and second changeover switches 92 and 96 are switched as shown by the solid line.
The control device 86 controls the first and second heat sources 32 and 33 via the second thermistor 82 in the sheet passing state control.
The heat generation control of is executed.

Here, in this sheet passing state, the first thermistor 80 is connected to the heating roll rotation abnormality control device 94C via the second changeover switch 96. The control device 94C includes a first
Roll 3 based on the detection result from thermistor 80
The temperature abnormality of No. 4 can be detected. For example, when the surface temperature Th of the heating roll 34 exceeds an allowable range in which safety can be ensured, the heating roll rotation abnormality control device 94C outputs a control signal to a relay 98, and switches the switch 90 via the relay 98. Cut and heat roll 3
The power supply to the first heat source 32 built in the power supply 4 is forcibly shut off, and overheating is prevented in advance to ensure safety.

In FIG. 13, the second heat source 33
The circuit configuration related to this is omitted.

In the first modified example described above,
Although the control procedure is configured such that the energization times to the first and second heat sources 32 and 33 are the same time, the present invention is not limited to such a setting, and for example, a timer and a latch circuit may be used. The time for energizing the second heat source 33 may be set to be longer than the time for energizing the first heat source 32 by using the method described above. Generally, the heat generation capacity of the second heat source 33 built in the pressure roll 30 is set smaller than the heat generation capacity of the first heat source 32 built in the heat roll 34. Because.

[0130]

As described above, according to the present invention, there is provided a fixing device which does not deteriorate the fixing property even when the conveying speed of the unfixed sheet, that is, the paper passing speed is increased. Become.

Further, according to the present invention, there is provided a fixing device capable of substantially maintaining the surface temperature of the fixing roll at the fixing temperature even when the conveying speed of the unfixed sheet, that is, the paper passing speed is increased. Will be provided.

[0132]

[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 diagram showing an arrangement state of a first heat source in a heating roll.

FIG. 4 is a front view showing a configuration of a driving mechanism.

FIG. 5 is a block diagram showing a system configuration for controlling the temperature of a heat source.

FIG. 6 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. 7 is a flowchart showing a main routine of a control procedure for controlling a heat source in the control device.

8 is a flowchart showing a subroutine of standby state control in the main routine shown in FIG. 7;

FIG. 9 is a flowchart illustrating a subroutine of sheet passing state control in the main routine shown in FIG. 7;

FIG. 10 is a diagram showing a change in the temperature of the fixing belt on each roll when the control procedure shown in FIGS. 7 to 9 is executed.

FIG. 11 is a flowchart showing a procedure of a first modified example of a subroutine of standby state control in the fixing device according to the present invention.

FIG. 12 is a flowchart illustrating a control procedure of a first modified example of a subroutine of a sheet passing state control in the fixing device according to the present invention.

FIG. 13 is a circuit diagram schematically showing a circuit configuration for detecting an abnormality of a control device in the fixing device according to the present invention.

FIG. 14 is a front view schematically showing a configuration of a conventional fixing device.

FIG. 15 shows a fixing device having a conventional configuration shown in FIG.
FIG. 9 is a diagram illustrating a change in the temperature of the fixing belt on each roll when a control operation is performed in a state where the surface temperature of the heating roll is kept constant.

FIG. 16 shows a fixing device having a conventional configuration shown in FIG.
FIG. 7 is a diagram illustrating a change in the temperature of the fixing belt on each roll when the priority control is performed.

FIG. 17 is a diagram showing a change in temperature during continuous paper feeding when the priority control shown in FIG. 16 is executed.

[Explanation of symbols]

 Reference Signs List 10 Fixing device 12 Housing 14 Bottom plate 16 Side plate 18 Upper cover part 20 Left cover part 22 Swing lever 24 First support shaft 26 Second support shaft 28 Fixing roll 28A Core part 28B Roll body 30 Pressure roll 30A Core metal Unit 30B Roll body 32 First heat source 33 Second heat source 34 Heating roll 36 Fixing belt 38 Oil application roll 40 First coil spring 42 Second coil spring 44 Guide plate 46 Inlet port 48 Paper discharge path 50 Lower paper discharge Roll 52 Drive mechanism 54 Upper paper 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 Idle gear 74 Third driven gear 76 Peeling claw 78 Discharge Paper sensor 80 First thermistor 82 Second thermistor 84 84 Third thermistor 86 Controller 88A First heater driver 88B Second heater driver 88C Third heater driver 90 Switch 92 First selector switch 94A Fixing roll rotation control device 94B Heating roll standby control device 94C Heat roll rotation abnormality control device 96 Second changeover switch 98 Relay EB Endless belt GE Output gear S Unfixed sheet

Claims (6)

[Claims] An image forming apparatus comprising: a fixing roll; and a pressure roll that rolls in contact with the fixing roll at a predetermined pressure. In one direction to fix the unfixed toner on the sheet, wherein the fixing roller is disposed adjacent to the side opposite to the side on which the pressure roll is disposed. A heating roll having a heat generating means disposed therein, the sheet being passed endlessly between the heating roll and the fixing roll, and receiving heat transfer from the heat generating means and passing through the rolling contact portion. A heat transfer belt for heating the unfixed toner, and a standby state control for maintaining a surface temperature of the heating roll in a predetermined temperature range in a standby state. And a control means for performing a paper passing state control to maintain a degree within a predetermined temperature range a fixing device according to claim. 2. A fixing roll comprising: a fixing roll; and a pressurizing roll which rolls in contact with the fixing roll at a predetermined pressure. In one direction to fix the unfixed toner on the sheet, wherein the fixing roller is disposed adjacent to the side opposite to the side on which the pressure roll is disposed. A heating roll having a heat generating means disposed therein, the sheet being passed endlessly between the heating roll and the fixing roll, and receiving heat transfer from the heat generating means and passing through the rolling contact portion. A heat transfer belt for heating the unfixed toner, a determination unit for determining whether the standby state or the paper passing state, and a case where the determination unit determines the standby state, the surface temperature of the heating roll is set to a predetermined temperature range. Keep in And control means for executing a paper-passing state control for maintaining the surface temperature of the fixing roll within a predetermined temperature range when the paper-passing state is determined. apparatus. 3. The apparatus according to claim 2, wherein said discriminating means discriminates a sheet passing state when a sheet passing command is received, and discriminates a standby state when no sheet passing command is received.
3. The fixing device according to claim 1. 4. The apparatus according to claim 1, wherein the control unit further includes a first detection unit that detects a surface temperature of the heating roll, and a second detection unit that detects a surface temperature of the fixing roll. Controlling the heat generating means based on a detection result of the first detecting means, and controlling the heat generating means based on a detection result of the second detecting means in the sheet passing state control. Claim 1
Or the fixing device according to 2. 5. The apparatus according to claim 1, further comprising: second heat generating means built in said pressure roll; and third detection means for detecting a surface temperature of said pressure roll. The fixing device according to claim 1. 6. The control device according to claim 5, wherein said control means controls said second state based on a detection result of said third detection means in said standby state control.
The fixing device according to claim 5, wherein the heat generating unit is controlled.