JP2003107938A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent rise of the temperature at a nonpaper passing part when papers of a small size pass through continuously. SOLUTION: This fixing device is provided with a fixing roller 24, a pressurizing roller 26, a heating roller 28 arranged separated from the fixing roller, a fixing belt 32 bridged to this heating roller and a fixing roller, a heating source 30 incorporated in the heating roller for heating the fixing belt, a spring 36 imparting prescribed tension to the fixing belt, and a control mechanism 60 for controlling the heating source to fix unfixed toner by making a sheet carrying the unfixed toner pass between the pressurizing roller and the fixing roller. The thickness of the heating roller is set to be in a range >=0.1 mm and <=.7 mm. A control mechanism 60 controls driving of the heating source to stop in a standby state. The heating source is provided with a first heater 30A having a heating range corresponding to the maximum size of the sheet desired to fix and a second heater having a heating range narrower than that of this first heater 30A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in a copying machine, a printer, a facsimile, etc., for melting and pressure-bonding unfixed toner on a sheet and fixing it on the sheet.

[0002]

2. Description of the Related Art In a recent fixing device for an electrophotographic apparatus, as shown in FIG. 12, a fixing roller R1 and a heating / tensioning roller (hereinafter simply referred to as "heating roller").
A technique has been developed in which a belt fixing method in which a fixing belt B is stretched between R3 and a pressure roller R2 that presses the fixing belt B from below is provided, and preheating of the recording medium D are combined. As a result, 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 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 improved, and a clear fixed image without offset can be obtained even when oilless or 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 roller system.

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

An oil application roller R4 is provided above the fixing belt B. A guide plate G serving as a recording medium support is provided below the fixing belt B with a gap.
Is provided, and a heating path P for the recording medium is formed between the lower portion of the fixing belt B and the guide plate G. The fixing belt B is
The heating roller R3 is pressed by the pressing lever U in the direction to be separated from the fixing roller R1, so that a desired tension is obtained, and the fixing roller R1 drives the fixing roller R1 to perform stable rotation without slips or looseness. Can be done.

[0005]

The belt-type fixing device having the above-mentioned structure has the above-mentioned characteristics, but
It takes a so-called warming-up time for raising the temperature in the nip portion to the fixing possible temperature at the time of turning on the power supply or restarting printing (specifically, waiting time exceeding 30 seconds, which is pointed out in the literature etc. The problem was pointed out. That is, in the belt type fixing device,
Due to its structure, the heater H built in the heating roller R3
For example, in order to raise the temperature in the nip portion to the fixing possible temperature by turning on the halogen lamp, first, the outer peripheral surface of the heating roller R3 itself is raised to the fixing target temperature, and the outer peripheral surface of the heating roller R3 is heated. It is necessary to heat the fixing belt B which is in contact with the fixing belt B, and to transfer heat to the nip portion as the fixing belt B travels endlessly to heat the nip portion to a fixable temperature.

As described above, in comparison with the conventional fixing device composed of the combination of the heating roller and the pressure roller, the warming-up time is inevitably long under the same conditions. Therefore, it is conceivable that the heater H is driven to control the heat generation of the heating roller R3 during standby, and the outer peripheral surface of the heating roller R3 is maintained at a predetermined standby temperature.

However, in the recent demand for energy saving, it is extremely wasteful to drive the heater H to consume energy because of the standby state in which the printing operation may be restarted at any time. And it does not match the demands of the times.

On the other hand, in recent years, on the other hand, since the heater incorporated in the heating roller corresponding to each of the large size and the small size of the sheet is disposed over the entire width direction of the heating roller in recent years, It has been pointed out that the temperature of the non-sheet passing portion rises during continuous feeding of small size paper, and the offset resin and bearings arranged at the end of the heating roller are thermally damaged. Improvement is required.

The present invention has been made in view of the above-mentioned circumstances, and a main object of the present invention is to provide a fixing device capable of preventing an increase in temperature of a non-sheet passing portion during continuous feeding of small size sheets. Is to provide.

Another object of the present invention is to provide a fixing device capable of shortening the warming-up time and improving the usability for consumers while surely achieving energy saving.

[0011]

[Means for Solving the Problems]
According to a first aspect of the present invention, in a fixing device according to the present invention, a fixing roller, a pressure roller that contacts the fixing roller at a predetermined pressure, and a fixing roller that is separated from the fixing roller. A heating roller provided, a fixing belt endlessly wound around the heating roller and the fixing roller, and a built-in heating roller, which heats the fixing belt and transfers the fixing roller and the pressure roller. Heat generating means for heating the unfixed toner on the sheet passing through the sheet, tension applying means for applying a predetermined tension to the fixing belt, and control means for controlling the heat generating means. In a fixing device for fixing the unfixed toner on the sheet by passing the carried sheet along the one direction in the rolling contact portion, the thickness (t) of the heating roller is 0. It is set in a range of 1 mm or more and 0.7 mm or less, and the control means controls to stop the driving of the heat generating means in the standby state, and the heat generating means corresponds to the maximum width size of the sheet to be fixed. It is characterized in that it is provided with a first heater having a heat generation range described above and a second heater having a heat generation range narrower than the first heater.

According to a second aspect of the present invention, the fixing device according to the second aspect of the present invention includes a fixing roller, a pressure roller that comes into rolling contact with the fixing roller at a predetermined pressure, and a fixing roller that is separated from the fixing roller. The heating roller, a fixing belt endlessly wound around the heating roller and the fixing roller, and the heating roller, which is built in the heating roller, heats the fixing belt to transfer the contact portion of the fixing roller and the pressure roller. An unfixed toner is carried on the surface by a heating means for heating the unfixed toner on the passing sheet, a tension applying means for applying a predetermined tension to the fixing belt, and a control means for controlling the heating means. In the fixing device for fixing the unfixed toner on the sheet by passing the formed sheet through the rolling contact portion in one direction, the thickness (t) of the heating roller is 0. It is set in the range of mm or more and 0.7 mm or less, and the control means controls to stop the driving of the heat generating means in the standby state, and the heat generating means sets the size of the minimum width of the sheet to be fixed. It is characterized by including a second heater having a corresponding heating range and a first heater having a heating range obtained by excluding the heating range of the second heater from the heating range corresponding to the maximum width size. .

According to the third aspect of the fixing device of the present invention, the total heat capacity X (cal / ° C.) of the heating roller and the fixing belt satisfies the relationship of 2.4 ≦ X ≦ 32. The feature is that it is set to.

According to a fourth aspect of the fixing device of the present invention, the control means controls so that only the first heater is driven in the warming-up state from the standby state. It is characterized by doing.

According to a fifth aspect of the fixing device of the present invention, the control means drives the first and second heaters at the same time in the warming-up state from the standby state. It is characterized by controlling as follows.

According to a sixth aspect of the fixing device according to the present invention, the control means, in the state where the warming-up is completed, is the first or the first, depending on the size of the sheet to be passed. It is characterized in that the second heater is selectively driven and controlled.

According to a seventh aspect of the fixing device of the present invention, the control means selectively selects the heating mode in accordance with the size of the sheet to be fed in the state where the warm-up is completed. It is characterized by switching.

According to the eighth aspect of the fixing device of the present invention, the control means drives only the first heater when the size of the sheet to be fed is large. It is characterized by controlling so that only the second heater is driven in the case of a small size.

According to the ninth aspect of the fixing device of the present invention, the control means controls the size of the sheet to be passed next, even if the size of the sheet to be passed is small. Is large in size, it is controlled so that only the first heater is driven.

According to a tenth aspect of the fixing device according to the present invention, the fixing belt is provided with a metallic endless base material.

According to the eleventh aspect of the fixing device of the present invention, the endless base material is made of nickel electroforming.

According to a twelfth aspect, the fixing device according to the present invention is characterized in that the fixing belt includes an endless base material made of synthetic resin.

According to the thirteenth aspect of the fixing device of the present invention, the endless base material is made of polyimide.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION 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 is fixed as a housing structure to an electronic image forming apparatus (not shown) such as a frame of an electronic printer. Housing 1
It is equipped with 2. The housing 12 includes a bottom plate 14 directly fixed on the device frame, and side plates 16 standing upright from both front and rear edges of the bottom plate 14. Incidentally, although FIG. 1 is drawn as a front view and the details will be described later, the unfixed sheet having unfixed toner carried on the upper surface is conveyed from the right side to the left side in the drawing through a conveyance mechanism (not shown). It is set to be transported.

Here, a sliding bracket 18 on which a heating roller 28, which will be described later, is rotatably supported is slidable in the upper part of the housing 12 with respect to both side plates 16 in the vertical direction in the figure. Is attached to. Further, a swing bracket 20 on which a pressure roller 26, which will be described later, is rotatably supported is rotatably supported around the support shaft 22 with respect to both side plates 16 in the lower part of the housing 12. It is supported by a plate.

The fixing device 10 has, as a roller structure, a fixing roller 24 rotatably supported on both side plates 16 so as to be rotatable about a fixed axis, and substantially below the fixing roller 24 (specifically, left in the drawing). Of the fixing roller 24 and the pressure roller 26 rotatably supported by the swing bracket 20 around a fixed axis set parallel to the fixed axis of the fixing roller 24 in a state of rolling contact with the fixing roller 24 at an angle. The heating roller 28 is rotatably supported by the sliding bracket 18 in a state of being positioned substantially above.

Further, the fixing device 10 includes the heating roller 2
A heating source 30 such as a halogen lamp, which is disposed inside 8 (which will be described later in detail; the heating source 30 includes first and second heaters 30A and 30B);
A fixing belt (heat transfer belt) 32 wound endlessly around the fixing roller 24 and the heating roller 28 is further provided.

The fixing roller 2 will be described in detail later.
4 is configured as an elastic roller, while the pressure roller 26
Is composed of a roller having a hardness on the roller which is harder than that of the elastic roller. On the other hand, the swing bracket 20 is urged by the first coil spring 34 to rotate about the support shaft 22 in the direction in which the pressure roller 26 is in pressure contact with the fixing roller 24. As a result, the fixing roller 24 and the pressure roller 26
At the rolling contact portion (nip portion) of the fixing roller 24 and the rolling contact portion of the fixing roller 24, the fixing roller 24 and the rolling roller contact each other with a predetermined pressure contact force.
Will be indented at the rolling contact part. That is, the nip width is set to be sufficiently secured.

Further, the fixing device 10 is provided between each end of the sliding bracket 18 and the corresponding side plate 16,
A second coil spring 36 is further provided for urging the heating roller 28 in a direction away from the fixing roller 24 and applying a predetermined tension to the fixing belt 32. The second coil springs 36 are provided in front and rear pairs at the left and right ends, respectively.

Further, a take-in guide plate 38 for guiding the unfixed sheet toward the rolling contact portion is attached to the above-mentioned housing 12, and the fixed sheet which has passed the rolling contact portion and the fixing operation is completed is discharged. A paper discharge guide plate 40 that conveys the paper toward the paper mouth is attached. Further, the housing 12 has an outer peripheral surface of the fixing roller 24,
The portion where the fixing belt 32 is not wound, and
A thermistor 42 is attached to detect the surface temperature of a portion located immediately upstream of the rolling contact portion in the rotation direction of the fixing roller 24. Here, in this embodiment, the thermistor 42 employs a contact type structure in which the surface temperature of the detected portion is detected by contacting the surface of the detected portion.

The temperature detection position of the thermistor 42 is not limited to the above-mentioned outer peripheral surface of the fixing roller 24 and the portion where the fixing belt 32 is not wound, but is wound around the outer periphery of the fixing roller 24. The outer peripheral surface of the rotating fixing belt 32 may be attached so as to detect the surface temperature of a portion located immediately upstream of the rolling contact portion with respect to the rotation direction of the fixing roller 24. .
In this case, the thermistor 42 is preferably a non-contact type.

Then, the leading end of the unfixed sheet conveyed toward the fixing device 10 via a conveying mechanism (not shown) first touches the upper surface of the take-in guide plate 38, and is slanted upward while being guided by this. Further, the unfixed sheet guided by the take-in guide plate 38 first comes into contact with the outer peripheral surface of the pressure roller 26 and then the outer peripheral surface of the pressure roller 26. It is set so as to be guided along the rolling contact portion between the fixing roller 24 and the pressure roller 26.

In the fixing device 10 having the above-described structure, the unfixed sheet S conveyed onto the take-in guide plate 38 via the conveying mechanism (not shown) takes in the lower surface on which the unfixed toner is not adhered. While being contacted and supported by the guide plate 38, the fixing belt 32 is guided toward the rolling contact portion (nip portion) between the fixing roller 24 and the pressure roller 26 around which the fixing belt 32 is wound, and the fixing rollers 24 and 26 are pressed against each other. By being inserted in this state, the unfixed toner is thermocompression-bonded and fixed on the sheet.

The various constituent elements described above will be described individually in sequence below. {Explanation of the fixing roller 24}
A cored bar portion 24A that is rotatably supported by the side plate 16 via a bearing 44 (shown in FIG. 2), and a roller that is coaxially arranged around the cored bar portion 24A and on which the fixing belt 32 is wound. And a main body 24B. The outer diameter of the fixing roller 24 is 25.0 m in this embodiment.
It is set to m. Here, in this one embodiment,
The cored bar portion 24A is formed of an iron shaft having a diameter of 15 mm, and the roller body 24B is a silicone rubber heat resistant elastic body (specifically, an ascended roller on the roller) attached to the outer periphery of the cored bar portion 24A with a thickness of 5 mm. C hardness is 23 degrees).

As shown in FIG. 2, a first driven gear 46 is coaxially attached to a shaft portion located at one end of the cored bar portion 24A via a one-way clutch 48, which will be described in detail later. The first driven gear 46 is meshed with a second driven gear 50 coaxially attached to one end of a metal core portion 26A of the pressure roller 26, which will be described later. On the other hand, although not shown in detail, the second driven gear 50
A drive gear forming a part of the drive mechanism 52 is meshed with. In this way, the driving force from the driving mechanism 52 is transmitted to the second driven gear 50 via this driving gear as a rotational force in the counterclockwise direction in FIG.
The rotational force is transmitted to the driven gear 46 as a clockwise force in the figure, and the rotational force is transmitted to the fixing roller 24 via the one-way clutch 48.

{Description of One-Way Clutch 48} Here, the one-way clutch 48 allows rotation of the fixing roller 24 relative to the first driven gear 46 in the clockwise direction in the drawing, but in the counter-clockwise direction in the drawing. It is configured to lock relative rotation, in other words, to integrally rotate both. That is, the fixing belt 32 is the pressure roller 26.
The fixing roller 24 is frictionally engaged with the fixing belt 24.
2 is frictionally engaged with the fixing roller 2 by the pressure roller 26.
4 and the fixing belt 32 are driven (rotated together), the peripheral speed of the fixing roller 24 rotating clockwise in the drawing is
The peripheral speed of the pressure roller 26 is the same as that of the pressure roller 26, and the rotation of the fixing roller 24 is set to be slightly faster than the rotation of the first driven gear 46.

{Explanation of the pressure roller 26} As described above, the pressure roller 26 includes the core metal portion 26A rotatably supported by the side plate 16 via the bearing 54 and the outer periphery of the core metal portion 26A. And a roller body 26B disposed coaxially with the roller main body 26B, and the roller outer diameter is set to 24 mm. Here, in this embodiment, the cored bar portion 26A is
Formed from an iron pipe with an outer diameter of 21 mm and a wall thickness of 2 mm,
The roller body 26B has a thickness of 1.5 on the outer periphery of the cored bar portion 26A.
It is formed of a silicone rubber heat-resistant elastic body (specifically, a roller having a ASKER C hardness of 74 to 75 degrees on a roller harder than the fixing roller 24 described above) mounted in mm.

As described above, the second driven gear 50 is coaxially fixed to the shaft portion provided at one end of the cored bar portion 26A, and the second driven gear 50 has the above-mentioned structure. The first driven gear 46 meshes with each other, and the driving force from the first driven gear 46 is directly transmitted to the second driven gear 50 via a drive gear (not shown), so that the pressure roller 26 is opposite to the fixing roller 24. Is configured to be rotationally driven in the counterclockwise direction.

In this embodiment, the pressure roller 26 is set as the main drive for conveying the unfixed sheet, and the peripheral speed of the fixing roller 24 is increased even when the fixing roller 24 is thermally expanded. The gear ratios of the first and second driven gears 46 and 50 are set so as not to become higher than the peripheral speed of the pressure roller 26. That is, the rotation speed when the fixing roller 24 is rotated by the first driven gear 46 is the same as that of the fixing belt 32.
It is set so as to be slightly slower than the rotational speed at which the pressure roller 26 is frictionally engaged with and rotated by the pressure roller 26.

On the other hand, in this embodiment, the pressure roller 26 is not located immediately below the fixing roller 24, but is located in the conveying direction of the unfixed sheet rather than below the fixing roller 24. When the line segment passing through both the center points of the heating roller 28 and the fixing roller 24 is used as the base line, the base line, the fixing roller 24, and the pressure roller 26 are disposed along the downstream side. It is arranged at a position such that the angle formed by a line segment passing through both center points of is a predetermined acute angle. The line segment passing through the center points of both the fixing roller 24 and the pressure roller 26 is set to be substantially orthogonal to the transport direction of the unfixed sheet.

{Explanation of Heating Roller 28} In this embodiment, the heating roller 28 incorporating the above-mentioned heating source 30 has a diameter of 18 mm and a wall thickness of 0.1 mm on the outer peripheral surface of an iron pipe cored bar. It is composed of a PTFE coating layer having a thickness of 20 μm. That is, the heating roller 28 is configured to have a thin cored bar for the purpose of shortening the warming-up time as described later. Both ends of the heating roller 28 have bearings 5
6 is rotatably supported via 6 and each bearing 5
A collar 58 made of a heat-resistant resin, polyetheretherketone (PEEK), is inserted inside 6 to prevent the fixing belt 32 from meandering and shifting during endless running.

Inside the heating roller 28, the heating source 3
Although the first and second heaters 30A and 30B as 0 are installed side by side, in this embodiment, the first heater 30A has a large sheet size. The halogen lamp is set to be turned on in the case of (A3 portrait or A4 landscape) and has a maximum output of 800 W. In addition, the second heater 30B
Is set to turn on when the size of the sheet to be fed is small (A4 portrait or smaller), and the maximum output is 6
It is composed of a 00W halogen lamp.

Here, the above-mentioned first and second heaters 3
As shown in FIG. 3, 0A and 30B are formed to have respective width dimensions. That is, the first heater 30A corresponding to the large size is set to have a width smaller than the width of the fixing belt 32 and larger than the width of the large sheet. The second heater 30B corresponding to the small size is set to have a width dimension smaller than the large size sheet width dimension and larger than the small size sheet width dimension.

{Explanation of the fixing belt 32} The above-mentioned fixing belt 32 is 1 square cm of the fixing belt 32 so that the unfixed toner on the unfixed sheet S can be fixed to the fixing temperature without giving an excessive amount of heat. The heat capacity per unit is 0.
Those in the range of 002 cal / ° C to 0.025 cal / ° C are preferable.

Therefore, in this embodiment, FIG.
As shown in FIG. 2, the fixing belt 32 includes an endless belt base 32a made of polyimide resin having an inner diameter of 40 mm and a thickness of 70 μm, and a PFA having a thickness of 30 μm coated on the outer peripheral surface (surface layer) of the belt base 32a. And the heat-resistant release layer 32b. In addition, in order to improve the fixing image quality, the thickness of 3
An elastic layer made of silicone rubber or the like may be coated to a thickness of 00 μm. In this case, the PFA heat-resistant release layer 32b is coated on the outer peripheral surface of the elastic layer.

Here, it goes without saying that the present invention is not limited to the use of the polyimide resin as the belt base 32a, and a nickel electroformed metal belt can be used. When the nickel electroformed metal belt is used as the belt base 32a, the thickness of the belt base 32a is, for example, 4 mm.
The surface of the belt base 32a is coated with a heat-resistant silicone rubber with a thickness of 300 μm.
Further, on the outer periphery of this heat-resistant silicone rubber layer, as in the case where the material of the belt base 32a is polyimide resin, a thickness of 3
A structure is adopted in which the heat-resistant release layer 32b made of PFA and covered with 0 μm is coated.

{Explanation of Tension Applying Mechanism to Fixing Belt 32} As described above, in this embodiment, the heating roller 28 is separated from the fixing roller 24 as a mechanism for applying tension to the fixing belt 32. The second coil spring 36 that biases the second coil spring 36 is provided.

That is, the heating roller 28 is urged through the sliding bracket 18 by the urging force of the second coil spring 36.
The fixing belt 32, which is biased in the direction away from the fixing roller 24 and is endlessly stretched between the heating roller 28 and the fixing roller 24, is stretched in a tensioned state with a predetermined tension.

As described above, by the action of the second coil spring 36, the fixing belt 32 frictionally engages with the pressure roller 26 and rotates together, and in accordance with the rotation of the fixing belt 32, the fixing roller 24 rotates. Is driven by the fixing belt 32 in a stable state without slipping or loosening.

{Structure of Control System} On the other hand, the fixing device 10 drives and controls the above-mentioned driving mechanism 52, and also includes the heating source 30 (that is, the first and second heaters 30A, 30A) incorporated in the heating roller 28. 30B) for heat generation control,
As shown in FIG. 5, a control device 60 is provided. To the control device 60, only one thermistor 42 is connected as described above for heat generation control of the heating source 30 (specifically, heat generation control at the time of simultaneous start of fixing belt rotation control). The heating source 30 is configured to control heat generation based only on the detection result.

From the viewpoint of heat generation control, the control device 60 has first and second heater drivers 62A and 62B.
Are connected, and are configured to control the first and second heaters 30A and 30B as heating sources via the first and second heater drivers 62A and 62B, respectively. Further, the control device 60 controls the fixing belt 32.
From the viewpoint of running control of the printer, it has an input terminal for receiving a sheet passing command (print start signal) from a printer control unit (not shown) and an output terminal for outputting a print permission signal to the printer control unit. The switch 64 is connected.

{Description of Heat Generation Control Method by Control Device 60} Next, a heat generation control method (control procedure) of the heating source 30 in the control device 60, which is a feature of the present invention, will be described.

First, the control device 60 energizes the heating source 30 and turns on the corresponding first or second heater (halogen lamp) to generate heat only under the following two conditions. Is set. That is, (1) a print start signal, that is, a print start signal from a printer controller (not shown) that controls the entire electronic printer (not shown),
When the temperature detected by the thermistor 42 is a ready state (or warm-up state) until the fixing temperature is detected after the fixing operation start signal is output; (2) The temperature detected by the thermistor 42 can be fixed When the temperature is detected and a print permission signal is output to the printer control device, and based on this, the fixing operation state from when the printer control device starts the printing operation to when the print end signal is output is defined; Only in the two cases, the heating source 30 is set to generate heat. And
In the case of (1) above, only the first heater 30A corresponding to the large size is energized (that is, the second heater 30B is not energized) and only this is driven to generate heat. There is.

On the other hand, in the case of the above (2), the first or second heater 30 is used depending on the size of the sheet to be passed.
A and 30B are set to be selectively driven. More specifically, when it is determined that the size of the sheet to be passed is large, it is set unconditionally so that the first heater 30A corresponding to the large size is selectively driven. Has been done. In addition, when it is determined that the size of the sheet to be passed is a small size, in principle, the second heater 30B corresponding to the small size is set to be selectively driven. However, even when the size of the sheet to be passed is small in this way, if the size of the sheet to be passed immediately after is large, the second heater 30B is not driven, It is set to selectively drive the first heater 30A for large size.

In the case where the standby state from the output of the print end signal to the output of the next print start signal is defined, the control device 60 sets the heating source 30 to the stopped state and does not perform any operation. It is set not to generate heat.

As described above, the control device 60 controls the heating source 30 in the waiting state for printing, that is, in the waiting state.
Since no heat generation operation is performed via the, the effect of energy saving (power saving) is surely achieved.

When the power switch 64 is turned on, the printer controller is set to output a print start signal unconditionally in this embodiment, whereby the operator can set the power switch 64. When is turned on, the printable state is quickly achieved.

On the other hand, in this standby state, the heating source 30 is not operated at all so that the heating roller 28
The surface temperature of the heating roller 28 is reduced to the room temperature level.
Since the thickness of the heating roller 28 is thin, the condition (1) ready state is defined and the heating roller 30 heats up from the room temperature even when the heating roller 28 is heated from the room temperature state. The temperature rise time until the outer peripheral surface of the heating roller 28 reaches the predetermined target fixing temperature after being transmitted to the outer peripheral surface in a short time is extremely short.

As described above, the time t1 from the activation of the heating source 30 until the outer peripheral surface of the heating roller 28 reaches the predetermined fixing target temperature, and the fixing belt 32 heated on the outer peripheral surface of the heating roller 28 are The total time t2 until the rolling contact portion rises to a predetermined fixing-enabling temperature due to the endless traveling is a so-called warming-up time. As described later, the heating source 30 is started. Accordingly, in a state where the endless belt 32 starts traveling in synchronization with this, t1 is about 6 seconds and t2 is about 9 seconds.
It was seconds. That is, even when the temperature of the heating roller 28 is raised from the room temperature under the above-mentioned condition (1) in this embodiment, the warming-up time is about 15 seconds, which is the same as that of the operator. It is a value that can significantly clear the target 30 seconds as an allowable warm-up time, and the effect that the workability is reliably maintained in good condition is achieved without frustrating the worker. Become.

The optimum range of the wall thickness of the heating roller 28 as a means for shortening the warm-up time will be described later in detail.

Here, in the above-described embodiment, the heating source 30 is provided with the first and second heaters 30A and 30B, and the first and second heaters are provided depending on the size of the sheet to be passed.
Although it has been described that the heaters 30A and 30B are selectively driven and controlled, the fixing roller and the pressure roller will be described below when the first or second heaters 30A and 30B are selectively driven in this manner. The surface temperature distribution of the fixing belt 32 immediately before the entry position into the rolling contact portion (nip portion) will be described according to the selected case.

First, as described above, when (1) the ready state (warming up state) is defined,
Only the large-sized first heater 30A is selectively driven to generate heat. In this case, as described above with reference to FIG. 3, the heat generation range of the first heater 30A is set larger than the width dimension of the large size sheet.
Therefore, the fixing belt 32 can be uniformly heated over almost the entire area in the width direction and exhibit a flat temperature distribution. This means that in the fixing operation state described later, regardless of the size of the sheet to be passed, the sheet can be heated without any problem.

As described above, (2) when the fixing operation state is defined, the first or second heater 30A, 30B is selectively driven according to the size of the sheet to be passed. It is in.

When it is determined that the size of the sheet to be passed is large, the first heater 30A for large size is always driven selectively.
In this case, as shown in FIG. 3, the heat generation range of the first heater 30A is set larger than the width dimension of the large size sheet. Therefore, due to the heat absorption of the sheet being passed,
Even if the surface temperature of the fixing belt 32 drops, the surface temperature of the fixing belt 32 is maintained at the fixable temperature in a range exceeding the width of a large size sheet. As a result, as shown in FIG. 6, even if the surface temperature is lowered over a portion in contact with a large-sized sheet, the surface temperature of the fixing belt 32 is still maintained at the fixable temperature. The fixability of the unfixed toner on the size sheet will be well maintained.

When it is determined that the size of the sheet to be passed is small, in principle, the second heater 30B for small size is selectively driven. In this case, as shown in FIG. 3, the second heater 30B
Although the heat generation range is smaller than the width dimension of the large size sheet, it is set larger than the width dimension of the small size sheet. In this way, even if the surface temperature of the fixing belt 32 drops due to heat absorption by the small-sized sheet during paper passing, the fixing belt 32 fixes the surface temperature within a range exceeding the width of the small-sized sheet. Since the surface temperature of the fixing belt 32 is maintained at the possible temperature, as shown in FIG. 7, the surface temperature of the fixing belt 32 is still maintained at the fixing possible temperature even if the surface temperature of the small-sized sheet is lowered. As a result, the fixing property of the unfixed toner on the small-sized sheet is maintained well.

As described above, when the size of the sheet to be passed is small, the second heater 3 corresponding thereto is used.
Since 0B is selectively driven, an energy saving (power saving) effect can be reliably achieved as compared with the conventional technology that uniformly drives the heater corresponding to the width of the maximum size sheet. Become.

On the other hand, as described above, even if the size of the sheet to be passed is small, if it is determined in advance that the size of the sheet to be passed immediately after is the large size, The large-sized first heater 30A is set to be selectively driven without driving the second heater 30B. As described above, even when the first heater 30A for large size is selectively driven in a situation where a small size sheet is passed, as shown in FIG.
For example, even if the surface temperature of the small-sized sheet is lowered, the surface temperature of the fixing belt 32 is still maintained at the fixable temperature, and the unfixed toner is fixed on the small-sized sheet. Sex will be well maintained.

In the state where the small-sized sheet is passed as described above, the merit of selectively driving the large-sized first heater 30A instead of the small-sized second heater 30B is as follows. It is as follows.

That is, if it is attempted to control the driving so that only the second heater 30B for the small size is turned on in the state where the small-sized sheet is passed, the large-sized sheet is immediately passed. In such a case, even if the first heater 30A for large size is switched to be selectively driven, the surface temperature on the fixing belt 32 does not rise in time, and particularly for small size. Second heater 30
At both ends outside the heat generation range of B, the fixing possible temperature cannot be ensured and fixing failure may occur. However, as in this embodiment, immediately before the sheet to be passed is switched to a large size. In the state in which a small-sized sheet is being passed, the first heater 30A for the large size is previously prepared.
Since it is switched to and driven selectively, the temperature drop at both ends does not occur as described above, and a good fixing operation is executed over the entire area of the large size sheet.

{Description of Control Method of Drive Mechanism 52 by Control Device 60} Next, a control method of the drive mechanism 52 in the control device 60 will be described. In this embodiment, when the above-mentioned condition (1) is satisfied, the control device 60 activates the drive motor (not shown) in synchronization with the activation of the heating source 30, and the first and second drive motors are activated. Driven gear 4
6 and 50 are rotationally driven, and along with this, the fixing belt 32 is set to run endlessly.

In the state where the above-mentioned condition (2) is satisfied, the fixing operation of the unfixed sheet is executed. Therefore, the control device 60 performs the fixing operation similarly to the case of the above-mentioned condition (1). It goes without saying that the belt 32 is set to run endlessly.

Here, the drive mechanism 5 in the controller 60
As the control mode of No. 2, as described above, the drive control may be performed so that the fixing belt 32 runs in an endless manner in synchronization with the activation of the heating source 30, or a predetermined time may be elapsed from the activation of the heating source 30. During the interval, the fixing belt 32 is run endlessly at a running speed (first running speed) lower than the predetermined fixing running speed (second running speed), and after a lapse of a predetermined time, the fixing belt 32 is fixed at the predetermined fixing running speed. The belt 32 may be set to run endlessly. As described above, by causing the fixing belt 32 to run endlessly at low speed at the beginning, it is possible to further shorten the warming-up time.

The switching timing of the traveling speed of the fixing belt 32 is not limited to the time when the predetermined time elapses as described above. For example, the temperature detected by the thermistor 42 is higher than the predetermined fixable temperature. Even if the target temperature is set to be low, the same effect can be obtained even when the target temperature is specified.

Needless to say, the above-mentioned low traveling speed (first traveling speed) does not include zero speed, but the first traveling speed can be set to zero. Of course. In this case,
Until the speed switching timing, the heating source 30 is activated, but the running of the fixing belt 32 is stopped. In this way, the fixing belt 32 is attached to the heating source 3
By driving the vehicle with a delay from the start of 0,
It is possible to shorten the warm-up time.

The above points are summarized in Table 1 below.

[0077]

[Table 1]

As is clear from Table 1, on the data,
It seems that the fixing belt 32 made of polyimide resin is more effective in shortening the warming-up time than the nickel electroforming belt. However, in the case of the nickel electroforming belt, the surface is made to have flexibility. For the purpose of improving image quality,
In the case where the silicone rubber is coated and made of polyimide resin, there is a difference that the silicone rubber is not coated. Since this silicone rubber functions as a heat insulating layer, the warming-up time is extended correspondingly. That is, regardless of whether the fixing belt 32 is made of nickel electroforming or polyimide, substantially the same result is obtained under the same conditions.
We were able to achieve within 0 seconds.

Even if the endless running of the fixing belt 32 is started in a state synchronized with the activation of the heating source 30 as described above, the target warming-up time of 30 seconds or less can be achieved, but the initial value of the fixing belt 32 is reduced. It was found that slowing the running speed is more effective from the viewpoint of shortening the warm-up time. That is, the heating source 30
From the viewpoint of shortening the warm-up time, it has been found that it is optimal to stop the traveling of the fixing belt 32 at the time of starting and then drive and control the drive mechanism 52 so as to endlessly drive the belt.

{Verification of the optimum range of the thickness of the heating roller 28} The thinner the optimum range of the thickness of the heating roller 28, the shorter the temperature raising time is, which is preferable, but it is too thin. If too much, the second belt spring 36 loses the urging force of the second coil spring 36 that applies a predetermined tension to the fixing belt 32, and cannot maintain its own shape, resulting in bending. When the heating roller 28 bends in this way,
The fixing belt 32 is not evenly contacted, and the fixing belt 3
This is not preferable because it causes a problem that heat is not uniformly transmitted to the fixing member 2 and a problem of the deviation of the fixing belt 32 during running.

On the other hand, if the biasing force of the second coil spring 36 is weakened too much, the fixing belt 32 will be loosened, which is not preferable. Therefore, first, the setting condition of the urging force by the second coil spring 36 that does not cause the fixing belt 32 to loosen was verified.

For this verification, the urging force of the second coil spring 36 was gradually increased from 500 g / one side as shown in Table 2 to find a range in which the fixing belt 32 was not loosened.

[0083]

[Table 2]

As is clear from Table 2, the fixing belt 3
In order to prevent slack from occurring in No. 2, the urging force of the second coil spring 36 is at least 1500 g /
It turns out that one side is required. In other words, it has been found that the heating roller 28 needs to have a strength that can withstand the urging force of the 1500 g / second coil spring 36 on one side.

The maximum thickness of the heating roller 28 is
Based on the description in the literature, etc., the warming-up time was set within the range of 30 seconds. Here, as the fixing belt 32 heated on the outer peripheral surface of the heating roller 28 travels endlessly, the time t2 until the temperature of the rolling contact portion rises to a predetermined fixable temperature is as shown in Table 2 above. Since it is known that the heating time is about 20 seconds, the target value of the time t1 from the activation of the heating source 30 to the rise of the outer peripheral surface of the heating roller 28 to a predetermined fixing temperature is set to 10 seconds.

Next, with the biasing force of the second coil spring 36 set to 1500 g / one side, the outer diameter of the heating roller 28 is varied from 12 mm to 30 mm, and the wall thickness at each outer diameter is varied. Then, the amount of deflection, t1 and the weight of each were measured. The results are shown in Table 3.

[0087]

[Table 3]

Based on the results of Table 3, in FIG. 9, in the relationship between the outer diameter of the heating roller 28 and the wall thickness, the deflection amount is 0.2 mm or less, and t1 is within 10 seconds. Is hatched. As is clear from FIG. 9, the thickness of the heating roller 28 is 0.1 mm or more and 0.7 or more.
It has been found that the range within mm is the optimum range that satisfies the above conditions.

In FIG. 9, if the thickness of the heating roller 28 becomes thinner than 0.1 mm, the pressing roller may be deformed such as dented only by pushing it by hand, which is a problem. Even if it is good, the minimum line of 0.1 mm is shown as the allowable thickness.

Here, in the above-mentioned embodiment, the thickness is set to 0.1 mm when the outer diameter of the heating roller 28 is set to 18 mm, and it goes without saying that there is no problem.

As described above, in the present invention, since the thickness of the heating roller 28 is set in the range of 0.1 mm or more and 0.7 mm or less, for example, the heating source 30 is stopped during standby and the heating roller 28 is Even if the temperature is lowered to room temperature, the warming-up time is achieved in a state where it is less than 30 seconds which is the limit value allowed for the waiting time, and both operability and energy saving can be achieved at once. It is possible, and this invention has extremely high industrial applicability.

As described above, it has been found that it is effective to reduce the thickness of the heating roller 28 in order to shorten the warming-up time. However, as described above, the thickness of the heating roller 28 is reduced. In the set state, next, the heating roller 2 which is the greatest feature of the present invention
The definition of the optimum range of the total heat capacity X of 8 and the fixing belt 32 will be described in detail below.

In the case of the roller fixing method which is implemented by the conventional two-roller structure including the fixing roller and the heating roller, the warming-up is completed when the heating roller itself reaches the fixable temperature T1. However, in the case of the belt type fixing system as in the present invention, the inlet temperature of the rolling contact (nip) portion between the pressure roller 24 and the fixing roller 26 with the fixing belt 32 interposed therebetween is the fixing possible temperature. T
When it reaches 1, the warm-up is completed.

Therefore, in order to regulate the warming-up time in the belt type fixing system, the fixing belt 3
The whole 2 needs to be heated, and therefore, the heat capacity of the fixing belt 32 as well as the heat capacity of the heating roller 28 must be taken into consideration in the calculation.

Here, the following formula is known as a formula for calculating the warm-up time (WUT) in the case of the roller fixing system.

WUT = (T1−T2) × P ÷ (E × 1000) (A) In addition, T1: fixing possible temperature (° C.), T2: normal temperature (° C.),
P: Heat capacity (KJ / ° C), E: Supply energy (W ・
s), and heat capacity P = volume (cubic cm) × specific gravity (kg)
/ Cubic cm) x specific heat (kJ / KgK).

That is, when the warming-up time (WUT) of the belt-type fixing method is calculated by using the above calculation formula (A), the heat capacity P includes not only the heat roller 28 but also the heat capacity of the fixing belt 32. It has to be calculated in the state. Below, based on the above-mentioned WUT calculation formula (A), the heating roller 28 and the fixing belt 3 are
The upper limit value and the lower limit value (that is, the optimum range) of the total heat capacity X of 2 will be verified in detail.

In the verification of the total heat capacity X, as a precondition, the urging force of the second coil spring 36 that regulates the tension of the fixing belt 32 is set to a minimum of 1.5 kg / one side, and the heating that can withstand this is applied. The roller 28 has a wall thickness of 0.
The minimum of 1 mm is as described above.
In addition, the minimum thickness of the heating roller 28 is 0.1
By setting the thickness to mm, it is only necessary to consider iron as the material. This is because it is difficult to process aluminum with a thickness of 0.3 mm or less in the current processing technology, and from this viewpoint, when considering the minimum value of the wall thickness, only iron should be considered as the material. Become.

The thickness of the heating roller 28 is 0.3 mm.
In the above cases, the difference between the materials of iron and aluminum is that, when viewed as a heat capacity, the difference in material is included in specific heat x specific gravity, and it is not necessary to separately verify. is there. Therefore, in the following verification, the material of the heating roller 28 is treated as iron.

Next, as a control mode of the drive mechanism 52,
As described above, during the drive control mode in which the fixing belt 32 runs in the endless belt in synchronization with the activation of the heating source 30 (hereinafter referred to as rotation start), and during the predetermined time from the activation of the heating source 30, the fixing is performed. There are two drive control modes (hereinafter referred to as “start after rest”) in which the belt 32 is stopped. However, since the rotating time is different between the two modes, the fixing roller 24, the pressure roller 28, The heat loss from the fixing belt 32 to the air is different, which results in WU
There will be a difference in T. However, WUT is 3
The choice is free within the range that can be achieved within 0 seconds.

Further, there is a difference in heat source (supply source) as an important item in verifying the WUT. That is, although there is a difference in the electric power (wattage) used in the electronic copying apparatus or the electronic printer, since it is generally around 800 (W), in this verification, the large output side of the heating source 30 is used. It is assumed that the power consumption of a certain first heater 30A is 800 (W).

Further, regarding the material of the fixing belt 32,
As mentioned above, there are nickel electroformed metal bases and polyimide synthetic resin bases as the base material. When a nickel electroformed base material is used, the base material is made of silicone rubber. The structure in which the elastic layer of PFA and the release layer made of PFA are coated on the elastic layer is adopted.
On the other hand, when a polyimide base material is used, a structure in which the PFA release layer is directly coated on the base material is used.

Further, the fixable temperature T1 is generally around 165 ° C. in the case of color toner, so T
It shall be verified as 1 = 165 ° C. Under such an assumption, in order to achieve the WUT of 30 seconds or less, the total heat capacity X of the heating roller 28 and the fixing belt 32, which is 30 seconds or less in the above formula (A), and the heat radiation It is necessary to take into consideration the plus and other factors that take into account

Specifically, as a result of repeated experiments, the inventors of the present invention have found that it is sufficient to add the following numerical value to the above-mentioned formula (A) as a plus component. (I) The base material of the fixing belt 32 is made of polyimide, and (i-1) the rotation start: 9 to 10 seconds (i-2) the stationary start: 5 to 6 seconds (ii) When the base material of the fixing belt 32 is made of nickel electroforming and (ii-1) is a rotation start: 20 to 21 seconds (ii-2) is a start after stationary: 12 to 14 seconds

The physical properties of the materials constituting the fixing belt 32 are shown in Table 4 below.

[0106]

[Table 4]

As described above, the lower limit of the total heat capacity X of the heating roller 28 and the fixing belt 32 is calculated in consideration of the plus amount in the expression (A). First, the combination of the outer diameter and the wall thickness of the heating roller 28 capable of maintaining the deflection during the fixing operation of the heating roller 28 to be 0.2 mm or less, and the inner diameter 18
mm, wall thickness 0.1 mm and weight 11 g were selected. Then, the heat capacity of each of the case where the base material of the fixing belt 32 is made of nickel electroforming and the case where it is made of polyimide is selected, and the smaller value of the calculation results is selected.

Specifically, the heating roller 28, the base material of the fixing belt 32, and the PF as the release layer of the fixing belt 32.
By calculating the lower limit values of the respective heat capacities of A and A, and adding the respective lower limit values, the heating roller 28 and the fixing belt 3
The lower limit of the total heat capacity X with 2 was calculated.

Here, when the base material of the fixing belt 32 is made of nickel electroforming, since the outer diameter of the base material is 40 mm, the thickness is 40 μm, and the axial length is 234 mm, the heat capacity thereof is , Π × 4 × 0.004 × 23.4 × 8.9 ×
It becomes 0.10 = 1.05 cal / ° C.

On the other hand, when the base material of the fixing belt 32 is made of polyimide, the base material has an outer diameter of 40 mm and a thickness of 70.
μm and the axial length is 234 mm, the heat capacity of this is π × 4 × 0.007 × 23.4 × 1.4 × 0.2.
4 = 0.69 cal / ° C.

Here, it has been found that the heat capacity of the base material of the fixing belt 32 is smaller when the material thereof is made of polyimide than when it is made of electroformed nickel. Based on this result, a polyimide base material was used as the base material of the fixing belt 32 when the lower limit of the heat capacity was verified.

When the heating roller 28 has an outer diameter of 18 mm, a wall thickness of 0.1 mm, and an axial length of 270 mm, and is made of iron, the heat capacity of the heating roller 28 is π × 1.8 ×.
0.01 x 27.0 x 7.83 x 0.11 = 1.32ca
l / ° C.

Further, the thickness of the release layer made of PFA is 30 μm.
Therefore, the heat capacity of this release layer is π × 4 × 0.00
It is 3 × 23.4 × 2.1 × 0.25 = 0.46 cal / ° C. Therefore, the lower limit of the total heat capacity X of the heating roller 28 and the fixing belt 32 is 1.32 (heat capacity of the heat roller 28) +0.69 (heat capacity of the polyimide base material) +0.46 (heat capacity of the PFA release layer). ) = 2.47 cal / ° C.

Next, the heating roller 28 and the fixing belt 32.
In order to calculate the upper limit of the total heat capacity X of
The maximum allowable time of the UT, which is 30 seconds, is subtracted from the above-mentioned minimum value of plus 5 seconds to obtain 25 seconds. Then, in the above-mentioned formula (A), at 800 (W), the heat capacity P for reaching from room temperature 20 ° C. to 165 ° C. in 25 seconds is calculated, and as a result, the total heat capacity X is set to 3 as the upper limit value.
Obtained 1.4 cal / ° C.

As a result, the lower limit of the total heat capacity X of the heating roller 28 and the fixing belt 32 is 2.47 cal / ° C.
And the upper limit value of 31.4 cal / ° C., the optimum range of this total heat capacity X (cal / ° C.) is 2.4 ≦ X ≦ 3.
It turned out to be 2. It is needless to say that 2.47 ≦ X ≦ 31.4 is more preferable as the optimum range.

As described above, by setting the total heat capacity of the heating roller 28 and the fixing belt 32 to fall within the above range, the warming-up time (WUT) can be more surely shortened to ( More specifically, 30
(Within seconds).

Needless to say, the present invention is not limited to the configuration of the above-described embodiment and can be variously modified without departing from the scope of the present invention.

For example, in the above-mentioned embodiment, the arrangement of the oil applying roller for applying the releasing oil on the outer peripheral surface of the fixing belt 32 is not described.
It is needless to say that the present invention is not limited to such a configuration in which the oil applying roller is not provided, and that a configuration in which the oil applying roller is provided may be adopted. In this case, since the oil application roller is pressed against the fixing belt 32 with a predetermined pressing force, it can be used in cooperation with the second coil spring 36 as the tension applying means described above. Further, it can be used instead of the second coil spring 36.

Further, in the above-mentioned embodiments, the core metal 28a of the heating roller 28 is described as being formed of an iron pipe, but the present invention is not limited to such a structure, and the SUS is not limited thereto. Needless to say, the pipe may be made of stainless steel or aluminum pipe.

Further, in the above-mentioned embodiment, it is explained that only the heat source 30 built in the heating roller 28 is provided as the heat generating means, but the present invention is not limited to such a constitution, and is described above. The pressure roller 26 may be configured so as to include a second heating source incorporated therein. In this case, the second heating source may be a halogen lamp of, for example, 250 W whose maximum output is set smaller than that of the heating source 30 built in the heating roller 28.

It is needless to say that the heating source 30 may use a planar heating element in addition to the halogen lamp described above. That is, its heat generation type,
It goes without saying that the shape of heat generation is not limited at all.

Further, in the above-mentioned embodiment, the first heater 30A has been described as being disposed over the entire width dimension of the large size sheet, but the present invention is limited to such a configuration. First, in FIG. 10 and FIG.
Also, as shown respectively as a second modified example, it may be configured.

The first modification will be described below with reference to FIG. In the first modified example, the sheets to be passed are set so as to be conveyed in a so-called center-aligned state, and as shown in the drawing, the first heater 30A is used.
Is configured in a state in which the central portion corresponding to the second heater 30B is just missing. In other words, the second heater 30B having a heat generation range corresponding to a small size sheet
It is configured to generate heat only in the protruding portion corresponding to the sheet width dimension of a larger size.

A second modification will be described with reference to FIG. In the second modified example, the sheets to be passed are set so as to be conveyed in a so-called edge-aligned state, and as shown in the figure, the first heater 30A is just the second heater 30B. It is configured in a state where the end portion corresponding to is missing. In other words, as in the case of the above-described first modified example, only the protruding portion corresponding to the sheet width dimension of the size larger than the second heater 30B having the heating range corresponding to the sheet of the small size generates heat. Is configured.

In the first and second modified examples configured in this way, the second modified example corresponds to the second embodiment.
The second heater 30B directly corresponds to the heater 30B of the first heater 30B, but the first heater 30A in the above-described embodiment is the first heater 30B in this modification.
And the second heaters 30A and 30B are set to correspond to each other when they are simultaneously driven.

As described above, by constructing the first and second modified examples, the same effect as that of the above-described embodiment can be obtained.

[0127]

As described in detail above, according to the present invention, the thickness of the heating roller is set to be thin and a plurality of heaters corresponding to the size of the sheet to be passed are provided, so that a small-sized sheet can be processed. It is possible to provide a fixing device capable of preventing a temperature rise of a non-sheet passing portion during continuous sheet feeding.

Further, according to the present invention, it is possible to provide a fixing device capable of shortening the warming-up time and improving the usability for the customer while surely achieving energy saving.

[Brief description of 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 cross-sectional view showing a supporting state at an end portion of each roller in the fixing device shown in FIG.

FIG. 3 is a diagram showing an arrangement state and a heat generation range of first and second heaters provided as a heating source.

FIG. 4 is a front view showing the configuration of a fixing belt.

FIG. 5 is a block front view schematically showing a configuration of a control system.

FIG. 6 is a diagram showing a distribution state of the surface temperature of the fixing belt at the nip entrance when a large-sized sheet is being fed while the large-sized first heater is selectively driven.

FIG. 7 is a diagram showing a distribution state of the surface temperature of the fixing belt at the nip entrance when a small-sized sheet is being passed while the second small-sized heater is selectively driven.

FIG. 8 is a diagram showing a distribution state of the surface temperature of the fixing belt at the nip entrance when a small-sized sheet is being fed while the large-sized first heater is selectively driven.

FIG. 9 is a diagram showing the relationship between the outer diameter of the heating roller and the wall thickness.

FIG. 10 is a diagram showing a first modification of the first heater.

FIG. 11 is a diagram showing a second modification of the first heater.

FIG. 12 is a diagram schematically showing a configuration of a conventional belt-type fixing device.

[Explanation of symbols]

10 Fixing device 12 housing 14 Bottom plate 16 side plate 18 Sliding bracket 20 swing bracket 22 spindle 24 fixing roller 24A core bar 24B roller body 26 Pressure roller 26A core 26B roller body 28 Heating roller 30 heating source 30A first heater 30B Second heater 32 fixing belt 34 First Coil Spring 36 Second coil spring 38 Intake guide plate 40 Paper ejection guide plate 42 Thermistor 44 bearing 46 First driven gear 48 one-way clutch 50 Second driven gear 52 Drive mechanism 54 bearing 56 bearing 58 colors 60 control device 62A First heater driver 62B Second heater driver 64 power switch

Claims (13)

[Claims] 1. A fixing roller, a pressure roller for rolling contact with the fixing roller at a predetermined pressure, a heating roller arranged apart from the fixing roller, and an endless member for hanging the heating roller and the fixing roller. The fixing belt that has been passed over and a heating unit that is built in the heating roller and that heats the fixing belt to heat the unfixed toner on the sheet that passes through the rolling contact portion of the fixing roller and the pressure roller; A sheet having tension applying means for applying a predetermined tension to the belt and control means for controlling the heat generating means, and a sheet having unfixed toner carried on its surface passes through the rolling contact portion in one direction. Thus, in the fixing device that fixes the unfixed toner on the sheet, the thickness (t) of the heating roller is 0.1 mm or more and 0.7 mm or more.
The control unit controls the heat generation unit to stop driving in a standby state, and the heat generation unit sets a heat generation range corresponding to the maximum width size of the sheet to be fixed. A fixing device comprising: a first heater having the first heater; and a second heater having a heat generation range narrower than that of the first heater. 2. A fixing roller, a pressure roller for rolling contact with the fixing roller at a predetermined pressure, a heating roller arranged apart from the fixing roller, and an endless suspension of the heating roller and the fixing roller. The fixing belt that has been passed over and a heating unit that is built in the heating roller and that heats the fixing belt to heat the unfixed toner on the sheet that passes through the rolling contact portion of the fixing roller and the pressure roller; A sheet having tension applying means for applying a predetermined tension to the belt and control means for controlling the heat generating means, and a sheet having unfixed toner carried on its surface passes through the rolling contact portion along one direction. Thus, in the fixing device that fixes the unfixed toner on the sheet, the thickness (t) of the heating roller is 0.1 mm or more and 0.7 mm or more.
The control unit controls the heating unit to stop driving in the standby state, and the heating unit sets a heating range corresponding to the minimum width size of the sheet to be fixed. And a first heater having a heat generation range obtained by excluding the heat generation range of the second heater from the heat generation range corresponding to the maximum width size. 3. The total heat capacity X (cal / ° C.) of the heating roller and the fixing belt is set so as to satisfy the relationship of 2.4 ≦ X ≦ 32. The fixing device described in 1. 4. The control means controls so that only the first heater is driven in a state where the standby state is warmed up.
The fixing device described in 1. 5. The fixing device according to claim 2, wherein the control unit controls the first and second heaters to be simultaneously driven in a state where the standby state is warmed up. . 6. The control means selectively drives and controls the first or second heater in accordance with the size of the paper to be passed in the state where the warm-up is completed. The fixing device according to 1 or 2. 7. The control means, in a state where the warm-up is completed, in accordance with a size of a sheet to be fed.
The fixing device according to claim 1, wherein the heating mode is selectively switched. 8. The control means controls so that only the first heater is driven when the size of the sheet to be fed is large, and when the size of the sheet is small, the second heater is driven. The fixing device according to claim 7, wherein only the fixing device is controlled to be driven. 9. The control means drives only the first heater even when the size of the sheet to be passed is small and the size of the sheet to be passed next is large. The fixing device according to claim 8, wherein the fixing device is controlled so as to be controlled. 10. The fixing belt comprises a metallic endless base material.
The fixing device described in 1. 11. The fixing device according to claim 11, wherein the endless base material is made of nickel electroforming. 12. The fixing device according to claim 1, wherein the fixing belt includes an endless base material made of synthetic resin. 13. The fixing device according to claim 12, wherein the endless base material is made of polyimide.