JP2002174975A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device improved in the handleability of a user by shortening warming-up time while surely realizing energy saving. SOLUTION: This fixing device 10 is equipped with a fixing roller 24, a pressure roller 26, a heating roller 28 disposed while separating from the roller 24, a fixing belt 32 laid over the rollers 28 and 24 endlessly, a heating source 30 incorporated in the roller 28 and heating unfixed toner on a sheet and a tensile force applying means for applying specified tensile force to the belt 24. In the device 10, the thickness (t) of the roller 28 is set so that a value at which the shape of the roller 28 is kept against the specified tensile force may be a minimum limit and a value at which the time required to make the temperature of the roller 28 rise from 20 deg.C to 180 deg.C by starting the heating source 30 is within 15 seconds may be a maximum limit.

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 copier, a printer, a facsimile or the like, for melting and pressing unfixed toner on a sheet and fixing the toner on the sheet.

[0002]

2. Description of the Related Art In a recent fixing device for an electrophotographic apparatus, as shown in FIG. 6, a fixing roller R1 and a heating / tension roller (hereinafter simply referred to as "heating roller") R.
A technique has been developed that combines a belt fixing method in which a fixing belt B is stretched between the three and a pressing roller 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 roller method.

The configuration 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 along the transport direction of the recording medium). A 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. Further, a guide plate G as a recording medium support is provided with a gap below the fixing belt B.
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 a direction separating from the fixing roller R1 to obtain a desired tension, and is driven by the fixing roller R1 to rotate stably without slipping or loosening. Can be done.

[0005]

The belt-type fixing device having the above configuration has the above-described features,
When the power is turned on or when printing is resumed, a so-called warming-up time for raising the temperature in the nip portion to a fixable temperature takes a long time (specifically, a waiting time exceeding 30 seconds as pointed out in the literature and the like). 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
In order to raise the temperature at the nip to a fixable temperature by turning on a halogen lamp, for example, first, the outer peripheral surface of the heating roller R3 itself is heated to a fixing target temperature, and the outer peripheral surface of the heating roller R3 is heated. It is necessary to heat the fixing belt B that is in contact with it, transfer heat to the nip portion with the endless running of the fixing belt B, and heat the nip portion to a fixable temperature.

As described above, the warm-up time is longer under the same conditions than in the conventional fixing device including the combination of the heating roller and the pressure roller. Therefore, during standby, it is conceivable that the heater H is driven to control the heat generation of the heating roller R3 so that the outer peripheral surface thereof 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 due to the standby state where the printing operation may be restarted. And do not match the demands of the times.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and a main object of the present invention is to provide a fixing device capable of shortening a warming-up time and improving a user's convenience while reliably achieving energy saving. It is to provide.

[0009]

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 roller, a pressing roller that is in contact with the fixing roller at a predetermined pressure, and a distance from the fixing roller. A heating roller provided, a fixing belt that is endlessly wound around the heating roller and the fixing roller, and a heating roller that is built in the heating roller and heats the fixing belt to form a contact portion between the fixing roller and the pressure roller. Heat generating means for heating the unfixed toner on the sheet passing therethrough; and tension applying means for applying a predetermined tension to the fixing belt. In a fixing device that fixes the unfixed toner on the sheet by passing the toner in one direction, the thickness (t) of the heating roller is set to be opposite to the tension by the tension applying unit. The value that can maintain the shape of the body is set to the minimum, and the value that sets the time required for the heating roller itself to rise from 20 ° C. to 180 ° C. within 15 seconds by activation of the heating means as the maximum limit. It is characterized by:

According to a second aspect of the present invention, there is provided a fixing device, comprising: a fixing roller; a pressure roller which rolls on the fixing roller at a predetermined pressure; and a distance from the fixing roller. Heating roller, a fixing belt that is endlessly wrapped around the heating roller and the fixing roller, and a fixing belt that is built in the heating roller and heats the fixing belt to change the rolling contact portion between the fixing roller and the pressure roller. A heat generating unit for heating the unfixed toner on the passing sheet; and a tension applying unit for applying a predetermined tension to the fixing belt. In the fixing device for fixing the unfixed toner on the sheet by passing along the one direction, the thickness (t) of the heating roller may be such that the tension by the tension applying unit is 1500 g. The values that can maintain its shape against the acting on the heating roller side and minimum, the heating roller itself by the activation of the heating means 2
It is characterized in that a value in which the time until the temperature rises from 0 ° C. to 180 ° C. is within 15 seconds is set as the maximum limit.

According to a third aspect of the present invention, there is provided a fixing device, wherein a fixing roller, a pressing roller which rolls on the fixing roller at a predetermined pressure, and a distance from the fixing roller are provided. Heating roller, a fixing belt that is endlessly wrapped around the heating roller and the fixing roller, and a fixing belt that is built in the heating roller and heats the fixing belt to change the rolling contact portion between the fixing roller and the pressure roller. A heat generating unit for heating the unfixed toner on the passing sheet; and a tension applying unit for applying a predetermined tension to the fixing belt. In a fixing device that fixes the unfixed toner on the sheet by passing along the one direction, the thickness (t) of the heating roller is such that the amount of deflection due to the tension of the tension applying unit is reduced. .2 mm is set to a minimum value, and a maximum value is set to a value within 15 seconds for the heating roller itself to rise in temperature from 20 ° C. to 180 ° C. by activation of the heating means. It is characterized by.

According to a fourth aspect of the present invention, there is provided a fixing device, comprising: a fixing roller; a pressure roller which rolls on the fixing roller at a predetermined pressure; and a distance from the fixing roller. Heating roller, a fixing belt that is endlessly wrapped around the heating roller and the fixing roller, and a fixing belt that is built in the heating roller and heats the fixing belt to change the rolling contact portion between the fixing roller and the pressure roller. A heat generating unit for heating the unfixed toner on the passing sheet; and a tension applying unit for applying a predetermined tension to the fixing belt. In a fixing device that fixes the unfixed toner on the sheet by passing along one direction, the thickness (t) of the heating roller is set in a range of 0.1 mm to 0.7 mm. It is characterized in that it is.

According to a fifth aspect of the present invention, the fixing device further includes a temperature measuring means for measuring a temperature of the fixing roller in order to control a heat generation state of the heat generating means. It is characterized by.

According to a sixth aspect of the present invention, in the warming-up control of the heating means, the fixing device controls the heat generation of the heating means at the start of the warming-up, and delays the heating of the fixing belt with a delay. A second temperature measuring means for measuring the temperature of the heating roller when the traveling is started is further provided.

According to a seventh aspect of the present invention, the temperature measuring means includes a thermistor for measuring a temperature of an outer peripheral portion of the fixing belt located at an outer periphery of the fixing roller. It is characterized by:

Further, according to the invention described in claim 8, the fixing device according to the present invention is characterized in that the temperature measuring means includes a thermistor for measuring the temperature of the outer peripheral surface of the fixing roller.

According to a ninth aspect of the present invention, in the fixing device, the heat generating means includes a halogen lamp built in the heating roller.

According to a tenth aspect of the present invention, in the fixing device, the outer diameter of the heating roller is set to a minimum of 12 mm.

According to the eleventh aspect, the fixing device according to the present invention is characterized in that the pressure roller has a built-in second heat generating means for heating the pressure roller. .

[0020]

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.

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), for example, a frame of an electronic printer. Housing 1
2 is provided. The housing 12 includes a bottom plate 14 directly fixed on the apparatus frame, and side plates 16 erected from both front and rear edges of the bottom plate 14. FIG. 1 is a front view, and the details will be described later. The unfixed sheet having the unfixed toner carried on the upper surface is moved from right to left in the figure via a transport mechanism (not shown). It is set to be transported.

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

Further, the fixing device 10 has a roller configuration in which a fixing roller 24 is rotatably supported on both side plates 16 so as to be rotatable around a fixed axis, and substantially below the fixing roller 24 (specifically, the left side in FIG. A pressure roller 26 rotatably supported by the swing bracket 20 about a fixed axis set parallel to the fixing 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 located substantially above.

The fixing device 10 includes a heating roller 2
8, a heating source 30 such as a halogen lamp, and a fixing belt (heat transfer belt) 32 endlessly wound around the fixing roller 24 and the heating roller 28.
And further provided.

Here, although the details will be described later, the fixing roller 2
4 is configured as an elastic roller, while the pressure roller 26
Is composed of a roller having a higher on-roller hardness than the elastic roller. On the other hand, the swing bracket 20 is urged to rotate about the support shaft 22 by the first coil spring 34 in a direction in which the pressure roller 26 is pressed against the fixing roller 24. As a result, the fixing roller 24 and the pressure roller 26
At the mutual rolling contact portion (nip portion) of the fixing roller 24 with the fixing roller 24
Is brought into a state depressed at the rolling contact portion. That is, the nip width is set to be sufficiently ensured.

The fixing device 10 is interposed 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 to apply a predetermined tension to the fixing belt 32. The second coil spring 36 is provided at each of the left and right ends, one pair at the front and rear.

A take-in guide plate 38 for guiding an unfixed sheet toward the transfer portion is attached to the housing 12, and a fixed sheet that has passed through the transfer portion and has completed the fixing operation is discharged. A paper discharge guide plate 40 that conveys the paper toward the paper exit is attached. Further, the housing 12 has an outer peripheral surface of the fixing roller 24,
A 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 with respect to the rotation direction of the fixing roller 24 from the rolling contact portion. Here, in this embodiment, the thermistor 42 employs a contact-type structure in which the surface temperature of the portion to be detected is detected by contacting the surface of the portion to be detected.

The temperature detection position of the thermistor 42 is not limited to the above-described outer peripheral surface of the fixing roller 24, and is not limited to the portion where the fixing belt 32 is not wound. 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 with respect to the rotation direction of the fixing roller 24 from the rolling contact portion. .
In this case, the thermistor 42 is preferably a non-contact type.

The leading end of the unfixed sheet conveyed to the fixing device 10 via a conveying mechanism (not shown) first contacts the upper surface of the take-in guide plate 38, and is guided obliquely upward by the guide. The unfixed sheet guided by the take-in guide plate 38 first contacts the outer peripheral surface of the pressure roller 26, and then the outer peripheral surface of the pressure roller 26. , And guided to the rolling contact portion between the fixing roller 24 and the pressure roller 26.

In the fixing device 10 having such a schematic configuration, the unfixed sheet S conveyed onto the take-in guide plate 38 via a not-shown conveyance mechanism takes in the lower surface where no unfixed toner is attached. While being contacted and supported by the guide plate 38, it is guided toward a rolling contact portion (nip portion) between the fixing roller 24 and the pressure roller 26 around which the fixing belt 32 is wound. As a result, the unfixed toner is thermocompressed and fixed on the sheet.

Hereinafter, the various components described above will be sequentially described individually. << Description of the fixing roller 24 >>
A core 24A rotatably supported on the side plate 16 via a bearing 44 (shown in FIG. 2), and a roller disposed coaxially around the core 24A and around 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.
m. Here, in this embodiment,
The core part 24A is formed of an iron shaft having a diameter of 15 mm, and the roller body 24B is formed of a silicone rubber heat-resistant elastic body (specifically, asuka on the roller) having a thickness of 5 mm attached to the outer periphery of the core part 24A. C hardness is 23 degrees).

As shown in FIG. 2, a first driven gear 46 is mounted on a shaft located at one end of the cored bar 24A coaxially therewith via a one-way clutch 48, which will be described in detail later. The first driven gear 46 meshes with a second driven gear 50 which is coaxially attached to one end of a cored bar 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
Is engaged with a drive gear forming a part of the drive mechanism 52. 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 counterclockwise rotation force in FIG.
, And transmitted to the fixing roller 24 via a one-way clutch 48.

<< Description of One-Way Clutch 48 >> The one-way clutch 48 allows the fixing roller 24 to rotate relative to the first driven gear 46 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. That is, the fixing belt 32 is
And the fixing roller 24 is fixed to the fixing belt 3.
2 is frictionally engaged with the fixing roller 2 by the pressing roller 26.
4 and the fixing belt 32 are driven (rotated), the peripheral speed of the fixing roller 24 rotating clockwise in the drawing is:
The rotation speed of the fixing roller 24 is set to be slightly faster than the rotation of the first driven gear 46 so that the rotation speed of the fixing roller 24 becomes equal to the peripheral speed of the pressure roller 26.

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

The shaft provided at one end of the metal core 26A has the second driven gear 50 coaxially fixed thereto as described above, and the second driven gear 50 The first driven gear 46 is engaged with the second driven gear 50, and the driving force from the first driven gear 46 is directly transmitted to the second driven gear 50 via a driving gear (not shown), so that the pressure roller 26 is opposite to the fixing roller 24. Is configured to be driven to rotate 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 ratio of the first and second driven gears 46 and 50 is set so that the peripheral speed of the pressure roller 26 does not become faster. That is, the rotation speed when the fixing roller 24 is rotated by the first driven gear 46 is the rotation speed of the fixing belt 32.
The rotation speed is set to be slightly lower than the rotation speed at the time of rotating by frictional engagement with the pressure roller 26 via the.

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 direction of transporting the unfixed sheet rather than immediately below the fixing roller 24. When a line segment passing through both center points of the heating roller 28 and the fixing roller 24 is used as a base line, the base line and the fixing roller 24 and the pressing roller 26 Are arranged so that the angle formed by the line segment passing through the two center points becomes a predetermined acute angle. A line segment passing through both center points of the fixing roller 24 and the pressing roller 26 is set so as to be substantially orthogonal to the conveying direction of the unfixed sheet.

{Description of Heating Roller 28} The heating roller 28 incorporating the first heating source 30 described above has a diameter of 20.1 mm and a thickness (t) of 0.25 in this embodiment.
20mm thick PT on the outer peripheral surface of the iron pipe core
It is composed of a coating of a FE coating layer. That is, as a feature of the present invention, the heating roller 28 is configured to have a thin cored bar for the purpose of shortening the warm-up time as described later. Note that both ends of the heating roller 28 are
The bearing 56 is rotatably supported via a bearing.
A collar 58 made of a heat-resistant resin, polyetheretherketone (PEEK), is inserted into the inside of the fixing belt 32 to prevent the fixing belt 32 from meandering and leaning during endless running.

A first heating source 30 as a heating means is built in the heating roller 28. In this embodiment, the first heating source 30 has a maximum output of 800 W. It consists of a halogen lamp.

{Description of Fixing Belt 32} The fixing belt 32 has a size of one 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 applying an excessive amount of heat. Heat capacity per unit is 0.
Those in the range of 002 cal / ° C to 0.025 cal / ° C are preferred. For this reason, in this embodiment, as shown in FIG. 3, the fixing belt 32 has an endless belt base 32a made of polyimide resin having an inner diameter of 40 mm and a thickness of 90 μm, and an outer peripheral surface of the belt base 32a. (A surface layer) and a heat-resistant release layer 32b of PFA covered with a thickness of 30 μm.

Here, in the present invention, it is needless to say that a metal belt made of nickel electroforming can be used without being limited to using a polyimide resin as the belt base 32a. When the nickel electroformed metal belt is used as the belt base 32a, the thickness of the belt base 32a is, for example, 3
A belt having a thickness of 300 μm coated with heat-resistant silicone rubber,
Further, the outer periphery of the heat-resistant silicone rubber layer has a thickness of 3 in the same manner as when the material of the belt base 32a is a polyimide resin.
A configuration is adopted in which a heat-resistant release layer 32b of PFA coated with 0 μm is coated.

{Description of Mechanism for Applying Tension to Fixing Belt 32} As described above, in this embodiment, as a mechanism for applying tension to the fixing belt 32, a direction in which the heating roller 28 is separated from the fixing roller 24 is used. And a second coil spring 36 that urges the second coil spring 36.

That is, the heating roller 28 is urged by the urging force of the second coil spring 36 through the sliding bracket 18.
The fixing belt 32 is biased in a direction away from the fixing roller 24, and thus the fixing belt 32 wrapped around the heating roller 28 and the fixing roller 24 endlessly is tensioned to 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, and according to 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.

{Configuration of Control System} On the other hand, this fixing device 10 controls the driving of the above-described driving mechanism 52 and also controls the heat generation of the heating source 30 incorporated in the heating roller 28 as shown in FIG. In addition, a control device 60 is provided. As described above, only one thermistor 42 is connected to the control device 60 for heat generation control of the heating source 30 (specifically, heat generation control at the time of simultaneous rotation start control of the fixing belt). The heat source 30 is configured to control heat generation based only on the detection result.

The control device 60 is connected to a heater driver 62 from the viewpoint of heat generation control, and is configured to control a halogen lamp as the heating source 30 via the heater driver 62. Further, from the viewpoint of running control of the fixing belt 32, the control device 60 outputs an input terminal for receiving a paper passing command (print start signal) from a printer control unit (not shown) and outputs a print permission signal to the printer control unit. An output terminal is provided, and a power 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 controller 60 is set so as to energize the heating source 30 to turn on the halogen lamp and generate heat only under the following two conditions.
(1) A print start signal from a printer control device (not shown) that controls the entire electronic printer (not shown),
When a ready state from when the fixing operation start signal is output to when the temperature detected by the thermistor 42 detects the feasible temperature is specified; (2) The temperature detected by the thermistor 42 detects the feasible temperature and prints An allowance 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; , The heating source 30 is set to generate heat.

In a case where a standby state from the output of the print end signal to the output of the next print start signal is specified, the control device 60 sets the heating source 30 to the stop state and sets any state. Is set so as not to generate heat.

As described above, the control device 60 controls the heating source 30 in the print waiting state, that is, in the standby state.
Since no heat generation operation is performed via the circumstance, the effect of energy saving is reliably achieved.

When the power switch 64 is turned on, the printer control device is set so as to output a print start signal unconditionally in this embodiment. , The printable state is quickly achieved.

On the other hand, when the heating source 30 is not operated at all in the standby state, the heating roller 28
Although the surface temperature of the heating roller 28 decreases to the room temperature level, the thickness (t) of the heating roller 28 is reduced as described above.
Since it is formed as a thin wall having a thickness of 0.25 mm, the above-mentioned condition (1) ready state is defined, and the heating roller 28
When the temperature rises from the room temperature state, the heat of the heating source 30 is transmitted to the outer peripheral surface of the heating roller 28 within a short time, and the temperature of the outer peripheral surface of the heating roller 28 rises to a predetermined fixing target temperature. The warming time will be very 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 rises to the predetermined fixing target temperature, and the fixing belt 32 heated by the outer peripheral surface of the heating roller 28, The total time of the time T2 required for the contact portion to rise to a predetermined fixing temperature due to the endless running is a so-called warming-up time. Accordingly, in a state in which the running of the endless belt 32 is started in synchronization with this, T1 is about 6 seconds, and T2 is about 9 seconds.
Seconds. That is, in this embodiment, even when the temperature of the heating roller 28 is increased from the room temperature under the condition (1) described above, the warming-up time is about 15 seconds, which is determined by the operator in the literature. It is a value that can significantly clear the target of 30 seconds as an allowable warm-up time, and the effect that the workability is reliably maintained without irritating the worker is achieved. Become.

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

{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, in a state where the above-described condition (1) is satisfied, the control device 60 starts the first and second drive motors (not shown) in synchronization with the start of the heating source 30. Driven gear 4
6 and 50 are driven to rotate, and accordingly, the fixing belt 32 is set to run endlessly.

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

Here, the driving mechanism 5 in the control device 60
As described above, as the control mode 2, the driving control may be performed so that the fixing belt 32 runs endlessly in a state synchronized with the activation of the heating source 30, or a predetermined time after the activation of the heating source 30. During this time, the fixing belt 32 is driven 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, fixing is performed at the predetermined fixing running speed. The belt 32 may be set to run endlessly. As described above, by initially causing the fixing belt 32 to run endlessly at a low speed, the warming-up time can be further reduced.

The switching timing of the traveling speed of the fixing belt 32 is not limited to the above-mentioned predetermined time, and, for example, the detection temperature of the thermistor 42 may be lower than the predetermined feasible temperature. The same effect can be obtained by defining the timing at which the temperature reaches the target temperature set lower.

It is needless to say that the low traveling speed (first traveling speed) is not a concept including zero speed, but it is also possible to set the first traveling speed to zero. Of course. In this case,
Until the speed switching timing, the heating source 30 is activated, but the traveling of the fixing belt 32 is stopped. As described above, the fixing belt 32 is
By driving the vehicle with a delay from the start-up of 0,
It is possible to shorten the warm-up time.

The above points are summarized in Table 1 below.

[0061]

[Table 1]

As is apparent from Table 1, the data
The fixing belt 32 seems to be more effective in shortening the warming-up time than the nickel electroformed belt made of the polyimide resin. However, in the case of the nickel electroformed belt, the surface is made flexible. For the purpose of improving image quality,
When coated with silicone rubber and made of polyimide resin, there is a difference that the silicone rubber is not coated. In addition, since the silicone rubber functions as a heat insulating layer, the warm-up time is longer by that much. That is, under the same conditions, substantially the same result was obtained regardless of whether the fixing belt 32 was made of nickel electrocast or polyimide.
Within 0 seconds could be achieved.

Even if the endless running of the fixing belt 32 is started in synchronization with the activation of the heating source 30 as described above, the warming-up time target of 30 seconds or less can be achieved. It was found that reducing the running speed was more effective from the viewpoint of shortening the warm-up time. That is, the heating source 30
It has been found that stopping the running of the fixing belt 32 at the time of startup and controlling the driving of the drive mechanism 52 so that the endless running is performed later is optimal from the viewpoint of shortening the warm-up time.

{Verification of the Optimum Range of the Thickness (t) of the Heating Roller 28} The optimum range of the thickness (t) of the heating roller 28 is preferably such that the thinner the thickness, the shorter the time required to raise the temperature. However, if it is too thin, the second coil spring 36 that applies a predetermined tension to the fixing belt 32 is used.
Loses its biasing force and cannot maintain its own shape, but bends. When the heating roller 28 bends in this way, the fixing roller 32 does not contact uniformly with the fixing belt 32, and the heat is not uniformly transmitted to the fixing belt 32, and the fixing belt 32 moves during running. Is not preferred.

On the other hand, if the urging force of the second coil spring 36 is excessively weakened, the fixing belt 32 is undesirably loosened. For this reason, first, the setting conditions of the urging force by the second coil spring 36 so as not to cause the fixing belt 32 to loosen were verified.

For this verification, as shown in Table 2, the urging force of the second coil spring 36 was sequentially set to be stronger from 500 g / one side, and a range where the fixing belt 32 did not loosen was found.

[0067]

[Table 2]

As is apparent from Table 2, the fixing belt 3
In order to prevent the slack from occurring in the second coil spring 2, the urging force of the second coil spring 36 is at least 1500 g /
It turned out that it was necessary to be one side. In other words, it has been found that it is necessary for the heating roller 28 to have a strength enough to withstand the urging force of the second coil spring 36 on the one side of 1500 g.

The maximum thickness of the heating roller 28 (t) is determined by the warm-up time of 3
The range was set within 0 seconds. Here, the heating roller 28
As the fixing belt 32 heated on the outer peripheral surface travels endlessly, the time T2 until the rolling contact portion rises to a predetermined fixable temperature is about 20 seconds at maximum from Table 1 described above. Therefore, the target value of the time T1 from the activation of the heating source 30 to the time when the outer peripheral surface of the heating roller 28 rises to a predetermined fixable temperature is set to 10 seconds.

Next, with the urging force of the second coil spring 36 set at 1500 g / one side, the outer diameter of the heating roller 28 is varied from 12 mm to 30 mm, and the thickness (t) at each outer diameter is varied. Was varied, and the amount of deflection T1 and the weight of each were measured. Table 3 shows the results.

[0071]

[Table 3]

Based on the results in Table 3, FIG. 5 shows that the relationship between the outer diameter of the heating roller 28 and the thickness (t) shows that the deflection amount is 0.2 mm or less and T1 is within 10 seconds. Are indicated by hatching. As is apparent from FIG. 5, the thickness (t) of the heating roller 28 is 0.1 m.
It has been found that a range of not less than m and not more than 0.7 mm is an optimum range satisfying the above conditions.

In FIG. 5, if the thickness (t) of the heating roller 28 is 0.1 mm or less, the heating roller 28 may be deformed by pressing it by hand. Even if the relationship is good, the allowable thickness is 0.1 mm as the lowest line and is cut.

In the embodiment described above, the thickness (t) is set to 0.25 mm when the outer diameter of the heating roller 28 is set to 20.1 mm, and there is no problem. Needless to say.

As described above, in the present invention, the thickness (t) of the heating roller 28 is set in the range of 0.1 mm or more and 0.7 mm or less. Even if the roller 28 is lowered to the room temperature, the warm-up time in a state where the allowable value of the waiting time is less than 30 seconds is achieved, and both operability and energy saving are achieved at once. Thus, the present invention has extremely high industrial applicability.

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 arrangement of the oil application roller for applying the release oil to 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 a configuration in which such an oil application roller is not provided, but may employ a configuration in which an oil application roller is provided. In this case, since the oil application roller comes into pressure contact with the fixing belt 32 with a predetermined pressure contact force, the oil application roller can be used in cooperation with the second coil spring 36 as the above-described tension applying means, Further, it can be used instead of the second coil spring 36.

In the above-described embodiment, the core 28a of the heating roller 28 has been described as being formed from an iron pipe. However, the present invention is not limited to such a configuration, and the SUS 28 Needless to say, it may be formed from a stainless steel or aluminum pipe.

Further, in the above-described embodiment, the description has been made such that only the heating source 30 incorporated in the heating roller 28 is provided as the heat generating means. However, the present invention is not limited to such a configuration, and It may be configured to include a second heating source built in the pressure roller 26 described above. In this case, the second heating source may be constituted by, for example, a 250 W halogen lamp 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 as described above. That is, its heat generation type,
It goes without saying that the shape of the heat generation is not limited at all.

In the above-described embodiment, the target value of the time T1 from the start of the heating source 30 to the time when the outer peripheral surface of the heating roller 28 rises to a predetermined fixing temperature is set to 10 seconds. Is not limited to such a numerical value, and it goes without saying that the same effect can be obtained within 15 seconds.

[0082]

As described above, according to the present invention, there is provided a fixing device capable of shortening the warming-up time and improving the user's convenience while reliably achieving energy saving. Become.

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

FIG. 3 is a front view showing a configuration of a fixing belt.

FIG. 4 is a block front view schematically showing a configuration of a control system.

FIG. 5 is a diagram illustrating a relationship between an outer diameter dimension and a wall thickness of a heating roller.

FIG. 6 is a diagram schematically showing a configuration of a conventional belt-type fixing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Fixing apparatus 12 Housing 14 Bottom plate 16 Side plate 18 Sliding bracket 20 Swing bracket 22 Support shaft 24 Fixing roller 24A Core part 24B Roller body 26 Pressure roller 26A Core part 26B Roller body 28 Heating roller 30 Heat source 32 Fixing belt 34 First coil spring 36 Second coil spring 38 Intake guide plate 40 Discharge 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 Collar 60 Control device 62 Heater driver 64 Power switch

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H05B 3/00 335 H05B 3/00 335 F term (Reference) 2H033 AA21 AA30 AA32 BA25 BA31 BA32 BB13 BB18 BB30 CA07 CA27 3J103 AA02 AA12 AA71 AA85 BA03 FA20 FA30 GA57 GA58 GA60 3K058 AA03 AA61 AA81 BA18 CA61 CE12 CE17 DA02 GA06

Claims (11)

[Claims] An image forming apparatus comprising: a fixing roller; a pressure roller which rolls on the fixing roller at a predetermined pressure; a heating roller disposed apart from the fixing roller; A delivered fixing belt, a heating unit built in the heating roller, heating the fixing belt, and heating unfixed toner on a sheet passing through a rolling contact portion of the fixing roller and the pressure roller; Tension applying means for applying a predetermined tension to the belt, wherein the sheet having unfixed toner carried on its surface passes through the rolling contact portion along one direction, thereby removing the unfixed toner from the sheet. In the above fixing device, the thickness (t) of the heating roller is minimized to a value that can maintain its own shape against the tension generated by the tension applying unit, and is used to start the heating unit. The heating roller itself is 2
A fixing device characterized in that a value in which a time until a temperature rises from 0 ° C. to 180 ° C. is within 15 seconds is set as a maximum limit. 2. A fixing roller, a pressure roller which rolls on the fixing roller at a predetermined pressure, a heating roller spaced apart from the fixing roller, and an endless loop between the heating roller and the fixing roller. A delivered fixing belt, a heating unit built in the heating roller, heating the fixing belt, and heating unfixed toner on a sheet passing through a rolling contact portion of the fixing roller and the pressure roller; Tension applying means for applying a predetermined tension to the belt, wherein the sheet having unfixed toner carried on its surface passes through the rolling contact portion along one direction, thereby removing the unfixed toner from the sheet. In the fixing device for fixing the heating roller on the upper side, the thickness (t) of the heating roller may maintain its own shape against the fact that the tension by the tension applying means acts on the heating roller at 1500 g / one side. The value that can be held is minimized, and the heating roller itself becomes 20
A fixing device characterized in that the maximum time is set to a value within 15 seconds until the temperature is raised from 180 ° C. to 180 ° C. 3. A fixing roller, a pressure roller which rolls in contact with the fixing roller at a predetermined pressure, a heating roller spaced apart from the fixing roller, and an endless loop between the heating roller and the fixing roller. A delivered fixing belt, a heating unit built in the heating roller, heating the fixing belt, and heating unfixed toner on a sheet passing through a rolling contact portion of the fixing roller and the pressure roller; Tension applying means for applying a predetermined tension to the belt, wherein the sheet having unfixed toner carried on its surface passes through the rolling contact portion along one direction, thereby removing the unfixed toner from the sheet. In the above fixing device, the thickness (t) of the heating roller is minimized so that the amount of deflection due to the tension of the tension applying means is within 0.2 mm, The heating roller is 2
A fixing device characterized in that a value in which a time until a temperature rises from 0 ° C. to 180 ° C. is within 15 seconds is set as a maximum limit. 4. A fixing roller, a pressure roller which rolls in contact with the fixing roller at a predetermined pressure, a heating roller spaced apart from the fixing roller, and an endless loop between the heating roller and the fixing roller. A delivered fixing belt, a heating unit built in the heating roller, heating the fixing belt, and heating unfixed toner on a sheet passing through a rolling contact portion of the fixing roller and the pressure roller; Tension applying means for applying a predetermined tension to the belt, wherein the sheet having unfixed toner carried on its surface passes through the rolling contact portion along one direction, thereby removing the unfixed toner from the sheet. In the above fixing device, the thickness (t) of the heating roller is 0.1 mm or more and 0.7 mm or more.
The fixing device is set to a range of not more than mm. 5. A method for controlling a heating state of said heating means,
The fixing device according to claim 1, further comprising a temperature measurement unit configured to measure a temperature of the fixing roller. 6. In the warming-up control of the heating means, the heating means controls the heating of the heating means at the start of the warming-up, and when the running of the fixing belt is started later, the temperature of the heating roller is measured. The fixing device according to claim 5, further comprising: a second temperature measuring unit. 7. The fixing device according to claim 5, wherein the temperature measuring unit includes a thermistor that measures a temperature of an outer peripheral portion of the fixing belt located on an outer periphery of the fixing roller. 8. The fixing device according to claim 5, wherein said temperature measuring means includes a thermistor for measuring a temperature of an outer peripheral surface of said fixing roller. 9. The fixing device according to claim 1, wherein said heat generating means includes a halogen lamp built in said heating roller. 10. The heating roller has an outer diameter of at least 12 m.
The fixing device according to claim 9, wherein m is set to m. 11. The fixing device according to claim 1, wherein the pressure roller includes a second heat generating means for heating the pressure roller.