JP2003248396A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus by which the warm-up time of both a fixing roller and a pressure roller is reduced in the image forming apparatus using an external heating/fixing system. <P>SOLUTION: A heat source at the inside of a heating roller is switched to high electric power at the point of time when the surface temperature of the pressure roller exceeds control temperature B which is lower than the control temperature A of the fixing roller at the time of stand-by control, and the energizing of the heat source at the inside of the pressure roller is stopped, and warm-up is completed at the point of time when the surface temperature of the fixing roller reaches the specified temperature A. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a fixing device that inserts a sheet carrying an unfixed toner image through a nip of a pair of heated rollers to heat and melt the unfixed toner on the sheet to fix it on the sheet. Image forming apparatus. In particular,
The present invention relates to an image forming apparatus using an external heating fixing device that heats the surface of a fixing roller from the outside.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, an unfixed toner image is formed between the nip of a roller pair heated by a heat source incorporated in at least one roller of a roller pair forming a nip. A heat roller fixing method is used in which the carried paper is inserted to fix the toner on the paper. In such a heat roller fixing method, the heat capacity of the fixing roller is large, and it takes a long time for the heat to propagate from the heat source such as a halogen lamp built in the fixing roller to the roll surface. As a result, there is a problem that the image output operation cannot be executed promptly because the warm-up time from turning on the power of the image forming apparatus main body to reaching the fixing temperature at which fixing is possible requires several minutes. Further, even in the energy saving mode in which the control temperature of the fixing roller surface is changed to a lower level after image output, there is a problem that it takes a long time to return to the fixing temperature again, and the control temperature is fixed so that image output can be restarted in a short time. There was a problem that many energy saving effects could not be expected unless the temperature was lowered so much, and improvement was desired.

In order to shorten the warm-up time and the power consumption in the conventional heat roller fixing method, for example, Japanese Patent Laid-Open No. 1999-2446 has been used in recent years.
An external heating method such as that described in Japanese Patent Laid-Open No. 1-83242 has been proposed. In this publication, a heating roller for heating the fixing roller from the outside is used, which is suitable for causing heat to propagate to the surface of the fixing roller. However, no means for better heat transfer from the heating roller to the fixing roller is disclosed, and for the pressure roller forming a nip with the fixing roller, the heat of the heating roller is passed through the fixing roller. Is propagated and reached, the temperature rise is slow. For this reason, the external heating type fixing method of the present disclosure has a limit in shortening the warm-up time, and it is difficult to accurately control the pressure roller temperature even if the surface of the fixing roller is controlled. Therefore, in order to accelerate heating of the pressure roller, for example, Japanese Patent Laid-Open No. 2001-154529 proposes a method in which an internal heating source is provided for all of the fixing roller, the pressure roller, and the heating roller. However, if the limited power consumption of the image forming apparatus is directed to the heating source in the three rollers, the heat generation amount of the heating roller decreases, so that the temperature rise of the fixing roller surface becomes slow and it is difficult to shorten the warm-up time. There will be problems such as Further, in order to satisfactorily fix the toner on the paper, the temperature of the fixing roller that is in direct contact with the toner mainly influences, and it is necessary to set the temperature near the melting temperature of the toner. The pressure roller needs to be heated to some extent in order to maintain the paper temperature.

[0004]

[Problems to be Solved by the Invention]. Therefore, the first aspect of the present invention
In view of the problem of the external fixing method, it is an object of the present invention to provide an image forming apparatus in which the warm-up time of both the fixing roller and the pressure roller is reduced as much as possible. A second object of the present invention is to provide an image forming apparatus that can reach a high fixing roller surface temperature and a low pressure roller surface temperature in a short time without wasting power. .

[0005]

In order to achieve the above object, the invention of claim 1 is to provide a fixing roller for fixing unfixed toner on a sheet, and a heat source inside so as to contact the fixing roller. A pressure roller that forms a nip through which a sheet is inserted, and a heat source that can switch between two levels of power consumption, high power and low power, are provided inside, and heat that heats the fixing roller by contacting the surface of the fixing roller. The roller, the fixing roller surface temperature detecting means, the pressure roller surface temperature detecting means, the heat source of the heating roller and the heat source of the pressure roller are energized, and the heating roller, the pressure roller and the fixing roller are In the standby control, the control means maintains the surface temperature of the fixing roller within a predetermined range around the control temperature A. An image for energizing and controlling the heat source inside the heating roller and the heat source of the pressure roller so that the surface temperature of the pressure roller is maintained within a predetermined range centered on a control temperature B lower than the control temperature A. In the forming device, at the start of warm-up, the control means is
Each roller is rotated to start the energization control of the heat source inside the heating roller at low power, and the energization control of the heat source inside the pressure roller is started so that the surface temperature of the pressure roller is centered around the control temperature B. When the temperature within the predetermined range is reached, the heat source inside the heating roller is switched to high power to stop the energization of the heat source inside the pressure roller, and then the surface temperature of the fixing roller falls within the predetermined range around the control temperature A. It is characterized by ending the warm-up when it reaches. According to the invention of claim 1, after the warm-up is started, the pressure roller itself is heated until the temperature reaches the control temperature B lower than the control temperature A of the fixing roller, and the pressure roller is controlled. When the temperature is equal to or higher than the temperature B, the electric power of the heat source of the pressure roller is diverted to the electric power of the heat source of the heat roller. It

According to a second aspect of the invention, in the image forming apparatus according to the first aspect, in the image forming apparatus according to the first aspect, both the heating roller and the pressure roller are metal rollers or metal rollers. And a resin layer covering the surface thereof, and the fixing roller comprises a cored bar and an elastic body formed around the cored bar.
According to the invention of claim 2, since the main part of the heating roller is made of metal which is a good conductor of heat, the heat generated from the heat source inside the heating roller is propagated to the heating roller surface in a shorter time, thereby warming up. It is possible to further reduce the time. Further, since the fixing roller is made of an elastic body with respect to the heating roller which is a rigid body, the nip width required for good heat conduction is secured. Furthermore, since the pressure roller is made of metal with respect to the fixing roller that is an elastic body, the nip necessary for fixing is secured, and since it is made of metal that is a good conductor of heat, heating of the pressure roller surface is also promoted. It

Further, the invention of claim 3 is provided with a heat source whose power consumption can be switched between two stages of high power and low power,
A fixing roller for fixing the unfixed toner on the sheet, a pressure roller that includes a heat source and forms a nip through which the sheet is inserted by contacting the fixing roller, a fixing roller surface temperature detection unit, and a pressure roller In the standby control, a surface temperature detecting unit, a control unit that electrically controls the heat source of the fixing roller and the heat source of the pressure roller, and drive-controls at least one of the pressure roller and the fixing roller are provided. The control means maintains the fixing roller surface temperature within a predetermined range centered on the control temperature A, and maintains the pressure roller surface temperature within a predetermined range centered on a control temperature B lower than the control temperature A. In the image forming apparatus, the heat source of the fixing roller and the heat source of the pressure roller are energized. The pressure roller surface temperature is controlled within a predetermined range centered on the control temperature B by rotating the rotor to start energization control of the heat source of the fixing roller at low electric power and starting energization control of the heat source inside the pressure roller. When it reaches within
After the heat source inside the fixing roller is switched to high power to stop energizing the heat source inside the pressure roller, the warm-up is terminated when the surface temperature of the fixing roller reaches a predetermined range around the control temperature A. It is characterized by According to the third aspect of the present invention, after the warm-up is started, the pressure roller itself is also heated until the pressure roller reaches the control temperature B lower than the control temperature A of the fixing roller. When the temperature exceeds the control temperature B, the electric power of the pressure roller heat source is diverted to the electric power of the fixing roller heat source, so the heating of the fixing roller is accelerated without wasteful heating of the pressure roller, thereby significantly reducing the warm-up time. To be done.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of an apparatus body constructed according to the present invention will be further described below with reference to the accompanying drawings. FIG. 1 is a perspective view showing an external configuration of an image forming apparatus 200 according to the first embodiment of the present invention. FIG. 2 is a front view showing the internal configuration of the image forming apparatus 200. Figure 3
FIG. 4 is a schematic diagram showing an open / closed state of a document cover as viewed from the right side surface of the image forming apparatus 200, with the document feeder not shown.

As shown in FIGS. 1 and 2, the image forming apparatus 2
00 is the main body housing 11 and the upper housing 1 above it.
It is partitioned by 1 U and a document feeding section 14 which is placed on the upper part of the upper housing so as to be able to be flattened. A sheet material stack space portion 12 is formed in an intermediate portion between the main body housing 11 and the upper housing 11U so as to extend inward in a substantially horizontal direction from the right side surface. The sheet material stack space portion 12 receives the sheet material discharged laterally from the main body housing,
An upper sheet tray 1 and a lower sheet tray 2 for stacking are provided. As described above, in the so-called in-body sheet discharge type image forming apparatus in which the sheet discharging unit is provided inside the image forming apparatus main body, since it is necessary to provide the space occupied by the sheet stack space, it is required to make the image forming unit compact. Also in the apparatus, the compact and low-cost one-component developing method is advantageous.

The upper housing 11U has a built-in exposure unit 15 for exposing an original at an image reading position to read an image, and an operation panel 13 and an original placing plate 21 made of a transparent glass plate are arranged on the upper surface thereof. It is set up. Above the upper housing 11U, a document transport unit 14 for transporting a document to an image reading position R for reading a document image is placed. As shown in FIG. 3, the document cover 14d is supported by the hinge portion 9 on the inner side of the machine so that it can be flattened on the upper housing. The document cover 14d is normally placed at the closed position shown by the solid line and can be opened to the open position shown by the broken line. The image forming apparatus 200 is capable of performing two types of document image reading, a sheet through system and a document fixing system. First, the sheet-through method is a method in which an image of a document passing through the image reading position R is read by the closed document feeding unit 14 by the exposure unit 15 which is fixedly arranged facing the image reading position. Further, the original fixed type method is a method in which the original conveying section 14 is opened, an original is placed on the upper surface of the original placing plate 21, and the exposure section 15 is moved to read an image. The present embodiment will be described as an example based on the sheet-through method.

The main body housing 11 is a lower housing 11.
It can be divided into D and the connecting housing 11C above it. The lower housing 11D incorporates a paper feed unit, an image forming unit that forms a toner image on the paper, and a fixing unit that fixes the toner image on the paper. Connection housing 11
C has a built-in paper feed path for feeding the fixed paper and discharging it toward the sheet tray in the sheet material stack space.

The structure of the upper housing 11U will be described with reference to FIGS. An operation panel 13 is provided on the front side of the upper housing 11U. The document feeding unit 14 includes a document feeding tray 14a, a document feeding unit main body 14b, a document discharging tray 14c, and a document cover 14d. The document discharge tray 14c is formed directly on a part of the upper surface of the document cover 14d. A document feed tray 14a is provided at the upstream end of the extension of the document transport path d, and a document discharge tray 14c is provided at the downstream end of the extension of the document transport path d. The document reading unit main body 14b has a pickup roller 22 along the document transport path d from the upstream side to the downstream side in the document transport direction.
A conveyance roller pair 23, a registration roller pair 24, and a discharge roller pair 25 are provided. The transport roller pair 23 is composed of a drive roller 23a and a separation roller 23b. The separation roller 23b rotates in the opposite direction to the drive roller 23a only when the rotational load is below a predetermined torque, and is driven to rotate with the drive roller 23a when the rotational load exceeds a predetermined torque.

Registration roller pair 24 and discharge roller pair 25
An image reading unit R is provided between them. At the image reading position R, a white reference plate 26 for shading correction is provided in a direction facing the original placing plate 21, and the white reference plate 26 above the white reference plate 26 is pressed against the original placing plate 21. And a document pressing portion 26a. The document conveyance path d is curved so as to be inverted between the conveyance roller pair 23 and the image reading position R. Each sensor is provided from the upstream side to the downstream side of the document conveyance path d. That is, the document detection sensor S1 is provided at the center of the document feed tray 14a.
Is provided, and the paper feed sensor S is provided on the downstream side of the pair of transport rollers 23.
2 and a discharge sensor S3 is provided on the downstream side of the discharge roller pair 25.

The following description will be made on the basis of a so-called sheet-through original reading method in which an original is exposed by a fixed exposure lamp while the original is conveyed and moved by the original conveying section. The M originals set with the image surface upward on the original feeding tray 14a are pressed against the pickup roller 22 with a predetermined pressure by the set original pressing member 6b biased upward by the spring member 6a. When the copy start button on the operation panel 13 is turned on, the pickup roller 22 and the carry roller 23 are rotationally driven by a primary paper feeding drive means (not shown). A plurality of originals set on the original feed tray 14a are normally sent from the upper surface side to the pair of conveying rollers 23 by the pickup roller 22. Transport roller pair 23
For the plurality of originals sent to, the uppermost one is separated by the separating roller 23b and is conveyed toward the registration roller pair 24. After the leading edge of the document is conveyed by a predetermined distance after being detected by the sheet feeding sensor S2, the driving roller 23a of the conveying roller pair 23 is stopped by stopping the operation of the sheet feeding driving means.
Then, the rotation driving of the pickup roller 22 is stopped, and the primary sheet feeding is completed. The leading edge of the document is a pair of registration rollers 24
It is stopped by being pressed by the nip portion and having a bend formed at its tip.

After a lapse of a predetermined time from the completion of the primary paper feeding,
Secondary paper feeding is started. That is, the registration roller pair 24 is rotationally driven by the operation of the secondary paper feeding drive means (not shown). The document is conveyed by the registration roller pair 24 toward the image reading position R and the discharge roller pair 25, and finally by the discharge roller pair 25.
is discharged onto c. Completion of image reading of one original is detected by detecting the passage of the trailing edge of the original by the paper ejection sensor S3 provided on the downstream side of the pair of ejection rollers. The paper ejection sensor S3 has a counting function of counting the number of originals each time the originals are fed and conveyed. If the original set detection sensor S1 detects a subsequent original, the second and subsequent originals are conveyed. Continued. When the document passes through the image reading position R, the white reference plate 26 and the document pressing portion 26a convey the document placing plate 21 while lightly pressing the surface of the document placing plate 21 so that the image surface of the document opposes the document placing plate. Optical scanning is performed by the lamp 27.

Next, the exposure section 15 will be described. Figure 2
In, the exposure lamp 27, the reflection plate 28, the first mirror 29, the second mirror 30, the third mirror 31, and the condenser lens 3
2 and an image sensor, for example, a line type CCD 33. The exposure lamp 27 and the first mirror 29 are mounted on a first carriage (not shown), and the second mirror 30 and the third mirror 31 are mounted on a second carriage (not shown). When the document image is set to be read by the sheet-through method, the first carriage moves directly below the image reading position R, and the light irradiation light from the exposure lamp 27 exposes the moving document. The irradiation light is the first mirror 29 and the second mirror 3.
0, the third mirror 31, and the condenser lens 32 through the CCD 3
After reaching 3, the signal is read so as to be an electric signal through photoelectric conversion processing. Further, when the original image is read by the original fixing method, the original image placed on the original placing plate 21 is scanned by the exposure unit 15 to scan the CCD.
A reduced image is formed on 33, and a photoelectric conversion process is performed to read it as an electric signal.

Continuing to refer to FIG. 2, the lower housing 11D forming the main body housing 11 and the connecting housing 1
The structure of the lower housing in 1C will be described. A sheet cassette 34 is provided in the paper feed section below the lower housing 11D.
The image forming unit 36 and the fixing device 37 are incorporated. The sheet material P stored in the sheet cassette 34 is delivered one by one by the delivery roller 34a. An openable / closable manual paper feed tray 35 is provided on the lower left side of the lower housing 11D, and the sheet material P set in the manual paper feed tray 35 is also fed by a feeding roller 35a.
It is sent out one by one.

Next, the image forming section will be described. The photosensitive drum 201 is a positively chargeable amorphous silicon photosensitive drum having an outer diameter of 40 mm, and rotates at a speed of 200 mm / sec in the illustrated direction during driving. Incidentally, in order to save energy in this copying machine, no drum heater is provided near the photoconductor drum as a countermeasure against image deletion. The surface of the photoconductor drum 38 is + due to the corona discharge generated from the main charger 202 to which a high voltage of 5 KV is applied.
After being uniformly charged to 250V, the light potential from the laser scanning unit 40 is increased by bright light + 10V.
And an electrostatic latent image consisting of a dark potential of +250 V is formed. Further, the electrostatic latent image is rotationally moved to the developing position by the rotation of the photoconductor. Developing sleeve 3 inside the developing device 300
Reference numeral 01 is made of non-magnetic aluminum, and a developing magnet is formed by arranging a fixed magnet inside. Development sleeve 3
01 has an outer diameter of 20 mm, is rotatably supported with a gap of 300 μm from the photosensitive drum 201, and is 360 mm / in the same direction as the photosensitive drum when driven.
Spin at a speed of seconds. The developing unit 300 is filled with positively charged magnetic toner having a volume average particle diameter of 9 μm (median diameter by Coulter counter), and a thin toner layer is formed on the surface of the developing sleeve by a notch plate (not shown). The developing sleeve 301 has a DC voltage of +100 V and a frequency of 2
A developing bias voltage is applied in which KHZ and an AC electric field having a peak-to-peak voltage of 2 KV are superimposed. The toner conveyed to the developing area flies from the sleeve surface by the developing bias and develops the exposed portion on the surface of the photosensitive drum 201.

The sheets fed one by one from the sheet cassette 34 or the manual feed tray 35 and conveyed upward through the conveying path 3 are synchronized with the toner image on the photoconductor approaching the roller transfer section 42. , Registration roller 4
The conveyance timing is adjusted by and the sheet is conveyed between the photosensitive drum 38 and the transfer roller 42. As a result, most of the toner in the toner image is transferred onto the sheet by passing the roller transfer section while the leading edge of the sheet coincides with the leading edge of the toner image portion. Part of the toner remaining on the surface of the photoconductor drum without being transferred onto the sheet is removed by the cleaning device 50 provided at the most downstream side. The sheet on which the toner image is transferred is fixed on the sheet by the fixing device 50 to obtain a copy.

The sheet passing through the fixing nip is conveyed upward as it is along the vertical conveying path 42 in the vertical direction. When the vertical transport path 42 enters the connecting housing 11C and passes the transport roller pair 43, it branches into a horizontal transport path 44 to the right and a transport path 45 diagonally above, and a branching claw that sorts the transport direction of the paper at the branch point. 46 is provided. In FIG. 2, the sheet is distributed to the horizontal transport path 44 in the traveling direction and discharged onto the lower sheet tray 2.

Next, the internal structure of the fixing device 50 will be described in detail with reference to FIG. The left direction in the figure indicates the upper direction inside the image forming apparatus 200, and the right direction in the figure indicates the image forming apparatus 2.
00 indicates the downward direction. The fixing roller 51 and the pressure roller 52 are in pressure contact with each other to form a fixing nip portion.
The heating roller 53 for heating 1 is in pressure contact. The thermistor 54 as a means for detecting the surface temperature of the fixing roller 51.
A thermistor 55 as a means for detecting the surface temperature of the pressure roller 52 and a thermistor 56 as a means for detecting the surface temperature of the heating roller 53 are provided so as to contact the respective roller surfaces. A halogen lamp 57 as a heating source is provided inside the heating roller 53, and a halogen lamp 58 as a heating source is provided inside the pressure roller 52. On the body side of the image forming apparatus, the thermistors 54, 5
Based on the detected temperatures of 5, 56, halogen lamps 57, 58
A control unit 70 is provided for controlling the rotational drive of the fixing roller 53 by supplying electric power while controlling the electric power.

The fixing roller 51 comprises an iron cored bar 51a having an outer diameter of 12 mm, an elastic layer 51b having a thickness of 6.5 mm coated on the surface of the cored bar 51a, and an elastic layer for enhancing the releasability. The surface of 51b is covered with a PFA tube layer 51c having a thickness of 70 μm. The elastic layer 51b is formed of a silicone rubber foam having an Asuka C hardness of 25 degrees. Further, the fixing roller receives a drive current from the control unit 70 so that the peripheral speed becomes 100 mm / sec, which is the same speed as the photosensitive drum 4, and is rotated by a drive unit (not shown).

The pressure roller 52 has an aluminum roller body 52a having an outer diameter of 25 mm and a wall thickness of 1 mm, and a PTFE layer having a thickness of 15 μm applied to the surface of the roller body 52a to enhance the mold releasability. It consists of and.
A halogen lamp 58 having a maximum power consumption of 400 W is built in the roller body 52a. Pressure roller 52
Is pressed against the fixing roller 51 by an urging means (not shown) and is driven to rotate according to the rotation of the fixing roller 51.

The heating roller 53 has an aluminum roller body 53a having an outer diameter of 25 mm and a wall thickness of 0.5 mm, and a halogen lamp 57 provided inside the roller body 53a.
It consists of and. The halogen lamp 57 can be switched between low power consumption of 700w and high power consumption of 1100w. The heating roller 53 is pressed against the fixing roller 51 by an urging means (not shown) and is driven to rotate according to the rotation of the fixing roller 51.

In this image forming apparatus, a power switch for the entire image forming apparatus is provided on an operation display section (not shown). Warm-up starts according to the settings stored when the power switch is turned on. The control temperature A on the surface of the fixing roller during standby is set to 160 ° C, and the control temperature B on the surface of the pressure roller is set to 120 ° C.

Simultaneously with the start of heating, the fixing roller starts to rotate at the same peripheral speed of 100 mm / sec as when outputting an image, and the heating roller and the pressure roller are driven to rotate by the fixing roller. Halogen lamp 57 inside the heating roller 53
Illuminates and heats with a power consumption of 700 W, and the halogen lamp 58 inside the pressure roller 52 illuminates and heats with a power consumption of 400 W. When the surface temperature of the pressure roller reaches 120 ° C., the halogen lamp 58 is de-energized, and at the same time, the power consumption of the halogen lamp 57 is increased from 700 W to 1100 W to speed up the heating of the fixing roller. Here, when the surface temperature of the fixing roller 51 reaches 160 ° C., the warm-up is finished, the energization of the halogen lamp 53 is once turned off, and the control shifts to the standby control.

At the end of the warm-up, the control is switched to the standby control, the fixing roller is decelerated to a peripheral speed of 1/4 of the image output, and the heating roller 53 and the pressure roller 5 are driven.
2 also rotates accordingly. In the standby control, the halogen lamp 57 inside the heating roller 53 is on / off controlled so as to keep the fixing roller 51 warm in the range of 160 ° C. ± 3 ° C. at a power consumption of 700 W. Further, the halogen lamp 58 inside the pressure roller 52 is on / off controlled so as to keep the temperature of the fixing roller 52 within the range of 120 ° C. ± 3 ° C. at a power consumption of 400 W. At the time of image output, the fixing roller returns to the original peripheral speed of 100 mm / sec.

When a predetermined time has passed since the last image output, the standby control is shifted to the energy saving mode. The surface temperature of the fixing roller 51 is 120 ° C.
The halogen lamp 57 inside the heating roller 53 is turned on and off at a power consumption of 700 W so that the temperature is within the range of ± 3 ° C., and the surface temperature of the pressure roller 52 is 120.
The halogen lamp 58 inside the pressure roller 52 has a power consumption of 400 W so that the temperature is in the range of ± 3 ° C.
The off control is performed.

The above-mentioned predetermined time for shifting from the standby control to the energy saving mode can be selected in 1-minute increments on the operation display unit. In the energy-saving mode and the standby state where the energy-saving mode is not entered, the fixing roller 51 is set to 1 when outputting an image.
Rotation is controlled at a peripheral speed of / 4. The transition to the standby mode, where the energy saving mode is canceled and image output is possible immediately,
This is performed when the print button of the image forming apparatus main body is turned on or when an image output signal is issued from the external PC device.

Next, operation control during warm-up will be described with reference to the flow chart shown in FIG. When the user turns on the power switch of the image forming apparatus in step 1, the process proceeds to step 2. In step 2, the fixing roller is rotated at a constant speed, and power is supplied to both the halogen lamp inside the heating roller and the halogen lamp built into the pressure roller. At this time, the halogen lamp inside the heating roller has a low power of 700 W, and the halogen lamp inside the pressure roller has a power of 400 W. Further, the heating roller and the pressure roller are also rotated in accordance with the rotation of the fixing roller. In step 3, the surface temperature T1 of the fixing roller is counted up by 1 ° C., the surface temperature T2 of the pressure roller is counted up by 1 degree, and in step 4, T2 is compared with the control temperature 120 ° C. of the pressure roller. . If T2 is less than 120 ° C., the process returns to step 3, and the energization and heating of the halogen lamps of the pressure roller and the heating roller are continued. The count-up of T2 is continued, and every time the count-up of 1 ° C. is performed, T2 is compared with 120 ° C. in step 4. T2 is 1
When the temperature rises to 20 ° C or higher, the process proceeds to step 5, the power supply to the halogen lamp inside the pressure roller is stopped, and the halogen lamp inside the heating roller is changed from 700W to 1100.
The power consumption is increased to W, and the temperature rise of the fixing roller is accelerated. In step 6, the surface temperature T1 of the fixing roller
Will continue to count up, and in step 7 T
1 and 16 is the fixing roller control temperature during standby control
Compare with 0 ° C. If T1 is less than 160 ° C., the process returns to step 6 to continue energization and heating of the halogen lamp of the heating roller. In step 7, when T1 reaches the fixing roller control temperature of 160 ° C. during the standby control, the warm-up ends.

In this embodiment, the control temperature A of the fixing roller is set to 160 ° C. However, the control temperature A is not limited to this, and the best toner fixing property can be obtained according to the melting characteristics of the toner and the process conditions of the image forming apparatus. The temperature can be appropriately selected so as to be obtained, and for example, the range of 140 to 210 ° C. is a suitable temperature range.

In the present embodiment, the control temperature B of the pressure roller is set to 120 ° C. However, the control temperature B is not limited to this, and the best toner fixing property can be obtained according to the melting characteristics of the toner and the process conditions of the image forming apparatus. The temperature range can be appropriately selected so that the temperature range of 80 to 140 ° C. is a suitable temperature range.

In the present embodiment, the peripheral speed of the fixing roller in the standby control after the warm-up is completed and in the energy saving mode is set to 1/4 of that at the time of image formation, but the present invention is not limited to this and 1/6 to etc. The fast range is preferably used,
It is also possible to rotate intermittently. Further, although only the fixing roller is driven and the external heating roller and the pressure roller are driven to rotate, the present invention is not limited to this, and the driving may be given so as not to cause a difference in peripheral speed. One of the heating roller and the pressure roller may be driven to rotate the remaining rollers. Further, in the present embodiment, the control temperature of the surface of the fixing roller and the pressure roller in the energy saving mode is set to 120 ° C. However, it is not limited to this, and the range of 70 to 150 ° C. can be preferably used. Further, the control temperature may be set not only in one stage but also in a plurality of stages, and the control temperature may be gradually shifted to the low temperature side according to the lapse of unused time from the last image formation.

A thermistor 54 is provided on the surface of the fixing roller 51.
Cleaning roller 6 for maintaining the surface of the fixing roller in a clean state on the upstream side of the fixing nip and on the downstream side of the fixing nip.
1 is in contact with the surface of the pressure roller 52, and the cleaning roller 62 for maintaining the pressure roller surface in a clean state is in contact with the surface of the thermistor 55 on the upstream side of the thermistor 55. There is. As a result, toner components do not remain on the surface of the fixing roller, the pressure roller, and the heating roller that contacts the fixing roller. Therefore, even if the rollers are rotated during warm-up, the toner solids will not damage each roller. To be done. Also, even during standby such as energy saving mode or standby other than image output, each roller surface is continuously or intermittently rotated and the cleaning roller keeps each roller surface clean.
Each roller is prevented from being damaged.

In the present embodiment, the external heating roller body and the pressure roller body are made of aluminum, but the invention is not limited to this, and metals such as iron, copper, nickel and stainless steel can be used. Further, although the core metal of the fixing roller main body and the core metal are made of iron, the present invention is not limited to this, and metals such as aluminum, copper, nickel and stainless can be used.

In the fixing roller 51, the thickness of the elastic layer 51b coated on the surface of the cored bar 51a is 6.5 mm, but the thickness is not limited to this and a range of 2 to 15 mm can be preferably used. The silicon rubber forming the elastic layer 51b has an Asuka C hardness of 25 degrees, but the present invention is not limited to this, and the Asuka C hardness is 10 to 90.
The thing of the degree can be used conveniently. The releasable layer coated on the surface of the elastic layer 51b is formed of PFA (tetrafluoroethylene-
Although a per-fluoroalkyl vinyl ether copolymer) tube is used, it is not limited thereto, and PTFE
It is possible to select from fluororesins such as (polytetrafluoroethylene), PVF (polyvinyl fluoride), and ECTFE (ethylene-chlorotrifluoroethylene copolymer). Furthermore, the thickness of this release layer is 70 μm.
However, it is preferably used in the range of 20 to 100 μm.

The aluminum roller body of the pressure roller 52 has a thickness of 1.0 mm, but the thickness is not limited to this, and a thickness of 0.5 to 3 mm can be preferably used. The release layer on the surface of the roller body 52a is P
Although TFE (polytetrafluoroethylene) is used, other than that, PFA layer (tetrafluoroethylene-per-fluoroalkyl vinyl ether copolymer), PVF (polyvinyl fluoride), ECTFE (ethylene-chlorotrifluoroethylene copolymer) ) And other fluororesins. The thickness of this release layer is 15 μm
However, it is preferably used in the range of 10 to 100 μm.

The thickness of the heating roller 53 is 0.5 mm, but the thickness is not limited to this, and a thickness of 0.2 to 2.0 mm is preferably used.

In the present embodiment, the halogen lamp having a power consumption of 400 W inside the pressure roller is used, but the present invention is not limited to this, and a halogen lamp having a power consumption of 300 to 600 W is preferably used. Also, the halogen lamp inside the heating roller has a power consumption of 400 W at a low power, but the power consumption is not limited to this.
Those in the range of 600 W are preferably used. Furthermore, the power consumption of the halogen lamp inside the heating roller at high power is 1
Although the one of 100 W is used, it is not limited thereto, and the one of 800 to 1,400 W is preferably used.

[0040]

When the warm-up is started, both the pressure roller and the heating roller are heated, and when the pressure roller exceeds the control temperature B of the pressure roller lower than the control temperature A of the fixing roller during the standby control. Since the power supply to the pressure roller is stopped and the power is devoted to increase the electric power of the heating roller heat source, both the minimum heating of the pressure roller and the shortening of the warm-up time are achieved. Furthermore, since the main part of the heating roller is made of metal, which is a good conductor of heat, the heat generated from the heat source inside the heating roller can be propagated to the heating roller surface in a shorter time, further shortening the warm-up time. It will be possible. Furthermore, since the fixing roller is made elastic with respect to the heating roller which is a rigid body,
The nip width required for good heat transfer is ensured. Furthermore, since the pressure roller is made of metal with respect to the fixing roller that is an elastic body, the nip necessary for fixing is secured, and since it is made of metal that is a good conductor of heat, heating of the pressure roller surface is also promoted. It

[Brief description of drawings]

FIG. 1 is a perspective view showing an external configuration of an image forming apparatus 200 according to a first embodiment of the present invention.

2 is a front view showing the internal configuration of the image forming apparatus 200. FIG.

FIG. 3 illustrates an image forming apparatus 20 in which a document transport unit is not shown.
5 is a schematic view showing the open / closed state of the document cover as viewed from the right side of FIG.

FIG. 4 is a schematic view detailing the internal structure of the fixing device 50 in cross section.

FIG. 5 is a flowchart showing a control flow of a fixing roller and a pressure roller.

[Explanation of symbols]

50 fixing device 200 image forming apparatus 51 fixing roller 51 pressure roller 51a core metal 51b elastic layer 51c PFA tube layer 52 Pressure roller 52a roller body 52b PTFE layer 53 heating roller 53a Roller body 54 Thermistor 55 Thermistor 56 thermistor 57 halogen lamp 58 halogen lamp 70 Power supply control unit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05B 3/00 335 H05B 3/00 335 F term (reference) 2H033 AA30 BA25 BA26 BA27 BA32 BB03 BB04 BB13 BB14 BB18 BB23 BB29 BB30 BB37 CA03 CA07 CA23 CA28 CA30 CA40 CA48 3J103 AA02 AA14 AA51 BA41 GA02 GA66 HA03 HA04 HA41 HA53 3K058 AA03 AA81 BA18 CA12 CA22 CA61 CA92 CB02 CE22 CE26 DA02 GA06

Claims (3)

[Claims] 1. A fixing roller for fixing unfixed toner on a sheet, a pressure roller for internally forming a heat source and forming a nip for inserting the sheet by contacting the fixing roller, and high power consumption. And a low-power heat source that can be switched between two stages, a heating roller that heats the fixing roller by contacting the fixing roller surface, a fixing roller surface temperature detecting means, and a pressure roller surface temperature detection. And a control means for controlling energization of the heat source of the heating roller and the heat source of the pressure roller, and drivingly controlling at least one of the heating roller, the pressure roller, and the fixing roller. The control means maintains the fixing roller surface temperature within a predetermined range around the control temperature A and controls the pressure roller surface temperature lower than the control temperature A. An image forming apparatus for controlling energization of a heat source inside a heating roller and a heat source of a pressure roller so as to maintain the temperature within a predetermined range centered on a degree B, wherein the control means at the start of warm-up includes: Each roller is rotated to start the energization control of the heat source inside the heating roller at low power, and the energization control of the heat source inside the pressure roller is started so that the surface temperature of the pressure roller is centered around the control temperature B. When the temperature within the predetermined range is reached, the heat source inside the heating roller is switched to high power to stop the energization of the heat source inside the pressure roller, and then the surface temperature of the fixing roller falls within the predetermined range around the control temperature A. An image forming apparatus, characterized in that the warm-up is finished when the temperature is reached. 2. Each of the heating roller and the pressure roller is composed of a metal roller or a metal roller and a resin layer covering the surface thereof, and the fixing roller is an elastic body formed around a cored bar and its periphery. The image forming apparatus according to claim 1, comprising: 3. A fixing roller for fixing unfixed toner on a sheet, the fixing roller having a heat source capable of switching power consumption between high power and low power, and a heat source. A pressure roller that forms a nip through which a sheet is inserted, a fixing roller surface temperature detection unit, and a pressure roller surface temperature detection unit are provided, and the heat source of the fixing roller and the heat source of the pressure roller are energized and controlled. , A control means for driving and controlling at least one of the pressure roller and the fixing roller, and in the standby control, the control means maintains the surface temperature of the fixing roller within a predetermined range around the control temperature A. At the same time, the heat source of the fixing roller and the heat source of the pressure roller are connected so that the surface temperature of the pressure roller is maintained within a predetermined range around the control temperature B lower than the control temperature A. In the image forming apparatus to be controlled, at the start of warm-up, the control means rotates each roller to start low-power energization control of the heat source of the fixing roller and energization of the heat source inside the pressure roller. When the control starts and the surface temperature of the pressure roller reaches a predetermined range around the control temperature B, the heat source inside the fixing roller is switched to high power, and the heat source inside the pressure roller is stopped. After that, when the surface temperature of the fixing roller reaches a predetermined range around the control temperature A, the warm-up is ended.