JPH0887191A - Fixing device - Google Patents

Abstract

PURPOSE: To provide a fixing device capable of shortening its starting time and saving its energy by decreasing the rising speed of a temperature in the paper nonpassing part of a heating roller regardless of a simple constitution. CONSTITUTION: This fixing device is constituted so as to provide a heat conduction means 80 for making temperature distribution in the axial direction of the heating roller 62 uniform at a part nearer the downstream side in the rotational direction than the contact position (nip part) 66 of the heating roller 62 with a pressure roller 64. The heat conduction means 80 is constituted so as to be driven and rotated by pressing a temperature uniformizing roller 90 formed by combining a copper pipe material 90b as a member having high heat conductivity outside a core material 90a to the heating roller 62. Thus, the cross-sectional area of the heating roller 62 is apparently increased and unevenness in the temperature distribution in the axial direction can be eliminated without changing the performance of a nip part 66 most affecting a capacity and start-up time for fixing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example, an electrostatic copying machine,
The present invention relates to a fixing device applied to an image forming apparatus such as a laser printer, and more particularly, to a heating roller type fixing device for welding a developer image made of powder developer onto an image carrier.

[0002]

2. Description of the Related Art In recent years, a heating roller type fixing device has been widely used in an electrophotographic image forming apparatus because it has a feature of being capable of stable fixing while having a small size.

In this heating roller type fixing device, a heating roller that heats and conveys an image carrier (paper) carrying a developer image (toner image) made of powder developer (toner), and the heating roller. On the other hand, a pressure roller that conveys the image carrier while pressing the image carrier is provided, and the image carrier passes through a fixing point, which is a pressure contact portion (nip portion) between the heating roller and the pressure roller. The developer image on the carrier is fused and pressure-bonded.

Conventionally, in this heating roller type fixing device, an aluminum member having a large thickness and a large heat capacity has been used as the heating roller, but at a predetermined temperature (about 180 ° C.) required for fixing. Not only does it take a long time to start up, but there is also a problem that the power consumption increases, and improvements have been desired.

Therefore, recently, in order to shorten the rise time of the fixing device and aim at the energy saving effect, it has been considered to reduce the heat capacity of the fixing device by reducing the thickness of the heating roller.

However, the thinning of the heating roller reduces the cross-sectional area thereof, and the temperature distribution in the axial direction tends to be non-uniform. There is a drawback that the temperature of the paper passing portion (non-passing area) is likely to rise. That is, conventionally, A3
When A4 size paper is continuously fed vertically to the size fixing device, the temperature of the non-sheet passing part is
The temperature may rise from 60 ° C to 80 ° C above the set temperature, which is extremely undesirable in terms of safety and other aspects.

Therefore, in order to cope with this, a plurality of heaters corresponding to the size of the paper are provided to selectively heat the sheets according to the size, a heating roller having a heat pipe incorporated therein, or air inside the heating roller. Although those that positively induce flow have been proposed, considering cost, maintainability, and miniaturization, they are not practical solutions and are not in practical use at present.

[0008]

As described above, in the heating roller type fixing device, when the heating roller is thinned to reduce the heat capacity in order to shorten the rise time of the fixing device and obtain the energy saving effect, The current situation is that the temperature distribution in the axial direction tends to be non-uniform, and the temperature rise in the non-sheet passing portion is likely to occur, which has not been put to practical use.

The present invention has been made in view of the above circumstances. An object of the present invention is to reduce the temperature rise in the non-sheet passing portion of the heating roller while having a simple structure, and to start up the fixing device. It is to provide a fixing device that can save time and save energy.

[0010]

As a first means for solving the above-mentioned problems of the present invention, a heating roller for heating and conveying an image carrier carrying a developer image composed of a powder developer, A fixing unit that is composed of a pressure roller that conveys the image carrier while pressing the image carrier against the heating roller; a fixing unit that melts and fixes the developer image on the image carrier; and a surface of the heating roller of the fixing unit, and A heat conduction member made of a material having a high heat conductivity, which is provided in contact with a downstream portion of the heating roller in the rotational direction of the heating roller and a contact position of the pressure roller; The heat conduction means for equalizing the temperature in the axial direction is provided.

As a second means, a heating roller that heats and conveys an image carrier carrying a developer image composed of a powder developer, and the image carrier is pressed against the heating roller. A fixing unit that includes a pressure roller that conveys the image of the developer on the image carrier, and a fixing unit that melts and fixes the developer image on the image carrier, and a surface of the heating roller of the fixing unit and a contact position between the heating roller and the pressure roller. A heat radiating member made of a material having a high thermal conductivity, which is provided downstream of the heating roller in the rotational direction and is provided so as to come in contact with and away from a non-passage area associated with the size change of the image carrier, and the heat radiating member. Is provided with a heat radiation member contacting / separating means for contacting the non-passage area due to the size change of the image carrier, and a heat radiation means for equalizing the temperature in the axial direction of the heating roller. It is a thing.

As a third means, a heating roller that heats and conveys an image bearing member carrying a developer image composed of a powder developer, and the image bearing member is pressed against the heating roller. A fixing unit that includes a pressure roller that conveys the toner, and that fixes and fixes the developer image on the image carrier; and a surface of the pressure roller of the fixing unit, and a contact position between the heating roller and the pressure roller. Also has a heat-conducting member made of a material having a high thermal conductivity, which is provided in contact with the downstream portion of the pressure roller in the rotational direction, and the temperature in the axial direction of the pressure roller is made uniform so that The heating roller is configured to have a heat conducting means for making the temperature distribution in the axial direction uniform.

As a fourth means, a heating roller that heats and conveys an image bearing member carrying a developer image made of a powder developer, and the image bearing member is pressed against the heating roller. A fixing unit that includes a pressure roller that conveys the toner, and that fixes and fixes the developer image on the image carrier; and a surface of the pressure roller of the fixing unit, and a contact position between the heating roller and the pressure roller. Is a downstream portion in the rotation direction of the pressure roller, and is provided with a heat dissipating member made of a material having a high thermal conductivity, the heat dissipating member being provided so as to come into contact with and separate from a non-passage area due to a size change of the image carrier A heat radiating member contacting / separating unit is provided for bringing the heat radiating member into contact with a non-passage area associated with the size change of the image carrier, and the temperature in the axial direction of the pressure roller is made uniform to thereby cause the axial direction of the heating roller. Radiator for uniform temperature distribution It is obtained by a structure formed by including and.

As a fourth means, there is provided a fixing device for fixing a developer image composed of a powder developer on an image carrier, which is fed in a one-sided reference state shifted in one direction, regardless of size, A heating roller that accommodates a rod-shaped heat source inside and that conveys while heating the image carrier that carries the developer image,
A fixing unit that includes a pressure roller that conveys the image carrier while pressing the image carrier against the heating roller, and a fixing unit that melts and fixes the developer image on the image carrier, and a rod-shaped heat source in the heating roller of the fixing unit. And a heat source moving means for moving in the axial direction so as to correspond to the passing portion of the image bearing member.

[0015]

According to the fixing device of the first means, the surface of the heating roller and the downstream portion in the rotation direction of the heating roller from the contact position between the heating roller and the pressure roller are made of a material having high thermal conductivity. Since the heat conducting members that have been contacted are brought into contact, apparently,
By increasing the thickness of the heating roller except for the nip part (heating part that is the contact position with the pressure roller), the thermal conductivity is improved.
It is possible to reduce the temperature unevenness in the heating roller axial direction and reduce the temperature rise in the non-sheet passing portion of the heating roller.
This makes it possible to shorten the rise time of the fixing device and save energy.

According to the fixing device of the second means, the size of the image carrier is changed on the surface of the heating roller and on the downstream side in the rotation direction of the heating roller from the contact position between the heating roller and the pressure roller. Since the heat dissipation member made of a material with high thermal conductivity was brought into contact with the non-passage area, apparently the heat of the non-sheet passing portion of the heating roller was dissipated, and temperature unevenness in the heating roller axial direction was eliminated. It is possible to reduce the temperature rise and the temperature rise in the non-sheet passing portion of the heating roller. This makes it possible to shorten the rise time of the fixing device and save energy.

According to the fixing device of the third means, a material having a high thermal conductivity is provided on the surface of the pressure roller and on the downstream side in the rotation direction of the pressure roller from the contact position between the heating roller and the pressure roller. Since the heat-conducting member composed of is contacted, apparently the temperature distribution in the axial direction of the pressure roller is positively made uniform to reduce the temperature rise in the non-sheet passing portion of the heating roller rolling on it. You can This makes it possible to shorten the rise time of the fixing device and save energy.

According to the fixing device of the fourth means, the size of the image carrier is changed on the surface of the pressure roller and on the downstream side of the contact position between the heating roller and the pressure roller in the rotational direction of the pressure roller. Since the heat dissipation member made of a material with high thermal conductivity is brought into contact with the non-passage area due to the heat transfer, the heat of the non-sheet passing portion of the pressure roller is apparently radiated, and the shaft of the pressure roller is apparently radiated. It is possible to positively uniformize the temperature distribution in the direction and reduce the temperature rise in the non-sheet passing portion of the heating roller that is in contact with the temperature distribution. This makes it possible to shorten the rise time of the fixing device and save energy.

According to the fixing device of the fifth means, the rod-shaped heat source in the heating roller is moved in the axial direction so as to correspond to the passage portion of the image bearing member. It is possible to prevent an increase in the temperature of the sheet passing portion, which makes it possible to shorten the rising time of the fixing device and save energy.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described in detail below with reference to FIGS. FIG. 1 shows the first embodiment of the present invention.
1 illustrates an internal configuration of an image forming apparatus 1 to which a fixing device 50 according to an exemplary embodiment is applied.

An image forming means 4 for forming an image by an image forming process such as charging, exposure, development, transfer and cleaning is built in the apparatus main body 2 which is a casing. Further, a platen glass 6 as a document placing table and a platen cover 8 for pressing the document D set on the platen glass 6 are provided on the upper surface of the apparatus main body 2.

Further, at the front edge of the upper surface of the apparatus main body 2,
A control panel (not shown) as an input / display means is arranged. On the bottom of the apparatus main body 2, a sheet (transfer material) as an image carrier to be supplied to the image forming unit 4.
A paper feed cassette 10 accommodating P is attached, and a manual paper feed tray 12 is provided on the right side of the apparatus main body 2,
On the left side of the apparatus main body 2, a paper discharge tray 14 that accommodates the fixed paper P is installed.

The image forming means 4 is constructed as follows. That is, as shown in FIG. 1, a photoconductor drum 16 as an image support is rotatably provided in a substantially central portion of the apparatus main body 2.

A pre-exposure device 18 as a residual charge removing means for irradiating the photosensitive drum 16 with light along the rotation direction (direction of arrow A) around the photosensitive drum 16 to remove residual charges. , A charging device 20 as a charging means for uniformly charging the surface of the photoconductor drum 16, an LED erasing array 22 for removing charges in a non-image forming area, an exposing means (electrostatic means) arranged in an upper portion of the apparatus main body 2. The electrostatic latent image formed on the surface of the photosensitive drum 16 by slit exposure by the optical system moving type exposure device 24 as a latent image forming means) is formed by using a powder developer (hereinafter referred to as toner). A developing device 26 as a developing means for developing is sequentially arranged.

Further, a toner image as a powder image formed on the photosensitive drum 16 is fed from the paper feed cassette 10 or the manual paper feed tray 12 as a paper as an image carrier (plain paper, OHP sheet, etc.). A transfer device 28 as a transfer unit for transferring the toner image onto the photoconductor drum P, a peeling device 30 as a peeling device for peeling the paper P on which the toner image is transferred from the photoconductor drum 16, and a toner remaining on the photoconductor drum 16. A cleaner device 32 as a cleaning means for dropping is sequentially arranged.

Further, in the main body 2 of the apparatus, the paper P that is taken out and fed from the paper feeding cassette 10 through the paper feeding device 34 including a pickup roller and a paper feeding roller or the paper is fed from the manual paper feeding tray 12. The paper transport path 4 that guides the paper P fed through the device 36 to the paper discharge tray 14 via the image transfer portion 38 between the transfer device 28 and the photoconductor drum 16.
0 is formed.

A pair of registration rollers 42, which is located upstream of the image transfer unit 38 in the sheet conveying path 40 and serves both as an aligning means and a conveying means, is further upstream as a sheet detecting means. A pre-registration roller detector 44 is provided, and an entrance guide 46 serving as a guiding means is provided between the registration roller pair 42 and the image transfer section 38.
Is provided.

Further, there is a state in which a conveying device 48 having an endless belt, a heating roller type fixing device 50 of the present invention, and a paper discharge roller pair 52 are arranged on the downstream side of the image transfer portion 38. Has become.

In copying the document D, the photoconductor drum 16 rotates in the direction of arrow A, and the pre-exposure device 18 removes the residual charge, and then the charging device 20.
Are uniformly charged by.

Next, the photosensitive drum 1 which is uniformly charged.
6 is scanned by the optical system moving type exposure device 24 and the document D is slit-exposed on the photoconductor drum 16, and an electrostatic latent image corresponding to the document D is formed on the photoconductor drum 16. .

The electrostatic latent image formed on the photosensitive drum 16 is developed with toner applied by the developing device 26,
A toner image is formed on the photoconductor drum 16. On the other hand, in parallel with the operation of forming the toner image on the photosensitive drum 16, the paper P fed from the paper feed cassette 20 or the manual paper feed tray 22 strikes the stopped registration roller pair 42 and the leading edge thereof. Repositioning is performed.

Then, after the leading edge is detected by the registration roller pre-detector 44 and a predetermined time has elapsed, the registration roller pair 42 rotates and the conveyance of the sheet P toward the image transfer portion 38 is started. The conveyed paper P is taken in by the approach guide 46.
The leading end of the sheet P is guided by the sheet P so as to be in close contact with the photoconductor drum 16 and is sent to the image transfer unit 38.
The toner image on the photoconductor drum 16 is transferred to the paper P by the action of.

Then, the paper P on which the toner image is transferred is
After being peeled by the peeling device 30 by AC corona discharge, the toner image is guided to the fixing device 50 via the conveying device 48, and the toner image is fused and fixed on the paper P by the fixing device 50. After that, the paper P is discharged onto the paper discharge tray 14 by the paper discharge roller pair 52.

On the other hand, after the toner image is transferred onto the paper P, the cleaner device 32 removes the residual toner from the photoconductor drum 16 to enable the next copying operation. next,
The fixing device 50 according to the first embodiment of the present invention will be described with reference to FIGS.

First, the overall structure will be described with reference to FIG. The fixing device 50 is located on the upper surface side of the paper transport path 40 and has a heating roller (heat roller) 62 having a heater lamp 60 as a heat source therein, and the paper transport path 20.
Pressure roller (press roller) 64 provided on the lower surface side of the
It is configured with.

The pressure roller 64 is a pressure mechanism (not shown).
Is pressed against the heating roller 62 by
The heating roller 62 is driven in the arrow direction by a drive motor (not shown), and the pressure roller 64 is driven to rotate in the arrow direction.

Further, on the circumference of the heating roller 62, the contact position (nip portion) 6 between the heating roller 60 and the pressure roller 62.
A peeling claw 7 that peels the sheet P from the heating roller 62 and guides it in the direction of the sheet discharge roller pair 52 toward the downstream side in the rotation direction of the sheet roller 6.
4, a cleaning member 76 for removing offset toner such as toner and paper dust, a thermistor 78 for detecting the temperature of the heating roller 62, and a heat conducting unit 80 described later are sequentially provided on the heating roller 62.

The thermistor 74 is connected to a control circuit (not shown) and supplies the detected surface temperature of the heating roller 62 to the control circuit. When the surface temperature is lower than the fixing temperature, the power supply to the heater lamp 60 as a heat source is continued, and when the surface temperature exceeds the fixing temperature, the power supply to the heater lamp 60 is cut off. The surface temperature of the heating roller 62 is always in a certain range, that is, a temperature (1
The temperature is controlled to keep about 80 ± 5 ° C.).

Further, the heating roller 62 and the pressure roller 6
4 is surrounded by a housing 72 composed of an upper casing 68 and a lower casing 70, and has a structure in which heat does not escape to the outside as much as possible so as to secure a favorable temperature atmosphere necessary for fixing.

Further, the entrance side of the fixing means 82 comprising the heating roller 62 and the pressure roller 64, that is, the heating roller 6
The fixing point 66, which is the pressure contact portion between the pressure roller 64 and the pressure roller 64.
An inlet guide 84, which is a guide unit, is provided on the front side of, and the sheet P on which the toner image is formed is guided to the fixing point 66 via the inlet guide 84.

An exit guide 86, which is a guide means, is provided on the discharge side of the fixing point 66, and is configured to guide the paper P passing through the fixing point 66 to the discharge roller pair 52. There is.

The heating roller 6 which is the fixing point
When the paper P passes through the contact position (nip portion) 66 between the 0 and the pressure roller 62, the toner T on the paper P is heated and melted, and at the same time, the toner P penetrates and is fixed by the pressure of the nip portion. It Further, as the heating roller 60, the pressure roller 62, and the discharge roller pair 52 rotate, the discharge tray 1
4 is ejected.

Further, in this embodiment, the heating roller 62 is made of iron having an outer diameter of 30 mm and a thickness of 0.8 mm in order to shorten the rise time of the fixing device and save energy, that is, to eliminate residual heat during standby. It uses rollers and has a small heat capacity. Further, in order to prevent toner offset, a Teflon coating of 100 μm is applied to the surface.

Similarly, the pressure roller 64 has an outer diameter of 30.
A 5 mm thick silicone rubber is wound around a metal core material having a thickness of 5 mm to form a nip. Also, the heat source 6
0 uses a 600W halogen lamp heater,
The thermistor 78 controls ON / OFF.

Incidentally, usually used in the electrophotographic system,
Copiers, printers, etc. have a structure in which the paper P, which is a transfer material, is selectively used from the business card size to the A3 size (or there is one corresponding to a larger size), and the fixing device also has various sizes. The paper P of is to enter.

In the fixing device 50 in which the heating roller 62 is thinned for the purpose of reducing the heat capacity in order to aim at the energy saving effect as in this embodiment, the cross-sectional area of the heating roller 62 is reduced, and as described above. Small size paper P
In the case of continuously fixing the sheet, the temperature distribution in the axial direction of the heating roller 62 tends to be non-uniform, and the temperature of the non-sheet passing portion, which is the non-passing area of the sheet P, tends to rise.

Therefore, in this embodiment, the heating roller 62 is used.
The heat conducting means 80 is provided to make the temperature distribution in the axial direction uniform. The heat conducting means 80 is shown in FIGS.
As shown in FIG. 7, a temperature equalizing roller 90 is pressed as a heat conducting member, which is a combination of a core material 90a having an outer diameter of 10 mm and a copper pipe material 90b having a high outer diameter of 20 mm and a thickness of 5 mm, which is a member of high heat conductivity. It is designed so that it can be rotated by being driven.

As a result, without changing the performance of the fixing and the performance of the nip portion 66 that most affects the rise time,
Apparently, it has the effect of increasing the cross-sectional area of the heating roller 62,
It has become possible to eliminate temperature unevenness in the axial direction.

That is, conventionally, when the A4 size paper P is continuously fed vertically to the A3 size fixing device, the set temperature is 1
The temperature of the non-sheet-passing portion was increased from 60 ° C. to 80 ° C. with respect to 80 ° C., but it was possible to suppress the temperature to 40 ° C. or less by providing the temperature uniformizing roller 90.

5 and 6 show a modification of the above-mentioned first embodiment. It should be noted that only parts different from the first embodiment described above will be described, the same parts will be denoted by the same reference numerals, and redundant description will be omitted.

In the modification of the first embodiment, instead of the temperature equalizing roller 90 as a heat conducting member, a temperature equalizing member 90 'having a leaf spring structure made of a 0.8 mm thick copper plate is used as the heating roller 62. In order to improve heat conduction in the axial direction, the thickness of the non-contact portion is increased to 5 mm in order to improve heat conduction in the axial direction.

Temperature equalizing roller 9 of the first embodiment described above.
It has been experimentally confirmed that it is possible to suppress the temperature of the non-sheet passing portion to 40 ° C. or less, as in the case of 0. In addition,
Temperature equalizing roller 90 and temperature equalizing member 9 having a leaf spring structure
Regarding the setting position of 0 ', it is important to prevent the contact portion from being contaminated downstream of the cleaning member 76, but the roller shape is superior in terms of life performance, and the surface of the temperature uniformizing roller 90 is Needless to say, it can be easily inferred that the performance can be further stabilized by providing a cleaning member.

Regarding the thermal conductivity, 50 W / (m · K) is necessary because the effect can be recognized even with iron. Further, if the nip width between the temperature equalizing roller 90 and the temperature equalizing member 90 'with the heating roller 62 is large, the effect can be further enhanced, and the heat transfer coefficient of silicon rubber or the like can be improved. It goes without saying that the same effect can be expected by adding the material.

Next, a second embodiment of the present invention will be described with reference to FIGS. 7 and 8. It should be noted that only parts different from the first embodiment described above will be described, the same parts will be denoted by the same reference numerals, and redundant description will be omitted.

In the second embodiment, the surface of the heating roller 62 and the downstream portion in the rotation direction of the heating roller 62 with respect to the contact position (nip portion) 66 between the heating roller 62 and the pressure roller 64, the paper P is used. Paper non-passage area (area indicated by diagonal lines in FIG. 8) 62A, 62A as non-passage area due to size change of
To the non-passage areas 62A, 62A associated with the size change of the paper P, and the heat radiation roller 100 as a heat radiation member made of a material having a high thermal conductivity and provided so as to be able to come into contact with and separate from the heat radiation roller 100. Heat dissipation means 1 including heat dissipation roller contacting / separating means 102 as a heat dissipation member contacting / separating means
04 is incorporated to make the temperature of the heating roller 62 uniform in the axial direction.

The heat-dissipating roller 100 has a core material 100a having an outer diameter of 10 mm and copper pipe materials 100b and 100b, which are members having a high heat conductivity and having an outer diameter of 20 mm and a thickness of 5 mm, attached to the outside of the paper material. Pipe material according to
00b and 100b are pressed against the non-sheet passing portions 62A and 62A so as to be driven and rotated.

Further, the heat radiating roller contacting / separating means 102 holds the core member 100a of the heat radiating roller 100, and has an arm 108 having a support shaft 106 as a rotation center, and a solenoid 110 which is an operation source for rotationally displacing the arm 108. Have and. Then, the operation of the dedicated paper feed cassette provided for each size is detected to turn on / off the solenoid 110, and the pipe material 10 disposed at both ends of the heat radiation roller 100.
0b and 100b are pressed against the non-sheet passing portions 62A and 62A and are separated from each other.

As a result, the fixing ability and the performance of the nip portion 66, which most affects the rise time, are not changed.
It has become possible to prevent the temperature rise of the non-sheet passing portions 62, 62A.

That is, conventionally, when the A4 size sheet P is continuously fed vertically to the A3 size fixing device, the set temperature is 1
Although the temperature of the non-sheet passing portion was increased from 60 ° C. to 80 ° C. with respect to 80 ° C., it was possible to suppress the temperature to 40 ° C. or lower by providing this heat radiation roller 100.

9 and 10 show a first modification of the above-mentioned second embodiment. It should be noted that only the portions different from the above-described embodiment will be described, the same portions will be denoted by the same reference numerals, and redundant description will be omitted.

In the modification of the second embodiment, instead of the heat dissipation roller 100 as a heat dissipation member, a heat dissipation plate 100 'having a leaf spring structure made of a 0.8 mm thick copper plate is used as the heating roller 62.
In order to improve the heat conduction in the axial direction, the thickness of the non-contact part is increased by 5 mm.
There is.

Further, it is experimentally confirmed that fins are provided for heat dissipation like a normal heat sink to further improve the heat dissipation effect, and it is possible to suppress the temperature to 40 ° C. or less like the roller shape. ing.

The heat radiating roller 100 and the heat radiating plate 100 '.
As for the setting position of the cleaning member 76, it is important to prevent the contact portion from being contaminated downstream of the cleaning member 76, but the roller shape is superior in terms of life performance, and the heat dissipation roller 10
It goes without saying that the performance can be further stabilized by further providing a cleaning member on the surfaces of the 0 pipe materials 100b and 100b.

Regarding the thermal conductivity, 50 W / (m · K) is necessary because the effect can be recognized even with iron. Further, if the nip width of the heat radiating roller 100 or the heat radiating plate 100 'with the heating roller 62 is large, the effect can be further increased, and a material for improving the heat transfer coefficient is added to silicon rubber or the like. It goes without saying that similar effects can be expected with this.

11 and 12 show a second modification of the above-mentioned second embodiment. It should be noted that only the portions different from the above-described embodiment will be described, the same portions will be denoted by the same reference numerals, and redundant description will be omitted.

The second modification of the second embodiment has a size such that it can contact both the heating roller 62 and the pressure roller 64.
In addition, the opening 120 having a size that allows the sheet P to pass through in the center
a heat dissipation plate 120 having a leaf spring structure having a, and a heat dissipation plate 120
Non-passage areas 62A, 62A due to the size change of the paper P
A heat radiating means 124 composed of a heat radiating plate contacting / separating means 122 as a heat radiating member contacting / separating means is incorporated to make the temperature of the heating roller 62 in the axial direction uniform and to radiate the heat radiated energy from the heating roller 62. This is used for heating the pressure roller 64, which makes it possible to further aim at the energy saving effect.

The heat radiating plate 120 is rotatably supported by a support shaft 126, and the solenoid 12 as the heat radiating roller contacting / separating means 122 is provided at the upper end of the heat radiating plate 120.
8 are connected. Then, the operation of the dedicated paper feed cassette provided for each size is detected, the solenoid 128 is turned on and off, and the paper of a small size that requires heat radiation of the non-paper passing portions 62A, 62A of the heating roller 62. When P passes, the vertical frame portions 120b and 120b of the heat sink 120 are set to the positions shown by the solid lines in FIG.
The lower frame portion 1 while being pressed against the non-sheet passing portions 62A, 62A of
20c is brought into contact with the pressure roller 62. Further, when fixing a large size paper P that does not require heat dissipation, the heat dissipation plate 120 is set to the position shown by the chain double-dashed line in FIG. 11 and is retracted from the paper conveyance path 40.

In the second embodiment (including the modification), the ON / OFF operation of the solenoids 110 and 128 is detected by the operation of the dedicated sheet feeding cassette provided for each size, and the solenoid is brought into contact with and separated from the solenoid. I am making it work,
It is also possible to provide another paper size detection mechanism to select the operation.

Next, a third embodiment of the present invention will be described with reference to FIGS. Only the parts different from the above-mentioned first embodiment (FIGS. 3 and 4) will be described.
The same portions will be denoted by the same reference numerals and redundant description will be omitted.

In the third embodiment, the surface of the pressure roller 64 is brought into contact with a temperature uniformizing roller 90 as a heat conducting member made of a material having a high thermal conductivity, and the pressure roller 64 is pressed.
By making the temperature of the heating roller 62 uniform in the axial direction, the temperature distribution of the heating roller 62 in the axial direction is made uniform. Also in this example, it was confirmed that the temperature rise of the non-sheet passing portion was suppressed to a low level.

15 and 16 show a modification of the above-mentioned third embodiment. It should be noted that only parts different from the modification example (FIGS. 5 and 6) of the above-described first embodiment will be described, the same parts will be denoted by the same reference numerals, and redundant description will be omitted.

In the modification of the third embodiment, a temperature equalizing member 90 'having a leaf spring structure as a heat conducting member made of a material having high heat conductivity is brought into contact with the surface of the pressure roller 64. By making the temperature of the pressure roller 64 in the axial direction uniform, the temperature distribution of the heating roller 62 in the axial direction is made uniform. Also in this example, it was confirmed that the temperature rise of the non-sheet passing portion was suppressed to a low level.

Next, a fourth embodiment of the present invention will be described with reference to FIGS. Only the parts different from the second embodiment (FIGS. 7 and 8) will be described.
The same portions will be denoted by the same reference numerals and redundant description will be omitted.

In the fourth embodiment, the non-sheet passing portions (hatched areas in FIG. 18) 64A and 64A as the non-passing areas due to the size change of the paper P of the pressure roller 64 are contacted and separated. A heat radiating roller 100 as a heat radiating member, which is freely provided and is made of a material having a high thermal conductivity, and a non-passage area 64A for changing the size of the paper P.
A heat radiating means 104 including a heat radiating roller contacting / separating means 102 as a heat radiating member contacting / separating means to be brought into contact with 64 A is incorporated, and the temperature of the pressure roller 64 in the axial direction is made uniform, so that the temperature of the heating roller 62 in the axial direction is increased. The temperature distribution is made uniform. Also in this example, it was confirmed that the temperature rise of the non-sheet passing portion was suppressed to a low level.

19 and 20 show a modification of the above-mentioned fourth embodiment. It should be noted that only parts different from the above-described embodiment (FIGS. 9 and 10) will be described, the same parts will be denoted by the same reference numerals, and redundant description will be omitted.

In the modification of the fourth embodiment, the heat dissipation plate 10 having a leaf spring structure is used instead of the heat dissipation roller 100 of the fourth embodiment.
0'is a non-sheet passing portion (a shaded area in FIG. 20) as a non-passing area due to the size change of the paper P of the pressure roller 64.
It was configured to be brought into contact with and separated from 64A and 64A, and it was confirmed that the temperature rise of the non-sheet passing portion was suppressed to a low level also in this example.

Next, referring to FIG. 21, the fifth embodiment of the present invention will be described.
An example will be described. It should be noted that only the portions different from the above-described embodiments will be described, the same portions will be denoted by the same reference numerals, and redundant description will be omitted.

This embodiment is a fixing device applied to an image forming apparatus in which a sheet P is conveyed in a one-sided reference state in which the sheet P is moved in one direction regardless of size, and a halogen lamp which is a rod-shaped heat source in the heating roller 62. The heater lamp moving means 130 as a heat source moving means for moving the heater lamp 60 such as the above in the axial direction is provided, and the position of the heater lamp 60 is changed so as to correspond only to the passage portion of the paper P.

Further, it is desirable that the guide for moving the heater lamp 60 and the cables for power supply (both not shown) are made of heat-resistant resin. In this embodiment, TI polymer manufactured by Toray Industries, Inc. is used. Is used.

The heater lamp moving means 130 uses the heater holder 132 for holding the heater lamp 60 as the solenoid 1.
The heater lamp 60 is moved by the ON / OFF operation of the solenoid 134 based on the mounting operation of the sheet feeding cassette 10 for each paper size (not shown).
Is moved in the axial direction by 80 mm or less in accordance with A3 size and A4 vertical size. This makes it possible to prevent the temperature rise of the non-sheet passing portion of the heating roller without changing the fixing ability and the rising time.

Further, it is possible to consider movement in accordance with a fine paper size, but in reality, there are few opportunities to continuously print sizes other than those mentioned above, and this movement means causes a practical problem. Not not.

Further, in this embodiment, the operation is performed based on the operation of the paper feed cassette dedicated to each paper size (not shown), but a dedicated size paper size detection mechanism may be provided. In addition, it goes without saying that the present invention can be variously modified and implemented without departing from the spirit of the present invention.

[0083]

Since the present invention has been described above,
The following effects are obtained. According to the fixing device of the first aspect, the heat conduction is made of a material having high heat conductivity on the surface of the heating roller and on the downstream side in the rotation direction of the heating roller from the contact position between the heating roller and the pressure roller. Since the members are brought into contact with each other, the thickness of the heating roller other than the nip portion (the heating portion where the pressure roller is in contact) is apparently increased to improve the thermal conductivity and to improve the temperature unevenness in the heating roller axial direction. And the temperature rise in the non-sheet passing portion of the heating roller can be reduced. As a result, it is possible to shorten the rise time of the fixing device and save energy.

According to the fixing device of the second aspect,
Consists of a material with high thermal conductivity in the non-passage area of the surface of the heating roller and in the downstream of the contact position between the heating roller and the pressure roller in the rotation direction of the heating roller due to the size change of the image carrier. Since the heat dissipating member is contacted, the heat of the non-sheet passing portion of the heating roller is apparently radiated to reduce the temperature unevenness in the axial direction of the heating roller and the temperature rise in the non-sheet passing portion of the heating roller is reduced. Can be made. As a result, it is possible to shorten the rise time of the fixing device and save energy.

According to the fixing device of the third aspect,
Since the surface of the pressure roller, and the downstream portion in the rotational direction of the pressure roller from the contact position between the heating roller and the pressure roller, the heat conductive member made of a material having high heat conductivity is brought into contact with the pressure roller,
Apparently, the temperature distribution in the axial direction of the pressure roller can be positively made uniform to reduce the temperature rise in the non-sheet passing portion of the heating roller rolling on the pressure roller. As a result, it is possible to shorten the rise time of the fixing device and save energy.

According to the fixing device of the fourth aspect,
A material having a high thermal conductivity with respect to the non-passage area of the surface of the pressure roller and the downstream portion in the rotation direction of the pressure roller from the contact position between the heating roller and the pressure roller due to the size change of the image carrier. Since the heat dissipating member constituted by the above is brought into contact, apparently the heat of the non-sheet passing portion of the pressure roller is dissipated, and the temperature distribution in the axial direction of the pressure roller is positively made uniform and transferred to this. It is possible to reduce the temperature rise in the non-sheet passing portion of the heating roller. As a result, it is possible to shorten the rise time of the fixing device and save energy.

According to the fixing device of the fourth aspect,
Since the rod-shaped heat source in the heating roller is moved in the axial direction so as to correspond to the passage portion of the image carrier, it is possible to prevent the temperature rise of the non-sheet passing portion of the heating roller, and thereby, Shortening the start-up time of the fixing device,
Energy saving can be achieved.

[Brief description of drawings]

FIG. 1 is a sectional front view showing an internal configuration of an image forming apparatus to which a first embodiment of a fixing device of the present invention is applied.

FIG. 2 is a sectional side view showing the overall configuration of the first embodiment of the fixing device of the present invention.

FIG. 3 is a schematic side view of a main part according to the first embodiment of the present invention.

FIG. 4 is a schematic perspective view of a main part according to the first embodiment of the present invention.

FIG. 5 is a schematic side view of essential parts according to a modification of the first embodiment of the present invention.

FIG. 6 is a schematic perspective view of a main part according to a modification of the first embodiment of the present invention.

FIG. 7 is a schematic side view of a main part according to the second embodiment of the present invention.

FIG. 8 is a schematic perspective view of a main part according to a second embodiment of the present invention.

FIG. 9 is a schematic side view of a main part according to a first modification of the second embodiment of the present invention.

FIG. 10 is a schematic perspective view of a main part according to a first modification of the second embodiment of the present invention.

FIG. 11 is a schematic side view of a main part according to a second modification of the second embodiment of the present invention.

FIG. 12 is a schematic perspective view of a main part according to a second modification of the second embodiment of the present invention.

FIG. 13 is a schematic side view of a main part according to the third embodiment of the present invention.

FIG. 14 is a schematic perspective view of a main part according to a third embodiment of the present invention.

FIG. 15 is a schematic side view of a main part according to a modification of the third embodiment of the present invention.

FIG. 16 is a schematic perspective view of a main part according to a modification of the third embodiment of the present invention.

FIG. 17 is a schematic side view of a main part according to the fourth embodiment of the present invention.

FIG. 18 is a schematic perspective view of a main part according to a fourth embodiment of the present invention.

FIG. 19 is a schematic perspective view of a main part according to a modification of the fourth embodiment of the present invention.

FIG. 20 is a schematic perspective view of a main part according to a modification of the fourth embodiment of the present invention.

FIG. 21 is a schematic perspective view of a main part according to a fifth embodiment of the present invention.

[Explanation of symbols]

P ... Paper (image carrier), 40 ... Paper transport path, 50 ... Fixing device, 60 ... Heater lamp (heat source), 62 ... Heating roller (heat roller), 62A ... Paper non-passing area of heating roller, 64 ... Addition Pressure roller (press roller), 64A ... Paper non-passage area of pressure roller, 66 ... Contact position (nip portion), 78 ... Thermistor, 80 ... Heat conducting means, 82 ... Fixing means, 90 ... Temperature equalizing roller (heat Conductive member), 90
a ... Core material, 90b ... Pipe material, 90 '... Temperature equalizing member (heat conducting member), 100 ... Radiating roller (radiating member), 1
00 '... heat dissipation plate (heat dissipation member), 100a ... core material, 100
b ... Pipe material, 102 ... Heat radiating roller contacting / separating means (heat dissipating member contacting / separating means), 104 ... Heat dissipating means, 106 ... Spindle, 108
... arm, 110 ... solenoid, 120 ... heat sink, 12
2 ... Radiating plate contacting / separating means (radiating member contacting / separating means), 124 ... Radiating means, 126 ... Spindle, 128 ... Solenoid, 130 ...
Heater lamp moving means, 132 ... Heater holder, 134
…solenoid.

Claims (5)

[Claims] 1. A heating roller which conveys an image bearing member carrying a developer image made of powder developer while heating it, and a pressure roller which conveys while pressing the image bearing member against the heating roller. A fixing unit configured to melt and fix the developer image on the image carrier, and a rotation direction of the heating roller relative to a surface of the heating roller of the fixing unit and a contact position between the heating roller and the pressure roller. A heat conducting member that is provided in contact with the downstream portion and is made of a material having a high heat conductivity, and that has a heat conducting means that equalizes the temperature in the axial direction of the heating roller. Characterizing fixing device. 2. A heating roller for heating and carrying an image carrier carrying a developer image composed of a powder developer, and a pressure roller for carrying the image carrier while pressing the image carrier against the heating roller. A fixing unit configured to melt and fix the developer image on the image carrier, and a rotation direction of the heating roller relative to a surface of the heating roller of the fixing unit and a contact position between the heating roller and the pressure roller. A heat radiating member, which is a downstream portion, is formed of a material having a high thermal conductivity and is provided so as to come in contact with and away from a non-passage area associated with the size change of the image bearing member, and the heat radiating member of the image bearing member. 2. A fixing device comprising: a heat radiation member contacting / separating means for contacting a non-passage area associated with a size change, and a heat radiation means for equalizing the temperature in the axial direction of the heating roller. 3. A heating roller that heats and conveys an image bearing member carrying a developer image made of a powdery developer, and a pressure roller that conveys while pressing the image bearing member against the heating roller. And a fixing unit configured to melt and fix the developer image on the image carrier, and a surface of the pressure roller of the fixing unit, and a position of the pressure roller more than a contact position between the heating roller and the pressure roller. A heat conducting member made of a material having a high heat conductivity provided in contact with a downstream portion in the rotation direction is provided, and the temperature of the pressure roller in the axial direction is made uniform by making the temperature in the axial direction of the heating roller uniform. A fixing device, comprising: a heat conducting means for making the temperature distribution uniform. 4. A heating roller for heating and carrying an image carrier carrying a developer image made of a powder developer, and a pressure roller for carrying the image carrier while pressing the image carrier against the heating roller. And a fixing unit configured to melt and fix the developer image on the image carrier, and a surface of the pressure roller of the fixing unit, and a position of the pressure roller more than a contact position between the heating roller and the pressure roller. A heat radiating member, which is a downstream portion in the rotation direction and is provided so as to come into contact with and separate from a non-passage area associated with the size change of the image carrier, and made of a material having high thermal conductivity; A heat-dissipating member contacting / separating means for contacting a non-passage area due to a size change of the body is provided, and the temperature in the axial direction of the pressure roller is made uniform, thereby making the temperature distribution in the axial direction of the heating roller uniform And heat dissipating means Fixing device characterized by. 5. A fixing device for fixing a developer image composed of a powder developer on an image carrier, which is fed in a one-sided reference state in one direction regardless of size, and which houses a rod-shaped heat source. And a heating roller that conveys the image bearing member carrying the developer image while heating it, and a pressure roller that conveys the image bearing member while pressing the image bearing member against the heating roller. And a heat source moving unit for moving a rod-shaped heat source in the heating roller of the fixing unit in the axial direction so as to correspond to a passage portion of the image carrier. A fixing device characterized by the following.