JP3869936B2 - Fixing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention is used for a copying machine, a laser beam printer, a facsimile, and the like.Regarding fixing device.
[0002]
[Prior art]
For example, a heat fixing device in an image forming apparatus such as a copying machine, a printer, or a facsimile, that is, a heat fixable developer (toner) by an appropriate image forming process such as an electrophotographic method, an electrostatic recording method, or a magnetic recording method. Unfixed toner image (target image information) formed and supported on the surface of a recording material (transfer material sheet, printing paper, electrofax sheet, electrostatic recording sheet, etc.) using an indirect (transfer) method or a direct method As a heating device for heat-fixing an unfixed developer image corresponding to the above to a recording material, a heating device of a heat roller type has been generally used.
[0003]
This heating roller type heating device is a pressure nip portion between a heating roller (fixing roller) heated by a built-in heat source such as a halogen heater and maintained at a predetermined temperature and a pressure roller having elasticity pressed against the heating roller. The recording material is introduced into the (fixing nip portion) and is nipped and conveyed, whereby the unfixed toner image on the surface of the recording material is thermally fixed by the heat of the fixing roller.
[0004]
Recently, a film heating type heating apparatus has been proposed and put into practical use (for example, JP-A-63-313182, JP-A-1-263679, JP-A-2-157878, JP-A-4-4-1). No. 44075 to 44083, Japanese Patent Laid-Open No. 4-204800 to 204984, etc.).
[0005]
In this heating apparatus, a recording material as a material to be heated is brought into close contact with a heating body fixedly supported by a supporting member via a heat-resistant and thin film material, and the film material is slid and moved to the heating body. This is a system and configuration in which the heat is applied to the recording material through a film material, and can be utilized as an apparatus for thermally fixing an unfixed toner image as a permanently fixed image on the surface of the recording material. In addition, for example, it is widely used as a device that heats a recording material carrying a toner image to modify the surface properties such as gloss, a device that performs a hypothetical process, and a device that heats a sheet-like material to be heated. Can do.
[0006]
Such a heating device of the film heating system has a heating element having a low heat capacity with a high temperature rise, for example, an insulating / good thermal conductive ceramic base material, and energization provided on the surface of the base material. A so-called ceramic heater having a heat generating resistive heating layer as a basic component can be used, and a thin film with a low heat capacity can be used as a film material. There is no need to supply power to the heating element, and the heating element can be sufficiently heated up to a predetermined temperature before the recording material reaches the fixing nip even if the recording material as the material to be heated passes immediately. It has advantages such as shortening the wait time (quick start performance: on-demand operation) and power saving, and suppressing the temperature rise in the image forming apparatus main body. It is ones.
[0007]
Here, all of the unfixed toner carried on the surface of the recording material is appropriately heated and melted and fixed on the surface of the recording material. If there is too much hot offset toner, electrostatic fixing roller, toner offset to the fixing film, etc., these toners are transferred to the fixing roller or fixing film in contact with the surface of the recording material, and these fixing rollers In addition, the toner transferred to the fixing film further transfers to the pressure roller between paper sheets and the like, and adheres to the fixing roller, the fixing film, and the pressure roller, thereby causing toner contamination.
[0008]
In order not to accumulate toner stains, the surface layer of the fixing roller, fixing film, and pressure roller used in the fixing device is made of a fluororesin layer such as PTFE, PFA, FEP, etc. In general, a release layer made of a silicone rubber layer such as LTV, RTV is provided.
[0009]
[Problems to be solved by the invention]
However, the release layer such as a fluororesin used for the surface layer of the fixing roller, the fixing film, and the pressure roller in the above-described conventional example cannot completely eliminate the toner contamination. For this reason, when toner dirt adheres to the toner contact surface such as the fixing roller and fixing film, the fixing roller and fixing film are always heated to the toner melting temperature during image formation, so that the toner dirt is in a molten state. When the next recording material reaches the fixing nip portion, it is mixed with the toner image on the surface and moved to the recording material side, or moved to the pressure roller between papers. There is no state that is continuously dirty.
[0010]
On the other hand, in the case of the pressure roller side, the toner stain is once offset to the fixing roller and the fixing film and then transferred to the pressure roller. Since the pressure roller is lower in temperature than the fixing roller and the fixing film, the moved toner stain does not always exist on the pressure roller in a completely melted state. In particular, in an on-demand type fixing device using a fixing film, the pressure roller is not heated except for the paper passing, so that the temperature hardly rises and the temperature rises to about 100 ° C. at the maximum. For this reason, the toner stains offset and transferred to the pressure roller as described above hardly melt on the pressure roller. Further, since the toner image on the surface of the recording material does not come into contact with the pressure roller side, the toner stain is rarely brought to the toner image, and once the stain is accumulated, the stain is accumulated. When toner stains on the pressure roller are accumulated, the releasability of the pressure roller is reduced, so that a recording material (especially when the recording material is an OHP film) is wound around or accumulated on the pressure roller. There is a disadvantage that the toner stains the recording material at once.
[0011]
In particular, recently, electrophotographic printers are widely used all over the world, and accordingly, recording materials used in the printers are also diversified.
[0012]
For example, in the European market, recording materials that are stiff and have good whiteness are preferred, and CaCO is a filler used in recording materials._Three Is often used. However, CaCO_Three If the toner adheres to the pressure roller, the releasability of the pressure roller is deteriorated, and the above-described toner contamination on the pressure roller is promoted and further deteriorated. This CaCO_Three The adhesion to the pressure roller becomes worse in a low humidity environment. Further, the toner contamination of the pressure roller becomes worse in a low temperature environment.
[0013]
For example, CaCO in an environment with a temperature of 15 ° C. and a humidity of 10%_Three When a sheet passing durability test is performed using a recording material containing 10 to 15% of the toner, the pressure roller starts to become dirty when the number of passing sheets is 1000 to 2000, and toner contamination occurs on the recording material with almost the same number of sheets. The image is defective.
[0014]
  The present invention has been made in view of the above circumstances, and prevents toner stains from accumulating on the fixing rotator, so that the recording material wraps around the fixing rotator and the toner stains accumulated on the fixing rotator all at once. Prevented problems such as dirty recording materialsProvide fixing deviceIt is for the purpose.
[0015]
[Means for Solving the Problems]
  To achieve the above object, the present invention provides:A cylindrical fixing film, a heating body that contacts the inner peripheral surface of the fixing film, and a pressure that is in contact with the outer peripheral surface of the fixing film and forms a fixing nip portion with the heating body via the fixing film A roller and the pressure rollerA rotation control unit that controls rotation; and a temperature control unit that controls the temperature of the heating member, and heats the recording material carrying an unfixed toner image while being nipped and conveyed by the fixing nip portion. In the fixing device for fixing the unfixed toner image thereon, the temperature control unit controls the temperature of the heating body after the rotation of the pressure roller is stopped by the rotation control unit at the end of image formation, and the fixing Temperature control to heat the nip to a temperature above the toner softening pointAfter that, the temperature of the fixing nip portion is lowered to fix the toner in the fixing nip portion to the fixing film.It is characterized by that.
[0024]
[Action]
  The present inventionAccording to this, first, the toner in the fixing nip portion of the toner adhering to the offset or the like is surely melted, so that the toner mass can be larger than before the melting. When the fixing rotator is rotated after such a state, the toner tends to adhere to the rotator as the contact surface. Next, when the recording material on which an image is formed passes through the fixing nip portion, the toner attached to the fixing rotator is transferred to the recording material and discharged together with the recording material. The offset toner at this time is a small amount of toner that is invisible because the recording material is passed through several to several tens of sheets, and the toner discharged to the recording material is naturally visible. There are no levels.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0034]
<Embodiment 1>
FIG. 1 shows an image forming apparatus according to the present invention, that is, an image forming apparatus provided with a fixing device according to the present invention. 1 is a longitudinal sectional view showing a schematic configuration of a laser beam printer as an example of an image forming apparatus according to the present invention.
[0035]
First, the configuration of a laser beam printer (hereinafter referred to as “image forming apparatus”) will be described with reference to FIG.
[0036]
The laser beam printer shown in FIG. 1 includes a drum-type electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 1 as an image carrier. The photosensitive drum 1 is rotatably supported by the apparatus main body M, and is rotationally driven at a predetermined process speed in the direction of the arrow R1 by a driving unit (not shown).
[0037]
Around the photosensitive drum 1, a charging roller (charging device) 2, an exposure unit 3, a developing device 4, a transfer roller (transfer device) 5, and a cleaning device 6 are disposed almost in order along the rotation direction. .
[0038]
A sheet feeding cassette 7 that stores a sheet-like recording material P such as paper is disposed below the apparatus main body M, and the sheet feeding roller 15 is sequentially arranged from the upstream side along the conveyance path of the recording material P. , A transport roller 8, a top sensor 9, a transport guide 10, a fixing device 11, a transport roller 12, a paper discharge roller 13, and a paper discharge tray 14 according to the present invention are arranged.
[0039]
Next, the operation of the image forming apparatus having the above configuration will be described.
[0040]
The photosensitive drum 1 that is rotationally driven in the direction of arrow R1 by a driving means (not shown) is uniformly charged to a predetermined polarity and a predetermined potential by a charging roller 2.
[0041]
The photosensitive drum 1 after charging is subjected to image exposure L based on the image information by the exposure means 3 such as a laser optical system on the surface, and the charge of the exposed portion is removed to form an electrostatic latent image.
[0042]
The electrostatic latent image is developed by the developing device 4. The developing device 4 includes a developing roller 4a. A developing bias is applied to the developing roller 4a to attach toner to the electrostatic latent image on the photosensitive drum 1 and develop (develop) it as a toner image.
[0043]
The toner image is transferred to the recording material P such as paper by the transfer roller 5. The recording material P is stored in the paper feed cassette 7, fed by the paper feed roller 15, transported by the transport roller 8, and transferred between the photosensitive drum 1 and the transfer roller 5 via the top sensor 9. It is conveyed to the nip part. At this time, the leading edge of the recording material P is detected by the top sensor 9 and is synchronized with the toner image on the photosensitive drum 1. A transfer bias is applied to the transfer roller 5, whereby the toner image on the photosensitive drum 1 is transferred to a predetermined position on the recording material P.
[0044]
The recording material P carrying the unfixed toner image on the surface by transfer is transported to the fixing device 11 along the transport guide 10, where the unfixed toner image is heated and pressurized and fixed on the surface of the recording material P. . The fixing device 11 will be described in detail later.
[0045]
The recording material P after the toner image is fixed is transported by the transport roller 12 and discharged onto the discharge tray 14 on the upper surface of the apparatus main body M by the discharge roller 13.
[0046]
On the other hand, after the toner image has been transferred, the toner remaining on the surface (hereinafter referred to as “transfer residual toner”) that has not been transferred to the recording material P is removed by the cleaning blade 6a of the cleaning device 6 to form the next image. To be served.
[0047]
By repeating the above operation, image formation can be performed one after another.
[0048]
Next, an example of the fixing device 11 according to the present invention will be described in detail with reference to FIG. This figure is a longitudinal sectional view along the conveyance direction (arrow K direction) of the recording material P.
[0049]
A fixing device 11 shown in the figure includes a ceramic heater (hereinafter simply referred to as “heater”) 20 as a heating body for heating toner, a fixing film (fixing rotating body) 25 including the ceramic heater 20, and The main components are a pressure roller 26 as another fixing rotator in contact with the fixing film 25, a temperature control means 27 for controlling the temperature of the ceramic heater 20, and a rotation control means 28 for controlling the conveyance of the recording material P. It is comprised as a structural member.
[0050]
The ceramic heater 20 is formed by forming a resistor pattern 20b on a heat-resistant base material 20a such as alumina by printing, for example, and covering the surface with a glass layer 20c. ), Which is long in the left-right direction perpendicular to (), that is, longer than the width of the recording material P. The ceramic heater 20 is supported by a heater holder 22 attached to the apparatus main body M. The heater holder 22 is a member formed in a semicircular shape with a heat resistant resin, and also acts as a guide member for guiding the rotation of the next fixing film 25.
[0051]
The fixing film 25 is formed of a heat-resistant resin such as polyimide in a cylindrical shape, and is loosely fitted to the ceramic heater 20 and the heater guide 22 described above. The fixing film 25 is pressed against the ceramic heater 20 by a later-described pressure roller 26, so that the back surface of the fixing film 25 is brought into contact with the lower surface of the ceramic heater 20. The fixing film 25 is configured to rotate in the arrow R25 direction as the recording material P is conveyed in the arrow K direction by the rotation of the pressure roller 26 in the arrow R26 direction. Note that both left and right end portions of the fixing film 25 are regulated by guide portions (not shown) of the heater holder 22 so that they do not come off in the longitudinal direction of the ceramic heater 20. Further, grease is applied to the inner surface of the fixing film 25 in order to reduce sliding resistance between the ceramic heater 20 and the heater guide 22.
[0052]
The pressure roller 26 is provided with a heat-resistant release layer 26b having elasticity such as silicone rubber on the outer peripheral surface of a metal cored bar 26a. The fixing film is formed from below by the outer peripheral surface of the release layer 26b. 25 is pressed against the ceramic heater 20 to form a fixing nip portion N with the fixing film 25. If the width (nip width) in the rotation direction of the pressure roller 26 in the fixing nip portion N is a, the nip width a is such that the toner on the recording material P can be suitably heated and pressed. Is set.
[0053]
The rotation control means 28 includes a motor 29 that rotates the pressure roller 26 and a CPU 30 that controls the rotation of the motor 29. As the motor 29, for example, a stepping motor or the like can be used, and the pressure roller 26 can be rotated intermittently by a predetermined angle in addition to continuously rotating the pressure roller 26 in the direction of the arrow R26. That is, the recording material P can be stepped while the pressure roller 26 is repeatedly rotated and stopped.
[0054]
The temperature control means 27 includes a thermistor (temperature detection element) 21 attached to the back surface of the ceramic heater 20 and a CPU 23 that controls the triac 24 based on the temperature detected by the thermistor 21 and controls the energization of the ceramic heater 20. Have.
[0055]
As described above, the fixing device 11 heats the toner on the recording material P by the ceramic heater 20 while nipping and conveying the recording material P at the fixing nip portion N by the rotation of the pressure roller 26 in the direction of arrow R26. At this time, by controlling the rotation of the pressure roller 26 by the rotation control means 28, the feeding of the recording material P can be appropriately controlled, and the temperature of the ceramic heater 20 is appropriately controlled by the temperature control means 27. Is something that can be done.
[0056]
Next, details of the present invention will be described below.
[0057]
FIG. 7 shows the surface of the fixing film (described as “film surface” in FIGS. 3 to 7) and the pressure roller 26 when an image is formed (hereinafter referred to as “print”) using a conventional fixing sequence. The temperature state of is shown. In the conventional fixing temperature control, the heater 20 is turned off during the post-rotation, so the temperature of the pressure roller and the fixing film is lowered. In such a state, the toner adhering to the surface of the fixing film was transferred to the pressure roller 26 without being softened.
[0058]
In the present embodiment, when printing is finished, the temperature of the toner adhering to the fixing film 25 at the fixing nip N is raised to a temperature higher than the softening temperature, and the respective toners are combined and not transferred to the pressure roller 26. Adjust the temperature.
[0059]
In order to soften the offset toner adhering to the fixing film 25 or the like, the toner temperature needs to be 120 ° C. or higher.
[0060]
FIG. 3 shows the relationship between the fixing temperature control at that time and the temperature of the fixing film surface and the pressure roller 26.
[0061]
The post-rotation / post-temperature control in FIG. 3 is a temperature control when the printing is finished. As is apparent from the figure, the fixing temperature adjustment temperature is 185 ° C., which is almost the same as the conventional one, but the post-rotation immediately after printing maintains a constant temperature unlike the conventional one. Then, the temperature of the pressure roller is increased to 120 ° C. at which the toner is softened. When the operation is further stopped, the pressure roller temperature and the film surface temperature in the fixing nip N are controlled to a temperature at which the toner is sufficiently softened by performing rapid heating. This facilitates the expansion of the pressure roller 26 and allows the toners in the fixing nip N to be combined. When the toner is combined, the temperature is cut.
[0062]
Since the fixing nip portion N is composed of the pressure roller 26 having a large heat capacity and the fixing film 25 having a small heat capacity and easy to cool down, the fixing film is higher than the pressure roller 26 whose temperature is gradually decreased at a temperature of 120 ° C. or higher. A state where the surface is cooled (see C in FIG. 3) occurs. Accordingly, the combined toner starts to adhere to the cooled fixing film 25.
[0063]
When the fixing device 11 is rotated in such a state, even when it is difficult to hold each toner, it is easy to hold the toner on the fixing film 25 by combining the toner. Then, the transfer of the toner held on the fixing film 25 at the fixing nip N to the pressure roller 26 can be reduced. When the fixing device 11 is rotated, the toner adhering to the fixing film 25 side can be further increased by lowering the temperature of the fixing nip portion N to a temperature equal to or lower than the softening point of the toner.
[0064]
Further, since the recording material P that has entered the fixing nip portion N is at room temperature, a temperature difference is generated between the surface of the fixing film and the recording material P. The toner held on the fixing film 25 in the fixing nip portion N is invisible to the eye, and this toner adheres onto the recording material P and is discharged.
[0065]
The portion of the outer peripheral surface of the pressure roller 26 that stops at the fixing nip portion N after printing is different every time the pressure roller 26 is stopped. Therefore, the entire periphery of the outer peripheral surface of the pressure roller 26 is obtained by repeating printing. Dirt can be spit out over. Thereby, it is possible to prevent dirt such as toner from accumulating on the pressure roller 26.
[0066]
When intermittent durability (2 sheets / 10 minutes) is performed by the conventional temperature control, the pressure roller is contaminated with about 2000 sheets. On the other hand, this embodiment is used to control the temperature of the post-rotation temperature adjustment at 165 ° C., the post-temperature adjustment at 200 ° C. for 5 seconds, and the fixing nip temperature at the next printing to 100 ° C. or less. As a result, the amount of toner adhering to the pressure roller 26 can be reduced to less than half, and no toner smearing was observed even with intermittent durability of 4000 sheets.
[0067]
According to the present embodiment, even when there is a variation in the surface coating of the pressure roller 26, the adhesion of the toner to the pressure roller 26 can be effectively prevented. This eliminates the need for higher precision than necessary, and thus it is possible to improve the yield of the pressure roller 26 and thus reduce the cost.
[0068]
<Embodiment 2>
In the first embodiment described above, the toner is held on the fixing film 25 by adjusting the temperature of the post-rotation, thereby preventing the pressure roller 26 from being contaminated with toner, paper powder, or the like. As a result, the contamination of the pressure roller 26 is considerably reduced, but there is still no sufficient margin for the durable life. In this embodiment, in order to further reduce the contamination of the pressure roller 26, the toner transferred to the pressure roller 26 is eliminated by controlling the temperature of the fixing film surface and the pressure roller 26 before printing. Made it possible.
[0069]
FIG. 4 shows the temperature control of the present embodiment. Note that the overall configuration of the image forming apparatus and the configuration of the fixing device 11 are the same as those in the first embodiment described above, and therefore, a duplicate description thereof will be omitted.
[0070]
  Conventionally, as shown in FIG. 7, heating is started simultaneously with the start of rotation of the motor. In contrast, in the present embodiment, when a print signal is sent, a portion of the surface of the pressure roller 26 that is located at the fixing nip portion N is in a state where there is no temperature difference between the surface of the fixing film and the pressure roller 26. Control to move, that is, control to start rotation before starting heating is included. In that case,ofThe temperature of the fixing film surface and the pressure roller 26 is shown. As can be seen from FIG.During pre-rotationSince the surface temperature of the fixing film is rapidly increased and the temperature of the pressure roller 26 is gently increased, the toner in the fixing nip portion N is transferred to the pressure roller 26 having a lower temperature. In the present embodiment, the pressure roller 26 is rotated before the heating is started, so that the pressure roller is rotated.26The portion located in the fixing nip portion N can be moved to reduce the transfer of the toner held on the fixing film 25 to the pressure roller 26 in the fixing nip portion N. It is more effective if the temperature of the fixing nip N at this time is equal to or lower than the softening point of the toner. In addition, performing rotation by an amount corresponding to the nip width a of the fixing nip portion N in a state where there is no temperature difference is more effective for reducing the transfer of toner to the pressure roller 26.
[0071]
Further, since the recording material P that has entered the fixing nip portion N is at room temperature, a temperature difference is generated between the surface of the fixing film and the recording material P. The toner held on the fixing film 25 in the fixing nip portion N is invisible to the eye, and this toner adheres onto the recording material P and is discharged.
[0072]
Conventionally, dirt was generated on the pressure roller 26 after about 2000 sheets of intermittent durability (2/10 minutes). By using this embodiment, a durable life of about 6000 sheets could be secured. As a result, toner can be prevented from accumulating on the pressure roller 26, the cost of the fixing device 11 including the pressure roller 26 can be lowered, and the cost can be reduced. It becomes possible to extend the durable life.
[0073]
<Embodiment 3>
In the first embodiment and the second embodiment described above, the toner adhering to the pressure roller 26 is reduced by reducing the amount of toner transferred from the surface of the fixing film to the pressure roller 26 in each of the pre-rotation and the post-rotation. It was possible to suppress the dirt such as paper dust and to extend the durable life of the fixing device 11. Further, the contamination of the pressure roller 26 is considerably reduced by this.
[0074]
However, the toner transferred from the fixing device 11 to the recording material P may appear as a visible image defect due to variations in the surface coating and processing dimensions of the pressure roller 26.
[0075]
Therefore, in this embodiment, by controlling the pre-rotation and post-rotation control and optimizing the transfer toner amount, the toner contamination of the fixing device 11 is reduced, and an image defect is not generated, depending on the situation. Each control was performed before and after rotation.
[0076]
FIG. 5 shows such fixing temperature control. The temperature of the fixing film surface and the pressure roller 26 when this control is performed is shown in the figure. In the present embodiment, the pre-rotation control used in the second embodiment is adopted, and the post-rotation control suitable for it is used.
[0077]
  In Embodiment 2, the amount of toner transferred from the fixing film surface to the pressure roller 26 can be reduced as compared with the conventional temperature control. However, in order to hold more toner on the fixing film 25 in the previous rotation, in this embodiment, control is performed to heat the fixing nip portion N as in the first embodiment at the end of the previous printing.And combinedToner is maximized and invisibleDuring printingIt is discharged onto the recording material P. By changing the temperature control for post-rotation and post-temperature control, it becomes possible to optimize the amount of toner binding and the transfer amount to the recording material P on the surface of the fixing film.
[0078]
According to this embodiment, the post-rotation temperature is 165 ° C., the post-temperature control is 200 ° C. for 5 seconds, and the fixing nip portion N is moved by the pre-rotation. No stain was observed even with the above durability, and no visible stain appeared in the output image.
[0079]
These controls provide many advantages over the prior art, such as extending the life of the fixing device 11 and eliminating the occurrence of image defects.
[0080]
  <Reference example>
  In the first, second, and third embodiments described above, dirt such as toner adhering to the pressure roller 26 and the like is cleaned by cleaning a portion of the surface of the pressure roller 26 that stops at the fixing nip N for each print. Has been prevented. BookReference exampleThen, as shown in FIG. 6, it is possible to extend the durability life by always performing the cleaning sequence during standby.
[0081]
As shown in FIG. 6, after the printing is completed, the thermistor (temperature detection element) 21 determines that the fixing nip portion N is sufficiently cooled. The cleaning effect is improved by repeating the movement of the fixing nip portion N as described above.
[0082]
  BookReference exampleDuring the standby, after repeating the pre-rotation 12mm, temperature control at 200 ° C for 5 seconds, and waiting to cool down to 20 ° C, the dirt that had been generated on 2000 sheets in the past is more than 50000 sheets No stain was observed.
[0083]
  BookReference exampleAccordingly, accumulation of dirt on the pressure roller 26 can be effectively prevented, so that the grade of the fixing device 11 can be lowered and the cost can be reduced. Furthermore, it is possible to extend the durability life of the fixing device 11.
[0085]
【The invention's effect】
As described above, according to the present invention, accumulation of toner stains on the fixing rotator can be effectively prevented, so that the recording material wraps around the fixing rotator and toner stains accumulated on the fixing rotator can be prevented. It is possible to prevent such a problem that the recording material is soiled at once.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus according to the present invention.
FIG. 2 is a longitudinal sectional view showing a schematic configuration of a fixing device according to the present invention.
FIG. 3 is a diagram illustrating a relationship between control in Embodiment 1 and temperatures of a fixing film and a pressure roller.
FIG. 4 is a diagram illustrating a relationship between control of Embodiment 2 and temperatures of a fixing film and a pressure roller.
FIG. 5 is a diagram illustrating a relationship between control in Embodiment 3 and temperatures of a fixing film and a pressure roller.
[Fig. 6]Reference exampleFIG. 6 is a diagram showing the relationship between the control of the toner and the temperature of the fixing film and the pressure roller.
FIG. 7 is a diagram illustrating a relationship between conventional control and temperatures of a fixing film and a pressure roller.
[Explanation of symbols]
1 Image carrier (photosensitive drum)
11 Fixing device
20 Heating body (heater)
21 Temperature sensing element (Thermistor)
22 Heater holder
23 CPU
24 Triac
25 Fixing rotating body (fixing film)
26 Fixing Rotator (Pressure Roller)
27 Temperature control means
28 Rotation control means
29 Motor
30 CPU
N Fixing nip
P Recording material

Claims (3)

A cylindrical fixing film;
A heating element in contact with the inner peripheral surface of the fixing film;
A pressure roller that is in contact with the outer peripheral surface of the fixing film and forms a fixing nip portion with the heating body via the fixing film;
Rotation control means for controlling the rotation of the pressure roller ;
Temperature control means for controlling the temperature of the heating body,
In a fixing device that heats a recording material carrying an unfixed toner image while being nipped and conveyed at the fixing nip portion, and fixes the unfixed toner image on the recording material.
The temperature control means controls the temperature of the heating body after the rotation of the pressure roller is stopped by the rotation control means at the end of image formation, and heats the fixing nip portion to a temperature equal to or higher than the softening point of the toner. And a fixing device that lowers the temperature of the fixing nip portion to fix the toner in the fixing nip portion to the fixing film . When the rotation of the pressure roller at the start of image formation starts and the temperature of the fixing nip is equal to or higher than the softening point of the toner, the rotation control unit lowers the temperature of the fixing nip below the softening point of the toner. The fixing device according to claim 1, wherein the pressure roller starts rotating after being lowered. Said rotation control means, said during image formation start at the start rotation of the pressure roller, before starting the energization of the heating body, to claim 1, characterized in that to start the rotation of the pressure roller The fixing device described.

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