JP2017044953A - Image heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image heating device with reduced latency time irrespective of completion timing of an image heating operation by controlling temperature difference between a paper passing area and a non-paper passing area until completion of a job.SOLUTION: An image heating device has: first and second rotors; first and second detection means for detecting temperature of the first rotor in a first area in which a recording material with predetermined width passes through a nip part and a second area outside the first area; heating means for heating the first rotor so that detected temperature of the first detection means becomes first temperature and second temperature (higher than the first temperature) when basis weight of the recording material with the predetermined width is first basis weight and second basis weight larger than the first basis weight; and cooling means for cooling the first rotor in the second area so that the detected temperature of the second detection means becomes third temperature higher than the first temperature and fourth temperature higher than the third temperature when the basis weight of the recording material with the predetermined width is the first and second basis weight.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image heating apparatus suitable for an image forming apparatus such as a multifunction peripheral such as an electrophotographic system, a copying machine, a printer, and a fax machine.

  As a means for fixing an unfixed image (toner image) formed in an image forming unit such as an electrophotographic method in an image forming apparatus, a fixing means comprising a fixing member having a heat source and a pressure member pressed against the fixing member Thermal fixing in which toner is welded to a recording material is widely used. Here, as the recording material, a transfer sheet, electrofax sheet, electrostatic recording paper, OHP sheet, printing paper, format paper, or the like is used.

  In recent years, a film heating type fixing device has been put into practical use from the viewpoint of quick start and energy saving. For example, a pressure contact nip is formed by sandwiching a thin fixing film as a heat transfer member between a ceramic heater as a heating member and a pressure roller as a pressure member, and pressurizing with the fixing film in the nip portion A recording material on which an unfixed toner image is formed and supported between the rollers is introduced.

  The unfixed toner image is fixed on the surface of the recording material by applying pressure at the fixing nip portion while applying heat of the ceramic heater through the fixing film by being nipped and conveyed together with the fixing film. Furthermore, a fixing method has been proposed in which a pressure member is disposed through a belt so as to face the fixing roller.

  The background of the market demand for improving the quick start property as described above is that, in the usage method in the market, a situation in which a plurality of jobs with a small number of copies are output dominates. In the case of the above usage, waiting time for starting up the fixing device and waiting time between jobs are unavoidable at present, and it is actually stressing the user. It is.

  Therefore, in order to improve user satisfaction, there is a strong demand for shortening the startup operation time and shortening the waiting time between jobs. In particular, it is urgent to shorten the waiting time, which tends to be long and frequently occurs.

  In order to meet the demands of the market, as a technology that contributes to the reduction of the waiting time, there is known a configuration in which a blower fan is provided in the fixing device and the member is cooled by blowing air to the fixing member or the pressure member. In Patent Document 1, a cooling fan for cooling the fixing member of the fixing device is provided, and after the fixing operation is completed, the fan is operated to perform control to quickly shift the fixing member temperature to an acceptable temperature for the next job.

  Further, in Patent Document 2, in order to prevent the temperature of the surface of the fixing member passing through the non-sheet passing area of the fixing member from being excessively increased, a cooling fan for cooling the fixing non-passing area is provided. Control is performed to cool the non-sheet passing area. That is, there has been proposed control for uniforming an excessive temperature difference between the sheet passing area and the non-sheet passing area of the fixing member during the fixing operation by cooling the fixing non-sheet passing area during the sheet passing.

JP 2006-171237 A JP 2007-187816 A

  However, in the control for cooling the fixing member after completion of the fixing operation as proposed in Patent Document 1, it is difficult to cope with the influence due to the excessive temperature rise of the fixing member during the sheet passing. As an example of excessive temperature rise, there is a case where small size paper having a width smaller than the maximum size paper is continuously fixed in the fixing region. In this case, the temperature of the non-sheet passing area passing surface of the fixing member is excessively increased with respect to the sheet passing area surface temperature. This is because in the non-sheet passing area where the sheet does not pass, heat is partially stored as much as heat is not taken away by the paper (temperature increase of the non-sheet passing portion).

  When such a non-sheet passing portion temperature rise occurs, it takes time to cool the non-sheet passing area of the fixing member even after the fixing operation is finished, and a lot of waiting time ( Wait Time) is required.

  Further, the ON / OFF control of the cooling fan at a predetermined temperature as proposed in Patent Document 2 has the following problems. That is, depending on the sheet passing conditions, the fixing member temperature in the non-sheet passing area rapidly increases when the fan is in the OFF state, and it is difficult to control the temperature near the timing when the fan is turned on. End up.

  In the cooling fan ON-OFF control, since the temperature fluctuation range of the fixing member is large, for example, when the fixing operation is finished before the temperature of the fixing non-sheet passing area reaches the temperature at which the fan is turned ON, the fixing is performed. There is a case where a considerable temperature difference is caused between the sheet passing area and the non-sheet passing area (FIG. 10).

  An object of the present invention is to provide an image heating apparatus in which the waiting time is reduced by controlling the temperature difference between the paper passing area and the non-paper passing area until the end of the job, regardless of the end timing of the image heating operation. is there.

  In order to achieve the above object, an image heating apparatus according to the present invention includes first and second rotating bodies that form a nip portion for heating a recording material on which an image is formed, and the first rotating body. A first recording medium that detects a temperature of the first rotating body in a first region in which a recording material having a predetermined width narrower than a recording material having a maximum width size that can be introduced into the apparatus in the longitudinal direction passes through the nip portion. Detecting means, a second detecting means for detecting the temperature of the first rotating body in a second region outside the first region in the longitudinal direction, and heating the recording material having a predetermined width. When the basis weight of the recording material of the predetermined width is the first basis weight, the first rotating body is heated so that the detection temperature of the first detection means becomes the first temperature, and the When the basis weight of the recording material having a predetermined width is a second basis weight larger than the first basis weight, Heating means for heating the first rotating body so that the detection temperature of the detection means becomes a second temperature higher than the first temperature, and when the recording material of the predetermined width is heated, the predetermined width When the basis weight of the recording material is the first basis weight, in the second region, the detection temperature of the second detection means is a third temperature higher than the first temperature. When the first rotating body is cooled and the basis weight of the recording material having the predetermined width is the second basis weight, the detection temperature of the second detection means is higher than the third temperature. And cooling means for cooling the first rotating body in the second region so as to reach a temperature.

  Further, another image heating apparatus according to the present invention includes first and second rotating bodies that form a nip portion for heating a recording material on which an image is formed, and a longitudinal direction of the first rotating body. First detection means for detecting the temperature of the first rotating body in a first region in which a recording material having a predetermined width narrower than a recording material having a maximum width size that can be introduced into the apparatus passes through the nip portion. And a second detection means for detecting the temperature of the first rotating body in a second region outside the first region in the longitudinal direction, and when heating the recording material having the predetermined width, When the basis weight of the recording material having the predetermined width is the first basis weight, the first rotating body is heated so that the detection temperature of the first detection means becomes the first temperature, and the predetermined width of the recording material is set. If the basis weight of the recording material is a second basis weight that is larger than the first basis weight, the first detecting means Heating means for heating the first rotating body so that the known temperature is a second temperature higher than the first temperature, a fan for blowing air toward the first rotating body, When heating the recording material of a predetermined width, the basis weight of the recording material of the predetermined width when the recording material of the predetermined width when the recording means for guiding the air blown from the fan to the second region is heated. In the case of the first basis weight, the fan starts to be driven after the detected temperature of the second detection means becomes equal to or higher than a third temperature higher than the first temperature, and the predetermined width is reached. When the basis weight of the recording material is the second basis weight, the fan starts to be driven after the detection temperature of the second detection means becomes equal to or higher than a fourth temperature higher than the third temperature. Control means for controlling the fan as described above.

  According to the present invention, by controlling the temperature difference between the sheet passing area and the non-sheet passing area until the end of the job, the waiting time is reduced regardless of the end timing of the fixing operation.

Sectional drawing of the image forming apparatus carrying the image heating apparatus which concerns on the 1st Embodiment of this invention Sectional drawing of the image heating apparatus which concerns on 1st Embodiment (AA of FIG. 1) Sectional drawing (BB of FIG. 2) of the image heating apparatus which concerns on 1st Embodiment Block diagram of the controller in the first embodiment The flowchart which shows operation | movement of the image heating heater in 1st Embodiment. The flowchart which shows operation | movement of the cooling fan in 1st Embodiment. Non-sheet passing portion temperature rise and fan wraparound schematic diagram in the first embodiment Transition diagram of thermistor temperature transition and cooling fan input power ratio in the first embodiment Detection temperature chart of cooling transition of non-sheet passing portion in the first embodiment Detected temperature chart during cooling fan ON-OFF control by conventional control

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

<< First Embodiment >>
(Image forming device)
FIG. 1 is a cross-sectional view of an image forming apparatus 400 equipped with a fixing device as an image heating apparatus according to an embodiment of the present invention. Four cartridges 7 (7a to 7d) arranged side by side in the vertical direction are a photosensitive drum unit 26 (26a to 26d) having a photosensitive drum 1 (1a to 1d) as an electrophotographic photosensitive member, and a developing unit 4. (4a-4d).

  The photosensitive drum 1 is rotationally driven clockwise (Q direction) in FIG. 2 by a driving member (not shown). Further, around the photosensitive drum 1, a cleaning member 6 (6a to 6d), a charging roller 2 (2a to 2d), and a developing unit 4 are arranged in the order of the rotation direction. The cleaning member 6 removes the toner agent remaining on the photosensitive drum 1 after transferring the toner image formed on the photosensitive drum 1 onto the intermediate transfer belt 5. The toner agent removed by the cleaning member 6 is collected in a removed toner chamber in the photoreceptor unit 26 (26a to 26d).

  The charging roller 2 charges the surface of the photosensitive drum 1 uniformly. After the surface of the photosensitive drum 1 is charged by the charging roller 2, laser light is exposed to the surface of the photosensitive drum 1 from the scanner unit (exposure unit) 3 through the unit openings 32 (32 a to 32 d). As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 1. In the present embodiment, the scanner unit 3 is disposed below the cartridge 7.

  The developing unit 4 supplies toner agent to the electrostatic latent image formed on the photosensitive drum 1 and develops the electrostatic latent image as a toner image. The developing unit 4 is in contact with the photosensitive drum 1 to supply a toner agent to the surface of the photosensitive drum 1, and a developing roller 25 (25a to 25d) that supplies the toner agent to the surface of the photosensitive drum 1, and the developing roller 25 is in contact with the developing roller 25 Supply rollers 34 (34a to 34d) are provided.

  Here, when forming an image on the recording material S, first, the electrostatic latent image formed on the surface of the photosensitive drum 1 by the scanner unit 3 is developed as a toner image by the cartridge 7 and transferred to the intermediate transfer belt 5. The

  The intermediate transfer belt 5 is stretched around a driving roller 10 and a tension roller 11 and is driven in the direction of arrow R in FIG. Further, a primary transfer roller 12 (12a to 12d) is disposed inside the intermediate transfer belt 5 so as to face each photosensitive drum 1, and a transfer bias is applied by a bias applying unit (not shown). It has become. For example, in the case of using a negatively charged toner agent, a toner image is primarily transferred onto the intermediate transfer belt 5 sequentially by applying a positive bias to the primary transfer roller 12.

  Then, the four-color toner images are conveyed to the secondary transfer unit 15 in a state where the intermediate transfer belt 5 is overlaid. At this time, the toner agent remaining on the intermediate transfer belt 5 after the secondary transfer to the recording material S is removed by the transfer belt cleaning device 23, and the removed toner agent passes through a waste toner conveyance path (not shown). The toner is collected in a waste toner collecting container (not shown).

  On the other hand, in synchronization with the image forming operation described above, the recording material S is fed toward the secondary transfer unit 15 by the conveyance mechanism including the feeding device 13 and the registration roller pair 17. The feeding device 13 includes a feeding cassette 24 that stores a plurality of recording materials S, a feeding roller 8 that feeds the recording materials S, and a transport roller pair 16 that transports the fed recording materials S. doing.

  The feeding cassette 24 is configured to be detachable from the image forming apparatus 1. The user pulls out the feeding cassette 24 and removes it from the image forming apparatus 1, and then sets the recording material S and inserts it into the image forming apparatus 1 to complete the replenishment of the recording material S.

  Among the recording materials S stored in the feeding cassette 24, the feeding roller 8 is pressed against the recording material S located at the uppermost position, and is separated one by one by the separation pad 9 as the feeding roller 8 rotates. (Friction piece separation method) The recording material S is conveyed. The recording material S conveyed from the feeding device 13 is conveyed to the secondary transfer unit 15 by the registration roller pair 17. In the secondary transfer unit 15, a four-color toner image on the intermediate transfer belt 5 can be secondarily transferred onto the conveyed recording material S by applying a positive bias to the secondary transfer roller 18. Is possible.

  Then, the recording material S is fed from the secondary transfer unit 15 and conveyed to the fixing device 40, and heat and pressure are applied to the image transferred to the recording material S to fix the image on the recording material S. Thereafter, the recording material S on which the toner image is fixed is discharged to the discharge tray 20 by the discharge roller pair 19.

  1 is a cooling fan, and 500 is a control circuit as a control unit, which will be described in detail later together with the fixing device 40. In FIG. 1, reference numeral 550 denotes an external information terminal that transmits a print job signal to the control circuit 500 of the printer 400.

(Image heating device)
Next, the configuration of the fixing device 40 as the image heating device in the present embodiment will be described in detail. The fixing device 40 according to this embodiment that fixes a toner image on a recording material by heating at the nip portion includes first and second fixing members that form a nip portion where the recording material including the toner image is nipped and conveyed. As a fixing film 101 and a pressure roller 106. The fixing method includes a belt (film) heating method using a fixing film 101 as an endless belt in which an elastic layer is formed on a cylindrical thin metal base layer, and a pressure roller driving method.

  2 is a cross-sectional view (cross-sectional view taken along line AA in FIG. 1) of the fixing device 40 in the present embodiment, and FIG. 3 is a cross-sectional view (cross-sectional view taken along line BB in FIG. 2) of the fixing device 40.

  In FIG. 3, a fixing device 40 includes a pressure roller 106 as a pressure member, a ceramic heater 100 as a heating member or a heating element, and a cylindrical fixing film 101 as a fixing member. In addition, a pressure contact member 103 that is installed at both ends of the cylindrical fixing film and forms a nip portion N between the fixing flange 104 that restricts the moving amount in the film longitudinal direction and the pressure roller 106 with the fixing film 101 interposed therebetween. Is provided. Further, a stay 102 is provided on the inner surface side of the fixing film in order to ensure the strength of the pressure contact member 103.

(Film unit)
Here, a film unit 111 is a combination of the fixing film 101, a ceramic heater (hereinafter referred to as a heater) 100, a pressure contact member 103, a stay 102, and a fixing flange 104.

1) Fixing Film A fixing film 101 as a first rotating body is a heat-resistant film (belt) as a heat generating member that transfers heat to the recording material P, with an elastic layer formed on a cylindrical thin metal base layer. Yes, the pressure contact member 103 is loosely fitted. In order to reduce the heat capacity and improve the quick start property, the fixing film 101 has a film thickness of 100 μm or less, preferably 50 μm or less and preferably 20 μm or more. Specifically, a single layer of PTFE, PFA, FEP or a composite layer film in which PTFE, PFA, FEP or the like is coated on the outer peripheral surface of polyimide, polyamideimide, PEEK, PES, PPS or the like can be used. It can also be made of metal.

2) Heater 100 is a heater as a heating means. The heater 100 is basically composed of an elongated thin plate-like ceramic substrate and an energization heating resistor layer provided on the substrate surface, and the temperature rises with a steep rise characteristic as a whole by energization of the heating resistor layer. It is a low heat capacity heater. The heater 100 is fitted and supported in a fitting groove 103 a provided on the lower surface of the pressure contact member 103 along the longitudinal direction.

3) Press-contact member The press-contact member 103 is a heat-resistant and heat-insulating member having a substantially semicircular cross section whose longitudinal direction is the direction intersecting the recording material conveyance direction. The pressure contact member 103 serves to back up the fixing film 101, pressurize the nip portion N formed by pressure contact with the pressure roller 106, and transport stability when the fixing film 101 rotates. The pressure contact member 103 is made of a material having good insulation and heat resistance such as phenol resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, PFA resin, PTFE resin, and LCP resin. .

4) Stay The stay 102 is a member for imparting longitudinal strength to the pressure contact member 103 by pressing against the back surface of the relatively flexible resin pressure contact member 103 and for correcting the pressure contact member 103.

5) Fixing flange The fixing flange 104 shown in FIGS. 3 and 1 is fitted to both ends of the assembly of the pressure contact member 103 and the stay 102 to guide the rotation of the fixing film 101 and prevent the fixing film 101 from coming off. ing. In FIG. 1, the fixing flanges 104 disposed at both ends of the fixing film 101 are applied with pressure by a pressure plate (not shown) that is rotatably attached to the fixing frame 112, and pressurizes with the film unit 111. The roller 106 is pressed in the direction of arrow P in FIG.

(Thermistor)
The thermistor 105 as temperature detecting means detects the temperature at a predetermined position in the width direction (longitudinal direction) of the fixing belt (film) on the inner side of the fixing belt. Feedback to 500 (FIG. 1).

  As shown in FIG. 3, the thermistor 105 contacts the inner surface of the fixing film to detect the temperature, and a temperature detecting element portion 105a for biasing the temperature detecting element portion 105a to the fixing film with a predetermined contact pressure. A leaf spring portion 105b having elasticity is provided. Furthermore, the thermistor 105 includes a holding portion 105 c for fixing and attaching to the pressure contact member 103. The leaf spring portion 105b is made of stainless steel and also serves as a conduction path for the temperature detection element portion 105a.

  In the present embodiment, three thermistors 105 are arranged along the longitudinal direction of the fixing film 101 indicated by a broken line in FIG. 2, and the longitudinal direction (width direction) F side is 105F, the center is 105C, and the longitudinal direction R side is. 105R. Further, the thermistor 115 is arranged at the center in the longitudinal direction of the heater 100.

  The thermistor 105 </ b> C (FIG. 2) as the first detection unit is a thermistor that controls the temperature control of the fixing device 40. As will be described in detail later, energization to the heater 100 is controlled via the control circuit 500 (FIG. 1) so that the detected temperature maintains the fixing target temperature (first temperature) (heating control). The thermistors 105 </ b> F and 105 </ b> R as the second detection means are symmetrically arranged on both end sides with respect to the center portion in the longitudinal direction of the fixing film 101. Then, the rotational speed of the cooling fan 60 is controlled via the control circuit 500 (cooling control) so that the detected temperature is maintained at a predetermined temperature (end target temperature) equal to or higher than the fixing target temperature. The thermistor as the temperature detecting means can be replaced with a thermopile.

(Pressure member)
In FIG. 3, the pressure roller 106, which is a second rotating means as a pressure member, is driven to rotate by being transmitted with a fixing motor (not shown) attached in the image forming apparatus 500. Then, the fixing film 101 is rotated in the direction of arrow E in FIG.

  The pressure roller 106 is composed of a metal cored bar 106a and a heat-resistant and elastic material layer such as silicone rubber, fluororubber, and fluororesin that is concentrically formed and coated around the cored bar in a roller shape. A release layer is provided on the surface layer. For example, the release layer may be made of a material having good release properties and heat resistance such as fluororesin, silicone resin, fluorosilicone rubber, fluororubber, silicone rubber, PFA, PTFE, FEP.

  Bearing members 113 (FIG. 1) made of heat-resistant resin such as PEEK, PPS, liquid crystal polymer, and the like are attached to both ends of the cored bar 106a, and are rotatably held on the side plate of the fixing frame 112.

(Cooling fan and shutter)
Cooling fans 60F and 60R as cooling means provided at both ends in the longitudinal direction (width direction) of the fixing film 101 are mounted in the image forming apparatus 400 (FIG. 1). Then, the non-sheet-passing area of the fixing film 101 (the end area that is the non-passing portion of the recording material) is cooled by blowing air in the direction of arrow d in FIG. Specifically, air is sent to the non-sheet passing area (end area) of the fixing film 101 and cooled by a signal from a control circuit 500 (FIG. 1) as a control section in the image forming apparatus 400.

  A shutter 61 (FIG. 3) disposed between the cooling fan 60 and the fixing film 101 is attached to the fixing device 40. Then, a signal from the control circuit 500 (FIG. 1) in the image forming apparatus 400 is opened and closed along the longitudinal direction (c direction in FIG. 2) of the fixing film 101 by a driving unit (not shown). That is, when the non-sheet passing portion is cooled by the cooling fans 60F and 60R at the end portions, the shutter 61 moves to a position corresponding to the paper size. Here, at the maximum sheet passing size, the shutter 61 is closed and the cooling fans 60F and 60R at the ends are stopped.

  The areas blown by the cooling fans 60F and 60R at the end are as follows. In FIG. 2, the cooling fans 60F and 60R are inserted into the area (between 112F and 61F) formed between the shutter end portions (61F and 61R) and the fixing frames 112F and 112R (between 112F and 61R) and between the 112R and 61R. The wind is blown. Thus, the non-sheet passing portion region of the fixing film 101 is formed to be cooled. Here, the distance between 112F-61F and 112R-61R is controlled by the width of the paper to be passed, and in the present embodiment, it corresponds to A5R to SRA3 sizes.

(Fixing device temperature control (heating control))
FIG. 4 is a block diagram of the controller in the temperature control (heating control) of the sheet passing portion (recording material passage portion) in the fixing member of the fixing device according to the present embodiment, and FIG. It is. A control circuit 500 serving as a control unit that performs temperature control (heating control) of the heater 100 in the fixing device 40 maintains the detected temperature information input from the thermistor 105C at the fixing target temperature (first temperature). The amount of heating is controlled.

  That is, in FIG. 5, when an image forming operation is started by a copying operation (S100), image forming information is notified from the external host device 150 (S101). Although the fixing target temperature (first temperature) can be changed, the target temperature determining unit 503 determines the fixing target temperature (first temperature) for each operation mode corresponding to the image forming information (S102). Then, the detected temperature is input from the thermistor 105C (S103), and the difference calculation unit 504 calculates the difference between the fixing target temperature (first temperature) and the detected temperature (S104). In accordance with the calculated difference, the heater required heat amount determination unit 505 determines the amount of heat required for the heater 100 (S105).

  Then, the detected temperature is input from the thermistor 115 (S106), and the actual supply heat amount determining unit 506 determines the actual supply heat amount to the heater 100 (S107). The determined actual supply heat amount is converted into an electric energy by the heater electric power supply determining unit 507 (S108), and the supplied electric energy is notified to the heater drive circuit (S109). Thus, until the end of the paper passing job, desired power is supplied to the heater 100, and the heating amount of the heater 100 is controlled so that the temperature detected by the thermistor 105C maintains the fixing target temperature (first temperature).

(Cooling fan speed control (cooling control))
Next, the rotational speed control (cooling control) of the cooling fan in the fixing device according to the present embodiment will be described with reference to the controller block diagram of FIG. 4 and the flowchart of the cooling control operation of FIG. In addition to the temperature control (heating control) of the heater 100 described above, the control circuit 500 serving as a control unit that controls the rotational speed of the cooling fan 60 has detected temperature information input from the thermistors 105F and R as a predetermined target temperature ( (End target temperature) is maintained.

  That is, in FIG. 6, the image forming operation is started as in the temperature control temperature control (heating control), and the fixing target temperature (first temperature) is determined for each operation mode corresponding to the information (S200 to S202). . Then, based on the fixing target temperature (first temperature), the target temperature (end target) of the portion (fixing non-sheet passing portion) where the thermistors 105F, R detect the temperature offset to the predetermined temperature high temperature side. Temperature) is set in the end target temperature determination unit 508 (S203).

  Here, the end target temperature is a predetermined temperature higher than the fixing target temperature (first temperature) or equal to the fixing target temperature (first temperature). The fixing target temperature (first temperature) can be changed to a different value, and the end target temperature can be changed when the fixing target temperature (first temperature) is changed to a different value. ) Can be changed.

  Next, the detected temperatures from the thermistors 105F and R are input (S204), and the difference calculation unit 509 calculates the difference between the end target temperature and the detected temperature (S205). According to the calculated difference, the rotational speed of the cooling fan 60 is determined by the fan rotational speed determination unit 510 (S206). When the required number of rotations of the fan is determined, the amount of power supplied to the cooling fan 60 is determined by the fan power supply amount determination unit 511 so as to be the number of rotations (S207). Then, the determined power supply amount is notified to the fan drive circuit (S208).

  As a result, power is supplied until the cooling fan 60 reaches a desired rotational speed until the end of the paper passing job, and the temperature of the fixing non-sheet passing portion is set to the predetermined end target temperature (fixing target temperature (first temperature)). To maintain the temperature linked to At this time, in this embodiment, the cooling fan as the cooling means variably controls the cooling intensity in multiple stages as will be described in detail later.

(Adequacy of setting the end target temperature)
Here, it is desirable to satisfy the following requirements for setting the end target temperature. (1) Satisfying edge fixability, (2) The temperature of the non-sheet passing area of the fixing member is not deviated from the temperature of the sheet passing area, (3) The fixing film 101 or the fixing heater 100 is damaged. The temperature range should not be.

  First, in order to satisfy (1), at least the end target temperature needs to be equal to or higher than the fixing target temperature (first temperature). However, the temperature of the non-sheet passing area is almost always higher than that of the sheet passing area due to the effect of the temperature rise of the non-sheet passing section. The temperature tends to be slightly lower than that at the center of the paper passing area (FIG. 7). Therefore, in the fixing configuration of this embodiment, the end target temperature is set to a temperature that is at least about 10 ° C. higher than the fixing target temperature (first temperature).

  Next, regarding (2), it is required that the end target temperature be as close to the fixing target temperature (first temperature) as possible. Here, as a more desirable requirement, considering that the above (1) and (2) are satisfied, the end target temperature is controlled in the vicinity of a temperature offset from the fixing target temperature (first temperature) to the high temperature side by 10 ° C. It is preferable.

  Furthermore, the following control is more preferable among the controls near the temperature offset from the fixing target temperature (first temperature) to the high temperature side by 10 ° C. That is, if the temperature is shifted to the low temperature side, there is a possibility that a fixing defect at the end of the recording material (paper) may occur. Control (maintaining so as not to lower the offset temperature) is more preferable.

  Finally, regarding (3), it is desirable to control the end target temperature at a temperature that does not exceed the heat resistance temperature of the fixing film 101 and its peripheral members. The heat-resistant temperature of the fixing film 101 of this embodiment is about 230 ° C., and if the temperature of 220 ° C. or higher is continued, the elastic layer will deteriorate. Therefore, it is desirable not to change the end temperature at a temperature of 220 ° C. or higher.

  Here, as shown in FIG. 10, it is necessary to provide a margin of about 20 ° C. in order to cope with the rapid temperature rise of the non-sheet passing portion. When the end temperature reaches the upper limit temperature of 200 ° C., cooling is performed. It is preferable to suppress the temperature rise by maximizing the rotation speed of the fan 60.

  In summary, the end target temperature is a control temperature (first temperature plus 10 ° C. or higher) whose lower limit is a value offset from the fixing target temperature (first temperature) to the high temperature side by 10 ° C. It is desirable to make the mode uniform 200 ° C. as the upper limit.

  Here, in order to control at the above-described end target temperature, in the present embodiment, the cooling intensity is variably controlled in multiple stages with respect to the cooling fan as the cooling means. Hereinafter, control of the operation of the cooling fan 60 will be described. In the present embodiment, the operation of the cooling fan 60 is started when the temperature detected by the thermistors 105F, R reaches the end target temperature. When the temperature detected by the thermistors 105F and R in the non-sheet passing area (non-sheet passing portion) reaches 200 ° C. or more, the cooling fan 60 is operated at the maximum rotation speed.

  When the temperature detected by the thermistors 105F and R does not reach 200 ° C. as the upper limit temperature, the rotational speed of the cooling fan 60 is set to the non-sheet passing area (non-sheet passing section). Change continuously according to the detected temperature. Here, the fixing target temperature (first temperature) can be changed to a different value, and the end target temperature can be changed when the fixing target temperature (first temperature) is changed to a different value. It can be changed according to the temperature), but the upper limit temperature is not changed.

(Setting power input to cooling fan)
The number of rotations of the cooling fan is defined by the amount of power input to the fan drive circuit 515. The number of revolutions of the cooling fan 60 is 100% (10 W in the apparatus of the present embodiment) necessary for outputting the maximum number of revolutions, and the input required for the larger input value of the thermistors 105F, R Calculate and determine the percentage of energy.

  The ratio of the input power amount per 1 ° C. differs depending on the set fixing target temperature (first temperature), and follows the following equation.

Input power ratio (% / ° C.) = 100 (%) / [200 (° C.) − (Fixing target temperature + 10 ° C.)]
... (Formula 1)
The temperature value 200 (° C.) in the above (Equation 1) is the detected temperature of the thermistors 105F and R.

  Here, if the fixing target temperature (first temperature) is equal to or exceeds the upper limit temperature, the end target temperature is set equal to the upper limit temperature, and the cooling fan 60 is operated at the maximum rotational speed. Is desirable.

(Temperature transition in control execution)
FIG. 8 is a diagram showing a change in the temperature of each thermistor and a change in the ratio of the input power amount of the cooling fan when the above-described control is mounted on the image forming apparatus 400 and the sheet is passed. The condition is plain paper A4 size 80 gsm continuous paper feed, and the fixing target temperature (first temperature) is set to 170 ° C.

  After the thermistor 105C reaches the fixing target temperature (first temperature), the thermistors 105F and R are affected by the temperature rise of the non-sheet passing portion, and the temperature rises. At the timing when the thermistors 105F and R detect 180 ° C. (first temperature plus 10 ° C.) or more, power is supplied to the cooling fan 60, and the cooling fan starts rotating. As the end temperature increases as the temperature of the non-sheet passing portion increases, the ratio of the amount of electric power according to the calculation result of the above equation (Equation 1) increases, so the rotation speed of the cooling fan 60 increases and the cooling effect increases.

  As a result, the non-sheet passing portion temperature is equal to or lower than the upper limit temperature (200 ° C.) and the end target temperature (the first temperature plus 180 ° C. which is 10 ° C.) is the lower limit. The temperature can be controlled in the vicinity of 180.degree.

(Confirmation of control effectiveness)
FIG. 9 shows the results of a test performed to confirm the effectiveness of control (cooling transition of the surface temperature of the fixing film 101 after outputting continuous paper A4 size 80 gsm for 3 minutes for 3 minutes). In this test, when the non-sheet-passing area temperature (thermistor 105F, R detection unit) is controlled around 180 ° C. using the above-described control (test 1), and when the upper limit temperature is around 200 ° C. Two tests (test 2) were conducted. The experiment (test 2) controlled in the vicinity of 200 ° C. simulates the case where the cooling control is not performed by the cooling fan and the case where the cooling fan is turned on and off.

  As a result of this test, the time taken for the edge temperature to decrease to near the fixing target temperature (170 ° C. as the first temperature) after completion of the fixing operation is about 3 seconds in the case of control near 180 ° C. (test 1). In the case of control near 200 ° C. (test 2), it was about 12 seconds.

  Considering that the current startup control time is around 15 seconds, and that the time required for immediate printing after returning from the machine's hibernation state is around 5 seconds, this control (Test 1) is a waiting time (Wait It can be said that this is effective for reducing the (Time).

(Heating control and cooling control corresponding to the paper type)
In the present embodiment, heating control and cooling control corresponding to the paper type are performed.

1) Heating control corresponding to paper type A recording material having a predetermined width narrower than the recording material of the maximum width size that can be introduced into the apparatus in the longitudinal direction of the fixing film as the first rotating body passes through the nip portion. A thermistor 105C is provided as a first detection means for detecting the temperature of the fixing film in the first region (central region). When the recording material having a predetermined width is heated, if the basis weight of the recording material is the first basis weight, the fixing film is heated so that the temperature detected by the thermistor 105C becomes the first temperature. In addition, when the basis weight of the recording material having a predetermined width is a second basis weight larger than the first basis weight, fixing is performed so that the temperature detected by the thermistor 105C is a second temperature higher than the first temperature. Heat the film.

2) Cooling control corresponding to the paper type When the recording material having a predetermined width is heated and the basis weight of the recording material having the predetermined width is the first basis weight, the detected temperatures of the thermistors 105F and R are higher than the first temperature. The fixing film is cooled in the second region (the end region outside the first region in the longitudinal direction) so that the third temperature becomes higher. In addition, when the basis weight of the recording material having the predetermined width is the second basis weight, the fixing film in the second region so that the temperature detected by the thermistors 105F and R is a fourth temperature higher than the third temperature. Cool down.

  Here, Table 1 shows the temperature control temperature (fixing target temperature) corresponding to the paper type, the operation start temperature of the end fan (end target temperature), and the MAX operating temperature of the end fan.

  As shown in Table 1 above, the detected temperature of the thermistor 105C is the first temperature when it is the first basis weight, and the detected temperature of the thermistor 105C is higher than the first temperature when it is the second basis weight. The central region (first region) is heated so that the second temperature becomes higher.

  For example, the basis weight as the second basis weight, which is larger than the first basis weight, with respect to the temperature adjustment temperature (170 ° C. as the first temperature) in the A4 plain paper with the basis weight of 80 as the first basis weight The temperature control temperature of 100 A4 plain paper (180 ° C. as the second temperature) is high.

  And when it is 1st basic weight, an edge part area | region is cooled with an edge part fan so that detection temperature of the thermistors 105F and R may become 3rd temperature higher than 1st temperature. In the case of the second basis weight, the end region is cooled by the end fan so that the detected temperature of the thermistors 105F and R becomes a fourth temperature higher than the second temperature.

  When the third temperature (180 ° C. as the first basis weight) or the fourth temperature (190 ° C. as the second basis weight) as the end target temperature is reached, the operation of the end fan is started. In Table 1, the end fan operation start temperature for A4 plain paper with a basis weight of 80 is lower than the end fan operation start temperature for A4 plain paper with a basis weight of 100. This is because the higher the basis weight, the higher the temperature control temperature, and the higher the non-sheet passing temperature.

  Further, the end fan operation start temperature of the B5 plain paper with a basis weight of 80 is lower than the end fan operation start temperature of the A4 plain paper with the basis weight of 80. This is because the narrower the paper width, the greater the distance between the edge thermistor and the paper edge, and a temperature difference between the edge thermistor and the paper edge. A correction value of about minus 2 ° C. is added.

  The rotation speed of the fan when the edge thermistor of B5 plain paper with a basis weight of 80 is 180 ° C. is faster than the rotation speed of the fan when the edge thermistor of A4 plain paper with a basis weight of 80 is 180 ° C. . This is because, as the paper width is narrower, the shutter opens more widely, so that the dynamic pressure on the non-sheet passing portion due to air blowing decreases. Therefore, it is necessary to rotate the fan more in order to cool the non-sheet passing portion.

  Here, regardless of the basis weight of the paper, when the end thermistor reaches 200 ° C., the end fan is driven fully open. When continuous paper feeding (about 500 sheets) is performed in a high temperature environment, the temperature of the non-paper passing part may gradually increase even if the air flow (rotational speed) of the end fan is gradually increased. . In such a case, when the temperature reaches 200 ° C., the end fan is finally fully opened.

(Effect of this embodiment)
As described above, in the fixing device as the image heating device to which the present embodiment is applied, the temperature difference between the sheet passing area and the non-sheet passing area on the surface of the fixing member can be controlled with a predetermined temperature difference even when a small size is continuously passed. In addition, the above relationship can be continued even when the paper passing job is completed. For this reason, the temperature of the non-sheet passing area (non-passing portion) from the end of the fixing operation can be quickly transferred to the target temperature of the next job, and the waiting time can be reduced.

(Modification)
Although the preferred embodiments of the present invention have been described in the above-described embodiments, the present invention is not limited to these embodiments, and various modifications are possible within the scope of the gist.

(Modification 1)
In the above-described embodiment, the upper limit temperature for maximizing the cooling of the cooling unit in at least one of the first and second fixing members is provided, and the end target temperature is controlled to be lower than the upper limit temperature. Is not limited to this. That is, such an upper limit control is not performed, and if a member that breaks beyond the upper limit temperature is generated, an image heating apparatus based on the idea of replacing the member can be obtained.

(Modification 2)
In the above-described embodiment, the end portion on the fixing film side is cooled in order to suppress the temperature rise of the non-sheet passing portion. However, the end portion on the pressure roller side may be cooled, or the fixing film side, the pressure roller Both sides may be cooled. Further, the temperature detecting means for detecting the temperature of the non-passing portion may be arranged on at least one side of the fixing film side and the pressure roller side. Similarly, the temperature detecting means for detecting the temperature of the passage portion may be arranged on at least one side of the fixing film side and the pressure roller side.

(Modification 3)
In the embodiment described above, the cooling means is a blower fan whose cooling intensity is variable by changing the number of revolutions or the amount of input power, but the present invention is not limited to this. For example, it may be a blower fan in which the cooling strength is variable by changing at least one of the number of times the voltage to be applied is turned on / off per unit time and the time interval of turning on / off. Further, it may be a blower fan that makes the cooling intensity variable by changing the intensity of the applied voltage.

  Further, the cooling means is not limited to the cooling fan, and any cooling means such as a heat pump or a device using a Peltier element can be used.

  In the above-described embodiment, the heater is used as the heating unit. However, the present invention is not limited to this, and any heating unit such as a self-heating type heating unit using electromagnetic induction can be used.

(Modification 4)
The image heating apparatus according to the present invention includes a control unit that controls the temperature difference between the sheet passing area and the non-sheet passing area on the surface of the fixing member with a predetermined temperature difference. And this control part is not restricted to the case where it is a control part (CPU with which an image forming apparatus is equipped) which combines control concerning image formation, and control concerning image heating. That is, it may be a control unit that exclusively performs control relating to image heating.

  The image heating apparatus according to the present invention is not limited to one fixed inside the image forming apparatus, but may be a unit that can be removed and replaced outside the image forming apparatus. In this case, it may be removed and replaced including the control unit, or may be removed and replaced except for the control unit. In addition, the image heating apparatus according to the present invention may be used alone by the image heating apparatus independently of the image forming apparatus.

(Modification 5)
In the above-described embodiment, the endless belt is provided on the first rotating body. However, the endless belt may be provided on the second rotating body facing the first rotating body. An endless belt may be provided on both the first rotating body and the second rotating body.

  In the above-described embodiment, the case where the rotating body (pressure roller) as the rotating body and the pressing body presses the fixing rotating body (fixing belt) is shown. However, the present invention is not limited to this, and the present invention can be similarly applied to a case where a rotating body as an opposing body is pressed from a fixing belt (film) as a fixing rotating body, not as a pressing body. Here, the opposing body is a member that faces the fixing rotator, presses against the fixing rotator, forms a fixing nip portion, and clamps the moving recording material at the fixing nip portion.

  In the above-described embodiment, the pressure rotating body (pressure roller) that rotates together with the fixing rotating body is shown as the pressure body. However, the present invention is not limited to this, and a flat plate shape fixed as the pressure body. Applicable to pressure pad.

  In the above-described embodiment, the recording paper is described as the recording material. However, the recording material in the present invention is not limited to paper. Generally, a recording material is a sheet-like member on which a toner image is formed by an image forming apparatus. For example, regular or irregular plain paper, cardboard, thin paper, envelope, postcard, seal, resin sheet, OHP sheet, Includes glossy paper. In the above-described embodiment, for the sake of convenience, the recording material (sheet) P has been described using terms such as passing paper, paper passing portion, and non-paper passing portion. It is not limited.

  In the above-described embodiment, the fixing device that fixes an unfixed toner image on the sheet has been described as an example. However, the present invention is not limited to this, and the toner that is assumed on the sheet in order to improve the gloss of the image. The present invention can be similarly applied to an apparatus for heating and pressurizing an image (also an image heating apparatus in this case).

60, 60F, 60R ... Cooling fan, 100 ... Ceramic heater, 101 ... Fixing film, 106 ... Pressure roller, 500 ... Control circuit (control unit)

Claims (6)

First and second rotating bodies that form a nip portion for heating the recording material on which an image is formed, and a recording material having a maximum width size that can be introduced into the apparatus in the longitudinal direction of the first rotating body. A first detecting means for detecting the temperature of the first rotating body in a first region in which a recording material having a narrow predetermined width passes through the nip portion;
Second detection means for detecting the temperature of the first rotating body in a second region outside the first region in the longitudinal direction;
When the recording material having the predetermined width is heated, when the basis weight of the recording material having the predetermined width is the first basis weight, the detection temperature of the first detection unit is set to the first temperature. When the basis weight of the recording material having the predetermined width is a second basis weight that is larger than the first basis weight, the temperature detected by the first detection means is the first detection unit. Heating means for heating the first rotating body so as to have a second temperature higher than the temperature;
When the recording material having the predetermined width is heated, when the basis weight of the recording material having the predetermined width is the first basis weight, the detection temperature of the second detection unit is higher than the first temperature. When the basis weight of the recording material having the predetermined width is the second basis weight in the second region, the second detecting means Cooling means for cooling the first rotating body in the second region such that the detected temperature becomes a fourth temperature higher than the third temperature;
An image heating apparatus comprising: First and second rotating bodies that form a nip portion for heating the recording material on which an image is formed, and a recording material having a maximum width size that can be introduced into the apparatus in the longitudinal direction of the first rotating body. A first detecting means for detecting the temperature of the first rotating body in a first region in which a recording material having a narrow predetermined width passes through the nip portion;
Second detection means for detecting the temperature of the first rotating body in a second region outside the first region in the longitudinal direction;
When the recording material having the predetermined width is heated, when the basis weight of the recording material having the predetermined width is the first basis weight, the detection temperature of the first detection unit is set to the first temperature. When the basis weight of the recording material having the predetermined width is a second basis weight that is larger than the first basis weight, the temperature detected by the first detection means is the first detection unit. Heating means for heating the first rotating body so as to have a second temperature higher than the temperature;
A fan for blowing air toward the first rotating body;
Guiding means for guiding the air blown from the fan to the second region when the recording material having the predetermined width is heated;
When the recording material having the predetermined width is heated, when the basis weight of the recording material having the predetermined width is the first basis weight, the detection temperature of the second detection unit is higher than the first temperature. When the basis weight of the recording material having the predetermined width is the second basis weight so that the fan starts driving after the temperature becomes 3 or more, the detected temperature of the second detection means is the first temperature. An image heating apparatus comprising: control means for controlling the fan so that the fan starts driving after reaching a fourth temperature higher than a temperature of 3. When the temperature detected by the second detection means is the fourth temperature when the recording material having the predetermined width of the second basis weight is heated, the control means has a first rotation speed per unit time. Drive the fan so that the value of
When the temperature detected by the second detection means is the fourth temperature when the recording material having the predetermined width with the first basis weight is heated, the control means has a first rotation speed per unit time. The image heating apparatus according to claim 2, wherein the fan is driven so as to have a second value larger than the value of the image heating device. When the detection temperature of the second detection means is equal to or higher than a fifth temperature higher than the fourth temperature when heating the recording material of the predetermined width,
The said control means drives the said fan so that the rotation speed per unit time may become a 3rd value larger than a 2nd value irrespective of the basic weight of a recording material. Image heating device. When the recording material narrower than the recording material having the predetermined width is heated, the guide means is arranged in a third region outside the region in which the narrow recording material passes through the nip portion in the longitudinal direction. Guide the air flow from the fan,
When the detection temperature of the second detection means is the fourth temperature when the recording material having the second basis weight and the narrow width is heated, the control means has the number of rotations per unit time. The image heating apparatus according to claim 3, wherein the fan is driven so as to have a third value larger than the first value. When the recording material narrower than the recording material having the predetermined width is heated, the guide means is arranged in a third region outside the region in which the narrow recording material passes through the nip portion in the longitudinal direction. Guide the air flow from the fan,
When heating the recording material having the first basis weight and the narrow width, the control means has a temperature detected by the second detection means higher than the first temperature and higher than the third temperature. The image heating apparatus according to claim 2, wherein the fan is controlled so that the fan starts to be driven after a low sixth temperature is reached.