JP2006106686A - Heating apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating apparatus having a heating member A and a pressure member 17 which are mutually brought into press-contact to hold, convey and heat a member to be heated P by a nip portion N formed between both of them, and capable of restraining the curl of the outputted member to be heated P, or an image forming apparatus equipped with the heating apparatus as a fixing device. <P>SOLUTION: The heating apparatus is equipped with a temperature detector 18 for detecting the temperature of the heating member A, and a power control means for controlling the detected temperature of the heating member to a target temperature. A paper conveyance interval temperature which is the target temperature of the heating member set in a paper conveyance interval which is a period from end of heating the M-th member to be heated up to start of heating the M+1-th member to be heated in continuous heating of N members to be heated or in a certain period in the paper conveyance interval is set to a temperature higher than the heating temperature of the member to be heated which is the target temperature of the heating member when heating the M+1-th member to be heated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heating apparatus that heats and discharges a material to be heated to be conveyed by a heating unit.

  More specifically, the present invention relates to a heating apparatus that includes a heating body and a pressure body that are in pressure contact with each other, and sandwiches and conveys a material to be heated at a nip portion formed between them.

  The present invention also relates to an image forming apparatus such as a printer or a copying machine provided with the heating device as an image heating and fixing device.

  Hereinafter, for convenience, a fixing device as a heating device that heats and fixes an image in the image forming apparatus will be described as an example.

  A general fixing device is a recording material (hereinafter referred to as a recording material) in which a heating body (heating member) and a pressure body (pressure member) are pressed to form a nip portion, and an unfixed image is formed and supported on the nip portion. In this case, the unfixed image is heated and pressure-fixed on the surface of the recording medium by the heat of the heating body. The apparatus configuration includes a film heating system and a roller heating system.

  As described in Patent Documents 1 and 2, the film heating type fixing device includes a heating unit (heating source) fixed and supported as a heating body, and a flexible member that slides on the heating unit. The assembly is used. The pressure member forms a heating means and a fixing nip portion through the flexible member, and sandwiches and conveys a recording medium carrying an unfixed image at the fixing nip portion and passes through the flexible member. The recording medium is heated by the heat of the heating means.

  More specifically, a so-called ceramic heater having a low heat capacity and a fast temperature rise is generally used as the heating means. As the flexible member, a thin film film (hereinafter abbreviated as a film) having a single layer structure or a composite layer structure based on a heat resistant resin or metal is used. Then, the film is sandwiched between the ceramic heaters fixedly supported and the pressure roller is brought into pressure contact with each other to form a fixing nip portion. The film is slid in close contact with the ceramic heater surface in the fixing nip portion. In such a configuration, the recording medium is introduced between the film in the fixing nip portion and the pressure roller, and the heat of the ceramic heater is applied to the recording medium through the film by moving the fixing nip portion together with the film. To do.

  A ceramic heater as a heating means includes a thermistor sensor (hereinafter referred to as a thermistor sensor) which is provided with a heating resistor that generates heat when energized on one surface of a thin plate-shaped substrate mainly composed of ceramics and the other surface of the substrate. Are abutted and arranged.

  The roller heating type fixing device uses a cylindrical heat roller (hereinafter referred to as a fixing roller) provided with heating means such as a halogen heater inside or outside as a heating body. A pressure roller as a heating element is pressed against the fixing roller to form a fixing nip portion. A recording medium is introduced between the fixing roller and the pressure roller at the fixing nip portion, and recording is performed by the heat of the fixing roller. Heat the medium. A thermistor as a temperature detecting member is in contact with the fixing roller.

  In the fixing device, the temperature of the heating body is controlled by controlling the energization from the commercial power source to the heating means so that the temperature detected by the thermistor falls within a predetermined range from the target temperature. .

  Next, the temperature control of the heating body in the continuous fixing process step for a plurality of recording media in the fixing device will be described with reference to FIG. FIG. 16 is a graph showing changes in the detected temperature of the thermistor in the continuous fixing process for a plurality of recording media.

  When the image forming apparatus including the fixing device starts an image forming process for a series of recording media including a plurality of N recording media, energization from the commercial power source to the heating unit is started, and the thermistor detection temperature is stopped. The temperature is raised from temperature a to temperature b and temperature c.

  The energization from the commercial power source to the heating means is performed so that the temperature detected by the thermistor reaches the fixing temperature (recording medium heating temperature) d immediately before time T1 when the first recording medium carrying an unfixed image enters the fixing nip portion. The temperature is controlled to be raised. The detected temperature is controlled to be maintained within a predetermined range from the fixing temperature d over a period T1 to T2 in which the recording medium is subjected to fixing processing.

  Next, between the end of the fixing process of the first recording medium and the start of the fixing process of the second recording medium, the energization from the commercial power source to the heating means is performed so that the temperature detected by the thermistor is the fixing temperature d or The temperature is controlled so as to be maintained at a value within a predetermined width of the inter-paper temperature e lower than that. In addition, by maintaining the value between the sheet temperature e lower than the fixing temperature d within a predetermined range, it is possible to save power consumption and to eliminate excessive temperature rise in the non-sheet passing region of the outer peripheral surface of the pressure roller. it can.

The temperature of the heating element is controlled as described above, and heat is supplied from the heating element in contact with one surface of the recording medium during the heat treatment of the recording medium. On the other hand, heat is also supplied from a pressurizing member in contact with the other surface of the recording medium. Since the pressurizing body itself does not have a heating means, the heat that is heated from the surface of the heating body between the paper and stored in the pressurizing body is transferred to the recording medium in the paper.
JP-A-63-313182 JP-A-6-149103

  However, in the fixing device, the temperature of the heating body is controlled between the sheets so as to be equal to the fixing temperature d or lower than the fixing temperature d.

  Due to heat radiation from the surface of the pressure member and heat conduction to the inside of the pressure member and peripheral parts, the surface temperature of the pressure member is necessarily lower than the temperature of the surface of the heating member heated at the fixing temperature d. Further, the temperature of the surface of the pressurizing member is lowered by transferring heat to the recording medium while the paper is being passed.

  As a result, the surface temperature of the pressure member becomes considerably lower than the temperature of the surface of the heating member, and a large difference appears in the amount of heat applied to the front and back of the recording medium when performing the heat fixing operation at the fixing nip portion of the fixing device. There is a risk that.

  In particular, when the recording medium is made of a material containing moisture such as paper, there is a difference in the amount of moisture that evaporates from the front and back of the recording medium. There is a problem that the medium warps and curls.

  In particular, when the environment where the image forming apparatus or the recording medium is placed is a high humidity environment, when the recording medium contains a lot of moisture, when the recording medium lacks thickness, rigidity, etc., the curl becomes severe.

  If the curl is severe, the output recording media cannot be neatly stacked or bound, and the convenience of the output recording medium is impaired.

  In addition, when outputting continuously, it becomes impossible to orderly stack on the discharge stacking unit of the image forming apparatus, and the output recording medium falls or scatters, and the discharge order is changed. In addition, the curled output recording medium may block the recording medium discharge portion of the image forming apparatus, cause the recording medium to bend or wrinkle, or may stay and disable the image forming apparatus. Absent.

  Therefore, the present invention includes a heating device that can suppress curling of the output heated material, and an image heating and fixing device for the recording material, and suppresses curling of the output recording material. It is an object of the present invention to provide an image forming apparatus that can be used.

  A typical configuration of the heating apparatus according to the present invention for achieving the above object has a heating body and a pressure body that are pressed against each other, and sandwiches and conveys the material to be heated at a nip formed between the two. In the heating apparatus that performs the heat treatment, a plurality of N pieces to be heated are provided with a temperature detection body for detecting the temperature of the heating body, and power control means for controlling the detected temperature of the heating body to the target temperature. During the interval from the end of the heat treatment of the Mth material to be heated in the continuous heat treatment to the material to the start of the heat treatment of the M + 1th material to be heated, between papers, or within the paper The paper-to-paper temperature that is the target temperature of the heating body set in the period is set to a temperature that is higher than the heating material heating temperature that is the target temperature of the heating body during the heat treatment of the M + 1th heating material. A heating device, which is characterized.

  That is, by setting the target temperature of the heating body between the papers to be higher than the target temperature during the heating material heating process, the temperature of the pressing body is raised between the papers, and the heating body during the heating material heating process The temperature of the heated body during the heat treatment of the heated material is reduced and the difference between the surface temperature of the pressurized body and the surface temperature of the pressurized body is reduced, the amount of heat supplied to the heated material from the heated body side, and from the pressurized body side The difference in the amount of heat transmitted to the material to be heated can be reduced to suppress warpage and curling of the material to be heated.

Example 1
(1) Example of Image Forming Apparatus FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a laser beam printer (hereinafter abbreviated as a printer) 1 as an example suitably showing an image forming apparatus of the present embodiment.

  The printer 1 has a known image forming process in which an image corresponding to image information provided from an external image information providing apparatus (not shown) such as a host computer is formed and recorded on a sheet-like recording medium P. This is an image forming apparatus in a form that conforms to an electrophotographic system.

  The printer 1 exposes a drum-shaped rotatable electrophotographic photosensitive member 2 as a latent image carrier and a process cartridge 4 holding a developing device 3 and an outer peripheral surface of the photosensitive member 2 according to image information. A laser scanner unit (hereinafter abbreviated as a scanner) 5 that forms an electrostatic latent image, a roll-shaped rotatable transfer body 6 that performs an image transfer process on the recording medium P, and a recording medium P that has undergone the image transfer process. And a fixing device 7 that performs a fixing process by heating and pressing.

  In addition to the photosensitive member 2 and the developing device 3, the process cartridge 4 provided in the printer 1 also holds a primary charging mechanism 8 that charges the outer peripheral surface of the photosensitive member 2 to a specified potential distribution before the exposure processing step by the scanner 5. ing. The process cartridge 4 is detachably supported by the printer body. When maintenance such as repair of the photosensitive member 2 and supply of developer to the developing device 3 is necessary, the maintenance is performed by opening the cover 9 supported by the main body so as to be opened and closed and then replacing the process cartridge 4 together. Speeding up and simplification.

  The primary charging mechanism 8 held in the process cartridge 4 charges the outer peripheral surface of the photoreceptor 2 to a specified potential distribution by applying a specified bias from a commercial power source or the like before the exposure processing step by the scanner 5. ing.

  A scanner 5 provided in the printer 1 is a laser La modulated in accordance with a digital pixel signal generated based on image information from an image information providing device, and through a window 4a provided in the process cartridge main body. Exposure scanning is performed on the outer peripheral surface of the charged photoreceptor 2. Thereby, an electrostatic latent image corresponding to the image information is formed on the outer peripheral surface of the photoreceptor 2.

  Next, a series of image forming processes in the printer 1 will be described. First, when the printer 1 is instructed to start a series of image forming processes, the photosensitive member 2 starts to rotate at a specified peripheral speed in the clockwise direction of the arrow K1, and a specified bias is applied. The primary charging mechanism 8 charges the outer peripheral surface of the photoreceptor 2 to a specified potential distribution.

  Next, a charged portion on the outer peripheral surface of the photosensitive member 2 is scanned and exposed by the scanner 5 in accordance with image information from the image information providing apparatus, so that an electrostatic latent image corresponding to the image information becomes the portion. Formed. The electrostatic latent image is visualized into a visible image by the developer of the developing device 3.

  On the other hand, the recording medium P is separated and fed from the paper feed cassette 11 by the paper feed roller 12 driven at a predetermined timing. A plurality of recording media P are stacked and accommodated in the paper feed cassette 11 and are detachably supported by the printer body. The recording medium P fed from the paper feed cassette 11 is fed to a transfer nip portion formed between the photosensitive member 2 and the transfer member 6 by a registration roller pair 12a at a predetermined control timing. Is being nipped and conveyed. In the nipping and conveying process, the visible image on the photosensitive member 2 side is sequentially transferred to the recording medium P side by the transfer member 6.

  The recording medium P that has been subjected to the transfer process is discharged from the printer discharge unit 13 to the outside of the apparatus via the fixing discharge unit 10 that is rotatably supported after being subjected to the fixing process by the fixing device 7. Then, the images are stacked on the tray 14 on the upper surface of the printer main body, and a series of image forming processes is completed.

(2) Fixing device 7
Next, the fixing device 7 provided in the printer 1 will be described. FIG. 2 is a schematic perspective view of a main part showing a schematic configuration of the fixing device 7, and FIG. 3 is a schematic sectional view. The fixing device 7 is a heating device of a film heating method and a pressure member driving method.

  A ceramic heater 15 is a heating means (heating source). As will be described later, the recording medium (recording material) P, which is a material to be heated, has a horizontally long and thin wall in the direction of the recording medium conveyance direction FP on the conveyance path surface, and has a low heat capacity as a whole. Receives power and generates heat to quickly raise the temperature.

  Reference numeral 19 denotes a heat-resistant and heat-insulating heater holder. The heater holder 19 is a horizontally long rigid member having a substantially semicircular arc shape in cross section and having a direction that intersects the recording medium conveyance direction FP as a longitudinal direction. For example, it is made of a phenol-based thermosetting resin. The ceramic heater 15 is fitted and fixedly supported in a heater fitting groove 19a formed and provided along the longitudinal direction at a substantially central position on the lower surface of the heater holder 19.

  Reference numeral 16 denotes a cylindrical or endless belt-like flexible member. In the present embodiment, the flexible member 16 is formed on the outer peripheral surface of an endless belt having polyimide as a main component in order to improve the temperature rising rate of the fixing nip portion by reducing the heat capacity. It has a two-layer structure in which an endless strip mainly composed of PTFE is coated, and the total thickness is 100 μm or less. Hereinafter, the flexible member 16 is referred to as a film. The configuration of the film 16 is not limited to this embodiment, and may be another effective structure for reducing the heat capacity. For example, a single layer structure of an endless strip mainly composed of PTFE, PFA or FEP which is a heat-resistant material, or PTFE on an outer peripheral surface of an endless strip mainly composed of polyimide, polyamideimide, PEEK, PES or PPS. , A two-layer structure in which an endless strip having PFA or FEP as a main component is coated. Further, a single layer structure based on a metal layer or a composite layer structure may be used. Further, the total thickness of the film 16 is not limited to this embodiment, but is preferably 100 μm or less, more preferably 20 μm or more and 50 μm or less in order to efficiently reduce the heat capacity.

  The cylindrical film 16 is loosely fitted to the heater holder 19 to which the ceramic heater 15 is attached. That is, the cylindrical film 16 has an inner peripheral length that is longer than the outer peripheral length of the heater holder 19 by a predetermined length, for example, about 3 mm, and is thus fitted on the heater holder 19 without tension.

  The heating element A is composed of the ceramic heater 15, the heater holder 19, the film 16, and the like.

  Reference numeral 17 denotes a pressure roller as a pressure body. The pressure roller 17 includes a cylindrical or substantially cylindrical cored bar 17A made of metal such as aluminum, and an elastic layer 17B mainly composed of silicone rubber having good releasability coated on the outer peripheral surface thereof. It is an elastic roller.

  The pressure roller 17 has both ends of the cored bar 17A supported in a freely rotating manner between unillustrated apparatus side plates. Above the pressure roller 17, the heating element A is arranged in parallel with the ceramic heater 15 facing downward, and both ends of the heater holder 19 are pressed against the pressure roller 17 by the biasing springs 20 and 20. It is configured to be in a pressed state with a predetermined pressing force against the elasticity of the elastic layer 17B of the roller. As a result, the ceramic heater 15 and the pressure roller 17 are pressed against each other with the film 16 interposed therebetween, and a body wearing nip portion N that is a pressure nip portion having a predetermined width is formed by elastic deformation of the elastic layer 17B of the pressure roller. .

  The pressure roller 17 is driven to rotate in the counterclockwise direction indicated by an arrow in FIG. 3 when the driving force of the drive mechanism M is transmitted to the drive gear G provided at the end of the core of the pressure roller. By driving the pressure roller 17, a rotational force acts on the film 16 by the frictional force between the pressure roller 17 and the outer surface of the film 16 in the fixing nip portion N. For this reason, while the inner surface of the film 16 slides in close contact with the lower surface of the ceramic heater 15 in the fixing nip N, the outer periphery of the heater holder 19 is rotated in the clockwise direction indicated by the arrow with a peripheral speed substantially corresponding to the peripheral speed of the pressure roller 17. Followed rotation. The heater holder 19 also serves as a guide member for the film 16 that is driven to rotate.

  In the state where the film 16 is driven to rotate by the pressure roller 17 and the ceramic heater 15 is heated to a predetermined temperature by energization, an unfixed toner image t is formed and supported from the image forming unit side. The recording medium P is introduced between the film 16 and the pressure roller 17 in the fixing nip N. Then, the recording medium P is brought into close contact with the outer surface of the film 16 and passes through the fixing nip portion N while being overlapped with the film 16.

  In the process of passing through the fixing nip N, the thermal energy of the ceramic heater 15 is applied to the recording medium P through the film 16, and the unfixed toner image t on the recording medium P is heated and melted and fixed. The recording medium P passes through the fixing nip portion N and is separated from the surface of the film 16 and discharged. tb indicates a fixed toner image on the recording medium P.

  Since the film 16 slides in close contact with the ceramic heater 15, grease is applied to the inside of the film 16 in order to prevent abrasion and reduce sliding resistance.

(3) Ceramic heater 15
FIG. 4 is a schematic configuration diagram of an example of the ceramic heater 15 as a heating means. This ceramic heater 15 is
1) A ceramic substrate (insulating substrate) 15A made of highly insulating ceramics such as horizontally long alumina, aluminum nitride, silicon carbide and the like whose longitudinal direction is perpendicular to the recording medium conveying direction FP on the conveying path surface of the recording medium P;
2) The ceramic substrate 15A is coated and baked on the surface side of the ceramic substrate 15A along the length by screen printing or the like into a linear or narrow strip having a thickness of about 10 μm and a width of about 1 to 5 mm. For example, Ag / Pd (silver Palladium), RuO ₂ , Ta ₂ N and other heating resistors 15B,
3) Electrode portions 15C and 15C made of Ag / Pt (silver / platinum), which are electrically connected to both longitudinal ends of the heating resistor 15B.
4) An insulating protective layer 15D such as a thin glass coat or fluororesin coat that is electrically insulated and can withstand sliding against the film 16 provided on the surface of the heating resistor 15B.
5) a thermistor 18 as a temperature detector provided on the back side of the ceramic substrate 15A;
Etc.

  In the ceramic heater 15, the side on which the insulating protective layer 15D is provided is the surface side, and the film 16 slides on the surface of the insulating protective layer 15D. The ceramic heater 15 is fitted into a heater fitting groove 19a (FIG. 3) formed along the length of the lower surface of the heater holder 19 with the heater surface facing outward, and is adhered and held with a heat resistant adhesive.

  Reference numerals 21 and 21 denote power supply connectors, which are fitted to the electrode portions 15C and 15C of the ceramic heater 15 fixedly supported by the heater holder 19, and the electric contacts on the power supply connector side are in contact with the electrode portions 15C and 15C, respectively. Become. 22 is a commercial power supply (AC), 23 is a triac, and 24 is a power (energization) control means (CPU). The ceramic heater 15 is heated rapidly and steeply due to heat generated by the heating resistor 15B by being fed from the commercial power source 22 via the triac 23 between the electrode portions 15C and 15C.

  The temperature rise of the ceramic heater 15 is detected by a thermistor 18 which is a temperature detector, and electrical analog information of the detected temperature is input to an analog / digital conversion circuit (A / D conversion circuit) 25 and digitized for power control. Input to means 24.

  The power control means 24 to which digital information corresponding to the detected temperature of the thermistor 18 is input controls the energization from the commercial power supply 22 to the heating resistor 15B so that the detected temperature of the thermistor 18 becomes a value within a predetermined range from the target temperature. It is supposed to be.

  In the present embodiment, as the energization control from the commercial power supply 22 to the heating resistor 15B by the power control means 24 based on the temperature detected by the thermistor 18, the energization phase for each half wave period of the commercial power supply 22 is controlled. (Phase control), switching of energization to either one of conduction or interruption for each half-wave period (wave number control) and the like are employed.

(4) Anti-curl mode By the way, in the fixing device 7, during the heat fixing process, when the heat fixing process is performed while the recording medium P is nipped and conveyed by the fixing nip portion N, the surface of the recording medium P is detected. Although the ceramic heater 15 in contact with the film 16 on the heating body A side generates heat, the pressure roller 17 side that is a pressure body in contact with the back surface of the recording medium P does not have a heat source. For this reason, when the heat fixing operation is performed at the fixing nip portion N of the fixing device 7, there is a large difference in the amount of heat applied to the front and back of the recording medium P.

  When the recording medium P is made of a water-containing material such as paper, a difference occurs in the amount of water evaporated from the front and back of the recording medium P. Therefore, the shrinkage / expansion amount changes between the front and back surfaces of the recording medium P, and after the fixing operation The recording medium P has a problem of curling (paper warp).

  If a second heat source is also provided on the pressure roller 17 side and the pressure roller is heated by the second heat source, the surface temperature of the pressure roller can be set, and the temperature difference in the fixing nip portion N can be set. However, the fixing device becomes complicated and expensive.

  Therefore, in the present embodiment, the anti-curl mode is set as the anti-curl mode from the end of the fixing process to the Nth recording medium to the start of the fixing process to the N + 1th recording medium in the continuous fixing process step for a plurality of recording media. The target temperature of the heating element A in the inter-paper period is set to a temperature higher than the target temperature of the heating element A in the recording medium fixing process period.

  Here, in the heating device of the film heating system, the temperature of the heating element A is substantially equal to the temperature of the ceramic heater 15 which is a heating means.

  The temperature control of the ceramic heater 15 (that is, the temperature control of the heating element A) in the continuous processing step for a plurality of recording media in the present embodiment will be described with reference to FIG. The following temperature control is performed by the power control means 24 based on the temperature detected by the thermistor 18.

  As the image forming process on a series of recording media is started, the rotation of the pressure roller 17 is started, and energization from the commercial power supply 22 to the ceramic heater 15 on the heating body A side is started. As a result, the temperature detected by the thermistor 18 rises from temperature a to temperature b and temperature c, and the pressure roller 17 as the pressure body also heats the ceramic heater 15 through the film 16 on the heating body A side. It is warmed by.

  The detected temperature of the thermistor 18 (that is, the temperature of the heating body A) is raised to the fixing temperature d by time T1 when the first recording medium carrying the unfixed image enters the fixing nip N. Further, the triac 23 is controlled by the power control means 24 so that the detected temperature is maintained at a value within a predetermined range from the fixing temperature d from time T1 to time T2 during which the recording medium is subjected to fixing processing. Thus, energization from the commercial power supply 22 to the heating resistor 15B is controlled.

  Next, the temperature detected by the thermistor 18 is maintained at a value within a predetermined width from the inter-sheet temperature e from the end of the fixing process of the first recording medium to the start of the fixing process of the second recording medium. Therefore, the triac 23 is controlled, and energization from the commercial power supply 22 to the heating resistor 15B is controlled. The temperature e as the inter-paper temperature is set higher than the temperature d as the fixing temperature.

  Thereafter, the power control unit 24 switches the target temperature to the inter-sheet temperature e after the completion of the N-th fixing process, and when the N + 1-th fixing process starts, the thermistor detection temperature returns to a value within a predetermined range from the fixing temperature d. As described above, the target temperature is switched to the fixing temperature d before the N + 1th fixing process is started.

  Next, the effect in this embodiment is demonstrated. First, Experiment 1 was performed to confirm how the fixing temperature d, the inter-paper temperature e, and the inter-paper length affect the curl amount and stackability of the fixed recording medium.

[Experiment 1]
The fixing temperature d is fixed, the difference between the fixing temperature d and the inter-paper temperature e is changed to 0 ° C., 5 ° C., 10 ° C., and 15 ° C., and the length between the papers is 0.5 seconds and 1 second, respectively. The curling amount and stackability of the fixed recording medium were evaluated by changing to 2 seconds, 3 seconds, and 5 seconds.

Since it takes some time for the ceramic heater temperature to reach the target temperature after the energization of the ceramic heater 15 is controlled, an experiment for increasing the difference between the fixing temperature d and the inter-paper temperature e under a short paper interval condition is not going. The recording medium used for the paper-passing experiment was Xerox 4024 paper, basis weight 75 g / m ² , temperature 30 ° C./humidity 80%, taken out of the wrapping paper and left for about 3 days. The amount of water was about 10%.

  The specific configuration of the fixing device used in this experiment is as follows. In the fixing device 7 configured in the same manner as in FIGS. 2 to 4, the pressure roller 17 is provided with an elastic layer 17 </ b> B of foamed rubber having a thickness of 4 mm on an aluminum cored bar 17 </ b> A and molded to an outer diameter of 25 mm. The pressure roller 17 and the ceramic heater 15 were pressed into contact with each other at 96 N (9.8 kg) via an endless film 16 having a surface layer made of 10 μm PFA on the outer peripheral surface of a base layer made of polyimide resin of 60 μm. .

  In this experiment, an image forming apparatus using the above fixing device was used. The conveyance speed of the recording medium P is 111 mm / second at which an LTR size recording material can be conveyed at a throughput of 20 PPM, and the fixing temperature control (fixing temperature d) while the recording medium passes through the fixing nip N is 180 ° C. It was.

The image forming apparatus used in this experiment has the same configuration as that in FIG. 1, and the recording medium discharged from the fixing device 7 after the fixing process is output onto the paper discharge tray 14 and stacked. The printer paper discharge unit 13 including a paper discharge roller and a paper discharge roller is located 40 mm above the surface of the paper discharge tray 14 and is about 300 sheets of paper if it is smooth paper with a basis weight of 75 g / m ² without curling. Paper loading is possible.

  Using the image forming apparatus, fixing processing was performed continuously for 100 sheets in an environment of an air temperature of 30 ° C./humidity of 80%.

  As shown in FIG. 6, the curling amount measurement was performed by placing the fixed recording medium P on a horizontal desk 100 and measuring the distance of the recording medium P from the square desk. 30 sheets were extracted from the top of the recording medium loaded and discharged, and the average value of the four corners of the aligned 30-sheet bundle was shown.

  Regarding the stackability evaluation, the case where the recording medium loaded on the paper discharge tray 14 protrudes from the area of the paper discharge tray 14 having a width of 316 mm and a width of 386 mm, which is 10 cm longer and wider than the size of the recording medium, is indicated by Δ. In addition, the paper discharged from the paper discharge tray 14 is more disturbed, the paper protrudes more than 20 cm from the area of the paper discharge tray 14, or the recording medium is rounded up to block the paper discharge section of the fixing device, causing wrinkles or corner breakage. What occurred was marked as x.

  Table 1 shows the results of experiments conducted under the above conditions.

  The experiment results in which the fixing temperature d and the inter-paper temperature e are the same temperature, and the length between the papers is within 3.0 seconds, the curling of the fixed paper is large, the output paper is bulky, and the fixing of 100 continuous sheets Paper dropped from the paper output tray during processing.

  When the fixing temperature d and the inter-paper temperature e are d <e and the difference is increased, the curl amount is reduced and the stackability is improved.

  In addition, as the length between the papers was increased, the curl amount decreased and the loadability improved.

  However, when the fixing temperature d and the inter-paper temperature e were kept at the same temperature, 100 sheets could not be stacked even when the length between the papers was increased.

  In order to explain the experimental result, FIG. 7 shows the result of measuring the surface temperature of the pressure roller temperature 17 in the continuous fixing process in the experiment.

  The temperature of the pressure roller 17 during the continuous fixing process is raised between the papers by being heated from the ceramic heater 15 through the film 16, and since the recording medium P is deprived of heat, the temperature is decreased during the fixing process. It changes while going up and down.

  Table 2 shows the maximum temperature of the pressure roller 17 during the 100-sheet continuous fixing process and the difference between the fixing temperature d and the pressure roller temperature at that time. The fixing temperature d is a target temperature for controlling the heater surface, and is different from the temperature on the film surface. I will write it down for your reference.

  The fixing temperature d and the inter-paper temperature e are set to the same temperature, and the length between the papers is 0.5 sec. As a result, the pressure roller temperature was low. This is considered to be because the amount of the pressure roller heated between the sheets is small. From this result, it can be explained that the curl was large because the difference between the temperature of the ceramic heater 15 and the temperature of the pressure roller during heating and fixing was large and the difference in the amount of heat applied to the front and back of the paper at the fixing nip N was large.

  When the fixing temperature d and the inter-paper temperature e were kept at the same temperature, and the paper interval was increased, the temperature of the pressure roller 17 increased. However, the pressure roller temperature was almost saturated with a certain temperature difference from the fixing temperature d even when the inter-paper length was increased beyond a certain level.

  The temperature of the pressure roller 17 is lower than the temperature of the ceramic heater 15 being heated due to the heat resistance and heat capacity of the film 16 existing between the ceramic heater 15 and the pressure roller 17 and other peripheral components. Saturates. As a result of the previous paper-passing experiment and temperature measurement, it can be seen that the difference in the amount of heat applied to the front and back of the paper during the fixing process cannot be made so small that curl can be completely corrected.

  By simply heating the pressure roller 17 with the target temperature between the sheets as the fixing temperature d and making the distance between the sheets longer, the difference between the pressure roller temperature and the temperature of the ceramic heater 15 during the fixing process is changed to the film 16, It can be seen that it cannot be made smaller than the thermal energy loss due to thermal resistance and heat capacity to other peripheral components.

  In the experimental results, the inter-paper temperature e is raised to a temperature higher than the fixing temperature d, the pressure roller 17 is heated, and the fixing temperature d is lowered to a temperature lower than the inter-paper temperature e during the fixing process. The difference between the pressure roller temperature and the ceramic heater temperature during the fixing process can be reduced. The result of the previous paper passing experiment can be explained by the fact that the difference in the amount of heat applied to the front and back of the paper during the fixing process can be made small enough to correct the curl.

  As described above, the method for setting the inter-paper temperature e to a temperature higher than the fixing temperature d is a recording medium P that has been subjected to the fixing process as compared with the method for setting the inter-paper temperature e to be equal to or lower than the fixing temperature d. It can be seen that it is excellent in curl reduction and loadability.

  That is, for example, by executing the anti-curl mode shown in Table 3, even if a recording medium with a large amount of moisture is used, the user does not need to perform extra work such as re-distorting the recording medium or aligning the recording medium. The recording medium output to the quality can be used without stress. In the curl countermeasure mode, the inter-paper temperature e is set 20 ° C. higher than the fixing temperature d. Since the difference between the inter-paper temperature e and the fixing temperature d is large and it takes time to switch the temperature, the inter-paper length is set to 3.0 seconds. Table 1 shows that curling and loading are effective.

  Also, in addition to the curl countermeasure modes shown in Table 3, a throughput priority mode is provided so that users who do not care about curling, environments where curling does not occur, users who use paper, users who prioritize throughput, etc. automatically or manually. The throughput priority mode can be selected. Thereby, an output image can be obtained promptly as needed.

  In FIG. 8, reference numeral 26 denotes a selection unit for the curl countermeasure mode and the throughput priority mode. The power control means 24 executes the temperature control of the ceramic heater 15 according to the curl countermeasure mode or the throughput priority mode selected by the selection means 26.

  In the throughput priority mode, the throughput is prioritized over the anti-curl mode, and the paper interval is shortened. The paper interval length in this throughput priority mode is set to as short a time as possible, for example, as long as a device other than the fixing device such as a paper feeding device that feeds the recording medium to the image forming device or an unfixed image forming device permits. For example, the length between sheets is 0.5 sec. And

  In order to make the gap between the sheets as short as possible, the fixing temperature and the gap between the sheets are set to the same temperature, and the temperature switching between the sheets, which takes time, is not performed every time. However, when the fixing process is continuously performed in a large amount, the temperature control temperature is switched by a predetermined number Z.

  For example, at the timing Td when the Z-th fixing process is completed, the inter-sheet temperature and the fixing temperature are switched from h1 to h2, and are controlled to temperatures 5 degrees lower than before the timing Td.

  Even in the fixing mode in which the sheet interval is short, when the fixing process is continuously performed, the temperature of the pressure roller and the entire fixing device gradually increases, and an excessive amount of heat is applied to the recording medium P. When an excessive amount of heat is applied to the developer on the recording medium, the developer is excessively melted, the viscosity is extremely lowered, and is transferred to the film 16 to cause image defects.

  FIG. 9 shows changes in the heater temperature adjustment temperature and the pressure roller temperature during continuous paper feeding in the throughput priority mode in which the above control is performed. FIG. 9 also shows the transition of the heater temperature adjustment temperature and the pressure roller temperature in the curl priority mode for reference. At the time of temperature switching in the throughput priority mode, the inter-paper temperature is temporarily higher than the fixing temperature, but since it is only a temporary state, the temperature difference between the pressure roller temperature and the fixing temperature is not sufficiently small. .

  In the throughput priority mode, the temperature difference between the pressure roller during fixing and the fixing temperature is smaller than that in the curl priority mode. In this throughput priority mode, 100 sheets continuously under an environment of 30 ° C./80% humidity. When the fixing process is performed, curling and stacking properties deteriorate.

  Therefore, even if the temperature control of the fixing device that switches between the fixing temperature and the inter-paper temperature is performed, there may be a case where a sufficient curling countermeasure effect cannot be obtained unless it is controlled as in the curling countermeasure mode in this embodiment. .

  For example, when continuously fixing paper whose width is narrower than the maximum size of the recording medium that can be used by the fixing device (hereinafter referred to as a small size), the paper interval is made longer than the throughput priority mode, The temperature is set lower than the fixing temperature. Generally, when a small size is continuously fixed, for example, an area where the recording medium of the pressure roller does not contact (non-sheet passing portion) is heated so that heat is not taken away, and the non-sheet passing portion becomes high temperature. As described above, by setting the inter-sheet temperature to a temperature lower than the fixing temperature, the temperature of the non-sheet passing portion of the pressure roller can be lowered between the sheets, and the edge temperature rise can be reduced.

  However, in this case, the curling countermeasure effect cannot be obtained unlike the curl countermeasure mode because the pressure roller temperature is not raised and the fixing temperature is lowered during paper passing.

  As described above, by setting the target temperature of the heating body between the papers to be higher than the target temperature at the time of the heated material heating process, the temperature of the pressurized body is increased between the papers to heat the heated material. During the treatment, the temperature of the heating body is lowered. As a result, the difference between the surface temperature of the heating body during the heat treatment of the heated material and the surface temperature of the pressurized body is reduced, the amount of heat supplied to the heated material from the heated body side, and the heated material from the pressurized body side. It is possible to reduce the difference in the amount of heat transmitted to the substrate and suppress the warpage and curling of the heated material.

  Further, in a fixing device that heats and fixes a recording medium while nipping and conveying a recording medium at a pressure contact portion between a heating body having a heat generation source and a pressure body having no heat generation source, the inter-paper temperature e is higher than the fixing temperature d. Set to. Thereby, for example, even in a high-humidity environment, or when using a recording medium with a lot of moisture or a recording medium with low paper strength, curling of the recording medium subjected to the fixing process can be suppressed. Accordingly, it is possible to prevent the image forming apparatus from dropping from the stacking surface, reversing the printing order, wrinkling, corner breakage, and the like, and the user can use it without correcting or aligning it.

(Example 2)
The schematic configuration of the image forming apparatus according to this embodiment is the same as that of the first embodiment. In this embodiment, as shown in FIG. 10, there is provided means 27 for detecting the moisture content of the recording medium, and the power control means 24 is a paper according to the moisture content of the recording medium detected by the moisture content detecting means 27. The temperature difference between the intermediate temperature e and the fixing temperature d and the length between the sheets are changed.

  The electrical analog information of the water content of the recording medium detected by the water content detection means 27 is input to the analog-digital conversion circuit (A / D conversion circuit) 28, digitized, and input to the power control means 24.

  As the moisture amount detection means 27 of the recording medium P, for example, there are an electrical resistance type, a high frequency resistance type, a high frequency capacity type, a microwave type, and the like, and any moisture amount detection method may be used. Further, for example, in order to simplify the configuration, a method of estimating the moisture content of the recording medium from a flowing current amount by applying a voltage while sandwiching and conveying the recording medium by the conveying means may be used. Alternatively, a method of estimating the moisture content of the recording medium P from the current flowing through the transfer body 6 when a voltage is applied during the transfer process in the transfer unit may be used.

  If the amount of water in the recording medium is large, the amount of water that evaporates during the fixing process also increases, and the amount of shrinkage of the recording medium increases. Conversely, if the amount of water is small, curling will be difficult and no curling measures will be required.

  An experiment was conducted to confirm how the moisture content of the recording medium P affects the curl and stackability of the recording medium that has been subjected to the fixing process.

The recording medium used in the paper-passing experiment was left in an environment of Xerox 4024 paper, basis weight 75 g / m ² , temperature 30 ° C./humidity 80%, and the water content of the paper was 4.0% and 7.0%. 10.0% was used.

  The image forming apparatus used in the experiment has the same configuration as that of Experiment 1 of Example 1, and thus the description thereof is omitted. The image forming apparatus is installed in an environment where the temperature is 30 ° C./humidity 80%, the fixing temperature is fixed at 180 ° C., and the difference between the fixing temperature and the inter-paper temperature is changed to 0 ° C., 5 ° C., 10 ° C., and 15 ° C. The experiment was conducted. In addition, the length between the sheets was changed to 0.5 second, 1 second, 2 seconds, 3 seconds, 6 seconds, 12 seconds, and 15 seconds, respectively, and the same as in the test of [Experiment 1] in Example 1). In addition, 100 sheets were continuously fixed, and the loading state of the recording medium subjected to the fixing process was evaluated. The experimental results are shown in Table 4.

  The smaller the moisture content, the better the loadability, and the higher the moisture content, the worse the loadability. With a recording medium having a moisture content of 4.0%, the stackability was good even when the difference in paper temperature was 0 ° C. and the paper length was 0.5 seconds.

  When such a recording medium is used, it is more beneficial for the user to reduce the difference between the inter-paper temperature e and the fixing temperature d, shorten the inter-paper length, and increase the throughput.

  On the other hand, a recording medium with a moisture content of 10.0% tends to curl. When the difference between the paper temperature e and the fixing temperature d is controlled at 0 ° C. and the paper length is 0.5 seconds, the fixed recording medium is It curled up and dropped from the loading tray 14 one after another. Also, it was strongly curled up and could not be used as it was. In this case, even if the time until the continuous fixing process is completed is short, the user is forced to perform extra work such as alignment of recording media and correction of distortion.

  When the difference between the inter-paper temperature e and the fixing temperature d was increased to 20 ° C. and the inter-paper length was 3.0 seconds, curling was suppressed and 100 sheets could be stacked with good alignment. Although the time until the completion of the continuous fixing process is extended, the output record can be used immediately without any trace by the user.

  As can be seen from the above experimental results, the method of changing the temperature difference between the fixing temperature d and the inter-paper temperature e and the inter-paper length according to the amount of moisture maximizes throughput while maintaining good curl and stackability. It is possible to perform the optimum control with respect to the state of the recording medium used by the user.

  That is, for example, as shown in Table 5, anti-curl measures are taken for poorly curled paper, and high-quality output recording paper is stressed without forcing extra work such as correcting distortion and aligning recording materials. You can use it without. Moreover, paper that is difficult to curl can be provided to the user promptly with a high throughput.

  As described above, the moisture content of the recording material is detected, and the temperature difference between the target temperature of the heating body between the paper and the target temperature during the heat treatment is set. This makes it possible to reduce the temperature difference between the paper-to-paper temperature and the fixing temperature, and to smoothly switch between the paper-to-paper and heat treatment, thereby speeding up the heat treatment throughput. it can. In addition, in the case of a recording material that easily curls, the temperature difference between the paper-to-paper temperature and the fixing temperature can be increased to suppress warping and curling of the recording material, and the optimum temperature according to the state of the recording material. Control can be performed.

(Example 3)
The schematic configuration of the image forming apparatus according to this embodiment is the same as that of the first embodiment. In this embodiment, as shown in FIG. 11, an environment detection unit 29 that detects the temperature, humidity, or both of the environment in which the image forming apparatus is installed is provided, and the power control unit 24 detects the environment detection unit 29. In accordance with the result, the temperature difference between the inter-paper temperature e and the fixing temperature d and the inter-paper length are changed.

  Electrical analog information of the environment temperature and / or humidity detected by the environment detection means 29 is input to an analog-digital conversion circuit (A / D conversion circuit) 30 and digitized and input to the power control means 24. To do.

  There is a high possibility that the paper used in the image forming apparatus installed in a high-temperature and high-humidity environment is moisture-absorbed paper that is compatible with the environment.

  From the high temperature and high humidity environment to the low temperature and low humidity environment, the moisture content of the paper when the paper was left in each environment for 3 days was measured.

a: The moisture content of the paper left in the environment of temperature 32 ° C. and humidity 80% was 11.0% b: The moisture content of the paper left in the environment of temperature 25 ° C. and humidity 50% was 7.0% C: The moisture content of the paper left in an environment with a temperature of 15 ° C. and a humidity of 10% was 3.5% The moisture content of the paper left in an environment of temperature a of 32 ° C. and a humidity of 80% was large, From the experimental results of Example 1, it can be seen that curling is likely to occur. The amount of water in the paper left in an environment of temperature c of 15 ° C. and humidity of 10% is large, and it can be seen from the experimental results of Example 2 that it is difficult to curl.

  In other words, as shown in Table 6, curl measures are taken for poorly curled paper, and high-quality output recording paper is used without stress, without forcing the user to perform extra work such as correcting distortion and aligning recording materials. I can have you. In addition, paper that is difficult to curl can be provided to the user promptly with a high throughput.

  In this embodiment, one example of detecting both temperature and humidity is shown. However, since a recording medium adapted to a high humidity environment has a large amount of moisture, even if only humidity is detected, a sufficient effect can be obtained. It is done.

  In addition, since the absolute humidity is higher in a high temperature environment than in a low temperature environment, a recording medium adapted to a high temperature environment is likely to have a large amount of moisture. Even if only the temperature is detected, there is an effect though it is not sufficient.

  In the present embodiment, an example in which a temperature sensor and a humidity sensor are used as the environment detection means 27 is shown. However, the same effect can be obtained by a method of estimating by using a resistance value fluctuation of an ion conductive transfer body without using a sensor. Is obtained.

  As described above, the temperature difference between the target temperature of the heating body between the paper and the target temperature during the heat treatment is set according to the temperature, humidity, or both of the environment where the heating device is installed. Thus, the following effects can be obtained. In other words, in an environment where the recording material is difficult to curl, the temperature difference between the paper temperature and the fixing temperature can be reduced, and the heat treatment throughput can be increased by smoothly switching between the paper space and the heat treatment. Also, in an environment where the recording material tends to curl, the temperature difference between the paper temperature and the fixing temperature can be increased to suppress warping and curling of the recording material, depending on the environment where the heating device is installed. Optimal temperature control can be performed.

Example 4
The schematic configuration of the image forming apparatus in the present embodiment is the same as that of the first embodiment. In the present embodiment, as shown in FIG. 12, a detection unit 31 that detects the thickness, type, or both of the recording medium is provided, and the power control unit 24 detects the thickness of the recording medium detected by the detection unit 31, The temperature difference between the inter-paper temperature and the fixing temperature and the inter-paper length are changed according to the type or both.

  The electrical analog information of the thickness, type, or both of the recording medium detected by the detection means 31 is input to the analog-digital conversion circuit (A / D conversion circuit) 32, digitized, and input to the power control means 24. To do.

  The recording medium thickness / type detection means 31 is, for example, a sensor that contacts the sensor to measure the thickness and surface roughness, and determines the thickness and surface roughness from the reflected light by irradiating light with a contact type. Although there is a non-contact optical type for measuring and judging, any detection means may be used.

  An experiment was conducted to confirm how the thickness and type of the recording medium affect the curling of the recording medium after the fixing treatment.

  The recording medium used in the paper passing experiment was one that was taken out of the wrapping paper and left for 3 days in an environment of 30 ° C. temperature / 80% humidity.

When the difference between the fixing temperature d and the inter-paper temperature e is increased to 0 ° C. and the inter-paper length is 0.5 seconds,
When the difference between the fixing temperature d and the inter-paper temperature e is increased to 10 ° C. and the length between the papers is 1.5 seconds,
When the difference between the fixing temperature d and the inter-paper temperature e is extended to 20 ° C. and the inter-paper length is 3.0 seconds,
In the same manner as the stackability evaluation in [Experiment 1] of Example 1, 100 sheets were continuously fixed, and the stacking state of the fixed recording media was evaluated. The experimental results are shown in Table 7.

  As a result of the experiment, a paper type having a large basis weight has less curl, and a paper type having a small basis weight tends to have poor curl. Further, among the paper types, the BOND paper and the recycled paper tended to be poorly curled.

In the case of smooth paper, the curl of the paper type having a basis weight of 64 g / m ² is particularly bad. I couldn't stand it. The difference between the fixing temperature and the inter-paper temperature was increased to 15 ° C., and curling could be suppressed by controlling the gap between the papers. On the other hand, for a paper type of 105 g paper or more, the difference between the fixing temperature and the inter-paper temperature is 0 ° C., and the inter-paper interval is 0.5 sec. The curl was not bad even with the control up to. Non-smooth paper such as BOND paper and recycled paper tended to have poor curl with a paper type of 80 g paper or less. This also increases the difference between the fixing temperature and the inter-paper temperature to 20 ° C., and the inter-paper interval is 3.0 sec. With the free control, curling could be suppressed.

  As can be seen from the above experimental results, the temperature difference between the fixing temperature d and the inter-paper temperature e is determined by detecting the thickness / paper type of the recording medium and determining whether the paper is smooth paper or non-smooth paper, and the basis weight. Change the paper interval. Thus, while maintaining good curl, the throughput can be maximized and optimum control can be performed on the state of the recording medium used by the user.

  In other words, as shown in Table 8, measures against curling are taken for poorly curled paper, and high-quality recording paper is used without stress without forcing the user to perform extra work such as correcting distortion and aligning recording materials. I can have you. Moreover, paper that is difficult to curl can be provided to the user promptly with a high throughput.

  As described above, in the present embodiment, the temperature difference between the target temperature of the heating body between the paper and the target temperature during the heat treatment is set according to the thickness and type of the recording material. As a result, in the case of a recording material that is difficult to curl, the temperature difference between the paper-to-paper temperature and the fixing temperature can be reduced, and the paper-to-paper and heat treatment can be smoothly switched to increase the heat treatment throughput. In addition, in the case of a recording material that easily curls, the temperature difference between the paper temperature and the fixing temperature can be increased to suppress warping and curling of the recording material, and optimal temperature control according to the state of the recording material Can be done.

(Example 5)
The schematic configuration of the image forming apparatus in the present embodiment is the same as that of the first embodiment. In the present embodiment, as shown in FIG. 13, the power control unit 24 is provided with a counter function unit 24a that counts the number of sheets subjected to continuous fixing processing, and the power control unit 24 performs continuous fixing counted by the counter function unit 24a. The temperature difference between the inter-paper temperature e and the fixing temperature d and the inter-paper length are changed according to the number of processed sheets.

  According to the inventor's study, it has been found that the curl of the recording paper fixed on the first sheet is smaller than the curl of the recording paper fixed on the tens of sheets among the recording sheets subjected to the continuous fixing process. Yes.

  0.5 sec. The sheet-to-paper temperature e and the fixing temperature d are set to the same temperature, and 100 sheets are continuously fixed as in the stacking evaluation in [Experiment 1] of Example 1, and the recording medium that has been fixed is stacked. The condition was evaluated.

  FIG. 14 shows the transition of the pressure roller temperature in the case of the above experiment. When the first sheet was fixed, the pressure roller surface temperature was high, and the difference between the heater temperature and the pressure roller surface temperature was relatively small. Thereafter, the temperature of the pressure roller surface decreases every time the paper is passed. This is because, before the fixing process for the first sheet, there is a period in which the heater temperature is raised to the target temperature, and therefore the temperature of the pressure roller surface is increased. However, since the interval between the second and subsequent sheets is short, the amount of heat taken away by the recording medium when passing the sheet is greater than the amount of heat supplied to the pressure roller between the sheets. The temperature has dropped. For this reason, the initial curling of the recording paper subjected to the continuous fixing process is the best. Thereafter, the temperature of the pressure roller rises little by little, but the temperature does not rise sufficiently unless a large amount of continuous paper is passed. A large amount of recording paper with poor curl and stackability is output.

  Therefore, in this embodiment, the temperature difference between the inter-paper temperature e and the fixing temperature d and the inter-paper length are changed according to the number of continuous fixing sheets. For example, as shown in Table 10, fixing control is performed.

  In the fixing control of Table 10, 100 sheets were continuously fixed as in the stacking evaluation in [Experiment 1] of Example 1, and the stacking state of the fixed recording media was evaluated. The experimental results are shown in Table 11.

  As can be seen from the above experimental results, in the fixing control in this embodiment, the curling and stacking properties are good.In the initial stage when the continuous fixing process is started, the fixing control giving priority to the throughput is performed. The output image can be provided promptly.

  Depending on the number of sheets, the gap between the papers is widened and the difference between the fixing temperature and the paper-to-paper temperature is set large so that curling does not worsen, and even if a large amount of paper is output to the stacking unit of the image forming device, Can be aligned and loaded without dropping or reversing the output order. Therefore, it is possible to allow a user who has fixed a large number of sheets to use a high-quality output recording sheet without stress without forcing extra work such as correcting distortion and arranging recording materials.

  As described above, in the present embodiment, the number of continuously heat-treated sheets is counted, and the target temperature of the heating body between the paper and the target at the time of the heat treatment are determined according to the counted number of continuously heat-treated sheets. Set the temperature difference from the temperature. As a result, while the number of printed sheets is small and the number of recording materials to be ejected and loaded is small, the temperature difference between the paper-to-paper temperature and the fixing temperature is reduced, and the paper-to-paper temperature and the heat treatment are smoothly switched, so that the heat treatment throughput is reduced. Can speed up. On the other hand, if the number of printed materials increases and the number of recording materials that are ejected and stacked increases, the temperature difference between the paper-to-paper temperature and the fixing temperature is increased to suppress warping and curling of the recording material, making it ideal for stacking recording materials. Temperature control can be performed.

(Example 6)
The schematic configuration of the image forming apparatus and the like in this embodiment is the same as that of Example 1, but in this example, a heat roller type fixing device is used.

  In the first embodiment, an example of a laser beam printer provided with a film heating type fixing device 7 is shown. When performing control to change the heater temperature between the paper and during the fixing process, a film heating method in which the heat capacity of the ceramic heater 15 serving as a heating means is small and the temperature control accuracy and responsiveness are good is suitable. However, in the present invention, even in other fixing methods such as a heat roller method, the surface temperature of the heat roller (fixing roller), which is a heating element, is increased between the sheets in the same manner as in the first to fifth embodiments. It is clear from the experimental results of Example 1 that the same effect can be obtained if the control can be performed at a low level during the processing.

  The heat roller type fixing device has a structure as shown in FIG. 15, for example. That is, for example, a heating source 41 such as a halogen heater is provided inside the fixing roller 40 provided with a release layer made of fluororesin or the like on the surface of a cylindrical member made of metal or the like, and the thermistor 18 in contact with the fixing roller 40 is provided. Energization control is performed based on the detected temperature.

  Conventionally, since the heat capacity of the fixing roller is larger than that of the film heating method, it has been disadvantageous for performing temperature control in which the target temperature is switched violently. Thus, a fixing roller that enables rapid temperature rise has also been realized. Similar to the film heating method, such a fixing device is suitable for carrying out the present invention, and can perform the same control as in the first to fifth embodiments.

[Others]
1) In a film heating type heating apparatus, the ceramic heater 15 as a heating means is of course not limited to that of the configuration of the embodiment. A so-called back surface (back surface) heating type ceramic heater may be used in which a heating resistor is disposed on the surface of the heater substrate opposite to the surface on which the flexible member slides. Instead of a ceramic insulating substrate, a metal plate whose surface is subjected to an insulating coating treatment can also be used.

  The heating means is not limited to a ceramic heater. For example, an electromagnetic induction heat generating member can be used.

  The heating of the flexible member by the heating means can be an internal heating method or an external heating method. An apparatus configuration in which the temperature of the flexible member itself is detected by a temperature detector can also be used.

  It is also possible to make the flexible member itself have an electromagnetic induction exothermic property and generate heat by the exciting means.

  The driving method of the flexible member is not limited to the pressing body driving method of the embodiment. A driving roller may be provided on the inner peripheral surface of the endless flexible member and driven while applying tension to the flexible member. Thus, it is possible to adopt a device configuration that travels and moves while feeding it out.

  The pressure body is not limited to a roller body, and may be a belt body.

  2) In the roller heating type heating apparatus, the heating roller can be heated by the heating means using an internal heating system or an external heating system.

  The heating means is not limited to a halogen heater. It is also possible to make the heat roller itself heat-generating by electromagnetic induction and generate heat by the exciting means.

  The pressure body is not limited to a roller body, and may be a belt body.

  3) The temperature detector is not limited to the thermistor. Various types of contact type or non-contact type can be used.

  4) In the present invention, the heating device is not limited to a film heating type or roller heating type device. Any heating apparatus may be used as long as it has a heating body and a pressure body that are in pressure contact with each other, and sandwiches and conveys the material to be heated at a nip formed between them.

  The heating device of the present invention is not limited to the fixing device of the embodiment, but also an image heating device that is supposed to be worn, an image heating device that reheats a recording medium that carries an image to improve the surface properties such as gloss, and a recording medium It can be used as a heat treatment apparatus such as drying, heat laminating, hot press wrinkle removal, hot press curl removal, and the like.

1 is a schematic cross-sectional view illustrating a schematic configuration of an image forming apparatus in Embodiment 1. FIG. FIG. 2 is a perspective model view of a main part showing a schematic configuration of a fixing device. FIG. 2 is a schematic cross-sectional view illustrating a schematic configuration of a fixing device. It is a figure explaining schematic structure of an example of a ceramic heater. It is a figure which shows an example of transition of the thermistor detection temperature in a continuous fixing process. 3 is a schematic diagram illustrating a method for measuring curl of a recording medium in Experiment 1 in Example 1. FIG. FIG. 5 is a diagram illustrating an example of changes in the thermistor detection temperature and the pressure roller surface temperature in the continuous fixing process in Example 1. It is a block diagram of a heater temperature control system including selection means for a curl countermeasure mode and a throughput priority mode. 6 is a diagram illustrating an example of changes in the thermistor detection temperature and the pressure roller surface temperature in the continuous fixing process in the throughput priority mode in Embodiment 1. FIG. FIG. 6 is a block diagram of a heater temperature control system including a moisture detection unit for a recording medium in Embodiment 2. FIG. 10 is a block diagram of a heater temperature control system including environment detection means in Embodiment 3. FIG. 10 is a block diagram of a heater temperature control system including detection means for detecting the thickness and / or type of a recording medium in Example 4. FIG. 10 is a block diagram of a heater temperature control system including a counter function unit that counts the number of sheets subjected to continuous fixing processing in Example 5. FIG. 10 is a diagram illustrating an example of changes in the detected temperature of the thermistor and the pressure roller surface temperature in the continuous fixing process in Example 5. FIG. 10 is a schematic cross-sectional view illustrating a schematic configuration of a heat roller type fixing device in Example 6. The figure which shows an example of the transition of the detection temperature of the thermistor in the conventional continuous fixing process.

Explanation of symbols

1 Laser beam printer (image forming device)
7 Fixing device 13 Paper discharge unit 14 Paper discharge tray A Heating element 15 Ceramic heater (heating means, heating source)
15A Substrate 15B Heating resistor 15C Electrode 15D Protective layer 16 Film (heating body, flexible member)
17 Pressure roller (Pressure body)
18 Thermistor (temperature detector)
19 Holder 22 Commercial power supply 23 Triac 24 CPU (power control means)
25 Analog-digital conversion circuit N Fixing nip P Recording medium (heated material)

Claims (20)

In a heating apparatus that includes a heating body and a pressure body that are in pressure contact with each other, and sandwiches and conveys a material to be heated in a nip formed between the two,
A temperature detection body for detecting the temperature of the heating body, and power control means for controlling the detected temperature of the heating body to a target temperature,
In the interval between papers during the period from the end of the heat treatment of the Mth material to be heated in the continuous heat treatment to a plurality of N materials to be heated, from the end of the heat treatment of the M + 1th material to be heated, Alternatively, the temperature between the papers, which is the target temperature of the heating body set in a certain period of time between the papers, is higher than the heating material heating temperature, which is the target temperature of the heating body during the heat treatment of the M + 1th heating material. Heating device characterized by being set to temperature.   2. The heating according to claim 1, further comprising means for detecting a moisture content of the heated material, wherein the temperature difference between the paper temperature and the heated material heating temperature is changed according to the moisture content of the heated material. apparatus.   A means for detecting the temperature and / or humidity of the environment where the heating device is installed is provided, and the temperature difference between the paper temperature and the heating temperature of the heated material is determined according to the temperature and / or humidity of the environment. The heating device according to claim 1, wherein the heating device is changed.   A means for detecting the thickness and / or type of the material to be heated is provided, and the temperature difference between the paper-to-paper temperature and the material to be heated is changed according to the thickness and type of the material to be heated. The heating apparatus according to claim 1.   2. The number of sheets of the material to be heated that has been continuously heat-treated is counted, and the temperature difference between the inter-paper temperature and the material to be heated is changed in accordance with the counted number of continuously heat-treated materials. The heating device described.   The heating body has a heating means fixedly supported and a flexible member that slides with the heating means, and the pressure body forms a nip portion with the heating means through the flexible member, 6. The heating apparatus according to claim 1, wherein the heated material is sandwiched and conveyed by the nip portion, and the heated material is heated by the heat of the heating means via the flexible member. .   The heating device according to any one of claims 1 to 5, wherein the heating body is a heat roller.   In the interval between papers during the period from the end of the heat treatment of the Mth material to be heated in the continuous heat treatment to a plurality of N materials to be heated, from the end of the heat treatment of the M + 1th material to be heated, Alternatively, the temperature between the papers, which is the target temperature of the heating body set in a certain period of time between the papers, is higher than the heating material heating temperature, which is the target temperature of the heating body during the heat treatment of the M + 1th heating material. A first mode that is set to a temperature, and a second mode that is not set to a temperature higher than the heating material heating temperature that is the target temperature of the heating body during the heat treatment of the M + 1th heating material. The heating device according to any one of claims 1 to 7, characterized in that   In the first mode, the interval between papers during continuous printing is changed according to at least one of the temperature, humidity, thickness of the material to be heated, and the type of environment in which the heating device is installed. The heating apparatus according to claim 8, wherein:   An image heating and fixing apparatus comprising: an image forming unit that forms and supports an unfixed image on a recording material; and an image heating and fixing device that heats and fixes the unfixed image formed and supported on the recording material. An image forming apparatus comprising the heating device according to any one of claims 1 to 9. In an image forming apparatus having a fixing device that includes a heating body and a pressure body that are in pressure contact with each other, and sandwiches and conveys a recording material on which a toner image is formed at a nip portion formed between them and heat-fixes the recording material.
A temperature detector for detecting the temperature of the heating element;
Power control means for controlling the detected temperature of the heating element to a target temperature, and
The power control unit has a curl reduction mode for reducing curling of a fixed recording material when images are continuously formed on a plurality of recording materials. In the curl reduction mode, the recording material is fixed. An image forming apparatus, characterized in that a period for setting a target temperature of a heating body to a temperature between sheets higher than a target temperature at the time of fixing a recording material is provided during a period between sheets.   Furthermore, the apparatus includes a means for detecting the moisture content of the heated material, and changes the temperature difference between the inter-paper temperature and the target temperature when fixing the recording material according to the moisture content of the heated material. The image forming apparatus according to claim 11.   Furthermore, a means for detecting the temperature or humidity of the environment where the heating device is installed is provided, and the temperature difference between the temperature between the paper and the target temperature at the time of fixing the recording material is determined according to the temperature or humidity of the environment. The image forming apparatus according to claim 11, wherein the image forming apparatus is changed.   Further, the recording medium is provided with a means for detecting the thickness or type of the recording material, and the temperature difference between the temperature between the paper and the target temperature at the time of fixing the recording material is changed according to the thickness or type of the recording material. The image forming apparatus according to claim 11.   12. The image forming apparatus according to claim 11, wherein a temperature difference between the inter-paper temperature and a target temperature at the time of fixing the recording material is changed according to the number of recording materials on which images are continuously formed.   The heating element has a heating element fixedly supported and a flexible member that slides with the heating element, and the pressing body forms a nip portion with the heating element via the flexible member, 12. The image formation according to claim 11, wherein the recording material is nipped and conveyed at the nip portion, and the toner image formed on the recording material is heated and fixed by heat from the heating element via the flexible member. apparatus.   The image forming apparatus according to claim 11, wherein the heating body is a heat roller.   In the curl reduction mode, the “interval between sheets during continuous printing” changes according to at least one of the temperature, humidity, thickness of the material to be heated, and the type of environment in which the heating device is installed. The image forming apparatus according to claim 11, wherein:   Furthermore, it has a non-curl reduction mode in which a period for setting the target temperature of the heating body to a temperature between the papers higher than the target temperature at the time of fixing the recording material is not provided in the period between the sheets where the recording material is not fixed. The image forming apparatus according to claim 11, wherein the image forming apparatus is an image forming apparatus. The image forming apparatus according to claim 19, wherein an interval between sheets during continuous printing is larger in the curl reduction mode than in the non-curl reduction mode.

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