JP4669721B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device for fixing an image made of toner on a recording medium, and an image of an electrophotographic copying machine having a fixing device, a laser beam printer, a facsimile, or a multifunction device having at least two of these functions. The present invention relates to a forming apparatus.

  FIG. 18 is an explanatory diagram of a conventional electrophotographic image forming apparatus. A conventional electrophotographic image forming apparatus 100, such as a copying machine and a laser printer, includes a photosensitive drum 101 on which an electrostatic latent image is formed, a charging roller 102 that performs charging processing in contact with the photosensitive drum 101, and a laser. Recording means 103 such as a beam, a developing roller 104 for attaching toner to the electrostatic latent image on the photosensitive drum 101, a power pack 105 for applying a DC voltage to the charging roller 102, and a toner image on the photosensitive drum 101 are recorded. A transfer roller 106 that performs transfer processing on paper 107, a cleaning device 108 that cleans the photosensitive drum 101 after the transfer processing, a surface potential meter 109 that measures the surface potential of the photosensitive drum 101, and a heating and fixing roller 111 and a heating roller The roller-type heat fixing device 110 is composed of a pressure roller 112.

  In the image forming apparatus 100 using this electrophotographic system, a photosensitive layer of a rotating photosensitive drum 101 is uniformly charged by using a charging roller 102 and then exposed by an exposure unit 103 such as a laser beam to electrostatic latent. An image is formed, and the electrostatic latent image is developed with toner to form a toner image. The toner image is transferred onto the recording paper 107, and the recording paper 107 is transferred from the heat fixing roller 111 and the pressure roller 112. The toner image is thermally fixed by being passed through a thermal fixing device 110 of a roller type.

  In such a heat fixing device of the image forming apparatus 100, a tetrafluoroethylene resin (PTFE) coated on the outer peripheral surface of a cored bar made of a hollow cylindrical body of metal such as aluminum to prevent toner adhesion, A heat fixing roller 111 provided with a release layer made of a fluororesin such as tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin (PFA) or tetrafluoroethylene / hexafluoropropylene copolymer resin (FEP) is provided. Although being used, the heating and fixing roller 111 has a heater such as a halogen lamp disposed in the hollow portion of the metal core along the rotation center line, and the heating and fixing roller 111 is heated from the inside by its radiant heat. Then, the recording paper 107 is allowed to pass between the heat fixing roller 111 and the pressure roller 112 to adhere to the recording paper 107. The in which toner is adapted to be fixed on the recording sheet under pressure while softened by heat of the heating fixing roller 111.

  The heat fixing roller 111 provided with a fluororesin layer on the metal core is excellent in releasability, but is inferior in flexibility and elasticity, so it is suitable for full color copying machines and full color laser printers that require gloss. I can't respond. In full-color copying machines and laser printers that form these glossy images, four color toners of red (magenta), blue (cyan), yellow (yellow), and black (black) are used. Since it is necessary to mix these color toners in a molten state, the color toner is made to have a low melting point so that it can be easily melted. It is necessary to mix. For this reason, flexibility is one of the characteristics required for the surface of the fixing member (roller, belt).

  In order to impart flexibility to the surface of such a fixing member, a conventional full-color fixing roller for glossy images has a rubber layer excellent in releasability and durability such as silicone rubber and fluororubber on the silicone rubber roller. There is a heat fixing roller provided.

  The heat roller fixing method keeps the entire heat roller at a predetermined temperature, so that the heat capacity is increased. Therefore, the heat roller fixing method is suitable for increasing the printing speed. However, the heat roller fixing method is quite suitable for heating the heat roller to a predetermined temperature. Time is required and this also increases power consumption to heat the entire heat roller.

  In recent years, energy conservation activities have become active, and shortening of the rise time is being studied. As one of them, there has been proposed a belt-fixing type fixing device that heats toner on recording paper through a film-like endless belt heated by a heater (Japanese Patent Laid-Open No. 2001-201978 (Patent Document 1), etc.). .

  FIG. 19 is an explanatory diagram of a conventional belt-type fixing device C. FIG. As shown in FIG. 19, a fixing device C used in a conventional electrophotographic image forming apparatus is wound (stretched) around a fixing roller 2 and a heating roller 4 facing the fixing roller 2. D) an endless fixing belt 6; a means for heating the fixing belt 6; and a pressure roller 3 that presses the fixing roller 2 through the fixing belt 6 to form a nip portion.

  Heating sources (such as heaters) 5 a and 5 b are incorporated in the heating roller 2 and the pressure roller 3 as means for heating the fixing belt 6, and the portion of the heating roller 4 on which the fixing belt 6 is stretched. Further, temperature sensors (thermistors) 7a and 7b for detecting temperatures are arranged on the surface of the pressure roller 3, respectively, so that the fixing belt 6 and the surface of the pressure roller 3 are controlled to have predetermined temperatures, respectively. It has become. In this example, the heating source 5b in the pressure roller 3 is turned on after the paper discharge is completed, and is controlled to a predetermined temperature only during standby (only when not fixing). In FIG. 19, P is transfer paper, T is unfixed toner, and G is a guide plate for conveying the transfer paper to the fixing device C.

  Such a belt-type thermal fixing device C allows a recording medium P such as recording paper to pass between the fixing belt 6 heated by the heating roller 4 and the pressure roller 3, so that the recording medium P is placed on the recording medium P. The adhering toner T is pressed by the pressure roller 3 while being softened by the heat of the fixing belt 6 and fixed on the recording paper.

  According to the conventional belt-type fixing device C, the thin film-like fixing belt 6 is directly heated, so that the predetermined temperature is reached in a short time after the power is turned on, and therefore the waiting time after the power is turned on is reduced. Moreover, since only a necessary part is heated, there is an advantage that power consumption is low.

  In the above description, an example in which a heating source is arranged inside the heating roller 4 has been described. However, a technique in which a heating source is arranged outside the heating roller 4 as shown in a model in FIG. 20 is also known. In this example (fixing device D), an electromagnetic induction heating coil 200 and a core 201 are arranged as a heating source, a metal thin film layer is provided on the fixing belt 6 ′, and the metal thin film layer of the fixing belt 6 ′ is electromagnetic induction heated. It was the structure which generates heat by the method.

  However, in the above-described prior art, since electric power is distributed and heated at two places, that is, a heating roller and a pressure roller, the rise time until the temperature at which the nip portion can be fixed becomes long.

  Therefore, in order to speed up the rise time, power is concentrated and supplied only to the heating roller 4 side at the time of start-up, so that the rise time is shortened.

  However, in the case of a fixing device for a copying machine, for example, when it is desired to perform copying immediately from a standby state, these fixing devices are fixing belt type devices using a fixing belt, so that the entire fixing belt reaches a fixing temperature. It is necessary to perform idling, and it takes time until fixing is possible.

  For this reason, after the paper discharge is finished, the heating source on the pressure roller side is energized to control the pressure roller so that it reaches a predetermined temperature close to the heating roller, and when the temperature of the nip portion becomes low, the roller is driven. Thus, the belt is heated from both the heating roller and the pressure roller. By doing so, since the entire fixing belt 6 reaches the fixing temperature during the time Tb from when the transfer paper reaches the fixing nip portion from the paper feeding position, it is possible to immediately copy (see FIG. 21). This shows a case where the standby state is long and the sheet is passed from a state where the temperature is controlled at the fixing temperature by heating with a heating roller and a pressure roller during that time).

  However, even if the control is performed in this way, even if an attempt is made to pass the sheet immediately in the standby state immediately after the discharge of one or a series of recording media is completed, Since the fixing belt is not sufficiently heated, and the temperature of the pressure roller 3 does not reach the predetermined temperature, it is longer than Tb as shown in FIG. 22 until the temperature at which the nip portion can be fixed. Time Tc is required, and during this time idle rotation is required, causing a problem that copying cannot be performed immediately.

  Furthermore, in addition to heating the heating roller 4 as described above, if a heating source is provided also on the pressure roller 3 side, the cost increases accordingly. However, if there is no heating source on the pressure roller 3 side, a long idle rotation is required until the fixing temperature is reached when the paper is passed, and the waiting time until the copy can be made becomes long. There was a problem.

  Here, in order to shorten the rise time of the fixing device recently, there is a case where a large power of about 80% of the MAX value at a general outlet is supplied to the heat source of the fixing device for the start-up. . However, in this case, the heating roller is originally made to have a small diameter (about 25 mm) in order to accelerate the temperature rise, and its thickness is as thin as 0.3 mm, so when starting up (when the fixing belt does not rotate) The temperature of the part where the fixing belt is stretched is not easily raised because the heat conduction is poor, and the temperature of the part where the fixing belt is not stretched rises immediately (this temperature change is schematically shown in FIG. 3). .

Here, if the temperature is detected and controlled in the stretched part, the part that is not stretched becomes very hot, and when the fixing belt starts to be driven, the fixing belt touches the part where the temperature is high. As a result, the problem of deterioration occurred.
JP 2001-201978 A

  Various improvements have been made to the conventional fixing device with the main aim of shortening the time until fixing is possible after startup (power-on) as described above. However, these techniques are sufficient for shortening the time until fixing is possible when the fixing operation is once performed and the fixing operation is performed again after one or a plurality of recording media are discharged. The effect was not mentioned.

  The present invention improves the above-mentioned conventional problems, that is, the waiting time for the temperature rise is extremely short, even when paper feeding is resumed and when starting up, even though it does not require intensive large power, Another object is to provide a fixing device that does not require a waiting time.

According to a first aspect of the present invention, there is provided a fixing device comprising: an endless fixing belt stretched between a fixing roller and a heating roller facing the fixing roller; and a nip portion in pressure contact with the fixing roller via the fixing belt . A fixing device for fixing an unfixed image on the recording medium by heat and pressure when the recording medium passes through the nip portion. A fixing belt heating means for heating the belt, a fixing belt temperature detecting means for detecting the temperature of the fixing belt, a roller driving means for driving a roller in the fixing device, and an inside of the heating roller when the fixing device is started up Heating by the fixing belt heating means is started, and the temperature of the fixing belt measured by the fixing belt temperature detecting means reaches a predetermined driving start temperature lower than the temperature at the time of fixing. After, with the launch control means for starting the drive of the roller in the fixing device, the fixing belt heating means for heating said fixing belt to heat the fixing belt by supplying heat rays from inside the heating roller to the heating roller A small size heater having a long halogen heater in the axial direction of the heating roller, the halogen heater being divided into at least two in the length direction, and the heating area of the first halogen heater among these heat sources being supplied to the fixing device The second halogen heater is for heating the non-heated area of the first heat source, and is heated simultaneously with the first halogen heater, so that the second halogen heater is larger than the small size recording medium. An area corresponding to a large recording medium can be heated, and
The first halogen heater is characterized in that the first halogen heater is disposed closer to the portion where the fixing belt of the heating roller is stretched than the second halogen heater inside the heating roller .

The fixing device of the present invention according to claim 2, in the fixing device according to claim 1, has a reflecting portion for centrally supplying the heat rays from the halogen heater to the fixing belt retaining portion of the heating roller It is characterized by being.

According to a third aspect of the present invention, there is provided a fixing device comprising : an endless fixing belt stretched between a fixing roller and a heating roller facing the fixing roller; and a nip portion in pressure contact with the fixing roller via the fixing belt. A fixing device for fixing an unfixed image on the recording medium by heat and pressure when the recording medium passes through the nip portion. A fixing belt heating means for heating the belt, a fixing belt temperature detecting means for detecting the temperature of the fixing belt, a roller driving means for driving a roller in the fixing device, and an inside of the heating roller when the fixing device is started up Heating by the fixing belt heating means is started, and the temperature of the fixing belt measured by the fixing belt temperature detecting means reaches a predetermined driving start temperature lower than the temperature at the time of fixing. After that, the fixing belt heating means for heating the fixing belt includes heating control means for starting driving of the roller in the fixing device, and heats the fixing belt by supplying heat rays to the heating roller from the inside of the heating roller. A linear halogen heater that is long in the axial direction of the heating roller is provided, and the linear heat source is divided into at least two in the length direction, and the heating area of the first halogen heater among these halogen heaters is provided in the fixing device. Corresponding to the supplied small-size recording medium, the second halogen heater heats the non-heated area of the first heat source and is heated simultaneously with the first halogen heater so that the small halogen heater is heated. An area corresponding to a recording medium having a size larger than that of the recording medium can be heated, and the second halogen heater is more inside the heating roller than the first halogen heater. Disposed close to the fixing belt is stretched portion of the heat roller, and it has a reflecting portion for centrally supplying the heat rays from the first halogen heater to the fixing belt retaining portion of the heating roller It is characterized by.

According to a fourth aspect of the present invention, there is provided an image forming apparatus having the fixing device according to any one of the first to third aspects.

According to the fixing device of the present invention according to claim 1, a heating source for heating the pressure roller and a temperature sensor for detecting the temperature of the pressure roller are not necessarily required, so that the cost can be reduced, and The driving of the rollers in the fixing device is started after the temperature of the fixing belt measured by the heating roller temperature detecting means at the start-up of the fixing device reaches a predetermined driving start temperature lower than the temperature at the time of fixing. The temperature of the nip portion can be increased more quickly to the fixing processable temperature.
Further, when the size of the recording medium to be fixed is small, a first halogen heater that heats a portion corresponding to the small recording medium is used, and electric power reserved for heating is used as the first heat source. Therefore, it is possible to quickly fix the necessary portion and fix it quickly. Further, since the first halogen heater is disposed closer to the portion of the heating roller where the fixing belt of the heating roller is stretched than the second halogen heater, the fixing belt of the heating roller by the concentrated power is used. Since the unstretched portion is prevented from rising to an unnecessary high temperature, deterioration of the belt is also prevented. When fixing on a larger recording medium, the first halogen heater and the second halogen heater are used together. At this time, the electric power secured for heating is distributedly supplied to these two halogen heaters. Therefore, although the second halogen heater is disposed closer to the non-stretching portion of the fixing belt of the heating roller than the first halogen heater, the non-stretching portion of the heating roller becomes an unnecessary high temperature. Is prevented.

According to the fixing device of the present invention according to claim 2, because it has a centrally fed reflector portion to the fixing belt retaining portion of the heat ray heating roller from halogen heater, heat deterioration of the heating roller and the fixing belt Can be prolonged, and the heat supply to the fixing belt is made more efficient, so that the heat supply to the nip portion through the fixing belt is also efficient and the temperature of the nip portion is increased. The temperature rise to the fixing processable temperature can be made quicker. Further, at this time, if the reflection part is provided on the glass tube of the halogen heater, the number of parts can be reduced and the reflection part can be easily formed by ceramic coating or metal vapor deposition. Therefore, the heating by the halogen heater becomes more efficient, and the temperature of the nip portion can be raised to a predetermined temperature more quickly.

According to the fixing device of the present invention according to claim 3, a heating source for heating the pressure roller and a temperature sensor for detecting the temperature of the pressure roller are not necessarily required, so that the cost can be reduced, and The driving of the rollers in the fixing device is started after the temperature of the fixing belt measured by the heating roller temperature detecting means at the start-up of the fixing device reaches a predetermined driving start temperature lower than the temperature at the time of fixing. The temperature of the nip portion can be increased more quickly to the fixing processable temperature.
Furthermore, when the size of the target recording medium for fixing is small, the first using a halogen heater, a first halogen power reserved for the heating of heating a portion corresponding to the small recording medium Since it is possible to concentrate on the heater , the required portion can be quickly heated, and can be fixed quickly. In addition , the first halogen heater is more heated than the second halogen heater to the fixing belt of the heating roller because the first halogen heater has a reflecting portion for supplying heat rays from the halogen heater to the fixing belt suspension of the heating roller in a concentrated manner. Despite being arranged close to the non-stretching part, the non-stretching part of the heating roller does not reach an unnecessarily high temperature, so that the fixing belt is prevented from deteriorating and the heating part is effectively heated. Can be supplied. In addition, since the second halogen heater is disposed near the fixing belt stretch portion of the heating roller, the necessary portion of the heating belt can be efficiently heated even when the size of the recording medium is large. As a result, the temperature of the nip portion can be quickly raised.

According to the image forming apparatus of the present invention according to claim 4 , since the fixing device as described above is included, it is possible to quickly start and restart image fixing.

  The fixing device of the present invention will be described in detail below with reference to the drawings.

<Fixing Device A According to the Present Invention>
The fixing device A is a device for fixing an image made of toner on a medium (recording medium) such as paper or film. For example, as an example of the fixing device A, FIG. FIG. 2 shows a control block diagram of the MPU 10A.

  This fixing device A is provided inside the heating roller 4 and the endless fixing belt 6 stretched around the fixing roller 2 and the heating roller 4 facing the fixing roller 2. The heating roller 4 is heated by heating the heating roller 4 from the inside. A fixing belt heating means A1 (in this example, a halogen heater 5a made of a halogen lamp) that heats the fixing belt 6 via the fixing belt 6, and a pressure roller 3 that presses against the fixing roller 2 via the fixing belt 6 to form a nip portion. And have. The glass tube of the halogen heater 5a is provided with a ceramic coating on the left side in FIG. 1 to heat the heat rays from the halogen heater 5a to the suspension of the fixing belt 6 of the heating roller 4, ie, to the right side in the figure. It has a reflection part 5a1 (applied to approximately half of the side surface of the glass tube) directly formed on the glass of the halogen heater 5a. In this example, the halogen heater 5a is fixed by sheet metal processing at the end of the halogen heater 5a so that the heat rays from the halogen heater 5a to the fixing belt 6 suspension of the heating roller 4 are effectively supplied. Although it is performed by screwing with a jig, the halogen heater 5a may be fixed by other methods (the same applies hereinafter).

  Conventionally, since the inside of the heating roller is uniformly heated with a halogen lamp, as shown in FIG. 3, the temperature on the side where the belt is stretched (the side where the belt is stretched) rises. The temperature is lower than the temperature rise on the non-clad side (the side where the belt is not stretched), the high temperature part is always in contact with the fixing belt and deterioration occurs, and the temperature of the roller part that conducts heat to the belt is low. However, the heat ray can be intensively supplied to the heating roller portion that transfers heat to the belt by the reflecting portion 5a1. As a result, the heat transfer efficiency is increased, and the temperature rise at the nip portion is finally accelerated. In addition, the belt can be prevented from deteriorating.

  Further, a heater 5 b is built in the pressure roller 3 as pressure roller heating means A 4, and the nip portion can be heated via the fixing belt 6.

  Further, the temperature of the surface of the fixing belt 6 and the surface of the pressure roller 3 in the portion stretched around the heating roller 4 is measured in the vicinity of the portion of the fixing belt 6 and the pressure roller 3 stretched around the heating roller 4, respectively. Temperature sensors (a thermistor is used in this example) 7a and 7b are arranged as a fixing belt temperature detection means A2 and a pressure roller temperature detection means A5, respectively. Thus, the temperature of the fixing belt 6 and the temperature of the pressure roller 3 are controlled to predetermined temperatures.

  FIG. 4 is a partially enlarged cross-sectional view showing the configuration of the fixing belt 6. The substrate 6a, the elastic layer 6b, and the release layer 6c are configured from the belt inner side. The substrate 6a is an endless belt-like substrate formed of a heat resistant resin, and polyimide, polyamideimide, polyetheretherketone (PEEK) or the like can be used as the material of the heat resistant resin. Considering the rigidity and heat capacity of the belt, the thickness of the base material is desirably in the range of 20 μm to 100 μm. The elastic layer 6b is necessary for obtaining uniformity of the glossiness of the image to be fixed, and heat-resistant rubber such as silicone rubber or fluorine rubber having a thickness of about 100 μm to 300 μm is used. Since the release layer 6c is in pressure contact with the transfer paper and the toner, the elastic layer 6b is coated with a thickness of 10 μm or more and 50 μm or less made of a fluorine resin having excellent heat resistance and durability.

  The heating roller 4 usually has a barrel outer diameter of 20 to 30 mm and a metal core (stainless steel, iron, aluminum, etc.), and its thickness is the total thickness of the fixing belt 6 in order to speed up the start of heating. It is desirable that it is not more than twice the thickness (usually not less than 0.1 mm and not more than 0.9 mm) and not less than 0.2 mm and not more than 0.4 mm. Further, the surface is subjected to a surface treatment (alumite treatment or fluororesin coating) for preventing the metal core from being scraped, and the inside is painted so as to improve the light absorption and becomes black.

  The fixing roller 2 is made of aluminum, iron, or the like, and in this example, a heat insulating layer is disposed on the outside of a core metal having an outer diameter of 40 mm. The heat insulating layer is made of heat-resistant silicone rubber (including sponge). The lower the thermal conductivity of the material constituting the heat insulating layer, the more effective, and it is desirable that the material is generally 0.2 W / m / K or less.

  The pressure roller 3 usually has a barrel outer diameter of 20 mm or more and 50 mm or less, made of metal (stainless steel, iron, aluminum, etc.) and a wall thickness of 0.3 mm or more and 3 mm or less, and an outer periphery of the core metal. A heat-resistant elastic layer such as silicone rubber having a thickness of 0.2 mm to 5 mm disposed on the surface, and a fluororesin coated on the outer periphery of the heat-resistant elastic layer so that the film thickness is 10 μm to 200 μm Consists of a release layer.

  In the pressure roller 3, an electric heater 5b is disposed as pressure roller heating means A4 for heating the pressure roller 3.

  Further, in order to improve the separation property of the transfer paper P from the fixing belt 6, the surface hardness of the pressure roller 3 is made higher than the surface hardness of the fixing roller 2, so that the transfer paper P faces downward between the fixing belt 6 and the pressure roller 3. The fixing nip portion (shown as a model in FIG. 1) is formed. On the exit side of the fixing nip portion, a paper discharge detection sensor 8 (a photoelectric sensor is used in this example) for detecting completion of paper discharge of the recording medium from the fixing nip portion is provided as a paper discharge detection means.

  In FIG. 1, P is transfer paper, T is unfixed toner, and G is a guide plate that conveys the transfer paper to the fixing device 1.

  As the temperature of the fixing belt 6, the temperature of the fixing belt 6 stretched around the heating roller 4 is measured by the temperature sensor 7a, and the surface temperature of the pressure roller 3 is measured by the temperature sensor 7b, respectively, and the input port IA1 of the MPU 10A is measured. And IA2 to be input into the MPU 10A. In this example, a signal notifying completion of discharge of the recording medium from the fixing nip portion detected by the discharge detection sensor 8 which is a discharge detection means A7 including a photoelectric sensor is input from the input port IA3 of the MPU 10A to the MPU 10A. Entered. Note that an input port indicated by reference numeral IA0 of the MPU 10A is a port for inputting a startup instruction signal input from the outside (developing device or the like) into the MPU 10A.

  On the other hand, the halogen heater 5a as the fixing belt heating means A1 and the electric heater 5b as the pressure roller heating means A4 are controlled by signals output from the output ports OA1 and OA2 of the MPU 10A, respectively. Further, the fixing roller 2, the heating roller 4, the fixing belt 6 suspended by these rollers, and the electric motor 9 as the roller driving means A8 for driving the pressure roller 3 are transmitted by a signal output from the output port OA3 of the MPU 10A. Be controlled.

  The MPU 10A includes a CPU that is a central processing circuit, a RAM that is a random access memory for temporary data storage, and a ROM that is a read-only memory for storing various control constants and CPU operation programs. is doing.

  As can be understood from FIG. 2, the fixing device A according to the present invention has two systems of control means, that is, a start-up control system and a drive / heating / stop / restart control system.

  Here, first, the startup control system will be described. The start-up control means A10 controls the fixing belt heating control means A3 after turning on the power, turns on the halogen heater 5a inside the heating roller 4 by the fixing belt heating means A1, and starts heating the heating roller 4. In this example, the pressure roller heating control means A6 is also controlled to start heating the pressure roller 3. Start-up control when the temperature of the portion of the fixing belt 6 suspended from the heating roller 4 detected by the temperature sensor 7a serving as the fixing belt temperature detecting means A2 reaches a predetermined driving start temperature lower than the temperature at the time of fixing. The means A10 controls the electric motor 9 which is the roller driving means A8 to start driving the rollers in the fixing device A and the fixing belt. In the fixing belt heating control means A3, the temperature of the fixing belt 6 suspended from the heating roller 4 detected by the temperature sensor 7a serving as the fixing belt temperature detecting means A2 is a predetermined fixing temperature (for example, 160 to 180 ° C.). ) To control the halogen heater 5a as the fixing belt heating means A1. The pressure roller heating control means A6 is based on the pressure roller surface temperature signal detected by the pressure roller temperature detection means A5 so as to keep the temperature of the pressure roller 3 at a predetermined pressure roller temperature. Control the heating by.

  The portion of the fixing belt stretched around the heating roller by such control that the roller is driven after the temperature of the fixing belt 6 suspended from the heating roller 4 reaches a driving start temperature lower than the fixing temperature. As shown by a solid line in FIG. 5 (“idle rotation from the middle”), the portion of the fixing belt stretched around the heating roller when the roller is driven simultaneously with the start of the temperature increase (FIG. 5). The fixing temperature can be reached earlier by time Ta than the middle broken line “idle rotation from the beginning”).

  In this example, since electric power is concentrated and supplied to the heating roller 4 at the time of start-up, the time required to reach the fixing temperature can be shortened. FIG. 6 shows a case where electric power is distributed and heated to the fixing belt 6 and the pressure roller 3 (“prior art” in the figure), for example, 700 W is supplied to the heating roller 4 and 500 W is supplied to the pressure roller 3. A temperature rise state of a portion of the fixing belt stretched around the heating roller when electric power is concentrated on the heating roller 4 (heating concentration) is shown. It can be understood from FIG. 6 that when the power is concentrated on the heating roller 4, the time to reach the fixing temperature is shortened by the time t.

  Next, drive / heating / stop / restart control means will be described. The driving / heating / stop / restart control means A9 receives a paper feed signal from the outside of the fixing apparatus informing the supply of the recording medium P to the fixing apparatus A, and the pressure roller surface detected by the pressure roller temperature detecting means A5. The heating of the pressure roller 3 by the pressure roller heating control means A6 for maintaining the predetermined pressure roller temperature by heating the pressure roller 3 by the pressure roller heating means A4 based on the temperature signal is stopped, and the fixing device A When the roller driving is stopped, the roller driving means A8 is controlled to start the roller driving, and then the fixing to one or a plurality of continuous recording media P is completed, and the (last) recording medium P After receiving the paper discharge signal from the paper discharge detecting means A7 indicating that the paper is discharged from the nip portion, the temperature control of the pressure roller 3 to the predetermined pressure roller temperature by the pressure roller heating control means A6. Is started, and when the temperature of the pressure roller 3 detected by the pressure roller temperature detecting means A5 reaches a predetermined pressure roller temperature (for example, 150 to 170 ° C.), the roller driving means A8 is controlled and fixed. The drive of the roller in the apparatus is stopped. In the above description, when the driving / heating / stop / restart control means A9 receives the paper passing signal from the outside of the fixing device again after receiving the paper discharging signal from the paper discharging detecting means A7, the series of the above is immediately performed. The operation is performed again from the beginning.

  Here, the driving / heating / stop / restarting control means A9 of the fixing device A according to the present invention controls the roller driving means A8 after receiving the paper discharge signal from the paper discharge detecting means A7, and the rollers in the fixing device A. Is provided with roller driving speed control means A9a for controlling the driving speed to be slower than the driving speed at the time of fixing.

  Here, in such a fixing device A shown in FIG. 7, a temperature sensor that measures a position immediately before the nip portion of the fixing belt 6 in FIG. 1 when the driving speed of the roller is lowered after the recording medium is discharged from the nip portion. The detected temperature change is indicated by a solid line, and the temperature change when the roller is driven at the same driving speed as that at the time of fixing is indicated by a dotted line. As shown in FIG. 7, when the temperature of the fixing belt is increased after the paper discharge is completed, the driving speed is lowered (“linear speed is slow” in FIG. 7) and the constant speed is maintained (“conventional linear speed” in FIG. 4). ) Is faster than Here, it has been confirmed that when the driving speed is reduced within the range of the normal fixing speed to 1/5 of the speed condition during low-speed operation, a sufficient nip temperature increase promoting effect can be obtained. .

  Control at the time of start-up in this apparatus A is performed by the start-up control means A10 or the like, and the heating roller and the heating source of the pressure roller, that is, the halogen heater 5a as the fixing belt heating means and the electric heater 5b as the pressure roller heating means. The heating starts, and the fixing belt is not driven until the heating roller 4 reaches a predetermined temperature (lower than the temperature at the time of fixing). Can be rapidly raised to a temperature at which fixing can be performed.

  Here, the operation of the MPU 10A in FIG. 1 of the fixing device A according to the present invention will be specifically described with reference to the flowchart of FIG.

  When the power is turned on, the program starts (step Sa1). A heater-on signal is output to the output port OA1 of the MPU 10A, and the halogen heater 5a in the heating roller 4 is turned on (step Sa2). In step Sa3, similarly, a heater-on signal is output to the output port OA2, and energization to the heater 5b in the pressure roller 3 is started.

  In step Sa4, the temperature signal of the fixing belt 6 suspended from the heating roller 4 input from the input port IA1 is checked, and the temperature of the fixing belt 6 suspended from the heating roller 4 is stored in the MPU 10A ROM in advance. The process waits until reaching the drive start temperature, and after the temperature of the fixing belt 6 in the portion suspended from the heating roller 4 reaches the drive start temperature, the process proceeds to step Sa5.

  In step Sa5, a normal drive start signal is output to the output port OA3, and driving of the rollers in the fixing device A and the fixing belt is started at the fixing speed by the electric motor 9 serving as roller driving means.

  Next, in step Sa6, it is checked whether or not the temperature of the heating roller input from the input port IA1 has reached the fixing temperature. If the temperature is lower than the fixing temperature, the process proceeds to step Sa7 and a heater-on signal for turning on the halogen heater 5a is received. When the temperature is higher than the hour temperature, the process proceeds to step Sa8, and a heater off signal for turning off the halogen heater 5a is output to the output port OA1 (if the same signal is continuously input, the state indicated by the previous signal is These steps Sa6 to Sa8 are operations for maintaining the temperature during fixing of the fixing belt 6 suspended from the heating roller 4. Therefore, these similar operations are hereinafter referred to as “fixing”. This is referred to as “temperature maintaining control operation for fixing the belt 6”).

  In step Sa9, it is checked whether or not the pressure roller temperature input from the input port IA2 has reached a predetermined pressure roller temperature (previously stored in the ROM in the MPU 10A). If the heater on signal for starting energization to the electric heater 5b proceeds to step Sa10 and the temperature is equal to or higher than the predetermined pressure roller temperature, the process proceeds to step Sa11 and the heater off signal for ending energization to the electric heater 5b is output to the output port OA2. (These steps Sa9 to Sa11 are operations for maintaining the predetermined pressure roller temperature of the pressure roller 3, and therefore these similar operations are hereinafter referred to as “predetermined pressure roller temperature control operation of the pressure roller 3”. say).

  In step Sa12, it is checked whether or not a paper passing signal notifying the supply of the recording medium P to the fixing device A is input to the input port IA0. If a paper passing signal is received, the process proceeds to step Sa13, and no paper passing signal is received. In this case, the process returns to step Sa6 and steps Sa6 to Sa12 are repeated.

  Steps Sa1 to Sa12 are functions of the MPU 10A from when the power is turned on until a sheet passing signal is received. The MPU 10A includes the start-up control unit A10 and the fixing unit among the unit control units of the fixing device A according to the present invention. It functions as a belt heating control means A3 and a pressure roller heating control means A6.

  In step Sa13, a heater-off signal is output to the output port OA2, and heating of the pressure roller 3 (maintaining a predetermined pressure roller temperature) is stopped. In step Sa14 to step Sa16, fixing temperature maintenance control of the fixing belt 6 is performed. Next, in step Sa17, fixing on one or a plurality of continuous recording media P is completed, and the (last) recording medium P is completed. It is checked whether or not a paper discharge end signal indicating that the paper has been discharged from the nip portion is input to the input port IA3. If a paper passing end signal has been received, the process proceeds to step Sa18, where the paper passing end signal is If not, since the fixing operation is in progress, the process returns to step Sa14, and steps Sa14 to Sa17 are repeated.

  In step Sa18, a gradual drive start signal is output to the output port OA3, and control is performed to make the drive speed of the roller in the fixing device slower than the drive speed at the time of fixing.

  In step Sa19, a heater-on signal is output to the output port OA2, and heating of the pressure roller 3 is resumed. In steps Sa20 to Sa22, the fixing belt 6 is maintained at the fixing temperature maintaining operation, and in steps Sa23 to Sa25, the pressure roller 3 is heated. Each predetermined pressure roller temperature control operation is performed. At this time, when the pressure roller reaches the predetermined pressure roller temperature, a drive stop signal is output to the output port OA3 in step Sa26 to stop the roller driving. In step Sa27, it is checked whether or not a sheet passing signal to the fixing device A has arrived at the input port IA0. If there is no sheet passing, the process returns to step Sa20 to repeat steps Sa20 to Sa27, and when a sheet passing is notified, step Sa28. Then, a normal drive start signal is output to the output port OA3 to start roller driving at the fixing speed, and the process returns to Step Sa13, and Steps Sa13 to Sa28 are repeated thereafter.

  Steps Sa12 to Sa28 are functions of the MPU 10A after the first sheet passing signal is received after the start-up, and the MPU 10A is the fixing belt heating among the device control means of the fixing device A according to the present invention. It functions as control means A3, pressure roller heating control means A6, drive / heating / stop / restart control means A9, roller drive speed control means A9a, and start-up control means A10.

  The fixing device A includes an endless fixing belt 6 stretched between a fixing roller 2 and a pressure roller 4 facing the fixing roller 2, and a fixing belt for heating the fixing belt inside the pressure roller 4. A heating roller A1 and a pressure roller 3 that presses against the fixing roller 2 via the fixing belt 6 to form a nip portion are formed. When the recording medium P passes through the nip portion, the recording medium is heated and pressured. A fixing device for fixing an unfixed image on P, a pressure roller heating means A4 for heating the pressure roller 3; a pressure roller temperature detecting means A5 for detecting the temperature of the pressure roller 3; Based on the signal from the pressure roller temperature detection means A5, the pressure roller heating means A4 is controlled to keep the pressure roller 3 at a predetermined pressure roller temperature, and the rollers in the fixing device A are controlled. To drive A driving means A8, a paper discharge detecting means A7 for detecting that the recording medium P has been discharged from the nip portion, and a paper passing signal for notifying the supply of the recording medium P to the fixing apparatus A are received. When the heating of the pressure roller 3 by the pressure roller heating control means A6 is stopped and the roller driving is stopped, the roller driving means A8 is controlled to start the roller driving, and then the recording medium P is moved to the nip portion. After receiving the paper discharge signal from the paper discharge detecting means A7 indicating that the pressure roller 3 is discharged, the pressure roller heating control means A6 starts heating the pressure roller 3 and then the pressure roller temperature detecting means A5 When the detected temperature of the pressure roller 3 reaches the predetermined pressure roller temperature, the roller driving means A8 is controlled to stop driving of the roller in the fixing device A. The drive / heating / stop / restart control means A9 controls the roller drive means A8 to drive the rollers in the fixing device A after receiving the paper discharge signal from the paper discharge detection means A7. It has roller drive speed control means A9a for controlling the speed to be slower than the drive speed at the time of fixing (corresponding to the fixing device of claims 1 and 2).

  Further, the fixing device A is located inside the heating roller 4 and has a fixing belt heating means A1 for heating the fixing belt 6, and a fixing belt temperature detecting means for detecting the temperature of the heating roller 4 suspension of the fixing belt 6. A2, the roller driving means A8 for driving the roller in the fixing device A, and the heating by the fixing belt heating means A1 in the heating roller 4 when the fixing device A is started up, are measured by the fixing belt temperature detecting means A2. The fixing belt 6 includes start-up control means A10 for starting driving of the rollers in the fixing device A after the temperature of the fixing belt 6 reaches a predetermined driving start temperature lower than the temperature at the time of fixing. From the halogen lamp, the fixing belt heating means A1 for heating heats the fixing belt 6 by supplying the heating roller 4 with heat rays from the inside of the heating roller 4. A fixing device having a halogen heater 5a and a reflecting portion 5a1 for intensively supplying heat rays from the halogen heater 5a to the fixing belt suspension of the heating roller 4 (fixing according to claims 7 and 8). Corresponds to the device).

  Such a fixing device A can be incorporated as a fixing device in the conventional electrophotographic image forming apparatus shown in FIG. At that time, the heat fixing roller 111 in FIG. 18 is replaced with an endless fixing belt 6 stretched between the fixing roller 2 and the heating roller 4 facing the fixing roller 2, and the pressure roller 112 in FIG. Replace with roller 3 and incorporate.

  In the above description, the fixing belt heating means A1 is provided in the pressure roller 4. However, as shown in FIG. 20, a metal thin film layer is provided on the fixing belt, and the electromagnetic induction heating is provided near the fixing belt. The coil and the core may be arranged, and the metal thin film layer of the fixing belt 6 may be heated by an electromagnetic induction heating method.

<Fixing device B according to the present invention>
Next, another example B of the fixing device according to the present invention will be described with reference to the drawings. The fixing device B is a device for fixing an image made of toner on a medium (recording medium) such as paper or film. FIG. 9 shows a main part of the device and an MPU 10B electrically connected thereto. The block diagram of control is shown.

  The fixing device B is provided inside the heating roller 4 and the endless fixing belt 6 stretched around the fixing roller 2 and the heating roller 4 facing the fixing roller 2. The heating roller 4 is heated from the inside by heating the heating roller 4. A fixing belt heating means A1 (in this example, a halogen heater 5a made of a halogen lamp) that heats the fixing belt 6 via the fixing belt 6, and a pressure roller 3 that presses against the fixing roller 2 via the fixing belt 6 to form a nip portion. And have. In the glass tube of the halogen heater 5a, the reflection portion 5a1 for supplying the heat rays from the halogen heater 5a intensively to the fixing belt 6 suspension of the pressure roller 4, that is, the right side in the drawing, on the left side in the drawing. (A ceramic coating provided directly on the glass tube, which is applied to approximately half of the side surface of the glass tube) is provided (members corresponding to the fixing device A are given the same reference numerals). The members such as the fixing belt 6, the pressure roller 3, the heating roller 4, and the sensor have the same configuration as the members of the fixing device A). In FIG. 9, P is transfer paper, T is unfixed toner, and G is a guide plate for conveying the transfer paper to the fixing device B.

  In the fixing device B, as in the fixing device A, heat rays can be intensively supplied to the heating roller portion that transfers heat to the belt by the reflecting portion 5a1, and as a result, the heat transfer efficiency increases, and finally the temperature rise in the nip portion increases. The speed can be increased and deterioration of the belt can be prevented. FIG. 11 shows the heat generation distribution in the longitudinal direction of the heater in the heating roller 4. The dotted line is the amount of heat generated in the ceramic coating side, and the solid line is the amount of heat generation in the direction opposite to the direction in which the ceramic coating is provided (on the anti-ceramic coating side). When the reflection part 5a1 by ceramic coating is not provided, it becomes the calorific value shown as "normal state" over the perimeter.

  In the vicinity of the fixing belt 6 stretched around the heating roller 4, a temperature sensor (a thermistor is used in this example) 7a for measuring the temperature of the surface of the fixing belt 6 stretched around the heating roller 4 is a fixing belt temperature. As described later, the fixing device B is arranged so as to control the temperature of the fixing belt 6 to a predetermined temperature based on measurement data from the temperature sensor 7a.

  As the temperature of the fixing belt 6, the temperature of the fixing belt 6 in the portion stretched around the heating roller 4 is measured by the temperature sensor 7 a and is input into the MPU 10 B from the input port IB 1 of the MPU 10 B. Further, in this example, a signal notifying completion of discharge of the recording medium from the fixing nip portion detected by the discharge detection sensor 8 which is a discharge detection means B7 including a photoelectric sensor is input from the input port IB2 of the MPU 10B into the MPU 10B. Entered.

  On the other hand, the halogen heater 5a as the fixing belt heating means B1 is controlled by a signal output from the output port OB1 of the MPU 10B. Further, the fixing roller 2, the heating roller 4, the fixing belt 6 suspended by these rollers, and the electric motor 9 as the roller driving means A8 for driving the pressure roller 3 are transmitted by a signal output from the output port OB2 of the MPU 10B. Be controlled.

  The MPU 10B includes a CPU that is a central processing circuit, a RAM that is a random access memory that also has a temporary data storage, and a read-only memory that stores various control constants and CPU operation programs. A certain ROM is attached.

  As can be understood from FIG. 10, the fixing device B according to the present invention mainly has two systems of control means, that is, a start-up control system and a roller drive stop / redrive control system.

  Here, the startup control system is the same as the startup control system of the fixing device A. After the power is turned on, the start-up control unit B10 controls the fixing belt heating controller B3 to turn on the halogen heater 5a inside the heating roller 4 by the fixing belt heating unit B1 and start heating the heating roller 4. Start-up control when the temperature of the portion of the fixing belt 6 suspended from the heating roller 4 detected by the temperature sensor 7a serving as the fixing belt temperature detecting means B2 reaches a predetermined driving start temperature lower than the temperature at the time of fixing. The means B10 controls the electric motor 9 as the roller driving means B8 to start driving the rollers and the fixing belt in the fixing device B. In the fixing belt heating control means B3, the temperature of the fixing belt 6 suspended from the heating roller 4 detected by the temperature sensor 7a which is the fixing belt temperature detecting means B2 is a predetermined fixing temperature (for example, 160 to 180 ° C.). ) To control the halogen heater 5a, which is the fixing belt heating means B1.

  As shown in FIG. 5, as in the fixing device A, the roller driving is performed after the temperature of the fixing belt 6 suspended from the heating roller 4 reaches the driving start temperature lower than the fixing temperature. Can quickly reach the fixing temperature. Similarly to the fixing device A, when starting up without starting driving the roller until reaching a predetermined temperature, the influence of heat radiation is reduced, and further, the time until reaching the fixing temperature is shortened. Can do.

  Next, the roller drive stop / redrive control system will be described. After starting up the roller drive stop / redrive control means B9, the fixing to one or a plurality of continuous recording media P is completed, and the (last) recording medium P is discharged from the nip portion. After receiving the paper discharge signal from the paper discharge detection means B7 shown, the roller drive is stopped.

  Thereafter, the time is measured by the RAM timer Tt1 of the MPU 10B from the time when the driving of the roller is stopped. After the first predetermined time T1 recorded in the ROM in advance, the roller driving means B8 is controlled to control the timer Tt2 in the RAM of the MPU 10B. The roller in the fixing device is driven until the time measured by the above reaches the second predetermined time T2 recorded in the ROM, and then the driving is stopped. Thereafter, the intermittent standby operation is repeated for the roller drive stop at time T1 and the roller drive at time T2 in the same manner. When the sheet passing signal is notified to the fixing device during this repetition, the intermittent standby operation is stopped, Immediately shifts to the roller driving state at the time of fixing. Here, the roller driving speed control means B9a controls the roller driving means B8 when driving the roller in the intermittent standby operation so as to make the driving speed of the roller in the fixing device B slower than the driving speed at the time of fixing. .

  In the present example, the times T1 and T2 take into consideration the use environment of the fixing device until the fixing belt 6 is not completely cooled, a sheet passing signal is notified to the fixing device, and the recording medium reaches the nip portion. It is determined so that the temperature of the nip portion can be fixed within the time, that is, the waiting time is substantially zero.

  Here, the operation of the MPU 10B in FIG. 9 of the fixing device B according to the present invention will be specifically described with reference to the flowchart of FIG.

  When the power is turned on, the program starts (step Sb1). A heater-on signal is output to the output port OB1 of the MPU 10B, and the halogen heater 5a in the heating roller 4 is turned on (step Sb2).

  In step Sb3, the temperature signal of the fixing belt 6 suspended from the heating roller 4 input from the input port IB1 is checked, and the temperature of the fixing belt 6 suspended from the heating roller 4 is stored in the ROM in the MPU 10B in advance. The process waits until reaching the drive start temperature, and after the temperature of the fixing belt 6 in the portion suspended from the heating roller 4 reaches the drive start temperature, the process proceeds to step Sb4.

  In step Sb4, a normal drive start signal is output to the output port OB2, and the rollers in the fixing device B and the fixing belt are started to be driven at the fixing speed by the electric motor 9 as roller driving means.

  Next, in step Sb5, it is checked whether or not the temperature of the heating roller input from the input port IB1 has reached the fixing temperature. If the temperature is lower than the fixing temperature, the process proceeds to step Sb6 and a heater on signal for lighting the halogen heater 5a is received. If the temperature is higher than the hour temperature, the process proceeds to step Sb7, and a heater off signal for turning off the halogen heater 5a is output to the output port OB1 (if the same signal is continuously input, the state indicated by the previous signal is These steps Sb5 to Sa7 are operations for maintaining the temperature during fixing of the fixing belt 6 suspended from the heating roller 4. Therefore, these similar operations are hereinafter referred to as “fixing”. This is referred to as “temperature maintaining control operation for fixing the belt 6”).

  In the next step Sb8, it is checked whether or not a paper passing signal notifying the supply of the recording medium P to the fixing device B is input to the input port IB0. If a paper passing signal is received, the process proceeds to step Sb9, and the paper passing signal is received. If not, the process returns to step Sb5 and steps Sb5 to Sb8 are repeated.

  Steps Sb1 to Sb8 are functions of the MPU 10B from when the power is turned on until a sheet passing signal is received. The MPU 10B includes the start-up control means B10, the fixing belt among the apparatus control means of the fixing device B according to the present invention. It functions as heating control means B3 and pressure roller heating control means A6.

  In step Sb9 to step Sb11, fixing temperature maintenance control of the fixing belt 6 is performed. Next, in step Sb12, the fixing to one or a plurality of continuous recording media P is completed, and the (last) recording medium P is completed. It is checked whether or not a paper discharge end signal indicating that the paper has been discharged from the nip portion has been input to the input port IB2. If a paper passing end signal has been received, the process proceeds to step Sb13, where the paper passing end signal is If not, since the fixing operation is in progress, the process returns to step Sb9, and steps Sb9 to Sb12 are repeated.

  In step Sb13, a drive stop signal is output to the output port OB2, and the driving of the rollers in the fixing device is stopped.

  In step Sb14, the RAM timer Tt1 of the MPU 10B is initialized and then started. Next, in steps Sb15 to Sb17, a fixing temperature maintaining control operation for the fixing belt 6 is performed. In step S18, it is checked whether or not a paper passing signal for notifying the input port IB0 of paper passing to the fixing device B is received. Is output to start normal driving of the roller, the process returns to step Sb9, and the fixing operation from steps Sb9 to Sb12 is performed. On the other hand, if there is no paper passing signal in step Sb18, the process proceeds to step Sb20, where it is checked whether the timer Tt1 has reached T1 which is the first predetermined time recorded in the ROM in advance. Sometimes, the process proceeds to step Sb21. If it has not been reached yet, the process returns to step Sb15, and steps Sb15 to Sb20 are repeated to keep the roller drive stopped.

  In the next step Sb21, a gradual drive start signal is output to the output port OB2, and the roller drive is performed at a speed slower than that at the time of fixing.

  In step Sb22, the RAM timer Tt2 of the MPU 10B is initialized and then started. Next, in step Sb23 to Sb25, a fixing temperature maintaining control operation for the fixing belt 6 is performed. Thereafter, in step Sa26, it is checked whether or not a paper passing signal notifying the input port IB0 of paper passing to the fixing device B has been received. After outputting a signal to start normal driving of the roller, the process returns to step Sb9, and the fixing operation from steps Sb9 to Sb12 is performed. On the other hand, if there is no sheet passing signal in step Sb26, the process proceeds to step Sb27, where it is checked whether the timer Tt2 has reached T2, which is a second predetermined time recorded in the ROM in advance. Sometimes, the process returns to step Sb15 to proceed to the roller driving stop operation for the first predetermined time of steps Sb15 to Sb20. If not reached yet, the process returns to step Sb23, and steps Sb23 to Sb27 are repeated for the second predetermined time. The roller drive is maintained until the value is reached.

  During the steps Sb13 to Sb23, the MPU 10B stops driving the roller and stops driving the roller after receiving the paper discharge signal from the paper discharge detecting means B7 indicating that the recording medium P is discharged from the nip portion. After the first predetermined time elapses, the roller driving unit is controlled to function as roller drive stop / redrive control unit B9 that drives the roller in the fixing device B until the second predetermined time elapses.

  The fixing device B includes an endless fixing belt 6 stretched between a fixing roller 2 and a heating roller 4 facing the fixing roller 2, a fixing belt heating unit for heating the fixing belt 6 inside the heating roller 4, And a pressure roller 3 that forms a nip portion in pressure contact with the fixing roller 2 via the fixing belt 6, and is undecided on the recording medium P by heat and pressure when the recording medium P passes through the nip portion. A fixing device for fixing a received image T, a roller driving unit B8 for driving a roller in the fixing device B, a paper discharge detecting unit B7 for detecting that the recording medium P is discharged from the nip portion, and a recording After receiving a paper discharge signal from the paper discharge detecting means B7 indicating that the medium P has been discharged from the nip portion, the driving of the roller is stopped, and the roller is stopped after the first predetermined time has elapsed from the stop of the driving of the roller. The fixing device includes a roller driving stop / redrive control unit B9 for driving the rollers in the fixing device B until the second predetermined time elapses after the moving unit B8 is controlled. The drive control means B9 controls the roller drive means B8 so that the drive speed of the rollers in the fixing device B after receiving the paper discharge signal from the paper discharge detection means B7 is slower than the drive speed at the time of fixing. It has roller drive speed control means B9a to perform (corresponding to the fixing device of claims 4 and 5).

  Further, the fixing device B is located inside the heating roller 4, a fixing belt heating means B 1 for heating the fixing belt 6, and a fixing belt temperature detecting means for detecting the temperature of the heating roller 4 suspension portion of the fixing belt 6. B2, roller driving means B8 for driving the roller in the fixing device B, and heating by the fixing belt heating means B1 in the heating roller 4 when the fixing device B is started up, and measurement is performed by the fixing belt temperature detecting means B2. The fixing belt 6 includes start-up control means B10 that starts driving the rollers in the fixing device B after the temperature of the fixing belt 6 reaches a predetermined driving start temperature lower than the temperature at the time of fixing. From the halogen lamp, the fixing belt heating means B1 for heating heats the fixing belt 6 by supplying the heating roller 4 with heat rays from the inside of the heating roller 4. A fixing device having a halogen heater 5a and a reflecting portion 5a1 for intensively supplying the heat rays from the halogen heater 5a to the fixing belt suspension side of the heating roller 4 (fixing according to claims 7 and 8). Corresponds to the device).

  Such a fixing device B can be incorporated as a fixing device in the conventional electrophotographic image forming apparatus shown in FIG. At that time, the heat-fixing roller 111 in FIG. 18 is replaced with an endless fixing belt 6 stretched by the fixing roller 2 and the heat roller 4 facing the fixing roller 2, and the pressure roller 112 in FIG. Replace with roller 3 and incorporate.

  In the above description, the fixing belt heating means B1 is provided in the pressure roller 4. However, as shown in FIG. 20, a metal thin film layer is provided on the fixing belt and the electromagnetic induction heating is provided near the fixing belt. The coil and the core may be arranged, and the metal thin film layer of the fixing belt may be heated by an electromagnetic induction heating method.

<Fixing devices B ′ and B ″ according to the present invention>
Here, in general, the fixing device performs fixing on recording media of various sizes. At this time, the heating roller is heated together with a first heat source corresponding to fixing of a small recording medium, a second heat source corresponding to fixing of a large recording medium together with the first heat source, a first heat source, and a second heat source. A heating roller is provided with a plurality of heat sources, such as a third heat source corresponding to fixing of a large recording medium, and selectively heating and supplying only areas necessary for fixing the recording medium supplied thereto. It is possible to concentrate the electric power allowed for heating the necessary part on the necessary part, and as a result, it is possible to speed up the heating of the necessary part.

  At this time, the first heat source may be at the highest temperature. Therefore, in the region of the heating roller heated by the first heat source, the fixing belt non-stretching portion does not deteriorate the fixing belt. In the heating roller, the heating belt is arranged close to the portion where the fixing belt is stretched, or the first heat source is a halogen heater composed of a halogen lamp, and the heat rays from the halogen heater are applied to the fixing belt suspension portion of the heating roller. A reflector (provided directly on the glass tube by a ceramic coating on approximately half of the side surface of the glass tube) is provided for concentrated supply. Particularly in the latter case, the second heat source can be disposed closer to the portion where the fixing belt of the heating roller is stretched, even inside the heating roller having a small space. As a result, the heating by the second heat source can be performed. The heating of the non-stretching portion of the fixing belt of the roller becomes efficient, and the heating of the non-stretching portion of the fixing belt of the heating roller by the first heat source having the reflection portion is combined with the efficiency of the nip. The required temperature of the part is quickly raised, and a fixing operation without waiting time is possible.

  Here, examples of heating regions of the first heat source and the second heat source are modeled as halogen heater filaments 6a (for the first heat source) and 6b (for the second heat source) in FIGS. FIG. 14 is an explanatory diagram of an example of a temperature adjustment method using these heaters. In these model diagrams, a portion where the filaments are dense is a heating region.

  In FIG. 14, the fixing belt heating means for heating the fixing belt 6 has a linear heat source that is long in the axial direction of the heating roller 4 for heating the fixing belt 6 by supplying the heating roller 4 with heat rays from the inside of the heating roller 4. This linear heat source is divided into at least two in the length direction, and the heating area of the first heat source 21 among these heat sources corresponds to a small-size recording medium supplied to the fixing device, and the second heat source 22. Is for heating the non-heated area of the first heat source 21 and can heat the area corresponding to a recording medium larger than the small-sized recording medium by being heated simultaneously with the first heat source 21. In addition, the first heat source 21 is disposed in the heating roller 4 closer to the portion where the fixing belt 6 of the heating roller 4 is stretched than the second heat source 22. The first heat source 21 and the second heat source 22 have ON / OFF circuits 23a and 23b, temperature control circuits 24a and 24b, and temperature sensors 7a1 and 7a2, respectively. The heating roller is the first heat source 21 and the second heat source 22. Each of the two heat sources 22 can be controlled to a predetermined temperature.

  As such a heating mechanism, for example, such a heating mechanism is incorporated in the fixing belt temperature detecting means B2 and the fixing belt heating control means B3 of the fixing device B to form a fixing device B ′ (corresponding to claim 9). Similarly to the fixing device B, the device B ′ can be used as a fixing device in the conventional image forming apparatus shown in FIG. At that time, for example, in conjunction with the operation panel, depending on the size of the selected recording medium, only the first heat source 21 or both the first heat source 21 and the second heat source 22 are energized. The portion of the heating roller corresponding to the recording medium to be fixed is heated, so that the portion of the fixing belt corresponding to the heating-necessary portion of the nip portion can be centrally heated as compared with the case where the fixing device B is used. Since it becomes possible, it can be fixed quickly.

  Further, according to such a heating mechanism, the temperature change of the fixing belt non-stretched part from immediately after the start of heating until the temperature at fixing is reached is indicated by a solid line as “conventional” as indicated by a broken line in FIG. In addition, it can be seen that the maximum temperature is lower than in the conventional case where one halogen heater is provided in the central portion of the heating roller, and deterioration of the fixing belt can be effectively prevented.

  Further, FIG. 16 shows that the fixing belt heating means for heating the fixing belt 6 has a linear heat source that is long in the axial direction of the heating roller 4 for heating the fixing belt 6 by supplying the heating roller 4 with heat rays from the inside of the heating roller 4. The linear heat source is divided into at least two in the length direction, and the heating area of the first heat source 21 among these heat sources corresponds to a small-size recording medium supplied to the fixing device, and the second The heat source 22 heats a non-heated area of the first heat source 21 and heats an area corresponding to a recording medium larger than the small-sized recording medium by being heated simultaneously with the first heat source 21. The second heat source 22 is disposed closer to the portion of the heating roller 4 where the fixing belt 6 is stretched than the first heat source 21, and the first heat source 21 is a halogen lamp. From That a halogen heater, and has a reflecting portion 25 for centrally supplying the heat rays from the halogen heater to the fixing belt retaining portion of the heating roller. The first heat source 21 and the second heat source 22 have ON / OFF circuits 23a and 23b, temperature control circuits 24a and 24b, and temperature sensors 7a1 and 7a2, respectively. The heating roller is the first heat source 21 and the second heat source 22. Each of the two heat sources 22 can be controlled to a predetermined temperature.

As such a heating mechanism, for example, such a heating mechanism is incorporated in the fixing belt temperature detecting means B2 and the fixing belt heating control means B3 of the fixing device B to form a fixing device B ″ (corresponding to claim 10). The apparatus B ″ can be combined with the image forming apparatus shown in FIG. 18 in the same manner as the fixing apparatus B, and can be an apparatus such as a copying machine or a facsimile provided with the image forming and fixing apparatus.
The first heat source 21 or both the first heat source 21 and the second heat source 22 are energized according to the size of the selected recording medium in conjunction with the operation panel of the copying machine or the like at that time. As a result, the portion of the heating roller corresponding to the recording medium to be fixed is heated, so that the portion of the fixing belt corresponding to the heating-necessary portion of the nip portion is concentratedly heated as compared with the case where the fixing device B is used. Therefore, it is possible to fix quickly.

  Furthermore, according to such a heating mechanism, the temperature change of the non-fixing belt stretched portion immediately after the start of heating until the temperature at fixing is reached is indicated by a solid line as “conventional” as indicated by a broken line in FIG. In addition, it can be seen that the maximum temperature is lower than in the conventional case where one halogen heater is provided in the central portion of the heating roller, and deterioration of the fixing belt can be effectively prevented.

  Since the fixing device according to the present invention has a rapid temperature rise during start-up or re-passage, the fixing operation can be performed with little or no waiting time after receiving a paper-passing signal. It can be suitably applied to an image forming apparatus such as a copying machine of a type, a laser beam printer, a facsimile, or a complex machine having at least two of these functions.

FIG. 2 is a model diagram illustrating an outline of a fixing device A according to the present invention. FIG. 4 is a block diagram of control of the fixing device A according to the present invention. It is a figure which shows the conventional problem (difference of the behavior of the temperature by the site | part in a heating roller). FIG. 3 is a model cross-sectional view of a fixing belt used in the fixing device A according to the present invention. FIG. 10 is a diagram comparing a temperature rising state by the fixing device according to the present invention with a case of a fixing device according to the prior art. FIG. 10 is a diagram comparing a temperature rising state by the fixing device according to the present invention with a case of a fixing device according to the prior art. FIG. 10 is a diagram comparing a temperature rising state by the fixing device according to the present invention with a case of a fixing device according to the prior art. 6 is a flowchart showing the operation of the MPU 10A of the fixing device A according to the present invention. FIG. 3 is a model diagram illustrating an outline of a fixing device B according to the present invention. It is a block diagram of control of the fixing device B according to the present invention. It is explanatory drawing explaining the difference in the emitted-heat amount of the heater by the reflecting plate 5a1. 6 is a flowchart showing an operation of the MPU 10B of the fixing device A according to the present invention. It is the figure which showed typically the example of the heating area | region of a 1st heat source and a 2nd heat source as a filament of a halogen heater. (A) Filament 6a (for the first heat source) (b) Filament 6b (for the second heat source) It is explanatory drawing which shows a state when the heat source of a heating roller is formed from two, a 1st heat source and a 2nd heat source. It is a figure which shows the result of having investigated the temperature change of the fixing belt non-stretching part from immediately after a heating start to the temperature at the time of fixing reaching. It is explanatory drawing which shows the other state when the heat source of a heating roller is formed from two, a 1st heat source and a 2nd heat source. It is a figure which shows the result of having investigated the temperature change of the fixing belt non-stretching part from immediately after a heating start to the temperature at the time of fixing reaching. It is an explanatory view of a conventional electrophotographic image forming apparatus. It is an explanatory view of a conventional belt-type fixing device C. It is explanatory drawing of the other fixing apparatus D of the conventional belt system. FIG. 6 is a diagram showing a temperature change when a conventional belt type fixing device passes a sheet after a while after starting up. FIG. 10 is a diagram illustrating a temperature change when a sheet is passed immediately after the start-up of a conventional belt-type fixing device.

Explanation of symbols

A, B Fixing device according to the present invention A1 Fixing belt heating means A2 Fixing belt temperature detection means A3 Fixing belt heating control means A4 Pressure roller heating means A5 Pressure roller temperature detection means A6 Pressure roller heating control means A7 Paper discharge detection Means A8 Roller drive means A9 Drive / heating / stop / restart control means A9a Roller drive speed control means B1 Fixing belt heating means B2 Fixing belt temperature detecting means B3 Fixing belt heating control means B7 Paper discharge detecting means B8 Roller driving means B9 Roller driving Stop / re-drive control means B9a Roller drive speed control means 2 Fixing roller 3 Pressure roller 4 Heating roller 5a Halogen heater 5a1 Reflecting portion 5b Heater 6 Fixing belt 7a, 7b Temperature sensor (thermistor)
10A, 10B MPU

Claims (4)

A fixing roller and a heating roller and an endless fixing belt that is stretched by opposing the fixing roller, a pressure roller to form a nip portion in pressure contact with the fixing roller via the fixing belt, the recording medium In a fixing device that fixes an unfixed image on the recording medium by heat and pressure when passing through the nip portion,
A fixing belt heating means for heating the fixing belt inside the heating roller;
Fixing belt temperature detecting means for detecting the temperature of the fixing belt;
Roller driving means for driving the roller in the fixing device; and
When the fixing device is started up, heating by the fixing belt heating means in the heating roller is started, and the temperature of the fixing belt measured by the fixing belt temperature detecting means reaches a predetermined driving start temperature lower than the temperature at the time of fixing. And a start-up control means for starting driving of the rollers in the fixing device ,
The fixing belt heating means for heating the fixing belt has a long halogen heater in the axial direction of the heating roller for heating the fixing belt by supplying heat rays to the heating roller from the inside of the heating roller. The heating area of the first halogen heater among these heat sources corresponds to a small-size recording medium supplied to the fixing device, and the second halogen heater is an unheated area of the first heat source. And a region corresponding to a recording medium larger than the small-sized recording medium can be heated by being heated simultaneously with the first halogen heater, and
The fixing device, wherein the first halogen heater is disposed closer to a portion where the fixing belt of the heating roller is stretched than the second halogen heater in the heating roller . The fixing device according to claim 1, characterized in that has a reflecting portion for centrally supplying the heat rays from the halogen heater to the fixing belt retaining portion of the heating roller. A fixing roller and a heating roller and an endless fixing belt that is stretched by opposing the fixing roller, a pressure roller to form a nip portion in pressure contact with the fixing roller via the fixing belt, the recording medium In a fixing device that fixes an unfixed image on the recording medium by heat and pressure when passing through the nip portion,
A fixing belt heating means for heating the fixing belt inside the heating roller;
Fixing belt temperature detecting means for detecting the temperature of the fixing belt;
Roller driving means for driving the roller in the fixing device; and
Heating by the fixing belt heating means in the heating roller is started when the fixing device is started up, and the temperature of the fixing belt measured by the fixing belt temperature detecting means reaches a predetermined driving start temperature lower than the temperature at the time of fixing. And a start-up control means for starting driving of the rollers in the fixing device ,
The fixing belt heating means for heating the fixing belt has a linear halogen heater that is long in the axial direction of the heating roller for heating the fixing belt by supplying a heating wire to the heating roller from the inside of the heating roller. The halogen heater is divided into at least two in the length direction, and the heating area of the first halogen heater among these halogen heaters corresponds to a small-sized recording medium supplied to the fixing device, and the second halogen heater is the first halogen heater. The non-heated area of the heat source is heated, and the area corresponding to the recording medium larger than the small-sized recording medium can be heated by being heated simultaneously with the first halogen heater,
The second halogen heater is disposed closer to the portion where the fixing belt of the heating roller is stretched than the first halogen heater inside the heating roller, and
A fixing device having a reflecting portion for intensively supplying heat rays from a first halogen heater to a fixing belt suspension portion of a heating roller . An image forming apparatus comprising the fixing device according to claim 1.

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