JP4632834B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device for an image forming apparatus such as a copying machine or a printer, and an image forming apparatus equipped with the fixing device.

  In general, in an electrophotographic image forming apparatus used in a copying machine or the like, an electrostatic latent image of an original image is generated on the surface of a photosensitive member by light reflection, and the electrostatic latent image is visualized as a toner image by a development process. Then, the image is transferred to a sheet-like recording material as a recording medium. The recording material onto which the toner image has been transferred is conveyed to a fixing device, the unfixed toner image is fixed on the recording material, and the recording material is discharged to a paper discharge tray outside the image forming apparatus.

  As the fixing device, a heating roller, a heating roller type fixing device in which a nip portion is formed by contact between the heating roller and the pressure roller, and a heating roller and the heating roller are disposed in parallel with each other. An endless fixing belt suspended from a fixing roller disposed at a position, or a fixing belt that has a built-in heater and generates heat, and a nip portion is formed by contact between the fixing belt and the pressure roller. There is a heat belt type fixing device. In any type of fixing device, the recording material onto which the toner image is transferred is passed through the formed nip portion, and fixing is performed by pressurizing and heating in a predetermined manner in the passing process.

  Various image forming apparatuses configured to obtain a predetermined fixing temperature by controlling a predetermined heating source have been proposed.

  It is known that the heating roller target temperature is calculated from the pressure roller temperature, and the heating element is turned on when the actually measured heating roller temperature is lower than the target temperature (for example, Patent Document 1). reference).

  When fixing with a heating roller and an endless pressure belt, a heating resistor layer is provided on the endless pressure belt, and the heat generation of the heating resistor layer is controlled based on the temperature detection result of the endless pressure belt. Is known (see, for example, Patent Document 2).

  The fixing roller is equipped with a fixing heater and a thermistor for temperature detection, and the pressure porter is equipped with a pressure heater and the thermistor. Is known (for example, see Patent Document 3).

  It also has a heating roller with a non-contact temperature detector and a pressure roller with a contact temperature detector, and controls the heater of the heating roller based on the temperature of the pressure roller in order to speed up the start-up immediately after the power is turned on. A fixing device is known in which the heater of the heating roller is controlled based on the temperature of the heating roller or the pressure roller after this control (see, for example, Patent Document 4).

  In addition, a heating roller having a heater, a support roller disposed in parallel with the heater, a fixing roller, a fixing belt suspended from the supporting roller, and a pressure that presses against the fixing belt to form a nip portion. A roller, a thermistor that detects the temperature of the fixing heater and the fixing roller, and a thermistor that detects the temperature of the pressure heater and the pressure roller, and the target heating roller temperature is calculated based on the pressure roller temperature detection and is calculated There is known one in which a halogen heater lamp of a heating roller is controlled based on a target heating roller temperature and a heating roller detection temperature (see, for example, Patent Document 5). According to this configuration, even if the actual temperature of the pressure roller changes, the target heating roller temperature is reset to an appropriate temperature according to the temperature change, so that the temperature of the nip portion is always the optimum temperature state. Therefore, a fixed image having a desired glossiness can be stably formed.

JP 2002-251099 A (Japanese Patent Laid-Open No. 2003-302853) JP-A-11-273830 Japanese Patent Application Laid-Open No. 2002-221871 JP 2003-149987 A

  However, in each of the conventional configurations described above, there is a problem in that it is insufficient to precisely control the temperature of the fixing member in contact with the unfixed toner image.

  Accordingly, the present invention provides a fixing device that solves the above-described problems of the prior art and can precisely control the temperature of a fixing member that contacts an unfixed toner image with a simple configuration, and an image forming apparatus equipped with the fixing device. For the purpose.

In order to solve the above problems, a first aspect of the present invention, a second rotating member that forms a first rotary member having a first heat source, the nip portion in contact with the first rotating body a first temperature detection unit, a second temperature detector for detecting the temperature of the second rotary member in each control cycle, the comprising detecting the temperature of the first rotating member in each control cycle, the nip In a fixing device that passes a recording medium having an unfixed toner image in the section and fixes the toner image on the recording medium, a control section that controls on / off of the first heating source is provided , The evaluation set in advance from the difference between the detected temperature and the target value detected last time by the first and second temperature detectors, and the difference between the detected temperature and the target value detected this time by the first and second temperature detectors Select an evaluation from the table, and a decision table created in advance based on the selected evaluation And controlling said first heating source by a PWM control by selecting a more duty ratio in each control cycle of the first heat source.

The invention according to claim 2, in claim 1, further provided with a second heat source for heating the second rotating body, wherein the control unit, first, detected previously detected by the second temperature detector Based on the selected evaluation, an evaluation is selected from a preset evaluation table based on the difference between the temperature and the target value and the difference between the detected temperature and the target value detected this time by the first and second temperature detection units. The first heating source and the second heating source are controlled by PWM control by selecting duty ratios of the first heating source and the second heating source from a determination table prepared in advance. To do.

A third aspect of the present invention is an image forming apparatus equipped with the fixing device according to the first or second aspect .

Since the present invention is configured as described above, the control unit uses the first and second temperature detection units to detect the difference between the detected temperature and the target value detected last time by the first and second temperature detection units. The evaluation is selected from a preset evaluation table based on the difference between the detected temperature detected this time and the target value, and the duty for each control cycle of the first heating source is determined from a determination table created in advance based on the selected evaluation. Since the first heating source is controlled by PWM control by selecting the ratio, the temperature of the first rotating body is set in consideration of heat transfer between the first rotating body and the second rotating body. , It can be controlled more precisely. That is, since the duty ratio for each control cycle of the first heating source is determined in consideration of the tendency of the change that occurred between the temperature state detected last time and the temperature state detected this time, and controlled by PWM control . As a result, the control accuracy of the fixing temperature obtained can be improved.

The best mode for carrying out the present invention will be described with reference to the embodiments shown in the accompanying drawings. First, the problems to be solved by the image forming apparatus according to the present invention are as described above, but further supplemented are as follows.
In each of the above conventional configurations, there is no clear relationship between at least the temperature detected by each and the amount of heat generated from each heating source. That is, in each of these configurations, the heating operation of the heating source is controlled based on the temperature difference between the measured temperature at the time of each temperature detection and the fixing temperature of the control target in the continuous flow of time. There are only. In other words, at the time of detecting each temperature, the relationship between the measured temperature of the member and the control temperature is only qualitatively known. For this reason, the temperature obtained as a result of this heating control not only continues to fluctuate near the fixing temperature, but pursuing the temperature accuracy by the heating control may require complicated processing and configuration, It is disadvantageous and difficult in terms of cost.

  Therefore, in the present invention, in order to deal with this by quantitatively grasping the thermal state of the member from the detected member temperature at the start of the control cycle, divided by a certain length of time called the control cycle. The amount of heating is a quantitative amount of heat provided in the control cycle. That is, the quantity of heat that is insufficient for the member is calculated and found, and in order to resolve this quantity of heat, the amount of heating as the quantitative quantity of heat specified in the control cycle is calculated in the same way. Looking for. Therefore, grasping the mutual quantitative relationship between the shortage of heat and the supply heat in this way, it is first determined whether or not to heat the heating source, and then the supply by the heating operation in the control cycle. Since the heating amount is accurately calculated, the temperature of the fixing member obtained from the supply heating amount determined and calculated in this way is precisely controlled, and the resulting member temperature is controlled as the fixing temperature. The stability and accuracy of the target temperature can be improved.

  Next, an image forming apparatus as a premise of the present invention will be described first. FIG. 1 is a front view showing a schematic overall configuration of an image forming apparatus (full-color copying machine) provided with a fixing device of the present invention.

  As shown in FIG. 1, the full-color copying machine 1 (image forming apparatus) forms an electrostatic latent image by the exposure device 2 optically writing on the outer peripheral surface of the photosensitive member 3 that is charged in a predetermined manner. An image forming unit 4 that visualizes and transfers an image, and a plurality of box-shaped sheet feeding cassettes 5 in which sheets P as recording media of various sizes are stacked and stored are provided in multiple stages in the vertical direction. Unit 6, fixing device 7 for fixing the toner image transferred by image forming unit 4 onto paper P conveyed from paper feeding unit 6, and a document on a contact glass (not shown) placed on the contact glass. The document reading unit 11 reads the document image of the document surface in contact with the glass for the electrostatic latent image, and the document transport unit 12 transports the document to the document reading unit 11.

  The image forming unit 4 includes an image forming unit 13 that forms a color toner image. The image forming unit 13 includes photoreceptors 3Y, 3M, 3C, and 3K corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (K). Each of the image forming units 13 is different only in the color of the toner, and the other portions have the same configuration. Therefore, the configuration of the yellow (Y) photoreceptor 3Y will be described. An exposure device 2 including a developing device 14, a laser irradiator 15, a mirror 16 and the like around the photoconductor 3Y, which develops an electrostatic latent image formed on the peripheral surface of the photoconductor 3Y with toner, and the photoconductor 3 A charging roller 17 that generates a corona discharge between them and uniformly charges the surface of the photosensitive member 3; a static elimination device (not shown) that returns a peripheral surface of the photosensitive member 3Y to an initial state by applying a predetermined voltage; The intermediate transfer belt 22 is sandwiched between the cleaning device 21 that removes the toner remaining on the peripheral surface of the photosensitive member 3Y and the photosensitive member 3Y, and the toner image is transferred onto the intermediate transfer belt 22. A roller 23 and the like are provided.

  Next, a copy operation as an image forming operation by the full-color copying machine 1 will be briefly described. That is, when the user places a document on the document transport unit 12 or on the contact glass of the document reading unit 11 and presses a copy switch (not shown), the copying operation of the full-color copying machine 1 starts. Is done.

  A document placed on a document surface with the document surface down is conveyed from the document conveying unit 12 to the document reading unit 11 when the document is placed on the document conveying unit 12, and the document reading unit 11 determines the size of the document. The original image is read, and a toner image is formed on the photoreceptor 3 of the image forming unit 4 by an electrophotographic process based on the original image, that is, by a series of image forming processes in which the above-described units operate in cooperation. It is formed. At the same time, the paper P stacked in the paper feed cassette 5 is conveyed to the image forming unit 4. Then, the paper P is conveyed at a timing with the photoreceptor 3, and the toner image formed on the photoreceptor 3 by the image forming unit 4 is transferred to the conveyed paper P. The sheet P on which the toner image has been transferred is conveyed to the fixing device 7, where the unfixed toner image is fixed on the sheet P and discharged onto the discharge tray 24 for image formation. The copy operation is completed as an operation. Upon completion of copying, the document is returned from the document reading unit 11 to the document transport unit 12.

  Next, an electrical configuration for controlling the image forming operation of the full-color copying machine 1 will be described. FIG. 2 is a block diagram of a control device that controls the overall operation of the full-color copying machine 1 such as image formation and others related to image formation.

  The system control board 51 is a control device that controls the entire image forming system, that is, a control unit that controls the operation of each part of the full-color copying machine 1. The system control board 51 includes a CPU, ROM, RAM, nonvolatile RAM, A calendar function chip including various timing functions is provided, and switches and sensors provided in each part and a reading control board 52 are connected by wiring. That is, the system control board 51 acquires sensor information from various sensors for fixing, and also controls the heating operation of the fixing device 7 to a predetermined level. The reading control board 52 is configured to read a document image with a CCD (not shown) or the like, convert the image information into a digital signal, and transfer it to the system control board 51.

  Therefore, the system control board 51 controls the timing of the entire system, input / output control of the operation / display unit 53, control of operations of the fixing device 7, FAX, printer, scanner, etc., interface with the application unit, and image formation processing As the various settings, image information data scaling, filter, image processing parameter / data such as γ, and storage and accumulation control of image information data using an image memory are performed.

  The system control board 51 can be set in various modes by key input, and is connected to an operation / display section 53 that can be displayed on an LED, an LCD, a touch panel, etc. A control plate 54 is connected. The image information data is output from the system control board 51 and written to the writing control board 54.

  In addition, the system control board 51 is connected to an I / O control board 57. The I / O control board 57 includes input / output signals for various actuators such as motors and various sensors and switches. Has been. That is, the I / O control plate 57 includes an entire system (scanner unit) such as a toner sensor 55 for detecting the toner concentration in the developing device 14 and supplying the developing device 14 with toner from the main body. The output signals from various sensors and actuators provided in the printer unit) are input and aggregated, the output signals to the motor, solenoid, clutch, high voltage power source 56, etc. are aggregated, and various image forming I / O 61 The input / output signals of the image forming data are aggregated. The system control portion of the system control board 51 is configured to perform various controls according to the I / O data of the I / O control board 57. This control includes the presence / absence information of the paper P in the paper feed cassette 5 and the manual feed tray 8, the size information of the paper P, the driving timing of the registration roller for transporting the paper that is driven and timed to the photosensitive member 3, and the like. .

  Next, the physical configuration of the fixing device 7 of the first embodiment used in the full-color copying machine 1 will be described. That is, as shown in FIG. 3, the fixing device 7 includes a fixing roller 28, a heating roller 26 that is opposed to the fixing roller 28 at a predetermined distance, and a fixing roller 28, and the fixing roller 28 and the heating roller 26. An endless fixing belt 27 that is stretched, and a pressure roller 31 that is urged to face the fixing roller 26 through the fixing belt 27 and toward the fixing roller 26, are mainly configured. A nip portion that secures a predetermined pressure is formed between the outer peripheral surface of the fixing belt 27 wound around the fixing roller 28 and the pressure roller 31 in contact therewith. The heat generated by the halogen heater 25b provided in is supplied through the fixing belt 27 so as to ensure a predetermined fixing temperature in the nip portion.

  More specifically, a fixing roller 28 is pivotally supported by the casing 42 at a substantially central position of the casing 42, and is spaced apart from the fixing roller 28 in a substantially obliquely upper right direction in FIG. A heating roller 26 is pivotally supported with the axes parallel to each other. An endless fixing belt 27 is suspended between the heating roller 26 and the fixing roller 28 as a first rotating body.

  The fixing belt 27 has a configuration in which, in addition to flexibility and tensile strength as the belt, predetermined heat resistance, heat conductivity, compressive strength in the thickness direction, and the like necessary for heat and pressure fixing are secured. Has been. That is, for example, the fixing belt 27 has a base made of a heat-resistant resin, and the thickness of the base is set to 30 to 100 μm from the balance between heat conduction and strength, and the surface thereof is paper P and paper. Since the surface toner is pressed and contacted with the toner above, a surface layer with excellent releasability and heat resistance is required. Therefore, the surface layer is coated with a surface release layer such as a fluororesin. Under the mold layer, an elastic layer made of heat-resistant rubber such as silicone rubber or fluorine rubber is provided in order to obtain image uniformity.

  A pressure roller 31 is pivotally supported below the fixing roller 28 so as to be in contact with a portion wound around the fixing roller 28, and the roller axis is in a direction approaching the roller axis of the fixing roller 28. It is configured to be displaceable for a predetermined distance, and is urged with a predetermined urging force secured in the same direction by an elastic member (not shown) such as a spring. Therefore, the pressure roller 31 is in contact with the fixing belt 27 of the portion wound around the fixing roller 28, and forms a nip portion that secures a predetermined pressure therebetween.

  Reference numeral 33 denotes a tension roller for preventing the fixing belt 27 from loosening. That is, the tension roller 33 is pivotally supported between the heating roller 26 and the fixing roller 28 so as to be in contact with the outer peripheral surface of the fixing belt 27, and the roller shaft can be displaced by a predetermined distance toward the outer peripheral surface side. It is configured and is urged by an elastic member (not shown) such as a spring in the same displacement direction. Accordingly, the tension roller 33 constantly contacts the outer peripheral surface of the fixing belt 27 that occupies the position and rotates continuously while applying a pressing force to the outer peripheral surface, so that the fixing belt 27 is always in a tension state. The fixing belt 27 is prevented from loosening.

  The heating roller 26 is formed in a hollow roller shape having a predetermined thermal conductivity, and a halogen heater 25b is installed therein as a heating source. The halogen heater 25b has a structure in which a tungsten filament wire and an inert gas are enclosed in a glass tube in a sealed tube shape, and the filament wire is energized to generate heat. That is, the halogen heater 25b is an electric heater that generates an amount of heat corresponding to the energization amount.

  In addition, a cleaning roller 34 is rotatably supported so as to be in contact with the fixing belt 27 wound around the fixing roller 28 and above the fixing roller 28. The cleaning roller 34 is fixed to the fixing roller 27 in contact therewith. The remaining toner on the fixing belt 27 is removed by being driven to rotate following the movement of the belt 27 surface. Further, an oil application roller 35 is provided for applying the impregnated oil by rotating in contact with the cleaning roller 34 and rolling on the surface thereof. A conveyance guide 36 extending in substantially the same direction is provided before and after the horizontal conveyance direction with respect to the nip formed by the fixing roller 28 and the pressure roller 31.

  In the vicinity of the heating roller 26, a thermistor 37b as a temperature sensor as a first temperature detection unit is disposed, and the sensor terminal of the thermistor 37b is placed on the surface of the fixing belt 27 in a portion in contact with the outer periphery of the heating roller 26. The thermistor 37b is in sliding contact, and is configured to detect and output the temperature of the fixing belt 27 of the portion. A thermistor 37a, which is a temperature sensor as a second temperature detector, is disposed on the lower surface of the pressure roller 31 so that the sensor terminal is in sliding contact. The thermistor 37a adjusts the temperature of the pressure roller 31. It is configured to detect and output. That is, the thermistors 37 a and 37 b are connected to the system control board 51 by wiring, and the temperatures detected by the thermistors 37 a and 37 b are input to the system control board 51.

  In the fixing device 7 configured as described above, as a basic fixing operation, the sheet P on which the toner image is transferred to the upper surface thereof by the image forming unit 4 is conveyed to the nip portion, and the leading end in the conveying direction is When sandwiched between the fixing belt 27 and the pressure roller 31, it passes through the nip portion at a traveling speed defined by the fixing belt 27 and the pressure roller 31 rotating in the direction of the arrow. The toner image on the surface of the paper P is fixed on the paper P by being heated. The fixing belt 27 supplies heat for fixing to the nip portion. That is, the belt surface of the fixing belt 27 is in contact with the unfixed toner image transferred onto the upper surface of the paper P so that the unfixed toner image can be melted at least at the temperature of the fixing belt 27. The fixing belt 27 is heated by a heating roller 26 in contact with the fixing belt 27, and the heating roller 26 is heated by a halogen heater 25b as an electrical heating source disposed therein. Yes.

  Next, the electrical configuration of the fixing device 7 according to the first embodiment related to the control of the heat necessary for fixing, that is, the fixing temperature will be described.

  As shown in FIG. 4, the electrical configuration directly related to the operation control of the halogen heater 25b is wired to a system control board 51, and each output signal from each part is input to the system. I / O control board 57 as an input / output signal converging part for transferring each control signal to the control board 51 and outputting each output signal to each part based on a command signal from the system control board 51, and necessary for each operation to each part PSU 58 for supplying a large amount of electric power is provided. The I / O control plate 57 is connected to output lines for the detected temperatures of the thermistor 37a and thermistor 37b, while the PSU 58 is connected to a power supply line for driving the heater of the halogen heater 25b.

  The input terminal of the PSU 58 is connected to a commercial AC power source (not shown), and at least a PSU (Power Supply Unit) that converts an AC current input from the terminal into a predetermined voltage or current, adjusts it, and supplies it to each unit. Power Supply Unit), which includes a circuit group for generating a power source that generates and outputs a predetermined DC power source from an AC power source, a circuit group for driving the halogen heater 25b to a predetermined heater, and the like. That is, the PSU 58 generates power necessary mainly for the control system, mainly power necessary for the drive system and medium / high voltage power in the digital copying machine 1, and supplies the power to each part, and also the halogen heater 25b. The heating power can be supplied in a predetermined manner.

  As a circuit group related to the halogen heater 25b mounted on the PSU 58, at least an AC power cutoff relay, a triac, a snubber circuit, and the like (not shown) are provided.

  When an abnormality occurs in the image forming apparatus, the relay receives an operation signal through a path of another system from the abnormality detection configuration without passing through the system control board 51, and outputs an output signal based on a command signal from the system control board 51. The power supply to the halogen heater 25b is cut off by operating so as to cut off.

  The triac and snubber circuit is a component for PWM (Pulse Width Modulation) control, that is, a circuit or element for variably controlling the power supplied by the pulse width modulation method. The power from the PSU 58 is used as a halogen as an electric heater. The heater 25b is supplied with a predetermined adjustment or conversion as the heat generation operation power so that the switching operation can be performed based on the duty ratio of the PWM control signal, which is the lighting rate, and the power supply amount can be increased or decreased. It is configured. The duty ratio can be arbitrarily set by a command signal from the system control board 51. In the first embodiment, the duty ratio is set to a predetermined fixed value such as 50%.

  Accordingly, the heating operation of the halogen heater 25b that heats the fixing belt 27 via the heating roller 26 is specifically controlled by a triac, a snubber circuit, or the like that energizes and interrupts the supply current at a predetermined cycle. The operation power supplied to the heater is at least quantitatively controlled, and on / off control of whether the heat generation operation of the halogen heater 25b is operated or not is performed. The processing for controlling the operation of these triac and relay circuits is performed by the CPU provided in the system control board 51, and a predetermined command signal is issued by the processing judgment of this CPU, and specific processing is performed based on this command signal. A signal that defines a specific operation is transmitted to the triac and relay circuit via the port of the I / O control board 57, and is executed with these signals in a predetermined manner.

  The system control plate 51 receives the temperature detection signal of the fixing belt 27 detected by the thermistor 37b and the temperature detection signal of the pressure roller 31 detected by the thermistor 37a via the I / O control plate 57. A control judgment program for the halogen heater 25b is executed for each predetermined control period, both the detected temperatures are acquired, a necessary heating amount is calculated in the control period, and based on the calculated heating amount At least, it is determined whether or not the halogen heater 25b is to be turned on and off, and the halogen heater 25b is controlled to be turned on in a predetermined manner. That is, the system control board 51 acquires the fixing belt detection temperature and the pressure roller detection temperature as current data of each member at the start of each control cycle, and determines whether to turn on or off in the control cycle. A command signal for executing the determination result is issued to the PSU 58 to cause the triac and snubber circuit to execute the heating operation of the halogen heater 25b in a predetermined control cycle unit. I have to.

  Next, the control configuration of the system control board 51 will be described. That is, the control configuration of the fixing device 7 according to the first embodiment using the above-described physical configuration and electrical configuration will be described. That is, a configuration in which the heating operation of the halogen heater 25b as a heating source is turned on and off in a predetermined manner and the temperature of the fixing belt as the first rotating body is precisely controlled will be described.

  First, a basic outline will be described. FIG. 5A is a determination table for determining ON / OFF, and FIG. 5B is a conceptual explanatory diagram showing the quantitative relationship between the optimum heat capacity of the fixing belt and the current heat storage amount of the fixing belt. FIG. 5C is a conceptual explanatory diagram showing a quantitative relationship between the optimum heat capacity of the pressure roller and the current heat storage amount of the pressure roller.

  In the first embodiment, two members, the first rotating body and the second rotating body, are selected as the members directly related to the fixing temperature, and these members defined in the optimum fixing temperature state are selected. Based on the theoretical heat capacity of each member, the actual heat storage amount of each member that can be estimated by calculating from the detected temperature of each member obtained by actual measurement with respect to the theoretical heat capacity of each member. Comparing and grasping the deficient or excessive heat quantity of each member, and calculating the heat quantity lost due to other factors other than these by using the actual machine that has been calculated or actually manufactured in advance. Whether or not to heat the heating source is determined for each control cycle.

  That is, firstly, the heat capacity of each member at the optimum fixing temperature state is determined in advance, and secondly, the detected temperature obtained from each member reflects the current amount of heat stored in that member. Assuming that the temperature is the result, the heat storage amount is calculated backward from the detected temperature. Third, the heat capacity is compared with the current heat storage amount to calculate the excess or deficient heat amount. The amount of heat lost due to other factors is added to the amount of heat that is insufficient, and the amount of heat calculated in this way is used as the amount of heat that needs to be replenished to the member that is directly related to the fixing temperature.

  More specifically, the amount of heat necessary for obtaining the optimum image quality, that is, the amount of heat necessary for securing and maintaining the optimum fixing temperature in the nip portion is the amount of heat generated from the halogen heater 25b as a heat source. And the heat capacity of the fixing belt 27 and other deprived heat amounts. That is, in the configuration of the first embodiment, the heating roller 26 applies heat to the fixing belt 27, whereas the fixing belt 27 applies heat to the fixing roller 28, the pressure roller 31, and the paper. You will be robbed.

  It should be noted that the heat generated by the halogen heater 25b as the heating source is transmitted almost directly to the heating roller 26, and the heating source temperature and the temperature of the heating roller 26 can be regarded as equivalent. Further, the temperature of the heating roller 26 and the temperature of the fixing belt 27 in contact with the heating roller 26 are substantially equivalent, and the thermistor 37b that detects the temperature of this portion is heated simultaneously with the fixing belt temperature. It can be considered that the temperature of the roller 26 is detected. Furthermore, the fixing belt 27 is wound around the fixing roller 28 over almost a half of its outer periphery, and the remaining half of the periphery of the fixing roller 28 is surrounded by the inner periphery of the fixing belt 27 and the heating roller 26. Although there is a flow of heat through, it can be regarded as a member that has substantially no thermal influence. Therefore, after all, it can be considered that the fixing belt 27 belongs to a member on the heat supply side, and the pressure roller 31 belongs to a member on the heat consumption side.

  Next, for example, if only the detected fixing belt temperature is lower than the target temperature T, it can be considered that the amount of heat generated from the halogen heater 25b is simply insufficient.

  The target temperature T is determined in advance from the amount of heat stored in the member, that is, the theoretical heat capacity when the fixing belt 27 and the pressure roller 31 are at the optimum fixing temperature. That is, the fixing belt 27 and the pressure roller 31 in a state where this heat capacity is secured are set to temperatures detected by the thermistors as the respective temperature sensors. Further, the heat capacities of the fixing belt 27 and the pressure roller 31 in the optimum fixing temperature state are the volume as the size of the member defined by various dimensions of the identification belt 27 and the pressure roller 31, Although it can be calculated from thermal characteristics such as thermal conductivity and specific heat defined by the materials of the fixing belt 27 and the pressure roller 31, it is actually obtained using an actual machine.

  That is, in more detail, with respect to the theoretical heat capacity A of the fixing belt 27 in a state in which an appropriate fixing temperature is ensured, which is represented by the area of the solid upright rectangular shape on the left side in FIG. If the current heat storage amount of the fixing belt 27 calculated from the actually measured temperature of the fixing belt 27 is less than the theoretical heat capacity A, the current heat storage amount is shown in FIG. (B) On the left side in the figure, the area of the upright rectangular parallelepiped shape shorter than the upright rectangular parallelepiped is shown, and the area surrounded by the broken line is the amount of heat that the fixing belt 27 lacks. .

  On the other hand, for example, if the detected fixing belt temperature is substantially equal to the target temperature T, but the detected pressure roller temperature is lower than the target temperature T, the heat of the heating roller 26 is increased by the fixing belt. 27, the pressure roller 31 continues to be robbed for some reason. For this reason, as a result, the fixing temperature of the nip portion is lower than the optimum temperature. In other words, in the above case, although it is detected that the fixing belt temperature is maintained at an appropriate temperature, an appropriate fixing temperature cannot be obtained as a result.

  More specifically, with respect to the theoretical heat capacity B of the pressure roller 31 in a state in which an appropriate fixing temperature is ensured, which is represented by the area of a solid upright rectangular shape on the left side in FIG. If the current heat storage amount of the pressure roller 31 calculated from the measured temperature of the pressure roller 31 is less than the theoretical heat capacity B, the current heat storage amount is 5 (c) is represented by an area portion of an upright rectangular parallelepiped shape shorter than the upright rectangular parallelepiped shape on the left side, and the area portion indicated by a broken line of the difference is deprived of heat for some reason. The amount of heat is insufficient for the pressure roller 31.

  On the other hand, conversely to the above, the fixing temperature of the nip portion may rise above the optimum temperature. That is, if the detected fixing belt temperature is substantially equal to the target temperature T, but the detected pressure roller temperature is higher than the target temperature T, the heat of the heating roller 26 causes the fixing belt 27 to pass through. For some reason, it continues to be accumulated in the pressure roller 31. As a result, the fixing temperature of the nip portion increases.

  After all, in the configuration of the fixing device 7, it is sufficient if the amount of heat generated from the halogen heater 25 b as the amount of heating is balanced between the amount of heat taken and the amount of heat stored in the fixing belt 27.

  Therefore, in order to avoid a situation in which an appropriate fixing temperature cannot be obtained at the nip portion even though the fixing belt temperature is maintained at an appropriate temperature for fixing as described above, only the temperature detection of the fixing belt is performed. In addition to the fixing belt temperature, the pressure roller temperature is also used as a determination material, and the detected temperature is not used as it is for the control determination. The detected temperature is taken as a result of reflecting the amount of heat stored in each member, and based on the quantitative amount of heat as a basic unit, it is first determined whether or not to perform a heating operation.

Specifically, for example, when the heat capacity of the fixing belt 27 in the optimum temperature state is A and the heat capacity of the pressure roller 31 in the same temperature state is B, the necessary heating amount is as follows. Calculated from equation (1).
Necessary heating amount = a + b + c (1)
However,
a = (heat capacity A of the fixing belt) − (current heat storage amount calculated from the detected temperature of the fixing belt)
b = (heat capacity B of the pressure roller) − (current heat storage amount calculated from the temperature detected by the pressure roller)
c = (The amount of heat taken away by others)
Note that the value of c in the above equation (1) is a predetermined fixed value that can be calculated from the structure of the fixing device and the configuration of each member. That is, the value of c is, for example, the amount of heat that is spontaneously released from the fixing belt and the pressure roller and does not serve the fixing temperature during the lapse of the control period, and these members are maintained and controlled near the fixing temperature. Therefore, it can be a constant value.

  In the first embodiment, since the heating operation is turned on / off in a predetermined control cycle unit, the heating amount when the heating operation is turned on, that is, when the heating operation is performed, is a fixed constant amount. That is, when this is turned on, the heating operation is continued for the time during which the control cycle elapses. For this reason, the value obtained by integrating the heat generation amount per unit time of the halogen heater 25b by the time of the control cycle becomes the heating amount by the control to turn on / off the heating operation in a specific control cycle unit. In the first embodiment, for example, the control period is set to 1 second.

More specifically, as a substitute for the series of calculation processes using the above equation (1), a determination table in which the results of calculation processes are registered is used for control.
That is, instead of using the above equation (1), that is, instead of a series of calculation processes, a determination data table as an equivalent is created in advance, and this determination table is used for control judgment. . That is, in the determination table, in each column where the fixing belt detection temperature and the pressure roller detection temperature are cross-checked, whether these detection temperatures are used is ON or OFF as a result of the above-described series of calculation processing in advance. The value of is registered.

  As shown in FIG. 5A, this determination table is configured in a matrix of 5 rows and 5 columns, each row in the vertical direction is for the fixing belt detection temperature, and each column in the horizontal direction is added. It is used for the pressure roller detection temperature. Further, the temperature range is set to a predetermined value so that sufficient control accuracy can be ensured between each detected temperature as the input parameter and the on / off determination result as the output parameter.

In the determination table, T represents a target temperature, + 6 ° C represents T + 6 ° C, + 3 ° C represents T + 3 ° C, -3 ° C represents T-3 ° C, and -6 ° C represents T-6 ° C. That is,
In the column of −6 ° C., the detected temperature X is T−6 ° C. ≧ X,
In the column of −3 ° C., the detected temperature X is T−3 ° C. ≧ X> T−6 ° C.
In the column of T, the detected temperature X is T ° C ≧ X> T−3 ° C.
In the column of + 3 ° C., the detected temperature X is T + 3 ° C. ≧ X> T ° C.
In the column of + 6 ° C., the detected temperature X is X> T + 3 ° C.,
Are selected respectively. In other words, when it is determined that the detected temperature X is lower than the target temperature T-3 ° C. and within the temperature range higher than the target temperature T-6 ° C., the column of −3 ° C. Selected as a column. Similarly, when it is determined that the detected temperature X is lower than the target temperature T ° C. and within the temperature range higher than the target temperature T−3 ° C., the T column is selected as a row or a column. The

  In each of the fields in which each of these fixing belt detection temperatures and each pressure roller detection temperature are cross-checked with the former as a row and the latter as a column, an on / off value determined as a result of calculation as follows: Is registered in advance. That is, when a certain fixing belt detection temperature and a certain pressure roller detection temperature are detected as a certain temperature condition, the necessary heating amount is calculated by using the above-described Equation 1 by combining these detection temperatures. The calculated heating amount is compared with the heating amount supplied in the control cycle, which is a fixed value in the first embodiment, and the heating operation is performed in the control cycle. Whether to turn on or off is registered in advance in the corresponding combination column. In addition, as the value of each detected temperature in each combination used for the above calculation, either the median value of the temperature range in each column, the upper limit value, or the lower limit value is determined according to the design specifications such as the device configuration and control configuration. Are selected and used as appropriate.

  Specifically, a certain fixing belt detection temperature and a certain pressure roller detection temperature are substituted into Equation 1 above to calculate a necessary heating amount. More specifically, the current heat storage amount of the fixing belt is calculated from a certain fixing belt detection temperature, and is subtracted from the heat capacity A to obtain the above a at the fixing belt detection temperature. Similarly, the current heat storage amount of the pressure roller is calculated from a certain pressure roller detection temperature, and is subtracted from the heat capacity B to obtain the above b. Then, the calculated a and b and the above c are added, and the added value is set as a necessary heating amount. The calculated necessary heating amount is compared with the heating amount supplied in the control cycle, which is a fixed value in the first embodiment, and basically, the calculated necessary heating amount is a fixed value supply heating. When the amount exceeds the supply heating amount and exceeds the supply heating amount, the off value is registered. When the amount is small, the off value is registered.

  Even when the fixing belt detected temperature Xa is equal to the target temperature T for the fixing belt and the fixing belt detected temperature Xb is equal to the target temperature T for the fixing belt, the amount of heat c to be taken away is also lost. Although this occurs, in the first embodiment, the heating amount is a fixed value, so an off value is registered. That is, since the amount of heat c is relatively small compared to the amount of heating supplied in the control cycle, it is assumed that the fixing temperature exceeds the target temperature T to the extent that some trouble occurs when a fixed amount of heating is supplied. Yes.

  Therefore, in the fixing device 7 configured as described above, the data table shown in FIG. 5A is stored and stored in the storage means such as the ROM of the system control board 51, and is determined in advance. The temperature of the fixing belt 27 and the temperature of the pressure roller 31 are detected at the start of each control cycle for each control cycle (for example, 1 second), and the respective temperature detection signals are input to the system control plate 51. Referring to this data table, based on the reference result of this table, it is determined whether the halogen heater 25b is turned on to perform a predetermined heat generation operation, or is turned off whether the heat generation operation is not performed, and this determination is executed. Accordingly, the heat generation operation of the halogen heater 25b is precisely controlled, and an appropriate amount of heating due to this heat generation can be obtained. That is, the heating of the halogen heater 25b during the control period is based on on / off registered in advance in a column where the row corresponding to the detected temperature of the fixing belt 27 and the column corresponding to the detected temperature of the pressure roller 31 intersect. The operation is controlled on and off.

  As described above, according to the fixing device of the first embodiment, the heat storage amount of each member is estimated from the temperature state of each member, the current heat storage amount of each estimated member, and the optimum fixing amount. A heat source that supplies a constant amount of heat in its control cycle, based on the overall required heat amount obtained by comparing both the theoretical heat amount of each member in the temperature state and calculating Is controlled to turn on and off the heat generated from the heating source under proper conditions, and the necessary and insufficient heating obtained by calculation is determined. With respect to the amount, it is possible to secure a calorific value adapted to the amount to be filled by supplementing the heating amount, and as a result, the temperature of the first rotating body can be controlled more precisely. In other words, the fixing temperature at the nip portion can be more strictly managed, and the image quality can be improved by the fixing.

  In particular, instead of on / off control based on the difference between the target temperature defined simply by the optimum fixing temperature and the detected temperature, the basic concept is the quantity of heat under time-divided conditions called control cycles. Since the control is determined to be on / off, the temperature state obtained as a result of the control is also reflected in the quantity of heat and the control characteristics such as accuracy, accuracy, reliability, etc. are good, and higher temperature control characteristics can be obtained. Can do.

  Further, in the heat belt type fixing device of the image forming apparatus, the fixing belt directly contacts the pressure roller in the non-sheet passing portion, and heat is transferred from the fixing belt to the pressure roller. For this reason, the image quality is affected by the temperature rise of the pressure roller. In other words, hot offset tends to occur when the temperature of the paper becomes high due to the pressure roller having such a temperature rise. On the other hand, in the first embodiment, the temperature of not only the heating roller but also the pressure roller is detected and the heating source is controlled so that the fixing temperature can be strictly managed and the image quality can be improved. Can do.

  In particular, in the first embodiment, the determination table of FIG. 5A is used to determine whether the heating operation as a so-called fixing device is on or off. It is possible to flexibly cope with configuration changes. That is, it is only necessary to change the on value or the off value registered in a specific column of the determination table.

  In the first embodiment, as shown in the determination table, the temperature division units of the fixing belt 27 and the pressure roller 31 serving as the determination criteria are set to 3 ° C. units and set to be equal to each other. However, the present invention is not limited to this, and different division units may be set. Moreover, although it divided by target temperature T +/- 3 degreeC and T +/- 6 degreeC, you may set arbitrary values not only this value. Furthermore, regarding the temperature range, the control cycle, the fixed duty ratio and the control cycle, the values may be set to appropriate values according to the material and configuration of each member and the structure of the fixing device itself. The same applies to each of the embodiments.

  Next explained is the second embodiment of the invention. In addition, the same code | symbol is attached | subjected to the member of the same structure as above-mentioned 1st Embodiment, and description is abbreviate | omitted or simplified. That is, the description will focus on the differences from the first embodiment, and the configuration, control, operation by the control, and action obtained by the control that are not described in the second embodiment are the same as those in the first embodiment. The same as the embodiment.

  In the second embodiment, by using the concept of the heat capacity of each member described above, in addition to controlling the heating operation of the heating source by integrally determining whether the heating amount is excessive or insufficient with respect to the heat capacity of each member, Furthermore, in accordance with the actual situation, the amount of heat generated as an operation content by the heating operation is finely increased / decreased, and the heating amount supplied from the heating source with respect to the calculated necessary heating amount is precisely optimized and controlled. I have to. In other words, in the first embodiment, either one of heat generation operation on (100%) and heat generation operation off (0%) is alternatively selected based on the belt temperature and the pressure roller temperature. On the other hand, in the second embodiment, the on / off state is divided into multi-stages (several out of 0% to 100%) consisting of several stages. Thus, the control configuration is such that any one of these steps is selected, and the amount of heat generated from the heating source is precisely increased or decreased for control.

  That is, in the second embodiment, the halogen heater 25b is configured to be heater-driven by PWM control that increases or decreases the amount of power supplied to the halogen heater 25b based on a variably set duty ratio. As shown in FIG. 4, a determination table for determining the duty ratio is created in advance.

  The determination table shown in FIG. 6 has the control cycle for the necessary heating amount calculated as insufficient due to the combination of the fixing belt detection temperature and the pressure roller detection temperature that can be calculated as described above. A variable duty ratio is set in advance in each column that is cross-matched with the above combination so as to supply a substantially equal amount of heat. That is, the value of a is calculated from the heat capacity A and a certain fixing belt detected temperature, the value b is calculated from the heat capacity B and the pressure roller detected temperature, and the calculated values of a and b, The sum obtained by adding the above values of c becomes a necessary heating amount calculated from a combination of a certain fixing belt detection temperature and a certain pressure roller detection temperature, and in accordance with this heating amount, approximately the same amount in the control cycle. A numerical value of the duty ratio that defines the amount of power to supply the amount of heat is previously registered in the column corresponding to the combination. In addition, when a necessary heating amount becomes a negative value in a certain combination, that is, when it can be calculated that the heat storage state of the member is excessive, naturally, “OFF” is registered as a duty ratio of 0%. .

  More specifically, the duty ratio that defines the heating amount of the halogen heater 25b by setting the power supply amount to the halogen heater 25b that is supplied during a certain control cycle is expressed by the following equation (1). It can be determined by equation (2). Although it is basically calculated from the equation of the amount of heat applied to the fixing belt 27 and the like and the amount of heat matured in the heating roller 26, the amount of heat from the halogen heater 25b is changed by setting the duty ratio. Since it can be arbitrarily adjusted, the duty ratio is set so that this heating amount is quantitatively equal to the necessary heating amount.

For example, when the heating amount as the maximum heat output that can be generated by the halogen heater 25b is 600 W, the lighting rate during the control cycle as the duty ratio is calculated from the following equation.
(Lighting rate) = (a + b + c) / 600 W (2)

  As described above, the system control plate 51 can set the duty ratio of the halogen heater 25b to a predetermined value according to the calculated required heating amount, and can control the heating operation by the heating source with this duty ratio. . In other words, the system control plate 51 can control the heating amount of the heating source to be supplied in an amount that matches the calculated required heating amount based on the set duty ratio.

  In the determination table, since the heating amount is variable in the second embodiment, the detection temperature Xa of the fixing belt is equal to the target temperature T for the fixing belt, and the detection temperature Xb of the fixing belt is Even when the target temperature T is equal to the target temperature T for the fixing belt, the heat amount c lost due to the loss is generated. Therefore, a duty ratio corresponding to the heat amount c is set and registered. In other words, a duty ratio of “30%” is set in order to supply a heating amount equal to the heat amount c in the current control cycle.

  The system control plate 51 is configured to change the heating amount of the halogen heater 25b by changing the duty ratio for turning on / off the halogen heater 25b.

For example, when the predetermined control cycle is 1 second and the duty ratio is 50%, the time for which the halogen heater 25b is turned on is calculated as follows.
1 (second) x 50/100 = 0.5 (second)
As a result, the halogen heater 25b is energized for 0.5 seconds to turn on the heating operation. Thus, the supply heating amount from the halogen heater 25b is variably controlled.

  In the second embodiment, as in the first embodiment, the difference between the detected temperature of the fixing belt 27 and the target temperature T of the fixing belt 27 stored in advance, the detected temperature of the pressure roller 31 and the previously detected temperature. A difference from the stored target temperature T of the pressure roller 31 is calculated. Then, with reference to the determination table shown in FIG. 6, these calculation results are cross-matched, and the duty ratio in the cross-checked column is determined as the duty ratio for the heating operation in the control cycle.

  The control operation of the fixing device 7 according to the second embodiment will be described with reference to the flowchart shown in FIG.

  That is, at least when the image forming operation is started, the system control board 51 starts measuring a predetermined control cycle with the time measuring function and starts the control operation including the following steps. At the start of this control cycle, the thermistor 37b first detects the temperature of the fixing belt 27 (step S1). The target temperature T is subtracted from the fixing belt detection temperature Xa to obtain an A value (step S2). The thermistor 37a of the pressure roller 31 detects the temperature of the pressure roller 31 (step S3). The target temperature T is subtracted from the pressure roller detection temperature Xb to obtain a B value (step S4). Referring to the determination table shown in FIG. 6 for the values of A and B, the duty ratio of 0% as off or the numerical value% of 30%, 50%, 70% or 100% as on Determine the duty ratio. That is, each column corresponding to A and B is selected, and the duty ratio registered in the column obtained by cross-checking these columns is set as the duty ratio that defines the amount for supplementing the necessary heating amount. Is selected and determined for execution of the control cycle (step S5). Based on the determined duty ratio, it is determined whether or not to turn off the halogen heater 25b (step S6). As a result of this determination, when it is off, that is, when a duty ratio of 0% is determined as off, the halogen heater 25b is turned off and no heating operation is performed during the control cycle (step S7). If the result of determination in step 6 is not off, that is, if the duty ratio of some positive numerical value% is determined to be on, the halogen heater 25b is turned on during the control cycle based on the value of the duty ratio. Is done. In other words, the halogen heater 25b performs the heating operation in such a manner that the determined duty ratio value is a ratio, that is, the heating on-time length is equal to the time length of the control cycle. Is executed (step S8). Specifically, PWM control based on the set duty ratio is executed, and the amount of power corresponding to the duty ratio is supplied to the halogen heater 25b. The halogen heater 25b is heated. Then, the system control board 51 continues to perform the control time measurement at least during the image forming operation such as copying of a plurality of copies at the same time. The series of processes that are started is repeated.

  As described above, according to the fixing device of the second embodiment, in addition to the function and effect of the first embodiment, the amount of heat generated to be supplied to the heating source is set to a predetermined duty. Based on the ratio, the variable control configuration can be increased or decreased in multiple stages instead of at least two on / off stages. It is possible to secure a calorific value that is further adapted to the amount to be supplemented by the necessary heating amount, and as a result, more precisely control the temperature of the first rotating body. Can do. In other words, the fixing temperature at the nip portion can be more strictly managed, and the image quality can be improved by the fixing.

  Further, in the first embodiment, the determination table is used to set the heating amount during the heating operation as a so-called fixing device, so the duty ratios in the respective columns in the determination table as parameters are reset. This makes it possible to flexibly cope with changes in the configuration of the fixing device. In particular, since the calculated required heating amount and the supply heating amount supplied by the heating source are clearly faced to determine or determine the supply heat amount by the heating source, the apparatus configuration that has a large thermal influence It is possible to easily and surely cope with changes in the above. That is, for example, the heating amount can be visually changed even if the duty ratio of each column is determined by repeatedly testing with an actual machine.

  For this reason, for example, it is possible to easily grasp the tendency of each column of the decision table as a whole, and it is not necessary to grasp the influence that affects another column by correcting a certain column. As a result, it is possible to satisfactorily secure the control balance using the determination table, and to increase the completeness of the temperature control by the actual machine in a short development period.

  On the other hand, setting errors can be prevented even if the total number of columns is large. That is, if the duty ratio registered in each column is compared with the duty ratios registered in the columns around the column, it can be identified at a glance whether it is an inappropriate value. For this reason, even in a configuration in which a large number of columns are used in this determination table and finer control is performed, the completeness and reliability can be improved.

  Next explained is the third embodiment of the invention. In addition, the same code | symbol is attached | subjected to the member of the same structure as above-mentioned 2nd Embodiment, and description is abbreviate | omitted or simplified. That is, the description will focus on the differences from the second embodiment, and the configuration, control, operation by the control, and action obtained by the control that are not described in the third embodiment are the same as those in the second embodiment. The same as the embodiment.

  In the third embodiment, as an outline of the basic control content, as a first processing stage, a temperature change tendency is determined as a control result in the previous control cycle, and as a second processing stage, this time The amount of heat lost during the current control cycle from the trend of temperature change as well as the required amount of heating at that time that can be calculated from the detected temperature at that time acquired at the start of the control cycle The predicted amount of heat loss calculated in this way is added to the required amount of heating to determine the amount of heating to be supplied in the current control cycle. In this case, it is possible to predict and calculate the amount of heat that becomes excessive during the current control cycle from the tendency of temperature change, but so-called so-called predicted excess heat is treated as a loss of heat that takes a negative value. The terms in this specification are expressed in terms of the amount of heat loss.

  Specifically, as the first processing stage, the tendency of each temperature change as the previous control result is determined for each member. That is, each member records and saves the detected temperature of the previous control cycle, and compares the stored detected temperature with each detected temperature acquired in the current control cycle, thereby executing the control executed in the previous control cycle. It is determined that the tendency of the temperature change obtained by the above corresponds to a certain stage among several preset stages.

  More specifically, the change from the previous detected temperature to the current detected temperature is set in advance using each evaluation table prepared in advance for each of the fixing belt 27 and the pressure roller 31 as each member. It is determined that it corresponds to one of the five stages.

That is, as shown in FIG. 8A, the evaluation table for the fixing belt detected temperature is configured in a matrix of 3 rows and 3 columns, and is divided into three in the horizontal direction for the previous detected temperature. The detected temperature of the fixing belt is divided into three sections in the vertical direction, and as these section items, the fixing belt detected temperature is sequentially −3 ° C. (a state lower than the target temperature T−3 ° C.) and + 3 ° C. (target A state higher than the temperature T + 3 ° C.) and T (a state within a temperature range sandwiched between these two temperature ranges as other temperatures) are assigned. Further, in the column defined from the combination of the two previous and present fixing belt detection temperature states, that is, the column referenced by cross-checking from the two selected items, the following 5 items are preliminarily set according to the combination. The evaluation result of one of the two stages is registered.
LL (significantly lower than the target temperature T) <LM (lower than the target temperature T) <MM (appropriate and almost equal to the target temperature T) <HN (higher than the target temperature T) ) <HH (much higher than target temperature T)

Therefore, if one of the three items is selected from the previous and current fixing belt detection temperatures, the evaluation result registered in the column in which these two selected items are cross-matched. Is obtained.
As shown in FIG. 8B, the evaluation table for the pressure roller detection temperature has basically the same 3 × 3 matrix configuration, and similarly, the evaluation result is predetermined in each column. Since it is registered, explanation is omitted.

  In other words, in these evaluation tables, it is determined whether or not the suitability of the previous control, that is, whether or not the target temperature T has been obtained, and if not, the temperature of the member decreases. It is determined whether it has changed to a higher or higher direction, and the degree of change in this direction is evaluated in two stages. That is, for example, the tendency to change “low direction” in a certain member is “low” “lowest”, and the control tendency to “high direction” is “high” “highest”, respectively. Judge in two steps. In other words, the previous control result is evaluated from the previous detected temperature as the control result by the previous control cycle, the previous control result is evaluated from the current detected temperature as the control result by the previous control cycle, and these evaluations are performed. This time control is decided by predicting the result obtained as an extension of the result.

  Next, as the second processing stage, the supply heating amount was calculated and prepared in advance so as to predict and cope with the results obtained from these temperature change trends, that is, as an extension of these temperature change trends. With reference to the determination table, the duty ratio that defines the supply heating amount supplied from the heating source, that is, the electric power supplied to the substantial heating source, when the heating operation is performed in the current control cycle is determined.

In other words, as a substitute for the series of calculation processes in the second processing stage described above, a decision table in which the results of calculation processes are registered is used.
As shown in FIG. 9, this determination table is configured in a matrix of 5 rows and 5 columns, and each row in the vertical direction is for the evaluated degree of change in fixing belt temperature, and each column in the horizontal direction is evaluated. The pressure roller temperature change degree is used. Also, in this determination table, a duty ratio that defines the amount of heating to be supplied in the control cycle is registered in each column that is cross-checked based on the temperature change tendency of the two members of the fixing belt and the pressure roller. The supply heating amount corresponding to this duty ratio is the predicted amount of heat loss of each member calculated from the temperature change tendency of each of the two members in advance for each combination of the temperature change trends of the two members, and It is set as the sum total of the required heating amount of each member calculated similarly to 1st Embodiment.

  Next, an application example of the third embodiment will be specifically described. That is, in the fixing device 7 according to the third embodiment, the thermistor 37b disposed at a predetermined location near the fixing belt 27 shown in FIG. 27, the detected temperature of the fixing belt is input to the system control plate 51, and the thermistor 37a disposed in the vicinity of the pressure roller 31 detects the temperature of the pressure roller 31. The detected pressure roller detected temperature is input to the system control plate 51.

  In the third embodiment, the system control board 51 shown in FIG. 3 is shown in FIGS. 8 (a), 8 (b) and 9 as in the second embodiment. Each previously created table is stored, and at a predetermined control cycle, each detected temperature is obtained from the thermistor 37a and the thermistor 37b, and based on these detected temperatures, the necessary heating amount is calculated using each table, The heating operation of the halogen heater 25b as a heating source in the control cycle is controlled so that the calculated heating amount is obtained.

  Next, the control operation of the third embodiment configured as described above will be briefly described. That is, first, the detected temperature of the fixing belt 27 detected in the previous control cycle and the detected temperature of the pressure roller 31 detected in the same control cycle are stored and saved in the memory of the system control plate 51. Then, at the start of the current control cycle, the system control plate 51 acquires the detected temperature of the fixing belt 27 and the detected temperature of the pressure roller 31 by the thermistor 37a and the thermistor 37b. That is, the detected temperature of the fixing belt 27 detected in the current control cycle and the detected temperature of the pressure roller 31 detected in the current control cycle are input to the system control plate 51. The system control board 51 fixes the stored detected temperatures and the input detected temperatures with reference to the evaluation tables for the respective members shown in FIGS. 8A and 8B. It is determined by evaluating whether the temperature change state of the belt 27 and the pressure roller 31 is one of the above five stages. Next, the system control plate 51 refers to the determination table shown in FIG. 9 and uses the evaluation results of the fixing belt 27 and the pressure roller 31 evaluated in this manner, and uses the halogen as a heating source in the control cycle. The duty ratio for controlling the heating operation by the heater 25b is determined. For this reason, in the control cycle, the amount of electric power based on the determined numerical value of the duty ratio is supplied to the halogen heater 25b, and the halogen heater 25b generates heat corresponding to the amount of electric power, that is, specified by the numerical value of the duty ratio. The heating operation of the supplied heating amount is executed. The system control board 51 stores and saves the fixing belt detection temperature and the pressure roller detection temperature obtained in the current control cycle as the previous temperature for evaluation in the next control cycle. That is, the previous temperature is updated in this way.

  Next, the control operation of the fixing device 7 of the third embodiment will be described in more detail with reference to the flowchart shown in FIG.

  That is, at least when the image forming operation is started, the system control board 51 starts measuring a predetermined control cycle with the time measuring function and starts the control operation including the following steps. At the start of this control cycle, the thermistor 37b first detects the fixing belt temperature as the current temperature of the fixing belt 27 (step S1). The previously determined fixing belt temperature stored and stored is compared with the current fixing belt temperature detected this time. That is, referring to the evaluation table for the fixing belt, the column corresponding to the previous fixing belt temperature and the column corresponding to the current fixing belt temperature are cross-checked, and the evaluation result registered in the cross-checked column is A. (Step S2). For the evaluation in the next control cycle, the current temperature of the fixing belt 27 is stored and saved as the previous temperature (step S3). The thermistor 37a of the pressure roller 31 detects the pressure roller temperature of the pressure roller 31 as the current temperature (step S4). The previously obtained pressure roller temperature stored and stored is compared with the current pressure roller temperature detected this time, and the obtained degree of change is defined as B. That is, referring to the evaluation table for the pressure roller, the column corresponding to the previous pressure roller temperature and the column corresponding to the current pressure roller are cross-checked, and the evaluation result registered in this cross-checked column Is set to B (step S5). The current temperature of the pressure roller 31 is stored as the previous temperature (step S6). With reference to the determination table, the duty ratio of the halogen heater 25b is determined by the cross-matched column using the temperature change degrees A and B (step S7). Based on the determined duty ratio, it is determined whether or not the halogen heater 25b of the heating roller 26 is turned off. That is, when the duty ratio is 0% and it is OFF, it is determined that the duty ratio is OFF (step S8). If it is determined in step 8 that the halogen heater 25 is off, the halogen heater 25 is turned off (step S9). If it is determined that the step 8 is on, the halogen heater 25 of the heating roller 26 is turned on at a rate based on the determined value of the duty ratio (step S10).

In the state where the copying machine 1 is operating and before the copying operation as the image forming operation, at least in the fixing device 7 in which the fixing belt 27 is controlled to a predetermined standby temperature, this standby temperature is detected last time for both members. In the first image forming operation in which the copying operation is performed immediately after the power is first turned on for the fixing device 7 that is not controlled to the temperature or the standby temperature, the current detection temperature of both members is assumed to be the previous detection temperature. The same applies to the following embodiments.
In addition, the system control board 51 continues the time measurement for the control in the same manner at least during the image forming operation such as the copying of a plurality of copies, and when the start time of the control cycle is measured, the above-described step S1 is started. A series of control processes to be started are repeated, and the same applies to each of the following embodiments.

  As described above, according to the fixing device of the third embodiment, in addition to the operational effects of the first embodiment, the fixing belt detected temperature, which is the temperature of the first rotating body, and the second rotation. The pressure roller detection temperature, which is the temperature of the body, is pre-determined from the detected member temperature as an extension of this change trend, based on the change that occurred between the temperature state detected last time and the temperature state detected this time. The heating amount other than the necessary heating amount is predicted, and the supply heating amount corresponding to the total heating amount of these two is supplied from the heating source. Can be corrected to an appropriate heating control, and the supplied heating amount becomes more appropriate, and as a result, the fixing temperature can be precisely controlled.

  In each evaluation table of FIG. 8A and FIG. 8B, the temperature division unit is 3 ° C., but is not limited to this, and may be smaller than this, and each member and each division The temperature ranges assigned to may not be equal to each other but may be different. Therefore, in these cases, the temperature range and the temperature division can be more adapted to each member. Although the number of evaluation stages is five, the number of stages is not limited to this and may be increased. Therefore, when the number of stages is increased, the number of stages for evaluating the detected temperature is increased, and the evaluation accuracy can be improved. As a result, the temperature control can be performed more precisely.

  Next explained is the fourth embodiment of the invention. In addition, the same code | symbol is attached | subjected to the member of the same structure as above-mentioned 3rd Embodiment, and description is abbreviate | omitted or simplified. That is, the description will focus on the differences from the third embodiment, and the configuration, control, operation by the control, and action obtained by the control that are not described in the fourth embodiment are the same as those of the third embodiment. The same as the embodiment.

  In the fourth embodiment, a halogen heater 25a as a second heating source is added to the pressure roller 31 as the second rotating body, and the temperature detected by the thermistor 37a as the second temperature detection unit is set. Based on this, the second heating source is configured to be controlled in a predetermined manner. In the fourth embodiment, the control of the first heating source and the second heating source as the control configuration is independent of each other. That is, the control configuration of the first heating source including the thermistor 37a and thermistor 37b as sensors, the system control plate 51 as a controller, and the halogen heater 25b as an actuator, and the thermistor 37a as a sensor and the system control plate as a controller The control structure of the second heating source composed of 51 and the halogen heater 25a as an actuator is controlled independently and independent from each other even if the same component is shared.

  That is, in the fixing device 7 of the fourth embodiment, as shown in FIG. 11, the pressure roller 31 is formed in a hollow roller shape having a predetermined thermal conductivity, and the second roller is formed in the inside thereof. A halogen heater 25a is installed as a heating source. Since the halogen heater 25a itself has substantially the same configuration as the halogen heater 25b built in the heating roller 26, the description of the configuration is omitted.

  In the fixing device 7, the thermistor 37 b disposed at a predetermined location near the fixing belt 27 detects the temperature of the fixing belt 27 and inputs the detected fixing belt detection temperature to the system control plate 51. At the same time, the thermistor 37 a disposed in the vicinity of the pressure roller 31 detects the temperature of the pressure roller 31 and inputs the detected pressure roller detected temperature to the system control plate 51. Yes.

  Further, as shown in FIG. 12, the PSU 58 is connected to a halogen heater 25a, and is provided with the above-described relay for AC power supply cutoff (not shown) dedicated to the halogen heater 25a, a triac, a snubber circuit, and the like. Therefore, the halogen heater 25b of the heating roller 26 and the halogen heater 25a of the pressure roller 31 are driven independently by their respective triacs (for example, PWM control for increasing / decreasing the amount of heating at ON / OFF or ON based on the duty ratio). Is configured to be possible.

  In the fixing device 7, the control of the existing halogen heater 25 b provided on the heating roller 26 is the control configuration of the first embodiment, the control configuration of the second embodiment, or the control of the third embodiment. The configuration is basically used as it is.

  In the fourth embodiment, the control of the halogen heater 25a newly provided in the pressure roller 31 is detected by the existing thermistor 37a provided in the vicinity of the pressure roller 31 with respect to the target temperature T. When the detected pressure roller temperature is lower than the target temperature T and lower than the target temperature T, the heater is turned on as an electric heater. On the other hand, when the detected temperature is higher than the target temperature T and higher than the target temperature T, the heater is turned on. It is controlled to turn off. That is, in the former case, the halogen heater 25a is energized in a predetermined manner from the PSU 58 and the heat generation power is supplied to cause the halogen heater 25a to generate heat. In the latter case, no power is supplied. The heating operation is not performed while the lamp is turned off.

  As described above, according to the fixing device of the fourth embodiment, in addition to the operational effects of the third embodiment, the pressure roller as the second rotating body is used as the second heating source. A second halogen heater that is a pressure heater is additionally provided, and the heating operation of the added pressure heater is controlled in a predetermined manner, so that at least the pressure roller is removed from the member that consumes heat. It becomes a member on the side supplying heat. Therefore, at least the thermal stability of the pressure roller can be increased, and the pressure roller is actively controlled to generate heat from its dedicated heating source instead of passively receiving heat. Thus, the difference between the heat capacity B of the pressure roller as the optimum heat storage amount of the pressure roller and the current heat storage amount can be reduced, and the value of b described above can be kept small. Become. For this reason, as a result, the temperature of the first rotating body can be precisely controlled. That is, it is possible to reduce the deficient required heating amount calculated at the start time of each control cycle described above, and to reduce the amount of heat supply burden handled by the first halogen heater as the heating heater as the first heating source. Since it can be reduced, the amount of heat generated from the heater can be reduced, and the heating amount can be controlled more precisely.

  Note that the temperature detection of the pressure heater and the lighting control of the pressure heater based on the temperature detection may be performed constantly without any particular control period, but the present invention is not limited to this. Similarly to the control cycle, the control may be performed for each control cycle, that is, the temperature may be detected at the start of the control cycle, and the lighting control of the control cycle may be performed. The control cycle of the pressure heater and the control cycle of the pressurizing heater may be set to be synchronized with each other in the same time cycle, and further, either one of time or asynchronous, or both may be different. .

  Next explained is the fifth embodiment of the invention. In addition, the same code | symbol is attached | subjected to the member of the same structure as above-mentioned 4th Embodiment, and description is abbreviate | omitted or simplified. That is, the description will focus on the differences from the fourth embodiment, and the configuration, control, operation by the control, and action obtained by the control that are not described in the fifth embodiment are the same as those in the fourth embodiment. The same as the embodiment.

  In the fifth embodiment, in the fixing device 7 shown in FIG. 11, the system control plate 51 performs the control based on the pressure roller detection temperature in the above-described fourth embodiment in the first temperature detection unit. The halogen heater 25a as the second heating source is controlled in consideration of the fixing belt detection temperature by the thermistor 37b.

  That is, in the fifth embodiment, the thermistor 37b disposed at a predetermined location near the fixing belt 27 detects the temperature of the fixing belt 27 and detects this, as in the fourth embodiment. The detected temperature of the fixing belt is input to the system control plate 51, and the thermistor 37a disposed in the vicinity of the pressure roller 31 detects the temperature of the pressure roller 31, and the detected pressure roller detected temperature is detected. The system control board 51 is configured to input.

  The system control plate 51 controls the halogen heater 25a provided on the pressure roller 31 by adding the fixing belt detection temperature detected by the existing thermistor 37b to the control based on the pressure roller detection temperature described above. It is configured. That is, the system control plate 51 detects not only the temperature of the pressure roller 31 but also the temperature of the fixing belt 27 to control the heating operation of the halogen heater 25a in order to control the halogen heater 25a. ing.

  Specifically, in the fifth embodiment, the control of the halogen heater 25a provided on the pressure roller 31 is either the control configuration of the first embodiment or the control configuration of the second embodiment. Either one of the control configurations is basically used as it is.

  That is, as one configuration of the fifth embodiment in which the control configuration of the first embodiment is used to control the halogen heater 25a, the system control plate 51 is configured to detect the fixing belt detection temperature and the temperature at the start of the control cycle. The determination table shown in FIG. 5A indicates whether the pressure roller detection temperature is acquired as the current data of each member, and then whether the halogen heater 25a is turned on or kept off in the control cycle. , And using these detected temperatures in the determination table.

  Therefore, in one configuration of the fifth embodiment, the temperature of the fixing belt 27 and the temperature of the pressure roller 31 are detected at the start of each control cycle every predetermined control cycle (for example, 1 second). Each temperature detection signal is input to the system control board 51, and the ON state for causing the halogen heater 25a to perform a predetermined heat generation operation based on the result of referring to the determination table shown in FIG. Or whether the heat generation operation is not performed is determined, and this determination is executed during the control period. Thus, the heat generation operation of the halogen heater 25a is precisely controlled so that at least the pressure roller 31 can obtain an appropriate amount of heating due to this heat generation. In other words, depending on whether the row corresponding to the detected temperature of the fixing belt 27 and the column corresponding to the detected temperature of the pressure roller 31 intersect with each other, either on or off is registered in advance. The heating operation of the halogen heater 25a is controlled to be either on or off.

  On the other hand, as the other configuration of the fifth embodiment in which the control configuration of the second embodiment is used to control the halogen heater 25a, the system control plate 51 detects the fixing belt detected temperature at the start of the control cycle. The pressure roller detection temperature is acquired as the current data of each member, and the duty ratio defining the power supplied to the halogen heater 25a in the control cycle is referred to the determination table shown in FIG. Determination is made using these detected temperatures in the determination table.

  Therefore, in the other configuration of the fifth embodiment, the temperature of the fixing belt 27 and the temperature of the pressure roller 31 are detected at the start time of each control cycle every predetermined control cycle (for example, 1 second). Each temperature detection signal is input to the system control board 51, and the duty ratio for the halogen heater 25a is determined based on the reference result of this table with reference to the determination table shown in FIG. During the period, based on the determined duty ratio, control is performed by adjusting the amount of power supplied to the halogen heater 25a. Thus, the heat generation operation of the halogen heater 25a is precisely controlled so that at least the pressure roller 31 can obtain a more appropriate heating amount due to the heat generation. That is, the numerical value of the duty ratio registered in the column where the row corresponding to the detected temperature of the fixing belt 27 and the column corresponding to the detected temperature of the pressure roller 31 intersect is supplied to the halogen heater 25a during the control period. The amount of electric power is determined as a prescribed value, and the amount of heating by the heating operation of the halogen heater 25a during the control period is controlled in accordance with this numerical value.

  As described above, according to the fixing device of the fifth embodiment, on / off of the second heating source can be controlled more precisely in addition to the operational effects of the fourth embodiment. That is, at least the required heating amount is calculated, not the on / off control based on the difference from the simple target temperature, and the heating operation is controlled on / off based on the calculated required heating amount. The amount of heating supplied by the operation becomes appropriate even by simple on / off control. In particular, in the configuration in which the supply heating amount is variable, it is possible to provide a supply heating amount in an amount more suitable for the required heating amount with respect to the pressure roller. Therefore, the temperature control accuracy of the pressure roller itself can be improved, and accordingly, the temperature of the fixing belt as the first rotating body can be controlled more precisely.

  In the fifth embodiment, the fixing belt determination table is used for the control for the heating operation of the halogen heater provided in the pressure roller as the second heating source. However, this is only an example. Of course, it is desirable to create a determination table dedicated to the pressure roller and use it for the control. In other words, considering the thermal characteristics depending on the structure and dimensions of the pressure roller and the heat transfer characteristics of the halogen heater itself arranged in the pressure roller, the ON / OFF values in each column and the duty ratio It is desirable that these numerical values are set as appropriate, and are actually values verified by actual machines.

  Next, a sixth embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the member of the same structure as above-mentioned 5th Embodiment, and description is abbreviate | omitted or simplified. That is, the description will focus on the differences from the fifth embodiment, and the configuration, control, operation by the control, and action obtained by the control that are not described in the sixth embodiment are the same as those in the fifth embodiment. The same as the embodiment.

  In the sixth embodiment, a control configuration similar to that of the third embodiment is used for controlling the second heating source. That is, in the sixth embodiment, as in the third embodiment, as the first processing stage, each evaluation table of FIG. 8A and FIG. Thus, the tendency of each temperature change is determined, and the supply heating amount of the second heating source is determined using the determination table shown in FIG. 9 as the second processing stage.

  In the sixth embodiment, the second heating source is controlled to be turned on / off based on the temperatures detected by the first and second temperature detection units, and the second heating source is turned on when the second heating source is turned on. The heating amount is calculated, and the heating amount of the second heating source is controlled based on the calculated heating amount.

  Specifically, in the fixing device 7 shown in FIG. 11, the system control plate 51 controls on / off of the halogen heater 25b based on the degree of change in the detected temperature of each member detected by the thermistor 37a and the thermistor 37b. The heating amount of the halogen heater 25b when the halogen heater 25b is turned on is calculated, and the heating amount of the halogen heater 25 is controlled based on the calculated heating amount, and the detected temperature of each member detected by the thermistor 37a and the thermistor 37b. Based on the degree of change, the halogen heater 25a is turned on / off, the heating amount of the halogen heater 25a when the halogen heater 25a is turned on is calculated, and the heating amount of the halogen heater 25a is controlled based on the calculated heating amount. I am doing so. That is, the system control board 51 stores the previously created tables shown in FIG. 8A, FIG. 8B, and FIG. 9, and starts the control operation at every predetermined control cycle. Then, the heating operations of the halogen heater 25a and the halogen heater 25b are controlled in parallel.

  Therefore, in the sixth embodiment, in addition to the control operation of the third embodiment, first, the detected temperature of the fixing belt 27 detected in the previous control cycle and the pressure detected in the same control cycle. The detected temperature of the roller 31 is stored and saved in the memory of the system control board 51. Then, at the start of the current control cycle, the system control plate 51 acquires the detected temperature of the fixing belt 27 and the detected temperature of the pressure roller 31 by the thermistor 37a and the thermistor 37b. That is, the detected temperature of the fixing belt 27 detected in the current control cycle and the detected temperature of the pressure roller 31 detected in the current control cycle are input to the system control plate 51. The system control board 51 fixes the stored detected temperatures and the input detected temperatures with reference to the evaluation tables for the respective members shown in FIGS. 8A and 8B. It is determined by evaluating whether the temperature change state of the belt 27 and the pressure roller 31 is any of the above five stages. Next, the system control plate 51 refers to the determination table shown in FIG. 9 and uses the evaluation results of the fixing belt 27 and the pressure roller 31 evaluated in this manner, and uses the halogen as a heating source in the control cycle. The duty ratio for controlling the heating operation by the heater 25a is determined. For this reason, in the control cycle, the amount of electric power based on the determined numerical value of the duty ratio is supplied to the halogen heater 25a, and the halogen heater 25a generates heat corresponding to the amount of electric power, that is, specified by the numerical value of the duty ratio. The heating operation of the supplied heating amount is executed.

  As described above, according to the fixing device of the sixth embodiment, in addition to the operational effects of the fifth embodiment, the second heating source can be precisely controlled. That is, between the temperature state detected last time and the temperature state detected this time in the detected temperature of the fixing belt, which is the temperature of the first rotating body, and the pressure roller detected temperature, which is the temperature of the second rotating body. The amount of heat that is newly lost or added as an extension of this change trend in the control cycle is predicted from the change, and the predicted amount of heat loss is calculated based on the detected member temperature. Since the heating amount of the heating source is supplied according to the total heat amount in addition to the amount, inappropriate heating control related to the second heating source can be corrected to appropriate heating control at an early stage. At the same time, at least the amount of heat supplied to the pressure roller becomes more appropriate, and the second heating source can be precisely controlled. As a result, the fixing temperature can be precisely controlled.

  In the sixth embodiment, the determination table created for the first heating source is used. Of course, a determination table created in advance for the second heating source may be used. That is, in the determination table for the second heating source, the numerical value of the duty ratio in each column is used for various characteristics such as the heat output performance of the second heating source, the heat transfer efficiency to the pressure roller, and the heat of the pressure roller. Depending on general characteristics, it may be selected as appropriate.

  In the sixth embodiment, the control cycle for the first heating source and the control cycle for the second heating source may be set to be synchronized with each other at the same time cycle, Furthermore, either one or both of time and asynchronous may be different.

  Next, a seventh embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the member of the same structure as above-described 6th Embodiment, and description is abbreviate | omitted or simplified. That is, the description will focus on the differences from the sixth embodiment, and the configuration, control, operation by the control, and the action obtained by the general operation not described in the seventh embodiment are the same as those in the sixth embodiment. The same as the embodiment.

  The seventh embodiment is configured to perform the heating operation by linking the first heating source and the second heating source more closely than the control configuration of the sixth embodiment. Yes.

  In the seventh embodiment, as in the sixth embodiment, as the first processing stage, the evaluation tables in FIGS. 8A and 8B are used for each member. Each temperature change tendency is determined, and as a second processing stage, each supply heating amount of each heating source provided in each member is calculated and set individually using one determination table. In other words, the duty ratios that define the heating amounts supplied from the heating sources are determined simultaneously and in association with each other.

  Specifically, in the seventh embodiment, the determination table shown in FIG. 13 is created in advance and recorded on the system control board 51. As in the third embodiment, this determination table is configured in a matrix of 5 rows and 5 columns, and each row in the vertical direction is used for the degree of change in the fixing belt temperature evaluated, and each column in the horizontal direction. However, it is for the evaluated pressure roller temperature change degree. In each of the fields that are cross-matched, two numerical values for each heating source that are calculated and set in advance are registered.

  That is, in each cross-matched column, the target result is obtained by predicting the result obtained when the duty ratio set in the previous control cycle is maintained as it is and correcting the predicted result. As can be seen, during the period of the control cycle, the supply heat amount from each heating source is calculated in advance as the total heat amount to be supplied, and two numerical values for setting the respective duty ratios are registered. . In other words, in each column, the halogen heater 25b as the first heating source and the halogen heater 25a as the second heating source are controlled in consideration of the temperature change tendency and thermal efficiency of each member. In the cycle, the heating operation is performed in cooperation with each other, and as a result, the necessary heating amount and heat loss amount can be supplemented.

  In order to replenish the necessary heating amount and the predicted heat loss calculated in this way in the control cycle, each of these heating heat sources allocated to the halogen heater 25b and the halogen heater 25a is ensured. In the column, the value of the duty ratio for the halogen heater 25b and the value of the duty ratio for the halogen heater 25a are written and registered together. The numerical value indicated by “1:” at the top of the column is the numerical value of the duty ratio set for the halogen heater 25b of the heating roller 26 for heating the fixing belt 27, and “2:” is added. The numerical value indicated by the above is the numerical value of the duty ratio set for the halogen heater 25 a that heats the pressure roller 31.

  For example, referring to the evaluation table of FIG. 8A from the previous and current fixing belt detection temperatures, the degree of change in the fixing belt temperature is MM (not substantially equal to the target temperature T) by the evaluation table. Evaluating and referring to the evaluation table of FIG. 8B from the previous and current pressure roller detection temperatures, the degree of change in the pressure roller temperature is considerably lower than LL (target temperature T). 13), the determination table in FIG. 13 is referred to, and the column of the fixing belt temperature change MM and the pressure roller temperature change LL column are registered in the cross-matched column. The numerical values of the duty ratios for the halogen heater 25a and the halogen heater 25b are determined simultaneously and collectively. That is, a duty ratio of “50%” is set for the halogen heater 25 b as a heat supply source of the fixing belt 27 and as an indirect heating source, while a halogen heater as a direct heating source of the pressure roller 31. A duty ratio of “100%” is set for 25a. For this reason, in this case, the temperature of the pressure roller 31 tends to decrease considerably despite the fact that the temperature of the fixing belt 27 is properly maintained. The amount is determined to be larger than the supply heating amount for the fixing belt 27. As a result, the temperature control for the pressure roller 31 whose member temperature tends to decrease considerably is immediately corrected, and as this correction, the pressure roller 31 can be directly and efficiently heated.

  The control operation of the fixing device 7 of the seventh embodiment configured as described above will be described with reference to the flowchart shown in FIG.

  That is, at least when the image forming operation is started, the system control board 51 starts measuring a predetermined control cycle with the time measuring function and starts the control operation including the following steps. At the start of this control cycle, first, the thermistor 37b of the fixing belt 27 detects the temperature of the fixing belt 27 (step S1). The current temperature of the fixing belt 27 is compared with the previous temperature, and the degree of change is A (step S2). The current temperature of the fixing belt 27 is stored as the previous temperature (step S3). The thermistor 37a of the pressure roller 31 detects the temperature of the pressure roller 31 (step S4). The current temperature of the pressure roller 31 is compared with the previous temperature, and the degree of change is B (step S5). The current temperature of the pressure roller 31 is stored as the previous temperature (step S6). With reference to the determination table, the duty ratios of the halogen heater 25b and the halogen heater 25a are respectively determined using the degrees of change A and B. That is, each duty ratio registered in the cross-checked column is selected and determined for execution of the current control cycle (step S7). Next, based on the determined duty ratio for the halogen heater 25b, it is determined whether or not to turn off the halogen heater 25b of the heating roller 26 (step S8). If it is determined in step 8 that the halogen heater 25b is to be turned off, the halogen heater 25b is turned off (step S9). As a result of the determination in step 8, when it is determined that the heater is turned on, the halogen heater 25b of the heating roller 26 is turned on at a rate corresponding to the value of the duty ratio determined for the halogen heater 25b (step S10). Next, based on the determined duty ratio for the halogen heater 25a, it is determined whether or not to turn off the halogen heater 25a of the pressure roller 31 (step S11). If it is determined in step 11 that the halogen heater 25a is turned off, the halogen heater 25a is turned off (step S12). If it is determined as a result of the determination in step 11 that the heater is turned on, the halogen heater 25a of the pressure roller 26 is turned on at a rate corresponding to the value of the duty ratio determined for the halogen heater 25a (step S13).

  As described above, according to the fixing device of the seventh embodiment, in addition to the operational effects of the sixth embodiment, the heating amount of the first heating source and the heating amount of the second heating source are changed. Can be controlled more precisely. That is, the supply heating amount from the first heating source and the supply heating amount from the second heating source are linked to each other, and each supply heating amount is set, and each of the linked heating amounts is Since each heating source of the first heating source and the second heating source is adapted to the temperature change tendency of each member to be heated, the temperature change tendency of the member becomes the target temperature. The heating control corrected immediately can be corrected immediately, and the member responsible for the heating source can be directly and efficiently heated for this correction. For this reason, while being able to control more precisely, a reliable and favorable control result is obtained.

  On the other hand, in such a single determination table, since the respective duty ratio values for the first heating source and the second heating source are registered in the respective columns, the two heating sources are used. It becomes easy to ensure a good balance of heating amount, that is, a control balance. In other words, in the same column as a certain combination condition, the relationship between the two heating amounts can be clearly defined and clearly understood, and a close relationship can be formed between the two. It becomes.

  On the other hand, in a short development period, it is possible to increase the degree of perfection of this heating control for an actual machine. That is, for example, even if the two duty ratios in each column are determined by repeatedly testing with an actual machine, the respective heating amounts can be visually changed in relation to each other. For this reason, it is possible to develop a close relationship between the two in a direction in which a good result can be obtained while confirming the influences that cannot be obtained by the calculation formula. As a result, the completeness of the control configuration of the seventh embodiment in the actual machine can be increased.

  The heating roller, the fixing belt and the pressure roller as the configuration of the fixing device described in each of the above-described embodiments, and the halogen heater as the heating source are only a preferable example. Needless to say, can be changed, modified, etc. as appropriate within the scope of the claims. For example, the present invention can also be applied to a configuration in which a plurality of heating sources such as two heaters are arranged on the heating roller. Further, as a first heating source disposed inside the fixing belt as the first rotating body, a heating resistor layer may be provided in the fixing belt. That is, the fixing belt may be configured as a resistance heating element in which a base layer, a resistance heating layer, and a release layer are sequentially stacked, and may be configured to cause resistance heating by energizing the resistance heating layer. Furthermore, although the thermistor is used as the temperature detection unit, the temperature detection unit is not limited to the thermistor, and other temperature detection elements may be used.

According to the second aspect of the present invention, the control unit detects the difference between the detected temperature and the target value detected last time by the first and second temperature detection units, and the current detection by the first and second temperature detection units. The evaluation is selected from a preset evaluation table based on the difference between the detected temperature and the target value, and the duty of the first heating source and the second heating source is determined from a determination table created in advance based on the selected evaluation. Since the first heating source and the second heating source are controlled by PWM control by selecting the ratio , the second rotating body becomes a member on the heat supply side, and the heating handled by the first heating source The amount can be reduced and at least the thermal stability of the second rotating body can be increased. As a result, the temperature of the first rotating body can be controlled more precisely. In addition, the first heating source and the second heating source can be linked to each other and more precisely controlled.

According to the third aspect of the present invention, since the image forming apparatus includes the fixing device according to the first or second aspect , at least the temperature of the first rotating body can be precisely controlled. As a result, the fixing temperature can be secured well, and as a result, high-quality image quality can be obtained.

1 is a schematic front view showing an overall configuration of an image forming apparatus equipped with a fixing device of the present invention, showing an image forming apparatus as a premise of the present invention. 1 is a block diagram of a control device showing an electrical configuration related to a fixing device according to a first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing the overall configuration of the fixing device, showing the fixing device of the first embodiment. FIG. 2 is a block diagram showing the electrical configuration directly related to the halogen heater as a heating source of the fixing device of the first embodiment. 3 is a determination table for determining ON / OFF as a heating operation of a heating source in the fixing device of the first embodiment. FIG. 5 is a conceptual explanatory diagram showing a quantitative relationship between a theoretical heat capacity of a fixing belt under an optimal fixing temperature state and a current heat storage amount of the fixing belt that can be calculated from an actually measured fixing belt temperature. A conceptual illustration showing the quantitative relationship between the theoretical heat capacity of the pressure roller under the optimum fixing temperature and the current heat storage amount of the pressure roller that can be calculated from the measured pressure roller temperature. is there. FIG. 5 is a determination table for determining a duty ratio for controlling power supply to a heating source of the fixing device according to the second embodiment of the present invention. FIG. It is the flowchart which showed the control operation of this 2nd Embodiment. The fixing device of 3rd Embodiment of this invention is shown, (a) is an evaluation table for evaluating the change tendency of the detection temperature of the last control period and the detection temperature of this time control period in a fixing belt, (b) ) Is an evaluation table for evaluating the change tendency between the detected temperature of the previous control cycle and the detected temperature of the current control cycle in the pressure roller. The fixing device of this 3rd Embodiment is shown, The determination table for determining the duty ratio for the electric power supply control to the heat source of this fixing device from the temperature change tendency of a heating roller and the temperature change tendency of a pressure roller It is. It is the flowchart which showed the control action of 3rd Embodiment of this invention. FIG. 10 is a schematic cross-sectional view illustrating the entire configuration of a fixing device according to a fourth embodiment of the present invention. FIG. 10 is a block diagram showing the electrical configuration directly related to a halogen heater as a heating source of the fixing device of the fourth embodiment. FIG. 17 shows a fixing device according to a seventh embodiment of the present invention, and a determination for simultaneously determining each duty ratio for setting the amount of power supplied to each heating source provided in each of the fixing belt and the pressure roller. It is a table. It is the flowchart which showed the control action of 7th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Full color copying machine (image forming apparatus) 2 Exposure apparatus 3 Photoconductor 4 Image forming part 5 Paper feed cassette 6 Paper feed part heater 7 Fixing device 8 Manual feed tray 11 Document reading part 12 Document conveying part 13 Image forming unit 14 Developing apparatus 15 Laser irradiator 16 Mirror 17 Charging roller 21 Cleaning device 22 Intermediate transfer belt 23 Primary transfer roller 24 Paper discharge tray 25b Halogen heater (heating source)
25a Halogen heater (second heating source)
26 Heating roller 27 Fixing belt (first rotating body)
28 Fixing roller 31 Pressure roller (second rotating body)
33 Tension roller 34 Cleaning roller 35 Oil application roller 36 Transport guide 37a Thermistor (second temperature detection unit)
37b Thermistor (first temperature detector)
42 Casing 51 System control board (control unit)
52 Reading Control Board 53 Operation / Display Unit 54 Writing Control Board 55 Toner Sensor 56 High Voltage Power Supply 57 I / O Control Board 58 PSU (Power Supply Unit) 61 Various I / Os for Image Formation
P paper T target temperature (target temperature for temperature control)

Claims (3)

A first rotating body having a first heating source, a second rotating body that is in contact with the first rotating body to form a nip portion, and a first that detects the temperature of the first rotating body for each control cycle And a second temperature detection unit for detecting the temperature of the second rotating body for each control cycle, and passing a recording medium having an unfixed toner image in the nip portion, In a fixing device for fixing the toner image to a recording medium,
A controller for controlling on / off of the first heating source ;
This control unit is based on the difference between the detected temperature and the target value detected last time by the first and second temperature detecting units, and the difference between the detected temperature and the target value detected this time by the first and second temperature detecting units. Select an evaluation from a preset evaluation table,
Fixing, wherein the first heating source is controlled by PWM control by selecting a duty ratio for each control cycle of the first heating source from a decision table prepared in advance based on the selected evaluation. apparatus. A second heating source for heating the second rotating body;
The control unit is based on the difference between the detected temperature and the target value detected last time by the first and second temperature detecting units, and the difference between the detected temperature and the target value detected this time by the first and second temperature detecting units. Select an evaluation from a preset evaluation table,
The first heating source and the second heating source are controlled by PWM control by selecting duty ratios of the first heating source and the second heating source from a determination table prepared in advance based on the selected evaluation. The fixing device according to claim 1 , wherein the fixing device is controlled. Image forming apparatus equipped with the fixing device according to claim 1 or 2.

Images