JP2007025232A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To finely control temperatures by causing a temperature of a first rotating body and that of a second rotating body to follow the variance of temperature due to operations of the rotating bodies in a fixing device provided with a pair of rotating bodies. <P>SOLUTION: The fixing device which allows a recording medium to pass between the pair of rotating bodies to fix an image onto the recording medium, includes a halogen heater 15 for heating a fixing belt 10, a heating thermistor 18 for detecting a temperature of the fixing belt 10, an encoder 21 for detecting a speed of the rotating body of the fixing belt 10, and a system control plate 30 which calculates an amount of heating of the halogen heater 15 by PID control in accordance with information of the heating thermistor 18 for detecting the temperature of the fixing belt 10 and controls the amount of heating of the halogen heater 15 on the basis of the calculated amount of heating. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixing device such as a copying machine, a printer, or a facsimile machine.

  2. Description of the Related Art Conventionally, there is known an image forming apparatus that controls a heater of a heating roller by a detection output of a temperature detection device of a heating roller or a temperature detection device of a pressure roller. Here, the heater of the heating roller is controlled based on the temperature of the pressure roller, and the heater of the heating roller is controlled based on the temperature of the heating roller. Furthermore, the heater of the heating roller is controlled based on the temperature change of the pressure roller (see, for example, Patent Document 1, FIG. 4, and FIG. 5).

  Further, the target heating roller temperature is calculated based on the pressure roller detection temperature, and the heating source of the heating roller is controlled based on the calculated target heating roller temperature and the heating roller detection temperature (for example, Patent Document 2, FIG. 3). reference).

Japanese Patent Application Laid-Open No. 2002-221871 JP 2002-149987 A

  In the conventional techniques as described above, the heating source of the heating roller is controlled according to the detected temperature of the pressure roller. However, since the heating source of the heating roller is simply turned on and off based on the detected temperature of the pressure roller, there is a problem that precise temperature control cannot be performed.

  The present invention has been made in view of the above, and in a fixing device including a pair of rotating bodies, the temperature of the first rotating body and the temperature of the second rotating body are changed to temperature fluctuations due to the operation of the rotating body. The purpose is to make it possible to achieve precise temperature control.

  In order to solve the above-described problems and achieve the object, the invention according to claim 1 is a first rotating body and a second rotating body opposed to the first rotating body and biased with a predetermined pressure. In a fixing device for fixing an image on a recording medium by passing the recording medium between a pair of rotating bodies, a heating source for heating the first rotating body, and a temperature of the first rotating body are set. According to the information of the first temperature detection unit to detect, the first speed detection unit to detect the speed of the first rotating body, and the speed detection unit to detect the speed of the first rotating body, And a control unit that calculates the heating amount of the heating source by PID control and controls the heating amount of the heating source based on the calculated heating amount.

  According to the first aspect of the present invention, not only the on / off of the heating source is controlled based on the current detected temperature by the first temperature detecting unit, but also based on the past detected temperature and the speed of the first rotating body, By calculating the heating amount of the heating source and controlling the heating amount of the heating source so as to be the calculated heating amount, the temperature of the first rotating body is precisely determined in consideration of the temperature fluctuation due to the operation of the belt. It becomes possible to control.

  The invention according to claim 2 further includes a second speed detection unit that detects a speed of the first rotating body, and the control unit is configured according to information of the second speed detection unit. The heating amount of the heating source is calculated, and the heating amount of the heating source is controlled so as to be the calculated heating amount.

  According to the second aspect of the invention, in the first aspect, not only the on / off of the heating source is controlled based on the temperature detected by the first temperature detection unit and the speed of the fixing belt 10, but also the second speed detection unit. The heating amount of the heating source is calculated on the basis of the speed information obtained by controlling the heating amount of the heating source so as to be the calculated heating amount, that is, the temperature of the second rotating body, that is, the first and second rotations. In consideration of heat transfer between the bodies, the temperature of the first rotating body can be precisely controlled.

  The invention according to claim 3 further includes a second heating source for heating the second rotating body, and the control unit further includes the second heating source according to information of the second speed detection unit. The second heat source is PID-controlled.

  According to the invention of claim 3, in claim 2, the temperature of the second rotating body can be controlled by controlling the second heating source. Thereby, the heat transfer between the first and second rotating bodies can be controlled, and as a result, the temperature of the first rotating body can be precisely controlled.

  The fixing device according to the present invention (Claim 1) not only controls on / off of the heating source based on the current temperature detected by the first temperature detector, but also detects the past detected temperature and the speed of the first rotating body. Based on the above, the heating amount of the heating source is calculated, and the heating amount of the heating source is controlled so as to be the calculated heating amount. The effect is that it can be precisely controlled.

  Further, the fixing device according to the present invention (Claim 2) is not only based on the temperature detected by the first temperature detection unit and the speed of the fixing belt 10 but also on / off of the heating source. In order to calculate the heating amount of the heating source based on the speed information by the speed detecting unit 2 and to control the heating amount of the heating source so as to be the calculated heating amount, the temperature of the second rotating body, that is, the first Considering the heat transfer between the second rotating bodies, the temperature of the first rotating body can be precisely controlled.

  The fixing device according to the present invention (Claim 3) can control the temperature of the second rotating body in Claim 2 by controlling the second heating source. Thereby, the heat transfer between the first and second rotating bodies is controlled, and as a result, the temperature of the first rotating body can be precisely controlled.

  Exemplary embodiments of a fixing device according to the present invention will be explained below in detail with reference to the accompanying drawings.

(Embodiment)
According to the present invention, in a fixing device including a pair of rotating bodies (a fixing belt and a pressure roller), the temperature of the fixing belt (heating roller) and the temperature of the pressure roller are made to follow the temperature fluctuation caused by the operation of the rotating body. Thus, precise temperature control can be realized. Hereinafter, a specific example will be described.

  FIG. 1 is a block diagram showing a configuration example of a fixing device according to an embodiment of the present invention. In the figure, reference numeral 10 is a fixing belt as a first rotating body, reference numeral 11 is a fixing roller, reference numeral 12 is a heating roller, reference numeral 13 is a pressure roller, reference numerals 14 to 16 are halogen heaters, reference numeral 17 is a pressure thermistor, reference numeral Reference numeral 18 denotes a heating thermistor, reference numeral 20 denotes a PSU (power supply unit), reference numerals 21 and 22 denote encoders, reference numeral 31 denotes an I / O control board, and reference numeral 30 denotes a system control board.

  That is, the heating roller 12 and the fixing roller 11 are wound around an endless fixing belt. Further, the pressure roller 13 that is a second rotating body arranged to face the fixing roller 11, the heating thermistor 18 that detects the surface temperature of the heating roller 12, and the surface temperature of the pressure roller 13 are detected. A pressure thermistor 17 for detecting, an encoder 21 for detecting the speed of the fixing belt 10, and an encoder 22 for detecting the speed of the pressure roller 13 are provided. With this configuration, the recording paper to which the toner is attached passes between the fixing roller 11 and the pressure roller 13 so that the toner is fixed on the recording paper by the action of heat and pressure.

  FIG. 2 is a block diagram showing the configuration of the control system of the image forming apparatus (digital copying machine) in which the fixing device according to the embodiment of the present invention is mounted. In the figure, numeral 30 is a system control board, numeral 31 is an I / O control board, numeral 32 is a reading control board, numeral 33 is an operation / display unit, numeral 34 is a writing control board, numeral 35 is T (toner density). A sensor, reference numeral 36 denotes various image forming I / Os, and reference numeral 37 denotes a high voltage power source.

  The read control board 32 is a main operation for generating a CCD for reading document information and its timing, and transfers the read output to the system control board 30 as a digital signal. The system control board 30 includes a CPU, a ROM, a RAM, a nonvolatile RAM, and a calendar function chip, and controls the timing of the entire system, input / output control of the operation / display unit 33, and other application (FAX, printer, scanner) units (not configured). Control of the entire system, such as I / F (interface) and operation control with the image), image processing (magnification, filter, gamma correction, etc.) of image information data, and storage / accumulation control of image information data using an image memory I do. The writing control plate 34 includes an LD (laser diode) for exposure and a driving unit thereof, and performs writing work based on image data from the system control plate 30. The I / O control board 31 is a collection part of various signals of the entire system (scanner unit, printer unit), input signals of actuators, etc., output signals of motors, solenoids, clutches, high voltage power supplies, etc. The thermistor output is input to an ADC (AD converter), and the system control unit performs various controls based on the I / O data. Also included are paper presence / absence information on the paper feed tray and manual feed tray, size information, and a registration sensor for transferring the transfer paper. The operation / display unit 33 includes a display unit using key inputs for setting various modes, an LED, an LCD, a touch panel, and the like, and is controlled by the system control board 30.

  A unit related to driving of the fixing heater will be described with reference to a block diagram shown in FIG. Here, a case where halogen heaters 14, 15, and 16 are used as a heat source will be described as an example. On the PSU 20, a circuit for generating a power source and a circuit for driving the fixing halogen heaters 14, 15, 16 are arranged. The heater drive is composed of a relay for AC power cut-off, a triac that turns ON / OFF at a specific cycle, a snubber circuit, and the like.

  The relay / triac ON / OFF processing is executed through a port of the I / O control board 31 according to a judgment of a CPU (not shown) on the system control board 30. Each fixing heater (halogen heater) can be driven independently (ON / OFF) by each triac. The heating roller 12 includes a central heater whose light distribution is close to the center and an end heater close to the end, and the pressure roller 13 includes a single heater whose light distribution is flat. To do.

  Next, a control example of the fixing device configured as described above will be described. In order to fix the toner on the recording paper, it is necessary to maintain the temperature of the fixing nip portion (the contact portion between the fixing roller 11 and the pressure roller 13) at a temperature necessary for toner fixing. In order to keep the temperature of the fixing nip portion optimum, the target temperatures T of the heating roller 12 and the pressure roller 13 are set in advance. The belt-type fixing device of FIG. 1 has temperature detection elements not only on the heating roller 12 side but also on the pressure roller 13 side. In this example, a thermistor is used as the temperature detection element.

  In the block diagram shown in FIG. 4, the following arithmetic expressions for controlling PID (P: Proportional, I: Integral, D: Differential) are prepared in advance (including each constant). The lighting control of the heating roller heater (halogen heater 15) is performed from the temperature detected by the heating thermistor 18 in consideration of the speed information detected by the encoder 21. This PID calculation is performed by the CPU 25 in the system control unit 30.

PID1 = [(KPI × (Buff1 + Buff0) + KD1 × (2 × Buff1−Buff0−Buff2) + KI1 × (Target−Buff0)] × KS1 × S1
here,
[1] KP1 = proportional constant for PID calculation
[2] KT1 = integration constant for PID calculation
[3] KD1 = differential constant of PID calculation
[4] Buff0 = current fixing heater temperature
[5] Buff1 = previous fixing heater temperature
[6] Buff2 = previous previous fixing heater temperature
[7] Target = target fixing temperature
[8] S1 = Fixing belt operating speed
[9] KS1 = speed constant 1
It is.

  In the above equation, KP1, KI1, and KD1 are proportional, integral, and differential constants of each PID, Buff0, Buff1, and Buff2 are temperatures detected by the respective time-series heating thermistors 18, Target is a target temperature, and PID1 is Indicates the operation amount.

  The specific operation is as follows. The temperature of the heating roller 12 is detected by the heating thermistor 18 at a predetermined control cycle, for example, every second. The operation amount is calculated by the above PID calculation formula from the difference between the current temperature of the heating roller 12 and the target temperature 2 seconds before and 1 second ago. Further, the operation amount is corrected based on the current speed, and the heater is controlled with the operation amount for a control period (1 second).

  In FIG. 4, the PID arithmetic expression is set in this way, but is not limited to this expression. Naturally, a plurality of weighting means for calculating the difference for Buff 0 to 2 and correcting with the operating speed S1 of the encoder 21 are used. Is possible. The control cycle is also an example, and is not limited to this value.

  Next, an example in which the value of the encoder 2 is added to the elements of the PID calculation in the above will be described. FIG. 5 is a control block diagram thereof. Similar to the above, the temperature of the heating roller 12 is detected by the heating thermistor 18. The operation amount is calculated from the difference between the time-series roller temperature and the target temperature using a PID arithmetic expression. The halogen heater 15 is controlled by correcting the speed detected by the encoder 21 and the encoder 22 by the operation amount.

  In FIG. 5, the PID arithmetic expression is set in this way, but is not limited to this expression. Naturally, a plurality of means can be used for calculating the difference for Buff0 to Buff2 and for weighting correction by the speeds S1 and S2. .

  Next, an example in which a heating source (halogen heater 16) is added to the pressure roller 13 will be described. The temperature control of the heating roller 12 here is controlled by any one of the methods described above.

  The specific operation is as follows. The pressure thermistor 17 detects the temperature of the pressure roller 13 every predetermined control period, for example, every second. The operation amount is calculated by the following PID calculation formula from the difference between the current roller temperature and the target temperature 2 seconds ago and 1 second ago. Further, the operation amount is corrected based on the current speed, and the heater is controlled with the operation amount for a control period (1 second).

PID = PID1 + KS2 × S2
here,
[10] KS2 = speed constant 2
[11] S2 = the operation speed of the encoder 22.

  Although the case where one halogen heater is included in each of the heating roller 12 and the pressure roller 13 has been described, for example, two heaters are included in the heating roller 12 or the heating roller 12 and the fixing roller 14. It can also be applied to the case where a heater is built in.

  Moreover, although the example which uses a thermistor as a temperature detection part and an encoder as a speed detection part was described, of course, it is not limited to a thermistor and an encoder, and other temperature detection elements and speed detection elements can naturally be used. It is.

  Next, the control operation of the series of fixing devices described above will be described with reference to the flowcharts shown in FIGS. 6A, 6B, and 7. These controls are executed when the CPU 25 of the system control unit 30 controls the PUS 20 via the I / O control board 31.

  First, in FIG. 6A, the current (current) temperature is detected from the heating thermistor 18 of the heating roller 12 (step S11), the operation amount is calculated from the previous and previous values, the current value, and the target temperature, and the speed is further increased. Correction (PID1) is executed (step S12). Subsequently, lighting control of the heater 1 (halogen heater 15) is executed in accordance with the operation amount (step S13).

  6B, the current (current) temperature is detected from the pressure thermistor 17 of the pressure roller 13 (step S21), the operation amount is calculated from the previous and previous values, the current value, and the target temperature, and the speed is further increased. Correction (PID1) is executed (step S22). Subsequently, the lighting control of the heater 2 (halogen heater 16) is executed according to the operation amount (step S23).

  In FIG. 7, the current (current) temperature is detected from the heating thermistor 18 of the heating roller 12 (step S31), the operation amount is calculated from the previous and previous values, the current value and the target temperature, and speed correction (PID1) is performed. Is executed (step S32). Subsequently, correction (PID) based on the speed of the pressure roller 13 is performed (step S33), and lighting control of the heater 1 (halogen heater 15) is executed according to the operation amount (step S34).

  Thus, according to the embodiment described above, not only the on / off of the heating source (halogen heater 15) is controlled based on the current detected temperature by the first temperature detection unit (heating thermistor 18), Based on the past detected temperature and the speed of the fixing belt 10, the heating amount of the heating source (halogen heater 15) is calculated, and the heating amount of the heating source is controlled so as to be the calculated heating amount. Thereby, the temperature of the first rotating body (fixing belt 10) can be precisely controlled in consideration of temperature fluctuations due to the operation of the belt.

  Further, based on the temperature detected by the first temperature detection unit (heating thermistor 18) and the speed of the fixing belt 10, not only the on / off of the heating source (halogen heater 15) is controlled, but also the second speed detection unit (pressurization). Based on the speed information by the thermistor 17), the heating amount of the heating source (halogen heater 16) is calculated, and the heating amount of the heating source (halogen heater 16) is controlled so as to be the calculated heating amount. Accordingly, the temperature of the second rotating body (pressure roller 13), that is, the heat transfer between the first and second rotating bodies is taken into consideration, and the temperature of the first rotating body (fixing belt 10) is made precise. Can be controlled.

  Moreover, the temperature of the second rotating body (pressure roller 13) can be controlled by controlling the second heating source (halogen heater 16). Thereby, the heat transfer between the first and second rotating bodies can be controlled, and as a result, the temperature of the first rotating body (fixing belt 10) can be precisely controlled.

  As described above, the fixing device according to the present invention is useful for a fixing device mounted on an image forming apparatus such as a copying machine, a printer, and a facsimile machine. In particular, the heater lighting control of a heating roller and a pressure roller is controlled. It is suitable for an image forming apparatus using a fixing device controlled by the values of the roller surface temperature and traveling speed.

1 is a block diagram illustrating a configuration example of a fixing device according to an embodiment of the present invention. 1 is a block diagram illustrating a configuration of a control system of an image forming apparatus (digital copying machine) on which a fixing device according to an embodiment of the present invention is mounted. FIG. 3 is a block diagram illustrating a unit configuration related to driving of a fixing heater. FIG. 6 is a block diagram illustrating a control operation 1 (PID1 calculation) of the fixing device according to the embodiment of the present invention. It is a block diagram which shows the control operation 2 (PID calculation) of the fixing device concerning embodiment of this invention. 5 is a flowchart showing a control operation of a heater of the fixing device according to the embodiment of the present invention. 6 is a flowchart showing a control operation of a pressure heater of the fixing device according to the embodiment of the present invention. 6 is a flowchart showing a control operation of a heater and a pressure heater of the fixing device according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fixing belt 11 Fixing roller 12 Heating roller 13 Pressure roller 14, 15, 16 Halogen heater 17 Pressure thermistor 18 Heating thermistor 20 PSU
21, 22 Encoder 25 CPU
30 System control board 31 I / O control board

Claims (3)

By passing the recording medium between a pair of rotating bodies composed of a first rotating body and a second rotating body opposed to the first rotating body and biased with a predetermined pressure, an image is recorded on the recording medium. In the fixing device for fixing,
A heating source for heating the first rotating body;
A first temperature detector for detecting the temperature of the first rotating body;
A first speed detector for detecting the speed of the first rotating body;
According to the information of the first speed detection unit, the heating amount of the heating source is calculated by PID control, and the heating unit of the heating source is controlled based on the calculated heating amount;
A fixing device comprising: And a second speed detector for detecting the speed of the first rotating body,
The control unit calculates a heating amount of the heating source according to information of the second speed detection unit that detects a speed of the second rotating body, and controls the heating source so as to be the calculated heating amount. The fixing device according to claim 1, wherein the heating amount is controlled. And a second heating source for heating the second rotating body,
The fixing device according to claim 2, wherein the control unit further performs PID control of the second heating source in accordance with information of the second speed detection unit.

Images