JP2006195294A - Image forming apparatus and image fixing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that has a fixing device capable of smoothly rising a fixing temperature up to a warmup completion temperature by detecting the voltage of a commercial power source and by switching the control coefficient of PID control based on the detected voltage of the commercial power source. <P>SOLUTION: The circuit block includes: a fixing heater relay control section 11 that controls power source supply to a fixing heater 15 such that power is supplied when a power source is ON and it is turned OFF when the fixing heater 15 becomes abnormal; a zero cross detecting section 12 that detects the zero cross of an AC voltage and uses a zero cross signal as a reference for the timing of turning ON/OFF the heater; a fixing heater control section 13 that controls supply of power to the fixing heater by using a triac in response to a heater control signal; an AC voltage detecting section 14 converting from an AC voltage to a DC voltage so that a commercial voltage is detected on the side of a control substrate by a transformer; and a DC power source 18 for supplying the DC voltage to each part via the control substrate 8. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus and an image fixing method, and more particularly to a control method of a fixing heater for transferring and fixing a toner image onto a recording sheet.

Conventionally, when power is supplied to a fixing heater used in an image forming apparatus, the temperature of the fixing unit is monitored by a thermistor or the like, and the temperature is controlled by controlling the energization time per unit time and the duty of the non-energization time. Yes. As the temperature control method, a method is used in which the energization time per unit time and the duty of the non-energization time are determined by PID (Proportional Integration and Differential) control based on the target temperature and the past temperature history. However, in this control method, since the temperature control is performed under the same conditions even if the fixing heaters and power supply voltages having different resistance values are different for each user, the AC input voltage of the commercial power supply is above the rating. However, the warm-up end time should be short, but it takes longer time than the rated input voltage.
As a conventional technique, Patent Document 1 discloses a heater power supply unit that supplies power to a fixing heater as a heater power source by controlling on / off of power from an input external power source, and an external power source that is detected by an input voltage detection unit. Input voltage monitoring means for detecting whether or not the input voltage is less than or equal to a predetermined upper limit voltage value, and when the input voltage monitoring means detects that the input voltage of the external power source is greater than or equal to a predetermined upper limit voltage value, An image recording apparatus including an abnormal voltage countermeasure unit that stops power supply from the heater power supply unit to the fixing heater and prohibits the operation of the plotter is disclosed.
Further, Patent Document 2 detects the pulse width tw of the zero-cross signal, calculates the time at which the pulse width is in the center (tw / 2), and calculates the time from the rising edge time at which the zero-cross signal is turned on (pulse). An image forming apparatus is disclosed in which a phase is controlled by shifting a phase by α and β by applying a trigger at a timing of a delay time of width / 2).
JP 2000-29348 A JP-A-10-186908

However, the prior art disclosed in Patent Document 1 stops power supply from the heater power supply means to the fixing heater when it detects that the input voltage of the external power supply is equal to or higher than a predetermined upper limit voltage value. Therefore, there is a problem that the allowable range of the input voltage fluctuation is narrow.
The prior art disclosed in Patent Document 2 is an invention that makes the zero cross point accurate, and the shift of the zero cross point with respect to the voltage fluctuation is reduced, but the fixing temperature control by the voltage fluctuation is not mentioned.
In view of such problems, the present invention can smoothly raise the fixing temperature to the warm-up end temperature by detecting the voltage of the commercial power supply and switching the control coefficient in the PID control based on the detected commercial power supply voltage. An object of the present invention is to provide an image forming apparatus provided with a fixing device that can be used.

In order to solve this problem, the present invention provides an image forming apparatus in which a toner image is transferred to a recording paper to form a visible image, and the visible image is fixed to the recording paper by a fixing heater. Temperature control means for controlling the fixing temperature of the fixing heater to a constant temperature, voltage detection means for detecting the voltage of a commercial power source supplied to the fixing heater, and temperature for detecting the temperature of the fixing portion heated by the fixing heater Detecting means, and the temperature control means is a PID control as means for determining a ratio between the energizing time and the non-energizing time per unit time based on the temperature result detected by the temperature detecting means. The voltage detection means detects the voltage of the commercial power supply, and controls to switch the control coefficient of the PID control based on the result of the detection voltage. To.
When a fixing heater is used for the fixing unit, temperature control of the fixing unit is performed by detecting the temperature of the fixing unit with a thermistor or the like and controlling with a feedback loop. Further, when PID control is used as a means for determining the ratio between the energizing time and the non-energizing time per unit time based on the temperature result detected by the temperature detecting means, the fixing heater is determined by the control coefficient. The ratio of the energization time to the non-energization time can be changed. In the present invention, the control coefficient for PID control is switched based on the voltage of the commercial power supply.
According to a second aspect of the present invention, the timing for changing the control coefficient is a warm-up time when the power is turned on.
When the power is turned on, the fixing temperature is generally low. Therefore, when the power is turned on, warm-up is performed to turn on the fixing heater until a predetermined fixing temperature is reached. Since this warm-up takes a relatively long time, the control coefficient is changed using this time.

According to a third aspect of the present invention, the timing for changing the control coefficient is a warm-up time for returning from the low power mode or the energy saving mode.
When the image forming operation is not performed for a predetermined time in the normal mode, the mode is shifted to the low power mode or the energy saving mode. At this time, the fixing heater is turned off. When a command for starting an image forming operation (for example, document insertion) is issued, the fixing heater is turned on and warmed up in order to return from the low power mode or the energy saving mode to the normal mode. Since this warm-up is relatively long, the control coefficient is changed using this time.
According to a fourth aspect of the present invention, the timing for changing the control coefficient is a warm-up time when shifting from the standby temperature to the image formable temperature.
When not in the low power mode or the energy saving mode, there is a standby temperature mode in which the temperature of the fixing device is lowered when an image forming operation does not occur for a predetermined time in order to save energy even in the normal mode. The present invention changes the control coefficient at the time of warm-up when an image forming operation occurs from this standby temperature mode and the temperature shifts to an image formable temperature.
According to a fifth aspect of the present invention, in the image fixing method, a toner image is transferred to a recording paper to form a visible image, and the visible image is fixed on the recording paper by a fixing heater, and the fixing temperature of the fixing heater is controlled to a constant temperature. A temperature control step, a voltage detection step for detecting a voltage of a commercial power source supplied to the fixing heater, and a temperature detection step for detecting a temperature of the fixing unit heated by the fixing heater, the temperature control step In the case of using PID control as means for determining the ratio of the energization time to the fixing heater per unit time and the non-energization time based on the temperature result detected in the temperature detection step, the voltage detection step The voltage of the commercial power supply is detected, and the control coefficient of the PID control is switched based on the result of the detected voltage.
The present invention has the same effect as that of the first aspect.

According to the first and fifth aspects of the invention, in the PID control in which the ratio of the energization time to the non-energization time to the fixing heater can be changed by the control coefficient, the control coefficient is switched based on the voltage of the commercial power supply. Even if the voltage of the commercial power source fluctuates, the fixing temperature can be controlled smoothly.
Further, in claim 2, since the control coefficient is changed at the time of warm-up when the power is turned on, the change of the control coefficient is completed before the transition from the power on to the normal mode, and the fixing temperature control is immediately performed for the voltage fluctuation. Can respond.
Further, in claim 3, since the control coefficient is changed at the time of warm-up returning from the low power mode or the energy saving mode, the change of the control coefficient is completed after returning from the low power mode or the energy saving mode to shifting to the normal mode. Thus, the fixing temperature control can be immediately responded to the voltage fluctuation.
According to the fourth aspect of the present invention, since the control coefficient is changed when the standby temperature is shifted to the image formable temperature, the change of the control coefficient is completed before the transition from the standby temperature to the image formable temperature, and the voltage fluctuation is immediately caused. On the other hand, it is possible to cope with fixing temperature control.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .
FIG. 1 is a block diagram showing an example of a printer apparatus according to an embodiment of the present invention. The printer apparatus 100 includes photosensitive drums for each color and a toner supply unit. The image forming unit 1 transfers an image on the photosensitive drum onto a recording paper, and a fixing unit 2 fixes the image transferred onto the transfer paper. An optical writing unit 3 for forming an image on the photosensitive drum by controlling a portion where the toner is applied to the photosensitive drum by irradiating the photosensitive drum with a laser diode and a portion where the toner is not attached to the photosensitive drum; The operator stores the operation unit 4 that is a part for setting the printer state, the ROM 5 that stores programs and fixed parameters for controlling the printer apparatus 100, and the initial settings of the color printer. The RAM 6 is backed up by a battery, and is connected to the host via a LAN or the like. A communication I / F7 for controlling the input and output data etc., also includes portions a and CPU for controlling the printer device configured to include a controller 8 that controls each unit through a bus 9, a. Note that the image forming operation of the printer apparatus 100 is the same as that of a known printer apparatus, and a description thereof will be omitted.
FIG. 2 is a circuit block diagram for controlling the fixing heater of the fixing unit 2 of the present invention. The same components will be described with the same reference numerals. This circuit block is a part that controls the supply of power to the fixing heater 15, and is energized when the power is turned on. The fixing heater is controlled to be turned off when the fixing heater 15 becomes abnormal. Relay controller 11 detects zero cross of AC voltage, zero cross signal is used as reference for timing of heater ON / OFF, and cross heater is used to control energization of fixing heater using heater control signal The fixing heater control unit 13, the AC voltage detection unit 14 that converts the AC voltage into the DC voltage so that the commercial voltage can be detected on the control board side by the transformer, and the DC voltage to each part via the control board 8. And a DC power supply unit 18 for supplying power.

Next, the control operation of the fixing unit 2 will be described with reference to FIG. When the power is turned on, the commercial power source 17 is supplied from the commercial power source 17 to the DC power source unit 18 to convert the AC voltage into a predetermined DC voltage and supply it to each unit. As a result, the control board (controller) 8 is activated, and the AC voltage is converted into a DC voltage level by the AC voltage detector 14 and input as the AC voltage detection voltage 14a. The controller 8 detects the level, selects a control coefficient corresponding to the level, determines the duty of the fixing heater 15, and performs PID control (details will be described later). Further, the controller 8 outputs a relay control signal 11b to turn on the relay 11a in the fixing heater relay control unit 11. Thereby, the commercial power source 17 is supplied to the fixing heater 15 through the contact of the relay 11a. Since the other end of the fixing heater 15 is connected to the fixing heater control unit 13, the controller 8 outputs a fixing heater control signal 13 a based on the zero cross detection signal 12 a detected by the zero cross detection unit 12 to control the fixing heater. The fixing heater 15 is turned on / off by controlling the section 13.
When the fixing heater 15 is used for the fixing unit 2, the temperature control of the fixing unit 2 is controlled by a feedback loop by detecting the temperature of the fixing unit 2 with a thermistor or the like. Further, when PID control is used as means for determining the ratio of the energization time to the fixing heater 15 per unit time and the non-energization time based on the temperature result detected by a thermistor or the like, the fixing heater is determined by the control coefficient. The ratio of the energization time to 15 and the non-energization time can be changed. In the present invention, this control coefficient is switched based on the voltage of the commercial power supply 17.

Here, PID control will be described. PID control is used to suppress the temperature ripple of the fixing heater 15 and to eliminate the temperature overshoot of the fixing heater. The duty of the energization time per unit time to the fixing heater 15 is controlled by PID control. Formula (1) is used as a duty calculation formula by PID control. Duty to be set: MVn is
MVn = MV (n−1) + ΔMV (1)
Set as
However,
MVn: current duty MV (n−1): previous duty ΔMV: a value calculated by the PID calculation formula based on the temperature history. An example is shown in Formula (2).
ΔMV = KP * (Buff1−Buff0) + KDM * (2 * Buff1−Buff0−Buff2) / KDD + KIM * (Target−Buff0) / KID (2)
KP: PID operation proportional constant KIM: PID operation integration constant numerator KID: PID operation integration constant denominator KDM: PID operation differential constant numerator KDD: PID operation differential constant denominator Buff0: current fixing heater temperature Buff1: Previous fixing heater temperature Buff2: Previous previous fixing heater temperature Target: Target fixing temperature KP, KIM, KID, KDM, KDD (hereinafter referred to as PID coefficient) are rated from the input lower limit voltage according to the detected value of the AC voltage. The PID coefficient is stored as the PID coefficient when the temperature of the fixing heater is raised from the power-on to the voltage to the warm-up end temperature, from the energy saving or low power mode to the warm-up end temperature, and from the standby state to the printable temperature. Similarly, the PID is used when the temperature of the fixing heater is increased from the power ON to the warm-up end temperature from the rated voltage to the input upper limit voltage, the energy-saving or low-power mode to the warm-up end temperature, and the standby to printable temperature. Retained as a coefficient.

FIG. 3 is a flowchart for explaining a control coefficient switching method in the PID control of the present invention. When an energization start command is issued to the fixing heater (S1), the AC voltage detection voltage 14a is detected to detect the AC voltage (S2). As a result, it is determined whether or not the AC voltage is equal to or lower than the rated voltage (S3). If the AC voltage is equal to or lower than the rated voltage (YES route in S3), it is further determined whether or not the apparatus is turned on (S4). ), If the power is ON (YES route in S4), a control coefficient with the power ON and the AC voltage below the rated voltage is selected (S5). If the power is OFF in step S4 (NO route in S4), it is determined whether or not it is in low power or energy saving mode (S6). If it is in low power or energy saving mode (YES route in S6). Then, the control coefficient is selected in the low power or energy saving mode and the AC voltage is equal to or lower than the rated voltage (S7). If it is not the low power or energy saving mode in step S6 (NO route in S6), the control coefficient is selected in the standby mode and the AC voltage is equal to or lower than the rated voltage (S8).
On the other hand, if the voltage is equal to or higher than the rated voltage in step S3 (NO route in S3), it is further determined whether or not the apparatus is powered on (S9). If the power source is ON (YES route in S9). Then, a control coefficient with the power ON and the AC voltage equal to or higher than the rated voltage is selected (S10). If the power is OFF in step S9 (NO route in S9), it is determined whether or not it is in a low power or energy saving mode (S11), and if it is in a low power or energy saving mode (YES route in S11). Then, the control coefficient is selected in the low power or energy saving mode and the AC voltage is equal to or higher than the rated voltage (S12). If it is not the low power or energy saving mode in step S11 (NO route in S11), the control coefficient is selected in the standby mode and the AC voltage is equal to or higher than the rated voltage (S13).

  Thus, by determining what the state of the apparatus is, the control coefficient can be switched to an appropriate value. As a timing for switching the control coefficient, when the power is turned on, the fixing temperature is generally low. Therefore, when the power is turned on, warm-up is performed to turn on the fixing heater until a predetermined fixing temperature is reached. Since this warm-up takes a relatively long time, the control coefficient is switched using this time. When the image forming operation is not performed for a predetermined time in the normal mode, the mode is shifted to the low power mode or the energy saving mode. At this time, the fixing heater is turned off. When a command for starting an image forming operation (for example, document insertion or the like) is issued, the fixing heater is turned on to warm up in order to return from the low power mode or the energy saving mode to the normal mode. Since this warm-up takes a relatively long time, the control coefficient is switched using this time. Further, when not in the low power mode or the energy saving mode, in order to save energy even in the normal mode, there is a standby temperature mode in which the temperature of the fixing device is lowered when the image forming operation does not occur for a predetermined time. In the present invention, the control coefficient is switched at the time of warm-up when an image forming operation occurs from this standby temperature mode to shift to an image formable temperature.

1 is a block configuration diagram illustrating an example of a printer apparatus according to an embodiment of the present invention. The circuit block diagram which controls the fixing heater of the fixing part 2 of this invention. The flowchart explaining the switching method of the control coefficient in the PID control of this invention.

Explanation of symbols

8 control board, 11 fixing heater relay control section, 12 zero cross detection section, 13 fixing heater control section, 14 AC voltage detection section, 15 fixing heater, 18 DC power supply section

Claims (5)

In an image forming apparatus in which a toner image is transferred to a recording paper to form a visible image, and the visible image is fixed on the recording paper by a fixing heater.
Temperature control means for controlling the fixing temperature of the fixing heater to a constant temperature, voltage detection means for detecting the voltage of a commercial power source supplied to the fixing heater, and temperature for detecting the temperature of the fixing portion heated by the fixing heater Detecting means,
When the temperature control means uses PID control as means for determining the ratio of the energization time to the fixing heater per unit time and the non-energization time based on the temperature result detected by the temperature detection means, An image forming apparatus, characterized in that a voltage of the commercial power source is detected by a detecting unit, and control is performed so as to switch a control coefficient of the PID control based on a result of the detected voltage.   The image forming apparatus according to claim 1, wherein the timing for changing the control coefficient is a warm-up time when power is turned on.   The image forming apparatus according to claim 1, wherein the timing for changing the control coefficient is a warm-up for returning from the low power mode or the energy saving mode.   The image forming apparatus according to claim 1, wherein the timing for changing the control coefficient is a warm-up time when the temperature is shifted from the standby temperature to the image-formable temperature. In an image fixing method in which a toner image is transferred to a recording paper to form a visible image, and the visible image is fixed on the recording paper by a fixing heater.
A temperature control step for controlling the fixing temperature of the fixing heater to a constant temperature; a voltage detection step for detecting a voltage of a commercial power supply supplied to the fixing heater; and a temperature for detecting the temperature of the fixing portion heated by the fixing heater. A detection step;
In the temperature control step, when PID control is used as a means for determining a ratio between the energization time and the non-energization time per unit time based on the temperature result detected in the temperature detection step,
An image fixing method, wherein the voltage of the commercial power source is detected by the voltage detecting step, and the control coefficient of the PID control is switched based on the result of the detected voltage.

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