JP2009070627A - Heater controller and heater control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heater controller and a heater control method capable of aiming at simplification of a structure and reduction of a processing load and restraining generation of a flicker. <P>SOLUTION: When temperature of a fixing unit 10 is less than a predetermined temperature, a CPU 35 changes turning on and off of electricity to a heater at every zero cross point by switching an HON signal at an ON state or an OFF state according to three conditions. The first condition is that first and second heater-on periods are made as one zero cross period, the second condition is that a heater-off period is made as one zero cross period to three zero cross periods, and the third condition is that a third or later heater-on period is one of one zero cross period and two zero cross periods. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heater control device and a heater control method for controlling on / off of energization to a heater.

  In a device that incorporates a large load such as a heater that operates intermittently and whose current consumption greatly fluctuates during operation, for example, a facsimile machine that includes a fixing unit including a heater that consumes a relatively large current, such as a halogen lamp, A large inrush current occurs when the lamp is turned on. When the facsimile machine is connected to a commercial power supply, the inrush current generated when the halogen lamp is lit causes a voltage drop in the commercial power supply, which causes a flicker phenomenon that adversely affects other equipment connected to the common commercial power supply. . For example, when another device connected to a common commercial power source is a fluorescent lamp, the flickering of the fluorescent lamp occurs as a flicker phenomenon.

  As a first conventional technique for suppressing the occurrence of a flicker phenomenon, there is a fixing control device that controls a fixing device having a plurality of heaters and performing zero-cross lighting by triac. The fixing control device sequentially turns on the heaters one by one when the fixing heaters are turned on. Furthermore, with respect to one heater, when the frequency of the power supply used is x, a clock with a frequency of 2x / N (N is a positive integer) and an ON / OFF duty of 1 / N or (N-1) / N Turn on the light intermittently for a specified time. After the stipulated time is over, normal lighting is performed, and then the next heater is lit.

  For example, in the case of N = 3, if the time from the time when the AC voltage becomes 0 volt to the time when it next becomes 0 volt, that is, the half cycle of the AC is the zero cross cycle, the heater is turned on and off is ON, second and third zero-cross periods are OFF, fourth zero-cross period is ON, fifth and sixth zero-cross periods are OFF, seventh zero-cross period is ON, eighth and ninth zero-cross periods are OFF, and first After 10 zero-cross periods, it is normally lit, that is, turned on. A signal having a frequency of 2x / N is supplied by a dedicated oscillation circuit (see, for example, Patent Document 1).

  FIG. 7 is a diagram showing a configuration of the heater control device 9 of the second conventional technique. FIG. 8 is a time chart showing on / off control operation of energization of the heater by the heater control device 9. The heater control device 9 includes a fixing unit 70, a power supply unit 80, and a control board unit 90. The fixing unit 70 includes a heater 71 and a thermistor 72. The power supply unit 80 includes an AC power supply connection plug 81, a zero cross detection circuit 82, a triac 83, and a logical product (AND) circuit 84. The control board unit 90 includes an A / D (Analog-to-Digital) unit 91, a HON signal output unit 92, a CPU (Central Processing Unit) 95, and a zero-cross input unit 96.

  In the fixing unit 70, the heater 71 is turned on when AC power is supplied from a commercial power source to which the AC power supply connection plug 81 is connected, and raises the temperature of the fixing unit 70. The thermistor 72 detects the temperature of the fixing unit 70 and sends temperature information representing the detected temperature to the CPU 95 via the A / D unit 91 of the control board unit 90.

  In the power supply unit 80, the zero-crossing detection circuit 82 has detected the time when the voltage of the AC power supplied from the commercial power supply through the AC power supply connection plug 81 becomes 0 volts, that is, the zero-crossing point, and has detected the zero-crossing point. Is input to the AND circuit 84 and sent to the CPU 95 via the zero cross input unit 96 of the control board unit 90 to interrupt the CPU 95. The triac 83 turns on the HON signal output from the heater-on (abbreviation: HON) signal output unit 92 according to the output of the AND circuit 84, that is, every time a pulse signal indicating the detection of the zero cross point is input ( Whether the AC power supplied from the commercial power source to which the AC power supply connection plug 81 is connected is supplied to the heater 71 according to whether it is ON) or OFF (OFF).

  In the control board unit 90, when the temperature represented by the temperature information given from the thermistor 72 is lower than the target temperature, the CPU 95 controls the HON signal for each interrupt from the zero cross detection circuit 82 via the zero cross input unit 96. Start the soft timer. When an interrupt by the soft timer occurs, the CPU 95 turns the HON signal ON or OFF as shown in the time chart of FIG. The HON signal is output by the HON signal output unit 92 and input to the AND circuit 84.

  A zero-cross interrupt process is performed for each interrupt from the zero-cross detection circuit 82 via the zero-cross input unit 96. In the zero cross interrupt process, a soft timer of time Tc is started. When the time Tc elapses due to the soft timer, an interrupt is generated by the soft timer, and the HON signal control process is performed. In the HON signal control process, control is performed to turn the HON signal ON or OFF.

  For the flicker phenomenon, an international standard has been established by the International Electrotechnical Commission (IEC), and it is necessary to satisfy the standard by this international standard. For example, the heater 71 is continuously turned on after being switched on, off, off, on, off, off for each zero cross point.

  To achieve this, in the HON signal control process, the HON signal is turned ON at the first interrupt, the HON signal is turned OFF at the second and third interrupts, and the HON is turned on at the fourth interrupt. The signal is turned ON, the HON signal is turned OFF at the fifth and sixth interruptions, and the temperature indicated by the temperature information of the fixing unit 70 given from the thermistor 72 reaches the target temperature at the seventh and subsequent interruptions. In order to continuously turn on the power to the heater, the HON signal is kept ON. In the example shown in FIG. 8, the heater current flows after the second half cycle, the fifth half cycle, and the eighth half cycle of the AC voltage waveform.

Japanese Patent Application Laid-Open No. 11-52782

  In the first conventional technique, the fixing device is controlled by using a signal having a frequency of 2x / N. However, an oscillation circuit needs to be used to supply a signal having a frequency of 2x / N. There is a problem that becomes complicated.

  In the second conventional technique, the CPU is controlled to turn on / off the power to the heater. However, the CPU, that is, the computer is interrupted by a pulse signal indicating that the zero-cross point is detected. Therefore, there is a problem that the circuit configuration is complicated. In the second conventional technique, when the zero cross point is monitored by the CPU without using the interrupt circuit, it is necessary to monitor the zero cross point at a short time interval, and there is a problem that a large processing load is applied to the CPU.

  An object of the present invention is to provide a heater control device and a heater control method capable of simplifying the configuration and reducing the processing load and suppressing the occurrence of flicker.

The present invention is a zero cross detecting means for detecting a time point when the voltage of the AC power supplied from the AC power supply source having a predetermined frequency and supplied to the heater becomes 0 volts,
When the time point when the voltage becomes 0 volt is detected by the zero cross detection means, the energization to the heater is turned on / off by switching whether to supply the AC power supplied from the power supply source to the heater. Switching means;
Temperature detecting means for detecting the temperature of the heating object heated by the heater;
When the temperature of the heating object detected by the temperature detection means is lower than the predetermined temperature, the switching means is repeatedly turned on and off alternately for a predetermined number of times, and then the temperature detection means Control means for turning on energization of the heater by the switching means until the temperature of the heating object detected by reaches a predetermined temperature,
The control means
Heater on period in which energization of the heater is turned on, among the periods in which the switching means is repeatedly turned on and off alternately for a predetermined number of times when the half cycle of the alternating current is 1 zero cross period The first and second heater on periods are set to one zero cross period, the third and subsequent heater on periods are set to one of one zero cross period and two zero cross periods, and the heater is energized. The heater control device is characterized in that the heater-off period to be turned off is any one of 1 zero cross cycle, 2 zero cross cycle, and 3 zero cross cycle.

Further, according to the present invention, the control means provides the switching means with a heater control signal for turning on / off the power to the heater,
The switching means turns on the energization to the heater when the zero cross detection means detects the time when the voltage becomes 0 volts when the heater control signal supplied from the control means is on, and the control When the heater control signal supplied from the means is off and the time point when the voltage becomes 0 volts is detected by the zero cross detection means, the energization to the heater is turned off,
When the control means gives the heater control signal to the switching means, the maximum period in which one zero-cross period, which is the half cycle of the alternating current, varies is the maximum zero-cross period Tmax, and the minimum period in which the zero-cross period varies is the minimum zero-cross period Tmin. and when,
When the temperature of the heating object detected by the temperature detection means is lower than a predetermined temperature, the heater control signal is turned on during the first period T0 that satisfies T0 <Tmin.
During the second period T1 that satisfies 3 × Tmax−Tmin <T1 <4 × Tmin−Tmax after the first period T0 has elapsed, the heater control signal is turned off,
After the second period T1, the heater control signal is turned on during the third period T2 that satisfies 4 × Tmax−Tmin <T1 + T2 <5 × Tmin−Tmax.
The heater control signal is turned off after the third period T2 has elapsed and during the fourth period T3 that satisfies 6 × Tmax−Tmin <T1 + T2 + T3 <7 × Tmin−Tmax.
When m is an even integer of 4 or more, the heater control signal is turned on after the mth period Tm−1 has elapsed and for the (m + 1) th period Tm that satisfies Tmax <Tm <2 × Tmin. ,
When n is an odd integer of 5 or more, the heater control signal is turned off after the nth period Tn−1 has elapsed and for the (n + 1) th period Tn that satisfies Tmax <Tn <2 × Tmin. It is characterized by doing.

  Further, the present invention is characterized in that the first period T0 is determined such that a difference time between the first period T0 and the minimum zero cross period Tmin falls within a predetermined time.

Further, the present invention is a heater control method for controlling on / off of energization to a heater to which AC power is supplied from an AC power supply source having a predetermined frequency,
A temperature detection step for detecting the temperature of the heating object heated by the heater;
When the temperature of the heating object detected in the temperature detection step is less than a predetermined temperature, the heater is turned on and off alternately and repeatedly for a predetermined number of times, and then detected in the temperature detection step. A control step of turning on the power to the heater until the temperature of the heating object reaches a predetermined temperature,
In the control step, when the half cycle of the alternating current is set to 1 zero cross cycle, the heater on period in which the energization to the heater is turned on among the periods in which the energization to the heater is alternately turned on and off repeatedly for a predetermined number of times. The first and second heater on periods are set to one zero cross period, the third and subsequent heater on periods are set to one of one zero cross period and two zero cross periods, and the heater is energized. The heater control method is characterized in that the heater-off period to be turned off is any one of 1 zero cross cycle, 2 zero cross cycle, and 3 zero cross cycle.

  According to the present invention, the zero cross detection means detects the time point when the voltage of the AC power supplied from the AC power supply source of the predetermined frequency and supplied to the heater becomes 0 volts, and the switching means detects the zero cross. When the time point at which the voltage becomes 0 volt is detected by the means, energization to the heater is turned on and off by switching whether to supply the AC power supplied from the power supply source to the heater, and the temperature The temperature of the heating object heated by the heater is detected by the detection means.

  Then, when the temperature of the heating object detected by the temperature detecting means is lower than a predetermined temperature, the control means causes the switching means to repeatedly turn on and off the heater alternately and for a predetermined number of times. After that, energization of the heater is turned on by the switching means until the temperature of the heating object detected by the temperature detecting means reaches a predetermined temperature.

  Further, when the control means sets the half cycle of the alternating current to one zero-crossing period, the heater is energized during a period in which the switching means is repeatedly turned on and off alternately for a predetermined number of times. The first and second heater-on periods are set to one zero-cross period, and the third and subsequent heater-on periods are one of one zero-cross period and two zero-cross periods. The heater off period for turning off the energization of the heater is one of the 1 zero cross period, the 2 zero cross period, and the 3 zero cross period.

  Therefore, since it is possible to control on / off of the energization to the heater without using the oscillation circuit and the interrupt circuit by detecting the zero cross point, it is possible to simplify the circuit configuration and reduce the manufacturing cost of the heater control device. it can. Furthermore, since no interruption is generated in the computer at each zero cross point, and it is not necessary to monitor the zero cross point by the computer, the processing load on the computer can be reduced. Furthermore, since it is possible to control ON / OFF of the power supply to the heater at the zero cross point, the occurrence of flicker can be suppressed.

  Further, according to the present invention, in controlling on / off of energization to a heater supplied with AC power from an AC power supply source having a predetermined frequency, in the temperature detection step, the heating object heated by the heater is controlled. Detect temperature. In the control step, when the temperature of the heating object detected in the temperature detection step is lower than a predetermined temperature, the heater is turned on and off alternately and repeatedly for a predetermined number of times, and then in the temperature detection step. Energization of the heater is turned on until the detected temperature of the heating object reaches a predetermined temperature.

  Further, in the control step, when the half cycle of the alternating current is set to one zero cross cycle, the energization to the heater is turned on during a period in which the energization of the heater is alternately turned on and off repeatedly for a predetermined number of times. The heater on period, wherein the first and second heater on periods are 1 zero cross periods, and the third and subsequent heater on periods are one of 1 zero cross periods and 2 zero cross periods, The heater-off period during which energization is turned off is any one of 1 zero cross cycle, 2 zero cross cycle, and 3 zero cross cycle.

  Therefore, if the heater control method according to the present invention is applied to a computer, it is possible to control on / off of energization to the heater without using an oscillation circuit and an interrupt circuit based on detection of a zero cross point, so that the circuit configuration is simplified. Manufacturing cost can be reduced. Furthermore, since no interruption occurs in the computer and it is not necessary to monitor the zero cross point by the computer, the processing load on the computer can be reduced. Furthermore, since it is possible to control ON / OFF of the power supply to the heater at the zero cross point, the occurrence of flicker can be suppressed.

  FIG. 1 is a block diagram showing a configuration of a heater control apparatus 1 according to an embodiment of the present invention. The heater control device 1 is a device that controls on / off of energization to a heater used in, for example, a facsimile machine, a printing device, and a copying machine. The heater control method of the present invention is processed by the heater control device 1.

  The heater control device 1 includes a fixing unit 10, a power supply unit 20, and a control board unit 30. The fixing unit 10 includes a heater 11 and a thermistor 12. The heater 11 is constituted by a halogen lamp, for example, and generates heat by the power supplied from the power supply unit 20. The thermistor 12 that is a temperature detecting means is a temperature sensor that detects the surface temperature of a heating object that is heated by the heater 11, for example, a heating roller (not shown) provided in the fixing unit 10 with the heater 11 therein. The temperature information indicating the detected temperature is sent as an analog signal to an A / D (Analog-to-Digital) unit 31 of the control board unit 30 described later.

  The power supply unit 20 includes an AC power supply connection plug 21, a zero cross detection circuit 22, a triac 23, and a logical product (AND) circuit 24. The AC power supply connection plug 21 is a plug for connecting to an AC power supply source having a frequency of 50 Hz or 60 Hz, for example, a commercial power supply. The zero-cross detection circuit 22 serving as a zero-cross detection means detects a point in time when the voltage of the AC power supplied from the commercial power source to which the AC power source connection plug 21 is connected becomes 0 volts (hereinafter sometimes referred to as “zero-cross point”). A pulse signal indicating that the zero cross point has been detected is input to the AND circuit 24.

  The triac 23 serving as switching means supplies AC power supplied from a commercial power source connected to the AC power source connection plug 21 to the heater 11 when the output of the AND circuit 24 is on. The AND circuit 24 serving as switching means has a HON signal, which is a heater control signal output from a heater-on (abbreviation: HON) signal output unit 32 of the control board unit 30 described later, turned on (ON), and a zero-cross detection circuit 22. When the pulse signal from is on, an on signal is output.

  The control board unit 30 includes an A / D unit 31, a HON signal output unit 32, a RAM (Random Access Memory) 33, a ROM (Read Only Memory) 34, a CPU (Central Processing Unit) 35, and a data bus 39. The A / D unit 31 converts an analog signal indicating temperature information from the thermistor 12 into a digital signal, and sends the converted digital signal to the CPU 35. The HON signal output unit 32 outputs a HON signal for controlling on / off of energization to the heater in accordance with an instruction from the CPU 35. The HON signal output from the HON signal output unit 32 is input to the AND circuit 24 of the power supply unit 20.

  The RAM 33 is composed of a readable / writable semiconductor memory, and temporarily stores data being calculated. The ROM 34 is constituted by a read-only semiconductor memory, and includes a control program for controlling the heater control device 1, a load program for loading the control program into the RAM 33, and a flicker countermeasure table 40 (see FIG. 3) described later. Remember.

  The CPU 35 that is a control means is a computer, and by executing a load program stored in the ROM 34, the control program stored in the ROM 34 is read out and stored in the RAM 33, and the control program stored in the RAM 33 is executed. The CPU 35 controls the A / D unit 31 and the HON signal output unit 32 by executing a control program stored in the RAM 33. The data bus 39 is a bus that connects the A / D unit 31, the HON signal output unit 32, the RAM 33, the ROM 34, and the CPU 35 and enables data transmission / reception.

  The heater control device 1 includes a temperature reading unit and a flicker countermeasure control unit. The temperature reading unit and the flicker countermeasure control unit are functions realized by the CPU 35 executing a control program stored in the RAM 33.

  FIG. 2 is a time chart showing the operation of the temperature reading process by the temperature reading unit included in the heater control device 1. The temperature reading unit is activated at regular time intervals Tr, for example, every 10 milliseconds (ms). The period Ts is a temperature reading process time that the temperature reading unit processes.

  The temperature reading unit reads temperature information indicating the temperature of the heating object detected by the thermistor 12 via the A / D unit 31. If the temperature indicated by the temperature information is a predetermined target temperature, for example, if the object to be heated is a heating roller, a temperature suitable for fixing, specifically, if it does not reach 190 degrees Celsius, the HON signal is turned ON, A soft timer is started to cause the flicker countermeasure control unit to perform flicker countermeasure control processing. When the temperature indicated by the temperature information reaches a predetermined target temperature, the HON signal is turned OFF. The flicker countermeasure control unit starts a process in which the time of the soft timer activated by the temperature reading unit elapses, and controls the HON signal to turn on / off the power to the heater 11.

  FIG. 3 is a diagram showing an example of the flicker countermeasure table 40 used for the flicker countermeasure control process. The flicker countermeasure table 40 stored in the ROM 33 is a table indicating the timer time for each value of the control variable flicker. The timer time is an end code indicating a period in which the HON signal is turned on or a period in which the HON signal is turned off, or the end. In the flicker countermeasure table 40 shown in FIG. 3, when the value of the control variable flicker is “0” to “5”, the first period T0 to the sixth period T5 are shown, respectively, and the control variable flicker is shown. For the value of “6”, the end code “FF” indicating the end is shown.

  The flicker countermeasure control unit switches the HON signal from ON to OFF or from OFF to ON, and then the soft timer for the flicker countermeasure control unit to perform the flicker countermeasure control processing is displayed in the flicker countermeasure table 40. Start in time. When the timer time shown in the flicker countermeasure table 40 is the end code “FF” indicating the end, the soft timer is stopped after the HON signal is switched from OFF to ON, and the flicker countermeasure control process is terminated.

  FIG. 4 is a time chart showing an on / off control operation of the heater 11 by the heater control device 1. In the temperature reading process performed by the temperature reading unit, if the temperature of a heating roller (not shown) provided in the fixing unit 10 does not reach a predetermined target temperature, the HON signal is turned ON and an interrupt for flicker countermeasure control processing is performed. Is started after the first period T0 has elapsed.

  When the time of the first period T0 elapses, an interrupt by the soft timer occurs, and the first flicker countermeasure control process by the flicker countermeasure control unit is performed. In the first flicker countermeasure control process, the HON signal is turned OFF, and a soft timer for generating an interrupt for the next flicker countermeasure control process after the second period T1 has elapsed is started. Thereafter, every time an interrupt is generated by the soft timer, flicker countermeasure control processing is performed, and the HON signal is alternately switched from OFF to ON or from ON to OFF, and the soft timer is started at the next timer time.

  The period in which the energization of the heater 11 is turned on is a period of one zero cross cycle from the time when the zero cross point is detected by the zero cross detection circuit 22 while the HON signal is ON. One zero cross period is a time from a zero cross point to the next zero cross point, that is, a half cycle of alternating current. In the time chart shown in FIG. 4, zero-cross points are detected in the third period T2, the fifth period T4, and the seventh period T6, and the heater 11 is in the period of one zero-cross cycle from these zero-cross points. A current flows and energization of the heater 11 is turned on.

  The period when the HON signal is ON and the period when the HON signal is OFF, for example, the first to seventh periods T0 to T6 are determined so as to satisfy the three conditions. The first condition is a heater on period in which energization to the heater 11 is turned on, and the first and second heater on periods are set to one zero cross cycle. In other words, the first and second heater-on periods are not set to be longer than the 2 zero cross period, which is a period twice as long as the 1 zero cross period. The second condition is that the heater off period during which the energization to the heater 11 is turned off is any one of a 1 zero cross period, a 2 zero cross period, and a 3 zero cross period that is three times the 1 zero cross period. The third condition is that the third and subsequent heater-on periods are any one of a 1 zero cross period and a 2 zero cross period.

  In this way, the zero cross detection circuit 22 detects a time point when the voltage of the AC power supplied from the AC power supply source having a predetermined frequency and supplied to the heater 11 becomes 0 V, and the triac 23 and the AND circuit 24 are detected. Thus, when the zero crossing detection circuit 22 detects the time when the voltage becomes 0 volts, the heater 11 is energized by switching whether to supply the AC power supplied from the power supply source to the heater 11. Is turned on and off, and the thermistor 12 detects the temperature of the heating object heated by the heater 11.

  Then, when the temperature of the heating object detected by the thermistor 12 is lower than the predetermined temperature by the CPU 35, the energization of the heater 11 is alternately turned on and off in the triac 23 and the AND circuit 24 over a predetermined number of times. After the repetition, the heater 11 is turned on by the triac 23 and the AND circuit 24 until the temperature of the heating object detected by the thermistor 12 reaches a predetermined temperature.

  Further, when the CPU 35 sets the half cycle of the alternating current to one zero cross cycle, the heater 11 is repeatedly turned on and off alternately and repeatedly for a predetermined number of times in the triac 23 and the AND circuit 24. 11 is a heater-on period in which energization to 11 is turned on, the first and second heater-on periods being one zero-cross period, and the third and subsequent heater-on periods are one of one zero-cross period and two zero-cross periods The heater off period during which the energization to the heater 11 is turned off is any one of the 1 zero cross period, the 2 zero cross period, and the 3 zero cross period.

  Therefore, since it is possible to control ON / OFF of the energization to the heater 11 without using the oscillation circuit and the interrupt circuit by detecting the zero cross point, the circuit configuration is simplified and the manufacturing cost of the heater control device 1 is reduced. be able to. Further, since no interruption occurs in the CPU 35, that is, the computer for each zero cross point, and it is not necessary to monitor the zero cross point by the computer, the processing load on the computer can be reduced. Furthermore, since it is possible to control ON / OFF of the power supply to the heater at the zero cross point, the occurrence of flicker can be suppressed.

When the one zero cross period, that is, the half period of the alternating current is T, the maximum period in which the zero cross period varies is the maximum zero cross period Tmax, and the minimum period in which the one zero cross period varies is the minimum zero cross period Tmin, the first period T0 is From the first condition described above, a value satisfying Equation (1) is determined.
T0 <Tmin (1)

  That is, the first period T0 is set to be less than the minimum zero cross cycle Tmin. In order to increase the probability of turning on the heater 11 in the first period T0, the difference between the first period T0 and the minimum zero cross period Tmin is set to a predetermined time, specifically, flicker countermeasures. The time required for processing is determined.

  Thus, the first period T0 is determined so that the time difference between the first period T0 and the minimum zero-crossing period Tmin is within a predetermined time, so that the first period T0 is supplied to the heater 11 in the first period T0. The probability of turning on the power can be increased.

The second period T1 is determined to be a value that satisfies Expression (2) from the above-described second condition.
3 * Tmax-Tmin <T1 <4 * Tmin-Tmax (2)

The third period T2 is determined to be a value that satisfies Expression (3) from the first condition and the second condition described above.
4 * Tmax-Tmin <T1 + T2 <5 * Tmin-Tmax (3)

  That is, since the first period T0 is less than the minimum zero-cross cycle Tmin, there may be a case where there is no zero-cross point in the first period T0 and the energization to the heater 11 cannot be turned on. The third period T2 is determined so that there is always a zero cross point in the third period T2.

The fourth period T3 is determined to be a value satisfying Expression (4) from the above-described second condition.
6 × Tmax−Tmin <T1 + T2 + T3 <7 × Tmin−Tmax (4)

When the variable m is an even integer greater than or equal to 4, the (m + 1) th period Tm is determined to be a value satisfying the expression (5) from the above-described third condition.
Tmax <Tm <2 × Tmin (5)

When the variable n is an odd integer of 5 or more, the (n + 1) th period Tn is determined to be a value satisfying the expression (6) from the above-described second condition.
Tmax <Tn <2 × Tmin (6)

  For example, in the case of an alternating current with a frequency of 50 Hz, the one zero cross period, that is, the half period T of the alternating current is 10 ms, and the one zero cross period varies around 5%, for example, the maximum zero cross period Tmax is 10.526 ms, and Assuming that the minimum zero-crossing period Tmin is 9.524 ms, the first to sixth periods T0 to T5 can be calculated from, for example, T0 = 9.513 ms, T1 = 22.066 ms from the above formulas (1) to (6), T2 = 10.537 ms, T3 = 21.042 ms, T4 = 10.537 ms, and T5 = 19.037 ms.

  In this way, the CPU 35 gives a HON signal for turning on and off the heater 11 to the triac 23 and the AND circuit 24, and the HON signal given from the CPU 35 by the triac 23 and the AND circuit 24 is ON. In this case, when the time point at which the voltage becomes 0 volts is detected by the zero cross detection circuit 22, the energization to the heater 11 is turned on, and when the HON signal supplied from the CPU 35 is OFF, the voltage is detected by the zero cross detection circuit 22 When the time point when the voltage becomes 0 volts is detected, the energization of the heater 11 is turned off.

  Then, when the HON signal is given to the triac 23 and the AND circuit 24 by the CPU 35, the maximum period in which the 1 zero cross period, which is a half period of alternating current, varies is the maximum zero cross period Tmax, and the minimum period in which the 1 zero cross period varies is minimized. If the temperature of the heating object detected by the thermistor 12 is lower than a predetermined temperature when the zero-cross cycle Tmin is set, the HON signal is turned ON during the first period T0 that satisfies the equation (1). .

  Further, the HON signal is turned OFF after the first period T0 has elapsed and during the second period T1 satisfying the expression (2), and after the second period T1 has elapsed, the expression (3) The HON signal is turned ON during the third period T2 that satisfies the condition, and the HON signal is turned OFF after the third period T2 has elapsed and during the fourth period T3 that satisfies the expression (4). The When m is an even integer of 4 or more, the HON signal is turned ON after the m-th period Tm−1 has elapsed and for the (m + 1) -th period Tm that satisfies Equation (5), and n Is an odd integer greater than or equal to 5, the HON signal is turned OFF after the nth period Tn−1 has elapsed and during the (n + 1) th period Tn that satisfies the above equation (6).

  Therefore, the CPU 35, that is, the computer, can control ON / OFF of the energization to the heater 11 based on the AC frequency and the asynchronous 1 zero cross period. That is, even if the zero cross point is not informed to the computer by interruption, it is possible to control the on / off of the energization to the heater 11, so that the processing load on the computer can be reduced. Furthermore, since it is possible to control ON / OFF of the power supply to the heater at the zero cross point, the occurrence of flicker can be suppressed.

  FIG. 5 is a flowchart showing a processing procedure of temperature reading processing by the temperature reading unit. When the temperature reading unit is activated at a constant time interval Tr, for example, every 10 ms, the process proceeds to step A1.

  In step A <b> 1, the temperature reading unit acquires temperature information indicating the temperature of the heating roller provided in the fixing unit 11 detected by the thermistor 12 through the A / D unit 31 within a predetermined period Ts. In step A2, it is determined whether the temperature information has been acquired n times, for example, 10 times. If it has been acquired n times, the process proceeds to step A3. If it has not been acquired n times, the temperature reading process is terminated.

  In step A3, an average value of temperatures indicated by the latest n times of temperature information among the temperature information acquired in step A1 is calculated. In step A4, the average value calculated in step A3 is stored in a variable Pc representing temperature. In Step A5, it is determined whether or not the temperature Pc is lower than the target temperature Pt. If the temperature Pc is not less than the target temperature Pt, in other words, if the temperature Pc has reached the target temperature Pt, the process proceeds to step A6. If the temperature Pc is less than the target temperature Pt, in other words, the temperature Pc is the target temperature. If Pt has not been reached, the process proceeds to step A9.

  In step A6, the soft timer is stopped. This soft timer is a timer for starting the flicker countermeasure control unit. In step A7, the HON signal is set to “0”, that is, OFF. In step A8, the control variable flicker is set to “0” and the temperature reading process is terminated.

  In step A9, the HON signal is set to “1”, that is, ON. In step A10, a soft timer for activating the flicker countermeasure control unit is activated. The time of the soft timer in step A10 is the time of the first period T0. In step A11, the control variable flicker is set to “1”, and the temperature reading process is terminated. In the flowchart shown in FIG. 5, Step A1 to Step A4 are temperature detection steps, and Step A5 to Step A11 are control steps.

  FIG. 6 is a flowchart showing a processing procedure of flicker countermeasure control processing by the flicker countermeasure control unit. When the flicker countermeasure control unit is activated by the soft timer, the process proceeds to step B1.

  In Step B1, it is determined whether or not the value of the control variable flicker is “0”. If the value of the control variable flicker is “0”, the process proceeds to step B11. If the value of the control variable flicker is not “0”, the process proceeds to step B2. In step B2, the timer time Tn corresponding to the value of the control variable flicker is acquired from the flicker countermeasure table 40 stored in the ROM 34. In Step B3, it is determined whether or not the timer time Tn acquired in Step B2 is an end code “FF”. In step B3, if the timer time Tn is the end code “FF”, the process proceeds to step B9. If the timer time Tn is not the end code “FF”, the process proceeds to step B4.

  In step B4, the soft timer is started for the timer time Tn. In step B5, it is determined whether or not the value of the control variable flicker is an odd number. In step B5, if the value of the control variable flicker is an odd number, the process proceeds to step B8, and if the value of the control variable flicker is not an odd number, in other words, if the value of the control variable flicker is an even number, step Proceed to B6. In step B6, the HON signal is set to “1”, that is, ON. In step B7, “1” is added to the control variable flicker, and the flicker countermeasure control process is terminated.

  In Step B8, the HON signal is set to “0”, that is, OFF, and the process proceeds to Step B7. In step B9, the HON signal is set to “1”, that is, ON. In step B10, the control variable flicker is set to “0”. In step B11, the soft timer is stopped and the flicker countermeasure control process is terminated. In the flowchart shown in FIG. 6, step B1 to step B11 are control steps.

  As described above, in controlling on / off of energization to the heater 11 to which AC power is supplied from an AC power supply source having a predetermined frequency, in steps A1 to A4 of the temperature reading process shown in FIG. The temperature of the heating object heated by the heater 11 is detected. In step A5 to step A11 of the temperature reading process shown in FIG. 5 and step B1 to step B11 of the flicker countermeasure control process shown in FIG. 6, detection is performed in step A1 to step A4 of the temperature reading process shown in FIG. When the temperature of the object to be heated is lower than a predetermined temperature, the heater 11 is turned on and off alternately and repeatedly for a predetermined number of times, and thereafter, steps A1 to A4 of the temperature reading process shown in FIG. The energization of the heater 11 is turned on until the temperature of the heating object detected in step 1 reaches a predetermined temperature.

  Further, in step A5 to step A11 of the temperature reading process shown in FIG. 5 and step B1 to step B11 of the flicker countermeasure control process shown in FIG. 6, when the half cycle of the alternating current is 1 zero cross cycle, the heater 11 Among the periods in which the energization of the heater is turned on and off alternately and repeatedly for a predetermined number of times, the heater on period in which the energization of the heater 11 is turned on, and the first and second heater on periods are set to 1 zero cross cycle The third and subsequent heater on periods are set to one of the 1 zero cross period and the 2 zero cross period, and the heater off period for turning off the heater 11 is set to the 1 zero cross period, the 2 zero cross period, and the 3 zero cross. Any one of the periods is assumed.

  Therefore, if the heater control method according to the present invention is applied to the CPU 11, that is, the computer, it is possible to control on / off of the energization to the heater 11 without using the oscillation circuit and the interrupt circuit based on the detection of the zero cross point. The configuration can be simplified and the manufacturing cost can be reduced. Furthermore, since no interruption occurs in the computer and it is not necessary to monitor the zero cross point by the computer, the processing load on the computer can be reduced. Furthermore, since it is possible to control ON / OFF of the power supply to the heater at the zero cross point, the occurrence of flicker can be suppressed.

  The above-described embodiment is merely an example of the present invention, and the configuration can be changed within the scope of the present invention. For example, in step A3 of the flowchart shown in FIG. 5, an average value of the temperatures indicated by the temperature information acquired ten times is calculated, and this average value is set as a temperature Pc for controlling on / off of energization of the heater 11. However, the present invention is not limited to such a configuration. For example, in consideration of the variation in temperature indicated by the acquired temperature information, in step A3, the remaining temperature obtained by removing the temperature of the singular value from the temperature indicated by the acquired temperature information. You may make it calculate an average value using.

  More specifically, since the temperature information acquisition start time and the acquisition end time are likely to vary, the temperature information acquired for the second to ninth times among the temperature information acquired ten times is employed. And the average value of the remaining temperature except the temperature of the maximum value and the temperature of the minimum value among the temperatures indicated by the temperature information acquired for the second to ninth times is calculated, and the average value of the calculated temperatures is It is good also as temperature Pc which controls ON / OFF of electricity supply to the heater 11.

  Alternatively, in order to make a determination using the temperature information at a time closer to the timing for determining the temperature in step A5 of the flowchart shown in FIG. 5, among the temperature information acquired ten times, M before the end of temperature information acquisition. For example, temperature information for four times acquired for the sixth to ninth times is employed. And the average value of the remaining temperature except the temperature of the maximum value and the temperature of the minimum value among the temperatures indicated by the temperature information acquired at the sixth to ninth times is calculated, and the average value of the calculated temperatures is It is good also as temperature Pc which controls ON / OFF of electricity supply to the heater 11. Even when configured as described above, the same effects as those of the above-described embodiment can be obtained.

It is a block diagram which shows the structure of the heater control apparatus 1 which is one Embodiment of this invention. 3 is a time chart showing an operation of a temperature reading process by a temperature reading unit included in the heater control device 1. It is a figure which shows an example of the table 40 for a flicker countermeasure used for a flicker countermeasure control process. 4 is a time chart showing an on / off control operation of energization of the heater 11 by the heater control device 1. It is a flowchart which shows the process sequence of the temperature reading process by a temperature reading part. It is a flowchart which shows the process sequence of the flicker countermeasure control process by a flicker countermeasure control part. It is a figure which shows the structure of the heater control apparatus 9 of the 2nd prior art. 6 is a time chart showing an on / off control operation of energization of the heater by the heater control device 9;

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,9 Heater control apparatus 10,70 Fixing unit 11,71 Heater 12,72 Thermistor 20,80 Power supply unit 21,81 AC power supply connection plug 22,82 Zero cross detection circuit 23,83 Triac 24,84 Logical product (AND) Circuit 30, 90 Control board unit 31, 91 A / D section 32, 92 HON signal output section 33 RAM
34 ROM
35,95 CPU
40 Flicker countermeasure table 96 Zero cross input section

Claims (4)

Zero-cross detection means for detecting a time point when the voltage of the AC power supplied from the AC power supply source having a predetermined frequency and supplied to the heater becomes 0 V;
When the time point when the voltage becomes 0 volt is detected by the zero cross detection means, the energization to the heater is turned on / off by switching whether to supply the AC power supplied from the power supply source to the heater. Switching means;
Temperature detecting means for detecting the temperature of the heating object heated by the heater;
When the temperature of the heating object detected by the temperature detection means is lower than a predetermined temperature, the switching means is repeatedly turned on and off alternately for a predetermined number of times, and then the temperature detection means Control means for turning on energization of the heater by the switching means until the temperature of the heating object detected by reaches a predetermined temperature,
The control means
Heater on period in which energization of the heater is turned on, among the periods in which the switching means is repeatedly turned on and off alternately for a predetermined number of times when the half cycle of the alternating current is 1 zero cross period The first and second heater on periods are set to one zero cross period, the third and subsequent heater on periods are set to one of one zero cross period and two zero cross periods, and the heater is energized. A heater control device characterized in that the heater off period to be turned off is one of a 1 zero cross cycle, a 2 zero cross cycle, and a 3 zero cross cycle. The control means provides the switching means with a heater control signal for turning on / off the energization of the heater,
The switching means turns on the energization to the heater when the zero cross detection means detects the time when the voltage becomes 0 volts when the heater control signal supplied from the control means is on, and the control When the heater control signal supplied from the means is off and the time point when the voltage becomes 0 volts is detected by the zero cross detection means, the energization to the heater is turned off,
When the control means gives the heater control signal to the switching means, the maximum period in which one zero-cross period, which is the half cycle of the alternating current, varies is the maximum zero-cross period Tmax, and the minimum period in which the zero-cross period varies is the minimum zero-cross period Tmin. and when,
When the temperature of the heating object detected by the temperature detection means is lower than a predetermined temperature, the heater control signal is turned on during the first period T0 that satisfies T0 <Tmin.
During the second period T1 that satisfies 3 × Tmax−Tmin <T1 <4 × Tmin−Tmax after the first period T0 has elapsed, the heater control signal is turned off,
After the second period T1, the heater control signal is turned on during the third period T2 that satisfies 4 × Tmax−Tmin <T1 + T2 <5 × Tmin−Tmax.
The heater control signal is turned off after the third period T2 has elapsed and during the fourth period T3 that satisfies 6 × Tmax−Tmin <T1 + T2 + T3 <7 × Tmin−Tmax.
When m is an even integer of 4 or more, the heater control signal is turned on after the mth period Tm−1 has elapsed and for the (m + 1) th period Tm that satisfies Tmax <Tm <2 × Tmin. ,
When n is an odd integer of 5 or more, the heater control signal is turned off after the nth period Tn−1 has elapsed and for the (n + 1) th period Tn that satisfies Tmax <Tn <2 × Tmin. The heater control device according to claim 1, wherein:   3. The heater control device according to claim 2, wherein the first period T <b> 0 is determined such that a time difference between the first period T <b> 0 and the minimum zero cross period Tmin is within a predetermined time. A heater control method for controlling on / off of energization to a heater to which AC power is supplied from an AC power supply source having a predetermined frequency,
A temperature detection step for detecting the temperature of the heating object heated by the heater;
When the temperature of the heating object detected in the temperature detection step is lower than a predetermined temperature, the heater is turned on and off alternately and repeatedly for a predetermined number of times, and then detected in the temperature detection step. A control step of turning on the power to the heater until the temperature of the heating object reaches a predetermined temperature,
In the control step, when the half cycle of the alternating current is set to one zero cross cycle, the heater on period in which the energization to the heater is turned on among the periods in which the energization to the heater is alternately turned on and off repeatedly for a predetermined number of times. The first and second heater on periods are set to one zero cross period, the third and subsequent heater on periods are set to one of one zero cross period and two zero cross periods, and the heater is energized. A heater control method, wherein the heater off period to be turned off is one of a 1 zero cross cycle, a 2 zero cross cycle, and a 3 zero cross cycle.

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