JP2824325B2 - Heater drive control method for equipment with heater - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on / off controlled heater for an electrophotographic image forming apparatus such as an optical printer such as a laser printer, an electrophotographic copying machine, and a facsimile machine. The present invention relates to a heater drive control method for a device including

[Conventional technology]

Generally, in an electrophotographic image forming apparatus such as a laser printer, in order to fix a toner image transferred from a photoreceptor surface onto a transfer sheet, a fixing unit that heats and presses with a fixing roller to fix the toner image is used. ing.

The fixing unit is heated by a built-in heater of the fixing roller so that the surface temperature of the fixing roller (hereinafter, also simply referred to as “fixing temperature”) falls within an appropriate temperature range favorable for image formation. Temperature control.

In this temperature control, the lower limit temperature and the upper limit temperature are set in advance as an appropriate temperature range. Generally, the surface temperature of the fixing roller is detected by a temperature sensor such as a thermistor disposed near the fixing roller, and the detected temperature is determined. When the temperature is lower than the lower limit of the appropriate temperature, the heater is turned on, and when the temperature is higher than the upper limit of the appropriate temperature, the heater is turned off.

Note that a halogen heater of about 500 W to about 100 W is used for the heater, and since a commercial power supply of 100 V AC is normally supplied to this heater, a current of about 5 A to about 10 A is consumed.

By the way, one image forming apparatus such as a laser printer may be connected to each host machine such as a personal computer. However, when a large number of such host machines are installed in an office or the like, the image forming apparatus is also connected to the host machine. The same number must be installed.

[Problems to be solved by the invention]

However, since wiring work in offices and the like is generally performed with an allowable current of 20 A, there is a limit to the number of image forming apparatuses having heaters with large power consumption as described above. However, there is an inconvenience that the number of installations must be reduced or wiring work must be performed again.

The present invention has been made in view of the above points, and an object of the present invention is to make it possible to install more than a specified number of devices while avoiding power over.

[Means for solving the problem]

In order to achieve the above object of the present invention, a plurality of devices each having a heater which is controlled to be turned on / off are connected by a common signal line and synchronized so that a device number can be set to each device. In accordance with the set value, the generation timing of the heater lighting signal generated when the heater is turned on is determined within the above-mentioned synchronous cycle, and the device in which the heater is turned on is set at the determined self generation timing. Is generated and transmitted to the above signal line, and a device in which the heater is not lit counts a heater lit signal transmitted from another device within the synchronous period before turning on the heater, and the count value is set. The heater itself is turned on only when the value is less than the value, so that the number of devices in which the heater is turned on does not exceed the set value.

Also, a plurality of devices each having a heater which is controlled to be turned on / off are connected by a common signal line. In synchronization with the devices, a device number can be set to each device, and any one of the devices can be set as a master. The master device stores the device numbers of the devices according to the priority order, sends the device numbers to the signal lines in the priority order at different timings in the synchronization cycle, and turns on the heater. When the device number sent from the master device matches its own device number, it generates a heater lighting signal and sends it to the above signal line, and a device whose heater is not turned on tries to turn on the heater. In this case, the heater lighting signal transmitted from another device is counted within the above-mentioned synchronization cycle, and after the device number transmitted from the master device matches its own device number, the heater lighting signal is transmitted. The heater is turned on only when the count value is less than the set value, so that the number of devices with the heater turned on does not exceed the set value, and the master device stores the device immediately after the heater is turned off. The priority of the assigned device number is shifted to the lowest.

In order to synchronize between each device, AC
It is preferable to detect the zero cross point of the power input.

(Operation)

In the heater drive control method according to the first aspect, the device in which the heater is turned on generates a heater turn-on signal at its own generation timing determined in the synchronous synchronization and sends it to another device to turn on the heater. Before the device that does not turn on the heater, the heater lighting signal transmitted from the other device is counted during the above-mentioned synchronization cycle, and the heater is turned on so that the count value is within the set value (allowable power range). The heater is turned on only when the number of devices is less than the number of devices (equivalent to the number of devices), so that it is possible to install more devices than the specified number in a normal office-level environment.

Further, in the heater drive control system of the second aspect, the master device sends out the device numbers of the respective devices stored in accordance with the priority order to the respective devices at different timings within the synchronization cycle in the priority order, and the heater is turned on. When the device number sent from the master device matches its own device number, the device that is performing the operation generates a heater lighting signal and sends it to each device, and the device whose heater is not turned on tries to turn on the heater. In this case, the heater lighting signal sent from another device within the above-mentioned synchronization cycle is counted, and after the device number sent from the master device matches its own device number, the count value is set to the set value (allowable power). ), The heater is turned on only when the heater is turned off when the heater is turned off, and the master device is turned off. Since the priority of the device number stored for the subsequent device is moved to the lowest order, it becomes possible to install more than the specified number of devices in the same manner as in the above-described heater drive control method, and all This device can equally have the opportunity to turn on the heater.

In addition, as long as each device is installed in the same office, the zero-cross point of the AC power input to each device is substantially the same.

Therefore, if each device detects the zero-cross point of the AC power input to synchronize between the devices, the signal cable for synchronizing between the devices becomes unnecessary, and the cost is reduced. Has the advantage that the installation and movement of the apparatus can be facilitated.

〔Example〕

Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.

FIG. 1 is a circuit diagram showing an apparatus having a heater according to one embodiment of the present invention.

In FIG. 1, devices 1, 2,..., 10 are provided with heaters which are controlled to be turned on and off, respectively. The devices are connected by a common coaxial cable (signal line) 11, and these devices are connected to one another. Make up one system. Each of these devices 1,
2, ... 10 shall be installed in the same office.

The apparatus 1 comprises a power supply unit (PSU) 15, a device number set switch 16, a microphone computer (hereinafter abbreviated as "CPU") 17, a heater control circuit 18, a heater 19, a line driver / receiver 20, and the like.

When an AC from a commercial power supply of 100 V is input by turning on a main switch (not shown), the power supply unit 15 purifies various voltages and distributes and supplies the voltages to various parts in the apparatus 1. However, illustration of the power supply line is omitted.

In addition, the power supply unit 15 is provided with a synchronization detection circuit for detecting a zero-cross point (zero-cross point) of the commercial power supply in order to synchronize between the devices, and the synchronization detection circuit supplies the CPU 17 with the zero-cross point at the zero-cross point. A one-shot zero-cross signal is output.

The device number set switch 16 uses a quadruple date switch, and inputs a 4-bit digital signal to the CPU 17 in accordance with a combination of opening and closing by the switches 16a to 16d.

The CPU 17 is a microcomputer composed of a microprocessor, ROM, RAM, I / O, and the like, and controls the entire apparatus 1 as a whole.

The heater control circuit 18 turns on the heater 19 when the heater-on signal (high-level signal) is input by the CPU 17, and turns off the heater 19 when the heater-on signal is no longer input.
Turn off the light.

The line driver / receiver 20 is composed of two inverters 20a,
A signal from the CPU 17 is inverted by the inverter 20a and sent to the coaxial cable 11 as a heater lighting signal to be described later.The heater lighting signal from the coaxial cable 11 is inverted by the inverter 20b to the CPU 17 Output.

Since the configurations of the devices 2 to 10 are substantially the same as those of the device 1, illustration and description thereof are omitted.

Next, the operation of the embodiment thus constructed will be specifically described with reference to the flow chart of FIG. 2 and the timing charts of FIGS. 3 and 4.

Each of the power supply units of the devices 1, 2,... 10 generates various voltages by alternating current from the commercial power supply 100V AC and supplies them to the respective units including the CPU, and detects the gross cross point a shown in FIG. Then, a one-shot zero-cross signal shown in FIG.

After that, each CPU starts an internal timer, and then inputs 4-bit digital signals from each device signal set switch having a different combination of opening and closing of each switch, and according to each signal, a different device is used. The number is set, and the generation timing of the heater lighting signal generated when the heater is turned on within the cycle of the commercial power supply 100 V AC is determined according to the set value.

That is, in the apparatus 1, since the switches 16a to 16d of the device number set switch 16 are all open as shown in FIG. 1, the CPU 17 sets "1" as the apparatus number, and generates the heater lighting signal generation timing. Is determined as the zero cross point (the point in time at which the zero cross signal is input) as shown in FIG.

In the devices 2,..., Although not shown, the opening and closing of each switch of the device number set switch are respectively performed.
By different combinations of closing, each CPU sets "2",... "10" as the device number, and the generation timing of the heater lighting signal is determined from the input timing of the zero cross point as shown in FIG. 2t, 3t, 4t, 5t, 6
It is determined at the point in time when t and 7t [ms] are sequentially sent.

When the frequency of the commercial power supply is set to 50 [Hz], the period becomes 20 [ms].
[Ms].

Here, assuming that the current consumption when the heater is lit in any one of the devices is 5A and that a switchboard for 20 [A] is installed in the office, the devices 1, 2, and …
Up to four (specified number) of the ten can turn on the heater.

Therefore, it is assumed that “4” is set as the specified number in the CPU of each of the devices 1, 2,...

Now, the devices whose heaters are lit are, for example, devices 1, 4, 6
If there are three devices, another device can turn on the heater.

In this state, when it is necessary to turn on the heater in the apparatus 8, that is, based on a detection signal from a thermistor (not shown) installed near the heater, the heater temperature (for example, a fixing roller having a built-in heater in an image forming apparatus) is detected. When the surface temperature falls below the appropriate temperature, the built-in
The CPU starts the processing shown in FIG. This processing is performed in common by the CPUs in all the apparatuses.

First, the heater shown in FIG. 4C is turned on within the cycle of the commercial power supply 100 V AC from the zero cross point a shown in FIG. 4A (the input point of the zero cross signal shown in FIG. 4B) to the zero cross point b. In addition to counting and storing the heater lighting signal (low level signal) shown in FIG. 4C transmitted from the devices 1, 4, and 6, which are transmitted, the device number of the transmission source is also stored.

Next, the count value becomes the set value (specified number) “4”.
It is determined whether or not the count value is less than “3”.
Therefore, the process proceeds to the next step, and the heater lighting signal is generated from the next zero crossing point b shown in FIG. 4A to immediately before the timing of generating the heater lighting signal of the self (device 8) shown in FIG. Check if the value has increased.

That is, the heater lighting signals sent from other devices are counted during the period, and the device number of the sending source is obtained. By checking the number (count value) and its device number, it can be determined whether or not the heater lighting signal has increased.

If the heater lighting signal has not increased, the fourth
As shown in FIG. 3 (c), a heater lighting signal is generated at its own generation timing and transmitted to the coaxial cable 11 and
A heater-on signal is sent to the heater control circuit at the next zero cross point c shown in FIG.
After 1, 4, and 6, the heater of the self (device 8) is turned on.

Next, it is checked whether or not the heater temperature has reached the proper temperature. At first, since the temperature is lower than the proper temperature, a heater lighting signal is generated again at its own generation timing and transmitted to the coaxial cable 11, and thereafter the proper temperature is outputted. The process is repeated until the process reaches.

Then, when the heater temperature becomes appropriate to the appropriate temperature, the heater ON signal to the heater control circuit is stopped and the heater is turned off, and the output of the heater ON signal is also stopped to terminate the processing.

When the heater needs to be turned on in the device 8 and the heater needs to be turned on in the device 9 at the same time, the device 9 also outputs a heater lighting signal. Since the lighting signal is output, the number of the devices in which the heaters are lit is the specified number of four devices, and the device 9 is in a standby state.

In such a case, if it is not necessary to turn on the heater in any of the devices 2, 3, 5, and 7 when the heater is turned off in any of the devices 1, 4, and 6, By the same processing as in the case, the heater lighting signal is generated at its own generation timing, and the heater can be turned on by the heater ON signal at the next zero cross point.

As described above, in this embodiment, the heater-on device generates the heater lighting signal at its own generation timing determined within the cycle of the commercial power supply 100 V AC (from the zero cross point to the next zero cross point). Before the device in which the heater is not lit turns on the heater, the heater lighting signal transmitted from the other device is counted during the above-mentioned period, and the count value is set to a set value (specified number). When the value is less than, the heater lighting signal sent from another device is counted from the next zero crossing point to just before the generation timing of the own heater lighting signal, and the count value is counted within the same period as the previous time. Turns on its own heater only when it is below the value, so it is possible to install more than the specified number of devices in a normal office-level environment It made.

Before the device whose heater is not turned on turns on the heater within the cycle of the commercial power supply (from immediately after the generation timing of the own heater lighting signal to immediately before the generation timing of the next own heater lighting signal). The heater lighting signal sent from another device may be counted, and the heater itself may be turned on only when the count value is less than the set value.

Further, in this embodiment, the specified number is set as the set value, but a value obtained by subtracting “1” from the specified number is set as the set value, and the apparatus in which the heater is not turned on is commercialized before the heater is turned on. The heater lighting signal transmitted from another device is counted during the cycle of the power supply, and when the count value is equal to or smaller than the set value (specified number of units minus one), the timing immediately before the generation timing of the own heater lighting signal from the next zero cross point. Of course, the heater lighting signal sent from another device during this period may be counted.

FIG. 5 is a circuit diagram showing an apparatus provided with a heater according to another embodiment of the present invention. Parts corresponding to those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

In the figure, devices 21, 22,... 30 are provided with heaters that are controlled to be turned on and off, respectively. The devices are connected by a common external cable (signal line) 31, and these devices are connected to one another. Make up one system. Each of these devices
21,22, ... 30 shall be installed in the same office.

The CPU 35 is a microcomputer composed of a microprocessor, ROM, RAM, I / O, etc., and controls the entire device 21 as a whole.

Line driver / receiver 36 is 10 inverters 36a
36j and five pull-up resistors R2 to R6.
The 4-bit digital signal indicating the device number from the external cable 31 is inverted by the inverters 36a, 36c, 36e, and 37g and sent to the external cable 31 as the device number code, and the device number codes from the external cable 31 are converted into the inverters 36b, 36d, and 36f. Inverted at 36h, C
Output to PU35.

Since the configurations of the devices 22 to 30 are substantially the same as those of the device 21, illustration and description thereof are omitted.

Next, the operation of the thus constructed embodiment will be described with reference to the flowcharts of FIGS. 6 and 7 and FIGS. 8A and 8B.
This will be described in detail with reference to the timing chart shown in FIG. Each of these timing charts is a series.

Each power supply unit of the devices 21, 22, ... 30 is 100V commercial power
A variety of voltages are generated by the alternating current supplied from the CPU and supplied to each unit including the CPU, and a zero-cross point a shown in FIG. 8A (a) is detected, and a one-shot zero-cross signal shown in FIG. Is output.

After that, each of the CPUs starts the internal timer, and then inputs 4-bit digital signals from the device signal set switches having different combinations of opening and closing of the switches, and different device numbers corresponding to the respective signals. (Device number code) is set.

That is, in the device 21, since all the switches 16a to 16d of the device number set switch 16 are all open as shown in FIG. 5, "1" is set as the CPU 35 device number.

Also, in the devices 22,... 30, although not shown,
Each CPU sets "2"... "10" as a device number according to a different combination of opening / closing of each switch of the device number setting switch.

Here, in this embodiment as well, it is assumed that up to four of the devices 21, 22,... 30 can turn on the heater similarly to the above-described embodiment, and the CPU of each device 21, 22,. It is assumed that “4” is set as the specified number for each.

Now, the devices whose heaters are lit are, for example, devices 21, 24,
Assuming that there are 26 devices, another device can turn on the heater.

In this apparatus, when it becomes necessary to turn on the heater in the apparatus 28, the CPU starts the processing shown in FIG. This processing is performed in common by the CPUs in all the apparatuses.

First, in the period of the commercial power supply 100 V AC from the zero cross point a to the zero cross point b shown in FIG. 8A (a), the devices 21, 24,
In addition to counting the heater lighting signal (low level signal) shown in (c) of FIG. 3 transmitted from 26, the device number of the transmission source is obtained and stored.

Next, it is determined whether or not the count value is less than the set value "4". Here, since the count value is "3", the process immediately proceeds to the next step, and the next zero cross point b shown in FIG. , Until the device number code (device number) sequentially transmitted from the master device to be described later at the timing shown in FIG. 3D matches its own device number “8”, that is, from the zero-cross point b to the device. It is checked whether the heater lighting signal has increased until the number code "8" is received.

If the heater lighting signal has not increased, a heater lighting signal is immediately generated and sent to the external cable 31,
At the next zero cross point c shown in FIG. 8B (a), a heater-on signal is sent to the heater control circuit, and as shown in FIG. 8 (d), following the device numbers 21, 24, and 26, the self (device 28) Turn on the heater.

Next, it is checked whether or not the heater temperature has reached the proper temperature. At first, since the heater temperature is lower than the proper temperature, when the device number code sent from the master device matches its own device number, the heater lighting signal is output. External cable generated
Then, the process is repeated until an appropriate temperature is reached.

Then, when the heater temperature reaches the appropriate temperature, the transmission of the heater ON signal to the heater control circuit is stopped to turn off the heater, the output of the heater ON signal is also stopped, and the process is terminated.

On the other hand, if the device having the set switch with all four switches in the open state is determined as the master device, since the switches 16a to 16d of the device number set switch 16 of the device 21 are all open, the CPU 35 The device 31 is set as a master device by a 4-bit digital signal from the switch, and thereafter, the above-described process of FIG. 6 and the process of FIG. 7 dedicated to the master device are performed in parallel.

When the process of FIG. 7 starts, first, the device numbers "1" to "10" of ten units are stored in the priority order memory (predetermined area of the RAM) in the CPU 35 in accordance with the priority order (the first is the order of the device numbers). The first device number “1” of the device numbers “1” to “10” stored in the priority order memory is read out at the zero cross point a of the commercial power supply 100 VAC shown in FIG. 8A (a). Then, the device number code “1” shown in FIG. 4D is output from the line driver / receiver 36 and sent to the external cable 31.

Next, it is determined whether or not the heater lighting signal (low level signal) has been received. First, since the heater lighting signal is received in response to the transmission of the apparatus number code “1”, subsequently, the previous apparatus number code is transmitted. It is determined whether a heater lighting signal has been received at the time of transmitting “1”.

Since the transmission of the device number code is the first time since the start of this process, the process immediately shifts to the delay process of t [ms].

Here, this delay process is a process for prohibiting the transition to the next process for t [ms] in order to obtain the transmission timing of each device number code. As the delay time t, the frequency of the commercial power supply is set to 50 [ms]. Hz], the cycle is 20 [ms]
Therefore, it is sufficient to expect about 2 [ms], which is one tenth of that.

Accordingly, the CPU 35 of the master device 21 changes the device number codes "1" to "10" to t [ms] as shown in FIG. 8A.
It will be sent out every time it passes.

When the delay processing of t [ms] is completed, it is next determined whether this processing has been repeated for the number of apparatuses (10 times).
Since this is the first time, the next device number “2” in the priority order memory is read out, and the line driver / receiver 36 reads the next device number “2”.
The device number code “2” shown in FIG. 8A (d) is output and sent to the external cable 31.

Then, it is determined again whether or not the heater lighting signal has been received. However, this time, since the heater lighting signal is not received in response to the transmission of the device number code “2”, subsequently, the previous device number code “2” is received. It is determined whether a heater lighting signal has been received at the time of transmission.

Since the transmission of the device number code "2" is the first time since the start of this process, t [ms]
After that, the same processing as described above is repeated, and when this processing is repeated for the number of apparatuses, the process returns to the determination of whether or not a zero cross point has been reached, and the next zero cross point b shown in FIG. Then, the first device number "1" in the priority memory is read out again, and the device number code "1" shown in FIG.

Thereafter, the same processing as described above is repeated, and after the next zero cross point c shown in FIG. 8B (a) has elapsed, the line driver / receiver 36 outputs the device number code "4" shown in FIG. When the heater turn-on signal from the device 24 corresponding to the device number code "4" is not received as shown in FIG. Shifts to the determination as to whether or not the heater lighting signal has been received at the time of sending out.

Since the heater lighting signal was received from the device 24 last time as shown in FIG. 8A (c), the content stored in the priority memory was changed, that is, the device number “4” stored in the priority memory was changed. ”To the lowest order,
Proceed to the delay process of [ms].

As a result, the transmission order of the device number codes from the line driver / receiver 36 after the next zero cross point d shown in FIG. 8B (a) is changed as shown in FIG. 8 (d).

That is, "5" is transmitted next to the device number code "3", and finally the device number code "4" is transmitted.

As described above, in this embodiment, the master device stores the device numbers of the respective devices stored in accordance with the priority order at different timings within one cycle of the commercial power supply (from the zero cross point to the next zero cross point). When the heater is turned on, the device with the heater turned on generates a heater lighting signal and sends it to each device when the device number sent from the master device matches its own device number, and the heater is not turned on When the device is to light the heater, the device counts a heater lighting signal transmitted from another device during the cycle of the commercial power supply, and when the count value is less than the set value, the device starts counting from the next zero crossing point. Until the device number from the master device matches its own device number, the heater lighting signals sent from other devices are counted, and the count value is calculated. The heater itself turns on only when the count value is less than the count value within the same period as the previous one, and the caster device sets the lowest priority of the device number stored for the device immediately after the heater is turned off. As in the above-described embodiment, more than a specified number of devices can be installed, and all devices can have equal opportunities to turn on the heater.

When a device whose heater is not turned on tries to turn on the heater, when the device number from the master device matches its own device number, the device number is set immediately after the match until the next match. It is also possible to count the heater lighting signal transmitted from another device within the cycle of the commercial power supply and turn on the heater only when the count value is less than the set value.

Also, in each of the above-described embodiments, the synchronization between the devices is detected by detecting the zero-cross point of the commercial power (AC power) input in each device. There is an advantage that the cost is reduced by eliminating the necessity of a credit cable, and the installation and movement of the device are facilitated.

[Effect of the invention]

As described above, according to the first aspect of the present invention, it is possible to install more than a prescribed number of devices in a normal office-level environment.

Further, according to the second aspect of the invention, the same effect as that of the first aspect of the invention can be obtained, and the opportunity to turn on the heater can be equally provided to all the devices.

Further, according to the third aspect of the present invention, a signal cable for synchronizing each device can be eliminated, thereby reducing costs and facilitating installation and movement of the devices. can get.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an apparatus provided with a heater according to an embodiment of the present invention. FIG. 2 is a flow chart showing the processing operation by a CPU of each apparatus. FIGS. 3 and 4 show this embodiment. FIG. 5 is a circuit diagram showing a device having a heater according to another embodiment of the present invention, and FIG. 6 is a flow chart showing a common processing operation by the CPU of each device. FIG. 7 is a flowchart showing a dedicated processing operation by the CPU of the master device, and FIGS. 8A and 8B are timing charts for explaining the operation of this embodiment. 1 to 10, 21 to 30 Equipment 11 Coaxial cable 15, Power supply unit 16 Device number set switch 17, 35 Microcomputer (CPU) 18 Heater control circuit 19 Heater 20, 36 …… Driver / receiver 31 …… External cable

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03G 21/00 502 G03G 21/00 502 G05D 23/00 G05D 23/00 E (56) References JP-A-2-123924 (JP) JP-A-4-184457 (JP, A) JP-A-3-143225 (JP, A) JP-A-3-21320 (JP, A) JP-A-52-129813 (JP, A) 48-95632 (JP, A) JP-A-56-4801 (JP, A) JP-A-57-157479 (JP, A) JP-A-60-123011 (JP, U) (58) Fields investigated (Int. (Cl. ⁶ , DB name) H05B 3/00 310 G03G 15/20 109 G03G 21/00 370 G03G 21/00 396 G03G 21/00 398 G03G 21/00 502

Claims (3)

(57) [Claims] 1. A plurality of devices each having a heater which is controlled to be turned on / off are connected by a common signal line and synchronized, so that a device number can be set to each device, and the set value is set to the set value. Accordingly, the generation timing of the heater lighting signal generated when the heater is turned on is determined within the synchronization cycle, and the device in which the heater is turned on generates the heater lighting signal at the determined own generation timing, and The device that sends out the signal to the signal line and the heater is not turned on counts the heater lighting signal sent from another device within the synchronization period before turning on the heater, and only when the count value is less than the set value. A heater drive control system characterized in that its own heater is turned on so that the number of devices in which the heater is turned on does not exceed a set value. 2. A plurality of devices each having a heater which is controlled to be turned on and off are connected by a common signal line and synchronized, so that a device number can be set to each device and any one of them can be set. A table as a master device, the master device stores the device numbers of the respective devices according to priority, and sends the respective device numbers to the signal lines in the priority order at different timings within the synchronization cycle, When the device number sent from the master device matches its own device number, the device whose heater is lit generates a heater lighting signal and sends it to the signal line. When the lighting is to be performed, the heater lighting signal transmitted from another device is counted within the synchronization cycle, and the device number transmitted from the master device is set to its own device number. After the coincidence, the heater is turned on only when the count value is less than the set value, so that the number of the devices in which the heater is turned on does not exceed the set value, and the heater of the master device is turned off. A heater drive control method wherein the priority of the device number stored for the immediately succeeding device is shifted to the lowest. 3. The heater drive control system according to claim 1, wherein each device is synchronized with each other in order to synchronize the devices.
A heater drive control method characterized by detecting a zero-cross point of AC power input.