Image forming device

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to an image forming apparatus such as a copying machine, a facsimile apparatus, and a printer apparatus, and particularly to power saving.

【0002】

[Conventional technology]

Devices having a power saving mode such as setting the temperature of a heat source such as a fixing heater to a temperature lower than the preheating temperature during standby when copying is not performed by a copier or the like or interrupting the current of a fixing heater or the like are widely used. .. As a device that realizes this power saving mode, for example, as shown in JP-A-6-54102 and JP-A-9-185298, the power saving mode is performed after the fixing heater is turned off by the CPU that controls the entire device. It shifts to and operates only the CPU and its surroundings, and turns off the power of other parts. In this power saving mode, the CPU monitors the temperature of the fixing heater and checks the runaway of the CPU with a watchdog timer, etc. to prevent abnormal overheating of the fixing heater due to hardware abnormality or software runaway, and recovery conditions. Is also monitored. Further, as shown in Japanese Patent Application Laid-Open No. 10-308833, a dedicated CPU that monitors only the recovery condition from the power saving mode is provided, and in the power saving mode, the power of the CPU that controls the entire device is turned off. The power supply is directly controlled by the monitoring CPU.

【0003】

[Problems to be Solved by the Invention]

However, in the power saving device shown in Japanese Patent Application Laid-Open No. 6-54102, it is difficult to realize significant power saving because the MPU is completely operating even in the power saving mode. Further, the power saving device shown in Japanese Patent Application Laid-Open No. 10-308833 or the like needs to be provided with an MPU dedicated to monitoring, which increases the cost. In addition, there is a disadvantage that there is a risk of erroneous energization of the fixing heater control circuit due to runaway of the dedicated MPU.

【0004】

The present invention remedies this disadvantage and stops the operating clock of the MPU that controls the entire device in the power saving mode, and immediately stops the clock if the temperature of the fixing heater is abnormal. It is an object of the present invention to provide an image forming apparatus capable of returning from a power saving mode to improve reliability and realizing a lower power saving mode.

【0005】

[Means for solving problems]

In the image forming apparatus according to the present invention, when shifting from the standby state to the power saving mode, the MPU that controls the entire device cuts off the energization of the fixing heater, shifts to the power saving mode, and executes the stop mode of the MPU. It is characterized by returning from the power saving mode when there is an interrupt input of the MPU.

【0006】

Further, when shifting from the standby state to the power saving mode, the power saving mode transition program and the power saving mode recovery program are written in the memory built in the MPU, and the power saving written in the memory built in the MPU. The mode transition program and the power saving mode recovery program shift to the power saving mode and return from the power saving mode.

【0007】

Further, when the temperature of the fixing heater rises in the power saving mode, an interrupt for returning from the power saving mode is input to the MPU.

【0008】

BEST MODE FOR CARRYING OUT THE INVENTION

The main control unit of the image forming apparatus of the present invention is connected to a fixing relay that is connected to an AC power supply and is turned on / off by a fixing relay trigger signal output from the MPU that controls the entire device, and an input side is connected to the output end of the fixing relay. The zero cross detection circuit connected to the interrupt terminal INT1 where the output side inputs the MPU control interrupt signal, and the overgate and MPU whose output side is connected to the interrupt terminal that inputs the MPU power saving mode recovery interrupt signal. It has an inverter with an input side connected to a terminal that outputs a heater trigger signal. The MPU inputs the fixing temperature from the temperature detection thermistor provided on the surface of the fixing roller having the fixing heater of the fixing part, outputs the trigger signal of the fixing relay to turn on / off the fixing relay, and also to the fixing heater control part. Outputs the fixing heater trigger signal. The zero-cross detection circuit detects the zero-cross point of the AC input waveform input from the AC power supply via the fixing relay, and inputs the zero-cross signal to the interrupt terminal INT1 of the MPU to interrupt. The fixing heater trigger signal output from the MPU is input to the interrupt terminal INT2 of the MPU via the orgate together with the wake-up trigger signal to be input to cancel the power saving mode.

【0009】

Then, when the standby mode elapses for a certain period of time, the power saving mode transition program and the interrupt service program of the interrupt terminal INT2 are written in the RAM built in the MPU, and the power saving mode transition routine is entered. When entering the power saving mode transition routine, the MPU outputs a fixing heater trigger signal to cut off the current flowing through the fixing heater to allow interrupts at the interrupt terminal INT2. After that, the MPU stop command is issued to the MPU. Stop the clock, put the MPU in stop mode and enter power saving mode. In this state, when a wake-up trigger signal for executing a copy operation or the like is input to the interrupt terminal INT2 of the MPU, the stop mode of the MPU is released, and the MPU cancels the power saving mode and masks the interrupt terminal INT2. After that, it shifts to the main routine and executes normal processing.

【0010】

[Example]

FIG. 1 is a schematic configuration diagram of a digital copier according to an embodiment of the present invention. As shown in the figure, the digital copier includes the copier body 1, the automatic document feeder (ADF) 2, the finisher 3 with stapler and shift tray, the double-sided reversing unit 4, the paper feed tray 5, the large-capacity paper feed tray 6, and It consists of a paper output tray 7. As shown in the block diagram of FIG. 2, the copying machine main body 1 has a scanner unit 11, a writing unit 12, an image forming unit 13, a paper feeding unit 14, and a fixing unit 15.

【0011】

As shown in FIG. 2, the electrical control unit of the digital copier includes a main control unit 22 having an MPU 21 for controlling the operation of the entire device such as image formation sequence and fixing control, and a CPU 23 for controlling the operation of the scanner unit 11 and the like. It has a scanner control unit 24. The main control unit 22 and the scanner control unit 24 are connected to a scanner interface that transfers image data by a serial interface. The memory control unit 25, the write control unit 26, the motherboard 27, the input / output control unit 28, and the power supply control unit 29 are connected to the main control unit 22, and the scanner unit 11, ADF2, and the operation unit 30 are connected to the scanner control unit 24. It is connected. The memory control unit 25 controls the operation of the hard disk 31. The writing control unit 26 controls the operation of the laser diode, the scanner motor, and the like of the writing unit 12 of the copying machine main body 1. The motherboard 27 is an application expansion unit for realizing multiple functions, and is equipped with an FCU 32 equipped with a facsimile function, a printer application board 33, a scanner application board 34, and an external expansion I / F board 35. The input / output control unit 28 controls the input / output of the writing unit 12, the image forming unit 13, the paper feeding unit 14, the fixing unit 15, the finisher 3, and the double-sided reversing unit 4 of the copying machine main body 1. The power supply control unit 29 controls the power supplied to the high-voltage power supply 36, the fixing heater control unit 37, each part of the device, and the like.

【0012】

As shown in the circuit diagram of FIG. 3, the main control unit 22 has a fixing relay 221 connected to the AC power supply 291 of the power supply control unit 29 and turned on / off by the fixing relay trigger signal output from the MPU 21, and the input side is fixed. The output side is connected to the zero cross detection circuit 222 connected to the interrupt terminal INT1 which is connected to the output end of the relay 221 and the output side inputs the control interrupt signal of the MPU21, and the interrupt terminal INT2 which inputs the interrupt signal for returning to the power saving mode of the MPU21. It has an inverter 224 whose input side is connected to the terminal I / O that outputs the fixing heater trigger signal of the connected or gate 223 and MPU21. The MPU 21 inputs the fixing temperature from the temperature detection thermistor 152 provided on the surface of the fixing roller having the fixing heater 151 of the fixing portion 15 and outputs the trigger signal of the fixing relay 221 to turn on / off the fixing relay 221. The fixing heater trigger signal is output to the fixing heater control unit 37. The zero-cross detection circuit 222 detects the zero-cross point of the AC input waveform input from the AC power supply 291 via the fixing relay 221 and inputs the zero-cross signal to the interrupt terminal INT1 of the MPU 21 to interrupt. The on-duty of the fixing heater 151 is determined by the time from this zero cross point. The fixing heater trigger signal output from the MPU21 is input to the interrupt terminal INT2 of the MPU21 via the orgate 223 together with the wake-up trigger signal to be input to cancel the power saving mode. As a result, in the power saving mode, an interrupt is generated when either the fixing heater trigger signal or the wake-up trigger signal is at low level L, and the MPU 21 returns from the clock stop mode. Further, when the mode is other than the power saving mode, the interrupt terminal INT2 is masked so that an interrupt does not occur when the current of the normal fixing heater 151 is controlled.

【0013】

The fixing heater control unit 37 has a semiconductor switch connected in series with the photocoupler 371 and the fixing heater 151, for example, a resistor 373 connected in parallel with the triac 372 and a capacitor 374, and sends a fixing heater trigger signal from the MPU 21 to the photocoupler PC. The temperature of the fixing heater 151 is controlled by turning on / off the triac 372 connected to the fixing heater 151 by inputting to the primary side. Here, a pulse transformer may be used instead of the photocoupler PC.

【0014】

When performing a copying operation, a printing operation, or the like in the image forming apparatus configured as described above, the MPU 21 of the main control unit 22 is operated by the operator when the power is turned on, as shown in the flowchart of the operation of the main routine in FIG. Perform normal processing such as copying operation according to the instruction (step S1). During this normal processing, the MPU 21 sends a trigger signal to the fixing relay 221 to turn on the fixing relay 221 and also outputs a fixing heater trigger signal to the fixing heater control unit 37 to turn on the triac 372 to keep the temperature of the fixing roller at a constant temperature. Control. When the normal processing such as this copying operation is completed and the standby mode is entered (step S2), the MPU 21 determines whether the standby mode has been continued for a predetermined period of time, and is in the standby mode for a certain period of time. After that (step S3), the power saving transition program and the interrupt service program of the interrupt terminal INT2 are written from the hard disk 31 or the like to the RAM built in the MPU 21 (step S4). If the MPU21 has a built-in ROM, the power saving transition program and the interrupt service program for the interrupt terminal INT2 should be written in advance at the time of shipment from the factory. The MPU21 then jumps to the power saving mode transition routine (step S5).

【0015】

Upon entering the power saving mode transition routine, the MPU 21 outputs a fixing heater trigger signal to turn off the triac 372 and cut off the current flowing through the fixing heater 151 (step S11), as shown in the flowchart of FIG. Next, enable interrupts at interrupt terminal INT2 (step S12). After that, the stop command of MPU21 is issued to stop the clock of MPU21, the MPU21 is put into the stop mode, and the power saving mode is entered (steps S13 and S14). In this state, wait for the interrupt input of interrupt terminal INT2 (step S15).

【0016】

In this way, the current flowing through the fixing heater 151 is cut off and the operation of the MPU 21 is stopped, so that a power saving mode with low power consumption can be realized. Further, when the stop mode of the MPU 21 is executed, the RAM or ROM built in the MPU 21 is used to shift to the power saving mode, so that it is possible to prevent the select signal of the memory such as the hard disk 31 from becoming undefined.

【0017】

As shown in the flowchart of FIG. 6, when the wake-up trigger signal for executing the copying operation or the like is input to the interrupt terminal INT2 of the MPU21 in the power saving mode, the stop mode of the MPU21 is released (step S21). , MPU21 cancels the power saving mode, masks the interrupt terminal INT2 (step S22), and then shifts to the main routine to execute normal processing (step S23).

【0018】

If the temperature of the fixing heater 151 rises abnormally in the power saving mode, a fixing heater trigger signal is input to the interrupt terminal INT2 of the MPU21 to restore the clock of the MPU21 from the stop mode and set the temperature of the fixing heater 151 to a predetermined temperature. To control.

【0019】

[Effect of the invention]

As described above, when shifting from the standby state to the power saving mode, the MPU that controls the entire device cuts off the energization of the fixing heater, shifts to the power saving mode, and executes the stop mode of the MPU. , Since the power saving mode is restored when the MPU interrupt input is received, the low power consumption power saving mode can be realized at low cost and with high reliability.

【0020】

In addition, when shifting from the standby state to the power saving mode, the power saving mode transition program and the power saving mode recovery program are written in the memory built into the MPU, and the written power saving mode transition program and power saving are performed. Since the power saving mode is shifted to and returned from the power saving mode by the program for returning from the mode, it is possible to prevent the select signal of the ROM, the external memory, etc. from becoming undefined.

【0021】

Further, when the temperature of the fixing heater rises in the power saving mode, an interrupt for returning from the power saving mode is input to the MPU to return from the power saving mode, so that the reliability can be improved.

[Simple explanation of drawings]

[Figure 1]

It is a schematic block diagram of the digital copier of the Example of this invention.

[Figure 2]

It is a block diagram which shows the structure of the electrical control part of the said Example.

[Fig. 3]

It is a circuit diagram which shows the structure of the fixing heater control part of the said Example.

[Fig. 4]

It is a flowchart which shows the main routine of the said Example.

[Fig. 5]

It is a flowchart which shows the routine for transitioning to the power saving mode of the said Example.

[Fig. 6]

It is a flowchart which shows the routine for returning to the power saving mode of the said Example.

[Explanation of symbols]

21 MPU, 22 Main control unit, 37 Fixing heater control unit, 221 Fixing relay, 222 Zero cross detection circuit, 223 Orgate, 224 Inverter, 151 Fixing heater, 152 Thermistor.