JP3710281B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a facsimile, a copying machine, and a printer, and more particularly to an image forming apparatus having a function of detecting an abnormal voltage of a commercial power source and protecting the apparatus.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, some image forming apparatuses such as facsimiles, copying machines, and printers have a function of protecting the apparatus from power supply abnormality. For example, in the technique described in Japanese Patent Application Laid-Open No. 8-19163, a fuse that matches a current that flows during a standby state and a fuse that matches a current that flows during operation are provided, and the two fuses are switched according to the state of the apparatus. ing. In the technique described in Japanese Patent Laid-Open No. 6-351230, an overvoltage suppressing element such as a varistor or an arrester is used to protect a device from an abnormal voltage such as a lightning strike.
[0003]
[Problems to be solved by the invention]
However, in the technique described in Japanese Patent Application Laid-Open No. 8-19163, if the fuse blows due to voltage abnormality, the device cannot be used until the fuse is replaced. In addition, since the standby fuse is blown, if the operational fuse is used during standby, it may not be blown when the voltage of the commercial power supply is high apart from lightning. If this high voltage state continues for a long time, the dehumidifying heater or the like used in the copying machine or the like becomes high temperature, and an abnormality may occur in the machine.
The technique described in Japanese Patent Application Laid-Open No. 6-351230 is intended to absorb surge voltage such as lightning strike. When a high voltage is applied for a long time due to power failure or the like, a varistor or arrester for absorbing surge voltage is used. It will be damaged.
Therefore, the problem to be solved by the present invention is to monitor the voltage of the commercial power supply, and when the voltage becomes abnormally high, shut off the input from the commercial power supply to reliably prevent the apparatus from being damaged or malfunctioning due to the abnormal voltage. An object of the present invention is to provide an image forming apparatus having a protective function.
[0004]
[Means for Solving the Problems]
To solve the above problem, an image forming apparatus according to the first aspect of the present invention, a switch having a reset function for shutting off the AC input from the commercial power supply, the full-wave rectifying an AC input from the commercial power source and AC-DC conversion means for converting the DC output to the a / D converting means for converting the voltage value of the DC output into a digital value, the AC input error by the output value output from the a / D conversion means an abnormality detecting means for detecting said abnormal when the detection means detects the predetermined time abnormality in after finishing a series of image forming operation, the control for controlling to shut off the input from the commercial power source by the switch Means .
The image forming apparatus configured as described above monitors a DC voltage obtained by full-wave rectification of an input from a commercial power source, that is, a voltage before stabilization, and if an input voltage abnormality is detected for a certain period of time, a copying operation or printer After the operation during the image forming operation such as the operation is finished, the input from the commercial power supply is shut off, so that the apparatus can be reliably prevented from being damaged or malfunctioning due to an abnormal voltage.
[0005]
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the abnormality detecting unit is the fixed time that serves as a criterion for abnormality detection in accordance with an output value from the A / D converting unit. It is characterized by changing.
According to the image forming apparatus configured as described above, the magnitude of the input voltage from the commercial power supply and the detection time thereof are shortened as the input voltage from the commercial power supply increases, for example, the fixed time that is a criterion for abnormality detection is shortened. Accordingly, it is possible to cut off the input from the commercial power source in the event of an abnormality, so that the downtime of the apparatus due to the cut off of the commercial power source can be minimized.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a principal circuit diagram of a copying machine showing an example of an embodiment of the present invention. Here, the description of the configuration of known parts such as the electrophotographic process unit and the paper transport unit of the copying machine is omitted, and the configuration and operation of the part directly related to the present invention will be mainly described.
The circuit shown in FIG. 1 is generally composed of a switch with a reset function (hereinafter simply referred to as a switch) 1, a relay 2, a dehumidifying heater 3, an arrester 4, a varistor 5, a DC power supply unit 6, a control circuit 7, and the like.
The switch 1 is configured so that the ON state is maintained by a magnet when the switch 1 is manually switched to the ON state. The switch 1 can be manually switched to the OFF state. However, when the coil 1a is energized, a repulsive force is generated in a direction to open the contact, and the switch 1 returns to the OFF state. Therefore, in this example, when an abnormality occurs, the coil 1a is energized to switch the switch 1 to the OFF state, and the input from the commercial power supply (AC power supply) 8 is cut off. The control circuit 7 controls the energization of the coil 1a.
In the energy saving mode, the relay 2 does not supply power to the power system such as the fixing heater and the exposure lamp, but supplies power only to the minimum necessary power consumption elements such as the dehumidifying heaters 3a to 3c. work. At this time, the coil for operating the relay 2 is not energized. That is, the relay 2 is configured to close the contact on the dehumidifying heater side in the normally closed state, and the contact is provided to supply power to the power system such as the fixing heater and the exposure lamp during the copying operation. Switch.
The dehumidifying heaters 3a to 3c are provided in each paper feeding unit and are activated (energized) when the copying operation is not performed, such as in the energy saving mode.
[0007]
The arrester 4 is an overvoltage suppression element provided to prevent damage to the device when a lightning strike occurs, and works to release the input current to the ground when an excessive voltage is input to the AC input. . The varistor 5 functions to absorb noise caused by excessive voltage as described above. The DC power supply unit 6 includes an AC / DC conversion circuit 8 that performs full-wave rectification on the input from the AC power supply 8 to a DC voltage, and voltage stabilization for stabilizing the DC voltage after full-wave rectification and supplying it to the control circuit 7 and the like. Circuit 10. The AC / DC converter circuit 9 steps down the input voltage from the AC power source 8 by the transformer 9a, converts it to direct current by the full-wave rectifier circuit 9b, and smoothes it by the capacitor 9c. The voltage from the AC / DC converting circuit 9 is not only input to the voltage stabilizing circuit 10, but is also divided by resistors Ra, Rb, Rc and the like and input to the A / D converting circuit of the control circuit 7. Since this voltage is not stabilized, it fluctuates in conjunction with the voltage fluctuation of the AC input. Therefore, if this voltage is checked, the voltage value and state of the input voltage from the AC power source 8 can be known.
[0008]
The control circuit 7 includes a CPU 7a that performs overall control of the entire copier, a ROM 7b that stores programs to be executed by the CPU 7a and necessary data, a RAM 7c that the CPU 7a uses as a work area for various processes, and the like. In addition, peripheral circuits such as a timer 7d, an A / D conversion circuit 7e, and an I / O are included.
In the case where a DC-DC switching regulator is used in the voltage stabilization circuit, an AC voltage abnormality may be detected using a signal from the zero cross detection circuit. Although the voltage is high, the DC voltage from the AC-DC converter may be divided by resistors Ra, Rb, Rc and the like and input to the A / D conversion circuit 7e of the control circuit 7 (see FIG. 2). ).
As described above, the input voltage from the AC power supply 8 is converted to a DC voltage (DC voltage) by the full-wave rectifier circuit 9b, and the DC voltage is detected by A / D conversion. Voltage fluctuation can be detected with extremely high accuracy. It is also possible to detect a voltage fluctuation that does not blow the fuse.
[0009]
Next, the operation of this embodiment will be described according to the voltage abnormality detection flow shown in FIGS.
In the flow shown in FIG. 3, in order to check the AC voltage, the CPU 7a periodically checks the A / D input port (Port2) and compares it with a voltage comparison table stored in advance in the ROM 7b. It is determined whether or not there is an input (S1).
If an abnormal voltage is input (Yes in S1), the timer counter value is incremented by 1 (S2). If the timer counter value does not reach the preset predetermined value N (No in S3), another program is executed. Execute. The A / D input port (Port 2) is checked again. If the voltage is not abnormal, the timer is cleared (S9). Therefore, in the case of a temporary voltage increase, the switch 1 cannot be turned off.
When the counter value of the timer reaches a predetermined value N set in advance (Yes in S3), it is determined whether copying is being executed (S4). If it is being executed (Yes in S4), the new copy operation is stopped, but a series of copy operations being executed is executed (S5), and after the sheet on which the copy image is formed is discharged (S6), the output port A signal for turning off the relay (RA) 2 is output to (Port 1) (S7). If the copy is not being executed, the signal is immediately output without performing the processes of steps S5 and S6. After the signal output, the CPU 7a outputs a signal for releasing the switch 1 (a signal for energizing the coil 1a of the switch 1) to (Port0) (S8). As a result, the input from the AC power supply 8 is cut off, and the device is protected from abnormal voltage.
In addition, when the power supply is cut off at the time of abnormal voltage using a fuse, a breaker, etc., if the abnormal voltage is input, the power supply is cut off immediately even during the image forming operation. In this way, if copying is being executed, a series of copying operations being executed is executed (S5), the paper on which the copy image is formed is discharged out of the apparatus (S6), and then the power is shut off. No mechanical abnormality such as a jam due to fuse blown or breaker breakage during the copying operation does not occur, and it is possible to avoid wasting paper during copy image formation. (This corresponds to claim 1)
In the flow shown in FIG. 4, in order to check the AC voltage, the CPU 7a periodically checks the A / D input port (Port2) to determine whether or not an abnormal voltage has been input (S11). In this case, when a value (hereinafter referred to as A / D input value) input to the A / D input port (Port2) is a predetermined value N3, it is determined that an abnormal voltage is input (Yes in S11). The counter value of the timer is incremented by 3 (S12). Then, it is checked whether or not the counter value of the timer has reached N3 (S13). If it is not N3 (No in S13), another program is executed.
If the counter value of the timer is N3 (Yes in S13), it is determined whether copy is being executed (S14). If copying is in progress (Yes in S14), the new copying operation is canceled, but a series of copying operations being executed is executed (S15), and the paper on which the copy image is formed is discharged (Yes in S16). Then, a signal for turning off the relay (RA) 2 is output to the output port (Port1) (S17). If the copy is not being executed, the signal is immediately output without performing the processing of steps S15 and S16 (S17).
[0010]
After the signal output, the CPU 7a outputs a signal for releasing the switch 1 (a signal for energizing the coil 1a of the switch 1) to (Port0) (S18). As a result, the input from the AC power supply 8 is cut off, and the device is protected from abnormal voltage.
If the AD input value is not N3 (No in S11), it is checked whether the AD input value is N2 (S19). As a result, if the AD input value is N2 (Yes in S19), the timer counter value is incremented by 2 (S20), and it is checked whether the counter value is N2 (S21). As a result, if it is not N2 (No in S21), another program is executed.
On the other hand, if the counter value of the timer is N2 (Yes in S21), it is determined that an abnormal voltage has been input, the process proceeds to step S14, and processing similar to the above is performed (S14 to S18). As a result, the input from the AC power supply 8 is cut off, and the device is protected from abnormal voltage.
If the AD input value is neither N3 nor N2 (No in S11, No in S19), if the AD input is not N2, it is checked whether the AD input is N1 (S22). As a result, when the AD input value is N1 (Yes in S22), the counter value of the timer is incremented by 1 (S23), and it is checked whether the counter value is N1 (S25). As a result, if it is not N1 (No in S25), another program is executed.
[0011]
On the other hand, if the counter value of the timer is N1 (Yes in S25), it is determined that an abnormal voltage has been input, the process proceeds to step S14, and processing similar to the above is performed (S14 to S18). As a result, the input from the AC power supply 8 is cut off, and the device is protected from abnormal voltage.
If the AD input is not N3, N2 or N1 (No in S11, No in S19, No in S22), it is determined that no abnormal voltage is input, and the timer is cleared (S24). Therefore, in the case of a temporary voltage increase, the switch 1 cannot be turned off.
In the above, the values of N3, N2, and N1 are made to correspond to different magnitudes of abnormal voltages, respectively, and set such that N3 <N2 <N1, so that the larger the abnormal voltage, the more the abnormality detection judgment criteria. The detection time can be shortened. In this way, by shutting down the input from the AC power supply 8 in the event of an abnormality according to the magnitude of the abnormal voltage and the detection time thereof, the downtime of the apparatus due to the commercial power supply being interrupted can be minimized. (This corresponds to claim 2)
[0012]
【The invention's effect】
As described above, according to the first aspect of the present invention, the DC voltage obtained by full-wave rectification of the input from the commercial power source, that is, the voltage before stabilization is monitored, and if an input voltage abnormality is detected for a certain period of time, After the operation during the image forming operation such as the copying operation or the printer operation is finished, the input from the commercial power supply is shut off, so that the apparatus can be reliably prevented from being damaged or malfunctioning due to an abnormal voltage.
According to the invention of claim 2, in addition to the effect of claim 1, in addition to the effect of claim 1, the input from the commercial power source is shortened as the input voltage from the commercial power source is increased to shorten the predetermined time that is a criterion for detecting abnormality. According to the magnitude of the voltage and its detection time, it is possible to cut off the input from the commercial power source at the time of abnormality, so that the downtime of the apparatus due to the commercial power source being cut off can be minimized.
[Brief description of the drawings]
FIG. 1 is a main part circuit diagram of a copying machine showing an example of an embodiment of the present invention.
FIG. 2 is a partial circuit diagram illustrating another configuration example of the circuit of FIG. 1;
FIG. 3 is a flowchart showing an operation example of the embodiment of the present invention.
FIG. 4 is a flowchart showing another operation example of the embodiment of the present invention.
[Explanation of symbols]
1 Switch with reset function, 1a coil, 2 relay, 3 dehumidifying heater, 4 arrester, 5 varistor, 6 DC power supply unit, 7 control circuit, 7e A / D conversion circuit, 7a CPU (abnormality detection means), 7b ROM, 7a CPU, 7c RAM, 7d timer, 8 AC power supply (commercial power supply), 9a transformer, 9b full-wave rectifier circuit, 9c capacitor, 10 voltage stabilization circuit.

Claims (2)

A switch having a reset function for cutting off the AC input from the commercial power supply, AC / DC conversion means for converting the AC input from the commercial power supply into a DC output by full-wave rectification, and a digital value for the voltage value of the DC output an a / D converting means for converting, and abnormality detecting means for detecting an abnormality of the AC input by an output value outputted from the a / D converting means, when said abnormality detecting means detects a predetermined time abnormality An image forming apparatus comprising: a control unit configured to control so that an input from the commercial power source is interrupted by the switch after a series of image forming operations is terminated.   2. The image formation according to claim 1, wherein the abnormality detection unit can change the predetermined time as a determination criterion for detecting an abnormality in accordance with an output value from the A / D conversion unit. apparatus.

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