JPH1130929A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the sacrifice of fixability and productivity in a device and to control a heater with a simple constitution by optimally controlling the number of voltage fluctuations caused by a current rushing into the heater, in accordance with each state of the device, so as to suppress the fluctuation of a power supply voltage and the inhibition of a higher harmonic to a commercial power source as little as possible, without adding a hardware part and a filter member. SOLUTION: In this device, at least a turning off threshold when the formation of an image is not operated is set to be a value different from and higher than a lighting threshold when the formation of the image is not operated and the lighting and turning off thresholds when the formation of the image is not operated are set to make the control period of the heater 17 when the formation of the image is not operated longer than that when the formation of the image is operated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer,
The present invention relates to an image forming apparatus such as a facsimile.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer and a facsimile, a heater such as a halogen lamp is generally used as a heat source of a fixing device. JP-A-6-2
Japanese Patent Application Laid-Open No. 82199 discloses a heater lamp control method for an electrophotographic printing apparatus. Each time power is supplied to a heater lamp, the supply current, which is always limited to a low level, is controlled for a certain time without affecting the temperature control of the heater lamp. To prevent a large inrush current from flowing. Also, JP-A-6-3481
Japanese Patent Application Laid-Open No. 72-72139 discloses an image forming apparatus in which a heater branch end is switched when a heater of a fixing device is not energized to protect a contact portion and reduce electric noise.

[0003]

The above-mentioned JP-A-6-282
In the heater lamp control method described in Japanese Patent Application Publication No. 199, a circuit for supplying a limited current is provided, and a supply current limited at a low level is supplied to the heater lamp for a certain time each time power is supplied to the heater lamp. Space and cost for adding parts, and each part (especially triac) by constantly energizing the heater with a limited current supply
Is concerned about its reliability. In addition, Japanese Patent Application Laid-Open No. Hei 6-2821
No. 99 does not disclose any harmonics generated when the heater is constantly turned on by the supply of the limited current.

In the image forming apparatus described in Japanese Patent Application Laid-Open No. 6-348172, a tap is provided as a branch end in the heater itself, and the switching is performed to protect the contact portion and reduce electric noise. Is the power supply voltage fluctuation,
Concerns and suppression of harmonics are described in JP-A-6-3481.
No. 72 describes it. In the prior art, protection from inrush current to the heater is performed, but this is only to protect the components, such as power supply voltage fluctuation, suppression of harmonics to the commercial power supply, and generation level. There is no one that considers such factors.

In an image forming apparatus having a fixing device using a halogen lamp as a heat source, a rush current at the start of lighting peculiar to the halogen lamp and a phase control of a halogen lamp driving voltage for preventing the rush current are controlled by surroundings. It often affects devices that use commercial power. For example, a voltage drop caused by an inrush current causes a change in the amount of light of the lighting equipment or a distortion in the commercial power supply voltage waveform itself. In general, most of the image forming apparatus is in a standby state during a power-on period, so that noise generated by driving a cooling fan in the apparatus in the standby state is always generated.

According to the present invention, the number of voltage fluctuations caused by an inrush current to a heater can be optimally controlled in each state of the apparatus, and suppression of power supply voltage fluctuations and harmonics to a commercial power supply can be achieved without adding hardware parts and filter members. The heater can be controlled with a simple configuration without sacrificing the fixing performance and the productivity of the apparatus. Even if control is performed and operation is performed again during a certain period of time, the fixability is not reduced, and the time required to return from non-operation to operation can be reduced, and power can be saved. It is possible to maintain the device normally during non-operation and prevent noise from being generated, without adding a nichrome wire etc. peculiar to the operation of the device in a low temperature environment during non-operation. Conclusion It is possible to improve the margin, and to provide an image forming apparatus capable of improving the margin for condensation of the imaging unit.

[0007]

According to one aspect of the present invention, there is provided a fixing device using a heater as a heat source, heater driving means for driving the heater, and a member heated by the heater. A temperature detecting means for detecting the temperature of the heater, and turning on the heater based on a predetermined lighting threshold value according to the detected temperature of the temperature detecting means; and a predetermined light-off threshold value according to the detected temperature of the temperature detecting means. Control means for controlling the heater by turning off the heater on the basis of
At least the light-off threshold value during non-operation of image formation is set to a value different from the light-up threshold value during non-operation of image formation and a high value, and the control cycle of the heater during non-operation of image formation is The non-operation lighting threshold and the light-off threshold are set so as to be wider than the heater control cycle during operation.

According to a second aspect of the present invention, there is provided a fixing device using a heater as a heat source, heater driving means for driving the heater, temperature detecting means for periodically detecting a temperature of a member heated by the heater, The heater is turned on based on a predetermined lighting threshold value according to the temperature detected by the temperature detecting means, and the heater is turned off based on a predetermined light-off threshold value based on the temperature detected by the temperature detecting means. In the image forming apparatus having a control unit that controls the heater by performing the above, at least the light-off threshold value at the time of non-operation of image formation is set to a value different from the light-up threshold value at the time of non-operation of image formation and a high value. And
The difference between the turn-on threshold and the turn-off threshold during non-operation of image formation is set to be larger than the difference between the turn-on threshold and the turn-off threshold during operation.

The invention according to claim 3 is the invention according to claim 1 or 2
In the above-described image forming apparatus, the lighting threshold value and the light-off threshold value in the non-operation time are predetermined constant values.

The invention according to claim 4 is the invention according to claim 1 or 2.
In the image forming apparatus described above, the change of the light-off threshold value and the light-on threshold value during the non-operation time is performed after a certain time has passed during the non-operation time period.

[0011] The invention according to claim 5 is the invention according to claim 1 or 2.
In the above-described image forming apparatus, the change of the light-off threshold value and the light-on threshold value during the non-operation time is performed so as to gradually decrease during the non-operation time period.

The invention according to claim 6 is the first or second invention.
In the image forming apparatus described above, both the non-operation threshold value and the non-operation threshold value are lower than the non-operation threshold value.

According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, a cooling fan for cooling the inside of the image forming apparatus is provided, and when the image forming apparatus is not operating, the blowing of the cooling fan is stopped. At the same time, the non-operation threshold value of the apparatus when it is not operating is set to a temperature at which there is no thermal influence on other components except the fixing device constituting the image forming apparatus.

The invention according to claim 8 is the first or second invention.
The image forming apparatus according to claim 1, further comprising: an image forming unit that performs an image forming operation; and a second temperature detecting unit that detects a temperature of the image forming unit. The image forming unit performs the image forming based on a detected temperature result of the second temperature detecting unit. The light-off threshold value is set when the device is not operating.

[0015] The invention according to claim 9 is the invention according to claim 1 or 2.
The image forming apparatus according to claim 1, further comprising: an image forming unit that performs an image forming operation; a second temperature detecting unit that detects a temperature of the image forming unit; and a cooling fan that cools the inside of the image forming apparatus. The driving state of the cooling fan is changed when the device is not operating, based on the temperature detected by the temperature detecting means.

[0016]

FIG. 3 shows a schematic circuit configuration of a first embodiment of the present invention. The first embodiment is an embodiment of an image forming apparatus including a copying machine, and peripheral devices such as a document feeding device, a transfer paper sorting device, a duplex unit, a staple unit, and a large-volume paper feeding device are selected in the apparatus main body. It is possible to install it. In the apparatus main body, a document on a document table is read by a scanner, and an image signal from the scanner is sent to an exposure unit.

An image bearing member made of a photosensitive member, for example, a photosensitive drum is rotated by a main drive motor and uniformly charged by a charging device, and then exposed by an exposure device in accordance with an image signal from the scanner, and is statically charged. An electrostatic latent image is formed, and the electrostatic latent image is developed by a developing device to form a toner image.
After being transferred from a selected one of 20 or a manual feed table to a transfer sheet as a transfer material fed through a registration roller, the sheet is fixed by a fixing device and discharged.

The photosensitive drum is cleaned by a cleaning device after the transfer of the toner image, and is discharged by a discharge lamp. In the fixing device, a fixing roller and a pressure roller are pressed against each other by a pressure mechanism and are rotationally driven by a driving source, and the fixing roller is heated by a halogen heater as a fixing heater. The surface temperature of the fixing roller is detected by a thermistor as temperature detecting means.

The document feeder feeds a document onto a platen of the apparatus body, and discharges the document on the platen after copying is completed. The transfer paper sorting device sorts the transfer paper discharged from the apparatus main body, and the staple unit binds the transfer paper. The duplex unit reverses the front side copy transfer paper discharged from the apparatus body in the duplex mode, and then feeds it to the registration roller. This transfer paper is sent out at a predetermined timing by the registration roller, and on the back surface, the photosensitive drum After the toner image is transferred by the transfer means, the toner image is fixed by the fixing device and discharged.

When the duplex unit is not attached to the apparatus main body, the transfer paper for the front side copy in the duplex mode is
The sheet is conveyed from the fixing device to the intermediate tray, and is turned over from the intermediate tray and fed to the registration rollers. The transfer paper is sent out at a predetermined timing by a registration roller, and after the toner image on the photosensitive drum is transferred to the back surface by the transfer means, the toner image is fixed by the fixing device and discharged. In addition, the large-volume paper feeder feeds the transfer paper to the registration roller when selected.

The above configuration of the first embodiment is well known. The microcomputer including the CPU 11, the ROM 12, and the RAM 13 forms a control unit. CPU11
Is operated by selecting each chip via a decoder 29 and using a latch circuit 28 to read the ROM 12 and the RAM 13
Specify the address of The CPU 11 operates while using the RAM 13 in accordance with programs and fixed data in the ROM 12, and exchanges signals with the system control unit.

The paper feeding devices 18 to 20 are well known, and receive signals from the CPU 11 by the serial / parallel receivers 21 to 23 and use a driver to pick up a solenoid (SOL), a paper feeding clutch (CL), and a tray lock SOL. Drive the ascent motor, paper (transfer paper)
The detection signals of the size sensor, the paper end sensor, the tray set sensor, the connection detection sensor, the middle slave sensor, and the right door open sensor are transmitted to the CP via the input gate array 24.
Transfer to U11 or RAM13.

The exposure means receives an image signal from the scanner or the like via the video gate array 25 by the CPU 11 and receives a semiconductor laser (L) based on the image signal.
D) The LD is driven by the drive circuit. The laser beam from the LD is deflected and scanned by a polygon mirror and is irradiated on the photosensitive drum. In addition, detection signals of a middle sensor, a registration sensor, a fixing sensor, a paper ejection sensor, a cartridge door open sensor, an abutment opening sensor, a feedback voltage of a high voltage power supply, a thermistor, a density, etc. An analog signal from a sensor or the like is transferred to the CPU 11 or the RAM 13 via the gate array 26.

The CPU 11 further includes a relay CL for feeding and conveying, an intermediate CL, a resist CL, a door lock SOL for a cartridge, a pinch SOL, a pressure SOL, a conveying motor, an opening motor, The control unit controls a contact / separation solenoid, a main drive motor, a blade SOL, a toner supply SOL, a polygon motor, the above-described heater as a fixing heater, a high-voltage power supply, a static elimination lamp, a toner density sensor, and the like.

FIG. 4 shows a zero-cross signal generating circuit according to the first embodiment, and FIG. 5 shows voltage waveforms at various parts thereof.
In the first embodiment, electric power is supplied from a general commercial power supply AC. The zero cross signal generation circuit shown in FIG. 4 generates a zero cross signal at a zero cross point of the input voltage from the commercial power supply AC. That is, the zero-cross signal generation circuit includes a rectifier circuit DB, a photocoupler PC,
The power supply unit includes a transistor Tr, resistors R _{1 to} R ₅ and a capacitor C, and a ground GND.
And a predetermined DC voltage such as +5 V is applied from the power supply unit.

The AC voltage input from the commercial power supply AC is
Full-wave rectification is performed by a rectifier circuit DB via a circuit including resistors R ₁ and R ₂ and a capacitor C, and applied to the base of the transistor Tr via a photocoupler PC. It turns on near the point, and a zero-cross signal is output from an output terminal (part B) connected to the collector of the transistor Tr.

FIG. 1 shows a heater drive control section according to the first embodiment, and FIG. 2 shows signal waveforms of the respective sections. CPU 11,
ROM 12, RAM 13, interrupt controller 14, P
The I / O 15 constitutes control means, and a zero-cross signal from the B section of the zero-cross signal generation circuit is input to the interrupt terminal INT1 of the interrupt controller 14 and is interrupted at the falling edge of the zero-cross signal. The heater drive circuit 16 supplies the heater 1 with an AC input from a commercial power supply AC.
The heater 17 is turned on / off using the reference of the drive timing 7 as the zero cross signal.

The CPU 11 starts the phase angle timer in response to the interruption by the zero cross signal. A predetermined value is set in the phase angle timer, and when the phase angle timer counts the predetermined value, a time-over interrupt occurs. C
When the time-over interrupt occurs, the PU 11 outputs a heater trigger signal to the heater drive circuit 16, and the heater drive circuit 16 turns on a heater drive element including a heater triac, so that an AC input from the commercial power supply AC is used for heater drive. The heater 17 is energized through the element. The CPU 11 turns off the heater trigger signal to the heater drive circuit 16 in response to the next zero-cross signal to turn off the heater triac, thereby turning off the power supply to the heater 17.

If the phase angle timer value is large, the voltage of the heater 17 (lighting voltage or effective voltage of the heater 17) becomes small, and if the phase angle timer value is small, the voltage of the heater 17 becomes large. As described above, the CPU 11 changes the phase angle timer value from the large value to the small value little by little, and finally sets the heater trigger signal to a low level to turn on the heater 17 so that the heater 17 does not generate an inrush current unique to the halogen heater. 17 can be turned on after turning off.

In recent years, various measures have been taken for electric equipment based on standards such as power supply harmonics and voltage fluctuation rules for electric equipment. The power supply harmonics are regulated by harmonic components that flow from the electric device to the commercial power supply. When the phase control of the power supplied from the commercial power supply AC to the heater 17 is performed by the triac as described above, the power supply harmonics flow to the commercial power supply AC by switching the triac. The harmonic components increase. Voltage fluctuations are regulated by the number of times of rapid fluctuations in current consumption, such as inrush current to the heater, and fluctuation levels. A sudden increase in current causes an instantaneous voltage drop in the surrounding commercial power supply line. Raises flickering of equipment. These regulations are all EN standards.

In an image forming apparatus, power consumption and power consumption are generally different between a standby state (non-operation when image hair is not formed) and an operation (operation during image formation). The device whose electric energy was around 150 Wh,
During operation, it often exceeds 500 Wh. For example, in an image forming apparatus in which a toner image is formed on a transfer sheet and fixed by a fixing device including a fixing roller and a heater, and a phase control of a supply voltage to the heater and a soft start lighting of the heater are performed, the fixing device is in operation. As a result, the amount of heat is largely taken by the rotation of the transfer paper and the fixing roller, so that the heater is turned on at a high duty ratio and the power consumption increases. Further, during operation, the power consumption of the control circuit and the drive circuit (the circuit for driving the motor, the fan, and the illumination lamp) also increases, and the power consumption of elements other than the heater naturally increases.

In the standby mode, since the power consumption of the control circuit and the drive circuit (the circuit for driving the motor, the fan, and the illumination lamp) is small, the ratio of the harmonic components generated when the heater is soft-started is extremely low. growing. However, if soft start lighting of the heater is not performed, the power supply voltage fluctuation level becomes extremely large. Also, as can be said at the time of operation, the heater lighting method that balances both harmonics and voltage fluctuations differs depending on the power consumption and power amount of the device.

Further, the voltage fluctuation differs depending on the capacity of the heater. FIG. 6 shows an example of the difference in Pst depending on the capacity of the heater. Here, Pst is a value indicating the voltage fluctuation level within a predetermined time by the flicker meter, and becomes a small value if the voltage fluctuation level and the occurrence frequency are small, respectively.
It can be said that the device has a small voltage fluctuation level. FIG. 6 shows values in a standby state of the image forming apparatus in which the heater lighting method is the same and only the heater capacity is different.

FIG. 7 shows an example of the difference in Pst depending on the number of soft starts of the heater. FIG. 7 shows values during operation of the image forming apparatus in which only the number of soft starts is changed while the heater capacity is the same. FIG. 8 shows an example of a difference in harmonics depending on the number of soft starts of the heater. In FIG. 8, ○ indicates that the harmonic generation level is determined to be within the EN standard, and x indicates that the harmonic generation level is determined to be outside the EN standard. FIG. 8 shows the harmonic generation level, which differs depending on the operation mode (difference in power consumption of the device).

In the first embodiment, a document feeder, a transfer paper sorting device, a duplex unit, and a staple unit as peripheral devices can be selectively attached to the apparatus main body. Electricity is not constant,
The heater 17 depends on the presence / absence of a document feeder, a transfer paper sorter, a duplex unit, a staple unit, whether or not these peripherals are used as an operation mode, and at what duty ratio these peripherals are operated. The optimal lighting method differs greatly. That is, the optimal lighting method of the heater 17 differs depending on the configuration as described above.

Therefore, in the first embodiment, the lighting method of the heater 17 is changed by the CPU 11 as follows according to the operation mode of the apparatus. As a result, both harmonic and voltage fluctuation levels can be well balanced without requiring a large power line filter or the like in the device.

That is, in the first embodiment, the fixing temperature control by turning on / off the heater 17 is based on the temperature obtained by the temperature detecting means for detecting the temperature of the fixing roller. In order to reduce power consumption and reduce the number of inrush currents at the start of lighting of the heater 17 during non-operation, the fixing temperature control is performed based on the temperature obtained by the temperature detecting means. Different thresholds for turning off the heater 17 are provided for the non-operating state, and these thresholds are set to be lower than the operating state threshold value. The threshold value for turning off the heater 17 during non-operation is set to a level at which the temperature overshoot of the heater 17 does not affect the apparatus, and the number of voltage fluctuations caused by the rush current is optimally suppressed in each state of the apparatus.

That is, during non-operation (standby), the fixing roller temperature becomes the lighting threshold value of the heater 17 and the heater 17 starts continuous lighting. When the fixing roller temperature becomes the lighting threshold value of the heater 17, the heater 17 is immediately turned on. Is turned off, but overshoot of the fixing roller temperature occurs. By considering the overshoot amount in advance and setting the threshold value for turning off the heater 17 in the non-operation time lower than the threshold value for turning off the heater 17 in the operation time, the uselessness due to the overshoot of the fixing roller temperature is reduced. Heat stress is not applied to the fixing device, and power consumption is saved by reducing the threshold value, which is effective in suppressing generated voltage fluctuation, harmonics, and noise terminal voltage.

In the first embodiment, the turning on / off of the heater 17 is performed based on the temperature obtained by the temperature detecting means.
The fixing temperature control by the light-off control is a fixing temperature control that gives priority to the fixing property of the transfer paper during operation, and a fixing temperature control that can save power and reduce the number of rush currents at the start of lighting specific to the heater 17 during non-operation. In addition, based on the temperature obtained by the temperature detecting means, different thresholds for turning on the heater 17 are set between the operation and the non-operation, and these thresholds are set lower than the threshold during the operation. I do. The threshold value for turning on the heater 17 during non-operation is set to a lower limit that does not affect copy productivity (first copy productivity), and the number of voltage fluctuations caused by the rush current itself is optimally suppressed in each state of the apparatus.

Here, in the stand-by state, shortening the lighting time of the heater 17 and reducing the number of times of lighting of the heater 17 as much as possible are effective in suppressing the generated voltage fluctuation, harmonics, noise terminal voltage, and power consumption. It is. However, if the fixing roller temperature is set too low in the standby state, the image forming operation cannot be started immediately after the power is turned on (the time required for the fixing roller temperature to return to a predetermined temperature at which the fixing roller can be fixed becomes longer), and the fixing roller temperature becomes higher. Causes the operator to wait until the temperature rises to a predetermined temperature, and the productivity is reduced. Therefore, in the standby state, by giving a difference between the lighting threshold value and the turning-off threshold value of the heater 17, the heater 17 that has been turned on is continuously turned on until the fixing roller temperature reaches the turning-off threshold value. As a result, the number of times the heater 17 is turned on can be reduced, which is effective in suppressing the generated voltage fluctuation, harmonics, and noise terminal voltage. Further, the time required from the start of the image forming operation to the time when the transfer paper reaches the fixing device is substantially the same as the time required for the fixing roller temperature to return from the lighting threshold to the image forming operable temperature. With this setting, the operator does not have to wait until the fixing roller temperature rises to the image forming operable temperature, and the productivity does not decrease.

Further, in the first embodiment, the cycle of the fixing temperature control by turning on / off the heater 17 is controlled based on the temperature obtained by the temperature detecting means. And a fixing temperature control cycle longer than the fixing temperature control cycle during the operation described above so as to save power and reduce the number of inrush currents at the start of lighting specific to the heater 17 when not in operation. Based on the temperature obtained by the temperature detecting means, the cycle of fixing temperature control by turning on / off the heater 17 is set to be different between when the apparatus is operating and when it is not operating,
The number of voltage fluctuations caused by the rush current itself is optimally suppressed in each state of the device.

That is, the absolute value of the control temperature of the fixing device,
Since the suppression of the temperature fluctuation contributes to the improvement of the fixing property of the transfer paper and the suppression of the wrinkling of the transfer paper, the abnormality detection processing also detects the temperature fluctuation and the like minutely. In the standby state, a fixing temperature control method that can suppress voltage fluctuations and harmonics is used. The absolute value of the fixing control temperature and the suppression of the fixing temperature fluctuation are reduced by the rise time of the apparatus (the time required for transition from the standby state to the operating state). If there is no difference, there is no effect on productivity and the like. Therefore, when the processing capacity of the control means is operating, the control cycle of turning on / off the heater 17 is advanced from the level of temperature fluctuation or the like, and the standby state is slowed down in the standby state. Can be reduced, and it is effective in suppressing the generated voltage fluctuation, harmonics, and noise terminal voltage, and is also effective in deteriorating the filament of the heater 17 itself. Heater 1
7 life extension is possible.

Specifically, the lighting method of the heater 17 is changed as follows.

In operation: Number of soft starts of the heater 17: 10 to 15 times Lighting threshold of the heater 17: 183 ° C. Lighting threshold of the heater 17: 185 ° C. Fixing temperature detection cycle: 0.8 seconds (On / off update of the heater 17) Period) Standby: Number of soft start of heater 17: 5 times Threshold value for turning on heater 17: 140 ° C Threshold value for turning off heater 17: 160 ° C Fixing temperature detection cycle: 0.8 seconds or more (longer than 0.8 seconds during operation) (Cycle) (On / off update cycle of heater 17) Number of soft starts of heater 17: At the time of operation, it is appropriately determined at the start of image forming operation between 10 and 15 times by mounting each peripheral device. During standby, the value is set to a value smaller than the number of soft starts during operation in consideration of the influence of harmonics.

Threshold value for turning on / off the heater 17: During operation, the temperature of the fixing roller itself and the temperature ripple greatly affect the fixing property of the transfer sheet and the wrinkles of the transfer sheet during fixing. Are set to different values close to each other so as to reduce the temperature ripple of the heater 17. During standby, reducing the number of times the heater 17 is turned on / off during the standby time as much as possible is advantageous for harmonics and voltage fluctuations, and the problem of the temperature of the fixing roller can be dealt with immediately when an image forming operation is requested. The fixing roller temperature is high, and there is no problem of the temperature ripple of the fixing roller. Therefore, the heater 17
The time required for the fixing roller temperature to return to the temperature required during the image forming operation (185 ° C. in the first embodiment) by turning on
If the time required for the transfer paper to reach the fixing device from the start of operation is set to be substantially the same, the operator does not have to wait until the fixing roller temperature rises to a predetermined temperature, and the productivity is reduced. Does not occur. However, simply lowering the threshold value for turning on / off the heater 17 only slightly reduces the number of times the heater 17 is turned on / off. Therefore, the difference between the threshold value for turning on and off the heater 17 is sufficiently increased. As a result, the temperature change of the fixing roller becomes as shown in FIG.
The number of times the heater 17 is turned on / off is greatly reduced.

Fixing temperature detection cycle: A long on / off update cycle of the heater 17 (update cycle of the heater trigger signal) is advantageous for harmonics and voltage fluctuations, but as described above during standby, Since the difference between the threshold value for turning on the heater 17 and the threshold value for turning off the heater 17 is large, the on / off cycle of the heater 17 itself becomes long, and there is not much change even when the fixing temperature detection cycle is operated. By the way, if the difference between the lighting threshold value and the turning-off threshold value of the heater 17 during standby is about 15 deg, the ON / OFF cycle of the heater 17 is about 50 seconds, and the difference between the lighting threshold value and the turning-off threshold value of the heater 17 is 20 deg. , The ON / OFF cycle of the heater 17 is about 50 seconds. If the difference between the lighting threshold value and the light-off threshold value of the heater 17 is 40 deg, the on / off cycle of the heater 17 is about 90 seconds.

As shown in FIG. 10, the CPU 11 determines whether or not an image forming operation (copying operation) is being performed, and if the image forming operation is not being performed (if the image forming operation is not performed, the CPU 11 is in a standby state). Values are set according to the configuration and state of the apparatus (presence / absence of each peripheral device, operation mode), the lighting threshold of the heater 17 is set to 140 ° C., and the extinguishing threshold of the heater 17 is set to 160 ° C. The target value is set according to the configuration and state of the apparatus (presence / absence of each peripheral device, operation mode), and the lighting threshold value of the heater 17 is set to 183 ° C. and the extinguishing threshold value of the heater 17 is set to 185 ° C.

Then, the CPU 11 updates the on / off state of the heater 17, that is, if the lighting threshold value of the heater 17 is higher than the value obtained by sampling the input value from the temperature detecting means (the lighting threshold value of the heater 17 is fixed). If the temperature is higher than the surface temperature of the roller), a flag such as "heater on request" is set to turn on the heater, and if the lighting threshold value of the heater 17 is lower than a value obtained by sampling the input value from the temperature detecting means, Resets the "heater on request". Further, the CPU 11 samples and holds the input value from the temperature detecting means.

As described above, the CPU 11 controls the heater 17 according to the fixing temperature detection cycle or the heater ON / OFF update cycle.
Is turned on / off. The CPU 11 causes the heater 17 to be actually turned on / off by the heater drive circuit 16 based on the zero-cross signal. In addition to the above, the fixing temperature detection cycle itself may be changed by the state and configuration of the apparatus in addition to the target value setting processing. Further, if the standby state is divided into a normal standby state and a preheating standby state, and the threshold value for turning on / off the heater 17 is set in a finer stepwise manner in each state, power saving besides harmonic and voltage fluctuations can be achieved. The effect can be further improved.

As shown in FIG. 11, the CPU 11 changes the number of soft starts of the heater 17 depending on the presence or absence of each peripheral device for pre-processing and post-processing and the presence or absence of operation. That is, the CPU 11
It is determined whether or not the image forming operation is being performed. If the image forming operation is not being performed, the number of soft starts of the heater 17 is set to five. The CPU 11 sets the number of soft starts of the heater 17 to 10 during the image forming operation, and sets a document feeder (DF), a staple unit, and the like in the apparatus main body.
Transfer paper sorting device (FIN), duplex unit (DP
X), a document feeder (DF), a staple unit / transfer paper sorter (FIN), a double-sided printer, based on an input signal from each sensor that detects the connection of a large paper feeder (BANK). Unit (DPX), high-volume paper feeder (BANK), determine whether or not it is connected, and feed the original to the main body of the device (DF), staple unit / transfer paper sorter (FIN), duplex unit (DPX) or one of the large-volume sheet feeding devices (BANK), the number of soft starts of the heater 17 is increased by one.

Further, the CPU 11 controls the document feeder (D
F) to determine whether or not the document feeder (D
If F) is operating, the number of soft starts of the heater 17 is increased by one, and it is determined whether or not the staple unit / transfer paper sorting device (FIN) is operating, and the staple unit / transfer paper sorting device (FIN) is operated. If) is in operation, the number of soft starts of the heater 17 is increased twice. Further, the CPU 11 determines whether the duplex unit (DPX) and the large-volume sheet feeding device (BANK) are operating, and if the duplex unit (DPX) and the large-volume sheet feeding device (BANK) are operating, the heater Increase the number of soft starts of 17 by one. In the first embodiment, when a multifunction peripheral having functions such as a facsimile and a printer in addition to a copying function is provided,
By changing the ten times in FIG. 11 by the application of the facsimile, the printer, or the like, it is possible to set a more optimal number of soft starts of the heater 17.

As shown in FIG. 12, the CPU 11 changes the number of soft starts of the heater 17 depending on the size of the transfer sheet selected and used for image formation. That is, C
The PU 11 determines whether the frequency (power supply frequency) of the AC input from the commercial power supply AC is 50 Hz or 60 Hz. If the power supply frequency is 50 Hz, the transfer paper selected and used for image formation is used. (Hereinafter referred to as transfer paper)
If the size of the transfer paper is either A3 or B4, the number of soft starts of the heater 17 is set to 12; if the size of the transfer paper used is A4 or B5, the number of soft starts of the heater 17 is set to 11; Transfer paper size is A3,
If none of B4, A4, and B5, the number of soft starts of the heater 17 is set to 10 times.

The CPU 11 operates at a power supply frequency of 60H.
z, the size of the transfer paper used is A3, B4,
If it is any of A4, the number of soft starts of the heater 17 is 12 times, and if the size of the transfer paper used is B5, the number of soft starts of the heater 17 is 11 times, and the size of the transfer paper is A3, B4, A4. , B5, the number of soft starts of the heater 17 is set to 10.

In addition to the above, for manual feeding frequently using special paper, processing such as changing the set temperature and the number of soft starts of the heater 17 may be separately performed. Also, since the amount of heat required for fixing the toner image differs depending on the type of the transfer paper, a configuration is adopted in which the destination can be recognized in the image forming apparatus, and the heater shown in FIGS. The number of soft starts of 17 may be set in more detail for each destination. This makes it possible to perform optimal processing for different paper types, different power supply voltages, different harmonics, regulation of power supply voltage fluctuations, and standards.

FIG. 13 shows the processing in the zero-cross interrupt performed by the zero-cross signal. The CPU 11 performs the processing shown in FIG. 13 in the zero-crossing interrupt processing performed by the zero-crossing signal, and first determines whether or not the frequency has been detected. Frequency detection means that the frequency of the commercial power supply AC is 50/6
Since the frequency is 0 Hz, the CPU 11 normally detects the power supply frequency in a frequency detection routine (not shown) as follows.

That is, the CPU 11 sets a predetermined period (50 seconds) during a period in which the heater trigger signal for driving the heater 17 to the heater driving circuit 16 is turned off at the time of starting up the apparatus.
Counting the number of times a zero-cross signal interrupt occurs within about 0 ms). Then, the CPU 11 determines whether the power supply frequency is 50 Hz or 60 Hz based on the count number, and thereby determines the subsequent heater 17.
The setting of the phase angle timer value at the time of soft start is determined.

If the frequency has not been detected, the CPU 11 jumps to the frequency detection routine. If the frequency has been detected, the CPU 11 determines whether or not there is a "heater on request" (set). The heater trigger signal to the heater drive circuit 16 is turned off (if not set), the heater 17 is turned off, and the soft start (S start) end flag is reset to 0.

The CPU 11 issues a "heater-on request"
If there is, it is determined whether the S start end flag is set to 1 or not. If the soft start of the heater 17 is completed and the S start end flag is set to 1, a heater trigger signal to the heater drive circuit 16 is generated. Turn on heater 1
Turn 7 on. Therefore, when the heater 17 is already lit, the heater trigger signal is continuously turned on without performing a new soft start process. This is because there is no occurrence of inrush current and there is no concern about power supply voltage fluctuation.

The CPU 11 determines that the soft start of the heater 17 has not been completed and the S start end flag is 0.
If it is set, the phase angle timer is set and the phase angle timer is started, and the number of times the phase angle timer is started is counted. Then, the CPU 11 determines whether or not the number of starts of the phase angle timer has reached the number of soft starts, and sets the S start end flag to 1 when the number of starts of the phase angle timer has reached the number of soft starts. .

Accordingly, when newly turning on the heater 17, the CPU 11 sets the phase angle timer, starts the phase angle timer, counts the number of times the phase angle timer starts, and the number of times of the start is as shown in FIG. If the number of soft start times is equal to the number of soft start times determined by the processing shown in FIG.
The start end flag is set to 1, and the heater trigger signal is continuously turned on without performing the soft start processing in the subsequent zero cross interruption processing.

As described above, the first embodiment is an embodiment according to the first aspect of the present invention, and includes a fixing device using the heater 17 as a heat source, and a heater driving circuit as heater driving means for driving the heater 17. 16, temperature detecting means for detecting the temperature of a fixing roller as a member heated by the heater 17, and lighting of the heater 17 based on a predetermined lighting threshold value according to the temperature detected by the temperature detecting means, A CPU 11 for controlling the heater 17 by turning off the heater 17 based on a predetermined light-off threshold value in accordance with the temperature detected by the temperature detecting means;
12, RAM 13, interrupt controller 14, PI / O
In the image forming apparatus having the control unit comprising the control unit 15, at least the light-off threshold value when the image formation is not in operation is set to a value different from the light-up threshold value when the image formation is not in operation, and is set to a high value. Since the control threshold of the heater 17 at the time of non-operation is set to be wider than the control cycle of the heater 17 at the time of the image forming operation, the threshold value of the non-operation and the threshold value of the non-operation are set. The lighting time of the heater per unit of time becomes longer, the inrush current and voltage fluctuation related to the lighting and extinguishing of the heater per unit of time become smaller, and the number of voltage fluctuations caused by the inrush current to the heater is optimized for each state of the device. Controllable,
Suppression of power supply voltage fluctuations and harmonics to the commercial power supply can be suppressed as much as possible without the addition of hardware components and filter members, without sacrificing fixing performance or device productivity.

Further, the first embodiment is an embodiment of the present invention according to claim 2, wherein a fixing device using the heater 17 as a heat source, a heater driving circuit 16 as heater driving means for driving the heater 17 are provided. A temperature detecting means for periodically detecting the temperature of a fixing roller as a member heated by the heater 17; and turning on the heater 17 based on a predetermined lighting threshold value in accordance with the temperature detected by the temperature detecting means. A CPU 1 for controlling the heater 17 by turning off the heater 17 based on a predetermined light-off threshold value in accordance with the temperature detected by the temperature detecting means.
1, ROM 12, RAM 13, interrupt controller 1
4. In the image forming apparatus having the control unit including the PI / O 15, at least the light-off threshold value when the image forming is not in operation is set to a value different from the light-up threshold value when the image forming is not in operation and to a high value. Since the difference between the light-on threshold and the light-off threshold during non-operation of image formation is set to be larger than the difference between the light-on threshold and the light-off threshold during operation, the light-on time of the heater per unit number becomes longer during non-operation. Inrush current and voltage fluctuations related to turning on and off the heater per unit number are reduced, and the number of voltage fluctuations caused by the inrush current to the heater can be optimally controlled in each state of the device. The suppression of waves can be suppressed as much as possible without the addition of hardware components and filter members, without sacrificing fixing performance and productivity of the apparatus.

Further, the first embodiment is an embodiment of the invention according to claim 3, and in the image forming apparatus according to claim 1 or 2, the lighting threshold value and the light-off threshold value at the time of non-operation are predetermined. Therefore, the same effect as the image forming apparatus according to claim 1 or 2 is obtained,
Further, the heater can be controlled with a simple configuration.

Further, the first embodiment is an embodiment of the invention according to claim 6, wherein in the image forming apparatus according to claim 1 or 2, both the light-off threshold and the light-up threshold in the non-operation time are both in the operation time. , Which has the same effect as the image forming apparatus according to claim 1 or 2,
Further, the average temperature of the fixing roller during non-operation can be reduced, and power can be saved.

FIG. 14 shows the configuration of the second embodiment of the present invention. In the second embodiment, in the first embodiment, an image signal from the scanner is subjected to predetermined processing in an image processing unit, and is sent to the exposure unit. The above-described photosensitive drum, charging means, exposure means, developing device, transfer means,
The cleaning device, the discharging lamp, and the fixing device constitute an image forming unit that forms an image on transfer paper, and the image forming unit performs the above-described image forming operation. The image processing unit is a CPU 1
One doubles.

The non-operation threshold value of the heater 17 during the non-operation of the image formation is determined by the heater 1 during the non-operation of the image formation.
7 is set to a value that is different from the lighting threshold value of No. 7 and is set to a high value, and the control cycle of the heater 17 during the non-operation of the image formation is set to be longer than the control cycle of the heater 17 during the operation of the image formation. A lighting threshold value and a light-off threshold value at the time are set. Further, when the heater 1 is not operated during image formation,
The light-off threshold value of the heater 17 is set at the time of non-operation of the image forming operation.
Is different from the lighting threshold value of the heater 17 and is set to a high value, and the difference between the lighting threshold value and the turning-off threshold value of the heater 17 when the image forming is not in operation is the difference between the lighting threshold value and the turning-off threshold value of the heater 17 during the operation. Set larger than

The cooling fan 30 in the apparatus is a cooling fan for cooling the inside of the apparatus main body, and is controlled by the CPU 11 through the output gate array 27 and the driver 31.
Alternatively, it is controlled by the CPU 11 through the output gate array 27, the driver 32, and the cooling fan drive voltage dividing resistor 33. CPU 11, ROM 12, RAM1
3. CPU such as interrupt controller 14, PI / O15
The peripheral components constitute a control unit, which controls not only the temperature of the fixing device but also the operation unit, sequence control for image formation, image processing control, and the like.

The heater drive circuit 16 comprises a drive circuit section and the above-mentioned zero-cross signal generation circuit section. The drive circuit section includes a triac, a triac trigger coupler, an SN coil for removing noise of the triac, a capacitor, and the like.
To drive the fixing heater 17. The heater drive circuit 16 turns on / off the fixing heater 17 under the control of the CPU 11 using the reference of the driving timing of the fixing heater 17 as the zero cross signal.

In the fixing device thermistor for detecting the surface temperature of the fixing roller, an output signal corresponding to the surface temperature of the fixing roller changes in resistance value (voltage change). Therefore, the output signal of the fixing device thermistor is analog / digital. The data is converted into a digital value by the converter and input to the CPU 11.
The CPU 11 controls the heater drive circuit 16 based on a temperature detection signal input from the fixing device thermistor via an analog / digital converter to turn on / off the fixing heater 17 to set the surface temperature of the fixing roller to the set temperature. The temperature is controlled to be maintained, and the set temperature is set to 180 ° C. during the image forming operation. The cooling fan 30 in the device is
Controlled by the CPU 11 via the drivers 31 and 32, during image forming operation, the CPU 11 rotates at a high speed to maximize the air discharging effect.

Generally, the temperature control of the fixing device is performed as follows. The zero-cross signal generation circuit generates a zero-cross signal at a zero-cross point of the AC voltage input from the commercial power supply AC, and uses the timing of the rise and fall of the zero-cross signal as an external interrupt signal for control and uses this as an external interrupt signal from the commercial power supply AC. This is used as a reference for controlling the supply voltage to the fixing heater 17.

The CPU 11 starts the phase angle timer in response to the interruption by the zero cross signal. A predetermined value is set in the phase angle timer, and when the phase angle timer counts the set value, a time-over interrupt occurs.
When the time-over interrupt occurs, the CPU 11 outputs a heater trigger signal to the heater drive circuit 16, and the heater drive circuit 16 turns on the heater drive element composed of the heater triac, so that the AC input from the commercial power supply AC becomes the heater triac. Fixing heater 1 through
7 is energized. The heater drive circuit 16 turns off the heater triac in response to the next zero-cross signal and turns off the power supply to the fixing heater 17.

When the phase angle timer value is large, the fixing heater 17
(Lighting voltage or effective voltage of the fixing heater 17) decreases, and if the phase angle timer value is small, the voltage of the fixing heater 17 increases. As described above, the CPU 11 changes the phase angle timer value from the large value to the small value little by little, and finally sets the heater trigger signal to a low level (a state in which the fixing heater 17 is turned on), thereby turning on the fixing heater 17. The fixing heater 17 can be turned on from off without the occurrence of an inrush current unique to the heater.

When the temperature detected by the temperature detecting means for detecting the surface temperature of the fixing roller is lower than the set temperature, the fixing heater (halogen heater) 17 is turned on by the method described above. Further, the cooling fan 30 in the apparatus generally has a configuration in which a plurality of modes such as high-speed rotation, low-speed rotation, and stop can be selected. During the image forming operation, the cooling fan 30 is driven by the driver 31 to rotate at high speed. In the standby state, the setting can be changed to each mode.
That is, the CPU 11 controls the driver 3 during the image forming operation.
1, the cooling fan 30 in the apparatus is rotated at a high speed, and the drivers 31 and 32 are controlled in the standby state to control the cooling fan 30 in the apparatus.
Is the setting mode.

FIG. 15 shows the operation timing of the second embodiment. In the standby state, the temperature of the fixing device is controlled by the phase control of the fixing heater 17 at about 180 ° C., which is substantially the same as the set temperature during the image forming operation, until a predetermined time T1 elapses from the end of the image forming operation. The fan 30 is driven by the driver 32 via the resistor 33 to maintain the low-speed rotation.

However, even if it is controlled at the same 180 ° C., the threshold value for turning on and the threshold value for turning off the fixing heater 17 are different from those during the image forming operation. Once the fixing heater 17 is turned on, the fixing heater 17 is turned on continuously until the detected temperature of the fixing device thermistor reaches a threshold temperature for turning off. This allows
The number of times the fixing heater 17 is turned on per unit time can be reduced, which is effective for suppressing voltage fluctuation, harmonics, and noise terminal voltage.

The image forming operation can be performed based on the time required for the transfer paper to reach the fixing device from the start of the image forming operation and the surface temperature of the fixing roller when the fixing heater 17 is turned on at the start of the image forming operation. If the time required to return to a normal temperature is set to be substantially the same, the operator does not have to wait until the surface temperature of the fixing roller rises to a temperature at which the image forming operation can be performed at the start of the image forming operation. The productivity of image formation does not decrease (the time for returning the surface temperature of the fixing roller to the temperature at which the image forming operation can be performed at the start of the image forming operation is not required). Further, since the surface temperature of the fixing roller is maintained at a high temperature, the cooling fan 30 cannot be completely stopped at the time of standby, so that the cooling fan 30 slightly generates noise at the time of standby.

Therefore, in the second embodiment, after a predetermined time T1 has elapsed from the end of the image forming operation, the control temperature of the fixing roller is greatly reduced, for example, to 80 ° C., and the cooling fan 30 is stopped from the low-speed rotation state. Let it. At this time,
Since the surface temperature of the fixing roller is about 180 ° C., the fixing heater 17 is turned off until the surface of the fixing roller cools down to about 80 ° C. naturally.

If the surface temperature of the fixing roller is about 80 ° C., the temperature rise of each unit in the second embodiment is at a level that does not cause a problem even when the cooling fan 30 is turned off. As compared with the case where the cooling fan 30 is rotated at a low speed by controlling the temperature to 180 ° C., the temperature of the image forming unit and the like slightly increases. In this state, the second embodiment can stand by in a noiseless state. The surface temperature of the fixing roller gradually decreases from the time when the control temperature of the fixing roller is lowered to 80 ° C. and the cooling fan 30 is stopped until a predetermined time T2 elapses, and thereafter, about 80 ° C.
Will remain.

At the time T3 when the surface temperature of the fixing roller reaches about 80 ° C., the control temperature of the fixing roller is returned to 180 ° C. at the start of the image forming operation and the cooling fan 30 is rotated at a high speed. It takes about 20 seconds for the surface temperature to return to the fixing temperature. However, at T2, since the surface temperature of the fixing roller is 80 ° C. or higher, the return time is a time from 0 to 20 seconds, and the return time is shorter than at T3. As described above, even in a fixing device in which the surface temperature of the fixing roller requires about 40 seconds to reach a temperature at which an image forming operation of 180 ° C. can be performed from the room temperature level, the surface temperature of the fixing roller is 80 ° C.
From 180 ° C to about 20 to 25 seconds.

FIG. 16 shows a part of the processing flow of the CPU 11. The CPU 11 checks whether or not the image forming operation has been completed. When the image forming operation is completed, the CPU 11 sets the control temperature of the fixing roller to 180 ° C., which is the same as during the image forming operation, and drives the fixing heater 17 in a standby state. Here, the fixing heater 1
There is a gap between the lighting threshold and the turning-off threshold of 7;
The threshold temperature for turning on the fixing heater 17 is set at 176 ° C., and the threshold temperature for turning off the fixing heater 17 is set at 184 ° C.

When the fixing heater 17 is driven in a standby state, the CPU 11 outputs a temperature detection signal from a fixing device thermistor for detecting the temperature of the fixing device (surface temperature of the fixing roller) at a predetermined period, as shown in detail in FIG. Sampling is performed, and the detected temperature of the thermistor for the fixing device (the surface temperature of the fixing roller) is turned on by the temperature detection signal.
It is checked whether the temperature is 6 ° C. or lower. If the detected temperature of the thermistor for the fixing device is lower than the threshold temperature 176 ° C. for lighting, the heater driving circuit 16 turns on the fixing heater 17.
Further, the CPU 11 checks whether or not the detected temperature of the fixing device thermistor is equal to or higher than a threshold temperature for turning off the light by using the temperature detection signal. If so, the heater driving circuit 16 turns off the fixing heater 17. For this reason,
The fixing heater 17 is turned on / off as shown in FIG. 18, and the surface temperature of the fixing roller is controlled as shown in FIG.

Therefore, once turned on, the fixing heater 17 is turned on continuously until the temperature detected by the fixing device thermistor reaches the threshold temperature for turning off. Thus, the number of times the fixing heater 17 is turned on per unit time can be reduced. Next, the CPU 11 outputs the output gate array 27.
, The trigger signal Trg1 to the driver 31 is turned off and the trigger signal Trg2 to the driver 32 is turned on to rotate the cooling fan 30 at low speed.

The CPU 11 performs the above-described processing and starts a TI timer for measuring T1.
Then, the CPU 11 checks whether or not the T1 timer has counted up T1, and when the T1 timer has counted up T1, sets the control temperature of the fixing roller to 80 ° C.
The standby heater of the fixing heater 17 is driven. In this case, there is a difference between the threshold value for turning on the fixing heater 17 and the threshold value for turning off the fixing heater 17. Generally, the control temperature of the fixing roller is set to 80 ° C. because the SN characteristic of the fixing device thermistor is reduced.
The difference between the threshold value for turning on the fixing heater 17 and the threshold value for turning off the fixing heater 17 when the fixing heater 17 is driven in a standby state is the difference between the threshold value for turning on the fixing heater 17 and the threshold value for turning off the fixing heater 17 when the control temperature of the fixing roller is 180 ° C. It is better to make it larger than to have

The CPU 11 sets the control temperature of the fixing roller to 8
When the fixing heater 17 is driven in the standby state at 0 ° C., the temperature detection signal from the thermistor for the fixing device is transmitted for a predetermined period in the same manner as in the case where the control temperature of the fixing roller is set to 180 ° C. The temperature detection signal is used to check whether the detected temperature of the fixing device thermistor (surface temperature of the fixing roller) is equal to or lower than the lighting threshold temperature, and the detected temperature of the fixing device thermistor is turned on. If not, the fixing heater 17 is turned on by the heater driving circuit 16, and it is checked whether or not the detected temperature of the fixing device thermistor is equal to or higher than the light-off threshold temperature based on the temperature detection signal, and the detected temperature of the fixing device thermistor is checked. Is higher than the light-off threshold temperature, the heater driving circuit 16 turns off the fixing heater 17. The lighting threshold temperature and the turning-off threshold temperature in this case are the lighting threshold temperature when the control temperature of the fixing roller is 80 ° C.,
This is the threshold temperature for turning off the light.

Therefore, once turned on, the fixing heater 17 is turned on continuously until the temperature detected by the fixing device thermistor reaches the threshold temperature for turning off. Further, the CPU 11
Are drivers 31 and 32 through an output gate array 27
To turn off the cooling fan 30 by turning off the trigger signals Trg1 and Trg2. The CPU 11 executes the processing flow shown in FIG. 6 even when the power is turned on.

Generally, most of the image forming apparatus is in a standby state in which no image forming operation is performed during the power-on period. Therefore, the driving method of the fixing heater 17 is changed as described above to change the commercial power supply voltage waveform itself. By changing the number of times of the phase control of the fixing heater drive voltage that easily causes distortion, the amount of voltage fluctuation caused by the rush current can be suppressed, and the control temperature of the fixing heater can be reduced stepwise during standby as described above. An energy saving effect can be obtained by lowering it.

As described above, the second embodiment is an embodiment of the invention according to claim 4, and is defined as claim 1 or claim 2.
In the image forming apparatus described above, the change of the light-off threshold value and the lighting threshold value during the non-operation time is performed after a lapse of a predetermined time during the non-operation time, and thus the same effect as the image forming apparatus according to the first or second aspect is obtained, Further, even during non-operation, since the same heater control as during operation is performed for a certain period, even if the heater is operated again during the certain period, the fixability is not reduced.

Further, the second embodiment is an embodiment of the invention according to claim 5, wherein in the image forming apparatus according to claim 1 or 2, the change of the light-off threshold and the light-up threshold during the non-operation is performed. Since it is performed so as to gradually decrease during non-operation, the same effect as the image forming apparatus according to claim 1 or 2 can be obtained, and further, the time when returning from non-operation to operation again can be reduced. it can.

In many cases, a charging roller is used for a photosensitive member charging device in an image forming unit of an image forming apparatus. Since the charging roller has a temperature dependence of impedance, the temperature of the charging roller or a temperature near the charging roller is measured by a thermistor or the like. Is generally detected and the voltage applied to the charging roller is corrected. If a low temperature is detected as the temperature of the charging roller, the apparatus itself is expected to be in a low-temperature environment, and there is a concern about a condensation phenomenon due to a rapid change in room temperature and humidity caused by a heating appliance or the like. If water droplets adhere to the image forming unit due to dew condensation, an abnormal image is generated for a considerable period of time.

Therefore, in the third embodiment of the present invention, in the second embodiment, a charging roller is used as the charging means, a voltage is applied to the charging roller from a power supply device, and the temperature of the charging roller itself or the charging roller is charged. The temperature near the roller is detected as the temperature of the charging roller by the temperature detecting means for the charging roller such as a thermistor, and the correcting means corrects the voltage applied from the power supply device to the charging roller by the temperature detection signal from the temperature detecting means for the charging roller. I do.

Then, at time T2, the CPU 11 sets the control temperature of the fixing roller at the standby time of 80 ° C. to a temperature at which the cooling fan 30 can be stopped before and after the time (T2) according to the temperature detection signal from the charging roller temperature detecting means. At the start of the forming operation, the surface temperature of the fixing roller is changed stepwise until the surface temperature returns to a temperature at which the image forming operation can be performed. This allows
With respect to the operation of the apparatus in a low-temperature environment, the condensation margin can be improved without adding a unique nichrome wire heater or the like.

FIG. 19 shows the CPU 11 according to the third embodiment.
3 shows a part of the processing flow of FIG. When the T1 counter counts up T1, the CPU 11 changes the control temperature of the fixing roller during standby to 80 ° C. before and after the temperature in response to the temperature detection signal from the charging roller temperature detection unit, and then changes the control temperature. To drive the fixing heater 17 in a standby state. In this case, the CPU 11 sets the light-off threshold value during non-operation to a temperature that does not thermally affect other components other than the fixing device constituting the image forming apparatus.

That is, when the T1 counter counts up T1, the CPU 11 samples a temperature detection signal from the charging roller temperature detecting means, checks the temperature of the charging roller based on the temperature detection signal, and determines whether the temperature of the charging roller is lower. If the temperature is low, it is determined that dew condensation is likely to occur, and the control temperature of the fixing roller is changed so as to increase the temperature inside the apparatus. That is, the CPU 11 sets the threshold temperature for turning off the fixing heater 17 to 80 ° C. and the threshold temperature for turning on the fixing heater 17 to 70 ° C. unless the temperature of the charging roller is 15 ° C. or less.

If the temperature of the charging roller is lower than 15 ° C. and higher than 5 ° C., the CPU 11 sets the threshold temperature for turning off the fixing heater 17 to 80 ° C. and the threshold temperature for turning on the fixing heater 17 to 75 ° C. If the temperature is not higher than 0 ° C., the threshold temperature for turning off the fixing heater 17 is set to 85 ° C., and the threshold temperature for turning on the fixing heater 17 is set to 80 ° C.

Thereafter, the CPU 11 drives the fixing heater 17 in the standby state at the set threshold temperature for turning off the fixing heater 17 and the threshold temperature for turning on the fixing heater 17 in the same manner as in the first embodiment, thereby turning the fixing heater 17 on. The cooling fan 30 is turned on / off, and the trigger signals Trg1 and Trg2 to the drivers 31 and 32 are turned off via the output gate array 27 to stop the cooling fan 30.

The third embodiment is an embodiment of the invention according to claim 7, wherein the image forming apparatus according to claim 6 is provided with a cooling fan 30 for cooling the inside of the image forming apparatus. When the device is not operating, the cooling fan 30
Is stopped, and the light-off threshold value when the apparatus is not operating is set to a temperature that does not thermally affect other components other than the fixing device constituting the image forming apparatus. Item 6 has the same effect as the image forming apparatus described in Item 6, and furthermore, the temperature detecting means for detecting the temperature of the fixing device is a temperature that does not thermally affect other components even if the cooling fan is not operated. Since the temperature can be determined only from the temperature detection result, the apparatus can be normally maintained during non-operation and noise can be prevented.

Further, the third embodiment is an embodiment of the invention according to claim 8, wherein in the image forming apparatus according to claim 1 or 2, an image forming section for performing an image forming operation;
2. The image forming apparatus according to claim 1, further comprising a second temperature detecting unit configured to detect a temperature of the image forming unit, wherein the non-operating state of the image forming apparatus is set based on a result of the temperature detected by the second temperature detecting unit. Or the same effect as that of the image forming apparatus described in Item 2 can be obtained, and the dew condensation margin can be improved without adding a nichrome wire or the like peculiar to the operation of the apparatus in a low-temperature environment during non-operation.

FIG. 20 shows C in the fourth embodiment of the present invention.
3 shows a part of a processing flow of the PU 11. In the fourth embodiment, in the second embodiment, a charging roller is used as a charging unit as in the third embodiment, and a voltage is applied to the charging roller from a power supply device. The nearby temperature is detected as the temperature of the charging roller by the charging roller temperature detecting means such as a thermistor, and the correcting means corrects the voltage applied to the charging roller from the power supply device by the temperature detection signal from the charging roller temperature detecting means. .

Then, since the off state of the cooling fan 30 promotes a rise in temperature inside the apparatus and is advantageous for dew condensation, the CPU 11 determines the timing of the image forming section based on the temperature detection signal from the charging roller temperature detecting means. Etc., for example, T
1 is changed stepwise so as to be shorter as the temperature of the charging roller is lower, and the dew condensation margin is improved. That is, when starting the T1 timer, the CPU 11 samples a temperature detection signal from the charging roller temperature detecting means and checks the temperature of the charging roller based on the temperature detection signal. If not, the threshold temperature for turning off the fixing heater 17 is set to 80 ° C., the threshold temperature for turning on the fixing heater 17 is set to 70 ° C., and T1 is set to 5 °.
Set to minutes and start T1 timer.

If the temperature of the charging roller is less than 15 ° C. and greater than 5 ° C., the CPU 11 sets the threshold temperature for turning off the fixing heater 17 to 80 ° C., sets the threshold temperature for turning on the fixing heater 17 to 75 ° C. To 2 minutes and start the T1 timer. When the temperature of the charging roller is 5 ° C. or less, the CPU 11 sets the threshold temperature for turning off the fixing heater 17 to 85 ° C. and sets the threshold temperature for turning on the fixing heater 17 to 80 ° C.
, Set T1 to 30 seconds and start the T1 timer.

When the T1 timer counts up T1, the CPU 11 drives the fixing heater 17 in the standby state at the set threshold temperature for turning off and the threshold temperature for turning on the fixing heater 17 in the same manner as in the above embodiment. The fixing heater 17 is turned on / off, and trigger signals Trg1, Trg to the drivers 31, 32 via the output gate array 27 are output.
g2 is turned off and the cooling fan 30 is stopped.

The fourth embodiment is an embodiment of the present invention according to claim 9, and in the image forming apparatus according to claim 1 or 2, the image forming section for performing an image forming operation, and the image forming section A second temperature detecting means for detecting the temperature of the apparatus, and a cooling fan 30 for cooling the inside of the apparatus, and the driving of the cooling fan 30 when the apparatus is not operating is operated based on the detected temperature result of the second temperature detecting means. Claim 1 to change the state
Alternatively, the same effects as those of the image forming apparatus described in Item 2 can be obtained, and the margin of the image forming unit against dew condensation can be improved. In the above-described embodiment, the threshold value for turning on and the threshold value for turning off light are immediately changed upon judging the end of the image forming operation, and the timer T1 is operated. However, the image forming apparatus frequently uses the image forming apparatus. After a predetermined time elapses after the forming operation is completed, the threshold value for turning on and the threshold value for turning off the light are changed,
1 may be activated.

[0103]

As described above, according to the first aspect of the present invention, with the above-described configuration, the lighting time of the heater per unit number of times becomes longer in the non-operation time, and the rush of turning on and off the heater per unit number of times is achieved. Current and voltage fluctuations are reduced,
The number of voltage fluctuations caused by the inrush current to the heater can be optimally controlled in each state of the equipment, and the suppression of power supply voltage fluctuations and harmonics to the commercial power supply can be minimized without adding hardware parts and filter members. In addition, the fixing performance and the productivity of the apparatus are not sacrificed.

According to the second aspect of the present invention, with the above configuration, the lighting time of the heater per unit number of times becomes longer in the non-operation time, and the rush current and voltage fluctuation related to the lighting and extinguishing of the heater per unit number of times are reduced. Therefore, the number of voltage fluctuations caused by the rush current to the heater can be optimally controlled in each state of the device, and the suppression of power supply voltage fluctuations and harmonics to the commercial power supply can be minimized without adding hardware parts and filter members. Without sacrificing fixing performance and productivity of the apparatus.

According to the third aspect of the present invention, with the above configuration, the same effects as those of the image forming apparatus according to the first or second aspect can be obtained, and the heater can be controlled with a simple configuration.

According to the fourth aspect of the present invention, with the above-described configuration, the same effects as those of the image forming apparatus according to the first or second aspect can be obtained. Therefore, even if the operation is performed again during the certain period, the fixability is not reduced.

According to the fifth aspect of the present invention, with the above configuration, the same effects as those of the image forming apparatus according to the first or second aspect are exhibited, and the time required to return from the non-operation time to the operation time is reduced. be able to.

According to the sixth aspect of the present invention, with the above configuration, the same effects as those of the image forming apparatus according to the first or second aspect are exhibited, and the average temperature of the fixing roller during non-operation can be reduced. Power can be saved.

According to the seventh aspect of the present invention, the above configuration has the same effect as that of the image forming apparatus of the sixth aspect, and further has a thermal effect on other components even without the operation of the cooling fan. Since the temperature of the fixing device can be known only from the temperature detection result of the temperature detecting means for detecting the temperature of the fixing device, the device can be normally maintained during non-operation and noise can be prevented.

According to the eighth aspect of the present invention, with the above configuration, the same effects as those of the image forming apparatus according to the first or second aspect are obtained, and further, the operation is unique to the operation of the apparatus in a low-temperature environment during non-operation. The dew condensation margin can be improved without adding a nichrome wire or the like.

According to the ninth aspect of the present invention, with the above configuration, the same effects as those of the image forming apparatus according to the first or second aspect can be obtained, and the margin of the image forming section against dew condensation can be improved. .

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a heater drive control unit according to a first embodiment of the present invention.

FIG. 2 is a waveform chart showing signal waveforms of respective units according to the first embodiment.

FIG. 3 is a block diagram schematically showing a circuit configuration of the first embodiment.

FIG. 4 is a circuit diagram showing a zero-cross signal generation circuit according to the first embodiment.

FIG. 5 is a waveform chart showing voltage waveforms at various parts of the zero-cross signal generation circuit.

FIG. 6 is a diagram illustrating an example of a difference in Pst depending on a capacity of a heater.

FIG. 7 is a diagram illustrating an example of a difference in Pst depending on the number of soft starts of a heater.

FIG. 8 is a diagram illustrating an example of a difference in harmonics depending on the number of soft starts of a heater.

FIG. 9 is a diagram illustrating a change in the temperature of the fixing roller according to the first embodiment.

FIG. 10 is a flowchart showing a processing flow of a CPU in the first embodiment.

FIG. 11 is a flowchart showing another processing flow of the CPU.

FIG. 12 is a flowchart showing another processing flow of the CPU.

FIG. 13 is a flowchart showing another processing flow of the CPU.

FIG. 14 is a block diagram illustrating a circuit configuration according to a second embodiment of the present invention.

FIG. 15 is a timing chart showing operation timings of the second embodiment.

FIG. 16 is a flowchart showing a part of a processing flow of a CPU in the second embodiment.

FIG. 17 is a flowchart showing a part of FIG. 16 in detail.

FIG. 18 is a diagram showing ON / OFF of a fixing heater and a change in a fixing roller surface temperature in the second embodiment.

FIG. 19 is a flowchart illustrating a part of a processing flow of a CPU according to the third embodiment of the present invention.

FIG. 20 is a flowchart illustrating a part of a processing flow of a CPU according to the fourth embodiment of the present invention.

[Explanation of symbols]

 11 CPU 12 ROM 13 RAM 14 Interrupt Controller 15 PIO 16 Heater Drive Circuit 17 Fixing Heater AC Commercial Power Supply 30 Cooling Fan 31, 32 Driver

Claims (9)

[Claims] A fixing device that uses a heater as a heat source; a heater driving unit that drives the heater; a temperature detecting unit that detects a temperature of a member heated by the heater; Control means for controlling the heater by turning on the heater based on a predetermined lighting threshold value and turning off the heater based on a predetermined light-off threshold value according to the temperature detected by the temperature detecting means. In the image forming apparatus having the above, at least the light-off threshold value when the image forming is not in operation is set to a different value and a high value from the lighting threshold value when the image forming is not in operation, and the heater when the image forming is not in operation The lighting threshold and the turning-off threshold during the non-operation are set such that the control cycle of the heater is longer than the control cycle of the heater during the image forming operation. An image forming apparatus comprising. 2. A fixing device using a heater as a heat source, heater driving means for driving the heater, temperature detecting means for periodically detecting a temperature of a member heated by the heater,
The heater is turned on based on a predetermined lighting threshold value according to the temperature detected by the temperature detecting means, and the heater is turned off based on a predetermined light-off threshold value based on the temperature detected by the temperature detecting means. In the image forming apparatus having control means for controlling the heater by performing the above, at least the light-off threshold value during non-operation of image formation is set to a value different from the light-up threshold value during non-operation of image formation and a high value. An image forming apparatus, wherein a difference between a lighting threshold value and a light-off threshold value during non-operation of image formation is set to be larger than a difference between a lighting threshold value and a light-off threshold value during operation. 3. The image forming apparatus according to claim 1, wherein the lighting threshold value and the light-off threshold value during the non-operation time are predetermined constant values. 4. The image forming apparatus according to claim 1, wherein the change of the light-off threshold value and the light-on threshold value during the non-operation time is performed after a lapse of a predetermined time during the non-operation time period. 5. The image forming apparatus according to claim 1, wherein the change of the light-off threshold and the light-up threshold during the non-operation is performed so as to gradually decrease during the non-operation. apparatus. 6. The image forming apparatus according to claim 1, wherein both the non-operation threshold value and the non-operation threshold value are lower than the non-operation threshold value. 7. The image forming apparatus according to claim 6, further comprising a cooling fan for cooling the inside of the image forming apparatus, and stopping the blowing of the cooling fan when the image forming apparatus is not operating. An image forming apparatus characterized in that a light-off threshold value during operation is set to a temperature at which there is no thermal influence on other components except a fixing device constituting the image forming apparatus. 8. The image forming apparatus according to claim 1, further comprising: an image forming unit for performing an image forming operation; and a second temperature detecting unit for detecting a temperature of the image forming unit. An image forming apparatus, wherein the light-off threshold value in a non-operating state of the image forming apparatus is set based on a temperature detected by a detecting unit. 9. An image forming apparatus according to claim 1, wherein an image forming section for performing an image forming operation, second temperature detecting means for detecting a temperature of the image forming section, and cooling of the apparatus. An image forming apparatus, comprising: a cooling fan for performing the operation; and changing a driving state of the cooling fan when the apparatus is not operating, based on a temperature detected by the second temperature detecting unit.