JP3242585B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of a heat fixing unit in an image forming apparatus for fixing a toner image formed by an electrophotographic process on a transfer material by a heat fixing unit, and more particularly, to a heating unit. The present invention relates to an image forming apparatus provided with a thermal fixing unit using a ceramic heater system.

[0002]

2. Description of the Related Art A conventional heat fixing device as a heat fixing device in an image forming apparatus using an electrophotographic process is an unfixed image (toner image) formed on a transfer material by an image forming means such as an electrophotographic process. Is fixed on a transfer material, and a heat roller type heat fixing device using a halogen heater as a heat source or a film heating type heat fixing device using a ceramic heater as a heat source is used.

In these heat fixing apparatuses, a heater is generally connected to an AC power supply via a switching control element such as a triac, and power is supplied from the AC power supply. The fixing device is provided with a temperature detecting element, for example, a thermistor temperature sensing element. The temperature detecting element detects the temperature of the fixing device, and based on the detected temperature information, the engine controller determines the wave number of the switching element. By turning on / off by control or phase control, power supply to the heater is turned on / off, and the temperature of the fixing device is temperature-controlled to a target constant temperature.

Further, when the temperature of the fixing device is controlled at a certain set temperature, the temperature of the fixing device is improved in accordance with printing conditions such as the number of prints, single-sided / double-sided, and paper size in order to improve the fixability. Conventionally, when it is necessary to greatly change the regulated temperature, the set temperature is switched to the required target temperature at a time, and the power to the heater is controlled by PI control or PID control so that the temperature of the fixing device becomes the target temperature. Was.

[0005] For example, in continuous double-sided printing, when shifting from front-side fixing to back-side fixing, in order to improve the fixability, the temperature control temperature A during front-side fixing is switched to the temperature control temperature B during back-side fixing. May be necessary,
The following control is performed.

FIG. 7 shows a timing chart of this control. For example, when it is necessary to reduce the temperature from the temperature control temperature A to the temperature control temperature B when shifting from the front-side fixing to the back-side fixing, the set temperature is reduced at a stretch as indicated by 201 and the change in the set temperature is followed. Therefore, the electric power supplied to the ceramic heater is changed to a necessary maximum as indicated by 202. By the change of the supplied power, the temperature of the ceramic heater is switched from the temperature A to the temperature B as indicated by 203. Similarly, when shifting from the back side to the fixing of the front side,
The set temperature is increased from the controlled temperature B to the controlled temperature A at a stretch, and the supplied power is changed to a necessary maximum so as to correspond to the change in the set temperature.

As described above, conventionally, when the temperature of the fixing device is switched from one temperature-regulated temperature to the next target temperature in accordance with printing conditions such as the number of prints, single-sided / double-sided printing, and paper size, The target temperature was changed at a stretch.

[0008]

However, when temperature control is performed by PI control, if the set temperature is greatly changed at once, the power supply changes abruptly, causing a change in power supply voltage. When the forming device is a high-speed machine, the power consumption of the fixing device increases, so that the amount of change in current increases, and flicker noise may occur.

When the temperature control is performed by PID control, even if the set temperature is greatly changed at a time, the temperature of the fixing device is gradually changed by setting the control constant,
Power supply voltage fluctuations can be reduced, but the control is complicated and it is difficult to manage the time until the temperature of the fixing device reaches the target temperature, so when the image forming apparatus becomes a high-speed machine, In some cases, the effect became significant. In particular, when it is necessary to switch the temperature of the fixing device between the front side and the back side in double-sided printing, that is, when the front side temperature is higher than the back side temperature, the target temperature may be increased for each one side printing. , The flicker noise may increase.

In particular, when the phase of the ceramic heater is controlled, the conduction angle corresponding to the supplied power is different for each commercial power supply voltage. Therefore, when the input voltage fluctuation of the commercial power supply (for example, 85V-140V) is considered, the uniformity is obtained. If the conduction angle is set for all commercial power supply voltages,
Even if there is no problem when the first commercial power supply voltage (for example, 100 V) is input, the second commercial power supply voltage (for example, 120 V)
At the time of input, flicker noise or harmonic distortion may occur.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which does not generate flicker noise and harmonic distortion even when the temperature is greatly changed at a time.

[0012]

According to the first aspect of the present invention, the above object is to form an unfixed developer image on a transfer material by an image forming means, and to form an unfixed developer image on the transfer material by a heat fixing means. An image forming apparatus for fixing the developer image, wherein a power supply unit for supplying power to the thermal fixing unit, a temperature detecting unit for detecting a temperature of the thermal fixing unit, and setting a temperature of the thermal fixing unit. Temperature setting means, and power control means for controlling the power supply means such that power corresponding to the difference between the temperature set by the temperature setting means and the temperature detected by the temperature detection means is supplied. have a eyes of the heat fixing unit in a state where power to the heat fixing means is supplied
When changing the target temperature from a first temperature to a second temperature, above
The temperature setting means is supplied by the power supply means.
The detected temperature is set to the set temperature so that the
This is achieved by changing the set temperature stepwise irrespective of whether or not it has reached .

Further, according to the second invention of the present application,
The above object is to provide an image forming apparatus in which an unfixed developer image is formed on a transfer material by an image forming unit, and a developer image on the transfer material is fixed by a heat fixing unit. Power supply means for supplying, temperature detecting means for detecting the temperature of the heat fixing means, temperature setting means for setting the temperature of the heat fixing means, temperature set by the temperature setting means and the temperature detecting means And a power control unit that controls the power supply unit based on a result of the determination by the determination unit. When the set temperature of the heat fixing unit is changed by the temperature setting unit while the power is being supplied, this is achieved by changing the supplied power stepwise at regular intervals.

Further, according to the third invention of the present application, the above object is achieved by the fact that the heat source of the heat fixing means of the first invention or the second invention is a ceramic heater.

According to a fourth aspect of the present invention,
The above object is achieved by the electric power control means according to any one of the first to third inventions controlling electric power supplied from the electric power supply means by a phase angle of conduction.

Furthermore, according to the fifth aspect of the present application, the object may power any one of the power control means of the first invention to the third invention, supplied by the power supply means Is controlled by the wave number of the commercial power supply.

[0017]

That is, in the first invention according to the present application, the set temperature of the temperature control of the heat fixing means is changed stepwise at predetermined time intervals to the target temperature, so that the amount of change in the power supplied to the heat source is changed. To reduce flicker noise. When this control is added to the PI control, the temperature of the heat fixing unit is gradually changed by simple control even when the target temperature is largely changed.

Further, in the second invention according to the present application, the amount of change in the power supplied to the heat fixing means is limited, and the supplied power is changed stepwise until the temperature of the heat fixing means reaches the target temperature. By doing so, flicker noise is reduced.

Further, in the third invention according to the present application, since the heat source of the heat fixing means of the first invention or the second invention is a ceramic heater, the temperature control with good responsiveness while reducing flicker noise. Is performed.

Further, in the fourth invention according to the present application, the power control means according to any one of the first invention to the third invention is characterized in that the power supplied by the power supply means is
Since the control is performed based on the conducting phase angle, appropriate temperature control with less overshoot and undershoot is performed while reducing flicker noise.

Further, in the fifth invention according to the present application, the power control means according to any one of the first to third inventions may be configured such that the power supplied by the power supply means is
Since control is performed based on the wave number of the commercial power supply, appropriate temperature control with less overshoot and undershoot is performed while reducing flicker noise.

[0023]

[0024]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) FIG. 1 is a schematic structural view of an image forming apparatus using an electrophotographic process according to a first embodiment of the present invention, and shows, for example, a case of a laser printer.

Hereinafter, the configuration and operation will be described. Laser printer main body 101 (hereinafter referred to as main body 101)
Is a cassette 102 for storing recording paper S as a transfer material.
A cassette paper presence / absence sensor 103 for detecting the presence / absence of the recording paper S in the cassette 102; a cassette size sensor 104 comprising a plurality of micro switches for detecting the size of the recording paper S in the cassette 102;
A paper feed roller 105 that feeds out the recording paper S is provided.

A pair of registration rollers 106 for synchronously transporting the recording paper S is provided downstream of the paper feed roller 105. On the downstream of the pair of registration rollers 106, the recording paper S based on the laser beam from the laser scanner 107 is used.
An image forming unit 108 for forming a toner image is provided thereon. That is, in the laser printer of the present embodiment, the laser scanner unit 107 and the image forming unit 108 constitute an image forming unit.

Further, a fixing device 109 is provided downstream of the image forming section 108 as a heat fixing means for thermally fixing the toner image formed on the recording paper S.
Downstream of the printer 9, there are provided a paper discharge sensor 110 for detecting the paper conveyance state of the paper discharge unit, a paper discharge roller 111 for discharging the recording paper S, and a loading tray 112 for loading the recording paper S on which recording has been completed. I have.

The laser scanner unit 107 includes a laser unit 113 that emits a laser beam modulated based on an image signal (image signal VDO) sent from an external device 131 described later, and a laser beam from the laser unit 113. It comprises a polygon motor 114 for scanning light onto a photosensitive drum 117 described later, an imaging lens group 115, a return mirror 116, and the like.

The image forming unit 108 includes a photosensitive drum 117, a primary charging roller 119, a developing unit 120, and a transfer charging roller 12 necessary for a known electrophotographic process.
1, a cleaner 122 and the like. The fixing device 109 includes a fixing film 109a and a pressure roller 109.
b, ceramic heater 109c as heat source provided inside fixing film 109a, ceramic heater 109
It comprises a thermistor 109d as a temperature detecting means for detecting the surface temperature of c.

The main motor 123 applies a driving force to the sheet feeding roller 105 via a sheet feeding roller clutch 124 and a driving force to the registration roller pair 106 via a registration roller 125, and further includes a photosensitive drum 117. Driving force is also applied to each unit of the image forming unit 108, the fixing device 109, and the paper discharge roller 111.

Reference numeral 126 denotes an engine controller which controls the electrophotographic process by the laser scanner 107, the image forming unit 108, and the fixing device 109, and controls the conveyance of the recording paper in the main body 101.

Reference numeral 127 denotes a video controller, which is a general-purpose interface (such as Centronics or RS232C) with an external device 131 such as a personal computer.
The image information transmitted from the general-purpose interface is expanded into bit data, and the bit data is transmitted to the engine controller 126 as a VDO signal.

Next, the ceramic heater 109c provided in the fixing device 109 in the image forming apparatus described above.
2 is shown in FIG. In FIG. 1, reference numeral 1 denotes an AC power supply for connecting the present image forming apparatus.
The ceramic heater 109c is caused to generate heat by supplying to the heater. The supply of power to the ceramic heater 109c is controlled by turning on and off power by a triac 4 as a power supply unit. Resistance 5, 6
Is a bias resistor for the triac 4, and the phototriac coupler 7 is a device for ensuring a creepage distance between the primary and the secondary. By energizing the light emitting diode of the phototriac coupler 7, the triac 4 is turned on. The resistor 8 is a resistor for limiting the current of the phototriac coupler 7 and is turned on / off by the transistor 9. The transistor 9 operates via a resistor 10 in accordance with a signal from an engine controller 126 as a temperature setting unit, a determination unit, and a power control unit.

The AC power supply 1 supplied via the AC filter 2 is rectified by the rectifier 12 and
3, input to the transistor 16 via the Zener diode 14 and the capacitor 15. As a result, the zero cross point (the point at which the voltage switches between positive and negative) of the commercial AC power supply 1 is detected and reported to the engine controller 126. For example, when the AC power supply 1 is at the zero cross point, the transistor 16 is turned off, and the voltage of the resistor 19 becomes L
It becomes OW and is notified to the engine controller 126. The photocoupler 18 is a device for securing a creepage distance between the primary and the secondary, and the resistors 17 and 19 are resistors for limiting a current flowing through the photocoupler 18.

The engine controller 126 uses the zero-cross signal as a trigger to turn on / off the triac 4 by phase control or wave number control. Also, 109d
Is a thermistor as temperature detecting means for detecting the temperature of the ceramic heater 109c. The temperature detected by the thermistor 109d is monitored by the engine controller 126, and the temperature to be supplied to the ceramic heater 109c is calculated by comparing with the set temperature of the ceramic heater 109c set inside the engine controller 126, The power is converted into a phase angle (phase control) or a wave number (wave number control) corresponding to the supplied power, and the engine controller 126 sends an ON signal to the transistor 9 according to the control condition.

With the above control circuit, the fixing device 10
The temperature 9 is maintained at a predetermined temperature. For example, in continuous double-sided printing, the temperature adjustment temperature A for front side printing and the temperature adjustment temperature B for back side printing are alternately switched in order to improve fixability. May be necessary.

However, when the temperature control temperature is switched in this manner, the conventional apparatus may generate flicker noise and harmonic distortion.

Therefore, in this embodiment, when the temperature of the ceramic heater 109c is the temperature A and the engine controller 12
6, when the temperature of the ceramic heater needs to be changed to the temperature B due to printing conditions, flicker noise and harmonic distortion are suppressed by performing the following control.

FIG. 3 shows a schematic timing chart of the control in this embodiment. First, at the time of transition from front-side fixing to back-side fixing, when the temperature is to be reduced from the temperature-adjusted temperature A to the temperature-adjusted temperature B, the set temperature is decreased by a constant temperature ΔT for a certain time Δt as shown in FIG. Decrease the set temperature. Therefore, it takes a time of (A−B) / ΔT × Δt to decrease from the temperature control temperature A to the temperature control temperature B, and the set temperature 21 changes stepwise with a small change amount. Gradually change. Further, by appropriately setting the times Δt and ΔT, the temperature of the heater can be gradually changed as indicated by 23.

On the other hand, at the time of the transition from the back side fixing to the front side fixing, the set temperature is similarly increased by a certain temperature for a certain period of time as shown at 21, and the set temperature is gradually changed from the temperature control temperature B to the temperature control temperature A. Up.

The time for switching the fixing temperature control temperature from the temperature A to the temperature B or vice versa needs to be changed to within the time between the front and back printing, and this time can be controlled by Δt. The time of temperature control can be managed by simple control.

As described above, according to the printing conditions, for example, the front side print and the back side print of the two-sided print,
When switching the temperature control temperature, the set temperature is
By performing control to change the temperature stepwise, the supplied power changes gradually, and the power change when switching the temperature adjustment temperature becomes small, so that the steep power supply voltage fluctuation, that is, flicker noise is reduced. It becomes possible.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention. Points that are the same as those in the first embodiment will be omitted.

In this embodiment, when it is necessary to reduce the temperature from the temperature control temperature A to the temperature control temperature B when shifting from the front surface fixing to the rear surface fixing, as shown in FIG.
Although the set temperature is reduced at once, the supply power is switched stepwise so as to reduce the change in the power supplied to the ceramic heater, such as 32.

That is, the temperature of the heater is changed from the temperature A to the temperature B.
Even if it is necessary to reduce the supply power by ΔW ′ (≫ΔW) to reduce the power supply to
Control is performed to reduce the supply power by ΔW at regular time intervals. Then, as shown by 33, the temperature B
When it becomes lower, return to normal control. If the temperature control temperature is constant and the normal temperature is controlled, a single change
The power does not change more than W.

On the other hand, at the time of the transition from the backside fixing to the frontside fixing, the heater power is similarly controlled by increasing the constant power at regular intervals as indicated by 32.

As described above, according to the printer conditions, for example, the front side print and the back side print of the two-sided print,
By performing control such that the supply power is changed stepwise at regular time intervals when switching the temperature control temperature, the power change when switching the temperature control temperature is small, so that a sharp power supply voltage fluctuation, that is, flicker Noise can be reduced.

(Third Embodiment) FIG. 5 shows a third embodiment of the present invention. The AC power supply 1 is a ceramic heater 109
c, and turns on / off the power supplied by a power control circuit 41 (configured by a triac 4, resistors 5, 6, a phototriac coupler 7, a resistor 8, a transistor 9, and a resistor 10 shown in FIG. 2). And that ON
The / OFF control is performed by the engine controller 126 using the zero-cross detection circuit 44 (the rectifier 12 and the resistor 1 shown in FIG. 2).
3, a Zener diode 14, a capacitor 15, a transistor 16, a resistor 17, a photocoupler 18, and a resistor 19). Further, by comparing the temperature of the heater 109c detected by the thermistor 109d with the set temperature of the ceramic heater 109c set in the engine controller 126, the power to be supplied to the ceramic heater 109c is calculated, and the power to be supplied is calculated. Is converted to a phase angle corresponding to the power to be controlled, and the engine controller 126
1 is sent an ON signal to perform temperature control.

The AC power supply 1 is rectified by a rectifier 45, smoothed by a capacitor 46,
And supplied to the engine controller 126 as a power supply voltage.

Therefore, in the present embodiment, the commercial power supply voltage detecting circuit 43 is provided as a voltage discriminating means. For example, when there is a voltage fluctuation from 85 V to 140 V in a 100 V system, the input commercial power supply is classified into the voltage class A (for example, , 85V-
110V) or voltage division B (for example, 120V-14
0V) is notified to the engine controller 126. Then, based on the notification signal, the engine controller 126 as a phase angle setting unit:
The phase control is performed using the conversion table of the supplied power and the phase angle corresponding to the input voltage. Of course, three or more voltage divisions may be used.

[0052]

[Table 1]

By performing the above-described control, optimal control corresponding to each commercial power supply can be performed, and the required phase angle can be finely set for each power supply voltage, so that flicker caused by fluctuations in the power supply voltage can be achieved. Noise and harmonic distortion can be reduced.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to FIG. This embodiment is the third
The difference from the third embodiment is that the commercial power pressure detecting means is a changeover switch 50. For example, changeover switch 5
When 0 is on, the input voltage is set to the voltage of the voltage division A, and when it is off, the input voltage is set to the voltage of the voltage division B. When the changeover switch 50 is turned on / off, the engine controller 126 Report voltage. The engine controller 126 can perform phase control at a phase angle suitable for a commercial power supply based on the notification signal as in the third embodiment, and reduce flicker noise and harmonic distortion caused by fluctuations in the commercial power supply. Can be achieved.

The pulse interval of the zero-cross signal from the zero-cross detection circuit 44 is determined by the engine controller 126.
By monitoring at the commercial frequency (50 / 60H
z) is detected, and power control can be performed by setting the phase angle corresponding to each commercial frequency, as in the case where the setting of the phase angle is changed by the commercial power supply voltage.

[0056]

As described above, the first embodiment according to the present application is described.
According to the invention, by changing the set temperature of the temperature control of the heat fixing unit stepwise to the target temperature at regular intervals, the amount of change in the power supplied to the heat source is limited, and flicker noise is reduced. be able to. When this control is added to the PI control, the temperature of the heat fixing unit can be gradually changed by simple control even when the target temperature is largely changed.

According to the second invention of the present application,
By limiting the amount of change in the power supplied to the heat fixing unit and changing the supplied power stepwise until the temperature of the heat fixing unit reaches the target temperature, flicker noise can be reduced.

Further, according to the third aspect of the present invention, since the heat source of the heat fixing means of the first aspect or the second aspect is a ceramic heater, a temperature with good responsiveness while reducing flicker noise is obtained. Control can be performed.

According to the fourth invention of the present application,
Since the power control means according to any one of the first to third inventions controls the power supplied by the power supply means based on the phase angle at which the power is supplied, overshoot and undershoot can be achieved while reducing flicker noise. Appropriate temperature control with few chutes can be performed.

Further, according to the fifth aspect of the present invention, the power control means according to any one of the first to third aspects further comprises:
Since the control is performed based on the wave number of the commercial power supply, it is possible to perform appropriate temperature control with less overshoot and undershoot while reducing flicker noise.

[0061]

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a control and drive circuit of the fixing device according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating control of a fixing device according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a second embodiment of the present invention.

FIG. 5 is a diagram showing a third embodiment of the present invention.

FIG. 6 is a diagram showing a fourth embodiment of the present invention.

FIG. 7 is a diagram showing a conventional example.

[Explanation of symbols]

Reference Signs List 4 triac (power supply means) 41 power control circuit (power supply means) 43 voltage detection circuit (voltage determination means) 50 changeover switch (voltage determination means) 101 laser printer (image forming apparatus) 107 laser scanner section (image formation means) 108 Image forming unit (image forming unit) 109 Fixing device (thermal fixing unit) 109c Ceramic heater (heat source) 109d Thermistor (temperature detecting unit) 126 Engine controller (temperature setting unit, determination unit, power control unit, phase angle setting unit) S Recording paper (transfer material)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 13/20 G03G 15/20

Claims (5)

(57) [Claims] An image forming apparatus for forming an unfixed developer image on a transfer material by an image forming means and fixing the developer image on the transfer material by a heat fixing means. Power supply means for supplying temperature, a temperature detection means for detecting the temperature of the heat fixing means, a temperature setting means for setting the temperature of the heat fixing means, a temperature set by the temperature setting means and the temperature detection The temperature detected by the means
Have a power control means for controlling said power supply means so that the power corresponding to the difference is supplied, the target temperature of the heat fixing unit in a state where power to the heat fixing means is supplied
When changing from a first temperature to a second temperature, the temperature set
The power supplied by the power supply means.
As the detected temperature reaches the set temperature,
An image forming apparatus characterized in that a set temperature is changed stepwise regardless of whether or not the temperature is set. 2. An image forming apparatus, wherein an unfixed developer image is formed on a transfer material by an image forming means and a developer image on the transfer material is fixed by a heat fixing means. Power supply means for supplying temperature, a temperature detection means for detecting the temperature of the heat fixing means, a temperature setting means for setting the temperature of the heat fixing means, a temperature set by the temperature setting means and the temperature detection An image forming apparatus comprising: a determination unit that compares and determines the temperature detected by the unit; and a power control unit that controls the power supply unit based on a determination result of the determination unit. An image forming apparatus, wherein when the temperature setting unit changes the set temperature of the heat fixing unit while power is supplied to the power supply, the power supply is changed stepwise at regular time intervals. 3. The image forming apparatus according to claim 1, wherein the heat source of the heat fixing unit is a ceramic heater. 4. The image forming apparatus according to claim 1, wherein the power control unit controls the power supplied by the power supply unit based on a phase angle at which the power is supplied. 5. The image forming apparatus according to claim 1, wherein the power control unit controls the power supplied by the power supply unit based on the wave number of the commercial power supply.