JPH08254910A - Fixing device - Google Patents

Abstract

PURPOSE: To prevent a rush current from being generated because the resistance value of a fixing heater is increased with the change of voltage by performing the supply of power by the voltage changed at a specified voltage change rate to the fixing heater. CONSTITUTION: When an on-signal is outputted as the detected result of the sensor 5 of a temperature detection circuit 6, a supply voltage control circuit 2 supplies the power according to the characteristic of the voltage which is changed by setting the voltage change rate to <500V/second to a halogen heater 4. In such a case, when the heater voltage begins to rise because of the characteristic, a heater current begins to flow but the voltage is low at the time of starting the supply, so that a high current does not flow even when the value of the heater resistance is low. When the heater current gradually begins to flow, the heater resistance also gradually beings to rise. Therefore, when the heater current attains a rated value, the value of the heater resistance is very high, so that the heater current attains the rated value without generating the rush current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in a copying machine, a printer or the like, and more particularly to a fixing device in consideration of inrush current.

[0002]

2. Description of the Related Art Generally, in an electrophotographic image forming apparatus, an electric signal (image signal) corresponding to the density of image information (original image) of an original is converted into an electric signal (laser light) and the like. An electrostatic latent image is formed on the photoconductor drum by using it. Then, this electrostatic latent image is developed into a toner image and then transferred to a recording sheet, and the toner image on the recording sheet is heated by a heater of a fixing device to be fused and fixed.

As a heater (fixing heater) of such a fixing device, a heat source such as a halogen heater or a heater using a nichrome wire is used. Then, such a fixing heater is built in the heat roller.

As a fixing heater of this type, a fixing heater of about several hundred W is used in a small image forming apparatus, and a fixing heater having a larger capacity is used in a device which forms an image at high speed.

Then, according to the detection result of the temperature sensor arranged in the vicinity of the heat roller, ON / OFF control of power supply to the fixing heater is carried out so that a constant fixing temperature is maintained.

[0006]

In this type of fixing device, a large inrush current may flow to the fixing heater at the moment when the power supply is switched from off to on.

This situation will be described with reference to FIG. At a certain timing, from the commercial power supply to the halogen heater of the heater part, A
C100V is supplied (FIG. 8 (a)). The resistance value of the halogen heater, to which no current was supplied until then, increases from R1 to R2 due to the supply of power (FIG. 8B). Therefore, since the heater current starts to flow to the low resistance value R1 at the same time as the power supply, the inrush current I1
Flows (FIG. 8 (c)). Then, as the resistance value increases to R2, the heater current decreases to I2.

When such an inrush current I1 is generated, a voltage drop occurs due to an electric resistance around an outlet of a commercial power supply which supplies power to the image forming apparatus or indoor wiring, and drops to V1. After that, when the heater current becomes I2, the power supply voltage also recovers to V2.

In particular, since the voltage drop caused by the above-mentioned inrush current is large instantaneously, it may affect peripheral equipment and lighting equipment. For example, when the voltage supplied to the lighting device drops, a phenomenon called flicker in which the illuminance drops momentarily may occur.

When actually measured in a halogen heater rated at 500 W, a current of 8 A was flowing as an inrush current although the steady current I2 was 5 A. Then, the power supply voltage dropped to 97V, and flicker was generated.

The present invention has been made in view of the above problems, and an object thereof is to realize a fixing device capable of suppressing the occurrence of a voltage drop of a power source due to an inrush current.

[0012]

The inventor of the present application has conducted earnest research to improve the problem of inrush current caused by ON / OFF of the fixing heater in the temperature control of the conventional fixing device. The present invention has been completed by finding out a new method regarding power supply for temperature control of the above.

That is, the present invention as a means for solving the problems and its preferable range are as described in the following (1) to (5). (1) A first means for solving the problem is a fixing heater that melts and fixes a toner image on a recording paper by heat, and an electric power generated by a voltage that is changed with a voltage change rate of less than 500 V / sec for the fixing heater. And a power supply unit for supplying power.

(2) A second means for solving the problem is a fixing heater for melting and fixing a toner image on a recording paper by heat, and a first voltage and a second voltage which are lower than a rated voltage with respect to the fixing heater. And a power supply unit that supplies power by alternately applying a voltage.

(3) A third means for solving the problem is a fixing heater for fusing and fixing a toner image on a recording sheet by heat, and a first voltage and a second voltage which are lower than a rated voltage with respect to the fixing heater. And a power supply unit that supplies power by alternately applying a voltage and a predetermined voltage change rate.

(4) A fourth means for solving the problem is a fixing heater for melting and fixing a toner image on a recording paper by heat, and a predetermined heater for the fixing heater when the fixing heater is not fixing. Generates a first electric power for generating a first amount of heat required to maintain the temperature, and a second amount of heat required to maintain a predetermined temperature while the fixing heater is performing fixing. And a power supply unit that alternately supplies the second power for supplying the power to the fixing device.

(5) A fifth means for solving the problem is to control the phase of an alternating current with respect to a fixing heater for fusing and fixing a toner image on a recording sheet by heat and the electric power supplied to the fixing heater. And a power supply unit that supplies power with the effective voltage change rate of less than 500 V / sec.

[0018]

[Action]

(1) In the first means for solving the problem, the power supply means causes the voltage change rate to be 500 V / V with respect to the fixing heater.
Electric power is supplied by the voltage changed in less than a second.

By using the voltage having such a voltage change rate, the resistance value of the fixing heater also rises as the voltage changes, so that the occurrence of the inrush current can be prevented. (2) In the second means for solving the problem, the electric power is supplied to the fixing heater by the electric power supply means while alternately applying the first voltage and the second voltage which are less than the rated voltage. Be seen.

By alternately applying the first and second voltages as described above, a rapid voltage rise is eliminated, and the resistance value becomes a constant value even when the voltage is switched from a low value to a high value. Since it is rising, inrush current can be prevented from occurring.

(3) In the third means for solving the problem, the first voltage and the second voltage, which are less than the rated voltage, are alternately applied to the fixing heater by the power supply means at a predetermined voltage change rate. Electric power is supplied in a state of being switched and applied.

Using such first and second voltages,
By switching and applying alternately at a predetermined voltage change rate, a rapid voltage rise disappears, and the resistance value of the fixing heater also changes with the voltage change, so that the occurrence of inrush current can be prevented.

(4) In the fourth means for solving the problem, the power supply means generates the first amount of heat necessary for maintaining the predetermined temperature when the fixing heater is not fixing. And the second electric power for generating the second amount of heat required for maintaining a predetermined temperature while the fixing heater is performing fixing are alternately supplied.

Using such first and second powers,
By supplying alternately, abrupt voltage rise disappears and inrush current can be prevented from occurring. (5) In the fifth means for solving the problem, the phase of the alternating current supplied by the power supply means is controlled, and the electric power is changed by changing the voltage change rate of the effective voltage with respect to the fixing heater to less than 500 V / sec. Is supplied.

By using the phase control of the alternating current as described above, the resistance value of the fixing heater also rises with the change of the effective voltage due to the phase-controlled current, so that the generation of the inrush current can be prevented.

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a fixing device according to an embodiment of the present invention. 2 to 5 are time charts for explaining the operation of this embodiment.

<Structure of Fixing Device> FIG. 1 shows a schematic structure of a fixing device according to an embodiment of the present invention. In FIG. 1, a power source 1 is a source of power for supplying power to the fixing device, and FIG. 1 shows a case where an AC commercial power source is used as it is. The supply voltage control circuit 2 is a power supply means for controlling and supplying the voltage when supplying the power from the power source 1 to the heater described later at a predetermined voltage change rate or current change rate (effective voltage change rate).

The heater section 3 is a heating means incorporated in the heat roller of the fixing device, and in this embodiment, the halogen heater 4 will be described as an example of the heat source. The sensor 5 detects the temperature of the heater unit 3, and supplies the detection result to a temperature detection circuit 6 described later.

The temperature detection circuit 6 receives the detection result of the sensor 5 and generates an ON / OFF signal for switching the heating / stopping of the halogen heater 4 and supplies it to the supply voltage control circuit 2.

<Operation of Fixing Device (1)> The operation of the fixing device configured as described above will be described below. When the ON signal is output as the detection result of the temperature detection circuit 6, the supply voltage control circuit 2 supplies electric power to the halogen heater 4. Here, the supply voltage control circuit 2 of the present embodiment supplies the electric power according to the voltage characteristic that the voltage change rate is changed to less than 500 V / sec.

In the conventional fixing device, the control of the power supply to the halogen heater was simply ON / OFF control, and therefore the voltage change rate exceeded 500 V / sec. This far exceeds the resistance rise characteristic of the halogen heater, and is a major cause of inrush current.

Therefore, by setting the voltage change rate to less than 500 V / sec, the resistance value increasing characteristic due to the red heat of the halogen heater 4 follows, and the occurrence of inrush current can be prevented.

That is, when the heater voltage (FIG. 2A) starts to rise with the above characteristics, the heater current also starts to flow.
Since the voltage is low at the start of supply, a large current does not flow even if the heater resistance is a low value R1. Then, in this way, the heater current gradually starts to flow,
The heater resistance also begins to rise gradually (FIG. 2 (b)). Therefore, when the heater current reaches the rated value (for example, AC100V), the heater resistance also has a sufficiently large value, and the heater current reaches the rated value I2 without generating the inrush current. Therefore, a sudden drop in the power supply voltage does not occur, and only the normal voltage drop V2 occurs. Therefore, the flicker phenomenon does not occur.

The voltage change rate of less than 500 V / sec means that the voltage change time is 0.2 sec or more at a power supply voltage of AC100V. As the voltage change rate decreases, the heater current rises gradually, but according to experiments, the voltage change time is about 0.2 seconds to 0.3 seconds (voltage change rate: 500 V / second to 333 V / second). Satisfactory results were obtained. Further, in the usual case, the time during which the electric current is passed through the halogen heater is about 1 second to several seconds, so that no problem will occur even if the voltage change time of about 0.2 to 0.3 seconds exists. Has been confirmed.

<Operation of Fixing Device (2)> Next, the second operation of the fixing device will be described below with reference to FIG.
When the OFF signal is output as the detection result of the temperature detection circuit 6, the supply voltage control circuit 2 supplies power to the halogen heater 4 with the first heater voltage V1. When the ON signal is output as the detection result of the temperature detection circuit 6, the supply voltage control circuit 2 supplies electric power to the halogen heater 4 with the second heater voltage V2. Here, regarding the first heater voltage and the second heater voltage,
The relationship of 0 <V1 <V2 <rated voltage is established.

As described above, by supplying power to the halogen heater at a predetermined voltage during the OFF signal as the detection result of the temperature detection circuit, the heater resistance is larger than R1 (heater current OFF resistance value). It is R1 '. As a result, even if the heater voltage is increased later, the occurrence of inrush current can be reduced.

Further, it is turned on as the detection result of the temperature detection circuit.
By supplying electric power to the halogen heater at a predetermined voltage lower than the rated voltage during the signal period, generation of inrush current can be reduced.

That is, instead of turning on / off the heater voltage as in the conventional case, the first voltage V1 and the second voltage V2 are alternately switched and supplied to the halogen heater to reduce the generation of inrush current. It will be possible.

<Experimental Example 1> When an experiment was conducted with the following numerical values under the conditions of the above operation (2), good results were obtained.

-Conditions Rated heater power: 500W Rated heater voltage: 100V First heater voltage: 60V Second heater voltage: 70V-Result Heater current when the first heater voltage is supplied: 3.0
A Heater current when supplying the second heater voltage: 3.5
A Inrush current when switched to the second heater voltage: 4.0
A Power supply voltage change component: about 1 V As described above, the increase due to the inrush current was about 0.5 A, which was negligible. Further, even if this rush current occurs, it is a value smaller than the conventional rated current value 5A. For this reason, the change in the power supply voltage was sufficiently small, and good results were obtained in which flicker did not occur.

<Operation of Fixing Device (3)> Next, the third operation of the fixing device will be described with reference to FIG.
When the OFF signal is output as the detection result of the temperature detection circuit 6, the supply voltage control circuit 2 supplies power to the halogen heater 4 with the first heater voltage V1.

When an ON signal is output as the detection result of the temperature detection circuit 6, the supply voltage control circuit 2 supplies electric power to the halogen heater 4 with the second heater voltage V2 at a predetermined voltage increase rate. . Here, regarding the first heater voltage and the second heater voltage, 0 <V1 <V2
<Make sure that the relationship of rated voltage holds.

As described above, by supplying electric power to the halogen heater at a predetermined voltage during the OFF signal as a detection result of the temperature detection circuit, the heater resistance is larger than R1 (heater current OFF resistance value). The value is R1 '.
As a result, even if the heater voltage is increased later, the occurrence of inrush current can be reduced.

Further, it is turned on as the detection result of the temperature detection circuit.
By supplying electric power to the halogen heater at a predetermined voltage lower than the rated voltage during the signal period, generation of inrush current can be reduced. Further, when switching between the first heater voltage and the second heater voltage, it is also possible to reduce the occurrence of inrush current by increasing the voltage at a predetermined voltage increase rate (decreasing at a voltage decrease rate).

That is, instead of turning on / off the heater voltage as in the conventional case, the first voltage V1 and the second voltage V2 are adopted, and these voltages are gradually switched at a predetermined rate of change to a halogen heater. It is possible to reduce the occurrence of inrush current by supplying the inrush current.

As described above, the change in the heater resistance follows the change in the heater voltage. Therefore,
When the heater current changes to I1 'and I2', the inrush current component does not occur.

In such a case, good results can be obtained by using a value of less than 500 V / sec as described above as the predetermined voltage change rate. Further, in this case, the same operation is realized by changing the heater voltage at a predetermined rate of change and by controlling the heater current with constant current (two constant current controls, I1 'and I2'). It

<Experimental Example 2> When an experiment was conducted with the following numerical values under the conditions of the above operation (3), good results were obtained.

-Conditions Rated heater power: 500 W Rated heater voltage: 100 V First heater voltage: 60 V Second heater voltage: 70 V Voltage change rate: 499 V / sec-Result Heater current when the first heater voltage is supplied : 3.0
A Heater current when supplying the second heater voltage: 3.5
A Inrush current when switching to the second heater voltage: not measurable Change in power supply voltage: about 0.5 V As described above, the increase in current due to the inrush current did not occur. For this reason, the change in the power supply voltage was sufficiently small, and good results were obtained in which flicker did not occur.

<Operation of Fixing Device (4)> Next, the fourth operation of the fixing device will be described below with reference to FIG.
Here, control is performed by determining the electric power supplied to the halogen heater according to the electric power required in each operating state.

When the OFF signal is output as the detection result of the temperature detection circuit 6, the power due to convection and radiation (P11), the heating and heat retention of the roller unit (P12), the power due to the thermal diffusion (P13) to each part of the device, Is required.

Therefore, the electric power W1 corresponding to the total electric power P1 of P11 to P13 is supplied to the halogen heater when the OFF signal is output as the detection result of the temperature detection circuit 6.

As the detection result of the temperature detection circuit 6, O
When the N signal is output, the power absorbed by the recording paper (P21), the power required for fusing the toner (P22) and the power increased by the rotation of the roller (P23) are required.

Therefore, the electric power W2 (P1 + P2) corresponding to the total electric power P2 of P21 to P23 is supplied to the halogen heater when the ON signal is output as the detection result of the temperature detection circuit 6.

Further, in the calculation of each power described above, it is possible to correct by referring to the environment such as temperature and humidity. Then, it can be realized by previously obtaining and setting the values of voltage and current according to the above power.

In this way, by switching the electric power supplied to the halogen heater in consideration of the two kinds of power, the characteristics as shown in FIG. 3 or FIG. 4 can be obtained. Since the power to be switched is optimized to a value necessary for the situation, temperature control can be performed without waste. Also,
Therefore, there is an advantage that the number of times of turning on / off is reduced.

<Embodiment by Current Control> In the above description of each embodiment, the voltage supplied to the halogen heater 4 is controlled. Besides controlling such voltage, it is also possible to control the phase angle of the alternating current.

FIG. 6 is a block diagram showing an example of a circuit for controlling the phase angle of current. Here, the phase control circuit 7
Controls the phase angle of the alternating current, and supplies such current to the heater current 4. For example, the phase control circuit 7 is composed of a switching circuit such as a combination of a triac and a diac.

In this case, the phase signal generation circuit 8 generates a signal for phase control by the ON / OFF signal output from the temperature detection circuit 6. This phase control signal (for example,
The phase control circuit 7 changes the phase angle of the current according to the voltage signal.

FIG. 7 (a) shows the waveform of the alternating current whose phase angle is controlled. The effective voltage in this case is shown in FIG. 7 (b).
Is shown in. That is, by controlling the phase angle of the alternating current, the same effect as the voltage control can be obtained.

By using this type of phase control circuit 7,
It is possible to realize both the circuit based on the voltage change rate and the circuit based on the switching of voltage and power. Further, the phase signal generation circuit 8 can generate a necessary signal by a time constant circuit by CR, a signal by data written in the ROM, or the like in order to signal a predetermined rising (falling) rate.

[0062]

According to the present invention, the following effects are obtained. (1) The inrush current is generated because the resistance value of the fixing heater rises as the voltage changes by supplying electric power to the fixing heater with a voltage changed at a voltage change rate of less than 500 V / sec. Can be prevented.

(2) By supplying electric power to the fixing heater while alternately applying the first voltage and the second voltage, which are lower than the rated voltage, a rapid voltage rise is eliminated, and Since the resistance value rises to a constant value even when the voltage switches from a low value to a high value, it is possible to prevent the occurrence of an inrush current.

(3) By supplying the electric power to the fixing heater while alternately switching the first voltage and the second voltage, which are less than the rated voltage, at a predetermined voltage change rate and applying the electric power, Since the voltage rise is prevented and the resistance value of the fixing heater also changes with the change in voltage, the occurrence of inrush current can be prevented.

(4) When the fixing heater is fixing, the first electric power for generating the first amount of heat required to maintain a predetermined temperature when the fixing heater is not fixing, and when the fixing heater is fixing Second required to maintain a certain temperature in
By alternately supplying the second electric power for generating the amount of heat, the sudden voltage increase (change) disappears, and the occurrence of inrush current can be prevented.

(5) Phase control is performed by supplying electric power to the fixing heater by controlling the phase of the alternating current, and by supplying electric power that is changed with the voltage change rate of the effective voltage being less than 500 V / sec. Since the resistance value of the fixing heater also rises as the effective voltage changes due to the applied current, the occurrence of inrush current can be prevented.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating a configuration of a fixing device according to an exemplary embodiment of the present invention.

FIG. 2 is a time chart showing an operation of the fixing device that performs control according to a predetermined voltage increase rate according to the embodiment of the present invention.

FIG. 3 is a time chart showing the operation of the fixing device that controls the voltage switching according to the embodiment of the present invention.

FIG. 4 is a time chart showing the operation of the fixing device that controls the voltage switching and the voltage increase rate according to the embodiment of the present invention.

FIG. 5 is a time chart showing the operation of the fixing device for controlling the power setting according to the embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a fixing device that controls a phase angle of current according to an embodiment of the present invention.

FIG. 7 is a time chart showing the operation of the fixing device that controls the phase angle of the electric current according to the embodiment of the present invention.

FIG. 8 is a time chart showing the operation of a conventional fixing device.

[Explanation of symbols]

 1 power supply 2 supply voltage control circuit 3 heater section 4 halogen heater 5 sensor 6 temperature detection circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Miwa 2970 Ishikawacho, Hachioji City, Tokyo Konica Co., Ltd.

Claims (5)

[Claims] 1. A fixing heater that melts and fixes a toner image on a recording paper by heat, and a power supply unit that supplies power to the fixing heater with a voltage changed at a voltage change rate of less than 500 V / sec. A fixing device characterized by being provided. 2. A fixing heater that melts and fixes a toner image on a recording sheet by heat, and a first voltage and a second voltage that are less than a rated voltage are alternately applied to the fixing heater to supply power. A fixing device comprising: 3. A fixing heater that melts and fixes a toner image on a recording paper by heat, and a first voltage and a second voltage, which are less than a rated voltage, are alternately applied to the fixing heater at a predetermined voltage change rate. A fixing device comprising: a power supply unit that applies power to supply power. 4. A fixing heater for fusing and fixing a toner image on a recording paper by heat, and a first heater required for maintaining a predetermined temperature with respect to the fixing heater when the fixing heater is not fixing. A first electric power for generating a heat quantity and a second electric power for generating a second heat quantity required for maintaining a predetermined temperature while the fixing heater is fixing are alternately supplied. A fixing device comprising: 5. A fixing heater for fusing and fixing a toner image on a recording sheet by heat, and a voltage change rate of an effective voltage of 50 by controlling a phase of an alternating current with respect to electric power supplied to the fixing heater.
A fixing device comprising: a power supply unit that supplies a power that has been changed to less than 0 V / sec.