JP2003084622A - Electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problems that (1): a failure in an image forming process such as a carrier sticking is generated by the interruption of the input of AC in an electrophotographic device having an AC-DC converter and a DC-DC converter in order to make the power source circuit of the device to be a common power source circuit for use for a plurality of destinations and (2): higher harmonics are generated in the conventional measure for preventing an inrush current generated at the time of starting the supplying of power to a fixing heater and they affect peripheral equipments or the like. SOLUTION: In this electrophotographic device, (1) after the supplying of power to the fixing heater is stopped at the time of interrupting of the input of AC, the output of the DC-DC converter is stopped and (2) the supplying of power to the heater is controlled by PWM control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus, and more particularly to a power supply circuit for the electrophotographic apparatus.

[0002]

2. Description of the Related Art Generally, in an electrophotographic apparatus, a toner image is formed on an image bearing member, and the toner image on the image bearing member is transferred onto a recording material and fixed to form a toner image on the recording material. A photoconductor is used as an image carrier, and an electrophotographic device that forms a toner image on the photoconductor by charging, exposing, and developing, and an intermediate transfer member is used as the image carrier, and is formed on the photoconductor by charging, exposing, and developing. There is an electrophotographic device or the like that transfers the formed toner image to an intermediate transfer body and forms a toner image on the intermediate transfer body.
Further, there is an electrophotographic apparatus in which a dielectric is used in place of the photoconductor, an electrostatic latent image is formed on the dielectric by charging, and a toner image is formed by development.

(1) Generally, a power supply circuit of an electrophotographic apparatus converts a commercial AC voltage into a DC voltage of a predetermined level by an AC-DC converter and supplies a drive voltage to each part of the apparatus. Since the commercial AC voltage is 100 V in Japan and 200 V in Europe, which differs depending on the country or region, it is necessary to incorporate different AC-DC converters for each destination.

(2) As a fixing device for fixing a toner image on a recording material, a thermal fixing device for fixing a toner image by heating is generally used, and a halogen lamp is often used as a fixing heater for heating. Since the halogen lamp has a low resistance value of about several Ω to several tens of Ω at a low temperature, there is a problem that a rush current of about 40 to 60 A is generated when the fixing device is started up and various problems occur. That is, a voltage drop occurs in the wiring to which the electrophotographic apparatus is connected, which affects the operation of other devices and causes the fluorescent lamp to flicker.

[0005]

(1) In order to rationalize a system incorporating different power supply circuits for each destination,
Common C-DC converter and AC-DC
AC-D using a converter and a DC-DC converter
The C converter converts the AC voltage of various voltages into a DC voltage of a constant level, and the DC voltage of the constant level is converted to DC-D.
It is considered that a C converter is used to convert a plurality of direct current voltages for driving the respective parts of the device, whereby a power supply circuit is made common.

In such a power supply circuit, the fixing heater of the fixing device and the DC-DC converter are connected in parallel to the AC-DC converter. When such a configuration is adopted, the output of the DC-DC converter is immediately cut off when the AC power supply is cut off due to an accident, disconnection of an outlet, or the like, which causes a phenomenon of disturbing image formation. There is. That is, when the developing bias power source is shut off, carrier adhesion occurs in which carriers in the developing device are transferred and adhered to the photoconductor.

A first object of the present invention is to prevent an obstacle in an image forming process caused by interruption of an AC power source.

(2) The following measures are taken against the above-mentioned problem caused by the inrush current generated at the start of energization of the fixing heater.

As shown in FIG. 1A, phase control is performed to control the conduction angle Φ of the drive current of the fixing heater, and at the start of energization, the fixing heater is preheated to suppress the inrush current.

As shown in FIG. 1B, wave number control is performed to turn on / off the drive current of the fixing heater in half-wave units, and at the start of energization, the fixing heater is preheated to suppress the inrush current. In addition, in FIG. 1, the shaded portion is a power feeding portion.

As shown in FIG. 2, a resistor R is connected in series to the fixing heater HT, and a current is supplied to the fixing heater HT and the resistor R at the start of energization of the fixing heater HT, after which the temperature of the fixing heater HT rises. Then, the switch SW is closed and the resistor R is short-circuited.

However, the above measures have the following problems. In the above measures (1) and (2), harmonics are generated and affect the surrounding environment. In particular, it may violate harmonic regulations in Europe. Further, with the above measures, the frequency of the drive current is lowered and the fluorescent lamp flickers. For example, when the wave number control for turning off the 1/3 half wave with respect to the alternating current of 50 Hz is performed, it is substantially 33 Hz.
The fixing heater is driven by the driving current having the frequency f, which causes flickering of the fluorescent lamp.

In the above measures, when the resistor R having a small resistance value is used, the electric power consumed by the resistor R becomes large and the resistor R overheats. In order to avoid this overheating, a resistor with a large rated power is required, which causes a problem of increasing the volume and cost of the resistor R. Further, if the resistance value of the resistor R is increased, there is a problem that the preheating of the fixing heater HT, that is, the effect of increasing the temperature of the fixing heater HT and increasing the resistance value is impaired.

A second object of the present invention is to solve the above-mentioned problems in the conventional measures against the inrush current.

[0015]

The above-mentioned objects of the present invention are achieved by the following inventions.

1. AC-DC converter for converting AC voltage to output DC voltage of a predetermined level, DC-DC converter for converting output level of the AC-DC converter to output DC voltage, fixing heater, input of the AC voltage Having an input detection circuit for detecting interruption and a control means,
The control means performs control to stop the power supply to the fixing heater and then stop the output of the DC-DC converter based on an input cutoff detection signal of the input detection circuit. Electrophotographic device.

2. 2. The electrophotographic apparatus according to 1 above, wherein the DC-DC converter and the fixing heater are connected in parallel to the AC-DC converter.

3. The DC-DC converter has a plurality of output terminals, and the control means performs control to delay a stop time of an output of a part of the plurality of output terminals more than a stop time of another output. The electrophotographic apparatus according to 1 or 2 above.

4. 4. The electrophotographic apparatus according to any one of the items 1 to 3, wherein the output of the DC-DC converter that delays the stop time is a power source of a developing bias.

5. Fixing heater, resistor connected in series to the fixing heater, power source for supplying current to the fixing heater and the resistor, voltage detecting means for detecting voltage applied to the resistor, and detection of the voltage detecting means An electrophotographic apparatus having control means for controlling the power supply based on a signal, wherein the power supply has PWM conversion means,
The electrophotographic apparatus, wherein the control means controls the current supplied to the fixing heater by controlling the PWM conversion means.

6. The power supply includes an AC-DC converter that converts a commercial AC voltage into a DC voltage of a predetermined level, and the PWM-converted output of the power supply has a fundamental frequency equal to or higher than the frequency of the AC voltage. 6. The electrophotographic apparatus described in 5 above.

7. The control means supplies electric power to the fixing heater in a state in which a voltage is applied to the resistor at the start of power supply to the fixing heater, and the resistor is applied when the detection voltage of the voltage detecting means reaches a predetermined value. 7. The electrophotographic apparatus according to 5 or 6 above, which is short-circuited.

8. 8. The control unit performs control such that the power consumed by the resistor at the start of power supply to the fixing heater is equal to or lower than the rated power of the resistor. The electrophotographic apparatus according to 1.

9. 8. The electrophotographic apparatus according to 7, wherein the control unit short-circuits the resistor after reducing the duty ratio of the output of the power source in the control of short-circuiting the resistor.

10. Item 10. The control unit controls the fixing temperature by controlling the duty ratio of the output of the power source in the fixing step of fixing the toner image on the recording material. Electrophotographic device.

[0026]

<First Embodiment> FIG. 3 is a diagram showing a power supply circuit in an electrophotographic apparatus according to a first embodiment of the present invention. The illustrated power supply circuit includes a commercial AC power supply 10
From, for example, an AC voltage of 100 V is supplied. In the figure, reference numeral 20 is an AC-DC converter that converts an alternating voltage into a predetermined level of direct current voltage. In the illustrated example, 10
AC input of various voltages such as 0V and 200V is converted into a DC voltage of 350V. Reference numeral 30 is a DC-DC converter, and in the illustrated example, a DC voltage of 350V is driven by 24V.
Converted to DC voltage and 5V DC voltage for control. In the illustrated example, 24V which outputs a 24V DC voltage for driving
(1) Output 31, 24V (2) Output 32 and 5 for control
It has a 5V output 33 for outputting a V DC voltage. As described above, in the present embodiment, two sets of 24V (1) outputs 31, 24V (2) that output the driving 24V DC voltage are provided.
It has an output 32. The 24V (1) output 31 is used as a power source for a developing bias power source and a motor for driving a rotary polygon mirror (hereinafter referred to as a polygon motor) as a deflecting means of an exposure apparatus having a laser diode. 24V
(2) The output 32 is used as a power source for a charging device, a transfer device, a static eliminator, various light sources other than the fixing heater, and various motors. The 5V output 33 is used as a power source for the control means for system control and the control means for control provided in each unit such as the image processing unit and the operation unit. An input detection circuit 40 detects the voltage value of the input AC voltage and the interruption of the AC power supply 10. The AC-DC converter 20 operates by being controlled by the input level detection signal S1 of the input detection circuit 40, and outputs a constant (eg 350V) DC voltage for input voltages of different levels such as 100V and 200V. 5
Reference numeral 0 denotes a control means, which controls the entire power supply circuit shown in the figure, and in particular, performs various cutoff controls by the input cutoff detection signal S2 of the input detection circuit 40. A fixing device 60 includes a fixing power switch 61 and a fixing heater 62. A halogen lamp is used as the fixing heater 62. As shown, the DC-DC converter 30 and the fixing heater 62 are
It is connected in parallel to the C-DC converter 20.

FIG. 4 shows an AC-DC converter and a DC-DC.
It is a time chart which shows interruption control of a power supply using a converter.

When the input of the AC power supply 10 is cut off, the control means 50 maintains the operation of each part within the usable range of the output of the AC-DC converter 20, and when the usage limit is reached, the control means 50 sends the power to each part. Controls to cut off the input. That is, even after the AC power supply 10 is cut off, in a range in which the electric charge accumulated in the main capacitor 21 of the AC-DC converter 20 can operate, each part continues to operate, and when each limit is reached, each part is stopped. The control means 50 performs. In the example shown,
After the interruption time t1 of the AC power supply 10, each part is continuously operated, and at time t2, 24V (1) output 31 and 24V (2) are output.
The output 32 is stopped, then the 5V output 33 is stopped at time t3, and finally the power supply to the fixing heater 62 is stopped at time t4. In the control for operating each part within the range of the allowable voltage, as shown in FIG. 4, each part is stopped relatively early and almost at the same time.

In the first embodiment of the present invention, when the AC input is cut off, the energization of the fixing heater is first stopped to extend the storage time of the output of the DC-DC converter. FIG. 5 is a time chart of an example of the power shutoff control according to the first embodiment of the present invention. In FIG. 5, after the AC power supply 10 is cut off at time T1, the power supply to the fixing heater 62 is stopped at the first time T2. By stopping the power supply to the fixing heater 62, the AC-D
The electric charge of the main capacitor 21 of the C converter 20 is retained without being consumed early. As a result, the attenuation of the output Vout of the AC-DC converter 20 is delayed, so
Time T3 to stop 4V (1) output 31 and 24V (2) output 32 and time T3 to stop 5V output 33 for control
4 can be delayed.

These controls are performed by the control means 50 based on the input cutoff detection signal S2 from the input detection circuit 40. That is, the control means 50 first stops the power supply to the fixing heater 62 by the input cutoff detection signal s2 of the input detection circuit 40, and then stops the 24V (1) output 31 and the 24V (2) output 32. Finally, the 5V output 33 is stopped.

As can be seen from the figure, the attenuation of the output Vout of the AC-DC converter 20 is delayed, resulting in 24V.
(1) The stop time of the output 31 is delayed from the conventional t2 (see FIG. 4) to T3. Therefore, the carrier adhesion that the carrier is transferred from the developing device to the photoconductor and adheres due to the stop of the developing bias is effectively prevented.

FIG. 6 is a time chart of another example of the power shutoff control in the first embodiment of the present invention. In FIG. 6, the control means 50 firstly determines the fixing heater 6 at time T2 based on the input cutoff detection signal S2 from the input detection circuit 40.
2 is stopped and 24V (2) output 3 at almost the same time T3
Stop 2. That is, the power supply for driving which may be immediately stopped is immediately stopped. As a power supply capable of such an immediate stop, there are a charging power supply, a light source power supply, a motor power supply, and the like. Next, at time T4, 24V (1) output 31
And finally the 5V output 33 is stopped at time T5.

By immediately stopping the 24V (2) output 32 of the DC-DC converter 30 together with the fixing heater 62, the output voltage Vout of the AC-DC converter 20.
Is further delayed, as shown, the stop time T4 of the 24V (1) output 31 and the stop time T5 of the 5V output 33.
Is later delayed. Therefore, the time for maintaining the developing bias is greatly delayed, and problems such as carrier adhesion are effectively prevented. Further, the delay of the stop time of the developing bias alleviates the restrictions imposed on the image forming process, enables stable image formation, and expands the degree of freedom in mechanical design.

<Second Embodiment> FIG. 7 shows a power supply circuit of an electrophotographic apparatus according to a second embodiment of the present invention.

The illustrated power supply circuit includes a commercial AC power supply 10
From, for example, an AC voltage of 100 V is supplied. 20
Is an AC-DC converter, which converts, for example, an AC voltage of 100V into a DC voltage of 370V. 70 is PWM
The output of the AC-DC converter 20 is P
WM conversion to output power of various values and output PWMo
Output ut. A fixing device 60 has a fixing heater 62 including a halogen lamp. Reference numeral 90 denotes a resistor in series with the fixing heater 62, which supplements the resistance value that the fixing heater 62 lacks when the power is turned on. Reference numeral 50 denotes a control means for controlling the whole, and particularly controls the power supplied to the fixing heater 62 when the power is turned on. 80 is a resistor 90
Is a voltage detecting means for detecting the terminal voltage of the. Computing means 1
00 calculates the control amount of the PWM control based on the output of the voltage detection means 80. A switch 110 short-circuits the resistor 90.

The calculation means 100 eliminates the inrush current generated at the start of power supply to the fixing heater 62, and the resistor 9
A control amount for keeping the rated power of 0, a voltage level for short-circuiting the resistor 90, which will be described later, a control amount for PWM control before the short-circuit, and the like are calculated. Fixing heater 6
2 is started, that is, when the temperature of the fixing heater 62 is low and the resistance value thereof is low, the fixing heater 62 and the resistor 9 are
The detection voltage of the voltage detection means 80, which is a voltage divided by 0, shows a high value. The control means 50 controls the PWM conversion means 70 based on the output of the calculation means 100, and the PWM conversion means 70 outputs the output PWMout having a low duty ratio. Therefore, when power supply to the fixing heater 62 is started, a large value of inrush current is prevented from flowing to the fixing heater 62, and the power consumed by the resistor is suppressed.

When the temperature of the fixing heater 62 rises and its resistance value reaches a predetermined value, the voltage detected by the voltage detecting means 80, that is, the output of the calculating means 100 falls below a predetermined value. The control means 50 closes the switch 110 and short-circuits the resistor 90. As a result, the fixing heater 62
Since all the electric power is supplied to the fixing unit, the fixing process is performed with high energy utilization efficiency.

During the PWM control when the fixing device 60 starts up, that is, when the power supply to the fixing heater 62 is started, the control means 50 controls the fixing heater 62 and the resistor 90 within the rated power range of the resistor 90. Control the current to flow. Further, in the control for short-circuiting the resistor 90, the control means 50 may perform the control for short-circuiting the resistor 90 while maintaining the duty ratio, but prior to the short-circuiting, the duty ratio of the output PWMout of the PWM conversion means 70 is changed. It is more desirable to prevent inrush current from occurring at the time of short circuit by lowering.

FIG. 8A shows the transition of the current value at the start of power supply to the fixing heater in the control of the conventional electrophotographic apparatus. In the conventional control, the peak currents + P1 and -P1 of 40 A or more are generated at the start of power supply when the temperature of the fixing heater is low.

FIG. 8B shows the transition of the current value and the duty ratio of the output PWMout of the PWM conversion means 70 at the start of power supply to the fixing heater 62 in the second embodiment of the present invention. At the start of power supply, the duty ratio is 50%
To 100% in the steady operation of the fixing device 60 by continuously increasing the duty ratio from the time when the switch 110 is closed, so that the current value at the time of starting the power supply is equal to + P1 or −P1. Is + P
2, -P2 can be suppressed.

In the second embodiment, the PWM conversion means 70 is also used for power supply control of the fixing heater 62 during the steady operation of the fixing device 60.

The control means 50 controls the PWM conversion means 70 based on the output of the temperature detection means 63 for detecting the fixing temperature of the fixing device 60. FIG. 9 shows the fixing device 60 according to the second embodiment.
3 is a time chart of control in steady operation of. The curve C1 is the fixing device 60 detected by the temperature detecting means 63.
(For example, the surface temperature of the fixing roller), the curve C2 is the duty ratio of the output PWMout of the PWM conversion means 70, and the curve c3 is the amount of heat supply to the fixing heater 62 per unit time.

When the fixing device 60 starts up, electric power having a high duty ratio is supplied to the fixing heater 62. Therefore, the heat supply amount per unit time is large and the temperature rises linearly. When the temperature reaches the upper limit, the temperature detecting means 6
The control means 50 controls to reduce the duty ratio by the signal of No. 3. By repeating the control of raising and lowering the duty ratio, the temperature of the fixing device 60 converges on the control temperature,
It is maintained at a constant value.

FIG. 10 shows a time chart of the conventional temperature control in comparison with the temperature control of the above embodiment. In FIG. 10, C1 indicates the temperature of the fixing device, C2 indicates on / off of the output of the power supply circuit, and C3 indicates the amount of heat supplied to the fixing heater.

Since the conventional temperature control simply turns on / off the output of the power supply circuit, the heat supply amount per unit time changes intermittently as indicated by C3. Therefore, the temperature C1 of the fixing device fluctuates up and down as shown in the figure, causing a temperature ripple. For this reason, the melting degree of the binder resin of the toner is not uniform, and there is a problem that the image quality is affected.

According to the present embodiment, the temperature ripple is eliminated as shown in FIG. 9, and the above-mentioned problems are effectively eliminated.

[0047]

According to the first and second aspects of the present invention, troubles in the image forming process such as carrier adhesion due to the stop of the developing bias which occurs when the input of the AC voltage is cut off can be prevented.

According to the third aspect of the present invention, it is possible to sufficiently secure the input holding time required when the AC voltage input is cut off, so that it is possible to more effectively prevent the obstacle that occurs when the input is cut off.

According to the fourth aspect of the present invention, carrier adhesion that occurs when input is cut off is effectively prevented.

According to the fifth aspect of the invention, the inrush current generated at the start of power supply to the fixing heater is effectively prevented. As a result, it is possible to effectively prevent other devices, fluorescent lamps, etc. in the wiring area of the electrophotographic apparatus from being affected by the activation of the electrophotographic apparatus.

According to the sixth aspect of the present invention, the flicker of the fluorescent lamp in the surroundings caused by the operation of the electrophotographic apparatus is effectively prevented.

According to the seventh aspect of the invention, it is possible to effectively eliminate the inrush current that tends to occur when the start-up control of the fixing device is changed to the steady control.

According to the invention of claim 8, overheating of the resistor connected in series with the fixing heater is effectively prevented.

According to the ninth aspect of the invention, the inrush current that tends to occur when the resistor connected in series with the fixing heater is short-circuited is effectively prevented.

According to the tenth aspect of the invention, it is possible to effectively prevent the temperature ripple that occurs when the fixing temperature is controlled.

[Brief description of drawings]

FIG. 1 is a diagram showing conventional current control.

FIG. 2 is a diagram showing a drive circuit of a conventional fixing heater.

FIG. 3 is a diagram showing a power supply circuit in the electrophotographic apparatus according to the embodiment of the present invention.

FIG. 4 is a time chart showing cutoff control of a common power source.

FIG. 5 is a time chart showing an example of power-off control in the electrophotographic apparatus according to the first embodiment of the present invention.

FIG. 6 is a time chart showing another example of the power shutoff control in the electrophotographic apparatus according to the first embodiment of the present invention.

FIG. 7 is a diagram showing a power supply circuit of an electrophotographic apparatus according to Embodiment 2 of the present invention.

FIG. 8 is a second embodiment of a conventional electrophotographic apparatus and the present invention.
FIG. 6 is a diagram showing a transition of a current value at the start of power supply to the fixing heater in the control of the electrophotographic apparatus according to the present invention.

FIG. 9 is a time chart of control in steady operation of the fixing device according to the second embodiment of the present invention.

FIG. 10 is a time chart of conventional temperature control.

[Explanation of symbols]

10 AC power supply 20 AC-DC converter 30 DC-DC converter 40 input detection circuit 50 control means 60 fixing device 62 fixing heater 70 PWM conversion means 80 Voltage detection means 90 resistor 100 computing means 110 switch

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Peng Yuho             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             In the company (72) Inventor Shinobu Kishi             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             In the company (72) Inventor Umin Soma             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             In the company F term (reference) 2H027 DA01 DE05 EA05 EA12 EC06                       ED09 EJ17 EK07                 2H033 AA02 BB18 BC01 CA43 CA44                 2H073 AA10 BA01 BA09 BA21 BA41

Claims (10)

[Claims] 1. An AC-DC converter that converts an AC voltage to output a DC voltage of a predetermined level, a DC-DC converter that converts the output level of the AC-DC converter and outputs a DC voltage, a fixing heater, An input detection circuit for detecting input interruption of the AC voltage,
The control means has a control for stopping the power supply to the fixing heater based on the input cutoff detection signal of the input detection circuit, and then for stopping the output of the DC-DC converter. An electrophotographic device characterized by being performed. 2. The electrophotographic apparatus according to claim 1, wherein the DC-DC converter and the fixing heater are connected in parallel to the AC-DC converter. 3. The DC-DC converter has a plurality of output terminals, and the control means performs control for delaying a stop time of an output of a part of the plurality of output terminals more than a stop time of another output. The electrophotographic apparatus according to claim 1 or 2, wherein: 4. The electrophotographic apparatus according to claim 1, wherein the output of the DC-DC converter that delays the stop time is a power source of a developing bias. 5. A fixing heater, a resistor connected in series to the fixing heater, a power supply for supplying a current to the fixing heater and the resistor, a voltage detecting unit for detecting a voltage applied to the resistor, and An electrophotographic apparatus having control means for controlling the power supply based on a detection signal of a voltage detection means, wherein the power supply has a PWM conversion means, and the control means controls the PWM conversion means to fix the fuse. An electrophotographic apparatus characterized by controlling an electric current supplied to a heater. 6. The power source has an AC-DC converter for converting a commercial AC voltage into a DC voltage of a predetermined level,
6. The PWM-converted output of the power supply has a fundamental frequency equal to or higher than the frequency of the AC voltage.
The electrophotographic apparatus according to 1. 7. The control means supplies electric power to the fixing heater with a voltage applied to the resistor at the start of power supply to the fixing heater, and the detection voltage of the voltage detecting means reaches a predetermined value. 7. The electrophotographic apparatus according to claim 5, wherein the resistor is short-circuited at times. 8. The control means performs control such that the power consumed by the resistor at the start of power supply to the fixing heater is equal to or lower than the rated power of the resistor. 7. The electrophotographic apparatus according to any one of items 7. 9. The electrophotographic apparatus according to claim 7, wherein in the control for short-circuiting the resistor, the control unit short-circuits the resistor after lowering the duty ratio of the output of the power source. . 10. The control means controls the fixing temperature by controlling the duty ratio of the output of the power source in the fixing step of fixing the toner image on the recording material. The electrophotographic apparatus according to any one of items.