JP2005003710A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To relax a drop of the input voltage of a direct current power source caused by an inrush load, an inrush current, a line impedance, etc. <P>SOLUTION: The input voltage V<SB>in</SB>of the direct current power source DC inputted from an alternating current power source AC may have a voltage drop caused by a line impedance Z, a shutoff device F, a noise filter NF, either a choke coil L serving as a power factor modifying means connected to the input upstream of the direct current power source DC or a bypass means connected parallel to the choke coil L, a heater 73 connected to the input side of the direct current power source DC without using the choke coil L between them, or a fixing motor M connected to the output side of the direct current power source DC. When a voltage value detected by a voltage detection part PT is equal to or lower than a reference voltage value Vs, a bypass circuit 200 is conducted for a predetermined length of time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in a power supply circuit of an image forming apparatus.
[0002]
[Prior art]
When power is supplied from an AC power supply to a device equipped with a DC power supply, the input voltage of the DC power supply depends on the line impedance, wiring resistance inside the device, noise filter, power factor correction coil, etc. A voltage drop occurs. When the input voltage of the DC power supply falls below the power supply operation limit voltage value, the output voltage of the DC power supply fluctuates, and the load supplied with power from the DC power supply may not obtain a desired operation. In particular, in the case of a load that generates an inrush current, the input voltage of the DC power supply drops instantaneously. Examples of loads that generate inrush current include driving loads such as motors and heat source loads such as lamps and heaters.
[0003]
Also, due to the recent trend of multi-function, high-function, miniaturization, etc. of OA (Office Automation) equipment, the load capacity for the power supply device is increasing, and strict voltage stability is required.
In the image forming apparatus, there are many power loads such as a drive source such as a motor, an exposure lamp, and a heater arranged in various places. As a power source for driving in the image forming apparatus and driving various power loads, A direct current power source that is directly or transformed from an alternating current power source is provided. At the start of copying in the image forming apparatus, a plurality of motors and lamps are activated and lit to generate an inrush current. There is a problem that loads such as a plurality of motors and heaters cannot operate properly due to a sudden drop in the input voltage of the DC power supply due to the inrush current, resulting in problems in image formation.
[0004]
Therefore, it is necessary to design the DC power supply with a lower operating limit voltage, and the standard of circuit elements used for the DC power supply must be set to a standard product compatible with a large current, resulting in an increase in circuit cost. Therefore, as a DC power source for an image forming apparatus, a switching power source having high conversion efficiency, small size and light weight, and a wide input voltage range is often used. However, it is known that the switching power supply has a problem that noise is easily generated.
[0005]
For example, in Patent Document 1, when a load current of a switching power supply is detected and the load current reaches a predetermined value, a choke coil for suppressing harmonic current and a power thermistor for suppressing inrush current are connected by a triac or relay according to an external signal. Has disclosed a switching regulator that prevents a short-circuit current and a harmonic current generation at a light load and an inrush current when a power switch is turned on.
[0006]
In Patent Document 2, a first choke coil for suppressing high frequency, a second choke coil for suppressing harmonics and a changeover switch that bypass the first choke coil are arranged in parallel between the AC power source and the rectifying element. The switch is turned off when the output current of the DC power is less than the predetermined value, and turned on when the output current exceeds the predetermined value to suppress the harmonic current and improve the power factor. A regulator is disclosed.
[0007]
In Patent Document 3, a first choke coil for suppressing high frequency, a second choke coil for suppressing harmonics and a changeover switch that bypass the first choke coil are arranged in parallel between the AC power source and the rectifying element. The current detection means for detecting the average value of the current flowing through the switching element is provided, and when the average value of the current detected by the current detection means is below a predetermined value, the changeover switch is turned off and exceeds the predetermined value. In other words, a switching regulator is disclosed that is turned on when the output power is large and the high power factor can be maintained by constantly suppressing the harmonic component of the input current of the power source even if the output power fluctuates greatly.
[0008]
Also, in Patent Document 4, either a choke input rectifier circuit or an active filter circuit is switched as an operating circuit based on a control signal from a power supply device, and control of switching operation is based on a control signal input to a control input terminal. By doing so, a power supply device that reduces unnecessary noise generated by the power supply device and improves power supply efficiency is disclosed.
[0009]
[Patent Document 1]
JP-A-8-149822
[Patent Document 2]
JP-A-8-205519
[Patent Document 3]
Japanese Patent Laid-Open No. 9-23646
[Patent Document 4]
JP-A-9-121547
[0010]
[Problems to be solved by the invention]
However, the above document only discloses a technique for improving efficiency and power factor including reduction of the input current of the DC power supply, and does not improve the operation when the input voltage is low. Due to a decrease in input voltage due to a load such as a motor or a lamp, the DC power supply may be stopped, damaged, or momentarily stopped, which may cause problems in the image forming apparatus. Further, the invention described in Patent Document 1 has a configuration in which the bypass control of the choke coil and the thermistor is performed by the DC power supply unit.
[0011]
An object of the present invention is to alleviate a decrease in input voltage of a DC power source due to an inrush load, an inrush current, a line impedance, and the like.
[0012]
[Means for Solving the Problems]
The invention according to claim 1 is a DC power source to which electric power is input from an AC power source, a power factor improving means connected to the input side of the DC power source, an output side of the DC power source, and an inrush current. A bypass unit connected in parallel to the power factor correction unit, and the bypass unit is electrically connected for a predetermined time when power supply to the load is started or when operation of the load is started. It is characterized by having a control means for making it possible.
[0013]
According to the first aspect of the present invention, bypass means is provided in parallel with the power factor improving means, and bypassing is performed simultaneously with the start of power feeding or operation of the load that generates the inrush current connected to the output side of the DC power supply. By making the means conductive, it is possible to prevent a drop in the input voltage of the DC power source by the amount of voltage drop due to the current flowing through the power factor improving means and the impedance of the power factor improving means. Further, it is possible to alleviate the decrease in the input voltage of the DC power supply due to the line impedance from the AC power supply regardless of the installation conditions of the image forming apparatus, and to avoid the malfunction of the DC power supply caused by the voltage decrease.
[0014]
The invention according to claim 2 is a DC power source to which electric power is input from an AC power source, a power factor improving means connected to the input side of the DC power source, an output side of the DC power source, and an inrush current. An image forming apparatus comprising: a load to be generated; and a heater connected to an input side of the power factor improving unit. The image forming apparatus includes a bypass unit connected in parallel to the power factor improving unit. Control means for conducting for a predetermined time at the start of power supply to the heater or at the start of operation of the load or the heater is provided.
[0015]
According to the second aspect of the present invention, the bypass means is provided in parallel with the power factor improving means, and the power supply start of the load connected to the output side of the DC power supply or the heater connected to the input side is started. By connecting the bypass means at the same time as the start of the operation of the load or the heater connected to the input side that generates an inrush current or the voltage drop due to the impedance of the power factor improvement means and the impedance of the power factor improvement means Only the input voltage drop of the DC power supply can be prevented.
[0016]
A third aspect of the present invention is the image forming apparatus according to the first or second aspect, further comprising voltage detection means for detecting an input voltage of the DC power supply, wherein the control means is detected from the input voltage detection means. The bypass means is turned on when the input voltage reaches a predetermined value or less.
[0017]
According to the third aspect of the present invention, the AC voltage source that is the minimum required for the detection voltage value from the voltage detection means for detecting the input voltage of the DC power source to output power from the DC power source to the high load is provided. By making the bypass means conductive only when the input voltage value is less than or equal to the input voltage value, a normal power factor improving means can be used without conducting the bypass means at a voltage value that can be driven without any inconvenience.
[0018]
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the control unit includes a time measuring unit that measures a conduction time of the bypass unit. .
[0019]
According to the fourth aspect of the present invention, the timing means for timing the time for which the bypass means is conducted is provided, and is set based on the disappearance time of the inrush current at the start of power supply to the load or at the start of load operation. By measuring the predetermined time, the drop in the input voltage of the DC power supply can be mitigated with respect to the time during which a sudden voltage drop due to the inrush current occurs.
[0020]
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the load is a motor that drives a heating roller of a fixing device, and the heater is a heater of the fixing device. It is characterized by being.
[0021]
According to the fifth aspect of the present invention, when power supply to the fixing motor or the heater of the fixing device is started, or when the operation of the fixing motor or the heater is started (that is, when the fixing motor or the heater is started or lit). )), By conducting the bypass means, it is possible to avoid malfunctions such as stop, breakage, and momentary interruption of the DC power supply of the image forming apparatus at the start of copying, so that image formation is not affected. It can be performed.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
This embodiment is an example of a DC motor that supplies power to a fixing motor that drives a heating roller of a fixing device and a heater that heats the heating roller in the image forming apparatus.
[0023]
FIG. 1 shows a cross-sectional configuration of a mechanism portion of the image forming apparatus 1 in the present embodiment. As shown in FIG. 1, the image forming apparatus 1 is roughly composed of an image reading unit 10 and a printing unit 20.
[0024]
The image reading unit 10 includes a scanner including a light source, a lens, a CCD (Charge Coupled Device), and the like. The reflected image of the light irradiated on the document is imaged and photoelectrically converted to read the document image, and print To the unit 20. Here, the original image is not limited to image data such as graphics and photographs, but also includes text data such as characters and symbols.
[0025]
The printing unit 20 includes an image forming unit 30, a cleaning unit 40, an intermediate transfer belt 50, a paper feeding unit 60, and a fixing unit 70.
[0026]
The image forming unit 30 includes a photosensitive drum 31 that is a photosensitive member, a charging device 32, an exposure device 33, a developing device 34, and a cleaning device 35.
[0027]
The intermediate transfer belt 50 is rotatably supported by a plurality of rollers, and rotates as each roller rotates. The intermediate transfer belt 50 is pressed against the photosensitive drum 31 by the primary transfer roller 51. As a result, each toner developed on the surface of the photosensitive drum 31 is transferred to the intermediate transfer belt 50 at the pressure contact position by the primary transfer roller 51, and the toner is sequentially transferred in a superimposed manner. Then, after the toner image is transferred to the recording paper P by the secondary transfer roller 52, the residual toner is removed by the cleaning unit 40 from the intermediate transfer belt 50 from which the recording paper P is separated by curvature.
[0028]
In the paper feeding unit 60, the recording paper P stored in the paper trays 61, 62, 63 is fed by a paper feeding roller 64, and passes through a plurality of intermediate rollers 65A, 65B, 65C, 65D and a registration roller 66. It is conveyed to the next transfer roller 52. The toner image transferred to the intermediate transfer belt 50 is transferred onto the recording paper P surface by the secondary transfer roller 52. The recording paper P is heat-fixed by the fixing unit 70 on the toner image transferred to the recording paper P. The recording paper P that has been subjected to the fixing process is sandwiched between paper discharge rollers 67 and placed on a paper discharge tray 68.
[0029]
The fixing unit 70 includes a heating roller 71 and a pressure roller 72 that presses against the heating roller 71 to form a nip portion N. The fixing unit 70 rotates and heats the heating roller 71 and the pressure roller 72 to heat and press the recording material P inserted through the nip portion N, and the toner image on the recording material P is placed on the recording material P. Let it settle.
[0030]
FIG. 2 shows a cross-sectional view of the fixing unit 70.
As shown in FIG. 2, the heating roller 71 includes a heat-resistant release layer 71a and a cored bar layer 71b. A heater 73 is provided as a heater for heating the heating roller 71 inside the metal core layer 71b. The heat-resistant release layer 71a is made of fluororesin or silicon rubber, and the cored bar layer 71b is made of aluminum or iron. A halogen lamp or the like is used for the heater 73.
The pressure roller 72 includes an elastic layer 72a and a cored bar layer 72b. The elastic layer 72a is made of silicon rubber or the like, and the core metal layer 72b is made of aluminum or iron.
The heating roller 71 and the pressure roller 72 described above are rotationally driven by the fixing motor M via a plurality of gears and the like.
[0031]
FIG. 3 shows a configuration example of a control system for the power supply circuit, the fixing motor M, and the heater 73 in the image forming apparatus 1.
As shown in FIG. 3, AC power from the AC power source AC is supplied to the DC power source DC via the cutoff device F, the noise filter NF, and the voltage detection unit PT. The direct current power source DC converts the supplied alternating current power into direct current power. The DC power is supplied to the fixing motor M via the drive circuit unit DV. The power supply to the fixing motor M is controlled based on the motor control signal SM from the control unit 100 in the drive circuit unit DV.
On the other hand, the AC power at the output end of the voltage detector PT is branched and supplied to the heater 73 as well. The AC power to the heater 73 is ON / OFF controlled based on a heater control signal SH from the control unit 100.
A choke coil L as a power factor improving means is inserted in series at the input portion of the DC power source DC, and a bypass circuit portion 200 according to the present invention is connected in parallel to the choke coil L. The bypass circuit unit 200 is ON / OFF controlled by a bypass control signal SB from the control unit 100.
Z represents a line impedance including a wiring resistance, a capacitance component, and an inductance component existing in the power supply path of the AC power supply AC.
The voltage detector PT detects a change in the input AC voltage in real time, and outputs the detected voltage value V to the controller 100. The control unit 100 performs ON / OFF control of the bypass circuit unit 200 and the heater control unit 74 based on the input detection voltage value V. The control timing will be described later in the explanation of the operation.
[0032]
There are elements that cause various voltage drops in the path from the AC power supply AC to the DC power supply DC. These elements are the line impedance Z depending on the installation location and power distribution status of the image forming apparatus 1, the cutoff device F in the image forming apparatus 1, the noise filter NF, and the choke coil L or choke connected before the input of the DC power source DC. One of the bypass circuit units 200 connected in parallel to the coil L is a heater 73 connected to the input side of the DC power source DC without passing through the choke coil L. Further, as a factor causing a voltage drop, there is an inrush current generated when the fixing motor M is started.
[0033]
The control unit 100 includes a bypass circuit timer as a time measuring unit having a function of measuring a predetermined time T for making the bypass circuit unit 200 conductive for a predetermined time, and a reference voltage value Vs for making the bypass circuit unit 200 conductive. Is set. The detection voltage value V input from the voltage detection unit PT is compared with the reference voltage value Vs, and when the detection voltage value V is equal to or less than the reference voltage value Vs, the conduction command of the bypass circuit unit 200 is output, and the predetermined time T A bypass control signal SB that outputs a shut-off command after elapse is held.
[0034]
The predetermined time T is generated when the inrush current generated when the fixing motor M is started up (that is, when power supply is started or when the operation is started) and when the heater 73 is turned on. Is set based on the time until the inrush current to be restored to the current value of the normal load. In the present invention, the predetermined time T is set when the fixing unit 70 is started up (starting of the fixing motor M and power supply to the heater 73), but when the fixing motor M is started up and when the heater 73 is turned on. In order to take measures individually, the conduction time T may be set individually, and is preferably set based on the time until the inrush current of the load connected to the DC power source DC returns to the current value of the normal load. .
[0035]
The reference voltage value Vs is an input voltage value from the AC power supply AC that is the minimum necessary for outputting power from the DC power supply DC to a high load.
That is, when the load such as the fixing motor M and the heater 73 is started, the input voltage of the DC power source DC is determined by taking into account the impedance in the image forming apparatus 1 including the choke coil L and the line impedance Z of the AC power source AC. The voltage value is set so as not to be lower than the operation limit voltage.
When the voltage is equal to or lower than the predetermined voltage Vs, the bypass circuit unit 200 is turned on because there is a possibility that the fixing unit 70 may be activated. Note that when another load is being driven, the input voltage value of the DC power supply DC has already decreased, but when the voltage value exceeds the reference voltage value Vs, it can be started without any inconvenience. A normal choke coil L is used without making the circuit part 200 conductive.
[0036]
The control unit 100 may be a control unit unique to the fixing unit 70, or is connected to each unit in the image forming apparatus 1 so as to be able to transmit and receive various information to and from each other, and receives information from each unit. The received information may be determined, information such as an operation instruction as a determination result may be output to each unit, and included in the control unit of the image forming apparatus 1 that controls each unit.
[0037]
FIG. 4 shows a configuration circuit example of the bypass circuit unit 200 used in FIG.
As shown in FIG. 4, the bypass circuit unit 200 is a switching element connected in parallel with the choke coil L. The triac TR1, the resistors R1, R2, R3, and R4, the capacitor C1, and the phototriac Tf are included.
[0038]
The series circuit formed by the resistor R1 connected in parallel to the triac TR1 and the capacitor C1 is a snubber circuit, which absorbs harmonic pulses such as switching noise generated by the triac TR1, and protects the triac TR1 from overvoltage and noise. Has the function of
[0039]
The phototriac Tf includes a light emitting diode D and a triac TR2, and the triac TR2 has a function of conducting in both directions only when a current flows through the light emitting diode D.
[0040]
The triac TR1 is driven by resistors R2 and R3 and a phototriac Tf. The current flowing between the T1 terminal and the T2 terminal can be controlled by the current flowing through the gate terminal G of the triac TR1, and the current flowing through the gate terminal G is controlled by the phototriac Tf.
[0041]
When a current flows through the light emitting diode D of the phototriac Tf based on the bypass control signal S from the control unit 100, a current flows through the triac TR2 of the phototriac Tf. When a current flows through the triac TR2, a current flows through the gate terminal G of the triac TR1, and a current flows between the T1 terminal and the T2 terminal of the triac TR1. When a current flows between the T1 terminal and the T2 terminal of the triac TR1, the current flowing through the choke coil L flows through the bypass circuit unit 200 having a low impedance.
[0042]
When there is no bypass control signal S from the control unit 100, no current flows through the triac TR2 of the phototriac Tf, so no current flows through the triac TR1, and a current flows through the choke coil L.
[0043]
FIG. 5 shows an operation flow of the bypass circuit unit 200 based on a signal from the control unit 100.
At the start of copying, when the fixing unit 70 is activated from the control unit 100, it is determined whether the detected voltage value V from the voltage detecting unit PT is equal to or lower than the reference voltage value Vs (step S1).
When the detected voltage value V is equal to or lower than the reference voltage value Vs, a bypass control signal is output from the control unit 100 to the phototriac Tf in the bypass circuit unit 200 so that the bypass circuit unit 200 is conducted, and a current flows through the triac T1. As a result, the bypass circuit unit 200 is turned on based on the signal (step S2). At the same time, the counting of the predetermined time T by the bypass circuit timer is started (step S3). At the same time that the bypass circuit unit 200 is turned on, the fixing motor M is started, the heating roller 71 and the pressure roller 72 rotate, and then the heater 73 is turned on.
[0044]
When the time measured by the bypass circuit timer has passed the predetermined time T (step S4: YES), the bypass control signal S is output to the phototriac Tf in the bypass circuit unit 200 so as to shut off the bypass circuit unit 200. Is blocked based on the signal (step S5). At the same time, the counting of the predetermined time T by the bypass timer is cleared (step S6). When the predetermined time T has not elapsed, the bypass circuit unit 200 is kept conductive.
[0045]
FIG. 6 shows the input voltage V of the DC power supply DC with respect to time. _in And the relationship with the control signal. The input voltage V according to the invention _in Is indicated by a solid line, and the conventional input voltage V _in Is indicated by a broken line.
[0046]
First, the input voltage V of the DC power source DC of the conventional image forming apparatus _in Will be described.
When the copy start signal SS is turned on at the copy start time t1, the fixing motor control signal SM is turned on and the fixing motor M is started. The input voltage V of the DC power source DC is determined by the line impedance Z from the AC power source AC and the impedance in the image forming apparatus 1. _in When the fixing motor M is in a state of being easily lowered, the input voltage V _in May drop rapidly and fall below the power supply operating limit voltage.
[0047]
V _in Reference numeral 1 denotes an input voltage of the DC power source DC due to an inrush current generated when the conventional fixing motor M is started.
Due to the inrush current generated when the fixing motor M is started, the output current of the DC power source DC is increased, and the input current of the DC power source DC is increased. Therefore V _in The voltage drop of 1 is the current (inrush current) increased by starting the fixing motor M, the line impedance Z, the cutoff device F, the noise filter NF, the voltage detection unit PT, the choke coil L, and the image forming apparatus 1. A sudden voltage drop occurs due to the wiring resistance.
[0048]
V _in Reference numeral 2 denotes the input voltage of the DC power source DC during steady rotation after the fixing motor M is started.
After the fixing motor M is started (after the rush current disappears), a normal load current of the normal fixing motor M flows and stabilizes at a steady rotation. Since the steady load current is smaller than the inrush current generated at the start-up, the input current of the DC power source DC is reduced. Therefore, this V _in The voltage drop of 2 is caused by the steady load current and line impedance Z of the fixing motor M, the interruption device F, the noise filter NF, the voltage detection unit PT, the choke coil L, the wiring resistance in the image forming apparatus 1, and the like.
[0049]
Next, when the heater control signal SH from the control unit 100 is turned on at t2, the heater control unit 74 supplies power to the heater 73. Since the heater 73 has a low impedance (cold resistance) until the temperature of the filament in the lamp rises immediately after lighting, an inrush current is generated. Due to the inrush current generated when the heater 73 is turned on, the input voltage V _in May drop rapidly and become below the power supply operating limit voltage.
[0050]
V _in Reference numeral 3 denotes an input voltage of the DC power source DC due to an inrush current generated by supplying electric power to the heater 73.
Electric power is supplied to the heater 73 by the heater controller 74. Inrush current is generated by the cold resistance of the lamp. Therefore, this V _in 3 is caused by an inrush current and the line impedance Z on the AC power supply AC side of the heater 73, the cutoff device F, the noise filter NF, the voltage detection unit PT, and the like.
[0051]
V _in 4 indicates the input voltage of the DC power source DC after the generated inrush current is stabilized after the heater 73 is supplied with electric power (after the inrush current disappears).
Since the lamp impedance rises as the lamp warms up after supplying power to the heater 73, the inrush current disappears and the normal load current of the heater 73 flows. Therefore, this V _in The voltage drop of 4 is caused by the consumed load current and the line impedance Z, the cutoff device F, the noise filter NF, the voltage detection unit PT, and the like during steady lighting of the heater 73.
[0052]
Next, the input voltage V of the DC power source DC of the image forming apparatus 1 including the bypass circuit unit 200 according to the present invention. _in Will be described.
At the copy start time t1, when the copy start signal SS is turned ON, the fixing motor control signal SM is turned ON and the fixing motor M is started. When the fixing motor control signal SM is turned on and the detected voltage value V is equal to or lower than the reference voltage value Vs, the bypass control signal SB is turned on and the bypass circuit unit 200 is turned on, and at the same time a predetermined time T by the bypass circuit timer. Will start timing.
[0053]
V _in Reference numeral 5 denotes an input voltage of the DC power source DC due to an inrush current generated when the fixing motor M is started at t1 and a steady load current consumed during steady rotation after the start.
The current input to the DC power source DC flows through the bypass circuit unit 200 without passing through the choke coil L because the impedance of the bypass circuit unit 200 is small. Therefore, it is possible to prevent the voltage drop due to the inrush current generated when starting the fixing motor M flowing through the choke coil L, the steady load current consumed during steady rotation after the start-up, and the impedance of the choke coil L, and suddenly. Voltage drop can be prevented. Therefore, this V _in 5 is caused by the load current of the fixing motor M flowing through the bypass circuit unit 200, the line impedance Z, the cutoff device F, the noise filter NF, the voltage detection unit PT, and the like.
[0054]
Next, when power is supplied to the heater 73 at time t2, the heater 73 is connected to the AC power supply side without going through the bypass circuit unit 200. _in When the voltage drop shown in FIG. _in The voltage drop shown in 4 occurs.
[0055]
V _in 6 indicates an input voltage of the DC power source DC generated when the bypass circuit unit 200 is shut off.
When the time measured by the bypass circuit timer is t3 when the predetermined time T has elapsed, the bypass circuit unit 200 is shut off based on the bypass control signal SB. Since the steady load current of the fixing motor M flowing through the bypass circuit unit 200 flows to the choke coil L at the time of interruption, a voltage drop occurs due to the steady load current of the fixing motor M and the impedance of the choke coil L.
[0056]
The example in which the fixing motor M is first activated and then the electric power is supplied to the heater 73 has been described. However, the electric power may be supplied to the heater 73 and then the fixing motor M may be activated. You may supply the input voltage V of the DC power supply when supplying power _in The order is not limited as long as the voltage does not fall below the power supply operating limit voltage.
[0057]
In the present invention, the image forming apparatus provided with the DC power source DC for supplying power to the fixing motor M and the heater 73 has been described. However, the load connected to the DC power source DC is not limited to the fixing motor M, and the paper is fed. A plurality of motors for driving rollers used in the section may be connected, and the same effect can be obtained even with a load that requires a large load in a short time. Further, the present invention is not limited to the heater 73 connected to the input side of the DC power source DC without passing through the choke coil L, and may be an exposure lamp.
[0058]
【The invention's effect】
According to the first aspect of the present invention, the bypass means is provided in parallel with the power factor improving means, and the inrush current is generated at the start of feeding the load that generates the inrush current connected to the output side of the DC power source. By making the bypass means conductive simultaneously with the start of the load operation, it is possible to prevent a drop in the input voltage of the DC power supply by the voltage drop due to the current flowing through the power factor improving means and the impedance of the power factor improving means. Further, it is possible to alleviate the decrease in the input voltage of the DC power supply due to the line impedance from the AC power supply regardless of the installation conditions of the image forming apparatus, and to avoid the malfunction of the DC power supply caused by the voltage decrease.
[0059]
According to the second aspect of the present invention, the same effect as in the first aspect can be obtained, and the bypass means is provided in parallel with the power factor improving means, and the inrush current connected to the output side of the DC power supply is reduced. By turning on the bypass means at the same time as the start of power supply of the heater connected to the load or input side to be generated or the operation of the heater connected to the load or input side to generate an inrush current, the power factor improving means A drop in the input voltage of the DC power source can be prevented by the voltage drop due to the flowing current and the impedance of the power factor improving means.
[0060]
According to the third aspect of the present invention, the detection voltage value from the voltage detection means for detecting the input voltage of the direct current power source can be obtained from the direct current power source as well as the same effects as in the first and second aspects. By bypassing the bypass means only when the voltage is less than or equal to the input voltage value from the AC power supply that is the minimum necessary to output power to a high load, the bypass means is made conductive at a voltage value that can be driven without any inconvenience. Ordinary power factor improving means can be used without any problem.
[0061]
According to the fourth aspect of the present invention, the same effect as in the first to third aspects can be obtained, as well as the time measuring means for measuring the time for which the bypass means is turned on, and when the power supply to the load is started. Or, by measuring the predetermined time set based on the disappearance time of the inrush current at the start of the load operation, the input voltage drop of the DC power supply is mitigated with respect to the time when the sudden voltage drop due to the inrush current occurs. be able to.
[0062]
According to the fifth aspect of the invention, it is possible to obtain the same effect as that of the first to fourth aspects, as well as at the start of power supply to the fixing motor or heater of the fixing device, or of the fixing motor or heater. When the operation is started (that is, when the fixing motor or the heater is started and turned on), the bypass unit is turned on to prevent malfunction such as stop, breakage, or momentary power failure of the DC power supply of the image forming apparatus at the start of copying. Therefore, the image formation can be performed without affecting the image formation.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an internal configuration of an image forming apparatus 1 to which the present invention is applied.
2 is an example of a cross-sectional view of a fixing unit 70 provided in the image forming apparatus 1 of FIG.
FIG. 3 is an example of a configuration block diagram of the image forming apparatus 1;
4 is an example of a configuration circuit of a bypass circuit unit 200 used in FIG. 3;
FIG. 5 is an operation flow of the bypass circuit unit 200 based on a signal from the control unit 100;
FIG. 6 shows the input voltage V with respect to the time of the DC power supply DC. _in It is a relationship diagram with the control signal.
[Explanation of symbols]
1 Image forming device
10 Image reader
100 control unit
20 Print section
200 Bypass circuit
30 Image forming unit
31 Photosensitive drum
32 Charging device
33 Exposure equipment
34 Developing device
35 Cleaning device
40 Cleaning section
50 Intermediate transfer belt
51 Primary transfer roller
52 Secondary transfer roller
60 Paper feeder
61, 62, 63 Paper tray
64 Paper feed roller
65A, 65B, 65C, 65D Intermediate roller
66 Registration Roller
67 Paper discharge roller
68 Output tray
70 Fixing part
71 Heating roller
71a Heat-resistant release layer
71b Metal core layer
72 Pressure roller
72a Elastic layer
72b Core metal layer
73 Heater
74 Heater controller
AC AC power supply
DC DC power supply
DV drive circuit
F shut-off device
G Gate terminal
L Choke coil
M fixing motor
N nip
NF noise filter
P Recording paper
PT voltage detector
SB bypass control signal
SH Heater heater control signal
SM Fixing motor control signal
SS Copy start signal
T conduction time
V detection voltage value
V _in Input voltage
Vs reference voltage

Claims (5)

Image forming comprising: a DC power source to which electric power is input from an AC power source; power factor improving means connected to the input side of the DC power source; and a load connected to the output side of the DC power source to generate an inrush current In the device
Bypass means connected in parallel to the power factor improving means,
Control means for conducting the bypass means for a predetermined time at the start of power supply to the load or at the start of operation of the load;
An image forming apparatus. A DC power source to which power is input from an AC power source, a power factor improving means connected to the input side of the DC power source, a load connected to the output side of the DC power source and generating an inrush current, and the power factor improving An image forming apparatus comprising: a heater connected to an input side of the means;
Bypass means connected in parallel to the power factor improving means,
A control means for conducting the bypass means for a predetermined time at the start of power supply to the load or the heater, or at the start of operation of the load or the heater;
An image forming apparatus. The image forming apparatus according to claim 1 or 2,
Voltage detecting means for detecting an input voltage of the DC power supply,
The control means makes the bypass means conductive when the input voltage detected from the input voltage detection means reaches a predetermined value or less;
An image forming apparatus. The image forming apparatus according to claim 1,
The control means comprises a time measuring means for measuring the conduction time of the bypass means;
An image forming apparatus. In the image forming apparatus according to any one of claims 1 to 4,
The load is a motor that drives a heating roller of the fixing device, and the heater is a heater of the fixing device;
An image forming apparatus.

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