JP2006058396A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which has a heating means to receive power supply from a primary side of a power supply device and in which the standby time is shortened by supplying sufficient electric power to the heating means while the fault due to voltage drop of commercial electric power is surely suppressed. <P>SOLUTION: The image forming apparatus is equipped with the power supply device to receive the commercial power from an AC power supply 90 on a primary side, to subject the power to prescribed conversion by a power conversion section 30 and to output the power to a secondary side and supplies the power from the primary side to a first and a second heaters 11 and 12 constituting a fixing device. A controller 40 detects the current supplied from the AC power supply 90 by a current rectifier 100, and controls the supply current to the first and the second heaters 11 and 12 by AC power regulation circuits 13 and 14 according to a difference ΔI between a maximum permissible current value and a current detection value by the current rectifier 100, and an increase or a decrease of the secondary side load in such a manner that the power can be supplied as much as possible within the range of the maximum permissible power that can be supplied from the AC power supply 90. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly to control of electric power supplied to a heating unit such as a heater of a fixing device in an electrophotographic image forming apparatus.

  For example, an electrophotographic image forming apparatus such as a copying machine includes a power supply device that performs predetermined conversion on commercial power input from the primary side using a transformer, a rectifier circuit, and the like, and outputs the result to the secondary side. The main body for image formation is mounted as a fixing device or an option for receiving the rectified DC power from the secondary side of the power supply device and for thermally fixing the toner image transferred to the paper. The sorter, the duplex unit, and the like receive power from the primary side of the power supply device.

  In order to start image formation in such an image forming apparatus, the temperature of the fixing device must be set to a predetermined value. For this reason, after the energization of the fixing device is started, a standby state is entered until the temperature reaches a predetermined value, and image formation cannot be performed during that time. In order to shorten the waiting time, it is necessary to increase the current (hereinafter referred to as “heater current”) or power supplied to the heater in the fixing device. However, when the heater current is increased, depending on the inrush current at the start of energization of the heater and the size of the load on the secondary side, the commercial power supplied to the image forming apparatus becomes excessive, and the voltage of the commercial power supply becomes high. This causes a problem such as flickering in the indoor lamp in which the image forming apparatus is installed.

  On the other hand, Patent Document 1 discloses an image forming apparatus that is configured by mounting options such as a duplex unit and a large-volume paper feeding unit, and includes a mounting state and an operating state of the options on a ROM on a control board. An image forming apparatus is disclosed that is stored in a table, measures the temperature of each part of the system, and manages the power load capacity based on the temperature.

Patent Document 2 proposes a heating device characterized by having means for controlling the maximum power that can be supplied by measuring the commercial power line voltage and current input to the device. The above-mentioned heating device is provided as a fixing means for thermally fixing a received image to a recording material, and the maximum supplyable power including the main body power supply of the image forming apparatus is set, and the maximum supplied power is changed according to the operation of the image forming apparatus main body There has been proposed an image forming apparatus characterized in that it has means for automatically controlling.
JP-A-6-242644 Japanese Patent Laid-Open No. 10-301442

  However, in the image forming apparatus disclosed in Patent Document 1, the power load capacity is not managed in real time, but is managed based on the ROM table and managed with safety (margin) in mind. Commercial power cannot be fully utilized up to the maximum allowable power that does not cause problems such as flicker.

  Further, the heating device and the image forming apparatus disclosed in Patent Document 2 do not directly detect the current supplied to the heating device or the image forming apparatus from the commercial power supply line that is a commercial power supply line. It is configured to detect a current that flows after rectifying and smoothing the alternating current of the power line. In such a current detection method, the current supplied to the image forming apparatus from the primary side of the commercial power supply line of the power supply apparatus does not have a one-to-one relationship between the waveform and instantaneous value of the current supplied to the fixing apparatus after smoothing. Further, the current corresponding to all the input amount of commercial power to the image forming apparatus is not detected. Further, in such an image forming apparatus, when the load fluctuation on the secondary side is not directly reflected in the control of the supplied power, the influence of the load fluctuation on the secondary side appears in the measurement result of the commercial power line voltage and current. This is reflected in the control of the supplied power. For this reason, when the load fluctuation on the secondary side occurs, the responsiveness of power control becomes a problem due to the presence of a delay element such as a smoothing capacitor. Due to this responsiveness problem, the commercial power cannot be fully utilized up to the maximum allowable power while reliably preventing problems due to the voltage drop of the commercial power.

  In addition, although the power consumption or current consumption of the heating member such as a heater used in the fixing device is managed by the component specification, the allowable range is set for the specification of the heating member in consideration of the productivity of the image forming apparatus. In addition, with regard to the commercial power supply, an allowable value is set for the commercial power supply voltage fluctuation. Here, the conventional image forming apparatus is designed so that the worst value of the combination of both is less than the allowable value of the commercial power supply capacity in consideration of the allowable specification range of the heating member and the allowable range of fluctuation of the commercial power supply voltage. In other words, it was driven in a state where there was a margin in commercial power capacity under conditions other than the combination that would be the worst value.

  Therefore, the present invention is an image forming apparatus having a heating unit that receives power supply from the primary side of a power supply device, reliably suppressing problems caused by a drop in the voltage of commercial power, and component variations of the heating member and commercial power supply voltage. An object of the present invention is to provide an image forming apparatus capable of absorbing fluctuations and utilizing the power supply capacity to the upper limit, supplying sufficient power to the heating means, and shortening the standby time.

The first invention includes a power supply device that performs predetermined conversion on commercial power input from the primary side and outputs the converted power to the secondary side, and a heating unit that receives supply of power from the primary side of the power supply device 1 An image forming apparatus comprising: a secondary side load unit; and a secondary side load unit that receives power supply from a secondary side of the power supply device,
The power supply device
Detecting means for detecting a current value indicating an input amount of the commercial power to the image forming apparatus;
The electric power supplied to the heating unit is controlled based on the difference between the allowable current value determined in advance as the current indicating the maximum allowable input amount of the commercial power and the current value detected by the detection unit. And a power control means.

According to a second invention, in the first invention,
When the load fluctuation occurs on the secondary side, the power control means controls the power supplied to the heating means according to the load fluctuation.

According to a third invention, in the second invention,
When the load increases on the secondary side, the power control unit suppresses an increase in power supplied to the heating unit for a predetermined time.

According to a fourth invention, in the second invention,
When the load increases on the secondary side, the power control unit controls the supply power so that the supply power to the heating unit decreases by an amount corresponding to the increase in the load, and the decrease in the supply power Thereafter, an increase or decrease in the power supplied to the heating means is suppressed for a predetermined time.

A fifth invention is the fourth invention,
The power control means includes
A first storage means for storing a table indicating a maximum value and a minimum value of a change amount of power consumption due to a state change between an operation state and a standby state for each component of the secondary load section;
When any one of the constituent elements of the secondary load section is changed from the standby state to the operating state, it is determined that the load increases on the secondary side, and the supply power decreases based on the table. The amount to be made is the maximum value of the amount of change in power consumption of the component to be brought into the operating state.

A sixth invention is the second invention, wherein:
When the load decreases on the secondary side, the power control unit controls the supply power so that the supply power to the heating unit increases by an amount corresponding to the decrease in the load, and increases the supply power. Thereafter, an increase or decrease in the power supplied to the heating means is suppressed for a predetermined time.

A seventh invention is the sixth invention, wherein
The power control means includes
A first storage means for storing a table indicating a maximum value and a minimum value of a change amount of power consumption due to a state change between an operation state and a standby state for each component of the secondary load section;
When any one of the constituent elements of the secondary load section is changed from the operating state to the standby state, it is determined that the load is reduced on the secondary side, and the supply power is increased based on the table. The amount to be made is a minimum value of the amount of change in power consumption of the component to be put in the standby state.

In an eighth aspect based on the first aspect,
The power control means stops control of power supplied to the heating means based on the difference for a predetermined time after energization of the heating means is started.

According to a ninth invention, in any one of the first to eighth inventions,
A fixing device including the heating unit;
An image is formed by electrophotography.

According to a tenth invention, in any one of the first to eighth inventions,
The heating means includes a plurality of heaters,
A switching element connected in series to each heater in order to adjust the power supplied to each heater by phase control,
The power control means includes
A table showing the relationship between the current of each heater and the firing angle of the switching element, and / or a table showing the relationship between the currents of two or more heaters constituting the plurality of heaters and the firing angle of the switching element. Second storage means for storing
The power supplied to the heating means is controlled by controlling the firing angle of the switching element based on a table indicating the relationship between the current of the heater energized among the plurality of heaters and the firing angle of the switching element. It is characterized by doing.

The eleventh aspect of the invention includes a power supply device that performs predetermined conversion on commercial power input from the primary side and outputs the commercial power to the secondary side, and heating means that receives supply of power from the primary side of the power supply device 1 In an image forming apparatus comprising a secondary load section and a secondary load section that receives power supply from the secondary side of the power supply apparatus, a method for controlling the power supplied to the heating means,
A detection step of detecting a current value indicating an input amount of the commercial power to the image forming apparatus;
Based on the difference between the allowable current value determined in advance as the current value indicating the maximum allowable input amount of the commercial power and the current value detected in the detection step, the power supplied to the heating means is And a power control step for controlling.

In a twelfth aspect based on the eleventh aspect,
In the power control step, when a load fluctuation occurs on the secondary side, the power supplied to the heating means is controlled according to the load fluctuation.

  According to the first invention as described above, the current value indicating the actual input amount of commercial power to the image forming apparatus is detected, and the detected allowable current value indicating the maximum value of the allowable input amount of commercial power is detected. Since the power supplied to the heating means is controlled based on the difference from the current value, even if there is a variation in the current flowing through the heating means or a load variation on the secondary side and its variation, the input amount of the commercial power As much power as possible can be supplied to the heating means within a range not exceeding the allowable value. Thereby, the temperature of heating object can be made to reach desired temperature in a short time, without generating the malfunction by the voltage drop of a commercial power source.

  According to the second invention as described above, when a load fluctuation occurs on the secondary side of the power supply device, the power supplied to the heating means is controlled in accordance with the load fluctuation. Therefore, even if it takes time for the load fluctuation on the secondary side to be reflected in the detected current value on the primary side, it is more possible to avoid overcurrent due to a delay in the response of the primary side current. Can be supplied to the heating means.

  According to the third invention as described above, when the load increases on the secondary side of the power supply device, the increase in power supplied to the heating means is suppressed for a predetermined time, so Even when there is a delay in the response of the primary side current detection value, the supply current from the commercial power supply does not exceed the allowable value, and the voltage of the commercial power supply is not reduced.

  According to the fourth invention as described above, when the load increases on the secondary side of the power supply device, the supply power is controlled so that the supply power to the heating means is reduced by an amount corresponding to the increase, Thereafter, the increase or decrease in the supplied power is suppressed for a predetermined time, so that even if there is a delay in the response of the primary side current detection value to the secondary side load fluctuation, the supply current from the commercial power supply is allowed. Exceeding the value can be reliably avoided.

  According to the fifth invention as described above, the increase amount of the secondary side load of the power supply device is determined in consideration of variation by referring to a predetermined table, and when the secondary side load increases, the increase is increased. Since the power supplied to the heating means is reduced by the maximum amount, the supply current from the commercial power supply can be easily and reliably avoided from exceeding the allowable value.

  According to the sixth invention as described above, when the load decreases on the secondary side of the power supply device, the supply power is controlled so that the supply power to the heating means increases by an amount corresponding to the decrease in the load. After that, since increase / decrease of the supplied power is suppressed for a predetermined time, even if there is a delay in the response of the primary side current detection value to the secondary side load fluctuation, the current supply from the commercial power supply The power supplied to the heating means can be increased while reliably avoiding an overcurrent.

  According to the seventh invention as described above, the amount of decrease in the secondary side load of the power supply apparatus is determined in consideration of variation by referring to a predetermined table, and when the secondary side load decreases, the decrease Since the supply power to the heating means is increased by the minimum amount, the supply power to the heating means can be increased while easily and reliably avoiding the supply current from the commercial power supply exceeding the allowable value. .

  According to the eighth invention as described above, the predetermined time after the energization of the heating means is started, the allowable current value indicating the maximum value of the allowable input amount of the commercial power and the detected value of the supply current from the commercial power source Since the control of the power supplied to the heating means based on the difference between the power supply and the heating means is stopped, the voltage drop of the commercial power supply due to the inrush current at the start of energization of the heating means is avoided or reduced, and thus connected to the commercial power supply. Flickering phenomenon that occurs in electric lamps is suppressed or alleviated.

  According to the ninth aspect as described above, since the power supplied to the heating unit of the fixing device is controlled in the electrophotographic image forming apparatus including the fixing device that consumes a large amount of power, the voltage of the commercial power supply is reduced. It is possible to effectively shorten the waiting time until the start of the fixing process without incurring the trouble.

  According to the tenth invention as described above, when the heating means includes a plurality of heaters, the relationship between the current of the heater energized among the plurality of heaters and the firing angle of the switching element for power adjustment is obtained. Since the firing angle of the switching element is controlled based on the table shown, it is possible to control the heating means by referring to an appropriate table according to the paper size to be subjected to the fixing process, whether or not warming up, etc. High-precision power control becomes possible.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
<1. Overall configuration and operation>
FIG. 1 is a cross-sectional view schematically showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus is an electrophotographic image forming apparatus such as a copying machine, and includes an image forming unit 1, a paper feeding unit 2, a fixing device 3, a document reading unit 4, a power supply / control device 5, and the like. A main body tray 6 and a sorter unit 7 are provided. In this image forming apparatus, the power source / control device 5 receives AC power (commercial power) from a commercial AC power source, appropriately converts power as necessary, and supplies the power to each unit. By performing the above operation, an image is formed on the sheet.

  The document reading unit 4 has a document placing table made of transparent glass or the like on the upper surface, and a scanner optical system that reads an image of the document on the document placing table. The image data obtained by reading the image of the document by the document reading unit 3 is subjected to predetermined image processing in the power source / control device 5 and then supplied to the image forming unit 1.

  The image forming unit 1 forms an electrostatic latent image corresponding to the image of the original by irradiating the surface of the photoconductor with a laser beam based on the image data. The visual image is developed, and the toner image formed on the surface of the photosensitive member by the development is transferred to the paper supplied from the paper feeding unit 2.

  The sheet on which the toner image is transferred by the image forming unit 1 is sent to the fixing device 3. The fixing device 3 includes a heating roller and a pressure roller disposed on a conveyance path for conveying a sheet on which the toner image is transferred from the image forming unit 1 to the main body tray 6 or the sorter unit 7. The heating roller has a built-in heating means such as a halogen heater, for example, and when performing the fixing process, the heating means is heated by being supplied with power from the power source / control device 5 and is kept at a predetermined temperature. The The fixing device 3 in the present embodiment includes two heaters 11 and 12 extending in the longitudinal direction of the heating roller, and as shown in FIG. 2, the first heater 11 has a predetermined paper size. The heating unit has a corresponding length L1 (for example, 220 mm), and the second heater 12 has two heating units respectively disposed at positions corresponding to both sides of the heating unit of the first heater 11. . Assuming that the length of one heating portion of the second heater 12 is L2 (for example, 55 mm), by energizing both the first and second heaters 11 and 12, for a sheet having a width of L1 + L2 + L2 (for example, 330 mm) A fixing process can be performed. Note that when the heat treatment is performed on a sheet having a relatively narrow width L1, only the first heater 11 needs to be energized.

  The sheet on which the toner image has been transferred is heated and pressed by passing through the fixing nip portion of the fixing roller 3 by the heating roller and the pressure roller, whereby the toner image is fixed on the sheet. The sheet on which the toner image is fixed in this manner is conveyed to the main body tray 6 or the sorter unit 7 through the conveyance path and discharged.

<2. Configuration from the viewpoint of power supply>
FIG. 3 is a functional block diagram illustrating the configuration of the image forming apparatus according to the present embodiment viewed from the viewpoint of power supply. This image forming apparatus receives AC power on the primary side from a commercial AC power supply (hereinafter abbreviated as “AC power supply”) 90 that is set to have a constant voltage (constant amplitude), and with respect to the power. For example, a power conversion unit 30 is provided that performs predetermined conversion using a transformer, a rectifier circuit, or the like, and outputs the converted power to the secondary side. A primary side load unit 10 including first and second heaters 11 and 12 and an optional load unit 15 such as a sorter unit 7 or a double-sided feeding unit is connected to the primary side of the power conversion unit 30, and the power conversion unit A secondary side load unit 20 including each drive circuit of the main body such as the image forming unit 1 and a control unit 40 which will be described later are connected to the secondary side of 30. The primary load unit 10 is supplied with the first AC power adjustment circuit 13 for adjusting the power supplied to the first heater 11 and the power supplied to the second heater 12 as components of the heating means. A second AC power adjustment circuit 14 for adjustment is also provided.

  In addition, the image forming apparatus is connected to the secondary side of the power conversion unit 30, and the driving circuit (secondary load unit) 20 of the main body unit such as the image forming unit 1, the first and second heaters 11, 12, a power conversion unit 30, a control unit 40 for controlling the sorter unit 7 and the like constituting the optional load unit 15 are provided. The control unit 40, together with the power conversion unit 30 and the current transformer 100 described later, constitutes the power source / control device 5 shown in FIG. 1, functions as a power control unit, and operates each drive circuit of the image forming apparatus. It also functions as a means for controlling.

  Further, the image forming apparatus includes a variable for measuring an AC current that is a current indicating the power input from the AC power supply 90 to the image forming apparatus (current supplied from the AC power supply 90 to the image forming apparatus). A flow device 100 is provided, and the control unit 40 controls the power supplied to the first and second heaters 11 and 12 based on the AC current detection value Iac obtained by the current transformer 100 (details will be described later). ).

<3. Circuit configuration example>
FIG. 4 is a circuit diagram showing an example of a specific circuit configuration of the image forming apparatus according to the present embodiment, and parts corresponding to the components shown in FIG. 3 are given the same reference numerals. Hereinafter, the circuit configuration example shown in FIG. 4 will be described.

  The 1st and 2nd alternating current power adjustment circuits 13 and 14 in the primary side load part 10 are implement | achieved using the triac. Moreover, the primary side load part 10 has the zero cross detection circuit 16 which detects the zero cross point of a primary side alternating current using the Zener diode 162, the light emitting diode 17, etc. FIG. The triacs of the first and second AC power adjusting circuits 13 and 14 are controlled to the first heater 11 and the second heater 12 by controlling the firing angle based on the zero cross point detected by the zero cross detection circuit 16. Adjust the power supply.

  The power conversion unit 30 is configured using a full-wave rectification circuit 31 including four diodes that rectifies AC power received from the AC power supply 90, a field effect transistor (hereinafter abbreviated as “FET”) 322, and a transformer 321. The switching regulator 32 is provided. A phototransistor 33 is connected to the gate terminal of the FET 322, and the phototransistor 33 is turned on / off by light from a light emitting diode 48 provided in the control unit 40, thereby switching oscillation (whether oscillation is performed). Whether to stop) is controlled.

  The control unit 40 includes a microcomputer 49 (hereinafter referred to as “microcomputer”) 49, a phototransistor 47 that receives light from the light emitting diode 17 in the zero-cross detection circuit 16, and the first and second AC power adjustment circuits 13 and 14. LED 41 and 42 for controlling the firing angle of the triac at the primary side, relay control unit 43 for controlling the supply / cutoff of power to the primary side load unit 10, and on / off of the phototransistor 33 in the switching regulator 32 A light emitting diode 48 is included. The light emitting diodes 41, 42, 48 and the relay control unit 43 are driven by the microcomputer 49, thereby controlling the power conversion unit 30 and controlling the heater current (power supplied to the first and second heaters 11, 12). Control) is performed.

<4. Configuration and operation for heater current control>
In the present embodiment, the microcomputer 49 executes a predetermined program stored in the built-in memory, thereby controlling the heater current, that is, controlling the power supplied to the first and second heaters 11 and 12. Specifically, the microcomputer 49 drives the light emitting diodes 41 and 42 to change the firing angles of the triacs in the first and second AC power adjustment circuits 13 and 14, whereby the first and second heaters 11 and 12 are changed. The current flowing through the heater (heater current) is controlled. In the following, the first and second AC power adjustment circuits 13 and 14 operate so that the firing angles of the triacs corresponding to the first and second heaters 11 and 12 are the same, and the current flowing through the first heater 11 In the following description, it is assumed that the heater current I1 + I2, which is the sum of I1 and the current I2 flowing through the second heater 12, is controlled by the firing angle. In the memory in the microcomputer 49, when the triac firing angle in the first and second AC power adjustment circuits 13 and 14 is changed to be the same (hereinafter referred to as “ignition angle φ”), the ignition is performed. A table indicating the relationship between the angle φ and the heater current I1 + I2 is stored in advance. More specifically, as shown in FIG. 6, as the relationship between the firing angle φ and the heater current I1 + I2, the maximum value and the minimum value of the heater current I1 + I2 corresponding to each firing angle φ are obtained. A table showing the relationship between the angle φ and the maximum value of the heater current I1 + I2 and the relationship between the ignition angle φ and the minimum value of the heater current I1 + I2, that is, a table as shown in FIG. 7 (hereinafter referred to as “ignition angle control table”). Is stored in advance in a memory in the microcomputer 49.

Further, a table (hereinafter referred to as “the change in the amount of increase / decrease in the secondary side load) generated when each drive circuit constituting the secondary side load of the power conversion unit 30 changes between the operation state and the standby state (hereinafter,“ variable ”). Secondary load table ") is stored in advance in a memory in the microcomputer 49. This secondary load table is a table as shown in FIG. 8, and when each drive circuit constituting the secondary load changes between an operating state and a standby state, a current supplied to each drive circuit ( (More generally, power consumption) shows how much it changes, and the maximum amount of this change (the amount of decrease when changing from the operating state to the standby state and the amount of increase when changing from the standby state to the operating state) Values and minimum values are shown for each drive circuit. Based on the secondary load table, the microcomputer 49 functioning as a control means for each drive circuit determines whether the secondary load is reduced depending on which drive circuit is operated or stopped at each time point. It can be done. In the table shown in FIG. 8, the maximum value of the current change amount corresponding to the change amount of the power consumption due to the state change between the operation state and the standby state for each drive circuit constituting the secondary load unit 20. The minimum value is directly shown, but instead of this, the maximum current corresponding to the power consumption in the operation state and in the standby state for each drive circuit constituting the secondary load unit 20 is shown. By indicating the value and the minimum value, it may be configured to indirectly indicate the maximum value and the minimum value of the current change amount corresponding to the change amount of the power consumption due to the state change between the operation state and the standby state. .
When creating the secondary load table, the maximum value and the minimum value are obtained in consideration of variations in parts of the drive circuit and the drive motor.

  In the present embodiment, the microcomputer 49 uses as much current as possible to the first and second heaters 11 and 12 within a range in which the AC current detection value Iac detected by the current transformer 100 does not exceed the predetermined allowable value ILim. Is operated according to the predetermined program in order to control the ignition angle φ based on the ignition angle control table. FIG. 5 is a flowchart showing the operation of the microcomputer at this time, that is, a flowchart showing a processing procedure for controlling the heater current. The operation of the microcomputer for controlling the heater current in this embodiment will be described below with reference to FIG.

  First, an ignition angle (hereinafter referred to as “drive ignition angle”) at which the heater current I1 + I2 becomes a preset value (hereinafter referred to as “heater current set value”) Ih is set in the ignition angle control table (FIG. 7). The first and second heaters 11, 12 are determined based on the triac firing angle φ in the first and second AC power adjustment circuits 13, 14 so that the triac firing angle φ becomes the driving firing angle. Is energized (step S10). At this time, considering the actual heater current variation, the firing angle at which the maximum value of the heater current I1 + I2 becomes the heater current set value Ih is defined as the drive firing angle. For example, when the heater current set value Ih is 10 [A], the drive firing angle is set to 137 [deg] with reference to the firing angle control table of FIG. 7 (see FIG. 6). The firing angle control table stores a plurality of firing angles φ at a predetermined interval, and a maximum value and a minimum value of the heater current I1 + I2 corresponding to each of the plurality of firing angles φ. The firing angle corresponding to an intermediate value stored in the firing angle control table is calculated by interpolation.

  After energization of the first and second heaters 11 and 12 is started, the apparatus waits for a predetermined time (for example, 200 msec) (step S12), and during this time, an increase in supply power (heater current) to the first and second heaters ( And decrease) are suppressed. This is to prevent flicker from occurring in the lamp connected to the AC power source due to the voltage drop of the AC power source 90 due to the inrush current to the first and second heaters 11 and 12.

  Next, the detection value of the AC current detected by the current transformer 100 is acquired as the AC current detection value Iac (step S14), and the allowable value ILim set in advance as the maximum allowable AC current is acquired. The difference ILim−Iac from the detected AC current value Iac is calculated as a current margin ΔI (step S16). Then, it is determined whether or not the current margin ΔI is positive (step S18). Since the voltage of the AC power supply 90 can be assumed to be constant, the allowable value ILim indicates the maximum allowable input amount of commercial power from the AC power supply 90 to the image forming apparatus, and the AC current detection value Iac is 3 shows the actual input amount of commercial power from the AC power supply 90 to the image forming apparatus.

  As a result of the determination in step S18, if the current margin is not positive, the AC current detection value Iac is equal to or larger than the allowable value ILim. Therefore, the current margin ΔI is subtracted from the heater current set value Ih, and the subtraction result Ih− ΔI is set as a new heater current setting value Ih (step S24). Then, with reference to the ignition angle control table, the ignition angle φ is determined such that the maximum value of the heater current I1 + I2 becomes the new heater current setting value Ih. 2 The triac in the AC power adjusting circuits 13 and 14 is driven (step S25). Thus, after changing the ignition angle φ according to the update of the heater current set value Ih, the process returns to step S14.

  As a result of the determination in step S18, if ΔI is positive, the process proceeds to step S20, and it is determined whether or not the secondary load of the power conversion unit 30 is reduced. Specifically, when the microcomputer 49 functioning as the control means of each drive circuit sets the operation circuit among the drive circuits constituting the secondary load to the standby state, it is determined that the secondary load decreases. .

  As a result of the determination in step S20, when the secondary side load decreases, the process proceeds to step S26, and the primary side converted value Id corresponding to the decrease in the secondary side load is calculated. Specifically, referring to the secondary load table in FIG. 8, the minimum amount of change (in this case, the amount of decrease) due to the state change of the current supplied from the operating state to the drive circuit to be set to the standby state A value is obtained, and a primary side converted value Id of this minimum value is calculated. Then, the current margin ΔI and the primary side converted value Id are added to the heater current set value Ih, and the addition result Ih + ΔI + Id is set as a new heater current set value Ih (step S28). Here, the primary side converted value Id added to obtain a new heater current set value Ih is the primary side converted value of the minimum value of the current change amount (decrease amount) of the drive circuit to be set in the standby state. This is because the variation of the driving current is taken into consideration. Next, with reference to the ignition angle control table of FIG. 7, the ignition angle φ is determined such that the maximum value of the heater current I1 + I2 becomes a new heater current setting value Ih. The triac in the first and second AC power adjustment circuits 13 and 14 is driven (step S29). After changing the ignition angle φ in accordance with the update of the heater current set value Ih in this way, the apparatus waits for a predetermined time (for example, 1 second) necessary for the AC current to respond to the decrease in the secondary load. (Step S30). During this standby, increase / decrease in heater current (increase / decrease in power supplied to the first and second heaters 11 and 12) is suppressed, and then the process returns to step S14.

  As a result of the determination in step S20, if the secondary load does not decrease, the process proceeds to step S22 to determine whether or not the secondary load increases. Specifically, when the microcomputer 49 functioning as a control unit for each drive circuit sets a standby state among drive circuits constituting the secondary load to an operating state (when activated), the secondary load Is determined to increase.

  When the secondary load increases as a result of the determination in step S22, the process proceeds to step S32, and the primary side converted value Iu corresponding to the increase in the secondary load is calculated. Specifically, referring to the secondary load table in FIG. 8, the maximum amount of change (in this case, the increase amount) due to the state change of the current supplied to the drive circuit to be brought into the operating state from the standby state A value is acquired, and a primary side converted value Iu of this maximum value is calculated. Then, the current margin ΔI is added to the heater current set value Ih and the primary side converted value Iu is subtracted, and the addition / subtraction result Ih + ΔI−Iu is set as a new heater current set value Ih (step S34). Here, the primary side converted value Iu subtracted to obtain a new heater current set value Ih is the primary side converted value of the maximum value of the current change amount (increase amount) of the drive circuit to be brought into the operating state. This is because the variation of the driving current is taken into consideration. Next, with reference to the ignition angle control table of FIG. 7, the ignition angle φ is determined such that the maximum value of the heater current I1 + I2 becomes a new heater current setting value Ih. The triac in the first and second AC power adjustment circuits 13 and 14 is driven (step S35). After changing the ignition angle φ in accordance with the update of the heater current set value Ih in this way, the apparatus waits for a predetermined time (for example, 1 second) necessary for the AC current to respond to the increase in the secondary load. (Step S36). During this standby, the increase / decrease in the heater current is suppressed, and then the process returns to step S14.

  As a result of the determination in step S22, when the secondary side load does not increase, there is no change in the secondary side load. In this case, the process proceeds to step S38, the current margin ΔI is added to the heater current set value Ih, and the addition result Ih + ΔI is set as a new heater current set value Ih. Then, with reference to the ignition angle control table, an ignition angle φ is determined such that the maximum value of the heater current I1 + I2 becomes a new heater current setting value Ih, and the first and second alternating currents are determined based on the ignition angle φ. The triac in the power adjustment circuits 13 and 14 is driven (step S39). Thus, after changing the ignition angle φ according to the update of the heater current set value Ih, the process returns to step S14.

  After returning to step S14, the above processing (steps S14 to S39) is repeatedly executed while the first and second heaters 11 and 12 are energized.

  In the above processing, when the secondary load is increased as a result of the determination in step S22, the heater current set value Ih is updated by executing steps S32 to S35, and the ignition is performed according to the update. The angle φ is changed, but instead, the process proceeds directly from step S22 to step S36 as shown by the dotted line in FIG. 5 to update the heater current set value Ih and change the ignition angle φ. You may make it wait for predetermined time (for example, 1 second) required for AC current to respond to the said increase of a secondary side load, without performing.

<5. Effect>
According to the embodiment, the current supplied from the AC power supply 90 to the image forming apparatus is detected in real time as the AC current detection value Iac (step S14 in FIG. 5), and the AC current detection value Iac and the commercial power are allowed. The heater current I1 + I2 is adjusted by controlling the firing angle φ according to the current margin ΔI = Lim−Iac, which is the difference from the AC current allowable value ILim corresponding to the maximum input amount. At this time, the first and second AC power adjustment circuits 13 and 14 operate at the firing angle φ such that the maximum value of the heater current I1 + I2 becomes the heater current set value Ih updated according to the current margin ΔI. . In this way, the power supplied to the first and second heaters 11 and 12 is adjusted according to the current margin ΔI based on the AC current detection value Iac detected in real time. The first and second heaters 11 and 11 receive as much power as possible within a range that does not exceed the allowable value of the input amount of commercial power from the AC power supply 90 to the image forming apparatus even if there are load fluctuations and variations on the side. 12 can be supplied. Thus, without causing a problem due to a voltage drop of the commercial power supply, a waiting time from the start of energization to the first and second heaters 11 and 12 to the start of the fixing process, that is, until the fixing roller reaches a predetermined temperature. The waiting time can be shortened.

  Further, according to the above embodiment, whether or not the secondary load is increased or decreased and the amount of increase or decrease are determined based on the reference to the secondary load table (FIG. 8) by the microcomputer 49 (steps S20 and S22 in FIG. 5). ) When the secondary load is increased or decreased, the ignition angle φ is controlled without waiting for the increase or decrease to be reflected on the primary side (reflection to the AC current detection value Iac) (steps S28 and S29). , S34, S35), the supply current (supply power) to the first and second heaters 11 and 12 can be adjusted with good responsiveness. Therefore, the first and second heaters 11 and 12 can be controlled according to the increase or decrease of the secondary load while avoiding an overcurrent due to a delay in the response to the AC current on the primary side of the fluctuation of the secondary load. Large power can be supplied. In addition, when the secondary load decreases, the added amount Id (see step S28) of the heater current set value Ih corresponding to the decrease is changed from the drive circuit that causes the decrease of the secondary load, that is, from the operating state to the standby state. This corresponds to the minimum value of the current change amount (decrease amount) of the drive circuit to be performed. In addition, when the secondary load increases, the subtraction amount Iu (see step S34) of the heater current set value Ih corresponding to the increase is determined from the driving circuit that causes the increase of the secondary load, that is, from the standby state to the operating state. This corresponds to the maximum current change amount (increase amount) of the drive circuit to be performed. Therefore, in consideration of the variation in the drive current corresponding to the increase / decrease in the secondary load, as much power as possible to the first and second heaters 11 and 12 within the allowable input power (AC current allowable value) range. (Heater current) can be supplied. As a result, it is possible to reduce the waiting time from the start of energization to the first and second heaters 11 and 12 to the start of the fixing process while reliably preventing problems due to the voltage drop of the AC power supply 90.

  Furthermore, according to the embodiment, after the start of energization of the first and second heaters 11 and 12 (step S10), the first and second heaters are changed according to the increase / decrease in the AC current detection value Iac and the secondary load. 11 and 12 is waited for a predetermined time before the control process for adjusting the supply power (heater current), that is, the process of steps S14 to S39 in FIG. 5 (hereinafter referred to as “heater current control process”) is started. (Step S12). As a result, the heater current control process for increasing the heater current as much as possible within the allowable range is started after the heater current is stabilized. Therefore, AC due to the inrush current at the start of energization of the first and second heaters 11 and 12 is started. A voltage drop of the power supply 90 is avoided or reduced, and as a result, a flicker phenomenon that occurs in a lamp or the like connected to the AC power supply is suppressed or alleviated.

<6. Modification>
In the above embodiment, in steps S24, S28, S34, and S38 of the heater current control process (FIG. 5), the current margin ΔI = Lim−Iac, which is the difference between the AC current detection value Iac and the AC current maximum allowable value ILim. Based on the heater current set value Ih, the current margin ΔI is added to or subtracted from the heater current set value Ih before the update. However, the current margin ΔI is an amount to be increased or decreased with respect to the AC current detection value Iac, and the amount to be increased or decreased with respect to the heater current set value Ih before the update is considered as ΔI × (Ih / Iac). Can do. Therefore, ΔI may be changed to ΔI × (Ih / Iac) in the equation indicating the updated heater current set value Ih calculated in steps S24, S28, S34, and S38.

  In the above embodiment, when the fixing device 3 is operated, both the first and second heaters 11 and 12 are energized at the same time. However, when the width of the sheet to be subjected to the fixing process is narrow (when the width is equal to or less than L1). ), As already described with reference to FIG. 2, only the first heater 11 needs to be energized. In this case, the microcomputer 49 has an ignition angle control table showing the relationship between the ignition angle φ and the maximum value and the minimum value of the heater current I1 flowing in the first heater 11 in its built-in memory as shown in FIG. A table as shown is also stored. Then, by referring to this firing angle control table, the heater current I1 is controlled according to the current margin ΔI and the increase or decrease of the secondary load, and the first heater 11 is handled according to the flowchart shown in FIG. The firing angle φ of the triac in the first AC power adjustment circuit 13 is controlled.

  By the way, in the case of such a configuration, the actual contents of the control process represented by the flowchart of FIG. 5 and the firing angle control table referred to in the process include an operation mode in which only the first heater 11 is energized, and the above-described implementation. The mode is switched between the operation modes in which both the first and second heaters 11 and 12 are energized as in the embodiment, and this switching is performed depending on the paper size to be subjected to the fixing process, whether the warm-up is performed, or the like. . Normally, only the second heater 12 is not energized. However, when it is necessary to energize only the second heater 12, the microcomputer 49 also includes an ignition angle control table as shown in FIG. By storing in the internal memory, only the second heater 12 can be energized to control the heater current I2. In general, when the fixing device 3 includes a plurality of heaters, a firing angle control table for each heater and / or a firing angle control table for a combination of heaters that can be used is prepared (for example, a microcomputer). The heater current can be accurately controlled by referring to the firing angle control table for the heater that is actually energized among the plurality of heaters or a combination thereof.

  In the above embodiment, the presence or absence and the increase / decrease amount of the secondary load of the power conversion unit 30 are determined based on the secondary load table as shown in FIG. At the same time, a measuring means such as a current transformer for detecting the secondary side load current is provided, and in the heater current control process (FIG. 5), the detected value of the secondary side load current by the measuring means is used. The primary side converted value Id corresponding to the decrease in the secondary load and the primary side converted value Iu corresponding to the increase in the secondary load may be determined (see steps S26 and S32).

  In the above embodiment, the electrophotographic image forming apparatus has been described as an example, but the present invention is not limited to this. That is, if the image forming apparatus includes a power supply device that performs predetermined conversion on commercial power input from the primary side and outputs the commercial power to the secondary side, and includes a heating unit that receives power supply from the primary side, The present invention can also be applied to an image forming apparatus using a method other than the electrophotographic method. For example, the present invention can be applied to an image forming apparatus having a heating unit using a magnetic induction heating method or a heating unit using a heating resistor. However, since the electrophotographic image forming apparatus includes a fixing device that consumes a large amount of power, the present invention is particularly effective in such an image forming apparatus.

1 is a cross-sectional view schematically showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 4 is a diagram for explaining a configuration of a heater in the fixing device in the image forming apparatus according to the embodiment. FIG. 3 is a functional block diagram illustrating a configuration viewed from a viewpoint of power supply of the image forming apparatus according to the embodiment. FIG. 3 is a circuit diagram illustrating an example of a specific circuit configuration in the image forming apparatus according to the embodiment. It is a flowchart which shows the process sequence for control of the heater current in the said embodiment. It is a figure which shows the relationship between the ignition angle and heater electric current (sum of the electric current which flows into a 1st and 2nd heater) in the said embodiment. It is a figure showing the table which shows the relationship between the ignition angle and heater electric current (sum of the electric current which flows into a 1st and 2nd heater) in the said embodiment. It is a figure which shows the table which stores the maximum value and minimum value of the amount of current change when each drive circuit which comprises the secondary side load in the said embodiment changes between an operation state and a standby state. FIG. 5A is a diagram showing a table showing the relationship between the ignition angle and the current of the first heater, and FIG. 5B is a diagram showing a table showing the relationship between the ignition angle and the current of the second heater. is there.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image formation part 2 ... Paper feed part 3 ... Fixing device 4 ... Document reading part 5 ... Power supply / control apparatus 6 ... Main body tray 7 ... Sorter part 10 ... Primary side load part 11 ... 1st heater 12 ... 2nd heater DESCRIPTION OF SYMBOLS 13 ... 1st alternating current power adjustment circuit 14 ... 2nd alternating current power adjustment circuit 16 ... Zero cross detection circuit 20 ... Secondary side load part (each drive circuit of a main body)
DESCRIPTION OF SYMBOLS 30 ... Power conversion part 32 ... Switching regulator 40 ... Control part 41,42 ... Light emitting diode 49 ... Microcomputer (power control means)
90 ... Commercial AC power supply (AC power supply)
100 ... Current transformer I1 ... Current of the first heater I2 ... Current of the second heater Iac ... AC current detection value

Claims (12)

A power supply device that performs predetermined conversion on commercial power input from the primary side and outputs the commercial power to the secondary side, and a primary load section that includes heating means that receives supply of power from the primary side of the power supply device; An image forming apparatus including a secondary load unit that receives power from the secondary side of the power supply device,
The power supply device
Detecting means for detecting a current value indicating an input amount of the commercial power to the image forming apparatus;
The power supplied to the heating means is controlled based on the difference between the allowable current value determined in advance as the current value indicating the maximum allowable input amount of the commercial power and the current value detected by the detecting means. An image forming apparatus comprising: a power control unit configured to perform power control.   2. The image forming apparatus according to claim 1, wherein the power control unit controls power supplied to the heating unit according to the load variation when a load variation occurs on the secondary side.   The image forming apparatus according to claim 2, wherein the power control unit suppresses an increase in power supplied to the heating unit for a predetermined time when a load increases on the secondary side.   When the load increases on the secondary side, the power control unit controls the supply power so that the supply power to the heating unit decreases by an amount corresponding to the increase in the load, and the decrease in the supply power 3. The image forming apparatus according to claim 2, wherein after that, increase / decrease in power supplied to the heating means is suppressed for a predetermined time. The power control means includes
A first storage means for storing a table indicating a maximum value and a minimum value of a change amount of power consumption due to a state change between an operation state and a standby state for each component of the secondary load section;
When any one of the constituent elements of the secondary load section is changed from the standby state to the operating state, it is determined that the load increases on the secondary side, and the supply power decreases based on the table. The image forming apparatus according to claim 4, wherein the amount to be set is a maximum value of a change amount of power consumption of a component to be in the operation state.   When the load decreases on the secondary side, the power control unit controls the supply power so that the supply power to the heating unit increases by an amount corresponding to the decrease in the load, and increases the supply power. 3. The image forming apparatus according to claim 2, wherein after that, increase / decrease in power supplied to the heating means is suppressed for a predetermined time. The power control means includes
A first storage means for storing a table indicating a maximum value and a minimum value of a change amount of power consumption due to a state change between an operation state and a standby state for each component of the secondary load section;
When any one of the constituent elements of the secondary load section is changed from the operating state to the standby state, it is determined that the load is reduced on the secondary side, and the supply power is increased based on the table. The image forming apparatus according to claim 6, wherein the amount to be set is a minimum value of a change amount of power consumption of a component to be set in the standby state.   2. The image according to claim 1, wherein the power control unit stops control of power supplied to the heating unit based on the difference for a predetermined time after energization of the heating unit is started. Forming equipment. A fixing device including the heating unit;
The image forming apparatus according to claim 1, wherein an image is formed by an electrophotographic method. The heating means includes a plurality of heaters,
A switching element connected in series to each heater in order to adjust the power supplied to each heater by phase control,
The power control means includes
A table showing the relationship between the current of each heater and the firing angle of the switching element, and / or a table showing the relationship between the currents of two or more heaters constituting the plurality of heaters and the firing angle of the switching element. And second storage means for storing
The power supplied to the heating means is controlled by controlling the firing angle of the switching element based on a table indicating the relationship between the current of the heater energized among the plurality of heaters and the firing angle of the switching element. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. A power supply device that performs predetermined conversion on commercial power input from the primary side and outputs the commercial power to the secondary side, and a primary load section that includes heating means that receives supply of power from the primary side of the power supply device; In an image forming apparatus comprising a secondary side load unit that receives supply of power from the secondary side of the power supply device, a method for controlling the power supplied to the heating means,
A detection step of detecting a current value indicating an input amount of the commercial power to the image forming apparatus;
Based on the difference between the allowable current value determined in advance as the current value indicating the maximum allowable input amount of the commercial power and the current value detected in the detection step, the power supplied to the heating means is And a power control step for controlling. The method according to claim 11, wherein, in the power control step, when a load fluctuation occurs on the secondary side, the power supplied to the heating unit is controlled according to the load fluctuation.

Images