JP4828349B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to a technique for controlling power supply to a fixing unit that fixes toner onto a recording sheet by heat.

In an image forming apparatus such as a copying machine, in order to shorten the time required for the fixing roller to reach the fixing possible temperature at the start-up time or in the energy saving mode in which the power supply to the fixing heater is stopped and ready for printing. In addition, there is an image forming apparatus that heats the fixing roller by supplying a large current to the fixing heater using both a commercial power source and an auxiliary power source (for example, an electric double layer capacitor). Since the voltage of a single electric double layer capacitor used as an auxiliary power source in this image forming apparatus is low (normally 2.5 V), the voltage of the electric double layer capacitor is supplied to the fixing heater by a booster circuit as shown in Patent Document 1 below. There has been proposed a method in which the electric power of the electric double layer capacitor is supplied to the fixing heater after being boosted to a voltage suitable for the supply of the fixing heater.
JP 2003-297526 A

  Generally, halogen heaters used as fixing heaters have a low resistance in a room temperature state before heating, and when a voltage at the start of heating is applied, an inrush current that is several to several tens of times the rated current flows. In the boost circuit, the coil is saturated due to the inrush current, and does not function normally. Therefore, the electric double layer capacitor and the boost circuit supply power when the inrush current flows when the fixing roller starts heating. Not to be controlled. However, if the control waits for the inrush current to settle and avoids the inrush current in this way, the rise time required until the fixing heater can perform the necessary heating is extended, and the fixing roller can be fixed. There is a problem that the time for reaching the temperature becomes long. Also, a configuration has been proposed in which an inrush current prevention circuit for avoiding the inrush current is provided between the booster circuit and the fixing heater and the booster circuit is driven while suppressing the current. In this case, the inrush current prevention circuit is provided. Is essential.

  The present invention has been made in view of the above-described problems. Even during a period in which an inrush current flows, the auxiliary power supply is changed from the auxiliary power source to the second fixing heater while avoiding the adverse effects caused by the inrush current in the booster circuit with an inexpensive configuration. An object of the present invention is to reduce the time required for supplying electric power and causing the fixing roller to reach a fixing possible temperature.

The invention according to claim 1 is an auxiliary power source comprising a capacitor;
A first fixing heater that is driven by electric power from an external power source and a second fixing heater that is composed of a halogen heater and is driven by electric power from the auxiliary power source, and heats a fixing unit that fixes toner onto recording paper A fixing heater,
A primary side is connected to the auxiliary power source, and one end on the secondary side is connected to the second fixing heater, and the other end on the secondary side is connected to the auxiliary power source by an isolated converter from the auxiliary power source. A boosting circuit that boosts the output voltage of the second fixing heater and outputs the boosted output voltage to the second fixing heater;
Bypass switching means for switching whether the booster circuit bypasses the output from the auxiliary power supply when power from the auxiliary power supply is supplied to the second fixing heater;
Control means for controlling power supply to the fixing heater,
The second fixing heater has one end connected to the secondary side of the booster circuit and the other end connected to the auxiliary power source.
The control means drives the first fixing heater with the output from the external power supply at the initial driving stage of the fixing heater, and outputs the auxiliary power supply with the bypass switching means bypassing the booster circuit. And the second fixing heater is driven, and after the elapse of a period when an inrush current flows through the second fixing heater, the bypass switching means is not allowed to bypass the booster circuit, and the output of the booster circuit is output from the auxiliary power supply. The image forming apparatus is supplied to the second fixing heater in a superimposed manner.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the bypass switching unit has a position on the secondary side of the booster circuit and a position in front of the connection portion with the fixing heater. The output of the auxiliary power supply can be supplied to the second fixing heater by bypassing the booster circuit by being short-circuited to a position before the connection portion with the auxiliary power supply. Is.

  A third aspect of the present invention is the image forming apparatus according to the first or second aspect, wherein the insulating converter is an insulating transformer.

  In these configurations, the control means drives the first fixing heater with the output from the external power source at the initial stage of driving of the fixing heater, and bypasses the booster circuit with the bypass switching means, and outputs with the output from the auxiliary power supply. The second fixing heater is driven. As a result, even during the period in which the inrush current flows, power can be supplied from the auxiliary power source to the second fixing heater without causing an adverse effect due to the inrush current in the booster circuit, so that the fixing roller reaches the fixable temperature. The time required for this can be shortened.

The invention according to claim 4 is the image forming apparatus according to any one of claims 1 to 3, further comprising a timer for measuring time,
The control means switches the bypass switching means and switches the output of the booster circuit to the auxiliary circuit when an elapse of a predetermined time that the inrush current has reached has been measured by the timer. It is superimposed on the output of the power source and supplied to the second fixing heater.

  In this configuration, since it is assumed that the inrush current has been reduced when the predetermined time is measured by the timer, the control means can determine the period during which the inrush current flows in the booster circuit by a simple process.

A fifth aspect of the present invention is the image forming apparatus according to any one of the first to third aspects, further comprising a current detection unit that detects a value of a current flowing through the second fixing heater,
The control means switches the bypass switching means and superimposes the output of the booster circuit on the output of the auxiliary power supply when the current detection means detects a value indicating a state where the inrush current is reduced. The second fixing heater is supplied.

  According to this configuration, since the control means detects that the value indicating the state where the inrush current is reduced is detected by the current detection means, the inrush current is reduced, so the period during which the inrush current flows in the booster circuit. Can be determined with high accuracy.

A sixth aspect of the present invention is the image forming apparatus according to any one of the first to third aspects, further comprising temperature detecting means for detecting a temperature of the second fixing heater,
The control means switches the bypass switching means to superimpose the output of the booster circuit on the output of the auxiliary power supply when a temperature indicating a state where the inrush current is reduced is detected by the temperature detection means. The second fixing heater is supplied.

  According to this configuration, since the control means detects that the temperature indicating the state where the inrush current has been reduced by the temperature detection means and has reached the state where the inrush current has decreased, the period during which the inrush current flows through the booster circuit Can be determined by a simple process.

  According to the first to third aspects of the present invention, electric power is supplied from the auxiliary power source to the second fixing heater without causing an adverse effect due to the inrush current in the booster circuit even during the period when the inrush current flows. In addition, the time required for the fixing roller to reach the fixing possible temperature can be shortened. Further, it is not necessary to provide an expensive inrush current prevention circuit unlike the prior art, and an inexpensive configuration is sufficient.

  According to the fourth and sixth aspects of the invention, the period during which the inrush current flows through the booster circuit can be determined by a simple process.

  According to the fifth aspect of the present invention, the period during which the inrush current flows in the booster circuit can be determined with high accuracy.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a side view schematically showing an internal configuration of a multifunction peripheral as an example of an image forming apparatus according to an embodiment of the present disclosure. The multifunction device 1 has functions such as a copy function, a printer function, a scanner function, and a facsimile function. The multi-function device 1 includes a main body 2, a stack tray 3 disposed on the left side of the main body 2, a document reading unit 5 disposed on the top of the main body 2, and an upper side of the document reading unit 5. And a document feeding unit 6 disposed.

  An operation unit 47 is provided at the front part of the multifunction machine 1. The operation unit 47 displays a start key 471 for a user to input a print execution instruction, a ten key 472 for inputting the number of copies to be printed, operation guide information for various copying operations, and the like. A display unit 473 formed of a liquid crystal display or the like having a touch panel function, a reset key 474 for resetting setting contents set in the display unit 473, and a stop key for stopping a printing (image forming) operation being executed 475 and a function switching key 477 for switching between a copy function, a printer function, a scanner function, and a facsimile function.

  The document reading unit 5 includes a scanner unit 51 including a CCD (Charge Coupled Device) sensor and an exposure lamp, and a document table 52 and a document reading slit 53 made of a transparent member such as glass. The scanner unit 51 is configured to be movable by a drive unit (not shown). When reading a document placed on the document table 52, the scanner unit 51 is moved along the document surface at a position facing the document table 52, and the document image is scanned. The image data acquired while scanning is output to the control unit 10 (FIG. 2). Further, when reading a document fed by the document feeding unit 6, the document is moved to a position facing the document reading slit 53 and synchronized with the document feeding operation by the document feeding unit 6 via the document reading slit 53. The image of the original is acquired and the image data is output to the control unit 10.

  The document feeding unit 6 includes a document placing unit 61 for placing a document, a document discharge unit 62 for discharging a document whose image has been read, and a document placed on the document placing unit 61. A document transport mechanism 63 including a paper feed roller (not shown), a transport roller (not shown) and the like for feeding the paper one by one to a position facing the document reading slit 53 and discharging it to the document discharge section 62 is provided. The document conveyance mechanism 63 further includes a sheet reversing mechanism (not shown) that reverses the document and reversely conveys the document to a position facing the document reading slit 53, and scans both sides of the document through the document reading slit 53. 51 can be read.

  The document feeding unit 6 is provided so as to be rotatable with respect to the main body unit 2 so that the front side thereof can move upward. By moving the front side of the document feeder 6 upward to open the upper surface of the document table 52, the operator can place a read document, for example, a book in a spread state, on the upper surface of the document table 52. It has become.

  The main body 2 includes a plurality of paper feed cassettes 461, a paper feed roller 462 that feeds the recording paper from the paper feed cassette 461 one by one and transports it to the recording unit 40, and a recording paper transported from the paper feed cassette 461. And a recording unit 40 for forming an image.

  The recording unit 40 outputs an optical beam or the like based on the image data acquired by the scanner unit 51 to expose the photosensitive drum 43, and a developing unit 44 that forms a toner image on the photosensitive drum 43. A transfer unit 41 that transfers the toner image on the photosensitive drum 43 to the recording paper; a fixing device 7 that heats the recording paper to which the toner image is transferred and fixes the toner image on the recording paper; Conveying rollers 463 and 464 that are provided in the sheet conveying path and convey the recording sheet to the stack tray 3 or the discharge tray 48 are provided.

  When forming images on both sides of the recording paper, the recording unit 40 forms an image on one side of the recording paper, and then the recording paper is nipped by the conveyance roller 463 on the discharge tray 48 side. . In this state, the conveyance roller 463 is reversed to switch back the recording paper, and the recording paper is sent to the paper conveyance path 49 to be conveyed again to the upstream area of the recording unit 40, and an image is formed on the other surface by the recording unit 40. Thereafter, the recording paper is discharged to the stack tray 3 or the discharge tray 48.

  FIG. 2 is a schematic diagram showing the fixing device 7 provided in the multifunction machine 1 and the surrounding internal configuration. The fixing device 7 includes a first power switch 71, an auxiliary power unit 72, a fixing roller 73, an auxiliary power switch 74, and a charging switch 75.

  The fixing roller 73 includes a pressure roller that applies pressure to the recording paper, and a heat roller that applies heat to the recording paper. The toner image on the recording paper is formed by sandwiching the recording paper between the two rollers in a press-contact state. Fix on recording paper. A fixing heater 730 for heating is provided in the heat roller of the fixing roller 73. FIG. 2 particularly shows the fixing heater 730 portion. The fixing heater 730 includes a first fixing heater 731 and a second fixing heater 732. The first fixing heater 731 is a halogen heater that generates heat with electric power supplied from an AC commercial power supply 8 (external power supply). The second fixing heater 732 is a halogen heater that generates heat with electric power supplied from the auxiliary power supply unit 72.

  The first power switch 71 is provided between the commercial power supply 8 and the first fixing heater 731, and determines whether or not to supply AC100V power from the commercial power supply 8 to the first fixing heater 731, that is, the first power switch 71. This is an open / close switch that switches whether to drive (heat generation) the fixing heater 731. The first power switch 71 turns on or off the power supply of, for example, AC 100 V from the commercial power supply 8 based on an open / close signal input from the control unit 10 that controls the overall operation of the multifunction machine 1.

  The auxiliary power switch 74 is provided between the auxiliary power unit 72 and the second fixing heater 732, and determines whether or not power from the auxiliary power unit 72 is supplied to the second fixing heater 732, that is, the second fixing heater. This is an open / close switch for switching whether to drive (heat generation) 732. The auxiliary power switch 74 switches whether to supply power from the auxiliary power unit 72 to the second fixing heater 732 based on the open / close signal input from the control unit 10.

  The charging switch 75 is an open / close switch that is provided between the commercial power supply 8 and the auxiliary power supply unit 72 and switches whether power from the commercial power supply 8 is supplied to the auxiliary power supply unit 72. The charging switch 75 also turns on or off the power supply from the commercial power supply 8 based on the open / close signal input from the control unit 10. The control unit 10 turns on the charging switch 75 when the power consumption of the commercial power supply 8 is low in the multifunction device 1 such as when the sleep mode of the multifunction device 1 is executed (when waiting for printing) or when the main power is off. Charging by the charging device 721 and the power storage device 722 is performed.

  The auxiliary power supply unit 72 is provided as an auxiliary power supply for the commercial power supply 8 in order to supply power to the second fixing heater 732. The auxiliary power supply unit 72 includes a charging device 721, a power storage device 722, and a booster device 723.

  Charging device 721 is an AC / DC converter for charging power storage device 722, and outputs a current obtained by rectifying AC 100 V of commercial power supply 8, which is AC power, to power storage device 722.

  The power storage device (an example of an auxiliary power supply in the claims) 722 is configured by one electric double layer capacitor or a plurality of electric double layer capacitors connected in series. The power storage device 722 charges the electric double layer capacitor with the current from the charging device 721 as an electric charge, and discharges the electric charge charged in the electric double layer capacitor and outputs the electric charge to the booster 723 as a discharging current.

  A booster (an example of a booster circuit in the claims) 723 takes a voltage output from the power storage device 722 as an input voltage and boosts the input voltage to a predetermined voltage suitable for the second fixing heater 732 as a load. Then, the boosted power is supplied to the second fixing heater 732. The booster 723 is an isolated DC / DC converter in which an input side and an output side are insulated by an insulated transformer.

  The control unit (control unit) 10 controls the overall operation of the multifunction machine 1. The control unit 10 controls the first power switch 71, the auxiliary power switch 74, and the charging switch 75 to be turned on and off.

  Further, a timer 11 is connected to the control unit 10. The timer 11 measures the passage of a predetermined time. The predetermined time is a time when an inrush current (described later) generated when heating of the second fixing heater 732 starts to be reduced. For example, the rated current is supplied to the second fixing heater 732. This is the time expected to reach a flowing state. The predetermined time is appropriately set by a manufacturer or the like by a test or the like according to the performance of the second fixing heater 732.

  Until the passage of the predetermined time is measured by the timer 11, the control unit 10 bypasses a bypass switch 723 e (FIG. 3) described later, and the output from the power storage device 722 bypasses the booster 723 and the second When the timer 11 measures the passage of the predetermined time, the output from the power storage device 722 does not bypass the booster 723 and the booster 723 is switched to be supplied to the fixing heater 732. The bypass switch 723e is switched so that the voltage superposed with the voltage boosted by 723 is supplied to the second fixing heater 732.

  Next, the configuration of the booster 723 will be described. FIG. 3 is a circuit diagram illustrating a schematic configuration of the booster 723 and a connection relationship between the power storage device 722 and the second fixing heater 732.

  As shown in FIG. 3, the booster 723 includes a transformer 723a, a MOS transistor 723b, a PWM controller 723c, a smoothing circuit 723d, and a bypass switch 723e.

  A transformer (an example of an insulated converter) 723a is an insulated transformer, and includes a primary winding and a secondary winding that have a turn ratio suitable for generating a voltage necessary for the second fixing heater 732. . One end of the primary winding of the transformer 723a is connected to one end (+ voltage side) of the power storage device 722, and the other end of the primary winding is connected to the drain terminal of the MOS transistor 723b. Further, both ends of the secondary winding of the transformer 723a are connected to the smoothing circuit 723d.

  The MOS transistor 723 b is for switching the discharge current input from the power storage device 722. As described above, in the MOS transistor 723b, the drain terminal is connected to the other end of the primary winding of the transformer 723a, the source terminal is connected to the other end (−voltage side) of the power storage device 722, and the gate terminal is PWM. It is connected to the controller 723c. With the above configuration, the primary side of the transformer 723a is connected to the power storage device 722, and power from the power storage device 722 is output to the transformer 723a.

  When receiving an ON signal for driving the booster 723 from the control unit 10, the PWM controller 723 c is supplied with electric power from the power storage device 722 to the booster 723, and drives the booster 723 from the controller 10. When the off signal to be stopped is received, the switching operation of the MOS transistor 723b is controlled so that power supply from the power storage device 722 to the boosting device 723 is stopped.

  The PWM controller 723c generates a PWM signal so that the voltage output as the auxiliary power supply voltage from the smoothing circuit 723d becomes a predetermined constant value, and supplies the PWM signal to the gate terminal of the MOS transistor 723b. Thus, the switching operation of the MOS transistor 723b is controlled. As a result, even if the charging voltage of the electric double layer capacitor of the power storage device 722 gradually decreases due to discharging and the input voltage of the boosting device 723 decreases, the driving voltage of the second fixing heater 732 is held at a constant value, 2 Heat generation of the fixing heater 732 is stabilized.

  The smoothing circuit 723d includes diodes D1 and D2, which are connected as shown in FIG. 3, a coil L, and a capacitor C, and smoothes the secondary winding voltage supplied from the secondary winding of the transformer 723a and outputs it as an auxiliary power supply voltage. To do. One of the output ends of the smoothing circuit 723d is connected to one end (+ voltage side) of the power storage device 722 in the same manner as one end of the primary winding of the transformer 723a. As the diode D2, a diode having an instantaneous withstand voltage is used so as not to be damaged by the inrush current generated at the initial driving of the second fixing heater 732. In addition, the other side of the output terminal of the smoothing circuit 723 d and the negative voltage side of the power storage device 722 are connected to the second fixing heater 732.

  That is, the auxiliary power supply unit 72 includes a booster 723 in which the input side (primary side) and the output side (secondary side) are insulated by the transformer 723a, and the primary side of the booster 723 is connected to the power storage device 722. Since one end of the secondary side is connected to the power storage device 722 and the other end of the secondary side is connected to the second fixing heater 732, the auxiliary power supply voltage at the power output terminal of the auxiliary power supply unit 72 is A voltage obtained by adding (superimposing) the charging voltage of 722 and the output voltage of the booster 723 is obtained.

  The bypass switch (bypass switching mechanism) 723 e is a switching mechanism that switches whether the electric power from the power storage device 722 is supplied to the second fixing heater 732 by bypassing the booster 723. As shown in FIG. 3, the bypass switch 723 e short-circuits the position before the connection portion with the fixing heater 730 and the position before the connection portion with the power storage device 722 on the secondary side of the booster 723. Let it be connected. Thereby, the bypass switch 723 e can supply the electric power from the power storage device 722 to the second fixing heater 732 by bypassing the booster 723. As described above, the bypass switch 723e is controlled to be switched by the control unit 10.

  Next, the control at the time of starting up the fixing device 7 will be described. 4 is a flowchart showing control at the time of starting up the fixing device 7, FIG. 5 is a circuit diagram showing a current path at the initial stage of starting up the fixing device 7, and FIG. 6 is a circuit showing a current path at the latter stage of starting up the fixing device 7. FIGS. 7A to 7D are timing charts of the heater drive signal, converter drive signal, output current, and output voltage when the fixing device 7 is started up.

  When the main power source of the multi-function device 1 is turned on by an operation by the operator (YES in S1), the control unit 10 turns on the first power switch 71 to supply power from the commercial power source 8 to the first fixing heater 731. And the first fixing heater 731 is driven (S2).

  Further, the control unit 10 turns off the charging switch 75 (S3). Then, control unit 10 turns on bypass switch 723e and switches bypass switch 723e so that the electric power from power storage device 722 bypasses booster 723 (S4). Further, the control unit 10 turns on the auxiliary power switch 74 so that the power from the auxiliary power unit 72 is supplied to the second fixing heater 732 (S5).

  That is, as shown in FIG. 7, when the main power supply of the multifunction device 1 is turned on, the control unit 10 drives the first fixing heater 731 (FIG. 7A), but turns on the bypass switch 723e. Thus, the output from the power storage device 722 not boosted by the booster 723 is supplied to the second fixing heater 732 (FIG. 7D). When the second fixing heater 732 is driven by the electric power supplied from the power storage device 722, an inrush current is applied to the second fixing heater 732 due to voltage application to the second fixing heater 732 that is in a low temperature state in the initial stage of driving. As shown in FIG. 5, the current path bypasses the booster 723 and flows to the second fixing heater 732 through a bypass switch 723e as shown in FIG. In this case, since the inrush current which is a large current exceeding the rating does not flow through the coil L, the coil L is not saturated, and thus the coil L is not burdened.

  Thereafter, when the timer 11 measures the passage of the predetermined time (the time when the inrush current is assumed to be in a lowered state, for example, the time when the current is assumed to settle to the rated current) (YES in S6). Then, the control unit 10 turns off the bypass switch 723e and switches the bypass switch 723e so that the power from the power storage device 722 is boosted by the booster 723 (S7). Further, the control unit 10 transmits an ON signal for driving the booster 723 to the PWM controller 723c, and sets the MOS transistor 723b so that the power from the power storage device 722 is supplied to the booster 723. Switching is performed (S8). That is, the control unit 10 causes the booster 723 to perform a boosting operation. As a result, after the inrush current reaches a reduced state, a voltage obtained by superimposing the voltage boosted by the booster 723 on the output voltage from the power storage device 722 is supplied to the second fixing heater 732.

  That is, as shown in FIG. 7, when the inrush current reaches a reduced state (FIG. 7 (c)), the control unit 10 turns off the bypass switch 723e (FIG. 7 (b)). As a result, the current path is as shown in FIG. 6, and the voltage from the power storage device 722 boosted by the booster 723 is superimposed and output to the second fixing heater 732 (FIG. 7D). Then, since the booster 723 is not affected by the inrush current, a rated current flows through the second fixing heater 732 and the booster 723 (FIG. 7C). The coil L functions normally as an inductor without being affected by the inrush current, and is boosted normally by the booster 723.

  For example, when using a second fixing heater 732 made of a halogen heater driven at a rating of 75 A / 26 A and a power storage device 722 made of an electric double layer capacitor having a full charge voltage of 40 V, the input voltage of 40 V is boosted to 75 V and output. A boosting device 723 having the performance to do this is used. At this time, because of the characteristics of the halogen heater, the resistance value is about 1/10 of the rated value at low temperatures before heat generation, so an inrush current of nearly 200 A flows when the initial voltage is applied. The inrush current does not flow through the booster 723, and no adverse effect due to the inrush current occurs in the booster 723. Thereby, even in the configuration including the booster 723, the power of the power storage device 722 can be supplied to the second fixing heater 732 from the initial driving time, so that the rise time as the fixing heating system can be shortened. The controller 10 is configured to start the boosting operation by the booster 723 after the inrush current is settled (for example, after 100 msec from the time when the first fixing heater 731 and the second fixing heater 732 are driven) ( FIG. 7C shows an example in which 500 msec is elapsed after the driving of the first fixing heater 731 and the second fixing heater 732), and the booster 723 has a rated current that does not adversely affect the boosting operation ( For example, 26A) flows, and by the superposition of the boosted voltage, the start-up as a fixing heating system can be performed more efficiently.

  In the process shown in FIG. 4, the control unit 10 has been described as driving the booster 723 after turning off the bypass switch 723e (S7) (S8), but the control unit 10 sets the bypass switch 723e. If it is after turning on (S4), the timing which drives the booster 723 is not ask | required.

  In addition, this invention is not limited to the thing of the said embodiment, The aspect described below can be employ | adopted further.

  (1) For example, in the above embodiment, the control unit 10 switches the bypass switch 723e when the elapse of a predetermined time is measured by the timer 11 so that the boosting operation by the booster 723 is started. However, as shown in FIG. 8, instead of the timer 11, an ammeter (current detection means) 91 is connected between the auxiliary power unit 72 and the second fixing heater 732, and the control unit 10 When a value indicating a state where the inrush current is reduced by 91 (for example, a value lower than the rated current value) is detected, the boosting operation by the boosting device 723 may be started by switching the bypass switch 723e. (That is, the process is performed in place of S6 in FIG. 4). In this case, since the control unit 10 controls the drive of the booster 723 based on the current value detected by the ammeter 91, the period during which the inrush current flows through the booster 723 can be determined with high accuracy. The booster 723 can be driven while reliably avoiding the current.

  (2) Further, as shown in FIG. 9, instead of the timer 11, a temperature detection device (temperature detection means) 92 for detecting the temperature of the second fixing heater 732 is provided in the vicinity of the second fixing heater 732, for example, a thermostat. When the temperature detecting device 92 detects a temperature indicating a state where the inrush current is reduced, the control unit 10 switches the bypass switch 723e and starts the boosting operation by the boosting device 723. (In other words, this processing is performed in place of S6 in FIG. 4). In this case, since the control unit 10 performs drive control of the booster 723 based on the temperature detected by the temperature detector 92, the period during which the inrush current flows through the booster 723 can be determined by a simple process. The booster 723 can be driven while reliably avoiding the inrush current.

  (3) In the above embodiment, the transformer 723a is used for the booster 723. However, the present invention is not limited to this, and an isolated DC / DC converter using an insulating means different from the transformer is applied to the booster 723. May be.

  In addition, the image forming apparatus according to the present invention is not limited to the multifunction machine 1 and may be another image forming apparatus, and the configuration and processing shown in FIGS. 1 to 9 are merely one embodiment of the present invention. However, the configuration and processing of the present invention are not limited to these.

1 is a side view schematically showing an internal configuration of a multifunction peripheral as an example of an image forming apparatus according to an embodiment of the present disclosure. FIG. 2 is a schematic diagram illustrating a fixing unit provided in the multifunction peripheral and a peripheral internal configuration. It is a circuit diagram which shows the schematic structure of a pressure | voltage rise apparatus, and the connection relation of an electrical storage apparatus and a 2nd fixing heater. 6 is a flowchart illustrating control at the time of starting up the fixing device. FIG. 3 is a circuit diagram showing a current path at the initial start-up of the fixing device. FIG. 4 is a circuit diagram illustrating a current path in a late stage of startup of the fixing device. (A) to (d) are timing charts of a heater drive signal, a converter drive signal, an output current, and an output voltage when the fixing device is started up. It is a figure which shows schematic structure of other embodiment of this invention. It is a figure which shows schematic structure of other embodiment of this invention.

Explanation of symbols

1 MFP 7 Fixing Device 8 Commercial Power Supply 10 Control Unit 11 Timer 71 First Power Switch 72 Auxiliary Power Supply Unit 73 Fixing Roller 74 Auxiliary Power Switch 75 Charging Switch 91 Ammeter 92 Temperature Detection Device 721 Charging Device 722 Power Storage Device 723 Boosting Device 723a Transformer 723b MOS transistor 723c PWM controller 723d Smoothing circuit 723e Bypass switch 730 Fixing heater 731 First fixing heater 732 Second fixing heater C Capacitors D1, D2 Diode L Coil

Claims (6)

An auxiliary power source consisting of a capacitor;
A first fixing heater that is driven by electric power from an external power source and a second fixing heater that is composed of a halogen heater and is driven by electric power from the auxiliary power source, and heats a fixing unit that fixes toner onto recording paper A fixing heater,
A primary side is connected to the auxiliary power source, and one end on the secondary side is connected to the second fixing heater, and the other end on the secondary side is connected to the auxiliary power source by an isolated converter from the auxiliary power source. A boosting circuit that boosts the output voltage of the second fixing heater and outputs the boosted output voltage to the second fixing heater;
Bypass switching means for switching whether the booster circuit bypasses the output from the auxiliary power supply when power from the auxiliary power supply is supplied to the second fixing heater;
Control means for controlling power supply to the fixing heater,
The second fixing heater has one end connected to the secondary side of the booster circuit and the other end connected to the auxiliary power source.
The control means drives the first fixing heater with the output from the external power supply at the initial driving stage of the fixing heater, and outputs the auxiliary power supply with the bypass switching means bypassing the booster circuit. And the second fixing heater is driven, and after the elapse of a period when an inrush current flows through the second fixing heater, the bypass switching means is not allowed to bypass the booster circuit, and the output of the booster circuit is output from the auxiliary power supply. An image forming apparatus superposed on the second fixing heater and supplied to the second fixing heater.   The bypass switching means is connected on the secondary side of the booster circuit by short-circuiting a position before the connection portion with the fixing heater and a position before the connection portion with the auxiliary power supply. The image forming apparatus according to claim 1, wherein an output of the auxiliary power supply can be supplied to the second fixing heater by bypassing the booster circuit.   The image forming apparatus according to claim 1, wherein the insulating converter includes an insulating transformer. A timer for measuring time,
The control means switches the bypass switching means and switches the output of the booster circuit to the auxiliary circuit when an elapse of a predetermined time that the inrush current has reached has been measured by the timer. The image forming apparatus according to claim 1, wherein the image forming apparatus is supplied to the second fixing heater while being superimposed on an output of a power source. A current detecting means for detecting a value of a current flowing through the second fixing heater;
The control means switches the bypass switching means and superimposes the output of the booster circuit on the output of the auxiliary power supply when the current detection means detects a value indicating a state where the inrush current is reduced. The image forming apparatus according to claim 1, wherein the image forming apparatus is supplied to the second fixing heater. Temperature detecting means for detecting the temperature of the second fixing heater;
The control means switches the bypass switching means to superimpose the output of the booster circuit on the output of the auxiliary power supply when a temperature indicating a state where the inrush current is reduced is detected by the temperature detection means. The image forming apparatus according to claim 1, wherein the image forming apparatus is supplied to the second fixing heater.

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