JP2016122038A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can calculate input voltage.SOLUTION: An image forming apparatus comprises: a fuser that has a radiation heater built therein; a first detection part that can detect the temperature of the fuser; a power source circuit for a heater that can create and reduce a DC voltage from an AC power source and apply the DC voltage to the radiation heater; a control part that determines a duty ratio on the basis of a result of detection performed by the first detection part and performs PWM control of an output current from the power source circuit for a heater with the determined duty ratio; and a second detection part that can detect an input current to the power source circuit for a heater. The control part determines an input voltage to the radiation heater (S04) from a result of detection performed by the second detection part, relationship between voltage and current in the radiation heater, and determined duty ratio, and controls the operation of the image forming apparatus on the basis of the determined input voltage (S08).SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus including a fixing device incorporating a radiation heater.

  Conventionally, as the image forming apparatus as described above, for example, there is an apparatus described in Patent Document 1 below. An image forming apparatus disclosed in Patent Document 1 includes a plurality of heating elements that generate heat when power is supplied from an AC power source, a thermistor that detects the temperature of each heating element, and a current detection circuit that detects a current value flowing through each heating element. And a CPU for controlling the temperature of each heating element by controlling the power supplied to each heating element.

  The CPU calculates the maximum supplyable power ratio based on the current value that can be supplied to each heating element, the current value that is detected by the current detection circuit, and the temperature that is detected by the thermistor. It is estimated that the input voltage of the heating element has dropped.

JP2013-218841A

  However, the image forming apparatus disclosed in Patent Document 1 has a problem in that an input voltage itself cannot be calculated, and thus a value of a current flowing through a power cord of the image forming apparatus cannot be appropriately controlled.

  Therefore, an object of the present invention is to provide an image forming apparatus capable of calculating an input voltage.

  According to one aspect of the present invention, a fixing device including a radiation heater, a first detection unit capable of detecting the temperature of the fixing device, a direct current voltage generated from an alternating current power source, stepped down, and applied to the radiation heater. A heater power supply circuit, a control unit that determines a duty ratio based on a detection result of the first detection unit, and performs PWM control on an output current of the heater power supply circuit with the determined duty ratio, and a power supply to the heater power supply circuit A second detection unit capable of detecting an input current, and the control unit, from the detection result of the second detection unit, the relationship between the current and voltage in the radiation heater, and the determined duty ratio, The present invention is directed to an image forming apparatus that obtains an input voltage to the radiation heater and controls the operation of the image forming apparatus based on the obtained input voltage.

  According to the above aspect, it is possible to provide an image forming apparatus that can calculate the input voltage itself.

FIG. 2 is a schematic diagram when the inside of the image forming apparatus is viewed from the front. FIG. 2 is a schematic diagram illustrating a main part in the image forming apparatus. FIG. 6 is an operation flowchart of the image forming apparatus. It is an operation | movement flowchart of the image forming apparatus which concerns on a 2nd modification.

<< First column: Overall configuration and printing operation of image forming apparatus >>
1 and 2, an image forming apparatus 1 is, for example, a copying machine, a printer, a facsimile machine, or a multifunction machine having these functions, and prints a full-color image on a sheet-like print medium (for example, paper). To do. For this purpose, the image forming apparatus 1 generally includes a paper feeding unit 2, a registration roller pair 3, an image forming unit 4, a fixing device 5, a control circuit board 6, a power supply unit 7, and a display unit 8. And comprising.

  An unused print medium is stacked on the paper feed unit 2. In the paper feed unit 2, several rollers rotate to send out the print media one by one to the transport path FP indicated by a broken line in FIG. The registration roller pair 3 is provided on the conveyance path FP and on the downstream side of the paper feeding unit 2. The registration roller pair 3 temporarily stops the print medium sent out from the paper feeding unit 2 and then rotates it to send it out to the secondary transfer area at a predetermined timing.

  The image forming unit 4 generates a toner image on the intermediate transfer belt by, for example, a well-known electrophotographic method and tandem method. Here, as is well known, the image forming unit 4 generates a toner image of each color, and Y (yellow), M (magenta), C (cyan), K (black) photosensitive drums and developing rollers. Etc.

  The intermediate transfer belt rotates and conveys the toner image toward the secondary transfer region while carrying the toner image. A print medium is fed from the registration roller pair 3 to the secondary transfer area, and a toner image is conveyed from the image forming unit 4. In the secondary transfer region, the toner image is transferred from the intermediate transfer belt to the print medium and sent to the fixing device 5.

  A printing medium is introduced into the fixing device 5 from the secondary transfer region. In the fixing device 5, the built-in heating roller and pressure roller rotate so that the introduced print medium passes between nips formed by both rollers. During the passage, the print medium is heated and pressurized, and as a result, the toner is fixed on the print medium. The print medium sent out from the fixing device 5 is discharged as a printed matter onto the tray of the image forming apparatus 1.

  The image forming apparatus 1 is provided with a plurality of motors M for rotating each component described above. FIG. 1 illustrates five motors M1 to M5. The configuration rotated by each of the motors M1 to M5 is as shown in Table 1 below.

  A CPU, ROM, RAM, and the like are mounted on the control circuit board 6 as the control unit CC2. The CPU executes the program stored in the ROM while using the RAM as a work area. The controller CC2 controls the rotation of the various motors M. In addition, the control unit CC2 performs various controls, but what is important in this embodiment is to obtain the input voltage Vin to the radiation heater 53.

  The power supply unit 7 is connected to, for example, a commercial AC power supply Vac, and, for example, a + 24V constant voltage Vc1, a + 5V constant voltage Vc2, and a voltage to be supplied to the radiation heater 53 from an AC voltage input from the AC power supply Vac. Generate Vin. The constant voltage Vc1 is supplied to, for example, various motors M, and the constant voltage Vc2 is supplied to, for example, the control unit CC2.

  The display unit 8 is a touch panel, for example, and displays various types of information generated by the control unit CC2.

<< Second column: Detailed configuration of main part of image forming apparatus >>
Next, with reference to FIG. 2, the structure of the principal part of this embodiment, ie, the fixing device 5, the control circuit board 6, and the power supply part 7 is demonstrated.
As shown in FIG. 2, the fixing device 5 includes a heating roller 51 and a pressure roller 52 that contact each other to form a nip. Both rollers 51 and 52 extend in the front-rear direction of the image forming apparatus 1 and rotate based on a control signal from the control unit CC2.

The heating roller 51 has a cylindrical core bar extending in the front-rear direction. It is preferable to reduce the heat capacity of the heating roller 51 by appropriately setting the thickness and outer diameter of the cored bar.
Further, in the heating roller 51, a radiant heater 53 is built in the cored bar. The radiant heater 53 is typically a halogen heater, and is a heater by a light heating method. The radiation heater 53 has a predetermined light emission length (for example, about 310 mm) in the front-rear direction, and has a power consumption of 1000 W or more, for example.

  When the voltage Vin is applied to the radiation heater 53 as described above by a heater power supply circuit 72 to be described later, a current Iinh flows through a filament typically made of tungsten, and the filament generates heat and lights up. Here, as is well known, the resistivity of tungsten increases as the ambient temperature increases. In other words, the radiant heater 53 has a resistance-temperature characteristic in which the resistance value increases as the ambient temperature increases.

  In the vicinity of the heating roller 51 described above, a first detection unit S1, which is a thermistor, for example, is provided. The detection unit S1 outputs a signal TEMP correlated with the temperature of the heating roller 51 (for convenience, hereinafter simply referred to as temperature) to the control unit CC2.

The power supply unit 7 generally includes a low-voltage power supply circuit 71 and a heater power supply circuit 72.
The low-voltage power supply circuit 71 generally includes a first fuse F1, a first full-wave rectifier circuit 711, an active filter 712, a first DC / DC converter 713, a second DC / DC converter 714, and current detection. First resistor R1 and second resistor R2, and a power supply control circuit CC1.

  The full-wave rectifier circuit 711 is a diode bridge having four rectifier diodes D1 to D4, and is connected to the L terminal (that is, the live terminal) of the AC power supply Vac via the fuse F1 and N of the AC power supply Vac. Connected to terminal (ie, neutral terminal). Such a full-wave rectifier circuit 711 performs full-wave rectification on the AC voltage supplied from the AC power supply Vac.

  When switching element Q1 is turned on in active filter 712, energy is stored in reactor L1. Further, when the switching element Q1 is turned off, the capacitor C1 is charged by the energy of the reactor L1, and as a result, the voltage Vdc across the capacitor C1 is controlled to a constant voltage of, for example, 400V. Thereby, the input power factor of the low-voltage power supply circuit 71 is improved.

  In the DCDC converter 713, when the switching element Q2 is turned on, a current flows to the primary side of the switching transformer T1, and energy is stored in the core. However, since the direction of the rectifier diode D16 is reverse, no induced current flows on the secondary side. On the other hand, by turning off the switching element Q2, the energy stored in the core is released, and a current flows through the rectifier diode D16. Further, the current is smoothed by the capacitor C2, and the constant voltage Vc1 is output.

  In the DCDC converter 714, as with the DCDC converter 713, when the switching element Q3 is turned on, a current flows only in the primary side of the switching transformer T2, and energy is stored in the core. Conversely, when the switching element Q2 is turned off, the core energy is released, and a current flows through the rectifier diode D14. Further, the current is smoothed by the capacitor C3, and the constant voltage Vc2 is output.

The resistor R1 is connected between the rectifier diode D16 and the + 24V terminal, and the resistor R2 is connected between the rectifier diode D14 and the + 5V terminal. Part of the current flowing through the resistors R1 and R2 is input to the power supply control circuit CC1 as currents I24V and I5V.
The power supply control circuit CC1 outputs a signal Pout representing a value obtained by multiplying the values of the input currents I24V and IV5 by + 24V and + 5V (that is, power consumption of the low-voltage power supply circuit 71) to the control unit CC2.

  The heater power supply circuit 72 generally includes a second fuse F2, a second full-wave rectifier circuit 721, a step-down chopper circuit 722, a third full-wave rectifier circuit 723, and a smoothing circuit 724.

  The full-wave rectifier circuit 721 is a diode bridge having four rectifier diodes D5 to D8, connected to the L terminal via a fuse F2, and connected to the N terminal. The full-wave rectifier circuit 721 performs full-wave rectification on the AC voltage from the AC power supply Vac.

  A radiation heater 53 as a load is connected to the step-down chopper circuit 722. In step-down chopper circuit 722, heater control circuit CC3 turns on / off switching element Q3 in accordance with control signal PWMR indicating the pulse width and duty ratio from control unit CC2. Here, the pulse widths are equally spaced at a certain frequency. With this control signal PWMR, the direct current from the full-wave rectifier circuit 721 is output with pulse width modulation at equal intervals. Hereinafter, the direct current chopped by the equal interval pulse width modulation is referred to as an input current Iinh to the radiation heater 53. When switching element Q3 is turned on, current Iinh flows through reactor L2 and radiation heater 53. During this time, reactor L2 stores a part of current Iinh flowing through it as magnetic energy.

  On the other hand, when the switching element Q3 is turned off, the magnetic energy stored in the reactor L2 is released as the current Iinh and starts to flow to the radiation heater 53. This current Iinh returns to the coil L2 via the diode D15.

  By the operation of the heater power supply circuit 72 as described above, the waveform of the input current Iinh to the radiation heater 53 becomes a pseudo sine wave, and is a power factor between the input current Iinh and the input voltage Vin. The power factor of the power source circuit 72 is approximately 100%.

In addition, a coil serving as the second detector S2 is provided on the power supply line connecting the fuse F2 and the full-wave rectifier circuit 721. Specifically, the coil is disposed so that the power supply line penetrates the coil. When an alternating current flows through the power supply line, an induced electromotive force correlated with the alternating current is generated at both ends of the coil. In other words, the second detector S <b> 2 detects an input current to the heater power supply circuit 72.
In addition, the second detector S2 may be provided downstream of the above-described full-wave rectifier circuit 721. In other words, the PWM current generated by the heater power supply circuit 72 may be detected.

  The full-wave rectifier circuit 723 is a diode bridge having four diodes D9 to D12, and full-wave rectifies the induced electromotive force applied by the second detector S2, and outputs the resultant to the smoothing circuit 724.

  In order to measure the input current Iinh, it is necessary to obtain an average value or an effective value with a period sufficiently longer than a period (20 ms or about 16.7 ms) corresponding to the frequency (50 Hz or 60 Hz) of the AC power supply Vac. Therefore, the smoothing circuit 724 is a first-order lag circuit, and obtains an average value or an effective value of the input current to the heater power supply circuit 72 from the output voltage of the full-wave rectifier circuit 723, and represents a signal representing one of the values. Output to the control unit CC2 as IH.

<< third column: operation of main part of image forming apparatus >>
Next, with reference to FIG. 3 etc., the operation | movement of the principal part of this embodiment is demonstrated.
First, when the image forming apparatus 1 is turned on, a known warm-up operation is started (S01). Thereafter, when a print job arrives at the image forming apparatus 1 from an external personal computer or the like (not shown), execution of the print job is started and fixing temperature control is performed (S02).

Hereinafter, the fixing temperature control will be outlined.
After the start of the print job, the control unit CC2 determines the duty ratio by PID control (Proportional-Integral-Derivative control) based on the detected temperature TEMP of the detection unit S1. Thereafter, the controller CC2 generates the control signal PWMR described above and outputs it to the heater control circuit CC3. The heater control circuit CC3 turns on / off the switching element Q3 in accordance with the input control signal PWMR, whereby the current Iinh is supplied to the radiation heater 53. By such temperature control, the temperature of the radiant heater 53 is made substantially constant at the target temperature.

  By the way, when a predetermined time (for example, about 0.5 seconds) elapses after the start of the print job, the resistance value of the radiation heater 53 is stabilized and the input current Iinh is also stabilized. Thereafter, the controller CC2 obtains an average value or an effective value of the input current Iinh from the output signal IH of the smoothing circuit 724 (S03).

Here, it is known that the relationship between the input current Iinh of the radiant heater 53 and the input voltage Vin is expressed by the following expression (1), where the rated input voltage is Vinr and the rated input current Vinr. .
Iinh / Iinr = (Vin / Vinr) ^0.54 (1)
When the above equation (1) is transformed, the following equation (1 ′) is obtained.
Iinh = Iinr × (Vin / Vinr) ^0.54 (1 ′)

When the rated power of the radiant heater 53 is Wr, the rated input current Iinr when the rated input voltage Vinr is applied is obtained by the following equation (2).
Iinr = Wr / Vinr (2)

When the duty ratio during PWM control is D, the input current when the duty ratio is D is Iinh (D), and the efficiency of the heater power supply circuit 72 is ηh, Iinh (D) is 3).
Iinh (D) = Iinh × ((Vin × D × ηh) / Vinr) ^0.54 (3)
Further, when the above equation (3) is modified, the following equation (3 ′) is obtained.

  Since known Vinr, Vinr, and ηh are known, they are held in advance by the control unit CC2. The control unit CC2 obtains the input voltage Vin by substituting these Vinr, Vinr, ηh, D set by PWM control, and Iinh obtained from the input signal IH into the above equation (3 ′) ( S04).

When the efficiency of the low-voltage power supply circuit 71 is ηlv, the power factor is cosφlv, and the power consumption of the power supply control circuit CC1 (that is, the value indicated by the signal Pout) is Pout, the input current Iinlv to the low-voltage power supply circuit 71 is Is expressed by the following equation (4).
Iinlv = Pout / (ηlv × cosφlv × Vin) (4)
Here, since ηlv and cos φlv are known, they are held in advance by the control unit CC2. The control unit CC2 obtains Iinlv by substituting the known ηlv, cos φlv, Pout indicated by the signal IH, and Vin obtained from the above equation (3 ′) into the above equation (4) (S05).

The combined current Iin flowing through the power cord of the image forming apparatus 1 connected to the AC power supply Vac is expressed by the following equation (5).
Iin = Iinh + Iinlv
= Iinh + Pout / (ηlv × cosφlv × Vin) (5)
The control unit CC2 obtains Iin by substituting Iinh obtained from the input signal IH and Iinh obtained from the above equation (4) into the above equation (5) (S06).

  Next, the controller CC2 determines whether or not the obtained combined current Iin exceeds 15A, which is the rated current value of the AC power supply Vac (S07).

  If No, the control unit CC2 returns to S03, but if Yes, the load current of the low-voltage power supply circuit 71 and / or the heater power supply circuit 72 is reduced (S08). In this embodiment, for example, in order to reduce the load current of the low-voltage power supply circuit 71, the interval between two continuous print media is increased. In addition, depending on the value of the combined current Iin, printing itself may be stopped, or the printing medium conveyance speed (that is, the system speed of the image forming apparatus 1) may be reduced.

  When the above S08 ends, the control unit CC2 returns to S03.

<< 4th column: Effect of image forming apparatus >>
As described above, according to the image forming apparatus 1, the input voltage Vin itself can be calculated by detecting the current Iinh flowing through the radiation heater 53. Further, the input current Iinlv to the low-voltage power supply circuit 71 connected in parallel to the heater power supply circuit 72 can be obtained from the calculated input voltage Vin. Based on these, the image forming apparatus 1 can be appropriately controlled so that the current value Iin flowing through the power cord of the image forming apparatus 1 is less than the rated current of the AC power supply Vac.

<5th column: Appendix>
The second detector S2 detects the input current to the heater power circuit 72 as described above. When the input current becomes excessive, the control unit CC2 may suppress the input current by reducing the duty ratio indicated by the control signal PWMR.

  Further, the efficiency ηlv and the power factor cosφlv vary depending on the currents I24V and I5V flowing through the load connected to the + 24V terminal or the + 5V terminal. Therefore, the characteristics of ηlv and cos φlv with respect to each load current are measured in advance, and a table representing the measurement results is stored in the control unit CC2. When the control unit CC2 obtains the current load currents I24V and I5V from the input signal Pout, the control unit CC2 may obtain the corresponding ηlv and cosφlv from the table and substitute them into the equation (4).

<Sixth column: first modification>
In the above embodiment, the rated power Wr of the radiant heater 53 is assumed to be constant. However, the rated power Wr of the radiation heater 53 usually has a solid difference of about ± 3%. In order to compensate for this individual difference, for example, in the production line, after the resistance value of the radiation heater 53 is stabilized, the manufacturer measures the input current Iinr to the heater power supply circuit 72 when the rated input voltage is applied, Store in the control unit CC2. The control unit CC2 uses this input current value Iinr in S04.

<Seventh column: second modification>
Further, as shown in FIG. 4, when the input voltage Vin obtained in S04 is outside the use range of the image forming apparatus 1 (S010), the control unit CC2 cannot guarantee the operation of the image forming apparatus 1. May be displayed on the display unit 8 or the operation of the image forming apparatus 1 may be stopped (S011).

  The image forming apparatus according to the present invention can calculate an input voltage and is suitable for a printer or the like.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 5 Fixing device 53 Radiation heater S1 1st detection part S2 2nd detection part CC2 Control part 7 Power supply part 71 Low voltage power supply circuit 72 Power supply circuit for heaters 724 Smoothing circuit 8 Display part

Claims (12)

A fixing device with a built-in radiation heater;
A first detector capable of detecting the temperature of the fixing device;
A heater power supply circuit capable of generating a DC voltage from an AC power source, stepping down the voltage, and applying it to the radiation heater;
A control unit that determines a duty ratio based on a detection result of the first detection unit, and performs PWM control of an output current of the heater power supply circuit at the determined duty ratio;
A second detector capable of detecting an input current to the heater power circuit,
The control unit obtains an input voltage to the radiation heater from the detection result of the second detection unit, the relationship between the current and voltage in the radiation heater, and the determined duty ratio, and based on the obtained input voltage. An image forming apparatus that controls the operation of the image forming apparatus.   The image forming apparatus according to claim 1, further comprising: a smoothing circuit that obtains an effective value or an average value with a period longer than a period of the AC power source from a detection result of the second detection unit.   After the resistance change of the radiation heater is stabilized, the control unit is configured to detect the radiation from the detection result of the second detection unit, the relationship between the current and the voltage in the radiation heater, and the predetermined duty ratio. The image forming apparatus according to claim 1, wherein an input voltage to the heater is obtained.   The said 2nd detection part is any one of Claims 1-3 arrange | positioned so that detection of either the input alternating current to the said power supply circuit for heaters and the direct current generated by the said power supply circuit for heaters is possible The image forming apparatus described in 1. The input voltage of the radiation heater is Vin, the input current of the radiation heater obtained from the detection result of the second detection unit is Iinh, and the rated input current when a known Vinr is applied as the rated input voltage of the radiation heater Is known Iinr, power efficiency of the heater power supply circuit is known ηh, and the predetermined duty ratio is D,
The Vin is

The image forming apparatus according to claim 1, which is obtained by:   The image forming apparatus according to claim 1, wherein the second detection unit is used to control an input current to the heater power supply circuit. The controller is
When the output current of the heater power supply circuit is PWM controlled at 100% as the predetermined duty ratio, and the rated input voltage is applied to the radiation heater while the resistance change of the radiation heater is stable The input current value at is obtained from the detection result of the second detection unit and stored,
The image formation according to claim 1, wherein the input voltage of the radiation heater is obtained based on the stored input current value of the radiation heater and the characteristics of the input voltage of the radiation heater with respect to the input current. apparatus.   8. The PWM control according to claim 1, wherein the PWM control is a PWM control with an equal pulse width, and a power factor between an input voltage and an input current to the radiation heater is 100%. Image forming apparatus. A low-voltage power supply circuit that generates a voltage applied to a load other than the radiation heater;
The control unit further includes:
The power consumption of the low-voltage power supply circuit is obtained, the obtained output voltage of the low-voltage power supply circuit, the obtained input voltage to the radiation heater, and the power factor known by the operation mode of the image forming apparatus, Find the input current value to the circuit,
The image forming apparatus according to claim 5, wherein a combined current of the obtained input current to the low-voltage power supply circuit and the obtained input current to the radiation heater is obtained.   The image forming apparatus according to claim 9, wherein the control unit further controls the image forming apparatus so that the obtained value of the combined current becomes a predetermined value or less.   The image forming apparatus according to claim 10, wherein the control unit stops a printing operation by the image forming apparatus or reduces a printing speed.   The control unit according to any one of claims 1 to 9, wherein when the obtained input voltage to the radiation heater exceeds a predetermined value, the control unit stops the operation of the image forming apparatus or notifies the fact. The image forming apparatus described.

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