JP2018155900A - Image forming apparatus, method for controlling heater, and program - Google Patents

Abstract

An image forming apparatus that controls energization timing of a heater based on zero-cross timing is provided with a technique that is not easily affected by variation in responsiveness of a photocoupler. In a printer power supply unit, a current sensor is disposed on a first line connecting a rectifier circuit and a first input terminal to which power from an external AC power source is input, and fixing. When the heater 82 is energized, a point at which the current value output from the current sensor 55 becomes zero is detected and set as a zero-cross point. When the heater 82 is not energized, the peak of the charging current to the smoothing capacitor 431 is detected. Set the zero cross point (zero cross timing). [Selection] Figure 3

Description

  The present invention relates to an image forming apparatus including a heater, a heater control method, and a program.

  2. Description of the Related Art Conventionally, an image forming apparatus that forms an image by an electrophotographic method is known to include a fixing device having a heater and a heating roller heated by the heater. A technique is also known in which a switching element such as a triac is arranged to control energization to the heater so that the surface temperature of the heating roller becomes a desired temperature.

  As a document disclosing the energization control of the heater used in the image forming apparatus, for example, there is Patent Document 1. In Patent Document 1, an image forming apparatus including a zero-cross detection circuit having a bridge diode and a photocoupler, the zero-cross detection circuit outputs a zero-cross detection signal that is turned on at the time of zero-cross of the voltage value of an AC commercial power supply, and a CPU Discloses a configuration for controlling energization to the heater using a zero cross detection signal.

Japanese Patent Laying-Open No. 2004-303469 (for example, FIG. 8)

  In order to reduce the noise generated when switching the switching element and the inrush current generated at the start of power supply to the heater, the image forming apparatus reduces the voltage value of the AC commercial power supply as disclosed in Patent Document 1. The energization timing of the heater is controlled based on the zero cross timing. Therefore, it is desired to detect the zero cross timing with high accuracy. However, when the zero cross timing is detected using a photocoupler as disclosed in Patent Document 1, it is difficult to detect the zero cross timing with high accuracy due to variations in the response of the photocoupler.

  The present invention has been made to solve the above-described problems of the prior art. That is, an object of the present invention is to provide a technique that is less susceptible to variations in response of photocouplers in an image forming apparatus that controls the heater energization timing based on the zero cross timing.

In order to solve the above problems, the image forming apparatus of the present invention has the following configuration.
A converter having a rectifying circuit for rectifying an alternating current from an external power supply; a capacitor for smoothing the current rectified by the rectifying circuit; a first line connecting the external power supply and the converter; A current sensor arranged on one line and outputting a signal corresponding to the amount of current flowing on the first line; a heater; a second line connecting the branch point on the first line and the heater; A switching element disposed on the second line; and a controller, wherein the controller detects a current amount based on a signal from the current sensor, and based on the detected current amount, the capacitor A current amount characteristic corresponding to the charging of the current is detected, a zero cross timing is detected based on the detected current amount characteristic, and the detected zero cross timing is detected. Based on the grayed, controls the switching element, characterized in that.

  An image forming apparatus disclosed in this specification includes a converter having a rectifier circuit that rectifies an alternating current from an external power supply, a capacitor that smoothes the current rectified by the rectifier circuit, an external power supply, and the converter. A first line to be connected, a current sensor arranged on the first line and outputting a signal corresponding to the amount of current flowing on the first line, a heater, a branch point on the first line, and the heater are connected. A second line; a switching element disposed on the second line; and a controller. The controller detects a current amount based on a signal from the current sensor, and a capacitor based on the detected current amount. The current amount characteristic corresponding to the charging of the current is detected, the zero cross timing is detected based on the detected current amount characteristic, and the switch is detected based on the detected zero cross timing. Since controlling the quenching device, by a current sensor on the first line, detects the current amount characteristics corresponding to at least charge (e.g. changes and peaks from zero), it can detect the zero-cross timing from the current amount characteristics.

  A heater control method and program for realizing the functions of the apparatus are also novel and useful.

  According to the present invention, in the image forming apparatus that controls the energization timing of the heater based on the zero cross timing, a technique that is hardly affected by the variation in the response of the photocoupler is realized.

1 is a cross-sectional view illustrating a schematic configuration of a printer according to a first embodiment. FIG. 2 is a block diagram illustrating an electrical configuration of a printer. It is a circuit diagram which shows the electric constitution of a power supply part. It is a flowchart which shows the control procedure concerning heater control. It is a flowchart which shows the control procedure regarding zero cross detection. It is a flowchart which shows the control procedure of a peak detection process and a zero cross detection process. It is drawing which shows the relationship between the change of the voltage value of a commercial power source, and the change of the current value measured with a current sensor. It is drawing which shows the relationship between the change of the electric current value measured with a current sensor, and zero cross detection. It is drawing which shows the relationship between the change of the electric current value measured with the current sensor concerning Embodiment 2, and zero cross detection. It is drawing which shows the relationship between the change of the electric current value measured with the current sensor concerning Embodiment 3, and zero cross detection. It is a flowchart which shows the control procedure of the peak detection process concerning Embodiment 3, and a zero cross detection process. FIG. 6 is a circuit diagram illustrating an electrical configuration of a printer according to a fourth embodiment. 10 is a flowchart illustrating a control procedure related to zero-cross detection according to a fourth embodiment.

(Embodiment 1)
Hereinafter, a printer as an example embodying an image forming apparatus according to the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are drawn with simplified or modified exaggeration as appropriate, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily the same as those in the examples. In the present embodiment, the present invention is applied to a laser printer capable of forming a color image, but it goes without saying that the present invention may be applied to a laser printer capable of forming a monochrome image. Absent.

FIG. 1 is a cross-sectional view illustrating a schematic configuration of the printer according to the first embodiment.
In the figure, a printer 100 is a so-called tandem color laser printer. The printer 100 includes process units 10Y, 10M, 10C, and 10K for each color of yellow (Y), magenta (M), cyan (C), and black (K). The process unit 10 </ b> K includes a photoreceptor 2, a charger 3, and a developing device 4. The other color process units 10Y, 10M, and 10C have the same configuration. In addition, the printer 100 includes a main motor for driving the photosensitive member 2, the developing device 4, and the like. Further, the printer 100 has an exposure device 6 common to each color above the process units 10Y, 10M, 10C, and 10K for each color.

  The exposure device 6 includes a polygon motor for rotationally driving the polygon mirror, a motor driving unit for controlling the polygon motor, and the like.

  Further, the printer 100 includes a transfer belt 7, a thermal fixing device 8, a paper feed tray 91, and a paper discharge tray 92. Further, the heat fixing device 8 includes an upper heating roller 81, a fixing heater 82 disposed in the heating roller 81, a temperature sensor 83 made of, for example, a thermistor element disposed near the heating roller 81, and A pressure roller 84 disposed below the heating roller 81 and a drive motor for driving the heating roller 81 are provided. The heating roller 81 is heated to a predetermined temperature by the fixing heater 82, and the surface temperature of the heating roller 81 is detected by the temperature sensor 83. The heating roller 81 is an example of the rotating body of the present invention, and the fixing heater 82 is an example of the heater of the present invention.

Next, the overall operation of the printer 100 will be briefly described.
The printer 100 is connected to a host device (not shown) such as a personal computer via a network, for example. Further, the printer 100 receives a plurality of print data from a host device and forms an image based on the print data, and a plurality of modes such as a sleep mode and a standby mode that are appropriately set according to the status of the printer 100 when no image is formed. In the following description, the print mode and the sleep mode will be mainly described. In the following description, the entire printing operation in the printing mode will be briefly described. In particular, image formation by the process unit 10K will be described.

  That is, in the printing operation in the printing mode, the printer 100 charges the photoreceptor 2 with the charger 3 and then exposes it with the exposure device 6. Thereby, an electrostatic latent image based on the image data is formed on the surface of the photoreceptor 2. Further, the printer 100 forms a toner image by developing the electrostatic latent image with the developing device 4.

  Further, the printer 100 pulls out the sheets stored in the paper feed tray 91 one by one and conveys them to the transfer belt 7. The transfer belt 7 includes a transfer roller 5 on the inner side of the contact position with the photosensitive member 2, and transfers the toner image on the photosensitive member 2 to the sheet when the sheet passes between the photosensitive member 2 and the transfer roller 5. To do. Further, the printer 100 heats the toner image placed on the sheet by the heating roller 81 of the heat fixing device 8 when the sheet passes between the heating roller 81 and the pressure roller 84 of the heat fixing device 8. To heat-fix the sheet. Thus, the sheet on which the image is formed is discharged to the paper discharge tray 92.

  When performing color printing, the printer 100 forms toner images of the respective colors in the process units 10Y, 10M, and 10C of other colors, and sequentially transfers them to a sheet. Thereby, the toner images of the respective colors are superimposed on the sheet. Then, a color image is formed by fixing the superimposed toner images on the sheet.

FIG. 2 is a block diagram showing the electrical configuration of the printer. Next, the electrical configuration of the printer 100 will be described with reference to FIG.
That is, the printer 100 includes a controller 30 including a CPU 31, a ROM 32, a RAM 33, and an NVRAM (nonvolatile RAM) 34. The printer 100 includes a motor 11 as an example of a DC 24V load, an operation panel 35, a network interface 36, a USB interface 37, and a heat fixing device 8, which are electrically connected to the controller 30. Yes. The motor 11 may be a main motor for driving the photosensitive member 2 and the developing unit 4, a polygon motor provided in the exposure unit 6, or a driving motor for driving the heating roller 81. It may be a combination thereof.

  Further, the printer 100 includes a power supply unit 40 that is electrically connected to the controller 30. In the printing mode, the power supply unit 40 supplies power to the controller 30, the motor 11, and the fixing heater 82 of the heat fixing unit 8. Connected so that it can be supplied.

  The ROM 32 stores various control programs for controlling the printer 100, various settings, initial values, and the like. The RAM 33 is used as a work area from which various control programs are read, or as a storage area for temporarily storing data. The CPU 31 controls each component of the printer 100 while storing the processing result in the RAM 33 or the NVRAM 34 according to the control program read from the ROM 32. The RAM 33 or the NVRAM 34 is an example of the storage unit of the present invention.

  The network interface 36 is hardware for communicating with a host device connected via a network. The USB interface 37 is hardware for communicating with a device connected based on the USB standard. The operation panel 35 is hardware that is responsible for displaying a notification to the user and receiving an instruction input by the user.

FIG. 3 is a circuit diagram showing the electrical configuration of the power supply unit. Next, the electrical configuration of the power supply unit 40 will be described with reference to FIG. 3.
In the figure, an AC power of 100 V, for example, is supplied from an external power source 411 to a first input terminal 41 constituting a power input unit of the power supply unit 40. The voltage of the external power supply 411 is not limited to 100V, and may be 200V, for example. Note that the external power source 411 is configured by a commercial AC power source outside the printer 100.

  The input terminal of the noise filter 60 is connected to the first input terminal 41 via the first line L1 and the second line L2. The noise filter 60 removes noise from the subsequent stage of the noise filter 60.

  An AC / DC converter 43 is connected to the output terminal of the noise filter 60. The AC / DC converter 43 is connected between the rectifier circuit 42 formed of a diode bridge connected to the output terminal of the noise filter 60 and the output terminal of the rectifier circuit 42, and the smoothing capacitor 431 that smoothes the output current of the rectifier circuit 42. And a transformer 432 having a primary winding connected between the output terminals of the rectifier circuit 42 via a switching element 433, and a rectifying / smoothing circuit 44.

  Therefore, AC power supplied from the first input terminal 41 and output from the output terminal of the noise filter 60 is full-wave rectified by the rectifier circuit 42 and then smoothed by the smoothing capacitor 431. The smoothing capacitor 431 is an example of the capacitor of the present invention, and the AC / DC converter 43 is an example of the converter of the present invention. Further, the smoothing capacitor 431 may be composed of a plurality of capacitors connected in parallel.

  The rectifying / smoothing circuit 44 connected to the secondary winding of the transformer 432 includes a rectifying element 441 and a smoothing capacitor 442, and after rectifying the power output from the secondary winding of the transformer 432 by the rectifying element 441, The output is smoothed by the capacitor 442. For example, the DC 24V power output from the rectifying / smoothing circuit 44 is supplied to the DC 24V load represented by the motor 11 via the first output terminal 45.

  Further, the DC / DC converter 46 is connected to the first output terminal 45 via the second input terminal 52, and therefore, the DC 24V power output from the first output terminal 45 is the DC / DC converter. 46. The DC / DC converter 46 converts 24V power to 3.3V, and the power output from the DC / DC converter 46 is supplied to the controller 30 and the like.

  A shunt regulator 61 is connected between the output side of the rectifying / smoothing circuit 44 and the first output terminal 45. Therefore, the output voltage of the rectifying / smoothing circuit 44 is detected and error amplified by the shunt regulator 61 and fed back to the power supply control IC 63 via the photocoupler 62.

  The power supply control IC 63 is for switching control of the switching element 433 of the AC / DC converter 43.

  One end side of the third line L3 is connected to the first branch point P1 provided on the first line L1, and the other end side of the third line L3 is fixed via the electromagnetic relay 49. The heater 82 is connected to one terminal. The electromagnetic relay 49 is an example of the relay member of the present invention.

  In addition, one end side of the fourth line L4 is connected to the second branch point P2 provided on the second line L2, and the other end side of the fourth line L4 is, for example, from a triac element. It is connected to the other terminal of the fixing heater 82 through the configured switching element 50. The switching element 50 is an example of the switching element of the present invention.

  The energization timing of the switching element 50 is controlled by a heater control signal from the controller 30 via the phototriac coupler 51. When the switching element 50 continuously receives an ON signal from the controller 30, the switching element 50 continues to be energized even at the next zero cross timing, and when the ON signal is not continuously received from the controller 30, the next external power supply A non-energized state is established at the zero cross timing of the voltage input from 411. The zero cross timing of the voltage input from the external power supply 411 corresponds to the timing at which the voltage value of the external power supply 411 input from the first input terminal 41 passes zero volts.

  In the present embodiment, the electromagnetic relay 49 is disposed on the third line L3 and the switching element 50 is disposed on the fourth line L4. However, the electromagnetic relay 49 is disposed on the third line L3 or the fourth line L4. The electromagnetic relay 49 and the switching element 50 may be arranged in series. The first branch point P1 and the second branch point P2 are examples of the branch point of the present invention, and the third line L3 and the fourth line L4 are examples of the second line of the present invention. .

  The contact of the electromagnetic relay 49 is controlled by a relay control signal from the controller 30.

  That is, in the printing mode, the electromagnetic relay 49 is controlled to be in a closed state (energized state) by a relay control signal from the controller 30, and in the sleep mode, the contact is controlled to be in an open state (non-energized state). . Further, in the printing mode, when opening of the cover is detected via a switch (not shown) for detecting opening / closing of the cover of the printer 100, the energized state is changed to the non-energized state by the relay control signal from the controller 30. It is controlled and the safety of the device is ensured.

  The phototriac coupler 51 outputs a control signal to the switching element 50 based on the heater control signal from the controller 30. As a result, when the switching element 50 continuously receives the ON signal from the controller 30, the switching element 50 continues to be energized at the next zero cross timing, and when the ON signal is not continuously received from the controller 30, the switching element 50 comes next. The external power supply 411 is turned off at the zero cross timing.

  Therefore, in the printing mode, the first line L1, the first branch point P1, the third line L3, the electromagnetic relay 49, the switching element 50, the fourth line L4, the second branch point P2, and the second line. Electric power is supplied from the external power source 411 to the fixing heater 82 via L2, thereby heating the heating roller 81. Further, when the electromagnetic relay 49 or the switching element 50 is in a non-energized state, power is not supplied to the fixing heater 82.

  Between the first input terminal 41 and the first branch point P1 on the first line L1, for example, a hall-type current sensor 55 using a Hall element is disposed, and the first line L1 It is possible to measure the current value of the alternating current flowing above. Specifically, the current sensor 55 has a sampling period sufficiently finer than half of the AC period of the power supplied from the external power supply 411 and sufficiently finer than a time width in which one capacitor input current is generated. The value can be measured. The measured current value is output to the controller 30 as a current sensor signal via the second output terminal 47 and the third input terminal 48 in real time. The current sensor 55 is an example of the current sensor of the present invention.

  As the current sensor, instead of the current sensor 55 capable of measuring the absolute value of the current value of the alternating current flowing on the first line L1, the relative value of the alternating current relative to the current value of zero is used. It is also possible to use a comparative current sensor capable of measuring the current amount, and the current value and the relative current amount are examples of the current amount of the present invention. Further, the current sensor 55 may be disposed between the first input terminal 41 on the second line L2 and the second branch point P2. The first line L1 and the second line L2 are examples of the first line of the present invention.

  FIG. 7 shows a waveform of a current value measured by the current sensor 55. In the printing mode, the smoothing capacitor 431 is discharged by the power supplied to the controller 30 or the like, and the terminal voltage is lowered. Thereafter, when the voltage of the power supplied from the external power supply 411 rises, the voltage output from the rectifier circuit 42 rises and exceeds the terminal voltage of the smoothing capacitor 431, so that the smoothing capacitor 431 is rapidly charged. . Therefore, as shown on the left side of FIG. 7, the current value measured by the current sensor 55 changes while taking a steep pulse-like value with an interval as time passes.

  Here, “charging” includes a charging process and / or full charging, and may also be referred to as capacitor input. Further, a change in current value (amount of current) with the passage of time is an example of a current amount characteristic of the present invention.

  Further, in a state where power is supplied to the fixing heater 82 in the printing mode, in addition to the rapid charging current to the smoothing capacitor 431, the power supplied to the fixing heater 82 is combined.

  Further, in the sleep mode, the power output from the AC / DC converter 43 is not supplied to the 24V load, is supplied only to the controller 30, and further, the power is not supplied to the fixing heater 82. When the power is supplied to the controller 30, only the capacitor input current generated is mainly seen as a waveform.

  FIG. 4 is a flowchart showing a control procedure related to heater control. Next, the control procedure will be described with reference to FIG. Note that the control shown in FIG. 4 is executed by the controller 30 at predetermined time intervals during the print mode period.

  That is, first, in step 1 (hereinafter referred to as S1), the controller 30 determines whether or not printing based on print data from the host device is continuing, and if printing is not continuing (S1: NO). This process ends.

  On the other hand, if printing is continuing (S1: YES), the controller 30 compares the detected temperature value of the temperature sensor 83 with the reference temperature value in S2. In S3, if the detected temperature value of the temperature sensor 83 exceeds the reference temperature value in the comparison of S2, it is determined that power supply to the fixing heater 82 is not necessary (S3: NO), and the process returns to S1. .

  If the detected temperature value of the temperature sensor 83 is lower than the reference temperature value in the comparison of S2, the controller 30 determines that power supply to the fixing heater 82 is necessary (S3: YES), and proceeds to S4. To do.

  Next, in S4, the controller 30 controls the switching element 50 to the energized state based on the zero cross timing updated in the processing of S17 and S22 shown in FIG. Is then fed back to S1.

  As described above, in the present embodiment, when the heating roller 81 is heated, the switching element 50 is energized and controlled based on the latest zero cross timing updated in real time, that is, based on the highly accurate zero cross timing, and the fixing heater 82 is supplied with power. Is supplied. Therefore, there is a low possibility that a sudden inrush current or noise is generated with the energization control of the switching element 50. The process of S4 is an example of the switching element control step and the switching element control process of the present invention.

  FIG. 5 is a flowchart showing a control procedure related to zero cross detection. Next, the control procedure will be described with reference to FIG. The control shown in FIG. 5 is activated when the printer 100 is turned on or when print data is received from the host device and the printer 100 is shifted to the print mode. After that, the controller is set at predetermined time intervals during the print mode period. 30.

  That is, in S11, the AC / DC converter 43 oscillates by repeatedly turning the switching element 433 on and off repeatedly in a short time by the power supply control IC 63, whereby power is supplied from the power supply unit 40 to the controller 30 and the like. (S12).

  Next, in S13, the controller 30 continuously acquires the output value of the current sensor 55, that is, the current value. After that, in S14, the controller 30 charges the smoothing capacitor 431 based on the acquired current value. The value peak detection process and the zero cross detection process, that is, the subroutine shown in FIG. 6 is executed.

FIG. 6 is a flowchart showing the control procedure of the peak detection process and the zero-cross detection process. Next, details of the peak detection process and the zero-cross detection process will be described with reference to FIGS.
That is, in S41, the controller 30 detects the timing X1 based on the acquired current value by continuously acquiring the current value of the current sensor 55. As shown in FIG. 8, the timing X1 is a timing at which the current value of the current sensor 55 falls below the threshold value −α.

  Next, in S42, the controller 30 detects the timing X2 based on the acquired current value by continuously acquiring the current value of the current sensor 55. As shown in FIG. 8, the timing X2 is a timing at which the current value of the current sensor 55 exceeds the threshold value −α.

Next, in S43, the controller 30 calculates the peak timing P11 shown in FIGS. 7 and 8 based on the detected timing X1 and timing X2. The peak timing P11 of the charging current value to the smoothing capacitor 431 can be detected by calculating the following equation. The timing P11 is an example of the first timing of the present invention.
P11 = X1 + (X2-X1) / 2

  Next, in S44, the controller 30 detects the timing Y1 based on the acquired current value by continuously acquiring the current value of the current sensor 55. This timing Y1 is a timing at which the current value of the current sensor 55 exceeds the threshold value α as shown in FIG.

  Next, in S45, the controller 30 detects the timing Y2 based on the acquired current value by continuously acquiring the current value of the current sensor 55. This timing Y2 is a timing when the current value of the current sensor 55 falls below the threshold value α as shown in FIG. Note that the threshold value α and the threshold value −α are examples of the first predetermined amount of the present invention.

Next, in S46, the controller 30 calculates the peak timing P12 of the charging current value shown in FIGS. 7 and 8 based on the timing Y1 and the timing Y2. The peak timing P12 of the charging current value to the smoothing capacitor 431 can be detected by calculating the following equation. Timing P12 is an example of the second timing of the present invention.
P12 = Y1 + (Y2-Y1) / 2

Next, in S47, the controller 30 calculates the zero-cross point Z1 shown in FIGS. 7 and 8 based on the charging current value peak timing P11 and the charging current value peak timing P12. This zero cross point Z1 can be detected by calculating the following equation.
Z1 = P11 + (P12-P11) / 2

  In this way, the zero cross point (for example, indicated by Z1 in FIGS. 7 and 8) is detected by sequential calculation based on the current value of the current sensor 55 that changes with time. The zero cross point Z1 is stored in the RAM 33 or the NVRAM 34 as elapsed time information (time stamp). The zero cross point Z1 is an example of the zero cross timing, and the zero cross timing may be stored in the RAM 33 or the NVRAM 34 as a time difference between the previously detected zero cross timing and the next (current) zero cross timing. .

  The processes of S41 to S43 and S44 to S46 are examples of the current amount detection step, the current amount characteristic detection step, the current amount detection process, and the current amount characteristic detection process of the present invention, and the process of S47 is the present invention. It is an example of a zero cross timing detection step and a zero cross timing detection process.

The description of the subroutine shown in FIG. 6 is completed, and the description returns to the description of the control procedure related to zero cross detection shown in FIG.
That is, in S15, the controller 30 controls the energized state by closing the contact of the electromagnetic relay 49 based on the zero cross point Z1 (zero cross timing) set in S14, and proceeds to the next S16. Thus, in this embodiment, since the electromagnetic relay 49 is controlled based on the zero cross point Z1 set in S14, there is a possibility that noise is generated in the electromagnetic relay 49 and the switching element 433 at that time. In addition, the electrical load on the contacts of the electromagnetic relay 49 is reduced, and the influence on the life is low.

  Next, in S16, the controller 30 determines whether or not the fixing heater 82 is energized. If it is determined that power is being supplied (S16: YES), in S17, the controller 30 continuously acquires the current value of the current sensor 55, and at the timing when the acquired current value becomes zero. Based on this, the zero cross point is detected, then the zero cross point stored in the RAM 33 or NVRAM 34 is updated, and the process returns to S16.

  Specifically, while the fixing heater 82 is energized, the current sensor 55 also adds and measures the alternating current supplied to the fixing heater 82, so the current value output from the current sensor 55 is as shown in FIG. As shown on the right side, the value changes so as to swing up and down continuously with the passage of time. Therefore, the controller 30 detects a point where the current value becomes zero (for example, indicated by P13 in FIG. 7) and sets it as a zero cross point (for example, indicated by Z2 in FIG. 7). In this manner, while the fixing heater 82 is energized, S16 to S17 are sequentially executed, whereby the zero cross point Z2 stored in the RAM 33 or NVRAM 34 is sequentially updated to the latest zero cross point Z2.

  At this time, the timing when the current value becomes zero and the zero cross point Z2 are stored in the RAM 33 or the NVRAM 34 as elapsed time information (time stamp). The zero cross point Z2 is an example of the zero cross timing, and the zero cross timing may be stored in the RAM 33 or the NVRAM 34 as a time difference between the previously detected zero cross timing and the next (current) zero cross timing. .

  In S16, when the controller 30 determines that the energization is not performed (S16: NO), the process proceeds to S18, where it is determined again whether the fixing heater 82 is not energized. If it is determined that the current is not energized (S18: YES), the process proceeds to S19, and the controller 30 continues the detected peak of the charging current to the steep pulsed smoothing capacitor 431 more than the predetermined number A. It is then determined whether it has been detected. If it is equal to or less than the predetermined number A (S19: NO), in the next S20, the controller 30 continuously acquires the output value of the current sensor 55, that is, the current value.

  Thereafter, in S21, the controller 30 executes the subroutine shown in FIG. 6 and then returns to S18. Note that the determination in S19 is made based on the number of later-described time information stored in the RAM 33 or the NVRAM 34, or the number of time difference information between the previously detected zero cross timing and the next (current) zero cross timing. The Further, as the predetermined number A, a number of 3 to 10 is set.

On the other hand, when more than the predetermined number A is continuously detected (S19: YES), the controller 30 proceeds to S22 and executes the latest zero cross point (for example, FIG. 7) calculated by executing S21. Is stored in place of the zero cross point stored in the RAM 33 or the NVRAM 34 and sequentially updated to the latest zero cross point. The process of S21 is an example of the current detection step and the zero cross detection step of the present invention.
As described above, while the fixing heater 82 is not energized, S18 to S22 are sequentially executed, whereby the zero-cross points stored in the RAM 33 or the NVRAM 34 are sequentially updated to the latest one.

  As described above, in the present embodiment, the zero cross point is set when the predetermined number A or more of the peaks of the charging current to the smoothing capacitor 431 are detected. Therefore, the zero cross point can be set with high accuracy. Further, when no current is applied, the zero cross point (for example, indicated by Z1 in FIG. 7) is detected by detecting the peak of the charging current to the smoothing capacitor 431 (for example, indicated by P11 and P12 in FIG. 7) and calculating the middle thereof. Therefore, the zero cross point can be detected with high accuracy, and the latest zero cross point is sequentially updated. As a result, the switching element 50 can be switched at an appropriate timing, so that inrush current and noise generated during energization control of the fixing heater 82 can be reduced.

  On the other hand, if it is determined in S18 that the fixing heater 82 is not de-energized (S18: NO), the controller 30 proceeds to S23 and determines whether or not printing is finished. If it is determined that printing is complete (S23: YES), this process ends. On the other hand, if it is determined that printing is not finished (S23: NO), the controller 30 returns to S16 and repeats the above-described processing from S16 to S23. As a result, the latest zero cross point is always detected and updated and stored in the RAM 33 or NVRAM 34.

(Embodiment 2)
FIG. 9 is a diagram illustrating a relationship between a change in the current value measured by the current sensor according to the second embodiment, peak detection, and zero-cross detection, and details thereof will be described below with reference to FIGS. 9 and 6. . In addition, in the description, the same code | symbol is attached | subjected and demonstrated to what has the same effect as Embodiment 1. FIG.
That is, in the first embodiment, when detecting the peak of the current value measured by the current sensor, the detection of the timing X1, the timing X2, the timing Y1, and the timing Y2 in S41, S42, S44, and S45 shown in FIG. In the present embodiment, charging to the smoothing capacitor 431 measured by the current sensor 55 is obtained by comparing the charging current value to the smoothing capacitor 431 measured by the current sensor 55 with the threshold value −α and the threshold value α. A change amount of the current value per unit time, that is, a differential value, a threshold value Y, and a threshold value -Y are used. The threshold value Y and the threshold value -Y are examples of the second predetermined amount of the present invention.

Specifically, in the control procedure of the peak detection process and the zero cross detection process shown in FIG.
That is, in S41, the controller 30 continuously acquires the current value of the current sensor 55, and changes the timing per unit time of the acquired current value, that is, the timing X1 based on the differential value of the current value of the current sensor 55. To detect. As shown in FIG. 9, the timing X1 is the timing at which the differential value of the current value of the current sensor 55 reaches the threshold Y only after rising from zero.

  Next, in S42, the controller 30 continuously acquires the differential value of the current value of the current sensor 55, based on the amount of change per unit time of the acquired current value, that is, based on the differential value of the current value of the current sensor 55. The timing X2 is detected. As shown in FIG. 9, this timing X2 is a timing at which the differential value of the current value of the current sensor 55 rises from zero and reaches the threshold value -Y for the second time. That is, in one charging waveform, there are two timings when the differential value of the current value passes the threshold value Y and the threshold value -Y, and among the four timings, X1 is the timing when the threshold value is first passed, and X2 Is the timing when the threshold value is finally passed.

  Next, in S44, the controller 30 continuously obtains the current value of the current sensor 55, based on the amount of change per unit time of the obtained current value, that is, based on the differential value of the current value of the current sensor 55, the timing Y1. Is detected. As shown in FIG. 9, the timing Y1 is the timing at which the differential value of the current value of the current sensor 55 reaches the threshold Y only after rising from zero.

  Next, in S45, the controller 30 continuously acquires the current value of the current sensor 55, based on the amount of change per unit time of the acquired current value, that is, based on the differential value of the current value of the current sensor 55, the timing Y2 Is detected. As shown in FIG. 9, this timing Y2 is the timing at which the differential value of the current value of the current sensor 55 rises from zero and reaches the threshold value for the fourth time.

  As described above, in the present embodiment, by using the amount of change per unit time of the charging current value to the smoothing capacitor 431 measured by the current sensor 55, that is, the differential value, the change in the charging current can be grasped more accurately. It is possible to set the zero cross point accurately.

(Embodiment 3)
FIG. 10 is a diagram illustrating a relationship between a change in current value measured by the current sensor according to the third embodiment and peak detection and zero-cross detection. FIG. 11 is a control procedure of peak detection processing and zero-cross detection processing. The details will be described below with reference to FIGS. 10 and 11. In addition, in the description, the same code | symbol is attached | subjected and demonstrated to what has the same effect as Embodiment 1. FIG.

  That is, in the first embodiment, when the peak of the current value measured by the current sensor is detected, the timing X1, the timing X2, the timing Y1, and the timing Y2 shown in FIG. 8 are obtained in S41, S42, S44, and S45 shown in FIG. Thereafter, in S43 and S46, the peak timing P11 of the charging current value and the peak timing P12 of the charging current value were obtained based on these timing X1, timing X2, timing Y1 and timing Y2.

  However, in the present embodiment, as in the first embodiment, S41, S42, S44 and S45 shown in FIG. 6 are not executed, that is, the timing X1, the timing X2, the timing Y1 and the timing Y2 shown in FIG. 8 are obtained. Instead, in S51 and S51 shown in FIG. 11, the amount of change per unit time of the charging current to the smoothing capacitor 431 measured by the current sensor 55, that is, the differential value and the predetermined amount (threshold) Y are used. Thus, the charging current value peak timing P11 and the charging current value peak timing P12 are obtained.

  That is, in this embodiment, in S51 shown in FIG. 11, the controller 30 determines that the amount of change per unit time of the charging current value to the smoothing capacitor 431 measured by the current sensor 55, that is, the absolute value of the differential value is After exceeding a predetermined amount (threshold value) Y, the timing when it becomes zero, that is, the timing when the positive / negative of the differential value of the charging current value is switched is detected as the peak timing P11 of the charging current value.

  Next, in S52, the controller 30 changes the amount of change of the next charging current value per unit time, that is, the timing when the absolute value of the differential value becomes zero after exceeding the predetermined amount (threshold value) Y, that is, The timing at which the positive / negative of the differential value of the charging current value switches is detected as the peak timing P12 of the charging current value.

  Thus, in this embodiment, the amount of change per unit time of the charging current to the smoothing capacitor 431, that is, the differential value is used, and the absolute value of the differential value of the charging current value to the smoothing capacitor 431 is a predetermined amount. Since the timing when it becomes zero after exceeding (threshold) Y, that is, the timing when the positive / negative of the differential value of the charging current value is switched is detected as the timing (P11, P12) of the charging current value, the zero cross point Can be accurately detected.

  In the present embodiment, only the predetermined amount (threshold) Y is used. However, using the predetermined amount (threshold) Y and the predetermined amount (threshold) −Y, the differential value of the current value of the current sensor 55 is the threshold Y. Current sensor until the second threshold value -Y is reached (passed) or until the threshold value -Y is reached (passed) until the threshold value Y is reached (passed). The timing at which the differential value of the current value 55 becomes zero, that is, the timing at which the positive / negative of the differential value of the charging current value is switched may be detected as the peak timing (P11, P12) of the charging current value.

(Embodiment 4)
FIG. 12 is a circuit diagram illustrating the electrical configuration of the printer according to the fourth embodiment, and the details thereof will be described below with reference to FIG. In addition, in the description, the same code | symbol is attached | subjected and demonstrated to what has the same effect as Embodiment 1. FIG.

  In other words, the present embodiment is different from the first embodiment in the arrangement position of the current sensor 55. In the present embodiment, the first branch point P1 and the rectifier circuit 42 on the first line L1 are arranged. Has been placed. Therefore, the current sensor 55 can measure only the charging current value to the smoothing capacitor 431. The current sensor 55 may be disposed between the second branch point P2 and the rectifier circuit 42 on the second line L2.

  As described above, in the present embodiment, the current sensor 55 only measures the charging current to the smoothing capacitor 431, and thus a small current sensor 55 corresponding to the magnitude of the charging current can be used. The detection accuracy can be improved.

  FIG. 13 is a flowchart showing a control procedure related to zero-cross detection. Next, the control procedure will be described with reference to FIG. The control shown in FIG. 13 is activated when the printer 100 is turned on or when print data is received from the host device and the print mode is shifted from the sleep mode. After that, during the print mode period, a predetermined time interval is used. And executed by the controller 30. In the description, S31 to S35 shown in FIG. 13 are the same as S11 to S15 shown in FIG.

  That is, the controller 30 proceeds to S36 after processing S35. In S36, the controller 30 continuously acquires the output value from the current sensor 55, that is, the current value, and proceeds to S37.

  Next, in S37, the controller 30 executes a subroutine shown in FIG. 6 to calculate a zero cross point (for example, indicated by Z1 in FIG. 6), and updates the zero cross point stored in the RAM 33 or NVRAM 34 (S38). .

  Thereafter, in S39, the controller 30 determines whether or not the printing is finished, and when it is judged that the printing is finished (S39: YES), the process is finished. On the other hand, when it is determined that the printing is not finished (S39: NO), the controller 30 returns to S36 and repeats the processes from S36 to S39 described above. As a result, the zero cross points stored in the RAM 33 or the NVRAM 34 are sequentially updated.

  Thus, the zero cross point updated and stored in the RAM 33 or the NVRAM 34 in S38 is used in the energization control of the heater in S4 shown in FIG. As described above, in this embodiment, the peak of the charging current to the smoothing capacitor 431 (for example, indicated by P12 and P11 in FIG. 7) is detected and the zero cross point (for example, indicated by Z1 in FIG. 7) is set. Therefore, it is possible to set the zero cross point with high accuracy, and thereby it is possible to reduce inrush current and generated noise during energization control of the fixing heater 82.

  In addition, this Embodiment is only a mere illustration and does not limit this invention at all. Therefore, the present invention can be variously improved and modified without departing from the scope of the invention. For example, the image forming apparatus is not limited to a printer, and can be applied as long as it has a function of forming an image by an electrophotographic method, such as a copier, a FAX apparatus, or a multifunction peripheral. The printer 100 according to the embodiment is a color printer and includes four process units 10K, 10C, 10M, and 10Y. However, the printer 100 may be a monochrome printer including one process unit.

  In the first embodiment, when the fixing heater 82 is energized, in S17, the current value of the current sensor 55 is continuously acquired, and the zero cross point is set based on the acquired current value of zero. However, the peak value of the current value output from the current sensor 55 (for example, indicated by P14 and P15 in FIG. 7) is detected, and the intermediate point thereof is the zero cross point (for example, indicated by Z3 in FIG. 7). And the zero cross point stored in the RAM 33 or the NVRAM 34 may be updated.

  In the above-described case, when a certain threshold value is set and the fixing heater 82 is energized, the zero cross point is estimated using the peak value of the current value output from the current sensor 55 that exceeds the set threshold value. When the fixing heater 82 is not energized, the zero cross point is estimated using the peak value of the charging current to the smoothing capacitor 431 output from the current sensor 55 that is below the set threshold value. You can do that. In this way, the zero cross point can be estimated with higher accuracy.

  In the first embodiment, when the fixing heater 82 is not energized, the zero cross point is set based on the peak of the charging current to the smoothing capacitor 431. In the initial state of switching from energization to non-energization, the zero cross point detected and set during energization of the fixing heater 82 may be used. However, when the time elapses, it may differ from the actual zero cross timing of the commercial power. Therefore, it is desirable to set the zero cross point based on the peak of the charging current to the smoothing capacitor 431 after the predetermined time elapses.

  In the first to fourth embodiments, the peak of the charging current to the smoothing capacitor 431 (for example, indicated by P12 in FIG. 7) is detected, and the peak of the adjacent charging current (for example, indicated by P11 in FIG. 7). ) Is set as a zero cross point (for example, indicated by Z1 in FIG. 6), but is not an intermediate point between adjacent charging current peaks (for example, indicated by P11 in FIG. 7). A point corrected by a correction value from a point (zero cross point) may be set as the zero cross timing.

  Further, in the first to fourth embodiments, the peak of the charging current to the smoothing capacitor 431 (for example, indicated by P12 in FIG. 7) is detected, and the peak of the adjacent charging current (for example, indicated by P11 in FIG. 7). Is set as a zero cross point (for example, indicated by Z1 in FIG. 6), but the correction value COR is added to the peak of the charging current to the smoothing capacitor 431 (for example, indicated by P12 in FIG. 7). An intermediate point between the timing obtained by adding the correction value COR to the adjacent charging current peak (for example, indicated by P11 in FIG. 7) may be set as the zero cross timing.

DESCRIPTION OF SYMBOLS 100 Printer 6 Exposure device 8 Thermal fixing device 81 Heating roller 82 Fixing heater 83 Temperature sensor 30 Controller 31 CPU
40 power supply unit 41 first input terminal 42 rectifier circuit 43 AC / DC converter 431 smoothing capacitor 50 switching element 55 current sensors L1 to L4 first to fourth lines P1 to P2 first to second branch points

Claims (13)

A converter having a rectifier circuit for rectifying an alternating current from an external power source, and a capacitor for smoothing the current rectified by the rectifier circuit;
A first line connecting the external power supply and the converter;
A current sensor disposed on the first line and outputting a signal corresponding to the amount of current flowing on the first line;
A heater,
A second line connecting the branch point on the first line and the heater;
A switching element disposed on the second line;
A controller,
With
The controller is
Detecting the amount of current based on the signal from the current sensor;
Based on the detected current amount, a current amount characteristic corresponding to charging of the capacitor is detected,
Based on the detected current amount characteristic, zero cross timing is detected,
Controlling the switching element based on the detected zero-cross timing;
An image forming apparatus. The image forming apparatus according to claim 1,
The controller is
Detecting a timing between a first timing at which the current amount characteristic is detected and a second timing at which the current amount characteristic is detected after the first timing as the zero cross timing;
An image forming apparatus. The image forming apparatus according to claim 1 or 2,
The controller is
Detecting the timing at which the detected magnitude of the current quantity passes through a first predetermined quantity smaller than the magnitude of the peak quantity of the current quantity in charging the capacitor as the current quantity characteristic;
An image forming apparatus. The image forming apparatus according to claim 1,
The controller is
As the current amount characteristic, a timing at which the positive / negative of the detected change amount of the current amount is switched is detected.
An image forming apparatus. The image forming apparatus according to claim 1 or 2,
The controller is
Detecting the timing at which the magnitude of the detected change amount of the current amount passes the second predetermined amount as the current amount characteristic;
An image forming apparatus. The image forming apparatus according to any one of claims 1 to 3,
A relay member for opening and closing the second line;
The controller is
Based on the detected zero cross timing, determine the timing to output a close command to the relay member,
An image forming apparatus. The image forming apparatus according to any one of claims 1 to 6,
An image forming unit for forming a toner image on a sheet;
A rotating body that is heated by the heater and contacts a sheet on which a toner image is formed by the image forming unit;
A temperature sensor that outputs different signals according to the temperature of the rotating body;
With
The controller is
Controlling the switching element based on a signal from the temperature sensor;
An image forming apparatus. The image forming apparatus according to any one of claims 1 to 7,
The current sensor is disposed on the first line and between the external power source and the branch point.
An image forming apparatus. The image forming apparatus according to claim 8.
The controller is
In the state where the heater is not energized, the current amount characteristic is detected based on the detected current amount.
An image forming apparatus. The image forming apparatus according to claim 8 or 9, wherein
A storage unit,
The controller is
Storing the zero cross timing detected during the first state in which power is supplied to the heater in the storage unit;
From the first state to the second state in which power is not supplied to the heater,
The zero cross timing for a predetermined number of times after changing from the first state to the second state is specified from the zero cross timing stored in the storage unit,
After the number of times of the zero cross timing after the change from the first state to the second state exceeds the predetermined number of times, the zero cross timing is determined based on the detected current amount characteristics;
An image forming apparatus. The image forming apparatus according to any one of claims 1 to 7,
The current sensor is disposed on the first line and between the branch point and the converter.
An image forming apparatus. A converter having a rectifier circuit for rectifying an alternating current from an external power source, and a capacitor for smoothing the current rectified by the rectifier circuit;
A first line connecting the external power supply and the converter;
A current sensor disposed on the first line and outputting a signal corresponding to the amount of current flowing on the first line;
A heater,
A second line connecting the branch point on the first line and the heater;
A switching element disposed on the second line;
A method of controlling the heater of an image forming apparatus comprising:
A current amount detection step of detecting a current amount based on a signal from the current sensor;
A current amount characteristic detection step for detecting a current amount characteristic corresponding to charging of the capacitor based on the detected current amount;
A zero-cross timing detection step for detecting zero-cross timing based on the detected current amount characteristic;
A switching element control step for controlling the switching element based on the detected zero-cross timing;
A method for controlling the heater, comprising: A converter having a rectifier circuit for rectifying an alternating current from an external power source, and a capacitor for smoothing the current rectified by the rectifier circuit;
A first line connecting the external power supply and the converter;
A current sensor disposed on the first line and outputting a signal corresponding to the amount of current flowing on the first line;
A heater,
A second line connecting the branch point on the first line and the heater;
A switching element disposed on the second line;
An image forming apparatus comprising:
A current amount detection process for detecting a current amount based on a signal from the current sensor;
A current amount characteristic detection process for detecting a current amount characteristic corresponding to charging of the capacitor based on the detected current amount;
Zero-cross timing detection processing for detecting zero-cross timing based on the detected current amount characteristic;
A switching element control process for controlling the switching element based on the detected zero-cross timing;
A program characterized by having executed.

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