JP2012237873A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device with an induction heater that controls electric power with high accuracy even if an input voltage to be applied to an induction heating coil has waveform distortion.SOLUTION: The image forming device includes: peak voltage detection means 107 for detecting a peak value of an input voltage to be input to a coil 103; effective voltage detecting means 108 for detecting an effective value of the input voltage; voltage value determining means for determining a voltage value for calculating power on the basis of the peak value of the input voltage and the effective value of the input voltage; and power control means for controlling power to be supplied to a fixing device using the determined voltage value.

Description

  The present invention relates to an image forming apparatus including an induction heating device used to heat a heating element of a fixing device.

  For example, image forming apparatuses such as copiers, printers, facsimiles, and the like, and multifunction digital image forming apparatuses called MFP (Multi Function Peripherals) that integrate the functions of these apparatuses include a heating element of a fixing device. Some heating sources include an induction heating device.

  As such an induction heating device, for example, a commercial AC voltage is full-wave rectified and converted into a direct current and applied to a coil for induction heating, for example, and an insulated gate bipolar transistor connected in series with the coil for induction heating, for example 2. Description of the Related Art Conventionally, a system that controls power supplied to a heating element of a fixing device by controlling on / off of a switching element made of (IGBT: Insulated Gate Bipolar Transistor) has been used.

  In this case, the amount of power supplied to the heating element of the fixing device varies depending on the duty ratio of the on / off of the switching element. Conventionally, the peak value of the input voltage and the heating element are heated to a predetermined temperature. The duty ratio is determined from the necessary power value (for example, Patent Document 1).

JP 2003-098860 A

  By the way, during the operation of the induction heating apparatus, voltage fluctuation may occur in commercial input AC (50/60 Hz). If the peak value of the fluctuating input voltage is large, the switching for switching the induction heating coil is performed. An excessive voltage may be applied to the element, and the switching element may be destroyed.

  In addition, distortion of the input voltage waveform has a great influence on the power supply. The distortion of the input voltage waveform is a phenomenon that occurs due to the deterioration of the generator and is often seen in the third region. When waveform distortion occurs, the relationship between the actual effective voltage Vrms and the peak voltage Vp at the input voltage deviates from the relationship Vrms = Vp / √2 as in a normal sine wave.

  However, the conventional induction heating device that determines the ON / OFF duty ratio of the switching element based on the peak value of the input voltage cannot perform accurate power control on the input voltage in which waveform distortion has occurred. There was a drawback.

  The present invention has been made in view of such a technical background, and can perform high-precision power control even when waveform distortion occurs in the input voltage applied to the induction heating coil. It is an object of the present invention to provide an image forming apparatus including an induction heating device.

The above problem is solved by the following means.
(1) A fixing device having a heating element, an induction heating coil for heating the heating element, a peak voltage detection means for detecting a peak value of an input voltage input to the coil, and the input voltage Based on the effective voltage detection means for detecting the effective value, the peak value of the input voltage detected by the peak voltage detection means, and the effective value of the input voltage detected by the effective voltage detection means, a power control voltage An image forming system comprising: a voltage value determining unit that determines a value; and a power control unit that controls power supplied to the fixing device using the voltage value determined by the voltage value determining unit. apparatus.
(2) A DC power supply device comprising: a rectifier that rectifies AC power; and a semiconductor switching element that performs power conversion to supply the power rectified by the rectifier to each part of the image forming apparatus body, 2. The image forming apparatus according to item 1, wherein the effective voltage detecting means is provided in the DC power supply device.
(3) The image forming apparatus according to (1) or (2), wherein the power control unit corrects the power control voltage value determined by the voltage value determination unit in accordance with a load factor of the DC power supply device.

  According to the invention described in (1), the voltage value for power control is based on the peak value of the input voltage detected by the peak voltage detecting means and the effective value of the input voltage detected by the effective voltage detecting means. Since the power supplied to the fixing device is controlled using the determined voltage value, the power supplied to the fixing device is controlled using only the peak value of the input voltage as in the prior art. Compared to the case, the actual effective value of the input voltage detected by the effective voltage detecting means can be considered. As a result, even if a waveform distortion occurs in the input voltage applied to the induction heating coil, the image forming apparatus can perform an accurate power control.

  According to the invention described in the preceding item (2), induction heating can be performed by diverting what is provided in a DC power supply device that rectifies AC power and supplies it to each part of the image forming apparatus main body as effective voltage detection means. It is not necessary to provide a dedicated effective voltage detection means for control, and the configuration of the apparatus can be simplified.

  According to the invention described in item (3) above, the power control voltage value determined by the voltage value determining means is corrected according to the load factor of the DC power supply device, so that more accurate power control can be performed. it can.

1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. (A) is a circuit diagram showing an example of a peak voltage detection circuit, and (B) is a waveform diagram of an input voltage. It is a circuit diagram which shows an example of an effective voltage detection circuit. It is a wave form diagram of the effective voltage detected by the effective voltage detection circuit. 1 is a block diagram of an image forming apparatus in which an effective voltage detection circuit is provided in a DC power supply device. It is a wave form diagram for demonstrating that an effective voltage changes with the DC load in an apparatus, when using the effective voltage detection circuit of a DC power supply device. It is a flowchart for demonstrating operation | movement of an electric power control part. It is a flowchart which shows the subroutine of the voltage value determination process of step S02 and S05 in the flowchart of FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing the configuration of an image forming apparatus according to an embodiment of the present invention.

  The image forming apparatus 1 includes an induction heating device 10, a main body control unit 20, and a fixing device 30.

  The induction heating apparatus 10 includes a full-wave rectifier circuit 102, an induction heating coil (inductor) 103, a capacitor 104, a switching element 105, an IGBT drive circuit 106, a peak voltage detection circuit 107, and an effective voltage detection. A circuit 108, an input current detection circuit 109, and a power control unit 110 are provided.

  The full-wave rectifier circuit 102 performs full-wave rectification on a commercial power supply 101, which is a 50/60 Hz 100-V AC power supply, and converts it into direct current.

  The coil 103 receives the output of the full-wave rectifier circuit 102 as an input voltage, and induction-heats a heating element (not shown) of the fixing device 30 that is magnetically coupled.

  The capacitor 104 is connected in parallel with the coil 103, and forms a resonance circuit 112 with the coil 103.

  The switching element 105 is connected in series with the coil 103 to form a closed loop from the commercial power supply 101 to the commercial power supply 101 through the full-wave rectifier circuit 102, the resonance circuit 112, the switching element 105, and the full-wave rectifier circuit 102. . The type of the switching element 105 is not limited, but in this embodiment, the above-described insulated gate bipolar transistor (IGBT) is used.

  The IGBT drive circuit 106 performs high-frequency switching drive of the switching element 105 by turning on and off the switching element 105 based on an instruction from the power control unit 110.

  The peak voltage detection circuit 107 detects a peak value Vp of the input voltage V0 input from the full-wave rectification circuit 102 to the coil 103. The peak voltage detection circuit 107 includes a capacitor 107a charged by an input voltage V0 as shown in FIG. 2A, for example, and the capacitor 107a is shown in FIG. 2B by the input voltage V0. In addition, since the input voltage is charged up to a peak value (also referred to as a peak voltage) Vp, the peak voltage Vp is detected by detecting the maximum value of the charging voltage. Since the peak voltage Vp is a large value, the peak voltage detection circuit 107 is actually provided with a circuit that transforms or divides the peak voltage Vp to reduce the voltage value to be handled.

  The effective voltage detection circuit 108 detects an effective value (also referred to as effective voltage) Vrms of the input voltage V0. For example, as shown in FIG. 3, the effective voltage detection circuit 108 includes a choke input type rectifier including a choke coil 108a connected in series to the rectifier circuit 102 and a capacitor 108b for charging the output of the choke coil 108a. In such an effective voltage detection circuit 108, even if the input voltage V0 is a sine wave as shown by a one-dot chain line in FIG. 4A, a distortion wave as shown by a broken line in FIG. Even in such a case, the effective value Vrms can be detected by the output of the capacitor 108b. However, since there is a ripple in the output of the capacitor 108b, in order to use it as a detection voltage, when using the AD port of the CPU provided in the power control unit 110, it is preferable to perform an averaging process.

  Incidentally, the effective value can be detected by connecting the output waveform of the full-wave rectifier circuit 102 to the AD port of the CPU and detecting the instantaneous voltage. However, this method requires high-speed sampling for one cycle of the output waveform and high-speed calculation after sampling in order to detect the effective value with high accuracy, and the arithmetic circuit becomes expensive. On the other hand, when the circuit as shown in FIG. 3 is used, the CPU only has to average the sampling results of several points with respect to the choke input waveform, so that it is not necessary to provide an expensive arithmetic circuit. Highly accurate effective value detection can be performed.

  The input current detection circuit 109 detects a current input to the coil 103 via the full wave rectification circuit 102.

  The power control unit 110 controls the power supplied to the heating element of the fixing device 30 by controlling on / off of the switching element 105 via the IGBT drive circuit 106, and includes a CPU, ROM, and RAM (not shown). Etc.

  Specifically, the power control voltage value is determined from the peak voltage detected by the peak voltage detection circuit 107 and the effective value detected by the effective voltage detection circuit 108, and the determined voltage value and the input current are determined. The power is calculated using the input current value detected by the detection circuit 109, and if there is a difference between the calculated power value and the required power value instructed from the image forming apparatus main body side, the duty ratio determining unit Operations such as changing the duty ratio of the drive pulse signal of the switching element 105 determined at 110a are performed.

  The control circuit 21 of the main body control unit 20 includes a CPU, a ROM, a RAM, and the like (not shown), and instructs the power control unit 110 to start power supply and a necessary power value of the fixing device 30.

  In the embodiment of FIG. 1, the effective voltage detection circuit 108 is provided in the induction heating device 10. However, the effective voltage detection circuit 108 may be generally provided in the DC power supply device of the image forming apparatus 1. Many.

  Therefore, the effective voltage detection circuit provided in the DC power supply device may be used as a part of the induction heating device 10.

  The configuration of the main part of the image forming apparatus 1 in this case is shown in the block diagram of FIG. The image forming apparatus 1 includes a DC power supply device 22 for rectifying AC power from a commercial power supply 101 and supplying DC power to a DC load 23 in the image forming apparatus 1. A switching regulator is provided that includes a semiconductor switching element that performs power conversion to supply the generated power to the DC load 23 in the image forming apparatus 1. Further, an effective voltage detection circuit 108 for detecting an effective value of the input voltage V0 after rectification is provided.

  The effective value detected by the effective voltage detection circuit 108 is input to the control circuit 21 of the main body control unit 20, and together with information on the required power value from the control circuit 21 to the fixing device 30, the power control unit 110 of the induction heating device 10. Sent to. The induction heating device 10 controls the power from the peak value of the input voltage detected by the peak voltage detection circuit 107 in the heating device 10 and the effective value transmitted from the control circuit 21 of the main body control unit 20. A voltage value is determined, and the input power is calculated using the voltage value and the input current value detected by the input voltage detection circuit 109.

  When the effective value is detected by the effective voltage detection circuit 108 provided in the DC power supply device 22 of the image forming apparatus 1, the DC load 23 in the apparatus is in the vicinity of the rating as shown in FIG. It is desirable to use the effective value of the rectified voltage. This is because, in the case of a light load, the rectified voltage is shifted as shown in FIG.

  Therefore, in this embodiment, the power control voltage value determined by the peak value of the input voltage detected by the peak voltage detection circuit 107 and the effective value of the input voltage detected by the effective voltage detection circuit 108 is Correction can be made according to the load factor of the DC power supply 22. For example, the load factor differs between standby and printing of the image forming apparatus 1, and in the case of a light load, the effective value is made smaller than the detected effective value, and the power control voltage value is made smaller. .

  FIG. 7 is a flowchart illustrating a power control process executed by the power control unit 110.

  In step S01, an instruction of the power supply value P1 supplied to the fixing device side is received from the control circuit 21 of the main body control unit 20. Next, in step S02, control voltage value determination processing is executed. This process will be described later.

  Next, in step S03, the control voltage value determined in step S02 is corrected according to the load factor of the DC power supply 22, and then in step S04, a drive pulse signal for the switching element 105 is temporarily determined. The duty ratio of the drive pulse signal is determined as follows, for example.

  In other words, the relationship between the control voltage value, the duty ratio of the drive signal of the switching element 105, and the power supplied to the fixing device is held in advance in the power control unit 109 as a table, and the duty determination unit 110a Based on the control voltage value and the power supply value supplied to the fixing device, the duty ratio of the drive signal for the switching element 105 is selected from the table.

  Next, in step S05, control voltage value determination processing is executed again, and in step S06, the control voltage value determined in step S02 is corrected in accordance with the load factor of the DC power supply device 22. Next, in step S07, after detecting the input current based on the output of the input current detection circuit 109, in step S08, the supply power value P2 is calculated using the determined control voltage value and input current value. calculate.

  In step S09, the power value P1 instructed from the control circuit 21 of the main body control unit 20 is compared with the calculated power value P2, and if they are not equal (NO in step S09), the switching element 105 is driven in step S10. After changing the duty ratio of the signal, the process returns to step S05. If they are equal (YES in step S09), the process directly returns to step S05.

  FIG. 8 is a flowchart showing a subroutine of control voltage value determination processing in steps S02 and S05 of the flowchart of FIG.

  In step S021, the peak voltage value is detected based on the output of the peak voltage detection circuit 107, and then in step S022, the effective value is detected based on the output of the effective voltage detection circuit 108. In step S023, the control voltage value is determined, and then the process returns.

  As described above, in this embodiment, the power control voltage value is determined based on the peak value of the input voltage detected by the peak voltage detection circuit 107 and the effective value of the input voltage detected by the effective voltage detection circuit 108. Since the power supplied to the fixing device side is controlled using the determined voltage value, the power supplied to the fixing device side is controlled using only the peak value of the input voltage as in the prior art. In comparison with this, the actual effective value of the input voltage detected by the effective voltage detection circuit 108 can be taken into consideration. As a result, even if a waveform distortion occurs in the input voltage applied to the induction heating coil, the image forming apparatus can perform an accurate power control.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Induction heating apparatus 20 Main body control part 21 Control circuit 22 DC power supply apparatus 30 Fixing apparatus 101 Commercial power supply 102 Full wave rectifier circuit 103 Coil 104 Capacitor 105 Switching element 107 Peak voltage detection circuit 108 Effective voltage detection circuit 109 Input current Detection circuit 110 Power control unit

Claims (3)

A fixing device having a heating element;
A coil for induction heating for heating the heating element;
Peak voltage detection means for detecting a peak value of an input voltage input to the coil;
Effective voltage detection means for detecting an effective value of the input voltage;
Voltage value determining means for determining a power control voltage value based on the peak value of the input voltage detected by the peak voltage detecting means and the effective value of the input voltage detected by the effective voltage detecting means;
Power control means for controlling power supplied to the fixing device using the voltage value determined by the voltage value determination means;
An image forming apparatus comprising: A DC power supply device comprising: a rectifying unit that rectifies AC power; and a semiconductor switching element that performs power conversion to supply the power rectified by the rectifying unit to each part of the image forming apparatus body,
The image forming apparatus according to claim 1, wherein the effective voltage detection unit is provided in the DC power supply device.   The image forming apparatus according to claim 1, wherein the power control unit corrects the power control voltage value determined by the voltage value determination unit according to a load factor of the DC power supply device.

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