JP5520855B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a technique for controlling fixing heating by an induction heating type fixing heating device.

  2. Description of the Related Art An induction heating type fixing heating device that supplies a high frequency current to an exciting coil to generate heat to be heated and an image forming apparatus equipped with the same are known. This fixing heating device has a characteristic that the higher the frequency of the high frequency current supplied to the exciting coil, the lower the power consumed by the fixing heating device, and the lower the frequency of the high frequency current, the higher the power consumed by the fixing heating device. is there. In the fixing heating device, the power consumption during actual heating is fed back and PID control is performed on the frequency of the high-frequency current according to this power consumption in order to bring it closer to the power required to maintain the temperature of the heated object constant. To supply stable power.

  Further, as shown in Patent Document 1 below, when the power is turned on, all the power obtained by subtracting the amount of power consumed by other than the fixing device is supplied to the exciting coil and heated. Proposal is also made for a copying apparatus that is heated by supplying power obtained by subtracting the power consumed by the auxiliary device added to each configuration of the copying apparatus and the copying apparatus from the allowable input power as the auxiliary apparatus further added to the apparatus operates. Has been.

JP 2005-122124 A

  In the case of the image forming apparatus disclosed in Patent Document 1, the total power used by the entire image forming apparatus including the optional device is frequently depending on the operation of the optional device connected to the image forming apparatus. If it changes, the change in the power supplied to the fixing heating device cannot catch up with the frequent change in the total power, and the total power of the image forming apparatus may exceed the allowable power of the commercial power supply. In order to solve this problem, fixed power control is performed in which the power supplied to the exciting coil is set to the lowest value that does not exceed the allowable power of the commercial power supply even when the total current reaches the maximum value. However, when fixed power control is performed in this way, even if there is a margin in the power that can be supplied to the fixing heating device within the allowable power range of the commercial power supply, depending on the operation of the optional equipment, etc. Since electric power is not supplied to the fixing heating device, there is a problem that electric power cannot be efficiently supplied to the fixing heating device.

  The present invention has been made to solve the above-described problem, and an object of the present invention is to make it possible to efficiently supply power to a fixing heating device by using the allowable power of a commercial power source more effectively than in the past during image formation. And

An image forming apparatus according to one aspect of the present invention includes an excitation coil that generates heat by heating an object to be heated by electromagnetic induction,
A temperature detector for detecting the temperature of the heated object;
A main body side control unit for driving and controlling the image forming apparatus;
A first current detection unit that detects a value of a drive current used for driving the image forming apparatus under the control of the main body side control unit;
A current supply controller for supplying a high-frequency current to the exciting coil while changing the frequency;
A second current detector for detecting a value of a current supplied to the exciting coil;
A voltage detection unit for detecting a value of a power supply voltage supplied to the excitation coil;
In order to set the surface temperature of the heated object detected by the temperature detection unit to a predetermined surface temperature used at the time of image formation, the current value detected by the second current detection unit is fed back and commercialized. A fixing current calculation unit that calculates a value of a current to be supplied to the exciting coil using a current value corresponding to a rated current value of a power source as a target value;
By subtracting, from the current value detected by the second current detection unit, the value obtained by subtracting the pre-stored rated current value of the commercial power supply from the drive current value detected by the first current detection unit, An allowable current calculation unit for calculating a value of a current supplied to the exciting coil;
A frequency setting unit that outputs a frequency corresponding to the current value calculated by the fixing current calculation unit and the allowable current calculation unit to the current supply control unit;
A switching unit that switches whether to cause the fixing current calculation unit or the allowable current calculation unit to calculate the value of the current to be supplied to the excitation coil according to the drive current value detected by the first current detection unit; Ru equipped with.

  In the present invention, the power supplied to the excitation coil is set by either the fixing current calculation unit or the allowable current calculation unit according to the drive current value detected by the first current detection unit. When it is necessary to return the supplied power within the rated power of the commercial power supply in a short time, the value of the current supplied to the exciting coil is calculated by the allowable current calculator that can change the power supplied to the exciting coil significantly. If the power supplied to the exciting coil does not need to be changed suddenly in a short time, the current value is calculated by the fixing current calculating unit that can accurately change the value of the current supplied to the exciting coil by feedback control. It is possible to perform control such as In other words, according to the present invention, it is possible to efficiently supply power to the fixing heating device including the exciting coil by using the allowable power of the commercial power source more effectively than in the past at the time of image formation.

In the above configuration, when the drive current value detected by the first current detection unit exceeds a rated current value of a commercial power source, the switching unit sets a current value to be supplied to the excitation coil. When the drive current value calculated by the allowable current calculation unit and detected by the first current detection unit does not exceed the rated current value of the commercial power supply, the value of the current supplied to the excitation coil is The fixing current calculation unit switches so as to calculate.

  According to this invention, the total current used in the entire image forming apparatus exceeds the rated current value of the commercial power supply, and the power supplied to the exciting coil needs to be rapidly changed in a short time. In this case, the allowable current calculation unit has significantly changed the supply current to the excitation coil to an appropriate value, and the total current used in the entire image forming apparatus does not exceed the rated current value of the commercial power supply. When it is not necessary to change the power supplied to the exciting coil abruptly in a short time, the current supplied to the exciting coil can be accurately changed by the fixing current calculation unit. As a result, even if the total power of the entire image forming apparatus exceeds the allowable power of the commercial power supply, it is possible to immediately avoid the situation.

Further, in the above configuration, the allowable current calculation unit obtains a value obtained by subtracting a pre-stored rated current value of a commercial power source from a drive current value detected by the first current detection unit. When the value subtracted from the current value detected by the unit exceeds a predetermined fixing upper limit current value that is smaller than the rated current value of the commercial power source, the fixing upper limit current value of the current supplied to the exciting coil It is calculated as a value.

According to the present invention, since the value of the current supplied to the exciting coil is smaller than the rated current value of the commercial power source, the total current used in the entire image forming apparatus exceeds the rated current value of the commercial power source. In such a situation, when the supply power to the excitation coil is changed to a suitable value in a short time, the supply power to the excitation coil after the change is surely reduced below the rated power of the commercial power supply. It becomes possible.
An image forming apparatus according to another aspect of the present invention includes an exciting coil that heats a heated body by electromagnetic induction, a temperature detection unit that detects a temperature of the heated body, and a main body side that drives and controls the image forming apparatus A control unit, a first current detection unit that detects a value of a drive current used to drive the entire image forming apparatus under the control of the main body side control unit, and a frequency of a high-frequency current to the excitation coil is changed. A current supply control unit that supplies power, a second current detection unit that detects a value of a current supplied to the excitation coil, a voltage detection unit that detects a value of a power supply voltage supplied to the excitation coil, and the temperature In order to set the surface temperature of the heated object detected by the detection unit to a predetermined surface temperature used at the time of image formation, the current value detected by the second current detection unit is fed back, and the quotient Using a current value corresponding to the rated current value of the power supply as a target value, a fixing current calculation unit that calculates a value of a current supplied to the exciting coil, and a drive current value detected by the first current detection unit are stored in advance. An allowable current calculation unit that calculates a value of a current supplied to the exciting coil by subtracting a value obtained by subtracting a rated current value of a commercial power source from a current value detected by the second current detection unit; A frequency setting unit that outputs a frequency corresponding to the current value calculated by the fixing current calculation unit and the allowable current calculation unit to the current supply control unit, and a drive current value detected by the first current detection unit. When the value exceeds the rated current value of the commercial power supply, the allowable current calculation unit calculates the value of the current supplied to the exciting coil, and the driving power detected by the first current detection unit Value if not a value exceeding the rated current value of the commercial power supply, and a switching unit for switching the value of the current supplied to the exciting coil so that the fixing current calculator calculates.

  According to the present invention, the allowable power of the commercial power source can be used more effectively than before when forming an image, and the power can be efficiently supplied to the fixing heating device.

1 is a side view schematically showing an internal configuration of an image forming apparatus according to an embodiment of the present invention. It is a block diagram for demonstrating the operation | movement function of the main body side control part relevant to control of a fixing device, an induction heating apparatus, and the said fixing device. It is a figure which shows the example of a some frequency change pattern with a graph. 6 is a flowchart illustrating control of supply current to an exciting coil by an IH control unit during a fixing operation of the fixing device. It is a figure which shows the example of the current control by an IH control part with a graph. FIG. 4 is a diagram illustrating a relationship between power supplied to an exciting coil, power consumed by each operation mechanism unit other than the fixing device in the image forming apparatus, and total power consumed by the image forming apparatus.

  Hereinafter, embodiments of an induction heating device, a fixing device, and an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a side view schematically showing an internal configuration of an image forming apparatus 1 according to an embodiment of the present disclosure. The image forming apparatus 1 may be a copying machine, a printer, a facsimile machine, or the like, and may be an image forming apparatus having a process for fixing a toner image placed on a sheet by pressing and heating. The image forming apparatus 1 includes a main body unit 2, a stack tray 3 disposed on the left side of the main body unit 2, a document reading unit 4 disposed on the top of the main body unit 2, and a document reading unit 4. A document feeder 5 is provided.

  An operation unit 6 is provided at the front portion of the image forming apparatus 1. The operation unit 6 displays a power key, a start key for a user to input a print execution instruction, a numeric keypad for inputting the number of copies to be printed, operation guide information for various copying operations, and the like. Has a display unit 9 or the like including a liquid crystal display or the like having a touch panel function.

  The document reading unit 4 includes an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) and a scanner unit 13 including an exposure lamp, a document table 14 formed of a transparent member such as glass, and a document reading slit. 15 is provided. The scanner unit 13 is configured to be movable by a drive unit (not shown). When reading a document placed on the document table 14, the scanner unit 13 is moved along the document surface at a position facing the document table 14, and the document image is displayed. Image data acquired while scanning is output to an image memory (not shown). When reading the document fed by the document feeding unit 5, the document is moved to a position facing the document reading slit 15 and synchronized with the document feeding operation by the document feeding unit 5 via the document reading slit 15. The image of the original is acquired and the image data is output to the image memory.

  The document feeder 5 includes a document placement unit 16 for placing a document, a document discharge unit 17 for discharging a document whose image has been read, and one document placed on the document placement unit 16. A document transport mechanism 18 including a paper feed roller, a transport roller (not shown), and the like for feeding the paper one by one to a position facing the document reading slit 15 and discharging it to the document discharge section 17 is provided.

  Further, the document feeding unit 5 is provided so as to be rotatable with respect to the main body unit 2 so that the front side thereof can move upward. By moving the front side of the document feeder 5 upward to open the upper surface of the document table 14, the user can place a read document, for example, a book in a spread state, on the upper surface of the document table 14. ing.

  The main body 2 includes a plurality of paper feed cassettes 19, a paper feed roller 20 that feeds the paper from the paper feed cassette 19 one by one and transports it to the image forming unit 21, and an image on the paper transported from the paper feed cassette 19. And an image forming unit 21 for forming the image.

  The image forming unit 21 outputs a laser beam or the like based on the image data acquired by the scanner unit 13 to expose the photosensitive drum 22, and forms an electrostatic latent image on the surface of the photosensitive drum 22. A developing unit 24 that forms a toner image by attaching toner to the surface of the photosensitive drum 22 on which the electrostatic latent image is formed; and a transfer unit 25 that transfers the toner image on the photosensitive drum 22 to a sheet. Prepare.

  The fixing device (fixing heating device) 28 includes a heat roller 26 and a pressure roller 27 that heat the paper on which the toner image is transferred to melt and fix the toner image on the paper.

  In the paper conveyance path in the image forming unit 21, conveyance roller pairs 30 and 31 that convey the paper to the stack tray 3 or the discharge tray 29 are provided.

  When images are formed on both sides of a sheet, after the image is formed on one side of the sheet by the image forming unit 21, the sheet is nipped between the pair of transport rollers 30 and 31 on the discharge tray 29 side. To do. In this state, the conveyance roller pairs 30 and 31 are reversed to switch back the paper, and the conveyance roller pairs 38 and 39 send the paper to the paper conveyance path 32 and convey it again to the upstream area of the image forming unit 21. After the image is formed on the other side by 21, the paper is discharged to the stack tray 3 or the discharge tray 29.

  FIG. 2 is a block diagram for explaining the operation functions of the fixing device 28, the induction heating device 10, and the main body side control unit 51 related to the control of the fixing device 28.

  The main body side control unit 51 is configured by a CPU (Central Processing Unit) or the like, reads a program in accordance with an instruction signal or the like input from each component of the image forming apparatus 1, and executes processing. The image forming apparatus 1 is comprehensively controlled by outputting an instruction signal to the functional unit.

  The main body side control unit 51 generates a fixing instruction signal for causing the fixing device 28 to start a fixing operation at the time of image formation, and a current cutoff instruction signal for stopping the supply of high-frequency current to the excitation coil 43 by the drive circuit 42. Output to.

  Further, the main body side control unit 51 includes a fixing current calculation unit 511, an allowable current calculation unit 512, and a switching unit 513.

  Based on the surface temperature of the heat roller 26 detected by the temperature sensor 44, the fixing current calculation unit 511 uses the surface temperature of the heat roller (heated body) 26 as a predetermined surface temperature (for example, used for image formation). 180 to 200 ° C.), the current value detected by the first current detector 48 is fed back, and the current value corresponding to the rated current value of the commercial power supply (as an example, in advance of the rated current value of the commercial power supply). The value of the current supplied to the exciting coil 43 is calculated as a target value obtained by setting a current value that is smaller by a predetermined value, for example, 14.6 A. When the rated current value of the commercial power supply is 15 A and the rated power is 1500 W. Details of calculation of the fixing current by the fixing current calculation unit 511 will be described later. The fixing current calculation unit 511 outputs the calculated current value to the IH control unit 41 as a fixing current value.

  The allowable current calculation unit 512 calculates the rated current of the commercial power source (a preset fixed value, for example, 15 A. Rated power) from the driving current used for driving the entire image forming apparatus 1 detected by the first current detection unit 48. By subtracting the value obtained by subtracting 1500 W) from the current value detected by the first current detector 48, the allowable current value that can be supplied to the exciting coil 43 is calculated. The allowable current calculation unit 512 outputs the calculated current value to the IH control unit 41 as the allowable current value.

  It should be noted that the allowable current calculation unit 512 has a predetermined fixing upper limit current value (for example, the fixing device 28 in the image forming apparatus 1) in which the allowable current value calculated as described above is smaller than the rated current value of the commercial power source. Even when all the operating mechanisms 7 other than those are operating, even if a high frequency current is supplied to the exciting coil 43, the drive current value detected by the second current detector 48 exceeds the rated current value of the commercial power supply. If the value exceeds the supply current value to the exciting coil 43 that is assumed to be absent, the fixing upper limit current value is calculated as the allowable current value. For example, when the rated current value of the commercial power source is 15 A, the predetermined value is 2 A, and the fixing upper limit current value is 13 A.

  The switching unit 513 supplies either the fixing current calculation unit 511 or the allowable current calculation unit 512 to the excitation coil 43 according to the drive current value of the entire image forming apparatus 1 detected by the first current detection unit 48. Switch whether to calculate the value of.

  The first current detection unit 48 detects the value of the drive current used for driving the image forming apparatus 1 under the control of the main body side control unit 51.

  The fixing device 28 includes a heat roller 26, a pressure roller 27 (not shown in FIG. 2), an IH control unit 41, a drive circuit 42, an excitation coil 43, a temperature sensor 44, a voltage detection unit 45, and a second current detection unit 46. Have The induction heating device 10 includes an IH control unit 41, a drive circuit 42, an excitation coil 43, a temperature sensor 44, a voltage detection unit 45, and a current detection unit 46. It should be noted that a portion of the induction heating device 10 excluding the exciting coil 43 may be provided in the main body 2 of the image forming apparatus 1 separately from the fixing device 28.

  The exciting coil 43 is provided inside a cylindrical heat roller 26 made of a conductive material. In the present embodiment, the heat roller 26 is an example of an object to be heated as referred to in the claims.

  The temperature sensor (temperature detection unit) 44 is a sensor that detects the surface temperature of the heat roller 26. The temperature sensor 44 outputs the detected surface temperature to the main body side control unit 51.

  The voltage detector 45 detects the power supply voltage supplied to the exciting coil 43 in the heat roller 26 and outputs the detected voltage value to the IH controller 41.

  The second current detector 46 detects the high-frequency current supplied to the exciting coil 43 in the heat roller 26 and outputs the detected current value to the IH controller 41.

  The drive circuit (current supply control unit) 42 is driven by control by the IH control unit 41 and supplies a high-frequency current to the excitation coil 43 at a frequency output from the IH control unit 41. An induction eddy current is generated in the main body of the heat roller 26 made of a conductive material by a high-frequency magnetic field generated in the exciting coil 43 by this current supply, and the heat roller 26 generates heat.

  An IH (Induction Heating) control unit 41 is configured by a CPU or the like, and controls the drive circuit 42 according to an instruction signal output from the main body side control unit 51. Specifically, the IH control unit 41 calculates the frequency of the high-frequency current supplied to the exciting coil 43 when the heat roller 26 is caused to generate heat based on the fixing instruction signal output from the main body side control unit 51 to calculate the drive circuit. Output to 42. Further, when a current interruption instruction signal is output from the main body side control unit 51, the IH control unit 41 performs current interruption control on the drive circuit 42. By this current interruption control, the drive circuit 42 stops the supply of the high frequency current to the exciting coil 43.

  The IH control unit (frequency setting unit) 41 sets a frequency corresponding to the current value output from the fixing current calculation unit 511 and the allowable current calculation unit 512 and outputs the set frequency to the drive circuit 42.

  The frequency setting by the IH control unit 41 is, for example, the upper limit power obtained by multiplying the current value output from the fixing current calculation unit 511 or the allowable current calculation unit 512 by the voltage value detected by the voltage detection unit 45. The frequency of the high-frequency current supplied to the exciting coil 43 is directly calculated using the surface temperature of the heat roller 26 detected by the temperature sensor 44 and the voltage value detected by the voltage detector 45. . In this case, the IH control unit 41 includes a frequency change pattern storage unit (not shown). The frequency change pattern storage unit includes a ROM, a non-volatile memory, and the like, and a frequency change pattern that is a frequency pattern of a high-frequency current to the exciting coil 43 that changes according to the upper limit power is a voltage detected by the voltage detection unit 45. A plurality of storage tables are stored according to the temperature detected by the temperature sensor 44.

FIG. 3 is a graph showing an example of the plurality of frequency change patterns. In FIG. 3, as an example, the frequency change pattern used when the surface temperature T is 50 ° C. and the power supply voltage value V is 120 (V) is shown by a solid line, and the surface temperature T is 150 ° C. and the power supply voltage value V is 120 ( The frequency change pattern used in the case of V) is indicated by a broken line, the frequency change pattern used when the surface temperature T is 50 ° C. and the power supply voltage value V is 100 (V) is indicated by a one-dot chain line, and the surface temperature T is 150 ° C. A frequency change pattern used when the power supply voltage value V is 100 (V) is indicated by a two-dot chain line. However, this is not intended to limit the number of frequency change patterns stored in the frequency change pattern storage unit to four. Many frequency change patterns are stored in the frequency change pattern storage unit so as to correspond to the surface temperature T of the heat roller 26 immediately before the start of supply of various high-frequency currents and the power supply voltage value V supplied to the heat roller 26. Is preferred.

  The IH control unit 41 reads a frequency change pattern corresponding to the detection voltage by the voltage detection unit 45 and the temperature detected by the temperature sensor 44 from the frequency change pattern storage unit, and sets the frequency corresponding to the value of the upper limit power to the read frequency The frequency of the high-frequency current calculated from the change pattern and supplied to the exciting coil 43 is set to the calculated frequency.

  If the frequency change pattern corresponding to the voltage detected by the voltage detector 45 and the temperature detected by the temperature sensor 44 is not stored in the frequency change pattern storage unit, the IH control unit 41 stores the frequency change pattern in the frequency change pattern storage unit. The frequency of the high-frequency current is calculated by linear interpolation based on the frequency change pattern.

As an example of the linear interpolation by the IH control unit 41, the frequency f [V = 110, T of the high frequency current supplied to the exciting coil 43 when the belt temperature T = 100 ° C., the power supply voltage V = 110 V, and the upper limit power Pt = 1000 W. = 100, Pt = 1000] is shown.
From the frequency change pattern shown in FIG.
f1 [V = 100, T = 50, Pt = 1000] = 24.6 [kHz] ... Equation (1)
f2 [V = 120, T = 50, Pt = 1000] = 27.1 [kHz] ... Formula (2)
f3 [V = 100, T = 150, Pt = 1000] = 23.2 [kHz] ... Equation (3)
f4 [V = 120, T = 150, Pt = 1000] = 25.6 [kHz] ... Equation (4)
The following is calculated by linear interpolation based on Equation (1) and Equation (2).
f5 [V = 110, T = 50, Pt = 1000] = (110 -100) x (f2-f1) / (120-100) + f1 = 25.8 [kHz] (5)
The following is calculated by linear interpolation based on Equation (3) and Equation (4).
f6 [V = 110, T = 150, Pt = 1000] = (110 -100) x (f4-f3) / (120-100) + f3 = 24.3 [kHz] (6)
The following is calculated by linear interpolation based on Equation (5) and Equation (6).
f7 [V = 110, T = 100, Pt = 1000] = (100 -50) x (f6-f5) / (150-50) + f5 = 25.1 [kHz] (7)
From the above, when the belt temperature T = 100 ° C., the power supply voltage V = 110 V, and the upper limit power Pt = 1000 W, the IH control unit 41 has the frequency f [V = 110, T = 100, Pt = 1000], 25.1 [kHz] (equation (7)) calculated by the linear interpolation is used.

  In the present embodiment, the IH control unit 41 performs frequency setting control by table control based on the frequency change pattern stored in the frequency change pattern storage unit as described above.

  Thus, the IH control unit 41 changes the power value supplied to the excitation coil 43 by changing the frequency of the high-frequency current output to the drive circuit 42 in accordance with the increase or decrease of the value of the upper limit power, thereby exciting the excitation coil 43. Control is performed so that the power value supplied to the coil 43 matches the value of the upper limit power.

  Next, the supply current control to the exciting coil 43 by the IH control unit 41 during the fixing operation of the fixing device 28 will be described. FIG. 4 is a flowchart showing supply current control to the exciting coil 43 by the IH control unit 41 during the fixing operation of the fixing device 28. FIG. 5 is a graph showing an example of current control by the IH control unit 41. FIG. 6 shows the relationship between the power supplied to the exciting coil 43, the power consumed by each operation mechanism unit other than the fixing device 28 in the image forming apparatus 1, and the total power consumed by the image forming apparatus 1. It is a figure.

  For example, when the main body side control unit 51 receives an instruction to start an image forming operation (YES in S1), the fixing current calculation unit 511 determines the temperature of the heat roller 26 based on the surface temperature of the heat roller 26 detected by the temperature sensor 44. In order to set the surface temperature to a predetermined surface temperature used at the time of image formation, the current value detected by the first current detection unit 48 is fed back, and the current value corresponding to the rated current value of the commercial power supply is used as the target value. The value of the current (fixing current) supplied to the excitation coil 43 is calculated by PID control and output to the IH control unit 41 (S2).

  For example, the fixing current calculation unit 511 compares the surface temperature A of the heat roller 26 detected by the temperature sensor 44 with a predetermined surface temperature B used at the time of image formation, and the surface temperature A becomes the surface temperature B. If not, the fixing current value Q (n) is calculated as follows.

MVn = Kp (En-En1) + Ki En + Kd (En-2 * En1 + En2)
Q (n) = Q (n-1) + MVn * C
En2 = It-Im2
En1 = It-Im1
En = It-Im
MVn: Increase / decrease amount of current value (operation amount)
Kp, Ki, Kd: Constant
Q (n): Fixing current value
Q (n-1): Previous fixing current value
C: Constant to increase or decrease MVn
It: A current value corresponding to the rated current value of the commercial power supply (for example, a value lower than the rated current 15A, such as 14.6A)
Im: current value detected by the first current detector 48
Im1: Previous current value detected by the first current detector 48 (when calculating the previous fixing current)
Im2: the current value of the last time detected by the first current detection unit 48 (when the fixing current was calculated the last time)
When the fixing current value Q (n) calculated in S2 is input to the IH control unit 41, the IH control unit 41 has a frequency corresponding to the fixing current value Q (n) (frequency output to the drive circuit 42). Is derived by the calculation method shown above (S3). The IH control unit 41 outputs the calculated frequency to the drive circuit 42, and the drive circuit 42 supplies a high-frequency current having the frequency to the excitation coil 43.

  Here, the switching unit 513 of the main body side control unit 51 determines whether the drive current value detected by the first current detection unit 48 exceeds the rated current value of the commercial power supply (S4). When the switching unit 513 determines that the drive current value detected by the first current detection unit 48 exceeds the rated current value of the commercial power supply (YES in S4), the allowable current calculation unit 512 determines the allowable current value. Is set so that the allowable current value output from the allowable current calculation unit 512 is input to the IH control unit 41 (S8). The allowable current calculation unit 512 calculates the allowable current value as follows, for example.

  Allowable current value Q (n), actual drive current value Im (A) during driving of the image forming apparatus 1, rated current value Imr (A) of commercial power, current value Ims of current supplied to the excitation coil 43 In the case of (A), the allowable current calculation unit 512 calculates the allowable current value as allowable current value Q (n) = current value Ims− (drive current value Im (A) −rated current value Imr (A)). To do.

  For this reason, when the drive current value Im (A) is larger than the rated current value Imr (A), the drive current value Im (A) is calculated from the current value Ims (A) of the current that has been supplied to the excitation coil 43 until then. ) And the rated current value Imr (A) is the allowable current value Q (n), and if the rated current value Imr (A) is greater than the drive current value Im (A) The value obtained by adding the absolute value of the difference between the drive current value Im (A) and the rated current value Imr (A) to the current value Ims (A) of the current supplied to the coil 43 is the allowable current value Q (n). It becomes.

  Note that when the allowable current value Q (n) exceeds the above-described fixing upper limit current value, the allowable current calculating unit 512 calculates the fixing upper limit current value as the allowable current value.

  Then, the IH control unit 41 calculates the frequency (frequency output to the drive circuit 42) corresponding to the allowable current value input from the allowable current calculation unit 512 by the calculation method described above (S6). The IH control unit 41 outputs the calculated frequency to the drive circuit 42, and the drive circuit 42 supplies a high-frequency current having the frequency to the excitation coil 43.

  If the switching unit 513 determines that the drive current value detected by the first current detection unit 48 does not exceed the rated current value of the commercial power supply (NO in S4), the fixing current calculation unit 511 performs the fixing operation. The setting for calculating the current value is maintained, and the setting is made such that the fixing current value output from the fixing current calculation unit 511 is input to the IH control unit 41 (S5). The IH control unit 41 calculates a frequency corresponding to the fixing current value (frequency output to the drive circuit 42) by the calculation method described above (S6), and outputs the calculated frequency to the drive circuit 42. The drive circuit 42 supplies a high-frequency current having the frequency to the exciting coil 43.

  Until the main body side control unit 51 reaches a state of outputting a current interruption instruction signal to the IH control unit 41, the IH control unit 41, the switching unit 513, the fixing current calculation unit 511, and the allowable current calculation unit 512 are S4 to S6, When the process of S8 is repeated (NO in S7) and the main body side control unit 51 reaches a state of outputting a current interruption instruction signal to the IH control unit 41 (YES in S7), the IH control unit 41 moves to the excitation coil 43. The supply power control is terminated.

  According to the above control, as shown in FIG. 5, when the total drive current in the entire image forming apparatus 1 detected by the first current detection unit 48 is equal to or less than the rated current of the commercial power supply, the excitation coil 43 Since the supplied current value is the fixing current value calculated by the fixing current calculation unit 511, the fixing current value does not increase rapidly, and each operation is gradually started from the rated current value of the commercial power supply by PID control. The value approaches the limit value obtained by subtracting the drive current value of the mechanism 7. On the other hand, when the total drive current value of the entire image forming apparatus 1 increases and exceeds the rated current value of the commercial power supply due to driving of each operation mechanism 7 or the like, the allowable current value calculated by the allowable current calculation unit 512 is As a result, the value of the current supplied to the exciting coil 43 is reduced by an amount that is immediately exceeded. In this way, when the current value supplied to the excitation coil 43 decreases and the total drive current of the entire image forming apparatus 1 decreases and a margin is generated up to the rated current of the commercial power supply, the current is supplied to the excitation coil 43 again. Since the current value to be used is the fixing current value calculated by the fixing current calculation unit 511, the fixing current value gradually changes by the PID control.

  Further, as shown in FIG. 6, the IH control unit 41 has the maximum power that can be supplied to the excitation coil 43 according to the power consumption consumed by each operation mechanism unit other than the fixing device 28 in the image forming apparatus 1. Power (difference between peak power, which is the maximum power that the image forming apparatus 1 can accept from a commercial power supply, and power consumption consumed by each operation mechanism unit other than the fixing device 28 in the image forming apparatus 1), Since the power is supplied to the exciting coil 43, the total power amount of the power supplied to the exciting coil 43 and the power consumed by each operation mechanism unit other than the fixing device 28 approaches the rated power of the commercial power source. Thereby, the power from the commercial power source can be supplied to the maximum for heating the heat roller 26, and the power obtained from the commercial power source can be used effectively. Even if the total power amount of the power supplied to the excitation coil 43 and the power consumed by each operation mechanism unit other than the fixing device 28 temporarily exceeds the rated power of the commercial power source, It is possible to quickly return the total amount within the rated power of the commercial power source.

  Note that, according to each of the above embodiments, even when the driving power necessary for each operation mechanism 7 other than the fixing device 28 of the image forming apparatus 1 frequently changes, the total driving power of the entire image forming apparatus 1 is The state where the rated power of the commercial power supply is not always exceeded is maintained on average, and the power of the commercial power supply can be efficiently used for heating by the fixing device 28. Since the electric power can be efficiently supplied to the fixing device 28, the surface temperature of the heat roller 26 can be rapidly raised, and the time required for warming up the image forming apparatus 1 can be shortened.

  Further, even when an optional device is added to the image forming apparatus 1 and driven, and the total driving power of the entire image forming apparatus 1 is changed, the entire image forming apparatus 1 including the added optional device is changed. When the total drive current value is detected by the first current detection unit 48 and used for the upper limit power calculation by the upper limit power calculation unit 511, the total drive power of the entire image forming apparatus 1 including the added optional device. However, the power of the commercial power source can be efficiently used for heating by the fixing device 28 while maintaining the state where the rated power of the commercial power source does not exceed the rated power.

  Similarly, when the image forming apparatus 1 is mass-produced, even when the total drive current value of each apparatus differs due to component variations unique to each apparatus, in the power supply control to the excitation coil 43 according to each of the above embodiments, It is not necessary to perform control in which a margin is set in anticipation of a difference in the total drive current value for each device. For this reason, the image forming apparatus 1 can be designed to be robust regardless of the operation mode or the state of each apparatus.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, in the above-described embodiment, the exciting coil 43 and the heat roller 26 are shown as examples of the heated object, and the fixing device 28 and the image forming apparatus 1 are shown as examples to which the induction heating device according to the present invention is applied. However, this is not intended to limit the present invention.

  Further, the feedback control shown in the above embodiment is merely an example, and is not intended to limit the feedback control performed in the present invention to the contents shown above.

  In the above embodiment, the calculation of various current values and various powers used for controlling the supply current to the exciting coil 43 is performed by the main body side control unit 51. However, this configuration is merely an example. The various current values and various electric powers may be calculated in the IH control unit 41.

  1 to 6 is only one embodiment of the configurations and processes of the induction heating device 10, the fixing device 28, and the image forming apparatus 1 according to the present invention, and the induction heating device according to the present invention. 10 is not intended to limit the fixing device 28 and the image forming apparatus 1 to the configuration and processing.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Induction heating apparatus 26 Heat roller 27 Pressure roller 28 Fixing apparatus 41 IH control part 42 Drive circuit 43 Excitation coil 44 Temperature sensor 45 Voltage detection part 46 2nd electric current detection part 48 1st electric current detection part 51 Main body side Control unit 511 Fixing current calculation unit 512 Allowable current calculation unit 513 Switching unit

Claims (2)

An exciting coil that heats the object to be heated by electromagnetic induction;
A temperature detector for detecting the temperature of the heated object;
A main body side control unit for driving and controlling the image forming apparatus;
A first current detection unit that detects a value of a drive current used for driving the entire image forming apparatus under the control of the main body side control unit;
A current supply controller for supplying a high-frequency current to the exciting coil while changing the frequency;
A second current detector for detecting a value of a current supplied to the exciting coil;
A voltage detection unit for detecting a value of a power supply voltage supplied to the excitation coil;
In order to set the surface temperature of the heated object detected by the temperature detection unit to a predetermined surface temperature used at the time of image formation, the current value detected by the second current detection unit is fed back and commercialized. A fixing current calculation unit that calculates a value of a current to be supplied to the exciting coil using a current value corresponding to a rated current value of a power source as a target value;
By subtracting, from the current value detected by the second current detection unit, the value obtained by subtracting the pre-stored rated current value of the commercial power supply from the drive current value detected by the first current detection unit, An allowable current calculation unit for calculating a value of a current supplied to the exciting coil;
A frequency setting unit that outputs a frequency corresponding to the current value calculated by the fixing current calculation unit and the allowable current calculation unit to the current supply control unit;
When the drive current value detected by the first current detection unit exceeds a rated current value of a commercial power source, the allowable current calculation unit calculates a value of a current to be supplied to the excitation coil, and When the drive current value detected by the one current detection unit is not higher than the rated current value of the commercial power supply, switching is performed so that the fixing current calculation unit calculates the value of the current supplied to the excitation coil. An image forming apparatus comprising a switching unit. The allowable current calculation unit includes a current detected by the second current detection unit obtained by subtracting a pre-stored rated current value of a commercial power source from a drive current value detected by the first current detection unit. claim the value obtained by subtracting from the value, if above the fixing upper limit current value to a predetermined smaller than the rated current value of the commercial power source, for calculating the fixing upper limit current value as the value of current supplied to the exciting coil the image forming apparatus according to 1.

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