JP5470289B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to control of current supplied to an image forming apparatus.

  When the AC line voltage input to the image forming apparatus is measured and the maximum value is detected, the maximum power supplied to the fixing device is controlled so that the power consumption of the image forming apparatus main body does not exceed a certain value. A technique has been proposed (see, for example, Patent Document 1).

JP-A-10-301442 (paragraph 0034 to paragraph 0041)

  FIG. 10 is a graph showing an example of a change in the total current supplied to the image forming apparatus when the main switch is turned on and a copying operation is performed in the image forming apparatus. The horizontal axis represents time (seconds), and the vertical axis represents total current (A). In the case of an AC 100V commercial power supply, for example, in Japan, the upper limit value of the current is set to 15A.

  As shown in this graph, when the total current supplied to the image forming apparatus is measured and the threshold value of the total current is controlled to a value close to the upper limit value (for example, 14 A), the total current exceeds the threshold value. The total current is controlled to decrease until the total current falls below the threshold value. For this reason, if the control is repeated frequently, the average value of the total current becomes small, so that the performance (printing speed, etc.) of the image forming apparatus cannot be fully exhibited.

  An object of the present invention is to provide an image forming apparatus capable of increasing an average value of total currents input to the image forming apparatus.

  An image forming apparatus according to the present invention that achieves the above object is an image forming apparatus that forms an image on a sheet and outputs the sheet, and is operated by a current supplied from a commercial power source to the image forming apparatus. Corresponding to a load used for executing the function, a first threshold value serving as a threshold value of a total current input from the commercial power source to the image forming apparatus, and a predetermined load among the loads Next, a threshold value storage unit that stores a second threshold value that is larger than the first threshold value in advance, and monitors the total current. (1) Other than when the predetermined load is activated Uses the first threshold value as the threshold value to determine whether the monitored total current is greater than the first threshold value; and (2) operation of the predetermined load When the second threshold is used as the threshold A total current monitoring unit for determining whether or not the monitored total current is greater than the second threshold; and in (1), the monitored total current is the first threshold Control to lower the total current on condition that the total current is larger, and control to lower the total current on condition that the monitored total current is larger than the second threshold in (2). A total current control unit.

  In the present invention, the threshold value of the total current is not set uniformly, but is increased when a predetermined load is activated. This is because, for example, an inrush current that occurs immediately after power is supplied to the load has a very short period, and is ignored even if the total current exceeds the first threshold value due to the inrush current. However, in order to ensure the safety of the image forming apparatus, control is performed to lower the total current on condition that the second threshold value is exceeded. According to the present invention, it is possible to reduce the number of times control is performed to reduce the total current when the total current exceeds the first threshold value, so that the average value of the total current input to the image forming apparatus can be increased. It becomes possible. Further, the control for reducing the total current when the total current exceeds the thresholds (first threshold value, second threshold value) may cause noise generation. Since the number of times of executing can be reduced, noise generation can be reduced.

  In the above configuration, the predetermined load is a plurality of different types of loads, and the second threshold is set to a different value according to the plurality of different types of loads, and the threshold storage unit Is remembered.

  This configuration takes into account that the value of the inrush current differs depending on the type of load (for example, the fixing heater and the paper conveyance system motor), so that the preferable value as the second threshold value is different. In the case where the second threshold value is uniformly set for a plurality of different types of loads, the second threshold value is set based on the load for which the second threshold value must be minimized in consideration of the safety of the image forming apparatus. A threshold of 2 must be set. As a result, when the total current exceeds the second threshold value, there is a possibility that the number of times of executing the control for reducing the total current is increased. According to the above configuration, the second threshold value having a different value is set for a plurality of different types of loads according to the respective loads. Accordingly, since the number of times of executing the control for reducing the total current when the total current exceeds the second threshold can be reduced, the average value of the total current input to the image forming apparatus can be increased. It becomes possible.

  In the above-described configuration, the total current monitoring unit is configured to use the second threshold as the threshold value until a predetermined period elapses after a current is supplied to the predetermined load and the operation is started. The first threshold value is used as the threshold value after the period has elapsed.

  According to this configuration, the threshold value is not set to the second threshold value over the entire period when the predetermined load is operated, but the operation is started by supplying current to the predetermined load. The threshold value is set as the second threshold value until a predetermined period elapses from that time, and the first threshold value is set after the elapse of the period. For this reason, the second threshold value can be set for the inrush current, and control for reducing the total current can be avoided if the second threshold value is not exceeded even if the inrush current occurs. Since the first threshold value is changed after the rush current generation period has elapsed, if the first threshold value is exceeded for some reason other than the rush current, the total current is reduced, so that the safety of the image forming apparatus is increased. Sex can be secured.

  In the above configuration, the image forming apparatus includes a fixing heater for fixing the image on the sheet, and the total current control unit performs control for reducing the current supplied to the fixing heater to reduce the total current.

  Since the current supplied to the fixing heater is relatively large, the total current exceeding the first threshold value and the second threshold value can be quickly reduced by controlling the current supplied to the fixing heater to decrease. Can do. Thereby, the safety of the image forming apparatus can be improved.

  In the above configuration, in the case of (2), the total current control unit performs control to forcibly turn off the fixing heater to lower the total current.

Since the second threshold value is larger than the first threshold value, for the safety of the image forming apparatus, when the total current exceeds the second threshold value, it is necessary to quickly reduce the total current. According to this configuration, when the total current monitored exceeds the second threshold value during the operation of a predetermined load, the fixing heater is forcibly turned off to reduce the total current. For this reason, compared with the case where the electric current supplied to a fixing heater is reduced by feedback control, the total electric current can be reduced rapidly.
Another image forming apparatus according to the present invention is an image forming apparatus that forms an image on a sheet and outputs the image, and is operated by a current supplied from a commercial power source to the image forming apparatus, The load used for execution, the first threshold value serving as the threshold value of the total current input from the commercial power source to the image forming apparatus, and the predetermined load among the loads are associated with the load. A threshold value storage unit that stores in advance a second threshold value that is greater than the first threshold value, and monitors the total current; (1) Using the first threshold as a threshold and determining whether the monitored total current is greater than the first threshold; (2) when operating the predetermined load, Using the second threshold as a threshold, A total current monitoring unit for determining whether or not the monitored total current is greater than the second threshold; and in (1), the monitored total current is greater than the first threshold The total current is controlled to decrease the total current in the condition (2), and the control is performed to decrease the total current on the condition that the monitored total current is larger than the second threshold in (2). A control unit, wherein the predetermined load is a plurality of different types of loads, and the second threshold is set to a different value according to the plurality of different types of loads, and the threshold is set. Stored in a value storage unit, and the total current monitor unit in (2) sets a period for setting the second threshold value associated with the first load among the plurality of loads. The second threshold associated with the second load. For a period that overlaps with a period for setting a value, the lower second threshold is selected to determine whether the monitored total current is greater than the selected second threshold. .

  According to the present invention, it is possible to increase the average value of the total current input to the image forming apparatus.

1 is a diagram illustrating an outline of an internal structure of an image forming apparatus according to an embodiment. FIG. 2 is a block diagram illustrating a configuration of the image forming apparatus illustrated in FIG. 1. FIG. 3 is a block diagram illustrating a configuration of a threshold storage unit, a total current monitor unit, and a total current control unit provided in the image forming apparatus according to the present embodiment. It is a table | surface which shows an example of the 1st threshold value and 2nd threshold value which were memorize | stored in the threshold value memory | storage part. 6 is a graph illustrating an example of a relationship between a voltage signal output from a current-voltage conversion unit of a total current monitoring unit and a total current input to the image forming apparatus. 6 is a flowchart for explaining an example of a copy operation of the image forming apparatus according to the present embodiment (part 1); 6 is a flowchart for explaining an example of a copy operation of the image forming apparatus according to the present embodiment (part 2). 6 is an example of a graph illustrating control of total current in the image forming apparatus according to the present embodiment. It is an example of the graph explaining control of total current when a threshold value is uniformly set to 14A. 5 is a graph illustrating an example of a change in total current input to the image forming apparatus when a main switch is turned on and a copying operation is performed in the image forming apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an outline of the internal structure of an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 can be applied to, for example, a digital multifunction machine having functions of a copy, a printer, a scanner, and a facsimile. The image forming apparatus 1 includes an apparatus main body 100, a document reading unit 200 disposed on the apparatus main body 100, a document feeding unit 300 disposed on the document reading unit 200, and an operation disposed on the upper front surface of the apparatus main body 100. Part 400 is provided.

  The document feeder 300 functions as an automatic document feeder, and can continuously send a plurality of documents placed on the document placement unit 301 to the document reading unit 200.

  The document reading unit 200 includes a carriage 201 on which an exposure lamp or the like is mounted, a document table 203 made of a transparent member such as glass, a CCD (Charge Coupled Device) sensor (not shown), and a document reading slit 205. When reading a document placed on the document table 203, the document is read by the CCD sensor while moving the carriage 201 in the longitudinal direction of the document table 203. On the other hand, when reading a document fed from the document feeding unit 300, the carriage 201 is moved to a position facing the document reading slit 205, and the document fed from the document feeding unit 300 is scanned. Reading is performed by the CCD sensor through the reading slit 205. The CCD sensor outputs the read original as image data.

  The apparatus main body 100 includes a sheet storage unit 101, an image forming unit 103, and a fixing unit 105. The sheet storage unit 101 is disposed at the lowermost part of the apparatus main body 100 and includes a sheet tray 107 that can store a bundle of sheets. In the bundle of sheets stored in the sheet tray 107, the uppermost sheet is sent out toward the sheet conveyance path 111 by driving the pickup roller 109. The sheet is conveyed to the image forming unit 103 through the sheet conveyance path 111.

  The image forming unit 103 forms a toner image on the conveyed paper. The image forming unit 103 includes a photosensitive drum 113, an exposure unit 115, a developing unit 117, and a transfer unit 119. The exposure unit 115 generates light modulated according to image data (image data output from the document reading unit 200, image data transmitted from a personal computer, image data received by facsimile, etc.), and is uniformly charged. Irradiate the circumferential surface of the photosensitive drum 113. As a result, an electrostatic latent image corresponding to the image data is formed on the peripheral surface of the photosensitive drum 113. In this state, a toner image corresponding to image data is formed on the peripheral surface by supplying toner from the developing unit 117 to the peripheral surface of the photosensitive drum 113. This toner image is transferred by the transfer unit 119 to the sheet conveyed from the sheet storage unit 101 described above.

  The sheet on which the toner image is transferred is sent to the fixing unit 105. In the fixing unit 105, heat and pressure are applied to the toner image and the paper, and the toner image is fixed on the paper. The paper is discharged to the stack tray 121 or the paper discharge tray 123.

  The operation unit 400 includes an operation key unit 401 and a display unit 403. The display unit 403 has a touch panel function, and displays a screen including soft keys. The user operates the soft keys while viewing the screen to make settings necessary for executing functions such as copying.

  The operation key unit 401 is provided with operation keys including hard keys. Specifically, a start key 405, a numeric key 407, a stop key 409, a reset key 411, a function switching key 413 for switching between copy, printer, scanner, and facsimile are provided.

  A start key 405 is a key for starting operations such as copying and facsimile transmission. A numeric keypad 407 is a key for inputting numbers such as the number of copies and a facsimile number. A stop key 409 is a key for stopping a copying operation or the like halfway. A reset key 411 is a key for returning the set contents to the initial setting state.

  The function switching key 413 includes a copy key, a transmission key, and the like, and is a key for switching between a copy function and a transmission function. When the copy key is operated, an initial copy screen is displayed on the display unit 403. When the transmission key is operated, an initial screen for facsimile transmission and mail transmission is displayed on the display unit 403.

  FIG. 2 is a block diagram showing a configuration of the image forming apparatus 1 shown in FIG. The image forming apparatus 1 has a configuration in which an apparatus main body 100, a document reading unit 200, a document feeding unit 300, an operation unit 400, a control unit 500, and a communication unit 600 are connected to each other by a bus. Since the apparatus main body 100, the document reading unit 200, the document feeding unit 300, and the operation unit 400 have already been described, description thereof will be omitted.

  The control unit 500 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an image memory, and the like. The CPU executes control necessary for operating the image forming apparatus 1 on the above-described components of the image forming apparatus 1 such as the apparatus main body 100. The ROM stores software necessary for controlling the operation of the image forming apparatus 1. The RAM is used for temporary storage of data generated during execution of software, storage of application software, and the like. The image memory temporarily stores image data (image data output from the document reading unit 200, image data transmitted from a personal computer, image data received by facsimile, etc.).

  The communication unit 600 includes a facsimile communication unit 601 and a network I / F unit 603. The facsimile communication unit 601 includes an NCU (Network Control Unit) for controlling connection of a telephone line with a destination facsimile and a modulation / demodulation circuit for modulating / demodulating a signal for facsimile communication. The facsimile communication unit 601 is connected to the telephone line 605.

  A network I / F unit 603 is connected to a LAN (Local Area Network) 607. A network I / F unit 603 is a communication interface circuit for executing communication with a terminal device such as a personal computer connected to the LAN 607.

  Next, the load in this embodiment is demonstrated. The load is activated by a current supplied from the commercial power source to the image forming apparatus 1 and is used for executing functions of the image forming apparatus 1. The function means a copy function, a printer function, a facsimile function, a scanner function, a sheet post-processing function (for example, a function for punching or stapling a sheet on which an image is formed), and the like. Specifically, the load is, for example, a motor 19 (FIG. 3) of a paper transport system used for transporting paper in the apparatus main body 100, and used to change the paper transport path in order to reverse the paper in double-sided printing. A solenoid used for feeding a document in the document feeding unit 300, a fixing heater 25 (FIG. 3), a CCD sensor of the document reading unit 200, a motor for moving the carriage 201 of the document reading unit 200, and an operation unit 400. Meaning electronic components (touch panel, backlight, etc.) constituting the communication unit 600.

  FIG. 3 is a block diagram illustrating the configuration of the power supply unit 11, the threshold storage unit 13, the total current monitor unit 15, and the total current control unit 17 provided in the image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 forms an image on a sheet based on the image data, and the fixing unit 105 fixes the image on the sheet and outputs it.

  The power supply unit 11 generates a power supply voltage used for the operation of the image forming apparatus 1 using an AC voltage supplied from the commercial power supply AC. The image forming apparatus 1 includes a plurality of power supply units that generate direct currents having different voltages, one of which is shown in FIG. The power supply unit 11 generates a power supply voltage that drives the motor 19 of the paper conveyance system of the image forming apparatus 1. The image forming apparatus 1 includes a power line 21. The power supply line 21 connects the plurality of power supply units (including the power supply unit 11) and the fixing unit 105 of the image forming apparatus 1 to the commercial power supply AC.

  The power supply unit 11 rectifies and smoothes the AC voltage supplied from the commercial power supply AC through the power supply line 21 to generate a DC power supply voltage Vd. The power supply voltage Vd is supplied to the motor 19. In the power supply unit 11, the power supply voltage Vd is fed back and controlled so that the power supply voltage Vd becomes a predetermined constant voltage.

  The motor 19 of the paper transport system is controlled by the motor control unit 23. The motor control unit 23 is realized by a CPU, a RAM, and a ROM provided in the control unit 500 shown in FIG.

  The fixing unit 105 includes a fixing heater 25 and a temperature detection element 27. The fixing heater 25 is, for example, a halogen lamp. The fixing heater 25 generates heat, and the toner of the toner image is heated and melted to fix the image on the paper. The temperature detection element 27 is a thermistor, for example, and detects the temperature of the fixing heater 25. The detected signal is sent to the fixing heater controller 29. The fixing heater control unit 29 is realized by a CPU, a RAM, and a ROM provided in the control unit 500 shown in FIG.

  The triac 31 and the gate trigger circuit 33 are used for phase control of the fixing heater 25. A series circuit of the fixing heater 25 and the triac 31 is connected to the power line 21. The fixing heater control unit 29 generates a control signal S1 based on the signal detected by the temperature detection element 27. The trigger pulse generated by the gate trigger circuit 33 is controlled by the control signal S1 to control the temperature of the fixing heater 25.

  The threshold value storage unit 13 stores a first threshold value and a second threshold value in advance. The threshold storage unit 13 is realized by a ROM provided in the control unit 500 shown in FIG. FIG. 4 is a table showing an example of the first threshold value and the second threshold value stored in the threshold value storage unit 13. The first threshold value and the second threshold value are threshold values of the total current input from the commercial power supply AC to the image forming apparatus 1. The second threshold value is larger than the first threshold value.

  The first threshold value is used to make the total current input to the image forming apparatus 1 smaller than the upper limit value of the commercial power supply AC. Therefore, the first threshold value is selected to be smaller than the upper limit value (15A) and close to the upper limit value. Here, the first threshold value is, for example, 14A.

  The second threshold value is stored in the threshold value storage unit 13 in association with a predetermined load among the loads that are activated by the current supplied to the image forming apparatus 1 from the commercial power supply AC. A value larger than the first threshold value and the upper limit value is selected as the second threshold value. Here, the second threshold value is set to 17A and 20A, for example.

  The second threshold value of 20A is stored in the threshold value storage unit 13 in association with the fixing heater 25. Since the inrush current that flows when the fixing heater 25 is operated is relatively large, the total current may exceed 15A and reach the vicinity of 20A. Therefore, 20A is used as the second threshold value when the fixing heater 25 is operated.

  The second threshold value of 17A is stored in the threshold value storage unit 13 in correspondence with the paper conveyance system motor 19. The inrush current that flows when the motor 19 is operated is smaller than the inrush current that flows when the fixing heater 25 is operated, but may exceed 15A and reach 17A. Therefore, 17A is used as the second threshold value when the motor 19 is operated. The voltage signals V1, V2, and V3 will be described in the total current monitor unit 15.

  Although the fixing heater 25 and the motor 19 have been described as an example of the load for setting the second threshold value, the present invention is not limited to these loads, and the total current exceeds the first threshold value due to the occurrence of an inrush current. The second threshold value may be set for other loads (for example, a solenoid used to change the paper conveyance path in order to reverse the paper in duplex printing).

  The threshold value storage unit 13 stores a period T1 corresponding to the fixing heater 25, and stores a period T2 corresponding to the motor 19 of the paper transport system.

  The period T1 is the same as or slightly longer than the period in which the inrush current flowing through the fixing heater 25 is generated when the fixing heater 25 is operated. When the inrush current occurs, the total current becomes larger than the upper limit value (15A). Therefore, even if the total current exceeds the first threshold value (14A) in the period T1, the fixing heater 25 is not forcibly turned off.

  The period T2 is set to be the same as or slightly longer than the period in which the inrush current flowing through the motor 19 is generated when the motor 19 of the paper transport system is operated. When the inrush current occurs, the total current becomes larger than the upper limit value (15A). Therefore, the motor 19 is not forcibly turned off during the period T2 even if the total current exceeds the first threshold value (14A). The periods T1 and T2 are determined according to the load. Therefore, the period T1 and the period T2 may be the same or different.

  The total current monitor unit 15 monitors the total current supplied to the image forming apparatus 1 from the commercial power supply AC, and (1) uses the first threshold value as a threshold value except when a predetermined load is operated. Determining whether the monitored total current is greater than the first threshold, and (2) using a second threshold as a threshold when a predetermined load is activated It is determined whether the total current is greater than the second threshold value.

  The total current monitor unit 15 includes a current transformer 35, a current-voltage conversion unit 37, a threshold selection unit 39, and a comparator 41. The current transformer 35 is connected to the power supply line 21 and includes a primary winding and a secondary winding. A part of the power supply line 21 is a primary winding of the current transformer 35. A total current supplied to the image forming apparatus 1 flows through the power line 21, and the total current is converted into a minute current by the current transformer 35. A current-voltage converter 37 is connected to the secondary winding of the current transformer 35 through which a minute current flows. The current-voltage conversion unit 37 includes, for example, a resistor, a rectifier diode, a smoothing capacitor, and the like that are connected in parallel to the secondary winding of the current transformer 35. The current / voltage converter 37 obtains a voltage signal corresponding to the minute current.

  FIG. 5 is a graph showing an example of the relationship between the voltage signal and the total current supplied to the image forming apparatus 1. The voltage signal is proportional to the total current. If the total current is 20A, the voltage signal is V1, if the total current is 17A, the voltage signal is V2, and if the total current is 14A, the voltage signal is V3. V1> V2> V3.

  The threshold selection unit 39 is realized by a CPU, a ROM, and a RAM included in the control unit 500 of the image forming apparatus 1. The threshold selection unit 39 selects a threshold corresponding to the operation status from the threshold storage unit 13 according to the operation status of the image forming apparatus 1. More specifically, the threshold value selection unit 39 has a 20A-th time until a period T1 elapses after the current is supplied to the fixing heater 25 by the control of the fixing heater control unit 29 and the fixing heater 25 starts operating. 2 is selected (actually, the voltage signal V1 is selected). Then, after the elapse of the period T1, the threshold selection unit 39 selects the first threshold instead of the second threshold of 20A.

  The threshold selection unit 39 keeps the second threshold value of 17A from the start of the operation of the motor 19 when the current is supplied to the paper conveyance system motor 19 under the control of the motor control unit 23 until the period T2 elapses. (Actually, the voltage signal V2 is selected). Then, after the elapse of the period T2, the threshold selection unit 39 selects the first threshold instead of the second threshold of 17A. If there is a period in which the period T1 and the period T2 overlap, the lower second threshold value is selected. In other cases, the threshold selection unit 39 selects the first threshold of 14A (actually, the voltage signal V3 is selected).

  The comparator 41 compares the total current supplied to the image forming apparatus 1 with the threshold selected by the threshold selection unit 39. Actually, the voltage signal output from the current-voltage conversion unit 37 is compared with the voltage signal corresponding to the threshold selected by the threshold selection unit 39.

  The total current control unit 17 performs control to lower the total current on condition that the monitored total current is larger than the first threshold value. When the predetermined load is operated, the monitored total current is Control is made to lower the total current on the condition that it is larger than the second threshold value. The total current control unit 17 includes a forced off signal generation circuit 43 and a selection circuit 45.

  The forced off signal generation circuit 43 generates a forced off signal S2. This signal S <b> 2 is generated when the comparator 41 determines that the total current supplied to the image forming apparatus 1 is larger than the threshold value selected by the threshold selection unit 39. The gate trigger circuit 33 forcibly turns off the fixing heater 25 by the forced off signal S2.

  When both the control signal S1 from the fixing heater control unit 29 and the forced off signal S2 from the forced off signal generation circuit 43 are input, the selection circuit 45 selects the forced off signal S2 and outputs it to the gate trigger circuit 33. .

  Next, the operation of the image forming apparatus 1 according to the present embodiment will be described using a copy operation as an example. 6 and 7 are flowcharts for explaining this operation.

  When the image forming apparatus 1 is powered on, the fixing heater control unit 29 generates a control signal S1 (step S1). The control signal S1 is sent to the gate trigger circuit 33 via the selection circuit 45, and the gate trigger circuit 33 generates a trigger pulse. Thereby, phase control of the fixing heater 25 is started.

  When the fixing heater 25 is activated, the threshold selection unit 39 selects the second threshold (20A) (step S3). The selected second threshold value is input to the comparator 41.

  The threshold selection unit 39 starts measuring the period T1 (step S5). Since the total current becomes larger than the first threshold value (14A) due to the inrush current flowing through the fixing heater 25, the total current exceeds the first threshold value (14A) in the period T1, which is the generation period of the inrush current. Also, the fixing heater 25 is not forcibly turned off. However, for the safety of the image forming apparatus 1, if the total current exceeds the second threshold (20A in this case), the fixing heater 25 is forcibly turned off to control the total current to be lowered.

  The threshold selection unit 39 determines whether the period T1 has elapsed (step S7). If the threshold selection unit 39 determines that the period T1 has not elapsed (No in step S7), the process proceeds to step S9.

  In step S9, the comparator 41 determines whether or not the total current is larger than the second threshold value. If the comparator 41 determines that the total current does not exceed the second threshold value (20A) (No in step S9), the process returns to step S7.

  If the comparator 41 determines that the total current exceeds the second threshold value (Yes in step S9), the forced-off signal generation circuit 43 generates the forced-off signal S2. When the control signal S1 and the forced off signal S2 are input, the selection circuit 45 gives priority to the forced off signal S2 and sends it to the gate trigger circuit 33. Based on the forced off signal S2, the gate trigger circuit 33 forcibly turns off the fixing heater 25 (step S11). Then, the process returns to step S9.

  When the threshold selection unit 39 determines that the period T1 has elapsed (Yes in step S7), the threshold selection unit 39 selects the first threshold (14A) (step S13), and the second The first threshold value is sent to the comparator 41 instead of the threshold value (20A).

  When the start key 405 (FIG. 1) is operated after the warm-up of the image forming apparatus 1 is completed, the copying operation of the image forming apparatus 1 starts (step S15).

  The comparator 41 determines whether or not the total current is larger than the first threshold value (step S17). If the comparator 41 determines that the total current exceeds the first threshold value (Yes in step S17), the forced-off signal generation circuit 43 generates the forced-off signal S2. When the control signal S1 and the forced off signal S2 are input, the selection circuit 45 gives priority to the forced off signal S2 and sends it to the gate trigger circuit 33. Based on the forced off signal S2, the gate trigger circuit 33 forcibly turns off the fixing heater 25 (step S19). Then, the process returns to step S17.

  If the comparator 41 determines that the total current does not exceed the first threshold (No in step S17), the threshold selection unit 39 causes the motor control unit 23 to operate the motor 19 of the paper transport system. It is determined whether or not it has been started (step S21). If the threshold selection unit 39 determines that the operation of the motor 19 of the paper transport system has started (Yes in step S21), the threshold selection unit 39 selects the second threshold (17A). (Step S23 in FIG. 7), the data is sent to the comparator 41. Further, the threshold selection unit 39 starts measuring the period T2 (step S25). The processing after step S25 is the same as that of the fixing heater 25. Step S27 corresponds to step S7, step S29 corresponds to step S9, and step S31 corresponds to step S11. As a result, even if an inrush current is generated in the motor 19 and the total current is increased, if it is equal to or less than the second threshold value (17A), it is ignored and control for decreasing the total current is not performed.

  When the threshold selection unit 39 determines that the period T2 has elapsed (Yes in step S27), the threshold selection unit 39 selects the first threshold (14A) (step S33), and the second The first threshold value is sent to the comparator 41 instead of the threshold value (17A). Then, the process proceeds to step S17.

  If it is determined that the operation of the paper transport system motor 19 has not started (No in step S21), the threshold selection unit 39 determines whether or not the paper on which the image is formed has been output (step S35). . The output of the sheet on which the image is formed means that the sheet on which the image is formed is discharged onto the stack tray 121 or the discharge tray 123 shown in FIG. If the threshold selection unit 39 determines that the sheet is not output (No in step S35), the process returns to step S17. If the threshold selection unit 39 determines that the sheet has been output (Yes in step S35), the copying operation of the image forming apparatus 1 ends.

  The effect of this embodiment will be described. FIG. 8 is an example of a graph for explaining the control of the total current in the image forming apparatus 1 according to the present embodiment. FIG. 9 is an example of a graph for explaining the control of the total current when the threshold value is uniformly set to 14A. These graphs are presented for convenience in explaining the control of the total current, and do not represent actual data. 8 and 9, the horizontal axis represents time, and the vertical axis represents total current. (A) shows the case where the total current is not controlled by the threshold value, (B) shows the case where the total current is controlled by the threshold value, and (C) shows the lighting duty of the fixing heater 25 based on the control signal S1. (D) shows the generation period of the forced-off signal S2.

  As shown in FIGS. 8B and 9B, if the area indicated by hatching between the first threshold value 14A and the total current graph line is small, the total current If the average value is large and the area of the region is large, the average value of the total current is small.

  In the control described with reference to FIG. 9, the total current is uniformly controlled with 14A as a threshold value. Therefore, as shown in FIG. 9B, the total current is generated every time an inrush current is generated in the fixing heater 25 and the motor 19. The threshold is exceeded. For this reason, the number of times of control for decreasing the total current by decreasing the duty ratio for turning on the fixing heater 25 is increased, and as a result, the average value of the total current is lowered.

  On the other hand, in the present embodiment shown in FIG. 8, the period during which the inrush current is generated in the fixing heater 25 is the second threshold (20A), and the period during which the inrush current is generated in the motor 19 is the second threshold ( 17A), and during the other periods, the total current is controlled as the first threshold value (14A). Therefore, since control for lowering the total current is not performed every time an inrush current occurs, the average value of the total current can be increased.

  As described above, in the present embodiment, the threshold value of the total current is not uniformly set, but the first threshold value (14A) and the second threshold value (17A, 20A) larger than this. ) Is set. The second threshold value is set in a period (T1, T2) in which a predetermined load (fixing heater 25, motor 19) starts operating and an inrush current is generated. This is because the inrush current generated immediately after power is supplied to the load has a very short period, so that even if the total current exceeds the first threshold value due to the inrush current, it is ignored. However, in order to ensure the safety of the image forming apparatus 1, control is performed to lower the total current on condition that the second threshold value is exceeded. As described above, according to the present embodiment, the number of times of executing the control for reducing the total current when the total current exceeds the first threshold value can be reduced, so that the average of the total current input to the image forming apparatus 1 can be reduced. The value can be increased. In addition, the control for lowering the total current when the total current exceeds the thresholds (first threshold value, second threshold value) may cause noise generation. Since the number of times control is executed can be reduced, noise generation can be reduced.

  In the present embodiment, as shown in FIG. 4, the predetermined load is a plurality of different types of loads (fixing heater 25, motor 19), and the second threshold is a plurality of different types of loads. Accordingly, different values (20A, 17A) are stored in the threshold storage unit 13. This is because the magnitude of the inrush current differs depending on the type of load, and thus the preferable value as the second threshold value is considered. In the case where the second threshold value is uniformly set for a plurality of different types of loads, in consideration of the safety of the image forming apparatus 1, the load on which the second threshold value must be minimized is used as a reference. A second threshold must be set. As a result, when the total current exceeds the second threshold value, there is a possibility that the number of times of executing the control for reducing the total current is increased. According to this embodiment, the second threshold value having a different value is set for a plurality of different types of loads according to each load. Accordingly, since the number of times of executing the control for reducing the total current when the total current exceeds the second threshold value can be reduced, the average value of the total current input to the image forming apparatus 1 can be increased. Is possible.

  Further, in the present embodiment, the total current monitoring unit 15 has a predetermined period (T1, T2) after the current is supplied to a predetermined load (fixing heater 25, motor 19) to start the operation. The second threshold value is used as the threshold value until the time has elapsed, and the first threshold value is used as the threshold value after the period has elapsed. Therefore, according to the present embodiment, instead of setting the threshold value to the second threshold value over the entire period when the predetermined load is operated, current is supplied to the predetermined load. The threshold is set to the second threshold until a predetermined period elapses after the operation is started, and the first threshold is set after the period elapses. For this reason, the second threshold value can be set for the inrush current, and control for reducing the total current can be avoided if the second threshold value is not exceeded even if the inrush current occurs. Since the first threshold value is changed after the rush current generation period has elapsed, if the first threshold value is exceeded for some reason other than the rush current, the total current is reduced, so that the image forming apparatus 1 Safety can be ensured.

  Further, according to the present embodiment, the total current control unit 17 performs control to reduce the total current by performing control to reduce the current supplied to the fixing heater 25. Since the current supplied to the fixing heater 25 is relatively large, the total current exceeding the first threshold value and the second threshold value can be quickly obtained by controlling the current supplied to the fixing heater 25 to be lowered. Can be lowered. Thereby, the safety of the image forming apparatus 1 can be improved.

  In this embodiment, when the total current exceeds the second threshold value and the total current is controlled to be reduced, the fixing heater 25 is forcibly turned off to reduce the total current. Since the second threshold value is larger than the first threshold value, for the safety of the image forming apparatus 1, when the total current exceeds the second threshold value, it is necessary to quickly reduce the total current. According to this configuration, if the monitored total current exceeds the second threshold value when a predetermined load is activated, the fixing heater 25 is forcibly turned off to reduce the total current. For this reason, compared with the case where the electric current supplied to the fixing heater 25 is reduced by feedback control, the total electric current can be reduced rapidly.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 13 Threshold storage part 15 Total current monitor part 17 Total current control part 19 Paper conveyance system motor (an example of load)
25 Fixing heater (example of load)
AC commercial power

Claims (4)

An image forming apparatus that forms an image on paper and outputs the image,
A load that is operated by a current supplied from a commercial power source to the image forming apparatus and is used to execute the function of the image forming apparatus;
From a first threshold value that is a threshold value of a total current input from the commercial power source to the image forming apparatus, and a first load value that is associated with a predetermined load among the loads. A threshold value storage unit that stores a large second threshold value in advance;
Monitoring the total current; (1) using the first threshold as the threshold except when the predetermined load is operating, and the monitored total current is the first threshold And (2) using the second threshold value as the threshold value when the predetermined load is operating, and the total current monitored is the second threshold value. A total current monitor that determines whether or not the value is greater than the value;
In (1), the total current is controlled to be reduced on condition that the monitored total current is larger than the first threshold value. In (2), the monitored total current is A total current control unit that performs control to reduce the total current on condition that it is larger than a second threshold ;
The predetermined load is a plurality of different types of loads, and the second threshold value is set to a different value according to the different types of loads, and is stored in the threshold value storage unit. And
In the (2), the total current monitor unit is associated with a period for setting the second threshold value associated with the first load and the second load among the plurality of loads. For a period that overlaps the period for setting the second threshold value, the lower second threshold value is selected, and the monitored total current is greater than the selected second threshold value. An image forming apparatus that determines whether the size is large . The total current monitoring unit uses the second threshold value as the threshold value until a predetermined period elapses after the current is supplied to the predetermined load and the operation is started. The image forming apparatus according to claim 1, wherein the first threshold value is used as the threshold value after the elapse of the period. A fixing heater for fixing the image to the paper;
The image forming apparatus according to claim 1, wherein the total current control unit performs control to reduce the total current by performing a control to reduce a current supplied to the fixing heater. The image forming apparatus according to claim 3 , wherein in the case of (2), the total current control unit performs control to forcibly turn off the fixing heater to reduce the total current.

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