JP2005258346A - Power control device, image forming apparatus and power control program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently suppress a rush current allowed to flow into a load within suitable control time by changing the increase rate of power supply time while considering a resistance characteristic for the temperature of the load and to prevent the increase of a flicker value by suppressing the voltage variation of a commercial power supply. <P>SOLUTION: An image forming apparatus is provided with a fixing device 23 constituted of a heater 27 whose resistance characteristic for temperature is positive, a thermistor 29 for detecting the circumferential face temperature of a heat roller 25, and so on. When the circumferential face temperature of the heat roller 25 which is heated by the heater 27 is reduced to less than a set temperature, soft start control for supplying power to the heater 27 for supply time in which the half period of voltage wavelength of a commercial power supply 70 is set to the longest time within prescribed time through a TRIAC 52 and then gradually increasing the supply time finally up to the full time of the half period is performed. In this case, the prescribed time is divided into two small sections and the increase rate of the supply time is increased in each small section. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention forms an image on a power control apparatus that controls power supply to a load such as a heater having a positive resistance characteristic to temperature, a power control program, and a recording medium (hereinafter referred to as a sheet) to which the power control apparatus is applied. The present invention relates to an image forming apparatus that performs the above.

  2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus includes a fixing device that firmly fixes a developer image (toner image) formed on the surface of a sheet.

  Generally, a fixing device includes a heating roller, a fixing roller, a heater, a temperature detection unit, and the like. The heating roller and the fixing roller heat, pressurize, melt, and fix the developer image formed on the surface of the paper that passes through the formed fixing portion (nip portion). The heater heats the heating roller. The temperature detection unit includes temperature detection means (thermistor) and the like, and detects the peripheral surface temperature of the heating roller near the fixing unit.

  In order to stably fix the developer image on the surface of the paper, it is necessary to maintain the temperature of the fixing unit at an optimum temperature. For this reason, the CPU that controls the operation of the image forming apparatus based on the result detected by the temperature detection unit performs ON / OFF control of the heater.

  As a heater serving as a heat source for the fixing device, a halogen heater or the like having excellent thermal response is generally used. The halogen heater has a positive resistance characteristic in which the resistance value increases as the temperature rises. Therefore, when electric power is supplied from a commercial power supply (AC power supply) to a halogen heater at a low temperature, an inrush current that reaches 10 times the current value that normally flows through the heater may flow due to the low resistance value. The influence on the peripheral equipment due to the voltage drop of the power supply could not be ignored.

  In addition, the European CE mark has an international standard that defines "voltage fluctuation and flicker limit values for devices whose input current per phase is 16 A or less" with respect to power supply voltage fluctuations. Is regulated so that lighting etc. does not flicker.

  Thus, various proposals have been made for conventional image forming apparatuses that are configured to suppress the inrush current flowing through the heater. As a typical example, there is a configuration that performs soft start (soft start on) control using phase control (see, for example, Patent Document 1).

Specifically, as shown in FIG. 10, at the start of heater power supply, power supply is started when the phase angle of the voltage waveform of the commercial power supply reaches a specified phase angle, and power is supplied at the zero cross timing of the commercial power supply voltage. Stop supplying. When the above process is repeated a plurality of times, the specified phase angle is gradually decreased every time the specified energization time elapses to increase the heater power supply time. As a result, the supply time finally becomes the full time of a half cycle of the AC power supply, and the heater is always in the ON state. There is also a configuration in which the specified phase angle is decreased for each cycle of the voltage waveform of the commercial power supply.
JP 2002-268447 A

  However, since the soft start control in consideration of the resistance characteristic with respect to the temperature of the heater is not performed in the configuration of the above-described Patent Document 1, the inrush current flowing through the heater may not be sufficiently suppressed. This is because the power supply time increases before the heater temperature rises to some extent, and a large amount of power may be supplied to the heater having a low resistance value.

  Therefore, it may be possible to suppress the occurrence of inrush current by reducing (gradually) the increase rate of the power supply time to the heater with respect to the elapsed time of soft start control, but the control time of soft start control is long. As a result, it takes time to increase the temperature of the heater. Therefore, it takes time to raise the heating roller to the set temperature.

  In the configuration in which the supply time is increased every time the specified energization time elapses, the specified phase angle is fixed during the specified energization time. Therefore, when the supply time after the specified energization time elapses (changes), the current flowing through the heater increases instantaneously. As a result, when the heater temperature is low, a large inrush current is generated with an instantaneous increase in current, and an increase in flicker value due to voltage fluctuation of the commercial power supply is not sufficiently prevented.

  The object of the present invention is to sufficiently suppress the inrush current flowing through the load within an appropriate control time by changing the rate of increase in the power supply time in consideration of the resistance characteristics with respect to the temperature of the load, and An object of the present invention is to provide a power control apparatus, a power control program, and an electrophotographic apparatus equipped with the power control apparatus that can suppress fluctuation and prevent an increase in flicker value.

  In order to solve the above problems, the present invention has the following configuration.

(1) Provided with a commercial power supply for supplying power to a load having a positive resistance characteristic to temperature, and when the temperature of the heated object heated by the load drops below a set temperature, the voltage waveform of the commercial power supply within a predetermined time Soft start control for supplying power to the load over a supply time having the longest half cycle of the power supply, gradually increasing the supply time, and finally supplying power to the load as the total time of the half cycle. In a power control device comprising a control means for performing,
The increase rate of the supply time is increased for each of a plurality of small sections constituting the predetermined time.

  In this configuration, when the temperature of the heated object heated by the load drops below the set temperature, the supply time for supplying power to the load is such that the half-cycle time of the voltage waveform of the commercial power supply is the longest time. Soft start control that gradually increases within a predetermined time is performed. Further, the predetermined time is divided into a plurality of small sections, and the rate of increase in the supply time increases as the transition from the first small section at the start of the soft start control to the last small section at the end of the control. That is, the rate of increase in supply time is lower in the first small section.

  Therefore, the rate of increase in the supply time is lower in the first small section, and the short supply time is maintained without increasing the supply time. As a result, only a small amount of power is supplied to the load at a low temperature at the beginning of the soft start control, that is, a low resistance value. Thereafter, in a small section where the increase rate of the supply time is higher than that in the first small section, a large amount of power is supplied to the load in a state where the temperature has risen to some extent, that is, in a state where the resistance value has increased.

  (2) The supply time at the start of the soft start control is 50% or less of the half-cycle time.

  In this configuration, since the initial value of the supply time in the first small section at the start of the soft start control is 50% or less of the half-cycle time, it suddenly becomes a load in a low temperature state, that is, a low resistance state. Large power is not supplied.

  (3) The control means monotonously increases the supply time over the entire predetermined time.

  In this configuration, the supply time is set based on, for example, a single exponential function in which the supply time monotonously increases over the predetermined time of the soft start control and the increase rate increases in a plurality of small sections.

  (4) The supply time is a fixed value of 50% or less of the half-cycle time in the first small section at the start of soft start control among the plurality of small sections.

  In this configuration, the first small section at the start of soft start control uses a fixed value (increase rate = 0%) with a supply time of 50% or less of a half cycle, and the increase ratio increases in the subsequent small sections. The supply time will gradually increase. Therefore, the fluctuation of the current flowing through the load in a low temperature state, that is, a state where the resistance value is low, and the current value are small.

(5) comprising storage means for storing in advance the value of the supply time for each elapsed time from the start of the soft start control;
The control means performs the soft start control using the value of the supply time read from the storage means.

  In this configuration, since the soft start control is performed using the value of the supply time stored in advance, it is not necessary to perform a process for obtaining the supply time.

  (6) The control means gradually decreases the supply time from the state in which power is supplied to the load over the entire time of the half cycle when the heated object reaches or exceeds a preset temperature, and finally Soft stop control for stopping power supply is performed, and soft stop control is performed using the value of the supply time read from the storage means.

  In this configuration, the soft start control is completed and the soft stop control is performed using the supply time value stored for the soft start control from the state in which power is supplied to the load for the entire period of the half cycle. Power supply is stopped. The predetermined time is divided into a plurality of small sections, and the rate of decrease in the supply time decreases as the transition from the first small section at the start of the soft stop control to the last small section at the end of the control. Therefore, it is not necessary to store a new supply time value for soft stop control in the storage means, and it is not necessary to newly provide a process for obtaining the supply time.

  In addition, in the first small section where the supply time is long and the decrease rate is high, high power is supplied to the load in a high temperature state, that is, a high resistance value state. Further, in the last small section where the supply time is longer than that of the first small section and the decrease rate is low, a small amount of power is supplied to the load in a state where the temperature is lowered, that is, in a state where the resistance value is low.

(7) In an image forming apparatus that forms an image by fusing and fixing a developer image transferred to a recording medium using a fixing device having a heating means having a positive resistance to temperature.
(1)-(6) is provided, The electric power control apparatus described in (6) is provided, and electric power is supplied to a heating means from the said AC power supply, It is characterized by the above-mentioned.

  In this configuration, the power supply of the heating unit provided in the fixing device is controlled by the power control device described in any one of (1) to (6) provided in the image forming apparatus.

(8) a first step of determining whether or not a temperature of a heated object heated by a load having a positive resistance characteristic to temperature is lower than a set temperature; and the temperature of the heated object is lower than a set temperature When the power is supplied to the load within a predetermined time, the supply time with the half cycle of the voltage waveform of the commercial power supply as the longest time is finally gradually increased to the full time of the half cycle. A power control program comprising: a second step;
The second step is a step of increasing an increase rate of the supply time for each of a plurality of small sections in the predetermined time.

  In this configuration, when it is determined in the first step that the temperature of the heated object heated by the load is lower than the set temperature, the soft start control is started in the second step for a predetermined time and power is supplied to the load. The supply time is gradually increased. In the second step, the increase rate of the supply time is increased for each of a plurality of small sections dividing the predetermined time.

  Therefore, if the initial value of the supply time of the first small section at the start of the soft start control where the load temperature is low is reduced, the rate of increase in the supply time is lower in the first small section, so the temperature is low, That is, only a small amount of power is supplied to a load with a low resistance value. Thereafter, in a small section where the increase rate of the supply time is higher than that in the first small section, a large amount of power is supplied to the load in a state where the temperature has risen to some extent, that is, in a state where the resistance value has increased.

  According to the present invention, the following effects can be obtained.

  (1) By increasing the increase rate of the supply time as the transition from the first small section at the start of the soft start control to the last small section at the end of the control, the increase rate of the supply time is lower in the first small section, A short supply time can be maintained without increasing the supply time. As a result, only a small amount of power is supplied to the load having a low resistance value, so that the current flowing through the load can be reduced, and the occurrence of an inrush current can be appropriately suppressed. Thereafter, a large amount of power is supplied to the load having a high resistance value, but since the current flowing through the load is small due to the high resistance value, the occurrence of an inrush current can be appropriately suppressed. As a result, it is possible to prevent the voltage of the commercial power source from becoming unstable and increasing the flicker value.

  (2) By setting the initial value of the supply time in the first small section at the start of the soft start control to 50% or less of the half-cycle time, a large amount of power is suddenly supplied to the load with a low resistance value. Since it can prevent, generation | occurrence | production of the inrush current in load can be suppressed more appropriately. Thereby, it is possible to more appropriately prevent the voltage of the commercial power source from becoming unstable and increasing the flicker value.

  (3) By increasing the supply time monotonously over the entire predetermined time of the soft start control, for example, the increase of the supply time and the increase rate of the supply time can be controlled only by using a single exponential function. Therefore, it is not necessary to provide storage means for storing the supply time, and soft start control can be performed with a simple process.

  (4) By setting the supply time to a fixed value of 50% or less of a half cycle over the first small section at the start of soft-start control, the fluctuation and current value of the current flowing through the load having a low resistance value can be reduced. It is possible to prevent the inrush current from occurring in the first small section. Thereby, it is possible to more appropriately prevent the voltage of the commercial power source from becoming unstable and increasing the flicker value.

  (5) By performing the soft start control using the value of the supply time stored in advance, it is not necessary to perform a process for obtaining the supply time, and the configuration of the soft start control can be simplified. In addition, since the supply time can be controlled with accuracy according to the operating speed of the control means, soft start control can be performed with high precision in the control means.

  (6) By performing the soft stop control using the supply time value stored for the soft start control, it is not necessary to store a new supply time value for the soft stop control in the storage means. Increase in storage capacity can be suppressed. Further, it is not necessary to perform processing for obtaining the supply time by the control means, and the configuration of the soft start control can be simplified.

  In addition, in the last small section where the supply time is shorter than the first small section and the rate of decrease is low, only a small amount of power is supplied to the load having a low resistance value, so that the occurrence of inrush current can be appropriately suppressed. . As a result, it is possible to appropriately prevent the commercial power supply voltage from becoming unstable and increasing the flicker value.

  (7) By applying the power control device described in any one of (1) to (6) to the image forming apparatus and controlling the power supply of the heating unit provided in the fixing device, the inrush power of the heating unit is increased. Generation | occurrence | production can be suppressed appropriately. As a result, it is possible to appropriately prevent the commercial power supply voltage from becoming unstable and increasing the flicker value.

  Hereinafter, an image forming apparatus according to the best embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory diagram showing the configuration of a digital copying machine which is an image forming apparatus according to an embodiment of the present invention. A digital copying machine (hereinafter referred to as a copying machine) 1 includes an image reading unit 10, an image processing unit (not shown), an image forming unit 20, and the like, and read image information or image information received from a connected network or the like. The image is formed on the paper based on the above.

  The image reading unit 10 reads the image information of the document, converts it into an electrical signal, and transmits it to the image processing unit. The image processing unit performs predetermined image processing on the received document image information. The image forming unit 20 includes a laser scanning unit (hereinafter referred to as “LSU”) 21, a photosensitive drum 22, a developing unit 23, a fixing device 24, and the like, and image information of a document subjected to image processing in the image processing unit. The image is formed on the paper based on the above. The LSU 21 scans a circumferential surface of the photosensitive drum 22 that is charged in advance with a light beam such as a laser beam based on the image information of the original to form an electrostatic latent image.

  The photosensitive drum 22 is supported rotatably. The developing unit 23 supplies a developer to the peripheral surface of the photosensitive drum 22 and visualizes (develops) the electrostatic latent image into a toner image. The fixing device 24 includes a heating roller (corresponding to a heated body of the present invention) 25, a fixing roller 26, and the like, and fuses and fixes the toner image transferred to the paper. The heating roller 25 and the pressure roller 26 are rotatably supported, and allow the sheet to pass through a fixing portion (nip portion) 28 between the heating roller 25 and the pressure roller 26. The heating roller 25 includes a heater 27 (for example, a halogen heater) inside the hollow cylinder, and heat-fixes the paper when the paper passes through the fixing unit 28. The heater 27 corresponding to the heating means (load) of the present invention has a positive resistance characteristic to temperature, and heats the peripheral surface of the heating roller 25 from the inside.

  The copying machine 1 accepts a copy start request when a copy start button (not shown) is pressed by the user or receives a print request signal transmitted from a PC (personal computer) or the like via a network or the like, and then performs an image forming operation. Start. When a copy start request is received, the document reading unit 10 reads the image information of the document, and the electrostatic latent image is formed on the peripheral surface of the photosensitive drum 22 based on the image information subjected to predetermined image processing by the image processing unit. Form an image. Thereafter, the toner image obtained by visualizing the electrostatic latent image is transferred to a sheet. Next, the sheet is passed through the fixing unit 28, the toner on the sheet is melted and fixed, firmly fixed on the sheet, and discharged onto the sheet discharge tray 30 to complete the image forming operation.

  When receiving the above-described copy start request or the like, the copying machine 1 starts supplying power to the heater 27 to start image formation and heats the peripheral surface temperature of the heating roller 25 to the set temperature. To do. During the image forming operation, a CPU described later controls the heating operation of the peripheral surface temperature of the heating roller 25.

  FIG. 2 is a block diagram showing a schematic configuration of the digital copying machine according to the embodiment of the present invention. The copier 1 includes a power supply unit 50 and a control unit 60. The power supply unit 50 includes a zero-cross signal detection circuit 51 and a triac 52, and supplies power from the connected commercial power supply 70 to the heater 27. The zero cross signal detection circuit 51 detects the zero cross signal of the voltage waveform of the commercial power supply 70 and transmits it to the CPU 63 via the input / output device (I / O) 64 constituting the control unit 60.

  The triac 52 receives a trigger signal from the CPU 63 via the input / output device (I / O) 65 constituting the control unit 60 and starts supplying power to the heater 27. Further, the triac 52 cuts off the power supply to the heater 27 regardless of the polarity at the zero cross timing (voltage value is 0) of the voltage waveform of the commercial power supply 70 during the power supply.

  The control unit 60 includes a RAM (Random Access Memory) 61, a ROM (Read Only Memory) 62, a CPU (Central Processing Unit) 63, input / output devices 64 and 65, an A / D converter 66, a memory 67, and the like. The entire operation of the copying machine 1 is controlled. The RAM 61 is used as a work area for temporarily storing data. The ROM 62 stores a predetermined program for controlling the power supply of the heater 27 and the like. A CPU 63 corresponding to the control means of the present invention controls the operation of the entire copying machine 1 based on a predetermined program.

  The A / D converter 66 receives an analog signal that is temperature information of the peripheral surface of the heating roller 25 transmitted from the thermistor 29 provided in the fixing device 24 via the comparator 67. Thereafter, it is converted into a digital signal and transmitted to the CPU 63. The memory 67 as the storage means of the present invention is nonvolatile and stores a specified count value (supply time) for soft start control described later.

  The fixing device 24 includes a thermistor 29. The thermistor 29 is disposed downstream of the fixing unit 28 in the rotation direction of the heating roller 25, detects the temperature of the peripheral surface of the heating roller 25, and transmits it to the CPU 63.

  The power supply unit 50 and the control unit 60 correspond to the power control device of the present invention.

  FIG. 3 is a flowchart showing a procedure of power supply control to the heater according to the embodiment of the present invention. The CPU 63 performs soft start control over a predetermined time when power supply to the heater 27 is started. In the soft start control, power is supplied to the heater 27 over a supply time that takes the longest half period of the voltage waveform of the commercial power supply 70 (the heater 27 is turned on). At this time, as shown in FIG. 4, the supply time is gradually increased and finally power is constantly supplied to the heater 27 over a half-cycle time, that is, the heater 27 is always turned on.

  In addition, 300 specified count values for each half cycle (10 ms) of the voltage waveform of the commercial power supply are stored in the memory 67 from addresses 0 to 299, and the specified count value stored in the address i (i = 0... 299) is stored as T. Expressed as (i). Further, control is performed in units of 10 ms corresponding to a half cycle of 20 ms, which is a commercial power supply 70 of 50 Hz in Europe.

  First, when a copy start request or the like is received, the peripheral surface temperature of the heating roller 25 detected by the thermistor 27 is compared with the set temperature (S1). If it is determined in S1 that the peripheral surface temperature of the heating roller 25 is lower than the set temperature, it is determined whether or not the value of i in the memory 67 is 0 or less (S2), that is, whether to start soft start control. Judge whether or not. A state where the address i for reading the designated count value stored in the memory 67 is 0 or less indicates a state where the copying machine 1 is started or the heater 27 is in an OFF state and soft start control is possible.

  Therefore, if it is determined that the value of i is larger than 0 in S2, it is determined that the heater 27 is always ON, and the process returns to S1. If it is determined in S2 that the value of i is 0 or less, the initial value 0 is set to the value of i (S3), and the process of S4 is repeated until it is determined that a zero cross signal has been received. If it is determined in S4 that the zero cross signal has been received, the designated count value stored in the address i of the memory 67 is read, the timer is started, and the count is started (S5). Further, in step S5, the heater 27 is turned off. In this embodiment, the heater 27 is turned off when the triac 52 is turned off from on, using the xerox timing of the voltage waveform of the commercial power supply 70 as a trigger.

  Thereafter, it is determined whether or not the count value has been counted up to the designated count value (S6), and the process of S6 is repeated until the count value has been counted up to the designated count value. If it is determined in S6 that the count value has increased to the specified count value, the heater 27 is turned on by turning on the triac 52 (S7), and the value of i is incremented by 1 (S8).

  Next, it is determined whether or not the value of i exceeds the last address value (299) in which the designated count value is stored, that is, whether or not the soft start control is finished (S9). If it is determined in S9 that the value of i does not exceed the last address value, the process returns to S4. If it is determined in S9 that the value of i has exceeded the last address value, a process of always turning on the heater 27, for example, a control of turning on the triac 52 every time a zero cross signal is received is started (S10), and the process returns to S1. .

  As a result of the above processing, as shown in FIG. 5, the power supply time to the heater 27 increases in a predetermined time of 3 seconds. In the soft start control, the predetermined time is divided into small sections of a first half section (2 seconds) and a second half section (1 second). In the first half of the start of the soft start control, as shown in FIG. 6, the power supply time to the heater 27 for each half cycle of the voltage waveform of the commercial power supply 70 is fixed to 2 milliseconds (specified count value is 8 milliseconds). . In the second half, control is performed with an increase rate of the supply time being 8 milliseconds / second (a decrease rate of the specified count value is 8 milliseconds / second). When the soft start control ends after 3 seconds of the predetermined time has elapsed, power is supplied to the heater 27 for a half period (10 ms) of the voltage waveform of the commercial power supply 27, and the heater 27 is always in the ON state.

  Here, as shown in FIG. 5, the increase rate of the supply time is changed in the first half section and the second half section in order to suppress the occurrence of the inrush current in the heater 27. That is, the heater 27 has a lower resistance value as the temperature is lower, and a higher resistance value as the temperature is higher. For this reason, the heater 27 having a lower temperature is more likely to cause a current to flow, and an inrush current is likely to occur.

  Therefore, with the configuration of the above example, when the temperature of the heater 27 is low, only a small amount of electric power is supplied until the temperature of the heater 27 rises to some extent, so that the occurrence of an inrush current can be appropriately suppressed. Thereby, the voltage fluctuation of the commercial power supply 70 can be suppressed appropriately. Further, in the latter half section where the temperature of the heater 27 has risen to some extent, the increase rate of the supply time is larger than in the first half section, but the resistance value of the heater 27 is larger than the resistance value of the heater 27 in the first half section. Therefore, since the current flowing through the heater 27 is small due to the high resistance value, the occurrence of an inrush current can be appropriately suppressed. Therefore, an increase in flicker value can be appropriately suppressed.

  Further, by storing a designated counter (supply time) in the memory 67 in advance, it is not necessary to perform a process for obtaining the supply time, and the configuration of the soft start control can be simplified. In addition, since the supply time can be controlled with accuracy according to the clock speed for driving the CPU 63, the CPU 63 can perform soft start control with high accuracy.

  It is not necessary to perform the same soft start control for all the heaters 27. For example, if the heater 27 has a certain resistance value at room temperature, the supply time in the first half section can be increased to 2.5 milliseconds, 3 milliseconds,... It is also possible to make the supply time shorter than 2 milliseconds in the above example. The same applies to the increase rate of supply time in the second half section.

  On the other hand, when it is determined in S1 that the peripheral surface temperature of the heating roller 25 is equal to or higher than the set temperature, it is determined whether or not the value of i is larger than 0, that is, whether or not the soft stop control is started (S11). When the address i is larger than 0, the soft start control is finished and the heater 27 is always on. If it is determined in S11 that the value of i is 0 or less, that is, if it is determined that the heater 27 is OFF, the process returns to S1.

  Here, the soft stop control in which the power supply time to the heater 27 is gradually shortened is performed when the heater 27 is turned off from the constantly ON state, and when the power supply is suddenly stopped, the voltage of the commercial power supply 70 changes. This is to prevent the flicker value from increasing due to the occurrence of the above. This is because, in particular, in the heater 27 having a large steady-state current in a constantly ON state and good heat responsiveness, instantaneous voltage fluctuation increases.

  If it is determined in S11 that the value of i is larger than 0, the last address value (299) in which the designated count value is stored is set as the value of i (S12). Next, the process of S13 is repeated until it is determined that a zero cross signal has been received. If it is determined in S13 that the zero cross signal has been received, the designated count value stored in the address i of the memory 67 is read, the timer is started, and the count is started (S14). Further, in step S13, a process for turning off the heater 27 is performed. In this embodiment, the heater 27 is turned off when the triac 52 is turned off from on using the zero cross timing of the voltage waveform of the commercial power supply 70 as a trigger.

  Thereafter, it is determined whether or not the count value has been counted up to the designated count value (S15), and the process of S15 is repeated until the count value is counted up to the designated count value. If it is determined in S15 that the count value has been counted up to the specified count value, the heater 27 is turned on by turning on the triac 52 (S16), and the value of i is decreased by 1 (S17).

  Next, it is determined whether or not the value of i is smaller than the initial value (0), that is, whether or not the soft stop control has ended (S18). If it is determined in S18 that the value of i is larger than the initial value, the process returns to S13. If it is determined in S18 that the value of i is smaller than the initial value, the heater 27 is turned off (S19), and the process returns to S1.

  Here, the specified count value for the soft start control is also used in the soft stop control because it is not necessary to store the new specified count value for the soft stop control in the memory 67, and the storage capacity of the memory 67 is increased. It is because it can suppress. Moreover, it is not necessary to perform processing for obtaining the supply time by the CPU 63, and the configuration of the soft stop control can be simplified.

  Further, by using the designated counter value for soft start control, the rate of decrease of the supply time (designated count value) can be reduced in the first half and the second half as shown in FIG. It can be reduced every time. Therefore, in the second half small section where the supply time is shorter than that in the first half section and the rate of decrease is low, only a small amount of power is supplied to the heater 27 having a low resistance value, so that the occurrence of an inrush current can be appropriately suppressed. Thereby, it is possible to more appropriately prevent the voltage of the commercial power source from becoming unstable and increasing the flicker value.

  In addition, as described above, the supply time is fixed in the second half section, and the temperature of the heater 27 in the first half section of the soft stop control is kept substantially constant in the second half section, or the supply time is set so as to gently fall. It is possible to lengthen the 28 temperature ripple period. As a result, the number of times of power supply to the heater 27 per hour is reduced, and a favorable result can be obtained for the flicker value.

  Note that the heater 27 in the always-on state is much higher than the set temperature of the heating roller 25. This is to quickly raise the peripheral surface temperature of the heating roller 25 to the set temperature. Accordingly, the heater 27 is held at a very high temperature until the peripheral surface temperature of the heating roller 25 rises to the set temperature or higher after the soft start control is finished.

  Here, the reason why the soft start control is performed not only when the copying machine 1 is started but also every time when the power supply to the heater 27 is started is that there is a similar effect other than at the time of starting. That is, the heating roller 25 is configured such that heat is difficult to escape in order to appropriately fix the sheet. Therefore, the heater 27 when the peripheral surface temperature of the heating roller 25 becomes equal to or lower than the set temperature does not decrease to the temperature when the copying machine 1 is started, but decreases to a temperature close thereto.

  Further, the peripheral surface temperature of the heating roller 25 does not rise to the set temperature during the soft start control for which the predetermined time is very short.

  In the embodiment of the present invention, the supply time at the start of the soft start control is 2 milliseconds. However, the present invention is not particularly limited to this. Although there is a problem in control accuracy, it is desirable to start the control with a supply time as short as possible in order to suppress the inrush current immediately after the start of power supply as much as possible. Here, the maximum supply time is ½ or less of the half cycle of the voltage waveform of the commercial power supply 70. This is to prevent a large inrush current from flowing to the heater 27 at the start of the soft start control.

  In the embodiment of the present invention, the soft start control is performed with the supply time in the first half section as shown in FIG. 4 being a fixed value, but the present invention is not particularly limited to this. In this control, the rate of increase in the supply time is increased for each small section, and may be set in accordance with the resistance characteristic of the heater 27. For example, as shown in FIG. 8, the rate of increase in supply time in the first half section (2 seconds) is 0.75 milliseconds / second, and the rate of increase in supply time in the second half section (1 second) is 8 milliseconds / second. Even if the start control is performed, the same effect as described above can be obtained.

Furthermore, as shown in FIG. 9, the same effect as described above can be obtained by performing soft start control that monotonously increases over the entire predetermined time in the first half section and the second half section. That is, in order to increase monotonously over the entire predetermined time, control is performed using a single function. 9, the supply time and y (ms), is based on the elapsed time from the soft-start control starts to y = 0.1x ^4.1 +1 to X (ms). As a result, the CPU 63 does not store the designated count value (supply time) in the memory 67 while simply increasing the rate of increase in the second half (1 second) compared to the rate of increase in the first half (2 seconds). Supply time can be determined. The coefficient of the function described above is determined according to the resistance characteristic with respect to the temperature of the heater 27.

  In the embodiment of the present invention, the copier 1 is used. However, the present invention is not particularly limited to this, and a power supply control device that controls power supply of a load having a positive resistance characteristic to temperature, and the power supply control. The same effect as described above can be obtained even if the apparatus includes the apparatus.

1 is an explanatory diagram showing a configuration of a digital copying machine that is an image forming apparatus according to an embodiment of the present invention; FIG. 1 is a block diagram showing a schematic configuration of a digital copying machine according to an embodiment of the present invention. It is explanatory drawing for demonstrating the soft start control which concerns on embodiment of this invention. It is a figure which shows the supply time of the electric power to the heater for soft start control with respect to the elapsed time from the soft start control start which concerns on embodiment of this invention. It is a figure which shows the electric power supply to a heater with respect to the voltage waveform of the commercial power source in soft start control which concerns on embodiment of this invention. It is a flowchart which shows the procedure of the electric power supply control to the heater which concerns on embodiment of this invention. It is a figure which shows the supply time of the electric power to the heater for soft start control with respect to the elapsed time from the soft stop control start which concerns on embodiment of this invention. It is a figure which shows the supply time of the electric power to the heater for soft start control with respect to the elapsed time from the soft start control start which concerns on embodiment of this invention. It is a figure which shows the supply time of the electric power to the heater for soft start control with respect to the elapsed time from the soft start control start which concerns on embodiment of this invention. It is a figure which shows the fixing heater input current waveform example in the conventional soft start control.

Explanation of symbols

1-Copier 23-Fixing device 25-Heating roller 27-Heater 50-Power supply unit 52-Triac 60-Control unit 63-CPU
70-Commercial power supply

Claims (8)

A commercial power source that supplies power to a load having a positive resistance characteristic to temperature, and when the temperature of a heated object heated by the load falls below a set temperature, a half cycle of the voltage waveform of the commercial power source within a predetermined time Control means for performing soft start control for supplying power to the load over a supply time having the longest time, gradually increasing the supply time, and finally supplying power to the load as the entire time of the half cycle In a power control device comprising:
The power control apparatus characterized by increasing an increase rate of the supply time for each of a plurality of small sections constituting the predetermined time.   2. The power control apparatus according to claim 1, wherein the supply time at the start of the soft start control is 50% or less of the half-cycle time.   The power control apparatus according to claim 1, wherein the control unit monotonously increases the supply time over the predetermined time.   2. The power control according to claim 1, wherein the supply time is a fixed value equal to or less than 50% of the time of the half cycle in the first small section at the start of soft start control among the plurality of small sections. apparatus. Comprising storage means for storing in advance the value of the supply time for each elapsed time from the start of the soft start control,
The power control apparatus according to claim 1, wherein the control unit performs the soft start control using the value of the supply time read from the storage unit.   The control means gradually reduces the supply time from the state in which power is supplied to the load over the entire time of the half cycle when the heated body reaches a set temperature or higher, and finally supplies power. The power control apparatus according to claim 5, further comprising soft stop control for stopping, and performing soft stop control using the value of the supply time read from the storage unit. In an image forming apparatus for forming an image by fusing and fixing a developer image transferred to a recording medium using a fixing device having a heating means having a positive resistance to temperature,
An image forming apparatus comprising the power control device according to claim 1, wherein power is supplied from the AC power source to a heating unit. A first step of determining whether or not a temperature of a heated object heated by a load having a positive resistance characteristic with respect to temperature is lower than a set temperature; and a predetermined time when the temperature of the heated object is lower than a set temperature A time for supplying electric power to the load within the time, and a supply time having a half period of the voltage waveform of the commercial power supply as a longest time is gradually increased to the entire time of the half period. A power control program comprising:
The power control program according to claim 2, wherein the second step is a step of increasing an increase rate of the supply time for each of a plurality of small sections in the predetermined time.

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