JP2006235305A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To alleviate production of DC component to AC, flowing of current of a fixed direction to the contact point of a connector connecting a control circuit and a heater and distortion of a current wave form becoming large, by equalizing positive half wave which is AC flowing in the positive direction and negative half wave which is AC flowing in the reverse direction when the current flowing to a heater for heating is equalized. <P>SOLUTION: An image forming apparatus is provided with a heating body to which the AC is supplied and which performs heating, a power control means controlling switching energizing and non-energizing of the heating body for each half wave of the current wave form of the AC, and the image forming apparatus uses symmetrical energizing control which is provided with two or more unit patterns where patterns for switching energizing or non-energizing is set according to each amount of power supplied to the heating body with a specified number of half waves as one control unit and which makes equivalent positive half waves with AC flowing in the positive direction and negative half waves with AC flowing in the reverse direction, even when the unit pattern with the number of energizing becoming an odd number is provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a printer or a copying machine, and more particularly to control used for a fixing device.

Conventionally, for example, in an image forming apparatus such as an electrophotographic copying machine or a laser beam printer, a transfer (indirect) method or directly on a surface of a recording material (transfer material, photosensitive paper, electrostatic recording paper, printing paper, etc.) For example, an on-demand system is known as a heating apparatus (heat fixing apparatus) for thermally fixing an unfixed developer image (toner image) formed and supported by the system. An on-demand heating apparatus uses, as a heating member, a low-heat capacity heater such as a ceramic heater and a heat-resistant film (fixing film) that slides on the heater. When the heating heater is energized, the fixing film and the pressure roller are heated, the output of the sensor for detecting the surface temperature of the fixing film is input to the temperature controller, the heating heater is turned on / off, and the predetermined temperature is reached. Is maintained. A pressure roller as a pressure member is pressed against a heater for heating through the fixing film to form a heating nip portion (fixing nip portion), and unfixed between the fixing film and the pressure roller in the fixing nip portion. A recording material on which a toner image is formed and supported is passed and nipped and conveyed. The toner of the unfixed toner image is melted by the heat from the heater for heating through the fixing film to fix the image on the surface of the recording material. The current to be supplied to the heater is energized and de-energized every half cycle (half wave) of the commercial power supply. The control program calculates the power according to the value of the temperature sensor, and the triac is turned on accordingly. Control by turning off / off. Many heating devices of the film heating system have been proposed and put into practical use (see, for example, Patent Document 1 to Patent Document 17).
JP-A-63-313182 Japanese Patent Laid-Open No. 1-263679 Japanese Patent Laid-Open No. 2-157878 JP-A-4-44075 JP-A-4-44076 JP-A-4-44077 JP-A-4-44078 JP-A-4-44079 JP-A-4-44080 JP-A-4-44081 JP-A-4-44082 JP-A-4-44083 JP-A-4-204980 JP-A-4-204981 JP-A-4-204982 JP-A-4-204983 JP-A-4-204984

  However, when the current flowing through the heater is made uniform, if the positive half-wave in which the alternating current flows in the positive direction and the negative half-wave in which the alternating current flows in the reverse direction are not uniform, the direct current with respect to the alternating current Components are generated, the transformer of the commercial power supply generates heat, current in a certain direction flows through the contact points of the connector connecting the control circuit and the heater, and the contact part is affected by migration, etc. The voltage waveform of the dual-purpose power supply is a sine wave, but the load increases and the distortion of the current waveform increases.

  The present invention has been made to solve the above-described problems of the prior art, and the object of the present invention is to provide a positive half wave in which an alternating current flows in the positive direction and a negative half wave in which the alternating current flows in the reverse direction. Provide control to make uniform.

  In order to achieve the above object, the invention according to claim 1 is directed to a conveying unit that conveys recording paper from a paper feeding unit to a paper discharging unit, and an image that forms an unfixed toner image directly or indirectly on the recording paper being conveyed. An image forming apparatus having a forming unit and a heating and fixing unit that heat-fixes an unfixed toner image formed on the recording paper on the recording paper. Power control means for controlling switching of energization / non-energization of the heating body for each half wave of the current waveform, and energization with a predetermined half-wave number as one control unit according to the amount of power supplied to the heating body Provided with a plurality of unit patterns in which a switching pattern of de-energization is set, and having power control means for obtaining a predetermined amount of power by repeating the unit patterns, and alternating with a positive half-wave in which an alternating current flows in the positive direction. Current, characterized in that it has a negative energization symmetrical control to equalize the half-wave flows in the opposite direction.

  Furthermore, in the image forming apparatus according to claim 1, in the image forming apparatus according to claim 1, in the energization symmetric control, when a pattern having an even energization half wave number is selected from unit patterns, the predetermined half wave number is set to one control unit. On the other hand, when an odd pattern (hereinafter referred to as an odd energization pattern) is selected, the energies are the same as when the energization half wave number is set to an even number by adding or subtracting the energization half wave number. One control unit half wave number calculating means for calculating the half wave number per control unit is provided, and the half wave number calculated by the one control unit half wave number calculating means is defined as one control unit.

  Further, according to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the odd-numbered energization patterns of the plurality of unit patterns each have two types of patterns, and one of the two types of patterns is an alternating current. A positive half-wave with a current flowing in the positive direction has a pattern that is one half wave greater than a negative half-wave with a negative direction, and the other has one half-wave with a negative half-wave that is one half-wave higher than the positive half-wave. If there are many patterns and an odd energization pattern is selected during power control, two types of patterns are alternately executed.

  Further, according to a fourth aspect of the present invention, in the image forming apparatus according to the first or third aspect, in the energization symmetric control, the number of odd-numbered energization patterns selected from the start to the end of the power control is the same. When there is an odd number of energization pattern selection times determination means for determining whether the number of times was an odd number of times, and when the odd number of energization patterns selected by the odd number of energization pattern selection times determination means at the end of power control is determined to be an odd number of times, the power control ends Immediately after that, one half wave is energized.

  Further, according to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the odd number energization pattern selection number determination means includes an odd number energization pattern count means for counting the number of selected odd number energization patterns, and the power control. It is characterized in that it is determined whether or not the number of counts counted by the odd-numbered energization pattern counting means at the end is an odd number.

  Further, the invention according to claim 6 is the image forming apparatus according to claim 4, wherein the odd number energization pattern selection number determination means has an odd number energization pattern inversion flag that inverts the flag when the odd number energization pattern is selected, It is characterized in that it is determined whether the odd energization pattern is selected an odd number of times in the state of the odd energization pattern inversion flag at the end of power control.

  The invention according to claim 7 is characterized in that the image forming apparatus according to any one of claims 1 to 6 is a laser beam printer.

  According to the present invention, the direct current component is not included in the consumed alternating current, and abnormal heat generation of the transformer of the power supply equipment can be prevented. Moreover, the migration which arises in the contact part of the connector which connects a heating body and a control circuit can be prevented. Furthermore, since the load is reduced, the distortion of the current waveform is reduced and the power efficiency can be improved. Further, as described in claim 3, one of the types of patterns has a pattern in which the positive half-wave in which the alternating current flows in the positive direction is one half wave more than the negative half-wave in which the negative current flows in the negative direction. Has a pattern in which the wave number of the negative half wave is one half wave greater than the wave number of the positive half wave, and when the odd-number energization pattern is selected during the power control, by alternately executing the two types of patterns, Since control can be performed in a desired power switching cycle (one control unit) regardless of even and odd energization patterns, power control with good responsiveness can be realized.

  Embodiments of the present invention will be described below in detail based on examples with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration related to the present invention. Reference numeral 200 denotes a main body main controller (heater control means) of the laser beam printer, 207 denotes an AC power supply unit of the laser beam printer, and 209 denotes a heat fixing device (heat fixing means) of the laser beam printer. The main control unit includes a zero cross detection unit 201, a fixing temperature adjustment control unit 202, and an A / D port (A / D converter) 203. The AC power supply unit includes a power source 206, a heater drive circuit (heater control means) 204, a switch (triac) 208 for opening and closing the fixing heater circuit, and a zero cross detection circuit 205. The heat fixing device has a fixing heater 210 and a fixing device temperature detecting means 211.

  FIG. 2 is a schematic side sectional view of a tandem color image. As shown in FIG. 2, in the tandem color image forming apparatus, the transfer material set in the transfer material cassette 150 is taken out one by one by the paper feed roller 151 at the lower part of the main body device, and is transferred to the image forming unit by the roll pair 140. Be fed. In the image forming unit, a transfer conveyance belt 11a for conveying a transfer material is stretched flat in a transfer material conveyance direction (from the bottom to the top in the figure) by a plurality of rotating rollers, and a bias is applied to the most upstream portion. The applied adsorbing roller 153 causes the transfer material to be electrostatically adsorbed to the transfer conveyance belt 11a. Also, four drum-shaped image carriers (hereinafter referred to as photosensitive drums) 101C, 101Y, 101M, and 101Bk are arranged in a straight line so as to face the belt conveyance surface, and constitute an image forming unit. ing. Each of the photosensitive drums 101C, 101Y, 101M, and 101Bk sequentially surrounds the vicinity of the peripheral surface thereof, and a transfer member (hereinafter referred to as a transfer roller) is disposed across the charging surface, the developing device, and the transfer surface of the transfer transfer belt 11a. Has been. Each developing unit accommodates toners of C (cyan), Y (yellow), M (magenta), and Bk (black) from the upstream side in the transfer material conveyance direction (lower side in FIG. 1). Each color image is sequentially transferred onto a transfer material conveyed by the transfer conveyance belt 11a, thereby forming a color image. This transfer material is conveyed to a fixing unit 152 located on the upper side of the apparatus, and the image is fixed and discharged.

  FIG. 3 is a sectional view of the heat fixing device. Reference numerals 154 and 155 denote a fixing member 154 (heating member) and a pressure member 155, which are in contact with each other to form a fixing nip portion (heating nip portion) N. The fixing member 154 includes a heating body 157 (heating heater), a heating body holder 156, a cylindrical heat resistant film 158 (fixing film), and the like. The pressure member 155 is an elastic pressure roller. The elastic pressure roller 30 is held by a bearing member (not shown), and a fixing film 158 is sandwiched between the downward surface of the heater 157 fixedly supported on the lower surface side of the heating body holder 156, and a pressure (not shown) is provided. The pressure is sufficiently applied from both ends in the longitudinal direction by the means so as to form a fixing nip portion N necessary for heat fixing. Reference numeral 159 denotes a temperature detection element such as a thermistor (hereinafter referred to as a thermistor) provided with a hollow portion in the heater holder, and detects the temperature raised in accordance with the heat generation of the heating element layer 157.

  FIG. 4 shows the relationship between the voltage of the commercial power supply and the current waveform of the heater. A zero cross signal is output at the rising and falling edges of the commercial power supply voltage at 0V. The fixing temperature control unit calculates a heater energization amount based on temperature information detected from the A / D port, and outputs a heater control signal based on the energization amount and a zero cross signal. Further, when the heater control signal is at the “HIGH” level, control is performed so that a current for energizing the heater flows.

  FIG. 5 is a diagram showing the relationship between the energization table for energizing the heater and the power consumption of the heater. The heat generation amount of the heater is divided into 17 steps (0% to 100%), and a unit pattern (energization pattern) in which one control unit is set to 8 waves (16 half waves) is set so that the energization amount of the heater can be controlled. The heater temperature is read and the energization amount of the heater is determined so as to reach a desired temperature, and the control signal is turned ON / OFF according to the control unit pattern to control the current flowing through the heater. In the figure, n indicates the number of energizations during 16 half-waves, and the output P (%) in the figure indicates the amount of power calculated by P = n / 16 × 100. M in the figure indicates the m-th half wave among the 16 half waves. For example, in the case of energizing 50% of power, the filled timing of the figure (1st half wave, 3rd half wave, 6th half wave, 7th half wave, 10th half wave, 13th half wave among 16 half waves, 14th half wave, 16th half wave), and energizes 8 half waves of the 16 half waves. At this time, when starting from the falling edge of the zero cross, it is shown that a black half portion outputs a negative half wave, and a gray portion outputs a positive half wave.

  However, when a pattern with an odd number of energization half-waves is used as in the control unit pattern of FIG. 5, a positive half-wave in which an alternating current flows in the positive direction and a negative half-wave in which the alternating current flows in the reverse direction. And are not equal. Therefore, as shown in FIG. 6, a pattern with an even number of energizing half-waves has 8 control unit patterns (16 half-waves), and a pattern with an even number of energizing half-waves has 16 waves (32 half-waves). By setting the wave), the positive and negative energization half-wave numbers can be made equal.

  As described above, according to the first embodiment, the positive half wave in which the alternating current flows in the positive direction and the negative half wave in which the alternating current flows in the reverse direction can be made completely equal. A direct current component is not included in the current, and abnormal heat generation of the transformer of the power supply equipment can be prevented. Moreover, the migration which arises in the contact part of the connector to which a heating body and a control circuit belong can be prevented. Furthermore, since the load is reduced, the distortion of the current waveform is reduced and the power efficiency can be improved.

  In the first embodiment, the control unit pattern has a plurality of control unit patterns, the energization half-wave number of the control unit pattern is an even number, and a predetermined half-wave number is calculated so that the power amount is matched accordingly. A method has been described in which the positive half-wave flowing in the positive direction is equal to the negative half-wave flowing alternating current in the reverse direction. In the second embodiment, a method will be described in which the positive half wave in which the alternating current flows in the positive direction and the negative half wave in which the alternating current flows in the reverse direction are made equal while the control unit pattern is kept constant.

  FIG. 1 is a block diagram showing a configuration used in the present embodiment, an abandoned diagram showing an open configuration of the image forming apparatus, a cross-sectional view of a heating fixing device, and a voltage of a commercial power source and a current waveform of a heater in FIG. 2, 3, and 4, description thereof is omitted here.

  FIG. 7 is a diagram showing the relationship between the energization table for energizing the heater and the power consumption of the heater. Read the heater temperature by setting a control unit pattern with eight wavelengths (16 half-waves) of the commercial power supply as a set of predetermined half-wave numbers so that the heater's heat generation amount can be controlled in 17 stages The energization amount of the heater is determined so as to reach a desired temperature, and the control signal is turned ON / OFF according to the control unit pattern to control the current flowing through the heater. Among the unit patterns, for the patterns having an even number of energized half waves, the numbers of positive half waves and negative half waves are made equal, and the patterns of I (n) and J (n) are set to be the same. For patterns with an odd number of energization half-waves, when starting from the falling edge of the zero cross, the I (n) table is set so that the positive half-wave is energized one more than the negative half-wave. , J (n) is set so that the negative half-wave is energized one more than the positive half-wave.

  FIG. 8 is an operation flow for energizing the positive half wave in which the alternating current flows in the positive direction and the negative half wave in which the alternating current flows in the reverse direction. When printing is started, in order to heat the fixing device, energization of the heater current is started by the fixing temperature adjustment control means (S101). For the odd pattern among the plurality of unit patterns, when starting from the falling edge of zero cross, the positive half wave is energized one more than the negative half wave in the table of I (n). The J (n) table is set so that the negative half-wave is energized one more than the positive half-wave. From the start of energization to the end of energization, every time an odd-number energization table is selected, the fixing temperature adjustment control unit performs control to switch between the I (n) and J (n) tables (S103). When the power control is finished, the energization is also finished (S104).

  As described above, according to the second embodiment, the positive half wave in which the alternating current flows in the positive direction and the negative half wave in which the alternating current flows in the reverse direction can be equalized. The DC component is not included in the power supply, and abnormal heat generation of the transformer of the power supply equipment can be prevented. Moreover, the migration which arises in the contact part of the connector which connects a heating body and a control circuit can be prevented. Furthermore, since the load is reduced, the distortion of the current waveform is reduced and the power efficiency can be improved.

  In the second embodiment, the method of equalizing the positive half wave in which the alternating current flows in the positive direction and the negative half wave in which the alternating current flows in the reverse direction while keeping the control unit pattern constant is described. In the third embodiment, control in which the wave number of the positive half wave and the negative half wave completely coincide with each other will be described.

  The block diagram showing the configuration used in the present embodiment, the abandoned diagram showing the open configuration of the image forming apparatus, the sectional view of the heat fixing device, the voltage of the commercial power supply and the current waveform of the heater are the diagrams of the first and second embodiments. 1, 2, 3, and 4, description thereof is omitted here. Moreover, since the figure which showed the relationship between the electricity supply table which supplies electricity to a heater, and the power consumption of a heater is shown by FIG. 7 of Example 2, description is abbreviate | omitted here.

  FIG. 9 is an operation flow for energizing the positive half wave in which the alternating current flows in the positive direction and the negative half wave in which the alternating current flows in the reverse direction. When printing is started, in order to heat the fixing device, energization of the heater current is started by the fixing temperature adjustment control means (S201). First, it is turned OFF to initialize an odd energization table selection flag that is reversed when an odd energization table is selected (S202). At the start of energization, in a pattern where the energization half-wave number is an odd number, when starting from the falling edge of zero cross, the positive half wave is one more than the negative half wave in the table of I (n). In the table of J (n), the negative half wave is set to be one more than the positive half wave (S203). Every time an odd energization table is selected from the start of energization to the end of energization, the odd energization table selection flag is inverted (S204, S205, S206). After the energization is completed, if the odd energization table selection flag is ON, it indicates that the positive half wave is one half wave more. Therefore, in order to equalize the positive and negative energization half wave numbers, One half-wave energization is completed (S208). Even if a counter is used instead of the odd energization selection flag, the positive half-wave in which the alternating current flows in the positive direction can be made equal to the negative half-wave in which the alternating current flows in the reverse direction. The counter is incremented every time the odd energization table is selected, and if the counter is odd after the energization is completed, the negative half wave may be energized by one half wave.

  As described above, according to the third embodiment, the positive half-wave in which the alternating current flows in the positive direction and the negative half-wave in which the alternating current flows in the reverse direction can be made completely equal. The direct current component is not included in the alternating current, and abnormal heat generation of the transformer of the power supply equipment can be prevented. Moreover, the migration which arises in the contact part of the connector to which a heating body and a control circuit belong can be prevented. Moreover, since control can be performed without changing the power switching cycle (one control unit) as in the first embodiment by the control that outputs half-wave at the end, power control with high responsiveness can be realized.

It is a block diagram which shows the structure regarding this invention. 1 is a schematic configuration diagram of an embodiment of an applicable color image forming apparatus used in the present invention. It is sectional drawing of a heat fixing device. It is a figure which shows the relationship between the voltage of a commercial power source, and the current waveform of a heater. It is a figure which shows the relationship between the electricity supply table which supplies electricity to a heater, and the power consumption of a heater. It is a figure which shows the relationship between the electricity supply table which supplies electricity to a heater, and the power consumption of a heater. It is a figure which shows the relationship between the electricity supply table which supplies electricity to a heater, and the power consumption of a heater. It is an operation flow for energizing equally a positive half-wave in which an alternating current flows in a positive direction and a negative half-wave in which an alternating current flows in a reverse direction. This is an operation flow for energizing the positive half-wave in which the alternating current flows in the positive direction and the negative half-wave in which the alternating current flows in the reverse direction completely and equally.

Explanation of symbols

11 Transfer material transport means 11a Transfer transport belt 11b Transfer transport belt drive rollers 11c, 11d, 11e Transfer transport belt driven roller 16 Development separation plate 101 Photosensitive drum 102 Transfer device 103 Development roller 104 Charging roller 106 Image writing device 108 Scanner unit 141 Registration sensor 150 Paper feed unit 151 Pickup roller 152 Fixing unit 153 Adsorption roller 154 Fixing film unit 155 Pressure roller 156 Heater holder 158 Fixing film 200 Main body main control unit 204 Heater drive circuit,
205 Zero cross detection circuit 208 Triac 210 Heater 211 Thermistor

Claims (7)

  Conveying means for conveying recording paper from a paper feeding section to a paper discharging section, image forming means for directly or indirectly forming an unfixed toner image on the recording paper being conveyed, and unfixed toner formed on the recording paper In an image forming apparatus having a heating and fixing means for heating and fixing an image on the recording paper, the heating body is heated by being supplied with an AC current, and the heating body is energized / de-energized every half wave of the AC current waveform. A plurality of unit patterns having a power control means for controlling the switching, and setting a switching pattern of energization / non-energization with a predetermined half-wave number as one control unit according to each amount of power supplied to the heating element (Energization pattern) is provided, and power control means for obtaining a predetermined amount of power by repeating the unit pattern is provided, and the wave number of the positive half-wave in which the alternating current flows in the positive direction and the negative number in which the alternating current flows in the reverse direction Having a energization symmetry control to equalize the half-wave wavenumber image forming apparatus according to claim.   2. The image forming apparatus according to claim 1, wherein in the energization symmetry control, when a pattern having an even number of energization half-waves is selected among unit patterns, a predetermined half-wave number is selected as one control unit, while an odd pattern is selected. In this case, one control unit half-wave number calculating means for calculating a half-wave number per control unit so that the amount of power coincides with the fact that the energization half-wave number is made even by adding or subtracting the energization half-wave number. And an image forming apparatus that controls the half wave number calculated by one control unit half wave number calculating means as one control unit.   2. The image forming apparatus according to claim 1, wherein an odd number of the plurality of unit patterns has two types of patterns, and one of the two types of patterns is a positive half in which an alternating current flows in a positive direction. The wave number of the wave is one half wave higher than the wave number of the negative half wave flowing in the negative direction, and the other has a pattern in which the wave number of the negative half wave is one half wave higher than the wave number of the positive half wave. An image forming apparatus that alternately executes two types of patterns when an odd pattern is selected during power control.   4. The image forming apparatus according to claim 1, wherein the energization symmetry control is an odd number that determines whether the number of selected odd patterns is an odd number of times from the start to the end of the power control. If the odd number of patterns selected by the odd pattern selection number determination means at the end of power control is determined to be an odd number of times, one half wave immediately after the end of power control. An image forming apparatus that is energized.   5. The image forming apparatus according to claim 4, wherein the odd-number pattern selection number determination means includes an odd-number pattern count means for counting the number of selected odd-number patterns, and the odd-number pattern at the end of power control. An image forming apparatus for determining whether or not the count number counted by the counting means is an odd number.   5. The image forming apparatus according to claim 4, wherein the odd-number pattern selection frequency determination means has an odd-number pattern inversion flag that inverts the flag when an odd-number pattern is selected, and is odd when power control is finished. An image forming apparatus comprising: determining whether an odd pattern is selected an odd number of times in a pattern inversion flag state.   The image forming apparatus according to claim 1, wherein the image forming apparatus is a laser beam printer.