JP2007003663A - Heater controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a temperature change width, without having to conduct complex calculations order to maintain temperature of a heat roller at a target temperature. <P>SOLUTION: The heater controller includes a temperature sensor 70 that measures the temperature of the heat roller 208; a section-determining part 12 that obtains a temperature difference between the measured temperature of the heat roller 208 obtained by the temperature sensor 70, and the target temperature of the heat roller 208 and determines the temperature section of a section determination table 16, to which the temperature difference belongs; a state-specifying part 13 that specifies the present temperature transition state of the heat roller 208, based on the temperature section determined previously by the section-determining part 12 and the temperature section determined this time by the part 12; and a duty ratio determining section 14, with which the temperature section determined this time by the section determining part 12 and the duty ratio, corresponding to the temperature transitional state specified by the state-specifying part 13, are determined by referring to a duty ratio determining table 17. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heater control device for duty-controlling the temperature of a heating roller used in a fixing device of an image forming apparatus.

  Conventionally, a heater control device that controls the duty of a heater that heats the temperature of the heating roller detects the temperature of the heating roller with a temperature sensor such as a thermistor, and if the detected temperature exceeds a certain target temperature, the duty ratio of the pulse signal To reduce the temperature of the heating roller, and if the detected temperature is lower than the target temperature, the duty ratio of the heating roller is increased by increasing the duty ratio of the pulse signal to increase the temperature of the heating roller. Is maintained at the target temperature.

  FIGS. 7A and 7B show tables that are referred to when the conventional heater control apparatus determines the duty ratio. The table shown in FIG. 7A includes a temperature difference item indicating the difference between the measured temperature of the heating roller and the target temperature, and a temperature category item indicating which temperature category the temperature difference belongs to. In this table, the target temperature is set to 150 degrees, and when the measured temperature is 153 degrees or more, the temperature difference belongs to the temperature category A, and when the measured temperature is 151 degrees to 152 degrees, the temperature difference is the temperature section B. If the measured temperature is 150 degrees, the temperature difference belongs to temperature category C, if the measured temperature is 148 degrees to 149 degrees, belongs to temperature section D, and the measured temperature is 147 degrees or less, the temperature difference Belongs to temperature category E.

  Then, the conventional heater control device determines the temperature section with reference to the duty ratio determination table shown in FIG. 7A, and determines the duty ratio for the determined temperature section with reference to the table shown in FIG. It was.

  FIG. 8 is a graph showing a temperature change of a conventional heater, where the vertical axis indicates temperature and the horizontal axis indicates time. At time t1, the heater temperature is 146 degrees, which is lower by 3 degrees or more than the target temperature of 150 degrees, so the temperature section E is determined with reference to the duty ratio determination table shown in FIG. The duty ratio of the pulse signal from time t1 to time t2 is 100%.

At time t2, since the heater temperature is 148 degrees, temperature section D is determined, and the duty ratio of the pulse signal from time t2 to t3 is 60%. In this way, the temperature of the heater is measured at a constant cycle, and the heater is controlled by a pulse signal having a duty ratio corresponding to the temperature difference between the measured temperature and the target temperature. Patent Document 1 is disclosed as a document showing the above-described technique.
JP-A-6-149122

  However, when performing such duty control, there is a time delay in the response of the temperature sensor and the heat conduction to the surface of the heating roller, so the delay in the actual response is large, and therefore the temperature fluctuation range (ripple temperature) is large. Problem arises.

  Here, it is considered to switch the heater on and off when the target set temperature is reached. First, the heater is turned on, the temperature is raised toward the target set temperature, and when the target temperature is reached, the heater is turned off, but even if it is turned off, the heater temperature does not stop rising immediately. Overshoot. Therefore, if it is not desired to heat the heater above the target temperature, it is necessary to turn off the heater before reaching the target temperature.

  On the other hand, when the temperature is decreasing, the opposite is true: when the temperature reaches the target set temperature and the heater is turned on, heat is transferred to the heater surface immediately. Undershoot occurs because there is not. In this example, the explanation was made simply by turning the heater on and off, but it is necessary to set the duty ratio earlier in the duty control as well.

  That is, in the conventional method, since the duty ratio is determined without considering whether the heater temperature is rising or falling, the temperature fluctuation range is increased as described above. A problem will occur.

  An object of the present invention is to provide a heater control device capable of reducing the temperature fluctuation range without performing complicated calculation when maintaining the temperature of the heating roller at the target temperature.

  A heater control device according to the present invention is a heater control device that duty-controls a heater that heats a heating roller, and includes a temperature measuring unit that measures the temperature of the heating roller, and a temperature of the heating roller that is measured by the temperature measuring unit. A division determining unit that calculates a temperature difference from a target temperature of the heating roller, and that determines which temperature segment the temperature segment belongs to within a predetermined temperature range; and the classification determination unit Based on the previously determined temperature class and the currently determined temperature class, the state specifying means for specifying the current temperature transition state of the heating roller, the temperature class determined by the class determining unit this time, and the status specifying means Duty ratio determination that determines a predetermined duty ratio as the duty ratio of the pulse signal that controls the heater with respect to the temperature transition state specified by Characterized in that it comprises a stage.

  Further, in the above configuration, when the state specifying means is a temperature section that shows a higher temperature difference in the temperature section determined this time than the temperature section previously determined by the section determination means, the temperature transition state is increasing. When the temperature determination unit is determined to be lower than the previously determined temperature class, the temperature transition state is specified to be falling, It is preferable that the temperature transition state is in equilibrium when the temperature classification determined by the classification determination unit and the temperature classification determined this time are the same temperature classification.

  Further, in the above configuration, the duty ratio determining means increases the duty ratio as the temperature difference is larger, and the duty ratio is higher when the temperature transition state is in equilibrium than when the temperature transition state is increasing. It is preferable to increase the duty ratio when the temperature transition state is lowering than when the temperature transition state is in equilibrium.

  In the above configuration, it is preferable that the state specifying unit specifies the temperature transition state in accordance with a plurality of temperature sections determined by the section determining unit within a certain period.

  According to the first aspect of the present invention, the temperature section to which the temperature difference between the temperature of the heating roller and the target temperature belongs is determined, and the temperature transition state of the heating roller is determined from the previously determined temperature section and the currently determined temperature section. Is determined, and a predetermined duty ratio is determined for the temperature difference and the temperature transition state. That is, since the duty ratio is determined in consideration of not only the temperature difference of the heating roller with respect to the target temperature but also the temperature transition state of the heating roller, the temperature fluctuation range should be reduced when maintaining the heating roller at the target temperature. Can do. Further, since the duty ratio is determined in advance for the temperature transition state and the temperature classification, the duty ratio can be determined without performing a complicated calculation.

  According to the second aspect of the present invention, since the temperature transition state is determined according to the previously determined temperature segment and the currently determined temperature segment, the temperature transition state can be accurately determined.

  According to the third aspect of the present invention, the duty ratio is increased as the temperature difference is increased, and the time during which the heater is turned on is lengthened. Therefore, the heating roller can be quickly brought close to the target temperature, and during the descent, the balance is maintained. Since the duty ratio is increased in the order of increasing and increasing, and the time for turning on the heater is lengthened, overshoot and undershoot can be reduced.

  According to the fourth aspect of the present invention, since the temperature transition state is specified according to the plurality of temperature segments determined in the past, the temperature transition state can be specified more accurately.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic side view mainly showing a mechanical configuration of an image forming apparatus when a heater control apparatus according to an embodiment of the present invention is applied to an image forming apparatus such as a digital multifunction peripheral, a network printer, or a facsimile machine. . The image forming apparatus includes a main body unit 200, a sheet post-processing unit 300 disposed on the left side of the main body unit 200, an operation unit 400 for a user to input various operation commands and the like, and an upper part of the main body unit 200. The document reading unit 500 disposed in the document reading unit 500 and the document feeding unit 600 disposed above the document reading unit 500.

  The operation unit 400 includes an operation panel 401, a start key 402, a numeric keypad 403, and the like. The operation panel 401 displays various operation screens and various operation buttons for the user to input various operation commands. The start key 402 is used for the user to input a print execution command and the like, and the ten key 403 is used for inputting the number of copies to be printed.

  The document feeding unit 600 includes a document placement unit 601, a document discharge unit 602, a paper feed roller 603, a document transport unit 604, a contact glass 605, and the like, and the document reading unit 500 includes a scanner 501 and the like. The paper feed roller 603 feeds out the original set on the original placement unit 601, and the original transport unit 604 transports the fed originals one by one on the scanner 501.

  The scanner 501 sequentially reads the conveyed document, and the read document is discharged to the document discharge unit 602. When the scanner 501 reads a document placed on the contact glass 605, the scanner 501 slides in the A direction to read the document.

  The main body 200 includes a plurality of paper feed cassettes 201, a plurality of paper feed rollers 202, a transfer roller 203, an intermediate transfer body roller 204, a photosensitive drum 205, an exposure device 206, and development for each color of yellow, magenta, cyan, and black. Apparatuses 207Y, 207M, 207C, and 207K, a heating roller 208, a discharge port 209, a discharge tray 210, and a recording paper transport unit 211 are provided.

  The heating roller 208 is composed of a pair of opposed rollers that rotate about a direction orthogonal to the conveyance direction of the recording paper P. The roller on the image forming surface side is made of a metal that is a hollow cylindrical body. It has a core body 50 and an elastic body layer 60 such as silicon rubber provided on the outer peripheral surface of the core body 50, and a known heater 80 (not shown in FIG. 1, see FIG. 2) is provided inside the core body 50. It is arranged. A temperature sensor 70 for detecting the temperature of the surface of the heating roller 208 is disposed in the vicinity of the heating roller 208.

  The photosensitive drum 205 is uniformly charged by a charging device (not shown) while rotating in the direction of the arrow. The exposure device 206 converts the modulation signal generated based on the image data of the document read by the document reading unit 500 into a laser beam and outputs it, and forms an electrostatic latent image on the photosensitive drum 205 for each color. The developing devices 207Y, 207M, 207C, and 207K supply each color developer to the photosensitive drum 205 to form a toner image for each color.

  The intermediate transfer body roller 204 transfers the toner images of each color from the photosensitive drum 205 and forms a color toner image on the intermediate transfer body roller 204.

  On the other hand, the paper feeding roller 202 pulls out the recording paper from the paper feeding cassette 201 in which the recording paper is stored, and the recording paper transport unit 211 transports the drawn recording paper to the transfer roller 203. The transfer roller 203 transfers the toner image on the intermediate transfer roller 204 to the conveyed recording paper. The recording paper to which the toner image has been transferred is conveyed to the heating roller 208 by the recording paper conveyance unit 211, and the heating roller 208 heats the transferred toner image and fixes it to the recording paper. Thereafter, the recording paper is conveyed to the discharge port 209 by the recording paper conveyance unit 211 and is carried into the paper post-processing unit 300. The recording paper is also discharged to the discharge tray 210 as necessary.

  The paper post-processing unit 300 includes a carry-in port 301, a recording paper transport unit 302, a carry-out port 303, a stack tray 304, and the like. The recording paper transport unit 302 sequentially transports the recording paper carried into the carry-in port 301 from the discharge port 209 and finally ejects the recording paper from the carry-out port 303 to the stack tray 304. The stack tray 304 is configured to move up and down in the direction of the arrow in accordance with the number of recording sheets stacked from the carry-out port 303.

  FIG. 2 is a block diagram of the image forming apparatus shown in FIG. In FIG. 2, only parts related to the heater control device according to the present invention are shown, and other parts are omitted.

  As shown in FIG. 2, the image forming apparatus includes a control unit 10, a temperature sensor 70, a heater 80, and an operation unit 400. The control unit 10 includes a CPU, a RAM, a ROM, and the like, and implements various functions for controlling the image forming apparatus by executing a control program stored in the ROM. In the image forming apparatus according to the present embodiment, in particular, the target temperature setting unit 11, the segment determining unit 12, the state specifying unit 13, the duty ratio determining unit 14, the pulse signal generating unit 15, the segment determining table 16, and the duty ratio determining. The function of the table 17 is provided.

  The target temperature setting unit 11 sets a target temperature of the heating roller 208 in accordance with an operation command from the user made using the operation unit 400. The classification determination unit 12 calculates a temperature difference between the measured temperature of the heating roller 208 detected by the temperature sensor 70 and the target temperature set by the target temperature setting unit 11 at a predetermined cycle, and the temperature to which the calculated temperature difference belongs. The classification is determined with reference to the classification determination table 16.

  FIG. 4 is a diagram showing the classification determination table 16. The classification determination table 16 includes items of temperature difference and temperature classification. In the item of temperature difference, the column described as “+3” indicates that the temperature difference of the measured temperature with respect to the target temperature is 3 degrees or more. In this case, the temperature difference belongs to the temperature category A. The column described as “+1 to +3” indicates that the temperature difference between the target temperature and the measured temperature is 1 degree or more and less than 3 degrees. In this case, the temperature difference belongs to the temperature category B. The column described as “−1 to +1” indicates that the temperature difference between the target temperature and the measured temperature is −1 degree or more and less than 1 degree. In this case, the temperature difference belongs to the temperature category C. The column described as “−3 to −1” indicates that the temperature difference between the target temperature and the measured temperature is −3 degrees or more and less than −1 degree. Belongs. In addition, the column described as “˜−3” indicates that the temperature difference between the target temperature and the measured temperature is less than −3 degrees, and in this case, the temperature difference belongs to the temperature category E.

  The state specifying unit 13 compares the temperature category (previous temperature category) to which the temperature difference previously determined by the category determination unit 12 belongs with the temperature category (current temperature category) to which the currently determined temperature difference belongs, and the state of the heating roller 208 Specify whether the transition state is rising, balancing, or falling.

  The duty ratio determination unit 14 determines a duty ratio corresponding to the temperature classification determined by the classification determination unit 12 and the temperature transition state of the heating roller 208 specified by the state specification unit 13 with reference to the duty ratio determination table 17. To do.

  FIG. 5 is a diagram showing the duty ratio determination table 17. The duty ratio determination table 17 includes items of temperature division, rising, balancing, and falling, and each column has a duty of a pulse signal corresponding to the temperature divisions A to E and the temperature transition state of the heating roller 208. Values expressing the ratio as a percentage are listed. As shown in FIG. 5, in the temperature sections B, C, and D, the duty ratio is set higher as it goes from rising to falling to reduce overshoot and undershoot.

  The pulse signal generation unit 15 generates a pulse signal having the duty ratio determined by the duty ratio determination unit 14 and outputs the pulse signal to the heater 80 to heat the heater 80. The temperature sensor 70 is composed of a thermistor, measures the temperature of the surface of the heating roller 208 at a predetermined cycle under the control of the segment determination unit 12, and outputs the measured temperature to the segment determination unit 12.

  Next, the control of the heater 80 by the image forming apparatus will be described using the flowchart shown in FIG. In this flowchart, the target temperature is assumed to be 150 degrees. First, in step S <b> 1, the target temperature setting unit 11 sets a target temperature for the heater 80. Here, the target temperature setting unit 11 may set a predetermined target temperature according to the ambient temperature of the heating roller 208, the print mode selected by the user via the operation unit 400, or the like. The temperature may be input via the operation unit 400, and the input temperature may be set as the target temperature.

  In step S <b> 2, the temperature sensor 70 measures the temperature of the heating roller 208. In step S3, the division determination unit 12 subtracts the target temperature from the measured temperature measured by the temperature sensor 70 to calculate a temperature difference ΔT, and this temperature difference ΔT is assigned to which temperature division of the division determination table 16 shown in FIG. Decide if it belongs. Here, the division determination unit 12 acquires the measurement temperature at a constant period (for example, 200 ms), calculates the temperature difference ΔT every time the measurement temperature is acquired, and to which temperature category the temperature difference ΔT belongs. decide. The determined temperature section is temporarily stored in a RAM or the like, and is erased when a certain period longer than the above period elapses. For example, when the measured temperature is 154 degrees, the temperature difference ΔT is determined to belong to the temperature section A, and when the measured temperature is 152 degrees, it is determined to belong to the temperature section B.

  In step S4, the state identification unit 13 compares the previous temperature segment calculated by the segment determination unit 12 with the current temperature segment, and when the current temperature segment shows a temperature difference higher than the previous temperature segment (for example, the current temperature segment). If the temperature category is determined to be temperature category A and the previous temperature category is determined to be temperature category B), the temperature transition state is identified as increasing, and the current temperature category shows a lower temperature difference than the previous temperature category In the case (for example, when the current temperature section is determined as the temperature section B and the previous temperature section is determined as the temperature section A), it is specified that the temperature transition state is falling, and the current temperature section and the previous temperature section are the same. If it is a temperature category, it is specified that the temperature transition state is in equilibrium.

  In step S5, the duty ratio determining unit 14 determines the duty ratio corresponding to the temperature classification determined in step S3 and the temperature transition state specified in step S4 with reference to the duty ratio determination table 17. For example, if it is determined in step S3 that the temperature difference ΔT belongs to the temperature category C, and it is specified in step S4 that the temperature transition state is increasing, the duty ratio is determined to be 10%.

  In step S6, the pulse signal generation unit 15 generates a pulse signal having the determined duty ratio and outputs the pulse signal to the heater 80. The heater 80 is turned on while the received pulse signal is at a high level to heat the heating roller 208. .

  Here, as shown in FIG. 5, the duty ratio increases in descending order, in equilibrium, and in increasing order in the temperature sections B, C, and D as shown in FIG. 5. Therefore, overshoot that occurs when the temperature of the heating roller 208 is rising and undershoot that occurs when the temperature of the heating roller 208 is decreasing are reduced, and the temperature fluctuation range with respect to the target temperature can be reduced.

  In the above embodiment, the temperature transition state is specified by comparing the previous temperature section and the current temperature section. However, the present invention is not limited to this, and the temperature section determined in the past than the previous temperature section and the current temperature are not limited thereto. The temperature transition state may be specified by using the division, that is, using the current temperature division and a plurality of temperature divisions determined in the past. Further, the temperature transition state may be specified by comparing the current measured temperature with the past measured temperature regardless of the temperature classification. Also in this case, as the past measurement temperature, the previous measurement temperature may be used as the past measurement temperature, or a plurality of measurement temperatures measured within a certain period before the previous one may be used as the past measurement temperature. Good.

  In the above embodiment, the duty ratio is determined using the duty ratio determination table 17 shown in FIG. 5, but the present invention is not limited to this. The duty ratio is determined using the duty ratio determination table 18 shown in FIG. You may decide. The duty ratio determination table 18 shown in FIG. 6 further includes items that the temperature transition state is rising (sudden) and falling (sudden) with respect to the duty ratio determination table 17 shown in FIG. It is characterized by five transition states. Here, rising (sudden) means that the rate of temperature increase is higher than that of rising, and falling (sudden) means that the rate of temperature decrease is higher than that of falling. In this case, the state specifying unit 13 specifies that the temperature transition state is rising (sudden) when the current temperature section rises by two stages relative to the previous temperature section, and if the current temperature section rises one stage, If the transition state is specified to be rising, if it is lowered by two stages, the temperature transition state is specified to be falling (steep), and if it is lowered by one stage, the temperature transition state is specified to be falling. Good.

  In this case as well, as with the duty ratio determination table 17, in the same temperature section, the duty ratio is set higher in the order of descending (steep), descending, balancing, rising, and rising (steep). Further, overshoot and undershoot can be reduced.

1 is a diagram illustrating a mechanical configuration of an image forming apparatus when a heater control device according to the present invention is applied to the image forming apparatus. FIG. 2 shows a block diagram of the image forming apparatus shown in FIG. 1. 3 is a flowchart showing temperature control of a heating roller by the image forming apparatus. It is drawing which shows the division | segmentation determination table. It is drawing which shows a duty ratio determination table. It is drawing which shows a duty ratio determination table. (A), (b) has shown the table referred in the conventional duty control. It is drawing which shows the relationship between the temperature of a heating roller by conventional duty control, and time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Control part 11 Target temperature setting part 12 Classification determination part 13 State specification part 14 Duty ratio determination part 15 Pulse signal generation part 16 Classification determination table 17 Duty ratio determination table 18 Duty ratio determination table 70 Temperature sensor 80 Heater 208 Heating roller 400 Operation Part

Claims (4)

A heater control device for duty-controlling a heater for heating a heating roller,
Temperature measuring means for measuring the temperature of the heating roller;
The temperature difference between the temperature of the heating roller measured by the temperature measuring means and the target temperature of the heating roller is calculated, and the calculated temperature difference belongs to which temperature category among the temperature categories classified for each predetermined value range. A category determination means for determining whether or not
Based on the previously determined temperature category and the currently determined temperature category, the state specifying unit for specifying the current temperature transition state of the heating roller;
Duty ratio determining means for determining, as the duty ratio of the pulse signal for controlling the heater, a predetermined duty ratio for the temperature classification determined by the classification determining means this time and the temperature transition state specified by the state specifying means A heater control device comprising:   The state specifying means specifies that the temperature transition state is rising when the temperature section determined this time is higher than the temperature section determined last time by the section determination means, and the temperature transition state is increasing. In the case where the temperature category determined this time is a temperature category indicating a lower temperature difference than the temperature category determined last time by the category determination means, the temperature determination state is specified as falling, and the category determination means 2. The heater control device according to claim 1, wherein when the determined temperature segment and the currently determined temperature segment are the same temperature segment, the temperature transition state is identified as being in equilibrium. The heater is turned on longer as the duty ratio is larger,
The duty ratio determining means increases the duty ratio as the temperature difference is larger, and increases the duty ratio when the temperature transition state is in equilibrium than when the temperature transition state is increasing, and the temperature 3. The heater control device according to claim 1, wherein the duty ratio is higher when the transition state is lower than when the transition state is in equilibrium.   The heater control device according to any one of claims 1 to 3, wherein the state specifying unit specifies the temperature transition state according to a plurality of temperature sections determined by the section determination unit within a predetermined period. .

Images