JP2011232616A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate temperature of a sheet by arranging a heating part for heating the sheet without arranging a temperature detection part for detecting the temperature of the sheet.SOLUTION: An image forming apparatus includes paper feed cassettes 461a, 461b, 461c; thermal insulation heaters 612a, 612b, 612c, 13 for heating the sheets to be stored in a paper feed device 10; an in-apparatus temperature detection part 82 for detecting in-apparatus temperature; an external temperature detection part 81; and a temperature estimation part 106 for estimating that the temperature of the sheets is equal to external temperature or the in-apparatus temperature in a case where a temperature difference between an inside and an outside, being a difference between the in-apparatus temperature and the external temperature, is substantially zero when a power source of the self apparatus is turned on, and also estimating the temperature of the sheets by adding a first addition value A to the external temperature when the temperature difference between an inside and an outside is not substantially zero.

Description

  The present invention relates to an image forming apparatus that fixes a toner image on a sheet by heating.

  2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus that forms an image using toner includes a fixing device that fixes the toner image onto a sheet by heating. Such an image forming apparatus includes a heater that heats the temperature of the fixing device to a temperature necessary for fixing the toner onto the paper. In addition, a thermistor that detects the temperature outside the machine, a thermistor that detects the temperature inside the machine, a thermistor that detects the temperature of the paper, and a thermistor that detects the temperature of the paper storage unit, A technique for reducing noise and power consumption of the cooling fan by controlling the temperature of the fixing device and the rotation speed of the cooling fan according to any detected temperature is also known (see, for example, Patent Document 1).

  Further, when the paper absorbs moisture, there is a problem that paper jam easily occurs. For this reason, there is also known an image forming apparatus that prevents moisture absorption of a sheet by heating the sheet stored in the sheet storage unit (for example, see Patent Document 2).

JP 2008-96824 A JP 2006-227275 A

  By the way, Patent Document 1 describes an image forming apparatus including four temperature detection units for detecting an outside temperature, for detecting an in-machine temperature, for detecting a temperature of a sheet, and for detecting a temperature of a sheet storage unit. Since such a temperature detection unit is expensive, it is desired to reduce the number of temperature detection units to reduce the cost. In the image forming apparatus described in Patent Document 1, since only one of the four temperature detection units is used, there is no problem even if the number of temperature detection units for detecting the paper temperature is reduced. However, the image described in Patent Document 2 is acceptable. In the case where the sheet is heated as in the forming apparatus, the temperature of the sheet is different from the temperature inside the apparatus, so that the necessity of detecting the temperature of the sheet is great.

  In particular, in an image forming apparatus including a plurality of paper storage units, a plurality of temperature detection units are required to detect the temperature of the paper stored in each paper storage unit, resulting in an increase in cost.

  An object of the present invention is to provide an image forming apparatus that includes a heating unit that heats a sheet and that can estimate the temperature of the sheet without including a temperature detection unit that detects the temperature of the sheet.

  An image forming apparatus according to the present invention includes a paper storage unit that stores paper, a heating unit that heats the paper stored in the paper storage unit, an image forming unit that forms an image on the paper, and the image forming unit An in-machine temperature detection unit that detects an in-machine temperature that is the temperature inside the housing that houses the device, an out-of-machine temperature detection unit that detects an outside temperature that is the temperature outside the housing, and the power of the own device are turned on When the internal / external temperature difference, which is the difference between the internal temperature detected by the internal temperature detection unit and the external temperature detected by the external temperature detection unit, is set to a determination value set in advance to determine zero. If not, the temperature of the paper stored in the paper storage unit is estimated to be equal to the external temperature or the internal temperature, and when the internal / external temperature difference exceeds the determination value, the external temperature is By adding a predetermined first addition value, And a temperature estimation unit that estimates a temperature of the paper stored in the serial sheet storing section.

  According to this configuration, when the power of the own device is turned on, the internal / external temperature difference is less than a predetermined determination value for determining zero, that is, the internal / external temperature difference is substantially zero. Sufficient time has passed since the power was turned off last time, the outside temperature and the inside temperature become almost equal, the paper stored in the image forming device and paper storage section cools, and the outside temperature and inside temperature are almost the same. It is thought that the temperature is equal. Therefore, in such a case, the temperature estimation unit estimates that the temperature of the paper stored in the paper storage unit is equal to the outside temperature or the inside temperature. Also, when the power supply of the device is turned on, if the temperature difference between the inside and outside exceeds the judgment value, it is considered that the temperature of the image forming apparatus has not cooled down sufficiently since the power was turned off last time. . In such a case, since the temperature of the paper stored in the paper storage unit is considered to be higher than the temperature outside the machine, the temperature estimation unit adds the first addition value to the temperature outside the machine, Estimate the temperature of the stored paper.

  Accordingly, the temperature of the paper can be estimated without including a heating unit that heats the paper and a temperature detection unit that detects the temperature of the paper.

  Moreover, it is preferable that the said temperature estimation part sets the said 1st addition value so that a said 1st addition value becomes large, so that the said internal / external temperature difference is large.

  The greater the internal / external temperature difference, the more the paper stored in the paper storage unit is not cooled from the state of being overheated by the heating unit before, and the temperature is considered high. By setting the first addition value so that the first addition value becomes larger, the accuracy of the estimation of the sheet temperature is improved.

  The heating unit further includes a timing unit that measures an elapsed time after the heating of the paper by the heating unit is started, and the temperature estimation unit is heated by the heating unit. When the temperature of the sheet reaches a steady time set as a time required for the steady state to be reached, the temperature of the sheet is estimated by adding a predetermined second addition value to the initial temperature, It is preferable that a value set in advance as the upper limit value of the second addition value is set as the second addition value.

  When the power of the machine is turned on and heating of the paper is started by the heating unit, the temperature gradually increases until the steady time elapses after the heating starts, and when the steady time is exceeded, the temperature becomes steady. It will not rise any further. Therefore, the temperature estimation unit estimates the sheet temperature by adding the preset upper limit value of the second addition value to the initial temperature when the elapsed time counted by the timing unit becomes equal to or longer than the steady time. can do.

  The heating unit further includes a time measuring unit that measures an elapsed time after the heating of the paper by the heating unit is started, and the temperature estimation unit is configured to estimate the temperature of the paper when the power of the own device is turned on. Is the initial temperature, the current temperature of the sheet is estimated by adding a second addition value to the initial temperature, and the elapsed time measured by the time measuring unit within a range not satisfying a preset steady time It is preferable to set the second added value so that the value becomes larger as the value becomes longer.

  After the apparatus is turned on and the heating unit starts heating the sheet, the sheet temperature gradually rises during a period in which the elapsed time measured by the timing unit is less than the steady time. Therefore, the temperature estimation unit estimates the sheet temperature by setting the second addition value so that the value increases as the elapsed time measured by the timing unit becomes longer in a range that is less than the steady time. be able to.

  The paper storage unit further includes a paper remaining amount detection unit that detects the remaining amount of paper stored in the paper storage unit, and the temperature estimation unit further increases the remaining amount detected by the paper remaining amount detection unit. It is preferable that the second addition value is set so that the value of the second addition value becomes small.

  As the remaining amount of the paper stored in the paper storage unit increases, the heat capacity of the paper increases, so that it takes time for the temperature of the paper heated by the heating unit to rise. Therefore, the temperature estimation unit sets the second addition value so that the value of the second addition value becomes smaller as the remaining amount of paper detected by the remaining paper amount detection unit increases, thereby the temperature of the paper. The estimation accuracy of can be improved.

  Further, it is preferable that the remaining paper amount detection unit detects the height of the sheets stacked and stored in the paper storage unit as the remaining amount.

  Since the thermal capacity of the paper is determined by the volume of the paper, detecting the remaining amount of paper as the height of the paper has a higher correlation with the thermal capacity regardless of the thickness of the paper than detecting the number of sheets. As a result, the estimation accuracy of the paper temperature can be improved.

  The paper size acquisition unit further acquires a paper size indicating the size of the paper stored in the paper storage unit, and the temperature estimation unit further includes a paper size detected by the paper size acquisition unit. It is preferable to set the second addition value so that the second addition value becomes smaller as the value becomes larger.

  Since the heat capacity of the paper is determined by the volume of the paper, even if the remaining amount of paper is the same, the larger the paper size, the larger the heat capacity than when the paper size is small. Therefore, the temperature estimation unit sets the second addition value so that the second addition value decreases as the size of the paper detected by the paper size acquisition unit increases, thereby increasing the estimation accuracy of the paper temperature. Can be improved.

  The image forming unit includes an exposure unit that forms an electrostatic latent image by exposing the photosensitive drum, and a toner that develops the electrostatic latent image formed on the photosensitive drum using toner. A developing unit that forms an image, a transfer unit that transfers the toner image formed by the developing unit to the paper, and a fixing that heats the paper conveyed from the transfer unit and fixes the toner image on the paper And a fixing power control unit that controls the amount of power supplied to heat the fixing unit, and the fixing power control unit increases the temperature of the paper estimated by the temperature estimation unit, It is preferable to reduce the supply amount of the electric power.

  An exposure unit that forms an electrostatic latent image by exposing the photosensitive drum, a developing unit that forms a toner image by developing the electrostatic latent image formed on the photosensitive drum with toner, and development An electrophotographic image forming apparatus comprising: a transfer unit that transfers a toner image formed on a sheet to the sheet; and a fixing unit that heats the sheet conveyed from the transfer unit and fixes the toner image on the sheet In the fixing unit, if the temperature of the sheet is high, less heat is required for fixing. Therefore, the fixing power control unit reduces wasteful power consumption by reducing the amount of power supplied to heat the fixing unit as the paper temperature estimated by the temperature estimation unit increases. It becomes possible to reduce.

  The image forming apparatus having such a configuration can estimate the sheet temperature without including a heating unit that heats the sheet and a temperature detecting unit that detects the temperature of the sheet.

1 is a structural diagram schematically illustrating an internal configuration of a copying machine that is an example of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating an example of an electrical configuration of the copier illustrated in FIG. 1. It is explanatory drawing which looked at the paper feed cassette shown in FIG. 1 from the top. It is explanatory drawing which shows an example of the addition value table used for the temperature estimation part shown in FIG. 2 to set a 2nd addition value. 3 is a flowchart showing an example of the operation of the copying machine shown in FIG. 3 is a flowchart showing an example of the operation of the copying machine shown in FIG.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted. FIG. 1 is a structural diagram schematically showing an internal configuration of a copying machine as an example of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing an example of the electrical configuration of the copying machine 1 shown in FIG. The image forming apparatus is not limited to a copying machine, but may be a printer, a facsimile, or a multifunction machine having these functions.

  The copying machine 1 includes a main unit 2, a stack tray 3 disposed on the left side of the main unit 2, a document reading unit 5 disposed on the top of the main unit 2, and an upper side of the document reading unit 5. A document feeding unit 6 disposed and a sheet feeding device 10 (sheet storage unit) disposed on the right side of the main body unit 2 and capable of storing a large amount of sheets are provided.

  The main body 2 includes a plurality of paper feed cassettes 461a, 461b, and 461c (paper storage units), and paper feed rollers 462a that feed out the papers one by one from the paper feed cassettes 461a, 461b, and 461c to the image forming unit 40. 462b and 462c, a conveyance path 465 for conveying the sheet fed from the sheet feeding device 10 to the image forming unit 40, and an image on the sheet unloaded from the sheet feeding cassettes 461a, 461b and 461c and the sheet feeding device 10. The image forming unit 40 that forms the image and the control unit 100 that controls the operation of the entire apparatus are housed in the housing 21.

  A power switch 22 is provided on the upper right side of the main body 2. As shown in FIG. 2, the copying machine 1 includes a power supply unit 23 that converts a commercial AC power supply voltage, for example, AC 100 V, into a predetermined DC voltage and supplies it to each unit in the copying machine 1. The commercial AC power supply voltage is supplied to the power supply unit 23 via the power switch 22. When the power switch 22 is turned off, the copying machine 1 stops operating and the power switch 22 is turned on. When the power is turned on, the copying machine 1 is started.

  The power switch 22 is not necessarily limited to the primary side of the power supply unit 23, that is, the one that turns on and off the commercial AC power supply voltage, but is connected to the secondary side of the power supply unit 23, that is, from the power supply unit 23 to each part in the copier 1. The supplied voltage may be turned on or off. The power switch 22 may be an operation switch that outputs a control signal that instructs the control unit 100 to turn on or off the power supply voltage, for example, when operated by a user.

  A substantially rectangular operation panel 47 is provided at the front of the copying machine 1. The operation panel unit 47 includes a display unit 473 and an operation key unit 476. The display unit 473 is configured by, for example, a liquid crystal display having a touch panel function. The operation key unit 476 includes various key switches such as a start key for the user to input a print execution instruction and a numeric keypad for inputting the number of copies to be printed.

  By operating the operation panel unit 47, the user can select a paper storage unit used for image formation from the paper supply cassettes 461 a, 461 b, 461 c and the paper supply device 10. Further, the user can set the paper size of the paper stored in the paper feed cassettes 461a, 461b, and 461c and the paper thickness value indicating the thickness by operating the operation panel unit 47. ing.

  The document reading unit 5 includes a scanner unit 51 including a CCD (Charge Coupled Device) 512, an exposure lamp 511, and the like, and a document table 52 and a document reading slit 53 made of a transparent member such as glass. The scanner unit 51 is configured to be movable by a drive unit (not shown). When reading a document placed on the document table 52, the scanner unit 51 is moved along the document surface at a position facing the document table 52, and the document image is scanned. The image data acquired while scanning is output to the control unit 100. Further, when reading a document fed by the document feeding unit 6, the document is moved to a position facing the document reading slit 53 and synchronized with the document feeding operation by the document feeding unit 6 via the document reading slit 53. The image of the original is acquired and the image data is output to the control unit 100.

  The document feeding unit 6 includes a document placing unit 61 for placing a document, a document discharge unit 62 for discharging a document whose image has been read, and a document placed on the document placing unit 61. A document transport mechanism 63 is provided that feeds the sheets one by one to transport them to a position facing the document reading slit 53 and discharges them to the document discharge section 62.

  The image forming unit 40 includes a paper transport unit 411, an optical scanning device 42, a photosensitive drum 43, a developing unit 44, a transfer unit 41, and a fixing unit 7. A conveyance path 46 for conveying sheets from the sheet feeding cassettes 461a, 461b, 461c to the stack tray 3 or the discharge tray 48 via the fixing unit 7 is provided. The photosensitive drum 43 and the transfer unit 41 are disposed along a conveyance path 46 from the paper feed cassettes 461a, 461b, and 461c to the fixing unit 7.

  The paper transport unit 411 is provided in the transport path 46, and includes a transport roller 412 that supplies the paper transported by the paper feed rollers 462 a, 462 b, and 462 c to the photosensitive drum 43, and a paper stack tray 3 or discharge tray 48. Conveying rollers 463, 464, etc. are provided.

  The optical scanning device 42 forms an electrostatic latent image on the photosensitive drum 43 by outputting laser light or the like based on the image data output from the control unit 100 and exposing the photosensitive drum 43. The developing unit 44 develops the electrostatic latent image on the photosensitive drum 43 with toner to form a toner image. The transfer unit 41 transfers the toner image on the photosensitive drum 43 to a sheet.

  The fixing unit 7 heats the sheet on which the toner image is transferred to fix the toner image on the sheet. The fixing unit 7 includes a heat roller 71 and a pressure roller 72.

  The heat roller 71 and the pressure roller 72 are arranged to face each other so as to nip the sheet conveyed from the transfer unit 41 through the conveyance path 46. The fixing unit 7 heats the sheet on which the toner image is transferred to melt the toner image and fix the sheet on the sheet. The configuration is not limited to the example in which the heat roller 71 and the pressure roller 72 are disposed to face each other. For example, a configuration in which a belt is interposed between the heat roller 71 and the pressure roller 72 may be employed.

  An unillustrated heater is disposed inside the heat roller 71. The heater generates heat and the heat roller 71 is heated by the power supplied from the power supply unit 73 described later.

  The paper feeding device 10 includes a housing 11, a paper base 12 on which the stacked paper is mounted, a lift motor (not shown) that drives the paper base 12 to move up and down, a paper that is stacked on the paper base 12, and transports the main body 2. A paper feed roller 351 and the like that are conveyed to the path 465 are provided. Further, the paper tray 12 is provided with a moisture-preserving heater 13 (heating unit) for heating the paper on the paper tray 12.

  Elevating plates 613a, 613b, and 613c configured to be moved up and down by a motor (not shown) are provided at the bottoms of the sheet feeding cassettes 461a, 461b, and 461c, respectively. A bundle of sheets is placed on the elevating plates 613a, 613b, and 613c, and the sheets are stored in the sheet feeding cassettes 461a, 461b, and 461c. The paper feed cassettes 461a, 461b, and 461c are provided with a lift position sensor (not shown) that detects the lift positions of the lift plates 613a, 613b, and 613c.

  FIG. 3 is an explanatory view of the paper feed cassettes 461a, 461b, and 461c shown in FIG. 1 as viewed from above. A handle 611 for pulling out the paper feed cassettes 461a, 461b, 461c from the main body 2 is provided on the front panel of the paper feed cassettes 461a, 461b, 461c shown in FIG. At the bottoms of the paper feed cassettes 461a, 461b, and 461c, moisture keeping heaters 612a, 612b, and 612c (heating units) for heating the paper are disposed, respectively.

  The heat retaining heaters 612a, 612b, 612c, and 13 are set to about 20 W to 30 W, for example, and start to generate heat in response to a control signal from the control unit 100.

  The control unit 100 includes, for example, a central processing unit (CPU) that executes predetermined arithmetic processing, a read only memory (ROM) that stores a predetermined control program, and a storage unit that temporarily stores data. A random access memory (RAM), a timer circuit, and peripheral circuits thereof. As shown in FIG. 2, the control unit 100 includes a document reading unit 5, an image forming unit 40, an operation panel unit 47, a power supply unit 73, an external temperature detection unit 81, an internal temperature detection unit 82, and a fixing temperature detection unit. 83 and the heat retaining heaters 612a, 612b, 612c, 13 are connected.

  The outside temperature detection unit 81, the inside temperature detection unit 82, and the fixing temperature detection unit 83 are temperature sensors configured using a thermal element such as a thermistor or a thermocouple, for example.

  The external temperature detector 81 is disposed so as to be exposed to the outside through an opening provided in the housing 21, for example. As a result, the outside temperature detector 81 detects the outside temperature te, which is the temperature outside the housing 21.

  The in-machine temperature detection unit 82 is disposed at an appropriate position in the casing 21, preferably in the vicinity of the optical scanning device 42. As a result, the in-machine temperature detector 82 detects the in-machine temperature ti, which is the temperature in the housing 21. Further, when the housing of the optical scanning device 42 expands or contracts even slightly due to a temperature change, the scanning position of the photosensitive drum 43 by the scanning light such as laser light shifts, and the quality of the image formed on the paper is low. to degrade. Therefore, an in-machine temperature detection unit 82 is disposed in the vicinity of the optical scanning device 42 so that the ambient temperature of the optical scanning device 42 is detected as the in-machine temperature ti, and the influence of the temperature is canceled according to the in-machine temperature ti. By controlling the scanning operation by the optical scanning device 42, the image quality is improved.

  The fixing temperature detector 83 is disposed in contact with the fixing unit 7 or in the vicinity of the fixing unit 7 to detect the temperature tf of the fixing unit 7.

  The control unit 100 executes, for example, a control program stored in the ROM, so that the copy control unit 101, the remaining paper amount detection unit 102, the paper size acquisition unit 103, the paper selection unit 104, the time measurement unit 105, and the temperature estimation unit 106. , And the fixing power control unit 107.

  For example, the power supply unit 73 supplies the commercial power supply voltage to the heat roller 71 to cause the heat roller 71 to generate heat. The power supply unit 73 is configured using a switching element that opens and closes an AC voltage such as a commercial power supply voltage. Then, the power supply unit 73 turns on and off such an AC voltage at a duty ratio according to a control signal from the fixing power control unit 107, thereby supplying power according to an instruction from the fixing power control unit 107. The heat roller 71 is supplied.

  The power supply unit 73 controls the voltage and current supplied to the heat roller 71 in accordance with a control signal from the fixing power control unit 107, thereby heating the power according to the instruction from the fixing power control unit 107. The roller 71 may be supplied.

  The copy control unit 101 controls the operation of each unit in the apparatus and executes copying of a document image. Specifically, the copy control unit 101 transmits image data read from the document by the document reading unit 5 to the image forming unit 40, and causes the image forming unit 40 to perform image formation of the image. Further, when the power supply switch 22 is turned on and activated, the copy control unit 101 starts the heat generation of the heat retaining heaters 612a, 612b, 612c, and 13.

  The heat retaining heaters 612a, 612b, 612c, and 13 may be configured to start generating heat as they are when the power switch 22 is turned on.

  The remaining paper amount detection unit 102 detects the remaining amount of paper stored in the paper supply cassettes 461 a, 461 b, 461 c and the paper supply apparatus 10. Specifically, for example, when the remaining paper amount detection unit 102 detects the amount of paper stored in the paper supply device 10, the paper base 12 on which the paper is loaded is positioned at the lower limit position. Is lifted at a constant speed by a lift motor.

  Then, the remaining paper amount detection unit 102 measures the time it takes for the upper surface of the stacked paper to contact the paper feed roller 351 after the paper table 12 starts to rise. As a result, the remaining time of the paper, that is, the height of the paper loaded on the paper tray 12 (thickness of the paper bundle) is higher (thicker), and the remaining amount is shorter, so that the time counting is shorter and the paper height remains lower. Since the time count becomes longer as the amount is smaller, the remaining paper amount detection unit 102 can calculate the remaining amount of paper stored in the paper feeding device 10 from this measured time.

  Further, the remaining paper amount detection unit 102 can detect the remaining amount (height) of the paper stored in the paper feed cassettes 461a, 461b, and 461c as follows, for example. That is, the sheet remaining amount detection unit 102 raises the lifting plates 613a, 613b, and 613c by a lift motor (not shown), and the upper surface of the sheets stacked on the lifting plates 613a, 613b, and 613c is the feed rollers 462a, 462b, and 462c. In contact with each other. In this state, the remaining paper amount detection unit 102 detects the positions of the lifting plates 613a, 613b, and 613c by a lifting / lowering position sensor (not shown), thereby remaining sheets stored in the sheet feeding cassettes 461a, 461b, and 461c. The amount (height) can be detected.

  Alternatively, the remaining paper amount detection unit 102 calculates the value obtained by multiplying the number of sheets stored in the sheet feeding cassettes 461a, 461b, 461c, and the sheet feeding apparatus 10 by the thickness of each sheet. It may be used as the remaining amount.

  Note that the remaining amount detection unit 102 may detect the remaining amount of paper by any method, and the detection method is not limited.

  The paper size acquisition unit 103 receives an operation instruction made by the user using the operation panel unit 47, for example, and acquires the paper size of the paper stored in the paper supply device 10 or the paper supply cassettes 461a, 461b, and 461c. .

  The paper size acquisition unit is a guide plate (cursor) configured to be movable in accordance with the paper size in the paper feed cassettes 461a, 461b, and 461c as described in, for example, Japanese Patent Application Laid-Open No. 2008-96824. ) And the size of the paper can be detected by various methods such as detecting the size of the paper stored in each paper feed cassette from the position of the guide plate.

  The paper selection unit 104 accepts an operation instruction from the operation panel unit 47 by the user, and in response to the operation instruction, the paper storage unit used for image formation is changed to the paper feed cassettes 461a, 461b, 461c, and the paper feeding device 10. Choose from.

  The time counting unit 105 measures the elapsed time Tk after the heat generation of the heat retaining heaters 612a, 612b, 612c, and 13 is started by the copy control unit 101, respectively. In the case where the heat retaining heaters 612a, 612b, 612c, 13 start to generate heat as the power switch 22 is turned on, the time measuring unit 105 determines the elapsed time after activation as the heat retaining heaters 612a, 612b, 612c. , 13 may be counted as the elapsed time Tk after the start of heat generation.

  The temperature estimation unit 106 estimates the temperatures tpa, tpb, tpc, and tpd of the paper sheets stored in the paper feeding cassettes 461a, 461b, and 461c and the paper feeding device 10, respectively.

  Specifically, when the power switch 22 is turned on to start the copying machine 1 and the control unit 100 starts operating, the temperature estimation unit 106 immediately executes the following initial temperature estimation process. That is, as the initial temperature estimation process, the temperature estimation unit 106 includes an internal / external temperature difference that is a difference between the internal temperature ti detected by the internal temperature detection unit 82 and the external temperature te detected by the external temperature detection unit 81. tie is calculated using the following formula (1).

Internal / external temperature difference tie = ti-te (1)
When the temperature difference tie between the inside and outside is less than a predetermined determination value tz for determining zero, the temperature estimation unit 106 is stored in the sheet feeding device 10 and the sheet feeding cassettes 461a, 461b, and 461c. It is estimated that initial temperatures tsa, tsb, tsc, and tsd, which are temperatures when the power is turned on, are equal to the outside temperature te. Note that the fact that the internal / external temperature difference tie is less than the judgment value tz means that the external temperature te and the internal temperature ti are substantially equal, so it is of course possible to use the internal temperature ti instead of the external temperature te. Good.

  Further, when the inside / outside temperature difference tie exceeds the determination value tz, the temperature estimation unit 106 estimates the initial temperature ts by adding a predetermined first addition value A to the outside temperature te.

  As the determination value tz, for example, a value obtained by adding a certain margin to the temperature measurement error of the outside temperature detector 81 or the inside temperature detector 82 is used. Thereby, if the internal / external temperature difference tie does not satisfy the determination value tz, the internal / external temperature difference tie which is the internal / external temperature difference of the housing 21 can be determined to be substantially 0 ° C.

  If the internal / external temperature difference tie is substantially 0 ° C., the previous copying machine 1 is used, the internal temperature ti rises due to heat generated by the image forming unit 40 and the fixing unit 7, and the heat retaining heaters 612 a, 612 b, 612 c. 13, the sheet temperatures tpa, tpb, tpc, tpd rise, and then the power is turned off, enough to make the in-machine temperature ti and the sheet temperatures tpa, tbb, tpc, tpd equal to the outside temperature te. Means that a long time has passed.

  Therefore, when the internal / external temperature difference tie is less than the determination value tz, the temperature estimation unit 106 determines the initial temperatures tsa, tsb, tsc, and the like of the paper stored in the paper supply device 10 and the paper supply cassettes 461a, 461b, and 461c. By estimating that tsd is equal to the outside temperature te, it is possible to estimate the initial paper temperatures tsa, tsb, tsc, and tsd.

  If the internal / external temperature difference tie exceeds the determination value tz, it means that the time required for the copying machine 1 to sufficiently cool has not yet elapsed after the previous power-off. Then, since it is considered that the temperature of the sheet is still higher than the outside temperature te, the temperature estimation unit 106, when the inside / outside temperature difference tie exceeds the determination value tz, the predetermined first addition value to the outside temperature te. By adding A, the initial temperatures tsa, tsb, tsc, and tsd can be estimated.

  In this case, the larger the internal / external temperature difference tie, the higher the temperature of the sheet, so the first addition value A is set to a larger value as the internal / external temperature difference tie increases. The first addition value A is obtained by, for example, experimentally measuring the relationship between the internal / external temperature difference tie and the paper temperature after the copier 1 that has been operated and sufficiently warmed is turned off, and the first and second temperature differences tie and the first For example, it is stored in the ROM as an LUT (Look Up Table) for associating the added value A. Then, the temperature estimation unit 106 may set the first addition value A associated with the internal / external temperature difference tie by referring to the LUT.

  In this case, the first addition value A corresponding to the paper feeding cassettes 461a, 461b, 461c and the paper feeding device 10 may be set.

  Further, when the power switch 22 is turned on to turn on the power and the heating of the paper by the heat retaining heaters 612a, 612b, 612c, 13 is started, the paper temperature tp gradually increases. Then, regarding the period until the temperature tp reaches the steady state, the elapsed time after the heating of the sheet is started, that is, the elapsed time Tk measured by the timing unit 105 becomes longer, so that the sheet temperature tpa, tpb, tpc, tpd will rise.

  Therefore, the time until the temperature tp reaches the steady state is set in advance as the steady time Tu, and the temperature estimation unit 106 for the period until the elapsed time Tk measured by the time measuring unit 105 reaches the steady time Tu, The second addition value B is set so that the value increases as the elapsed time Tk increases. The temperature estimation unit 106 calculates and estimates the temperatures tpa, tpb, tpc, and tpd by adding the second addition value B to the initial temperatures tsa, tsb, tsc, and tsd, respectively.

  By the way, the temperature tpa, tpb, tpc, tpd of the sheets stored in the sheet feeding cassettes 461a, 461b, 461c and the sheet feeding apparatus 10 increases as the remaining amount of the sheet increases and the heat capacity increases. It becomes difficult.

  Therefore, the temperature estimation unit 106 considers the heat capacity of the sheet, and the second addition value B is set such that the second addition value B decreases as the remaining amount detected by the remaining sheet detection unit 102 increases. Set.

  Further, the heat capacity of the paper increases as the size increases even if the remaining amount of paper is the same. Therefore, the temperature estimation unit 106 sets the second addition value B so that the second addition value B decreases as the size of the paper detected by the paper size acquisition unit 103 increases.

  FIG. 4 shows the addition values used by the temperature estimation unit 106 shown in FIG. 2 to set the second addition values Ba, Bb, Bc, and Bd corresponding to the sheet feeding cassettes 461a, 461b, and 461c and the sheet feeding device 10. It is explanatory drawing which shows an example of a table. The added value table shown in FIG. 4 includes parameters for the remaining amount of paper, the paper size, and the elapsed time Tk, the second added value Ba of paper stored in the paper feed cassette 461a, and a paper feed cassette 461b. B00 which is the second addition value Bb of the paper stored in B, c00 to c15 which are the second addition value Bc temperature tpc of the paper stored in the paper feeding cassette 461c, and the paper stored in the paper feeding device 10 Are associated with d00 to d15, which are the second addition values Bd. Such an addition value table as a LUT (Look Up Table) is stored in advance in, for example, a ROM.

  In the addition value table shown in FIG. 4, the second addition values Ba, Bb, Bc, and Bd are associated with each other when the remaining amount of paper is large and small. A large amount is a case where it is greater than or equal to a preset remaining amount, and a small amount is a case where the remaining amount of paper is less than the set remaining amount.

  In FIG. 4, for the sake of simplicity, an example in which the remaining amount of paper is roughly divided into two cases, a large amount and a small amount, is shown, but the second addition values Ba, Of course, it is possible to set Bb, Bc, and Bd.

  Regarding the remaining amount of paper, the second addition values Ba, Bb, Bc, and Bd when the conditions other than the remaining amount of paper are the same are set to be smaller when the amount is larger than when the amount is smaller. Yes. For example, the conditions other than the remaining amount of paper are the same, a01 <a09 for a01 and a09, and b06 <b14 for b06 and b14, a00 to a15, b00 to b15, c00 to c15, and d00 to d15. Value is set.

  In the addition value table shown in FIG. 4, the second addition values Ba, Bb, Bc, and Bd are associated with the sheet size A3 (large) and A4 (small), respectively. FIG. 4 shows an example in which the paper size is roughly divided into two cases of A3 and A4 to simplify the description. However, the second addition values Ba and Bb are finely divided into three or more cases. , Bc, Bd may be set.

  Regarding the paper size, the second addition values Ba, Bb, Bc, and Bd when the conditions other than the paper size are the same are set so that the value is smaller in the case of A3 (large) than in the case of A4 (small). Has been. For example, a00 to a15, b00 to b15, c00 to c15, and d00 to d15 are set such that c00 <c04 is the same for c00 and c04, and d02 <d06 is the same for d02 and d06. Value is set.

  Furthermore, in the addition value table shown in FIG. 4, the second addition values Ba, Bb, Bc, and Bd are associated with each other when the elapsed time Tk is T0, T1, T2, and T3. Here, T0 <T1 <T2 <T3. Further, in FIG. 4, in order to simplify the description, an example in which four elapsed times Tk, T0, T1, T2, and T3 are used is shown, but the second time is finely divided using five or more elapsed times Tk. Of course, the addition values Ba, Bb, Bc, and Bd may be set.

  Regarding the elapsed time Tk, the second addition values Ba, Bb, Bc, and Bd when the conditions other than the elapsed time Tk are the same are larger when the elapsed time Tk is longer than when the elapsed time Tk is short. It is set to be. For example, the conditions other than the elapsed time Tk are the same, a00 <a03 between a00 and a03, and d02 <d03 between d02 and d03, a00 to a15, b00 to b15, c00 to c15, and d00 to d15. Value is set.

  The temperature estimation unit 106 refers to, for example, the addition value table illustrated in FIG. 4, and the elapsed time Tk, the remaining paper amount, and the paper size acquired by the time measuring unit 105, the remaining paper amount detection unit 102, and the paper size acquisition unit 103. 2nd addition value Ba, Bb, Bc, Bd matched with is acquired.

  The fixing power control unit 107 performs feedback control by controlling the amount of power supplied by the power supply unit 73 so that the temperature tf of the fixing unit 7 detected by the fixing temperature detection unit 83 becomes a predetermined target temperature tx. .

  Further, the fixing power control unit 107 causes the power supply unit 73 to reduce the target temperature tx of the paper storage unit selected by the paper selection unit 104 as the paper temperature estimated by the temperature estimation unit 106 increases. Reduce power supply.

  Next, the operation of the copying machine 1 configured as described above will be described. 5 and 6 are flowcharts showing an example of the operation of the copying machine 1 shown in FIG. First, when the power switch 22 is turned on and the power is turned on (step S1), the heat retaining heaters 612a, 612b, 612c, and 13 are turned on by the copy control unit 101 (step S2). Then, the heating heaters 612 a, 612 b, 612 c, and 13 start heating the paper stored in the paper feed cassettes 461 a, 461 b, and 461 c and the paper feeder 10.

  Next, the time measuring unit 105 starts measuring the elapsed time Tk after the heating of the sheet is started (step S3). Then, the outside temperature te is detected by the outside temperature detecting unit 81, the inside temperature ti is detected by the inside temperature detecting unit 82 (step S4), and the outside temperature te is subtracted from the inside temperature ti by the temperature estimating unit 106. Then, the internal / external temperature difference tie is calculated (step S5).

  Next, the temperature estimation unit 106 compares the internal / external temperature difference tie with the determination value tz (step S6). If the internal / external temperature difference tie does not reach the determination value tz (YES in step S6), the temperature estimation unit 106 estimates that the initial temperatures tsa, tsb, tsc, and tsd are equal to the external temperature ta (step S7). ), The process proceeds to step S10. On the other hand, if the internal / external temperature difference tie is equal to or greater than the determination value tz (NO in step S6), the temperature estimation unit 106 sets the first addition value A according to the internal / external temperature difference tie (step S8), and the external temperature The first addition value A is added to ta to estimate initial temperatures tsa, tsb, tsc, and tsd (step S9), and the process proceeds to step S10.

  The initial temperatures tsa, tsb, tsc, and tsd are used as the temperatures tpa, tpp, tpc, and tpd until the temperatures tpa, tpb, tpc, and tpd are estimated in steps S11 and S14 described later.

  As described above, by the processing of steps S1 to S9, the sheet feeding cassettes 461a, 461b, 461c and the sheet feeding apparatus 10 are not provided with the temperature sensor for detecting the sheet temperature, and the sheet feeding cassettes 461a, The initial temperatures tsa, tsb, tsc, and tsd, which are the temperatures of the sheets 461b and 461c and the sheet in the sheet feeding device 10, can be estimated.

  Next, in step S10, the temperature estimation unit 106 compares the elapsed time Tk measured by the time measuring unit 105 with the steady time Tu (step S10). If the elapsed time Tk is equal to or longer than the steady time Tu (NO in step S10), the paper cassettes 461a, 461b, and 461c and the paper temperature in the paper feeder 10 are considered to have already reached a steady state. As the temperature rise value from the outside temperature te when reaching steady when the paper cassettes 461a, 461b, 461c and the paper in the paper feeder 10 are heated by the heat retaining heaters 612a, 612b, 612c, 13 The preset upper limit values Tlma, Tlmb, Tlmc, Tlmd are set as the second addition values Ba, Bb, Bc, Bd (step S11), and the process proceeds to step S14.

  On the other hand, if the elapsed time Tk does not reach the steady time Tu (YES in step S10), the remaining amount of paper and the paper size stored in the paper storage cassettes 461a, 461b, 461c and the paper storage units of the paper supply device 10 are determined. Are acquired by the remaining paper amount detecting unit 102 and the paper size acquiring unit 103, respectively (step S12).

  Then, the temperature estimation unit 106 refers to, for example, the addition value table shown in FIG. 4 and corresponds to the remaining paper amount and the paper size stored in the paper storage unit and the elapsed time Tk measured by the time measuring unit 105. Second addition values Ba, Bb, Bc, Bd are acquired (step S13), and the second addition values Ba, Bb, Bc, Bd are added to the initial temperatures tsa, tsb, tsc, tsd, respectively, Temperatures tpa, tpb, tpc, tpd are calculated (step S14), and steps S10 to S14 are repeated again.

  As described above, by the processing of steps S1 to S14, the paper feed cassettes 461a, 461b, 461c, and the paper feed cassettes 461a, 461b, 461c, and the paper feed device 10 are not provided with a temperature sensor that detects the temperature of the paper. The temperatures tpa, tpb, tpc, tpd of the paper stored in the paper device 10 can be estimated. And the estimated value of temperature tpa, tpb, tpc, tpd is always updated by the process of step S1-S14.

  Next, temperature control of the fixing unit 7 based on the temperatures tpa, tpb, tpc, tpd will be described with reference to FIG. The temperature control shown in FIG. 6 is executed in parallel with steps S1 to S14 shown in FIG. 5, and based on the latest temperatures tpa, tpb, tpc, tpd obtained in steps S1 to S14, the power supply unit The supplied power 73 is controlled.

  First, the paper selection unit 104 selects one of the paper feeding cassettes 461a, 461b, 461c and the paper feeding device 10 (step S21).

  Next, based on the temperature of the paper stored in the paper storage unit selected by the paper selection unit 104 among the latest temperatures tpa, tpb, tpc, tpd obtained in steps S1 to S14, the fixing power control unit 107 sets the target temperature tx (step S22).

  Then, the power supplied from the power supply unit 73 to the fixing unit 7 is controlled by the fixing power control unit 107 so that the temperature of the fixing unit 7 becomes the target temperature tx (step S23).

  As described above, the target temperature tx is lowered as the temperature of the paper stored in the paper storage unit selected by the paper selection unit 104 is increased by the processing in steps S21 to S23, and the power supply amount by the power supply unit 73 is reduced. The lower the temperature is, the higher the target temperature tx is, and the power supply amount by the power supply unit 73 is increased.

  Here, since the fixing unit 7 requires less heat for fixing as the paper temperature is higher, the target temperature tx is lowered as the paper temperature is higher to reduce the power supply amount by the power supply unit 73. As a result, wasteful power consumption can be reduced, and as a result, power consumption can be reduced.

  In addition, although the temperature estimation part 106 showed the example which estimates the paper temperature tpa, tbb, tpc, tpd based on elapsed time Tk, paper remaining amount, and paper size, based on only elapsed time Tk, The paper temperatures tpa, tpb, tpc, tpd may be estimated.

  In addition to the elapsed time Tk, the temperature estimation unit 106 does not need to use both the remaining paper amount and the paper size, and may be configured to use either the remaining paper amount or the paper size.

DESCRIPTION OF SYMBOLS 1 Copy machine 2 Main body part 3 Stack tray 5 Original reading part 6 Original feeding part 7 Fixing part 10 Paper feeding device 11,21 Case 12 Paper base 13,612,612a, 612b, 612c, Thermal insulation heater 22 Power switch 23 Power supply Section 40 Image forming section 41 Transfer section 42 Optical scanning device 43 Photosensitive drum 44 Developing section 46 Transport path 47 Operation panel section 48 Discharge tray 71 Heat roller 72 Pressure roller 73 Power supply section 81 External temperature detection section 82 In-machine temperature detection section 82 83 Fixing temperature detection unit 100 Control unit 101 Copy control unit 102 Remaining paper amount detection unit 103 Paper size acquisition unit 104 Paper selection unit 105 Timing unit 106 Temperature estimation unit 107 Fixing power control unit 351 Paper feed roller 411 Paper conveyance unit 412 Conveyance roller 461a, 461b, 461c Paper feed cassette 473 Display unit 47 Operation key section 613a, 613b, 613c Elevating plate A First addition value B, Ba, Bb, Bc, Bd Second addition value Tk Elapsed time Tu Upper limit value ta Outer temperature te Outer temperature ti Inboard temperature tie Incoming / outer temperature difference ts , Tsa, tsb, tsc, tsd initial temperature tx target temperature tz judgment value

Claims (8)

A paper storage section for storing paper;
A heating unit for heating the paper stored in the paper storage unit;
An image forming unit for forming an image on the paper;
An in-machine temperature detection unit that detects an in-machine temperature that is a temperature in a housing that houses the image forming unit;
An external temperature detector that detects an external temperature that is an external temperature of the housing;
The internal / external temperature difference, which is the difference between the internal temperature detected by the internal temperature detector and the external temperature detected by the external temperature detector when the power of the own device is turned on, is determined to be zero. Is less than the preset judgment value, it is estimated that the temperature of the paper stored in the paper storage unit is equal to the outside temperature or the inside temperature of the machine, and the inside / outside temperature difference is determined as the judgment value. An image forming apparatus comprising: a temperature estimating unit that estimates a temperature of the paper stored in the paper storage unit by adding a predetermined first addition value to the outside temperature when the temperature exceeds the predetermined temperature. The temperature estimator is
The image forming apparatus according to claim 1, wherein the first addition value is set such that the first addition value increases as the internal / external temperature difference increases. A timer unit for measuring an elapsed time after the heating of the paper by the heating unit is started;
The temperature estimator is
When the elapsed time measured by the time measuring unit is equal to or longer than the steady time set as the time required for the temperature of the paper heated by the heating unit to be in a steady state, the temperature of the paper is The value estimated by adding a predetermined second addition value to the initial temperature and set in advance as an upper limit value of the second addition value is set as the second addition value. Or the image forming apparatus of 2. A timer unit for measuring an elapsed time after the heating of the paper by the heating unit is started;
The temperature estimator is
The initial temperature is the temperature of the paper estimated when the power of the machine is turned on,
The temperature of the sheet at the present time is estimated by adding a second addition value to the initial temperature, and the value increases as the elapsed time measured by the timing unit in a range that does not satisfy a preset steady time. The image forming apparatus according to any one of claims 1 to 3, wherein the second addition value is set so as to increase. A paper remaining amount detection unit for detecting the remaining amount of paper stored in the paper storage unit;
The temperature estimator is
5. The image according to claim 4, wherein the second addition value is set such that the value of the second addition value decreases as the remaining amount detected by the sheet remaining amount detection unit increases. Forming equipment. The paper remaining amount detection unit
The image forming apparatus according to claim 5, wherein a height of a sheet stacked and stored in the sheet storage unit is detected as the remaining amount. A paper size acquisition unit that acquires a paper size indicating the size of the paper stored in the paper storage unit;
The temperature estimator is
The second addition value is set such that the second addition value decreases as the size of the paper detected by the paper size acquisition unit increases. 2. The image forming apparatus according to item 1. The image forming unit includes:
An exposure unit that forms an electrostatic latent image by exposing the photosensitive drum;
A developing unit that forms a toner image by developing the electrostatic latent image formed on the photosensitive drum with toner;
A transfer unit that transfers the toner image formed in the developing unit to the paper;
A fixing unit that heats the sheet conveyed from the transfer unit and fixes the toner image on the sheet;
A fixing power control unit that controls a supply amount of power for generating heat in the fixing unit;
The fixing power control unit
The image forming apparatus according to claim 1, wherein the power supply amount is decreased as the temperature of the sheet estimated by the temperature estimation unit is higher.

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