JP2013114214A - Control device, image forming apparatus, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a fact that a specified medium differs from an actual medium even if there is no means for detecting a current flowing in a heating part or means for detecting the thickness of a medium.SOLUTION: A transfer part 14 transfers an image on a determined kind of medium. An electromagnetic induction part 53 of a fixing part 15 heats a medium with a heat quantity in accordance with supplied power to fix the image onto the medium. A measurement part 55 of the fixing part 15 measures temperature thereof. A control part 11 instructs the power to be supplied to the fixing part 15 so that the temperature measured by the measurement part 55 approaches a target temperature set in accordance with the kind of media and supplies the fixing part with the aforementioned power. The control part 11 detects an event that the instructed power exceeds a predetermined condition stored in a storage part 12 in accordance with the kind of medium.

Description

  The present invention relates to a control device, an image forming apparatus, and a program.

  Various types of media are used as the medium on which the image is formed by the image forming apparatus, and the amount of heat required to fix the image on each medium may differ depending on the type. Therefore, if the type of medium instructed by the user is different from the type of medium actually used for image formation, there may be a problem that the fixing of the image formed on the medium becomes insufficient. . In order to prevent such a trouble, an image forming apparatus that detects that an instructed medium is different from an actual medium has been developed.

Patent Document 1 includes a current detection unit that flows to the fixing device, and the input / output unit, the switching element, and the drive circuit are detected based on whether the detected current is a predetermined value or more and the input / output of the input cutoff signal and the drive start signal. An image forming apparatus that detects an abnormality is disclosed.
Patent Document 2 discloses an image forming apparatus that includes a detection unit that detects the thickness of a sheet and changes the fixing temperature in accordance with the detected sheet thickness.

JP 2003-295679 A JP 2005-37871 A

  An object of the present invention is to detect that the indicated medium is different from the actual medium without means for detecting the current flowing through the heating unit and means for detecting the thickness of the medium.

  In order to solve the above-described problem, the control device according to claim 1 of the present invention heats the medium with a heat amount corresponding to the supplied power, and measures the temperature of the heating unit that fixes the image transferred to the medium. And measuring the power to be supplied to the heating unit so that the temperature measured by the measuring unit approaches a target temperature that is a target temperature set according to the type of the medium An instructing unit, a supply unit that supplies the heating unit with electric power having a magnitude instructed by the instructing unit, and a power instructed by the instructing unit are stored in advance according to the type of the medium It is characterized by comprising a detection unit that detects that the condition has been deviated and a control unit that performs control according to the detection result of the detection unit.

  According to a second aspect of the present invention, in the control device according to the first aspect, the control unit detects that the power of the magnitude indicated by the instruction unit has deviated from the condition. In this case, the target temperature is corrected according to the detection result, and the instruction unit is instructed to indicate the magnitude of the electric power so as to approach the corrected target temperature.

  According to a third aspect of the present invention, in the control device according to the first or second aspect, the control unit detects that the power of the magnitude indicated by the instruction unit has deviated from the condition. Is detected, a type different from the type of the medium is specified according to the detection result, the target temperature is corrected to a target temperature set according to the specified type, and the corrected target is corrected. The instruction unit is configured to instruct the magnitude of the electric power so as to approach the temperature.

  According to a fourth aspect of the present invention, an image forming apparatus according to any one of the first to third aspects and the control device according to any one of the first to third aspects and a medium heated by an amount of heat corresponding to the supplied power are transferred to the medium. A heating unit for fixing an image, the heating unit for measuring the temperature by the measurement unit, a transfer unit for transferring the image to the medium, and the transfer unit or the heating unit at a predetermined speed. A transport unit that transports the control unit, and the control unit detects the determined speed when the detection unit detects that the amount of power instructed by the instruction unit has deviated from the condition. And correcting the speed according to the result, and transporting the medium at the corrected speed.

  An image forming apparatus according to claim 5 of the present invention exposes the control device according to any one of claims 1 to 3, an image carrier, and a surface of the image carrier to form an electrostatic latent image. An exposure unit to be formed; a developing unit that develops the electrostatic latent image formed on the surface of the image carrier with a developer; and an image developed by the developing unit according to an applied voltage on the medium. A transfer unit that transfers, and a heating unit that heats the medium with an amount of heat corresponding to the supplied electric power and fixes the image transferred to the medium, the heating unit measuring the temperature by the measurement unit When the detection unit detects that the power of the magnitude indicated by the instruction unit has deviated from the condition, the control unit determines a voltage to be applied to the transfer unit according to the detection result. And apply the corrected voltage. Characterized in that to transfer the image to the transfer portion.

  According to a sixth aspect of the present invention, there is provided an image forming apparatus that exposes an electrostatic latent image by exposing the control device according to any one of the first to third aspects, an image carrier, and a surface of the image carrier. An exposure unit to be formed; a development unit that develops the electrostatic latent image formed on the surface of the image carrier with a developer; a replenishment unit that replenishes the development unit with a specified amount of developer; and the development A transfer unit that transfers the image developed by the means to the medium, and a heating unit that heats the medium with an amount of heat corresponding to the supplied electric power and fixes the image transferred to the medium. A heating unit for measuring the temperature, and the control unit replenishes the developing unit when the detection unit detects that the power of the magnitude indicated by the instruction unit has deviated from the condition. Correct the amount of developer to be corrected according to the detection result The amount of by specifying the replenishing portion, characterized in that to supply the amount of the developer.

  An image forming apparatus according to a seventh aspect of the present invention is the image forming apparatus according to the fourth aspect, wherein the detection unit performs detection after the medium is conveyed to the transfer unit or the heating unit by the conveyance unit. It is characterized by.

  An image forming apparatus according to an eighth aspect of the present invention is the image processing apparatus according to any one of the fourth to seventh aspects, wherein the power threshold is a power threshold corresponding to the type of the medium, and deviates from the power threshold. A storage unit that stores a time threshold value that is a threshold value of a time during which the power is kept instructed, and the detection unit deviates from the power threshold value over a period exceeding the time threshold value stored in the storage unit. When the power continues to be instructed by the instructing unit, it is detected that the power deviates from the condition.

  An image forming apparatus according to a ninth aspect of the present invention is the image forming apparatus according to the eighth aspect, wherein the time threshold is a threshold determined according to a time during which the medium passes through the heating unit. To do.

  According to a tenth aspect of the present invention, there is provided a program for heating a medium with an amount of heat corresponding to supplied electric power, fixing an image transferred to the medium, and a measuring section for measuring a temperature of the heating section. An electric power supplied to the heating unit so that the temperature measured by the measurement unit approaches a target temperature that is a target temperature set according to the type of the medium. An instruction unit for instructing the size of the power supply unit, a supply unit for supplying the heating unit with the electric power of the magnitude indicated by the instruction unit, and the electric power of the magnitude indicated by the instruction unit according to the type of the medium This is a program for functioning as a detection unit that detects that the condition deviates from the previously stored condition and a control unit that performs control according to the detection result of the detection unit.

According to the control device of the first aspect, even if there is no means for detecting the current flowing through the heating unit or means for detecting the thickness of the medium, it is detected that the indicated medium is different from the actual medium. can do.
According to the control device of the second aspect, even when there is no means for detecting the current flowing through the heating unit or means for detecting the thickness of the medium, when the indicated medium is different from the actual medium, It is possible to cause the heating unit to perform a fixing process according to the actual medium.
According to the control device of the third aspect, even when there is no means for detecting the current flowing through the heating unit or means for detecting the thickness of the medium, when the indicated medium is different from the actual medium, It is possible to cause the heating unit to perform a fixing process set in accordance with an actual medium.
According to the image forming apparatus of the fourth aspect, even when there is no means for detecting the current flowing through the heating unit or means for detecting the thickness of the medium, the indicated medium and the actual medium are different. The medium can be transported at a speed matched to the actual medium.
According to the image forming apparatus of the fifth aspect, even when there is no means for detecting the current flowing through the heating unit or means for detecting the thickness of the medium, the indicated medium and the actual medium are different. The image can be transferred to the medium with a transfer voltage that matches the actual medium.
According to the image forming apparatus of the sixth aspect, even when there is no means for detecting the current flowing through the heating unit or the means for detecting the thickness of the medium, the indicated medium and the actual medium are different. The amount of developer supplied to the developing device can be adjusted according to the actual medium.
According to the image forming apparatus of the seventh aspect, it is possible to improve the detection accuracy by excluding the power before the medium is conveyed.
According to the image forming apparatus of the eighth aspect, it is possible to improve the accuracy of detecting that the instructed medium is different from the actual medium as compared with the case where the time threshold value is not stored.
According to the image forming apparatus of the ninth aspect, detection can be performed based on the contribution of heat taken away by the medium.
According to the program of claim 10, even if there is no means for detecting the current flowing through the heating unit or means for detecting the thickness of the medium, it is detected that the indicated medium is different from the actual medium. be able to.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to an exemplary embodiment. 3 is a block diagram for explaining that each unit of the image forming apparatus is controlled by a control unit. FIG. It is a figure which shows an example of a setting table. It is a figure which shows an example of a threshold value table. FIG. 3 is a diagram illustrating an outline of a fixing unit. FIG. 6 is a flowchart showing the operation of the image forming apparatus according to the present embodiment. It is a figure for demonstrating the relationship between an electric power instruction | indication value and the conditions described in the threshold value table.

1. Embodiment 1-1. Configuration FIG. 1 is a diagram showing an overall configuration of an image forming apparatus 1 according to the present embodiment. As shown in FIG. 1, the image forming apparatus 1 includes a control unit 11, a storage unit 12, developing units 13Y, 13M, 13C, and 13K, a transfer unit 14, a fixing unit 15, a transport unit 16, and an operation unit. Part 17. Note that the symbols Y, M, C, and K indicate configurations corresponding to yellow, magenta, cyan, and black toners, respectively. Each of the developing units 13Y, 13M, 13C, and 13K is different only in the toner used, and there is no significant difference in the configuration. Hereinafter, when it is not necessary to particularly distinguish each of the developing units 13Y, 13M, 13C, and 13K, the alphabet at the end of the code indicating the color of the toner is omitted and referred to as “developing unit 13”.

  FIG. 2 is a block diagram for explaining that each unit of the image forming apparatus 1 is controlled by the control unit 11. The control unit 11 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and a computer program (hereinafter simply referred to as a program) in which the CPU is stored in the ROM or the storage unit 12. Are read and executed to control each unit of the image forming apparatus 1. In addition, the control unit 11 functions as the instruction unit 111, the supply unit 112, and the detection unit 113 by executing the program.

The operation unit 17 includes operation buttons and the like for inputting various instructions, receives an operation by the user, and supplies a signal corresponding to the operation content to the control unit 11.
The storage unit 12 is a large-capacity storage unit such as a hard disk drive, and stores a program read by the CPU of the control unit 11. In addition, the storage unit 12 stores a setting table 121 and a threshold value table 122 that are used by the control unit 11 to execute the above-described program.

  FIG. 3 is a diagram illustrating an example of the setting table 121. In the setting table 121, various parameters used for image formation are described for each paper type. For example, in the setting table 121 shown in FIG. 3, the fixing temperatures T1, T2, T3,..., Which are temperatures (target temperatures) of the fixing unit 15 that are set as target values in feedback control (described later) performed by the control unit 11 are set. The set value of the conveyance speeds u1, u2, u3,... That is the conveyance speed of the paper P by the conveyance unit 16, and the set value of the transfer voltages V1, V2, V3,. Are associated with paper types ty1, ty2, ty3,..., Which are symbols for identifying the types. In FIG. 3, the unit of each parameter is omitted.

  The control unit 11 performs an image forming process for each type of paper based on the setting table 121. For example, when receiving an instruction from the user via the operation unit 17 to perform image forming processing using the paper P of the paper type ty1, the control unit 11 refers to the setting table 121 and the temperature of the fixing unit 15 is Feedback control is performed to instruct the power supplied to the fixing unit 15 so as to approach the fixing temperature T1 associated with the paper type ty1 as the target temperature. Further, the control unit 11 controls the transport unit 16 so that the speed at which the paper P is transported becomes the transport speed u1, and the potential difference between the primary transfer roll 35 or the secondary transfer roll 42 and the intermediate transfer belt 41 is transferred. The developing unit 13 or the transfer unit 14 is controlled to be equal to the voltage V1.

  FIG. 4 is a diagram illustrating an example of the threshold value table 122. The threshold value table 122 describes conditions for detecting whether or not the paper type instructed by the user is different from the paper type that is actually conveyed. Specifically, the threshold value table 122 includes power that should be instructed when the temperature of the fixing unit 15 is feedback-controlled using the fixing temperature set in the setting table 121 in association with the paper type of the paper as a target value. And the upper and lower limits of the set of the time during which the power is instructed are described for each paper type. In FIG. 4, the unit of each value is omitted.

  For example, the threshold value table 122 shown in FIG. 4 associates the upper limit power Pa1, Pa2, Pa3,... And the upper limit time ta1, ta2, ta3,... With the paper types ty1, ty2, ty3,. This is because when the temperature of the fixing unit 15 is controlled to be the fixing temperatures T1, T2, T3,... Shown in the setting table 121 for each paper P of the paper types ty1, ty2, ty3,. 11 represents a set of the upper limit power and time that should be indicated by 11. That is, when the user instructs the operation unit 17 to use the paper P of the paper type ty1, if the paper P of the paper type ty1 is used correctly, the control unit 11 causes the power exceeding the power Pa1 to be applied for the time ta1. The threshold table 122 indicates that no power is indicated over time and no power less than power Pb1 is indicated over time tb1. The control unit 11 refers to the threshold value table 122 and applies the power value instructed by the feedback control described above to the upper limit or lower limit conditions associated with the paper type of the paper P in the threshold value table 122. And the control part 11 functions as the detection part 113 which detects this, when the value of this electric power deviates from this condition.

  The time thresholds such as the time ta1 and the time tb1 described above may be determined according to the time during which one sheet P passes through the fixing unit 15. As a result, the time during which the paper P has not passed through the fixing unit 15 is excluded from the detection target of the detection unit 113.

  The conveyance part 16 has a container and a conveyance roll. The container accommodates a sheet P as a medium that has been cut into a predetermined size. The paper P accommodated in the container is taken out one by one by a transport roll in accordance with an instruction from the control unit 11, and is transported to the transfer unit 14 via a paper transport path. The medium is not limited to paper, and may be a resin sheet, for example.

  Each developing unit 13 includes a photosensitive drum 31, a charger 32, an exposure device 33, a developing device 34, a primary transfer roll 35, and a drum cleaner 36. The photosensitive drum 31 is an image carrier having a charge generation layer and a charge transport layer, and is rotated in the direction of an arrow D13 in the drawing by a drive unit (not shown). The charger 32 charges the surface of the photosensitive drum 31. The exposure device 33 includes a laser emission source, a polygon mirror, and the like (both not shown), and a photoconductor after the laser light corresponding to the image data is charged by the charger 32 under the control of the control unit 11. Irradiation toward the drum 31. Thereby, a latent image is held on each photosensitive drum 31. The image data may be acquired from an external device by the control unit 11 via a communication unit (not shown). The external device is, for example, a reading device that reads an original image or a storage device that stores data indicating an image.

  The developing unit 34 contains a two-component developer containing toner of any one of Y, M, C, and K and a magnetic carrier such as ferrite powder. The tip of the magnetic brush formed on the developing unit 34 comes into contact with the surface of the photosensitive drum 31 so that the toner is exposed on the surface of the photosensitive drum 31 by the exposure device 33, that is, the image line of the electrostatic latent image. An image is formed (developed) on the photosensitive drum 31.

  The primary transfer roll 35 generates a predetermined potential difference at a position where the intermediate transfer belt 41 of the transfer unit 14 faces the photosensitive drum 31, and the image is transferred to the intermediate transfer belt 41 by this potential difference. The drum cleaner 36 removes untransferred toner remaining on the surface of the photosensitive drum 31 after image transfer, and removes the surface of the photosensitive drum 31. That is, the drum cleaner 36 removes unnecessary toner and charges from the photosensitive drum 31 in preparation for the next image formation.

  The transfer unit 14 includes an intermediate transfer belt 41, a secondary transfer roll 42, a belt conveyance roll 43, and a backup roll 44, and determines an image formed by the developing unit 13 according to a user operation. Transfer means for transferring to the paper P of the specified paper type. The intermediate transfer belt 41 is an endless belt member, and the belt conveyance roll 43 and the backup roll 44 stretch the intermediate transfer belt 41. At least one of the belt conveyance roll 43 and the backup roll 44 is provided with a drive unit (not shown), and moves the intermediate transfer belt 41 in the direction of arrow D14 in the drawing. Note that the belt conveyance roll 43 or the backup roll 44 that does not have a driving unit rotates following the movement of the intermediate transfer belt 41. As the intermediate transfer belt 41 moves and rotates in the direction of the arrow D14 in the drawing, the image on the intermediate transfer belt 41 is moved to a region sandwiched between the secondary transfer roll 42 and the backup roll 44.

  The secondary transfer roll 42 transfers the image on the intermediate transfer belt 41 onto the paper P conveyed from the conveyance unit 16 by a potential difference with the intermediate transfer belt 41. The belt cleaner 49 removes untransferred toner remaining on the surface of the intermediate transfer belt 41. Then, the transfer unit 14 conveys the paper P on which the image is transferred to the fixing unit 15.

  The fixing unit 15 fixes the image transferred onto the paper P by heating. FIG. 5 is a diagram showing an outline of the fixing unit 15. The fixing unit 15 includes a heating belt 51, a pressure roll 52, an electromagnetic induction unit 53, a casing 54, a measuring unit 55, a pressing pad 56, and a holder 57. The casing 54 accommodates the electromagnetic induction part 53. The holder 57 supports the pressing pad 56 in the direction of the arrow shown in FIG. 5, that is, in the direction in which the pressure roll 52 is disposed. The electromagnetic induction unit 53 includes an exciting coil to which high frequency power is supplied from a power source (not shown) according to an instruction from the control unit 11. The heating belt 51 is constituted by an endless belt member whose original shape is a cylindrical shape, and has a conductive layer along the cylindrical shape. When electric power is supplied to the exciting coil, a high frequency magnetic field is generated around it, and this acts on the conductive layer of the heating belt 51 to generate an eddy current inside the conductive layer. Then, the heating belt 51 generates heat by Joule heat of eddy current, whereby the paper P in contact with the heating belt 51 is heated. As a result, the combination of the heating belt 51 and the electromagnetic induction unit 53 (corresponding to the heating unit in the present invention) heats the medium with the amount of heat corresponding to the supplied power, and fixes the image transferred to the medium to the medium. . As a material constituting the conductive layer, for example, metals such as Au, Ag, Al, Cu, Zn, Sn, Pb, Bi, Be, and Sb, and metal alloys thereof are used.

  The pressure roll 52 assists the heating of the paper P by the heating belt 51 by pressing the paper P conveyed by the conveyance unit 16 against the heating belt 51 while being rotated by a driving unit (not shown). The heating belt 51 is driven and rotated by the pressure roll 52 by the frictional force from the pressure roll 52. The pressing pad 56 is an example of a pressing member, and is constituted by an elastic body such as silicone rubber or fluorine rubber, and is supported by the holder 57 at a position facing the pressure roll 52. The pressing pad 56 is disposed in a state of being pressed from the pressure roll 52 via the heating belt 51 and presses the heating belt 51 from the inside toward the direction of the pressure roll 52 (the direction of the arrow shown in FIG. 5). . As a result, a nip portion is formed between the heating belt 51 and the pressure roll 52. The paper P is conveyed so as to pass through the nip portion.

  The measuring unit 55 is disposed inside the heating belt 51 and measures the temperature of the heating belt 51. The measuring unit 55 includes, for example, a thermocouple, and measures the temperature of the heating belt 51 by measuring the voltage of the thermoelectromotive force generated thereby. The measured temperature is transmitted to the control unit 11. The control unit 11 controls the high frequency power supplied to the exciting coil of the heating belt 51 so that the temperature of the heating belt 51 approaches the set value. That is, the control unit 11 supplies the electromagnetic induction unit 53 so that the temperature of the heating belt 51 measured by the measurement unit 55 approaches the target temperature set according to the paper type of the paper P in the setting table 121. It functions as an instruction unit 111 that instructs power to be transmitted. In addition, the control unit 11 functions as a supply unit 112 that supplies power instructed as the instruction unit 111 to the electromagnetic induction unit 53. The heating belt 51 controlled so as to approach the above-described preset temperature performs a fixing process for heating the sheet P conveyed to the nip portion via the intermediate transfer belt 41. The sheet P that has undergone the fixing process by the fixing unit 15 is discharged by the transport unit 16 to a sheet storage area provided in the upper portion of the image forming apparatus 1.

1-2. Operation FIG. 6 is a flowchart showing the operation of the image forming apparatus 1 according to the present embodiment. The control unit 11 of the image forming apparatus 1 determines whether an image forming instruction is received from the user via the operation unit 17 (step S1). Then, the control unit 11 continues this determination while determining that an instruction for image formation has not been received (step S1; NO). When it is determined that an image formation instruction has been received (step S1; YES), the control unit 11 controls each unit of the image forming apparatus 1 and starts an image formation process (step S2).

  Next, the control unit 11 determines whether or not the first sheet P is transported to the fixing unit 15 by the transport unit 16 (step S3). While it is determined that the first sheet P is not yet conveyed to the fixing unit 15 (step S3; NO), the control unit continues this determination. When it is determined that the paper P has been conveyed to the fixing unit 15 (step S3; YES), the control unit 11 monitors an instruction value (hereinafter referred to as an electric power instruction value) of high frequency power supplied to the fixing unit 15 (step S4). ).

  The control unit 11 functions as an example of the detection unit 113 in the present invention, and determines whether the monitored power instruction value has deviated from the upper limit condition of the threshold table 122 (step S5). FIG. 7 is a diagram for explaining the relationship between the power instruction value and the conditions described in the threshold value table 122. The horizontal axis in FIG. 7A is the elapsed time t starting from t0 when the first sheet P is conveyed to the fixing unit 15, and the vertical axis is the temperature of the heating belt 51 of the fixing unit 15. It is. 7B to 7D, the horizontal axis represents the elapsed time t, and the vertical axis represents the power instruction value.

  When feedback control such as PID (Proportional-Integral-Derivative) control is performed, an input value is determined based on a deviation between a target value and an output value, an integral of the deviation, a differential of the deviation, and the like. The measuring unit 55 of the fixing unit 15 measures the temperature of the heating belt 51 of the fixing unit 15 as a control output value. For example, when an instruction to perform image formation using the paper P of the paper type ty1 is received from the user, the control unit 11 specifies the fixing temperature T1 corresponding to the paper type ty1 and uses this as a target value for feedback control. To do. As shown in FIG. 7A, the measured temperature T (t) of the heating belt 51 is controlled so as to approach the fixing temperature T1 as time passes.

  At this time, the control unit 11 functions as an example of the instruction unit 111 in the present invention, and this deviation approaches 0 based on the deviation between the measured temperature T (t) and the fixing temperature T1 that is the target value. Thus, the power supplied to the fixing unit 15 is instructed as an input value. Here, when the paper P of the paper type ty1 instructed by the user is correctly used for image formation, the power instruction value includes the power Pa1 that is the upper limit and the power that is the lower limit in the threshold table 122 as shown in FIG. It converges with Pb1. Therefore, even if the power instruction value may exceed the power Pa1, the time does not exceed ta1, and even if it exceeds the power Pb1, the time does not exceed tb1.

  On the other hand, when the paper type of the paper P that is actually used for image formation is not the paper type ty1 instructed by the user, the paper P takes more heat from the fixing unit 15 than when it is the paper type ty1. There is a case. For example, when the actual paper type of the paper P is thicker than the paper type ty1 designated by the user, the amount of heat that the paper P takes from the fixing unit 15 per unit area is larger than that of the paper type ty1. That is, in this case, the heat of the fixing unit 15 is easily lost to the paper P, and more power is required to maintain the temperature of the fixing unit 15 at the fixing temperature T1.

  At this time, as shown in FIG. 7C, the power instruction value is higher than that when the correct paper type is used for image formation (see FIG. 7B), and is often the upper limit power Pa1. Over. When the power instruction value exceeds the power Pa1 at the elapsed time t1 and the time ta1 or more has passed in that state, it is determined that the power instruction value has deviated from the upper limit condition of the threshold value table 122 (step S5; YES) In other words, the control unit 11 functions as the detection unit 113 and detects that the electric power having the magnitude indicated by the instruction unit 111 has deviated from the condition stored in advance according to the type of the medium. This detection may be performed, for example, by the elapsed time t2 when the power instruction value returns to the power Pa1 or less ({t2-t1}> ta1). At this time, the control unit 11 performs the following correction process (hereinafter referred to as a first correction process) (step S6). On the other hand, when determining that the power instruction value does not deviate from the upper limit condition of the threshold value table 122 (step S5; NO), the control unit 11 sets the monitored power instruction value to the lower limit condition of the threshold value table 122. It is determined whether or not a departure has occurred (step S7). When determining that the power instruction value does not deviate from the lower limit condition (step S7; NO), the control unit 11 advances the process to step S9.

  The first correction process is a correction process that is performed when the power instruction value exceeds the upper limit because the actually transported sheet takes more heat than the sheet of the sheet type instructed by the user. For example, when the paper type ty1 instructed by the user is plain paper, the control unit 11 reads the parameters read from the setting table 121 and stores them in the RAM. And so on.

  Further, when the paper type of the paper P that is actually used for image formation is not the paper type ty1 instructed by the user, the heat taken by the paper P from the fixing unit 15 is less than when the paper type is ty1. There is a case. For example, when the actual paper type of the paper P is thinner than the paper type ty1 designated by the user, the amount of heat that the paper P takes from the fixing unit 15 per unit area is smaller than that of the paper type ty1. That is, in this case, the heat of the fixing unit 15 is not easily taken away by the paper P. That is, since the temperature of the paper P is easily increased as compared with the case where the paper of the paper type ty1 is used, it is consumed in order to maintain the temperature of the fixing unit 15 at the fixing temperature T1. It is necessary to suppress electric power.

  At this time, as shown in FIG. 7 (d), the power instruction value is lower than that when the correct paper type is used for image formation (see FIG. 7 (b)), and is often the lower limit power Pb1. Below. When the elapsed time t3, the power command value is lower than the power Pb1, and when the time tb1 has passed in that state, it is determined that the power command value has deviated from the lower limit condition of the threshold value table 122 (step S7; YES) ). This determination may be performed, for example, by the elapsed time t4 when the power instruction value returns to the power Pb1 or more ({t4-t3}> tb1). At this time, the control unit 11 performs the following correction process (hereinafter referred to as a second correction process) (step S8).

  The second correction process is a correction process that is performed when the power instruction value falls below the lower limit because the actually conveyed sheet does not take more heat than the sheet of the sheet type instructed by the user. In this correction processing, for example, when the paper type ty1 instructed by the user is thick paper, the parameters read by the control unit 11 from the setting table 121 and stored in the RAM are set to plain paper that does not take more heat than thick paper. And so on. The control unit 11 performs feedback control based on the corrected setting, and determines the power instruction value. The control unit 11 functions as an example of the supply unit 112 in the present invention, and supplies the power indicated by the power instruction value to the electromagnetic induction unit 53 of the fixing unit 15.

  Then, the control unit 11 determines whether or not the last sheet has been discharged from the fixing unit (step S9). If it is determined that the last sheet has been discharged (step S9; YES), this process ends. On the other hand, when it is determined that the last sheet has not yet been discharged from the fixing unit (step S9; NO), the control unit 11 returns the control to step S4.

  With the above operation, even when a paper type different from the paper type designated by the user is used for image formation, the image forming apparatus 1 detects this abnormality and performs a correction process corresponding thereto. Therefore, as compared with the case where this configuration is not used, the number of sheets with insufficient heat and insufficient image fixing, and on the other hand, sheets with excessive heat and altered images are reduced.

2. Modification The above is the description of the embodiment, but the contents of this embodiment can be modified as follows. Further, the following modifications may be combined.

2-1. Correction Process In the above-described embodiment, the control unit 11 of the image forming apparatus 1 performs the first correction process when it is determined that the power instruction value has deviated from the upper limit of the threshold value table 122, and when it is determined that the power instruction value has deviated from the lower limit. Although the second correction process is performed, the first correction process and the second correction process are not limited to those shown in the embodiment. That is, in the case of the first correction process performed when the power instruction value exceeds the upper limit, each parameter read out from the setting table 121 and stored in the RAM by the control unit 11 is more likely to take heat than the instructed paper type. However, for example, only the transport speed may be corrected, and the speed at which the paper P is transported by the transport unit 16 may be slowed so that heat is easily taken from the paper P. Further, in the case of the second correction process performed when the power instruction value is below the lower limit, the speed at which the transport unit 16 transports the paper P may be increased to make it difficult to remove heat from the paper P.

  In addition, the control unit 11 may increase the transfer voltage in the transfer unit 14 as the first correction process when it is determined that the power instruction value has deviated from the upper limit of the threshold value table 122. In this case, since the heating amount is excessive, it is only necessary to increase the amount of toner transferred to the paper P so as to match the amount of heat by increasing the transfer voltage.

  Further, the developing device 34 has a storage space for storing the two-component developer, a replenisher for supplying the consumed toner to the storage space, and a stirrer for stirring the two-component developer in the storage space. In the accommodation space of the developing device 34, for example, a toner concentration sensor that detects the toner concentration using magnetic permeability is provided, and the toner concentration in the accommodation space detected by the toner concentration sensor becomes the target toner concentration. Thus, the toner replenishment amount is adjusted by the control unit 11. Therefore, when the control unit 11 determines that the power instruction value has deviated from the upper limit of the threshold value table 122, the control unit 11 replenishes the accommodation space of the developing device 34 by increasing the target value of the toner density described above as the first correction process. The amount of toner may be increased.

  The control unit 11 may lower the transfer voltage in the transfer unit 14 as the second correction process when it is determined that the power instruction value has deviated from the lower limit of the threshold value table 122. In this case, since the amount of heating is insufficient, if the amount of toner transferred onto the paper P is large, sufficient heat does not reach the fixing and a fixing failure tends to occur. Therefore, in this case, it is only necessary to reduce the transfer voltage to reduce the amount of toner transferred to the paper P so that the toner is fixed to the paper P even with a small heating amount.

  In addition, when the control unit 11 determines that the power instruction value has deviated from the lower limit of the threshold value table 122, the control unit 11 replenishes the accommodation space of the developing device 34 by reducing the above-described target value of toner density as the second correction process. The amount of toner may be reduced.

  In short, when the control unit 11 detects that a paper type different from the paper type designated by the user has been used for image formation, the control unit 11 is set by the setting table 121 according to the detection result, for example. The fixing temperature (target temperature) may be corrected, the speed at which the paper P is transported by the transport unit 16 may be corrected, or the transfer voltage in the transfer unit 14 may be corrected.

  Moreover, the control part 11 does not need to perform the above-mentioned correction process. In this case, when the control unit 11 detects that the power instruction value has deviated from the upper limit or the lower limit described in the threshold value table 122, the control unit 11 may perform control according to the detection result. For example, the control unit 11 may notify the user that the power instruction value has deviated from the conditions described in the threshold value table 122 using a notification device such as a display unit having a screen or a sound emitting unit that outputs sound. Good. The user informed of this may specify the paper type of the paper P that is actually conveyed, and correct the image formation instruction in accordance with the specified paper type. Further, when the control unit 11 detects that the power of the instructed power instruction value has deviated from the condition, the control unit 11 may stop the image forming process as control according to the detection result. In short, the control unit 11 of the image forming apparatus 1 may detect this when the instructed power deviates from a prestored condition according to the type of medium, and perform control according to the detection result.

2-2. Threshold Table In the above-described embodiment, the threshold table 122 describes the upper and lower limits of the set of the power that should be instructed by the control unit 11 and the time during which the power is instructed for each paper type. However, the conditions described in the threshold value table 122 are not limited to this. For example, the threshold value table 122 may describe either the upper limit or the lower limit. Whether the upper limit, the lower limit, or both of them are described in the threshold value table 122 may be different for each paper type.

  Further, the threshold value table 122 may describe an upper limit or a lower limit of a value obtained by averaging the power instruction values instructed by the control unit 11 over a predetermined period. In this case, the control unit 11 calculates the average value of the power instruction values by integrating the instructed power instruction value over the above period and dividing the integrated value by the period. Then, the control unit 11 compares the calculated average value with the upper limit or lower limit described in the threshold value table 122 and determines whether or not the power instruction value has deviated from the conditions indicated in the threshold value table 122. Good.

  Further, the threshold value table 122 may describe an upper limit or a lower limit of the temperature measured by the measuring unit 55. In this case, the control unit 11 compares the temperature measured by the measurement unit 55 with the upper limit or lower limit described in the threshold value table 122, and determines whether or not this temperature has deviated from the conditions indicated in the threshold value table 122. Just judge.

2-3. Program A program executed by the control unit 11 of the image forming apparatus 1 is readable by a computer device such as a magnetic recording medium such as a magnetic tape or a magnetic disk, an optical recording medium such as an optical disk, a magneto-optical recording medium, or a semiconductor memory. It can be provided in a state stored in a recording medium. It is also possible to download this program via a network such as the Internet. Note that various devices other than the CPU may be applied as the control means exemplified by the control unit 11. For example, a dedicated processor or the like is used.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 11 ... Control part, 111 ... Instruction part, 112 ... Supply part, 113 ... Detection part, 12 ... Memory | storage part, 121 ... Setting table, 122 ... Threshold table, 13 ... Developing part, 14 ... Transfer part 15 ... Fixing unit, 16 ... Conveying unit, 17 ... Operating unit, 31 ... Photoconductor drum, 32 ... Charger, 33 ... Exposure device, 34 ... Developer, 35 ... Primary transfer roll, 36 ... Drum cleaner, 41 ... Intermediate transfer belt, 42 ... secondary transfer roll, 43 ... belt transport roll, 44 ... backup roll, 49 ... belt cleaner, 51 ... heating belt, 52 ... pressure roll, 53 ... electromagnetic induction section, 54 ... casing, 55 ... Measuring unit 56 ... Pressing pad 57 ... Holder

Claims (10)

A measurement unit that measures the temperature of a heating unit that heats the medium with an amount of heat corresponding to the supplied power and fixes the image transferred to the medium;
An instruction unit for instructing the magnitude of electric power to be supplied to the heating unit so that the temperature measured by the measurement unit approaches a target temperature that is a target temperature set according to the type of the medium;
A supply unit for supplying the heating unit with electric power having a magnitude indicated by the instruction unit;
A detection unit for detecting that the power of the magnitude instructed by the instruction unit deviates from a condition stored in advance according to the type of the medium;
A control unit that performs control according to a detection result of the detection unit. The control unit corrects the target temperature according to the detection result when the detection unit detects that the power of the magnitude instructed by the instruction unit deviates from the condition. The control apparatus according to claim 1, wherein the instruction unit is configured to instruct the magnitude of the electric power so as to approach the target temperature. When the detection unit detects that the power of the magnitude indicated by the instruction unit has deviated from the condition, the control unit specifies a type different from the type of the medium according to the detection result, The target temperature is corrected to a target temperature set according to the specified type, and the instruction unit is instructed to indicate the magnitude of the power so as to approach the corrected target temperature. The control device according to claim 1 or 2. The control device according to any one of claims 1 to 3,
A heating unit that heats the medium with an amount of heat corresponding to the supplied power and fixes the image transferred to the medium, the heating unit measuring the temperature by the measurement unit;
A transfer portion for transferring an image to the medium;
A transport unit that transports the medium to the transfer unit or the heating unit at a determined speed,
The control unit corrects the determined speed to a speed according to the detection result when the detection unit detects that the power of the magnitude instructed by the instruction unit deviates from the condition. The image forming apparatus, wherein the medium is conveyed to the conveyance unit at the corrected speed. The control device according to any one of claims 1 to 3,
An image carrier,
An exposure unit that exposes the surface of the image carrier to form an electrostatic latent image;
A developing unit that develops the electrostatic latent image formed on the surface of the image carrier with a developer;
A transfer unit that transfers an image developed by the developing unit to the medium in accordance with an applied voltage;
A heating unit that heats the medium with an amount of heat corresponding to the supplied power and fixes the image transferred to the medium, the heating unit measuring the temperature by the measurement unit,
The control unit corrects the voltage applied to the transfer unit to a voltage corresponding to the detection result when the detection unit detects that the power of the magnitude instructed by the instruction unit deviates from the condition. Then, by applying the corrected voltage, the image is transferred to the transfer unit. The control device according to any one of claims 1 to 3,
An image carrier,
An exposure unit that exposes the surface of the image carrier to form an electrostatic latent image;
A developing unit that develops the electrostatic latent image formed on the surface of the image carrier with a developer;
A replenishing unit for replenishing the developing unit with a specified amount of developer;
A transfer portion for transferring the image developed by the developing means to the medium;
A heating unit that heats the medium with an amount of heat corresponding to the supplied power and fixes the image transferred to the medium, the heating unit measuring the temperature by the measurement unit,
The control unit responds to the detection result with the amount of developer to be replenished to the developing unit when the detecting unit detects that the power of the magnitude instructed by the instruction unit deviates from the condition. An image forming apparatus, wherein the amount is corrected to an amount, and the corrected amount is designated in the replenishing unit to supply the amount of developer. The image forming apparatus according to claim 4, wherein the detection unit performs detection after the medium is conveyed to the transfer unit or the heating unit by the conveyance unit. A storage unit that stores a power threshold value that is a power threshold value according to the type of the medium, and a time threshold value that is a time threshold value during which power that deviates from the power threshold value is instructed;
The detection unit is configured such that the power deviates from the condition when the instruction unit continues to instruct power having a magnitude that deviates from the power threshold over a period exceeding the time threshold stored in the storage unit. The image forming apparatus according to claim 4, wherein the image forming apparatus is detected. The image forming apparatus according to claim 8, wherein the time threshold is a threshold determined according to a time during which the medium passes through the heating unit. A heating unit that heats the medium with an amount of heat corresponding to the supplied power and fixes the image transferred to the medium;
A computer of an image forming apparatus comprising: a measuring unit that measures the temperature of the heating unit;
An instruction unit for instructing the magnitude of electric power to be supplied to the heating unit so that the temperature measured by the measurement unit approaches a target temperature that is a target temperature set according to the type of the medium;
A supply unit for supplying the heating unit with electric power having a magnitude indicated by the instruction unit;
A detection unit for detecting that the power of the magnitude instructed by the instruction unit deviates from a condition stored in advance according to the type of the medium;
The program for functioning as a control part which performs control according to the detection result by the detection part.

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