JP2010054993A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which can detect drop of AC voltage of a fixing heater with simple constitution, and can change operation of respective sections in accordance with the drop of the AC voltage. <P>SOLUTION: The image forming apparatus includes a power supply section, a printing section, a fixing section to perform fixing of a sheet printed by the printing section, and a heater energized to generate heat so as to heat a member included in the printing section or the fixing section. The apparatus includes a time measuring section which measures the AC voltage of the power supply section and measures a time interval from a point of time when an absolute value of the AC voltage is less than a predetermined value to a point of time when it is more than the predetermined value. The apparatus includes a control changing section which monitors whether the time interval measured by the time measuring section exceeds the predetermined time, and changes a control method related to energizing processing of the heater or error disposal when the time interval exceeds the predetermined time. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that detects a decrease in AC voltage and changes a processing operation.

  In image forming apparatuses such as copiers, printers, and fax machines, a powder developer (hereinafter referred to as “toner”) is used, and an electrostatic latent image formed on an image carrier such as a photosensitive drum is formed with toner. Generally, the toner image is visualized and the toner image is transferred onto a recording medium (hereinafter referred to as “sheet”), and then a fixing process is performed.

  The image forming apparatus as described above conveys a sheet stored in a paper feed cassette to an image forming unit along a sheet conveyance path, and prints a toner image on the sheet by the image forming unit. Then, the sheet on which the toner image is printed is conveyed to the fixing unit, and the sheet on which the toner image is fixed by the fixing unit is discharged onto the discharge tray by the sheet discharge unit. There are a plurality of methods for fixing the toner image by the fixing unit, and in particular, thermal fixing using a fixing heater is widely used.

In relation to the above, Patent Document 1 discloses a fixing heater current control device including a fixing heater control circuit for adjusting a fixing temperature. The fixing heater current control device performs energization control of the fixing heater based on the selected standby mode and the environmental conditions of the AC power supply. Thereby, the fall and fluctuation | variation of an alternating voltage can be made small.
JP-A-9-101718

  However, the fixing heater current control device of Patent Document 1 uses a dedicated circuit for detecting the AC voltage of the fixing heater. For this reason, there has been a problem that the apparatus configuration is likely to be complicated and is disadvantageous in terms of space saving.

  The present invention has been devised to solve the above-described problems, and can detect a decrease in the AC voltage of the fixing heater with a simple configuration, and can change the operation of each part in accordance with the decrease in the AC voltage. A possible image forming apparatus is provided.

  In order to achieve the above object, an image forming apparatus of the present invention includes a power supply unit, a printing unit, a fixing unit that fixes a sheet printed by the printing unit, and heat generated by energization to include the fixing unit. In an image forming apparatus comprising a heater for heating a member to be heated, an AC voltage output from the power supply unit and applied to the heater is measured, and an absolute value of the AC voltage is set to a predetermined value. When the time measurement unit that measures the time interval from the time point below to the time point above and the time interval measured by the time measurement unit exceeds a predetermined time, the voltage value of the AC voltage is reduced And a control changing unit that changes the control method related to the heater energization process or the error process.

  According to this, the image forming apparatus of the present invention heats a member included in the fixing unit by generating heat by energization, and a power source unit, a printing unit, a fixing unit that fixes a sheet printed by the printing unit. And a heater. Further, the power supply unit includes a time measuring unit that measures an AC voltage for heating the heater, and measures a time interval from the time when the absolute value of the AC voltage is less than a predetermined value to the time when the absolute value is exceeded. Yes. Furthermore, it is monitored whether the time interval measured by the time measuring unit exceeds a predetermined time, and if it exceeds, it is determined that the voltage value of the AC voltage has decreased, and the heater energization process or error process is performed. A control change unit for changing a related control method is provided. This utilizes the characteristic that the time interval from the start point to the end point becomes longer as the AC voltage decreases. For this reason, the fall of an alternating voltage is detectable by simple software processing. Further, by changing the control method related to the heater in accordance with the voltage drop, it is possible to avoid a shortage of heat in the heater or a false detection of a heater failure due to the voltage drop.

  In order to achieve the above object, the image forming apparatus of the present invention generates a zero-cross signal that generates a zero-cross signal in which the signal level is switched between when the absolute value of the AC voltage of the power supply unit falls below and exceeds a predetermined value. And the time measuring unit acquires the time interval using the zero cross signal.

  According to this, the image forming apparatus of the present invention includes a zero cross signal generation unit that generates a zero cross signal from the AC voltage of the power supply unit. The time measuring unit acquires the above-described time interval using this zero cross signal. Specifically, the width of both edges of the rectangular wave of the zero cross signal is acquired as the above-described time interval.

  In order to achieve the above object, the image forming apparatus of the present invention includes a temperature detection body that detects the temperature of the fixing unit, and measures the temperature increase rate of the fixing unit using the temperature detection body. A failure detection unit that detects the failure of the heater by comparing the temperature increase rate with a predetermined reference value, and the control change unit has a time interval exceeding a predetermined time. In addition, the failure detection unit is instructed to reduce the value of the reference value.

  According to this, the image forming apparatus of the present invention uses the temperature detector to measure the temperature rise rate of the fixing unit, and compares the measured temperature rise rate with a predetermined reference value, thereby causing a failure of the heater. A failure detection unit that detects occurrence is provided. In addition, the control change unit considers that the AC voltage drop has occurred when the measured time interval exceeds a predetermined value, and instructs the failure detection unit to reduce the reference value of the temperature rise rate of the heater. To do. As a result, it is possible to avoid erroneous detection of a heater failure caused by the AC voltage drop.

  In order to achieve the above object, the image forming apparatus of the present invention includes a printing speed control unit that controls a printing speed of the printing unit, and the control change unit has the time interval exceeding a predetermined time. In this case, the printing speed control unit is instructed to advance the processing start timing of the printing speed reduction process performed by the printing speed control unit when the temperature of the printing unit decreases during printing.

  According to this, the image forming apparatus of the present invention includes a printing speed control unit that controls the printing speed of the printing unit. When the measured time interval exceeds the predetermined value, the control change unit considers that an AC voltage drop has occurred and changes the value related to the printing speed of the printing speed control unit. Specifically, the process start timing of the printing speed reduction process is advanced when the temperature of the heater decreases during printing. Thereby, it is possible to avoid a decrease in fixability due to a decrease in the temperature of the heater.

  In order to achieve the above object, the image forming apparatus according to the present invention is configured such that when the main power is turned on or when the power saving state in which the temperature of the fixing unit is lowered by controlling energization to the heater is released. A state control unit that shifts the printing unit to a printable state is provided, and the control change unit starts shifting the printing unit to a printable state when the time interval exceeds a predetermined time. The state control unit is instructed to reduce the estimated rate of temperature increase from the start of the transition to the completion of the transition or to increase the estimated completion time from the start of the transition to the completion of the transition.

  According to this, the image forming apparatus of the present invention includes a state control unit that shifts the printing unit to a printable state when the main power is turned on or when the power saving state is canceled. When the measured time interval exceeds a predetermined value, the control change unit considers that an AC voltage drop has occurred, and changes a value related to the transition process to the printable state performed by the state control unit. . Specifically, the estimated temperature increase rate of the heater from the start of the transition of the printing unit to the printable state to the completion of the transition is reduced, or the estimated completion time until the transition is completed is increased. Thereby, it is possible to avoid a shortage of fixability immediately after the transition to the printable state.

  According to the present invention, it is possible to detect a decrease in AC voltage by software processing using a sine wave of AC voltage, a zero cross signal, or the like without using a dedicated voltage detection device. Therefore, it can be implemented with a simple device configuration and is advantageous in terms of space saving.

  Further, according to the present invention, in the fixing heater failure detection process, the failure detection condition is changed when a decrease in AC voltage is detected, so that erroneous detection of the occurrence of failure can be prevented.

  Further, according to the present invention, when a decrease in AC voltage is detected during continuous printing, the fixing speed due to a decrease in the temperature of the fixing unit is avoided by reducing the printing speed at a timing earlier than usual. Can do.

  Further, according to the present invention, when the main power is turned on or when shifting from the power saving state to the printable state, the shift to the printable state is performed by correcting the value used for the process for shifting to the printable state. It is possible to avoid shortage of fixability at the fixing portion immediately after.

  An image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings. In addition, embodiment shown here is an example and this invention is not limited to embodiment shown here.

<1. Schematic configuration of the device>
Here, an outline of the image forming apparatus 1 according to an embodiment of the present disclosure will be described with reference to FIG. 2. FIG. 2 is a schematic cross-sectional view seen from the front showing the schematic configuration of the image forming apparatus 1.

  As shown in FIG. 2, the image forming apparatus 1 has a main body 4 having a box shape. An image reading device 2 is disposed above the main body 4 and a document conveying device 3 placed on the upper surface thereof is provided.

  Here, first, a schematic configuration of the document conveying device 3 will be described.

  The document conveying device 3 is attached to the main body 4 so as to be openable and closable with the back side of the sheet of FIG. The document feeder 3 corresponds to an automatic document feeder generally called ADF (Auto Document Feeder). The document transport device 3 includes a document stacking tray 10, a document pickup roller 12, a document transport roller pair 13, a document discharge roller pair 14, in order from the document transport tray 11 along the document transport path 11 from the upstream side in the document transport direction. A document discharge tray 15 and the like are provided.

  The document placement tray 10 can place a plurality of documents, and is connected to the upstream end of the document transport path 11. The document pick-up roller 12 is disposed at a position where the document pick-up roller 12 contacts the uppermost document among the documents on the document loading tray 10. When a document reading or image formation execution instruction is issued to the image forming apparatus 1, the document pickup roller 12 sends the document toward the document transport path 11.

  The document sent to the document transport path 11 passes through the upper surface of the document passage surface 51 while being guided by a plurality of document transport roller pairs 13 and guides. Although details will be described later, the document is read by the image reading device 2 at this time. Then, the document that has been read passes through the guide, the document transport roller pair 13 and the document discharge roller pair 14 and is discharged to the discharge tray 15.

  Next, a schematic configuration of the main body unit 4 will be described.

  The main body 4 includes therein a sheet supply unit 20, a sheet conveyance path 24, an image forming unit 30 (= printing unit), a fixing unit 40, a sheet discharge unit 43, and the like. A paper discharge space is provided at a position above the center of the main body 4. Therefore, these configurations will be described along the conveyance path of the sheet S. In FIG. 2, the conveyance path of the sheet S in the main body 4 is illustrated by a solid line arrow.

  First, the sheet supply unit 20 is for sending out a sheet S such as a copy sheet or an OHP sheet toward the image forming unit 30, and is provided at the lowermost part of the main body unit 4. The sheet supply unit 20 includes a sheet feeding cassette 21, a sheet placing plate 22, and a sheet feeding roller 23.

  The paper feed cassette 21 is for stacking and storing a plurality of sheets S, and has a box shape and an open top surface, and is detachable by being pulled out from the main body portion 4 for sheet supply. A sheet placement plate 22 on which a plurality of sheets S are placed is provided in the paper feed cassette 21. In addition, a paper feed roller 23 is provided on the upper part of the paper feed cassette 21 on the downstream side in the sheet conveying direction (upper left position in FIG. 2).

  The sheet conveyance path 24 is for conveying the sheet S in the image forming apparatus 1, and conveys the sheet S from the sheet supply unit 20 to the sheet discharge unit 43 through the image forming unit 30 and the fixing unit 40. . Therefore, the sheet conveyance path 24 is formed so as to penetrate the main body portion 4 in the vertical direction. The sheet conveyance path 24 includes a plurality of guide plates (not shown) for guiding the conveyance roller pair 25 and the sheet S.

  A registration roller pair 26 is provided in front of the image forming unit 30 on the upstream side in the sheet conveyance direction. The registration roller pair 26 temporarily stops the conveyed sheet S, and sends the sheet S toward the image forming unit 30 at a predetermined timing and speed so that the toner image is transferred at an appropriate position of the sheet S.

  The image forming unit 30 forms a toner image of an image to be formed based on a document read by the image reading device 2 or image data input to the image forming device 1 and transfers the toner image to the sheet S. In the example of FIG. 2, it is arranged at a position slightly to the left of the center of the main body 4. The image forming unit 30 includes a photosensitive drum 31 as an image carrier, a charging device 32, an exposure device 33, a developing device 34, a transfer roller 36, a cleaning device 37, and the like.

  The photosensitive drum 31 is disposed at a substantially central position of the image forming unit 30 and is rotationally driven in a predetermined direction (clockwise in FIG. 2) by a driving device (not shown). For example, the photosensitive drum 31 is configured to have a positively charged OPC or amorphous silicon photosensitive layer on the outer peripheral surface of an aluminum drum. Then, after an electrostatic latent image is formed on the peripheral surface of the photoconductive drum 31, toner is supplied to form a toner image on the peripheral surface of the photoconductive drum 31.

  In the example of FIG. 2, the charging device 32 is disposed facing diagonally upward to the right of the photosensitive drum 31, and charges the peripheral surface of the photosensitive drum 31 with a predetermined potential. In this embodiment, a corona charger is used as the charging device 32. However, as long as the surface of the photosensitive drum 31 can be charged to a predetermined potential, the charging device 32 using a charging roller or a brush may be used.

  In the example of FIG. 2, the exposure device 33 is disposed on the right side of the photosensitive drum 31 and the charging device 32. The exposure device 33 irradiates the photosensitive drum 31 with light on the circumferential surface of the uniformly charged photosensitive drum 31 based on the image data of the image to be formed, and scans the circumferential surface of the photosensitive drum 31. , Expose. Thereby, an electrostatic latent image is formed on the peripheral surface of the photosensitive drum 31.

  In the example of FIG. 2, the developing device 34 is provided below the photosensitive drum 31, accommodates toner, charges the toner to a predetermined potential, and forms the toner on the peripheral surface of the photosensitive drum 31. Supply toward the electrostatic latent image. A developing roller 35 is provided in the developing device 34 at a position facing the photosensitive drum 31 with a predetermined gap for supplying toner. The developing roller 35 rotates in a predetermined direction while carrying toner on the peripheral surface. When a predetermined voltage is applied to the developing roller 35, the toner flies toward the image carrier, and the electrostatic latent image is developed.

  In the example of FIG. 2, the transfer roller 36 is supported so as to be rotatable diagonally to the left of the photosensitive drum 31. The transfer roller 36 is for transferring the toner image formed on the photosensitive drum 31 to the sheet S, and abuts on the photosensitive drum 31 to form a nip for transfer. When the sheet S enters the nip, a voltage having a polarity opposite to the charging polarity of the photosensitive drum 31 is applied to the transfer roller 36, and the toner image is transferred to the sheet S.

  The cleaning device 37 is disposed above the photosensitive drum 31 in the example of FIG. The cleaning device 37 removes and collects residual toner, dust, and the like on the peripheral surface of the photosensitive drum 31. In this embodiment, a blade formed to extend in the axial direction of the photosensitive drum 31 is brought into contact with the photosensitive drum 31. However, as long as the photosensitive drum 31 can be cleaned, a roller may be used, or a blade and a roller may be used in combination.

  The fixing unit 40 presses and heats the toner image transferred to the sheet S to melt the toner and fix the toner image on the sheet S. The fixing unit 40 includes a heating roller 41, a pressure roller 42, and the like. The heating roller 41 is provided with a heater 82 (FIG. 3). The heater 82 warms the heating roller 41 to a temperature at which the toner can be melted. The pressure roller 42 is formed using an elastic material such as silicon rubber.

  The heating roller 41 and the pressure roller 42 are pressed to form a nip. The sheet S on which the toner image is transferred enters the nip, thereby fixing the toner to the sheet S. The sheet S that has been fixed is conveyed to the discharge unit 43. The paper is discharged by a discharge roller pair 45 toward a discharge tray 44 provided on the side of the discharge portion 43.

  Next, a schematic configuration of the image reading apparatus 2 will be described.

  As shown in FIG. 2, the image reading apparatus 2 in the present embodiment has a box-shaped housing 50 provided on the upper portion of the main body 4. A document passage surface 51, a document transport guide 53, and a document placement surface 52 are arranged on the upper surface of the image reading apparatus 2 from the left side of FIG.

  The document passage surface 51 is a surface through which a document conveyed by the document conveying device 3 passes while contacting. A reading unit 60, which will be described later, is placed under the document passage surface 51, and the document is read by passing the document. On the other hand, when the document conveying device 3 cannot be used, for example, when reading a book or a newspaper, the document placing surface 52 is placed with the document conveying device 3 lifted and the document to be read facing downward. It is a surface to do.

  The reading of the original on the original placing surface 52 is performed by placing the reading unit 60 below the original placing surface 52 and moving it horizontally from the home position to the right in FIG. 2 by the wire 54 and the take-up drum 55. . The document passage surface 51 and the document placement surface 52 are formed of a rectangular plate-like member having a certain thickness made of a translucent material such as glass.

  As shown in FIG. 2, a document conveyance guide 53 is provided so as to be sandwiched between the document passage surface 51 and the document placement surface 52. The document conveyance guide 53 has a curved surface for guiding the document that has passed through the document passage surface 51 to the document discharge roller pair 14 and guiding the document obliquely upward.

  As shown in FIG. 2, a wire 54, a winding drum 55, a lens 56, an image sensor 57, a reading unit 60, and the like are disposed in the housing 50 of the image reading device 2.

  The reading unit 60 includes a first reading unit 601 and a second reading unit 602. Note that the first reading unit 601 is disposed above and the second reading unit 602 is disposed below. A wire 54 is attached to the first and second reading units 601 and 602, the other end of the wire 54 is connected to the winding drum 55, and the winding drum 55 rotates, so that the reading unit 60 is moved in the horizontal direction. Move to. Note that the number of the wires 54 and the winding drum 55 is not limited to the number shown in the figure, and may be a combination of a plurality of wires.

  For example, two wires 54 are wound around one winding drum 55, and the two wires 54 extend in different directions in the longitudinal direction (in FIG. Only the book is shown) It is wound around a winding drum 55. Two wires (a total of four wires) per side are appropriately bridged by a plurality of pulleys (not shown), and the two wires 54 are connected to the first reading unit 601 and the second reading unit 602. When the forward / reverse rotation of the motor is controlled, the reading unit 60 can be moved freely along the scanning direction.

  A specific reading operation will be described. Light emitted from the light source of the reading unit 60 strikes the document 19 on the document placement surface 52, and the reflected light is reflected by the first mirror of the first reading unit 601. Is reflected toward the upstream side in the scanning direction. A second mirror of the second reading unit 602 is disposed on the optical path, and the second mirror reflects light downward. Further, a third mirror is disposed on the optical path, and the third mirror reflects light toward the downstream side in the scanning direction.

  Thereafter, the reflected light is condensed on the lens 56, imaged by an image sensor 57 constituted by, for example, a CCD line sensor, etc., and converted into an electrical signal corresponding to the image density. Then, these scanning operations are successively performed from the home position where the reading unit 60 is first positioned to the document edge, so that the entire document image is read and the document image is converted into data.

<2. Device functional configuration>
Next, the functional configuration of each device included in the image forming apparatus 1 according to an embodiment of the present disclosure will be described with reference to the block diagram of FIG.

  As shown in the block diagram of FIG. 3, the image forming apparatus 1 of the present embodiment includes at least a sheet supply unit 20, an image forming unit 30, a fixing unit 40, a flash memory 71, an EEPROM 72, a power supply unit 80, and Zero cross signal generation circuit 81 (= zero cross signal generation unit), heater 82, control unit 90, reading unit 60 provided in the image reading apparatus 2, control unit 100 provided in the document conveying device 3, flash memory 111, EEPROM 112, document The conveyance unit 120 and the power supply unit 130 are included. In addition, about the apparatus which has already demonstrated in FIG. 2, description is abbreviate | omitted here.

  The flash memory 71 is a recording device that temporarily records various data held by the main body unit 4. The flash memory 71 has a role of recording, for example, a control program used by the control unit 90 to control each device, processing data generated by various controls, setting data, user data, and the like.

  The EEPROM 72 is a kind of semiconductor memory and is a ROM (read-only memory) that can electrically erase data. Different from the flash memory 71, writing / erasing can be performed in units of 1 byte.

  The power supply unit 80 supplies a driving voltage to each device included in the main body unit 4. The power supply unit 80 receives power from, for example, an external commercial power supply (not shown) or an internal battery (not shown), and performs rectification from AC to DC, voltage adjustment, and the like. Furthermore, the power supply unit 80 supplies electric power by applying an AC voltage to a heater 82 described later. Accordingly, the fixing unit 40 is heated by energizing the heater 82.

  The zero-cross signal generation circuit 81 generates a zero-cross signal from a waveform (hereinafter referred to as “full-wave rectified wave”) obtained by rectifying a sine wave of an AC voltage of the power supply unit 80 by a full-wave rectifier circuit (not shown), for example. The zero-cross signal generation circuit 81 switches from the High signal to the Low signal or from the Low signal to the High signal at the time when the full-wave rectified wave falls below and exceeds the predetermined threshold voltage. Note that the zero cross signal is generally used in processing for timing the heater 82 to be turned on.

  In the present embodiment, as shown in FIG. 5, a zero cross signal that switches from a Low signal to a High signal when the full-wave rectified wave 201 and the full-wave rectified wave 202 are below the threshold voltage D is used. In addition, the zero cross signal in a figure has shown the zero cross signal corresponding to the full-wave rectified wave 201 when an alternating voltage is normal. When the AC voltage decreases, for example, the full-wave rectified wave 202 is obtained, and the period during which the zero-cross signal is a high signal becomes longer.

  The heater 82 generates heat when an AC voltage is applied from the power supply unit 80, and heats a member included in the fixing unit 40, for example, the heating roller 41.

  The control unit 90 performs printing processing, sheet conveyance processing, and the like by controlling the operation of each device constituting the main body unit 4. The control unit 90 is composed of a plurality of microprocessors, for example. The control unit 90 is a central part that controls each device, for example, the image forming apparatus 1, calculates data, and performs image processing. Details of the functional units (time measuring unit 91 to state control unit 95 in FIG. 1) realized by the control unit 90 executing a predetermined program will be described later.

  The control unit 100, the flash memory 111, the EEPROM 112, and the power supply unit 130 included in the document conveying device 3 have substantially the same configuration as the control unit 90, the flash memory 71, the EEPROM 72, and the power supply unit 80 described above. Description is omitted. The power supply unit 130 may be connected to the power supply unit 80 and receive power supply.

  The document transport unit 120 places and transports a document and moves the document to the reading unit of the reading unit 60. In the example of FIG. 2, the document placing tray 10 to the document discharge tray 15 correspond to this.

  Next, functional units included in the control unit 90 will be described with reference to FIG. As shown in FIG. 1, the control unit 90 includes a time measurement unit 91, an operation mode change unit 92 (= control change unit), a failure detection unit 93, a printing speed control unit 94, and a state control unit 95.

  The time measurement unit 91 monitors the sine wave of the AC voltage of the power supply unit 80 or the zero cross signal generated by the zero cross signal generation circuit 81. Then, the time interval from the time when the absolute value of the AC voltage is less than the predetermined value to the time when the absolute value is exceeded is acquired using a rectangular wave of the zero cross signal shown in FIG.

  The operation mode changing unit 92 detects the AC voltage drop of the power supply unit 80 using the above-described time interval acquired by the time measuring unit 91. Specifically, for example, as shown in FIG. 5, two points when the full-wave rectified wave falls below and above a predetermined threshold voltage D, that is, a time interval T between both edges of the zero-cross signal, are predetermined. The time interval Tc, which is a reference value, is compared.

  When the interval T is longer than Tc, the operation mode changing unit 92 considers that an AC voltage drop has occurred. This is based on the fact that the time interval T from the time when the voltage falls below the threshold voltage D in FIG. 5 to the time when it rises again becomes larger than the reference value Tc because the AC voltage decreases and the curve of the full-wave rectified wave becomes gentle. is doing.

  Although the value of Tc can be changed as appropriate, for example, when the AC voltage at normal time is 100 V, the time interval when the AC voltage drops to 85 V is set as the time interval Tc. This is because the operation of the image forming apparatus 1 cannot be guaranteed when the AC voltage is less than 80V, and therefore the time interval Tc, which is a reference value, is set from 85V, which is a value with a little margin. When the reduction of the AC voltage is detected as described above, the operation mode change unit 92 instructs the failure detection unit 93 to the state control unit 95 described below to change the operation mode (= control method).

  The failure detection unit 93 monitors the temperature of the heating roller 41 included in the fixing unit 40 and the heater temperature of the heater 82 for heating the heating roller 41. For example, measurement is performed using a heat sensor (not shown) included in the fixing unit 40, and failure detection of the heater is performed based on the measured heater temperature.

  The failure detection unit 93 holds a failure detection condition that the heater temperature “should reach the predetermined temperature within a predetermined time and is regarded as a failure if not reached”. When receiving an instruction to change the operation mode from the operation mode change unit 92, the failure detection unit 93 extends the length of the predetermined time or reduces the value of the predetermined temperature in the above-described failure detection condition.

  This is because when the AC voltage is low, the rate of temperature increase is reduced, so that a malfunction detection may occur. Specifically, for example, the condition of “successfully increasing 50 degrees in 10 seconds” is set to “successfully increasing 30 degrees in 10 seconds” or “successfully increasing 50 degrees in 15 seconds”. To reduce the failure detection conditions.

  The printing speed control unit 94 controls the printing speed of the image forming unit 30. The printing speed control unit 94 performs control to reduce the printing speed when the temperature drops during printing, that is, when the heating by the heater 82 cannot catch up. However, when the AC voltage is reduced, there is a problem that if the speed reduction is performed at a normal timing, the heater temperature is too low and fixing cannot be performed properly.

  Accordingly, when receiving an instruction to change the operation mode from the operation mode changing unit 92, the printing speed control unit 94 shifts to a printing speed reduction process at a timing earlier than usual, and reduces the conveyance speed of the sheet S. It should be noted that how much the timing is advanced can be appropriately changed without departing from the gist of the present invention.

  The state control unit 95 performs a transition process for shifting the image forming unit 30 to a printable state when the main power is turned on or the power saving state is canceled. The state control unit 95 sets the printable state before the image forming unit 30 reaches the printable temperature, thereby shortening the printing time of the first first page. This utilizes the fact that there is a time difference of several seconds from when the sheet supply unit 20 starts feeding to when it reaches the image forming unit 30. Using this time difference, the state shifts to a printable state several seconds before the state where printing is actually possible, and the conveyance of the sheet S is started.

  Therefore, if the sheet S is not actually ready for printing between the image forming unit 30 after the conveyance of the sheet S is started, printing fails. For this reason, in the above control, the rate of temperature rise of the heater 82 in the time difference of several seconds and the length of the time difference are important. For example, when the AC voltage is low, the temperature increase rate decreases, and there is a possibility that the temperature assumed when the sheet S arrives at the image forming unit 30 cannot be reached.

  Therefore, upon receiving an operation mode change instruction from the operation mode change unit 92, the state control unit 95 corrects the temperature increase rate related to the above processing and the timing at which the conveyance of the sheet S is started. For example, the timing for starting sheet conveyance (= the timing for shifting to a printable state) is delayed, or the estimated temperature increase rate is reduced. This avoids insufficient fixability in the image forming unit 30 immediately after the transition to the printable state.

<3. Power monitoring operation>
Here, the power supply monitoring operation of the image forming apparatus 1 according to the embodiment of the present disclosure will be described with reference to the flowchart of FIG.

  The processing flow illustrated in FIG. 4 is started when the power supply of the image forming apparatus 1 is activated and the state of the power supply unit 80 can be monitored by the zero cross signal generation circuit 81 and the time measurement unit 91. The time measurement unit 91 that has entered the power monitoring enable state acquires a zero cross signal from the zero cross signal generation circuit 81 in step S110.

  Next, the time measurement part 91 detects the time interval T shown in FIG. 5 in step S120. Next, in step S130, the operation mode changing unit 92 branches the process depending on whether or not the detected time interval T exceeds a predetermined time interval Tc. When exceeding, in step S140, the operation mode changing unit 92 instructs the failure detecting unit 93 to change the operation mode, that is, to change the detection condition in detecting the heater failure.

  Further, in step S150, the operation mode changing unit 92 instructs the printing speed control unit 94 to change the operation mode, that is, to change the speed down timing in the printing speed speed down control. Further, in step S160, the operation mode change unit 92 changes the operation mode with respect to the state control unit 95, that is, the estimated temperature increase rate when shifting to the printable state, or arrives at the image forming unit 30 from the start of conveyance of the sheet S. After instructing the correction of the estimated time difference until completion, etc., the process proceeds to step S110 again.

  Returning to step S130 and explaining it, if the time interval T does not exceed the time interval Tc in step S130, the operation mode changing unit 92 determines that the failure detection unit 93 to the state control unit 95 are in the normal mode, that is, the operation mode in step S170. It is determined whether or not the apparatus is operating in a state where it has not received a mode change instruction from the changing unit 92.

  If it is the normal mode, the process proceeds again to step S110. If it is not the normal mode, the operation mode changing unit 92 gives an instruction for returning to the normal mode to each unit in step S180, and then proceeds to step S110 again. Note that this process can be terminated at an arbitrary timing, for example, when the power of the image forming apparatus 1 is turned off.

  According to the present embodiment described above, it is possible to detect a decrease in the AC voltage of the power supply unit 80 caused by, for example, a octopus wiring or the like only by software processing using an existing zero cross signal. Further, by changing the operation of each functional unit after the detection, it is possible to avoid a decrease in fixability in the image forming unit 30 and the fixing unit 40.

[Other embodiments]
The present invention has been described above with reference to preferred embodiments and examples. However, the present invention is not necessarily limited to the above-described embodiments, and various modifications can be made within the scope of the technical idea. be able to.

Therefore, the present invention can also be applied to the following embodiments.
(A) In the present embodiment, the image forming apparatus 1 is described as an example of the object of the present invention. However, if the present invention is implemented in an image forming apparatus other than the above, the same effect is achieved. For example, the present invention can be implemented in an image forming apparatus such as a copying machine, a multi-function machine, and a FAX apparatus.

  (B) In this embodiment, various functional units related to the voltage drop detection process of the present invention, for example, the time measuring unit 91 to the state control unit 95 are realized by executing a program on an arithmetic processing unit such as a microprocessor. However, various processing units may be realized by a plurality of circuits.

  (C) In this embodiment, the operation mode changing unit 92 uses the zero-cross signal to detect the AC voltage drop and switch the operation mode. However, the zero-cross signal is not used, and the AC voltage sine wave is used. The form which performs a fall detection may be sufficient. For example, on the positive side of the sine wave, first, the time when the value becomes the predetermined value K is measured. Next, a time point at which the negative value becomes a predetermined value −K (a value obtained by inverting K) is measured. Then, the time interval Tk between these two points is measured, and when this time interval exceeds a predetermined time interval Ta, it is considered that the AC voltage has dropped, and the control mode related to the heater 82 is changed. The value of the time interval Ta can be changed as appropriate.

  (D) In this embodiment, the AC voltage drop detection using the zero-cross signal and the operation mode switching are performed in the image forming apparatus 1, but the document conveying apparatus 3 and an optional apparatus (not shown) (for example, a finisher) Or a mailbox). When implemented in the document conveying device 3, the control unit 100 has a function as a control change unit, and performs power supply monitoring with a zero cross signal obtained from the power supply unit 130. When a decrease in AC voltage is detected, the operation of the document conveyance unit 120 or the like is changed. As a result, when the document conveying device 3 is movable independently of the image forming apparatus 1, it operates in an operation mode corresponding to the AC voltage of the power supply unit 130 without being affected by the voltage drop of the image forming apparatus 1. be able to.

  (E) In this embodiment, the zero cross signal is constantly monitored and the operation of each part is controlled, but the AC voltage using the zero cross signal is confirmed only once when the power is turned on, and the operation mode of each part is determined. After the determination, the operation mode may not be changed until the power is stopped. According to this form, in the operation form in which the change of the AC voltage is unlikely to occur, the resources of the control unit 90 can be effectively utilized by reducing the number of processes.

It is a block diagram which shows the function structure of the function part with which the control part of this invention is provided. 1 is a cross-sectional view of a schematic configuration of an image forming apparatus of the present invention viewed from the front. 2 is a block diagram illustrating a functional configuration of the image forming apparatus of the present invention. FIG. It is a flowchart which shows the processing flow of the power supply monitoring process of this invention. It is a graph which shows the full wave rectification wave and zero cross signal which are used for the power supply monitoring process of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image reading apparatus 2 Image forming apparatus 3 Document conveying apparatus 30 Image forming part (printing part)
40 Fixing Unit 80 Power Supply Unit 81 Zero Cross Signal Generation Circuit (Zero Cross Signal Generation Unit)
82 heater 91 time measuring unit 92 operation mode changing unit (control changing unit)
93 Failure detection unit 94 Printing speed control unit 95 Status control unit

Claims (5)

A power supply unit, a printing unit, a fixing unit that fixes a sheet printed by the printing unit, a heater that heats a member included in the fixing unit by generating heat when energized,
In an image forming apparatus comprising:
A time measurement unit that measures an AC voltage output from the power supply unit and applied to the heater, and measures a time interval from a time point when the absolute value of the AC voltage is lower than a predetermined value to a time point higher When,
When the time interval measured by the time measuring unit exceeds a predetermined time, it is determined that the voltage value of the AC voltage has decreased, and a control method related to energization processing or error processing of the heater An image forming apparatus comprising: a control changing unit that changes A zero-cross signal generating unit for generating a zero-cross signal in which the signal level is switched at a time point when the absolute value of the AC voltage of the power supply unit falls below and exceeds a predetermined value;
The image forming apparatus according to claim 1, wherein the time measurement unit acquires the time interval using the zero-cross signal. A temperature detector for detecting the temperature of the fixing unit; and measuring the rate of temperature rise of the fixing unit using the temperature detector and comparing the measured rate of temperature rise with a predetermined reference value. A failure detection unit for detecting the occurrence of a failure in the heater,
The control change unit instructs the failure detection unit to reduce the value of the reference value when the time interval exceeds a predetermined time. Image forming apparatus. A printing speed control unit for controlling the printing speed of the printing unit;
When the time interval exceeds a predetermined time, the control change unit advances the processing start timing of the printing speed reduction process performed by the printing speed control unit when the temperature of the printing unit decreases during printing. The image forming apparatus according to claim 1, wherein an instruction is given to the printing speed control unit. A state control unit that shifts the printing unit to a printable state when the main power is turned on or when the power-saving state in which the temperature of the fixing unit is lowered by controlling energization to the heater is released;
When the time change exceeds a predetermined time, the control change unit reduces an estimated temperature increase rate from when the state control unit starts to shift the printing unit to a printable state until the transfer is completed. The image forming apparatus according to claim 1, wherein the state control unit is instructed to increase an estimated completion time from the start of transition to the completion of transition.

Images