JP2007058082A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimize specifications of a stepping motor which drives a fixing unit by reducing the load torque of the stepping motor. <P>SOLUTION: An image forming apparatus has a conveyance system comprising a drum 101, a DC brushless motor which drives a paper feed system, and the stepping motor driving a fixation and paper discharge system. Driving switching is carried out during both-surface printing and a plurality of rotations of an electrophotographic printer configured to supply part of driving from the DC brushless motor to a fixation driving side as well to reduce the load torque of the stepping motor during a start. Consequently, the electric energy supplied to a fixing heater is reduced and noise is reducible. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention describes an image forming apparatus that has a function of conveying paper on both sides by rotating a paper discharge roller forward and backward, and also has a configuration in which a fixing roller is also driven by a reversing motor.

  Conventionally, the double-sided conveyance of this type of electrophotographic printer has a configuration as disclosed in, for example, Japanese Patent Application Laid-Open No. H11-228707.

  Hereinafter, conventional double-sided conveyance will be described with reference to FIGS.

  Conventionally, this type of electrophotographic printer has a configuration as shown in FIG.

  Here, 1 is a photosensitive drum for forming an electrostatic latent image, 2 is a charging roller for uniformly charging the photosensitive drum 1, and 5 is an optical for scanning the laser beam on the photosensitive drum 1. Unit 6, a laser beam emitted from the optical unit 5, 3 a developing unit for developing the electrostatic latent image formed on the photosensitive drum 1 by the laser beam with toner, and 4 a photosensitive drum 1 Transfer roller charger for transferring the toner image on a predetermined sheet, 7 is a fixing unit for melting the toner on the sheet and fixing it on the sheet, 8 is a standard cassette for loading sheets to be printed, 9 Is a standard cassette feed roller that picks up paper from a standard cassette, 10 is a manual feed tray, 11 is a manual feed roller, 12 is a first discharge roller for discharging paper out of the machine, and 12 'is connected to a forward / reverse motor Only forward rotation during single-sided continuous printing A reversing roller for reversing and feeding the paper to a double-sided conveyance path, which will be described later, 13 is a registration roller for registering the leading edge for printing the conveyed paper, and 14 is a TOP sensor for detecting the leading edge of the paper. , 15 is a paper discharge sensor for confirming whether or not the paper has normally been discharged from the fixing device, 16 is a sensor for detecting the presence or absence of paper in the standard cassette, 17 is a sensor for detecting the presence or absence of manual paper, and 18, 19 Is a double-sided conveyance roller that conveys the paper for duplex printing sent from the reversing roller 12 'at the time of double-sided reversal, and 20 temporarily stops the sheet conveyed at the time of double-sided printing and requests printing on the second side of both sides. It is a double-sided sensor that detects the leading edge of the sheet in order to confirm the stop position for restarting the sheet conveyance after receiving.

  Conventionally, in such a configuration, each roller and the drive motor are connected as shown in FIG.

  The paper feed, photosensitive drum, double-sided transport, etc. are all connected to a DC brushless motor that rotates in a fixed direction, and the paper feed roller is connected via a solenoid to turn it on and off.

  Further, only the reversing roller for reversing is connected to a stepping motor capable of forward and reverse rotation.

The double-sided conveyance roller needs to be temporarily stopped in order to wait for a printing request on the second side of both sides, and is therefore connected to a solenoid for turning it on and off.
Further, the fixing device is always driven by a stepping motor at the time of double-sided printing or before multiple rotations.
Japanese Patent Registration No. 3445175

  In the above conventional example, the fixing device is always driven by a stepping motor during double-sided printing or before multiple rotations, so the fixing device rotates at the same speed as during normal printing even when the paper is not fixed. Therefore, extra power is supplied to maintain the temperature of the pressure roller. Further, since the stepping motor is driven, there has been a problem that the excitation sound of the motor, the driving sound, and the driving sound of the fixing device have to be reduced during double-sided printing.

In order to solve the above-described problems, an electrostatic latent image is formed on the photosensitive drum by a sheet feeding unit that feeds a sheet to be printed from a predetermined sheet position and sends it to a conveyance path, and a laser beam that blinks according to image information. A transfer unit that visualizes the electrostatic latent image with toner and transfers the image onto a predetermined sheet that has been fed, and a toner that is transferred to the sheet by the transfer unit and that fixes the toner onto the sheet. A fixing unit; a discharging unit for discharging the fixed sheet to a predetermined position outside the apparatus; a fixing roller that forms the fixing unit; and a sheet that forms the discharging unit downstream of the fixing roller. A first driving means for driving the roller, a second driving means comprising at least one driving system for driving other than the conveying system from the fixing roller to the paper discharge roller, and the paper discharge roller in the paper discharge direction And on the other side And a double-sided conveying means connected to the second driving means for receiving paper and feeding it again to the photosensitive drum when rotated, and the first driving means has three states: normal rotation, stop and reverse The rotation direction switching means for rotating the fixing roller to the side for discharging the paper regardless of whether it is forward rotation or reverse rotation, and the second driving means have a predetermined reduction ratio. A gear train, a fixing roller that is driven by the first driving unit via a one-way function, and an auxiliary driving unit that drives the paper discharge roller at a rotational speed corresponding to a reduction ratio,
The first driving means and the second driving means are both rotated at a rated rotational speed to stop the driving of the first driving means and the first transport mode for performing processing from paper feeding to fixing / paper discharging. The second driving means and its auxiliary driving means are used to drive from the paper feed to the photosensitive drum at a rated rotational speed, and from the fixing to the paper discharge at a low speed rotational speed by the auxiliary driving means. An image forming apparatus comprising: a transport mode switching unit configured to switch between the first transport mode and the second transport mode based on a predetermined condition.

  The conveyance mode switching means is configured to remove the nip of the fixing roller driven by the first driving means and the nip of the reverse roller for conveying the paper to the double-sided conveyance means during double-sided printing after the trailing edge of the paper to be printed is removed. The image forming apparatus according to claim 1, wherein the image forming apparatus is switched to a second conveyance mode.

  The transfer mode switching means is a residual paper generated by JAM or the like in the machine during a rotation provided at a predetermined timing after turning on the power or during a rotation provided at a predetermined timing after opening / closing the process cartridge door. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is switched to the second conveyance mode when there is no image.

As described above, according to the present invention, in order to solve the above-described problem, the paper feeding unit that feeds the paper to be printed from a predetermined paper position and sends it to the transport path, and the laser beam that blinks according to the image information Then, after forming an electrostatic latent image on the photosensitive drum, the electrostatic latent image is visualized with toner, and transferred to a predetermined paper that has been fed. A fixing unit for fixing the transferred toner onto a sheet, a discharging unit for discharging the fixed sheet to a predetermined position outside the apparatus, a fixing roller constituting the fixing unit, and a fixing roller A second drive comprising a first drive means for driving a paper discharge roller constituting the discharge means downstream and at least one drive system for driving other than a conveying system from the fixing roller to the paper discharge roller. Means and said A double-sided conveying means connected to the second driving means for receiving paper and feeding it again to the photosensitive drum when the paper discharge roller rotates in the direction opposite to the paper discharge direction, the first driving means A rotation direction switching means that is operable in three states of normal rotation, stop, and reversal, and that always rotates the fixing roller to the paper discharge side regardless of normal rotation or reverse rotation; The second drive means is a gear train having a predetermined reduction ratio, a fixing roller driven by the first drive means via a one-way function, and an auxiliary drive means for driving the paper discharge roller at a rotational speed corresponding to the reduction ratio. And
The first driving means and the second driving means are both rotated at a rated rotational speed to stop the driving of the first driving means and the first transport mode for performing processing from paper feeding to fixing / paper discharging. The second driving means and its auxiliary driving means are used to drive from the paper feed to the photosensitive drum at a rated rotational speed, and from the fixing to the paper discharge at a low speed rotational speed by the auxiliary driving means. An image forming apparatus comprising: a transport mode switching unit configured to switch between the first transport mode and the second transport mode based on a predetermined condition.

  The conveyance mode switching means is configured to remove the nip of the fixing roller driven by the first driving means and the nip of the reverse roller for conveying the paper to the double-sided conveyance means during double-sided printing after the trailing edge of the paper to be printed is removed. The image forming apparatus according to claim 1, wherein the image forming apparatus is switched to a second conveyance mode.

  The transfer mode switching means is a residual paper generated by JAM or the like in the machine during a rotation provided at a predetermined timing after turning on the power or during a rotation provided at a predetermined timing after opening / closing the process cartridge door. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is switched to the second conveyance mode when there is no image.

  By providing the above-mentioned image forming apparatus, it is possible to switch to the second conveyance mode at the time of double-sided printing or pre-multiple rotation, and reduce the rotation speed of the fixing unit, so that excess power is used to maintain the pressure roller temperature. It is possible to eliminate the input. Since the stepping motor is stopped, it is possible to reduce excitation sound, driving sound, and fixing device driving sound. In addition, the temperature rise of the stepping motor and motor driver IC can be reduced.

Example 1
FIG. 1 schematically shows a cross section of a printer mechanism section in a first embodiment of the present invention.

  Here, 101 is a photosensitive drum for forming an electrostatic latent image, 102 is a charging roller for uniformly charging the photosensitive drum 1, and 105 is an optical for scanning the laser beam on the photosensitive drum 1. The unit 106 is a laser beam emitted from the optical unit 105, 103 is a developing unit for developing the electrostatic latent image formed on the photosensitive drum 101 by the laser beam with toner, and 104 is the photosensitive drum 101. Transfer roller charger for transferring the toner image on a predetermined sheet, 107 a fixing unit for melting the toner on the sheet and fixing it on the sheet, 108 a standard cassette for loading sheets to be printed, 109 Is the standard cassette feed roller that picks up paper from the standard cassette, 110 is the manual feed tray, 111 is the manual feed roller, 112 is the first discharge roller for discharging the paper out of the machine, and 112 'is discharged during single-sided continuous printing In the direction The paper can be rotated to discharge the paper, and the paper can be rotated to the side of feeding the paper to the double-sided conveyance unit after the paper is discharged to a predetermined position in order to send the paper to the double-sided conveyance unit during double-sided printing. It is a two-discharge roller and also has a reversing function. 113 is a registration roller for registering the leading edge for printing the conveyed paper, 114 is a TOP sensor for detecting the leading edge of the paper and measuring the length of the paper being conveyed, and 115 is for normally discharging the fixing device. A paper discharge sensor for confirming whether or not the paper is finished, 116 is a sensor for detecting the presence or absence of paper in the standard cassette, 117 is a sensor for detecting the presence or absence of manual paper, and 118 is for canceling the double feed of the fed paper. , 119 is a conveying roller for feeding the fed and separated printing paper to the registration unit, 120 is a first duplex conveying roller for feeding the sheet reversed by the reversing roller 112 ′ to the duplex conveying unit, 121 Is a second double-sided conveyance roller for feeding from the double-sided conveyance unit to the registration unit, and 122 is a position for waiting for a print request at a predetermined position in front of the first double-sided conveyance roller before the reverse roller. This is a double-sided reversing sensor for detecting the position. FIG. 2 is a block diagram showing a printer control unit according to the present invention. 301 communicates with the host computer, receives the image data, develops the received image data into information that can be printed by the printer, and exchanges signals and serial communication with the printer engine control unit described later. 302 is a printer controller, 302 is an exchange of signals with the printer controller, an engine control unit for controlling each unit of the printer engine via serial communication, and 303 is a command for serial communication performed between the controller and the engine control unit / With bidirectional function in status line. 304 is a serial synchronization clock for transferring the command status, 305 is a vertical synchronization signal indicating to the controller that the paper has been conveyed and the sensor has reached the TOP sensor / TOP signal, 306 is horizontal synchronization for image output A signal / BD signal, 307 is an image signal. 308 is a paper conveyance control unit that feeds and conveys paper to be printed and performs paper conveyance until printing after printing based on instructions from the engine control unit. 309 is a sensor of each of the TOP sensor, paper ejection sensor, and paper presence sensor. Paper presence / absence sensor input unit that transmits the status to the engine control unit, 310 is a jam detection unit that detects paper jam based on instructions from the engine control unit, and 311 is engine control for scanner motor drive and laser ON / OFF control 312 is an optical system control unit that is executed based on an instruction of the engine unit, 312 is a high voltage system control unit that executes a high voltage output necessary for an electrophotographic process such as charging, development, transfer, etc. A fixing temperature control unit 314 performs temperature control of the fixing device based on an instruction and detects abnormality of the fixing device, and 314 is a failure detection unit that detects a failure of a functional unit in the printer.

  The sheet conveyance control unit controls two types of motors as shown in FIG. First, the motor is composed of two motors: a DC brushless motor 401 that drives a paper feed system, a registration unit, a drum system, and a double-sided transport system, and a stepping motor 402 that drives a fixing system and a paper discharge / reverse system. The DC brushless motor is connected to a drive train to a stepping motor via a predetermined reduction gear 404 and a one-way roller 405. This one-way roller 405 rotates after releasing the drive from the DC brushless motor during the period when the drive by the stepping motor is rotating at high speed, and only when the drive from the DC brushless motor is faster This is a roller having a function of generating torque for the drive train on the stepping motor side.

  The feed rollers 109 and 111 are connected to a DC brushless motor via solenoids because they must be stopped in a predetermined time. The other rollers connected to the DC brushless motor are always rotating in a constant rotation direction when the DC brushless motor is driven. On the other hand, since the fixing roller system connected to the stepping motor rotates in a fixed direction even when both sides are reversed, the pendulum gear connected to the pendulum gear 403 is connected to the gear train connected with the rotation direction of the stepping motor. The fixing system roller connected to the element is always rotated in a fixed direction, that is, in the direction of discharging the paper regardless of the rotation direction of the stepping motor. Further, since the paper discharge roller 112 'is connected to the stepping motor via a normal gear train, it is configured to rotate forward and backward as the stepping motor rotates forward and backward. FIG. 4 is a diagram illustrating the configuration of the pendulum gear in detail. The paper discharge roller is connected to the reversing motor through a three-stage gear. On the other hand, the pressure roller is connected through a pendulum gear on the way, and is configured to be connected to gear A or gear B based on the rotation direction of the reversing motor. Further, a gear train from the main motor is connected to the drive system of the reversing motor through a One Way mechanism.

  With reference to the flowchart in FIG. 5, the control for switching to the second conveyance mode in the double-sided printing in the control unit configuration as described above will be specifically described.

  First, when a double-sided print request is received from a state waiting for a print instruction from the printer controller, various drive systems, that is, a DC brushless motor and a stepping motor are sequentially started. After the motor is started, temperature control of the fixing heater is started and electrophotography around the drum Various high voltages of the process, that is, primary charging, developing bias, and transfer bias are sequentially started. Thereafter, when the temperature of the fixing heater reaches a predetermined temperature, a sheet for printing is fed from the sheet feeding port. After the paper feeding is started, the presence / absence state of the TOP sensor for timing the writing position is monitored, and when the leading edge of the paper is detected, a vertical synchronization signal is output to the printer controller and image writing is permitted. After that, the timing at which the trailing edge of the paper exits the paper ejection sensor is monitored, and a timer for waiting for a predetermined time is started from the detection timing of the trailing edge of the paper ejection sensor. After that, it is a time corresponding to the time required to pass through the nip of the reversing roller. Then, the driving of the stepping motor is stopped when the trailing edge of the sheet passes through the reverse roller nip. Then, since the fixing device and the paper discharge unit are driven only by the auxiliary drive from the DC brushless motor, the fixing device and the paper discharge unit start rotating at a rotational speed lower than the rated rotational speed. At this rotational speed, even if the target temperature of the fixing heater is the same, the energized power is reduced. Driving noise is reduced because the fixing device is driven at a low speed. Since the stepping motor is stopped, there is no drive sound or excitation sound. In addition, the temperature rise of the stepping motor and motor driver IC can be reduced.

(Example 2)
In the second embodiment, control for switching to the second transport mode at the time of multiple front rotation will be described based on the flowchart of FIG.

  Possibility to automatically discharge the residual paper generated by JAM etc. in the machine during the rotation provided at a predetermined timing after turning on the power or during the rotation provided at the predetermined timing after opening / closing the process cartridge door If there is no DC brushless motor, only the DC brushless motor is driven, and the fixing device and the paper discharge unit are driven only by the auxiliary drive from the DC brushless motor, and therefore start rotating at a rotational speed lower than the rated rotational speed. As a result, the driving sound of the fixing device, the driving sound of the stepping motor, and the excitation sound as shown in the first embodiment are not generated, and a silent effect can be obtained.

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Claims (3)

An electrostatic latent image is formed on the photosensitive drum by a paper feeding unit that feeds paper to be printed from a predetermined paper position and sends it to the conveyance path, and a laser beam that flashes in accordance with image information. The electrostatic latent image is visualized with toner and transferred to a predetermined paper that has been fed, and the fixing means for fixing the toner transferred onto the paper by the transfer means to the paper. Discharge means for discharging the discharged paper to a predetermined position outside the apparatus, a fixing roller that constitutes the fixing means, and a first discharge roller that drives the paper discharge roller that constitutes the discharge means downstream of the fixing roller. A second driving unit comprising a driving unit, at least one driving system for driving other than the conveying system from the fixing roller to the paper discharge roller, and when the paper discharge roller rotates in a direction opposite to the paper discharge direction. Receive the paper A double-sided conveying means connected to the second driving means for feeding again to the photosensitive drum, and the first driving means is operable in three states of normal rotation, stop and reverse, The rotation direction switching means for always rotating the fixing roller to the side for discharging the paper regardless of the forward rotation or the reverse rotation, the second driving means has a gear train of a predetermined reduction ratio, and a one-way function. A fixing roller that is driven by the first driving unit, and an auxiliary driving unit that drives the paper discharge roller at a rotational speed corresponding to the reduction ratio,
The first driving means and the second driving means are both rotated at a rated rotational speed to stop the driving of the first driving means and the first conveying mode for performing processing from paper feeding to fixing / paper discharging. The second driving means and its auxiliary driving means are used to drive from the paper feed to the photosensitive drum at a rated rotational speed, and from the fixing to the paper discharge at a low speed rotational speed by the auxiliary driving means. An image forming apparatus comprising: a transport mode switching unit configured to switch between the first transport mode and the second transport mode based on a predetermined condition.   The conveyance mode switching means is configured to remove the nip of the fixing roller driven by the first driving means and the nip of the reverse roller for conveying the paper to the double-sided conveyance means during double-sided printing after the trailing edge of the paper to be printed is removed. The image forming apparatus according to claim 1, wherein the image forming apparatus is switched to a second conveyance mode.   The transfer mode switching means is a residual paper generated by JAM or the like in the machine during a rotation provided at a predetermined timing after turning on the power or during a rotation provided at a predetermined timing after opening / closing the process cartridge door. 2. The image forming apparatus according to claim 1, wherein when there is no possibility of automatically discharging the sheet, the mode is switched to the second transport mode.

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