JP4836757B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to a technique for forming an image by fixing a colorant such as toner by heat and pressure.

In recent years, image forming apparatuses are required to shorten the first copy time to reduce the waiting time of the user, and to further reduce the power consumption until the start of the first copy. For this reason, for the purpose of shortening the first copy time, a technique for energizing the induction heater when the apparatus is turned on and heating the fixing means such as a fixing roller is disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-43026 (Patent Document 1). ).
JP 2002-43026 A

  By using the induction heater, the fixing means can be efficiently heated. On the other hand, since the induction heater has high heating efficiency, the fixing unit can be heated quickly. However, in order to prevent overheating of the fixing unit, the heating roller constituting the fixing unit can be rotated simultaneously with the heating. Necessary.

  On the other hand, when the power of the image forming apparatus is turned on, it is necessary to identify the state whether to start up without discharging the transfer paper or to start up in the reserved paper supply state so as to discharge the transfer paper. Conventionally, if this determination is not completed, the drive control sequence such as the rotation process of the fixing unit cannot be determined, and even if the induction heater is mounted, the heating efficiency of the induction heater cannot be fully utilized. There was a problem.

  The present invention has been made in view of the above prior art. In the present invention, the fixing means is configured as a thermomagnetic motor in order to increase the efficiency of heating of the fixing means by the induction heating means. The thermomagnetic motor includes a heating roller formed including a hollow magnetic shunt alloy drum, a permanent magnet, and induction heating means.

  The heating roller starts rotating with a rotational torque caused by a change in magnetic characteristics due to the temperature given by the induction heating means and a magnetic field gradient generated by the permanent magnet, and prevents the heating roller from being locally overheated. For this reason, in the image forming apparatus of the present invention, is a paper supply reservation made when the image forming apparatus is turned on or returned from the energy saving mode (hereinafter referred to as start-up in this specification)? The induction heating means can be activated without determining whether or not. The heating roller repeats heating and cooling processes by the induction heating means in the presence of a permanent magnet, and the induction heating means is energized even before the fixing means starts the control process synchronized with the transfer of the transfer paper. By simply setting up the fixing means at high speed while preventing overheating of the fixing means.

  Therefore, according to the present invention, the fixing unit can be preheated while preventing the overheating of the fixing unit even during the paper feed reservation determination period and the setup time when the image forming apparatus is started up. Power saving can be achieved.

That is, in the present invention,
A heating roller including a magnetic shunt alloy drum;
A pressure roller for applying a nip pressure to the heating roller;
Induction heating means for induction heating the heating roller;
A permanent magnet for generating a rotational torque by the magnetic flux density distribution of the heating roller;
There is provided an image forming apparatus comprising: the induction heating unit; and a control unit that starts heating the heating roller in response to start-up of the image forming apparatus.

  The permanent magnet according to the present invention may be disposed at a position where the heating roller is rotated in the transfer paper conveyance direction of the image forming apparatus with respect to the induction heating unit. The permanent magnet of the present invention can be positioned outside or inside the heating roller at a position including a boundary region between a heating region and a non-heating region of the heating roller by the induction heating means. Cooling means for cooling the non-heated area of the heating roller of the present invention can be provided. In the present invention, drive resistance control means for minimizing the drive resistance of the heating roller can be provided during a period in which the heating roller receives a rotational torque due to the magnetic flux density distribution.

Moreover, according to the present invention,
An image forming method in an image forming apparatus for fixing a developer onto a transfer paper by heat and pressure, comprising a heating magnetic roller comprising an induction heating means, a permanent magnet and a magnetic shunt alloy, the induction heating means There is provided an image forming method in which heating by is started in response to start-up of the image forming apparatus, and the heating roller is rotated by generating a thermomagnetic distribution on the heating roller by the induction heating means.

  In the present invention, the driving resistance of the heating roller can be minimized during the period of heating the heating roller by the induction heating means, and the heating roller can be rotated by the rotational torque generated by the thermomagnetic motor.

  The present invention will be described below with reference to embodiments shown in the drawings, but the present invention is not limited to the embodiments shown in the drawings.

  FIG. 1 shows an embodiment of an image forming apparatus 10. An image forming apparatus 10 shown in FIG. 1 includes a developing unit 12, an image carrier 14 such as a photosensitive drum, and a fixing unit 16. The image carrier 14 is scanned with a light beam such as a semiconductor laser or LED from the direction indicated by the arrow A in an image shape, and the electrostatic charge formed on the image carrier 14 is modulated into an image shape. Carries a latent image. The electrostatic latent image carried on the image carrier 14 is developed by developing means 12 containing a developer such as toner, and the electrostatic latent image is developed. The image carrier 14 further rotates in the direction of the transfer paper 20, and the toner image on the image carrier 14 is transferred to the transfer paper 20 by a transfer bias applied between the image carrier 14 and the transfer means 18.

  The transfer paper 20 carrying the toner image is conveyed to the fixing unit 16 as the image carrier 14 and the transfer unit 18 rotate. The fixing unit 16 applies heat and pressure to the transfer paper 20 and the toner on the transfer paper 20 to heat and fix the toner to the transfer paper 20 to form a solid printed matter. More specifically, the fixing unit 16 nips the transfer paper 20 between the heating roller and the pressure roller 24 disposed via the transfer paper 20 to fix the toner by heat and pressure.

  In the present embodiment, the fixing unit 16 includes a thermomagnetic motor. The thermomagnetic motor includes a heating roller 22 including a magnetic alloy drum, induction heating means, and permanent magnets (none of which are shown), and magnetic flux density generated by heating by the induction heating means. It is configured to be rotationally driven by a gradient. Drive resistance control means 26 is disposed on the heating roller 22 and the pressure roller. The drive control means 26 can include an electromagnetic clutch, a solenoid, a stepping motor, and the like. When the heating roller 22 is driven by the thermomagnetic motor, the drive resistance control unit 26 sets the drive resistance to the lowest state that is about the rotational friction.

  The magnetic shunt alloy has a property of losing magnetism when the temperature is increased, and alloy materials such as Mn—Cu, Mn—Zn, Fe—Ni, and Ni—Cu, such as calmalloy (Ni—Cu). -Fe), climax (Fe-Ni alloy), and thermo palm (Fe-Ni alloy) can be used. By changing the elemental composition ratio of the magnetic shunt alloy, the Curie temperature can be changed, and the magnetic shunt alloy that can be suitably used in this embodiment has a Curie point in the range of approximately 80 ° C. to 200 ° C. Preferably there is. By using a magnetic shunt alloy that has a Curie point in this range, it prevents thermal deterioration of the material constituting the release layer and elastic layer such as silicone rubber to prevent offset, and sufficiently starts preheating and fixing. It becomes possible to provide temperature.

  In another embodiment, the drive resistance control means 26 may be arranged in any one or a different combination with respect to the heating roller 22 and the pressure roller 24. For example, a solenoid, a stepping motor or the like is used as the driving resistance control means 26 for the pressure roller 24, an electromagnetic clutch is used for the heating roller 22, and the driving resistance of the heating roller 22 is set to the electromagnetic clutch release and nip. It can be lowered using both pressure relief. However, the driving resistance control means 26 may be mounted on either the heating roller 22 or the pressure roller 24 as an electromagnetic clutch, solenoid, or stepping motor. The drive resistance control means 26 is controlled so as to minimize the drive resistance during the period in which the heating roller 22 is rotated by the thermomagnetic motor so as not to affect the rotation by the thermomagnetic motor.

  FIG. 2 shows a detailed embodiment of the fixing means 16 described in FIG. In the embodiment shown in FIG. 2, the transfer paper 20 is nipped between the heating roller 22 and the pressure roller 24 and conveyed. In the vicinity of the heating roller 22, an induction heating means 28 and a permanent magnet 34 are arranged. The heating roller 22, the induction heating means 28, and the permanent magnet constitute the thermomagnetic motor of this embodiment.

  The induction heating means 28 is configured by winding an exciting coil 32 around a ferrite core 30 or the like, and generates an eddy current in the magnetic alloy drum of the heating roller 22 for resistance heating. Further, a release layer such as silicone rubber or Teflon (registered trademark) is formed on the surface of the heating roller 22 in order to prevent offset of toner or the like.

  The permanent magnet 34 includes an S pole side and an N pole side, and an S pole 34 a and an N pole 34 b are arranged in the circumferential direction of the heating roller 22. The permanent magnet 34 is disposed in the circumferential direction along the position where the temperature difference of the heating roller is maximized, and efficiently generates rotational torque. As the heating roller 22 rotates, the heating roller 22 is heated at a position that receives the action of the magnetic field of the induction heating unit 28, is cooled by contacting the pressure roller 24 as the heating roller 22 rotates, and is cooled again. The location returns to the position where it receives the action of the magnetic force of the permanent magnet 34.

  In the embodiment shown in FIG. 2, the heating roller 22 is heated by the induction heating unit 28, and the induction heating unit 28 heats the magnetic shunt alloy drum of the heating roller 22 to a temperature equal to or higher than the Curie point. The magnetism of the magnetic shunt alloy is lost. On the other hand, in the non-heated area where the heating roller 22 is not heated, the magnetic shunt alloy drum of the heating roller 22 is cooled to recover its magnetism.

  For this reason, the side near the induction heater 28 of the heating roller 22 receives induction heating, becomes a heating region, and has a temperature equal to or higher than the Curie point. On the other hand, the lower side of the heating roller is a non-heated region and is kept at a temperature below the Curie point. As a result, the magnetic shunt alloy drum constituting the heating roller 22 generates a magnetic flux density distribution. In this case, the lower region of the heating roller 22 receives an attractive force by the permanent magnet 34, and generates a rotational torque without applying a driving force from the outside when the induction heater 28 is energized. When the heating roller 22 is rotationally driven using rotational torque from a thermomagnetic motor, an electromagnetic clutch is released and rotational resistance is reduced to about rotational friction by a command from a fixing control means described later. The

  Further, the pressure roller 24 will be described. The pressure roller 24 has a structure in which the surface of a core material such as a drum such as aluminum is covered with elastic rubber, silicone rubber, or the like. The pressure roller 24 applies a fixing pressure to the transfer paper and the toner while forming an appropriate nip region with the heating roller 22. In the present embodiment, the pressure roller 24 is rotatably held so that the drive resistance can be controlled by the drive resistance control means 26. In the present embodiment, the drive resistance control means 26 also opens the electromagnetic clutch so that the pressure roller 24 can rotate freely during the period when the fixing means 16 is driven only by the thermomagnetic motor, or the pressure roller. 2 is retracted and pressed in the direction indicated by arrow B in FIG. 2 so as not to adversely affect the driving force of the thermomagnetic motor.

  FIG. 3 shows an embodiment of a control circuit implemented in the image forming apparatus 10 of the present embodiment. The control circuit 40 shown in FIG. 3 can be configured as a module of a main control circuit of the image forming apparatus 10 or can be configured as a dedicated module that is independently mounted for fixing control. The control circuit 40 shown in FIG. 3 includes a control board 44 including a central processing unit (hereinafter simply referred to as a CPU) 48, a fixing control means 42 for controlling the fixing means 16 using an induction heater, and an induction In order to control the magnetic field generated by the heater 28, a zero-cross detection circuit 54 that detects the magnetic flux generated by the induction heating means 28 is included.

  The CPU 48 sends a control signal to the fixing heating roller control means 60 of the fixing control means 42 via the output port 68. When the fixing heating roller control unit 60 receives the control signal, the fixing heating roller control unit 60 sets the operation of the fixing control unit 42 to be in a state of being rotationally driven by the thermomagnetic motor, and monitors the temperature in the fixing process using the induction heating unit 28. Is stopped, and the control is transferred to the CPU 48.

  The CPU 48 outputs a PWM signal for controlling the heating of the induction heating means 28 from the output port 66 to the IH inverter 52 via the interface (I / F) 50, and from the output port 68 to the ON / OFF of the IH inverter 52. An OFF control signal is output to the IH inverter 52 via the interface 50 to control the IH inverter 52.

  The CPU 48 also includes an interrupt port 70 and a data input port 72. The interrupt port 70 receives an interrupt signal for notifying the abnormality of the IH inverter 52 from the interface 50 as an abnormality notification, and the thermomagnetic motor. In response to the abnormality, the fixing control means 42 is controlled. Further, the CPU 48 receives a signal from the temperature detection element 60 such as a thermopile or thermistor from the data input port 72, and includes the heating roller 22, the pressure roller 24, and the drive resistance control means 26 indicated by broken lines in FIG. The heating / pressure control of the fixing unit 16 is performed. The temperature detecting element 60 is installed immediately before the nip region between the heating roller 22 and the pressure roller 24, and continuously detects the temperature during a period other than when the fixing control means 42 is driven by the thermomagnetic motor. And send a signal to the CPU 48.

  The CPU 48 further sends a signal for reducing the drive resistance during the thermomagnetic motor drive period to the drive resistance control circuit 56 via the output port 74. When the drive resistance control circuit 56 receives the signal from the output port 74, it drives the electromagnetic clutch, solenoid, or stepping motor to decrease the drive resistance, and when the output of the output port 74 is not asserted (this implementation) In the embodiment, it is assumed that each signal becomes LOW), and the driving resistance is returned so that the fixing resistance is returned to the normal driving mode.

  The interrupt port 76 of the CPU 48 determines that the image forming apparatus 10 has entered the image output mode by monitoring the signal output from the paper feed notification unit 46 and the like. The CPU 48 determines a notification of conveyance start from the paper feed notification unit 46 as a hardware interrupt. In response to the determination, the CPU 48 issues / stops the control signal and drives the drive resistance control means 26 to determine whether to heat the fixing control means 42 in the normal mode or drive the thermomagnetic motor. Issuing / stopping of the service is controlled.

  FIG. 4 shows an embodiment of the control timing of the control circuit shown in FIG. The image forming apparatus 10 according to the present embodiment starts processing by turning on the power or returning from the energy saving mode, and the activation mode signal or the power signal of the image forming apparatus 10 is asserted (in this embodiment, the signal state is HIGH). (1), and whether or not paper feeding is scheduled at that time is determined using, for example, a command signal to the conveyance sensor.

  In the embodiment shown in FIG. 4, since the sheet feeding is not reserved when the image forming apparatus 10 starts processing, the CPU 48 asserts a control signal. At the same time, the CPU 48 asserts the ON / OFF trigger of the IH inverter, and since the CPU 48 is not notified of the paper feed reservation from the paper feed notifying unit 46 immediately after the start of processing, the CPU 48 sets the drive signal to the non-asserted state and performs heating. The driving resistance of the roller 22 is set to the lowest state. At this stage, the heating roller 22 rotates as a thermomagnetic motor to prevent the heating motor 22 from being overheated locally.

  Thereafter, when the CPU 48 receives a hardware interrupt signal from the paper feed notification unit 46 (2), the CPU 48 changes the control signal to a non-asserted state (3), and when the control signal 64 is deasserted, The drive signal 74 is asserted (4), the rotational force is transmitted to the heating roller 22, and at the same time, the nip pressure is applied. Thereafter, when the timer period elapses or the interrupt signal from the paper feed notification unit 46 is deasserted after the paper feed notification unit 46 starts interrupting (5), the CPU 48 shifts the control signal to the asserted state (6). ).

  At this stage, the CPU 48 further shifts the drive signal to the non-asserted state (7), and minimizes the drive resistance of the heating roller 22. Thereafter, the CPU 48 starts rotation driving and preheating by the thermomagnetic motor again, and thereafter executes control of the fixing unit 16 using the thermomagnetic motor until a hardware interrupt from the paper feed notification unit 46 is asserted. To do.

  Moreover, the control timing shown by the broken line in FIG. 4 shows the control timing when the conventional induction heating means 28 not using the thermomagnetic motor is used. When the thermomagnetic motor is not used, the drive control of the heating roller 22 cannot be started until the operation mode is determined by a command from the paper feed notification unit 46. For this reason, conventionally, the heating by the induction heating means 28 is performed when there is no reservation for paper feed when the power is turned on or in the energy saving mode, or until the judgment of the paper feed command is completed and the rotation of the heating roller 22 is started. Therefore, the induction heating means 28 cannot be heated at high speed and with low power consumption.

  In the form shown by the broken line in FIG. 4, the sheet feeding reservation is not made when the image forming apparatus 10 is turned on. Therefore, the rotation control of the heating roller 22 is not executed, and the image forming apparatus 10 is fed with a sheet feeding notification unit. When the notification from 46 is made, heating is started from a state without preheating. For this reason, the user wastes most of the period during which the paper feed notification is asserted as the heating waiting time of the fixing unit 16, and in this embodiment, as indicated by the arrow in FIG. The time until the copy time can be shortened. As a result, the power consumption can be reduced while improving the printing efficiency.

  FIG. 5 shows an embodiment of a flowchart of an image forming method executed by the image forming apparatus 10. The process shown in FIG. 5 is started when the image forming apparatus 10 is activated in step S100. Note that “when the image forming apparatus 10 is activated” includes not only when the image forming apparatus 10 is powered on but also when returning from the energy saving mode. In step S101, the image forming apparatus 10 indicates whether or not it is in a state of receiving paper at the time of startup, for example, a notification or flag indicating that another functional unit has started functioning for a print job command. Refer to and judge.

  As a result of the determination in step S101, if it is determined that there is paper passing (yes), the process is branched to step S104, and heating of the heating roller 22 is started. In the present embodiment, the heating in step S104 is performed using the induction heating means 28. However, in this case, the driving is performed not by the thermomagnetic motor but by the transport motor. In step S105, the heating roller 22 is heated to such an extent that it can maintain a fixing temperature range even when the pressure roller 24 is brought into contact with it. The process waits for the paper 20 to enter the nip area, and the process ends in step S106.

  On the other hand, if it is determined in step S101 that the image output mode is not selected (no), the process branches to step S102, the drive resistance to the heating roller 22 is released, and the drive resistance is set to the lowest state in step S103. The heating roller 22 is preheated using the driving force of the thermomagnetic motor using the induction heating means 28 and the permanent magnet 34, the image output mode is determined in step S101, and the image output mode is determined. Preheating is continued until.

  FIG. 6 shows a second embodiment of the fixing means 16. In the fixing unit 16 shown in FIG. 6, a permanent magnet 34 used for a thermomagnetic motor is arranged inside a magnetic shunt alloy drum constituting the heating roller 22. In addition, the fixing unit 16 includes a cooling unit 36 such as a cooling fan for cooling the lower region of the heating roller. In the embodiment shown in FIG. 6, the lower portion of the heating roller 22 can be efficiently cooled, and the rotational force by the thermomagnetic motor can be increased. In this embodiment, the space of the fixing unit 16 can be efficiently used.

  Furthermore, in the second embodiment, the permanent magnets 34 can be arranged closer to each other in the region where the temperature difference of the magnetic shunt alloy drum is the largest, without being disturbed by the size of the induction heater 28, and the thermomagnetic motor. As a result, the driving force can be generated more effectively.

  In other embodiments, a plurality of permanent magnets 34 may be arranged according to the spatial margin of the fixing unit 16.

  Although the present invention has been described with the embodiments shown in the drawings, the present invention is not limited to the embodiments shown in the drawings, and those skilled in the art have conceived other embodiments, additions, modifications, deletions, and the like. It can be changed within the range that can be performed, and any embodiment is included in the scope of the present invention as long as the operation and effect of the present invention are exhibited.

1 is a diagram illustrating an embodiment of an image forming apparatus. The figure which showed embodiment of the fixing means. FIG. 3 is a diagram illustrating an embodiment of a control circuit mounted on the image forming apparatus. The figure which showed the control timing of the control circuit of FIG. 5 is a flowchart of an embodiment of an image forming method. The figure which showed 2nd Embodiment of the fixing means.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image processing apparatus, 12 ... Developing means, 14 ... Image carrier, 16 ... Fixing means, 18 ... Transfer means, 20 ... Transfer paper, 22 ... Heating roller, 24 ... Pressure roller, 26 ... Drive resistance control means, 28 ... induction heating means, 30 ... ferrite core, 32 ... exciting coil, 34 ... permanent magnet, 36 ... cooling fan, 40 ... control circuit, 42 ... fixing control means, 44 ... control board, 46 ... paper feed notification section, 48 ... CPU, 50 ... I / F, 52 ... IH inverter, 54 ... zero cross detection circuit, 56 ... drive resistance control circuit, 58 ... temperature detection element, 60 ... fixing heating roller control means, 64 ... control signal, 66 ... PWM Output port 68 ... Output port 70 ... Interrupt port 72 ... Data input port 74 ... Output port 76 ... Interrupt port

Claims (7)

A heating roller including a magnetic shunt alloy drum;
A pressure roller for applying a nip pressure to the heating roller;
Induction heating means for induction heating the heating roller;
A permanent magnet for generating a rotational torque by the magnetic flux density distribution of the heating roller;
An image forming apparatus comprising: the induction heating unit: a control unit that starts heating the heating roller in response to start-up of the image forming apparatus.   The image forming apparatus according to claim 1, wherein the permanent magnet is disposed at a position where the heating roller is rotated in a transfer paper conveyance direction of the image forming apparatus with respect to the induction heating unit.   The image according to claim 1, wherein the permanent magnet is positioned outside or inside the heating roller at a position including a boundary region between a heating region and a non-heating region of the heating roller by the induction heating unit. Forming equipment.   The image forming apparatus according to claim 3, further comprising a cooling unit that cools the non-heated area of the heating roller.   The image according to any one of claims 1 to 4, further comprising drive resistance control means for minimizing a drive resistance of the heating roller during a period in which the heating roller receives a rotational torque due to the magnetic flux density distribution. Forming equipment.   An image forming method in an image forming apparatus for fixing a developer onto a transfer paper by heat and pressure, comprising a heating magnetic roller comprising an induction heating means, a permanent magnet and a magnetic shunt alloy, the induction heating means An image forming method in which heating by is started in response to start-up of the image forming apparatus, and the heating roller is rotated by generating a thermomagnetic distribution on the heating roller by the induction heating means.   The image formation according to claim 6, wherein a driving resistance of the heating roller is minimized during a period in which the heating roller is heated by the induction heating unit, and the heating roller is rotated by a rotational torque generated by the thermomagnetic motor. Method.

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