JP2019174729A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform different energization control for two fixing heaters with one switching element. SOLUTION: A fixing device 9 includes fixing heaters 11-1 and 11-2. The switching unit 14 is provided commonly to the two fixing heaters 11-1 and 11-2. The fixing heater 11-1 conducts a full-wave rectified AC current of a commercial power supply by a full-wave rectifier circuit 12, and the fixing heater 11-2 supplies a half-wave rectifier circuit 13 with a half-wave rectifier circuit 13 The rectified current is conducted. Then, the controller 31 turns on the switching unit 14 during a period in which the conduction direction of the alternating current is the forward direction (a) when the energization control of both the fixing heaters 11-1 and 11-2 is performed. (B) When the energization control of only the fixing heater 11-1 is performed, the switching unit 14 is turned on during a period in which the conduction direction of the alternating current is the reverse direction. [Selection] Figure 2

Description

  The present invention relates to an image forming apparatus.

  An electrophotographic image forming apparatus includes a fixing device that heats a fixing roller to fix a toner image on printing paper. In an image forming apparatus, two fixing heaters provided on a fixing roller are controlled by one control circuit (see, for example, Patent Document 1).

JP-A-9-258598

  In general, in order to control the energization to the two fixing heaters independently, it is necessary to control the energization to the two fixing heaters by two switching elements.

  In the image forming apparatus described above, two fixing heaters are connected in parallel, and energization of the two fixing heaters is similarly controlled by a control circuit. Therefore, it is difficult to control the energization to the two fixing heaters independently by turning on / off one switching element.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that performs different energization control on two fixing heaters with one switching element.

  An image forming apparatus according to the present invention includes a fixing device including a first fixing heater and a second fixing heater, a full-wave rectification circuit that full-wave rectifies an alternating current from a commercial power supply, and an alternating current from the commercial power supply. A half-wave rectifier circuit for half-wave rectifying the alternating current from the commercial power source by allowing the alternating current to pass when the conducting direction is a forward direction and blocking when the conducting direction of the alternating current is a reverse direction; A switching unit common to the two fixing heaters and a controller for controlling the switching unit. The first fixing heater is energized with a current that has been full-wave rectified by the full-wave rectification circuit, and the second fixing heater is energized with a current that has been half-wave rectified by the half-wave rectification circuit. The controller (a), when performing energization control of both the first fixing heater and the second fixing heater, in part or all of the period in which the conduction direction of the alternating current is the forward direction, When the switching unit is turned on and (b) the energization control of the first fixing heater is performed without performing the energization control of the second fixing heater, the AC current conduction direction is in the reverse direction. In part or all, the switching unit is turned on.

  According to the present invention, it is possible to obtain an image forming apparatus that performs different energization control for two fixing heaters with one switching element.

  These and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

FIG. 1 is a side view showing a part of a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a circuit diagram showing a part of the electrical configuration of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a diagram illustrating an example of an arrangement range of the two fixing heaters 11-1 and 11-2 in FIG. FIG. 4 is a diagram showing waveforms of voltages applied to the fixing heaters 11-1 and 11-2 in FIGS.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a side view showing a part of a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus shown in FIG. 1 is an apparatus having an electrophotographic printing function, such as a printer, a facsimile machine, a copying machine, or a multifunction machine.

  The image forming apparatus of this embodiment has a tandem color developing device. The color developing device includes photosensitive drums 1a to 1d, exposure devices 2a to 2d, and developing devices 3a to 3d. The photoconductor drums 1a to 1d are four-color photoconductors of cyan, magenta, yellow, and black.

  The exposure devices 2a to 2d irradiate the photosensitive drums 1a to 1d with laser light to form electrostatic latent images. The exposure apparatuses 2a to 2d include a laser diode that is a light source of laser light and optical elements (lenses, mirrors, polygon mirrors, etc.) that guide the laser light to the photosensitive drums 1a to 1d.

  Further, around the photosensitive drums 1a to 1d, a charger such as a scorotron, a cleaning device, a static eliminator and the like are arranged. The cleaning device removes residual toner on the photosensitive drums 1a to 1d after the primary transfer, and the static eliminator neutralizes the photosensitive drums 1a to 1d after the primary transfer.

  Each of the developing devices 3a to 3d is mounted with a toner cartridge filled with toners of four colors of cyan, magenta, yellow and black, and the toner is supplied from the toner cartridge and constitutes a developer together with the carrier. The developing devices 3a to 3d attach the toner to the electrostatic latent images on the photosensitive drums 1a to 1d to form a toner pattern.

  The photosensitive drum 1a, the exposure device 2a, and the developing device 3a develop magenta, and the photosensitive drum 1b, the exposure device 2b, and the developing device 3b develop cyan, the photosensitive drum 1c, and the exposure device. Yellow development is performed by the device 2c and the developing device 3c, and black development is performed by the photosensitive drum 1d, the exposure device 2d, and the developing device 3d.

  The intermediate transfer belt 4 is an annular image carrier that contacts the photosensitive drums 1a to 1d and primarily transfers the toner images on the photosensitive drums 1a to 1d. The intermediate transfer belt 4 is stretched around the driving roller 5 and circulates in the direction from the contact position with the photosensitive drum 1d to the contact position with the photosensitive drum 1a by the driving force from the driving roller 5.

  The transfer roller 6 brings the conveyed paper into contact with the intermediate transfer belt 4 and secondarily transfers the toner image on the intermediate transfer belt 4 to the paper. The sheet on which the toner image is secondarily transferred is conveyed to the fixing device 9.

  The roller 7 has a cleaning brush, and the cleaning brush is brought into contact with the intermediate transfer belt 4 to remove the toner remaining on the intermediate transfer belt 4 after the transfer of the toner image onto the paper.

  The sensor 8 is an optical sensor used for measuring the density of the toner pattern, and irradiates the intermediate transfer belt 4 with a light beam and detects the reflected light. For example, when adjusting the toner density, the sensor 8 irradiates a predetermined region of the intermediate transfer belt 4 with a light beam, detects the reflected light, and outputs an electrical signal corresponding to the light amount.

  The fixing device 9 fixes the toner image that has been secondarily transferred onto a sheet by a heating and pressing method.

  FIG. 2 is a circuit diagram showing a part of the electrical configuration of the image forming apparatus according to the embodiment of the present invention.

  As shown in FIG. 2, the fixing device 9 includes two fixing heaters 11-1 and 11-2. The fixing heaters 11-1 and 11-2 are heaters of resistance heating elements, and are disposed in the fixing roller. For example, the fixing heaters 11-1 and 11-2 are planar heaters.

  FIG. 3 is a diagram illustrating an example of an arrangement range of the two fixing heaters 11-1 and 11-2 in FIG. As shown in FIG. 3, the fixing heater 11-2 may be dispersed at a plurality of locations. That is, the plurality of heater elements are connected in series to form one fixing heater 11-2.

  For example, as shown in FIG. 3, part or all of the arrangement range of the fixing heater 11-1 in the axial direction of the fixing roller of the fixing device 9 and the arrangement range of the fixing heater 11-2 in the axial direction of the fixing roller of the fixing device 9. Are partly or entirely different from each other. That is, one arrangement range of the fixing heaters 11-1 and 11-2 may include the other arrangement range, or a part of one arrangement range of the fixing heaters 11-1 and 11-2 is arranged in the other arrangement range. The arrangement range may overlap, that is, one arrangement range of the fixing heaters 11-1 and 11-2 may not overlap the other arrangement range (for example, as shown in FIG. 3).

  In this embodiment, the fixing device 9 can fix a toner image on a first size printing paper (for example, A4) and a second size printing paper (for example, A3) larger than the first size. For -1 and 11-2, a heater element corresponding to the width of the printing paper on which the toner image can be fixed is used.

  Further, in this embodiment, the arrangement range of the fixing heater 11-1 in the axial direction of the fixing roller of the fixing device 9 includes at least the passing range of the first size printing paper (A4 in FIG. 3). In FIG. 3, the arrangement range of the fixing heater 11-1 is substantially the same as the passage range of the first size printing paper (A4 in FIG. 3). Instead, the arrangement range of the fixing heater 11-1 may be substantially the same as the passage range of the second size printing paper (A3 in FIG. 3).

  Further, in this embodiment, the arrangement range of the fixing heater 11-2 in the axial direction of the fixing roller of the fixing device 9 is from the passing range of the second size printing paper (A3 in FIG. 3) to the first size printing paper. (A4 in FIG. 3) is a range excluding the passing range.

  Further, as shown in FIG. 2, between the commercial power supply and the fixing heaters 11-1 and 11-2, a full-wave rectifier circuit 12, a half-wave rectifier circuit 13, a switching unit 14, a fuse FS1, a relay CR, and Choke coils LC1 and LC2 are provided.

  The full-wave rectifier circuit 12 full-wave rectifies an alternating current from a commercial power source. In FIG. 2, the full-wave rectifier circuit 12 is a diode bridge.

  The half-wave rectifier circuit 13 allows the AC current from the commercial power source to pass when the AC current conduction direction is the forward direction, and prevents the AC current from flowing from the commercial power source when the AC current conduction direction is the reverse direction. Half-wave rectification of the alternating current. In FIG. 2, the half-wave rectifier circuit 13 is a power diode.

  The current that has been full-wave rectified by the full-wave rectifier circuit 12 is conducted to the fixing heater 11-1. A current half-wave rectified by the half-wave rectifier circuit 13 is conducted to the fixing heater 11-2. FIG. 4 is a diagram showing waveforms of voltages applied to the fixing heaters 11-1 and 11-2 in FIGS. As shown in FIG. 4, a voltage that has been full-wave rectified by the full-wave rectifier circuit 12 is applied to the fixing heater 11-1. A voltage half-wave rectified by the half-wave rectifier circuit 13 is applied to the fixing heater 11-2.

  The switching unit 14 includes a switching element (in this case, a bidirectional thyristor) common to the two fixing heaters 11-1 and 11-2. This switching element is connected in series to the fixing heater 11-1 and the fixing heater 11-2.

  The switching unit 14 turns on / off the energization to the fixing heaters 11-1 and 11-2 by the switching element. Note that the switching element of the switching unit 14 may be a unidirectional thyristor, a power transistor, or the like.

  The image forming apparatus illustrated in FIGS. 1 and 2 includes a power supply circuit 15 and a control board 16 that is supplied with power from the power supply circuit 15.

  The power supply circuit 15 generates DC power from a commercial power supply at a predetermined reference voltage (for example, 24 volts), and supplies power to the controller 31 that controls the fixing heaters 11-1 and 11-2.

  In the power supply circuit 15, AC power obtained from a commercial power source is rectified by the diode bridge DB, and the rectified DC power is stepped down to a rated voltage and output by a DC / DC converter. In front of the diode bridge DB, a fuse FS2, choke coils LC3 and LC4, and the thermistor TH are provided. Further, a smoothing capacitor C1 is provided after the diode bridge DB.

  The DC / DC converter portion of the power supply circuit 15 includes a converter switching element Q1, a control unit 21, a transformer TR, and a rectifier circuit 22.

  Converter switching element Q <b> 1 is connected to the primary winding of transformer TR and performs a switching operation in accordance with a control signal from control unit 21. Here, converter switching element Q1 is a field effect transistor (FET).

  The control unit 21 is a circuit (for example, an IC chip) that outputs a control signal for controlling on / off of the converter switching element Q1.

  The rectifier circuit 22 includes a diode D and a smoothing capacitor C2, and rectifies AC power induced in the secondary side winding of the transformer TR to generate DC power. The control unit 21 adjusts the duty of the control signal so that the rectified DC voltage becomes a predetermined voltage.

  In addition, a controller 31 is provided on the control board 16. Therefore, the output voltage of the power supply circuit 15 is applied to the controller 31 as the power supply voltage.

  The controller 31 includes an ASIC (Application Specific Integrated Circuit), a processor that operates according to a control program, and the like, and controls the switching unit 14 by applying a heater control signal to the switching element of the switching unit 14. One or both of 1 and 11-2 are on / off controlled to control the temperature distribution of the fixing roller in the axial direction of the fixing roller of the fixing device 9 and the like.

  Specifically, the controller 31 (a) when performing energization control of both the fixing heater 11-1 and the fixing heater 11-2, during the period T1 in which the conduction direction of the alternating current of the commercial power source is the forward direction. In part or all, the switching unit 14 is turned on to energize both the fixing heater 11-1 and the fixing heater 11-2, and (b) the fixing heater 11- without performing energization control of the fixing heater 11-2. When the energization control 1 is performed, the fixing heater 11 is turned on without energizing the fixing heater 11-2 by turning on the switching unit 14 in part or all of the period T2 in which the conduction direction of the alternating current is reverse. 1 is energized.

  For example, the controller 31 detects the phase of the AC voltage of the commercial power supply (zero cross timing of phase 0 degrees and zero cross timing of phase 180 degrees), and specifies the period T1 and the period T2 based on the phase difference.

  Next, the operation of the image forming apparatus will be described.

  As described above, the control of the fixing heaters 11-1 and 11-2 can be switched according to the period (period T1 or period T2) in which the switching unit 14 is turned on. Corresponding to the distribution, the arrangement range of the fixing heater 11-1 and the arrangement range of the fixing heater 11-2 are determined.

  Then, the controller 31 performs the on / off control of the switching unit 14 in a predetermined pattern in at least one of the period T1 and the period T2, so that the temperature distribution of the fixing roller becomes a desired temperature distribution.

  When the arrangement range of the fixing heater 11-1 and the arrangement range of the fixing heater 11-2 correspond to the size of the printing paper as shown in FIG. 3, for example, when printing is performed on A4 size printing paper, The controller 31 does not turn on the switching unit 14 in the period T1, and the switching unit so that the temperature distribution of the fixing heater (arrangement range of the fixing heater 11-1) becomes a desired temperature distribution in the period T2. 14 is turned on for a predetermined time, and the fixing heater 11-2 is not energized, but the fixing heater 11-1 is energized.

  In this case, when printing is performed on A3 size printing paper, the controller 31 causes the temperature distribution of the fixing heater (arrangement range of the fixing heater 11-1) to be a desired temperature distribution in the period T1. In addition, the switching unit 14 is turned on for a predetermined time, and the switching unit 14 is turned on for a predetermined time so that the temperature distribution of the fixing heater (arrangement range of the fixing heater 11-2) becomes a desired temperature distribution even during the period T2. Then, both the fixing heater 11-1 and the fixing heater 11-2 are energized.

  As described above, according to the embodiment, the fixing device 9 includes the fixing heater 11-1 and the fixing heater 11-2. The full-wave rectifier circuit 12 full-wave rectifies an alternating current from a commercial power source. The half-wave rectifier circuit 13 allows the alternating current from the commercial power supply to pass when the alternating current from the commercial power supply is forward and when the alternating current is in the reverse direction. Half-wave rectifies the current. The switching unit 14 is provided in common to the two fixing heaters 11-1 and 11-2. The controller 31 controls the switching unit 14. The fixing heater 11-1 is energized by the current that has been full-wave rectified by the full-wave rectifier circuit 12, and the fixing heater 11-2 is energized by the current that has been half-wave rectified by the half-wave rectifier circuit 13. When the controller 31 (a) performs energization control of both the fixing heater 11-1 and the fixing heater 11-2, the controller 31 performs switching in part or all of the period in which the conduction direction of the alternating current is the forward direction. When the energization control of the fixing heater 11-1 is performed without performing the energization control of the fixing heater 11-2 with the unit 14 turned on, a part of the period in which the conduction direction of the alternating current is in the reverse direction Alternatively, in all, the switching unit 14 is put into a state.

  Thereby, different energization control is performed on the two fixing heaters 11-1 and 11-2 by one switching element. Therefore, since the number of switching elements can be smaller than the number of fixing heaters 11-1 and 11-2, the cost of the apparatus can be reduced.

  Various changes and modifications to the above-described embodiment will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing its intended advantages. That is, such changes and modifications are intended to be included within the scope of the claims.

  The present invention is applicable to, for example, an electrophotographic image forming apparatus.

9 Fixing device 11-1 Fixing heater 11-2 Fixing heater 12 Full-wave rectifier circuit 13 Half-wave rectifier circuit 14 Switching unit 31 Controller

Claims (3)

A fixing device comprising a first fixing heater and a second fixing heater;
A full-wave rectification circuit for full-wave rectification of alternating current from a commercial power supply;
By passing the alternating current from the commercial power supply when the alternating current conduction direction is a forward direction, the alternating current from the commercial power supply is blocked by passing the alternating current from the commercial power supply. A half-wave rectifier circuit for wave rectification,
A switching unit common to the two fixing heaters;
A controller for controlling the switching unit,
The first fixing heater is energized with a current that has been full-wave rectified by the full-wave rectification circuit,
The second fixing heater is energized with a current half-wave rectified by the half-wave rectification circuit,
The controller (a) in the case where the energization control of both the first fixing heater and the second fixing heater is performed, the switching is performed during a part or all of a period in which the conduction direction of the alternating current is a forward direction. And (b) a part of a period in which the conduction direction of the alternating current is in the reverse direction when the energization control of the first fixing heater is performed without performing the energization control of the second fixing heater. Or in all, turning on the switching unit;
An image forming apparatus. A part or all of the arrangement range of the first fixing heater in the axial direction of the fixing roller of the fixing unit and a part or all of the arrangement range of the second fixing heater in the axial direction of the fixing roller of the fixing unit are mutually Differently
The controller controls the switching unit to control the temperature distribution of the fixing roller in the axial direction of the fixing roller of the fixing device;
The image forming apparatus according to claim 1. The fixing device can fix a toner image on a first size printing paper and a second size printing paper larger than the first size;
The arrangement range of the first fixing heater in the axial direction of the fixing roller of the fixing device includes at least a passage range of the first size printing paper,
The arrangement range of the second fixing heater in the axial direction of the fixing roller of the fixing device is a range obtained by removing the passing range of the first size printing paper from the passing range of the second size printing paper;
The image forming apparatus according to claim 1.

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