JP2006349711A - Image fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image fixing device capable of surely preventing a "flicker" phenomenon without using an auxiliary electric heater such as a sub-electric heater. <P>SOLUTION: The image fixing device fixes an image on the surface of an image carrier under heat by applying a DC current, obtained by rectifying a commercial AC power source, to an electric heater. The image fixing device includes: a pattern generator that transmits a temporal application pattern signal upon a command from a control device when pre-heating and heating of the electric heater end; a full-wave rectifier by which the current subjected to full-wave rectification is applied to the electric heater during a regular operation; a zero-cross point detector that detects a timing signal when a DC voltage from the full-wave rectifier is zero; and a switching element that applies a half-wave rectified current to the electric heater from the full-wave rectifier according to the timing of the zero-cross point detector during the transmission of an application pattern signal from the pattern generator when preheating and heating end. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image on the surface of an image carrier, and more particularly, to an image fixing device of an image forming apparatus.

As is well known, in image forming apparatuses such as various printers, electrostatic copying machines, plate-making machines, etc., an image that incorporates an electric heater to fix an image formed on the surface of a base (image carrier) such as paper. It has a fixing device.
FIG. 1 shows the heater energization state from when the power button is turned on until the conventional image fixing apparatus reaches the target temperature. The heater on / off energization pattern is set in advance under monitoring by the temperature detector. From the figure, the energization (current application) time is long when the temperature of the image fixing device is low, and the energization time is shortened and the interval time is lengthened as the temperature detected by the temperature detector approaches the target temperature. And maintain at the target temperature.

By the way, since a general image forming apparatus uses a commercial AC power source as an energy source, the voltage of the commercial AC power source to which the image forming apparatus is connected is not locally localized at the time of power-on preheating that consumes a large amount of power or at the end of the operation. A stable “flicker” phenomenon is often a problem.
In other words, the image fixing device incorporated in the image forming apparatus is a heating roller fixing device incorporating an electric heater or an oven fixing device in which the surface of a plate-like electric resistor, which is an electric heater, is coated with an insulating material. Since the electric heater with a large calorific value is incorporated for shortening and high-speed processing, the “flicker” phenomenon occurs in any structure.

For this reason, conventionally, an auxiliary heater different from the heater is incorporated in the heating roller, and the auxiliary heater having a small heat generation amount is energized at the time of preheating by turning on the power of the image forming apparatus, and the heating roller temperature is increased to a certain temperature. Later, he devised to energize the electric heater.

Specifically, in Japanese Patent Laid-Open No. 2002-328561, a quartz tube heater (sub-heater) different from the halogen heater (main heater) is incorporated in the heating roller, and the pre-heater is energized for pre-heating during pre-heating. "Inrush current" that causes "flicker" phenomenon is mitigated.
Japanese Patent Application Laid-Open No. 2005-84549 proposes a structure in which a second heating unit similar to the sub-heater described above is incorporated in the fixing roller.
JP2002-328561 JP-A-2005-84549

However, any of the structures for preventing the “flicker” phenomenon in the conventional image fixing apparatus needs to incorporate a preheating sub-heater in a narrow heating roller. In addition, there are problems in that the assembly process is complicated and the parts cost is high.
An object of the present invention is to provide an image fixing apparatus capable of reliably preventing the “flicker” phenomenon without using an auxiliary heater such as a sub-heater in view of the problems of the conventional image fixing apparatus as described above.

  In order to achieve this object, the present invention is directed to an image fixing device that applies a DC current rectified from a commercial AC power source to a heater to heat and fix an image on the surface of the image bearing member. A pattern generator that transmits a temporal application pattern signal at the end of preheating and heating, a full wave rectifier that applies the full-wave rectified current to the heater during normal operation, and a DC voltage from the full-wave rectifier is zero A zero-cross point detector for detecting a timing signal at the time, and a half-wave rectified current from the full-wave rectifier according to the timing of the zero-cross point detector during a pre-heating time from the pattern generator and a transmission time of the applied pattern signal at the end of heating. An image fixing apparatus is provided that includes a switching element that applies a voltage to the heater.

  According to the present invention, since it is not necessary to incorporate a preheating auxiliary heater in a narrow space, there is no reduction in manufacturing costs and no excessive space, and the “flicker” phenomenon can be prevented.

In the description of the preferred embodiments of the invention described below,
1) The applied pattern signal from the pattern generator at the end of preheating and heating applies a half-wave rectification energization timing time signal to the full-wave rectifier and a full-wave rectified current from the full-wave rectifier to the switching element. An image fixing device including a full-wave rectification timing time signal having an interval of
2) Between the zero-cross point detector and the pattern generator, and between the pattern generator and the switching element, a light-emitting diode that is turned on by a transmission signal and light reception that is sensitive to a signal from the light-emitting diode. A first photocoupler and a second photocoupler each including an element, and the zero crosspoint detector and the switching element which are electromagnetically primary by the first photocoupler and the second photocoupler, The present invention proposes an image fixing device in which electrical safety is improved by disconnecting a pattern generator on the secondary side of the control system.

The details of the embodiment of the present invention will be described below with reference to FIGS.
FIG. 2 is a block diagram of the image fixing apparatus according to the present invention. In the figure, reference numeral “1” denotes a full-wave rectifier to which commercial AC power is input to the primary side.

The full-wave rectifier 1 is constituted by, for example, a diode bridge, applies a direct current obtained by full-wave rectification of the primary commercial alternating current to an electric heater (not shown) of the image fixing device, and heats the electric heater.
The pattern generator 2 generates a predetermined pattern signal corresponding to a signal input signal from a control device (not shown), and based on the output pattern of the pattern generator 2, the image fixing device is preheated and the heating is completed. Sometimes a half-wave rectified current is applied to the electric heater.

  Here, a control unit of the image forming apparatus (for example, a control apparatus of the plate making machine) receives an output signal and a power on / off signal from a temperature detection element (for example, thermistor) of the image fixing apparatus, and preheats the image fixing apparatus. The pattern generator 2 is controlled in accordance with the state of the image forming apparatus by determining whether the heating is completed by turning off the power during normal operation.

  A part of the output of the full-wave rectifier 1 is input to the zero cross point detector 3, the time of zero current rectified by the full wave is detected, and the pattern generator synchronized with the zero current of the zero cross point detector 3. The switching element 4 is switched by a command from No. 2, and half-wave rectified direct current is applied to the electric heater during preheating and heating, and full-wave rectified direct current voltage is applied to the electric heater during normal operation.

Details of the direct current applied to the electric heater at the time of preheating and at the end of heating will be described with reference to FIGS.
3A shows the state of the direct current applied to the electric heater during the preheating time, and FIG. 3B shows the end of heating when the power button is turned off.

As understood from FIG. 3A, the half-wave rectified current / voltage of the commercial AC power supply is applied to the electric heater in the preheating time of the image fixing device via the switching element 4. Thus, the power consumption of the electric heater in this case is about 50% if the normal operation is 100%.
On the contrary, the power consumption of the electric heater immediately after the power button of the image forming apparatus is turned off is about 50% in the normal operation as understood from FIG.

FIG. 4 is a time chart of power consumption of the electric heater in the image fixing device. Compared with the conventional image fixing device in which only the full-wave rectified DC voltage (100%) is controlled to be turned on and off in the electric heater, the first embodiment is described. Then, when the electric heater is preheated and when the heating is completed, power consumption is about 50%.
Therefore, it is possible to prevent a sudden change in power consumption at the time of preheating and the end of heating in the image fixing device, and to mitigate “flicker” generated in peripheral devices of the commercial AC source. Of course, in the present invention, it is not necessary to incorporate an auxiliary electric heater in a narrow fixing roller or the like, and the manufacturing cost is also low.

In the first embodiment, the first photocoupler 5 and the second photocoupler 5 that electromagnetically separate the primary side having a large voltage / current and the secondary side having a small voltage / current formed by the control device or the pattern generator 2. A photocoupler 6 is provided.
That is, the first photocoupler 5 includes a light emitting diode that is turned on by an output signal from the zero cross point detector 3 and a light receiving element that receives light from the light emitting diode. The light receiving element is an output from the full-wave rectifier 1. When the voltage is zero, a timing signal is sent to the pattern generator 2 by turning off the light emitting diode.

  The second photocoupler 6 has a light emitting diode that is turned on by an output signal from the pattern generator 2, and controls a direct current applied to the electric heater by an output of a light receiving element that receives light from the light emitting diode.

  That is, the electromagnetic coupling between the primary side including the zero cross point detector 3 and the switching element 4 on the high electric side and the secondary side including the pattern generator 2 and the control device is made to be the first photocoupler 5. And by separating with the second photocoupler 6, the adverse effect of disturbance can be eliminated.

  4 is a time chart corresponding to FIG. 3A in the second embodiment. That is, the preheating time of the image fixing device is divided into a first section, a second section, and a third section, and a pattern signal that is different for each section is transmitted from the pattern generator 2.

More specifically, in the first section, a half-wave rectified direct current is applied to the electric heater, and in the second section, about half of the time—full-wave rectified direct current and the remaining half of the time— In the third period immediately before the half-wave rectified current is applied and the normal operation is started, approximately 2/3 time-full-wave rectified DC is applied, and the remaining 1/3 time-half-wave rectified current is applied. .
Therefore, when the power consumption of the electric heater during operation is 100%, the power consumption in the first section is about 50%, the power consumption in the second section is about 70%, and the power consumption in the third section. The power is about 80%, and the preheating time can be shortened while gradually increasing the power consumption to prevent the “flicker” phenomenon.

  In the above description of the embodiments of the present invention, the image fixing device of the plate making machine is exemplified. However, it is obvious that the present invention can be applied to an image fixing device such as an electrophotographic copying machine and a printer. The type of the image fixing device to be applied is not limited to the heat fixing roller structure, and can be applied to an oven type fixing device.

FIG. 10 is an explanatory diagram of a relationship between a temperature at the time of preheating of a conventional image fixing device and an energization time. 1 is a block diagram of an image fixing device in Embodiment 1 of the present invention. 4 is a time chart at the time of preheating and at the end of heating of the image fixing device. It is a macroscopic comparison diagram of the image fixing device of the present invention shown in comparison with the conventional case. It is a time chart in Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Full wave rectifier 2 Pattern generator 3 Zero cross point detector 4 Switching element 5 1st photocoupler 6 2nd photocoupler

Claims (3)

  In an image fixing apparatus that applies a DC current rectified from a commercial AC power source to a heater to heat and fix an image on the surface of the image carrier, a pre-heating of the heater and a temporal application pattern at the end of heating in response to a command from the controller A pattern generator for transmitting a signal, a full-wave rectifier for applying the full-wave rectified current to the heater during normal operation, and a zero cross point detector for detecting a timing signal when the DC voltage from the full-wave rectifier is zero And a switching element that applies a half-wave rectified current from the full-wave rectifier to the heater in accordance with the timing of the zero-cross point detector during the transmission time of the application pattern signal at the end of preheating and heating from the pattern generator. An image fixing device.   The applied pattern signal from the pattern generator at the end of preheating and heating includes a half-wave rectification energization timing time signal for the full-wave rectifier and an interval for applying a full-wave rectified current from the full-wave rectifier to the switching element. The image fixing apparatus according to claim 1, further comprising a full-wave rectification timing time signal having Between the zero cross point detector and the pattern generator, and between the pattern generator and the switching element, a light emitting diode that is lit by a transmission signal and a light receiving element that is sensitive to a signal from the light emitting diode, A first photocoupler and a second photocoupler each including the zero crosspoint detector and the switching element which are electromagnetically primary by the first photocoupler and the second photocoupler, and a control system The image fixing device according to claim 1, wherein the electrical safety is improved by disconnecting from the pattern generator on the secondary side.