JP2005338561A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power consumption or to secure fixation by determining the power amount to be supplied to a heat generating part of a thermal fixing apparatus based on the detection of the temperature of the heat generating part of the thermal fixing apparatus in supplying the power for printing on the 2nd side after waiting for the 2nd side image data at the time of both-side printing. <P>SOLUTION: Regarding a system using a stepping motor independent from a main motor in order to drive a fixing unit and reverse a paper at the time of both-side printing, in reversing the paper with a forward and backward changeover drive of the stepping motor, and also, at the standby time of the 2nd side image data at the time of both-side printing, power supply to a ceramic heater for the fixing unit is interrupted or the supplied power amount is reduced, and after receiving the 2nd side image data, the temperature of a temperature detecting means such as a thermistor is monitored in order to detect the temperature of the ceramic heater, and the optimum power amount is determined based on the result, and in the case of the short image data standby time, the supplied power amount is reduced, and the power consumption is reduced, on the other hand, in the case of the long image data standby time, the fixation is secured. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a second-side image data standby time during double-sided printing and heater control of a thermal fixing device in an image forming apparatus.

2. Description of the Related Art Conventionally, in an image forming apparatus such as a laser printer, a main motor that is a drive source for conveying paper, a paper discharge conveyance path through which a printing surface is discharged downward, and a face-down paper discharge roller pair and a face-down paper discharge roller pair rotate. A reversing mechanism for reversing the direction, a rotation reversing mechanism for the face-down paper discharge roller pair, reverses the single-sided printing paper on the paper discharge conveyance path, and guides it to the double-sided printing conveyance path, a heating part such as a ceramic heater And a pressure fixing unit such as a pressure roller, and the heat fixing device such as a fixing device for fixing the developer on the paper by heat, the face-down paper discharge roller pair and the fixing device rotate independently of the main motor. It has a stepping motor to be driven, and when the paper is reversed by switching the forward / reverse switching of the stepping motor or when waiting for the second image data for double-sided printing, Lowering the cutoff or input power amount of power to Ramikkuhita, after receiving the dihedral th image data, when turning on the power to the ceramic heater, it was constant.
JP 2002-132804 A

  However, since the power input to the ceramic heater is constant after receiving the second-side image data for double-sided printing, if the data standby time is long, the temperature of the pressure roller will drop, and the fixability cannot be secured. There was sex.

  The present invention has been made paying attention to the above points, and detects the temperature of the heat generating portion of the heat fixing device when the power for the second side printing is turned on after waiting for the second side image data during the duplex printing. It is an object of the present invention to provide an image forming apparatus that can reduce power consumption or secure fixing performance by determining the amount of power input to a heat generating part.

In order to achieve the above object, an image forming apparatus according to claim 1, 2, 3, and 4 includes a main motor that is a drive source for conveying paper, a paper discharge conveyance path and a face on which a printing surface is discharged downward. It has a reversing mechanism that reverses the rotation direction of the down paper discharge roller pair and the face down paper discharge roller pair. A pair of reversing paper guide rollers that lead to the sheet, a paper heater sandwiched between a ceramic heater and a pressure roller, and a fixing device that heat-fixes the developer on the paper, a face-down paper discharge roller pair, and a fixing device rotate independently of the main motor Has a stepping motor to drive,
When reversing the paper by forward / reverse switching drive of the stepping motor or waiting for the second side image data for double-sided printing, cut off the power to the ceramic heater of the fixing unit or lower the input power amount, and after receiving the second side image data, To detect the temperature of the heater, the temperature of the temperature detection means such as a thermistor is monitored, and the optimum input power amount is determined based on the result. In the case where the power consumption is reduced and the image data standby time is long, the fixing property is ensured.

  That is, the technical contents of the present invention can solve the above-described problems by including the following configuration.

  (1) In an image forming apparatus using an electrostatic photographic process, a main motor that is a driving source for conveying paper, a paper discharge conveyance path through which a printing surface is discharged downward, a pair of face down paper discharge rollers, and face down paper discharge A reversing mechanism for reversing the rotation direction of the roller pair, and a reversing sheet guiding roller pair for reversing the single-sided printing paper on the paper discharge conveyance path by the rotation reversal mechanism of the pair of face-down paper discharge rollers, and leading to the double-sided printing conveyance path, heating unit And a stepping motor that sandwiches the sheet by the pressure unit and heat-fixes the developer on the sheet, a pair of face-down discharge rollers and a heat fixing unit that rotates and drives independently of the main motor, An image forming apparatus characterized by shutting off power to a heat generating portion of a heat fixing device when a sheet is reversed by forward / reverse switching drive of a stepping motor.

  (2) In the image forming apparatus according to (1), when the sheet is reversed by forward / reverse switching driving of the stepping motor, the amount of electric power supplied to the heat generating portion of the heat fixing device is reduced.

  (3) In the image forming apparatus according to (1) or (2), the power to the heat generating portion of the heat fixing device is cut off or the amount of input electric power is reduced during standby of the second side image data for double-sided printing.

  (4) In any one of the above (1) to (3), a temperature for detecting the temperature of the heat generating portion of the heat fixing device when the power for the second side printing is turned on after waiting for the second side image data during the duplex printing. An image forming apparatus characterized in that the amount of electric power supplied to a heat generating portion is determined by the temperature of a detection means.

According to the present invention, by the image forming apparatus according to the first, second, third, and fourth aspects,
A main motor that is a drive source for conveying paper, a paper discharge path for discharging the printing surface downward, a reversing mechanism that reverses the rotation direction of the face-down paper discharge roller pair and the face-down paper discharge roller pair, The developer on the paper is sandwiched by the reverse paper guide roller pair, the ceramic heater and the pressure roller, which reverses the single-sided printing paper on the paper discharge conveyance path by the rotation reversal mechanism of the down paper discharge roller pair and leads to the double-sided print conveyance path. A fixing unit for heat fixing, a face-down paper discharge roller pair, and a stepping motor for rotating the fixing unit independently of the main motor,
When reversing the paper by forward / reverse switching drive of the stepping motor or waiting for the second side image data for double-sided printing, cut off the power to the ceramic heater of the fixing unit or lower the input power amount, and after receiving the second side image data, By monitoring the temperature of the thermistor for detecting the temperature of the heater and determining the optimal input power based on the result, when the image data standby time is short, the input power amount is reduced and the power consumption is reduced. When the image data standby time is long, the fixing property can be ensured.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  FIG. 1 is a cross-sectional view illustrating the configuration of a laser beam printer. In FIG. 1, 101 is a laser beam printer main body, and 103 is a paper cassette. The paper cassette paper presence / absence detection sensor S1 detects the presence / absence of paper in the cassette. By driving the pair of cassette paper feed rollers 103a and 103b, the paper is carried in the direction L1, and the top sensor S2 detects the image writing timing and the leading and trailing edges of the paper. A laser scanner unit 104 modulates laser light based on image data, and forms an electrostatic latent image while scanning on the photosensitive drum 105a. The surface of the photosensitive drum is charged in advance by the charger 105 b, and the electrostatic latent image irradiated on the photosensitive drum 105 a is developed with toner by the developing device 105 c and transferred to the paper by the transfer unit 106. The toner image on the sheet is fixed by applying heat and pressure to the sheet by the thermal fixing device 107. The thermal fixing device 107 includes a heating body and a thermistor that detects the temperature of the heating body, and fixes the image to the paper by applying heat and pressure to the paper after the transfer process. The paper discharge sensor S3 detects the timing at which the paper passes the fixing unit 107, the face-up paper discharge roller pair 108 conveys the paper that has passed the thermal fixing device 107, and the face-up tray 108 or the face-down paper discharge unit 109. Discharge.

  FIG. 2 is a diagram for explaining forward / reverse switching when a pendulum gear is used to explain an embodiment of the present invention.

  In FIG. 2, 201 is a fixing reversing motor, 202 is a face-down discharge roller gear, 203 is a face-down discharge idler gear, 204 is a pendulum gear, 205 is an idler gear, 206 is a pressure roller gear, and 207 is a discharge roller gear.

  The face-down paper discharge roller gear 202 is rotated forward and backward through the face-down paper discharge idler gear 203 by forward and reverse rotation of the fixing reversal motor 201 to switch back the paper. Regardless of the rotation direction of the fixing reversal motor 201, the pressure roller gear 206 must always rotate in a certain direction. Therefore, the pressure roller gear 206 is driven via the fixing reversal motor 201, pendulum gear 204, and idler gear 205. ing.

  FIG. 3 is a diagram for explaining forward / reverse switching when a one-way clutch gear is used to explain an embodiment of the present invention.

  In FIG. 3, reference numeral 301 denotes a fixing reversal motor, 302 a face-down paper discharge roller gear, 303 a face-down paper discharge idler gear, 304 a one-way clutch gear, 305 a pressure roller gear, and 306 an idler gear.

  By forward / reverse rotation of the fixing reversal motor 301, the face-down paper discharge roller gear 302 is rotated forward and backward via the face-down paper discharge idler gear 303 to switch back the paper. Regardless of the direction of rotation of the fixing reversal motor 301, the pressure roller gear 305 must always rotate in a fixed direction, so the one-way clutch gear 304 is used to drive the pressure roller gear 305. The one-way clutch gear 304 is a double gear, and the lower gear and the pressure roller gear 305 are engaged with each other. The pressure roller gear 305 always rotates in a fixed direction because it rotates in a fixed direction regardless of the rotation direction of the fixing reversal motor 301.

  When the forward / reverse switching is performed for both the pendulum gear and the one-way clutch gear, the pressure roller gear is stopped for about 50 to 100 ms as the gear switching time.

  FIG. 4 is a diagram showing the time and the number of rotations at the time of forward / reverse switching of the stepping motor for explaining the embodiment of the present invention. After normal rotation in normal rotation, the rotational speed is decreased stepwise, and then hold excitation is performed for a period of time so that the vibration of the motor is attenuated and stabilized before starting rotation in reverse rotation. At the time of hold excitation, the rotation of the stepping motor is stopped. The hold excitation time is approximately 200 to 300 ms, although it depends on the inertia and load of the motor. Thereafter, the rotational speed is increased step by step, and the motor is driven at steady rotation. The same applies to the case of reverse rotation to normal rotation.

  FIG. 5 is a timing chart for explaining the first embodiment of the present invention.

  The printing operation is started, the rotation speed of the fixing reversing motor is increased stepwise and the energization to the heater is started. Thereafter, the sheet is driven at a steady rotational speed, the sheet passes through the fixing device, the first side is fixed, and the energization to the heater is cut off or the input power amount is lowered after a lapse of a certain time after the trailing edge of the sheet reaches the sheet discharge sensor. After that, the rotation speed of the fixing reversing motor is lowered step by step, and hold excitation is performed for a period in which the vibration is attenuated and stabilized. At that time, the pressure roller is stopped. In order to print the second side, the fixing reversing motor is switched to reverse rotation in order to feed the sheet to the duplex conveying path. After driving the motor, power is turned on again. The rotational speed is increased step by step and driven at a steady rotational speed. Here, the drive of the motor is stopped in order to wait for the image data on the second side. At that time, the power supply to the heater is cut off or the amount of input power is reduced.

  As shown in FIG. 5, the waiting time is 1 second. Since the waiting time is short, the thermistor temperature has not dropped, so the power input on the second side is reduced to 70%. The motor is driven in reverse rotation, and the reverse rotation is switched to the normal rotation after a predetermined time has elapsed since the trailing edge of the sheet reaches the double-sided sensor. The rotation speed of the fixing reversing motor is increased stepwise, power is turned on again, and printing on the second side is performed. When switching the motor from reverse rotation to normal rotation, the energization to the heater is once cut off or the input electric energy is lowered.

  FIG. 6 is a timing chart for explaining the second embodiment of the present invention.

  In the first embodiment, the printing operation is started, the rotation speed of the fixing reversing motor is increased stepwise by normal rotation, and energization to the heater is started. Thereafter, the sheet is driven at a steady rotational speed, the sheet passes through the fixing device, the first side is fixed, and the energization to the heater is cut off or the input power amount is lowered after a lapse of a certain time after the trailing edge of the sheet reaches the sheet discharge sensor. After that, the rotation speed of the fixing reversing motor is lowered step by step, and hold excitation is performed for a period in which the vibration is attenuated and stabilized. At that time, the pressure roller is stopped. In order to print the second side, the fixing reversing motor is switched to reverse rotation in order to feed the sheet to the duplex conveying path. After driving the motor, power is turned on again. The rotational speed is increased step by step and driven at a steady rotational speed. Here, the drive of the motor is stopped in order to wait for the image data on the second side. At that time, the power supply to the heater is cut off or the amount of input power is reduced.

  As shown in FIG. 6, the waiting time is 5 seconds. Because the waiting time is long, the thermistor temperature has dropped significantly, so the input power on the second side is raised to 100%. The motor is driven in reverse rotation, and the reverse rotation is switched to the normal rotation after a predetermined time has elapsed since the trailing edge of the sheet reaches the double-sided sensor. The rotation speed of the fixing reversing motor is increased stepwise, power is turned on again, and printing on the second side is performed. When switching the motor from reverse rotation to normal rotation, the energization to the heater is once cut off or the input electric energy is lowered.

Sectional drawing explaining the structure of the laser beam printer which shows the Example of this invention The figure explaining the Example of this invention The figure explaining the Example of this invention The figure explaining the Example of this invention Timing chart for explaining the first embodiment of the present invention Timing chart for explaining a second embodiment of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Laser beam printer main body 103 Paper cassette 103a Cassette feed roller 103b Conveying roller pair 104 Laser scanner unit 105a Photosensitive drum 105b Charger 105c Developer 106 Transfer part 107 Heat fixing device 108 Face-up discharge roller pair 109 Face-up tray 110 Face-down paper discharge unit S2 Top sensor S3 Paper discharge sensor 201 Fixing reversal motor 202 Face-down paper discharge roller gear 203 Face-down paper discharge idler gear 204 Pendulum gear 205 Idler gear 206 Pressure roller gear 207 Paper discharge roller gear 301 Fixing reversal motor 302 Face-down paper discharge Roller gear 303 Face-down discharge idler gear 304 One-way clutch gear 305 Pressure roller gear 306 Idler gear

Claims (4)

In an image forming apparatus using an electrophotographic process, a main motor that is a driving source for conveying a sheet, a discharge conveyance path that discharges a printing surface downward, a face-down discharge roller pair, and a face-down discharge roller pair It has a reversing mechanism that reverses the rotation direction, and a reversing paper guide roller pair that reverses the single-sided printing paper on the paper discharge conveyance path by the rotation reversal mechanism of the face-down paper discharge roller pair and leads it to the double-sided printing conveyance path, heat generation part and pressure A stepping motor that sandwiches the sheet by the section and heat-fixes the developer on the sheet, a face-down paper discharge roller pair, and a heat fixing device that rotates and drives independently of the main motor,
An image forming apparatus characterized in that when a sheet is reversed by forward / reverse switching drive of a stepping motor, power to a heat generating portion of a heat fixing device is cut off.   2. The image forming apparatus according to claim 1, wherein when the paper is reversed by forward / reverse switching driving of the stepping motor, the amount of electric power supplied to the heat generating portion of the heat fixing device is reduced.   3. The image forming apparatus according to claim 1, wherein the power to the heat generating portion of the heat fixing device is cut off or the amount of input electric power is reduced during standby of the second side image data for double-sided printing.   4. The heat generation apparatus according to claim 1, wherein when the power for second-side printing is turned on after waiting for the second-side image data during double-sided printing, heat is generated by the temperature of the temperature detecting means for detecting the temperature of the heat generating portion of the heat fixing device. An image forming apparatus characterized by determining an amount of electric power input to a unit.

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