JP2015004891A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply a stable voltage to an apparatus and prevent the turn-off of a power source of the apparatus to allow the normal operation of the apparatus.SOLUTION: An image forming apparatus of the present invention includes a fixing unit that fixes images with a heater unit, and a power source unit that supplies power to the heater unit. The power source unit includes a voltage detection unit that detects an input voltage, and a heater on-off switching unit that turns on and off the heater unit. The heater on-off switching unit switches on and off of the heater unit on the basis of a result of the voltage detection by the voltage detection unit during the turn-off of the heater.

Description

  The present invention relates to an image forming apparatus having a fixing device.

  The conventional image forming apparatus includes a plurality of heaters as a heat source of the fixing device. In such an image forming apparatus, when energization of each of the heaters is started, the inrush current is suppressed by limiting the heater energization time, and the reduction of the AC input voltage is mitigated.

  Conventionally, the heater is controlled by detecting the difference between the AC voltage when there is no load (heater off) and the AC voltage when the heater is on.

  An example of such a conventional image forming apparatus is disclosed in Patent Document 1.

Japanese Unexamined Patent Publication No. 2011-170079

  However, in general, in an image forming apparatus, in addition to the inrush current of the heater, the image forming apparatus is affected by the line impedance caused by the installation location of the device and the power distribution state, the wiring resistance inside the apparatus, and the coil. Due to this influence, there is a problem that the AC input voltage is reduced, the stable power supply cannot be performed, the apparatus power supply does not operate, and the apparatus cannot operate normally. That is, if a plurality of heaters are turned on at the same time, the AC input voltage will drop due to other factors combined, a stable voltage cannot be supplied, the device power supply will not operate, and the device will not operate normally. is there.

  In order to solve the above-described problem, the present invention provides an image forming apparatus including a fixing device that performs fixing by a heater unit and a power supply unit that supplies power to the heater unit, wherein the power supply unit detects an input voltage. And a heater on / off switching unit for turning on / off the heater unit, and the heater on / off switching unit switches on / off of the heater unit based on a detection voltage result by the voltage detection unit when the heater is turned off. It is characterized by that.

  Since the present invention has the above-described features, it is possible to prevent a decrease in input voltage due to a heater inrush current, a line impedance caused by an installation location of a device and a power distribution state, a wiring resistance or a coil inside the device, and the like, and a stable voltage can be supplied. Can be operated normally.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. 1 is a functional block diagram illustrating the configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a circuit diagram illustrating a detailed configuration of a power supply unit and a heater unit of the image forming apparatus according to the first embodiment of the present invention. 6 is a time chart illustrating changes in voltage and the like of an image forming apparatus according to a comparative example. 3 is a time chart showing changes in voltage and the like of the image forming apparatus according to the first embodiment of the present invention. 6 is a time chart showing changes in voltage and the like when the AC voltage value is changed in the image forming apparatus of FIG. 5. It is a block diagram which shows the structure of the image forming apparatus which concerns on 2nd Embodiment of this invention from a functional surface. FIG. 6 is a block diagram illustrating a power supply unit of an image forming apparatus according to a second embodiment of the present invention. 6 is a time chart showing changes in voltage and the like of an image forming apparatus according to a second embodiment of the present invention. 6 is a flowchart illustrating print control processing of an image forming apparatus according to a second embodiment of the present invention.

  The image forming apparatus according to the present invention detects an AC input voltage when the heater of the fixing device is turned off, and performs heater on / off control. Hereinafter, embodiments of the present invention will be described.

[First Embodiment]
(A-1) Configuration In the first embodiment, a stable voltage is supplied by detecting a decrease in AC voltage when the heater is turned off and turning off one or more of the plurality of heaters during warm-up or printing. Thus, the apparatus power is not turned off, and the apparatus operates normally. The specific configuration of the image forming apparatus according to the present exemplary embodiment will be described below.

  FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus 100 according to the present embodiment. The image forming apparatus 100 is roughly divided into a paper feeding unit 1, an image forming unit 2, a fixing unit 3, and a paper discharge unit 4. The configuration of the image forming apparatus 100 will be described below in the order of printing operations.

  The paper feeding unit 1 includes a paper cassette 5 for setting paper, pickup rollers 6, 7, 8 for feeding paper, and registration rollers 9, 10 for transporting paper to the image forming unit 2. It is configured.

  In the case of a color printing apparatus, the image forming unit 2 is divided for each process color. That is, in the color printing apparatus, four units are arranged in the order of black (K), yellow (Y), magenta (M), and cyan (C) from the right side in the drawing. Each unit includes a photosensitive drum 11 that is an electrostatic latent image carrier, a charging roller 12 that contacts the photosensitive drum 11 and charges the surface of the photosensitive drum 11 uniformly with a high voltage, and a toner that contacts the photosensitive drum 11. A developing roller 13 as a carrier and a toner supply roller 14 that contacts the developing roller 13 and supplies toner to the developing roller 13 are configured.

  Further, the LED head 15 as an exposure unit is disposed on the photosensitive drum 11. Further, separable toner cartridges 16 are arranged corresponding to the respective colors. A transfer belt 17 and a transfer roller 18 are disposed below each unit. The transfer belt 17 is a transfer body that conveys the paper and transfers the toner image formed on the photosensitive drum 11 to the paper. The transfer roller 18 is in contact with the photosensitive drum 11 via the transfer belt 17.

  The fixing unit 3 is a fixing device that performs fixing by a heater unit. In the fixing unit 3, a fixing roller 19 for fixing the toner transferred onto the paper is disposed. Inside the fixing roller 19, a heater 20 typified by a halogen lamp and a temperature detection sensor 21 typified by a thermistor for detecting the surface temperature of the fixing roller 19 are arranged. In the fixing unit 3, the fixing roller 19 heated by the heater 20 and adjusted to the set temperature based on the temperature detected by the temperature detection sensor 21 heats and pressurizes the toner transferred onto the paper and fixes it on the paper. .

  The paper discharge unit 4 is provided with a discharge roller 22 for discharging the paper that has been fixed by the fixing unit 3 to the stacker 23 on the upper surface of the apparatus housing.

  FIG. 2 is a functional block diagram of the configuration of the image forming apparatus according to the present exemplary embodiment. The image forming apparatus shown in FIG. 2 mainly includes a power supply unit 500, a fixing unit 600, and a control unit 700.

  The power supply unit 500 is a power supply unit for supplying power to the heater unit. The power supply unit 500 is roughly divided into a rectification / smoothing circuit 501, a voltage detection circuit 502, a DC-DC conversion unit 503, an AC zero cross circuit 504, and a heater on / off circuit 505. The power supply unit 500 generally operates with an AC voltage output from the commercial power supply 1000. The rectification / smoothing circuit 501 rectifies and smoothes the AC voltage. The voltage detection circuit 502 is a voltage detection unit for detecting an input voltage. The voltage detection circuit 502 detects the input voltage when the heater is off. Here, the voltage detection circuit 502 detects a rectified and smoothed AC voltage. The DC-DC conversion unit 503 supplies a DC voltage to the control unit 700. As an example, 24 VDC is supplied to the actuator system, and 5 VDC and 3.3 V are supplied to the logic system. The type of DC voltage output from the power supply unit 500 is generally determined by matching with the control unit. The AC zero cross circuit 504 is a circuit that outputs an AC zero cross signal to a CPU 701 described later. A heater on / off circuit 505 is a circuit (heater on / off switching unit) that switches on / off of the heater unit based on a detection voltage result by the voltage detection circuit 502 when the heater is turned off by a heater on / off control signal output from a CPU 701 described later. . The heater on / off circuit 505 controls on / off of one or more heater units based on the detection voltage result. Here, since there are two heaters, a main heater and a sub heater, on / off of these two heater sections is controlled.

  The fixing unit 600 is roughly divided into a heater unit 601 and a temperature detection sensor 602. The function of the fixing unit 600 is as described above (explanation based on FIG. 1).

  The control unit 700 includes a CPU 701, a ROM 702, a RAM 703, a temperature detection unit 706, a sensor on / off circuit 707, a high voltage power source 708, a head control unit 709, and an actuator drive unit 710.

  The CPU 701 is a device that operates according to a program written in a ROM 702 of a non-volatile storage component that stores programs and setting data, and performs overall control and heater on / off control of the image forming apparatus. The CPU 701 includes a time measurement counter 711 and the like. A RAM 703 is a memory for storing and reading data. The temperature detection unit 706 divides the output of the temperature detection sensor 602 of the fixing unit 600 by resistance and outputs a temperature detection signal to the CPU 701. The sensor on / off circuit 707 is composed of a transistor, and outputs a sensor off signal from the CPU 701 in the power saving mode to turn off the power supplied to various sensors described later. The high voltage power source 708 is a power source that applies a high voltage to the photosensitive drum and various rollers of the image forming unit 2 described with reference to FIG. The head control unit 709 is a control unit that controls on / off of the LED head 15 described with reference to FIG. The actuator driver 710 is a dedicated driver that outputs a drive signal to an actuator 801 described later based on a logic signal output from the CPU 701.

  Further, the paper feed unit 1, the image forming unit 2, and the paper discharge unit 4 are as described in FIG. The reference numerals are the same as those in FIG.

  The various sensors 800 include a paper travel path sensor (not shown) for detecting a paper position and a sensor for correcting image density and color misregistration provided in the paper feeding unit 1, the image forming unit 2, the fixing unit 600, and the paper discharging unit 4. And so on.

  The actuator 801 is driven by the actuator driving unit 710 described above, and is provided with a motor, a clutch, a solenoid, and an air cooling fan (not shown) disposed in the paper feeding unit 1, the image forming unit 2, the fixing unit 600, and the paper discharge unit 4. Etc. These are controlled by the control unit 700 to realize an image forming operation.

  FIG. 3 is a circuit diagram showing the detailed configuration of the power supply unit 500 and the heater unit 601 described with reference to FIG. The power supply unit 500 is roughly divided into a protection element 2000, a filter 2001, a rectification / smoothing circuit 501, a voltage detection circuit 502, a DC-DC conversion unit 503, an AC zero cross circuit 504, and a heater on / off circuit 505.

  The protection element 2000 includes a fuse for overcurrent protection and a varistor for lightning surge protection. The filter 2001 is generally composed of a common or choke coil and a capacitor. The rectifying / smoothing circuit 501 includes a rectifying diode 5001 and an electrolytic capacitor 5002. The rectifier diode 5001 is composed of four diodes, and generally a bridge diode containing four elements is often used.

  Further, in order to suppress the inrush current of the electrolytic capacitor 5002 when the power is turned on, an inrush suppression circuit (not shown) is provided at the input section. Use a thermistor or a circuit that combines a resistor and a switching device such as a triac or relay.

  The voltage detection circuit 502 includes Zener diodes 6001 and 6006, photocouplers 6002 and 6003, and transistors 6004 and 6005. Although two Zener diodes 6001 and 6006 are illustrated, three or more Zener diodes 6001 and 6006 may be selected depending on the detection voltage or the like. Transistors 6004 and 6005 are NPN transistors, and their collector terminals are connected to a heater on / off control signal. When a voltage drop is detected, the outputs of the photocoupler 6002 and the photocoupler 6003 are at the Hi level, and the register 604 and the transistor 6005 are turned on. The configuration of the voltage detection circuit is an example, and the configuration is not particularly limited.

  The DC-DC converter 503 is as described above with reference to FIG. The AC zero-cross circuit 504 includes a rectifier diode 4001 and a photocoupler 4002, and outputs a Hi level to the CPU 701 at the zero-cross point. The configuration of the AC zero-cross circuit 504 is an example, and the configuration is not particularly limited.

  The heater on / off circuit 505 includes a phototriac 3001 that is output from the CPU 701 and is turned on / off by a main heater on / off control signal, a phototriac 3003 that is turned on / off by a sub heater on / off control signal, and a switch unit that is turned on / off by the phototriac 3001 being turned on / off. And a triac 3004 which is a switch unit that is turned on / off when the photo triac 3003 is turned on / off. Although two circuits are shown in FIG. 3, depending on the number of heaters used, there may be a configuration of one circuit or three or more circuits. The heater on / off circuit 505 is connected to the heater unit 601.

  The heater unit 601 includes heat sources 7001 and 7002 typified by a halogen lamp, and a thermostat 7003 for protection. When the triac 3002 of the heater on / off circuit 505 is turned on, a voltage is supplied to the heat source 7001. In addition, when the triac 3004 of the heater on / off circuit 505 is turned on, a voltage is supplied to the heat source 7002. The temperature of the heat sources 7001 and 7002 is set to a state that is always recognized. Although the temperature of the heat sources 7001 and 7002 may be indirectly measured by the temperature detection sensor 602, a temperature sensor (not shown) is attached to the heat sources 7001 and 7002, and the temperature of the heat sources 7001 and 7002 is directly measured. You may do it. When the power is turned on, the CPU 701 detects the temperature state of the heat sources 7001 and 7002 of the heater unit 601 from the thermistor signal.

(A-2) Operation Next, the operation of the image forming apparatus having the above configuration will be described. Hereinafter, the operation of the image forming apparatus according to the present embodiment will be described in comparison with a conventional image forming apparatus.

  FIG. 4 is a time chart showing changes in voltage and the like of the image forming apparatus of the comparative example. 5 and 6 are time charts showing changes in voltage and the like of the image forming apparatus of the present embodiment. In these time charts, the vertical axis represents voltage or current, and the horizontal axis represents time.

  First, the time chart of the comparative example of FIG. 4 will be described. The waveforms of the comparative example in FIG. 4 are the AC voltage, DC output voltage, AC zero cross signal, main heater control signal, sub heater control signal, and heater current from the top. The abscissa represents the operation mode of the apparatus. The order of the operation modes is an example.

  The AC voltage V1rms is supplied to the power supply unit 500 by turning on a power switch of a device (not shown) at a point (t1) in the comparative example of FIG. Here, V1rms is assumed to be less than the rated voltage, assuming that the AC voltage is reduced due to the line impedance caused by the installation location of the equipment and the distribution status. In Japan, the minimum value of the rated voltage is generally 90V, which is 10% less than the rated 100V. After supplying the AC voltage V1rms, the smoothing capacitor 5002 of the power supply unit 500 is charged, and the DC-DC conversion unit 503 starts outputting the DC output voltages DC24V, 5V, and 3.3V. The time until the DC output voltage reaches a steady state is about several hundred ms. In addition, an AC zero cross signal is output together with the output of the DC output voltage.

  Next, at the point (t2), the DC output voltage reaches a steady state, and warm-up is started. The heater on / off control at the start of warm-up turns on all the heaters in the case of a plurality of heaters. Further, particularly in the case of a halogen lamp, the resistance value at the cold start is as low as several Ω, and the inrush current at the start of energization of the heater is very high. Therefore, for a predetermined time when the heater is turned on, phase control is performed using an AC zero cross signal for the purpose of suppressing inrush current. Note that, when the temperature is high at the start, the resistance value increases, so that the influence of the voltage drop is small at a high temperature, but increases at a low temperature.

  Here, an outline of phase control will be described. First, the CPU 701 detects the edge of the AC zero cross signal twice or more. The AC voltage is rectified by the diode 4001 of the AC zero cross circuit 504, and the photodiode of the photocoupler 4002 is turned off when the AC voltage is below a certain threshold. That is, only in the vicinity of the zero cross point, the photodiode of the photocoupler 4002 is turned off, and the phototransistor of the photocoupler 4002 is turned off. As a result, an Hi level AC zero cross signal is output to the CPU 701 at the zero cross point. Although the time width of the Hi level depends on the circuit configuration and the AC input voltage, it is about 1 to 2 ms. Although the number of times of detection is arbitrary, it is detected 3-4 times in consideration of erroneous detection. Edge detection may be either negative edge or positive edge detection. After the edge detection of the AC zero cross signal is confirmed, the inrush current is suppressed by turning on the heater at an arbitrary point in the AC voltage phase 90-180 ° from the AC zero cross point. In this case, since the resistance value changes depending on the heater temperature, when the heater temperature measured by the temperature sensor is low, the on phase angle of phase control is turned on at a position close to 180 ° (a point where the voltage is as low as possible), and when the heater temperature is high, the resistance value is 90. Turn on at a close angle (high voltage point).

  The main heater control signal, the sub heater control signal, and the heater current start time at the point (t2) in the comparative example of FIG. 4 are waveforms simulating the above. Based on the rated voltage ± 10% and heater resistance-temperature characteristics, the number of phase control and the phase angle are set. The above is the outline of phase control.

  Next, at the point (t2) in the comparative example of FIG. 4, the CPU 701 outputs the main heater control signal Hi level and the sub heater control signal Hi level. As a result, the photo triacs 3001 and 3003 of the heater on / off circuit are turned on, and the triacs 3002 and 3004 are turned on. Thereby, electricity supply to the heat sources 7001 and 7002 is started.

  At this time, the AC voltage drops to V2rms, which is lower than V1rms when the heater is turned off, due to the inrush current of the heater. When V2 is outside the operating voltage range of the power supply control IC (not shown) in the DC-DC converter 503 or lower than the brown-in voltage, the switching operation of the power supply control IC is stopped.

  The point (t3) in the comparative example in FIG. 4 simulates the timing when the DC output voltage starts to droop due to the stoppage of power supply switching. In the comparative example of FIG. 4, an example is described in which the DC output voltage does not recover after drooping. As a result, the display on the operation panel (not shown) is turned off.

  Some have a restart function depending on the circuit configuration, type of power supply control IC, and the like. When the AC voltage is restored with this restart function, the switching operation of the power supply control IC is also restored. In this case, the operation is repeated from (t1) to (t4). Specifically, power supply switching stop ⇒ DC output voltage droop ⇒ Heater off ⇒ AC voltage recovery ⇒ Power supply switching recovery ⇒ DC output power supply recovery ⇒ Heater on ⇒ AC voltage drop ⇒ Power supply switching stop may be repeated. In this case, the display on the operation panel (not shown) is repeatedly turned off and on, and blinks. The above is the description of the comparative example.

  Next, the time chart of this embodiment of FIG. 5 will be described. The waveforms of the present embodiment in FIG. 5 are AC voltage, rectification / smoothing voltage, DC output voltage, voltage detection coupler 6002 output, voltage detection coupler 6003 output, main heater control signal, sub heater control signal, and heater current from the top. The AC zero cross signal is the same as that in the comparative example of FIG. The abscissa represents the operation mode of the apparatus. The order of the operation modes is an example. The AC voltage V1rms is supplied to the power supply unit 500 by turning on a power switch of a device (not shown) at a point (t1 ′) in the present embodiment in FIG. Here, as in the comparative example, it is assumed that the AC voltage V1rms is lowered due to the line impedance caused by the installation location of the equipment and the power distribution state, and is less than the rated voltage.

  Next, at the point (t2 '), after the AC voltage V1rms is supplied, the DC output voltage DC24V, 5V, 3.3V output is started.

  Here, the voltage detection circuit will be described. In order to detect a peak voltage obtained by rectifying and smoothing the AC effective voltage, the voltage detection value is about 100 × √2 = 141 V in the case of AC 100 V input. Further, by selecting the Zener diodes 6001 and 6006, it is possible to have two arbitrary threshold values Vz1 and Vz2. These threshold values are determined in the range from the AC rated voltage Min to the power supply control IC operating voltage. As an example, two threshold values are set as follows: Vz1 = power supply control IC operating voltage Min × margin 1.1 = 50 × √2 × 1.1 = 78 V, Vz2 = AC input voltage Min × √2 × margin 0.95 = 90 × If √2 × 0.95 = 120V, it is necessary to select a Zener diode 6001 having a Zener voltage of around 80V and a Zener diode 6006 having a Zener diode voltage of around 40V. The margin is determined arbitrarily. The relationship between the rectified / smoothed voltages V1peak and V3peak obtained by rectifying and smoothing the AC voltage by the rectifying / smoothing circuit 501 of the power supply unit 500 and the thresholds Vz1 and Vz2 of the voltage detection circuit is Vz2> V1peak> V3peak> Vz1. .

  In the case of 85V AC input, the Zener diode 6001 is turned on, the photodiode inside the photocoupler 6003 is turned on, and the phototransistor inside the photocoupler 6003 is turned on, so that the output of the photocoupler 6003 becomes Lo. Since the transistor 6004 connected to the output of the photocoupler 6003 is turned off, the main heater on / off control signal connected to the transistor 6004 becomes controllable by the CPU 701.

  On the other hand, the Zener diode 6006 is off, the photodiode inside the photocoupler 6002 is turned off, and the phototransistor inside the photocoupler 6002 is turned off, so that the output of the photocoupler 6002 becomes Hi. Since the transistor 6005 connected to the output of the photocoupler 6002 is turned on, the sub-heater on / off control signal connected to the transistor 6005 is fixed to Lo. Since the heater ON / OFF control signal output from the CPU 701 is Hi active, the sub heater ON / OFF control signal is fixed to OFF with hardware. The above is the description of the voltage detection circuit.

  Next, at the point (t3 ′), the output of the voltage detection coupler 6002 becomes Lo and the output of the voltage detection coupler 6003 becomes Hi, so that the main heater control signal can be controlled and the sub heater control signal is fixed off.

  Next, at the point (t4 '), the DC output voltage reaches a steady state, and warm-up is started. Unlike the comparative example, only the main heater is turned on because the sub heater is fixed off. Therefore, it is possible to suppress an AC voltage drop, and there is an effect that normal operation can be continued without going out of the operating voltage range of the power supply control IC.

  Next, at the point (t5 ′), after the warm-up is completed, if a print instruction is not generated, a standby state is entered. When a plurality of heaters are provided and divided into a high power heater and a low power heater, all the heaters are turned off or only the low power heaters are turned on during standby. The sub-heater is mainly used as a warm-up aid. In the present embodiment, when the AC voltage drop occurs, the sub heater is fixed off with hardware, so that the main heater is turned on or the sub heater is turned off during standby. FIG. 5 shows an example in which the AC voltage drop continues, and the heater is turned off during standby.

  Next, when a printing instruction is issued at the point (t6 '), printing is started. The above is the description of the time chart of FIG.

  Next, the time chart of this embodiment of FIG. 6 will be described. The difference from the time chart of FIG. 5 is the AC voltage value. The relationship between the AC voltages V1rms and V3rms in FIG. 5 and V4rms in FIG. 6 is V1rms> V3rms> V4rms. The relationship between the rectified / smoothed voltage V4peak and the thresholds Vz1 and Vz2 of the voltage detection circuit is Vz2> Vz1> V4peak. That is, this is an example in which the main heater and the sub heater are fixed off.

  At the point (t1 ″), the AC voltage V1 is supplied to the power supply unit 500 by turning on a power switch of a device (not shown).

  At the point (t2 ″), after the AC voltage V1 is supplied, the DC output voltage DC24V, 5V, 3.3V output is started.

  At the point (t3 ″), the Zener diode 6001 is turned off, the photodiode inside the photocoupler 6003 is turned off, and the phototransistor inside the photocoupler 6003 is turned off, so that the output of the photocoupler 6003 becomes Hi. Since the transistor 6004 connected to the output of the photocoupler 6003 is on, the main heater on / off control signal connected to the transistor 6004 is fixed to Lo.

  On the other hand, the Zener diode 6006 is off, the photodiode inside the photocoupler 6002 is turned off, and the phototransistor inside the photocoupler 6002 is turned off, so that the output of the photocoupler 6002 becomes Hi. Since the transistor 6005 connected to the output of the photocoupler 6002 is turned on, the sub heater on / off control signal connected to the transistor 6005 is fixed to Lo.

  Next, at the point (t4 ″), warm-up is started, and the CPU 701 outputs the main heater control signal Hi and the sub heater control signal Hi. However, since the transistors 6004 and 6005 are fixed to Lo, the heater is turned on. Don't be.

  At the point (t5 ″), the temperature detection sensor 602 of the fixing unit detects the temperature for a predetermined time, and when the CPU 701 determines that the temperature is low, the operation panel display (not shown) indicates a low temperature error, and the operation stops in the device error state. Become.

(A-3) Effect As described above, according to the first embodiment, by detecting a decrease in the AC voltage when the heater is turned off and turning off one or more of the plurality of heaters during warming up or printing, A stable voltage can be supplied, the apparatus power supply is not turned off, and the apparatus operates normally. In addition, an effect that device error display due to a decrease in AC voltage can be obtained.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the present embodiment, the heater on / off circuit 505 serving as a heater on / off switching unit shifts the on timing of one or more heaters based on the detection voltage result. In this embodiment, since there are two heaters, a main heater and a sub heater, specifically, the voltage detection result is output to the CPU, and both the main heater and the sub heater are turned on by shifting the on timing, so that the warm-up time This makes it possible to shorten the time, enable the sub heater to be turned on during standby, and shorten the time from the printing instruction to the start of printing.

(B-1) Configuration First, a configuration of an image forming apparatus according to the second embodiment will be described. FIG. 7 is a functional block diagram of the configuration of the image forming apparatus according to the second embodiment. The image forming apparatus of this embodiment is different from the image forming apparatus of the first embodiment in that the output of the voltage detection circuit 9000 of the power supply unit 500 is connected to the CPU 701 of the control unit 700. Other configurations are the same as those of the image forming apparatus according to the first embodiment shown in FIG.

  FIG. 8 is a block diagram showing a power supply unit according to the second embodiment. This power supply unit is different from the first embodiment in that the output of the photocoupler 9004 of the voltage detection circuit 9000 is a voltage drop 2 signal and the output of the photocoupler 9003 is a voltage drop 1 signal, and the voltage detection circuit of the first embodiment. The point is that the transistors 6004 and 6005 of 502 are deleted. The structure of other parts is the same as that of the first embodiment. For this reason, the same code | symbol as 1st Embodiment is attached | subjected to the part similar to 1st Embodiment, and the description is abbreviate | omitted.

 By outputting the voltage detection result of the voltage detection circuit 9000 described above to the CPU 701 and turning on both the main heater and the sub-heater at different timings, the warm-up time can be shortened. As a result, unlike the heater off by the hardware circuit of the first embodiment, the sub heater can be turned on during standby, and the time from the print instruction to the start of printing can be shortened.

  In addition, it is possible to notify the user of a voltage drop abnormality, such as by displaying an apparatus error display as an AC voltage drop error.

(B-2) Operation Next, the operation of the image forming apparatus of this embodiment will be described based on the time chart of FIG. FIG. 9 is a time chart showing changes in voltage and the like of the image forming apparatus of the present embodiment. In this time chart, the vertical axis represents voltage or current, and the horizontal axis represents time. The waveforms of this embodiment in FIG. 9 are AC voltage, rectification / smoothing voltage, DC output voltage, voltage drop 2 signal, voltage drop 1 signal, main heater control signal, sub heater control signal, and heater current from the top. Since the AC zero cross signal is the same as that of the first embodiment, the description thereof is omitted. The abscissa represents the operation mode of the apparatus. The order of the operation modes is an example.

  The AC voltage V1′rms is supplied to the power supply unit 500 by turning on a power switch of a device (not shown) at the point (T1) in the present embodiment in FIG. Here, as in the first embodiment, V1′rms is assumed to be less than the rated voltage, assuming that the AC voltage is reduced due to the line impedance caused by the installation location of the equipment and the power distribution state.

  Next, at the point (T2), after supplying the AC voltage V1'rms, the DC output voltage DC24V, 5V13.3V output is started.

  At the point (T3), the voltage drop 2 signal becomes Lo output and the voltage drop 1 signal becomes Hi output.

  Here, the voltage detection circuit will be described. In order to detect a peak voltage obtained by rectifying and smoothing the AC effective voltage, the voltage detection value is about 100 × √2 = 141 V in the case of AC 100 V input. Further, by selecting the Zener diodes 9001 and 9002, two arbitrary threshold values Vz1 'and Vz2' can be provided, and the threshold values are determined within a range from the AC input voltage Min to the power supply control IC operating voltage. As an example, two threshold values are set as follows: Vz1 ′ = power supply control IC operating voltage Min × margin 1.1 = 50 × √2 × 1.1 = 78 V, Vz2 ′ = AC input voltage Min × √2 × margin 0.95 = If 90 × √2 × 0.95 = 120V, it is necessary to select a Zener diode 9001 having a Zener voltage around 80V and a Zener diode 9002 having a Zener diode voltage around 40V. The margin is determined arbitrarily. The relationship between the rectified / smoothed voltages V1'peak and V3'peak and the thresholds Vz1 'and Vz2' of the voltage detection circuit is Vz2 '> V1'peak> V3'peak> Vz1'.

  If the input voltage is 85V AC, the Zener diode 9001 is turned on, the photodiode inside the photocoupler 9003 is turned on, and the phototransistor inside the photocoupler 9003 is turned on, so that the output of the photocoupler 9003 becomes Lo. This output is a voltage drop 1 signal and is input to the CPU 701.

  On the other hand, the Zener diode 9002 is off, the photodiode inside the photocoupler 9004 is turned off, and the phototransistor inside the photocoupler 9004 is turned off, so that the output of the photocoupler 9004 becomes Hi. This output is a voltage drop 2 signal and is input to the CPU 701. The above is the description of the voltage detection circuit.

Next, at the point (T4), the DC output voltage reaches a steady state, and warm-up is started. The CPU 701 to which the voltage drop 1 signal is input as Lo and the voltage drop 2 signal is input as Hi outputs the main heater control signal Hi to turn on the main heater, and after a predetermined time has passed, outputs the sub heater control signal Hi to output the sub heater. Turn on. The elapsed time is set so that the sub heater is turned on after the main heater inrush current converges. Here, as an example, it is set to 600 ms. The relationship between the polarities of the voltage drop 1 signal and the voltage drop 2 signal and the on / off control of the main heater and the sub heater is as follows.

  Next, at the point (T5), after the warm-up is completed, if no print instruction is issued, a standby state is entered. When a plurality of heaters are provided and divided into a high power heater and a low power heater, all the heaters are turned off or only the low power heaters are turned on during standby. The sub-heater is mainly used as a warm-up aid.

  In the present embodiment, it is assumed that the sub-heater is turned on during standby for the purpose of reducing not only the warm-up time but also the time from the printing instruction to the start of printing. From the viewpoint of reducing power consumption, the sub-heater may be turned off during standby as in the first embodiment.

  (T6) When a print instruction is issued at the point, printing is started. The CPU 701 to which the voltage drop 1 signal is input Lo and the voltage drop 2 signal is input Hi outputs the main heater control signal Hi to turn on the main heater, and after a predetermined time has passed, outputs the sub heater control signal Hi to turn on the sub heater. Let In this embodiment, the main heater and the sub heater are turned on during printing. However, depending on the heater power configuration, the main heater and the sub heater may be turned on during warm-up, and only the main heater may be turned on during printing. The above is the description of the time chart of the present embodiment in FIG.

  Next, the print control process of the image forming apparatus according to the present embodiment will be described with reference to the flowchart of FIG.

  STEP 1: DC output voltages DC 24 V, 5 V, and 3.3 V are supplied to the control unit 700 by turning on a power switch of a device (not shown).

  STEP 2: The CPU 701 of the control unit 700 determines whether or not it is the first voltage drop based on the polarity of the voltage drop 1 signal output from the voltage detection circuit 9000. Lo output is normal and Hi output is low.

  STEP 3: When the voltage drop 1 signal output Lo is input to the CPU 701, the CPU 701 determines that the first voltage is normal, and then determines the second voltage drop by the polarity of the voltage drop 2 signal output from the voltage detection circuit 9000. It is determined whether or not there is. As with the voltage drop 1 signal, the Lo output is normal and the Hi output is low.

  STEP 4: When the voltage drop 2 signal output Hi is input to the CPU 701, it is determined that the second voltage is abnormal, and warm-up is started.

  STEP 5: The main heater control signal Hi is output from the CPU 701, and the sub heater control signal Hi is output after a predetermined time has elapsed.

  STEP 6: When the voltage drop 2 signal output Lo opposite to STEP 4 is input to the CPU 701 as the determination result of STEP 3, it is determined that the second voltage is normal, and warm-up is started.

  STEP 7: The CPU 701 simultaneously outputs the main heater control signal Hi and the sub heater control signal Hi.

  STEP 8: The temperature detection sensor output of the fixing unit 600 is fed back to the CPU 701, heater on / off control is performed, and the warm-up is completed after reaching the target temperature.

  STEP 9: The control unit 700 accepts a print instruction from the host 802 or the like. Applications can be accepted during the warm-up period before STEP9. It is determined whether a print instruction is generated and printing is started.

  STEP 10: When a print instruction is not generated, the process shifts to a standby mode.

  STEP 11: It is determined whether or not it is the first voltage drop based on the polarity of the voltage drop 1 and 2 signals output from the voltage detection circuit 9000. Lo output is normal and Hi output is low.

  STEP 12: When the voltage drop 1, 2 signal output Lo is input to the CPU 701, it is determined that the first and second voltages are normal, the sub heater on / off control is started, and the process returns to the print waiting state of STEP 9.

  STEP 13: When a print instruction is issued in STEP 9, the CPU 701 outputs a main heater control signal Lo and a sub heater control signal Lo, and the heater on / off control is terminated.

  STEP 14: The CPU 701 determines whether or not it is the first voltage drop based on the polarity of the voltage drop 1 signal output from the voltage detection circuit 9000. As above, Lo output is normal and Hi output is low.

  STEP 15: When the voltage drop 1 signal output Lo is input to the CPU 701, the CPU 701 determines that the first voltage is normal, and then the second voltage drop depends on the polarity of the voltage drop 2 signal output from the voltage detection circuit 9000. It is determined whether or not there is. As above, Lo output is normal and Hi output is low.

  STEP 16: When the voltage drop 2 signal output Hi is input to the CPU 701, the CPU 701 determines that the second voltage is abnormal and starts printing.

  STEP 17: The main heater control signal Hi is output from the CPU 701, and the sub heater control signal Hi is output after a predetermined time has elapsed.

  STEP 18: If the voltage drop 2 signal output Lo, which is the reverse of STEP 16, is input to the CPU 701, it is determined that the second voltage is normal, and printing is started.

  STEP 19: The CPU 701 simultaneously outputs the main heater control signal Hi and the sub heater control signal Hi.

  STEP 20: The temperature detection sensor output of the fixing unit 600 is fed back to the CPU 701, heater on / off control is performed, and printing is completed.

  STEP 21: After printing is completed, the CPU 701 outputs the main heater control signal Lo and the sub heater control signal Lo, and ends the heater on / off control.

  STEP 22: When the voltage drop 1 signal output Hi is input to the CPU 701 in STEPs 2, 11, and 14, it is determined that the first voltage is abnormal, and the operation of the apparatus is stopped. In addition, an AC voltage drop error is displayed on the operation panel to inform the user of the abnormality.

(B-3) Effect As described above, according to the second embodiment, it is possible to shorten the warm-up time by outputting the voltage detection result to the CPU 701 and turning on both the main heater and the sub-heater while shifting the on-timing. It becomes. Further, unlike the heater off by the hardware circuit of the first embodiment, the sub heater can be turned on during standby, and the time from the printing instruction to the start of printing can be shortened. In addition, it is possible to notify the user of a voltage drop abnormality, such as changing the device error display to an AC voltage drop error.

(C) Modified Example In the above-described embodiments, the case where the main heater and the sub heater are provided is described as an example. However, the present invention can also be applied to an apparatus including three or more heaters. In this case, each heater is turned on / off by a heater on / off circuit 505 connected to each heater. For example, one or more of the three or more heaters are turned on / off, each heater is turned on / off in turn, or all the heaters are turned on / off simultaneously.

  In the first embodiment, the threshold value is provided and the main heater and the sub heater are selectively turned on / off by comparing the input voltage with the threshold value. However, when three or more heaters are provided, 1 or 2 is provided. The above heaters are selectively turned on / off.

  In the second embodiment, the main heater and the sub-heater are shifted on timing to turn on both the main heater and the sub-heater. The time for shifting the on timing, that is, the on-timing time difference is adjusted according to the temperature of each heater. You may make it do. Specifically, the main and sub on-timing time difference is lengthened when each heater is low temperature, and is shortened when each heater is high temperature. In this case, the temperature of the heater unit 601 is detected by the temperature detection sensor 602. Further, a temperature sensor that directly detects the temperature of the heater unit 601 may be newly provided. The CPU 701 captures this temperature information, compares it with a preset value, and changes the on-timing time difference. The change in the on-timing time difference is not limited to a two-stage change performed only once, but may be a three-stage or more change. The optimal time difference and the number of changes are set according to the characteristics of the heat sources 7001 and 7002.

  In addition, the function of selectively turning on and off the plurality of heaters of the first embodiment may be combined with the function of shifting the on timing of the second embodiment. For example, one of the three heaters may be turned off, and the other two may be turned on by shifting the on timing. The same applies when four or more heaters are provided.

  The present invention is not limited to the embodiments and the like, and various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention. The effects of the present invention are not limited to the contents described above. Moreover, the content of the member which appears in the whole specification is an illustration to the last, Comprising: It is not limited to these description. Various additions, modifications, combinations, partial deletions, and the like can be made without departing from the concept and spirit of the present invention derived from the contents defined in the claims and equivalents thereof.

    Each of the above embodiments has been described with respect to a printer device, particularly a tandem color four-color printer device, but the present invention is not limited to this. The present invention can also be applied to other image forming apparatuses such as a printer apparatus having five or more colors, a printer apparatus having less than four colors, a monochrome printer apparatus, and a copying apparatus.

  1: paper feeding unit, 2: image forming unit, 3: fixing unit, 4: paper discharge unit, 5: paper cassette, 6, 7, 8: pickup roller, 9, 10: registration roller, 11: photosensitive drum, 12 : Charging roller, 13: developing roller, 14: toner supply roller, 15: LED head, 16: toner cartridge, 17: transfer belt, 18: transfer roller, 19: fixing roller, 20: heater, 21: temperature detection sensor, 22: discharge roller, 23: stacker, 100: image forming apparatus, 500: power supply unit, 501: rectification / smoothing circuit, 502: voltage detection circuit, 503: DC-DC conversion unit, 504: AC zero cross circuit, 505: heater ON / OFF circuit, 600: fixing unit, 601: heater unit, 602: temperature detection sensor, 700: control unit, 701: CPU, 702: ROM, 703: RAM, 706: temperature detection unit, 7 7: Sensor on / off circuit, 708: High voltage power supply, 709: Head control unit, 710: Actuator drive unit, 711 counter, 800: Sensor, 801: Actuator, 1000: Commercial power supply, 2000: Protection element, 2001: Filter, 3001: Phototriac, 3002: Triac, 3003: Phototriac, 3004: Triac, 4001: Rectifier diode, 4002: Photocoupler, 5001: Rectifier diode, 5002: Electrolytic capacitor, 6001, 6006: Zener diode, 6002, 6003: Photocoupler, 6004, 6005: Transistor, 7001, 7002: Heat source, 7003: Thermostat, 9000: Voltage detection circuit, 9001, 9002: Zener diode, 9004: Photocap , 9003: Photo-coupler.

Claims (8)

An image forming apparatus comprising: a fixing device that performs fixing by a heater unit; and a power supply unit that supplies power to the heater unit.
The power supply unit includes a voltage detection unit that detects an input voltage, and a heater on / off switching unit that turns the heater unit on and off.
The image forming apparatus according to claim 1, wherein the heater on / off switching unit switches on / off of the heater unit based on a detection voltage result of the voltage detection unit when the heater is off.   The image forming apparatus according to claim 1, wherein the heater on / off switching unit turns on or off one or more heaters based on the detection voltage result.   The image forming apparatus according to claim 1, wherein the heater on / off switching unit shifts an on timing of one or a plurality of heaters based on the detection voltage result.   The image forming apparatus according to claim 1, wherein the voltage detection unit includes a Zener diode, a photocoupler, and a transistor.   The image forming apparatus according to claim 4, wherein a threshold value is set by the Zener diode.   The image forming apparatus according to claim 1, wherein the heater on / off switching unit is a circuit.   The image forming apparatus according to claim 6, wherein the circuit uses a switch element.   The image forming apparatus according to claim 3, wherein an on-timing of the heater on / off switching unit is controlled by a control unit.

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