JP2004219832A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the opening/closing state of an opening/closing mechanism from being erroneously detected and also to reduce power consumption at the standby time. <P>SOLUTION: The image forming apparatus is equipped with a power source circuit generating voltage to be supplied to an internal circuit, a high voltage generation circuit 2 generating high voltage from the voltage generated by the power source circuit, the opening/closing mechanism provided in an apparatus main body, a switch 15 provided between the power source circuit and the high voltage generation circuit and changing a conduction state interlocked with the opening/closing mechanism, and a control part 6 controlling the driving of the high voltage generation circuit based on the voltage applied through the switch, and forms an image according to an electrophotographic process. A diode 30 preventing the flow of current from the high voltage generation circuit 2 to the control part is provided in the apparatus. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus, and more particularly to detection of an open / closed state of a door that is opened when exchanging consumables in an image forming apparatus that forms an image according to an electrophotographic process.
[0002]
[Prior art]
2. Description of the Related Art Laser beam printers (hereinafter, also referred to as LBPs) have become widespread in recent years due to their printing speed and high printing quality, coupled with progress in price reduction.
[0003]
LBP uses an electrophotographic process, in which toner is attached to a latent image formed by a laser on a rotating photoreceptor (drum), developed, transferred to recording paper, and then heated and fixed to perform printing. .
[0004]
FIG. 2 is a block diagram showing a schematic control configuration of a general laser beam printer. As shown in FIG. 2, a general LBP is composed of a low-voltage generating circuit 1, a high-voltage generating circuit 2, a laser scanning unit 3, a heating and fixing unit 4, a transporting unit 5, and a control circuit 6 that controls these units. It is configured. The low-voltage power supply circuit 1 supplies power to other units, and the control circuit 6 transmits a control signal to all other units except the low-voltage power supply circuit 1.
[0005]
The output of the high voltage generation circuit 2 is connected to the rotating photoconductor. Since the rotating photoconductor and the toner container are consumables, they are configured to be easily removed by a user, and can be removed by opening and closing a door attached to the exterior.
[0006]
As described above, the LBP configured so that the user can easily contact the inside of the device is provided with a switch that operates in conjunction with the opening and closing of the door, and supplies power to the high-voltage circuit 2 when the door is open. Shut off and take protective measures to prevent electric shock from the user. Further, the control circuit 6 detects the open / closed state of the door according to whether or not the voltage is reduced by opening / closing the switch.
[0007]
FIG. 3 is a circuit diagram showing a configuration of a part related to development and a part of the control circuit 6 in the high voltage generator 2. With reference to this figure, a mechanism for opening and closing the door will be described.
[0008]
3, reference numeral 50 denotes a developing DC generation circuit; 60, an ASIC; 11, 13, 14, 16, 19, 22, 23, resistors; 12, 17, and 18 transistors; 20, an electrolytic capacitor; Is a door interlock switch. Power of 24 V, 3.3 V, etc. is supplied from the low-voltage power supply circuit 1.
[0009]
In FIG. 3, when the door is closed, the switch 15 is closed, and 24 V is supplied to the signal line 24R. Then, the voltage of 24 V is applied to the resistors 22 and 23, and the divided voltage is applied to the signal line 24. Here, for example, assuming that the resistance 22 is 220 kΩ and the resistance 23 is 33 kΩ, a voltage of 3.13 V is applied to the signal line 24, and the ASIC 60 detects this voltage and determines that the door is closed. On the other hand, when the door is opened and the switch 15 is open, the signal line 24 is connected to GND via the resistor 23, so that the voltage is 0 V, and the ASIC determines that the door is open.
[0010]
When a print signal is input to the ASIC 60 with the door closed, the ASIC 60 drives the high voltage generation circuit 2. Here, the operation of generating a development output in the high voltage generation circuit will be described.
[0011]
First, the ASIC 60 outputs a rectangular wave to the signal line 27. The resistor 11 and the transistor 12 amplify the voltage of the signal input from the signal line 27, for example, amplify a signal having an amplitude of 3.3V into a signal having an amplitude of 24V. The resistors 16 and 19 and the transistors 17 and 18 constitute a push-pull circuit for current-amplifying the amplified signal having an amplitude of 24 V. The DC signal of the amplified signal is cut by a DC component cut capacitor 20 at the subsequent stage, boosted by a transformer 21, and converted into a rectangular wave having an amplitude of, for example, 1300 V or more. Thereafter, the output is added to the output of the developing DC generation circuit 50 and applied to the photoconductor as a development output 26.
[0012]
When the ASIC 60 malfunctions and outputs a rectangular wave when the door is opened, the voltage 24R supplied to the current amplification circuit is cut off and the output is not performed, so that the user is safe from electric shock and the like. Is secured.
[0013]
[Problems to be solved by the invention]
Normally, the signal line 27 is set to a fixed level except during development output. When the signal line 27 is set at the L level, the transistor 12 is turned off, and when the switch 15 is closed, 24 V is applied to the bases of the transistors 17 and 18 so that the transistor 17 is turned on and the transistor 18 is turned off. Become. Therefore, electric charges are accumulated in the capacitor 20.
[0014]
When the door is opened, the voltage of the signal line 24R should drop to 0V, but the charge stored in the capacitor 20 and the voltage of 24V applied to the base of the transistor 17 should be reduced. Due to the voltage, a current is generated in the resistors 16, 22, and 23, and a predetermined voltage may be generated in the signal line 24. In this case, the door may be erroneously detected as being closed.
[0015]
In order to prevent such erroneous detection, it is conceivable to supply 24 V applied to the resistor 11 from the signal line 24R after passing through the switch 15. However, in this case, the switch 15 is opened. At this time, the transistor 18 is turned on, and the charge stored in the capacitor 20 is rapidly discharged. Then, a voltage is generated on the secondary side of the transformer 21, causing a problem that toner scatters on the photoconductor.
[0016]
For the above reasons, in the circuit configuration shown in FIG. 3, the signal line 27 is set to the H level, the transistor 12 is turned on, the transistor 17 is turned off, and the transistor 18 is turned on. When 15 is open, it is necessary to ensure that the voltage of the signal line 24R becomes 0V. Therefore, a current always flows through the resistor 11, thereby increasing the power consumed during standby.
[0017]
The present invention has been made in view of the above situation, and has as its object to prevent erroneous detection of the open / close state of the opening / closing mechanism and reduce power consumption during standby.
[0018]
[Means for Solving the Problems]
An image forming apparatus as one embodiment of the present invention that achieves the above object is an image forming apparatus that forms an image according to an electrophotographic process,
A power supply circuit for generating a voltage to be supplied to the internal circuit;
A high voltage generation circuit that generates a high voltage from a voltage generated by the power supply circuit;
An opening / closing mechanism provided in the device main body;
A switch that is provided between the power supply circuit and the high-voltage generation circuit and that changes a conduction state in conjunction with the opening / closing mechanism;
A control unit that controls driving of the high-voltage generating circuit based on a voltage applied through the switch;
Backflow prevention means for preventing a current from flowing from the high voltage generation circuit to the control unit.
[0019]
That is, according to the present invention, a power supply circuit that generates a voltage to be supplied to an internal circuit, a high voltage generation circuit that generates a high voltage from a voltage generated by the power supply circuit, an opening / closing mechanism provided in an apparatus main body, and a power supply circuit A switch provided between the switch and the high-voltage generation circuit to change the conduction state in conjunction with the opening and closing mechanism; and a control unit that controls the driving of the high-voltage generation circuit based on a voltage applied through the switch. In an image forming apparatus for forming an image according to an electrophotographic process, a backflow preventing means for preventing a current from flowing from a high voltage generating circuit to a control unit is provided.
[0020]
With this configuration, it is possible to prevent a current flowing from the high voltage generation circuit to the control unit when the switch is in a non-conductive state, so that the voltage applied to the control unit via the switch is different from when the switch is in a conductive state. There is a large change between the state of conduction and the state of conduction.
[0021]
Therefore, erroneous detection of the opening / closing state of the opening / closing mechanism can be prevented, and power consumption during standby can be reduced.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In each of the drawings, similar parts are denoted by the same reference numerals, and description thereof will be omitted.
[0023]
<First embodiment>
As described above, the present invention is an image forming apparatus that forms an image according to an electrophotographic process, and includes a power supply circuit that generates a voltage to be supplied to an internal circuit, and a high-voltage circuit that generates a high voltage from a voltage generated by the power supply circuit. A voltage generating circuit, an opening / closing mechanism provided in the apparatus main body, a switch provided between the power supply circuit and the high-voltage generating circuit, which changes a conduction state in conjunction with the opening / closing mechanism, and is applied via the switch. An image forming apparatus comprising: a control unit that controls driving of a high-voltage generation circuit based on a voltage; and a backflow prevention unit that prevents a current from flowing from the high-voltage generation circuit to the control unit. The embodiment also has the following features.
[0024]
The backflow prevention means is a diode, and the high voltage generation circuit generates a high voltage used for developing the latent image formed on the photoconductor.
[0025]
The opening and closing mechanism is a door that is opened when exchanging consumables.
[0026]
The voltage generated by the power supply circuit is 24V, and the voltage generated by the high voltage generation circuit is 1300V or more.
[0027]
FIG. 5 is a diagram showing a configuration of an image forming apparatus (laser beam printer) 1200 according to the present invention, in which a photosensitive drum 1201 which is a member to be charged and rotates in a direction indicated by an arrow A in FIG. Charging device 1202, a developing device for developing an electrostatic latent image formed on photoconductor drum 1201 by laser 1210 into a visible image, and a developer remaining on photoconductor drum 1201 after transfer of the visible image And a cleaning device 1220 for removing the toner.
[0028]
The developing device includes a toner 1205 as a developer contained in a developing container (cartridge) 1206, a remaining amount detecting unit for detecting the remaining amount of the toner, a developing sleeve 1203 that carries and transports the toner, and a developing sleeve 1203 that is carried by the developing sleeve 1203. The cleaning device 1220 includes a developing blade 1204 that regulates the toner layer to a uniform thickness, and a cleaning blade that scrapes toner remaining on the photosensitive drum 1201 and stores the toner scraped by the cleaning blade. Waste developer container.
[0029]
The paper as a recording medium accommodated in the paper feed cartridge 1230 is supplied to the developing device one by one in the direction indicated by the arrow B in the drawing, and an image is formed with toner in the developing device and fixed by the fixing device 1240. Is discharged. Reference numeral 1250 denotes a communication unit that receives image data and control data to be recorded from a host device, and also, for example, controls the status of the image forming apparatus such as when the remaining amount of toner, paper, or the like becomes a predetermined amount or less. Notify the device. A control circuit 1260 controls the entire image forming apparatus, and includes a CPU, a memory, and the like.
[0030]
The schematic control configuration of the image forming apparatus of the present embodiment is the same as that of FIG. 2 described above, and the details are omitted.
[0031]
FIG. 1 is a circuit diagram showing, similarly to FIG. 3, a portion related to development of the high-voltage generating circuit 2 and a configuration related to opening and closing of a door of the control circuit 6 in the present embodiment.
[0032]
1 differs from the circuit of FIG. 3 in that a diode 30 is provided between the resistors 16 and 24R. Further, in the present embodiment, the logic of the signal line 27 at the normal time is at the L level, and the transistor 12 is set to be in the OFF state.
[0033]
In FIG. 1, when a print signal is input to the ASIC 60 with the door closed, the ASIC 60 outputs a rectangular wave via the signal line 27. The resistor 11 and the transistor 12 amplify the signal input from the signal line 27 to an amplitude of 24V. The resistors 16 and 19 and the transistors 17 and 18 current-amplify the amplified signal having an amplitude of 24V. At this time, although the diode 30 exists, a sufficient current flows into the resistor 16 because the voltage supplied through the signal line 24R is high. The signal amplified by the transistors 17 and 18 has its DC component cut by a DC component cutting capacitor 20 at the subsequent stage, is boosted by a transformer 21, and is converted into a rectangular wave having an amplitude of, for example, 1300 V or more. Thereafter, the output is added to the output of the developing DC generation circuit 50 and applied to the photoconductor as a development output 26.
[0034]
On the other hand, when the door is opened, the transistor 12 is turned off, and a voltage of 24 V is applied to the base of the transistor 17. Further, since the transistor 18 is turned off, a voltage of 24 V is applied to the collector of the transistor 17 and the resistor 16. However, since the diode 30 is provided between the resistor 16 and the signal line 24R, the voltage of 24V is not applied to the resistors 22 and 23, and the voltage of the signal line 24 becomes 0V.
[0035]
As described above, according to the present embodiment, erroneous detection of the open / closed state of the door can be prevented, and power consumption during standby can be reduced.
[0036]
<Second embodiment>
Hereinafter, a second embodiment of the present invention will be described. The description of the same parts as those in the first embodiment will be omitted, and the description will focus on the characteristic parts of the present embodiment.
[0037]
In the first embodiment, an example in which the present invention is applied to a developing circuit as a high voltage generating circuit has been described. However, the present invention can be similarly applied to other high voltage generating circuits. In the second embodiment, the present invention is applied to a transfer circuit that generates a high voltage used for transferring a latent image developed on a photoconductor to a recording medium, as a high voltage generation circuit.
[0038]
FIG. 4 is a circuit diagram showing, similarly to FIG. 3, a portion related to transfer of the high-voltage generating circuit 2 and a configuration related to opening and closing of a door of the control circuit 6 in the embodiment.
[0039]
4, an ASIC 60 outputs a PWM signal 27 and a pulse signal 28 as a transfer drive signal. The PWM signal 27 is converted into a voltage of 0 to 3.3 V by a resistor and a capacitor (not shown) according to the duty. The converted signal is input to the non-inverting terminal of the OP amplifier 35. The OP amplifier 35 and the resistors 34 and 36 amplify the 0 to 3.3 V signal input to the non-inverting terminal into a 0 to 24 V signal by a non-inverting amplifier circuit. The amplified signal of 0 to 24 V is input to the resistor 33 and the base of the transistor 32, and controls the voltage applied to the transformer 39.
[0040]
Therefore, the ASIC 60 can control the voltage applied to the transformer 39 by controlling the duty of the output signal line 27. On the other hand, the pulse signal 28 output from the ASIC 60 drives the transistor 37 via the resistor 38. With such a configuration, an AC wave having the same frequency as the pulse signal 28 with the amplitude set by the PWM signal 27 is input to the transformer 39 and boosted by the transformer 39.
[0041]
The diodes 41, 43, 45 and the capacitors 40, 42, 44 constitute a double rectifier circuit, rectify and add the output of the transformer 39, and output it as a transfer output 47.
[0042]
Also in the present embodiment, when the switch 15 is opened and the PWM signal 27 is output, a voltage of 24 V is applied to the collector of the transistor 32. However, since the diode 30 is provided between the resistor 31 and the signal line 24R, the voltage of 24V is not applied to the resistors 22 and 23, and the voltage of the signal line 24 becomes 0V.
[0043]
As described above, according to the present embodiment, erroneous detection of the open / closed state of the door can be prevented, and power consumption during standby can be reduced.
[0044]
<Other embodiments>
In the embodiment described above, the present invention is applied to a laser beam printer. However, the embodiment has a high-voltage generating circuit, and a high voltage is generated according to a signal detected when an opening / closing mechanism provided in the apparatus main body is opened. It will be understood that the present invention can be applied to other devices as long as the image forming device is configured to control the driving of the voltage generating circuit.
[0045]
For example, as the form of the image forming apparatus according to the present invention, in addition to those provided integrally or separately as an image output terminal of an information processing apparatus such as a computer, a copying apparatus combined with a reader or the like, and a facsimile having a transmission / reception function It may take the form of an apparatus.
[0046]
【The invention's effect】
As described above, according to the present invention, when the switch is in the non-conductive state, the current flowing from the high voltage generation circuit to the control unit can be blocked. It changes greatly between the state and the non-conductive state.
[0047]
Therefore, erroneous detection of the opening / closing state of the opening / closing mechanism can be prevented, and power consumption during standby can be reduced.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a configuration related to a high-voltage generation circuit for development and opening and closing of a door according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing a schematic control configuration of a general laser beam printer.
FIG. 3 is a circuit diagram showing a configuration related to a high-voltage generation circuit for development and opening and closing of a door in a conventional laser beam printer.
FIG. 4 is a circuit diagram illustrating a configuration related to a high-voltage generation circuit related to transfer and opening / closing of a door according to a second embodiment of the present invention.
FIG. 5 is a diagram illustrating a schematic configuration of an image forming apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Low voltage power supply circuit 2 High voltage generation circuit 3 Laser scanning means 4 Heating and fixing means 5 Transport means 6 Control circuit 12 Transistor 15 Door switch 17, 18 Transistor 20 Capacitor 21 Transformer 30 Diode 50 DC generation circuit 60 for development ASIC

Claims (1)

An image forming apparatus that forms an image according to an electrophotographic process,
A power supply circuit for generating a voltage to be supplied to the internal circuit;
A high voltage generation circuit that generates a high voltage from a voltage generated by the power supply circuit;
An opening / closing mechanism provided in the device main body;
A switch that is provided between the power supply circuit and the high-voltage generation circuit and that changes a conduction state in conjunction with the opening / closing mechanism;
A control unit that controls driving of the high-voltage generating circuit based on a voltage applied through the switch;
An image forming apparatus comprising: a backflow prevention unit configured to prevent a current from flowing from the high voltage generation circuit to the control unit.

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