JP3591557B2 - Charging device and image forming device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a charging device including a discharge wire, a high-voltage power supply using a piezoelectric transformer that applies a high voltage thereto, and an image forming apparatus using the same . The most typical application of this charging device is a charging device for charging a photoconductor in electrophotographic image formation, but other applications, such as recording a toner image on a photoconductor using corona discharge It can also be applied to paper transfer devices, air purifiers, sterilizers or static eliminators.
[0002]
[Prior art]
In any of the applications, since a high voltage is applied to the discharge wire, fine dust adheres to the discharge wire mainly due to electrostatic attraction, and if the dust is left for a long time, the adhered matter is fixed and it becomes difficult to remove. Therefore, conventionally, at regular or required times, the cleaning wire is used to wipe off the discharge wire to remove dirt. There is also a stain prevention method of applying a high voltage of opposite polarity to the discharge wire to reject foreign substances attached to the discharge wire.
[0003]
On the other hand, there is also a proposal in which the discharge wire is vibrated while the use of the discharge wire is suspended to shake off the foreign matter attached to the discharge wire. JP-A-58-18966 and JP-A-58-194063 disclose a vibrator obtained by attaching a piezoelectric element plate to a metal vibrating piece and applying a high-voltage AC to the piezoelectric element. To excite.
[0004]
By the way, a step-up transformer for generating a high voltage applied to a discharge wire is relatively bulky and heavy. Thus, Japanese Patent Publication No. 6-24434 discloses a high-voltage DC power supply circuit in which a capacitor is inserted in series on the secondary side of a winding transformer to drive a piezoelectric transformer to reduce the size of the winding transformer.
[0005]
[Problems to be solved by the invention]
Conventionally, in a charging device using a discharge wire, there is a problem that a substance having a polarity opposite to an applied voltage adheres to the discharge wire, or a floating substance adheres to the discharge wire. Therefore, in order to remove foreign matter adhering to the discharge wire, a method of applying a high voltage having a polarity opposite to the normal polarity to the discharge wire at a predetermined timing and a method of using a cleaning device for mechanically cleaning the surface of the wire are used. Are known.
[0006]
However, each of these methods has a problem that the apparatus becomes large, expensive, and heavy, and a problem that the cleaning operation cannot be performed during the charging operation.
[0007]
SUMMARY OF THE INVENTION It is a first object of the present invention to provide a charging device for preventing a discharge wire from being stained without adding a special cleaning device. In addition, the power supply device of the charging device is reduced in size, weight and cost. A second object of the present invention is to provide a charging device with high reliability, and a third object of the present invention to provide a charging device with high reliability, and a simple and inexpensive power supply device for controlling the output of the charging device with a constant current. This is the fourth purpose.
[0008]
[Means for Solving the Problems]
(1) Discharge wire (5),
A piezoelectric transformer for providing a high voltage to the discharge wire (9),
Means for connecting one end to the output of the piezoelectric transformer of the discharge wire (7/16)
Means for electrically exciting the input of said piezoelectric transformer (30 to 48),
and,
Means for transmitting the vibration of the piezoelectric transformer to said discharge wire (7/15)
A charging device (QC, MC) comprising:
[0009]
In addition, in order to facilitate understanding, the symbols of the corresponding elements of the embodiment shown in the drawings and described later are added in the parentheses for reference.
[0010]
According to this, the means (30 to 48) electrically excites the input of the piezoelectric transformer (9), so that the piezoelectric transformer (9) generates a high voltage, a high voltage is applied to the discharge wire, and the discharge is performed. The wire (9) performs charging, for example, charging of the photoconductor OPC. When the piezoelectric transformer (9) is electrically excited, the piezoelectric transformer (9) vibrates mechanically. Since the transmission means (7/15) transmits the vibration of the piezoelectric transformer (9) to the discharge wire (5), when the discharge wire (5) is charging (for example, charging the photoconductor OPC), the discharge wire (5) vibrates and hinders the attachment of foreign matter. That is, there is an effect of preventing foreign matter from adhering to the discharge wire during the charging operation, and thereby stable charging characteristics can be maintained for a long time. Since no special shaker is used, no special shaker is required.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
(2) the discharge end and the means for storing in close proximity to the output of the piezoelectric transformer wires (6), and said piezoelectric section transformer mechanical vibrations (B, D) means for securing to said storage means (8 The charging device according to the above (1), further comprising:
[0012]
In the means (6), since one end of the discharge wire (9) and the piezoelectric transformer (9) are stored close to each other, the possibility of high voltage leakage or attenuation is low, and the charging device (QC, MC) High reliability. Also, there is little high frequency noise to the surroundings. The node of the vibration (B, D) of the piezoelectric transformer (9) , that is, the stationary point, is fixed to the storage means (6) by the fixing means (8), and the fixing means (8, ) Supports the piezoelectric transformer (9), so that the fixing means (8) and the storage means (6) supporting it do not mechanically vibrate, and therefore the bases (1,2,2) of the charging device (QC, MC). Since 6) does not vibrate, there is no particular problem in mounting the charging device (QC, MC) to a device using the same (for example, a copying machine; FIG. 5).
[0013]
( 3 ) The charging device according to (1) or (2), wherein the natural vibration of the piezoelectric transformer (9) is different from the natural vibration of the discharge wire (5), and the length of the discharge wire is different. MC). According to this, since the discharge wire (5) does not resonate (vibrate with a large amplitude) at its natural frequency (resonance frequency), fluctuations in charging characteristics due to occurrence of a large amplitude and abnormal discharge do not occur. Further, the stability of the vibration of the discharge wire (5) is high, and excessive mechanical stress due to the large amplitude is not applied to the discharge wire (5), so that the discharge wire (5) is less fatigued.
[0014]
( 4 ) The charging device (QC; FIG. 1) according to the above (1) , (2) or (3), wherein the output end of the piezoelectric transformer (9) and the discharge wire (5) are directly connected. .
[0015]
( 5 ) It further comprises means (12, 13) for rectifying and smoothing the output of the piezoelectric transformer (9), and the connecting means (16) connects the output of the rectifying and smoothing means to one end of the discharge wire (5). The charging device (MC; FIG. 2) according to the above (1) , (2) or (3), characterized in that:
[0016]
(6) The piezoelectric input transformer (9) is connected to the secondary side winding transformer (48) primary and secondary are insulated,
The winding in series with the primary winding of the transformer, the DC power source connected to the transistor in (DC24V between 27/29) (47),
The rectifying smoothing means (12, 13) in the rectified smoothed inserted output current detection resistor in series to the GND side of the DC voltage (58), and,
As the voltage of the output current detection resistor is equal to the target voltage, control means for controlling the width of a pulse for driving the transistor (44),
The charging device (MC; FIG. 2) according to the above (5), comprising :
[0017]
According to this, since the secondary high voltage of the winding transformer (48) is further boosted by the piezoelectric transformer (9), the primary / secondary turns ratio of the winding transformer (48) is low and both the number of coil turns and the iron core are small. As a result, the power supply circuit (HVM) is small, lightweight, and inexpensive. The output reference potential terminal (60) of the high-voltage power supply is directly connected to the structure (GND) of the device (FIG. 5) using the charging device (MC), and the object to be charged (OPC) is connected to the structure (GND). Since the connection can be made directly, the configuration of the used device (FIG. 5) for mounting the charging device can be simplified.
[0018]
(7) The charging device (QC, MC) according to any one of the above (1) to (6 ) ,
A photoconductor (OPC) charged by the charging device ,
Means for exposing the photoreceptor to form an electrostatic latent image;
Means for developing the electrostatic latent image (YD, MD, CD) ;
Means for transferring the visible image formed by the development onto paper (TC) , and
Means for fixing the visible image on the paper,
An image forming apparatus characterized by comprising ( FIG. 5) .
[0019]
Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.
[0020]
【Example】
-1st Example-
FIG. 1 shows a charging device MC according to the first embodiment. The first embodiment is mounted on an electrophotographic color printer shown in FIG. First, the color printer shown in FIG. 5 will be described. In this color printer, the photoreceptor OPC is uniformly charged by the main charger MC, and the three primary colors of light yellow (Y), magenta (M), and cyan (C) Writes the decomposed image information, that is, exposes the photoreceptor OPC with light modulated with the image information to form an electrostatic latent image corresponding to each color, and develops the electrostatic latent image corresponding to each color by developing units YD, MD, and CD corresponding to each color. The toner image is moved on the transfer paper by the transfer charger TC, that is, transferred, and the transfer paper is separated from the photoconductor by the separation charger QC. Then, the separated transfer paper is sent to a fixing device (not shown), and the toner image is fixed on the transfer paper by heating and pressing.
[0021]
A high DC voltage is applied to a discharge wire of the main charger MC by a DC high-voltage power supply HVM, and the photoconductor is charged to a constant potential by corona discharge generated by the discharge wire. The composite high voltage power supply HVTQ applies a DC high voltage to the transfer charger TC and an AC high voltage to the separation charger QC. Corona discharge from each discharge wire generates charge for transfer and removes charge for separation. Done.
[0022]
In an electrophotographic printer, a small amount of floating substances such as toner from a developing device, paper powder from transfer paper, and silicon gas from a fixing device exist. The discharge wire has a problem that these suspended matters adhere during charging or non-operation, and conventionally, it was necessary to periodically clean the wire. Particularly, in a color printer, three-color development is performed on the photoconductor before transfer, so that the toner on the photoconductor easily adheres to the discharge wire.
[0023]
Referring to FIG. 1 showing a separation charger QC which is a first embodiment of the charging device of the present invention. One end of the discharge wire 5 is connected to one end of the spring 4, and the other end of the spring 4 is engaged with the pin 3 of the resin case 1. The other end (power receiving end) of the discharge wire 5 is hooked and connected to a conducting wire 7 with a hook protruding from an output end of the piezoelectric transformer 9. The piezoelectric transformer 9 is fixed by an adhesive to a fixing projection 8 integrated with the case 6 in the resin case 6 at a position of a node of the vibration (described later). The input lead wire 10 of the piezoelectric transformer 9 is connected to the connector 11 and receives an AC driving voltage from the composite high voltage power supply HVTQ. The resin cases 1 and 6 at both ends are connected by metal plates (metal cases) 2 on both sides. The metal case 2 is connected to GND (equipment earth potential) and has the function of improving the uniformity of corona discharge.
[0024]
When an electric vibration (oscillation voltage) is applied to the input of the piezoelectric transformer 9, a mechanical vibration is generated, and the piezoelectric transformer 9 resonates with a natural vibration substantially proportional to a longitudinal dimension of the piezoelectric transformer. This mechanical vibration is converted into electric vibration, and an AC voltage appears at the output. The ratio between the input voltage and the output voltage is almost the ratio between the thickness and the length, and a large boosting ratio can be obtained.
[0025]
FIG. 4 is a diagram illustrating a state of mechanical vibration of the piezoelectric transformer 9. Points B and D are nodes of vibration and have no mechanical displacement. That is, it is a stationary point. The fixing of the piezoelectric transformer 9 is performed in the sections B and D as described above. A, C and E are places where the displacement is maximum (antinode of vibration). The resonance frequency of the piezoelectric transformer 9 in this embodiment is 73 KHz.
[0026]
As shown in FIG. 1, by applying an AC high voltage obtained from the piezoelectric transformer 9 directly to the discharge wire 5, + charges and − charges are generated alternately around the discharge wire 5, and a nearby charged object is removed. It works to remove electricity. The charging device of the first embodiment (FIG. 1) is used in the separation charging device QC of FIG. 5, and removes the contact charge between the photoconductor OPC and the transfer paper to separate the transfer paper from the photoconductor. Is used to
[0027]
Since the output end 7 where the mechanical displacement of the piezoelectric transformer 9 is maximum and the discharge wire 5 are connected via a hook for connecting the lead 7, the discharge wire 5 receives the vibration of the piezoelectric transformer 9. Vibrate. Notches are provided in the resin case 6 so that the discharge wires 5 do not come into contact with the resin case 6. The connection hook of the lead 7 is formed by fixing a conductive wire having a hook shape to the output end of the piezoelectric transformer 9 with a conductive adhesive. It is also possible to make a hole in the output end of the piezoelectric transformer 9 and use it as a connection part of the discharge wire.
[0028]
-2nd Example-
FIG. 2 shows a charging device according to the second embodiment. This is used as the main charger MC shown in FIG. 5, and a high DC voltage is applied to the discharge wire 5. The discharge wire 5, the spring 4, the resin case 1, the pin 3, the fixing portion 8 of the piezoelectric transformer, and the metal case 2 have the same configuration and function as those in FIG. The other power receiving end of the discharge wire 5 is hooked and fixed to the pin 17 of the resin case 6. The input lead wire 10 of the piezoelectric transformer 9 is connected to the connector 11 and receives a driving signal from the outside. The output of the piezoelectric transformer 9 is rectified and smoothed by a diode 12 and a capacitor 13 via a lead 16, and a high DC voltage is supplied to a pin 17. The discharge wire 5 connected to the pin 17 generates a charge by a high DC voltage and charges a nearby object.
[0029]
One end of an L-shaped vibration transmission member 15 made of a lightweight insulating material is adhesively fixed to an output end of the piezoelectric transformer 9. At the other end, there is a wedge-shaped notch where the discharge wire 9 is sandwiched and supported, and the vibration of the piezoelectric transformer 9 is transmitted to the discharge wire 5.
[0030]
The piezoelectric transformer 9 and the vibration transmitting member 15 may have a structure in which a hole is provided at the output end of the piezoelectric transformer, and the vibration transmitting member 15 is inserted and fixed there, or is placed in a state of being connected to the piezoelectric transformer. The discharge wire 5 and the vibration transmitting material 15 may be bonded and fixed, or may have a structure in which the tip is hooked and hooked on the wire, or a structure in which the discharge wire 5 and the vibration transmitting material 15 are placed in contact with each other. The vibration transmitting member 15 may have any shape other than the L-shape depending on the positions of the piezoelectric transformer 9 and the discharge wire 5.
[0031]
The discharge wire 5 has a natural frequency determined by the length. When the same vibration as the natural frequency is applied to the wire 5, the discharge wire 5 swings with a large amplitude. When the discharge wire vibrates greatly, the distance between the discharge wire 5 and the metal case 2 becomes short, causing abnormal discharge. Alternatively, since the distance between the discharge wire 5 and the photoconductor OPC fluctuates, there arises a problem that stable charging or static elimination cannot be performed. Also, large amplitude wire vibrations can cause mechanical stress or fatigue on the wire. Therefore, the length of the discharge wire 5 is determined so that the frequency of the piezoelectric transformer 9 and the natural frequency of the discharge wire 5 are different, that is, the discharge wire 5 does not resonate with the vibration of the piezoelectric transformer 9.
[0032]
FIG. 3 shows a configuration of a high-voltage power supply HVM for exciting the piezoelectric transformer 9 of FIG. When 24 V DC is connected to the power input terminals 27 and 29 and the trigger terminal 28 is set to the low level L, the transistor 38 is turned on (conducting), and power is supplied to the switching regulator (SW regulator) IC 44. Here, the IC 44 used was TL494 manufactured by Texas Instruments (TI). The IC 44 performs switching at a frequency determined by the capacitor 42 and the resistor 43. Here, the frequency is 73 KHz. By driving the transistor 47 ON / OFF (non-conducting) by the stitching signal from the IC 44, the primary side of the winding transformer 48 is excited, and a step-up AC is obtained on the secondary side of the winding transformer 48.
[0033]
The secondary side of the winding transformer 48 is connected to the input of the piezoelectric transformer 9, drives the piezoelectric transformer 9, and further obtains a high-voltage alternating current at the output side of the piezoelectric transformer 9. The diode 12 and the capacitor 13 rectify and smooth this high-voltage alternating current to a high-voltage direct current. The output voltage is stepped down by the resistors 14 and 55 and is fed back to the IC 44. The output current is detected by the resistor 58 and returned to the IC 44. The capacitors 54 and 57 are for removing high frequency components. The primary and secondary transformers 48 are insulated. When this insulation type transformer is not used, it is necessary to insulate the photoconductor OPC from the GND of the printer and directly connect the photoconductor OPC to the GND (60) which is the output reference potential terminal of the high-voltage power supply HVM. By using the isolation transformer 48, the photoconductor OPC is directly connected to the GND of the printer. That is, the photoconductor OPC is connected to the equipment ground in the most general form.
[0034]
The target value of the output current and the target value of the output voltage of the high-voltage power supply HVM shown in FIG. 3 are generated by the reference power supply circuit inside the IC 44 and the resistors 32 and 33, and the IC 44 compares this with the detected value. The pulse width for driving the transistor (47) is controlled according to the difference. In this embodiment, the target value of the output voltage is a value that limits the maximum output voltage due to no load or the like. While the output voltage is less than the maximum voltage, the IC 44 determines that the output current detected by the resistor 58 is equal to the target value. PWM (Pulse Width Modulation) control of ON / OFF driving of the transistor 47 so that In a usage mode in which the constant voltage control is prioritized and the maximum current due to a load abnormality such as an output short circuit is limited, the detection resistor 58 is changed to a value that detects the current when an abnormality such as an output short circuit occurs.
[0035]
The charging device MC of the second embodiment shown in FIG. 2 is used as the main charger MC in FIG. 5, and the high-voltage power supply HVM shown in FIG. 3 is the high-voltage power supply HVM shown in FIG. A charging device having the same structure as that of the second embodiment shown in FIG. 2 is used as the charging device TC. The high-voltage power supply (within HVTQ) of the transfer charger TC has the same circuit configuration as the high-voltage power supply shown in FIG. Has become. In FIG. 5, a main charger MC is used to apply a charge to the photoreceptor OPC to make the surface potential of the photoreceptor OPC a predetermined value. It is used for drawing to the transfer paper side.
[Brief description of the drawings]
FIG. 1 is a plan view of a charging device QC according to a first embodiment of the present invention.
FIG. 2 is a plan view of a charging device MC according to a second embodiment of the present invention.
FIG. 3 is an electric circuit diagram of a high-voltage power supply HVM that supplies power to a discharge wire 5 of the charging device MC illustrated in FIG.
FIG. 4 is a plan view of the piezoelectric transformer 9 shown in FIGS. 1 and 2, and exaggerated graphs also show displacements of respective portions in a longitudinal direction due to vibration.
FIG. 5 is a block diagram showing a schematic configuration of a color printer equipped with the charging devices QC and MC shown in FIGS. 1 and 2.
[Explanation of symbols]
1: resin case 2: metal case 3: pin 4: spring 5: discharge wire 6: resin case 7: lead with hook 8: fixing projection 9: piezoelectric transformer 10: input lead Lead wire 11: Connector 12: Diode 13: Capacitor 14: Resistance 15: Vibration transmitting material 16: Lead wire 17: Pin 27, 29: DC power input terminal 28: Trigger terminal 44: Regulator IC

Claims (7)

Discharge wire,
A piezoelectric transformer for providing a high voltage to the discharge wire,
Means for connecting said piezoelectric transformer output and one end of the discharge wire,
Said piezoelectric transformer means to electrically excite the input, your and,
Means for transmitting the vibration of the piezoelectric transformer to the discharge wire,
A charging device comprising: 2. The apparatus according to claim 1, further comprising: means for storing one end of the discharge wire and the output of the piezoelectric transformer close to each other ; and means for fixing a node of mechanical vibration of the piezoelectric transformer to the storage means. A charging device according to claim 1. Natural vibration of the piezoelectric transformer of the natural oscillation and the discharge wire are different, charging device according to claim 1 or claim 2, characterized in that the length of the discharge wire. 4. The charging device according to claim 1 , wherein an output terminal of the piezoelectric transformer and the discharge wire are directly connected. The piezoelectric further comprising means for rectifying and smoothing the output of the transformer, the connecting means according to claim 1, claim 2 or claim, characterized in that for connecting the one end of the output and the discharge wires of the rectifying and smoothing means 4. The charging device according to 3 . The piezoelectric transformer of the input end is connected to the secondary side, the primary and secondary insulating windings transformer,
The winding in series with the primary winding of the transformer, which is connected to a DC power source transistor,
The rectifying smoothing means rectified smoothed DC voltage inserted output current detection resistor in series to the GND side, and,
As the voltage of the output current detection resistor is equal to the target voltage, control means for controlling the width of a pulse for driving the transistor,
The charging device according to claim 5, further comprising: A charging device according to any one of claims 1 to 6,
A photoreceptor charged by the charging device,
Means for exposing the photoreceptor to form an electrostatic latent image;
Means for developing the electrostatic latent image,
Means for transferring the visible image formed by the development onto paper, and
Means for fixing the visible image on the paper,
An image forming apparatus comprising:

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