JP3352809B2 - Corona discharge device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a copying machine, a printer,
The present invention relates to a corona discharge device such as a charging device, a transfer device, and a static elimination device used in an electrophotographic image forming apparatus such as a facsimile apparatus.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus such as a copying machine, an electrostatic latent image is formed by exposing a surface of a photoconductor (image carrier) charged by a charging device to an exposure device. After the latent image is visualized by attaching toner with a developing roller in the developing device, the latent image is transferred to a sheet fed from a sheet feeding unit by a transfer device, and then the residual charge on the photoconductor is removed by a charge removing device. Like that.

In such an image forming apparatus,
Corona discharge devices are widely used for charging devices, transfer devices, static eliminators, and the like. This corona discharge device is disclosed in, for example, JP-A-1-221768 and JP-A-2-625.
As disclosed in Japanese Unexamined Patent Publication No. 67-162, Japanese Unexamined Patent Publication No. 2-162369, etc., a cleaning member (wire cleaner) is provided. Some are capable of cleaning the charge wire by reciprocating to and from a location.

In such a corona discharge device, sensors are provided at the standby position and the return position of the cleaning member, and the cleaning member is detected by the sensors at the standby position and the return position, and the cleaning is performed based on the detection signals. There is one in which the member is reciprocated between the standby position and the folded position to perform the cleaning operation of the charge wire,
Cost increase by providing position detection sensor,
This has led to an increase in the size of the device and the complexity of the device.

In view of the above, there is provided means for detecting a current flowing through the drive motor for moving the cleaning member, particularly a lock current when the cleaning member reaches the turn-back position or the standby position and is stopped. A corona discharge device has been proposed in which the switching of the direction of movement of the cleaning member is controlled by detecting the movement of the cleaning member, whereby the cleaning member is reciprocated between the standby position and the turnback position to perform the cleaning operation of the charge wire. .

[0006]

However, in such a corona discharge device, when the drive motor is overloaded due to mechanical variations, a large current may flow even when the cleaning member is moving. Yes, by erroneously detecting this as a lock current, the cleaning member may switch or stop its movement direction before reaching the turn-back position or the standby position, making it impossible to reliably remove dirt on the charge wire. Therefore, there is a problem that discharge unevenness occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to enable cleaning of a charge wire by a cleaning member in a corona discharge device without providing a position detecting sensor.

[0008]

In order to achieve the above object, the present invention provides a charge wire for performing a corona discharge, a casing made of a grounded conductor provided along the charge wire, and a charge wire. A power supply for applying a discharge voltage, a cleaning member for cleaning the charge wire by reciprocating between a standby position at both ends thereof and a turnback position along the charge wire, and a drive motor for moving the cleaning member. In the corona discharge device having the following,

That is, a part of the cleaning member is formed of a conductor, and when the cleaning member is at the standby position or the folded position, the conductor portion is not electrically connected to the casing. A leakage current detecting means configured to electrically connect the conductor portion to the casing, and to detect a leakage current flowing to the casing through the conductor portion of the cleaning member when a discharge voltage is applied to the charge wire by a power supply; And moving direction switching means for switching the moving direction of the cleaning member depending on whether or not the leak current is detected by the leak current detecting means when the motor is driven.

Further, it is preferable to provide an intermittent application means for intermittently applying a discharge voltage to the charge wire by the power supply while the cleaning member is moving.

[0011]

In the corona discharge device according to the present invention, the conductor is not electrically connected to the casing when the cleaning member is at the standby position or the folded position, and when the cleaning member is located at other positions, the conductor is connected to the casing. It is configured to be electrically connected, and switches the moving direction of the cleaning member depending on the presence or absence of leakage current detection when driving the drive motor, so a position detection sensor is provided for cleaning the charge wire by the cleaning member. You can do without it.

Further, by causing the power supply to intermittently apply the discharge voltage to the charge wire during the movement of the cleaning member, the generation of ozone can be reduced.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 2 is a perspective view showing a schematic example of a main part of an image forming apparatus according to an embodiment of the present invention, and FIG. 1 is a perspective view showing a configuration example of a charging device (corona discharge device).

The charging device 1 is provided close to the outer peripheral surface of the photosensitive drum 2 of the image forming apparatus, and has two charge wires 11 and 11 (FIG. 1) for performing corona discharge.
Only one is visible), a casing 12 made of a conductor such as a metal plate, a power supply unit 36 for applying a discharge voltage to the charge wire 11, and a cleaner as a cleaning member for cleaning the charge wire 11 (shown in FIG. 2). (Omitted) 13, a drive motor 14 for moving the cleaner 13, a drive device including a worm 15 and a worm wheel 16, which constitute a worm gear, a feed screw 17, and the like.

The casing 12 is provided along the charge wire 11 so as to surround the upper portion and both side portions thereof, and is connected to a grounded housing (such as a storage cover of the charging device 1) 26. Stoppers 1 for rotatably supporting the feed screw 17 at both ends and restricting movement of the cleaning member 13 due to rotation of the feed screw 17.
8, 19 are provided. The stoppers 18 and 19 are made of an insulating member.

The position where the cleaner 13 contacts the stopper 18 on the front side in FIG. 2 is the standby position, and the position where the cleaner 13 contacts the stopper 19 on the rear side is the turnback position. In this embodiment, the conductor portion is not electrically connected to the casing 12 when it is located at a position, and the conductor portion is electrically connected to the casing 12 when it is located at other positions. In this example, an insulating seal 20 is attached to a position corresponding to the standby position and the folded position of the casing 12. In addition,
The location may be made of an insulating member.

The charge wire 11 is stretched by fixing both ends thereof to a casing 12 via an insulating member (not shown).
Cleaning the charge wire 11 by reciprocating in the directions indicated by arrows A and B shown in FIG. 1 between the stopper 18 at the standby position and the stopper 19 at the turn-back position at both ends thereof along the charge wire 11. Can be.

The cleaner 13 is, for example, as shown in the bottom view of FIGS. It is composed of a cleaner pad 22 made of four insulating materials for cleaning, an electrode 23 for generating a leak between the charge wire 11, and a holder 24 to which the cleaner pad 22 and the electrode 23 are fixed. ing.

The holder 24 is attached to the slider 21 so as to be rotatable at a predetermined angle by its shaft 21a, and the electrode 23 is brought close to the charge wire 11 within a range where the electrode 23 is not in contact with the charge wire 11 at any of the rotation positions. Is provided. Furthermore, when a discharge voltage is applied to the charge wire 11 by the power supply unit 36 and a leak occurs between the cleaner 23 and the electrode 23 when the cleaner 13 is located at a position other than the standby position or the folded position, the leak current is reduced. At least portions of the cleaner 13 that form a current path between the electrode 23 and the casing 12 (such as the holder 24 and the slider 21) are formed of a conductive member so as to flow to the ground.

The feed screw 17 is formed of an insulating material such as a synthetic resin, and both ends thereof are rotatably supported by a pair of stoppers 18 and 19 fixed to both ends in the longitudinal direction of the casing 12. The slider 21 of the cleaner 13 is attached to the male screw part of the feed screw 17 by engaging the female screw part. A worm wheel 16 is attached to one end of the feed screw 17, and the worm wheel 16 meshes with the worm 15 attached to the rotation shaft of the drive motor 14.

Therefore, when the drive motor 14 rotates in the direction of arrow C (reverse rotation) in FIG. 1, the feed screw 17 rotates in the direction of arrow E via the worm 15 and the worm wheel 16, so that the cleaner 13 is moved in the direction of arrow E. Move in the indicated A direction (forward direction). When the drive motor 14 rotates in the direction of arrow D (forward rotation), the feed screw 17 rotates in the direction of arrow F, so that the cleaner 13 moves in the direction of arrow B (return direction).

When the cleaner 13 is waiting at the standby position and when it is moving in the direction of arrow A, the holder 24 is at a position orthogonal to the feed screw 17 as shown in FIG. Reference numeral 22 does not contact the charge wire 11, but when the cleaner 13 abuts against the stopper 19 at the turnback position and temporarily stops, or as indicated by an arrow B in FIG.
4, the holder 24 is rotated counterclockwise by a mechanism (not shown) to bring the cleaner pad 22 into contact with the charge wire 11 for cleaning.

FIG. 5 is a block diagram showing an example of a control unit of an image forming apparatus provided with the charging device 1. As shown in FIG. The control unit of the image forming apparatus includes a central processing unit (hereinafter referred to as a “CP”).
U ”) 31, memory 32, A / D converter 3
3. A microcomputer comprising an I / O port 34, etc., and a PWM generator 35, a power supply unit 36, a motor driver 37, a display unit 38, and the like. And also functions as intermittent application means.

The CPU 31 totally controls the entire control section by a program in the memory 32. Memory 32
Is an R that stores programs and other fixed data
The OM and the RAM used by the CPU 31 as a work memory or the like during data processing.

The A / D converter 33 includes a power supply unit 3
6 receives the discharge current detection signal output from
/ D conversion and read by the CPU 31. The I / O port 34 includes a PWM generator 35 and a motor driver 3
7, and various signals are exchanged with the display unit 38 and the like.

The PWM generator 35 has a PWM (pulse width modulation) with a duty specified by the CPU 31.
The signal is output to the power supply unit 36. Power supply unit 36
When a PWM signal is input from the PWM generator 35, a discharge voltage corresponding to the duty is applied to the charge wire 11 of the charging device 1 to cause corona discharge, and the outer periphery of the photosensitive drum 2 with the cored bar 2a grounded. Charge the surface.

That is, the transistor Q1 performs an on / off operation in accordance with the duty of the PWM signal output from the PWM generator 35 to interrupt the DC voltage + V applied to the primary side of the transformer T, and to apply a high voltage to the secondary side. Generate a pulse. The voltage is rectified by a voltage doubling rectifier circuit 39 including diodes D1 and D2 and capacitors C1 and C2, and converted into a DC high voltage. The high voltage (negative voltage in this example) is applied as a discharge voltage from the point a to the charge wire 11 of the charging device 1 via the resistor R1 to cause corona discharge.

At this time, the discharge causes the photosensitive drum 2
Is converted into a voltage by the resistor R2, and the voltage is output to the A / D converter 33 as a signal (discharge current detection signal) indicating the value of the discharge current. . C3 is a capacitor for smoothing a noise component. When a leak occurs between the charge wire 11 and the electrode 23 of the cleaner 13 and the leak current flows to the ground via the conductor portion of the cleaner 13 and the casing 12, the discharge current increases. . Further, when the discharge voltage is positive, the discharge current detection voltage becomes negative, so that it may be output to the A / D converter 33 through an inversion circuit.

The motor driver 37 receives signals from the CPU 31
The drive motor 1 of the cleaner 13 is controlled by the motor forward rotation signal or the motor reverse rotation signal transmitted through the / O port 34.
4 is rotated forward or backward. The display unit 38 is installed outside the image forming apparatus, and displays various information sent from the CPU 31 via the I / O port 34.

Here, the CPU 31 of FIG. 5 performs control so that the value obtained by A / D conversion of the discharge current detection signal by the A / D converter 33 becomes equal to the target voltage (indicating the target discharge current value). Although the constant current control (or the constant voltage control) is performed, when the discharge voltage is applied to the charge wire 11 by the power supply unit 36, the moving direction of the cleaner 13 may be switched depending on whether or not the leak current is detected. it can.

That is, when the cleaner 13 is at the standby position or the folded position, the conductor is not electrically connected to the casing 12, so that no leak occurs between the electrode 23 and the charge wire 12, but the cleaner 13 Is present at a position other than the standby position or the folded position, the conductor portion is electrically connected to the casing 12, so that leakage occurs, and the discharge current becomes extremely larger than normal and becomes discontinuous. , Cleaner 13
The leakage current flowing to the casing 12 through the conductor portion can be detected. Therefore, the position of the cleaner 13 can be determined based on the presence or absence of the detection, and the movement direction can be switched.

FIG. 6 is a flowchart showing an example of the operation of cleaning the charge wire by the control unit shown in FIG. This routine is executed by the CPU 31, for example, after a predetermined number of image forming operations set in advance are completed. First, when a predetermined timing (timing for starting the operation of cleaning the charge wire) is reached, the drive motor 14 is turned on and rotated in the reverse direction, and the discharge voltage is forcibly applied to the charge wire 11 by the power supply unit 36 to detect the discharge current. By checking the value, it is determined whether or not a leak current flowing to the casing 12 through the conductor portion of the cleaner 13 has been detected.

When the drive motor 14 is rotated in the reverse direction, the cleaner 13 moves from the standby position in the direction of arrow A, and its conductor is electrically connected to the casing 12. At this time, the discharge voltage is applied to the charge wire 11. Is applied, a leak occurs between the charge wire 11 and the electrode 23 of the cleaner 13, and a leak current flows through the conductor portion of the cleaner 13 to the casing 12, so that the A / D converter 33 to detect.

Thereafter, when the leak current is no longer detected, it is determined whether the drive motor 14 has been rotated in the reverse direction. If so, it is determined that the cleaner 13 has reached the turn-back position, and the rotation direction is changed. By changing the direction (reverse rotation → forward rotation), the direction of movement of the cleaner 13 is switched, the cleaner 13 is moved from the folded position in the direction of arrow B, and it is determined whether or not the leak current is detected again.

When the cleaner 13 moves from the folded position in the direction of arrow B, the conductor portion is electrically connected to the casing 12 again, so that the leak current flowing through the casing 12 through the conductor portion is reduced by the A / D converter 33. When the leakage current is no longer detected, it is again determined whether or not the drive motor 14 has been reversely rotated.

This time, since the rotation was forward, the cleaner 13
Is determined to have returned to the standby position, the application of the discharge voltage to the charge wire 11 is stopped, the drive motor 14 is turned off, and the cleaning operation of the charge wire 11 ends.

FIG. 7 is a flowchart showing another example of the operation of cleaning the charge wire by the control unit shown in FIG. This routine is also executed by the CPU 31, for example, after a predetermined number of image forming operations set in advance are completed. First, at a predetermined timing (timing for starting the operation of cleaning the charge wire), the drive motor 14 is turned on and rotated in the reverse direction, and then a cleaner movement timer (not shown) is started.

When the value of the timer reaches the set value T, the timer value is cleared and the power supply unit 36 forcibly applies a discharge voltage to the charge wire 11 to check the discharge current value. It is determined whether or not it has been detected. The set value T is set to a value such that the discharge voltage can be applied to the charge wire 11 several times while the cleaner 13 moves in one direction.

When the leakage current is detected, the application of the discharge voltage to the charge wire 11 is stopped, and then the timer for moving the cleaner is started again. Thereafter, the same operation as described above is repeated, and the discharge voltage to the charge wire 11 is repeated. Is applied intermittently, and when the leakage current is no longer detected, after the application of the discharge voltage to the charge wire 11 is stopped, it is determined whether the drive motor 14 has been rotating in the reverse direction until now.

If the drive motor 14 has been rotating in the reverse direction until now, it is determined that the cleaner 13 has reached the turn-back position, and the rotation direction of the drive motor 14 is changed (reverse rotation → forward rotation). Switching the moving direction of the cleaner 13,
After moving the cleaner 13 from the folded position in the direction of arrow B, the cleaner moving timer is started again, and thereafter the same operation as described above is repeated to intermittently apply the discharge voltage to the charge wire 11.

Thereafter, when the leakage current is no longer detected, the application of the discharge voltage to the charge wire 11 is stopped, and it is determined whether the drive motor 14 has been rotated in the reverse direction. Then, it is determined that the cleaner 13 has returned to the standby position, the drive motor 14 is turned off, and the cleaning operation of the charge wire 11 ends.

As described above, in this embodiment, when the cleaner 13 is at the standby position or the folded position, the conductor portion is not electrically connected to the casing 12; Is electrically connected to the casing 12, and as shown in FIG. 6 or FIG. 7, when the drive motor 14 is driven, the moving direction of the cleaner 13 is switched depending on whether or not a leak current is detected. Cleaning of the charge wire 11 can be performed without providing a position detecting sensor.

Further, as shown in FIG.
During the movement of the power supply unit 36,
If the application of the discharge voltage to 1 is performed intermittently,
Ozone generation is reduced.

In this embodiment, the cleaner pad 22 comes into contact with the charge wire 11 when the cleaner 13 comes into contact with the stopper 19 at the turn-back position and stops, or when the cleaner 13 subsequently moves in the direction of arrow B. Holder 24
Rotates so that the charge wire 11 can be cleaned. However, the following may be performed.

That is, when the cleaner 13 comes into contact with the stopper 18 at the standby position and stops, the cleaner pad 22 separates from the charge wire 11 and the cleaner 13 moves as indicated by arrow A.
When the movement in the direction starts, the holder 24 is rotated so that the cleaner pad 22 comes into contact with the charge wire 11 or the cleaner pad 22 is always in contact with the charge wire 11 so that the cleaner pad 22 is always in contact with the charge wire 11. The cleaning of the charge wire 11 may be performed while moving in any direction of the direction B.

The embodiment in which the present invention is applied to a charging device which is a corona discharge device has been described above. However, the present invention is not limited to this, and can be applied to other corona discharge devices such as a transfer device and a static eliminator. Things.

[0047]

As described above, according to the present invention, the charge wire can be cleaned by the cleaning member without using the position detecting sensor. According to the invention of claim 2, generation of ozone can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration example of a charging device of FIG. 2;

FIG. 2 is a perspective view showing an example of a main part of an image forming apparatus according to an embodiment of the present invention.

FIG. 3 shows a charge wire 11 and a cleaner 1 in FIG.
FIG. 6 is a bottom view showing a state during forward movement of the cleaner showing a relationship with No. 3;

FIG. 4 is a bottom view showing the state of the cleaner when returning.

FIG. 5 is a block diagram illustrating an example of a control unit of the image forming apparatus of FIG. 2;

FIG. 6 is a flowchart showing an example of a charge wire cleaning operation by the control unit of FIG. 4;

FIG. 7 is a flowchart showing another example of the charge wire cleaning operation.

[Explanation of symbols]

 1: charging device 2: photosensitive drum 11: charge wire 12: casing 13: cleaner 14: drive motor 15: worm 16: worm wheel 17: feed screw 18, 19: stopper 20: insulating seal 21: slider 22: cleaner pad 23: Electrode 24: Holder 31: CPU 32: Memory 33: A / D converter 34: I / O port 35: PWM generator 36: Power supply unit 37: Motor driver 38: Display 39: Double voltage rectifier circuit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 13/02 G03G 15/02

Claims (2)

(57) [Claims] 1. A charge wire for performing corona discharge, a casing made of a grounded conductor provided along the charge wire, a power supply for applying a discharge voltage to the charge wire, A corona discharge device having a cleaning member that cleans the charge wire by reciprocating between a standby position and a turnback position at both ends thereof, and a drive motor for moving the cleaning member. When the cleaning member is at the standby position or the folded position, the conductor portion is not electrically connected to the casing, and when the cleaning member is at another position, the conductor portion is A discharge voltage is applied to the charge wire by the power supply. A leak current detecting means for detecting a leak current flowing through the casing through the conductor portion of the cleaning member when the cleaning member moves, and detecting whether or not the leak current is detected by the leak current detecting means when the drive motor is driven. A corona discharge device comprising a moving direction switching means for switching. 2. The corona discharge device according to claim 1, further comprising intermittent applying means for intermittently applying a discharge voltage to said charge wire by said power supply during movement of said cleaning member. Image forming apparatus.