JPH06149021A - Discharge electrode cleaner for corona discharger for image forming device - Google Patents

Abstract

PURPOSE:To appropriately and easily set a locking level for obtaining a timing of reversely rotating a motor and the timing of stopping the motor at the time of cleaning a discharge wire without being influenced by the environment of using a corona discharger, and nonuniformity in the characteristics of a discharge wire cleaning member driving motor. CONSTITUTION:A motor current is incorporated at fixed time intervals when the discharge wire 20 for the corona discharger 4 is cleaned by a cleaning member 21 so as to obtain the mean value of the motor current, and the locking level is calculated by multiplying the mean value by a prescribed multiple, and the motor 30 is reversely rotated and stopped when the motor current in the middle of cleaning exceeds the locking level, that is, when the cleaning member 21 arrives at the terminal position of forth and back movement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge electrode cleaning device for a corona discharger used in an image forming apparatus such as an electrophotographic copying machine.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine or a facsimile, an electrostatic latent image of an original or electric information is formed on a photoreceptor or a photoreceptor based on reflected light or an electric information signal obtained by exposing and scanning the original. The electrostatic latent image is formed on a dielectric material to develop it into a visible image, and this visible image is transferred onto a recording paper and then fixed to form a recorded image. FIG. 4 shows a schematic configuration of an electrophotographic copying machine. A document G placed on a document table 1 which reciprocates in the arrow direction is illuminated by an illumination lamp 2 and light reflected from the document G is rotated in the arrow direction. The electrostatic latent image of the original G is formed on the photoconductor 3a by projecting it onto the photoconductor 3a of the rotating drum 3. Around the rotating drum 3, a strip electrode 4 for uniformly charging the photoconductor 3a, a removal electrode 5 for removing unnecessary charges on the photoconductor 3a, a developing device 6, a transfer electrode 7, and a separation electrode 8 are provided. Further, another removing electrode 9 for removing charges remaining on the photoconductor 3a after the transfer and a cleaning device 10 for removing residual toner on the photoconductor 3a are sequentially arranged. The electrostatic latent image formed on the photoconductor 3a is developed into a visible image by the developing device 6, and the visible image is a recording paper P fed by the transport device 12 from a paper feeding device 11 such as a cassette. It is transferred onto the upper surface by the transfer electrode 7. After the transfer, the recording paper P is separated from the photoconductor 3a by the separation electrode 8,
The sheet is conveyed to the fixing device 14 by the conveying device 13, is fixed there, and is ejected to the sheet ejection tray 15.

In an apparatus for forming an image by such an electrophotographic process, a corona discharger is widely used for the strip electrode 4, the transfer electrode 7, the separation electrode 8 and the removal electrode 9. The corona discharger is a thin box-shaped shield member extending in the axial direction of the rotary drum 3 and has a thin wire of tungsten or stainless as a discharge electrode stretched in the longitudinal direction at the center, and both ends thereof are supported by insulating members. At the time of use, a high voltage is applied to the discharge wire to generate corona discharge, and the charge generated by the corona discharge is applied to the photoreceptor 3
The toner on the photoconductor 3a is electrostatically attracted by being attached on the surface a, or charged, and transferred, separated, and discharged.

By the way, since the discharge wire of the corona discharger is contaminated with toner and dust as it is used, the discharge effect is reduced or uneven discharge occurs, which causes deterioration of image quality. Therefore, in the conventional electrophotographic copying machine, the user or service person occasionally removes the corona discharger and wipes the dirt of the discharge wire with a soft cloth,
For intermediate and higher grade machines, a motor-driven cleaning device is provided, and for example, the cleaning device is reciprocated for every predetermined number of copies to remove dirt on the discharge wire (Japanese Patent Laid-Open No. 54-54). 28633).

[0005]

Various cleaning devices for discharge electrodes are known, and a cleaning member provided with a pad so as to contact the discharge wire is used by a motor through a screw or a pulley and a wire. There are a reciprocating type, a type that ejects compressed air from a nozzle to scatter and remove dirt on the discharge wire, and a type that sucks and removes dirt on the discharge wire by suction from an air suction hole.

In this type of discharge electrode cleaning device, a motor capable of rotating in the forward and reverse directions is used to reciprocate the cleaning member along the discharge wire. The motor is started from the standby position of the cleaning member and the opposite side is used. The motor is reversely rotated when it reaches the end position and stopped when it is returned to the standby position. A method of controlling by the energization time to the motor is conceivable in order to obtain the timing to reverse or stop the motor. However, this method has a problem that the reverse rotation and stoppage of the motor cannot be accurately controlled because the load of the motor changes depending on how dirty the discharge wire is.

As another method, micro switches and sensors are provided at the standby position and the opposite end position of the cleaning member,
A method of using the on / off signal and the output signal is known, but a space for installing the micro switch is required, or a high voltage is applied to the discharge wire, so that the micro switch or the sensor is connected to the discharge wire. Cannot be installed close to. Therefore, a method of utilizing this lock current is known, paying attention to the fact that when the cleaning member reaches the opposite end position or the standby position, the motor is locked and an extremely large lock current flows through the motor. The method of using this lock current is to detect the motor current, and when the motor current exceeds the lock level determined based on the lock current, the cleaning member reaches the opposite end position or standby position. This is the method of stopping the energization to the motor when it is judged that the motor current for the cleaning device drive motor has a considerable variation due to the ambient temperature, the resistance of the motor winding, and other factors. When the lock level is reached, the torque of the motor varies considerably depending on the operating environment and the characteristics of the motor, which makes it difficult to determine the lock level.

The present invention has been made in view of the above points, and the timing for reversing or stopping the motor for driving the discharge electrode cleaning member of the corona discharger is set without being affected by variations in the operating environment and motor characteristics. The purpose is to set the lock level to be appropriate and easy.

[0009]

In order to achieve the above-mentioned object, the present invention drives a cleaning member which reciprocates along a discharge electrode of a corona discharger to clean the discharge electrode and a cleaning member. A motor capable of rotating in the normal and reverse directions, a calculating means for calculating a lock level based on an average value of the motor current during movement of the cleaning member, and the cleaning member moving forward and backward when the motor current exceeds the lock level. The discharge electrode cleaning member is constituted by the motor control means for reversing and stopping the motor when it reaches the end position.

[0010]

With the above configuration, the motor current is detected at a constant time interval while the cleaning member is moving, the average value of the detected motor current is obtained, and the average value is multiplied by a predetermined multiple to calculate the lock level. To do. When the motor current during the movement of the cleaning member exceeds this lock level, the motor is reversed and stopped assuming that the cleaning member has reached the end positions of the forward movement and the backward movement.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. Figure 1
FIG. 3 is a block diagram of a control circuit of a motor for driving a discharge electrode cleaning member of a corona discharger according to the present invention used in an electrophotographic copying machine as an example of an image forming apparatus. In this example,
Each time the number of copies reaches a predetermined number, for example, the strip electrode 4
The cleaning member 20 with a pad 21a is reciprocated in order to clean the discharge wire 20 of the corona discharger used as (see FIG. 4).

In FIG. 1, reference numeral 22 is a copy counter for counting the number of copies, 23 is a CPU for instructing start, reverse rotation, stop of a motor 30 for reciprocating the cleaning member 20 and calculating a lock level described later, 24. Is a driver for driving the motor 30, and 25 is an A / D converter for A / D converting a value detected at a point as a voltage drop of the resistor R connected to the driver 24, that is, the motor current I. is there.

Next, the calculation of the lock level will be described with reference to the flow chart shown in FIG.

When the number of copies recounted by the copy counter 22 reaches a certain value, the CPU 23 drives the driver 2
By sending the start signal START and the motor forward rotation signal F to 4, the cleaning operation of the discharge wire is started. When the driver 24 receives the start signal START and the normal rotation signal F, the motor 30 rotates in the normal direction (F-1), whereby the cleaning member 21 starts to move from the standby position until then, and the discharge wire 20 is cleaned. . During this time, the current flowing through the motor 30 flows through the resistor R, so that the voltage at the point a is A / D converted by the A / D converter 25 and taken into the CPU 23 (F-2). In this case, the motor current I is taken in at regular time intervals (for example, every 2 seconds). The acquisition of the A / D converted motor current is performed a predetermined N times (F-
3) At the time when the data is fetched N times, the lock level I _r is calculated by the following equation 1 (F-4).

[0015]

## EQU1 ## I _R = M × ΣIn / N (M is a multiple, for example, 3 to 5) N times the motor current is taken into the CPU 30 to obtain the lock level I _R , the cleaning member 21 is on the opposite side from the standby position. It suffices to do this just before reaching the end position of.
FIG. 3 shows the lock level I _R calculated by taking in the motor current N times. After calculating the lock level I _R , the motor current I detected at point a in FIG. 1 is compared with the lock level I _R (F-5), and when I> I _R is satisfied, C
The PU 23 determines that the cleaning member 21 has reached the opposite end position, and sends a reverse rotation signal (R) to the driver 24 to reverse the rotation of the motor 30 (F-6). As a result, the cleaning member 21 starts moving in the opposite direction toward the standby position, and cleans the discharge wire 20 again. During this time, the motor current I is compared with the lock level I _R already obtained in step (F-4) (F-7), and when I> I _R is established, the CPU 23 sends a stop signal STOP to the driver 24, and the motor 30 To stop.

As described above, the motor current is detected each time the cleaning member 21 actually performs the cleaning operation, the motor current values are integrated to obtain the average motor current, and the average motor current is multiplied by a multiple M. Te seeking lock level I _R, since so as to detect the timing of the reversal and stopping of the motor for the cleaning member driven by the lock level I _R, the winding of the ambient temperature and motor resistance, depending on other factors In addition, the reverse rotation and stop of the cleaning member can be controlled at a timing suitable for the usage state of the motor.

In the above embodiment, only the motor current during the forward movement in which the cleaning member moves from the standby position to the opposite end position is used to calculate the lock level. However, the motor current during the forward movement and the motor current during the backward movement are used. The motor currents may be separately used for the calculation. Generally, since the load on the motor is smaller in the backward movement than in the forward movement, the lock level obtained from the motor current during the backward movement is smaller than the lock level obtained from the motor current during the forward movement. For this reason, for example, even if the cleaning member is stopped due to some cause during the backward movement, it is possible to quickly stop the energization of the motor, which is preferable in terms of control.

[0018]

As described above, according to the present invention,
Since the lock level for timing the reverse rotation and the stop of the cleaning member drive motor can be appropriately and easily set according to the motor regardless of the characteristics of the motor, variations in winding resistance, ambient temperature, and other factors. The torque at the time of reverse rotation and at the time of stop can be controlled to be almost constant.

[Brief description of drawings]

FIG. 1 is a block diagram of a control circuit of a motor for driving a discharge electrode cleaning member of a corona discharger according to the present invention used in an electrophotographic copying machine as an example of an image forming apparatus.

FIG. 2 is a flowchart showing a control operation of a motor by the control circuit shown in FIG.

FIG. 3 shows motor current uptake and lock level.

FIG. 4 is a schematic configuration diagram of an electrophotographic copying machine as an example of an image forming apparatus.

[Explanation of symbols]

 1 Document Plate 4 Band Electrode 7 Transfer Electrode 8 Separation Electrode 20 Discharge Wire 21 Cleaning Member 23 CPU 24 Driver 25 A / D Converter 30 Motor

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Etsuichi Maekawa 2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica Stock Company

Claims (3)

[Claims] 1. A cleaning member that reciprocates along a discharge electrode of a corona discharger to clean the discharge electrode, a motor that rotates the cleaning member forward and backward, and a motor current during movement of the cleaning member. Calculating means for calculating a lock level based on an average value of the motor and motor control for reversely rotating and stopping the motor as the cleaning member reaches the end positions of forward and backward movements when the motor current exceeds the lock level. And a discharge electrode cleaning device for a corona discharger of an image forming apparatus. 2. The discharge electrode cleaning device according to claim 1, wherein the calculation means calculates a lock level during the forward movement of the cleaning member. 3. The discharge electrode cleaning device according to claim 1, wherein the cleaning member has a pad for cleaning while contacting the discharge electrode.