JPS589185A - Abnormal state detecting method of photosensitive body surface - Google Patents

Abstract

PURPOSE:To detect a scratch of a photosensitive body, its peeling-off and a thunderbolt, by comparing a reflection level of the surface of a photosensitive body which has been developed, with the first comparison value decided by the lowest value of the reflection level, when energizing a charge, and also, comparing said level with the second comparison value decided by the highest value of the reflection level, when deenergizing the charge. CONSTITUTION:A phototransistor 302 detects and amplifies TRa photodetecting voltage, and inputs it as voltage (a) to the lowest value and highest value holding circuits 321, 322 and high peak detecting comparators 331, 332 through analog gates 311, 322. The comparator 331 and the comparator 332 output the respective high level outputs (e), (d) when light quantity detecting voltage (a) is higher than output voltage (c), and when said voltage (a) is lower than output voltage (b), respectively, input them to light emission diodes 351, 352 from counters 341, 342, respectively, also not only control a timing controlling circuit 36 but also detect the photosensitive surface in accordance with energizing and deenergizing the charge, and detect a scratch of the photosensitive body, peeling-off, discharge, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to abnormality detection on a photoreceptor surface of an electrophotographic apparatus.

In electrophotography, the surface of a photoreceptor is charged in advance and image light is projected onto it to form a latent image, and this latent image is developed with toner to transfer the toner image onto recording paper. The surface of the photoreceptor is thinly laminated on a conductive layer and is easily scratched when removing jammed paper, cleaning, or maintenance. Furthermore, discharge between the charger wire of a charger or a static eliminator and a conductive layer, so-called lightning strikes, causes peeling and unevenness on the surface of the photoreceptor. Toner tends to adhere to scratches on the photoreceptor surface, causing black streaks on recorded images. Toner does not adhere to areas where the photoreceptor is peeled off or struck by lightning, resulting in white spots on the recorded image. These black streaks and white spots degrade the quality of recorded images.

An object of the present invention is to detect defects on the surface of a photoreceptor that cause black streaks and white spots.

When the charger is deenergized during the standby period or during the 9-jung operation, substantially no toner is on the surface of the photoreceptor after the development stage, but toner is on the scratched uneven portion. On the other hand, when the charger is energized, a toner film is formed over the entire surface, but no charge is applied to peeled off parts or parts struck by lightning, so toner is not deposited thereon. Therefore,
When detecting light reflection on the surface of the photoconductor after development, when the charger is not energized, the amount of reflected light decreases at black stripes, and when the charger is energized, the amount of reflected light decreases at peeled areas and lightning strike areas. increase

The present invention utilizes such development to energize and deenergize the charger in a predetermined pattern while driving the photoreceptor of an electrophotographic device, and to adjust the level of light reflected on the surface of the photoreceptor through the developing section by changing the charging The surface of the photoconductor that passes directly under it when the device is energized is compared with the first comparison value determined by the lowest value of the reflected light level.When the reflected light level becomes higher than the first comparison value, peeling of the photoconductor and When a lightning strike is detected, the level of reflected light is smaller than the second comparison value determined by the highest value of the reflected light level on the surface of the photoconductor that passed directly under it when the charger was de-energized. Detects scratches and peeling of the photoconductor, as well as lightning strikes.

FIG. 1 shows the mechanism of one type of copying machine embodying the present invention. To explain this mechanical part, contact glass plate 1
The image of the document 3 placed above and pressed against the contact glass plate 1 by the presser plate 2 is illuminated by the illumination lamp 4;
First mirror 5, second mirror 6, lens 8, third mirror 9
, the fourth mirror 10, the magnification setting lens 25, and the slit 7, and are projected onto the photosensitive drum 11. The illumination lamp 4, the first mirror 5, and the second mirror 6 are scan-driven in the directions of arrows AR2 and AR3 along the touch glass plate 1 in synchronization with the rotation of the photosensitive drum 11 in the direction of arrow AR1. . As a result, the entire image of the document 3 is projected onto the surface of the photoreceptor drum 11, and a latent image corresponding to the image is formed. - This latent image is developed by the developing device 12, and the developed toner is placed directly under the transfer charger 13.
The image is transferred onto the recording paper fed by the registration rollers 14. The toner image on the recording paper is fixed by a fixing roller 15, and the recording paper after the fixing is sent onto a paper discharge tray 17 by a conveyance roller 16. 18 is an electrostatic charger, 19
20 is a cleaning roller, and 21 is a cleaning blade. The recording apparatus shown in FIG. 1 is of a two-stage paper feeding type in which two cassettes 221 and 222 can be attached and detached. By selectively driving one of the paper feed rollers 231 and 232, the cassette 221
Alternatively, the recording paper in 222 is sent out to the registration rollers 14. The magnification of the recorded image is determined by the magnification setting lens 25.
The lens 25 moves to the arrow A according to the specified magnification.
It is driven and positioned in the R4 direction.

Between the transfer charger 13 and the cleaning roller 20,
A light emitting diode 301 that projects light onto the photoreceptor surface and a phototransistor 302 that detects reflected light from the photoreceptor surface are arranged.

FIG. 2 shows the configuration of an abnormality detection device that performs abnormality detection according to the present invention, together with a light emitting diode 30 and a phototransistor 302. In FIG. 2, the phototransistor 302 generates a voltage at its emitter terminal according to the amount of light received, the transistor Tra amplifies this voltage, and the
The transmitter voltage a becomes a voltage approximately proportional to the amount of received light. This light amount detection voltage a is applied to the analog gates 311 and 312.
The signal is applied to the lowest value hold circuit 321 and the highest value hold circuit 322 via the circuit 322, and further applied to the comparator 331 for high peak detection and the comparator 332 for low peak detection. The hold voltages of the hold circuits 331 and 332 are applied to these comparators 331 and 332, respectively, and the first comparator 331 has a light amount detection voltage a higher than the output voltage C (first comparison value) of the hold circuit 321. produces a high level "1" output e when the second comparator 3 is high.
32 produces an output d of high level "1" when the light amount detection voltage a is lower than the output voltage b (second comparison value) of the hold circuit 322. These outputs e and d are applied to counters 341 and 342, respectively, and to light emitting diodes 351 and 352, respectively, via an amplifier (LIBD driver).

A timing control circuit 36 controls turning on/off of analog gates 31t and 312 and clearing of counters 341 and 342. A detection instruction signal for instructing abnormality detection, a timing pulse synchronized with the rotation of the photosensitive drum 11, and an initialization signal are applied to the timing control circuit 36 from the central control device of the copying machine. In other embodiments, the elements below the transistor Tra are installed in an abnormality detection operation panel separate from the copying machine, and are connected to the phototransistor 302 with a connector during maintenance, and the timing control circuit 36 is also installed in the center of the copying machine. The connector is connected to the control device,
A detection instruction is given to the timing control circuit 36 by operating a key switch on the abnormality detection operation panel, and a specific control signal is applied to the central control unit of the copying machine.

In any case, in the timing control circuit 36, the counter 37 counts timing pulses while the detection instruction signal is at a high level "1", and the time Td during which the photoreceptor surface of the charger 18, 19 moves directly below the phototransistor 302 The flip-flop F2 is inverted at intervals of , and the output of F,2 is
1'' is given to the central control unit of the copying machine as a charger 18, 19 energization instruction signal. “1” of the Q output of flip-flop F2 turns on (opens) the analog gate 3]+.
As a signal, the analog output "1" is applied to the analog gate 312 as a gate-on (open) signal.

FIG. 3 shows signals of various parts of the circuit shown in FIG. 2.

The operation of the abnormality detection device shown in FIG. 2 will be described below with reference to the time chart shown in FIG. 3. In response to an abnormality detection input operation or entry into the abnormality detection step by its own program, the central controller of the copying machine rotates the drum 11 and energizes the developing device 12. After a time period greater than or equal to Td has elapsed since the start of this process, the central controller 341 sends an initialization pulse to the timing control circuit 36 and the counter 341.
342, and then the detection instruction signal is set to "1" and is given to the timing control circuit 36 together with the timing pulse.

In the abnormality detection device (FIG. 2), counters 341 and 342 are cleared by the initialization pulse, and flip-flop F1 of timing control circuit 36 is reset.

Next, in the timing control circuit 36,
The first output timing pulse of ANI is applied to the set end S of the flip-flop F1 through the AND gate AN'2, which sets Fl and turns off the AND gate AN2 (gate closed). F2 is reset and counter 37 is cleared. The initial state has now been set (initialized). From this initial state, the counter 37 counts up every time a timing pulse arrives, and when the count value reaches a value equivalent to Td, the flip-flop F2 is inverted and the counter 37 is cleared.

As a result, during the first time period Tdl from initialization, the charger 1
8. -19 is energized, the first gate 311 is turned off, the second gate 312 is turned on, and the charger 18.
The starting end of the photosensitive surface charged by the energization is the phototransistor 3
After the delay time Td reaching just below 02, the counter 37
F2 is inverted and the counter 37 is cleared by the Td count of
．． 19 is deactivated, 3b is on, and 312 is off. Similarly, in the third time period Td3, the charger 18, 19 is energized, 31
2 off and 312 on. The same applies below.

Time Td1. during which the uncharged photosensitive surface moves directly below the phototransistor 302. Td3...Td(2n-1
)... Since the second analog gate 312 is on, the light amount detection voltage a is the highest value hold circuit 3.
22 and comparator 332. Hold circuit 3
22, the voltage a is divided by the resistor R21*R22, so the output of the circuit 322, that is, the second comparison value, is the highest value of the light amount detection voltage a, as shown by the dashed line in FIG. It is a value multiplied by (R21+R22). Therefore, if toner adheres to defects such as black streaks, peeling, lightning strikes, etc., the light amount detection voltage a decreases to the level shown in FIG. 2 Pmt l Pm2 + PflL3...
..., and when these arrive, the second comparator 3
32's output d becomes high level "1" and the counter 342
counts up and the light emitting diode 352 lights up. That is, the light emitting diode 352 lights up for each defect,
A counter 342 counts the number of defects.

Time Td2. during which the charged photosensitive surface moves directly below the phototransistor 302. Td4.・・・・・・Td(2%)・
Since the first analog gate 311 is on during ..., the light amount detection voltage a is kept at the lowest value hold circuit 32.
1 and to comparator 331. , hold circuit 3
21, the voltage a is divided by the resistor Rtt+R12, so the output of the circuit 321, that is, the first comparison value C is the lowest value of the light quantity detection type l pressure a, as shown by the dashed line C in FIG. The value is multiplied by R12/(RIl+R12). Therefore, when toner is not attached to defective parts such as peeling parts and lightning strike parts, voltage a rises in level Pnx* PH1, PR3+ as shown in Fig. 2, and when these occur, The output e of the first comparator 331 becomes a high level, the counter 341 counts up, and the light emitting diode 351 lights up.In other words, the light emitting diode 351 lights up for each defect, and the counter 3
4t counts the number of defects.

The operator knows the distribution and amount (density) of defects by lighting the light emitting diodes 351 and 352 when an abnormality is detected. The central control unit of the copying machine resets the detection instruction signal (sets it to "O") after a predetermined time and sets the detection instruction signal to "O".
It reads the count value of l+342 and compares it with a predetermined value to issue an alarm.

As described above, according to the present invention, abnormalities on the surface of the photoreceptor are automatically and mechanically detected instead of "examining the image on the recording paper in detail".

In addition, in the photoreceptor charging zone, black streaks Pm]rP,
3 (FIG. 3) shows a large level decrease, while the low level decrease PrIL2. P□4 etc. are often peeled off with no toner left (white spots on recording paper).

In another embodiment to distinguish between this peeling, the output of the highest value hold circuit 322 is further divided so that the voltage is slightly lower than the comparison value and the white area is the level (Pmz.

The black streak level (P, , 1, P-3) is lower than that of R14).
) is obtained, and the signal a is compared with b2 using another set of comparators. If a≦b2, it is judged as a black streak, and if b2<a≦b, it is judged as peeling. The configuration is as follows.

One more light emitting element is added to the light emitting elements (351, 352) and these sections are activated to emit light.

[Brief explanation of the drawing]

FIG. 1 is a side view showing one type of copying machine embodying the present invention, FIG. 2 is a circuit diagram showing the configuration of one apparatus embodying the present invention, and FIG. It is a time chart showing signals. 1: Contact glass plate 2: Holding plate 3: Document 4: Lighting light

Claims (3)

[Claims] (1) While driving the photoreceptor of the electrophotographic device, the charger is energized and deenergized in a predetermined pattern, and the level of reflected light on the surface of the photoreceptor that has passed through the developing section is adjusted to the level of light that passes directly below the photoreceptor when the charger is energized. The photoreceptor surface is compared with a first comparison value determined by the lowest reflected light level, and the photoreceptor surface that passes directly under it when the charger is de-energized is compared with a second comparison value determined by the highest reflected light level. A method for detecting abnormalities on the body surface. (2) A method for detecting an abnormality on a photoreceptor surface according to claim (1), wherein the first comparison value is a value obtained by multiplying the lowest value by a coefficient smaller than 1. (3) The method for detecting an abnormality on the surface of a photoreceptor according to claim (1), wherein the second comparison value is a value obtained by multiplying the highest value by a coefficient smaller than 1.