JPS6325351B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus. The color copying machine has four developing units: yellow (Y), magenta (M), cyan (C), and black BK. While one developing device corresponding to each exposure filter is being driven, the other developing devices scrape off the toner on the sleeve so that no other undesignated developer adheres to the drum. However, if the transfer member jams while one developing device is being driven, or if the power is turned off for some reason, the toner adhering to the sleeve will come into contact with the drum and all functions will stop.

When the power is turned on again when the jam processing is completed or the power can be turned on again, the drum rotates to a designated position (home position) and stops. However, while the drum rotates to the home position, the charges already on the drum adhere to the developer on the sleeve in contact with the drum, causing the drum to rotate. Since the image visualized on the drum is an image that has been stopped during the previous copying operation, it is cleaned by a blade as an unnecessary developing image on the transfer paper and discarded outside as waste toner. If such occurrences occur frequently, the amount of toner consumed increases. Normally, 80% of the toner attached to the drum is transferred to the transfer material, and the amount of toner remaining on the drum surface is about 20%, so the amount of toner cleaned by the blade is extremely small. However, when the copying machine's operation is interrupted due to a jam or the power is turned off, and when the copying machine starts again, the cleaning amount is 100% cleaning of the toner adhering to the drum. It is necessary to have a surplus in the toner conveying capacity after cleaning. In addition, during continuous full-color copying, two developing devices must be driven in an overlapping manner in order to increase the copying speed. When the drums are restarted after the drums have stopped with the toner of two developing devices in contact with the drum, the toner attached to the drum by one developing device may get mixed into the other developing device. . Therefore, for example, yellow (Y) toner is mixed with cyan (C) toner, making it difficult to reproduce good colors.

In view of the above points, the present invention provides an improved image forming apparatus.

The present invention solves the above-mentioned problems caused by conventional jamming, and includes a photosensitive drum on which a latent image is formed;
In an image forming apparatus having a developing device that supplies developer to the photosensitive drum and develops a latent image by contact, the image forming apparatus includes a jam detecting means, and a power supply for restarting image formation after the detection signal of the detecting means is generated. The image forming apparatus is characterized by comprising means for responsively disabling development using the developer of the developing device to prevent the developer from adhering to the photosensitive drum.

Specific configurations related to the present invention are listed below.

Another object of the present invention is that when the power is turned off during a copying operation, the toner adhering to the drum is removed by scraping off the developer on the developing sleeve that is in contact with the drum as soon as the power is turned on again, so that toner does not adhere to the drum. To provide a developer control device that can prevent color mixing with other developers by rotating the developer to a drum home position.

Another object of the present invention is to form a latent image on an insulator by an electrostatic recording method, and then develop it by adhering developer powder consisting of an iron powder carrier and powder toner to a magnet, and then sequentially developing the adsorbed developer powder. Even if the power is turned off during development, the scraping and shielding member for each color is activated in advance to mix the developer and prevent it from entering the device. The present invention provides a multicolor developer control device that prevents toner from flying away.

Other objects of the present invention will become clear from the description of the embodiments given below in conjunction with the drawings. The details of the present invention will be explained below using examples and with reference to the drawings.

FIG. 1 shows a sectional view of an embodiment of an electronic copying machine to which a developing device control device according to the present invention is applied. First, the surface of the drum 1 is a three-layer photoreceptor using a CdS photoconductor, is rotatably supported on a shaft 2, and starts rotating in the direction of an arrow 3 in response to a copy command.

When the drum 1 rotates to the normal position, the original placed on the original platen glass 4 is illuminated by an illumination lamp 6 integrated with the first scanning mirror 5, and the reflected light is used for the first scanning. It is scanned by mirror 5 and second scanning mirror 7. The first scanning mirror 5 and the second scanning mirror 7 move at a speed ratio of 1:1/2, so that the original is scanned while the optical path length in front of the lens 8 is always kept constant. After passing through the lens 8 and the third mirror 9, the reflected light image is color-separated by a color separation filter 10 if necessary, and further passes through the fourth mirror 11 and the dust-proof sealing glass 12 to the exposure section 1.
3, an image is formed on drum 1.

After the drum 1 is neutralized by a static eliminator 14 and then charged (for example, +) by a primary charger 15, an image irradiated by an illumination lamp 6 is slit exposed in an exposure section 13.

At the same time, AC or primary static electricity removal with a polarity opposite to that of the primary (for example -) is performed using a static eliminator 16, and then a high-contrast electrostatic latent image is formed on the drum 1 by full-surface exposure using a full-face exposure lamp 17.

The electrostatic latent image on the photosensitive drum 1 is then transferred to a developing device 18.
It is visualized as a toner image. Developer 1
8 is yellow 181, magenta 182, cyan 1
Consists of four developers for 83 and black 184,
A toner image of the required color is obtained by a developing device designated in accordance with the color separation filter used for exposure.

The transfer paper 201 in the cassette 191 is fed into the machine by the paper feed roller 211, roughly timed by the first register roller 221, accurate timing by the second register roller 23, and gripped by the gripper 24. .

Next, while the transfer paper 201 passes between the transfer charger 25 and the drum 1, the toner image on the drum 1 is transferred onto the transfer paper. The gripper 24 holds the transfer paper 2
01 is rotated by the required number of rotations, and an image of the required number of colors is transferred. After the transfer is completed, the transfer paper is released from the gripper 24, guided to the conveyor belt 27 by the separating claws 26, and further transferred to the fixing roller pair 28,
29, where it is fixed by pressure and heating, and then discharged onto a tray 30.

After the transfer, the surface of the drum 1 is cleaned by a cleaning device 31 composed of an elastic blade, and the drum 1 moves on to the next cycle.

FIG. 2 is a side view illustrating the developing unit of the developing device of the above-mentioned specific example apparatus. In the developing unit, a cylindrical sleeve 21 made of a non-magnetic material and rotatably supported is provided in a unit housing 20.
A magnetic roller 22 is provided which is fixed at zero or movable relative to the sleeve. The developer K accumulated in the lower part of the unit housing 20 is held on the sleeve surface by the magnetic field formed by the magnetic roller, forming a developing brush. In order to adjust the height of the developing brush, the doctor blade 23 is fixedly installed in the unit housing 20 so that its tip is kept at a predetermined distance from the surface of the sleeve 21.

The sleeve 21 rotates in the direction of the arrow, and the developer held on the sleeve surface is adjusted to a predetermined spike with a doctor blade 23, and then comes into contact with the surface of the photoreceptor 10, and the static formed on the surface Develop the electronic image. The developer used for development is scraped off from the surface of the sleeve 21 by a scraper blade 24 whose tip is in contact with the surface of the sleeve 21.
On the other hand, the magnetic pole of the magnetic roller inside the sleeve is placed near the scraper blade as shown in the figure.
By not arranging them, the scraping efficiency of the scraper blade is increased and re-adhesion is prevented. A stirring member 25 is disposed at the bottom of the unit housing 20 for stirring the scraped developer, the accumulated developer, and the replenishing developer from a supply means (not shown). A developer scraping member 26 is rotated by a shaft 28 provided at the end of the housing 20 . Reference numeral 27 denotes a DC solenoid that moves the scraping member 26, and when the coil is energized, the movable piece 29 brings the developer scraping member 26 into contact with the sleeve 21 using the shaft 28, which is sucked in the A direction, as a fulcrum. FIG. 3 shows a circuit for driving and controlling the scraping member 26, and will be described in detail. 55 is a detection circuit that detects a power-on signal and converts it into a pulse. A level converter 56 generates a TTL level logic signal. The output of the level converter 56 triggers the well-known timer ICQ10, and the output of the timer ICQ10 is connected to a resistor R10 and a capacitor C
It becomes H level for the time determined by 10, which turns on transistor Q11 and turns on relay 50.
to drive. Contacts 50a and 50b of the relay 50 are connected to clutches Cl1, Cl2, Cl3, and Cl for driving each color developer.
4. Developer scraping solenoids SL1, SL2,
Drives SL3 and SL4. 51 is a shaping circuit,
At the falling edge of transistor Q11 (timer Q1
0) outputs a trigger pulse to the control circuit 52. This signal sends a copy-enabled condition signal to the control section of the copying machine. Q16, Q17, Q18, and Q19 are transistors for driving the clutches Cl1, Cl2, Cl3, and Cl4 that drive the developing device, and are controlled by Y, M, C, and BK control signals sent from the control section CC of the copying machine. Then, the designated developing devices 181 to 184 are driven in accordance with the color separation filters used in exposure. Q
12, Q13, Q14, and Q15 are transistors for driving DC solenoids SL1, SL2, SL3, and SL4, which bring the developer scraping member 26 into contact with the sleeve 21 and cut off the spikes of developer depending on the paper size while the developing device is running. be.

The operation of the embodiment configured as described above will be explained with reference to the timing diagram shown in FIG. The waveform is shaped by , and a power-on signal is output as shown in a of FIG. The timer ICQ10 is triggered by this signal, and the resistor R10 and capacitor C1
H level for a time T determined by 0 (Fig. 4b)
is output, turning on transistor Q11. Therefore, the relay 50 is driven, and its contacts 50a, 5
0b is shorted, clutch Cl1~Cl4, solenoid
SL1 to SL4 operate. Due to the action of the clutch and solenoid, the drum of the developing device rotates for a time T, and the scraping member 26 comes into contact with the sleeve 21 for a time T, so that the developer on the sleeve 21 is cut off. After time T has elapsed, the developer on the sleeve 21 runs out, and one condition for the copying operation is satisfied. When the timer output becomes L level after T time, it changes from L level to H level and outputs a copy enable signal e to the control unit CC. Needless to say, the conditions for enabling copy operation include the weight/up of the fixing heater, the remaining amount of toner, the remaining amount of paper in the cassette, etc. After the copying operation starts, each developing device is driven at each development timing of Y, M, C, and BK, toner is deposited on the drum 1, and a visible image of the required paper size is formed. After time t, a cutting signal is sent to the DC solenoid SL1, the toner on the sleeve is scraped off, and excess developer is prevented from being adsorbed on the drum, and then the rotation of the developing device is stopped.

If the copy paper is jammed or the main is cut for some reason while the developing device is being driven in the above-described operation (timing chart S), the rotation will stop while the developer remains on the sleeve 21 in contact with the drum. . Therefore, when the jam is cleared or the power is supplied after the power is turned on again (Fig. 4 Main SW
ON) or (before starting the copying operation) the developer and scraping member are activated as described above to scrape off the developer on the sleeve in contact with the drum 1, so when the copying machine is restarted, other Color mixing with the developer can be prevented.

Although the above embodiment has been explained using a timer circuit and a relay, such parts can easily be constructed from other circuit components.

As described above, the present invention is configured to prevent the developer from adhering to the drum before starting the copying operation, so color mixing with other developers can be prevented, and since excess toner is not adsorbed to the drum, the toner It prevents skipping, reduces toner consumption, and provides good copies.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a copying machine, FIG. 2 is an explanatory diagram of a developer control device according to the present invention, FIG. 3 is a circuit diagram of a developer control device according to the present invention, and FIG. 4 is a signal waveform diagram. . SL1~SL4...Solenoid, Cl1~Cl4...
Clutch.

Claims (1)

[Scope of Claims] 1. An image forming apparatus including a photosensitive drum on which a latent image is formed, and a developing device that supplies developer to the photosensitive drum to contactly develop the latent image, comprising: a jam detection means; means for disabling development by the developer in the developing device in response to power being turned on again to resume image formation after the detection signal of the detection means is generated, and suppressing the developer from adhering to the photosensitive drum; An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a color image forming apparatus having a plurality of the developing devices, and the suppressing means has a timer for performing the operation for a predetermined period of time. Device.