JPH08278690A - One component developing device - Google Patents

Abstract

PURPOSE: To provide a high speed - high grade one component developing device capable of getting rid of a ghost image. CONSTITUTION: This device is composed of a developing roller 9 provided opposite to a photoreceptor in rotatably, a recovering roller 11 opposite to the developing roller 9 in rotatably and a recovering bias voltage power source 23 applying recovering bias voltage to the recovering roller 11. Then, the device is provided with a supplying roller 10 provided opposite to the developing roller 9, a supplying bias voltage power source 22 applying the supplying bias voltage to the supplying roller 10, and a transporting roller 12 provided opposite to the supplying roller 10 and the recovering roller 11 in rotatably. The device is provided with a low frequency alternating current voltage power source device 21 applying the lower frequency alternating voltage to the transporting roller 12 for forming an electric field so as to attract toner on recovering roller 11 in the direction to the transporting roller 12, in a position on the recovering roller 11 opposed to the transporting roller 12, and to attract the toner on the transporting roller 12 in the direction to the supplying roller 10, in a position on the transporting roller 12 opposed to the supplying roller 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a one-component developing device for electrophotography.

[0002]

2. Description of the Related Art Conventionally, a one-component developing device has been widely used as one of developing devices used in electrophotographic image forming apparatuses. A one-component developing device usually frictionally charges a one-component toner by a regulating member such as a blade and a developing roller,
A charged toner layer is formed on the developing roller and development is performed. The one-component developing device is capable of sharp and developing without edge effect, and does not require toner concentration control or a stirring process, and is therefore compact and excellent in cost.

[0003]

In the one-component developing device, the charged toner layer on the surface of the developing roller needs to be replaced every time the developing roller rotates. If the charged toner layer on the surface of the developing roller is not replaced, the charged toner layer whose toner has been consumed in the form of a developed image will be used for the next development, resulting in a so-called ghost image. In the one-component developing method, replacement of the charged toner layer on the surface of the developing roller is usually performed by scraping off the charged toner layer with a regulating member.

However, since the charged toner layer is attracted to the developing roller by electrostatic attraction, it is necessary to increase the scraping force of the regulating member in order to completely remove it. However, when the scraping force of the regulating member is increased, the stress on the toner particles, the developing roller, and the regulating member increases. When the stress on the toner particles, the developing roller, and the regulating member increases, it becomes difficult to form the charged toner layer, the developing state becomes unstable, and the durability of the toner and the developing device deteriorates. In particular, when increasing the speed of the developing device, it was necessary to increase the scraping force of the regulating member. For this reason, if the speed of the one-component developing method is increased, it is likely that a ghost image is generated, the developing state becomes unstable, and the durability of the toner and the developing device deteriorates. Therefore, it is difficult to use the one-component developing device for high-speed development.

If the charged toner layer is replaced by scraping the regulating member, the charge of the toner will be lost when the charged toner layer is scraped. At this time, the charge of the toner is lost nonuniformly, so that the toner is likely to aggregate. Therefore, if the toner is removed from the developing roller and then the toner is transferred to another roller, circulated and reused, the developability deteriorates. Therefore, when the toner is supplied to the developing roller, it is necessary to charge the toner to a predetermined potential at once by the frictional force between the developing roller and the regulating member. In order to charge the toner to a predetermined potential at one time, it is necessary to increase the frictional force between the developing roller and the regulating member, and increasing the frictional force between the developing roller and the regulating member causes stress on the toner particles, the developing roller and the regulating member. growing.

To solve the above problems, the charged toner layer on the surface of the developing roller can be exchanged and circulated without strongly pressing the regulating member, and high-speed high-quality development with no ghost image can be achieved. It is to provide a one-component developing device for performing.

[0007]

In order to solve the above-mentioned problems, a one-component developing device for electrophotography of the present invention has a developing roller rotatably provided facing a photoconductor and a developing roller facing the developing roller. A rotatable recovery roller, a recovery bias voltage power supply that applies a recovery bias voltage to the recovery roller, a supply roller rotatably provided facing the developing roller, and a supply bias voltage applied to the supply roller. The supply bias voltage power supply, the supply roller, and the conveying roller rotatably provided so as to face the collecting roller, and the toner on the collecting roller in the direction of the conveying roller at the facing portion of the conveying roller and the collecting roller. Creates an attractive electric field,
A low-frequency alternating voltage power supply device that applies a low-frequency alternating voltage that is set so as to form an electric field that attracts the toner on the conveying roller toward the supply roller, is provided at the facing portion of the conveying roller and the supply roller. .

[0008]

According to the developing device of the present invention, the charged toner layer on the surface of the developing roller can be exchanged and circulated without pressing the regulating member under strong pressure. Therefore, the toner removed from the surface of the developing roller can be returned to the developing roller in a charged state for development. By using the charged toner layer formed in this manner for development, high density development is possible without ghost images and noise. Further, since the peripheral speed of the developing roller can be kept low, the developer is less scattered and deteriorated even in the high-speed developing region, and high density and high quality development can be performed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the structure of an image forming apparatus according to the present invention.

The photoreceptor 1 is positively charged by the corona charger 2 and then exposed in the exposure unit 3 to form an electrostatic latent image. The photoreceptor 1 has -100 to 20
A bias voltage of 0 V is applied by the photoconductor bias power source 20. The electrostatic latent image on the photoconductor 1 is developed by the developing device 4 by the action of the bias voltage applied to the photoconductor 1 to form a toner image. The toner image thus formed is transferred by the transfer charger 5 onto the conveyed copy paper 8. The copy sheet 8 is separated from the photoconductor 1 by the separation charger 6, and the toner image on the copy sheet 8 is fixed by a fixing device (not shown). Further, the residual toner on the photoconductor 1 is removed by the cleaner 7, and the next image forming process is started.

FIG. 2 is an enlarged sectional view of the developing device 4.

The developing device 4 mainly includes a developing roller 9, a supplying roller 10, a collecting roller 11, a conveying roller 12, and
It is composed of a toner hopper 13.

The developing roller 9 is made of a conductive metal, a hard resin, or the like.
They are opposed to each other with a gap of about 0 μm. Supply roller 1
0, the collection roller 11, and the conveyance roller 12 are made of conductive rubber or metal, and all rotate counterclockwise at a speed of 240 RPM. The supply roller 10 and the collection roller 11 are respectively the developing roller 9 and the developing roller 9.
They are arranged at intervals of 200 μm. further,
The transport roller 12 is arranged at a distance of 100 to 200 μm from the supply roller 10 and the collection roller 11.

The toner hopper 13 is provided so as to face the supply roller 11 and the transport roller 12, and is filled with the positive polarity toner 15. In addition, the supply roller 11 has
The brushes 14 face each other with a predetermined interval.

The developing roller 9 has an AC bias power source 21.
Therefore, the AC bias voltage (1 KHz, 1.5 KVp-p) is applied. The supply bias power supply 22 applies a positive supply bias voltage to the supply roller 10, and the recovery bias power supply 23 applies a negative recovery bias voltage to the recovery roller 11.

An AC bias power source 21 is connected to the conveying roller 12 via a condenser 26. Further, a conveyance bias power source 24 is connected to the conveyance roller 12 via an inductance circuit 25. The carrier bias power supply 24 applies a carrier bias voltage that is a rectangular wave low-frequency alternating voltage.

Since the capacitor 26 passes only the high frequency alternating current, only the high frequency alternating current AC bias voltage is passed, and the carrier bias voltage which is the low frequency alternating voltage is prevented from flowing into the AC bias power source 21 and the developing roller 9. There is. On the other hand, the inductance circuit 25 passes only the low-frequency alternating voltage of the high-frequency alternating current, and therefore passes only the carrier bias voltage which is the low-frequency alternating voltage, and prevents the AC bias voltage of the high-frequency alternating current from flowing into the carrier bias power supply 24. ing. By the operation of such a circuit, only the AC bias voltage of the AC bias power source 21 is applied to the developing roller 9, and the AC bias voltage of the AC bias power source 21 and the transport bias of the transport bias power source 24 are applied to the transport roller 12. The voltages are superimposed and applied.

FIG. 3 is an explanatory diagram showing the relationship among the recovery bias voltage, the supply bias voltage, and the carrier bias voltage.

The supply bias voltage is a positive DC bias voltage that is the same as the toner polarity, the recovery bias voltage is a negative DC bias voltage that is the opposite polarity of the toner polarity, and the absolute values of both voltages are 100V. Is. Further, the carrier bias voltage is a square wave of +400 V to −400 V and 34 Hz.

As is clear from the figure, the maximum negative value is -400.
When the voltage is V, the potential difference from the recovery bias voltage (-100V) is -300V, and when the carrier bias voltage is the maximum positive value + 400V, the potential difference from the supply bias voltage (+ 100V) is + 300V.

Since only the AC bias voltage is applied to the developing roller 9, the positively charged toner on the developing roller 9 moves to the collecting roller 11 by the action of the collecting bias voltage and the AC bias voltage. Furthermore, the collection roller 1
The positively-charged toner that has moved above 1 is removed from the carrying roller 12 by the action of the potential difference between the recovery bias voltage and the carrying bias voltage and the AC bias voltage that is superimposed and applied when the carrying bias voltage has a negative maximum value. Move to the collection roller 11.

Since the carrier bias voltage is a rectangular wave,
The transport roller 12 is alternately charged to the maximum positive value and the maximum negative value. Therefore, the collecting roller 11 to the conveying roller 12
Toner is moved only to the portion facing the collecting roller 11 when the transport bias voltage has a positive maximum value. Therefore, the toner on the collecting roller 11 moves to the transport roller 12 at a constant interval as the transport roller 12 rotates, and adheres to the transport roller 12 in a striped pattern. The interval and width of the toner adhering portions formed on the carrying roller 12 are determined by the rotation cycle of the carrying roller 12 and the cycle of the carrying bias voltage. Therefore, the sum (n) of the numbers of toner-attached portions and non-attached portions formed on the transport roller 12
Can be calculated by the following equation (1). TV / 2 = TR / n (1) where, TV = conveyance bias voltage cycle TR = conveyor roller rotation cycle n = the number of toner-adhered and non-adhered areas on the conveyor roller In the example, the frequency of the transport bias voltage is set to 34 Hz and the rotation speed of the transport roller 12 is set to 240 RPM based on the equation (1) so that n = 17. For this reason, a total of 17 toner-attached portions and non-attached portions are formed on the transport roller 12. In other words, the width of the toner attachment portion and the non-adhesion portion is 1/17 of the entire circumference of the transport roller 12.
Becomes Further, in this embodiment, the transport roller 12
The interval between the facing portion of the supply roller 10 and the facing portion of the transport roller 12 and the collecting roller 11 is 2/17 of the entire circumference of the transport roller 12 on the developing roller 9 side and 15/17 of the entire circumference of the transport roller 12 on the opposite side. Is configured to be. Therefore,
The transfer bias voltage is applied to the transfer roller 12 and the recovery roller 11.
During the movement from the facing portion of the above to the facing portion of the transport roller 12 and the supply roller 10, the positive and negative are exchanged an odd number of times.
That is, the portion (toner adhering portion) facing the collecting roller 11 when the conveyance bias voltage has the maximum negative value is the conveyance roller 1.
The rotation of 2 causes the conveyance bias to take a positive maximum value when it comes to the portion facing the supply roller 10.
When the transport bias voltage has the maximum positive value, the positively charged toner moves from the transport roller 12 to the supply roller 10 due to the action of the potential difference between the transport bias voltage and the supply bias voltage and the AC bias voltage applied in a superimposed manner. . At this time, new toner attached to the charged toner also moves to the supply roller 10 while the transport roller 12 moves in the portion facing the toner hopper 13.

The toner attached to the supply roller 10 in this manner is conveyed to the portion facing the developing roller 9 by the rotation of the supply roller 10. The brush 14 provided close to the surface of the supply roller 10 contacts the toner conveyed to the portion facing the developing roller 9 and disturbs the toner layer to make the toner layer uniform. The toner conveyed to the portion facing the developing roller 9 moves to the developing roller 9 by the action of the supply bias and the AC bias voltage applied to the developing roller 9. Since the toner layer on the supply roller 10 is almost completely removed by the developing roller 9, the toner does not adhere to the downstream portion of the portion facing the developing roller 9.
Therefore, the toner does not move from the supply roller 10 to the transport roller 12 even when the transport bias voltage reverses and becomes negative. Further, when the portion where the charged toner has moved from the carrying roller 12 to the supplying roller 10 faces the collecting roller 11, the carrying bias voltage is synchronized so as to become negative again, so that the toner moves to the collecting roller 11 in reverse. There is no such thing.

On the other hand, the toner layer moved onto the developing roller 9 flies due to the action of the bias voltage applied to the photoconductor 1 and the AC bias voltage applied to the developing roller 9.
It moves and is developed.

After the development, the toner layer on the developing roller 9 is almost completely collected by the collecting roller.

In this way, the toner collected by the collecting roller 11 returns to the supply roller 10 via the conveying roller 12 and is circulated and used for development. This time,
All the toner layers are supplied from the supply roller 10 to the developing roller 9 and used for development, and then are almost completely collected by the collecting roller, and the toner layer on the surface of the developing roller 9 is replaced every rotation. Therefore, almost no residual image (ghost image) remains. Further, while the toner is circulating, it may come into contact with the toner 15 in the toner hopper 13,
Alternatively, the brush 14 rubs the surface, or the opposing portion of each roller receives a disturbing effect due to the diffusion action of the AC electric field, so that even if the residual image remains, it disappears.

In order to achieve the above steps, the half cycle of the transfer bias voltage applied to the transfer roller 12 in a superimposed manner is an odd fraction of the rotation cycle of the transfer roller 12, so that the supply roller 10 and the recovery roller 10 can be recovered. It suffices that the temporal distance of the facing portion of the roller 11 with respect to the transport roller 12 is an even multiple of a half cycle of the transport bias voltage.

According to the present invention, the charged toner can be circulated without burdening the toner. In addition, the charged toner contacts the uncharged toner in a wide range during the circulation process. At this time, the charged toner conveyed in the uncharged toner acts like a kind of charging core, and has an action of facilitating the charging of the uncharged toner. Therefore, uncharged toner can be efficiently charged, and stable toner charging can be achieved even during high-speed development. Further, since the disturbance is sufficiently performed in the process of circulating the toner, the ghost image is also prevented.

The polarities of the supply bias voltage and the recovery bias voltage of the developing device of the present embodiment are opposite to the case of using the positive polarity toner when the polarity of the toner is negative, and the supply bias voltage is The negative polarity and the recovery bias voltage have the positive polarity. Further, in the present embodiment, the development is performed by the bias voltage applied to the photoconductor, but the DC bias voltage may be applied to the developing roller. DC on the developing roller
When applying the bias voltage, it is necessary to set the voltage values of the supply bias voltage, the recovery bias voltage, and the carrier bias voltage by shifting by the applied voltage value.

Further, as the developing bias voltage, an AC bias voltage for flying the developing toner may be applied to the supply roller and the collecting roller, and a DC bias voltage may be applied to the developing roller.

The AC bias voltage used in the present invention is preferably about 1 to 2 KHz and 1 to 3 KVp-p, and the absolute values of the supply bias voltage and the recovery bias voltage are both 100 to 300 V. On the other hand, the waveform of the carrier bias voltage may be a sine wave or a rectangular wave, but it is necessary that the maximum value is larger than the absolute value of the bias voltage applied to the supply / collection roller by a predetermined value or more. Specifically, the value of the transport bias voltage is in the range of 300 to 600 V, and at least the absolute value of the voltage applied to the supply roller and the collection roller is
It is desirable to have a maximum value higher than 100V.

Further, a plurality of conveying rollers may be arranged close to each other in the toner tank, and AC bias voltage and conveying bias voltage may be applied to every other roller so that the charged toner circulates. With such a configuration, the uncharged toner can be charged at high speed.

The present invention may be applied to a contact type developing device. When the developing device is of a contact type, it is preferable that the developing roller 9 is formed of a soft and elastic conductive rubber, or a thin cylindrical sleeve such as metal or plastic is used.

[0034]

In the developing device of the present invention, the charged toner can be circulated without burdening the toner, and the uncharged toner can be efficiently charged. Therefore, even during high speed development, uniform and stable toner charging can be achieved. Further, since the disturbance is sufficiently performed in the process of circulating the toner, the ghost image is also prevented. Further, since the charged toner is all conveyed by the electrostatic force, the toner is not forced. Therefore, toner aggregation does not occur, and high-quality development is possible.

[Brief description of drawings]

FIG. 1 shows a configuration of an image forming apparatus according to the present invention.

FIG. 2 is an enlarged cross-sectional view of a developing device according to the present invention.

FIG. 3 is an explanatory diagram showing a relationship among a recovery bias voltage, a supply bias voltage, and a carrier bias voltage.

[Explanation of symbols]

 1 Photoconductor 2 Corona Charger 3 Exposure Unit 4 Developing Device 5 Transfer Charger 6 Separation Charger 8 Copying Paper 7 Cleaner 9 Developing Roller 10 Supply Roller 11 Recovery Roller 12 Conveying Roller 13 Toner Hopper 14 Brush 15 Toner 20 Photosensitive Bias Power Supply 21 AC Bias Power supply 22 Supply bias power supply 23 Recovery bias power supply 24 Carrier bias power supply 25 Inductance circuit 26 Capacitor

Claims (2)

[Claims] 1. A developing roller rotatably provided facing the photoconductor, a collecting roller rotatably facing the developing roller, and a collecting bias voltage power supply for applying a collecting bias voltage to the collecting roller. A supply roller rotatably provided facing the developing roller; a supply bias voltage power supply applying a supply bias voltage to the supply roller; and a supply roller rotatably provided opposite the supply roller and the collecting roller. An electric field that attracts the toner on the collecting roller toward the conveying roller is formed at the conveying roller and the facing portion of the conveying roller and the collecting roller, and the toner on the conveying roller is supplied at the facing portion of the conveying roller and the supplying roller. A power supply having a low frequency alternating voltage power supply for applying a low frequency alternating voltage to the transport roller set to create an electric field that attracts towards the roller. Single-component developing device for child photographs. 2. The relationship between the cycle of the low frequency alternating voltage, the cycle of rotation of the carrying roller, and the sum of the number of toner adhering portions and non-adhering portions formed on the conveying roller is TV / 2 = TR / n where TV = cycle of low frequency alternating voltage TR = cycle of rotation of transport roller n = sum of the number of toner-adhered portions and non-adhered portions on the transport roller, and the toner-adhered portion formed on the transport roller The one-component developing device for electrophotography according to claim 1, wherein the sum of the number of non-adhesive portions is odd.