JPH04116679A - Device for recovering developer - Google Patents

Abstract

PURPOSE:To stably recover a toner charged to normal polarity, a toner charged to the reverse polarity and a carrier whether they are magnetic or not by impressing potentials of opposite polarities on the dielectric parts and the electrical conductor part of the surface of a roll for recovering a developer. CONSTITUTION:A roll 3 for recovering a developer, a means 4 to impart electric charges to the dielectric parts 31 of the roll 3 and a means V2 to impress potential whose polarity is reverse to the surface potential of the parts 31 impressed by an electric charge imparting means V3 on the electrical conductor part 32 are arranged. Since potentials of opposite polarities are impressed on the dielectric parts 31 and the conductor part 32 of the surface of the roll 3, a scattered toner charged to normal polarity is recovered by the parts 31, and a toner charged to the reverse polarity and causing fog and in the case of using a carrier a scattered carrier are recovered by the part 32. The toner and carrier can be recovered whether they are magnetic or not and stable recovery can be carried out with high recovering efficiency over a long period of time without causing a short circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developer recovery device in an electrophotographic image forming apparatus such as a copying machine or a printer.

[Conventional technology]

It is well known that some image forming apparatuses of this type use a one-component developer made of toner, and others use a two-component developer made of toner and carrier.

In these image forming apparatuses, a developing device supplies charged toner to an electrostatic latent image formed on an electrostatic latent image carrier, thereby turning the latent image into a visible image.

By the way, in high-speed image forming apparatuses such as high-speed copying machines and high-speed printers, after toner is replenished to the developing device,
Because the time until development is short, the toner is subjected to development with an insufficient amount of charge, and the development roll that carries toner and supplies it to the electrostatic latent image rotates quickly. It is known that toner and carrier tend to scatter.

Such scattering of toner and carrier adversely affects image quality and contaminates the inside of the image forming apparatus.

In addition, due to the toner coming into contact with parts made of various materials in the developing device, it is charged to a polarity opposite to the normal charging polarity, and this reversely charged toner adheres to the background of the image, causing the background capri phenomenon. It is also known that

As a means to solve such problems,
Publication No. 4941 teaches that a member rotating in the opposite direction to the surface movement direction of the electrostatic latent image carrier is used to push back the scattered developer so that it does not come out of the device.

Furthermore, Japanese Patent Application Laid-open No. 142351/1983 teaches that a magnetic member for attracting unnecessary developer is disposed on the downstream side of the development area on the surface of the electrostatic latent image carrier.

Furthermore, Japanese Patent Application Laid-open No. 61-264364 discloses that a fog removing means to which a voltage of the same polarity as the normally charged toner supplied to the electrostatic latent image is applied is disposed between the developing device and the transfer device. It teaches you to collect reverse polarity toner.

[Problem to be solved by the invention]

However, with the method of pushing back the scattered developer using the counter-rotating member, the scattered developer cannot be reliably recovered, and furthermore, there is a problem that heavy objects such as carriers pass through without being pushed back. .

Furthermore, the method of adsorbing the developer using the magnetic member has a problem in that it can only be applied to magnetic developers.

Furthermore, there is a problem in that the fog removing means to which a voltage of the same polarity as the normally charged toner is applied cannot collect the scattered normally charged toner.

Therefore, a method can be considered in which a roll made of two types of conductors is used and a bias having the same polarity as the toner and a bias having the opposite polarity are applied to each roll. However, in this case, it is necessary to insert an insulator between the conductors.

Since voltages of opposite polarity are applied to the two conductors, this insulator requires a certain thickness to prevent dielectric breakdown. For this reason, a part of the surface of the developer recovery roll is occupied by an insulator that is not originally necessary for developer recovery, and the structure of the developer recovery roll is as shown in FIG. If B has a half-cylindrical shape with insulator C sandwiched between them, manufacturing is easy, but uniform recovery will not be possible unless the rotation speed of the recovery roll is increased. However, since the collection roll itself is small in diameter,
Considering bearing wear, etc., unless the rotation speed is slowed down, long-term durability will be poor.

Therefore, when the rotational speed is reduced, the surface of the collection roll needs to be structured as shown in FIGS. 11 and 12, for example, in order to ensure uniformity of collection. However, in this case, the structure is complicated, making it difficult to manufacture, and the total area of the insulator C increases, resulting in a further decrease in recovery efficiency.

Furthermore, there is a risk that conductor A and conductor B may be short-circuited due to the contamination of foreign substances such as low-resistance substances such as magnetic toner.
Difficult to use in practice.

Furthermore, in these collection rolls, the surrounding electric field is weak due to the insulator C, and the developer collection efficiency is correspondingly poor.

The present invention can recover normally charged toner, reversely charged toner, and carriers, regardless of whether they are magnetic or not, with high recovery efficiency, without fear of electrical short circuit, and for a long period of time. An object of the present invention is to provide a developer recovery device that can stably recover developer over a long period of time.

[Means to solve the problem]

The developer recovery device of the present invention that achieves the above object includes a developer recovery roll having a dielectric portion and a conductive portion on its surface, a means for applying an electric charge to the dielectric portion, and a means for applying electric charge to the conductor portion. The device is characterized in that it includes means for applying a potential of opposite polarity to the surface potential of the dielectric portion.

In the present invention, "a potential with a polarity opposite to the surface potential of the dielectric portion" includes a case where the potential is zero, that is, a ground state.

[For production]

According to the developer recovery device of the present invention, potentials of opposite polarities are applied to the dielectric portion and the conductive portion on the surface of the developer recovery roll, and the scattered normally charged toner is applied to the dielectric portion and the fog is removed to the conductive portion. When oppositely charged toner and carrier are used, the scattered carrier is collected, or conversely, oppositely charged toner, which causes fog, is collected on the dielectric portion, and when carrier is used, the scattered carrier is collected. The carrier is collected, and the scattered normally charged toner is collected on the conductor portion.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cross section of an embodiment incorporated into a developing device of an image forming apparatus.

This developing device includes a casing 14 and a developing sleeve 11 in an opening at the end of the casing. This sleeve 11 is a photosensitive drum P which is an electrostatic latent image carrier.
It faces C with a slight gap, and is rotated clockwise in the figure by a drive means (not shown). Note that the photosensitive drum PC is rotationally driven in the counterclockwise direction in the figure.

Inside the sleeve 11 is a fixed magnet body 1 having an S pole and an N pole.
2 is built-in. A developing bias power supply V+ (150V) is connected to the developing sleeve 11.

The sleeve 11 has five height regulating plates 13 supported by the casing 14! I'm in S. Further, behind the sleeve 11, a bucket roller (not shown) or the like is arranged.

The developer recovery device 200 includes a developer recovery cartridge 20 that is removably attached to the casing 14 below the developing sleeve 11 .

This cartridge includes a box 2 having an open portion facing the photoreceptor drum PC, and a developer collection roll 3 facing the photoreceptor drum PC with a slight gap at the opening of the box 2. The roll 3 is rotationally driven in the counterclockwise direction in the figure by a drive means (not shown).

Inside the box 2, a charger 4 is disposed behind the recovery roll 3 and faces the recovery roll 3. This charger 4 is connected to a power source v3 (-5KV). Further, a scraper 5 is in contact with the recovery roll 3 on the upstream side of the charger 4.

As shown in FIG. 2, the collection roll 3 has a large number of dielectric parts 31 uniformly distributed on its surface, and the parts other than the dielectric parts are made into conductive parts 32.

A power source Vz (+100V) is connected to this conductor portion 32.

Note that the arrangement pattern of the dielectric portion 31 and the conductive portion 32 of the roll 3 is not limited to that shown in FIG. 2, and other examples include patterns shown in FIGS. 3 to 6, respectively.

However, in the pattern shown in FIG. 6, the conductor portion 32 needs to be electrically conductive below the surface.

According to the developing device 1 and the developer recovery device 200 described above, an electrostatic latent image is developed and the developer is recovered as follows.

A developer consisting of a negatively charged magnetic carrier and a positively charged toner is contained in the casing 14 of the developing device 1, and the developer is stirred by a bucket roller (not shown), so that the carrier becomes negative and the toner becomes positive. It is charged and supplied onto the developing sleeve 11. The developer supplied to the sleeve 11 is held in the shape of a spike by the action of the fixed magnet 12 inside the sleeve, and as the sleeve 11 rotates, it is transported to the development area facing the photosensitive drum PC, and the height of the spike is regulated on the way. The height of the ears is regulated by the plate 13.

On the other hand, the surface of the photosensitive drum PC is uniformly charged with a charge of -600 V by a charging charger (not shown), and then exposed to image light, and the potential of the background portion of the image is lowered to about 50 V, forming an electrostatic latent image.

When this latent image reaches the developing area, the developing sleeve 11
Positively charged toner is supplied from above under the application of a bias Vr = -150V to form a visible image. Note that this visible image is transferred onto a transfer material by a transfer device (not shown), fixed onto the transfer material by a fixing device (not shown), and then discharged to the outside of the machine.

On the other hand, the recovery roll 3 is driven counterclockwise in the figure by a drive means (not shown), and the charger 4 brings the potential of the dielectric part 31 on the roll surface close to -150V, and the potential of the conductor part 32 increases. Power supply V2=+100V
The polarity is approximately +100V, which is opposite to the surface potential of the dielectric part.
It is assumed that the potential is .

Therefore, the normally charged positively charged toner scattered during the development is removed from the dielectric portion 3 at a negative potential on the surface of the collection roll 3.
On the other hand, the negatively charged scattered carriers and the oppositely charged (negatively) charged toner that is about to scatter and adhere to the image background are attracted to the surface of the conductor section 32 which has a positive potential. adhere to.

The developer adhering to the surface of the collection roll in this way is scraped off by the scraper 5 and stored in the box 2.

When the recovered developer accumulates in the box 2, the cartridge 20 can be pulled out, the developer removed, and then loaded back into its original position.

The surface of the collection roll 3 is composed of a dielectric part and a conductor part. Therefore, the entire roll surface contributes to developer collection, which improves the collection efficiency, and as shown in FIG. Since a strong wrap-around electric field (an electric field that does not go toward the photoreceptor drum) is generated between the body part 32 and the dielectric part 31, the developer can be collected without disturbing the image development, and
Furthermore, developer recovery efficiency is also improved.

Furthermore, although the collection roll 3 has a dielectric part and a conductor part dispersed, it is easy to manufacture, and as shown in the collection rolls shown in FIGS. 10 to 12, electric There is no possibility that a short circuit will occur.

In addition, as mentioned above, the developer recovery efficiency is high, so developer can be recovered sufficiently without increasing the roll rotation speed, and the lower the roll rotation speed, the less damage to the bearings, etc., and the longer the roll will last. The developer can be collected stably over a long period of time.

Next, the embodiment shown in FIG. 8 will be described.

This developer recovery device 201 is incorporated into the developing device 2A. The recovery device 201 includes a recovery roll 3 having the same surface structure as the developer recovery roll and having a built-in fixed magnet 6 instead of the developer recovery cartridge 20 shown in FIG.

Also in this developing device 2A, the bias power supply V+ (150V) is connected to the developing sleeve 11, and the power supply V+ (150V) is connected to the conductor portion 32 of the collection roll 3 of the collection device W2O1.
t (+100V) is connected, and the dielectric part 31 of the roll 3 is connected to the power supply ■3 via the conductive charging brush 7 (
-700V) is applied.

Also in this embodiment, the scattered normally positively charged toner adheres to the dielectric portion of the collection roll 3, and the negatively charged carrier and oppositely charged toner adhere to the conductor portion 31 and are collected.

However, the magnetic carrier is not limited to the potential of the conductor portion 31 of the collecting roll 3, but also the potential of the photosensitive drum PC in the fixed magnet body 6.
It also adheres to the collection roll due to the magnetic force of the n4 pole facing the. Therefore, developer recovery can be performed more reliably than in the embodiment of FIG.

The carrier thus collected is conveyed to the S5 pole of the fixed magnet body 6 as the collection roll 3 rotates. S, pole carrier is S next to it.

Because the polarity is the same as that of the fixed magnet body 1 in the developing sleeve 11
2 N, jump to the pole and be collected.

In this example, S, the pole is S, the pole is N, and the pole is slightly N from the center of the pole.
, set opposite to the part closer to the pole.

This is because the S-pole repels the S-pole and prevents the magnetic brush formed by the S-pole from coming into contact with the collection roll 3, and also prevents the lines of magnetic force from flowing from the S-pole to the N-pole. This is to cause the developer accumulated to some extent at the S and pole to jump. Further, in order to prevent the developer of the S pole from coming into contact with the developing sleeve 11, the S pole is placed opposite to the low height of the magnetic brush between the poles S and N.

In this embodiment, since the carrier is constantly accumulated on the S pole, the toner collected on the collection roll 3 is scraped off by this carrier and collected into the developing sleeve 11 together with the carrier. Furthermore, since the toner is agitated with the carrier from the time it is scraped until it is collected into the developing sleeve 11, there is an advantage that the amount of charge is improved.

FIG. 9 shows still another embodiment incorporated into the developing device 2B. In the case where the magnet body 12 in the developing sleeve 11 rotates like this developer collecting device 202, the developer collecting roll 3 If the magnet 8 is also disposed inside the sleeve 11, the magnet 8 rotates as the rotating magnet 12 inside the sleeve 11 rotates.

In this case, the magnetic field near the collection roll changes, and the carrier collection rate is improved compared to the case where the magnet body is fixed.

In addition, in FIG. 9, a positive voltage is applied to the charger 9 that applies an electric charge to the dielectric portion of the developer-side collection roll 3 from the power source y+3, and a negative voltage is applied to the collection roll 3 from the power source y+2. .

Therefore, in this case, the dielectric portion 31 on the collection roll 3
The negatively charged carrier and the oppositely charged toner are collected, and the positively charged toner scattered on the conductor portion 32 of the roll 3 is collected. The charger 9 also serves as a pre-transfer charger for increasing the amount of charge on the toner to improve transfer before transferring the toner image on the photosensitive drum to a transfer material.

In addition, in FIG. 9, 10 is a developer scraping scraper that comes into contact with the collection roll 3, and 100 is a scraper 1.
This is a rotating member that sends the developer scraped off by the 0 to the rear.

In the embodiments shown in FIGS. 1 and 8 described above, the positively charged toner that is normally charged on the dielectric part 31 of the collection roll 3 is collected by adsorption of the oppositely charged toner and carrier on the conductor part 32. However, this is because when the carrier adheres to the conductor part 32, the charge of the carrier leaks, so that the carrier can be peeled off from the collection roll 3 more easily than when the carrier adheres to the dielectric part 31. . However, the dielectric part may collect the oppositely charged toner and the carrier, and the conductor part may collect the normally charged toner.

In addition, in any of the above embodiments, the developer recovery efficiency varies depending on the potential applied to the dielectric portion 31 and the conductor portion 32 of the recovery roll 3, so the toner charge amount tends to decrease at high temperature and high humidity. As a result, normally charged scattered toner increases, so a method such as combining a temperature sensor or a humidity sensor and increasing the potential when the temperature is high and humidity may be adopted. However, if the potential is increased too much, the adhesion between the collection roll and the toner increases, making it difficult to separate them, so under normal circumstances, the potential should be kept low.

In addition, since the toner charge amount changes depending on the B/W ratio of the document image, such as the toner charge amount decreases when the B/W ratio of the document is the same, the dielectric portion Alternatively, the voltage applied to the conductor portion may be changed.

The present invention is not limited to the above embodiments, but can be implemented in various other ways.

For example, an alternating power source may be connected to the conductor portion of the developer recovery roll. Further, the conductor portion may be grounded to have a zero potential as long as the developer can be recovered.

Further, although the embodiments described above are directed to two-component developers, the present invention is also applicable to one-component developers, and can be applied to both magnetic and non-magnetic developers.

〔Effect of the invention〕

According to the developer collection device of the present invention, it is possible to collect normally charged toner, reversely charged toner, and carrier, regardless of whether they are magnetic or not. It can be collected stably over a long period of time without fear of short circuits.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention together with a part of a developing device, FIG. 2 is a front view of a developer recovery roll, and FIGS. 3 to 6 are a dielectric portion of the developer recovery roll. FIG. 7 is a diagram showing another example of the arrangement pattern of the conductor portion, FIG. 7 is a portion showing a wrap-around state of the electric field between the dielectric portion and the conductor portion in the developer recovery roll, and FIG. 8 is a diagram showing another example of the arrangement pattern of the conductor portion. FIG. 9 is a sectional view showing a further embodiment of the present invention together with a part of the developing device, and FIGS. 10 to 12 are each considered as a developer recovery roll. FIG. 4 is a diagram illustrating an example of a gain but a disadvantage. 1.2A, 2B...Developing device 200.201.202...Developer recovery device 3...
Developer recovery roll 3'1...Dielectric part 32...Conductor part 4...Charge imparting charger V, ,V! , V,...Power supply 6...Fixed magnet 7...Conductive brush 8...Rotating magnet 9...Charge imparting charger ■ ■...Power supply

Claims (1)

[Claims] (1) A developer collection roll having a dielectric part and a conductive part on the surface, a means for applying an electric charge to the dielectric part, and a polarity opposite to the surface potential of the dielectric part caused by the electric charge applying means to the conductor part. What is claimed is: 1. A developer recovery device comprising means for applying a potential of