JPH0384569A - Developing device - Google Patents

Abstract

PURPOSE:To stably form an image with high magnetic field density by switching an electric field in the transfer direction of toner particles from a developer carrier to a toner particle carrier at the time of development or in the transfer direction of toner particles from the toner particle carrier to the developer carrier when development is not performed. CONSTITUTION:A developing bias is applied by an AC power source 14 and a DC power source 15 which are connected to a toner carrier roller 6 to perform noncontact development, and a DC power source 16 and a ground terminal 18 are connected to the developer carrier roller 1 so that they can be switched through a switch 17; while the toner carrier roller 6 is in developing operation, the DC power source 16 is connected to apply a bias and when no development is performed, switching to a grounding state is entered. In the developing operation, a sufficient amount of toner can, therefore, be supplied to the toner carrier roller 6, but when no development is performed, toner on the toner carrier roller 6 is removed and collected onto the developer carrier roller 1. Consequently, the developing device capable of forming a print image with high image density is obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention belongs to the field of development technology that uses a two-component developer in which magnetic particles and toner particles are mixed. The present invention relates to a developing device for forming a thin layer of electrostatic latent images and developing an electrostatic latent image.

[Prior Art] As a conventional developing device using a two-component developer containing a mixture of toner particles (hereinafter referred to as toner) and magnetic particles (hereinafter referred to as carrier), first of all, there is a method disclosed in Japanese Patent Application Laid-open No. 116240/1983.
Examples include those shown in the No. Publication.

This device includes a means for stirring a developer consisting of toner and a carrier to triboelectrically charge the toner, a conductive roller provided in contact with an electrostatic latent image holder and the developer, and a conductive roller that is in contact with the toner. A means for applying a bias voltage with a polarity opposite to the charging polarity is provided, and the frictionally charged toner from the developer is once attached to the conductive roller to form a coating layer of only toner on the conductive roller. This toner layer is transferred to an electrostatic latent image carrier and developed.

Next, as a second conventional example, a magnetic field generating means or a developing sleeve as a developer carrier disposed therein, and a toner layer that contacts the circumferential surface of the developing sleeve and is conveyed to a developing area are formed to a predetermined thickness. It is known that a so-called blade is provided to restrict the carrier and transport only the toner. Regarding the above device, Japanese Patent Application Laid-Open No. 82-969
There is one shown in Publication No. 56. In this device, a blade is brought into elastic contact with a developing sleeve, and the toner is agitated by circulating carrier in the vicinity of the blade to ensure a sufficient so-called tribo to apply the toner.

[Problems to be Solved by the Invention] However, in the first conventional example, when the toner concentration of the developer becomes higher than permissible, the amount of toner adhering to the conductive roller becomes excessively large, causing image fogging and toner There was a problem in that it caused scattering.

Furthermore, in the second conventional example, a sufficient space is required to circulate the carrier sufficiently, and unless the amount of carrier is kept to a small amount, it is not possible to freely circulate the carrier to obtain the tribo. For this purpose, the existence rate of carrier on the surface of the developing sleeve near the plate must be 1.
As a result, with such a small amount of carrier, the amount of toner conveyed is insufficient, and the toner cannot be sufficiently conveyed to the development area, resulting in a so-called ghost phenomenon.

In addition, in a device in which the blade itself is a magnetic member and uses magnetic force to regulate the carrier, an immobile layer of the carrier is formed near the blade, which prevents the circulation of the carrier and the supply of toner to the developing sleeve. However, there is a problem in that the amount of noise is insufficient, resulting in a ghost phenomenon.

The present invention solves the above-mentioned problems and provides a toner thin layer forming device that can obtain an appropriate amount of toner thin layer even if the toner concentration is high and can stably form a high density image. It is an object.

[Means for Solving the Problems] According to the present invention, the above object is as follows: A developer storage container that stores a two-component developer consisting of magnetic particles and toner particles, and a developer storage container formed in front of the developer storage container. In a developing device including a developer carrier rotatably disposed at an opening and having a magnetic field generating means inside, the developer carrier is located in front of the developer carrier and is carried by the developer carrier. toner particle carriers rotatably arranged opposite to each other at positions in contact with the developer; a developer regulating member that comes into contact with the toner particle carrier to regulate the passage of the developer; and a voltage applying means that applies a voltage to the developer carrier and the toner particle carrier, the developer carrier and the toner particle carrier; This is achieved by comprising an electric field switching means for switching the direction of an electric field formed between the toner particle carrier and the toner particle carrier.

[Function] According to the present invention, the voltage applying means for applying voltage to the developer carrier and the toner particle carrier switches the direction of the electric field formed between the developer carrier and the toner particle carrier. The electric field switching means switches the electric field in the direction in which the toner particles are transferred from the developer carrier to the toner particle carrier during development, and supplies the toner particles from the toner particle carrier during non-development. The toner particles are removed by switching the electric field in the direction in which the toner particles are transferred to the agent carrier.

[Embodiment] A first embodiment of the present invention will be described with reference to FIGS. 1 to 5 of the accompanying drawings.

In FIG. 1, l is An that can rotate in the A direction.

A developer carrying roller is a developer carrying member made of a conductive material such as 808 or a resin material, and is arranged to protrude into the front opening of a hopper 7 which is a developer storage container that accommodates carrier 3 and toner 4 as magnetic particles. be done. A magnet roller 2 serving as a magnetic field generating means is fixedly disposed inside the developer carrying roller l. The magnet roller 2 is
Nil, Sll, N12. S12, and a toner carrying roller 6 serving as a downstream toner particle carrying member.
A magnetic pole Sit is disposed at a portion Q facing the .

A doctor blade 5, which is a developer regulating member, is disposed above the developer carrying roller 1 at a distance g, and regulates the amount of developer applied. The doctor blade 5 may be a magnetic member or a non-magnetic member, or may be a combination of these members.

The spacing g between the doctor blade 5 and the developer carrying roller I at the opposing portion G is set to 600 wells 1, and the magnetic pole Nil of the magnet roller 2 is disposed toward the vicinity of the opposing portion G. The above-mentioned magnetic pole Nil is arranged in order to stabilize developer application, and it is better to arrange it toward the upstream side in the rotational direction of the developer carrying roller l than the above-mentioned opposing part G. In order to stabilize the circulating flow C, it is preferable that the angle θ between the opposing portion and the magnetic pole Nil be in the range of 5@≦θ≦15″.

A toner carrying roller 6 is a toner particle carrying member, and is made of a conductive material such as An, SO9, or resin.
are arranged close to each other so as to be in contact with the developer carried thereon, and are rotatable in the direction B.

An elastic blade 8 serving as a developer regulating member is in contact with the toner carrying roller 6. The elastic plate 8 is located downstream of the opposing portion Q of the developer carrying roller I and the toner carrying roller 6 in the rotational direction of the toner carrying roller 6.
are arranged so that their ends abut at point P.

The elastic blade 8 is biased and in contact with the toner carrying roller 6, so that it is elastically deformed as shown in FIG. Note that the end of the elastic blade 8 here refers to the tip of the blade or the vicinity including the tip, and the elastic blade 8 is inclined downstream in the rotational direction B of the toner carrying roller 6 from the end. It is installed in a so-called counter format.

A photosensitive drum IO, which is a latent image carrier, is disposed opposite to the front of the toner carrying roller 6 described in E.
The upper electrostatic latent image is developed with the toner on the toner carrying roller 6.

A stirring member 13 mixes and stirs the carrier 3 and the toner 4, and is disposed behind the developer carrying roller l.

The toner carrying roller 6 is connected to an AC power supply 14 and a DC power supply 15 which are voltage application means, and the developer carrying roller l is also connected to a DC power supply 16 which is a voltage application means and a ground terminal 17 which is connected to a switch which is an electric field switching means. 18 are switchably connected.

Next, the operation of the apparatus of this embodiment as described above will be explained.

The rotational force of the developer carrying roller l, the magnetic force of the magnet roller 2, and gravity act on the developer, which is a mixture of carrier 3 and toner 4, stored in the hopper 7, and a circulating flow C of the developer is formed. be done. The carrier 3 and the toner 4 are mixed and agitated by this circulation flow C and the action of the stirring member 13 provided below the hopper 7, and the toner 4 is charged with frictional electrification.

The developer in which the carrier 3 and toner 4 are mixed is applied in an appropriate amount onto the developer carrying roller l while being regulated by a doctor blade 5. On the other hand, the developer returned to the hopper 7 by the doctor blade 5 forms the above-mentioned circulation flow C, is mixed and stirred again, and is used for coating.

The developer coated on the developer carrying roller I in this manner is conveyed to the portion Q facing the toner carrying roller 6 as the developer carrying roller I rotates.

Here, the state of the developer in the opposing portion Q will be explained using FIG. 2.

First, the developer (
Arrow A) indicates that the opposing portion Q receives the action of the magnetic field formed by the magnetic pole 311 disposed on the side of the developer carrying roller l, thereby forming the spikes 20 of the magnetic brush. In FIG. 2, the magnetic field lines are represented by point iiF. Within the bristles 20, a flow U due to the conveying force caused by the rotation of the developer carrying roller 1 and a flow V caused by the frictional force caused by the rotation of the toner carrying roller 6 are generated in different directions. That is, a flow shown by arrow U occurs near the developer carrying roller 1, and a flow shown by arrow V occurs near the toner carrying roller 6. The flow V is generated as the toner carrying roller 6 rotates, and the above-mentioned elastic blade 8 is urged to contact the toner carrying roller 6, so that the toner applied onto the toner carrying roller 6 is moved. Otherwise, the developer is repelled by the tip surface of the elastic plate 8 (arrow W). These developers rejoin the flow shown by arrow U, some of which circulates as shown by arrow V, and the rest returns to the hopper 7 as shown by arrow X.

In this way, the circulating flow of developer (arrow U → arrow V → arrow W
→By forming the arrow U), the toner is sufficiently triboelectrically charged, and furthermore, the developer and the toner carrying roller 6 are strongly rubbed. This not only makes it possible to apply a sufficient amount of sufficiently charged toner to the toner carrying roller 6, but also makes it possible to apply a sufficient amount of sufficiently charged toner to the toner carrying roller 6 without being used for development.
It also has the effect of replacing the toner remaining on the top with new toner, making it possible to erase the previous image history.

Further, the arrangement position of the magnetic pole 311 also plays an important role in smoothly varnishing the circulation flow.

In this embodiment, by arranging the magnetic pole Sll on the downstream side in the rotational direction of the developer carrying roller l than the contact portion of the elastic plate 8, the flow in the direction of arrow W is smoothly changed to the flow in the direction of arrow U. It is merged with In other words, a magnetic force acts on the carrier 3 that has been repelled in the direction of the arrow W at the abutment portion in the direction of the arrow, making it difficult to merge with the flow in the direction of the arrow U.

In this example, the strength of the magnetic pole S11 is set to 600
In addition, the developer carrying roller l and the toner carrying roller 6
The interval between the two is set to 7001L■.

The effects of toner supply and peeling in the opposing portion QC as described above are further improved by the effects of the voltage application means and the electric field switching means. The functions of the voltage applying means and the electric field switching means will be explained below.

First, as a developing method in this embodiment, an AC power source 14 connected to the toner carrying roller 6 and a DC type @t are used.
Non-contact development is performed by applying a development bias using S. In this embodiment, the voltage of the latent image formed on the photosensitive drum 10 is set to -60 Ov in the non-image area and -10 Ov in the V1 image area, and the negative latent image is developed using negatively charged toner. Reversal development was performed. Also, AC power supply 1
4, 1600 Hz; 15OOVp-p, DC power source 15, Q5oov was applied. Note that the distance between the photosensitive tram 10 and the toner carrying roller 6 is set to be wider than the toner layer thickness, and in this embodiment, the distance is 300 mm.
It was set to ILm.

Next, a direct current of -aoov' is applied to the developer carrying roller l.
l@i17 and 0vlvvc ground terminal 18 are connected to switch 18 so as to be switchable. When the toner carrying roller 6 is in a developing operation, it is switched to a DC power supply of -800 V to apply a bias, and when not in development, it is switched to Ov as a grounded state. With this setting, during the developing operation, an electric field acts in the direction in which the toner 4 is transferred from the developer carrying roller l to the toner carrying roller 6, so that a sufficient amount of toner is supplied to the toner carrying roller 6. be done.

On the other hand, during non-development, an electric field acts in the direction of transfer from the toner carrying roller 6 to the developer carrying roller 1, so that the toner on the toner carrying roller 6 is removed and collected by the developer carrying roller l. In this way, a developed image with sufficient density can be obtained during development, and toner scattering can be prevented during non-development.

Next, the bias switching operation of the developer carrying roller l when printing operations are performed continuously will be explained using the timing chart of FIG. First, photosensitive drum 1
0 starts rotating, and then charging and exposure are performed in that order.

At this time, the bias voltage applied to the toner carrying roller 6 and the developer carrying roller l is OV, and the time required for the latent image formed on the photosensitive tram 10 to reach the development position, that is, the position where the toner carrying roller 6 is disposed, is OV. A DC voltage of -800V is applied with a delay. The voltage is applied to the toner carrying roller 6 and the developer carrying roller l at the same time.

Next, when the development for 1 minute of pudding is completed, the switch 18
is switched to Ov, which is the bias voltage to the developer carrying roller l. After this, the above sequence is repeated. When all fog printing is completed, the developer carrying roller l
Subsequently, the bias voltage to the toner carrying roller 6 is also set to OV, charging and rotation of the photosensitive tram 10 are stopped, and the continuous printing operation is completed. By switching to the bias Ov of the developer carrying roller 1 between each print when printing is performed continuously in this way, it is possible to bring the toner carrying roller 6 into a non-developing state without stopping the toner carrying roller 6. This eliminates the need to stop and restart the toner carrying roller 6, and mechanical vibrations at the time of restarting do not adversely affect latent image formation, unlike in conventional devices. It also prevents the toner from scattering during non-development.

By the way, from the developer carrying roller l to the toner carrying roller 6
The amount of toner transferred to the developer largely depends on the toner concentration of the developer. That is, when the toner concentration is high, the amount of transfer is large, and conversely, when the toner concentration is low, the amount of transfer is small. Generally, when the amount of toner applied is too large, it causes image fogging and toner scattering, and when it is too small, sufficient image density cannot be obtained.

In the present invention, the toner concentration of the developer is set relatively high, and more toner than necessary is always supplied from the developer carrying roller l to the toner carrying roller 6, so that an excess of toner is produced at the abutting portion P of the elastic blade 8. Since the structure is configured to scrape off toner, there is an advantage that constant and uniform toner application can always be obtained without the need for a developer concentration control mechanism. In experiments conducted by the inventors, it was found that Toner weight/
It was possible to obtain uniform toner application over a wide range of 10 to 40% (carrier weight x 100%). Such a range of toner density can be set naturally without providing any control mechanism.

Next, the contact portion P of the elastic blade 8 will be explained using FIG. 4.

The elastic blade 8 is configured such that its end portion comes into contact with the toner carrying roller 6. With this configuration, the elastic blade 8 can scrape off excess toner applied to the toner carrying roller 6 and allow an appropriate amount of toner to pass through. This corresponds to the toner 4 and carrier 3 applied and conveyed to the toner carrying roller in the opposing portion Q.
Among them, one of the carriers 3 having a large particle size cannot pass through the gap between the contact portion P between the toner carrying roller 6 and the elastic blade 8 and is scraped off, and the toner is strongly adhered electrostatically. This is due to the effect that only toner with a relatively high amount of charge slips through against the sliding force of the elastic blade 8, and toner with weak adhesion is scraped off.

In this way, an appropriate amount of toner thin layer is formed on the surface of the toner carrying roller 6 after passing through the contact portion P of the first elastic plate 8. Here, the appropriate amount means that sufficient density for one image can be obtained;
This refers to the range in which there is no image fogging and no toner scattering in the surrounding area, and according to experiments by the present inventors, when a toner whose main component is styrene/acrylic resin is used, the range is 0.5 to 1.
2-g/cm" preferably 0.7-1.0 mg/cm'
This is the amount of toner applied.

Regarding the setting direction of elastic play)=8, there are two types: one is to press the tip of the elastic plate 8 at the edge angle, and the other is to press it from the ventral surface. In the former type, as shown in FIG. 8, if the elastic blade 8 is set too high, all of the applied toner 4 will be removed. In the latter form,
As shown in FIG. 9, if the tip of the elastic blade 8 rises too much, the carrier 3 becomes clogged in the lifted area 11, which tends to cause uneven toner application. Therefore, it is necessary to urge the end of the elastic blade 8, that is, the tip of the blade or the vicinity including the tip, so as to contact the toner carrying roller 6.

FIG. 5 is a diagram illustrating the amount of deflection of the elastic blade 8.

In FIG. 5, the two-dot chain line indicates the elastic plate when the toner carrying roller 6 is not present, and the solid line indicates the elastic blade when the toner carrying roller 6 is actually present.

The amount of deflection h of the elastic blade 8 (the length between the bottom surface of the elastic blade 8 and the intersection S with the toner carrying roller 6 and the bottom end T of the elastic blade 8 assuming that the toner carrying roller 6 does not exist) is as follows: In order to urge the tip of the elastic blade 8 or the vicinity including the tip to come into contact with the toner carrying roller 6, it is preferable to set it to 0.5 to 2.0.

As for the material of the elastic blade 8, it is preferable to select and use a material that is used as a regulating member for the carrier 3 and which imparts the expected charge polarity to the toner 4 through friction when it comes into contact with the toner 4. Although it depends on the material, for example, ethylene propylene, fluororubber, natural rubber, polychlorobutadiene, N, B, R, etc. are used to positively charge a toner whose main component is polystyrene, and to charge it negatively. Silicone rubber, polyurethane, styrene-butadiene rubber, etc. are used.

The hardness of the rubber described above is preferably 50'' to 706 in terms of JISA hardness.

If the angle exceeds 70°, the elasticity of the rubber becomes strong and the pressure at the abutting portion becomes too high, so that only an excessively thin toner layer can be obtained and sufficient image density cannot be obtained. On the other hand, 5
If the rubber is less than 0.06, the elasticity of the rubber is weak and the toner layer becomes excessively thick, causing image fogging and toner scattering.

As the carrier 3 used in this embodiment, conventionally known ferromagnetic or paramagnetic particles can be used. For example, metal particles such as iron, chromium, nickel, cobalt, triiron tetroxide,
An alloy of gamma ferric oxide, chromium dioxide, manganese oxide, ferrite, etc., a resin carrier in which the above magnetic particles are dispersed in a resin material, a coated carrier in which the above magnetic particles are coated with a resin material, etc. can be used. In addition, since the carrier 3 is not applied to the surface of the toner carrying roller 6, it is possible to use either a conductive carrier or an insulating carrier.

Regarding the particle size of the carrier 3 and toner 4, in order to reliably control the carrier 3 by the above-mentioned elastic blade 8, the particle size of the toner 4 is 1 to 20 μm, and the particle size of the carrier 3 is 40 to 2 μm.
It is preferable to configure it as 00 p, m.

It should be noted that it is preferable to add minute irregularities to the surfaces of the developer carrying roller l and the toner carrying roller 6 rather than making them mirror-finished in order to uniformly apply the toner. Alternatively, a resin or a resin in which conductive particles such as carbon are dispersed may be applied.

Next, a second embodiment of the present invention will be described using FIG. 6.

In this embodiment, instead of providing separate DC power supply and ground terminals for the developer carrying roller 6, a terminal 19 connected to the AC power supply 14 of the toner carrying roller 6 is provided, and the grounding portion is shared. .

In this embodiment, the developer carrying roller l during the developing operation is
Since the potential is the same as that of the toner carrying roller 6, the supply of toner from the developer carrying roller 1 to the toner carrying roller 6 is carried out exclusively by the reflection force caused by the toner tribo. However, during non-development, an electric field acts in the direction from the toner carrying roller 6 to the developer carrying roller l, so that the toner can be removed reliably.

Next, a third embodiment of the present invention will be described using FIG. 7.

This embodiment is an apparatus in which a plurality of the developing devices of the first embodiment described above are arranged around a photosensitive drum to form a multicolor image.

In FIG. 7, 10 is a photosensitive drum, and above the photosensitive drum 10 is a first charger! 00 is arranged.

A first developing device 1 having yellow toner is located downstream of the first charger 100 in the rotational direction of the photosensitive tram 10.
01. Second charger 102. A second developing device 103 having magenta toner, a third charger 104, and a third developing device ios having cyan toner are arranged in this order.

A first exposure beam 105 is emitted on the surface of the photosensitive drum 10 between the first charger 100 and the first developing device 101;
A second exposure beam 107 is applied to the surface of the photosensitive drum 10 between the second charger 102 and the second developing device 103, and a second exposure beam 107 is applied to the surface of the photosensitive drum 10 between the third charger 104 and the third developing device i 105. are irradiated with a third exposure beam 108, respectively.

Furthermore, the photosensitive drum l is further connected to the third developing device 105.
A transfer charger 109 and a cleaning device 110 are provided on the downstream side of O in the rotational direction.

In the color electronic device according to this embodiment, there are two modes: a mode in which one or more developing devices are selectively operated, and a mode in which all developing devices are operated.
By selecting one of them, a desired monocolor print or full color print can be created.

However, when the above-mentioned monochrome printing mode was selected, the following problems occurred.

In this mode, it is necessary to stop the operation of the developing devices other than the developing device used.

As a means for this, there is a method of stopping the rotation of the toner carrying roller 6, but when using this method, vibrations at the time of startup may be transmitted to the exposure optical system, causing pitch unevenness when forming a latent image. Ta.

Furthermore, when a method of stopping the developing bias is used, the toner carrying roller 6 coated with toner continues to rotate without being used for development, ie, so-called idle rotation. Therefore, there have been problems such as toner scattering and excessive frictional electrification of the toner.

However, according to this embodiment, since the supply of the developing bias can be stopped after the toner on the toner carrying roller 6 is removed, the above-mentioned disadvantage can be solved and clear color images can always be obtained.

[Effects of the Invention] As described above, with the configuration of the present invention, it is possible to stably apply a thin layer of toner over a wide range of toner concentrations in the developer.

This eliminates the need for a toner density control mechanism and allows
With a simple configuration, it is possible to realize a small-sized developing device that is always free from image fogging and toner scattering, leaves no history of previous development, and can form print images with high image density.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a schematic configuration of an apparatus according to a first embodiment of the present invention, FIG. 2 is an enlarged view showing the vicinity of the facing portion of the toner particle carrier and developer carrier of the apparatus shown in FIG. 1, and FIG. 1 is a timing chart showing the operation of the device shown in FIG. 1, FIG. 4 is an enlarged view of the vicinity of the developer regulating member of the device shown in FIG. 1, and FIG. 5 is an enlarged view showing the amount of deflection of the developer regulating member of the device shown in FIG. 1. , FIG. 6 is a sectional view showing a schematic configuration of an apparatus according to a second embodiment of the present invention, FIG. 7 is a sectional view showing a schematic configuration of an apparatus according to a third embodiment of the present invention, and FIG. 8 is a sectional view showing a schematic configuration of an apparatus according to a third embodiment of the present invention. A diagram showing an example of how to install the regulating member,
FIG. 9 is a diagram showing another example of how to attach the developer regulating member of the conventional device. l...Developer carrier (developer carrier roller) 2.
...Magnetic field generating means (magnet roller) 3...
... Magnetic particles (carrier) 4 ... Toner particles (toner)

Claims (2)

[Claims] (1) A developer storage container that stores a two-component developer consisting of magnetic particles and toner particles, and an opening formed in the front of the developer storage container that has a magnetic field generating means inside and is rotatably arranged. In the developing device, the toner is rotatably disposed in front of the developer carrier and in contact with the developer carried by the developer carrier. a particle carrier, and a developer that contacts the toner particle carrier on the downstream side in the rotational direction of the toner particle carrier than the opposing portion of the toner particle carrier and the developer carrier to restrict passage of the developer. a voltage applying means for applying a voltage to the developer carrying member and the toner particle carrying member; the voltage applying means forms a gap between the developer carrying member and the toner particle carrying member; A developing device comprising an electric field switching means for switching the direction of an electric field. (2) The developer according to claim 1, wherein the developer regulating member is disposed such that its tip is oriented in a direction opposite to the rotational direction of the toner carrying roller, and is made of an elastic body. Device. (3) The voltage application means is a DC power supply, and the electric field switching means is configured to direct the toner particles in the direction in which the toner particles are transferred from the developer carrier to the toner particle carrier during the developing operation, and in the direction in which the toner particles are transferred from the toner particle carrier during the non-developing operation. 2. The developing device according to claim 1, wherein the developing device is configured to switch the electric field in a direction in which the developer is transferred to the developer carrier.