JPH1063087A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably stick a developer to a developing roller by stirring the developer on the circumference of a supplying roller for supplying the developer to the developing roller, with an air flow, so as to excellently keep flowability. SOLUTION: The developer 21 in a developer reservoir 22 is supplied to the developing roller 25 by the supplying roller 24, to be primarily electrified and stuck. Then, the developer stuck to the developing roller is regulated to make the thickness of a layer constant by a regulating member 27, so that the developer is secondarily electrified. In the supplying roller 24, both of a rotary shaft and a roller part consist of stepped cylinders having hollow structure. Then, a large number of geometric air holes are helically made in a line, in the outer peripheral part of the roller part. Then, air is supplied to the hollow part of the supplying roller 24 from an air supplying mechanism 31 through a first duct 29, to stir the developer of the circumference with the flow of the air blown from the air holes of the supplying roller 24. The air in the developer reservoir 22 is discharged into a second duct 33 with a filter 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an electrophotographic image forming apparatus such as a laser printer to develop an electrostatic latent image with a developer.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open Publication No. 63-85654 and Japanese Patent Laid-Open Publication No.
No. 2 is known. Japanese Patent Application Laid-Open No. 63-85654 discloses an apparatus in which a stirrer 2 for stirring a developer in a developer storage tank is provided at a central portion of a developer storage tank 1 for storing the developer, as shown in FIG. This developer storage tank 1
A supply roller 3 and a developing roller 4 are provided at the bottom of the. Then, the developer stirred by the stirrer 2 is supplied to the developing roller 4 by the supply roller 3, and at this time, the developer is primarily charged on the developing roller by friction at a contact portion between the supply roller 3 and the developing roller 4. Let it. Further, the developer adhered to the developing roller 4 is regulated by the regulating member 5 to a constant thin layer thickness. At this time, the developer is further secondary-charged due to friction at a contact portion between the regulating member 5 and the developing roller 4.
The developer on the developing roller 4 to which the secondary charge has adhered selectively adheres to the electrostatic latent image formed by exposure at the position of the photoconductor 6. Thus, the electrostatic latent image is developed into a visible image.

In Japanese Patent Application Laid-Open No. 4-344672, as shown in FIG. 11, a brush roller 12 and a developing roller 13, which are supply rollers, are provided at the bottom of a housing 11 for storing a developer. The brush roller 12 includes a cylindrical body 14 having a large number of air holes and a bristle brush 15 formed on an outer surface of the cylindrical body 14. Further, a cylindrical hollow body 17 having an air outlet 16 at a predetermined position in the brush roller 12 is non-rotatably disposed. The developer in the housing 11 is pressed and supplied to the developing roller 13 by the brush roller 12, and the developer on the developing roller 13 is supplied to the photosensitive drum 19 after being regulated to a thin layer thickness by the blade 18. It has become so. In the brush roller 12, air is supplied into the hollow body 17 from an air source, and the air is discharged from the air outlet 16 of the hollow body 17 to the outside of the brush roller 12 through the ventilation hole of the tubular body 14, and At this time, the developer adhering to the bristle brush 15 is removed by the action of air. Thereby, clogging of the bristle brush 15 is prevented.

[0004]

SUMMARY OF THE INVENTION Japanese Patent Application Laid-Open No. 63-8565
In the device disclosed in Japanese Patent Application Laid-Open No. 4 (1993) -189, the primary charge adhesion amount of the developer due to the contact friction between the supply roller 3 and the development roller 4 is smaller than the secondary charge adhesion amount of the developer due to the contact friction between the regulating member 5 and the development roller 4. Very few. For this reason, in order to perform the development satisfactorily, it is necessary to improve the fluidity of the developer near the supply roller 3 so that the developer adheres to the development roller 4 efficiently. However, since this publication discloses a configuration in which the developer in the developer storage tank 1 is stirred only by the stirrer 2, it is insufficient to maintain good fluidity of the developer near the supply roller 3, This tendency was particularly remarkable when a one-component non-magnetic toner was used as the developer.

[0005] Therefore, in the initial state of the developer in the developer storage tank 1, even if good fluidity can be secured, the fluidity deteriorates as time passes. In addition, while good fluidity can be ensured while the amount of the developer in the developer storage tank 1 is large, if the amount is reduced by use, the fluidity deteriorates. For this reason, in Japanese Patent Application Laid-Open No. 63-85654, when the developer in the developer storage tank 1 is used for a long time or decreases, the fluidity of the developer near the supply roller is reduced. And the amount of developer adhering to the developing roller is reduced. In particular, when a large amount of developer must be supplied as in black solid printing, image quality deterioration due to insufficient supply of developer is reduced. There was a problem to invite.

Japanese Patent Application Laid-Open No. 4-344672 discloses a structure in which air is discharged from the air outlet 16 of the hollow body 17 to the outside of the brush roller 12 through the ventilation hole of the cylindrical body 14. Since the inside of the housing 11 has a substantially closed structure, the amount of air discharged from the brush roller 12 prevents the bristle brush 15 from being clogged.
1 is an amount that does not increase the atmospheric pressure in the brush roller 12 (an amount that can escape from a slight gap in the housing).
There is no action to stir the developer around. Therefore, the fluidity of the developer around the brush roller 12 deteriorates as time passes even if good fluidity can be secured in the initial state of the developer in the housing 11. Further, the primary charging of the developer to the developing roller 13 is caused by the contact friction between the developing roller and the bristle brush 15 of the brush roller, and the adhesion tends to be incomplete. For this reason, even in Japanese Patent Application Laid-Open No. 4-344672, the amount of the developer attached to the developing roller is small, and particularly when a large amount of the developer needs to be continuously supplied as in black solid printing. However, there is a problem that image quality is deteriorated due to insufficient supply of the developer.

Therefore, according to the first to third aspects of the present invention, the developer around the supply roller for supplying the developer to the developing roller is always stirred by the air flow, so that the fluidity can always be maintained in a good condition. Provided is a developing device capable of always stably performing primary charging of a developer to a roller.
According to a second aspect of the present invention, there is provided a developing device capable of further improving the stirring of the developer around the supply roller by blowing out a complicated air flow spirally from the supply roller. Also,
The invention according to claim 3 further provides a developing device capable of reliably preventing the developer in the developer storage tank from being released to the outside together with air.

[0008]

According to the first aspect of the present invention,
The developer in the developer storage tank is supplied to the developing roller by a supply roller to be primary-charged and adhered, and the developer adhered to the developing roller is regulated to a constant layer thickness by a regulating member and secondary-charged.
In the developing device for developing an electrostatic latent image with the secondary charged developer, the supply roller has a hollow structure and has a number of air blowing holes in the outer peripheral portion for stirring the developer around the supply roller with an air flow. The supply roller is supplied with an amount of air capable of stirring the developer around the supply roller by an air flow blown out from the air discharge hole of the supply roller into the hollow portion of the supply roller, and the air in the developer storage tank is discharged. is there. Thereby, the fluidity of the developer around the supply roller is increased. According to a second aspect of the present invention, in the developing device according to the first aspect, the supply roller has a plurality of geometrically shaped air blowing holes spirally arranged on an outer peripheral portion.

According to a third aspect of the present invention, a developer in a developer storage tank is supplied to a developing roller by a supply roller to cause primary charging, and the developer attached to the developing roller is fixed to a certain layer by a regulating member. In a developing device in which the thickness is regulated and secondary charged, and an electrostatic latent image is developed with the secondary charged developer, the supply roller has a hollow structure, and the developer around the supply roller is formed around the supply roller by air. A large number of air blowing holes for stirring by a flow are provided, and the hollow portion of the supply roller and the inside of the developer storage tank are connected by a duct through an air supply mechanism between the supply roller and the hollow portion of the supply roller by the air supply mechanism. An object of the present invention is to supply an amount of air capable of stirring the developer around the supply roller by an air flow blown out from an air blowout hole of the supply roller.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) As shown in FIG. 1, a stirrer 23 is disposed below a central portion of a developer storage tank 22 for storing a developer 21 such as a one-component non-magnetic toner. The developer 21 inside is agitated. A supply roller 24 is disposed at a bottom opening in the developer storage tank 22, and a developing roller 25 is provided in front of the supply roller 24.
Are arranged close to each other, for example, with a gap of about 0.1 mm between them. The developing roller 25 is in contact with the photosensitive drum 26 at the front.

A regulating member 27 for regulating the thickness of the toner layer to be constant is disposed above the developing roller 25, and the rear end of the regulating member 27 is pressed by a spring 28 so that the leading end of the regulating member 27 is moved. The surface of the developing roller 25 is pressed.

As shown in FIG. 2, the supply roller 24 is formed of a stepped cylindrical body having both a rotating shaft 24a and a roller portion 24b having a hollow structure, and has a geometrical outer periphery of the roller portion 24b. A large number of air blowing holes 24c, 24c,... Are spirally formed in one row. The supply roller 24 has a structure in which one of the rotation shafts 24a has an end face closed,
The other has a structure in which the end face is open, and the rotating shaft 24a having the open end face is connected to one end of the first duct 29 via a highly secure joint.

The other end of the first duct 29 is connected to the propeller 3
0 is connected to the air outlet 31a of the air supply mechanism 31 provided with zero. In addition, a second filter is provided on the upper side surface of the developer storage tank 22 through a filter 32 for preventing the discharge of the developer 21.
One end of the duct 33 is connected. And the second
The other end of the duct 33 is connected to the air inlet 31b of the air supply mechanism 31.

In the developing device having such a configuration, the stirrer 2
The rotation of 3 stirs the developer 21 in the developer storage tank 22. The rotation of the propeller 30 causes the air supply mechanism 3 to rotate.
1 sucks air from the second duct 33 side and blows out the air to the first duct 29 side. This air is supplied to the hollow portion of the supply roller 24 that rotates counterclockwise as indicated by the arrow in the drawing. In this way, an intricately entangled airflow is blown out around the supply roller 24 from a number of spiral air blowout holes 24c opened in the outer peripheral portion of the supply roller 24. At this time, the amount of air is such that the developer 21 around the supply roller 24 can be sufficiently agitated by the air flow.

Thus, the developer 2 around the supply roller 24 is
1 is sufficiently stirred by the airflow blown out from the air blowout hole 24c, and good fluidity is secured. In addition, the developer 21 near the developing roller 25 violently collides with the surface of the developing roller 25 due to the air flow, whereby the developer 21 is primarily charged to the developing roller 25.

The air blown from the supply roller 24 into the developer storage tank 22 flows into the second duct 33 via the filter 32 provided above, and returns to the air supply mechanism 31. As a result, the pressure in the developer storage tank 22 does not rise. At this time, the developer 21 tries to flow into the second duct 33 while being mixed with the air flow, but is blocked by the filter 32 and does not enter the air supply mechanism 31. That is, it is possible to reliably prevent the developer 21 in the developer storage tank 22 from being released to the outside together with the air.

The developer 21 attached to the developing roller 25 is
Further, the toner is secondarily charged by the regulating member 27 and regulated to a thin layer thickness, and is conveyed to the photosensitive drum 26. Then, the electrostatic latent image is selectively attached to the electrostatic latent image formed on the surface of the photosensitive drum 26 by exposure, depending on the state of potential. Thus, the electrostatic latent image is developed by the developer 21 to become a visible image, and this visible image is subsequently transferred to a recording medium by transfer.

As described above, the developer 2 in the developer storage tank 22 is
1 is stirred by a stirrer 23, and
The developer 21 around the supply roller 24 is agitated by the airflow blown out from the many air blowing holes 24 c of the supply roller 24, so that the developer 21 around the supply roller 24 has good fluidity and the development roller 25 In this way, the primary charging is efficiently and stably performed. Accordingly, it is possible to sufficiently cope with a case where a large amount of developer must be continuously supplied from the developing roller 25 to the photosensitive drum 26 efficiently, such as black solid printing, and deterioration of image quality due to insufficient developer supply is caused. Never.

In this embodiment, as the supply roller, a supply roller 24 in which a number of geometric air blowing holes 24c, 24c,. Although used, it is not necessarily limited to this. For example, as shown in FIG.
spiral air blowing holes 24c, 24 formed in the outer peripheral portion of b.
Even if a supply roller 241 is used in which two rows of c,... are arranged so that the spirals intersect each other, a spiral air blowing hole 24c formed in the outer peripheral portion of the roller portion 24b as shown in FIG. , 24c,... Are arranged in a row of four, for example, even if a supply roller 242 is used.
As shown in FIG. 7, spiral air blowing holes 24c, 24c,... Formed in the outer peripheral portion of the roller portion 24b are arranged in two rows of four, for example, and supply rollers 243 arranged so that the spirals cross each other are used. Is also good. If the supply rollers 241 to 243 shown in FIGS.
The air flow blown out from c is further complicatedly entangled, and the stirring effect can be further enhanced. The number of rows of the air blowing holes 24c is not limited to four, but may be two, three, or five.

(Second Embodiment) The same parts as those in the first embodiment are denoted by the same reference numerals, and only different parts will be described. In this case, the supply roller 244 is arranged in contact with the developing roller 25 as shown in FIG. As shown in FIG. 7, the supply roller 244 is formed of a stepped cylindrical body in which both the rotating shaft 24a and the roller portion 24b have a hollow structure, and the outer peripheral portion of the roller portion 24b is the same as in the first embodiment. There are many geometric air outlets.
And the air permeability is good at the outer peripheral portion of the roller portion 24b,
In addition, a sponge 24d that does not hinder the primary charging of the developer 21 is provided.

As the sponge 24d, a urethane foam sponge 24d1 shown in FIG. 8A and a urethane honeycomb sponge 24d2 shown in FIG. I have. When such a sponge 24d is used, it is arranged in contact with the developing roller 25 with a nip width of about 2 mm.

In this embodiment, the developer 21 in the developer storage tank 22 stirred by the stirrer 23 adheres to the supply roller 244 and is supplied to the development roller 25, and the developer 21 at the contact portion with the development roller 25 By violently colliding against the surface of the developing roller 25 due to friction caused by rotation and a complicated air flow blown out from the supply roller 244, primary charging is performed on the surface of the developing roller 25. Then, the developer 21 attached to the developing roller 25 is further secondary charged by the regulating member 27 and regulated to a thin layer thickness, and is conveyed to the photosensitive drum 26. Then, the photosensitive drum 26
Is selectively adhered to an electrostatic latent image formed by exposure on the surface of the substrate according to the state of potential. In this way, the electrostatic latent image is
In step 1, the image is developed into a visible image, which is subsequently transferred to a recording medium by transfer.

As described above, even if the supply roller 244 having the sponge 24d attached to the outer peripheral surface is used, the supply roller 244 may be used.
The surrounding developer 21 is agitated by a complicated airflow blown out from the supply roller 244 to ensure fluidity. Further, the developer 21 is prevented from accumulating in the gap between the sponges 24d due to the blown air flow. The developer 21 is efficiently and stably formed on the surface of the developing roller 25 by friction caused by rotation at a contact portion with the developing roller 25 and collision with the surface of the developing roller 25 by a complicated air flow blown from the supply roller 244. Then, primary charging is performed. Accordingly, it is possible to sufficiently cope with a case where a large amount of developer must be continuously supplied from the developing roller 25 to the photosensitive drum 26 efficiently, such as black solid printing, and deterioration of image quality due to insufficient developer supply is caused. Never.

(Third Embodiment) The same parts as those in the first embodiment are denoted by the same reference numerals, and only different parts will be described. As shown in FIG. 9, the second duct 33 is omitted, and the developer storage tank 22 communicates with the outside via a filter 32 provided on the upper side surface, and the air supply mechanism 31 is provided.
The air inlet 31b is also in communication with the outside.

In the developing device having such a configuration, the air supply mechanism 31 draws in air from the outside and blows out the air toward the first duct 29 by the rotation of the propeller 30. This air is supplied to the hollow portion of the supply roller 24 that rotates counterclockwise as indicated by the arrow in the drawing. In this way, a complicatedly entangled air flow is blown out around the supply roller 24 from a number of spiral air blow holes 24c opened in the outer peripheral portion of the supply roller 24.
At this time, the amount of air is such that the developer 21 around the supply roller 24 can be sufficiently agitated by the air flow.

Thus, the developer 2 around the supply roller 24 is
1 is sufficiently stirred by the airflow blown out from the air blowout hole 24c, and good fluidity is secured. Moreover, the developer 21 near the developing roller 25 violently collides with the surface of the developing roller 25 due to the air flow, whereby the developer 21 is efficiently and stably primary-adhered to the developing roller 25. The air released from the supply roller 24 into the developer storage tank 22 is filtered by the filter 32 provided above.
Is released to the outside through Thereby, the developer storage tank 2
2. Prevent the pressure inside 2 from rising. At this time, the developer 21 tries to be released to the outside while being mixed with the air flow, but is blocked by the filter 32. In this way, it is possible to reliably prevent the developer 21 in the developer storage tank 22 from being released to the outside.

Therefore, also in this embodiment, since the developer 21 is efficiently and stably primary-charged to the surface of the developing roller 25, the developer 21 is moved from the developing roller 25 to the photosensitive drum 26, as in black solid printing. Even when it is necessary to supply a large amount of the developer efficiently, it is possible to sufficiently cope with the problem, and the image quality is not deteriorated due to the insufficient supply of the developer.

[0028]

As described above, according to the first to third aspects of the present invention, the developer around the supply roller for supplying the developer to the developing roller is always stirred by the air flow, so that the fluidity can always be maintained well. Thus, the primary charging of the developer to the developing roller can always be performed efficiently and stably. Therefore, it is possible to sufficiently cope with a case where a large amount of developer must be supplied efficiently from the developing roller for development such as black solid printing, and image quality degradation due to insufficient developer supply is not caused. Absent. In addition, it is possible to prevent the pressure in the developer storage tank from rising due to the air flow.

Further, according to the second aspect of the present invention, the developer around the supply roller can be more favorably agitated by blowing out a complicated air flow spirally from the supply roller.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a perspective view showing the appearance of a supply roller in the embodiment.

FIG. 3 is an exemplary perspective view showing a modification of the supply roller according to the embodiment;

FIG. 4 is a perspective view showing a modification of the supply roller according to the embodiment.

FIG. 5 is an exemplary perspective view showing a modification of the supply roller according to the embodiment;

FIG. 6 is a sectional view showing a second embodiment of the present invention.

FIG. 7 is an exemplary perspective view showing the appearance of a supply roller according to the embodiment;

FIG. 8 is a partially enlarged view showing a configuration of a sponge of a supply roller in the embodiment.

FIG. 9 is a sectional view showing a third embodiment of the present invention.

FIG. 10 is a sectional view showing a conventional example.

FIG. 11 is a sectional view showing another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 ... Developer 22 ... Developer storage tank 24 ... Supply roller 24c ... Air blowing hole 25 ... Developing roller 27 ... Restriction member 29, 33 ... Duct 31 ... Air supply mechanism

Claims (3)

[Claims] 1. A developer in a developer storage tank is supplied to a developing roller by a supply roller to cause primary charging, and the developer attached to the developing roller is regulated to a constant layer thickness by a regulating member. In the developing device, which is charged next and develops an electrostatic latent image with the secondary charged developer, the supply roller has a hollow structure, and a plurality of the peripheral portions of the developer around the supply roller are agitated by an air flow. Air supply holes are provided, and an amount of air capable of stirring the developer around the supply roller is supplied to the hollow portion of the supply roller by an air flow blown out from the air supply hole of the supply roller, and the inside of the developer storage tank is supplied. A developing device for discharging air. 2. The developing device according to claim 1, wherein the supply roller has a plurality of geometrically shaped air blowing holes spirally arranged on an outer peripheral portion. 3. A developer in a developer storage tank is supplied to a developing roller by a supply roller to cause primary charging, and the developer attached to the developing roller is regulated to a constant layer thickness by a regulating member. In the developing device, which is charged next and develops an electrostatic latent image with the secondary charged developer, the supply roller has a hollow structure, and a plurality of the peripheral portions of the developer around the supply roller are agitated by an air flow. Air supply hole, and a hollow portion of the supply roller and the inside of the developer storage tank are connected by a duct via an air supply mechanism between the supply roller and the developer supply tank. A developing device for supplying an amount of air capable of stirring the developer around the supply roller by an air flow blown out from an air discharge hole of the roller.