JPH04371979A - Developing device for electrophotographic device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for an electrophotographic apparatus which develops an electrostatic latent image using a developer charged by stirring.

[0002] In an electrophotographic apparatus, a developer is generally charged in order to develop an electrostatic latent image, and in the so-called two-component development method using toner and carrier as the developer, the developer is stirred. triboelectrically charged.

0003

2. Description of the Related Art FIG. 6 shows a developing device of a conventional electrophotographic apparatus, in which 91 and 92 are elongated rod-shaped shafts 91a,
The screws 92a are first and second rotating screws having continuous spiral blades protruding from the screws 92a, and are driven to rotate in relatively opposite directions.

[0004] Toner is supplied to the first rotating screw 91 from a hopper (not shown) through a toner inlet 93 . Then, together with the carrier, the first rotating screw 91 stirs the carrier and transports it in a direction perpendicular to the plane of the paper. The developer that has reached the end of the first rotary screw 91 is conveyed in the opposite direction to the first rotary screw 91 while being stirred by the second rotary screw 92, and at that end, the developer is returned to the first rotary screw 91. It is pushed out toward the rotating screw 91 side and circulates. This movement causes the developer to become triboelectrically charged.

A portion of the developer is transferred to the second rotating screw 9
The developer is pushed out laterally from a developer outlet 94 formed on the side of the developer roller 2, and is supplied to the surface of a developing roller 96 while being stirred by an auxiliary stirring roller 95.

The charged toner thus supplied to the surface of the developing roller 96 is made into a constant layer thickness by a layer thickness regulating blade 97 for regulating the layer thickness of the toner, and is conveyed to a developing section 98. There, the electrostatic latent image on the photosensitive drum 89 is developed. Reference numeral 99 denotes a developer stripping blade for stripping off developer with a reduced toner concentration remaining on the surface of the developing roller 96 without being used for development.

[0007]

However, as shown in FIG. 6, in the developing device of the conventional electrophotographic apparatus, the inner wall surface of the housing 90 around the rotary screws 91, 92 and the inner wall surface of the housing 90 around the rotary screws 91, 92 are Since there was a large space between the outer edge and the rotating screws 91 and 92, when the rotating screws 91 and 92 were driven to rotate, some of the toner 100 was removed from the rotating screws 91 and 92.
It was staying around. As a result, a large amount of toner is required to obtain a predetermined toner density, and the toner 100 in the retention area is supplied to the developing roller 96 without being sufficiently charged, which causes printing defects such as so-called fogging. It had become.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a developing device for an electrophotographic apparatus in which the developer does not stagnate while the developer is being conveyed while being stirred.

[0009]

[Means for Solving the Problems] In order to achieve the above object, a developing device for an electrophotographic apparatus according to the present invention provides a developing device that is charged by stirring, as shown in FIG. 1 for explaining an embodiment. a developing roller 50 that conveys the developer to the developing section 60 for developing the electrostatic latent image; developer stirring and conveying means 41 and 42 that conveys the developer to the developing roller 50 while stirring; The developer agitation conveyance means 4
The developer agitation and conveyance means 41 and 42 are connected to the developer agitation and conveyance means 41 and 42 in a portion other than the toner inlet portion 47 for supplying toner to the developer agitation and conveyance means 41 and 42 and the developer outlet portion 49 for sending out the developer from the developer agitation and conveyance means 41 and 42. In a developing device for an electrophotographic apparatus having a housing 40 surrounding the housing 40, the cross-sectional shape of the space within the housing 40 is approximately the same as the cross-sectional shape of the developer agitation conveyance means 41, 42, and the developer agitation conveyance means It is characterized in that it is formed in dimensions that create a slight gap between the outer edges of the means 41 and 42.

It is preferable that the gap is larger than the particle size of the developer and within a range that does not reduce the efficiency of conveying the developer by the developer stirring and conveying means 41 and 42. A thickness of about 0.5 to 1 mm is desirable.

Further, the developer stirring and conveying means may be a rotating screw having spiral blades, and the developer stirring and conveying means may be an endless belt with blades having a plurality of screen-like blades erected thereon. etc. may be used.

0012

[Operation] The cross-sectional shape of the space inside the housing 40 is approximately the same as the cross-sectional shape of the developer agitation and conveyance means 41 and 42, and is dimensioned to create a slight gap with the outer edges of the developer agitation and conveyance means 41 and 42. Therefore, the agitation and conveyance movement of the developer agitation and conveyance means 41 and 42 is not hindered at all by the housing 40, and the developer agitation and conveyance means 41 and 4
Since there is only a small gap between the developer 2 and the inner wall of the housing 40, the developer transported while being stirred does not stagnate on the way.

[0013]

[Embodiment] An embodiment will be described with reference to the drawings.

FIG. 2 shows a laser beam printer to which the present invention is applied. However, the present invention can be applied to copying machines, facsimile machines, and other electrophotographic devices.

In FIG. 2, around the photosensitive drum 1 rotating in the direction of the arrow, there are a charger 2, an exposure device 3, a developer 4,
A transfer device 5, a static elimination lamp 6, and a cleaner 7 are arranged, and the surface of the photosensitive drum 1 is first negatively charged by corona discharge from the charger 2.

Next, when light corresponding to the image to be recorded is applied to this surface from the exposure device 3, the potential of the exposed portion decreases, and an electrostatic latent image is formed on the surface of the photosensitive drum 1. be done. When this latent image area passes through the developing device 4, negatively charged toner (developer) adheres to it, and development with the toner is performed.

On the other hand, the sheets 8 on which images are printed are fed one by one to a position where they come into contact with the toner image formed on the photosensitive drum 1 by the action of a pick roller 9 and a standby roller 10. A transfer device 5 is installed below the photosensitive drum 1 on the back side of the paper 8 so as to apply a positive charge to the paper 8. Therefore, the toner image formed on the surface of the photosensitive drum 1 is attracted to the positive charge of the paper 8 and transferred thereto.

The paper 8 onto which the toner image has been transferred is transferred to the fixing device 1.
The toner image is fixed on the paper 8 by heat and pressure.

The surface of the photosensitive drum 1 on which the toner has been transferred to the paper 8 is neutralized by the static eliminating lamp 6, and the residual toner is cleaned by the cleaner 7, returning to the initial state.
It is charged again by the charger 2.

FIG. 1 is a side sectional view of the above-mentioned developing device 4, and FIG. 3 is a plan sectional view thereof. In the figure, 41 and 42 are first and second rotating screws of the same shape, each having continuous spiral blades protruding from elongated rod-shaped shafts 41a and 42a, and are rotatably installed in the housing 40. It is being Gears 43 and 44 fixed to the ends of each shaft 41a and 42a mesh with each other, so that the first and second rotating screws 41 and 42 rotate in relatively opposite directions.

In the upper part of the first rotary screw 41, a part of the housing 40 is provided with a toner inlet 47 for receiving toner from the hopper 46, through which the toner is supplied from the hopper 46. Toner falls onto the first rotating screw 41. The toner is agitated with the carrier there and becomes electrically charged.

Furthermore, the first and second rotating screws 41,
42 is partitioned by a partition wall 48 which is a part of the housing 40, but the partition wall 48 is not formed at both ends. Therefore, the toner supplied to the first rotating screw 41 is stirred together with the carrier by the rotation of the two rotating screws 41 and 42, and is triboelectrically charged while the toner is
and F, both rotating screws 41, 42
It is conveyed in the axial direction and circulates.

A developing roller 50 is pivotally supported in a chamber formed on the side of the second rotating screw 42, and the housing 4
0 has a large opening between the second rotating screw 42 and the developing roller 50 to form a developer outlet section 49.

[0024] Therefore, the developer conveyed while being stirred by the second rotating screw 42 is pushed out laterally from the developer outlet portion 49 toward the developing roller 50.

The housing 40 has this developer outlet section 49
It is formed so as to surround the first and second rotating screws 41 and 42 in a portion other than the aforementioned toner inlet portion 47, that is, on the entire surface of the developer stirring and conveying portion. The cross-sectional shape of the space inside the housing 40 is the same circular shape as the first and second rotating screws 41 and 42, and the inner wall surface of the housing 40 is the same as the first and second rotating screws 41 and 42.
1 and 42 with a slight gap of about 0.5 to 1 mm overall.

This gap depends on the assembly accuracy of the first and second rotating screws 41 and 42 and the
This setting is made in consideration of the torque reduction caused by the resistance caused by the developer entering between the housing 40 and the housing 40 and being crushed, and the developer conveyance efficiency.

Therefore, the rotational movement of the first and second rotating screws 41 and 42 for stirring and transporting the developer is not hindered by the housing 40, and
Since the gap between the outer edge of each rotating screw 41, 42 and the inner wall surface of the housing 40 is small, the toner is conveyed while being stirred without being stagnated on the way.

Second rotating screw 42 and developing roller 5
0, an auxiliary stirring roller 52 having four flat stirring blades 51 is provided. The auxiliary stirring roller 52 is rotationally driven by a gear mechanism 54 in conjunction with the first and second rotating screws 41 and 42 and the developing roller 50, and is pushed out from the developer outlet portion 49 by the second rotating screw 42. The developer is supplied to the developing roller 50 while being stirred.

The charged developer thus supplied to the surface of the developing roller 50 is made to have a constant layer thickness by a layer thickness regulating blade 56 for regulating the layer thickness of the developer, and is then delivered to the developing section 60. The photosensitive drum 1 is transported, and the electrostatic latent image on the photosensitive drum 1 is developed there. 58 is a developer stripping blade for stripping off the developer remaining on the surface of the developing roller 50 without being used for development.

FIGS. 4 and 5 show a second embodiment of the present invention, in which the above-mentioned first and second rotating screws 41
, 42, an endless bladed endless belt 72 having a large number of screen-like flat blades 71 is rotatably driven to agitate and convey the toner.

In this case as well, the cross-sectional shape of the space inside the housing 70 is the same as the cross-sectional shape of the endless belt 72 with blades, except for the toner inlet portion 47 and the developer outlet portion 75. The endless belt 72 is dimensioned to have a slight gap of about 0.5 to 1 mm with respect to the outer edge thereof.

[0032] Such a winged endless belt 72 can be made of metal, plastic, rubber, or the like. 76, 77, and 78 are a motor, a rotation transmission gear, and a drive shaft for rotationally driving the endless belt 72 with blades.

[0033]

According to the developing device of the electrophotographic apparatus of the present invention, the cross-sectional shape and size of the space within the housing is substantially the same as the cross-sectional shape of the developer agitation and conveyance means, and the outer edge of the developer agitation and conveyance means is substantially the same. Since the agitation and conveyance movement of the developer agitation and conveyance means is not obstructed by the housing, there is only a slight gap between the developer agitation and conveyance means and the inner wall of the housing. Therefore, the developer that is transported while being stirred does not stagnate on the way.

Therefore, the developer supplied to the developing device can be used efficiently and effectively for development, and good development can be performed without printing defects such as fogging.
It has excellent effects such as no shortening of developer life.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a first embodiment.

FIG. 2 is a configuration diagram of the printer of the first embodiment.

FIG. 3 is a plan sectional view of the first embodiment.

FIG. 4 is a side sectional view of the second embodiment.

FIG. 5 is a plan cross-sectional view of the second embodiment.

FIG. 6 is a side sectional view of a conventional example.

[Explanation of symbols]

40 Housing 41 First rotating screw (developer stirring and conveying means)
42 Second rotating screw (developer stirring and conveying means)
47 Toner inlet section 49 Developer outlet section 50 Developing roller 60 Developing section

Claims (5)

[Claims] Claim 1: A developer that is charged by stirring,
A developing roller (50) that conveys the electrostatic latent image to the developing section (60), and a developer stirring and conveying means (41) that conveys the developer to the developing roller (50) while stirring. , 42) and the developer agitation conveyance means (41
, 42).
) and a housing (40) that surrounds the developer agitation and conveyance means (41, 42) in a portion other than the developer outlet section (49) for sending out the developer from the developer agitation and conveyance means (41, 42). In the developing device for an electrophotographic apparatus, the cross-sectional shape and size of the space in the housing (40) is substantially the same as the cross-sectional shape of the developer agitation and conveyance means (41, 42), and the developer agitation and conveyance means (41,
42) A developing device for an electrophotographic apparatus, characterized in that the developing device is formed in dimensions that create a slight gap with the outer edge of the device. 2. The gap according to claim 1, wherein the gap is larger than the particle size of the developer and is within a range that does not reduce the efficiency of conveying the developer by the developer agitation conveyance means (41, 42). Developing device for electrophotographic equipment. 3. The developing device for an electrophotographic apparatus according to claim 1, wherein the gap is 0.5 to 1 mm. 4. Claim 1, wherein the developer stirring and conveying means is a rotating screw (41, 42) having spiral blades.
3. A developing device for an electrophotographic apparatus according to 2 or 3. 5. The developer agitation and conveyance means is an endless belt with blades (7) having a plurality of screen-like blades standing upright.
2) The developing device for an electrophotographic apparatus according to claim 1, 2 or 3.