JPH0743998A - Developing device - Google Patents

Abstract

PURPOSE:To prevent reduction in the image density of a recorded image by preventing defective toner from being heaped on the rear side of a toner stirring chamber, with the lapse of time, in what is called a side dispensing system developing device supplying toner from one end part in the longitudinal direction of a developing device to the other end part. CONSTITUTION:In the developing device provided with a toner carrier 2 carrying one-component toner to a developing region facing an electrostatic latent image carrier D, the toner stirring chamber 12 provided along the axial direction of the toner carrier 2, a toner feeding path 13 which is provided projectingly on one end of the toner stirring chamber 12 and into which the toner is dropped from a toner box and a toner carrying member 31 carrying the toner from the toner feeding path 13 to the toner stirring chamber 12 and making the toner flow from the side of the toner feeding path 13 to the other end side in the toner stirring chamber 12, toner circulating means 34 and 35 circulating the toner along the axial direction of the toner carrier 2 are provided on the rear side region in the flowing direction of the toner in the toner stirring chamber 12, as a characteristic.

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 a laser printer or an electrophotographic copying machine, and more specifically, a so-called side dispense type developing device in which toner is supplied to the developing device from its longitudinal end. Regarding the improvement of the device.

[0002]

2. Description of the Related Art As a so-called side dispense type developing device, a developing device disclosed in Japanese Patent Application Laid-Open No. 3-267963 is known. This developing device is provided with a toner agitating chamber provided along the axial direction of the toner carrier, and at one end of the agitating chamber, a toner carry-in passage is provided so as to project from the developing device, and the toner carrying-in passage is provided from the toner box. The replenishment toner dropped in is carried into the toner stirring chamber from the toner carrying-in path by the toner carrying member. Then, the toner carried into the toner stirring chamber flows from the toner carrying-in passage side (hereinafter, supply side) toward the inner side by the pressing force of the toner carried in later, and diffuses into the toner stirring chamber. It is like this.

[0003]

However, in this conventional developing device, since the toner flows in one direction from the front side to the rear side in the toner stirring chamber, it is difficult to be consumed because the particle size is large. There is a drawback that defective toner easily accumulates on the rear side of the toner agitating chamber over time. For this reason, when an electrostatic latent image is actually developed using this developing device and a recording image is formed on a recording sheet such as paper, when the recording image is formed in the image area corresponding to the rear side of the toner stirring chamber. There is a problem in that the density gradually decreases and image loss occurs.

The present invention has been made in view of the above problems, and an object of the present invention is to prevent defective toner from accumulating on the rear side of the toner agitating chamber with the passage of time, thereby recording. It is an object of the present invention to provide a developing device capable of preventing a decrease in image density of an image.

[0005]

In order to achieve the above object, the developing device of the present invention comprises a toner carrier which conveys a one-component toner to a developing area facing the electrostatic latent image carrier, and the toner carrier. A toner stirring chamber provided along the axial direction of the carrier, a toner carrying-in passage projecting from one end of the toner stirring chamber into which toner is dropped from the toner box, and the toner carrying-in passage from the toner carrying-in passage to the toner stirring chamber. In the toner agitating chamber from the toner carrying-in path side (supply side) to the other end side (back side). A toner circulating means for circulating the toner along the axial direction of the toner carrier is provided in the inner region.

In the above technical means, the toner circulating means forms a circulating flow of toner along the axial direction of the toner carrier in the inner region of the toner agitating chamber, and the toner circulating flow is provided at the inner side of the toner agitating chamber. The configuration may be appropriately changed as long as the defective toner unevenly accumulated is mixed with the good toner flowing from the supply side.

Here, the back side region of the toner stirring chamber in which the toner circulating means is disposed is a region including at least the back side end portion of the toner stirring chamber, and the width of the region may be designed arbitrarily. Absent. For example, toner circulating means may be provided over the entire stirring chamber.

Further, the toner circulating means is required to have a function to convey the toner toward the inner side of the toner stirring chamber and convey the toner accumulated in the inner side toward the supply side. If the toner conveyance force in the direction is smaller than the toner conveyance force in the supply side direction, the amount of toner accumulated on the inner side of the toner agitation chamber decreases with the passage of time, and the density of the formed recorded image may partially decrease. There is. Therefore, in order for the good toner that contributes to the development of the electrostatic latent image to be deposited almost uniformly over the entire area of the toner agitating chamber, the toner carrying amount in the inner direction of the toner agitating chamber is the toner carrying amount in the feeding side direction. It is preferably larger than the amount.

Further, from the viewpoint of reducing the size of the toner circulating means, the toner circulating means is formed by fixing two spiral toner conveying members having different winding directions and winding diameters to one rotating shaft. Preferably.

Further, when the two spiral toner conveying members are thus fixed to one rotating shaft to form the toner circulating means, the spiral toner conveying member having a large winding diameter and the spiral toner having a small winding diameter are formed. In order to maintain the balance of the carrying force with the carrying member, a part of the outer circumference of the former should be covered with an arc-shaped carrying auxiliary wall to appropriately prevent the toner from diffusing around the spiral toner carrying member. preferable.

[0011]

According to the above technical means, the toner circulation means forms a circulation flow of toner in the inner region of the toner agitating chamber, and the defective toner which is apt to be accumulated in the inner side of the toner agitating chamber is accumulated in the toner agitating chamber. Mix with newly supplied toner.
As a result, the defective toner diffuses into the area where the toner circulating means is arranged, and the ratio of the defective toner to the total amount of the toner in the inner side of the toner stirring chamber decreases, so that the electrostatic latent image is developed. It is possible to prevent a partial reduction in density of the formed toner image.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The developing device of the present invention will be described in detail below with reference to the accompanying drawings. As shown in FIGS. 1 and 2, the developing device of the present embodiment is provided with a developing roll 2 disposed at one end of the housing 1 and having a part of the outer peripheral surface exposed to the outside of the housing 1.
(Toner carrier), toner stirring chamber 12 provided in housing 1 along the axial direction of developing roller 2, and one mixing shaft 3 arranged so as to penetrate through stirring chamber 12. It consists of and.

First, the developing roll 2 comprises a rotatable cylindrical sleeve 22 disposed on the outer periphery of a substantially cylindrical magnet member 21 which is fixed and supported, and the magnetic toner in the stirring chamber 12 is removed. The magnetic force of the magnet member 21 attracts the outer peripheral surface of the sleeve 22 and conveys it to the developing area facing the electrostatic latent image carrier D as the sleeve 22 rotates. A blade 23 for thinning the attracted magnetic toner is pressed against the outer peripheral surface of the sleeve 22, and the blade 23 is fixed to the upper portion of the housing 1 by a bolt 24. In FIG. 1, reference numeral 25 is a tracking roll arranged coaxially with the developing roll 2 via a bearing so as to maintain a gap between the developing roll 2 and the electrostatic latent image carrier D, and reference numeral 26 is a housing. 1 is a sealing member that seals between the housing 1 and the developing roller 2 in order to prevent the toner from leaking out.

The mixing shaft 3 is provided so as to pass through a toner carrying-in passage 13 which is provided so as to project from the agitating chamber 12 and the housing 1 and communicates with the agitating chamber 12. The toner dropped from the toner box (not shown) located in the above position into the stirring chamber 12 is carried into the stirring chamber 12, and the toner is supplied from the stirring chamber 12 to the developing roller 2 and further stirred. Has a role of forming a circulating flow of toner in the inner region of the.

Gears 27 and 28 are fitted to one end of the developing roll 2 and the mixing shaft 3 in the axial direction thereof, and are connected to a drive motor (not shown) so as to rotate at a predetermined rotation speed. It has become. In the developing device of this embodiment, the side on which the toner carry-in path 13 is provided is called the front side, and the side on which the gears 27 and 28 are arranged is called the rear side.

On the other hand, a toner level sensor 4 (hereinafter referred to as a sensor) for detecting the amount of toner accumulated in the stirring chamber 12 is attached to one side of the stirring chamber 12. This sensor 4
Has a piezoelectric element on the detection surface exposed in the stirring chamber 12, and detects the presence or absence of toner based on the vibration state of the piezoelectric element. The mounting position of the sensor 4 is assumed to be a case where an electrostatic latent image is formed with the front side of the electrostatic latent image carrier D as a reference, and is set to a central position of A4 size which is considered to be most frequently developed. .

Further, in this developing device, the sensor 4
In order to prevent erroneous detection of the toner level due to toner remaining on the detection surface, the cleaning member 5 for the detection surface is provided. The cleaning member 5 is a resin sheet such as mylar screwed to the mixing shaft 3,
The toner attached to the detection surface is scraped off as the mixing shaft 3 rotates.

Next, a specific structure of the mixing shaft 3 will be described. This mixing shaft 3
While a spiral plate-shaped toner conveying member (auger) 31 is provided in a portion corresponding to the carry-in passage 13, a portion of the stirring chamber 12 corresponding to the vicinity of the carry-in passage 13 has a toner conveying amount per unit time from the auger 31. It has a large spiral coil-shaped toner conveying member (agitator) 32. This is to reduce the toner density in the carry-in passage 13 and prevent the toner from becoming agglomerate in the carry-in passage 13, and thus the toner can be smoothly carried into the stirring chamber 12. There is. In this embodiment, the diameter of the auger is 12 mm, the diameter of the carry-in path is 14 mm, the diameter of the agitator is 26 mm, the diameter of the stirring chamber is 28 mm, and the diameter of the agitator is set larger than the diameter of the auger.
The toner transport amount per unit time is increased.

Further, the mixing shaft 3 has a stirring bar 33 provided substantially parallel to the shaft 3 and continuing from the agitator 32, and the toner is stirred in the stirring chamber 12 as the member 3 rotates. It is configured to be agitated by and pushed out from the agitating chamber 12 in the direction of the developing roll 2.

Furthermore, the mixing shaft 3 has two spiral coil-shaped toner conveying members 3 having different winding directions and winding diameters corresponding to the inner region of the stirring chamber 12.
4, 35 are provided. The toner conveying member (small diameter agitator) 34 having a small winding diameter is wound in a direction of feeding the toner to the rear side of the stirring chamber when the mixing shaft 3 is rotated, while the toner conveying member (large diameter agitator) 35 having a large winding diameter. Is wound in a direction in which the toner is returned to the front side when the mixing shaft 3 is rotated. In this embodiment, small and large agitators 34, 35
Both of them are made of non-magnetic stainless steel with a diameter of 1.5 mm, the small diameter agitator 34 is wound with an outer diameter of 16 mm and a pitch of 15 mm, and the large diameter agitator 35 is wound with an outer diameter of 26 mm and a pitch of 35 mm.

The small-diameter agitator 34 and the large-diameter agitator 35 may be arranged over the entire length of the stirring chamber 12 from the front side to the rear side. If the toner accumulation level at the installation position fluctuates, the sensor 4 may erroneously detect the toner accumulation level in the agitation chamber 12. Therefore, in this embodiment, the agitators 34, 35 are provided only in the area extending from the sensor 4 to the rear side. Was arranged.

Further, as shown in FIG. 2, the agitating chamber 12 covers a part of the outer periphery of the large-diameter agitator 35, and extends toward the rear side of the sensor 4 and the auxiliary conveyance wall 6 is provided.
Is provided. When comparing the toner conveying force of the small diameter agitator 34 and the toner conveying force of the large diameter agitator 35, the toner is guided along the rotation axis of the mixing shaft 3 in the small diameter agitator 34, but the large diameter agitator 3 is guided.
In the case of No. 5, the toner diffuses to the outer circumference, so that the toner conveying force of the large diameter agitator 35 becomes extremely smaller than that of the small diameter agitator 34. However, when the conveyance assisting wall 6 is provided as in this embodiment, the toner does not diffuse to the outer periphery of the large diameter agitator 35, so that the toner conveying force of the large diameter agitator 35 is improved and the toner conveyance of the small diameter agitator 34 is improved. The balance between the force and the toner conveying force of the large diameter agitator 35 can be maintained.

In the developing device of this embodiment having the above structure, the toner is conveyed and agitated as follows. First, the toner dropped from the toner box into the carry-in passage 13 is carried into the stirring chamber 12 from the carry-in passage 13 by the auger 31, and further, the agitator 32 moves the inside of the stirring chamber 12 to the image portion area facing the developing roll 2. Be transported. After that, the toner flows from the front side to the rear side by the pressing force of the toner sent into the stirring chamber 12.

The toner passing through the position where the sensor 4 is disposed is slowly conveyed to the rear side by the small-diameter agitator 34 and strikes the rear end of the stirring chamber 12 as it is. Further, the toner hitting the end portion on the rear side is conveyed from the rear side to the front side by the large diameter agitator 35. Then, the toner returned from the rear side to the front side is mixed with new toner flowing from the front side in the vicinity of the cleaning member 5, and is again conveyed to the rear side by the small diameter agitator 34.

That is, in this developing device, a gentle toner circulation flow is formed in a region on the inner side of the stirring chamber 12 in the toner flow direction, and the toner reaching the rear side of the stirring chamber 12 circulates in the region. Mixed with fresh toner.
Therefore, defective toner that tends to accumulate on the rear side of the agitating chamber 12 is mixed with new toner and diffuses into the area from the sensor 4 to the rear side, so that the recorded image density in the area corresponding to the rear side of the developing device is aged. It is possible to prevent the decrease.

In order to confirm the effects of the present invention, the results of repeatedly forming recorded images with the developing device of this embodiment are shown in FIG. As is clear from this figure, in the conventional developing device in which the toner circulation flow is not formed, the toner particle size distribution on the rear side is within the allowable range of 15 μm as the number of copies increases.
However, in the developing device of the present embodiment, even if the number of copies increases, the toner particle size distribution on the rear side can be suppressed to 15 μm or less, and a good image with little density decrease over a long period of time can be obtained. I was able to get it.

In this embodiment, the small-diameter agitator 34 conveys the toner to the rear side and the large-diameter agitator 35 conveys the toner to the front side to form a circulating flow. However, the winding direction of each agitator 34, 35 is changed. In the opposite direction to the above embodiment,
The small diameter agitator 34 may convey the toner to the front side and the large diameter agitator 35 may convey the toner to the rear side to form a circulation flow.

[0028]

As described above, according to the developing device of the present invention, the toner circulating means forms the circulation flow of toner in the inner region of the toner stirring chamber and is biased toward the inner side of the toner stirring chamber. Since the defective toner that easily accumulates is mixed with the toner newly supplied to the toner stirring chamber, the defective toner does not accumulate on the rear side of the toner stirring chamber over time,
It is possible to prevent a partial decrease in the image density of the recorded image.

[Brief description of drawings]

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

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a graph showing a toner particle size distribution on the rear side of the developing device.

[Explanation of symbols]

1 ... Housing, 2 ... Developing roll (toner carrier), 3
… Mixing shaft, 4… Toner level sensor, 5…
Cleaning member, 12 ... Toner stirring chamber, 13 ... Toner carry-in path,
31 ... Toner conveying member, 34 ... Small diameter agitator, 35 ...
Large diameter agitator

Front page continued (72) Inventor Takayuki Sunaga 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Toru Ishikawa 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd.

Claims (4)

[Claims] 1. A toner carrier for conveying a one-component toner to a developing area facing the electrostatic latent image carrier, a toner stirring chamber provided along the axial direction of the toner carrier, and the toner stirring. The toner carrying-in passage is provided at one end of the chamber for dropping the toner from the toner box, and the toner carrying member for carrying the toner into the toner stirring chamber from the toner carrying-in passage is provided. In the developing device that flows from the road side to the other end side, a toner circulation unit that circulates the toner along the axial direction of the toner carrier is provided in the back side region of the toner stirring chamber in the toner flow direction. A developing device characterized in that 2. The developing device according to claim 1, wherein the amount of toner conveyed by the toner circulating means is such that the amount conveyed in the inner direction of the toner stirring chamber is larger than the amount conveyed in the toner carry-in path direction. And developing device. 3. The developing device according to claim 1, wherein the toner circulating means is formed by fixing two spiral toner conveying members having different winding directions and winding diameters to one rotation shaft. Characteristic developing device. 4. The developing device according to claim 3, wherein, of the two spiral toner conveying members, a part of the outer periphery of the spiral toner conveying member having a large winding diameter is covered with a conveyance auxiliary wall. Development device.