JP2002062721A - Developing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing apparatus, capable of obtaining proper images by controlling toner concentration to aimed fixed level, without having the toner concentration increase, when the toner in a toner in the storage part is decreased. SOLUTION: This developing apparatus is equipped with the toner storage part 9 storing the toner, a developer storage part 8 storing two-component developer consisting of the toner and magnetic carrier, a rotatable developer carrier 3 carrying the two-component developer, and a developer regulating member 5 regulating the developer amount on the developer carrier 3. In the apparatus, by having the toner concentration self-control with taking the toner in the storage part 9 in the storage part 8 by the developer carrier 3, and the rotational speed of the stirring member in the storage part 9 is controlled by a toner end sensor 10.

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 for an image forming apparatus utilizing electrophotographic technology, such as a copying machine and a laser printer.

[0002]

2. Description of the Related Art A system for self-controlling toner concentration with a small amount of developer is described as follows. When toner is supplied to a developer on a developer carrier (developing sleeve) through a toner supply opening and the toner concentration rises, the developing The transfer resistance of the developer in the developer storage chamber with respect to the developer on the developer carrier increases, and a ball phenomena occurs in the transfer of the developer, causing a second developer regulating member (hereinafter, referred to as a “predoctor”). In this system, a developer pool is formed in a portion, the toner supply opening is closed, and the toner density is controlled by the bulk of the developer. In the developing device of this system, the amount of the two-component developer including the magnetic carrier and the toner accommodated in the developer accommodating portion is small, and the developer is uniformly carried in the axial direction of the developer carrying member. Compared with the normal two-component development method, the magnetic carrier is less, the torque of the device is greatly reduced, and the toner is taken in by the movement of the magnetic carrier, so the mixing ratio of toner and magnetic particles (hereinafter `` toner concentration '' ) Can be simplified. That is, it is advantageous for miniaturization and cost reduction. In this system, the toner density can be controlled by changing the amount of the magnetic carrier contained in the initial developer containing portion, thereby changing the bulk of the developer.

For example, in the method of setting an initial developer in a small-volume developer system disclosed in Japanese Patent Application Laid-Open No. 8-314254, a developer is preset at a limit or more that can be held by the magnetic force of a developing roller, and after a predetermined number of rotations, The excess toner is stored in the toner storage section. In other words, in the small-volume developing system, the bulk of the developer near the toner container and the toner supply opening determines the toner self-control, the deflection of the developing sleeve, the gap deviation between the photosensitive drum and the developing sleeve, and the gap between the doctor blade and the developing sleeve. Since toner density unevenness is caused by uneven developer amount due to deviation, such unevenness is eliminated by setting a large amount of agent and pre-rotating to drop the agent. Further, in the method of setting the initial developer of the small-volume developer system disclosed in Japanese Patent Application Laid-Open No. 9-6133, the developer is preset to a value exceeding the limit that can be held by the magnetic force of the developing roller, rotated a predetermined number of times, and dropped by its own weight. A cavity is provided so that excess agent does not adhere to the developing roller again. According to the initial agent setting method disclosed herein, component accuracy, gap deviation, and agent setting unevenness can be corrected, and toner density unevenness is less likely to occur.

[0004]

However, in the small-volume developer system, when the toner in the toner storage section is consumed and decreases, an appropriate pressure of the toner from the toner storage section against the agent pool formed in the predoctor section. The balance is lost, and toner is conveyed to the reservoir in the pre-doctor section at a different pressure than normal, so the toner replenishment balance in the reservoir in the pre-doctor section is disrupted, the toner concentration rises, and background contamination occurs. Therefore, there is a problem that the toner in the toner container cannot be used up completely.

In view of the above problems, in the present invention, when the amount of toner in the toner container decreases, it is possible to control the target toner concentration without increasing the toner concentration and obtain a good image. It is an object of the present invention to provide a developing device which can perform the developing.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, a toner accommodating section for accommodating a toner, and a developer accommodating a two-component developer composed of a toner and a magnetic carrier are provided. A housing, a rotatable developer carrier for carrying the two-component developer, and a developer regulating member for regulating the amount of developer on the developer carrier, wherein the developer carrier comprises a latent image in a developing device. While being opposed to the carrier,
In a developing device having a magnetic field generating means inside, a developer layer formed by a developer regulating member along the peripheral surface of the developing carrier, and taking the toner in the toner containing section into the developer containing section, a toner end sensor is used. This is a developing device that controls the rotation speed of the stirring member in the toner container. The invention according to claim 2 is the developing device according to claim 1, wherein the rotation of the stirring member in the toner storage unit is intermittently performed by the toner end sensor. The invention according to claim 3 is
The toner end sensor is a magnetic permeability sensor
A developing device according to claim 1.

According to the first aspect of the present invention, the rotation speed of the agitator can be changed by controlling the amount of toner in the toner container with the toner end sensor. For example, when the amount of toner in the toner storage unit is large, the rotational speed of the agitator is reduced in order to always keep an appropriate pressure balance of the toner from the toner storage unit with respect to the agent pool formed in the predoctor unit. The function is to prevent background contamination caused by an increase in toner density, runaway due to accumulation of agent on the developing roller, and density unevenness. According to the second aspect of the present invention, the rotation of the agitator is intermittently controlled by controlling the amount of toner in the toner storage section by the toner end sensor. For example, when the amount of toner in the toner storage chamber is large, by stopping the agitator so as not to send too much toner to the agent reservoir formed in the pre-doctor section,
The function is to prevent background contamination caused by an increase in toner density, runaway due to accumulation of agent on the developing roller, and density unevenness. According to a third aspect of the present invention, the toner end sensor is a magnetic permeability sensor.
When the toner contains a magnetic substance, the toner end can be easily detected by using a magnetic permeability sensor.

[0008]

Embodiments of the present invention will be described below in detail. FIG. 1 is a schematic diagram illustrating a configuration of a developing device according to an embodiment of the present invention. FIG. 2 is a graph showing the relationship between the remaining amount of toner and the rotation speed of the agitator in the developing device of the present invention. FIG. 3 is a time chart showing the relationship between the output of the end sensor and the agitator in the developing device of the present invention.

(First Embodiment) This developing device is arranged on a side of a cylindrical photosensitive member 4 as a latent image carrier, and has an opening formed toward the photosensitive member 4. A developing sleeve 3 made of a non-magnetic material as a developer carrying member, on the surface of which a developer 1 made of toner and a magnetic carrier is partially exposed from the opening, and fixed inside the developing sleeve 3 A magnet roller as the generated magnetic field generating means, a doctor blade 5 as a first developer regulating member for regulating the amount of developer carried and conveyed on the developing sleeve 3, a developer accommodating case 7, a toner accommodating section And a toner hopper 9 and the like. Further, a toner end sensor 10 is provided below the toner storage section 9 and near the toner supply port.

The toner end sensor 10 used here
May be any of a detection method using a piezoelectric element, a detection method using an ultrasonic sensor, and a method for detecting a transfer load of a transfer member such as the agitator 11. In the case of a toner containing a magnetic material, a detection method using a magnetic permeability sensor may be used.

The developer accommodating case 7 accommodates the developer which is not supplied to the developing position opposite to the photosensitive member 4 and whose development is stopped by the doctor blade 5 between the developing sleeve 3 and the developing sleeve 3. The part 8 is formed. A magnet roller 5 fixedly arranged inside the developer sleeve 4
Among them, a magnetic pole for supporting the developer 1 in the developer accommodating section 8 on the developing sleeve 3 is arranged at a position facing the developer accommodating section 8. Further, the toner container 9 has a toner supply opening 7 adjacent to the upstream side of the developer storage unit 8 in the developer transport direction and facing the surface of the developing sleeve 3, and is adjacent to the toner supply opening 7. In the space, an agitator 9 is disposed as a toner replenishing member that sends out new toner 2 in the toner storage unit 9 indicated by reference numeral 11 while stirring it toward the toner replenishing opening 7. The position of the rotating shaft and the length of the wings of the agitator 9 are adjusted so that the outermost track of the agitator 9 does not swing to the developer.

In the developing device having the above structure, the developer 1 carried on the developing sleeve 3 is conveyed to the doctor blade 5 side along with the rotation of the developing sleeve 3 and is regulated by the doctor blade 5 to be thin. Stratified. The thinned developer 1 is transported to a development area facing the photoconductor 4. Then, in the development area, toner is supplied to the electrostatic latent image formed on the photoconductor 4 in a contact or non-contact manner, and the electrostatic latent image is visualized. Thereafter, the developer 1 is conveyed on the side of the toner replenishing opening 7 along with the rotation of the developing sleeve 3 and sent out by the agitator 11 in the toner accommodating portion 9 to supply new toner 2 supplied from the toner replenishing opening 7. Then, the process returns to the developer accommodating section 8. Then, the internal pressure of the developer 1 containing the new toner 2 at the regulating portion by the doctor blade 5 increases, and the toner of the developer 1 is frictionally charged. As described above, the toner in the developer 1 on the developing sleeve 3 can be charged by the internal pressure of the developer in the developer accommodating section 8, so that a paddle or a screw or the like for charging or stirring the developer is used. A complicated stirring and conveying mechanism is not required.

On the other hand, a part of the developer 1 which is not supplied to the developing area and is prevented from proceeding by the doctor blade 5 is transferred to the toner container 9 by the internal pressure and gravity of the developer 1 itself in the developer container 8. To the toner supply opening 7. Developer 1 that has moved to the vicinity of toner supply opening 7
Is regulated by a pre-doctor 6 which is a second developer regulating member disposed on the upstream side of the doctor blade 5, is attracted to the developing sleeve 3 side by the magnetic force of the magnetic pole, and is again rotated with the rotation of the developing sleeve 3. By being conveyed to the side 5, the developer circulates in the developer accommodating section 8. Further, in the developing device having the above configuration, when the amount of toner supplied to the developer 1 increases and the toner concentration increases, the bulk of the developer 1 increases accordingly. It moves toward the pre-doctor 6 which is a member,
The developer 1 which is regulated by the pre-doctor 6 but cannot be regulated forms a developer stagnant portion and covers the opening of the toner supply opening 7. Therefore, the amount of toner taken into the developer 1 on the developing sleeve 3 is reduced. Due to this decrease in the amount of toner taken in, the toner concentration of the developer 1 is always kept at a certain concentration or less. Conversely, when the toner concentration of the developer 1 decreases, the bulk of the developer 1 decreases, so that the developer stagnation portion does not block the toner replenishment opening 7. Toner is taken in,
The toner density of the developer 1 is always kept at a certain level or higher.

When it is desired to change the toner concentration, the volume of the developer can be changed and controlled by changing the amount of the magnetic carrier contained in the developer containing section 8. For example, if the carrier amount is reduced from a certain amount, the bulk of the agent decreases, so that the amount of toner taken in from the toner supply opening 7 increases, and the toner concentration of the developer 1 can be increased.
As described above, since the toner density can be controlled within a substantially constant range, a complicated toner density control mechanism using a toner density sensor, a toner replenishing member, or the like is unnecessary. In the developing device employing this system, the amount of the two-component developer 1 composed of the magnetic carrier and the toner accommodated in the developer accommodating section 8 is small, and the developer 1 is uniformly distributed in the axial direction of the developing sleeve 3. It is carried. In the toner concentration self-control of this system, the amount of toner 2 taken in varies depending on the bulk of the developer 1 near the developer accommodating section 8 and the toner replenishing opening 7.
As a result, the toner density differs.

Therefore, even if the developer is uniformly set on the developing sleeve 3, the deflection of the developing sleeve 3, the straightness of the doctor blade 5, the straightness of the pre-doctor blade 6 (the end of the developer accommodating portion 8), and the like. As a result, the gap between the developing sleeve 3 and the photosensitive member 4, the gap between the doctor plate # 5 and the developing sleeve 3, and the gap between the pre-doctor 6 and the developing sleeve 3 are different, and toner density unevenness occurs. Therefore, the accuracy of each is important. The gap between the pre-doctor 6 and the developing sleeve 3 has an effect on the stability of the toner concentration self-control, and it has been found that the narrower the gap is, the more stable the toner density is. Since it is known that the toner density becomes more stable with the amount of 1, the leading end (predoctor 6) of the developer accommodating portion 8 near the toner replenishment opening 7 is more in contact with the sleeve 3 than the other developer accommodating portions. The gap must be narrow,
With only the above-described method, the developer is moved to the toner replenishing side of the developer accommodating section 8 by the magnetic force of the developing roller 3 so that the developer
Since more toner remains, there is a disadvantage that the toner concentration is self-controlled to a lower level.

An agent reservoir 12 formed in 6 parts of the predoctor.
In addition, the toner 2 is replenished too much and the density rises, causing runaway due to background contamination or agent pool on the developing sleeve 3, or conversely, the density becomes low due to insufficient toner replenishment, causing abnormal images. However, the toner 2 in the developer accommodating section 8 is always detected by the magnetic permeability sensor 10, and the rotational speed of the agitator 11 is changed according to the amount of toner in the developer accommodating section 8. Since the toner 2 is always fed to the agent reservoir 12 formed in the predoctor 6 at a constant pressure, high image quality can always be provided.

The developing conditions of the embodiment are shown below. (Machine setting conditions) Photoconductor linear velocity: 120 mm / sec Gap Gp between the developing sleeve and the photoconductor drum: 0.3 to
0.5 mm Gd1 between developing sleeve and doctor blade: 0.
3 to 0.5 mm Gap between developing sleeve and predactor Gd2: 0.5 to
1.5 mm developing sleeve diameter: 16φ Ratio of linear speed of developing roller to linear speed of photoreceptor: 1.5 to 3.
0 (Development conditions) Charge potential: -850 to -950 V Development bias: -600 to -700 V (Developer) Carrier: Material: magnetite or iron Average particle size: 40 to 50 μm Toner: Magnetic material (magnetite) amount: 15 to 15 40% by weight Silica amount: 0.5 to 1.0% by weight Toner carrier coverage: 50 to 120% Toner charge amount Q / M: 10 to 30 μc / g

(Second Embodiment) Background contamination due to an increase in toner concentration due to excessive toner supply to the agent reservoir 12 formed in the predoctor 6, runaway due to agent accumulation on the developing sleeve 3, and insufficient toner supply The toner 2 in the developer accommodating portion 8 is always detected by the magnetic permeability sensor 10, and the agitator 11 rotates when the toner 2 is large. Move, stop or move intermittently. When the amount of the toner 2 is small, if the toner 2 is intermittently moved while being adjusted so that the toner 2 can always be fed to the agent reservoir formed in the predoctor 6 at a constant pressure, a high-quality image can always be provided.

[0019]

As described above, in the developing device according to the first aspect, if the rotation amount of the agitator is controlled by detecting the amount of the toner in the toner storage unit by the toner end sensor, the toner can be transferred to the pre-doctor unit. Since the toner is supplied to the formed agent reservoir with an appropriate pressure, an increase in the toner density is suppressed, and the background contamination and runaway do not occur, and the density reduction due to the density reduction and the density unevenness can be prevented. In the developing device according to the second aspect, if the toner in the toner storage chamber is detected by the toner end sensor and the agitator is rotated intermittently, irrespective of the amount of toner in the toner storage chamber, background fouling, runaway, and density increase due to the density increase. It is possible to prevent the density from becoming low and the density from becoming uneven due to the decrease. In the developing device according to the third aspect, the toner in the toner storage chamber can be easily detected by the magnetic permeability sensor with a simple structure, and the amount of toner remaining in the toner storage chamber can be easily detected to control the agitator.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a developing device according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the remaining amount of toner and the agitator rotation speed in the developing device of the present invention.

FIG. 3 is a time chart showing a relationship between an output of an end sensor and an agitator in the developing device of the present invention.

[Description of Signs] 1 developer 2 toner 3 developing sleeve 4 photoreceptor 5 doctor blade 6 predoctor 7 toner replenishment opening 8 developer storage 9 toner storage (toner hopper) 10 permeability sensor 11 agitator 12 agent in predoctor Pool

Continued on front page F term (reference) 2H027 DD02 DE04 DE07 EA06 EC06 EC09 ED10 2H031 AA01 AA09 AA11 AA16 AB03 AB09 AC08 AC13 AC17 AC30 BA04 BC03 DA01 EA03 2H077 AA12 AA16 AA35 AB04 AB13 AC03 AD06 AD13 AD17 AD22 BA02 DA02 DA02 DA02

Claims (3)

[Claims] 1. A toner accommodating section for accommodating a toner, a developer accommodating section for accommodating a two-component developer including a toner and a magnetic carrier, a rotatable development carrier for carrying a two-component developer, and a developer. A developer regulating member that regulates an amount of developer on the carrier, wherein the developer carrier is disposed in the developing device so as to face the latent image carrier, and has a magnetic field generating means therein; In a developing device that forms a developer layer with a developer regulating member along the peripheral surface of the developer and takes in the toner in the toner container into the developer container, the toner end sensor controls the rotation speed of the stirring member in the toner container. A developing device. 2. The developing device according to claim 1, wherein the rotation of the stirring member in the toner container is intermittently performed by the toner end sensor. 3. The developing device according to claim 1, wherein the toner end sensor is a magnetic permeability sensor.