JPH05127530A - Developing device for image forming device - Google Patents

Abstract

PURPOSE:To achieve the accurate quantitative-control of the concentration of the toner in developer and to make a device compact by means of the simple constitution. CONSTITUTION:A replenishment toner storage hopper 20 is provided on the top of a developer container 18, storing developer 24, via a mesh 19 through which toner particles can pass. A magnet roller 17 in which NS-pair magnetic poles are uniformly arranged around the periphery so that they are alternately arrayed the circumferential direction is arranged close to the mesh 19 below the replenishment toner storage hopper 20 in the developer container 18 so that it can be rotated and driven. Thus, toner (a) in the replenishment toner storage hopper 20 is scraped towards the developer container 18 by the use of a magnetic brush formed on the periphery of the magnet roller 17. Also, magnets 25a-25d or magnetic bodies are arranged in the vicinity of the developer container 18. By the change in a magnetic field produced in the area between the magnet roller 17 and them, the flowability and stirring performance of the developer 24 are improved, thereby speeding up the rise of the amount of the electrification and preventing the solidification of the developer 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device in an image forming apparatus such as an electrostatic photocopier.

[0002]

2. Description of the Related Art As a developer used in an electrostatographic copying machine which is an image forming apparatus, there are used a one-component type developer consisting only of magnetic toner and a two-component type developer obtained by mixing a non-magnetic toner and a magnetic carrier. There are things. In the case of a two-component developer, the non-magnetic toner is electrostatically adsorbed on the magnetic carrier by frictional charging and is accommodated in the developer container.

For example, when a positive image is developed on a photoconductor of an electrostatographic copying machine by a developing device using the above-mentioned two-component developer, the nonmagnetic toner constituting one component of the developer is used as a nonmagnetic toner. Toner that has a polarity opposite to that of the charge is used, and this toner is electrostatically adsorbed on the electrostatic charge remaining portion of the photoconductor. The magnetic carrier and the non-magnetic toner contained in the developer container are agitated by an agitator, and only the non-magnetic toner is replenished into the developer container in the amount of consumption.

In such a conventional developing device, as a method for controlling the toner concentration of the developer to be constant,
The following are adopted. A magnetic permeability sensor is used to measure the magnetic permeability of the developer, the toner concentration is calculated from the measured value, and non-magnetic toner is replenished so that the toner concentration becomes constant. The level sensor is used to measure the level of the developer contained in the developer container, the toner concentration is calculated from the measured level, and the nonmagnetic toner is replenished so that the toner concentration, that is, the developer contained level becomes constant. What to do. A photo sensor such as a CCD camera or photo camera is used to measure the image density developed on a specified potential on the photoconductor, and non-magnetic toner is replenished so that the measured value becomes constant. It measures the resistance value of the developer and replenishes non-magnetic toner so that the measured value is constant. A latent image of a specified width formed on a photoconductor is developed, the line width is measured by a thin line width measurement sensor, and nonmagnetic toner is replenished so that the measured value becomes constant. A brush made of a fixed amount of magnetic carrier is formed on the outer circumference of the magnet roller provided inside the opening of the toner tank, and the rotation of this magnet roller causes the toner from the toner storage tank to be electrostatically attracted to the magnetic carrier side by friction. A device in which both the toner and the magnetic carrier on the outer peripheral surface of the magnet roller are scraped off and supplied to the photoconductor side in a fixed amount (JP-A-50-149352).

[0005]

However, the conventional developing device described above has the following problems.
In the case of the method of controlling the toner density to be constant using the magnetic permeability sensor, the phenomenon that the toner density increases with time even if the magnetic permeability is the same due to deterioration of the magnetic carrier due to long-term use, etc. Therefore, there is a problem that the charge amount of the toner is lowered and the toner is easily scattered or fogged. The method that keeps the amount of developer in the developer container constant based on the measured value of the level of the developer stored by the level sensor is to check the change in the total amount of developer, so the toner concentration can be controlled with high accuracy. There is a problem that you cannot do it. In the method of measuring the density of the image developed on the photoconductor by the photo sensor of the above, the surface of the photo sensor is easily soiled by the scattered toner, and the toner density cannot be accurately controlled to be constant without proper maintenance. There is a point. In the method of measuring the resistance value of the developer, the resistance value of the developer changes over time even with the same toner concentration due to the deterioration of the magnetic carrier due to long-term use, and the toner concentration can be accurately controlled to be constant. There is a problem that you cannot do it. Similar to the method, the method also has a problem that the toner surface cannot be accurately and uniformly controlled because the surface of the sensor is soiled by the scattered toner and the like. In the method of combining the magnet roller and another roller to supply the developer in a fixed amount, since many rollers are used, the mechanism becomes complicated and the developing device becomes large. Further, an excessive amount of toner may be replenished, resulting in a decrease in toner charge amount, fogging, and scattering.

In view of the above-mentioned conventional drawbacks, the present invention enables the toner concentration of the developer to be quantitatively controlled with a simple structure and enables the apparatus to be made compact and to sufficiently stir the developer in the developer container. The present invention is to provide a developing device for an image forming apparatus that can perform the above.

[0007]

In order to achieve the above object, the present invention provides a replenishment toner storage hopper connected to an upper portion of a developer container for storing a developer through a mesh through which toner particles can pass. A magnet roller, in which a pair of NS magnetic poles are evenly arranged on the circumferential surface so as to be alternately arranged in the circumferential direction, can be driven to rotate below the replenishment toner storage hopper in the developer container in proximity to the mesh. And a magnet or a magnetic body is arranged in the peripheral portion of the developer container.

[0008]

When the developer is a two-component developer, when the toner in the developer container is reduced, a part of the magnet roller that is rotationally driven in the developer container is exposed on the developer, and the exposed magnet roller A magnetic brush is formed on the peripheral surface of the magnetic carrier by magnetic attraction of the magnetic carrier, and the non-magnetic toner on the side of the toner storage hopper is scraped off through the mesh by the ears of the magnetic brush and taken into the developer container to replenish the toner. To be done. When the magnet roller is hidden by the developer due to the toner replenishment, the magnetic brush disappears and the toner replenishment stops. By repeating this operation, the toner density is kept constant. In the developer container, since the developer in the developer container is agitated by the rotation of the magnet roller, solidification of the developer is prevented by this, and the developer is arranged in the peripheral portion of the magnet roller and the developer container. The magnetic field changes in the area between the magnet and the magnetic substance, and the stirring property and fluidity of the developer are activated, so that the charge amount of the replenishment toner rises quickly and the magnetic carrier and toner are crushed. Prevention of solidification of the developer in the developer container is further promoted.

When the developer is a magnetic one-component toner, when the toner in the developer container is reduced and a part of the magnet roller is exposed on the developer, the magnetic toner of the magnetic toner is attached to the exposed peripheral surface of the magnet roller. A magnetic brush is formed by adsorption, and the toner on the replenishment toner storage hopper side is similarly taken into the developer container side by the scraping operation of the brush of the magnetic brush and the magnetic attraction force of the magnet roller. Also in this case, the magnetic toner is crushed by the change in the magnetic field generated in the region between the magnet roller and the magnet or magnetic material arranged in the peripheral portion of the developer container, and the developer is solidified in the developer container. Prevention is promoted.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure in the vicinity of the developing section of the electrostatographic copying machine, and FIG. 2 is a cross-sectional view showing the outline of the electrostatographic copying machine.

In the electrostatographic copying machine according to this embodiment, a photoconductor 2 having a photosensitive layer 1 on its outer peripheral surface is horizontally mounted on a main body 3 of the copying machine, and a charging device 4 and an optical device are provided around the photoconductor 2. System moving type exposure device 5, developing device 6, charger type transfer device 7, copy paper separating device 8, and cleaning device 9
Are arranged in this order in the rotation direction of the photoconductor 2 (indicated by arrow R). In addition, from the paper feeding unit 10 to the transfer device 7
A sheet feeding / conveying means 11 and a sheet discharging / conveying means 13 are arranged from the copy sheet separating device 8 to the fixing device 12, respectively, and a pair of sheet discharging rollers 14 and a sheet discharging tray 15 are provided.

As shown in FIG. 1, the developing device 6 comprises a developing sleeve 16 and a magnet roller 17 arranged in a developer container 18. Mesh on top of developer container 18
A toner hopper 20 is connected via 19.

The developing sleeve 16 is formed by rotatably fitting the outer circumference of a fixed roller 22 in which a plurality of magnets 21 are evenly arranged on the circumferential surface so that N poles and S poles are alternately arranged in the circumferential direction. The developer container 18 is made to face the photoconductor 2 facing it from the opening 18a and is driven to rotate in the opposite direction to the photoconductor 2 by a driving means (not shown) during a copying operation of the electrostatic photocopier.

The magnet roller 17 has a structure in which the fixed roller 22 is formed on the peripheral surface of a rotary roller 23 made of ferrite or the like.
Similarly, the N poles and the S poles are evenly arranged so as to be alternately arranged in the circumferential direction, and a part of the circumferential surface is the mesh 19
Is located at the bottom of the toner hopper 20 so that
During the copying operation of the electrostatic photocopier, for example, the developing sleeve
It is rotationally driven in the same direction as 16 by a driving means (not shown).

The mesh 19 allows the non-magnetic toner a, which is one component of the two-component developer 24, to pass therethrough and does not allow the magnetic carrier b, which is another component of the two-component developer 24, to pass through. It is set to roughness.

The peripheral portion of the developer container 18, that is, the upper and lower portions of the developer container 18 corresponding to the middle of the developing sleeve 16 and the magnet roller 17, and the magnet roller.
In order to eliminate the solidification pool of the developer 24, which is apt to occur in each region in the developer container 18 as shown by the symbol S in FIG. 1, at the portion directly below 17 and the side of the magnet roller 17 by the change of the magnetic field. The rotary magnets 25a to 25d are arranged. These rotary magnets 25a to 25d are, for example, driven to rotate in the same direction as the magnet roller 17, and the magnetic poles on the peripheral surface of the magnet roller 17 are always the same as the magnetic poles on the peripheral surface of the opposing magnet roller 17. It is driven to rotate in synchronization with 17.

Next, the operation of the developing device will be described with reference to FIGS. 3 and 4. The two-component developer 24 contained in the developer container 18 is, for example, in a state where the negatively charged non-magnetic toner a is electrostatically adsorbed to the positively charged magnetic carrier b, and the magnetic carrier b is developed. Magnetically attracted to the peripheral surface of the sleeve 16. That is, the developer 24 is the developing sleeve.
Adsorbed as a magnetic brush on the peripheral surface of 16. By the rotation of the developing sleeve 16, the developer 24, which is a magnetic brush on the peripheral surface, approaches the surface of the photoconductor 2. Developer approaching
Among the 24, the non-magnetic toner a having a polarity opposite to that of the positive charge forming the latent image of the photoconductor 2, that is, negatively charged, adheres to the positive charging area forming the latent image of the photoconductor 2. The magnetic carrier b is collected in the developer container 18 while being adsorbed on the developing sleeve 16 without adhering to the surface of the photoreceptor 2.

When the developer 24 in the developer container 18 is consumed and decreases from the full state of FIG.
When the toner density of 24 decreases, a part of the peripheral surface of the magnet roller 17 is exposed on the developer 24 as shown in FIG. As a result, the magnetic brush 26 formed as shown in FIG. 4 by the magnetic attraction of the developer 24 stands on the exposed peripheral surface, and the ears of the magnetic brush 26 rub the mesh 19 as the magnet roller 17 rotates. .. That is, the non-charged non-magnetic toner a accommodated in the toner hopper 20 side is taken into the developer container 18 through the mesh 19 by the scraping effect of the magnetic brush 26 by the ears, and FIG.
Toner is replenished as shown in FIG. At this time, the magnetic carrier b forming the magnetic brush 26 and the toner hopper
Friction charging with the non-magnetic toner a accommodated on the 20 side is also performed, and the non-charged non-magnetic toner a is negatively charged,
The magnetic toner a on the toner hopper 20 side is also added by the effect of the electrostatic attraction force to the magnetic carrier b charged positively.
Are sucked toward the developer container 18 side.

By replenishing the toner, the magnet roller 17
When the toner is completely covered with the developer 24 and the magnetic brush 26 disappears, the toner supply is stopped. By repeating such an operation, the toner density is always kept constant.

In the developer container 18, since the magnet roller 17 is rotated during the copying operation of the electrostatic photocopier, the developer 24 in the developer container 18 is agitated by this rotation. As a result, due to frictional charging between the non-magnetic toner a and the magnetic carrier b, for example, the non-magnetic toner a is negatively charged and the magnetic carrier b is positively charged as described above, and the non-magnetic toner a is electrostatically attached to the magnetic carrier b. Adsorbed and developer 24
Is prevented from solidifying.

In a high temperature and high humidity environment, simply by stirring by rotating the magnet roller 17, the fluidity and the stirring property of the developer 24 are insufficient in the region indicated by the symbol S in FIGS. Although it is not saturated and solidification and accumulation are not sufficiently eliminated, the magnet roller 17 is rotated by the rotary magnets 25a to 25d that are rotationally driven in synchronization with the magnet roller 17.
A repulsive magnetic field is intermittently generated between the rotary magnets 25a to 25d and the repulsive magnetic field, so that the repulsive magnetic field improves the fluidity and agitating property of the developer 24, and the charge amount rises quickly and crushes. As a result, the solidification and the accumulation are eliminated, and the developer 24 is uniformly stored in the developer container 18. As a result, the charging failure of the toner is eliminated, and it is possible to prevent the toner from scattering in the copying machine and fogging on the image.

In the above embodiment, the two-component developer 24
However, the toner concentration can be kept constant in a similar manner even when a one-component type developer consisting of only magnetic toner is used.

That is, in this case, on the magnet roller 17 in the developer container 18, a magnetic brush is formed by magnetic attraction of magnetic toner on the peripheral surface portion exposed as the developer decreases, and the mesh 19 by the magnetic brush is formed. The magnetic toner on the toner hopper 20 side is taken into the developer container 18 due to the scraping effect. At this time, due to the magnetic attraction force of the magnet roller 17, the toner hopper
The magnetic toner on the 20 side is taken into the developer container 18 side.

Further, the solidification and accumulation of the magnetic toner, which is the developer, in the developer container 18 are similarly driven by the rotation of the magnet roller 17 and the rotary magnets 25a to 25d which are driven to rotate in synchronization therewith. It is promoted by the repulsive magnetic field generated intermittently between and.

Further, in the above embodiment, in order to eliminate the solidification and accumulation of the developer 24 in the developer container 18, the developer container
The case where the rotary magnets 25a to 25d which are rotationally driven in synchronization with the magnet roller 17 are arranged in the peripheral portion of 18 has been described. However, instead of the rotary magnets 25a to 25d, as shown in FIG. The magnets 27a to 27c may be fixedly arranged around the periphery of 18. The other structure is the same as that of the previous embodiment.

In the case of this embodiment, as the magnet roller 17 rotates, the magnet roller 17 and the magnets 27a.about.
An attractive magnetic field and a repulsive magnetic field are alternately generated between the magnetic field 27c and the magnetic field 27c, and the change in the magnetic field promotes the solidification elimination of the developer 24. The toner density control operation is the same as in the previous embodiment.

Further, a magnetic material may be fixedly arranged instead of the magnets 27a to 27c of the above embodiment. In this case, the repulsive magnetic field is not generated by the rotation of the magnet roller 17, but the magnetic body disposed on the peripheral portion of the developer container 18 strengthens the magnetic field due to the magnetic poles on the peripheral surface of the magnet roller 17, and The change in the magnetic field due to the rotation spreads over a wide area in the developer container 18, and the change in the magnetic field can eliminate solidification, accumulation, and insufficient charging of the developer 24.

[0028]

According to the present invention, which has the above-described structure, a replenishment toner storage hopper is connected to the upper portion of the developer container for storing the developer via a mesh through which toner particles can pass, and a pair of NSs are provided. A magnet roller, which is evenly arranged on the circumferential surface so that the magnetic poles are alternately arranged in the circumferential direction, is arranged so as to be rotatably driven under the replenishment toner storage hopper in the developer container in proximity to the mesh. Since a magnet or magnetic material is placed around the container, it is possible to quantitatively control the toner concentration with high accuracy with a simple configuration without using various sensors, and to supply sufficient charge to the toner quickly and It can also prevent solidification and accumulation.

[Brief description of drawings]

FIG. 1 is a sectional view showing a developing section of an electrostatographic copying machine in which an embodiment of a developing device of the present invention is incorporated.

FIG. 2 is a cross-sectional view showing an outline of the electrostatic photocopier.

FIG. 3 is an explanatory diagram showing an operation of the developing device.

FIG. 4 is a schematic view showing a magnetic brush formed on a peripheral surface of a magnet roller of the developing device.

FIG. 5 is a sectional view showing a developing section of an electrostatographic copying machine in which another embodiment of the developing device of the invention is incorporated.

[Explanation of symbols]

17 ... Magnet roller, 18 ... Developer container, 19 ... Mesh, 20 ... Replenishment toner accommodating hopper, 25a to 25d ... Rotating magnet, 27a to 27c ... Magnet

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Tatsuo Imafuku, 1-2-2 Tamatsukuri, Chuo-ku, Osaka-shi, Osaka Prefecture Mita Industry Co., Ltd. (72) Toyonori Inoue 1-2-chome Takuma, Osaka-shi, Osaka No. 28 in Mita Industry Co., Ltd. (72) Inventor Takuya Kadota 1-2-2 Tamatsukuri, Chuo-ku, Osaka-shi, Osaka Mita Industry Co., Ltd.

Claims (1)

[Claims] 1. An upper part of a developer container containing a developer,
A replenishment toner storage hopper is continuously provided through a mesh through which toner particles can pass, and a magnet roller, which is evenly arranged on the circumferential surface so that a pair of NS magnetic poles are alternately arranged in the circumferential direction, is brought close to the mesh. A developing device for an image forming apparatus, wherein the developer container is rotatably arranged below the replenishment toner storage hopper, and a magnet or a magnetic material is arranged around the developer container.