JPS63208076A - Developing device - Google Patents

Abstract

PURPOSE:To improve the responsiveness in toner concn. detection so that development with high image quality is executed by setting the volume in a region part for detecting the toner concn. at the volume smaller than the volume in the other part within a developer housing part. CONSTITUTION:The voltage of a sensor 15 induced by the alternate electric field impressed to a developing sleeve is changed by the mixing ratio of the toner and magnetic particles of a developer 19 acting on the sensor, i.e., the toner concn. of the developer 19 to produce a sensor output. The sensor output is inputted as the information on the present toner concn. of the developer 19 to a control circuit. The detecting region part is formed to the volume smaller than the volume in the other part of the developing region so that the sensor 15 is quickly covered by a slight change in the volume of the developer 10. The replenishment of the toner-component at a proper ratio at a proper time and the quick and uniform dispersing and mixing of the replenishing toner- component in and with the developer over the entire part thereof based on the quickly detected value of the toner concn. at the current point of the time of the developer are thereby permitted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a developing device provided with a toner concentration detection means for detecting the toner concentration of a developer made of toner, magnetic particles, and the like.

(Prior art) In the case of a developing device that uses a developer consisting of toner and magnetic particles, only the toner is consumed during development, so if left as is, the toner concentration of the developer will gradually decrease. As a result, the density of the formed image decreases.

Therefore, this type of developing device has an f-stage that detects the developer toner concentration in the developer storage section, an f-stage that stirs and conveys the developer in the developer storage section, a replenishment toner storage section, and a replenishment toner storage section. The toner concentration detection stage detects the degree of decrease over time in the toner concentration of the developer in the developer storage section, and then
The detection information is input to the control circuit, and when the toner concentration decrease reaches a predetermined permissible lower limit, the above-mentioned replenishment toner replenishment conveyance -
The first stage is operated to introduce a portion of the replenishment toner into the developer storage section. The replenishment toner is quickly mixed and dispersed throughout the developer in the developer storage section by the developer agitation and conveyance f stage, and the toner concentration of the developer has increased to a predetermined value due to toner replenishment. When the C degree detection means detects this, the operation of the replenishment toner conveyance means is stopped, thereby controlling the toner concentration of the developer to a predetermined substantially constant value.

One of the requirements for reliable and highly accurate toner concentration control is the accuracy and reliability of the toner concentration detection means. The first stage of toner C degree detection is an optical detection method that uses the amount of reflected light from the developer.
Magnetic sensing method using magnetic permeability, electrical sensing method using dielectric constant.

Detection methods that utilize volume changes, density changes, etc., or complex detection methods that use a combination thereof, are known.

(Problem to be solved by the invention) However, in any case of the above detection method, for example, if the developer is not sufficiently stirred or mixed in the toner concentration detection section, or if there is a problem in the detection section. When there is not more than a certain amount of developer present, or when a large amount of developer accumulates and adheres to the detection part and the developer is not replaced quickly.

A problem arises in that the toner concentration control system malfunctions.

In particular, concentration detection methods that directly detect the physical property values (reflectance, dielectric constant, etc.) of the developer, for example, only the toner is used during development, so the volume of the developer is always set to a certain predetermined value. In volume detection methods that control toner replenishment, if the developer does not quickly decrease or increase in the detection unit in response to toner consumption and replenishment, the toner concentration control system may malfunction. It shows a state like that.

Therefore, when using the one-volume detection method, the configuration conditions of the detection section are a very important factor in order to improve the detection accuracy.

(9. Objective of the Invention) The present invention was devised in view of the above circumstances, and an object thereof is to provide a developing device that can improve the responsiveness of toner concentration detection and perform high-quality image development. shall be.

(15?! Akira no l!E required) In order to achieve such an object, the present invention provides a toner concentration detection area in which a toner concentration detection means for the developer is provided in a storage portion for the developer made of toner and magnetic particles. In a developing device having a toner concentration detection area, the volume of the toner concentration detection area is smaller than the volume of other parts in the developer storage area.

(Example) Embodiments of the present invention will be described in detail below based on the drawings.

In Figure 1, what is A? It is a drum-shaped or belt-shaped photoreceptor that serves as an IW image holder, and is driven to move in the direction of the arrow at a predetermined speed, and a latent image is formed by an image forming process device (not shown), which is then visualized by the developing device 21B. Developed as an image.

In the developing device B, l is a developing container.

The interior is divided by a partition wall 2 into a toner storage section 3 and a developer storage section 4 that stores a developer made of toner and magnetic particles. Toner storage i! The toner stored in the toner 13 and the developer in the developer storage section 4 are not shown in the figure. The toner stored in the toner storage section 3 is sequentially transported toward the partition wall 2 by rotationally driving the toner transport members 6+ and 6z, and is replenished into the developer storage section 4 from the toner replenishment port 16.

Reference numeral 7 denotes a developer carrying member disposed within the developer storage section 4, and is constituted by a developing sleeve 7 made of non-magnetic eI film with a built-in magnet roll 72.

The lower surface of the right side of the developing sleeve 7 is exposed to the outside through an opening provided in the developer storage section 4, and the developing device 71B is connected to the externally exposed surface of the developing sleeve 71 or to the latent image holder A.
It is positioned and held by the support member so as to face the surface with a predetermined small gap therebetween.

S1-S:1. N1 to Nff indicate the magnetized positions of the magnet roll 7. The magnet roll 72 is fixedly supported at both ends and does not rotate, and is driven to rotate around the outer developing sleeve 71 or the magnet roll 72 at a predetermined circumferential speed in the direction of the arrow.

8.9 in the developer storage section 4, the developing sleeve 7;
These are screw shafts serving as the developer agitation and conveyance stage F, which are disposed vertically in substantially parallel directions, and are each driven to rotate in the direction of the arrow. 17 is a developer circulation regulating member provided between the screw shafts 8.9 of the upper door.

10.14 is a developing sleeve 7 disposed at the upper and lower parts of the developer storage section 4, a developer circulation area designating member on the circumferential surface, and 11
．． 13 is disposed on the bottom side of the developer storage section 4 in order to prevent the stored developer from flowing and leaking toward the latent image holder A from the gap between the bottom surface of the developer storage section 4 and the lower surface of the developing sleeve 71. Magnetic member and magnet, 12 is a developing sleeve 71
In order to regulate the layer thickness of the developer formed on the circumferential surface of the developing sleeve 71, the developing sleeve 71 is disposed on the -L side with its lower side facing the upper surface of the developing sleeve with a predetermined small gap therebetween. It is a non-magnetic plate.

Reference numeral 15 denotes a sensor that detects a change in the volume of the developer in the developer storage section 4. The output of this sensor is inputted to a control circuit (not shown), and the toner conveying member 61. The rotational drive of 62 is controlled.

When the developing device 2i is in operation, the developing sleeve 71, screw shaft 8,
9 are rotated at predetermined speeds, and an alternating voltage is applied between the developing sleeve 71 and the latent image holder A by a bias power source S.

In this embodiment, the sensor 15 is connected to the developing sleeve 71.
The sensor's pressure induced by the seven-point alternating IPi electric field applied to the sensor changes depending on the mixing ratio of the toner and magnetic particles of the developer acting on the sensor (i.e., the toner concentration of the developer) and becomes the sensor output. About the composition.

The volume of the developer conveyed by the screw shaft 9 changes depending on the mixing ratio of toner and magnetic particles and covers the sensor 15, and the above-mentioned sensor voltage changes corresponding to the mixing ratio and becomes the sensor output. The sensor output is input to the control circuit as current toner concentration information of the developer.

Furthermore, in this embodiment, the volume of the detection area is smaller than the other part of the development area, as shown in FIG. It is formed to be.

That is, such a configuration is adopted in the case of a developing device that uses a developer containing toner and magnetic particles as a developer.
Since only the toner is consumed during development,
In order to always keep the toner concentration of the developer in the developer container at an appropriate level, it is necessary to quickly detect the current toner concentration of the developer, replenish the appropriate amount of toner at the right time based on that detection, and replenish the amount of developer to the replenishment toner. Quick and uniform dispersion mixing throughout is required.

In this case, in a detection method that utilizes a change in the volume of the developer, the movement of the developer in the detection section is a very important factor in terms of the responsiveness of the detection.

Therefore, as shown in FIGS. 1 and 3, the developer is transferred (A) using stirring/conveying screws 8 and 9.

In the case where the developer is conveyed in the (b) direction and circulated in the longitudinal direction of the developing sleeve 7.

At a certain predetermined amount of developer, the conveying portions of the screws 8 and 9 become equal, and the developer 19 becomes horizontal as shown in FIG. Therefore, in this state, toner replenishment [] (Fig. 1 16)
), the supplied toner falls onto the lower screw 9, which upsets the balance of the conveyance 14 of the upper and lower screws 8 and 9, and the increased volume is conveyed in the 517I (b) direction, causing the toner concentration detection sensor 15 to be detected. cover.

Therefore, by making the detection area narrower than other areas in the developer storage unit and reducing the volume of the detection area, the sensor 1 can be
5 is quickly covered, which affects the responsiveness of detecting a change in volume, that is, the responsiveness of detecting toner concentration.

In addition, the developer storage section 4 is moved downward by the screw shaft 8.9.
The developer inside the developing sleeve 71 is sufficiently stirred in the longitudinal direction of the developing sleeve 71, and a substantially uniform mixing ratio of toner and magnetic particles is obtained in the vicinity of the developing sleeve 7, and there is substantially no unevenness in each part of the developing sleeve 7 in the longitudinal direction. or be removed.

The screw shafts 8 and 9 rotate in the directions of the arrows, so that the developer in the developer storage section 4 is divided into the developer near the first screw shaft 8 and the developer near the lower screw shaft 9, respectively. 1 for the longitudinal direction of the screw shaft, for example, screw 8
The developer in the vicinity moves along the length of the screw shaft as indicated by the arrow in Figure 3 (
As shown in (a), the developer near the screw shaft 9 is moved in opposite directions from the front side to the back side of the developer storage section 4 in the direction of the arrow (b), and , 9, the screw blades 8+, 9+ of the upper and lower screw shafts 8.9 are set in opposite directions so that the screw blades 8+, 9+ of the upper and lower screw shafts 8.9 are transported while rotating around the shafts as the screw shafts 8.9 rotate.

Further, in this embodiment, the distance between the lower screw shaft 9 and the circulation regulating member 14 is arranged so as to become narrower toward the downstream side in the WI feeding direction. With this configuration, the developer conveying force becomes stronger as it goes downstream in the conveying direction of the lower screw 9.

The movement of the developer in the developer storage section 4 on the cross section of the developer storage section is caused by the rotation of the developing sleeve 7 and the screw shaft 8.
, 9, the magnetic field of the magnet roll 72, the presence of the developer circulation area designating member 10° 14, and the circulation regulating member 17,
Due to the frictional force between the developing sleeve 71 and the developer, the gravity of the developer, etc., a cyclic fi motion as shown by the white arrow in FIG. 1 occurs.

As a result, magnetic particles containing the developer, that is, toner, in the vicinity of the surface area of the developing sleeve 71 facing into the developer reservoir of the developer storage section 4 are transferred to the magnetic roll 72 inside the sleeve 7.
As the developing sleeve 71 rotates, it is adhered and held as a magnetic brush adsorption layer by the magnetic force of the developing sleeve 71, and is transported to the non-magnetic blade 12 position, and in the process of passing through the non-magnetic plate 12 position, the layer thickness is regulated, and the toner-containing particles are The magnetic particles pass through the developing section a (the facing portion of the latent image holder A and the developing sleeve 7, near the magnetic pole N2) in the form of a thin layer of static magnetic particles.

In the process of passing through the developing section a, the developing sleeve 7
The toner of the developer layer on the I side moves and adheres to the A side of the latent image carrier in accordance with the latent image pattern, and toner development of the latent image on the surface of the Wf image carrier is sequentially performed.

The developer layer on the side of the developing sleeve 71 that has been subjected to development and has passed through the developing section a is transferred into the developer storage section 4 by the subsequent rotation of the developing sleeve 7, and is deposited in the magnetic pole S2. N.

Due to the magnetic field, the developer is held in the sleeve 71 and transported back to mix with the developer in the developer storage section 4 .

As the toner in the developer in the developer storage section 4 is consumed to develop the latent image, the mixing ratio with magnetic particles decreases over time.The degree of this decrease is detected by the sensor 15 and the detection information is obtained. is input to a control circuit (not shown), and when the degree of decrease reaches a predetermined allowable lower limit, the signal causes the toner storage unit 3 to
The toner supplying member 61.6□ inside is rotated, whereby the toner in the toner storage section 3 is sequentially introduced and replenished into the developer storage section 4 from the toner supply [ ] 16.

The replenished toner is taken into the developer in the developer storage unit 4 as shown below and is mixed uniformly and quickly throughout the developer.This toner replenishment causes the developer in the developer storage unit 4 to When the sensor 15 detects that the volume of the toner replenishing member 6. ．． 6. rotational drive is stopped. As a result, the mixing ratio of the toner to the magnetic particles of the developer in the developer storage section 4 is always kept approximately constant, resulting in stable high-quality images. I can do many things.

That is, the toner supplied from the toner replenishment 1116 into the developer storage section 4 is moved into the existing developer by the screw shaft 9 on the F side in the direction (B) along the axis [stirring and stirring while rotating by L]. It is transported and mixed and dispersed. Then, the developer moves through the developing sleeves 7, h, is circulated or regulated between the circulation regulating member 17 and the magnetic pole S1, and after developing the latent image holder A is returned to the developer storage section 4 and transported. sleeve 7
, "-, and the developer moved and rotationally conveyed by the screw shaft 8 in the direction (a) along the shaft, and are mixed and stirred, and some of the developer moves in the direction of the screw shaft 9. A part is the developer circulation area designation member l on the 1- side.

The liquid flows through the plate toward the non-magnetic plate 12, where the layer thickness is regulated, and is held on the developing sleeve 7I and conveyed to the developing section a, where it is used for developing a latent image. The developer transported in the direction of the screw shaft 8 is transported in the axial direction of the screw shaft 8 in the opposite direction to the screw shaft 9, with some of the developer being transported toward the sleeve and some of it toward the screw shaft 9. Ru. Screw shaft 8
When the sleeve 7I moves in the axial direction, the developer on the surface of the sleeve 7I is made almost uniform in the axial direction.

The developer circulation regulating member 17 has a magnetic pole S on the sleeve 71 side.
In addition to regulating the circulation and conveyance of the developer near z, it also plays the role of a guide plate for the screw shaft 8 or 9, and also stabilizes the stirring and conveyance of the developer. ing. Further, there is a gap between the sleeve 71 and the developing container 1 on the opposite side thereof, which functions to guide a portion of the developer circulated and conveyed by the screw shaft 8 toward the screw shaft 9.

When the magnetic member 18 is provided at the tip of the developer circulation regulating member 17 on the side of the sleeve 71, a magnetic field is generated between the regulating member 17 and the magnetic pole S, which improves the circulation of the developer on the sleeve 71 near the magnetic pole S1. It can be strongly regulated. Furthermore, the magnetic member 1
8 may be a magnet, or the developer circulation regulating member 1
It is also possible to configure 7 itself from a magnetic material. When using a magnet, the magnetic pole is S, and if the magnet is of different polarity, the regulation of developer circulation is strengthened.If the magnet is of the same polarity, the circulation is improved, and the developer in the sleeve 71L and the developer in the developer storage section 4 are It was observed that learning ability improved.

As the sensor 15, in addition to the developer volume sensing method used in the apparatus of this embodiment, a piezoelectric element, an inductance change sensing element f., an antenna method using an alternating bias, or the like may be used.

Incidentally, in the embodiment described above, the rotational directions of the screw shafts 8 and 9 and the developing sleeve 71 as the developer stirring/conveying means are not limited to those in the embodiment.

Further, the stirring/conveying means 8 and 9 are not limited to screw shafts, but may also be rotary blades, and the number of magnetic poles and the magnetic pole axis of the magnet roll 7□ are not limited to those in the embodiments.

(Effect of 94 Light) As described above, according to the present invention, after narrowing the volume of the toner concentration detection area in the developer storage section, the sensor is quickly covered by the increase in minute volume. As a result, the responsiveness of toner concentration detection has improved, and it has become possible to consistently perform stable high-quality image development.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a developing device according to an embodiment of the present invention, FIG. 2 is a schematic sectional view of a toner concentration detection area, and FIG. 3 is a schematic explanatory view showing the direction in which developer is conveyed by upper and lower screw shafts.
FIGS. 4 and 5 are schematic cross-sectional views illustrating the movement of the developer in the toner concentration detection area as the volume of the developer changes. 8・9...-screw shaft, 15-...sensor, 19...
・Developer.

Claims (2)

[Claims] (1) In a developing device having a toner concentration detection area in which a toner concentration detection means for the developer is provided in a developer storage made of toner and magnetic particles, the volume of the toner concentration detection area is defined as the developer storage. A developing device characterized in that its volume is smaller than that of other parts within the unit. (2) Claim 1, wherein the toner concentration detection means is a sensor that detects a change in the volume of the developer.
Developing device described in Section 1.