JPH05323794A - Developing device - Google Patents

Abstract

PURPOSE:To provide a developing device capable of preventing the mulfunction of a toner concentration sensor, on a developing device provided with the toner concentration sensor. CONSTITUTION:The developing device is provided with, at least, a developing roller 20, carrying/stirring means (spiral screws) 24 and 25 stirring and electrostatically charging a two-component developer 28, and supplying it to the developing roller 20, a container 29 which houses the developer 28, the developing roller 20, and the carrying/stirring means 24 and 25, and whose bottom part is in a shape so as to be along the outer peripheries of the carrying/stirring means 24 and 25, and the toner concentration sensor 31 fitted into the hole 29b of the container 29 under the carrying/stirring means 24 and 25. The toner concentration sensor 31 is attached so as not to lower the end surface 32 of the sensor 31 than the bottom surface 29c of the container 29.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device equipped with a toner density sensor.

Some electrophotographic devices such as electrophotographic printers and copying machines use a developing device using a two-component developer. This developing device is equipped with a toner density sensor that detects the toner density, and when the toner density detected by the sensor is below a predetermined value, the toner is replenished to keep the print density constant.

[0003]

2. Description of the Related Art FIG. 4 is an overall schematic view of a conventional electrophotographic apparatus, in which 1 is a photosensitive drum (electrostatic latent image forming medium) and 8 is a paper accommodating portion. Around the photosensitive drum 1, a charging device 2, an exposing device 3, a developing device 4, a transfer device 5, a discharging lamp 6 and a cleaner 7 are arranged. The recording paper 100 is accumulated and stored in the paper storage unit 8, and recording on the recording paper 100 is performed by the following means.

In recording, the photosensitive drum 1 is rotated in the direction of the arrow, and the surface of the photosensitive drum 1 is entirely negatively charged by corona discharge of the charger 2. Next, when light according to a predetermined pattern is applied from the exposure device 3 to this surface, the charge of the exposed portion is reduced and an electrostatic latent image is formed. When this latent image area passes through the developing device 4, negatively charged toner adheres to it and a toner image is formed.

On the other hand, the recording paper 100 in the accommodating portion 8 is supplied one by one to the position where it comes into contact with the toner image on the photosensitive drum by the action of the pick roller 9 and the standby roller 10. The transfer device 5 is arranged below the photosensitive drum 1 with the recording paper sandwiched therebetween, and is configured to give a positive charge to the recording paper 100. Therefore, the toner image formed on the photosensitive drum 1 is attracted to the positive charge of the recording paper 100 and transferred onto it.

The recording paper 100 carrying the toner image is sandwiched between the heat roller 12 which constitutes the fixing device 11 and the rubber roller 13 which is pressed and rotated by the heat roller 12, and the toner image is recorded on the recording paper 100 by heat and pressure. It is fixed. After that, the recording paper 100 is discharged to the outside by the discharge roller 14. Further, the surface of the photosensitive drum 1 after the transfer is completely destaticized by the destaticizing lamp 6, the residual toner is cleaned by the cleaner 7, the initial state is restored, and the above cycle is repeated again. Although the negative charging process is described in the above description, the positive charging process is the same.

The developing device 4 is Japanese Patent Application No. 3-292729 (filed on November 8, 1991) proposed by the present applicant.
The structure is as shown in FIG. 5A is a plan view, and FIG. 5B is A in FIG.
-A sectional view, in the figure, 20 is a developing roller, 23 is a doctor blade, 24 and 25 are spiral screws as a conveying and stirring means, 26 is a collecting roller, 27 is a collecting blade, 2
Reference numeral 8 is a developer. Each of these members is housed in the container 29.

The developing roller 20 comprises a sleeve 21 for carrying the developer 28, and magnet groups 22a, 22b, 22c, 22d and 22e contained in the sleeve 21. The developer 28 is a mixture of a carrier, which is magnetic powder, and a resinous toner. The doctor blade 23 is for forming a developer layer having a constant thickness on the developing roller 20, and the collecting roller 26 is for collecting the developer accumulated around the developing roller 20 and the doctor blade 23. Reference numeral 27 is for collecting the residual developer on the developing roller 20.

A spiral screw 2 which is a conveying and stirring means.
Reference numerals 4 and 25 are provided with right-handed screw-shaped spiral blades, and the developer 28 is fed in the direction of the arrow in FIG.
Developing roller 20 while circulatingly moving (parallel to the axial direction of
The toner is charged by agitating the carrier and the toner. A partition plate 38 separates the spiral screws 24 and 25.

The general flow of the developer 28 is as follows. The developer 28 is stirred by the spiral screw 25 and moves to the spiral screw 24 on the developing roller 20 side. The moved developer 28 is supplied to the developing roller 20 side as the spiral screw 24 rotates. Then, it is attracted by the magnets 22c and 22d of the developing roller 20 and adheres onto the sleeve 21. The developer 28 on the developing roller 20 is
By the rotation of the sleeve 21, the sleeve 21 is moved to a developing portion (a position where the developing roller 20 faces the photosensitive drum) and is provided for development.

The developer remaining on the developing roller 20 after the development is peeled off from the developing roller 20 by the collecting blade 27 and returned to the spiral screw 24. Further, the developer 28 not adhered to the sleeve 21 is collected by the collecting roller 2
It is returned to the spiral type screw 24 by 6.

Thus, the developer 28 used for the development
Is, for example, a toner concentration of 5.5% made up of a ferrite carrier having a particle diameter of 60 μm and a resin toner having a particle diameter of 11 μm.
However, when tired, the chargeability of the toner becomes unstable due to the effect of toner filming on the carrier, and the toner charge amount changes. Then, a print failure such as a change in image density (decrease in print density, increase in fog, etc.) occurs. Therefore, it is necessary to replace the developer 28 that has been used for a certain period (e.g., used for 20,000 sheets).

An automatic replenishment and recovery mechanism of the developer for enabling the exchange of the developer will be described with reference to FIG. 1 in the figure
Reference numeral 01 is a developer replenishing chamber, 102 is a waste developer collecting chamber, and these are cartridged together with the shutters 103 and 104 to form a replenishing and collecting mechanism. Developer supply room 101
Is divided into a toner portion 101a for storing toner and a carrier portion 101b for storing a carrier. Replenishing rollers 105 are provided at the exits of the toner portion 101a and the carrier portion 101b, respectively.

When replenishing the carrier, the shutter 103 is moved leftward from the position shown in FIG. 6 by a predetermined amount by a drive system (not shown). Thereby, the hole 103 of the shutter 103
a is opposed to the opening 106 of the carrier portion 101b, and the carrier in the carrier portion 101b is supplied into the container 29 through the hole 103a and the hole 30a of the container cover 30.

When replenishing the toner, the shutter 103 is moved to the right from the position shown in FIG. 6 by a predetermined amount. As a result, the hole 103b of the shutter 103 is closed in the toner portion 101.
The toner in the toner portion 101 a faces the opening 107 of the a and is supplied into the container 29. In either case of replenishment, the replenishment roller 105 is driven to rotate to assist the replenishment. Note that the shutter 104 is closed as shown in the drawing when supplying these.

At the time of collecting the waste developer, the shutter 104 is moved to the right from the illustrated position by a predetermined amount and the spiral screws 24 and 25 are rotated. As a result, the waste developer in the container 29 is removed from the hole 29 a at the bottom of the container 29 and the shutter 104.
It is collected in the developer collecting chamber 102 through the hole 104a.
At the time of automatic replacement of the developer, the developer in the container 29 is removed, and then a new developer is replenished. The replenished carrier and toner are mixed and charged by rotating the spiral screws 24 and 25, and are conveyed.

Incidentally, in order to keep the toner concentration of the developer in the container 29 at a predetermined value, the rotation of the replenishing roller 105 is
It is controlled by the output of the toner concentration sensor 31 (see FIG. 5B). The toner concentration sensor 31 has a spiral screw 24, which is a good toner flow location in the apparatus, so as not to cause erroneous detection of toner concentration and cause printing defects when toner or the like is accumulated in the developing apparatus. It is located below.

The container 29 of the developing device 4 having the above-described structure and operation has a bottom shape along the outer circumference of the spiral screws 24 and 25. With such a bottom shape, the gap between the spiral screws 24 and 25 and the bottom of the container 37 becomes uniform and small, and the residual amount of the developer in the container at the time of replacing the developer becomes small. Therefore, even if a new developer is replaced, printing defects such as fogging and density change can be eliminated.

The toner concentration sensor 3 for the container 29
1 mounting structure is shown in FIG. FIG. 7A is a perspective view of the toner concentration sensor 31, and FIG. 7B is a side view showing details of the toner concentration sensor 31 mounting portion. As is apparent from FIG. 7B, the toner concentration sensor 31 includes the spiral screw 24.
Is attached to the container 29 underneath (where the flow of the developer is good), and the sensor portion 31a thereof is fitted into the hole 29b of the container 29.

[0020]

However, in the conventional toner concentration sensor mounting structure, the end surface 32 of the sensor portion 31a is prevented from coming into contact with the spiral screw 24 as shown in FIG.
As shown in (B), it is lower than the bottom surface 29c of the container 29. As a result, toner or the like stays between the end surface 32 and the hole 29b, causing the sensor to malfunction and causing printing failure.

An object of the present invention is to provide a developing device capable of preventing malfunction of the toner density sensor.

[0022]

To achieve the above object, in the present invention, a developing roller and a two-component developer are circulated and moved to be supplied to the developing roller and rotated to stir the developer. And a container for accommodating the developer, the developing roller, and the conveying and agitating means, and having a bottom shape along the outer periphery of the conveying and agitating means; In a developing device having at least a toner concentration sensor attached by fitting a sensor portion into a hole of a container, the toner concentration sensor is attached so that an end face of the sensor portion does not fall below the bottom surface of the container. (1st structure) characterized by this.

Further, in the developing device having the above-mentioned first structure, the outer periphery of the portion of the conveying and stirring means facing the sensor portion of the toner concentration sensor is notched so that the end face of the sensor portion does not hit. The configuration (second configuration).

[0024]

Since the end surface of the sensor portion of the toner concentration sensor does not fall below the bottom surface of the container, the accumulation of toner and the like, which has been a problem in the past, is eliminated. Therefore, it is possible to prevent malfunction of the sensor and eliminate the cause of defective printing. Further, in the case of the second configuration, the distance between the transport stirring member and the inner wall of the container does not need to be changed from the conventional one.

[0025]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 is a side view showing the details of the toner concentration sensor mounting portion of this embodiment. As is apparent from this figure, in the present invention, the toner concentration sensor 31 is provided with the end surface 3 of the sensor portion 31a.
2 is attached so that it does not go down below the bottom surface 29c of the container 29. That is, the toner concentration sensor 31 has the end surface 3
2 is attached so as to coincide with or project from the upper end of the peripheral wall of the hole 29b. This eliminates the retention of toner and the like near the end surface 32, which has been a problem in the past.

Further, in this example, as shown in detail in FIG. 2, the outer periphery of the portion of the spiral screw 24 facing the toner concentration sensor 31 is cut out. 33 is a notch part. This is the same as the toner concentration sensor 31 as described above.
This is to prevent the spiral screw 24 and the end surface 32 of the toner concentration sensor 31 from interfering with each other even if the mounting position is higher than in the conventional case.
There is no need to change the distance between the inside of the container and the inner surface of the container. FIG. 3 is a side view of the developing device of the present invention having the toner concentration sensor mounting structure. The configuration of the electrophotographic apparatus to which this developing device is applied is the same as that shown in FIG.

In the above description, an example in which a spiral screw is used as the conveying and stirring means has been described, but the present invention is also applicable to the case where a shaft having a plurality of stirring blades is attached instead of the spiral screw. It is possible.

[0029]

As described above, according to the present invention, since the toner concentration sensor is attached so that the end surface of the sensor portion does not go down below the bottom surface of the container, there is a problem in the vicinity of the end surface of the sensor portion, which has been a problem in the past. There is no retention of toner, etc. Therefore, it is possible to prevent the malfunction of the sensor and prevent the occurrence of defective printing.

Further, the outer periphery of the portion of the conveying / stirring means facing the toner concentration sensor is cut out so that the end surface of the toner concentration sensor does not hit, so that the distance between the conveying / stirring means and the inner surface of the container is changed as compared with the conventional case. You don't have to.

[Brief description of drawings]

FIG. 1 is a side view showing details of a toner concentration sensor mounting portion according to an exemplary embodiment of the present invention.

FIG. 2 is a perspective view showing a shape of a spiral screw according to an embodiment of the present invention.

FIG. 3 is a side view of the developing device according to the embodiment of the present invention.

FIG. 4 is an overall configuration diagram of a conventional electrophotographic apparatus.

5A and 5B are structural explanatory views of a conventional developing device, FIG. 4A is a plan view, and FIG. 4B is a cross-sectional view taken along line AA of FIG. 4A.

FIG. 6 is an explanatory diagram of a developer replenishing and collecting mechanism.

7A and 7B are explanatory views of a conventional toner concentration sensor mounting structure, FIG. 7A is a perspective view of the toner concentration sensor, and FIG. 7B is a side view showing details of a toner concentration sensor mounting portion.

[Explanation of symbols]

 20 developing roller 24, 25 spiral screw (conveying and stirring means) 28 developer 29 container 29b hole 29c bottom surface 31 toner concentration sensor 31a sensor portion 32 end surface 33 notch portion

Claims (2)

[Claims] 1. A developing roller, a conveying and stirring means for circulatingly moving a two-component developer to supply it to the developing roller, and rotating the developer to charge the toner to charge the toner. A container that accommodates a roller and a conveying and stirring means, and has a bottom shape along the outer circumference of the conveying and stirring screw; and a toner attached by fitting a sensor unit into a hole of the container under the conveying and stirring means. A developing device comprising at least a concentration sensor, wherein the toner concentration sensor is attached so that an end surface of the sensor portion does not fall below a bottom surface of the container. 2. The developing device according to claim 1, wherein an outer circumference of a portion of the toner concentration sensor of the conveying and stirring means facing the sensor portion is cut out so that an end face of the sensor portion does not hit.