JPS6358467A - Image forming device - Google Patents

Abstract

PURPOSE:To manage toner concentration with high reliability and to obtain a stably formed image having high picture quality by increasing the efficiency of agitation of a developer in the downstream side of the direction of carrying the developer. CONSTITUTION:Toner replenished from a toner replenishing port 16 into a developer container 4 is agitated and carried by a screw shaft 9 in the lower side while moving it in axial direction and mixed and dispersed in existing developer. In such a case, a developer circulation area designating member 14 is formed to make it gradually higher toward the downstream direction of a screw shaft to enhance the efficiency of agitation of the developer and also to prevent the sudden carrying of developer of high toner concentration, and to make the toner concentration of developer in the direction of the screw shaft 9 uniform in the vicinity of a developer carrier 7. The developer agitated and mixed sufficiently moves on a developing sleeve 71, and the circulation is controlled between a circulation control member 17 and a magnetic pole S3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus such as an electrophotographic copying apparatus and an electrostatic recording apparatus used for various purposes, and in particular to an image forming apparatus in which toner and magnetic particles (carrier) are mixed. A latent image holding member is formed by carrying the developer contained in the latent image holding member. ! ! The present invention relates to an image forming apparatus equipped with a developing device for developing an image.

Beauty. Generally, a developing device included in an image forming device such as an electrophotographic copying device or an electrostatic recording device used for various purposes uses a two-component developer having a mixture of toner and magnetic particles (carrier). However, in terms of development characteristics, the mixing ratio of toner and carrier (toner concentration) is an extremely important factor in stabilizing image quality. Therefore, in order to obtain good image quality, it is necessary to accurately detect the toner concentration in the developer used and consumed, strictly control the amount of toner replenishment according to the change, and to (developer concentration) must be kept constant.

In other words, in order to always keep the toner concentration of the developer at an appropriate level regardless of toner consumption, it is necessary to quickly detect the current toner concentration of the developer, replenish the amount of toner in a timely and quantitative manner based on the detected value, and develop the amount of replenished toner. It is necessary to quickly and uniformly disperse and mix the entire developer and to transport the developer quickly to the toner concentration detection section.

Therefore, this type of developing device has a developer storage section and a replenishment toner storage section, and further includes a means for detecting the toner concentration of the developer in the developer storage section, and a means for stirring and transporting the developer in the developer storage section. and means for conveying the toner in the replenishment toner storage section to the developer storage section. With the configuration of refusing, the toner concentration detection means detects the degree of decrease in the toner concentration of the developer in the developer storage portion over time, inputs the detection information to the control circuit, and determines that the toner concentration decrease has reached a predetermined allowable lower limit. At this time, the replenishment toner conveying means is operated to introduce a portion of the toner in the replenishment toner storage section 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 conveyance means, and the toner concentration detection means detects that the toner concentration of the developer has increased to a predetermined value due to toner replenishment. When detected, the operation of the replenishment toner conveying means is stopped. In this way, the toner concentration of the developer is automatically managed and controlled to a predetermined substantially constant value.

In a developing device having such a configuration, one of the requirements for performing reliable and highly accurate toner concentration management control is to improve the accuracy and reliability of the toner concentration detection means, and also to increase the accuracy and reliability of the toner concentration detection means. It is important that the toner is quickly dispersed and mixed into the developer. For example,
When the developer in an unstirred and dispersed state is conveyed onto the developer carrying member, a phenomenon of fogging occurs on the image on the latent image holder and the final copy, and as a result, toner concentration management becomes difficult. A situation occurs where the control system malfunctions.

To explain further, 1. According to research experiments conducted by the present inventors, the toner replenished into the developer storage section is moved along the developer transport direction by a stirring/transporting means, and is dispersed and mixed in the developer. However, even when toner is replenished uniformly in a certain area from the upstream side to the downstream side with respect to the developer transport direction, the toner is not sufficiently dispersed and mixed into the developer. In reality, the toner concentration increases toward the downstream side in the developer transport direction, resulting in surplus toner, and unstirred and mixed developer may be transported to the developer carrying member. I found out that 0
The present invention is based on this new knowledge.

An object of the present invention is to improve the toner concentration management control system by increasing the agitation efficiency of the developer on the downstream side in the developer transport direction, and to provide an image forming apparatus that can form a high-quality developed image. It is to be.

The above object is achieved by an image forming apparatus according to the present invention.

To summarize, the present invention provides an image forming apparatus that develops a latent image formed on a latent image carrier using a developing device containing a two-component developer containing a mixture of toner and carrier to form a visible image. In this, the developing device includes a developer supporting member that carries the developer and develops the latent image on the surface of the latent image carrier;
a means for stirring and transporting the developer; and a developer circulation device disposed between the developer carrying member and the developer stirring and transporting means to regulate the amount of developer circulating and transported by the developer stirring and transporting means. and an area designation member.

A preferred embodiment of the present invention is an image forming apparatus, characterized in that the developer circulation area designating member is formed so that a developer transport regulating effect is greater on the downstream side in the developer transport direction than on the upstream side. According to the above, the developer stirring/conveying means has an upper agitating/conveying means and a lower agitating/conveying means located above and below the developer carrying member, and the developer circulation area designating member is arranged between the developer carrying member and the lower agitating/conveying means. It is arranged between the transport means and the transport means.

An embodiment of an image forming apparatus according to the present invention will be described below with reference to the drawings.

FIG. 4 shows an embodiment of an image forming apparatus according to the present invention.0 If the image forming apparatus is an electrophotographic copying apparatus, it is an electrophotographic photoreceptor (or a dielectric material, etc. in an electrostatic recording apparatus). The drum-shaped latent image holder A is driven to rotate around a shaft 100 in the direction of the arrow at a predetermined circumferential speed. Around the latent image carrier A, a latent image forming device section C1 forms a latent image on the peripheral surface of the latent image carrier A, a developing device B develops the latent image on the latent image carrier A, and a developing device B develops the latent image on the latent image carrier A. A transfer device ID that transfers the developed image onto the transfer material P is arranged. The transfer material P to which the developed image has been transferred by the transfer device HD is sequentially peeled off from the latent image holding member A and introduced into the fixing device HE, and after the image is fixed, it is discharged outside the machine as an image-formed product. After the image transfer, the surface of the latent image holding member A is cleaned with a cleaner F, and is repeatedly used for image formation.

Referring to FIG. 1, one embodiment of development device B is illustrated in detail. Developing equipment! B has a developer container 1, and inside the developer container 1 is provided with a partition wall 2 and a replenishment toner storage section 3, and a developer that stores a two-component developer mainly consisting of a mixture of toner and magnetic particles (carrier). It is divided into a storage section 4. The toner stored in the toner storage part 3 and the developer in the developer storage part 4 are omitted in FIG. The stored toner in the toner storage section 3 is transferred to the toner conveying member 6. ．． By rotationally driving the toner 6z, the toner is sequentially conveyed in the direction of the partition wall 2, and is replenished into the developer accommodating portion 4 from the toner replenishing port 16.

Further, a developer carrying member 7 is disposed within the developer storage section 4 of the developing device 1, and the developer carrying member 7 includes a magnet roll 71 and a developing sleeve made of a non-magnetic material and containing the magnet roll 71. 71. S, ~S,
, N, -N3 indicate the magnetized positions of the magnet roll 72. The magnet roll 71 is fixedly supported at both ends and does not rotate, and the outer developing sleeve 71 is driven to rotate around the magnet roll 72 at a predetermined circumferential speed in the direction of the arrow.

According to this embodiment, the lower left surface of the developing sleeve 71 in FIG. They are arranged opposite to the A side with a predetermined gap therebetween.

In this embodiment, a developer stirring/conveying means is provided in the developer storage section 4 to supply the developer to the developer holding member 7 and to uniformly mix and stir the developer in the developer storage section 4. , the developer mixing/stirring means includes upper and lower developer stirring/conveying means 9 disposed substantially parallel to the developing sleeve 7I and vertically relative to the developing sleeve 7I.
．． 10 is provided. Usually, the developer stirring/conveying means is a screw shaft, which is rotated in the direction of the arrow. Further, a developer circulation regulating member 17, which will be described later, is disposed between the upper and lower agitating/conveying means 8.9.

The upper and lower parts of the developer storage section 4 and the developing sleeve 7
A developing sleeve 71 is provided between I and the developer stirring and conveying means.
A circulation area designation member 10.14 is provided to define a circulation area for developer on the circumferential surface, and the circulation area designation member 14
The stored developer flows and leaks toward the latent image holder A from the gap between the bottom surface of the developer storage section 4 and the bottom surface of the development sleeve 7I in the lower part of the developer storage section 4 extending from the developer container opening to the developer container opening. The magnetic member 11 and the magnet 13 are used to prevent
is provided. Furthermore, a developing sleeve 7I is provided in the upper portion of the developer storage section 4 extending from the other circulation area designating member 10 to the developer container opening in order to regulate the layer thickness of the developer formed on the circumferential surface of the developing sleeve 7I. A non-magnetic blade 12 is provided with a predetermined clearance from the upper surface of the blade.

The concentration of the developer in the developer storage section 4 (toner and magnetic particles A sensor 15 is arranged to detect the mixing ratio. Of course, the sensor can also be provided at other locations. The output of the sensor is input to a control circuit (not shown), and the toner conveying member 61 in the toner storage section 3 is controlled accordingly.
．． The rotational drive of 82 is controlled.

When the developing device is in operation, the developing sleeve 7I and the developer stirring/conveying means, that is, the screw shaft 8.9, are each rotated at a predetermined speed in the direction of the arrow in FIG. An alternating voltage is applied by a bias power supply S.

Due to the rotation of the screw shaft 8.9, the developer in the developer storage section 4 is sufficiently stirred in the direction of the developing sleeve 7I, and a substantially uniform toner to carrier mixing ratio is obtained near the developing sleeve 7I. The density unevenness in the long direction of the developing sleeve 71 is removed.

The screw shafts 8 and 9 rotate in the directions of the arrows, but the developer in the developer storage section 4 is separated from the developer near the upper screw shaft 8 and the developer near the lower screw shaft 9. The twist directions of the screw blades of the upper and lower screw shafts 8 and 9 are set to be opposite to each other so that the screw blades of the upper and lower screw shafts 8 and 9 are conveyed in opposite directions to the longitudinal direction of the screw shafts.

Furthermore, in this embodiment, the developer conveying force in the longitudinal direction of each of the upper screw shaft 8 and the lower screw shaft 9 is such that the lower screw shaft 9 is relatively larger. The length and interval of the screw blades of both screw shafts 8 and 9 are set so that the screw shaft 9 is larger than that of the screw shaft 8.

According to the developing device configured as described above, 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 7I, the rotation of the screw shafts 8 and 9, and the rotation of the magnet roll 71. Magnetic field, developer circulation designated member 1
0.14, developer circulation regulating member 17, developing sleeve 71
Due to the frictional force between the developer and the developer, the gravity of the developer, etc., a circular flow motion as shown by the white arrow in FIG. 1 occurs.

Therefore, the area in view of the developing sleeve 71 facing the developer reservoir of the developer storage section 4, that is, the area surrounded by the developing sleeve 7I and both the developer agitating and transporting means 8 and 9, has an area in the vicinity thereof. A carrier containing developer, that is, toner, is adhered and held as a magnetic brush adsorption layer by the magnetic force of the magnet roll 7 in the sleeve 7I, and is conveyed to the non-magnetic blade 12 position as the developing sleeve 71 rotates, and is transferred to the non-magnetic blade 12 position. In the process of passing through, the layer thickness is regulated, and the magnetic particles become a thin layer of a small amount of magnetic particles containing toner, and pass through the developing section a (the facing part of the Ml image carrier A and the developing sleeve 71, near the magnetic pole N).

During the process of passing through the developing section a, the developing sleeve 71 is
The toner in the developer layer on the side moves and adheres to the side A of the latent image carrier in accordance with the latent image pattern, and the toner development of the latent image on the side A of the latent 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 held in the developer storage section 4 by the rotation of the developing sleeve 71 and on the surface of the sleeve 7i by the magnetic field of the magnetic poles Sz, N. The developer is transported back to the developer storage section 4.
It mixes with the developer inside.

As the toner in the developer in the developer storage section 4 is consumed to develop the latent image, the mixing ratio with the carrier decreases over time, and the degree of the decrease is detected by the sensor 15.
The detection information is input to a control circuit (not shown), and when the degree of decrease reaches a predetermined allowable lower limit, the signal is sent to the toner supply member 6 in the toner storage section 3. ．． 6z rotates, whereby the toner in the toner storage section 3 is sequentially introduced and replenished into the developer storage section 4 through the toner supply port 16.

The replenished toner is taken into the developer in the developer storage section 4 and mixed evenly and quickly throughout the developer. As a result of such toner replenishment, the toner mixture ratio of the developer in the developer storage section 4 increased to a predetermined allowable increase value.
When detected by the toner supply member 61, 62
rotational drive is stopped. In this way, the mixing ratio of the toner to the magnetic particles of the developer in the developer storage section 4 is always kept substantially constant, and a stable high-quality image can always be obtained.

To explain further, in this embodiment, the toner supplied from the toner supply port 16 into the developer storage section 4 is stirred and conveyed while moving in the axial direction by the lower screw shaft 9, and is mixed into the existing developer. distributed. At this time, the toner supplied from the toner supply port 16 is uniformly replenished in the axial direction of the screw shaft 9.
Toner is accumulated and the amount of toner increases as it goes to the left in the direction of the arrow in the figure. Therefore, according to the present invention, the developer circulation area designating member 14 is formed to be gradually higher in the downstream direction of the screw shaft 9 as shown in FIG. While gradually increasing the stirring efficiency, the developer with high toner concentration is prevented from being rapidly transported toward the developer carrying member 7, and the developer in the axial direction of the screw shaft 9 is prevented from being transported near the developer carrying member 7. The toner density is made uniform.

In this way, the sufficiently agitated and mixed developer moves on the developing sleeve 7I, and is transferred to the circulation regulating member 17 and the magnetic pole S3.
Circulation is regulated between In other words, the sleeve 71 that has been returned to the developer storage section 4 after being developed on the WI image carrier.
The upper developer joins with the developer conveyed by the screw shaft 8 and is mixed and stirred, some of which moves toward the screw shaft 8, and some of which moves toward the upper developer circulation area designation member l.
The liquid flows through O to the non-magnetic blade 12 side and is held on the developing sleeve 7I, where the layer thickness is regulated, 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. When the sleeve 7 is moved in the axial direction by the screw shaft 8
The developer on one surface is almost uniformly distributed in the axial direction.

The developer circulation regulating member 17 regulates the circulation and conveyance of the developer near the magnetic pole S3 on the sleeve 71 side, and also serves as a guide plate for the screw shaft 8 or 9.
It also contributes to stabilizing developer stirring and transport. Further, there is a gap between the sleeve 71 and the developing container 1 on the opposite side thereof, which also serves to guide a portion of the developer circulated and conveyed by the screw shaft 8 toward the screw shaft 9.

The developer circulation regulating member 17 has a tip on the sleeve 7I side,
When the magnetic member 18 is provided as shown in FIG. 1, a magnetic field is generated between the magnetic member 18 and the magnetic pole S3, thereby making it possible to more strongly restrict the circulation of the developer on the sleeve 71 near the magnetic pole S3. The magnetic member 18 may be a magnet, or the developer circulation regulating member 17 itself may be made of a magnetic material.According to research experiments conducted by the present inventors, when a magnet is used, When the magnet 18 has a different polarity from the magnetic pole S3, the regulation of developer circulation is strengthened, and when the magnet 18 has the same polarity, the circulation improves, and the exchange of the developer on the sleeve 7I and the developer in the developer storage section 4 is improved. It was observed that it improved.

In this embodiment, the above-mentioned toner concentration detection sensor 15
In this configuration, a sensor voltage induced by an alternating electric field applied to the developing sleeve 71 changes depending on the mixture ratio of toner and carrier in the developer acting on the sensor (i.e., the toner concentration of the developer), and becomes the sensor output. It was taken as the property of Therefore, the volume of the developer conveyed by the screw shaft 9 changes due to mixing with the toner and carrier and covers the sensor 15, and the sensor voltage changes corresponding to the mixing, resulting in a sensor output, and the developer is input to the control circuit as current toner density information. When detecting toner concentration, rapid conveyance of developer to the detection part is a necessary condition, but in addition,
In the case of volume detection, it is desirable that the volume at the detection part changes greatly in response to changes in toner concentration.In the present invention, as shown in FIG. A sensor 15 is provided at the most downstream part, and the circulation area designation member 14 is gradually raised in the downstream direction.
By surrounding the sensor 15 in the toner concentration detection section and configuring the detection section so that the volume of the detection section is narrow, the sensor 15 will be covered by the developer even if the volume increases by a minute amount, making the response of the sensor extremely fast. Can be done.

As the sensor 15, a piezoelectric element, an inductance change detection element, or an antenna system using an alternating bias electric field can be used.

In the above embodiment, the developer circulation area specifying member 14 is configured to be gradually raised in the downstream direction of the screw shaft 9, but as shown in FIG. A shaped member 19 may be arranged, and the mesh member 19 may be formed so that the mesh size of the mesh member becomes finer so that the wasteful regulating effect becomes stronger toward the downstream side.

Release "LΩ" 1! In the image forming apparatus of the present invention configured as described above, toner concentration management control can be performed reliably and with high precision by increasing the agitation efficiency of the developer on the downstream side in the developer transport direction by the developer agitation/transport means. This method has the effect that stable, high-quality image formations can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of a developing device used in an image forming apparatus according to the present invention. FIG. 2 is a front view of the developer area specifying member seen from the developing sleeve side of FIG. 1. FIG. 3 is a front view of another embodiment of the developer area specifying member as seen from the developing sleeve side, similar to FIG. 2. FIG. 4 is a schematic diagram of an embodiment of an image forming apparatus according to the present invention. 7: Developer carrying member 8.9: Developer stirring/conveying member IO: Upper developer circulation area designation member 14: Lower developer circulation area designation member 17: Developer circulation regulation member

Claims (1)

[Claims] 1) Image formation in which a latent image formed on a latent image carrier is developed to form a visible image using a developing device containing a two-component developer containing a mixture of toner and carrier. In the apparatus, the developing device includes a developer carrying member that carries the developer and develops the latent image on the surface of the latent image carrier, a means for stirring and transporting the developer, and the developer carrying member and the developer. Stirring/
and a developer circulation area designation member disposed between the developer agitation and the amount of developer circulation conveyed by the conveyance means, the developer circulation area designation member being arranged in a direction in which the developer is conveyed. An image forming apparatus characterized in that the image forming apparatus is formed so that the effect of regulating developer transport is greater on the downstream side than on the upstream side. 2) The developer stirring/conveying means has an upper stirring/conveying means and a lower stirring/conveying means located above and below the developer carrying member, and the developer circulation area designating member has a developer carrying member and a lower stirring/conveying means.
The apparatus according to claim 1, which is arranged between the apparatus and the conveying means.