JPH0619315A - Developing device - Google Patents

Abstract

PURPOSE:To keep toner concentration proper and restrain the scattering of toner, the coagulation of developer and the abrasion of a toner concentration sensor so as to keep image quality excellent by absorbing the dispersion of an initial developer filling amount, the fluctuation of a developer supply amount to a sensor or the fluctuation of the apparent density of developer caused by the effect of the diminishment of the developer by image forming and improving the controlling accuracy of the toner concentration in the developer. CONSTITUTION:Two-component developer X containing magnetic carrier is used and a toner concentration detecting sensor (AIDC sensor) 22 for detecting the toner concentration in the developer based on the change of the magnetic permeability of the developer X is arranged in a part of a carrying path for the developer X in this developing device, where the sensor 22 is supported by a coil spring 22a allowing the sensor to retreat in accordance with the pressure of the developer applied on the sensor 22 so that it can be returned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for visualizing an electrostatic latent image on an electrostatic latent image carrier in an electrophotographic image forming apparatus such as a copying machine or a printer. In particular, a two-component developer containing a magnetic carrier is used, and a toner concentration detection sensor for detecting the toner concentration in the developer based on a change in the magnetic permeability of the developer is arranged in a part of the developer conveyance path. Regarding the device.

[0002]

2. Description of the Related Art In a developing device using a two-component developer, the toner in the developer is consumed while the development is repeated. Therefore, a toner concentration detecting sensor for detecting the toner concentration in the developer is usually provided. Therefore, new toner is replenished so as to supplement the consumed toner based on the toner concentration information from the detection sensor.

Typical examples of the toner concentration detecting sensor are, for example, JP-A-49-81040 and JP-A-50.
There are so-called ATDC sensors disclosed in JP-A-99552, JP-A-52-123242 and JP-A-52-127241. These toner concentration detection sensors detect the toner concentration in the developer based on a change in the magnetic permeability of the developer containing a magnetic carrier, in other words, a change in the inductance of the sensor coil based on the change in the magnetic permeability. Is.

That is, when the toner concentration in the developer decreases, the magnetic carrier amount in the developer flowing into the sensor increases, the magnetic permeability of the developer increases, and when the toner concentration increases, conversely, It utilizes the fact that the amount of magnetic carrier in the developer flowing into the sensor decreases and the magnetic permeability decreases, so that a constant amount of developer is constantly supplied to the sensor, in other words, to the sensor. It is assumed that a developer with a constant bulk density is always supplied. If this is not done, even if the toner concentration is constant, the magnetic permeability will fluctuate, resulting in erroneous detection.

[0005]

However, in reality, the density of the developer supplied to the sensor is constant due to variations in the amount of the initial developer loaded, a decrease in the developer in image formation of copying and printing, and the like. Does not turn into For example, a developing device of the type shown in FIG. 6, namely, a bucket roller BR, a spiral roller SR adjacent to one side of the roller BR, and a developing sleeve DS adjacent to the other side of the roller BR.
And the magnet body MR in the sleeve DS, the developer is supplied to the developing sleeve DS while the developer is mixed and stirred in the bucket roller BR, and is held on the sleeve DS based on the magnetic force of the magnet body MR. While being conveyed to the developing area by rotation, the developer is conveyed to both ends of the bucket roller BR and flown into both ends of the spiral roller SR from the developing roller. The agent is conveyed to the central part of the roller by left and right spiral blades having different directions or similar blades SR1 and SR2, and an ATDC sensor provided in the central part by a scraping plate IB provided on the roller shaft of the central part. In the developing device that passes the developer onto the SN and causes it to flow into the bucket roller BR again, and conveys the developer in a figure eight shape as a whole, actually, There are variations in the amount of developer flowing from both sides to Irarurora SR central, therefore the sensor S
The developer bulk density on N varies.

As a result, even if the toner density is appropriate, the following problems of high toner density or low toner density occur. Amount of developer Bulk density of developer Apparent toner concentration Replenishment of toner Change in toner concentration High High Low ON High density Low Low High OFF Low density As a result of such high toner density, deterioration of image quality (fogging phenomenon, etc.) , Toner scattering, developer agglomeration (clogging state), abrasion of sensor SN surface (shortening of life), etc., resulting in low toner density, resulting in deterioration of image quality (image with poor density), etc. To do.

Therefore, the present invention uses a two-component developer containing a magnetic carrier, and detects the toner concentration in the developer based on a change in the magnetic permeability of the developer in a part of the developer conveying path. A developing device having a detection sensor, which absorbs a variation in the developer supply amount to the sensor or a variation in the bulk density thereof due to variations in the initial developer loading amount, the influence of the decrease in the developer due to image formation, and the like. The accuracy of controlling the toner concentration in the developer can be improved, and the toner concentration can be maintained at an appropriate level, resulting in problems such as toner scattering, developer aggregation, and toner concentration sensor wear. An object of the present invention is to provide a developing device capable of suppressing the above-mentioned problem and maintaining good image quality.

[0008]

The developing device of the present invention for solving the above-mentioned problems uses a two-component developer containing a magnetic carrier and is based on a change in the magnetic permeability of the developer in a part of the conveying path of the developer. And a toner concentration detecting sensor for detecting the toner concentration in the developer, the sensor being supported by an urging means that allows the sensor to retract so as to be able to return in accordance with the developer pressure applied thereto. Is characterized by.

As the urging means, there are various types such as a coil spring, a leaf spring, a sponge, an air spring, a combination thereof, or the like, which constantly applies a biasing force toward the center of the developer flowing into the toner concentration detection sensor so as to be able to retract. It is possible that

[0010]

According to the developing device of the present invention, when a large amount of developer flows into the toner concentration detecting sensor and the bulk density of the developer is high, the pressure exerted on the sensor by the developer increases, and conversely,
When the amount of the developer flowing onto the sensor is small and the bulk density of the developer is low, the pressure exerted on the sensor by the developer is reduced. Therefore, when the pressure is high, the sensor is While the pressure is low so as to absorb the pressure, the sensor is advanced by the biasing means when the pressure is low, and as a result, the bulk density of the developer flowing over the sensor is The toner density is made constant and the toner density is properly detected.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of the developing device A according to one embodiment, and FIG.
FIG. 3 is a cross-sectional view of a part of a toner concentration detecting section in the apparatus,
FIG. 3 is a schematic perspective view of the bucket roller, the developer conveying screw, the AIDC sensor and the like in the apparatus A.

The developing device A comprises a developer supplying section 1, a toner concentration detecting section 2, a developing section 3, a developer stirring section 4 and a toner replenishing section 5. The developer supply unit 1 is provided with a bucket roller 12, which is shown in the drawing as one of the left and right side plates 13, a bucket 14 and a bucket which are installed in parallel with each other at a predetermined interval between the side plates. It is provided with a transverse feed blade 15 arranged inside 14. This bucket roller is rotationally driven in the clockwise direction in the figure by a driving unit (not shown), scoops the two-component developer X containing toner and magnetic carrier with the bucket 14 and supplies it to the developing section 3, while the developing agent flowing into this roller is supplied. Side-feeding agent 1
The roller is moved toward the left and right ends by 5.

With the rotation of the bucket roller 12, a part of the developer X is supplied to the left and right ends of the toner concentration detecting portion 2 through a hole (not shown) of the partition wall W. It The toner concentration detecting unit 2 is provided in FIGS.
1, a developer conveying screw 21 is provided, and the screw 21 is rotated clockwise in FIG. 1 by a driving means (not shown) so that the developer supplied from the bucket roller 12 has different spiral directions. Part 21
R and 21L convey from the left and right end portions to the central portion 21a.
There is no conveying blade in the central portion, and a screw shaft 21S passes through, and a developer scraping plate 21B is projectingly provided on the shaft 21S. An ATDC sensor 22 that detects the toner concentration is provided below the shaft 21S. This central part 2
The developer X flowing into the 1a from the left and right is the scraping plate 21.
It is scraped up by B, passes over the detection surface 22b of the sensor 22, and is returned to the bucket roller 12 from the central hole W1 of the partition wall W. The sensor 22 is fitted in the developing device case K so as to be able to move up and down, and is supported by a coil spring 22a from below. This spring is a holder HL fixed to the case K.
Supported by. The sensor 22 is a spring 22a.
A biasing force is constantly applied to the screw shaft 21S by the urging force of. The sensor is raised by the spring 22a,
It is regulated by the sensor flange 22s coming into contact with the case step Ka.

A magnet sheet Mg1 extending in the width direction of the bucket roller 12 is provided on the upper end portion of the partition wall W on the toner concentration detecting portion 2 side.
Faces the outermost movement locus circle C of the bucket 14 of the roller 12 with a predetermined gap. The developing section 3 includes an upper developing section 31a and a lower developing section 31b below the upper developing section 31a. The upper developing section 31a includes a fixed magnet roll 32a and a developing sleeve 33a that rotates around it, and the lower developing section 31b includes a fixed magnet roll 32b and a developing sleeve 33b that rotates around it. These developing sleeves 33a and 33b are rotationally driven in the clockwise direction in the drawing by a driving means (not shown).

Note that the upper developing sleeve 33a faces the spike height regulating member 35, which is a developer regulating member. The developer stirring unit 4 is provided above the bucket roller 12 and at a position where the developer is collected from the spike height regulating member 35, and includes a casing member 41 and a stirring roller 45 housed in the casing member 41. The casing member 41 is entirely made of an iron material which is a magnetic material, one end 42 of which faces the spike height regulating member 35, and the opposite end 43 of which faces the bucket roller 12. The agitation roller 45 includes an agitation blade 44, and is rotationally driven in the clockwise direction in the drawing by a driving unit (not shown).

The end portion 43 of the casing member 41 is provided with a magnet sheet Mg2 extending in the width direction of the bucket roller 12, and this sheet Mg2 has a predetermined gap with respect to the outermost peripheral movement locus circle C of the bucket 14 of the bucket roller 12. Is facing you. A space on the bucket roller 12 between the sheet Mg2 and the magnet sheet Mg1 becomes a toner replenishment area TS. And
The sheet Mg1 exists at the entrance of the area, and the sheet Mg2 exists at the exit of the area.

The toner replenishing section 5 is provided with a toner reservoir chamber 53 arranged above the agitating roller 45 and a toner replenishing chamber 51 provided beside it, and a brush roller 54 is provided in the toner reservoir chamber 53 and the toner replenishing chamber 53 is provided. A toner transport member 52 is provided in the replenishment chamber 51. A toner replenishing port 55 is formed between the toner reservoir chamber 53 and the developer agitating section 4, and a perforated plate 56 such as a wire mesh is arranged at the replenishment port, and the brush roller 54 is the perforated plate. While touching 56,
It is rotationally driven in the clockwise direction in the drawing by a driving means (not shown). The toner conveying member 52 is rotationally driven in the counterclockwise direction in the figure by a driving unit (not shown).

The developing device described above is incorporated in an image forming apparatus such as a copying machine so that the developing sleeves 33a and 33b of the developing portion face the photoconductor drum PC with a predetermined developing gap. According to this developing device, the developer supply unit 1
The rotation of the bucket roller 12 causes the developer X to be supplied to the lower developing sleeve 33b in the developing unit 3,
The developer supplied in this manner is held on the sleeve based on the magnetic force of the magnet roll 32b, is conveyed as the sleeve rotates, and comes to a position facing the upper developing sleeve 33a. Here, based on the magnetic forces of the lower magnet roll 32b and the upper magnet roll 32a, it moves onto the upper developing sleeve 33a and reaches the spike height regulating member 35 with the rotation of the sleeve, where the conveyance amount is regulated, The developer that has passed through the member 35 reaches the first developing area 34a as the upper sleeve 33a rotates, and develops the electrostatic latent image on the photosensitive drum PC here. The developer that has passed through the developing area 34a is passed from the upper sleeve 33a onto the lower sleeve 33b, and reaches the second developing area 34b with the rotation of the sleeve 33b, where the electrostatic latent image is surely re-established. After the development, the excess developer is conveyed to the developer supply unit side with the rotation of the sleeve, separated from the sleeve 33b at the separation magnetic pole N5 of the magnet roll 32b, and the developer supply unit 1
Flow into.

On the other hand, a part of the developer X which is moved by the rotation of the bucket roller 12 is supplied to both ends of the screw 21 in the toner concentration detecting section 2 and is moved from here to the central part thereof as the screw 21 rotates. Then, the toner concentration detection sensor 22 is being scraped by the scraping plate 21B.
After the toner density is detected by passing over the detection surface 22b, the toner flows into the developer supply unit 1 again.

At this time, when the amount of developer flowing into the toner concentration detecting sensor 22 is large and the developer bulk density is high,
The pressure exerted by the developer on the sensor 22 increases, and conversely, when the amount of the developer flowing onto the sensor 22 is small and the bulk density of the developer is low, the pressure exerted by the developer on the sensor 22 decreases. According to the fluctuation of the developer pressure, when the pressure is high, the sensor 22 is lowered and retracted against the spring 22a so as to absorb this pressure, and when the pressure is low, the sensor 22 is moved by the spring 22a. As a result, the bulk density of the developer flowing upward on the sensor 22 as a whole is made constant, and the toner concentration is properly detected.

Therefore, the accuracy of toner density control based on the toner density information from the sensor 22 is improved,
The toner density can be maintained appropriately, and as a result, toner scattering due to high density, developer aggregation, wear of the toner density sensor, etc. can be suppressed, and deterioration of image quality due to high density or low density can be suppressed. it can. Here, a developer having a toner concentration of 6% is used, and the detection surface 22b of the sensor 22 has a spring 2
The distance α (see FIG. 2) between the surface 22b and the lower surface of the screw shaft 21S when placed at the upper limit by 2a is set to about 3 mm, and the thickness β of the developer flowing into the screw central portion 21a (see FIG. 2) is set. ) Was changed in the range of 4 to 6 mm, the detected toner concentration was substantially constant regardless of the change of the inflow developer thickness β as shown by the line I in FIG. For comparison, when the distance α was fixed to about 3 mm, the detected toner concentration fluctuated greatly as shown by line II in FIG.

The developer X ₁ blocked from being conveyed by the spike height regulating member 35 is the casing member 4 of the developer stirring section 4.
From the end 42 of No. 1 into the casing member,
It is agitated by the rotation of the agitating roller 45 in the member and drops onto the bucket roller 12 from the casing member end portion 43 side. The toner replenishing section 5 is operated so as to replenish a required amount of toner according to the toner concentration detected by the toner concentration detecting sensor 22. The toner replenishment unit 5 replenishes the new toner by supplying the toner supplied to the toner reservoir chamber 53 by the rotation of the toner conveying member 52 in the toner replenishment chamber 51 to the porous plate 56 and the toner replenishment by the rotation of the brush roller 54 of the chamber 53. It is supplied into the developer stirring section 4 through the port 55.

The new toner supplied to the developer agitating section flows into the developer X ₁ by the rotation of the agitating roller 45.
The bucket roller 12 of the developer supply unit 1 is mixed and stirred with
It is dropped and supplied. In the series of operations described above, the developer X mixed and agitated in the roller by the rotation of the bucket roller 12 is rotated by the roller bucket 1 along with the rotation of the roller.
4 is conveyed while forming a developer layer so that the developer layer is scooped backward from the top of the bucket according to the rotation speed of the roller 12 and the magnet sheet Mg1 at the entrance of the toner replenishment area TS and The developer layer formed on the outer circumference of the bucket roller regulates the thickness of the developer layer to a thin one by the formed developer ears and reaches the toner replenishment area TS.

Therefore, the outer peripheral portion of the bucket roller that has reached the toner replenishment area TS has no developer layer between the buckets, or even if it is formed, it collapses immediately and falls into the roller 12. Therefore, in the toner supply area TS, the developer X ₁ containing new toner, which is supplied from the developer stirring unit 4 and drops onto the bucket roller 12, smoothly drops into the roller 12 from between the buckets, The developer there is sufficiently mixed and stirred, and the toner is sufficiently charged.

Bucket 1 arrives at toner supply area TS
Although the developer X has already been stored on the developer 4, a part of the developer X ₁ that has fallen from the developer agitator 4 is further piled up on it. Then, the bucket moves to the developing unit 3 in this piled state, and further, in the middle thereof, due to the action of the magnet sheet Mg2 and the developer ears formed thereon, all or part of the piled portion. Is scraped off, falls into the bucket roller 12, is mixed and agitated with the developer X there, and the toner is sufficiently charged. In this way, the developer regulated to an appropriate amount by the magnet sheet Mg2 is supplied to the developing unit 3 as described above, and is subjected to smooth development to form a high quality image.

Since the casing member 41 in the developer stirring section is made of a magnetic material, the magnetic forces of the upper and lower magnet rolls 32a and 32b in the developing section 3 may be blocked by this member 41 and reach the stirring section 4. Therefore, the developer X ₁ collected in the agitating section 4 after being prevented from being conveyed by the spike height regulating member 35 is agitated with good fluidity without being affected by magnetic force, and new toner is supplied from the toner replenishing section 5 here. When the toner is replenished to the toner, it is sufficiently mixed and stirred with the toner, so that the chargeability of the toner is stable in this respect as well.
After obtaining the expected toner charge amount, the toner flows into the developer supply unit and is used for development. As a result, the image quality of the image obtained by the image forming apparatus is improved, toner scattering is suppressed,
The reliability of the entire device is improved.

Next, another embodiment of the present invention will be described with reference to FIG. In the developing device shown in FIG. 5, the conveying screw 2
10 and the bucket roller 120 are arranged so as to separate the partition wall WB, and the conveying screw 210 is inclined upward from the front side where the toner supply port P is located to the rear side. Partition wall WB
Has a developer passage port H at a position slightly closer to the back side than the toner supply port P and a developer passage port H at the back side.

The developer already in the developing device and the toner replenished from the toner replenishing port P are conveyed by the conveying screw 2
By the rotation of 10 and the inclination of the screw,
Proceed to the back side while being stirred while receiving a slight return action,
It moves from the passage port H on the back side to the bucket roller 120 side, is conveyed in the opposite direction while being stirred by the rotation of the bucket roller, and circulates so as to shift from the passage port H on the front side to the screw 210 side. Then, the bucket roller 120
A part of the toner is supplied to the developing roller SL having a built-in magnet body during the conveyance by.

The developer supplied in this way is transferred to the roller S.
Along with the rotation of L, it is conveyed to a developing area facing the photoconductor drum while the conveyance amount is regulated by a brush height regulating plate (not shown), and is used for developing the electrostatic latent image. Screw 21
On the lower surface of 0, there is AI at a position slightly front side of the passage opening H on the back side.
The detection surface of the DC sensor 22 faces. This sensor 22
Like the sensor 22 in FIG. 1, the coil spring is supported by a coil spring (not shown) so that it can descend and return according to the pressure variation of the developer flowing into the sensor.

Therefore, also in this sensor 22, the toner concentration is properly detected in a state where the fluctuation of the bulk density of the inflowing developer is absorbed. It should be noted that the sensor 22 may be provided at a position nearer to the toner supply port P and slightly behind the developer passage port H.

[0031]

As described above, according to the present invention, a two-component developer containing a magnetic carrier is used, and a part of the developer carrying path is filled with a developer based on a change in magnetic permeability of the developer. A developing device provided with a toner concentration detection sensor for detecting toner concentration, wherein a variation in the amount of developer supplied to the sensor due to variations in the initial developer loading amount, a decrease in the developer due to image formation, or the like The accuracy of controlling the toner concentration in the developer can be improved by absorbing the fluctuation of the density, and the toner concentration can be maintained at an appropriate level accordingly, which in turn spreads the toner, agglomerates the developer, and the toner. It is possible to provide a developing device capable of suppressing the occurrence of problems such as wear of the density sensor and maintaining good image quality.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a part of a toner concentration detection unit in the developing device of FIG.

3 is a schematic perspective view of a bucket roller, a developer carrying screw, an AIDC sensor and the like in the developing device of FIG.

FIG. 4 is a graph showing a detected toner concentration with respect to a change in developer flow thickness flowing into an AIDC sensor.

FIG. 5 is a cross-sectional view of another embodiment of the present invention seen from above.

FIG. 6 is a cross-sectional view of the conventional example seen from above.

[Explanation of symbols]

 A, B Developing device X Two-component developer 12, 120 Bucket roller 21, 210 Developer conveying screw 22 AIDC sensor 22a Sensor support coil spring 22b Sensor detection surface

Claims (1)

[Claims] 1. A toner concentration detection sensor that uses a two-component developer containing a magnetic carrier and detects the toner concentration in the developer based on a change in the magnetic permeability of the developer in a part of the developer transport path. In the disposed developing device, the sensor is supported by an urging means that allows the sensor to retreat in accordance with the developer pressure applied thereto.