JPH0611968A - Toner concentration detecting method and device thereof - Google Patents

Abstract

PURPOSE:To provide a toner concentration detecting method and device thereof of a developing device to use two-component developer consisting of toner and carrier, by which stagnation of toner due to the rugged surface or electrostatic adsorption is eliminated so as to maintain favorable fluidity, and the toner concentration is detected stably and correctly. CONSTITUTION:A surface containing the detecting face 22a of a concentration sensor 22 and in the vicinity thereof is polished so as to be in the surface roughness in a range from 0.1 to 1.0 micrometer, coated with a protecting member 23 made of zirconia ceramics of thin plate having thickness of 0.1-0.2mm, a gap G between the surface of the protecting member 23 and the outer circumferential face of a paddle 13 is maintained at a decided size, and toner concentration is detected by passing the toner through the gap G.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner concentration detecting method and apparatus for a developing device using a two-component developer composed of toner and carrier.

In the electrophotographic process, the toner concentration of the two-component developer has a great influence on the print quality (image quality), so it is necessary to detect the toner concentration as accurately as possible and stably for a long period of time. .

[0003]

2. Description of the Related Art Conventionally, as a method for detecting the toner density in a developing device, there is one disclosed in Japanese Patent Application Laid-Open No. 3-239275. This is because the concentration sensor is inserted and attached from the outside to the inside of the container wall at a location where the developer always flows in the developing device, and the magnetic permeability of the developer passing on the detection surface of the concentration sensor is measured. Thus, the toner density is detected.

In such a toner concentration detecting method, the concentration sensor forms a magnetic circuit by a coil, and changes in the magnetic permeability of the developer passing through the magnetic circuit are converted into an electric signal and detected. Therefore, if a magnetic substance or a conductor is present in the magnetic circuit, accurate detection cannot be performed, so that a synthetic resin or the like is exclusively used as a member for supporting the concentration sensor.

Further, in the example described in the above-mentioned publication, in order to maintain good fluidity of the developer, a polyester film or mylar sheet is attached to a region including the detection surface of the density sensor and its peripheral portion. Coated to reduce friction with the developer.

[0006]

However, even the above-mentioned conventional detection method has a problem that the toner stays on the surface of the polyester film or mylar sheet due to long-term use and the fluidity of the developer is lowered. It was

As a result of detailed observation and consideration of the flow state of the developer on the surfaces of various films and materials, the present inventor has found that factors that have a great influence on the flowability are the frictional resistance of the surface and the state of surface irregularities. , And the charge amount.

That is, since the conventional polyester film or mylar sheet attached on the detection surface has a rough surface and is a thin film, the unevenness of the surface of the support plate (container wall) supporting the concentration sensor is obtained. Was discharged as it was, and the surface was further roughened, and the developer was likely to stay in the uneven portions on the surface of the film.

Further, in the polyester film and the mylar sheet, static electricity is apt to be generated due to friction with the developer, and the retention of the toner is apt to occur due to adsorption of the generated static electricity.

Therefore, the accumulated toner is fused and gradually becomes a large lump, which deteriorates the fluidity of the developer on the detection surface, lowers the detection accuracy, and sometimes an abnormal value is detected. Was reached.

The present invention provides a toner concentration detecting method and apparatus capable of eliminating toner stagnation due to surface irregularities and electrostatic attraction, maintaining good fluidity, and stably and accurately detecting toner concentration. It is intended to be provided.

[0012]

In order to solve the above-mentioned problems, the method according to the invention of claim 1 is, as shown in FIGS. 2 and 4, a paddle for stirring toner provided in a developing device 1. Concentration sensor 2 arranged so as to face the outer peripheral surface of 13
A method for detecting the toner density according to 2,
The surface of the density sensor 22 including the detection surface 22a in the vicinity thereof is covered with a thin plate-shaped protective member 23 made of ceramics having a surface roughness smaller than the particle diameter of the toner, and the surface of the protective member 23 and the paddle 13 are covered. The toner density is detected by keeping the gap G from the outer peripheral surface of the device at a predetermined size and passing the toner through the gap G.

The device 15, 15a according to the invention of claim 2
Are sensor support members 21, 21a having sensor fitting holes 31, 41a, 42a, and the sensor fitting holes 31, 41.
a, 42a to be fitted into the sensor support members 21, 21a
A density sensor 22 integrally provided with the sensor 22 having a detection surface 22a at its tip for detecting the toner density, and the sensor support members 21, 2 in the vicinity thereof including the detection surface 22a.
1a is provided integrally with the sensor support member so as to cover the surface thereof, and has a thin plate-like protective member 23 made of ceramics whose surface roughness is smaller than the particle diameter of the toner. .

The sensor support member 21a of the device 15a according to the third aspect of the present invention includes a support substrate 41 and the support substrate 41.
And an elastic cushioning support member 42 attached to the protection member 23. The protection member 23 is attached to the surface of the cushioning support member 42 with a gap G between the protection member 23 and the detection surface 22a of the concentration sensor 22. It is composed.

In the devices 15 and 15a according to the invention of claim 4, the protective member 23 is made of zirconia ceramics.
In the devices 15 and 15a according to the fifth aspect of the present invention, the thickness of the protective member 23 is 0.1 to 0.2 mm.

In the devices 15 and 15a according to the sixth aspect of the present invention, the protective member 23 is polished so that the surface roughness is in the range of 0.1 to 1.0 micrometer.

[0017]

Since the protective member 23 is made of ceramics whose surface roughness is smaller than the particle diameter of the toner, the toner does not stay on the surface of the protective member 23 and the developer flows extremely well. Ceramics have a very small amount of charge, static electricity due to friction with the developer is hard to be generated, and the static electricity generated is quickly neutralized because it is a high resistance conductor, so electrostatic attraction of toner does not occur, and therefore The retention of toner due to this does not occur. Since it has rigidity, even if the surface roughness of the surface of the sensor support member 21 is bad, it is not affected by it and the surface state finished with high accuracy can be maintained.

Further, since the developer is passed through the gap G held to a predetermined size to detect the toner concentration, the detection can be accurately performed.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view of a main part of a developing device 1 according to the present invention, FIG. 2 is an enlarged view of a density detecting device 15 shown in FIG.
FIG. 3 is a view of the concentration detecting device 15 shown in FIG.

In FIG. 1, the developing device 1 includes a container wall 11,
It comprises a mag roll 12, which is provided in a developing device surrounded by a container wall 11, a paddle 13 for stirring toner, and a density detection device 15 which is fitted in a cutout part of the container wall 11.

Referring to FIGS. 2 and 3, the concentration detecting device 1
5 includes a sensor support member 21, a concentration sensor 22, and a protection member 23. The sensor support member 21 is formed of a synthetic resin material into a substantially rectangular plate shape, and has a circular sensor fitting hole 31 and a sensor mounting recess 32.

The concentration sensor 22 has a circular detection surface 22a at its tip, and in a state where the detection surface 22a is fitted in the sensor fitting hole 31 described above, it is integrated with the sensor support member 21 by a screw (not shown). It is installed.

The protective member 23 is in the form of a rectangular thin plate, and is attached to the surface of the sensor support member 21 with an adhesive or the like so as to cover the detection surface 22a of the concentration sensor 22 and its peripheral portion. .

The protective member 23 is made of zirconia ceramics (for example, Z-201N manufactured by Kyocera Corp.). Zirconia ceramics is formed into a thin rectangular plate having a plate thickness of 0.1 to 0.2 mm, more preferably 0.15 to 0.2 mm by molding or cutting, and has a surface roughness of 0.1 to 1 by polishing. It is polished to a mirror surface of 0.0 μm, more preferably 0.1 to 0.2 μm.

The thickness of the zirconia ceramics is 0.1 to
The reason why the thickness is 0.2 mm is that if it is less than that, the strength becomes weak and it is easily cracked, and if it is more than that, the detection surface 22a is separated from the developer, and the detection sensitivity is significantly lowered.

The surface roughness of the zirconia ceramics is set within the above range because the particle diameter of the toner generally used is about 2 to 15 μm so that the toner does not enter the irregularities on the surface of the zirconia ceramics. In order to do so, it is necessary to make the surface roughness sufficiently smaller than the particle size of the toner.

Zirconia ceramics (Zr
An example of the characteristics of O ₂ ) is a specific gravity of 5.5 to 6, Vickers hardness (load of 500 g) of 1250 to 1350 kg /
mm ² , bending strength 10,000 to 20,000 kg / c
m ² , dielectric strength 1.0 kv / mm, volume resistivity (20
C.) 2.2 × 10 ¹² Ω · cm.

The concentration detecting device 15 is arranged so that the detecting surface 22a of the concentration sensor 22 faces the outer peripheral surface of the paddle 13, and is fixed to the container wall 11 with a screw. Gap between the surface of the protective member 23 and the paddle 13
The size of G is set to a constant reference value (for example, 0.35 mm) within the range of 0.2 to 2.0 mm.

The concentration detecting device 15 constructed as described above
In the above, since the surface roughness of the protective member 23 is sufficiently smaller than the particle diameter of the toner, the toner does not stay on the surface irregularities, and the developer flows extremely well.

Further, zirconia ceramics has a very small charge amount, static electricity due to friction with the developer is hard to be generated, and since it is a high resistance conductor, the static electricity generated is quickly neutralized, so that the electrostatic charge of the toner is reduced. Adsorption does not occur, and therefore, retention of toner due to this does not occur.

The zirconia ceramics have a dense surface with a surface roughness of the raw material of 1 to 2 μm. However, when polishing is performed, the pressure causes the particles on the surface to be crushed and a gap between the particles to be formed. It disappears or becomes small, the surface can be mirror-finished, the strength and impact resistance are high, and the fracture from the boundary of particles unlike sapphire or alumina hardly occurs.

Further, since the zirconia ceramics has rigidity, even if the surface roughness of the surface of the sensor supporting member 21 is bad, the zirconia ceramics is not affected by the roughness and the surface state finished with high precision can be maintained. it can.

Therefore, the developer passing through the gap G flows well without stagnation, there is no problem such as deterioration of detection accuracy due to stagnation and detection of abnormal value, and the toner concentration is stable and accurate over a long period of time. Can be detected.

The present inventor selects zirconia ceramics as the material of the protective member 23 until the zirconia ceramics are selected.
The protective member 23 was manufactured by using various other materials and tested, which will be described.

The materials tested were plastics, plastics coated with Teflon (trade name) in a film form, carbon coatings, glass coatings, glass fiber-containing materials, sapphire ceramics, alumina ceramics,
Selected from zirconia ceramics.

[Frictional resistance] (1) The film-shaped one has a large frictional resistance because irregularities on the surface of the base thereof appear. (2) The glass-coated product was peeled off in a few hours due to friction with the developer. (3) Therefore, the coated material is unsuitable in terms of friction, and as a conclusion, it must be a single material with rigidity.

[Amount of Charge] (1) Static electricity is generated by friction, and the result of measurement of the amount of charge is as follows.

Plastic 10 kv carbon film 2.0 to 3.0 kv glass coat, glass fiber 1.0 kv ceramics 0.1 kv Therefore, plastic is unsuitable, and ceramics are most preferable. (2) The material charged by the above (1) was held so that the surface thereof had an inclination of 45 degrees, and the toner was dropped onto the surface from above to observe the fluidity on the surface. As a result, toner adhesion occurred on the carbon film.
With ceramics, the toner did not adhere and slipped down.

[Surface Roughness] (1) With respect to sapphire ceramics, alumina ceramics, and zirconia ceramics, the results of observing the distance (hole diameter) between particles on the surface are as follows.

Sapphire ceramics 5-10 μm Alumina ceramics 5-10 μm Zirconia ceramics 1-2 μm Zirconia ceramics are the most dense.

[Strength] (1) The results of measuring impact resistance of sapphire ceramics, alumina ceramics, and zirconia ceramics are as follows.

Sapphire ceramics 5 kg Alumina ceramics 5 kg Zirconia ceramics 15 kg or more Since zirconia ceramics have the highest impact resistance and the instantaneous impact force of the developer is about 2 to 5 kg, only zirconia ceramics are suitable.

From the above results, the protective member 23 made of zirconia ceramics as shown in the above-mentioned embodiment was used. Next, another embodiment of the concentration detecting device will be described.

FIG. 4 is a sectional view of a concentration detecting device 15a according to another embodiment of the present invention. The constituent elements having the same functions as those of the concentration detecting device 15 described above are designated by the same reference numerals to simplify or omit the description.

The concentration detecting device 15a includes the sensor support member 2
1a, a density sensor 22, and a protection member 23. The sensor support member 21a is made of a synthetic resin or the like, and has a recess 41
It is composed of a support substrate 41 having b, and a cushioning support member 42 fitted and mounted in the recess 41b.

The buffer support member 42 is made of, for example, an elastic material such as silicone rubber or urethane rubber, and elastically bends due to the pressing force of the protective member 23, and restores to its original state when the pressing force disappears.

The protection member 23 is attached to the surface of the buffer support member 42. Further, the density sensor 22 is
A space is provided between the detection surface 22 a and the protection member 23, which are fitted into the sensor fitting holes 41 a and 42 a provided in the support substrate 41 and the buffer support member 42.

Therefore, according to the density detecting device 15a, when a toner lump or a foreign substance mixed in the developer enters the gap G, the pressure at that portion rises. Since the buffer support member 42 is pushed, the cushioning support member 42 is bent, so that the toner mass and the like pass through the gap G. After the toner lumps and the like have passed through the gap G, the buffer support member 42 returns to its original state, and the protective member 23 also returns to its original position.

Therefore, toner particles and the like are protected by the protective member 23.
Alternatively, since the surfaces of the paddles 13 are not attached to the paddles 13 and the surfaces thereof are prevented from being scraped off by an abnormal pressure, the gap G is kept constant, and the toner concentration is accurately and stably detected.

In the above-mentioned embodiment, the protective member 23 has a rectangular shape of 60 mm square, but its size and shape can be variously changed. In addition, the sensor support member 21,
The shape, size, material and the like of the concentration sensor 22, the support substrate 41, and the buffer support member 42 can be variously changed in accordance with the gist of the present invention.

[0051]

According to the present invention, it is possible to prevent the toner from staying due to surface irregularities and electrostatic attraction, maintain good fluidity, and stably and accurately detect the toner concentration.

According to the third aspect of the present invention, even when a lump of toner or the like enters the gap, it is prevented from adhering to the surface of the protective member or the paddle or scraping the surface.
According to the invention of claim 4, it is easy to make the surface of the protective member 23 sufficiently denser than the particle diameter of the toner, and the mechanical strength is large.

According to the fifth aspect of the present invention, the strength necessary for the protective member can be obtained, and the influence on the detection sensitivity of the density sensor is small, and the density sensor generally used can perform accurate detection.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a developing device according to the present invention.

FIG. 2 is an enlarged view of the concentration detection device shown in FIG.

FIG. 3 is a view on arrow III of the concentration detection device shown in FIG.

FIG. 4 is a cross-sectional view of a concentration detector according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Developer 13 Paddle 15,15a Density detection device 21,21a Sensor support member 22 Density sensor 22a Detection surface 23 Protective member 31,41a, 42a Sensor insertion hole 41 Support substrate 42 Buffer support member G Gap (gap)

Claims (6)

[Claims] 1. A method for detecting toner density by a density sensor (22) arranged so as to face an outer peripheral surface of a paddle (13) for stirring toner provided in a developing device (1). Then, the surface in the vicinity of the density sensor (22) including the detection surface (22a) is covered with a thin plate-like protective member (23) made of ceramics having a surface roughness smaller than the particle diameter of the toner, The toner density is detected by keeping a gap (G) between the surface of the member (23) and the outer peripheral surface of the paddle (13) at a predetermined size and allowing the toner to pass through the gap (G). Toner density detection method. 2. A toner density detecting device (15) (15a) arranged so as to face an outer peripheral surface of a paddle (13) for agitating toner provided in a developing device (1), the sensor fitting Sensor support members (21) (21a) having holes (31) (41a) (42a), and the sensor support members (21) (21a) fitted into the sensor fitting holes (31) (41a) (42a). ) And a detection surface (22) for detecting the toner concentration.
a) a concentration sensor (22) having a tip portion and a sensor support member (21) (21a) including the detection surface (22a) and its vicinity so as to cover the surface of the sensor support member integrally with the sensor support member. And a thin plate-shaped protective member (23) made of ceramics, the surface roughness of which is smaller than the particle diameter of the toner. 3. The sensor support member (21a) comprises a support substrate (41) and an elastic buffer support member (42) attached to the support substrate (41), and the protection member (23). Is attached to the surface of the buffer support member (42) with a gap (G) between it and the detection surface (22a) of the concentration sensor (22). The toner concentration detection device described. 4. The protective member (23) is made of zirconia ceramics, as claimed in claim 2 or 3.
The toner concentration detection device described. 5. The protective member (23) has a thickness of 0.1 to 0.1.
The toner density detecting device according to claim 4, wherein the toner density detecting device has a diameter of 0.2 mm. 6. The protective member (23) has a surface roughness of 0.
The toner concentration detecting device according to claim 4 or 5, wherein the toner concentration detecting device is polished to a range of 1 to 1.0 μm.