JP6980599B2 - Airflow classifier - Google Patents

Description

The present invention relates to an air flow classifier that classifies powder raw materials into at least two classes. The present invention also relates to a so-called airflow classification machine, which divides a powder raw material into only two types, fine powder and coarse powder.

Conventionally, the airflow classifiers shown in Patent Document 1 and Patent Document 2 are known. These conventional airflow classifiers have a Coanda block 28 and a raw material supply nozzle 12 as shown in FIG. 7B of the present application. A side surface 28b is formed on the upper surface 28a of the Coanda block 28 with a step. The raw material supply nozzle 12 has a lower side surface 12a and a nozzle inner bottom surface 12b. A nozzle opening 12c is provided at the tip of the raw material supply nozzle 12. The powder raw material is emitted from the nozzle opening 12c into the classification region.

In this conventional air flow classifier, the tip E of the Coanda block 28 is a curved surface. Further, the lower side wall of the raw material supply nozzle 12 is housed in the stepped side surface 28b. As a result, the tip of the inner bottom surface 12b of the nozzle, that is, the bottom surface 12d of the nozzle opening 12c was adjusted to the same height as the surface 28a of the Coanda block 28. Conventionally, when the bottom surface 12d of the nozzle opening 12c and the surface 28a of the Coanda block 28 are on the same surface, the Coanda effect generated at the tip E of the Coanda block 28 can be effectively utilized. It was considered advantageous.

However, according to the experiment of the present inventor, it is found that if the bottom surface 12d of the nozzle opening 12c and the surface 28a of the Coanda block 28 are continuous and the same surface, the classification accuracy may not necessarily be high. It came to. In order to clarify the cause of this, the present inventor conducted many experiments. As a result of the experiment, when the bottom surface 12d of the nozzle opening 12c and the surface 28a of the Coanda block 28 are on the same surface, the powder flow ejected from the nozzle opening 12c of the raw material supply nozzle 12 swells immediately after the injection. Therefore, it repels at the surface 28a of the Coanda block 28 and swells upward, so that the powder flow is separated from the tip portion E of the coanda block 28, and therefore, the Coanda effect realized at the tip portion E can be obtained. We came to the conclusion that it would not be possible to receive it properly, and as a result, the classification effect would be reduced.

Japanese Unexamined Patent Publication No. 2004-230313 Japanese Unexamined Patent Publication No. 6-226208

The present invention has been made based on the above findings, and prevents turbulence in the powder flow in the vicinity of the nozzle opening of the raw material supply nozzle to improve the accuracy of classification based on the Coanda effect. The purpose is to do.

Another object of the present invention is to further improve the performance of the air flow classifier disclosed in Japanese Patent Application No. 2016-230922.

The airflow classifier according to the present invention is an airflow classifying machine that classifies powder raw materials into at least two classes, and includes a Coanda block and a raw material supply nozzle provided so as to realize a Coanda effect on the powder raw materials. It has at least one classification edge forming a powder transport path corresponding to at least two classes, and the bottom of the nozzle opening of the raw material supply nozzle is spaced apart from the surface of the Coanda block. A flow adjusting member is provided between the nozzle opening and the upper surface of the Coanda block.

In the conventional air flow classifier, for example, as shown in FIG. 7B, the bottom surface 12d of the nozzle opening 12c of the raw material supply nozzle 12 and the surface 28a of the Coanda block 28 are aligned on the same surface. In the case of this configuration, the airflow injected from the nozzle opening 12c swells immediately after the injection, the swelled airflow repels the surface 28a of the Coanda block 28, and the repulsed airflow moves away from the tip E of the Coanda block 28. As a result, the Coanda effect generated at the tip E of the Coanda block 8 could not be effectively utilized for the classification of fine powder.

On the other hand, in the present invention, for example, as shown in FIG. 5A, a gap Z1 is provided between the upper surface 8a of the Coanda block 8 and the bottom 12d of the nozzle opening 12c. Therefore, even if the airflow jetted from the nozzle opening 12c swells, the airflow does not repel on the surface 8a of the Coanda block 8. Therefore, the airflow forms a smooth airflow along the tip E of the Coanda block 8, for example, as shown in FIG. 7A, and as a result, a highly accurate classification effect can be obtained.

Further, if the flow adjusting member 14 is not provided in front of the nozzle opening 12c, a space is formed between the upper surface 8a of the tip portion E of the Coanda block 8 and the lower surface of the nozzle opening 12c, and the space is disturbed. Flow may occur. When this turbulence occurs, the classification accuracy may decrease, and the upper surface 8a of the Coanda block 8 may be significantly worn. On the other hand, if the flow adjusting member 14 is provided in the above space as in the present invention, the generation of turbulent flow can be prevented in the vicinity of the nozzle opening 12c, and as a result, high classification accuracy can be realized, and the Coanda block 8 can be achieved. Can prevent damage due to wear.

In the second aspect of the air flow classifier according to the present invention, the upper surface of the flow adjusting member is an inclined surface inclined with respect to the inner bottom surface of the nozzle of the raw material supply nozzle. According to the present invention, the generation of turbulent flow can be prevented more reliably.

In the third aspect of the air flow classifier according to the present invention, the upper end of the flow adjusting member on the nozzle opening side coincides with the bottom of the nozzle opening of the raw material supply nozzle. According to the present invention, the generation of turbulent flow can be prevented more reliably.

In the fourth aspect of the airflow classifier according to the present invention, the cross-sectional shape of the portion of the Coanda block that realizes the Coanda effect is an arc shape, and the bottom of the nozzle opening of the raw material supply nozzle starts the arc shape. It is arranged according to.

With this configuration, the airflow containing the powder raw material can be smoothly and smoothly sent to the portion of the Coanda block that realizes the Coanda effect, and as a result, the powder raw material can be classified with high accuracy.

Conventionally, the nozzle opening of the raw material supply nozzle is in the raw material supply direction from the point where the tip of the Coanda block on the upper surface of the Coanda block starts (that is, the point where the arc shape starts) (for example, the point indicated by reference numeral P1 in FIG. 4). It was arranged at a position of, for example, 10 mm toward the upstream side. On the other hand, in the fourth aspect of the present invention, the nozzle opening is arranged at the point where the tip of the Coanda block starts (for example, at the place of reference numeral P1 in FIG. 4). That is, the position of the nozzle opening is arranged at a position lowered by, for example, 10 mm toward the downstream side in the raw material supply direction as compared with the conventional configuration.

With this configuration, the airflow containing the powder raw material can be smoothly and smoothly sent to the part of the Coanda block that realizes the Coanda effect, and as a result, the powder raw material can be classified with high accuracy. Became.

In the fifth aspect of the airflow classifier according to the present invention, the distance between the bottom of the nozzle opening of the raw material supply nozzle and the surface of the Coanda block is the thickness of the wall member forming the raw material supply nozzle. It is formed by a nozzle. According to this configuration, the configuration of the present invention can be easily realized.

In the sixth aspect of the invention of the airflow classifier according to the present invention, the raw material supply direction defined by the raw material supply nozzle is inclined with respect to the horizontal direction when the powder transport path is arranged in the vertical direction. ..

According to this configuration, the powder raw material can be smoothly and reasonably fed to the portion of the Coanda block that realizes the Coanda effect (for example, the arc-shaped portion of the cross section at the tip of the Coanda block). As a result, fine powder can be classified with high accuracy from the powder raw material by effectively utilizing the Coanda effect.

In the present invention, for example, as shown in FIG. 5A, a gap is provided between the upper surface of the Coanda block and the bottom of the nozzle opening, so that even if the airflow jetted from the nozzle opening swells, The airflow does not repel the surface of the Coanda block. Therefore, the airflow forms a smooth airflow along the tip portion (E) of the Coanda block (8), for example, as shown in FIG. 7A, and as a result, a highly accurate classification effect can be obtained. ..

For example, in FIG. 5A, if the flow adjusting member 14 is not provided in front of the nozzle opening 12c, a space is formed between the upper surface 8a of the tip portion E of the Coanda block 8 and the lower surface of the nozzle opening 12c. , There is a risk of turbulence occurring in this space. When this turbulence occurs, the classification accuracy may decrease, and the upper surface 8a of the Coanda block 8 may be significantly worn. On the other hand, if the flow adjusting member 14 is provided in the above space as in the present invention, the generation of turbulent flow can be prevented in the vicinity of the nozzle opening 12c, and as a result, high classification accuracy can be realized, and the Coanda block 8 can be achieved. Can prevent damage due to wear.

It is a figure which shows one Embodiment of the airflow classifier which concerns on this invention. It is a perspective view which shows one Embodiment of the classification main body which is a main part of FIG. It is a front view of the classification main body of FIG. It is an enlarged view which shows the tip part of the Coanda block which is the main part of FIG. FIG. 3 is an enlarged view showing a tip portion of a raw material supply nozzle, which is a main portion of FIG. 3. It is a figure which shows the raw material transfer pipe which is the main part of the airflow classifier of FIG. It is a figure which shows the flow of the powder particle in the vicinity of a Coanda block, (a) is the thing of this invention, (b) is the conventional thing. (A) and (b) are sectional views showing an embodiment of a flow adjusting member, respectively. (A) and (b) are sectional views showing another embodiment of a flow adjusting member, respectively. (A) and (b) are sectional views showing still another embodiment of a flow adjusting member, respectively. It is sectional drawing which shows the further embodiment of the flow adjustment member. It is a graph which shows an example of an experiment result. It is a graph which shows another example of an experimental result.

Hereinafter, the airflow classifier according to the present invention will be described based on the embodiment. Needless to say, the present invention is not limited to this embodiment. Further, in the drawings attached to the present specification, the components may be shown at a ratio different from the actual one in order to show the characteristic parts in an easy-to-understand manner.

(overall structure)
FIG. 1 shows an embodiment of an airflow classifier according to the present invention. The airflow classifying machine 1 shown here has a classifying main body 2, a raw material supply system 3, and a powder recovery system 4. The classification main body 2 is a portion where a process of separating (that is, classifying) the raw material powder into fine powder and coarse powder is performed. The raw material supply system 3 is a portion that supplies the raw material powder G to the classification main body 2. The powder recovery system 4 is a portion for recovering fine powder as a product obtained by the classification treatment and coarse powder that is not a product. In FIG. 1, the arrow HH direction indicates a horizontal direction. The direction perpendicular to the horizontal direction H is the vertical direction. The vertical downward direction is the direction in which gravity acts.

As shown in FIG. 2, the classification main body 2 has a front side plate 7a and a rear side plate 7b. A Coanda block 8, an opposed block 9, a classification edge 10, and a transport block 11 are provided between the front side plate 7a and the rear side plate 7b.

The product produced by the airflow classifier 1 of FIG. 1 can be made into various powders, but in the present embodiment, it is assumed that toner used in an electrophotographic apparatus such as a laser printer is produced. Toner is a powder composed of micro-sized particles in which colored particles such as graphite and pigment are attached to chargeable plastic particles. Of course, the product is not limited to toner.

In the present embodiment, the toner is a fine powder having a size equal to or less than the classification boundary value among the powder raw materials. The coarse powder, which is a powder having a size exceeding the classification boundary value, is a powder that is removed from the product. After the coarse powder is pulverized, it is again classified by the air flow classifier 1 as a powder raw material. The classification boundary value is preferably a value in the range of 8 μm to 12 μm, and more preferably 10 μm.

In the present embodiment, the present invention is applied to an airflow classifying machine having a function of dividing a powder raw material into two classes of fine powder and coarse powder, a so-called airflow classifying machine. However, the present invention can also be applied to an air flow classifier having a function of dividing a powder raw material into three or more classes.

(Classification body)
FIG. 3 shows a state in which the front side plate 7a is removed from the classification main body 2 of FIG. As shown in FIG. 3, the raw material supply nozzle 12 is provided on the upper surface 8a of the Coanda block 8. The lower side surface 12a of the raw material supply nozzle 12 is in contact with the surface 8a of the Coanda block 8.

The right side surface of the classification edge 10, the right side surface of the transfer block 11, and the lower surface of the Coanda block 8 form a fine powder transfer path T1 as a powder transfer path. The facing block 9 has a protruding portion 9a, an upward inclined surface 9b, and a downward inclined surface 9c. The protruding portion 9a protrudes toward the Coanda block 8. The upper inclined surface 9b is inclined so as to be separated from the Coanda block 8 as the distance from the protrusion 9a increases. The lower inclined surface 9c is inclined so as to be separated from the Coanda block 8 as it goes downward from the protrusion 9a. A coarse powder transport path T2 as a powder transport path is formed by the left side surface of the classification edge 10, the left side surface of the transfer block 11, and the lower inclined surface 9c of the facing block 9.

The classification edge 10 is rotatable about the shaft 13. By this rotation, the position of the tip of the classification edge 10 can be changed in the left-right direction. By rotating the classification edge 10, the area of the upper end opening of the fine powder transport path T1 and the coarse powder transport path T2 (that is, the area of the powder intake port) can be changed. By changing the area of the powder intake port in this way, it becomes possible to adjust the classification boundary value of the powder raw material.

In FIG. 2, at the upper end of the classification main body 2, the air flow introduction port M1 is formed by the upper ends of the side plates 7a and 7b, the upper ends of the facing blocks 9, the tip of the raw material supply nozzle 12, and the tip of the Coanda block 8. There is. A fine powder discharge port M2 is formed at the lower end of the fine powder transport path T1. A coarse powder discharge port M3 is formed at the lower end of the coarse powder transport path T2.

(Coanda block and raw material supply nozzle)
FIG. 4 shows an enlarged view of the Coanda block 8 and the raw material supply nozzle 12. The cross-sectional shape of the tip E of the Coanda block 8 is formed into an arc shape. The tip portion E has a first tip portion E1 and a second tip portion E2. The first tip E1 and the second tip E2 are continuous. The cross-sectional shape of the first tip portion E1 is an arc shape having a radius r1. The cross-sectional shape of the second tip portion E2 is an arc shape having a radius r2. r1 <r2.

r1 and r2 are appropriately set according to the type of the powder raw material and the material of the Coanda block 8, but in the present embodiment using the powder raw material as the toner, 5 mm <r1 <30 mm, more preferably 10 mm <. r1 <20 mm, more preferably r1 = 15 mm. On the other hand, it is preferably 15 mm <r2 <40 mm, more preferably 20 mm <r2 <30 mm, and even more preferably r2 = 25 mm.

The position of the tip of the raw material supply nozzle 12, that is, the position of the nozzle opening 12c is set back from the tip of the Coanda block 8 by a distance D1. This distance D1 is an arbitrary distance, but in the present embodiment, this distance D1 is aligned with the point P1 at which the arc shape of the tip E of the Coanda block 8 starts, as shown in FIG. However, the distance D1 at which the nozzle opening 12c is arranged with respect to the tip of the Coanda block 8 does not necessarily have to match the point P1 at which the arc shape starts.

Regarding this, in the conventional air flow classifier, at the point where the tip E of the Coanda block 8 starts on the upper surface 8a of the Coanda block 8, that is, at a position 10 mm from the point P1 where the arc shape starts to the upstream side of the raw material supply. The distance D1 was set. Also in this embodiment, the distance D1 can be set at a position of 10 mm from the point P1 where the arc shape starts to the upstream side of the raw material supply. Alternatively, the distance D1 can be set at other appropriate distance positions.

Further, the raw material supply nozzle 12 is inclined by an angle α with respect to the horizontal direction H. The term "horizontal direction" as used herein means that when the fine powder transport path T1 and the coarse powder transport path T2 as the powder transport path are arranged so as to face the vertical direction (that is, the classification main body 2 stands in the vertical direction in FIG. 1). (When) means the horizontal direction. In this embodiment, the straight line portion 8b of the surface 8a of the Coanda block 8 is inclined by the same angle α with respect to the horizontal. Therefore, the lower side surface 12a of the raw material supply nozzle 12 is in full contact with the linear portion 8b of the surface 8a of the Coanda block 8.

The angle α is appropriately set according to the type of the powder raw material and the material of the raw material supply nozzle 12, but in the present embodiment in which the powder raw material is used as the toner, the angle α is 0 ° <α <90 °, preferably 0 ° <α <90 °. 10 ° <α <45 °, more preferably 20 ° <α <40 °. More preferably, α = 28 °.

The straight line portion 8b of the surface 8a of the Coanda block 8 extends in the tangential direction of the arc shape of the first tip portion E1 of the Coanda block 8. Therefore, the raw material supply nozzle 12 extends in the tangential direction of the arc shape of the tip portion E of the Coanda block.

By forming the cross-sectional shape of the tip E of the Coanda block 8 into an arc shape, and further, the position of the nozzle opening 12c at the tip of the raw material supply nozzle 12 is provided so as to be retracted rearward by a distance D1 from the tip of the Coanda block 8. The fine powder of the powder raw material emitted from the nozzle opening 12c enters the fine powder transport path T1 while being attracted to the tip E of the Coanda block 8 according to the Coanda effect.

The Coanda effect is the attraction of a jet of viscous fluid to a nearby wall. This is due to the fact that the jet has the property of drawing in the surrounding fluid.

As described above, the distance D1 can be set to an arbitrary value, but as shown in FIG. 4, if the distance D1 is adjusted to the point where the tip E of the Coanda block 8 starts, that is, the point P1 where the arc shape starts, the above It is convenient to realize the Coanda effect when the raw material supply nozzle 12 is tilted at an angle α as described above.

(The tip of the raw material supply nozzle)
5 (a) and 5 (b) show the Coanda block 8 and the raw material supply nozzle 12 in an enlarged manner. FIG. 5 (b) is a diagram according to arrow A in FIG. 5 (a). In FIG. 5A, the distance from the upper surface 8a of the Coanda block 8 to the bottom 12d of the nozzle opening 12c of the raw material supply nozzle 12 is Z1. Further, the distance from the upper surface 8a of the Coanda block 8 to the center line X0 of the raw material supply nozzle 12 is Z2. These distances Z1 and Z2 are distances including the thickness of the lower wall member of the raw material supply nozzle 12. Therefore, Z1 and Z2 can be adjusted by adjusting the thickness of the lower wall member of the raw material supply nozzle 12.

Z1 and Z2 are appropriately set according to the type of the powder raw material and the material of the raw material supply nozzle 12, but in the present embodiment using the powder raw material as the toner, 2 mm <Z1 <5 mm, more preferably Z1. = 3 mm. On the other hand, it is preferably 4 mm <Z2 <8 mm, more preferably 5 mm <Z2 <7 mm, and even more preferably Z2 = 6 mm.

In FIG. 5B, the cross-sectional shape of the raw material supply nozzle 12 can be an appropriate shape as needed, but in the present embodiment, it is rectangular. The rectangular vertical length L1 is, for example, L1 = 12 mm, and the horizontal length L2 is, for example, L2 = 25 mm.

The cross-sectional shape of the nozzle opening 12c of the raw material supply nozzle 12 can be appropriately formed as needed, but in the present embodiment, it is a rectangular shape long in the horizontal direction. The rectangular vertical length L3 is, for example, L3 = 6 mm, and the horizontal length L4 is, for example, L4 = 15 mm.

FIG. 7B shows a conventional structure in which the height Z1 at the bottom of the nozzle is less than 2 mm. Specifically, the height Z1 = 0 mm from the Coanda block surface 28a at the bottom 12d of the nozzle opening 12c. In both the case of the present embodiment (Z1 is present) shown in FIG. 5A and the conventional example (Z1 is not present) shown in FIG. 7B, when the airflow is jetted from the nozzle opening 12c, the airflow is blown. Expands to become a jet at the moment when it comes out of the nozzle opening 12c. In the conventional example shown in FIG. 7 (b) where Z1 is less than 2 mm, the jet expanded at the nozzle opening 12c repels the surface 28a of the Coanda block 28, so that the airflow expands only on the upward side and the Coanda block. I'm away from 28. If this happens, the expected Coanda effect may not be obtained.

On the other hand, when Z1 in FIG. 5A exceeds 5 mm, the airflow jetted from the nozzle opening 12c travels to a region far away from the Coanda block 8. Therefore, the airflow cannot sufficiently receive the Coanda effect, and as a result, the fine powder cannot be classified with high accuracy.

Considering the above, it is preferable that 2 mm <Z1 <5 mm. As a result, as shown in FIG. 7A, it is possible to advance the jet flow of the airflow immediately after being jetted from the nozzle opening 12c while expanding it in a well-balanced manner. Therefore, it becomes possible to form a smooth air flow along the tip E of the Coanda block 8, and as a result, a highly accurate classification effect can be obtained.

(Raw material supply system)
Returning to FIG. 1, the raw material supply system 3 includes an air pump 16 as an air flow supply source, an ejector 17 as a raw material dispersion device, and a raw material transfer pipe 18 for transporting powder raw materials toward the raw material supply nozzle 12. Have. The air pump 16 forms an air flow flowing in the raw material transfer pipe 18. The ejector 17 disperses the powder raw material in the air flow.

The raw material transfer pipe 18 provided on the upstream side of the raw material supply nozzle 12 is curved in one direction (downward, which is the direction in which gravity acts in this embodiment). The direction in which the raw material transfer pipe 18 is bent is related to the direction in which the classification main body 2 is installed. As shown in FIG. 1, the classification main body 2 of the present embodiment is provided in a state of standing vertically and vertically. Then, the powder raw material is classified while flowing vertically downward. In this state, the raw material transfer pipe 18 is bent downward, which is one direction.

If the powder raw material is classified while flowing vertically upward, the raw material transport pipe 18 is bent upward in one direction. If the powder raw material is classified while flowing in the left-right direction, the raw material transfer pipe 18 is bent to the left or right, which is one direction.

In the case of the present embodiment, for example, as shown in FIG. 6, the raw material transfer pipe 18 is bent under the conditions of a bending angle range β = 28 °, a bending length L5 = 260 mm, and a bending radius r3 = 562 mm. By bending the raw material transfer pipe 18 in this way, a centrifugal force having a magnitude corresponding to the mass of the powder particles contained in the powder raw material flowing in the raw material transfer pipe 18 is applied to each powder particle. As a result, the coarse powder is collected on the outer peripheral side of the raw material transfer pipe 18, and the fine powder is collected on the inner peripheral side of the raw material transfer pipe 18, and as a result, dispersion according to the particle size of the powder raw material is promoted. In this way, if the powder raw material is dispersed by the curved raw material transfer pipe 18 before the Coanda effect is executed at the tip E of the Coanda block 8, the fine powder is separated by the Coanda effect at the tip of the Coanda block 8. The phenomenon of flowing along the portion E can be reliably executed.

If such a dispersion treatment by centrifugal force is performed in or near the Coanda effect region at the tip of the Coanda block 8, the airflow may be turbulent and a good Coanda effect may not be obtained. On the other hand, if the dispersion treatment according to the centrifugal force is performed in advance inside the raw material transfer pipe 18 as in the present embodiment, a stable and efficient Coanda effect can be realized without causing turbulence of the air flow. ..

(Powder recovery system)
In FIG. 1, the powder recovery system 4 includes a fine powder suction pipe 21 connected to a fine powder discharge port M2 of a classification main body 2, a fine powder cyclone 22 as a powder recovery means for storing powder, and a classification main body 2. It has a coarse powder suction pipe 23 connected to the coarse powder discharge port M3, and a coarse powder cyclone 24 as a powder recovery means for storing the powder. A blower 25, which is a gas suction device, is provided after the cyclones 22 and 24. When the blower 25 is operated, the air inside the classification main body 2 is sucked, and the air is introduced as an air flow from the air flow introduction port M1. This air flow passes through the vicinity in front of the tip portion E of the Coanda block 8 and flows into the fine powder transport path T1 and the coarse powder transport path T2 as the powder transport path. The powder recovery means is not limited to the cyclone.

(Overall operation)
In FIG. 1, the blower 25 operates to form an air flow inside the classification body 2. Specifically, the airflow from the upper airflow introduction port M1 to the lower fine powder discharge port M2 and the airflow from the airflow introduction port M1 to the lower coarse powder discharge port M3 are in the vicinity of the front of the tip portion E of the coranda block 8. Is formed in. Further, when the air pump 16 is operated and the powder raw material G is further charged into the ejector 17, the powder raw material is dispersed in the air flow by the ejector 17. When the airflow containing the powder raw material enters the curved raw material transport pipe 18, the coarse powder is aligned to the outside and the fine powder is aligned to the inside by the action of centrifugal force.

Then, in FIG. 3, the powder raw material is ejected from the nozzle opening 12c of the raw material supply nozzle 12. The coarse powder of the injected powder raw material flies far and enters the coarse powder transport path T2 due to the influence of the inertial force. The injection direction S of the powder raw material by the raw material supply nozzle 12 is a direction along the center line X0 of the raw material supply nozzle 12. The injection direction S points to a position below the apex of the protruding portion 9a of the facing block 9. Therefore, the coarse powder blown by the inertial force surely enters the coarse powder transport path T2.

On the other hand, the fine powder of the powder raw material travels along the arcuate surface of the tip E due to the Coanda effect generated at the tip E of the coanda block 8 and enters the fine powder transport path T1. In the present embodiment, the particles having a diameter of more than 10 μm are coarse powders, and the particles having a diameter of 10 μm or less are fine powders. In the present embodiment, as shown in FIG. 6, since the raw material transfer pipe 18 provided in the front stage of the raw material supply nozzle 12 is curved, the coarse powder is collected in the outer region by the action of centrifugal force, and the fine powder is collected in the inner region. Collected in. Therefore, the Coanda effect at the tip E of the Coanda block 8 functions effectively, and the coarse powder and the fine powder are classified with high accuracy by the classification edge 10.

In FIG. 1, the fine powder obtained by classification is stored as a product in the fine powder cyclone 22 through the fine powder suction pipe 21. On the other hand, the coarse powder obtained by classification is stored in the coarse powder cyclone 24 through the coarse powder suction pipe 23. Coarse flour is contained as non-product flour. The coarse powder is subjected to a pulverization treatment as necessary, and then again charged into the ejector 17 as a powder raw material.

(Flow adjustment member)
In FIG. 4, a flow adjusting member 14 is provided in front of the nozzle opening 12c of the raw material supply nozzle 12. As shown in FIGS. 5A and 5B, the flow adjusting member 14 is filled in the space between the bottom of the nozzle opening 12d of the raw material supply nozzle 12 and the surface 8a of the tip E of the Coanda block 8. It is a member. The flow adjusting member 14 can be integrally formed of the same material when forming the tube wall member of the raw material supply nozzle 12, or is formed as a single member separate from the tube wall member of the raw material supply nozzle 12. You can also do it. As shown in FIG. 5B, the flow adjusting member 14 is provided over the entire width of the Coanda block 8. In some cases, the flow adjusting member 14 may be partially provided in the width direction of the Coanda block 8.

When the flow adjusting member 14 is formed as a single member separate from the pipe wall member of the raw material supply nozzle 12, the lower pipe wall member of the raw material supply nozzle 12 is formed on the straight portion 8b of the upper surface 8a of the Coanda block 8. A flow adjusting member 14 is provided on the front surface of the nozzle opening 12c. Alternatively, after the flow adjusting member 14 is fixed at a predetermined position on the upper surface 8a of the Coanda block 8, the raw material supply nozzle 12 is fixed on the linear portion 8b of the upper surface 8a of the Coanda block 8. It is desirable that the flow adjusting member 14 is made of a material that is not easily worn, for example, stainless steel SUS304 or a wear-resistant steel plate.

The flow adjusting member 14 can be formed, for example, as shown in FIG. 8A. In FIG. 8A, the upper surface 14a of the flow adjusting member 14 is an inclined surface that is inclined with respect to the nozzle inner bottom surface 12b. The inclined surface 14a is formed as a flat surface (that is, a straight cross section) that does not curve. The inclined surface 14a is a tangent to the arc shape of the tip portion E of the arc shape of the Coanda block 8 when viewed in cross section.

FIG. 8B shows another embodiment of the flow adjusting member 14. In FIG. 8B, the upper surface 14a of the flow adjusting member 14 is an inclined surface that is inclined with respect to the nozzle inner bottom surface 12b. The inclined surface 14a is formed as a flat surface (that is, a straight cross section) that does not curve. The inclined surface 14a is not a tangent line of the arc shape of the tip portion E of the arc shape of the coranda block 8 when viewed in cross section, but is a linear flat inclined surface shorter than the tangent line.

FIG. 9A shows still another embodiment of the flow adjusting member 14. In FIG. 9A, the upper surface 14a of the flow adjusting member 14 is formed as a curved surface instead of a flat flat surface. In particular, the upper surface 14a in FIG. 9A is formed as a curved surface that is convex with respect to the tip E of the Coanda block 8.

FIG. 9B shows still another embodiment of the flow adjusting member 14. In FIG. 9B, the upper surface 14a of the flow adjusting member 14 is formed as a curved surface instead of a flat flat surface. In particular, the upper surface 14a in FIG. 9B is formed as a curved surface that is concave with respect to the tip E of the Coanda block 8.

FIG. 10A shows still another embodiment of the flow adjusting member 14. In each of the embodiments shown in FIGS. 8 (a), 8 (b), 9 (a) and 9 (b), the upper end, that is, the tip end of the flow adjusting member 14 coincides with the bottom end 12d of the nozzle opening. On the other hand, in the embodiment of FIG. 10A, the upper end of the flow adjusting member 14 is not aligned with the nozzle opening bottom base 12d, but is aligned with the position below the nozzle opening bottom base 12d. Even with this configuration, the occurrence of turbulence can be reduced.

FIG. 10B shows still another embodiment of the flow adjusting member 14. In the flow adjusting member 14 described above, the upper surface thereof is an inclined surface. On the other hand, the upper surface of the flow adjusting member 14 in FIG. 10B is a stepped surface. Such a stepped surface can also reduce the occurrence of turbulence.

FIG. 11 shows still another embodiment of the flow adjusting member 14. The flow adjusting member 14 of this embodiment is formed of a single plate material. This one plate material is fixed to the upper surface 8a of the Coanda block 8 on the front surface of the nozzle opening 12c. Such a single plate 14 can also reduce the occurrence of turbulent flow. It is desirable that this one plate material is made of a material that is hard to wear, for example, stainless steel SUS304 or wear-resistant steel plate.

(Effect obtained by this embodiment)
(1) In the conventional air flow classifier, for example, as shown in FIG. 7B, the bottom surface 12d of the nozzle opening 12c of the raw material supply nozzle 12 and the surface 28a of the Coanda block 28 are aligned on the same surface. .. In the case of this configuration, the airflow injected from the nozzle opening 12c swells immediately after the injection, the swelled airflow repels the surface 28a of the Coanda block 28, and the repulsed airflow moves away from the tip E of the Coanda block 28. As a result, the Coanda effect generated at the tip E of the Coanda block 8 could not be effectively utilized for the classification of fine powder.

On the other hand, in the present invention, for example, as shown in FIG. 5A, a gap Z1 is provided between the upper surface 8a of the Coanda block 8 and the bottom 12d of the nozzle opening 12c. Therefore, even if the airflow jetted from the nozzle opening 12c swells, the airflow does not repel on the surface 8a of the Coanda block 8. Therefore, the airflow forms a smooth airflow along the tip E of the Coanda block 8, for example, as shown in FIG. 7A, and as a result, a highly accurate classification effect can be obtained.

(2) Further, in FIG. 4, since the raw material supply direction S by the raw material supply nozzle 12 is tilted by an angle α with respect to the horizontal, the conventional material supply direction is set to the horizontal direction as shown in FIG. 7 (b). Compared with the case, the powder raw material can be supplied as a smooth air flow to the tip portion E of the Coanda block 8 in FIG. Therefore, the function of the Coanda effect imparted to the powder raw material at the tip portion E can be further enhanced.

(3) Further, since the raw material transfer pipe 18 provided in the front stage of the raw material supply nozzle 12 in FIG. 6 is curved downward in one direction, the coarse powder of the powder raw material is formed by the action of centrifugal force. Collects in the outer region of the raw material transport pipe 18, and fine powder collects in the inner region of the raw material transport pipe 18. Therefore, the Coanda effect at the tip E of the Coanda block 8 can be effectively utilized to classify fine powder and coarse powder with high accuracy.

If the process of separating the coarse powder and the fine powder by the centrifugal force generated by bending the powder flow is attempted in the vicinity of the tip E of the Coanda block 8, the air flow may be disturbed at the tip E, in which case. In some cases, it may be difficult to effectively classify fine powder by the Coanda effect. On the other hand, in the present embodiment, as shown in FIG. 6, the coarse powder and the fine powder are separated by centrifugal force at the raw material transfer pipe 18 located at a distance from the tip E of the Coanda block 8. , The airflow at the tip E of the Coanda block 8 is not disturbed, and therefore the Coanda effect can be effectively utilized.

(4) Further, in FIGS. 3 and 4, since the raw material supply nozzle 12 extends in the tangential direction of the arc shape of the tip portion E of the Coanda block 8, the airflow containing the powder raw material is applied to the Coanda block 8. It becomes possible to lead to the tip portion E reasonably, and as a result, the function of the Coanda effect generated on the powder raw material at the tip portion E can be further enhanced.

(5) Further, since the cross-sectional shape of the tip portion E of the Coanda block 8 is formed by the first tip portion E1 having a small radius and the second tip portion E2 having a continuous large radius, the Coanda block. The function of the Coanda effect generated on the powder raw material at the tip portion E of 8 can be further enhanced.

(6) In FIG. 4, if the flow adjusting member 14 is not provided in front of the nozzle opening 12c, a space is formed between the upper surface 8a of the tip portion E of the Coanda block 8 and the lower surface of the nozzle opening 12c. , Turbulence may occur in this space. When this turbulence occurs, the classification accuracy may decrease, and the upper surface 8a of the Coanda block 8 may be significantly worn. On the other hand, as shown in FIGS. 4, 8, 9, 10 and 11, if the flow adjusting member 14 is provided in the above space, the generation of turbulent flow can be prevented in the vicinity of the nozzle opening 12c. As a result, high classification accuracy can be realized, and damage due to wear of the Coanda block 8 can be prevented.

(Other embodiments)
Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to the embodiments and can be variously modified within the scope of the invention described in the claims.

For example, in the above embodiment, the present invention is applied to a so-called airflow two-class machine that classifies powder raw materials into two classes of coarse powder and fine powder. However, the present invention relates to an airflow classifier for classifying powder raw materials into three classes of coarse powder, intermediate powder, and fine powder (for example, JP-A-2004-230313, particularly the airflow classifier shown in FIG. 6). Can also be applied. Alternatively, the present invention can also be applied to an air flow classifier that classifies powder raw materials into four or more classes. It should be noted that increasing the number of classifications can be realized, for example, by setting the number of classification edges 10 to two or more in FIG.

Next, in the embodiment shown in FIG. 1, the raw material transfer pipe 18 is curved downward in relation to setting the flow direction of the air flow in the classification main body 2 from top to bottom. However, when the flow direction of the airflow in the classification main body 2 is set from the bottom to the top or in the left-right direction, the bending direction of the raw material transfer pipe 18 is appropriately selected accordingly.

Next, in the embodiment shown in FIG. 4, the portion that realizes the Coanda effect is an arc-shaped portion E, and a continuous structure of a first portion E1 having a particularly small diameter and a second portion E2 having a particularly large diameter is used. However, the portion that realizes the Coanda effect may be a portion having a single diameter, or may be a curved surface shape other than an arc shape in some cases.

(Example 1: Comparison of classification efficiency)
The classification performance of the airflow classifier of the present invention (FIG. 8A) was compared with the classification performance of the airflow classifier having the configuration of FIG. 8A in which the flow adjusting member was removed. Specifically, the classification performance of both airflow classifiers was compared by the classification efficiency of both airflow classifiers when the toner having an average particle size of 6.5 μm was classified using both airflow classifiers.

The Coanda block near the nozzle opening of the raw material supply nozzle of the present invention is provided with an inclined surface toward the arc-shaped tip of the Coanda block due to the presence of the flow adjusting member. In the airflow classifier having the configuration in which the flow adjusting member is removed, a step is formed between the nozzle opening and the surface of the Coanda block.

The classification efficiency was evaluated by comparing the measurement results of the particle size distribution. The particle size distribution was measured using Multisizer3 (wet electrical resistance supplement) and Helos & Rodos (dry laser diffraction type).

First, in the classification process in the apparatus of the present invention and the classification process in the device to be compared, the classification yield was changed under the following two conditions. One is a condition that the fine powder which is a product is 71% and the coarse powder which is not a product is 29%. The other one is a condition that the fine powder which is a product is 93% and the coarse powder which is not a product is 7%. FIG. 12 shows the classification efficiency of the apparatus of the present invention and the classification efficiency of the apparatus to be compared when the classification yield is changed between the above two types, plotted on a graph based on the measurement result of the particle size distribution. Is.

The classification efficiency (a, c) by the classifier using the Coanda block of the present invention (FIG. 8 (a)) is the Coanda block of the technology to be compared (the configuration in which the flow adjusting member is removed in FIG. 8 (a)). Results showing higher classification efficiency than the classification efficiency (b, d) by the classifier used were obtained.

The particle size distribution was measured by two measurement methods, Multisizer 3 (wet electric resistance supplement) and Helos & Rodos (dry laser diffraction type), but there are differences (separation diameter, efficiency%) depending on the measurement method. However, all of them show the result that the classification efficiency is superior when the coranda block of the present invention is used.

(Example 2: Verification of wear reduction)
The toner having an average particle size of 6.5 μm was classified using the air flow classifier of the present invention (FIG. 8A). Further, the toner having an average particle diameter of 6.5 μm was classified by using the technique to be compared (the technique in which the flow adjusting member was removed in FIG. 8A). Then, the wear durability of the coanda block in the airflow classifier of the present invention was compared with the wear durability of the coanda block in the comparative technique.

The comparison of wear durability was evaluated by comparing the weight of the Coanda block before and after the classification test. As a result, the airflow classifier of the present invention wears very little. On the other hand, in the Coanda block in the technology to be compared, a dent was observed at the tip of the Coanda when about 200 kg of toner was treated, and a weight loss of about 2.5 g was confirmed.

FIGS. 13 and 1 show the results of measuring the amount of toner classification and the amount of wear of the Coanda block when the toner is classified. From this result, by adopting the flow adjusting member according to the present invention, it was possible to suppress the generation of turbulent flow in the vicinity of the nozzle opening immediately after the raw material airflow was ejected from the nozzle opening. In this way, the rectifying effect on the raw material airflow was improved, and as a result, the wear of the Coanda block was reduced.

The wear test of the Coanda block was performed using a Coanda block made of resin (for example, made of conductive polyacetal). By forming the Coanda block with stainless steel or a material having wear resistance higher than that of stainless steel, it is considered that the wear resistance of the Coanda block can be further improved.

1: Air flow classifier, 2: Classifying body, 3: Raw material supply system, 4: Powder recovery system, 7a: Front side plate, 7b: Rear side plate, 8: Coanda block, 8a: Surface, 8b: Straight part, 9: Opposing block, 9a: protruding part, 9b: upward inclined surface, 9c: downward inclined surface, 10: classification edge, 11: transfer block, 12: raw material supply nozzle, 12a: lower side surface, 12b: inner bottom surface of nozzle, 12c: Nozzle opening, 12d: Nozzle opening bottom, 13: Shaft, 14: Flow adjusting member, 14a: Upper surface, 16: Air pump (air flow supply source), 17: Ejector (raw material disperser), 18: Raw material transfer pipe, 21 : Fine powder suction tube, 22: Fine powder suction tube, 23: Coarse powder suction tube, 24: Coarse powder suction tube, 25: Blower (gas suction device), 28: Coanda block, 28a: Upper surface, 28b: Side surface, α: Tilt angle of raw material supply nozzle, β: Bending angle range of raw material transfer pipe, D1: Nozzle opening retract distance, E: Tip, E1: First tip, E2: Second tip, G: Powder raw material, H: horizontal direction, L1, L2, L3, L4: length, L5: bending length, M1: air flow inlet, M2: fine powder discharge port, M3: coarse powder discharge port, P1: arc shape Starting point, r1, r2: radius, r3: bending radius, T1: fine powder transport path (powder transport path), T2: coarse powder transport path (powder transport path), X0: center line of raw material supply nozzle, Z1: Distance to the bottom of the nozzle opening, Z2: Distance to the nozzle center line

Claims (6)

In an air flow classifier that classifies powder raw materials into at least two classes,
A Coanda block and a raw material supply nozzle provided to realize the Coanda effect on powder raw materials,
It has at least one classification edge, which forms a powder transport path corresponding to the at least two classes.
The bottom of the nozzle opening of the raw material supply nozzle is arranged at intervals with respect to the surface of the Coanda block.
An air flow classifier characterized in that a flow adjusting member is provided between the nozzle opening and the upper surface of the Coanda block.
The airflow classifier according to claim 1, wherein the upper surface of the flow adjusting member is an inclined surface inclined with respect to the inner bottom surface of the nozzle of the raw material supply nozzle.
The airflow classifier according to claim 1 or 2, wherein the upper end of the flow adjusting member on the nozzle opening side coincides with the bottom of the nozzle opening of the raw material supply nozzle.
The cross-sectional shape of the portion of the Coanda block that realizes the Coanda effect is an arc shape.
The airflow classifier according to any one of claims 1 to 3, wherein the bottom of the nozzle opening of the raw material supply nozzle is arranged so as to coincide with the point where the arc shape starts.
From claim 1, the distance between the bottom of the nozzle opening of the raw material supply nozzle and the surface of the Coanda block is formed by the thickness of the wall member forming the raw material supply nozzle. The airflow classifier according to any one of claims 4.
Any of claims 1 to 5, wherein the raw material supply direction defined by the raw material supply nozzle is inclined with respect to the horizontal direction when the powder transport path is arranged in the vertical direction. The airflow classifier described in one.

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