JP7070015B2 - Powder supply method - Google Patents

Description

The present invention relates to a method of supplying powder charged into a hopper from the hopper.

Conventionally, there is a powder supply method in which powder is charged into a hopper and the powder is supplied from an opening provided at the bottom of the hopper. In such a powder supply method, for example, depending on the type of powder, the powders may adhere to each other in the hopper to form a bridge, and the powder may not fall into the opening. When a bridge occurs, the amount of powder supplied varies widely. Therefore, a technique for suppressing the bridge has been conventionally proposed. For example, Patent Document 1 discloses a powder supply technique in which a rotating stirring member is provided in a hopper, and the powder is stirred by the stirring member to suppress a bridge.

Japanese Unexamined Patent Publication No. 2013-139333

However, if the stirring member is provided in the hopper, there is a problem that the powder and the stirring member come into contact with each other. For example, consolidation of powder may occur between the stirring member and the inner wall surface of the hopper. When consolidation occurs, the weight of the powder supplied from the hopper varies, and the weighing accuracy deteriorates. Further, when the stirring member that comes into direct contact with the powder is provided, foreign matter derived from the stirring member may be mixed in the powder.

The present invention has been made to solve the problems of the above-mentioned conventional techniques. That is, the problem is to provide a supply method for supplying powder from a hopper, which is a technique for suppressing the generation of bridges without providing a member in contact with the powder.

The powder supply method according to one aspect of the present invention, which has been made for the purpose of solving this problem, is a powder supply method for supplying powder from a hopper, in which the powder is charged into the hopper and the lower part of the hopper is charged. The powder is supplied from the opening of the hopper, and the hopper is rotated around a rotation axis passing through the inside of the opening while the powder is inside the hopper, and the hopper is rotated at a constant forward rotation speed. The forward rotation over the forward rotation period and the reverse rotation at a constant reverse rotation speed over the reverse rotation period are alternately repeated.

According to the powder supply method in one aspect described above, forward rotation and reverse rotation of the hopper are alternately repeated, so that an inertial force acts on the powder inside the hopper when the rotation direction is reversed. The inertial force causes the powder to move away from the hopper, which suppresses the formation of bridges. Since the hopper can be rotated from the outside of the hopper, it is not necessary to provide a member that comes into contact with the powder inside the hopper.

According to the present invention, a technique for supplying powder from a hopper and suppressing the generation of bridges without providing a member in contact with the powder is realized.

It is a schematic block diagram which shows the powder supply apparatus of this embodiment. It is a schematic perspective view which shows the connection part of the powder supply device. It is a schematic sectional drawing which shows the connection part of the powder supply apparatus. It is explanatory drawing which shows the example of the moving direction of a powder. It is explanatory drawing which shows the example of the case where consolidation occurs in the powder. It is explanatory drawing which shows the example of the case where the bridge occurs in the powder. It is explanatory drawing which shows the example of the reversal timing in a rotation direction. It is explanatory drawing which shows the experimental result of an Example and a comparative example.

Hereinafter, the powder supply method of this embodiment will be described in detail with reference to the attached drawings. This embodiment is a supply method for supplying powder from a hopper.

As shown in FIG. 1, the powder supply device 1 used in the present embodiment controls the hopper portion 10, the screw portion 20, the connection portion 30, the hopper drive unit 40, and the screw drive unit 50, as shown in FIG. A unit 60 is provided. In the powder supply device 1 of the present embodiment, for example, a lid member (not shown), a charging device, or the like is connected above the hopper portion 10, and powder is continuously charged into the hopper portion 10.

As shown in FIG. 1, the hopper portion 10 is a funnel-shaped container arranged in the vertical direction, and has a hollow truncated cone shape with a larger opening area toward the upper side. The hopper portion 10 communicates with the screw portion 20 via the connecting portion 30. The hopper portion 10 has a configuration that allows the screw portion 20 to rotate about the rotation shaft 11. The rotation shaft 11 is the central shaft of the hopper portion 10. The hopper unit 10 is rotationally driven by the hopper drive unit 40 in either the forward or reverse direction. That is, the hopper drive unit 40 can rotate the hopper unit 10 in both the forward direction and the reverse direction.

As shown in FIG. 1, the screw portion 20 communicates a cylindrical discharge cylinder 21 arranged in the horizontal direction, a screw 22 arranged in the discharge cylinder 21, and the discharge cylinder 21 and the hopper portion 10. A tube 23 and the like are provided. The screw 22 is rotationally driven in one direction by the screw drive unit 50 to push out the powder between the screw blades to one end side. An opening 211 is provided on one end side of the discharge cylinder 21, and the powder extruded by the screw 22 is discharged from the opening 211. If the inside of the discharge cylinder 21 is appropriately filled with powder, the amount of powder discharged from the screw portion 20 can be controlled by the size and pitch of the screw blades and the rotation speed of the screw.

As shown in FIG. 1, the connecting portion 30 rotatably connects the lower portion of the hopper portion 10 and the connecting pipe 23 of the screw portion 20 to each other. The hopper drive unit 40 rotates only the hopper unit 10 with the discharge cylinder 21 and the connecting pipe 23 of the screw unit 20 fixed. The screw drive unit 50 rotates the screw 22 of the screw unit 20 at a predetermined rotation speed. Then, the control unit 60 controls the hopper drive unit 40 and the screw drive unit 50.

As shown in FIGS. 2 and 3, the connecting portion 30 connects the opening 12 at the lower part of the hopper portion 10 and the connecting pipe 23 of the screw portion 20. FIG. 3 is a cross-sectional view in the radial direction of FIG. As shown in FIG. 3, the connecting portion 30 includes an annular bearing 31, a fixing screw 32, and a holding portion 33. The bearing 31 includes a ball 311, an inner ring 312, and an outer ring 313, and the ball 311 holds the inner ring 312 and the outer ring 313 rotatably with each other. The inner ring 312 of the bearing 31 is fixed to the hopper portion 10 by the fixing screw 32. The outer ring 313 of the bearing 31 is fixed to the connecting pipe 23 of the screw portion 20 via the holding portion 33.

In this embodiment, the rotation shaft 11 shown in FIG. 1 passes through the center of the opening 12. The opening 12 of the hopper portion 10 has the same diameter as the connecting pipe 23, and slides on the end face forming the opening of the connecting pipe 23. Therefore, the opening 12 and the connecting pipe 23 are connected without any gap or step, and are always in communication with each other even if the hopper portion 10 is rotated. The hopper drive unit 40 rotationally drives the hopper unit 10 at a position above the range shown in FIGS. 2 and 3.

The powder to be supplied by the powder supply device 1 of the present embodiment is, for example, a conductive material used for manufacturing electrodes of a lithium ion secondary battery, and is an ultralight powder having a bulk density of 0.1 g / cm ³ or less. be. When manufacturing an electrode for a lithium ion secondary battery, a highly conductive carbon material powder such as acetylene black powder may be added to the electrode active material as a conductive material. In order to continuously manufacture electrodes with stable performance, it is desirable to continue to supply the conductive material with a stable supply amount.

In addition, in this specification, "bulk density" means loose bulk density. The looseness density is determined by gently filling a container with the freely dropped powder and grinding it to obtain a predetermined volume, and measuring the weight of the obtained powder. In powders with a small bulk density such as acetylene black powder, the powders tend to adhere to each other and bridges are likely to occur.

The powder supply device 1 of the present embodiment supplies the powder P, for example, as shown by an arrow in FIG. The powder P is thrown into the hopper portion 10 from above, moves downward in the hopper portion 10 due to gravity, and further falls to the screw portion 20 via the connecting portion 30. The screw portion 20 supplies the powder P contained in the predetermined space between the screw blades from the opening 211 by the rotation of the screw 22. If the powder P is not compacted or bridges are not generated and the inside of the screw portion 20 is appropriately filled with the powder P, the supply amount of the powder P per unit time is predetermined according to the rotation speed of the screw 22. Will be the weight of.

On the other hand, for example, as shown in FIG. 5, when the powder P is consolidated in the hopper portion 10, the powder P may partially become a lumpy powder Q. The powder Q is in a state of being compressed more than the powder P by consolidation, and has a higher bulk density than the powder P. When the powder in the screw portion 20 is mixed with the lumpy powder Q, the weight of the powder P supplied per unit time may be larger than that in the case without consolidation.

Further, when a bridge is generated, for example, as shown in FIG. 6, a hollow portion having a small amount of powder P may be formed in the screw portion 20. In the hollow portion, the powder P is not supplied even if the screw 22 is rotated. Therefore, the weight of the powder P supplied per unit time with the bridge generated may be smaller than that without the bridge.

In the powder supply device 1 of the present embodiment, the hopper unit 10 is rotated by the hopper drive unit 40, and the rotation direction thereof is periodically reversed, so that forward rotation and reverse rotation are alternately repeated. Specifically, as shown in FIG. 7, for example, the control unit 60 of the present embodiment reverses the rotation direction after the normal rotation of the constant rotation period t at a predetermined rotation speed after the start of rotation, and the inversion period r. After that, the reverse rotation of the constant rotation period t is performed. The inversion period r is a period required for inversion in the rotation direction, and is determined according to the configuration of the hopper unit 10 and the hopper drive unit 40, the rotation speed in the constant rotation period t, and the like. In this embodiment, the rotation speed and the constant rotation period t are the same for the forward rotation and the reverse rotation, and each inversion period r is the same.

Then, the control unit 60 of the powder supply device 1 controls the hopper drive unit 40 so that the constant rotation period t is shorter than the delivery period T. The delivery period T is a period until the powder corresponding to the width of the connecting pipe 23 of the screw portion 20 is delivered by the screw 22. The pipe width of the connecting pipe 23 is the maximum opening width in the delivery direction of the screw 22 at the communication point between the connecting pipe 23 and the discharge pipe 21, which is the opening diameter of the connecting pipe 23 and the opening 12 of the hopper portion 10 in this embodiment. The opening diameter of.

The delivery period T is calculated as follows. For the volume of powder corresponding to the pipe width, the volume of powder sent by one rotation of the screw 22 is V (m ³ ), the pipe width is w (m), and the length of one pitch of the screw 22 is L (. If m), it is (V × w / L) (m ³ ). Further, the volume of the powder delivered per second is (V × n / 60) (m ³ ), where n (rpm) is the rotation speed of the screw 22. Therefore, the transmission period T (s) is expressed by the following equation 1.
T = (V × w / L) / (V × n / 60)
T = (60 × w) / (n × L)… Equation 1
Then, the control unit 60 determines the constant rotation period t (s) so that t <T.

Due to the reversal of the rotation direction, an inertial force acts on the powder in the hopper portion 10 to suppress the generation of bridges. Even if the bridge is generated during the constant rotation period t, the bridge is broken during the inversion period r, and the powder corresponding to the pipe width falls on the screw portion 20. By setting t <T, the next inversion is performed before the powder supplied to the screw portion 20 by the previous inversion passes through the pipe width, and the powder corresponding to the pipe width is again sent to the screw portion 20. Will be supplied. That is, even if a bridge is generated in the hopper portion 10, the powder due to the next inversion is supplied while the cavity portion by the bridge is within the pipe width, so that the cavity is filled with the powder. Therefore, the fluctuation of the supply amount from the screw portion 20 is suppressed.

Subsequently, in the powder supply device 1 of the present embodiment and the two types of devices of the comparative example, a powder having a bulk density of about 0.05 g / cm ³ was supplied and the amount discharged from the screw portion 20 was measured. The result of is explained. In this experiment, the same type of screw portion is used in Example 1 using the powder supply device 1 of the present embodiment, Comparative Example 1 having a scraper inside the hopper, and Comparative Example 2 having a knocker outside the hopper. 20 was used to discharge the same kind of powder.

In Example 1, the constant rotation period t was set to be smaller than the transmission period T, and the rotation direction was periodically reversed as shown in FIG. That is, the constant rotation period t of the first embodiment satisfies t <T. In Comparative Example 1, a scraper that rotates along the inner wall surface to stir the powder is provided inside the hopper, and the scraper is rotated in one direction at a constant speed. In Comparative Example 2, a knocker that hits the outer wall surface of the hopper to give vibration to the hopper was provided, and the knocker was periodically driven at the same interval as the constant rotation period t of the first embodiment.

In this experiment, the rotation speed of the screw 22 was changed, each supply experiment was performed a plurality of times, and the weight of the powder discharged in 30 seconds (30-second discharge amount) was measured. The results of the experiment are shown in FIG. In FIG. 8, the rotation speed (rpm) of the screw 22 is on the horizontal axis, and the 30-second discharge amount (g) is on the vertical axis. The results of Example 2 are indicated by "◇". Further, the theoretical value of the 30-second discharge amount is calculated from the configuration of the screw portion 20 and the like, and a straight line of the theoretical value ± 1% is shown in FIG. The theoretical value ± 1% is the range of the amount of the conductive material supplied at the time of manufacturing the electrode.

As shown in FIG. 8, even if the rotation speed was increased, the emission amount was within the range of the theoretical value ± 1% only in Example 1. According to the powder supply device 1 of the present embodiment, it was confirmed that an appropriate supply amount can be secured even if the rotation speed of the screw 22 is increased.

In Comparative Example 1, as shown in FIG. 8, the emission amount became larger than the theoretical value as the rotation speed increased, and the variation in the emission amount was also large. In Comparative Example 1, it is presumed that the powder was consolidated between the scraper and the inner wall of the hopper. Further, in the discharge of Comparative Example 1, a foreign substance presumed to be derived from the scraper was found. Since the scraper comes into contact with the powder, the bridge can be mechanically broken, but the scraper may be scraped. That is, in stirring with a scraper, there is a possibility that the measurement accuracy may be deteriorated due to consolidation and foreign matter may be mixed into the powder.

In Comparative Example 2, as shown in FIG. 8, the emission amount was smaller than the theoretical value as the rotation speed increased, and in particular, the deviation from the theoretical value was large at the rotation speed of 400 rpm or more. This is presumed to be due to the powder bridge. With ultra-lightweight powder, the vibration of the hopper is not easily transmitted to the powder, and there is a high possibility that the generation of bridges cannot be suppressed by external impact from the knocker.

As described in detail above, according to the powder supply method of the present embodiment, the hopper portion 10 is rotated and forward rotation and reverse rotation are alternately repeated. Therefore, the powder in the hopper portion 10 is rotated by reversing the rotation direction. Inertial force acts on the surface, and the generation of bridges can be suppressed. Further, since the hopper portion 10 is not provided with a member such as a stirring member that comes into contact with the powder, the possibility of foreign matter being mixed is small.

It should be noted that this embodiment is merely an example and does not limit the present invention in any way. Therefore, as a matter of course, the present invention can be improved and modified in various ways within the range not deviating from the gist thereof. For example, the powder supplied by the supply method of the present invention is not limited to the conductive material. It is particularly useful when supplying a powder having a bulk density of 0.1 g / cm ³ or less.

Further, in the present embodiment, the inversion is repeated at a fixed cycle, but the period until the next inversion may be shorter than the transmission period T, and may not be at regular intervals. Further, the constant rotation period t and the rotation speed may be different between the forward rotation and the reverse rotation, and may not be constant regardless of the rotation direction. Even in that case, it is preferable to perform the next inversion at a timing shorter than the transmission period T from the immediately preceding inversion period r. Further, it is not necessary to keep the hopper portion 10 constantly rotating, and there may be a stop period.

Further, the timing at which the rotation of the hopper portion 10 is started may be after the powder is charged into the hopper portion 10 or before the powder is charged. It is desirable to repeat the forward rotation and the reverse rotation of the hopper portion 10 at least during the period when the hopper portion 10 has the powder and the screw portion 20 is operated to supply the powder.

Further, the shape of the hopper portion 10 is not limited to a cone, and may be an elliptical cone or a pyramid. Further, the hopper portion 10 is not limited to the funnel shape, and may be, for example, a cylindrical shape. Further, the screw 22 may be a uniaxial type or a biaxial type.

Further, in the present embodiment, the hopper portion 10 arranged in an upright position is shown, but for example, a hopper arranged at an angle with respect to the rotation axis may be used. Further, the rotation axis of the hopper may be deviated from the central axis of the hopper portion 10. However, it is desirable that the rotation axis is at a position that passes through the inside of the opening 12.

1 Powder supply device 10 Hopper part 11 Rotating shaft 12 Opening P Powder

Claims (1)

It is a powder supply method that supplies powder from a hopper.
The powder is put into the hopper, and the powder is put into the hopper.
The powder is supplied from the opening at the bottom of the hopper,
With the powder inside the hopper, the hopper is rotated around a rotation axis passing through the inside of the opening.
The hopper is alternately rotated in the forward direction at a constant forward rotation speed for a forward rotation period and in the reverse rotation at a constant reverse rotation speed for a reverse rotation period .
A powder supply method characterized by this.

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