JP3865737B2 - Powder flow sensor - Google Patents

Description

  The present invention relates to a powder flow rate sensor that accurately measures the flow rate of powder flowing in a flow path.

  Conventionally, when a powder is cut out and transported, for example, Patent Document 1 proposes a method of automatically cutting out a powder and transporting it quantitatively. That is, in this method, as shown in FIG. 6, for example, a piezoelectric element 32 that is a means for generating ultrasonic vibration is attached to one end of a hollow pipe 31 made of acrylic, and an AC voltage is applied by an AC power source 33. Then, a vibration in the radial direction is given by the piezoelectric element 32, a traveling wave is generated in the longitudinal direction by the vibration, and the traveling wave is attenuated toward the other end portion, whereby the inside of the hollow pipe 31 is indicated by an arrow F. The powder is intended to be conveyed in the direction.

Patent Document 2 describes a flow sensor that detects a change in capacitance of powder.
Japanese Patent Laid-Open No. 4-125214 JP-A-8-271301

  However, when trying to cut out a small amount of powder by the conventional method described above, there is a drawback that it takes time to adjust the AC voltage applied to the piezoelectric element 32. In particular, when trying to apply to a batch process that cuts out quantitatively, it is time consuming because the accuracy must be confirmed by weighing with a weighing rod or electronic scale, so accuracy is sacrificed in the mass production process. In fact, the actual situation is to increase speed and efficiency.

  Further, in the flow sensor described in Patent Document 2, since the measured value varies greatly depending on the atmospheric environmental conditions such as temperature and humidity, in order to obtain the accuracy for practical use, these environmental changes are performed by some means. There is a great difficulty that it must be corrected without time delay.

  The present invention has been made in order to solve the above-described problems of the prior art, and realizes a powder flow rate sensor that continuously and accurately measures the flow rate of powder flowing in a flow path. For the purpose.

  The present invention provides a measurement electrode provided in a powder flow path and detects the flow rate of the powder as a change in capacitance, and responds to changes in the environmental conditions in which air is sent and the measurement electrode is placed. And a reference electrode used for correction is a capacitance type powder flow rate sensor configured to be provided in parallel, and preferably, the measurement electrode is a powder flow path. A source electrode and a sense electrode forming a curved pair disposed opposite to the outer periphery of the cylindrical tube, and a pair of guard electrodes provided between them, and the reference electrode is fed with air 2. The powder according to claim 1, comprising a curved pair of source and sense electrodes disposed opposite to the outer periphery of the cylindrical tube, and a pair of guard electrodes provided between them. It is a body flow sensor.

  According to the present invention, while measuring electrodes and reference electrodes are used in combination to correct changes in environmental conditions, flow measurement is performed in real time and continuously with high accuracy without directly contacting the powder. Therefore, for example, there is an excellent effect that accurate cutting control can be performed when a powder is quantitatively cut out using a powder supply device.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a side view showing the structure of a powder flow rate sensor according to an embodiment of the present invention in a partial cross section, and FIG. 2 is a cross sectional view taken along the line II in FIG.

  As shown in FIGS. 1 and 2, a measurement electrode 12 for detecting the flow rate of powder as a change in capacitance in an outer cylinder 11 and a reference electrode 13 used for correction corresponding to a change in environmental conditions are arranged in parallel. It is provided and configured.

  The measurement electrode 12 is provided between the source electrode 15 and the sense electrode 16 that form a curved pair disposed opposite to the outer periphery of a cylindrical tube 14 such as a quartz glass tube that is used as a powder flow path, and in the middle thereof. The reference electrode 13 includes a source electrode 19 and a sense electrode 20 that form a curved pair disposed opposite to the outer periphery of a cylindrical tube 18 such as a quartz glass tube, and the like. It is comprised with a pair of guard electrode 21 provided in the middle. Air is sent from the air supply device 23 to the reference electrode 13 through the air supply pipe 22.

  Then, the dielectric constant ε of the powder to be measured is set in advance in the powder flow rate calculation control device 7 as a circuit constant, and air is supplied from the air supply device 23 to the reference electrode 13 prior to the measurement. The environmental condition of the atmosphere in which the body is placed is measured and given as a correction value to the powder flow rate calculation control device 7 of FIG. 4 to be described later.

  Next, the flow rate of the powder supplied from the stack 1 to the powder transport cylinder 3 is measured by the measurement electrode 12 and is processed by the powder flow rate calculation control device 7. In this way, by correcting the atmospheric environmental conditions using the reference electrode 13, the zero point drift of the capacitive flow sensor can be kept low, and the linearity can be dramatically improved. Is possible.

  FIG. 3 is a side view showing another configuration example of the measurement electrode. In this example, the source electrode 15 and the sense electrode 16 of the measurement electrode 12 are formed by being wound in a spiral shape with an angle θ as shown in FIG. By doing so, the influence of the passage position of the powder on the measurement value is reduced, and a more accurate flow rate can be measured. Note that the winding angle θ is 45 °, for example, in JP-A-8-271301. However, this Japanese Patent Application Laid-Open No. 8-271301 has no specific description about the value of the length L of each of the source electrode 15 and the sense electrode 16.

  As a result of repeating various experimental studies, the inventors have found that the length L of each of the source electrode 15 and the sense electrode 16 is 360 ° around the cylindrical tube 14 when the angle θ is 45 °. I found a good thing. That is, by setting it to 360 °, even if there is a powder density difference in the plane of one cross section when passing through the cylindrical tube 14, the source electrode 15 and the sense electrode 16 arranged at 360 ° Since all the positions of the electric flux density are recorded and pass through the entire distance, the average value is detected. If the length L is smaller than 360 °, the distance across the electrode becomes shorter, which causes an error. On the other hand, if the length L is larger than 360 °, the position of the same electric flux density is re-recorded. It doesn't make sense for accuracy.

  Furthermore, it is not limited to 360 ° that makes a round of the cylindrical tube 14, but if it is set to an integral multiple of 360 °, the same powder will be reliably recorded over all positions of the electric flux density under the same conditions. This can be said to be preferable because the accuracy can be further increased. On the contrary, when the density difference of the powder in one cross section does not matter so much, it is needless to say that the cylindrical tube 14 does not necessarily have a length of 360 °.

  Further, when the length L of the source electrode 15 and the sense electrode 16 of the measurement electrode 12 is limited as described above, it is natural that the measurement conditions of the reference electrode 13 are matched with those of the measurement electrode 12. It is desirable that the lengths of the source electrode 19 and the sense electrode 20 are similarly limited.

  Next, an example of the usage state of the powder flow rate sensor of the present invention will be described with reference to the block diagram of FIG. Reference numeral 1 denotes a stack for storing the powder 2, and 3 is a powder transport cylinder made of a cylindrical tube made of acrylic or the like for transporting the powder 2, and an upper end opening thereof is connected to a lower end supply port 1 a of the stack 1. Reference numeral 4 denotes a powder supply device that is attached to the horizontal portion 3a of the powder conveying cylinder 3. For example, an ultrasonic vibration device using a piezoelectric element, a screw feeder, a table feeder, a belt conveyor, or the like is used.

  Reference numeral 5 denotes a powder flow rate sensor that is attached to the vertical portion 3b of the powder conveying cylinder 3 and drops down the vertical portion 3b of the powder conveying cylinder 3. For example, the static flow sensor of the present application using the principle of capacitance is used. A capacitive flow sensor is suitable. 6 is a powder container such as a capsule.

  Reference numeral 7 denotes a powder flow rate calculation control device such as a microcomputer, which inputs a flow rate signal from the powder flow rate sensor 5 through an AD converter or the like, and based on a predetermined cutout amount W (g) given in advance. The level of applied voltage to be applied to the powder supply device 4 is calculated, and a control signal is output to the powder supply device 4 based on the calculated value, and the amount of powder to be fed into the powder container 6 in a feedback manner Control.

  With this configuration, the powder 2 accommodated in the stack 1 is sent to the horizontal portion 3 a of the powder transport cylinder 3 by starting the powder supply device 4 and passes through the powder supply device 4. The powder 2 that has fallen naturally passes through the vertical portion 3b, passes through the powder flow rate sensor 5, and is filled in the powder container 6. The amount of the powder 2 filled in the powder container 6 is measured by the powder flow rate calculation control device 7 collecting and analyzing the output signal of the powder flow rate sensor 5, and controls the powder supply device 4 each time. By doing so, quantitative cutout is performed.

  In the configuration of FIG. 4, the powder flow rate sensor of the present invention is used to quantitatively measure light calcium carbonate S-10 powder, which is one of the standard powders of the brand name APPIE (Japan Powder Industrial Technology Association). As a result of performing control of cutting out n = 5 times for each of 4 types of 2g, 4g, 6g, and 8g, as shown in FIG. 5, the results were as follows: high: 4.7%, minimum: 0.1%, average: 2.5% Could get.

It is a side view which shows the structure of the electrostatic capacitance type powder flow sensor used for this invention in a partial cross section. It is II sectional view taken on the line of FIG. It is a side view which shows the other structural example of the measurement electrode used for an electrostatic capacitance type powder flow sensor. It is a block diagram which shows an example of the usage condition of the powder flow sensor of this invention. It is a characteristic view which shows an example of the measurement result by this invention. It is a perspective view which shows the prior art example of powder conveyance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stack 1a Lower end supply port 2 Powder 3 Powder conveyance cylinder 3a Horizontal part 3b Vertical part 4 Powder supply apparatus 5 Powder flow rate sensor 6 Powder container 7 Powder flow rate calculation control apparatus
10 Capacitive flow sensor
11 outer cylinder
12 Measuring electrode
13 Reference electrode
14, 18 Cylindrical tube
15, 19 Source electrode
16, 20 sense electrodes
17, 21 Guard electrode
22 Air supply pipe
23 Air supply device
31 Hollow pipe
32 Piezoelectric element
33 AC power supply

Claims (2)

  Measurement electrode (12) provided in the powder flow path to detect the flow rate of the powder as a change in capacitance, and changes in environmental conditions in which air is sent and the measurement electrode (12) is placed And a reference electrode (13) used for correction corresponding to a capacitance type powder flow rate sensor. A source electrode (15) and a sense electrode (16) that form a curved pair in which the measurement electrode (12) is disposed opposite to the outer periphery of a cylindrical tube (14) that is a powder flow path, and these And a pair of guard electrodes (17) provided in the middle, and the reference electrode (13) forms a curved pair disposed facing the outer periphery of the cylindrical tube (18) into which air is fed 2. The powder flow rate sensor according to claim 1, comprising an electrode (19) and a sense electrode (20), and a pair of guard electrodes (21) provided between them.

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