Air bubble detector and fixed amount discharge device using said air bubble detector

Abstract

An air bubble detector according to the present invention comprises: a pump that causes a liquid to flow inside piping; a plurality of flowmeters; and a determination unit.　The plurality of flowmeters are arranged in series in the piping. The pump repeatedly initiates and stops pumping from the upstream side of the flowmeters so as to generate a pulsating flow in the liquid. From the difference between the flow rate of the liquid as obtained from an upstream flowmeter and the flow rate of the liquid as obtained from a downstream flowmeter, the determination unit detects whether there are air bubbles that have been mixed into the liquid flowing through the piping. Therefore, even if the viscosity of the liquid is high, the presence or absence of air bubbles retained in the liquid can be measured.

Description

Bubble detection device and metering discharge device using the same 【0001】 The present invention relates to a bubble detection device and a metering discharge device using the same, and more particularly, to a bubble detection device capable of detecting bubbles mixed in a high-viscosity liquid and a metering discharge device using the same. 【0002】 Since a dispenser can discharge a fixed amount of liquid, it is used for various applications such as adhesion and sealing. However, if bubbles are mixed in the liquid, even if the extrusion amount is constant, the amount of liquid discharged will change, and the accuracy of the discharge amount will decrease. 【0003】 Patent Document 1 discloses a flow meter that measures the flow rates of a liquid and bubbles by utilizing the fact that in a vertically arranged pipe, the flow velocity of bubbles mixed in the liquid flowing from bottom to top becomes faster on the downstream side than on the upstream side by the amount of buoyancy. 【0004】 Japanese Patent Application Laid-Open No. 2016-40544 【0005】 However, since the flow meter of Patent Document 1 utilizes the fact that bubbles in the liquid float due to buoyancy and the liquid and bubbles separate over time, for example, it cannot be measured in a high-viscosity liquid such as an adhesive or grease, and the amount of bubbles that continue to be held in the high-viscosity liquid cannot be measured. 【0006】 The present invention has been made in view of the problems of such conventional technologies, and an object thereof is to provide a bubble detection device capable of measuring the presence or absence of bubbles held in a liquid even when the viscosity of the liquid is high, and a metering discharge device using the same. 【0007】 As a result of intensive studies to achieve the above object, the present inventor has found that by repeating the pumping and stopping of the liquid to generate a pulsating flow in the liquid in the pipe and changing the volume of the bubbles mixed in the liquid, the above object can be achieved, and the present invention has been completed. 【0008】In other words, the bubble detection device of the present invention comprises a pump for flowing liquid into a pipe, a plurality of flow meters, and a determination unit. The plurality of flow meters are arranged in series in the pipe, the pump repeatedly pumps and stops from upstream of the flow meters to create a pulsating flow in the liquid, and the determination unit detects the presence or absence of bubbles mixed in the liquid flowing in the pipe based on the difference between the liquid flow rate obtained from the upstream flow meter and the liquid flow rate obtained from the downstream flow meter. 【0009】 Furthermore, the quantitative dispensing device of the present invention comprises a liquid tank, a dispensing valve, and a bubble detection device, wherein the liquid tank is located upstream of the bubble detection device, and the dispensing valve is located downstream of the bubble detection device. The bubble detection device is the bubble detection device of the present invention, and the flow meter on the upstream side and the flow meter on the downstream side are arranged with an interval such that the volume of the piping between them is twice the amount of one dispensing. 【0010】 According to the present invention, a pulsating flow is generated in the liquid inside the pipe, changing the volume of air bubbles mixed in the liquid. Therefore, it is possible to provide a bubble detection device that can detect the presence or absence of air bubbles mixed in a liquid even if the liquid has high viscosity, and a quantitative dispensing device using the bubble detection device. 【0011】 This is a schematic diagram showing an example of the quantitative dispensing device of the present invention. This graph shows a temporary flow rate difference between the upstream and downstream sides of a location where no air bubbles are present. This diagram illustrates the relationship between the presence or absence of air bubbles and whether the liquid can be used. This graph shows the flow rates measured by flow meters at the location of air bubble contamination and before and after it. 【0012】 <Bubble Detection Device> The bubble detection device of the present invention will now be described in detail. The bubble detection device of the present invention detects bubbles mixed in the liquid flowing through the pipe 4, and as shown in Figure 1, comprises a pump 3 for flowing the liquid into the pipe, a plurality of flow meters 1, and a determination unit 2. 【0013】The multiple flow meters 1 described above are arranged in series at predetermined intervals from the upstream side to the downstream side of the piping 4, with two flow meters forming a set of flow meter groups, and each flow meter in the flow meter group measures the flow rate at the location where it is placed. 【0014】 The pump 3 described above is located upstream of the upstream flow meter 1a, which is part of the flow meter group, and repeatedly pumps and stops, changing the pressure in the piping and creating a pulsating flow in the liquid flowing through the piping. By creating a pulsating flow in the liquid in the piping in this way, the volume of air bubbles mixed in the liquid changes. 【0015】 In other words, as the pressure increases due to the start of pumping, as shown in the upper part of Figure 2, if no air bubbles are present, the liquid is incompressible, so the liquid starts flowing simultaneously on both the upstream and downstream sides when pumping begins. On the other hand, if air bubbles are present, the bubbles collapse first and absorb the applied pressure, so the liquid does not flow. After the bubbles have sufficiently collapsed, the pressure is transmitted to the liquid and the liquid starts flowing. As shown in the lower part of Figure 2, a temporary flow rate difference occurs between the upstream and downstream sides of the point where the air bubbles are present. 【0016】 The bubble detection device of the present invention has a determination unit that obtains the flow rate at each location using two flow meters that constitute a set of flow meter groups, and detects the presence or absence of bubbles mixed in the liquid from the temporary deviation in the flow rate as shown in the lower part of Figure 2. 【0017】 Furthermore, from the graph of the time change in flow velocity shown at the bottom of Figure 2, the area enclosed by the flow rate change curve on the upstream side and the flow rate change curve on the downstream side can be determined, and from this, the amount of bubbles can be measured. 【0018】 Since the amount of bubbles measured by the bubble detection device of the present invention is the sum of the bubbles present between the two flow meters, it is possible to measure the amount of bubbles mixed in even if each individual bubble is small. 【0019】Furthermore, since the above area changes depending on the pressure, pumping speed, and viscosity of the liquid during pumping, by investigating the relationship between the above area and the amount of bubbles mixed in under the operating conditions in advance, it is possible to measure the amount of bubbles mixed in the liquid even if the liquid has high viscosity. In addition, in this invention, "high viscosity" means that the viscosity at 20°C is approximately 110 mPa·s or higher. 【0020】 The bubble detection device of the present invention preferably has three or more flow meters. By having three or more flow meters, multiple flow meter groups can be formed, making it possible to determine whether or not bubbles are present in each flow meter group, and thus improving the resolution by making it possible to pinpoint the location of bubbles in the piping. In addition, it becomes possible to detect the amount of bubbles mixed in per unit length of piping from the amount of bubbles present between the upstreammost flow meter and the downstreammost flow meter. 【0021】 In the above-mentioned piping, it is preferable that the diameter of the section where the flow meter is installed is smaller than that of other sections. By making the diameter of the piping smaller only at the location where the flow meter is installed, the flow velocity at that location increases, improving detection accuracy, while minimizing the impact on the average diameter of the entire piping. This suppresses the increase in fluid transfer resistance, and since it does not require a smaller pump or high pressure resistance of the piping, it is possible to reduce the overall cost of the system. 【0022】 As a pump that repeatedly pumps and stops as described above, examples of pumps that can be used include piston pumps, plunger pumps, diaphragm pumps, and grease guns using a bubble syringe system. 【0023】 The above-mentioned flow meter is preferably an ultrasonic flow meter. An ultrasonic flow meter is a flow meter that utilizes the property of ultrasound to penetrate and propagate through objects, and can be installed on the outside of a pipe to measure the flow rate inside the pipe, so there is no pressure loss due to the flow meter. 【0024】 In addition, if air bubbles are present in the liquid, some of the ultrasonic waves are reflected at the interface between the liquid and the bubbles, causing the ultrasonic waveform to become distorted. This allows for the detection of the moment when the bubbles pass through the flow meter. 【0025】 Furthermore, as described above, by combining the bubble position identified by the flow meter group with the bubble position caused by the distortion of the ultrasonic waveform, it is possible to avoid misidentification of flow meter malfunction (failure) due to the distortion of the ultrasonic waveform. 【0026】 The determination unit described above can synchronize the measured values ​​of the multiple flow meters when the liquid flow is in a steady flow or stopped state. 【0027】 When a liquid is flowing at a constant speed or is stopped, the pressure on the liquid in the piping does not change, so the flow rate measured by all flow meters will be the same. 【0028】 At this time, by aligning all the measurement values ​​from the multiple flow meters mentioned above, variations between the flow meters can be corrected, improving the accuracy of detecting the amount of bubbles mixed in the liquid. 【0029】 <Quantitative Dispensing Device> The quantitative dispensing device of the present invention comprises a liquid tank 6, a pipe 4 through which the liquid flows, a pump 3 for pressurizing the liquid, a plurality of flow meters 1, a determination unit 2, and a discharge valve 5 for dispensing liquid from the pipe 4, and is a device that dispenses a fixed amount of liquid, and the pipe 4, the pump 3, the plurality of flow meters 1 and the determination unit 2 constitute the bubble detection device of the present invention. 【0030】 Since the quantitative dispensing device of the present invention is equipped with the above-mentioned bubble detection device, it can detect the amount and location of bubbles mixed in the piping. Therefore, by discarding the liquid in the area where bubbles are mixed in and using only the liquid in the area where bubbles are not mixed in, the amount of liquid used can always be kept constant. 【0031】 Specifically, the upstream and downstream flow meters that make up a set of flow meter groups are placed at an interval such that the volume of the piping between them is twice the volume of a single discharge. 【0032】As shown in Figure 3, by discarding the liquid from the location where air bubbles are detected, plus the liquid from the two locations before and after that location—a total of three discharge volumes—even if small air bubbles below the detection limit are present in addition to the discharge volume at the location where air bubbles were detected, that discharge volume will be discarded, making it possible to use only the liquid from locations without air bubbles. 【0033】 In this process, instead of pumping the entire amount for one discharge at once, the pumping and stopping cycle is repeated multiple times to deliver the equivalent amount. This improves the resolution of areas where air bubbles are present, thereby increasing the accuracy of the amount of liquid used. 【0034】 The quantitative dispensing device of the present invention may further include a discharge valve 7. This discharge valve is positioned to divide the volume of the piping between two flow meters that constitute a set of flow meters by half. 【0035】 This allows one of the two discharge volumes of liquid between the two flow meters—the upstream liquid—to be discharged outside the piping. 【0036】 In particular, when there are three or more flow meters and multiple groups of flow meters, by installing a discharge valve between two flow meters that make up the downstream flow meter group, bubbles can be detected by the upstream flow meter group and discharged from the piping without leaving any bubbles behind. The presence or absence of bubbles can then be reconfirmed by the downstream flow meter group, allowing for continuous use of the liquid discharged from the discharge valve. 【0037】 Furthermore, the liquid discharged from the aforementioned discharge valve can be returned to the liquid tank and deaerated for reuse. 【0038】 As described above, the quantitative dispensing device of the present invention allows for the discharge of liquid from areas where air bubbles have been introduced, and the accuracy of the liquid discharge volume is high. This eliminates variations in the amount of adhesive or grease applied, making it possible to apply the adhesive or grease without excess or deficiency. 【0039】 The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples. 【0040】 [Example] A bubble detection device as shown in Figure 1 was fabricated, and bubbles were introduced at three locations: upstream of the two flow meters, between the two flow meters, and downstream of the two flow meters. The flow rate at each location where the two flow meters were placed was measured. Figure 4 shows graphs of the flow rates measured by the upstream and downstream flow meters. 【0041】 In Figure 4, the first peak in the graph where the bubbles are between the two flow meters and downstream of the two flow meters shows a significantly higher flow rate downstream. This is because the system was pressurized with the downstream discharge valve closed and then opened; therefore, the first peak was ignored. 【0042】 When the bubbles are upstream of the flow meter group, and when the bubbles are downstream of the flow meter group, the graphs of the upstream and downstream flow meters overlap and show almost the same flow rate. However, when the bubbles are within the flow meter group, that is, between the two flow meters, the flow rate of the downstream flow meter changes with a delay compared to the flow rate of the upstream flow meter. Therefore, it was confirmed that the bubble detection device of the present invention can detect the amount and location of the bubbles that have been introduced. 【0043】 1a Flow meter (upstream) 1b Flow meter (downstream) 2 Judgment unit 3 Pump 4 Piping 5 Discharge valve 6 Liquid tank 7 Discharge valve

Claims

1. A bubble detection device comprising a pump for flowing liquid into a pipe, a plurality of flow meters, and a determination unit for detecting the amount of bubbles mixed in the liquid, wherein the plurality of flow meters are arranged in series in the pipe, the pump generates a pulsating flow in the liquid by repeatedly pumping and stopping from upstream of the flow meters, and the determination unit detects the presence or absence of bubbles mixed in the liquid flowing in the pipe based on the difference between the liquid flow rate obtained from the upstream flow meter and the liquid flow rate obtained from the downstream flow meter.

2. The bubble detection device according to claim 1, characterized in that it estimates the amount of bubbles from the area enclosed by the upstream flow rate time change curve obtained from the upstream flow meter and the downstream flow rate time change curve obtained from the downstream flow meter.

3. The bubble detection device according to claim 1, characterized in that it has three or more of the above-mentioned flow meters.

4. The bubble detection device according to claim 1, characterized in that the diameter of the piping at the location where the flow meter is installed is smaller than that of other locations.

5. The bubble detection device according to claim 1, wherein the flow meter is an ultrasonic flow meter.

6. The bubble detection device according to claim 1, characterized in that the determination unit aligns the measured values ​​of the plurality of flow meters when the liquid flow is in a steady flow or stopped state.

7. A quantitative dispensing device comprising a liquid tank, a discharge valve, and a bubble detection device, wherein the liquid tank is located upstream of the bubble detection device and the discharge valve is located downstream of the bubble detection device, and which dispenses a fixed amount of liquid, wherein the bubble detection device is the bubble detection device described in any one of claims 1 to 6, and the upstream flow meter and the downstream flow meter are arranged at an interval such that the volume of the piping between them is twice the amount of liquid dispensed in one discharge.

8. The quantitative discharge device according to claim 6, further comprising a discharge valve, wherein the discharge valve is positioned to divide the volume of the piping between the two flow meters by half.

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