Detection method

Abstract

Provided is a detection method capable of detecting clogging of a nozzle with high accuracy even in a case where a powder vertically falls or a case where the nozzle has a plurality of ejection ports in a powder coating device that uses carrier gas to transport powder and eject the powder from the nozzle. The detection method for detecting clogging of a nozzle in a powder coating device that uses carrier gas to transport powder and eject the powder from the nozzle includes: a measurement step of measuring a flow rate of the carrier gas using an ultrasonic flowmeter; and a detection step of detecting clogging of the nozzle based on the measured flow rate of the carrier gas.

Description

Technical Field

[0001] This invention relates to a detection method. Background Technology

[0002] In manufacturing processes such as laser cladding, a technique for spraying powder with good repeatability and uniformity is needed. Patent Document 1 discloses a powder coating apparatus for monitoring the flow state of powder flowing within a conduit. This powder coating apparatus monitors the flow state of the powder by measuring the powder flow rate using a microwave sensor or by measuring the internal pressure of the conduit using a pressure sensor.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2004-24989 Summary of the Invention

[0004] Depending on the structure of the powder coating apparatus, the method disclosed in Patent Document 1 sometimes cannot accurately and sufficiently detect nozzle blockage.

[0005] For example, in structures where powder falls within a vertically positioned conduit, it is difficult to detect nozzle clogging based on powder flow rate. This is because the powder falling velocity is almost constant and unrelated to nozzle clogging. Furthermore, in cases where the nozzle has multiple outlets, it is difficult to detect nozzle clogging based on the internal pressure of the conduit. This is because even if only a portion of the nozzle is clogged, the internal pressure of the conduit is unlikely to change, making it difficult to distinguish from the effects caused by variations in external pressure (atmospheric pressure).

[0006] Therefore, for powder coating devices with the above structure, there is also a need for a method that can detect nozzle blockage with high precision.

[0007] The present invention was made in view of this situation and provides a detection method that can detect nozzle blockage with high precision in a powder coating apparatus that uses a carrier gas to transport powder and spray powder from a nozzle, even in the case of a structure where the powder falls vertically or where the nozzle has multiple spray ports.

[0008] The detection method of the present invention relates to a powder coating apparatus that uses a carrier gas to transport powder and spray the powder from a nozzle, and detects the clogging of the nozzle. The detection method includes the following steps: a measurement step, measuring the flow rate of the carrier gas using an ultrasonic flow meter; and a detection step, detecting the clogging of the nozzle based on the measured flow rate of the carrier gas.

[0009] Invention Effects

[0010] The present invention provides a detection method that can detect nozzle blockage with high precision in powder coating apparatuses that use carrier gas to transport powder and spray powder from nozzles, even in the case of a structure where the powder falls vertically or where the nozzle has multiple spray ports. Attached Figure Description

[0011] Figure 1 This is a schematic cross-sectional view of a powder coating apparatus that applies the detection method described in this embodiment.

[0012] Figure 2 This is a flowchart of the detection method involved in this embodiment.

[0013] Figure 3 This is a graph showing the time variation of the carrier gas flow rate measured in this embodiment.

[0014] Figure 4 It means Figure 3 A graph showing the cumulative flow of the flow over time intervals t=1 to 13 [s]. Detailed Implementation

[0015] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, for clarity, the following description and drawings are appropriately simplified. The right-handed xyz coordinate system shown in the figures is used to facilitate the explanation of the positional relationships of the constituent elements; the positive direction of the z-axis is vertically upward. In this invention, the "~" indicating a numerical range includes the values ​​listed before and after it as the lower and upper limits.

[0016] The detection method described in this embodiment detects nozzle blockage in a powder coating apparatus that uses carrier gas to transport powder and spray powder from a nozzle. Figure 1 This is a schematic cross-sectional view of the powder coating apparatus 1 using the detection method described in this embodiment. Figure 1 As shown, the powder coating apparatus 1 includes a conduit 11, an ultrasonic flow meter 12, and a nozzle 13.

[0017] The conduit 11 is a tube extending vertically, with its lower end connected to the nozzle 13. During powder coating, carrier gas G and powder P are introduced from the upper side of the conduit 11, pass through the interior of the conduit 11 and the nozzle 13, and are then ejected from the injection port 131 located at the front end of the nozzle 13. In this embodiment, the nozzle 13 has multiple injection ports 131.

[0018] The ultrasonic flow meter 12 is used to measure the flow rate of carrier gas G within the conduit 11 and is installed on the outer wall of the conduit 11. The ultrasonic flow meter 12 includes a pair of ultrasonic transceivers 121a and 121b. The ultrasonic transceivers 121a and 121b are respectively positioned upstream and downstream of the carrier gas G, separated by the conduit 11. The flow rate of the carrier gas G is calculated based on the velocity difference of the ultrasonic waves U between the ultrasonic transceivers 121a and 121b.

[0019] Here, for reference Figure 1 ,use Figure 2The detection method involved in this embodiment will be described. Figure 2 This refers to the detection method involved in this embodiment. For example... Figure 2 As shown, the flowchart of the detection method according to this embodiment includes a measurement step S1 and a detection step S2. The measurement step S1 and the detection step S2 are executed, for example, by a computer (not shown) that controls the powder coating apparatus 1.

[0020] In measurement step S1, the flow rate of carrier gas G is measured using ultrasonic flow meter 12. Next, in detection step S2, based on the flow rate of carrier gas G measured in measurement step S1, blockage of nozzle 13 is detected. For example, if the flow rate of carrier gas G is less than a predetermined threshold, it is determined that blockage has occurred in nozzle 13.

[0021] As explained in the embodiments described later, in the event of blockage in the nozzle 13, the flow rate of the carrier gas G will decrease even in the case of a structure where the powder falls vertically or in the case where the nozzle has multiple injection ports. Therefore, according to the detection method of this embodiment, nozzle blockage can be detected with high precision in a powder coating apparatus having the above-described structure.

[0022] Furthermore, in measurement step S1, it is preferable to measure the flow rate of the carrier gas G near the nozzle 13. The flow rate of the carrier gas G near the nozzle 13 changes sensitively to the blockage of the nozzle 13, thus enabling more accurate detection of nozzle blockage. Specifically, by placing the ultrasonic flow meter 12 near the nozzle 13, the flow rate of the carrier gas G near the nozzle 13 can be measured.

[0023] Furthermore, in detection step S2, the number of blockages in the multiple injection ports 131 can be detected based on the flow rate of the carrier gas G. For example, the flow rate can be divided according to a threshold in the following manner to detect the number of blockages: if the flow rate of the carrier gas G is below the first threshold, it is determined that there is more than one blockage; if it is below the second threshold, it is determined that there are more than two blockages.

[0024] Furthermore, in the measurement step S1, the flow rate of the carrier gas G is measured from the reference time determined based on the time when the powder P is introduced into the powder coating apparatus 1 until a predetermined time has elapsed. In the detection step S2, the blockage of the nozzle 13 can be detected based on the cumulative value of the flow rate of the carrier gas G.

[0025] The following is a specific example. First, in the measurement step S1, the flow rate of the carrier gas G is measured from the time the powder P is introduced into the powder coating apparatus 1 until a predetermined time has elapsed. Next, in the detection step S2, if the cumulative flow rate of the carrier gas G over the predetermined time is less than a predetermined threshold, it is determined that a blockage has occurred in the nozzle 13. In this way, the influence of changes in the flow rate of the carrier gas G over time can be reduced, and the blockage of the nozzle 13 can be detected with higher accuracy.

[0026] [Example]

[0027] Next, specific embodiments of the present invention will be described. In this embodiment, the flow rate of the carrier gas as the powder passes through a powder coating apparatus having a structure in which powder falls vertically, and having four spray nozzles, was measured. The measurement was repeated by changing the number of spray nozzles with blockages to "0 (no blockage)", "1", "2", "3", and "4".

[0028] Figure 3 This is a graph showing the time variation of the carrier gas flow rate measured in this embodiment. Figure 3 The horizontal axis represents time t (in seconds), and the vertical axis represents the relative flow rate of the carrier gas. A solid line represents the case where the number of blocked injection nozzles is 0, a short dashed line represents 1, a long dashed line represents 2, a single-dotted line represents 3, and a double-dotted line represents 4. Additionally, in... Figure 3 In the graph, the time t when the powder is introduced into the powder coating device is set to t=1 [s].

[0029] like Figure 3 As shown, regardless of the number of blockage points, the carrier gas flow rate decreases immediately after the powder is introduced into the powder coating apparatus (t=1–3 s). This is believed to be because the powder acts as a resistance to the flow of the carrier gas. Furthermore, the flow rate remains almost constant during the period the powder passes through the powder coating apparatus (t=3–11 s), and increases immediately after the powder is sprayed (t=11–13 s). This is believed to be because the powder disappears from the powder coating apparatus, making the carrier gas flow more easily. Afterwards (t=13–16 s), the flow rate before the powder is introduced into the powder coating apparatus (t=0–1 s) remains almost the same.

[0030] Figure 4 It means Figure 3 A graph showing the cumulative flow of water during the time intervals t=1 to 13 [s]. (Example) Figure 4As shown, it can be seen that the cumulative flow decreases as the number of blocked locations increases. In this embodiment, the cumulative flow (relative amount) is 244 when there are 0 blocked locations, 241 when there is 1 blocked location, 237 when there are 2 blocked locations, 232 when there are 3 blocked locations, and 223 when there are 4 blocked locations.

[0031] Therefore, in the powder coating device in the above experiment, when measuring the flow rate under the same conditions, if the cumulative flow rate at time t=1~13[s] is 242 or higher, it can be determined that there is no blockage; if it is 238~241, it can be determined that there is 1 blockage; if it is 233~237, it can be determined that there are 2 blockages; if it is 224~232, it can be determined that there are 3 blockages; and if it is below 223, it can be determined that there are 4 blockages.

[0032] Thus, it was confirmed that even in the case of a structure where the powder falls vertically or in the case of a nozzle with multiple nozzle orifices, the number of nozzle orifices blocked is correlated with the flow rate of the carrier gas, and the blockage of the nozzle orifices can be detected based on the flow rate of the carrier gas.

[0033] The above description describes specific embodiments, but the present invention is not limited to the above embodiments. The present invention is not limited to the above embodiments and can be appropriately modified without departing from the spirit of the invention.

[0034] Symbol Explanation

[0035] 1-Powder coating device, 11-Conduit, 12-Ultrasonic flow meter, 121a, 121b-Ultrasonic transceiver, 13-Nozzle, 131-Injection port, G-Carrier gas, P-Powder, U-Ultrasonic.

Claims

1. A detection method, characterized in that, In a powder coating apparatus that uses a carrier gas to transport powder and spray the powder from a nozzle, detecting nozzle blockage includes the following steps: The measurement procedure involves using an ultrasonic flow meter to measure the flow rate of the carrier gas. and The detection step involves detecting nozzle blockage based on the measured flow rate of the carrier gas.

2. The detection method according to claim 1, characterized in that, The nozzle has multiple injection ports. In the detection step, several blockages are detected in the plurality of injection nozzles.

3. The detection method according to claim 1, characterized in that, In the measurement step, the flow rate of the carrier gas near the nozzle is measured.

4. The detection method according to claim 1, characterized in that, In the measurement step, the flow rate of the carrier gas is measured from a reference time determined based on the moment when the powder is introduced into the powder coating apparatus until a predetermined time has elapsed. In the detection step, the nozzle blockage is detected based on the cumulative value of the carrier gas flow rate.

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