High concentration dust sensor

Abstract

To provide a high-concentration dust sensor which enables high dust concentrations to be stably measured over a long period and enables measurement accuracy to be improved, thereby enabling a maintenance period to be significantly extended.SOLUTION: The high-concentration dust sensor comprises a housing 10, a ventilation device 20, an air circulation device 30, a microparticle detection sensor 40, and a control device 50. The housing has a suction port 12 and an exhaust port 14. The ventilation device forms a ventilation air flow B1 for introducing dust-containing air G through the suction port and discharging from the exhaust port, and forms a primarily processed air A1 having had dust P removed by gravity settling effect in a primary dust-removal space S1. The air circulation device forms a circulation air flow B2 in the housing that is spatially or temporally isolated from the ventilation air flow, and forms a microparticle-containing air A2 having had dust removed again by gravity settling effect in a secondary dust-removal space S2. The microparticle detection sensor measures a microparticle concentration Y of the microparticle-containing air. The control device calculates an external dust concentration X from the microparticle concentration Y, by using a conversion coefficient K.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a high concentration dust sensor that measures the dust concentration inside a tunnel during excavation. [Background technology]

[0002] In tunnel excavation work, large amounts of dust are generated during processes such as blasting, mechanical excavation, waste disposal, concrete spraying, etc. Therefore, from the viewpoint of occupational safety and health, guidelines on dust control have been established, and there is a demand for measuring dust concentrations inside tunnels.

[0003] To meet this demand, the use of gravimetric and coefficient method measuring instruments is recommended. Gravimetric measuring instruments are devices based on the mass concentration measurement method, in which the weight of a filtered sample is measured and divided by the air flow rate to calculate the concentration. Although they are highly accurate, they are difficult to operate. Coefficient method measuring instruments are devices based on the relative concentration indication method, which calculates the concentration by multiplying the count (number of particles per unit time) measured by a relative concentration meter (digital dust meter) by a mass concentration conversion coefficient. However, coefficient method measuring instruments have problems such as high power consumption, batteries that do not last a day, being expensive, and requiring calibration every few months, which is too costly.

[0004] Therefore, it has been proposed to use a dust sensor device based on a light scattering method (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-126046, "Particle detection sensor, dust sensor, air conditioner, and method for controlling particle detection sensor" [Patent Document 2] International Publication No. 2017 / 217078, "Photoelectric dust sensor device and air conditioning equipment" Summary of the Invention [Problem to be solved by the invention]

[0006] The "dust sensor device based on the light scattering method" is composed of a light receiving section and a light emitting section. When particles that have entered the detection area are irradiated with an infrared light emitting diode from the light emitting section, scattered light is generated by the suspended dust particles, and this scattered light is received by the light receiving section. This causes a voltage corresponding to the amount of light received to be output. Hereinafter, the dust sensor device based on the light scattering method will be referred to simply as a “particle detection sensor.” Such particle detection sensors are already commercially available from several companies.

[0007] However, when the above-mentioned existing particulate matter detection sensor is used to measure the dust concentration inside a tunnel during excavation, the following problems arise. (1) The dust concentration in the tunnel is 2-3 mg / m3 during processes such as blasting, mechanical excavation, waste disposal, and concrete spraying. 3 The concentration is higher than this. In contrast, existing particulate detection sensors are primarily intended for detecting particulate matter in house ducts and distinguishing between cigarette smoke and can only detect low concentrations (e.g., 0 to 0.6 mg / m 3 Therefore, even if this particle detection sensor is used to measure the dust concentration inside a tunnel during excavation, the detection output becomes saturated and it is not possible to measure high dust concentrations. (2) When existing particulate detection sensors are used to measure the dust concentration inside a tunnel during excavation, the high concentration of dust causes the internal mechanism of the sensor to become dirty with dust in a short period of time (for example, about three weeks), making it impossible to continue using the sensor. In addition, the dust inside the tunnel contains large particles with a particle size exceeding 2.5 μm, so if a filtration-type dust filter is used, the dust filter will become clogged in a short period of time and will not be able to be used continuously.

[0008] The present invention has been devised to solve such problems. That is, the object of the present invention is to provide a high-concentration dust sensor that can stably measure high-concentration dust concentrations inside a tunnel being excavated for a long period of time, thereby improving measurement accuracy and significantly extending the maintenance interval. [Means for solving the problem]

[0009] According to the present invention, there is provided a hollow housing having an intake port and an exhaust port and otherwise sealed; a ventilation device that introduces dust-containing air having an external dust concentration from the outside through the air intake port, ventilates a part of the inside of the housing, and forms a ventilation airflow that is exhausted from the air exhaust port; an air circulation device that forms a circulating airflow in the housing that is spatially or temporally isolated from the ventilation airflow; The ventilation device has a primary dust removal space that reduces the flow velocity of the ventilation airflow and forms primary treated air from which a portion of the dust has been removed by a gravitational settling effect, The air circulation device has a secondary dust removal space that reduces the flow rate of the circulating airflow and forms fine particle-containing air from which a portion of the dust has been re-removed by a gravitational settling effect, Furthermore, a particle detection sensor for measuring a particle concentration of the particle-containing air; A high concentration dust sensor is provided, which includes a control device that controls the ventilation device, the air circulation device, and the particulate matter detection sensor, and calculates the external dust concentration using a conversion coefficient that converts the particulate matter concentration to the external dust concentration. Effect of the Invention

[0010] According to the configuration of the present invention, the ventilation device reduces the flow velocity of the ventilation airflow in the primary dust removal space and forms primary treated air from which some of the dust has been removed by the gravitational settling effect, so that some of the dust (e.g., relatively large-diameter dust) can be effectively removed without the risk of clogging.

[0011] In the secondary dust removal space, the air circulation device reduces the flow rate of the circulating air current and forms particulate-containing air from which a portion of the dust (e.g., relatively small-diameter dust) has been re-removed by the gravitational settling effect. This reduces the dust concentration in the particulate-containing air to a low concentration (e.g., 0 to 0.6 mg / m) suitable for existing particulate detection sensors. 3 ) and the particle concentration of the particle-containing air can be accurately measured by the particle detection sensor.

[0012] Furthermore, the control device can accurately calculate the external dust concentration using a conversion coefficient for converting the fine particle concentration into the external dust concentration.

[0013] Therefore, high concentrations (e.g., 2–3 mg / m3) in the tunnel during excavation 3 This enables stable measurement of dust concentration (external dust concentration) of up to 100m2 or more for a long period of time, thereby improving measurement accuracy and significantly extending maintenance intervals. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a block diagram of a particulate detection sensor disclosed in Patent Document 1. [Diagram 2] 1 is an overall configuration diagram of a high concentration dust sensor according to the present invention; [Diagram 3] FIG. 1 is a diagram showing an example of measurement of dust concentration in a tunnel using an existing particulate matter detection sensor. [Figure 4] 1 is a cross-sectional view showing an embodiment of a high concentration dust sensor according to the present invention. [Diagram 5] FIG. 5 is a cross-sectional view taken along line AA in FIG. [Figure 6] FIG. 11 is a cross-sectional view showing an embodiment of a comparator. [Figure 7] These are the measurement results of dust concentration inside the tunnel using test machines 1 and 2 and the comparison machine. [Figure 8] FIG. 13 is a diagram showing the transition of detection values ​​during a period when the dust level is low. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, common parts in each drawing are given the same reference numerals, and duplicated explanations will be omitted.

[0016] 1 is a block diagram of the particulate detection sensor disclosed in Patent Document 1. The particulate detection sensor is composed of a light-emitting element 1, a driving section 2, a light-receiving section 3, a pulse counter 4, a signal processing section 5, and a control section 6.

[0017] The light emitting element 1 projects projection light E1 onto a particle to be detected. The light emitting element 1 is, for example, a light emitting diode (LED) or a laser diode (LD).

[0018] The driving unit 2 drives the light-emitting element 1. The light-receiving unit 3 receives scattered light E2 from the fine particles. The pulse counter 4 counts the digitized binary pulse signal output from the light-receiving unit 3. The signal processing unit 5 stores and calculates the count value of the pulse counter 4. The control unit 6 controls the signal processing unit 5, the driving period of the light-emitting element 1, and the pulse count period of the pulse counter 4.

[0019] With this configuration, particles P that have entered the detection area A are irradiated with the infrared light emitting diode from the light emitting element 1, generating scattered light E2 due to the airborne dust, which is received by the light receiving unit 3. This causes a voltage corresponding to the amount of light received to be output, making it possible to measure the dust concentration in the detection area A.

[0020] FIG. 2 is a diagram showing the overall configuration of a high concentration dust sensor 100 according to the present invention. In this figure, a high concentration dust sensor 100 according to the present invention comprises a housing 10 , a ventilation device 20 , an air circulation device 30 , a particulate detection sensor 40 , and a control device 50 .

[0021] The housing 10 is hollow and has an intake port 12 and an exhaust port 14, and is otherwise sealed. In this example, the housing 10 is a rectangular parallelepiped with internal dimensions of width B, depth D, and height H. It is preferable that the height H is greater than the width B and the depth D. The intake port 12 and the exhaust port 14 are provided facing the inside of the tunnel (the right side of the figure in this example), in that order from below.

[0022] The ventilation device 20 introduces dust-containing air G from the outside through the intake port 12, ventilates a part of the inside of the housing, and forms a ventilation airflow B1 that is exhausted from the exhaust port 14. In this example, the ventilation device 20 has a ventilation fan 22 that is fixed to the inside of the exhaust port 14 and forms a ventilation airflow B1. The ventilation device 20 also has a primary dust removal space S1 that reduces the flow velocity of the ventilation airflow B1 and forms primary treated air A1 from which part of the dust P has been removed by the gravitational settling effect.

[0023] The primary dust removal space S1 is located upstream of the ventilation airflow B1, and removes dust particles P having a relatively large diameter as compared with the air circulation device 30. In the primary dust removal space S1, the ventilation airflow B1 is decelerated to a flow speed capable of removing relatively large-diameter dust P by the gravitational settling effect. The removed large-diameter dust P moves to, for example, the lower part of the housing 10 and accumulates.

[0024] The air circulation device 30 forms a circulating airflow B2 inside the housing that is spatially or temporally isolated from the ventilation airflow B1. The air circulation device 30 also has a secondary dust removal space S2 that reduces the flow speed of the circulating airflow B2 and forms fine particle-containing air A2 from which some of the dust P has been re-removed by the gravitational settling effect. The secondary dust removal space S2 is located in the middle of the circulating airflow B2, i.e., in the space outside the fine particle detection sensor 40, and removes dust P with a relatively small diameter compared to the ventilation device 20.

[0025] By "spatially isolated" it is meant that most of the recirculating airflow B2 does not come into direct contact with the ventilation airflow B1, and only a portion of the ventilation airflow B1 mixes with the recirculating airflow B2, for example by diffusion. In this example, the entire circulating airflow B2 is located relatively far from the upstream side of the ventilation airflow B1, and a portion of the circulating airflow B2 is located relatively close to the downstream side of the ventilation airflow B1, and a portion of the primary processing air A1 is mixed into the circulating airflow B2. Therefore, in this case, the circulating air flow B2 becomes fine particle-containing air A2 that contains a portion of the primary treatment air A1.

[0026] "Temporally isolated" means that the ventilation airflow B1 and the circulation airflow B2 are not formed at the same time. In the embodiment described later, this means an operation in which the ventilation fan 22 and the circulation fan 32 are alternately operated, with an interval period (rest period) being provided after the circulation fan 32 is stopped. In this case, when the ventilation fan 22 stops operating, the ventilation airflow B1 ceases to flow and the gravitational settling effect becomes prominent, so that the circulating airflow B2 becomes fine particle-containing air A2 from which dust has been further removed from the primary treatment air A1.

[0027] The air circulation device 30 has a circulation fan 32 that forms a circulating airflow B2. The circulation fan 32 is positioned so as to suck in the circulating airflow B2 from one end of the through-hole 42 of the particulate matter detection sensor 40 and discharge it from the other end (the right side in the figure). The circulating airflow B2 discharged from the through-hole 42 forms a circulating flow that passes through the outer space of the particulate matter detection sensor 40 and returns to the one end of the through-hole 42. This circulating airflow B2 contains a part of the primary treated air A1 in the secondary dust removal space S2 (the space outside the particulate detection sensor 40), and is decelerated to a flow velocity capable of removing relatively small-diameter dust P by the gravitational settling effect. The removed small-diameter dust P moves, for example, below the housing 10, and a part of it is exhausted from the exhaust port 14 together with the ventilation airflow B1, and the remainder is deposited below the housing 10.

[0028] The particulate matter detection sensor 40 measures the particulate matter concentration Y of the particulate matter-containing air A2. The particulate matter detection sensor 40 is the above-mentioned existing particulate matter detection sensor (a dust sensor device based on a light scattering method), and has a through hole 42 at its center, with a detection area A set at the middle position of the through hole 42.

[0029] The control device 50 controls the ventilation device 20, the air circulation device 30, and the particulate detection sensor 40, and calculates the dust concentration in the dust-containing air G (hereinafter, "external dust concentration X"). The control device 50 is, for example, a computer (for example, a microcomputer) having an input / output device, a storage device, and an arithmetic unit. The control device 50 may be installed inside or outside the housing 10, or in a remote location away from the housing 10.

[0030] The control device 50 stores in the storage device a conversion coefficient K for converting the fine particle concentration Y into the external dust concentration X. The control device 50 also calculates the external dust concentration X using the conversion coefficient K by the arithmetic unit. The conversion coefficient K can be obtained by measuring the fine particle concentration Y and the external dust concentration X in advance using the high concentration dust sensor 100 of the present invention and another precise concentration measuring instrument (for example, a gravimetric measuring instrument or a coefficient measuring instrument).

[0031] For example, if the external dust concentration X / fine particle concentration Y = conversion factor K is defined, It can be calculated using the formula: external dust concentration X = conversion factor K x fine particle concentration Y.

[0032] The control device 50 preferably simultaneously operates the ventilation fan 22 of the ventilation device 20 and the circulation fan 32 of the air circulation device 30. In this case, an interval period may be provided during which the ventilation fan 22 and the circulation fan 32 are simultaneously stopped. Furthermore, more preferably, the control device 50 may alternately operate the ventilation device 20 and the air circulation device 30 to temporally isolate the ventilation airflow B1 from the circulation airflow. In addition, an interval may be provided between the operations of the ventilation device 20 and the air circulation device 30 during which both are stopped. EXAMPLES

[0033] (Example of measurement using an existing particle detection sensor) FIG. 3 is a diagram showing an example of measurement of dust concentration in a tunnel using an existing particulate matter detection sensor. In this figure, (A) is the initial state, and (B) is after 50 days have passed. In each figure, the horizontal axis is the elapsed time in one day, and the vertical axis is the sensor output (unitless). Hereinafter, times when high concentrations of dust are generated due to blasting, mechanical excavation, debris disposal, concrete spraying, etc. will be referred to as "high dust periods," and conversely, times when "dust concentrations are clearly extremely low" will be referred to as "low dust periods."

[0034] In Figure 3, in the initial state (A), the output at low dust levels is approximately 90, and at high dust levels it is approximately 750. In contrast, after 50 days (B), the output at low dust levels has risen to approximately 550, and the detection output is saturated for part of the peak concentration at high dust levels. The increase in output when the dust level is low is thought to be due to contamination of the light emitting element or light receiving element of the particulate detection sensor. Therefore, from these results, it can be said that if existing particulate detection sensors are used as they are, it will not be possible to accurately measure the dust concentration inside a tunnel during excavation over a long period of time. EXAMPLES

[0035] FIG. 4 is a cross-sectional view showing an embodiment of a high concentration dust sensor 100 according to the present invention, and FIG. 5 is a cross-sectional view taken along line AA in FIG.

[0036] The dimensions of each part of the manufactured high concentration dust sensor 100 are as follows. Internal dimensions of the housing 10: width B70mm, depth D40mm, height H125mm. Internal volume: approx. 330cm 3 . Diameters d1 and d2 of the intake port 12 and exhaust port 14: 14 mm each (area 1.54 cm2). The axial distance L2 between the intake port 12 and the exhaust port 14 is 37 mm. The axis distance L3 between the exhaust port 14 and the circulation fan 32 is 28 mm. Distances L1 and L4 in the figure: 28 mm and 27 mm, respectively. The diameters of the ventilation fan 22 and the circulation fan 32, d3 and d4, are 13 mm (area 1.33 cm 2 ). Rated air volume of the ventilation fan 22 and the circulation fan 32: approx. 0.012 m 3 / min(=200cm 3 / s). The air flow speed is about 150cm / s. The diameter d5 of the through hole 42 of the particulate matter detection sensor 40 is 8 to 9 mm.

[0037] (rectifier grid 24) In this example, the ventilation device 20 has a straightening grid 24 that is installed in the primary dust removal space S1 and diffuses the introduced dust-containing air G to reduce its flow velocity and form primary treated air A1 by the gravitational settling effect. In this example, the straightening grid 24 has a container-like shape with a diameter d6 larger than the diameter d1 of the intake port 12 and open on one side (the right side in the figure) inside the intake port 12. A positioning round bar 23 with a diameter d7 is provided at the center of the left end in the figure of the straightening grid 24. The doughnut-shaped portion between the diameters d6 and d7 is a honeycomb section 25 with an opening dimension of approximately 3 mm. The diameter d6 is about 30 mm, the diameter d7 is about 12 mm, and the area of ​​the honeycomb portion 25 is about 5.94 cm 2 It is.

[0038] With the above-mentioned structure, the opening dimension of the honeycomb portion 25 is large (about 3 mm), so that there is almost no possibility that dust (for example, less than 1 mm in maximum diameter) contained in the dust-containing air G will become clogged in the honeycomb portion 25. In addition, since the fan diameter d3 of the ventilation fan 22 is approximately the same as the diameters d1, d2 of the intake port 12 and the exhaust port 14, the flow velocity of the dust-containing air G introduced from the outside through the intake port 12 is equivalent to the blowing speed of the ventilation fan 22 (approximately 150 cm / s). In addition, the hollow portion of the straightening grid 24 with a diameter d6 acts as a chamber, and the dust-containing air G is uniformly dispersed in the honeycomb section 25. At this time, since the area of ​​the honeycomb section 25 is large compared to the area of ​​the air intake 12, the flow velocity of the dust-containing air G passing through the honeycomb section 25 is decelerated to approximately 40 cm / s, and primary treated air A1 is formed from the dust-containing air G with relatively large-diameter dust P removed by the gravitational settling effect.

[0039] The above-mentioned straightening grid 24 is not essential and can be omitted. Even if the straightening grid 24 is omitted, the same effect can be obtained by providing a sufficient primary dust removal space S1 to diffuse the dust-containing air G introduced inside the intake port 12, reduce its flow velocity, and form primary treated air A1 through the gravitational settling effect.

[0040] (Baffle Plate 26) In this example, the ventilation device 20 has a baffle plate 26 located upstream (left side in the figure) of the ventilation fan 22 and separated by a gap (about 6 mm) from the ventilation fan 22. In this example, the baffle plate 26 is a flat plate larger than the fan aperture d3. With this configuration, the primary treated air A1 leaving the straightening grid 24 flows into the ventilation fan 22 through the gap between the baffle plate 26 and the ventilation fan 22, causing the flow of the primary treated air A1 to become disturbed around the baffle plate 26, making it easier for part of the primary treated air A1 to become mixed into the ventilation airflow B1. Incidentally, the above-mentioned baffle plate 26 is not essential and can be omitted. Even if the baffle plate 26 is omitted, by positioning a portion of the circulating airflow B2 relatively close to the downstream side of the ventilation airflow B1, it is possible to mix a portion of the primary treated air A1 into the circulating airflow B2.

[0041] Other configurations in FIGS. 4 and 5 are similar to those in FIG. EXAMPLES

[0042] Using the high concentration dust sensor 100 manufactured in Example 2, the following two operation modes were tested. Operation mode 1 of test machine 1: simultaneous operation of ventilation fan 22 and circulation fan 32. Operation mode 2 of test machine 2: Alternate operation of ventilation fan 22 and circulation fan 32. In this case, the ventilation fan 22 was operated for 8 seconds, the circulation fan 32 was operated for 2 seconds, and the interval after the circulation fan 32 was stopped was 50 seconds.

[0043] FIG. 6 is a cross-sectional view of an embodiment of a comparator 60. For comparison with the test machines 1 and 2, a comparison machine 60 was produced by removing the ventilation fan 22 and the baffle plate 26 in Figures 4 and 5 and by moving the air circulation device 30 and the particle detection sensor 40 to the inside of the exhaust port 14. In this case, the axial distance L2 between the intake port 12 and the exhaust port 14 was changed from 37 mm in the test machines 1 and 2 to 55 mm. In the case of the comparative machine 60, the above-mentioned circulating airflow B2 is not formed, and the entire amount of the primary treated air A1 leaving the straightening grid 24 passes through the particulate detection sensor 40 without circulating, and is exhausted from the exhaust port 14. The other configurations are the same as those in Figs.

[0044] The above-mentioned test machines 1 and 2 and comparative machine 60 were installed at a position 100 m (±0.5 m) from the cutting edge of a tunnel under excavation work, and the dust concentration was detected.

[0045] FIG. 7 shows the results of measurements of dust concentration inside the tunnel using test machines 1 and 2 and comparison machine 60. In this figure, (A) is the first day of the experiment, and (B) is 57 days later. In each figure, the horizontal axis is the elapsed time in one day, and the vertical axis is the detection value (unitless) of the particle detection sensor.

[0046] In Figure 7(A), there are large peaks around 9:00 and 15:00, which indicate an increase in dust concentration during blasting. In this figure, the increase and decrease in the detection values ​​over time for testers 1 and 2 and comparison device 60 are almost the same. When the concentration increases, testers 1 and 2 show lower detection values ​​than comparison device 60, which indicates that this is due to the gravitational settling effect. Therefore, it can be said that the detection values ​​of the testers 1 and 2 are each proportional to the comparator 60.

[0047] In FIG. 7(B), there is a data loss due to a power outage for about an hour from 6 p.m. In this figure, the increase and decrease in the detection values ​​over time for the test machines 1 and 2 and the comparison machine 60 are almost the same as in Figure 7(A). However, there is a large difference in the detected concentration value for "low dust concentration".

[0048] In the case of the comparison machine 60, the circulating airflow B2 was not formed, and the entire amount of the primary treatment air A1 leaving the straightening grid 24 passed through the inside of the particulate detection sensor 40 without circulating, so that dust accumulated inside and the concentration detection value rose significantly from the first day, even when the dust level was low.

[0049] In the testing machine 1, the dust concentration of the particulate-containing air A2 introduced to the particulate detection sensor 40 by the air circulation device 30 is low, so that internal accumulation in the particulate detection sensor 40 is more mitigated than in the comparison machine 60, and the increase in the concentration detection value at low dust levels is about 1 / 4 of that of the comparison machine 60.

[0050] In testing machine 2, the gravity settling effect is enhanced due to the calm inside the housing during the interval period, and the ventilation fan 22 is then operated, so that the dust concentration of the primary treated air A1 inside the housing can be lowered than in testing machine 1. Furthermore, when the ventilation fan 22 stops operating, the flow of the ventilation airflow B1 disappears and the gravity settling effect acts prominently, so that the dust concentration of the circulating airflow B2 can be further reduced when the ventilation fan 22 stops operating and the circulation fan 32 is operated. Therefore, in testing machine 2, the concentration detection value at low dust levels has hardly increased from the first day.

[0051] In the case of the comparator 60, the peak of the concentration detection value just before 18:00 is saturated, and it is no longer possible to measure the external dust concentration. In test machines 1 and 2, peak saturation did not occur, and it is clear that the measurement accuracy of dust concentration can be maintained.

[0052] FIG. 8 is a diagram showing the transition of detection values ​​during low dust levels over a period of time. In this figure, the horizontal axis represents the number of days that have passed, and the vertical axis represents the detection value (unitless) of the particulate matter detection sensor 40.

[0053] In Figure 8, the detection values ​​at low dust levels on the first day were all the same, at approximately 25. On the 57th day, the detection values ​​at low dust levels rose to 600 for the comparison machine 60, 200 for the test machine 1, and 60 for the test machine 2. This increase is due to internal accumulation in the particulate detection sensor 40, and essentially, in this embodiment, it is preferable to maintain the low dust detection value on the first day. However, when measuring dust in a tunnel, a slight increase in the low dust detection value is acceptable, while not being able to measure at peak times is unacceptable. Therefore, in this embodiment, it is important to be able to measure at peak times. In other words, the main purpose of the high concentration dust sensor 100 of the present invention is to measure the dust concentration when there is a high dust content.

[0054] In FIG. 8, if the allowable detection value at low dust levels is 200, the maintenance cycles for each machine can be estimated to be approximately 23 days for comparison machine 60, approximately 57 days for test machine 1, and approximately six months for test machine 2, which is much longer than 57 days. Therefore, in the case of test machines 1 and 2, a long maintenance period can be obtained.

[0055] According to the embodiment of the present invention described above, the ventilation device 20 reduces the flow velocity of the ventilation airflow B1 in the primary dust removal space S1, and forms the primary treated air A1 from which part of the dust has been removed by the gravitational settling effect. This makes it possible to effectively remove part of the dust (e.g., dust having a relatively large diameter) without the risk of clogging.

[0056] In the secondary dust removal space S2, the air circulation device 30 reduces the flow velocity of the circulating airflow B2 and forms fine particle-containing air A2 from which a part of the dust P (e.g., dust P with a relatively small diameter) has been re-removed by the gravitational settling effect. As a result, the dust concentration of the fine particle-containing air A2 is reduced to a low concentration (e.g., 0 to 0.6 mg / m) suitable for the existing fine particle detection sensor 40. 3 ), and the particle detection sensor 40 can accurately measure the particle concentration Y of the particle-containing air A2.

[0057] Moreover, the control device 50 can accurately calculate the external dust concentration X using a conversion coefficient K for converting the fine particle concentration Y into the external dust concentration X.

[0058] Therefore, high concentrations (e.g., 2–3 mg / m3) in the tunnel during excavation3 This allows the dust concentration (external dust concentration X) of up to 1000 MPa (or more) to be measured stably for a long period of time, thereby improving measurement accuracy and significantly extending the maintenance interval.

[0059] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0060] A detection area, A1 primary treatment air, A2 particulate-containing air, B width, B1 ventilation airflow, B2 circulation airflow, D depth, d1~d7 diameter, E2 Scattered light, G Dust-containing air, H Height, K Conversion factor, P Dust, S1 Primary dust removal space, S2 Secondary dust removal space, X External dust concentration, Y Particulate concentration, 1 Light emitting element, 2 Drive unit, 3 Light receiving unit, 4 Pulse counter, 5 signal processing unit, 6 control unit, 10 housing, 12 intake port, 14 exhaust port, 20 Ventilation device, 22 Ventilation fan, 23 Round bar, 24 Baffle grid, 25 honeycomb portion, 26 baffle plate, 30 air circulation device, 32 circulation fan, 40 particle detection sensor, 42 through hole, 50 control device, 60 comparator, 100 High concentration dust sensor

Claims

1. a hollow housing having an intake port and an exhaust port and otherwise sealed; a ventilation device that introduces dust-containing air having an external dust concentration from the outside through the air intake port, ventilates a part of the inside of the housing, and forms a ventilation airflow that is exhausted from the air exhaust port; an air circulation device that forms a circulating airflow in the housing that is spatially or temporally isolated from the ventilation airflow; The ventilation device has a primary dust removal space that reduces the flow velocity of the ventilation airflow and forms primary treated air from which a portion of the dust has been removed by a gravitational settling effect, The air circulation device has a secondary dust removal space that reduces the flow rate of the circulating airflow and forms fine particle-containing air from which a portion of the dust has been re-removed by a gravitational settling effect, Furthermore, a particle detection sensor for measuring a particle concentration of the particle-containing air; A high concentration dust sensor comprising: a control device that controls the ventilation device, the air circulation device, and the particulate matter detection sensor, and calculates the external dust concentration using a conversion coefficient that converts the particulate matter concentration to the external dust concentration.

2. The ventilation device has a ventilation fan fixed to the inside of the exhaust port and forming the ventilation airflow, 2. The high concentration dust sensor according to claim 1, wherein the ventilation airflow is decelerated in the primary dust removal space to a flow velocity capable of removing relatively large-diameter dust particles by a gravitational settling effect.

3. The high concentration dust sensor according to claim 2, wherein the ventilation device has a straightening grid installed in the primary dust removal space, diffusing the ventilation airflow to reduce its flow velocity, and forming the primary treated air by gravitational settling effect.

4. The air circulation device has a circulation fan that forms the circulating airflow, 2. The high concentration dust sensor according to claim 1, wherein the circulating air flow includes a portion of the primary treatment air, and is decelerated in the secondary dust removal space to a flow velocity capable of removing relatively small diameter dust particles by gravitational settling effect.

5. The entire circulation airflow is located relatively far from the upstream side of the ventilation airflow, 2. The high concentration dust sensor according to claim 1, wherein a portion of the circulating airflow is located relatively close to a downstream side of the ventilation airflow, and a portion of the primary process air is mixed into the circulating airflow.

6. The high concentration dust sensor according to claim 1 , wherein the control device alternately operates the ventilation device and the air circulation device to temporally isolate the ventilation airflow and the circulation airflow.

7. 7. The high concentration dust sensor according to claim 6, further comprising an interval during which both the ventilation device and the air circulation device are stopped between operations.

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