Collection device, measurement system, collection method, and measurement method for particulate material

Abstract

A collection device (4) collects a particulate material (M) generated by friction contact. This collection device (4) is provided with: a suction duct unit (6) that suctions air containing the particulate material (M); a rectification unit (7) that rectifies a flow (F) of the air in the suction duct unit (6) into a laminar flow state; a wind exhaust unit (9) that exhausts the air suctioned into the suction duct unit (6) to the outside of the suction duct unit (6); and a collection unit (8) that collects, in the suction duct unit (6), the air flowing in the suction duct unit (6) in the laminar flow state.

Description

Particulate matter sampling device, measurement system, sampling method, and measurement method

[0001] The present invention relates to a particulate matter sampling device for sampling particulate matter generated by frictional contact.

[0002] In conventional brake wear measurements (hereinafter referred to as Prior Art 1), when collecting particles generated from the brakes, a method is often used in which a dust-collecting enclosure is placed around the entire brake unit, sampling air is sent in using a HEPA filter or the like, and the air containing the particles is sucked into a duct (a fixed-volume sample collection device) or the like (see, for example, Non-Patent Document 1).In addition, in conventional brake wear measurements (hereinafter referred to as Prior Art 2), there is also a method in which only the brake unit is covered and the air containing the particles is sucked into a duct (see, for example, Non-Patent Document 2).

[0003] A conventional brake dust measuring device (hereinafter referred to as Prior Art 3) includes a housing that surrounds the brake device, a supply duct that supplies air to the housing, an air exhaust duct that exhausts the air supplied into the housing through straight and curved pipes, and a particle measuring device that collects brake dust particles and the like that are generated when the brakes are applied in the air exhaust duct (see, for example, Patent Document 1). This conventional brake dust measuring device supplies air to the air supply duct by a fan system and also purifies the air before supplying it via an inlet filter.

[0004] Hiroyuki Hagino, Motoaki Oyama, Sousuke Sasaki, “Laboratory testing of airborne brake wear particle emissions using a dynamometer system under urban city driving cycles”, Atmospheric Environment, 2016, 131, p.269-278

[0005] Marcel Mathissen, Theodoros Grigoratos, Tero Lahde, Rainer Vogt, “Brake Wear Particle Emissions of a Passenger Car Measured on a Chassis Dynamometer”, Atmosphere, 2019, 10, 556

[0006] Special Publication No. 2020-520448

[0007] In Prior Art 1 to 3, quantitative measurement of particle emissions from brake equipment requires suction of the entire amount, and for this purpose, equipment that covers the entire source is used, but this is large in scale and requires significant installation and operation costs. Furthermore, in Prior Art 1 to 3, if there is a bend in the duct, the flow velocity distribution within the duct may become unstable. Furthermore, Prior Art 1 to 3 measure particles emitted from automobile brake equipment, but when measuring particles generated by frictional contact between the wheels of a railway vehicle and the brake shoes of the brake equipment, the strong rotational wind generated by the high-speed rotation of the wheels of the railway vehicle scatters the particles, making measurement difficult.

[0008] In the dust collectors typically used in bench brake testing machines, the duct diameter must be large to ensure a sufficient suction flow rate from the particle source to the duct. As a result, the flow inside the duct is unstable, and the flow velocity inside the duct does not match the flow velocity inside the dust collector sampling tube, making isokinetic suction difficult.

[0009] The problem to be solved by the present invention is to provide a technique that enables stable collection of air containing particulate matter flowing through a suction duct from a collection section.

[0010] The first invention is a particulate matter collection device that collects particulate matter generated by frictional contact, and is a collection device that includes a suction duct section that sucks in air containing the particulate matter, a rectifying section that rectifies the air flow within the suction duct section into a laminar flow state, an exhaust section that discharges the air sucked into the suction duct section outside the suction duct section, and a collection section that collects the air flowing within the suction duct section within the suction duct section.

[0011] The second invention is a collection device that, in the collection device of the first invention, further includes a dust collection section that causes heavier particulate matter to fall and collect it, and the dust collection section discharges air containing lighter particulate matter into the suction duct section.

[0012] A third invention is a collection device in which, in the collection device of the first or second invention, the suction duct section sucks in air containing the particulate matter in the direction of the wind generated by the movement of the frictional contact members.

[0013] A fourth invention is a collecting device according to any one of the first to third inventions, wherein the suction duct section draws air containing the particulate matter from below upward.

[0014] A fifth invention is a collecting device according to any one of the first to third inventions, wherein the suction duct section sucks the air containing the particulate matter in a horizontal direction.

[0015] A sixth invention is a collection device according to any one of the first to fifth inventions, wherein the total length of the straight pipe section of the suction duct section is L, the inner diameter of the suction duct section is D, the distance from the inlet of the suction duct section to the collection port of the collection section is 0.4L to 0.8L, the inner diameter of the straightening grid of the straightening section is 0.02D to 0.10D, and the length of the straightening grid is 0.5D to 1.0D.

[0016] A seventh aspect of the present invention is a measurement system that includes the sampling device of any one of the first to sixth aspects of the present invention and measures the particulate matter sampled by the sampling device.

[0017] The eighth invention is a method for collecting particulate matter generated by frictional contact, which includes rectifying the air flow within a suction duct section that sucks in air containing the particulate matter so that the air flow within the suction duct section is laminar, discharging the air sucked into the suction duct section to the outside of the suction duct section, and collecting the air flow flowing within the suction duct section within the suction duct section.

[0018] A ninth invention is a measurement method that includes the sampling method of the eighth invention and measures the particulate matter sampled by the sampling method.

[0019] According to the present invention, air containing particulate matter flowing through the suction duct can be stably collected from the collection section.

[0020] FIG. 1 is a diagram schematically showing the overall configuration of a measurement system according to a first embodiment, and is a diagram showing a sampling device in a schematic longitudinal cross section. FIG. 1 is a cross section taken along line II-II in FIG. 1. FIG. 1 is a cross section taken along line III-III in FIG. 1. FIG. 2 is a cross section diagram schematically showing a circular straightening grid as the straightening grid of the straightening section of the sampling device for particulate matter according to the first embodiment. FIG. 3 is a cross section diagram schematically showing a honeycomb core straightening grid as the straightening grid of the straightening section of the sampling device for particulate matter according to the first embodiment. FIG. 4 is a cross section diagram schematically showing a rectangular straightening grid as the straightening grid of the straightening section of the sampling device for particulate matter according to the first embodiment. FIG. 5 is a cross section diagram showing an enlarged V portion of FIG. 1. FIG. 6 is a schematic diagram showing the dimensions of each part of the sampling device for particulate matter according to the first embodiment. FIG. 7 is a schematic diagram of the sampling device for explaining the action and effect of the sampling device for particulate matter according to the first embodiment. FIG. 8 is a schematic diagram of a sampling device serving as a comparative example for explaining the action and effect of the sampling device for particulate matter according to the first embodiment. FIG. 9 is a longitudinal cross section diagram schematically showing a sampling device for particulate matter according to a second embodiment. 1 is a graph showing the measurement results of particulate matter collected by the particulate matter collecting device according to the embodiment, when the initial wheel speed is 65 [km / h]. FIG. 2 is a graph showing the measurement results of particulate matter collected by the particulate matter collecting device according to the embodiment, when the initial wheel speed is 95 [km / h]. FIG. 3 is a schematic diagram of a modified example of the collecting device. FIG. 4 is a schematic diagram of a modified example of the collecting device.

[0021] (First Embodiment) Hereinafter, the first embodiment will be described in detail with reference to the drawings. FIG. 1 is a diagram schematically illustrating the overall configuration of a measurement system for measuring particulate matter during braking of a wheel 1 and a brake device 2 as measurement targets, and shows a sampler 4 in a schematic longitudinal cross section. In FIG. 1, the measurement system is composed of components other than the wheel 1 and the brake device 2 as measurement targets, and is equipped with a sampler 4 and a particle measuring device 11. The wheel 1 shown in FIG. 1 is a member that comes into rolling contact with the rail. As shown in FIG. 2, the wheel 1 includes a tread 1a that comes into contact with the top surface of the rail and receives frictional resistance, and a flange surface 1b formed continuously on the outer periphery of the wheel 1 to prevent the wheel from coming off. The wheel 1 is a component of a wheelset that supports a railway vehicle and is an actual wheel used on the railway vehicle. The wheel 1 may be an integrally rolled wheel in which the tire and a wheel core are integrated by rolling high-carbon steel, or a wheel with a tire in which the tire is shrink-fitted onto the wheel core. Here, the integrally rolled wheel includes, for example, an AR (as rolled) wheel that is not subjected to heat treatment, an SQ (slack quenched) wheel used for electric or diesel railcars, which has a fine pearlite structure near the surface to make it less susceptible to thermal cracking, and an RQ (rim quenched) wheel used for electric or Shinkansen (registered trademark) railcars, which has a tempered martensite structure near the surface to increase strength. The tire-mounted wheel includes, for example, a rolled wheel core made of high-carbon steel or a cast steel wheel made of cast steel. The wheel 1 is mounted on a brake performance testing machine that can control brake pressing force, deceleration, torque, etc. under a wide range of conditions, from locomotives to commuter trains and Shinkansen equivalents, and can perform tests equivalent to those in actual running.

[0022] The brake device 2 shown in Figures 1 and 2 is a device for applying brakes. The brake device 2 is a basic brake device that operates mechanically via a lever mechanism or the like by flowing air or hydraulic pressure specified by a brake control device into a brake cylinder to generate frictional force. The brake device 2 is a tread brake device that presses a brake shoe 3 against the tread 1a of a wheel 1 to generate frictional force as braking force. The brake device 2 shown in Figures 1 and 2 is, for example, a unit brake in which each component is unitized, and is a one-sided brake brake that presses the brake shoe 3 against the tread 1a of the wheel 1 from one side of the wheel 1. The brake device 2 is attached to a brake performance testing machine that evaluates the performance of tread brakes, and is an actual brake device used on a railway vehicle. The brake device 2 is equipped with a brake shoe 3.

[0023] The brake shoe 3 is a member that generates frictional force by being pressed against the tread 1a of the wheel 1. As shown in Fig. 1, the brake shoe 3 is a brake friction material (shoe) that has an arc-shaped appearance, and the back surface of the brake shoe 3 is held by a brake shoe head (mounting portion (shoe head)). The brake shoe 3 has a friction surface (lining surface) 3a that comes into frictional contact with the tread 1a. As shown by the solid lines in Figs. 1 and 2, the brake shoe 3 advances toward and is pressed against the tread 1a of the wheel 1 when the brake is applied. As shown by the two-dot chain lines in Figs. 1 and 2, the brake shoe 3 retracts from and separates from the tread 1a of the wheel 1 when the brake is released. The brake shoes 3 may be, for example, synthetic brake shoes molded mainly from synthetic resin, ordinary cast iron brake shoes made from ordinary cast iron composed mainly of flake graphite and pearlite, alloy cast iron brake shoes made by adding a certain amount or more of special elements such as phosphorus and chromium to ordinary cast iron brake shoes, high-phosphorus cast iron brake shoes with a higher phosphorus content than alloy cast iron brake shoes, or sintered alloy brake shoes made by adding multiple metal powders such as iron and copper and powder such as graphite and then sintering and press-molding them. The brake shoes 3 are actual brake shoes used on railway vehicles, just like the wheels 1.

[0024] The sampling device 4 shown in Fig. 1 is a device that collects particulate matter M generated by frictional contact. As shown in Figs. 2 and 4A to 4C, the sampling device 4 makes the flow velocity distribution of the flow F containing particulate matter M generated by frictional contact between the wheel 1 and the brake shoe 3 approximately uniform. As shown in Fig. 1, the sampling device 4 is a small, vertical dust collecting device that extends vertically so as to guide the flow F from below to above, and can be easily attached and detached to an existing device such as a brake performance testing machine. The sampling device 4 includes a dust collecting unit 5 shown in Figs. 1 and 2, a suction duct unit 6 shown in Figs. 1 to 3 and 5, a rectifying unit 7 shown in Figs. 1 and 3, a sampling unit 8 shown in Figs. 1 and 5, an exhaust unit 9 shown in Fig. 1, and a support unit 10. The sampling device 4 ensures a suction flow rate of the air sucked into the suction duct 6, and sucks the air in the suction duct 6 into the sampling unit 8 at a speed equal to the flow rate of the air in the suction duct 6, thereby sampling particulate matter M. As shown in Figures 1 and 5, the sampling device 4 makes the flow velocity distribution of the air flow F in the suction duct 6 almost uniform, thereby sucking the air in the sampling unit 8 at almost the same flow rate as the air flow F in the suction duct 6.

[0025] The particulate matter M shown in Figures 1 and 5 is a substance generated by frictional contact. The particulate matter M is generated mainly by wear of the brake shoe 3 due to frictional contact between the wheel 1 and the brake shoe 3. The particulate matter M is suspended particulate matter, dust, wear powder, or wear debris, which are fixed fine particles of micrometer size. Suspended particulate matter is, for example, a substance with a particle diameter of 10 μm or less, and includes, among particles suspended in the atmosphere, PM10 with a particle diameter of approximately 10 μm or less, PM2.5 (fine particulate matter) with a particle diameter of approximately 2.5 μm or less, or ultrafine particles with a particle diameter of approximately 0.1 μm or less. Dust is, for example, fine, powder-like solid particles suspended in the gas, such as solid suspended matter with a particle diameter of less than 75 μm.

[0026] The dust collecting section 5 shown in FIG. 1 is configured to collect heavy particulate matter M ２ The dust collecting section 5 is a part that collects light particulate matter M １ The air containing the light particulate matter M is discharged into the suction duct 6. １is, for example, suspended particulate matter or dust. Heavy particulate matter M ２ The dust collection unit 5 is, for example, abrasion powder or wear debris. As shown in Figures 1 and 2, the dust collection unit 5 is a casing member having a rectangular parallelepiped or cubic appearance. The dust collection unit 5 accommodates the contact surface where the wheel 1 and the brake shoe 3 come into contact, the brake shoe 3, and the brake shoe head that holds the brake shoe 3, so as to cover these. The dust collection unit 5 collects relatively heavy particulate matter M ２ The dust collection unit 5 functions as a dust collection box that collects dust. Since the dust collection unit 5 forms a cavity, the air flow F within the dust collection unit 5 becomes turbulent due to the rotational wind generated by the rotation of the wheel 1. Here, the turbulent state refers to a state in which various fluid elements are mixed together and the air flows irregularly. The dust collection unit 5 has a suction port 5a shown in Figures 1 and 2 and a discharge port 5b shown in Figure 1.

[0027] The suction port 5a shown in Figures 1 and 2 is a portion that draws air from outside the dust collection unit 5 into the dust collection unit 5. The suction port 5a opens to the side of the dust collection unit 5 so that a predetermined gap (e.g., about 10 mm) △ is formed between the suction port 5a and the wheel 1 to reduce the effect of rotational wind generated by the rotation of the wheel 1. The discharge port 5b shown in Figure 1 is a portion that discharges the air flow F containing particulate matter M. The discharge port 5b opens to the top surface of the dust collection unit 5 as shown in Figures 1 and 2 so as to discharge the air flow F containing particulate matter M from the dust collection unit 5 toward the flow straightening unit 7. The dust collection unit 5 is detachably attached to a brake performance testing machine.

[0028] The suction duct 6 shown in Figures 1 to 3 and 5 is a section that draws in air containing particulate matter M. The suction duct 6 draws in air containing particulate matter M in the direction of the rotational wind generated by the rotation of the frictionally contacting wheels 1, and also draws in air containing particulate matter M from below upward. The suction duct 6 includes a straight pipe section 6A extending vertically and a curved pipe section (elbow) 6B that directs the flow F flowing vertically within the straight pipe section 6A to the left-right direction (horizontal direction) at a 90-degree angle. The downstream end of the straight pipe section 6A is connected to the upstream end of the curved pipe section 6B. The suction duct 6 functions as an air conduit that guides air in the dust collection section 5 to the exhaust section 9. As shown in Figures 2 and 3, the suction duct 6 is a flow path with a circular cross section, such as a round duct, made of transparent or translucent synthetic resin. As shown in Figure 1, the suction duct section 6 has an inlet 6a and an outlet 6b. The inlet 6a is the part into which air from the dust collecting section 5 flows. The inlet 6a is formed at the lower end of the suction duct section 6 and is connected to the outlet 5b of the dust collecting section 5. The outlet 6b is the part from which air from the suction duct section 6 flows out. The outlet 6b is formed at the upper end of the suction duct section 6. The suction duct section 6 has a constant inner diameter from the inlet 6a on the upstream side to the outlet 6b on the downstream side.

[0029] The rectifying unit 7 shown in Figures 1 and 3 rectifies the air flow F in the suction duct 6 into a laminar flow. The rectifying unit 7 rectifies the air flow F in the suction duct 6 into a laminar flow so that the air flowing in a laminar flow state in the suction duct 6 can be collected by the collection unit 8 within the suction duct 6. Here, the laminar flow state refers to a state in which each fluid element flows regularly in a constant line in the direction of the flow F, and the streamline of the flow F is always parallel to the tube axis, as shown in Figures 1 and 5. The rectifying unit 7 allows the turbulent air flow F flowing into the suction duct 6 to pass through, thereby rectifying the turbulent air flow F into a unidirectional air flow F. The flow straightening unit 7 generates a flow (Hagen-Poiseuille flow) F within the suction duct 6, with a flow velocity distribution symmetrical about the center line of the straight pipe section 6A, such that the flow velocity decreases toward the inner wall of the suction duct 6, becomes zero at the inner wall of the suction duct 6, and is greatest at the center of the suction duct 6. In FIGS. 1 and 5, to conceptually illustrate the flow velocity distribution of the air flow straightened to a laminar flow state, multiple arrows of lengths corresponding to the flow velocity are arranged in parallel, with the apexes of each arrow connected in a mountain-like shape. The flow straightening unit 7 is located upstream of the collection unit 8 and near the inlet 6a of the suction duct 6. The flow straightening unit 7 is equipped with a flow straightening grid 7a, as shown in FIGS. 1, 3, and 4A-4C.

[0030] The straightening grid 7a shown in Figures 1, 3, and 4A to 4C is a member that divides the inside of the suction duct 6 into multiple compartments in order to straighten the air flow F within the suction duct 6. The straightening grid 7a is made up of multiple thin tubes of a predetermined length and inner diameter that are arranged in a grid pattern with no gaps in the radial direction of the suction duct 6. The straightening grid 7a is a circular tube with a circular cross section as shown in Figures 3 and 4A, a honeycomb core that is a honeycomb-shaped structure with a hexagonal cross section as shown in Figure 4B, or a square tube (square pipe) with a square cross section as shown in Figure 4C.

[0031] The sampling unit 8 shown in FIGS. 1 and 5 is a part that samples the air flowing within the suction duct 6. The sampling unit 8 samples the air flowing in a laminar flow state within the suction duct 6. The sampling unit 8 has a sampling port 8a at the tip of the sampling unit 8 that samples the air within the suction duct 6 by aspirating it. The sampling unit 8 is a thin-tube probe (sampling tube) that is inserted into the suction duct 6. The sampling unit 8 penetrates the curved tube portion 6B of the suction duct 6 and guides the air containing particulate matter M aspirated through the sampling port 8a to the measuring unit 11b of the particle measuring device 11. The sampling unit 8 aspirates air from within the suction duct 6 into the sampling unit 8 so that the flow velocity of the air flowing within the sampling unit 8 is equal to or slightly faster than the flow velocity of the air flowing within the suction duct 6. The collection section 8 is arranged so that the portion inserted into the suction duct section 6 is parallel to the inner wall of the suction duct section 6 so that the collection port 8a is located on the center line of the straight pipe section 6A of the suction duct section 6.

[0032] The exhaust section 9 shown in FIG. 1 exhausts air from the suction duct 6 to the outside of the suction duct 6 so as to maintain a laminar flow state of the air flow F within the suction duct 6. The exhaust section 9 draws air into the suction duct 6 and exhausts it from the suction duct 6 so as to prevent a swirling flow from occurring within the suction duct 6. The exhaust section 9 includes an intake port 9a connected to the outlet port 6b of the suction duct 6 to draw in air from the suction duct 6, a rotating cylindrical rotor 9b, a casing 9c rotatably enclosing the rotor 9b, an electric motor 9d for rotating the rotor 9b, multiple blades 9e protruding from the outer peripheral surface of the rotor 9b at intervals in the circumferential direction, and an outlet port 9f for blowing out the air drawn in through the intake port 9a. The exhaust section 9 is, for example, a multi-blade fan such as a sirocco fan. The exhaust unit 9 uses a centrifugal blower that sucks in air from the suction duct 6 through the suction port 9a and blows this air out of the outlet 9f in a centrifugal direction as an exhaust fan that exhausts air from the suction duct 6. In order to suppress the emission of particulate matter M between the wheel 1 and the suction port 5a of the dust collecting unit 5, the exhaust unit 9 sucks in the dust collecting unit 5 and the suction duct 6 so that negative pressure is created inside the dust collecting unit 5, and exhausts the air perpendicular to the rotation axis of the exhaust unit 9.

[0033] The support part 10 is a part that supports the exhaust part 9. The support part 10 is a frame-shaped member made of metal such as an aluminum frame, and is disposed parallel to the suction duct part 6. The upper end of the support part 10 supports the exhaust part 9, and the lower end of the support part 10 is detachably attached to a brake performance testing machine.

[0034] The particle measuring device 11 is a device for measuring particulate matter M flowing within the suction duct 6. The particle measuring device 11 sucks in air containing particulate matter M flowing within the suction duct 6 and measures the particulate matter M flowing within the suction duct 6. The particle measuring device 11 measures, for example, a number concentration representing the number of particulate matter M per unit volume in the gas, and a particle size distribution, which is a histogram with the size of the particulate matter M on the horizontal axis and the frequency on the vertical axis. The particle measuring device 11 includes an internal filter unit that allows only particulate matter M within the particle diameter range to be measured to pass through. As shown in FIG. 1 , the particle measuring device 11 includes a connection unit 11a, a measurement unit 11b, a filter unit 11c, and a suction unit 11d. The connection unit 11a is a portion that connects to the rear end of the sampling unit 8. The connection unit 11a introduces the air containing particulate matter M flowing within the sampling unit 8 into the measurement unit 11b. The measurement unit 11b is a unit that measures the number concentration and particle size distribution of particulate matter M. The measurement unit 11b measures suspended particulate matter such as PM10, PM2.5, or ultrafine particles with a particle diameter of 10 μm or less as a measurement target. The measurement unit 11b measures the number concentration and particle size distribution of particulate matter M, for example, by utilizing the principle that the amount of scattered light generated by particulate matter M contained in the air sucked by the sampling unit 8 changes in proportion to the mass of the particulate matter M. The filter unit 11c is a unit that removes particulate matter M. The filter unit 11c removes particulate matter M from the air flowing in from the measurement unit 11b and discharges the removed air to the suction unit 11d. The suction unit 11d is a unit that sucks air flowing through the suction duct unit 6 into the measurement unit 11b through the sampling unit 8. The suction unit 11d sucks air into the collection unit 8 at a constant flow rate from the suction duct 6 so that the flow rate of the air flowing in the collection unit 8 is equal to or slightly faster than the flow rate of the air flowing in the suction duct 6. The suction unit 11d is a pump or the like that sucks air into the collection unit 8 in order to sample a small amount of air at a constant flow rate from the air flowing in the suction duct 6.

[0035] The flow velocity measuring device 12 shown in FIG. 1 is a device for measuring the flow velocity of air flowing through the suction duct 6. The flow velocity measuring device 12 includes a hot wire (probe) 12a and a measuring unit 12b. The hot wire 12a is a portion that receives the air flow F in the suction duct 6. The hot wire 12a is a heated thin metal wire that is inserted into the straight pipe portion 6A of the suction duct 6. The measuring unit 12b is a portion that measures the flow velocity of air flowing through the suction duct 6. The measuring unit 12b measures the flow velocity of air flowing through the suction duct 6 by utilizing the phenomenon that the amount of heat transferred from the hot wire 12a to the surrounding air depends on the air velocity. The measuring unit 12b measures the flow velocity based on a change in electrical resistance that occurs when the hot wire 12a receives the air flow F and the temperature of the hot wire 12a changes.

[0036] Next, the optimum range of dimensions of each part in the particulate matter sampling device according to the first embodiment will be described. As shown in FIG. 6, if the total length of the straight pipe section 6A of the suction duct section 6 is L and the inner diameter of the suction duct section 6 is D, the distance L from the inlet 6a of the suction duct section 6 to the sampling port 8a of the sampling section 8 is Ｐ is 0.4L to 0.8L, the inner diameter d of the straightening grid 7a of the straightening section 7 is 0.02D to 0.10D, and the length l of the straightening grid 7a is 0.5D to 1.0D. Here, in the case of the honeycomb core shown in FIG. 4B and the square shown in FIG. 4C, the inner diameter d of the straightening grid 7a is the diameter of the inscribed circle that contacts the inner surface of these.

[0037] Next, the operation of the particulate matter sampling device according to the first embodiment will be described. In order to stably measure particulate matter M using the particle measuring device 11 shown in FIGS. 1 and 5 , it is necessary to match the flow velocity of air flowing through the suction duct 6 with the flow velocity of air flowing through the sampling unit 8, which is drawn from the suction duct 6 to the sampling unit 8. To achieve this, it is necessary to make the flow velocity distribution of the air flowing through the suction duct 6 uniform, and to make the air flow F within the suction duct 6 a laminar flow. In the first embodiment, as shown in FIG. 1 , air within the suction duct 6 is sucked in by the exhaust unit 9, and the air flow F flowing through the suction duct 6 is rectified by the rectifier unit 7 so as to prevent a swirling flow from occurring in the air flow F within the suction duct 6.

[0038] Unlike the collection device 4 shown in Fig. 7A, the collection device 104 shown in Fig. 7B does not have a rectifying unit 7, and sends air from the bottom of the dust collection unit 105 into the dust collection unit 105 and the air supply duct unit 106 by an air supply unit 109 different from the exhaust unit 9. The origin O shown in Figs. 7A and 7B is the center of the lower end of the suction duct unit 6 and the air supply duct unit 106, and x is a position away from the origin O in the upward direction. The flow rate Q(x)[m 3 / s] is expressed by the following equation 1.

[0039]

[0040] Here, ρ in Equation 1 is the density of air [kg / m 3 ], μ is the viscosity coefficient of air, D is the inner diameter [mm] of the suction duct portion 6 and the air supply duct portion 106, and dP / dx is the pressure gradient that represents the rate of change of the pressure P between the origin O and the position x in the suction duct portion 6 and the air supply duct portion 106.

[0041] In the sampling device 104 shown in Figure 7B, the air flow F within the air supply duct 106 is in a turbulent state, and the pressure gradient within the air supply duct 106 shown in Equation 1 is dP / dx>0 (positive pressure gradient), causing separation and backflow in the wall boundary layer within the air supply duct 106, resulting in turbulent transition. As a result, the flow velocity distribution within the air supply duct 106 becomes non-uniform, and the flow velocity of the air flowing within the air supply duct 106 fluctuates. On the other hand, in the sampling device 4 shown in Figure 7A, the air within the suction duct 6 is sucked in by the exhaust unit 9, and the air flowing within the suction duct 6 is rectified by the rectifier unit 7 so as to prevent swirling flow from occurring within the suction duct 6. Therefore, the air flow F in the suction duct 6 passing through the rectifying section 7 becomes laminar, and the pressure gradient in the suction duct 6 shown in Equation 1 becomes dP / dx≦0 (negative pressure gradient), so separation and backflow do not occur in the wall boundary layer in the suction duct 6. As a result, the flow velocity of the air flowing in the suction duct 6 and the flow velocity of the air flowing in the sampling section 8 are approximately the same, and the particle measuring device 11 accurately measures the particulate matter M that has been neatly dispersed in the suction duct 6.

[0042] Next, a method for collecting and measuring particulate matter according to the first embodiment will be described. When the exhaust air section 9 shown in Fig. 1 starts operating, the exhaust air section 9 sucks in air from the dust collection section 5 and the suction duct section 6, creating a negative pressure inside the dust collection section 5 and the suction duct section 6. When the brake performance tester starts operating and the wheel 1 begins to rotate, a rotating wind is generated in the rotational direction of the wheel 1 as the wheel 1 rotates. As a result, air is sucked into the dust collection section 5 through the gap △ between the wheel 1 and the suction port 5a of the dust collection section 5, and the air flows from the dust collection section 5 toward the suction duct section 6.

[0043] When the brake device 2 brakes based on a brake command output by the brake performance tester, the friction surface 3a of the brake shoe 3 comes into close contact with the tread 1a of the wheel 1, as shown by the solid lines in Figures 1 and 2. As a result, as shown in Figure 1, a braking force is applied to the wheel 1 due to the frictional force acting between the tread 1a and the frictional surface 3a, and particulate matter M is generated by frictional contact between the wheel 1 and the brake shoe 3. At this time, because there is a negative pressure inside the dust collection unit 5, the particulate matter M is prevented from flowing out of the dust collection unit 5 through the gap △ between the wheel 1 / brake shoe 3 and the suction port 5a of the dust collection unit 5.

[0044] The rotation of the wheel 1 generates a rotating wind, which makes the flow F in the dust collecting section 5 turbulent, and the light particulate matter M １ and heavy particulate matter M ２ Most of the heavy particulate matter M is collected at the bottom of the dust collecting section 5. ２ falls, and light particulate matter M １ Along with some heavy particulate matter M ２ flows into the suction duct 6 from the outlet 5b of the dust collecting section 5, and some of the heavy particulate matter M ２ The dust falls from the suction duct 6 into the dust collecting section 5 due to its own weight.

[0045] As shown in Figure 1, the exhaust unit 9 is disposed downstream of the suction duct 6, so that air is drawn into the suction duct 6 by the exhaust unit 9 in a manner that prevents swirling airflow from occurring within the suction duct 6. Furthermore, the rectifying unit 7 is disposed upstream of the suction duct 6, so that the air flow F flowing from the dust collecting unit 5 into the suction duct 6 is regulated. Therefore, as shown in Figures 1 and 5, the air flow F does not separate from the wall surface within the suction duct 6, the flow velocity distribution of the air flow F within the suction duct 6 is substantially uniform, and the air flow F within the suction duct 6 downstream of the rectifying unit 7 is in a laminar state. The exhaust unit 9 draws air in a state in which particulate matter M is neatly dispersed within the suction duct 6 at a predetermined suction flow rate, so that the flow velocity of the air flowing within the suction duct 6 substantially matches the flow velocity of the air drawn by the sampling unit 8 and flowing within the sampling unit 8.

[0046] As a result, the particulate matter M that has passed through the flow straightening unit 7 is sucked from the sampling unit 8 into the measuring unit 11b of the particle measuring device 11 at a flow velocity that is approximately the same as the flow velocity of the air flowing through the suction duct 6, and the measuring unit 11b measures the number concentration and particle size distribution of the particulate matter M. Since the exhaust unit 9 sucks in the air within the suction duct 6 so as not to generate a swirling flow within the suction duct 6, the flow F within the suction duct 6 is maintained in a laminar state, and the exhaust unit 9 discharges the air within the suction duct 6 to the outside of the suction duct 6.

[0047] The first embodiment provides the following advantageous effects. (1) In the first embodiment, the suction duct 6 draws in air containing particulate matter M, the rectifying unit 7 rectifies the air flow F within the suction duct 6 into a laminar flow state, the exhaust unit 9 discharges the air drawn into the suction duct 6 to the outside of the suction duct 6 so as to maintain the laminar flow state of the air flow F within the suction duct 6, and the sampling unit 8 samples the air flowing in a laminar flow state within the suction duct 6. This makes the flow velocity distribution of the air flow F around the sampling port 8a of the sampling unit 8 within the suction duct 6 approximately uniform, thereby suppressing flow velocity fluctuations in the air flow F within the suction duct 6 and stabilizing the flow velocity distribution of the air flow F within the suction duct 6. As a result, the flow velocity of the air flowing within the suction duct 6 and the flow velocity of the air flowing within the sampling unit 8 can be made approximately the same, allowing air containing particulate matter M to be stably sampled from the sampling unit 8 at a constant velocity. Furthermore, by drawing air from the dust collecting unit 5 into the suction duct 6 by the exhaust unit 9 without generating a swirling flow, air can also be drawn from the inner wall surface of the suction duct 6. As a result, fluctuations in the flow rate of the air flowing within the suction duct 6 are suppressed, stabilizing the flow rate of the air flowing within the suction duct 6 and making the flow rate distribution within the suction duct 6 approximately uniform. For example, by using a centrifugal blower such as a sirocco fan as the exhaust unit 9 to draw air from the dust collecting unit 5 into the straight pipe section 6A of the suction duct 6, fluctuations in the flow rate of the air flowing within the suction duct 6 can be easily suppressed and the flow rate stabilized.

[0048] (2) In the first embodiment, among the particulate matter M generated by frictional contact, the heavy particulate matter M ２ The particulate matter M generated by frictional contact is collected by the dust collecting unit 5. １ The air containing the heavy particulate matter M is discharged into the suction duct portion 6. ２ The light particulate matter M can be collected in the dust collecting section 5 by dropping it under its own weight. １ The air flow F containing the particulate matter M can be rectified by the rectifying section 7, and the particulate matter M in a neatly dispersed state within the suction duct section 6 can be collected by the collecting section 8.

[0049] (3) In the first embodiment, the suction duct 6 draws in air containing particulate matter M in the direction of the rotational wind generated by the movement of the wheel 1 in frictional contact. For example, when measuring particulate matter generated by frictional contact between a vehicle tire and a road surface, a flow containing particulate matter is guided laterally from within a cover covering the tire and road surface toward the measurement device. This causes a problem in that the direction of the tangential force acting on the contact surface between the tire and the road surface is perpendicular to the direction of the flow, and relatively large particulate matter that falls to the bottom of the cover is picked up by the rotational wind generated by the rotation of the tire. In the first embodiment, the flow generated by the rotation of the wheel 1 is tangential to the contact point between the wheel 1 and the brake shoe 3, and most of the particulate matter M generated by frictional contact is discharged in the tangential direction of the contact point. Therefore, the flow F can be rectified by the rectifying unit 7 by drawing air into the suction duct 6 so that the direction of the rotational wind generated by the rotation of the wheel 1 coincides with the direction of the flow F in the suction duct 6. In addition, since the rotating wind can be prevented from blowing toward the bottom of the dust collecting section 5, the heavy particulate matter M that has fallen to the bottom of the dust collecting section 5 can be prevented from falling. ２ This can prevent the wire from rolling up.

[0050] (4) In the first embodiment, the suction duct 6 sucks air containing particulate matter M from below upward. Therefore, heavy particulate matter M such as relatively large wear powder and wear debris that is not fine particles is sucked in. ２ The dust can be collected in the dust collection unit 5 by gravity. In addition, since the device is a vertically extending device, rather than a horizontally extending device like those in the prior arts 1 to 3, it is possible to improve portability and to easily install the device. Furthermore, the air filter can effectively remove the light particulate matter M １ Heavy particulate matter M ２ Therefore, it is not necessary to remove the light particulate matter M １ and heavy particulate matter M ２ This can separate the air from the intake duct 6, and can prevent the air flow rate in the intake duct 6 from decreasing due to the air filter.

[0051] Second Embodiment In the following, parts that are the same as those shown in Figures 1 to 7 are designated by the same reference numerals, and detailed description thereof will be omitted. The control device 13 shown in Figure 8 is a device that controls the operation of the exhaust unit 9 of the sampling device 4 based on the measurement results of the flow velocity measurement device 12. The control device 13 controls the rotation of the electric motor 9d of the exhaust unit 9 so that the flow velocity of the air flowing through the suction duct unit 6 becomes a predetermined flow velocity based on the output signal (flow velocity signal) output by the measurement unit 12b of the flow velocity measurement device 12. The control device 13 adjusts the rotation speed of the electric motor 9d to adjust the flow rate of air drawn into the suction duct unit 6, for example, so that the flow velocity of the air flowing through the suction duct unit 6 becomes approximately the same as the flow velocity of the air flowing through the sampling unit 8.

[0052] In addition to the effects of the first embodiment, the particulate matter sampling device according to the second embodiment has the following effects. In the second embodiment, the control device 13 controls the operation of the exhaust unit 9 based on the measurement results of the flow velocity measurement device 12. Therefore, for example, the operation of the exhaust unit 9 can be feedback-controlled based on the measurement results of the flow velocity of the air flowing through the suction duct unit 6, and fluctuations in the flow velocity of the air flowing through the suction duct unit 6 can be suppressed. As a result, the flow velocity distribution of the air flow F around the sampling port 8a of the sampling unit 8 becomes approximately uniform, and the flow velocity distribution of the air flow F within the suction duct unit 6 can be stabilized.

[0053] Next, a specific example will be described. The sampling device 4 shown in Fig. 6 was attached to a braking performance testing machine at the Railway Technical Research Institute, and the flow velocity of the air in the suction duct 6 when the air in the suction duct 6 was discharged by the exhaust section 9 was measured by the flow velocity measuring device 12 shown in Fig. 1. Furthermore, as shown in Figs. 1 and 2, particulate matter M generated when the brake shoe 3 was pressed against the wheel 1 was measured by the particle measuring device 11. The wheel 1 shown in Figs. 1 and 2 was a wheel for a conventional line. The brake shoe 3 was an actual synthetic brake shoe. The flow straightening section 7 in Figs. 1, 5, and 6 is a flow straightening section formed by bundling together a number of commercially available straws with a circular cross section, as shown in Fig. 4A, and packing them so as to block the suction duct 6. The exhaust section 9 shown in Fig. 1 is an industrial fan with an air volume of 2.4 m 3 Measurements were performed at a rate of [rpm].

[0054] The graphs shown in Figures 9A and 9B are the measurement results obtained by the particle measuring device 11 shown in Figure 6, where Figure 9A shows the measurement results when the initial wheel speed is 65 [km / h] and Figure 9B shows the measurement results when the initial wheel speed is 95 [km / h]. As shown in Figures 1 and 2, the amount of particles [mg / m] generated when the brake shoe 3 is pressed against the wheel 1 with a pressing force of 10 [kN] in response to a brake command is 3 9A and 9B, the flow velocity of the air flowing through the suction duct 6 was approximately constant, and the flow velocity distribution within the suction duct 6 was also approximately constant, confirming that the air flow F within the suction duct 6 could be rectified into a laminar flow by the rectifying unit 7.

[0055] In addition, the ratio of the kinetic energy at an initial velocity of 95 km / h to that at an initial velocity of 60 km / h was approximately 2.1 times, and the particle amount measured at an initial velocity of 60 km / h was 7.5 mg / m 3 ], the particle amount measured at an initial velocity of 95 [km / h] was 18.0 [mg / m 3 When comparing the ratios of particle number and particle number, it was confirmed that the particle number ratio was approximately 2.4 times higher, almost the same as the kinetic energy ratio. Therefore, as the rotational speed of the wheel 1 increases and the kinetic energy increases, the particle amount also increases, and it was confirmed that the particle amount can be accurately measured even when the influence of the rotational wind caused by the rotation of the wheel 1 and the influence of turbulence in the airflow inside the dust collection unit 5 become stronger.

[0056] The dimensions of each part of the sampling device 4 used for the measurements were total length L: 900 [mm], inner diameter D: 150 [mm], distance L Ｐ : 450 [mm] = 0.5L, inner diameter d: 6 [mm] = 0.04D, length l: 80 [mm] = 0.53D, and it was confirmed that each dimension was within the optimum range of the dimensions of each part of the sampling device 4. In addition, the flow rate of the sirocco fan was 2.4 [m 3 The theoretical value of the flow velocity of the air flowing through the suction duct 6 at a flow rate of 2.26 [m / s] was found to be 2.26 [m / s], and the measured values ​​of the flow velocity shown in Figures 9A and 9B were almost identical to the theoretical value.

[0057] The present invention should not be construed as being limited to the above-described embodiments. Various modifications and alterations are possible, as described below, and are within the scope of the present invention. (1) In the above-described embodiments, the brake device 2 for a railway vehicle was described as an example. However, the present invention can also be applied to brake devices for other means of transportation, such as automobiles, motorcycles, and bicycles. Furthermore, in the above-described embodiments, the brake device 2 is described as a tread brake device. However, the present invention can also be applied to a disc brake device that generates braking force by pressing a friction material against a disk that rotates integrally with the axle, or a rail brake device that generates braking force by pressing a friction material directly against the top surface of the rail. Furthermore, in the above-described embodiments, the sampling device 4 is described as being attached to a braking performance testing machine. However, the present invention can also be applied to a case where the sampling device 4 is attached to a bogie of a railway vehicle traveling on a rail.

[0058] (2) In the above-described embodiment, the particle measuring device 11 is used to measure suspended particulate matter such as PM10, PM2.5, or ultrafine particles with a particle diameter of 10 μm or less. However, the present invention can also be applied to measuring dust, wear powder, or wear debris using the particle measuring device 11. Furthermore, in the above-described embodiment, the particulate matter M generated when the wheel 1 and the brake shoe 3 come into frictional contact is measured. However, the frictional contact between the wheel 1 and the brake shoe 3 is not limited to the wheel 1 and the brake shoe 3. For example, the present invention can also be applied to measuring particulate matter generated by frictional contact between the driving-side friction material and the driven-side friction material of a clutch device that transmits power from the driving side to the driven side, frictional contact between a grounding brush that dissipates power from a rotating body and the rotating body, frictional contact between a workpiece and tools, frictional contact between a trolley wire and a slider, or frictional contact between a wheel and a rail. Furthermore, in the above-described embodiment, an example was given in which one of the multiple members in frictional contact rotates and the other member is stationary, but the present invention can also be applied to a case in which both members in frictional contact rotate.

[0059] (3) In the above-described embodiment, an example was given of a case in which one member is in frictional contact with the other member while rotating and the other member is stationary, but the present invention can also be applied to a case in which both members are in frictional contact while moving linearly, or a case in which one member is in frictional contact while rotating and the other member is in frictional contact while moving linearly.Furthermore, in the above-described embodiment, an example was given of a case in which the cross-sectional shape of the flow straightening grid 7a is circular, rectangular, or hexagonal, but the present invention can also be applied to a case in which the cross-sectional shape is elliptical, triangular, or polygonal.

[0060] (4) In the above-described embodiment, the suction duct 6 is used to draw air in a vertical direction (longitudinal direction). However, the present invention can also be applied to a case in which the suction duct 6 draws air in a horizontal direction (lateral direction). For example, a sampler 4X as shown in FIG. 10 or a sampler 4Y as shown in FIG. 11 may be configured. Although not shown in FIGS. 10 and 11 , a particle measuring device 11 is connected to the rear end of the sampler 8, as in the above-described embodiment. This constitutes a measurement system equipped with the sampler 4X or sampler 4Y. Furthermore, although the bending direction of the curved pipe 6B is shown as an upward direction in FIG. 10 and a downward direction in FIG. 11 , it may also be horizontal (toward or away from the viewer in FIG. 10 ). Furthermore, in the above-described embodiment, a centrifugal blower such as a sirocco fan is used in the exhaust section 9. However, the present invention can also be applied to a case in which a turbofan, which is a centrifugal blower similar to a sirocco fan, is used in the exhaust section 9.

[0061] [Summary] The contents disclosed in this specification can be summarized as follows.

[0062] (First invention) A particulate matter collecting device that collects particulate matter generated by frictional contact, comprising: a suction duct section that sucks in air containing the particulate matter; a rectifying section that rectifies the air flow in the suction duct section into a laminar flow state; an exhaust section that discharges the air sucked into the suction duct section to the outside of the suction duct section; and a collecting section that collects the air flowing in the suction duct section within the suction duct section.

[0063] (Second Invention) The collection device of the first invention, further comprising a dust collection section that causes heavier particulate matter among the particulate matter to fall and collect it, and the dust collection section discharges air containing lighter particulate matter among the particulate matter into the suction duct section.

[0064] (Third Invention) The collecting device according to the first or second invention, wherein the suction duct section sucks in the air containing the particulate matter in the direction of wind generated by the movement of the frictionally contacting members.

[0065] (Fourth Invention) The collecting device according to any one of the first to third inventions, wherein the suction duct section draws the air containing the particulate matter from below upward.

[0066] (Fifth Invention) The sampling device according to any one of the first to third inventions, wherein the suction duct section horizontally sucks in the air containing the particulate matter.

[0067] (Sixth Invention) A collection device according to any one of the first to fifth inventions, wherein the total length of the straight tube section of the suction duct section is L, the inner diameter of the suction duct section is D, the distance from the inlet of the suction duct section to the collection port of the collection section is 0.4L to 0.8L, the inner diameter of the straightening grid of the straightening section is 0.02D to 0.10D, and the length of the straightening grid is 0.5D to 1.0D.

[0068] (Seventh Invention) A measurement system comprising the sampling device of any one of the first to sixth inventions, and measuring the particulate matter sampled by the sampling device.

[0069] (8th Invention) A method for collecting particulate matter generated by frictional contact, comprising: rectifying the flow of air within a suction duct section that draws in air containing the particulate matter so that the air flow within the suction duct section becomes laminar; discharging the air drawn into the suction duct section to the outside of the suction duct section; and collecting the air flow flowing within the suction duct section within the suction duct section.

[0070] (Ninth Invention) A measuring method including the sampling method of the eighth invention, for measuring the particulate matter sampled by the sampling method.

[0071] 1 Wheel 1a Tread 2 Brake device 3 Brake shoe 3a Friction surface 4 Sampling device 5 Dust collecting section 6 Suction duct section 6A Straight pipe section 6B Bent pipe section 7 Rectifying section 7a Straightening grating 8 Sampling section 8a Sampling port 9 Exhaust section 10 Support section 11 Particle measuring device 12 Flow rate measuring device M Particulate matter M １ Light particulate matter M ２ Heavy particulate matter F Flow △ Gap

Claims

1. A particulate matter sampling device for sampling particulate matter generated by frictional contact, comprising: a suction duct section for sucking in air containing the particulate matter; a straightening section for straightening the air flow within the suction duct section into a laminar flow state; an exhaust section for discharging the air sucked into the suction duct section outside the suction duct section; and a sampling section for sampling the air flowing within the suction duct section.

2. The collection device according to claim 1, further comprising a dust collection section that causes heavier particulate matter among the particulate matter to fall and collect it, and the dust collection section discharges air containing lighter particulate matter among the particulate matter into the suction duct section.

3. A sampling device as described in claim 1 or 2, wherein the suction duct section sucks in air containing the particulate matter in the direction of wind generated by the movement of the frictionally contacting members.

4. A sampling device as claimed in any one of claims 1 to 3, wherein the suction duct section draws in air containing the particulate matter from below towards above.

5. A sampling device as claimed in any one of claims 1 to 3, wherein the suction duct section sucks in air containing the particulate matter in a horizontal direction.

6. A collection device as claimed in any one of claims 1 to 5, wherein the total length of the straight tube section of the suction duct section is L, the inner diameter of the suction duct section is D, the distance from the inlet of the suction duct section to the collection port of the collection section is 0.4L to 0.8L, the inner diameter of the straightening grid of the straightening section is 0.02D to 0.10D, and the length of the straightening grid is 0.5D to 1.0D.

7. A measurement system comprising a sampling device according to any one of claims 1 to 6, for measuring the particulate matter sampled by the sampling device.

8. A method for collecting particulate matter generated by frictional contact, comprising: straightening the air flow in a suction duct section that draws in air containing the particulate matter so that the air flow in the suction duct section is in a laminar state; discharging the air drawn into the suction duct section to the outside of the suction duct section; and collecting the air flow flowing within the suction duct section within the suction duct section.

9. A method for measuring the particulate matter collected by the collection method according to claim 8.

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