Modular low noise muffler for commercial vehicles

Abstract

The invention relates to a muffler (1) for a compressed air system, comprising: an air inlet (3) for a compressed air flow, a first muffling device (4) arranged downstream of the air inlet (3); a second muffling device (6) arranged downstream of the first muffling device (4); a grille (8) arranged downstream of the second muffling device (6), the grille comprising at least two channels (9) through which the compressed air flow is adapted to exit the muffler (1), where the first muffling device (4) has a smaller diameter than the second muffling device (6), and where the first muffling device (4) has a smaller diameter than the second muffling device (6). The second muffler device (6) has at least partially a higher density than the first muffler device (4). Such an improved muffler (1) is able to perform sound attenuation suitable for specific requirements (e.g., technical guidelines, standards), thus enabling lower noise compared to systems in the prior art.

Description

Technical Field

[0001] The invention relates to a modular silencer, in particular for achieving low noise levels in compressed air systems in commercial vehicles. Background Art

[0002] Systems using compressed gases, such as compressed air systems, can release large amounts of compressed gas into the environment in a short period of time. This decompression of the gas can result in significant noise. However, noise emissions must be kept below acceptable levels, so silencers are often required for compressed gas systems.

[0003] In commercial electric vehicles, most of the noise is generated by high-speed airflow mixing with ambient air.

[0004] In the prior art, WO2019 / 063350A1 is known, which discloses a noise reducer for a compressed air system, the noise reducer having an inlet channel and a chamber for receiving a sound-absorbing material. In this case, the inlet channel and the chamber are separated perpendicularly to the compressed air flow by a separation plate, which has a plurality of openings in the outer peripheral area of ​​the compressed air flow so as to introduce the compressed air into the chamber. This noise reducer has the function of suppressing the noise generated by the compressed air flow, such as the noise generated in the valve releasing the compressed air.

[0005] For electric commercial vehicles equipped with pneumatic brake systems, extremely low noise is extremely important. Currently, according to ISOR362, EEC92 / 97 and EEC R51, the valve assembly through which compressed air flows should meet the maximum 72dB (A) requirement within a distance of 7m.

[0006] However, for electric commercial vehicles with pneumatic brakes (electric motors are very quiet compared to other engines), the maximum noise value of 72 dB(A) at a distance of 7 m is still too high. Summary of the invention

[0007] Therefore, there is a need for a new type of silencer which is capable of reducing noise emissions to below 68 dB(A) within 7 m of the vehicle, or preferably to below 60 dB(A).

[0008] The technical problem of the present application can therefore be seen as providing an improved silencer capable of performing silencers adapted to specific requirements (eg technical guidelines, standards) and thus achieving lower noise values ​​compared to systems according to the prior art.

[0009] In particular, noise generated externally, such as noise generated by a valve that discharges compressed air to the atmosphere, should be suppressed because the most prominent part of the noise is generated by the mixing of compressed air (flowing at a high speed) with ambient air.

[0010] The object of the present application is achieved by a silencer according to claim 1 and by the use of a silencer according to claim 16. Further advantageous embodiments of the present application are the subject matter of the dependent claims.

[0011] The silencer according to the invention comprises: an inlet for a compressed air flow, a first silencer arranged downstream of the inlet, and a second silencer arranged downstream of the first silencer. A grille is arranged downstream of the second silencer, the grille comprising at least two channels through which the compressed air is adapted to leave the silencer. In this context, the first silencer has a smaller diameter than the second silencer, and the second silencer has at least partially a higher density than the first silencer.

[0012] This means that the second muffler device may comprise a portion having the same density as the first muffler device (eg downstream of the first muffler device), but may also comprise a portion having a higher density than the first muffler device (eg upstream of the grille).

[0013] In particular, the second silencer increases the surface area of ​​the outflow of compressed gas (in particular compressed air) to reduce the turbulence intensity of the outflow.

[0014] The grid drives the gas flow as uniformly as possible and further increases the surface area of ​​the outflow to reduce the turbulence intensity of the outflow.

[0015] The effect of this arrangement is that the surface flow velocity can be reduced. The overall surface of the silencer is increased. Nevertheless, axial space can still be saved, namely by the reduced diameter of the first silencer.

[0016] By varying the diameter and density of the first and second silencers, the noise level can be varied. Usually, the air velocity through the silencer is high. The energy of the noise generated is related to the velocity. With the silencer according to the invention, the flow velocity can be reduced with increasing silencer surface, in particular with the second silencer.

[0017] The first muffler has a smaller diameter (compared to the second muffler), which results in a smaller cross-sectional area available for the flow of compressed air. In addition, the use of a material with a lower density (compared to the second muffler) results in fewer solid parts, but more voids, microchannels, etc. that can be used for flow. After the transition to the second muffler, there is at least partially a higher density (i.e., more solid parts, but fewer voids, microchannels, etc. that can be used for flow), however, this is compensated by a larger diameter (i.e., a larger cross-sectional area). As a result, the flow rate is reduced and there is a smooth transition (with low flow resistance) from the first muffler to the second muffler. The high-density portion of the second muffler improves the uniformity of the flow because the higher density helps to improve the distribution in the second mesh, which is particularly important when the air leaves the muffler. With this arrangement, the flow resistance in the entire muffler can be maintained at the same level.

[0018] Preferably, the first muffler has an equal or smaller height than the second muffler. Since the second muffler can have a higher height, it is possible to ensure that the airflow with reduced velocity passes through the height of the second muffler (staying longer), so the muffler performance is further improved.

[0019] Preferably, an intermediate element is arranged between the first silencer device and the second silencer device.

[0020] The intermediate element can distribute the air flow appropriately between the two silencers.

[0021] Thus, the air flow from the first muffler device to the second muffler device can be distributed in a more uniform manner.The distribution element can be pushed into the second mesh or comprised in the second mesh.

[0022] However, the intermediate element may also have the function of separating the first and second silencer devices and holding them in their respective housings.

[0023] Preferably, the first muffler device and / or the second muffler device comprises a fibrous material, preferably a fibrous web, even more preferably a fibrous web comprising polyethylene.

[0024] This material effectively dampens the noise produced by compressed gases, especially compressed air.

[0025] Preferably, at least two channels in the grid are polygonal, or preferably hexagonal, or alternatively rounded in cross-section.

[0026] By means of a hexagonal arrangement, the space can be utilized in the most efficient way. For such a hexagonal channel, the effective flow surface is most preferred, since the residual area of ​​the solid grid structure, which can form a dead zone, is small. Thus, the ratio between the channel area and the area covered by the solid (i.e., grid) increases. Thus, such a structure allows the highest ratio of effective flow area to total grid area. Thus, the optimal discharge area is available for the flow of compressed air over the grid area.

[0027] Preferably, the height of the first muffler is between 20 and 40 mm. In addition, the height of the second muffler is between 20 and 40 mm. Experiments have shown that such a height is most effective for achieving a noise level below 60 db (A).

[0028] Preferably, the diameter of the first muffler is at most 65 mm, preferably at most 62 mm, and / or the diameter of the second muffler is at least 80 mm, preferably at least 90 mm, more preferably at least 100 mm. This depends on the specific application. This solution helps to most effectively increase the surface area of ​​the outflow, thereby most effectively reducing the turbulence and intensity of the outflow.

[0029] Preferably, the length of at least two channels of the grid is at least 3 mm, preferably between 4 mm and 200 mm, more preferably at least 5 mm, even more preferably at least 7 mm, most preferably at least 10 mm.

[0030] The longer the channel, the higher the flow homogenization effect. Generally speaking, a channel of at least 3 mm makes the flow more uniform, so that noise generated by the flow itself can be avoided. A channel with a length of at least 3 mm ensures a uniform flow of the gas, so that turbulence is reduced in the mixing area where the high-pressure gas mixes with the ambient air.

[0031] Therefore, a passage of at least 3 mm can effectively reduce the noise generated by the mixing of air flowing out of the chamber and the silencer. Therefore, a passage of at least 3 mm helps to avoid noise generated by turbulence.

[0032] Preferably, the cross-sectional area of ​​the at least two channels decreases from the inlet of the channel to the smallest diameter portion and increases from the smallest diameter portion towards the outlet of the channel.

[0033] The specific shape of the channel is similar to a nozzle and usually has optimized flow characteristics. Such a nozzle shape can reduce the flow rate.

[0034] The cross-sectional area of ​​at least two of the channels is specifically streamlined, reducing separation vortices and resistance vortices that may form behind the grille. Such streamlined channels reduce resistance caused by the grille and also reduce flow resistance that affects the operating speed of pneumatic valves, etc. In addition, such streamlined channels can reduce the size and intensity of vortices (formed when compressed air mixes with ambient air) behind the grille, thereby reducing the noise energy generated by turbulence.

[0035] Thus, turbulent wakes (eddies) can be effectively reduced, in particular by reducing the turbulence intensity in the grid, which is formed by the wakes generated by the separation of air through the grid.

[0036] Preferably, the portion of smallest diameter (eg approximately in the middle of the channel length) has a cross-sectional area which is between 80% and 95%, preferably more than 85%, of the cross-sectional area of ​​the channel inlet and / or channel outlet.

[0037] This geometric constraint simulates the shape of the nozzle. With such a shape of the channels, the flow velocity of the compressed gas is reduced. This geometric constraint results in lower resistance at the inlet and shorter wake at the outlet. Moreover, due to the shape of the nozzle, the mixing point / area (of pressurized gas and ambient gas) moves towards the grid and the separation wake decreases with its size. Moreover, the flow core (the velocity profile leaving each channel of the grid) becomes wider, resulting in a very uniform flow with less turbulence and therefore less noise.

[0038] Furthermore, due to the shape of the nozzle, the mixing point / area (of pressurized gas and ambient gas) moves away from the grid and the separation wake decreases with its size. In addition, the flow core (the velocity profile leaving each channel of the grid) becomes wider, resulting in a very uniform flow with less turbulence and therefore less noise.

[0039] In one embodiment, the inlet of the channel and the outlet of the channel have the same cross-sectional area, which results in a uniform flow. The cross-sectional area is the area over which the air flows in the inlet, outlet or a length therebetween.

[0040] Preferably, the cross-sectional area of ​​the channel is greater at the inlet of the channel than at the smallest diameter portion and at the channel outlet, and the cross-sectional area of ​​the channel is greater at the outlet of the channel than at the smallest diameter portion. By means of this nozzle design, a very uniform flow can be ensured.

[0041] In this case, the channel acts as a mixer, concentrating the airflow at the outlet of the channel.

[0042] Alternatively, the cross-sectional area of ​​the channel is larger at the outlet of the channel than at the portion of smallest diameter and at the inlet of the channel, wherein the cross-sectional area of ​​the channel is larger at the inlet of the channel than at the portion of smallest diameter.

[0043] This nozzle design is a diffuser which also results in a very rapid pressure drop, but without generating noise, in particular by moving the mixing zone (of pressurized air and ambient air) away from the grille.

[0044] Preferably, the first muffler is arranged in the first shell, and the second muffler is arranged in the second shell. More preferably, the first shell and the second shell can be connected by a snap connection structure. A snap connection or ultrasonic welding can also be performed.

[0045] This design with different housings allows a modular design of the silencer, wherein the silencer can be tailored to specific sound-absorbing requirements.

[0046] The snap-on connection allows for low installation effort and easy maintenance.

[0047] Preferably, a seal is provided in the first housing, the seal being adapted to seal the connection between the first housing and the valve housing. This configuration helps to avoid uncontrolled leakage between the silencer and the valve interface.

[0048] A preferred use of the silencer according to the present application is in brake systems, in particular brake systems of commercial vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Hereinafter, preferred embodiments of the present invention are described with reference to the accompanying drawings.

[0050] Figure 1 a) shows the modular design of the silencer, where two different silencer arrangements are shown.

[0051] Figure 1 b) shows the Figure 1 a) Similar design, however, the second silencer is divided into two parts with different densities.

[0052] Figure 2 a) shows a schematic arrangement of a silencer according to the present application located below a valve. Here, a sectional view is shown. Figure 4 b) shows the air flow in such a silencer.

[0053] Figure 3 Shown with Figure 2 Similar embodiments.

[0054] Figure 4 a) shows the Figure 2 Similar embodiments. Figure 4 b) shows the air flow in such a silencer.

[0055] Figure 5 a) shows another embodiment of the silencer according to the present application, wherein Figures 1 to 4 In comparison, the thickness of the intermediate element is greater. Figure 5 b) shows the air flow in such a silencer.

[0056] Figure 6 A detailed view of the grille is shown. DETAILED DESCRIPTION

[0057] exist Figure 1 In a), a silencer 1 according to the present application is shown. Here, there is a first shell 2 and a second shell 5. A first silencer 4 is arranged in the first shell 2, and a second silencer 6 is arranged in the second shell 5. An intermediate element 7 is arranged between the first silencer 4 and the second silencer 6, and the intermediate element is a flat plate with a plurality of openings. Below the second silencer, a grille 8 with a plurality of channels 9 is used. There is a snap-on connection structure 10 between the first shell 2 and the second shell 5. It can be seen that the diameter of the first silencer 4 is smaller than the diameter of the second silencer 6. In addition, compared with the first silencer 4, the density of the second silencer is higher.

[0058] Figure 1 b) shows the Figure 1 a) Similar design, however, the second muffler 6 is divided into two parts with different densities, an upper part 6a and a lower part 6b. The density of the upper part 6a is similar or equal to the density of the first muffler 4. Compared with the upper part 6a and the first muffler 4, the lower part 6b has a higher density.

[0059] The lower portion 6 b improves the uniformity of the flow, since the higher density contributes to an improved flow distribution, which is particularly important when the air leaves the silencer 1 through the grille 8 .

[0060] exist Figure 2 In a), the arrangement of the silencer 1 according to the present application below the valve V is shown. The inlet 3 of the silencer 1 is arranged at the outlet of the valve V, and the first silencer 4 is arranged just downstream of the inlet 3. An intermediate element 7 is arranged below the first silencer 4, similar to Figure 1 A second muffler is arranged below the intermediate element 7, below which a grille 8 with a plurality of channels 9 is arranged. A snap-fit ​​connection 10 is provided between the first housing 2 and the second housing 5, on which a seal 11 is provided for connection to the valve V. The first muffler 4 protrudes to a certain extent into the second muffler 6. Figure 2 b) shows the flow in such a silencer 1. The different densities of the first silencer 4 and the second silencer 6 are not shown in FIG. Figure 2It can be seen that the compressed air flows radially downwards after the intermediate element 7 , but is slightly deflected at the outer radial portion of the first silencer 4 and protrudes into the second silencer 6 .

[0061] exist Figure 3 In the embodiment, the grille 8 with the channel 9 and Figure 2 In this embodiment, the first muffler 4 does not protrude into the second muffler 6.

[0062] exist Figure 4 In the embodiment a), the grille 8 with the channels 9 and Figure 3 The first muffler 4 does not protrude into the second muffler 6. Figure 4 b) shows the flow within such a silencer 1 . Figure 4 The different densities of the first silencer 4 and the second silencer 6 are not shown in b). It can be seen that the compressed air flows radially downwards after the intermediate element 7.

[0063] exist Figure 5 In the embodiment of a), the intermediate element 7 has a specific shape, it is thicker and has a tapered channel. In this embodiment, the first muffler 4 does not protrude into the second muffler 6. Figure 5 b) shows the flow in such a silencer 1. The different densities of the first silencer 4 and the second silencer 6 are not shown in FIG. Figure 5 b). It can be seen that the compressed air flows radially downwards after the intermediate element 7. The conical opening of the intermediate element 7 disperses the air flow in the second muffler 6.

[0064] Figure 6 A detailed view of an example of a grid 8 is shown. Each channel 9 has an inlet 9a, a portion with the smallest diameter 9b and an outlet 9c. Thus, the cross-sectional area decreases from the inlet 9a to the portion with the smallest diameter 9b and then increases again until the outlet 9c. The channels 9 have a polygonal cross section (and shape). The cross section of the wall 9d between the channels 9 is rhombus-shaped.

[0065] However, a rounded or oval cross section of the channel 9 is also possible.

[0066] For example, the first muffler 4 and the second muffler 6 can be connected by gluing or welding (for example to the intermediate element 7). The first muffler 4 and the second muffler 6 can be manufactured by rolling a mesh. For example, the upper and lower parts of the mesh can be woven (with different densities) in one step, for example, and the diameter of the rolled mesh increases when rolling. In this case, the intermediate element 7 is not required.

[0067] Reference numerals list

[0068] 1 Muffler inlet opening

[0069] 2. First shell

[0070] 3 Entrance

[0071] 4. First silencer / mesh

[0072] 5 Second shell

[0073] 6. Second silencer / mesh

[0074] 6a upper part

[0075] 6b lower part

[0076] 7 Intermediate Components

[0077] 8 Grille

[0078] 9 channels

[0079] 10 Snap-on connection structure

[0080] 11 Seals

[0081] V valve housing

Claims

1. A silencer (1) for a compressed air system, comprising: an air inlet (3) for a compressed air flow, A first silencer (4) arranged downstream of the air inlet (3); a second silencer (6) arranged downstream of the first silencer (4); a grille (8) arranged downstream of the second silencer (6), the grille (8) comprising at least two channels (9), the compressed air flow being adapted to leave the silencer (1) through the at least two channels (9), wherein the first silencer (4) has a smaller diameter than the second silencer (6), And wherein the second silencer (6) has at least partially a higher density than the first silencer (4).

2. The muffler according to claim 1, wherein: The first silencer (4) has an equal or smaller height than the second silencer (6).

3. The silencer (1) according to claim 1 or 2, wherein: An intermediate element (7) is arranged between the first silencer (4) and the second silencer (6).

4. The silencer (1) according to any one of the preceding claims, wherein: The first muffler device (4) and / or the second muffler device (6) comprises a fibrous material, preferably a fiber mesh, more preferably a fiber mesh comprising polyethylene.

5. The silencer (1) according to any one of the preceding claims, wherein: The cross-section of at least two channels (9) of the grid (8) is polygonal, preferably hexagonal, or rounded.

6. The silencer (1) according to any one of the preceding claims, wherein: The height of the first silencer (4) is between 20 mm and 40 mm, and / or the height of the second silencer (6) is between 20 mm and 40 mm.

7. The silencer (1) according to any one of the preceding claims, wherein: The diameter of the first muffler (4) is at most 65 mm, preferably at most 62 mm, and / or the diameter of the second muffler (4) is at least 80 mm, preferably at least 90 mm, more preferably at least 100 mm.

8. The silencer (1) according to any one of the preceding claims, wherein: The length of the at least two channels (9) is at least 3 mm, preferably between 4 mm and 200 mm, more preferably at least 5 mm, even more preferably at least 7 mm, most preferably at least 10 mm.

9. The silencer (1) according to any one of the preceding claims, wherein: The cross-sectional areas of the at least two channels (9) decrease from the channel inlet (9a) to the smallest diameter portion (9b), and increase from the smallest diameter portion (9b) toward the channel outlet (9c).

10. The silencer (1) according to any one of the preceding claims, wherein: The cross-sectional area of ​​the smallest diameter portion (7b) of the at least two channels (7) is between 80% and 95%, preferably more than 85%, of the cross-sectional area of ​​the inlet (7a) of the at least two channels and / or the outlet (7c) of the at least two channels.

11. The silencer (1) according to any one of the preceding claims, wherein: The inlet (9a) of the at least one channel (9) and the outlet (9c) of the at least one channel (9) have the same cross-sectional area.

12. The silencer (1) according to any one of claims 1 to 10, wherein: The cross-sectional area of ​​the at least one channel (9) at the inlet (9a) of the at least one channel is larger than the cross-sectional area at the minimum diameter portion (9b) and the outlet (9c) of the at least one channel, and the cross-sectional area of ​​the at least one channel (9) at the outlet (9c) of the at least one channel is larger than the cross-sectional area at the minimum diameter portion (9b).

13. The silencer (1) according to any one of claims 1 to 10, wherein: The cross-sectional area of ​​the at least one channel (9) at the outlet (9c) of the at least one channel is larger than the cross-sectional area at the minimum diameter portion (9b) and the inlet (9a) of the at least one channel, and the cross-sectional area of ​​the at least one channel (9) at the inlet (9a) of the at least one channel is larger than the cross-sectional area at the minimum diameter portion (9b).

14. The silencer (1) according to any one of the preceding claims, wherein: The first silencer (4) is arranged in the first shell (2), and the second silencer (6) is arranged in the second shell (5). The first shell (2) and the second shell (5) are preferably connectable via a snap-on connection structure (10).

15. The silencer (1) according to any one of the preceding claims, wherein: A sealing member (11) is provided at the first housing (2), and the sealing member (11) is suitable for sealing the connection between the first housing (2) and the housing of the valve (V).

16. Use of a silencer (1) according to any one of claims 1 to 15 for a brake system, preferably a brake system (B) of a commercial vehicle.

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