DE102013016086A1 - Method and device for dimensioning an interference silencer in a compressed air brake system of a motor vehicle - Google Patents

Abstract

Method and device for dimensioning an interference silencer (7) in an air brake system in a motor vehicle, in particular in compressed air lines (3) between a valve (4), such as brake value transmitter, relay valve, axle modulator or trailer control valve and a reservoir pressure vessel (1), wherein the interference silencer (7 ) consists of two parallel, in the compressed air lines (3) inserted line elements (8, 9), of which the first, longer line element (8) has a length approximately equal to the wavelength λ of the vibration in the compressed air line (3) and the second, shorter Conduit element (9) has a length approximately equal to half the wavelength λ / 2 of the vibration in the compressed air line (3). The interference muffler (7) serves to extinguish by the switching of the valve (4) triggered, noise-forming vibrations in the compressed air line (3) or to reduce as much as possible.

Description

The invention relates to a method for dimensioning an interference sound attenuator for damping sound pressure pulses in compressed air lines in a compressed air brake system in a motor vehicle, in particular in compressed air lines between a valve, such as brake value transmitter, relay valve, axle modulator or trailer control valve and a reservoir pressure vessel, a device for damping sound pressure pulses in compressed air lines an air brake system in a motor vehicle, a compressed air brake system in a motor vehicle with an interference muffler and the use of an interference muffler in a compressed air brake system in a motor vehicle.

The structure and operation of a brake value transmitter are for example in the DE 33 43 172 A1 , that of a relay valve in the DE 195 10 492 A1 and that of a trailer control valve in the DE 196 09 222 A1 described. The structure and operation of these units in a compressed air system of a vehicle are not the subject of the present invention and therefore not described in detail, but it is hereby referred to in this regard to the cited references.

Silencer in conjunction with the mentioned units are for example in the DE 10 2009 029 968 A1 . DE 196 09 222 A1 and the DE 10 2008 029 489 A1 shown and described. These are independent components which are detachably attached to a vent outlet on a housing of a brake value transmitter, a relay valve, an axle modulator or a trailer control valve, wherein the noise damper comprises a housing in which a damping means, for example in the form of a knitting roll of thermoplastic threads , is arranged. Such silencers are only suitable for being located at venting outlets of valves, but they are less likely to suppress or dampen sound pressure pulses in compressed air ducts resulting from the switching of valves.

Applicant's prior art has attempted to damp the sound pressure pulses by placing a buffer volume directly on a valve that switches air pressure rapidly, decreasing the switching speed of the valve, or acoustically adjusting the flow resistances on the valve. However, these solutions have proven to be costly, have been associated with operational risk, for example, by the deposition of water in the buffer volume, and led to slow pressure changes, which are to be avoided for a pressure control in an antilock braking system of a vehicle.

Against this background, the invention has the object to provide a cost-effective solution for the damping of sound pressure pulses in compressed air lines between a valve, such as brake signal, relay valve, axle modulator or trailer control valve and a reservoir pressure vessel in a compressed air brake system in a motor vehicle.

• a) Messen eines durch Betätigung des Ventils entstehenden Druckimpulses an dem mit dem Vorratsdruckbehälter über eine Druckluftleitung verbundenen Ventil;
• b) Messen eines durch die Betätigung des Ventils entstehenden Druckimpulses an dem mit dem Ventil über die Druckluftleitung verbundenen Vorratsdruckbehälter;
• c) Ermitteln der Schwingungsdauer der zwischen dem Ventil und dem Vorratsdruckbehälter auftretenden, durch die Druckimpulse angeregten Schwingung;
• d) Ermitteln der Wellenlänge λ der Schwingung aus deren Schwingungsdauer;
• e) Einfügen zweier paralleler Leitungselemente in die Druckluftleitung, von denen das erste Leitungselement eine Länge etwa gleich der Wellenlänge λ der Schwingung und das zweite Leitungselement eine Länge etwa gleich der halben Wellenlänge λ/2 der Schwingung aufweist.

This object is achieved by a method for dimensioning an interference sound attenuator for damping sound pressure pulses in compressed air lines in a compressed air brake system in a motor vehicle, in particular in compressed air lines between a valve, such as brake value transmitter, relay valve, axle modulator or trailer control valve and a reservoir pressure vessel with the steps:

• a) measuring a pressure pulse generated by actuation of the valve at the connected to the reservoir pressure vessel via a compressed air line valve;
• b) measuring a generated by the actuation of the valve pressure pulse at the connected to the valve via the compressed air line reservoir pressure vessel;
• c) determining the oscillation period of occurring between the valve and the reservoir pressure, excited by the pressure pulses oscillation;
• d) determining the wavelength λ of the oscillation from its oscillation period;
• e) inserting two parallel line elements in the compressed air line, of which the first line element has a length approximately equal to the wavelength λ of the oscillation and the second line element has a length approximately equal to half the wavelength λ / 2 of the oscillation.

The method is based on the finding that two sound waves of the same wavelength λ, which are shifted from one another by half the wavelength phase, cancel each other out if they also have the same amplitude. The principle of operation of such an interference muffler is in Chapter 10.8 of the publication "Fluid Acoustics in Theory and Practice", 3rd ed., Published in the expert publisher with the subtitle "contact and study, Bd. 474 disclosed.

The principle of operation of an interference silencer is based on the fact that a duct or a pipeline is divided into two pipes connected in parallel, the lengths of which differ by λ / 2.

For dimensioning the interference silencer in a compressed air brake system, it is important to first determine whether the Sound pressure pulse when switching the valve leads to audible vibrations in the compressed air line. For this purpose, it must first be determined whether a pressure pulse arising on actuation of the valve arrives at the reservoir pressure vessel. If this is the case, the wavelength λ of the oscillation in the compressed air line excited by the pressure pulse is determined by mapping the measured oscillations, for example on an oscilloscope, and measuring the oscillation period. As is known, the wavelength of a vibration can be calculated from the equation λ = V _S × T, in which λ = wavelength, V _S = sound velocity and T = vibration duration.

Once the wavelength λ of the vibration is known, the interference muffler can be dimensioned by inserting two parallel duct members into the compressed air duct, of which the first duct member has a length approximately equal to the wavelength λ of the vibration and the second duct member has a length approximately equal to half the wavelength Have λ / 2 of the oscillation.

These parallel line elements can be inserted at any point in the compressed air line, but they are preferably inserted directly on the valve in the compressed air line, the parallel line elements can be connected via Y-connectors.

According to another embodiment, which can be with a valve having two mutually connected in the valve ports perform, the two parallel line elements can be connected to one another with the two interconnected terminals on the valve and on the other hand by means of a Y-connector, whereby a Y-connector can be omitted.

Since the running time of the vibrations passing through the line elements is influenced by frictional effects in the line elements and the deflections, whereby the energy flow through the two line elements is different, a uniform energy flow can be achieved by appropriate dimensioning of the cross sections of the two line elements, wherein the cross section of the first , longer line element is preferably about twice as large as the cross section of the second, shorter line element is selected.

Furthermore, an optimization of the attenuation by means of the interference sound attenuator can be achieved if the length and / or the diameter of the first, longer or the second, shorter line element are incrementally changed in small steps until an optimal noise attenuation is achieved.

As is known, the speed of sound changes significantly with the air temperature. Thus, the sound velocity at an air temperature of -40 ° C is only 306.23 m / s, at + 20 ° C already 343.38 m / s and at + 80 ° C 376.89 m / s. This can be taken into account by changing the length of the two line elements as a function of the usual operating temperature. But since this measure requires complicated control devices and control devices, it is sufficient in most cases to set the length of the two line elements to an average temperature of + 20 ° C.

The above-mentioned object is further achieved by a device for damping sound pressure pulses in compressed air lines in a compressed air brake system in a motor vehicle, in particular in compressed air lines between a valve, such as brake signal, relay valve, axle modulator or trailer control valve and a reservoir pressure vessel, consisting of a in or the compressed air lines arranged interference muffler with two parallel, different length line elements, which are dimensioned and arranged according to the method defined above.

Another solution to the above-mentioned problem consists of a compressed air brake system in a motor vehicle with compressed air lines between a valve, such as brake signal, relay valve, axle modulator or trailer control valve and a reservoir pressure vessel with an arranged in the compressed air line interference muffler with two parallel, different length line elements, according to the above dimensioned and arranged are mentioned.

Finally, the object mentioned above is also solved by the use of a dimensioned according to the above-mentioned method and arranged interference muffler in a compressed air brake system in a motor vehicle with compressed air lines between a valve, such as brake signal, relay valve, axle modulator or trailer control valve and a reservoir pressure vessel.

The invention will be explained below with reference to two, shown in the accompanying drawings embodiments. In the drawing shows

1 an interference muffler arrangement according to the invention between a reservoir pressure vessel and a valve according to a first embodiment,

2 an interference damper assembly according to a second embodiment, and

3 a schematic representation of a measuring arrangement for determining the wavelength λ of the excited by the switching of the valve oscillations in the compressed air line between the valve and a reservoir pressure vessel.

In the DE 10 2006 041 009 A1 the same applicant is shown and described an air brake system for a motor vehicle, in which the inventive interference muffler can be integrated. For details and the operation of this brake system, reference is made to this document whose contents are fully made the subject of the disclosure of the present invention.

An inventive interference muffler 7 is in 1 in a compressed air line 3 between a storage pressure vessel 1 and a valve 4 arranged. At the valve 4 it can be a brake value transmitter, a relay valve, an axle modulator or a trailer control valve. The interference silencer 7 consists of a first line element 8th and a second conduit element arranged parallel thereto 9 , The two line elements 8th . 9 are with the compressed air line 3 by means of a first Y-connector 10 as well as with a compressed air line connection 5 at the valve 4 by means of a second Y-connector 10 ' connected and thus through the two Y-connectors 10 . 10 ' merged.

The length of the first conduit element 8th is approximately equal to the wavelength λ of the switching of the valve 4 in the compressed air line 3 excited vibrations, while the length of the second conduit element 9 only about half the wavelength λ / 2 of the vibrations is. The valve 4 is over an exit 6 with a valve, not shown, through the valve 4 connected to actuated component of a compressed air brake system of a motor vehicle. For example, it may be at the valve 4 around the in 1 of the DE 10 2006 041 009 A1 shown brake value transmitter 16 act, via a compressed air line, not shown, with the local first reservoir pressure vessel 18 and / or the local second reservoir pressure vessel 20 connected is. In this compressed air line, the interference silencer 7 be arranged. It is also possible to use the interference silencer 7 in the local compressed air line 36 from the local storage pressure vessels 18 . 20 for trained as a relay valve local air quantity enhancing valve device 34 to arrange.

In 2 is a valve 4 ' shown, the two pressure line connections 5a . 5b which is inside the valve 4 ' connected to each other. This connection is indicated by dotted lines. Accordingly, the first line element can be 8th' to the compressed air line connection 5a and the second conduit element 9 ' to the compressed air line connection 5b connect so that the two line elements 8th' . 9 ' of the interference muffler 7 ' only by a single Y-connector 10 with the compressed air line 3 to the reservoir pressure vessel 1 are connected.

Out 3 shows a measuring arrangement, by means of which the wavelength λ by the switching of the valve 4 in the compressed air line 3 can determine excited vibrations. For this purpose is at the line connection 2 of the reservoir pressure vessel 1 a first pressure sensor 11 and at the compressed air line connection 5 of the valve 4 a second pressure sensor 12 arranged. The by switching the valve 4 Triggered pressure pulses occur at the line connection 2 of the reservoir pressure vessel 1 as well as at the compressed air line connection 5 at the valve 4 on and lead to vibrations in the compressed air line 3 with a frequency of, for example, about 400 Hz, which are audible as knocking and disturbing, so that they should be suppressed as possible or at least strongly attenuated. The of the two pressure sensors 11 . 12 generated measuring signals are sent to an oscilloscope 13 passed, which is suitable, the wavelength λ of the vibrations in the compressed air line 3 to determine. From the wavelength λ, the length of the first line element can be 8th , which should be approximately equal to the wavelength λ, as well as the length of the second line element 9 , which should be about equal to half the wavelength λ / 2, determine, so that the interference muffler 7 . 7 ' in the in the 1 and 2 training illustrated way.

Preferably, the interference silencers 7 . 7 ' to the compressed air line connection 5 of the valve 4 or at the compressed air line connections 5a . 5b of the valve 4 ' However, they can also be located anywhere in the compressed air line 3 are located. By the length measurement of line elements 8th . 9 ; 8th' . 9 ' as a function of the wavelength λ, the phase shift of the through these line elements 8th . 9 ; 8th' . 9 ' set current oscillations of 180 °, so that the through these conduit elements 8th . 9 ; 8th' 9 ' wandering vibrations when meeting in the area of Y-connectors 10 or the compressed air line connections 5a . 5b largely cancel each other out.

The energy flow through the two line elements 8th . 9 ; 8th' . 9 ' should be as equal as possible, therefore, the amplitudes of the by these line elements 8th . 9 ; 8th' . 9 ' migratory vibrations should be as equal as possible. Accordingly, the cross sections of the two line elements can be 8th . 9 ; 8th' . 9 ' dimension accordingly, for example by the cross section of the longer line elements 8th . 8th' twice as large as the cross section of the shorter line elements 9 ; 9 ' is trained.

A further optimization of the damping by the Interferenzschalldämpfer 7 . 7 ' can be achieved when the length and / or diameter of the first, longer line element 8th . 8th' or the second, shorter line element 9 . 9 ' is incrementally and gradually changed until a maximum noise attenuation is achieved.

In a test arrangement according to 3 an oscillation period T of 2.2503 m / s was determined, which corresponds to a frequency f = 444.39 Hz. This results in a wavelength λ _S = V _S × T = 343.38 m / s × 2.2503 m / s = 0.7727 m, where λ is the wavelength, Vs = the speed of sound at + 20 ° C and T the oscillation period is. Accordingly, results for the length of the first, longer line element 8th . 8th' a value of 0.7727 m and for the length of the second, shorter line element 9 . 9 ' a value of 0.3864 m.

The speed of sound in the compressed air line 3 and the conduit elements 8th . 9 ; 8th' . 9 ' is below the theoretically ideal speed of sound. This may be due to friction effects of the compressed air on the line surfaces and the Umlenkradien the lines. Due to the reduced speed of sound, the vibrations require a longer time to the longer, first line elements 8th . 8th' opposite the second, shorter line elements 9 . 9 ' to go through. To take this into account, the length of the shorter, second conduit member became 9 . 9 ' incrementally and incrementally increased in five-centimeter increments, thereby significantly improving the damping by the interference muffler 7 . 7 ' was achieved up to an achievable optimum value.

To be sure that the noise attenuation is actually due to the interference muffler 7 . 7 ' was effected in a control experiment, the first, longer line element 8th . 8th' removed and the corresponding connections closed. In this experimental arrangement were clearly heard noise, whereby the effectiveness of the interference sound damper according to the invention 7 . 7 ' was confirmed.

All the features mentioned in the preceding description of the figures, in the claims and in the introduction to the description can be used both individually and in any combination with one another. The invention is thus not limited to the described and claimed feature combinations, but all feature combinations are to be regarded as disclosed.

LIST OF REFERENCE NUMBERS

1

Reservoir pressure vessel

2

line connection

3

Compressed air line

4, 4 '

Valve

5, 5a, 5b

Compressed air line connection

6, 6 '

output

7, 7 '

interference silencer

8, 8 '

First line element

9, 9 '

Second conduit element

10

Y-connector

11

First pressure sensor

12

Second pressure sensor

13

oscillograph

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 3343172 A1 [0002]
• DE 19510492 A1 [0002]
• DE 19609222 A1 [0002, 0003]
• DE 102009029968 A1 [0003]
• DE 102008029489 A1 [0003]
• DE 102006041009 A1 [0023, 0025]

Claims (10)

Method for dimensioning an interference silencer ( 7 . 7 ' ) for damping sound pressure pulses in compressed air lines ( 3 ) in an air brake system in a motor vehicle, in particular in compressed air lines ( 3 ) between a valve ( 4 . 4 ' ), such as brake value transmitter, relay valve, axle modulator or trailer control valve and a reservoir pressure vessel ( 1 ) comprising the steps of: a) measuring one by operating the valve ( 4 . 4 ' ) produced pressure pulse at the with the reservoir pressure vessel ( 1 ) via a compressed air line ( 3 ) connected valve ( 4 . 4 ' ); b) measuring one by actuating the valve ( 4 . 4 ' ) produced pressure pulse at the with the valve ( 4 4 ' ) via the compressed air line ( 3 ) associated reservoir pressure vessel ( 1 ); c) determining the period of oscillation between the valve ( 4 . 4 ' ) and the reservoir pressure vessel ( 1 ) occurring, excited by the pressure pulses oscillation; d) determining the wavelength λ of the oscillation from its oscillation period; e) inserting two parallel line elements ( 8th . 9 ; 8th' . 9 ' ) into the compressed air line ( 3 ), of which the first line element ( 8th . 8th' ) has a length approximately equal to the wavelength λ of the oscillation and the second line element ( 9 . 9 ' ) has a length approximately equal to half the wavelength λ / 2 of the oscillation. Method according to Claim 1, in which the parallel line elements ( 8th . 9 ; 8th' . 9 ' ) via Y-connectors ( 10 ) get connected. Method according to Claim 1 or 2, in which the parallel line elements ( 8th . 9 ; 8th' . 9 ' ) directly on the valve ( 4 . 4 ' ) into the compressed air line ( 3 ). Method according to Claim 1 or 2, in which the parallel line elements ( 8th . 9 ; 8th' . 9 ' ) on the one hand with two interconnected terminals ( 5a . 5b ) on the valve ( 4 ' ) and on the other hand by means of a Y-connector ( 10 ). Method according to one of claims 1 to 4, wherein by appropriate dimensioning of the cross sections of the two line elements ( 8th . 9 ; 8th' 9 ' ) the energy flow through the two line elements ( 8th . 9 ; 8th' 9 ' ) is divided equally. Method according to Claim 5, in which the cross-section of the first, longer line element ( 8th . 8th' ) about twice as large as the cross section of the second, shorter line element ( 9 . 9 ' ) is selected. Method according to one of claims 1 to 6, wherein an optimization of the attenuation by stepwise, incrementally changing the length and / or the diameter of the first, longer line element ( 8th . 8th' ) or the second, shorter line element ( 9 . 9 ' ) is carried out. Device for damping sound pressure pulses in compressed air lines ( 3 ) in an air brake system in a motor vehicle, in particular in compressed air lines ( 3 ) between a valve ( 4 . 4 ' ), such as brake value transmitter, relay valve, axle modulator or trailer control valve and a reservoir pressure vessel ( 1 ), consisting of one in the or the compressed air line (s) ( 3 ) arranged interference muffler ( 7 . 7 ' ) with two parallel, different length line elements ( 8th . 9 ; 8th' 9 ' ), which are dimensioned and arranged according to the method according to one of claims 1 to 7. Air brake system in a motor vehicle with compressed air lines ( 3 ) between a valve ( 4 . 4 ' ), such as brake value transmitter, relay valve, axle modulator or trailer control valve and a reservoir pressure vessel ( 1 ) with one in the compressed air line ( 3 ) arranged interference muffler ( 7 . 7 ' ) with two parallel, different length line elements ( 8th . 9 ; 8th 9 ' ), which are dimensioned and arranged according to the method according to one of claims 1 to 7. Use of an interference muffler (according to the method according to one of claims 1 to 7) and arranged ( 7 . 7 ' ) in an air brake system in a motor vehicle with pressure lines ( 3 ) between a valve ( 4 . 4 ' ), such as brake value transmitter, relay valve, axle modulator or trailer control valve and a reservoir pressure vessel ( 1 ).

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