RU40797U1 - STAND FOR ACOUSTIC RESEARCHES OF WHEELED VEHICLES - Google Patents

Abstract

Specifically, the device relates to the design of the stands, including soundproofing devices used for experimental acoustic studies of wheeled vehicles, mainly passenger cars. The stand, in particular, contains noise insulation devices to reduce the background noise emitted by tires of a wheeled vehicle rotating on running drums. New is that the soundproofing device is made in the form of volumetric double-sided sound-absorbing screens, the structure of which includes a combination of mutually mating layers of a bearing perforated metal sheet and layers of self-adhesive sound-absorbing porous fibrous or open-cell foam material with an external protective soundproof layer located on both sides of it; sound-absorbing screens are installed directly opposite the car tires with the possibility of providing clearance-free contact with the surface of the body and floor of the test chamber, while the mounting bases of the screens are made in the form of two plates with adjustment grooves that are fixed in the standard groove guides of the dynamic drum stand with the possibility of selective selection and fixing the position of the screens depending on the track of the vehicle under study, the front panels of the screens have a technological an aperture for installing the stop restrictive roller of the bench guard, and the end part of the side and top panels is made in the form of an elastic allowance for sound-absorbing material.

The use of the inventive stand allowed to reduce the influence of "spurious" background noise emitted from the side of the tires rotating on the running drums, especially at high rotation speeds. At the same time, the accuracy and objectivity of the results of measurements of the noise characteristics of the studied individual units, assemblies and systems of a wheeled vehicle increased.

Description

The utility model relates to techniques for studying the sources of noise of wheeled vehicles, performed in an acoustic semi-anechoic chamber with a rigid sound-reflecting floor chamber, and specifically relates to the designs of stands, including soundproof devices used for experimental acoustic studies of wheeled vehicles, mainly passenger cars.

Solving the problem of reducing acoustic pollution of the environment and improving the acoustic comfort of land wheeled vehicles is an important urgent task for developers and researchers of transport equipment, requiring large material, time and intellectual costs. The most mobile and productive research and development processes, in particular, wheeled vehicles in noise and vibration comfort, are experimental studies carried out in bench conditions, using a variety of techniques to simulate speed and load conditions identical to the road (field) test conditions (for example, dynamic stands with running drums), stationary measuring and analyzing equipment. Constant weather and road conditions independent of the test conditions, the convenience of taking and analyzing measurement information contribute to the wider spread of bench studies of vibro-acoustic processes in land wheeled vehicles. Due to the fact that the main vibro-noise source of a vehicle is its power plant - internal combustion engine (ICE) and, in particular, its gas exchange system, including an intake system and an exhaust system, as the most intense gas-dynamic noise sources, it is very important to carry them out research and development on a dynamic bench while simulating various speed and load conditions

(changing the speed of the internal combustion engine, the opening angle of the throttle, etc.) under similar conditions of a free sound field (in which the vehicle is located on the freeway or field conditions during its operation).

A fairly complete imitation of the conditions of high-speed and load modes of vehicle movement in real road conditions can be achieved at stands with running drums, the practice of which is widely used in enterprises producing motor vehicles and research institutes. On the other hand, it is possible to realize the conditions of a free sound field by placing this dynamic stand with running drums in a special building - a semi-anechoic or anechoic acoustic chamber.

In this regard, modern research technologies of acoustic processes that are implemented on vehicles (cars, tractors, motorcycles and other types of wheeled vehicles) include, in particular, the use of special low-noise running drums, which allow simulating various speed and load modes of energy and transmission units of vehicles in the conditions of their placement in special anechoic or semi-anechoic acoustic chambers that contribute to the formation of free sound field in the measurement zones.

Anechoic (completely muffled) or semi-anechoic (muffled, with a reflective floor) test chambers are a room mounted on a separate foundation, vibration-isolated from the main building. Such a camera houses a dynamic stand with running drums (or a motor brake stand), vibration-proof from the main building and the camera body. The drive and brake installation are located in the basement, or located on the same level with the camera, in a special machine room. To approximate the acoustic properties of the camera to a free sound field, directional matching of the acoustic impedances (resistance) of the air in the free space of the camera and in the porous structure of the sound-absorbing material lining (lining) sound-reflecting surfaces of walls, ceilings, and floors is performed. That is why the design of sound-absorbing wall cladding (floor,

the ceiling) of the chamber is made porous and has a structural density (porosity) that varies gradually along the depth of the coating in the direction of propagation of sound waves to the rigid sound-reflecting surface of the walls (floor, ceiling). Moreover, the highest density of the porous sound-absorbing cladding is realized directly at the walls of the chamber, and the lowest is on the outer (receiving) surface layer of the sound-absorbing lining of the walls and ceiling of the test chamber. The necessary conditions for such a wave matching of sound propagation and absorption media in the zones of walls and ceilings are achieved, in particular, by using various wedge-shaped volumetric sound absorbers (wedges, backstage). The main materials from which sound absorbers are made are open-cell polyurethane foam, fiberglass, superthin basalt fiber, vinipore with flame retardant impregnation.

During bench acoustic studies of units, assemblies and systems of a wheeled vehicle mounted on the running drums of a dynamic stand, it is usually very difficult to achieve the necessary accuracy of the results of measurements of sound levels when evaluating the acoustic characteristics of various designs of the vehicle’s elements under study (for example, exhaust system, intake , body parts of the power unit, transmission units, etc.). The reason for the difficulty in obtaining objective results is the presence of a high level of "parasitic" masking noise background at the measurement point (in the installation area of the measuring microphone) near the element under study (exhaust pipe cut-off, intake pipe, ICE case) emitting sound. The high “spurious noise background”, understood in this case as “interference”, is transmitted to the measuring zone, to a large extent, in the form of noise emitted by tires rotating on the drums of the bench, which are in contact with the working surface of the running drums of the bench and emit noise due to this interaction. In particular, such a negative influence of background tire noise on the results of measuring the acoustic characteristics of individual noise sources of a wheeled vehicle dominates at high wheel speeds of the vehicle under study.

Known dynamic stand with running drums for acoustic research of wheeled vehicles, presented in the publication

Walter Seeger "Geraususchabstrahlung eines Verbrennungsmotors. Einfluss der Ansaug - und Absauggerausche auf das Fahrzeug-lnnengerausch". Automobil-lndustrie, 1985, No. 5, p. 515 ... 526. Here, in particular, estimates of the noise levels and spectra of ICE intake and exhaust systems were carried out on an Opel-Kadett GSI car mounted on a bench with running drums in a semi-anechoic acoustic chamber (see figures 1, 3 of this publication). The measuring microphone was located in close proximity to the sound element of the car’s investigated sound element (exhaust pipe cut-off, inlet pipe). A significant drawback of the design of the known acoustic test bench for wheeled vehicles is the absence of soundproofing devices that provide soundproofing of the measurement area with a microphone from “spurious” noise background - in particular, created by vehicle tires rotating on running drums, which does not allow high-quality, high accuracy, assessment of sound-damping characteristics of various design options of mufflers of exhaust system, intake, volume su- explore the structure-borne noise of the power unit.

There is a well-known stand for measuring the external noise level of a passenger car of the Volkswagen Acoustic Research Center, the construction of which is described in detail in the publication “Das neue Volkswagen - Akustikzentrum in Wolfsburg. Teil 1: Prufstande ", ATZ, 2003, No. 3, pp. 250-260. A roller stand with an independent drive for each wheel is located in a semi-anechoic chamber measuring 25 * 20 * 6 m. The walls and ceiling of the chamber are covered with sound-absorbing cladding that meets the current level, technical development, which is a combination of combined panel resonators and asymmetrically structured absorbers and providing minimal sound reflection . To the left and right, at a distance of 7.5 m from the axial line of the car’s movement, there are so-called “measuring tracks” with 38 microphones (see figure 2 of this publication). The cycle of measurements of external noise of an accelerating car can be carried out either manually by a person in the car, or by means of programmed control using an autopilot. The disadvantage of the presented design of the acoustic stand is its narrow focus, the possibility of a qualitative assessment of only the external noise of the car as a whole. Objective noise investigation,

radiated by individual systems, components and assemblies of a car is difficult due to the absence of noise insulation devices such as acoustic screens, caps, capsules, etc., which purposefully suppress noise radiation from specific sources, creating high levels of “spurious” noise interference, for research and quantitative estimates weaker noise sources emitted and optimized in lapping processes.

From the certificate for a utility model of the Russian Federation No. 20750, IPC7 B 60 R 13/08, publ. November 27, 2001, BI No. 33, a bench construction is known for researching the effectiveness of the noise-damping characteristics of exhaust silencers of wheeled vehicle engines,

containing a soundproofing screen, contributing to the weakening of "spurious noise" interference at the measurement points (microphone installation locations). When conducting acoustic research on the exhaust system of ICE vehicles, a mobile soundproofing screen is installed in the immediate vicinity in the rear (bumper) area of the car. The exhaust pipe of the main muffler, through the extension nozzle and the channel of the screen window, is discharged into the free zone of the test chamber, separated by the screen from the vehicle mounted on the running drums. The design of the soundproofing screen presented in this utility model provides soundproofing of only the measurement zone in the area of the rear of the vehicle and does not sufficiently reduce the noise interference generated by the interaction zone of the vehicle’s wheels and drive wheels of the bench. As a result of the measurement of noise levels of the studied radiation sources, they are distorted by the influence of one of the most significant sources of the noise “spurious” (background) contribution at the measurement point of the vehicle’s rotating tires mounted on the running drums of the dynamic stand.

A device is known for a sound insulating screen for suppressing the sound emitted by the tires of a moving vehicle (application UK 2163103 and G 10 K 11/16), made in the form of a two-wall structure, the inner space of which contains both sound-absorbing materials and special resonant cavities formed between the inner surfaces the walls. Between the surfaces of the lower end of the screen and the surface of the road surface there is a small air gap.

The disadvantages of the device are its relatively low sound-insulating ability (lightweight thin-walled structure mounted on the body, air gap) and relatively narrow, in this regard, the working range of the muffled sound frequencies.

A well-known stand for acoustic research of wheeled vehicles of the company CEVAA (Center d'Essais Vibro-Acoustique pour I'Automobile), presented in the publication "Movements. All moving so fast! ”, Vehicle News, No. 268, June 2003, pp. 77-79. If necessary, to isolate the background noise emitted by the rotating tires of the car, a soundproofing screen is installed opposite the wheel, made in the form of a volumetric metal casing, in the inner cavity of which a panel of sound-absorbing material is mounted. However, the directly external surface of the screen shell in this design is made of a metal sheet and therefore is sound-reflecting, which leads to the appearance of distortions of real sound fields in the measurement zones. Sound waves emitted by the studied components, assemblies and systems of the car are additionally reflected in this case from the hard metal surfaces of the screen casing, falling into the space of the measuring zone around the test object under investigation, with the measuring microphones installed in it, which directly affects the accuracy and objectivity of research and development work. In addition, the metal structure of the known screen casing is vibration-excitable, which receives vibration from the floor of the test chamber, which can lead to dynamic (vibration) excitation of a thin-walled metal shell and, accordingly, additional re-emission in the form of structural "spurious" noise into the measurement zone.

A well-known stand for acoustic studies of wheeled vehicles, presented in the publication "Akustik-und Schwingungs-komfort des neuen BMW 5er", Sonderausgabe von ATZ und MTZ, 2003, pp. 154-159, adopted as a PROTOTYPE. This publication, in particular, provides an example of a study of the noise of a BMW 5 Series car under bench test conditions on running drums of a dynamic stand installed in an acoustic semi-anechoic chamber. Opposite the rear wheels

soundproofing screens are installed to reduce the “spurious” background noise of tires when examining the acoustic characteristics of individual vehicle noise sources, for example, noise emitted by an open cut of the exhaust pipe of an engine exhaust system. The screen is a mobile, easily portable device, with special handles for moving the screen during installation and dismantling in the space of the test chamber. The design of the soundproofing screen has similar design flaws as the screen of the CEVAA acoustic stand described above.

The proposed technical solution can significantly eliminate the above disadvantages.

The essence of the utility model lies in the fact that in the well-known stand for acoustic research of wheeled vehicles (mainly a passenger car), which contains, in particular, sound-insulating devices to reduce the background "spurious" noise emitted by tires of a wheeled vehicle rotating on running drums - noise-insulating the device is made in the form of volumetric double-sided sound-absorbing screens, the structure of which includes a combination of tightly mating layers of the bearing perforation ovannogo metal sheet and disposed on both sides thereof layers of a self-adhesive porous sound absorbing fibrous or open cell foam with an external sound transmission protective layer; sound-absorbing screens are installed directly opposite to tires of the car with a dense gap-free contact with a surface of a body and a floor of a test chamber. At the same time, the mounting bases of the screens are made in the form of 2 plates with adjusting grooves, which are fixed in the standard groove guides of the dynamic drum stand and allow the use of selective sampling and fixing the position of the screens depending on the track of the vehicle under study;

the front panels of the screens have a technological opening for installing the stop restrictive roller of the protective fence of the stand, and the end part of the side and upper panels is made elastic in the form of an allowance for sound-absorbing material without a hard metal layer.

The essence of the utility model is illustrated graphically.

Figures 1-4 show an acoustic semi-anechoic chamber with a stand installed therein as a utility model for acoustic research of a wheeled vehicle. The positions in figure 1-4 are indicated:

1 - external concrete shell semi-anechoic chamber;

2 - inner concrete shell semi-anechoic chamber;

3 - sound-absorbing cladding type cladding;

4 - springs;

5 - the foundation of a dynamic drum stand;

6 - hard reflective floor;

7 - running drums;

8 - a test vehicle;

9 - mounting cable;

10 - measuring microphones;

11 - a protective fence of the stand;

12 - persistent restrictive roller;

13 - regular groove guides of a dynamic drum stand;

14 - sound-absorbing screen.

Figure 5, 6, 7 presents in 3 projections the design of a sound-absorbing screen.

On Fig presents a section along aa sound-absorbing screen.

Figure 9 shows the mounting of the base plates of the sound-absorbing screen in the standard groove guides of the dynamic drum stand.

The stand for acoustic research of wheeled vehicles contains volumetric double-sided sound-absorbing screens 14 mounted directly opposite to the tires, with tight, clearance-free contact with the body surface of the test vehicle 8, in particular, the car, and the floor surface 6 of the test chamber, and fixed in standard groove guides 13 dynamic drum stand. The design of sound-absorbing screens consists of a front 15, two side 16 and the top 17 panels. The panel structure includes a combination of tightly at right angles to mutually mating layers of a bearing perforated metal sheet

18 (see Fig. 8) and layers of self-adhesive sound-absorbing porous fibrous or open-cellular foam material 19 located on both sides of it with an external protective sound-transparent layer 20. The protective sound-transparent layer 20 is made primarily of washable, fire-resistant, moisture-oil-gas-resistant material, such as a polyester film that does not absorb these substances into the porous structure of a sound-absorbing material that can be easily cleaned with a vacuum cleaner or wet cleaning. Perforation with holes of the supporting metal sheet 18 allows to reduce its possible noise radiation from possible dynamic (vibrational) excitation due to the formation of conditions for a short acoustic circuit realized through perforation holes between the front and back surfaces of the perforated sheet. Double-sided lining with sound-absorbing material of the supporting metal sheet, together with its perforated structure, provides more efficient absorption of sound waves emitted by tires rotating on running drums, allowing sound waves to penetrate through the perforated holes into the area of the external porous layers of sound-absorbing panels and thereby weaken the sound energy with a thicker porous layer of material, including both the inner and the outer lining of the screen. In addition, the noise component is formed, which is formed as a result of reflection of sound from the hard outer surfaces of the screen panels, due to their manufacture from a perforated, weakly reflective sound, metal sheet with two-sided lining by sound-absorbing material, which favorably affects the weakening of negative distortion of sound fields in the measuring zones ( installation microphones). To increase the bending stiffness of the design of the sound-absorbing screens, the bearing perforated metal sheet is reinforced with a supporting tube 21 of a closed profile, for example, square (in Fig. 5-7, the tube is shown by a dashed line). The bases of the screens are made in the form of two metal plates 22 with adjusting grooves 23 and are rigidly fixed with set screws 24 in the standard groove guides 13 of the dynamic drum stand (see Fig. 9). This design of the bases with the use of adjustment grooves allows you to adjust the location of the sound-absorbing screens in

depending on the track of the vehicle under investigation. The lining of the sound-absorbing material 19 of the supporting perforated metal sheet 18 of the side 1 b and the top 17 panels is made with an allowance (in Figs. 6 and 7, the allowance border is highlighted with a thin dashed line) - thus, the end part of the screens in contact with the test object is elastic, without hard metal layer, which allows for tight, gapless contact of the ends of the screens with the car body. The front panel 15 of the sound-absorbing screens at the bottom has a technological opening 25 for installing a thrust restrictive roller of the bench guard.

The application of the inventive design of the stand for acoustic research of wheeled vehicles allows you to reduce the influence of "spurious" background noise emitted from the tires rotating on the running drums, especially at high speeds, and, thus, improve the accuracy and objectivity of the measurement results of the noise characteristics of the individual units, assemblies and systems of a wheeled vehicle.

Claims (1)

A stand for acoustic research of wheeled vehicles, mainly a passenger car, containing, in particular, sound-insulating devices for reducing background noise emitted by tires of a wheeled vehicle rotating on running drums, characterized in that the sound-insulating device is made in the form of volumetric double-sided sound-absorbing screens, the structure of which includes a combination of mutually mating layers of a bearing perforated metal sheet and located on both sides layers of self-adhesive sound-absorbing porous fibrous or open-cell foam material with an external protective sound-transparent layer, sound-absorbing screens are installed directly opposite the car tires with the possibility of providing clearance-free contact with the surface of the body and floor of the test chamber, while the mounting bases of the screens are made in the form of two plates with adjustment grooves which are fixed in the standard groove guides of the dynamic drum stand with the possibility of To selectively select cookies and fix the position of the screens depending on the track of the vehicle under study, the front panels of the screens have a technological opening for installing the stop restrictive roller of the bench guard, and the end part of the side and upper panels is made in the form of an elastic allowance for noise-absorbing material.