Air supply unit for a vehicle

The invention relates to an air supply unit for a vehicle with pneumatic Devices, esp. With air springs, which has a compressor and a muffler contains.

From DE 198 35 491 A1 is a pneumatic device for a vehicle in the form known a level control system, has the air springs. In such must level control systems eg for regulating the level of the vehicle from the air be drained or refilled air springs by means of the compressor, wherein the air is usually performed through an air dryer. is especially the discharge of the air coupled with a loud, unpleasant noise. There is therefore a Need such Niveuaregelanlagen with silencers equip.

With an air supply unit, which from the subsequently published DE 101 21 582 is known, the silencer on a plurality of successively arranged chambers, the manner of a diffuser on narrowing channels are interconnected. Furthermore, softboards eg from sintered material provided with a plurality of fine channels through which is hindurchgeletet the air. This air supply unit already has a significant noise reduction can be achieved. However, the muffler has the disadvantage in that it requires a certain minimum diameter, and a minimum length. at many modern vehicles is the installation space so cramped that the silencer is difficult to accommodate because of its volume. Moreover, the production is of Muffler consuming because it has a complicated structure in its interior and is made of a variety of items, such as diffusers, composed.

The invention is therefore based on the object, an air supply unit of the to provide the aforementioned type is available which has a muffler can be installed even in very cramped conditions in the vehicle and in a simple Manner can be produced.

This object is achieved in that the muffler of a or more hoses made of rubber or a rubber-like material and has is divided by constrictions in its interior into several chambers.

In contrast to previously known silencers are dispensed with in this form on Flappers, sintered disks, foam fillings like which and the unhindered air discharge the unobstructed air intake in the way. Thus, the exhaust noise is the Air supply unit is not significantly longer than for an air supply unit without silencer. Also, the occurring resistance to the compressor must overcome when sucking and discharging, substantially lower than in conventional mufflers.

The muffler is an air discharge hose, which makes no separate enclosure necessary. The space problem that is always in damping measures, is thus overcome. The hose has a smaller diameter than known silencers. by virtue of its flexibility, it can be virtually installed in any manner in the vehicle. Thus may be located even under unfavorable circumstances in the vehicle muffler. The silencer is made up of very simple parts. Both its preparation as also its mounting on the air supply unit are possible in a simple manner. It can be used on standard, commercially available components.

The hose can be produced for example by injection, being by inserting a correspondingly shaped core, the constrictions in one piece into the tube can be formed. This embodiment of the invention is advantageous when the silencer is to be produced in large numbers. The silencer is made in one piece, additional steps, such as the assembly of Individual parts can be omitted. According to another advantageous embodiment of the Invention, the muffler of several tube sections assembled, the are interconnected by connecting pieces, wherein the connection pieces additionally assume the function of the throttle bodies. This embodiment of the Invention is particularly advantageous when the silencer only in lower Quantities needed as standard, not specialized items will be used can.

In the air supply apparatus according to the invention could through the muffler a reduction DERS exhaust noise, but also the intake noise and knocking noises the compressor can be achieved by at least 7 dBA. Sound attenuation on the one hand by the throttle bodies causes at which the sound energy at especially the short-term, very intensive air flow during deflation from the plant is swirled and converted into heat. On the other hand affects the soft material of the Hose damping. In the air supply apparatus according to the invention could in Compared to the known air supply apparatus mentioned above, the one from comprising hard components existing silencer, not only a better noise reduction be achieved, but the remaining noise is pleasant and less hard. A high quality of noise attenuation, by appropriate Features of the hose material can be achieved. It has been shown that a particularly good Damping was achieved when the hose has a Shore hardness between 70 and 80, preferably of about 75 (indicated in Shore A) was obtained.

As a third essential effect for noise reduction effect in the invention Reflections in the chambers defined by a cancellation of the sound phase-shifted, reflected sound waves cause the same frequency. To this effect optimal use, in an advantageous embodiment of the invention are the Chambers formed so that their lengths in an integer ratio to the Wavelength of those portions of the sound are to be primarily attenuated. The muffler can be thus optimized by choosing suitable dimensions, these dimensions, however, depend on the absorbing noise and thus to on the other components of the air supply unit, esp. of the compressor, are. Furthermore, a strong reduction of low frequencies (up to 1000 Hz) is effected, since these sound waves can not propagate, because their wavelength is greater than the Distances between the constrictions.

According to an advantageous embodiment of the invention, the silencer a tube in which the chambers are arranged one behind the other so that they from the Air can flow through them in sequence. Such an embodiment of Invention has the advantage, especially to be simple and a ultra slim exhibit silencer.

In another advantageous embodiment of the invention, the silencer in its central portion, two or more mutually parallel hoses. These Embodiment has the advantage of a particularly short and compact design. At a Silencers of this construction, the air flow is split into parallel streams and according to a certain distance together again. The sound waves propagate in the parallel hoses and overlap each other at the places where they again are brought together, wherein the extinction of phase shifted Sound waves of the same frequency comes. In this muffler, two or more Chambers arranged in parallel, wherein the branching points also can also be designed as throttles. This muffler is particularly well in the manner described above from several tube sections and establish connection pieces, the connection pieces ramifications exhibit.

It lies within the scope of the invention, mufflers in series and with parallel chambers to be combined.

Further details of the invention will be explained with reference to the drawing, in which Embodiments of the invention are shown. Show it:<dl tsize="6"><dt>Fig. 1</dt><dd>a level control system for a vehicle with an inventively Air supply unit in a schematic representation,</dd><dt>FIG. 2</dt><dd>a muffler for the air supply unit of FIG. 1 in longitudinal section;</dd><dt>Fig. 3</dt><dd>a comparison with FIG. 2 modified embodiment of the silencer in Longitudinal section and</dd><dt>Fig. 4</dt><dd>another relative to FIG. 2 modified embodiment of the silencer in longitudinal section.</dd></dl>

FIG. 1 shows a level control system in a simplified representation. For the air supply unit include a compressor 1 which can be driven by a motor 2, and a silencer 3 and an air dryer 4. The pneumatic elements by the air supply unit to be supplied with air, are air springs 5, of which only one is shown in FIG. 1 for simplicity. The air springs 5 ​​are each valves 6 upstream, the individual air springs 5 ​​individually controlled via the can be. In the complex are more valves 7 and 8 and a check valve 9 provided. The valves 6, 7 and 8 are actuated electromagnetically. You can an electronic control unit 10 are controlled.

The draining or sucking air can eg for level control of a vehicle Air suspension used. To fill the compressed air system with air, sucking the compressor 1 air from the atmosphere via the muffler 3, and it promotes the above located air dryer 4 and the check valve 9 via the passage in position Valves 6 to the air springs 5. The check valve 9 ensures that the air freely added to the system, but only controlled via the valve 8 again can be discharged. For release of air from the system, the valves 6, 7 and 8 opened. Through the valve 7 is in the air supply unit when draining the Compressor 1 bypassed. The air then flows through the air dryer 4 and the Silencer 3 in the reverse direction and passes to the outside. With this construction the System ensures that both the inflow of air to the plant as well as the Discharge of air from the system, a sound attenuation takes place. In addition, the air is always out via the air dryer 4, wherein it is dried at the inflow into the plant and the effluents from the plant, the portion retained by the air dryer 4 moisture is discharged to the outside.

The silencer 3 will now be explained with reference to Figures 2 to 4. FIG. Of the Silencer according to FIG. 2 consists of individual cylindrical tube sections 11 rubber, z, B. NBR (acrylonitrile Butadienn rubber) or ACM (acrylate elastomer) with a Shore A hardness 75. The tubing sections 11 are open at one end and provided at the other end with connectors 12, each of the free end towards having a shoulder 13 with a reduced diameter, which open in the inserted end of the adjacent Schlauchabschittes 11th The connecting pieces 12 are integrally formed on the hose sections eleventh Alternatively, however, they can also are manufactured separately and connected to the hose sections 11th The Connectors 12 are penetrated by holes 14, mainly in extending longitudinally of the muffler and the diameter of which is significantly lower So that constrictions formed as the inner diameter of the tube sections 11 will. Zusammengestzt give the tube sections 11 a tube in his Having a plurality of inner chambers 15 which are arranged one behind the other and through the Choke points are 14 separate. This hose is further at one end to a tube section 16 is provided which has no connecting piece 12 so that the Hose at both ends open. The one end of the hose is connected to the connected air supply unit, while the other end leads to the outside (Fig. 1), so that air that is absorbed or released from the air supply unit, by the hose is passed.

The muffler shown in FIG. 3 is similar in operation to that of FIG. 2. It is but not composed of individual sections, but consists of a single tube 17 made of rubber, which at its inner diameter projections 18 which form the constrictions 14 and integrally pass into the hose 17th Between the throttling points 14 turn chambers 15 are formed. such a Muffler can for example by molding in einr form a core for training the structures are produced in the interior of the hose 17th

In the case of silencers according to Figures 2 and 3, the chambers 15 may be approximately twice as long be like the throttle bodies 15 and the inner diameter of the tube 17 or the Tube sections 11 and 16 about twice as large as that of the throttle points fourteenth Typical dimensions for a model with three throttle bodies had are: Total length 200 mm, length of the chambers 40 mm, diameter of 10 mm chambers, Diameter of throttling points 4.5 mm, wall thickness of the tube 2 mm.

In the Ausführugsbeispiel shown in Fig. 4, two tube sections 19 and 20 arranged in parallel. In their ends connectors 21 and 22 are used. The connection of the muffler to the air supply unit as well as its Exit to the outside via the tube sections 23 and 24, which are also on the Connection pieces 21 and 22 are pushed. The connecting pieces 21 and 22 have channels for guiding the air that branch at 26th The diameter of the Channels 25 is less than the inner diameter of the tube sections. The Connectors 21 and 22 thus act simultaneously as throttle points. The Tube sections 19 and 20 thus forming two chambers 27 and 28, the parallel are arranged to each other. The tubing sections 19, 20, 23 and 24 consist of Rubber, such as NBR or an acrylate elastomer. The connectors can be made of Plastic, for example, are made of polyamide.

The air is coming in the muffler of the tube section 23 or 24 in the branches 26 in the Verbindugsstücken 21 or 22 in two parallel split flows, which resulted in the tube sections 19 and 20 and in the second connector 22 or 21 together again. The sound propagates from along the same paths. In the branching 26 in the first connector 21 22 or the sound is divided into two fronts, which in the second connecting piece 22 or 21 are superimposed and thereby extinguish partly mutually.

LIST OF REFERENCE NUMBERS

(Is part of the description)

<dl tsize="7" compact="compact"><dt>1</dt><dd>compressor</dd><dt>2</dt><dd>motor</dd><dt>3</dt><dd>silencer</dd><dt>4</dt><dd>air dryer</dd><dt>5</dt><dd>air spring</dd><dt>6, 7, 8</dt><dd>Solenoid valves</dd><dt>9</dt><dd>check valve</dd><dt>10</dt><dd>electronic counterpart control</dd><dt>11</dt><dd>tubing section</dd><dt>12</dt><dd>joint</dd><dt>13</dt><dd>paragraph</dd><dt>14</dt><dd>constriction</dd><dt>15</dt><dd>chamber</dd><dt>16</dt><dd>tubing section</dd><dt>17</dt><dd>hose</dd><dt>18</dt><dd>head Start</dd><dt>19, 20</dt><dd>tube sections</dd><dt>21, 22</dt><dd>Verbindusgsstücke</dd><dt>23, 23</dt><dd>tube sections</dd><dt>25</dt><dd>channel</dd><dt>26</dt><dd>branch</dd><dt>27, 28</dt><dd>chambers</dd></dl>