Air supply unit for a vehicle

The invention relates to an air supply apparatus for a vehicle having pneumatic devices, esp. With air springs, which contains a compressor and a muffler.

From the <patcit id="pcit0001" dnum="DE19835491A1"><text>DE 198 35 491 A1</text></patcit> is a pneumatic device for a vehicle in the form of a level control system is known which has air springs. In such level control systems, for example, must be drained to the level control of the vehicle air from the air springs or filled by means of the compressor, wherein the air is usually led via an air dryer. Especially the deflation is associated with loud, unpleasant noise. There is therefore a need to provide such Niveuaregelanlagen with silencers.

From the <patcit id="pcit0002" dnum="WO9305970A"><text>WO93 / 05970</text></patcit> discloses an air supply unit with two mufflers. The first silencer is connected to the compressor inlet. The second muffler is disposed on the outlet valve of the valve block.

In an air supply unit, which consists of the post- <patcit id="pcit0003" dnum="DE10121582"><text>DE 101 21 582</text></patcit> is known, the silencer on a plurality of successively arranged chambers which are connected to each other about diffuser-like constricting channels. Further, porous sheets are made of sintered material, for example provided with a plurality of fine channels through which the air is hindurchgeletet. This air supply unit a significant noise reduction already been achieved. However, the muffler has the disadvantage that it requires a certain minimum diameter, and a minimum length. In many modern vehicles, the installation space is so cramped that the muffler is difficult to accommodate because of its volume. Moreover, the production of the silencer is complicated, since it has a complicated structure in its interior and is formed from a plurality of individual parts, such as diffusers, assembled.

The invention is therefore based on the object to provide an air supply apparatus of the aforementioned type is available, which has a silencer, which can be installed even in very cramped conditions in the vehicle and is easy to manufacture.

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

Unlike previously known silencers is dispensed in this form to flappers, sintered disks, foam fillings, etc. available to the unrestricted air discharge and the unobstructed air intake in the way. Thus, the exhaust noise of the air supply unit is not significantly longer than with an air supply unit without silencer. In addition, the resistance occurring, the compressor must overcome the sucking and discharging is much less than 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. Due to its flexibility, it can be virtually installed in any manner in the vehicle. Thus, the silencer may also be placed under unfavorable conditions in the vehicle. The silencer is made up of very simple parts. Both its manufacture and its assembly at the air supply unit are possible in a simple manner. It can be used on standard, commercially available components.

The tube can be produced, for example by injection molding, wherein the throttle bodies may be integrally formed in the tube by engagement of a correspondingly shaped core. 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 is composed, which are joined together by connectors, the connecting pieces additionally assume the function of the throttle bodies. This embodiment of the invention is particularly advantageous when the muffler only required in smaller numbers as default, not specialized items can be used.

In the air supply apparatus according to the invention a reduction DERS exhaust noise, but also the intake noise and knocking noises of the compressor could be achieved by at least 7 dBA through the muffler. The soundproofing is firstly through the choke points causing at which the sound energy is swirled especially in the short term, very intensive air flow during deflation from the plant and converted into heat. Secondly, the soft material of the tube has a damping effect. In the air supply apparatus according to the invention was compared to the known air supply apparatus mentioned above, which has a existing of hard parts muffler, be achieved not only a better noise reduction, but the remaining noise is also more comfortable and less harsh. A high quality of noise suppression can be achieved by suitable properties of the hose material. It has been found that a particularly good Damping could be achieved if the tube having a Shore hardness between 70 and 80, preferably of about 75 (indicated in Shore A).

As a third essential effect for noise reduction effect in the invention reflections in the chambers, leading to extinction of sound through phase-shifted, reflected sound waves of the same frequency. To fully benefit from this effect, in an advantageous embodiment of the invention, the chambers are designed so that their lengths are in an integer ratio to the wavelength of those portions of the sound to be attenuated priority. The muffler thus can be optimized by the choice of suitable dimensions, however, these dimensions depend on the noise to be attenuated and thus by the other components of the air supply unit, esp. Of the compressor, is. Furthermore, a strong reduction of low frequencies (up to about 1000 Hz) effects, as these acoustic waves can not propagate, because their wavelength is greater than the distances between the throttle points.

According to an advantageous embodiment of the invention, the muffler consists of a tube in which the chambers are arranged one behind the other, so that they can be traversed by the air in turn. Such an embodiment of the invention has the advantage, particularly easy to be and to have a particularly slim silencer.

In another advantageous embodiment of the invention, the silencer on its central portion, two or more mutually parallel hoses. This embodiment has the advantage of a particularly short and compact design. In a muffler of this construction, the air flow is split into parallel streams and brought together again after a certain distance. The sound waves propagate in the parallel tubes and overlap each other at the points where they are brought together again, whereby it comes to the cancellation of phase shifted sound waves of the same frequency. In this muffler, two or more chambers are arranged parallel to one another, wherein the branch points may also be simultaneously formed as throttle points. This silencer is particularly suitable to manufacture in the manner described above from a plurality of tube sections and related fittings, wherein the fittings have branches.

It lies within the scope of the invention to combine with silencers in series and in parallel chambers.

Further details of the invention will be explained with reference to the drawing, are shown in the embodiments of the invention. Show it:<dl id="dl0001"><dt>Fig. 1</dt><dd>a level control system for a vehicle with an air supply apparatus according to the invention in a schematic representation,</dd><dt>FIG. 2</dt><dd>a muffler for the air supply unit to <figref idrefs="f0001">Fig. 1</figref> in longitudinal section,</dd><dt>Fig. 3</dt><dd>an opposite <figref idrefs="f0002">FIG. 2</figref> modified embodiment of the silencer in longitudinal section and</dd><dt>Fig. 4</dt><dd>another against <figref idrefs="f0002">FIG. 2</figref> modified embodiment of the silencer in longitudinal section.</dd></dl>

<figref idrefs="f0001">Fig. 1</figref> shows a level control system in a simplified representation. To the air supply unit includes a compressor 1 which can be driven by a motor 2, and a muffler 3 and an air dryer 4. The pneumatic elements that are to be supplied by the air supply unit with air, are air springs 5, of which<figref idrefs="f0001">Fig. 1</figref> for simplicity only one is shown. The air springs 5 ​​are respectively valves 6 upstream, via which the individual air springs 5 ​​can be individually controlled. In the complex more valves 7 and 8 and a check valve 9 are provided. The valves 6, 7 and 8 are actuated electromagnetically. They can be controlled by an electronic control unit 10th

The discharge or suction of air can for example be used for level control of a vehicle with air suspension. To fill the compressed air system with air, the compressor sucks 1 air from the environment via the muffler 3 and discharges it via the air dryer 4 and the check valve 9 on the transactions within passage position valves 6 to the air springs 5. ensures The check valve 9 that added the air unhindered into the system, but only controlled via the valve 8 again can be drained. For discharging air from the system, the valves 6, 7 and 8 are opened. Through the valve 7 is bypassed when discharging the air supply unit of the compressor first The air then flows through the air dryer 4 and the silencer 3 in the reverse direction and passes to the outside. By this construction of the plant is ensured that both the inflow of air to the system as well as the discharge of air from the system, a sound attenuation takes place. In addition, the air is always performed via the air dryer 4, where it is dried during inflow into the system and the effluents from the plant, the portion retained by the air dryer 4 moisture is discharged to the outside.

The muffler 3 will now be based on the <figref idrefs="f0002">Figures 2 to 4</figref> are explained in detail. The muffler according to<figref idrefs="f0002">FIG. 2</figref> consists of individual cylindrical tube sections 11 made of rubber, for example, B. NBR (acrylonitrile Butadienn rubber) or ACM (acrylate elastomer) having a Shore hardness of 75. The tubing sections 11 are open at one end and at the other end with connectors 12, respectively towards the free end a shoulder 13 with have a reduced diameter which is inserted into the open end of the adjacent Schlauchabschittes eleventh The connecting pieces 12 are integrally formed on the hose sections eleventh Alternatively, however, they can also be produced separately and connected to the hose sections 11th The connecting pieces 12 are penetrated by bores 14, which mainly extend in the longitudinal direction of the muffler, and whose diameter is considerably smaller than the inner diameter of the hose portions 11, so that the throttle points are formed. Zusammengestzt give the hose sections 11 a tube having a plurality of chambers 15 in its interior, which are arranged in succession and separated by the throttling points fourteenth This hose is also provided at one end with a tubular section 16, which has no connecting piece 12, so that the tube is open at both ends. The one end of the hose connected to the air supply unit, while the other end leads to the outside (<figref idrefs="f0001">Fig. 1</figref>), So that air that is absorbed or released from the air supply unit, is passed through the tube.

The muffler according to <figref idrefs="f0002">Fig. 3</figref> similar in its mode of action from the <figref idrefs="f0002">FIG. 2</figref>, It is not composed of individual portions, but consists of a single tube 17 made of rubber, which at its inner diameter of projections 18 that form the constrictions 14 and pass integrally into the hose 17th Between the throttling points 14 turn chambers 15 are formed. Such a muffler can be produced for example by molding in einr form a nucleus for the formation of the structures inside the hose 17th

On mufflers in accordance with the <figref idrefs="f0002">Figures 2 and 3</figref> can the chambers 15 to be about twice as long as the throttle bodies 15 and the inner diameter of the tube 17 or the tube sections 11 and 16 is about twice the size of the throttle bodies 14. Typical dimensions for a model with three throttle bodies had are: total length 200 mm, length of the chambers 40 mm, diameter of the chambers 10 mm, diameter of the throttling points 4.5 mm, wall thickness of the hose 2 mm.

In the in <figref idrefs="f0002">Fig. 4</figref> Ausführugsbeispiel illustrated 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 access to the outside via the tube sections 23 and 24, which are also pushed onto the connecting pieces 21 and 22 respectively. The connectors 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 tubing sections 19 and 20 thus forming two chambers 27 and 28 which are arranged in parallel. The tubing sections 19, 20, 23 and 24 are made 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 divided into the silencer from the tube section 23 or 24 in the branching 26 in the Verbindugsstücken 21 and 22 in two parallel flows, which resulted in the hose sections 19 and 20 and combined again in the second connecting piece 22 and 21 is , The sound propagates along the same paths. In the branching 26 in the first connector 21 or 22, the sound is divided into two fronts, which are superimposed in the second connector 22 and 21 and thereby extinguish partly mutually.

LIST OF REFERENCE NUMBERS (is part of the description)

<dl id="dl0002" 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>