Patent ID: 12227051

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An air suspension system6, depicted schematically inFIG.1, for a vehicle axle2of a vehicle includes an air spring8a,8bhaving a spring bellows10a,10bfor each vehicle wheel4a,4bof the vehicle axle2, a valve block12having a changeover valve14, configured as a 3/2-way solenoid switching valve, a shut off valve16a,16b, configured as a 2/2-way solenoid switching valve, for the air spring8a,8bof each vehicle wheel4a4b, and a pressure sensor18a,18bfor measuring the bellows pressure in each of the spring bellows10a,10bof the air springs8a,8b. Here, the pressure sensors18a,18bare pressure-voltage transducers and form a sensor arrangement1′.

Via the changeover valve14, which is connected by an electric control line36to an electronic control unit34, a working pressure line20can be connected alternately to a vent outlet24provided with a muffler26or to a pressure-carrying supply line28. Connected to the supply line28is a storage reservoir30, in which compressed air is stored under a supply pressure. Via the two shutoff valves16a,16b, which are connected on the inlet side, via a T piece22, to the working pressure line20and are each connected by an electric control line38a,38bto the electronic control unit34in terms of signal transmission, a respective connection line32a,32bleading to the spring bellows10a,10bof the associated air spring8a,8bcan alternately be connected to the working pressure line20or shut off from the latter.

In the unactuated, that is, deenergized, state of the changeover valve14, the working pressure line20is connected to the vent outlet24and is thus unpressurized. In the actuated, that is, energized, state of the changeover valve14, the working pressure line20is connected to the supply line28and is thus under the supply pressure of the storage reservoir30.

In the unactuated, that is, deenergized, state of the shutoff valves16a,16b, these are in each case closed, and the connection lines32a,32bare shut off from the working pressure line20. To lower the bellows pressure in the spring bellows10a,10bof the associated air spring8a,8b, all that is required is to open the relevant shutoff valve16a,16b, as a result of which air is released from the respective spring bellows10a,10b. To increase the bellows pressure in the spring bellows10a,10bof the associated air spring8a,8b, on the other hand, the switching over of the changeover valve14and the opening of the relevant shutoff valve16a,16bare required, as a result of which air is admitted to the respective spring bellows10a,10b.

The pressure sensors18a,18bare arranged in or on the valve block12and are each connected at the outlet of the associated shutoff valve16a,16bto the connection line32a,32bof the spring bellows10a,10bof the associated air spring8a,8b. The pressure sensors18a,18bare each connected to the electronic control unit34by a respective electric sensor line40a,40b.

As illustrated by way of example in the diagram ofFIG.2for air admission to the spring bellows10a,10bof an air spring8a,8b, the bellows pressure pBpresent in the relevant spring bellows10a,10band the air pressure pSpresent at the outlet of the associated shutoff valve16a,16band detected by the associated pressure sensor18a,18bdeviate to a relatively great extent from one another during the air admission process since pressure peaks and pressure fluctuations occur at the outlet of the relevant shutoff valve16a,16bowing to the opening and closing thereof. Accurate control of air admission and release to and from the spring bellows10a,10bon the basis of the sensed air pressures pSis thus not yet possible via the sensor arrangement1′ shown inFIG.1.

To solve this problem, a sensor arrangement1according to the disclosure is provided, which is illustrated in the schematic depiction of a corresponding air suspension system6′ for a vehicle axle2of a vehicle inFIG.3. The pressure sensors18a18bare now each connected, via a filter arrangement42a,42bacting as a low-pass filter, to the connection line32a,32bof the spring bellows10a,10bof the associated air spring8a,8b. The filter arrangements42a,42beach include a pneumatic restrictor44a,44band a relatively small pressure reservoir46a,46b, which are each arranged in series between the associated connection line32a,32band the relevant pressure sensor18a,18b. Here, the volume of the respective pressure reservoirs46a,46bis smaller than the smallest possible volume that can be set for the respectively associated spring bellows10a,10b.

By connecting the pressure sensors18a,18bto the connection line32a,32bof the spring bellows10a,10bof the associated air spring8a,8bin each case via a filter arrangement42a,42bacting as a low-pass filter, the pressure peaks and pressure fluctuations caused, in particular, by the opening and closing of the associated shutoff valve16a,16bare damped and filtered out in such a way that the air pressures pSmeasured via the connected pressure sensors18a,18blargely correspond to the bellows pressures pBin the spring bellows10a,10bof the associated air springs8a,8b.

The restrictors44a,44bof the filter arrangements42a,42bare of adjustable configuration in respect of their opening cross section, allowing accurate adaptation of the filter arrangements42a,42bto the dimensions of the respective connection line32a,32band of the spring bellows10a,10bof the associated air spring8a,8b. In order to achieve the desired effect as a low-pass filter, the restrictor44a,44band the pressure reservoir46a,46bof the filter arrangements42a,42bare each dimensioned in such a way that the ratio of the square of the greatest possible opening diameter dDR_maxof the restrictor44a,44bto the volume VDBof the pressure reservoir46a,46bis at least as great as the ratio of the square of the line diameter dALof the associated connection line32a,32bto the smallest possible volume VB_minof the spring bellows10a,10bof the associated air spring8a,8b(dDR_max2/VDB≥dAL2/VB_min).

It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.

LIST OF REFERENCE SIGNS (PART OF THE DESCRIPTION)

1sensor arrangement (according to the disclosure)1′ sensor arrangement2vehicle axle4a,4bvehicle wheels6,6′ air suspension systems8a,8bair springs10a,10bspring bellows12valve block14changeover valve16a,16bshutoff valves18a,18bpressure sensors20working pressure line22T piece24vent outlet26muffler28supply line30storage reservoir32a,32bconnection line34electronic control unit36control line38a,38bcontrol line40a,40bsensor line42a,42bfilter arrangement44a,44brestrictor46a,46bpressure reservoird diameterdALdiameter of the connection linedDRopening diameter of the restrictordDR_maxgreatest possible opening diameter of the restrictorp pressurePBbellows pressurepSsensed air pressureV volumeVBvolume of the one or more spring bellowsVB_minsmallest possible volume of the one or more spring bellowsVDBvolume of the pressure reservoir