SENSOR ARRANGEMENT FOR AN AIR SUSPENSION SYSTEM OF A VEHICLE

Abstract

A sensor arrangement for an air suspension system of a vehicle has a change-over valve for each air spring of a vehicle axle or of multiple, adjacent tandem axles, and has a shutoff valve for the air spring of each vehicle wheel of the axle or for each of the air springs on each side of the tandem axles. The respective changeover valve and the shutoff valves are structurally combined in a valve block arranged at a distance from the air springs. For measuring the pressure in each of the bellows of the air springs, pressure sensors are arranged in or on the valve block. Each of the pressure sensors is connected at the output of the shutoff valve associated with the sensor to the connection line of the bellows of the associated air spring or of the bellows of the associated air springs.

Claims

1. A sensor arrangement for an air suspension system of a vehicle, the vehicle having a vehicle axle with wheels or multiple, adjacent tandem axles defining two vehicle sides, the air suspension system having a changeover valve for air springs of the vehicle axle or multiple, adjacent tandem axle, the air springs including corresponding spring bellows, the air suspension system further having a shutoff valve for the air spring of each vehicle wheel of the vehicle axle or for each air spring on each vehicle side of the multiple, adjacent tandem axles, the corresponding changeover valve and shutoff valves being structurally combined in a valve block arranged at a distance from the air springs, the sensor arrangement comprising: a plurality of pressure sensors, wherein each of the spring bellows of the air springs has one of said plurality of pressure sensors associated therewith for measuring a bellows pressure in the associated spring bellows of the air springs; said pressure sensors being arranged in or on the valve block; each of said plurality of pressure sensors being connected at an output of a corresponding one of the shutoff valves to a connection line of the spring bellows of the corresponding air spring or the spring bellows of the corresponding air springs; a plurality of filter arrangements acting as low-pass filters; and, each of said pressure sensors being connected to the connection line of the spring bellows of the corresponding air spring or of the spring bellows of the corresponding air springs via one of said plurality of filter arrangements.

2. The sensor arrangement of claim 1, wherein said filter arrangements each include a restrictor and a pressure reservoir; and, said restrictor and said pressure reservoir of each filter arrangement are arranged between corresponding ones of the connection lines and said plurality of pressure sensors.

3. The sensor arrangement of claim 2, wherein the pressure reservoirs have a volume smaller than a smallest possible volume of the corresponding spring bellows.

4. The sensor arrangement of claim 2, wherein said restrictors of said filter arrangements each define an opening cross section; and, said filter arrangements are configured such that said opening cross sections are adjustable.

5. The sensor arrangement of claim 2, wherein said restrictor and said pressure reservoir of said filter arrangements are each dimensioned such that a ratio of a square of a greatest possible opening diameter (d.sub.DR_max) of said restrictor to a volume (V.sub.DB) of said pressure reservoir is at least as great as a ratio of a square of the line diameter (d.sub.AL) of the corresponding connection line to a smallest possible volume (V.sub.B_min) of the spring bellows of the corresponding air spring or of the spring bellows of the corresponding air springs (d.sub.DR_max.sup.2/V.sub.DB≥d.sub.AL.sup.2/V.sub.B_min).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The invention will now be described with reference to the drawings wherein:

[0017] FIG. 1 shows an air suspension system for a vehicle axle of a vehicle having a centralized arrangement of pressure sensors in a schematic view;

[0018] FIG. 2 shows the pressure curves for the bellows pressure of a spring bellows and for the pressure detected by a pressure sensor during an air admission process in a diagram; and,

[0019] FIG. 3 shows an air suspension system for a vehicle axle of a vehicle having a sensor arrangement according to the disclosure in a schematic view.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] An air suspension system 6, depicted schematically in FIG. 1, for a vehicle axle 2 of a vehicle includes an air spring 8a, 8b having a spring bellows 10a, 10b for each vehicle wheel 4a, 4b of the vehicle axle 2, a valve block 12 having a changeover valve 14, configured as a 3/2-way solenoid switching valve, a shut off valve 16a, 16b, configured as a 2/2-way solenoid switching valve, for the air spring 8a, 8b of each vehicle wheel 4a 4b, and a pressure sensor 18a, 18b for measuring the bellows pressure in each of the spring bellows 10a, 10b of the air springs 8a, 8b. Here, the pressure sensors 18a, 18b are pressure-voltage transducers and form a sensor arrangement 1′.

[0021] Via the changeover valve 14, which is connected by an electric control line 36 to an electronic control unit 34, a working pressure line 20 can be connected alternately to a vent outlet 24 provided with a muffler 26 or to a pressure-carrying supply line 28. Connected to the supply line 28 is a storage reservoir 30, in which compressed air is stored under a supply pressure. Via the two shutoff valves 16a, 16b, which are connected on the inlet side, via a T piece 22, to the working pressure line 20 and are each connected by an electric control line 38a, 38b to the electronic control unit 34 in terms of signal transmission, a respective connection line 32a, 32b leading to the spring bellows 10a, 10b of the associated air spring 8a, 8b can alternately be connected to the working pressure line 20 or shut off from the latter.

[0022] In the unactuated, that is, deenergized, state of the changeover valve 14, the working pressure line 20 is connected to the vent outlet 24 and is thus unpressurized. In the actuated, that is, energized, state of the changeover valve 14, the working pressure line 20 is connected to the supply line 28 and is thus under the supply pressure of the storage reservoir 30.

[0023] In the unactuated, that is, deenergized, state of the shutoff valves 16a, 16b, these are in each case closed, and the connection lines 32a, 32b are shut off from the working pressure line 20. To lower the bellows pressure in the spring bellows 10a, 10b of the associated air spring 8a, 8b, all that is required is to open the relevant shutoff valve 16a, 16b, as a result of which air is released from the respective spring bellows 10a, 10b. To increase the bellows pressure in the spring bellows 10a, 10b of the associated air spring 8a, 8b, on the other hand, the switching over of the changeover valve 14 and the opening of the relevant shutoff valve 16a, 16b are required, as a result of which air is admitted to the respective spring bellows 10a, 10b.

[0024] The pressure sensors 18a, 18b are arranged in or on the valve block 12 and are each connected at the outlet of the associated shutoff valve 16a, 16b to the connection line 32a, 32b of the spring bellows 10a, 10b of the associated air spring 8a, 8b. The pressure sensors 18a, 18b are each connected to the electronic control unit 34 by a respective electric sensor line 40a, 40b.

[0025] As illustrated by way of example in the diagram of FIG. 2 for air admission to the spring bellows 10a, 10b of an air spring 8a, 8b, the bellows pressure p.sub.B present in the relevant spring bellows 10a, 10b and the air pressure p.sub.S present at the outlet of the associated shutoff valve 16a, 16b and detected by the associated pressure sensor 18a, 18b deviate 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 valve 16a, 16b owing to the opening and closing thereof. Accurate control of air admission and release to and from the spring bellows 10a, 10b on the basis of the sensed air pressures p.sub.S is thus not yet possible via the sensor arrangement 1′ shown in FIG. 1.

[0026] To solve this problem, a sensor arrangement 1 according to the disclosure is provided, which is illustrated in the schematic depiction of a corresponding air suspension system 6′ for a vehicle axle 2 of a vehicle in FIG. 3. The pressure sensors 18a 18b are now each connected, via a filter arrangement 42a, 42b acting as a low-pass filter, to the connection line 32a, 32b of the spring bellows 10a, 10b of the associated air spring 8a, 8b. The filter arrangements 42a, 42b each include a pneumatic restrictor 44a, 44b and a relatively small pressure reservoir 46a, 46b, which are each arranged in series between the associated connection line 32a, 32b and the relevant pressure sensor 18a, 18b. Here, the volume of the respective pressure reservoirs 46a, 46b is smaller than the smallest possible volume that can be set for the respectively associated spring bellows 10a, 10b.

[0027] By connecting the pressure sensors 18a, 18b to the connection line 32a, 32b of the spring bellows 10a, 10b of the associated air spring 8a, 8b in each case via a filter arrangement 42a, 42b acting as a low-pass filter, the pressure peaks and pressure fluctuations caused, in particular, by the opening and closing of the associated shutoff valve 16a, 16b are damped and filtered out in such a way that the air pressures p.sub.S measured via the connected pressure sensors 18a, 18b largely correspond to the bellows pressures p.sub.B in the spring bellows 10a, 10b of the associated air springs 8a, 8b.

[0028] The restrictors 44a, 44b of the filter arrangements 42a, 42b are of adjustable configuration in respect of their opening cross section, allowing accurate adaptation of the filter arrangements 42a, 42b to the dimensions of the respective connection line 32a, 32b and of the spring bellows 10a, 10b of the associated air spring 8a, 8b. In order to achieve the desired effect as a low-pass filter, the restrictor 44a, 44b and the pressure reservoir 46a, 46b of the filter arrangements 42a, 42b are each dimensioned in such a way that the ratio of the square of the greatest possible opening diameter d.sub.DR_max of the restrictor 44a, 44b to the volume V.sub.DB of the pressure reservoir 46a, 46b is at least as great as the ratio of the square of the line diameter d.sub.AL of the associated connection line 32a, 32b to the smallest possible volume V.sub.B_min of the spring bellows 10a, 10b of the associated air spring 8a, 8b (d.sub.DR_max.sup.2/V.sub.DB≥d.sub.AL.sup.2/V.sub.B_min).

[0029] 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)

[0030] 1 sensor arrangement (according to the disclosure)

[0031] 1′ sensor arrangement

[0032] 2 vehicle axle

[0033] 4a, 4b vehicle wheels

[0034] 6, 6′ air suspension systems

[0035] 8a, 8b air springs

[0036] 10a, 10b spring bellows

[0037] 12 valve block

[0038] 14 changeover valve

[0039] 16a, 16b shutoff valves

[0040] 18a, 18b pressure sensors

[0041] 20 working pressure line

[0042] 22 T piece

[0043] 24 vent outlet

[0044] 26 muffler

[0045] 28 supply line

[0046] 30 storage reservoir

[0047] 32a, 32b connection line

[0048] 34 electronic control unit

[0049] 36 control line

[0050] 38a, 38b control line

[0051] 40a, 40b sensor line

[0052] 42a, 42b filter arrangement

[0053] 44a, 44b restrictor

[0054] 46a, 46b pressure reservoir

[0055] d diameter

[0056] d.sub.AL diameter of the connection line

[0057] d.sub.DR opening diameter of the restrictor

[0058] d.sub.DR_max greatest possible opening diameter of the restrictor

[0059] p pressure

[0060] P.sub.B bellows pressure

[0061] p.sub.S sensed air pressure

[0062] V volume

[0063] V.sub.B volume of the one or more spring bellows

[0064] V.sub.B_min smallest possible volume of the one or more spring bellows

[0065] V.sub.DB volume of the pressure reservoir