Hydropneumatic suspension unit as well as hydropneumatic suspension system

A hydropneumatic suspension system arranged on a bogie for a vehicle, particularly for a rail vehicle, and one hydropneumatic suspension unit respectively which is contained in the suspension system. For this purpose, the spring accumulator, the reservoir, the tank and the control unit are arranged in the area of the at least one spring strut, so that an essentially self-sufficient suspension unit is obtained. The suspension system may be used and connected to a levelling unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the representation in FIG. 1, a suspension system in this embodiment has two suspension units 2 each mounted on a frame on a bogie 1 of the vehicle. In this case, the suspension system is used for damping shocks and vibrations of the bogie 1 with respect to the car body of the vehicle which is not shown here and which is arranged above the suspension units 2 . The active axis of each suspension unit 2 is arranged perpendicular to the wheel axes of the bogie 1 . The two suspension units 2 jointly support the car body at a line which is not shown and which connects the upper ends of the suspension units 2 and is situated parallel to the wheel axes. In this case, the suspension system is situated essentially in the center between the wheel axes of the bogie 1 . In addition, each suspension unit 2 is arranged outside the respective wheel disk of the bogie 1 , an arrangement in the wheel disk plane also being possible. As illustrated in the detail in FIG. 2 , each suspension unit 2 has a carrier or manifold 21 on which a spring strut 22 , a spring accumulator 23 , a reservoir 24 , a control unit 25 and a tank 26 are fastened. The control unit 25 has an electric motor 251 , an electronic control module 252 and valve or pressure transducing units 253 . These components are essentially coupled directly to one another through the carrier or manifold 21 so that no casing expenditures are required between the latter. For the purpose of completeness, it should also be pointed out that the suspension unit 2 also has additional valves, level sensors, a hydraulic pump etc. as well as a covering, which are not shown here. The level sensor may be integrated, for example, into the suspension unit 2 or may be mounted externally. As illustrated in FIG. 2 , the parts components of the suspension unit 2 are arranged on both sides of the spring strut axis. FIG. 3 shows a modified construction in which a suspension unit 2 ′ is essentially divided into two parts units. On the one hand, the spring strut 22 with the directly flanged-on spring accumulator 23 and the reservoir 24 form a unit on carrier 21 A; while the control unit 25 and the tank 26 are provided separately thereof on carrier 21 B. A connection line 27 is used as the connection between carrier 21 A and 21 B which, however, according to the representation, may have a very short length because, in addition, all components are arranged in the area of the spring strut 22 . In this case, the connection line 27 is shown as a hydraulic hose. FIG. 4 is a schematic operational diagram of a first embodiment of the suspension system according to the invention. In addition to the two suspension units 2 , level sensors 4 assigned to each suspension 2 and a joint levelling unit 5 are provided. The level sensors 4 supply corresponding information to the levelling unit 5 which, in turn, emits a control signal to the control unit 25 of each suspension unit 2 . Here, the levelling unit 5 can be centrally arranged on the bogie 1 , on or in the car body or it can also be assigned to a suspension unit 2 . By this construction, an overflow function can be implemented without any casing expenditures because a purely electronic pressure monitoring of the system pressure can take place in the two levelling circuits. In this case, when a differential pressure, which is preferably adjusted with respect to the software, is exceeded, an electrically controlled drain valve is actuated which, as a rule exist for each unit, whereby the required pressure compensation becomes possible. For detecting the pressure in the two suspension units 2 , one electric pressure sensor respectively is provided which can be utilized, for example, also for the electric load detection. Thus, no pressure detection of the respective other side is required by way of a hydraulic medium, since in this construction there are only signal cables between the suspension units. The installation expenditures for the required signal cables can be further reduced if the levelling unit 5 is assigned to one of the suspension units 2 or is integrated therein. FIG. 5 illustrates second embodiment of the suspension system according to the invention in which the levelling unit 5 has two differential-pressure control valves 51 and 52 which are assigned to the respective suspension units 2 . Each differential-pressure control valve 51 and 52 respectively is connected with the other suspension unit 2 by a pressure gauge line or mini gauge line, so that it is provided with the pressure level of this levelling circuit. Starting from a previously set differential pressure between the two suspension units 2 , the respective differential-pressure control valve 51 or 52 respectively will open up and will drain oil from the respective levelling circuit into the tank 26 of the suspension unit 2 , until the differential pressure again falls below the predetermined limit value. Here, the oil quantity in the suspension system cannot change. Since only two pressure gauge lines are used for the two connection lines between the car body sides, casing expenditures can essentially be avoided. Such pressure gauge lines have significantly smaller dimensions than hydraulic tube lines or hydraulic hoses and can be laid in an easier or more flexible manner. A pressure adjustment is by an offset signal which is transmitted by an upright oil pressure column, which is closed in itself, in a pressure gauge line from one differential-pressure sensor to another differential-pressure sensor of the differential pressure control valves. Thus, no pressure compensation takes place by a fluid mass flow. FIG. 6 illustrates a third embodiment of the suspension system according to the invention, here the two differential-pressure control valves 51 and 52 being arranged as a separate unit on the bogie 1 or on the car body. In addition, this construction has one hydraulic line respectively from the levelling unit 5 to the suspension units 2 . Another hydraulic line connects the tanks 26 of the suspension units 2 with one another in order to prevent an unacceptably high amount of oil on one car body side in the event of an overflow of oil. According to FIG. 7 , the differential-pressure control valves 51 and 52 in a fourth embodiment can also be assigned to a suspension unit 2 , so that they are not present as a separate module. In a fifth embodiment of the present invention according to FIG. 8 , the differential pressure control valves 51 and 52 may also each be assigned to the suspension units 2 . An additional hydraulic line will then be required in order to form the levelling circuit. In addition to the embodiments indicated here, the invention permits additional design principles. Thus, some of the components of the electric control unit 25 or additional electric components may be arranged on the bogie 1 or on the car body, the control unit 25 interacting with these components. As a result, the stress on one portion of the electric components can be reduced within certain limits. In addition, it is possible to arrange the spring accumulator 23 , the reservoir 24 , the tank 26 and the control unit 25 in a star-shaped manner around the respective spring strut 22 . Also, when larger loads are to be absorbed, two or several spring struts 22 can be arranged directly side-by-side, which are then supplied or controlled by a common spring accumulator 23 , reservoir 24 , tank 26 or a joint control unit 25 . Furthermore, spring struts 22 which are arranged on one side of the vehicle in a mutually spaced manner can also be serviced by joint supply and control components. When the levelling unit 5 is arranged on the car body or on the bogie 1 , it can also control more than two suspension units 2 arranged laterally on the vehicle. The invention thus provides a hydropneumatic suspension system for a vehicle, particularly for a rail vehicle, and a hydropneumatic suspension unit respectively which is contained in the suspension system, and by means of which the casing expenditures for the suspension system can clearly be reduced. As a result, the mounting and the maintenance of the system can be significantly simplified. Although the present invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only, and is not to be taken by way of limitation. The spirit and scope of the present invention are to be limited only by the terms of the appended claims.