In the prior art there have been known different types of valves mainly using tiltable plates of flaps which can be brought in abutment with a respective valve seat. Such an arrangement is for example known from the document PL-B1- 161022 disclosing a single flap, three-way valve in which a single flap is switchable between two positions in which the flap closes either one of two outlets for communicating the other outlet with an inlet. The actuation system of such type of valve comprises a rod member of an actuator at the one end of which an actuating lever is hinged, said lever being fixedly connected to a pin carrying the single flap and being rotatably supported in a valve housing. The rod member of the actuator is switchable between two positions, in which the flap closes either one of the valve outlets.

It is an object of the invention to provide a valve having an improved function.

The object of the invention is achieved by the combination of the features set forth in claim 1. According to these features, the actuating force of the actuator is applied such that at least one hinge portion of a mechanism for alternatingly closing and opening the valve outlets remains resiliently biased by the actuator in each of its closing/opening positions. Preferable embodiments of the invention are set forth in the subclaims.

In the following the invention is further illustrated by embodiments with reference to the enclosed figures.

In the figures Fig. 1 shows a first embodiment of the three-way valve according to the invention; Fig. 2 shows a second embodiment of the three-way valve according to the invention in a first switching; Fig. 3 shows the three-way valve according to the second embodiment in a second switching position; and Fig. 4 illustrates the compressor side of a turbocharger boosting system for an internal combustion engine in which a three-way valve according to the invention is used.

According to Fig. 1 in the first embodiment of the valve according to the invention a valve housing 1 comprises one inlet 3 and two outlets 5 and 7 formed in one piece housing.

The outlets 5 and 7 are formed as pipe members the inner ends of which are machined such that they form respective valve seats 9 and 11 matching respective sealing surfaces formed by two respective flaps 13,15. The flaps 13,15 are formed as circular plates and are arranged concentrically and in parallel with regard to each other. The plates are connected by an axially extending jointing element 17 which is fixedly connected to a lever 19 pivotally. supported on a pivot pin 21 being fixedly connected to the valve housing 1. The end of the lever 19 opposing the end fixedly connected to the jointing element 17 is hinged on an actuating rod 23.

In the position shown in Fig. 1 a pushing force F is applied to the actuating rod 23 by an actuator which is not particularly shown in the figure, such that the mechanism for

alternatingly closing and opening the outlets, namely the lever 19, remains resiliently biased by the actuator in the closed position of the second outlet 7. By means of this arrangement, the flap 15 is prevented from being detached from the valve seat 11 by possible vibrations and thus the wear of the hinged portion is diminished. Since hinge portions are usually formed by a bushing which is arranged with play on a pin of the hinge portion, such bushing is brought by the pushing force F in a certain position which does not change even if vibration occur. Thus, there is almost no wear of the actuating mechanism, so that the operational reliability of the valve can be significantly increased.

In order to achieve a tightening of possible play in each of the pivoting portions established by the hinge 25 and the pivot pin 21 the pushing force of the actuator is applied in a direction which is inclined with regard to the line connecting the pivot pin 21 and the hinge 25, so that the bearing portion of the lever 19 at the pin 21 is also tightened by a pulling resultant force of the actuating force F.

A second embodiment of the valve according to the invention shown in Fig. 2 differs from the embodiment shown in Fig. 1 in that there are two separate flaps 113,115 providing an "outside-in"closing of valve seats 109 and 111, respectively, which is opposite to the"inside-out"closing mechanism of the first embodiment. Such a mechanism has a particular advantage in cases where the gas pressure in the inlet 103 is to be used as operational pressure for influencing the actuation of at least one of the flaps 113, 115.

As shown in the arrangement illustrated by Fig. 2 each flap 113,115 is fixedly attached to a corresponding L-shaped lever 119a, 119b, wherein said levers are pivotally supported

on the valve housing 101 by respective pivot pins 21a, 21b.

The levers 119a and 119b are connected at their ends opposite to the portions pivotally connected with the pivot pins 21a, 21b to a third lever 127 by means of respective hinge portions 25a, 25b. An actuating rod 123 is hinged on a portion of the connecting lever 127 which is located between the hinge portions 25a, 25b of the respective actuating levers 119a, 119b. By means of the actuating rod 123 a force F is applied by an actuator which is not particularly shown in Fig. 2 in a direction which is inclined to the direction of extension of each of the actuating levers 119a, 119b.

Independently of the particular straight form of the actuating levers 119a, 119b, the direction of the force F should be preferably always inclined to each direction determined by the line connecting the pivot portion with the hinge portion of each of the actuating levers. As a result all moving parts of the valve actuating mechanism can be tightened, thus avoiding the negative influence of vibrations causing untight closing of the flaps and wear at the valve as explained above with regard to the first embodiment.

As shown in Fig. 3, even if the closing-opening position of the valve actuating mechanism is changed, the actuating force F of the actuator still remains in a direction which is inclined to the direction determined by a line connecting each of the pivot and hinge portions of each actuating lever, so that the actuating mechanism still remains resiliently tightened.

Each of the embodiments of the three-way valve shown in Figs.

1-3 is preferably used in a turbocharger boosting system shown in Fig. 4. Such a turbocharger boosting system comprises a first compressor 41 and second compressor 43 arranged in parallel to each other and supplied by respective passages 45,47 with fresh air from an air filter 49. The air compressed by the compressors 41,43 is fed to an internal

combustion engine 51 via an intercooler 53. At the outlet of the second compressor 43, there is provided a three-way valve 55 of the type described above with reference to Figs. 1 to 3. By means of the valve 55 a by-pass passage 57 is branched- off and also connected back with the intake side of the compressors 43 and 41.

The invention described above is not limited to the particular embodiments shown in the figures and explained in the description. The elements of the valve actuating mechanism can be designed in any particularly preferable manner. Different designs can also be provided for the flaps, the valve seats, the inlet and the outlets of the valve.