The present invention relates in general to improvements in a combustion engine system having a turbocharger for providing pressurized air to an internal combustion engine. The invention relates in particular to a part of a turbocharger accommodating movable parts of a variable nozzle mechanism.

In the prior art, turbochargers are generally known as devices for supplying high pressure air to the intake manifold of an internal combustion engine such as a reciprocating piston engine of the type commonly used in personal and commercial vehicles, in particular in diesel engines. Such turbochargers comprise in general a turbine housing connected to an exhaust gas manifold receiving hot exhaust gases discharged from the engine. The turbine housing typically comprises a volute passage configured for guiding the exhaust gases to a turbine wheel to be carried by a rotatable shaft commonly connected to a compressor impeller. The turbine wheel driven by the exhaust gases drives the impeller, which in turn serves for compression and charging of fresh air to be supplied to the intake manifold of the internal combustion engine.

In turbochargers particularly used with relatively small personal car engines, it is desirable to control the operation of the turbocharger so as to supply charge air to the engine only at a certain pressure level according to a certain control depending on the driving conditions. For this purpose, usually a variable nozzle device or mechanism consisting of a plurality of movable vanes is used for regulating the supply of exhaust gases to the turbine wheel. For this purpose, the variable nozzle device comprises a plurality of movable control parts which are usually accommodated in a compartment being arranged separately from the volute passage.

It is an object of the present invention to provide an improved turbocharger in which the movable parts of a turbocharger mechanism are less susceptible to damages during the turbocharger operation. It is a further object of the present invention to provide an internal combustion engine system comprising such a turbocharger.

The above objects are achieved by the combination of the features set forth in the independent claims herein. Further developments of the invention are defined in the dependent claims.

According to an aspect of the present invention, there is provided a turbocharger having a ventilated compartment accommodating movable parts of a turbocharger mechanism.

The turbocharger mechanism is preferably a vane actuating mechanism of a variable nozzle device.

The ventilation may provided by communicating the compartment either with fresh air or preferably with exhaust gas.

According to one embodiment of the turbocharger, the ventilated compartment is formed between a center housing and a turbine housing having an exhaust gas volute, and the exhaust gas volute is communicated with the compartment by a ventilation hole or passage.

According to another embodiment of the turbocharger, the compartment is formed- between a center housing and' a cartridge, the cartridge holding the variable nozzle device within a turbine housing having an exhaust gas volute, and the exhaust gas volute is communicated with the compartment by a ventilation hole or passage. The cartridge may have an insert substantially consisting of an inner sleeve portion and an outer peripheral portion holding a nozzle ring of the variable nozzle device and being provided with the ventilation hole or passage. Further, the ventilation hole or passage may radially overlap with the outer periphery of the compartment accommodating the vane actuating mechanism.

According to another embodiment of the turbocharger, the variable nozzle device comprises a nozzle ring carrying the movable parts and being fitted in a turbine housing having an exhaust gas volute, the compartment is formed between a center housing having the turbine housing attached thereto and the nozzle ring being fitted in the turbine housing, and the exhaust gas volute is communicated with the compartment by a ventilation hole or passage.

In the above embodiments of the turbocharger, the ventilation hole or passage preferably extends in a direction inclined to the turbine center axis which is also the axis of the volute.

Further, the projection of the axis of the ventilation hole or passage in a plane extending radially to the turbine center may form with the turbine center axis an angle of between 15 to 25°, and/or the projection of the axis of the ventilation hole or passage in a plane extending parallel to the turbine center axis may establish with the turbine center axis an angle of between 40 to 50°.

According to another aspect of the present invention, there is provided an internal combustion engine system comprising a turbocharger as discussed above, where the compartment is ventilated by a hole or passage provided in the bottom part of the turbocharger.

The above solutions have been the result of extensive tests in which it has been confirmed that in particular the moving parts of a variable nozzle device are subject to corrosion which in some cases causes severe damage to the components of the variable nozzle device, in particular to the unison ring responsible for the angular adjustment of the vanes. Further, it has been found that corrosion is magnified by the high temperature particularly developed by diesel engine exhaust gases, the low pH value of the environment causing acid formation, the ambient air humidity rate and the low external temperatures during the winter period.

The vane mechanism parts are usually made of a material sensitive to corrosion caused by a condensation in the compartment accommodating these parts, in particular the unison ring. Very often a huge amount of corrosion is found on the center housing side of the compartment accommodating the unison ring and the actuating mechanism of the vanes, which corrosion not only causes vane mechanism sticking but could also detrimentally affect the turbine housing.

In order to solve the above problems, the solutions according to the present invention have been provided. By — * O

means of these solutions, the corrosion and/or the sticking of the unison ring can be significantly reduced.

According to one embodiment of the invention, on the one hand, a ventilation hole or passage acts as a drain when the turbocharger is stopped. On the other hand, the ventilation hole or passage preferably provides a venturi effect during the operation of the turbocharger to actively depress the cavity area and remove any corrosive components.

In the following, the invention is further illustrated with reference to the enclosed drawings. In the drawings:

Fig. 1 shows an axial cross-sectional view of a turbocharger housing of a turbocharger;

Fig. 2 shows an axial cross-sectional view of a turbocharger housing of a turbocharger according to the first embodiment of the invention at the position of a ventilation hole or passage;

Fig. 3 shows a perspective view of the turbocharger housing of a turbocharger according to the first embodiment of the invention as well as a cross-sectional view of the part thereof comprising the ventilation hole or passage along the cutting line A-A in Fig. 2;

Fig. 4 shows an axial cross-sectional view of a turbine part of a turbocharger according to a second embodiment of the invention;

Fig. 5 shows an axial cross-sectional view of a turbine part-of- a turbocharger according"to "a irhird embodiment" of" the invention; and

Fig. 6 shows an axial cross-sectional view of a turbine part of a turbocharger according to a fourth embodiment of the invention.

A turbocharger according to a first embodiment of the invention comprises a turbocharger housing 1 shown in Fig. 1 which by means of a flange portion 3 thereof can be attached to a center housing of a turbocharger which is not illustrated on this drawing. The turbocharger housing 1 comprises at the side of the flange portion 3 an inner circular opening 7 into which a not particularly shown nozzle ring of the turbocharger is fitted. The nozzle ring forms together with an opposing ring-shaped flange 9 of the turbocharger housing a circular nozzle 11 through which exhaust gas guided by a volute portion 5 of the housing is directed to a not particularly shown turbine wheel. Such a nozzle ring usually supports the movable shafts of a circular arrangement of vanes axially protruding into the nozzle space.

On the side of the nozzle ring opposite to the side facing the ring shaped flange 9, there is provided a not particularly shown vane actuating mechanism typically including vane arms being fixedly connected to the vane shafts, the ends of which engage into the inner circumference of a unison ring. These and further elements of the vane actuating mechanism are, for example, particularly shown and explained in the publication EP 0 226 444 Al, which is herewith incorporated by reference to the present description.

The space confined between the nozzle ring and the center n

housing, both of which are not particularly shown in Fig. 1, forms a compartment 13 accommodating the vane actuating mechanism. As further illustrated by Fig. 2, the vane actuating mechanism accommodating compartment 13 is communicated to the inner side of the volute portion 5 by a ventilation passage 15. In the present embodiment the passage 15 extends along an axis k the projection of which in a plane extending radially to the turbine center axis x in Fig. 2 forms with this axis an angle α of between 15 to 25°, whereas the projection of the axis Jc in a plane extending parallel to the turbine center axis x (i.e. a plane perpendicular to the previously described center axis plane) establishes an angle β of between 40 to 50° with this axis as shown in Fig. 3.

In the present embodiment, the passage 15 has preferably a circular cross section with a diameter of 2,75 + 0, 50 mm.

It has to be noted that Fig. 2 shows the turbocharger housing in its upside-down position, which means that the ventilation passage 15 is machined in a portion of the turbocharger housing which forms the bottom part thereof when mounted to the center housing and the thus assembled turbocharger is mounted to the combustion engine. Thus any condensate which can impair the function of the vane actuating mechanism can be reliably drained from the compartment 13 to the inner side of the volute where it is evacuated by the exhaust gas. Since the ventilation passage 15 is inclined to the direction of the exhaust gas stream in the volute portion 5 an additional suction effect by the ventilation passage 15 is created which enhances the drainage of condensate. A second embodiment of the turbocharger according to the invention is shown in Fig. 4. This figure illustrates mainly the turbine part of the turbocharger comprising a turbine housing 101 coupled to a center housing 117 in which a shaft 119 of a turbine wheel 121 is rotatably supported.

The turbine part shown in Fig. 4 comprises an insert 123 substantially consisting of an inner sleeve portion 125 and an outer peripheral portion 127 being connected to the sleeve portion by a plurality of legs or struts 129. The outer peripheral portion 127 of the insert 123 is provided with a circular opening in which a nozzle ring 131 is fitted. The nozzle ring 131 supports rotatable shafts of vanes 133 axially protruding into the space of a nozzle 111 formed between the nozzle ring 131 and an opposing ring-shaped flange of the inner sleeve portion 125. The insert 123 and the nozzle ring 131 constitute a cartridge 109 which holds the variable nozzle device within the turbine housing 101. The cartridge 109 is mounted to the center housing 117. In this arrangement, exhaust gas delivered via the volute portion 105 of the turbine housing 101 passes radially between the struts 129 to the nozzle 111 where it is further guided by the vanes 133 to the turbine wheel 121.

On the side of the nozzle ring 131 facing the center housing 117, there is provided a vane actuating mechanism including vane arms being fixedly connected to vane shafts, the ends of which engage into the inner circumference of a unison ring 135, wherein the unison ring is freely rotatable on rollers 137 and dowels 139 supported on the nozzle ring 131. The outer peripheral portion 127 of the insert 123 has a ventilation hole or passage 115 by means of which a compartment 113 between the nozzle ring and center housing 117 accommodating the vane actuating mechanism is communicated to the inner side of the volute portion 105 of the turbine housing 101. The position and shape of the hole or passage 115 is the same as the passage 15 described above with regard to the first embodiment. This means that the turbocharger comprising the insert 123 is designed and mounted such that in operation the hole or passage 115 is located in the bottom part of the turbocharger where the accumulation of condensate in the compartment 113 due to the gravitation is expected.

In the second embodiment, the hole or passage 115 is preferably provided in a position circumferentially between the legs or struts 129 as can be gathered from the partial cross section view in Fig. 4. According to this figure, the position of the hole or passage 115 is further preferably such that it overlaps radially with the outer periphery 141 of the compartment 113. Thus, a reliable drain of condense from the compartment 113 to the outside space of the volute 105 can be provided.

A third embodiment of the turbocharger according to the invention is shown in Fig. 5. Again, this figure illustrates mainly the turbine part of a turbocharger having a turbine housing 201 coupled to a center housing 217.

The turbine part shown in Fig. 5 comprises an insert 223 substantially consisting of an inner sleeve portion and a ring-shaped flange which is mounted to the turbine housing 201 and forms a nozzle. The insert" 223 supports "a nozzle ring 231. The nozzle ring 231 is fitted in the turbine housing 201 and supports rotatable shafts of vanes 233 axially protruding into the space of the nozzle formed between the nozzle ring 231 and the opposing ring- shaped flange of the insert 223. In this arrangement, exhaust gas delivered via the volute portion 205 of the turbine housing 201 passes radially to the nozzle where it is further guided by the vanes 233 to the turbine wheel.

On the side of the nozzle ring 231 facing the center housing 217, there is provided a vane actuating mechanism including vane arms being fixedly connected to vane shafts, the ends of which engage into the inner circumference of a unison ring 235, wherein the unison ring is freely rotatable on rollers 237 and dowels 239 supported on the nozzle ring 231. The vane actuating mechanism is accommodated in a compartment 213 which is formed between the center housing 217 and the nozzle ring 231 fitted in the turbine housing 201.

A bottom part of the nozzle ring 231 is provided with a ventilation passage 215 by means of which the compartment 213 between the nozzle ring 231 and the center housing 217 is communicated to the inner side of the volute portion 205 of the turbine housing 201. The ventilation passage 215 forms an angle with the turbine center to provide an additional suction effect which enhances the drainage of condensate.

A fourth embodiment of the turbocharger according to the invention is shown in Fig. 6. The fourth embodiment is similar to the third embodiment shown in Fig. 5 except for the ventilation of the compartment accommodating the vane actuating mechanism.

In the turbine part shown in Fig. 6, a ventilation hole 315 is formed in the wall of the turbine housing 301 which forms a bottom part of the compartment 313 and communicates the compartment 313 with the inner side of the volute portion 305 of the turbine housing 301. With the ventilation hole 315 being provided in the bottom part of the compartment 313, any condensate which can impair the function of the vane actuating mechanism can be more reliably drained from the compartment 313 to the inner side of the volute portion 315 as compared with the third embodiment shown in Fig. 5.