Fresh air system for an internal combustion engine

A fresh air system for supplying combustion chambers of an internal combustion engine with fresh air may include a housing, through which at least one fresh air path passes, and a flap mechanism, which includes at least one flap adjustably mounted on the housing. The flap may be rotatably adjustable between a closed position, in which the flap closes off the fresh air path in a fluid-tight manner and an opened position, in which the flap opens the fresh air path for fresh air to flow through. The flap mechanism may include a spring-elastic preload element, which supports itself on the housing and preloads the flap against at least one of the opened position and the closed position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Patent Application No. 10 2013 223 137.7, filed Nov. 13, 2013, the contents of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

A fresh air system for internal combustion engines usually is to mean a device which serves for admitting fresh air into one or multiple combustion chambers of the internal combustion engine. In the case of a supercharged internal combustion engine, compression of the fresh air for example with the help of an exhaust gas turbocharger usually takes place within the fresh air system.

BACKGROUND

With respect to the effectiveness of the combustion processes taking place in the combustion chambers, adapting the air mass flow flowing through the fresh air system to a current rotational speed of the internal combustion engine, which in turn is determined by the frequency with which the process steps are cyclically carried out during the combustion in the combustion chamber, is of decisive importance. Modern fresh air systems are therefore often equipped with a flap mechanism, by means of which the line cross section of the fresh air path present in the fresh air system varies and thus the air mass flow rate that can flow through the fresh air path in a certain time interval can be adjusted.

However, problematic with such a flap mechanism often prove to be the vibration characteristics of the same, for the flap which is typically rigidly fastened to a pivot shaft is usually exposed to very high mechanical loads through the fresh air flowing through the fresh air path during the operation of the fresh air system. Since said pivot shaft is usually mounted only at the end side on a housing of the fresh air system, it is especially the combination of flap and pivot shaft that is susceptible to resonance-induced excitation of natural oscillations. Such oscillations can manifest themselves to the outside in the form of disturbing rattling or clattering noises, but always bring about increased wear of the components concerned in continuous operation.

SUMMARY

The present invention therefore sets itself the objective of creating a fresh air system in which the abovementioned disadvantages are partly or even completely eliminated and which is characterized in particular by improved wear resistance. The invention furthermore sets itself the objective of providing an internal combustion engine with such a fresh air system. Finally, the invention sets itself the objective of complementing a motor vehicle with such an internal combustion engine.

The mentioned objects are solved through the subject of the independent patent claims. Preferred embodiments are subject of the dependent patent claims.

The basic idea of the invention accordingly is to provide said flap mechanism with a spring-elastic preload element which supports itself on the housing and preloads the flap of the flap mechanism either against an opened or a closed position of the flap arranged in the fresh air path. Such a preload element generates a continuously active preload force onto the flap independently of the current flap position of the flap, so that the flap is automatically moved into the opened position or into the closed position without the action of any additional external force, such as can be actively generated for example by an actuator that is drive-connected to the pivot shaft of the flap mechanism, provided it has not already assumed this position anyhow. In the latter case, the preload force acting on the flap ensures an additional holding moment—in addition to the holding moment actively generated by an actuator during operation and acting on the flap—as a result of which the entire flap mechanism can be particularly effectively protected against undesirable natural oscillations including said “rattling” of the flap.

With suitable dimensioning of the spring-elastic characteristics of the preload element for example by suitably determining the value of the spring constant a principle of action known as “failsafe” function to the specific person skilled in the art can be additionally realised, with which in the case of a failure of the actuator the flap is automatically moved into the opened or closed position by the preload element—in the latter case against the fluid pressure generated by the fresh air—and fixed in the same as it were.

In a preferred embodiment, at least two, preferentially four, such fresh air paths are provided instead of only a single fresh air path. Typically, the number of the fresh air paths corresponds to the number of combustion chambers of the internal combustion engine, so that each fresh air path is assigned to exactly one combustion chamber. Distribution of the fresh air over the individual fresh air paths may be effected for example by means of a device known in the field of engine development as fresh gas distributor and can be directly integrated in the fresh air system. Corresponding to the number of fresh air paths, the requirement of providing a flap for the optional opening or closing of the individual fresh air paths also arises. The different flaps can altogether be mounted on a common pivot shaft which permits a simultaneous pivot adjustment of the individual flaps in the fluid paths. Typically, the fresh air paths in this case extend in the region of the flaps parallel to one another so that the pivot shaft can extend transversely to the individual fresh air paths.

Particularly advantageous in terms of production meanwhile proves to be an embodiment in which the spring-elastic preload element is formed as a leaf spring or coil spring. This allows mounting said leaf or coil spring for the desired preloading of the flap(s) in a simple manner with respect to assembly at one end—i.e. with a first end portion—on the housing of the fresh air system and on the other end—with a second end portion—on the pivot shaft or, alternatively to this, on the flap itself.

In order to keep the installation space required for fastening the preload element on the housing as small as possible it is advisable to form a support region designed pocket-like on the housing. On the housing walls of such a pocket, the first end portion of the leaf or coil spring can support itself.

Depending on the manner in which the preload element is arranged between pivot shaft or flap and housing, either a tension spring arrangement or a compression spring arrangement can materialise. In the case of the first mentioned arrangement the preload element, starting from a starting position, is transferred from said relaxed position into a tensioned state by rotating the pivot shaft. In the latter case, the pivot movement by contrast results in a compression of the preload element so that it is subjected to compressive press. In both mentioned cases, the preload force generated by the preload element and acting on the pivot shaft is increased. Depending on the installation situation in the fresh air system, a realisation as tension or compression spring arrangement can prove to be advantageous in terms of design. Designing the preload element as a coil spring proves to be particularly advantageous for use in a compression spring arrangement.

A mechanically stable fastening of the preload element designed as a leaf or coil spring can be achieved in that on the pivot shaft a recess that is designed complementarily to the second end portion of the leaf or coil spring is arranged, which is rotatably arranged on the pivot shaft with respect to the same. Such a recess may be provided for example directly in the pivot shaft or be directly moulded on in the flap. Alternatively to this it is also conceivable however to equip a separate holding element with such a recess and to fasten the holding element on the pivot shaft in a rotationally fixed manner or form said holding element integrally on said pivot shaft. Alternatively to this, such a holding element can also be fastened to the flap or be moulded onto the same. There are a wide range of options available to the person skilled in the art for permanently fixing the leaf spring in such a recess: conceivable for example is fastening by means of screwing, clipping in or injection overmoulding. Simple inserting of the second end portion into the recess is generally also conceivable.

In the event that the recess is not provided on the pivot shaft but on the flap, be it directly on the flap itself or on a holding element fastened to the flap or integrally moulded onto the same, it proves to be advantageous to provide the recess in a bearing region of the flap, in which the same or the pivot shaft is pivot-adjustably mounted on the housing.

A mechanically durable stable fastening of the leaf or coil spring requires providing a recess with adequate recess depth. Since however the depth of the recess that can be maximally realised in a pivot shaft or in a holding element with cylindrical design is limited, it is appropriate to equip the holding element with an extension projecting to the outside, in which the recess for receiving the leaf or coil spring can be provided.

In the case that the preload element is designed as a leaf spring it is recommended to form the first end portion of the leaf spring curved even in a state in which it is not yet mounted in the fresh air system, i.e. in the relaxed state. Such a quality of the leaf spring allows keeping the installation space required for the installation in the housing of the fresh air system small.

For the controlled movement of the pivot shaft and the at least one flap attached thereon the flap mechanism is preferably equipped with an actuator that is in particular electrically driven and drive-connected to the pivot shaft, by means of which actuator the flap can be pivot-adjusted between the opened and the closed position.

The invention furthermore relates to an internal combustion engine comprising at least one combustion chamber, which internal combustion engine is fluidically connected to a fresh air system with one or multiple features mentioned above. The invention furthermore relates to a motor vehicle with such a fresh air system.

Further important features and advantages of the invention are obtained from the subclaims, from the drawings and from the associated figure description with the help of the drawings.

Preferred exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein same reference characters relate to same or similar or functionally same components.

DETAILED DESCRIPTION

FIGS. 1aand 1billustrate a part view of a fresh air system1according to the invention, which shows the flap mechanism3arranged in an adequately dimensioned housing2of the fresh air system1.FIG. 2shows said flap mechanism3in a separate representation. The same comprises in the example scenario ofFIG. 2four flaps5fastened on a common pivot shaft4in a rotationally fixed manner (the flaps5are not shown in the representation ofFIGS. 1aand 1b).

The four flaps5are each arranged in a fresh air path (not shown) of the fresh air system1, so that the four fresh air paths are closed off in a fluid-tight manner by the flaps5by rotating the pivot shaft4, which is mounted on the housing2in a rotatably adjustable manner, into a closed position of the flaps5. In an opened position by contrast the flaps5open the fresh air paths for fresh air to flow through so that it can be admitted into combustion chambers fluidically connected downstream of the fresh air system1. Obviously, the flaps5can also be positioned in an intermediate position between said opened and closed position.

The flap mechanism3is now equipped with a spring-elastic preload element6in the form of a leaf spring7which supports itself on the housing2, preloading the flaps5either against their opened or the closed position.FIG. 1ashows the leaf spring7in a position which is assigned to an opened position of the flaps5, whileFIG. 1bby contrast shows leaf spring7in a position which corresponds to closed position of the flaps5.

FIGS. 3aand 3bshow rough schematic examples of possible geometrical designs of the leaf spring7which for example can be formed as a flat metal strip. Such a leaf spring7comprises a first end portion8for supporting on the housing2of the fresh air system1and a second end portion9for supporting on the pivot shaft4.

In the example ofFIG. 3a, the first end portion8of the leaf spring7is designed curved. Such a quality of the leaf spring allows keeping the installation space required for installing the leaf spring7in the housing2of the fresh air system1relatively small. A curved design of the leaf spring7however is not limited to its first end portion8only: in the example ofFIG. 3bfor example the entire leaf spring7except for the second end portion9is designed curved.

In order to now keep the installation space required for fastening the leaf spring7on the housing as small as possible it is advisable to form a support region10designed pocket-like on the housing2, which is schematically shown in theFIGS. 1a/1b. On the housing walls of such a pocket the first end portion8of the leaf spring7can then support itself.

Mechanically stable fastening of the preload element8formed as a leaf spring7in the exemplary scenario can—also in the event that another spring5, for example an already mentioned coil spring is used—be achieved in that on the pivot shaft4a holding element14is provided, in which the recess11is arranged. As shown in the figures, the holding element14can be designed as a separate component and be fastened to the pivot shaft4in a rotationally fixed manner. Alternatively to this however it is also conceivable to integrally mould the holding element14on the pivot shaft4(not shown). In a further version the recess11can also be provided directly on the pivot shaft4(not shown).

In a further version of the example, which inFIG. 2is exemplarily shown only for a single flap5in dashed representation for the sake of clarity, the preload element6, for example in the form of the already mentioned leaf spring7, can also support itself on the flap5. For this purpose, a recess11which was already discussed above in connection with the pivot shaft4can also be provided on the flap5. Analogously to the above example, the recess11can be directly provided in the flap5or as shown in dashed representation inFIG. 2be provided in a holding element14, which is explained above in connection with the pivot shaft4and shown in theFIGS. 1aand 1b. If the recess11—be it directly or indirectly in said holding element14—is provided in the flap5, it proves to be advantageous to arrange the recess in the region of the flap5in which the same or the pivot shaft4is mounted on the housing2. This region is exemplarily marked inFIG. 2for a single flap5with the reference number15.

In all cases, the second end portion9of the leaf spring7can be inserted in the recess11for supporting on the pivot shaft4or on the flap5. In order to be able to provide the recess11with a particularly large recess depth for the stable fixing of the leaf spring7, an extension12is provided on the holding element14of substantially hollow-cylindrical form, in which in turn said recess11is arranged.

For illustration,FIG. 5shows the flap mechanism3with leaf spring7inserted in the recess11. For durably fixing the leaf spring7in the recess11the person skilled in the art has a plurality of options, conceivable for example are fastening by means of screwing, clipping or injection overmoulding. Simple inserting of the second end portion9into the recess11is also easily conceivable.

Depending on the manner in which the preload element6is arranged between pivot shaft4and housing2a tension spring arrangement (schematically shown inFIG. 6) or compression spring arrangement (schematically shown inFIG. 7) can prove to be as a particularly advantageous form of realisation in terms of design. In the case of the tension spring arrangement shown inFIG. 6the preload element6is subjected to tensile loading starting out from a starting position shown inFIG. 6by rotating the pivot shaft4or the flap5in the direction of rotation D and transferred into a state which is elongated with respect to the starting position. In the case of the compression spring arrangement shown inFIG. 7, a pivot movement of the pivot shaft4in pivot direction D by contrast results in a compression of the preload element6, so that the same is subjected to compression loading. In both cases, the preload force generated by the preload element6and acting on the pivot shaft4or the flap5is increased. Depending on the installation situation in the fresh air system1, realisation as tension or compression spring arrangement can prove to be advantageous.

For the control movement of the pivot shaft4and the at least one flap5attached thereon the flap mechanism3is preferably equipped with an in particular electrically driven actuator that is drive-connected to the pivot shaft4, which actuator is roughly schematically shown inFIG. 2and marked with the reference number13.