Internal combustion engine

An internal combustion engine may include at least one cylinder, a first outlet valve and a second outlet valve for directing exhaust gas out from a combustion chamber of the at least one cylinder. The first outlet valve may include a first valve opening and a first valve body where the first valve opening is adjustable between a closed position and an open position. The second outlet valve may include a second valve opening and a second valve body where the second valve body is adjustable between a closed position and an open position. An adjusting lever may adjust one or both of the first valve body and the second valve body between the open position and the closed position.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Germany Patent Application No. 10 2016 210 679.1, filed on Jun. 15, 2016, the contents of which are hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The invention relates to an internal combustion engine.

BACKGROUND

Internal combustion engines with several cylinders can have several outlet valves for each cylinder, by means of which the exhaust gas generated in the combustion chamber, delimited by the respective cylinder, can be directed out from the combustion chamber in a synchronized manner. For this, the available outlet valves are adjustable respectively between an open position and a closed position. In the closed position, a valve body of the respective outlet valve closes a valve opening, associated therewith, and in the open position the valve body frees the valve opening for flowing through by exhaust gas.

It often proves to be a problem here that precisely during opening of the outlet valves, owing to the high gas pressure of the exhaust gas which is generated in the combustion chambers, very great forces can act on the valve bodies. These forces lead to a high mechanical stress in particular of the components which are provided for controlling the valve bodies, such as for instance an adjusting lever for adjusting the valve bodies, or a valve train for controlling said adjusting lever.

It is therefore an object of the present invention to provide an improved embodiment of an internal combustion engine, in which the above-mentioned problems are eliminated or at least only still occur in reduced form.

This problem is solved by the subject matter of the independent claims. Preferred embodiments are the subject of the dependent claims.

SUMMARY

A fundamental idea of the invention is, accordingly, to construct a first and a second outlet valve for directing exhaust gas out from the combustion chamber of an internal combustion engine such that after the adjusting of a first valve body of the first outlet valve by a predetermined adjustment travel away from a closed position, the second valve body of the second outlet valve still closes the second valve opening.

In this way, the forces acting on the valve bodies by the exhaust gas in the combustion chamber can be reduced. This also leads to a reduction of the mechanical stress on the components which are provided for controlling the valve bodies, such as for instance the adjusting lever for adjusting the valve bodies, or the valve train for controlling the adjusting lever. As a result, the risk of damage to the internal combustion engine, in particular of the said components, is therefore considerably reduced.

An internal combustion engine according to the invention comprises at least one cylinder, in which a combustion chamber is present. Furthermore, the internal combustion engine comprises a first outlet valve and a second outlet valve for directing exhaust gas out from the combustion chamber of the cylinder. The first outlet valve comprises a first valve opening and a first valve body. The first valve body is adjustable here between a closed position, in which it closes the valve opening, and an open position, in which it frees the valve opening for flowing through by the exhaust gas. Accordingly, the second outlet valve comprises a second valve opening and a second valve body. The second valve body is adjustable between a closed position, in which it closes the second valve opening, and an open position, in which it frees the valve opening for flowing through by the exhaust gas. The internal combustion engine further comprises a shared adjusting lever, rotatable about a rotation axis, by means of which the two valve bodies are adjustable simultaneously between their respective open position and their respective closed position. According to the invention, the two valve bodies are constructed such that after the adjusting of the first valve body by a predetermined adjustment travel away from its closed position, the second valve body still closes the second valve opening.

In a preferred embodiment, the predetermined adjustment travel is between 0.1 mm and 0.5 mm. Experimental investigations have shown that in this way a particularly high load removal of the adjusting lever and therefore also of a valve train cooperating with the adjusting lever can be achieved, without this involving output losses in the internal combustion engine. In variants of this embodiment, other values are also conceivable for the predetermined adjustment travel.

For a particularly simple technical realization of the time-delayed opening of the two outlet valves, which is essential to the invention, it is proposed according to a further preferred embodiment to realize the two outlet valves such that the second valve body in the closed position of the first outlet valve projects deeper into the second valve opening than the first valve body into the first valve opening. When both valve bodies are moved out from the valve openings, the second valve body is still arranged in the second valve opening, when the first valve body is already situated outside the first valve opening, so that the principle of time-delayed opening of the two outlet valves, which is essential to the invention, is implemented.

In an alternative simple technical realization of the time-delayed opening of the two outlet valves, which is essential to the invention, it is proposed according to another preferred embodiment to arrange the second valve body in the open position of the two outlet valves at a smaller distance relative to the second valve opening than the first valve body relative to the first valve opening. Said distance can be measured here respectively along a direction perpendicular to an opening plane defined by the respective valve opening. When both valve bodies are moved away from the valve openings, the second valve body is thus still arranged at the second valve opening when the first valve body is already situated at a distance from the first valve opening, so that also the principle of time-delayed opening of the two outlet valves, which is essential to the invention, is implemented.

Particularly expediently, the distance difference of the two valve bodies in the open position corresponds substantially to the predetermined adjustment travel. This makes it possible to realize the time-delayed opening of the two outlet valves, which is essential to the invention, in a technically simple manner.

In a further preferred embodiment, the first valve body has a first body height and the second valve body has a second body height. In this variant, the second body height is greater than the first body height. This variant also makes it possible to realize the time-delayed opening of the two outlet valves, which is essential to the invention, in a technically simple manner.

In an advantageous further development, the two valve bodies have respectively substantially the geometry of a cylinder with a first or respectively a second cylinder height. In this further development, the second cylinder height is greater than the first cylinder height. This embodiment also permits the time-delayed opening of the two outlet valves, which is essential to the invention, to be realized.

Particularly preferably, the difference of the two body heights, in particular of the two cylinder heights, corresponds substantially to the amount of the predetermined adjustment travel.

In another preferred embodiment, the two valve bodies have respectively substantially identical body heights, in particular substantially identical cylinder heights. In this embodiment, the two valve bodies, in particular the two cylinders, are arranged on the adjusting lever, offset axially to one another by the predetermined adjustment travel. This variant permits the two valve bodies to be manufactured and used as identical parts.

Expediently, the rotation axis of the adjusting lever can run parallel to a rotation axis of the cam follower roller and/or to a rotation axis of the camshaft. Such an embodiment is particularly compact in construction.

Particularly preferably, the adjusting lever has a first lever arm, on which the two valve bodies are arranged. Furthermore, in this variant, the adjusting lever has a second lever arm, on which the cam follower base body is arranged.

In an advantageous further development, the internal combustion engine has a valve train for driving the adjusting lever. According to this advantageous further development, the valve train comprises a camshaft and a cam follower which is drivingly connected with the adjusting lever. Furthermore, a first cam, mounted in a torque-proof manner on the camshaft, and a second cam, arranged in a torque-proof manner and axially adjacent to the first cam, are provided. Here, the cam follower is axially adjustable between a first position, in which it is drivingly connected with the first cam, and a second position, in which it is drivingly connected with the second cam.

Particularly expediently, the cam follower can have a cam follower base body rigidly connected with the adjusting lever, and a roller, mounted rotatably on the cam follower base body. In the first position of the cam follower, this roller is drivingly connected with the first cam, and in the second position of the cam follower it is drivingly connected with the second cam. The cam follower base body is also known under term “roller pin” to the relevant specialist in the art.

Further important features and advantages of the invention will emerge from the subclaims, from the drawings and from the associated figure description with the aid of the drawings.

It shall be understood that the features mentioned above and to be explained further below are able to be used not only in the respectively indicated combination, but also in other combinations or in isolation, without departing from the scope of the present invention.

Preferred example embodiments of the invention are illustrated in the drawings and are explained further in the following description, wherein the same reference numbers refer to identical or similar or functionally identical components.

DETAILED DESCRIPTION

FIG. 1illustrates in a rough diagrammatic illustration the structure of an internal combustion engine100according to the invention. The internal combustion engine100comprises a cylinder102, indicated roughly diagrammatically inFIG. 2. The internal combustion engine can have further cylinders, not illustrated in further detail in the figures, which can be constructed in an analogous manner to the cylinders illustrated with the aid of the figures. A combustion chamber103is present in the cylinder102.

According toFIG. 1, the internal combustion engine100furthermore comprises a first outlet valve104aand a second outlet valve104bfor directing exhaust gas out from the combustion chamber103of the cylinder102. The first outlet valve104acomprises a first valve opening105aand a first valve body106a. The first valve body106ais adjustable between a closed position, in which it closes the first valve opening105a, and an open position, in which it frees the first valve opening105afor flowing through by the exhaust gas. The second outlet valve104bcomprises a second valve opening105band a second valve body106b. The second valve body6bis adjustable between a closed position, in which it closes the second valve opening105b, and an open position, in which it frees the valve opening105bfor flowing through by the exhaust gas.

Further technical details of the internal combustion engine100, such as for example inlet valves for directing fresh or respectively charge air into the cylinder102, and a piston arranged adjustably in the combustion chamber103, are known to the relevant specialist in the art and are not the focus of the present invention and therefore, for reasons of clarity, are not illustrated inFIG. 1.

As the illustration ofFIG. 1directly shows, the internal combustion engine100has an adjusting lever101which is rotatable about a rotation axis D. By means of the adjusting lever101, the two valve bodies106a,106bcan be adjusted simultaneously between their respective open position and their respective closed position. An axial direction a is defined here by the rotation axis D of the adjusting lever101.

FIG. 2shows the internal combustion engine100ofFIG. 1in a top view along the axial direction a. As evidenced byFIG. 2, the two valve bodies106a,106bcan have respectively substantially the geometric shape of a cylinder107a,107b.

The two valve bodies106a,106bof the internal combustion engine100are constructed such that after the adjusting of the first valve body106aby a predetermined adjustment travel s away from its closed position, the second valve body106bstill closes the second valve opening105b. This characteristic of the two valve bodies106a,106b, which is essential to the invention, is explained below with the aid ofFIGS. 3 to 6:

FIG. 3shows in a highly simplified, diagrammatic illustration the two outlet valves104a,104bin their respective closed position, in which the two valve openings105a,105bare closed by the respectively associated valve bodies106a,106b. The two valve bodies106a,106b, as indicated inFIGS. 3 to 6, can have respectively substantially the geometric shape of a cylinder107a,107b. The valve bodies106a,106bcan have, in a known manner, a valve shaft, which towards the cylinder102of the internal combustion engine100continues into a valve plate with an increased diameter compared to the valve shaft. For reasons of clarity, such a structural embodiment of the valve bodies106a,106bis not illustrated inFIGS. 3 to 6.

Through a movement of the adjusting lever101(the latter is likewise not shown inFIGS. 3 to 6for reasons of clarity), the two valve bodies105a,105bare moved away from the valve openings106a,106b(cf. arrow108inFIG. 3). The movement of the first valve body106abrings about an immediate freeing of the first valve opening106, whereas the second valve opening105bstill remains closed by the second valve body106b.

FIG. 4shows a position of the two outlet valves104a,104b, in which as a consequence of this movement, the first valve body106aof the first outlet valve104awas moved by the predetermined adjustment travel away from the closed position shown inFIG. 3. The second valve body106bof the second outlet valve104bwas also adjusted by means of the control lever101by the same predetermined adjustment travel s, but in the position shown inFIG. 4—just as in the position according toFIG. 3—still closes the second valve opening105b. This predetermined adjustment travel s can be, for example, between 0.1 mm and 0.5 mm. However, other values are also conceivable, according to application-specific requirements.

In the position of the two valve bodies106a,106baccording toFIG. 4, exhaust gas A can therefore exit from the combustion chamber103through the first outlet valve104a(cf. arrow109inFIG. 4), but not through the second outlet valve104b. Only a further moving of the control lever101and a movement, accompanying this, of the two valve bodies106a,106bbeyond the predetermined adjustment travel also brings about a freeing of the second valve opening105bby the second valve body106b, so that exhaust gas A can now exit from the combustion chamber103both through the first outlet valve104aand also through the second outlet valve104b(arrows110). The two valve bodies106a,106bcan be adjusted into their open position by further adjusting of the control lever101, in which they are adjusted to a maximum extent away from their closed position. The diagrammatic illustration ofFIG. 6shows the open position of the two outlet valves104a,104b.

In the open position of the two outlet valves104a,104b, a distance d2of the second valve body106bto the second valve opening105bis less than a distance d1of the first valve body16ato the first valve opening105a.

The distance difference Δd=d1−d2of the two valve bodies106a,106bin the open position to the respective valve opening105a,105bcorresponds substantially to the predetermined adjustment travel s, therefore Δd=s.

As the illustration ofFIG. 4shows, to realize the distance difference Δd a second cylinder height h2of the second cylindrical valve body106bcan be greater than a first cylinder height h1of the first cylindrical valve body106a. In this case, the difference of the two cylinder heights h1, h2corresponds substantially to the amount of the predetermined adjustment travel s. The same principle can be followed to realize the distance difference Δd, when the two valve bodies106a,106bdo not have a cylindrical shape, but rather a different suitable geometric shape with a first and a second body height k1, k2, which is measured along a direction which runs perpendicularly to an opening plane of the respective valve opening105a,105b. In this more general case, the difference of the two body heights k1, k2corresponds substantially to the amount of the predetermined adjustment travel s.

In an alternative variant, which is not shown inFIGS. 3 to 6, the two valve bodies106a,106bcan have respectively substantially the geometry of a cylinder with identical cylinder heights h1, h2, therefore h1=h2. In order to ensure that also in this case, after the adjusting of the first valve body106aby the predetermined adjustment travel s away from its closed position, the second valve body106bis still situated in its closed position, the two cylindrical valve bodies106a,106bwith the same cylinder heights h1, h2are arranged, axially offset to one another by the predetermined adjustment travel s, on the adjusting lever101.

The offset opening of the two outlet valves104a,104bor respectively of the two valve openings105a,105b, which is essential to the invention, can also be realized in a further variant with identically constructed valve bodies106a,106b, when the second valve body106bin the closed position of the first outlet valve104aprojects deeper into the second valve opening105bthan the first valve body1056ainto the first valve opening105a(not shown in the figures). With a simultaneous movement of the two valve bodies106a,106b, the second valve opening105bis freed only later than the first valve opening105a, so that also in this variant the opening of the two outlet valves104a,104btakes place offset to one another.

FIGS. 7 and 8illustrate in diagrammatic illustration an example of a valve train1of the internal combustion engine100for controlling the adjusting lever101. The valve train1comprises a camshaft2and a cam follower3. A first cam4ais mounted in a torque-proof manner on the camshaft2. Axially adjacent to the first cam4a, a second cam4bis arranged on the camshaft2, likewise in a torque-proof manner with respect thereto.

The cam follower3adjustable along the axial direction a between a first position, in which it is drivingly connected with the first cam4a, and a second position, in which it is drivingly connected with the second cam4b.FIG. 7shows the cam follower3in said first position,FIG. 8shows the cam follower3in its second position. The cam follower3can have a cylindrically constructed cam follower base body5, on the circumferential side of which a hollow-cylindrically constructed cam follower roller6is rotatably mounted. The cam follower base body5is also known to the relevant specialist in the art under the term “roller pin” or “displacement axis.” The drive connection of the two cams4a,4bwith the cam follower3takes place in a known manner via the cam follower roller6. Here, the rotary movement of the camshaft2is converted by means of the cams4a,4binto a rotary movement of the adjusting lever101about the rotation axis D. The rotary movement of the adjusting lever101is, in turn, accompanied by a movement of the outlet valves104a,104bbetween their respective open or respectively closed position.

In the first position of the cam follower3, shown inFIG. 7, the cam follower roller6is coupled with the first cam4a, inFIG. 2with the second cam4b. The cam follower roller6controls (not shown) via a suitably constructed mechanical coupling arrangement, in particular in the manner of an actuator, a valve for adjusting between an open and a closed state. Practical technical realization possibilities of such a coupling are not part of the present invention, but are known to the relevant specialist from the prior art in various forms, so that a more detailed explanation in this respect can be dispensed with.

The cam follower3ofFIG. 7has a mechanical adjustment arrangement7, cooperating with the camshaft2, for the axial adjustment of the cam follower3between the first and the second position. The mechanical adjustment arrangement7comprises for this a first adjustable mechanical engagement element8a. The first mechanical engagement element8acooperates with a first slide guide9a, present on the camshaft2, for the axial adjusting of the cam follower3from the first position shown inFIG. 7into the second position. In an analogous manner, the mechanical adjustment arrangement7has an adjustable second mechanical engagement element8b. The second engagement element8bcooperates with a second slide guide9b, present on the camshaft3, for the axial adjusting of the cam follower3from its second into the first position.

The mechanical adjustment arrangement7further comprises a first actuator10a, by means of which the first engagement element8ais adjustable between a first position, shown inFIG. 7, in which it engages into the first slide guide9a, and a second position, shown inFIG. 8, in which it does not engage into the first slide guide9a. The mechanical adjustment arrangement7also comprises a second actuator10b, by means of which the second engagement element8bis adjustable between a first position, in which it engages into the second slide guide9b, and a second position, in which it does not engage into said second slide guide9b.

The first actuator10ais adjustable between an inactive position and an active position. For this purpose, the two actuators10a,10bcan be constructed as linearly adjustable, electrically driven actuators. The mechanical adjustment arrangement7is realized in this case as an electromechanical adjustment arrangement. In other words, electrically driven actuators10a,10bare comprised here by the term “mechanical adjustment arrangement”7.

The two actuators10a,10bare controllable by a control arrangement11of the valve train1for adjusting between their active position and their inactive position. This adjustability is realized such that the first actuator10ain the inactive position is out of contact with the first engagement element8a. In the course of an adjustment from its inactive position into its active position, the first actuator10aadjusts the first engagement element8athrough mechanical contact from its second into its first position.

The adjustment of the first engagement element8afrom the first into the second position can preferably be brought about by means of the stroke movement of the cam follower3, in particular by means of the cam follower base body5. Here, the cam follower3is moved by the stroke movement brought about by the first or second cam4a,4bin the direction of the first actuator10a. When the latter is in its active position, then through the stroke movement of the cam follower3and therefore of the first engagement element8a, this is pressed against the first actuator10aand is adjusted thereby into its second position.

In this state, the first engagement element8aengages into the first slide guide9a, so that the cam follower3, owing to the rotary movement of the camshaft2, is moved by means of the first slide guide9a, arranged thereon, axially from its first into the second position. The second actuator10bis also adjustable between an inactive position and an active position. This adjustability is realized such that the second actuator10bin the active position is out of contact with the second engagement element8b. In the course of an adjusting from its inactive position into its active position, the second actuator10badjusts the second engagement element8bthrough mechanical contact from its second into its first position.

The adjustment of the second engagement element8bfrom the first into the second position is preferably also brought about by means of the stroke movement of the cam follower3, in particular by means of the cam follower base body5. Here, the cam follower3is moved by the stroke movement brought about by the first or second cam4a,4bin the direction of the second actuator8b. When the latter is in its active position, then through the stroke movement of the cam follower3and therefore of the second engagement8b, this is pressed against the second actuator10band is therefore adjusted thereby into its second position.

In this state, the second engagement element8bengages into the second slide guide9b, so that the cam follower3owing to the rotary movement of the camshaft2, by means of the second slide guide9aarranged thereon, is moved axially from its second into the first position.

The first actuator10ahas a linearly adjustable (cf. arrow15a) first adjustment element12a. The latter can partially project from a first housing16aof the first actuator10aand be arranged linearly adjustably relative thereto. A face side13aof the first adjustment element12a, facing the first engagement element8a, which can be constructed in a pin- or bolt-like manner, presses, on moving of the first engagement element8ainto the first slide guide9a, against a face side14aof the first engagement element8alying opposite the first adjustment element12a. The second actuator10bhas a linearly adjustable (cf. arrow15b) second adjustment element12b. The latter can partially project from a second housing16bof the second actuator10band be arranged linearly adjustably relative thereto. A face side13bof the second adjustment element12b, facing the second engagement element8b, which can be constructed in a pin- or bolt-like manner, presses, on moving of the second engagement element8binto the second slide guide9b, against a face side14bof the second engagement element8blying opposite the second adjustment element12b.

As the illustration ofFIG. 8shows, the cam follower3also has a cam follower fixing arrangement17for the detachable fixing of the cam follower3in the first or second position. The cam follower fixing arrangement17comprises a spring-loaded cam follower fixing element18. In the first position of the cam follower3, the cam follower fixing element18engages into a first mount19aprovided on the cam follower3, and in the second position of the cam follower3engages into a second mount19bprovided on the cam follower3. Preferably, the first mount19a, as illustrated inFIG. 2, is realized as a first circumferential groove20a, which is arranged on a circumferential side21of the cam follower3. The second mount is realized accordingly as a second circumferential groove20barranged axially at a distance on the circumferential side21.

AsFIGS. 7 and 8clearly demonstrate, the cam follower3for the two engagement elements8a,8b, preferably for both engagement elements8a,8b, has respectively a first or respectively second engagement element fixing arrangement22a,22bfor the detachable fixing of the first or respectively second engagement element8a,8bin the first or second position. As can be seen, the two engagement element fixing arrangements22a,22bhave respectively a spring-loaded fixing element23a,23b, which in the first position of the respective engagement element8a,8bis received in a first mount24a,24bprovided on the respective engagement element8a,8b. In the second position of the cam follower, the fixing element23a,23bis received in a second mount25a,25bprovided on the cam follower. The first and the second engagement element8a,8bhave respectively a base body29a,29bconstructed in a bolt-like or pin-like manner. On a circumferential side of the base body29a,29bthe first mount24a,24bis formed as a first circumferential groove27a,27b, and the second mount25a,25bis formed as a second circumferential groove28a,28barranged axially at a distance on the circumferential side.

In the following, with the aid of the illustration ofFIGS. 7 and 8, an adjusting of the cam follower3from the first into the second position is explained. In the scenario ofFIG. 1, the cam follower3is situated in the first position, in which its cam follower roller6is drivingly connected with the first cam4a.

If an adjustment of the cam follower3is to take place from its first into its second axial position, then the first engagement element8aof the mechanical adjustment arrangement7, as shown inFIG. 7, is brought into engagement with the first slide guide9a. This takes place by means of the first electric actuator10a.

The first actuator10a, as already explained, is adjustable between an inactive position shown inFIG. 7and an active position—indicated by dashed lines inFIG. 1. In the inactive position, the first actuator10ais mechanically out of contact with the first engagement element8a. In the course of an adjusting from its inactive position into its active position, the first actuator10aadjusts the first engagement element8athrough mechanical contact from its second into its first position. In the first position, the first engagement element8aengages into the first slide guide9a(cf.FIG. 7), so that the cam follower3through the rotary movement of the camshaft2by means of the first slide guide9ais moved axially from its first into its second position, which is illustrated inFIG. 2. After the bringing into engagement of the first engagement element8awith the first slide guide9a, the first actuator10acan be moved back by the control arrangement11into its inactive position again.

The first slide guide9a—just as the second slide guide9b—can have a ramp structure, not shown in the figures, such that the first engagement element8ais brought out of engagement with the first slide guide, as soon as the cam follower3has reached the second axial position. In this second position, the second cam4bis in driving connection with the cam follower roller6. The adjusting of the cam follower3from the second position back into the first position can take place by means of the second actuator10b, of the second engagement element8band of the second slide guide9bin an analogous manner to the transition, explained previously, from the first into the second position of the cam follower3.