EP3564502A1 - Variable valve drive - Google Patents

Abstract

The invention relates to a variable valve train (10), in particular with a sliding cam system (14), for an internal combustion engine. The variable valve train (10) includes a cam carrier (22) having first and second cams (28, 29) and first to third engagement tracks (32, 34, 36). A first actuator (24) is configured to engage the first engagement track (32) in a first axial direction in order to displace the cam carrier (22). A second actuator (26) is adapted to engage the second cam track (34) in a second axial direction opposite to the first axial direction to displace the cam carrier (22) and to displace the cam carrier (22) in the first axial direction to engage the third engagement track (36). The variable valve train (10) can have the advantage that even if the first actuator (24) fails, a displacement of the cam carrier (22) normally effected by the first actuator (24) is possible, namely by the second actuator (26).

Description

The invention relates to a variable valve train, in particular with a sliding cam system, for an internal combustion engine.

Valve-controlled internal combustion engines have one or more controllable intake and exhaust valves per cylinder. Variable valve trains allow flexible control of the valves to change the opening time, closing time and / or valve lift. As a result, the engine operation can be adapted, for example, to a specific load situation. For example, a variable valve train can be realized by a so-called sliding cam system.

From the DE 196 11 641 C1 is an example of such a sliding cam system is known, with which the operation of a gas exchange valve is made possible with several different lifting curves. For this purpose, a sliding cam with at least one, several cam tracks having cam portion rotatably but axially displaceably mounted on the camshaft having a Hubkontur, in which an actuator is introduced in the form of a pin from radially outside to produce an axial displacement of the sliding cam. Due to the axial displacement of the sliding cam, a different valve lift is set in the respective gas exchange valve. The sliding cam is thereby locked relative to the camshaft by the axial displacement thereof in its axial relative position on the camshaft.

From the DE 10 2011 050 484 A1 For example, an internal combustion engine having a plurality of cylinders, a cylinder head, and a cylinder head cover is known. For the actuation of gas exchange valves at least one rotatably mounted camshaft with at least one axially displaceable on the respective camshaft sliding cam is provided. The respective sliding cam has at least one slotted section with at least one groove. To effect an axial displacement of the respective sliding cam, an actuator is provided. The actuator is mounted in the cylinder head or in the cylinder head cover.

A disadvantage of known systems may be that in case of failure of an actuator no axial displacement of the sliding cam according to the failed actuator associated axial displacement is possible. Thus, under certain circumstances, the valve timing of the gas exchange valves can not be changed. In a particularly unfavorable case, for example, a gas exchange valve, which is operated by means of the sliding cam system in an engine braking operation, can not be switched back to normal operation.

The invention is based on the object to provide an alternative and / or improved variable valve train, with which in particular the disadvantages of the prior art can be overcome.

The object is solved by the features of the independent claim. Advantageous developments are specified in the dependent claims and the description.

The invention provides a variable valve train, in particular with a sliding cam system, for an internal combustion engine. The variable valve train has a shaft and a cam carrier, which is arranged rotationally fixed and axially displaceable on the shaft (for example by means of axial profiling, in particular splined shaft connection or splined shaft connection). The cam carrier has a first cam and a second cam (eg, axially offset from the first cam, in particular adjacent to the first cam), a first engagement track, a second engagement track, and a third engagement track (eg, touch engagement track and / or Fail-safe intervention lane). The variable valve train includes a first actuator configured to (eg, by means of a pin of the actuator) for displacing the cam carrier in a first axial direction (eg, parallel to the longitudinal axis of the shaft and / or the cam carrier) to intervene the first intervention track. The variable valve train includes a second actuator configured to engage and displace the cam carrier in a second axial direction opposite the first axial direction (eg, by means of a pin of the second actuator) to move the cam carrier of the cam carrier in the first axial direction (eg, by means of the pin of the second actuator) to engage in the third engagement track.

The variable valve train may have the advantage that even if the first actuator fails, a displacement of the cam carrier normally effected by the first actuator is possible, namely by the second actuator. For this purpose, the second actuator can engage in the third engagement track. Conveniently, the third engagement track can thus serve as a touch intervention track or fail-safe intervention track. This can be made possible, for example, that even if the first actuator fails, a switchover between an engine braking operation and a normal operation of the internal combustion engine is possible.

In particular, the variable valve train may include a power transmission device that selectively establishes an operative connection between the first cam and a gas exchange valve (eg intake valve or exhaust valve) of the engine or between the second cam and the gas exchange valve depending on an axial position of the cam carrier.

The first engagement track, the second engagement track and / or the third engagement track can expediently be helical (helical) at least in sections.

For example, the first actuator may have a slidable pin for engaging in the first engagement track. Alternatively or additionally, the second actuator may comprise a slidable pin for selectively engaging the second engagement track or the third engagement track.

In particular, the shaft and the cam carrier can form a camshaft of the internal combustion engine.

In one embodiment, engagement of the first actuator with the first engagement track causes displacement of the cam carrier from a first axial position (on the shaft) to a second axial position (on the shaft). Alternatively or additionally, an engagement of the second actuator in the third engagement track causes a displacement of the cam carrier from the first axial position to the second axial position. It is possible that an engagement of the second actuator in the second engagement track causes a displacement of the cam carrier from the second axial position to the first axial position.

Suitably, in the first axial position, an engine braking operation of the internal combustion engine and in the second axial position a normal operation of the internal combustion engine can be effected.

In particular, the first actuator can engage only in the first engagement track when the cam carrier is in the first axial position. Alternatively or additionally, the second actuator can engage only in the second engagement track when the cam carrier is in the second axial position. Alternatively or additionally, the second actuator can engage only in the third engagement track when the cam carrier is in the first axial position.

In a further embodiment, when the second actuator engages in the third engagement track, one end of an ejection section of the third engagement track is reached before the cam carrier reaches the second axial position. Alternatively or additionally, upon engagement of the second actuator in the third engagement track, the cam carrier is accelerated (eg, by rotation of the shaft and the cam carrier) so that the cam carrier still continues to move out of the third engagement track after ejection of the second actuator, in particular in the free flight , moved to the second axial position. It is for example possible that a pin of the second actuator is ejected from the third engagement track (for example by means of an ejection ramp of the third engagement track) before the cam carrier reaches the second axial position. This allows a comparatively short third engagement track.

Suitably, the cam carrier can be locked by a locking device in the first axial position and / or the second axial position.

In one embodiment, in the first axial position of the cam carrier, the power transmission device makes an operative connection between the second cam and the gas exchange valve, and the second cam is configured as an engine brake cam. Alternatively or additionally, the internal combustion engine is operated in the first axial position of the cam carrier in an engine braking mode.

Suitably, the engine brake cam initially held closed by the engine brake cam operated exhaust valve (gas exchange valve) in the compression stroke and / or in the exhaust stroke and then open. As a result, a single or double decompression in the exhaust system can be effected, whereby the internal combustion engine can be braked.

For example, the power transmission device in the second axial position of the cam carrier can establish an operative connection between the first cam and the gas exchange valve. The first cam may be configured to effect normal operation of the gas exchange valve, for example, exhaust valve (and thus the internal combustion engine).

In a further embodiment, the variable valve drive has a control unit which is designed to control the first actuator and / or the second actuator (eg directly or indirectly).

The term "control unit" may refer to electronics and / or mechanical control, which can take over control tasks and / or control tasks depending on the training. Although the term "control" is used herein, it may be convenient to include "rules" or "feedback control" as well.

For example, control unit can control the first actuator and / or the second actuator directly or indirectly. For example, the control unit may drive an actuator directly by energizing an electromagnet or an electric motor of the electric actuator. It is also possible for the control unit to actuate an actuator indirectly by switching a fluid valve or a fluid pump. The fluid valve or the fluid pump is in fluid communication with the actuator (for example, hydraulic actuator or pneumatic actuator) for controlling a supply of a fluid to the actuator.

Suitably, the actuators can be designed as electrical, pneumatic and / or hydraulic actuators. When using, for example, electrical actuators, in particular very fast switching times can be realized, for example in the single-digit millisecond range. This may be advantageous in terms of Einspurvermögens in the third engagement track.

In one embodiment variant, the control unit is designed to control the second actuator for intervention in the third engagement track (for example directly or indirectly) (for example only) if the first actuator and / or an axial displacement by the first actuator has a malfunction. For example, the malfunction can be detected by the control unit. Thus, the third engagement lane can be used as a touch intervention lane or fail-safe intervention lane in particular only if the first actuator does not work.

In a further embodiment variant, the control unit is designed to control an engine speed of the internal combustion engine below or to a predetermined limit value (eg 1000 rpm, 900 rpm, 800 rpm, 700 rpm, 600 rpm, 550 rpm, 500 rpm) before and / or while it drives the second actuator to engage in the third engagement track (for example, directly or indirectly). Alternatively or additionally, the control unit is designed to lower and / or maintain an engine speed of the internal combustion engine to an idling speed (eg approximately 600 rpm) before and / or while engaging the second actuator to engage in the third engagement track (for example, directly or indirectly). At the lower engine speed, in particular lower forces act during the shifting process of the cam carrier. As a result, the third engagement track can be dimensioned comparatively small and / or with a large pitch. Further, at low engine speeds, free flight of the cam carrier to complete the shifting operation can be surely and repeatably performed.

It is possible that the control unit after a displacement of the cam carrier by engagement of the second actuator in the third engagement track again allows a higher engine speed and / or no longer limits an engine speed.

It is also possible that the control unit is designed to prevent after a displacement of the cam carrier by engagement of the second actuator in the third engagement track a new return shift by engaging the second actuator in the second engagement track.

In a further embodiment variant, the control unit is configured to control the second actuator in several successive attempts (for example twice, three times, four times, etc.) to engage in the third engagement track (for example directly or indirectly) until the cam carrier moves into the second Axial position is shifted.

In one embodiment, the control unit is designed to prevent an axial displacement of the cam carrier by engaging the second actuator in the second engagement track in case of malfunction of the first actuator.

In a further embodiment, a length, in particular an arc length, the third engagement track is shorter than a length, in particular an arc length, the first engagement track and / or a length, in particular an arc length, the second engagement track. Alternatively or additionally, a length, in particular an arc length, of the third engagement track is in a range of less than or equal to 90 ° NW (camshaft angle) (eg, less than or equal to 60 ° NW) and / or greater than or equal to 20 ° NW (eg. B. greater than or equal to 30 ° NW). The NW ranges may be different depending on the application, cam size, etc., for example.

For example, the length of the third engagement track may be less than or equal to one half of the length of the first engagement track and / or the second engagement track.

In one embodiment, a depth (eg, maximum depth) of the third engagement track is less than a depth (eg, maximum depth) of the first engagement track and / or a depth of the second engagement track. Alternatively or additionally, a depth (eg maximum depth) of the third engagement track is in a range less than or equal to 2 mm and / or greater than or equal to 1 ° mm. The depth may, for example, depending on the application, cam size, etc. be different.

For example, the depth of the third engagement track may be less than or equal to one half of the depth of the first engagement track and / or the second engagement track.

In a further embodiment, a pitch of the third engagement track is greater than a pitch of the first engagement track and / or a pitch of the second engagement track. Alternatively or additionally, an axial extension of the third engagement track along an axial axis of Cam carrier smaller than an axial extension of the first engagement track along the axial axis of the cam carrier and / or an axial extension of the second engagement track along the axial axis of the cam carrier. It is possible that the third engagement track is dimensioned smaller than the first engagement track and / or the second engagement track.

The smaller dimensioning of the third engagement track in comparison to the first and second engagement track can take their use as a touch intervention track into account. The smaller dimensioning can be made possible by the displacement of the cam carrier is carried out when engaged in the third engagement track at a predetermined, low engine speed at which lower forces act.

In one exemplary embodiment, a beginning of an entry section, in particular a retraction ramp, of the third engagement track adjoins an end of an ejection section, in particular an ejection ramp, of the second engagement track, in particular in a circumferential direction about the cam carrier (eg with a short distance in the single-digit NW). Area).

In a further embodiment, the cam carrier has a fourth engagement track and the first actuator is adapted to engage in the fourth engagement track for moving the cam carrier in the second axial direction. Alternatively or additionally, engagement of the first actuator in the fourth engagement track causes a displacement of the cam carrier from a second axial position of the cam carrier in a first axial position of the cam carrier.

Conveniently, the features described herein associated with the third engagement track may equally be implemented at the fourth engagement track.

Suitably, the cam carrier, the shaft and the actuator device can form a sliding cam system.

The invention also relates to a motor vehicle, in particular a commercial vehicle (for example a truck or omnibus), with a variable valve train as disclosed herein.

It is also possible to use the device as disclosed herein for passenger cars, large engines, off-highway vehicles, stationary engines, marine engines, etc.

Figur 1

eine isometrische Ansicht eines beispielhaften variablen Ventiltriebs gemäß der vorliegenden Offenbarung;

Figur 2

eine Draufsicht bzw. eine Ansicht von oben auf den beispielhaften variablen Ventiltrieb; und

Figur 3

eine Detaildarstellung eines Abschnitts eines Nockenträgers des beispielhaften variablen Ventiltriebs.

The preferred embodiments and features of the invention described above can be combined with one another as desired. Further details and advantages of the invention will be described below with reference to the accompanying drawings. Show it:

FIG. 1

an isometric view of an exemplary variable valve train according to the present disclosure;

FIG. 2

a top view and a view from above of the exemplary variable valve train; and

FIG. 3

a detailed view of a portion of a cam carrier of the exemplary variable valve train.

The embodiments shown in the figures are at least partially identical, so that similar or identical parts are provided with the same reference numerals and to the explanation of which reference is also made to the description of the other embodiments or figures in order to avoid repetition.

The FIGS. 1 and 2 show a variable valve train 10. The variable valve train 10 has a shaft (camshaft) 12, a sliding cam system 14, a power transmission device 16, a first gas exchange valve 18 and a second gas exchange valve 20. The gas exchange valves 18, 20 may be, for example, intake valves or exhaust valves of a cylinder of an internal combustion engine.

The variable valve train 10 may be used to adjust the valve timing curves of the first and second gas exchange valves 18, 20. The variable valve train 10 is associated with an internal combustion engine (not shown). The internal combustion engine can be included, for example, in a commercial vehicle, for example a bus or a lorry. The internal combustion engine may have one or more cylinders.

The sliding cam system 14 has a cam carrier 22 and an actuator device with a first actuator 24 and a second actuator 26.

The cam carrier 22 is rotatably and axially displaceably arranged on the shaft 12, z. Example by means of an axial profiling of the outer circumference of the shaft 12 and the inner circumference of the cam carrier 22 (eg. Spline connection or spline connection). It is possible that a plurality of cam carrier 22 may be arranged on the shaft 12 in order to actuate, for example, gas exchange valves of a plurality of cylinders of the internal combustion engine. The cam carrier 22 has four cams 28-31, a first engagement track (shift gate) 32, a second engagement track (shift gate) 34 and a third engagement track 36 (see FIG. 3 , not visible in FIG. 1 and 2 ) on. As described in detail hereinabove, the third engagement track 36 serves, in particular, as a touch engagement track in the event that the first actuator 24 fails.

The cam carrier 22 together with the shaft 12 forms a camshaft. The shaft 12 with the cam carrier 22 is arranged as overhead camshaft (OHC). The shaft 12 with the cam carrier 22 may be part of a double camshaft (DOHC) system or may be provided as a single overhead camshaft (SOHC).

The four cams 28-31 may have different cam contours for generating different valve timing curves for the gas exchange valves 18, 20. The cams 28-31 may be at least partially designed as Nullhubnocken. The different cam contours of the cams 28-31 can be used, for example, to reduce consumption, for thermal management or for the realization of an engine brake. In the embodiment described here, the second cam 29 is formed as an engine brake cam. An engine braking function by the engine brake cam can, for example, be realized in that an exhaust valve actuated by the engine brake cam is initially kept closed in the compression stroke and / or in the exhaust stroke and then opened. As a result, a (double) decompression is effected in the exhaust system, which slows down the internal combustion engine. The assigned cylinder is not fired. In addition, the fourth cam 31 may be formed, for example, as a Nullhubnocken.

The four cams 28-31 are arranged offset from one another along a longitudinal axis of the cam carrier 22. The first cam 28 is disposed adjacent to the second cam 29. The third cam 30 is disposed adjacent to the fourth cam 31. The first and second cams 28, 29 selectively serve to actuate the first gas exchange valve 18. The third and fourth cams 30, 31 are selectively for actuating the second gas exchange valve 20. The cams 28, 29 and 30, 31 are at opposite ends of the cam carrier 22nd arranged. In other embodiments, additional cams, fewer cams and / or alternative arrangements of the cams may be provided, e.g. B. a central arrangement of the cam on the cam carrier.

The actuators 24, 26 may be electrically (eg, electromotive, electromagnetic), pneumatically and / or hydraulically actuated. In the illustrated embodiment, the actuators are electrically actuated (see electrical connections at their upper ends).

The sliding cam system 14 may additionally include a locking device (not shown). The locking device may be designed so that it secures the cam carrier 22 axially in the desired axial positions on the shaft 12. For this purpose, the locking device, for example, have an elastically biased locking body. The blocking body can engage in a first axial position of the cam carrier 22 in a first recess of the cam carrier 22 and engage in a second axial position of the cam carrier 22 in a second recess of the cam carrier 22. The locking device may be provided for example in the shaft 12.

The power transmission device 16 has a first power transmission element 40, a second power transmission element 41, a lever axis 42 and a plurality of bearing blocks 43. The power transmission elements 40, 41 are rotatably arranged on the lever axis 42, so that they are pivotable about the lever axis 42. The lever axis 42 is mounted or held in the bearing blocks 43. The shaft 12 is rotatably mounted in the bearing blocks 43. For example, separate bearing blocks for the lever axis 42 and the shaft 12 may also be provided. The actuators 24 and 26 are supported by a support device 46 on the lever axis 42.

In the embodiment shown, the power transmission elements 40, 41 as a rocker arm and the lever axis 42 thus formed as a rocker shaft. However, it is also possible, for example, that the force transmission elements 40, 41, for example, as a drag lever and the lever axis 42 is thus formed as a drag lever axis.

In the illustrated embodiment, the first power transmission element 40 is used to actuate the first gas exchange valve 18 and the second power transmission element 41 for actuating the second gas exchange valve 20. However, it is also possible that, for example, several gas exchange valves are actuated by means of only one force transmission element, for example with the interposition of a valve bridge.

The power transmission elements 40, 41 each have a cam follower 44, 45, for example in the form of a rotatably mounted roller. The cam followers 44, 45 follow a cam contour of the cams 28-31 as a function of an axial position of the cam carrier 22.

With reference to the FIGS. 1 to 3 the operation of the actuators 24, 26 in cooperation with the engagement tracks 32, 34 and 36 is described below.

The first engagement track 32, the second engagement track 34 and the third engagement track 36 (only in FIG FIG. 3 visible) are provided centrally on the cam carrier 22. It is also possible that the engagement tracks are arranged eccentrically, for. B. end of the cam carrier. The engagement tracks 32, 34 and 36 extend helically (helically) as depressions (grooves or scenes) in the cam carrier 22 about a longitudinal axis of the shaft 12.

For the axial displacement of the cam carrier 22 radially displaceable pins (24), 26A (see FIG. 3 ) of the actuators 24, 26 selectively engage in the engagement tracks 32, 34, 36 (track). Specifically, a pin 24A of the first actuator 24 may selectively engage the first engagement track 32 for shifting the cam carrier 22 from a first axial position to a second axial position. In the FIGS. 1 to 3 is the cam carrier 22, for example. Shown in the second axial position. The pin 24A of the first actuator 24 can only engage in the first engagement track 32 for shifting to the second axial position when the cam carrier 22 is in the first axial position.

The pin 26A of the second actuator 26 may in turn selectively engage the second engagement track 34 when the cam carrier 22 is in the second axial position. Then, the cam carrier 22 is shifted from the second axial position back to the first axial position (to the right in FIG FIG. 3 ).

In the in the Figures 1-3 illustrated second axial position of the cam carrier 22, the gas exchange valves 18, 20 of the first cam 28 and the third cam 30 are actuated. In detail, the first gas exchange valve 18 is actuated by the first cam 28 and the second gas exchange valve 20 is actuated by the third cam 30.

In the first axial position of the cam carrier 22, the gas exchange valves 18, 20 of the second cam 29 and the fourth cam 31 are actuated. In detail, the first gas exchange valve 18 is actuated by the second cam 29 and the second gas exchange valve 20 by the fourth cam 31.

As already mentioned, the second cam 29 may be configured as an engine brake cam and the fourth cam 31 as a zero-stroke cam. Thus, in the first axial position of the cam carrier 22, an engine braking operation of the internal combustion engine can be effected. In contrast, for example, in the second axial position of the cam carrier 22, a normal operation of the internal combustion engine can be effected.

The axial displacement of the cam carrier 22 is triggered by the extended pin 24A, 26A of the respective actuator 24, 26 being stationary relative to an axial direction of the shaft 12. Consequently, due to the helical shape of the engagement tracks 32, 34, the slidable cam carrier 22 is displaced in a longitudinal direction of the shaft 12 when one of the extended pins 24A, 26A engages the respective engagement track 32, 34. At the end of the axial displacement operation, the extended pin 24A, 26A of the respective actuator 24, 26 is guided by the respective engagement track 32, 34 via an ejection lamp opposite to the extension direction and thus retracted or ejected. The pin 24A, 26A of the respective actuator 24, 26 comes out of engagement with the respective engagement track 32, 34th

As long as the actuators 24 and 26 are functional, it is possible to switch as desired between the first axial position and the second axial position of the cam carrier 22. Thus, for example, in the first axial position, an engine braking operation and in the second axial position, a normal operation of the gas exchange valves 18, 20 can be realized.

However, it is conceivable that the first actuator 24 fails. As a consequence, can no longer be switched by means of the first actuator 24 from the first axial position of the cam carrier 22 for the engine braking operation to the second axial position of the cam carrier 22 for normal operation. In order nevertheless to allow an axial displacement of the cam carrier 22 from the first axial position to the second axial position, the third engagement track 36 is provided for the second actuator 26. In particular, in the case of a malfunction of the first actuator 24 can still be switched to normal operation by means of the second actuator 26 yet.

The third engagement track 36 is designed as a touch intervention track, which is expediently used by the second actuator 26 only when the first actuator 24 fails. This can be done, for example, by an in FIG. 2 Control unit 38 shown schematically are detected. The control unit 38 may be in communication with the first actuator 24 and the second actuator 26 and, for example, one or more further components of the internal combustion engine, in particular for controlling a rotational speed of the internal combustion engine. It is possible that the control unit 38 controls the first actuator 24 and / or the second actuator 26 directly or indirectly.

The third engagement track 36 may also extend at least partially helically. The third engagement track 36 may in particular be shallower (less deep) and shorter (less long) than the engagement tracks 32, 34. For example, an arc length of the third engagement track in a range between 20 ° NW and 90 ° NW, z. B. between 30 ° NW and 60 ° NW (Cam angle), whereas an arc length of the engagement tracks 32, 34 may be larger, for example, between 120 ° NW and 160 ° NW or more. It is possible that a depth of the third engagement track 36 is in a range between 2 mm and 3 mm, whereas a depth of the engagement tracks 32, 34 may be larger, for example 3 mm to 6 mm, in particular approximately 4.5 mm. In addition, the third engagement track 36 may have a greater pitch than the engagement tracks 32, 34.

The third engagement track 36 is thus designed to enable a switchover from the first axial position to the second axial position in a comparatively small area, in particular in comparison with the engagement tracks 32, 34. It should be noted that the engagement tracks 32, 34 and 36 expediently only in the base circle area of the cams 28-31 are positioned, since only here a switching between the cams 28-31 may be possible. The geometry adjustments of the third engagement track 36 with respect to the engagement tracks 32, 34 are made possible in that this is used in particular only as emergency touch track. The emergency switching may take place at a comparatively low, predetermined engine speed (and thus camshaft speed). In this case, lower forces act on displacement of the cam carrier 22.

For example, if the controller 38 detects that the first actuator 24 malfunctions and desires to shift back from the first axial position to the second axial position, the controller 38 may set the engine speed to a predetermined speed, for example, an idle speed of, for example, 600 rpm , lower. After the pin 26A of the second actuator 26 has traversed an extension section (eg, exit ramp) 34A of the second engagement track 34 without being actuated, the second actuator 26 is driven, for example energized, by the control unit 38 , The pin 26A of the second actuator 26 then enters the retraction section or the retraction ramp 36E of the third engagement track 36, which adjoins the extension section 34A of the second engagement track 34 at a slight distance, for example in the single-digit NW range (see FIG FIG. 3 ). Due to the low rotational speed of the shaft 12, there is sufficient time for meshing in the third engagement track 36.

The pin 26A of the second actuator 26 then causes displacement of the cam carrier 22 from the first axial position toward the second axial position. In this case, the pin 26A can already be ejected from the third engagement track 36 by means of an ejection section or extension section 36A of the third engagement track 36 before the cam carrier 22 actually reaches the second axial position. After the ejection of the pin 26A, the cam carrier 22 moves, so to speak, in the defined free flight to the second axial position in which he is locked by the locking device (not shown). The cam carrier 22 is thus accelerated by engagement of the pin 26A in the third engagement track 36 so that it can reach the second axial position in free flight. At the same time, the acceleration may be selected so that the cam carrier 22 does not abut too strongly against the corresponding axial stop of the second axial position, in order to prevent excessive rebound with the consequence of an impossible locking in the second axial position.

It is possible that the control unit 38 makes several attempts until the cam carrier 22 is actually moved by the engagement of the pin 26A in the third engagement track 36 in the second axial position and locked in this functional.

After displacement of the cam carrier 22 by engagement in the third engagement track 36, the control unit 38 can again allow a higher engine speed. Alternatively or additionally, the controller 38 can expediently prevent the cam carrier 22 from being displaced again into the first axial position by means of the second actuator 26.

It is, for example, also possible that a fourth engagement track (not shown in the figures) is provided in the cam carrier 22, by means of which the first actuator 24, for example. In case of malfunction of the second actuator 26, an axial displacement of the cam carrier 22 from the second axial position in the can cause first axial position. The fourth engagement track may be formed analogously to the third engagement track 36 and used.

The invention is not limited to the preferred embodiments described above. Rather, a variety of variants and modifications is possible, which also make use of the inventive idea and therefore fall within the scope. In particular, the invention also claims protection of the subject matter and the features of the subclaims independently of the claims referred to. In particular, the features of independent claim 1 are independently disclosed. In addition, the features of the subclaims are independent of all features of independent claim 1 and, for example, regardless of the features relating to the presence, the arrangement and / or the configuration of the shaft, the cam carrier, the power transmission device, the first actuator and / or the second actuator of independent claim 1.

LIST OF REFERENCE NUMBERS

10

Variable valve train

12

wave

14

Sliding cam system

16

Power transmission device

18

First gas exchange valve

20

Second gas exchange valve

22

cam support

24

First actor

24A

pen

26

Second actor

26A

pen

28

First cam

29

Second cam

30

Third cam

31

Fourth cam

32

First intervention lane

34

Second intervention lane

34A

extension leg

36

Third intervention lane

36A

extension leg

36E

entry section

38

control unit

40

First power transmission element

41

Second power transmission element

42

lever axis

43

bearing block

44

cam follower

45

cam follower

46

carrying device

Claims (15)

Variable valve train (10), in particular with a sliding cam system (14), for an internal combustion engine, comprising: a shaft (12); a cam carrier (22) rotatably and axially slidably disposed on the shaft (12) and having a first cam (28), a second cam (29), a first engagement track (32), a second engagement track (34) and a third Engaging track (36); a first actuator (24) adapted to engage the first engagement track (32) for translating the cam carrier (22) in a first axial direction; and a second actuator (26) adapted to engage the cam carrier (22) in a second axial direction opposite the first axial direction to engage the second engagement track (34) and to displace the cam carrier (22) in the first Axial direction in the third engagement track (36) intervene. A variable valve train (10) according to claim 1, wherein: an engagement of the first actuator (24) with the first engagement track (32) causes displacement of the cam carrier (22) from a first axial position to a second axial position; and an engagement of the second actuator (26) in the third engagement track (36) causes a displacement of the cam carrier (22) from the first axial position to the second axial position; and optional: an engagement of the second actuator in the second engagement track (34) causes a displacement of the cam carrier (22) from the second axial position to the first axial position. A variable valve train (10) according to claim 1 or claim 2, wherein: upon engagement of the second actuator (26) with the third engagement track (36), one end of an ejection section (36A) of the third engagement track (36) is reached before the cam carrier (22) reaches the second axial position; and or upon engagement of the second actuator (26) in the third engagement track (36) of the cam carrier (22) is accelerated so that the cam carrier (22) after the ejection of the second actuator (26) from the third engagement track (36) even further, especially in free flight, moved to the second axial position; and or a pin (26A) of the second actuator (26) is ejected from the third engagement track (36) before the cam carrier (22) reaches the second axial position. A variable valve train (10) according to claim 2 or claim 3, wherein: a power transmission device (16) in the first axial position of the cam carrier (22) makes an operative connection between the second cam (29) and the gas exchange valve (18, 20), and the second cam (29) is designed as an engine brake cam, and / or the internal combustion engine is operated in the first axial position of the cam carrier (22) in an engine braking mode. The variable valve train (10) of any one of the preceding claims, further comprising:
a control unit (38) which is designed to control the first actuator (24) and / or the second actuator (26). A variable valve train (10) according to claim 5, wherein:
the control unit (38) is designed to control the second actuator (26) for engagement in the third engagement track (36) when the first actuator (24) and / or an axial displacement by the first actuator (24) has a malfunction. A variable valve train (10) according to claim 5 or claim 6, wherein: the control unit (38) is adapted to lower and / or maintain an engine speed of the engine below or to a predetermined threshold before and / or while driving the second actuator (26) to engage the third engagement track (36); and or the control unit (38) is adapted to lower and / or maintain an engine speed of the internal combustion engine to an idling speed before and / or while it drives the second actuator (26) to engage in the third engagement track (36). A variable valve train (10) according to any one of claims 5 to 7, wherein:
the control unit (38) is designed to control the second actuator (26) in several successive attempts to engage in the third engagement track (36) until the cam carrier (22) is displaced into the second axial position. A variable valve train (10) according to any one of claims 5 to 8, wherein:
the control unit (38) is adapted, in the event of a malfunction of the first actuator (24), to prevent an axial displacement of the cam carrier (22) by engaging the second actuator (26) in the second engagement track (34). Variable valve train (10) according to one of the preceding claims, wherein: a length, in particular an arc length, the third engagement track (36) is shorter than a length, in particular an arc length, the first engagement track (32) and / or a length, in particular an arc length, the second engagement track (34); and or a length, in particular an arc length, the third engagement track (36) in a range less than or equal to 90 ° NW and / or greater than or equal to 20 ° NW. Variable valve train (10) according to one of the preceding claims, wherein: a depth of the third engagement track (36) is smaller than a depth of the first engagement track (32) and / or a depth of the second engagement track (34); and or a depth of the third engagement track (36) is in a range less than or equal to 2 mm and / or greater than or equal to 1 mm. Variable valve train (10) according to one of the preceding claims, wherein: a slope of the third engagement track (36) is greater than a pitch of the first engagement track (32) and / or a pitch of the second engagement track (34); and or an axial extent of the third engagement track (36) along an axial axis of the cam carrier (22) smaller than an axial extent of the first engagement track (32) along the axial axis of the cam carrier (22) and / or an axial extent of the second engagement track (34) along the axial axis of the cam carrier (22) is; and or the third engagement track (36) is dimensioned smaller than the first engagement track (32) and / or the second engagement track (34). Variable valve train (10) according to one of the preceding claims, wherein:
a beginning of an entrance section (36E), in particular a retraction ramp, the third engagement track (36) at one end of a discharge section (34A), in particular an ejection ramp, the second engagement track (34), in particular in a circumferential direction around the cam carrier (22) adjacent , Variable valve train (10) according to one of the preceding claims, wherein: the cam carrier (22) has a fourth engagement track; and the first actuator (24) is adapted to engage in the fourth engagement track for moving the cam carrier (22) in the second axial direction; and or an engagement of the first actuator (24) in the fourth engagement track causes a displacement of the cam carrier (22) from a second axial position of the cam carrier (22) in a first axial position of the cam carrier (22). Motor vehicle, in particular commercial vehicle, with a variable valve train (10) according to one of the preceding claims.

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