EP3434871B1 - Sliding cam system - Google Patents

Description

The invention relates to a sliding cam system for an internal combustion engine.

Valve-controlled internal combustion engines have one or more controllable inlet and outlet valves per cylinder. Variable valve drives allow flexible control of the valves to change the opening time, closing time and / or the valve lift. This means that engine operation can be adapted to a specific load situation, for example. For example, a variable valve drive can be implemented using a so-called sliding cam system.

From the DE 196 11 641 C1 an example of such a sliding cam system is known, with which the actuation of a gas exchange valve with several different lift curves is made possible. For this purpose, a sliding cam with at least one cam section having a plurality of cam tracks is mounted on the camshaft in a rotationally fixed but axially displaceable manner, which has a stroke contour into which an actuator in the form of a pin is inserted from radially outside to generate an axial displacement of the sliding cam. The axial displacement of the sliding cam sets a different valve lift for the respective gas exchange valve. After axial displacement of the same relative to the camshaft, the sliding cam is locked in its axial relative position on the camshaft in that, depending on the axial relative position, at least one spring-loaded locking ball, which is received and supported in the camshaft, engages in at least one locking groove.

The sliding cam system can take up a considerable amount of space. In particular, an arrangement of the actuators for moving a cam carrier (sliding cam) can be a challenge in tight spaces. Typically, the actuators are attached to a frame connected to the cylinder head or cylinder head cover.

From the DE 10 2011 050 484 A1 an internal combustion engine with a plurality of cylinders, a cylinder head and a cylinder head cover is known. To actuate gas exchange valves, at least one rotatably mounted camshaft with at least one slide cam that can be axially displaced on the respective camshaft is provided. The respective sliding cam has at least one link section with at least one groove. An actuator is provided to effect an axial displacement of the respective sliding cam. The actuator is mounted in the cylinder head or in the cylinder head cover.

The JP 2013 060823 A discloses a sliding cam system with a camshaft, a cam carrier and pistons which can be retracted and extended parallel to the camshaft for moving the cam carrier.

The JP S58 90338 U discloses a control device for opening and closing an intake valve. A camshaft can be displaced along its longitudinal direction by means of an actuating element engaging one end of the camshaft.

The JP S60 75603 U and the WO 201/163252 A1 disclose further variable valve trains.

The invention is based on the object of providing an improved or alternative sliding cam system which, in particular, has a construction that is optimized in terms of installation space.

The object is achieved by a sliding cam system according to the independent claim. Advantageous developments are given in the dependent claims and the description.

The sliding cam system for an internal combustion engine has a camshaft. The sliding cam system has a cam carrier which is arranged on the camshaft in a rotationally fixed and axially displaceable manner. The cam carrier has a first shift gate and a second shift gate. The sliding cam system has a first actuator with an element (for example retractable and extendable element) that can be displaced along a longitudinal axis of the camshaft. The element is designed in particular as a pin. The element can be brought into contact with the first shift gate for the axial displacement of the cam carrier in a first direction. The sliding cam system also has a second actuator with an element that can be displaced along the longitudinal axis of the camshaft (for example, element that can be retracted and extended). The element is designed in particular as a pin. The element can be brought into contact with the second shift gate for the axial displacement of the cam carrier in a second direction, which is opposite to the first direction.

The provision of one or more axially acting actuators enables a space-optimized arrangement of the actuators compared to systems with radially acting actuators. In particular, the axially acting actuators can be integrated into existing structures along the camshaft.

If only one actuator is used, this actuator can, for example, be designed to be double-acting. This enables an axial displacement of the cam carrier in both directions along the longitudinal axis of the camshaft. The actuator can move the cam carrier, for example, in a first direction against an elastic pretensioning element. In an opposite direction, the actuator can enable the cam carrier to be displaced by the elastic pretensioning element by retracting the displaceable element. It is also possible to use a different mechanism which, in combination with only one actuator, enables an axial displacement of the cam carrier between a first axial position and a second axial position.

When using two actuators, the first actuator can move the cam carrier from a second axial position into a first axial position. The second actuator can move the cam carrier from a first axial position into a second axial position. In the first axial position, a first cam of the cam carrier can be in operative connection with at least one gas exchange valve. In the second axial position, a second cam of the cam carrier can be in operative connection with the at least one gas exchange valve.

In a particularly preferred embodiment, the first actuator is received in or on a first bearing block which rotatably supports the camshaft. As an alternative or in addition, the second actuator is accommodated in or on a second bearing block which rotatably supports the camshaft. The actuators therefore do not require any separate installation space. Instead, the actuators can be integrated directly into the existing bearing blocks of the camshaft without requiring additional space.

In particular, the first actuator can be attached to the first bearing block and / or the second actuator can be attached to the second bearing block.

In addition, hydraulic fluid can be supplied to the first actuator and / or the second actuator via the bearing blocks. This means that no additional space is required for the hydraulic lines. Likewise, for example, an electrical line and / or a pneumatic line for the first actuator and / or the second actuator can be provided in or on the first and / or second bearing block.

In one embodiment, the first shift gate and / or the second shift gate is step-shaped. The stepped design of the shift gate can enable the actuators to be contacted in a simple manner by the displaceable elements. The movable elements of the actuators can press against a shoulder of the respective, stepped shift gate when the cam carrier is to be moved.

In a further embodiment, the first shift gate are arranged on a first end of the cam carrier and the second shift gate are arranged on an opposite second end of the cam carrier. In this way, a travel path of the displaceable elements can be minimized. The actuators can be arranged directly next to the ends of the cam carrier.

In one embodiment, the first shift gate has an actuator contact surface which extends in a circumferential direction around the longitudinal axis of the camshaft. Alternatively or In addition, the second shift gate has an actuator contact surface which extends in a circumferential direction around the longitudinal axis of the camshaft. A displacement of the cam carrier can be implemented via a contact between the displaceable elements of the actuators and the corresponding actuator contact surfaces. In addition, in a further development, a contact with the corresponding actuator contact surfaces can be used to dampen the displacement of the cam carrier.

In a further exemplary embodiment, the actuator contact surface of the first shift gate has a first ramp and a second ramp. The first ramp of the actuator contact surface of the first shift gate increases a distance between the first actuator and the actuator contact surface of the first shift gate with respect to a direction of rotation of the camshaft. The second ramp of the actuator contact surface of the first shift gate reduces a distance between the first actuator and the actuator contact surface of the first shift gate with respect to a direction of rotation of the camshaft.

Alternatively or additionally, the actuator contact surface of the second shift gate has a first ramp and a second ramp. The first ramp of the actuator contact surface of the second shift gate increases a distance between the second actuator and the actuator contact surface of the second shift gate with respect to a direction of rotation of the camshaft. The second ramp of the actuator contact surface of the second shift gate reduces a distance between the second actuator and the actuator contact surface of the second shift gate with respect to a direction of rotation of the camshaft.

The ramps enable the cam carrier to be displaced by contact with the displaceable elements. If, for example, the displaceable element of the first actuator contacts the second ramp of the actuator contact surface of the first shift gate, the cam carrier is displaced in the first direction while the cam carrier rotates together with the camshaft. If, on the other hand, the displaceable element of the second actuator contacts the second ramp of the actuator contact surface of the second shift gate, the cam carrier is displaced in the second direction while the cam carrier rotates together with the camshaft.

In particular, the first and second ramp of the first and second shift gate can be arranged such that a displacement of the cam carrier is only possible within a base circle area of the cams of the cam carrier.

In one embodiment variant, the first actuator and / or the second actuator is actuated hydraulically, electrically and / or pneumatically.

In a further embodiment variant, an axial displacement of the cam carrier is damped hydraulically. The damping can enable locking (axial securing) of the cam carrier.

According to the invention, the sliding cam system has a first elastic element which pretensions the cam carrier in the second direction. Alternatively or additionally, the sliding cam system has a second elastic element which pretensions the cam carrier in the first direction. The elastic elements enable damping of the displacement movement of the cam carrier. If the cam carrier is displaced in the first direction, for example by the first actuator, the first elastic element can dampen the displacement movement of the cam carrier.

According to the invention, the first elastic element supports the cam carrier on a bearing block for rotatably mounting the camshaft and is rotatably mounted about the longitudinal axis of the camshaft with respect to the bearing block or the cam carrier. Alternatively or additionally, the second elastic element supports the cam carrier on a bearing block for rotatably mounting the camshaft and is rotatably mounted about the longitudinal axis of the camshaft with respect to the bearing block or the cam carrier. The bearing blocks of the camshaft, which are already present, can thus be used to support the elastic elements for damping the displacement movement of the cam carrier. The rotatable mounting of the elastic elements is provided in order to prevent the elastic elements from dragging on the cam carrier or bearing block, since the elastic elements in the embodiment either rotate with the cam carrier or are fixed on the bearing block.

In one embodiment, the sliding cam system has a first hydraulic damping cylinder which is arranged to dampen an axial displacement of the cam carrier in the first direction. As an alternative or in addition, the sliding cam system has a second hydraulic damping cylinder which is arranged for damping an axial displacement of the cam carrier in the second direction.

In a further development, the sliding cam system also has a first throttle, which is arranged downstream of the first hydraulic damping cylinder, and / or a second throttle, which is arranged downstream of the second hydraulic damping cylinder.

A resistance for hydraulic fluid flowing out of the hydraulic damping cylinders can be built up via the throttles, whereby a desired damping can be realized.

In one embodiment, the second actuator dampens an axial displacement of the cam carrier when the first actuator axially displaces the cam carrier in the first direction. Alternatively or additionally, the first actuator dampens an axial displacement of the cam carrier when the second actuator axially displaces the cam carrier in the second direction. This means that the damping functionality can be integrated directly into the actuators.

In a further embodiment variant, the second actuator dampens an axial displacement of the cam carrier hydraulically and / or via an elastic element of the second actuator. Alternatively or additionally, the first actuator dampens an axial displacement of the cam carrier hydraulically and / or via an elastic element of the first actuator.

The invention also relates to a variable valve drive for an internal combustion engine. The variable valve train includes a slide cam system as disclosed herein. The variable valve drive has at least one gas exchange valve and a force transmission device (for example a tappet, rocker arm or rocker arm). Depending on an axial position of the cam carrier, the force transmission device optionally sets a first cam of the cam carrier in operative connection with the at least one gas exchange valve or a second cam of the cam carrier in operative connection with the at least one gas exchange valve.

According to a further aspect, the invention also relates to a motor vehicle, in particular a utility vehicle, with a sliding cam system as disclosed herein or a variable valve train as disclosed herein. The utility vehicle can be, for example, an omnibus or a truck.

Figur 1

eine perspektivische Ansicht eines variablen Ventiltriebs mit einem Schiebenockensystem; und

Figur 2

eine Schemadarstellung einer Ausführungsform des Schiebenockensystems;

Figur 3

eine Schemadarstellung eines Beispiels des Schiebenockensystems;

Figur 4

eine Schemadarstellung eines Beispiels des Schiebenockensystems;

Figur 5

eine Schemadarstellung eines Beispiels des Schiebenockensystems; und

Figuren 7 bis 18

Schemadarstellungen eines Beispiels des Schiebenockensystems zur Erläuterung der Funktionsweise eines beispielhaften Schiebenockensystems.

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 are described below with reference to the accompanying drawings. Show it:

Figure 1

a perspective view of a variable valve train with a sliding cam system; and

Figure 2

a schematic representation of an embodiment of the slide cam system;

Figure 3

Fig. 3 is a schematic diagram of an example of the slide cam system;

Figure 4

Fig. 3 is a schematic diagram of an example of the slide cam system;

Figure 5

Fig. 3 is a schematic diagram of an example of the slide cam system; and

Figures 7 to 18

Schematic representations of an example of the sliding cam system to explain the mode of operation of an exemplary sliding cam system.

The embodiments shown in the figures match at least in part, so that similar or identical parts are provided with the same reference symbols and reference is made to the description of the other embodiments or figures for their explanation in order to avoid repetition.

The Figure 1 shows a variable valve drive 10. The variable valve drive 10 can, for example, be part of an internal combustion engine of a commercial vehicle, in particular a truck or a bus. The variable valve drive 10 has a first gas exchange valve 12, a second gas exchange valve 14, a sliding cam system 16, a force transmission device 18, a first bearing block (bearing body) 20 and a second bearing block (bearing body) 22.

The variable valve drive 10 is used to adapt an activation of the gas exchange valves 12, 14. In particular, an opening time, a closing time and / or a valve lift of the gas exchange valves 12, 14 can be adapted. The gas exchange valves 12, 14 can be inlet valves or outlet valves.

The bearing blocks 20, 22 support a camshaft 24 in a rotatable manner. In addition, the rocker arm shaft 42 is attached to the bearing blocks 20, 22. The bearing blocks 20, 22 can be fastened, for example, to a fastening frame or a cylinder head of the internal combustion engine. In other embodiments, the camshaft 24 and the rocker arm shaft 42 can be mounted separately from one another, for example.

The sliding cam system 16 has the camshaft 24, a cam carrier 26, a first actuator 28 and a second actuator 30.

The cam carrier 26 is arranged on the camshaft 24 in a rotationally fixed and axially displaceable manner. The cam carrier 26 has a first cam 32, a second cam 34, a first shift gate 36 and a second shift gate 38.

The first cam 32 and the second cam 34 are arranged adjacent to each other. The first cam 32 and the second cam 34 have different cam contours. The first cam 32 and the second cam 34 are provided in a central region of the cam carrier 26. Depending on an axial position of the cam carrier 26 with respect to the camshaft 24, the force transmission device 18 creates an operative connection between the first cam 32 and the gas exchange valves 12, 14 or between the second cam 34 and the gas exchange valves 12, 14.

In detail, the force transmission device 18 has a rocker arm 40 and a rocker arm shaft 42. The rocker arm 40 follows a cam contour of the first cam 32 or the second cam 34 via a cam follower 44 depending on the axial position of the cam carrier 26. The cam follower 44 is designed as a rotatably mounted roller. The rocker arm 40 is mounted rotatably about the rocker arm axis 42. In a valve lift range of the cam 32 or 34, the gas exchange valves 12, 14 are actuated accordingly via the rocker arm 40. In other embodiments, the force transmission device 18 can have a rocker arm or a tappet, for example.

In the in Figure 1 The example shown is the cam carrier 26 in a first axial position. In the first axial position, the force transmission device 18 produces an operative connection between the first cam 32 and the gas exchange valves 12, 14. The cam carrier 26 can be moved into a second axial position (to the left in Figure 1 ) can be moved. In the second axial position, the power transmission device 18 puts the second cam 34 in operative connection with the gas exchange valves 12, 14. The cam carrier (sliding cam) 26 can be moved along the axial direction of the camshaft 24 by the interaction of the first actuator 28, the second actuator 30, the first shift gate 36 and the second shift gate 38 are moved.

The first actuator 28 is received and fastened in the first bearing block 20. The second actuator 30 is received and fastened in the second bearing block 22. The attachment and The inclusion of the actuators 28, 30 in the bearing blocks 20, 22 is advantageous for reasons of space. There is no need to provide a separate installation space for the actuators 28, 30.

The first shift gate 36 and the second shift gate 38 are arranged on opposite axial ends of the cam carrier 26. The first shift gate 36 interacts with the first actuator 28 to shift the cam carrier 26 from the second axial position into the first axial position. The cam carrier 26 can be displaced in a first direction by the first actuator 28 and the first shift gate 36. The second shift gate 38 interacts with the second actuator 30 to shift the cam carrier 26 from the first axial position into the second axial position. The cam carrier 26 can be displaced in a second direction by the second actuator 30 and the second shift gate 38. The second direction is opposite to the first direction. The first and second directions extend parallel to a longitudinal axis of the camshaft 24.

Each actuator 28, 30 has a displaceable pin 46, 48. The pin 46 of the first actuator 28 is in Figure 1 covered by the first bearing block 20. The pins 46, 48 are slidable in an axial direction of the camshaft 24. Instead of the pins 46, 48, other displaceable elements can also be used for displacing the cam carrier 26.

The first shift gate 36 and the second shift gate 38 are step-shaped. In detail, the shift gate 36, 38 each have an actuator contact surface 50, 52. The actuator contact surfaces 50, 52 extend in a circumferential direction around the longitudinal axis of the camshaft 24. The actuator contact surface 50 has a first ramp 50A and a second ramp 50B. The first ramp 50A increases a distance between the first actuator 28 and the actuator contact surface 50 with respect to a direction of rotation of the camshaft 24. The second ramp 50B reduces a distance between the first actuator 28 and the actuator contact surface 50 with respect to a direction of rotation of the camshaft 24 52 a first ramp 52A and a second ramp 52B. The first ramp 52A increases a distance between the second actuator 30 and the actuator contact surface 52 with respect to a direction of rotation of the camshaft 24. The second ramp 52B reduces a distance between the second actuator 30 and the actuator contact surface 52 with respect to a direction of rotation of the camshaft 24. In other words , In the area of the first ramps 50A, 52A the actuator contact surfaces 50, 52 extend spirally (helically) in a direction to each other with respect to a direction of rotation of the camshaft 24. In the area of the second ramps 50B, 52B the actuator contact surfaces 50, 52 extend spirally (helically) in the opposite direction with respect to a direction of rotation of the camshaft 24.

To move the cam carrier 26 from the second axial position into the first axial position, the pin 46 of the first actuator 28 is extended. The pin 46 of the first actuator 28 is extended such that the pin 46 is fully extended when the cam carrier 26 reaches a rotational position in which a start of the second ramp 50B passes the pin 46 by rotating the camshaft 24. For example, the pin 46 may extend as it passes the first ramp 50A over the pin 46 due to the rotation of the camshaft 24. Due to the ramp 50B, the extended pin 46 pushes the cam carrier 26 from the second axial position to the first axial position.

The cam carrier 26 is displaced from the first axial position to the second axial position in an analogous manner by the pin 48 of the second actuator 30. Due to the ramp 52B of the actuator contact surface 52, the extended pin 48 pushes the cam carrier 26 into the second axial position.

The sliding cam system 16 can additionally have a locking device (not shown). The locking device can be designed such that it axially secures the cam carrier 26 in the first axial position and the second axial position. For this purpose, the locking device can, for example, have an elastically pretensioned locking body. In the first axial position of the cam carrier 26, the locking body can engage in a first recess of the cam carrier and in the second axial position of the cam carrier 26 it can engage in a second recess of the cam carrier 26. The locking device can be provided in the camshaft 24, for example.

The actuators 28 and 30 can be, for example, hydraulically operated actuators. In the following description, exemplary embodiments for hydraulic systems for actuating the actuators 28 and 30 are described.

The Figure 2 shows a hydraulic system 53. The hydraulic system 53 has a main hydraulic line 54, a first connecting line 56 and a second connecting line 58.

The first actuator 28 is connected to the main hydraulic line 54 via the first connecting line 56. The second actuator 30 is connected to the main hydraulic line 54 via the second connecting line 58. A first electrically operated 2-way valve 60, a first mechanically operated 2-way valve 62 and a first control valve 64 are in the first connecting line 58 for controlling an inflow of hydraulic fluid to the first actuator 28 arranged. A second electrically operated 2-way valve 66, a second mechanically operated 2-way valve 68 and a second control valve 70 are arranged in the second connecting line 58 for controlling an inflow of hydraulic fluid to the second actuator 30.

To move the cam carrier 26 by the first actuator 28, an electrical release is first effected by the first electrically operated 2-way valve 60. The first electrically operated 2-way valve 60 establishes a fluid connection between the main hydraulic line 54 and the first mechanically operated 2-way valve 62 . By means of the first mechanically operated 2-way valve 62 it can be ensured, for example, that the cams 32, 34 (see FIG Figure 1 ) is switched. Within the cam base circle, the mechanically operated 2-way valve 62 establishes a fluid connection between the main hydraulic line 54 and the first actuator 28 via the released, first electrically operated 2-way valve 60. The hydraulic fluid passes through the first control valve 64 and causes the pin 46 of the first actuator 28 to extend. The pin 46 of the first actuator 28 touches the actuator contact surface 50 of the first shift gate 36 and moves the cam carrier 26 into the first axial position. Here, the cam carrier 26 rotates in a circumferential direction about the longitudinal axis of the camshaft 24 (see Figure 1 ). The first control valve 64 is designed as a controllable check valve. The first control valve 64 prevents the hydraulic fluid from flowing back from the first actuator 28 as long as a control pressure from the first connecting line 56 is present. Hydraulic fluid flowing out of the first actuator 28 can, for example, be drained into a hydraulic fluid chamber (not shown) of the internal combustion engine. The hydraulic fluid space can be, for example, an oil space of the internal combustion engine.

In order to move the cam carrier 26 by the second actuator 30, the second electrically operated 2-way valve 66 is first electrically released. Within the cam base circle, the second mechanically operated 2-way valve 68 can establish a fluid connection between the second actuator 30 and the main hydraulic line 54. The pin 48 of the second actuator 30 extends, touches the actuator contact surfaces 52 and displaces the cam carrier 26 into the second axial position while the cam carrier 26 rotates.

To dampen the axial displacement of the cam carrier 26, elastic elements 72, 74, for example springs, are provided. The elastic elements 72, 74 support the cam carrier 26 on the first bearing block 20 and the second bearing block 22. For this purpose, the elastic elements 72, 74 can be rotated on the corresponding bearing block, for example via ball bearings 20, 22 stored. As an alternative, the elastic elements 72, 74 could also be fastened to the bearing blocks 20, 22 and, for example, be rotatably connected to the cam carrier 26 via ball bearings.

In the Figure 2 is also symbolically referring to Figure 1 The locking device described for the cam carrier 26 is denoted by a reference numeral 76.

The Figure 3 shows another hydraulic system 78. The hydraulic system 78 differs from the hydraulic system 53 of FIG Figure 2 in particular in the damping of the axial displacement of the cam carrier 26. The hydraulic system 78 has a first damping cylinder 80 and a second damping cylinder 82 for damping the axial displacement of the cam carrier 26.

A piston of the first damping cylinder 80 extends when the pin 46 of the first actuator 28 extends. If the cam carrier 26 finally contacts the piston of the first damping cylinder 80 during the axial displacement to the first axial position, the piston of the first damping cylinder 80 is pushed in. In the process, hydraulic fluid is pushed out of the first damping cylinder 80. The hydraulic fluid is conducted to a hydraulic fluid chamber of the internal combustion engine via a first throttle 84. By pushing out the hydraulic fluid, the axial movement of the cam carrier 26 is damped.

In an analogous manner, a piston of the second damping cylinder 82 extends when the pin 48 of the second actuator 30 extends. Hydraulic fluid is pushed out of the second damping cylinder 82 when the piston of the second damping cylinder 82 is pushed in by the cam carrier 26. The expelled hydraulic fluid passes the second throttle 86 and reaches the hydraulic fluid chamber of the internal combustion engine.

When hydraulic fluid is pushed out of the first damping cylinder 80, a first check valve 88 prevents the hydraulic fluid from being conducted from the first damping cylinder 80 to the first actuator 28. Likewise, a second check valve 90 prevents hydraulic fluid pushed out of the second damping cylinder 82 from being conducted to the second actuator 30.

The first damping cylinder 80 damps an axial displacement of the cam carrier 26 to the second axial position. The second damping cylinder 82 damps an axial displacement of the cam carrier 26 to the first axial position. The chokes 84, 86 provide a resistance for represents the hydraulic fluid flowing out of the corresponding damping cylinder 80, 82, so that a desired damping is made possible.

The advantage of using the damping cylinders 80, 82 over the use of the elastic elements 72, 74 (cf. Figure 2 ) lies in the fact that no elastic restoring force, but only damping by the damping cylinders 80, 82 is brought about.

The Figure 4 FIG. 14 shows another hydraulic system 92. Hydraulic system 92 differs from hydraulic system 78 from FIG Figure 3 in particular in the fact that no separate damping cylinders are provided. The damping of the axial displacement of the cam carrier 26 is instead carried out by the actuators 28, 30 themselves.

In detail, the hydraulic system 92 has a first mechanically operated 4-way valve 94 and a second mechanically operated 4-way valve 96. The first mechanically operated 4-way valve 94 is activated by the first electrically operated 2-way valve 60. The second mechanically operated 4-way valve 96 is controlled by the second electrically operated 2-way valve 66. In addition, the hydraulic system 92 has a third electrically operated 2-way valve 98 and a fourth electrically operated 2-way valve 100.

For the axial displacement of the cam carrier 26 into the first axial position, the first mechanically operated 4-way valve 94 is activated by the first electrically operated 2-way valve 60. The first mechanically operated 4-way valve 94 establishes a fluid connection between the main hydraulic line 54 and the first actuator 28. The pin 46 of the first actuator 28 extends. The cam carrier 26 is shifted in a direction towards the first axial position.

In order to dampen the axial displacement of the cam carrier 26 in the event of a displacement to the first axial position, the third electrically operated 2-way valve 98 establishes a fluid connection between the second actuator 30 and the main hydraulic line 54. The extended pin 48 of the second actuator 30 contacts the cam carrier 26 as the cam carrier 26 moves to the first axial position. The pin 48 is pushed into the second actuator 30. Hydraulic fluid is pushed out of the second actuator 30. The expelled hydraulic fluid arrives at the correspondingly set second mechanically operated 4-way valve 96 via the first throttle 84 to the hydraulic fluid chamber of the internal combustion engine. When the hydraulic fluid is pushed out, the displacement movement of the cam carrier 26 is damped.

In a similar manner, the cam carrier 26 can be displaced into the second axial position by the second actuator 30. The displacement movement of the cam carrier 26 can then be damped by the first actuator 28. For this purpose, the fourth electrically operated 2-way valve 100 and the first mechanically operated 4-way valve 94 are switched accordingly.

When hydraulic fluid is pushed out of the first actuator 28, the first check valve 88 prevents the hydraulic fluid from flowing back to the fourth electrically operated 2-way valve 100. Likewise, the second check valve 90 prevents hydraulic fluid pushed out of the second actuator 30 from being conducted to the third electrically operated 2-way valve 98.

The advantage of this example is in particular that no separate damping cylinders or elastic elements have to be provided for damping the axial displacement of the cam carrier 26.

The Figure 5 FIG. 14 shows another hydraulic system 102. Hydraulic system 102 differs from hydraulic system 92 from FIG Figure 4 in particular that a common throttle 104 is provided instead of two separate throttles 84, 86. In addition, the valves 94, 96 have other neutral positions than in FIG Figure 4 on.

The Figures 6 to 18 show a further hydraulic system 106 with an exemplary configuration for the first actuator 28 and the second actuator 30. FIGS Figures 6 to 15 show the sequence of a displacement of the cam carrier 26 by the first actuator 28 to the first axial position, while the cam carrier 26 moves together with the camshaft 24 (see FIG Figure 1 ) rotates.

The hydraulic system 106 has a first electrically operated 2-way valve 108 and a second electrically operated 2-way valve 110. In addition, the hydraulic system 106 has a first control valve 112 and a second control valve 114 as well as a first check valve 116 and a second check valve 118. In addition, the hydraulic system 106 has the first throttle 84 and the second throttle 86.

In addition to the pin 46, the first actuator 28 has a displaceable piston 120, a first displaceable sleeve 122, a second displaceable sleeve 124, a first elastic element 126, a second elastic element 128 and a third elastic element 130. The first elastic member 126 biases the piston 120 in a direction opposite to the pin 46. The second elastic member 128 supports the pin 46 against the first Sleeve 124 from. The third elastic element 130 biases the second sleeve 124 in a direction towards the piston 120. An axial movement of the pin 46 when the pin 46 is extended is limited by the second sleeve 124. The pin 46 is guided in the sleeves 122, 124.

The second actuator 30 is constructed identically to the first actuator 28, with a piston 132, a first sleeve 134, a second sleeve 136, a first elastic element 138, a second elastic element 140 and a third elastic element 142.

The Figure 6 shows the first actuator 28 and the second actuator 30 in a non-actuated state. Pins 46 and 48 are retracted. The first and second electrically operated 2-way valves 108, 110 are switched in such a way that hydraulic fluid is conducted from the first actuator 28 and the second actuator 30 to a hydraulic fluid chamber of the internal combustion engine.

The Figure 7 shows the first actuator 28 at the beginning of an actuation. The first electrically operated 2-way valve 108 allows hydraulic fluid to pass from a hydraulic fluid source. The hydraulic fluid is conducted into a control fluid space for displacing the first sleeve 122.

The Figure 8 shows that the hydraulic fluid conducted into the control fluid space for displacing the first sleeve 122 has displaced the first sleeve 122 together with the second sleeve 124 and the pin 46 in the direction of the actuator contact surface 50. The first sleeve 122, the second sleeve 124 and the pin 46 have shifted against the pretensioning force of the third elastic element 130. The third elastic member 130 is compressed. The pin 46 touches the actuator contact surface 50 in an area in which the actuator contact surface 50 is at the greatest distance from the first actuator 28.

As a result of the displacement of the second sleeve 124 and the pin 46, a hydraulic channel of the second sleeve 124 is aligned with a hydraulic channel of the pin 46. The hydraulic channel of the second sleeve 124 and the hydraulic channel of the pin 46 establish a fluid connection between the hydraulic fluid source and a control fluid space for displacing the piston 120. Hydraulic fluid flows through the hydraulic channels of the second sleeve 124 and the pin 46 to the control fluid space for displacing the piston 120.

The Figure 9 shows that the hydraulic fluid conducted into the control fluid space for displacing the first piston 120 has displaced the piston 120 in a direction towards the actuator contact surface 50. The piston 120 has moved against the pretensioning force of the first elastic element 126. The piston 120 contacts the pin 46 to lock it into place.

The Figures 10 and 11 show that pin 46 eventually engages second ramp 50B as cam carrier 26 rotates. The pin 46 latched by the piston 120 pushes the cam carrier 26 in a direction towards the second actuator 30.

The Figure 12 shows that the cam carrier 26 touches the pin 48 via the actuator contact surface 52 at the end of the displacement movement caused by the first actuator 28. As a result of the contact, the pin 48 is displaced against the pretensioning force of the second elastic element 140 in the direction of the piston 132 of the second actuator 30. As a result, a displacement movement of the cam carrier 26 is damped.

The Figure 13 shows that the pretensioning force of the second elastic element 140 has moved the pin 48 back into its starting position. The cam carrier 26 was thereby shifted a little in the direction of the first actuator 28. The cam carrier 26 now lies centrally between the first actuator 28 and the second actuator 30. In this position, the locking device 76 (cf., for example, FIG Figures 2 to 5 ) the cam carrier 26 axially on the camshaft 24 (see Figure 1 ) to back up.

The Figure 14 shows that the first electrically operated 2-way valve 108 has been switched over. The first electrically operated 2-way valve 108 establishes a fluid connection between the first actuator 28 and a hydraulic fluid chamber of the internal combustion engine via the first throttle 86. The hydraulic fluid from the control chamber for moving the piston 120 flows back through the hydraulic channels of the second sleeve 124 and the pin 46 in the direction of the first electrically operated 2-way valve 108. In addition, the hydraulic fluid flows from the control chamber for moving the piston 120 via the first Control valve 112 in the direction of the first electrically operated 2-way valve 108. At the same time, hydraulic fluid flows out of the control chamber to move the first sleeve 128 in the direction of the first electrically operated 2-way valve 108.

The Figure 15 shows that, due to the outflow of the hydraulic fluid, the piston 120 has shifted in a direction opposite to the second actuator 30 according to the pretensioning force of the first elastic element 126. In addition, the first sleeve 122, the second sleeve 124 and the pin 46 have moved together opposite to the second actuator 30 in accordance with the pretensioning force of the third elastic element 130. The pin 46 is retracted.

From the in Figure 15 In the state shown, the cam carrier 26 can be displaced back into the second axial position by actuating the second actuator 30. How the The second actuator 30 for moving is identical to that of the first actuator 28 when moving into the first axial position. The mode of operation of the first actuator 28 for damping the displacement movement is also identical to that of the second actuator 30 when damping the displacement into the first axial position.

In the Figures 16 to 18 it is shown that the cam carrier 26 is only displaced by the first actuator 28 when the pin 46 is in engagement with the ramp 50B at the maximum distance. If the pin 46 comes into engagement with the actuator contact surface 50 on the ramp 50B or outside the ramp 50B, there is no displacement of the cam carrier 26.

The Figure 16 shows similar to Figure 6 the first actuator 28 and the second actuator 30 in a non-actuated state. Pins 46 and 48 are retracted. The first and second electrically operated 2-way valves 108, 110 are switched in such a way that hydraulic fluid is conducted from the first actuator 28 and the second actuator 30 to a hydraulic fluid chamber of the internal combustion engine.

The Figure 17 shows the first actuator 28 at the beginning of an actuation. The first electrically operated 2-way valve 108 allows hydraulic fluid to pass from a hydraulic fluid source. The hydraulic fluid is conducted into a control fluid space for displacing the first sleeve 122. The pin 46 is already in contact with the actuator contact surface 50. In other words, the pin 46 touches the actuator contact surface 50 in an area in which the actuator contact surface 50 is at the smallest distance from the first actuator 28.

The Figure 18 shows that the hydraulic fluid conducted into the control fluid space for moving the first sleeve 122 has moved the first sleeve 122 together with the second sleeve 124 in the direction of the actuator contact surface 50. Here, however, the pin 46 has not shifted with the first sleeve 122 and the second sleeve 124 in the direction of the actuator contact surface 50, since the pin 46 was already in contact with the actuator contact surface 50. The relative displacement between the first sleeve 122 and the pin 46 leads to a compression of the second elastic element 128. The hydraulic channels of the pin 46 and the second sleeve 124 are not aligned with one another. As a result, no fluid connection is established between the first electrically operated 2-way valve 108 and the control chamber for moving the piston 120.

The pin 46 will not extend until it is in contact with the first ramp 50A (see FIG Figure 1 ) and the area of the actuator contact surface 50 in which the actuator contact surface 50 is at the greatest distance from the first actuator 28. It can thus be ensured that an axial displacement of the cam carrier 26 only takes place in the area of the base circle.

The invention is not restricted to the preferred exemplary embodiments described above. In particular, the invention also claims protection for the subject matter and the features of the subclaims independently of the claims referred to.

List of reference symbols

10

Variable valve train

12th

Gas exchange valve

14th

Gas exchange valve

16

Sliding cam system

18th

Power transmission device

20th

First bearing block

22nd

Second bearing block

24

camshaft

26th

Cam carrier

28

First actuator

30th

Second actuator

32

First cam

34

Second cam

36

First shift gate

38

Second shift gate

40

rocker arm

42

Rocker arm axis

44

Cam follower

46

pen

48

pen

50

Actuator contact surface

50A

First ramp

50B

Second ramp

52

Actuator contact surface

52A

First ramp

52B

Second ramp

53

Hydraulic system

54

Hydraulic main line

56

First connection line

58

Second connection line

60

First electrically operated valve

62

First mechanically operated valve

64

First control valve

66

Second electrically operated valve

68

Second mechanically operated valve

70

Second control valve

72

First elastic element

74

Second elastic element

76

Locking device

78

Hydraulic system

80

First damping cylinder

82

Second damping cylinder

84

First throttle

86

Second throttle

88

First check valve

90

Second check valve

92

Hydraulic system

94

First mechanically operated 4-way valve

96

Second mechanically operated 4-way valve

98

Third electrically operated 2-way valve

100

Fourth electrically operated 2-way valve

102

Hydraulic system

104

Common thrush

106

Hydraulic system

108

First electrically operated 2-way valve

110

Second electrically operated 2-way valve

112

First control valve

114

Second control valve

116

First check valve

118

Second check valve

120

piston

122

First sleeve

124

Second sleeve

126

First elastic element

128

Second elastic element

130

Third elastic element

132

piston

134

First sleeve

136

Second sleeve

138

First elastic element

140

Second elastic element

142

Third elastic element

Claims (13)

1. Sliding cam system (16) for an internal combustion engine, comprising:

   a cam shaft (24);

   a cam carrier (26), which is arranged rotationally fixedly and axially movably on the cam shaft (24), wherein the cam carrier (26) comprises a first shifting gate (36) and a second shifting gate (38) ;

   a first actuator (28) with an element (46) able to move along a longitudinal axis of the cam shaft (24), especially a pin, which can be brought into contact with the first shifting gate (36) for the axial movement of the cam carrier (26) in a first direction; and

   a second actuator (30) with an element (48) able to move along the longitudinal axis of the cam shaft (24), especially a pin, which can be brought into contact with the second shifting gate (38) for the axial movement of the cam carrier (26) in a second direction which is opposite to the first direction;

   characterized by:

   a first elastic element (72), which biases the cam carrier (26) in the second direction, wherein the first elastic element (72) supports the cam carrier (26) on a second bearing block (22) for the rotary mounting of the cam shaft (24) and is mounted rotatably about the longitudinal axis of the cam shaft (24) relative to the second bearing block (22) or the cam carrier (26); and/or

   a second elastic element (74), which biases the cam carrier (26) in the first direction, wherein the second elastic element (74) supports the cam carrier (26) on a first bearing block (20) for the rotary mounting of the cam shaft (24) and is mounted rotatably about the longitudinal axis of the cam shaft (24) relative to the first bearing block (20) or the cam carrier (26).
2. Sliding cam system (16) according to Claim 1, wherein:

   the first actuator (28) is received in or on the first bearing block (20), which supports the cam shaft (24) in a rotating manner; and/or

   the second actuator (30) is received in or on the second bearing block (22), which supports the cam shaft (24) in a rotating manner.
3. Sliding cam system (16) according to Claim 1 or Claim 2, wherein:

   the first shifting gate (36) and/or the second shifting gate (38) has a steplike configuration; and/or

   the first shifting gate (36) is arranged at a first end of the cam carrier (26) and the second shifting gate (38) is arranged at an opposite second end of the cam carrier (26).
4. Sliding cam system (16) according to one of the preceding claims, wherein:

   the first shifting gate (36) comprises an actuator contact surface (50), which extends in a circumferential direction about the longitudinal axis of the cam shaft (24); and/or

   the second shifting gate (38) comprises an actuator contact surface (52), which extends in a circumferential direction about the longitudinal axis of the cam shaft (24).
5. Sliding cam system (16) according to Claim 4, wherein:

   the actuator contact surface (50) of the first shifting gate (36) comprises a first ramp (50A) and a second ramp (50B), wherein the first ramp (50A) of the actuator contact surface (50) of the first shifting gate (36) increases a distance between the first actuator (28) and the actuator contact surface (50) of the first shifting gate (36) relative to a rotary direction of the cam shaft (24) and the second ramp (50B) of the actuator contact surface (50) of the first shifting gate (36) decreases a distance between the first actuator (28) and the actuator contact surface (50) of the first shifting gate (36) relative to a rotary direction of the cam shaft (24); and/or

   the actuator contact surface (52) of the second shifting gate (38) comprises a first ramp (52A) and a second ramp (52B), wherein the first ramp (52A) of the actuator contact surface (52) of the second shifting gate (38) increases a distance between the second actuator (30) and the actuator contact surface (52) of the second shifting gate (38) relative to a rotary direction of the cam shaft (24) and the second ramp (52B) of the actuator contact surface (52) of the second shifting gate (38) decreases a distance between the second actuator (30) and the actuator contact surface (52) of the second shifting gate (38) relative to a rotary direction of the cam shaft (24).
6. Sliding cam system (16) according to one of the preceding claims, wherein the first actuator (28) and/or the second actuator (30) is hydraulically, electrically and/or pneumatically operated.
7. Sliding cam system (16) according to one of the preceding claims, wherein an axial displacement of the cam carrier (26) is dampened hydraulically.
8. Sliding cam system (16) according to one of the preceding claims, further comprising:

   a first hydraulic damping cylinder (80), which is disposed to dampen an axial displacement of the cam carrier (26) in the first direction; and/or

   a second hydraulic damping cylinder (82), which is disposed to dampen an axial displacement of the cam carrier (26) in the second direction.
9. Sliding cam system (16) according to Claim 8, further comprising:

   a first throttle (84), which is arranged downstream from the first hydraulic damping cylinder (80); and/or

   a second throttle (86), which is arranged downstream from the second hydraulic damping cylinder (82) .
10. Sliding cam system (16) according to one of the preceding claims, wherein:

    the second actuator (30) dampens an axial displacement of the cam carrier (26) when the first actuator (28) moves the cam carrier (26) axially in the first direction; and/or

    the first actuator (28) dampens an axial displacement of the cam carrier (26) when the second actuator (30) moves the cam carrier (26) axially in the second direction.
11. Sliding cam system (16) according to Claim 10, wherein
    the second actuator (30) dampens an axial displacement of the cam carrier (26) hydraulically and/or by an elastic element (140) of the second actuator (30); and/or
    the first actuator (28) dampens an axial displacement of the cam carrier (26) hydraulically and/or by an elastic element (128) of the first actuator (28).
12. Variable valve train (10) for an internal combustion engine, having:

    a sliding cam system (16) according to one of the preceding claims;

    at least one gas exchange valve (12, 14);

    a force transmission device (18), which in dependence on an axial position of the cam carrier (26) optionally places a first cam (32) of the cam carrier (26) in an operative connection with the at least one gas exchange valve (12, 14) or places a second cam (34) of the cam carrier (26) in an operative connection with the at least one gas exchange valve (12, 14).
13. Motor vehicle, especially utility vehicle, having a sliding cam system (16) according to one of Claims 1 to 11 or a variable valve train (10) according to Claim 12.

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