Variable lift valve train of an internal combustion engine

Patent metadata

Field	Value
Publication number	US-9540970-B2
Application number	US-201514624837-A
Country	US
Kind code	B2
Filing date	Feb 18, 2015
Priority date	Feb 19, 2014
Publication date	Jan 10, 2017
Grant date	Jan 10, 2017

Abstract

A method for operating an internal combustion engine with a sliding cam valve train that has a cam part ( 2 ) with three adjacent cams of different lifts (H, M, L) and a groove-shaped connecting link path with two path sections (S 1 , S 2 ) that lift in both axial directions of the cam part and are arranged completely one behind the other around the circumference is provided. An actuator ( 10 ) selectively couples two actuator pins ( 7, 8 ) in the connecting link path, in order to move the cam part. The base position of the cam part should be moved into a desired axial position during the operation of the internal combustion engine through successive coupling of the actuator pins in the connecting link path.

First claim

The invention claimed is:

1. A method for operating an internal combustion engine with a lift-variable gas-exchange valve train comprising an actuator and a camshaft with a carrier shaft and a cam part that is rotationally locked on the carrier shaft and is movable between three axial cam positions and has a group of three adjacent cams of different lifts and a groove-shaped connecting link path with a first path section and a second path section that lift in both axial directions of the cam part and are arranged completely one behind the other over a circumference of the cam part, the actuator being actuatable to selectively extend first and second actuator pins that are couplable into the connecting link path, in order to move the cam piece to one of the axial positions, and the cam part is reset into an outer target axial position during operation of the internal combustion engine, the first actuator pin in a base position phase is extended and retracted and the second actuator pin in a following second base position phase is extended and retracted, wherein the actuator is controlled as follows:
a) extending the first actuator pin at a circumferential path position that lies in front of the first path section and behind the second path section,
b) holding the first actuator pin in an extended position within a circumferential path angle that encloses the two path sections at least once,
c) retracting the first actuator pin from a circumferential path position that lies behind the second path section and in front of the first path section,
d) extending the second actuator pin at a circumferential path position that lies in front of the first path section and behind the second path section,
e) holding the second actuator pin in the extended position within a circumferential path angle that encloses the two path sections at least once,
f) retracting the second actuator pin from a circumferential path position that lies behind the second path section and in front of the first path section,
wherein the axial lift of the second path section shifts the cam part in the axial direction and wherein the second actuator pin is adjacent to the first actuator pin in the axial direction of the cam part base position.

2. The method according to claim 1 , further comprising performing steps (a)-(f) in the cam part base positions during a rotational speed run-up of a starting of the internal combustion engine.

3. The method according to claim 1 , wherein the gas-exchange valve is actuated in the cam part base position of the cams with a greatest lift.

4. A method for operating an internal combustion engine with a lift-variable gas-exchange valve train comprising an actuator and a camshaft with a carrier shaft and a cam part that is rotationally locked on the carrier shaft and is movable between three axial cam positions and has a group of three adjacent cams of different lifts and a groove-shaped connecting link path with a first path section and a second path section that lift in both axial directions of the cam part and are arranged completely one behind the other over a circumference of the cam part, the actuator being actuatable to selectively extend first and second actuator pins that are couplable into the connecting link path, in order to move the cam piece to one of the axial positions, and the cam part is reset into a middle target axial position during operation of the internal combustion engine, the first actuator pin in a base position phase is extended and retracted and the second actuator pin in a following second base position phase is extended and retracted, wherein the actuator is controlled as follows:
a) extending the first actuator pin at a circumferential path position that lies in front of the first path section and behind the second path section,
b) holding the first actuator pin in an extended position within a circumferential path angle that encloses the two path sections at least once,
c) retracting the first actuator pin from a circumferential path position that lies behind the second path section and in front of the first path section,
d) extending the second actuator pin at a circumferential path position that lies in front of the second path section and behind the first-path section,
e) holding the second actuator pin in the extended position within a circumferential path angle that encloses the two path sections at least once,
f) retracting the second actuator pin from a circumferential path position that lies behind the first second path section and in front of the first path section,
wherein the axial lift of the second path section shifts the cam part in the axial direction, in which the second actuator pin is adjacent to the first actuator pin.

Assignees

• Schaeffler Technologies Ag

Inventors

• Popp Markus
• Pfannenmuller Jan

Classifications

• F01L13/0036 Primary

  the valves being driven by two or more cams with different shape, size or timing or a single cam profiled in axial and radial direction · CPC title

• F01L2013/0052

  with cams provided on an axially slidable sleeve · CPC title

• F01L2013/101

  Electromagnets · CPC title