Adjustable camshaft

Patent metadata

Field	Value
Publication number	US-2016160709-A1
Application number	US-201514959983-A
Country	US
Kind code	A1
Filing date	Dec 4, 2015
Priority date	Dec 5, 2014
Publication date	Jun 9, 2016
Grant date	—

Abstract

An adjustable camshaft of an internal combustion engine may include an outer shaft and an inner shaft arranged coaxially to the outer shaft and rotatable over a predefined angle. At least one first cam may be connected rotationally fixedly to the inner shaft. A second cam may be arranged beside the first cam and may be connected rotationally fixedly to the outer shaft. The first cam and the second cam may each be operatively associated with a common valve. Rotation of the first cam relative to the second cam may impart an extension of a valve opening time of the valve. The first cam and the second cam may each include an identical circular segment section in an elevated region of valve lift. The circular segment section of the first cam and the second cam may merge without interruptions during rotation about the predefined angle range.

First claim

1 . An adjustable camshaft of an internal combustion engine, comprising:
an outer shaft and an inner shaft arranged coaxially to the outer shaft and rotatable over a predefined angle range, at least one first cam connected rotationally fixedly to the inner shaft, and a second cam arranged adjacently to the first cam and connected rotationally fixedly to the outer shaft, wherein the first cam and the second cam are each operatively associated with a common valve, and wherein rotation of the first cam relative to the second cam imparts an extension of a valve opening time of the valve, wherein the first cam and the second cams each have an identical circular segment section in an elevated region of valve lift, and wherein the first cam and the second cam are arranged in relation to one another such that even when the inner shaft is rotated to a threshold extent of the predefined angle range relative to the outer shaft, the circular segment section of the first cam merges without interruptions into the circular segment section of the second cam.

2 . The camshaft according to claim 1 , wherein the extension of the valve opening time spans over a crankshaft angle of 8°<α<25°.

3 . The camshaft according to claim 1 , wherein the circular segment section of the first cam and the circular segment section of the second cam have a constant radius in a camshaft angle range of 2° to 12.5°.

4 . The camshaft according to claim 1 , wherein the first cam and the second cams are identical.

5 . A valve drive system of an internal combustion engine, comprising:
a lift valve; and an adjustable camshaft including:
an outer shaft;
an inner shaft arranged coaxially to the outer shaft and rotatable over a predefined angle range;
a first cam connected rotationally fixedly to the inner shaft;
a second cam arranged beside the first cam and connected rotationally fixedly to the outer shaft, wherein the first cam and the second cam are each operatively associated with the lift valve, and wherein rotation of the first cam relative to the second cam imparts an extension of a valve opening time of the lift valve;
wherein the first cam and the second cam each include a circular segment section in an elevated region of valve lift, and wherein at least one of:
the circular segment section of the first cam and the circular segment section of the second cam are identical; and
the first cam and the second cam are arranged in relation to one another so that the circular segment section of the first cam merges uninterrupted with the circular segment section of the second cam when the inner shaft is rotated to a threshold extent of the predefined angle range relative to the outer shaft.

6 . The valve drive system according to claim 5 , wherein at least one of the first cam and the second cam includes a crowned outer contour.

7 . The valve drive system according to claim 5 , further comprising at least one of a cam follower and a tappet operatively connected with at least one of the first cam and the second cam and wherein the at least one of the cam follower and the tappet includes a double-crowned outer contour.

8 . An internal combustion engine comprising: a valve drive system, the valve drive system including:
a lift valve; and an adjustable camshaft including:
an outer shaft;
an inner shaft arranged coaxially to the outer shaft and rotatable over a predefined angle range;
a first cam connected rotationally fixedly to the inner shaft;
a second cam arranged beside the first cam and connected rotationally fixedly to the outer shaft, wherein the first cam and the second cam are each operatively associated with the lift valve, and wherein rotation of the first cam relative to the second cam imparts an extension of a valve opening time of the lift valve;
wherein the first cam and the second cam each include a circular segment section in an elevated region of valve lift, and wherein at least one of:
the circular segment section of the first cam and the circular segment section of the second cam are identical; and
the first cam and the second cam are arranged in relation to one another so that the circular segment section of the first cam merges uninterrupted with the circular segment section of the second cam when the inner shaft is rotated to a threshold extent of the predefined angle range relative to the outer shaft.

9 . The internal combustion engine according to claim 8 , wherein the internal combustion engine is configured as an Atkinson cycle engine.

10 . The internal combustion engine according to claim 8 , wherein at least one of the first cam and the second cam includes a crowned outer contour.

11 . The internal combustion engine according to claim 8 , wherein the valve drive system further includes at least one of a cam follower and a tappet operatively connected with at least one of the first cam and the second cam.

12 . The internal combustion engine according to claim 11 , wherein the at least one of the cam follower and the tappet includes a double-crowned outer contour.

13 . The internal combustion engine according to claim 8 , wherein the extension of the valve opening time of the lift valve spans over a crankshaft angle of 8°<α<25°.

14 . The internal combustion engine according to claim 8 , wherein the circular segment section of the first cam and the circular segment section of the second cam have a constant radius in a camshaft angle range of 2° to 12.5°.

15 . The internal combustion engine according to claim 8 , wherein the first cam and the second cam are configured identical to one another.

16 . The valve drive system according to claim 5 , wherein the extension of the valve opening time spans over a crankshaft angle of 8°<α<25°.

17 . The valve drive system according to claim 5 , wherein the circular segment section of the first cam and the circular segment section of the second cam have a constant radius in a camshaft angle range of 2° to 12.5°.

18 . The valve drive system according to claim 5 , wherein the first cam and the second cam are configured identical to one another.

19 . The valve drive system according to claim 6 , further comprising at least one of a cam follower and a tappet operatively connected with at least one of the first cam and the second cam.

20 . The valve drive system according to claim 19 , wherein the at least one of the cam follower and the tappet includes a double-crowned outer contour.

Assignees

• Mahle Int Gmbh

Inventors

• Altherr Patrick
• Kirschner Rolf

Classifications

• F01L13/0047 Primary

  the movement of the valves resulting from the sum of the simultaneous actions of at least two cams, the cams being independently variable in phase in respect of each other · CPC title

• Y02T10/12

  Improving ICE efficiencies · CPC title