Variable valve mechanism, engine, and automatic two-wheeled vehicle

Patent metadata

Field	Value
Publication number	US-2018010487-A1
Application number	US-201715639562-A
Country	US
Kind code	A1
Filing date	Jun 30, 2017
Priority date	Jul 5, 2016
Publication date	Jan 11, 2018
Grant date	—

Abstract

The present invention is capable of more smoothly changing a phase of a cam shaft in a rotation direction. A variable valve mechanism changes an opening/closing timing of an intake valve or an exhaust valve in response to an engine rotation speed. The variable valve mechanism includes: a cam sprocket which rotates in response to a rotation of a crank shaft; an intake cam shaft which is integrated with an intake cam and is provided to be rotatable relatively to the cam sprocket; and a link member that transmits a rotation from the cam sprocket to the intake cam shaft. The link member is supported by the cam sprocket to be swingable and swings in response to a change in rotation speed of the cam sprocket to rotate the intake cam shaft relatively to the cam sprocket.

First claim

What is claimed is:

1 . A variable valve mechanism which changes an opening/closing timing of an intake valve or an exhaust valve in response to an engine rotation speed, the variable valve mechanism comprising:
a cam sprocket which rotates in response to a rotation of a crank shaft; a cam shaft which is integrated with any one of intake side and exhaust side cams and is provided to be rotatable relatively to the cam sprocket; and a link member that engages with the cam sprocket and the cam shaft and transmits a rotation from the cam sprocket to the cam shaft, wherein the link member is supported by the cam sprocket to be swingable and swings in response to a change in rotation speed of the cam sprocket to rotate the cam shaft relatively to the cam sprocket.

2 . The variable valve mechanism according to claim 1 , wherein
the link member includes:
a swing shaft which is fixed to the cam sprocket;
a weight portion which is disposed to be separated from the swing shaft; and
an engagement portion which engages with an engagement pin provided in the cam shaft and transmits a rotation of the cam sprocket to the cam shaft;
the link member is supported by the cam sprocket to be swingable; and the weight portion moves outward in the radial direction of the cam sprocket and the engagement portion moves to move the engagement pin in accordance with the rotation of the cam sprocket so that the cam shaft rotates relatively to the cam sprocket.

3 . The variable valve mechanism according to claim 2 , further comprising:
an urging member that is locked to the link member and urges the weight portion inward in the radial direction of the cam sprocket, wherein in a non-swing state of the link member, a distance L 1 between a center of the swing shaft and a center of the engagement pin is smaller than a distance L 2 of an imaginary line connecting the center of the swing shaft to a locking position of the urging member on the link member.

4 . The variable valve mechanism according to claim 3 , wherein
in the non-swing state of the link member, an angle α formed by an imaginary line connecting the center of the swing shaft and the center of the engagement pin and a tangential line of a circle using a rotation axis of the cam shaft as a center and passing through the center of the engagement pin is smaller than angle β formed by an imaginary line connecting the center of the swing shaft and the locking position of the urging member and a center line of the urging member.

5 . The variable valve mechanism according to claim 2 , wherein
in the non-swing state of the link member, an imaginary line connecting the center of the swing shaft to the center of the engagement pin intersects at a substantially right angle to an imaginary line connecting the center of the rotation axis of the cam shaft and the center of the engagement pin.

6 . The variable valve mechanism according to claim 2 , wherein
the engagement portion is formed as a groove; and the groove is provided with a first holding position which receives the engagement pin while the link member does not swing to a predetermined position or more and a second holding position which receives the engagement pin while the link member swings to a predetermined position or more and a first stopper portion which protrudes toward a facing inner wall surface of the groove in the vicinity of the first holding position is provided in an inner wall surface disposed at a farther side from the swing shaft in the inner wall surface of the groove.

7 . The variable valve mechanism according to claim 6 , wherein
a second stopper portion which protrudes toward a facing inner wall surface of the groove in the vicinity of the second holding position is provided in the inner wall surface disposed at a close side to the swing shaft in the inner wall surface of the groove.

8 . The variable valve mechanism according to claim 7 ,
wherein the groove is provided with a substantially S-shaped moving line in which the center of the engagement pin in a front view bypasses the first stopper portion and the second stopper portion.

9 . The variable valve mechanism according to claim 3 , wherein
the urging member is disposed so that one end thereof is locked to a position near the weight portion in relation to the swing shaft and an angle β interposing the rotation axis of the cam sprocket among angles formed by an imaginary line passing through the locking position of the urging member and the center of the swing shaft and the center line of the urging member becomes an acute angle.

10 . The variable valve mechanism according to claim 3 , wherein
the link member includes a first link member disposed at one side with the rotation axis of the cam sprocket interposed therebetween and a second link member disposed at the other side; and the urging member includes a first urging member disposed at one side with the rotation axis of the cam sprocket interposed therebetween and a second urging member disposed at the other side.

11 . The variable valve mechanism according to claim 10 , wherein
the first link member and the second link member are disposed to be point-symmetrical to each other with respect to the center of the rotation axis of the cam sprocket and the first urging member and the second urging member are disposed to be point-symmetrical to each other with respect to the center of the rotation axis of the cam sprocket.

12 . The variable valve mechanism according to claim 10 , wherein
in the first link member and the second link member, the weight portion is disposed at one side and the engagement portion is disposed at the other side with respect to an imaginary line connecting the center of the swing shaft and the center of the rotation axis of the cam sprocket; one end of the first urging member is locked to a position near the weight portion in relation to the swing shaft of the first link member and the other end thereof is locked to a position near the engagement portion in relation to the swing shaft of the second link member; and one end of the second urging member is locked to a position near the weight portion in relation to the swing shaft of the second link member and the other end thereof is locked to a position near the engagement portion in relation to the swing shaft of the first link member.

13 . The variable valve mechanism according to claim 12 , wherein
a distance between a locking position of the first urging member at the side of the weight portion in the first link member and the center of the swing shaft of the first link member is larger than a distance between a locking position of the first urging member at the side of the engagement portion in the second link member and the center of the swing shaft of the second link member; and a distance between a locking position of the second urging member at the side of the weight portion in the second link member and the center of the swing shaft of the second link member is larger than a distance between a locking position of the second urging member at the side of the engagement portion in the first link member and the center of the swing shaft of the first link member.

14 . An engine comprising:
the variable valve mechanism according to claim 1 .

15 . An automatic two-wheeled vehicle comprising:
the engine according to claim 14 .

Assignees

• Suzuki Motor Corp

Inventors

• Tanaka Koichi
• Arase Kunio

Classifications

• F01L2305/00

  Valve arrangements comprising rollers · CPC title

• F01L2001/0475

  Hollow camshafts · CPC title

• F01L1/344 Primary

  changing the angular relationship between crankshaft and camshaft, e.g. using helicoidal gear · CPC title

• F01L2820/035

  Centrifugal forces · CPC title

• F01L2001/0535

  Single overhead camshafts [SOHC] · CPC title