AU734474B2

AU734474B2 - Valve timing system

Info

Publication number: AU734474B2
Application number: AU24994/97A
Authority: AU
Inventors: Frederick William Roberts
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-04-16
Filing date: 1997-04-16
Publication date: 2001-06-14
Anticipated expiration: 2017-04-16
Also published as: AU2499497A

Description

PAUL R TAYLOR ASS. Fax:61299683814 11 Apr '01 15:44 P.04

ROM

Valve Timing System The present invention relates to a power output improvement apparatus for an internal combustion engine and in particular to a valve timing system for an intennal combustion engine, which is also applicable to engines having multiinlet and multi-exhaust configurations per combustion chamber.

Many systems have been developed to increase the power output of internal combustion engines. Some of these utilise multiple valves, and variable valve timing such as BMW's patented Vanos variable valve timing system- The present invention provides a variable valve timing system comprising: a cam follower adapted to move the valve between its closed and open position, said follower having a contoured engagement surface; a cam, located on and driven by a cam shaft, and having a contact surface adapted to engage the engagement surface of the cam follower and move the cam follower to operate the valye, the contact surfarm of the carn being contoured at least along a portion thereof; and rotational means to rotate the cam follower relative to the plane of movement of the cam such that the contoured contact surface of the cam and contoured engagement surface of the cam follower engage each other earlier AtZ 11/04 '01 WED 15:17 [TX/RX NO 91011 PAUL R TAYLOR ASS. Fax :61299683814 S R0BI 11 Apr '01 15:44 P. -i r177111~ and disengage later, during rotational movement of the cams, than if the cam follower is not rotated.

The invention will now be described, by way of example, with reference to the accompanying drawings in which:

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figure 1 illustrates schematically a perspective view of a cam and cam follower of one embodiment of the present invention; figure 2 illustrates schematically a side view of the cam and cam follower of another embodiment of the present invention; figure 3 illustrates schematically a plan view of the cam follower shown in figure 2; figure 4 illustrates schematically a control rod assembly controlling four cam followers as illustrated in figure 3;

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005000 0 figure 5 illustrates schematically a close up view of the cam follower and rotational means shown in figure 4; figure 6 illustrates a plan view of the cam follower according to a further embodiment of the present invention; 11/04 '01 WED 15:17 [TX/RX NO 9101] WO 97/39222 PCT/AU97/00237 3 figure 7 illustrates a perspective view of an embodiment of the present invention applied to a push rod engine; figure 8 illustrates a sectional view through a cam follower assembly, in an overhead cam engine, illustrated in figure 7; and figure 9 illustrates a schematic sectional view taken in the direction of arrow IX in figure 8.

In one embodiment of the present invention, as shown in figure 1, the cam has a contoured outer or contact surface The contour can be of any desired profile, but is preferably v-shaped. The cam is supported on the cam shaft as is normal with internal combustion engines.

The cam follower operates the valve (not shown), and has a contoured upper engagement surface of any desired configuration.

However preferably the contour of the upper engagement surface of the cam follower and the contoured contact surface of the cam are complementary. In the present embodiment the contour on the upper surface of the cam follower is a v-shaped recess with the walls thereof at any desired angle.

WO 97/39222 PCT/AU97/00237 4 The general operation of the timing system of the present invention is the same as any standard timing system, in that as the cam shaft rotates at a speed determined by the engine speed such as at half the engine speed, the cam rotates around the cam shaft axis and the cam engagement surface on the lobe engages the cam follower, opening and closing the valve.

However in the present invention the cam follower is rotated about its axis a desired number of degrees as shown in figure 3, in accordance with the engine speed. Thus the v-shaped recess and the complementary vshaped contact surface of the cam are slightly out of alignment, so that the contact surface of the cam lobe engages the inclined plane of the wall of the v-shaped recess at a higher point, hence earlier in the cycle and disengage later, than when the v-shaped recess and the complementary vshaped contact surface of the cam are aligned. Therefore the valve is opened sooner and closed later, increasing the degrees of the cycle for which the valve is open, as the engine revolutions increase.

In the embodiment shown in figures 2 3, two rocker inserts are located in the v-shaped recess to maintain the geometric integrity of the alignment of the contact faces of the cam and cam follower to lessen wear on the cam The rocker inserts are fitted into the cam follower (4) so that they can rotate about their respective axes (9 10), as they are WO 97/39222 PCT/AU97/00237 engaged by the contoured contact surface of the cam during the rotation of the cam and the reciprocated rotation of the cam follower.(4).

One method of rotating the cam follower is shown in figures 4 wherein a control yoke (11) is pivotally attached, at one end, connected by two bolts (13) to the cam follower and at its other end to a control rod The yoke (11) is connected by a shaft (14) to a floating ball assembly (15) in the control rod Adjustment of the angular positions of the cam followers is carried out by means of an adjustment nut (16) which has a left hand threaded rod (17) and a right handed threaded rod (18) which engage in control rod (12).

The movement of the control rod (12) could be computer controlled by the engine revolutions or the driving mode or centrifugally controlled.

As shown in figure 6, the rocker inserts have their ends (19) which slide into respective grooves to prevent the inserts from falling out of their recesses (21).

In other embodiments not shown the angles of each engaging surface of the two rocker inserts of a particular cam follower and the respective complementary engaging surfaces of the cam could be different so that the valve is allowed to advance forward but with less delay in closing or with no delay in closing or vice versa. Further the engaging surfaces of the rocker WO 97/39222 PCT/AU97/00237 6 inserts could slope from the periphery of the cam follower to the centre line (26) of the cam follower {fig. 3} As shown in figure 7, an embodiment of the present invention is applicable to push rod engines. The control of the operation of the cam followers and the cams are the same as the other embodiments.

However, because of the need for accessibility to set the adjustments relating to the variable valve timing, it would be preferable that that camshaft cam followers and controls be located in a single assembly, which can be removed, as a whole, from the engine. Figure 7 shows a paired inlet and outlet valve arrangement.

As shown in figures 8 9, the cam follower centre is offset from the valve stem centre A semi circular groove (24) is milled in the underside of the cam follower to take up the rotation of the cam follower (4) relative to the valve stem The semi circular groove (24) can be milled to varying depths so that when the cam follower is rotated, the tappet clearance is maintained.

WO 97/39222 PCT/AU97/00237 7 Incorporating hydraulic valve lifters in the design would most likely compensate for the slight variations in tappet clearances. This would mostly apply to push rod engines.

It should be obvious to people skilled in the art that modifications and variations could be made to the above described embodiments without departing from the spirit or the scope of the present invention.

Claims

1. A variable valve timing system comprising: a cam follower adapted to move the valve between its closed and open position, said follower having a contoured engagement surface; a cam, located on and driven by a cam shaft, and having a contact surface adapted to engage the engagement surface of the cam follower and move the cam follower to operate the valve, the contact surface of the cam being contoured at least along a portion thereof; and rotational means to rotate the cam follower relative to the plane of movement of the cam such that the contoured contact surface of the cam and contoured engagement surface of the cam follower engage each other eailier and disengage later, during rotational movement of the cams, than if the cam follower is not rotated,

2. A variable valve timing system according to claim 1, wherein the contour of the cam follower engagement surface is v- shaped in profile.

3. A variable valve timing system preceding claims wherein two rocker inserts f the cam follower. according to any one of the orm the engagement surface of 11/04 '01 WED 15:17 [TX/RX NO 9101 11/04 '01 WED 15:17 [TX/RX NO 9101 WO 97/39222 PCT/AU97/00237 9

4. A variable valve timing system according to claim 3 wherein the rocker inserts are located, in the cam follower, in recesses, which have grooves into which the ends of the rocker inserts slide to retain the rocker inserts in the respective recesses.

A variable valve timing system according to any one of the preceding claims, wherein said rotational means comprises a control rod and each cam follower is held between two arm of a u-shaped yoke, with the yoke being connected by a shaft to a floating ball assembly on the control rod.

6. A variable valve timing system according to claim 5 wherein the control rod has means to vary its length between each floating ball assembly so as to align the cam with the cam follower as required.

7. A variable valve timing system substantially as hereinbefore described with reference to the accompanying drawings.