Internal-combustion engines – Valve – Valve head cooperates with manifold
Patent
1981-05-08
1983-10-04
Cuchlinski, Jr., William A.
Internal-combustion engines
Valve
Valve head cooperates with manifold
F01L 322
Patent
active
044072422
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
A problem met with in internal combustion engines is valve sinkage leading to reduced valve clearance and finally preventing full closing of the valve. The object of the present invention is to reduce or overcome this problem.
French Pat. No. 2385016 discloses a number of valve constructions which include an annular valve seat having an inner peripheral portion that is formed with a groove so as to produce a cantilevered lip that flexes when engaged by a valve member. However, none of the valves disclosed are engine valves and none possess a valve seat of the aforesaid kind having a frusto-conical valve face adapted to be engaged by a valve member coaxial with and movable along the axis of the valve face.
DISCLOSURE OF THE INVENTION
The invention is based on an appreciation of the fact that valve sinkage is caused by wear of the valve and valve seat induced mainly by relative movement of the engaging faces of the valve and valve seat when closed, and by inertia effects on closing the valve. It has been appreciated that such wear can be reduced by increasing the flexibility of the valve seat. This is achieved according to the invention by providing that said inner peripheral portion is cantilevered over at least the full width of the valve face as measured radially of the axis of the valve face so that said valve face is deflected in bending and shear when subjected to valve gas and inertia seating forces.
Preferably, said inner peripheral portion is undercut. The undercut may be formed by an annular groove in the inner wall of the valve seat adjacent to the valve engaging face, whether the valve seat is an integral part of a valve port body or is formed as an insert in the mouth of the valve port body. Alternatively, if the valve seat is formed as an insert, the undercut may be formed as a recess opening rearwards at the base of the insert.
It has been found that the inherent flexibility of the valve seat alone can be significantly increased in this manner, an increase of 30 percent deflection at the inner periphery of the valve seat being readily achieved and being regarded for practical purposes as a minimum worthwhile level of increased flexibility over the corresponding valve seat without the inner peripheral portion cantilevered.
The increased flexibility of the valve seat not only reduces the seating forces that develop during closure of the valve due to inertia effects, but also provides a more even distribution of the load between the engaging faces of the valve and valve seat and reduces sliding between these faces whenever the closed or partly closed valve is subjected to forces which are being reacted by the seating faces, it being immaterial whether the applied forces are due to gas or to inertia. Each of these effects in turn serves to reduce wear and thereby helps to alleviate or eliminate valve sinkage.
DESCRIPTION OF THE DRAWINGS
The invention will now be described by way of example with reference to the accompanying drawings in which
FIG. 1 is a schematic axial section of half of a diesel engine valve port body fitted with a valve seat insert according to the invention,
FIG. 2 is a section through the valve seat insert of FIG. 1 to a larger scale,
FIGS. 3 to 5 show how the valve seat insert of FIG. 2 can be modified to provide the greatest possible flexibility consistent with stress levels in the annular groove, FIG. 6 shows an alternative valve seat insert according to the invention,
FIG. 7 is a graph showing how valve seating forces vary with the flexibility of the valve seat,
FIG. 8 is a diagram showing displacement and stress of the valve engaging face of the insert of FIGS. 1 and 2 for a given force,
FIG. 9 is a diagram showing the sliding motion between the engaging faces of the valve and valve seat of FIGS. 1 and 2 for a given force, and
FIG. 10 is a section through part of yet another alternative valve seat assembly according to the invention.
BEST METHOD OF THE INVENTION
FIG. 1 shows a cylinder head body 1 fitted with a valve seat insert 2 for a valve 3.
REFERENCES:
patent: 2178895 (1939-11-01), Myers
patent: 3822680 (1974-07-01), Showalter et al.
patent: 4108132 (1978-08-01), Hayashi
Cuchlinski Jr. William A.
Massey-Ferguson-Perkins Limited
Thompson John C.
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