Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Making composite or hollow article
Patent
1996-06-12
1997-09-09
Jordan, Charles T.
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Making composite or hollow article
419 11, 419 25, 419 37, 419 38, 419 47, 419 54, 419 58, 75228, 75246, 29890122, 29DIG31, B22F 500, B22F 702
Patent
active
056666322
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to valve seat inserts for use in internal combustion engines.
Valve seat inserts which are retained in place by an interference fit in the cylinder head of an internal combustion engine are well known. Such inserts have tended in the past to be made of a single material, either by a casting or by a powder metallurgy route followed by machining to size.
More recently, two-layer valve seats made by powder metallurgy techniques have been made.
Two layer valve seat inserts comprise a seat face layer with which the seat of a popper valve usually makes contact, and a base or back-up layer which is in contact with a receiving recess in the cylinder head for example.
The functions fulfilled by each layer are distinct. Amongst other things, the seat face layer provides resistance to high temperature, hostile environments and repeated impact damage, whilst the base layer provides long term creep resistance to ensure that the interference fit of the insert in its recess does not relax too much.
U.S. Pat. No. 4,485,147 describes a two layer valve seat insert having copper powder mixed with the powder material which forms the base layer. During sintering, the copper melts and infiltrates the valve seat insert face layer. This is said to save the cost of pressing and handling separate copper alloy infiltrating blanks.
EP-A-0130604 describes a two layer valve seat insert for a diesel engine, the insert having a base layer with improved creep and wear resistance over that of the seat face layer. The two layer seat insert was produced by a double pressing operation. The valve seat inserts are made by pre-compacting the base layer and subsequently compacting a layer of a seat face alloy onto the pre-compacted base layer.
In order to reduce the cost of a valve seat insert it is desirable to provide the seat face layer in a material which is suitable for the service conditions. However, it is desirable to provide the base layer in a material which is suitable for maintaining the integrity of the interference fit in the cylinder head, but which material may be generally less highly alloyed, and therefore less expensive, than the seat face layer.
Furthermore, it is also desirable for cost reasons, to reduce the number of manufacturing steps involved in the production of a two layer valve seat insert. In this regard it is preferable to be able to compact both powder layers of the valve seat insert simultaneously. However, simultaneous compaction means that there is no individual control of the green densities of the two constituent layers.
According to a first aspect of the present invention, there is provided a method of making a two layer valve seat insert having a valve seat face layer and a base layer, the method comprising the steps of preparing two powder mixtures; a first powder mixture for forming the valve seat face layer; a second powder mixture for forming the valve seat base layer; sequentially introducing a predetermined quantity of each of said first and said second powder mixtures into a powder compacting die and having an interface therebetween substantially perpendicular to the axis of said die; simultaneously compacting said first and said second powder mixtures to form a green compact having two layers and sintering said green compact, wherein at least one of either the chemical composition or the physical characteristics of at least one of said first and said second powder mixtures is adjusted so as to result in said valve seat face layer and said valve seat base layer having substantially the same density after compaction.
The term "substantially the same density" is herein defined as a density variation of not more than 3% between the two layers, and preferably not more than 1.5%.
At least one of the first and second powder mixtures may have its chemical composition and/or physical characteristics such as powder particle shape, size distribution and apparent density, for example, adjusted so as to achieve substantially the same density in each layer
REFERENCES:
patent: 3790352 (1974-02-01), Niimi et al.
patent: 3856478 (1974-12-01), Iwata et al.
patent: 4035159 (1977-07-01), Hashimoto et al.
patent: 4346684 (1982-08-01), Vossieck
patent: 4424953 (1984-01-01), Takagi et al.
patent: 4472350 (1984-09-01), Urano
patent: 4485147 (1984-11-01), Nishino et al.
patent: 4505988 (1985-03-01), Urano et al.
patent: 4509722 (1985-04-01), Ebihara
patent: 4546737 (1985-10-01), Kazuoka et al.
patent: 4632074 (1986-12-01), Takahashi et al.
patent: 4671491 (1987-06-01), Kuroishi et al.
patent: 5080713 (1992-01-01), Oda et al.
patent: 5466276 (1995-11-01), Sato et al.
Brico Engineering Limited
Jenkins Daniel
Jordan Charles T.
LandOfFree
Valve seat insert of two layers of same compact density does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Valve seat insert of two layers of same compact density, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Valve seat insert of two layers of same compact density will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-78476