Machine element or mechanism – Gearing – Teeth
Patent
1998-06-04
2000-11-21
Fenstermacher, David M.
Machine element or mechanism
Gearing
Teeth
74434, F16H 5508
Patent
active
06148685&
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to sprockets and gears, and in particular to a construction for sprockets and gears which is made using dissimilar compatible powder metals.
2. Discussion of the Prior Art
Internal combustion engines must ensure that the piston motion which compresses the air/fuel mixture is coordinated with the intake and exhaust valves opening and closing by means of a timing system. The most common timing system utilizes two sprockets with teeth encompassed by a metal link chain. The crankshaft sprocket drives the chain which in turn applies torque to the camshaft sprocket, thereby turning it in unison. Typically, the camshaft sprocket is significantly larger than the crankshaft sprocket, to effect a speed reduction.
Camshaft sprockets are usually made from a metal stamping or machined casting of aluminum alloy or cast iron. Modern high output engines demand greater precision and improved endurance including tooth strength and wear resistance. An additional requirement is quietness, referred to as NVH quality (noise vibration and harshness).
In recent years, a new technique of manufacture is powder metallurgy (P/M). This involves the use of iron and other powders which are blended and then compacted into a preform shaped like the cam sprocket. A thermal treatment called sintering causes the compacted particles to bond together metallurgically forming a structural component. The P/M process has the benefit of large volume precision component manufacture.
In the case of high functional demands, for example a sprocket or gear, a P/M part has to be made to a high density. This generally requires a process sequence involving powder compaction, sintering, repressing and finally induction hardening. The high alloy and high density result in high cost in production and high weight, particularly in a large sprocket or gear. In addition, high density imparts a high modulus of elasticity to the P/M alloy which transmits noise (i.e. "rings" when subjected to mechanical vibration).
SUMMARY OF THE INVENTION
The invention provides an improved powder metal sprocket or gear of unitary construction having engagement teeth in a teeth region around the periphery of a body region in which the teeth region is of a different powder metal material than the body region. The two different powder alloys have properties tailored to the local functional requirements.
In a useful form, the teeth are made from an alloy steel which is hardenable. Preferably, this alloy hardens directly on cooling from the sintering furnace to eliminate any subsequent hardening steps. Alternatively, this alloy can be an induction hardening alloy.
Preferably, the teeth region extends to just below the teeth roots and is compacted to high density to ensure high tooth strength and wear resistance. The majority of the part inside of the teeth, which is the body, is made from a powder blend which can be compacted at low pressure to low density, yet exhibits high compacted strength to enable handling without cracking prior to sintering. The higher density of the teeth region provides high tooth strength and wear resistance, and the lower density of the body region reduces weight and deadens sound transmission.
In order to achieve adequate functional strength in the body of the finished product at a relatively low density, a metallurgical process known as liquid phase sintering is used. This produces a small amount of evenly distributed molten metal during sintering. This activates diffusion of the metal powder surfaces resulting in a stronger material and rounded micro-porosity which provides toughness. The low density of the body provides a low elastic modulus that tends to deaden sound. The low weight is an advantage in service since it requires less energy to accelerate and decelerate the sprocket. Weight savings of over 25% are possible with this approach.
In addition, the lower alloy level and lower weight of the body, plus avoidance of induction hardening, result in substantial cost reduct
REFERENCES:
patent: 2859635 (1958-11-01), Lee
patent: 3320663 (1967-05-01), Haller
patent: 3324544 (1967-06-01), Haller
patent: 3665585 (1972-05-01), Dunn et al.
patent: 3733921 (1973-05-01), Carveth
patent: 3762881 (1973-10-01), Dunn
patent: 3768327 (1973-10-01), Dunn et al.
patent: 3772935 (1973-11-01), Dunn et al.
patent: 3842646 (1974-10-01), Kuhn
patent: 4054449 (1977-10-01), Dunn et al.
patent: 4111031 (1978-09-01), Vennemeyer et al.
patent: 4145798 (1979-03-01), Sarnes
patent: 4172719 (1979-10-01), McGee et al.
patent: 4277544 (1981-07-01), Pietrocini
patent: 4595556 (1986-06-01), Umeha et al.
patent: 4677870 (1987-07-01), Alshareedah
patent: 4721598 (1988-01-01), Lee
patent: 4772340 (1988-09-01), Kawaguchi et al.
patent: 4793968 (1988-12-01), Mosser et al.
patent: 5049183 (1991-09-01), Saka et al.
patent: 5096037 (1992-03-01), Knoess et al.
patent: 5271287 (1993-12-01), Wadleigh
patent: 5273710 (1993-12-01), Zengin
patent: 5356721 (1994-10-01), Knoess
patent: 5390414 (1995-02-01), Lisowsky
patent: 5455000 (1995-10-01), Seyferth et al.
patent: 5540883 (1996-07-01), Jones et al.
patent: 5598631 (1997-02-01), Umezawa et al.
patent: 5659873 (1997-08-01), Seyrkammer
patent: 5659955 (1997-08-01), Plamper
patent: 5666632 (1997-09-01), Maulik
patent: 5724860 (1998-03-01), Sekiguchi et al.
patent: 5729822 (1998-03-01), Shivanath et al.
patent: 5738052 (1998-04-01), Meurer et al.
patent: 5881354 (1999-03-01), Shivanath et al.
patent: 5901336 (1999-05-01), Dombrowski
patent: 5902943 (1999-05-01), Schaffer et al.
Applicant's Exhibit A--Supplementary European Search Report for European Application No. 96944235.9, Dated Mar. 15, 2000.
Cadle Terry M.
Geiman Timothy E.
Landgraf Carl J.
Mandel Joel H.
Fenstermacher David M.
Zenith Sintered Products, Inc.
LandOfFree
Duplex sprocket/gear construction and method of making same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Duplex sprocket/gear construction and method of making same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Duplex sprocket/gear construction and method of making same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1247518