Patent Application
20080095654
In the drawings,
Referring to
More specifically, in the exemplary clutch assembly 10, the driving member 12 has a clutch face 22 that defines a first reference surface 24 that extends generally normal to the driving member's rotational axis 16. A plurality of recesses are defined in clutch face 22 of driving member 12, with each recess including a load-bearing shoulder that is operative to abuttingly engage a first end of a given strut 18 when the driving member 12 rotates in a first direction. While this embodiment of the invention contemplates any suitable configuration for the recesses of the driving member 12, in the exemplary clutch assembly 10 each recess 26 of the driving member 12 is adapted to receive a respective one of the assembly's struts 18. In such arrangement, struts 18 are nominally carried by the driving member 12 for rotation therewith about the axis 16.
Driven member 14 similarly includes a clutch face 34, in close-spaced opposition to the clutch face 22 of the driving member 12. Clutch face 34 also includes a reference surface 36 that extends generally normal to the driven member's rotational axis 16. The driven member's clutch face 34 also includes a plurality of recesses 38 which exceed the number of recesses in the driving member 12. Each of the driven member's recesses 38 is adapted to receive the second end of a given strut 18 when the strut's second end is urged into recess 38. Such urging is typically by a spring seated beneath the strut 18 in the driving members recess. Each of the driven member's recesses 38 includes a load-bearing shoulder 46 that is operative to engage the second end of a given strut 18 when the driving member 12 rotates in the first direction relative to the driven member 14. Driver member 14 includes a back face friction plate. This back face is subjected to intense localized heating in use.
The material for the clutch or transmission components of the present invention is a low alloy, low hardenability material that is subjected to an aggressive cooling or quenching operation to produce a strong martensitic, wear resistant metallic structure. The method of the present invention results in clutch or transmission components that have the desired properties.
In general, a method of manufacturing an automotive component in accordance with one aspect of the present invention comprises the steps of providing an initial pre alloy metal powder comprising, by weight, 0.35-0.55% nickel, 0.50-0.85% molybdenum, with the balance essentially iron. Then an additional 0.60-0.90% carbon, 1.0-3.0% copper metal powder are admixed to the initial metal powder to form an admixed metal powder. A suitable lubricant is added in accordance with powder metal practice to form a lubricated, admixed metal powder. The lubricated admixed metal powder is then die compacted, typically at a pressure of between 40 and 65 tons per square inch, to form a die compacted metal blank. The die compacted metal blank is then sintered to form a sintered metal blank. Such sintering typically is conducted at a temperature above 2000° F. (1090° C.), and more typically at a temperature between 2000° F. (1090° C.) and 2350° F. (1290° C.). The sintered metal blank, which is, in one embodiment of the present invention, either the driven or driving clutch component mentioned above, is then cooled or quenched to form a cooled metal blank. The quenching or cooling operation reduces the temperature of the sintered metal blank from between 1600° F. (870° C.) to 2000° F. (1090° C.) to a temperature of 450° F. (230° C.) and 500° F. (260° C.). It is desirable that such cooling or quenching be conducted at a rate between 1.9° F. (1.05° C.) and 5.5° F. (3.05° C.) per second. The cooled or quenched metal blank is then tempered at a temperature of between 350° F. (175° C.) and 450° F. (230° C.) for at least one hour. The resulting automotive component has a microstructure that is 50-80% martensitic, 20-50% bainitic, and a small percentage, usually less than 10%, fine pearlite.
Because this resulting automotive component material does not transform as readily to martensite, the component does not respond to localized hot spots in clutch or transmission automotive service. Because there is almost no untempered martensite, the resulting microstructure, which is up to 50% bainitic, eliminates fracture initiation sites thereby extending the serviceable life of the clutch or transmission component. Reduction in hardenablity, as compared to the high hardenability materials previously used in such clutch brake or transmission components, reduces the materials propensity to re-hardening which further prohibits crack development and propagation.
Certain examples of the method of carrying out the present invention follow:
In a method of manufacturing an automotive clutch component, an initial pre alloy metal powder of particle sizes between 250 and 1 micron was provided comprising, by weight, 0.45% nickel, 0.65% molybdenum, with the balance essentially iron.
An additional 0.7% graphite, and 1.75% copper metal powder of particle sizes between 150 and 1 micron, by weight, were admixed to form an admixed metal powder.
0.5% EBS was added as a lubricant to form a lubricated admixed metal powder.
The lubricated, admixed metal powder was compacted at a pressure of 45 tons per square inch.
The die compacted metal blank was then sintered at a temperature 2050° F. for 15 minutes.
The sintered metal blank was then quenched at a rate of 5.4° F. (3.00° C.) per second from an initial temperature of (2000° F.) (1090° C.) to a temperature of (500° F.) (260° C.) per use. The quenched metal blank was then tempered at a temperature of (380° F.) (190° C.) for 60 minutes.
The resulting material has a metal microstructure that was 50-55% martensitic, 45-50% bainitic and <5% fine pearlite. The Rockwell hardness of the resulting material was about HRA40.
In a method of manufacturing an automotive clutch component, an initial pre alloy metal powder of particle sizes between 250 and 1 microns was provided comprising, by weight, 0.45% nickel, 0.65% molybdenum, with the balance essentially iron.
An additional 0.9% graphite, and 1.75% copper metal powder of particle size between 150 and 1 micron, by weight, were admixed to form an admixed metal powder.
0.5% EBS was added as a lubricant to form a lubricated admixed metal powder.
The lubricated, admixed metal powder was compacted at a pressure of 45 tons per square inch.
The die compacted metal blank was then sintered at a temperature 2050° F. for 15 minutes.
The sintered metal blank was then quenched at a rate of 1.9° F. (1.05° C.) per second from an initial temperature of (2000° F.) (1090° C.) to a temperature of (500° F.) (260° C.) per use. The quenched metal blank was then tempered at a temperature of (380° F.) (1090° C.) for 60 minutes.
The resulting material has a metal microstructure that was 60-65% martensitic, 35-40% bainitic and <5% fine pearlite. The Rockwell hardness of the resulting material was about HRA50.
In a method of manufacturing an automotive clutch component, an initial pre alloy metal powder of particle size between 250 and 1 micron was provided comprising, by weight, 0.45% nickel, 0.65% molybdenum, with the balance essentially iron.
An additional 0.9% carbon, and 1.75% copper metal powder of particle size between 150 and 1 micron, by weight, were admixed to form an admixed metal powder.
5% EBS was added as a lubricant to form a lubricated admixed metal powder.
The lubricated, admixed metal powder was compacted at a pressure of 45 tons per square inch.
The die compacted metal blank was then sintered at a temperature 2050 for 15 minutes.
The sintered metal blank was then quenched at a rate of 1.9° F. (1.0° C.) per second from an initial temperature of (2000° F.) (1090° C.) to a temperature of (500° F.) (260° C.) per use. The quenched metal blank was then tempered at a temperature of (380° F.) (190° C.) for 60 minutes.
The resulting material has a metal microstructure that was 80% martensitic, 20% bainitic and <1% fine pearlite. The Rockwell hardness of the resulting material was about HRA58.
