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Патент США №

8636486

Автор(ы)

Colombo и др.

Дата выдачи

28 января 2014 г.

Accurate powder metal component, assembly and method



РЕФЕРАТ

The invention provides an accurate powder metal component having a body with opposed surfaces at least one of which has at least one projection of smaller cross-sectional area than the main portion of the body of the component. The distance from the free end of the projection to the opposite end of the component defines one dimension of the component that must be relatively accurate, in one embodiment to slide against and form a seal that inhibits liquid flow against another component of an assembly. In the manufacturing method, the powdered metal component is made by compaction to form the body including a projection at the end, is sintered and thereafter is reduced in the dimension between the end of the projection and the opposite end of the component by coining the free end of the projection so as to reduce the dimension to within a tolerance of the nominal specified dimension.

Авторы:

Gustavo Osvaldo Colombo (Chivilcoy, AR), Carlos E. Camelo (Worcester, MA), Ian W. Donaldson (Jefferson, MA)

Патентообладатель:
ИмяГородШтатСтранаТип

Gustavo Osvaldo Colombo
Carlos E. Camelo
Ian W. Donaldson
Chivilcoy
Worcester
Jefferson
N/A
MA
MA
AR
US
US

Заявитель:

GKN Sinter, LLC (Auburn Hills, MI)

ID семейства патентов

40429709

Номер заявки:

12/676,514

Дата регистрации:

05 сентября 2008 г.
PCT Filed: September 05, 2008
PCT No.: PCT/US2008/075377
371(c)(1),(2),(4) Date: March 04, 2010
PCT Pub. No.: WO2009/033007
PCT Pub. Date: March 12, 2009
Prior Publication Data
Document IdentifierPublication Date
US 20100178190 A1Jul 15, 2010

Отсылочные патентные документы США

Application NumberFiling DatePatent NumberIssue Date
60967870Sep 7, 2007

Класс патентной классификации США:

418/161; 418/160; 418/162; 418/163; 418/164; 418/165

Класс совместной патентной классификации:

B22F 3/164 (20130101); B22F 5/08 (20130101); F16H 55/06 (20130101); F04C 2/084 (20130101); B22F 2005/005 (20130101); F04C 2/10 (20130101); F04C 2230/22 (20130101)

Класс международной патентной классификации (МПК):

F04C 2/10 (20060101); F16H 55/08 (20060101); F16H 55/17 (20060101); B22F 3/00 (20060101); B22F 5/08 (20060101)

Область поиска:

;418/160-166

Использованные источники

[Referenced By]

Патентные документы США

4464141August 1984Brown
6244413June 2001Gutmann et al.
6370979April 2002Tauschek et al.
6425749July 2002Lettner et al.
6565341May 2003Bodzak
6626277September 2003Hauf
6974012December 2005Rau et al.
7607906October 2009Yates et al.
2003/0183479October 2003Rau et al.
2007/0071625March 2007Friedman
2008/0232994September 2008Hosono

Зарубежные патентные документы

2315630Oct 1974DE
S49-129203Dec 1974JP
S50-127808Oct 1975JP
S55-50405Apr 1980JP
S64-25485Feb 1989JP
H05-37926May 1993JP
2006-233771Sep 2006JP
2006-249953Sep 2006JP
10-2003-0023637Mar 2003KR

Другие источники


International Search Report and Written Opinion as mailed on Feb. 19, 2009 for International Patent Application PCT/US2008/075377. cited by applicant .
Japanese Patent Office, Notification of Reason for Refusal for corresponding Japanese Application No. 2010-524175, Dispatch Date: Mar. 12, 2013, which cites the references cited herein. cited by applicant.

Главный эксперт: Bomberg; Kenneth
Assistant Examiner: Singh; Dapinder
Уполномоченный, доверенный или фирма: Quarles & Brady LLP

Текст решения-прецедента



ПЕРЕКРЁСТНАЯ ССЫЛКА НА "РОДСТВЕННЫЕ" ЗАЯВКИ



The present application claims the benefit of U.S. Provisional Patent Application No. 60/967,870 filed Sep. 7, 2007, and the benefit of PCT International Application No. PCT/US2008/075377 filed on Sep. 5, 2008, both applications are incorporated herein by reference.

ФОРМУЛА ИЗОБРЕТЕНИЯ



We claim:

1. A sintered powder metal gerotor gear, comprising: at least one sintered powder metal gear including a body having external tooth surfaces and the body having opposed end surfaces, both of the end surfaces being formed with a projection that extends around at least a portion of the end surfaces of the body, the projection tapering to a flattened free end of the projection; wherein the flattened free end of the projection is obtained by plastically deforming the free end to obtain a lower porosity than a surface of at least one surface that is not plastically deformed so as to reduce a dimension from said free end to the other opposed surface to within a tolerance of a nominal specified dimension.

2. The powder metal gerotor gear of claim 1, wherein both opposed surfaces have at least one projection that tapers to a free end of the component, and both free ends are plastically deformed and of lower porosity than a surface of the adjacent surface that is not plastically deformed, so as to reduce a dimension between said free ends to within a tolerance of a nominal specified dimension.

3. The powder metal gerotor gear of claim 1, wherein the projection has arcuate sides adjacent to the free end.

4. The powder metal gerotor gear of claim 1, wherein the projection extends around a periphery of teeth of the component.

5. The powder metal gerotor gear of claim 1, wherein the projection includes a projection that extends around an axial hole that extends through the component.

6. The powder metal gerotor gear of claim 1, wherein the component is a gear and the projection includes projections that extend around a periphery of teeth of the gear, a portion of the end face at bases of the teeth, and a portion that extends around a hole through the gear.

7. The powder metal gerotor gear of claim 1, wherein the projections define a liquid reservoir on the end face.

8. A gerotor pump comprising: a housing at least one sintered powder metal gear including a body having external tooth surfaces and the body having opposed end surfaces, both of the end surfaces being formed with a projection that extends around at least a portion of the end surfaces of the body, the projection tapering to a flattened free end of the projection; wherein the flattened free end of the projection is obtained by plastically deforming the free end to obtain a lower porosity than a surface of at least one surface that is not plastically deformed so as to reduce a dimension from said free end to the other opposed surface to within a tolerance of a nominal specified dimension.


ОПИСАНИЕ




ЗАЯВЛЕНИЕ О НАУЧНЫХ ИССЛЕДОВАНИЯХ, ФИНАНСИРУЕМЫХ ПРАВИТЕЛЬСТВОМ



Not applicable.


ОБЛАСТЬ ТЕХНИКИ, К КОТОРОЙ ОТНОСИТСЯ ИЗОБРЕТЕНИЕ



This invention relates to sintered powered metal components that must be made to precise dimensions.


ПРЕДПОСЫЛКИ СОЗДАНИЯ ИЗОБРЕТЕНИЯ



Sintered powder metal components are well known in the art. An advantage of making a component of sintered powder metal is that it can be formed to near net shape. Usually, due to variability in the manufacturing process, if a powder metal part must have precise dimensions, it must have material removed by a machining process to obtain the required precision. Such processes result in time and tooling expense, and do not necessarily improve the material characteristics of the component, other than to make it of precise dimensions. This invention addresses these issues in some types of sintered powder metal components.


СУЩНОСТЬ ИЗОБРЕТЕНИЯ



The invention provides an accurate powder metal component, assembly and method in which the powder metal component has a body with opposed surfaces at least one of which has at least one projection of smaller cross-sectional area than the main portion of the body of the component. The distance from the free end of the projection to the opposite end of the component defines one dimension of the component that must be accurate. The powdered metal component is made by compaction to form the body including a projection at the end, is sintered and thereafter is reduced in the dimension between the end of the projection and the opposite end of the component by coining the free end of the projection so as to reduce the dimension to within a tolerance of the nominal specified dimension.

The invention may advantageously be applied to a pump gear, for example a gerotor gear.

The foregoing and other objects and advantages of the invention will appear in the detailed description which follows. In the description, reference is made to the accompanying drawings which illustrate a preferred embodiment of the invention.


КРАТКОЕ ОПИСАНИЕ РИСУНКОВ



Reference is hereby made to the following figures in which:

FIG. 1a is a perspective view of a sintered powder metal gerotor gear with coining projections;

FIG. 1b is a perspective view of the sintered powder metal gerotor gear with coining projections of FIG. 1a;

FIG. 2a is a perspective view of a coined sintered powder metal gerotor gear with coined projections;

FIG. 2b is a perspective view of the coined sintered powder metal gerotor gear with coined projections of FIG. 2b;

FIG. 3 is a perspective cross-sectional view of a coining apparatus;

FIG. 4 is a perspective cross-sectional view of the coining apparatus of FIG. 3;

FIG. 5 is a perspective cross-sectional view of the coining apparatus of FIG. 3;

FIG. 6a is a cross-sectional view of the coining apparatus of FIG. 3 illustrating flattening of the coining projections;

FIG. 6b is a detail view of the area 6b-6b of FIG. 6a illustrating flattening of the coining projections;

FIG. 7a is a perspective view of a sintered powder metal bushing component with coining projections;

FIG. 7b is a cross-sectional view of the sintered powder metal bushing component with coining projections of FIG. 7a;

FIG. 7c is a perspective view of a coined sintered powder metal bushing component with coined projections;

FIG. 7d is a cross-sectional view of the coined sintered powder metal bushing component with coined projections of FIG. 7c;

FIG. 8a is a perspective view of a sintered powder metal spacer component with coining projections;

FIG. 8b is a cross-sectional view of the sintered powder metal spacer component with coining projections of FIG. 8a;

FIG. 8c is a perspective view of a coined sintered powder metal spacer component with coined projections;

FIG. 8d is a cross-sectional view of the coined sintered powder metal spacer component with coined projections of FIG. 8c;

FIG. 9 is a micrograph of a coined PM material near the coined surface; and

FIG. 10 is a view of a gerotor pump with the cover of the housing partially removed to show the end faces of the gerotor gears that rotate against the cover.


ПОДРОБНОЕ ОПИСАНИЕ ИЗОБРЕТЕНИЯ



This invention relates to powder metal components that require a narrow range of dimensional tolerances. Several types of example components are described in the following paragraphs. One application that requires components of accurate dimensional tolerances is gerotor pumps. In this application, gerotor gears have a narrow thickness tolerance to ensure adequate sealing of the pump, since the ends of the gear seal against surfaces of the pump housing as illustrated in FIG. 10, at the sliding interface of the end of the gear against the pump housing. This example application is addressed in FIGS. 1 through 6. Referring to FIG. 1, a sintered powder metal gerotor pump gear 10 includes opposed surfaces 12, tooth surfaces 14, a bore 16, a chamfer 18 between the opposed surfaces 12 and the bore 16, and coining projections 20. The shape of coining projections 20 is preferably tapered, for example semi-circular, in cross-section to minimize surface area toward the free end. The free end of the projection is flattened and slides against the adjacent surface of the housing to create a sliding seal. Alternatively, the shape of coining projections 20 may be triangular, trapezoidal, or any other cross-sectional shape that tapers from a root or base of the projection that is integral with the body of the gear to a free end 21.

Coining projections 20 are located, in general, along the periphery of opposed surfaces 12 and extend axially. Preferably, coining projections 20 are located at locations on the opposed surfaces 12 to ensure adequate sealing against adjacent surfaces of a mating component, such as a pump housing, that the free ends of the projections slide against. For example, coining projections 20 may be located along the edges of the gear teeth, in a circular form adjacent to the root diameter of the gear teeth and in another circular form spaced radially inward of the root of the gear teeth, adjacent to the chamfer 18 that leads in to the axial bore 16 through the gear 10.

The gerotor gear size, i.e. bore diameter, number of teeth, diametral pitch, tooth pressure angle, gear thickness, and tooth profile shape, etc., may be determined as appropriate for the application in which the sintered powder metal gerotor gear 10 is used.

Referring to FIG. 2, a coined sintered powder metal gerotor gear 110 includes the above features with coined projections 120 formed from the coining projections 20. Coined projections 120 include coined free ends 121 as shown in FIG. 6. Inclusion of coined free ends 121 results in highly accurate overall thickness relative to a nominal specified dimension. Coined sintered powder metal gerotor gear 110 can meet a tolerance of less than 50 microns for the nominal specified dimension. It should be understood that overall thickness refers to the distance between coined free ends 121 on opposite opposed surfaces 12 of the coined sintered powder metal gerotor gear 110. Alternatively, overall thickness refers to the distance between a coined free end 121 and the opposite opposed surface 12 if coined projections 120 are only included on a single opposed surface 12.

Coined projections 120 have a trapezoid-like shape as shown in FIG. 6. The sides of coined projections 120 adjacent to the opposed surfaces 121 are arcuate due to the original semi-circular shape of coining projections 20. Coined projections 120 have a relative density of approximately 95% at their free ends compared to the original powder metal material. Advantageously, coined projections 120 have increased strength properties compared to a non-coined PM component, and are not as porous to provide improved sealing characteristics. Another benefit is that there is a lower surface contact area between the pump gears and the housing. Advantageously, the pockets or recesses between or surrounded by coined projections 120 create reservoirs for containing fluid, which in the case of hydraulic fluid is a lubricant, resulting in increased performance, efficiency, and durability.

For sub-assemblies such as hydraulic pumps, gears need to have a very tight overall thickness control to ensure adequate sealing surfaces for proper operation of the pump (minimal leakage or pressure loss). The thickness tolerances that are required for these pumps are less than 50 microns, usually less than 30 microns. Current manufacturing methods can't meet these tolerance levels without the addition of a secondary machining operation. The ribs of the current invention may be provided in powder metal punches (top and/or bottom) along the outer profile or perimeter or other surfaces on the ends of the parts. This feature provides a raised region that projects beyond the surface of the part faces, formed by the punches, that can be subsequently plastically deformed to a very accurate overall thickness tolerance during a coining operation. This deformation region provides the sealing surface for a pump assembly in the case of gerotor gears. During the application of a stress field on the porous material at the ends of the ribs during the coining operation causes a flattening of pores causing a decrease in thickness or elevation of the raised region, as shown in the micrograph of FIG. 9. With increasing thickness reduction, after attaining about 95% of full density, the compressive strength of material increases rapidly. The plastic deformation becomes the predominant densification mechanism with limited further closing of the pores.

The process for creating a coined sintered powder metal gerotor gear 110 is as follows: a powder metal mixture is created which may include iron, steel, aluminum, bronze, brass, or any mixture that is well known in the art for making conventional PM gerotor gears, or other parts if the invention is applied to a different part. The powder metal mixture is placed in a forming die and compacted in the die with punches from above and/or below. The forming die includes the negative shape of the tooth surfaces 14 on the powder metal part. The punches include the negative shape of the opposed surfaces 12 of the part, including the coining projections 20. Such apparatuses are well known in the art, and may be driven by hydraulic or mechanical devices. Next, the compacted powder metal gerotor gear is sintered. Sintering time, temperature, and environment can be chosen based on the selected powder metal mixture. Such combinations are well known in the art. Sintering results in a near net shape sintered powder metal gerotor gear 10. Typically after being cooled, sintered powder metal gerotor gear 10 is coined in a coining apparatus 22 as shown in FIG. 3. Coining apparatus 22 includes tooling components 24 (which may be carbide), a hydraulic actuator or press element 26, a fixture 27, a positive stop 28, and an internal diameter support 30. Tooling components 24 may include movable upper tooling component 32 and lower tooling component 34. Tooling components 24 also include coining surfaces 36 which contact and deform coining projections 20. Upper tooling component 32 includes flange 38 which contacts the positive stop 28. Positive stop 28 causes motion of upper tooling component 32 to cease, and therefore determines the overall thickness of the coined sintered powder metal gerotor gear 110.

Other embodiments for the coining apparatus are possible. For example, a mechanical press can replace the hydraulic press. Also, the bore 16 can include coining projections 20 which form an internal spline. These projections can be deformed by the internal diameter support 30 in the coining operation. In addition, modifications to the sintering process are possible. For example, the coined sintered powder metal gerotor gear 110 may be subjected to an infiltration process to further improve the strength characteristics of the component. Such modifications to the sintering process are well known in the art. In any case, the process results in coined sintered powder metal gerotor gear 110 with coined projections 120 and coined free ends 121.

The coining process is much quicker and less expensive than a machining operation. In addition, it can be used with a variety of powder metal materials that can be plastically deformed during a coining operation, such as iron, steel, aluminum, bronze, and brass.

This process can also be used to manufacture other types of components which have a narrow range of dimensional tolerances. For example, FIG. 7a shows a sintered powder metal bushing component 210 with coining projections 220. Coining the component results in coined sintered powder metal bushing component 310 with coined projections 320, as shown in FIG. 7c. Additionally, FIG. 8a shows a sintered powder metal spacer component 410 with coining projection 420. Coining the component results in coined sintered powder metal spacer component 510 with coined projection 520. In addition, there are other types of pumps and other machines, that have gears, gear-like components or other components with ends that slide or rotate against a surface and that must be sealed against that surface, that this invention could advantageously be applied to, for example a P-pump or a ringed pump.

A preferred embodiment of the invention has been described in considerable detail. Many modifications and variations to the preferred embodiment described will be apparent to a person of ordinary skill in the art. Therefore, the invention should not be limited to the embodiment described but should be defined by the claims that follow.

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