WO2010002806A1

WO2010002806A1 - Coating for a high pressure components

Info

Publication number: WO2010002806A1
Application number: PCT/US2009/049091
Authority: WO
Inventors: Bradley E. Bartley; David C. Mack
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2008-06-30
Filing date: 2009-06-29
Publication date: 2010-01-07
Anticipated expiration: 2010-12-30
Also published as: DE112009001611T5; CN102076954A

Abstract

An engine system is disclosed. The engine system has a first component (14) subject to pressurized fluid and having a first component surface (36) and a second component (18) subject to pressurized fluid and having a second component surface (34). The surface of the second component is mated to the first component surface, the second component rigidly connected to the first component. At least one of the first component surface and the second component surface has a coating (42), the coating having a coating hardness that is greater than a hardness of either of the first and second components.

Description

COATING FOR A HIGH PRESSURE COMPONENT

Technical Field

The present disclosure is directed to a high pressure component and, more particularly, to a coating for a high pressure component.

Background

Current engine systems attempt to improve engine performance by increasing the pressure of fuel provided for combustion. One such engine system uses a common rail fuel system that includes a high pressure pump that supplies high pressure fuel to a common rail or plenum that supplies the fuel to the individual fuel injectors of the engine. The conveyance of high pressure fuel in such systems subject the various components of the system, including rigid, static connections between components, to repeated loading. Because connected components may have different stiffness properties, the repeated high pressure loading may subject the rigid connections to micro-movement. Micro-movement may be microscopic displacement caused by a more flexible component that displaces more under load than a stiffer connected component. Micro-movement may cause fretting at the contact area between the two rigidly connected components, resulting in pitting of the contact surfaces of the components. U.S. Patent No. 6,439,203 (the '203 patent), issued to Cooke. describes a dynamic seal arrangement for a fuel injector. The seal arrangement of the '203 patent may fit around a reciprocating piston of the fuel injector to prevent a flow of fuel between chambers of the fuel injector as the piston displaces. The contact area between the piston and the seal arrangement may include a resistant coating to reduce wear from a surface of the piston sliding against a surface of the seal arrangement. Though the '203 patent may reduce wear in a dynamic seal between sliding components by use of a coating, it does not address fretting between two rigidly connected components that are subjected to relative micro- movement. The present disclosure is directed to overcoming one or more of the shortcomings set forth above and/or other problems in the art.

Summary of the Disclosure

In accordance with one aspect, the present disclosure is directed toward an engine system. The engine system includes a first component subject to pressurized fluid and having a first component surface and a second component subject to pressurized fluid and having a second component surface. The surface of the second component is mated to the first component surface, the second component rigidly connected to the first component. At least one of the first component surface and the second component surface includes a coating, the coating having a coating hardness that is greater than a hardness of either of the first and second components.

According to another aspect, the present disclosure is directed toward a fluid delivery assembly. The fluid delivery assembly includes a first component having a first component surface and a second component having a second component surface. The surface of the second component is mated to the first component surface, the second component rigidly connected to the first component. At least one of the surfaces includes a coating that prevents wear of the surfaces, the wear caused by pressurized fluid within the fluid delivery assembly.

Brief Description of the Drawings

Fig. 1 is a cross-sectional illustration of a portion of an exemplary high pressure component in the form of a high pressure fuel pump; and Fig. 2 is a cross-sectional illustration of an exemplary connection of the pump of Fig. 1.

Detailed Description

A machine such as, for example, a mobile or stationary machine that performs some type of operation associated with an industry such as mining, construction, farming, power generation, or transportation, may have an engine system including, among other things, a fuel supply system and an engine such as a diesel or gasoline engine, or a gaseous fuel-powered engine. The fuel system may include a common rail fuel system supplying high pressure fuel to individual fuel injectors of the engine. The common rail fuel system may include a high pressure pump for pressurizing fuel. Fig. 1 illustrates a portion of a cross-section of a high pressure pump 10 for use in a common rail fuel system. In particular, Fig. 1 illustrates a controllable inlet valve assembly 12 of high pressure pump 10 of a common rail fuel system. While the features of this disclosure will be disclosed in connection with a fluid delivery assembly such as high pressure pump 10 of a common rail fuel system, it is understood that the features are applicable to a wide range of components that are subject to pressurized fluid. Such other components could include, for example, components such as valves, filters, and/or fuel injectors located downstream of high pressure pump 10, or components outside an engine system that deliver high pressure fluid. Moreover, although described throughout as being applicable to a common rail fuel system, the teachings of the present disclosure are also equally applicable to other types of fuel systems, including mechanically actuated electronic fuel injector (MEUI) systems, hydraulically actuated electronic fuel injector (HEUI) systems, and intensified common rail fuel systems, in which portions of a high pressure pump may be included in the fuel injector.

In addition to valve assembly 12, high pressure pump 10 may also include a housing 14 for receiving valve assembly 12, and a solenoid assembly 15 for actuating valve assembly 12. High pressure pump 10 may also include a -A-

piston 17 reciprocating within a pump chamber 19 to raise the pressure of the fuel that is supplied to a control chamber through valve assembly 12.

Valve assembly 12 may include a valve element 16, a valve body 18, and a valve retainer 20. Valve element 16, valve body 18, and valve retainer 20 may be of any suitable shape such as, for example, a cylindrical shape. Valve body 18 may form the valve seat for valve element 16 and may have an inner diameter that is slightly larger than an outer diameter of valve element 16 so that valve body 18 receives valve element 16. Valve element 16 may be a "nail" shaped element, including a cylindrical shaft body and an end having a diameter that is larger than a diameter of the body. Valve element 16 may be rigidly coupled to an armature 21 and biased by a spring 23 toward an open position. Valve element 16 may displace along a single axis, guided by valve body 18, when actuated by solenoid assembly 15.

Valve retainer 20 may have first and second inner diameters 22 and 24 that are slightly larger than first and second outer diameters 26 and 28 of valve body 18, respectively, so that valve retainer 20 receives valve body 18. Housing 14 may have an inner diameter 30 that may be slightly larger than an outer diameter 32 of valve retainer 20 so that housing 14 receives valve retainer 20. Inner diameter 30 of housing 14 and outer diameter 32 of valve retainer 20 may include complementary threading so that housing 14 may threadably receive valve retainer 20. Valve retainer 20 may be threaded into housing 14 so that a surface 34 of valve body 18 may contact a surface 36 of housing 14 and so that a surface 38 of valve retainer 20 may contact a surface 40 of valve body 18, thereby rigidly clamping valve body 18 within housing 14. The rigid connection may prevent all relative movement between valve body 18, valve retainer 20, and housing 14 except for micro-movement (microscopic displacements). Valve body 18 and housing 14 may form a portion of pump chamber 19. It is contemplated that valve body 18, and additional components of high pressure pump 10, may be rigidly connected in any other suitable manner known in the art such as, for example, via bolting. Valve body 18 and housing 14 may be made from materials having different stiffness properties such as, for example, between 190 GPa (gigapascals) and 220 GPa. Valve body 18 and housing 14 may have hardness values such as, for example, between 0.8 GPa and 4.0 GPa. Because valve body 18 and housing 14 form a portion of pump chamber 19, these components may be subjected to numerous iterations of high pressure loading. Deformation of valve body 18 and housing 14 may vary under high pressure loading as a function of material stiffness. Under the same high pressure loading, more flexible materials may undergo larger deformations than relatively stiff er materials. This varying deformation may result in micro -movement between valve body 18 and housing 14, which may lead to fretting between surfaces 34 and 36. Fretting may also occur on any other rigidly connected surfaces of high pressure pump 10 that are subject to the pressurized fluid of the pump.

Fig. 2 illustrates an enlarged view of the rigidly connected surfaces 34 and 36 of valve body 18 and pump housing 14 shown in Fig. 1.

Valve body 18 and housing 14 may include coatings 42 and 44 that may protect surfaces 34 and 36, respectively, from wear due to relative micro-movement. Valve body 18 and housing 14 may also include optional bond layers 46 and 48, respectively. Optional bond layers 46 and 48 may be a suitable layer such as, for example, chromium, for improving an adhesion of coatings 42 and 44 to valve body 18 and housing 14, respectively. It is contemplated that coatings 42 and 44 may be applied to valve body 18 and housing 14 either with or without optional bond layers 46 and 48, respectively.

Coatings 42 and 44 may be hard coatings for protecting surfaces 34 and 36 from pitting and other damage from relative micro-movement such as, for example, fretting. Coatings 42 and 44 may have a thickness of approximately 5.0 microns or less. For example, coatings 42 and 44 may be between approximately 0.5 microns and 1.7 microns or between approximately 0.5 microns and 1.0 micron. Coatings 42 and 44 may be made from hard, wear resistant materials such as, for example, diamond- like carbon (DLC) materials or chromium nitride. Coatings 42 and 44, when made from DLC, may have a hardness of between approximately 8.0 and 40.0 GPa and may be deposited via any suitable deposition technique known in the art such as chemical vapor deposition or plasma-enhanced chemical vapor deposition. Coatings 42 and 44, when made from chromium nitride, may have a hardness of between approximately 12.0 and 30.0 GPa and may be deposited via any suitable deposition technique known in the art such as physical vapor deposition or arc vapor deposition. It is contemplated that the disclosed coatings may be applied to only one, or to multiple surfaces, of any rigid connection of high pressure pump 10.

Industrial Applicability

The disclosed coatings may be used in a wide range of fluid delivery components that are subject to high pressure loading such as high pressure fuel pumps, fuel injectors, and valves located downstream of high pressure pumps. The disclosed coatings may also be used in components located outside of the engine system such as, for example, components of after-treatment systems and hydraulic systems. The disclosed coatings may protect rigid, static connections that are subject to relative micro-movement from fretting or other damage due to micro-movement. High pressure pump 10 may pressurize the fuel to high pressures, subjecting valve body 18 and housing 14 to high pressure loading within pump chamber 19. Because valve body 18 and housing 14 may have different material stiffness properties, the high pressure loading may affect relative micro- movement to occur between valve body 18 and housing 14 because valve body 18 and housing 14 may deform differently under substantially identical high pressure loading conditions. Coatings 42 and 44 may prevent fretting, for example, between surface 34 of valve body 18 and surface 36 of housing 14.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed coatings. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed embodiments. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.

Claims

1. An engine system, comprising: a first component (14) subject to pressurized fluid and having a first component surface (36); a second component (18) subject to pressurized fluid and having a second component surface (34) that is mated to the first component surface, the second component rigidly connected to the first component; and at least one of the first component surface and the second component surface including a coating (42), the coating having a coating hardness that is greater than a hardness of either of the first and second components.

2. The engine system of claim 1, wherein the first and second components have different stiffness properties.

3. The engine system of claim 1, wherein the coating is made from diamond-like carbon and the coating hardness is between approximately 8.0 and 40.0 GPa.

4. The engine system of claim 1, wherein the coating is made from chromium nitride and the coating hardness is between approximately 12.0 and 30.0 GPa.

5. The engine system of claim 1, wherein a thickness of the coating is approximately 5.0 microns or less.

6. A fluid delivery assembly, comprising: a first component (14) having a first component surface (36); a second component (18) having a second component surface (34) that is mated to the first component surface, the second component rigidly connected to the first component; and at least one of the surfaces including a coating (42) that prevents wear of the surfaces, the wear caused by pressurized fluid within the fluid delivery assembly.

7. The fluid delivery assembly of claim 6, wherein the coating is made from diamond-like carbon and a hardness of the coating is between approximately 8.0 and 40.0 GPa.

8. The fluid delivery assembly of claim 6, wherein the coating is made from chromium nitride and a hardness of the coating is between approximately 12.0 and 30.0 GPa.

9. The fluid delivery assembly of claim 6, wherein the first component and the second component have different stiffness properties, the pressurized fluid affecting micro-movement between the first component and the second component.

10. The fluid delivery assembly of claim 6, wherein the wear is from fretting.