WO2012122201A2

WO2012122201A2 - Electronic hydraulic lifter and method

Info

Publication number: WO2012122201A2
Application number: PCT/US2012/027950
Authority: WO
Inventors: John C. MANGIAGLI
Original assignee: Dresser-Rand Company
Priority date: 2011-03-10
Filing date: 2012-03-07
Publication date: 2012-09-13
Also published as: WO2012122201A3

Abstract

Electronic hydraulic lifter apparatus and methods, with the apparatus including a lifter body and a piston disposed at least partially within the lifter body and configured to translate longitudinally with respect thereto. The apparatus further includes a first fluid reservoir disposed at least partially within the lifter body, the piston, or both and configured to receive an end of the piston, and a smart fluid disposed within the first fluid reservoir and configured to communicate with at least the end of the piston. The apparatus also includes an electrical connection coupled to the first fluid reservoir and operatively communicating with the smart fluid, with the electrical connection being configured to vary a viscoelastic property of the smart fluid by applying a field thereto.

Description

Electronic Hydraulic Lifter and Method

Background

[0001] This application claims priority to U.S. Patent Application Serial No. 61/451 ,314, which was filed March 10, 201 1. This priority application is hereby incorporated by reference in its entirety into the present application, to the extent that it is not inconsistent with the present application.

[0002] Gas engines use valves to control admittance of fuel and air to power cylinders, as well as to discharge exhaust gases therefrom. In many cases, these valves are actuated using a camshaft. As the camshaft turns, one or more cam followers follow the cam lobes, thereby translating the rotation of the camshaft into reciprocating linear movement of the cam follower. Each cam follower is connected to a pushrod assembly, and the pushrod assembly in turn connects to a rocker arm, which is pivotal and connects to the valve. The combination of cam follower, pushrod, and rocker arm is often known as a "valve tappet assembly." The reciprocating movement of the cam follower (tappet) is transmitted to the pushrod assembly, which causes the rocker arm to pivot, thereby opening and closing the valve.

[0003] One type of valve tappet assembly includes a hydraulic lifter. Among other advantages, the hydraulic lifter accounts for thermal expansion by providing a variable pushrod length. Accordingly, a conventional hydraulic lifter receives a flow of oil to expand the lifter to the optimal length. The hydraulic lifter then capitalizes on the incompressibility of the oil to provide an essentially solid structure in compression, thereby enabling lifting of the valve according to the rotation of the camshaft.

[0004] In some cases, however, it is desirable to allow the valve, especially if the valve is an intake or fuel valve, to remain closed beyond what is normally provided by the rotation of the camshaft. Designs that enable such altered valve timing often require a significant redesign of the gas engine, such as omitting a connection between the valve and the camshaft and/or providing complex hydraulic assemblies to provide the required valve lifting. While such hydraulic assemblies have been found to be generally suitable for many applications, it is often desirable to retain the camshaft and the connection between it and the valve, while avoiding such hydraulic systems. Therefore, what is needed is a simple yet effective electronic valve lifter that provides for variable operation of an engine valve.

Summary

[0005] Embodiments of the disclosure may provide an exemplary electronic hydraulic lifterfor a gas engine. The electronic hydraulic lifter may include a lifter body and a piston disposed at least partially within the lifter body and configured to translate longitudinally with respect thereto. The electronic hydraulic lifter may further include a first fluid reservoir disposed at least partially within the lifter body, the piston, or both and configured to receive an end of the piston, and a smart fluid disposed within the first fluid reservoir and configured to communicate with at least the end of the piston. The electronic hydraulic lifter may also include an electrical connection coupled to the first fluid reservoir and operatively communicating with the smart fluid, with the electrical connection being configured to vary a viscoelastic property of the smart fluid by applying a field thereto.

[0006] Embodiments of the disclosure may also provide an exemplary method for lifting a valve. The method may include biasing the valve closed, and following a cam lobe of a rotatable camshaft with a hydraulic lifter that is coupled to the valve. In one or more embodiments, the hydraulic lifter may include a lifter body, and a piston disposed within the lifter body. The hydraulic lifter may also include a first fluid reservoir disposed within the lifter body and receiving at least an end of the piston, and a smart fluid disposed within the first fluid reservoir and communicating with the piston. The hydraulic lifter may further include an electrical connection operatively communicating with the first fluid reservoir. The method may also include activating the smart fluid by energizing the electrical connection, to change one or more viscoelastic properties of the smart fluid and resist relative movement between the piston and the lifter body. The method may further include at least partially de-activating the smart fluid by at least partially de-energizing the electrical connection, to change the one or more viscoelastic properties of the smart fluid and allow for relative movement between the piston and the lifter body.

[0007] Embodiments of the disclosure may further provide an exemplary apparatus for lifting a valve in a gas engine. The apparatus may include a cylindrical lifter body having an upper end and a lower end, and a pushrod cup coupled to the upper end of the cylindrical lifter body, the pushrod cup configured to engage a rocker arm coupled to the valve. The apparatus may also include a cam follower coupled to the lower end of the cylindrical lifter body, the cam follower configured to engage a cam lobe of a rotatable camshaft, and an internal piston disposed at least partially within the lifter body and configured to translate longitudinally relative thereto. The apparatus may further include a first fluid reservoir disposed within the cylindrical lifter body proximal the lower end thereof, the internal piston extending at least partially into the firstfluid reservoir, and a second fluid reservoir disposed within the internal piston and between the first fluid reservoir and the upper end of the cylindrical lifter body. The apparatus may further include a smart fluid disposed within the first and second fluid reservoirs and communicating with the internal piston, the smart fluid including an electrorheological fluid, a magnetorheological fluid, or a combination thereof. The apparatus may also include a circulation line including a check valve, an orifice, or both and extending between the first and second fluid reservoirs, the circulation line being configured to channel the smart fluid from the first fluid reservoir to the second fluid reservoir. The apparatus may further include a return line including a check valve, an orifice, or both and extending between the first and second fluid reservoirs, with the return line being configured to channel the smart fluid from the second fluid reservoir to the first fluid reservoir. The apparatus may also include an electrical connection coupled to the first fluid reservoir and operatively communicating with the smart fluid. The electrical connection may be configured to apply an electric field or a magnetic field to the smart fluid to change the smart fluid from a relatively low-viscosityfluidic suspension to a relatively-high viscosity gel, a viscoelastic solid, or a combination thereof, to resist relative movement between the cylindrical lifter body and the internal piston.

Brief Description of the Drawings

[0008] The present disclosure is best understood from the following detailed description when read with the accompanying Figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0009] Figure 1 illustrates a diagrammatic view of an exemplary electronic hydraulic lifter, according to one or more aspects of the disclosure.

[0010] Figure 2 illustrates a flowchart of an exemplary method for actuating a valve, according to one or more aspects of the disclosure.

Detailed Description

[0011] It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the present disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the various Figures. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Finally, the exemplary embodiments presented below may be combined in any combination of ways, i.e., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure. [0012] Additionally, certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Further, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Additionally, in the following discussion and in the claims, the terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to." All numerical values in this disclosure may be exact or approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope. Furthermore, as it is used in the claims or specification, the term "or" is intended to encompass both exclusive and inclusive cases, i.e., "A or B" is intended to be synonymous with "at least one of A and B," unless otherwise expressly specified herein.

[0013] Moreover, as they are used herein, terms such as "up" and "down"; "above" and "below"; "upon"; "top" and "bottom"; "upward" and "downward"; and others indicative of position and/or direction refer to relative positions between structures and are not intended to denote a particular spatial orientation. It will thus be appreciated that embodiments of the following disclosure may be equally effective regardless of whether oriented as shown or rotated, flipped, upside-down, etc. from what is shown in the Figures of this disclosure.

[0014] Figure 1 illustrates an electronic hydraulic lifter 10, according to one or more embodiments. The electronic hydraulic lifter 10 generally includes a lifter body 12 and a piston 14, with the piston 14 being disposed concentrically with and at least partially in the lifter body 12. The piston 14 and the lifter body 12 are configured to translate longitudinally (as shown, up and down) with respect to each other. As such, the distance from a lower end 16 of the piston 14 to a lower end 18 of the lifter body 12 may vary, when desired. However, the distance between the lower end 16 of the piston 14 and the lower end 18 of the lifter body 12 may be generally constant during normal operation of the electronic hydraulic lifter 10, as will be described in greater detail below.

[0015] A bushing 17 may be provided to facilitate (e.g., guide, reduce friction, etc.) relative movement of the piston 14 and lifter body 12. The electronic hydraulic lifter 10 may also include one or more biasing members 19, which may be or include one or more springs, as shown. The biasing member 19 may be disposed between the lower end 16 of the piston 14 and a lower end 18 of the lifter body 12, and may bias the piston 14 upwards with respect to the lifter body 12.

[0016] The electronic hydraulic lifter 10 further includes a pushrod cup 20 coupled to an upper end 22 of the piston 14 and a cam follower 24 coupled to the lower end 18 of the lifter body 12. In various embodiments, the relative position of the lifter body 12 and the piston 14 may be switched, such that the cam follower 24 is coupled to the piston 14 and the pushrod cup 20 is coupled to the lifter body 12. As illustrated, the cam follower 24 may be a rolling cam follower; however, any suitable type of cam follower may be used without departing from this disclosure.

[0017] The electronic hydraulic lifter 10 also includes a first fluid reservoir 26. In an embodiment, the first fluid reservoir 26 is disposed proximal the lower end 18 of the lifter body 12. Moreover, the first fluid reservoir 26 is configured to receive at least a portion of the piston 14, for example, the lower end 16 thereof. At least a portion of the biasing member 19 may be disposed in the first fluid reservoir 26. Although not shown, in other embodiments, the first fluid reservoir 26 may instead be positioned proximal an upper end 28 of the lifter body 12 and may thus be configured to receive the upper end 22 of the piston 14.

[0018] The first fluid reservoir 26 contains an amount of smart fluid 27. The term "smart fluid" is generally defined herein to mean any composition that may be activated by the application of an electric field or a magnetic field, such that one or more viscoelastic properties of the smart fluid change. For example, one viscoelastic property that may change is the apparent viscosity of the smart fluid. In an embodiment, the smart fluid may normally be a fluidic suspension, which may generally include a liquid and dipolar and/or non-conductive particles, and typically has a relatively low viscosity. Upon activation, the smart fluid may change to relatively high (in comparison to the fluidic suspension) viscosity gel, a viscoelastic solid, a combination thereof, or the like. In other words, the smart fluid may increase in apparent viscosity, developing a shear yield stress, and/or increasing its shear yield stress, upon activation. Moreover, it will be appreciated that the activation may be a matter of degree, producing a range of activated states, for example, according to the magnitude and/or direction of the field applied. For example, during activation, the apparent viscosity of the smart fluid may be predictably varied by varying the properties of the field applied thereto.

[0019] Compositions that are capable of activating in the presence of an electric field are often referred to as "electrorheological fluids." One example, among many contemplated herein, of an electrorheological fluid is found in U.S. Patent No. 6,352,651 , the entirety of which is incorporated herein by reference, to the extent not inconsistent with the present disclosure. Compositions that change in the presence of a magnetic field are often referred to as "magnetorheological fluids." One example, among many contemplated herein, of a magnetorheological fluid is found in U.S. Patent No. 5,505,880, the entirety of which is incorporated herein by reference, to the extent not inconsistent with this disclosure. It will be appreciated that smart fluids may also include otherfluids that activate, consistent with the definition provided above.

[0020] The electronic hydraulic lifter 10 may also include one or more cooling fins 32 coupled to the lifter body 12, for example, proximal the first fluid reservoir 26. The cooling fins 32 may be coupled to the lifter body 12 in any suitable way, such as, for example, by welding, fastening, brazing, or forging, or may be integrally formed therewith. The cooling fins 32 may extend radially outward from the lifter body 12 and may be annular, but in other embodiments may have any suitable shape. Further, the cooling fins 32 may be used in conjunction with any device suitable to assist in the removal of heat therefrom, such as, for example, a fan, a flow of liquid coolant, and/or the like.

[0021] A second fluid reservoir 34 may be disposed within the piston 14. As shown, the second fluid reservoir 34 may be disposed above the first fluid reservoir 26, for example, between the first fluid reservoir 26 and the upper end 22 of the piston 14. In other embodiments, however, the relative positioning of the first and second fluid reservoirs 26, 34 may be switched, with the first fluid reservoir26 positioned above the second fluid reservoir 34. The second fluid reservoir34 generally includes an additional amount of the smart fluid 27, and is in fluid communication with the first fluid reservoir26, allowing circulation of the smart fluid 27 therebetween. In still other embodiments, the second fluid reservoir 34 may be located outside of the lifter body 12.

[0022] To activate the smart fluid 27 in the first, second, or both fluid reservoirs 26, 34, the electronic hydraulic lifter 10 includes one or more electrical connections (one shown: 30). The electrical connection 30 may be disposed proximal the first fluid reservoir 26 or, as shown, proximal the second fluid reservoir 34. In various embodiments, the electrical connection 30 may be a slidable contact, providing current while the electronic hydraulic lifter 10 reciprocates. In other embodiments, the electrical connection 30 may include one or more coils disposed around the lifter body 12 to provide induced current as the electronic hydraulic lifter 10 reciprocates. In still other embodiments, the electrical connection 30 may be a wired connection.

[0023] Further, the type of electrical connection 30 may depend on the type of smart fluid 27 employed, with coils, contacts, or other electric field-producing structures being suitable for use with electrorheological fluid and coils, electromagnets, or other magnetic structures being suitable for use with magnetorheological fluids. The electrical connection 30 is connected to a source of current (not shown), which may be computer-controlled to provide a selectable flow of electric current to energize the electrical connection 30. The electrical connection 30 operatively communicates with the smart fluid 27, as will be described in greater detail below, such that energizing the electrical connection 30 activates the smart fluid 27.

[0024] Moreover, the controller may be configured to vary the electric current supplied to the electrical connection 30, thereby predictably varying the viscoelastic properties of the smart fluid 27. Indeed, varying the electric current supplied to the electrical connection 30 may vary the magnitude of the field created thereby and applied to the smart fluid 27. In the presence of such a varying field, the viscoelastic properties of the smart fluid 27 may vary predictably. As such, the viscoelastic properties of the smart fluid 27 may be determined and controlled by the controller as a function of the current supplied to the electrical connection 30. [0025] A circulation line 36 extends between the first and second fluid reservoirs 26, 34, providing the fluid communication therebetween. Although shown as an external line, the circulation line 36 may be formed into the lifter body 12 or another structure, such that the circulation line 36 requires no additional fluid-transporting structures, but provides a flowpath for the smart fluid 27. In some embodiments, the circulation line 36 may also include one or more flow control devices 38. Such flow control devices 38 may be or include one or more valves, such as check valves, and/or one or more orifices. Other flow control devices 38, however, may also be used in addition to or in lieu of check valves and/or orifices. In various embodiments, the flow control devices 38 may not be required and may be omitted.

[0026] A return line 40 may also extend between and fluidly communicate with the first and second fluid reservoirs 26, 34. The return line 40 may be formed in the lifter body 12 or, as shown, through a bottom wall 42 of the piston 14. In an embodiment, the bottom wall 42 defines an orifice therein, which provides the return line 40 and allows rate-controlled fluid communication between the first and second fluid reservoirs 26, 34. Although not shown, the return line 40 may additionally or instead include an external fluid transporting structure (e.g., tubing), a valve, such as a check valve, and/or any other flow control devices as needed.

[0027] The electronic hydraulic lifter 10 may fit into a valve assembly as would a conventional hydraulic valve lifter and/or valve tappet. Accordingly, although not shown, the pushrod cup 20 may generally receive a rocker arm (not shown), which is pivotal and coupled to a valve. Without limitation, the rocker arm and valve connection may be similar to that described in U.S. Patent No. 2,923,282, the entirety of which is incorporated herein by reference, to the extent not inconsistent with this disclosure. However, a variety of other rocker arm and valve configurations are known in the art, and may be employed without departing from the scope of this disclosure. Further, as shown, the cam follower 24 may follow a cam lobe 44 of a camshaft 46.

[0028] In an embodiment, it may be desirable for the electronic hydraulic lifter 10 to act as a conventional valve tappet during at least a portion of the operation thereof. Accordingly, the electrical connection 30 is energized, thereby activating the smart fluid 27 at least in the first fluid reservoir 26. The activated smart fluid 27 forms a high-viscosity gel and/or a viscoelastic solid, and may be variable according to field strength, as discussed above. With the piston 14 extending into the first fluid reservoir 26, as shown, the activated smart fluid 27 resists relative movement between the piston 14 and the lifter body 12 by transmitting force between the lower end 18 of the lifter body 12 and the bottom wall 42 of the piston 14. Accordingly, the electronic hydraulic lifter 10 may form a substantially rigid structure, thereby transferring the rotational movement of the camshaft 46 into reciprocating linear movement. During the upstroke of the electronic hydraulic lifter 10, the rocker arm is pivoted, and thus lifts the valve from its seat. This provides for admittance of fuel or air into the valve, for example. During the downstroke, the rocker arm pivots back, thereby closing the valve, with the valve being biased toward its seat, for example.

[0029] When it is desired to diminish the flow of fluid into the cylinder, for example, to slow the speed of (i.e., govern) the engine, and/or to affect the timing of the valve actuation, the electrical connection 30 is completely or partially de-energized. Accordingly, the smart fluid 27 in one or both of the first and second fluid reservoirs 26, 34 returns to its relatively low-viscosity, fluidic state, or at least decreases in apparent viscosity (in the case of a partial de-energizing) and thus reduces or eliminates its impedance to the relative movement between the piston 14 and the lifter body 12.

[0030] When fully de-energized state, the electronic hydraulic lifter 10 may have essentially no up or downstroke. As such, when the camshaft 46 rotates such that the cam follower 24 engages the area of greatest radius of the cam lobe 44, the piston 14 moves farther into the lifter body 12; accordingly, the electronic hydraulic lifter 10 compresses rather than pushing on the rocker arm. The biasing member 19 ensures that the cam follower 24 continues to follow the cam lobe 44 and the pushrod cup 20 continues to engage the rocker valve as the camshaft 46 turns, thereby maintaining proper positioning of the electronic hydraulic lifter 10. However, the biasing member 19 generally does not provide sufficient force so as to independently pivot the rocker valve and open the valve, although in some embodiments contemplated herein, it may. The valve may thus remain shut while the smart fluid 27 is deactivated, regardless of the angular position of the camshaft 46 and cam lobe 44.

[0031] The smart fluid 27 may be de-activated during multiple, single, or partial rotations of the camshaft 44. For example, after a desired partial rotation, the smart fluid 27 may be re-activated via again energizing the electrical connection 30, thereby enabling the electronic hydraulic lifter 10 to again lift the valve according to the rotation of the camshaft 44. In this way, the valve lift and/or timing of the valve opening can be governed, for example, allowing a reduced amount of fuel, air, or both to and/or from the piston cylinder via the valve.

[0032] In other embodiments, de-energizing the electrical connection 30 and changing the smart fluid 27 back to its low-viscosity fluidic state may not completely disable the electronic hydraulic lifter 10 from lifting the valve. For example, the electronic hydraulic lifter 10 in the de-energized state may act similar to a conventional hydraulic lifter, capitalizing on the incompressibility of the smart fluid 27 to resist the movement of the piston 14 downward relative to the lifter body 12 and into the first fluid reservoir 26. In another example, the lower end 16 of the piston 14 may bottom out against the lower end 18 of the lifter body 12 during the rotation of the camshaft 46, causing the electronic hydraulic lifter 10 to begin a delayed upstroke after a partial rotation of the camshaft 46. Various other configurations for valve tappets and hydraulic lifters are known and may be used without departing from the scope of this disclosure. [0033] When partially de-energized, the electronic hydraulic lifter 10 may have a stroke rate that is delayed. Accordingly, the stroke rate of the electronic hydraulic lifter 10 may be out of phase with the rotation of the camshaft 46. Thus, the timing of the valve opening and closing may be modified by the partial de-energizing of the smart fluid 27.

[0034] The relative movement of the piston 14 and the lifter body 12 heats the fully or partially de- energized, fluidic smart fluid 27 in the first fluid reservoir 26. The cooling fins 32 may thus be provided to assist in the removal of excess heat; however, in some embodiments, it may be necessary to provide additional time and/or structures to further assist in the removal of heat from the smart fluid 27, to avoid overheating the smart fluid 27 and/or other components. Accordingly, the heated smart fluid 27 may be circulated through the circulation line 36 to the second fluid reservoir 34. While in the second fluid reservoir 34, the smart fluid 27 may be cooled using any suitable structures or devices, until it falls to the bottom of the second fluid reservoir 34, proximal the return line 40. The cooled smart fluid 27 may then be circulated through the return line 40 and back into the first fluid reservoir 26.

[0035] To circulate the heated smart fluid 27 from the first fluid reservoir 26 to the second fluid reservoir 34 and back, the electronic hydraulic lifter 10 may capitalize on the relative movement between the piston 14 and the lifter body 12. Accordingly, as the piston 14 is received into the first fluid reservoir 26, it displaces a proportional volume of the smart fluid 27. The smart fluid 27 is thereby forced through the circulation line 36 and into the second fluid reservoir 34. Similarly, when the piston 14 moves out of the first fluid reservoir 26, smart fluid 27 is drawn back into the first fluid reservoir 26 from the second fluid reservoir 34, via the return line 40. The flow control device 38 ensures that the smart fluid 27 is not returned to the first fluid reservoir 26 via the circulation line 36. Accordingly, a fluid circulation circuit is developed, whereby the smart fluid 27 maintains a nominal operating temperature, despite the heat energy introduced by the relative movement of the piston 14 and lifter body 12.

[0036] Figure 2 illustrates a flowchart of a method 200 for lifting a valve, according to one or more embodiments. The method 200 may proceed by operation of the electronic hydraulic lifter 10 discussed above with respect to Figure 1 ; accordingly, the method 200 may be best understood with reference thereto. The method 200 may include biasing a valve, such as a fuel valve in a gas engine, into a closed position, as at 202. The method 200 may also include following a cam lobe of a camshaft with a hydraulic lifter that is coupled to the valve, as at 204. In an embodiment, the hydraulic lifter includes a lifter body, a piston disposed within the lifter body, a first fluid reservoir disposed within the lifter body and receiving at least an end of the piston, a smart fluid disposed within the first fluid reservoir and communicating with the piston, and an electrical connection operatively communicating the first fluid reservoir. The method 200 may also include activating the smart fluid, as at 206. Such activating may be accomplished by energizing the electrical connection, thereby changing one or more viscoelastic properties of the smart fluid. For example, the smart fluid may change from a relatively low-viscosity fluidic suspension to a relatively high- viscosity gel, a viscoelastic solid, or a combination thereof. Thus, the activated smart fluid resists relative movement between the piston and the lifter body. The method 200 may also include deactivating the smart fluid, as at 208. The deactivating may be accomplished by de-energizing the electrical connection. Thus, the smart fluid changes back to a fluidic suspension, allowing for relative movement between the piston and the lifter body, such that the valve remains closed despite the rotation of the camshaft.

[0037] In one or more embodiments, the method 200 may also include governing an amount of fuel introduced to a piston of a gas engine by activating the smart fluid for a portion of a rotation of the camshaft and deactivating the smart fluid for a remaining portion of the rotation of the camshaft. The method 200 may further include pumping smart fluid into a second fluid reservoir using the relative movement of the piston and the lifter body. The method 200 may additionally include cooling the smart fluid in the second fluid reservoir, and pumping the smart fluid back into the first fluid reservoir using the relative movement of the piston and the lifter body.

[0038] In one or more embodiments, the method 200 may also include biasing the piston away from a lower end of the lifter body. In one or more embodiments, following the cam lobe, as at 204, further includes rolling a cam follower along the cam lobe, with the cam follower being coupled to the lower end of the lifter body. Further, the first fluid reservoir may be located proximal the lower end of the body, and the second fluid reservoir is located above the first fluid reservoir. The method 200 may also include transferring a rotational movement of the camshaft to a pivotal movement of a rocker arm coupled to the valve.

[0039] The foregoing has outlined features of several embodiments so that those skilled in the art may better understand the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.

Claims

Claims What is claimed is:

1. An electronic hydraulic lifter for a gas engine, comprising:

a lifter body;

a piston disposed at least partially within the lifter body and configured to translate longitudinally with respect thereto;

a first fluid reservoir disposed at least partially within the lifter body, the piston, or both and configured to receive an end of the piston;

a smart fluid disposed within the first fluid reservoir and configured to communicate with at least the end of the piston; and

an electrical connection coupled to the first fluid reservoir and operatively communicating with the smart fluid, the electrical connection being configured to vary a viscoelastic property of the smart fluid by applying a field thereto.

2. The electronic hydraulic lifter of claim 1 , wherein the field is an electric field and the smart fluid comprises electrorheological fluid.

3. The electronic hydraulic lifter of claim 1 , wherein the field is a magnetic field and the smart fluid comprises magnetorheological fluid.

4. The electronic hydraulic lifter of claim 1 , wherein the electrical connection is configured to change the smart fluid from a fluidic suspension to a gel, a viscoelastic solid, or a combination thereof.

5. The electronic hydraulic lifter of claim 1 , further comprising a biasing member configured to bias the piston away from a lower end of the lifter body.

6. The electronic hydraulic lifter of claim 1 , wherein the electrical connection is configured to vary the magnitude, direction, or both of the field to vary the viscoelastic property of the smart fluid.

7. The electronic hydraulic lifter of claim 1 , further comprising one or more cooling fins coupled to the lifter body and disposed proximal the first fluid reservoir, the one or more cooling fins being configured to remove heat from the smart fluid.

8. The electronic hydraulic lifter of claim 1 , further comprising a second fluid reservoir fluidly coupled to the first fluid reservoir.

9. The electronic hydraulic lifter of claim 8, further comprising:

a circulation line extending from the first fluid reservoir to the second fluid reservoir and configured to allow the smart fluid to be pumped from the first fluid reservoir to the second fluid reservoir; and

a return line extending from the second fluid reservoir to the first fluid reservoir and configured to allow the smart fluid to be pumped from the second fluid reservoir to the first fluid reservoir.

10. The electronic hydraulic lifter of claim 9, wherein the circulation line and return line are configured to allow the smart fluid to be pumped therethrough by relative translation between the piston and the lifter body.

1 1 . The electronic hydraulic lifter of claim 9, wherein the circulation line includes a check valve and the return line includes an orifice.

12. The electronic hydraulic lifter of claim 8, wherein the first fluid reservoir is disposed at least partially between a lower end of the lifter body and the end of the piston and the second fluid reservoir is disposed at least partially within the piston.

13. A method for lifting a valve, comprising:

biasing the valve closed;

following a cam lobe of a rotatable camshaft with a hydraulic lifter that is coupled to the valve, the hydraulic lifter comprising:

a lifter body;

a piston disposed within the lifter body;

a first fluid reservoir disposed within the lifter body and receiving at least an end of the piston;

a smart fluid disposed within the first fluid reservoir and communicating with the piston; and

an electrical connection operatively communicating with the first fluid reservoir; activating the smart fluid by energizing the electrical connection, to change one or more viscoelastic properties of the smart fluid and resist relative movement between the piston and the lifter body; and at least partially de-activating the smart fluid by at least partially de-energizing the electrical connection, to change the one or more viscoelastic properties of the smart fluid and allow for relative movement between the piston and the lifter body.

14. The method of claim 13, wherein:

activating the smart fluid comprises changing the smart fluid from a fluidic suspension to a viscoelastic solid, a gel having a higher viscosity than the fluidic suspension, or a combination thereof; and

at least partially de-activating the smart fluid comprises changing at least some of the smart fluid back to the fluidic suspension.

15. The method of claim 13, wherein at least one of activating the smart fluid and at least partially de-activating the smart fluid comprises varying the one or more viscoelastic properties of the smart fluid by varying a magnitude, a direction, or both of a field applied thereto, the field being created by energizing the electrical connection and variable by varying a current supplied to the electrical connection.

16. The method of claim 13, further comprising pumping smart fluid into a second fluid reservoir using relative movement between the piston and the lifter body.

17. The method of claim 16, further comprising:

cooling the smart fluid in the second fluid reservoir; and

pumping the smart fluid back into the first fluid reservoir using relative movement between the piston and the lifter body.

18. The method of claim 17, wherein following the cam lobe comprises rolling a cam follower along the cam lobe, wherein the cam follower is coupled to the lower end of the lifter body, the first fluid reservoir is located proximal the lower end of the lifter body, and the second fluid reservoir is located above the first fluid reservoir.

19. The method of claim 13, further comprising biasing the piston away from a lower end of the lifter body.

20. An apparatus for lifting a valve in a gas engine, comprising:

a cylindrical lifter body having an upper end and a lower end; a pushrod cup coupled to the upper end of the cylindrical lifter body, the pushrod cup configured to engage a rocker arm coupled to the valve;

a cam follower coupled to the lower end of the cylindrical lifter body, the cam follower configured to engage a cam lobe of a rotatable camshaft;

an internal piston disposed at least partially within the lifter body and configured to translate longitudinally relative thereto;

a first fluid reservoir disposed within the cylindrical lifter body proximal the lower end thereof, the internal piston extending at least partially into the first fluid reservoir;

a second fluid reservoir disposed within the internal piston and between the first fluid reservoir and the upper end of the cylindrical lifter body;

a smart fluid disposed within the first and second fluid reservoirs and communicating with the internal piston, the smart fluid comprising an electrorheological fluid, a magnetorheological fluid, ora combination thereof;

a circulation line including a check valve, an orifice, or both and extending between the first and second fluid reservoirs, the circulation line being configured to channel the smart fluid from the first fluid reservoir to the second fluid reservoir;

a return line including a check valve, an orifice, or both and extending between the first and second fluid reservoirs, the return line being configured to channel the smart fluid from the second fluid reservoir to the first fluid reservoir; and

an electrical connection coupled to the first fluid reservoir and operatively communicating with the smart fluid, wherein the electrical connection is configured to apply an electric field or a magnetic field to the smart fluid to change the smart fluid from a relatively low-viscosity fluidic suspension to a relatively-high viscosity gel, a viscoelastic solid, or a combination thereof, to resist relative movement between the cylindrical lifter body and the internal piston.