Patent ID: 12203457

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended, any alterations and further modifications in the illustrated embodiments, and any further applications of the principles of the disclosure as illustrated therein as would normally occur to one skilled in the art to which the disclosure relates are contemplated herein.

Referring to the Figures generally, the various embodiments disclosed herein relate to fuel-lubricated fuel pumps configured for various fuel pressures, including high fuel pressures. The configuration of the fuel pumps disclosed herein provide a plunger interface design which acts to improve the fatigue capability of the plunger at the plunger foot transition, reduce side loading forces at the plunger to decrease wear and scuffing power losses, and reduce the sliding motion of the plunger foot at the interface with the cam ring or roller.

The figures illustrate an eccentric pump with two plungers and two cam rings operating on a single cam lobe. The pump assembly has an eccentric cam of a camshaft. The eccentric cam rotates with the camshaft. There is a fluid film between the inner diameter of the cam ring and the outer diameter of the cam lobe such that the cam ring has a rotational degree of freedom relative to the cam. The two plungers reciprocate in accordance with the revolution of the cam ring to pressurize fuel which enters into and exits from the fuel pressurizing chambers which change in volume in response to the axial motion of the plungers. The two plungers, which out of phase with each other both share the same cam lobe, operate with separate cam rings. As a result of the design of the plunger and each plunger operating with its own cam ring, the dominant contact mechanism at the interface between the cam ring and the plunger foot is rolling and not sliding, which acts to improve the durability and performance of the pump, peak operating pressure capability, and packaging while minimizing cost. Additionally, having two separate cam rollers operating on the single lobe eliminates the need for two separate cam lobes which would otherwise separate the distance between the two cam rollers. This further reduces costs, needed space, and weight of the pump assembly.

Referring toFIG.1, a portion of an internal combustion engine10is shown as a simplified schematic. The engine10includes an engine body12, which supports an engine block14, a cylinder head16coupled to the engine block14, and a fuel system20. The engine body12further includes a crankshaft22, a plurality of pistons24, and a plurality of connecting rods26. The pistons24are configured for reciprocal movement within a plurality of engine cylinders28, with one piston24positioned in each engine cylinder28. Each piston24is operably coupled to the crankshaft22through one of the connecting rods26. A plurality of combustion chambers32are each defined by the combination of one piston24, cylinder head16, and engine cylinder28. The movement of the pistons24under the action of a combustion process in the engine10causes the connecting rods26to move the crankshaft22.

When the engine10is operating, a combustion process occurs in the combustion chambers32to cause movement of the pistons24. The movement of the pistons24cause movement of the connecting rods26, which are drivingly connected to the crankshaft22, and movement of the connecting rods26causes rotary movement of the crankshaft22. The angle of rotation of the crankshaft22may be measured by a control system to aid in timing the combustion events in the engine10and for other purposes. The angle of rotation of the crankshaft22may be measured in a plurality of locations, including a main crank pulley (not shown), an engine flywheel (not shown), an engine camshaft (not shown), or on crankshaft22.

The fuel system20includes a plurality of fuel injectors30positioned within the cylinder head16. Each fuel injector30is fluidly coupled to one combustion chamber32. In operation, the fuel system20provides fuel to the fuel injectors30, which is then injected into the combustion chambers32by the action of the fuel injectors30. As detailed further herein, the injection cycle may be defined as the interval that begins with the movement of a nozzle or needle element of the fuel injector30to permit fuel to flow from the fuel injector30into an associated combustion chamber32, and ends when the nozzle or needle element moves to a position to block the flow of fuel from the fuel injector30into the combustion chamber32.

In various embodiments, the crankshaft22may be operatively coupled with a camshaft of at least one fuel pump via a drive mechanism (e.g., a gear train, a timing belt, a timing chain, etc.) (not shown). The crankshaft22thus may drive the at least one fuel pump to pull fuel from the fuel tank in order to move fuel toward the fuel injectors30. In various embodiments, fuel system20includes an electric lift pump to pull fuel from the fuel tank and supply fuel to the at least one fuel pump. A control system (not shown) provides control signals to the fuel injectors30that determine operating parameters for each fuel injector30, such as the length of time the fuel injectors30operate and the number of fueling pulses per a firing or injection cycle period, thereby determining the amount of fuel delivered by each fuel injector30.

Referring toFIG.2, a fuel pump40may be a high-pressure, fuel-lubricated pump. The fuel pump40includes a housing42configured to support a plurality of components, such as a drive member, illustratively a camshaft44, configured to rotate about an axis of rotation50and at least one pumping assembly46. The camshaft44may be coupled to a drive mechanism (e.g., a gear, gear train, etc.) (not shown). In various embodiments, the at least one pumping assembly46is a unit barrel pumping assembly. In various embodiments, the at least one pumping assembly46is integral to the housing42. Illustratively, the pumping assembly46includes a first pumping assembly46apositioned on a first side48aof housing42and a second pumping assembly46bpositioned on a second, opposing side48bof the housing42. In various embodiments, the pumping assembly46may further include a third pumping assembly (not shown). The camshaft44is configured to extend through the housing42. As shown, the camshaft44is supported within a central cavity52of the housing42. The first pumping assembly46aand the second pumping assembly46bare positioned on opposing sides of the central cavity52in a direction perpendicular to the camshaft axis of rotation50. For instance, in various embodiments the first pumping assembly46aand the second pumping assembly46bare positioned approximately 180 degrees from each other relative to the axis of rotation50. In various embodiments, the first pumping assembly46aand the second pumping assembly46bmay be positioned in other configurations as may be dictated by the space constraints of the fuel pump40.

Referring now toFIGS.3-6, the housing42further supports a first cam roller54(e.g., cam ring) configured to engage a cam lobe56of the camshaft44. The first pumping assembly46aincludes a first plunger70, a first tension member68(e.g., a spring), and a first valve assembly72configured to regulate the flow of low-pressure fluid into and out of a first pumping chamber74. The first pumping chamber74is defined by a portion of the first plunger70and a portion of the first pumping assembly46a, as disclosed further herein. The first plunger70also is fluidly coupled to a first plunger outlet valve73of the first pumping assembly46a.

The first plunger70includes a first plunger foot76. The first plunger foot76is configured to contact and ride along (e.g., is in confronting relation with) the first cam roller54during operation of the fuel pump40. More particularly, during operation of the fuel pump40, the camshaft44rotates, which thereby rotates the cam lobe56. The camshaft44is an eccentric camshaft in that the center of rotation of the cam lobe56is offset relative to the axis of rotation50of the camshaft44. The first cam roller54surrounds the cam lobe56and is configured to rotate about the cam lobe56. A bushing58operating with a hydraulic film or fluid is positioned at the interface between the inner diameter of the first cam roller54and the outer diameter of the cam lobe56to facilitate the movement of the first cam roller54relative to the cam lobe56. The first plunger70is biased towards the first cam roller54because of the first tension member68such that the first plunger foot76maintains contact with the first cam roller54during rotation thereof. The contact of the first plunger foot76with the first cam roller54results in reciprocation of the first plunger70along the walls because the rotation of the cam lobe56moves the first plunger70along a first reciprocation axis82. The first reciprocation axis82is concentric with a center line of the first plunger70.

As the first plunger70reciprocates along the first reciprocation axis82(resulting in movement of the first plunger70), the first plunger foot76moves towards and away from axis of rotation50of camshaft44, thereby adjusting the volume of the first pumping chamber74. More particularly, when the cam lobe56rotates to a position towards the first pumping assembly46a, the first plunger70also moves towards the first pumping assembly46aand is in a top-dead-center position, thereby minimizing the volume of the first pumping chamber74.

As the camshaft44continues to rotate about the axis of rotation50and the cam lobe56rotates towards the second pumping assembly46b, the first plunger70reciprocates along the first reciprocation axis82and moves towards the axis of rotation50. Because of the first tension member68, the first plunger70is biased towards the first cam roller54and the first plunger70moves towards axis of rotation50, thereby increasing the volume of the first pumping chamber74. When the volume of the first pumping chamber74is maximized, the first plunger70is at a bottom-dead-center position and a maximum amount of fluid from the first pumping assembly46aflows therein.

Referring still toFIGS.3-4, the housing42further supports a second cam roller55(e.g., cam ring) configured to engage the cam lobe56of the camshaft44. In various embodiments, the housing42may further support a third cam roller (not shown), and the third pumping assembly is configured to interact with the third cam roller. The second pumping assembly46bincludes a second plunger71, a second tension member69(e.g., a spring), and a second valve assembly75configured to regulate the flow of low-pressure fluid into and out of a second pumping chamber77. The second pumping chamber77is defined by a portion of the second plunger71and a portion of the second pumping assembly46b. The second plunger71also is fluidly coupled to a second plunger outlet valve79of the second pumping assembly46b.

The second plunger71includes a second plunger foot81. The second plunger foot81is configured to contact and ride along (e.g., is in confronting relation with) the second cam roller55during operation of the fuel pump40. More particularly, during operation of the fuel pump40, the camshaft44rotates, which thereby rotates the cam lobe56. The camshaft44is an eccentric camshaft in that the center of rotation of the cam lobe56is offset relative to the axis of rotation50of the camshaft44. The second cam roller55surrounds the cam lobe56and is configured to rotate about the cam lobe56. The bushing58operating with a hydraulic film or fluid is positioned at the interface between the inner diameter of the second cam roller55and the outer diameter of the cam lobe56to facilitate the movement of the second cam roller55relative to the cam lobe56. The second plunger71is biased towards the second cam roller55because of the second tension member69such that the second plunger foot81maintains contact with the second cam roller55during rotation thereof. The contact of the second plunger foot81with the second cam roller55results in reciprocation of the second plunger71along the walls because the rotation of the cam lobe56moves the second plunger71along a second reciprocation axis83. The second reciprocation axis83is concentric with a center line of the second plunger71.

As the second plunger71reciprocates along the second reciprocation axis83(resulting in movement of the second plunger71), the second plunger foot81moves towards and away from axis of rotation50of camshaft44, thereby adjusting the volume of the second pumping chamber77. More particularly, when the cam lobe56rotates to a position towards the second pumping assembly46b, the second plunger71also moves towards the second pumping assembly46band is in a top-dead-center position, thereby minimizing the volume of the second pumping chamber77.

As the camshaft44continues to rotate about the axis of rotation50and the cam lobe56rotates towards the first pumping assembly46a, the second plunger71reciprocates along the second reciprocation axis83and moves towards the axis of rotation50. Because of the second tension member69, the second plunger71is biased towards the second cam roller55and the second plunger71moves towards the axis of rotation50, thereby increasing the volume of the second pumping chamber77. When the volume of the second pumping chamber77is maximized, the second plunger71is at a bottom-dead-center position and a maximum amount of fluid from the second pumping assembly46bflows therein.

The first plunger foot76and the second plunger foot81may have varying configurations. For example, in the embodiment shown inFIGS.3and4, each of the first plunger foot76and the second plunger foot81has a generally convex configuration. More particularly, a contact surface of each of the first cam roller54and the second cam roller55has a generally concave configuration corresponding with the convex geometric configuration of the at least one of the first plunger foot76and the second plunger foot81, respectively. In various configurations, at least one of the first plunger foot76and the second plunger foot81may be concave whereas the contact surface of at least one of the first cam roller54and the second cam roller55is convex, corresponding with the concave geometric configuration of the at least one of the first plunger foot76and the second plunger foot81, respectively. Due to the curved geometric configurations of the first plunger foot76and the first cam roller54, the load distribution at the first cam roller54and the first plunger foot76is increased. By increasing the load distribution at the contact surface, bending stresses on the first plunger foot76are reduced.

Additionally, the first cam roller54and the first plunger foot76, and the second cam roller55and the second plunger foot81, may have other varying configurations. For example, the first cam roller54, the first plunger foot76, the second cam roller55, and the second plunger foot81may have generally flat or linear configurations. The first flat geometric configuration of at least one of the first plunger foot76and the second plunger foot81corresponds with the second flat geometric configuration of at least one of the first cam roller54and the second cam roller55, respectively. For example, the first cam roller54, the first plunger foot76, the second cam roller55, and the second plunger foot81may have generally flat or linear configurations near the center of contact regions between the first plunger foot76and the first cam roller54and between the second plunger foot81and the second cam roller55, and then have surfaces near the outer limits of the contact regions in which the local axial separation distances between the surfaces of the first plunger foot76and the first cam roller54, and between the surfaces of the second plunger foot81and the second cam roller55, are increased to reduce edge loading magnitudes between the contacting surfaces.

Referring now toFIG.6, in various embodiments, the fuel pump40may further include a first controlling mechanism84and a second controlling mechanism85configured to control the relative location of the first cam roller54with respect to the first plunger70(e.g., the first reciprocation axis82). For instance, the first cam roller54and the first plunger foot76may be configured to cooperate with a first controlling mechanism84and a second controlling mechanism85disposed on the cam lobe56. In various embodiments, the first controlling mechanism84and a second controlling mechanism85may be disposed on the housing42. More particularly, the first controlling mechanism84and a second controlling mechanism85may control the first cam roller54with respect to the first plunger70, and if necessary, carry the thrust load. The second cam roller55and the second plunger foot81may be configured to cooperate with the second controlling mechanism85and a third controlling mechanism86disposed on the cam lobe56. In various embodiments, the second controlling mechanism85and a third controlling mechanism86may be disposed on the housing42. More particularly, the second controlling mechanism85and a third controlling mechanism86may control a relative location of the second cam roller55with respect to the second plunger71and, if necessary, carry the thrust load.

During typical operation of the fuel pump40, there is a first rolling motion between the first plunger foot76and the first cam roller54, and a second rolling motion (independent of the first rolling motion) between the second plunger foot81and the second cam roller55since the first plunger70and the second plunger71operate in conjunction with their unique cam ring (i.e., the first cam roller54and the second cam roller55, respectively).

In contrast, if the first plunger70and the second plunger71share the same cam ring/roller, the first plunger70and the second plunger71transmit forces which act on the cam ring in opposing rotational directions. The opposing force directions result in a sliding motion for at least one of the first plunger70and the second plunger71(e.g., between the plunger feet and its respective cam roller due to an imbalance in force applied through a full rotation of the cam lobe) at all times. This sliding generates heat, decreases efficiency, causes wear, etc. Thus, operating the first plunger70and the second plunger71each on its own unique cam ring (i.e., the first cam roller54and the second cam roller55, respectively), results in the relative interface motion being predominately rolling. A relative offset in the location along the axis of rotation50between the plungers and their corresponding elements enables the first plunger70and the second plunger71to independently control the axial location of each of the first cam roller54and the second cam roller55, respectively. By further rotationally offsetting the first plunger70and the second plunger71, the two pumping events are sufficiently out of phase of each other to both minimize the maximum positive and negative torques on the camshaft44.

As shown and explained herein, the fuel pump40includes two pumping members, the first pumping assembly46aand the second pumping assembly46b, each comprising the first plunger70and the second plunger71and the first cam roller54and the second cam roller55, respectively. As such, the first cam roller54rotates or revolves about the outer surface of the cam lobe56and the reciprocating motion of the first plunger70allows the contact surface at the interface of the first plunger foot76and the first cam roller54to rotate without the opposing force of the second plunger71as the second cam roller55simultaneously rotates or revolves about the outer surface of the cam lobe56, and vice versa. Positioning the first cam roller54and the second cam roller55on the same cam lobe56beneficially reduces the bending stresses on the camshaft44since the first cam roller54and the second cam roller55are in close proximately to each other. Further, by reducing the sliding effect between the plunger feet and the cam rollers, a reduction in friction and heat is observed which results in improved efficiency and a longer-life of the system.

While this specification contains many specific implementation details, these should not be construed as limitations on the scope of what may be claimed but rather as descriptions of features specific to particular implementations. Certain features described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

As utilized herein, the terms “generally,” and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the disclosure as recited in the appended claims.

The term “coupled” and the like, as used herein, mean the joining of two components directly or indirectly to one another. Such joining may be stationary (e.g., permanent) or moveable (e.g., removable or releasable). Such joining may be achieved with the two components or the two components and any additional intermediate components being integrally formed as a single unitary body with one another, with the two components, or with the two components and any additional intermediate components being attached to one another.

It is important to note that the construction and arrangement of the various systems shown in the various example implementations is illustrative only and not restrictive in character. All changes and modifications that come within the spirit and/or scope of the described implementations are desired to be protected. It should be understood that some features may not be necessary, and implementations lacking the various features may be contemplated as within the scope of the disclosure, the scope being defined by the claims that follow. When the language “a portion” is used, the item can include a portion and/or the entire item unless specifically stated to the contrary.

Also, the term “or” is used, in the context of a list of elements, in its inclusive sense (and not in its exclusive sense) so that when used to connect a list of elements, the term “or” means one, some, or all of the elements in the list. Conjunctive language such as the phrase “at least one of X, Y, and Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to convey that an item, term, etc. may be either X, Y, Z, X and Y, X and Z, Y and Z, or X, Y, and Z (i.e., any combination of X, Y, and Z). Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of X, at least one of Y, and at least one of Z to each be present, unless otherwise indicated.