Patent Application
20100316506
The present disclosure relates to internal combustion engines, and more specifically to engine fuel pump drive systems.
This section provides background information related to the present disclosure which is not necessarily prior art.
Engine assemblies typically include a fuel pump to provide pressurized fuel for combustion. Some engines include direct injection fuel systems where fuel is injected directly into the cylinders. Direct injection systems typically operate at high pressures. The high pressure requirements may require greater pump output capacity at low engine speed conditions than is needed during engine operation at higher engine speeds, resulting in system inefficiencies.
A fuel pump drive mechanism may include a fuel pump rocker arm and a fulcrum member. The fuel pump rocker arm may have a first end defining a cam lobe engagement region and a second end defining a fuel pump lifter engagement region. The fulcrum member may be engaged with the rocker arm and may be displaceable between first and second positions. The fulcrum member may engage the rocker arm at a first location between the first and second ends when in the first position and may engage the rocker arm at a second location between the first location and the second end when in the second position. The rocker arm may provide a first pump stroke for the lifter when the fulcrum member is in the first position and a second pump stroke for the lifter less than the first pump stroke when the fulcrum member is in the second position.
An engine assembly may include a fuel pump rocker arm, a fulcrum member, a cam lobe and a fuel pump. The fuel pump rocker arm may have first and second ends. The fulcrum member may be engaged with the rocker arm and may be displaceable between first and second positions. The fulcrum member may engage the rocker arm at a first location between the first and second ends when in the first position and may engage the rocker arm at a second location between the first location and the second end when in the second position. The cam lobe may be engaged with the rocker arm at the first end to displace the rocker arm. The fuel pump may include a lifter engaged with the rocker arm at the second end and may be driven by the displacement of the rocker arm. The rocker arm may provide a first pump stroke for the lifter when the fulcrum member is in the first position and a second pump stroke for the lifter less than the first pump stroke when the fulcrum member is in the second position.
A method of actuating an engine fuel pump may include operating the fuel pump at a first pump output capacity including engaging a fuel pump rocker arm at a first end with a cam lobe and engaging a fuel pump lifter with a second end of the rocker arm. The rocker arm may be supported at a first location between the first and second ends by a fulcrum member and the rocker arm may provide a first pump stroke corresponding to the first pump output capacity. The method may further include operating the fuel pump at a second pump output capacity less than the first pump output capacity including supporting the rocker arm at a second location between the first location and the second end. The cam lobe may engage the rocker arm at the first end and the second end of the rocker arm may engage the fuel pump lifter to provide a second pump stroke less than the first pump stroke when the rocker arm is supported at the second location.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.
Examples of the present disclosure will now be described more fully with reference to the accompanying drawings. The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
Referring now to
The fuel system 20 may include a fuel pump 24, a fuel tank 26, fuel injectors 28 and a fuel pump drive mechanism 30. The fuel pump 24 may be in fluid communication with the fuel tank 26 and the fuel injectors 28 and may provide a pressurized fuel flow to the cylinders 14 via the fuel injectors 28. In the present non-limiting example, the fuel system 20 may form a direct injection fuel system where the fuel injectors 28 are in direct fluid communication with the cylinders 14.
With additional reference to
The fuel pump drive mechanism 30 may be supported on an engine structure 12 and may include a fuel pump rocker arm 40, a fulcrum member 42 and an actuation mechanism 44. The rocker arm 40 may include first and second sides 46, 48 opposite one another. A cam engagement region 50 may be defined at a first end of the rocker arm 40 on the first side 46 and a fuel pump lifter engagement region 52 may be defined at a second end of the rocker arm 40 on the first side 46. The fulcrum member 42 may be engaged with the second side 48 of the rocker arm 40 at a location between the first and second ends.
The fulcrum member 42 may be coupled to the actuation mechanism 44 and may include first and second pivot regions 54, 56. The actuation mechanism 44 may be a mechanically actuated mechanism or an electrically actuated mechanism. By way of non-limiting example, exemplary mechanically actuated mechanisms may include hydraulically actuated mechanisms actuated in a manner similar to hydraulically actuated camshaft phasers. The electrically actuated mechanisms may include solenoid actuated mechanisms.
The actuation mechanism 44 may displace the fulcrum member 42 between first and second positions to modify the pivot location for the rocker arm 40. The fulcrum member 42 may engage the rocker arm 40 at a first location (L1) between the first and second ends when in the first position (
By way of non-limiting example, the fulcrum member 42 may be rotated between the first and second positions by the actuation mechanism 44. The first pivot region 54 may abut the rocker arm 40 at the first location (L1) and the second pivot region 56 may be free from engagement with the rocker arm 40 when the fulcrum member 42 is in the first position. The second pivot region 56 may abut the rocker arm 40 at the second location (L2) and the first pivot region 54 may be free from engagement with the rocker arm 40 when the fulcrum member 42 is in the second position. While illustrated as being rotated between the first and second positions, it is understood that a pivot for the rocker arm 40 may be adjusted in a variety of other ways, including, but not limited to displacement of a fulcrum member along a longitudinal extent of the rocker arm 40. Further, the present disclosure is not limited to two pivot locations. By way of non-limiting example, any discrete number or even a continuously variable number of pivot locations may be employed.
The first location (L1) may provide a pivot location for the rocker arm 40 that is closer to the cam engagement region 50 than a pivot location defined by the second location (L2). Therefore, the output (or capacity) of the fuel pump 24 may be increased or decreased by displacement of the fulcrum member 42 between the first and second positions. More specifically, the pump stroke of the lifter 32 may be adjusted by displacement of the fulcrum member 42.
As seen in
The fuel pump drive mechanism 30 may be utilized to provide desired fuel requirements without increasing pump size. By way of non-limiting example, the fulcrum member 42 may be in the first position during engine start conditions, including engine operating speeds of less than one thousand revolutions per minute (RPM). Conversely, the fulcrum member 42 may be in the second position during normal engine operation, including engine operating speeds of greater than one thousand revolutions per minute (RPM). The fulcrum member 42 may be displaced based on engine fuel demand.
