Patent Application
20110220064
The present disclosure relates generally to a single fluid fuel injection system, and more particularly to fuel injection systems with an auxiliary filling orifice.
Engines, including diesel engines, gasoline engines, natural gas engines, and other engines known in the art, exhaust a complex mixture of combustion related constituents. The constituents may be gaseous and solid material, which include nitrous oxides (NOx) and particulate matter. Due to increased attention on the environment, exhaust emission standards have become more stringent and the amount of NOx and particulate matter emitted from an engine may be regulated depending on the type of engine, size of engine, and/or class of engine.
Engineers have come to recognize that undesirable engine emissions, such as NOx, particulate matter, and unburnt hydrocarbons, can be reduced across an engine's operating range with fuel injection systems with maximum flexibility in controlling injection timing, flow rate, injection quantity, injection rate shapes, end of injection characteristics and other factors known in the art. However, it has also been observed that an injection strategy at one engine operating condition may decrease emissions at that particular operating condition, but actually produce an excessive amount of undesirable emissions at a different operating condition. Thus, for a fuel injection system to effectively reduce emissions across an engine's operating range, it must have the ability to produce several different rate shapes, have the ability to produce multiple injections, and produce injection timings and quantities with relatively high accuracy. Providing a fuel injection system that can perform well with regard to all of these different parameters over an entire engine's operating range has proven to be elusive.
In order to reduce hydrocarbon emissions, one strategy has been to seek an abrupt end to each injection event. This strategy flows from the wisdom that reducing poorly atomized fuel spray into the combustion chamber toward the end of an injection event can reduce the production of undesirable hydrocarbon and smoke emissions. In the case of fuel injectors equipped with direct control needle valves, an abrupt end of injection is often accomplished by applying high-pressure fluid to the back side of a direct control needle valve member to quickly move it toward a closed position while fuel pressure within the injection remains relatively high.
In one example common rail fuel injector disclosed in U.S. Pat. No. 6,814,302 to Stoecklein et al, a needle control chamber has one outlet and one inlet. At the end of injection the inlet fills the needle control chamber. A bypass conduit, which feeds first into a valve chamber and then into the outlet, may provide additional fuel flow to the needle control chamber. The use of a bypass conduit that feeds into the valve chamber and then the needle control chamber outlet has a drawback of inevitably affecting the start of injection. Moreover, the valve and valve chamber required to facilitate the bypass conduit add cost and variability to the operation of the injector.
The disclosed fuel injector with auxiliary filling orifice is directed to overcoming one or more of the problems set forth above.
In one aspect, a fluid injector including an injector body defining a high pressure inlet, a fuel supply passage, a low pressure drain, and at least one nozzle outlet. Also included is a check needle movable within the fluid injector between a first position at which the check needle blocks the at least one nozzle outlet and a second position at which the check needle at least partially opens the at least one nozzle outlet, the check needle including at least one opening hydraulic surface exposed to a fluid pressure of the fuel supply passage and at least one closing hydraulic surface exposed to a fluid pressure of a check needle control chamber, wherein said check needle control chamber is in selective fluid communication with the low pressure drain via a first orifice, and said check control chamber is in fluid communication with the nozzle supply passage via a second orifice, and said check needle control chamber is in selective fluid communication with the nozzle supply passage via a third orifice. The fluid injector also includes a control valve assembly having a valve member configured to selectively allow fluid communication via the first orifice between the low pressure drain and check control chamber.
In another aspect, an internal combustion engine including an engine housing defining a plurality of engine cylinders, and including a plurality of pistons each being movable within a corresponding one of the engine cylinders. Also included is a fuel system having a plurality of fuel injectors associated one with each of the plurality of engine cylinders, each of the fuel injectors including an injector body defining a high pressure inlet, a fuel supply passage, a low pressure drain, and at least one nozzle outlet. Also included is a check needle movable within the fluid injector between a first position at which the check needle blocks the at least one nozzle outlet and a second position at which the check needle at least partially opens the at least one nozzle outlet, the check needle including at least one opening hydraulic surface exposed to a fluid pressure of the fuel supply passage and at least one closing hydraulic surface exposed to a fluid pressure of a check needle control chamber, wherein said check needle control chamber is in selective fluid communication with the low pressure drain via a first orifice, and said check control chamber is in fluid communication with the nozzle supply passage via a second orifice, and said check needle control chamber is in selective fluid communication with the nozzle supply passage via a third orifice. The fluid injector also includes a control valve assembly having a valve member configured to selectively allow fluid communication via the first orifice between the low pressure drain and check control chamber.
In yet another aspect, a method of operating a fuel injector having a check needle, including the steps of supplying high pressure fuel to a nozzle chamber via a fuel supply passage. The method further includes the step of supplying high pressure fuel to a check needle control chamber via the fuel supply line and a z-orifice. Also included is a step of selectively supplying high pressure fuel to the check needle control chamber via the fuel supply line and an f-orifice. The method further includes a step of moving the check needle from its said first position to its said second position, wherein the check needle prevents fuel injection at the first position, and allows fuel injection at the second position; said moving step is accomplished by allowing fluid communication between the check needle control chamber and a low pressure drain via an a-orifice. The method also includes the step of moving the check needle from its second position to its first position by blocking fluid communication between the check needle control chamber and the low pressure drain via the a-orifice.
Referring to
When fuel injection system 14 is in operation, a transfer pump 24 draws low-pressure fuel through fuel supply line 26 and provides it to high-pressure pump 28. High-pressure pump 28 then pressurizes the fuel to desired fuel injection pressure levels and delivers the fuel to the common rail 18. The pressure in common rail 18 is controlled in part by safety valve 30, which spills fuel to the fuel return line 32 if the pressure in the common rail 18 is above a desired pressure. The fuel return line 32 returns fuel to the fuel tank 20.
Fuel injector 16 draws fuel from common rail 18 and injects it into a combustion cylinder 12 of the engine 10. Fuel not injected by fuel injector 16 is spilled to fuel return line 32. Electronic Control Module (ECM) 22 provides general control for the system. ECM 22 receives various input signals, such as from pressure sensor 34 and a temperature sensor 36 connected to common rail 18, to determine operational conditions. ECM 22 then sends out various control signals to various components including the transfer pump 24, high-pressure pump 28, and fuel injector 16.
Referring to
Check needle 70 is disposed within nozzle chamber 44. Check needle 70 may have a first end 72 and a second end 74. The first end 72 may be disposed within a lower check guide 76 and the second end 74 may be disposed within the upper check guide 68. A biasing spring 78, which is also disposed within the nozzle chamber 44, biases check member downward in a first position. In this first position, first end 72 of check needle 70 rests on seat 80 and blocks at least one tip orifice 82 disposed within injector tip 84. Check needle 70 is also movable to a second position wherein the first end 72 is at least partially out of contact with seat 80 and the at least one tip orifice 82 is partially unblocked.
Referring now to
In the embodiment shown in
An auxiliary, or third orifice 66 is in the upper check guide 68. The third orifice 66, which may also be called an f-orifice, is also in fluid communication with high-pressure fuel supply passage 42. The third orifice 66 may selectively be in fluid communication with check needle control chamber 86 via a check groove 94 and a check orifice 96. When check needle 70 is in its downward first position, third orifice 66 is out of fluid communication with check needle control chamber 86. In this position, third orifice 66 is blocked by a portion of check needle 70 known as a groove offset 98. When check needle 70 is in a second position, the third orifice 66 is no longer blocked by groove offset 98. In this position, third orifice 66 is in fluid communication with check needle control chamber 86.
The operation of injector 16 will now be explained. The opening and closing of check needle 70 is controlled in part by the presence of high-pressure fuel in fuel supply passage 42. When an injection event is not desired, the electrical actuator 56 of control valve assembly 46 is not energized. High-pressure fuel enters fuel injector 16 through high-pressure fuel supply inlet 40. High-pressure fuel is supplied to nozzle chamber 44 via the high-pressure fuel supply passage 42. High pressure fuel is also supplied to the check needle control chamber 86 via high pressure fuel supply passage 42 and the second orifice 64. The high pressure fuel within check needle control chamber 86 is prevented from escaping through the first orifice 62 by the valve member 50, which is blocking the same. The high-pressure fuel within the check needle control chamber 86 provides a hydraulic load on the distal surface 90 of check needle 70. This hydraulic load coupled with the downward force of biasing spring 78, holds check needle 70 in its first position wherein it rests on seat 80 and blocks the at least one tip orifice 82.
The high-pressure fuel that is provided to nozzle chamber 44 seeks to unseat check needle 70 by applying hydraulic pressure to various surfaces to the check needle 70. These forces seek to lift check needle 70 off of its seat 80. However, when the electrical actuator 56 control valve assembly 46 is deenergized, check needle 70 remains seated because the hydraulic forces applied to the check are countered by hydraulic load applied in the check needle control chamber 86 and the downward force of biasing spring 78.
When injection is desired, the electrical actuator 56 of control valve assembly 46 is energized. The electrical actuator 56 thus creates an electromagnetic field causing armature 52 and rod member 48 to overcome the force of biasing spring 58 and lift. When rod member 48 lifts, the downward force that was holding valve member 50 in place is removed. Thus, valve member 50 also lifts and the high pressure fuel within check needle control chamber 86 is allowed to drain out of the first orifice 62. This fuel ultimately drains out of the injector 16.
When the high pressure fuel drains out of the check needle control chamber 86 through the first orifice 62, the hydraulic load that was on top of the distal surface 90 of check needle 70 decays. At the same time, pressurized fuel is still being provided to nozzle chamber 44 via high pressure fuel supply passage 42. Because of the decay in the hydraulic load in the check needle control chamber 86, there is a pressure imbalance between the nozzle chamber 44 and the check needle control chamber. The higher pressure in the nozzle chamber 44 now applies hydraulic forces to the various surfaces of the check needle 70 causing it to lift off of seat 80. As the check needle 70 is unseated, pressurized fuel is injected into an engine cylinder 12 through the at least one tip orifice 82.
As the check needle 70 moves from its first position to its second position wherein it is out of contact with seat 80, it eventually travels a distance equal to that of the groove offset 98. When the check needle 70 moves a distance equal to that of the groove offset 98, the third orifice 66, which was heretofore blocked, comes into fluid communication with the check needle control chamber 86. In the embodiment shown in
When it is desirable to stop injection, electrical actuator 56 is deenergized. As the electromagnetic field generated by electrical actuator 56 dissipates, the force of biasing spring 58 acts on rod member 48 and armature 52. As rod member 48 and biasing spring 58 apply a downward force on valve member 50, it in turn returns to its position on orifice plate 60, wherein it blocks first orifice 62. When the first orifice 62 is blocked, check needle control chamber 86 begins to fill with high-pressure fuel. Initially, both the second orifice 64 and third orifice 66 provide high-pressure fuel to fill the check needle control chamber 86. However, as the high pressure fuel within check needle control chamber 86 begins to apply a hydraulic load on the distal surface 90 of check needle 70, check needle 70 begins to move downward toward seat 80. As check needle 70 moves downward, third orifice 66 will subsequently become blocked by groove offset 98. When this happens, third orifice 66 is no longer in fluid communication with check needle control chamber 86. The second orifice 64 then continues to fill the check needle control chamber 86 until the hydraulic load caused by the high pressure fluid in the check needle control chamber 86 and the downward force of biasing spring 78 cause check needle 70 to return to its first position. When check needle 70 returns to its seat 80, the tip orifice 82 is blocked and injection ends.
Referring now to
Point 108 represents the time at which the electrical actuator of a control valve assembly is deenergized. This point represents the beginning of the end of injection. As can be clearly seen, curve 102 moves to a zero fluid delivery rate significantly faster than curve 100. The reason for this is because on curve 102, the second and third orifices together (Curve 102) fill the check needle control chamber faster than the second orifice can on its own (Curve 100). Improved speed in filling the check needle control chamber leads directly to a faster closing of check needle and end of injection.
Referring now to
In the embodiment shown in
In operation, the embodiment shown in
At the end of injection, the embodiments of
Curve 110 on
Although not shown in
At end of injection time point 108, curve 110 functions very similarly to that of curve 102. In other words, after the drain or first orifice 162 is blocked, the high pressure fluid delivered to the check needle control chamber 186 from second orifice 164 and third orifice 166, acts to quickly close check needle 170. Here too, there may be a slight delay in end of injection because of the presence of the third orifice 166. However, even with this slight delay, the end of injection is still faster than injectors that do not use the techniques employed in this application.
The present disclosure finds a preferred application in common rail fuel injection systems. In addition the present disclosure finds preferred application in single fluid, namely fuel injection, systems. Although the disclosure is illustrated in the context of a compression ignition engine, the disclosure could find application in other engine applications, including but not limited to spark ignited engines.
The embodiments of
The above description is intended for illustrative purposes only and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate the various modifications that can be made to the illustrated embodiments without departing from the spirit and scope of the disclosure, which is defined in the terms of the claims set forth below.
