Patent Grant
6880766
The present invention relates generally to limiting leakage between components that define a high pressure space, and more particularly to implementation of a leak arrest volume around a planar sealing land between two components.
In many devices, such as fuel injectors, a plurality of components are positioned in contact with one another to define a high pressure space. These components are clamped together in an effort to prevent leakage through the planar sealing land between the components. In the case of fuel injectors, these components can be charged with sealing against leakage in the face of relatively high pressures, which can be on the order of 200 MPa or greater. Engineers have observed that when a leak develops between adjacent components, at such high pressures, it can sometimes act as a wedge to separate the two components creating an even larger leak path. In other words, as the leak penetrates the sealing land between the components, it remains at a relatively high pressure pushing the two components apart, which creates an even larger leak area. This action can cause even further component separation, resulting in even more leakage.
In the case of fuel injectors, this type of leakage is undesirable for several reasons. First, any leaked fuel that was at one time pressurized, arguably results in a waste of energy, since the fuel was pressurized from engine power but not injected into the same. In addition, leakage can undermine the ability to accurately predict the performance of a fuel injector. For instance, if fuel is being leaked that was expected to be injected, the fuel injector may be injecting less fuel than it should. In some fuel injectors, leakage can also reduce injection pressure. In addition, leakage can be a source of variable performance among a plurality of fuel injectors in a given engine. For instance, if each fuel injector exhibits substantially different leakage rates, that can cause differing fuel injector performance. In other words, the plurality of fuel injectors could be injecting different amounts of fuel based upon an identical set of control signals.
One previous strategy for dealing with sealing against leakage between fuel injector components with a planar interface, is to reduce the area of the planar surface so that more of the clamping load is concentrated in a smaller area. This strategy, for instance, is illustrated in co-owned U.S. Pat. No. 5,897,058, invented by Coldren et al. While such a strategy can be effective in many applications, other factors, such as spatial limitation features, can reduce the applicability of such a strategy. For instance, in some situations there may be so many fluid passageways, dow alignment bores and/or fastener bores that an implementation of a reduced sealing land area strategy can cause other undesirable effects, such as component distortion that may lead to even more leakage.
The present invention is directed to one or more of the problems set forth above.
In one aspect, a component sub-assembly includes a first component with a planar surface in contact with a planar surface of a second component. The first and second components define a high pressure space that passes through the planar surfaces at a perimeter. The first and second component define at least one leak arrest volume that is distributed to surround at least a majority of the perimeter.
In another aspect, a fuel injector includes a plurality of stacked components that include a first component and a second component in contact with one another in a plane. The first and second components define high pressure space that passes through the plane at a perimeter. The first and second components define at least one leak arrest volume that is distributed to surround at least a majority of the perimeter.
In still another aspect, a method of limiting leakage between components includes a step of placing a planar surface of a first component in contact with a planar surface of the second component to define a high pressure space with a perimeter. At least one leak arrest volume is defined between the first and second components. The leak arrest volume is distributed to surround at least a majority of the perimeter.
Referring to
Within fuel injector 10, fuel arriving from high pressure fuel source 18 travels through an unobstructed nozzle supply passage 24 to arrive at a nozzle chamber 25, which is shown blocked from fluid communication with nozzle outlet 23 by a needle portion 30 of direct control needle valve 11. Needle portion 30 includes an opening hydraulic surface 34 exposed to fluid pressure in nozzle chamber 25. Direct control needle valve 11 is normally biased downward to its closed position, as shown, by the action of a biasing spring 35 acting on a lift spacer 31, which is in contact with a top surface of needle portion 30. Direct control needle valve 11 also includes a piston portion 32 with a closing hydraulic surface 33 exposed to fluid pressure in a needle control chamber 37 and needle control passage 39. Opening hydraulic surface 34 is in opposition to closing hydraulic surface 33. When three way valve 14 is in a first position, needle control chamber 37 is fluidly connected to source of high pressure fuel 18 via needle control passage 39 and a high pressure passage 40 that connects at one end into nozzle supply passage 24. When valve 14 is at its second position, needle control chamber 37 is fluidly connected to low pressure reservoir 20 via needle control passage 39 and a low pressure passage 41. Three way valve 14 is moved between its first position and its second position by energizing and deenergizing electrical actuator 16. When high pressure exists in needle control chamber 37, direct control needle valve 11 will stay in, or move toward, its downward closed position, as shown. When needle control chamber 37 is connected to low pressure, direct control needle valve 11 will lift to its upward open position if fuel pressure acting on opening hydraulic surface 34 is above a valve opening pressure, which is preferably determined by a biaser, such as the preload of biasing spring 35. In practice, the valve opening pressure of direct control needle valve 11 is adjusted by choosing a VOP spacer 36 of an appropriate thickness. In addition, the lift distance of direct control needle valve 11 is controlled by choosing an appropriate thickness for lift spacer 31. Those skilled in the art will appreciate that in the disclosed embodiment, needle control chamber 37 is a closed volume.
Referring to
Although piston 32 could be located in a common body as lower seat component 45, it is preferably separated from the same by a relatively thin stop plate 75 and housed in its own piston guide body 76, as shown in
Valve member 42 is preferably operably coupled in a known manner to the moveable portion of an electrical actuator. In the illustrated embodiment, valve member 42 is attached to an armature 62 via a nut 66 that is threaded onto one end of valve member 42. In particular, an armature washer 63 rests upon an annular shoulder 58, upon which armature 62 is supported. Next, a nut washer 64 is placed in contact with the other side of armature 62 followed by a spacer 65, against which nut 66 bears. Armature 62 and hence valve member 42 are biased downward to close low pressure seat 51 by a suitable biaser, such as biasing spring 67. Those skilled in the art will appreciate that a hydraulically biaser could be an alternative to the mechanical bias shown. In addition, while electrical actuator 16 has been shown as a solenoid, those skilled in the art will appreciate that any other suitable electrical actuator, such as a piezo (disks and/or a bender) or a voice coil could be substituted in its place. A stator assembly 17 includes a stator 61, a coil 60 and preferably includes a female/male electrical socket connector to better facilitate bringing electrical energy to actuator 16 via conductors (not shown) penetrating down through injector body 22. Stator assembly 17 is preferably positioned within a carrier assembly 70 such that their respective bottom surfaces lie in a common plane. By doing so, a solenoid spacer 71 having an appropriate thickness can be chosen to provide a desired air gap between armature 62 and stator 61. Thus, solenoid spacer 71 is preferably a categorized part that comes in variety of slightly different thicknesses that allow different valves to perform similarly by choosing an appropriate thickness to provide uniformity in the armature air gap from one actuator to another.
In order to aid in concentrically aligning upper seat 50 with lower seat 51 along common centerline 38, valve member 42 includes an upper guide portion 54 with a close diametrical clearance (i.e. a guide clearance) with an upper guide bore 55 located in upper seat component 43. In addition, valve member 42 also preferably includes a lower guide portion 56 having a relatively close diametrical clearance with a lower guide bore 57 located in lower seat component 45. Thus, these guide regions tend to aid in concentrically aligning upper and lower seats 50 and 51 during the assembly of three way valve 14 as well as substantially fluidly isolating needle control chamber 37 from vented chamber 80 and/or armature cavity 82, regardless of the position of valve member 42. Because it is difficult to be certain, before assembly, the depth into seats 50 and 51 that valve member 42 will penetrate before coming in contact in closing that particular seat, three way valve 14 preferably employs a valve lift spacer 44 that is also a category part, and is preferably categorized in a plurality of different thickness groups. Thus, the distance that valve member 42 travels between upper and lower seats 50 and 51 is adjustable by choosing an appropriate thickness for valve lift spacer 44.
In order to reduce the influence of fluid flow forces on the movement of valve member 42, high pressure passage 40 and low pressure passage 41 preferably include flow restrictions 47 and 48, respectively, that are restrictive relative to a flow area across respective seats 50 and 51. While these flow restrictions could be located in upper seat component 43 and/or lower seat component 45, they are preferably located in valve lift spacer 44 as shown in FIG. 2. In particular, the flow characteristics through high pressure passage 40 can be relatively tightly controlled by including a cylindrical segment 47 having a predetermined length and flow area. Furthermore, cylindrical segment 47 is relatively restrictive to flow relative to that across upper seat 50. Those skilled in the art will appreciate that it is easier to control and consistently machine a flow characteristic via a cylindrical segment as opposed to attempting to consistently control a flow area between stationary seat component and moveable valve member 42. Likewise, low pressure passage 41 preferably includes a cylindrical segment 48 that is located in valve lift spacer 44. In order to differentiate the rate at which pressure changes can occur in needle control chamber 37, cylindrical segment 48 preferably has a different flow area relative to cylindrical segment 47. This feature is present in the illustrated example as a strategy by which the opening rate of the direct control needle valve is slowed relative to the closure rate of the same. In other words, when direct control needle valve 11 lifts toward its open position, fluid is displaced from needle control chamber 37 through the flow restriction defined by cylindrical segment 48. When direct control needle valve 11 is closed, high pressure fluid flows into needle control chamber 37 from high pressure passage 40 through the flow restriction defined by cylindrical segment 47. Since cylindrical segment 48 has a smaller flow area than cylindrical segment 47, in the illustrated embodiment, the opening rate of direct control needle valve 11 can be made slower than its closure rate, which is often desired.
In order to accommodate for the possibility of a slight angular misalignment between the centerline of valve member 42 and the respective centerlines of upper and lower seats 50 and 51, valve member 42 preferably includes spherical valve surfaces 52 and 53, which have a common center. Those skilled in the art will appreciate that spherical valve surfaces 52 and 53 can contact and close valve seats 50 and 51 even in the event of some minor angular misalignment between valve member 42 and its respective seats. In order to insure that the respective passageways, such as nozzle supply passage 24, provide the proper fluid connection as shown in
Referring now in addition to
Those skilled in the art will appreciate that vent passages 88 may not be desirable in the case of some fuel injectors. For instance, vent passages 88 would likely be desirable for common rail applications in which the fuel injector is maintained at relatively high pressures for the long durations between injection events, but vent passages 88 could be omitted in the case of fuel injectors that are only cyclically at high pressures. Because valve lift spacer 44 is a relatively thin component, leak arrest volume 98 and vent passage(s) 88 can potentially be manufactured via a coining or stamping process at the blank stage. If vent passage(s) 88 are omitted, leak arrest volume 98 should have a sufficiently large volume that its pressure can be maintained below some predetermined level, but that pressure has the ability to decay between injection events when pressure is low.
Referring now to
When fuel injector 10 is in operation, electro-hydraulic actuator 12 works in conjunction with direct control needle valve 11 to control both timing and quantity of each injection event. Each injection event is initialized by raising fuel pressure in high pressure source 18 to injection levels. In some systems, this is accomplished by maintaining a common rail at some desired pressure. Alternatively, source 18 can be a fuel pressurization chamber within a unit injector that is pressurized when a plunger is driven downward, which is usually accomplished with a cam or a hydraulic force. Because valve member 42 is biased downward to close low pressure seat 51, direct control needle valve 11 will stay in its downward closed position due to the high pressure force acting on closing hydraulic surface 33 of piston portion 32. Shortly before the timing at which the injection event is desired to start, electrical actuator 16 is preferably energized by supplying an excessive current to coil 60. Because the speed at which electrical actuator 16 operates is related to the current level supplied to coil 60, one preferably supplies the maximum available current, which can be substantially higher than an amount of current necessary to cause the armature to move against the action of the spring bias. When sufficient magnetic flux builds, armature 62 and valve member 42 are pulled upwards until spherical valve surface 52 contacts upper or high pressure seat 50. When this occurs, needle control chamber 37 is fluidly connected to low pressure fuel reservoir 20 via low pressure passage 41. Shortly before the desired end of an injection event, current to electrical actuator 16 is reduced or terminated to a level that allows spring 67 to push armature 62 and valve member 42 downward until spherical valve surface 53 comes in contact with low pressure seat 51. When this occurs, high pressure fluid originating in nozzle supply passage 24 flows through high pressure passage 40 past high pressure seat 50 and into needle control chamber 37. The high pressure force on piston 32 moves needle valve member 30 toward its closed position.
Like many fuel injectors, fuel injector 10 includes a plurality of stacked components 13 that need to be sealed against leakage at their various planar sealing land contact surfaces. In those areas where a potential leak could cause a component separation wedging affect, the present invention finds potential applicability. For instance,
The leak arrest volume should be distributed to sufficiently surround the high pressure perimeter that a wedging affect caused by a leak is prevented from causing substantial component separation which could lead to an even larger leakage. Although the leak arrest volumes preferably enclose the high pressure space in which they are sealing against leakage, they need not necessarily do so. For instance, passages 24 and 40 are not completely enclosed by leak arrest volume 98, but the leak arrest volume 98 is distributed to surround a majority of a perimeter around these passages.
The present invention is potentially advantageous in that leakage that exists between components can be limited by arresting a wedging affect that could cause even larger amounts of leakage. Those skilled in the art will appreciate that leakage is very undesirable in that it contributes to a number of undesirable affects, including energy wastage, altered injection amounts and variability among fuel injectors, among other potential problems. By appropriately locating leak arrest volumes according to the present invention, any leakage that does start to occur between components is prevented from substantially exacerbating into a large leak by connecting the leak to a low pressure space long before it reaches the perimetrical outer side surface that surrounds the two components. Alternatively, if the high pressure space is near the outer side surface of the components (
Although the present invention has been illustrated in the context of a fuel injector, those skilled in the art will appreciate that the concept of the present invention could find potential application in any component sub-assembly that includes a planar sealing land that is intended to prevent leakage from a high pressure space within the components.
It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present invention in any way. Thus, those skilled in the art will appreciate that other aspects, objects, and advantages of the invention can be obtained from a study of the drawings, the disclosure and the appended claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5474234 | Maley | Dec 1995 | A |
| 5803369 | Toyao et al. | Sep 1998 | A |
| 5897058 | Coldren et al. | Apr 1999 | A |
| 5901686 | Stockner et al. | May 1999 | A |
| 5992768 | Beatty et al. | Nov 1999 | A |
| 6260776 | Popp | Jul 2001 | B1 |
| 6666390 | Itou | Dec 2003 | B1 |
| Number | Date | Country | |
|---|---|---|---|
| 20040195348 A1 | Oct 2004 | US |
