Decoupled valve assembly and fuel injector using same

A valve assembly including an armature and a valve member that are coupled when the solenoid coil is de-energized but are decoupled after the solenoid coil is energized. A first spring biases the armature and the valve member to a closed valve seat position while a second spring having a smaller preload than the first spring biases the valve member to an open valve seat position. When the solenoid coil is energized, the magnetic force of the coil overcomes the force exerted by the first spring pulling the armature away from the valve member. The valve member moves to the open valve seat position by the force exerted by the second spring. When the coil is de-energized, the magnetic force decays, thereby allowing the armature and the valve member to re-couple.

TECHNICAL FIELD

The present disclosure relates generally to valve assemblies, and more particularly, to a fuel injector including a valve assembly having an armature and a valve member that may be decoupled.

BACKGROUND

Valve assemblies are commonly used in fuel injectors to control the flow of fuel through a nozzle outlet. One example of a valve assembly used in a fuel injector is a solenoid actuated valve assembly including a stator assembly, an armature, and a valve member. Typical solenoid actuated fuel injectors include a valve assembly that attaches the armature to a guide piece, which is coupled to the valve member. Due to movement of the guide piece under the influence of magnetic fields acting upon the armature via the stator assembly, the valve member moves between stops, such as a low-pressure seat and a high-pressure seat, which ultimately controls the flow of fuel passing through the nozzle outlet of the fuel injector. When the armature is coupled to the valve member, the valve assembly functions as a single unit, i.e., movement of the armature causes movement of the valve member, and vice versa. Coupling of the armature with the valve member throughout all modes of operation of the fuel injector may affect the performance of the fuel injector. For example, such coupling may hinder or compromise the various objectives of a solenoid actuated valve assembly, including maintaining the parallelism between the armature and the stator assembly, maintaining the perpendicularity of the guide piece to the stator assembly, minimizing side forces that may result in an imbalanced orientation and increased wear, minimizing the separation air gap between the armature and the stator assembly to maximize force, and enhancing the speed of armature travel.

Moreover, a coupled valve member has a valve travel distance equal to the armature travel distance, which may not always be desirable because the valve member only needs to travel a distance between the low-pressure seat and the high-pressure seat, while the armature needs to travel a greater distance between the initial air gap and the final air gap.

One example of a coupled valve member and an armature of a solenoid actuated valve assembly is provided in U.S. Pat. No. 7,347,383 (the '383 patent), which discloses an armature and a valve member that are connected together by a non-ferrous material in order to prevent any leakage of magnetic flux from the armature to the valve member. However, the '383 patent fails to address the problems associated with the physical coupling of the armature and the valve member such as the slower armature travel speeds, the inability to have different armature and valve member travel distances and travel speeds, and the difficulty of producing a single unit with ever-tighter tolerances so that the valve assembly can reduce variability when the armature is coupled to the valve member.

The present disclosure is directed to overcoming one or more of the problems set forth above.

SUMMARY

In one aspect, a valve assembly comprises an armature that is movable between a first armature position and a second armature position defined by an armature travel distance. A control valve member is movable between a first valve position and a second valve position defined by a valve travel distance. The armature travel distance is greater than the valve travel distance.

In another aspect, a fuel injector assembly comprises an injector body defining a nozzle outlet and a valve assembly includes an armature and a control valve member. The armature is movable between a first armature position and a second armature position that is defined by an armature travel distance. The control valve member is movable between a first valve position and a second valve position that is defined by a valve travel distance. The armature travel distance is greater than the valve travel distance.

In yet another aspect, a method of operating a fuel injector assembly includes the steps of initiating an injection event by decoupling an armature of a valve assembly from a control valve member of the valve assembly. The injection event ends by coupling the armature back to the control valve member.

DETAILED DESCRIPTION

Referring toFIGS. 1 and 2, an exemplary embodiment of a fuel injector10is illustrated. Although the embodiment described herein reflects the embodiment shown inFIGS. 1 and 2, those skilled in the art may appreciate that a fuel injector according to the present disclosure may be made in a wide variety of configurations, such as cam-actuated and hydraulically actuated fuel injectors.

The fuel injector10shown inFIGS. 1 and 2includes a valve needle member90that opens and closes a nozzle outlet92and a solenoid actuated valve assembly60, which includes a stator assembly21, an armature assembly40, and a control valve member61. The stator assembly21includes a solenoid coil29, a planar bottom surface26, and a guide sleeve31. The guide sleeve31has an inner guide surface32that defines a guide bore33.

The armature assembly40may include a flux piece45attached to a guide piece43that moves within the guide bore33of the stator assembly21perpendicular to the planar bottom surface26of the stator assembly21. The flux piece45may be threadably attached to the guide piece43via a contact pin41. The flux piece45may be made of a soft, magnetic material while the guide piece43may be made of a hard, non-magnetic material that can withstand the wear caused by any contact with the inner guide surfaces32of the guide sleeve31. This disclosure pertains to a wide array of different armature assemblies including the ones described herein and others that may fall within the spirit of the disclosure. In the present disclosure, the contact pin41of the armature assembly40has a control valve contact surface48. Further, the guide piece43may have a guide stop contact surface47.

The armature assembly40may be biased away from the planar bottom surface26of the stator assembly21by a first spring56having a first preload. A first spring spacer80may be placed adjacent the first spring56and may set the first preload. Because of the variations in components during production, category parts such as spring spacers may be selected from a wide variety of thickness dimensions to account for the variations of components used in one fuel injector from that of another.

Referring also toFIG. 3andFIG. 4, when the solenoid coil29is de-energized, the armature assembly40is at a first armature position, i.e., an initial air gap position, which defines an initial air gap74between a top surface50of the flux piece45and the planar bottom surface26of the stator assembly21. The initial air gap74is the maximum distance between the top surface50of the flux piece45and the planar bottom surface26of the stator assembly21during operation of the fuel injector10. The initial air gap74may be set using an over travel spacer52, whose thickness dimension is selected such that the initial air gap74is set at a predetermined distance. When the solenoid coil29is energized as shown inFIG. 4, the armature assembly40moves to a second armature position, i.e., a final air gap position, which defines a final air gap75between the top surface50of the flux piece45and the planar bottom surface26of the stator assembly21.

The final air gap75may be set using a final air gap spacer53, which, similar to the over travel spacer52, may have a thickness dimension selected such that the final air gap75of the fuel injector10is set at a predetermined distance. In an exemplary embodiment, the final air gap75is greater than zero, because contact between the flux piece45and the stator assembly21is undesirable. Further, when the solenoid coil29is in an energized state, the stop contact surface47of the guide piece43may be in contact with a guide contact surface55of final air gap spacer53. The distance between the initial air gap position and the final air gap position of the armature assembly40defines an armature travel distance.

The solenoid actuated valve assembly60also includes a control valve member61that is biased towards the armature assembly40via a second spring58having a second preload. A first end67of the control valve member61may be in contact with a second spring spacer81, which may set the preload of the second spring58. In an exemplary embodiment, the preload of the second spring58should be smaller than the preload of the first spring56. The control valve member61may have an armature contact surface49adjacent the armature assembly40. The control valve member61moves between two valve positions or stops, such as a first valve position, which may correspond to a low-pressure valve seat64and a second valve position, which may correspond to a high-pressure valve seat65. The control valve member61travels a valve travel distance76that is equal to the distance moved by the control valve member61between the low-pressure valve seat64and the high-pressure valve seat65. In an exemplary embodiment, the valve travel distance76is smaller than the armature travel distance, thereby allowing the armature assembly40to come out of contact with, i.e., decouple from, the control valve member61after the solenoid coil29is energized. When the control valve member61and the armature assembly40come out of contact with one another, then the control valve member61and the armature assembly40are considered to be decoupled. When the armature assembly40is decoupled from the control valve member61, the armature assembly40does not move with the control valve member61, but rather the armature assembly40moves independently of the control valve member61through an interaction with the magnetic field produced by the solenoid coil29. When the control valve member61and the armature assembly40come back into contact with one another, then the control valve member61and the armature assembly40are considered to be coupled, or recoupled. When the armature assembly40and the control valve member61are coupled, the movement of the control valve member61is at least partially dependent on the movement of the armature assembly40, and vice versa.

The control valve member61controls the movement of the valve needle member90by controlling the flow of high-pressure fuel passing between the low-pressure valve seat64and the high-pressure valve seat65. The valve needle member90in turn, controls the flow of fuel through the nozzle outlet92. The valve needle member90has an opening hydraulic surface93located, and exposed to fuel pressure, between a first end88and a second end89of the valve needle member90and a closing hydraulic surface94located at the first end88of the valve needle member90. The closing hydraulic surface94of the valve needle member90is exposed to the pressure inside a needle control chamber86. The opening hydraulic surface93of the valve needle member90may be located inside a nozzle chamber91. The nozzle chamber91may receive high-pressure fuel entering through a rail pressure inlet port99via a nozzle supply passage98. In the present disclosure, high-pressure fuel is coming from a common rail, and the nozzle chamber91may be fluidly connected to the rail pressure inlet port99via the unobstructed nozzle supply passage98, thereby maintaining rail pressure inside the nozzle chamber91. An unobstructed supply passage means the supply passage does not have any structures therein to affect the flow of fuel, such as a valve that may at least partially stop the supply of fuel by closing or partially closing the passage. Nevertheless, a fuel injector that includes an obstruction, such as an admission valve, in the nozzle supply passage98would still fall within the intended scope of the disclosure.

A pressure communication passage79establishes a fluid connection between the nozzle chamber91and the solenoid actuated valve assembly60. The pressure communication passage79also fluidly connects the nozzle chamber91to the needle control chamber86via a first flow restrictor95. The pressure communication passage79may have an unobstructed fluid passage to the needle control chamber86, meaning the fluid passage has no structure to affect the flow of fuel, such as a valve that may stop the flow of fuel through the pressure communication passage79.

A second flow restrictor96having a larger flow area than the first flow restrictor95fluidly connects the needle control chamber86to either high-pressure fuel or to a low-pressure fuel drain. When the control valve member61is at the low-pressure valve seat64, a first annular opening68fluidly connects the high-pressure fuel from the nozzle chamber91to the needle control chamber86via the second flow restrictor96. When the control valve member61is at the high-pressure valve seat65, the second flow restrictor96fluidly connects the needle control chamber86to a low-pressure drain83via a second annular opening69and the valve supply passage84. The needle control chamber86remains fluidly connected to the nozzle chamber91via the first flow restrictor95regardless of the position of the control valve member61. In the present disclosure, the valve supply passage84and the drain83are shown as dotted passages because passage84and drain83lie in a plane not depicted in the section views ofFIGS. 1 and 2. The valve supply passage84has a first end that opens into the second flow restrictor96, and a second end that opens into the region between the low-pressure valve seat64and the high-pressure valve seat65. This allows the valve supply passage84to fluidly connect the needle control chamber86to the drain83when the control valve member61is at the high-pressure valve seat65and to the high-pressure fuel from the nozzle chamber91when the control valve member61is at the low-pressure valve seat64. The drain83fluidly connects the second annular opening69to an external drain line. The first annular opening68may be located above the high-pressure valve seat65such that when the control valve member61is seated at the low-pressure valve seat64, the first annular opening68opens a fluid connection between the high-pressure nozzle chamber91and the needle control chamber86. The second annular opening69may be located below the low-pressure valve seat64, such that when the control valve member61is seated at the high-pressure valve seat65, the second annular opening69opens a fluid connection between the nozzle chamber91and the drain83via the needle control chamber86. Those skilled in the art may recognize that there are various ways of controlling the flow of fuel through the nozzle outlet92via a solenoid actuated valve assembly, including the direct operated check described herein. The direct operated check described herein allows the valve needle member90to be directly controlled by the movement of the control valve member61by varying the pressure acting inside the needle control chamber86.

A nozzle spring59may bias the valve needle member90towards the nozzle outlet92. When the valve needle member90blocks the nozzle outlet92, the valve needle member90is in a closed position such that no fuel exits the nozzle outlet92. The valve needle member90may move away from the nozzle outlet92against the direction of the bias of the nozzle spring59to an open position. When the valve needle member90is at the open position, fuel may eject from the nozzle outlet92.

Fuel injectors operate within high-pressure conditions and may be assembled by clamping stacked components on top of each other. Due to the high pressures within the injector body11, a load screw54or similar clamping mechanism may be used to hold the individual components together, including the valve assembly60, within the injector body11. Also, during the assembly of a fuel injector, those skilled in the art may appreciate the importance of aligning the guide piece43relative to the guide bore33such that the guide piece43may move freely within the guide bore33with minimal side forces acting on the inner guide surface32of the guide sleeve31, thereby reducing wear potential and eliminating slowdown of the travel speed of the armature assembly40.

In the present disclosure, the armature contact surface49of the control valve member61or the valve contact surface48of the armature assembly40may have a convex tip, while the other may have a flat tip. Further, either the stop surface47of the guide piece43or the guide stop surface55of the final air gap spacer53may also have a convex tip, while the other has a flat tip. Generally, when a convex tip makes contact with a flat tip, there is a point-to-surface contact, which may reduce side forces that potentially cause misalignment. The inter-relationship between a convex surface and a flat surface reduces the sensitivity to misalignment, and therefore further reduces the variability in performance by desensitizing the movement of the valve member from the misalignment of the armature assembly. Alternative embodiments may have two flat surfaces contact each other but any surface contours of the surfaces fall within the intended scope of the disclosure.

INDUSTRIAL APPLICABILITY

The present disclosure finds potential application in solenoid actuated valve assemblies in any engine or machine. For instance, the teachings of the present disclosure are pertinent to solenoid actuated valve assemblies where a valve member and an armature can be guided in their respective movements by different components of the valve assembly. The present disclosure has a general applicability in fuel injectors having a solenoid actuated valve assembly and a particular applicability in common rail fuel injectors.

Generally, a solenoid actuated valve assembly is in a first configuration when the solenoid coil is energized as shown inFIG. 3, and in a second configuration when the solenoid coil is de-energized as shown inFIG. 4. An injection event in a fuel injector is initiated when the solenoid coil is energized and ends when the solenoid coil is de-energized.

In the present disclosure, before an injection event is initiated, the solenoid coil29is de-energized. The armature assembly40and the control valve member61are biased towards a first configuration, where the valve contact surface48of the armature assembly40and the armature contact surface49of the control valve member61are in contact. In the first configuration, the armature assembly40and the control valve member61are coupled. The first spring56biases the armature assembly40towards the control valve member61, while the second spring58biases the control valve member61towards the armature assembly40. Because the first spring56has a greater preload than the second spring58, the valve member61may be seated at the low-pressure valve seat64.

When the valve assembly60is in the first configuration, the first annular opening68allows the needle control chamber86to have a fluid connection with the high-pressure nozzle chamber91via the pressure communication passage79and the valve supply passage84. In this configuration, high-pressure fuel from the rail pressure inlet port99passes through the nozzle chamber91, then passes through the pressure communication passage79up to the first annular opening68of the valve assembly60and through the valve supply passage84into the needle control chamber86via the second flow restrictor96. Also, high-pressure fuel from the nozzle chamber91passes into the needle control chamber86through the first flow restrictor95via pressure communication passage79. The high-pressure fuel in the needle control chamber86acts on the closing hydraulic surface94of the valve needle member90, thereby biasing the valve needle member90towards the nozzle outlet92, because the pressure exerted on the closing hydraulic surface94combined with the preload of the nozzle spring59is greater than the pressure acting on the opening hydraulic surface93. In this configuration, no fuel flows through the nozzle outlet92.

When the solenoid coil29is energized, the solenoid actuated valve assembly60moves towards the second configuration. The magnetic field around the coil29pulls the flux piece45towards the planar bottom surface26of the stator assembly21. The armature assembly40decouples from the control valve member61before the control valve member61begins to move towards the stator assembly21. In an exemplary embodiment, the armature assembly40moves at an initial acceleration that is greater than the initial acceleration of the control valve member61. The armature assembly40continues to accelerate towards the stator assembly21as the air gap between the armature assembly40and the stator assembly21decreases, due to the increased magnetic flux acting on the flux piece45. The control valve member61, on the other hand, has an acceleration that is determined at least partially by the material properties of the second spring58. By decoupling the armature assembly40from the control valve member61before the control valve member61begins to move, those skilled in the art will appreciate that the movements of the armature assembly40and the control valve member61are independent of each other, and therefore both the armature assembly40and the control valve member61are desensitized to the movement of the other. This may make the operation of solenoid actuated valve assemblies more predictable. The armature assembly40decouples from the control valve member61because the armature assembly40has an armature travel speed that is greater than a valve travel speed of the control valve member61. In an alternate embodiment, as the flux piece45is being pulled towards the stator assembly21by the magnetic flux of the solenoid coil29, both the armature assembly40and the control valve member61move together towards the stator assembly21until a later point in time, when the magnetic force acting on the armature assembly40pulls the armature assembly40out of contact with the control valve member61. In another alternate embodiment, the armature assembly40decouples from the control valve member61and moves towards the final air gap position of the armature assembly40once the control valve member61reaches the high-pressure valve seat65. This may happen if the armature assembly40has an armature travel speed that is equal to the travel speed of the control valve member61.

However, the exemplary embodiment of the disclosure teaches that the travel speed of the armature assembly40is greater than the travel speed of the control valve member61, thereby allowing the armature assembly40to decouple from the control valve member61before the control valve member61starts moving under the action of spring58. This is advantageous because decoupling the armature assembly40from the control valve member61desensitizes the control valve member61from the variability of the movement of the armature assembly40and vice versa, therefore allowing both the control valve member61and the armature assembly40to desensitize their own movements from the movements of the other component. The armature assembly40stops when the guide piece43of the armature assembly40makes contact with the stop spacer53at the final air gap position of the armature assembly40. The difference in the armature travel speed and the valve travel speed may depend upon the magnetic force acting on the flux piece45, as well as the preload of the first spring56and second spring58. The valve contact surface48of the armature assembly40and the armature contact surface49of the control valve member61are decoupled, i.e., not in contact, when the armature assembly40travels towards the stator assembly21faster than the control valve member61travels towards the high-pressure valve seat65. The control valve member61travels at a speed that is a function of the preload of the second spring58. Further, the control valve member61moves from the low-pressure valve seat64to the high-pressure valve seat65, and once the control valve member61reaches the high-pressure valve seat65, the control valve member61stays in the high-pressure valve seat65at least until the solenoid coil29is de-energized. The solenoid actuated valve assembly60is now in the second configuration when the control valve member61and the armature assembly40are decoupled and the armature assembly40is at the final air gap position.

When the control valve member61is seated at the high-pressure valve seat65, the control valve member61blocks the fluid connection between the first annular opening68with the valve supply passage84, and instead allows the second annular opening69to fluidly connect the needle control chamber86to the drain83via the valve supply passage84. Because the drain83is at a lower pressure than rail pressure, the pressure difference allows fuel, which was at high pressure inside the needle control chamber86, to flow through the second flow restrictor96into the drain83via the second annular opening69. The second flow restrictor96may have a greater flow rate than the flow rate of the first flow restrictor95. Therefore, more fuel can leave the needle control chamber86via the second flow restrictor96than the fuel that can enter the needle control chamber86via the first flow restrictor95. Hence, the pressure inside the needle control chamber86becomes lower as more fuel is leaving the needle control chamber86. As the pressure inside the needle control chamber86drops, the pressure acting on the closing hydraulic surface94also drops. Eventually, the pressure acting on the opening hydraulic surface93exceeds the combined force of the pressure acting on the closing hydraulic surface94and the preload of the nozzle spring59, causing the valve needle member90to move away from the nozzle outlet92, thereby opening the nozzle outlet92and allowing fuel to flow through the nozzle outlet92.

To end the injection event, the solenoid coil29is de-energized, thereby collapsing and causing quick decay of the magnetic field around the stator assembly21. The first spring56biases the armature assembly40towards the control valve member61and the control valve member61remains at the high-pressure valve seat65until the armature assembly40comes into contact with the control valve member61and recouples with the valve member61, whereby, the valve contact surface48of the armature assembly40presses upon the armature contact surface49of the control valve member61. Because the preload of the first spring56is greater than the preload of the second spring58, the armature assembly40is biased towards the control valve member61and thereby, the flux piece45travels from the final air gap position to the initial air gap position. The valve contact surface48of the armature assembly40recouples with the armature contact surface49of the valve member61before the control valve member61begins to move towards the low-pressure valve seat64. This is because the second spring58continues to bias the control valve member61towards the high-pressure valve seat65. However, when the armature assembly40contacts the control valve member61, the force from the first spring56pushes the control valve member61against the bias of the second spring58towards the low-pressure valve seat64. Hence, the control valve member61moves from the high-pressure valve seat65to the low-pressure valve seat64because the first spring56has a greater preload than the second spring58.

The solenoid actuated valve assembly60returns to the first configuration when the control valve member61is at the low-pressure valve seat64and the armature assembly40is at the initial air gap position and in contact with the control valve member61. When the control valve member61is seated at the low-pressure valve seat64, the first annular opening68allows the pressure communication passage to fluidly connect to the needle control chamber86via the second flow restrictor96. Because the needle control chamber86may no longer be fluidly connected to the low-pressure drain83but instead, be connected to the pressure communication passage79, which provides high-pressure fuel, high-pressure fuel may begin to accumulate in the needle control chamber86, thereby increasing the pressure acting on the closing hydraulic surface94of the valve needle member90. This pressure acting on the closing hydraulic surface94combined with the preload of the nozzle spring59eventually exceeds the pressure acting on the opening hydraulic surface93, and forces the valve needle member90to return to its closed position and stop any fluid from exiting the nozzle outlet92. Hence, no fuel will be flowing within the fuel injector10as the passages have returned to a steady pressure and the drain83is no longer fluidly connected to the needle control chamber86.

By separating the control valve member from the armature assembly, manufacturers may now isolate the problems pertaining to the armature and associated guide piece from the problems pertinent to the valve member and the associated orientation with the valve seats. The present disclosure allows manufacturers to design solenoid actuated valve assemblies that may be desensitized to offset centerlines. Further, the valve travel speed may now be determined by spring preloads, as opposed to the travel speed of the armature assembly, which is dictated by the solenoid. By making the valve travel speed independent of the armature travel speed, manufacturers may produce fuel injectors with less variability and more reliability. In addition, decoupling the armature assembly and the valve member may reduce the sensitivity to variations in solenoid operation. Finally, manufacturers may now produce fuel injectors that demonstrate a more consistent, predictable valve behavior in mass-produced valve assemblies having inherent geometrical tolerance differences.