Patent Application
20150204294
The present disclosure relates in general to high pressure pump systems, and, in particular, to a system and method for metering fluid to one or more high pressure pumping chambers.
Government imposed requirements for fuel economy and emissions reduction are one reason fuel systems manufacturers seek to provide precise control over the amount of fuel that is injected during injection events of a combustion cycle. More specifically, a goal of many high pressure fuel injection systems is to provide increased control of the amount of fuel injected by the fuel injectors of an internal combustion engine.
As shown in
In many such systems, metering valve 14 includes a variable area orifice operated by a solenoid. In certain embodiments, the linear position of a spool inside metering valve 14 controls the amount of fuel to be supplied to pumping chambers 16. As such, metering valve 14 may be configured to prevent fuel from passing to chambers 16 when metering valve 14 is fully closed. However, in many systems, the mechanical configuration of metering valve 14 is insufficient to completely prevent fuel flow, and some leakage occurs. Moreover, in some systems the pressure of the fuel supply 12 to metering valve 14 requires significant counter-force by valve 14 when valve 14 is moved to a partially opened position to maintain valve 14 in its desired position. Generally, this counter-force is provided by a high performance solenoid controlled by ECM 15. Finally, in order to deliver the fuel economy and emission reduction desired, it is desirable to provide a highly accurate mechanism for metering fuel to chambers 16 when valve 14 is opened.
According to one embodiment of the disclosure, a metering valve is provided comprising a barrel having a central bore, at least one inlet in flow communication with the central bore, and at least one outlet in flow communication with the central bore, and a spool disposed for reciprocal motion within the central bore of the barrel. In such an embodiment, the spool includes a ball tip, a metering edge, and at least one bore extending from a first orifice to a second orifice. The spool is moveable between a closed position, wherein the ball tip engages a conical seat formed in a wall of the barrel to prevent fluid flow between the at least one inlet and a lower chamber of the central bore and the metering edge is disposed in the lower chamber to prevent fluid flow between the lower chamber and the at least one outlet, and an opened position, wherein the ball tip is spaced apart from the conical seat to permit fluid flow between the inlet and the lower chamber and through the at least one bore of the spool into an upper chamber of the central bore to thereby equalize pressure of the fluid on the spool, and the metering edge is disposed in a flow path of the at least one outlet to permit fluid flow between the lower chamber and the at least one outlet. In one aspect of this embodiment, the valve further comprises a spring disposed in the lower chamber to bias the spool toward the opened position. In a variant of this aspect, the valve further comprises a solenoid for generating a magnetic flux as a function of input current, the magnetic flux causing a plunger in contact with the spool to move the spool toward the closed position against the biasing force of the spring. In another aspect of this embodiment, the valve further comprises a spring disposed in the valve to bias the spool toward the closed position, and a solenoid for generating a magnetic flus as a function of input current, the magnetic flux causing a plunger connected to the spool to move the spool toward the opened position against the biasing force of the spring. In another aspect, the barrel includes multiple outlets. In yet another aspect, the valve further comprises a plunger in contact with the spool, the plunger being positioned within a housing of the valve for guided movement as the spool is moved between the closed position and the opened position. In another aspect, the at least one bore extends substantially diagonally through a body of the spool from a side wall of the body to an upper surface of the body. In a variant of this aspect, fluid flow through the at least one bore causes rotation of the spool about a longitudinal axis of the spool. In still another aspect of this embodiment, when the spool is in a fully opened position, a plunger in contact with the spool engages a portion of a housing of the valve.
In another embodiment of the present disclosure, a system for metering fuel to at least one fuel pumping chamber is provided, comprising a fuel supply, an inlet metering valve having a first opening in flow communication with the fuel supply and a second opening in flow communication with the at least one pumping chamber, the valve further including a solenoid and a spool mounted within a housing for reciprocal movement between a plurality of opened positions, wherein fuel flows through the valve from the fuel supply to the at least one pumping chamber, and a closed position, wherein fuel is substantially prevented from flowing through the valve, and an ECM configured to provide signals to the solenoid to position the spool into the plurality of opened positions and the closed position. In this embodiment, the spool includes a ball tip at one end that engages a seating surface to prevent fuel flow when the spool is in the closed position, a metering edge disposed on an outer surface of the spool that cooperates with the second opening when the armature is in the plurality of opened positions to meter the quantity of fuel flowing through the valve, and the valve includes a flow path between a first chamber disposed between the first opening and the second opening and a second chamber disposed adjacent another end of the spool, the flow path permitting fuel flow between the first chamber and the second chamber to substantially equalize pressure exerted by the fuel on each end of the spool. According to one aspect of this embodiment, the valve includes a barrel having a central bore defining the first chamber adjacent the one end of the spool and the second chamber adjacent the other end of the spool. In a variant of this aspect, the barrel further defines the first opening and the second opening. In another variant, the barrel defines a plurality of outlets. Another aspect of this embodiment further comprises a spring disposed in the first chamber to bias the spool toward the plurality of opened positions. In a variant of this aspect, the solenoid generates a magnetic flux as a function of an input current from the ECM, the magnetic flux urging the spool to move toward the closed position against the biasing force of the spring. Another aspect further comprises a spring disposed within the valve to bias the spool toward the closed position, wherein the solenoid generates a magnetic flux as a function of an input current from the ECM, the magnetic flux urging the spool to move toward the plurality of opened positions against the biasing force of the spring. In yet another aspect, the valve further includes a plunger in contact with the spool, the plunger being positioned within the housing of the valve for guided movement as the spool is moved between the closed position and the plurality of opened positions. In still another aspect, the flow path includes at least one bore extending through the spool from a first orifice disposed in the first chamber to a second orifice disposed in the second chamber, the at least one bore permitting fuel flow between the first chamber and the second chamber to substantially equalize pressure exerted by the fuel on each end of the spool. In a variant of this aspect, the at least one bore extends substantially diagonally through a body of the spool from the first orifice to the second orifice such that fuel flow through the at least one bore causes rotation of the spool about a longitudinal axis of the spool. In another aspect of this embodiment, the flow path includes at least one groove extending from the first chamber to the second chamber. In a variant of this aspect, the at least one groove is formed in a side wall of a body of the spool. In still another aspect, the flow path includes at least one flat formed in a side wall of a body of the spool and extending from the first chamber to the second chamber. In yet another aspect, when the spool is in a fully opened position, a plunger in contact with the spool engages a portion of the housing of the valve to limit further movement of the spool away from the closed position.
In yet another embodiment of the present disclosure, a method of metering fuel to a fuel pumping chamber is provided, comprising supplying fuel to a metering valve, supplying a signal to the metering valve that activates a solenoid which moves a spool of the metering valve against a biasing force of a spring, and controlling the signal supplied to the metering valve to cause movement of the metering valve between a closed position, wherein a ball tip of the spool engages a conical seat at one opening of the valve to substantially prevent fuel from flowing through the valve, and a plurality of opened positions, wherein a metering edge of the spool is disposed within a flow path of another opening of the valve to permit a metered quantity of fuel to flow to the pumping chamber, and a bore extending through the spool distributes pressure exerted on the spool by the fuel to an upper surface of the spool. In one aspect of this embodiment, the valve includes a barrel having a central bore that receives the spool, the central bore defining a first chamber adjacent one end of the spool and a second chamber adjacent the upper surface of the spool. In a variant of this aspect, the barrel further defines the openings of the valve. In another variant, the spring is disposed in the first chamber to bias the spool toward the plurality of opened positions. In another aspect of this embodiment, the spring is disposed in the valve to bias the spool toward the closed position. In another aspect, supplying a signal includes generating a magnetic flux as a function of an input current supplied by an ECM, the magnetic flux urging the spool to move toward the closed position against the biasing force of the spring. In still another aspect, supplying a signal includes generating a magnetic flux as a function of an input current supplied by an ECM, the magnetic flux urging the spool to move out of the closed position against the biasing force of the spring. Another aspect of this embodiment further includes limiting movement of the spool away from the closed position by causing a plunger in contact with the spool to engage a portion of a housing of the valve.
The embodiments will be more readily understood in view of the following description when accompanied by the below figures and wherein like reference numerals represent like elements, wherein:
The embodiments disclosed herein are not intended to be exhaustive or limit the invention to the precise form disclosed in the following detailed description. Rather, the embodiments were chosen and described so that others skilled in the art may utilize their teachings.
Embodiments of an inlet metering valve according to the present disclosure are described herein in the context of a work machine having a high pressure fuel pump system 10 as depicted in
Referring now to
In the embodiment described herein, inlet 112 receives fuel from fuel supply 12 depicted in
In one embodiment, plunger 118 is formed as an elongated rod having an upper end 122 and a lower end 124 which contacts spool 120. In one embodiment, spool 120 includes a substantially cylindrical body 126 sized to fit within central bore 110 of barrel 104 with low clearance and for reciprocating movement in the manner described below. Spool 120 further includes a ball tip 128 at an end distal to lower end 124 of plunger 118, a circumferential metering edge 130, and bore 132 extending through body 126. More specifically, in one embodiment bore 132 extends from a lower orifice 134 disposed in a side wall 136 adjacent ball tip 128 and below metering edge 130 to an upper orifice 138 disposed in an upper surface 140 of body 126.
Barrel 104 further includes a conical seat 142 formed at the inner end of inlet 112 in lower wall 144 of barrel 104. Additionally, a spring 146 is disposed within a lower chamber 148 of central bore 110 between lower wall 144 of barrel 104 and metering edge 130. As is further described below, in one embodiment spring 146 biases spool 120 upwardly such that valve 100 is biased toward the opened position shown in
While not shown in the drawings, solenoid 106 of valve 100 is coupled to ECM 15 (
Referring now to
Valve 100 is moved from its closed position (
As the fluid fills lower chamber 148, it flows into lower orifice 134 of bore 132. The fluid further flows out of upper orifice 138 and fills upper chamber 154. With the pressure balance drilling provided by bore 132 in this manner, the pneumatic pressure placed on spool 120 by the fluid is substantially equalized between lower chamber 148 and upper chamber 154. As such, solenoid 106 does not need to be sized to overcome the upward biasing force of spring 146 in addition to the upward force applied to spool 120 by the fuel flowing into inlet 112.
When valve 100 is moved to an opened position such that metering edge 130 is positioned within the flow path of outlets 114, 116, fluid not only flows from lower chamber 148 through outlets 114, 116, fluid also flows through diagonal bore 132, into upper chamber 154, and from upper chamber 154, between spool 120 and the inner surface of central bore 110, through outlets 114, 116. The diagonal orientation of diagonal bore 132 and the fluid flow through bore 132 causes spool 120 to rotate or spin about its longitudinal axis. This rotation occurs each time valve 100 is moved to an opened position, and provides for distributed wear on the surfaces of spool 120.
While a diagonal bore 132 is shown in the drawings for providing the above-described pressure balancing, it should be understood that many different balancing configurations that provide a flow path between lower chamber 148 and upper chamber 154 may be employed. For example, grooves or flats may be formed in the outer surface of side wall 136 of spool 120, a plurality of ports may be formed through body 126, grooves may be formed on the inner surface of central bore 110, etc. In still other embodiments, the clearance between side wall 136 of spool 120 and the inner surface of central bore 110 may be adjusted such that fluid may flow around spool 120 between lower chamber 148 and upper chamber 154 to balance pressure exerted on spool 126.
As the current supplied to solenoid 106 is further reduced, plunger 118 moves upwardly within upper guide 150 and lower guide 152, and spool 120 moves further upwardly within central bore 110. Eventually, metering edge 130 is disposed in the flow path of outlets 114, 116 such that lower chamber 148 is in flow communication with outlets 114, 116. The knife edge formed by metering edge 130 not only functions to prevent fluid flow out of lower chamber 148 when metering edge 130 is positioned below outlets 114, 116, it also provides highly precise flow characteristics when metering edge is positioned in the flow path of outlets 114, 116. More specifically, the knife edge results in a very precise flow vs. solenoid 106 current curve.
The foregoing description has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the exemplary embodiments disclosed. Many modifications and variations are possible in light of the above teachings. It is intended that the scope of the invention be limited not by this detailed description of examples, but rather by the claims appended hereto.
