Patent Application
20250129760
The present disclosure relates generally to a fuel injector, and more particularly to a control valve in a fuel injector movable to a relief position to relieve fuel pressure.
Electrically actuated fuel injectors have been used for many years in a range of engine platforms. In a conventional design an injection valve is selectively opened and closed to control the injection of fuel into an engine cylinder at a desired injection timing, amount, and sometimes injection rate shape. Some fuel injectors rely principally upon a pressure of fuel supplied to the injector to actuate open an injection valve at a desired timing. Other systems employ a separate control valve that operates to directly control a closing hydraulic pressure on the injection valve to more precisely control the timing and manner of fuel injection. Designs are well-known where a pressurized fuel reservoir is provided that supplies pressurized fuel to multiple fuel injectors at an injection pressure. Other strategies, sometimes referred to as unit injectors, pressurize the fuel to an injection pressure within each individual fuel injector, employing a hydraulically-actuated or cam-actuated piston or plunger to perform the fuel pressurization. Many different versions and extensions directed to applications and improvements on these two basic strategies are known, especially in the field of compression-ignition engines.
Increasingly stringent regulations in recent years have continued to drive the search for improved and alternatively configured fuel injectors. It has long been observed that precise control over fuel injector operation can have various benefits respecting emissions and fuel efficiency. One factor well-known to improve emissions, at least in part by optimizing fuel spray vaporization and enabling rapid injection of precise amounts of fuel, is higher fuel pressure. Thus, engineers have been motivated to design fuel injectors that can inject fuel at very high injection pressures ranging into the hundreds of megapascals (mPa). While utilizing high injection pressures has proven beneficial in many instances, the hardware capabilities of fuel injectors can be tested under such conditions. U.S. Pat. No. 11,105,304B2 to Kim et al. is directed to a fuel injector employing a residually stressed solenoid housing for improved pressure capability.
In one aspect, a fuel injector includes an injector housing having a nozzle and a nozzle check movable to open and close the nozzle and including a closing hydraulic surface. The fuel injector further includes an electrically actuated control valve assembly having a control valve, and an armature. A high pressure passage, a low pressure drain, a control passage, a check control chamber fluidly connected to the control passage, and a valve seat are each formed in the injector housing, and a relief passage is formed by at least one of the injector housing or the control valve. The control valve is movable among the rest position in contact with the control valve seat and blocking the control passage from the low pressure drain to maintain a high pressure in the control chamber, a lifted injection position where the control passage is fluidly connected to the low pressure drain, and a lifted relief position where the high pressure passage is fluidly connected to the relief passage.
In another aspect, a fuel system includes a fuel supply and a fuel injector including therein a fuel inlet fluidly connected to the fuel supply, and a high pressure passage extending from a plunger cavity, a control passage, and a low pressure drain. The fuel injector further includes an electrically actuated spill valve fluidly between the fuel inlet and the plunger cavity, a nozzle check having a closing hydraulic surface exposed to a fluid pressure of the control passage, and an electrically actuated control valve. The control valve includes a 3-position valve blocking the control passage from the low pressure drain at a rest position, and fluidly connecting the control passage to the low pressure drain at a lifted injection position. The fuel injector further includes therein a relief passage, and the control valve fluidly connects the high pressure passage to the relief passage at a lifted relief position that is between the rest position and the lifted injection position.
In still another aspect, a method of operating a fuel system includes advancing a plunger in the fuel system to increase a pressure of fuel in a plunger cavity, and energizing or deenergizing a solenoid in a fuel injector during the advancing the plunger to move a control valve to a lifted relief position from one of a rest position blocking a control passage from a low pressure drain and a lifted injection position where the control passage is fluidly connected to the low pressure drain. The method further includes fluidly connecting a high pressure passage extending from the plunger cavity to a relief passage, based on the moving the control valve to the lifted relief position, to relieve a pressure of fuel in the plunger cavity, and holding a nozzle check closed via a pressure of fuel on a closing hydraulic surface of a nozzle check exposed to a fluid pressure of the control passage, during the relieving the pressure of fuel in the plunger cavity.
Referring to
Engine system 10 also includes a fuel system 18 having a fuel supply 20 containing a liquid fuel, and a fuel pump 22 structured to convey the fuel to one or more fuel injectors 24, as shown in
Fuel injector 24 includes an injector housing 26 having a nozzle 28 with a plurality of nozzle outlets 31 formed therein and each fluidly connecting to cylinder 16. Fuel injector 24 also includes a nozzle check 30 having, for example, the form of a needle valve or the like, moveable to open and close nozzle outlets 31 in nozzle 28 and having a closing hydraulic surface 32. Fuel injector 24 also includes an electrically actuated control valve assembly 34 having a control valve 36, and an armature 38. Control valve assembly 34 also includes a first biasing spring 40 and one or more second biasing springs 42, the purpose and functionality of which is further discussed herein. A solenoid 44 is also part of control valve assembly 34 and is energized by way of electrical control currents to magnetically attract armature 38 to move control valve 34 among a plurality of different positions, as also further discussed herein.
Fuel injector 24 also includes an electrically actuated spill valve assembly 46. Spill valve assembly 46 includes a spill valve 48, an armature 50, a biasing spring 52, and a solenoid 54. A spring stop 56 may be positioned at a fixed location in injector housing 26 between spring 40 and spring 52. Solenoid 54 and solenoid 44 may in some embodiments be positioned in a common solenoid assembly although the present disclosure is not thereby limited. The illustrated design employing spring stop 56 differs from certain other designs employing commonly housed solenoids for a control valve in a spill valve that utilize a common biasing spring. Solenoid 54 can be energized via electrical control currents to attract armature 50 for moving spill valve 46 between an open position and a closed position.
A high pressure passage 66, a low pressure drain 68, a control passage 70, a check control chamber 72 fluidly connected to control passage 70, and a valve seat 74 are each formed in injector housing 26. A relief passage 76 is formed by at least one of injector housing 26 or control valve 36, and in the illustrated embodiment is formed by injector housing 26. In other embodiments an annulus and/or a longitudinal or circumferential channel formed in an outer surface of control valve 36, or potentially even an internal passage, might form a pressure relief passage as contemplated herein. Injector housing 26 also has formed therein a high pressure branch passage 67, a plunger cavity 60, a fuel inlet 78, and a spill passage 80. Another branch passage not shown in
Spill valve 48 is fluidly between fuel inlet 78 and plunger cavity 60 and movable between an open position where plunger 58 reciprocates to draw fuel via fuel inlet 78 into and out of plunger cavity 60, and a closed position. When spill valve 50 is moved to a closed position, the fluid connection between fuel inlet 78 and spill passage 80 is blocked and moving plunger 58 toward an advanced position increases a pressure of fuel in plunger cavity 60, high pressure passage 66, and other locations fluidly connected to high pressure passage 66.
Depending upon the fuel injection strategy used, and potentially other factors, in certain instances a fuel pressure within fuel injector 24 can approach or exceed a desired fuel pressure limit when plunger 58 is advanced to pressurize fuel. The present disclosure contemplates a unique strategy for relieving or bleeding off fuel pressure selectively to avoid exceeding desired pressure limits, as further discussed herein.
To this end, control valve 34 may include a multi-position valve such as a 3-position valve movable among a rest position, a lifted injection position, and a lifted relief position. At the rest position control valve 36 is in contact with control valve seat 74 and blocks control passage 70 from low pressure drain 68 to maintain a high pressure in control chamber 72. At the lifted injection position control passage 70 is fluidly connected to low pressure drain 68, enabling a high pressure of fuel applied to nozzle check 30 from high pressure passage 66 to overcome the hydraulic pressure on closing hydraulic surface 32 and lift nozzle check 30 to inject a fuel into cylinder 16. At the rest position in contact with valve seat 74 control valve 36 permits high pressure to prevail in control chamber 72 and act on closing hydraulic service 32 to maintain nozzle check 30 closed. At the lifted relief position high pressure passage 66 is fluidly connected to relief passage 76 to enable excess pressure to be bled off to avoid over-pressurizing fuel injector 24. The bleeding of excess pressure occurs during advancing plunger 58 with spill valve 48 closed. In an embodiment, multiple injections can be performed per engine cycle, with pressure relief being performed between the multiple injections, as further discussed herein.
Referring also now to
In the illustrated embodiment, control valve 36 includes a sealing body 41 and is shown as control valve 36 might appear at a rest position with sealing body 41 in contact with injector housing 26 and where control passage 70 is fluidly connected to a high pressure branch passage 69 that extends to high pressure passage 66. At the rest position control passage 70 is blocked from low pressure drain 68 and also blocked from relief passage 76. Also shown in
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Either of the arrangements shown in
Operating fuel system 18 may include rotating cam 64 to advance plunger 58 to increase a pressure of fuel in plunger cavity 60. As discussed herein increasing a pressure of fuel in plunger cavity 60 may occur when spill valve 48 is in a closed position. Operating fuel system 18 may further include energizing or deenergizing solenoid 44, during the advancing plunger 58, to move control valve 36 from one of the rest position blocking control passage 70 from low pressure drain 68 or the lifted injection position where control passage 70 is fluidly connected to low pressure drain 68, to the lifted relief position. Positioning control valve 36 at the lifted relief position fluidly connects high pressure passage 66 to relief passage 76, to relieve a pressure of fuel in plunger cavity 58.
With the pressure relieved, control valve 36 may be moved from the lifted relief position to the rest position or to the lifted injection position. Moving control valve 36 to the lifted injection position or returning control valve 36 to the rest position blocks high pressure passage 66 from relief passage 70 to end pressure relief. Nozzle check 30 is held closed via a pressure of fuel on closing hydraulic surface 32 during relieving pressure of fuel in plunger cavity 60. As discussed above, control valve 36 can be moved to different positions depending upon the energy state of solenoid 44. In an embodiment, solenoid 44 can be energized a first time in an engine cycle to move control valve 36 to the lifted injection position during advancing plunger 58, and energized a second time in the same engine cycle to move control valve 36 to the lifted injection position during advancing plunger 58.
An initial energizing of solenoid 44 to move control valve 36 from the rest position to the lifted relief position may include energizing solenoid 44 to a first energy state, and each of energizing solenoid 44 a first time and energizing solenoid 44 a second time in the same engine cycle to move control valve 36 to the lifted injection position can include energizing solenoid 44 to a second, higher energy state. In this way it can be readily envisioned that control valve 36 might be moved from the rest position to the lifted relief position with a lower magnitude control current, in opposition to a lesser net spring bias, and then moved from the lifted relief position to the lifted injection position with a greater magnitude control current, in opposition to a greater net spring bias. In some applications, control valve 36 can also be toggled between the lifted relief position and the lifted injection position by alternating between the lower magnitude control current and the greater magnitude control current, relieving pressure between multiple injections in an engine cycle. Still other variations will be apparent to those skilled in the art.
Referring also now to
Control currents 301 show a spill current at 402 and a DOC current at 404 during one example engine cycle. In this example, spill valve 48 is initially open, and control valve 36 is initially at a lifted relief position, for example where a lower magnitude control current is applied to solenoid 44. At approximately 406 spill valve 48 is closed. At approximately the same time, or potentially earlier, at 410 the DOC current is reduced to permit nozzle check 30 to close. The DOC current 404 is then increased to a greater magnitude at approximately 411 to move control valve 36 from the rest position to a lifted injection position, and subsequently reduced at 412 to move control valve 36 to the rest position (closed) to end the fuel injection. At approximately 413 DOC current 404 is increased again to move control valve 36 again to the lifted injection position to start a second fuel injection. At 414 DOC current 404 is reduced once more, and thereafter toggled between the lifted injection position and the lifted relief position to perform a plurality of additional fuel injections. Accordingly, during a period of time shown generally at 408 where an over-pressurization risk exists the pressure relief events between injections can prevent over-pressurization.
The present description is for illustrative purposes only, and should not be construed to narrow the breadth of the present disclosure in any way. Thus, those skilled in the art will appreciate that various modifications might be made to the presently disclosed embodiments without departing from the full and fair scope and spirit of the present disclosure. Other aspects, features and advantages will be apparent upon an examination of the attached drawings and appended claims. As used herein, the articles “a” and “an” are intended to include one or more items, and may be used interchangeably with “one or more.” Where only one item is intended, the term “one” or similar language is used. Also, as used herein, the terms “has,” “have,” “having,” or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.
