Fuel injector control module with dampening

Abstract

Fluid in a chamber, through which a fuel control armature is moving, is used to dampen armature vibrations. This dampening effect is achieved by forming a passage through which the fluid flows as the actuator moves to a steady state position. This passage may be implemented in a control module for controlling fuel delivery in a fuel injector. The control module includes a control module housing defining the cavity. The armature is disposed at least partially within the cavity. The armature affects the flow of fuel in the injector by changing the area of a fuel port through which fuel passes. The fluid passage is formed as the armature moves towards a wall defining the cavity.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. application Ser. No. 10/196,894, filed Jul. 16, 2002.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to controlling the flow of fuel through an injector.

[0004] 2. Background Art

[0005] Fuel injectors provide controlled pulses of fuel for combustion in internal combustion engines. The flow of fuel through a fuel injector may be controlled by one or more solenoids that open ports, close ports, or otherwise affect the flow of fuel within the fuel injector through movement of a solenoid armature. Typically, each solenoid armature is biased in a first position by a mechanical spring and activated to a second position by a motive force provided by a solenoid electromagnet. When the motive force is removed, the spring returns the solenoid armature to its deactivated position. This deactivation results in ringing of the armature or other mechanical vibrations due to contact with a mechanical stop. Such vibrations interfere with or otherwise complicate the control of fuel flowing through the injector and may shorten the effective injector life.

[0006] What is needed is to minimize ringing and other vibrations caused by deactivation of a control solenoid within a fuel injector.

SUMMARY OF THE INVENTION

[0007] The present invention utilizes a fluid in a chamber, through which a fuel control armature is moving, to dampen armature vibrations. This dampening effect is achieved by forming a passage through which the fluid flows as the actuator moves to a steady state position.

[0008] A control module for controlling fuel delivery in a fuel injector is provided. The control module includes a control module housing defining a cavity containing a fluid. An armature is disposed to move within the cavity. A control valve is operated by movement of the armature. The control valve affects the flow of fuel by changing the area of a fuel port through which fuel passes. A drive moves the armature towards a first wall of the cavity when the drive is activated and moves the armature towards a second wall of the cavity when the drive is deactivated. A first fluid passage is formed as the armature moves towards the first wall. A second fluid passage is formed as the armature moves towards the second wall. Armature vibration is dampened as fluid moves through the first fluid passage and the second fluid passage.

[0009] In an embodiment of the present invention, at least one of the first fluid passage and the second fluid passage is formed by a dampener sleeve extending from the armature. A stop, which has a length in a direction of armature movement greater than a length of the dampener sleeve in the direction of armature movement, may be used to form the fluid passage. Alternatively, or in addition to the stop, the dampener sleeve may include at least one notch.

[0010] In another embodiment of the present invention, armature vibration dampening is provided by at least one of a first channel in the first wall forming the first fluid passage and a second channel in the second wall forming the second fluid passage.

[0011] In still another embodiment of the present invention, at least one of the first fluid passage and the second fluid passage is formed between a compression side and a dampener shim. The compression side may be circular and the dampener shim may define a circular opening having an opening radius smaller than the compression side radius. A stop may extend from the compression side a distance greater than the thickness of the dampener shim.

[0012] In yet another embodiment of the present invention, the armature defines a shoulder at least partially around the armature. At least one of the first fluid passage and the second fluid passage is formed between a dampener sleeve and the shoulder.

[0013] In a further embodiment of the present invention, the housing further defines a second cavity within which is at least partially disposed a second armature. The second armature forms at least one second armature fluid passage. Fluid exiting the second armature cavity through the at least one second armature fluid passage provides dampening of the second armature.

[0014] A method of controlling a flow of fuel in a fuel injector is also provided. An armature is moved in a cavity containing fluid so as to change an opening area of a fuel port. At least one of a first fluid passage and a second fluid passage is formed by the armature movement. The first fluid passage passes fluid between the armature and a first wall defining the cavity as the armature moves towards the first wall. The second fluid passage passes fluid between the armature and a second wall defining the cavity as the armature moves towards the second wall.

[0015] A method of injecting fuel into an engine is also provided. Fuel is compressed and supplied to an opening in an injector through a controlled path. The state of a solenoid in the injector is changed to control the flow of fuel along the path. The solenoid has an armature traveling through a cavity containing fluid. Changing the solenoid state causes the armature to approach a wall defining the cavity, forming a passage. Fluid is passed from between the armature and the wall through the passage, dampening vibrations.

[0016] The above objects and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a conceptualized cut view drawing of a fuel injector which may incorporate the present invention;

[0018] FIG. 2 is a schematic diagram illustrating the operation of a fuel injector which may incorporate the present invention;

[0019] FIG. 3 is a cut view drawing of a control module having a dampener sleeve according to an embodiment of the present invention;

[0020] FIG. 4 is a cut view drawing of a control module having a notched dampener sleeve according to an embodiment of the present invention;

[0021] FIG. 5 is a perspective view drawing of a notched dampener sleeve according to an embodiment of the present invention;

[0022] FIG. 6 is a cut view drawing of a control module defining a fluid passage channel according to an embodiment of the present invention;

[0023] FIG. 7 is a cut view drawing of a control module with a dampener shim according to an embodiment of the present invention;

[0024] FIG. 8 is a cut view drawing of a control module with a dampener sleeve according to an embodiment of the present invention;

[0025] FIG. 9 is a plot of graphs illustrating control valve bouncing;

[0026] FIG. 10 is a plot of graphs illustrating vibration reduction due to an embodiment of the present invention; and

[0027] FIG. 11 is a cut view drawing of a control module with dampening on solenoid activation and on solenoid deactivation according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0028] Referring to FIG. 1, a conceptualized cut view drawing of a fuel injector which may incorporate the present invention is shown. A fuel injector, shown generally by 20, includes injector body 22 defining a fuel outlet shown generally by 24. Plunger 26 disposed within injector body 22 pressurizes fuel 28 due to an external force applied to cam cup 30 overcoming bias force supplied by plunger spring 32. Fuel 28 in reservoir 34 is routed to fuel outlet 24 through fuel delivery path 36.

[0029] Nozzle needle 38 is biased by needle spring 40 around load pin 42 to seal off fuel outlet 24. Pressurized fuel 28 from reservoir 34 is routed through fuel delivery path 36 to fuel outlet 24. Pressurized fuel 28 pushes nozzle needle 38 back, opening fuel outlet 24 to permit the escape of fuel 28 from fuel injector 20. The flow of fuel along fuel delivery path 36 to fuel outlet 24 is controlled by control module 44 having at least one solenoid for controlling fuel delivery. As will be described in greater detail below, each solenoid has an armature biased by a spring to contact a wall defining a cavity when the solenoid is not energized by a signal from electrical connector 46. The armature and the wall form a passage as the armature approaches the wall. The passage passes fluid from between the armature and the wall into the remaining cavity to dampen armature vibrations.

[0030] Referring now to FIG. 2, a schematic diagram illustrating the operation of a fuel injector which may incorporate the present invention is shown. As cam 60 rotates, plunger 26 pressurizes fuel 28 in reservoir 34. Main control valve 62 in control module 44 is normally open, allowing fuel from reservoir 34 to dump through main control valve 62 into low pressure circuit 64. Control module 44 also includes normally closed needle control valve 66. Load pin 42 includes piston 68 in chamber 70. Chamber 70 fills from fuel delivery path 36 and empties through needle control valve 66 into low pressure circuit 64. When needle control valve 66 is not energized, pressurized fuel 28 within chamber 70 prevents nozzle needle 38 from opening fuel outlet 24. Thus, by controlling main control valve 62 and needle control valve 66, the shape of a fuel pulse exiting fuel outlet 24 may be controlled.

[0031] FIGS. 3, 4, 6-8 and 11 illustrate various embodiments of the present invention with cross-sectional views of control modules, some having both a main control valve and a needle control valve. Various techniques for dampening vibrations may be applied to either or both of the main control valve and the needle control valve. In addition, these techniques may be applied to either or both of the solenoid activated stroke or the solenoid deactivated stroke. Further, as will be recognized by one of ordinary skill in the art, the present invention applies to a wide variety of valves for controlling the flow of fuel within a fuel injector.

[0032] Referring now to FIG. 3, a cut view drawing of a control module having a dampener sleeve according to an embodiment of the present invention is shown. Control module 44 includes normally open main control valve 62 and normally closed needle control valve 66. The operation of both valves 62, 66 is similar. Each valve 62, 66 is implemented as an electromagnetic solenoid with an armature that moves to open or close a fuel flow port. As will be recognized by one skilled in the art, the present invention applies to valves or ports driven by any means.

[0033] Main control valve 62 is defined within control module housing 80. Stator block 82 is fixed within control module housing 80. Stator block 82 includes stator coil 84 which, when carrying sufficient current, activates main control valve 62. Main control valve 62 also includes an armature, shown generally by 86. Armature 86 is biased away from stator coil 84 by spring 88 pushing against flange 90. Thus, when main control valve 62 is deactivated, flange 90 is pushed by spring 88 towards contact wall 92 of control module housing 80. In the embodiment shown, contact wall 92 of housing 80 is formed by an interior portion of injector body 22.

[0034] Flange 90 is constructed of a magnetically attractable material such that, when stator coil 84 is energized, flange 90 is pulled against the force of spring 88 onto stator block 82. Shaft 94 is attached to flange 90. Shaft 94 passes through chamber 96 which is connected to high pressure fuel delivery path 36 via a port not shown. When main control valve 62 is energized, shaft 94 is hard against seat 98, sealing chamber 96 from fuel outlet 100. When main control valve 62 is not energized, spring 88 pulls shaft 94 away from seat 98 allowing fuel to pass from chamber 96 out through fuel outlet 100 to low pressure circuit 64.

[0035] Control module housing 80 defines cavity 102 through which passes flange 90 of armature 86. Cavity 102 is filled with fluid 104. Fluid 104 in cavity 102 in the embodiment shown is low pressure fuel. However, fluid 104 may be any fluid capable of dampening vibrations. Port 106 allows fluid 104 to escape cavity 102.

[0036] Prior to the present invention, de-energizing main control valve 62 caused spring 88 to force compression side 108 of flange 90 against contact wall 92. Flange 90 would bounce off contact wall 92 creating ringing and other vibrations. One problem with such ringing is a rapid opening and closing of chamber 96 to fuel outlet 100, decreasing the ability for main control valve 62 to precisely control the flow of fuel 28. In addition, vibrations decrease the effective life of fuel injector 20.

[0037] The present invention utilizes fluid 104 exiting through a passage formed as armature 86 moves towards contact wall 92 to dampen vibrations in armature 86. In the embodiment shown in FIG. 3, dampener sleeve 110 extends from flange 90 towards contact wall 92. Stop 112 also extends from armature 86. Stop 112 extends farther towards contact wall 92 than dampener sleeve 110 such that, when stop 112 contacts contact wall 92, fluid passage 114 is formed between dampener sleeve 110 and contact wall 92. As will be recognized by one skilled in the art, stop 112 may also extend from contact wall 92 towards contact flange 90 or shaft 94.

[0038] Dampener sleeve 110 may be formed from any suitable material such as, for example, steel. Dampener sleeve 110 may be press fit over flange 90, may be spot welded to flange 90, or may be attached by any other suitable means. Dampener sleeve 110 may also be formed as part of flange 90. Stop 112 is also preferably steel and may be formed as part of shaft 94, may be attached to shaft 94, may be attached to flange 90, may be formed as part of flange 90, or the like. A typical throw for armature 86 is about 180 microns with resulting gap distance for fluid passage 114 between dampener sleeve 110 and contact wall 92 of about 20 microns.

[0039] Control module housing 80 also contains normally closed needle control valve 66. Stator block 120 is fixed within control module housing 80. Stator block 120 includes stator coil 122 for carrying electrical current. A needle control valve armature, shown generally by 124, is biased away from stator coil 122 by spring 126. Armature 124 includes flange 128 made of a magnetically attractable material. When stator coil 122 carries sufficient current, flange 128 is pulled back against stator block 120, compressing spring 126. When stator coil 122 is de-energized, spring 126 forces flange 128 towards contact wall 130. Shaft 132 is fixed to flange 128. Shaft 132 passes through chamber 134 and contacts seat 136 to seal fuel inlet 138 from fuel outlet 140. Energizing stator coil 122 pulls shaft 132 away from seat 136 allowing pressurized fuel 28 to flow through fuel inlet 138 into chamber 134 through fuel outlet 140 and into low pressure circuit 64.

[0040] Control module housing 44 defines cavity 142 through which moves flange 128. Cavity 142 contains fluid 104 which may be, for example, low pressure fuel. Flange 128 has compression side 144 facing contact wall 130. Dampener sleeve 146 extends from compression side 144 towards contact wall 130 a distance such that fluid passage 114 between dampener sleeve 146 and contact wall 130 remains open when shaft 132 is against seat 136. Fluid 104 is forced through fluid passage 114 formed as flange 128 moves towards contact wall 130. Fluid 104 serves to dampen vibrations of armature 124 when needle control valve port 66 is de-activated.

[0041] Referring now to FIG. 4, a cut view drawing of a control module having a notched dampener sleeve according to an embodiment of the present invention is shown. Dampener sleeve 160 extends from flange 90 towards contact wall 92. When stator coil 84 is de-energized, spring 88 forces flange 90 towards contact wall 92 until dampener sleeve 160 strikes contact wall 92. Dampener sleeve 160 contains one or more notch 162 or similar opening. As dampener sleeve 160 approaches contact wall 92, notch 162 forms fluid passage 114 through which fluid 104 passes. Fluid 104, including fluid 104 escaping through fluid passage 114, dampens vibrations of armature 86.

[0042] Referring now to FIG. 5, a perspective view drawing of a notched dampener sleeve according to an embodiment of the present invention is shown. Dampener sleeve 160 is shown having two notches 162. As will be recognized by one of ordinary skill in the art, the number and size of notches 162 will depend on a variety of factors including the characteristics of fluid 104, the amount of dampening required for armature 86, the design of armature 86, the force applied to flange 90 by spring 88, and the like. Dampener sleeve 160 may be constructed of a variety of engineering materials such as, for example, steel. Dampener sleeve 160 may be press fit onto flange 90, may be spot welded, may be formed as part of flange 90, and the like.

[0043] Referring now to FIG. 6, a cut view drawing of a control module defining a fluid passage channel according to an embodiment of the present invention is shown. Dampener sleeve 170, similar in construction to dampener sleeve 160, extends from flange 90 towards contact wall 92. In this embodiment, dampener sleeve 170 may or may not include notches 162. Channel 172 is formed in contact wall 92 in a portion of contact wall 92 where dampener sleeve 170 contacts contact wall 92. As spring 88 forces flange 90 towards contact wall 92, channel 172 forms fluid passage 114 through which fluid 104 passes. Fluid 104 around flange 90 provides dampening of vibrations such as those caused when dampener sleeve 170 strikes contact wall 92.

[0044] Referring now to FIG. 7, a cut view drawing of a control module with a dampener shim according to an embodiment of the present invention as shown. Control module 44 includes dampener shim 180 extending from contact wall 92. Fluid passage 114 is formed between dampener shim 180 and compression side 108 of flange 90 as flange 90 moves towards contact wall 92.

[0045] In an embodiment, compression side 108 is circular. Dampener shim 180 defines a circular opening with a radius smaller than the radius of compression side 108. Stop 112 extends from shaft 94 towards contact wall 92. When stator coil 84 is de-energized, spring 88 forces armature 86 towards contact wall 92. Stop 112 approaches contact wall 92 leaving fluid passage 114 open between flange 90 and dampener shim 180.

[0046] Dampener shim 182 in needle control valve 66 defines fluid passage 114 between flange 128 and dampener shim 182. The height of dampener shim 182 is adjusted such that passage 114 remains open when shaft 132 is against seat 136.

[0047] Referring now to FIG. 8, a cut view drawing of a control module with a dampener sleeve according to an embodiment of the present invention is shown. Dampener sleeve 190 extends from contact wall 92 towards flange 90. Fluid passage 114 is formed between shoulder 192 on flange 90 and dampener sleeve 190. Dampener sleeve 190 and flange 90 are designed such that stop 112 on shaft 94 contacts contact surface 92 leaving fluid passage 114 opened.

[0048] Dampener sleeve 194 extends from contact wall 130. Fluid passage 114 is formed between shoulder 196 on flange 128 and dampener sleeve 194 as flange 128 moves towards contact wall 130. Fluid passage 114 remains open when shaft 132 is seated on seat 136.

[0049] Referring now to FIG. 9, a plot of graphs illustrating control valve bouncing is shown. These graphs illustrate operation of fuel injector 20, such as described with regards to FIGS. 1 and 2, prior to the present invention. Plot 210 shows current applied to stator coil 84 of main control valve 62. Similarly, plot 212 shows stator current applied to coil 122 of needle control valve 66. Plot 214 shows the movement of armature 86 in main control valve 62 to close main control valve 62. Plot 216 shows the motion of armature 124 in needle control valve 66 to open needle control valve 66. Closing main control valve 62 and opening needle control valve 66 allows nozzle needle 38 to move so that fuel 28 escapes from fuel outlet 24 in fuel injector 20. The motion of nozzle needle 38 is shown in plot 218.

[0050] After approximately 1.8 milliseconds, current to stator 122 is switched off to close nozzle needle 38. Deactivating nozzle needle control valve 66 prior to the present invention causes compression side 144 of flange 128 to bounce off contact wall 130 causing ringing 222 in plot 216. Ringing 222 causes needle control valve 66 to bounce between an opened state and a closed state, creating extensive delay 224 between control signal 212 and the close of nozzle needle 38 as shown in plot 218. Turning off stator current 210 to stator coil 84 causes main control valve 62 to de-energize. Prior to the present invention, compression side 108 of flange 90 would bounce off contact wall 92 causing ringing 226 seen plot 214.

[0051] Referring now to FIG. 10, a plot of graphs illustrating vibration reduction according to an embodiment of the present invention are shown. These graphs illustrate fuel injector 20 implementing dampening as described with regards to FIGS. 1-3. Plot 240 illustrates stator current for main control valve 62 and plot 242 illustrates stator current for needle control valve 66 substantially the same as the control currents 210 and 212, respectively, in FIG. 9. The movement of armature 86 in main control valve 62, shown by plot 244, exhibits greatly reduced ringing. The motion of armature 124 in needle control valve 66, illustrated by plot 246, shows no ringing whatsoever. The reduced vibrations in valves 62, 66 results in less delay, indicated by time 252, between control signal 242 to close nozzle needle 38 and the time which nozzle needle 38 actually closes. In addition, the greatly reduced ringing and vibration decreases the wear on elements within fuel injector 20.

[0052] Referring now to FIG. 11, a cut view drawing of a control module with dampening on solenoid activation and on solenoid deactivation according to an embodiment of the present invention is shown. A control module, shown generally by 260, includes stator block 262 fixed within control module housing 264. Stator block 262 includes stator coil 266 for carrying electrical current. Armature 268 is biased away from stator coil 266 by spring 270. Spring 270 rests against steel shim 271. Shim 271 is fixed in housing 264 by steel plug 272. Shim 271 sets the force applied by spring 270.

[0053] Armature 268 is connected to control valve 274, which affects the flow of fuel by changing the area of a fuel port, not shown. Armature 268 moves through fluid 276 in cavity 278 formed by housing 264, first wall 280 on stator block 262, and second wall 282 of housing 264 opposite stator block 262.

[0054] Armature 268 is made of a magnetically attractable material. When stator coil 266 carries sufficient current, armature 268 is pulled toward stator block 262, compressing spring 270, moving first compression side 284 of armature 268 towards first wall 280. When stator coil 266 is de-energized, spring 270 forces armature 268 away from stator block 262, moving second compression side 286 of armature 268 towards second wall 282.

[0055] Stator block 262 is formed with indented ring 290 on first wall 280 near housing 264. Armature 268 includes extended ring 292, which fits into indented ring 290 as first compression side 284 approaches first wall 280. A first passage, shown generally by 294, is formed between first compression side 284 and first wall 280, between indented ring 290 and extended ring 292, and between armature 268 and housing 264 as first compression side 284 approaches first wall 280. First passage 294 permits some fluid 276 to escape while compressing some fluid 276. This action dampens vibrations caused when first compression side 284 approaches first wall 280. In the embodiment illustrated a mechanical stop, outside the view of FIG. 11, prevents armature 268 from contacting stator block 262.

[0056] Armature 268 includes extended ring 296 on second compression side 286. As armature 268 is forced by spring 270 away from stator block 262, extended ring 296 forms a second passage, shown generally by 298, between second compression side 286 and second wall 282. A mechanical stop, provided by control valve 274, by a portion of second compression side 286 extending beyond extended ring 296, or the like, prevents extended ring 296 from striking second wall 282. Fluid 276, caught between compression side 286 and second wall 282 and escaping through second passage 298, dampens contact vibrations from armature 268.

[0057] While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.

Claims

1. A control module for controlling fuel delivery in a fuel injector comprising:

a control module housing defining a cavity containing a fluid;

an armature disposed to move within the cavity;

a control valve operated by movement of the armature, the control valve affecting the flow of fuel by changing the area of a fuel port through which fuel passes;

a drive for moving the armature, the drive operative to move the armature towards a first wall of the cavity when the drive is activated and to move the armature towards a second wall of the cavity when the drive is deactivated;

a first fluid passage formed as the armature moves towards the first wall, the first fluid passage remaining open to pass fluid; and

a second fluid passage formed as the armature moves towards the second wall, the second fluid passage remaining open to pass fluid;

wherein armature vibration is dampened as fluid moves through the first fluid passage and the second fluid passage.

2. A control module as in claim 1 wherein at least one of the first fluid passage and the second fluid passage is formed by a dampener sleeve extending from the armature.

3. A control module as in claim 2 further comprising a stop which has a length in a direction of armature movement greater than a length of the dampener sleeve in the direction of armature movement.

4. A control module as in claim 2 wherein dampener sleeve comprises at least one notch.

5. A control module as in claim 1 wherein armature vibration dampening is provided by at least one of a first channel in the first wall forming the first fluid passage and a second channel in the second wall forming the second fluid passage.

6. A control module as in claim 1 wherein at least one of the first fluid passage and the second fluid passage is formed between a compression side and a dampener shim.

7. A control module as in claim 6 wherein the compression side is circular and the dampener shim defines a circular opening having an opening radius smaller than the compression side radius.

8. A control module as in claim 7 further comprising a stop extending from the compression side a distance greater than the thickness of the dampener shim.

9. A control module as in claim 1 wherein the armature defines a shoulder at least partially around the armature, at least one of the first fluid passage and the second fluid passage formed between a dampener sleeve and the shoulder.

10. A control module as in claim 1 wherein the housing further defines a second cavity within which is at least partially disposed a second armature, the second armature forming at least one second armature fluid passage, wherein fluid exiting the second armature cavity through the at least one second armature fluid passage provides dampening of the second armature.

11. A method of controlling a flow of fuel in a fuel injector comprising:

moving an armature in a cavity containing fluid;

changing an opening area of a fuel port through the movement of the armature, thereby affecting the flow of fuel; and

forming at least one fluid passage, the at least one fluid passage comprising at least one of a first fluid passage and a second fluid passage, the first fluid passage for passing fluid between the armature and a first wall defining the cavity as the armature moves towards the first wall, and the second fluid passage for passing fluid between the armature and a second wall defining the cavity as the armature moves towards the second wall.

12. A method of controlling a flow of fuel in a fuel injector as in claim 11 wherein forming the at least one fluid passage comprises moving a dampener sleeve extending from the armature in a direction of armature motion.

13. A method of controlling a flow of fuel in a fuel injector as in claim 11 wherein forming the at least one fluid passage comprises capping a portion of a channel.

14. A method of controlling a flow of fuel in a fuel injector as in claim 11 wherein forming the at least one fluid passage comprises narrowing a gap between the armature and a dampener shim.

15. A method of controlling a flow of fuel in a fuel injector as in claim 11 wherein forming a fluid passage comprises narrowing a gap between a shoulder on the armature and a dampener sleeve fixed within the cavity.

16. A method of controlling a flow of fuel in a fuel injector as in claim 15 further comprising contacting a valve stop to prevent the gap from closing.

17. A fuel injector comprising:

an injector body defining a fuel outlet;

a fuel delivery path for delivering pressurized fuel to the fuel outlet; and

a control module connected to the fuel delivery path, the control module including at least one solenoid for controlling fuel delivery, each solenoid having an armature driven by the solenoid to approach a wall defining a cavity when the solenoid is energized, the armature and the wall forming a passage as the armature approaches the wall, the passage passing fluid to dampen vibrations caused by the armature approaching the wall.

18. A method of injecting fuel into an engine comprising:

compressing the fuel;

supplying the compressed fuel to an opening in an injector through a controlled path;

activating a solenoid in the injector to control the flow of fuel along the path, the solenoid having an armature traveling through a fluid containing cavity, the solenoid causing the armature to approach a wall defining the cavity;

forming a passage as the armature approaches the wall;

passing fluid from between the armature and the wall through the passage; and

dampening vibrations by passing the fluid.

19. A method of injecting fuel into an engine comprising:

compressing the fuel;

supplying the compressed fuel to an opening in an injector through a controlled path;

changing the state of a solenoid in the injector to control the flow of fuel along the path, the solenoid having an armature traveling through a fluid containing cavity, the solenoid state change causing the armature to approach a wall defining the cavity;

forming a passage as the armature approaches the wall;

passing fluid from between the armature and the wall through the passage; and

dampening vibrations by passing the fluid.

20. A method of injecting fuel into an engine comprising:

compressing the fuel;

supplying the compressed fuel to an opening in an injector through a controlled path;

energizing a solenoid in the injector to control the flow of fuel along the path, the solenoid having an armature traveling through a fluid containing cavity, the energized solenoid moving the armature to approach a first wall defining the cavity;

forming a first passage as the armature approaches the first wall, the first passage passing fluid from between the armature and the first wall;

de-energizing the solenoid in the injector moving the armature to approach a second wall defining the cavity; and

forming a second passage as the armature approaches the second wall, the second passage passing fluid from between the armature and the second wall.