GB2364104A

GB2364104A - Adjustable check stop for variable lift of the check valve member in a fuel injector

Info

Publication number: GB2364104A
Application number: GB0115631A
Authority: GB
Inventors: Chetan J Desai; Xinshuang Nan
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2000-06-29
Filing date: 2001-06-27
Publication date: 2002-01-16
Also published as: DE10128416A1; GB0115631D0

Abstract

The lift of the check valve member 20 can be restricted to a micrometering position by a check stop 22 that is hydraulically locked in place. The hydraulic lock is released to allow the check stop 22 to withdraw so that the check valve member 20 can move to its fully open position. The check stop 22 is located in a check stop control chamber 24 and an end of the spring-biassed check valve member 20 is located in a check valve control chamber 26. An electronically controlled valve 28 can open or close the fluid connection between the control line 12 and the check stop control chamber 24. The valve 28 may include a brass, piezo, or magnetotrictive element.

Description

2364104

1 Description

2 3 ADJUSTABLE CHECK STOP FOR VARIABLE CHECK LIFT 4 IN A FUEL INJECTOR 6 Technical Field

7 This invention relates generally to fuel 8 injectors utilizing check valves, and more 9 particularly to micrometering or varying fuel injection rates by using a variable-position check 11 stop.

12 13 Background Art

14 Over time, engineers have come to recognize that undesirable exhaust emissions can be reduced by 16 having the ability to produce at least three different 17 fuel injection rate shapes across the operating range 18 of a given engine These rate shapes include a ramp, 19 a boot shape, and square fuel injection profiles.

Engineers believe that by injecting a small amount of 21 fuel just before main fuel injection to "prime" a fuel 1 combustion chamber undesirable exhaust emissions and 2 engine noise can be reduced.

3 In addition, engineers also believe that by 4 producing a "split injection" of varying quantities of fuel, combustion efficiency at some operating 6 conditions, such as at idle, can be improved, and 7 noise (especially at idle) can be reduced.

8 Although there exist a wide variety of 9 mechanisms for pressurizing fuel in fuel injection systems, most fuel injectors include a spring biased 11 needle check valve to open and close the nozzle 12 outlet In most fuel injectors, the needle valve 13 member is only stoppable at two different positions:

14 fully open or fully closed Because the needle valve members in these fuel injectors are not normally 16 stoppable at a partially open position, fuel injection 17 mass flow can usually be controlled only through 18 changes in fuel pressure.

19 Hydraulic bias control of the check valve is also possible, such as taught in U S Patent 21 No 6,024,296 to Wear et al Dual-stage spring 22 nozzles have also been used, but these can produce 23 slower injection rate changes than desired Another 24 approach is dual nozzle design, but this is an expensive solution.

26 It would be advantageous to have a reliable 27 mechanism for accurately varying maximum check lift 28 for rate shaping purposes For example, being able to 29 selectively reduce maximum lift of the check valve member from one shot to the next could help provide 1 precise control of pre-metering, micrometering, and 2 post injection that is, injecting a very small 3 amount of fuel prior to or after a main injection.

4 This could improve operation of the fuel injector, especially to reduce noxious emissions and/or to 6 reduce noise of operation, as explained above.

7 Variable check lift could be advantageous for other 8 purposes as well Accurate methods of achieving very 9 small fuel volume pre-metering or micrometering are always of interest.

11 This invention is directed to addressing 12 these and other concerns associated with controlling 13 needle valve lift within fuel injectors.

14 Disclosure of the Invention

16 In a first aspect of the invention, a fuel 17 injector comprises a fuel chamber, an orifice, a check 18 valve, and a check stop The check valve is movable 19 in a first direction to a first check valve position that closes fluid communication between the fuel 21 chamber and the orifice, is movable in a second 22 direction to a second check valve position that 23 fluidly connects the fuel chamber with the orifice in 24 a restrictive manner, and is movable in the second direction to a third check valve position that fluidly 26 connects the fuel chamber with the orifice in a less 27 restrictive manner than the second position The 28 check stop is hydraulically movable between a first 29 stop position that limits movement of the check valve in the second direction to the second check valve 1 position, and a second stop position that allows the 2 check valve to move in the second direction to the 3 third check valve position.

4 In a second aspect of the invention, a method for controlling a check valve in a fuel 6 injector including a fuel chamber and an orifice 7 comprises moving the check valve in a first direction 8 to a first check valve position that closes fluid 9 communication between the fuel chamber and the orifice, hydraulically locking a check stop in a first 11 check stop position that limits movement of the check 12 valve in a second direction to a second check valve 13 position that fluidly connects the fuel chamber with 14 the orifice in a restrictive manner, moving the check valve in the second direction to the second check 16 valve position while the check stop is hydraulically 17 locked in the first check stop position, hydraulically 18 releasing the check stop to allow the check stop to 19 move in the second direction from the first check stop position, and moving the check valve in the second 21 direction past the second check valve position to a 22 third check valve position that fluidly connects the 23 fuel chamber with the orifice in a less restrictive 24 manner than the second position.

In a third aspect of the invention, a fuel 26 injector comprises a fuel chamber, an orifice, and a 27 check valve The check valve is movable in a first 28 direction to a first check valve position that closes 29 fluid communication between the fuel chamber and the orifice, is movable in a second direction to a second 1 check valve position that fluidly connects the fuel 2 chamber with the orifice in a restrictive manner, and 3 is movable in the second direction to a third check 4 valve position that fluidly connects the fuel chamber with the orifice in a less restrictive manner than the 6 second position The fuel injector also comprises 7 means for hydraulically controlling movement of a 8 check stop between a first stop position that limits 9 movement of the check valve in the second direction to the second check valve position, and a second stop 11 position that allows the check valve to move in the 12 second direction to the third check valve position.

13 14 Brief Description of the Drawings

Features of the invention can be better 16 understood with reference to the drawing figures, in 17 which:

18 FIG 1 is a schematic view of a first 19 embodiment of a fuel injector utilizing the invention; FIG 2 is a nozzle and check valve portion 21 of the fuel injector of FIG 1; and 22 FIGS 3 a and 3 b are an example bimetallic 23 actuator and electromagnetic actuator, respectively.

24 Best Mode for Carrying Out the Invention

26 A first embodiment of a fuel injector 10 27 utilizing the invention is shown with reference to 28 FIGS 1 and 2 The fuel injector 10 includes a 29 control line 12 and a nozzle 14 having a fuel chamber 16 and a number of orifices 18 A check valve 20 1 extends into the fuel chamber 16 A spring 21 2 provides mechanical closing bias on the check valve 3 20 A check stop 22 partially defines a check stop 4 control chamber 24 An end of the check valve 20 opposite the fuel chamber 16 and an end of the check 6 stop 22 opposite the check stop control chamber 24 7 partially define a check valve control chamber 26.

8 An electronically controlled valve 28 9 provides a closable fluid connection between the control line 12 and the check stop control chamber 24.

11 The electronically controlled valve 28 can be any 12 appropriate hydraulic valve known in the art, for 13 example a miniature bimetallic actuator type valve 30 14 such as shown in FIG 3 a, utilizing a brass, piezo, or magnetostrictive actuation element for example, or an 16 electromagnetic actuator 32 such as shown in FIG 3 b.

17 18 Industrial Applicability

19 Operation of the invention is now described with reference to FIGS 1 and 2 The fuel injector 10 21 provides pressurized fuel to the fuel chamber 16, 22 which produces a hydraulic opening force on the check 23 valve 20 High-pressure hydraulic fluid in the 24 control line 12 fills the check stop control chamber 24 and a check valve control chamber 26.

26 The spring 21 and the high-pressure 27 hydraulic fluid in the check valve control chamber 26 28 produce mechanical and hydraulic closing force, 29 respectively, on the check valve 20 In its closed 1 position the check valve 20 keeps pressurized fuel in 2 the fuel chamber 16 from reaching the orifices 18.

3 For micrometering of fuel from the fuel 4 injector 10, the electronically controlled valve 28 is closed while the control line 12 and the check stop 6 control chamber 24 are still filled with high-pressure 7 hydraulic fluid This produces a hydraulic lock in 8 the check stop control chamber 24 When the high- 9 pressure hydraulic fluid leaves the control line 12 and the check valve control chamber 26, and high- 11 pressure fuel is in the fuel chamber 16, the check 12 valve 20 opens to a micrometering position, where 13 further opening movement by the check valve 20 is 14 stopped by the check stop 22 in its hydraulically locked position At this position the fuel chamber 16 16 is fluidly connected with the orifices 18 in a 17 restrictive manner That is, the flow area between 18 the check valve 20 and the wall of the fuel chamber 16 19 is smaller than the total flow area of the orifices 18.

21 For full or main fuel injection the 22 electronically controlled valve 28 is opened, allowing 23 the high-pressure hydraulic fluid to leave the check 24 stop control chamber 24 Then, when high-pressure fuel is in the fuel chamber 16 the check stop 22 can 26 open to its fully open position, providing less 27 restricted or unrestricted fluid communication between 28 the fuel chamber 16 and the orifices 18.

29 The invention can be used in various types of fuel injectors with or without direct check 1 control, using hydraulic or mechanical actuation, etc.

2 Many additional variations of the invention are 3 possible For example, in the illustrated embodiments 4 fuel pressure in the fuel chamber is variable and direct check control is provided by varying hydraulic 6 pressure in the check control chamber Consequently 7 the check valve can be opened and closed by varying 8 the fuel pressure in the fuel chamber, varying the 9 hydraulic pressure in the check control chamber, and/or a combination thereof.

11 The invention can also be used with valve 12 covered orifice (VCO) or mini-sac nozzles The 13 invention can also be used with the fuel as the check 14 stop control fluid In some embodiments high-pressure fuel, from a rail for example, could be used to 16 operate the intensifier piston.

17 In other embodiments the control line may 18 not extend to provide hydraulic bias against the check 19 valve, so that opening and closing of the check valve is effected by using a mechanical closing bias and 21 varying the fuel pressure in the fuel chamber In yet 22 other embodiments the fuel pressure in the fuel 23 chamber could be constant and opening and closing of 24 the check valve could be effected by varying hydraulic fluid pressure in the check control chamber Many 26 other such combinations involving hydraulic and/or 27 mechanical biases can be made by those skilled in the 28 art while practicing the claimed invention.

29 Accordingly, while the invention has been illustrated and described in detail in the drawings 1 and foregoing description, such illustration and

2 description are to be considered illustrative or

3 exemplary and not restrictive; other variations to the 4 disclosed embodiments can be made by those skilled in the art while practicing the claimed invention from a 6 study of the drawings, the disclosure, and the

7 appended claims.

Claims

1 Claims

3 1 A fuel injector, comprising:

4 a fuel chamber; an orifice; 6 a check valve movable in a first direction 7 to a first check valve position that closes fluid 8 communication between the fuel chamber and the 9 orifice, movable in a second direction to a second check valve position that fluidly connects the fuel 11 chamber with the orifice in a restrictive manner, and 12 movable in the second direction to a third check 13 valve position that fluidly connects the fuel chamber 14 with the orifice in a less restrictive manner than the second position; and 16 a check stop hydraulically movable between 17 a first stop position that limits movement of the 18 check valve in the second direction to the second 19 check valve position, and a second stop position that allows the check valve to move in the second 21 direction to the third check valve position.

23 2 The fuel injector of claim 1, wherein 24 the check stop in the second stop position limits movement of the check valve in the second direction 26 to the third check valve position.

28 3 The fuel injector of either claim 1 or 29 claim 2, further comprising:

a control line; 1 a check stop control chamber partially 2 defined by the check stop; and 3 an electronically controlled valve 4 providing a closable fluid connection between the control line and the check stop control chamber.

6 7 4 The fuel injector of claim 3, wherein 8 the electronically controlled valve comprises a 9 bimetallic actuator.

11 5 The fuel injector of claim 3, wherein 12 the electronically controlled valve comprises an 13 electromagnetic actuator.

14 6 The fuel injector of any of claims 3 to 16 5, further comprising a check valve control chamber 17 fluidly connected with the control line and partially 18 defined by the check valve and the check stop.

19 7 A method for controlling a check valve 21 in a fuel injector including a fuel chamber and an 22 orifice, the method comprising:

23 moving the check valve in a first direction 24 to a first check valve position that closes fluid communication between the fuel chamber and the 26 orifice; 27 hydraulically locking a check stop in a 28 first check stop position that limits movement of the 29 check valve in a second direction to a second check valve position that fluidly connects the fuel chamber 31 with the orifice in a restrictive manner; 1 moving the check valve in the second 2 direction to the second check valve position while 3 the check stop is hydraulically locked in the first 4 check stop position; hydraulically releasing the check stop to 6 allow the check stop to move in the second direction 7 from the first check stop position; and 8 moving the check valve in the second 9 direction past the second check valve position to a third check valve position that fluidly connects the 11 fuel chamber with the orifice in a less restrictive 12 manner than the second position.

14 8 The method of claim 7, further comprising moving the check stop to a second check 16 stop position that limits movement of the check valve 17 in the second direction to the third check valve 18 position.

9 The method of either claim 7 or claim 21 8, wherein hydraulically locking the check stop in 22 the first check stop position comprises:

23 filling a check stop control chamber 24 partially defined by the check stop with high- pressure fluid from a control line; and 26 closing an electronically controlled valve 27 to close fluid communication between the check stop 28 control chamber and the control line.

1 10 The method of claim 9, wherein the 2 electronically controlled valve comprises a 3 bimetallic actuator.

4 11 The method of claim 9, wherein the 6 electronically controlled valve comprises an 7 electromagnetic actuator.

8 9 12 The method of any of claims 9 to 11, further comprising fluidly connecting the control 11 line with a check valve control chamber partially 12 defined by the check valve and the check stop.

13 14 13 A fuel injector, comprising:

a fuel chamber; 16 an orifice; 17 a check valve movable in a first direction 18 to a first check valve position that closes fluid 19 communication between the fuel chamber and the orifice, movable in a second direction to a second 21 check valve position that fluidly connects the fuel 22 chamber with the orifice in a restrictive manner, and 23 movable in the second direction to a third check 24 valve position that fluidly connects the fuel chamber with the orifice in a less restrictive manner than 26 the second position; and 27 means for hydraulically controlling 28 movement of a check stop between a first stop 29 position that limits movement of the check valve in the second direction to the second check valve 31 position, and a second stop position that allows the 1 check valve to move in the second direction to the 2 third check valve position.

4 14 The fuel injector of claim 13, wherein the check stop in the second stop position limits 6 movement of the check valve in the second direction 7 to the third check valve position.

9 15 A fuel injector substantially as hereinbefore described with reference to the 11 accompanying drawings.

13 16 A method for controlling a check valve 14 in a fuel injector including a fuel chamber and an orifice substantially as hereinbefore described with 16 reference to the accompanying drawings.