Injector for fuel-injection system

Abstract

 An injector (10) has a single tapered valve (22) controlling fuel flow to a plurality of outlet passages (20). The entrance to each outlet passage has an orifice (42a,42b,42c,42d,42e,42f) surrounded by a raised valve seat (28a,28b,28c,28d,28e,28f). Each valve seat (28a,28b,28c,28d,28e,28f) is separated from the other valve seats by a recessed space (38). The valve (22) pivots about one end thereof as it is displaced from the valve seats to allow fuel flow through the outlet passages, and is constrained against other motion within the injector. The valve seats (28a,28b,28c,28d,28e,28f) are clustered beneath the opposite, free end of the valve (22). The orifices are sized to compensate for the unequal lift of the tapered valve (22) from the valve seats (28a,28b,28c,28d,28e,28f).

Description

Technical field

[0001] This invention relates to a fuel-injection system for a multi-cylinder internal combustion engine in which a plurality of injection nozzles discharge fuel adjacent the engine inlet ports and a single injector meters the fuel to all of the injection nozzles as specified in the preamble of claim 1, for example as disclosed in EP-A-0 249 313.

[0002] An injector according to the present invention is characterised by the features specified in the characterising portion of claim 1.

Summary of the drawings

[0003] 

Figure 1 is a sectional view of a single injector that meters fuel to six injection nozzles in accordance with this invention.

Figure 2 is an enlarged sectional view of the lower portion of the Figure 1 injector, taken along the line 2-2 of Figure 1, showing an injector valve engaging its seat.

Figure 3 is a view similar to Figure 2, showing the injector valve lifted from its seat.

Figure 4 is an enlarged sectional view of the Figure 1 injector, taken along line 4-4 of Figure 1 and with various portions broken away, showing the relationship of the injector valve and the orifices through which the injector meters the fuel to the injection nozzles.

Detailed description

[0004] Referring to the drawings, an injector 10 has a body 12 that receives fuel through a plurality of radial inlet passages 14 surrounded by a filter 16. A distributor 18 threaded into the lower end of body 12 delivers fuel through six outlet passages 20, each of which directs fuel to an associated injection nozzle.

[0005] A valve 22 controls the delivery of fuel through passages 20. As shown in Figure 2, valve 22 is biased by a spring 24 to engage a planar surface 26 formed by raised valve seat lands 28, each one surrounding a respective one of the passages 20, and thereby to interrupt fuel delivery through passages 20.

[0006] Injector 10 includes a solenoid having a coil 30, a centre pole 32 surrounding spring 24, a spacer ring 34 surrounding valve 22 and sandwiched with a shim 36 between body 12 and distributor 18, and an armature formed by valve 22. Valve 22 is tapered from its thickest portion on the left as viewed in Figures 2-3 to its thinnest portion on the right. When coil 30 is energized as shown in Figure 3 to actuate valve 22, the thickest portion of valve 22 engages shim 36 and causes the valve to pivot about its left edge, thereby lifting the valve 22 from lands 28 to allow fuel delivery through passages 20.

[0007] Each land 28 is separated from the other lands by a recessed space 38 between the lands. The recessed space 38 assures that each land 28 is isolated from the other lands to minimize the effect or interaction of fuel delivery through any one passage 20 on fuel delivery through the other passages.

[0008] Because valve 22 pivots as it lifts from lands 28, the clearance between valve 22 and lands 28a and 28b is less than the clearance between valve 22 and lands 28c and 28d which in turn is less than the clearance between valve 22 and lands 28e and 28f. Unless otherwise compensated, the differences in clearance would create undesirable inequalities in fuel delivery through passages 20.

[0009] To minimize the differences in clearance, passages 20 are clustered beneath the right, free end of armature valve 22, and pins 40 hold valve 22 in alignment with passages 20. Pins 40 are imbedded in distributor 18 and constrain the movement of valve 22 to the pivotal motion described above, preventing valve 22 from rotating on distributor 18.

[0010] To compensate for the remaining differences in clearance, an orifice formed at the entrance to each passage 20 is sized to assure equal fuel delivery through passages 20. Orifices 42a and 42b associated with lands 28a and 28b are larger than orifices 42c and 42d associated with lands 28c and 28d, and orifices 42c and 42d in turn are larger than orifices 42e and 42f associated with lands 28e and 28f. In one embodiment, the clearance between valve 22 and lands 28a and 28b is about 0.0056 and the diameter of orifices 42a and 42b is about 0.041, the clearance between valve 22 and lands 28c and 28d is about 0.0060 and the diameter of orifices 42c and 42d is about 0.0395, and the clearance between valve 22 and lands 28e and 28f is about 0.0065 and the diameter of orifices 42e and 42f is about 0.038.

[0011] Specific dimensional units are not quoted for the above figures for the various clearances and diameters, since it is only the proportions of these figures, one to the other, which are significant.

[0012] Stated another way, the dimensional relationships between the respective clearances and the diameters of the orifices in this embodiment are such that the clearance between valve 22 and lands 28a and 28b is 86.15% of the clearance between valve 22 and lands 28e and 28f, and the clearance between valve 22 and lands 28c and 28d is 92.30% of the clearance between valve 22 and lands 28e and 28f; whilst the diameter of the orifices 42a and 42b is 108% of the diameter of orifices 42e and 42f, and the diameter of the orifices 42c and 42d is 104% of the diameter of orifices 42e and 42f.

[0013] Injector 10 also includes an invention as set forth in European patent application No. filed concurrently herewith.

Claims

1. An injector (10) comprising a distributor (18) having a plurality of outlet passages (20) and an orifice at the entrance of each of said passages (20) and a valve seat (28) surrounding said orifices, a tapered valve (22) biased to engage said valve seat (28) to interrupt fuel delivery through said outlet passages, and a valve actuator (30) adapted to pivotally displace said valve (22) from said valve seat (28) to allow fuel delivery through said passages (20), said valve (22) pivoting about one end thereof as it is displaced, characterised in that there is a valve seat (28a,28b,28c,28d,28e,28f) surrounding each orifice (42a,42b,42c,42d,42e,42f); the lift of said valve (22) from the valve seats (28e,28f) furthest from said end of said valve (22) is greater than the lift of said valve (22) from the valve seats (28a,28b) closest to said end of said valve (22); and said orifices (42a,42b,42c,42d,42e,42f) are sized to compensate for the differences in lift of the valve (22) from the associated valve seats (28a,28b,28c,28d,28e,28f), the orifices (42a,42b) associated with the valve seats (28a,28b) closest to said end of said valve (22) being larger than the orifices (42e,42f) associated with the valve seats (28e,28f) furthest from said end of said valve (22).

2. An injector (10) according to claim 1, characterised in that the lift of said valve (22) from the valve seats (28e,28f) furthest from said end of said valve (22) is about 0.0060; the lift of said valve (22) from the valve seats (28a,28b) is about 0.0056; the orifices (42a,42b) associated with the valve seats (28a,28b) closest to said end of said valve (22) have a diameter of about 0.041; and the orifices (42e,42f) associated with the valve seats (28e,28f) furthest from said end of said valve (22) have a diameter of about 0.038.

Drawing