Pole piece retention and insertion method

Abstract

A fuel injector includes an injector body which accommodates a pole piece of a solenoid actuator. A top portion of the injector body includes a cylindrically formed generally open-ended recessed portion. The recessed portions accommodates a generally cylindrical pole piece, wherein the pole piece includes a bore located along a central axis to provide a fuel flow path. The top portion of the pole piece includes a cylindrically formed recess so as to form a sleeve or lip portion.

Claims

1. A fuel injector comprising: an upper housing; and an injector body which accommodates a cylindrical pole piece, where a top portion of said injector body includes a cylindrically formed open-ended recessed portion, said recessed portion accommodating the cylindrical pole piece, wherein said cylindrical pole piece includes a bore located along a central axis which provides a fuel flow path and a top portion of said cylindrical pole piece includes a cylindrically formed recess so as to form a sleeve including a lip portion; wherein a weld is formed at a junction of a distal end of the upper housing, an upper end of the injector body, and a distal portion of said sleeve.

2. A fuel injector as claimed in claim 1, wherein the distal portion of said sleeve including said lip portion extends beyond a top end of the injector body.

3. A fuel injector as claimed in claim 1, wherein the distal end of the upper housing and the upper end of the injector body are each in contact with the distal portion of said sleeve.

4. A fuel injector as claimed in claim 1, wherein said weld joins at least two of the following: the distal end of the upper housing, the upper end of the injector body, and the distal portion of said lip or sleeve portion.

5. A fuel injector as claimed in claim 1, wherein an outer diameter (OD) of the sleeve or lip portion and an inner diameter (ID) of the sleeve or lip portion are dimensioned such that: $0.7<\frac{\mathrm{ID}}{\mathrm{OD}}<0\text{.99}.$

6. A fuel injector as claimed in claim 1, wherein a thickness (L) of the sleeve or lip portion and an outer diameter (OD) of the sleeve or lip portion are dimensioned such that: $0.1<\frac{L}{\mathrm{OD}}<0.5.$

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Preferred The present invention is now described by way of example with reference to the accompanying drawings in which:

(2) FIG. 1 shows a current known design showing the schematically the top portion of a solenoid operated fuel injector.

(3) FIG. 2 shows an arrangement according to one aspect.

(4) FIG. 3 shows the salient portion of FIG. 2 in more detail.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) FIG. 1 shows a current known design showing the schematically the top portion of a solenoid operated fuel injector.

(6) An injector outer housing 1 contains an injector body 2. The injector body is in the form of a generally hollow cylindrical housing has generally a closed upper end and contains the pole piece. The pole piece 3 comprises a generally cylindrical body and along the longitudinal central axis thereof is formed a fuel flow channel i.e. an internal fuel passage. An electrical connector piece 4 provides electrical connection and terminals. An upper housing 5 is fitted onto the arrangement as shown.

(7) The welding 6 is performed around/at the bottom (rim) portion and the top of the injector body after the pole piece is press fitted.

(8) FIG. 2 shows an arrangement according to one aspect which shows the pole piece/upper housing/injector body assembly. The same components have generally the same components as FIG. 1. Here the injector body 22 is formed open ended at the top. The pole piece 3 is fitted i.e. inserted into this open end. The weld portion has reference numeral 10.

(9) FIG. 3 shows the salient portion in more detail.

(10) The pole piece at the upper end has a sleeved portion 7 defining a circumferential rim or lip portion 8. At the bottom of the recess the fluid passage 9 is provided, and so a shoulder portion is formed.

(11) The pole piece sleeve forming the relatively long thin (circumferential) lip provides two functions: It is used as a backup lip for the welding to prevent weld splatters and by appropriate dimensioning, stresses are minimized in the area improving significantly the pressure strength of the injector pressure vessel, formed by the injector body and arrangement shown.

(12) Welding is performed through the upper housing and the injector body and partially through the pole piece maintaining the three components in a tight assembly. The weld region is shown with reference numeral 10.

(13) The inner diameter of the sleeve (ID) must be as close as possible to the outer diameter (OD) to prevent high difference of area. The lip length L must be sufficient to allow a “smooth stiffness transition” between the assemble components.

(14) The arrangement provides a decrease of the stress of the assembly under pressure while ensuring the retention of the pole piece through the weld.

(15) Preferably the range of the parameters can be defined as follow:

(16) $0.7<\frac{\mathrm{ID}}{\mathrm{OD}}<0.990.1<\frac{L}{\mathrm{OD}}<0.5$

(17) Where OD is the pole piece outer diameter, ID is the pole piece inner diameter, and L is the lip length defined between the center of the weld and the flat surface 11 of the pole piece.