METHOD FOR ADJUSTING A FUEL INJECTOR VALVE LIFT

Abstract: A method for controlling fuel injector lift control provides accurate lift dimensions over the life of the injector 10. The method can be implemented by sophisticated equipment for more automated operation but the steps of measuring and determining the spacing between the pole piece 18 and the armature member 26 and forming a spacer 12 as a result of such measurements, substantially follow the concept of dif­ ferential gaging 36 and stepper motor 52 controlled press 38. Once a spacer 12 is sized, it is mated with the housing member 14 and the valve body assembly 24 and held in place by unitiz­ ing the injector 10.

Description: This invention relates in general to a method for controlling fuel injector lift and more particularly to a low cost spacer and method for permanently establishing injector valve lift in production injectors. Most fuel injection systems, either single point or multipoint systems, use electromagnetic fuel injectors for controlling the flow of fuel into the engine. The amount of lift, the actual opening height of the valve, is directly proportional to the working air gap between the pole piece and the armature of the solenoid controlling the movement of the valve. The force of the solenoid is proportional to the square of the distance between the pole and the armature. The tolerance of the lift dimension of fuel injectors is plus or minus five microns (0,005 mm), therefore, very precise control of the working air gap of the solenoid is required. One of the more common means of accurately setting the lift of an injector is the placement of a precision ground spacer between the injector housing assembly and the valve body assembly. The spacer thickness is determined by accurately measuring the armature and the pole piece relative to axially spaced and aligned surfaces. From a comparison of these two measurements and with the addition of the measurement representing the desired lift, a ground spacer is added at assembly. This operation, which is also described as arising difficulties in US-A-4,509,693 requires the stockpiling of several different sizes of pre-ground spacers to be available during the assembly of the injectors resulting in hand assembly of each of the injectors and the resultant highly labor intensive product. In GB-A-2 058 466, there is used a plastically deformable spacer ring in an electromagnetic fuel injection valve. In this reference, the apparatus for setting the correct stroke of the armature during assembly of the valve cannot be applied to the injector of the present invention. It is an advantage of the present invention to control the lift of an injector by means of an automatic assembly process wherein each injector has a custom made lift control spacer. It is a further advantage to reduce the labor intensive cost of manufacturing fuel injectors. According to one aspect of the invention, these and other advantages result from a method for automatically adjusting a fuel injector valve lift and assembling an unitary fuel injector having a valve body member, an armature therein controlling the valve opening, a housing member having a pole piece magnetically coupled to the armature and a spacer member for fixing the lift, said method comprising the following steps of an automatic assembly process: forming a spacer having a first predetermined spacer thickness which is greater than the lift of the injector; measuring a first distance (Y) between one end of the armature and a first surface on the valve body member (24); measuring a second distance (X) between one end of the pole piece and a second surface on the housing member (14); calculating the desired spacer thickness according to said first and second distances and the desired armature lift; generating an electrical signal in response to said calculation; controlling, in response to the electrical signal, the stroke of a first press (38) having an upper and lower shoe means (54, 56) for limiting the final spacing of the anvils (58,60) of the press means when operated; positioning the spacer ring between said anvils of said first press; actuating the first press and compressing the spacer ring to said desired spacer thickness; and placing said desired spacer between the first and second surfaces of the valve body member and the housing member in a second press and forming a unitary fuel injector. According to another of its aspects, the invention relates to a system for automatically adjusting a fuel injector valve lift from a valve body member, an armature therein controlling the valve opening, a housing member having a pole piece magnetically coupled to the armature, each body member, pole piece, armature, and housing member having acceptable tolerance dimensioning with a spacer member having a calculated thickness fixing the lift of the injector, the system having a gaging device for measuring a first distance (Y) between one end of the armature and a first surface on the valve body member (24) and for measuring a second distance (X) between one end of the pole piece and a second surface on the housing member (14), a calculator to determine the desired spacer thickness according to the first and second distances and the desired armature lift and a generator responsive to said calculation to generate an electrical signal, a first press (38) having an upper and lower shoe means (54, 56) for limiting the final spacing of the anvils (58,60) of the press when operated, the system characterized by: spacer supply means supplying a spacer having a first predetermined spacer thickness which is greater than the lift of the injector between the anvils of the press; actuating means responsive to the electrical signal for actuating the first press to compress said spacer between the anvils to the desired spacer thickness; and a second press receiving said desired spacer between the first and second surfaces of the valve body member and the housing member, respectively, and assembling and forming a unitary fuel injector having a predetermined injector lift. In the drawings: Figure 1 is a sectional plan view of an injector illustrating the utilization of the spacer of the present invention. FIGURE 2 is a sectional plan view of one of the mating parts of the injector illustrating the one of the measured dimensions. FIGURE 3 is sectional plan view of another of the mating parts of the injector illustrating another of the measured dimensions. FIGURE 4 is a schematic drawing of the process utilized in the practice of the invention. DETAILED DESCRIPTION FIGURE 1 is an example of a top feed fuel injector 10 utilizing the spacer 12 of the present invention. The injector housing member 14 as shown in FIGURE 3 contains the solenoid coil 16 and the pole piece 18 for the electromagnetic circuit. The pole piece 18 illustrated in FIGURE 3, has an adjusting elongated tube 20 for the transporting of fuel the length of housing member 14 to the valve member 22 in the valve body assembly 24 of FIGURE 2. The upper portion of the valve member 22 is the armature member 26 and it is the space between the pole piece 18 and the armature member 26 that defines the "Lift" of the injector 10. Referring to FIGURE 3, there is illustrated the injector housing member 14 comprising the pole piece 18, connector cap 28 and solenoid coil 16 along with some of the seals 30 used in the injector 10. As illustrated in FIGURE 1, an adjusting elongated tube 20 is inserted in the pole piece 18. The adjusting elongated tube 20 has as one of its functions, to preload the bias spring 32. The bias spring 32 bears against the valve member 22 to close the valve 34 in the valve body assembly 24 of FIGURE 2. The upper portion of the valve member 22 is an armature member 26 which is magnetically attracted to the pole piece 18 under the control of the solenoid coil 16. The lower portion of the valve member 22 functions to seal the valve 34 when in its biased position and to open the valve 34 when the armature member 26 is attracted to the pole piece 18. The amount of travel of the armature member 26 is the Lift of the injector 10. Lift is proportional to the amount of valve 34 opening. As such, Lift is a fixed amount or dimension for each injector 10. Lift is a predetermined value that is designed into the injector 10 and as such has been set into the injector 10 at assembly by means of selection of properly ground spacer 12 placed between the pole piece 18 and the armature member 26. In prior art injectors, the Lift was set after the injector 10 was assembled by means of a threaded adjustment. In the present invention, Lift is determined by means of differential gaging 36 and the results of such gaging are supplied to a controlled press 38 for deforming an annealed ring from a ring supply 40 to the proper size. The sized ring or spacer 12 is then automatically assembled with the housing member 14 and the valve body assembly 24 which were subject to the differential gaging 36. Referring to FIGURES 2 and 3, the relationship between the measured dimensions, the spacer thickness and lift is as follows: From FIGURE 2 measure the distance "Y" between surface "a" and surface "b". From FIGURE 3 measure the distance "X" between surface "c" and surface "d". wherein: surface "a" is a first surface 42 of the valve body assembly 24; surface "b" is the surface 44 of the armature member 26; surface "c" is the surface 46 of the pole piece 18; surface "d" is a second surface 48 of the housing member 14; and the first and second surfaces 42,48 are axially aligned opposing surfaces that are spaced apart in the magnetic circuit of the completed injector 10. Refering to FIGURE 4, there is illustrated a schematic of the manufacturing system 50 for acomplishing the advantages of this invention. A housing member 14 and a valve body assembly 24 are individually gaged by differential gaging 36 to measure the "X" and "Y" dimensions. In accordance with the equation (1) spacer thickness = Lift + y-x, knowing the desired Lift, the spacer 12 thickness is determined. This value is supplied to a stepper motor 52 to position the lower shoe 54 of the press 38. The shoes 54,56 cooperate to limit the travel of the anvils 58,60 of the press 38 and thereby control the thickness of the spacer 12. In the preferred embodiment, the shoes 54,56 are a pair of tapered stops which have a two degree (2°) taper. The degree of taper is a mere matter of design as it is a function of the desired amount of horizontal travel for a given amount of vertical spacing. The anvils 58,60 of the press 38 are nominally spaced apart and depending upon the relative position of the shoes 54,56, the thickness of the spacer 12 is determined. The stepper motor 52, in response to the value of the differential gaging 36, will move the lower shoe 54 a linear distance proportional to the change in spacer 12 thickness from a nominal dimension. In the preferred embodiment, for each degree of taper, the spacer 12 thickness changes seventeen thousandths of an inch per inch (.017'') (.43mm) of travel of the lower shoe 54. The spacer 12, in the preferred embodiment, is an annealed split wire ring. The spacer 12 is placed between the anvils 58,60 of the press 38. The housing member 14 and the valve body assembly 24 are measured and the results of the differential gaging 36 are supplied to the control for the stepper motor 52. The lower shoe 54 is positioned and the press 38 is operated. The mating of the tapered upper shoe 56 and the tapered lower shoe 54 limits the travel of the press anvils 58,60, thereby controlling the thickness of the spacer 12. The spacer 12 is then removed from the press 38 and inserted in the housing member 14 on the second surfaces 48. The valve body assembly 24 with the seal 30 is placed in the housing member 14 with the first surface 42 on the spacer 12. The housing member 14 and the valve body assemby 24 are placed together in a second press and brought together retaining the spacer 12 between and in contact with the first and second surfaces 42,48. A swedging tool then curls over the end 62 of the housing member 14 to hold the housing member 14 and the valve body assembly 24 together. The spacer 12 may also be fabricated from a powered or sintered metal composition which is sized and then fired to harden. The hardened powered metal spacer is then placed between the housing member 14 and valve body assembly 24 abuting the first and second surfaces 42,48 and held in place as described above. The completed injector 10 is then removed from the second press and moved to subsequent operations 64 for further assembly and calibrations. The result at this time is an injector that has a predetermined Lift that is held to a tolerance that will provide very accurate fuel quanity discharge when actuated. There has thus been shown and described a method and article 12 for fuel injector lift control. The method can be implemented by more sophisicated equipment for more automated operation but the steps of measuring and determining the spacing between the pole piece 18 and the armature member 26 and forming the spacer 12 as a result of such measurements, will be substantially the same. Once a spacer 12 is sized, it is mated with the housing member 14 and the valve body assembly 24 and held in place.

Claims: Method for automatically adjusting a fuel injector valve lift and assembling an unitary fuel injector having a valve body member, an armature therein controlling the valve opening, a housing member having a pole piece magnetically coupled to the armature and a spacer member for fixing the lift, said method comprising the following steps of an automatic assembly process: forming a spacer having a first predetermined spacer thickness which is greater than the lift of the injector; measuring a first distance (Y) between one end of the armature and a first surface on the valve body member (24); measuring a second distance (X) between one end of the pole piece and a second surface on the housing member (14); calculating the desired spacer thickness according to said first and second distances and the desired armature lift; generating an electrical signal in response to said calculation; controlling, in response to the electrical signal, the stroke of a first press (38) having an upper and lower shoe means (54, 56) for limiting the final spacing of the anvils (58,60) of the first press when operated; positioning a spacer ring between said anvils of said first press; actuating the first press and compressing the spacer ring to said desired spacer thickness; and placing said desired spacer between the first and second surfaces of the valve body member and the housing member in a second press and forming a unitary fuel injector. A system for automatically adjusting a fuel injector valve lift from a valve body member (24), an armature (26) therein controlling the valve opening, a housing member (14) having a pole piece (18) magnetically coupled to the armature (26), each body member, pole piece, armature, and housing member having acceptable tolerance dimensioning with a spacer member (12) having a calculated thickness fixing the lift of the injector, the system having a gaging device (36) for measuring a first distance (Y) between one end of the armature (26) and a first surface (42) on the valve body member (24) and for measuring a second distance (X) between one end of the pole piece (18) and a second surface (48) on the housing member (14), a calculator to determine the desired spacer thickness according to the first and second distances and the desired armature lift and a generator responsive to said calculation to generate an electrical signal, a first press (38) having an upper and lower shoe means (54, 56) for limiting the final spacing of the anvils (58,60) of the press when operated, the system characterized by: spacer supply means (40) supplying a spacer having a first predetermined spacer thickness which is greater than the lift of the injector between the anvils (58,60) of the first press (38); actuating means (52) responsive to the electrical signal for actuating the first press (38) to compress said spacer between the anvils to the desired spacer thickness; and a second press receiving said desired spacer between the first and second surfaces of the valve body member (24) and the housing member (14), respectively, and assembling and forming a unitary fuel injector having a predetermined injector lift. The system of Claim 2 wherein the gaging device is a differential gaging device.

Inventors: HENSLEY, THOMAS EDWARD
Applicants: SIEMENS AKTIENGESELLSCHAFT
Application year: 1986
Main classification: F02M51
IPC codes: F02M51, F02M61, F02M65