FOR NEEDLE AND POPPET VALVE

FUEL INJECTORS

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to internal combustion engines, and more particularly relates to techniques for sensing the position of a needle or poppet valve in order to maximize the efficiency of engine operation and reduce unwanted exhaust emissions.

² - Description of the Prior Art

Diesel engines typically employ needle or poppet valves which are open and closed at timed intervals to inject desired amounts of fuel into the cylinder for combustion. In order to maximize fuel efficiency and minimize undesirable exhaust emissions, it is necessary to detect the opening of the valve in relation to the engine crankshaft position. The opening of the valve can then be set or controlled in timed relationship to the engine crankshaft position.

Known valves generally include a needle or poppet and a related seat. When the needle is in contact with the seat, the valve is closed. When the needle or poppet is lifted off the seat, the valve opens and fuel is metered through orifices into the engine cylinder. The initial displacement between the needle

- R__

or valve and its corresponding seat determine the beginning of injection. It is necessary to time or control the initial displacement of the needle or valve from the seat relative to the rotational position of the engine crankshaft, in order to maximize fuel efficiency, and at the same time reduce undesirable emissions.

It is known to determine timing by reference to visual markings on the engine flywheel. Techniques have also been developed to electronically measure the injection timing by determining needle position using inductive or capacitor devices positioned within a fuel injector nozzle holder; see U.S. Patents 4,066,059 and 4,096,841.

Creative Tool Company of Lyons, Illinois presently manufactures a product known as the "Diesel Tac-Time CT 4000". This device utilizes a split-nut transducer which is installed on an engine cylinder fuel line at either the injection pump or at the nozzle. Mechanical strains produced by pulses of fuel through the fuel line create a mechanical displacement of the line which is detected by the transducer.

SUMMARY OF THE INVENTION

The present invention contemplates a fuel injector or poppet fuel injection valve (collectively referred to as "fuel injection means") adapted to receive a position sensor to permit dynamic measurement of the needle or valve position, thus permitting determination of the beginning of injection point for engine timing. The injection means includes a needle or valve which is displaceable between open and closed positions. The injection means also includes an

internal chamber and means positioned within the chamber for biasing the needle or valve into the closed position. A passageway is provided in the injection means for establishing communication with the chamber from an external location. A sensor holder is position¬ ed within the chamber and aligned with the passageway for guiding the sensor into a predetermined position with respect to the needle or valve and for maintaining the sensor in a fixed position within the sensor holding means.

The sensor comprises a header of an electrically insulating material having opposed first and second surfaces and plural conductive leads, each lead separately coupled to the first surface of the header. Sensing means, such as a Hall effect detector, is mounted upon the second surface of the header for detecting a ' magnetic field and changes therein responsive to movement of the fuel injection means (such as the needle or poppet valve) . Metallization means between the first and second surfaces provide interconnection between the leads and the sensor. The leads, header and detector are all encapsulated, and are dimensioned for insertion into and out of a passageway in fuel injection apparatus including the fuel injection means. The sensor is dimensioned to pass through a passageway in the fuel injector apparatus, with the insulating encapsulating material and the header defining means which contact the passageway through which the sensor apparatus is positioned.

DESCRIPTION OF THE DRAWINGS

This invention is pointed out with particular¬ ity in the appended claims. However, other objects and advantages together with the operation of the invention may be better understood by reference to the following detailed description together with the following illustrations, wherein:

FIG. 1 is a partially cut away sectional view of a fuel injector including a needle position indicator according to the present invention.

FIG. 2 is a partially cut away perspective view particularly illustrating a Hall Effect sensor and mounting bracket in accordance with _, the present inven- tion.

FIG. 3 is a sectional view of a second embodiment of the Hall Effect sensor and its mounting bracket.

FIG. 4 is a sectional view of a fuel injector capable of receiving a needle position sensor.

FIG. 5 is a sectional view of one embodiment of the sensor holder which is positionable within the nozzle holder illustrated in FIG. 4.

FIG. 6 is a sectional view of a poppet fuel injector valve which has been modified in accordance with the present invention.

FIG. 7 is a sectional view of the poppet fuel injector valve illustrated in FIG. 6, taken along section line A-A. FIG. 8-10 illustrate top plan views of steps during the manufacture of one embodiment of a sensor in accordance with the present invention.

FIG. 11 is a top view of the sensor of Figures 8-10, with the encapsulating resin omitted.

FIG. 12 is a side view of Figure 11.

FIG. 13 is a bottom view of Figure 11, showing 5 the arrangement of the Hall Effect chip in the sensor.

FIG. 14 illustrates a portion of a fuel injector for an internal combustion engine, as employing the sensor of Figures 8-13.

FIG, 15 and 16 are side and bottom views, 10. respectively, of the encapsulated sensor of Figures 8- 13.

DETAILED DESCRIPTION OF THE INVENTION

5 In order to better illustrate the advantages of the invention and its contributions to the art, the various mechanical and electrical features of ^• a first preferred embodiment of a non-removable version of the invention will now be described in detail. 0 Referring to FIGS. 1 and 2, a commonly used fuel injector (10) is illustrated. Fuel injector (10) is of a conventional design and is commercially available from fuel injection equipment manufacturers such as Robert Bosch. A high pressure fuel line is 5 coupled to inlet port (12) of fuel injector (10) . Pressurized fuel is transferred from inlet port (12) through passageway (14) into the lower section of fuel injector (10) in which a needle valve is positioned. The needle valve includes a seat generally indicated by 0 reference number (16) and a needle (18) . A spring seat

(20) is held by the spring against the upper section of needle (18) and forms an upper extension of needle (18) .

Spring seat (20) moves in synchronization with the needle (18) .

A cylindrical spring (22) includes a central spring cavity or passageway (24) . Spring (22) is positioned within a cylindrical cavity (26) in fuel injector (10) . In the commercially manufactured version of fuel injector (10) , the upper end of the spring (22) contacts the upper end of cavity (26) while the lower end of spring (22) contacts spring seat (20) . In this manner spring (22) exerts a biasing force against the upper end of needle (18) to bias the lower end of needle (18) against needle seat (16) to maintain the needle valve in the closed position. ₍ Fuel pressure at an appropriate level within passageway (14) exerts a force on needle 18 and displaces the entire needle assembly including needle (18) and spring seat (20) upward. Upward displacements of needle (18) are generally on the order of 0.4 to 0.7 millimeters.

In the preferred embodiment of the first inven¬ tion, a cylindrical mounting bracket (28) includes a body which descends downward through the central spring cavity (24) of spring (22) . In the embodiment illustrated the body of mounting bracket (28) is approx¬ imately 25 millimeters long and has a diameter of 4.3 millimeters. Mounting bracket (28) also includes a flange (30) on the upper surface. Flange (30) is positioned between the upper surface of cavity (26) and the upper end of spring (22) . The upper biasing force exerted by spring (22) against the flange (30) which contacts the upper surface of cavity (26) serves to maintain mounting bracket (28) in a fixed position within the spring cavity (24) of spring (22) .

A commercially available three lead header

(32) is coupled to the lower portion of the body of mounting bracket (28) . Header (32) is a commercially

OMPI

available TO-46 device which has been modified by removing the flange which surrounds the commercially available version. Two of the leads of header (32) pass through insulators in the header and penetrate the lower surface of the device. The third lead is a ground lead which is coupled directly to the metallic body of the header. Header (32), utilized in the preferred embodi¬ ment of the first invention, is manufactured by Airpax Electronics Company of Cambridge, Maryland. The three electrical leads (34) extending upward from header (32) are fabricated from number thirty Teflon coated wire. Electrical leads (34) are routed upward through the body of mounting bracket (28) and pass through passageway (36) which forms a fuel leakage path by connecting the interior of cavity (26) through the hole (50) in mounting bracket (28) to fuel discharge port (38) . To permit electrical leads (34) to extend further upward and to be coupled to receptacle (40) , a passageway extention (42) is machined into the body of fuel injector (10).

A Hall effect sensor (44) is coupled to the lower surface of header (32) . Sensor (44) is manufac¬ tured on a single 1.245 m.m. by 1.270 m.m. integrated circuit chip by Sprague Electric Company of Concord, New Hampshire, and is designated by Model No. UGN-3501-M. This commercially available Hall effect sensor includes a voltage regulator, a Hall effect cell and an amplifier. A layer of epoxy encapsulation (46) sur¬ rounds the lower exposed surface of sensor (44) . The interior body of mounting bracket (28) is typically filled with a potting compound, such as epoxy material, to mechanically secure electrical leads (34) .

A samarium cobalt permanent magnet (48) is adhesively secured to the top surface of spring seat (20) . Magnet (48) is approximately two millimeters thick and is fabricated in a size which permits it to be positioned on the upper cylindrical surface of spring holder (20) without extending beyond the perimeter of this device. Magnet (48) is small, but produces a magnetic flux density of about 1200 Gauss. The upper surface of magnet (48) is separated from the lower surface of epoxy encapsulation (46) by a spacing of about one millimeter when the needle valve is in the resting or unactuated position. When needle (18) is displaced upward by about 0.4 to 0.7 millimeters as the needle valve is opened, the magnetic flux density in the vicinity of Hall effect sensor (44) is substantially changed, causing the output voltage of this device to change linearly in proportion to the displacement of needle (18) . This change in output voltage is trans¬ mitted by leads (34) to receptacle (40) . A monitoring device may be coupled to receptacle (40) and indicates both the upward and the downward displacements of needle

(18) which corresponds to either an increase or a decrease of the magnetic flux design within the cavity

(26). Referring now to FIG. 3, a modified version of the preferred embodiment of the present invention is disclosed. In this embodiment, permanent magnet (48) is coupled to the upper surface of header (32) . upward and downward displacements of spring seat (20) change the magnetic flux density in the vicinity of Hall effect sensor (44) since spring seat (20) is fabricated from a ferromagnetic material. These changes in the flux density cause changes in the output state of sensor (44)

in the same manner as that described above in connection with the embodiment illustrated in FIGS. 1 and 2.

FIG. 3 best illustrates that one or more vent holes (50) are positioned in the upper portion of mount- ing bracket (28) . Vent holes (50) permit the free flow of discharge fuel from cavity (26) into fuel discharge passageway (36) .

An oscilloscope may be coupled directly to receptacle (40) to monitor the output waveform generated by Hall effect sensor (44) . In this manner the timing of the needle valve opening and closing, the duration of injection, or continuous needle position can be monitored. In certain instances it may be desirable to couple a differentiator to receptacle (40) and couple an oscilloscope to the output of the differentiator. The differentiator produces a sharp readily disσernable voltage spike when the needle valve either opens or closes.

The needle position indicator of the invention may be included in each of the fuel injectors of an engine or may be included in only a single fuel injector since engine timing can be set by reference to the opening time of only a single needle valve. Alterna¬ tively, the needle position indicator of the invention may be included in a fuel injector which is maintained at a maintenance station. Whenever it is necessary to set engine timing, a mechanic can remove the convention¬ al fuel injector from the engine and insert a fuel injector including the needle position indicator of the invention. The engine timing can thus be readily set and monitored by electronic monitoring devices used by the mechanic. Use of the needle position indicator permits engine timing to be set while the engine is

OMPI

running and in addition enables engine timing to be on a continuous basis.

The needle position indicator of the invention may also be coupled to provide a feedback signal for use in a closed loop electronically controlled timing system for a fuel injection system. In another embodiment, the needle position indicator of the invention can be used to monitor wear of fuel injection system components by measuring engine timing changes, particularly at low speed. When the engine timing has changed a predeter¬ mined amount as indicated by relative timing of the opening of the needle valve, maintenance personnel can replace the appropriate fuel injection system element to prevent untimely mechanical failure. It would be apparent to those skilled in the art that the disclosed needle position indicator for a fuel injector may be modified in numerous ways and may assume many embodiments other than the preferred forms specifically set out and described above. For example, the invention can be incorporated in many different configurations of fuel injectors manufactured by many different organizations for use in passenger cars, tractors, trucks, ships, or any other type of diesel engine. Referring now to FIGS. 4 and 5, a second embod¬ iment of the needle position sensing system will now be described. This embodiment permits a needle position sensing device to be inserted into or removed from cylindrical cavity (26) without having to remove fuel injector (10) from the engine and without having to disassemble fuel injector (10) .

In the fuel injector embodiment illustrated in FIG. 4, a sensor passageway (52) is provided. The lower

portion of sensor passageway (52) is aligned with the hollow interior of sensor holding means (54) . The upper portion of sensor passageway (52) is inclined at an angle to the vertical, causing passageway (52) to inter- sect the exterior surface of fuel injector (10) at a desired location. Generally, the diameter of both the upper and lower sections of passageway (52) and the diameter of the upper section of sensor holding means (54) will be slightly larger than the diameter of an externally insertable sensing means (56) .

An aperture (58) is provided in the upper portion of sensor holding means (54) to permit unpres- surized fuel which has leaked into cylindrical cavity (26) to be discharged into the interior of sensor holding means (54) . The fuel passing through aperture (58) travels upward through sensor holding means (54) into the lower section of sensor passageway (52) . It will be generally desirable to provide a separate fuel leakoff passageway which may be oriented in a place perpendicular to the plane defined by the upper and lower sections of sensor passageway (52) . This separate fuel leak-off passageway is not specifically illustrat¬ ed in FIG. 4, but would extend between sensor passageway (52) and an exterior surface of fuel injector (10) . Leak-off fuel would then be coupled via a fuel discharge line back to the engine fuel tank.

The lower section of sensor holding means (54) includes a reduced diameter section indicated generally by reference number (60) . The diameter of section (60) is approximately equal to the maximum dimension of needle position sensing means (56) . The lower end of sensor holding means (54) includes means for preventing vertical translation of needle position sensor (56)

below a predetermined point. In the embodiment illu¬ strated in FIGS. 4 and 5, vertical translation prevent¬ ing means takes the form of a second reduced diameter section indicated generally by reference number (62) and includes a diameter less than the maximum diameter of needle position sensor (56) .

The upper portion of sensor passageway (52) is flared outward and is designed to receive a plug or cap (64) . Plug (64) includes a cylindrical lower section which is inserted into the sensor passageway (52) to prevent discharge of any leak-off fuel from this aperture in fuel injector (10) . Plug (64) may be manufactured from various different types of material such as rubber, plastic or cork and may assume many different configurations other than the specific configuration illustrated in FIG. 4. It may also be desirable to provide some type of locking means or threads for securely attaching plug (64) to sensor passageway (52) . Adaptions or modifications of this type would be well known by those skilled in the art.

As is illustrated in FIG. 4, the outer dimen¬ sion of sensor holding means (54) is less than the inner diameter of spring (22) . A flange (66) is formed by the upper end of sensor holding means (54) and serves to maintain the sensor holder in a fixed position within cavity (26) .

In the embodiment illustrated, a magnet (48) of the same type specified for the FIG. 1 embodiment is coupled to the upper surface of spring seat (20) to generate a magnetic field within the interior of cylindrical chamber (26) . As was discussed above, it is apparent that magnet (48) could be located at other positions within chamber (26) or alternatively could be

OMPI

coupled within sensing means (56) as is generally suggested by the configuration of the invention illu¬ strated in FIG. 3. In other embodiments, spring seat (20) , spring (22) or even other elements of the sensor holder might also be magnetized to provide the necessary magnetic flux density within the interior of cavity (26).

In this embodiment of the invention illustrat¬ ed in FIG. 4 including magnet (48) , a Hall effect sensor would be provided for sensing means (56) . This Hall effect device can be fabricated in the manner in connec¬ tion with the FIG. 1-3 embodiment discussed above. The Sprague Electric Company Hall effect sensor described above is also usable in this embodiment of the invention.

Many other different types of needle position sensing means could be substituted for the Hall effect sensor. For example, an eddy current proximity measur¬ ing device of a type generally similar to the proximity measuring system sold by Kaman Measurement Systems of Colorado Springs, Colorado could be utilized. An eddy current position sensing device uses an inductive operating principle to measure the distance between a coil (the sensing device) and a metallic object such as the moving needle spring seat system. The proximity of the sensor to the target material controls the operating amplitude of an oscillator. These amplitude variations are detected and electronically conditioned to provide an analog signal proportional to the displacement of the moving metallic object. The Kaman model KD-2400 proximity measuring system provides sensors of various dimensions. In the eddy current sensor version of the present invention, the sensor must be designed such that

it could be displaced through passageway (52) and inserted into sensor holder (56) as described above.

Inductive, capacitative or various other different kinds of sensing means could readily be adapted to be used with the fuel injector system illustrated in FIGS. 4 and 5.

A multi-conductor electrical cable (68) is coupled to sensing means (56) and serves a two-fold purpose. First, cable (68) provides electrical communication between an indicator unit (such as an oscilloscope) and sensing means (56) . Second, cable (68) serves as a tether for sensing means (56) and permits the removal and insertion of sensing means (56) into the desired fixed position in the lower portion of sensor holding means (54) . Cable (68) must be sufficiently flexible to flex around the corner formed between the upper and lower elements of sensor passage¬ way (52) . On the other hand, cable (68) must be sufficiently stiff to permit the user to externally apply a force which will cause sensing means (56) to be displaced into the appropriate position in the lower portion of sensor holding means (54) . As a result of the mechanical vibrations imparted by the engine to fuel injector (10) , it may be desirable for the operator to maintain a downward pressure or biasing force on cable (68) to maintain sensing means (56) firmly in position in the lower portion of sensor holding means (54) .

One of the primary advantages of the needle position sensing system described immediately above is a dramatic cost saving in comparison to the non-removable needle positions sensor illustrated in FIGS. 1-3. With the removable needle position sensing system, the

comparatively expensive sensor must only be inserted at the specific time when it is desired to adjust engine timing or to otherwise measure or control engine perfor¬ mance. Therefore, a single comparatively expensive sensor can at any time be inserted into or removed from a fuel injector of the type illustrated in FIG. 4.

If on the other hand, sensor (56) forms a part of a closed loop fuel injection system and therefore must be continuously present within fuel injector (10) , the removable feature of the present invention permits a defective sensor to readily be removed and replaced. It is thus not necessary to remove and replace the entire fuel injector assembly and thereby break the seal in the high pressure fuel injection system,.nor is it necessary to discard an entire fuel injector merely because the sensor has failed. In a closed loop fuel injection system of this type, cable (68) would be routed directly through the center of plug (64) so that plug (64) can be maintained in position in fuel injector (10) while cable (68) and sensor (56) are in position within fuel injector (10) .

It will be apparent to those skilled in the art that the disclosed removable needle position sensor system described above may be modified in numerous ways and may assume many embodiments other than the preferred forms specifically set out and described above. For example, needle position sensors not yet invented at the present time may be readily adaptable for use in the present invention or other presently available but excessively large position sensing devices- may be miniaturized in the future to a point where they can be inserted into the specially adapted fuel injector described above.

Referring now to FIGS. 6 and 7 of the present invention, a third embodiment is disclosed which is compatible with a poppet fuel injector. FIG. 6 represents an enlarged scale drawing of a miniaturized poppet fuel injector. Lucas C.A.V. Ltd. manufactures a miniaturized poppet fuel injector of the type illustrated in FIG. 6 under the trademark MICROJECTOR and this type of miniaturized fuel injector has been incorporated in the 350 cubic inch diesel engines utilized by General Motors in their diesel engine passenger vehicles. Certain structural modifications have been incorporated into this poppet valve as will be recited below. Unmodified, commercially available versions of this poppet fuel injector have a high pressure fuel line coupled to the upper end of the injector body. A cylindrical passageway permits a flow of pressurized fuel through the upper body of the injector into the chamber within which the poppet valve is incorporated. The poppet fuel injector illustrated in FIG. 6 receives pressurized fuel through a fuel inlet (70) . Fuel inlet fitting (72) may be fabricated from steel, such as Armco 17-4PH stainless, and includes a conical section indicated generally by reference number (74) . Conical section (74) tightly seals fuel inlet fitting

(72) to the body of fuel injector (76) . A locking nut

(73) maintains fuel inlet fitting (72) in fluid tight contact with the body of fuel injector (76) . A circular passageway (78) is cut in the inclined, exterior surface of the body of fuel injector (76) as illustrated in FIG. 6. Passageway (78) communicates with each of three vertically oriented fuel passageways indicated in FIGS. 6 and 7 by reference number (80) .

The lowermost portion of fuel passageways (80) opens into and communicates with a cavity (82) which houses poppet valve (84) . Poppet valve (84) is spring biased in ariN upward or closed position by spring (86) . A miniature, high power magnet (90) , such as a samarium cobalt permanent magnet, is coupled to the upper end surface of poppet valve (84) .

A cylindrical passage indicated generally by reference number (92) is drilled vertically downward along the vertical axis of fuel injector (76) . The lowermost extension of passageway (92) extends as close as possible to cavity (82) . A thin section of metal designated by reference number (94) separates the lowermost extension of passageway (92) from cavity (82) . This thin metal section, which in the illustrated embod¬ iment is 0.5 millimeters, also prevents the transfer of high pressure fuel from the interior of cavity (82) into the interior of passageway (92) , which is maintained fluid free and at an ambient air pressure. A valve position sensor (96) is dimensioned to fit within passageway (92) and is coupled to a Teflon wrapped four conductor stranded wire assembly (98) . A plastic cap (100) can be removed from fuel injector (76) to permit easy removal and reinsertion of valve position sensor (96) and wire assembly (98) into and out of passageway (92) . Valve position sensor (96) carries a retaining ring (102) which is positioned on wire assembly (98) such that cap (100) exerts a downward pressure on sensor (96) via wire (98) when cap (100) is screwed down against nut (73) .

While valve position sensor (96) could take the form of one of a different number of types of proximity sensing devices, inductive or Hall effect sensors can

--g SREAl^

readily be incorporated for use in the disclosed embodi¬ ment of the invention. A Hall effect sensor of the type discussed above can be manufactured on a single integrated circuit chip having dimensions of 1.5 by 1.5 millimeters or smaller. A dual cell Hall effect inte¬ grated circuit chip measuring 1.245 by 1.270 millimeters is manufactured by the Sprague Electric Company of Concord, Massachusetts. The integrated circuit chip is mounted on a ceramic header having a diameter of 2.2 millimeters. The entire Hall effect sensor assembly is epoxy encapsulated.

When a Hall effect device is incorporated within valve position sensor (96) , it is important to fabricate the body of fuel injector (76) from a material which will not become magnetized during, fabrication. Nitronic 60 stainless steel has been utilized in the preferred embodiment of the invention since this particular steel alloy has the required anti-magnetic property. In operation, poppet valve (84) is mechanical¬ ly displaced between open and closed portions as a result of fuel pressure overcoming the biasing force exerted by biasing spring (86) . Since magnet (90) is coupled to the upper end of poppet (84) , the up and down displacements of magnet (90) within cavity (82) modify the magnetic flux density which is sensed by valve position sensor (96) . These changes in magnetic flux density are converted into varying electrical output signals which are coupled to an externally positioned read-out device such as an oscilloscope by wire assembly (98).

The thin area of non-magnetic stainless steel designated by reference number (94) contains the

PI

pressurized fuel within chamber (82) , but permits the passage of magnetic flux generated by magnet (90) into the area within passageway (92) which is occupied by valve position sensor (96) . Valve position sensor (96) is thus subject only to ambient air pressure and does not have to be specially adapted to function within a high pressure region nor are special sealing techniques required to prevent the leakage of high pressure fuel from the area in which the sensor is located. It will be apparent to those skilled in the art that the disclosed valve position sensor for a poppet fuel injector may be modified in numerous ways and may assume many embodiments other than the preferred forms specifically set out and described above. For example, the present invention can be incorporated in many different configurations of fuel injector valves as long as the existing structure of the valve or an alternative restructured valve design can be implemented which permits a passageway to be bored within the fuel injector from an exterior surface into close proximity to the displaceable portion of the injector valve. Cylindrical passageway (92) could be accessed at a 30 degree angle as shown in FIG. 4 and the sensor inserted through a 30 degree passage. In that case the fuel inlet would be centrally located as in FIG. 4.

A detailed description of another embodiment of the present invention will now be described with reference to FIGS. 8-16.

The sensor employs an insulating header, the various features of which are best described with respect to its manufacture. Noting FIGS. 8-10, manufacture is initiated with a strip (110) of an

insulating material, such as alumina, through which spaced holes (112) are punched. It will be understood that a number of units may be manufactured simultaneous¬ ly with known microcircuit technology from the same strip of insulating material. However, in FIGS. 8 and 9, only the manufacture of a single header is shown.

After the punching of the holes (112) , the strip (110) is subjected to conventional cutting and metallizing operations to define the desired header usable for insertion into a fuel injection system. The resulting header structure (110) shown in FIG. 10 has four equal sides (118) , and four vias (120) each having metallization (124) therein. The cut (114) (FIG. 9) defines four radial corners (119) , the purpose of which will be described below. As thus manufactured, the header (110) of FIG. 10 is adapted for further operations to manufacture a sensor specifically for use with fuel injection apparatus in an internal combustion engine. Noting FIGS. 11, 12, and 13, the upper surface

(122) of the header (110) is provided with four metallized pads (126) in contact with the metallization

(124) in the vias (120) . These metal pads (126) may be deposited by known metallization deposit techniques. Four rigid metal pins (128) , preferably formed of a steel alloy such as Kovar, are each brazed to one of the metallized pads (126) on the first surface (122) . Preferably, each pin (128) includes ^' a groove (130) therein permitting the location of stripped ends (131) of flexible strands of an insulated multi-strand lead wire (131) to be welded to each pin (128) in the groove

(130) . While only one of the wires (131) is shown in the groove (130) of a single rigid pin (128) in FIG. 10,

it will be understood that a flexible wire is connected to each of the pins (128) .

Reference is now made to FIGS. 12 and 13. Metallization pads (138) are likewise deposited on the opposing surface (123) of the header (110) . An insulat¬ ing layer (132) , preferably also of alumina, is deposited on that surface (123) . A Hall effect detector chip (134) is bonded to the insulating layer (132) and carried by the surface (123) of the header (110) . Connecting bond wires (136) interconnect each metalli¬ zation pad (138) with a corresponding pad on the Hall effect chip (134) .

As shown in FIGS. 15 and 16, the sensor (141) includes an encapsulating resin (140). which is shaped as a cylinder with the periphery thereof lying flush with the radial corners (119) . The corners (119) may engage the hold sides during encapsulation, and the corners

(119) and encapsulation (140) in turn serve as a guide for the entire sensor (141) as it is inserted through a central passageway (152) (FIG. 14) of a fuel injector.

A typical passageway through which the sensor (141) of this invention may be inserted includes the passageway

(52) shown in FIG. 4 above.

FIG. 14 illustrates the sensor (141) fitted in the passageway (152) corresponding to the passageway

(52) in FIG. 4. The sensor (141) is positioned in the bottom of that passageway (152) in a holder (143) of a non-magnetic material, preferably stainless steel. The fuel injector includes a nozzle holder spring (142) and a spring seat (144) in FIG. 14. The seat (144) includes a spring centering plug (146) having a smaller diameter extension (148) thereon. A samarium cobalt magnet (150) is positioned on top of the extension (148) . A non-

-

magnetic cap (153) , preferably formed of stainless steel, is fitted over the magnet (150) , and is welded or brazed to the periphery of the extension (148) . The magnet (150) may be fixed within the cavity of the cap (152) with a suitable potting compound.

There has thus been described a unique and facile sensor for detecting the opening of a fuel injection valve to improve engine efficiency and minimize engine emissions.