Pressure-inductance transducer

Claim 2

In a fuel injection system for an internal combustion engine having an induction passage for air flow to the engine, a throttle disposed in said induction passage for controlling air flow therethrough, and electronically controlled means for delivering fuel to the engine in accordance with the inductance of a coil: a transducer for controlling the inductance of said coil in accordance with the Pressure in said induction passage downstream of said throttle comprising a nylon spool having an opening extending axially therethrough, said opening having a diameter at one end slightly larger than the diameter at the other end and having an annular shoulder providing a transition between said diameters, said spool including a projection extending radially into said opening adjacent the large diameter end thereof, said coil being wound about said spool, a nickel plated steel sleeve received in said opening and having one end abutting said shoulder, said sleeve having an annular recess receiving said projection whereby said sleeve is retained in said spool, the other end of said sleeve extending axially beyond the end of said spool, a ferrite cup having a circular end wall disposed at said end of said spool and a cylindrical wall of circular cross section surrounding said spool, said end wall having a central opening receiving said other end of said sleeve, a circular ferrite cap disposed at the other end of said spool and secured to said cup, said cap having a central opening, a teflon coated steel plunger guided in said sleeve and having a tapered end disposed adjacent said opening in said cap, said plunger, said cap, said cup, and said sleeve defining a flux path through and about said coil, said tapered end of said plunger defining an air gap with said cap, and means connected to said plunger and responsive to said induction passage pressure for axially positioning said plunger to control said air gap and thereby control the reluctance of said flux path and thus control the inductance of said coil.

Claim 3

The transducer of claim 1 which further comprises a cupped housing having an end wall and a peripheral wall, said end wall of said ferrite cup being disposed adjacent said end wall of said housing and said peripheral wall of said housing surrounding said cylindrical wall of said ferrite cup, a silicone rubber wafer disposed between said end wall of said ferrite cup and said end wall of said housing, a retainer ring disposed adjacent said ferrite cap and having a plurality of radially extending fingers engaging said peripheral wall to prevent axial movement of said ferrite cap and cup away from said housing end wall, and a silicone rubber wafer secured to said retainer ring between said ring and said cap, whereby said ferrite cap and cup are retained against displacement and cushioned against compression in said housing.

Claim 4

The transducer of claim 2 wherein said end wall of said housing has an axial recess receiving and aligning said sleeve.

Claim 5

The transducer of claim 1 which further comprises a brass member extending axially from said tapered end of said plunger through said opening in said cap and having a radially extending surface facing away from said plunger and a pin projecting axially from the center of said surface, a radially extending circular bimetallic disc having a central aperture receiving said pin, the high expansion side of said bimetallic disc abutting said radially extending surface and the low expansion side of said disc facing away from said surface, and a plate member extending radially from said pressure responsive means and having a rim engaging the periphery of said bimetallic disc, whereby the position of said plunger is adjusted to compensate for changes in plunger position, coil resistance and ferrite permeability due to changes in temperature.

Claim 6

In a fuel injection system for an internal combustion engine having an induction passage for air flow to the engine, a throttle disposed in said induction passage for controlling air flow therethrough, and electronically controlled means for delivering fuel to the engine in accordance with the inductance of a coil: a transducer for controlling the inductance of said coil in accordance with the pressure in said induction passage downstream of said throttle comprising a nylon spool having an opening extending axially therethrough, said opening hAving a diameter at one end slightly larger than the diameter at the other end and having an annular shoulder providing a transition between said diameters, said spool including a projection extending radially into said opening adjacent the large diameter end thereof, said coil being wound about said spool, a nickel plated steel sleeve received in said opening and having one end abutting said shoulder, said sleeve having an annular recess receiving said projection whereby said sleeve is retained in said spool, the other end of said sleeve extending axially beyond the end of said spool, a ferrite cup having a circular end wall disposed at said end of said spool and a cylindrical wall of circular cross section surrounding said spool, said end wall having a central opening receiving said other end of said sleeve, a circular ferrite cap disposed at the other end of said spool and secured to said cup, said cap having a central opening, a teflon coated steel plunger guided in said sleeve and having a tapered end disposed adjacent said opening in said cap, said plunger, said cap, said cup, and said sleeve defining a flux path through and about said coil, said tapered end of said plunger defining an air gap with said cap, a cupped housing having an end wall and peripheral wall, said end wall of said ferrite cup being disposed adjacent said end wall of said housing and said peripheral wall of said housing surrounding said cylindrical wall of said ferrite cup, said end wall having an axial recess receiving and aligning said sleeve, a retainer ring disposed adjacent said ferrite cap and having a plurality of radially extending fingers engaging said peripheral wall to prevent axial movement of said ferrite cap and cup away from said housing end wall, a silicone rubber wafer disposed between said end wall of said ferrite cup and said end wall of said housing, and a silicone rubber wafer secured to said retainer ring between said ring and said cap, whereby said ferrite cap and cup are retained against radial displacement and cushioned against axial compression in said housing, a brass member extending axially from said tapered end of said plunger through said opening in said cap and having a radially extending surface facing away from said plunger and a pin projecting axially from the center of said surface, a radially extending circular bimetallic disc having a central aperture receiving said pin, the high expansion side of said bimetallic disc abutting said radially extending surface and the low expansion side of said disc facing away from said surface whereby the position of said plunger is adjusted to compensate for changes in plunger position, coil resistance and ferrite permeability due to changes in temperature, a circular plate member having its outer rim engaging the periphery of said bimetallic disc, and means connected to said plate member and responsive to said induction passage pressure for axially positioning said plunger to control said air gap and thereby control the reluctance of said flux path and thus control the inductance of said coil.

Claim 7

In a fuel injection system for an internal combustion engine having an induction passage for air flow to the engine, a throttle disposed in said induction passage for controlling air flow therethrough, and electronically controlled means for delivering fuel to the engine in accordance with the inductance of a coil: a transducer for controlling the inductance of said coil in accordance with the pressure in said induction passage downstream of said throttle comprising a nylon spool having an opening extending axially therethrough, said opening hAving a diameter at one end slightly larger than the diameter at the other end and having an annular shoulder providing a transition between said diameters, said spool including a projection extending radially into said opening adjacent the large diameter end thereof, said coil being wound about said spool, a nickel plated steel sleeve received in said opening and having one end abutting said shoulder, said sleeve having an annular recess receiving said projection whereby said sleeve is retained in said spool, the other end of said sleeve extending axially beyond the end of said spool, a ferrite cup having a circular end wall disposed at said end of said spool and a cylindrical wall of circular cross section surrounding said spool, said end wall having a central opening receiving said other end of said sleeve, a circular ferrite cap disposed at the other end of said spool and secured to said cup, said cap having a central opening, a teflon coated steel plunger guided in said sleeve and having a tapered end disposed adjacent said opening in said cap, said plunger, said cap, said cup, and said sleeve defining a flux path through and about said coil, said tapered end of said plunger defining an air gap with said cap, a cupped housing having an end wall and peripheral wall, said end wall of said ferrite cup being disposed adjacent said end wall of said housing and said peripheral wall of said housing surrounding said cylindrical wall of said ferrite cup, said end wall having an axial recess receiving and aligning said sleeve, a retainer ring disposed adjacent said ferrite cap and having a plurality of radially extending fingers engaging said peripheral wall to prevent axial movement of said ferrite cap and cup away from said housing end wall, a silicone rubber wafer disposed between said end wall of said ferrite cup and said end wall of said housing, and a silicone rubber wafer secured to said retainer ring between said ring and said cap, whereby said ferrite cap and cup are retained against radial displacement and cushioned against axial compression in said housing, a brass member extending axially from said tapered end of said plunger through said opening in said cap and having a radially extending surface facing away from said plunger and a pin projecting axially from the center of said surface, a radially extending circular bimetallic disc having a central aperture receiving said pin, the high expansion side of said bimetallic disc abutting said radially extending surface and the low expansion side of said disc facing away from said surface whereby the position of said plunger is adjusted to compensate for changes in plunger position, coil resistance and ferrite permeability due to changes in temperature, a circular plate member having its outer rim engaging the periphery of said bimetallic disc, and means connected to said plate member and responsive to said induction passage pressure for axially positioning said plunger to control said air gap and thereby control the reluctance of said flux path and thus control the inductance of said coil.

Claim 8

The transducer of claim 5 wherein said pressure responsive means comprises an evacuated bellows having its exterior exposed to said induction passage pressure and having one end connected to said plate member, said transducer further comprising spring means biasing said plunger toward a maximum inductance position, an adjustable overrun stop screw extending from said housing end wall into the other end of said sleeve and abutting said plunger to limit travel thereof against the bias of said spring means in a minimum inductance direction, a calibration screw abutting the opposite end of said bellows, flexible diaphragm means carrying said calibration screw, a helical power spring having one end abutting said diaphragm to bias said diaphragm toward a maximum inductance position, an adjustable wide open throttle stop screw abutting said dIaphragm means to limit travel thereof in a maximum inductance direction, said diaphragm means being subjected on one side to substantially atmospheric pressure and on the other side to said induction passage pressure whereby said diaphragm means moves toward a minimum inductance position against the bias of said power spring in response to a decrease in said induction passage pressure below a predetermined value, stop means abutting said diaphragm means to limit movement of said diaphragm in a minimum inductance direction, and a power cut-in screw abutting the other end of said power spring, said power cut-in being adjustable for regulating the compression of said power spring to thereby establish said predetermined induction passage pressure value below which said diaphragm means moves toward a minimum inductance position, said calibration screw being adjustable with respect to said diaphragm to establish an initial position of said plunger.