Combustion monitoring system for fuel injected engines

• US 4,227,402 A
• Filed: 11/14/1978
• Issued: 10/14/1980
• Est. Priority Date: 11/14/1978
• Status: Expired due to Term

• Current Assignee: Creative Tool Company
• Original Assignee: Creative Tool Company
• Inventors: Dooley, Daniel J., Dooley, Joseph L., Dooley, Terrence L.
• Primary Examiner(s): Myracle, Jerry W.
• Application Number:
  US05/960,600
• Time in Patent Office: 700 Days
• Field of Search: 73/119 A, 73/753, 73/756, 73/115, 73/723, 310/338, 123/33 D
• US Class Current: 73/114.18
• CPC Class Codes: F02B 3/06 with compression ignition compression ignition engines using air or gas for blowing fuel into compressed air in cylinder F02B13/02
• CPC Class Codes: G01L 23/10 by pressure-sensitive members of the piezoelectric type
• CPC Class Codes: G01L 23/22 for detecting or indicating knocks in internal-combustion engines; Units comprising pressure-sensitive members combined with ignitors for firing internal-combustion engines

Abstract

A transducer and associated diagnostic system for fuel injected diesel engines of the type having glow plugs to provide supplementary ignition during starting and warm-up periods. A piezoelectric transducer unit is adapted to screw into the receptacle normally provided in each cylinder for a glow plug. The unit includes a piezoelectric element which is held under tension by a conductive rubber plug which coacts with a coaxial connector in transmitting the pressure indicative output signal. The transducer develops an electrical signal which varies in accordance with the pressure-time characteristic of the cylinder combustion chamber, the electrical signal representing performance of each cylinder being processed individually to provide timing and other valuable information or being combined with electrical signals developed for other cylinders of the engine in a comparative diagnostic system.

Claims

1. For use in a diagnostic system for a diesel engine of the type having a combustion chamber associated with each cylinder and a threaded port extending from each combustion chamber to the outer surface of the engine which is adapted to accept a glow plug, a transducer assembly comprising a metal housing having a shank portion threaded for a screw-type engagement with said threaded port and a head portion external to said shank portion and having a recessed cavity extending along the axis of said port, said shank portion having a forward end for extending into said port and acting as a pressure face within the cylinder and closing the inside surface of said cavity transverse to the axis of the port, said metal housing at least partially seating against said engine at said head portion and a piezoelectric element coupled to the inner end of the cavity in substantially the same plane in which said head portion is seated against said engine so as to develop an electrical signal during flexure of said housing resulting from pressure against said pressure face, and an electrical output means coupled to the outer end of said piezoelectric element for transmitting the electrical signal from said element.

2. A method for using the transducer of claim 1 with a diesel engine having a glow plug in one threaded port comprising:

removing the glow plug from the threaded port;

inserting and engaging in the vacated threaded port the shank portion of the transducer assembly and seating the head portion against the engine; and

electrically coupling instrumentation to the electrical output means to receive and monitor the electrical signal from the piezoelectric element.

3. For use in a diagnostic system for a diesel engine of the type having threaded receptacles extending outward from each cylinder for normally receiving a glow plug which aids ignition, a transducer assembly adapted to substitute for a glow plug and to seat in said glow plug receptacle in a plane transverse to the axis of the receptacle, said transducer assembly having a blunt forward end which is cylindrical in shape and threaded to conform to the complementary threads of said glow plug receptacle, said transducer assembly further having a rearward end coupled to an electrical output and a cavity formed in from the rearward end of said transducer and a piezoelectric element fixed in a plane transverse to the axis of said glow plug receptacle and affixed to the forward end of said cavity, said piezoelectric element being a circular disc of crystalline material, the forward side of said disc being bonded by an electrically conductive adhesive to the forward face of said cavity and the rearward side of said disc being electrically coupled to the electrical output such that an electrical potential is developed between the transducer and the output in response to mechanical stress transmitted to the forward end of said transducer from within the cylinder.

4. For use in a diagnostic system for a diesel engine of the type having threaded receptacles extending outward from each cylinder for normally receiving a glow plug which aids ignition, a transducer assembly adapted to substitute for a glow plug and to seat in any one of said glow plug receptacles in a plane transverse to the axis of the receiving receptacle, said transducer assembly having a blunt forward end which is cylindrical in shape and threaded to conform to the complementary threads of said glow plug receptacles, said transducer assembly further having a rearward end coupled to an electrical output end and a cavity formed in from the rearward end of said transducer and a piezoelectric element fixed in a plane transverse to the axis of the receiving glow plug receptacle and affixed to the forward end of said cavity in substantially the same plane in which said assembly is seated in said receiving glow plug receptacle for developing an electrical output signal in response to pressures acting on the forward end of said transducer assembly from within the cylinder.

5. The transducer assembly of claim 4 wherein said piezoelectric element is substantially perpendicular to the axis of said glow plug receptacle.

6. A method for detecting force waves in solid metal objects comprising the steps of:

(a) forming a cylindrical cavity in the metal such that the axis of the cavity is substantially perpendicular to the movement of the force wave to be detected;

(b) placing at the inner end of said cavity a flat piece of piezoelectric material having a first face in electrical contact with the inner end of said cavity and the second and opposite face facing outward from said cavity;

(c) inserting into said cavity from its outer end an element comprising an inner core of an elastic, conductive material within an outer sleeve of insulating material which surrounds said conductive material except for the forward and rearward ends thereof, the forward end of said conductive material being uninsulated and adapted to be pressed against the outward facing portion of said piezoelectric element; and

(d) positioning in said cavity a coaxial fitting of the type having a protruding central conductor shaft supported in spaced insulated relation to an outer cylindrical conductor, the central shaft of said coaxial fitting being adapted to conductively engage the rearward end of the conductive core upon positioning of said coaxial end fitting into said cavity, whereby said conductive core is compressed between the outward face of said piezoelectric element and said central conductor shaft of the coaxial fitting so as to provide an output terminal for the signal which develops in the piezoelectric material in response to the force waves.

7. The method of claim 6 wherein said element is cylindrical.

8. The method of claim 6 wherein said conductive core is rubber.

9. The method of claim 6 wherein threads are formed about the walls of said cavity and the coaxial fitting is threaded into said cavity.

10. A transducer for developing electrical signals in response to pressure in a chamber in a housing having a port from the outside of the housing to the chamber, comprising a body in engagement with the housing at the port having

a first surface thereon serving as a pressure-sensing face extending into the port;

a second surface thereon for at least partially seating against the housing at the port therein;

a cavity in said body extending from outside the chamber toward said pressure-sensing face and having an inner surface which is in proximity with said seating surface and is transverse to said port;

a piezoelectric element on the inner surface of said cavity for developing an electrical signal responsive to flexing of said housing due to pressure changes in the chamber;

a compressible plug disposed in said cavity and having a core of conductive elastomeric material and an outer sheath of insulating material, said sheath being open on opposing ends so that on one end the conductive material is adapted to contact the piezoelectric element;

means for compressing said plug within said cavity so that the conductive core contacts with said piezoelectric element; and

output terminal means coupled to the conductive core at the opposing end of said plug for receiving the electrical signal from said piezoelectric element.

11. The transducer of claim 10 wherein said plug is cylindrical.

12. The transducer of claim 10 wherein said elastomeric material is rubber.

13. The transducer of claim 10 wherein said sheath is heat shrinkable.

14. The transducer of claim 10 wherein said terminal means is a BNC bayonet connector.

15. A method for detecting force waves in solid metal objects comprising the following steps:

(a) forming a cylindrical cavity in the metal such that the axis of the cavity is substantially perpendicular to the movement of the force wave to be detected;

(b) placing at the inner end of said cavity a flat piece of piezoelectric material having a first face in electrical contact with the inner end of said cavity and the second and opposite face facing outward from said cavity;

(c) inserting into said cavity from its outer end an element comprising an inner core of elastic, conductive material within an outer sleeve of insulating material which surrounds said conductive material except for the forward and rearward ends thereof, the forward end of said conductive material being uninsulated and adapted to be pressed against the outward facing portion of said piezoelectric element;

(d) compressing said element against said piezoelectric material to stress said material; and

(e) contacting the rearward end of the conductive core to provide an output terminal for the signal which develops in the peizoelectric material in response to the force waves.

16. For use in a diagnostic system for a diesel engine of the type having a combustion chamber associated with each cylinder and a threaded port extending from each combustion chamber to the outer surface of the engine which is adapted to accept a glow plug, a transducer assembly comprising a metal housing having a shank portion threaded for a screw-type engagement with said threaded port and a head portion external to said shank portion and having a recessed cavity extending along the axis of said port, said shank portion having a forward end for extending into said port and acting as a pressure face within the cylinder and closing the inside surface of said cavity transverse to the axis of the port, said metal housing at least partially seating against said engine at said head portion and a piezoelectric element coupled to the inner end of the cavity so as to develop an electrical signal during flexure of said housing resulting from pressure changes against said pressure face, an element comprising an inner core of an elastic, electrically conductive material within an outer sleeve of insulating material which surrounds said conductive material except for the ends thereof, said element being inserted into said cavity and having one end in contact with said piezoelectric element, and an electrical output means coupled to the other end of said element for compressing said element against said piezoelectric element and for transmitting the electrical signal generated by said piezoelectric element.

17. For use in a diagnostic system for an internal combustion engine of the type having a combustion chamber associated with each cylinder and a threaded port extending from each combustion chamber to the outer surface of the engine which is adapted to accept a spark plug, a transducer assembly comprising a metal housing having a shank portion threaded for a screw-type engagement with said threaded port and a head portion external to said shank portion and having a recessed cavity extending along the axis of said port, said shank portion having a forward end for extending into said port and acting as a pressure face within the cylinder and closing the inside surface of said cavity transverse to the axis of the port, said metal housing at least partially seating against said engine at said head portion and a piezoelectric element coupled to the inner end of the cavity in substantially the same plane in which said head portion is seated against said engine so as to develop an electrical signal during flexure of said housing resulting from pressure against said pressure face, and electrical output means coupled to the outer end of said piezoelectric element for transmitting the electrical signal from said element.

18. For use in a diagnostic system for an internal combustion engine of the type having threaded receptacles extending outward from each cylinder for normally receiving a spark plug, a transducer assembly adapted to substitute for a spark plug and to seat in said spark plug receptacle in a plane transverse to the axis of the receptacle, said transducer assembly having a blunt forward end which is cylindrical in shape and threaded to conform to the complementary threads of said spark plug receptacle, said transducer assembly further having a rearward end coupled to an electrical output end and a cavity formed in from the rearward end of said transducer and a piezoelectric element fixed in a plane transverse to the axis of said spark plug receptacle and affixed to the forward end of said cavity in substantially the same plane in which said assembly is seated in said spark plug receptacle for developing an electrical output signal in response to pressures acting on the forward end of said transducer assembly from within the cylinder.