FIELD OF THE INVENTION

[0001 ] The present invention relates to spark-ignited internal combustion engi

BACKGROUND OF THE INVENTION

[0002] In internal combustion engines, it is conventional to initiate combustion with the use of spark plugs. In conventional spark plugs, a body which defines a longitudinal axis is provided. The body has, adjacent one end thereof, a metal ring which is orientated coaxially with the longitudinal axis. The body further includes a metal tube which: is orientated coaxially with the longitudinal axis; extends from the ring towards the other end of the body; and is externally-threaded for engagement in a corresponding threaded bore in an engine block in use. A porcelain insulator also forms part of the body. The insulator has a portion disposed inside the tube. This portion extends axially, from inside the tube, beyond the ring, and has an elongate void extending axially therethrough. An elongate positive electrode occupies the void and extends axially beyond the insulator to a terminus which defines the one end of the body. Conventional spark plugs also include an electrode leg. The electrode leg has two arms transversely connected to one another, with one arm extending axially from the ring and beyond the electrode and the other arm extending radially inwardly from the one arm so as to terminate in an end portion that is axially-spaced from the terminus. The spark gap in this conventional plug is the space defined between the positive electrode and the electrode leg. SUMMARY OF THE INVENTION

[0003] A spark plug forms one aspect of the invention. The plug, which is for use with an engine block/cylinder head having a threaded bore and is also for use with a spark plug wrench and an ignition wire, comprises a nut portion, a coupling portion, an insulator portion, a positive electrode and a ground electrode. The nut portion is adapted to be turned by the wrench. The coupling portion extends from the nut portion and is adapted to receive the ignition wire. The insulator portion extends from the nut portion and away from the coupling portion to an end. The positive electrode extends through and beyond the end of the insulator portion. The ground electrode includes a tubular metal portion and a cap portion to which the tubular portion extends. The tubular metal portion: extends from the nut portion in circumferentially surrounding relation to the insulator portion; terminates such that a portion of the insulator portion extends beyond the tubular metal portion; is orientated coaxially about and defines a longitudinal axis; and is externally-threaded for engagement in the threaded bore in said engine block in use. The cap portion is disposed in spaced relation to the insulator portion and defines a void having: a central portion into which the positive electrode extends; an annular channel surrounding the central portion; and a plurality of lobes, each being positioned with respect to the central portion in a manner analogous to the placement of the planet gears with respect to the sun gear in a planetary gear. The cap also has a central surface that is axially spaced from that portion of the insulator that protrudes beyond the tubular metal portion; and a convex surface that surrounds and extends to the central surface.

[0004] According to another aspect of the invention, the central surface can be orientated substantially normally to the longitudinal axis and substantially coplanar with the end of the positive electrode.

[0005] According to another aspect of the invention, the plurality of lobes can consist of three to seven lobes. [0006] According to another aspect of the invention, if R1 is the radius of each planet gear

R2 is the distance from the axis of each planet gear to the axis of the sun gear R3 is the outer radius of the ground electrode

R4 is the outer radius of the annular channel then

R1 : R2: R3: R4: R5 can be about 0.12: 0.305 : 0.475: 0.25

[0007] According to another aspect of the invention, the plurality of lobes can consist of seven lobes.

[0008] According to another aspect of the invention, the cap portion can have radially inwardly disposed fingers which separate the lobes from one another, each finger having a terminus to which said each finger extends, the thickness of the finger at the terminus as measured in the longitudinal direction being substantially equal to the length of that portion of the positive electrode that extends beyond the insulation.

[0009] Other advantages, features and characteristics of the present invention, as well as methods of operation and functions of the related elements of the structure, and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following detailed description and the appended claims with reference to the accompanying drawings, the latter being briefly described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a perspective view of a spark plug according to an

exemplary embodiment of the invention

[001 1 ] FIG. 2 is an enlarged view of encircled area 2 of FIG. 1

[0012] FIG. 3 is an end view of the structure of FIG. 1 ;

[0013] FIG. 4 is a side view of the structure of FIG. 1 ;

[0014] FIG. 5 is a view along 5-5 of FIG. 4; and

[0015] FIG. 6 is a view similar to FIG. 5, illustrative of an exemplary method of manufacture;

[0016] FIG. 7 is a perspective view of encircled area 7 of FIG. 6;

[0017] FIG. 8 is a plan view of the structure of FIG. 7;

[0018] FIG. 9 is a view along 9-9 of FIG. 8; and

[0019] FIG. 10 is a side view of the structure of FIG. 7.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT

[0020] As an initial matter, the spark plug 20 according to the exemplary embodiment shown in FIGS. 1 -4 is for use with an engine block/cylinder head having a threaded bore and also for use with a spark plug wrench and an ignition wire, all as is

conventional.

[0021 ] The plug 20 also comprises, as is conventional, a nut portion 22, a coupling portion 24, an insulator portion 26, a positive electrode 28 and a ground electrode 30.

[0022] As is conventional: the nut portion 22 is adapted to be turned by the wrench; the coupling portion 24 extends from the nut portion 22 and is adapted to receive the ignition wire; the insulator portion 26 extends from the nut portion 22 and away from the coupling portion 24 to an end; the positive electrode 28 extends through and beyond the end of the insulator portion 26. Also as is conventional, the ground electrode 30 includes a tubular metal portion 32 which: extends from the nut portion 22 in

surrounding relation to the insulator portion 26; terminates such that a portion 33 of the insulator portion 26 extends beyond the tubular metal portion 32; is orientated coaxially about and defines a longitudinal axis X-X and is externally-threaded for engagement in the threaded bore in said engine block in use.

[0023] However, in this spark plug, there is provided a cap portion 34 to which the tubular portion 32 extends and is circumferentially connected.

[0024] The cap portion 34:

• is disposed in spaced relation to the insulator 26 and defines a void 36 having: a central portion 38 into which the positive electrode 28 extends; an annular channel 40 surrounding central portion 38; and a plurality of lobes 42, each being positioned with respect to the central portion 38 in a manner analogous to the placement of the planet gears with respect to the sun gear in a planetary gear.

• has a plurality of radially inwardly disposed fingers 44 which separate the lobes 42 from one another, each finger 44 having a terminus to which said each finger extends, the thickness X1 of the finger at the terminus as measured in the longitudinal direction being substantially equal to the length X2 of that portion of the positive electrode that extends beyond the insulation

• has: (i) a central surface 46 that is axially spaced from that portion of the

insulator 26 that protrudes beyond the tubular portion 32 and is orientated substantially normally to the longitudinal axis X-X and substantially coplanar with the end of the positive electrode 28; and (ii) a convex surface 48 that surrounds and extends from the tubular metal portion 32 to the central surface 46.

[0025] The geometry of the cap portion is such that if R1 is the radius of each planet gear, R2 is the distance from the axis of each planet gear to the axis of the sun gear, R3 is the outer radius of the ground electrode and R4 is the outer radius of the annular channel, then R1 : R2: R3: R4: R5 is about 0.12: 0.305 : 0.475: 0.25

[0026] The spark plug of the exemplary embodiment has proven to be of substantial advantage in numerous tests that have been carried out. Autolite AR3932X modified AR3932X Gains

Table 1

[0027] Table 1 shows dynamometer tests carried out using a CRA Super Series Template 360 Chev Racing Engine with a 9:1 compression. Timing was set at 34. The carburetor used was a Holly 390 with 77 jets. Oil used was 15/40 viscosity. Fuel octane: 1 10. Load factor was set at 1 .21 . The left columns show developed torque and HP at RPM values between 5500 and 8000 using a set of new, standard Autolite AR3932X plugs. The middle columns shows the same data set for the same plugs, modified with the inventive cap portion. The right columns shown the torque and horsepower gains, which manifest at all measured speeds. OE Autolite AR473 Modified AR473 Gain

Table 2

[0028] Table 2 shows dynamometer tests carried out using a NASCAR-approved, NCATS Series Restricted 1 1/8" engine with 10: 1 compression. Timing was set at 30. The carburetor used was a Holly 390 with 64/64 jets. Oil used was 15/40 viscosity. Fuel octane: 94. Load factor was set at 1.21 . The left columns show developed torque and HP at RPM values between 4500 and 6500 using a set of new, standard Autolite AR473 plugs. The middle columns show the same data set for the same plugs, modified with the inventive cap portion. The right columns shown the torque and horsepower gains, which manifest all at all measured speeds. Autolite AR3932X modified AR3932X Gains

Table 3

[0029] Table 3 shows dynamometer tests carried out using a Chevy Big Block at 12:1 Compression. Timing was set at 32. The carburetor used was a Holly 850 with 77 jets Oil used was 15/40 viscosity. Fuel octane: 1 10. Load factor was set at 0.77. The left columns show developed torque and HP at RPM values between 4500 and 7000 using a set of new, standard Autolite AR3932X plugs. The middle columns show the same data set for the same plugs, modified with the inventive cap portion. The right columns shown the torque and horsepower gains, which manifest at all but 5500-5700 RPM. Autolite AR3932X modified AR3932X Gains

(.045 gap)

Table 4

[0030] Table 4 shows dynamometer tests carried out using a Chevy Big Block at 12:1 Compression, .045 gap. Timing was set at 32. The carburetor used was a Holly 850 with 77 jets. Oil used was 15/40 viscosity. Fuel octane: 1 10. Load factor was set at 0.77. The left columns show developed torque and HP at RPM values between 4500 and 7000 using a set of new, standard Autolite AR3932X plugs. The middle columns show the same data set for the same plugs, modified with the inventive cap portion. The right columns shown the torque and horsepower gains, which manifest at all but 5500-5800 RPM. HORSE POWER

COMPARISON

3932X Average RPM Average AR3932X ffl HP #2 HP #3 HP #1 HP #2 HP #3 HP

OE OE OE OE HP NS HP NS NS NS

572 569 571 570.6 4500 572 571 572 573

587 583 587 585.6 4600 587.6 588 588 587

603 599 604 602 4700 604.3 605 605 603

618 615 621 618 4800 621.3 622 623 619

632 629 636 632.3 4900 636.3 637 638 634

645 642 650 645.6 5000 650.3 651 653 647

660 655 662 659 5100 664.3 665 666 662

675 671 676 674 5200 678.6 680 679 677

691 689 692 690.6 5300 693.6 692 695 694

708 706 707 707 5400 709.6 708 711 710

724 723 724 723.6 5500 724.3 723 724 726

740 740 741 740.3 5600 740 739 739 742

754 754 755 754.3 5700 755 754 753 758

766 764 768 766 5800 767.6 765 768 770

775 774 778 775.6 5900 780.3 778 781 782

786 783 789 786 6000 791.6 790 791 794

795 794 797 795.3 6100 801.6 801 799 805

805 806 806 805.6 6200 811.6 810 809 816

813 814 813 813.3 6300 818.6 816 817 823

818 819 819 818.6 6400 826 825 825 828

821 823 825 823 6500 830.6 829 830 833

822 826 828 825.3 6600 833 831 833 835

822 828 830 826.6 6700 834.3 833 834 836

824 827 828 826.3 6800 836 834 837 837

822 826 824 824 6900 835 834 835 836

820 825 822 822.3 7000 835.3 836 834 836

Table 5 TORQUE

COMPARISON

OE NS

AR3932X Average RPM Average AR473

#1 TQ #2 TQ #3 TQ #1 TQ #2 TQ #3 TQ

OE OE OE OE TQ NS TQ NS NS NS

667 664 666 665.6 4500 667.3 667 667 668

671 666 671 669.3 4600 671 672 671 670

673 669 675 672.3 4700 676.3 676 677 676

676 673 680 676.3 4800 680.3 681 682 678

678 674 682 678 4900 683.6 683 684 684

678 674 683 678.3 5000 686 684 686 688

679 675 682 678.6 5100 685 685 686 684

682 678 683 681 5200 685.6 687 686 684

685 682 685 684 5300 688.3 688 689 688

688 687 688 687.6 5400 690 689 691 690

691 690 691 690.6 5500 691.6 690 692 693

694 694 695 694.3 5600 694 693 693 696

695 695 696 695.3 5700 695.6 695 694 698

694 692 695 693.6 5800 695 693 695 697

690 689 692 690.3 5900 694.3 692 695 696

688 686 690 688 6000 693 692 692 695

684 684 687 685 6100 690.3 690 688 693

682 683 683 682.6 6200 687.3 686 685 691

678 678 678 678 6300 682.6 681 681 686

671 672 672 671.6 6400 677.6 677 677 679

663 665 666 664.6 6500 671 670 670 673

654 657 659 656.6 6600 663 661 663 665

644 649 651 648 6700 653.6 653 653 655

636 639 640 638.3 6800 645.6 644 646 647

626 629 628 627.6 6900 635.6 635 636 636

615 619 617 617 7000 626.6 627 626 627

Table 6 [0031 ] Tables 5 and 6 show dynamometer tests for a Chevy Big Block. Timing was set at 32. The carburetor used was a Holly 850 with 77/77 jets. Oil used was 15/40 viscosity. Fuel octane: 1 10. Load factor was set at 0.77. In Table 5, the three left columns show developed horsepower at RPM between 4500 and 7000 using a set of new AR3932X plugs. The three right columns show the same data for the same plugs, modified with the inventive cap portion. Horsepower gains were obtained at all speeds but for 5600 RPM . In Table 6, the three left columns show developed torque at RPM between 4500 and 7000 using a set of new AR3932X plugs. The three right columns show the same data for the same plugs, modified with the inventive cap portion.

Torque gains were obtained at all speeds but for 5600 RPM

[0032] In each of the examples, reference is made to plugs that have been modified with the inventive cap portion. In this regard, it will be appreciated that, in each case, the reference/baseline plug mentioned was modified by grinding off the electrode leg thereof and welding a ring thereto, as illustrated by FIG. 6.

[0033] An exemplary ring is shown in FIGS. 7-10. This ring is produced from 304 2B stainless steel and is dimensioned as follows:

.060 radius .47"

.13" .05"

.07" radius .24"

.076R .47"

.031 " .13"

.028" [0034] However, it will be understood that these dimensions were selected such that the distance between the positive electrode and the ring is the distance specified by the manufacturer of the vehicle with which the modified plug was used. Variation from these dimensions are possible and indeed would be adopted in other engine

applications to meet the specifications of the engine manufacturer.

[0035] Further, whereas a seven lobe structure is disclosed, the plurality of lobes can consist of three to seven lobes.

[0036] Accordingly, it should be understood that the invention is to be limited only by the accompanying claims, purposively construed.