Method and apparatus for hardening axially spaced cams on a camshaft

An apparatus for inductively heating and then quench hardening axially spaced cams on a steel camshaft having a longitudinally extending rotational axis concentric with a plurality of axially spaced bearings with surfaces concentric to said rotational axis, said apparatus comprising:

• means for rotatably mounting said camshaft to rotate about a work axis coinciding with said rotational axis;
• an induction heating coil having an inner surface surrounds said work axis with an insulation gap and integral quenching openings for directing liquid inwardly from said heating coil toward said work axis;
• a high frequency power supply means for selectively energizing said heating coil with a power density within said heating coil of over about 20 KW/in.sup.2 ;
• an axially cooling assembly fixed with respect to said coil at an axially spaced position near said heating coil and including means for spraying a cooling liquid toward said work axis;
• first drive means for causing relative axial movement of said camshaft and said heating coil to position a cam in said heating coil during a hardening cycle, including an induction heating portion and quench hardening position;
• second drive means for rotating said camshaft about said work axis;
• means for controlling said second drive means for selective rotating said camshaft to an indexed position with said cam in said coil having a preselected fixed circumferential orientation during at least said heating portion of said hardening cycle;
• means for selectively operating said power supply means during said heating portion of said cam hardening cycle;
• means for selectively operating said cooling assembly during said at least said heating portion of said hardening cycle for a cam in said heating coil;
• control means for repeatedly operating said first drive means, said second drive means, power supply operating means, said cooling assembly operating means for axially indexing a further cam into said fixed orientation within said heating coil for hardening during a hardening cycle while a previously, axially adjacent, hardened cam is cooled in said cooling assembly;
• and, said indexed position is with the lobe of said cam in said coil being adjacent said insulating gap

An apparatus for inductively heating and then quench hardening axially spaced cams on a steel camshaft having a longitudinally extending rotational axis concentric with a plurality of axially spaced bearings with surfaces concentric to said rotational axis, said apparatus comprising:

• means for rotatably mounting said camshaft to rotate about a work axis coinciding with said rotational axis;
• an induction heating coil having an inner surface surrounding said work axis with an insulation gap and integral quenching openings for directing liquid inwardly from said heating coil toward said work axis;
• a high frequency power supply means for selectivity energizing said heating coil with a power density within said heating coil of over about 20 KW/in.sup.2 ;
• an auxiliary cooling assembly fixed with respect to said heating coil at an auxiliary spaced position near said heating coil and including means for spraying a cooling liquid toward said work axis, first drive means for causing relative axial movement of said camshaft and said heating coil to position a cam in said heating coil during a hardening cycle, including an induction heating portion and quench hardening portion;
• second drive means for rotating said camshaft about said work axis;
• means for controlling said second drive means for selective rotating said camshaft to an indexed position with said cam in said coil having a preselected fixed circumferential orientation during at least said heating portion of said hardening cycle;
• means for selectively operating said power supply means during said heating portion of said cam hardening cycle;
• means for selectively operating said cooling assembly during at least said heating portion of said hardening cycle for a cam in said heatiang coil;
• control means for repeatedly operating said first drive means, said second drive means, power supply operating means, said cooling assembly operating means for axially indexing a further cam into said fixed orientation within said heating coil for hardening during a hardening cycle while a previously, axially adjacent, hardened cam is cooled in said cooling assembly;
• and, eddy current detecting means for detecting the hardened quality of said cams after said cams have been sequentially hardened, said eddy current detecting means comprising an eddy current coil concentric with said work axis, means for progressively moving said eddy current coil along said camshaft, means for energizing said eddy current coil at least at each of said axially spaced cams;
• means for detecting the eddy current induced by said energized eddy current coil in each of said hardened cams;
• means for comparing the values of said detected eddy currents with a preselected map of acceptable values;
• and means for rejecting a camshaft when said eddy currents deviate from said preselected map of acceptable values.

A method of inductively heating and then quench hardening the surface of axially spaced cams on a steel camshaft having a longitudinally extending rotational axis concentric with a plurality of axially spaced bearings with surfaces concentric to said rotational axis, said cams having lobes with differing circumferential locations, said method comprising the steps of:

• (a) providing an induction heating coil having an inner surface surrounding said work axis with an insulation gap and integral quenching openings for directing liquid inwardly from said heating coil toward said work axis;
• (b) providing a high frequency power supply means for selectively energizing said heating coil with a power density within said heating coil of over about 20 KW/in.sup.2 ;
• (c) providing an auxiliary cooling assembly fixed with respect to said heating coil at an axially spaced position near said heating coil and including means for spraying a cooling liquid toward said work axis;
• (d) causing relative axial movement of said camshaft and said heating coil to position a cam in said heating coil during a hardening cycle including an induction heating portion and quench hardening portion;
• (e) rotating said camshaft about said work axis;
• (f) selective rotating said camshaft to an indexed position with said cam in said coil having a preselected fixed circumferential orientation during at least said heating portion of said hardening cycle;
• (g) selectively operating said power supply means during said heating portion of said cam hardening cycle;
• (h) selectively operating said cooling assembly during said at least said heating portion of said hardening cycle for a cam in said heating coil;
• (i) sequentially indexing further cams into said fixed orientation within said heating coil for hardening during a hardening cycle while a previously, axially adjacent, hardened cam is cooled in said cooling assembly;
• and,
• (j) detecting the hardened quality of said cams after said cams have been sequentially scanned by an eddy current coil concentric with said work.

A method of inductively heating and then quench hardening the surface of axially spaced cams on a steel camshaft having a longitudinally extending rotational axis concentric with a plurality of axially spaced bearings with surfaces concentric to said rotational axis said cams having lobes with differing circumferential locations said method comprising the following steps:

• (a) providing an induction heating coil having an inner surface surrounding said work axis with an insulation gap and integral quenching openings for directing liquid inwardly from said heating coil toward said work axis;
• (b) providing a high frequency power supply means for selectively energizing said heating coil with a power density within said heating coil of over about 20 KW/in.sup.2 ;
• (c) providing an auxiliary cooling assembly fixed with respect to said heating coil at an axially spaced position near said heating coil and including means for spraying a cooling liquid toward said work axis;
• (d) causing relative axial movement of said camshaft and said heating coil to position a cam in said heating coil during a hardening cycle including an induction heating portion and quench hardening portion;
• (e) rotating said camshaft about said work axis;
• (f) means for selective rotating said indexed position with said cam in said coil having a preselected fixed circumferential orientation during at least said heating portion of said hardening cycle;
• (g) selectively operating said power supply means during said heating portion of said cam hardening cycle;
• (h) selectively operating said cooling assembly during said at least said heating portion of said hardening cycle for a cam in said heating coil;
• (i) indexing a further cam into said fixed orientation within said heating coil for hardening during a hardening cycle while a previously, axially adjacent, hardened cam is cooled in said cooling assembly;
• and, controlling the sequencing of said method steps in accordance with the sensed position of the lobe on a selected one of said axially spaced cams.

An apparatus for inductively heating and then quench hardening the surfaces of axially spaced cams on a steel canshaft having a longitudinal axis, said apparatus comprising:

• an induction heating coil with a central opening and means for directing a quenching liquid from said coil inwardly in said opening;
• a power supply having an output frequency of 10 KHz to about 25 KHz and an output power to create a power density of at least 20 KW/in.sup.2 within said coil opening;
• means for moving said cam into said opening;
• means for energizing said coil with said power supply for a heating cycle of between 0.30 seconds and 1.5 seconds;
• means for actuating said quenching means immediately after said heating cycle for a quenching cycle;
• means for liquid cooling of portions of said camshaft adjacent said heating coil;
• and means for preventing said quenching liquid from flowing freely from said opening during said quenching cycle whereby said quenching liquid is directed toward substantially the full area of said surfaces.

An apparatus for inductively heating and then quench hardening the surfaces of axially spaced cams on a steel camshaft having a longitudinal axis, said apparatus comprising:

• an induction heating coil with a central opening and quenching means for directing a quenching liquid from said coil inwardly in said opening;
• a power supply having an output frequency of 10 KHz to about 25 KHz and an output power to create a power density of at least 20 KW/in.sup.2 within said coil opening;
• means for moving said cam into said opening;
• means for energizing said coil with said power supply for a heating cycle of between 0.30 seconds and 1.5 seconds;
• means for actuating said quenching means immediately after said heating cycle for a quenching cycle;
• and means for liquid cooling of portions of said camshaft adjacent said heating coil;
• said quenching means including a plurality of openings in the range of 0.60-0.90 inches in diameter and means for forcing quenching liquid through said openings at a pressure of about 15-20 psi whereby a relatively low velocity stream of said liquid is directed from said coil.