Dual-cone synchronizer with servo action

A manual transmission double-acting synchronizer apparatus operatively associated with a transmission shaft with said synchronizer apparatus located intermediate first and second gears journally mounted on said shaft, each of said gears having an externally splined surface concentrically formed thereon, said synchronizer apparatus comprising:

• a hub fixed on said transmission shaft intermediate said gears and having an externally splined surface formed thereon;
• a shift sleeve having an internally splined surface intermeshed with said hub externally splined surface and adapted for slidable axial travel relative to said hub in a first and second direction for selectively engaging said first and second gear splined surfaces, respectively, so as to alternately couple said first and second gears for rotation with said transmission shaft;
• a first blocker ring concentrically surrounding said transmission shift intermediate said first gear and said hub and having a first conical surface;
• a first inner cone ring concentrically surrounding said transmission shaft and having a second conical surface adapted to define a first clearance with said first conical surface;
• a first middle cone ring concentrically disposed in said first clearance having a first friction surface adapted to frictionally engage said first conical surface and a second friction surface adapted to frictionally engage said second conical surface for developing frictional cone torque therebetween upon energization of said apparatus upon movement of said shift sleeve in said first direction;
• a second blocker ring concentrically surrounding said transmission shaft intermediate said second gear and said hub and having a third conical surface;
• a second inner cone ring concentrically surrounding said transmission shaft and having a fourth conical surface adapted to define a second clearance with said third conical surface;
• a second middle cone ring concentrically disposed in said second clearance having a third friction surface adapted to frictionally engage said third conical surface and a fourth friction surface adapted to frictionally engage said fourth conical surface for developing frictional cone torque therebetween upon energization of said apparatus upon movement of said shift sleeve in said second direction;
• thrust means for moving one of said first and second blocker rings toward its associated gear during axial shifting operation of said shift sleeve for energizing said apparatus;
• and
• torque amplification means operatively interconnecting said first and second blocker rings to said first and second inner cone rings respectively, for causing at least one of said first blocker ring and said first inner cone ring to move axially relatively to the other for generating increased frictional engagement between said first and second conical surfaces and said first and second friction surfaces, respectively, when said shift sleeve is moved in said first direction, and wherein said torque amplification means causes at least one of said second blocker ring and said second inner cone ring to move axially relative to the other for generating increased frictional engagement between said third and fourth conical surfaces and said third and fourth friction surfaces, respectively, when said shift sleeve is moved in said second direction, said torque amplification means including a plurality of drive tangs longitudinally extending from said first and second inner cone rings and adapted to project into associated apertures formed in said first and second blocker rings, respectively, each said drive tangs having a circumferential width substantially less than the circumference of said inner ring such that said drive tang width is substantially narrow with respect to the circumferential distance between adjacent drive tangs and a cam surface on each of its longitudinal sides for defining a first acute angle and each said aperture forming complementary angled side wall means for defining a second acute angle such that said first angle is substantially equal to said second angle, said drive tang cam surfaces being a pair of symmetrical back-angled cam edges which diverge outwardly from a centerline of said drive tangs at said first acute angle, and wherein said side walls define a pair of symmetrically disposed blocker ring side walls which diverge outwardly at said second acute angle, and wherein said second acute angle being substantially equal to said first acute angle, whereby said frictional cone torque generated by said synchronizer apparatus is increased for a given input force exerted by a vehicle operator during said axial shifting operation.

In a synchronizer and gear assembly comprising:

• a longitudinally extending transmission shaft with at least one ratio gear journally mounted on said shaft, an externally splined hub fixed on said shaft and a shift sleeve having internal splines coupled to said hub external splines for slidable movement thereon to an operative position for engaging said ratio gear so as to couple said ratio gear in rotation with said shaft, a blocker ring having an internal cone surface defining a clearance with an external cone surface formed on an inner cone ring, a thrust mechanism disposed between said shift sleeve and said blocker ring for energizing said assembly upon sliding movement of said shift sleeve toward said ratio gear, a middle cone ring is concentrically disposed in said clearance adjacent said blocker ring internal cone surface, said middle cone ring defining an external cone surface adapted to frictionally engage said blocker ring internal cone surface said middle cone ring defining an internal cone surface adapted to frictionally engage said inner cone ring external cone surface, an improvement wherein said inner cone ring has a plurality of axially extending drive tangs which project into complementary aperture means formed in said blocker ring, a circumferential width substantially less than the circumference of said inner ring such that said drive tang width is substantially narrow with respect to the circumferential distance between adjacent drive tangs and said drive tangs disposed about its longitudinal center line for defining a back-angled cam edge which diverges outwardly from said centerline at a predetermined acute angle, said aperture means having an angled side wall which diverges outwardly at a second acute angle, whereby upon said shift sleeve being initially moved said thrust mechanism presses said blocking ring internal cone surface against said middle cone ring external friction surface for causing said middle cone ring internal friction surface to press against said inner cone ring external cone surface such that said inner cone ring is rotated relative to said blocker ring such that said drive tang back-angled cam edge slidably engages said opposed angled side wall formed in said blocker ring, said sliding engagement acting to draw said blocker ring toward said ratio gear such that said blocker ring internal cone surface and said inner cone ring external cone surface are drawn into tighter frictional engagement with said middle cone ring external friction surface and said middle cone ring internal friction surface, respectively, whereby the frictional cone torque developed by said assembly is increased for a given synchronizer axial input force.