Tension-reducing random sprocket

A sprocket comprising:

• a plurality of teeth disposed along a circumference of the sprocket, adjacent teeth having roots therebetween, each of the roots having a root radius defined as the distance between the center of the sprocket and a point along the root closest to the sprocket center in a radial direction, the sprocket teeth and roots disposed to receive and engage a circular loop of chain which operates at variable speeds;
• and
• at least three different root radii, including a first root radius, a second root radius and a third root radius, the second radius less than the first and the third less than the second,
• the at least three different root radii arranged in a sequence which uninterruptedly and continually repeats itself around the sprocket for distributing the tensions imparted to the chain by the sprocket to one or more preselected orders relative to the rotation of the sprocket, the distributed tensions effective to offset tensions imparted to the chain by forces external to the sprocket reducing maximum tension forces exerted on the chain relative to maximum tension forces in the system where the sprocket is a straight sprocket.

A method of distributing tensions imparted to a chain and sprocket system operating at variable speeds, the method comprising:

• providing a sprocket having a plurality of teeth separated by roots;
• providing each root with a root radius extending between the center of the sprocket and a point along the root closest to the sprocket center in a radial direction;
• providing at least three different root radii;
• and
• arranging the different root radii in a pattern which continually repeats itself at least two times for distributing the tensions imparted to the chain and sprocket system reducing maximum tension forces exerted on the chain relative to maximum tension forces in the system where the sprocket is a straight sprocket.

An automotive timing system comprising:

• a chain which operates at variable speeds, the chain having a plurality of pairs of links being interconnected by pins;
• and
• a generally circular sprocket mounted on a cam shaft having a plurality of teeth spaced about the periphery, the sprocket having roots located between pairs of adjacent teeth for receiving the chain pins,
• each of the roots having a root radius extending between the center of the sprocket and a point along the root closest to the sprocket center in a radial direction,
• at least one of the roots having a first root radius, at least one of the roots having a second root radius, and at least one of the roots having a third root radius, the second root radius being less than the first root radius and the third root radius being less than the second root radius, and
• the first, second, and third root radii arranged in a sequence which uninterruptedly and continually repeats itself at least two times and which maintains the distance between the chain pins substantially constant while the chain is engaged around the sprocket and effective to redistribute tensions imparted to the chain reducing maximum tension forces exerted on the chain during operation of the system.

An automotive drive system comprising:

• a chain subject to tension loading sources external to the drive chain, the chain having a plurality of links, each link formed of two or more plates interconnected by pins, each pin having a central longitudinal axis, and the links providing contact surfaces;
• the chain traveling in a loop about at least one sprocket in driving engagement with the chain and at least one sprocket in driven engagement with the chain, each sprocket having a central axis of rotation and plurality of surfaces spaced about the periphery of the sprocket disposed to engage the chain link contact surfaces;
• the sprocket engagement surfaces spaced a distance from the sprocket central axis to position the chain at a pitch radius defined by the distance between the sprocket central axis and the pin axis of a chain link engaged by the surfaces;
• and
• the engagement surfaces of at least one of the sprockets disposed to engage the chain at least at a first pitch radius, at least at a second pitch radius, and at least a third pitch radius, the first, second and third pitch radii being different and arranged in a pattern which continually repeats itself, with each rotation of the sprocket and the pattern imparting tensions to the chain at one or more sprocket orders effective to reduce maximum chain tensions during operation of the system relative to maximum chain tensions of the system where the sprocket is a straight sprocket.

An automotive drive system operable at variable speeds comprising:

• a chain subject to tension loads in a loop about at least one sprocket in driving engagement with the chain,
• and at least one sprocket in driven engagement with the chain, the system operating at one or more speeds where chain tensions reach a peak relative to chain tensions at other system speeds, the system having tensions imparted from sources other than the chain and sprocket,
• the chain having a plurality of links formed of two or more plates interconnected by pins, each pin having a central longitudinal axis and the links providing chain contact surfaces,
• the at least one sprocket having a central axis of rotation and a plurality of teeth end sprocket engagement surfaces between the teeth,
• the teeth and the sprocket engagement surfaces spaced about the periphery of the sprocket, the sprocket engagement surfaces disposed to engage the chain link contact surfaces,
• the sprocket engagement surfaces spaced a distance from the sprocket central axis to dispose the chain at a pitch radius defined by the distance between the sprocket central axis and the pin axis of a chain link engaged by the surfaces;
• and
• the engagement surfaces of at least one of the sprockets disposed to engage the chain to provide a sequence of at least a minimum pitch radius, at least a maximum pitch radius, and at least a intermediate pitch radii therebetween,
• the engagement surfaces maintaining the distance between adjacent pin axes of links engaged with the sprocket substantially constant, and
• the pitch radii sequence uninterruptedly and continually repeating itself at least twice with each rotation of the sprocket for imparting tensions to the chain timed with respect to tension loads imparted to the system from other sources effective to reduce maximum chain tensions at one or more of the peak tension speeds relative to the maximum chain tensions at said peak tension speeds where the sprocket is a straight sprocket.

A chain and sprocket drive system comprising:

• a chain having a plurality of pairs of links being interconnected by pins;
• one or more generally circular sprockets having a plurality of teeth spaced about their periphery, the sprocket having roots located between pairs of adjacent teeth for receiving the chain pins;
• each of the roots having a root radius extending between the center of the sprocket and a point along the root closest to the sprocket center in a radial direction;
• at least one of the roots having a first root radius, and at least one of the roots having a second root radius, at least one of the roots having a third root radius, the second root radius being less than the first root radius, the third root radius being less than the second root radius;
• and
• the first, second and third root radii arranged in a pattern that substantially continually repeats itself four times around the sprocket, the pattern effective to redistribute tensions imparted to the chain, reducing maximum tension forces exerted on the chain during operation of the system relative to the maximum tension forces in the system where the sprocket is a straight sprocket.