Thermoplastic jounce bumpers
View Patent ↗The invention provides vehicle suspension systems, and more particularly jounce bumpers made of elastomeric thermoplastic material, having improved design to maximize energy absorption.
1. A jounce bumper made of elastomeric thermoplastic material, comprising:
a hollow elongated tubular body having a wall, the tubular body having at least two bellows, each bellow being defined by a peak and a trough, the peak having a fillet radius of rs, the trough having a fillet radius of rc and a maximum wall thickness in the trough of Tmax; wherein rc is greater than rs, and wherein the ratio of Tmax, the maximum thickness of the wall in a trough to Tm, the thickness of the wall at intermediate points between peaks and troughs, is greater than or equal to 1.5, wherein the trough is defined by a wall arc having end points at said intermediate points where the wall thickness is Tm;
wherein each of said intermediate points is a point of tangency between a circle of radius rc and a circle of radius rs, or if rs and rc are not tangent, Tm is the wall thickness wherein each of said intermediate points is a midpoint of a line drawn tangent to circles rs and rc; and
wherein the force required to compress said jounce bumper to 50 percent relative deformation is at least 14 percent greater than the force required to compress a jounce bumper to 50 percent relative deformation which does not have a ratio of Tmax to Tm of greater than or equal to 1.5.
2. A jounce bumper according to claim 1 , wherein (Tmax/Tm), the ratio of maximum wall thickness in the trough to the thickness of the wall at said intermediate points, is greater than (Tmax/Tm) 1 ,
wherein (Tmax/Tm) 1 =3.43−0.05 P−0.222 SQRT (95−4.19 P+0.05P 2 −0.23Ri), where
Tmax is the maximum wall thickness at a trough;
Tm is the wall thickness wherein each of the intermediate points is a point of tangency between a circle of radius rc and a circle of radius rs, or if rs and rc are not tangent, Tm is the wall thickness wherein each of the intermediate points is a midpoint of a line drawn tangent to circles rs and rc;
SQRT is square root;
P is the pitch; and
Ri is the external radius at a trough.
3. A jounce bumper according to claim 2 comprising a thermoplastic elastomer that has a melt viscosity between 0.5 and 8 g/10 minutes, at 230° C. under 5 kg load measured according to ISO1133, and a hardness between at or about 45 and 60D measured at 1s according to ISO868.
4. A jounce bumper according to claim 2 comprising a thermoplastic elastomer that has a melt viscosity between 2 and 6 g/10 minutes, at 230° C. under 5 kg load measured according to ISO1133, and a hardness between at or about 45 and 60D measured at 1s according to ISO868.
5. A jounce bumper according to claim 2 comprising a thermoplastic elastomer that has a melt viscosity between 3 and 5 g/10 minutes, at 230° C. under 5 kg load measured according to ISO1133, and a hardness between at or about 45 and 60D measured at 1s according to ISO868.
6. A jounce bumper according to claim 1 comprising a thermoplastic elastomer that has a melt viscosity between 0.5 and 8 g/10 minutes, at 230° C. under 5 kg load measured according to ISO1133, and a hardness between at or about 45 and 60D measured at 1s according to ISO868.
7. A jounce bumper according to claim 1 comprising a thermoplastic elastomer that has a melt viscosity between 2 and 6 g/10 minutes, at 230° C. under 5 kg load measured according to ISO1133, and a hardness between at or about 45 and 60D measured at 1s according to ISO868.
8. A jounce bumper according to claim 1 comprising a thermoplastic elastomer that has a melt viscosity between 3 and 5 g/10 minutes, at 230° C. under 5 kg load measured according to ISO1133, and a hardness between at or about 45 and 60D measured at 1s according to ISO868.
9. A jounce bumper according to claim 1 comprising a thermoplastic elastomer that is selected from the group consisting of copolyetheresters and copolyesteresters that are copolymers having a multiplicity of recurring long-chain ester units and short-chain ester units joined head-to-tail through ester linkages, said long-chain ester units being represented by formula (A):
and said short-chain ester units being represented by formula (B):
wherein
G is a divalent radical remaining after the removal of terminal hydroxyl groups from poly(alkylene oxide)glycols having preferably a number average molecular weight of between about 400 and about 6000; R is a divalent radical remaining after removal of carboxyl groups from a dicarboxylic acid having a molecular weight of less than about 300; and D is a divalent radical remaining after removal of hydroxyl groups from a diol having a molecular weight preferably less than about 250; and wherein said copolyetherester(s) preferably contain from about 15 to about 99 wt-% short-chain ester units and about 1 to about 85 wt-% long-chain ester units.
10. A jounce bumper according to claim 1 wherein Tmax occurs substantially in the middle of the trough.
11. A method for the manufacture of a jounce bumper, comprising the step of:
shaping elastomeric thermoplastic material into a hollow elongated tubular body having a wall, the tubular body having at least two bellows, each bellow being defined by a peak and a trough, the peak having a fillet radius of rs, the trough having a fillet radius of rc and a maximum wall thickness at the trough of Tmax;
wherein rc is greater than rs, and wherein the ratio of Tmax, the maximum thickness of the wall at a trough, to Tm, the thickness of the wall at intermediate points between peaks and troughs, is greater than or equal to 1.5, wherein the trough is defined by a wall arc having end points at said intermediate points where the wall thickness is Tm;
wherein each of said intermediate points is a point of tangency between a circle of radius rc and a circle of radius rs, or if rs and rc are not tangent, Tm is the wall thickness wherein each of said intermediate points is a midpoint of a line drawn tangent to circles rs and rc; and
wherein the force required to compress said jounce bumper to 50 percent relative deformation is at least 14 percent greater than the force required to compress a jounce bumper to 50 percent relative deformation which does not have a ratio of Tmax to Tm of greater than or equal to 1.5.
12. A method of claim 11 , wherein the method of shaping comprises a shaping operation selected from the group consisting of injection molding, extrusion, and blow molding.
13. A method according to claim 11 wherein Tmax occurs substantially in the middle of the trough.
14. A method for absorbing shocks in an automobile suspension comprising using a jounce bumper to absorb energy from displacement of the suspension, wherein the jounce bumper is made of elastomeric thermoplastic material and comprises a hollow elongated tubular body having a wall, the tubular body having at least two bellows, each bellow being defined by a peak and a trough, the peak having a fillet radius of rs, the trough having a fillet radius of rc and a maximum wall thickness at the trough of Tmax; wherein rc is greater than rs, wherein the ratio of Tmax the thickness of the wall at a trough, to Tm, the thickness of the wall at intermediate points between peaks and troughs, is greater than or equal to 1.5
wherein the trough is defined by a wall arc having end points at said intermediate points where the wall thickness is Tm;
wherein each of said intermediate points is a point of tangency between a circle of radius rc and a circle of radius rs, or if rs and rc are not tangent, Tm is the wall thickness wherein each of said intermediate points is a midpoint of a line drawn tangent to circles rs and rc; and
wherein the force required to compress said jounce bumper to 50 percent relative deformation is at least 14 percent greater than the force required to compress a jounce bumper to 50 percent relative deformation which does not have a ratio of Tmax to Tm of greater than or equal to 1.5.