Centrifugal switch for pendulum vibration absorber
A crankshaft assembly for an internal combustion engine can include a crankshaft having a lobe with a pendulum absorber coupled thereto. The pendulum absorber can include a carrier, a pendulum, a pin and a centrifugal switch assembly. The carrier can be coupled to a body of the lobe and can have an opening therein. The pendulum can have an opening therein and the pin can extend through the pendulum opening and the carrier opening to pivotably couple the pendulum to the carrier. The switch assembly can be slidably positioned in a bore of the body and can have a lock member configured to selectively engage the pendulum based on a centrifugal force being below a predetermined threshold to lock movement of the pendulum relative to the carrier.
1. A crankshaft assembly for an internal combustion engine, comprising:
a crankshaft having a lobe with a pendulum absorber coupled thereto, the pendulum absorber including:
a carrier coupled to a body of the lobe and having an opening therein,
a pendulum having an opening therein, and
a pin extending through the pendulum opening and the carrier opening to pivotably couple the pendulum to the carrier; and
a switch assembly slidably positioned in a bore of the body and having a lock member configured to selectively engage the pendulum based on a centrifugal force being below a predetermined threshold to lock movement of the pendulum relative to the carrier, the switch assembly including:
a body coupled at a first end to a mass member and at a second opposite end to the lock member; and
a biasing member positioned in the bore and configured to engage the mass member to bias the switch assembly toward an engaged position where the lock member engages the pendulum to lock the pendulum,
wherein the crankshaft comprises a center of rotation, and wherein the mass member and a center of mass of the switch assembly are positioned on a first side of the center of rotation opposite the pendulum absorber and the lock member is positioned on a second opposite side of the crankshaft center of rotation.
2. The crankshaft assembly of claim 1 , wherein a weight of the mass member is selected such that the switch assembly is tuned to overcome a biasing force of the biasing member at a predetermined RPM based on the centrifugal force generated by rotation of the crankshaft being greater than the biasing force of the biasing member.
3. The crankshaft assembly of claim 2 , wherein when the crankshaft rotation speed is above the predetermined RPM, the switch assembly is configured to move in a direction away from the pendulum absorber against the biasing force of the biasing member to a disengaged position.
4. The crankshaft assembly of claim 3 , wherein the biasing member includes a compression spring.
5. The crankshaft assembly of claim 4 , wherein the biasing member includes a conical compression spring.
6. The crankshaft assembly of claim 3 , wherein the lock member includes a pair of spaced apart axially extending lock pins.
7. The crankshaft assembly of claim 6 , wherein the lock pins slidably engage channels in first and second opposed sides of the carrier.
8. The crankshaft assembly of claim 7 , wherein the lock pins selectively engage channels in opposed walls of the pendulum when the switch assembly is in the engaged position to lock the pendulum and are spaced apart from the pendulum channels when the switch assembly is in the disengaged position.
9. The crankshaft assembly of claim 8 , wherein the pendulum defines a hollow interior having first and second opposed inner walls, the carrier being received in the hollow interior between the first and second opposed inner walls, the pendulum channels being formed in the first and second opposed inner walls of the pendulum.
10. The crankshaft assembly of claim 9 , wherein the lock pins slidably engage carrier channels formed in opposed outer walls of the carrier and selectively slidably engage the pendulum channels formed in the first and second opposed inner walls of the pendulum such that the lock pins are positioned between the opposed outer walls of the carrier and the respective opposed inner walls of the pendulum when engaged with the pendulum.
11. The crankshaft assembly of claim 1 , wherein the pendulum opening and the carrier opening having an epicycloidal configuration that causes the pendulum to follow an epicycloidal path when the crankshaft rotates, and wherein the epicycloidal configuration lies on a continuum between a tautochronic configuration and a cycloidal configuration.
12. The crankshaft assembly of claim 11 , wherein the carrier includes a second opening and the pendulum includes a second opening and wherein a second pin extends through the second pendulum opening and the second carrier opening to pivotably couple the pendulum to the carrier, the second pendulum opening and the second flange opening having the epicycloidal configuration.
13. A crankshaft assembly for an internal combustion engine, comprising:
a crankshaft having a lobe with a pendulum absorber coupled thereto, the pendulum absorber including:
a carrier coupled to a body of the lobe and having an opening therein,
a pendulum having an opening therein, and
a pin extending through the pendulum opening and the carrier opening to pivotably couple the pendulum to the carrier, the pendulum opening and the carrier opening having an epicycloidal configuration; and
a centrifugal switch assembly slidably positioned in a bore of the body and having a biasing member and a lock member, the lock member configured to i) selectively engage the pendulum based on a centrifugal force being below a predetermined threshold to lock movement of the pendulum relative to the carrier, and ii) selectively disengage from the pendulum against a biasing force of the biasing member based on the centrifugal force being above the predetermined threshold, the switch assembly further comprising a body coupled at a first end to a mass member and at a second opposite end to the lock member, wherein the biasing member is configured to engage the mass member to bias the switch assembly toward an engaged position where the lock member engages the pendulum to lock the pendulum,
wherein the crankshaft comprises a center of rotation, and wherein the mass member and a center of mass of the switch assembly are positioned on a first side of the center of rotation opposite the pendulum absorber and the lock member is positioned on a second opposite side of the crankshaft center of rotation.
14. The crankshaft assembly of claim 13 wherein a weight of the mass member is selected such that the switch assembly is tuned to overcome the biasing force of the biasing member at a predetermined RPM based on the centrifugal force generated by rotation of the crankshaft being greater than the biasing force of the biasing member.
15. The crankshaft assembly of claim 14 , wherein when the crankshaft rotation speed is above the predetermined RPM, the switch assembly is configured to move in a direction away from the pendulum absorber against the biasing force of the biasing member to a disengaged position.
16. The crankshaft assembly of claim 14 , wherein the lock member includes a pair of spaced apart axially extending lock pins, the lock pins being in sliding engagement with channels formed in first and second opposed outer sides of the carrier and in selective engagement with channels formed in first and second opposed inner sides of the pendulum.
17. The crankshaft assembly of claim 16 , wherein the lock pins selectively engage the pendulum channels when the switch assembly is in the engaged position to lock the pendulum and are spaced apart from the pendulum channels when the switch assembly is in the disengaged position.