Rocker arm assembly and components therefor
A system for preloading a latch used in a variable valve actuation system for internal combustion engines is disclosed. It includes a rocker arm assembly having a first arm for operatively engaging the first cam for a first desired lift profile, and a second arm for operatively engaging the second cam for a second desired lift profile. A selectively-activatable latch to operatively latch the second arm with the first arm. An electronic control unit (ECU) communicates with an oil control valve that changes oil pressure to the latch to cause it to secure the arms together, or allow them to move independently. Due to the short time period required to operate the latch, the ECU provides a signal for the oil control valve to supply oil pressure or release oil pressure prior to the rocker arms being engaged with the base circle of the cams. This effectively preloads the latch causing it to react quickly and within the small time period allowed to latch.
1. A system for preloading a latch used in controlling variable valve actuation in an automobile, the system comprising:
at least a first and second cam each comprising a base circle portion and a lift portion;
a rocker arm assembly for operative engagement with the cams, the rocker arm assembly comprising:
a first arm for operatively engaging the first cam for a first desired lift profile,
a second arm for operatively engaging the second cam for a second desired lift profile, the second arm comprising a selectively-activatable latch to operatively engage the second arm with the first arm,
an electronic control unit (ECU); and
an oil control valve in electronic communication with the ECU, operatively coupled to the rocker arm assembly and at least one of supplying and releasing oil pressure to operate the latch based on an electronic signal received from the ECU;
wherein the ECU provides a signal for the oil control valve to at least one of supply oil pressure or release oil pressure prior to the first and second arms being engaged with the base circle portion of each respective first and second cams.
2. The system of claim 1 having at least two rocker arm assemblies, each rocker arm assembly comprising:
a first arm for operatively engaging the first cam for a first desired lift profile,
a second arm for operatively engaging the second cam for a second desired lift profile, the second arm comprising a selectively-activatable latch to operatively engage the second arm with the first arm,
wherein the selectively-activatable latch only operatively engages the first arm with the second arm while the first and second arms are operatively engaged with the base circle portion of the first and second cams,
wherein operative engagement of the first arm with the second arm achieves a first desired lift profile,
wherein operative disengagement of the first arm with the second arm achieves a second desired lift profile,
wherein the oil control valve is operatively coupled to the at least two rocker arm assemblies and at least one of supplies or releases oil pressure to operate each selectively-activatable latch based on electronic signals received from the ECU.
3. The system of claim 2 comprising at least two other switching rocker arm assemblies, each of the at least two other switching rocker arm assemblies comprising:
a first arm for operatively engaging the first cam for a first desired lift profile,
a second arm for operatively engaging the second cam for a second desired lift profile, the second arm comprising:
a selectively-activatable latch to operatively engage the second arm with the first arm,
and a second oil control valve operatively coupled to the at least two other switching rocker arm assemblies and at least one of supplying or releasing oil pressure to operate each selectively-activatable latch of the at least two other switching rocker arm assemblies based on electronic signals received from the ECU.
4. The system of claim 3 wherein all of the said rocker arm assemblies are coupled respectively to an engine cylinder.
5. The system of claim 3 wherein the selectively-activatable latch only operatively engages the first arm with the second arm while the first and second arms are operatively engaged with the base circle portion of the first and second cams.
6. The system of claim 5 wherein operative engagement of the first arm with the second arm achieves a first desired lift profile.
7. The system of claim 6 wherein operative disengagement of the first arm with the second arm achieves a second desired lift profile.
8. The system of claim 1 wherein the selectively-activatable latch only operatively engages the first arm with the second arm while the first and second arms are operatively engaged with the base circle portion of the first and second cams.
9. The system of claim 8 wherein operative engagement of the first arm with the second arm achieves a first desired lift profile.
10. The system of claim 9 wherein operative disengagement of the first arm with the second arm achieves a second desired lift profile.