Coating a Variable Cam Timing Vane with Molybdenum Disulfide to Reduce Internal Leakage
Publication Date: 2002-May-06
The IP.com Prior Art Database
The present invention relates to decreasing internal leakage within a hydraulically actuated VCT system to provide improved VCT performance
The present invention relates to decreasing internal leakage within a hydraulically actuated VCT system to provide improved VCT performance.
A 2-dimensional drawing of a typical VCT actuator, which is bolted to a camshaft, is shown in Figure 1. Advance of the VCT actuator, as shown in Figure 1, below, is effected by providing oil into the advance chamber which causes the vane to rotate in the advance direction and oil is drained out of the retard chamber. The VCT operates analogously in the retard direction, i.e., by providing oil to the retard chamber. The rate at which the VCT assumes a new position depends on a pressurized supply of engine oil into the appropriate chamber. Internal leakage degrades the actuation rate of the VCT and leads to an energy loss by requiring additional flow of pressurized oil into the chamber to maintain the position. In the extreme, internal leakage can lead to a VCT being unable to be actuated or unable to hold a position.
The actuator vane of Figure 1 is shown in a 3-dimensional CAD cutaway representation in Figure 2. Figure 2 shows chip seals that prevent, or limit, oil leakage past the tips of the tips of the vane. However, the seal on the front and rear faces of the vane depend on the manufacturing tolerance of the vane with respect to the housing. Further affecting the seal is the interface with the camshaft, should the camshaft have runout, i...