Composite engine part and fastener assembly and method of securing a composite part to an engine
A method of securing a composite plastic part to an engine with a bolt or a bolt and washer. The bolt has a head including teeth that are adapted to engage either the part or the washer. The bolt is tightened to cause the teeth to compress the surface of the part to resist rotation that may become loosened as a result of vibration of the engine. The part may be an intake manifold, a cam cover or an oil pan. Locking features, such as teeth, may be provided on the clamping surface of the bolt and on both surfaces of the washer. Alternatively, a knurled or serrated surface may be provided instead of the teeth.
1. A method of securing a composite plastic part to an engine with a bolt and a washer comprising:
providing the composite plastic part that defines a hole;
providing a first locking feature on a first surface of the washer that engages the part, the first locking feature including a first set of teeth, each of the teeth extending radially outward from an inner hole defined in the washer to a periphery of the washer, each of the teeth being a triangular prism having a base attached to the first surface and an edge opposite the base for engaging the part;
providing a second locking feature on a second surface of the washer;
providing a third locking feature on a washer engaging surface of the bolt; and
inserting the bolt through the hole and the washer and rotating the bolt in a first rotational direction to cause the third locking feature to engage the second locking feature to rotate the washer, wherein the washer is rotated by the bolt to cause the first locking feature to compress the surface of the part sufficiently to resist rotation in a second rotational direction caused by vibration of the engine.
2. The method of claim 1 wherein the second locking feature is a second set of teeth and the third locking feature is a third set of teeth.
3. The method of claim 2 wherein the first set of teeth is smaller than the second and third sets of teeth.
4. The method of claim 3 further comprising:
selecting the washer based upon a coefficient of friction value of the composite plastic part; and
rotating the bolt and the washer in the first rotational direction wherein the first set of teeth is driven into engagement with the part by the third set of teeth engaging the second set of teeth.
5. The method of claim 1 wherein the bolt directly engages the composite part without inserting a torque limiter sleeve in the composite part around the bolt.