| 摘要 |
In order to achieve great engine efficiency, heat, normally dissipated through the cooling system, is directed through the exhaust passage to increase the turbocharger output. Conventional iron base valve guides cannot operate effectively within the high temperature ranges. Therefore, ceramic valve guides capable of withstanding high temperature ranges are being used for increased engine durability. Unfortunately, ceramic valve guides are difficult to install into a cylinder head using any currently available techniques. The present invention provides a simple means for mounting a ceramic valve guide assembly (52) within a cylinder head (18). A ceramic sleeve (70) is inserted into a metallic sleeve (80). The ceramic sleeve (70) and the metallic sleeve (80) are machined so that an interference fit is obtained when assembled to define the valve guide assembly (52). The valve guide assembly (52) is installed into the cylinder head (18) in a normal manner. Proper selection of the dimensions and materials for the ceramic sleeve (70) and the metallic sleeve (80) will result in a design wherein the stresses and contact pressures of the ceramic sleeve (70), the metallic sleeve (80), and the cylinder head (18) are each kept reasonable at all conditions encountered during manufacturing, assembly, and operation of the engine. |
