| 摘要 |
<p>A gear pump or motor comprises a pair of gears (3,4) intermeshing to each other, a case body (5) accommodating the pair of gears, and a hard layer (15) formed on an inner surface of the case body. The hard layer is made of a material to be as hard as not to be cut by cog tips of the pair of gears. The hard layer may be a ceramic coating layer or a composite coating layer.</p> |
