This paper is on the improvement of the oil pump assembly for preventing low oil pressure symptoms of the K9 Self-Propelled howitzer engine. Although the TBO(Time Between Overhauls) of K9 self-propelled howitzer engine is 1,500 engine operating hours, 13.37 % of K9 Self-Propelled howitzer engines which were operated for only hundreds of hours suffered low oil pressure symptoms and failed to operate normally. Detailed investigation into the engine was conducted to establish the cause and generation mechanism of the symptoms and it was found that oil leakage due to abrasive wear of pressure relief valve piston housing occurred in the oil pump assembly. To prevent abrasive wear of piston housing, new design concept and design parameters of pressure relief valve have been proposed. Performance, durability and system installation test on the prototype based on the proposed design were followed and results validated the proposed design. Oil pump assembly based on this study is applied to mass production.

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