In an engine valve, a first sliding area formed at a valve head side in an outer face of a valve stem, and sliding along a stem guide, a second sliding area formed at an opposite side from the valve head side, and sliding along the stem guide, and a first small diameter area formed between the first sliding area and the second sliding area are formed. Further, in the engine valve, a length, in an axial direction of the valve stem, of the first sliding area abutting on the stem guide at a position where the engine valve is fully opened is longer as compared with a length, in the axial direction of the valve stem, of the second sliding area abutting on the stem guide at a position where the engine valve is fully closed.

In an engine valve, a first sliding area formed at a valve head side in an outer face of a valve stem, and sliding along a stem guide, a second sliding area formed at an opposite side from the valve head side, and sliding along the stem guide, and a first small diameter area formed between the first sliding area and the second sliding area are formed. Further, in the engine valve, a length, in an axial direction of the valve stem, of the first sliding area abutting on the stem guide at a position where the engine valve is fully opened is longer as compared with a length, in the axial direction of the valve stem, of the second sliding area abutting on the stem guide at a position where the engine valve is fully closed.

Provided is a reverse osmosis treatment system capable of simultaneously and efficiently recovering energy generated both at brine and permeate sides. The system comprises a branched portion configured to divide second to-be-treated water into third and fourth to-be-treated water; a high-pressure pump configured to pressurize the third to-be-treated water thereby to feed fifth to-be-treated water having a higher pressure than the to-be-treated water before divided; a displacement type of first energy recovery device configured to exchange pressures between the fourth to-be-treated water and brine thus separated by a reverse osmosis treatment device, thereby to produce sixth to-be-treated water having a higher pressure than the fourth one; and a second energy recovery device configured to raise a pressure of the third to-be-treated water located at a downstream side of the branched portion with a pressure of first permeate thus separated by the reverse osmosis treatment device.

Provided is a reverse osmosis treatment system capable of simultaneously and efficiently recovering energy generated both at brine and permeate sides. The system comprises a branched portion configured to divide second to-be-treated water into third and fourth to-be-treated water; a high-pressure pump configured to pressurize the third to-be-treated water thereby to feed fifth to-be-treated water having a higher pressure than the to-be-treated water before divided; a displacement type of first energy recovery device configured to exchange pressures between the fourth to-be-treated water and brine thus separated by a reverse osmosis treatment device, thereby to produce sixth to-be-treated water having a higher pressure than the fourth one; and a second energy recovery device configured to raise a pressure of the third to-be-treated water located at a downstream side of the branched portion with a pressure of first permeate thus separated by the reverse osmosis treatment device.