| 摘要 |
PROBLEM TO BE SOLVED: To provide a valve superior in durability, by reducing abrasion of a seat ring, by reducing operation torque, by reducing an increase in pressing force to a plug of the seat ring by a variation in fluid differential pressure. SOLUTION: Assuming a distance up to a contact part A between the plug 35 and the seat ring 50 from the flow passage axis 34 of a valve body 33 as (a), a distance b<SB>1</SB>up to an outer peripheral surface of a thin part 51A of a first holding part 51 from the flow passage axis 34 is set substantially equal to the distance (a). Here, the pressure receiving surface S<SB>1</SB>when pressing the seat ring 50 to the plug 35 by the fluid differential pressure P, is expressed by (b<SB>1</SB><SP>2</SP>- a<SB>1</SB><SP>2</SP>)×π, but since the b<SB>1</SB>is substantially equal to (a), the S<SB>1</SB>becomes substantially zero. Thus, the force F of pressing the seat ring 50 to the plug 35 by a variation in the fluid differential pressure, is reduced, compared with a conventional valve of setting the distance b1 up to a contact part B between the first holding member 51 and an O ring 54 from the flow passage axis 34, to be larger than the distance (a), and the valve of small operation torque is provided. COPYRIGHT: (C)2009,JPO&INPIT
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