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| Illustration 1 | g00521301 |
Typical Dashpot (A) Engine oil (B) Oil (piston cavity) (1) Spring seat (2) Dashpot spring (3) Piston (4) Seat (5) Overflow passage (6) Plug orifice (7) Oil passage (8) Reservoir (9) Passage | |
Governors on engines that require close regulation are equipped with a dashpot. The dashpot improves engine stability during sudden load changes.
Engine oil is supplied to the dashpot by oil passage (7) near the end of the riser shaft. The oil then flows through passage (9) and into reservoir (8). Excess oil leaves the reservoir through overflow passage (5) .
When spring seat (1) is moved by a change in speed, dashpot spring (2) moves piston (3) in seat (4). When the engine speed increases, piston (3) moves to the right. The oil in the piston cavity is placed under pressure as the oil is forced through orifice (6) and into reservoir (8) .
When engine speed decreases, piston (3) moves to the left. This causes a decrease in the pressure in the piston cavity. Oil is now pulled through orifice (6) from reservoir (8) .
Orifice (6) restricts the flow of oil to the piston cavity and from the piston cavity. This orifice causes a restriction to movement of piston (3) and spring seat (1). As the governor tries to move spring seat (1) faster, the dashpot resists the movement more.