| CPC F02M 63/005 (2013.01) [F02M 59/46 (2013.01); F02M 59/464 (2013.01); F02M 63/0036 (2013.01)] | 9 Claims |
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1. A fuel pump comprising:
a plunger adapted to reciprocate;
a pressurizing chamber adapted to increase and decrease its volumetric capacity through the reciprocation of the plunger;
a second chamber; and
a relief valve mechanism adapted to return a fuel to the pressurizing chamber,
wherein
the relief valve mechanism includes
a holder;
a relief valve, and
a seat member having a valve contact portion for seating the relief valve thereon,
the relief valve is disposed closer to the plunger than the seat member,
the seat member includes an annular groove portion which forms a space communicating with the pressurizing chamber between the annular groove portion and a fixing portion surrounding an outer peripheral surface of the seat member,
the space is provided at a position farther from the plunger than the valve contact portion,
a first gap is formed between a flange portion of the seat member and the holder of the relief valve,
an opening area of a peripheral surface of the first gap which faces the second chamber communicates a space generated near a valve contact portion with a plunger side of the pressurizing chamber,
a second gap is formed between an outer peripheral surface of the flange portion and an inner peripheral surface of the second chamber,
an opening area of a plane in the second gap which is orthogonal to a center line of the second chamber communicates a second space with a plunger side of the pressurizing chamber,
the opening area of the second gap is 1.25 times larger than an opening area of the first gap, and
a size of the opening area of the first gap is 0.16 mm or less.
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