Denso Corporation

Atsushi Utsunomiya

Kazufumi Serizawa

Shinya Sano

Fumiaki Arikawa

Toshiaki Hijima

Yuuta Hashimoto

Motoya Kanbara

Fumihiro Fujikake

A throttle portion is defined between an upper end of a sac chamber and a conical portion of a needle to have a throttle opening area S. Half of an area surrounded by the throttle portion, the needle, an inner wall of the sac chamber, and a lower end extended line in a cross section of the sac chamber taken along a sac center line is an injection hole upstream area S. A lift amount, when the throttle opening area Sis equal to an area which is calculated by multiplying an injection hole area Sby the number of the injection holes, is a predetermined lift amount L. A viscosity coefficient of fuel is &#x3c1;. An index value Sa, which is calculated in accordance with an equation as below, is set to 0.5 or greater. 

Fuel injection nozzle

In an injection hole of a nozzle, a maximum value of a longitudinal length of an inlet, which is measured in a direction of an inlet longitudinal axis of the inlet, is larger than a maximum value of a longitudinal length of an outlet, which is measured in a direction of an outlet longitudinal axis of the outlet. A rear end edge of an opening edge of the inlet is shaped into an arc. When the maximum value of the inlet is made larger than the maximum value of the outlet, an upstream end of the inlet can be placed at a further upstream side, so that a turn angle of a fuel flow can be reduced to increase the flow coefficient. Furthermore, when the rear end edge is shaped into the arc, the maximum value of the inlet can be increased.

In a nozzle, in a cross section including an axis of a nozzle body, a side surface and a seat surface are both smoothly connected to an arc of a circle inscribing both the side surface and the seat surface. A part of a needle which is adjacent to a tip end side of a seat portion is a cone having a diameter reduced toward a tip end side of the cone in the axial direction. Thus, no corner is on the seat surface or the side surface, and the two surfaces form one curved surface. Since a cavitation generated in a sack chamber can be reduced, even when an injection quantity is significantly small such that an injection port does not throttle an injection flow, a flow coefficient of the injection flow is improved and a penetration of a spray of the fuel can be maintained.

A fuel injector has a cylindrical nozzle body, a nozzle needle, a pressure chamber and an injection passage. The injection passage includes a first hole and a second hole. A minimum vertical distance between an outer periphery of a first nozzle hole outlet and a contact point relative to an axial center line of the first hole is defined as a vertical distance R. A minimum axial distance between the first nozzle hole outlet and the contact point relative to an axial center line of the first hole is defined as an axial distance L. An angle between the axial center line of the first nozzle hole and the outer periphery line of the fuel spray is defined as an injection angle &#x3b8;. The vertical distance R, the axial distance L and the injection angle &#x3b8; satisfy a formula: R/(L&#xd7;tan &#x3b8;)&#x3e;6.0.

Growing community of inventors

Kariya, Japan

Atsushi Utsunomiya