Injector

Abstract

An injector includes a boosting mechanism and a nozzle. The boosting mechanism boosts fuel, and the nozzle injects and supplies the fuel boosted by the boosting mechanism. The boosting mechanism includes a tubular piston and a column piston. The tubular piston has a bore, which extends through the tubular piston in a direction of a longitudinal axis of the tubular piston. The column piston is loosely received by the tubular piston and has an end portion, which projects from the tubular piston, and which is engaged with the tubular piston. The tubular piston is slidably received by a first cylinder. The end portion of the column piston is slidably received by a second cylinder, which is provided generally coaxially to the first cylinder, and which has a diameter different from that of the first cylinder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:

FIG. 1 is an explanation view showing a structure of an injector according to an embodiment of the present invention; and

FIG. 2 is a schematic view of a tubular piston and a column piston of a boosting mechanism taken along line II-II in FIG. 1.

Claims

1. An injector comprising: a boosting mechanism that boosts fuel; anda nozzle that injects and supplies the fuel boosted by the boosting mechanism, wherein:the boosting mechanism includes: a tubular piston that has a bore, which extends through the tubular piston in a direction of a longitudinal axis of the tubular piston; anda column piston that is loosely received by the tubular piston and has an end portion, which projects from the tubular piston, and which is engaged with the tubular piston;the tubular piston is slidably received by a first cylinder; andthe end portion of the column piston is slidably received by a second cylinder, which is provided generally coaxially to the first cylinder, and which has a diameter different from that of the first cylinder.

2. The injector according to claim 1, wherein: the boosting mechanism includes: a boosted chamber that is defined by one of the first and second cylinders, wherein the one is a small-diameter cylinder having a diameter smaller than the other one of the first and second cylinders, and the fuel to be boosted flows into and out of the boosted chamber; anda boosting chamber that is defined by the other one of the first and second cylinders, wherein the other one is a large-diameter cylinder having a diameter larger than the one, and the fuel, which acts as a boosting medium, flows into and out of the boosting chamber; andbiasing device that biases one of the tubular piston and the column piston in a direction for reducing pressure of the fuel in the boosted chamber, wherein the one of the tubular piston and the column piston is slidably received by the small-diameter cylinder.

3. The injector according to claim 1, wherein: the column piston is loosely received by the tubular piston to define an annular loosely receiving clearance; andthe annular loosely receiving clearance is defined such that a total clearance of the annular loosely receiving clearance in a direction approximately transverse to the longitudinal axis of the tubular piston is at least 20 μm.