Fuel injection valve
View Patent ↗A fuel injection valve has: a tubular body, a valve seat member, a valve body, a core tube, a bias spring, and an electromagnetic actuator. The core tube is press fitted into the tubular body. The core tube has a first end side opposing an absorption section of the valve body in such a manner as to form an axial gap interposed between the first end side of the core tube and the absorption section. The core tube has a second end side axially extending in the tubular body to a certain position on a way to the second end side of the tubular body. The axially extending second end side of the core tube has an outer periphery which is formed with a reduced diameter section for increasing an accuracy in positioning the core tube when the core tube is press fitted into the tubular body.
1. A fuel injection valve, comprising:
a stepped tubular body of a magnetic material, including a larger body section, a smaller body section smaller in sectional size than the larger body section, and a step portion connecting the larger body section and the smaller body section;
a valve seat fixed to a forward end of the smaller body section of the stepped tubular body;
a stepped core tube including a smaller tube section confronting the valve seat, and a larger tube section press fit in the smaller body section of the stepped tubular body, the larger tube section of the stepped core tube being formed with a reduced portion located in the smaller body section of the stepped tubular body;
a valve element disposed in the smaller body section of the tubular body, between the smaller tube portion of the core tube and the valve seat; and
an electromagnetic actuator disposed outside the stepped tubular body, and arranged to drive the valve element between the core tube and the valve seat.
2. The fuel injection valve as claimed in claim 1 , wherein the reduced portion is formed in a second tube end of the stepped core tube which extends from the second tube end to a first tube end toward the valve seat.
3. The fuel injection valve as claimed in claim 2 , wherein the larger body section and the stepped portion of the stepped core tube define a larger inside cavity sized to allow passage of the stepped core tube from the larger body section into the smaller body section, and the reduced portion of the larger tube section of the stepped core tube defines an annular space which is formed between the smaller body section and the reduced portion and which is open to the larger inside cavity formed by the larger body section and the step portion.
4. The fuel injection valve as claimed in claim 2 , wherein the stepped core tube is press fit in the smaller body section of the stepped tubular body by being inserted into the stepped tubular body from a second body end of the stepped tubular body which extends in a longitudinal direction from the second body end to a first body end that is the forward end of the smaller body section in which the valve seat is fixedly disposed until the reduced portion reaches the smaller body section beyond the step portion of the stepped tubular body.
5. The fuel injection valve as claimed in claim 2 , wherein the smaller body section of the stepped tubular body has a cylindrical inside wall surface; the larger tube section of the stepped core tube has a cylindrical outside wall surface which is fit in the cylindrical inside wall surface of the smaller body section of the stepped tubular body; and the reduced portion of the larger tube section has an outside circumferential surface confronting the cylindrical inside wall surface of the smaller body section across an annular space which is bounded between the cylindrical side wall surface of the smaller body section of the stepped tubular body and the outside circumferential surface of the reduced portion of the larger tube section of the core tube.
6. The fuel injection valve as claimed in claim 5 , wherein the outside circumferential surface of the reduced portion extends from a first surface end located at an end of the outside cylindrical wall surface of the larger tube section of the stepped core tube, to a second surface end located in the second end of the stepped core tube.
7. The fuel injection valve as claimed in claim 2 , wherein the larger tube section includes a main portion having a cylindrical outside surface, fit in the smaller body section of the stepped tubular body, and the reduced portion has a cylindrical outside surface whose diameter is smaller than a diameter of the cylinder outside surface of the main portion of the larger tube section.
8. The fuel injection valve as claimed in claim 2 , wherein the cylindrical outside surface of the main portion of the larger tube section extends from a second end to a first end toward the smaller tube section; the cylinder outside surface of the reduced portion extends from a second end located in the second end of the stepped core tube, to a first end; and the reduced portion has an annular step surface extending radially inwardly from the second end of the cylindrical outside surface of the main portion of the larger tube section to the first end of the cylindrical outside surface of the reduced portion.
9. The fuel injection valve as claimed in claim 2 , wherein the reduced portion includes a tapered portion.
10. The fuel injection valve as claimed in claim 9 , wherein the larger tube section has an outside cylindrical surface which is forcibly fit in the smaller body section of the stepped tubular body and which extends from a second end to a first end in a longitudinal direction of the stepped core tube; and the tapered portion of the reduced portion extends from a second end located in the second end of the stepped core tube to a first end located at the second end of the cylindrical outside surface of the larger tube section, and has a cross sectional size gradually decreasing from the first end of the tapered portion to the second end of the tapered portion.
11. The fuel injection valve as claimed in claim 2 , wherein the reduced portion of the stepped core tube is spaced inwardly from an inside surface of the smaller body section so as to form an annular space between the inside surface of the smaller body section and the reduced portion and thereby to allow the smaller body section to be deformed elastically into the annular space to prevent movement of the stepped core tube in the smaller body section of the stepped tubular body in a direction toward the larger body section.
12. The fuel injection valve as claimed in claim 2 , wherein the fuel injection valve further comprises a spring retainer fixed in the stepped core tube, and a bias spring disposed between the spring retainer and the valve element.
13. The fuel injection valve as claimed in claim 10 , wherein the bias spring includes a second end portion received inside the stepped core tube, and a first end portion received in an inside cavity formed in the valve element.
14. The fuel injection valve as claimed in claim 2 , the larger body section of the stepped tubular body extends from a second end to a first end in a longitudinal direction of the fuel injection valve; the smaller body section of the stepped tubular body extends from a second end to a first end in the longitudinal direction; the step portion of the stepped tubular body extends from the first end of the larger body section to the second end of the smaller body section so that a cross sectional size of the step portion decreases gradually from the first end of the larger body section to the second end of the smaller body section; and the reduced portion is formed so that an annular space is formed between the reduced portion and a second end portion of the smaller body section of the stepped tubular body.