A fuel injector comprising a valve needle for controlling fuel injection through an injector outlet, a control chamber for receiving fuel and a three-way control valve that controls fuel pressure within the control chamber to control opening and closing movement of the valve needle to control fuel injection through the outlet. The three-way control valve controls communication between (a) a first passage and a second passage and (b) a third passage and the second passage, and includes a first housing provided with a guide bore for a control valve member, whereby movement of the control valve member is guided within the guide bore and a first valve seat, defined by a second housing, with which an end of the control valve member is engageable to control communication between the first and second passages. The first housing is a control valve housing and the second housing is an injector housing, the injector housing being provided with a guide bore for the valve needle or a part carried by the valve needle. The control valve also defines a second valve seat defined by the first housing with which the control valve member is engageable to control communication between the second and third flow passages, and an intermediate housing located between the first and second housings, wherein the second passage is defined within the intermediate housing.
1. A fuel injector comprising a first fuel supply passage, a second fuel supply passage, a valve needle for controlling fuel injection through an injector outlet, a control chamber for receiving fuel and a three-way control valve that controls fuel pressure within the control chamber to control opening and closing movement of the valve needle to control fuel injection through the outlet,
wherein the three-way control valve controls communication between (a) a drain passage and an intermediate chamber and (b) the second fuel supply passage and the intermediate chamber, the control valve comprising:
a first housing provided with a first guide bore for a control valve member, the control valve member having a first end and a second end, whereby movement of the first end of the control valve member is guided within the first guide bore and movement of the second end of the control valve member is not guided,
a first valve seat, defined by a second housing, with which the second end of the control valve member is engageable to control communication between the drain passage and the intermediate chamber, wherein the first housing is a control valve housing and the second housing is an injector housing, the injector housing being provided with a second guide bore for the valve needle or for a part carried by the valve needle,
a second valve seat defined by the first housing with which the control valve member is engageable to control communication between the intermediate chamber and the second fuel supply passage, and
an intermediate housing located between the first and second housings, wherein the intermediate chamber is defined within the intermediate housing;
wherein the intermediate housing defines a lift stop for the valve needle or for a part carried by the valve needle.
2. A fuel injector comprising a first fuel supply passage, a second fuel supply passage, a valve needle for controlling fuel injection through an injector outlet, a control chamber for receiving fuel and a three-way control valve that controls fuel pressure within the control chamber to control opening and closing movement of the valve needle to control fuel injection through the outlet,
wherein the three-way control valve controls communication between (a) a drain passage and an intermediate chamber and (b) the second fuel supply passage and the intermediate chamber, the control valve comprising:
a first housing provided with a first guide bore for a control valve member, the control valve member having a first end and a second end, whereby movement of the first end of the control valve member is guided within the first guide bore and movement of the second end of the control valve member is not guided,
a first valve seat, defined by a second housing, with which the second end of the control valve member is engageable to control communication between the drain passage and the intermediate chamber, wherein the first housing is a control valve housing and the second housing is an injector housing, the injector housing being provided with a second guide bore for the valve needle or for a part carried by the valve needle,
a second valve seat defined by the first housing with which the control valve member is engageable to control communication between the intermediate chamber and the second fuel supply passage, and
an intermediate housing located between the first and second housings, wherein the intermediate chamber is defined within the intermediate housing; wherein the control chamber communicates with the intermediate chamber of the three-way control valve;
the fuel injector further comprising a first spill passage between the control chamber and the intermediate chamber which presents a fixed restriction to fuel flow out of the control chamber when the control valve member is moved away from the first valve seat;
the fuel injector further comprising an additional spill passage between the control chamber and the intermediate chamber which presents a restriction having a variable cross-sectional area to fuel flow out of the control chamber when the control valve member is moved away from the first valve seat.
3. A fuel injector as claimed in claim 2 , wherein the intermediate housing further comprises a cross slot on its surface to connect the additional spill passage with the intermediate chamber.
4. A fuel injector as claimed in claim 2 , whereby the valve needle, or a part carried by the valve needle, cooperates with the additional spill passage to provide a variable restriction to fuel flow out of the control chamber, depending on the extent of opening movement of the valve needle.
5. A fuel injector comprising a valve needle for controlling fuel injection through an injector outlet, a control chamber for receiving fuel, and a three-way control valve that controls fuel pressure within the control chamber thereby to control opening and closing movement of the valve needle to control fuel injection through the outlet,
wherein the three-way control valve controls communication between:
(a) a drain passage and an intermediate chamber and
(b) a second fuel supply passage and the intermediate chamber,
the control valve comprising:
a first housing provided with a first guide bore for a control valve member, whereby movement of a first end of the control valve member is guided within the first guide bore and movement of a second end of the control valve member is not guided,
a first valve seat, defined by a second housing, with which a head portion of the control valve member is engageable to control communication between the drain passage and the intermediate chamber,
a second valve seat defined by the first housing with which the head portion of the control valve member is engageable to control communication between the intermediate chamber and the second high pressure fuel passage, and
an intermediate housing located between the first and second housings, wherein the intermediate chamber is defined within the intermediate housing and wherein the intermediate housing defines a lift stop for the valve needle or for a part carried by the valve needle,
further comprising a first spill passage between the control chamber and the intermediate chamber which presents a fixed restriction to fuel flow out of the control chamber when the control valve member is moved away from the first valve seat;
the fuel injector further comprising an additional spill passage between the control chamber and the intermediate chamber which presents a restriction having a variable cross-sectional area to fuel flow out of the control chamber when the control valve member is moved away from the first valve seat.
6. A fuel injector as claimed in claim 5 , whereby the valve needle, or a part carried by the valve needle, cooperates with the additional spill passage to provide the variable restriction to fuel flow out of the control chamber, depending on the extent of opening movement of the valve needle.