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A fuel injector body has a fuel chamber and a valve seat around a fuel outlet. A valve body is positioned at the valve seat and a valve stem extends through the fuel outlet and fuel chamber. Engagement (disengagement) of valve body and valve seat closes (opens) the injector. The fuel chamber can com

A fuel injector body has a fuel chamber and a valve seat around a fuel outlet. A valve body is positioned at the valve seat and a valve stem extends through the fuel outlet and fuel chamber. Engagement (disengagement) of valve body and valve seat closes (opens) the injector. The fuel chamber can comprise primary and secondary chambers connected by a valve passage and a metering member that restricts fuel flow between the chambers, thereby providing a flow-dependent closing force that reduces the dependence of fuel flow through the injector on fuel inlet pressure and that makes that flow dependent on an injector actuating force. The injector body or the valve body can comprise a spray-shaping surface arranged at least partly around the valve seat, which spray-shaping surface is arranged to direct a spray of fuel flowing through the fuel outlet.

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1. A fuel injector comprising: (a) an injector body comprising a fuel chamber, a fuel inlet connected to the fuel chamber, a fuel outlet connected to the fuel chamber, and a valve seat around the fuel outlet;(b) a reciprocating valve extending through the fuel chamber and the fuel outlet and having

1. A fuel injector comprising: (a) an injector body comprising a fuel chamber, a fuel inlet connected to the fuel chamber, a fuel outlet connected to the fuel chamber, and a valve seat around the fuel outlet;(b) a reciprocating valve extending through the fuel chamber and the fuel outlet and having a central longitudinal axis;(c) wherein the valve and injector body are arranged so that movement of the valve in a first direction relative to the injector body causes engagement of the valve and the valve seat and substantially prevents fuel flow through the fuel outlet;(d) wherein the valve and injector body are arranged so that movement of the valve in a second direction relative to the injector body, the second direction being opposite the first direction, causes disengagement of the valve and the valve seat and enables fuel flow through the fuel outlet;(e) wherein the fuel outlet comprises a spray-shaping surface of the valve body arranged in a ring around the valve and positioned and shaped to be struck by fuel flowing through the fuel outlet;(f) wherein the spray-shaping surface is rotationally asymmetric around the central longitudinal axis of the valve and includes at least a circumferential portion having lengths, extending along the spray-shaping surface radially from the central longitudinal axis, that vary continuously over the circumferential portion, to form an end of the spray-shaping surface that undulates in the longitudinal direction; and(g) whereby the deflection of the fuel flowing through the fuel outlet at one circumferential point along the circumferential portion results in a spray pattern relative to the central longitudinal axis at that circumferential point that is different from the spray pattern relative to the central longitudinal axis in which the fuel flowing through the fuel outlet is deflected at another circumferential point along the circumferential portion. 2. A fuel injector comprising: (a) an injector body comprising a fuel chamber, a fuel inlet connected to the fuel chamber, a fuel outlet connected to the fuel chamber, and a valve seat around the fuel outlet;(b) a reciprocating valve extending through the fuel chamber and fuel outlet and having a central longitudinal axis;(c) an actuator coupled to the reciprocating valve and exerting a controllable, variable force on the reciprocating valve;(d) wherein:(i) the valve and injector body are arranged so that movement of the valve in a first direction relative to the injector body causes engagement of the valve and the valve seat and substantially prevents fuel flow through the fuel outlet;(ii) the valve and injector body are arranged so that movement of the valve in a second direction relative to the injector body, the second direction being opposite the first direction, causes disengagement of the valve and the valve seat and enables fuel flow through the fuel outlet;(iii) the fuel outlet comprises a spray-shaping surface of the valve body arranged in a ring around the valve and positioned and shaped to be struck by fuel flowing through the fuel outlet; and(iv) the spray-shaping surface is rotationally asymmetric around the central longitudinal axis of the valve and includes at least a circumferential portion having lengths, extending along the spray-shaping surface radially from the central longitudinal axis, that vary continuously over the circumferential portion, to form an end of the spray-shaping surface that undulates in the longitudinal direction; and(e) whereby the deflection of the fuel flowing through the fuel outlet at one circumferential point along the circumferential portion results in a spray pattern relative to the central longitudinal axis at that circumferential point that is different from the spray pattern relative to the central longitudinal axis in which the fuel flowing through the fuel outlet is deflected at another circumferential point along the circumferential portion. 3. The fuel injector of claim 2 wherein the actuator comprises a solenoid and wherein the force is controlled by a current of the solenoid. 4. A fuel injector comprising an injector body, a valve passage, a fuel inlet connected to the valve passage, a fuel outlet connected to the valve passage, a reciprocating valve extending through the valve passage and through the fuel outlet and having a central longitudinal axis, a valve seat around the fuel outlet, and a spray-shaping surface, arranged in a ring around the fuel outlet, positioned and shaped to be struck by fuel flowing through the fuel outlet, wherein the valve and injector body are arranged so that movement of the valve in a first direction relative to the injector body causes engagement of the valve and the valve seat and substantially prevents fuel flow through the fuel outlet and movement of the valve in a second direction relative to the injector body, the second direction being opposite the first direction, causes disengagement of the valve and the valve seat and enables fuel flow through the fuel outlet, and: (a) wherein the spray-shaping surface is rotationally asymmetric around the central longitudinal axis of the valve and includes at least a circumferential portion having lengths, extending along the spray-shaping surface radially from the central longitudinal axis, that vary continuously over the circumferential portion, to form an end of the spray-shaping surface that undulates in the longitudinal direction;(b) whereby deflection of the fuel flowing through the fuel outlet at one circumferential point along the circumferential portion results in a spray pattern relative to the central longitudinal axis at that circumferential point that is different from the spray pattern relative to the central longitudinal axis in which the fuel flowing through the fuel outlet is deflected at another circumferential point along the circumferential portion. 5. The fuel injector of claim 4 wherein the spray-shaping surface is a surface of the valve adjacent to a valve-seat-engaging portion of the valve. 6. The fuel injector of claim 4 wherein the spray-shaping surface is a surface of the valve body. 7. The fuel injector of claim 4 wherein the circumferential portion of the spray-shaping surface approximates half of the ring around the fuel outlet. 8. The fuel injector of claim 4 further comprising a second circumferential portion of the spray-shaping surface that has a constant spray-shaping angle. 9. The fuel injector of claim 4 further comprising a plurality of spray-guiding surfaces arranged to deflect at least a portion of the fuel flowing through the fuel outlet to a different circumferential position around the central longitudinal axis. 10. The fuel injector of claim 9 wherein the plurality of spray-guiding surfaces guide said at least a portion of the fuel through a set of slots around the fuel outlet, which slots extend radially from the central longitudinal axis.