CHARGE FORMING DEVICE WITH A THROTTLE VALVE PROVIDING CONTROLLED AIR FLOW
In at least some implementations, a throttle valve includes a valve shaft having an axis and a mounting surface, and a valve head secured to the valve shaft. The valve head has a front face and a rear face closer to the mounting surface than the front face, the mounting surface being located so that a thickness of the valve head between the front face and the rear face is not coincident with the axis. And the axis is closer to the front face than to the rear face, or the axis is coincident with the rear face, or the axis is offset from the front face by more than the distance between the front face and rear face.
1 . A throttle valve, comprising:
a valve shaft having an axis and a mounting surface; and
a valve head secured to the valve shaft, the valve head having a front face and a rear face closer to the mounting surface than the front face, the mounting surface being located so that a thickness of the valve head between the front face and the rear face is not coincident with the axis, and wherein the axis is closer to the front face than to the rear face, or the axis is coincident with the rear face, or the axis is offset from the front face by more than the distance between the front face and rear face.
2 . The throttle valve of claim 1 , wherein the front face is closer to the axis than is the rear face.
3 . The throttle valve of claim 1 , wherein the rear face is closer to the axis than is the front face.
4 . A charge forming device through which air flows to an engine, comprising:
a body having a throttle bore and a valve shaft bore, the throttle bore having an inlet through which air is received into the throttle bore, an outlet from which air exits the throttle bore, an axis between the inlet and the outlet, and the valve shaft bore extends through the throttle bore;
a valve shaft received in the valve shaft bore for rotation relative to the body, the valve shaft having an axis and a mounting surface located within the throttle bore; and
a valve head secured to the valve shaft, the valve head having a front face and a rear face closer to the mounting surface than the front face, the mounting surface being located so that a thickness of the valve head between the front face and the rear face is not coincident with the axis, and wherein the axis is closer to the front face than to the rear face, or the axis is coincident with the rear face, or the axis is offset from the front face by more than the distance between the front face and rear face.
5 . The charge forming device of claim 4 , wherein the front face is closer to the axis than is the rear face.
6 . The charge forming device of claim 4 , wherein the rear face is closer to the axis than is the front face.
7 . The charge forming device of claim 4 , which also includes a fluid feature through which fluid flows, and wherein the valve head is positioned relative to the axis to increase a gap between the valve head and the main body within the throttle bore to enable more air to flow past the valve head and to the fluid feature when the throttle valve is in the idle position.
8 . The charge forming device of claim 7 wherein the fluid feature is a boost venturi or a fuel port.
9 . A method of fitting a throttle valve to a charge forming device, comprising:
determining a first flow area of a first gap in an idle position of the throttle valve within a throttle bore of the charge forming device;
determining a second flow area of a second gap in the idle position of the throttle valve; and
selecting a combination of: 1) a throttle valve head; 2) a throttle valve shaft having a mounting surface in a particular location; and 3) a valve bore offset relative to an axis of the throttle bore, to achieve the determined first flow area and the determined second flow area, where the second flow area is different than the first flow area.
10 . The method of claim 9 wherein at least one of the first flow area and second flow area is sized to provide an air flow to a fluid feature downstream from the throttle valve shaft, wherein the air flow is increased compared to the air flow that would occur if the area of the first flow area and the second flow area were equal.