Internal-combustion engines – Engine speed regulator – Specific throttle valve structure
Patent
1989-03-09
1991-04-16
Argenbright, Tony M.
Internal-combustion engines
Engine speed regulator
Specific throttle valve structure
251 611, 1375991, 261 449, F02D 918, F02M 910, F16K 31126
Patent
active
050073958
DESCRIPTION:
BRIEF SUMMARY
The invention is concerned with a throttle valve for an internal combustion engine in which a flow path is defined between a central core and a tube having a resiliently flexible wall, which tube separates the flow path from an adjacent working fluid chamber, whereby changes in the pressure within the chamber cause deformation of the tube wall resulting in changes in the tube cross-section between a wide open throttle position and a valve closed position, the flexible walled tube being designed to take up a valve closed position when the pressures on its opposite sides are equal.
Such a throttle valve is described in European Patent Application EP-A-0 127 251 and will herein be termed a venturi throttle valve on account of the venturi flow created in the annular gap between the core and the resilient tube. The importance of the venturi flow is that it remains laminar and this is in contrast with normal throttle design in which turbulence is induced in order to assist in the atomisation and mixing of the fuel. Because the flow is laminar, the problems of a wet manifold are reduced and higher air velocities can be attained.
EP-A- 0 127 251 describes a venturi throttle valve in which the flexible tube in its relaxed state, that is to say when there is no pressure difference across it, adopts an hour glass configuration to seal against the centre core. However, the manufacture of such a tube gives rise to problems since it is difficult to achieve consistently and reliably a tube of the required dimensions and resilience.
With a view to mitigating the foregoing disadvantage of the prior art, the present invention provides a venturi throttle valve in which the flexible walled tube is uniformly cylindrical in its relaxed state.
Thus, in the present invention, the resilient tube which is used to seal against the central core in the minimum throttle position is not preformed into any particular shape, but is a cylinder of constant diameter and thickness so that the increased throttle opening achieved when vacuum is applied to the surrounding working chamber is repeatable and predictable.
A search has revealed the existence of certain fluid control valves using a flexible tube as a closure member in which the tube, in its relaxed state, is uniformly cylindrical. Examples of such control valves are to be found in GB 583,535 and GB 565,538. These are, however, large control valves for use in industrial applications which cannot be used to regulate the air supply to an engine cylinder. Furthermore, they are not venturi throttle valves since flow through them is not laminar. On the contrary, in the case of these valves, the fluid flow is divided into streams by being passed through a slotted member which tends to introduce turbulence.
In EP-A-0 127 251 mentioned above, the central core serves no useful purpose other that than as an abutment surface against which the resilient tube may effect a seal.
In accordance with a preferred embodiment of the present invention, the central core of the venturi throttle valve includes means for introducing fuel into the air stream flowing in the annular gap between the core and the surrounding resilient tube.
The means for introducing fuel into the air stream may conveniently be fuel metering jets.
As the gap between the resilient tube and the core may not be uniform about the circumference of the core, it is preferred to provide several metering jets distributed about the circumference of the core. This will automatically compensate for any lack of uniformity in the resilient tube without adversely affecting the accuracy of the fuel metering. The metering jets may conveniently be located at the widest part of the core to provide the maximum venturi vacuum and optimum atomization of the aspirated fuel.
It is alternatively possible for the means for introducing fuel into the air stream to be the fuel injection nozzles of a fuel injection system.
Conveniently, the central core includes a by-pass passage to supply air when the engine is idling thus avoiding the need for an external by-p
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Argenbright Tony M.
Drouillard Jerome R.
Ford Motor Company
Mates Robert E.
Sadler Clifford L.
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