Patent Application
20070170391
The present invention relates to an air throttle valve for controlling the air flowing through an internal combustion engine, such as a spark ignited or compression ignition internal combustion engine.
Throttle valves have been used with internal combustion engines for well over a century. Most commonly used throttle valves include a round or oval plate, usually made of brass or aluminum. The throttle plate extends through a slotted, or slab cut, rotatable shaft which passes through the walls of an air passage. Typically, the air passage may be incorporated in a device such as a throttle body for use within a fuel injected engine; alternatively, the air passage may be incorporated into the housing of a mixing device such as a carburetor. Throttle devices with oval plates rely upon a nearly line-on-line contact between the majority of the throttle blade periphery and the throttle housing to achieve a near-zero or low airflow condition corresponding to engine idle operation. However, to avoid sticking of the throttle plate it is necessary to maintain a clearance between the throttle plate and the bore within which the plate is housed. Unfortunately, it is very difficult to achieve a precise low flow condition with conventional valve geometry, because air leakage through the clearance regions causes widely varying airflow.
A throttle valve assembly according to present invention solves problems inherent with known throttle valves by providing a throttle plate having a spherical section which rides directly upon the throttle bore, so as to provide superior sealing of the throttle plate in the bore. Because the spherical section throttle plate has only a single defining dimension, the orientation issues arising with other plate geometries are avoided.
A throttle valve for internal combustion engine includes a generally cylindrical valve housing having inside diameter and a throttle plate pivotally mounted within the valve housing. The throttle plate includes a valve disc having an outer rim shaped as a spherical segment, with the valve disc having an outside diameter proximate the inner diameter of the valve housing. Pivots extend through apertures formed in the valve housing and into contact with the valve disc. The present throttle valve further includes a sensor for determining the rotational position of the throttle plate and a motor assembly for positioning a throttle plate. In a preferred embodiment, the throttle plate and the generally cylindrical valve housing may be formed from the same type of powdered metal, such as powdered iron, or other types of powdered or other metals known to those skilled in the art and suggested by this disclosure. The valve disc and valve housing may advantageously be coated with a manganese phosphate finish which impedes corrosion while serving as a break-in coating of the parts.
In order to operate the present assembly efficiently, the motor assembly may include a motor connected with a double or triple reduction gear train.
According to another aspect of the present invention, valve disc used in the present throttle body includes a ring-shaped structure surrounding a thinner circular core. The ring-shaped structure has an outer diameter shaped as a spherical segment, which allows the present valve disc to rotate within the throttle valve body or housing without binding or sticking.
According to another aspect of the present invention, the valve body or housing may be formed as a two piece assembly by separating a preform along fracture path extending through pivot apertures formed in the preform.
According to another aspect of the present invention, the valve disc may have integral and unitary pivots or, alternatively, the valve disk may have trunnions for accepting pivots inserted inwardly through apertures formed in the valve housing.
It is an advantage of a system according to the present invention that airflow to an engine may be very precisely controlled, notwithstanding the presence of contamination of the throttle bore, or extreme thermal gradients.
It is a further advantage of a system according to the present invention that the present throttle system may be manufactured without a need for excessive hand fitting of throttle valve discs within throttle valve bores.
It is a further advantage of a system according to the present invention that the throttle body and throttle valve may be constructed of the same material, so as to avoid problems with uneven thermal growth of the components.
It is a further advantage of a system according to the present invention that the present throttle valve assembly is more compact than known throttle valves, and is therefore useful for technical applications including not only main air throttles, but also manifold control valves and other air-routing and controlling applications. For this reason, as used herein, the terms “throttle valve” and “throttle system” refer to all of the previously enumerated types of air valves.
It is a further advantage of a system according to the present invention that the present throttle valve assembly is more resistant to damage from thermal excursions, such as those experienced either during backfire events or with engines operated with high exhaust gas recirculation (EGR) rates.
Other advantages, as well as features and objects of the present invention, will become apparent to the reader of this specification.
As shown in
Valve assembly 10 is useful for employment with a drive-by-wire system in which the control of an engine throttle is achieved solely by means of electronics, as opposed to a more conventional mechanical cable assembly. Because valve housing 14 is generally cylindrical, the housing may be mounted conveniently in an air induction system or, even in an air inlet manifold, without the need for additional threaded fasteners.
Throttle plate 22 has two trunnions, 34, formed integrally with ring-shaped structure 26 and circular core 30. As shown in
Throttle disc 22 and valve housing 14 may advantageously be coated with a manganese phosphate finish which impedes corrosion, while serving as a break-in coating for these parts. The manganese phosphate coating also serves as an abradable seal between disc 22 and inner diameter 18 of housing 14.
Notwithstanding that ball bearings 46 and 48 are shown with the various embodiments of the present invention, other types of antifriction bearings, or even plain bearing elements, could be used to practice present invention.
The inventors of the present throttle valve determined that the valve may be advantageously constructed from powdered metal such as ferrous or non-ferrous metals, or alternatively, other metallic or non-metallic composites or die or pressure-cast metals known to those skilled in the art and suggested by this disclosure. One advantageous combination is powdered iron, used for both throttle plate 22 as well as for housings 14 and 82. Forming throttle plate 22 and housings 14 and 82 from the same material will avoid problems due to differential thermal expansion, while allowing the spherical outer surface of throttle plate 22 to be finished by grinding to a very fine surface detail, including the outboard-most surfaces, 39, of trunnions 34. In this manner, the outer portions of trunnions 34 will remain in contact with valve housing 14 when valve disk 22 is rotated by the throttle operator, in this case motor 78 and gear train 66.
Although the present invention has been described in connection with particular embodiments thereof, it is to be understood that various modifications, alterations, and adaptations may be made by those skilled in the art without departing from the spirit and scope of the invention set forth in the following claims.
