GB2249348A

GB2249348A - I.C. engine throttle valve body

Info

Publication number: GB2249348A
Application number: GB9122821A
Authority: GB
Inventors: Claudio Zaccherini; George Robertson
Original assignee: Weber SRL
Current assignee: Weber SRL
Priority date: 1990-10-31
Filing date: 1991-10-28
Publication date: 1992-05-06
Also published as: DE4135806A1; IT9053356V0; IT220664Z2; IT9053356U1; GB9122821D0; FR2668544A1; BR9104794A

Abstract

An annular shoulder 12 between different diameter portions of the duct 3 which is immediately downstream of at least the upstream surface 5 of the valve disc 5 forms the same angle with the duct axis 7 as the disc in its minimum open position. <IMAGE>

Description

PERFECTED THROTTLED BODY FOR INTERNAL COMBUSTION ENGINE FUEL SUPPLY DEVICES The present invention relates to a throttled body for internal combustion engine fuel supply devices, particularly of the type featuring electromagnetic fuel metering and atomizing valves.

Throttled bodies of the aforementioned type substantially comprise a sleeve in which is formed a conduit for air or the air-fuel mixture; and a throttle valve located along the conduit, and having a shutter disc oscillating about an axis perpendicular to that of the conduit and designed, when closed, to substantially close off the conduit and form a predetermined angle with the conduit axis.

The oscillating disc is fitted to a shaft operated by control means for setting the shaft and, consequently, also the disc to a given angle, and so enabling supply of given quantities of air or mixture along the conduit under various operating conditions of the engine.

The shape and size of the disc are normally selected so that, when closed, the disc forms an angle of slightly less than 90' with the conduit axis.

Throttled bodies of the aforementioned type present numerous drawbacks.

Firstly, in time, carbon deposits are formed on the conduit portion downstream from the shutter disc, due to the burnt gas flowing in the opposite direction to the air or mixture inside the conduit. These carbon deposits tend to form a tough layer on the inside surface of the conduit, which layer varies in thickness along the conduit axis, and is maximum on the sections immediately downstream from the throttle valve disc.

The presence of this layer obviously narrows the section through which the air or mixture is fed along the conduit, which section is, in fact, defined, for a given disc-conduit angle, by the surfaces of the disc and that of the conduit. Consequently, for each disc angle, less than the theoretical amount of fluid is supplied. This is particularly serious in the case of very small sections, i.e. idling speed, in which case engine operation is particularly impaired by the reduced supply of mixture (or air).

The supply device may feature an idling speed control device, for ensuring a given supply of air or mixture along the conduit at minimum engine speed. This is achieved, however, by setting the disc to other than its theoretical angles. In fact, for ensuring supply sufficient for maintaining a given engine speed, the actuator on the above control device must set the disc to an open angle greater than that which would be required in the absence of said carbon layer.

Consequently, even assuming the correct supply of air or mixture is achieved under all operating conditions of the engine, the fact remains that the shutter disc is forced to operate in a range other than that for which it was designed, and in which the relationship between the variation in supply and the rotation angle of the disc is other than theoretical, and, more importantly, not guaranteed.

It is an object of the present invention to provide a throttled body of the type described briefly above, designed to overcome the above drawbacks; in particular, a throttled body which, even after prolonged operation of the device, provides for supplying theoretical amounts of air or mixture, for ensuring correct supply to the engine, particularly at minimum engine speed.

According to the present invention, there is provided a throttled body for an internal combustion engine fuel supply device, said body substantially comprising a conduit for the passage of air or air-fuel mixture; and a throttle valve located along said conduit and having a shutter disc oscillating about an axis perpendicular to the conduit axis, commencing from a closed position in which said disc substantially closes said conduit and forms a given angle with said conduit axis; characterised by the fact that the portion of said conduit immediately downstream from said disc in said closed position presents a larger section than the portion of said conduit immediately upstream from said disc, so as to produce, at the section separating said two portions, an annular shoulder lying substantially in a plane forming said given angle with said conduit axis.

The invention will now be described in detail with reference to the accompanying drawings, in which: Fig.l shows a schematic longitudinal section of the center portion of the throttled body according to the present invention, in which is formed the air or air-fuel mixture conduit; Fig.2 shows an enlarged detail of the Fig.l section; Fig.s 3 and 4 show the same section but with a number of design variations as compared with Fig.2; Fig.s 5 and 6, showing the same sections as in Fig.s 1 and 2, illustrate the condition of the conduit on the throttled body according to the present invention, after prolonged operation of the supply device.

The throttled body according to the present invention is designed for use on an internal combustion engine fuel supply device, particularly the type featuring an electromagnetic fuel metering and atomizing valve. A throttled body of this type substantially comprises a plate-shaped element 1 to which is fitted a sleeve 2 in which is formed a conduit 3 for the passage of air or air-fuel mixture in the direction of the arrows. Conduit 3 normally terminates inside a supply manifold (not shown) communicating with the engine cylinders.

The throttled body also comprises a throttle valve 4 located along conduit 3 and having a shutter disc 5 oscillating about an axis 6 perpendicular to the longitudinal axis 7 of conduit 3. Disc 5 oscillates commencing from a closed position (Fig.l) wherein disc 5 substantially closes conduit 3 and forms a given angle ao (Fig.1) with axis 7 of conduit 3.

According to the present invention, conduit portion 10 immediately downstream from disc 5 presents a larger section than conduit portion 11 immediately upstream from disc 5 (Fig.1), so as to produce, at section "f" (Fig.1) separating conduit portions 10 and 11, an annular shoulder 12 lying substantially in a plane forming said angle ao with axis 7 of conduit 3.

Disc 5 is so located along conduit 3 that, when in the closed position shown in Fig.1, the section "f" plane containing annular shoulder 12 is located between the planes containing upper surface "s" and lower surface "i" of disc 5. Though, in Fig.1, the section "f" plane is equidistant from those of surfaces "s" and "i", any intermediate configuration between the two limit configurations shown in Fig.s 3 and 4 may be adopted. In Fig.3, the plane of lower surface Wiw of disc 5 substantially lies in the same plane as section "f", whereas, in Fig.4, it is the upper surface "s" of disc 5 that lies in the same plane as section "f".

Surface 13 laterally defining disc 5 is conveniently a cylindrical surface portion, the axis of which substantially coincides with axis 7 of conduit 3 when disc 5 is closed.

Also, conduit portion 11 upstream from disc 5 conveniently presents a better surface finish than downstream conduit portion 10.

The throttled body described above operates as follows: During operation of the engine, a supply of air or air-fuel mixture is produced in known manner inside conduit 3.

The amount of air or mixture supplied is controlled by throttle valve 4, by rotating disc 5 to a given angle about axis 6. As of the closed position shown in Fig.l and defined by angle ao, therefore, various operating configurations are produced alongside a reduction in said angle.

At certain stages in the operation of the engine, a reverse stream of gas is produced through conduit 3 in the opposite direction to the air or supply mixture.

This gas stream, which contains suspended carbon particles, flows in said direction inside conduit portion 10. When it encounters lower surface "i" of disc 5 and shoulder 12 separating portions 10 and 11, the carbon particles settle in the cavity defined by shoulder 12 and the surface of portion 10. Fig.s 5 and 6 show a section of the layer 14 of carbon material so deposited after prolonged operation of the device. As shown in Fig.6, for any given angle a of disc 5 (assumed very small, as when operating at minimum engine speed), carbon layer 14 so formed results in substantially no reduction in the section of annular passage "p" along conduit 3.As shown also in Fig.6, said section is defined solely by lateral surface 13 of disc 5 and the surface of conduit portion 11, on which surfaces practically no carbon is deposited, this being deposited in the form of layer 14 inside the cavity defined by shoulder 12 and the surface of conduit portion 10.

Whatever the thickness of layer 14 inside said cavity, this has no effect on annular section "p".

The throttled body according to the present invention therefore provides for overcoming the aforementioned drawbacks typically associated with known types. In particular, it provides for maintaining constant air or mixture supply along conduit 3 regardless of engine speed and, more especially, at minimum engine speed which is the most critical in terns of supply. Moreover, it provides for maintaining the design relationship between variation in air or mixture supply and throttle angle a, regardless of the operating period of the body itself.

To those skilled in the art it will be clear that changes may be made to the embodiments described and illustrated herein without, however, departing from the scope of the present invention.

Claims

1) - A throttled body for an internal combustion engine fuel supply device, said body substantially comprising a conduit (3) for the passage of air or air-fuel mixture; and a throttle valve (4) located along said conduit (3) and having a shutter disc (5) oscillating about an axis (6) perpendicular to the conduit axis (7), commencing from a closed position in which said disc (5) substantially closes said conduit (3) and forms a given angle (ao) with said conduit axis (7); characterised by the fact that the portion (10) of said conduit (3) immediately downstream from said disc (5) in said closed position presents a larger section than the portion (11) of said conduit (3) immediately upstream from said disc (5), so as to produce, at the section separating said two portions, an annular shoulder (12) lying substantially in a plane forming said given angle (ao) with said conduit axis (7).

2) - A throttled body as claimed in Claim 1, characterised by the fact that said disc (5) is so located that, when in said closed position, said plane is located between the planes containing the upper surface (s) and lower surface (i) of said disc (5).

3) - A throttled body as claimed in Claim 1 or 2, characterised by the fact that the surface (13) laterally defining said disc (5) is a cylindrical surface portion, the axis of which substantially coincides with said conduit axis (7) when said disc (5) is in said closed position.

4) - A throttled body as claimed in one of the foregoing Claims, characterised by the fact that the surface of said conduit portion (11) upstream from said disc (5) presents a better surface finish than said conduit portion (10) downstream from said disc (5).

5) - A throttled body as claimed in one of the foregoing Claims, characterised by the fact that said conduit (3) is formed in a sleeve-shaped, die-cast metal element (2).

6) - A throttled body for an internal combustion engine fuel supply device, substantially as described and illustrated herein with reference to the accompanying drawings.