GB2254885A - Ic engine throttle valve - Google Patents

Description

2254835 INTERNAL COMBUSTION ENGINE MIXTURE SUPPLY DEVICE..

PARTICULARLY FOR VEHICLES The present invention relates to an internal combustion engine air or air- fuel mixture supply device, particularly for vehicles.

The mixture supply devices of internal combustion engines substantially comprise a cylindrical air (or mixture) supply conduit housing a throttle valve in the form of a disc, fitted to and controlled by a drive shaft, for regulating air or mixture supply to the engine along the supply conduit.

The throttle valve is fitted barycentrically to the shaft, that is, in such a manner that the shaft axis lies in the plane dividing the valve disc into two symmetrical portions; and the shaft itself presents return springs outside the supply conduit, for maintaining a predetermined idling position of the valve.

The shaft is controlled, via levers and cables. by the accelerator pedal, which presents return springs for restoring the pedal to the idle position.

In actual use, the only external forces (pressure and torque) exerted on the valve are those transmitted to it by the lever and cable drive via the supporting shaft, and those exerted by the return springs on the accelerator pedal and shaft, while, due to the barycentric position of the shaft in relation to the valve disc, the moment exerted on the valve by the difference in supply fluid pressure in the conduit upand downstream from the valve is totally ineffective.

The above solution presents a number of drawbacks. Firstly, when traveling at constant speed, the relatively low return pressure exerted by the springs on the accelerator pedal is not sufficient for adequately supporting the driver's foot resting on the pedal, thus resulting in fatigue of the driver who is constantly required to relieve the pressure exerted on the accelerator.

Secondly, when accelerating rapidly, particularly at low speed, the return pressure exerted by the springs on the accelerator pedal increases steadily, thus slowing down acceleration and giving the impression of poor pickup performance of the vehicle.

It is an object of the present invention to provide an internal combustion engine mixture supply device, particularly for vehicles, which, under steady speed conditions, provides for adequately supporting the driver's foot on the accelerator pedal and so eliminating driving fatigue, and which, when accelerating, particularly at low speed, provides for actually decreasing the return pressure on the accelerator as this is pressed, thus enabling rapid control of the pedal and a positive feeling of effective pickup and acceleration of the vehicle on the part of the driver.

According to the present invention, there is provided an internal combustion engine air or air-fuel mixture supply device substantially comprising an air or air-fuel mixture conduit controlled by a throttle valve in turn activated by the accelerator pedal via a drive and having a blade type shutter supported on a shaft oscillating about an axis perpendicular to the longitudinal axis of said conduit; a vacuum, produced by said engine, operating in the portion of said conduit downstream from said valve; characterized by the fact that said axis of said shaft is located a given distance from said longitudinal axis of said conduit, so that said oscillating shaft is subjected by the.air pressure on the surfaces of said shutter blade to a torque whereby said shutter blade is set to the closed position.

A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:

Fig.1 shows a schematic vertical section of the throttle valve on the supply device according to the present invention; Fig.2 shows a graph of the torque produced by the vacuum downstream from the valve as a function of the valve opening angle and for different values of a geometric parameter (eccentricity) characteristic of the valve; Fig.3 shows a graph of the torque produced by the vacuum as a function of the valve opening angle and for different constant engine speeds; Fig.4 shows a graph of the total torque on the valve as a function of the opening angle and under constant engine speed conditions; Fig.5 shows a graph of the total torque on the valve as a function of the opening angle and for different constant engine speeds.

Number 1 in Fig.1 indicates an internal combustion engine air or air-fuel mixture supply device comprising a substantially cylindrical supply conduit 2, and a throttle valve 3 substantially in the form of a disc oscillating inside supply conduit 2.

Conduit 2 is conveniently formed inside a sleeve 5, and normally communicates with a substantially known air (or air-fuel mixture) manifold (not shown) on the engine.

Valve 3 is supported and controlled by a shaft 4 perpendicular to the longitudinal axis of conduit 2 and connected to accelerator pedal 6 by a substantially known drive of any type comprising, for example, a lever 7 integral with shaft 4; a cable 8; and a return spring 9 for restoring pedal 6 to the idle position. At least one return spring 10 is conveniently fitted to shaft 4 outside conduit 2.

The disc of valve 3 is defined at the top and bottom by respective flat surfaces 11 and 12, and the axis of shaft 4 lies in a plane parallel to and equally spaced in relation to surfaces 11 and 12. Also, the disc of valve 3 is fitted eccentrically to shaft 4, i.e. at a distance Ilell in relation to the longitudinal axis "all of conduit 2.

The value of eccentricity Oell, on which the favourable characteristics of the device depend, may be selected from a wide range of values as defined later on.

The device according to the present invention operates as follows.

The vacuum formed in the intake manifold of the engine operates downstream from valve 3. For a given opening angle a of valve 3, said vacuum acts on bottom surface 12, while top surface 11 is subjected to substantially atmospheric pressure.

The combined pressures acting on surfaces 11 and 12 therefore produce a moment of other than zero on shaft 4, and in such a direction as to restore valve 3 to the closed position. This is due to the disc of valve 3 being fitted eccentrically to shaft 4, the axis of which substantially divides the valve into two unequal portions.

The curves in Fig.2 show the closing torque on valve 3 produced by the vacuum in conduit 2, downstream from valve 3, as a function of the opening angle a of the valve (ranging from amin to a max and for different Ile/d" ratios ("d" being the diameter of conduit 2).

As shown in Fig.2, the torque produced by the vacuum decreases alongside an increase in a, and, for a given opening angle a, increases alongside an increase in ratio "e/d".

The curves in Fig.3 show the closing torque on valve 3 produced by the vacuum in conduit 2, downstream from valve 3, as a function of the opening angle a of the valve (ranging from a min to a max) and for different constant engine speeds "n". As shown in Fig.3, the torque produced by the vacuum decreases alongside an increase in a, and, for a given opening angle a, increases alongside an increase in engine speed "n".

In addition to the torque produced by the vacuum in the intake manifold, the effect of which is shown in Fig.s 2 and 3, shaft 4 of valve 3 is also subjected to the closing torque produced by spring 9 and/or 10, as shown in Fig.4, wherein curve C 1 shows the closing torque on valve 3 produced solely by the vacuum in conduit 2 as a function of opening angle a, and which is therefore one of the Fig.3 curves relative to a given constant engine speed "n"; curve C 2 shows the closing torque on shaft 4 produced by springs 9 and 10, and which increases steadily alongside opening angle a; and curve Ctot shows the total closing torque produced, for each angle a, by the vacuum (curve Cj) and the springs (curve C 2) as a function of angle a and for a constant "e/d" ratio and engine speed "n".

_ As shown in Fig.4, under constant engine speed conditions, the closing torque produced by the vacuum in conduit 2, downstream from valve 3, is added to the torque produced by return springs 9 and 10.

Curve C tot therefore shows the combined effect of the vacuum and springs on shaft 4.

Fig.5 shows a number of curves C tot" as described with reference to Fig. 4, and each relative to a given engine speed "n".

The advantages of the device according to the present invention will be clear from an examination of Fig.5.

Supposing, for example, that the vehicle is traveling at constant speed corresponding to engine speed 'In" as represented by the top curve, and with a valve opening angle corresponding to point P, on the same curve. Under the above conditions, at point P1, the torque on shaft 4 is high enough to safely support the driver's foot on accelerator pedal 6 and so reduce driving fatigue.

Supposing, on the other hand, that the vehicle is traveling as represented by P 2 (low engine speed 'In" and small opening angle a of valve 3) and that the driver accelerates sharply on pedal 6. In this case. , the operating conditions of the vehicle vary as shown by the dotted line in Fig.5, and until a steady state is again restored,, for example,, at point P 3' To begin with, the total return torque on pedal 6 tends to fall, by virtue of being maintained temporarily constant by the inertia of the engine, thus assisting acceleration and giving the impression of rapid pickup of the vehicle, after which, it gradually returns to much the same value as previously, for adequately supporting the driver's foot on the accelerator pedal.

The advantages of the present invention will be clear from the foregoing description. When traveling at constant speed, the driver's foot is adequately supported on the accelerator pedal, whereas, when accelerating, particularly at low speed, the return torque, and consequently the pressure required on pedal 6, decreases when the pedal is pressed, to give the impression of rapid response (pickup) of the vehicle.

Testing has shown that, with a cylindrical conduit 2 and a circular valve 3, the best results are provided by an e/d (eccentricity/conduit diameter) ratio ranging between 0.05 and 0.3.

Eccentricity "e" is conveniently selected so that the torque produced by the air pressure (represented,, for example, by curve C in Fig.4) is high as compared with that of springs 9 and 10 on shaft 4 (represented, for example, by curve C 2 in Fig.4), at least when valve 3 is rotated from the closed position ( a min) to a 9 - position halfway between a min and a max This provides for a situation as shown in Fig.4 wherein the torque on valve 3 is produced mainly by the vacuum downstream from the valve, and only to a limited degree by springs 9 and 10.

It will of course be understood that the present invention has been described above purely by way of example, and that modifications of detail can be made within the scope of the invention.

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Claims (2)

1) - An internal combustion engine air or air-fuel mixture supply device substantially comprising an air or air-fuel mixture conduit controlled by a throttle valve in turn activated by the accelerator pedal via a drive and having a blade type shutter supported on a shaft oscillating about an axis perpendicular to the longitudinal axis of said conduit; a vacuum. produced by said engine, operating in the portion of said conduit downstream from said valve characterized by the fact that said axis of said shaft is located a given distance from said longitudinal axis of said conduit, so that said oscillating shaft is subjected by the air pressure an the surfaces of said shutter blade to a torque whereby said shutter blade is set to the closed position.

2) - A supply device as claimed in claim 1, wherein said conduit presents a circularsection, and said shutter blade is substantially in the form of a disc; characterized by the fact that the ratio of said distance and the diameter of said disc ranges between 0.05 and 0.3.

3) - A supply device as claimed in Claim 1 or

2. wherein said drive comprises at least one spring for counteracting displacement of said pedal for opening said valve; characterized by the fact that said - 11 distance between said axis of said shaft and said axis of said conduit is so selected that said torque produced by said air pressure is greater than that produced by said spring on said shaft, at least when said valve is rotated from the closed position to a position halfway between the closed and maximum open positions.

4) - An internal combustion engine air or air-fuel mixture supply device, particularly for vehicles. substantially as described and illustrated herein with reference to the accompanying drawings.