GB2109860A

GB2109860A - Fuel-air supply device for an internal combustion engine

Info

Publication number: GB2109860A
Application number: GB08232268A
Authority: GB
Inventors: Leonardo Grondona; Eraldo Giaccardi; Franco Gristotto
Original assignee: Fiat Auto SpA
Current assignee: Fiat Auto SpA
Priority date: 1981-11-20
Filing date: 1982-11-11
Publication date: 1983-06-08
Also published as: FR2516984A1; GB2109860B; ES268609Y; IT8168507A0; DE3242833A1; IT1145131B; ES268609U

Abstract

A fuel injector (5) disposed downstream of an air throttle valve (7, 11) is controlled by an electronic control unit (40) which has inputs from various sensors including a throttle valve position sensor (29). The to air throttle valve comprises a Venturi duct (8) and a frusto-conical valve core (11) arranged to be axially displaced within the duct (8) by operation of the engine accelerator control (24) so that sonic velocity occurs at the valve. With a throttle valve of this form the position sensor (29) signals the air flow. Specific dimensions of the duct (8) and the core 11 are disclosed. <IMAGE>

Description

SPECIFICATION Fuel-air supply device for internal combustion engines The present invention relates to a device for controlling the supply of fuel and air into an inlet manifold of an internal combustion engine.

One of the principle problems in the modern automotive industry is the optimisation of the relationship between the fuel consumption, power supplied, exhaust emissions and production costs for internal combustion engines.

At present two types of fuel-air supply device are known and in widespread use, namely the carburettor type and the indirect injection type.

Devices of this latter type include an air choke valve for controlling the flow of air through the inlet manifold, at least one electronicallycontrolled fuel injector located downstream of the air choke valve, and electronic control means for controlling the said at least one injector in dependence on various engine operating conditions including the intake air flow and the instantaneous engine angle (generally indicated by arrival at Top Dead Centre positions), the control means including respective sensor means for sensing the said various parameters. Other parameters which may be sensed by the control means are the speed of engine rotation and the engine coolant temperature.

The indirect injection type of device possesses certain advantages with regard to fuel consumption, power supplied and exhaust emissions, although it is more expensive from the production point of view. In this latter respect, one of the device components which contributes significantly to the production costs is the air-flow sensor and the associated part of the control means; such a sensor, is, however indispensable to the proper control of the air choke valve (typically a butterfly valve) if an optimum air-fuel ratio is to be maintained for the purpose of improving the efficiency of the engine.

The object of the present invention is to provide an improved fuel-air supply device of the indirect injection type which, while retaining the characteristics of reliability, economy of fuel consumption and power supplied, is of low cost, and can be quickly and simply installed and maintained.

According to the invention, this object is achieved by the provision of a fuel-air supply device of the aforesaid indirect injection type, in which the air choke valve is a variable-flow sonictype choke valve constituted by a Venturi-type duct of predetermined profile, and a frusto-conical valve core, also of predetermined profile, located coaxially within said duct and arranged to be displaceable axially therealong by operation of the engine accelerator control, the said sensor means for sensing the intake air flow being constituted by a position sensor responsive to the position of the valve core in said duct.

Further objects and advantages of the invention will become clearer from the following description made with reference to the appended drawings, provided purely by way of non-limiting example, and in which: Figure 1 is a view of a fuel-air supply device embodying the invention, certain details of the device being shown schematically; Figure 2 is a sectional view to an enlarged scale of a detail of Figure 1; and Figure 3 is a sectional view to an enlarged scale of a second detail of Figure 1.

With reference to the appended drawings, by 1 is shown the head of an internal combustion engine which in this particular case is a fourcylinder in-line engine but which in different applications of the fuel-air supply device of the invention could have a different number of cylinders which, moreover, could alternatively be disposed in a "V" or opposed configuration.

Naturally in these latter two cases it would be necessary to provide a fuel-air supply device for each bank of cylinders.

The head 1 is formed with the intake ducts for the engine cylinders, these ducts opening from a single inlet manifold 2. Where the head 1 does not provide such a disposition itself, the same arrangement can, of course, be achieved by using external ducting.

A curved tubular joining pipe 3 is connected to the inlet manifold 2 and is formed in its upper part with a seat 4 for a fuel injector 5 of known type shown schematically in the drawings.

Avariable-flow, sonic-type air choke valve is fixed to the tubular joining pipe by means of bolts 6 and is constituted by a cylindrical body 7 having an axial duct 8 in the form of a Venturi duct, the dimensions of which are calculated for optimum efficiency in relation to the air flow with which the engine is intended to be supplied.

The dimensions of the duct 8 are given below, it being understood that it will be necessary to vary the diameter of the duct uniquely in dependence on the maximum air flow it is desired to achieve according to the type of engine concerned.

Starting from the point of attachment to the tubular joining pipe 3, there is a 12 mm length with an angle of 97C 7.5' to the perpendicular to the axis of the duct 8, then a 10.5 mm length at 95" 26.47'; a 12.5 mm length at 920 17.44'; a 12.5 mm length at 900; a 12.5 mm length at 870 42.56'; a 5 mm length at 780 41.41'; a 17 mm length at 730 36.63'; and a 3 mm length at 280 36.63'.

The total length of the duct 8 is thus 85 mm, while the diameter of the outer edge of the last 3 mm length has been calculated at 50 mm for a 903 cc engine with a maximum speed of rotation of 5,600 rpm.

The wall of the first length has a hole 9 which communicates with a duct 10 connected to a pressure regulator controlled by the fuel-injector control system.

A frusto-conical valve core 11 is inserted coaxially in the duct 8 such that its smaller diameter end faces towards the joining pipe 3.

The dimensions of the valve core 11 are also calculated so as to achieve optimum efficiency in combination with the profile of the Venturi duct 8.

The dimensions of the valve core 11 are as follows: a cylindrical part 15 mm in length followed by a conical part 90 mm in length, in which the generatrix of the cone, the larger diameter of which is 30 mm, is inclined at 50 42.6' to the core axis.

Naturally these dimensions are also calculated for a four cylinder engine of the said type and obviously if the diameter of the duct 8 is varied it will also be necessary to vary the diameter of the valve core 11 so as to maintain the initial proportions unchanged.

The valve core 11 also has an axial hole 12 which extends over a substantial part of its length and in which is located a shaft 13; the shaft 13 has a diameter substantially equal to the diameter of the hole 12 and is mounted coaxially with the axis of the duct 8.

The shaft 13 is screwed into a seat 14 formed in a cylindrical cap 1 5 fixed coaxially by means of a pin 16 and bolts 17 to the cylindrical body 7.

The valve core 11 can be moved along the shaf-t 13 by means of a rod 18 fixed at one end to a hollow cylindrical body 1 9 which is slidable on the shaft 13 and is screwed into the larger diameter part of the valve core. The other end of the rod 18 projects through a hole in the cap 15 and is articulated to an arm 21 which is pivoted on the cap 15 by means of a slot 22 formed in the arm and apin 23 fixed to the cap.

The arm 21 is connected at its outer end to the engine accelerator cable 24 so that when the accelerator pedal is depressed, a corresponding displacement is brought about in the position of the valve core 11 within the Venturi duct 8.

A second rod 25 projects from a hole 26 formed in the cap 1 5 and is rigidly connected at one end to the hollow body 19 and at the other end to an arm 27 which is connected to the operating rod 28 of a resistive position sensor 29.

The sensor 29 serves to provide a signal indicative of the position of the valve core 11 and thus of the intake air flow. By varying the length of the shaft 25, the minimum setting of the sensor 29 can be adjusted.

A duct 31 provided with a filter 32 and serving for the intake of air from the atmosphere, is bolted to the cap 15 in correspondence with a hole 30.

The fuel injector 5 is controlled by an electronic control system which includes a number of sensors indicative of the operational state of the engine, these sensors including a temperature sensor 33, a Top Dead Centre point sensor 37 for providing an indication of the instantaneous engine angle, a phonic wheel sensor 42 for providing an indication of the engine speed, and the air flow sensor 29 of the air choke valve 38.

Said sensors are connected to an electronic control unit 40, of conventional type, which controls the operation of the injector in a known way as a function of the signals delivered by the sensors.

The injector 5 is also connected to the fuel supply system which includes a fuel tank 53, a fuel filter 54, and a pump 55 arranged in series.

Downstream of the pump 55 is disposed a pressure regulator 56 which is connected to the tank for the purpose of recycling excess fuel. The pressure regulator 56 is controlled by a signal coming from the position sensor 29 of the variable-flow air choke valve 38 through the electronic control unit 40.

The main characteristic of the variable-flow air choke valve 38 lies in the fact that it is a sonictype choke valve, that is, for each cross-sectional size of the circular annulus defined between the outer profile of the valve core 11 and the internal profile of the body 7, there is a corresponding specific air flow, at least within the more common range of engine operation. This means that in the device illustrated, the air flow can be defined instant by instant, by the simple use of the resistive position sensor 29 connected rigidly to the valve core 11 so as to signal its position continuously.

Claims

1. A device for controlling the supply of fuel and air into an inlet manifold of an Otto-cycle internal combustion engine, said device including an air choke valve for controlling the flow of air through the inlet manifold, at least one electronically-controlled fuel injector located downstream of the air choke valve, and electronic control means for controlling the said at least one injector in dependence on various engine operating parameters including the instantaneous engine angle and the intake air flow, the control means including respective sensor means for sensing said various parameters, said choke valve being a variable-flow sonic-type choke valve constituted by a body defining a Venturi-type duct of predetermined profile, and by a frusto-conical valve core, also of predetermined profile, located coaxially within said duct and arranged to be displaceable axially therealong by operation of the engine accelerator control, the said sensor means for sensing the intake air flow being constituted by a position sensor responsive to the position of the valve core in said duct.

2. A device according to Claim 1, wherein the said Venturi-type duct has a total length of 85 mm and comprises a first 12 mm length making an angle of 970 7.5' to the perpendicular to the axis of the duct, followed by a 10.5 mm length at 950 26.47'; a 12.5 mm length at 920 17.44'; a 12.5 mm length at 900; a 12.5 mm length at 870 42.56'; a 5 mm length at 780 41.41'; a 17 mm length at 730 36.63'; and a 3 mm length at 280 36.63'.

3. A device according to Claim 2, wherein the said frusto-conical valve core has a total length of 105 mm of which 15 mm is of cylindrical form and 90 mm of conical form, the generatrix of this conical portion being inclined at 50 42.6' to the core axis.

4. A device according to Claim 3, wherein the diameter of the outer edge of the last 3 mm length of the duct is 50 mm and the diameter of the larger end of the conical portion of the valve core is 30 mm.

5. A device for controlling the supply of fuel and air into an inlet manifold of an Otto-cycle internal combustion engine, said device being substantially as hereinbefore described with reference to the accompanying drawings.