AU427257B2 - Improvements in or relating to internal. combustion engines - Google Patents

Description

27.052/71 This invention relates to internal combustion engines. It is known that the exhaust effluent of such engines can produce-substantial quantities of gases, such as carbon monoxide and unburnt hydro- carbons, which create undesirable and even dangerous contamination of the atmosphere, especially under heavy traffic conditions in urban areas.

It is known that the presence of these gases in the exhaust effluent is due to incomplete combustion of the fuel supplied to the engines, and it is very difficult to achieve complete combustion in the engine combustion chanbers under all engine. operating conditions whilst maintaining good vehicle driveability at all times* It has, theref ore, been proposed to pass the exhaust gases from the engine cylinders through a reaction chamber in which residual fuel and combustible gases such as carbon' monoxide are burnt with additional air the combustion occuring spontaneously owing to the establishment within the reactor of conditions of temperature and pressure appropriate for such combustion. A problem arising in connection with such reactors is that of maintainirg continnous combustion therein, it being fou-nd that, under certain transient conditions of engine operation, such as

27,-052/71 during accelcration, the content of combustible material in the gases leaving the engine combustion chambers is so small that cumbustion in the reactor cannot be maintained. In an internal combustion engine provided with an exhaust combustion reactor, it is therefore desirable to ensure that the fuel content of the mixture supplied to the engine is always slafficient

to provide, in the gases exhausted from the engine cylinders, suffiaient fuel to maintain combustion in the exhaust combustion reactor. On the other hand,

it is obviously desirable to limit as much as possible the fuel which is burnt in the reactor, because not only is such fuel wasted and makes no contribution to the propulsion of the vehicle, but introduction of an excess of fuel to the reactor may cause damage to-the reactor due to the establishment therein of excessively high temperatures. It is the object of the present invention to provide an internal combustioh engine including an exhaust combustion reactor in which suf ficient fuel reaches the reac'tor under the-least favourable engine operating conditions to .ensure continued combustion therein without an undesirably high quantity of fuel being consumed in the reactor under any other engine operating conditions. According to the present Invention there

is provided an internal combustion engine having

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27.052/7f in combination thercewith an exhaust combustion reactor, wherein the said engine is supplied with fuel/air mixture through a carburetter of the air valve type comprising an induction passage, a throttle valve in said passage, and an air control valve in said passage upstream of tha throttle valve and in which variation in mixture strength is con- trolled by the maintenance of a substantially constant. depression in said induction passage between said throttle valve and said air control valve, which depression acts on the air control valve and on a fuel control valve so as to provide a related operation of both valves and therefore a continuous control of the fuel/air proportions in the mixture during all conditions of engine operation. Thus the fuel/air proportiins can be adjusted so, as to provide sufficient fuel for combust- ion in the exhaust combustion reactor under the most adverse engine operating conditions without there being a large excess of fuel burnt in the reactor under any other engine operating conditions. The control of mixture strength, particul- arly under transient conditions, is difficult to achieve and with the fixed choke typeofcbuet,

special arrangements of considerabl~e complexity are

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27,052/71 necessary to control the deceleration mode, while

during acceleration conditions, particularly from

low engine speeds at high load, it is impossible to

achieve ideal conditions. To offset the weakening

of the mixture which occurs due to the relative

density of fuel and air, 'acceleration' pumps and

similar devices are used to provide additional

fuel. The resultant mixture presented to the engine

provokes conditions which result in large variations

in the proportion of unburnt hydrocarbon and CO con-

tained in the exhaust, which cause problems in the

maintenance of combustion within the reactor.

The use of an air valve carburetter may be

exploited to avoid these problems since it may be

developed to provide a substantially constant mixture

ratio during the acceleration mode or, according to

one feature of the present invention, the fuel control

valve of the carburetter may be arranged to increase

the fuel-to-air ratio in the fuel/air mixture during

rapid acceleration conditions, when the quantity of

unburnt fuel in the gases leaving the engine cylinders

tends otherwise to be most reduced. Such an arrange-

ment has been found to give substantial reduction

in the exhaust pollutant levels.

To achieve this result, in a carburetter

427257 hi 27, 052/71 in which the fuel supply valve consists of an orifice opening into the induction passage of the carburetter and controlled by a profiled needle moving with the air valve, the needle is biassed so as to contact the wall of the orifice on the side nearer the inlet end of said induction passage.

The biassing of the said profiled needle

which controls the fuel supply orifice of the

carburetter, and is the subject of/e Patent Specification No. 1,144,405, produces a local flow

pattern of air in the region of the fuel orifice

which increases the suction on the fuel orifice

when the throttle is suddenly opened and thus causes

mixture enrichment under these conditions so that,

even though efficient combustion is maintained in

the engine cylinders under these conditions, suff-

icient fuel is available in the form of unburnt

hydrocarbon and CO to support.combustion in the

reactor.

There will now be described, by way of example and with reference to the accompanying

drawings, one arrangement of an internal combustion

engine embodying the invention.

In the drawings:-

427257

2 7,052/71 Figure 1 is a diagrammatic sectional

elevation of an internal combustion engine

including the carburetter and exhaust combustion

reactor;

Figure 2 is a sectional elevation of

an air valve carburetter suitable for use in the

combination of the invention; and

Figures 3 and 4 are sectional elevations of two forms of exhaust combustion reactor suitable

for use in the combination of the invention.

Referring to Figure 1 of the drawings,

the engine comprises the usual cylinder block

and cylinder head 11, and has a plurality of cylind-

ers only one of which is shown at 12. An induction manifold shown at 13 and connected to the cylinder

12 and which would, of course, be connected in an

actual engine to all the cylinders thereof, receives

fuel air mixture from a carburetter 14 or from a

plurality of such carburetters. The exhaust port of the engine cylinder 12 is connected by a

passage 16 to an exhaust combustion reactor 17

which is in turn connected througn an exhaust pipe

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2 7,052/71 18 to the atmosphere, the exhaust por'l-s of the other engine cylinders being also connected by passages corresponding to the passage 16, to the reactor 17. -Air to assist comibustion in the exhaust reac;tor 17 is supplied to the passage 16 and corresponding passages by an air pump 19 and conduit 21, a valve 20, commonly referred to as a-gulp valve, and further described hereinafter, being provided-in the conduit 21 to direct the air delivered by the pump 1,under certain conditions, through a conduit to the inlet manifold 13 instead of to the exhaust passages 16. The carburetter, w hich is shown diagram- matically in Figure 1 and in greater detail in Figure 2, is of the air valve type in which there are provided, in an induction passage 22, a throttle valve 23 and, upstream of the said throttle valve, an air control valve 24 comprising a slide 25 movable transversely of the induction passage and co- operating with a bridge 26 in the said passage to define a throat of variable area.* The slide 25 is connected, as shown in Figure 2, to a diaphragm 2V dividing into two chambers 28 and 29 a casing 51 arranged to one side of-the induction passage, -che slide 25 being biassed by a spring 52 towards a

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27,052/71 position in which it reduces the throat area to

a minimum and the diaphragm being acted on in the

chamber 29 by air at atmospheric pressure tending to

move the slide to increase the throat area, and being

acted on in the chamber 28 by the air pressure in

the induction passage 22 between the throttle valve

23 and the air control valve 24, the restriction of

air flow through the throat causing a depression

in the said part of the induction passage which,

acting in the chamber 28, tends to control the position,

of the air control valve to maintain such depression

constant.

A fuel supply orifice 33 opening into the

throat of the carburetter through the bridge 26 is

connected to a fuel chamber 34 in which fuel is

maintained at a constant level by a valve (not shown)

controlled by a float 35. The effective area of

the orifice 33 is controlled by a profiled needle 36

carried by the air valve slide 25 so as to increase

the effective area of the orifice as the throat area

is increased and to provide progressive control of

the quantity of fuel supplied.

The profiled needle 36 is mounted for

small angular movement relative to the air valve

271052/71 slide 25 and preferably, as shown in Figure 2, is biazsed so as to occupy a position in which it contacts the.wall of the orifice on the side of the latter nearer to the inlet end of the induction passage. The needle as shown in Figure 2, has a head 37 with a flat surface 38 urged by a spring 39 a~gainst an offset rib 41 on, a washer 42 mounted in a recess 43 in the slide. Alternatively the profiled needle .36 may be biassed so as to occupy a position In which it contacts-the wall of the orifice on the side of the latter nearer to the outlet end of the

induction passage. The movements of the air valve slide are damped In the usual manner by a piston 44 sliding in an oil-filled cylinder The exhaust combustion reactor 17 comprises an inner cylindrical chamber 46 to which the passages 16 fron the engine cylinders are connected and an outer surrounding chamber 47 to w~hich the exhaust gases pass from the inner chamber and from which the said gases pass through the exhaust pipe 18 to the atmosphere. The outer surroundinS chamber 47 is enclosed in an insulating jacket 4-8, Two alternative forms of exhaust combustion reactor are shown in Figures 3 and 4- respectively. In the form shown in Figure 3, the inner chamber 46. is Vorned by two -end-tubas-49 and a central tube 51 of smaller diameter, two of the passages 16 being connected one into each tube 49 and the other two passaeea 16 beinZ connected 5.ntu the tube 51. 427 25 7

27,05271 The tubes 49 overlap the tube 51 leaving annular passage's through which the exhaust gases, after burning in the inner chamber 46 pass, through an open-ended intermedi!ate tube 52 surrounding the tubes 49 and 51, into the outer chamber 47. In the formi of reactor 8hofin in Figure 4, the inner chamber 46 is defined by a single tube 53, closed at both ends and spaced at the said ends from the ends of the outer chamber 47, holes 54 in the

tube 53 leading into a surrounding annular space within an open-ended intermediate tube 5.5 through which the gases pass to the outer chamber 47. In Figure 4, only three inlet passages to the chamber 46 are showrn, it being assumed that two cylinders of a four-cylinder engine have their exhaust ports connected to a common central inlet passage .56. The insulating jacket 48 of the reactor may be filled with a heat insulating material or may be connected into the air supply conduit 21 so" that the air supplied by the pump 19 provides cooling of the reactor and is preheated before being fed into the chamber 46. The 'gulp valve' 20 already referred to

-is a valve of known form which is normally open to allow air to--flow directly to the reactor chamber 46 ts 27, 052/71 through the passages 16 and/or passage 56, but is so controlled by depression existing in the inlet manifold 13 as to be operated when the said depression is greatly increased to divert the air supply to the inlet manifold. Such greatly increased depression occurs during decelerati6n of the engine and produces a tendency to over-richness of the fuel/air mixture, which tendency is reduced by the operation of the gulp valve with !;he result that more efficient combustion takes place in the engine cylinders, there is less tendency of the engine to backfire, and the quantities of unburnt hydrocarbons and carbon monoxide in the exhaust gases are reduced.

The condition of enrichment above referred to is transient, and occurs immediately after the engine throttle valve is closed. A gulp valve, whilst reducing the emission of hydrocarbons and

carbon monoxide during the high peaks, of relatively short duration, which immediately follow the throttle valve closure, does not reduce the sustained increased

emission of hydrocarbons which follows as the engine continues to run with the throttle valve closed and is particularly due to poor combustion associated

with dilution of the mixture supplied to the

cylinders, at high manifold vacua, by exhaust gases.

427257

2 7,052 /71 To reduce this sustained emission of pollutant gases during engine deceleration, other

mixture controlling devices can be used which are readily applicable to carburetters of the air valve type. For example, the rqduction of com- bustion efficiency occurring due to -the return of exhaust guses to the engine cylinders whilst both inlet and exhaust valves are open can be minimized by the use of a by-pass valve as des- cribed in our -Iustralian.Patent Ajp~lic-ation Number 2579q/i~7 and shown at 57 in Figure 2, the said by-pass valve cpening when the induction manifold pressure falls below a predetermined level to allow a metered flow of fuel/air mixture to by-pass the throttle valve 23 and enter the engine cylinders, thus controlling the degree of-exhaust dilution, which occurs and at the same time providing a satisfactory combustible mixture. P~rovision may be made to provide further enrichmient of the by-pass mixture by the addition of an auxiliary fuel supply feeding into the by-pass passage controlled by the valve57 The operation of exhaust combustion reactors is well known and it is not-considered

necessary to describe such operation in detail he-rein.

427 25 7. -13.-

The claims definin~g 1heOn('lon are as follows 1. An internal combustion engine having in combination therewith An exhaust combustion reactor, the exhaust combustion reactor comprising a reaction chamber through which exhaust gases from the engine cylinders are passed and to which additional air is supplied so that residual fuel and combustible gaseous constituents. of the exhaust gases are burnt within the reaction chamber, the combustion occurring spontaneously owing to the establishment within the reactor of conditions of" temperature and pressure appropriate for such combustion, wherein the said engine is supplied with fuel/air mixture through a carburetter of the air valve type comprising an induction passage,.a throttle valve in said passage, and an air control valve in said passage upstream of the throttle valve and in which variation in mixture strength is controlled by the maintenance of a substantially constant depression in said induction passage between said throttle valve and said air control valve, which depression acts on the air control valve and on a fuel control valve so as to provide a related operation of both valves and therefore a continuous control of the fuel/air- proportions in the mixture during all conditions of engine operation. 2. -An internal combustion engine according to claim I wherein'the fuel control valve of the carburetter is arranged to increase the fuel-to-air ratio in the fuel/air mixture during rapid acceleration conditi~ons. 3. An internal combustion engine according

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Claims (1)

1. 27,052/71 to claim 2, wherein the said fuel control valve consists of an orifice opening into the induction passage of the carburetter and controlled by a

   profiled needle moving with the air valve, the

   needle being biassed, so as to contact the wall

   of the orifice on the side nearer to the inlet end

   of said induction passage.

   4. An internal combustion engine

   according to claim 1, wherein the carburetter is

   provided with a passage by-passing the throttle

   valve and controlled by a normally closed valve

   opened automatically by a fall in pTessure in the

   inlet manifold below a predetermined level.

   An internal combustion engine

   according to claim 1, wherein air is supplied to

   the exhaust combustion reaqtor by az air pump

   through a gulp valve operable by a fall in pressure

   in the inlet manifold below a predetermined value

   to re-direct the air supply to the oaid inlet

   manifold.

   6. An internal combustion engine having

   in combination therewith an exhaast" combustion

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   .27,05271 reactor, wherein the combination is substantially as described herein with reference to, and as shown in, the accompanying drawings.

   DATMD this 26th day of March, 1971.

   THE ZENITII CARBURBTTER COMPANY LIMZra

   Patent Attorneys for the Aplicants

   F.B. RICE COO,

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