Spark ignition fuel injection internal combustion engine

A spark-ignition fuel-injection internal combustion engine is provided with a measuring member in its induction system to measure the air flow and a fuel injection nozzle in its induction system downstream of the measuring member.

BACKGROUND OF THE INVENTION 
It is known that in engines of the kind described with port injection 
controlled by measurement of the air flow, it is possible to obtain a 
relatively accurate control of the fuel-air ratio. This makes it possible 
to reduce the polluting components present in the exhaust gases under 
almost all conditions of operation. 
However, it has now been found that at low temperatures and in the 
cold-running phase and as a consequence of the losses due to deposition of 
liquid fuel in the region around the injection nozzle with a cold inlet 
port, and also in the combustion chamber, it is necessary to enrich the 
mixture to balance out this effect. However, enrichment of the mixture 
makes the exhaust gas quality unsatisfactory under these operating 
conditions, at least until the operating temperature is reached and until 
therefore the fuel that is deposited in the inlet port is re-evaporated. 
However, it has also been found that even when the engine has reached its 
operating temperature slight deposits of liquid fuel can still take place 
in the inlet port and then when there are changes in the load which result 
in an increase in the depression in the induction system, these deposits 
evaporate suddenly and are picked up and lead to enrichment of the mixture 
and the undesired consequences already mentioned. 
SUMMARY OF THE INVENTION 
The aim of the invention is to avoid the above-mentioned drawbacks of the 
known device and to provide an induction system for an engine of the kind 
stated in the introduction in which deposits of fuel in the region of the 
inlet port are largely eliminated and good mixing is achieved without 
affecting the fuel-air ratio. 
This problem is solved according to the invention in that the induction 
system, which carries solely air, is split up into a part-load passage and 
a full-load passage and that a heater is arranged in a portion of the 
part-load passage that lies between the measuring member and the injection 
nozzle. 
It is true that, in engines with carburetors, not fuel injection, it is 
known to supply the fuel-air mixture through separate part-load and 
full-load passages. In these engines pre-heating of the fuel-air mixtue is 
provided in order to prevent separation and deposition of fuel within the 
induction system. However in this case the pre-heating can only be very 
limited as any stronger heating can upset the fuel-air ratio and moreover 
lead to a fall in volumetric efficiency. 
In the case of the present invention, by contrast, instead of a fuel-air 
mixture being heated, it is only air that is heated, and furthermore only 
that air which flows from the measuring member through the part-load 
passage. Because of this air which is relatively strongly heated by the 
heater and flows into the inlet port the fuel from the fuel injection 
nozzle is not deposited on the wall of the inlet port, which is heated by 
the air flow, but on the contrary this fuel is evaporated immediately into 
the air stream so that it is possible to form a very homogeneous and well 
pre-heated fuel-air mixture. Variation of the fuel-air ratio due to the 
heating cannot arise as the measuring member which sets a fuel delivery 
proportional to the quantity of air is mounted upstream, in the direction 
of the flow, of the part-load passage and upstream of the heater and 
accordingly the measurement of the air flow always takes place at the 
prevailing temperature of the measuring member. Even with a fall in the 
volumetric efficiency that might arise in the part-load range and 
originating from the heating, the fuel-air ratio remains constant by 
virtue of the fact that the measurement of the air flow is done at ambient 
temperature. A fall-off in volumetric efficiency manifested by a reduction 
in the power output of the engine can be counteracted by opening the 
throttle without upsetting the fuel-air ratio. By making use of this idea, 
quite apart from the improvement in mixture formation, in particular in 
the above-mentioned operating ranges in which the air flow is mainly 
through the part-load passage, there is good mixing, leading to a 
reduction in fuel consumption and therefore it makes enrichment of the 
mixture unnecessary and finally it reduces the quantity of pollution in 
the exhaust gas. 
In a range of operation extending beyond the part-load condition and right 
up to full load the air that is heated in the part-load passage is brought 
together at the inlet port, according to the position of the throttle in 
the full-load passage, with the unheated air flowing through the full-load 
passage. As under these operating conditions the air flow in the part-load 
passage is also appreciably faster than before, the heat transfer is 
automatically of reduced intensity (even in the presence of an increase in 
the heat input from the heater resulting from the increased power output) 
and so no overheating of the air flow can arise and also in these ranges 
of operation it is possible to obtain effective mixing in the inlet port 
without losing volumetric efficiency. Accordingly there is no need to 
provide means for disconnecting the induction heating, such as is 
sometimes provided in known engines. 
Where the engine is liquid-cooled, the heater can be formed by a heat 
exchanger connected to the coolant circuit of the engine. As the coolant 
heats up relatively quickly after the engine has started, and maintains a 
substantially predetermined temperature when the engine is running, 
correspondingly rapid and constant transfer of heat to the air flow can be 
achieved by this arrangement. 
Alternatively the heater can be formed by a heat-transfer wall common to 
the part-load passage and the exhaust system. Such a construction is of 
advantage where the exhaust pipe runs over the induction system. 
In an engine which has its exhaust system connected to a reactor, the 
heat-transfer wall is preferably in a region downstream of the reactor. 
The exhaust gases then meet the heat-transfer wall only when the reaction 
of the exhaust gases in the reactor has been largely concluded. In this 
way it is possible to avoid any disturbance of the reaction process by 
possible removal of heat in the heat-transfer process. As the exhaust 
gases are generally still at a very high temperature even after passing 
through the reactor, it is still possible to find a place for the 
heat-transfer wall that will give ample heat transfer to the part-load 
passage. 
Further details and features of the invention are revealed by the following 
description in conjunction with the drawings which illustrate two 
embodiments of the invention by way of example.

DETAILED DESCRIPTION 
Reference is made first to FIG. 1 in which the main components shown are 
the induction system and the exhaust system of a fuel-injection engine 1 
(the latter being illustrated only partially), with provision for 
measurement of the air flow. The induction system comprises an induction 
pipe portion 2 through which air for combustion flows in the direction of 
the arrows. Mounted at the inlet end 3 of the portion 2 is a measuring 
member 4 which is displaced in a nearly linear function by the flow of air 
through the portion 2 and which cooperates at X with means, not shown, 
that adjust the quantity of fuel delivery to be proportional to the air 
flow in accordance with the position of the member 4. Following the 
portion 2 in the direction of flow is a second portion 5 which is split up 
into a part-load passage 6 and a full-load passage 7, each with its own 
throttle valve 8 and 9. The passages 6 and 7 extend vertically which means 
they are perpendicular to the main longitudinal axis of the engine. After 
passing through the part-load passage 6 and full-load passage 7 the air is 
guided through a third induction pipe portion 10, which is attached to the 
engine 1 by means of flange 26, and thence to the inlet ports 11 of the 
engine 1. Mounted in each inlet port 11 is a fuel injection valve which 
delivers the quantity of fuel necessary for the formation of a fuel-air 
mixture, under the control of the measuring member 4. To discharge the 
burnt gases from the engine there is an exhaust system formed by an 
exhaust port 31 which, in the embodiment shown, leads into a reactor 13 
comprising a reactor chamber 15 enclosed by a housing 14. The reactor 13 
is mounted directly on the engine 1 and attached to it by a flange 29. To 
heat the combustion air, the part-load passage in the portion 10 and an 
exhaust passage 16 that follows the reactor chamber 15, have a common 
heat-transfer wall 17. The wall 17 forms parts of the induction pipe 
portion 10 and simultaneously forms the upper wall of the exhaust passage 
16 which at this point has a flanged engagement with the portion 10. 
When the engine 1 is running heat is imparted to the heat-transfer wall 17 
by the exhaust gas that flows in the direction of the arrow from the 
engine 1 through the exhaust port 31 via a tangential exhaust connection 
18, that opens into the reactor chamber 15, first directly into the 
chamber 15. In the chamber 15 the gas is guided by a sheet metal guide 19 
towards the wall of the reactor chamber 15 and simultaneously set into 
turbulent rotation to after-burn harmful components in the exhaust gas in 
a known way. Only when the reaction of the exhaust gases is largely 
complete does the hot exhaust gas flow through a stub 20 to the exhaust 
passage 16 and here, before passing to an exhaust pipe 21, it comes into 
contact with the heat transfer wall 17, ribs 32, extending in the 
direction of flow, being provided to increase the heat-transfer area. The 
air flowing through the induction pipe portion 10 into the engine 1 is 
thus strongly heated so that the fuel delivered by the nozzle 12 into the 
inlet port 11 cannot be deposited in the port 11 and accordingly is 
vapourised, with the result of improved mixture formation. 
As shown in FIG. 2 the air flowing through the part-load passge 6 passes 
from the induction pipe portion 5 through a chamber 22 in the portion 10 
and this chamber 22 widens out substantially to the width of the exhaust 
passage 16. In the portion 10 the flow of air is turned through about 
180.degree. around an intermediate wall 23 so that the air can come into 
contact with the entire width and length of the heat-transfer wall 17 that 
forms one wall of the portion 10. This guiding of the air and the fact 
that in the region of the throttle valve 8 the part-load passage 6 is 
nearer to the engine than the full-load passage results in a relatively 
long heating zone which allows the air to be intensively heated before it 
passes through the inlet port 11 into the engine 1. 
From FIG. 3, in which the induction pipe portion 2 is not shown, it will be 
seen that several guide webs 24 are mounted between the heat-transfer wall 
17 and the intermediate wall 23 and these webs serve to guide and 
distribute the air that enters from the part-load passage 6 and the 
chamber 22, distributing it across a transverse passage 30 in the 
direction towards to the openings 25 in the flange 26 of the portion 10. 
The guide webs 24 and the previously mentioned ribs 33 projecting from the 
intermediate wall 23 into the part-load passage 6 both have the effect of 
increasing the surface area of the part-load passage that is connected to 
the heat-transfer wall 17 and thereby achieve transfer of heat to the 
passing air. 
In the embodiment illustrated in FIG. 4 the same reference numerals have 
been used as in FIG. 1 for the same parts and the same reference numerals 
but with an index mark have been used for similar parts. Departing from 
the embodiment shown in FIG. 1, the part-load passage for heating the air 
for combustion in the induction pipe portion 10' comprises a heater formed 
by a heat exchanger 36 connected to the coolant circuit of the engine 1, 
in which this case is liquid-cooled. The heat exchanger 36 which, in this 
embodiment, is of the tube type with several tubes 37 and a number of fins 
38, is mounted in that part of the induction pipe portion 10' in which the 
air flowing from the part-load passage 6 into the chamber 22' is guided 
around an intermediate wall 23' in order to obtain a long heating zone. By 
this arrangement it is possible to provide within a small space a heat 
exchanger having a relatively large heat-transmitting surface area. 
In contrast to the embodiment of FIGS. 1 to 3, in this embodiment there is 
moreover no connection between the reactor 13' and the induction pipe 
portion 10' as the heating of the combustion air is done by the heat 
exchanger 36. The exhaust gases coming from the engine 1 therefore pass 
through the exhaust port 31 and an exhaust stub 18' opening tangentially 
into the reactor chamber 15', and into the reactor chamber 15', which is 
not shown in section and which is enclosed in a casing 14'. To ensure 
after-burning the exhaust gas is set into turbulent rotation by a sheet 
metal guiding surface 19' and on completion of the reaction it flows out 
through the exhaust pipe 21'. 
In FIG. 5 is shown how a supply connection 39 and an outlet connection 45 
are provided for connecting the heat exchanger 36 to the coolant circuit. 
The heat exchanger 36 is connected in the circuit in such a direction that 
the heat exchanger 36 has the liquid passing through it in the direction 
of the arrow, corresponding to the direction of flow of the air through 
the part-load passage. This means that the air first meets the region of 
the heat exchanger 36 which the liquid enters through the connection 39 
and it leaves the heat exchanger 36 in that region from which the liquid 
flows out through the connection 40. 
As shown in FIG. 6, the heat exchanger 36 extends over the whole of the 
cross sectional area of the chamber 22'. In this way the air for 
combustion is guided fully over and through the heat exchanger 36, to 
achieve rapid and intensive heat transfer to the air from the coolant, 
which heats up rapidly when the engine is running. 
In the above examples the throttle layout is such that with progressively 
increasing air requirements first the throttle valve 8 is opened and only 
after that one is fully open does the throttle valve 9 start to open. This 
means that following a cold start and in the warming up phase and also 
during idling, i.e., when the air requirements are relatively low, the air 
passes only through the part-load passage 6 under the sole control of the 
throttle valve 8. In operation beyond the part-load range air flows 
through the full-load passage 7. 
In order to reduce the flow of heated air on full-load an alternative 
layout for operating the throttle valves is such that by the time the 
valve 9 for the full-load passage 7 is fully open the valve 8 in the 
part-load passage 6 is almost closed again. 
A heat-insulating gasket 35 is provided between the induction pipe portions 
5 and 10 or 10' to prevent the heat from the portion 10 or 10' that has 
the heater in it from being transmitted to the full-load passage 7 and 
possibly leading to distortion of the throttle valves 8 and 9. 
To follow the path of the combustion air after opening of the full-load 
passage 7 FIGS. 1, 2 and 3 or FIGS. 4, 5 and 6 must be looked at together. 
In this case the air for combustion flows in the direction of the arrow 
shown in broken lines, past the throttle valve 9 into a damping chamber 27 
which is provided in the portion 5 and which balances out fluctuations 
which would otherwise have an adverse effect on the operation of the 
measuring member 4. From this damping chamber 27, the air passes to 
passages 28 or 28' which pass on both sides of the portion 5 and of the 
portion 10 or 10' with a positive clearance 34 or 34' in the region of the 
heater, and accordingly cannot pick up heat. The air emerging at 
relatively low temperature from the full-load passage 7 through the 
passages 28 or 28' and the heated air flowing in from the part-load 
passage 6, are mixed together in the region of the transverse passage 30 
or 30' before entering the induction ports 11 through the openings 25 or 
25'. This mixing avoids overheating of the combustion air, especially 
under full-load conditions, so good mixing can be obtained in the inlet 
ports 11 but without any fall in volumetric efficiency. 
By pre-heating only the air flowing through part-load passage 6, the 
operation in this range is improved as the pre-heating prevents 
condensation. Because the air that is supplied through the full-load 
passage 7 is not pre-heated, there is no reduction in the volumetric 
efficiency at full load. Pre-heating in this range of operation is 
unnecessary anyway as the engine is already warm by then whilst the 
correct temperature for mixture formation is set by the mixing of the two 
air flows. 
Thus the several aforenoted objects and advantages are most effectively 
attained. Although several somewhat preferred embodiments have been 
disclosed and described in detail herein, it should be understood that 
this invention is in no sense limited thereby and its scope is to be 
determined by that of the appended claims.