Device for the pneumatic injection of fuel into a cylinder of an internal combustion engine

A device is provided for the pneumatic injection of fuel into a cylinder of an internal combustion engine, comprising an injection chamber in communication with the inner chamber of the cylinder through two orifices with each of which a valve is associated. The injector comprises two outlet channels each directed towards one of the orifices of said injection chamber. The valves are controlled so as to open and close simultaneously. The invention applies in particular to high power two-stroke engines.

BACKGROUND OF THE INVENTION 
The invention relates to a device for the pneumatic injection of fuel into 
a cylinder of an internal combustion engine and more particularly, but not 
exclusively, a pneumatic injection device for a two-stroke engine. 
Two-stroke engines are known having one or more cylinders with, associated 
with each of the cylinders, a pneumatic fuel injection device for 
atomizing a liquid fuel by means of a pressurized gas which is generally 
compressed air and feeding the carburetted mixture obtained into the 
cylinder of the engine. The cylinder is fed with and swept by the fresh 
air independently of the pneumatic fuel injection which is initiated at a 
given time during the operating cycle of the engine. 
The pneumatic fuel injection device comprises a chamber which may be placed 
in communication with the inner chamber of the cylinder through at least 
one valve controlled by a cam. The injection chamber is fed with 
pressurized gas which may come either from an auxiliary reservoir or from 
a part of the engine producing this pressurized gas. 
In particular, it has been proposed to feed the injection device with 
compressed air from a capacity which is recharged by the pump housing 
providing the fresh air supply and scavenging of the cylinder of the 
engine. 
In the case of high power engines, the amounts of fuel injected into the 
cylinder are very considerable and require either a high amplitude lift of 
the valve placing the injection chamber in communication with the 
cylinder, or the use of a large diameter valve. By high power engine is 
meant more particularly engines delivering more than 25 to 30 kW per 
cylinder. 
In the case of very large engines, it is not possible to increase the 
diameter of the valves beyond a certain limit, since the inertia of the 
valve then becomes excessive. Similarly, it is not possible to increase 
the lift amplitude or time beyond a certain limit. 
In the case of large engines, it has been proposed to divide the injection 
device of each of the cylinders into two, using two valves and two liquid 
fuel injectors per cylinder. The drawbacks of this approach are however 
that the cost price of the engine is considerably increased and its 
adjustment is delicate. 
SUMMARY OF THE INVENTION 
The purpose of the invention is then to provide a device for the pneumatic 
injection of fuel into a cylinder of an internal combustion engine 
comprising a chamber which may be placed in communication with the inner 
chamber of the cylinder through at least one valve controlled for 
injection at a given time in the operating cycle of the engine, and fed 
with pressurized gas through a duct and with liquid fuel through a liquid 
injector, opening into the injection chamber, this device intended for a 
high power engine being capable of feeding large amounts of fuel into the 
chamber of the cylinder while being simple in structure and of low cost 
price making it possible to simplify the adjustment of the engine. 
To this end, the injection chamber comprises two orifices opening into the 
chamber of the cylinder with each of which is associated a valve and the 
injector comprises two outlet channels each directed to one of the 
orifices of the injection chamber.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In the figure, the upper part of the chamber of a cylinder 1 of a 
two-stroke engine can be seen which is covered and defined by a cylinder 
head 2 in which is formed the chamber 3 of an injection device. Chamber 3 
opens into cylinder 1, at the level of two circular orifices 4a and 4b 
through which the fuel mixture is injected. The cylinder head is machined 
and faced at the level of orifices 4a and 4b so as to form two seats on 
which the heads of two valves 5a and 5b come to bear respectively. Valves 
5a and 5b comprise rods mounted for sliding in the cylinder head 2 and 
associated at their ends with a cam and spring control device for opening 
and closing the valves 5a and 5b at given times during the operating cycle 
of the engine. 
The control device causes simultaneous opening and closing of valves 5a and 
5b. 
The cylinder head is machined so as to form a channel 6 opening into 
chamber 3 for supplying this injection chamber 3 with pressurized gas. 
Preferably, channel 6 is connected to a capacity in which compressed air is 
stored, for example from the pump housing communicating with the lower end 
of cylinder 1 and providing the fresh air supply and scavenging of the 
cylinder through one or more transfer ducts. 
A liquid fuel injector 8 is mounted inside the cylinder head so that its 
outlet nozzle 8a opens into the upper part of the injection chamber 3. 
Injector 8 is a twin jet injector whose outlet nozzle 8a comprises two 
channels 9a and 9b equally slanted with respect to the vertical and fed 
from a single channel 10. 
When injector 8 is operating, as shown in the figure, two jets 12a and 12b 
of liquid fuel are directed simultaneously towards the orifices 4a and 4b 
respectively. 
Nozzles 14a and 14b are disposed at the lower part of the injection chamber 
3, at the level of orifices 4a and 4b respectively. These nozzles 14a and 
14b may be advantageously formed by venturis as described in the patent 2 
575 521 filed jointly by the Institut Francais du Petrole and the firms 
Societes Automobiles Peugeot and Automobiles Citroen. Jets 12a and 12b are 
directed so as to reach the zone of apertures 4a and 4b, at the lower part 
of the injection chamber 3, through nozzles 14a and 14b. 
At the time of simultaneous opening of valves 5a and 5b, the pressurized 
air fed by channel 6 into chamber 3 (arrow 15) penetrates into this 
chamber at high speed, the pressure in the cylinder being, at the time of 
pneumatic injection, very much less than the pressure of the compressed 
air in the capacity connected to channel 6. The compressed air penetrates 
into nozzles 14a and 14b where it is further accelerated and causes 
atomization of the liquid fuel fed into chamber 3, through injector 8, in 
the form of jets 12a and 12b. The compressed air containing the atomized 
fuel droplets in suspension penetrates into the chamber of cylinder 1 
where it is mixed with the fresh scavenging air fed into the cylinder 
through a means independent of pneumatic injection device. 
During injection, valves 5a and 5b are open simultaneously, their 
respective heads being moved away from the seats surrounding apertures 4a 
and 4b. The flow section for the fuel in suspension in the compressed air 
is then twice the flow section uncovered by any one of the two valves. At 
the time of closure, the two valve heads are applied against the seats 
surrounding orifices 4a and 4b respectively for simultaneously closing the 
two communication passages between the injection chamber 3 and the chamber 
of cylinder 1. The simultaneous operation of valves 5a and 5b may be 
provided by using a single cam or two perfectly synchronized cams. Valves 
5a and 5b of identical size may thus, when they open, uncover an 
appreciable flow section for the fuel in suspension in the compressed air, 
while having heads whose diameter is limited. Each of the valves thus has 
a limited weight and inertia, which is favorable for the operation of the 
high speed engine. 
Furthermore, injector 8 introduces into chamber 3, at the level of venturis 
14a and 14b, in the form of two identical jets 12a and 12b, a double 
amount of liquid fuel with respect to that which would be introduced by a 
single injector associated with a single valve such as 5a and 5b. Jets 12a 
and 12b coming from channels 9a and 9b of identical section and fed from a 
single channel 10 have perfectly identical flow rates and speeds. The 
adjustment of the injection device is then particularly simple since this 
injection device comprises two identical assemblies operating 
simultaneously for the feeding of equal amounts of fuel. 
Thus, considerable fuel amounts may be fed into the chamber of the cylinder 
without using overdimensioned valves and an injection assembly requiring 
complex adjustment. 
The invention is not limited to the embodiment which has been described. 
Thus, it is possible to equip at least one of the fuel intake orifices 4a 
and 4b with a member deflecting the carburetted mixture jet, such as 
described in the patent application 2 575 522 filed jointly by the 
Institut Francais du Petrole and the firms Societes Automobiles Peugeot 
and Automobiles Citroen. The members for deflecting the carburetted 
mixture jet may each be machined in an annular part also forming the seat 
of the corresponding valve. 
In a particularly interesting embodiment, each of the two orifices is 
provided with a deflector. Each of these deflectors may be oriented so as 
to optimize the scavenging and combustion in the engine. Thus, in some 
cases, the deflectors may orient the jets in different directions. For 
example, in the case of a two-stroke engine having several transfer ports 
distributed on each side of the median axial plane of the cylinder passing 
through the exhaust port, the deflectors may be oriented for directing the 
jets on each side of the median plane in the direction of the transfer 
port. 
The pneumatic injection device of the invention may be used not only in the 
case of two-stroke engines, but also in the case of internal combustion 
reciprocal engines with one or more cylinders.