Process for delivering and for metering at least one additive to the combustion chamber of an engine and associated applications

The present invention relates to a process for delivering and for metering additives to the combustion chamber of an internal-combustion engine consuming a known and controlled amount of lubricant, according to which the lubricant consumed comprises at least one additive designed to improve the quality of the combustion in the chamber. In particular, the additive is designed to promote the combustion of an engine working with controlled self-ignition and to obtain operation in a wider speed and/or load range of the engine.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to the field of internal-combustion engines, 
notably self-ignition engines. 
More particularly, the present invention applies to engines that consume, 
for the operation thereof, a known and controlled amount of oil used for 
its lubricating properties. 
2. Description of the Prior Art 
For example, engines having an oil consumption regulated according to 
engine operation parameters such as the load or the speed are well-known. 
The oil consumption can also be linked with the fuel consumption according 
to a certain ratio. Engines thus working are for example: two-stroke 
gasoline engines with a pump sump, lost-oil lubricated, where the oil can 
be delivered to the intake system or mixed with the fuel in a proportion 
recommended by the manufacturer. 
There are also gasoline or diesel two-stroke engines referred to as "wet 
sump" engines (four-stroke type sump) for which a controlled oil 
consumption allows lubrication of the piston-jacket unit. This consumption 
can be obtained through a controlled lubricating oil escape into the 
combustion chamber via for example a relative seal at the level of the 
rings. 
It is also well-known to deliver lubricant to the intake air supplied by a 
compressor or a supercharger. 
Metering of the oil consumed by the engine and delivered by controlled 
supply to the combustion chamber of an engine is not limited to two-stroke 
engines, since there are known works on four-stroke engines with dry sumps 
used as air supercharging pumps that are also lost-oil lubricated. 
For these various types of motors, a very great number of lubricants are 
available on the commercial market. Each lubricant corresponds to a 
particular engine type according to specifications fixed by engine 
manufacturers and lubricant makers. For example, for two-stroke engines, 
down-market and very cheap commercial oils are available for simple 
two-wheeler applications (motorbike). Other lubricants are available for 
high-performance applications (motorcyles), others for marine applications 
(outboard). 
These various examples show that each lubricant is intended for a given 
specific engine. 
Furthermore, when the lubricant is thus consumed in a controlled way and 
therefore participates in the combustion of the engine, it may, according 
to the invention, be loaded with additives that will allow improvement of 
the quality of the combustion according to one or several quality criteria 
such as, for example, minimum pollutant emissions, the highest efficiency, 
the best cycle regularity, cleanliness, . . . etc. 
Usually, such additives are mixed with the fuel and they are then intended 
for specific functions such as pollutant emissions reduction, soot 
formation reduction, regeneration of filters located in the exhaust 
system, detergency. 
French Patent 2,702,009, U.S. Pat. No. 4,621,593 or European Patent 269,228 
disclose various methods for supplying an engine fuel with an additive. 
However, a marketed and distributed fuel already containing an additive is 
hard to conceive when the required additive is not necessary for a whole 
fleet of vehicles and would be necessary only and specifically for part of 
a fleet of vehicles on the market. 
Although the commercial distribution of fuels containing antifouling 
additives for example can be contemplated, it is not economically 
profitable to distribute an additive-containing fuel that would be 
specifically suited for two-wheelers with two-stroke engines and marine 
outboard engines. 
SUMMARY OF THE INVENTION 
The invention is a new and extremely simple solution for supplying the 
combustion chamber of engines with additives for specific applications, 
where the additive is not initially mixed with the fuel but with the 
lubricant. 
More precisely, the invention relates to a process for delivering and for 
metering additives to the combustion chamber of an internal-combustion 
engine consuming a known and controlled amount of lubricant, a process 
according to which the consumed lubricant comprises at least one additive 
designed to improve the quality of the combustion in the chamber. 
In particular, the additive is intended to promote the combustion of an 
engine working with controlled self-ignition and to obtain operation in a 
wider speed and/or load range of the engine. 
According to an embodiment of the invention, the additive-containing 
lubricant is mixed with the fuel by the user. 
According to another embodiment of the invention, the additive-containing 
lubricant is delivered to the engine intake by a specific metering device. 
A particular application of the invention relates to two-stroke engines 
with a lost-oil lubricated pump sump. 
The engine to which the invention applies to can be a two-stroke engine 
with an external compressor, whose lubricant consumption is obtained 
through controlled escape via the engine rings. 
Without departing from the scope of the invention, the engine may be a 
four-stroke engine with a lost-oil lubricated pump sump. 
According to a feature of the invention, metering of the lubricant can be 
controlled electronically as a function of parameters such as the speed, 
the load, the presence or absence of knocking, self-ignition operation or 
not, etc. . . . 
This feature thus allows indirect electronic control of the amount of 
additive delivered to the combustion chamber, via electronic lubricant 
metering.

DESCRIPTION OF THE INVENTION 
The process according to the invention uses consists in using an 
additive-containing lubricant, the formulation of the additive(s) being 
determined in order to obtain the required effect on the quality of the 
combustion, and in applying it to an engine in which the consumption of 
the lubricant is controlled by a suitable metering device (metering pump, 
calibrated escape, etc). Thus, the amount of lubricant and of fuel 
participating in the combustion being known, the lubricant according to 
the invention can precisely comprise the amount of additives that could 
have been required to participate in the efficient progress of the 
combustion. 
A particularly advantageous example of application of the process according 
to the invention is the supply of lubricant of a two-stroke engine with an 
additive so as to promote the self-ignition operation thereof by extending 
the operating range of the engine according to this self-ignition process. 
FIGS. 1 and 2 show curves of the engine power W as a function of their 
speed RM. The curve P.sub.max corresponding to the maximum power developed 
by the engine can be seen in each of the figures. 
FIG. 1 shows the operating range of a known two-stroke engine, that is for 
example the subject of the Assignee's French Patent 2,649,157. 
This known engine was designed to have the widest possible self-ignition 
operating range (1) at low speeds and low loads. 
FIG. 2 shows the same operating range of the engine when the lubricant 
consumed by the engine (in a ratio of about 2% of the fuel consumed) 
contains about 10% of additives promoting the controlled self-ignition 
process. This supply of additive to the lubricant according to the 
invention allows, in this example, to extend the self-ignition operating 
range to 100 to 200-rpm lower speeds. In fact, whereas in known engines 
(FIG. 1), self-ignition existed for engine speeds above about 1700 rpm, 
according to the invention (FIG. 2), self-ignition appears as soon as 1500 
rpm for the same engine power. 
In particular in the case of two-stroke engines (although application to 
four-stroke engines is in accordance with invention), there is a 
well-known particular combustion mode for which the engine can have a 
self-ignition operation. U.S. Pat. No. 4,445,468 describes an example of 
such an engine. 
Research work shows that this type of combustion is obtained at low loads 
and at rather high speeds. 
It is well-known that parameters linked with the operation of the engine, 
such as the compression ratio, the internal aerodynamics and the fresh 
gas/burned gas stratification, the temperature and the pressure in the 
cylinder at the start of the compression, etc. . . . , have a strong 
influence on the self-ignition operation and on the extent of the speed 
and load range where it is obtained. 
The parameters linked with the fuel, the composition, the physico-chemical 
characteristics (octane and cetane number, additives formulation, etc), 
can also have an influence on this combustion. In particular, recent work 
shows that certain additives fed into the fuel allow to extend this 
self-ignition operating range to low speeds with the aim of obtaining 
self-ignition at engine idling speed. Feeding these additives in a mixed 
form into the lubricant according to the invention allows the obtaining of 
the same effects in a very simple way. 
Extension of the self-ignition operating range is particularly interesting 
and sought-after since it allows avoiding of combustion irregularities 
typical notably of two-stroke engines at low load and low speed. 
Unburned hydrocarbon emissions are thus greatly reduced (by about 60%), the 
fuel efficiency and consumption are improved and the combustion is made 
particularly stable from one cycle to the next. 
It may therefore be advantageously contemplated, according to the 
invention, marketing additive-containing lubricants for two-stroke engines 
(two-wheelers, outboard) in order to increase the self-ignition operating 
range. 
According to an embodiment of the invention, the additive-containing 
lubricant is mixed with the fuel by the user. This may be the case for 
two-stroke engines supplied, at the level of the fuel tank, with an 
oil-fuel mixture according to a determined percentage. 
According to another embodiment of the invention, the additive-containing 
lubricant is delivered to the engine intake. This may be the case for 
two-stroke engines with so-called "separate lubrication" pump sumps where 
the user fills two tanks, the fuel tank and the lubricant tank. An oil 
metering system can then mix this oil with the fuel just prior to feeding 
the carburetor, or the metering system can deliver this oil to the engine 
intake.