EXHAUST GAS POST -TREATMENT SYSTEM

The present invention concerns an exhaust gas post-treatment system in particular of internal combustion engines.

It is known that the combustion of a fuel causes the formation, in addition to completely oxidised products - CO₂, H₂O -, also of a large number of secondary products, like non-combusted or partially combusted hydrocarbons, pyrolysis products and derivatives including soot.

In the case of Diesel engines soot is the main culprit for the formation of particulate, since providing a large specific surface allows the deposit of hydrocarbons, fuel aerosol or non-combusted lubricants and the like.

As well as the general problem of an increase in pollution of the environment, it is also suspected that particulate is a cancerogenous agent.

Amongst the measures that can be used to modify the composition of the exhaust gases in internal combustion engines, so-called post-treatment measures of emissions are becoming increasingly important.

A problem connected with post-treatment systems like for example the installation of an anti-particulate filter on a vehicle equipped with a thermal engine, in particular with spontaneous ignition, is due to the fact that it constitutes a modification of the structural, functional and equipment characteristics of the vehicle itself.

In the case of filtration of exhaust gases of a Diesel engine, the anti-particulate filter, be it arranged in series with the approved muffler or replacing it, generally creates a variation in the counterpressure at the exhaust and in the noisiness of the vehicle itself.

It is for this reason that the testing and validation bodies (Traffic Control Authority) require that all new characteristics be tested and that the vehicle and/or engine manufacturer gives the go-ahead.

This implies complexity and unacceptable times for carrying out the installation of post-treatment systems in general and of anti-particulate filters for Diesel engines, on vehicles that require such an intervention.

A device for filtering internal combustion engine exhaust gases is known for example from document US 6 185 934 B1, wherein an electrostatic filtering chamber, equipped with electrostatic filtering means, is provided for filtering the exhaust gases sucked from the exhaust silencer box outlet orifice of a motor vehicle. Another known exhaust filter device is shown for example in document US 3 417 549.

The Applicant has set itself the problem of how to reduce the concentration of harmful substances present in the exhaust gases of an internal combustion engine without interfering with the exhaust system of the engine itself.

The Applicant has solved the aforementioned problem by devising an exhaust gas post-treatment system according to what is outlined in claim 1.

Further characteristics of the invention form the object of the dependent claims.

The exhaust gas post-treatment system of an internal combustion engine according to the present invention intercepts the gases downstream of the muffler of the exhaust unit through an aspirator and feeds them to a blasting device that takes care of reducing the concentration of harmful substances, the aspirator has a flow rate of no less than the maximum volumetric flow rate of the exhaust gases and a pressure suitable for overcoming the maximum load losses of the blasting device, and it is equipped with a motor able to be operatively connected to the internal combustion engine so as to optimise the flow rate of the gases emitted by the internal combustion engine.

The system according to the present invention can be installed without interfering with the exhaust system and therefore counterpressure and noisiness of the internal combustion engine remain the same as when approved and validated by the competent bodies.

The installation of the system according to the present invention can therefore be carried out on any vehicle without requiring another validation.

The characteristics and advantages of an exhaust gas post-treatment system according to the present invention shall become clearer from the following description, given as a non-limiting example, referring to the attached figure in which a schematic view of the system is shown according to one of the possible embodiments of the invention.

The present invention provides an exhaust gas post-treatment system 10 for blasting harmful substances, by harmful substances meaning secondary combustion products, like non-combusted or partially combusted hydrocarbons, pyrolysis products and derivatives including soot and the like.

The system 10 is arranged downstream of the muffler 2 of an internal combustion engine M.

In particular, the system 10 is arranged downstream of the exhaust pipe 3 of the muffler 2 and has a suction cone 11, suitable for shielding the passage portion, i.e. the exhaust gas intake, from the turbulence due to the motion of the vehicle and to environmental conditions.

The suction cone 11 is connected through piping 12 to a blasting device 13 of the harmful substances present in the exhaust gases.

Depending upon the engine to which it must be applied, the system comprises a blasting device 13 mainly suitable for filtering particulate, in the case of Diesel engines, or dedicated to the treatment of the other polluting emissions in gas form or in the form of an aerosol in the case of controlled ignition engines.

In the case of a Diesel engine the blasting device can have both types of treatment, whereas in the case of a controlled ignition engine just the blasting device of volatile substances may be sufficient given the low soot production of this engine.

The system comprises an aspirator 14 with a flow rate equal to or greater than the maximum volumetric flow rate of the exhaust gases and with a pressure suitable for overcoming the maximum load losses of the blasting device.

The aspirator 14 that can be of the centrifugal or volumetric type can be installed upstream or downstream of the blasting device 13.

In the present embodiment, the aspirator 14 is installed downstream of the blasting device, since it advantageously works on gas that has already been treated.

The Applicant has discovered that one of the characteristics necessary for the post-treatment system to work correctly is that the sucked flow rate is as close as possible so as not to interfere with the volumetric flow rate of the exhaust gases.

To obtain such a result the Applicant has operatively connected the motor 15 of the aspirator to the internal combustion engine M.

According to the type of engine, such a connection can be made in different ways.

According to a first way, exemplified in the figures, an oleodynamic motor 15 has been used, fed through an oleodynamic pump 17 connected to the engine M through feed piping 16.

In this way a substantially direct proportionality is achieved between flow rate of the emissions of the engine M and flow rate of the suction system 10 sufficient to capture the emissions at any rotation speed of the engine.

In another totally equivalent embodiment, in the case of motorisation of the aspirator through an electric motor both in direct current and in alternating current, a control module is foreseen that varies the speed of the motor of the aspirator according to the number of revolutions of the internal combustion engine with the most suitable dependency law.

Moreover, Diesel engines can be connected directly to the motor 15 of the aspirator with mechanical transmission systems or with gears or belt-pulley systems or similar.

The blasting device can also be made by arranging a filter for the particulate and a device for treating volatile substances, aeriforms and aerosols, in series, in which the device for treating aeriforms and aerosols can be preceded or followed by the filter.

Of course, when sizing the aspirator it is necessary to keep in mind that the filter will have gradually increasing degrees of clogging up until the moment when it has to be replaced or regenerated.

The system from this point of view has the advantage of not imposing upon the manufacturer links to the maximum counterpressure allowed of the motor.