In internal combustion engines, both diesel and gasoline, the need often rises to have additives added to the fuel for improving the chemical-physical properties with respect to both the engine performances and polluting features of the exhaust gases.

It is known, for instance, to add urea to exhaust gases in order to reduce polluting NOx groups.

In particular, it is also known to add cerium salts (EolysT) or analogous to diesel fuel in diesel engines, in order to reduce the combustion point of residual particulate and provide for its complete disposal in the exhaust.

Cerium salts are added to diesel oil through a tank and a valve dosing a cerium solution directly in the fuel liquid stage, which is then introduced directly in the cylinder. The particulate is then burnt in an appropriate anti-particulate filter on the exhaust duct utilizing the low combustion point caused by the addition of the cerium salts.

Such a method has a drawback, since it has always the same quantity of cerium salts introduced in the fuel; as a result, said quantity cannot be dosed depending on the different engine requirements and filter conditions. Moreover, the cerium tank located adjacent or associated to the diesel fuel tank has a difficult access, which makes it difficult to check its level and fill it again. In addition, a pump and a dosing system of the amount of cerium salts in solution being introduced are required.

It is the aim of the present invention to solve the above drawbacks and provide an additive injector device for internal combustion engines having an improved and more efficient performance with respect to the existing solutions.

In this frame it is the main object of the present invention to provide an additive injector device for internal combustion engines and/or an additive injection method in internal combustion engines, which provide for managing the additive injection in a flexible manner.

A further object of the present invention is to provide an additive injector device for internal combustion engines, which allows easy access to the additive tank.

A further object of the present invention is to provide an additive injector device for internal combustion engines, which does not require any accessory pumping and/or dosing equipment.

In order to reach such aims, it is the object of the present invention to provide an additive injector device for internal combustion engines, incorporating the features of the annexed claims, which form an integral part of the description herein.

Further objects, features and advantages of the present invention will become apparent from the following detailed description and annexed drawings, which are supplied by way of non limiting example, wherein: Fig. 1 shows a basic schematics of an additive injection system for internal combustion engines according to the present invention; Fig. 2 shows a basic schematics of an additive injector device for internal combustion engines according to the present invention; Fig. 3 shows a basic schematics of a detail of the additive injection system for internal combustion engines of Figure 1; Fig. 4 shows a basic schematics of a preferred embodiment of the additive injection system for internal combustion engines of Figure 1.

In Figure 1 is represented a basic schematics of an additive injection system 1 according to the present invention in an engine with spark plug ignition. Therefore, it illustrates a-suction duct 2 feeding the air required for the combustion mixture from the motor-vehicle air intakes not shown here. The suction duct 2 has an interposed air filter 3 and a throttled body 4 located downstream, which comprises a throttle valve 5. An air plenum 6 downstream the throttled body 4 has a plurality of suction ducts 7, which depart from it and are ending in a cylinder head 8. The elements described above are all known and will not be described in detail.

An additive tank 9 is provided, from which an hydraulic circuit for additive intake 10 is departing, represented by a thick line. This hydraulic circuit for additive intake 10 is actuated by means of an intake pump 11, which has an additive filter 12 located downstream.

Downstream the additive filter 12, the hydraulic circuit 10 departs in a first branch 10a, which comprises a dosing device 13 and micro-injectors 14 arranged downstream of the device. The dosing device 13 is also connected through an air duct 27 to the suction duct 2. Said micro-injectors 14 to be described in detail with reference to Figure 2 are arranged in windows 15 obtained on the surface of the suction duct 2. The micro-injectors 14 belonging to the first branch 10a are arranged downstream the filter 3 and upstream the throttled body 4. Figure 1 is representing several pairs of micro-injectors 14 located in a tangential position to the suction duct 2 and at distance between them for ensuring even distribution of the additive in the air. The pairs of micro-injectors 14 are

located along the circumference of the external surface of the suction duct 2 and are fed by means of the branch 10a and dosing device 13.

The hydraulic circuit for additive intake 10 comprises further branches 10b, l Oc, l Od, 10e, each one of them including a dosing device 13 and each one of them fitted with a relevant duct 27, not represented for simplicity's sake, putting it in communication with the respective suction duct 7 and micro-injectors 14, analogous to the ones located in the suction duct, placed tangentially along the circumference on each suction duct 7.

An electronic control unit 16 is also provided, as commonly known, which has electric connections 17a, 17b, 17c, 17d and 17e to the micro-injectors 14 on the suction duct 2 and suction ducts 7, whereas through an electric connection 18 it receives a signal about the position of the throttle valve 5 as well as signals concerning other quantities from further sensors located on the motor-vehicle.

Figure 2 is representing a basic schematics of the micro-injector 14 according to the present invention. Said micro-injector 14 is a device similar to the ink jet printing heads, so-called'bubble- jet'. It consists, in fact, of a silicon substrate 19 about 500 pm thick, whereon a photopolymer layer 20 is deposited, in which a window is obtained forming a pressure chamber 21. A covering layer 22 delimits a micro-nozzle 23, which has a diameter of a few tenths of llm. A thin film heater 24 is deposited on the silicon substrate 19 in the pressure chamber 21. The additive in solution is conveyed to the pressure chamber 21, where the thin film heater 24 heats it up very rapidly at a temperature being apt to convert part of the solution into vapour, indicatively 200°C, causing a large number of tiny gas bubbles to form over the surface of the thin film heater 24 and rapidly join together to form a bubble 25, indicated in Figure 2, which pushes a drop 26 out of the micro-nozzle 23. The electric pulse to the thin film heater 24 is a short one, in the order of a few microseconds, but having a high power density estimated in hundreds of mW/m2. The kinetic energy of the drop 26 outside the micro-nozzle 23 is very small, just a few pJ. Therefore, a high frequency operation in the order of thousands of Hz can be obtained, with flow-rates in the order of cm3/min for each micro- injector 14. The drops 26 have a smaller size than 50 urn, so that a far better additive nebulization can be obtained with the micro-injectors 14 compared to the known electro-injectors.

The additive injection system in internal combustion engines lof Figure 1 operates as follows: the additive is fed through the additive pump 11 into the additive intake circuit 10. The dosing device 13 is used for feeding the micro-injectors 14 and supply the amount of additive required at a pressure equalling the one of the suction duct 2. The micro-injectors 14, whose thin film heater 24 is driven by the electronic unit 16, will spray the additive in the suction duct 2, if pertaining to the

branch 10a, or in the relevant suction ducts 7, if pertaining to the branches lOb, 10c, 10d, 10e, respectively.

The nebulized additive is projected in the air stream flowing in the suction duct 2 or suction ducts 7, forming the air-additive mixture that enters the cylinders and is appropriately used for the additivating function, such as to change the combustion temperature of the residual particulate in the instance of an additive consisting of cerium salts.

The electronic unit 16 receives information about the exhaust gases and filter state through the connection 18, so as to conveniently drive the spraying frequency of the micro-injectors 14 and eventually the number of active micro-injectors 14, in order to warrant an optimal additive injection with respect to the consumption and anti-pollution standards. In the case of cerium salts, for instance, a signal is sent by a pressure sensor to the unit 16 indicating the clogging level of the filter.

In figure 3 the dosing device 13 is represented, which receives as its inlet the branch 10a of the additive intake hydraulic circuit 10 and supplies the additive through an outlet duct 28 to the micro- injectors 14. In the upper portion of the dosing device 13, the inlet of the air duct 27 puts the dosing device 13 in communication with the suction duct 2. Inside the dosing device 13, a float 29 fitted with a pin shutter 30 is located in the upper portion. The additive pushed by the additive pump 11 enters the dosing device 13 from the branch 10a and flows down toward the micro-injectors 14 through the outlet duct 28. When the additive level inside the dosing device 13 is such to bring the pin shutter 30, located on the float 29, to clog the branch 10a, the additive feeding is interrupted.

The additive feeds the micro-injectors 14 by gravity until the additive level decreases and the pin shutter 30 releases the branch 10a. The function of the air duct 27 is to cause a reaction of the suction duct 2 pressure in the upper portion of the dosing device 13, where the additive does not arrive. In fact, the pressure inside the suction duct 2 changes depending on the engine revolutions and on the suction valve opening-closing intervals. In order to have a correct operation of the micro- injectors 14, a consistent differential pressure between air and additive must always be ensured.

Taking back the pressure of the suction duct 2 inside the dosing device 13, the additive pressure in the micro-injector 14 will follow the pressure evolutions in the suction duct 2. Obviously, in order to obtain an optimum pressure control in the dosing device 13, the duct 27 has to draw the pressure of the suction duct 2 in proximity to the micro-injectors 14. The same function is performed by the ducts 27 located in correspondence with the suction ducts 7.

The additive injection system in internal combustion engines according to the present invention is based on the use of micro-jet injectors in the suction ducts, analogously to micro-jet ink injectors for

ink-jet printers, since due to their smaller flow-rates compared to the known electro-injectors, said micro-jet injectors have reduced size and weight, a high operating frequency and a high additive nebulization capacity. Moreover, they show the feature to operate as additive injectors, performing a local pumping and outlet dosing function in the air conveying ducts. This means that the additive pump 11 applies a very low first pressure. The micro-injectors 14 receive the additive at said first pressure and, through the thin film heater 24, apply a pressure being apt to let a drop 26 of the desired size and speed, drops out of the micro-nozzle 23.

In Figure 4 a preferred embodiment of the systems according to the present invention is shown, which is particularly suited for the injection of cerium salts in order to lower the combustion point of the residual particulate in a diesel engine.

The additive is stored in a tank 100 located around the suction duct 102 of the diesel engine, i. e. the tank 100 is substantially hollow cylindrical shaped. The suction duct 102 is inclined for the air to flow through it from the bottom to the top; also the tank 100 is inclined, as usually done, so that the liquid additive contained therein develops a pressure head towards the bottom of the tank 100, where one or more micro-injectors 14 are located, insofar as the pressure is supplied by gravity to said micro-injector 14. Said micro-injector 14 is connected to the electronic unit 16, which also monitors and controls the pressure drop on the anti-particulate filter.

The pressure inside the tank 100 equals the pressure inside the suction duct 102, thanks to the tubing 127 connecting them analogously to the duct 27 of Figure 1.

In Figure 4 a sealing plug 104 can be seen on the tubing 127, which ensures an easy supply of the tank 100, the latter being properly manufactured using transparent material aimed to verify the additive level.

From the above description the features of the present invention as well as the relevant advantages thereof are clear.

The additive injector device for internal combustion engines according to the present invention provides advantageously for additivation to the suction duct, releasing it from the fuel intake operation in the cylinders and ensuring flexible additivation strategies through the appropriate operation of the electronic unit, which are suitable for the exhaust gases composition and filters state.

There is no need for a pump and metering device, since the additive can be dosed by gravity.

The additive tank is able to be advantageously located far from the cylinders; it can be easily filled and its level verified.

Moreover, the solution in which the additive tank surrounds the suction duct contributes advantageously to reduce suction noise.

It is obvious that many changes are possible for the man skilled in the art to the additive injector device for internal combustion engines and/or additive injection method in internal combustion engines described above by way of example, without departing from the novelty spirit of the innovative idea, as well as it is clear that in practical actuation of the invention the components may often differ in form and size from the ones described, and may be replaced with technical equivalent elements.

The additive injection system may be applied for the injection of additives differing from cerium salts. In particular, it can be used for the injection of urea, in order to reduce NOx groups in the exhaust gases. To this purpose, the micro-injectors can be arranged in the suction or exhaust duct with appropriate protecting means against overpressure and high temperature, or still in both these ducts.

Each micro-jet injector may be fitted with a plurality of micro-nozzles.

The micro-jet injectors may not only be of the'bubble-jet'type, but also piezoelectric micro-jet injectors, i. e. utilizing the expansion of a piezoelectric actuator instead of the additive vapour bubble. These piezoelectric micro-jet injectors may be more suited, e. g. , for oil injection, as well as for injection under high temperature conditions. Also the use of various micro-jet injectors is possible, being able to be analogously classified in the category of micro-ject injectors for ink jet printers, substantially providing for a lack of mechanical parts moving in the application means of the pressure to the additive in a micro-chamber.

The various micro jet injectors may perform different injection tasks.

Specific micro-jet injectors may be used for injecting fuel additives in the suction duct under particular operating conditions of the engine. These micro-jet injectors can be controlled by the electronic unit, which actuates them depending on performance optimisation and/or anti-pollution actions.

In particular, the additives may be used for reducing pollution in acceleration or deceleration transient phases, in start-ups or warm-ups, when the anti-pollution systems do not reach their optimal performances.

Moreover, special additives are apt to improve engine performances or to cleaning operations of the same engine during its functioning.

A further possibility is the use of micro-injectors in the conditioning/heating system, according to

the same arrangement used in the suction duct for adding fungicides, anti-bacteria or also only perfumed substances.

According to a further embodiment, the additive tank may be in the form of a removable cartridge associated to the micro-injector and to a proper connector for communicating to the electronic unit.

Thus, the cartridge can be rapidly replaced, instead of filling the tank.