DESCRIPTION

Field of application of the invention

The present invention relates to a filter for purifying the fuel gas of a vehicle.

Background art

Unfortunately, LPG (liquid propane gas) available as fuel for the engines of vehicles is very polluted presumably due to the rough process for distilling the petroleum required for the production thereof.

The pollutants present (mainly hydrocarbons having a high molecular weight and unsaturated hydrocarbons) are deposited in the pressure reducer of the vehicle LPG system and prevent the proper operation thereof. Moreover, the share that "escapes" the pressure reducer is deposited in the injectors of the engine, thus altering the dynamics thereof and making the whole system highly inefficient and making cleaning inescapable (often also replacing components).

The filters currently available on the market provide very limited protection that require replacement also within very contained mileage (1,000 to 5,000 km).

Therefore, the problem is generated of avoiding the breakdowns of car gas systems due to the gas impurities as a result of motor propulsion by introducing an optimal filter device.

A further problem is of increasing the life of the filter to the greatest extent possible, in terms also of the effectiveness and performance thereof.

Summary of the invention

The object of the present invention is a filter for purifying the fuel gas of a vehicle that aims to overcome all the aforesaid drawbacks.

The idea at the basis of the present invention therefore comes from the above-described needs and consists in proposing an "effective" filter which allows significantly reducing the maintenance required to keep efficient a common LPG system for motor propulsion for mileage in the range of 30,000 to 40,000 km.

A particular object of the present invention is a filter for purifying the fuel gas of a vehicle, a vehicle that comprises said filter, and a process for purifying the fuel gas of a vehicle, as better described in the claims, which form an integral part of the present description.

Brief description of the drawings

- l - The present invention is now described below in reference to two example embodiments hereinafter called Filter 1 and Filter 2 (and variants thereof), and in reference to the accompanying drawings, given by mere way of a non-limiting example, in which:

figure 1 shows a side section of Filter 1 the object of the invention, in which the components thereof are noted;

figure 2 shows in detail an internal section of Filter 1;

figure 3 shows in detail an external view of Filter 1 and the relative couplings;

figure 4 shows an external view, respectively upper, side and perspective view, of Filter 2; figure 5 shows in detail an internal section S-S of Filter 2;

figure 6 shows a block diagram of a part of the LPG fuel system of a vehicle in which Filter 2 is inserted.

The same numbers and reference letters in the drawings identify the same elements or components.

Detailed description of example embodiments

Filter 1, an object of the invention, is adapted to be interposed between the nozzle for supplying gas to the distribution system and the inlet mouth of the gas into the tank of the vehicle.

Filter 2, another object of the invention, is adapted to be inserted in line, i.e. in a LPG fuel system of a vehicle.

The filter object of the invention is based on the use as filtering element of a so-called "molecular sieve" material.

"Molecular sieves" are materials capable of separating molecules according to the sizes of the molecules. This ability is based on the presence in the material of minuscule pores of exact and uniform size, with a diameter comprised in particular between 3A and 10 A, according to the material.

Molecular sieves have a very large surface area inside the pores (600-700 m2/g). Molecules with larger pore sizes may not enter the material, while instead molecules with small enough sizes to penetrate the pores enter the material; in general, dipolar molecules are absorbed on the inner surface of the pores and remain trapped, while apolar molecules are not withheld. The filter object of the invention comprises a body 1 made of metal material, preferably steel. A material based on the so-called "molecular sieve" is placed inside of the body as filtering element 2, said material being preferably obtained by forming a desiccant charge made of 80% of 5 A molecular sieves and 20% of activated alumina, agglomerated with a suitable binder.

The filtering element allows the 'trapping' of the water, the hydrocarbons with high molecular weight and the unsaturated hydrocarbons responsible for the pollution of the gas and in the final analysis, for the malfunctioning of the whole vehicle combustion system. The operating principle of the filtering element lies in the filtering ability of the 5 A pores of the molecular sieve which allow the passage of the propane that has a molecular diameter of 4.9 A, while they prevent the passage by the propene that has a diameter of 5.1 A.

The molecular sieve of the present invention is of a different type from the ones used industrially, which require filter units in parallel with demanding counter rinsing. In this context, an innovative use is proposed both in the type and the method marked by the simplicity and efficiency of the technology proposed.

The filter object of the invention ensures the cleaning/efficiency of the vehicle system for mileage of at least 30,000 to 40,000 km. Its strength is the use of innovative materials which through mechanical/chemical filtration, allow the elimination of the pollutants from the gas. There is preferably present a spring element 5 in order to withhold the filtering element 2 stationary inside the filter.

Filter 1 (figures 1, 2, 3) has on one side of the body 1, a first coupling 3 to which a connector 6 is connected which allows the connection of the terminal of the supply system, while on the opposite side of the body 1, there is connected a second coupling 4 shaped so as to be connected to the external mouth of the tank of the vehicle.

The body therefore has, at the opposite sides, shapes which are equal to the ones of the normal connector used for supplying gas, thus replacing it.

The first (3) and the second (4) coupling have threads (7) suitable for allowing the respective connections.

The body (1) is preferably of closed, welded type.

Filter 1 allows also a self-cleaning effect: when the supply terminal is detached, there is a spontaneous backwashing due to the depressurization and flow in opposite direction; this generates a desorption of the dipolar molecules, thus cleaning at least partially the molecular sieves.

When the supply terminal is detached, a portion of gas in the conduit connecting the mouth to the tank goes back at high pressure, with subsequent backwashing of the filter: the gas that comes back is clean because it is filtered, therefore it in fact serves as rinsing and therefore also increases the useful life of the filter, thus ensuring effectiveness of up to 40,000 of mileage.

Filter 2 (figures 4, 5) has a similar internal shape as the one of the filter 1 and has external couplings 10 on the opposite sides which are suitable for connecting in series to the LPG supply system of the vehicle. In one example embodiment (figure 6), the filter 2 (1) is placed in series in the gas fuel conduit 61 of the vehicle, between the LPG tank 62 and the expansion vessel 63, which in turn is connected to the injectors 64. There preferably are valves 65 that allow the exclusion of the filter for all needs, for example repairs, cleaning, replacement etc. Other connection methods to the supply system are possible, according to possible particularities of said vehicle systems.

Since filter 2 is connected directly in line with the system, it does not have the possibility of self-cleaning, but since it has more generous sizes (the volume typical of the filter 1 is of about 80 ml, while the volume typical of the filter 2 is about 500 ml), it all the same ensures at least 30 to 40 thousand kilometres of autonomy prior to the normal inspection and fine- tuning procedure.

The filter object of the invention withholds moisture, sulphurous products and unsaturated compounds also having low molecular weight but in particular it withholds the moisture which reaches the expansion vessel, becomes acidic and since it is at high temperatures together with a portion of unsaturated hydrocarbons (butane, isobutene, propene), is capable of acting as acid polymerisation catalyst. Even though a not significant quantity of polymers is formed, they are capable of obstructing the LPG systems of the vehicles. Moreover, such polymers incorporate also the sulphurous residues that give off the classic smell of incrustations.

By partially eliminating the hydrocarbons with double bonds and totally eliminating the tar, the filter allows decreasing the emission of aromatic hydrocarbons (e.g. benzopyrene) at the car exhaust, which are one of the indicators of air pollution and carcinogens.

Moreover, there is a significant ecological effect: by avoiding the combustion of the tar or oily slime, the emission at the exhaust is much cleaner.

The presence of the filter does not slow down or hinder the dispensing of the gas or its regular flow in the vehicle fuel system because the useful gas having smaller molecular size than the one of the holes of the molecular sieve passes through the filter without slowing down. The same above-mentioned considerations and advantages are obtained also in the case of use of methane gas in addition to LPG. The filter which may be used is the same one, changing only if required the shape of the adapters at the two opposite sides according to the shape used in the dispensing of methane, and of the vehicle supply system.

Variants are possible to the non-limiting examples described above, without however departing from the scope of protection of the present invention.

The elements and the features illustrated in the various preferred embodiments may be combined with one another without however departing from the scope of protection of the present invention.

Those skilled in the art are capable of making the object of the invention from the above- indicated description without introducing further construction details.