"Method for controlling the supply of oil to an

internal combustion engine"

The present invention relates to a method for controlling the supply of oil to an internal combustion engine, in particular for detecting clogging of the oil filter upstream of the engine or the degree of "fuel contamination" in the lubricant oil.

This method is applicable to a system for supplying oil to an internal combustion engine, for example in a motor vehicle.

These days, motor vehicles normally have a programme of scheduled maintenance according to the number of kilometres travelled or years of service. One of the scheduled operations is the replacement of the oil filter. Indeed, due to the functioning of the engine this tends to become clogged owing to metal residues resulting from the wear of pistons, piston rings, bearings, etc.

Said operation is scheduled on the basis of general statistical data which suggest when to replace the filter. However, these data do not take account of the specifics of the vehicle in question, which may require that said operation be brought forward to prevent serious damage to the engine or, conversely, may allow the operation to be postponed, for example if the vehicle is not used very often.

Another reason for wear of the engine may be related to high amounts of fuel in the oil, as this affects the lubricant properties of the oil. The presence of excessive amounts of fuel in the oil is particularly evident in common rail injection diesel engines. Indeed, with such engines, to regenerate the diesel particulate filter, even in some operating conditions in which the engine temperature is relatively moderate, diesel is introduced towards the end of the combustion cycle: the purpose of this is to avoid complete combustion in the cylinder, but to heat the exhaust gases with post-combustion so that these gases in turn regenerate the diesel particulate filter. Some of this excess fuel unfortunately flows into the oil passing through the piston rings of the piston (blow by) .

It is therefore very important to be warned if there is too much fuel in the lubricant oil.

In this regard, the technical problem to be solved by the present invention is that of proposing a method for controlling the supply of oil to an internal combustion engine that overcomes the disadvantages of the prior art described above.

The solution to the technical problem discussed and the specific aims are substantially achieved by a method for controlling the supply of oil to an internal combustion engine comprising the technical features claimed in one or more of the attached claims.

Further features and advantages of the present invention will become clearer from the description, which is provided by way of indication, and is therefore not limiting, of a preferred but not exclusive embodiment of a control method, as illustrated in the schematic view of figure 1.

The subject matter of the present invention is a method for controlling the supply of oil to an internal combustion engine. Said method comprises a procedure for detecting a potentially dangerous condition for the correct operation of an internal combustion engine 1. Said potentially dangerous condition for the correct operation of the engine 1 is the clogging of the oil filter 3 upstream of the engine 1 or the excessive presence of fuel in the lubricant oil. Both of these conditions have a negative effect in terms of wear on the engine. Clogging of the filter may cause drops in pressure that can compromise proper lubrication or a by-pass of said filter, while an excessive amount of fuel in the oil can reduce the lubricating capacity thereof (as mentioned above) .

The procedure for detecting a potentially dangerous condition for the correct operation of the engine comprises the step of changing (at least by a pre- established value) the flow rate of oil that transits through a filter 3 and that is processed by a pump 2 for supplying oil to the engine. Preferably, the flow rate is changed by at least 20%. Said pump 2 takes oil from a tank (oil sump 6) to which it is subsequently returned (after passing through the engine 1) . The filter 3 is placed upstream of the engine 1. Advantageously, it is positioned between the pump 2 and the engine 1. In particular, the step of changing the flow rate of oil envisages increasing or decreasing said flow rate. The change in flow rate must be sudden. For example, said change must take place within a few tenths of a second, for example around 0.2 seconds.

The step of changing the flow rate of oil by means of the pump 2 may be performed by causing a change in the capacity of the pump. In such a case, the pump 2 will have a variable capacity, for example a pump with an impeller moving inside a stator. To change the capacity of the pump it is in this case possible to move the stator and the rotation shaft of the rotor relative to one another.

Additionally or alternatively, the step of changing the flow rate of oil by means of the pump 2 envisages varying the number of revolutions of the pump 2 (for example in the case of an electric pump) .

The abovementioned detection procedure also comprises the step of detecting the time that passes between changing the oil flow rate and a detection of a pre- established variation in a parameter connected at least with the pressure downstream of said filter 3. Advantageously, this takes place at a predetermined frequency (for example at first start-up, when the vehicle is new or after the filter is replaced) ; moreover, it is performed with temperatures within a predetermined range (to ensure that the surrounding conditions are as similar as possible each time a detection is performed; this is because the hotter the oil, the more fluid it is) ; in this regard, an oil temperature sensor may be used (placed for example upstream of the engine 1) .

The parameter connected with the pressure downstream of the filter 3 referred to above may be, for example:

- a pressure value supplied by a sensor 9 placed downstream of the filter; or

- a difference in pressure between downstream and upstream of the filter 3 (in which case, in addition to the sensor 9, use is made of an additional sensor 90 placed upstream of the filter 3) .

The variation in this parameter is a direct consequence of the change in the flow rate. If the flow rate of the pump 2 is changed, then the pressure varies downstream of the pump 2.

The pressure is typically measured in the main gallery of the system for conveying oil to the engine 1. Use is usually made of the pressure sensor 9 which is already provided in standard solutions. When the difference in pressure between downstream and upstream of the filter 3 is to be measured, the additional sensor 90, placed for example at the outlet of the pump 2, may be provided .

The abovementioned detection procedure also comprises the step of comparing with pre-established values the time that passes between changing the oil flow rate and a detection of the pre-established variation of the abovementioned parameter connected with pressure.

To be specific, if this time is above a pre-established threshold it means that the filter 3 should be replaced since it has a capping effect on the wave generated by the change in flow rate.

Moreover, information relating to the presence of fuel in the oil is also detected: the more fuel present in the oil, the more fluid the oil will be, therefore, the variation in flow rate will be acknowledged more quickly. The level of contamination of the oil by fuel may be identified in that for example it will be proportional to the delta pressure before and after the filter (which will change owing to the difference in fluidity of the oil) . The level of contamination will be greater when driving in the urban cycle than when driving in the extra-urban cycle. When driving in demanding cycles, uphill or at high temperature, the temperatures promote evaporation, preventing the build ^¬ up of carbonaceous residues, which are abrasive. This is especially important in view of the fact that the accumulation of fuel in the oil (vehicle operating mainly in urban cycle) can reach values such that evaporation becomes impossible. All of this continuously degrades the oil with a consequent loss of lubricant power, with an increase in consumption and carbon dioxide emissions, as well as environmental pollution owing to early oil changes which, if not carried out, will lead to extreme wear on the engine.

If, during the step of comparing said time with pre- established values, a fault is reported, it is transmitted :

- to an internal instrument inside the passenger compartment of a vehicle driven by the engine 1 ; or

- to a remote memory space to which access is possible via internet (for example the cloud) .

More generally, information related to the time that passes between the variation in the flow rate and detection of the variation in pressure may be transmitted to an instrument inside the passenger compartment or to a remote memory space (hence, said information may be sent in any case, not just in the event of a fault) .

Advantageously, the method further comprises a step of activating a reduction cycle of the level of fuel contamination in the oil (this would make it possible to evaporate the fuel which has flowed into the oil sump 6 even in mainly urban driving conditions) . For the reasons given above, this condition may be seen as an undesirable consequence of the need to regenerate a diesel particulate filter placed downstream of the engine 1; this will however be counteracted. In this regard, the reduction cycle of the level of fuel contamination in the oil comprises the step of heating the oil, which brings about the evaporation of the fuel present in the oil.

For example, the step of heating the oil brings about the heating of the fluid present in an oil sump 6 from which the oil is taken by means of the pump 2 and to which it is returned after passing through the engine 1. In this case, the evaporation of the fluid present in the oil sump 6 causes the evaporated fuel to be conveyed into a combustion chamber 10 of the engine through an oil separator 7 and a fuel suction system 8. The oil separator 7 is in communication with the sump 8 and separates the evaporated fuel (which flows in the fuel suction system 8) from particles of oil present in the evaporated fluid which return to the sump 6.

Heating of the oil may be achieved in a number of ways. For example, the step of heating the oil may comprise the step of making the pump 2 operate in a mode in which it assumes a higher maximum capacity than the maximum capacity envisaged in the mapping of operation. In other words, in a first operating mode, the pump 2 has a mapping that envisages a first value for the maximum capacity; the step of heating the oil comprises the step of making the pump 2 operate in a second operating mode in which it assumes a higher maximum capacity than the maximum capacity envisaged in the first operating mode.

The step of heating the oil may comprise a step of opening a conduit connecting downstream and upstream of the pump 2 so that a part of the oil flow by-passes the engine 1. Therefore, an excess flow rate of the pump (the latter being preferably blocked at maximum capacity) flows in said conduit, not all to prevent engine operating problems. In this way, the oil circulating heats up.

The step of heating the oil may optionally envisage:

- raising, temporarily, a thermal threshold at which a heat exchanger for heating the oil is activated; or

- changing, temporarily, the thermoregulation system of the engine (calibrating it not at 90°-100°C but at 120°-150°C) .

The method further comprises a procedure for tracking the successful change of an oil filter.

The tracking procedure comprises the steps of:

- periodically detecting through a sensor 9 the pressure downstream of the filter 3;

- retroactively adjusting at least, a first operating parameter of the pump 2 maintaining it on values that allow the pressure detected by the sensor 9 to be maintained within a prefixed range regardless of the degree of clogging of the filter (for example, this first operating parameter may be the rotation speed of the pump 2);

- monitoring the trend over time of the values of said at least one first parameter that allow the pressure detected by the sensor 9 to be maintained within a prefixed range regardless of the degree of clogging of the filter; this makes it possible to identify a variation of said values that is greater than a pre-established threshold in a range of time lower than a pre-established limit (to be specific, the replacement of a clogged filter with a new one causes a sharp reduction in pressure drops and hence the need to recalibrate the pump to keep the same level of pressure detected by the sensor 9) ;

- recording in memory means 4 associated with a control unit 5 the successful replacement of the filter 3 upon the detection of said variation (as mentioned above, said sharp variation indicates that there has been a variation in pressure drops and therefore it is deduced that the filter 3 has been replaced) .

This provides, if necessary, evidence that the oil filter was replaced regardless of what has been recorded in the paper documents issued by the garage following maintenance. It is thus possible to prevent failure to replace the oil filter, whether this be owing to it being forgotten in good faith or owing to fraudulent reasons.

The present invention provides significant advantages. First, it reduces costs and simplifies the method for identifying clogging of the oil filter and/or identifying the level of contamination of fuel in the oil. This is based on the use of mechanical pumps of variable capacity (MOP-VD) or electric pumps. Moreover, the need to replace the filter can be assessed on the basis of whether or not it is actually clogged and not with reference to statistical parameters, which are normally very conservative (thus, clearly, saving on running costs) .

The invention thus devised may be subject to a number of changes and variations, all of which come within the scope of the inventive concept which characterizes the invention. Moreover, all the details may be replaced by other technically equivalent elements. In practice, all the materials used, as well as the dimensions, may be whatever is required in each case.