Method for controlling a high pressure fuel pump for a direct injection system

Abstract

To provide a method for controlling a fuel pump for a direct injection system having a common rail.SOLUTION: This invention comprises: a step of determining a minimum threshold (QMIN) based on a pressure (PRAIL) in a common rail (3), a speed (n) of a heat engine (1), a temperature (TPUMP) of a high pressure pump (4) and an inlet pressure (PLOW) of the high pressure pump (4); a step of calculating a target fuel flow rate (Mref) instantaneously supplied to the common rail (3) by the high pressure pump (4), to obtain a desired pressure (PTARGET) in the common rail (3); and a step of comparing the target fuel flow rate (Mref) with the minimum threshold (QMIN, QTEMP); and a step of controlling the high pressure pump (4) based on the comparison between the target fuel flow rate (Mref) and the minimum threshold (QMIN, QTEMP).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This patent application claims priority from Italian Patent Application No. 102019000012300, filed on July 18, 2019, the disclosure of which is incorporated herein by reference in its entirety.

[0002] The present invention relates to a method for controlling a fuel pump for a direct injection system. Preferably, but not necessarily, the control method is used for a direct injection system in a spark ignition internal combustion engine operating with gasoline or a similar fuel. [Background technology]

[0003] As is known, a fuel - in this particular case gasoline - direct injection system is of the common rail type for an internal combustion engine and comprises a number of injectors, a common rail supplying pressurized fuel to the injectors, a high-pressure pump supplying fuel to the common rail and equipped with a flow regulator, a control unit for equalizing the fuel pressure inside the common rail to a desired value which varies over time depending on the operating conditions of the internal combustion engine, and a low-pressure pump supplying fuel from a tank by a supply duct to the high-pressure pump.

[0004] The control unit is coupled to the flow regulating device to control the flow rate of the high pressure pump so that the common rail is instantaneously supplied with the amount of fuel required to have a desired pressure in the common rail, and in particular the control unit adjusts the flow rate of the high pressure pump by feedback control using the value of the fuel pressure in the common rail as a feedback variable.

[0005] The operating cycle of the high-pressure pump substantially comprises three stages: an intake stage, which allows the passage of fuel into the pumping chamber of the high-pressure pump; a return stage, which allows the passage of fuel out of the pumping chamber towards the low-pressure circuit while the respective intake valve is kept open; and a pumping stage, which allows the fuel pressure in the pumping chamber to reach a value such as to cause a flow of fuel out of the pumping chamber towards the common rail while the respective intake valve is closed.

[0006] Experiments have shown that during the pumping phase there is a noticeable increase in the temperature of the high-pressure pump. In particular, with a pressure increase of 20-60 MPa, the temperature change at several points of the high-pressure pump is in the range of 30-50 °C, while with a pressure increase of 60-80 MPa the temperature change assumes much more significant values ​​in the range of 80 °C. Temperature changes in the range of 30-50 °C can already lead to cavitation problems. This makes the high-pressure pump unstable and almost unreliable. That is, it is no longer possible to be sure that the common rail is instantly supplied with the amount of fuel required to reach the desired pressure inside the common rail.

[0007] This phenomenon has been proven to be exacerbated when the high pressure pump is not operated at full load, i.e. when the desired pressure inside the common rail and the amount of fuel required to be delivered by the high pressure pump is lower than the maximum flow rate that can be delivered by the high pressure pump. When the high pressure pump is operated at full load (i.e. when the desired pressure inside the common rail and the amount of fuel required to be delivered by the high pressure pump is equal to the maximum flow rate that can be delivered by the high pressure pump), the heat generated during the pumping phase is removed through the fuel flow rate leaving the high pressure pump, and the removal of the heat generated during the pumping phase is proportional to the fuel flow rate of the high pressure pump.

[0008] Furthermore, it is characterised in that the high-pressure pump does not operate at full load, but at partial load, operation of the high-pressure pump has negative effects, particularly in terms of energy efficiency, and potential damage risks.

[0009] In particular, the energy used during the compression phase (and the resulting heat generated) is proportional to the mass of fuel captured by the respective intake valve (taking into account both the regulated fuel flow rate and the dead volume), whereas the heat removed is proportional to the only flow rate delivered (since the dead volume does not flow out of the high pressure pump and obviously the heat cannot be dissipated). As a result, the smaller the delivered flow rate, the greater the thermal overload. The useful energy transferred to the fuel by the system is also proportional to the only flow rate delivered.

[0010] On the other hand, as far as the potential damage risk of the high pressure pump is concerned, closing the intake valve away from the top dead center and away from the bottom dead center of the high pressure pump, i.e. when the speed of the pump piston is non-zero and the internal combustion engine operates at high speed, will lead to a rapid and significant pressure rise, which will result in mechanical vibrations with potential damage risks.

[0011] In order to avoid the occurrence of cavitation phenomena or damage to the high-pressure pump, several solutions have been suggested over the years, which are aimed in particular at limiting the temperature rise of the high-pressure pump during the pumping phase.

[0012] For example, to solve the cavitation problem, it is possible to increase the pressure of the fuel entering the high-pressure pump, but this solution also suffers from negative effects in terms of energy efficiency. Alternatively, the high-pressure pump can be equipped with a fuel recirculation circuit, which provides a drainage duct that transfers a portion of the fuel from the pump chamber to the tank, so that the heat generated during the pumping phase is dissipated through the flow of fuel leaving the high-pressure pump. However, this technical solution has significant drawbacks in terms of the overall dimensions of the injection system and is also disadvantageous from an economic point of view. Summary of the Invention [Problem to be solved by the invention]

[0013] It is therefore an object of the present invention to provide a method for controlling a fuel pump for a direct injection system which does not suffer from the above-mentioned drawbacks and which is in particular easy and economical to implement. [Means for solving the problem]

[0014] According to the present invention there is provided a method for controlling a fuel pump for a direct injection system according to the appended claims. [Brief description of the drawings]

[0015] The invention will now be described with reference to the accompanying drawings, which show non-limiting embodiments thereof. [Figure 1] FIG. 1 is a schematic diagram of a direct fuel injection system with some details removed for greater clarity. [Diagram 2] FIG. 2 is a block diagram showing a first variant of the operating logic of the method according to the invention. [Diagram 3] FIG. 3 is a block diagram showing a second variant of the operating logic of the method according to the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] In FIG. 1, the number 1 indicates as a whole a common rail fuel, in particular gasoline, direct fuel injection system for an internal combustion heat engine.

[0017] The direct injection system 1 comprises a number of injectors 2, a common rail 3 supplying fuel under pressure to the injectors 2, a high-pressure pump 4 supplying fuel to the common rail 3 through a feed duct 5 and equipped with a flow regulator 6, an electronic control unit 7 for equalizing the fuel pressure inside the common rail 3 to a desired value, and a low-pressure pump 8 for equalizing the desired value, which generally varies over time depending on the operating conditions of the internal combustion engine, and for supplying fuel from a tank 9 to the high-pressure pump 4 through a feed duct 10.

[0018] The electronic control unit 7 is connected to the flow regulator 6 to control the flow rate of the high pressure pump 4 in order to instantaneously supply the amount of fuel required to have a desired pressure in the common rail 3 to the common rail 3. Furthermore, the electronic control unit 7 controls the fuel pressure P RAIL The pressure sensor 11 detects the pressure in real time.

[0019] In the following, the method implemented by the electronic control unit 7 for controlling the high pressure pump 4 will be described.

[0020] This method involves determining, according to FIG. 2, a minimum threshold Q of fuel to be pumped per working cycle of the high-pressure pump 4. MIN This involves determining:

[0021] Minimum Threshold Q MIN is basically the pressure P in the common rail 3 detected by the pressure sensor 11. RAIL , the temperature T of the high pressure pump 4 PUMP , the inlet pressure P of the high pressure pump 4 LOW , the speed n of the heat engine 1, and the internal combustion engine load C.

[0022] Temperature T of high pressure pump 4 PUMP High pressure pump 4 (T PUMP-SENSOR ) can be detected by a dedicated temperature sensor housed in the PUMP-VIRTUAL ) can also be estimated.

[0023] More specifically, the electronic control unit 7 stores map low temperature data, which is a minimum threshold Q MIN (Open-loop) contribution factor Q to determine MIN-COLD Contribution factor Q MIN-COLD is the pressure P in the common rail 3 under low temperature conditions, i.e. RAIL and represents the minimum threshold of the pumped fluid under conditions far removed from the occurrence of the cavitation phenomenon for a given value of the speed n of the heat engine 1. In fact, the map low temperature data has as input the pressure P RAILand the speed n of heat engine 1, and based on the input values, the contribution factor Q MIN-COLD to provide.

[0024] Similarly, the electronic control unit also stores map high temperature data, which is MIN (Open-loop) contribution factor Q to determine MIN-HOT Contribution factor Q MIN-HOT is the pressure P RAIL and represents the minimum threshold of the pumped fluid under conditions close to the occurrence of the cavitation phenomenon for a given value of the speed n of the heat engine 1.

[0025] Finally, the electronic control unit 7 stores map vapor pressure data, which provides a coefficient K (expressed as a percentage), which is in turn related to the minimum threshold Q MIN The map vapor pressure data is also used to determine the inlet pressure P of the high pressure pump 4 as an input. LOW (known as "low pressure") and the temperature T of the high pressure pump 4 PUMP The latter receives the temperature (T PUMP-VIRTUAL ) or the temperature estimated by the estimation model (T PUMP-VIRTUAL The map vapor pressure data is expressed as the temperature T PUMP The curve of the fuel vapor pressure as a function of the temperature T of the high-pressure pump 4 is included. PUMP and the inlet pressure P of the high pressure pump 4 LOW Based on the map vapor pressure data, a coefficient K is provided which represents (in percentage) how far or how close the high pressure pump 4 is to the condition for the occurrence of the cavitation phenomenon.

[0026] Therefore, the minimum threshold Q MIN is calculated as follows:

[0027]

number

[0028] Q MIN Minimum threshold, K factor, Q MIN-COLD A minimum threshold "low temperature" contribution factor; Q MIN-HOT Minimum threshold "high temperature" contributor.

[0029] For example, it is clear that a value of coefficient K equal to 1 provided by the map vapor pressure data indicates that the high-pressure pump 4 is operating under conditions close to the occurrence of the cavitation phenomenon, whereas a value of coefficient K equal to 0 or 0.2 provided by the map vapor pressure data indicates that the high-pressure pump 4 is operating under conditions very far from the occurrence of the cavitation phenomenon.

[0030] Furthermore, the minimum threshold Q MIN To determine the contribution factor Q MIN-COLD Provides a map of low temperature data and contributing factors Q MIN-HOT It is noted that the maps providing high temperature data both contain contributions to increase energy efficiency and to reduce potential damage risks.

[0031] In other words, the contribution factor Q MIN-COLD and Q MIN-HOT are both determined so as to suppress temperature fluctuations in the high-pressure pump 4, while at the same time increasing energy efficiency and reducing the risk of potential damage.

[0032] According to a preferred embodiment, the method comprises determining an energy index I giving an indication of the susceptibility - or lack thereof - of the occurrence of cavitation phenomena of the high-pressure pump 4. The energy index I is preferably determined by the pressure P of the common rail 3 detected in real time by the pressure sensor 11. RAIL This disturbance is based on the strength of the disturbance in the signal with respect to time t 1 and 2 The time window is evaluated by the integers between

[0033] According to the first variant, the energy indicator I 1 is expressed as follows:

[0034]

number

[0035] According to the second variant, the energy indicator I 2 is expressed as follows:

[0036]

number

[0037] According to the third variant, the energy indicator I 3 is expressed as follows:

[0038]

number

[0039] t 1 , t 2 A time that defines the observation time window, P RAIL Actual pressure of common rail 3, P TARGET Target pressure in common rail 3, P RAIL-M Common rail 3 and actual average pressure in the observation window, INT The value of the integral component of the pressure control closed loop. INT M The average value of the integral component of the closed loop pressure control within the observation window.

[0040] Index I 1 and I 2 is the target fuel flow rate M ref is explicitly calculated when supplied under "normal" operating conditions (without deactivation) (as detailed below).

[0041] The energy index I is used inside the electronic control unit 7 to obtain adaptive functions aimed at optimizing the method, so that it can be adapted to high-pressure pumps 4 with different production variations.

[0042] In particular, the adaptation function involves storing threshold values ​​internal to the electronic control unit 7. The threshold values ​​preferably depend on the load (i.e. the injected fuel quantity Q F-INJ ) The threshold value is preferably also variable based on the speed n of the heat engine. Furthermore, the threshold value is also variable based on the amount Q F-INJ and the actual fuel flow rate of the high pressure pump 4.

[0043] The threshold value is preferably determined during an experimental setup phase. TARGET The threshold is continuously compared to the energy index I under resting conditions.

[0044] The threshold value is determined such that when the energy indicator I exceeds the threshold value, this indicates that the high-pressure pump 4 is operating under conditions close to (prone to) the occurrence of the cavitation phenomenon. Therefore, when the electronic control unit 7 detects that the energy indicator I has exceeded the threshold value, it sets the minimum threshold value Q MIN The quantity ΔQ MIN The target pressure P TARGET The amount of ΔP TARGET The design is such that the load is reduced by a factor of 100 and is designed for a given time.

[0045] According to a preferred variant, the quantity ΔP TARGET is at least 1MPa (ΔP TARGET is equal to (independent of the difference between the energy index I and the respective threshold). If the energy index I remains greater than the respective threshold, the quantity ΔP TARGET increases to 2MPa. As long as the energy index I does not return to a value smaller than the respective threshold, the quantity ΔP TARGET increases by 1 MPa.

[0046] Therefore, the minimum threshold QMIN is calculated as follows:

[0047]

number

[0048] Q MIN Minimum threshold, K factor, Q MIN-COLD A minimum threshold "low temperature" contribution factor; Q MIN-HOT A minimum threshold "high temperature" contributor; ΔQ MIN amount.

[0049] Preferably, the amount ΔQ MIN is variable and is at least 20 mg (quantity ΔQ MIN is equal to (independent of the difference between the energy index I and the respective threshold). If the energy index I remains greater than the respective threshold, the quantity ΔQ MIN The amount is increased to 40 mg. As long as the energy index I does not reach a value smaller than the respective threshold, the amount ΔQ MIN increases by 20 mg.

[0050] First, the minimum threshold Q MIN Once calculated, the method determines the minimum threshold value Q so as to increase energy efficiency and reduce potential damage risks, including temperature fluctuations generated during the pumping phase in the high pressure pump 4. MIN This involves controlling the high pressure pump 4 based on the

[0051] According to a further variant, shown in FIG. 3, the method further comprises the steps of: TEMP This involves calculating

[0052] More specifically, inside the electronic control unit 7, there is a contribution element Q TEMP To determine the (open loop) contribution factor Q MIN-COLD A map of low temperature data is stored that provides the contribution factor QMIN-COLD is the pressure P in the common rail 3 under low temperature conditions, i.e. RAIL and represents the minimum threshold of the pumped fluid under conditions far from the occurrence of the cavitation phenomenon for a given value of the speed n of the heat engine 1. In fact, the map low temperature data is taken as input the pressure P RAIL and the speed n of heat engine 1, and based on the input values, the contribution factor Q MIN-COLD to provide.

[0053] Similarly, further map high temperature data is stored in the electronic control unit, which is the contribution factor Q TEMP (Open-loop) contribution factor Q to determine MIN-HOT Contribution factor Q MIN-HOT is the pressure P of the common rail 3 under high temperature conditions, i.e. RAIL and represents the minimum threshold for the fluid to be pumped under conditions close to the onset of the cavitation phenomenon for a given value of the speed n of the heat engine 1.

[0054] Finally, stored within the electronic control unit 7 is map vapor pressure data, which provides a coefficient K (expressed as a percentage) and a contribution Q TEMP The map vapor pressure data is also used to determine the inlet pressure P of the high pressure pump 4 as an input. LOW (known as "low pressure") and the temperature T of the high pressure pump 4 PUMP The latter receives the temperature (T PUMP-SENSOR ) or the temperature estimated by the estimation model (T PUMP-VIRTUAL The map vapor pressure data is expressed as the temperature T PUMP The curve of the fuel vapor pressure as a function of the temperature T of the high-pressure pump 4 is included. PUMP and the inlet pressure P of the high pressure pump 4 LOW Based on the map vapor pressure data, a coefficient K is provided which represents (in percentage) how far or how close the high pressure pump 4 is to the condition for the occurrence of the cavitation phenomenon.

[0055] Therefore, the contribution factor Q TEMP is calculated as follows:

[0056]

number

[0057] Q TEMP A contributing factor for suppressing temperature fluctuations occurring during the pumping phase in the high-pressure pump 4; K factor, Q MIN-COLD Minimum threshold "bass" contribution, Q MIN-HOT Minimum threshold "high temperature" contributor.

[0058] In addition, the contribution factor Q TEMP is calculated as follows:

[0059]

number

[0060] Q TEMP a contribution to reducing temperature fluctuations occurring during the pumping phase in the high-pressure pump 4; K factor, Q MIN-COLD A minimum threshold "low temperature" contribution factor; Q MIN-HOT A minimum threshold "treble" contribution, ΔQ MIN amount.

[0061] Here, the quantity ΔQ MIN has the above meaning, is variable and is at least 20 mg (quantity ΔQ MIN is equal to (independent of the difference between the energy index I and the respective threshold). If the energy index I remains greater than the respective threshold, the quantity ΔQ MIN increases to 40 mg. As long as the energy index I does not reach a value smaller than the respective threshold, the amount ΔQ MIN increases by 20 mg.

[0062] In addition, this method reduces the contribution factor Q EEff and an additional contributing factor Q to reduce the potential risk of damage DAM This includes calculating

[0063] More specifically, map data is stored inside the electronic control unit 7, and the map data is a minimum threshold Q MIN To determine the energy efficiency (open loop) contribution factor Q EEff Contribution factor Q EEff is the pressure P of the common rail 3 RAIL and the amount of fuel injected by injector 2, Q F-INJ In fact, the map data takes as input the pressure P in the common rail 3. RAIL and the amount of energy injected by injector 2, Q F-INJ and based on the input values, EEff to provide.

[0064] Contributing factor Q EEff is preferably determined on the basis of the driving mode DV selected by the driver of the vehicle equipped with the heat engine 1. Advantageously, the contribution factor Q EEff is determined (weighed) depending on the position of the hand lever which identifies the driving / operating mode DV to be selected by the driver among a number of possible driving / operating modes DV. For example, the possible driving / operating modes DV consist of a sports driving / operating mode DV (enhancing performance), a normal driving / operating mode DV, an eco driving / operating mode DV (enhancing reduction of consumption), etc. Each possible driving / operating mode DV corresponds to a load (determined in the presetting stage).

[0065] Furthermore, inside the electronic control unit 7, a minimum threshold Q MIN To determine the (open loop) contribution factor Q DAM The map data providing the contribution factor Q is stored. DAM is the pressure P in the common rail 3 RAILand represents the minimum amount of fluid to be pumped in order to reduce the risk of potential damage for a given value of the speed n of the heat engine 1. In fact, the map data takes as input the pressure P RAIL and the speed n of heat engine 1, and based on the input values, the contribution factor Q DAM to provide.

[0066] Finally, the minimum threshold Q MIN is calculated. Preferably, a minimum threshold Q MIN is the contribution factor Q to suppress the temperature fluctuations generated during the pumping stage in the high pressure pump 4 TEMP , the contribution factor Q for increasing energy efficiency EEff and the contribution factor Q to reducing the potential damage risk DAM Alternatively, the minimum threshold Q MIN is the temperature fluctuation occurring during the pumping stage in the high pressure pump 4, a contributing factor Q that increases the energy efficiency EEff and the contributing factor Q that reduces the potential damage risk DAM Contribution factor Q to include TEMP This corresponds to the weighed average of

[0067] The method thus determines a target fuel flow rate M supplied to the common rail 3 by the high-pressure pump 4 so as to have a desired pressure inside the common rail 3. ref It is necessary to calculate instantly.

[0068] Next, the electronic control unit 7 calculates the target fuel flow rate M ref The minimum threshold Q min It is designed to be compared with

[0069] Target fuel flow rate M ref is the minimum threshold Q min If it is greater than (or equal to) the target fuel flow rate M ref Conversely, the target fuel flow rate M ref is the minimum threshold Q minIf it is smaller than the target fuel flow rate M ref is the minimum threshold Q min If it is less, the high pressure pump 4 will not operate.

[0070] The control unit 7 adjusts the flow rate of the high-pressure pump 4 to a minimum threshold Q min Larger target fuel flow rate M ref In other words, the control unit 7 is designed to control the alternation of the operating cycles, in which the high-pressure pump 4 is operated at a minimum threshold value Q min Target fuel flow rate M ref and idle operating cycles.

[0071] The electronic control unit 7 therefore implements a feedback control using the desired pressure inside the common rail 3, preferably detected in real time by a pressure sensor 11, as a feedback variable, and the pressure instantaneously supplied to the common rail 3 by the high-pressure pump 4. the goal Fuel flow rate M ref and the minimum threshold Q calculated according to the above formula [1] or [5] MIN The high pressure pump 4 is controlled for each operation cycle by comparing the above.

[0072] The method implemented by the electronic control unit 7 for controlling the high pressure pump 4 and described so far has several advantages.

[0073] In particular, the method described above does not involve an excessive computational load for the electronic control unit 7 and at the same time allows the manufacturer to avoid the occurrence of cavitation phenomena, to avoid damage to the high-pressure pump 4, to limit temperature fluctuations occurring during the pumping phase in the high-pressure pump 4 and to maintain the set value of the fuel pressure in the common rail 3. The present invention has the following aspects (configurations). [Aspect 1] A method for controlling a fuel pump (4) for a direct injection system of a heat engine (1) having a common rail (3), comprising the steps of: The minimum threshold (Q MIN ,Q TEMP ) A desired pressure (P TARGET In order to obtain a target fuel flow rate (M ref ) and The target fuel flow rate (M ref ) and the minimum threshold (Q MIN ,Q TEMP ) The target fuel flow rate (M ref ) and the minimum threshold (Q MIN ,Q TEMP controlling the high pressure pump (4) based on a comparison with A method comprising: The minimum threshold (Q MIN ,Q TEMP The step of determining the number of vertices (V) comprises the following sub-steps: The pressure in the common rail (3) (P RAIL ) and the speed (n) of the heat engine (1), a first contribution (Q MIN-COLD ) and the second contributing factor (Q MIN-HOT ) by determining the first contribution (Q MIN-COLD ) is the pressure (P RAIL ) and the minimum threshold for the fluid to be pumped under low temperature conditions far from the occurrence of the cavitation phenomenon for a given value of the speed (n) of the heat engine (1), and the second contribution (Q MIN-HOT ) is the pressure (P RAIL ) and a minimum threshold value of the pumped fluid under high temperature conditions close to the onset of the cavitation phenomenon for a given value of the speed (n) of the heat engine (1); The temperature of the high pressure pump (4) (T PUMP ) and the inlet pressure (P LOW determining a coefficient (K) based on the coefficient (K) representing the proximity of the high-pressure pump (4) to a condition for the occurrence of a cavitation phenomenon; The first contributing element (Q MIN-COLD ), the second contributing factor (Q MIN-HOT ) and the minimum threshold (Q MIN ,Q TEMP ) 23. A method comprising: [Aspect 2] The pressure in the common rail (3) (P RAIL ) and the amount of injected fuel (Q F-INJ ) based on the third contribution factor (Q EEff ) In order to reduce the risk of damage to the high pressure pump (4), the pressure in the common rail (3) (P RAIL ) and a fourth contribution (Q DAM ) The third contributing factor (Q EEff ) and the fourth contributing factor (Q DAM ) based on the minimum threshold (Q MIN ) 2. The method of embodiment 1, further comprising: [Aspect 3] The third contributing factor (Q EEff 3. The method according to claim 2, wherein the driving mode (DV) is determined depending on a driving mode (DV) selected for a vehicle equipped with the heat engine (1), preferably depending on a position of a hand lever among a plurality of possible positions. [Aspect 4] The first contributing element (Q MIN-COLD ) and the second contribution (Q MIN-HOT ) and the coefficient (K), a fifth contribution (Q TEMP ) The fifth contributing factor (Q TEMP ), and the third contribution (Q EEff ), and the fourth contributing element (Q DAM ) based on a comparison with the minimum threshold (Q MIN ) 4. The method of embodiment 2 or 3, further comprising: [Aspect 5] The fifth contributing factor (Q TEMP ) is calculated as follows: JPEG0007612349000008.jpg17170 Where: Q TEMP Fifth contributing factor, K factor, Q MIN-COLD The first contributing element, Q MIN-HOT Second contributing factor 5. The method of embodiment 4, wherein [Aspect 6] The minimum threshold (QMIN ) is the fifth contributing factor (Q TEMP ), the third contributing element (Q EEff ) and the fourth contribution (Q DAM 6. The method according to claim 4 or 5, wherein the maximum value of [Aspect 7] The target fuel flow rate (M ref ) is the minimum threshold (Q MIN ,Q TEMP ) is greater than the target fuel flow rate (M ref controlling the high pressure pump (4) to supply The target fuel flow rate (M ref ) is the minimum threshold (Q MIN ,Q TEMP ), controlling the high pressure pump (4) so ​​as not to supply fuel when the difference is less than The method according to any one of aspects 1 to 6, comprising: [Aspect 8] The minimum threshold (Q MIN ,Q TEMP The step of determining (a) comprises the following sub-steps: A step of calculating an energy index (I), the energy index (I) being a function of a pressure (P RAIL indicating the approach to the occurrence of a cavitation phenomenon in said high-pressure pump (4) or the lack thereof, based on the intensity of disturbances of the signal on the time window, said disturbances being evaluated by integration within an observation time window; Based on the energy index (I), the minimum threshold (Q MIN ,Q TEMP ) and The method according to any one of aspects 1 to 7, comprising: [Aspect 9] The desired pressure (P TARGET ) into the first quantity (ΔP TARGET 9. The method of claim 8, wherein the energy index (I) is increased by a first time interval if the energy index (I) exceeds a first threshold. [Aspect 10] The first amount (ΔP TARGET 10. The method of claim 9, wherein the energy index (I) is at least equal to 1 MPa and is preferably independent of the difference between the energy index (I) and the first threshold value. [Aspect 11] When the energy index (I) exceeds a first threshold, a second amount (ΔQ MIN ) by the minimum threshold (Q MIN ,Q TEMP 11. The method according to any one of aspects 8 to 10, further comprising the step of increasing [Aspect 12] The second amount (ΔQ MIN 12. The method according to claim 11, wherein the energy index (I) is at least equal to 20 mg and is preferably independent of the difference between said energy index (I) and said first threshold value. [Aspect 13] The target fuel flow rate (M ref ) is supplied, the energy index (I 1 ) is calculated as follows: JPEG0007612349000009.jpg18167 Where: t 1 、t 2 A time that defines the observation time window, P RAIL Actual pressure of the common rail (3), P TARGET the target pressure in the common rail (3), The method according to any one of aspects 8 to 12, wherein [Aspect 14] The target fuel flow rate (M ref ) is supplied, the energy index (I 2 ) is calculated as follows: JPEG0007612349000010.jpg20168 Where: t 1 、t 2 A time that defines the observation time window, P RAIL Actual pressure of the common rail (3), P RAIL-M The actual average pressure in the common rail (3) and in the observation window, The method according to any one of aspects 8 to 12, wherein [Aspect 15] The energy index (I 3 ) is calculated as follows: JPEG0007612349000011.jpg19165 Where: t 1 、t 2 A time that defines the observation time window, INT The value of the integral component of the pressure control closed loop. INT M The average value of the integral component of the closed loop of the pressure control within the observation window, The method according to any one of aspects 8 to 12, wherein

Claims

1. A method for controlling a fuel pump (4) for a direct injection system of a heat engine (1) having a common rail (3), comprising the steps of: A minimum flow threshold (Q MIN ) A desired pressure (P TARGET In order to obtain a target fuel flow rate (M ref ) and The target fuel flow rate (M ref ) and the minimum flow rate threshold (Q MIN ) and The target fuel flow rate (M ref ) and the minimum flow rate threshold (Q MIN controlling the high pressure fuel pump (4) based on a comparison with A method comprising: The step of determining the minimum flow threshold (QMIN) comprises the following sub-steps: The pressure in the common rail (3) (P RAIL ) and the speed (n) of the heat engine (1), a first contribution (Q MIN-COLD ) and the second contributing element (Q MIN-HOT ), the sub-step of determining the first contribution (Q MIN-COLD ) is the pressure (P RAIL ) and the minimum flow rate threshold of the pumped fluid under low temperature conditions far from the occurrence of cavitation phenomena for a given value of the speed (n) of the heat engine (1), and the second contribution (Q MIN-HOT ) is the pressure (P RAIL ) and a minimum flow rate threshold of the fluid to be pumped under high temperature conditions close to the onset of the cavitation phenomenon for a given value of the speed (n) of the heat engine (1); The temperature of the high pressure fuel pump (4) (T PUMP ) and the inlet pressure (P LOW a sub-step of determining a coefficient (K) based on the coefficient (K) representing the proximity of the high pressure fuel pump (4) to a condition for the occurrence of a cavitation phenomenon; The first contribution (Q MIN-COLD ), the second contributing element (Q MIN-HOT ) and the coefficient (K) based on the minimum flow rate threshold (Q MIN ) 23. A method comprising:

2. The pressure in the common rail (3) (P RAIL ) and the amount of fuel injected (Q F-INJ ) based on the third contribution factor (Q EEff ) In order to reduce the risk of damage to the high pressure fuel pump (4), the pressure in the common rail (3) (P RAIL ) and a fourth contribution (Q DAM ) The third contributing element (Q EEff ) and the fourth contributing element (Q DAM The minimum flow rate threshold (Q MIN ) The method of claim 1 further comprising:

3. The third contributing element (Q EEff 3. The method according to claim 2, wherein the driving mode (DV) selected for the vehicle equipped with the heat engine (1) is determined as a function of the position of a hand lever among a plurality of possible positions.

4. The first contribution (Q MIN-COLD ), and the second contribution (Q MIN-HOT ) and the coefficient (K), a fifth contribution factor (Q) for suppressing temperature fluctuations generated in the high pressure fuel pump (4) during the pumping phase. TEMP ) The fifth contributing factor (Q TEMP ), the third contributing element (Q EEff ), the fourth contributing element (Q DAM The minimum flow rate threshold (Q MIN ) Further comprising: The fifth contributing factor (Q TEMP ) is calculated as follows: [0010] Where: Q TEMP A fifth contributing element, K coefficient, Q MIN-COLD A first contributing element, Q MIN-HOT Second Contributor That is, The method according to claim 2 or 3.

5. The target fuel flow rate (M ref ) is the minimum flow rate threshold (Q MIN ) only when the target fuel flow rate (M ref controlling the high pressure fuel pump (4) to supply The target fuel flow rate (M ref ) is the minimum flow rate threshold (Q MIN ), controlling the high pressure fuel pump (4) so ​​as not to supply fuel when the difference is less than The method according to any one of claims 1 to 4, comprising:

6. The minimum flow rate threshold (Q MIN The step of determining the number of vertices includes the following sub-steps: A step of calculating an energy index (I), the energy index (I) being a function of the pressure (P) in the common rail (3) detected in real time by a pressure sensor (11). RAIL indicating the approach or lack of approach to the occurrence of a cavitation phenomenon in said high-pressure fuel pump (4) based on the intensity of disturbances of a signal on said signal, said disturbances being evaluated by integration within an observation time window; When the energy index (I) exceeds a first threshold, a second amount (ΔQ MIN ) by the minimum flow rate threshold (Q MIN ) and The method according to any one of claims 1 to 5, comprising:

7. The desired pressure (P TARGET ) into a first amount (ΔP TARGET 7. The method of claim 6, wherein the energy index (I) is decreased by a first time interval when the energy index (I) exceeds a first threshold.

8. The first amount (ΔP TARGET 8. The method of claim 7, wherein the energy index (I) is at least equal to 1 MPa and is independent of the difference between the energy index (I) and the first threshold value.

9. The second amount (ΔQ MIN 9. The method of claim 8, wherein the energy index (I) is at least equal to 20 mg and is independent of the difference between the energy index (I) and the first threshold value.

10. The target fuel flow rate (M ref The energy index (I 1 ) is calculated as follows: [0025] Where: t 1 , t 2 A time that defines the observation time window, P RAIL Actual pressure of the common rail (3), P TARGET Target pressure in the common rail (3), The method according to any one of claims 6 to 9,

11. The target fuel flow rate (M ref The energy index (I 2 ) is calculated as follows: [0030] Where: t 1 , t 2 A time that defines the observation time window, P RAIL Actual pressure of the common rail (3), P RAIL-M the actual average pressure in the common rail (3) and in the observation window, The method according to any one of claims 6 to 9,

12. The energy index (I 3 ) is calculated as follows: [0045] Where: t 1 , t 2 A time that defines the observation time window, INT The value of the integral component of the closed loop of the pressure control. INT M The average value of the integral component of the closed loop of the pressure control within the observation window, The method according to any one of claims 6 to 9,

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