Patent Grant
10830172
This patent application claims priority from Italian Patent Application No. 102018000005765 filed on May 28, 2018, the entire disclosure of which is incorporated herein by reference.
The invention relates to a method to determine an opening time of an electromagnetic fuel injector.
An electromagnetic fuel injector (for example like the one described in patent application EP1619384A2) normally comprises a cylindrical, tubular body having a central feeding channel which performs the function of a fuel duct and ends with an injection jet controlled by an injection valve operated by an electromagnetic actuator. The injection valve is provided with a plunger, which is rigidly connected to a movable armature of the electromagnetic actuator so as to moved by the action of the electromagnetic actuator between a closed position and an open position of the injection jet against the action of a closing spring which pushes the plunger towards the closed position. The valve seat is defined in a sealing element, which has the shape of a disc, seals the central channel of the support body on the lower side, and is crossed by the injection jet. The electromagnetic actuator comprises a coil, which is arranged on the outside around the tubular body, and a fixed magnetic pole, which is made of a ferromagnetic material and is arranged inside the tubular body so as to magnetically attract the movable armature.
The injection valve is normally closed due to the closing spring pushing the plunger to the closing position, in which the plunger presses against a valve seat of the injection valve and the movable armature is spaced apart from the fixed magnetic pole. In order to open the injection valve, i.e. move the plunger from the closing position to the opening position, the coil of the electromagnetic actuator is energized so as to generate a magnetic field which attracts the movable armature towards the fixed magnetic pole against the elastic force exerted by the closing spring; in the opening phase, the travel of the movable armature stops when the movable armature hits the fixed magnetic pole.
According to
The opening time of an electromagnetic injector is the time elapsing between the instant in which the energization of the electromagnetic actuator starts and the instant in which the injection valve actually starts opening; in the law of injection (shown in
Precisely knowing the opening time of an electromagnetic injector leads to better knowing the law of injection and, hence, allows for more precise fuel injections (especially when small quantities of fuel must be injected, thus causing the electromagnetic injector to operate in the ballistic operating area B).
Patent application WO2016091848A1 discloses a method to determine an opening time of an electromagnetic fuel injector: the electromagnetic fuel injector is controlled using a series of progressively increasing energization times of the electromagnetic actuator; for each control of the electromagnetic injector, the presence or the absence of a closing of the injection valve is detected; the opening time is identified, which is equal to an intermediate value between the last energization time of the electromagnetic actuator for which the absence of a closing of the injection valve was determined and the first energization time of the electromagnetic actuator for which the presence of a closing of the injection valve was determined.
The object of the invention is to provide a method to determine an opening time of an electromagnetic fuel injector, said method being capable of determining the opening time with a great precision and, in particular, being easy and economic to be implemented.
According to the invention, there is provided a method to determine an opening time of an electromagnetic fuel injector according to the appended claims.
The appended claims describe preferred embodiments of the invention and form an integral part of the description.
The invention will now be described with reference to the accompanying drawings, showing a non-limiting embodiment thereof, wherein:
In
According to
The electromagnetic actuator 14 comprises a coil 16, which is arranged on the outside around the tubular body 12 and is enclosed in a toroidal casing 17 made of a plastic material, and a fixed magnetic pole 18, which is made of a ferromagnetic material and is arranged inside the tubular body 12 in the area of the coil 16. Furthermore, the electromagnetic actuator 15 comprises a movable armature 19, which has a cylindrical shape, is made of a ferromagnetic material and is designed to be magnetically attracted by the magnetic pole 18 when the coil 16 is energized (i.e. a current flows through it). Finally, the electromagnetic actuator 15 comprises a tubular magnetic armature 20, which is made of a ferromagnetic material, is arranged on the outside of the tubular body 12 and comprises an annular seat 21 to house, on the inside, the coil 16, and a magnetic washer 22 with an annular shape, which is made of a ferromagnetic material and is arranged above the coil 16 to guide the closing of the magnetic flux around the coil 16.
The movable armature 19 is part of a movable equipment, which comprises, furthermore, a shutter or plunger 23 having an upper portion integral to the movable armature 19 and a lower portion cooperating with a valve seat 24) of the injection valve 15 so as to adjust, in a known manner, the flow of fuel towards the injection nozzle 11. In particular, the plunger 23 ends with a shutting head with a substantially spherical shape, which is designed to rest against the valve seat in a sealing manner.
The magnetic pole 18 is perforated at the centre and has a central through hole 25, which partially houses a closing spring 26, which pushes the movable armature 19 towards a closed position of the injection valve 15. In particular, inside the central hole 25 of the magnetic pole 18 there is fitted, in a fixed position, a striker element 27, which keeps the closing spring 26 compressed against the movable armature 19.
In use, when the electromagnetic actuator 14 is de-energized, the movable armature 19 is not attracted by the magnetic pole 18 and the elastic force of the closing spring 26 pushes the movable armature 19 together with the plunger 23 (i.e. the movable equipment) downwards up to a lower limit position, in which the shutting head of the plunger 23 is pressed against the valve seat 24 of the injection valve 15 insulating the injection nozzle 11 from the fuel under pressure. When the electromagnetic actuator 14 is energized, the movable armature 19 is magnetically attracted by the magnetic pole 18 against the elastic force of the closing spring 26 and the movable armature 19 together with the plunger 23 (i.e. the movable equipment) move upwards, due to the magnetic attraction exerted by the magnetic pole 18, up to the an upper limit position, in which the movable armature 19 strikes against the magnetic pole 18 and the shutting head of the plunger 23 is lifted relative to the valve seat 24 of the injection valve 15 allowing the fuel under pressure to flow through the injection nozzle 11.
According to
According to
The diagram of
According to
In the instant t1, the coil 16 of the electromagnetic actuator 14 is energized and, hence, starts producing a drive force, which counters the force of the closing spring 26; when the drive force generated by the coil 16 of the electromagnetic actuator 14 exceeds the force of the closing spring 26, namely in the instant t2, the position p of the plunger 23 (which is integral to the movable armature 19) starts changing from the closed position of the injection valve 15 (indicated with “Close” in
In the instant t3, the position p of the plunger 23 still has not reached the complete open position of the injection valve 15 and, due to the end of the logic control command c of the electromagnetic injector 4, it goes back to the closed position of the injection valve 15, which is reached in the instant t5 (i.e. in the moment in which the shutting head of the plunger 23 rests against the valve seat of the injection valve 15 is a sealing manner). Before the instant t5 (i.e. the moment in which the injection valve 15 is closed), the instant t4 is identified, in which the current i flowing through the coil 16 is cancelled (namely, reaches a zero value) and in which the voltage v applied to the ends of the coil 16 starts decreasing (in absolute value), moving towards a zero value. The closing time TC is the time interval elapsing between the instants t3 and t5, i.e. the time interval elapsing between the end of the logic control command c of the electromagnetic injector 4 and the closing of the electromagnetic injector 4. The closing time TC is also equal to the sum of a zeroing time TZ, which is comprised between the instants t3 and t4 and in which the current i flowing through the coil 16 is still present (and, hence, the electromagnetic actuator 14 still produces a magnetic attraction force for the movable armature 19), and a flying time TF, which is comprised between the instants t4 and t5 and in which the current i flowing through the coil is equal to zero and, hence, the sole elastic force generated by the closing spring 26 acts upon the movable armature 19.
In the instant t1, the voltage v applied to the ends of the coil 16 of the electromagnetic actuator 14 of the electromagnetic injector 4 is caused to increase until it reaches a positive turning-on peak, which serves the purpose of quickly increasing the current i flowing through the coil 16; at the end of the turning-on peak, the voltage v applied to the ends of the coil 16 is controlled according to the “chopper” technique, which involves cyclically changing the voltage v between a positive value and a zero value so as to keep the current i in the neighbourhood of a desired maintaining value (for the sake of simplicity, the cyclic change in the voltage v is not shown in
The diagram of
According to
In the instant t1, the coil 16 of the electromagnetic actuator 14 is energized and, hence, starts producing a drive force, which counters the force of the closing spring 26; however, the drive force generated by the electromagnetic actuator 14 never manages to overcome (exceed) the elastic force generated by the closing spring 26 and, therefore, the plunger 23 (which is integral to the movable armature 19) never moves from the closed position of the injection valve 15 (indicated with “Close” in
Hereinafter is a description of the procedure used by the electronic control unit 9 to determine the closing instant t5 of the electromagnetic fuel injector 4 (namely, to determine the closing time TC, which corresponds to the time interval elapsing between the instants t3 and t5, namely the time interval elapsing between the end of the logic control command c of the electromagnetic injector 4 and the closing of the electromagnetic injector 4).
As already mentioned above when discussing
At the end of the injection (i.e. after the end instant t3 of the injection), the electronic control unit 9 detects (measures) a voltage actuation time development v1 (shown in
In order to determine the voltage comparison time development v2, the electronic control unit 9 carries out beforehand, namely before determining the closing instant t5 of the electromagnetic injector 4, a test on the electromagnetic injector 4, which is controlled with an injection time TINJ (which, in turn, is equal to the time interval elapsing between the beginning instant t1 of the injection and the end instant t3 of the injection) that is so small that it cannot reach the opening of the injection valve 15 (namely, an injection time TINJ which belongs the initial area A of failed opening and is smaller than the opening time TO), as shown in
According to a possible, tough non-binding embodiment, the electronic control unit 9 is provided with a hardware anti-aliasing filter (namely, a physical anti-aliasing filter acting upon the analogue signal before the digitization), which acts upon the measurement of the voltage v at at least one end (namely, one terminal 100 or 101) of the coil 16 of the electromagnetic actuator 14. The anti-aliasing filter is an analogue signal used before the sampling of the signal of the voltage v, so as to narrow the band of the signal in order to approximately fulfil the Nyquist-Shannon sampling theorem.
When the shutting head of the plunger 23 hits the valve seat of the injection valve 15 (i.e. when the electromagnetic injector 4 closes), the movable armature 19, which is integral to the plunger 23, very quickly changes its law of motion (i.e. it almost instantly shifts from a relatively high speed to a zero speed and, if necessary, it could even make a small bounce which reverses the speed direction) and this basically instantaneous change in the law of motion of the movable armature 19 produces a perturbation in the magnetic field linked to the coil 16 and, hence, also determines a perturbation of the voltage v at the ends of the coil 16.
As a consequence, there is a (detectable) difference between the voltage actuation time development v1, which involves a closing of the injection valve 15 at the end of the movement of the plunger 23, and the voltage comparison time development v2, which does not involve a closing of the injection valve 15, as the plunger 23 does not move; this difference is due to the fact that in the voltage actuation time development v1, which involves a closing of the injection valve 15 at the end of the movement of the plunger 23, there is a perturbation due to the impact of the plunger 23 against the valve seat of the injection valve 15, whereas in the voltage comparison time development v2, which does not involve a closing of the injection valve 15, as the plunger 23 does not move, there is no perturbation due to the impact of the plunger 23 against the valve seat of the injection valve 15. By searching for this perturbation (due to the impact of the plunger 23 against the valve seat of the injection valve 15) in the comparison between the voltage actuation time development v1, which involves a closing of the injection valve 15 at the end of the movement of the plunger 23, and the voltage comparison time development v2, which does not involve a closing of the injection valve 15, as the plunger 23 does not move, it is possible to determine the closing instant t5 of the electromagnetic injector 4.
According to a preferred embodiment, the electronic control unit 9 synchronizes the voltage actuation time development v1 with the voltage comparison time development v2 by aligning, in a time-wise manner, a first instant t4 in which the actuation electric current i circulating through the coil 16 is cancelled with a second instant t4 in which the test electric current i circulating through the coil 16 is cancelled.
According to a preferred embodiment, the electronic control unit 9 calculates (by means of a simple subtraction) a voltage difference Δv (shown in
According to a preferred embodiment, the electronic control unit 9 calculates a first time derivative dΔv/dt of the voltage difference Δv (shown in
According to a possible, though non-limiting embodiment, in the closing instant t5 determined as described above, a predetermined time advance is applied, which makes up for the phase delays introduced by all the filters to which the voltage v is subjected; in other words, the closing instant t5 determined as described above is advanced by means of a predefined time interval in order to take into account the phase delays introduced by all the filters to which the voltage v at the ends of the coil 16 is subjected.
The electronic control unit 9 recognizes the presence of a closing of the electromagnetic injector 4 only if the voltage difference Δv, in absolute value, exceeds a first threshold, and/or recognizes the presence of a closing of the electromagnetic injector 4 only if the first time derivative dΔv/dt of the voltage difference Δv exceeds, in absolute vale, a second threshold. In other words, the electronic control unit 9 recognizes the absence of a closing of the electromagnetic injector 4 only if the voltage difference Δv, in absolute value, is below the first threshold and/or if the first time derivative dΔv/dt of the voltage difference Δv, in absolute vale, is below the second threshold. Hence, if the voltage difference Δv and/or the first time derivative dΔv/dt of the voltage difference Δv are too small (in absolute value), the electronic control unit 9 establishes that the voltage actuation time development v1 is completely similar to the voltage comparison time development v2 and, hence, there was no closing of the electromagnetic injector 4 (namely, a closing of the electromagnetic injector 4 is absent).
According to a possible embodiment, the test to detect the voltage comparison time development v2 is carried out immediately before each fuel injection, so that a voltage comparison time development v2 is used to determine the closing instant t5 of the electromagnetic injector 4 of one single corresponding injection taking place immediately after. In other words, for each fuel injection, at first, a specific voltage comparison time development v2 is (immediately) determined and then, right after that, the fuel injection is carried out and the specific voltage comparison time development v2 is used to determine the closing instant t5.
According to an alternative embodiment, the test to detect the voltage comparison time development v2 is carried out every now and then, so that a voltage comparison time development v2 is used to determine the closing instant t5 of the electromagnetic fuel injector 4 of different injections. In other words, a voltage comparison time development v2 applies to (can be used for) different injections taking place in different moments. In this case, different voltage comparison time developments v2 can be stored upon variation of the pressure of the fuel in the common-rail 5. Furthermore, different voltage comparison time developments v2 are detected and then statistically processed and periodically updated.
According to a possible embodiment, the voltage v is measured by the electronic control unit 9 between the two terminals 100 and 101 of the coil 16 when the first and the second voltage time developments v1 and v2 are detected; this solution involves a differential measurement, which is more complicated because it requires the use of two distinct voltage sensors connected to the two terminals 100 and 101 of the coil 16. Alternatively, the voltage v is measured by the electronic control unit 9 between the low-voltage terminal 101 of the coil 16 and an electric ground when the voltage time developments v1 and v2 are detected; this solution is simpler because it involves the use of one single voltage sensor connected to the low-voltage terminal 101 of the coil 16.
During the normal operation of the internal combustion engine 1, the electronic control unit 9 decides the values of the injection time TINJ for which the corresponding closing time TC must be known. It is generally unlikely that, in the short term, the engine control requires an electromagnetic injector 4 to be controlled exactly with an injection time TINJ for which the corresponding closing time TC must be known; as a consequence, the electronic control unit 9 “forces” the situation making sure that, in any case, (at least) one injection is carried out, which has an injection time TINJ for which the corresponding closing time TC must be known. In particular, the electronic control unit 9 establishes a rotation speed objective and a torque objective to be generated for an internal combustion engine 2 and, then, determines a total quantity Q of fuel to be injected based on the rotation speed objective and on the torque objective to be generated; subsequently, the electronic control unit 9 controls the electromagnetic fuel injector 4 using a first injection time TINJ1 for which a corresponding closing time TC is to be determined and determines a first partial fuel quantity Q1 which is actually injected using the first injection time TINJ1. At this point, the electronic control unit 9 determines a second partial fuel quantity Q2 equal to the difference between the total fuel quantity Q and the first partial fuel quantity Q1 and determines a second injection time TINJ2 based on the second partial fuel quantity Q2 so as to exactly inject the second partial fuel quantity Q2; finally, the electronic control unit 9 controls the electromagnetic fuel injector 4 using the second injection time TINJ2.
The electronic control unit 9 chooses the first injection time TINJ1 so that the difference between the total fuel quantity Q and the first partial fuel quantity Q1 exceeds a predetermined threshold value (namely is great enough to allow the second partial fuel quantity Q2 to be injected with an acceptable precision).
It should be pointed out that the method described above to determine the closing instant t5 of the electromagnetic injector 4 applies in any operating condition of the electromagnetic injector 4, i.e. both when the electromagnetic injector 4 operates in the ballistic area B, in which, in the end instant t3 of the injection, the plunger 23 still has not reached the complete open position of the injection valve 15, and when the electromagnetic injector 4 operates in the linear area C, in which, in the end instant t3 of the injection, the plunger 23 has reached the complete open position of the injection valve 15. However, knowing the closing instant t5 of the electromagnetic injector 4 is particularly useful when the electromagnetic injector 4 operates in the ballistic area B, in which the injection feature of the electromagnetic injector 4 is strongly non-linear and dispersed, whereas it generally is not very useful when the electromagnetic injector 4 operates in the linear area C, in which the injection feature of the electromagnetic injector 4 is linear and not very dispersed.
Hereinafter is a description of the procedure used by the electronic control unit 9 to determine the opening time TO of the electromagnetic fuel injector 4.
The electronic control unit 9 controls the electromagnetic fuel injector 4 using a series of progressively increasing energization times TINJ of the electromagnetic actuator 14 and determines, for each control of the electromagnetic injector 4, the presence or the absence of a closing of the injection valve 15 (i.e. whether the injection valve 15 actually opened or did not open) according to the procedure described above; finally, the electronic control unit 9 identifies the opening time TO equal to an intermediate value between the last energization time TINJ of the electromagnetic actuator 14 for which the absence of a closing of the injection valve 15 was determined and the first energization time TINJ of the electromagnetic actuator 14 for which the presence of a closing of the injection valve 15 was determined.
According to a preferred embodiment, the control unit 9 establishes an expected value of the opening time TO (for example, equal to a nominal value or equal to the last, previously estimated value) and centres the series of progressively increasing energization times TINJ of the electromagnetic actuator 14 on the expected value of the opening time TO.
According to a preferred embodiment, the electronic control unit 9 establishes a time resolution in determining the presence or the absence of a closing of the injection valve 15 and, then, increases the energization times TINJ of the electromagnetic actuator 14 of the series of progressively increasing energization times TINJ of the electromagnetic actuator 14 with an increase which is equal to the time resolution in determining the presence or the absence of a closing of the injection valve 15. The resolution in the ability, in the execution of a measurement, to detect small variations of the physical quantity being examined (namely, the ability to detect whether an opening of the injection valve 15 took place or did not take place).
According to a preferred embodiment, the presence or the absence of a closing of the injection valve 15 (i.e. whether the injection valve 15 actually opened or did not open) during the control of an electromagnetic injector 4 are determined as described above (namely, by analysing the voltage difference Δv and/or the first time derivative dΔv/dt of the voltage difference Δv); according to a different embodiment, the presence or the absence of a closing of the injection valve 15 (namely, whether the injection valve 15 actually opened or did not open) during the control of an electromagnetic injector 4 can be determined with different procedures from the one described above.
The embodiments described herein can be combined with one another, without for this reason going beyond the scope of protection of the invention.
The method described above to determine a closing instant of an electromagnetic fuel injector 4 has numerous advantages.
First of all, the method described above to determine a closing instant of an electromagnetic fuel injector 4 allows the actual closing instant of an electromagnetic injector 4 to be identified with a great precision. This result is obtained thanks to the fact that the “behaviour” of an electromagnetic injector 4 in the moment of the closing of the injection valve 15 (namely, the voltage actuation time development v1) is compared with “itself”, i.e. with the “behaviour” of the same identical electromagnetic injector 4 in the same identical conditions in the absence of an opening (and, hence, of a closing) of the injection valve 15 (namely, with the voltage comparison time development v2); in this way, the effect of all the unforeseeable variables (building tolerances, ageing of the the components, pressure of the fuel, work temperature . . . ) that determine an (even significant) dispersion in the operating mode is “neutralized”. When the voltage comparison time development v2 is acquired a few milliseconds before the acquisition of the voltage actuation time development v1, it is evident that the acquisitions take place not only on the same component (namely, the same electromagnetic injector 4), but also under the same identical surrounding conditions (fuel pressure, work temperature . . . ); by so doing, the comparison between the voltage actuation time development v1 and the voltage comparison time development v2 is not affected in any way by unforeseeable variables and allows the closing instant t5 of the injection valve 15 to be determined with a great precision.
As already mentioned above, knowing the actual closing instant of an electromagnetic injector 4 is very important when the injector is used to inject small quantity of fuel because, by so doing, the actual quantity of fuel that was injected by the injector with every injection can be estimated with a great precision. In this way, an electromagnetic fuel injector 4 can also be used in the ballistic area to inject very small quantities of fuel (about 1 milligram), ensuring at the same time an adequate precision of the injection. It should be pointed out that the precision in the injection of very small quantities of fuel is not reached by reducing the dispersion of the features of the injector (which is an extremely complicated and expensive operation), but it is reached thanks to the possibility of immediately correcting the differences from the ideal condition, using the fact of knowing the actual quantity of fuel that was injected by the injector with each injection (the actual quantity of fuel that was injected is estimated using the fact of knowing of the actual closing time).
Furthermore, the method described above to determine a closing instant of an electromagnetic fuel injector 4 is simple and economic to be implemented even in an existing electronic control unit 9, because it does not require additional hardware to be added to the hardware already normally present in fuel injection systems, does not need a significant calculation ability and does not involve a large memory space.
The method described above to determine the opening time TO of an electromagnetic fuel injector 4 has numerous advantages.
First of all, the method described above to determine the opening time TO allows the actual opening time TO of an electromagnetic injector 4 to be identified with a good precision. Knowing the actual opening time TO of an electromagnetic injector 4 is important because the opening time TO establishes, in the law of injection, the boundary between the initial area A of failed opening and the ballistic operating area B: indeed, if the injection time TINJ is smaller than the opening time TO, the injection valve 15 does not open and, hence, we are in the initial area A of failed opening, whereas, if the injection time TINJ is greater than the opening time TO, the injection valve 15 opens and, hence, we are in the ballistic operating area B (or, if the injection time TINJ is long enough, we are in the linear area C). Therefore, knowing the actual opening time TO of an electromagnetic injector 4 leads to better knowing of the corresponding law of injection and, hence, allows the electromagnetic injector 4 to be controlled with a greater precision.
Furthermore, the method described above to determine the opening time TO of an electromagnetic fuel injector 4 is simple and economic to be implemented even in an existing electronic control unit 9, because it does not require additional hardware to be added to the hardware already normally present in fuel injection systems, does not need a significant calculation ability and does not involve a large memory space.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102018000005765 | May 2018 | IT | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20060224299 | Cochet et al. | Oct 2006 | A1 |
| 20130073188 | Rosel | Mar 2013 | A1 |
| 20130104636 | Beer et al. | May 2013 | A1 |
| 20190360424 | Parotto | Nov 2019 | A1 |
| Number | Date | Country |
|---|---|---|
| 102009045307 | Apr 2011 | DE |
| 1619384 | Jan 2006 | EP |
| 2375036 | Oct 2011 | EP |
| 2016091848 | Jun 2016 | WO |
| Entry |
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| Search Report for Italian Patent Application No. 201800005765 dated Feb. 15, 2019. |
| Number | Date | Country | |
|---|---|---|---|
| 20190360423 A1 | Nov 2019 | US |
