|
(11) | EP 2 163 750 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
|
|
|
|
||||||||||||||||||||
| (54) | Method of driving fuel injectors arranged in an intake pipe above and below a butterfly valve |
| (57) A method of driving fuel injectors (8,9) arranged along an intake pipe (3) above
and below a butterfly valve (7) in an internal combustion engine (1); the driving
method comprises the steps of: connecting, during the construction of the system,
a first fuel injector (9) arranged "below" the butterfly valve (7) and a second fuel
injector (8) arranged "above" the butterfly valve (7) to a same output (11) of an
electronic control unit (10) by means of a switch (12); actuating, during normal operation,
the switch (12) for selectively connecting either the first fuel injector (9) or the
second fuel injector (8) to the electronic control unit so as to inject the fuel by
alternatively using the first fuel injector (9) or the second fuel injector (8); and
carrying out, for a given number of times before switching from the first fuel injector
(9) to the second fuel injector (8), a step of adapting which comprises normally driving
the first fuel injector (9) for feeding the amount of fuel required for the combustion,
and driving the second fuel injector (8) during the dead times of the first fuel injector
(9) for feeding an amount of fuel functional to the formation of a fluid fuel film
on the walls of the intake pipe (3).
|
TECHNICAL FIELD
[0001] The present invention relates to a method of driving fuel injectors arranged in an intake pipe above and below a butterfly valve.
BACKGROUND ART
[0002] High-performance internal combustion engines, specifically motorcycle engines, are generally free from intake manifold and each cylinder is directly connected to the airbox (containing the air cleaner) by means of a short intake pipe (or intake horn) adjusted by a corresponding butterfly valve. A corresponding fuel injector, which cyclically injects the fuel into the intake pipe itself, is inserted into each intake pipe; the fuel injector may be arranged either "above" the butterfly valve (i.e. upstream of the butterfly valve with respect to the cylinder and thus farther from the cylinder) or "below" the butterfly valve (i.e. downstream of the butterfly valve with respect to the cylinder and thus closer to the cylinder).
[0003] By positioning the fuel injector "above" the butterfly valve, it is possible to obtain a better mixing of the fuel with the aspirated fresh air and therefore it is possible to generate a greater drive torque when the butterfly valve is either completely or nearly completely open (i.e. when the internal combustion engine is at high revolution speeds); conversely, by positioning the fuel injector "above" the butterfly valve, the combustion control is difficult when the butterfly valve is nearly completely closed (i.e. when the internal combustion engine is at low revolution speeds, close to idling) and therefore the idle operation is very irregular. On the contrary, by positioning the fuel injector "below" the butterfly valve, it is possible to obtain a good combustion control when the butterfly valve is nearly completely closed (i.e. when the internal combustion engine is at low revolution speeds, close to idling), but on the other hand a lower drive torque is generated when the butterfly valve is completely or nearly completely open (i.e. when the internal combustion engine is at high revolution speeds).
[0004] In order to avoid penalizing the generation of drive torque when the butterfly valve is either completely or nearly completely open, and at the same time to avoid an irregular idling operation, it has been suggested to provide each intake pipe with a first fuel injector, which is arranged "below" the butterfly valve and is used at low speeds, and with a second fuel injector, which is arranged "above" the butterfly valve and is used at high speeds. The two fuel injectors of each intake pipe are always driven if the abilities of the electronic control unit of the injectors so allow; in this case, the fuel injector arranged "above" the butterfly valve will be substantially off at low speeds, while the fuel injector arranged "below" the butterfly valve could also be used at high speeds (in addition to the fuel injector arranged "above" the butterfly valve). Instead, when the abilities of the electronic control unit of the injectors do not allow to simultaneously drive the two fuel injectors, a switch must be comprised which is controlled by the electronic control unit to select which fuel injector is to be driven each time. It has been noted that a "torque gap" always occurs during the increase of the revolutions, when driving is switched from the fuel injector arranged "below" the butterfly valve to the fuel injector arranged "above" the butterfly valve, i.e. for a few seconds the drive torque generated by the engine undergoes a reduction which is clearly felt by the vehicle driver, and is thus very unpleasant. The "torque gap" which occurs upon the switching is due to the fact that when the fuel injector arranged "above" the butterfly valve carries out the first injections, the fuel does not reach the cylinder (or reaches it only to a minimum extent) because the fuel itself tends to deposit on the walls of the intake pipe forming a wet film on the walls themselves; only once such a wet film has been formed on the walls of the intake pipe, all the fuel injected by the fuel injector arranged "above" the butterfly valve actually enters into the cylinder and thus is involved in the combustion.
DISCLOSURE OF INVENTION
[0005] It is the object of the present invention to provide a method of driving fuel injectors arranged in an intake pipe above and below a butterfly valve, which driving method is free from the above-described drawbacks, and specifically, is easy and cost-effective to be implemented.
[0006] According to the present invention, a method of driving fuel injectors arranged in an intake pipe above and below a butterfly valve is provided as claimed in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The present invention will now be described with reference to the accompanying drawing, which illustrates a non-limitative embodiment thereof; specifically, the accompanying figure is a diagrammatic view of an internal combustion engine provided with injectors arranged below and above a butterfly valve, and which are driven in accordance with the driving method of the present invention.
PREFERRED EMBODIMENTS OF THE INVENTION
[0008] In the accompanying figure, number 1 indicates as a whole an internal combustion engine for motorcycles. The internal combustion engine 1 is provided with four cylinders 2 (only one of which is shown in the accompanying figure), each of which is connected to a corresponding intake pipe 3 (or intake horn) by means of two intake valves 4 (only one of which is shown in the accompanying figure) and to an exhaust pipe 5 by means of two exhaust valves 6 (only one of which is shown in the accompanying figure). Each intake pipe 3 originates from an airbox (containing an air cleaner) for receiving fresh air (i.e. air from the external environment) and is adjusted by a butterfly valve 7.
[0009] Each intake pipe 3 is provided with a fuel injector 8 arranged "above" the butterfly valve 7 (i.e. upstream of the butterfly valve 7 with respect to the cylinder 2 and thus farther from the cylinder 2) and with a further fuel injector 9 arranged "below" the butterfly valve 7 (i.e. downstream of the butterfly valve 7 with respect to the cylinder 2 and thus closer to the cylinder 2). An electronic control unit 10 supervises the operation of the internal combustion engine 1 and specifically drives the two fuel injectors 8 and 9 of each intake pipe 3.
[0010] The electronic control unit 10 is provided with only four outputs 11 for driving the eight fuel injectors 8 and 9; accordingly, for each intake pipe 3, the fuel injector 8 arranged "below" the butterfly valve 7 and the fuel injector 9 arranged "above" the butterfly valve 7 are connected to a same output 11 of the electronic control unit 10 by means of a switch 12 electronically controlled by the electronic control unit 10 itself. During the operation of the internal combustion engine 1, the electronic control unit 10 operates the corresponding switch 12 for each intake pipe 3 to selectively connect either the fuel injector 8 or the fuel injector 9 to the electronic control unit 10 so as to inject the fuel by alternatively using either the fuel injector 8 or the fuel injector 9. Normally, the switching between each fuel injector 8 and the corresponding fuel injector 9 is decided in accordance with the revolution speed, the engine load and/or the requested drive torque (at low revolution speeds, at low engine load and/or at low requested drive torque, the fuel injector 8 arranged "below" the butterfly valve 7 is used and vice versa).
[0011] Each switch 12 for switching from the fuel injector 9 to the fuel injector 8 is actuated without any particular contrivance, because no torque gap related to the formation of a fluid fuel film on the walls of the intake pipe 3 occurs during such a switching, being the fuel injector 9 arranged upstream of the fuel injector 8 along the intake pipe 3.
[0012] Instead, before switching from each fuel injector 8 to the corresponding fuel injector 9, the electronic control unit runs a step of adapting for a given, predetermined number of times. In other words, the switch 12 is actuated to definitively switch from the fuel injector 8 to the fuel injector 9 only once the step of adapting for the given number of times has been carried out.
[0013] The number of times that the step of adapting is carried out may be either set during the step of designing and remain always constant, or may be modified during the life of the internal combustion engine 1 by means of self-adapting strategies; in the latter case, for example, the electronic control unit 10 may verify the onset of torque gaps upon the switching from each fuel injector 8 to the corresponding fuel injector 9 and thus increase the number of times that the step of adapting is carried out in case of torque gaps arise after switching and vice versa.
[0014] For each intake pipe 3 (i.e. for each cylinder 2) the step of adapting comprises driving the fuel injector 8 by means of the electronic control unit 10 to carry out a fuel injection, which feeds the amount of fuel required for the combustion and has an opening event of the fuel injector 8 and a subsequent closing event of the fuel injector 8. At the time of the closing event of the fuel injector 8, the switch 12 is actuated to connect the fuel injector 9 to the electronic control unit 10, and thus the fuel injector 9 is driven by means of the electronic control unit 10 to carry out a fuel injection, which feeds an amount of fuel functional to the formation of a fluid fuel film on the walls of the intake pipe 3 and has an opening event of the fuel injector 9 and a subsequent closing event of the fuel injector 9; finally, at the time of the closing event of the fuel injector 9, the switch 12 is actuated to connect the fuel injector 8 to the electronic control unit 10 again.
[0015] In other words, during the step of adapting an intake pipe 3 (i.e. each cylinder 2), the fuel injector 8 is normally driven (i.e. exactly as before the step of adapting) to feed the amount of fuel required for the combustion into the cylinder 2, while the fuel injector 9 is driven during the dead times of the fuel injector 8 (i.e. when the fuel injector 8 remains closed according to the combustion needs of the cylinder 2) to feed an amount of fuel functional to the formation of a fluid fuel film onto the walls of the intake pipe 3.
[0016] According to a preferred embodiment, the steps of adapting each cylinder 2 are reciprocally time offset so that not all the steps of adapting are carried out at the same time, and specifically so that only one step of adapting is carried out at a time; in this manner, it is possible to further reduce the risk of drive torque irregularity because only one cylinder 2 switches from the fuel injector 8 to the fuel injector 9 at a time, while the other three cylinders 2 are working normally.
[0017] The above-described method of driving the fuel injectors 8 and 9 has many advantages, because it is simple and cost-effective to be implemented and simultaneously allows to either eliminate or however greatly reduce the onset of drive torque gaps when switching from the fuel injectors 8 arranged "below" the corresponding butterfly valves 7 to the fuel injectors 9 arranged "above" the corresponding butterfly valves 7 is required.
1. A method of driving fuel injectors (8, 9) arranged along an intake pipe (3) above
and below a butterfly valve (7); the driving method comprises the steps of:
connecting, during the construction of the system, a first fuel injector (8) arranged "below" the butterfly valve (7) and a second fuel injector (9) arranged "above" the butterfly valve (7) to a same output (11) of an electronic control unit (10) by means of a switch (12); and
actuating, during normal operation, the switch (12) for selectively connecting either the first fuel injector (8) or the second fuel injector (9) to the electronic control unit so as to inject the fuel by alternatively using the first fuel injector (8) or the second fuel injector (9);
the driving method is characterized in that a step of adapting is carried out for a given number of times before switching from the first fuel injector (8) to the second fuel injector (9), the step of adapting comprising in turn the steps of:
driving the first fuel injector (8) by means of the electronic control unit (10) for carrying out a fuel injection, which feeds the amount of fuel required for the combustion and has an opening event of the first fuel injector (8) and a following closing event of the first fuel injector (8);
actuating, at the time of the closing event of the first fuel injector (8) the switch (12) for connecting the second fuel injector (9) to the electronic control unit (10);
driving the second fuel injector (9) by means of the electronic control unit (10) for carrying out a fuel injection, which feeds an amount of fuel functional to the formation of a fluid fuel film on the walls of the intake pipe (3) and has an opening event of the second fuel injector (9) and a subsequent closing event of the second fuel injector (9); and
actuating, at the time of the event of closing the second fuel injector (9), the switch (12) for connecting the first fuel injector (8) to the electronic control unit (10).
2. A driving method according to claim 1, wherein during the step of adapting, the first
fuel injector (8) is normally driven for feeding the amount of fuel required for the
combustion, while the second fuel injector (9) is driven during the dead times of
the first fuel injector (8) for feeding an amount of fuel functional to the formation
of a fluid fuel film on the walls of the intake pipe (3).
3. A driving method according to claim 1 or 2, and comprising the further step of actuating
the switch (12) for definitively switching from the first fuel injector (8) to the
second fuel injector (9) only once the step of adapting for the given number of times
has been carried out.
4. A driving method according to claim 1, 2 or 3, and comprising the further step of
driving the second fuel injector (9) for carrying out a fuel injection which feeds
the amount of fuel required for the combustion only once the step of adapting for
the given, predetermined number of times has been carried out.
5. A driving method according to anyone of the claims from 1 to 4, and comprising the
further step of time offsetting, when several cylinders (2) exist, the steps of adapting
each cylinder (2) so that the steps of adapting are not carried out at the same time.
6. A driving method according to claim 5, and comprising the further step of time offsetting
the steps of adapting each cylinder (2) so as to carry out only one step of adapting
at a time.
7. A driving method according to anyone of the claims from 1 to 6, and comprising the
further step of always keeping constant the number of times that the step of adapting
is carried out.
8. A driving method according to anyone of the claims from 1 to 6, and comprising the
further step of varying the number of times that the step of adapting is carried out
by means of self-adaptation strategies.
9. A driving method according to claim 8, and comprising the further steps of:
verifying the onset of drive torque gaps after the switching from the first fuel injector (8) to the second fuel injector (9); and
increasing the number of times that the step of adapting is carried out in case the drive torque gaps arise after the switching from the first fuel injector (8) to the second fuel injector (9).
10. A driving method according to anyone of the claims from 1 to 9, and comprising the
further step of deciding the switching between the first fuel injector (8) and the
second fuel injector (9) according to the revolution speed, the engine load and/or
the required drive torque.