Patent Grant
9410516
1. Field of the Invention
The present invention relates to a method, a control device, and a computer program for operating a fuel system for an internal combustion engine.
2. Description of the Related Art
Fuel supply control valves, for example in a fuel system of an internal combustion engine, are known from the market. Fuel supply control valves are generally operated electromagnetically as switching valves having two switching positions, and frequently are an integral part of a high-pressure pump of the fuel system. The fuel supply control valve controls the fuel quantity pumped to a high-pressure accumulator (“rail”), from which fuel is led to the injectors of the internal combustion engine. An armature which is coupled to a valve element of the fuel supply control valve may be moved by magnetic force. The valve element, usually an inlet valve of the high-pressure pump, may strike against a valve seat or may be lifted from the valve seat. A supplied fuel quantity for the internal combustion engine, and thus, ultimately, the pressure in the rail, may be regulated in this way. A published German patent application document in this field is DE 10 2007 035 316 A1, for example.
The present invention has the advantage that an energization of an electrical actuating device for a metering device of a fuel system for an internal combustion engine may be reduced (so-called “reduced current control”). A speed of moving elements of the metering device as well as operating noise of the metering device, in particular in a low-speed range of the internal combustion engine, may be reduced in this way. The method according to the present invention allows the energization to be reduced as a function of a particular specimen of the metering device. Reliable switching of the metering device may still be achieved, essentially independently of specimen variations, temperatures, or an ohmic resistance of supply lines of the electrical actuating device.
The present invention relates to a method for operating a fuel system for an internal combustion engine, the metering device for measuring a delivery quantity of the fuel being openable and/or closable with the aid of the electrical actuating device, and a valve element of the metering device may switch into a first position when the actuating device is not activated, and into a second position when the actuating device is activated. The first position corresponds to a closed metering device, and the second position corresponds to an open metering device. In a first alternative, the method is characterized by the following steps:
Thus, starting from an activation of the electrical actuating device that is sufficient for reliably switching into the second position, the activation energy is reduced gradually, and the limiting case is “felt out,” so to speak, “from above.” At the same time, the first activation energy which is part of the limiting case is ascertained and subsequently used as a reference value for activating the electrical actuating device. The first activation energy is thus at least necessary as a limiting case in order to reliably switch the electrical actuating device. The electrical actuating device is preferably designed as an electromagnetic actuating device, and includes a coil and an armature which is movable by magnetic force. Alternatively, it is also conceivable to carry out the method according to the present invention with an electrical actuating device which includes a piezoactuator. The metering device corresponds to a so-called fuel supply control valve which includes, for example, an inlet valve situated upstream from a fuel pump of the fuel system.
A second alternative for ascertaining the limiting case is characterized by the following steps:
The second alternative of the method is thus analogously carried out in reverse order with respect to the first alternative. The activation energy is increased gradually, and the limiting case is “felt out,” so to speak, “from below.” Both described alternatives result in the same limiting case and the same first activation energy. It is understood that in both alternatives, the activation energy may also be gradually increased and decreased in alternation in a range around the presumed limiting case in order to accurately “sound out” the limiting case. Likewise, it is understood that in steps (b) the activation energy does not necessarily have to be changed in a strictly monotonic manner with each subsequent activation. Thus, it is certainly possible for multiple successive activations to use the same activation energy.
In the present case, “activation energy” is generally understood to mean a variation in time of a current flowing through the electrical actuating device. A switching characteristic of the electrical actuating device is thus a function of the time curve of the current (“current profile”) corresponding to an associated time integral. The time integral of the current multiplied by a voltage has the dimension of energy.
In one embodiment of the method, after step (c) the first activation energy is increased by an offset value, resulting in a second activation energy, the offset value being dimensioned in such a way that the valve element may robustly switch into the second position. The subsequent activation in step (d) with the second activation energy takes place in a similar way. The reliability of the switching corresponding to the offset value may thus be optionally improved, in that it becomes more robust with regard to disturbances such as changes in temperature and/or changes in voltage.
In one preferred embodiment of the method, the first position corresponds to a closed metering device, and the second position corresponds to an open metering device. As a result, it is possible for the metering device in the de-energized state to be closed by devices which control the fuel system, and for the fuel to not be able to flow uncontrolled. The fuel system may thus be kept in a defined state.
In a first option according to the present invention for ascertaining the limiting case, a pressure and/or a pressure change and/or a rate of pressure change in a pressure accumulator, in particular in a high-pressure accumulator (“rail”), of the fuel system is/are ascertained and compared to a threshold value. The limiting case may be recognized, for example, by a rise in the rail pressure over time. Appropriate threshold values may be predefined for this purpose. It may thus be ascertained, for example, whether a certain fuel pressure is exceeded, and/or whether, starting from an initial value of the fuel pressure, a pressure change has exceeded a predefined threshold value, and/or whether the rate of pressure change has exceeded a predefined threshold value. The limiting case may thus be ascertained in a particularly precise way.
In a second option according to the present invention for ascertaining the limiting case, a voltage and/or a current of the electrical actuating device is/are ascertained and evaluated. Comparatively rapid changes in the movement of the valve element result in a corresponding change in the movement of the armature, and thus, a corresponding change in a magnetic field surrounding the armature. According to Faraday's law of induction, a voltage is thus generated in a coil of the electromagnetic actuating device which is ascertainable at terminals of the electromagnetic actuating device.
In addition, it may be provided that the second activation energy and/or a time curve of the activation corresponding to the second activation energy or a time curve of the current is/are stored in a data store, using a characteristic map, for example. Thus, for the subsequent activation of the electromagnetic actuating device, the stored value may be read out from the data store, and therefore needs to be ascertained only occasionally or periodically during operation of the metering device. The availability of the stored final state may thus be increased by dispensing with the adaptation operations. In addition, it may be provided to store further variables or parameters, for example a speed of the internal combustion engine together with the activation energy or the time curve of the current.
A first alternative of the activation of the electromagnetic actuating device provides that a time curve of the activation includes a first phase having a monotonically increasing current curve, and that the time curve includes a subsequent second phase in which the electrical actuating device is activated with the aid of a pulse width modulation, and that a duration of the first phase and/or a pulse duty factor of the pulse width modulation within the second phase is/are changed in order to ascertain the limiting case. A first temporal “current profile” is thus described which is particularly suitable for carrying out the method.
A second alternative of the activation of the electromagnetic actuating device provides that the time curve of the activation includes a first phase having a monotonically increasing current curve, and that the time curve includes a subsequent second phase in which the electrical actuating device is energized with the aid of a regulatable current, and that a duration of the first phase and/or an intensity of the regulatable current within the second phase is/are changed in order to ascertain the limiting case. A second temporal “current profile” is thus described which is particularly suitable for carrying out the method.
A third alternative of the activation of the electromagnetic actuating device provides that the time curve of the activation includes a first phase in which the electrical actuating device is energized with the aid of a first regulatable current, and that the time curve includes a subsequent second phase in which the electrical actuating device is energized with the aid of a second regulatable current, the second current being lower than the first current, and that a duration of the first phase and/or an intensity of the second regulatable current is/are changed in order to ascertain the limiting case. A third temporal “current profile” is thus described which is particularly suitable for carrying out the method.
In addition, in the above-described three alternatives, the time curve of the activation may include a third phase, following the second phase, in which the electrical actuating is activated or energized with the aid of a pulse width modulation or a third regulatable current. Any premature drop of the valve element from the second position back into the first position due to currents which are possibly too low may thus be avoided. The effective current is generally higher in the third phase than in the second phase.
According to another embodiment of the method, the above-described offset value may be predefined as a function of the fuel pressure in the pressure accumulator and/or a fuel temperature and/or an electrical resistance of electrical lines attached to the electrical actuating device. The offset value may thus be dimensioned to be compatible with the existing operating parameters, so that the offset value may be selected to be comparatively small. The second activation energy is thus appropriately low without reducing the reliability of the switching of the valve element. Multiple offset values may preferably be stored as a function of multiple operating parameters in a characteristic map of the control and/or regulation device for the internal combustion engine.
The mentioned control and/or regulation device for the internal combustion engine is particularly useful for the method according to the present invention, since it already centrally contains a number of operating variables of the fuel system and the internal combustion engine for carrying out the method. The method is preferably carried out with the aid of a computer program.
The same reference numerals are used for functionally equivalent elements and variables in all the figures, even for different specific embodiments.
Downstream, piston pump 24 is connected to a pressure accumulator 28 (high-pressure accumulator, “common rail”) via a high-pressure line 26. A pressure sensor 30 is situated at pressure accumulator 28. Piston pump 24 includes a piston 32, which in the drawing is vertically movable, and in the present case drivable with the aid of an eccentric disk 34. Electrical actuating device 20 is activated by a control and/or regulation device 36 via electrical lines 35. Control and/or regulation device 36 includes a data store 37 and a computer program 39. In addition, control and/or regulation device 36 is connected to pressure sensor 30 via an electrical line 38.
It is understood that fuel supply control valve 22 may also be designed as a unit with piston pump 24 (see
During operation of fuel system 10, pre-feed pump 16 conveys fuel from fuel tank 12 into low-pressure line 18. Fuel supply control valve 22 controls the quantity of fuel that is supplied to a feed chamber 25 of piston pump 24. Fuel supply control valve 22 may be closed and opened as a function of a particular need for fuel. The fuel is gasoline or diesel fuel, for example.
In addition, piston pump 24 includes an inlet 46 which is connected to low-pressure line 18 via inlet valve 48, and an outlet 50 which is connected to high-pressure line 26 via an outlet valve 52. Inlet valve 48 includes a valve spring 53 and a valve element 54. Inlet valve 48 is hydraulically connected to feed chamber 25 via an opening (no reference numeral).
Valve element 54 may be forcibly held in a second position 47 (illustrated in dashed lines) with the aid of a valve needle 55, which is horizontally displaceable in the drawing and coupled to armature 44. A first position 45 corresponds to a closed metering device 22, and second position 47 corresponds to an open metering device 22.
If electrical actuating device 20 is not energized, inlet valve 48 may be closed by the force of valve spring 53 (“closed in the de-energized state”). When electrical actuating device 20 is energized, armature 44 may be moved to the right in the drawing against a lift stop 49 with the aid of magnetic force, and valve element 54 may thus forcibly switch from first position 45 into second position 47. As a result, inlet valve 48 opens. Due to the (active) switching of armature 44 or of valve element 54, operating noise may occur which corresponds to the particular intensity of the activation of electrical actuating device 20.
During operation of fuel system 10, piston pump 24 conveys fuel from inlet 46 to outlet 50, outlet valve 52 opening or closing, corresponding to a particular pressure difference between feed chamber 25 and outlet 50. At full delivery of piston pump 24, inlet valve 48 is acted on by a particular pressure difference between inlet 46 and feed chamber 25. For a desired partial delivery, starting at a predefined point in time, electrical actuating device 20 is energized during a delivery stroke, as the result of which inlet valve 48 is not able to close, and the fuel that is still present in feed chamber 25 is conveyed back into low-pressure line 18. The volumes of piston pump 24 situated within housing 40 are essentially filled with fuel.
The diagrams have the same time scale (time t). All three diagrams have a respective zero value of activation voltage 58 and of current 60 and of lift 62, which is shown slightly above an associated abscissa. All three diagrams have a first time range 64, which corresponds to a pick-up phase of armature 44, and a subsequent second time range 66, which corresponds to an energization during a holding phase of armature 44 at lift stop 49. In the bottom diagram, the zero value corresponds to a stop of armature 44 against resting seat 43, and a horizontal dashed line corresponds to lift stop 49.
The activation of solenoid 42 and of electrical actuating device 20 illustrated in
Activation voltage 58 is depicted in the top diagram. A second terminal (not illustrated) of solenoid 42 is continuously switched against a battery voltage 70. The first terminal (not illustrated) of solenoid 42 may be switched between battery voltage 70 and a ground potential (“0”) with the aid of an electronic switch, as the result of which solenoid 42 and electrical actuating device 20 are activated, and current 60 may flow.
A first phase 72 of an activation begins at a point in time t0. Activation voltage 58 is continuously switched to zero during first phase 72, as the result of which current 60 in solenoid 42 rises in an approximately ramp-shaped manner. At a subsequent point in time t1, at which armature 44 has not yet struck against lift stop 49, first phase 72 ends and a second phase 74 begins. During second phase 74, activation voltage 58 is clocked in the manner of a pulse width modulation, and current 60 assumes an approximately sawtooth-shaped time curve. Armature 44 strikes against lift stop 49 at a subsequent point in time t2. A pick-up duration (t2−t0) of armature 44 is longer than a duration (t1−t0) of first phase 72.
In addition, a pulse duty factor of the pulse width modulation which takes place in second phase 74 may be changed. It is thus possible to change the time curve of current 60 virtually arbitrarily, and thus, to optimize the switching characteristic of fuel supply control valve 22. At a point in time t3 following point in time t2, the activation, and thus the energization, of solenoid 42 is terminated. Armature 44 once again reaches resting seat 43 at a subsequent point in time t4.
The activation of electrical actuating device 20 may take place in various ways. For example, during first phase 72, electrical actuating device 20 may be activated with a monotonically increasing curve of current 60, or with a first regulatable current 60. Likewise, during second phase 74, electrical actuating device 20 may be activated in the manner of a pulse width modulation, or may be activated with a second regulatable current. In general, an average current 60 in second phase 74 is less than in first phase 72. In addition, a third phase (not illustrated) following second phase 74 may be provided in which electrical actuating device 20 is activated or energized with the aid of a pulse width modulation or a third regulatable current 60. An average current 60 is generally higher in the third phase than in second phase 74.
For ascertaining a limiting case, described in greater detail below, the lengths of the three phases and/or the currents flowing in the particular phases may be individually changed.
Current curve 78 characterizes a second activation of electrical actuating device 20, in which valve element 54 is activated with a reduced (“second”) activation energy. In the present case, “activation energy” is generally understood to mean a respective time curve of current 60. A first arrow 80 characterizes a point in time at which fuel supply control valve 22 opens, and a second arrow 82 characterizes a point in time at which fuel supply control valve 22 closes.
The second activation energy is a “first” activation energy which is increased by an offset value. The first activation energy corresponds to the above-mentioned limiting case in which valve element 54 only just or just no longer switches from first position 45 into second position 47. The offset value is dimensioned in such a way that the second activation energy is much lower than an activation energy which corresponds to current curve 76, although valve element 54 is able to switch into second position 47, and the reliability of the switching is therefore not reduced. It is apparent that the second activation energy of current curve 78 is only approximately two-thirds of the activation energy of current curve 76.
A check is made in a query block 90 as to whether a speed of the internal combustion engine is lower than a threshold value. If this is not the case, a branch is made back to the start of query block 90. If this is the case, a branch is made to a subsequent block 92. In block 92, electrical actuating device 20 is activated in a first cycle in such a way that valve element 54 is reliably forced into second position 47, for example using current curve 76.
With the aid of query block 90, a switch may be made between a first and a second type of operation of fuel supply control valve 22. The first type of operation characterizes comparatively high speeds, using a “maximum current profile” for activating electrical actuating device 20. The second type of operation characterizes comparatively low speeds, using a reduced current control (RECUR) of electrical actuating device 20. For example, the second type of operation characterizes so-called “close to idling” speeds.
Electrical actuating device 20 is activated in a subsequent block 94 in at least one second cycle with an activation energy which gradually drops by a difference value.
A fuel pressure (“pressure”) in pressure accumulator 28 which is ascertained with the aid of pressure sensor 30 is evaluated in a subsequent block 96. For example, a check is made as to whether the pressure and/or a pressure change and/or a rate of pressure change in pressure accumulator 28 has/have exceeded a threshold value. It is taken into account that when an instantaneous activation energy of electrical actuating device 20 is not, or no longer, sufficient to force valve element 54 from first position 45 into second position 47 during a delivery stroke, piston pump 24 carries out a so-called full delivery. This case of full delivery may be ascertained via a comparatively rapid rise in the pressure in pressure accumulator 28.
A check is made in a subsequent query block 98 as to whether a pressure change which exceeds the threshold value has been ascertained in preceding block 96. If this is not the case, the method is continued at the start of block 94, the activation energy being further decreased in block 94. However, if the threshold value has been exceeded, it is deduced that fuel supply control valve 22 is not, or no longer, open. This corresponds to a limiting case in which valve element 54 is only just or just no longer forced into second position 47. Alternatively or additionally, instead of the fuel pressure or in addition to the fuel pressure, activation voltage 58 and/or current 60 may be evaluated in blocks 96 and 98 in order to ascertain the limiting case.
A branch is then made to a subsequent block 100 in which the first activation energy corresponding to the limiting case is ascertained. The above-described offset value is ascertained or predefined as a function of the fuel pressure in pressure accumulator 28 and a fuel temperature and an electrical resistance of electrical lines 35, and is added to the first activation energy. The sum results in the second activation energy. The activation of electrical actuating device 20 is thus adapted to a specimen-dependent and/or speed-dependent switching characteristic of fuel supply control valve 22. The first and the second activation energy, and optionally the speed and a predefinable time curve of the activation, are stored in data store 37 for subsequent activations of electrical actuating device 20. This takes place using a characteristic map, for example.
Electrical actuating device 20 is subsequently activated with the second activation energy in a subsequent block 102. However, it is also possible to ascertain the first and the second activation energy as well as the offset value as a function of the speed of the internal combustion engine. Fuel supply control valve 22 may thus also be activated as a function of the speed. The procedure illustrated in
It is understood that the ascertainment of the described limiting case may correspondingly also take place in the reverse manner. Starting from an activation energy in which valve element 54 does not reliably switch into second position 47, this activation energy is increased gradually until the limiting case is reached. In addition, the activation energy may also be gradually increased and decreased in alternation, as the result of which the limiting case may be ascertained more accurately if necessary.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2012 208 614 | May 2012 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2013/058506 | 4/24/2013 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2013/174604 | 11/28/2013 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5230613 | Hilsbos | Jul 1993 | A |
| 7178506 | Kojima | Feb 2007 | B2 |
| Number | Date | Country |
|---|---|---|
| 199 45 618 | Mar 2001 | DE |
| 103 05 523 | Aug 2004 | DE |
| 10 2006 027823 | Dec 2007 | DE |
| 10 2007 035 316 | Jan 2009 | DE |
| 10 2010 021168 | Nov 2011 | DE |
| 10 2010 0439 | May 2012 | DE |
| 10 2011 085 277 | May 2013 | DE |
| WO 2006029931 | Mar 2006 | WO |
| Entry |
|---|
| International Search Report for PCT/EP2013/058506, dated Sep. 11, 2013. |
| Number | Date | Country | |
|---|---|---|---|
| 20150136090 A1 | May 2015 | US |
