Method for operating a fuel supply arrangement, control device for a fuel supply arrangement, fuel supply arrangement and computer program product

Abstract

 A method for operating a fuel supply arrangement (10) for an internal combustion engine is disclosed. The fuel supply arrangement (10) comprises a fuel reservoir (24), a pump (20) hydraulically coupled to the fuel reservoir (24) for pressurizing the fuel in the fuel reservoir, at least one fuel injection valve (26) hydraulically coupled to the fuel reservoir (24) for dispensing fuel from the fuel supply arrangement (10) through an injection nozzle (261) of the fuel injection valve (26), the fuel injection valve (26) comprising a valve needle (263) which is displaceable for sealing and unsealing the injection nozzle (261) and an electromagnetic actuator assembly (265) having a solenoid (267) for displacing the valve needle (263), and a control device (40) for energizing the solenoid (267) and for measuring an electrical current (I) through the solenoid (267). The method comprises energizing the solenoid (267) to displace the valve needle (263) to a fully open position for unsealing the injection nozzle (261) by means of operating the control device (40) in such fashion that the electrical current (I) through the solenoid (267), during a first period of time (T₁), rises to a peak value (I_P) and subsequently decreases to a value within a first current range (DI₁), and, in a subsequent second period of time (T₂), is maintained within the first current range (DI₁), the upper limit (I_1U) of the first current range (DI₁) having a smaller magnitude than the peak value (I_P) in the first period of time (T₁), operating the control device (40) for measuring the electrical current (I) through the solenoid (267) at least during the second period of time (T₂), determining a point in time (to) at which the valve needle (263) has reached the fully open position by means of evaluating the measured electrical current (I), and inferring the fuel pressure in the fuel reservoir (24) from the determined point in time (to) at which the valve needle (263) has reached the fully open position.
Further, a control device (40), a fuel supply arrangement (10) and a computer program product are disclosed.

Description

[0001] The present disclosure relates to a method for operating a fuel supply arrangement. Further, it relates to a control device for a fuel supply arrangement, to a fuel supply arrangement and to a computer program product.

[0002] Fuel supply arrangements may be used in internal combustion engines for dosing fuel into an intake manifold or directly into the combustion chamber of a cylinder of the internal combustion engine. The fuel supply arrangement may comprise a fuel reservoir for storing fuel and a fuel injector for injecting fuel into the intake manifold or the combustion chamber.

[0003] It is an object of the present disclosure to provide an improved method for operating a fuel supply arrangement. It is a further object of the present disclosure to provide a control device and a computer program product, respectively for carrying out the method.

[0004] These objects are achieved by a method, a control device and a computer program product according to the independent claims. Advantageous embodiments and developments are disclosed in the respective dependent claims.

[0005] According to one aspect, a method for operating a fuel supply arrangement for an internal combustion engine is disclosed. According to a further aspect, a control device for the fuel supply arrangement is disclosed, the control device being operable to carry out the method. According to another aspect, a computer program product is disclosed which is executable to perform the method. In particular, the computer program product comprises computer-readable instructions on an electronic storage medium, the instructions performing the method when loaded and executed in a suitable computer, in particular in the control device.

[0006] The fuel supply arrangement comprises a fuel reservoir, also known as fuel rail. The fuel supply arrangement further comprises a pump, in particular a high-pressure pump. The pump is hydraulically coupled to the fuel reservoir for pressurizing the fuel in the fuel reservoir.

[0007] Further, the fuel supply arrangement comprises at least one fuel injection valve which comprises an injection nozzle. The fuel injection valve is hydraulically coupled to the fuel reservoir for dispensing fuel from the fuel supply arrangement through the injection nozzle. The fuel injection valve further comprises a valve needle and an electromagnetic actuator assembly. The valve needle is displaceable for sealing and unsealing the injection nozzle.

[0008] The electromagnetic actuator assembly has a solenoid for displacing the valve needle. More specifically, the electromagnetic actuator assembly may have an armature which is mechanically coupled with the valve needle for displacing the valve needle to unseal the injection nozzle. The solenoid, when energized generates a magnetic field that may interact with the armature for moving the armature to displace the valve needle. Such electromagnetic actuators are known, in principle, to the person skilled in the art and, therefore, are not described in more detail, here.

[0009] Further, the fuel supply arrangement may comprise the control device. The control device is in particular operable to energize the solenoid and to measure an electrical current through the solenoid. The control device may be comprised by an engine control unit (ECU) or may be represented by an ECU.

[0010] The method comprises energizing the solenoid to displace the valve needle to a fully open position for unsealing the injection nozzle by means of operating the control device in such fashion that the electrical current through the solenoid, during a first period of time, rises to a peak value and subsequently decreases to a value within a first current range, and, in a subsequent second period of time, is maintained within the first current range. The first current range has an upper limit and a lower limit. The upper limit of the first current range has a smaller magnitude than the peak value in the first period of time. The durations of the first and second period of time are preferably selected such that the valve needle reaches the fully open position within the second period of time.

[0011] In an expedient embodiment, the method comprises subsequently energizing the solenoid for retaining the valve needle in the fully open position by means of operating the control device to decrease the current through the solenoid from the first current range to a value within a second current range and, during a third period of time subsequent to the second period of time, maintaining it within the second current range. The second current range has an upper limit and a lower limit. The upper limit of the second current range has a smaller magnitude than the lower limit of the first current range.

[0012] In a preferred embodiment of the method, the control device is subsequently operated for de-energizing the solenoid for re-sealing the injection nozzle, in particular by decreasing the current to a value below the second current range, preferably to 0.

[0013] The first period of time, the second period of time - and the third period of time where appropriate - preferably succeed each other to define a single injection event. The first period of time and/or the second period of time and/or the third period of time each may have a duration of 0.2 ms or more, in particular of 0.4 ms or more, in one embodiment. In one development, the first period of time and/or the second period of time and/or the third period of time each may have a duration of 1 ms or less.

[0014] During the second and/or third period of time, the current is preferably basically constant, i.e. it preferably deviates by 20 % or less, in particular by 10 % or less from the time average of the current in the respective period of time. For example, the difference between the upper limit and the lower limit of the respective (i.e. first or second) current range is 30 % or less, in particular 15 % or less, of the mean value of the upper limit and the lower limit. In one embodiment, the difference between the upper limit and the lower limit of the second current range and/or the difference between the upper limit and the lower limit of the third current range is 1.5 A or less, in particular 1 A or less.

[0015] In addition, the method comprises operating the control device for measuring the electrical current through the solenoid at least during the second period of time, and for determining a point in time at which the valve needle has reached the fully open position by means of evaluating the measured electrical current.

[0016] In an expedient embodiment, the method further comprises inferring the fuel pressure in the fuel reservoir from the determined point in time at which the valve needle has reached the fully open position. In particular, the time difference between the start of the first period of time and the point in time at which the valve needle has reached the fully open position may be related to the fuel pressure. This time difference is also abbreviated as "the opening time" in the following. More specifically, the opening time may increase when the fuel pressure increases. For example, the fuel pressure is directly proportional to the opening time.

[0017] With advantage, the method uses the fuel injection valve for determining the fuel pressure in the fuel reservoir. In this way, a separate pressure sensor can be omitted. Thus, in an advantageous embodiment, the fuel supply arrangement does not comprise a separate pressure sensor.

[0018] Determining the point in time at which the valve needle has reached the fully open position within the second period of time may be particularly simple and/or reliable. In particular, inferring the fuel pressure from the opening time may be more reliable than inferring the fuel pressure by means of monitoring the injector closing event, in particular for injection events having a comparatively short duration.

[0019] The method comprising the first, second and third period of time may be particularly advantageous when the control unit is operated to switch from a first voltage source to a second voltage source for energizing the solenoid, the switching in particular taking place during the second period of time or during a transient period between the second and third periods of time. In this way, the risk of an unintentional current drop, leading to a movement of the valve needle away from the fully open position is particularly low. This may be of particular importance if the fuel injection valve is constructed for operating at comparatively high fuel pressures, for example in the range 200 bar to 250 bar and, thus, a coil having a comparatively large impedance is required which may lead to particularly high peak values of the operating current.

[0020] In an expedient embodiment, the fuel supply arrangement has a plurality of fuel injection valves. For example, the fuel supply arrangement is provided for an internal combustion engine having multiple cylinders and each fuel injection valve of the fuel supply arrangement is assigned to one of the cylinders. In an expedient embodiment of the method, a point in time at which the respective fuel injection valve has reached the fully open position is determined for each of the fuel injection valves. With advantage, the fuel injection valves function as a plurality of fuel pressure sensors in this way so that the method allows for a particularly reliable operation and provides a particularly cost-efficient redundancy.

[0021] In an embodiment of the method, determining the point in time at which the valve needle has reached the fully open position comprises detecting a current minimum in the second period of time. Detecting the current minimum within the second period of time may involve a particularly uncomplicated evaluation of the current by the control device.

[0022] In one embodiment, the method comprises comparing the inferred fuel pressure to a predetermined fuel pressure and operating the control device to generate a signal if the inferred fuel pressure deviates from the predetermined fuel pressure at least by a predetermined amount. In one embodiment, the method comprises evaluating the inferred fuel pressure for detecting a failure of the fuel supply arrangement. For example, at least one of the following failure modes is detected: "fuel pressure outside the specified operating range", "fuel pressure too low", "fuel pressure too high", "damaged pump", "uncontrolled high fuel pressure because of inlet valve broken". In an expedient development, a warning message or an error message is generated from the signal. Thus, compliance with on-board diagnostic (OBD) requirements is easily achievable by means of the method.

[0023] In one embodiment, the pump is provided for pressurizing the fuel in the fuel reservoir to a pressure of 30 bar or more, in particular of 50 bar or more and of 150 bar or less, in particular of 100 bar or less. The method is particularly well suited for operating fuel supply systems in such - medium or relatively low - pressure ranges. The fuel supply system for operating at these pressure ranges can be manufactured particularly cost-efficient, in particular with respect to the fuel rail design. The torque losses from driving the pump may be particularly small in these pressure ranges. Moreover, particular small minimum fuel doses may be dispensable by the fuel injector in this way.

[0024] In one embodiment, the fuel supply arrangement is provided for operating at a constant fuel pressure in each operation condition of the internal combustion engine. Advantageously, this allows a particularly uncomplicated construction and operation of the fuel supply arrangement.

[0025] Further advantages, advantageous embodiments and developments of the method, the control device and the fuel supply arrangement will become apparent from the exemplary embodiments which are described below in association with schematic figures.

[0026] In the figures:

Figure 1

shows a schematic diagram of a fuel supply arrangement,

Figure 2

shows a schematic cross section of a portion of a fuel injection valve of the fuel supply arrangement, and

Figure 3

shows the current I through the solenoid of the fuel injection valve as a function of time t during one injection event of an exemplary embodiment of a method for operating the fuel supply arrangement.

[0027] In the exemplary embodiments and figures, similar, identical or similarly acting elements are provided with the same reference symbols. The figures are not regarded to be true to scale. Rather, individual elements in the figures may be exaggerated in size for better representability and/or better understanding.

[0028] Figure 1 shows a schematic diagram of a fuel supply arrangement 10 of an internal combustion engine. The internal combustion engine serves, for example, to drive a motor vehicle.

[0029] The fuel supply system 10 comprises a fuel tank 12, a first pump 14, a fuel dosing unit 16, a high-pressure pump 20, a fuel reservoir 24, at least one injection valve 26 and at least one combustion chamber 28.

[0030] For example, the internal combustion engine is a four-cylinder engine having four combustion chambers 28. Preferably, one injection valve 26 is associated to each combustion chamber 28.

[0031] The first pump 14 delivers fuel from the fuel tank 12 to an inlet of the fuel dosing unit 16. The fuel dosing unit 16 comprises an outlet which leads the fuel to the high-pressure pump 20.

[0032] Furthermore, the fuel supply arrangement 10 comprises a fuel supply line with different sections. A first fuel supply line section 22A hydraulically couples the fuel tank 12 and the first pump 14, a second fuel supply line section 22B hydraulically couples the first pump 14 with the fuel dosing unit 16 and a third fuel supply line section 22C hydraulically couples the fuel dosing unit 16 with the high-pressure pump 20.

[0033] The high-pressure pump 20 preferably has a delivery chamber with a jack valve disposed on its inlet side. It compresses the fuel to a high pressure between 40 bar and 150 bar, preferably between 50 bar and 100 bar, wherein the limits are included in each case. The high-pressure pump 20 may be designed to deliver fuel under error-free operation conditions with a constant or mainly constant pressure value, for example of around 90 bar. The high-pressure pump 20 is hydraulically coupled to the fuel reservoir 24 to deliver the fuel into the fuel reservoir 24, where the fuel is stored under the high pressure.

[0034] The at least one injection valve 26 is attached to that fuel reservoir 24 and has an injection nozzle 261 for dispensing fuel from the fuel supply arrangement 10 through the injection nozzle 261 directly into the associated combustion chamber 28 of the internal combustion engine.

[0035] Figure 2 shows a schematic cross section of a portion of one fuel injection valve 26 of the fuel supply arrangement 10, received in the associated combustion chamber 28.

[0036] The at least one injection valve 26 comprises valve needle 263 for sealing and unsealing the injection nozzle 261 and an electromagnetic actuator assembly 265 for displacing the valve needle 263. The electromagnetic actuator assembly 265 comprises a solenoid 267 for displacing the valve needle 263 in order to unseal the injection nozzle 261. The actuator assembly 265 further comprises a spring for biasing the valve needle 263 towards the injection nozzle 261 in order to seal the injection nozzle 261 when the solenoid 267 is not energized.

[0037] The fuel supply arrangement 10 additionally comprises a control device 40 (see

[0038] Figures 1 and 2). The control device 40 may also be denoted as an apparatus to operate the fuel supply arrangement 10. The control device 40 is electrically connected to the actuator assembly 265, in particular to the solenoid 267, so that is operable to impress a current I into the solenoid 267 and to measure the current I through the solenoid 267. For example, the control device 40 is connected to the actuator assembly 265 by means of one or more wires 30, the wires 30 in particular making part of a wire harness.

[0039] In the following, an exemplary embodiment of a method for operating the fuel supply arrangement 10 for injecting a fuel dose from the fuel reservoir 24 into one combustion chamber 28 is described. Preferably, the method comprises subsequently injecting fuel doses from the fuel reservoir 24 into each of the combustion chambers 28.

[0040] The control device 40 is operated to energize the solenoid 267 by means of impressing a current I into the solenoid. For example, the control device 40 is connected to at least one voltage source and supplies one or more voltage pulses to the solenoid 267.

[0041] Figure 3 shows the current I in Ampère through the solenoid 267 as a function of time t in milliseconds during one injection event.

[0042] Preceding the injection event, the fuel injection valve 26 is closed. There is no current I through the solenoid 267 and the valve needle 263 is in a closing position in which it seals the injection nozzle 261.

[0043] Starting at a point t_S in time, the control device 40 is operated for a first period of time T₁ to apply a voltage to the solenoid 267 in such fashion that the current I through the solenoid 267 rises to a peak value I_P and subsequently decreases to a value within a first current range DI₁. In a second period of time T₂, the second period of time T₂ directly following the first period of time T₁, the current I is maintained within the first current range DI₁. An upper limit I_1U of the first current range DI₁ has a smaller magnitude than the peak value I_P.

[0044] In the present exemplary embodiment, the first period of time T₁ starts at a point in time t_S of around 0.7 ms and has a duration of approximately 1 ms. The current I rises to a peak value I_P of 12 A in the first period of time T₁. The second period of time T₂ has a duration of ca. 0.7 ms. The first current range DI₁ is bounded by an upper limit I_1U of ca. 6.6 A and a lower limit I_1L of ca. 5.75 A. The difference between the upper limit I_1U and the lower limit I_1L of the first current range DI₁ is 0.85 A, i.e. less than 14 % of the mean value of the upper limit and the lower limit of (I_1U + I_1L) / 2 = 6.175 A. In other words, the current through the solenoid 267 is basically constant during the second period of time T₂.

[0045] The current I through the solenoid 267 effects a magnetic force which is transferred to the valve needle 263 to displace the latter from the closing position for unsealing the injection nozzle 261. The durations of the first and second periods of time T₁, T₂ are selected such that the valve needle 263 reaches a fully open position during the second period of time T₂. For example, the injection valve 26 has a mechanical stop element - such as a pole piece of the electromagnetic actuator assembly 265 - which is operable to block further displacement of the valve needle 263 when the latter reaches the fully open position.

[0046] The second period of time T₂ is directly followed by a first transient period T_D1 - having a duration of approximately 0.2 ms in the present embodiment - in which the control device 40 is operated to decrease the current through the solenoid 267 from the first current range DI₁ to a value within a second current range DI₂ and to maintain it within the second current range DI₂ for a third period of time T₃. An upper limit I_2U of the second current range DI₂ has a smaller magnitude than the lower limit I_1L of the first current range DI₁. Lowering the current I to the second current range DI₂ after the valve needle has reached its fully open position during the second period of time T₂ may advantageously result in a particularly low power consumption of the fuel supply arrangement 10 in spite of a comparatively short opening time T_O.

[0047] In the present exemplary embodiment, the third period of time T₃ may have a duration of approximately 0.6 ms. The duration of the third period of time T₃ may vary according to the amount of fuel to be dispensed during the injection event. The second current range DI₂ is bounded by an upper limit I_2U of ca. 3.5 A and a lower limit I_2L of ca. 2.75 A. The difference between the upper limit I_2U and the lower limit I_2L of the second current range DI₂ is 0.75 A, i.e. 24 % of the mean value of the upper limit and the lower limit of (I_2U + I_2L) / 2 = 3.125 A. In other words, the current through the solenoid 267 is basically constant during the third period of time T₃.

[0048] At the end of the third period of time T₃, the control unit 40 switches of the current I through the solenoid 267 so that the solenoid is de-energized. Thus, the current I through the solenoid 267 returns to 0 A during a second transient period T_D2 - having a duration of approximately 0.25 ms in the present embodiment - allowing the valve needle 263 to return to the closing position for re-sealing the injection nozzle 261.

[0049] Although being basically constant during the second period of time T₂, the current through the solenoid 267 is time-dependent in this period of time within the limits of the first current range DI₁. At least during the second period of time T₂, the control device 40 is operated to measure the current I through the solenoid 267 and to detect a current minimum, in particular corresponding to the lower limit I_1L of the first current range DI₁. The method makes use of the idea that the current minimum is correlated to the point in time to when the valve needle 263 has reached the fully open position. The control device 40 is operated to determine the point in time to corresponding to the current minimum - i.e. the point in time to when the valve needle 263 has reached the fully open position - and preferably calculates the opening time T_O of the valve needle 263, in particular as the difference between the start time t_S and the fully open time t_O: T_O = to - t_S.

[0050] The control device 40 is further operated to infer the fuel pressure in the fuel reservoir 24 from the fully open time to - more specifically from the opening time T_O. For example, the method may make use of the idea that there is a linear correlation between the opening time T_O and the fuel pressure in the fuel reservoir 24. This correlation can for example be stored in a memory unit of the control device 40 and can be used by the control unit 40 for calculating the fuel pressure from the opening time T_O.Therefore, a separate pressure sensor for measuring the fuel pressure in the fuel reservoir 24 is not needed and the fuel supply arrangement 10 does not comprise such a separate pressure sensor.

[0051] In one embodiment, the control device 40 is operable to monitor the inferred fuel pressure, in particular for detecting a failure of the fuel supply arrangement 10. For example, the control device 40 generates a signal if the inferred fuel pressure deviates from a predetermined fuel pressure at least by a predetermined amount. Preferably, the control device 40 is operable to generate a warning signal or a warning message if a failure of the fuel supply arrangement 10 is detected.

[0052] The control device 40 may comprise a processor unit and a memory unit. The memory unit may comprise computer readable instructions which, when executed by the processor unit, are operable to perform the method.

[0053] The invention is not limited to specific embodiments by the description on basis of these exemplary embodiments. Rather, it comprises any combination of elements of different embodiments. Moreover, the invention comprises any combination of claims and any combination of features disclosed by the claims.

Claims

1. Method for operating a fuel supply arrangement (10) for an internal combustion engine,
the fuel supply arrangement (10) comprising

- a fuel reservoir (24),

- a pump (20) hydraulically coupled to the fuel reservoir (24) for pressurizing the fuel in the fuel reservoir,

- at least one fuel injection valve (26) hydraulically coupled to the fuel reservoir (24) for dispensing fuel from the fuel supply arrangement (10) through an injection nozzle (261) of the fuel injection valve (26), the fuel injection valve (26) comprising a valve needle (263) which is displaceable for sealing and unsealing the injection nozzle (261) and an electromagnetic actuator assembly (265) having a solenoid (267) for displacing the valve needle (263), and

- a control device (40) for energizing the solenoid (267) and for measuring an electrical current (I) through the solenoid (267),

the method comprising:

- energizing the solenoid (267) to displace the valve needle (263) to a fully open position for unsealing the injection nozzle (261) by means of operating the control device (40) in such fashion that the electrical current (I) through the solenoid (267), during a first period of time (T₁), rises to a peak value (I_P) and subsequently decreases to a value within a first current range (DI₁), and, in a subsequent second period of time (T₂), is maintained within the first current range (DI₁), the upper limit (I_1U) of the first current range (DI₁) having a smaller magnitude than the peak value (I_P) in the first period of time (T₁),

- operating the control device (40) for measuring the electrical current (I) through the solenoid (267) at least during the second period of time (T₂),

- determining a point in time (to) at which the valve needle (263) has reached the fully open position by means of evaluating the measured electrical current (I),

- inferring the fuel pressure in the fuel reservoir (24) from the determined point in time (to) at which the valve needle (263) has reached the fully open position.

2. The method according to claim 1, wherein determining the point in time (to) at which the valve needle (263) has reached the fully open position comprises detecting a current minimum (I_1L) in the second period of time (T₂).

3. The method according to one of the preceding claims, further comprising, subsequent to the second period of time (T₂), energizing the solenoid (267) for retaining the valve needle (263) in the fully open position by means of operating the control device (40) to decrease the current (I) through the solenoid (267) from the first current range (DI₁) to a value within a second current range (DI₂) and, during a third period of time (T₃) subsequent to the second period of time (T₂), maintaining it within the second current range (DI₂), the upper limit (I_2U) of the second current range (DI₂) having a smaller magnitude than the lower limit (I_1L) of the first current range (DI₁).

4. The method according to one of the preceding claims, further comprising comparing the inferred fuel pressure to a predetermined fuel pressure and operating the control device (40) to generate a signal if the inferred fuel pressure deviates from the predetermined fuel pressure at least by a predetermined amount.

5. The method according to one of the preceding claims, wherein the fuel supply arrangement (10) is provided for operating at a constant fuel pressure in each operation condition of the internal combustion engine.

6. The method according to one of the preceding claims, wherein the fuel supply arrangement (10) does not comprise a separate pressure sensor for measuring the fuel pressure in the fuel reservoir (24).

7. The method according to one of the preceding claims, comprising evaluating the inferred fuel pressure for detecting a failure of the fuel supply arrangement (10).

8. A control device (40) for a fuel supply arrangement (10), the fuel supply arrangement (10) comprising

- a fuel reservoir (24),

- a pump (20) hydraulically coupled to the fuel reservoir (24) for pressurizing the fuel in the fuel reservoir (24),

- at least one fuel injection valve (26) hydraulically coupled to the fuel reservoir (24) for dispensing fuel from the fuel supply arrangement (10) through an injection nozzle (261) of the fuel injection valve (26), the fuel injection valve (26) comprising a valve needle (263) which is displaceable for sealing and unsealing the injection nozzle (261) and an electromagnetic actuator assembly (265) having a solenoid (267) for displacing the valve needle (267), and

- the control device (40)

wherein the control device (40) is operable to energize the solenoid (267) and to measure an electrical current (I) through the solenoid (267),
the control device (40) being operable to carry out the method according to one of the preceding claims.

9. A fuel supply arrangement (10) comprising

- a fuel reservoir (24),

- a pump (20) hydraulically coupled to the fuel reservoir (24) for pressurizing the fuel in the fuel reservoir (24),

- at least one fuel injection valve (26) hydraulically coupled to the fuel reservoir (24) for dispensing fuel from the fuel supply arrangement (10) through an injection nozzle (261) of the fuel injection valve (26), the fuel injection valve (26) comprising a valve needle (263) which is displaceable for sealing and unsealing the injection nozzle (261) and an electromagnetic actuator assembly (265) having a solenoid (267) for displacing the valve needle (263), and

- the control device (40) of claim 8.

10. A computer program product being executable to perform the method according to one of claims 1 to 7.

Drawing