Method and apparatus for operating a fuel supply system

Abstract

 The fuel supply system (10) comprises at least one injection valve (26) comprising a solenoid actuator. Furthermore the fuel supply system (10) comprises a high-pressure pump (20) delivering fuel with a given pressure in a fuel line or a manifold (24), the fuel line or the manifold (24) respectively being hydraulically coupled with an outlet of the high-pressure pump (20) and an inlet of the injection valve (26). The method comprises the following steps: The solenoid actuator is activated according to a predetermined activation signal with a given activation period (Ti) for effecting a fluid flow out of an injection nozzle of the injection valve (26). An actuator voltage (U C) is captured at least in a closing phase (T phase) which starts after the activation period (Ti), wherein the actuator voltage (U_C) represents a voltage induced in the solenoid actuator. It is detected if the fuel pressure of the fuel delivered by the high-pressure pump (20) is within a given range depending on the captured actuator voltage (U C) and a first signal is generated depending on the detection result. Additionally or alternatively the fuel pressure of the fuel delivered by the high-pressure pump (20) is determined depending on the captured actuator voltage (U_C) and a second signal is generated depending on the determined fuel pressure.

Description

[0001] The invention relates to a method and an apparatus for operating a fuel supply system for an internal combustion engine.

[0002] Increasingly stringent rules concerning the admissibility of noxious emissions from internal combustion engines which are arranged in vehicles render it necessary to take various measures which reduce the emission. One way to reduce these emissions is to improve the combustion process in the internal combustion engine.

[0003] In this regard, today's fuel supply systems, for instance gasoline direct injection systems, comprise a fuel pressure sensor arranged in a manifold of the internal combustion engine. The fuel pressure measurement values are used by an electronic control unit (ECU) to control in a closed loop mode the fuel pressure by means of limiting the amount of fuel introduced into the high-pressure pump during a filling phase of the high-pressure pump. The captured fuel pressure is also used for an On-Board-Diagnostic system (OBD system). OBD systems give a vehicle user or a repair technician access to state of health information for various vehicle sub-systems.

[0004] The object of the invention is to provide a method and an apparatus for operating a fuel supply system for an internal combustion engine which contributes to a reliable operation of the fuel supply system and a simpler manufacturing of the fuel supply system.

[0005] This obj ect is achieved by the features of the independent claims. Advantageous embodiments of the invention are given in the sub-claims.

[0006] The invention is distinguished by a method and a corresponding apparatus to operate a fuel supply system for an internal combustion engine. The fuel supply system comprises at least one injection valve comprising a solenoid actuator. Furthermore the fuel supply system comprises a high-pressure pump delivering fuel with a given pressure in a fuel line or a manifold, the fuel line or the manifold respectively being hydraulically coupled with an outlet of the high-pressure pump and an inlet of the injection valve. The method comprises the following steps: The solenoid actuator is activated according to a predetermined activation signal with a given activation period for effecting a fluid flow out of an injection nozzle of the injection valve. An actuator voltage is captured at least in a closing phase which starts after the activation period, wherein the actuator voltage represents a voltage induced in the solenoid actuator. It is detected if the fuel pressure of the fuel delivered by the high-pressure pump is within a given range depending on the captured actuator voltage and a first signal is generated depending on the detection result. Additionally or alternatively the fuel pressure of the fuel delivered by the high-pressure pump is determined depending on the captured actuator voltage and a second signal is generated depending on the determined fuel pressure.

[0007] In this way, advantageously, the fuel pressure in the fuel line respectively in the manifold can be easily determined and/or supervised. The fuel pressure in the fuel line respectively in the manifold can be easily determined and/or supervised by means already available in the fuel supply system. An additional pressure sensor capturing the fuel pressure of the fuel delivered by the high-pressure pump is not necessary anymore. The omission of the pressure sensor has the advantage of reducing costs, cabling efforts and the number of potential erroneous components. In this way, it is also possible to check if each individual injection valve operates with a correct fuel pressure.

[0008] The injection valve as single element and as a part of a larger population may have a rather predictable, stable and reliable behaviour during an opening and/or closing event.

[0009] The injection valve may comprise a valve needle preventing a fluid flow out of the injection nozzle in a closing position and enabling the fluid flow of the injection nozzle apart from the closing position. Detecting if the fuel pressure of the fuel delivered by the high-pressure pump is within a given range, or determining the fuel pressure of the fuel delivered by the high-pressure pump, is performed depending on the captured actuator voltage which may be captured during the closing phase but temporally before the valve needle reaches its closing position.

[0010] The actuator comprises, for example, an armature, which is for instance mechanically coupled with the valve needle, and a coil. A core may be assigned to the actuator. The coil and the core form an electromagnet. The actuator and other elements of the injection valve guiding and/or amplifying a magnetic field induced by the coil form an electro-magnetic circuit. An electrical behaviour of this electro-magnetic circuit can be characterized by the actuator voltage. During activation the magnetic field induced by the coil is controlled by the activation signal. In this way the armature is directly controlled by the activation signal during the activation period. After the activation period, when the activation signal has returned to zero or another off state this force coupling is interrupted and there is the closing phase. There is still some energy stored in the electro-magnetic circuit. During the closing phase the electro-magnetic circuit is discharged and the actuator voltage returns to zero. The invention is based on the finding that during the closing phase the movement of the armature and therefore the actuator voltage depends on the fuel pressure in the injection valve during this closing phase. Also an injector current depends on the fuel pressure in the injection valve during this closing phase. This injector current may be also used to determine and/or supervise the fuel pressure in the injection valve.

[0011] In an advantageous embodiment the high-pressure pump is designed to deliver, under error-free operation conditions, fuel with a constant or mainly constant pressure value. In this case no control of the fuel pressure is necessary. It may be sufficient to supervise the fuel pressure.

[0012] In a further advantageous embodiment the actuator voltage is captured at a given first time during the closing phase and it is detected if the fuel pressure is within a given range depending on a comparison of the value of the captured actuator voltage with a given maximum value and/or minimum value. In this way, advantageously, the fuel pressure in the fuel line, respectively in the manifold, can be easily supervised. Preferably the given first time is temporally before the valve needle reaches its closing position. In this further time section, between start of closing phase and a point of time the closing event is completed, the actuator voltage is also influenced by the fuel pressure. The actuator voltage in this further time section is related to the solenoid magnetic properties of the actuator and the actuator voltage is only slightly sensitive to a lifetime degradation of the actuator.

[0013] In a further advantageous embodiment it is detected if the actuator voltage reaches a given reference value and a detection time is captured when the actuator voltage reaches the reference value. It is detected if the fuel pressure is within a given range depending on a comparison of the detection time with a given maximum reference time and/or minimum reference time. In this way, advantageously, the fuel pressure in the fuel line, respectively in the manifold, can easily be supervised. Preferably the given reference value is chosen so that the actuator voltage reaches the reference value temporally before the valve needle reaches its closing position.

[0014] In a further advantageous embodiment an actuator voltage characteristic is captured at least for a given first period of time during the closing phase and it is detected if the fuel pressure is within a given range depending on the captured actuator voltage characteristic and a given actuator voltage characteristic diagram. Additionally or alternatively the fuel pressure is determined depending on the captured actuator voltage characteristic and the given actuator voltage characteristic diagram.

[0015] In this way, advantageously, the fuel pressure in the fuel line, respectively in the manifold, can easily be determined and/or supervised. Detecting if the fuel pressure of the fuel delivered by the high-pressure pump is within a given range and/or determining the fuel pressure of the fuel delivered by the high-pressure pump may be performed depending on a section of the captured actuator voltage characteristic and the given actuator voltage characteristic diagram which represent the captured, respectively the given, actuator voltage during the closing phase but temporally before the valve needle reaches its closing position. Detecting if the fuel pressure of the fuel is within a given range and/or determining the fuel pressure may be performed depending on a comparison of the actuator voltage characteristic and the given actuator voltage characteristic diagram. For the comparison a correlation function may be used. The captured actuator voltage characteristic may be noisy because of a system noise and/or noise from external sources. For evaluating the actuator voltage characteristic it may be advantageous to filter the actuator voltage characteristic by a smoothing filter to sub-press high frequency signal parts, which may be mainly caused by the noise.

[0016] In a further advantageous embodiment the injection valve comprises a valve needle preventing a fluid flow out of the injection nozzle in a closing position and enabling the fluid flow of the injection nozzle apart from the closing position. The actuator voltage characteristic is captured at least over a period of time during which the valve needle could reach the closing position. A closing time representing a time when the valve needle reaches the closing position is determined depending on the actuator voltage characteristic. It is detected if the fuel pressure is within the given range depending on the determined closing time. Alternatively or additionally the fuel pressure is determined depending on the determined closing time. In this way, advantageously, the fuel pressure of the high-pressure pump can be easily determined and/or supervised without additional effort. For a precise dosing of the fluid it is advantageous to know the closing time. Thus, the closing time is determined anyway by the system and is therefore available without additional measurement or calculation effort for determining and/or supervising the fuel pressure.

[0017] Exemplary embodiments of the invention are shown in the following with the aid of schematic drawings. These are as follows:

Figure 1

an embodiment of fuel supply system,

Figure 2

a diagram of an actuator voltage characteristic,

Figure 3

a first actuator voltage characteristic diagram,

Figure 4

a second actuator voltage characteristic diagram and

Figure 5

a third actuator voltage characteristic diagram.

[0018] Elements of the same design and function that appear in different illustrations are identified by the same reference character.

[0019] Figure 1 shows a schematic diagram of a fuel supply system 10 of an internal combustion engine. The internal combustion engine serves, for example, to drive a motor vehicle. 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 manifold 24, at least one injection valve 26 and at least one combustion chamber 28 associated to the at least one injection valve 26. The first pump 14 delivers from the fuel tank 12 fuel 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. Furthermore, the fuel supply system 10 comprises a fuel supply line with different sections. A first fuel supply line section 22' hydraulically couples the fuel tank 12 and the first pump 14, a second fuel supply line section 22" hydraulically couples the first pump 14 with the fuel dosing unit 16 and a third fuel supply line section 22''' hydraulically couples the fuel dosing unit 16 with the high-pressure pump 20. The high-pressure pump 20 preferably has a delivery chamber with a jack valve disposed on its inlet side, compresses the fuel to a very high pressure and delivers it into the manifold 24, wherein the fuel is stored under high pressure. The high-pressure pump 20 may be designed to deliver fuel under error-free operation conditions with a constant or mainly constant pressure value. The at least one injection valve 26 is attached to that manifold 24, which directly injects fuel into the associated combustion chambers 28 of the internal combustion engine.

[0020] The at least one injection valve 26 comprises a solenoid actuator. Furthermore the injection valve 26 may comprise a valve needle preventing a fluid flow out of the injection nozzle in a closing position and enabling the fluid flow of the injection nozzle apart from the closing position.

[0021] In Figure 1 additionally a control unit 40 is shown. This control unit 40 may also be called apparatus to operate the fuel system. The control unit 40 may comprise a processor unit and a memory unit. The control unit 40 is designed to activate the solenoid actuator according to a predetermined activation signal with a given activation period Ti for effecting a fluid flow out of the injection nozzle of the injection valve 26. Furthermore the control unit 40 is designed to capture an actuator voltage U_C at least in a closing phase T phase which starts after the activation period Ti, wherein the actuator voltage U_C represents a voltage induced in the solenoid actuator. The control unit 40 is designed to detect if the fuel pressure of the fuel delivered by the high-pressure pump 20 is within a given range depending on the captured actuator voltage U_C and to generate a first signal depending on the detection result and/or to determine the fuel pressure of the fuel delivered by the high-pressure pump 20 depending on the captured actuator voltage U_C and to generate a second signal depending on the determined fuel pressure.

[0022] The first signal may be send to an On-Board-Diagnostic (OBD) system. In case the fuel pressure is not correct the OBD system may generate an error and/or warning messages for a vehicle user. The second signal may be used, if necessary, to control in a closed loop mode the fuel pressure by means of limiting the amount of fuel introduced into the high-pressure pump 20 during a filling phase of the high-pressure pump 20.

[0023] Figure 2 shows a diagram of an actuator voltage characteristic Uc during an activation period Ti and a closing phase T_phase. The actuator is activated according to a predetermined activation signal with the given activation period Ti for effecting a fluid flow out of the injection nozzle of the injection valve 26. The actuator, for instance, comprises actuator control pins. The activation signal may be applied to these control pins. The actuator voltage U_C can, e. g., be measured on these control pins by sampling the actuator voltage U_C with given sampling instances.

[0024] The actuator comprises, for example, an armature, a coil and a core. The coil and the core form an electromagnet. The actuator and the other elements guiding and/or amplifying a magnetic field induced by the coil form an electro-magnetic circuit. An electrical behaviour of this electro-magnetic circuit can be characterized by the actuator voltage U_C. During the closing phase T phase the electro-magnetic circuit is discharged and the actuator voltage U_C returns to zero. Depending on an architecture of the injection valve 26 the armature may has a different dynamic behaviour and so a different impact on the actuator voltage U_C.

[0025] Figure 3 shows a first actuator voltage characteristic Uc diagram. The diagram comprises different actuator voltage traces, which have been captured for different fuel pressure values of the high-pressure pump 20.

[0026] With respect to the time line, the diagram of Figure 3 shows a time section of the closing phase T phase during which the valve needle could reach the closing position. The valve needle of the injection valve 26 reaching the closing position, for instance by contacting a seat, causes a change in the dynamic behaviour of the armature. This change can be detected depending on the captured actuator voltage characteristic Uc.

[0027] The actuator voltage characteristic Uc is captured at least over a period of time during which the valve needle could reach the closing position. For instance, the actuator voltage U_C may be captured during the activation period Ti and the closing phase T_phase. Alternatively it is also possible that actuator voltage U_C may be captured only during the closing phase T_phase. A variation of the armature dynamic, which happens in a moment the valve needle reaches the closing position, can be detected depending on a the actuator voltage U_C.

[0028] For instance, a minimum of a first temporal derivative of the actuator voltage characteristic Uc characterizes the time the valve needle reaches the closing position. The closing time t_close may be determined in correlation with the minimum of the first temporal derivate of the actuator voltage characteristic Uc. The closing time t close depends on the fuel pressure. If the fuel pressure is within the given range it may be detected depending on the determined closing time t_close, e. g. by comparing the determined closing time t_close with a given maximum and/or given minimum closing time. The fuel pressure may be determined depending on the determined closing time t_close and given reference closing times for different fuel pressures. The reference closing times may be determined during manufacturing and may be stored in the memory of the control unit 40.

[0029] Figure 4 shows a second actuator voltage characteristic Uc diagram. The diagram comprises different actuator voltage traces, which have been captured for different fuel pressure values of the high-pressure pump 20.

[0030] With respect to the time line the diagram of Figure 4 shows a further time section of the closing phase T phase, which comprises mainly a pre-closing phase, a period of time which starts with the closing phase T phase but ends temporally before the valve needle reaches the closing position. The actuator voltage U_C during that pre-closing phase is also influenced by the fuel pressure. The closing time t_close of the actuator may drift over time because of a lifetime degradation of the actuator. In contrast during the pre-closing phase the actuator voltage U_C is mainly influenced by parameters like the activation signal and/or the electro-magnetic circuit characteristics of the actuator. These parameters are more stable during lifetime of the injection valve 26. Therefore, evaluating the actuator voltage U_C during the pre-closing phase may provide more reliable results than the evaluation of the closing time t_close. According to specific injection valve 26 designs it might be also possible that the closing time t_close can not be determined depending on the actuator voltage characteristic Uc because the electro-magnetic circuit of the actuator does not provide such a closing signal.

[0031] As indicated in Figure 4 it may be detected if the actuator voltage U_C reaches a given reference value U_ref and a detection time is captured when the actuator voltage U_C reaches the reference value U_ref. It may be detected if the fuel pressure is within a given range depending on a comparison of the detection time with a given maximum reference time t_max and/or minimum reference time t_min. Preferably the given reference value U ref is chosen so that the actuator voltage U_C reaches the reference value U_ref temporally before the valve needle reaches its closing position.

[0032] Figure 5 shows a third actuator voltage characteristic Uc diagram. The diagram comprises different actuator voltage traces, which have been captured for different fuel pressure values of the high-pressure pump 20.

[0033] With respect to the time line the diagram of Figure 5 shows the further time section of the closing phase T_phase, which comprises mainly the pre-closing phase.

[0034] As indicated in Figure 5 the actuator voltage U C may be captured at a given first time t1 during the closing phase T_phase and it may be detected if the fuel pressure is within a given range depending on a comparison of the value of the captured actuator voltage U_C with a given maximum value U_max and/or minimum value U_min.

[0035] Additionally or alternatively the actuator voltage characteristic Uc is captured, at least for a given first period of time, during the closing phase T_phase and it is detected if the fuel pressure is within a given range depending on the captured actuator voltage characteristic Uc and the given actuator voltage characteristic diagram. Additionally or alternatively the fuel pressure is determined depending on the captured actuator voltage characteristic Uc and the given actuator voltage characteristic diagram. Detecting if the fuel pressure of the fuel is within a given range and/or determining the fuel pressure may be performed depending on a comparison of actuator voltage characteristic Uc and the given actuator voltage characteristic diagram. The given actuator voltage characteristic diagram with different actuator voltage traces may be determined during manufacturing and may be stored in the memory unit of the control unit 40.

[0036] Setting the first time t1 and/or the first period of time in the pre-closing phase may has got the advantage that during the pre-closing phase the actuator voltage U_C is mainly influenced by parameters like the activation signal and/or the electro-magnetic circuit characteristics of the actuator and may depend only slightly on lifetime degeneration.

Claims

1. Method to operate a fuel supply system (10) for an internal combustion engine, the fuel supply system (10) comprises:

- at least one injection valve (26) comprising a solenoid actuator and

- a high-pressure pump (20) delivering fuel with a given pressure in a fuel line or a manifold (24), the fuel line or the manifold (24) respectively being hydraulically coupled with an outlet of the high-pressure pump (20) and an inlet of the injection valve (26), wherein the method comprises the following steps:

- activating the solenoid actuator according to a predetermined activation signal with a given activation period (Ti) for effecting a fluid flow out of an injection nozzle of the injection valve (26),

- capturing an actuator voltage (U_C) at least in a closing phase (T_phase) which starts after the activation period (Ti), wherein the actuator voltage (U C) represents a voltage induced in the solenoid actuator,

- detecting if the fuel pressure of the fuel delivered by the high-pressure pump (20) is within a given range depending on the captured actuator voltage (U C) and generating a first signal depending on the detection result and/or

- determining the fuel pressure of the fuel delivered by the high-pressure pump (20) depending on the captured actuator voltage (U C) and generating a second signal depending on the determined fuel pressure.

2. Method according to claim 1, wherein
the high-pressure pump (20) is designed to deliver fuel under error-free operation conditions with a constant or mainly constant pressure value.

3. Method according to claim 1 or 2, further comprising:

- capturing the actuator voltage (U_C) at a given first time (t1) during the closing phase (T_phase) and

- detecting if the fuel pressure is within a given range depending on a comparison of the value of the captured actuator voltage (U_C) with a given maximum value (U_max) and/or minimum value (U min).

4. Method in accordance with one of the preceding claims, further comprising:

- detecting if the actuator voltage (U_C) reaches a given reference value (U_ref) and capturing a detection time when the actuator voltage (U_C) reaches the reference value (U_ref),

- detecting if the fuel pressure is within a given range depending on a comparison of the detection time with a given maximum reference time (t_max) and/or minimum reference time (t_min).

5. Method in accordance with one of the preceding claims, further comprising:

- capturing an actuator voltage characteristic (Uc) at least for a given first period of time during the closing phase (T_phase) and

- detecting if the fuel pressure is within a given range depending on the captured actuator voltage characteristic (Uc) and a given actuator voltage characteristic diagram and/or

- determining the fuel pressure depending on the captured actuator voltage characteristic (Uc) and the given actuator voltage characteristic diagram.

6. Method in accordance with one of the preceding claims, wherein the injection valve (26) comprises a valve needle preventing a fluid flow out of the injection nozzle in a closing position and enabling the fluid flow of the injection nozzle apart from the closing position, and

- capturing an actuator voltage characteristic (Uc) at least over a period of time during which the valve needle could reach the closing position,

- determining a closing time (t close) representing a time when the valve needle reaches the closing position depending on the actuator voltage characteristic (Uc),

- detecting if the fuel pressure is within the given range depending on the determined closing time (t close) and/or

- determining the fuel pressure depending on the determined closing time (t_close).

7. Apparatus to operate a fuel supply system (10) for an internal combustion engine, the fuel supply system (10) comprises:

- at least one injection valve (26) comprising a solenoid actuator and

- a high-pressure pump (20) delivering fuel with a given pressure in a fuel line or a manifold (24), the fuel line or the manifold (24) respectively being hydraulically coupled with an outlet of the high-pressure pump (20) and an inlet of the injection valve (26), wherein the apparatus is designed:

- to activate the solenoid actuator according to a predetermined activation signal with a given activation period (Ti) for effecting a fluid flow out of an injection nozzle of the injection valve (26),

- to capture an actuator voltage (U C) at least in a closing phase (T_phase) which starts after the activation period (Ti), wherein the actuator voltage (U C) represents a voltage induced in the solenoid actuator,

- to detect if the fuel pressure of the fuel delivered by the high-pressure pump (20) is within a given range depending on the captured actuator voltage (U_C) and to generate a first signal depending on the detection result and/or

- to determine the fuel pressure of the fuel delivered by the high-pressure pump (20) depending on the captured actuator voltage (U_C) and to generate a second signal depending on the determined fuel pressure.

Drawing