GB2500206A

GB2500206A - Common rail fuel injection system

Info

Publication number: GB2500206A
Application number: GB201204367A
Authority: GB
Inventors: Massimiliano Melis; Antonio Arpaia; Vincenzo Rampino
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2012-03-12
Filing date: 2012-03-12
Publication date: 2013-09-18
Also published as: GB201204367D0

Abstract

Disclosed is a common rail fuel injection system for a diesel internal combustion engine. The fuel injection system comprises first 601 and second fuel pumps 603 and a fuel injector 160 the pumps and fuel injector being linked by a common rail 606. A target injection amount based on a nominal fuel injection quantity and a correction amount is supplied by the first pump to the second pump which passes the fuel on to the fuel injector. The nominal fuel quantity is based on the engine operating point and the fuel correction value is based on a function of an index indicative of at least one among an injector static leakage, an injector dynamic leakage, a second pressure pump efficiency. The first pump may be a low pressure pump and the second pump may be a high pressure pump.

Description

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METHOD OF OPERATING A FUEL INJECTION SYSTEM OF AN INTERNAL

COMBUSTION ENGINE

TECHNICAL FIELD

The present disclosure relates to a method of operating a fuel injection system of an 10 internal combustion engine.

BACKGROUND

It is known that modem Diesel engines are provided with a fuel injection system for directly injecting fuel into the cylinders of the engine.

15 The fuel injection system generally comprises a fuel common rail and a plurality of electrically controlled fuel injectors, which are individually located in a respective cylinder of the engine and which are hydraulically connected to the fuel common rail through dedicated feeding conduits.

The fuel in the common rail is maintained at a high pressure by an high pressure 20 pump and enters the injector through a fluid inlet and is directed towards a control chamber in the upper portion of the injector and to a lower portion of the injector where a nozzle and a movable needle are provided.

The fuel is supplied to the high pressure pump by a low pressure pump, which is located in the fuel tank and provides a lower fuel pressure than the high pressure pump, 25 a fuel filter being provided between an outlet of the low pressure pump and an inlet of the high pressure pump.

The low- pressure pump of the known fuel injection systems is a pump having a fixed delivery fuel capacity which is calculated for supplying a sufficient quantity of fuel in the worse operating engine condition, i.e. when the requested fuel quantity to be injected 30 is at the maximum value.

A drawbacks of the above disclosed injection systems is that the operating of the pump always in the worse operating condition, i.e. independently from the actual fuel quantity requested for operating the engine, is the cause of an unnecessary fuel consumption due to the mechanical and electrical power absorption for operating the low 35 pressure pump.

An object of an embodiment of the invention is to provide a method of operating a

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fuel injection system for an internal combustion engine which allows the delivering of the actual fuel requested for operating the engine for each operating point.

Another object of an embodiment of the invention is to provide a fuel injection system for an internal combustion engine that can be controlled for supplying the actual 5 fuel requested for operating the engine for each operating point.

These and other objects are achieved by a method of operating a fuel injection system having the features recited in the independent claim.

The dependent claims delineate preferred and/or especially advantageous aspects.

10 SUMMARY

An embodiment of the invention provides a method of operating a fuel injection system of an internal combustion engine, wherein the injection system comprises a first pressure pump for supplying fuel to a second pressure pump, the second pressure pump providing a higher fuel pressure than the first pressure pump, and a fuel injector, 15 hydraulically connected to the second pressure pump through a fuel rail, for injecting the fuel into a cylinder of the engine, the method comprising the following steps:

- determining a nominal fuel quantity, to be injected, as a function of an engine operating point,

- determining a correction fuel quantity as a function of an index indicative of at 20 least one among an injector static leakage, an injector dynamic leakage, a second pressure pump efficiency,

- determining a target quantity of fuel to supply to the second pressure pump by adding the nominal and the correction fuel quantity,

- regulating a first pressure pump operating parameter for supplying the target fuel 25 quantity to the second pressure pump.

An advantage of this embodiment is that a target fuel quantity is supplied from the first pressure pump to the second pressure pump, such a value depending on the engine operating point. This allow a reduction of fuel consumption and C02 emission.

According to another embodiment of the invention, a rotation speed of the first 30 pressure pump is chosen as first pressure pump operating parameter.

An advantage of this embodiment is that the control of rotation speed of the pump allows to deliver the target fuel quantity.

A further embodiment of the invention provides that the index indicative of the static leakage and of the dynamic leakage is experimentally determined on the basis of an 35 energizing time, an index indicative of the engine life, a rail pressure, and an engine temperature.

An advantage of this embodiment is that an experimentally pre-determination of the index allows a faster operating of the control circuit.

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According to an embodiment of the invention, the index indicative of the second pressure pump efficiency is experimentally determined on the basis of an engine speed, an index indicative of the engine life, a rail pressure, and a temperature.

As for the previous embodiment of the invention, an advantage of this embodiment 5 is that an experimentally pre-determination of the index allows a faster operating of the control circuit.

According to another embodiment of the invention, the method of operating the injection system provides the further step to adjust the first pressure pump operating parameter on the basis of a comparison of a monitored fuel pressure value at an inlet of 10 the second pressure pump with a nominal fuel pressure value thereof, determined for the engine operating point.

An advantage of this embodiment is a more accurate delivery of the target fuel quantity.

According to a further embodiment of the invention, the monitored fuel pressure 15 value is a measured by a pressure sensor.

An advantage of this embodiment a reliable and economic way to measure the fuel pressure.

An embodiment of the invention provides a fuel injection system for an internal combustion engine, comprising a first pressure pump for supplying fuel to a second 20 pressure pump, the second pressure pump providing a higher fuel pressure than the first pressure pump, and a fuel injector, hydraulically connected to the second pressure pump through a rail, for injecting the fuel into a cylinder of the engine, and an engine control unit for controlling the operating of the first and second pressure pumps and of the injector, wherein the first pressure pump is a variable displacement pump. 25 An advantage of this embodiment of the invention is that a variable displacement pump delivers the target fuel quantity, which is correlated to the engine operating point, by varying the speed of rotation.

Another embodiment of the invention provides that the second pressure pump comprises a pressure sensor for monitoring the fuel pressure, said pressure sensor 30 being connected to the engine control unit.

This embodiment allows a more accurate delivery of the target fuel quantity.

The method according to the invention can be carried out with the help of a computer program comprising a program-code for carrying out all the steps of the method described above, and in the form of a computer program product on which the 35 computer program is stored. The method can be also embodied as an electromagnetic signal, said signal being modulated to carry a sequence of data bits which represent a computer program to carry out all steps of the method.

Another embodiment of the invention provides an internal combustion engine

comprising an engine block defining a cylinder and a fuel injection system according to the above disclosure.

Another embodiment of the invention provides an apparatus of operating an internal combustion engine according to the above disclosure, the apparatus comprising: 5 - means for determining a nominal fuel quantity, to be injected, as a function of an engine operating point,

- means for determining a correction fuel quantity as a function of an index indicative of at least one among an injector static leakage, an injector dynamic leakage, a second pressure pump efficiency,

10 - means for determining a target quantity of fuel to supply to second pressure pump by adding the nominal and the correction fuel quantity,

- means for regulating a first pressure pump operating parameter for supplying the target fuel quantity to the second pressure pump.

Another embodiment of the invention provides an automotive system comprising an 15 internal combustion engine according to the above disclosure and an Electronic Control Unit, wherein the Electronic Control Unit is configured to:

- determining a nominal fuel quantity, to be injected into the cylinder, as a function of an engine (110) operating point,

- determining a target quantity of fuel to supply to second pressure pump by adding the nominal and the correction fuel quantity,

The advantages of the engine, of the apparatus and of the automotive system embodiments of the invention are substantially the same of those of the method of operating the internal combustion engine provided with a fuel injection system according to the various embodiments of the invention.

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BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments will now be described, by way of example, with reference to the accompanying drawings, wherein like numerals denote like elements, and in which:

35 Figure 1 shows an automotive system;

Figure 2 is a cross-section of an internal combustion engine belonging to the automotive system of figure 1;

Figure 3 represents a cross-sectional view, with parts removed for reasons of clarity,

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of a fuel injection system according to an embodiment of the invention;

Figure 4 is a schematic representation of a control logic that can be employed to control the fuel injection system of Figures 3-4 according to an embodiment of the invention;

5 Figure 5 is a schematic representation of a control logic that can be employed to control the fuel injection system of Figures 3-4 according to a different embodiment of the invention.

DETAILED DESCRIPTION

10 Exemplary embodiments will now be described with reference to the enclosed drawings without intent to limit application and uses.

Some embodiments may include an automotive system 100, as shown in Figures 1 and 2, that includes an internal combustion engine (ICE) 110 having an engine block 120 defining at least one cylinder 125 having a piston 140 coupled to rotate a crankshaft 145. 15 A cylinder head 130 cooperates with the piston 140 to define a combustion chamber 150. A fuel and air mixture (not shown) is disposed in the combustion chamber 150 and ignited, resulting in hot expanding exhaust gasses causing reciprocal movement of the piston 140.

The fuel is provided by a fuel injection system 600, equipped with an injector 160, 20 that will be described in more detail hereinafter.

Each of the cylinders 125 has at least two valves 215, actuated by a camshaft 135 rotating in time with the crankshaft 145. The valves 215 selectively allow air into the combustion chamber 150 from the port 210 and alternately allow exhaust gases to exit through a port 220. In some examples, a cam phaser 155 may selectively vary the timing 25 between the camshaft 135 and the crankshaft 145.

The air may be distributed to the air intake port(s) 210 through an intake manifold 200. An air intake duct 205 may provide air from the ambient environment to the intake manifold 200. In other embodiments, a throttle body 330 may be provided to regulate the flow of air into the manifold 200.

30 In still other embodiments, a forced air system such as a turbocharger 230, having a compressor 240 rotationally coupled to a turbine 250, may be provided. Rotation of the compressor 240 increases the pressure and temperature of the air in the duct 205 and manifold 200. An intercooler 260 disposed in the duct 205 may reduce the temperature of the air. The turbine 250 rotates by receiving exhaust gases from an exhaust manifold 35 225 that directs exhaust gases from the exhaust ports 220 and through a series of vanes prior to expansion through the turbine 250. The exhaust gases exit the turbine 250 and are directed into an exhaust system 270. This example shows a variable geometry turbine (VGT) with a VGT actuator 290 arranged to move the vanes to alter the flow of

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the exhaust gases through the turbine 250. In other embodiments, the turbocharger 230 may be fixed geometry and/or include a waste gate.

The exhaust system 270 may include an exhaust pipe 275 having one or more exhaust aftertreatment devices 280. The aftertreatment devices may be any device 5 configured to change the composition of the exhaust gases. Some examples of aftertreatment devices 280 include, but are not limited to, catalytic converters (two and three way), oxidation catalysts, lean NOx traps 285, hydrocarbon absorbers, selective catalytic reduction (SCR) systems, and particulate filters (DPF).

Other embodiments may include an exhaust gas recirculation (EGR) system 300 10 coupled between the exhaust manifold 225 and the intake manifold 200.

Another EGR system (not represented for simplicity) could be coupled between the pipes after turbine and the pipe before compressor (low pressure EGR or long-route EGR).

The EGR system 300 may include an EGR cooler 310 to reduce the temperature of 15 the exhaust gases in the EGR system 300. An EGR valve 320 regulates a flow of exhaust gases in the EGR system 300.

The automotive system 100 may further include an Electronic Control Unit (ECU) 450 in communication with one or more sensors and/or devices associated with the ICE 110. The ECU 450 may receive input signals from various sensors configured to 20 generate the signals in proportion to various physical parameters associated with the ICE 110. The sensors include, but are not limited to, a mass airflow and temperature sensor 340, a manifold pressure and temperature sensor 350, a combustion pressure sensor 360, coolant and oil temperature and level sensors 380, a fuel rail pressure sensor 400, a cam position sensor 410, a crank position sensor 420, exhaust pressure and 2 5 temperature sensors 430, an EGR temperature sensor 440, and an accelerator pedal position sensor 445.

According to some embodiments of the invention, the ECU 450 may receive signals from the fuel injection system 600, as will be explained hereinafter.

Furthermore, the ECU 450 may generate output signals to various control devices 30 that are arranged to control the operation of the ICE 110, including, but not limited to, the fuel injectors 160, the throttle body 330, the EGR Valve 320, the VGT actuator 290, and the cam phaser 155. Note, dashed lines are used to indicate communication between the ECU 450 and the various sensors and devices, but some are omitted for clarity.

Turning now to the ECU 450, this apparatus may include a digital central processing 35 unit (CPU) in communication with a memory system, or data carrier 460, and an interface bus. The CPU is configured to execute instructions stored as a program in the memory system, and send and receive signals to/from the interface bus. The memory system may include various storage types including optical storage, magnetic storage, solid state

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storage, and other non-volatile memory. The interface bus may be configured to send, receive, and modulate analog and/or digital signals to/from the various sensors and control devices. The program may embody the methods disclosed herein, allowing the CPU to carryout out the steps of such methods and control the ICE 110.

5 In Figure 3 the fuel injection system 600, according to an embodiment of the invention is illustrated, the fuel injection system 600 comprising a first pressure (LP) pump 601, positioned within a fuel tank 602 containing fuel. The first pressure pump is a variable displacement pump operable for moving fuel to a second pressure (HP) pump 603 through a fuel line 604 equipped with a fuel filter 605. The second pressure pump 10 603 provides a higher fuel pressure than the first pump and it has the function to pressurize the fuel at a predetermined pressure value (as a function of a desired engine operating point) and to supply the pressurized fuel to a fuel rail 606 through an high pressure line 607. The second pressure (HP) pump is equipped with a pressure sensor 603a for measuring the fuel pressure at an inlet port of the second pressure (HP) pump 15 603, the pressure sensor 603a being electrically connected to the ECU 450.

The fuel rail 606 is hydraulically connected, through fuel lines 610, to the injectors 160 for injecting the fuel into the cylinders 125 (Fig.1).

The fuel injectors 160 are also connected back to the fuel tank 602 by means of a re-circulating fuel line 608 for discharging of static and dynamic fuel leakages which 2 0 occur during the operation of the injectors 160.

The first and the second pressure pumps are electrically connected to the ECU 450 which manages their operating mode according to the engine operating points.

Figure 4 is a schematic representation of a control logic that can be employed to operate the fuel injection system 600 of the engine.

2 5 According to the present embodiment of the invention the ECU 450 determines, for each engine operating point, i.e. for each engine load (EL) and engine speed (ES), a nominal fuel quantity (Qn) to be injected into a cylinder 125 of the engine 110 and a nominal pressure value (PN) at an inlet of the second pressure pump 603 (block 500).

A map, stored in the memory system 460, correlates each nominal fuel quantity to a 30 predetermined energizing time (ET) value (block 501) of the injectors 160, i.e. the time of activation of the injectors 160 for injecting the nominal fuel quantity (Qn) into the cylinders 125.

A correction fuel quantity to be injected is then calculated by keeping into account, during the injection of the nominal fuel quantity, both the static and the dynamic fuel 35 leakages of the injectors and the second pressure pump efficiency.

According to this embodiment of the invention the correction fuel quantity is determined by adding a first correction fuel quantity (block 502), keeping into account the static and the dynamic fuel leakages, and a second correction fuel quantity (block 503)

which keeps into account only the second pressure pump efficiency.

In detail the first correction fuel quantity (QL) (block 502) is experimentally predetermined on the basis of the energizing time (ET) of the injectors, an index indicative of the engine life, a fuel rail pressure value, and an intake air temperature.

5 While the second correction fuel quantity (Qa hp) (block 503) is experimentally pre determined on the basis of an engine speed, an index indicative of the engine life, a fuel rail pressure value, and an intake air temperature.

The correction fuel quantity is then added (adder 504) to the nominal fuel quantity determining a target fuel quantity (QT) to be injected for the engine operating point. 10 A map (block 505) correlates the target fuel quantity (QT) with a corresponding nominal driving current (lN) value to supply to the first pressure (LP) pump in order to vary a pump operating parameter, typically the pump speed, to deliver the target fuel quantity (Qt).

A different embodiment of the invention, illustrated in Fig. 5, provides a further step 15 (block 506) of comparing a monitored pressure value, measured by the pressure sensor 603a of the second pressure pump 603, with the nominal pressure value determined in the engine map (block 500). If the measured pressure value (Ps) differs from the nominal pressure value (PN) the nominal driving current value(lN) is adjusted with a correction current (Ic) for equalizing the measured and the nominal pressure values. 20 In greater detail the variation of the current supplied to the pump causes the variation of the pump speed thereby delivering the target fuel quantity (QT) at the nominal pressure value (PN).

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of 25 variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various 30 changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.

REFERENCE NUMBERS

100

automotive system

110

internal combustion engine (ICE)

120

engine block

5

125

cylinder

130

cylinder head

135

camshaft

140

piston

145

crankshaft

10

150

combustion chamber

155

cam phaser

160

fuel injector

180

fuel pump

190

fuel source

15

200

intake manifold

205

air intake duct

210

intake air port

215

valves of the cylinder

220

exhaust gas port

20

224

exhaust line

225

exhaust manifold

230

turbocharger

240

compressor

250

turbine

25

260

intercooler

270

exhaust system

275

exhaust pipe

280

exhaust aftertreatment device

290

VGT actuator

30

300

EGR system

310

EGR cooler

320

EGR valve

330

throttle body

340

mass airflow and temperature sensor

35

350

manifold pressure and temperature sensor

360

combustion pressure sensor

380

coolant and oil temperature and level sensors

400

fuel rail pressure sensor

9

410

420

430

445

450

460

500

501

502

504

505

506

600

601

602

603

604

605

cam position sensor crank position sensor exhaust pressure sensor accelerator pedal position sensor

Electronic Control Unit (ECU)

data carrier block block block block block block fuel injection system first pressure pump fuel tank second pressure pump fuel line fuel filter fuel rail high pressure line re-circulating fuel line fuel lines

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Claims

1. A method of operating a fuel injection system (600) of an internal combustion engine (110), wherein the injection system (600) comprises a first pressure pump (601)

5 for supplying fuel to a second pressure pump (603), the second pressure pump (603) providing a higher fuel pressure than the first pressure pump (601), and a fuel injector (160), hydraulically connected to the second pressure pump (603) through a fuel rail (606), for injecting the fuel into a cylinder (125) of the engine, the method comprising the following steps:

10 - determining a nominal fuel quantity, to be injected, as a function of an engine

(110) operating point,

- determining a correction fuel quantity as a function of an index indicative of at least one among an injector static leakage, an injector dynamic leakage, a second pressure pump efficiency,

15 - determining a target quantity of fuel to supply to the second pressure pump

(603) by adding the nominal and the correction fuel quantity,

- regulating a first pressure pump (601) operating parameter for supplying the target fuel quantity to the second pressure pump (603).

2. A method according to claim 1, wherein a rotation speed of the first pressure

20 pump is chosen as first pressure pump operating parameter.

3. A method according to any of the preceding claims, wherein the index indicative of the static leakage and of the dynamic leakage is experimentally determined on the basis of an energizing time, an index indicative of the engine life, a rail pressure, and an engine temperature.

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4. A method according to any of the preceding claims, wherein the index indicative of the second pressure pump efficiency is experimentally determined on the basis of an engine speed, an index indicative of the engine life, a rail pressure, and a temperature.

5. A method according to any of the preceding claims, which provides the further step to adjust the first pressure pump operating parameter on the basis of a comparison

30 of a monitored fuel pressure value at an inlet of the second pressure pump with a nominal fuel pressure value thereof, determined for the engine operating point.

6. A method according to claim 5, wherein the monitored fuel pressure value is a measured by a pressure sensor.

7. A fuel injection system for an internal combustion engine, comprising a first

35 pressure pump for supplying fuel to a second pressure pump, the second pressure pump providing a higher fuel pressure than the first pressure pump, and a fuel injector, hydraulically connected to the second pressure pump through a rail, for injecting the fuel into a cylinder of the engine, and an engine control unit (450) for controlling the operating

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of the first and second pressure pumps and of the injector, wherein the first pressure pump is a variable displacement pump.

8. A fuel injection system according to claim 7, wherein the second pressure pump comprises a pressure sensor (603a) for monitoring the fuel pressure, said pressure

5 sensor being connected to the engine control unit (450).

9. An internal combustion engine (110) comprising an engine block (120) defining at least one cylinder (125) and a fuel injection system (600) according to any of the claims from 7 to 8 arranged to inject fuel into the cylinder (125).

10. A computer program comprising a computer code suitable for performing the 10 method according to any of the claims 1 to 6.

11. A computer program product on which the computer program of claim 10 is stored.

12. An electromagnetic signal modulated as a carrier for a sequence of data bits representing the computer program according to claim 10.

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