Method for controlling fuel injection into an internal combustion engine in a hybrid vehicle

Abstract

Method for controlling fuel injection during combustion engine start-up in an electric hybrid vehicle (10), wherein the electric hybrid vehicle (10) comprises a combustion engine (12) suitable for driving a vehicle wheel (40), a plurality of cylinders and a fuel injector (26) assigned to each cylinder, an energy source (14), an electric machine (16) suitable for being supplied with energy by the energy source (14) to drive the combustion engine (12) or the vehicle wheel (40), and a control module for monitoring and controlling the electric hybrid vehicle (10), comprising the following steps: - Driving the internal combustion engine (12) with the help of the electric machine (16), - Determine whether the internal combustion engine (12) is in a target state, - Selecting a cylinder for fuel injection by determining the nearest cylinder to complete a full intake stroke, - Calculating the amount of fuel to be supplied to the cylinder, - Injecting the fuel quantity with the fuel injector (26), and - Repeating the selection, calculation and injection steps for a different cylinder for a predetermined number of iterations.

Description

[0001] The present invention relates generally to the operation of hybrid vehicles and, more particularly, to the operation of an internal combustion engine of an electric hybrid vehicle.

[0002] Methods for controlling the operation of an internal combustion engine in a hybrid vehicle are known from the control technology of internal combustion engines in hybrid vehicles, for example from US Pat. No. 5,818,115 A. This known method emphasizes driving an internal combustion engine at a predetermined speed to avoid a variation in torque output at the time the internal combustion engine is started. However, no details are given regarding the steps for implementing the control of the fuel injection and the control of the ignition timing of the internal combustion engine, nor are the vehicle emissions associated with so-called "overfueling" during engine start-up addressed.

[0003] From US 5 818 116 A a method for starting an internal combustion engine in a hybrid vehicle is known, in which, among other things, the engine waits for a target state to be reached during the start.

[0004] DE 101 04 232 A1 describes the application of correction factors for the fuel injection pulse lengths when starting an internal combustion engine (without specific reference to a hybrid vehicle).

[0005] US 2004 / 0 144 363 A1 describes a monitoring of a target state for the start of a fuel injection depending on the achievement of a certain intake manifold vacuum, wherein the achievement of a certain vacuum is supported by an electric motor.

[0006] EP 1 269 010 B1 deals with the criteria for an initial fuel injection, but not with the selection of a cylinder for this initial fuel injection.

[0007] JP H07 - 180 587 A deals with the correction of air / fuel ratios when starting an internal combustion engine by applying correction factors.

[0008] According to DE 42 41 459 A1, a fuel quantity / air quantity correction is carried out depending on a post-start counter.

[0009] The invention is based on the object of providing a method for controlling fuel injection during engine start-up that determines and provides a precise amount of fuel to be made available to a specific engine cylinder more quickly than the prior art, with the goal of lowering vehicle emissions. Furthermore, the aim is to avoid overfueling conditions while still providing sufficient fuel to promote a robust engine start.

[0010] These objects are achieved by methods having the features according to the independent patent claims. Advantageous embodiments are described in the dependent patent claims.

[0011] According to one aspect of the present invention, a method for controlling fuel injection during engine startup in an electric hybrid vehicle is provided. The electric hybrid vehicle includes an internal combustion engine, a power source, an electric machine, and a control module for monitoring and controlling the electric hybrid vehicle. The internal combustion engine is adapted to drive a vehicle wheel and includes a plurality of cylinders and a fuel injector associated with each cylinder. The electric machine is adapted to be powered by the power source to drive the internal combustion engine or the vehicle wheel.

[0012] The method comprises the steps of driving the internal combustion engine using the electric machine, determining whether the internal combustion engine is in a target state, selecting a cylinder for fuel injection, calculating an amount of fuel to be made available to the cylinder, injecting the amount of fuel with the fuel injector, and repeating the selection, calculation, and injection steps for another cylinder for a predetermined number of iterations to promote robust internal combustion engine starting and reduce vehicle emissions.

[0013] The internal combustion engine may include an air intake manifold configured to provide air to a plurality of cylinders. The step of determining whether the internal combustion engine is in a target state may include determining whether a pressure sensed in the air intake manifold is less than a first threshold, determining whether a number of cylinder events exceeds a second threshold, or determining whether a predetermined period of time has elapsed.

[0014] The step of calculating the amount of fuel to be made available to a cylinder may include the steps of determining a first air-fuel ratio value, calculating a second first and second air-fuel ratio value based on an engine cooling temperature and a counted number of cylinder events, adding the first and second air-fuel ratio values ​​to generate a target air-fuel ratio value, and determining the amount of fuel to be made available based on the target air-fuel ratio value.

[0015] The time required to calculate the first air-fuel ratio value may be greater than the time required to calculate the second air-fuel ratio value. The second air-fuel ratio value calculated during a current iteration may be lower than the second air-fuel ratio value calculated during a previous iteration. The amount of fuel provided to each cylinder may be constant for a subset of the predetermined number of iterations.

[0016] According to another aspect of the present invention, a method for controlling fuel injection during engine start-up in a hybrid electric vehicle is provided. The hybrid electric vehicle includes an engine, a power source, an electric machine, and a control module for monitoring and controlling the hybrid electric vehicle. The engine is adapted to drive a vehicle wheel and has a plurality of cylinders. The electric machine is adapted to be powered by the power source to selectively drive the engine or the vehicle wheel.

[0017] The method comprises the steps of driving the internal combustion engine using the electric machine, determining whether the internal combustion engine has a target speed, selecting a cylinder for fuel injection, calculating a first air-fuel ratio value and a second air-fuel ratio value, providing a target air-fuel ratio value to the cylinder based on the first and second air-fuel ratio values, incrementing a counter, and repeating the selecting, calculating, providing, and incrementing steps by means of the control module until the counter exceeds a predetermined value.

[0018] The first air-fuel ratio value may be greater than the second air-fuel ratio value. The target air-fuel ratio value may be decreased at each iteration to reduce vehicle emissions.

[0019] According to another aspect of the present invention, a method for controlling fuel injection during engine start-up in an electric hybrid vehicle is provided. The electric hybrid vehicle includes an internal combustion engine, a power source, an electric machine, a control module, and first, second, third, and fourth signals. The internal combustion engine is configured to drive a vehicle wheel and includes a plurality of cylinders, a fuel injector associated with each cylinder, an air intake manifold, a camshaft, a crankshaft, and an engine cooling system. The electric machine is configured to be supplied with power from a power source to drive the internal combustion engine or the vehicle wheel. The first signal is indicative of the pressure in the air intake manifold. The second signal is indicative of a camshaft position.The third signal indicates a crankshaft position. The fourth signal indicates an engine cooling temperature.

[0020] The method comprises the steps of driving the internal combustion engine using the electric machine, determining whether the internal combustion engine is in a target state, selecting a cylinder for fuel injection, calculating a target air-fuel ratio value, incrementing a counter value, providing an amount of fuel to each of the plurality of cylinders in a sequence based on the target air-fuel ratio value, and repeating the calculation, providing, and incrementing steps for a predetermined number of iterations.

[0021] The internal combustion engine may be in the target state when the first signal is less than a first threshold value. The step of selecting a cylinder may be based on the second and third signals. The step of calculating the target air-fuel ratio value may include providing a first target air-fuel ratio value, calculating a second target air-fuel ratio value based on the fourth signal and the counter value, and summing the first and second target air-fuel ratio values.

[0022] The invention is explained in more detail below by way of example with reference to the drawings. They show: Fig. 1 is a schematic diagram of an electric hybrid vehicle having an internal combustion engine; Fig. 2 a sectional view of an internal combustion engine along the section 2 - 2 in Fig. 1; Fig. 3 is a flowchart of a method for controlling fuel injection during engine start-up; Fig. 4 is a flowchart of another embodiment of the method for controlling fuel injection during starting of the internal combustion engine, and Fig. 5 a graphical representation of operating values ​​of the internal combustion engine during starting according to the procedure according to Fig. 3.

[0023] Fig. 1 shows a schematic representation of an electric hybrid vehicle 10 having an internal combustion engine 12, a power source 14, an electric machine 16, and at least one control module 18. The electric hybrid vehicle 10 may have any known powertrain configuration, such as series hybrid drives, parallel hybrid drives, or split hybrid drives.

[0024] The combustion engine 12 can be designed in any way. Fig. 1, the internal combustion engine 12 is designed as a four-stroke Otto engine with four cylinders in line. As can be seen from the Fig. 1 and Fig. As can be seen in Figure 2, the internal combustion engine 12 has a cylinder block with a plurality of cylinders numbered 1 to 4, with pistons 20 arranged therein for reciprocating movement. The pistons 20 are connected to a crankshaft 22 of the internal combustion engine. Furthermore, the internal combustion engine 12 has an air intake manifold 24, fuel injectors 26 associated with each cylinder, a camshaft 28, a plurality of valves 30, and a cooling system 32.

[0025] The air intake manifold 24 and the fuel injectors 26 are configured to provide pressurized air and pressurized fuel to each cylinder to promote combustion. The fuel injectors 26 are part of a fuel delivery system that can be configured to inject fuel directly or indirectly in a known manner. The fuel injectors 26 are controlled by the control module 18, which provides an injector control signal to the respective fuel injector 26. Specifically, each fuel injector 26 is opened for a period of time determined by the pulse width of its respective injector control signal.

[0026] The camshaft 28 is designed such that when it rotates, the valves 30 assigned to the cylinders are actuated in a known manner.

[0027] The cooling system 32 is configured to circulate a fluid, such as a coolant, through passages in the cylinder block to dissipate heat from the internal combustion engine 12 to the surrounding environment.

[0028] The energy source 14 may be embodied in any suitable manner, such as a battery, a battery pack with a plurality of electrically connected cells, a capacitor, or a fuel cell. Alternatively, a non-electrical energy source, such as a hydraulic energy source, may be used. For simplicity, the following description refers to an embodiment of the present invention with an electrical energy source.

[0029] The electric machine 16 can be designed in any suitable manner, for example as a motor, as a motor-generator or as a starter generator. Fig. 1, the electric machine 16 is connected to the internal combustion engine 12 and the energy source 14 such that the electric machine 16 can be supplied with energy from the energy source 14 and adapted to drive the internal combustion engine 12 or one or more of the vehicle drive wheels 40. The energy flow through the electric machine can also be reversed to charge the energy source or drive the internal combustion engine. In the embodiment shown in Fig. 1, the electric machine 16 is connected to a differential 42 which is connected to a pair of shafts 44, each shaft being connected to one of the vehicle drive wheels 40.

[0030] The control module 18 is responsible for monitoring and controlling various aspects of the electric hybrid vehicle 10. For example, the control module 18 may be connected to the internal combustion engine 12, the power source 14, and the electric machine 16 to monitor and control their operation and performance. In addition, the control module 18 also processes input signals from various sensors to determine the proportions of fuel and air, or the "fuel / air" ratio, for clean combustion. These sensors may include an air intake pressure sensor 50, a cooling water temperature sensor 52, a crankshaft position sensor 54, and / or a camshaft position sensor 56.

[0031] The air intake manifold pressure sensor 50 may be suitably configured and arranged at any suitable location, such as in the air intake manifold 22. The cooling temperature sensor 52 may be configured, for example, as a thermocouple arranged near the cooling system 32 or as a thermistor.

[0032] The crankshaft and camshaft position sensors 54, 56 are each arranged near the crankshaft 22 and the camshaft 28 to detect their rotational movements. The crankshaft and camshaft position sensors 54, 56 can be of any design. For example, they can be configured as encoders with optical or magnetic detection means.

[0033] With reference to the Fig. 3 and Fig. 4, two embodiments of a method for controlling fuel injection during engine start-up are described below, with further reference to the method described in the Fig. 1 and Fig. 2 hybrid vehicle shown.

[0034] As can be seen, the flowchart represents control logic that can be implemented using hardware, software, or a combination of hardware and software. The various functions can be executed, for example, using a programmed microprocessor.

[0035] The control logic may be implemented using any number of known programming or processing techniques or strategies and is not limited to the order or sequence illustrated. Furthermore, as illustrated, processing typically used in real-time control applications, such as control of internal combustion engine or vehicle subsystems, is preferred, rather than a purely sequential strategy. Pairwise processing, multitasking, or multithreaded systems and methods may also be employed to achieve the objects, features, and advantages of the present invention.

[0036] The present invention is independent of any particular programming language, operating system, processor, or circuitry to be developed and / or implemented in the illustrated control logic. Likewise, depending on the particular programming language and processing strategy, various functions in the illustrated sequence may be performed substantially simultaneously or in different sequences to achieve the features and advantages of the present invention.

[0037] The flowcharts in the Fig. 3 and Fig. 4 focuses on the steps for evaluating and delivering a desired amount of fuel to one or more of the engine cylinders to promote robust engine starting while preventing undesirable vehicle emissions. Specifically, the goal is to accelerate the engine to a desired speed before fuel is injected, thus achieving robust combustion, while also avoiding making too much fuel available, as excess fuel is not completely combusted. Such methodologies can be implemented when the engine is not running and determine, via other control logic, when it is desirable to start the engine.

[0038] According to the Fig. In the flowchart shown in Figure 3, the engine start sequence begins at 100 with the engine 12 being driven by the electric machine. Specifically, the energy source 14 supplies energy to the electric machine 16, and the electric machine 16 drives or rotates the engine 12.

[0039] At 102, the method determines whether the engine 12 is ready for fuel injection into one or more cylinders. Specifically, the method determines whether the engine 12 is in a target state, e.g., at a desired engine speed. This determination may be based on an air intake pressure, a timer, a counter, or combinations thereof, as described above.

[0040] The air intake manifold pressure decreases as the engine speed increases. If the air intake manifold pressure exceeds a threshold, the engine speed is insufficient, and the process returns to block 100. If the air intake manifold pressure is lower than the threshold, the method continues at block 104. The air intake manifold pressure signal may be provided by the air intake manifold pressure sensor 50. The threshold is a function of various vehicle and engine characteristics and may be determined by vehicle testing.

[0041] Alternatively, a timer can be started when the electric machine 16 begins to rotate the internal combustion engine 12. The internal combustion engine 12 has reached the target manifold pressure when a predetermined period of time has elapsed. The predetermined period of time can be determined by testing the vehicle.

[0042] Similarly, a counter may be incremented when the electric machine 16 begins to rotate the engine 12. The counter may be incremented, for example, in response to a cylinder event such as piston movement or the number of engine rotations. Engine rotation may be detected using crankshaft and / or camshaft position sensors 54, 56. The engine 12 has reached the target intake pressure when the counter exceeds a predetermined value, which is determinable by prior testing of the vehicle.

[0043] At 104, a cylinder is selected for fuel injection. Specifically, the method determines the next cylinder to complete a complete intake stroke. The control module 18 may perform this selection using signals from the crankshaft and / or camshaft position sensors 54, 56 along with the ignition sequence of the internal combustion engine 12.

[0044] Next, at 106, the method determines the appropriate amount of fuel to be provided to the selected cylinder. Determining the appropriate amount of fuel is performed in a three-step process. First, a base air-fuel ratio value is obtained or calculated. Next, a tune air-fuel ratio value is calculated. Third, the base air-fuel ratio value and the tune air-fuel ratio value are added to generate a target air-fuel ratio value.

[0045] The baseline air-fuel ratio is typically calculated by a computer-controlled electronic fuel injection system using a complex, computationally intensive algorithm based, in a known manner, on many input signals, such as throttle valve position, engine speed, air intake temperature, air intake manifold vacuum level, barometric pressure, exhaust oxygen level, and / or vehicle speed. The baseline air-fuel ratio may not accurately reflect current vehicle operating conditions due to delays inherent in processing the input signals and supplementary calculations. Consequently, the baseline air-fuel ratio may not accurately control the fuel delivery to the engine during start-up to reduce vehicle emissions.

[0046] A tuning air / fuel ratio value is used to correct deficiencies in the base air / fuel ratio value. The tuning air / fuel ratio value may be based on the cooling temperature and a counter value indicative of the number of sensed cylinder events. The cooling temperature may be provided by the cooling temperature sensor 52. The number of cylinder events may be based on signals from the crankshaft and / or camshaft position sensors 54, 56, as discussed above. The cooling temperature and counter signals may be used to reference tuning values ​​stored in a lookup table. Because the tuning air / fuel ratio value is based on fewer variables than the base air / fuel ratio value, it may be updated more quickly than the base air / fuel ratio value to more accurately determine fuel needs.

[0047] The appropriate amount of fuel is provided to the selected cylinder at 108. Specifically, the control module 18 provides an injector control signal having a desired pulse width corresponding to the target air-fuel ratio value to cause the fuel injector 26 to open and close as described above.

[0048] At 110, a counter is incremented to indicate that fuel injection into the selected cylinder has ended. This step can be positioned in any suitable sequence in the control logic.

[0049] At 112, the counter value is compared to a threshold. If the counter value is greater than the threshold, this indicates that the internal combustion engine 12 is operating on its own power. Consequently, no additional fuel is requested during the engine start-up sequence, and the flowchart ends at block 114. If the counter value does not exceed the threshold, the method returns to block 104 to select the next cylinder for fuel injection and repeat the following steps. The threshold may be determined by a vehicle test.

[0050] With reference to Fig. 4, a second embodiment of the method is explained. This embodiment is similar to that shown in Fig. 3. However, in this embodiment, the constant amount of fuel is provided to each cylinder for one iteration of the engine firing frequency once a cylinder is selected.

[0051] The method begins with steps 200, 202 and 204, 206 which correspond to steps 100, 102, 104 and 106 respectively.

[0052] The amount of fuel determined in step 206 is made available to each cylinder in the firing sequence at 208. The same amount of fuel is, for example, made available in the Fig. In the four-cylinder internal combustion engine shown in Figure 1, fuel is supplied sequentially to each of the four cylinders during an iteration of the process. The amount of fuel can change for each iteration.

[0053] Steps 210 and 212 correspond to steps 110 and 112, respectively. However, if the counter does not exceed the threshold, the method returns to block 206 at step 212 and does not select a new cylinder for fuel injection. The selection step does not need to be repeated because, once a cylinder is selected, the order of all subsequent fuel injections is known due to the repeating ignition sequence.

[0054] The procedure according to Fig. 3 is explained below with reference to Fig. 5. The horizontal axis in Fig.5 represents time (t). For ease of illustration, a series of time increments is represented by a plurality of spaced vertical lines. The leftmost vertical line is time (t=0), the next vertical line is time 1 (t=1), and so on. Along the vertical axis, various attributes of hybrid vehicles are represented, namely the engine speed, the intake manifold pressure, the counter value, the base air-fuel ratio value, the tuning air-fuel ratio value, the target air-fuel ratio value, and the fuel injection control pulses.

[0055] At t = 0, the internal combustion engine 12 is not operating and the engine speed is zero. The intake manifold pressure, or air intake manifold pressure, is high when no air is supplied to the internal combustion engine 12 for combustion. The counter and fuel / air values ​​are initially set to zero. Similarly, the fuel injection control signals are at zero or a low level, meaning the fuel injectors are closed.

[0056] Between t = 0 and t = 1, the control module 18 receives a signal to start the internal combustion engine 12. The control module 18 then calculates the base air-fuel ratio value. For simplicity, the base air-fuel ratio value is a constant in this example. However, the base air-fuel ratio value can change over time.

[0057] At t = 1, the combustion engine 12 begins to be driven by the electric machine 16.

[0058] Between t = 1 and t = 4, the engine speed increases as the electric motor 16 accelerates the engine. As the engine 12 accelerates, the air intake manifold pressure decreases because air can flow into the engine 12.

[0059] At t = 4, the engine speed is sufficient for fuel injection. The tuning air / fuel ratio is calculated and added to the base air / fuel ratio to obtain the target air / fuel ratio. Furthermore, the next cylinder available for fuel injection is selected. In this example, cylinder 1 is selected, and the hypothetical engine firing sequence is 1-2-3-4.

[0060] After the target air-fuel ratio value has been calculated, an injection control pulse is sent to the fuel injector for cylinder 1. The pulse causes the fuel injector to open and deliver fuel. The counter is incremented and compared to a threshold value. In this example, the threshold value is 12. If the counter value is below 12, the process steps are repeated. Specifically, at t = 5, 9, and 13 for cylinder 2, the fuel injector receives an injector control pulse; at t = 6, 10, and 14, the fuel injector for cylinder 3 receives an injector control pulse; and at t = 7, 11, and 15, the fuel injector for cylinder 4 receives an injector control pulse. Furthermore, the counter value is incremented after each pulse.In addition, in this example, the decreases in the tuning air / fuel ratio value are completed after an ignition sequence at t = 8, 12 and 16.

[0061] At t = 16, the counter value is equal to 13, which exceeds the threshold of 12. This causes the procedure to end and subsequent fuel injection pulses to be based only on the base air-fuel ratio value.

[0062] The method described above provides additional fuel, which is desirable for good combustion during engine start-up, but is unique in that this fuel is delivered to a suitable cylinder to improve combustion and result in lower emissions. Furthermore, the method facilitates rapid fueling adjustments in response to changing environmental conditions and vehicle performance attributes. Furthermore, the method allows computationally intensive calculations, such as baseline air-fuel ratio calculations, to be performed separately from the fueling adjustments performed for a cylinder event.

Claims

[1] A method for controlling fuel injection during engine start-up in an electric hybrid vehicle (10), the electric hybrid vehicle (10) comprising an internal combustion engine (12) adapted to drive a vehicle wheel (40), a plurality of cylinders and a fuel injector (26) associated with each cylinder, an energy source (14), an electric machine (16) adapted to be supplied with energy from the energy source (14) to drive the internal combustion engine (12) or the vehicle wheel (40), and a control module for monitoring and controlling the electric hybrid vehicle (10), comprising the following steps: - driving the combustion engine (12) by means of the electric machine (16), - determining whether the internal combustion engine (12) is in a target state, - Selecting a cylinder for fuel injection by determining the next cylinder to perform a complete intake stroke, - Calculating the amount of fuel to be made available to the cylinder, - Injecting the fuel quantity with the fuel injection nozzle (26), and - Repeat the selection, calculation and injection steps for another cylinder for a predetermined number of iterations. [2] The method of claim 1, wherein the internal combustion engine (12) further comprises an air intake manifold (24) adapted to provide air to a plurality of cylinders, characterized by that determining whether the internal combustion engine (12) is in a target state comprises determining whether a pressure detected in the air intake manifold (24) is lower than a first limit value. [3] Method according to claim 1 or 2, characterized bythat the step of determining whether the internal combustion engine (12) is in the target state comprises the step of determining whether a number of cylinder events exceeds a second limit value. [4] Method according to claim 1, characterized by that the step of determining whether the internal combustion engine (12) is in the target state comprises the step of determining whether a predetermined period of time has elapsed. [5] Method according to one of claims 1 to 4, characterized bythat the step of calculating the amount of fuel to be made available to a cylinder comprises providing a first air-fuel ratio value, calculating a second air-fuel ratio value based on an engine cooling temperature and a counted number of cylinder events, adding the first and second air-fuel ratio values ​​to generate a target air-fuel ratio value, and determining the amount of fuel to be made available based on the target air-fuel ratio value. [6] Method according to claim 5, characterized by that the time required to calculate the first air-fuel ratio value is longer than the time required to calculate the second air-fuel ratio value. [7] Method according to claim 5 or 6, characterized bythat the second air-fuel ratio value calculated during a current iteration is lower than the second air-fuel ratio value calculated during a previous iteration. [8] Method according to one of claims 1 to 7, characterized by that the amount of fuel made available to each cylinder is constant for a subset of the predetermined number of iterations. [9] A method for controlling fuel injection during engine start-up in an electric hybrid vehicle (10), the electric hybrid vehicle (10) comprising an internal combustion engine (12) adapted to drive a vehicle wheel (40) and comprising a plurality of cylinders, an energy source (14), an electric machine (16) adapted to be supplied with energy by the energy source (14) to selectively drive the internal combustion engine (12) or the vehicle wheel (40), and a control module for monitoring and controlling the electric hybrid vehicle (10), comprising the following steps: - driving the combustion engine (12) by means of the electric machine (16), - determining whether the internal combustion engine (12) is in a target state, - Selecting a cylinder for fuel injection by determining the next cylinder to perform a complete intake stroke, - calculating a first fuel / air ratio value and a second fuel / air ratio value indicative of an additional amount of fuel to be made available to the cylinder, - providing a target air / fuel ratio to a cylinder based on the first and second air / fuel ratio values; - Incrementing a counter, and - Repeating the selection, calculation, provision and incrementation steps with the control module until the counter exceeds a predetermined value.

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