Fuel injection control device for internal combustion engine

Abstract

To provide a fuel injection control device for an internal combustion engine that can highly accurately suppress variation in injection quantity relative to an injection pulse width in a cold idle state.SOLUTION: A fuel injection control device for an internal combustion engine stores a pulse width of an injection pulse signal in a cold idle state, as a pseudo-pulse width, detects an operation state of a fuel injection device when injecting a required injection amount of fuel with the pseudo-pulse width in a post-warming-up idle state, provides a pulse width correction value on the basis of a detection result of the operation state, and corrects a pulse width of an injection pulse signal with the pulse width correction value in a cold idle state.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a fuel injection control device for an internal combustion engine. [Background technology]

[0002] The fuel injection control device for an internal combustion engine in Patent Document 1 changes the fuel injection pressure during idle operation to a plurality of different fuel injection pressure levels, and calculates an injection amount correction amount corresponding to the deviation of the actual injection amount relative to the injection pulse time of the injector at the plurality of different fuel injection pressure levels for each cylinder by equally dividing the injection amount during learning control calculated when the learning prerequisites and learning execution conditions are met and performing n split injections, while performing FCCB correction (rotational speed fluctuation inter-cylinder injection amount correction) and ISC correction (average engine rotational speed correction). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-101625 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in a cold idle state (in other words, a fast idle state), there are cases where attempts are made to improve exhaust properties by implementing split injection, in which fuel injection per cycle is divided into multiple injections, or by increasing the fuel pressure to atomize the fuel spray. However, when split injection or increased fuel pressure is implemented, the injection pulse width per injection becomes shorter, and it may be necessary to use an injection pulse width in the nonlinear region, which results in large variations in the injection amount (actual valve opening time) relative to the injection pulse width.

[0005] When the engine is in a cold idle state and before air-fuel ratio feedback control has started, the effect of the variation in injection amount becomes large, so it is desirable to suppress the variation in injection amount by learning the variation in injection amount relative to the injection pulse width in the cold idle state and correcting the injection pulse width. However, because the amount of fuel injected per combustion cycle is large during cold idling, it is affected by fuel pressure pulsation, making it difficult to learn the variation in injection amount with high accuracy.

[0006] The present invention has been made in consideration of the conventional situation, and its object is to provide a fuel injection control device for an internal combustion engine that can suppress variations in injection quantity relative to injection pulse width with high accuracy during cold idling. [Means for solving the problem]

[0007] Therefore, in one aspect, the fuel injection control device for an internal combustion engine according to the present invention stores the pulse width of the injection pulse signal in a cold idle state as a pseudo pulse width, detects the operating state of the fuel injection device when the required injection amount is injected with the pseudo pulse width in an idle state after warming up, calculates a pulse width correction value based on the detection result of the operating state, and corrects the pulse width of the injection pulse signal in a cold idle state with the pulse width correction value. [Effects of the Invention]

[0008] According to the above invention, in a cold idling state, the variation in the injection amount relative to the injection pulse width can be suppressed with high precision. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a configuration diagram of a fuel injection system of an internal combustion engine. [Figure 2] 10 is a diagram showing the correlation between the injection pulse width and the injection amount, and the valve behavior of the fuel injector in a cold idle state and in an idle state after warming up; [Figure 3] 4 is a time chart for explaining a method for detecting a valve closing time. [Figure 4] FIG. 10 is a diagram showing the correlation between the valve closing time and the pulse width correction value. [Figure 5] 10 is a flowchart showing a procedure for learning a pulse width correction value. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described below. FIG. 1 is a configuration diagram showing one embodiment of an internal combustion engine for a vehicle. The internal combustion engine 101 includes a fuel injection valve 105 as a fuel injection device in each cylinder, and the fuel injection valve 105 injects fuel into the internal combustion engine 101 .

[0011] The control device 109 having the function of a fuel injection control device controls the operation of the internal combustion engine 101 by controlling the fuel injection by the fuel injection valve 105 and the like. The control device 109 is an electronic control device equipped with a microcomputer 109a, and the microcomputer 109a includes a microprocessor, a rewritable nonvolatile memory, and the like.

[0012] The intake air of the internal combustion engine 101 passes through an air flow meter 120, an electronically controlled throttle valve 119, and a collector 115 in that order, and is then drawn into a combustion chamber 121 via an intake port 110 and an intake valve 103 provided in each cylinder. Furthermore, the internal combustion engine 101 is provided with a variable fuel pressure device 129 that changes the pressure of the fuel that is pumped to the fuel injection valve 105 .

[0013] The variable fuel pressure device 129 has an electric low-pressure fuel pump 124 and an engine-driven high-pressure fuel pump 125 . The low-pressure fuel pump 124 sends fuel from the fuel tank 123 to the high-pressure fuel pump 125 .

[0014] On the other hand, the high-pressure fuel pump 125 increases the pressure of the fuel supplied from the low-pressure fuel pump 124 and sends the increased high-pressure fuel to the fuel injection valve 105 via a high-pressure fuel pipe 128 . The control device 109 adjusts the discharge amount of the high-pressure fuel pump 125 to control the pressure of the fuel supplied to the fuel injection valve 105 to a target fuel pressure. The fuel pressure sensor 126 detects the fuel pressure FP in the high-pressure fuel pipe 128 , that is, the fuel pressure FP supplied to the fuel injection valve 105 .

[0015] Then, the control device 109 sets the operation amount of an electromagnetic metering valve (not shown) that adjusts the discharge amount of the high-pressure fuel pump 125 based on the deviation ΔFP between the fuel pressure FP detected by the fuel pressure sensor 126 and the target fuel pressure FPtg, thereby bringing the fuel pressure FP detected by the fuel pressure sensor 126 closer to the target fuel pressure FPtg. That is, the control device 109 has a function of outputting a control signal for an electromagnetic metering valve that adjusts the discharge amount of the high-pressure fuel pump 125 as a fuel pressure control signal, and controlling the fuel pressure FP supplied to the fuel injection valve 105.

[0016] The fuel injection valve 105 injects fuel directly into the combustion chamber 121 of the internal combustion engine 101 . That is, the internal combustion engine 101 is a direct injection type internal combustion engine. The fuel injection valve 105 opens upon receiving an injection pulse signal output from the control device 109, and injects fuel into the combustion chamber 121 in an amount proportional to the pulse width of the injection pulse signal, that is, the valve opening control time.

[0017] The control device 109 calculates a required injection amount per combustion cycle according to engine operating conditions such as intake air flow rate, engine rotation speed, and coolant temperature, calculates an injection pulse width that allows the required injection amount to be injected under the fuel pressure at that time, and outputs an injection pulse signal of the injection pulse width to the fuel injection valve 105. In addition, the control device 109 performs split injection (in other words, multi-stage injection) control in which the required injection amount is injected in multiple increments when the internal combustion engine 101 is in a cold idle state, that is, when the internal combustion engine 101 is idling before warm-up is complete and the temperature of the internal combustion engine 101 is lower than the set temperature.

[0018] The internal combustion engine 101 also includes an ignition device having an ignition coil 107 and a spark plug 106 . The control device 109 controls the energization of the ignition coil 107 to control the generation of a spark by the spark plug 106 .

[0019] The air-fuel mixture in the combustion chamber 121 is ignited and burned by a spark generated by the spark plug 106 , and exhaust gas generated by the combustion is discharged from the combustion chamber 121 into the exhaust pipe 111 via the exhaust valve 104 . The exhaust pipe 111 is provided with a catalytic converter 112 that houses a three-way catalyst that purifies the exhaust gas.

[0020] The control device 109 acquires detection signals output by various sensors that detect the operating state of the internal combustion engine 101. In other words, the control device 109 acquires information about the operating state of the internal combustion engine 101 from the various sensors. The control system for the internal combustion engine 101 includes, as the various sensors, the fuel pressure sensor 126 mentioned above, a water temperature sensor 108 that detects a coolant temperature TW that represents the temperature of the internal combustion engine 101, a crank angle sensor 116 that measures the rotation angle of the crankshaft of the internal combustion engine 101, an air flow meter 120 that measures the intake air flow rate QA of the internal combustion engine 101, an air-fuel ratio sensor 113 that detects the air-fuel ratio based on the oxygen concentration of the exhaust gas upstream of the catalytic converter 112, and an accelerator opening sensor 122 that detects the opening degree ACC of the accelerator pedal operated by the vehicle driver.

[0021] Then, the control device 109 calculates the torque required for the internal combustion engine 101 based on the accelerator opening ACC detected by the accelerator opening sensor 122, and determines whether the internal combustion engine 101 is in an idling state. Furthermore, the control device 109 calculates the rotation speed NE of the internal combustion engine 101 based on the rotation angle of the crankshaft detected by the crank angle sensor 116 . Furthermore, the control device 109 determines, based on the coolant temperature TW detected by the water temperature sensor 108, whether the internal combustion engine 101 is in a cold state or has been warmed up, in other words, whether the warm-up has been completed.

[0022] Here, the control device 109 calculates a target intake air amount from a required torque set based on the accelerator opening ACC, and outputs an opening control signal based on this target intake air amount to the electronically controlled throttle valve 119 . In addition, the control device 109 calculates the ignition timing based on engine operating conditions such as the engine load and the engine rotation speed NE, and controls the ignition timing of the spark plug 106 by outputting an ignition control signal to the ignition coil 107 based on the calculated ignition timing.

[0023] Furthermore, the control device 109 determines the required injection amount for one combustion cycle based on the intake air flow rate QA, the engine rotation speed NE, the cooling water temperature TW, the air-fuel ratio, etc., and sets the injection pulse width for injecting the required injection amount from the fuel injection valve 105 according to the fuel pressure at that time. In addition, the control device 109 improves the exhaust gas properties in a cold idle state by implementing split injection control and / or promoting atomization by increasing the fuel pressure in the cold idle state.

[0024] Incidentally, when the control device 109 performs split injection control and / or increases the fuel pressure in a cold idle state, the injection pulse width for one injection becomes shorter, and an injection pulse width in a nonlinear region in the correlation between the injection pulse width and the actual injection amount may be used. FIG. 2 shows the correlation between the injection pulse width and the actual injection quantity, and also shows the valve behavior at the injection pulse width used in cold idling and at the injection pulse width used in warm idling.

[0025] The nonlinear region in the injection characteristics will be outlined below with reference to FIG. When the fuel injection valve 105 opens, the mover collides with the stator, causing the mover to bounce. If the injection pulse width falls before the bounding behavior converges, the time from the fall of the injection pulse width (in other words, the valve closing control command) to the time when the moving element actually reaches the valve closing position (hereinafter referred to as the "valve closing time TVC") will change due to the influence of the bounding behavior.

[0026] Then, as the valve closing time TVC changes, the actual valve opening time of the fuel injector 105 changes, causing variations in the actual injection amount relative to the injection pulse width. In this way, the region where the actual injection amount does not change linearly with respect to the injection pulse width due to the change in the valve closing time TVC affected by the bouncing behavior is the nonlinear region, and conversely, the region where the actual injection amount changes linearly with respect to the injection pulse width is the linear region.

[0027] When the control device 109 sets the injection pulse width in the nonlinear region by performing split injection control and / or increasing the fuel pressure in a cold idle state, an amount of fuel different from the required injection amount is injected from the fuel injection valve 105, and since the injection amount varies from one fuel injection valve 105 to another, the idle rotation speed fluctuates. Therefore, the control device 109 has a function (injection pulse width correction function) of suppressing the variation in injection amount between each fuel injection valve 105 by correcting the injection pulse width in the nonlinear region in the cold engine idle state for each fuel injection valve 105 according to the injection variation.

[0028] In the pulse width correction function, the control device 109 first detects, for each fuel injection valve 105, the valve closing time TVC when injection is performed with the injection pulse width TPsb used in split injection (and / or high fuel pressure) in a cold idle state. Then, based on the detected valve closing time TVC, the control device 109 learns the pulse width correction value THOS for each fuel injection valve 105 to align the actual injection amount with the required injection amount, in other words, to align the actual valve opening time with the required valve opening time.

[0029] The injection pulse width TPsb is a pulse width common to each cylinder (each fuel injector 105) that has not been subjected to correction processing using the pulse width correction value THOS. Then, the control device 109 corrects the injection pulse width TPsb for split injection (and / or high fuel pressure) in the cold idle state using the learned pulse width correction value THOS, and outputs an injection pulse signal with the corrected injection pulse width TPs to the fuel injector 105.

[0030] FIG. 3 is a time chart showing one embodiment of a method for detecting the valve closing time TVC. The detection method in FIG. 3 is a known detection method disclosed in, for example, Japanese Patent Application Laid-Open No. 2018-084240. This detection method is a method for detecting the valve closing completion timing of the fuel injection valve 105 based on a voltage change (a change in magnetic flux density occurring between the mover and the stator) after the injection pulse signal is turned off, and by capturing the voltage change occurring at the valve closing completion timing based on, for example, the second-order differential value of the voltage, the valve closing completion timing that occurs later after the injection pulse signal is turned off is detected.

[0031] When the control device 109 detects the timing at which the fuel injector 105 is closed, it obtains the time from the fall of the injection pulse signal (ON to OFF) to the timing at which the valve is closed as a valve closing time TVC. Then, the control device 109 searches for the pulse width correction value THOS corresponding to the obtained valve closing time TVC by referring to a correlation table between the valve closing time TVC and the pulse width correction value THOS, and sets the pulse width correction value THOS as the injection pulse width TPsb targeted for detection of the valve closing completion timing and the pulse width correction value THOS to be applied to the fuel injector 105.

[0032] FIG. 4 shows an example of a correlation table between the valve closing time TVC and the pulse width correction value THOS. In this correlation table, a standard valve closing time TVCb is used as a reference, and a pulse width correction value THOS is allocated so as to be proportional to the deviation of the actual valve closing time TVC from the standard valve closing time TVCb.

[0033] In other words, when the actual valve closing time TVC is longer than the standard valve closing time TVCb, the control device 109 sets a negative pulse width correction value THOS that decreases the injection pulse width TPs, and conversely, when the actual valve closing time TVC is shorter than the standard valve closing time TVCb, the control device 109 sets a positive pulse width correction value THOS that increases the injection pulse width TPs. The control device 109 corrects the injection pulse width TPsb using the pulse width correction value THOS and sets the result as the final injection pulse width TPs, thereby opening the fuel injection valve 105 for the same period as when the valve is closed with the standard valve closing time TVCb, so that the injection amount is aligned with the injection amount with the standard valve closing time TVCb.

[0034] Here, the control device 109 stores the injection pulse width TPsb used for split injection (and / or high fuel pressure) in the cold engine idle state as the pseudo pulse width TPP, and outputs an injection pulse signal with the pseudo pulse width TPP to the fuel injection valve 105 when the engine is in the idle state after warming up. The control device 109 then detects the valve closing time TVC when the valve is opened with the pseudo pulse width TPP, thereby learning the pulse width correction value THOS to be applied to the pseudo pulse width TPP.

[0035] After learning the pulse width correction value THOS, when the control device 109 uses an injection pulse width TPsb having the same pulse width as the pseudo pulse width TPP in a cold idle state, the control device 109 corrects the injection pulse width TPsb with the pulse width correction value THOS learned in the idle state after warming up. That is, the control device 109 learns the pulse width correction value THOS used in the cold idle state in the idle state after warming up.

[0036] When the engine is idling cold, the amount of fuel injected per combustion cycle is greater than when the engine is idling after warming up, resulting in larger fuel pressure pulsations. This fuel pressure pulsation makes it difficult to accurately detect the valve closing completion timing. For this reason, it is preferable that the pulse width correction value THOS be learned in an idling state after warming up, when the fuel injection amount per combustion cycle is small and the fuel pressure pulsation is relatively small.

[0037] However, in the cold idle state, split injection and high fuel pressure are performed, and the required injection amount is larger than after warm-up. Therefore, in the idle state after warm-up, there is almost no opportunity for injection with the injection pulse width TPsb used in the cold idle state. Therefore, when normal fuel injection is performed during idling after warming up, the control device 109 has almost no opportunity to learn the pulse width correction value THOS that can be used during cold idling.

[0038] Therefore, in the idle state after warming up, the control device 109 performs fuel injection with a pseudo pulse width TPP, which is the injection pulse width TPsb used in the cold idle state, and detects the valve closing time TVC at the pseudo pulse width TPP, thereby learning with high accuracy the pulse width correction value THOS used in fuel injection control in the cold idle state. FIG. 5 is a flowchart showing one example of a procedure for learning the pulse width correction value THOS, which is carried out by the control device 109 (microcomputer 109a).

[0039] In step S601, the control device 109 determines whether the internal combustion engine 101 is in an idling state based on the accelerator opening ACC, the engine rotation speed, and the like. If the internal combustion engine 101 is in an idle state, the control device 109 proceeds to step S602 and determines whether the fuel pressure fluctuation is below a predetermined value, in other words, whether the fuel pressure is in a predetermined stable state, based on the fuel pressure FP detected by the fuel pressure sensor 126.

[0040] If the internal combustion engine 101 is in an idling state and the fuel pressure is stable, the control device 109 proceeds to step S603. On the other hand, if the internal combustion engine 101 is not in an idle state, the control device 109 temporarily terminates this routine after the determination process of step S601, and if the fuel pressure is fluctuating even when the internal combustion engine 101 is in an idle state, the control device 109 temporarily terminates this routine after the determination process of step S602.

[0041] When the internal combustion engine 101 is in an idling state and the fuel pressure is stable, and the control device 109 proceeds to step S603, it determines whether the internal combustion engine 101 is in a cold state (in other words, in the process of warming up or is currently warming up) based on the coolant temperature TW detected by the water temperature sensor 108, etc. If the internal combustion engine 101 is in an idling state and a cold state, that is, in a cold idle state, the control device 109 proceeds to step S604 and subsequent steps.

[0042] In step S604, the control device 109 stores the injection pulse width TPsb per injection, which is set for split injection (and / or high fuel pressure) in the cold engine idle state, in the built-in nonvolatile memory as the pseudo pulse width TPP to be used for learning the pulse width correction value THOS, which is performed in the idle state after warming up. Next, in step S605 and subsequent steps, the control device 109 learns the pulse width correction value THOS in the cold idle state.

[0043] In step S605, the control device 109 detects the timing at which the fuel injection valve 105 completes closing when the fuel injection valve 105 is injected with the injection pulse width TPsb, that is, the timing at which the fuel injection valve 105 actually closes in response to the valve closing control command, for each fuel injection valve 105 of each cylinder. Next, in step S606, the control device 109 calculates, for each fuel injector 105 of each cylinder, the time from the falling edge of the injection pulse signal (valve closing control command) to the valve closing completion timing as a valve closing time TVC.

[0044] Then, in step S607, the control device 109 calculates the pulse width correction value THOS corresponding to the valve closing time TVC of each fuel injection valve 105 based on the correlation between the valve closing time TVC and the pulse width correction value THOS shown in the map illustrated in FIG. 4. When determining the pulse width correction value THOS from the valve closing time TVC, the control device 109 can search for the pulse width correction value THOS corresponding to the valve closing time TVC by referring to a table for determining the pulse width correction value THOS from the valve closing time TVC, as shown in FIG. 4, and can also calculate the pulse width correction value THOS based on a function that uses the valve closing time TVC as a variable.

[0045] In the next step S608, the control device 109 determines whether the number of times the pulse width correction value THOS has been calculated is equal to or greater than a predetermined value. If the number of calculations of the pulse width correction value THOS is less than the predetermined value, the reliability of the pulse width correction value THOS is not sufficient, and the control device 109 ends this routine without reflecting the obtained pulse width correction value THOS in the correction of the injection pulse width TPsb.

[0046] On the other hand, if the number of calculations of the pulse width correction value THOS is equal to or greater than the predetermined value, the control device 109 proceeds to step S609. In step S609, the control device 109 determines whether the absolute value of the deviation between the pulse width correction value THOS calculated from the previous injection operation (in other words, the previous value of the pulse width correction value THOS) and the pulse width correction value THOS calculated from the current injection operation (in other words, the current value of the pulse width correction value THOS) is below a predetermined value.

[0047] If the absolute value of the deviation between the previous value of the pulse width correction value THOS and the current value of the pulse width correction value THOS is equal to or greater than a predetermined value, the control device 109 determines that there is a possibility that the pulse width correction value THOS (valve closing time TVC) has been erroneously detected, and ends this routine without reflecting the calculated pulse width correction value THOS in the correction of the injection pulse width TPsb. On the other hand, if the absolute value of the deviation between the previous value of the pulse width correction value THOS and the current value of the pulse width correction value THOS is less than the predetermined value, the control device 109 determines that the learning error of the pulse width correction value THOS is sufficiently small, and proceeds to step S610 to correct the injection pulse width TPsb based on the learned pulse width correction value THOS.

[0048] In addition, as described above, in the cold idling state, due to the influence of fuel pressure fluctuations, the learning accuracy of the pulse width correction value THOS is lower than in the idling state after warming up. However, if the learning of the pulse width correction value THOS in the idle state after warming up has not progressed, the control device 109 supplementarily uses the pulse width correction value THOS learned in the cold idle state, thereby minimizing the variation in the injection amount in the cold idle state as much as possible. In other words, the control device 109 preferentially uses the pulse width correction value THOS learned based on the pseudo pulse width TPP in the idle state after warming up for correcting the injection pulse width TPsb in the cold idle state, and supplementarily uses the learning result in the cold idle state when learning in the idle state after warming up is not progressing.

[0049] Next, the learning of the pulse width correction value THOS in the idling state after warming up will be described in detail. If the control device 109 determines in step S603 that the internal combustion engine 101 is not in a cold state but is in a state after warm-up in which warm-up has been completed, that is, is in an idling state after warm-up, the process proceeds to step S611.

[0050] In step S611, the control device 109 reads out the pseudo pulse width TPP stored in the memory in order to perform fuel injection by an injection pulse signal with the pseudo pulse width TPP in an idling state after warming up. The pseudo pulse width TPP is the injection pulse width TPsb per injection in split injection (and / or high fuel pressure) in the cold idling state, which the control device 109 stored in step S604 described above.

[0051] In other words, the control device 109 reproduces the injection control in the cold idle state in the idle state after warming up by performing fuel injection with the injection pulse width TPsb used in the injection control in the cold idle state in the idle state after warming up, and learns the pulse width correction value THOS used to correct the injection pulse width TPsb in the cold idle state in the idle state after warming up.

[0052] Next, the control device 109 proceeds to step S612 and outputs a fuel pressure control signal to increase the pressure of the fuel supplied to the fuel injection valve 105 in order to inject the required injection amount in the idling state after warm-up using fuel injection with the pseudo pulse width TPP. In detail, the control device 109 calculates a target fuel pressure for injecting the required injection amount with the pseudo pulse width TPP from the pseudo pulse width TPP and the required injection amount, and outputs a control signal for adjusting the discharge amount of the high-pressure fuel pump 125 so that the actual fuel pressure becomes the target fuel pressure.

[0053] Here, if the fuel pressure is made higher than normal, the penetration force of the fuel spray increases, and the fuel injected directly into the cylinder from the fuel injection valve 105 becomes more likely to adhere to the piston crown surface and the like. Therefore, when the control device 109 increases the fuel pressure to inject the required injection amount with the pseudo pulse width TPP during idling after warm-up, the control device 109 brings the injection timing of the fuel injection valve 105 closer to the bottom dead center of the piston than when the fuel pressure is normal. By changing the injection timing in this way, the distance from the fuel injection valve 105 to the piston crown surface when the fuel injection valve 105 injects fuel increases, and the fuel spray is prevented from adhering to the piston crown surface or the like.

[0054] When fuel injection with the pseudo pulse width TPP is performed, the control device 109 proceeds to step S613, and detects the valve closing completion timing of the fuel injection valve 105 for each fuel injection valve 105 of each cylinder, similar to step S605. Next, in step S614, the control device 109 calculates, for each fuel injector 105 of each cylinder, the time from the falling edge of the injection pulse signal (valve closing control command) to the valve closing completion timing as a valve closing time TVC.

[0055] Then, in step S615, the control device 109 calculates the pulse width correction value THOS corresponding to the valve closing time TVC of each fuel injection valve 105 based on the correlation between the valve closing time TVC and the pulse width correction value THOS shown in the map illustrated in FIG. 4. The pulse width correction value THOS calculated by the control device 109 in step S615 is a correction value applied to the pseudo pulse width TPP, which is the injection pulse width TPsb used in the split injection in the cold engine idle state.

[0056] That is, the control device 109 learns the injection variation in split injection (and / or high fuel pressure) in the cold idle state in the idle state after warming up. When the engine is cold idling, the fuel injection amount (required injection amount) per combustion cycle is large, so it is affected by fuel pressure pulsation, making it difficult to learn the variation in injection amount (valve closing time) with high accuracy.

[0057] In contrast, when the engine is idling after warming up, the fuel injection amount (required injection amount) per combustion cycle is smaller than when the engine is idling cold, so the impact of fuel pressure pulsation is small and the variation in injection amount (valve closing completion timing) can be learned with high accuracy. In addition, in an idling state after warming up, the control device 109 increases the fuel pressure to inject the required injection amount with the pseudo pulse width TPP, so the speed of the moving element when the fuel injection valve 105 closes increases, which results in a large change in magnetic flux density when the moving element seats, improving the detection accuracy of the valve closing completion timing.

[0058] After determining the pulse width correction value THOS in step S615, the control device 109 proceeds to step S616. In step S616, the control device 109 determines whether the number of times the pulse width correction value THOS has been calculated is equal to or greater than a predetermined value.

[0059] If the number of calculations of the pulse width correction value THOS for the pseudo pulse width TPP is less than a predetermined value, the reliability of the pulse width correction value THOS is not sufficient, and the control device 109 ends this routine without saving the calculated pulse width correction value THOS as the pulse width correction value THOS to be used in the cold idle state. On the other hand, if the number of calculations of the pulse width correction value THOS is equal to or greater than the predetermined value, the control device 109 proceeds to step S617.

[0060] In step S617, the control device 109 determines, for each fuel injection valve 105, whether or not the absolute value of the deviation between the pulse width correction value THOS calculated from the previous injection operation with the pseudo pulse width TPP (in other words, the previous value of the pulse width correction value THOS) and the pulse width correction value THOS calculated from the current injection operation with the pseudo pulse width TPP (in other words, the current value of the pulse width correction value THOS) is below a predetermined value.

[0061] If the absolute value of the deviation between the previous value of the pulse width correction value THOS and the current value of the pulse width correction value THOS is equal to or greater than a predetermined value, there is a possibility that the pulse width correction value THOS (valve closing completion timing) has been erroneously detected, and therefore the control device 109 ends this routine without saving the obtained pulse width correction value THOS as the pulse width correction value THOS to be used in the cold idle state. On the other hand, if the absolute value of the deviation between the previous value of the pulse width correction value THOS and the current value of the pulse width correction value THOS is less than the predetermined value, the control device 109 determines that the learning error of the pulse width correction value THOS is sufficiently small, proceeds to step S618, and saves the pulse width correction value THOS calculated from the injection operation at the pseudo pulse width TPP in the built-in nonvolatile memory as the pulse width correction value THOS to be used for pulse width correction in the cold engine idle state.

[0062] When the control device 109 is in a cold idle state, if the pulse width correction value THOS learned during the idle state after warming up is stored in the built-in nonvolatile memory, the control device 109 corrects the injection pulse width TPsb using the pulse width correction value THOS. By correcting the injection pulse width TPsb in this way, the variation in the injection amount for each fuel injection valve 105 is reduced, and the rotational fluctuation in the idling state before the air-fuel ratio feedback control is started can be suppressed.

[0063] The technical ideas explained in the above embodiments can be used in appropriate combinations as long as no contradiction occurs. Furthermore, although the contents of the present invention have been specifically described with reference to preferred embodiments, it is obvious that a person skilled in the art can adopt various modified embodiments based on the basic technical idea and teachings of the present invention.

[0064] For example, in the process of determining the pulse width correction value THOS based on the detection result of the operating state of the fuel injection valve 105 as a fuel injection device, the control device 109 can detect the valve closing completion timing (in other words, the valve opening time or the valve closing time) as the operating state, and can also detect fluctuations in the idle rotation speed of the internal combustion engine 101 as the operating state of the fuel injection valve 105 and learn the pulse width correction value THOS so as to suppress fluctuations in the idle rotation speed. Furthermore, the control device 109 can learn the pulse width correction value THOS for each range of the coolant temperature that represents the temperature of the internal combustion engine 101.

[0065] Furthermore, the internal combustion engine 101 is not limited to a direct injection type internal combustion engine, and the learning process of the pulse width correction value THOS of the present invention can also be applied to a port injection type internal combustion engine in which a fuel injection device (fuel injection valve 105) injects fuel into the intake port 110 of the internal combustion engine 101. In addition, the pseudo pulse width TPP is stored in advance as a design value in a nonvolatile memory built into the control device 109, and the control device 109 can learn the pulse width correction value THOS by injecting the fuel with the pseudo pulse width TPP as the design value stored in the nonvolatile memory during an idle state after warming up.

[0066] Furthermore, the control device 109 calculates a pulse width correction value THOS used for pulse width correction in a cold idle state and stores the calculated value in a nonvolatile memory. If the deviation between the newly calculated pulse width correction value THOS and the stored pulse width correction value THOS exceeds a predetermined value, the control device 109 updates the memory value, thereby coping with deterioration over time of the fuel injection valve 105 (changes over time in injection variation characteristics). Furthermore, the control device 109 can perform averaging processing such as weighted averaging on the pulse width correction value THOS, and perform pulse width correction using the averaged pulse width correction value THOS. [Explanation of symbols]

[0067] 101... internal combustion engine, 105... fuel injection valve (fuel injection device), 109... control device (fuel injection control device)

Claims

1. 1. A fuel injection control device for an internal combustion engine that acquires information about an operating state of an internal combustion engine and outputs an injection pulse signal to a fuel injection device that injects fuel into the internal combustion engine, The pulse width of the injection pulse signal in a cold engine idle state is stored as a pseudo pulse width; detecting an operation state of the fuel injection device when the required injection amount is injected with the pseudo pulse width in an idling state after warming up; A pulse width correction value is calculated based on the detection result of the operating state. In a cold engine idle state, the pulse width of the injection pulse signal is corrected by the pulse width correction value. Fuel injection control device for internal combustion engines.

2. 2. The fuel injection control device for an internal combustion engine according to claim 1, Split injection is performed in which fuel is injected multiple times per combustion cycle during cold idling, The pseudo pulse width is a pulse width per one of the divided injections. Fuel injection control device for internal combustion engines.

3. 2. The fuel injection control device for an internal combustion engine according to claim 1, The operating state of the fuel injection device is an actual valve opening time relative to the pseudo pulse width, Fuel injection control device for internal combustion engines.

4. 2. The fuel injection control device for an internal combustion engine according to claim 1, When the required injection amount is to be injected with the pseudo pulse width during an idling state after warming up, a fuel pressure control signal is output to adjust the pressure of the fuel pumped to the fuel injection device to a pressure at which the required injection amount is to be injected with the pseudo pulse width. Fuel injection control device for internal combustion engines.

5. 5. The fuel injection control device for an internal combustion engine according to claim 4, the fuel injection device injects fuel directly into a cylinder of the internal combustion engine, When the fuel injection with the pseudo pulse width is performed by increasing the pressure of the fuel pumped to the fuel injection device, the injection timing of the fuel injection device is made closer to the bottom dead center of the piston. Fuel injection control device for internal combustion engines.

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