JP2010196480A - Fuel injection control device for multiple cylinder internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device for a multiple cylinder internal combustion engine, continuously keeping the amount of fuel injected appropriate after the actual amount of fuel injected is substantially converged by performing correction control between cylinders. <P>SOLUTION: With respect to the correction control between the cylinders for determining a learned value of injection quantity according to a variation in rotation fluctuation in the expansion stroke of each cylinder and correcting the amount of fuel injected, first correction control between the cylinders for determining the learned value of the injection quantity with respect to each cylinder per one cycle of an engine is performed when the learned value of the injection quantity is larger than a predetermined value. After that, when the learned value of the injection quantity is smaller than the predetermined value, the correction control between the cylinders is switched to second correction control between the cylinders for determining the average value of the variation in the rotation fluctuation for every 10 cycles of the engine and determining the learned value of the injection quantity with respect to each cylinder based on the average value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for a multi-cylinder internal combustion engine represented by an automobile engine or the like. In particular, the present invention relates to improvement of inter-cylinder correction control that is performed in order to make the combustion mode uniform in the expansion stroke of each cylinder.

  Conventionally, as disclosed in, for example, Patent Documents 1 to 3 below, in a multi-cylinder engine such as a diesel engine for automobiles, the combustion mode of each cylinder becomes uneven, and each expansion When there is a variation in rotational fluctuation in the stroke (combustion stroke), fuel injection control is performed to make these combustion modes uniform.

  For example, for a cylinder having a relatively high rotational fluctuation peak value (maximum crankshaft rotational speed during the expansion stroke), an injection amount learning value such that the rotational fluctuation peak value decreases during the next expansion stroke. In the next expansion stroke of the cylinder, fuel injection is executed with the fuel injection amount reflecting the injection amount learning value. Conversely, for a cylinder having a relatively low peak value of rotational fluctuation, an injection amount learning value is calculated such that the peak value of rotational fluctuation increases in the next expansion stroke, and in the next expansion stroke of the cylinder, Fuel injection is executed with the fuel injection amount reflecting the injection amount learning value. Hereinafter, the fuel injection control that eliminates the variation in rotational fluctuation among the cylinders in this way is referred to as inter-cylinder correction control.

  With this inter-cylinder correction control, engine vibration can be suppressed when the peak value of rotational fluctuation in each cylinder becomes substantially uniform. In addition, the fuel injection amount can be optimized, leading to an improvement in exhaust emission. In particular, this inter-cylinder correction control is executed during idling operation of the engine, and the idling speed can be stabilized.

JP 2008-101625 A JP 2008-14152 A JP-A-5-321742

  However, the conventional inter-cylinder correction control has the following problems.

(1) Influence of shot-to-shot variation In general, an injector mounted on an engine may cause a slight injection amount variation (for example, a variation of about ± 0.5 mm ^{3 with} respect to a target fuel injection amount) for each injection. is there. For example, when the target fuel injection amount is 5 mm ³ and the current actual fuel injection amount becomes 5.5 mm ^{3 due} to the injection amount variation, the injection amount learning value in the inter-cylinder correction control is − The amount is 0.5 mm ^3, and the amount of reduction is corrected by 0.5 mm ³ in the next fuel injection. In this case, when it is assumed that the actual fuel injection amount is 4.5 mm ³ when it is assumed that the reduction correction is not performed at the next fuel injection, the reduction correction is performed by the above injection amount learning value. Therefore, the fuel injection amount actually injected into the cylinder is 4.0 mm ³ . In this case, the actual fuel injection amount is significantly insufficient with respect to the target fuel injection amount. That is, by performing the inter-cylinder correction control, the actual fuel injection amount is deviated from the target fuel injection amount, and engine vibration is promoted. Such a situation may occur frequently in the conventional inter-cylinder correction control.

(2) Influence of flywheel damper Generally, a flywheel damper for absorbing the rotational fluctuation is connected to the crankshaft. Torque is transmitted to the transmission side via this flywheel damper while the vehicle is running, so that the vibration due to engine rotation fluctuation is suppressed by absorbing the rotation fluctuation in the power transmission system. Can do.

  However, during the idling operation of the engine (a state where torque transmission to the power transmission system is interrupted), the above-described rotational fluctuation absorbing effect cannot be obtained, and the expansion stroke of some cylinders of the engine is not achieved. The reaction of the rotational torque absorbed by the flywheel damper (the rotational torque absorbed by the flywheel damper and the reverse rotation torque) must be absorbed by the engine itself. That is, the reverse rotation torque from the flywheel damper is returned to the crankshaft, and the engine causes fluctuations in rotation due to the influence. That is, there is a rotational fluctuation factor that is not related to the fuel injection amount. In the inter-cylinder correction control, the injection amount learning value that reflects the rotational fluctuation due to the influence of the flywheel damper is obtained, so the fuel injection amount is increased or decreased more than necessary, and the fuel injection amount becomes larger than the appropriate value. There was a possibility that the engine vibration would increase due to deviation.

  As described above, in the conventional inter-cylinder correction control, there is a possibility that vibration due to the above-described variation between shots or vibration due to the flywheel damper may occur, and once the actual fuel injection amount is set to the target fuel Even immediately after convergence to injection, the fuel injection amount convergence state may be canceled within a short time and engine vibration may increase due to the above-described problems.

  The present invention has been made in view of such a point, and the object of the present invention is to make sure that the fuel injection amount is continuously appropriate after the actual fuel injection amount is substantially converged by the execution of the inter-cylinder correction control. An object of the present invention is to provide a fuel injection control device for a multi-cylinder internal combustion engine that is maintained.

-Principle of solving the problem-
The solution principle of the present invention taken in order to achieve the above object is that the inter-cylinder correction control (first inter-cylinder correction control) for equalizing the combustion mode in each expansion stroke of each cylinder of the multi-cylinder internal combustion engine. After the combustion mode is once made uniform by the above, by switching to the inter-cylinder correction control (second inter-cylinder correction control) that reduces the reflection degree of the injection amount learning value, the fuel injection amount after the homogenization becomes a short period. This makes it difficult for the situation to change greatly, and stabilizes the fuel injection amount.

-Solution-
Specifically, according to the present invention, during idling operation of an internal combustion engine, an injection amount learning value for equalizing the combustion mode in the expansion stroke of each of the plurality of cylinders is obtained for each cylinder, and the fuel corrected by the injection amount learning value A fuel injection control device for a multi-cylinder internal combustion engine capable of executing inter-cylinder correction control that performs fuel injection with an injection amount is assumed. This fuel injection control device is provided with combustion mode determination means, first inter-cylinder correction control execution means, and second inter-cylinder correction control execution means. The combustion mode determining means determines that the combustion mode in the expansion stroke of each of the plurality of cylinders is substantially uniform. The first inter-cylinder correction control execution means obtains the injection amount learning value for each cylinder for each cycle of the internal combustion engine when it is determined that the combustion mode has not yet been made uniform. First inter-cylinder correction control is performed in which fuel injection is performed with the fuel injection amount corrected by the injection amount learning value. Further, the second inter-cylinder correction control execution means makes the combustion mode substantially uniform by the first inter-cylinder correction control, and when the substantially uniform state of the combustion mode continues for a predetermined period, every second cycle of the internal combustion engine. The above-described injection amount learning value for each cylinder is obtained, and second-cylinder correction control is performed in which fuel injection is performed with the fuel injection amount corrected by this injection amount learning value.

  Due to this specific matter, the inter-cylinder correction control is started, and when the combustion mode in the expansion stroke of each of the plurality of cylinders has not been made uniform, the first inter-cylinder correction control is executed. That is, the injection amount learning value for each cylinder is obtained for each cycle of the internal combustion engine, and the fuel injection at the next expansion stroke is performed with the fuel injection amount corrected by the injection amount learning value. When the combustion mode is substantially uniformed by the first inter-cylinder correction control, and the substantially uniform state of the combustion mode continues for a predetermined period, the second inter-cylinder correction control is executed. That is, the injection amount learning value for each cylinder is obtained for each of a plurality of cycles of the internal combustion engine, and fuel injection is performed with the fuel injection amount corrected by the injection amount learning value. Thus, after the inter-cylinder correction control is switched to the second inter-cylinder correction control, the injection amount learning value for each cylinder is obtained for each of a plurality of cycles of the internal combustion engine. That is, the fuel injection amount can be shortened by lowering the correction frequency (correction amount and correction interval) of the fuel injection amount based on the injection amount learning value, compared to the case where the injection amount learning value for each cylinder is obtained for each cycle. It is possible to prevent a large change in the meantime. As a result, after switching to the correction control between the second cylinders, the fuel injection amount is continuously kept appropriate, and the convergence state of the fuel injection amount is released within a short time, and the internal combustion engine It is avoided that the vibration becomes large.

  Specifically, as a determination method of the combustion form determination means, when the difference between the peak values at which the rotational speed is highest in the expansion stroke of each cylinder is equal to or less than a predetermined amount, It is determined that the combustion form is substantially uniform.

  That is, for example, the peak value of the rotation fluctuation is obtained based on an output signal from a sensor or the like that detects the rotation speed of the crankshaft, for example, and whether or not the combustion mode is substantially uniform from the difference between the peak values in the expansion stroke of each cylinder. Can be determined.

  Specifically, as the operation of the second inter-cylinder correction control executed by the second inter-cylinder correction control execution means, the average value of the rotational fluctuations of each of the multiple cycles for each cylinder of the internal combustion engine (for example, each cylinder) The injection amount learning value is obtained from the average value of the peak values of the rotational fluctuations at, and fuel injection is carried out with the fuel injection amount corrected by the injection amount learning value.

  Thereby, during the execution of the correction control between the second cylinders, the displacement amount of the rotational fluctuation due to the influence of the shot-to-shot variation and the flywheel damper described above is offset to some extent. For this reason, it is possible to obtain the injection amount learning value based only on the rotation fluctuation caused by the deviation of the original fuel injection amount. That is, an injection amount learning value that can correct only the deviation amount of the fuel injection amount is obtained, and the fuel injection amount according to the learned injection amount can be obtained. For this reason, after switching to the correction control between the second cylinders, the fuel injection amount is continuously kept appropriate, and the vibration of the internal combustion engine can be reduced.

  Further, as the operation of the second inter-cylinder correction control executed by the second inter-cylinder correction control execution means, the following operation may be mentioned. That is, the number of cycles of the internal combustion engine for obtaining the average value of the rotational fluctuation is increased as the duration of the correction control between the second cylinders becomes longer.

  According to this, at the beginning of the start of the correction control between the second cylinders, the injection amount learning value is obtained at a relatively short interval, and the fuel injection amount is corrected. If the combustion mode is continuously made uniform, the injection amount learning value is gradually obtained at long intervals, and the fuel injection amount is corrected. For this reason, the longer the period in which the combustion mode is substantially uniform, the smaller the influence degree of the injection amount learning value, and the more stable fuel injection amount can be secured.

  Further, as the operation of the second inter-cylinder correction control executed by the second inter-cylinder correction control execution means, more specifically, at the time of switching from the first inter-cylinder correction control to the second inter-cylinder correction control. The larger the injection amount learning value is, the smaller the number of cycles of the internal combustion engine for obtaining the average value of rotational fluctuations at the beginning of the start of the second inter-cylinder correction control.

  According to this, even if the injection amount learning value at the time of switching from the first inter-cylinder correction control to the second inter-cylinder correction control is a relatively large value, the initial inter-cylinder correction control Since the calculation frequency of the injection amount learning value is sometimes increased, it is possible to obtain high convergence of the fuel injection amount.

  In the present invention, after the combustion mode is once uniformized by the first inter-cylinder correction control for obtaining the injection amount learning value for each cylinder for each cycle of the internal combustion engine, the injection amount learning value for each cylinder is obtained for every plurality of cycles. By switching to the correction control between the second cylinders, it is difficult to cause a situation in which the fuel injection amount after the uniformization changes greatly in a short period, and the fuel injection amount is stabilized. . For this reason, it becomes possible to continuously exhibit the vibration suppressing effect of the internal combustion engine by the inter-cylinder correction control.

It is a schematic block diagram of the engine which concerns on embodiment, and its control system. It is sectional drawing which shows the combustion chamber of a diesel engine, and its peripheral part. It is a block diagram which shows the structure of control systems, such as ECU. It is a flowchart figure which shows the procedure of correction | amendment control between cylinders. It is a wave form diagram which shows the rotation fluctuation of a crankshaft at the time of starting the count up of a learning value convergence counter. FIG. 4 is a timing chart showing an example of changes in the fuel injection amount deviation, the fuel injection amount, the learning value convergence counter count value, the inter-cylinder correction stabilization flag, and the engine vibration level during inter-cylinder correction control execution. is there.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a case where the present invention is applied to a common rail in-cylinder direct injection multi-cylinder (for example, in-line 4-cylinder) diesel engine (compression self-ignition internal combustion engine) mounted on an automobile will be described.

-Engine configuration-
First, a schematic configuration of a diesel engine (hereinafter simply referred to as an engine) according to the present embodiment will be described. FIG. 1 is a schematic configuration diagram of an engine 1 and its control system according to the present embodiment. Moreover, FIG. 2 is sectional drawing which shows the combustion chamber 3 of a diesel engine, and its peripheral part.

  As shown in FIG. 1, the engine 1 according to the present embodiment is configured as a diesel engine system having a fuel supply system 2, a combustion chamber 3, an intake system 6, an exhaust system 7 and the like as main parts.

  The fuel supply system 2 includes a supply pump 21, a common rail 22, an injector (fuel injection valve) 23, a shutoff valve 24, a fuel addition valve 26, an engine fuel passage 27, an addition fuel passage 28, and the like.

  The supply pump 21 pumps fuel from the fuel tank, makes the pumped fuel high pressure, and supplies it to the common rail 22 via the engine fuel passage 27. The common rail 22 has a function as a pressure accumulation chamber that holds (accumulates) the high-pressure fuel supplied from the supply pump 21 at a predetermined pressure, and distributes the accumulated fuel to the injectors 23. The injector 23 includes a piezoelectric element (piezo element) therein, and is configured by a piezo injector that is appropriately opened to supply fuel into the combustion chamber 3. Details of the fuel injection control from the injector 23 will be described later.

  The supply pump 21 supplies a part of the fuel pumped from the fuel tank to the fuel addition valve 26 via the addition fuel passage 28. The added fuel passage 28 is provided with the shutoff valve 24 for shutting off the added fuel passage 28 and stopping fuel addition in an emergency.

  The fuel addition valve 26 is configured so that the fuel addition amount to the exhaust system 7 becomes a target addition amount (addition amount that makes the exhaust A / F become the target A / F) by an addition control operation by the ECU 100 described later. In addition, it is constituted by an electronically controlled on-off valve whose valve opening timing is controlled so that the fuel addition timing becomes a predetermined timing. That is, a desired fuel is injected and supplied from the fuel addition valve 26 to the exhaust system 7 (from the exhaust port 71 to the exhaust manifold 72) at an appropriate timing.

  The intake system 6 includes an intake manifold 63 connected to an intake port 15a formed in the cylinder head 15 (see FIG. 2), and an intake pipe 64 that constitutes an intake passage is connected to the intake manifold 63. Further, an air cleaner 65, an air flow meter 43, and a throttle valve 62 are arranged in this intake passage in order from the upstream side. The air flow meter 43 outputs an electrical signal corresponding to the amount of air flowing into the intake passage via the air cleaner 65.

  The exhaust system 7 includes an exhaust manifold 72 connected to an exhaust port 71 formed in the cylinder head 15, and exhaust pipes 73 and 74 constituting an exhaust passage are connected to the exhaust manifold 72. In addition, a maniverter (exhaust gas purification device) 77 provided with a NOx storage catalyst (NSR catalyst: NOx Storage Reduction catalyst) 75 and a DPNR catalyst (Diesel Particle-NOx Reduction catalyst) 76, which will be described later, is disposed in the exhaust passage. Yes. Hereinafter, the NSR catalyst 75 and the DPNR catalyst 76 will be described.

The NSR catalyst 75 is an NOx storage reduction catalyst. For example, alumina (Al ₂ O ₃ ) is used as a support, and potassium (K), sodium (Na), lithium (Li), cesium (Cs), for example, is supported on this support. Alkali metal such as barium (Ba), alkaline earth such as calcium (Ca), rare earth such as lanthanum (La) and yttrium (Y), and noble metal such as platinum (Pt) were supported. It has a configuration.

The NSR catalyst 75 occludes NOx in a state where a large amount of oxygen is present in the exhaust gas, has a low oxygen concentration in the exhaust gas, and a large amount of reducing component (for example, an unburned component (HC) of the fuel). In the existing state, NOx is reduced to NO ₂ or NO and released. NO NOx released as NO ₂ or NO, the N ₂ is further reduced due to quickly reacting with HC or CO in the exhaust. Further, HC and CO are oxidized to H ₂ O and CO ₂ by reducing NO ₂ and NO. That is, by appropriately adjusting the oxygen concentration and HC component in the exhaust gas introduced into the NSR catalyst 75, HC, CO, and NOx in the exhaust gas can be purified. In the present embodiment, the oxygen concentration and HC component in the exhaust gas can be adjusted by the fuel addition operation from the fuel addition valve 26.

  On the other hand, the DPNR catalyst 76 is, for example, a porous ceramic structure carrying a NOx storage reduction catalyst, and PM in the exhaust gas is collected when passing through the porous wall. Further, when the air-fuel ratio of the exhaust gas is lean, NOx in the exhaust gas is stored in the NOx storage reduction catalyst, and when the air-fuel ratio becomes rich, the stored NOx is reduced and released. Further, the DPNR catalyst 76 carries a catalyst that oxidizes and burns the collected PM (for example, an oxidation catalyst mainly composed of a noble metal such as platinum).

  Here, the structure of the combustion chamber 3 of a diesel engine and its peripheral part is demonstrated using FIG. As shown in FIG. 2, a cylinder block 11 constituting a part of the engine body is formed with a cylindrical cylinder bore 12 for each cylinder (four cylinders), and a piston 13 is formed inside each cylinder bore 12. Is accommodated so as to be slidable in the vertical direction.

  The combustion chamber 3 is formed above the top surface 13 a of the piston 13. That is, the combustion chamber 3 is defined by the lower surface of the cylinder head 15 attached to the upper part of the cylinder block 11 via the gasket 14, the inner wall surface of the cylinder bore 12, and the top surface 13 a of the piston 13. A cavity 13 b is formed in a substantially central portion of the top surface 13 a of the piston 13, and this cavity 13 b also constitutes a part of the combustion chamber 3.

  The piston 13 has a small end portion 18a of a connecting rod 18 connected by a piston pin 13c, and a large end portion of the connecting rod 18 is connected to a crankshaft that is an engine output shaft. As a result, the reciprocating movement of the piston 13 in the cylinder bore 12 is transmitted to the crankshaft via the connecting rod 18, and the engine output is obtained by rotating the crankshaft. Further, a glow plug 19 is disposed toward the combustion chamber 3. The glow plug 19 functions as a start-up assisting device that is heated red when an electric current is applied immediately before the engine 1 is started and a part of the fuel spray is blown onto the glow plug 19 to promote ignition and combustion.

  The cylinder head 15 is formed with an intake port 15a for introducing air into the combustion chamber 3 and an exhaust port 71 for discharging exhaust gas from the combustion chamber 3, and an intake valve for opening and closing the intake port 15a. 16 and an exhaust valve 17 for opening and closing the exhaust port 71 are provided. The intake valve 16 and the exhaust valve 17 are disposed to face each other with the cylinder center line P interposed therebetween. That is, the engine 1 is configured as a cross flow type. The cylinder head 15 is provided with the injector 23 that directly injects fuel into the combustion chamber 3. The injector 23 is disposed at a substantially upper center of the combustion chamber 3 in a standing posture along the cylinder center line P, and injects fuel introduced from the common rail 22 toward the combustion chamber 3 at a predetermined timing. It has become.

  Furthermore, as shown in FIG. 1, the engine 1 is provided with a supercharger (turbocharger) 5. The turbocharger 5 includes a turbine wheel 52 and a compressor wheel 53 that are connected via a turbine shaft 51. The compressor wheel 53 is disposed facing the intake pipe 64, and the turbine wheel 52 is disposed facing the exhaust pipe 73. For this reason, the turbocharger 5 performs a so-called supercharging operation in which the compressor wheel 53 is rotated using the exhaust flow (exhaust pressure) received by the turbine wheel 52 to increase the intake pressure. The turbocharger 5 in the present embodiment is a variable nozzle type turbocharger, and a variable nozzle vane mechanism (not shown) is provided on the turbine wheel 52 side. By adjusting the opening of the variable nozzle vane mechanism, the engine 1 supercharging pressure can be adjusted.

  An intake pipe 64 of the intake system 6 is provided with an intercooler 61 for forcibly cooling the intake air whose temperature has been raised by supercharging in the turbocharger 5. The throttle valve 62 provided further downstream than the intercooler 61 is an electronically controlled on-off valve whose opening degree can be adjusted steplessly. It has a function of narrowing down the area and adjusting (reducing) the supply amount of the intake air.

  Further, the engine 1 is provided with an exhaust gas recirculation passage (EGR passage) 8 that connects the intake system 6 and the exhaust system 7. The EGR passage 8 is configured to reduce the combustion temperature by recirculating a part of the exhaust gas to the intake system 6 and supplying it again to the combustion chamber 3, thereby reducing the amount of NOx generated. In addition, the EGR passage 8 is opened and closed steplessly by electronic control, and the exhaust gas passing through the EGR passage 8 (recirculating) is cooled by an EGR valve 81 that can freely adjust the exhaust flow rate flowing through the passage. An EGR cooler 82 is provided.

-Sensors-
Various sensors are attached to each part of the engine 1, and signals related to the environmental conditions of each part and the operating state of the engine 1 are output.

  For example, the air flow meter 43 outputs a detection signal corresponding to the flow rate of intake air (intake air amount) upstream of the throttle valve 62 in the intake system 6. The intake air temperature sensor 49 is disposed in the intake manifold 63 and outputs a detection signal corresponding to the temperature of the intake air. The intake pressure sensor 48 is disposed in the intake manifold 63 and outputs a detection signal corresponding to the intake air pressure. The A / F (air-fuel ratio) sensor 44 outputs a detection signal that continuously changes in accordance with the oxygen concentration in the exhaust gas downstream of the manipulator 77 of the exhaust system 7. Similarly, the exhaust temperature sensor 45 outputs a detection signal corresponding to the temperature of the exhaust gas (exhaust temperature) downstream of the manipulator 77 of the exhaust system 7. The rail pressure sensor 41 outputs a detection signal corresponding to the fuel pressure stored in the common rail 22. The throttle opening sensor 42 detects the opening of the throttle valve 62.

-ECU-
As shown in FIG. 3, the ECU 100 includes a CPU 101, a ROM 102, a RAM 103, a backup RAM 104, and the like. The ROM 102 stores various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU 101 executes various arithmetic processes based on various control programs and maps stored in the ROM 102. The RAM 103 is a memory that temporarily stores calculation results of the CPU 101, data input from each sensor, and the like. The backup RAM 104 is a nonvolatile memory that stores data to be saved when the engine 1 is stopped, for example. Memory.

  The CPU 101, the ROM 102, the RAM 103, and the backup RAM 104 are connected to each other via the bus 107, and are connected to the input interface 105 and the output interface 106.

  The input interface 105 is connected with the rail pressure sensor 41, the throttle opening sensor 42, the air flow meter 43, the A / F sensor 44, the exhaust temperature sensor 45, the intake pressure sensor 48, and the intake temperature sensor 49. Further, the input interface 105 includes a water temperature sensor 46 that outputs a detection signal corresponding to the cooling water temperature of the engine 1, an accelerator opening sensor 47 that outputs a detection signal corresponding to the depression amount of the accelerator pedal, and an output shaft of the engine 1. A crank position sensor 40 that outputs a detection signal (pulse) every time the (crankshaft) rotates by a certain angle, and a vehicle speed sensor 4A that is provided on a drive shaft connected to the drive wheels and detects the traveling speed of the vehicle are connected. ing. On the other hand, the injector 23, the fuel addition valve 26, the throttle valve 62, the EGR valve 81, and the like are connected to the output interface 106.

  The ECU 100 executes various controls of the engine 1 based on the outputs of the various sensors described above. Further, the ECU 100 executes pilot injection, pre-injection, main injection, after-injection, and post-injection as fuel injection control of the injector 23. Further, the ECU 100 executes inter-cylinder correction control, which will be described later, based on the outputs of the various sensors described above, particularly the crank position sensor 40, the throttle opening sensor 42, and the vehicle speed sensor 4A.

-Inter-cylinder correction control-
Next, the inter-cylinder correction control that is the characteristic feature of this embodiment will be described. The feature of the inter-cylinder correction control according to the present embodiment is that the first inter-cylinder correction control and the second inter-cylinder correction control are switched at a predetermined timing.

  Specifically, in the situation where the combustion mode in the expansion stroke of each cylinder is not uniform, the first inter-cylinder correction control is performed. In this first inter-cylinder correction control, an injection amount learning value for each cylinder is obtained for each cycle of the engine 1 (each time an expansion stroke for four cylinders is completed), and fuel injection in which this injection amount learning value is reflected. Fuel injection in quantity is repeated every cycle.

  On the other hand, after the combustion mode is made substantially uniform by the first inter-cylinder correction control, the control is switched to the second inter-cylinder correction control. In this second inter-cylinder correction control, the injection amount learning value (each of each cylinder) is determined every plural cycles of the engine 1 (for example, every time the expansion stroke for four cylinders is completed 10 times (total of 40 expansion strokes are completed)). The average value of the rotational fluctuation of each cylinder (the injection amount learning value calculated based on the average value of the rotational fluctuation (the peak value of the rotational fluctuation) for each of the ten expansion strokes) is obtained, and this injection amount learned value is reflected. The fuel injection with the fuel injection amount thus performed is carried out until the next calculation of the injection amount learning value is executed. That is, the correction of the fuel injection amount in the second inter-cylinder correction control is performed for each of a plurality of cycles of the engine 1.

  The second inter-cylinder correction control is canceled when the target fuel injection is changed due to an increase in the electric load of the engine 1 or the like. Thereafter, the inter-cylinder correction control is changed to the first inter-cylinder correction control. Returned.

  Hereinafter, the procedure of inter-cylinder correction control will be specifically described. Further, in the following description, an example will be described in which it is determined whether or not the combustion mode in the expansion stroke of each cylinder is uniform based on variations in the respective rotation fluctuations.

  FIG. 4 is a flowchart showing a procedure of inter-cylinder correction control in the present embodiment. The routine shown in FIG. 4 is executed every predetermined time or every predetermined angle rotation of the crankshaft.

  First, in step ST1, it is determined whether inter-cylinder correction control is being executed. This inter-cylinder correction control is executed while the vehicle is stopped and the engine 1 is idling. For this reason, it is determined that the vehicle is stopped by the detection signal from the vehicle speed sensor 4A, the engine speed is determined to be the idling speed by the detection signal from the crank position sensor 40, and the accelerator opening sensor 47 When it is determined that the amount of depression of the accelerator pedal is “0” based on this detection signal, it is determined that inter-cylinder correction control is being executed, and YES is determined in step ST1.

  If the inter-cylinder correction control is not being executed and NO is determined in step ST1, this routine is temporarily terminated.

  If the inter-cylinder correction control is being executed and YES is determined in step ST1, the process proceeds to step ST2, and it is determined whether or not the inter-cylinder correction stabilization flag provided in advance in the RAM 103 is in an ON state. To do. This inter-cylinder correction stabilization flag indicates that the state in which the fuel injection amount converges because the injection amount learning value in the first inter-cylinder correction control is smaller than a predetermined value is only for a predetermined period (predetermined number of first inter-cylinder correction control). It is turned on when continuous. The ON / OFF switching operation of the inter-cylinder correction stabilization flag will be described later.

  At the beginning of the start of the first inter-cylinder correction control, the fuel injection amount has not yet converged since the injection amount learning value is relatively large, and the inter-cylinder correction stabilization flag is in the OFF state. A NO determination is made and the process moves to step ST3.

  In step ST3, an injection amount learning value for each cycle of the engine 1 is calculated (calculation of an injection amount learning value in the first inter-cylinder correction control). That is, all the expansion strokes from the first cylinder to the fourth cylinder (actually, the expansion strokes are performed in the order of the first cylinder → the third cylinder → the fourth cylinder → the second cylinder). ) Is completed once, and the injection amount learning value for each cylinder is calculated from the variation in rotation fluctuation of each cylinder. More specifically, for a cylinder having a relatively high peak value of rotational fluctuation (the maximum value of the rotational speed of the crankshaft in the expansion stroke), the peak value of rotational fluctuation decreases in the next expansion stroke. An injection amount learning value (an injection amount learning value for correcting the fuel injection amount to be reduced) is obtained. Conversely, for a cylinder with a relatively low peak value of rotational fluctuation, an injection quantity learning value (an injection quantity learning value for correcting the fuel injection quantity to be increased) such that the peak value of rotational fluctuation increases in the next expansion stroke. ) Is calculated (operation for calculating the injection amount learning value by the first inter-cylinder correction control execution means).

After obtaining the injection amount learning value for each cylinder in this way, the process proceeds to step ST4, and it is determined whether or not the absolute value of the obtained injection amount learning value is equal to or less than a predetermined value α (for example, 0.2 mm ³ ). Determination (combustion mode homogenization determination operation by combustion mode determination means). That is, it is determined whether the injection amount learning value is small and the correction amount of the fuel injection amount has converged within a predetermined range. For example, at the beginning of the first inter-cylinder correction control, the absolute value of the injection amount learning value is often larger than the predetermined value α, and this routine is repeated to execute the first inter-cylinder correction control. By being executed a plurality of times, the injection amount learning value gradually decreases, and the absolute value of the injection amount learning value decreases to a predetermined value α or less. The value of α is not limited to that described above, and is set as appropriate.

  If the absolute value of the injection amount learning value exceeds the predetermined value α and a NO determination is made in step ST4, the process proceeds to step ST5, where the learning value convergence counter provided in advance in the RAM 103 is reset (counting). Set the value to “0”). Thereafter, the process proceeds to step ST6, and each fuel injection amount injected into the cylinder in the next expansion stroke of each cylinder is set to a fuel injection amount reflecting the calculated injection amount learning value. As a result, the peak value of the rotational fluctuation in the cylinder in which the peak value of the rotational fluctuation in the previous expansion stroke is relatively high decreases, and conversely, the peak value of the rotational fluctuation in the previous expansion stroke is relatively low. If the cylinder is low, the peak value of rotational fluctuation will increase. That is, the fuel injection amount is corrected so that the difference in rotational fluctuation between the cylinders becomes smaller (the combustion mode becomes uniform) (first cylinder correction control by the first cylinder correction control execution means).

  On the other hand, if the absolute value of the injection amount learning value is equal to or less than the predetermined value α and the determination in step ST4 is YES, the process proceeds to step ST7, and the learning value convergence counter is incremented by “1”.

  FIG. 5 is a waveform diagram showing the rotational fluctuation of the crankshaft when the learning value convergence counter starts counting up. In FIG. 5, # 1 indicates the expansion stroke period of the first cylinder, # 3 indicates the expansion stroke period of the third cylinder, # 4 indicates the expansion stroke period of the fourth cylinder, and # 2 indicates the expansion stroke period. The expansion stroke period of the second cylinder is shown.

  In the rotational fluctuation waveform in the expansion stroke of the first four cylinders in FIG. 5, the peak value of the rotational fluctuation of the first cylinder exceeds the preset peak upper limit threshold value, so that the injection amount learning value Since the absolute value exceeds the predetermined value α, and the peak value of the rotational fluctuation of the fourth cylinder is below a preset peak lower limit threshold, the absolute value of the injection amount learning value exceeds the predetermined value α. It has been exceeded.

  As a result of the execution of the first inter-cylinder correction control, in the rotational fluctuation waveform in the expansion stroke of the latter four cylinders in FIG. And the absolute value of the injection amount learning value is equal to or less than the predetermined value α by being equal to or greater than the peak lower limit threshold. At this timing, YES is determined in step ST4, and the learning value convergence counter is incremented in step ST7.

  After the learning value convergence counter is incremented in step ST7, the process proceeds to step ST8, and it is determined whether or not the count value of the learning value convergence counter has reached a predetermined value β (for example, 50) or more. That is, the first inter-cylinder correction control is executed a plurality of times (the operations of step ST1 to step ST4, step ST7, step ST8, and step ST6 in this routine are executed a plurality of times in order), and YES in step ST4. Whether or not the determined number of times has reached the above-mentioned β, in other words, the state in which the correction amount of the fuel injection amount based on the injection amount learning value has converged within a predetermined range has been β times in the first inter-cylinder correction control. It is determined whether or not there is a continuous state.

  If the count value of the learning value convergence counter is still less than the predetermined value β, NO is determined in step ST8, and the process proceeds to step ST6. That is, each fuel injection amount injected into the cylinder in the next expansion stroke of each cylinder is set to a fuel injection amount reflecting the injection amount learning value calculated in the first inter-cylinder correction control. That is, as described above, the fuel injection amount is corrected so that the difference in rotational fluctuation between the cylinders becomes small (so that the combustion mode becomes uniform).

  On the other hand, if the count value of the learning value convergence counter is greater than or equal to the predetermined value β, a YES determination is made in step ST8 and the process proceeds to step ST9. In this step ST9, the inter-cylinder correction stabilization flag provided in advance in the RAM 103 is turned ON. Then, the process proceeds to step ST10 and the inter-cylinder correction control is switched from the first inter-cylinder correction control to the second inter-cylinder correction control.

  In the second inter-cylinder correction control, the injection amount learning value is calculated every N (for example, 10) cycles. Specifically, the rotation fluctuation (the peak value of the rotation fluctuation) for each cylinder is monitored every cycle of the engine 1, and this is repeated N times, and the average value is obtained for each cylinder. Based on this, an injection amount learning value for each cylinder is obtained. That is, instead of obtaining the injection amount learning value for each cycle, the system waits for the Nth cycle to end, and calculates the injection amount learning value based on the average value of the rotational fluctuations of the Nth cycle (second). Calculation operation of injection amount learning value by inter-cylinder correction control execution means). Note that the value of N is not limited to that described above, and is set as appropriate.

  According to the calculation operation of the injection amount learning value, the influence of the shot-to-shot variation and the effect of the flywheel damper are alleviated, and the injection amount learning value does not change greatly. That is, the fuel injection amount does not change significantly, and the converged fuel injection amount is maintained over a relatively long period.

  In this way, the injection amount learning value calculated after the end of the N cycles is used, and in step ST11, the fuel injection amount injected into the cylinder in the next expansion stroke of each cylinder is set to the calculated injection amount. The fuel injection amount reflecting the learning value is set (second cylinder correction control by the second cylinder correction control execution means).

  Thereafter, the process proceeds to step ST12, and it is determined whether or not the target fuel injection has been changed in accordance with an increase in the electric load of the vehicle (for example, the air conditioner is turned on). If the target fuel injection has not been changed, this routine is terminated as it is. In this case, since the inter-cylinder correction stabilization flag is kept ON, in the next routine, the determination at step ST2 is YES, and the second inter-cylinder correction control is continued.

  On the other hand, if the target fuel injection is changed and YES is determined in step ST12, the process proceeds to step ST13, the inter-cylinder correction stabilization flag is returned to OFF, and this routine is terminated. In this case, in the next routine, a NO determination is made in step ST2, and the process returns to the first inter-cylinder correction control after step ST3 described above.

  FIG. 6 shows the deviation amount of the fuel injection amount, the fuel injection amount corrected by the injection amount learning value, the count value of the learning value convergence counter, and the inter-cylinder correction stabilization when the inter-cylinder correction control according to the present embodiment is executed. It is a timing chart figure showing an example of a flag, a vibration level of engine 1, and each change.

  At timing T1 in FIG. 6, the engine is idling and inter-cylinder correction control (first inter-cylinder correction control) is started.

  At the beginning of the start of the first inter-cylinder correction control, the fuel injection amount deviation amount (deviation amount with respect to the target fuel injection) is also large, so that the injection amount learning value rapidly changes to a large value. In the inter-cylinder correction control, since the injection amount learning value is obtained for each cycle, the fuel injection amount also changes greatly, and the deviation amount of the fuel injection amount rapidly decreases. That is, it is a period in which the convergence is set high for shifting the fuel injection amount to an appropriate value. Along with this, the vibration level of the engine also decreases rapidly.

  At timing T2, when the injection amount learning value becomes smaller than the predetermined value and the variation range of the fuel injection amount converges within the predetermined range, the learning value convergence counter starts counting, and the injection amount learning value is within the predetermined range. During the convergence, the learning value convergence counter is incremented every time the injection amount learning is executed. During this time, the engine vibration level is kept low.

  Then, when the state where the injection amount learning value has converged to the predetermined range is continued and the count value of the learning value convergence counter reaches the predetermined value (timing T3), the inter-cylinder correction stabilization flag is turned ON, The inter-cylinder correction control is switched from the first inter-cylinder correction control to the second inter-cylinder correction control.

  After switching to the second inter-cylinder correction control in this way, the inter-cylinder correction stabilization flag is kept on and the second inter-cylinder correction control is continued until the target fuel injection is changed. . That is, the injection amount learning value is calculated every N cycles (for example, 10 times), and fuel injection reflecting the injection amount learning value is executed. In FIG. 6, at timing T4, the target fuel injection is changed due to an increase in the electric load of the vehicle, and accordingly, the count value of the learning value convergence counter is reset and the correction between cylinders is stabilized. The flag is turned off and the control is switched to the first inter-cylinder correction control. At timing T5, the change width of the fuel injection amount again converges within a predetermined range. At timing T6, the count value of the learning value convergence counter reaches the predetermined value, so that the inter-cylinder correction stabilization flag is turned on. Has been. That is, the control is switched to the second cylinder correction control.

  As described above, in the present embodiment, when the variation in rotational fluctuation in each expansion stroke of each cylinder is large (when the combustion mode is not yet uniform), the first inter-cylinder correction control is executed and the injection is performed. The calculation interval of the amount learning value is shortened so that the fuel injection amount converges to an appropriate value at an early stage. When the variation in rotational fluctuation in the expansion stroke of each cylinder is reduced by this inter-cylinder correction control (when the combustion mode becomes substantially uniform), the control is switched to the second inter-cylinder correction control, and the injection amount learning value is calculated. The interval is lengthened to prevent sudden changes in the fuel injection amount. That is, the correction frequency (correction amount and correction interval) of the fuel injection amount based on the injection amount learning value is made lower than in the first inter-cylinder correction control in which the fuel injection amount for each cylinder is corrected every cycle. Thus, it is possible to prevent the fuel injection amount from changing greatly during a short period of time. Thus, after switching to the correction control between the second cylinders, the fuel injection amount is continuously maintained appropriately, and the convergence state of the fuel injection amount is released within a short time, and the engine 1 It is avoided that the vibration becomes large.

(Modification 1)
Next, a first modification of the present invention will be described. This modification is a modification of the second inter-cylinder correction control. The configuration and operation of the engine 1 and the first inter-cylinder correction control are the same as those in the above-described embodiment. Accordingly, only the second cylinder correction control will be described here.

  In the second cylinder correction control in the embodiment described above, the injection amount learning value is calculated every N cycles (for example, 10 times). That is, the number of cycles for obtaining the average value of rotation fluctuations for calculating the injection amount learning value is a fixed value. In this modification, the number of cycles for obtaining the average value is variable.

  Specifically, when the correction control between the second cylinders is started, the rotation when the correction control between the second cylinders is continued with respect to the number of cycles for obtaining the average value of the rotation fluctuation at the beginning of the start. The number of cycles for obtaining the average value of fluctuations is gradually increased.

  For example, in the first correction control between the second cylinders when the correction control between the second cylinders is started, the average value of the rotational fluctuations is obtained when two cycles (four crankshaft rotations) are completed. The injection amount learning value is calculated based on the obtained value. In the second inter-cylinder correction control, the average value of the rotational fluctuation is obtained at the time when the five cycles (crankshaft 10 revolutions) are completed, and the injection amount learning value is calculated based on the average value. Perform the calculation. Furthermore, in the third inter-cylinder correction control, the average value of the rotational fluctuation is obtained at the time when the 10 cycles (20 crankshafts) are completed, and the injection amount learning value is calculated based on the average value. Perform the calculation. In the second inter-cylinder correction control thereafter, the average value of the rotational fluctuation is obtained every 10 cycles, and the injection amount learning value is calculated based on the average value. In this way, the number of cycles for obtaining the average value of the rotational fluctuation is increased as the duration of the correction control between the second cylinders becomes longer.

  According to this, the longer the period of the second cylinder correction control in which the combustion mode is substantially uniform, the smaller the degree of influence of the injection amount learning value, and the more stable fuel injection amount can be secured. Become.

(Modification 2)
Next, a second modification of the present invention will be described. This modification is also a modification of the second inter-cylinder correction control. The configuration and operation of the engine 1 and the first inter-cylinder correction control are the same as those in the above-described embodiment. Accordingly, only the second cylinder correction control will be described here.

  In this modification, in order to calculate the injection amount learning value in the second inter-cylinder correction control according to the magnitude of the injection amount learning value when switching from the first inter-cylinder correction control to the second inter-cylinder correction control. The number of cycles (10 in the above embodiment) for obtaining the average value of the rotational fluctuations is made variable.

  Specifically, the larger the injection amount learning value when the second inter-cylinder correction control is started, the smaller the number of cycles for obtaining the average value of the rotational fluctuation at the initial start of the second inter-cylinder correction control. (The calculation amount of the injection amount learning value is set high), and thereafter, the number of cycles for obtaining the average value of the rotational fluctuation when the second cylinder correction control is continued is gradually increased.

For example, the predetermined value α (threshold value for determining whether or not the injection amount learning value is within the predetermined range in the flowchart shown in FIG. 4) is set to be larger. For example, it is set to 0.5 mm ³ . When the injection amount learning value at the time of switching from the first inter-cylinder correction control to the second inter-cylinder correction control is 0.5 mm ³ , the first time when the second inter-cylinder correction control is started. In the second inter-cylinder correction control, when two cycles (four crankshaft rotations) are completed, an average value of rotational fluctuations is obtained, and an injection quantity learning value is calculated based on the average value. Correct the injection amount. In the second inter-cylinder correction control, the average value of the rotational fluctuation is obtained at the time when the five cycles (crankshaft 10 revolutions) are completed, and the injection amount learning value is calculated based on the average value. Calculation is performed to correct the fuel injection amount. Furthermore, in the third inter-cylinder correction control, the average value of the rotational fluctuation is obtained at the time when the 10 cycles (20 crankshafts) are completed, and the injection amount learning value is calculated based on the average value. Calculation is performed to correct the fuel injection amount. Then, in the second inter-cylinder correction control thereafter, an average value of rotational fluctuations is obtained every 10 cycles, and the fuel injection amount is corrected by calculating the injection amount learning value based on the average value. Go.

On the other hand, when the injection amount learning value at the time of switching from the first inter-cylinder correction control to the second inter-cylinder correction control is 0.3 mm ³ , the second inter-cylinder correction control is started. In the first second inter-cylinder correction control, the average value of the rotational fluctuation is obtained at the end of the five cycles (10 revolutions of the crankshaft), and the injection amount learning value is calculated based on the average value. To correct the fuel injection amount. In the second inter-cylinder correction control for the second time, the average value of the rotation fluctuation is obtained at the time when 10 cycles (for 20 rotations of the crankshaft) are completed, and the injection amount learning value is calculated based on the average value. Calculation is performed to correct the fuel injection amount. Then, in the second inter-cylinder correction control thereafter, an average value of rotational fluctuations is obtained every 10 cycles, and the fuel injection amount is corrected by calculating the injection amount learning value based on the average value. Go.

Further, when the injection amount learning value when switching from the first inter-cylinder correction control to the second inter-cylinder correction control is 0.2 mm ³ , 10 times as in the above-described embodiment. Every time the cycle (for 20 rotations of the crankshaft) is completed, an average value of rotational fluctuations is obtained, and an injection amount learning value is calculated based on the average value to correct the fuel injection amount. Thereafter, every time 10 cycles are completed, an average value of rotational fluctuations is obtained, and an injection amount learning value is calculated based on the average value, thereby correcting the fuel injection amount.

  According to this, it is possible to switch from the first inter-cylinder correction control to the second inter-cylinder correction control relatively early, and it is assumed that the injection amount learning value when the control is switched to the second inter-cylinder correction control. Even if the value is a relatively large value, since the calculation amount of the injection amount learning value is high at the initial stage of the correction control between the second cylinders, the convergence of the fuel injection amount can be obtained.

-Other embodiments-
In the embodiment and the modification described above, the case where the present invention is applied to a common rail in-cylinder direct injection multi-cylinder diesel engine mounted on an automobile has been described. The present invention is not limited to this, and can also be applied to a gasoline engine. The present invention can also be applied to engines used for purposes other than those for automobiles. Further, the present invention can be applied not only to an inline engine but also to a V engine, a horizontally opposed engine, and the like. Further, the number of cylinders, the fuel injection method, and other engine specifications are not particularly limited.

  Further, in the above-described embodiments and modifications, it is determined whether or not the combustion mode in each expansion stroke is substantially uniform based on variations in rotational fluctuation in each expansion stroke. The present invention is not limited to this, and the work amount in the expansion stroke of each cylinder may be obtained, and it may be determined whether or not the combustion mode has become substantially uniform based on the variation in the work amount.

  The present invention is applicable to inter-cylinder correction control for eliminating variation in rotational fluctuation of each cylinder in a common rail in-cylinder direct injection multi-cylinder diesel engine.

1 engine (internal combustion engine)
3 Combustion chamber 12 Cylinder bore

Claims (5)

Cylinder that obtains an injection amount learning value for equalizing the combustion mode in the expansion stroke of each of the plurality of cylinders during idling operation of the internal combustion engine for each cylinder and performs fuel injection with the fuel injection amount corrected by the injection amount learning value In the fuel injection control device for a multi-cylinder internal combustion engine capable of performing the intermediate correction control,
Combustion mode determination means for determining that the combustion mode in the expansion stroke of each of the plurality of cylinders is substantially uniform;
When it is determined that the combustion mode is not yet uniform, the injection amount learning value for each cylinder is obtained for each cycle of the internal combustion engine, and the fuel injection amount corrected by the injection amount learning value is used. First inter-cylinder correction control execution means for performing first inter-cylinder correction control for performing fuel injection;
When the combustion mode is substantially uniformed by the first inter-cylinder correction control and the combustion mode is substantially uniform for a predetermined period, the injection amount learning value for each cylinder is obtained for each of a plurality of cycles of the internal combustion engine. And a second inter-cylinder correction control executing means for performing second inter-cylinder correction control for performing fuel injection with the fuel injection amount corrected by the injection amount learning value. Engine fuel injection control device. In the fuel injection control device for a multi-cylinder internal combustion engine according to claim 1,
When the difference between the peak values at which the rotational speed is highest in the expansion stroke of each cylinder is equal to or less than a predetermined amount, the combustion form determination means substantially uniformizes the combustion form in the expansion stroke of each cylinder. A fuel injection control device for a multi-cylinder internal combustion engine, characterized by: In the fuel injection control device for a multi-cylinder internal combustion engine according to claim 1 or 2,
The second inter-cylinder correction control execution means obtains an injection amount learning value from an average value of rotation fluctuations of a plurality of cycles in each cylinder of the internal combustion engine, and uses the fuel injection amount corrected by the injection amount learning value. A fuel injection control device for a multi-cylinder internal combustion engine, characterized in that the fuel injection is performed. In the fuel injection control device for a multi-cylinder internal combustion engine according to claim 3,
The second inter-cylinder correction control execution means is configured to increase the number of cycles of the internal combustion engine for obtaining the average value of rotational fluctuations as the duration of the second inter-cylinder correction control increases. A fuel injection control device for a multi-cylinder internal combustion engine. In the fuel injection control device for a multi-cylinder internal combustion engine according to claim 3 or 4,
The second inter-cylinder correction control execution means increases the injection amount learning value at the time of switching from the first inter-cylinder correction control to the second inter-cylinder correction control. A fuel injection control device for a multi-cylinder internal combustion engine, characterized in that the number of cycles of the internal combustion engine for obtaining an average value of rotational fluctuations is set to be small.

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