Control device of engine

Abstract

To suppress regular combustion fluctuation between combustion cycles.SOLUTION: A control device of an engine comprises: an engine 1 having a cylinder 2 in which gas exchange occurs by opening and closing an intake valve 11 and an exhaust valve 12, and in which a plurality of cylinders operate by sequentially executing combustion cycles; a device that is attached to the engine, and related to combustion in each of the plurality of cylinders; and a controller 100 that controls operation of the engine by outputting a control signal to the device. The controller is an engine plant model 1000 that, based on a plant model that represents the regularity of combustion fluctuation between combustion cycles, estimates state quantities of the cylinders before combustion in each of the plurality of cylinders and outputs a control signal corrected based on the estimated state quantities to the device.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The technology disclosed herein relates to an engine control device. [Background technology]

[0002] Patent Document 1 describes a conventional internal combustion engine control device. This internal combustion engine control device performs EGR (Exhaust Gas Recirculation) control to return exhaust gas into the cylinder, calculates the temperature of gas in the cylinder and the EGR rate when both the intake valve and the exhaust valve are closed in the combustion cycle, and corrects ignition timing based on the calculated gas temperature and EGR rate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6594825 Summary of the Invention [Problem to be solved by the invention]

[0004] The conventional control device described in Patent Document 1 calculates the temperature of gas in the cylinder and the EGR rate after the intake valve closes, and corrects the ignition timing for that combustion cycle. In other words, the conventional control device measures the state variables of the cylinder for each cycle and corrects the control variables of the device.

[0005] In response to this, the inventors of the present application have newly discovered that combustion in a previous cycle affects combustion in a subsequent cycle, resulting in combustion fluctuations that have a pattern with the progression of the cycles.This long-term combustion fluctuation spanning multiple combustion cycles cannot be measured or suppressed by conventional control systems that measure the state quantities of the cylinders for each cycle.

[0006] The technology disclosed herein suppresses regular combustion fluctuations between combustion cycles. [Means for solving the problem]

[0007] The technology disclosed herein relates to an engine control device. an engine having cylinders in which gas exchange occurs by opening and closing intake valves and exhaust valves, and in which a plurality of the cylinders sequentially execute combustion cycles; a device attached to the engine and related to combustion in each of the plurality of cylinders; a controller that controls operation of the engine by outputting a control signal to the device; The controller estimates state quantities of the cylinders before combustion in each of the plurality of cylinders based on a plant model of the engine that represents regular combustion fluctuations between the combustion cycles, and outputs a control signal corrected based on the estimated state quantities to the device.

[0008] The controller controls combustion in each of the engine's cylinders by outputting control signals to the devices, and the engine operates by the cylinders sequentially executing combustion cycles.

[0009] The controller estimates the state quantities of the cylinders before combustion in each of the plurality of cylinders based on the plant model. By using the plant model, the controller can estimate the state quantities of the cylinders before combustion in each of the plurality of cylinders.

[0010] The plant model represents combustion fluctuations with regularity between combustion cycles. The combustion fluctuations with regularity between combustion cycles occur when combustion in a previous cycle affects combustion in a subsequent cycle. The controller corrects the control amount of the device based on the estimated cylinder state quantity. The controller corrects the control amount of the device so that the combustion fluctuations with regularity between combustion cycles are suppressed. The controller outputs the corrected control signal to the device, thereby suppressing the combustion fluctuations with regularity between combustion cycles.

[0011] The combustion fluctuations that have a regularity between combustion cycles can occur even during steady-state operation of the engine, that is, during operation in which the controlled variable of the device is maintained constant over time. The engine control device described above can suppress the combustion fluctuations during steady-state operation of the engine.

[0012] the plant model is a model that estimates a state quantity of the cylinder for each combustion cycle, The controller may estimate a temperature, an air amount, an amount of burned gas, and an amount of fuel as the state quantities of the cylinder based on the plant model.

[0013] A combustion variation with regularity between combustion cycles is not limited to a variation for each combustion cycle, but may be a periodic variation spanning two or more combustion cycles. Even if the period of the combustion variation between combustion cycles is a period consisting of two or more combustion cycles, the combustion variation with regularity between combustion cycles is the result of the combustion in the previous cycle continuously affecting the combustion in the subsequent cycle. Therefore, the plant model is a model that estimates the state quantity of the cylinder for each combustion cycle. Such a plant model is not limited to application to combustion variation with a specific period, but can be widely applied to combustion variation with regularity between combustion cycles. This increases the versatility of the plant model.

[0014] Furthermore, according to the inventors' research, one of the causes of the regular combustion variation between combustion cycles is believed to be the influence of unburned fuel in a previous combustion cycle on combustion in the following cycle through internal EGR gas. Therefore, the controller estimates the cylinder state quantities, namely, temperature, air amount, burned gas amount, and fuel amount, based on a plant model. The control variables of the devices are corrected based on the estimated temperature, air amount, burned gas amount, and fuel amount, thereby suppressing the combustion variation between combustion cycles.

[0015] The plant model may be a combined model of a physical model related to gas exchange in the cylinder and a statistical model related to combustion in the cylinder.

[0016] This allows a highly accurate plant model to be constructed in a simple manner.

[0017] the engine control device includes pressure sensors attached to the engine corresponding to each of the plurality of cylinders, and outputting signals corresponding to pressures in the cylinders to the controller; The controller may estimate the state quantity of the cylinder in which combustion will occur next, based on the combustion state in the cylinder based on the signal from the pressure sensor and the plant model, before the intake valve of the cylinder closes.

[0018] In addition to the regular combustion fluctuations between combustion cycles described above, combustion fluctuations also include random combustion fluctuations caused by factors such as variations in fuel injection amounts between multiple cylinders. Random combustion fluctuations can be identified by measuring the combustion state in the previous combustion cycle.

[0019] The controller measures the combustion state in the previous combustion cycle based on the signal from the pressure sensor. This allows the controller to grasp random combustion fluctuations that occurred in the previous combustion cycle before the next combustion in the cylinder. As described above, the controller can also grasp regular combustion fluctuations between combustion cycles based on the plant model. As a result, the controller can accurately estimate the state quantities of the next combustion in the cylinder before the next combustion in that cylinder.

[0020] The controller can also estimate the state quantities of the cylinder in which combustion will occur next based on the pressure sensor signal and the plant model once combustion in the previous combustion cycle has ended. The controller can estimate the state quantities of the cylinder at a relatively early timing, specifically, before the intake valve closes. The ability to estimate the state quantities of the cylinder at an early timing increases the number of devices that the controller can perform correction control on. This is advantageous for suppressing regular combustion fluctuations between combustion cycles.

[0021] The combustion state based on the signal of the pressure sensor may include an indicated mean effective pressure (IMEP) and a center of gravity (MFB50), where MFB50 is the crank angle at which the mass fraction burned is 50%.

[0022] According to the study by the present inventors, one example of combustion fluctuations with regularity between combustion cycles is the behavior in which the IMEP and MFB50 fluctuate over multiple combustion cycles, as if rotating on a two-dimensional plane of the IMEP and MFB50. By understanding the combustion state using the two parameters, IMEP and MFB50, the controller can effectively suppress combustion fluctuations with regularity between combustion cycles.

[0023] the device includes an injector attached to the engine corresponding to each of the plurality of cylinders and configured to inject fuel into the cylinder; The controller may adjust the fuel injection amount based on the estimated state quantity.

[0024] As mentioned above, one of the reasons for combustion variation between combustion cycles is that unburned fuel in a previous combustion cycle affects combustion in the subsequent cycle. In other words, if a large amount of unburned fuel is sent to a subsequent cycle via EGR gas, combustion in that cycle will be relatively good, and if a small amount of unburned fuel is sent to a subsequent cycle via EGR gas, combustion in that cycle will be relatively poor.

[0025] If the fuel injection amount is increased or decreased based on the estimated state quantity, combustion fluctuations between combustion cycles are suppressed.

[0026] The injector injects fuel at least during the intake stroke before the intake valve closes, The controller may adjust the amount of fuel injected by the injector during the intake stroke.

[0027] As described above, the controller can estimate the state quantities of the cylinder in which combustion will occur next before the intake valve of that cylinder closes, based on the combustion state in the cylinder based on the signal from the pressure sensor and the plant model. Therefore, the controller can adjust the amount of fuel injected by the injector during the intake stroke before the intake valve closes.

[0028] the device includes an intake valve mechanism that changes the opening and closing timing of the intake valve; The controller may adjust the opening and closing timing of the intake valve based on the estimated state quantity.

[0029] As described above, the controller can estimate the state quantities of the cylinder in which combustion will occur next before the intake valve of that cylinder closes, thereby realizing adjustment of the intake valve opening and closing timing.

[0030] the device includes a spark plug attached to the engine corresponding to each of the plurality of cylinders and configured to ignite an air-fuel mixture in the cylinder; The controller may adjust the ignition timing of the spark plug based on the estimated state quantity.

[0031] Adjusting the ignition timing changes the center of gravity of combustion, and is therefore effective in suppressing combustion fluctuations. [Effects of the Invention]

[0032] The engine control device described above can suppress regular combustion fluctuations between combustion cycles. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 shows the engine. [Figure 2] FIG. 2 is a block diagram of the engine control device. [Figure 3] Figure 3 shows the engine operating range map. [Figure 4] FIG. 4 shows the regular combustion variations between combustion cycles. [Figure 5] FIG. 5 shows an example of the mechanism by which regular combustion fluctuations occur. [Figure 6] Figure 6 shows the engine plant model. [Figure 7] FIG. 7 is a variable table relating to the plant model. [Figure 8] FIG. 8 is a control block diagram of the controller. [Figure 9] FIG. 9 shows a partial configuration of the control block. [Figure 10] FIG. 10 is a timing chart relating to engine control. [Figure 11] FIG. 11 illustrates the effect of the engine control disclosed herein. [Figure 12] FIG. 12 shows a partial configuration of a control block according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0034] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an engine control device will be described below with reference to the drawings. The engine control device described here is an example.

[0035] (Engine configuration) FIG. 1 shows an engine 1. FIG. 2 is a block diagram of a control device for the engine 1 including the engine 1. The engine 1 is mounted on an automobile. The engine 1 is a driving source for running the automobile. The engine 1 is operated by receiving a supply of fuel containing, for example, gasoline.

[0036] The engine 1 includes an engine body 1a having a plurality of cylinders 2. The engine body 1a has a plurality of cylinders 2. The plurality of cylinders 2 are arranged in a line, for example, in a direction perpendicular to the plane of the paper in FIG.

[0037] The engine body 1a has a cylinder block 3 in which cylinders 2 are formed, and a cylinder head 4 located on the cylinder block 3. Pistons 5 are fitted into the cylinders 2 so that they can reciprocate. The pistons 5 are connected to a crankshaft via connecting rods 8. A combustion chamber 6 is formed by the cylinders 2, the cylinder head 4, and the pistons 5. As the pistons 5 reciprocate, the cylinders 2 repeat a combustion cycle including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. The engine 1 operates by the multiple cylinders 2 sequentially executing their combustion cycles.

[0038] The cylinder head 4 has an intake port 9 and an exhaust port 10. The intake port 9 is connected to an intake passage 20. The intake port 9 is a port for introducing gas supplied from the intake passage 20 into the cylinder 2. The exhaust port 10 is connected to an exhaust passage 30. The exhaust port 10 is a port for guiding exhaust gas from the cylinder 2 to the exhaust passage 30.

[0039] The engine 1 has an intake valve 11 and an exhaust valve 12. The intake valve 11 opens and closes an intake port 9. The exhaust valve 12 opens and closes an exhaust port 10.

[0040] The engine 1 has an intake valve train. The intake valve train moves the intake valve 11. The intake valve train in this embodiment includes an intake S-VT 17. The intake S-VT 17 is electrically or hydraulically driven to continuously change the rotational phase of the intake camshaft relative to the crankshaft within a predetermined angle range. The opening and closing timings of the intake valve 11 are continuously advanced or retarded while maintaining a constant opening period of the intake valve 11. Note that the intake S-VT 17 is not limited to the structure described above.

[0041] The engine 1 has an exhaust valve train mechanism. The exhaust valve train mechanism drives the exhaust valve 12. The exhaust valve train mechanism of this embodiment includes an exhaust S-VT 18. The exhaust S-VT 18 is electrically or hydraulically driven to continuously change the rotational phase of the exhaust camshaft relative to the crankshaft within a predetermined angle range. The exhaust S-VT 18 continuously changes the opening and closing timings of the exhaust valve 12 to the advance or retard side while maintaining a constant exhaust valve opening period. Note that the exhaust S-VT 18 is not limited to the structure described above.

[0042] As described above, the intake passage 20 is connected to the intake port 9. The air cleaner 21 is disposed at the upstream end of the intake passage 20. The air cleaner 21 filters fresh air. The air that passes through the air cleaner 21 is supplied to the cylinder 2 via the intake passage 20 and the intake port 9.

[0043] The air flow sensor SN2 is located downstream of the air cleaner 21 in the intake passage 20. The air flow sensor SN2 outputs a signal corresponding to the air flow rate in the intake passage 20.

[0044] A throttle valve 22 is located downstream of the air flow sensor SN2 in the intake passage 20. The throttle valve 22 changes the size of the cross-sectional area of ​​the intake passage 20 through which air passes.

[0045] As described above, the exhaust passage 30 is connected to the exhaust port 10. The catalytic device 31 is located midway through the exhaust passage 30. The catalytic device 31 purifies the exhaust gas discharged from the cylinder 2. The catalytic device 31 includes, for example, a three-way catalyst. The three-way catalyst oxidizes HC and CO and reduces NOx, thereby removing emissions contained in the exhaust gas. Note that the catalytic device 31 is not limited to a three-way catalyst.

[0046] The engine 1 has spark plugs 13. The spark plugs 13 are attached to the cylinder head 4 for each cylinder 2. The spark plugs 13 forcibly ignite the air-fuel mixture in the combustion chamber 6. The ignition timing of the spark plugs 13 is specified by a controller 100, which will be described later.

[0047] The engine 1 has an injector 14. The injector 14 is attached to the cylinder head 4 for each cylinder 2. The injector 14 injects an amount of fuel designated by the controller 100 into the combustion chamber 6 at a predetermined time.

[0048] As shown in FIG. 2, the engine control device has a controller 100. The controller 100 controls the operation of the engine 1. The controller 100 is a control unit based on a well-known microcomputer. The controller 100 includes a CPU 101, a memory 102, and an input / output bus 103. The CPU 101 is a central processing unit that executes computer programs. These computer programs include basic control programs such as an OS, and application programs that are run on the OS and implement specific functions. The memory 102 stores various computer programs or data used when the computer programs are executed. This computer program is a control program for controlling the engine 1. The memory 102 is provided with a processing area that is used when the CPU 101 performs a series of processes. The input / output bus 103 inputs and outputs electrical signals to and from the controller 100.

[0049] The controller 100 is electrically connected to the airflow sensor SN2 described above. The airflow sensor SN2 outputs a signal to the controller 100. The controller 100 is also electrically connected to a crank angle sensor SN1, an accelerator opening sensor SN3, and a finger pressure sensor SN4. The crank angle sensor SN1 is attached to the cylinder block 3 and outputs a signal corresponding to the rotation of the crankshaft to the controller 100. The accelerator opening sensor SN3 is attached to the accelerator pedal mechanism and outputs a signal corresponding to the depression amount of the accelerator pedal to the controller 100. As shown in FIG. 1, the finger pressure sensor SN4 is attached to the cylinder head 4 for each cylinder 2. The finger pressure sensor SN4 outputs a signal corresponding to the pressure inside the cylinder 2 to the controller 100. The controller 100 receives signals from these sensors SN1-SN4.

[0050] The controller 100 determines the state of the engine 1 based on signals from the sensors SN1-SN4, and outputs control signals to the spark plug 13, the injector 14, the intake S-VT 17, the exhaust S-VT 18, and the throttle valve 22. The controller 100 controls the operation of the engine 1 by outputting control signals to each device.

[0051] 3 illustrates a map 300 relating to the control of the engine 1. The map 300 is stored in the memory 102 of the controller 100.

[0052] The map 300 is defined by the IMEP and rotation speed of the engine 1. The map 300 includes two regions, a first region 301 and a second region 302. More specifically, the first region 301 is a region where the air-fuel mixture in the cylinder 2 is burned by spark ignition, or in other words, the SI (Spark Ignition) region. The second region 302 is a region where the air-fuel mixture in the cylinder 2 is burned by compression ignition, or in other words, the HCCI (Homogeneous Charge Compression Ignition) region. The second region 302 is a region from low rotation to medium rotation and a medium load region within the entire operating range of the engine 1. The first region 301 is a region excluding the second region 302.

[0053] Next, to briefly explain the basic control of the engine 1, the controller 100 sets a target IMEP and a target rotation speed of the engine 1 based on signals from the crank angle sensor SN1, air flow sensor SN2, and accelerator position sensor SN3, and determines the operating range based on the set target IMEP and target rotation speed based on map 300 in Figure 3. Then, based on the determined operating range, the ECU 100 changes the opening and closing timing of the intake valve 11 and the exhaust valve 12, the fuel injection timing and injection amount, and whether or not to perform ignition and the ignition timing.

[0054] Specifically, when the operating state of engine 1 is in first region 301, intake S-VT 17 opens and closes intake valve 11 at a predetermined timing, and exhaust S-VT 18 opens and closes exhaust valve 12 at a predetermined timing. Injector 14 injects fuel into cylinder 2 during the intake stroke and / or compression stroke. Spark plug 13 ignites the air-fuel mixture near top dead center of compression.

[0055] On the other hand, when the operating state of the engine 1 is in the second region 302, the intake S-VT 17 opens and closes the intake valve 11 at a predetermined timing, and the exhaust S-VT 18 opens and closes the exhaust valve 12 at a predetermined timing. The injector 14 injects fuel into the cylinder 2 during the intake stroke. The spark plug 13 does not ignite the air-fuel mixture. The air-fuel mixture undergoes compression auto-ignition and burns near the top dead center of compression.

[0056] This engine 1 achieves high fuel economy by performing HCCI combustion in a certain operating range. However, HCCI combustion is limited to a narrow range due to knocking or misfire. The low-load limit of the second region 302 is limited by the temperature inside cylinder 2 not reaching the auto-ignition temperature, resulting in misfire. For example, introducing internal EGR gas into cylinder 2 can increase the temperature inside cylinder 2, potentially expanding the second region 302 toward the low-load side, as shown by the white arrow in Figure 3. However, if too much EGR gas is introduced into cylinder 2, fuel fluctuations increase. This increase in fuel fluctuations limits the expansion of the second region 302.

[0057] (Regular combustion fluctuations between combustion cycles) The inventors of the present application confirmed combustion fluctuations when the engine 1 was operated under conditions in which the amount of EGR gas into the cylinder 2 was increased. The engine 1 was operated with a lean air / fuel mixture with an excess air ratio λ exceeding 1 and HCCI combustion. FIG. 4 uses indicated mean effective pressure (IMEP) and combustion center of gravity (MFB50) as indicators of combustion fluctuations. The IMEP and MFB50 are plotted for each combustion cycle on a two-dimensional plane with the IMEP on the vertical axis and the MFB50 on the horizontal axis. The numbers 1, 2, and so on in FIG. 4 indicate the order of the combustion cycles. From FIG. 4, it can be seen that, as the cycle progresses from combustion cycle 1 to combustion cycle 2 to combustion cycle 3, the IMEP gradually decreases and the MFB50 gradually advances. Furthermore, as the cycle progresses from combustion cycle 3 to combustion cycle 4 to combustion cycle 5 to combustion cycle 6, the IMEP gradually increases and the MFB50 gradually advances. The IMEP and MFB50 in combustion cycle 7 are close to those in combustion cycle 1. In other words, combustion cycles 1, 2, and 3 are decrease phases in which the IMEP decreases and the MFB50 is retarded, while combustion cycles 4, 5, and 6 are increase phases in which the IMEP decreases and the MFB50 is retarded. In this case, the IMEP and MFB50 vary counterclockwise in FIG. 4 over multiple combustion cycles.

[0058] The inventors of the present application confirmed that combustion fluctuations occur over a six-combustion cycle period when they checked the statistical values, known as autocorrelation coefficients, for all combustion cycles under the operating conditions shown in Figure 4. As shown in Figure 4, the IMEP and MFB50 of combustion cycle 7 are close to those of combustion cycle 1, the IMEP and MFB50 of combustion cycle 8 are close to those of combustion cycle 2, and the IMEP and MFB50 of combustion cycle 9 are close to those of combustion cycle 3.

[0059] The inventors of the present application speculate as follows about the mechanism by which combustion fluctuations with regularity occur between combustion cycles. Figure 5 is a diagram for explaining the mechanism by which combustion fluctuations occur. The numbers 1, 2, ... on the left side of Figure 5 correspond to the combustion cycle numbers in Figure 4.

[0060] In combustion cycle 1, when there is little unburned fuel in the EGR gas, high-temperature EGR gas is drawn into cylinder 2, resulting in combustion with an advanced ignition timing. The center of gravity of combustion in combustion cycle 1 is on the advanced side, and the combustion efficiency, heat generation, and IMEP are all medium (i.e., average). The temperature of the exhaust gas resulting from combustion in combustion cycle 1 drops somewhat due to increased cooling loss, and the amount of unburned fuel in the exhaust gas increases compared to the previous cycle.

[0061] In combustion cycle 2, the low-temperature exhaust gas from combustion cycle 1 is drawn into cylinder 2, resulting in combustion with a delayed ignition timing. The center of gravity of combustion in combustion cycle 2 is more delayed than in combustion cycle 1, and the reduced combustion efficiency results in a decrease in heat generation and IMEP. The temperature of the exhaust gas from combustion in combustion cycle 2 is lower because the heat generation was lower, and the amount of unburned fuel in the exhaust gas also increases.

[0062] In combustion cycle 3, the ignition timing is further retarded by the intake of low-temperature exhaust gas from combustion cycle 2 into cylinder 2. Although combustion efficiency is further reduced, the decrease in heat generation and IMEP is small because some of the unburned fuel contained in the EGR gas is burned, and the exhaust gas temperature rises somewhat due to the reduction in cooling loss. The amount of unburned fuel in the exhaust gas is slightly reduced.

[0063] In combustion cycle 4, the EGR gas temperature is relatively high and there is a large amount of unburned fuel in the EGR gas, so the ignition timing is advanced to some extent. However, the ignition timing is not early enough to completely burn all of the unburned fuel in the EGR gas, and as a result, the heat release and IMEP are at average levels. The exhaust gas temperature rises, and the amount of unburned fuel in the exhaust gas decreases.

[0064] In combustion cycle 5, as in combustion cycle 4, the EGR gas temperature is high and the amount of unburned fuel in the EGR gas is large, so the ignition timing is further advanced, and the heat generation amount and IMEP increase further. Because cooling loss is small, the exhaust gas temperature is relatively high, and some of the unburned fuel is carried over to the next combustion cycle.

[0065] In combustion cycle 6, the EGR gas temperature is relatively high and there is a relatively large amount of unburned fuel, so the ignition timing is further advanced. Because the ignition timing is sufficiently early, all of the remaining unburned fuel is burned, resulting in a high calorific value and an increased IMEP. Because the exhaust gas temperature is still higher and there is little unburned fuel in the EGR gas, the next combustion cycle is essentially the same as combustion cycle 1.

[0066] The regular combustion fluctuations between combustion cycles described above are thought to be caused by the effects of the internal EGR gas on the combustion of subsequent combustion cycles, which are influenced by the temperature of the exhaust gas and the amount of unburned fuel.

[0067] The technology disclosed herein suppresses such regular combustion fluctuations between combustion cycles.

[0068] Note that combustion fluctuations that have regularity between combustion cycles are not limited to the combustion fluctuations with a six-combustion cycle period described above. The period of combustion fluctuations can be various. Furthermore, combustion fluctuations may have regularity that does not have periodicity. The technology disclosed herein can be widely applied to suppressing such combustion fluctuations that have regularity between combustion cycles.

[0069] (Control to suppress regular combustion fluctuations between combustion cycles) (Plant model) In order to suppress the combustion fluctuations that have a regularity between combustion cycles, the inventors of the present application created a plant model of the engine 1 that represents the combustion fluctuations. FIG. 6 shows a plant model 1000 of the engine 1. The combustion fluctuations described above were combustion fluctuations with a period of six combustion cycles, but combustion fluctuations between combustion cycles are the result of combustion in a previous cycle continuously affecting combustion in a subsequent cycle. Therefore, the plant model 1000 is a model that estimates the state quantity of cylinder 2 for each combustion cycle. This plant model 1000 is not limited to application to combustion fluctuations with a specific period and is highly versatile.

[0070] In order to be able to estimate the temperature and amount of unburned fuel inside the cylinder 2, which are related to the mechanism of combustion fluctuation described above, the plant model 1000 is configured to treat the temperature and amount of substance inside the cylinder 2 as in-cylinder state quantities, and transmit information about the combustion result of the previous combustion cycle to the in-cylinder state quantities of the next combustion cycle via internal EGR.

[0071] In consideration of simplification of the plant model 1000, the plant model 1000 is a model that combines a gas exchange model and a combustion model. The gas exchange model 1010 is a physical model, and the combustion model 1020 is a statistical model.

[0072] Furthermore, the changes in state quantities within one cycle require significantly different physics to be considered for each opening and closing event of the intake valve 11 and the exhaust valve 12. Therefore, as shown in Figure 6, individual models 1011, 1012, 1013, 1014, and 1015 were created for the gas exchange model 1010 to obtain the state quantities at each discrete timing within one combustion cycle. The plant model 1000 is structured to couple these models 1011, 1012, 1013, 1014, 1015, and 1020 to represent the phenomena of one combustion cycle in total.

[0073] Specifically, the IVO (Intake Valve Opening) model 1011, the IVC (Intake Valve Closing) model 1012, the woCombTDC (without Combustion Top Dead Center) model 1013, the combustion model 1020, the EVO (Intake Valve Opening) model 1014, and the EVC model 1015 are as follows: Note that Figure 7 shows the variables included in the models.

[0074] IVO Model 1011

[0075]

number

[0076] IVC Model 1012

[0077]

number

[0078] woCombTDC Model 1013

[0079]

number

[0080] Combustion Model 1020

[0081]

number

[0082] EVO Model 1014

[0083]

number

[0084] EVC Model 1015

[0085]

number

[0086] The inventors of the present application have confirmed that the above-described plant model 1000 reproduces combustion fluctuations with regularity between combustion cycles.

[0087] The above-described model is an example, and the technology disclosed herein is not limited to the above-described model.

[0088] (Engine control block) Figure 8 shows a control block of the engine 1 configured by the controller 100. The part surrounded by a dashed line in Figure 8 corresponds to the controller 100. The part surrounded by a two-dot chain line in Figure 8 relates to control that suppresses regular combustion fluctuations between combustion cycles. The control of the engine 1 is feedback control that estimates state quantities within the cylinder 2 in the next combustion cycle from the combustion state of the engine 1 in the previous combustion cycle, and outputs control signals to devices that have been corrected based on the estimated state quantities so as to suppress fluctuations in the IMEP and MFB50.

[0089] As described above, the controller 100 outputs control command amounts to the engine 1. The engine 1 operates by sequentially executing combustion cycles in the multiple cylinders 2 of the engine 1. The pressure sensor SN4 outputs a signal corresponding to pressure fluctuations in each of the multiple cylinders 2 to the controller 100.

[0090] The controller 100 calculates the IMEP and MFB50 as indicators of the combustion state in each of the multiple cylinders 2 based on the signal from the pressure sensor SN4, and inputs the measured IMEP and MFB50 to a subtractor 1001. The subtractor 1001 inputs the differences between the measured IMEP and MFB50 and the target IMEP and MFB50 to a state quantity estimator 1002.

[0091] The state quantity estimator 1002 is a Kalman filter created using the plant model 1000. The inputs to the state quantity estimator 1002 are the IMEP and MEB50 measured by the pressure sensor SN4, the target IMEP and MFB50, and the output of the feedback controller 1003 (described later), which is a delayed control value of the feedback controller 1003. The state quantity estimator 1002 estimates state quantities for the next combustion cycle, namely, the temperature in cylinder 2, the air amount, the burned gas amount, and the fuel amount, and outputs the estimated state quantities. The temperature in cylinder 2 is the temperature in cylinder 2 at the timing when the intake valve 11 closes, the air amount is the air amount in cylinder 2 at the timing when the intake valve 11 closes, the burned gas amount is the burned gas amount in cylinder 2 at the timing when the intake valve 11 closes, and the fuel amount is the fuel amount in cylinder 2 at the timing when the intake valve 11 closes.

[0092] The feedback controller 1003 receives the estimated state quantity, which is the output of the state quantity estimator 1002, and the target state quantity as input, and outputs a correction amount for the control amount of the device based on the estimated state quantity and the target state quantity so that fluctuations in the IMEP and MFB50 are suppressed, in other words, so that the state quantity in the cylinder 2 is maintained constant without fluctuating between combustion cycles. The feedback controller 1003 is an optimal regulator. The feedback controller 1003 is also created using the plant model 1000.

[0093] The controller 100 also includes a basic controller 1004. The basic controller 1004 corresponds to a so-called conventional controller. The basic controller 1004 sets a target torque based on signals from the crank angle sensor SN1, the air flow sensor SN2, and the accelerator opening sensor SN3, and outputs control amounts for devices of the engine 1 so that the target torque is realized.

[0094] Figure 9 shows the configuration of a portion 80 surrounded by a dashed line in Figure 8. The controller 100 outputs control instruction amounts to the intake S-VT 17, exhaust S-VT 18, spark plug 13, and injector 14, which are devices related to combustion in the engine 1.

[0095] Specifically, the basic controller 1004 outputs target IVO and IVC, which are the opening and closing timings of the intake valve 11, target EVO and EVC, which are the opening and closing timings of the exhaust valve 12, target ignition timing, which is the ignition timing of the spark plug 13, and target injection amount, which is the fuel injection amount of the injector 14.

[0096] Furthermore, the feedback controller 1003 outputs the correction amounts of IVO and IVC, the correction amounts of EVO and EVC, the correction amount of the ignition timing, and the correction amount of the fuel injection amount.

[0097] An adder 1005 adds these target amounts and correction amounts to set instruction amounts. The controller 100 outputs control instruction amounts for IVO and IVC to the intake S-VT 17, control instruction amounts for EVO and EVC to the exhaust S-VT 18, control instruction amounts for ignition timing to the spark plug 13, and control instruction amounts for the amount of fuel injected to the injector 14.

[0098] The intake S-VT 17 sets the rotational phase of the intake camshaft to achieve the commanded IVO and IVC, and the exhaust S-VT 18 sets the rotational phase of the exhaust camshaft to achieve the commanded EVO and EVC. The injector 14 injects a commanded amount of fuel into the cylinder 2 at a specific time during the intake stroke and / or compression stroke, and the spark plug 13 ignites the air-fuel mixture in the cylinder 2 at a commanded timing. Note that when the engine 1 performs HCCI combustion, the controller 100 does not output a control command amount to the spark plug 13.

[0099] FIG. 10 is a timing chart illustrating the timing at which the controller 100 outputs control command amounts to the devices. The horizontal axis of FIG. 10 represents the progression of the crank angle, and the vertical axis represents the pressure in the cylinder 2. FIG. 10 illustrates the change in pressure in the cylinder 2 over multiple combustion cycles. As described above, the controller 100 acquires information about the combustion state (i.e., IMEP[n] and MFB50[n]) in the previous combustion cycle (the n-th cycle) based on the signal from the pressure sensor SN4, and sets correction amounts for the devices in the next combustion cycle (the (n+1)-th cycle). Because the combustion state information can be acquired after combustion in the previous combustion cycle ends, the controller 100 can calculate control command amounts before the intake valve 11 in the next combustion cycle closes (see "Control Calculation Timing" in FIG. 10) and output control command amounts to the injector 14, the spark plug 13, the intake S-VT 17, and the exhaust S-VT 18 (see the dashed-dotted arrows in FIG. 10). As a result, the controller 100 can adjust the amount of fuel injected by the injector 14, whose injection timing is set during the intake stroke, as shown in FIG.

[0100] (Effect of control) Figure 11 shows the effect of control of the engine 1 to which the technology disclosed herein is applied. In Figure 11, the controller 100 outputs a corrected control command amount only to the injector 14. In other words, the fuel injection amount of the injector 14 is adjusted so as to suppress regular combustion fluctuations between combustion cycles.

[0101] For example, assuming that the fuel injection amount is adjusted in each of combustion cycles 1, 2, 3, 4, 5, and 6 shown in FIG. 5, the following describes how the fuel injection amount is adjusted in each of those combustion cycles 1, 2, 3, 4, 5, and 6. In combustion cycle 1, combustion occurs such that the amount of unburned fuel increases, so the controller 100 makes a correction to decrease the fuel injection amount of the injector 14, as shown at the right end of FIG. 5. Similarly, in combustion cycles 2 and 3, the controller 100 makes a correction to decrease the fuel injection amount of the injector 14. Conversely, in combustion cycle 4, combustion occurs such that the amount of unburned fuel decreases, so the controller 100 makes a correction to increase the fuel injection amount of the injector 14. Similarly, in combustion cycles 5 and 6, the controller 100 makes a correction to increase the fuel injection amount of the injector 14.

[0102] The horizontal axis of FIG. 11 represents the number of combustion cycles. The upper graph in FIG. 11 shows the fluctuations in the fuel injection amount, the middle graph shows the fluctuations in IMEP, and the lower graph shows the fluctuations in MFB50. The left side of C0 in FIG. 11 shows the fluctuations of each parameter when control to suppress regular combustion fluctuations between combustion cycles (i.e., this control) is not performed. The engine 1 is operating steadily, and the fuel injection amount is substantially constant, while IMEP and MFB50 fluctuate greatly. The right side of C0 shows the fluctuations of each parameter when this control is performed. Although the engine 1 is operating steadily, the fuel injection amount is corrected by executing this control, so the fluctuations in the fuel injection amount are large. On the other hand, it can be seen that the fluctuations in IMEP and MFB50 are suppressed.

[0103] Therefore, the technology disclosed herein can suppress regular combustion fluctuations between combustion cycles. Because regular combustion fluctuations between combustion cycles during steady-state operation of the engine 1 are suppressed, applying the technology disclosed herein to the controller 100 can expand the HCCI region toward the low load side in the operating region map shown in Figure 3. Expanding the HCCI region improves the fuel economy of the engine 1.

[0104] (Variation) FIG. 12 shows a modified example of the controller 100. This modified example is an example in which the engine 1 operates by SI combustion with an excess air ratio λ of the air-fuel mixture set to 1. FIG. 12 shows the configuration of the portion 80 enclosed by the dashed line in FIG. 8. A basic controller 1004 outputs a target IMEP. A feedback controller 1003 outputs an IMEP correction amount and an MFB50 correction amount. An adder 1005 adds the target IMEP and the IMEP correction amount to set a final target IMEP. Once the final target IMEP is set, a target air amount to be introduced into the cylinder 2 is determined. The IVO and IVC of the intake valve 11 and the EVO and EVC of the exhaust valve 12 are set based on the target air amount and the actual air amount measured based on the measurement signal of the airflow sensor SN2. The controller 100 outputs control instruction amounts for the IVO and IVC to the intake S-VT 17 and outputs control instruction amounts for the EVO and EVC to the exhaust S-VT 18. The intake S-VT17 adjusts the rotational phase of the intake camshaft, and the exhaust S-VT18 adjusts the rotational phase of the exhaust camshaft.

[0105] Further, a control instruction amount for the fuel injection amount is set based on the actual air amount so that the excess air ratio λ becomes 1. The controller 100 outputs the control instruction amount for the fuel injection amount to the injector 14. The injector 14 injects the instructed amount of fuel into the cylinder 2 at a specific time during the intake stroke and / or compression stroke.

[0106] Furthermore, once the final target IMEP is set, the target MFB50 is set. An adder 1005 adds the target MFB50 and the MFB50 correction amount. The controller 100 sets the final target MFB50 from the target MFB50, the MFB50 correction amount, and the actual air amount based on the measurement signal of the air flow sensor SN2. A control instruction amount for the ignition timing of the spark plug 13 is set from the final target MFB50 and the actual air amount. The controller 100 outputs a control instruction amount for the ignition timing to the spark plug 13. The spark plug 13 ignites the air-fuel mixture in the cylinder 2 at the instructed timing.

[0107] This control also makes it possible to suppress regular combustion fluctuations between combustion cycles.

[0108] In the technology disclosed herein, the controller 100 may output a control instruction amount to at least one of the intake S-VT 17, the exhaust S-VT 18, the spark plug 13, and the injector 14.

[0109] Furthermore, the technology disclosed herein is not limited to application to the engine 1 having the above-described configuration, but can be widely applied to engines having a variety of configurations. [Explanation of symbols]

[0110] 1 engine 11 Intake valve 12 Exhaust valve 13 Spark plug 14 Injector 100 Controllers 1000 Plant Models 2-cylinder SN4 Finger Pressure Sensor

Claims

1. an engine having cylinders in which gas exchange occurs by opening and closing intake valves and exhaust valves, and in which a plurality of the cylinders sequentially execute combustion cycles; a device attached to the engine and related to combustion in each of the plurality of cylinders; a controller that controls operation of the engine by outputting a control signal to the device; the controller estimates a state quantity of each of the plurality of cylinders before combustion based on a plant model of the engine that represents a regular combustion fluctuation between the combustion cycles, and outputs a control signal corrected based on the estimated state quantity to the device. Engine control device.

2. 2. The engine control device according to claim 1, the plant model is a model that estimates a state quantity of the cylinder for each combustion cycle, the controller estimates a temperature, an air amount, an amount of burned gas, and an amount of fuel as state quantities of the cylinder based on the plant model; Engine control device.

3. 3. The engine control device according to claim 2, the plant model is a combined model of a physical model related to gas exchange in the cylinder and a statistical model related to combustion in the cylinder. Engine control device.

4. The engine control device according to claim 2 or 3, a pressure sensor attached to the engine corresponding to each of the plurality of cylinders, the pressure sensor outputting a signal corresponding to the pressure in the cylinder to the controller; the controller estimates a state quantity of a cylinder in which combustion will occur next, based on the combustion state in the cylinder based on the signal from the pressure sensor and the plant model, before the intake valve of the cylinder closes. Engine control device.

5. 5. The engine control device according to claim 4, The combustion state based on the signal of the pressure sensor includes an indicated mean effective pressure (IMEP) and a combustion center of gravity (MFB50). Engine control device.

6. 5. The engine control device according to claim 4, the device includes an injector attached to the engine corresponding to each of the plurality of cylinders and configured to inject fuel into the cylinder; The controller adjusts the fuel injection amount based on the estimated state quantity. Engine control device.

7. 7. The engine control device according to claim 6, The injector injects fuel at least during the intake stroke before the intake valve closes, the controller adjusts the amount of fuel injected by the injector during the intake stroke. Engine control device.

8. 5. The engine control device according to claim 4, the device includes an intake valve mechanism that changes the opening and closing timing of the intake valve; The controller adjusts the opening and closing timing of the intake valve based on the estimated state quantity. Engine control device.

9. 5. The engine control device according to claim 4, the device includes a spark plug attached to the engine corresponding to each of the plurality of cylinders and configured to ignite an air-fuel mixture in the cylinder; The controller adjusts the ignition timing of the spark plug based on the estimated state quantity. Engine control device.

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