JP2007285194A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine improving fuel economy and stabilizing combustion by performing control according to the state of the internal combustion engine. <P>SOLUTION: The control device of the internal combustion engine 1 comprises a cylinder pressure detection means 15 for detecting cylinder pressure of the internal combustion engine 1 and a control means 20 for controlling the internal combustion engine by calculating a condition parameter value indicative of a combustion condition based on a detected value of the cylinder pressure detection means 15, by performing at least one of determination of a torque variation and determination of a misfire rate based on the condition parameter value and by changing ignition timing based on the determination result. Fine control can be performed according to a state of the internal combustion engine and combustion stabilization can be attained along with improvement of fuel economy. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine. More specifically, the present invention relates to a control device that controls ignition timing, and relates to a control device that functions suitably during idling operation.

  The state of the load changes every moment depending on the operating condition of the internal combustion engine. Therefore, various control devices for controlling an internal combustion engine in accordance with operating conditions have been proposed. For example, even when the internal combustion engine is in a light load state, such as during idling, fuel efficiency can be improved by performing appropriate control.

  For example, in Patent Document 1, the intake valve is opened at a first timing in a first idling operation region where the amount of heat generated by the combustion of fuel in the combustion chamber of the internal combustion engine is larger than a predetermined amount, and the combustion chamber is opened. Disclosed is an internal combustion engine control device that opens an intake valve at a timing later than the first timing in a second idling operation region in which the amount of heat generated by the combustion of fuel in the engine is smaller than a predetermined amount To do. The control device sets the minimum engine speed of the internal combustion engine in the idling operation region, and controls the amount of fuel supplied to the combustion chamber so as to ensure the set minimum engine speed. In the first idling operation region, the first engine speed is set to the minimum engine speed, and in the second idling operation region, the second engine speed that is smaller than the first engine speed is set to the minimum engine speed. . Thus, fuel efficiency is improved by changing the idling rotation target based on the amount of heat generated by the combustion of fuel.

JP 2002-349322 A

  However, the device of Patent Document 1 does not determine the limit value of the idling target in consideration of combustion conditions such as torque fluctuation and misfire. For this reason, when the set minimum engine speed is inappropriate, there is a concern that torque fluctuation may occur or the possibility of misfire increases and combustion becomes unstable.

  Accordingly, an object of the present invention is to provide a control device for an internal combustion engine that improves fuel efficiency and stabilizes combustion by performing control according to the state of the internal combustion engine.

  The object is to calculate a state parameter value indicating a combustion state based on a detected value of the in-cylinder pressure detecting means and a detected value of the in-cylinder pressure of the internal combustion engine, and to detect a torque fluctuation based on the state parameter value. This can be achieved by a control device for an internal combustion engine that includes control means for controlling at least one of determination and misfire ratio determination and changing the ignition timing based on the determination result.

  According to the present invention, the control means calculates the state parameter value indicating the combustion state, and at least one of determination of torque fluctuation and determination of the misfire ratio based on the state parameter value is performed to determine the ignition timing. change. Therefore, since detailed control according to the state of the internal combustion engine can be performed, fuel consumption can be improved and combustion can be stabilized.

  In addition, after the determination, the control means further reduces the rotational speed of the internal combustion engine, determines the second misfire ratio based on the state parameter value, and the determination result of the second misfire ratio is appropriate. At this time, the ignition timing may be advanced. In this case, it is possible to further improve fuel efficiency while reducing the rotational speed.

  Further, the state parameter can be a calorific value generated by burning the fuel in the cylinder. The calorific value can be calculated based on the relational expression PVκ where P is the in-cylinder pressure, V is the in-cylinder volume, and κ is the specific heat ratio.

  More preferably, the control means executes the control during an idling operation of the internal combustion engine.

  ADVANTAGE OF THE INVENTION According to this invention, the control apparatus of the internal combustion engine which aimed at the combustion stabilization while improving the fuel consumption by performing the control according to the state of the internal combustion engine can be provided.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram showing an internal combustion engine equipped with a control device according to the present invention. In the internal combustion engine 1, a piston 3 is disposed in a cylinder block 2 so as to be capable of reciprocating. Power is generated by reciprocating the piston 3 by burning a mixture of fuel (for example, gasoline) and air inside a combustion chamber 4 formed at the top of the piston 3. Although only one cylinder is shown in FIG. 1, the internal combustion engine 1 is preferably configured as a multi-cylinder engine, and the internal combustion engine 1 of the present embodiment is formed as a four-cylinder engine, for example.

  An intake port of each combustion chamber 4 is connected to an intake pipe 5 via an intake manifold. The same applies to the exhaust side, and the exhaust port of each combustion chamber 4 is connected to the exhaust pipe 6 via an exhaust manifold. In addition, an intake valve 16 that opens and closes an intake port and an exhaust valve 17 that opens and closes an exhaust port are disposed for each combustion chamber 4 in the cylinder head of the internal combustion engine 1. Each intake valve 16 and each exhaust valve 17 are opened and closed by a valve operating mechanism (not shown) having a variable valve timing function, for example. Further, the internal combustion engine 1 has a number of spark plugs 7 corresponding to the number of cylinders, and the spark plugs 7 are arranged on the cylinder heads so as to face the corresponding combustion chambers 4.

  An air cleaner 9, a throttle valve (in this embodiment, an electronically controlled throttle valve) 10 and a surge tank 8 are arranged in the intake pipe 5 from the upstream side. On the other hand, the exhaust pipe 6 is provided with a front-stage catalyst device 11a including a three-way catalyst and a rear-stage catalyst device 11b including a NOx storage reduction catalyst.

  The internal combustion engine 1 has a plurality of injectors 12. Each injector 12 is disposed so as to face the corresponding intake pipe 5 (inside the intake port), and injects fuel such as gasoline into each intake port. Although the internal combustion engine 1 of the present embodiment is described as a so-called port injection type gasoline engine, the present invention is not limited to this, and it goes without saying that the present invention can be applied to a so-called direct injection type internal combustion engine. . Needless to say, the present invention can be applied not only to a gasoline engine but also to a diesel engine.

  The spark plug 7, the throttle valve 10, each injector 12, the valve operating mechanism and the like are electrically connected to an ECU 20 that functions as a control device for the internal combustion engine 1. The ECU 20 includes a CPU, a ROM, a RAM, an input / output port, a storage device, etc., all not shown. As shown in FIG. 1, the ECU 20 is electrically connected to various sensors including an in-cylinder pressure sensor 15 that detects the pressure in the combustion chamber 4. The in-cylinder pressure sensor 15 is formed including a semiconductor element, a piezoelectric element, an optical fiber detection element, or the like, and is arranged in a number corresponding to the number of cylinders. Each in-cylinder pressure sensor 15 is disposed on the cylinder head so that the pressure receiving surface faces the corresponding combustion chamber 4, and is electrically connected to the ECU 20. The detection value of each in-cylinder pressure sensor 15 is sequentially given to the ECU 20 every predetermined time, and is stored and held by a predetermined amount in a predetermined storage area (buffer) of the ECU 20. The ECU 20 uses various types of maps and the like stored in the storage device, and based on the detection values of various sensors and the like, a spark plug 7, a throttle valve 10, an injector 12, Control the valve mechanism.

  In the above description, the in-cylinder pressure sensor 15 has been described as a sensor for detecting the state of the internal combustion engine. However, various sensors may be arranged to detect the state as in the case of a conventional internal combustion engine. For example, by providing the crank angle sensor 14 that detects the rotation speed of the crank angle, the rotation speed of the internal combustion engine can be confirmed based on the detection of the crank angle θ. Further, for example, an air flow meter that detects the amount of intake air, an intake pressure sensor that detects intake air pressure, an intake air temperature sensor that detects the temperature of intake air, and the like may be arranged in the intake pipe 5. Further, an exhaust pressure sensor for detecting the exhaust gas pressure is provided on the exhaust pipe 6 side, and an air-fuel ratio (A / F) of the internal combustion engine from the oxygen concentration and unburned gas concentration downstream of the exhaust purification catalyst 11b. A / F sensor for detecting) may be provided. Further, a water temperature sensor for detecting the temperature of the circulating cooling water and an oil temperature sensor for detecting the temperature of the circulating lubricating oil may be disposed around the crankshaft.

  Signals from the in-cylinder pressure sensor 15 and various sensors arranged at a plurality of locations as needed are supplied to the ECU 20. Therefore, the ECU 20 can accurately check the operation status of the internal combustion engine based on the detection signals from the sensors. The internal combustion engine 1 incorporates a control device that determines the possibility of torque and misfire from the in-cylinder pressure and optimally adjusts the ignition timing so as to suppress torque fluctuation and misfire. This control device is configured to include control means for confirming torque fluctuation and misfiring state based on the detected value of the in-cylinder pressure sensor 15 serving as in-cylinder pressure detecting means, and setting the optimal ignition timing to control the internal combustion engine. Yes. Thus, the stable combustion of the internal combustion engine can be achieved by determining the ignition timing in consideration of the torque fluctuation and misfire of the internal combustion engine. Such control is suitable at the time of light load operation that is easily affected by disturbance such as at idling operation. The control means is realized by a part of the ECU 20. Although the ECU for the control device may be provided independently, the configuration can be simplified by using the ECU 20 of the internal combustion engine 1 as in the present embodiment.

  FIG. 2 is a flowchart showing an example of a routine executed by the ECU 20 during idling operation of the internal combustion engine. The ECU 20 first reads the engine conditions from various sensors and confirms the ignition timing SA1 (S11). Further, the ECU 20 confirms the detection value of the in-cylinder pressure sensor 15 (S12), and calculates the indicated torque Ptrq (S13). The indicated torque is a torque obtained from the pressure of the combustion chamber of the engine, and can be regarded as work performed by fuel combustion.

  For example, the ECU 20 calculates the in-cylinder heat generation amount Q as a state parameter indicating the state of the internal combustion engine from the detection value of the in-cylinder pressure sensor 15. Based on this calorific value Q, the indicated torque Ptrq is calculated to check the torque fluctuation.

  The present invention has the following relationship among the crank angle θ detected by the crank angle sensor 14, the in-cylinder pressure (detected value) P detected by the in-cylinder pressure sensor 15, and the heat generation amount Q. Confirmed. The cylinder pressure detected by the cylinder pressure sensor 15 when the crank angle is θ is P (θ), the cylinder volume when the crank angle is θ is V (θ), and the specific heat ratio is κ. In this case, P (θ) · Vκ (θ obtained as a product of the in-cylinder pressure P (θ) and a value Vκ (θ) obtained by raising the in-cylinder volume V (θ) to a specific heat ratio (predetermined index) κ (Hereinafter simply referred to as PVκ) has a correlation with the change pattern of the heat generation amount Q in the cylinder. Therefore, the ECU 20 of the present embodiment obtains the heat generation amount Q from the detected in-cylinder pressure and the crank angle θ, and calculates the indicated torque based on the heat generation amount Q, so that the in-cylinder state can be reflected. Therefore, the internal combustion engine can be accurately controlled in response to variations in machine differences and changes in fuel properties.

  Specifically, the ECU 20 calculates the indicated torque Ptrq based on the amount of heat obtained as described above, and determines whether or not the torque difference dtrq is larger than a predetermined value α (S14). The torque difference dtrq here can be obtained, for example, as the difference between the indicated torque Ptrq calculated in a certain cycle and the indicated torque Ptrq calculated in the immediately preceding cycle.

  If the ECU 20 determines that the torque difference dtrq is greater than the predetermined value α in step S14, the ECU 20 delays the ignition timing SA2 delayed (delayed) by the predetermined time dSA from the previously confirmed ignition timing SA1. Calculate (S15). Then, the ECU 20 corrects the new ignition timing to the ignition timing SA2 (S19) and ends the processing by this routine. Generally, during idling operation of an internal combustion engine, the rotational speed is low, and the ignition timing is often set to the advance side, so that torque fluctuation tends to occur easily. In addition, it is susceptible to torque fluctuations due to the effects of minute combustion changes, fuel deterioration with time and changes in properties. However, the control device applied to the internal combustion engine 1 suppresses torque fluctuations by retarding the ignition timing when necessary while checking the state of the internal combustion engine in detail as described above. The combustion can be stabilized at times.

  When the ECU 20 determines that the torque difference dtrq is equal to or smaller than the predetermined value α in step S14, there is no problem with torque fluctuation. In this case, the ECU 20 calculates a misfire ratio Rmf (S16). The misfire ratio Rmf is obtained by (heat generation amount / low heating value). When the combustion efficiency of the injected fuel is high and the calorific value is large, the value of the misfire rate Rmf is large, and when the unburned fuel is large, the calorific value is small and the value of the misfire rate Rmf is small. The lower heating value is also called a true heating value, and is a heating value obtained by subtracting the evaporation heat of water vapor from the higher heating value. Here, this corresponds to the amount of heat generated when the fuel injected from the injector 12 is completely combusted. Further, the heat generation amount is the in-cylinder pressure detected by the in-cylinder pressure sensor 15 and the calorific value Q obtained from the above formula PVκ.

  The ECU 20 compares the value of the misfire ratio Rmf calculated in step S16 with a predetermined value β (S17). This predetermined value β is a threshold value set for determining whether or not the ignition timing can be corrected to the advance side. When the ECU 20 determines that the value of the misfire ratio Rmf is larger than the predetermined value β, the ECU 20 calculates an ignition timing SA3 advanced (advanced) by a predetermined time dSA from the previously confirmed ignition timing SA1 ( S18). Then, the ECU 20 corrects the new ignition timing to the ignition timing SA3 (S19), and ends the processing by this routine. As described above, when the internal combustion engine is idling, it is close to the advance angle side, but when it is determined that there is no problem of torque fluctuation in step S14 and that there is little possibility of misfire in the next step S16. The ignition timing is further adjusted to the advance side within a range where torque fluctuation does not occur. As a result, the ignition advance is made to near the limit while suppressing the torque fluctuation, so that the fuel consumption can be improved while achieving stable combustion of the internal combustion engine.

  FIG. 3 is a diagram collectively showing the relationship between the torque difference dtrq and the predetermined value α, and the misfire ratio Rmf and the predetermined value β. When the value of the torque difference dtrq exceeds the predetermined value α, an unacceptable torque fluctuation occurs. When the value of the misfire ratio Rmf is lower than the predetermined value β, unburned fuel increases due to misfire and combustion efficiency deteriorates. Therefore, the ECU 20 sequentially controls the ignition timing so that the torque difference dtrq and the misfire ratio Rmf obtained based on the calorific value obtained from the in-cylinder pressure by the in-cylinder pressure sensor 15 are within the respective threshold values. This makes it possible to approach the ignition timing MBT (Minimum advance for the Best Torque) at which the output and the combustion consumption rate are the best. Therefore, the internal combustion engine 1 to which the control device described above is applied becomes a highly reliable internal combustion engine that can achieve stable combustion while coping with disturbance and can also improve fuel efficiency.

  FIG. 4 is a flowchart showing another example of a routine executed by the ECU 20 during idling operation of the internal combustion engine. In this flowchart, control similar to that shown in FIG. 2 is executed and then the target rotational speed of the internal combustion engine is reduced. That is, the flowchart shown on the left side of FIG. 4 is the same as that of FIG. 2, and the ECU 20 performs the process based on the flowchart shown on the right side after executing the process similar to FIG. The process on the right side will be described assuming that the process on the left side has been completed.

  The ECU 20 confirms that the air conditioner, the cooling fan, etc. are in an off state and the load factor KL is not in a condition that increases (S21), and the load factor KL2 obtained by reducing the predetermined load factor dKL from the previous load factor KL1. Is calculated (S22). The load factor KL is also calculated from the output of the in-cylinder pressure sensor 15. The load factor KL is a numerical value representing the load state of the internal combustion engine. The load factor KL is a relative load when the load factor when the intake air amount of the internal combustion engine 1 is equal to the exhaust amount is 100%. It is a size. The load factor KL is 0% when there is no load and 100% when the load is full. In particular, the load factor KL is correlated with the intake air filling rate (intake air amount) into the cylinder, and the intake air filling rate into the cylinder increases as the load factor KL increases. Decreasing the load factor KL as described above in step S22 decreases the intake air amount and decreases the target rotational speed of the internal combustion engine.

  Here, the ECU 20 calculates a misfire ratio Rmf (S23), and checks whether or not the calculated value of the misfire ratio Rmf is larger than a predetermined value β (S24). Here, the determination of the misfire ratio Rmf is the same as described above, and when the ECU 20 determines that the value of the misfire ratio Rmf is greater than the predetermined value β, the ignition timing SA (SA1 to SA3 set in the process on the left side). The ignition timing SA4 advanced by the predetermined time dSA from any one of the above is calculated (S25). Then, the ECU 20 corrects the new ignition timing to the ignition timing SA4 and ends the processing by this routine (S27).

  On the other hand, when the ECU 20 confirms that the value of the misfire rate Rmf calculated in step S24 is equal to or less than the predetermined value β, the value of the misfire rate Rmf is deteriorated because the load factor KL is changed in step S22. Can be assumed. Therefore, the load factor KL is returned to the initial KL1 (S26), and the processing by this routine is terminated. When the ECU 20 executes the control shown in FIG. 4, the number of revolutions of the internal combustion engine is reduced and the ignition timing is brought closer to the advance side in a range where torque fluctuation does not occur. Therefore, fuel consumption can be further improved while achieving stable combustion. In the above embodiment, the case where the ECU 20 determines the torque fluctuation and the misfire ratio is described as a more preferable embodiment. However, the internal combustion engine can be determined by performing either the torque fluctuation determination or the misfire ratio determination. It is possible to stabilize the combustion.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

It is the schematic block diagram shown about the internal combustion engine provided with the control apparatus by this invention. 5 is a flowchart showing an example of a routine that the ECU 20 executes during idling operation of the internal combustion engine. It is the figure which showed collectively the relationship between a torque difference, predetermined value (alpha), a misfire ratio, and predetermined value (beta). 7 is a flowchart showing another example of a routine executed by the ECU 20 during idling operation of the internal combustion engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 5 Intake pipe 6 Exhaust officer 15 In-cylinder pressure sensor (cylinder pressure detection means)
20 ECU (control means)

Claims (5)

In-cylinder pressure detecting means for detecting the in-cylinder pressure of the internal combustion engine;
A state parameter value indicating a combustion state is calculated based on a detection value of the in-cylinder pressure detecting means, and at least one of determination of torque fluctuation or determination of misfire ratio is performed based on the state parameter value, A control device for an internal combustion engine, comprising: control means for controlling the internal combustion engine by changing an ignition timing based on a determination result. The control means further reduces the rotational speed of the internal combustion engine after the determination, determines the second misfire ratio based on the state parameter value, and the determination result of the second misfire ratio is appropriate. 2. The control apparatus for an internal combustion engine according to claim 1, wherein the ignition timing is sometimes advanced. 3. The control device for an internal combustion engine according to claim 1, wherein the state parameter is a calorific value generated by burning the fuel in the cylinder. 4. The control device for an internal combustion engine according to claim 3, wherein the calorific value is calculated based on a relational expression PVκ where P is the in-cylinder pressure, V is the in-cylinder volume, and κ is the specific heat ratio. . The control device for an internal combustion engine according to any one of claims 1 to 4, wherein the control means executes the control during an idling operation of the internal combustion engine.

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