JP2006312919A - Engine controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly control ignition timing even when there is aged deterioration, and individual difference coming from a manufacturing error or the like. <P>SOLUTION: An ignition timing correction amount is determined in response to a correlation value between a 50% burning point BP50[°ATDC] and torque ITQ. Since a correlation coefficient cor being lower than a reference value thrl which is a negative value means that the 50% burning point BP50 and the torque ITQ are distributed in a "descending" state as indicated by a sign (a), it can be estimated that the present ignition time is in a retardation side with respect to an MBT. Thus, in such a case, the ignition timing is corrected to a timing advance side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an engine control device, and more particularly to a device that changes operating conditions based on in-cylinder pressure in a combustion chamber of an engine.

  As shown in FIG. 3, the indicated torque of the internal combustion engine (the total torque obtained by adding the friction loss inside the engine to the net torque output from the engine output shaft) changes according to the ignition timing, and the ignition timing is retarded. When it is gradually moved from the limit value to the advance side, the indicated torque increases and then decreases. The vicinity of the apex of this torque characteristic curve is relatively flat, and when the ignition timing is gradually moved from the retard side to the advance side, the ignition timing immediately before reaching this flat portion is the MBT (Minimum advance for Best). Called Torque). Since MBT is a timing at which large torque is obtained and knocking does not occur, it is preferable that the ignition timing of the internal combustion engine be in the vicinity of MBT, and control is performed so that the ignition timing approaches MBT according to the state of the engine. The method is known as MBT control.

  For example, Patent Document 1 discloses a device that detects a timing (crank angle) at which the in-cylinder pressure becomes maximum and corrects an ignition timing according to a deviation between the detected maximum timing and a target timing (crank angle). is doing. In Patent Document 2, the combustion ratio is obtained based on the detection values of the in-cylinder pressure sensor and the crank angle sensor, and the target combustion ratio is obtained by referring to a map from operating conditions such as intake pipe negative pressure, rotation speed, and cooling water temperature. Discloses an apparatus for correcting the ignition timing in accordance with the deviation between the two.

No. 6-3192 Japanese Examined Patent Publication No. 62-53710

  However, in Patent Document 1, there is no description that the target time (crank angle) is dynamically set based on some operating condition, and the target time is considered to be a fixed value. Further, since Patent Document 2 obtains the target combustion ratio from the operating conditions by referring to the map, the relationship between the operating conditions and the target combustion ratio is still fixed. Therefore, in any case, if there is an individual difference due to a manufacturing error or aged deterioration, the set target value may be inappropriate.

  Accordingly, an object of the present invention is to provide a novel means for appropriately controlling the ignition timing even in the case where there are individual differences resulting from manufacturing errors or aging deterioration.

  The engine control device according to the present invention is an engine control device comprising ignition timing changing means for changing the ignition timing of a spark ignition type engine, wherein the first physical quantity includes information on the in-cylinder pressure in the combustion chamber of the engine, The apparatus further comprises a correction amount setting means for setting an ignition timing correction amount based on a correlation with a second physical quantity including information on the output of the engine, wherein the ignition timing changing means is an ignition set by the correction amount setting means. The ignition timing is changed according to the timing correction amount.

  In the present invention, the correction amount setting means sets the ignition timing correction amount based on the correlation between the first physical quantity including the in-cylinder pressure information and the second physical quantity including the engine output information. The ignition timing changing means changes the ignition timing according to the ignition timing correction amount set by the correction amount setting means. Therefore, according to the present invention, it is possible to appropriately control the ignition timing without using a fixed target value.

  The first physical quantity is preferably a crank angle when the combustion ratio in the combustion chamber is at a predetermined reference combustion ratio.

  The second physical quantity is preferably the indicated torque of the engine.

  The correction amount setting means may select either a predetermined positive correction amount or a predetermined negative correction amount according to the sign of the correlation value between the first physical quantity and the second physical quantity. Good. In this case, the desired effect of the present invention can be obtained with a simple configuration.

  A preferred embodiment of the present invention will be described below. In FIG. 1, an engine 1 according to an embodiment of the present invention is a so-called port injection type four-cycle internal combustion engine, which uses gasoline as fuel. The engine 1 generates power by burning a fuel / air mixture in a combustion chamber 3 formed in a cylinder block 2 and reciprocating a piston 4 in the combustion chamber 3. The engine 1 is preferably configured as a multi-cylinder engine, and the engine 1 of the present embodiment is configured as a four-cylinder engine, for example.

  The intake port of each combustion chamber 3 is connected to an intake pipe (intake manifold) 5, and the exhaust port of each combustion chamber 3 is connected to an exhaust pipe (exhaust manifold) 6. In addition, an intake valve Vi and an exhaust valve Ve are provided for each combustion chamber 3 in the cylinder head of the engine 1. Each intake valve Vi opens and closes a corresponding intake port, and each exhaust valve Ve opens and closes a corresponding exhaust port. Each intake valve Vi and each exhaust valve Ve are operated by, for example, a valve operating mechanism (not shown) having a variable valve timing function. Further, the engine 1 has a number of spark plugs 7 corresponding to the number of cylinders, and the spark plugs 7 are disposed in the cylinder heads so as to face the corresponding combustion chambers 3.

  The intake pipe 5 is connected to a surge tank 8 as shown in FIG. An air supply line is connected to the surge tank 8, and the air supply line is connected to an air intake port (not shown) via an air cleaner 9. A throttle valve (in this embodiment, an electronically controlled throttle valve) 10 and an air flow meter 21 are incorporated in the air supply line (between the surge tank 8 and the air cleaner 9). On the other hand, as shown in FIG. 1, a front-stage catalyst device 11 a including a three-way catalyst and a rear-stage catalyst device 11 b including a NOx storage reduction catalyst are connected to the exhaust pipe 6.

  Furthermore, the engine 1 has a plurality of injectors 12, and each injector 12 is disposed so as to face the inside of the corresponding intake pipe 5 (inside the intake port) as shown in FIG. Each injector 12 injects fuel such as gasoline into each intake pipe 5. Although the 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.

Each of the spark plugs 7, the throttle valve 10, the injectors 12, the valve operating mechanism and the like described above are electrically connected to an ECU 20 that functions as a control device for the engine 1. The ECU 20 includes a CPU, a ROM, a RAM, an input / output port, a storage device, and the like, all not shown. As shown in FIG. 1, the ECU 20 includes a crank angle sensor 14 provided in the vicinity of the crankshaft, the air flow meter 21 described above, an air-fuel ratio sensor (O ₂ sensor) 16 provided in the exhaust pipe 6, and a cylinder 6. Various sensors, such as a water temperature sensor, which are provided to detect the temperature of the cooling water are electrically connected. The ECU 20 uses the various maps stored in the storage device and also obtains the desired output based on the detection values of the various sensors and the like, so that each spark plug 7, the throttle valve 10, each injector 12, Control the mechanism.

  As the in-cylinder pressure sensor 15, various known devices including a semiconductor element, a piezoelectric element, or an optical fiber detection element can be used. Each in-cylinder pressure sensor 15 is disposed on the cylinder head so that the pressure receiving surface faces the corresponding combustion chamber 3, and is electrically connected to the ECU 20. Each in-cylinder pressure sensor 15 detects the in-cylinder pressure (relative pressure) in the corresponding combustion chamber 3 and gives a signal indicating the detected value to the ECU 20. The ROM of the ECU 20 stores various control programs including processing routines described later, various maps, and set values.

  Next, the control procedure of the combustion start timing, that is, the ignition timing in the engine 1 will be described with reference to FIG.

  In the engine 1, the ignition timing control routine of FIG. 2 is repeatedly executed for each combustion chamber 3. In FIG. 2, first, the ECU 20 determines whether a correction mode flag flag, which will be described later, is set to “1” (S101), and if negative, sets the value of a cycle number counter cyc, which will be described later, to “0”. Initialization is performed (S103).

  If the determination in step S101 is affirmative, the ECU 20 measures and stores the values of the engine speed Ne and the intake air amount Ga as the current operating state (S102). Next, the ECU 20 determines whether or not it is in a steady operation state by comparing the operation state (engine speed Ne, intake air amount Ga) between the previous cycle and the current cycle (S104). This determination is performed such that, for example, the absolute value of the deviation between the engine speed Ne and the intake air amount Ga between the previous cycle and the current cycle is below a predetermined value. When the engine 1 is not in the steady operation state, for example, when the engine 1 is in the transient operation state, such as during rapid acceleration, the result in Step S104 is negative and the process is returned.

  If it is a steady operation state, the correction mode flag flag is set to “1” (S105). The correction mode flag flag is an operation mode in which the ignition timing is corrected, and a predetermined area of the RAM in the ECU 20 is used for the flag. Next, the value of the cycle number counter cyc is incremented (S106).

  Next, in-cylinder pressure is measured (S107). The in-cylinder pressure is measured by repeatedly storing the detection value of the in-cylinder pressure sensor 15 for each predetermined crank angle (for example, 5 ° CA). The measurement range here is 360 ° CA over the compression stroke and the expansion stroke in order to reduce the calculation load and shorten the time. The process proceeds to step 108 on condition that the measurement of the measurement range is completed.

  In step S108, the 50% combustion point BP50 and the indicated torque ITQ are calculated and stored based on the detected value of the in-cylinder pressure within the measurement range obtained in step S107 and the crank angle at each measurement point. The 50% combustion point BP50 is a crank angle [° ATDC] at which the combustion ratio xb is 50%. The combustion ratio xb is calculated by the following formulas (1) and (2). The indicated torque ITQ is calculated by the following equations (3) and (4).

  Where Q is the amount of heat supplied to the gas in the cylinder, Qmax is its maximum value, κ is the specific heat ratio, P is the cylinder pressure, θ is the crank angle, V is the cylinder volume, W is the work, and Nc is the number of cylinders is there. The amount of heat Q supplied to the gas in the cylinder corresponds to a value obtained by subtracting an amount corresponding to heat loss to the wall surface from the amount of heat generated by combustion. The specific heat ratio κ is set to κ = 1.32 for simplicity.

  Next, it is determined whether the number of cycles is sufficient (S109). This determination may be made simply based on a comparison between the count value of the cycle number counter cyc and a predetermined reference value, or a plurality of the 50% combustion point BP50 and the indicated torque ITQ obtained within a predetermined crank angle range. May be based on whether the distribution or variation of the sample has reached a level suitable for use in correcting the ignition timing (for example, whether the deviation between each maximum value and minimum value exceeds a predetermined value). Also, a combination of these criteria (for example, logical product) may be used. The processes in steps S101 to S108 are repeatedly executed until the number of cycles becomes sufficient.

  If the number of cycles is sufficient, next, a correlation coefficient cor between the 50% combustion point BP50 and the indicated torque ITQ is calculated (S110). The correlation coefficient cor is calculated by the following equation (5).

  The calculated correlation coefficient cor is then compared with a reference value thr1 that is a predetermined negative value (S111). If the correlation coefficient cor is greater than or equal to the reference value thr1, the correlation coefficient cor is compared with a reference value thr2 that is a predetermined positive value (S112). In general, when one of the two variables shows a distribution that increases when the other increases, the correlation value takes a positive value (positive correlation), and when one increases, the other shows a distribution that decreases the other Since the correlation value takes a negative value (negative correlation), this embodiment uses this property to determine whether the current ignition timing is on the advance side with respect to the MBT from the value of the correlation coefficient cor itself. It is decided to determine whether it is on the retarded side.

  That is, in step S111, affirmation, that is, the fact that the correlation coefficient cor is below the negative reference value thr1, indicates that the 50% combustion point BP50 and the indicated torque ITQ are indicated by the symbol a in FIG. It means that the current ignition timing is on the retard side with respect to MBT because it means that it is distributed in a “downwardly right” state. Therefore, in such a case, the ignition timing is corrected to the advance side in step S112. This correction is performed by subtracting a predetermined advance amount (fixed value) from the current ignition timing [° ATDC].

  On the other hand, when the determination in step S113 is affirmative, that is, the correlation coefficient cor exceeds the positive reference value thr2, the 50% combustion point BP50 and the indicated torque ITQ are as indicated by symbol b in FIG. It means that the current ignition timing is on the advance side with respect to MBT, since it means that it is distributed in the “upward to right” state. Accordingly, in such a case, the ignition timing is corrected to the retard side in step S114. This correction is performed by adding a predetermined retardation amount (fixed value) to the current ignition timing [° ATDC].

  When thr1 ≦ cor ≦ thr2, it means that the 50% combustion point BP50 and the indicated torque ITQ are distributed in “substantially horizontal” as indicated by the symbol c in FIG. It can be estimated that the ignition timing is within a predetermined range from MBT. Therefore, in such a case, the ignition timing is not corrected.

  After the advance angle process (S112) or the retard angle process (S114) is performed as described above, the ECU 20 drives the spark plug 7 with the corrected ignition timing. In addition, after the advance processing (S112), retard processing (S114), or ignition timing correction non-execution determination (S113), the ECU 20 resets the correction mode flag flag to “0” (S115), and executes this routine. Exit.

  As a result of the above processing, in the present embodiment, the advance processing is performed when the ignition timing is retarded by a predetermined angle or more than MBT, and the retard is performed when the ignition timing is advanced by more than a predetermined angle from MBT. Each process is performed.

  As described above, in the present embodiment, the ignition timing correction is performed based on the correlation between the combustion ratio that is the first physical quantity including the in-cylinder pressure information and the indicated torque that is the second physical quantity including the engine output information. The amount is set, and the ignition timing is changed according to the set ignition timing correction amount. Therefore, according to the present embodiment, it is possible to appropriately control the ignition timing without using a fixed target value by using information on the in-cylinder pressure and the indicated torque, which are actual operating states of the engine 1. Even if there are individual differences due to manufacturing errors or aging deterioration, correction can be performed properly.

  In the present embodiment, the crank angle (50% combustion point BP50 [° ATDC]) when the combustion ratio in the combustion chamber is at the predetermined reference combustion ratio is used as the first physical quantity including the information on the in-cylinder pressure. However, the first physical quantity including the in-cylinder pressure information in the present invention includes, for example, a combustion period, that is, a period in which the combustion ratio is within a predetermined range (for example, between 10% and 90%), etc. The various parameters can be arbitrarily adopted.

  In the present embodiment, the indicated torque of the engine is used as the second physical quantity including the engine output information. However, as the second physical quantity including the engine output information in the present invention, for example, the crank Various other parameters including information on the output of the engine, such as the shaft torque and the angular velocity of the crankshaft, in particular, various parameters that can reflect the change in the output for each combustion cycle can be arbitrarily adopted.

  In the present embodiment, since either the predetermined positive correction amount or the predetermined negative correction amount is selected according to the sign of the correlation value between the first physical quantity and the second physical quantity, A desired effect can be obtained in the present invention with a simple configuration. However, instead of such a configuration, a map or function in which the correlation value between the first physical quantity and the second physical quantity and the correction amount of the ignition timing are associated in advance is created, and the correlation is made with this map or function. By inputting a value and calculating, different correction amounts may be set continuously or discretely according to the magnitude of the correlation value. In this case, it is particularly preferable to set the correction amount such that the absolute value of the correction amount gradually increases as the absolute value of the correlation value gradually increases.

  Further, since the calibration in the present embodiment is performed on-board, that is, during normal use of the engine (in the case of a vehicle, in-vehicle state and during normal use of the vehicle by the user), the internal combustion engine It is possible to suppress degradation in performance due to changes over time after shipment.

  In the above embodiment, the present invention has been described with a certain degree of concreteness, but various modifications and changes can be made to the present invention without departing from the spirit and scope of the invention described in the claims. It must be understood that. That is, the present invention includes modifications and changes that fall within the scope and spirit of the appended claims and their equivalents.

It is a schematic block diagram which shows the engine to which the control apparatus by this invention was applied. 2 is a flowchart for explaining an ignition timing correction routine executed in the internal combustion engine of FIG. 1. It is a graph which shows the relationship between ignition timing, a 50% combustion point, and the illustration torque.

Explanation of symbols

1 Internal combustion engine 3 Combustion chamber 7 Spark plug 12 Injector 14 Crank angle sensor 15 In-cylinder pressure sensor 20 ECU
21 Air flow meter

Claims (4)

In an engine control device comprising ignition timing changing means for changing the ignition timing of a spark ignition engine,
Correction amount setting means for setting an ignition timing correction amount based on a correlation between a first physical quantity including information on in-cylinder pressure in the combustion chamber of the engine and a second physical quantity including information on output of the engine; Prepared,
The engine control device according to claim 1, wherein the ignition timing changing means changes the ignition timing in accordance with an ignition timing correction amount set by the correction amount setting means. The engine control device according to claim 1,
The engine control apparatus according to claim 1, wherein the first physical quantity is a crank angle when a combustion ratio in the combustion chamber is a predetermined reference combustion ratio. The engine control device according to claim 1 or 2,
The engine control apparatus according to claim 2, wherein the second physical quantity is an indicated torque of the engine. The engine control device according to any one of claims 1 to 3,
The correction amount setting means selects either a predetermined positive correction amount or a predetermined negative correction amount in accordance with the sign of the correlation value between the first physical quantity and the second physical quantity. Engine control device.

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