JP2008095553A - Device and method for estimating ignition timing causing knocking in internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for estimating ignition timing causing knocking in an internal combustion engine capable of estimating the ignition timing causing knocking with high accuracy without spending much man-hour and time. <P>SOLUTION: The internal combustion engine is actually operated with a plurality of different ignition timing settings and a state quantity concerning self-ignition of the internal combustion engine is measured. A crank angle at which a self-ignition condition is satisfied is estimated based on the measured state quantity and the crank angle is calculated as a first judgment value C1. An unburned fuel quantity in a cylinder is calculated based on the measured state quantity and a limit crank angle at which unburned fuel of a quantity required for knock generation is calculated as a second judgment value Cb. Linear relation between setting values of ignition timing and the first judgment value C1 and linear relation between the setting values of ignition timing and the second judgment value Cb are calculated respectively and the ignition timing at which the first judgment value C1 and the second judgment value Cb agree with each other is calculated as ignition timing causing knocking based on the two linear relation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a knock generation ignition timing estimation apparatus and method for an internal combustion engine, and more particularly to an apparatus and method for estimating a knock generation ignition timing using a knock model.

  In the ignition timing control of an internal combustion engine, the ignition timing is advanced to the limit while being close to MBT while preventing knocking. The ignition timing at which knocking occurs (hereinafter referred to as knocking ignition timing) depends on the operating conditions of the internal combustion engine such as the intake air temperature, engine temperature, engine speed, and load. For this reason, conventionally, adaptation by an actual machine was performed under various operating conditions, and a knocking ignition timing was required for each operating condition. In the adaptation by the actual machine, a method was adopted in which the ignition timing at which knocking is surely not generated is set as an initial value, and the ignition timing is gradually advanced until knocking occurs.

Conventionally, a method for estimating the knocking ignition timing by calculation on a desk is also known. A so-called knock model is used to estimate the knock generation ignition timing. The knock model includes a model that predicts the timing at which self-ignition occurs and a model that calculates the amount of unburned fuel at the timing at which self-ignition occurs. As the former model, the Livengood-Wu model is generally used. For example, the Wiebe model can be used as the latter model. When the knock generation ignition timing is predicted using the knock model, first, the history of in-cylinder pressure is simulated by an engine model simulating an actual machine. By inputting the in-cylinder pressure data obtained by the simulation into the knock model, the self-ignition occurrence timing is calculated. If it is determined that the amount of unburned fuel necessary for the occurrence of knocking remains at the self-ignition generation timing, it can be estimated that the set value of the ignition timing at that time is the knock generation ignition timing.
JP 2004-245173 A JP 2004-332584 A

  However, in the conventional method for adapting to an actual machine, the man-hours and time required for the adapting work are enormous. This is because the search for the knock generation ignition timing has been started with the ignition timing having a sufficient margin as the initial value without giving a standard of the knock generation ignition timing in advance. The wider the search range for the knock generation ignition timing, the more man-hours and time required for the adaptation work.

  On the other hand, with the conventional method using the knock model, it is difficult to estimate the knocking ignition timing with high accuracy. This is because the in-cylinder pressure cannot be calculated with sufficiently high accuracy with the current engine model. Since the knock generation ignition timing is predicted using the in-cylinder pressure data, if the accuracy of the in-cylinder pressure data is low, the estimation accuracy of the knock generation ignition timing is also deteriorated. Although it is possible to measure in-cylinder pressure using an actual machine instead of the engine model, if actual machine measurement is performed for all operating conditions including ignition timing, a knock model that requires enormous man-hours and time The merit of using is reduced.

  By the way, the inventors of the present invention have a certain linear relationship between the crank angle (self-ignition crank angle) at which self-ignition conditions are predicted to be established and the ignition timing in the inventive process. I found it to be. It was also discovered that there is a certain linear relationship between the critical crank angle and the ignition timing where there is an amount of unburned fuel necessary for knocking. Using these findings, when the horizontal axis of the graph is the ignition timing and the vertical axis is the crank angle, a straight line showing the relationship between the self-ignition crank angle and the ignition timing, and the relationship between the limit crank angle and the ignition timing. By calculating the intersection point with the straight line indicating, the knocking ignition timing can be obtained. Each straight line can be approximated if there are at least two points of data.

  The present invention has been made based on the discovery as described above, and an object thereof is to make it possible to estimate the knocking ignition timing with high accuracy without taking a huge amount of man-hours and time.

In order to achieve the above object, a first invention provides a knock generation ignition timing estimation device for an internal combustion engine,
Operating condition setting means for setting the operating condition of the internal combustion engine including the ignition timing;
State quantity measuring means for actually operating the internal combustion engine under the operating conditions set in the operating condition setting means and measuring a state quantity relating to self-ignition of the internal combustion engine;
Predicting a crank angle at which a self-ignition condition is established based on the state quantity measured by the state quantity measuring means, and calculating the crank angle as a first judgment value;
The amount of unburned fuel in the cylinder is obtained based on the state amount measured by the state amount measuring means, and the limit crank angle at which the amount of unburned fuel necessary for the occurrence of knock exists is calculated as a second determination value. 2 judgment value calculation means;
The first determination value and the second determination value are acquired in a plurality of different ignition timing settings, the linear relationship between the ignition timing setting value and the first determination value, and the ignition timing setting value and the second determination value. And a knock generation ignition timing calculation means for calculating an ignition timing at which the first determination value and the second determination value coincide with each other based on the two linear relationships,
It is characterized by having.

The second invention is the first invention, wherein
Ignition timing initial setting means for retarding the knock generation ignition timing calculated by the knock generation ignition timing calculating means by a predetermined amount and setting it as an initial value of the ignition timing of the internal combustion engine;
A knock verification means for actually driving the internal combustion engine to verify whether or not knock occurs, and to advance the set value of the ignition timing by a predetermined amount until the occurrence of knock is detected;
When the knock verification means detects the occurrence of knock, the knock generation ignition timing determination means for determining the set value of the ignition timing at that time as the knock generation ignition timing;
Is further provided.

According to a third aspect of the present invention, there is provided a knock generation ignition timing estimation method for an internal combustion engine in order to achieve the above object.
A first step of setting operating conditions of the internal combustion engine including the ignition timing;
A second step of actually operating the internal combustion engine under the operating conditions set in the first step and measuring a state quantity related to self-ignition of the internal combustion engine;
A third step of predicting the success or failure of the self-ignition condition based on the state quantity measured in the second step, and calculating a crank angle at which the establishment of the self-ignition condition is predicted as a first determination value;
The amount of unburned fuel in the cylinder is obtained based on the state quantity measured in the second step, and a limit crank angle at which an amount of unburned fuel necessary for occurrence of knock exists is calculated as a second determination value. 4 steps,
The first determination value and the second determination value are acquired in a plurality of different ignition timing settings, the linear relationship between the ignition timing setting value and the first determination value, and the ignition timing setting value and the second determination value. And calculating the ignition timing at which the first determination value and the second determination value coincide with each other based on the two linear relationships as a knock generation ignition timing,
It is characterized by including.

Moreover, 4th invention is set in 3rd invention,
A sixth step of retarding the knocking ignition timing calculated in the fifth step by a predetermined amount and setting it as an initial value of the ignition timing of the internal combustion engine;
A seventh step of actually operating the internal combustion engine to verify whether knocking occurs and advancing the set value of the ignition timing by a predetermined amount until the occurrence of knocking is detected;
An eighth step of determining, when knocking is detected in the seventh step, a set value of the ignition timing at that time as a knocking ignition timing;
Is further included.

  According to the first and third aspects of the invention, the knocking ignition timing can be estimated based on the measured value (actual machine data) of the state quantity obtained by actually operating the internal combustion engine. Moreover, by grasping the linear relationship between the set value of the ignition timing and each determination value, the knocking ignition timing can be accurately estimated even from actual machine data under operating conditions in which knocking does not occur. Further, since the linear relationship between the set value of the ignition timing and each judgment value can be obtained if there is actual machine data at at least two ignition timings, it is not necessary to spend much man-hours and time to obtain the actual machine data. .

  According to the second and fourth aspects of the invention, it is possible to estimate the knocking ignition timing more accurately by actually operating the internal combustion engine and verifying whether or not knocking occurs at the set ignition timing. it can. At that time, the search range of the knock generation ignition timing is determined based on the knock generation ignition timing estimated using the knock model, and therefore, it is necessary to search for the knock generation ignition timing as compared with the conventional method for adapting to the actual machine. Man-hours and time can be greatly reduced.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a knock generation ignition timing estimation apparatus as an embodiment of the present invention. The knock generation ignition timing estimation device 10 is a device that operates the internal combustion engine (hereinafter referred to as the engine) 2 to acquire various data, and estimates the knock generation ignition timing of the engine 2 using the acquired data. The knock generation ignition timing estimation device 10 includes a driver 14 that controls the engine 2, various sensors 16 that are used to acquire data from the engine 2, and a computer 12 that performs various calculations.

The data necessary for estimating the knocking ignition timing is mainly the state quantity related to the self-ignition of the engine 2. The data includes measured values (cylinder pressure, equivalent ratio, octane number, H ₂ O concentration, etc.) and measured values. And predicted values calculated from the values (unburned gas temperature, combustion ratio, residual gas ratio, etc.). These data are not instantaneous values at a certain point in time but historical data over a plurality of cycles. Of the data, the actual measurement value is acquired from the engine 2 by the sensor 16, and the predicted value is calculated by the computer 12. In addition, actual machine tests for data acquisition are performed under various operating conditions, and the computer 12 calculates a knock generation ignition timing for each operating condition based on the acquired data. The computer 12 has a function of setting operating conditions for actual machine testing and instructing the driver 14. The operating conditions referred to here include the ignition timing of the engine 2. In this case, the computer 12 corresponds to the “operating condition setting means” according to the first invention. Further, the “state quantity measuring means” according to the first invention is realized by the computer 12, the driver 14 and the sensor 16.

  FIG. 2 is a flowchart for explaining a method of estimating the knocking ignition timing according to the present embodiment. The knock generation ignition timing estimation device 10 operates according to the routine shown in the flowchart of FIG. 2 so that the knock generation ignition timing of the engine 2 is estimated.

  In the first step S001 of the routine shown in FIG. 2, an actual machine test is performed at a plurality of points where only the ignition timing is changed among the operating conditions, and necessary data is acquired under each ignition timing. The acquired data is used for calculation of determination values Cl and Cb for determining knock occurrence in the next step S002.

  A known knock model is used to calculate the determination values Cl and Cb. The knock model is stored in the computer 12 as a program. The knock model includes a self-ignition prediction model and a knock determination value calculation model.

  The self-ignition prediction model is a model that predicts the crank angle at which the self-ignition condition is satisfied. In the present embodiment, the Livengood-Wu model is used as the self-ignition prediction model. The Livengood-Wu model is an integral formula of the reciprocal of the autoignition delay time expressed as a function of pressure and temperature. According to the Livengood-Wu model, the in-cylinder pressure and unburned gas temperature are used as input values to integrate the equation, and the crank angle at which the integrated value becomes 1 is obtained to predict the crank angle at which self-ignition occurs. can do. Data other than in-cylinder pressure and unburned gas temperature are used to determine the values of various parameters of the Livengood-Wu model.

  In step S002, a calculation based on the Livengood-Wu model is executed using the data acquired in step S001, and a crank angle at which self-ignition occurs (self-ignition crank angle) is predicted. This self-ignition crank angle becomes the first determination value Cl. The first determination value Cl is calculated for each of a plurality of ignition timings for which an actual machine test has been performed.

  The knock determination value calculation model is a model for calculating a limit crank angle where there is an amount of unburned fuel necessary for occurrence of knock. In the present embodiment, the Wiebe model is used as the knock determination value calculation model. According to the Wiebe model, it is possible to calculate the relationship between the crank angle and the combustion ratio (the total heat generation up to the crank angle with respect to the total heat generation of the supplied fuel). As the combustion rate increases, the amount of unburned fuel in the cylinder decreases. When the combustion rate is too high, there is no more fuel to be burned, so rapid combustion does not occur and knock does not occur. That is, the combustion ratio has an upper limit value at which knocking can occur. By using the Wiebe model, it is possible to calculate the crank angle at which the combustion ratio reaches the upper limit value, that is, the limit crank angle at which there is an amount of unburned fuel necessary to generate knock.

  In step S002, the value of each parameter of the Wiebe model is determined from the map based on the data acquired in step S001, and the limit crank angle is calculated by calculation using the Wiebe model. This limit crank angle becomes the second determination value Cb. The second determination value Cb is calculated for each of a plurality of ignition timings for which an actual machine test has been performed.

  The condition for the occurrence of knocking is that the amount of unburned fuel necessary for the occurrence of knocking remains at the self-ignition occurrence timing. When the ignition timing is delayed more than MBT, knocking does not occur because the self-ignition crank angle is on the retard side with respect to the limit crank angle. However, as the ignition timing is advanced, the self-ignition crank angle approaches the limit crank angle, and the self-ignition crank angle coincides with the limit crank angle before knocking occurs. It can be estimated that the ignition timing at that time, that is, the set value of the ignition timing when the first determination value Cl coincides with the second determination value Cb, is the knock generation ignition timing.

  In the present embodiment, knock generation ignition timing is estimated using the first determination value Cl and the second determination value Cb calculated in step S002 as follows. FIG. 3 is a diagram illustrating a relationship between the ignition timing and the first determination value Cl, and a relationship between the ignition timing and the second determination value Cb. The horizontal axis in the figure is the ignition timing, and the vertical axis is the crank angle. As shown in this figure, the relationship between the first determination value Cl and the ignition timing can be represented by a straight line L1. Further, the relationship between the second determination value Cb and the ignition timing can also be represented by a straight line L2. It has been confirmed by experiments that a certain linear relationship as shown in the figure exists between each of the determination values Cl and Cb and the ignition timing. If this fact is used, knock is generated by calculating the intersection of a straight line L1 indicating the relationship between the first determination value Cl and the ignition timing and a straight line L2 indicating the relationship between the second determination value Cb and the ignition timing. The ignition timing can be obtained.

  As shown in FIG. 4, each straight line L1, L2 can be approximated if there are at least two points of data. In step S003, the straight line L1 is approximately calculated from the first determination values Cl of the plurality of points calculated in step S002, and the straight line L2 is approximately calculated from the second determination values Cb of the plurality of points. Then, the ignition timing at which the two straight lines L1 and L2 intersect is calculated as the knock generation ignition timing.

  Thus, according to the knock generation ignition timing estimation method according to the present embodiment, the knock generation ignition timing is calculated based on the data (state quantity related to the self-ignition of the engine 2) obtained in the actual machine test of the engine 2. Can be sought. In addition, by calculating the two straight lines L1 and L2 indicating the relationship between the respective determination values Cl and Cb and the ignition timing, the knocking ignition timing can be obtained even from the data under the operating condition in which the knock does not occur. . Since the straight lines L1 and L2 can be approximated if there is actual machine data at at least two ignition timings, it is not necessary to spend much man-hours and time to obtain the actual machine data.

  However, if the number of data used for the approximate calculation of the straight lines L1 and L2 is small, the approximate accuracy of the straight lines L1 and L2 is lowered and the prediction error of the knocking ignition timing is increased accordingly. Therefore, in the estimation method of the knock generation ignition timing according to the present embodiment, the determined value of the knock generation ignition timing is obtained by a conformity test using an actual machine, and the knock generation ignition timing calculated from the intersection of the straight lines L1 and L2 (hereinafter, (Predicted ignition timing) is used as a reference value for searching for the knocking ignition timing by an actual machine test. The processes in steps S004 to S011 described below correspond to the conformance test using the actual machine.

In step S004, it is determined whether or not to retard the set value of the ignition timing in the actual machine test with respect to the predicted ignition timing. When it is estimated that the accuracy of the predicted ignition timing is high, the ignition timing is not retarded. Specifically, this is a case where the following conditions are satisfied.
Condition 1: The interval in the ignition timing direction of the data used for approximation of the straight lines L1 and L2 is large.
Condition 2: The number of data points used for approximation of the straight lines L1 and L2 is large.
Condition 3: The measurement error of the knock model input value such as in-cylinder pressure is small.

  If it is determined in step S004 that the ignition timing is retarded, the process of step S005 is performed. In step S005, the ignition timing set value is retarded with respect to the predicted ignition timing in accordance with the accuracy of the knock model. Here, the smaller the interval in the ignition timing direction of the data used to approximate the straight lines L1 and L2, the smaller the number of data points used to approximate the straight lines L1 and L2, and the larger the measurement error of the knock model input value I think that the accuracy of the knock model is low. Then, as the accuracy of the knock model is lower, the retard width with respect to the predicted ignition timing is set larger.

  In step S006, the ignition timing is set as determined by the processing in steps S004 and S005, and an actual machine test is performed. This actual machine test is performed under the same operating conditions as the actual machine test performed in step S001. In the actual machine test, a knock sensor is used to detect the occurrence of knock. After the actual machine test is completed, the determination in step S007 is performed.

  In step S007, it is determined whether knock has occurred in the actual machine test. If knock has not occurred, the process proceeds to step S008. In step S008, the ignition timing set value is advanced by a predetermined width from the current value. The advance angle width at this time is set to be much smaller than the retard angle width set in step S005.

  After the process of step S007, it progresses to step S006 again and an actual machine test is implemented. The processes in steps S006 to S008 are repeated until it is determined in step S007 that a knock has occurred. When it is determined in step S007 that knocking has occurred, the set value of the ignition timing at that time is determined as the knocking ignition timing. As described above, by verifying whether or not knocking occurs every time the ignition timing is reset, it is possible to estimate the knocking ignition timing more accurately.

  In the processing of steps S004 to S008, the knocking ignition timing is searched as shown in FIG. As shown in this figure, according to the knock generation ignition timing estimation method according to the present embodiment, the search range of the knock generation ignition timing is determined based on the predicted ignition timing calculated using the knock model. Compared with the conventional method that relies only on the actual machine test, the man-hours and time required for searching for the knocking ignition timing can be greatly reduced.

  In step S009, it is determined whether all tests have been completed. If all tests have been completed, this routine ends. If the test item remains, that is, if there remains an operation condition (test condition) that requires the estimation operation of the knock generation ignition timing, the process proceeds to step S010 to switch to the next test condition and determine the knock generation ignition timing. Continue the estimation work.

  In step S011, the data acquired in the actual machine test in step S006 is added as a matching point of the knock model. The parameters used in the knock model are determined according to the engine operating state (engine speed in FIG. 6), for example, as shown in FIG. When determining the parameter value used for calculation of the knock model, the value of the matching point is used as the parameter value for the engine speed at which the matching point exists. However, for engine speeds for which no matching point exists, interpolation calculation must be performed from neighboring matching points. If the data obtained in the actual machine test is added as the matching point, the interpolation accuracy when the parameter value is interpolated from the matching point can be improved. As a result, the knock generation ignition timing using the knock model The estimation accuracy can be improved. After the process of step S011, the process starts again from step 001.

  In the present embodiment, the processing of step S002 is executed by the knock generation ignition timing estimation device 10 to realize the “first determination value calculation means” and the “second determination value calculation means” of the first invention. The Further, the process of step S003 is executed by the knock generation ignition timing estimation device 10, whereby the “knock generation ignition timing calculation means” of the first invention is realized. Further, the processing of steps S004 and S005 is executed by the knock generation ignition timing estimation device 10, whereby the "ignition timing initial setting means" of the second invention is realized. Further, the knock generation ignition timing estimation device 10 executes the processing of steps S006 to S008, thereby realizing the “knock verification means” of the second aspect of the invention, and selecting the NO route in the determination of step S007. The "knock generation ignition timing determining means" of the second invention is realized.

  While the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  In the above-described embodiment, after the knock generation ignition timing is estimated using the knock model, that is, after the processing of steps S001 to S003, the verification of the knock generation ignition timing is performed by the conformity test by the actual machine, that is, the processing of steps S004 to S008. It is carried out. However, if the accuracy of the knock model is sufficiently high, the conformity test by the actual machine may be omitted, and the knock generation ignition timing calculated using the knock model may be set as the final value.

  Further, in FIG. 1, the knock generation ignition timing estimation device 10 is represented as one unit, but it may be configured as a system including a plurality of devices. In addition, the operation of estimating the knocking ignition timing performed according to the flowchart of FIG. 2 is not completely automated, and a part of the processing may be performed by a human.

It is a block diagram which shows the structure of the knock generation | occurrence | production ignition timing estimation apparatus as embodiment of this invention. It is a flowchart for demonstrating the estimation method of the knock generation ignition timing concerning embodiment of this invention. It is a figure which shows the relationship between ignition timing and 1st determination value Cl, and the relationship between ignition timing and 2nd determination value Cb. It is a figure for demonstrating the method of estimating a knock generation ignition timing from judgment value Cl and Cb. It is a figure shown about the search procedure of the knock generation ignition timing by a real machine test. It is a figure for demonstrating the fitting point of a knock model.

Explanation of symbols

2 Engine 10 Knock generation ignition timing estimation device 12 Computer 14 Driver 16 Sensor

Claims (4)

Operating condition setting means for setting the operating condition of the internal combustion engine including the ignition timing;
State quantity measuring means for actually operating the internal combustion engine under the operating conditions set in the operating condition setting means and measuring a state quantity relating to self-ignition of the internal combustion engine;
Predicting a crank angle at which a self-ignition condition is established based on the state quantity measured by the state quantity measuring means, and calculating the crank angle as a first judgment value;
The amount of unburned fuel in the cylinder is obtained based on the state amount measured by the state amount measuring means, and the limit crank angle at which the amount of unburned fuel necessary for the occurrence of knock exists is calculated as a second determination value. 2 judgment value calculation means;
The first determination value and the second determination value are acquired in a plurality of different ignition timing settings, the linear relationship between the ignition timing setting value and the first determination value, and the ignition timing setting value and the second determination value. And a knock generation ignition timing calculation means for calculating an ignition timing at which the first determination value and the second determination value coincide with each other based on the two linear relationships,
A knock generation ignition timing estimation device for an internal combustion engine, comprising: Ignition timing initial setting means for retarding the knock generation ignition timing calculated by the knock generation ignition timing calculating means by a predetermined amount and setting it as an initial value of the ignition timing of the internal combustion engine;
A knock verification means for actually driving the internal combustion engine to verify whether or not knock occurs, and to advance the set value of the ignition timing by a predetermined amount until the occurrence of knock is detected;
When the knock verification means detects the occurrence of knock, the knock generation ignition timing determination means for determining the set value of the ignition timing at that time as the knock generation ignition timing;
The knock generation ignition timing estimation apparatus for an internal combustion engine according to claim 1, further comprising: A first step of setting operating conditions of the internal combustion engine including the ignition timing;
A second step of actually operating the internal combustion engine under the operating conditions set in the first step and measuring a state quantity related to self-ignition of the internal combustion engine;
A third step of predicting the success or failure of the self-ignition condition based on the state quantity measured in the second step, and calculating a crank angle at which the establishment of the self-ignition condition is predicted as a first determination value;
The amount of unburned fuel in the cylinder is obtained based on the state quantity measured in the second step, and a limit crank angle at which an amount of unburned fuel necessary for occurrence of knock exists is calculated as a second determination value. 4 steps,
The first determination value and the second determination value are acquired in a plurality of different ignition timing settings, the linear relationship between the ignition timing setting value and the first determination value, and the ignition timing setting value and the second determination value. And calculating the ignition timing at which the first determination value and the second determination value coincide with each other based on the two linear relationships as a knock generation ignition timing,
A knock generation ignition timing estimation method for an internal combustion engine, comprising: A sixth step of retarding the knocking ignition timing calculated in the fifth step by a predetermined amount and setting it as an initial value of the ignition timing of the internal combustion engine;
A seventh step of actually operating the internal combustion engine to verify whether knocking occurs and advancing the set value of the ignition timing by a predetermined amount until the occurrence of knocking is detected;
An eighth step of determining, when knocking is detected in the seventh step, a set value of the ignition timing at that time as a knocking ignition timing;
The knock generation ignition timing estimation method for an internal combustion engine according to claim 3, further comprising:

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