JP2003049758A - Ignition timing control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately provide a knock generating ignition timing for determining a knock generating limit without using a large number of maps in the ignition timing control device of an internal combustion engine having a variable valve system allowing to vary the operating characteristics of an intake valve. SOLUTION: An internal energy Q0 before the compression of mixture fed into the combustion chamber of the internal combustion engine is calculated (Steps 10 to 106). In consideration of the power output of a piston delQ and a loss energy Qloss from a cylinder wall surface, an internal energy Q after the compression of the mixture is obtained (Steps 108 to 112). Based on the internal energy Q and an internal EGR rate r, a burning velocity v is obtained (Step 114). Based on the internal energy Q, burning velocity v, and a rotational speed NE, the knock generating ignition timing aknkcal is obtained (Step 118).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition timing control device for an internal combustion engine, and more particularly to an ignition timing control suitable for controlling an internal combustion engine equipped with a variable valve mechanism that makes the operating characteristics of an intake valve variable. Regarding the device.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 7-208310 discloses an ignition timing control device that learns the ignition timing in accordance with the knocking situation in an internal combustion engine. The ignition timing control device stores a map that defines the relationship between the operating state of the internal combustion engine and the basic ignition timing. Here, the basic ignition timing is a limit ignition timing at which knock is not generated for the fuel with the lowest octane number, which is scheduled for control.

The above-mentioned conventional ignition timing control device also includes
A map that defines the relationship between the operating state of the internal combustion engine and the maximum advance amount is stored. This maximum advance amount is the difference between the above-described basic ignition timing (the limit ignition timing for the fuel with the lowest octane number) and the limit ignition timing that does not cause knock with respect to the fuel with the highest octane number that is scheduled for control.

Further, the above-mentioned conventional ignition timing control device has
Internal combustion engine operating status and MBT (Minimumspark advance for B
est Torque) is stored in the map that defines the relationship. MBT is the limit ignition timing immediately before the output torque starts to decrease when the ignition timing is advanced under a constant operating condition.

The above-mentioned conventional ignition timing control device estimates the octane number of the fuel used during the operation of the internal combustion engine according to the knocking occurrence state. Then, based on the estimated octane number and the above MBT, the advance rate to be achieved for the fuel in use is obtained, and the advance rate is multiplied by the maximum advance amount to obtain the knock correction amount. Is calculated. The above-described conventional ignition timing control device determines the ignition timing at which knock does not occur by correcting the basic ignition timing base described above with the knock correction amount thus obtained.

By the way, the above-mentioned conventional ignition timing control device corresponds to an internal combustion engine provided with a variable valve mechanism for varying the operating characteristic of the intake valve. The relationship between the operating state of the internal combustion engine and the MBT, the operating state of the internal combustion engine, and the maximum amount of advance are determined depending on whether the intake valve exhibits operating characteristics that correspond to high-speed operation or when operating characteristics that correspond to low-speed operation. The relationship with is usually different.

For this reason, the conventional ignition timing control device stores two types of maps of the MBT and the maximum advance angle amount, which should be referred to during high speed operation and those referred to during low speed operation, respectively. Then, an appropriate map is selected according to the state of the variable valve mechanism to obtain the knock correction amount. As a result, in the conventional ignition timing control device described above, it is possible to always calculate an appropriate knock correction amount without being affected by the operation of the variable valve mechanism.

[0008]

However, there is a variable valve mechanism in which the operating characteristics of the intake valve can be changed steplessly. In an internal combustion engine in which such a variable valve mechanism is used, when the conventional method described above is applied,
In order to obtain the knock correction amount, it is necessary to prepare a huge number of maps for the MBT and the maximum advance amount.

To prepare such an enormous map, an enormous number of man-hours are required at the development stage of the internal combustion engine. Furthermore, if the enormous map is to be recorded, it becomes necessary to mount a large-capacity recording medium on the vehicle-mounted computer. As described above, the above-described conventional method causes various problems when it is attempted to be applied to a system that continuously changes the operation characteristics of the intake valve.

The present invention has been made in order to solve the above problems, and is a limit of knocking occurrence without using many maps even when the operating characteristics of the components of the internal combustion engine change. An object of the present invention is to provide an ignition timing control device capable of accurately determining knocking ignition timing.

[0011]

The invention according to claim 1 is
To achieve the above object, in an ignition timing control device for an internal combustion engine, an internal energy calculating means for calculating internal energy of a mixture gas supplied to a combustion chamber of the internal combustion engine, and a knock based on the internal energy Is generated, and knock generation ignition timing calculation means for calculating a knock generation ignition timing corresponding to a boundary between the ignition region in which knock does not occur and the ignition region in which knock does not occur are provided.

The invention according to claim 2 is the ignition timing control device for an internal combustion engine according to claim 1, wherein the internal energy calculating means calculates the internal energy of fresh air newly supplied to the combustion chamber. Means to acquire fresh energy,
Burned gas energy acquisition means for acquiring internal energy of burnt gas supplied to the combustion chamber, and internal EGR rate acquisition for obtaining an internal EGR rate corresponding to the ratio of fresh air and burnt gas supplied to the combustion chamber Means, internal energy of the fresh air, internal energy of the burnt gas, and the internal EG
Calculating means for calculating the internal energy of the air-fuel mixture based on the R ratio.

According to a third aspect of the present invention, there is provided the ignition timing control device for an internal combustion engine according to the first or second aspect, wherein the internal energy calculating means is configured such that the air-fuel mixture trapped in the combustion chamber is compressed. It is characterized by further comprising piston work amount obtaining means for obtaining a piston work amount received from the piston, and calculating means for calculating an internal energy of the air-fuel mixture based on the piston work amount.

According to a fourth aspect of the present invention, there is provided the ignition timing control device for an internal combustion engine according to the first or third aspect, wherein the internal energy calculation means is configured to extract a compression stroke from an air-fuel mixture trapped in a combustion chamber. It is characterized by further comprising: a loss energy acquisition means for determining a loss energy released to the cylinder wall surface; and a calculation means for calculating an internal energy of the air-fuel mixture based on the loss energy.

The invention according to claim 5 is the ignition timing control device for an internal combustion engine according to any one of claims 1 to 4, comprising an engine speed acquisition means for acquiring the engine speed of the internal combustion engine. The knock generation ignition timing calculation means obtains the knock generation ignition timing by using the rotation speed as basic data.

The invention according to claim 6 is the ignition timing control device for an internal combustion engine according to any one of claims 1 to 5, wherein the combustion speed of the air-fuel mixture in the combustion chamber of the internal combustion engine is acquired. It is characterized in that the knock generation ignition timing calculation means obtains the knock generation ignition timing by using the combustion speed as basic data.

The invention according to claim 7 is the ignition timing control device for an internal combustion engine according to any one of claims 1 to 6, wherein the required ignition timing corresponding to the operating state of the internal combustion engine is calculated. If the required ignition timing calculation means and the required ignition timing are within the ignition region where knock does not occur, the required ignition timing is set as the target ignition timing, and the required ignition timing does not fall within the ignition region where knock does not occur. In this case, a target ignition timing setting unit that sets the knock generation ignition timing as a target ignition timing is provided.

The invention according to claim 8 is the ignition timing control device for an internal combustion engine according to claim 7, wherein knock detection means for detecting knock of the internal combustion engine and ignition of a limit at which knock does not actually occur. Limit ignition timing detection means for detecting a timing, learning value recording means for recording a difference between the limit ignition timing and the target ignition timing as a knock learning value for each operating state of the internal combustion engine, and an operating state of the internal combustion engine A learning value reading means for reading a knock learning value corresponding to the learning value recording means, and a knock learning value read by the learning value reading means for correcting the target ignition timing to obtain a final ignition timing. Ignition timing determining means for determining
It is characterized by including.

The invention according to claim 9 is the ignition timing control device for an internal combustion engine according to any one of claims 1 to 8, wherein the internal combustion engine has variable operating characteristics of an intake valve. A variable valve mechanism is provided.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. It should be noted that elements common to each drawing are denoted by the same reference numerals, and redundant description will be omitted.

Embodiment 1. FIG. 1 is a conceptual diagram for explaining the configuration of the first embodiment of the present invention. The internal combustion engine 10 shown in FIG. 1 includes an intake valve 1 that opens and closes an intake port 12.
4 and an exhaust valve 18 that opens and closes the exhaust port 16. Further, the internal combustion engine 10 includes a variable valve mechanism 20 as a drive source of the intake valve 14. Variable valve mechanism 20
Can open and close the intake valve 14 while freely changing the valve opening timing IVO, the valve closing timing IVC, and the lift profile of the intake valve 14 within a range prepared in advance. In the following description, the individual lift profiles realized by the variable valve mechanism 20 are the maximum lift amounts given to the intake valve 14 by those profiles.
It will be distinguished by IVLMax.

A surge tank 20 communicates with the intake port 12 of the internal combustion engine 10. In the surge tank 20,
A PM sensor 22 for detecting the intake pipe pressure PM is attached. An electronically controlled throttle 24 is arranged upstream of the surge tank 20. Electronically controlled throttle 2
With No. 4, it is possible to realize an arbitrary throttle opening degree TA regardless of the depression amount of the accelerator pedal. An air flow meter 28 for detecting the intake air amount Ga flowing through the intake passage 26 is arranged further upstream of the electronic control throttle 24.

The air flow meter 28, the electronic control throttle 24, and the PM sensor 22 described above are connected to the ECU (Elect
ronic Control Unit) 30 is electrically connected.
Further, the ECU 30 is connected with various actuators incorporated in the variable valve mechanism 20 and various sensors for detecting the state of the variable valve mechanism 20. Furthermore, EC
U30 includes a rotation speed sensor 32 that detects the rotation speed NE of the internal combustion engine, a knock sensor 34 that detects the occurrence of knock from the vibration of the internal combustion engine 10, a cooling water temperature sensor 36 that detects the cooling water temperature THW of the internal combustion engine 10, and The air-fuel ratio A / of the air-fuel mixture being supplied to the internal combustion engine 10 from the oxygen concentration in the exhaust gas
An A / F sensor 38 for detecting F and the like are connected. EC
The U30 controls the variable valve mechanism 20 and the electronically controlled throttle 24 based on the outputs of these sensors.

Next, the basic contents of the ignition timing control executed in this embodiment will be described with reference to FIG. FIG. 2 is a diagram showing a process in which the final ignition timing aop ● is determined in the system of the present embodiment.
In FIG. 2, five circles denoted by reference numerals 40 to 48 correspond to crank angles from the intake top dead center to the compression top dead center. Acal that is displayed over the circles 40 and 42 is the required ignition timing determined corresponding to the operating state of the internal combustion engine 10. Further, aknkcal × displayed on the circles 40 and 42 is the knocking ignition timing corresponding to the limit on the advance side where it is expected that no knocking will occur.

The required ignition timing acal ○ and the knock occurrence ignition timing x are acal ○ depending on the operating state of the internal combustion engine 10.
It may be calculated so as to be on the retard side of aknkcal ×, or may be calculated so as to establish the opposite relationship. The circle 40 indicates the former case, while the circle 4
2 shows the latter case. The required ignition timing acal
The calculation method for ◯ and the calculation method for knocking ignition timing x will be described in detail later.

In the present embodiment, the knocking ignition timing x is used as a guard value on the advance side of the ignition timing.
Aopt * displayed over the circle 44 is the target ignition timing determined with the knock occurrence ignition timing x as the guard value. That is, in the system of the present embodiment, acal ○ is aknkcal
When calculated to the retarded side of X (in the case of circle 40), the required ignition timing acal ○ is directly set as the target ignition timing aopt ☆,
On the other hand, when acal∘ is calculated on the advance side of aknkcal × (in the case of circle 42), the knocking ignition timing aknkcal × is set as the target ignition timing aopt ☆.

The knocking ignition timing aknkcal × is an ignition timing theoretically calculated as a limit point at which knocking does not occur. Therefore, when the internal combustion engine 10 changes with time or the fuel properties change, knock may occur even at the knocking ignition timing aknkcal or at the ignition timing on the retard side. In other words, knocking ignition timing aknkcal
Even if the target ignition timing aopt ☆ obtained by using X as the guard value is used, knock may actually occur. Therefore,
In the present embodiment, the difference between the target ignition timing aopt ☆ and the ignition timing at which knock does not actually occur is learned as a knock learning value agknkΔ, and as shown by a circle 44, the knock learning value agkn
The value obtained by correcting the target ignition timing aopt ☆ with k △ is taken as the final ignition timing aop.

If normal combustion is obtained with the final ignition timing aop determined as described above, the circle 46
As shown in, the current knock learning value agknkΔ is maintained as it is as an appropriate value. On the other hand, when knocking occurs due to the finally determined ignition timing aop, the knock learning value agknkΔ is updated to a larger value, as indicated by the circle 48. When the knock learning value agknkΔ is updated to a large value, the final ignition timing aop is changed to the retard side from the current ignition timing from the next time onward, so that the occurrence of knock can be prevented. The system of the present embodiment realizes the function of minimizing the occurrence of knock without being influenced by the change over time of the internal combustion engine 10 or the change in the property of fuel by determining the ignition timing aop based on the principle described above. is doing.

In order to realize the above functions, the ECU will be described below.
The contents of the specific processing executed by the 30 will be described. In the present embodiment, the ECU 30 obtains the required ignition timing acal (ignition timing indicated by ◯ in FIG. 2) by the following method. That is, the ECU 30 obtains the required ignition timing acal by adding the required amount of advance angle retardation determined according to various situations to the basic ignition timing determined according to the operating state of the internal combustion engine 10.

The basic ignition timing is, specifically, the rotational speed NE,
Intake pipe pressure PM, intake valve opening timing IVO, closing valve IVC
And the maximum lift amount IVLMax, the air-fuel ratio A / F, and other ignition timings. On the other hand, the advance / retard request amount is a correction request amount regarding the ignition timing determined according to various situations such as a warm-up state of the internal combustion engine 10 and an acceleration / deceleration request. The ECU 30 can obtain the basic ignition timing and the advance / retard request amount, for example, by searching a map stored in advance.

Next, the ECU 30 controls the knocking generation ignition timing.
A method for obtaining aknkcal will be described. FIG. 3 shows an enlarged view of the combustion chamber 50 of the internal combustion engine 10. The principle of knock generation will be described below with reference to FIG. 3 before describing the specific processing contents for obtaining the knock generation ignition timing aknkcal.

As shown in FIG. 3, in the course of combustion of the air-fuel mixture inside the combustion chamber 50, the unburned gas 52 remaining at the end of the combustion chamber 50 is rapidly compressed. This unburned gas 52
May spontaneously ignite at one time as a result of the temperature rise associated with rapid compression. The knocking of the internal combustion engine 10 is considered to be caused by the spontaneous combustion of the unburned gas 52.

Knocking of the internal combustion engine 10 occurs when the unburned gas 52 is compressed at the end of the combustion chamber 50 as described above. Such uncombusted gas 52 is more likely to be compressed as the rotational speed NE of the internal combustion engine 10 is lower and the period in which the piston 54 is located near the compression top dead center is longer, and the combustion speed v of the air-fuel mixture is faster. It is easy to happen. Therefore, the knock of the internal combustion engine 10 is, as shown in FIG.
It tends to be less likely to occur as
As shown in FIG. 4B, the higher the combustion speed v of the air-fuel mixture, the more likely it is to occur.

The susceptibility to knocking in the internal combustion engine 10 also has a correlation with the internal energy Q of the unburned gas 52. That is, the knocking of the internal combustion engine 10 is caused by the spontaneous combustion of the compressed unburned gas 52 as described above. This spontaneous combustion is more likely to occur as the internal energy Q of the unburned gas 52 is higher. Therefore, in FIG.
As shown in (C), the knock of the internal combustion engine 10 is less likely to occur as the internal energy Q of the air-fuel mixture at the compression end is lower, and more likely to occur as the value Q increases.

As described above, whether knocking occurs in the internal combustion engine 10 is greatly influenced by the rotational speed NE, the combustion speed v, and the internal energy Q of the air-fuel mixture. Therefore, the knocking ignition timing aknkcal can be determined as a function of those parameters (NE, v, Q).

FIG. 5 is a flow chart of a routine executed by the ECU 30 to calculate the knocking ignition timing aknkcal. In the routine shown in FIG. 5, first, the energy Q1 of fresh air (a mixture of air and fuel) newly taken into the internal combustion engine 10 is calculated (step 1
00). The fresh air energy Q1 is a value substantially determined by the temperature of intake air (intake air temperature THA) and the pressure of intake air (intake pipe pressure PM). The ECU 30 executes the present step 10
At 0, the fresh air energy Q1 corresponding to the intake air temperature THA and the intake pipe pressure PM is calculated using a map or an arithmetic expression prepared in advance. The fresh energy Q1 is
It is dominated by intake air temperature THA rather than intake pipe pressure PM. Therefore, the fresh air energy Q1 may be determined based only on the intake air temperature THA.

In the internal combustion engine 10, during the transition from the exhaust stroke to the intake stroke, a period in which both the intake valve 14 and the exhaust valve 18 are open, that is, a valve overlap period may occur. During the valve overlap period, the burned gas (exhaust gas) remaining in the exhaust port 16 due to the differential pressure between the pressure (positive pressure) in the exhaust port 16 and the pressure (negative pressure) in the intake port 12. However, a phenomenon occurs in which the gas flows back into the intake port 12 through the combustion chamber 52.

During the valve overlap period, the burned gas thus flowing into the intake port 12 is closed again after the exhaust valve 18 is closed and the transition to the intake stroke is completed. Flow into. Therefore, under the operating condition in which the valve overlap period occurs, the internal combustion engine 1
A mixture of fresh air and burnt gas is supplied to the combustion chamber 52 of 0.

The internal energy Q of the air-fuel mixture in which the fresh air and the burned gas are mixed corresponds to the internal energy Q1 of the fresh air, the internal energy Q2 of the burned gas, and the ratio of the fresh air and the burned gas. Can be determined by the internal EGR rate r. Therefore, in the routine shown in FIG. 5, the energy Q2 of the burned gas is added after the processing of step 100.
Is calculated (step 102), and the internal EGR rate r
Is calculated (step 104).

The internal energy Q2 of burnt gas is substantially determined by the temperature of burnt gas (exhaust gas temperature) and the intake pipe pressure PM. Further, the exhaust gas temperature can be acquired by actual measurement or estimation based on the operating state of the internal combustion engine 10. In step 102, the ECU 30 uses a map or an arithmetic expression prepared in advance,
Internal energy Q corresponding to exhaust temperature and intake pipe pressure PM
Ask for 2. Incidentally, the internal energy Q2 of the burned gas is largely controlled by the exhaust temperature rather than the intake pipe pressure PM. Therefore, the internal energy Q2 may be determined based only on the exhaust temperature.

The internal EGR rate r is the rotational speed of the internal combustion engine 10.
It can be determined based on NE, intake pipe pressure PM, valve overlap period, and the like. In step 104, the ECU 30 uses a map or an arithmetic expression stored in advance to calculate the internal EG from those parameters.
The R rate r is calculated.

In the routine shown in FIG. 5, next, based on Q1, Q2 and r obtained as described above, the internal energy Q0 of the air-fuel mixture before compression, that is, the intake valve 14 is closed in the intake stroke. The internal energy Q0 of the air-fuel mixture at this stage is calculated (step 10
6).

The ECU 30 uses the arithmetic expression Q0 for obtaining the internal energy Q0 before compression from Q1, Q2 and r.
= H (Q1, Q2, r) is recorded. The arithmetic expression h (Q1, Q2, r) is an expression determined experimentally or by simulation. Step 106 above
Then, the internal energy Q0 is calculated by substituting Q1, Q2, r obtained in steps 100 to 104 into the calculation expression h (Q1, Q2, r).

FIG. 6 shows an example of the relationship between the internal energy Q0 before compression obtained in step 106 and the internal EGR rate r. The temperature of burnt gas is usually higher than the temperature of fresh air. Therefore, the internal energy Q of burnt gas
2 is usually larger than the fresh air energy Q1. If Q2> Q1, the higher the internal EGR rate r, the higher the internal energy Q0 should be. Therefore, as shown in FIG. 6, the internal energy Q0 obtained from the arithmetic expression h (Q1, Q2, r) has a larger value as the internal EGR rate r is higher.

In the routine shown in FIG. 5, next, the piston work amount delQ added to the mixture in the compression stroke is calculated (step 108). The piston work amount Q is substantially determined by the substantial compression ratio of the internal combustion engine 10. Further, the substantial compression ratio of the internal combustion engine 10 is determined by the crank angle at which the intake valve 14 is closed, that is, the closing timing IVC of the intake valve 14.
Determined by Therefore, the piston work delQ is
It can be determined based on the closing timing IVC of the intake valve 14.

FIG. 7 is a diagram showing the relationship between the piston work amount delQ and the valve closing timing IVC of the intake valve 14 obtained by the processing of step 108. As shown in this figure,
The piston work amount delQ takes a larger value as the closing timing IVC of the intake valve 14 approaches the intake bottom dead center (BDC) and the actual compression ratio of the internal combustion engine 10 increases. The ECU 30 stores a map or an arithmetic expression defining the relationship shown in FIG. 7 regarding the closing timing of the intake valve, the IVC, and the piston work amount delQ, and in step 108, the piston work amount is used by using them.
Calculate delQ.

In the routine shown in FIG. 5, the loss energy Qloss released from the air-fuel mixture to the cylinder wall surface or the like is calculated in the process of executing the compression stroke (step 11).
0). The lower the wall temperature, the more easily the heat of the air-fuel mixture is taken by a member such as a cylinder. Therefore, the loss energy Qloss is
The lower the wall temperature of the cylinder, the larger the value, and the higher the temperature, the smaller the value. Then, in a region where the wall temperature of the cylinder is sufficiently high, heat is transferred from the wall surface of the cylinder to the air-fuel mixture, and the loss energy Qloss becomes negative.

FIG. 8 is a diagram showing the above relationship established between the loss energy Qloss and the wall surface temperature of the cylinder. The ECU 30 stores a map or an arithmetic expression defining the relationship shown in FIG. 8 for both of them, and in step 110 described above, the piston work del
Calculate Q.

In the routine shown in FIG. 5, next, the internal energy Q of the air-fuel mixture at the compression end is calculated (step 112). Internal energy Q of air-fuel mixture at compression end
Is the internal energy Q0 of the mixture before compression
To the piston work delQ made in the compression stroke,
Further, it can be obtained by reducing the loss energy Qloss lost in the compression stroke. Therefore, the ECU 30
Q0, delQ and Ql obtained by the series of processes described above
The internal energy Q at the compression end is calculated by substituting oss into the following equation. Q = Q0 + delQ-Qloss

In the present embodiment, the internal energy Q, which is the first parameter for determining the knocking occurrence ignition timing aknkcal, is obtained by the series of processes described above.
Following these processes, in the routine shown in FIG. 5, the combustion speed v of the air-fuel mixture, which is the second parameter for determining the knocking occurrence ignition timing aknkcal, is calculated (step 114).

FIG. 9 shows the combustion speed v of the air-fuel mixture and the internal EGR.
The figure which shows the relationship with the ratio r for the case where the internal energy Q of the air-fuel mixture is q0 and the case where it is q1 is shown. However, the relation of q0> q1 is established between q0 and q1.

Since the burned gas is a gas which has already been burned once, the oxygen concentration in the burned gas is sufficiently lower than the oxygen concentration of fresh air. Therefore, as the proportion of burnt gas contained in the air-fuel mixture increases, the combustion speed v of the air-fuel mixture
Will fall. That is, as shown in FIG. 9, the combustion speed v of the air-fuel mixture decreases as the internal EGR rate r increases. Also,
The higher the internal energy Q of the air-fuel mixture, the more easily it burns. Therefore, as shown in FIG. 9, the combustion speed v becomes higher as the internal energy Q is higher.

As described above, the combustion speed v of the air-fuel mixture is greatly influenced by the internal EGR rate r and the internal energy Q. Then, the combustion speed v is almost uniquely determined for the combination of these two parameters (r and Q). In the present embodiment, the ECU 30 controls the arithmetic expression v = g (r,
Q) is recorded. The arithmetic expression g (r, Q) is an expression determined experimentally or by simulation. In step 114, the arithmetic expression g (r,
The combustion speed v is calculated by substituting the r obtained in step 104 and the Q obtained in step 112 into Q).

By the above-described processing, knock occurrence ignition timing
When the second parameter for obtaining aknkcal is obtained, next, the rotation speed NE which is the third parameter for obtaining aknkcal is detected (step 116).

Then, the internal energy Q, the combustion speed v, and the rotational speed NE obtained in the processing of steps 112 to 116 are substituted into the arithmetic expression aknkcal = f (NE, v, Q) to generate a knock. The ignition timing aknkcal is calculated (step 118). The arithmetic expression f (NE, v, Q) is an expression determined experimentally or by simulation. According to the processing of step 118, the knocking ignition timing aknkcal corresponding to the operating state of the internal combustion engine 10 can be accurately calculated according to the calculation expression f (NE, v, Q).

As described above, according to the system of this embodiment, the knocking ignition timing aknkcal is obtained based on the internal energy Q of the air-fuel mixture, the combustion speed v of the air-fuel mixture, and the rotational speed NE of the internal combustion engine 10. be able to. In the system of the present embodiment, the function of the variable valve mechanism 20 causes
The operating characteristics of the intake valve 14 (valve opening timing IVO, valve closing timing IVO, and maximum lift amount IVLMax) can be changed.
Knock generation ignition timing aknkcal uses, for example, IVO, IVC, IVLMax representing its operating characteristics, rotational speed NE representing the operating state of internal combustion engine 10, intake pipe pressure PM, and air-fuel ratio A / F as parameters. It can also be obtained by preparing maps and retrieving values corresponding to all parameters from those maps.

However, when such a method is adopted, the items to be defined in the map become enormous, and enormous man-hours are required for the preparation. Further, in order to store the map, it becomes necessary to secure a large memory capacity in the ECU 30. On the other hand, according to the method of the present embodiment, the knocking ignition timing aknkcal can be accurately obtained without using such a huge map. Therefore, the system of the present embodiment is an extremely excellent system for appropriately controlling the ignition timing while preventing knocking in the internal combustion engine 10 including the variable valve mechanism 20.

Next, with reference to FIG. 10, one technique for controlling the ignition timing by utilizing the knocking ignition timing aknkcal calculated as described above will be described. FIG. 10 shows a flowchart of a routine executed by the ECU 30 to control the ignition timing of the internal combustion engine 10 in the present embodiment. In the routine shown in FIG. 10, first, the parameters required for control are read. Specifically, the rotational speed NE of the internal combustion engine 10, the intake pipe pressure PM, the valve opening timing IVO of the intake valve 14, the valve closing timing IVC, the maximum lift amount IVLMax, and the air-fuel ratio A / realized by the internal combustion engine 10. F and the like are read (step 120).

Next, the required ignition timing acal is calculated based on the parameters read in step 120.
As described above, the required ignition timing acal is obtained by adjusting the basic ignition timing according to the operating state of the internal combustion engine 10 and adjusting the advance / retard request amount generated in response to various requests (step 122).

Next, the knocking ignition timing aknkcal is calculated. That is, the process of calculating the knocking ignition timing aknkcal is performed according to the routine shown in FIG. 5 (step 122).

Next, it is determined whether the required ignition timing acal is greater than the knocking ignition timing aknkcal (both are values represented by crank angle before top dead center BTDC ° CA). That is, the required ignition timing acal is the knocking ignition timing aknkcal
It is determined whether it is on the more advanced side (step 126).

As a result, acal> aknkcal does not hold,
That is, the required ignition timing acal is the knocking ignition timing aknk
When it is determined that the ignition timing is on the retard side of cal, the required ignition timing acal is directly set as the target ignition timing aopt (step 128).

On the other hand, in the above step 126, acal
If> aknkcal is satisfied, that is, if the required ignition timing acal is on the advance side of the knocking ignition timing aknkcal, the knocking ignition timing aknkcal is used as a guard value, and the value aknkcal is the target ignition timing. It is set as aopt (step 130).

In the routine shown in FIG. 5, the above step 1
After the processing of 28 or 130, the knock learning value agknk corresponding to the operating state of the internal combustion engine 10 is read (step 132). The knock learning value agknk is stored in the ECU 30 in association with each operating state of the internal combustion engine 10. More specifically, the rotational speed NE, the intake pipe pressure PM, the valve opening timing IVO of the intake valve 14, the valve closing timing IVC, the maximum lift amount IVLM.
The knock learning value agknk is stored in association with each operating state specified by ax and the air-fuel ratio A / F.
This knock learning value agknk is a value corresponding to the difference between the target ignition timing aopt and the limit ignition timing at which knock does not actually occur, as already described with reference to FIG. This step 1
At 32, the knock learning value ag stored in the ECU 30.
The value corresponding to the parameter read in step 120 is read from knk.

In the routine shown in FIG. 5, next, by subtracting the knock learning value agknk from the target ignition timing aopt,
The final ignition timing aop is determined (step 13
4). The ignition timing aop is a value corresponding to the limit ignition timing that can actually prevent the occurrence of knocking if the knock learning value agknk is a value suitable for the current situation.

Next, the internal combustion engine 10 is ignited by using the ignition timing aop obtained in step 134 (step 136). Next, it is determined whether knock has occurred as a result of the ignition (step 138).

As a result, when it is determined that knock has occurred, it can be determined that the knock learning value agknk does not match the current situation and is an excessively small value. in this case,
The ignition timing aop is reduced by a predetermined value K1, that is,
After changing to the value on the retard side by the predetermined value K1 (Step 1
40), the process of step 136 is performed again.

Thereafter, the above steps 136 to 140 are executed until it is determined in step 138 that no knock has occurred.
The process of is repeatedly executed. And step 138
If it is determined that the knock has not occurred, the ignition timing ao
The cumulative total of the correction value K1 subtracted from p is subtracted from the knock learning value agknk, and the value after the subtraction is the new knock learning value agknk.
It is stored as k (step 142).

As described above, according to the routine shown in FIG. 10, the target ignition timing aopt is determined by using the knocking ignition timing aknkcal theoretically obtained by calculation as the guard value, and the target ignition timing aopt is learned by knocking. Value agknk
By correcting with, it is possible to obtain the ignition timing aop that does not actually cause knock. Then, the knock learning value agknk can be constantly updated to a value adapted to the latest situation in accordance with the change over time of the internal combustion engine 10 and the change in fuel property. Therefore, according to the system of the present embodiment, the ignition timing of the internal combustion engine 10 can be appropriately controlled within the range where knock does not occur.

By the way, in the above-described first embodiment, in the routine shown in FIG. 10, the knock learning value agknk is updated only when the occurrence of knock is recognized, but the present invention is not limited to this. Not a thing. That is, the knock learning value agknk is set to a smaller value when the occurrence of knock is not recognized, that is, the ignition timing.
The value may be updated so that aop is advanced.

Embodiment 2. Next, referring to FIG.
The second embodiment of the present invention will be described. The system of the present embodiment is different from the routine shown in FIG. 10 in that the ECU 30 executes the routine shown in FIG.
This is similar to the system of the first embodiment. The routine shown in FIG. 11 is the same as the routine shown in FIG. 10 except for the processing after step 138.

That is, in the routine shown in FIG. 11 executed in this embodiment, when the occurrence of knock is recognized in step 138, the knock learning value is immediately thereafter.
After agknk is reduced by a predetermined value k1 (step 150)
The routine ends. If it is determined in step 138 that no knock has occurred, then this routine is immediately ended.

In the system of the first embodiment described above, when the occurrence of knock is recognized, thereafter, the processes of steps 136 to 140 are repeatedly executed until the ignition timing aop is updated to a value that does not cause knock. Then, after the situation in which knock does not occur is formed, the knock learning value agknk
Will be updated. In this case, steps 136-140
Although the knock learning value agknk corresponding to a specific operating state is updated during the repetition of, the operating state of the internal combustion engine 10 itself may change during the repetition. Therefore, in the case of the first embodiment, the correspondence between the knock learning value agknk and the operating state of the internal combustion engine 10 may deviate.

On the other hand, in the system of the present embodiment, as shown in FIG. 11, when the occurrence of knock is recognized for a specific knock learning value agknk, the knock learning value is immediately updated. be able to. That is, according to the system of the present embodiment, the knock learning value agknk read corresponding to a particular operating state can be updated to an appropriate value before the operating state changes. Therefore, according to the system of the present embodiment, the correspondence between the knock learning value agknk and the operating state of the internal combustion engine 10 can always be maintained correctly, and ignition with higher accuracy than in the case of the first embodiment. Timing control can be realized.

By the way, the first and second embodiments described above
Then, the learning value agknk is updated only when the occurrence of knocking is recognized with respect to the specific knock learning value agknk, but the present invention is not limited to this. That is, the knock learning value agknk may be updated to a smaller value, that is, a value that advances the ignition timing aop to the advance side when the occurrence of knock is not recognized.

In the above-described first or second embodiment, the ECU 30 executes the processes of steps 100 to 112 so that the "internal energy calculating means" in claim 1 performs the steps 118 or 124.
The "knock occurrence ignition timing calculation means" according to the first aspect is realized by executing the processing of 1.

Further, in the above-described first or second embodiment, the ECU 30 executes the process of the step 100, and the "fresh air energy acquisition means" in claim 2 executes the process of the step 102. The "burned gas energy acquisition means" according to claim 2 is executed, and the "internal EGR rate acquisition means" according to claim 2 is executed by executing the process of step 104.
By executing the processing of the step 112, the "calculating means" according to claim 2 is realized.

Further, in the above-described first or second embodiment, the ECU 30 executes the process of the step 108 so that the "piston work amount obtaining means" of the third aspect executes the process of the step 112. By executing, the "arithmetic unit" of claim 3 is realized.

Further, in the above-described first or second embodiment, the ECU 30 executes the process of step 110, and the "loss energy acquisition means" of claim 4 executes the process of step 112. By doing so, the "arithmetic means" described in claim 4 is realized.

Further, in the above-described first or second embodiment, the ECU 30 executes the processing of the above step 116 so that the "rotational speed obtaining means" according to claim 5 is obtained.
Is achieved, and the ECU 30 executes the above step 1
By executing the processing of 14, the "combustion rate acquisition means" according to claim 6 is realized.

Further, in the above-described first or second embodiment, the ECU 30 executes the process of step 122, so that the "requested ignition timing calculation means" of claim 7 causes the steps 126 to 130 to be performed. The "target ignition timing setting means" according to the seventh aspect is realized by executing the processing of.

In the first or second embodiment described above, the ECU 30 executes the process of step 138 so that the "knock detecting means" according to claim 8 can perform the steps 140 and 142, or the steps. By executing the processing of 150, the "limit ignition timing detecting means" and the "learning value recording means" of claim 8 execute the processing of step 132, and the "learning value read-out" of claim 8 is performed. By executing the processing of the step 134, the "means" respectively realizes the "ignition timing determining means".

[0083]

Since the present invention is constructed as described above, it has the following effects. Claim 1
According to the described invention, the knock generation ignition timing can be obtained based on the internal energy of the air-fuel mixture. The internal energy of the air-fuel mixture is a factor that directly determines the likelihood of knocking. Therefore, based on the internal energy, the knocking ignition timing can be directly obtained with high accuracy.

According to the second aspect of the invention, the internal energy of fresh air, the internal energy of burnt gas, and the internal EG
The internal energy of the air-fuel mixture before being compressed can be accurately obtained based on the R ratio.

According to the invention described in claim 3, by considering the piston work amount added to the mixture in the compression stroke,
The internal energy of the air-fuel mixture can be accurately obtained.

According to the fourth aspect of the present invention, the internal energy of the air-fuel mixture can be accurately obtained by considering the loss of energy released from the air-fuel mixture to the cylinder wall surface.

According to the fifth aspect of the present invention, the knocking ignition timing can be determined in consideration of the rotational speed of the internal combustion engine. The rotation speed of the internal combustion engine is a factor that directly determines the likelihood of knocking. Therefore, based on the rotation speed, the knocking ignition timing can be directly and accurately obtained.

According to the sixth aspect of the present invention, the knocking ignition timing can be determined in consideration of the combustion speed of the air-fuel mixture. The combustion speed of the air-fuel mixture is a factor that directly determines the likelihood of knocking. Therefore, based on the combustion speed, the knocking ignition timing can be directly and accurately obtained.

According to the seventh aspect of the invention, the target ignition timing can be determined with the knocking ignition timing as the guard value. Therefore, according to the present invention, the target ignition timing is
It is possible to prevent the knock from being set in an area where the knock is theoretically expected.

According to the eighth aspect of the present invention, the difference between the target ignition timing and the ignition timing at which knock does not actually occur is recorded as a knock learning value, and the ignition timing learning value is used to actually make the difference. The ignition timing that does not cause knock can be set as the final ignition timing.

According to the ninth aspect of the invention, the operating characteristic of the intake valve can be changed by the variable valve mechanism.
When the operating characteristic of the intake valve changes, the knocking ignition timing also changes. In the present invention, since the knock generation ignition timing is obtained based on the internal energy of the air-fuel mixture, it is possible to perform a relatively easy calculation without observing a number of parameters themselves changed by the variable valve mechanism,
The knocking ignition timing can be accurately obtained.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a configuration of a first or second embodiment of the present invention.

FIG. 2 is a diagram for explaining the basic contents of ignition timing control executed in the first embodiment of the present invention.

FIG. 3 is a diagram for explaining the principle of knocking in an internal combustion engine.

FIG. 4 is a diagram showing the relationship between knocking easiness, rotation speed, burning speed, and internal energy.

FIG. 5 is a flowchart of a routine that is executed to obtain a knocking ignition timing in the first embodiment of the present invention.

FIG. 6 is a diagram showing an example of a relationship between an internal EGR rate r and an internal energy Q0 of a mixture before compression.

[Fig. 7] Piston work amount delQ and intake valve closing timing IVC
It is a figure which shows the relationship with.

FIG. 8 is a diagram showing a relationship between loss energy Qloss released from the air-fuel mixture in a compression stroke and a cylinder wall surface temperature.

FIG. 9 is a diagram showing the relationship between the combustion speed v and the internal EGR rate r, using the internal energy Q of the air-fuel mixture as a parameter.

FIG. 10 is a flowchart of a routine executed to control ignition timing in the first embodiment of the present invention.

FIG. 11 is a flowchart of a routine executed to control ignition timing in the second embodiment of the present invention.

[Explanation of symbols]

10 Internal combustion engine 14 Intake valve 18 Exhaust valve 20 Variable valve mechanism 30 ECU (Electronic Control Unit) 32 rpm sensor 34 knock sensor acal (○) Required ignition timing aknkcal (×) Knock occurrence ignition timing aopt (☆) Target ignition timing aop (●) Final ignition timing agknk (△) Knock learning value Q1 fresh energy Q2 Burned gas energy Q0 Internal energy of mixture before compression delQ piston work Qloss energy loss Q Internal energy after compression of air-fuel mixture r Internal EGR rate v Burning speed of air-fuel mixture NE Internal combustion engine speed IVC intake valve closing timing IVO intake valve opening timing IVLMax Maximum intake valve lift

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02P 5/153 (72) Inventor Masanobu Kanamaru 1 Toyota-cho, Toyota-shi, Aichi Prefecture Toyota Automobile Co., Ltd. (72 ) Inventor Satoshi Watanabe 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Inventor Masaaki Konishi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F Term (reference) 3G022 DA02 EA02 FA05 FA06 GA01 GA05 GA07 GA08 GA13 3G084 BA05 BA17 BA23 DA38 EB08 EB17 FA11 FA19 FA25 FA29 FA33 FA37 FA38 3G092 AA11 BA09 DA01 DC01 EC05 EC09 FA16 HA05Z HA12 HA12X HC00Z HC05Z HC09X HD05Z HD07Z HE01Z HE03Z

Claims (9)

[Claims] 1. An internal energy calculating means for calculating internal energy of an air-fuel mixture supplied to a combustion chamber of an internal combustion engine, an ignition region in which knock occurs, and an ignition region in which knock does not occur, based on the internal energy. An ignition timing control device for an internal combustion engine, comprising: knock generation ignition timing calculation means for calculating a knock generation ignition timing corresponding to a boundary. 2. The internal energy calculation means acquires fresh air energy acquisition means for acquiring internal energy of fresh air newly supplied to the combustion chamber, and acquires internal energy of burnt gas supplied to the combustion chamber. Burned gas energy acquisition means, internal EGR rate acquisition means for obtaining an internal EGR rate corresponding to the ratio of fresh air and burned gas supplied to the combustion chamber, internal energy of the fresh air, and burned gas The ignition timing control device for an internal combustion engine according to claim 1, further comprising: a calculating unit that calculates the internal energy of the air-fuel mixture based on the internal energy and the internal EGR rate. 3. The internal energy calculating means is a piston work amount obtaining means for obtaining a piston work amount of a mixture gas confined in a combustion chamber received from a piston during a compression stroke, and the mixing process based on the piston work amount. 3. An ignition timing control device for an internal combustion engine according to claim 1 or 2, further comprising: a calculating unit that calculates the internal energy of the air. 4. The internal energy calculation means is a loss energy acquisition means for obtaining the loss energy released from the air-fuel mixture trapped in the combustion chamber to the cylinder wall surface during the compression stroke, and the mixture based on the loss energy. An ignition timing control device for an internal combustion engine according to claim 1 or 3, further comprising: a calculating unit that calculates the internal energy of the air. 5. A rotation speed acquisition means for acquiring the rotation speed of the internal combustion engine, wherein the knock generation ignition timing calculation means obtains the knock generation ignition timing using the rotation speed as basic data. Item 5. An ignition timing control device for an internal combustion engine according to any one of items 1 to 4. 6. A combustion speed acquisition means for acquiring a combustion speed of the air-fuel mixture in a combustion chamber of an internal combustion engine, wherein the knock generation ignition timing calculation means uses the combustion speed as basic data to determine the knock generation ignition timing. The ignition timing control device for an internal combustion engine according to any one of claims 1 to 5, wherein the ignition timing control device is determined. 7. A required ignition timing calculation means for calculating a required ignition timing corresponding to an operating state of an internal combustion engine; and when the required ignition timing is within an ignition region where knock does not occur, the required ignition timing is targeted. Ignition timing,
7. The target ignition timing setting means for setting the knock generation ignition timing as a target ignition timing when the required ignition timing is not within an ignition region where knock does not occur, according to any one of claims 1 to 6. 2. An ignition timing control device for an internal combustion engine according to claim 1. 8. A knock detection means for detecting knock of an internal combustion engine, a limit ignition timing detection means for detecting a limit ignition timing at which knock does not actually occur, and the limit ignition timing for each operating state of the internal combustion engine. Learning value recording means for recording a difference from the target ignition timing as a knock learning value; learning value reading means for reading a knock learning value corresponding to the operating state of the internal combustion engine from the learning value recording means; 8. An internal combustion engine according to claim 7, further comprising: ignition timing determining means for determining a final ignition timing by correcting the target ignition timing with the knock learning value read by the means. Ignition timing control device. 9. The ignition timing control device for an internal combustion engine according to claim 1, wherein the internal combustion engine is provided with a variable valve mechanism that varies the operating characteristics of the intake valve.