JP2012219757A - Internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly estimate a knock generation factor by a simple constitution without being affected by an operation state.SOLUTION: An ECU 50 calculates an unburnt fuel quantity in a cylinder in a knock-limit combustion ratio MFBmax as a fuel remaining quantity Kr at knock generation. The ECU also calculates the unburnt fuel quantity when the knock is not generated as a standard fuel remaining quantity Kth to calculate the difference (Kr-Kth) between both amounts as an index ΔK. Then the octane value of the fuel is estimated based on the index ΔK. Thereby the octane value of the fuel is correctly estimated based on the index ΔK not affected by a change in a load ratio to enhance the accuracy of knock avoiding control or the like. There is no need for setting the index ΔK at every operation state by a data map or a function expression, which helps to reduce the data amount necessary for control to greatly reduce the adaptive man-hours for adapting individual data to the operation state.

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly to an internal combustion engine control apparatus having a knock detection function.

  As a prior art, for example, as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2008-95553), a control device for an internal combustion engine having a knock detection function is known. In the related art, first, a state quantity related to self-ignition of the internal combustion engine is measured, and a crank angle at which the self-ignition condition is satisfied is calculated as a first determination value based on the measured state quantity. Further, the amount of unburned fuel in the cylinder is obtained based on the measured state quantity, and the limit crank angle at which the amount of unburned fuel necessary for the occurrence of knock exists is calculated as the second determination value. The knock generation ignition timing is calculated based on these determination values and the set value of the ignition timing.

JP 2008-95553 A JP 2004-332584 A

  By the way, in the above-described prior art, in order to calculate the ignition timing of knocking, the amount of unburned fuel in the cylinder, the limit crank angle at which there is an amount of unburned fuel necessary for knocking, etc. are used as parameters. Used. These parameters also vary depending on, for example, the operating state (load state) of the internal combustion engine, the octane number of the fuel, the amount of deposit deposited in the cylinder, and the like. However, the prior art does not fully consider the influence of these factors, and therefore there is a problem that it is difficult to accurately perform knock control.

  The present invention has been made to solve the above-described problems, and the object of the present invention is to accurately determine the cause of knocking and the timing of knocking with a simple configuration without being affected by the operating state. It is an object of the present invention to provide a control device for an internal combustion engine that can be estimated and can improve accuracy such as knock avoidance control.

The first invention has a function of calculating the combustion mass ratio during the combustion stroke based on the crank angle of the internal combustion engine and the in-cylinder pressure, and an amount of unburned fuel necessary for the occurrence of knock exists in the cylinder. A knock limit combustion ratio acquisition means for acquiring a limit combustion mass ratio as a knock limit combustion ratio;
A means for calculating the amount of unburned fuel as a remaining fuel amount at the time of knocking when the knocking actually occurs in a state where the combustion mass ratio during the combustion stroke coincides with the knock limit combustion ratio, Fuel remaining amount calculating means for calculating the remaining amount of fuel at the time of knock occurrence based on the amount of fuel supplied into the engine and the knock limit combustion ratio;
A reference remaining amount storage means in which a reference remaining amount that is an amount of the unburned fuel when knock does not occur in a state where a combustion mass ratio in a combustion stroke matches the knock limit combustion ratio;
Index calculating means for calculating the difference between the two by subtracting the reference remaining amount from the remaining fuel amount at the time of knock occurrence;
Octane number estimation means for estimating the octane number of the fuel based on the index;
Estimated timing setting means for setting the timing for operating the octane number estimating means to estimate the octane number of the fuel based on the operating state of the internal combustion engine;
It is characterized by providing.

  According to the second invention, the estimated time setting means is configured to operate the octane number estimating means when the speed at which the index changes is equal to or greater than a predetermined sudden change determination value.

  According to a third invention, the estimated time setting means is configured to operate the octane number estimating means when the internal combustion engine is started.

4th invention is provided with the deposit adhesion amount estimation means which estimates the adhesion amount of the deposit adhered in the cylinder based on the above-mentioned index,
The estimation time setting means is configured to operate the deposit adhesion amount estimation means to estimate the deposit adhesion amount when the octane number estimation means is not operated.

A fifth aspect of the present invention is a fuel remaining amount storage means for storing the amount of fuel remaining at the time of knock occurrence calculated by the fuel remaining amount calculating means;
The knock limit based on the amount of fuel supplied into the cylinder and the stored value of the fuel remaining amount at the time of knock generation in an arbitrary operation state including an operation state different from that at the time of calculation of the fuel remaining amount at the time of knock occurrence Knock limit combustion rate reverse calculation means for calculating the combustion rate,
Knock generation angle prediction means for calculating a crank angle at which knock occurs as a knock generation prediction angle by performing a predetermined integration process based on at least the in-cylinder pressure and the in-cylinder temperature;
By subtracting the crank angle corresponding to the knock limit combustion ratio from the predicted knock generation angle, the degree of crank angle that can advance the ignition timing without generating knock is defined as the ignition advance angle margin. Ignition advance margin calculation means for calculating.

  According to the first aspect of the present invention, it is possible to calculate the remaining amount of fuel at the time of knock occurrence, which is the amount of unburned fuel at the knock limit combustion ratio, and to determine the remaining fuel amount at the time of knock occurrence and the reference fuel remaining when no knock occurs. The difference from the quantity can be calculated as an index. Here, the amount of fuel remaining at the time of knock occurrence is substantially constant even when the load factor of the internal combustion engine changes, and the index calculated based on the amount of fuel remaining at the time of knock occurrence also affects the load factor. It becomes a parameter that is not. Therefore, according to the first aspect of the invention, the octane number of the fuel can be accurately estimated based on the index that is not affected by the change in the load factor. And various correspondence control can be performed exactly based on this estimation result, and accuracy, such as knock avoidance control, can be improved. In addition, since the index is not affected by the load factor, it is not necessary to set the index for each operation state using a data map or a function expression. As a result, the amount of data required for control can be reduced, and the number of man-hours for adapting individual data to the operating state can be greatly reduced.

  According to the second invention, since the octane number of the fuel often changes abruptly due to refueling or the like, the estimation time setting means estimates the octane number based on the index only when the index suddenly changes. Thereby, for example, the timing for estimating the octane number can be limited to a time when the value is likely to change, and a high effect can be obtained by a minimum estimation process.

According to the third aspect of the invention, the octane number of the fuel often changes when the internal combustion engine is started by refueling or the like while the internal combustion engine is stopped. Therefore, the estimated time setting means is
The octane number is estimated based on the index when starting the internal combustion engine. As a result, the same effect as that of the second aspect of the invention can be obtained, and the octane number of the fuel can be quickly estimated immediately after starting, so that it is possible to quickly cope with the case where the octane number is abnormal.

  According to the fourth invention, the deposit amount in the cylinder tends to gradually increase as the combustion is repeated after the internal combustion engine is started. Therefore, the estimation time setting means can limit the timing for estimating the deposit adhesion amount to a time when the value is likely to change, and a high effect can be obtained by a minimum estimation process. In addition, two different parameters (octane number and deposit adhesion amount) can be estimated individually based on the same index without adding a sensor, etc. Can be used properly. Therefore, the occurrence factors of knock can be detected individually, and appropriate responses can be taken for each occurrence factor.

  According to the fifth aspect of the present invention, once the amount of fuel at the time of knock occurrence is calculated in a certain operating state, the knock limit combustion ratio in an arbitrary operating state can be accurately and easily calculated based on that value. Based on the knock limit crank angle corresponding to the knock limit combustion ratio and the predicted knock generation angle, it is possible to calculate the ignition advance allowance that allows the ignition timing to advance without generating knock. it can. That is, the ignition timing at which knocking actually occurs can be easily predicted without measuring and estimating the in-cylinder pressure (combustion pressure) at the ignition timing at which knocking occurs.

  As a result, the ignition timing advance amount can be maximized within a range where knock does not occur, or the ignition timing retard amount when the occurrence of knock is avoided can be minimized. Can be further improved. In addition, the ignition advance margin is calculated in any operation state using the fact that the remaining amount of fuel at the time of knock occurrence is a constant value regardless of the operation state. It is not necessary to set for each operation state by the formula. As a result, the amount of data required for control can be reduced, and the number of man-hours for adapting individual data to the operating state can be greatly reduced.

It is a whole block diagram for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a characteristic diagram which shows the relationship between the octane number of fuel, and parameter | index (DELTA) K. It is a characteristic diagram which shows the relationship between the quantity of the deposits which adhere | attached in the cylinder, and parameter | index (DELTA) K. It is explanatory drawing which illustrated the characteristic of the knock limit combustion ratio MFBmax and the fuel remaining amount Kr at the time of knock generation. In Embodiment 1 of this invention, it is a flowchart of the control performed by ECU. In Embodiment 2 of this invention, it is a flowchart of the control performed by ECU. In Embodiment 3 of this invention, it is explanatory drawing which shows the relationship between the integral value by Livengood-Wu integral type | formula, a knock limit combustion ratio MFBmax, and the ease of generation | occurrence | production of a knock. In Embodiment 3 of this invention, it is a flowchart of the control performed by ECU.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
The first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an overall configuration diagram for explaining a system configuration according to the first embodiment of the present invention. The system according to the present embodiment includes an engine 10 as a multi-cylinder internal combustion engine. In FIG. 1, only one cylinder of the engine 10 is illustrated. Further, the present invention is applied to an engine having an arbitrary number of cylinders including a single cylinder. As shown in FIG. 1, a combustion chamber 14 is defined in each cylinder of the engine 10 by a piston 12, and the piston 12 is connected to a crankshaft 16 of the engine.

  Further, the engine 10 includes an intake passage 18 that sucks intake air into the combustion chamber 14 (cylinder) of each cylinder, and an exhaust passage 20 that exhausts exhaust gas from each cylinder. The intake passage 18 is provided with an electronically controlled throttle valve 22 that adjusts the intake air amount based on the accelerator opening and the like. A catalyst 24 for purifying exhaust gas is provided in the exhaust passage 20. Each cylinder has a fuel injection valve 26 for injecting fuel into the intake port, an ignition plug 28 for igniting an air-fuel mixture in the cylinder, an intake valve 30 for opening and closing the intake port with respect to the cylinder, and an exhaust port. And an exhaust valve 32 that opens and closes the cylinder with respect to the inside of the cylinder.

  The system according to the present embodiment includes a sensor system including sensors 40 to 48 and an ECU (Electronic Control Unit) 50 that controls the operating state of the engine 10. First, the sensor system will be described. The crank angle sensor 40 outputs a signal synchronized with the rotation of the crankshaft 16, and the air flow sensor 42 detects the intake air amount. The in-cylinder pressure sensor 44 is a known sensor that outputs a signal corresponding to the in-cylinder pressure, and is provided for each cylinder. The intake air temperature sensor 46 detects the temperature of intake air, and the knock sensor 48 detects the occurrence of knock based on the vibration state of the engine. In addition, the sensor system includes various sensors necessary for engine control (a throttle sensor that detects the opening of the throttle valve 22, a water temperature sensor that detects the temperature of engine cooling water, and an air-fuel ratio that detects the exhaust air-fuel ratio. Sensor, etc.).

  ECU50 is comprised by the arithmetic processing apparatus provided with the memory circuit containing ROM, RAM, a non-volatile memory etc., for example. Each sensor of the sensor system is connected to the input side of the ECU 50, and various actuators including the throttle valve 22, the fuel injection valve 26, the spark plug 28, and the like are connected to the output side of the ECU 50. In addition, the ECU 50 has a function of storing various data that changes in accordance with the crank angle as time series data together with the crank angle. This time-series data includes the output value of each sensor and various indexes, parameters, etc. calculated based on the output value.

  Then, the ECU 50 controls the operating state by driving each actuator while detecting engine operation information by the sensor system. Specifically, the engine speed (engine speed) and the crank angle are detected based on the output of the crank angle sensor 40, and the intake air amount is calculated based on the output of the air flow sensor 42. Further, the engine load (load factor) is calculated based on the intake air amount, the engine speed, and the like. Then, the fuel injection timing and ignition timing are determined based on the crank angle, and when these timings arrive, the fuel injection valve 26 and the spark plug 28 are driven. Thereby, the air-fuel mixture is combusted in the cylinder, and the engine can be operated.

[Features of Embodiment 1]
The present embodiment is characterized in that the octane number of fuel and the deposit amount in the cylinder are estimated based on the amount of unburned fuel (K value) remaining in the cylinder during the combustion stroke and the occurrence of knocking. Yes. The specific processing will be described below.

(Acquisition of knock limit combustion ratio MFBmax)
First, in the first process, for example, while gradually igniting the ignition timing, the crank angle at which knock actually occurs is detected, and the combustion mass ratio MFB (Mass Fraction of Burned fuel) at this crank angle is knock limit combustion. Acquired as a ratio MFBmax. Here, the knock limit combustion ratio MFBmax is defined as the limit (upper limit) combustion mass ratio at which the amount of unburned fuel necessary for the occurrence of knock exists in the cylinder.

Since the amount of unburned fuel remaining in the cylinder decreases as the combustion mass ratio increases, in a state where the combustion mass ratio is higher than a certain upper limit value, there is no burning fuel and knocking does not occur. That is, the combustion mass ratio has an upper limit value at which knocking can occur, and this upper limit value corresponds to the knock limit combustion ratio MFBmax. Further, the combustion mass ratio MFB at an arbitrary crank angle θ during the combustion stroke is calculated by the following equation (1) based on the parameter PV ^κ (θ) correlated with the heat generation amount during the combustion stroke.

Here, PV ^κ (θ) is multiplied by the in-cylinder pressure P detected at the crank angle θ by the in-cylinder pressure sensor 44 and the value V ^κ obtained by raising the in-cylinder volume V at the crank angle θ by the specific heat ratio κ. Is. PV ^κ (θs) is a value of PV ^κ (θ) at a crank angle θs at which the combustion stroke is started (for example, BTDC 60 ° CA with reference to the explosion top dead center), and PV ^κ (θe) is The value of PV ^κ (θ) at the crank angle θe (for example, ATDC 60 ° CA) at which the combustion stroke ends. Accordingly, when knocking occurs by gradually advancing the ignition timing, the knock limit combustion ratio MFBmax can be obtained by performing the calculation of the above equation (1) with the crank angle at this time being θ. .

(Calculation of remaining fuel level Kr when knock occurs)
In the next process, the K value when knocking actually occurs in a state where the combustion mass ratio MFB coincides with the knock limit combustion ratio MFBmax is calculated as the fuel remaining amount Kr at the time of knock generation. That is, the fuel remaining amount Kr at the time of knock occurrence is defined as the amount of unburned fuel remaining in the cylinder when the knock limit combustion ratio MFBmax is obtained by the above processing. The fuel remaining amount Kr at the time of knock generation is calculated by the following equation (2) based on the supply amount Q of fuel supplied (intake or injection) into the cylinder during one cycle and the knock limit combustion ratio MFBmax. Is done.

Kr = Q × (1-MFBmax) (2)

(Calculation of index ΔK)
On the other hand, the ECU 50 stores in advance a reference remaining amount Kth that is a K value during normal combustion in which knock does not occur. The reference remaining amount Kth corresponds to the K value when knock does not occur when the combustion mass ratio MFB coincides with the knock limit combustion ratio MFBmax. For example, the reference remaining amount Kth depends on the ignition timing, crank angle, in-cylinder pressure, etc. during normal combustion. It is set as a data map that changes accordingly. Then, in the next process, as shown in the following equation (3), the reference remaining amount Kth is subtracted from the remaining fuel amount Kr at the time of knock occurrence, thereby calculating an index ΔK that is the difference between them.

ΔK = Kr−Kth (3)

(Estimation of octane number and deposit amount)
As shown in FIGS. 2 and 3, the index ΔK calculated in this way has a certain correlation with the octane number of the fuel and the deposit amount in the cylinder. Here, FIG. 2 is a characteristic diagram showing the relationship between the octane number of the fuel and the index ΔK, and FIG. 3 is a characteristic diagram showing the relationship between the amount of deposit deposited in the cylinder and the index ΔK. More specifically, the index ΔK has a characteristic that increases as the octane number of the fuel decreases, and also increases as the deposit amount in the cylinder increases. The characteristics shown in these figures are stored in advance in the ECU 50 as a data map or the like.

  Therefore, by using the above characteristics, it is possible to estimate the octane number of the fuel and the deposit amount in the cylinder based on the index ΔK, and to execute appropriate response control according to the estimation result. As a specific example, first, as shown in FIG. 2, when the index ΔK is larger than a predetermined octane number determination value, the octane number of the fuel is out of the allowable range (lower than the threshold value that is an abnormality determination line). ). In this case, knocking is more likely to occur than when the octane number is within the allowable range.For example, the octane number warning light is turned on to prompt the user to change the fuel used, or the engine output or ignition timing. The corresponding control is performed such as restricting the advance angle of the valve more than usual. The octane number determination value is set, for example, corresponding to the lower limit value of the allowable range of the octane number.

  On the other hand, as shown in FIG. 3, when the index ΔK is larger than a predetermined deposit determination value, it is determined that the deposit adhesion amount in the cylinder is out of the allowable range (more than the threshold that is the abnormality determination line). To do. In this case, abnormal combustion such as knocking or pre-ignition is likely to occur. For example, a warning light for deposit is turned on to encourage engine maintenance, or the output of the engine or the advance timing of the ignition timing is regulated. The corresponding control is performed. The deposit determination value corresponds to, for example, the lower limit value of the allowable range of deposit adhesion, and is set separately from the octane number determination value.

(Control of estimated time)
Moreover, it is preferable to perform the estimation process (determination process) of the above-mentioned octane number and deposit adhesion amount according to the time when each value is likely to change. Therefore, in the present embodiment, when the index ΔK changes suddenly, the fuel octane number is estimated based on the index ΔK, and when the index ΔK does not change suddenly, the deposit adhesion amount is estimated based on the index ΔK. It is said. As a specific example, first, the ECU 50 calculates a difference between the latest value of the index ΔK calculated for each calculation cycle and the previous value of the index ΔK calculated in the previous calculation cycle as the index change amount ΔKd. This index change amount ΔKd corresponds to the speed at which the index ΔK changes. When the index change amount ΔKd is larger than the predetermined sudden change determination value Z, it is determined that the index ΔK has suddenly changed. When the index change amount ΔKd is equal to or less than the sudden change determination value Z, the index ΔK changes suddenly. Judge that it is not. The sudden change determination value Z is appropriately set based on experiments or the like.

  Here, the octane number of the fuel may change abruptly due to refueling or the like, and the deposit amount in the cylinder tends to gradually increase with repeated combustion. Accordingly, when the index ΔK changes suddenly, it is determined that this change is caused by a change in the octane number due to refueling or the like, so the estimation (determination) of the octane number is executed based on the index ΔK. On the other hand, when the index ΔK does not change suddenly (changes relatively slowly), it is determined that this change is caused by an increase in the deposit adhesion amount, so the deposit adhesion amount is estimated based on the index ΔK. (judge.

  According to this configuration, for example, the timing for estimating the octane number and the deposit adhesion amount can be limited to a time when these parameters are likely to change, and a high effect can be obtained by a minimum estimation process. Further, even if no sensor other than the in-cylinder pressure sensor 44 is added, two different parameters can be individually estimated based on the same index ΔK, and both estimation processes are appropriately used by simple control. be able to. Therefore, the occurrence factors of knock can be detected individually, and appropriate responses can be taken for each occurrence factor.

Next, the effect of the estimation process based on the index ΔK will be described with reference to FIG. FIG. 4 is an explanatory diagram illustrating characteristics of the knock limit combustion ratio MFBmax and the fuel remaining amount Kr at the time of knock occurrence. In this figure, θ ₉₀ and θ ₉₀ represent crank angles when the combustion mass ratios are 90% and 92%, respectively. First, FIG. 4A will be described. This diagram shows an operating state in which the knock limit combustion ratio MFBmax = 90% when, for example, the load factor (charging efficiency) KL = 40%. In this operating state, when the load factor KL increases to 60%, as shown in FIG. 4B, the fuel injection amount increases, so even if the combustion mass ratio is higher than 90% Knocks can occur. In this case, the knock limit combustion ratio MFBmax is increased to 92%, for example, according to the load factor KL, as shown in FIG. 4 (c).

  Thus, knock limit combustion rate MFBmax (and the crank angle corresponding to the combustion rate) varies with load factor KL. Accordingly, when knock avoidance control or the estimation process is performed using these values as indices, a process for correcting the indices according to the load factor KL is required. Specifically, for example, a knock limit combustion ratio MFBmax is created as a different data map or function formula for each operating state, and an operation for adapting different data for each operating state is required. On the other hand, the amount of unburned fuel at the knock limit combustion ratio MFBmax, that is, the fuel remaining amount Kr at the time of knock generation, as shown in FIGS. 4 (a) and 4 (c), even if the load factor KL changes, The value is almost constant.

  Similarly, the index ΔK calculated from the fuel remaining amount Kr at the time of knock occurrence is a parameter that is not affected by the load factor KL. Therefore, according to the present embodiment, it is possible to accurately estimate the octane number of the fuel and the deposit amount in the cylinder based on the index ΔK that is not affected by the change in the load factor KL. Then, various types of response control can be accurately executed based on these estimation results, and the accuracy of knock avoidance control and the like can be improved. Further, since the index ΔK (the remaining fuel amount Kr at the time of knock occurrence) is not affected by the load factor KL, it is not necessary to set it for each operating state by a data map or a function expression. As a result, the amount of data required for control can be reduced, and the number of man-hours for adapting individual data to the operating state can be greatly reduced.

[Specific Processing for Realizing Embodiment 1]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 5 is a flowchart of the control executed by the ECU in the first embodiment of the present invention. The routine shown in this figure is repeatedly executed while the engine is operating. In the routine shown in FIG. 5, first, in step 100, the engine operating state (engine speed, load factor) is set (controlled) to a predetermined value suitable for estimation processing.

  Next, at step 102, the ignition timing is gradually advanced to knock intentionally, and the knock sensor 48 detects the knock occurrence. In step 104, the combustion ratio at the time when the knock is detected is acquired as a knock limit combustion ratio MFBmax. Further, in step 106, based on the fuel supply amount Q and the knock limit combustion ratio MFBmax in one cycle, the fuel remaining amount Kr at the time of knock generation is calculated by the above equation (2), and in step 108, the calculated knock generation is performed. The remaining fuel amount Kr is stored in the ECU 50.

  Next, at step 110, since knocking was generated at step 102, knock avoidance control is executed. As this knock avoidance control, known control including ignition timing retardation or the like may be used, or control described in a third embodiment described later may be used. Next, in step 112, the index ΔK is calculated by the above equation (3) based on the knocking fuel remaining amount Kr and the reference remaining amount Kth. In step 114, it is determined whether or not the index ΔK has changed suddenly by the method described above.

  Here, when the determination in step 114 is established, it is determined that the index ΔK has suddenly changed due to refueling or the like, and therefore, in step 116, the control state is set to the combustion abnormality determination mode. In step 118, a data map (FIG. 2) showing the relationship between the index ΔK and the octane number of the fuel is referred to. In step 120, whether or not the octane number is less than the threshold value, that is, the index ΔK is the octane number determination value. It is judged whether it is larger than. If this determination is established, an octane number warning lamp is turned on in step 122, and other response control is executed as necessary. If the determination in step 120 is not established, this routine is terminated as it is.

  On the other hand, if the determination in step 114 is not established, it is determined that the index ΔK has increased moderately due to an increase in the deposit amount in the cylinder. Therefore, in this case, in step 124, the control state is set to the deposit determination mode, and in step 126, a data map (FIG. 3) showing the relationship between the index ΔK and the deposit amount in the cylinder is referred to. In step 128, it is determined whether or not the deposit adhesion amount is larger than the threshold value, that is, whether or not the index ΔK is larger than the deposit determination value. If this determination is established, a deposit warning lamp is turned on in step 130, and other response control is executed as necessary. On the other hand, if the determination in step 128 is not established, this routine is terminated as it is.

  In the first embodiment, step 104 in FIG. 5 shows a specific example of the knock limit combustion ratio acquisition means in claim 1, and step 106 shows a specific example of the remaining fuel amount calculation means. Step 112 shows a specific example of the index calculation means, and step 120 shows a specific example of the octane number estimation means. Further, step 114 shows a specific example of the estimation time setting means in claims 1, 2 and 4, and step 128 shows a specific example of the deposit adhesion amount estimation means in claim 4. On the other hand, the ECU 50 shows a specific example of the reference remaining amount storage means in claim 1.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. The present embodiment is characterized in that, in the same configuration and control as in the first embodiment, the octane number of the fuel is estimated when the engine is started, and the deposit adhesion amount is estimated after the engine is started. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 2]
As described above, it is preferable to execute the estimation process (determination process) of the octane number and the deposit adhesion amount in accordance with the time when each value is likely to change. Considering this point from a point of view different from that of the first embodiment, the octane number of the fuel often changes when the engine is started by refueling or the like while the engine is stopped. Further, the deposit adhesion amount in the cylinder does not increase suddenly when the engine is started, but increases when a certain amount of time has elapsed after the start (for example, when warm-up has progressed to some extent).

  For this reason, in the present embodiment, the octane number of the fuel is estimated based on the index ΔK when the engine is started, and the deposit amount in the cylinder is estimated based on the index ΔK after the start. Here, “at the time of start” means, for example, a period during cranking of the engine and until a predetermined time elapses after the start of the engine independent operation. Further, “after starting” means after the predetermined time has elapsed. The predetermined time is set as a time necessary for estimating the octane number of the fuel based on the index ΔK, for example.

  In the present embodiment configured as described above, it is possible to obtain substantially the same operational effects as in the first embodiment. In particular, in the present embodiment, the octane number of the fuel can be quickly estimated immediately after the engine is started, so that it is possible to quickly cope with the case where the octane number is abnormal.

[Specific Processing for Realizing Embodiment 2]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 6 is a flowchart of control executed by the ECU in the second embodiment of the present invention. In the routine shown in this figure, processing similar to that in the first embodiment (FIG. 5) is executed except for step 214. In step 214, it is determined whether or not the engine is in a starting state by the above-described method. If this determination is true, the octane number estimation process is executed in steps 216 to 222. If the determination in step 214 is not true, the deposit adhesion amount estimation process is executed in steps 224 to 230. To do.

  In the second embodiment, step 214 in FIG. 6 shows a specific example of the estimated time setting means in claims 1, 3 and 4. Specific examples of other means are the same as those in the first embodiment.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIG. 7 and FIG. In the present embodiment, in addition to the same configuration and control as in the first or second embodiment, the knock occurrence timing is predicted based on the fuel remaining amount Kr at the time of knock occurrence, and the knock avoidance control is executed. It is a feature. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 3]
As described with reference to FIG. 4, the fuel remaining amount Kr at the time of knock occurrence does not vary depending on the load factor KL. For this reason, in the present embodiment, the ease of occurrence of knock at the current ignition timing and the amount by which the current ignition timing can be advanced without generating knock are determined as the fuel remaining amount Kr at the time of knock occurrence. The configuration is estimated based on the above. Hereinafter, this estimation process will be specifically described.

  First, FIG. 7 is an explanatory diagram showing the relationship between the integral value based on the Livengood-Wu integral equation, the knock limit combustion ratio MFBmax, and the ease of occurrence of knock in Embodiment 3 of the present invention. In this figure, the knock limit crank angle θmfbmax is a crank angle corresponding to the knock limit combustion ratio MFBmax, and is defined as a crank angle at which the combustion mass ratio becomes equal to the knock limit combustion ratio MFBmax.

  The Livengood-Wu integral equation is a known prediction model that predicts a crank angle at which knocking occurs by performing a predetermined integration process based on at least the in-cylinder pressure and the in-cylinder temperature. Since this prediction model is described in, for example, Japanese Patent Application Laid-Open No. 2004-332584, Japanese Patent Application Laid-Open No. 2008-95593, Japanese Patent Application Laid-Open No. 2010-84621, etc., detailed description thereof is omitted. At the crank angle at which the integral value of the Livengood-Wu integral formula is 1, the occurrence of knocking is predicted. In the following description, the crank angle at which the integral value is 1 is referred to as a knock occurrence prediction angle θknock.

  FIG. 7 illustrates three cycles A, B, and C having different ignition timings. The characteristic line of each cycle has a characteristic that the characteristic line rises more rapidly as the ignition timing is advanced, that is, the characteristic that the predicted knock occurrence angle θknock becomes smaller (advanced). For example, in cycles A and B, the predicted knock occurrence angle θknock at which the integral value is 1 is equal to or smaller than the knock limit crank angle θmfbmax. Therefore, in cycles A and B, the crank angle reaches the predicted knock angle θknock in the region of the combustion mass ratio where knocking can occur. This means that in cycles A and B, knocking may occur even at the current ignition timing, and there is no room for the crank angle until the knocking occurs (there is no room for advancement of the ignition timing). ing.

  On the other hand, in cycle C, for example, the predicted knock occurrence angle θknock is larger than the knock limit crank angle θmfbmax. That is, in the cycle C, the crank angle reaches the knock prediction angle θknock in the region of the combustion mass ratio where knock does not occur. In the cycle C, when the ignition timing is advanced, the larger the amount of advance, the closer the knock generation predicted angle θknock approaches the knock limit crank angle θmfbmax, and knocking occurs when both coincide. .

  This means that in cycle C, there is a crank angle margin (a margin for advancing the ignition timing) before knocking occurs. If this margin is defined as the ignition advance margin Δθ, as shown in FIG. 7, the ignition advance margin Δθ is based on the knock occurrence predicted angle θknock and the knock limit crank angle θmfbmax as shown in (4) below. Calculated by the formula. In the cycle in which the ignition advance margin Δθ is positive as in the cycle C, the ignition timing can be advanced by Δθ without causing knock.

Δθ = θknock−θmfbmax (4)

  In the above equation (4), the predicted knock occurrence angle θknock can be obtained as the crank angle at which the integral value of the Livengood-Wu integral equation is 1 as described above. The knock limit crank angle θmfbmax is obtained as a crank angle at which the combustion mass ratio matches the knock limit combustion ratio MFBmax based on a previously stored data map, function equation, etc., and this knock limit combustion ratio MFBmax is Based on the knock occurrence fuel remaining amount Kr and the in-cylinder fuel supply amount Q calculated in the first and second embodiments, the following equation (5) is used.

MFBmax = 1-Kr / Q (5)

  Here, the above equation (5) is a modification of the above equation (2). That is, the remaining fuel amount Kr at the time of knock generation is maintained at a constant value even if the operating state of the engine (engine speed or load factor) changes compared to the time point when the equation (2) is calculated. Therefore, in the present embodiment, when the knocking occurrence fuel remaining amount Kr is calculated by the equation (2), the value is stored. Even when the operating state changes, a new operating state is obtained by performing the calculation of the above equation (5) based on the fuel supply amount Q in the operating state and the stored value of the fuel remaining amount Kr at the time of knock occurrence. The knock limit combustion ratio MFBmax corresponding to is calculated (back calculation).

  As described above, according to the present embodiment, once the knocked fuel remaining amount Kr is calculated in a certain operating state, the knock limit combustion ratio MFBmax in an arbitrary operating state is accurately and easily calculated based on that value. can do. Based on the knock limit crank angle θmfbmax corresponding to the knock limit combustion ratio MFBmax and the predicted knock generation angle θknock, the maximum advance angle at which the current ignition timing can be advanced without generating a knock The ignition advance margin Δθ, which is a quantity, can be calculated. That is, in the present embodiment, for example, the ignition timing at which knocking actually occurs can be easily predicted without measuring and estimating the in-cylinder pressure (combustion pressure) at the ignition timing at which knocking occurs.

  As a result, the ignition timing advance amount can be maximized within the range where knock does not occur, or the ignition timing retard amount when avoiding knock can be minimized, and ignition is avoided while avoiding knock. The timing can be controlled appropriately. Therefore, in addition to the effects of the first and second embodiments, the accuracy of knock avoidance control and the like can be further improved. In addition, since the ignition advance margin Δθ is calculated in an arbitrary operating state by utilizing the fact that the remaining fuel amount Kr at the time of knock occurrence is a constant value regardless of the operating state, the ignition advance margin Δθ is data There is no need to set it for each operating state using a map or function expression. Thereby, the amount of data required for control can be reduced and control can be simplified. Further, the number of man-hours for adapting individual data to the operating state can be greatly reduced.

[Specific Processing for Realizing Embodiment 3]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 8 is a flowchart of control executed by the ECU in the third embodiment of the present invention. The routine shown in this figure is executed in step 110 or 210 of the routine described in the first and second embodiments (FIGS. 5 and 6). In the routine shown in FIG. 8, first, in step 300, the engine operating state is set to an arbitrary operating state (engine speed or load) that is different from the time when the knocked fuel remaining amount Kr is calculated in step 106 or 206. Rate).

  Next, in step 302, the calculation of the equation (5) is executed based on the knocking remaining fuel amount Kr stored in step 108 or 208, and the knock limit corresponding to the changed operating state is executed. A combustion ratio MFBmax is calculated. In step 304, a knock limit crank angle θmfbmax corresponding to the knock limit combustion ratio MFBmax is calculated. In step 306, a predicted knock occurrence angle θknock at which the integral value of the Livengood-Wu integral equation is 1 is calculated, and in step 308, the ignition advance margin Δθ is calculated by the equation (4).

  Next, in step 310, it is determined whether or not the ignition advance margin Δθ is greater than zero. If this determination is satisfied, in step 312, the current ignition timing can be advanced by Δθ. In step 314, the ignition timing is actually advanced. In step 316, it is determined whether it is time to end the control of the ignition timing. If this determination is satisfied, this routine is ended. If the control is not terminated, the process returns to step 302 and the processes of steps 302 to 318 are repeated.

  On the other hand, if the determination in step 310 is not established, in step 318, it is predicted that knocking will occur, and if necessary, countermeasure control including retarding of the ignition timing and the like is executed. Then, returning to step 300, the processing of steps 300 to 318 is repeated.

  In the third embodiment, steps 108 and 208 in FIG. 5 or FIG. 6 show a specific example of the remaining fuel amount storage means in claim 5, and step 302 in FIG. 8 is the knock limit combustion rate reverse calculation means. A specific example is shown. Step 306 shows a specific example of the knock generation angle prediction means, and step 308 shows a specific example of the ignition advance margin calculation means.

  Moreover, although each structure was demonstrated separately in the said Embodiment 1-3, this invention is not restricted to this, For example, any 2 or 3 structures in Embodiment 1-3 are combined. Also good. That is, by combining the first and second embodiments, the octane number of the fuel is estimated when the index ΔK changes suddenly and when the engine is started, and in other cases, the deposit amount in the cylinder may be estimated. . Moreover, it is good also as a structure which performs the control demonstrated in Embodiment 3 in the structure of any one of Embodiment 1, 2, or the combination of both.

  In the first and second embodiments, both the octane number and the deposit amount are estimated. However, the present invention is not limited to this. For example, only the octane number is estimated when the index ΔK changes suddenly or when the engine is started. The deposit adhesion amount estimation process may not be executed. Moreover, in the said Embodiment 1, 2, the estimation process of an octane number or deposit adhesion amount shall be performed by comparison with a determination value (threshold value). However, the present invention is not limited to this, and the octane number and the deposit adhesion amount may be estimated as values that continuously change by referring to the characteristic data shown in FIGS. 2 and 3 based on the index ΔK.

  In the above-described embodiment, the engine in which fuel is injected into the intake port by the fuel injection valve 26 has been described as an example. However, the present invention is not limited to this, and may be applied to an in-cylinder injection type engine in which fuel is directly injected into the cylinder.

10 Engine (Internal combustion engine)
12 Piston 14 Combustion chamber 16 Crankshaft 18 Intake passage 20 Exhaust passage 22 Throttle valve 24 Catalyst 26 Fuel injection valve 28 Spark plug 30 Intake valve 32 Exhaust valve 40 Crank angle sensor 42 Air flow sensor 44 In-cylinder pressure sensor 46 Intake temperature sensor 48 Knock sensor 50 ECU (reference remaining amount storage means, remaining fuel amount storage means)
MFBmax Knock limit combustion ratio Q Fuel supply amount in cylinder Kr Fuel remaining amount (K value) when knock occurs
Kth reference fuel level (K value)
ΔK index Z sudden change judgment value θknock knock occurrence prediction angle θmfbmax knock limit crank angle Δθ ignition advance margin

Claims (5)

It has the function of calculating the combustion mass ratio during the combustion stroke based on the crank angle and the in-cylinder pressure of the internal combustion engine, and determines the limit combustion mass ratio at which the amount of unburned fuel necessary to generate knock exists in the cylinder. A knock limit combustion rate acquisition means for acquiring as a knock limit combustion rate;
A means for calculating the amount of unburned fuel as a remaining fuel amount at the time of knocking when the knocking actually occurs in a state where the combustion mass ratio during the combustion stroke coincides with the knock limit combustion ratio, Fuel remaining amount calculating means for calculating the remaining amount of fuel at the time of knock occurrence based on the amount of fuel supplied into the engine and the knock limit combustion ratio;
A reference remaining amount storage means in which a reference remaining amount that is an amount of the unburned fuel when knock does not occur in a state where a combustion mass ratio in a combustion stroke matches the knock limit combustion ratio;
Index calculating means for calculating the difference between the two by subtracting the reference remaining amount from the remaining fuel amount at the time of knock occurrence;
Octane number estimation means for estimating the octane number of the fuel based on the index;
Estimated timing setting means for setting the timing for operating the octane number estimating means to estimate the octane number of the fuel based on the operating state of the internal combustion engine;
A control device for an internal combustion engine, comprising:   The control apparatus for an internal combustion engine according to claim 1, wherein the estimated time setting means is configured to operate the octane number estimating means when a speed at which the index changes is equal to or greater than a predetermined sudden change determination value.   The control apparatus for an internal combustion engine according to claim 1 or 2, wherein the estimation time setting means is configured to operate the octane number estimation means when the internal combustion engine is started. A deposit adhesion amount estimating means for estimating the adhesion amount of the deposit adhered in the cylinder based on the index;
The said estimation time setting means becomes a structure which operates the said deposit adhesion amount estimation means at the time when the said octane number estimation means is not operated, and becomes a structure which estimates the adhesion amount of deposit. Control device for internal combustion engine. Fuel remaining amount storage means for storing the amount of fuel remaining at the time of knock occurrence calculated by the fuel remaining amount calculating means;
The knock limit based on the amount of fuel supplied into the cylinder and the stored value of the fuel remaining amount at the time of knock generation in an arbitrary operation state including an operation state different from that at the time of calculation of the fuel remaining amount at the time of knock occurrence Knock limit combustion rate reverse calculation means for calculating the combustion rate,
Knock generation angle prediction means for calculating a crank angle at which knock occurs as a knock generation prediction angle by performing a predetermined integration process based on at least the in-cylinder pressure and the in-cylinder temperature;
By subtracting the crank angle corresponding to the knock limit combustion ratio from the predicted knock generation angle, the degree of crank angle that can advance the ignition timing without generating knock is defined as the ignition advance angle margin. Means for calculating the ignition advance angle margin to be calculated;
The control apparatus for an internal combustion engine according to any one of claims 1 to 4, further comprising:

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