JP2013060885A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine which accurately estimates the amount of deposit in a cylinder.SOLUTION: This control device includes a cylinder internal pressure sensor 28. a first combustion period change amount ΔT1 between a first reference combustion period T0(KL1) calculated under a first load condition (KL1) in shipping an internal combustion engine 10 and a first combustion period T (KL1) calculated during operation after a reference state under the first load condition (KL1), and a second combustion period change amount ΔT2 between a second reference combustion period T0(KL2) calculated under a second load condition (KL2) in shipping and a second combustion period T (KL2) calculated during operation after the reference state under the second load condition (KL2), are calculated to estimate the amount of deposit in the cylinder based on a combustion period change amount ΔT12 as a difference between the first combustion period change amount ΔT1 and the second combustion period change amount ΔT2.

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly, to a control device for an internal combustion engine suitable as a device for estimating a deposit amount in a cylinder.

  Conventionally, for example, Patent Document 1 discloses an engine deposit amount detection device for calculating a deposit accumulation amount in a cylinder. Specifically, this conventional apparatus calculates the deposit accumulation amount in the cylinder based on the heat generation rate, the knock generation timing, and the actual knock intensity.

Japanese Patent Laid-Open No. 2005-226482 JP 2009-002241 A Japanese Patent Laid-Open No. 11-022541 JP 2008-196387 A Japanese Patent Laid-Open No. 7-29736

  When the air-fuel ratio, EGR gas amount, and the like are different, the knock generation timing and the knock intensity change. Therefore, in the method described in Patent Document 1, complicated logic is required to accurately estimate the deposit amount in the cylinder.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine that can accurately estimate the deposit amount in the cylinder.

A first invention is a control device for an internal combustion engine,
Combustion state acquisition means for acquiring the fuel state of the internal combustion engine;
Engine load acquisition means for acquiring the load of the internal combustion engine;
Comparison between the combustion state acquired under a plurality of load conditions and the reference combustion state acquired under the plurality of load conditions when the internal combustion engine is in a reference state in which no deposit is attached to the cylinder or the deposit is less attached A deposit accumulation amount estimating means for estimating the deposit accumulation amount in the cylinder based on the result;
It is characterized by providing.

The second invention is the first invention, wherein
The combustion state acquisition means includes
An in-cylinder pressure sensor for detecting the in-cylinder pressure;
Combustion period calculation means for calculating a combustion period in the cylinder based on the cylinder pressure detected by the cylinder pressure sensor;
Including
The deposit accumulation amount estimating means is configured to perform a first reference combustion period calculated under a first load condition among the plurality of load conditions when the internal combustion engine is in the reference state and during operation after the reference state. A difference between the first combustion period and the first combustion period calculated under the first load condition, and a second calculated under the second load condition among the plurality of load conditions when the internal combustion engine is in the reference state. After calculating the second combustion period difference between the reference combustion period and the second combustion period calculated under the second load condition during operation after the reference state, the first combustion period difference and the first combustion period difference are calculated. The deposit accumulation amount in the cylinder is estimated based on the magnitude of the difference between the two combustion period differences.

The third invention is the first invention, wherein
In the internal combustion engine, optimal ignition timing control for controlling the ignition timing to the optimal ignition timing during operation is executed,
The combustion state acquisition means includes a knock sensor that detects knock,
The deposit accumulation amount estimating means includes a first reference ignition timing when a knock is detected in a first load condition among the plurality of load conditions when the internal combustion engine is in the reference state, and after the reference state. A first ignition timing difference from a first ignition timing when a knock is detected under the first load condition, and a knock at a second load condition among the plurality of load conditions when the internal combustion engine is in the reference state And calculating a second ignition timing difference between a second reference ignition timing at the time of detection of a knock and a second ignition timing at a time when a knock is detected under the second load condition after the reference state. The deposit accumulation amount in the cylinder is estimated based on the magnitude of the difference between the first ignition timing difference and the second ignition timing difference.

According to a fourth invention, in any one of the first to third inventions,
Knock determination means for determining that a knock has occurred when a predetermined knock determination index value reaches a predetermined knock determination reference value;
A knock determination reference value changing means for making the knock determination reference value different depending on an operating region of the internal combustion engine when the deposit accumulation amount estimated by the deposit accumulation amount estimation means is equal to or greater than a predetermined value;
Is further provided.

The fifth invention is the fourth invention, wherein
The knock determination reference value changing means reduces the knock determination reference value used for a predetermined low rotation high load region when the deposit accumulation amount estimated by the deposit accumulation amount estimating means is equal to or greater than a predetermined value. It is characterized by that.

The sixth invention is the fourth or fifth invention, wherein
When the deposit accumulation amount estimated by the deposit accumulation amount estimating unit is greater than or equal to a predetermined value, the knock determination reference value changing unit is configured to apply to at least a part of the operation region other than the predetermined low rotation high load region. The knock determination reference value to be used is increased.

Further, a seventh invention is any one of the fourth to sixth inventions,
When the deposit accumulation amount estimated by the deposit accumulation amount estimation means is equal to or greater than a predetermined value, a predetermined knock suppression that suppresses the occurrence of knock when the operating range of the internal combustion engine becomes a predetermined low rotation high load region. It further comprises knock suppression control execution means for executing control.

  When deposits accumulate on the inner wall surface of the cylinder, the combustion rate increases. Further, the effect of deposit accumulation on the combustion speed varies depending on the load of the internal combustion engine. According to the first invention, the combustion state acquired under a plurality of load conditions and the plurality of loads when the internal combustion engine is in a reference state (a state in which no deposit is attached to the cylinder or the deposit is less attached). Based on the comparison result with the reference combustion state acquired under conditions, the deposit amount in the cylinder is estimated. This makes it possible to accurately estimate the deposit amount in the cylinder by utilizing the above knowledge.

  According to the second aspect of the invention, the determination based on the relative comparison of the change in the combustion period under the two load conditions is performed while using the in-cylinder combustion period as an index indicating the combustion state. As a result, even if the combustion speed may change due to changes in the properties of the fuel used, it is possible to accurately estimate the deposit amount without requiring complicated logic.

  According to the third aspect of the invention, the determination based on the relative comparison of the changes in the ignition timing under the two load conditions is performed while using the ignition timing at the time of knock detection as an index indicating the combustion state. As a result, even if the combustion speed may change due to changes in the properties of the fuel used, it is possible to accurately estimate the deposit amount without requiring complicated logic.

  If knocking occurs while deposits are attached to the cylinder inner wall surface, a part of the deposited deposits may be peeled off from the cylinder inner wall surface. The peeled deposit floats in the cylinder while burning when combustion is performed in the cylinder. It has been found that if such deposits remain after the next cycle, they become the ignition source for pre-ignition. According to the fourth invention, when the deposit accumulation amount is equal to or greater than the predetermined value, the knock determination reference value is different depending on the operation region, so that the occurrence frequency of knock is changed depending on the operation region. The As a result, it becomes possible to make the suppression and promotion of the peeling of the deposited deposit due to the occurrence of knocking different depending on the operation region. For this reason, by using the present invention, it is possible to control the peeling of the deposited deposit due to the occurrence of knock so that the occurrence of pre-ignition can be suppressed.

  According to the fifth aspect of the present invention, knocking is suppressed by reducing the knock determination reference value in the low rotation and high load region. As a result, peeling of the deposited deposit due to the occurrence of knock is suppressed, so that the occurrence frequency of the pre-ignition due to the peeling of the deposited deposit can be reduced in the low rotation high load region where the occurrence of the pre-ignition is a concern. it can.

  According to the sixth aspect of the present invention, the knock determination reference value is increased in the operation region other than the low rotation and high load region, thereby using the operation region where the occurrence frequency of pre-ignition is low, and using the knock, the deposit deposit is reduced. Peeling can be promoted.

  According to the seventh invention, when the deposit accumulation amount is equal to or greater than the predetermined value, the predetermined knock suppression control is executed when the operating region of the internal combustion engine becomes the low rotation high load region. . Thereby, in the situation where it is determined that the amount of deposit accumulation is large, it is possible to suitably suppress the occurrence of knock that causes the peeling of the deposit.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a P-theta diagram showing change of an in-cylinder pressure waveform at the time of combustion according to the presence or absence of deposit accumulation in a cylinder. It is a figure showing the change of the waveform of the mass combustion ratio (MFB) according to the presence or absence of the deposit accumulation in a cylinder on the horizontal axis of a crank angle. It is a figure showing the change of the relationship between the combustion period T and an engine load (load factor KL) according to the presence or absence of deposit accumulation in a cylinder. It is a figure showing the relationship between fuel period variation | change_quantity (DELTA) T ((DELTA) T1, (DELTA) T2) and (DELTA) T12, and the deposit accumulation amount, respectively. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure showing the change of the relationship between knock time ignition timing SA and engine load (load factor KL) according to the presence or absence of deposit accumulation in a cylinder. It is a figure showing the relationship between ignition timing variation | change_quantity (DELTA) SA ((DELTA) SA1, (DELTA) SA2) and (DELTA) SA12, and the deposit accumulation amount, respectively. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a figure showing the operating area of an internal-combustion engine using net mean effective pressure (BMEP) and an engine speed as an index which shows engine load. It is an image figure showing generation | occurrence | production of the preignition which makes the deposit adhering to the cylinder inner wall surface an ignition source. It is a figure showing a mode that deposit deposited in a combustion chamber is exfoliated (exfoliation from the top face of a piston as an example). It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a figure showing the relationship between combustion period variation | change_quantity (DELTA) T12 and the deposit accumulation amount in a cylinder. It is a figure showing the relationship between the occurrence frequency of preignition and the deposit amount.

Embodiment 1 FIG.
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes an internal combustion engine 10. Here, the internal combustion engine 10 is assumed to be a spark ignition type internal combustion engine (a gasoline engine as an example) provided with a supercharger (a turbocharger as an example). A piston 12 is provided in each cylinder of the internal combustion engine 10. A combustion chamber 14 is formed on the top side of the piston 12 in each cylinder. An intake passage 16 and an exhaust passage 18 communicate with the combustion chamber 14.

  An air flow meter 20 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 16 is provided in the vicinity of the inlet of the intake passage 16. An electronically controlled throttle valve 22 is provided downstream of the air flow meter 20. Each intake port 16a of the intake passage 16 is provided with a fuel injection valve 24 for injecting fuel into each intake port 16a. Each cylinder is provided with a spark plug 26 for igniting the air-fuel mixture in the combustion chamber 14. Furthermore, an in-cylinder pressure sensor 28 for detecting the in-cylinder pressure is disposed in each cylinder.

  The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 30. The ECU 30 includes a CPU, a memory (ROM and RAM), an input / output circuit including an A / D converter, and the like. In addition to the air flow meter 20 and the in-cylinder pressure sensor 28 described above, an internal combustion engine such as a crank angle sensor 32 for detecting the engine speed and a water temperature sensor 34 for detecting the engine cooling water temperature are input to the ECU 30. Various sensors for detecting the operating state of the engine 10 are connected. Further, various actuators for controlling the operation of the internal combustion engine 10 such as the throttle valve 22, the fuel injection valve 24, and the spark plug 26 described above are connected to the output portion of the ECU 30. The ECU 30 controls the operating state of the internal combustion engine 10 by operating various actuators according to a predetermined program based on the outputs of the various sensors described above.

  FIG. 2 is a P-θ diagram showing changes in the in-cylinder pressure waveform during combustion in accordance with the presence or absence of deposits in the cylinder. More specifically, FIG. 2 (A) shows a plurality of in-cylinder pressures under operating conditions in which the engine speed, load factor KL, ignition timing SA, etc. are the same in a state where deposits are accumulated in the cylinder. FIG. 2B shows a waveform, and FIG. 2B shows a plurality of cylinders under the same operating conditions as those in FIG. 2A in a state where no deposit is accumulated in the cylinder (factory state). It shows the internal pressure waveform. FIG. 3 is a graph showing changes in the waveform of the mass combustion ratio (MFB) according to the presence or absence of deposit accumulation in the cylinder, with the crank angle as the horizontal axis. The mass combustion ratio is an index value representing the ratio of the mass of the combustion gas to the mass of the fuel supplied into the cylinder, and is 0% at the time of ignition, and reaches 100% by complete combustion.

  During operation of the internal combustion engine 10, unburned components of fuel, oil, and the like may accumulate as deposits in the cylinder (in the combustion chamber 14). When deposits accumulate in the cylinder, the combustion state changes. Specifically, the combustion rate increases as the deposit accumulates even under the same operating conditions. For this reason, as shown in FIG. 2, the change in the in-cylinder pressure (combustion pressure) after ignition becomes steeper when the deposit is accumulated than when the deposit is not accumulated. Also, as shown in FIG. 3, the mass combustion rate changes more rapidly when deposits are deposited than when deposits are not deposited.

FIG. 4 is a diagram showing a change in the relationship between the combustion period T and the engine load (load factor KL) according to the presence or absence of deposit accumulation in the cylinder.
For the reasons already described with reference to FIGS. 2 and 3, the combustion period T in the case of deposit accumulation (adhesion) is the combustion period T0 in the case of no deposit accumulation on the cylinder inner wall surface as shown in FIG. It is shorter than that. Further, it has been found that as the influence of deposit accumulation on the combustion rate, the lower the load factor KL, the higher the combustion rate. As a result, in the case of deposit accumulation, as shown in FIG. 4, the combustion period T becomes shorter as the load factor KL is lower, and the difference from the value when there is no deposit accumulation becomes larger.

  As described above, through the earnest research of the present inventors, when deposits are accumulated on the inner wall surface of the cylinder, the knowledge that the influence on the combustion speed varies depending on the value of the load factor KL, more specifically, In other words, it was found that the lower the load factor KL, the higher the combustion rate. The present embodiment is characterized by a method for estimating the deposit amount in the cylinder based on the above knowledge.

  In the deposit accumulation amount estimation method of the present embodiment, two operating conditions with different loads of KL1 and KL2 (> KL1) are set in advance in a reference state (that is, a state at the time of factory shipment) in which the internal combustion engine 10 is new. Thus, a reference combustion period T0 (T0 (KL1) and T0 (KL2)) serving as an estimation reference is calculated and stored in the memory of the ECU 30. In addition, during the operation of the internal combustion engine 10, the first combustion period T (T (KL1) and second combustion period T (KL2)) is calculated under the two operating conditions (KL1, KL2).

  A first combustion period variation ΔT1 that is a difference (T0 (KL1) −T (KL1)) between the first reference combustion period T0 (KL1) and the first combustion period T (KL1) calculated during operation is obtained. Similarly, the second combustion period which is the difference (T0 (KL2) −T (KL2)) between the second reference combustion period T0 (KL2) and the second combustion period T (KL2) calculated during operation. A change amount ΔT2 is calculated. Further, a combustion period variation ΔT12 that is a difference (ΔT1−ΔT2) between the first combustion period variation ΔT1 and the second combustion period variation ΔT2 is calculated.

FIG. 5 is a graph showing the relationship between the fuel period variation amounts ΔT (ΔT1, ΔT2) and ΔT12 and the deposit accumulation amount.
The combustion period variation ΔT (ΔT1, ΔT2) under each load condition (KL1, KL2) is due to the fact that the combustion period T is gradually shorter than that of a new product as deposits accumulate, as shown in FIG. In the tendency as shown in FIG. 2, it increases as the deposit amount increases. Further, as described above, when the deposit is deposited, the lower the load factor KL is, the shorter the combustion period becomes. Therefore, the first combustion period variation ΔT1 on the lower load side is the second combustion period variation ΔT2. Bigger than. Furthermore, the lower the load factor KL, the greater the difference in combustion speed with respect to the reference state value. For this reason, as shown in FIG. 5A, the first combustion period variation ΔT1 under the operating condition of the load factor KL1 on the low load side is the second combustion period under the operating condition of the load factor KL2 on the high load side. The rate of change with respect to an increase in the amount of deposited deposit is larger than the amount of change ΔT2.

  As a result, the combustion period variation ΔT12, which is the difference between the first combustion period variation ΔT1 and the second combustion period variation ΔT2, becomes a positive value as shown in FIG. 5B, and the deposit accumulation amount. As it increases, it grows. Therefore, the combustion calculated periodically during operation is obtained by acquiring the relationship between the fuel period change amount ΔT12 and the deposit accumulation amount as shown in FIG. Based on the period change amount ΔT12, it is possible to estimate the deposit accumulation amount.

FIG. 6 is a flowchart showing a routine that is executed in advance when the internal combustion engine 10 is shipped from the factory in order to acquire the reference combustion period T0.
In the routine shown in FIG. 6, first, a predetermined first measurement condition for measuring the combustion period T is set (step 100). Here, as an example, the first measurement condition is a condition in which the engine speed is 1200 rpm, the load factor as KL1 is 35%, and the water temperature is 80 °. The load factor KL can be calculated based on the intake air amount measured by the air flow meter 20.

  Next, the first reference combustion period T0 (KL1) is measured using the in-cylinder pressure sensor 28 and the crank angle sensor 32 in a state where the internal combustion engine 10 is controlled so that the first measurement condition is obtained. (Step 102). More specifically, based on the in-cylinder pressure during combustion detected by the in-cylinder pressure sensor 28, the mass combustion ratio (see FIG. 3) is calculated for each predetermined crank angle according to a known relational expression. The combustion period T (in this case, the reference combustion period T0) is a crank angle period from the start of combustion in the cylinder (that is, when the mass combustion ratio becomes 0%) to when the mass combustion ratio reaches a predetermined value. Calculated. Next, the calculated first reference combustion period T0 (KL1) is stored in the memory of the ECU 30 (step 104).

  Next, a predetermined second measurement condition for measuring the combustion period T is set (step 106). Here, the second measurement condition is an example of a condition in which the load factor KL is different from that of the first measurement condition and the other operation condition parameters are combined. As an example of the condition where the engine speed is 1200 rpm and the load factor is 80 as KL2. %, And the water temperature is 80 °.

  Next, the second reference combustion period T0 (KL2) is measured using the in-cylinder pressure sensor 28 and the crank angle sensor 32 in a state where the internal combustion engine 10 is controlled so that the second measurement condition is obtained. (Step 108). Next, the calculated second reference combustion period T0 (KL2) is stored in the memory of the ECU 30 (step 110).

FIG. 7 is a flowchart showing a routine executed by the ECU 30 in order to estimate the deposit amount in the cylinder during the operation of the internal combustion engine 10.
In the routine shown in FIG. 7, first, the current first combustion period T (KL1) and second combustion period T (KL2) under predetermined first measurement conditions (load factor KL1) and second measurement conditions (load factor KL2). ) Are measured (step 200).

  Next, the first and second reference combustion periods T0 (KL1) and T0 (KL2) stored in the ECU 30 and the latest first and second combustion periods T (KL1) and T measured in step 200 above. (KL2) is used to calculate the first combustion period change amount ΔT1 and the second combustion period change amount ΔT2 (step 202).

  Next, a combustion period change amount ΔT12 that is the difference between the first combustion period change amount ΔT1 and the second combustion period change amount ΔT2 calculated in step 202 is calculated, and then based on the combustion period change amount ΔT12. The current deposit accumulation amount is estimated (calculated) (step 204). In the ECU 30, as shown in FIG. 5B, information (for example, a map) in which the relationship between the combustion period variation ΔT12 and the deposit accumulation amount is determined in advance through experiments or the like is stored in the memory. In this step 204, the current deposit accumulation amount is estimated from the latest combustion period change amount ΔT12 using such information. Therefore, according to this step 204, it is estimated that the larger the combustion period change amount ΔT12, the larger the deposit accumulation amount. In addition, in the internal combustion engine 10, engine control (for example, control described in a third embodiment described later) corresponding to the estimated latest deposit accumulation amount is performed (step 206).

  According to the routine shown in FIG. 7 described above, the combustion periods T (KL1) and T (KL2) with respect to the reference combustion periods T0 (KL1) and T0 (KL2) under two operating conditions with different loads KL1 and KL2. The first and second combustion period variation amounts ΔT1 and ΔT2 that are the differences are calculated, and the deposit accumulation amount is estimated based on the combustion period variation amount ΔT12 that is the difference between the variation amounts ΔT1 and ΔT2. Unlike such an estimation method, the method based on the judgment based on the change amount ΔT of the combustion period T under one load condition accurately estimates the deposit amount when the combustion speed changes due to a factor other than the deposit. Can not be. On the other hand, according to the estimation method of the present embodiment, a determination is made based on a relative comparison of changes in the combustion period T under the two load conditions (KL1, KL2). For this reason, even if the combustion speed may change due to changes in the properties of the fuel used, it is possible to accurately estimate the deposit amount without requiring complicated logic.

In the first embodiment described above, the ECU 30 executes the processing of step 102, 108, or 200, so that the “combustion state acquisition means” in the first aspect of the invention is based on the amount of intake air. By calculating the rate KL, the “engine load acquisition means” in the first invention realizes the “deposit accumulation amount estimation means” in the first invention by executing the processing of the above steps 202 and 204, respectively. Has been.
In the first embodiment described above, the “combustion period calculation means” in the second aspect of the present invention is realized by the ECU 30 executing the processing of step 102, 108 or 200. Further, the load factor KL1 and the load factor KL2 are the “first load condition” and the “second load condition” in the second invention, and the combustion period variation ΔT1 and the combustion period variation ΔT2 are “ The combustion period variation ΔT12 corresponds to the “difference between the first combustion period difference and the second combustion period difference” in the second aspect of the invention, corresponding to the “first combustion period difference” and the “second combustion period difference”, respectively. doing.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS.
FIG. 8 is a diagram for explaining a system configuration according to the first embodiment of the present invention. In FIG. 8, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  The system shown in FIG. 8 includes an internal combustion engine 40. The internal combustion engine 40 is configured similarly to the internal combustion engine 10 of the first embodiment described above except that a knock sensor 42 is provided instead of the in-cylinder pressure sensor 28. Knock sensor 42 is connected to ECU 30 provided in internal combustion engine 40. The knock sensor 42 is a sensor for detecting or predicting the occurrence of knock based on the vibration accompanying the combustion of the internal combustion engine 40 transmitted to the cylinder block.

  The system of this embodiment replaces the acquisition of the combustion state (combustion period T) using the in-cylinder pressure sensor 28 in the first embodiment described above, and the ignition timing when the knock sensor 42 detects the knock (hereinafter, “ (Referred to as “knock timing fire timing”) as an index value indicating the combustion state, and the deposit accumulation amount in the cylinder is estimated using the change in the knock timing fire timing.

  As a premise, in the internal combustion engine 40, optimal ignition timing control for controlling the ignition timing to the optimal ignition timing MBT is performed during operation. More specifically, the memory of the ECU 30 stores a basic ignition timing map that determines the basic ignition timing according to the operating state of the internal combustion engine 40 (for example, specified by the load factor KL and the engine speed). . In addition, during operation, the ignition timing is advanced or retarded according to the presence or absence of the knock detected by the knock sensor 42, so that the ignition timing is not affected by individual differences or changes with time of the internal combustion engine. Is controlled so as to be the optimum ignition timing MBT (immediately before the occurrence of knocking). More specifically, the knock timing fire timing is an ignition timing when a knock is detected when the optimum ignition timing MBT is obtained and the ignition timing is advanced.

  FIG. 9 is a diagram showing a change in the relationship between knock point ignition timing SA and engine load (load factor KL) depending on whether deposits are accumulated in the cylinder. More specifically, the vertical axis in FIG. 9 represents the knock timing fire timing SA using the advance angle with respect to the compression top dead center.

  As already described in the first embodiment, the combustion progresses faster when deposits are deposited on the inner wall surface of the cylinder than when deposits are not deposited. For this reason, when deposits are accumulated, the optimal ignition timing MBT moves to the retard side as compared with the case where no deposits are deposited. As a result, as shown in FIG. 9, when the deposit is accumulated, the knock point ignition timing SA becomes a retarded value as compared with the case where no deposit is accumulated.

  Furthermore, if deposits are accumulated, the lower the load factor KL, the faster the combustion. For this reason, when deposits are accumulated on the inner wall surface of the cylinder, the optimal ignition timing MBT moves to the retard side as the load factor KL is lower. As a result, when deposit is accumulated, as shown in FIG. 9, the knock point ignition timing SA becomes a more retarded value as the load factor KL is lower, and the value when there is no deposit accumulated. The difference increases.

  In the present embodiment, the deposit accumulation amount in the cylinder is estimated using the change in the knock point ignition timing SA accompanying the deposit accumulation as described above. Specifically, in the deposit accumulation amount estimation method according to the present embodiment, in the state in which the internal combustion engine 10 is new (that is, the state at the time of factory shipment), the loads 2 with different loads KL1, KL2 (> KL1) are different. The reference knock point fire timing SA0 (SA0 (KL1) and SA0 (KL2)), which serves as a reference for estimation under the two operating conditions, is calculated and stored in the memory of the ECU 30. In addition, during the operation of the internal combustion engine 10, the first knock point ignition timing SA (SA (KL1) and the first knock point ignition timing SA (KL2)) is calculated under the two operating conditions (KL1, KL2). Is done.

  Then, the first ignition timing that is the difference (SA0 (KL1) −SA (KL1)) between the first reference knock timing fire timing SA0 (KL1) and the first knock timing fire timing SA (KL1) calculated during operation. Similarly, the amount of change ΔSA1 is calculated. Similarly, the difference between the second reference knock timing fire timing SA0 (KL2) and the second knock timing fire timing SA (KL2) calculated during operation (SA0 (KL2) −SA (KL2)). )), The second ignition timing change amount ΔSA2 is calculated. Further, an ignition timing change amount ΔSA12 that is a difference (ΔSA1−ΔSA2) between the first ignition timing change amount ΔSA1 and the second ignition timing change amount ΔSA2 is calculated.

FIG. 10 is a graph showing the relationship between the ignition timing change amounts ΔSA (ΔSA1, ΔSA2) and ΔSA12 and the deposit accumulation amount.
As described above, the knock point ignition timing SA becomes a retarded value due to the fact that the combustion gradually becomes faster than the new article as the deposit accumulates. For this reason, the ignition timing change amount ΔSA (ΔSA1, ΔSA2) under each load condition (KL1, KL2) has a tendency as shown in FIG. 10A, and increases as the deposit accumulation amount increases. Further, as described above, when deposit is deposited, the lower the load factor KL is, the faster the combustion is, and thus the first ignition timing change amount ΔSA1 on the lower load side is more than the second ignition timing change amount ΔSA2. Also grows. Furthermore, the lower the load factor KL, the greater the difference in combustion speed with respect to the reference state value. For this reason, as shown in FIG. 10A, the first ignition timing change amount ΔSA1 under the operating condition of the load factor KL1 on the low load side is the second ignition timing under the operating condition of the load factor KL2 on the high load side. The rate of change with respect to an increase in the deposited amount is greater than the change amount ΔSA2.

  As a result, the ignition timing change amount ΔSA12 which is the difference between the first ignition timing change amount ΔSA1 and the second ignition timing change amount ΔSA2 is a positive value as shown in FIG. As it increases, it grows. Therefore, the ignition 30 periodically calculated during operation is obtained by acquiring the relationship between the ignition timing change amount ΔSA12 and the deposit accumulation amount as shown in FIG. It is possible to estimate the deposit accumulation amount based on the time variation ΔSA12.

  FIG. 11 is a flowchart showing a routine that is executed in advance at the time of factory shipment of the internal combustion engine 40 in order to acquire the reference knock point fire timing SA0. In FIG. 11, the same steps as those shown in FIG. 6 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 11, the first reference is made using the knock sensor 42 and the crank angle sensor 32 in a state where the internal combustion engine 10 is controlled so that the first measurement condition set in step 100 is obtained. Knock time fire timing SA0 (KL1) is measured (step 300). More specifically, the first reference knock point ignition timing SA0 (KL1), which is the ignition timing when a knock is detected when the ignition timing is gradually advanced under the first measurement condition, is acquired. Next, the measured first reference knock point ignition timing SA0 (KL1) is stored in the memory of the ECU 30 (step 302).

  Next, in a state where the internal combustion engine 40 is controlled so that the second measurement condition is obtained in the step 106, the same processing as in the step 300 is performed, whereby the second reference knock point ignition timing SA0 (KL2). Is measured (step 304). Next, the measured second reference knock point ignition timing SA0 (KL2) is stored in the memory of the ECU 30 (step 306).

FIG. 12 is a flowchart showing a routine executed by the ECU 30 in order to estimate the deposit amount in the cylinder during the operation of the internal combustion engine 40.
In the routine shown in FIG. 12, first, the current first knock time ignition timing SA (KL1) and the second knock time ignition under the predetermined first measurement condition (load factor KL1) and second measurement condition (load factor KL2). Time SA (KL2) is measured (step 400).

  Next, the first and second reference knock timing fire timings SA0 (KL1) and SA0 (KL2) stored in the ECU 30 and the latest first and second knock timing fire timings SA ( The first ignition timing change amount ΔSA1 and the second ignition timing change amount ΔSA2 are calculated using KL1) and SA (KL2) (step 402).

  Next, an ignition timing change amount ΔSA12 that is the difference between the first ignition timing change amount ΔSA1 and the second ignition timing change amount ΔSA2 calculated in step 402 is calculated, and then based on the ignition timing change amount ΔSA12. The current deposit accumulation amount is estimated (calculated) (step 404). As shown in FIG. 10B, the ECU 30 stores information (for example, a map) in which the relationship between the ignition timing change amount ΔSA12 and the deposit accumulation amount is determined in advance through experiments or the like. In step 404, the current deposit accumulation amount is estimated from the latest ignition timing change amount ΔSA12 using such information. Therefore, according to this step 204, it is estimated that the larger the combustion period change amount ΔT12, the larger the deposit accumulation amount. Therefore, according to this step 404, it is estimated that the larger the ignition timing change amount ΔSA12, the larger the deposit accumulation amount. In addition, in the internal combustion engine 40, engine control (for example, control described in a third embodiment described later) according to the estimated latest deposit accumulation amount is performed (step 406).

  According to the routine shown in FIG. 11 described above, the knock point ignition timing SA (KL1), SA with respect to the reference knock timing ignition timing SA0 (KL1), SA0 (KL2) under two operating conditions with different loads KL1, KL2. After the first and second ignition timing change amounts ΔSA1 and ΔSA2 that are the difference of (KL2) are calculated, the deposit accumulation amount is calculated based on the ignition timing change amount ΔSA12 that is the difference between the change amounts ΔSA1 and ΔSA2. Presumed. According to such an estimation method, a determination is made based on a relative comparison of changes in the knock point ignition timing SA under the two load conditions (KL1, KL2). For this reason, unlike the case where the determination based on the change amount ΔSA of the knock point ignition timing SA under one load condition is made as described in the first embodiment, the combustion is performed by changing the properties of the fuel used. Even if the speed changes, it is possible to accurately estimate the deposit amount without requiring complicated logic.

In the second embodiment described above, the ECU 30 executes the processing of step 300, 304, or 400, so that the “combustion state acquisition means” in the first aspect of the invention is based on the intake air amount and the like. By calculating the ratio KL, the “engine load acquisition means” in the first invention realizes the “deposit accumulation amount estimation means” in the first invention by executing the processing of steps 402 and 404, respectively. Has been.
Further, in the second embodiment described above, the “combustion period calculation means” in the second aspect of the present invention is realized by the ECU 30 executing the processing of step 102, 108 or 200. Further, the load factor KL1 and the load factor KL2 are the “first load condition” and the “second load condition” in the third invention, and the ignition timing change amount ΔSA1 and the ignition timing change amount ΔSA2 are “ The ignition timing change amount ΔSA12 corresponds to the “first ignition timing difference” and the “second ignition timing difference”, respectively, and “the difference between the first ignition timing difference and the second ignition timing difference” in the third aspect of the invention. doing.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIGS.
The system according to the present embodiment uses the hardware configuration shown in FIG. 1, and the internal combustion engine 10 according to the deposit accumulation amount sequentially estimated during operation by the estimation method according to the first embodiment described above. The control method is changed. Hereinafter, as an example, the contents used on the premise of the description of the first embodiment will be described. However, instead of this, the description in the second embodiment in which the deposit accumulation amount is estimated using the knock ignition timing SA using the hardware configuration shown in FIG. 8 may be used as a premise.

  FIG. 13 is a diagram showing the operating range of the internal combustion engine 10 using the net average effective pressure (BMEP) and the engine speed as indices indicating the engine load. FIG. 14 is an image diagram showing the occurrence of pre-ignition with the deposit attached to the inner wall surface of the cylinder as an ignition source.

  A region A on the low-rotation and high-load side as shown by hatching in FIG. 13 is a region where a phenomenon in which the air-fuel mixture self-ignites (pre-ignition) can occur before ignition by the spark plug 26 is performed. . As one of the causes of such pre-ignition, as shown in FIG. 14, it has been found that the deposit in the combustion chamber 14 may be an ignition source. More specifically, the deposit attached to the inner wall surface of the cylinder due to the occurrence of knock may be peeled off. Then, if the peeled deposit floats in the cylinder while burning and remains until after the next cycle, the deposit remaining in the cylinder becomes an ignition source, which is one of the causes of pre-ignition. It was.

  Therefore, in the present embodiment, when the deposit amount in the cylinder estimated by the method described in the first embodiment is a predetermined value or more, the following three engine controls (knock control methods) are changed. I did it. Note that these three engine controls are not limited to those executed at the same time as described below, and any one of them may be executed alone or in combination with any two. Good.

  Specifically, in the present embodiment, when the deposit amount in the cylinder is equal to or greater than a predetermined value, a knock determination level for determining whether or not knock has been detected in the region A on the low rotation high load side. Was lowered. FIG. 15 is a diagram illustrating a state in which the deposit accumulated in the combustion chamber 14 is peeled (for example, peeling from the top surface of the piston 12). When knocking occurs, as shown in FIG. 15, peeling of the deposited deposit, which causes pre-ignition, is promoted. Therefore, in the region A, by reducing the knock determination level, predetermined knock suppression control such as ignition timing retardation and fuel increase is performed even if a weak knock occurs.

  Further, in the present embodiment, when the deposit amount in the cylinder is equal to or greater than a predetermined value, the predetermined knock suppression control such as ignition timing retardation and fuel increase is performed when the region A is used. I tried to do it.

  Furthermore, in this embodiment, when the deposit accumulation amount in the cylinder is equal to or greater than a predetermined value, the knock determination level in the region B (see FIG. 13) other than the region A is increased. In the area B outside the area A, the possibility of occurrence of pre-ignition is reduced. Therefore, in the present embodiment, when such a region B is used, the knock determination level is increased to make it difficult to execute the predetermined knock suppression control, thereby increasing the frequency of occurrence of knock. Thereby, peeling of the deposit accumulated on the cylinder inner wall surface is promoted. Note that the occurrence frequency of knocking may be increased in a part of the region B shown in FIG. It is desirable that such control is performed in a high rotation range where the knocking noise is as small as possible. Further, in FIG. 13, the region B is illustrated as a partial region that covers a low engine load range and a wide engine speed range other than the region A, but the region B may be the entire region other than the region A. .

  FIG. 16 is a flowchart showing a control routine executed by the ECU 30 when the deposit amount is not less than a predetermined value in the third embodiment of the present invention. The process of this routine corresponds to the process of step 206 in the routine shown in FIG.

  In the routine shown in FIG. 16, first, the latest estimated value of the deposit amount calculated by the processing of the routine shown in FIG. 7 is acquired (step 500). Next, it is determined whether or not the acquired deposit accumulation amount is a predetermined value or more (step 502). As a result, when it is determined that the deposit accumulation amount is less than the predetermined value, the knock control method is not changed (step 504).

  On the other hand, when it is determined in step 502 that the deposit accumulation amount is equal to or greater than the predetermined value, a process for lowering the knock determination level in the region A is executed (step 506). The level of knock generated in the cylinder is, for example, the magnitude of vibration accompanying combustion detected using a knock sensor (not shown) provided in the internal combustion engine 10 (a sensor similar to the knock sensor 42 shown in FIG. 8). Can be grasped based on. By reducing the knock determination level by the processing of step 506, knock is detected even when weaker vibration is detected during combustion.

  Next, when the region A is used, the engine control is changed so that the predetermined knock suppression control such as the retard of the ignition timing and the fuel increase amount is performed (step 508). Next, processing for increasing the knock determination level in the region B is executed (step 510).

  Next, it is determined whether or not the reduction amount of the deposit accumulation amount during a predetermined period has become a predetermined value or less (step 512). As described above, by increasing the knock determination level in the region B, it is possible to increase the frequency of occurrence of knocking and promote the peeling of the deposited deposit. According to the determination in step 512, it is determined whether or not the deposit accumulation amount obtained after a predetermined period has changed due to the execution of the control for prompting the peeling of the deposit.

  As a result, when the determination at step 512 is not established, that is, while the effective reduction of the deposit accumulation amount is recognized by the execution of the control for promoting the peeling of the deposit, the determination at step 502 is established. As a condition, the execution of the knock control method in steps 506 to 510 is continued. On the other hand, if the determination in step 512 is satisfied, that is, if it can be determined that the deposit accumulation amount has not changed due to the execution of the above-described control that promotes deposit peeling, the knock control method is restored (during normal operation). A process of returning to control is executed (step 514).

  According to the routine shown in FIG. 16 described above, a weak knock occurs in a situation where it is determined that the deposit accumulation amount is large by lowering the knock determination level in the region A on the low rotation high load side. Even so, predetermined knock suppression control such as retarding the ignition timing and increasing the fuel amount is performed. As a result, it is possible to suppress the peeling of the deposited deposit that causes the occurrence of pre-ignition due to the occurrence of knocking, and the frequency of occurrence of pre-ignition can be reduced.

  Further, according to the above routine, when the deposit amount in the cylinder is equal to or greater than the predetermined value, when the region A is used, the ignition timing retardation, the fuel increase amount, etc. The predetermined knock suppression control is performed. Thereby, in the situation where it is determined that the amount of deposit accumulation is large, it is possible to suitably suppress the occurrence of knock that causes the peeling of the deposit.

  Further, according to the routine, by increasing the knock determination level in the region B other than the region A, the peeling of the deposited deposit is promoted using the knock using the operation region where the occurrence frequency of the pre-ignition is low. be able to.

FIG. 17 is a diagram showing the relationship between the combustion period variation ΔT12 and the deposit amount in the cylinder. FIG. 18 is a diagram showing the relationship between the occurrence frequency of pre-ignition and the deposit accumulation amount.
When the deposit accumulation amount is reduced by performing the above-described control that promotes the peeling of the deposit, the combustion speed is delayed so as to approach the value of the state without deposit accumulation. Therefore, as shown in FIG. For example, it moves from the X point toward the Y point. Then, as shown in FIG. 18, when the deposit amount that becomes the ignition source of the pre-ignition decreases, the occurrence frequency of the pre-ignition decreases (decreases). Also, as shown in FIG. 18, the occurrence frequency of pre-ignition is greater when deposits are deposited than when standard knock control (general knock suppression control in which the processes of steps 506 and 508 are not performed) is performed. When knock control (knock control when the processes of steps 506 and 508 are performed on the region A when the deposit accumulation amount is equal to or greater than the predetermined value) is performed, the occurrence of knocking is suppressed. Therefore, the deposition deposit is prevented from peeling off, so that it becomes low.

In the third embodiment described above, the knock determination level corresponds to the “knock determination reference value” in the fourth aspect of the present invention. Further, when the ECU 30 uses the output of the knock sensor 42 to determine whether knock has occurred or not, the “knock determination means” according to the fourth aspect of the present invention determines that the determination in step 502 is true. By executing the processing of 510, the “knock determination reference value changing means” in the fourth invention is realized.
Further, in the third embodiment described above, the “knock suppression control executing means” in the seventh aspect of the present invention is realized by executing the processing of step 508 when the ECU 30 makes the determination of step 502. Yes.

  Incidentally, in the first and second embodiments described above, the deposit amount in the cylinder is obtained by using the combustion state (combustion period T or knock point ignition timing SA) acquired under two different load conditions (KL1, KL2). I try to estimate. However, the present invention is not limited to this, and the number of load conditions for acquiring the combustion state may be three or more.

  In the first and second embodiments described above, the factory shipment time is used in order to acquire the reference combustion state (reference combustion period T0 or reference knock time fire timing S0). However, the reference combustion state acquired in the present invention is not necessarily limited at the time of factory shipment. That is, in the present invention, the reference state of the internal combustion engine when acquiring the reference combustion state is not limited to a state in which no deposit is attached in the cylinder (for example, at the time of factory shipment), but a state in which the deposit is less attached. (For example, a state immediately after cleaning the inside of the internal combustion engine and removing deposits in the cylinder after using the internal combustion engine for a certain period of time).

DESCRIPTION OF SYMBOLS 10, 40 Internal combustion engine 12 Piston 14 Combustion chamber 16 Intake passage 16a Intake port 18 Exhaust passage 20 Air flow meter 22 Throttle valve 24 Fuel injection valve 26 Spark plug 28 In-cylinder pressure sensor 30 ECU (Electronic Control Unit)
32 Crank angle sensor 34 Water temperature sensor 42 Knock sensor

Claims (7)

Combustion state acquisition means for acquiring the fuel state of the internal combustion engine;
Engine load acquisition means for acquiring the load of the internal combustion engine;
Comparison between the combustion state acquired under a plurality of load conditions and the reference combustion state acquired under the plurality of load conditions when the internal combustion engine is in a reference state in which no deposit is attached to the cylinder or the deposit is less attached A deposit accumulation amount estimating means for estimating the deposit accumulation amount in the cylinder based on the result;
A control device for an internal combustion engine, comprising: The combustion state acquisition means includes
An in-cylinder pressure sensor for detecting the in-cylinder pressure;
Combustion period calculation means for calculating a combustion period in the cylinder based on the cylinder pressure detected by the cylinder pressure sensor;
Including
The deposit accumulation amount estimating means is configured to perform a first reference combustion period calculated under a first load condition among the plurality of load conditions when the internal combustion engine is in the reference state and during operation after the reference state. A difference between the first combustion period and the first combustion period calculated under the first load condition, and a second calculated under the second load condition among the plurality of load conditions when the internal combustion engine is in the reference state. After calculating the second combustion period difference between the reference combustion period and the second combustion period calculated under the second load condition during operation after the reference state, the first combustion period difference and the first combustion period difference are calculated. 2. The control device for an internal combustion engine according to claim 1, wherein the deposit accumulation amount in the cylinder is estimated based on a difference between the two combustion period differences. In the internal combustion engine, optimal ignition timing control for controlling the ignition timing to the optimal ignition timing during operation is executed,
The combustion state acquisition means includes a knock sensor that detects knock,
The deposit accumulation amount estimating means includes a first reference ignition timing when a knock is detected in a first load condition of the plurality of load conditions when the internal combustion engine is in the reference state, and a time after the reference state. A first ignition timing difference from a first ignition timing when a knock is detected under the first load condition during operation of the engine, and a second of the plurality of load conditions when the internal combustion engine is in the reference state Second ignition timing difference between the second reference ignition timing when the knock is detected under the load condition and the second ignition timing when the knock is detected under the second load condition during operation after the reference state The internal combustion engine according to claim 1, wherein the deposit accumulation amount in the cylinder is estimated based on a difference between the first ignition timing difference and the second ignition timing difference. Control device. Knock determination means for determining that a knock has occurred when a predetermined knock determination index value reaches a predetermined knock determination reference value;
A knock determination reference value changing means for making the knock determination reference value different depending on an operating region of the internal combustion engine when the deposit accumulation amount estimated by the deposit accumulation amount estimation means is equal to or greater than a predetermined value;
The control device for an internal combustion engine according to any one of claims 1 to 3, further comprising:   The knock determination reference value changing means reduces the knock determination reference value used for a predetermined low rotation high load region when the deposit accumulation amount estimated by the deposit accumulation amount estimating means is equal to or greater than a predetermined value. The control apparatus for an internal combustion engine according to claim 4.   When the deposit accumulation amount estimated by the deposit accumulation amount estimating unit is greater than or equal to a predetermined value, the knock determination reference value changing unit is configured to apply to at least a part of the operation region other than the predetermined low rotation high load region. 6. The control apparatus for an internal combustion engine according to claim 4 or 5, wherein the knock determination reference value used in the step is increased.   When the deposit accumulation amount estimated by the deposit accumulation amount estimation means is equal to or greater than a predetermined value, a predetermined knock suppression that suppresses the occurrence of knock when the operating range of the internal combustion engine becomes a predetermined low rotation high load region. The control apparatus for an internal combustion engine according to any one of claims 4 to 6, further comprising knock suppression control execution means for executing control.

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