JP4867648B2 - Ignition control system for internal combustion engine - Google Patents

Description

  The present invention relates to a technique for controlling ignition of a spark ignition type internal combustion engine.

Conventionally, in a spark ignition type internal combustion engine, the ignition timing is advanced before MBT (Minimum spark advance for Best Torque), thereby promoting the temperature rise of the cooling water and thereby improving the warming-up property of the internal combustion engine. A technique is known (see, for example, Patent Document 1).
JP 2000-240547 A JP 2002-195141 A

  By the way, when the ignition timing is advanced ahead of MBT (hereinafter referred to as “over-advanced angle”), the combustion energy generated in the cylinder before compression top dead center (hereinafter referred to as “combustion energy before TDC”). Increase). The pre-TDC combustion energy is energy that resists the operation of the piston (operation from the bottom dead center toward the top dead center). For this reason, if the inertial energy of the internal combustion engine at the excessive advance angle is relatively small, the combustion energy overcomes the inertial energy of the internal combustion engine, and the piston moves backward from the top dead center side to the bottom dead center side (that is, the internal combustion engine is There is a possibility of reverse rotation).

  The present invention has been made in view of the above-described circumstances, and an object thereof is to prevent reverse rotation of an internal combustion engine in an ignition control system for a spark ignition internal combustion engine whose ignition timing can be advanced from MBT. is there.

  In order to solve the above-described problems, the present invention provides an ignition control system for an internal combustion engine capable of advancing the ignition timing ahead of MBT, on the condition that the inertial energy of the internal combustion engine is greater than a predetermined value. Allowed over-advanced angle.

  Specifically, an ignition control system for an internal combustion engine according to the present invention includes an over-advance angle means for advancing the ignition timing of a spark ignition type internal combustion engine before MBT, and an arithmetic means for calculating inertia energy of the internal combustion engine. And control means for permitting the advance of the ignition timing by the over-advance angle means on condition that the inertial energy calculated by the calculation means is larger than a predetermined value.

  According to such a configuration, when the inertial energy of the internal combustion engine is equal to or less than a predetermined value, the excessive advance angle of the ignition timing is prohibited. For this reason, the combustion energy before TDC does not become excessive when the inertial energy of the internal combustion engine is small. As a result, the reverse rotation of the internal combustion engine due to the excessive advance angle of the ignition timing can be avoided.

  In addition, when the internal combustion engine is operated, friction acts on the movable part of the internal combustion engine. For this reason, it is essential that the inertial energy of the internal combustion engine is larger than the friction as a condition for the internal combustion engine to rotate forward. Furthermore, in order for the internal combustion engine to rotate forward when the ignition timing is over-advanced, the inertial energy of the internal combustion engine needs to exceed the pre-TDC combustion energy in addition to the above-described friction. Therefore, it is preferable that the predetermined value is larger than the friction.

However, since the magnitude of the friction changes according to the temperature of the internal combustion engine and the temperature of the lubricating oil (in other words, the viscosity), the predetermined value is also changed according to the temperature of the internal combustion engine and the temperature of the lubricating oil. It is preferable. Since the temperature of the internal combustion engine and the temperature of the lubricating oil correlate with the temperature of the cooling water, the magnitude of the predetermined value may be changed according to the temperature of the cooling water.

  In the ignition control system for an internal combustion engine according to the present invention, when the over-advance angle of the ignition timing is performed by the over-advance angle unit, the control unit includes the inertia energy calculated by the calculation unit and the predetermined energy as the pre-TDC combustion energy. The advance amount of the ignition timing by the over-advance means may be determined so as to be less than or equal to the difference.

  This is because if the sum of the pre-TDC combustion energy and the friction is greater than the inertial energy of the internal combustion engine, the internal combustion engine is likely to reversely rotate.

  Further, in the ignition control system for an internal combustion engine according to the present invention, the control means, when the inertial energy calculated by the calculation means exceeds the target inertial energy, the inertial energy and the target inertial energy by the pre-TDC combustion energy. The advance amount of the ignition timing by the excessive advance means may be determined so that the difference is canceled out.

  When the actual inertial energy of the internal combustion engine exceeds the target inertial energy, the engine speed exceeds the target speed and excessively rises. On the other hand, when the inertia energy that exceeds the target inertia energy is offset by the combustion energy before TDC, an excessive increase in the engine speed is prevented.

  According to the present invention, reverse rotation of an internal combustion engine is prevented in an ignition control system for a spark ignition internal combustion engine that can advance the ignition timing ahead of MBT.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an ignition control system for an internal combustion engine according to the present invention.

  An internal combustion engine 1 shown in FIG. 1 is a four-stroke cycle spark ignition type internal combustion engine (gasoline engine) having a plurality of cylinders 2. The cylinder 2 of the internal combustion engine 1 is connected to the intake passage 30 through the intake port 3 and is connected to the exhaust passage 40 through the exhaust port 4.

  The intake port 3 is provided with a fuel injection valve 5 that injects fuel into the cylinder 2. The intake passage 30 is provided with a throttle valve 6 that controls the amount of air flowing through the intake passage 30. An intake pressure sensor 7 that measures the pressure (intake pressure) in the intake passage 30 is provided in the intake passage 30 downstream of the throttle valve 6. An air flow meter 8 that measures the amount of air flowing through the intake passage 30 is provided in the intake passage 30 upstream of the throttle valve 6.

  On the other hand, an exhaust purification device 9 is disposed in the exhaust passage 40. The exhaust purification device 9 includes a three-way catalyst, an NOx storage reduction catalyst, and the like, and purifies exhaust when it is in a predetermined activation temperature range.

  Further, the internal combustion engine 1 is provided with an intake valve 10 that opens and closes an open end of the intake port 3 facing the cylinder 2 and an exhaust valve 11 that opens and closes an open end of the exhaust port 4 facing the cylinder 2. The intake valve 10 and the exhaust valve 11 are driven to open and close by an intake camshaft 12 and an exhaust camshaft 13, respectively.

A spark plug 14 for igniting the air-fuel mixture in the cylinder 2 is disposed at the upper part of the cylinder 2. A piston 15 is slidably inserted into the cylinder 2. The piston 15 is connected to the crankshaft 17 via a connecting rod 16.

  A crank position sensor 18 that detects a rotation angle of the crankshaft 17 is disposed in the vicinity of the crankshaft 17. Furthermore, a water temperature sensor 19 for measuring the temperature of the cooling water circulating through the internal combustion engine 1 is attached to the internal combustion engine 1.

  The internal combustion engine 1 configured as described above is provided with an ECU 20. The ECU 20 is an electronic control unit that includes a CPU, a ROM, a RAM, and the like. The ECU 20 is electrically connected to various sensors such as the intake pressure sensor 7, the air flow meter 8, the crank position sensor 18, and the water temperature sensor 19 described above, and can input measurement values of the various sensors.

  The ECU 20 electrically controls the fuel injection valve 5, the throttle valve 6, and the spark plug 14 based on the measurement values of the various sensors described above. For example, the ECU 20 performs attached fuel reduction control for reducing the fuel attached to the wall surface in the cylinder 2.

  Hereinafter, the adhered fuel reduction control in this embodiment will be described.

  When the in-cylinder temperature is low, such as when the internal combustion engine 1 is in a cold state, fuel tends to adhere to the wall surface in the cylinder. Most of the fuel adhering to the wall surface in the cylinder (adhered fuel) is discharged from the cylinder without being burned without being used for combustion. At that time, if the exhaust purification device 9 is not heated to the activation temperature range, the above-mentioned unburned fuel component is released into the atmosphere without being purified.

  In particular, when the internal combustion engine 1 is started at an extremely low temperature, etc., the period from the start of the internal combustion engine 1 to the activation of the exhaust purification device 9 becomes longer and the amount of attached fuel increases. There is a risk of excessive unburned fuel components.

  On the other hand, in the attached fuel reduction control, the ECU 20 advances the operation timing (ignition timing) of the spark plug 14 ahead of MBT (over-advance angle) when the amount of attached fuel is expected to increase.

  According to the earnest experiment and verification by the inventor of the present application, when the ignition timing is over-advanced, as shown in FIG. 2, the unburned fuel discharged from the cylinder 2 increases as the advance amount increases. It has been clarified that the amount of the component (HC) is reduced.

  Although this mechanism has not been clearly clarified, it is thought to be due to the following mechanism.

  FIG. 3 shows a case where the ignition timing is over-advanced (ST1 in FIG. 3), a case where the ignition timing is set to MBT (ST2 in FIG. 3), and a case where the ignition timing is compression top dead center (TDC). FIG. 6 is a diagram illustrating a result of measuring a state in a cylinder 2 in each of the cases where it is set to (ST3 in FIG. 3). The solid line in FIG. 3 shows the case where the ignition timing is over-advanced, the broken line shows the case where the ignition timing is set to MBT, and the dashed line shows the case where the ignition timing is set to compression top dead center (TDC). Yes.

  In FIG. 3, when the ignition timing is over-advanced, combustion occurs before the compression top dead center, compared to when the ignition timing is set to MBT and when the ignition timing is set to compression top dead center (TDC). The amount of air-fuel mixture produced increases. For this reason, the peak of the heat energy generated by the combustion of the air-fuel mixture (see the heat generation rate, generated heat amount, and combustion mass ratio in FIG. 3) shifts to before the compression top dead center.

Therefore, in-cylinder pressure during the period from the compression stroke to the expansion stroke is obtained by a synergistic effect of the temperature increase / pressure increase effect due to the combustion of the air-fuel mixture and the compression effect due to the piston ascending operation (operation from the bottom dead center toward the top dead center). In addition, the peak value of the in-cylinder temperature increases significantly. As a result, it is considered that the fuel attached to the wall surface in the cylinder is vaporized and / or vaporized before being attached to the wall surface in the cylinder and used for combustion.

  Therefore, the ECU 20 causes the ignition timing to be over-advanced when the amount of fuel adhering in the cylinder is expected to increase. As a case where the amount of in-cylinder attached fuel is expected to increase, when the internal combustion engine 1 is cold-started, or when the internal combustion engine 1 is in a warm-up operation state, the actually measured value of the in-cylinder attached fuel amount exceeds the allowable amount. A case where the estimated value of the in-cylinder attached fuel amount exceeds the allowable amount or the like can be exemplified.

  As a method for actually measuring the amount of fuel adhering to the cylinder, a method for optically measuring the liquid film thickness in the cylinder 2 and a method for actually measuring it, or a sensor for measuring the conductivity in the cylinder 2 can be used. A method for converting the measured value of the sensor into the in-cylinder attached fuel amount can be exemplified.

  In addition, as a method of estimating the in-cylinder attached fuel amount, at least the cooling water temperature, the integrated fuel injection amount from the engine start, the integrated intake air amount from the engine start, the fuel injection amount, the intake pressure, and the air-fuel ratio are at least. A method of estimating from the correlation between one and the amount of in-cylinder attached fuel can be exemplified.

  When the amount of in-cylinder attached fuel is expected to increase, if the ignition timing is over-advanced, the in-cylinder attached fuel can be reduced and the unburned fuel component discharged from the cylinder 2 can be reduced. Is also possible.

  When the ignition timing over-advance is performed as described above, the combustion energy generated in the cylinder 2 before the compression top dead center increases as the ignition timing advance amount increases, as shown in FIG. (Pre-TDC combustion energy) increases.

  The pre-TDC combustion energy is energy that resists the operation of the piston 15 during the compression stroke (operation from the bottom dead center toward the top dead center). For this reason, if the pre-TDC combustion energy becomes excessive, the pre-TDC combustion energy may overcome the inertial energy of the internal combustion engine 1 and cause the piston 15 to reverse (move from the top dead center side to the bottom dead center side).

  When the internal combustion engine 1 is in operation, the crankshaft 17 rotates forward by the inertial energy of the internal combustion engine 1 overcoming the friction. For this reason, when the ignition timing is over-advanced when the energy obtained by subtracting the friction from the inertia energy (hereinafter referred to as “forward rotation energy”) is small, the internal combustion engine 1 can reversely rotate due to an increase in the pre-TDC combustion energy. There is sex.

  In contrast, in the attached fuel reduction control of this embodiment, the ECU 20 causes the crankshaft 17 to be forcibly rotated when the inertial energy is smaller than the friction as in the cranking of the internal combustion engine 1 (that is, by the driving force of the starter motor). When the forward rotation energy is small, over-advanced ignition timing is prohibited. Further, even when the forward rotation energy increases, the ECU 20 performs the over-advancement while limiting the advance amount of the ignition timing so that the pre-TDC combustion energy becomes smaller than the forward rotation energy.

  Here, the execution procedure of the over-advance angle when the internal combustion engine 1 is cold-started will be described with reference to FIG. In FIG. 5, the solid line shows the change in the actual inertial energy (Ee) of the internal combustion engine 1, and the alternate long and short dash line shows the change in the pre-TDC combustion energy (Ebtdc).

In FIG. 5, the inertial energy Ee becomes very small during the period from the start of the internal combustion engine 1 to the occurrence of the first explosion (cranking period) because the rotational speed of the crankshaft 17 is low. If the ignition timing is excessively advanced in such a state, most of the combustion energy of the initial explosion acts on the piston 15 as the pre-TDC combustion energy, which may lead to an increase in cranking torque and a start failure. There is.

  Therefore, in the period from the start of the internal combustion engine 1 to the occurrence of the first explosion (cranking period), the ECU 20 prohibits the excessive advance angle of the ignition timing.

  Next, in the continuous explosion period after the first explosion occurs, the ECU 20 prohibits the excessive advance angle of the ignition timing until the inertial energy Ee exceeds a predetermined value P1. The predetermined value P1 is a value determined as follows.

  The condition for forward rotation of the internal combustion engine 1 during execution of the over-advanced angle is that the inertial energy Ee becomes larger than the sum of the friction (F) acting on the movable part of the internal combustion engine 1 and the pre-TDC combustion energy Ebtdc. . In other words, the pre-TDC combustion energy Ebtdc is smaller than the normal rotation energy (= Ee−F). Therefore, the predetermined value P1 is preferably set to a value obtained by adding a certain amount to the friction F of the internal combustion engine 1.

  By the way, the friction F acting on the movable part of the internal combustion engine 1 changes according to the temperature of the internal combustion engine 1 and the temperature of the lubricating oil. For this reason, it is preferable that the predetermined value P1 is changed according to the temperature of the internal combustion engine 1 or the temperature of the lubricating oil. However, the temperature of the internal combustion engine 1 and the temperature of the lubricating oil correlate with the coolant temperature (measured value of the water temperature sensor 19). Therefore, the ECU 20 can determine the predetermined value P1 based on a map that defines the relationship between the coolant temperature and the predetermined value P1 as shown in FIG.

  Here, referring back to FIG. 5, when the inertial energy Ee exceeds the predetermined value P1 during the continuous explosion period after the initial explosion, the ECU 20 permits (starts) the ignition timing over-advanced angle. At this time, if the advance amount of the ignition timing is excessively increased, the pre-TDC combustion energy Ebtdc is excessively increased, so that the sum of the pre-TDC combustion energy Ebtdc and the friction F may exceed the inertial energy Ee.

  Therefore, the ECU 20 limits the advance amount of the ignition timing so that the pre-TDC combustion energy Ebtdc is equal to the difference (F−P1) between the inertial energy Ee and the predetermined value P1. When the advance amount at the time of over-advance is limited in this way, the pre-TDC combustion energy Ebtdc gradually increases as the inertia energy Ee increases in the period from the over-advance start to the complete explosion in FIG. Become. As a result, the sum of the pre-TDC combustion energy Ebtdc and the friction F does not exceed the inertial energy Ee ((Ebtdc + F) <Ee).

  Further, immediately after the internal combustion engine 1 is completely exploded, the inertial energy Ee becomes excessive, and therefore the engine speed may exceed the target speed (in this case, the target value of the first idle speed) and excessively increase. . When the engine speed exceeds the target first idle speed and increases excessively, there is a possibility that unburned fuel components discharged from the cylinder 2 may increase in addition to vibration and noise.

  In contrast, in this embodiment, the inertia energy (hereinafter referred to as “target inertia energy”) P2 when the engine speed has converged to the target first idle speed is experimentally obtained in advance. When the actual inertia energy Ee becomes larger than the target inertia energy P2, the ECU 20 determines that the excess inertia energy (hereinafter referred to as “surplus energy”) ΔEe (= Ee−P2) is the combustion energy before TDC. The advance amount at the time of over advance is determined so as to be offset by Ebtdc.

Specifically, the ECU 20 determines the advance amount of the ignition timing so that the pre-TDC combustion energy Ebtdc is equal to the sum (= Ee + P3) of the inertia energy Ee and the predetermined value P3. The predetermined value P3 corresponds to a value obtained by subtracting the friction F from the surplus energy ΔEe. Since the friction F changes according to the cooling water temperature, the ECU 20 may determine the predetermined value P3 based on a map that defines the relationship between the cooling water temperature and the predetermined value P3 as shown in FIG. When the advance amount of the ignition timing is determined by such a method, it is difficult for the engine speed to excessively increase immediately after the internal combustion engine 1 is completely exploded. As a result, in addition to an increase in vibration and noise, an increase in the amount of unburned fuel components discharged from the cylinder 2 can be suppressed.

  After the inertia energy Ee converges to the target inertia energy P2, the ECU 20 determines the advance amount of the ignition timing so that the pre-TDC combustion energy Ebtdc becomes equal to the difference between the inertia energy Ee and the predetermined value P1. May be.

  Next, the procedure for determining the ignition timing in the attached fuel reduction control in this embodiment will be described with reference to FIG. FIG. 8 is a flowchart showing an ignition timing control routine in the adhered fuel reduction control. The ignition timing control routine is a routine stored in advance in the ROM of the ECU 20 and is periodically executed by the ECU 20.

  In the routine of FIG. 8, the ECU 20 first determines in S101 whether or not the value of the ignition timing over-advancement execution flag is “1”. The over-advance angle execution flag is set to “1” when the in-cylinder attached fuel amount is expected to increase, and is reset to “0” when the in-cylinder attached fuel amount is expected not to increase.

  If a negative determination is made in S101, the ECU 20 ends the execution of this routine. In this case, the excessive advance angle of the ignition timing is not executed, and the ignition timing is set to the normal ignition timing.

  On the other hand, if an affirmative determination is made in S101, the ECU 20 proceeds to S102. In S102, the ECU 20 reads the measured value (cooling water temperature thw) of the water temperature sensor 19.

  In S103, the ECU 20 calculates a predetermined value P1 from the coolant temperature thw read in S102 and the map of FIG.

  In S104, the ECU 20 calculates the target inertia energy P2 from the coolant temperature thw read in S102 and the map shown in FIG.

In S105, the ECU 20 calculates the current inertial energy Ee of the internal combustion engine 1. The inertial energy Ee can be calculated based on the following equation.
Ee = (1/2) * I * ω ²

  In the above formula, I is the inertial mass of the movable part of the internal combustion engine 1, and ω is the angular velocity of the crankshaft 17.

  In S106, the ECU 20 determines whether or not the inertial energy Ee calculated in S105 is greater than the predetermined value P1 calculated in S103. If a negative determination is made in S106 (Ee ≦ P1), the ECU 20 returns to S102. On the other hand, when an affirmative determination is made in S106 (Ee> P1), the ECU 20 proceeds to S107.

In S107, the ECU 20 determines whether or not the inertial energy Ee calculated in S105 is equal to or less than the target inertial energy P2 calculated in S104. If an affirmative determination is made in S107 (Ee ≦ P2), the ECU 20 proceeds to S108.

  In S108, the ECU 20 obtains the ignition timing α at the time of overtravel so that the pre-TDC combustion energy Ebtdc is equal to the difference between the inertial energy Ee and the predetermined value P1 (= Ee−P1). At that time, the ECU 20 may determine the ignition timing α based on the relationship between the pre-TDC combustion energy Ebtdc and the ignition timing as shown in FIG.

  Thereafter, the ECU 20 executes an over advance angle of the ignition timing in accordance with the ignition timing α determined in S108. In this case, since the pre-TDC combustion energy Ebtdc is smaller than the forward rotation energy, reverse rotation of the internal combustion engine 1 is prevented.

  On the other hand, if a negative determination is made in S107 (Ee> P2), the ECU 20 proceeds to S109. In S109, the ECU 20 obtains the ignition timing β at the time of over-advance so that the pre-TDC combustion energy Ebtdc is equal to the sum (= Ee + P3) of the inertia energy Ee and the predetermined value P3. At that time, the ECU 20 may determine the ignition timing β based on the relationship between the pre-TDC combustion energy Ebtdc and the ignition timing as shown in FIG.

  Thereafter, the ECU 20 executes an over advance angle of the ignition timing in accordance with the ignition timing β determined in S109. In this case, the surplus energy ΔEe is offset by the pre-TDC combustion energy Ebtdc, so that an excessive increase in the engine speed is suppressed. As a result, in addition to an increase in vibration and noise, an increase in the amount of unburned fuel components discharged from the cylinder 2 can be suppressed.

  As described above, the ECU 20 executes the routine shown in FIG. 8 to realize the over-advance angle means, calculation means, and control means according to the present invention. As a result, the unburned fuel component discharged from the cylinder 2 can be reduced while preventing the reverse rotation of the internal combustion engine 1 due to the excessive advance angle of the ignition timing.

It is a figure showing the schematic structure of the ignition control system of the internal-combustion engine concerning the present invention. It is a figure which shows the relationship between the unburned fuel component (HC) discharged | emitted from the inside of a cylinder, and ignition timing. It is a figure which shows the relationship between an ignition timing and the state in a cylinder. It is a figure which shows the relationship between pre-TDC combustion energy and ignition timing. It is a timing chart which shows the execution procedure of the over advance angle when an internal combustion engine is cold-started. It is a figure which shows the map which defined the relationship between the predetermined value P1 and cooling water temperature. It is a figure which shows the map which defined the relationship between the predetermined value P3 and cooling water temperature. It is a flowchart which shows the ignition timing control routine in adhesion fuel reduction control. It is a figure which shows the map which defined the relationship between the ignition timing at the time of an advance angle, and the combustion energy before TDC.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Intake port 4 ... Exhaust port 5 ... Fuel injection valve 6 ... Throttle valve 7. ....... Intake pressure sensor 8 ... Air flow meter 9 ... Exhaust gas purification device 14 ... Spark plug 15 ... Piston 16 ... Connecting rod 17 ... Crank Shaft 18 ... Crank position sensor 19 ... Water temperature sensor 20 ... ECU
30 ... Intake passage 40 ... Exhaust passage

Claims (3)

Over-advance means for advancing the ignition timing of the spark ignition internal combustion engine before MBT;
Calculating means for calculating the magnitude of inertial energy formic the angular velocity of the inertial mass and the crankshaft of the movable portion of the internal combustion engine as a parameter,
Advancing the ignition timing by the over-advance means conditions is greater than the magnitude value greater than value at which the friction which acts on the movable portion of the magnitude the internal combustion engine of the calculated inertia energy formate by the calculating means Control means to allow
An ignition control system for an internal combustion engine, comprising:   The control unit according to claim 1, wherein the controller advances the over-advanced angle so that the combustion energy generated in the cylinder before compression top dead center is equal to or less than a difference between the inertia energy calculated by the calculating unit and the predetermined value. An ignition control system for an internal combustion engine, wherein an advance amount of ignition timing by means is determined.   3. The control unit according to claim 1 or 2, wherein the inertial energy calculated by the arithmetic unit exceeds the target inertial energy, the inertial energy and the target by combustion energy generated in a cylinder before compression top dead center. An ignition control system for an internal combustion engine, wherein an advance amount of ignition timing by the over-advance angle means is determined so that a difference from inertial energy is offset.

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