JP2007278098A - Combustion noise calculation device and combustion noise control system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for accurately calculating combustion noise in an internal combustion engine. <P>SOLUTION: The combustion noise in the internal combustion engine is calculated from an expression of CN=A×log<SB>10</SB>(Pmax)<SP>n1</SP>+B×log<SB>10</SB>(ΔPmax)<SP>n2</SP>+C×log<SB>10</SB>(dΔP/dt)<SP>n3</SP>+D×log<SB>10</SB>(d<SP>2</SP>ΔP/dt<SP>2</SP>)<SP>n4</SP>+E×log<SB>10</SB>(1/Ne)+F. Where, the combustion noise in the internal combustion engine is CN, a maximum value of cylinder pressure during a compression stroke and an exhaust stroke is Pmax, a maximum value of an increased amount of the cylinder pressure by combustion of fuel is ΔPmax, a maximum value of a first-grade time differential value of an increased amount of cylinder pressure in fuel combustion is dΔP/dt, a maximum value of a second-grade time differential value of an increased amount of cylinder pressure in fuel combustion is d<SP>2</SP>ΔP/dt<SP>2</SP>, and speed of the internal combustion ending is Ne. Wherein, A, B, C, D, E, F, n1, n2, n3, and n4 are coefficients. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a combustion noise calculation device for an internal combustion engine that calculates combustion noise in the internal combustion engine, and a combustion noise control system that controls the combustion noise.

  In an internal combustion engine, combustion noise may occur due to variations in the fuel injection amount and fuel injection timing from the fuel injection valve. Further, even in a transient state in which the combustion pattern in the internal combustion engine is changed with a change in the operating state of the internal combustion engine, combustion noise may be generated due to the fuel injection amount or the fuel injection timing deviating from the optimum values.

Patent Document 1 discloses a technique for detecting combustion noise in the internal combustion engine from a second-order time differential value of in-cylinder pressure. Further, in Patent Document 2, in an internal combustion engine that performs sub fuel injection at a time prior to main fuel injection, when the second-order time differential value of in-cylinder pressure when fuel burns does not match the target value, A technique for correcting the auxiliary fuel injection amount on the side where the second-order time differential value becomes smaller is disclosed.
JP 2001-123871 A JP-A-11-247703 JP 2002-188489 A

  An object of the present invention is to provide a technique capable of calculating combustion noise in an internal combustion engine with higher accuracy.

  The present invention calculates combustion noise based on a plurality of parameters that can be obtained from the in-cylinder pressure of an internal combustion engine and have correlation with combustion noise.

More specifically, the internal combustion engine combustion noise calculation apparatus according to the first invention is
In-cylinder pressure detecting means for detecting or estimating the in-cylinder pressure of the internal combustion engine,
at least,
The maximum value of the in-cylinder pressure during the compression stroke and the exhaust stroke;
The maximum amount of cylinder pressure rise due to fuel combustion,
The maximum value of the first-order time differential value of the amount of increase in the in-cylinder pressure when the fuel burns,
The maximum value of the second-order time differential value of the increase in the in-cylinder pressure when the fuel burns,
The time required for the compression and exhaust strokes;
Based on the above, combustion noise in the internal combustion engine is calculated.

  Combustion noise in an internal combustion engine is generated due to fluctuations in in-cylinder pressure. Therefore, all of the plurality of parameters related to the fluctuation of the in-cylinder pressure as described above are correlated with the combustion noise.

  However, depending on the operating state of the internal combustion engine, the maximum value of the first-order time differential value of the amount of increase in the in-cylinder pressure when the fuel combusts (hereinafter referred to as the first-order time differential maximum value) is combusted. If the degree of correlation with combustion noise is higher than the maximum value of the second-order time differential value of the increase in the in-cylinder pressure (hereinafter referred to as the second-order time differential maximum value), or the second-order time differential maximum value is the first order The degree of correlation with combustion noise may be higher than the time differential maximum value.

  Further, even if the first-order time differential maximum value or the second-order time differential maximum value is the same value, the maximum value of the in-cylinder pressure during the compression stroke and the exhaust stroke (hereinafter referred to as the maximum in-cylinder pressure) depending on the operating state of the internal combustion engine. The maximum amount of increase in the in-cylinder pressure due to fuel combustion (hereinafter referred to as the maximum amount of increase) may be different values.

  Therefore, by calculating the combustion noise in the internal combustion engine based on all of the plurality of parameters as described above, the combustion noise can be calculated with higher accuracy regardless of the operating state of the internal combustion engine. In addition, combustion noise can be calculated with higher accuracy even during a transition in which the combustion pattern in the internal combustion engine changes as the operating state of the internal combustion engine changes.

In the present invention, the combustion noise in the internal combustion engine is CN, the maximum in-cylinder pressure is Pmax, the maximum increase amount is ΔPmax, the first-order time differential maximum value is dΔP / dt, and the second-order time differential maximum value is Combustion noise in the internal combustion engine may be calculated from the following equation (1), where d ² ΔP / dt ² and the engine speed of the internal combustion engine are Ne.
CN = A × log ₁₀ (Pmax) ⁿ¹ + B × log ₁₀ (ΔPmax) ⁿ² + C × log ₁₀ (dΔP / dt) ⁿ³ + D × log ₁₀ (d ² ΔP / dt ² ) ⁿ⁴ + E × log ₁₀ (1 / Ne) + F Formula (1)
(However, A and B, C, D, E, F, n1, n2, n3, and n4 are coefficients)

The sound pressure level (unit: dB) representing the level of sound felt by human hearing is expressed by the following equation (2) from the Weber-Fechner law.
Sound pressure level = 20 log ₁₀ (P / P ₀ ) (2)
(P: Sound pressure, P ₀ : Reference sound pressure)

  Here, 1 / Ne in the equation (1) is the reciprocal of the engine speed, that is, the time required for the compression stroke and the exhaust stroke. That is, Expression (1) derives the combustion noise component caused by each parameter related to the variation in the in-cylinder pressure based on Expression (2), and calculates the combustion noise by synthesizing them. In addition, each coefficient in Formula (1) is a value predetermined by experiment etc. Further, each coefficient in the equation (1) may be set to an optimum value according to the internal combustion engine that is the target of the combustion noise calculation.

  According to Equation (1), the combustion noise CN can be calculated as a sound pressure level with a unit of dB, not a relative value. Therefore, the combustion noise can be calculated with higher accuracy regardless of the operating state of the internal combustion engine.

  In the present invention, the fuel injection may be executed a plurality of times during one combustion cycle in the internal combustion engine. In this case, the in-cylinder pressure increases every time the fuel injected by each fuel injection burns.

  Therefore, in the above case, the maximum value of the first-order time differential value of the increase amount of the in-cylinder pressure when the fuel injected by each fuel injection burns and the maximum value of the second-order time differential value of the increase amount of the in-cylinder pressure are set. Based on this, combustion noise in the internal combustion engine may be calculated.

  As a result, even when fuel injection is performed a plurality of times during one combustion cycle, the combustion noise can be calculated more accurately regardless of the operating state of the internal combustion engine.

  In the present invention, the fuel injection in the internal combustion engine may be performed by main fuel injection and sub fuel injection. Here, the auxiliary fuel injection is executed at a time before the main fuel injection and when the injected fuel is used for combustion. In this case, as described above, the in-cylinder pressure rises when the fuel injected by the auxiliary fuel injection burns and when the fuel injected by the main fuel injection burns.

Therefore, in the above case, the combustion noise in the internal combustion engine is CN, the maximum value of the in-cylinder pressure when the fuel injected by the auxiliary fuel injection burns is Psub, and the fuel injected by the main fuel injection burns The maximum value of the in-cylinder pressure at this time is Pmain, the maximum value of the increase in the in-cylinder pressure due to the combustion of the fuel injected by the auxiliary fuel injection is ΔPsub, and the increase in the in-cylinder pressure due to the combustion of the fuel injected by the main fuel injection Is the maximum first-order time differential when the fuel injected by the secondary fuel injection is burned, and is the first-order time differential maximum when the fuel injected by the main fuel injection is burned. The value is dΔP / dtmain, and the second-order time differential maximum value when the fuel injected by the sub fuel injection burns is d ² ΔP / dt ² sub. Then, the second-order time differential maximum value when the fuel injected by the main fuel injection is burned is d ² ΔP / dt ² main, the engine speed of the internal combustion engine is Ne, and the following equation (3) Combustion noise may be calculated.
CN = A × log ₁₀ [(Psub) ⁿ¹ + (Pmain) ⁿ¹ ] + B × log ₁₀ [(ΔPsub) ⁿ² + (ΔPmain) ⁿ² ] + C × log ₁₀ [(dΔP / dtsub) ⁿ³ + (dΔP / dt
main) ⁿ³ ] + D × log ₁₀ [(d ² ΔP / dt ² sub) ⁿ⁴ + (d ² ΔP / dt ² main) ⁿ⁴ ] + E × log ₁₀ (1 / Ne) + F (3)
(However, A and B, C, D, E, F, n1, n2, n3, and n4 are coefficients)

  As in equation (1), each coefficient in equation (3) is a value determined in advance by experiment or the like, and each coefficient is set to an optimum value according to the internal combustion engine for which combustion noise is calculated. Also good.

  Even if the fuel injection is performed by the main fuel injection and the sub fuel injection, the combustion noise CN can be calculated as a sound pressure level with the unit dB. Therefore, the combustion noise can be calculated with higher accuracy regardless of the operating state of the internal combustion engine.

  In the present invention, in addition to the above parameters, the combustion noise in the internal combustion engine is calculated based on the maximum value of the higher-order time differential value of the third or higher floor of the increase in the in-cylinder pressure when the fuel burns. Also good.

  The maximum value of the third-order or higher-order time differential value of the amount of increase in the in-cylinder pressure when the fuel is combusted is also correlated with the combustion noise, like the above-described parameters. Therefore, the calculation accuracy of the combustion noise can be improved by calculating the combustion noise also using the maximum value of the higher order time differential value.

A combustion noise control system for an internal combustion engine according to a second aspect of the invention includes a combustion noise calculation device for an internal combustion engine that calculates combustion noise in the internal combustion engine from the equation (1). Further, in the equation (1), A × log ₁₀ (Pmax) ⁿ¹ + B × log ₁₀ (ΔPmax) ⁿ² is a pressure component, C × log ₁₀ (dΔP / dt) ⁿ³ is a first-order time differential component of the increase in in-cylinder pressure, and D × log ₁₀ ( d ² ΔP / dt ² ) ⁿ⁴ is a second-order time differential component of the increase in in-cylinder pressure, E × log ₁₀ (1 / Ne) is a time component, and a correlation for calculating the degree of correlation of each component with combustion noise in the internal combustion engine A degree calculation means is provided. The first-order time derivative component of the pressure component and the increase amount of the in-cylinder pressure, the second-order time derivative component of the increase amount of the in-cylinder pressure, and the component having a higher degree of correlation with the combustion noise in the internal combustion engine are preferentially reduced. Thus, the combustion noise calculated by the combustion noise detection device is controlled to a predetermined value or less.

  Here, the predetermined value is a value not more than the upper limit value of the allowable range of combustion noise, and is a predetermined value.

The degree of correlation of the above components in equation (1) with respect to combustion noise may vary depending on the internal combustion engine that is the subject of combustion noise control. Therefore, among the above components in Equation (1), components having a higher degree of correlation with combustion noise in the internal combustion engine are preferentially reduced. Thereby, combustion noise can be efficiently reduced below a predetermined value.

A combustion noise control system for an internal combustion engine according to a third aspect of the invention includes a combustion noise calculation device for an internal combustion engine that calculates combustion noise in the internal combustion engine from the equation (3), and further includes the equation (3). A × log ₁₀ [(Psub) ⁿ¹ + (Pmain) ⁿ¹ ] + B × log ₁₀ [(ΔPsub) ⁿ² + (ΔPmain) ⁿ² ] is used as a pressure component, and C × log ₁₀ [(dΔP / dts
ub) ⁿ³ + (dΔP / dtmain) ⁿ³ ] as a first-order time differential component of the increase in the in-cylinder pressure, D × log ₁₀ [(d ² ΔP / dt ² sub) ⁿ⁴ + (d ² ΔP / dt ² main) ⁿ⁴ ] Is a second-order time differential component of the amount of increase in the in-cylinder pressure, E × log ₁₀ (1 / Ne) is a time component, and correlation degree calculating means for calculating the degree of correlation of each component with combustion noise in the internal combustion engine is provided. . The first-order time derivative component of the pressure component and the increase amount of the in-cylinder pressure, the second-order time derivative component of the increase amount of the in-cylinder pressure, and the component having a higher degree of correlation with the combustion noise in the internal combustion engine are preferentially reduced. Thus, the combustion noise calculated by the combustion noise detection device is controlled to a predetermined value or less.

  Here, like the second invention, the predetermined value is a value equal to or lower than the upper limit value of the allowable range of combustion noise, and is a predetermined value.

  Similar to the second invention, the degree of correlation of each component in equation (3) with respect to combustion noise may vary depending on the internal combustion engine that is subject to combustion noise control. In view of this, among the above components in Equation (3), components having a higher degree of correlation with combustion noise in the internal combustion engine are preferentially reduced. Thereby, like the second invention, the combustion noise can be efficiently reduced to a predetermined value or less.

  In the second and third inventions, when the time component is reduced to reduce the combustion noise, the engine speed of the internal combustion engine changes. This may affect the driving state of the vehicle equipped with the internal combustion engine.

  Therefore, in the second and third inventions, the combustion noise is reduced to a predetermined value or less by preferentially reducing, among the components excluding the time component, components having a higher degree of correlation with the combustion noise in the internal combustion engine. You may control.

  Thereby, the combustion noise can be efficiently reduced to a predetermined value or less while suppressing the influence on the driving state of the vehicle equipped with the internal combustion engine.

  According to the combustion noise calculation apparatus for an internal combustion engine according to the present invention, the combustion noise in the internal combustion engine can be calculated with higher accuracy. Further, according to the combustion noise control system for an internal combustion engine according to the present invention, the combustion noise can be efficiently reduced.

  Hereinafter, specific embodiments of a combustion noise calculation device and a combustion noise control system for an internal combustion engine according to the present invention will be described with reference to the drawings.

<Schematic configuration of internal combustion engine and its fuel system>
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its fuel system according to this embodiment. The internal combustion engine 1 is a diesel engine for driving a vehicle having four cylinders 2. A piston 3 is slidably provided in the cylinder 2 of the internal combustion engine 1.

  An intake port 4 and an exhaust port 5 are connected to the combustion chamber in the upper part of the cylinder 2. The openings of the intake port 4 and the exhaust port 5 to the combustion chamber are opened and closed by an intake valve 6 and an exhaust valve 7, respectively. The intake port 4 and the exhaust port 5 are connected to an intake passage 8 and an exhaust passage 9, respectively. The cylinder 2 is provided with a fuel injection valve 10 that directly injects fuel into the cylinder 2.

  The internal combustion engine 1 is provided with a fuel tank 14. One end of a fuel supply pipe 13 is inserted into the fuel tank 14, and the other end of the fuel supply pipe 13 is connected to the common rail 12. The fuel supply pipe 13 is provided with a fuel pump 15 that pumps fuel from the fuel tank 14 to the common rail 12. In addition, one end of four fuel supply branch pipes 11 is connected to the common rail 12. The other end of each fuel supply branch pipe 11 is connected to the fuel injection valve 10 of each cylinder 2. The fuel boosted in the common rail 12 is sent to the fuel injection valve 10 through the fuel supply branch pipe 11 and injected from the fuel injection valve 10.

  Further, the internal combustion engine 1 is provided with a pressure sensor 21 for detecting the pressure in the cylinder 2 and a water temperature sensor 22 for detecting the temperature of the cooling water in the water jacket provided in the internal combustion engine 1.

  The internal combustion engine 1 configured as described above is provided with an ECU 20 for controlling the internal combustion engine 1. The ECU 20 includes various sensors such as a pressure sensor 21, a water temperature sensor 22, a crank position sensor 23 that detects a crank angle of the internal combustion engine 1, and an accelerator opening sensor 24 that detects an accelerator opening of a vehicle on which the internal combustion engine 1 is mounted. Connected via electrical wiring. These output signals are input to the ECU 20.

  Further, the ECU 20 is electrically connected to the fuel injection valve 10 and the fuel pump 15. These are controlled by the ECU 20. In the present embodiment, the fuel injection from the fuel injection valve 10 is performed twice, that is, main fuel injection and sub fuel injection during one combustion cycle. The main fuel injection is performed at a time near the top dead center of the compression stroke. The auxiliary fuel injection is performed at a time before the main fuel injection and when the injected fuel is used for combustion.

<Combustion noise calculation method>
Next, a method for calculating combustion noise in the internal combustion engine 1 according to the present embodiment will be described. In the present embodiment, a plurality of parameters correlated with the combustion noise CN as shown in FIG. 2 are derived based on the in-cylinder pressure detected by the pressure sensor 21.

  FIG. 2 is a diagram illustrating changes in the compression stroke and the expansion stroke of a plurality of parameters calculated based on the in-cylinder pressure and the in-cylinder pressure. The vertical axis in FIG. 2A represents the in-cylinder pressure. Moreover, the solid line L1 in FIG. (A) represents the change of the in-cylinder pressure when the fuel burns in the combustion chamber. Moreover, the broken line L2 in FIG. (A) represents the change in the in-cylinder pressure when the piston 3 only moves without burning the fuel in the combustion chamber.

  The vertical axis in FIG. 2B represents the amount of increase in the in-cylinder pressure due to fuel combustion (that is, the value obtained by subtracting L2 from L1 in FIG. 2A). The vertical axis in FIG. 2C represents the first-order time differential value of the increase amount of the in-cylinder pressure. The vertical axis in FIG. 2D represents the second-order time differential value of the amount of increase in the in-cylinder pressure. 2 (a), (b), (c), and (d), the horizontal axis represents the crank angle.

Further, Psub in FIG. 2 (a) represents the maximum value of the in-cylinder pressure when the fuel injected by the sub fuel injection is combusted, and Pmain in FIG. 2 (a) is the fuel injected by the main fuel injection. It represents the maximum value of the in-cylinder pressure when burning. ΔPsub in FIG. 2B represents the maximum value of the increase in the in-cylinder pressure due to the combustion of the fuel injected by the sub fuel injection, and ΔPmain in FIG. 2B represents the combustion of the fuel injected by the main fuel injection. Represents the maximum value of the increase in the in-cylinder pressure. DΔP / dtsub in FIG. 2 (c) represents the first-order time differential maximum value when the fuel injected by the sub fuel injection burns, and dΔP / dtmain in FIG. 2 (c) is injected by the main fuel injection. Represents the first-order time differential maximum value when the fuel burned. D ² ΔP / dt ² sub in FIG. 2D represents the second-order time differential maximum value when the fuel injected by the sub fuel injection burns, and d ² ΔP / dt ² main in FIG. Represents the second-order time differential maximum value when the fuel injected by the main fuel injection burns.

The maximum value Psub of the in-cylinder pressure when the fuel injected by the auxiliary fuel injection burns, the maximum value Pmain of the in-cylinder pressure when the fuel injected by the main fuel injection burns, and the fuel injected by the auxiliary fuel injection The maximum value ΔPsub of the increase in the in-cylinder pressure due to the combustion of the fuel, the maximum value ΔPmain of the increase in the in-cylinder pressure due to the combustion of the fuel injected by the main fuel injection, and the first floor time when the fuel injected by the sub fuel injection burns Differential maximum value dΔP / dtsub, first-order time differential maximum value dΔP / dtmain when the fuel injected by the main fuel injection burns, second-order time differential maximum value d ² when the fuel injected by the auxiliary fuel injection burns Δ
All of P / dt ² sub and the second-order time differential maximum value d ² ΔP / dt ² main when the fuel injected by the main fuel injection burns are correlated with the combustion noise CN in the internal combustion engine 1. Further, the time required for the compression stroke and the exhaust stroke in the internal combustion engine 1 is also correlated with the combustion noise CN. The time required for the compression stroke and the exhaust stroke is represented by 1 / Ne when the engine speed of the internal combustion engine 1 is Ne.

Therefore, in this embodiment, the following formula (3) is used based on Psub and Pmain, ΔPsub, ΔPmain, dΔP / dtsub, dΔP / dtmain, d ² ΔP / dt ² sub, d ² ΔP / dt ² main, 1 / Ne. The combustion noise CN in the internal combustion engine 1 is calculated from '.
CN = A ′ × log ₁₀ [(Psub) ⁿ¹ ′ + (Pmain) ⁿ¹ ′] + B ′ × log ₁₀ [(ΔPsub) ⁿ² ′ + (ΔPmain) ⁿ² ′] + C ′ × log ₁₀ [(dΔP / dtsub) ⁿ³ ´
+ (DΔP / dtmain) ⁿ³ ′] + D ′ × log ₁₀ [(d ² ΔP / dt ² sub) ⁿ⁴ ′ + (d ² ΔP / dt ² main) ⁿ⁴ ′] + E ′ × log ₁₀ (1 / Ne) + F '... (3)'

  A ′ and B ′, C ′, D ′, E ′, F ′, n1 ′, n2 ′, n3 ′, and n4 ′ in Equation (3) ′ are coefficients. In the present embodiment, each coefficient is determined in advance by experiments or the like so as to be an optimum value for the internal combustion engine 1. This equation (3) ′ is stored in the ECU 20 in advance.

  According to equation (3) ′, the combustion noise CN is calculated as a sound pressure level with the unit dB. Here, the relationship between the calculated value of the combustion noise calculated by the equation (3) ′ and the measured value of the combustion noise is shown in FIG. In FIG. 3, the vertical axis represents the actual measurement value, and the horizontal axis represents the calculated value according to Expression (3) ′. As shown in FIG. 3, the value calculated by equation (3) ′ is almost the same as the actually measured value.

  In this way, by calculating the combustion noise in the internal combustion engine 1 based on all of the plurality of parameters correlated with the combustion noise, the combustion noise can be calculated with higher accuracy regardless of the operating state of the internal combustion engine 1. I can do it. In addition, combustion noise can be calculated with higher accuracy even during a transition in which the combustion pattern in the internal combustion engine 1 is changed as the operating state of the internal combustion engine 1 changes.

  Further, by calculating the combustion noise by the expression (3) ′, the combustion noise CN can be calculated not as a relative value but as a sound pressure level with a unit of dB.

<Modification>
In the above description, the case where the auxiliary fuel injection is performed once in one combustion cycle has been described. However, the auxiliary fuel injection may be executed twice or more. Also in this case, as in the case where the sub fuel injection is performed once, the maximum value of the first-order time differential value of the increase amount of the in-cylinder pressure and the increase amount of the in-cylinder pressure when the fuel injected by each fuel injection burns. Combustion noise is calculated using each maximum value of the second-order time differential value as a parameter. As a result, even when the auxiliary fuel injection is executed a plurality of times during one combustion cycle, the combustion noise can be calculated more accurately regardless of the operating state of the internal combustion engine 1.

Further, the fuel injection in the internal combustion engine 1 may be executed only by the main fuel injection. In this case, the combustion noise CN in the internal combustion engine 1 is calculated based on the following formula (1) ′.
_{CN = A'' × log 10 (Pmain} ) n1'' + B'' × log 10 (ΔPmain) n2'' + C'' × log 10 (dΔP / dtmain) n3'' + D'' × log 10 [(d 2 Δ
P / dt ² main) ^{n4 ″} + E ″ × log ₁₀ (1 / Ne) + F ″ (1) ′

  In Formula (1) ′, A ″ and B ″, C ″, D ″, E ″, F ″, n1 ″, n2 ″, n3 ″, and n4 ″ are coefficients. Further, each coefficient is determined in advance by experiments or the like so as to be an optimum value for the internal combustion engine 1 as in the case of the above formula (3) ′. In the modification, the expression (1) ′ is stored in the ECU 20 in advance.

  As described above, even when the fuel injection is only the main fuel injection, the operation state of the internal combustion engine 1 is calculated by calculating the combustion noise in the internal combustion engine 1 based on all of the plurality of parameters correlated with the combustion noise. Regardless, the combustion noise can be calculated with higher accuracy. Further, by calculating the combustion noise by the equation (1) ′, the combustion noise can be calculated as a sound pressure level with a unit of dB.

  In this embodiment, in addition to the first-order time differential maximum value and the second-order time differential maximum value, the maximum value of the third-order or higher higher-order time differential of the amount of increase in the in-cylinder pressure when the fuel burns is used as an internal combustion parameter. Combustion noise in the engine 1 may be calculated.

For example, as described above, in the case where fuel injection is performed by main fuel injection and one sub fuel injection, the maximum value of the third-order time derivative (hereinafter, three times) of the amount of increase in in-cylinder pressure when the fuel burns Is also used as a parameter, the third-order time differential maximum value when the fuel injected by the secondary fuel injection burns is dΔ ³ P / dt ³ sub, and is injected by the main fuel injection. Let dΔ ³ P / dt ³ main be the third-order time differential maximum when the fuel burns. At this time, the combustion noise CN in the internal combustion engine 1 is calculated from the following equation (4).
CN = A ″ ″ × log ₁₀ [(Psub) ⁿ¹ ″ ″ + (Pmain) ⁿ¹ ″ ″] + B ′ ″
× log ₁₀ [(ΔPsub) ^{n2 ″} ″ + (ΔPmain) ⁿ² ″ ″] + C ″ ″ × log ₁₀ [(dΔP / dtsub) ⁿ³ ″ ″ + (dΔP / dtmain) ⁿ³ ″ ″] + D ′ ″ ″ Log ₁₀ [(d ² ΔP / dt ² sub) ^{n4 ″} ″ + (d ² ΔP / dt ² main) ⁿ⁴ ″ ″] + G × log ₁₀ [(d ³ ΔP / dt ³ sub) ⁿ⁵ + (D ³ ΔP / dt ³ main) ⁿ⁵ ] + E ″ ″ × log ₁₀ (1 / Ne) + F ″ ″ (4)

  A ″ ″ and B ″ ″, C ″ ″, D ″ ″, F ″ ″, G, n1 ″ ″, n2 ″ ″, n3 ″ in the formula (4). ', N4 "', n5 are coefficients. Also in this case, each coefficient is determined in advance by experiments or the like so as to be an optimum value for the internal combustion engine 1.

The maximum value of the third-order or higher-order time differential value of the amount of increase in the in-cylinder pressure when the fuel is combusted is also correlated with the combustion noise, like the above-described parameters. Therefore, the calculation accuracy of the combustion noise can be improved by calculating the combustion noise also using the maximum value of the higher order time differential value.

  The schematic configuration of the internal combustion engine and its fuel system according to this embodiment is the same as that of the first embodiment. In this embodiment, the combustion noise in the internal combustion engine 1 is calculated by the same method as in the first embodiment.

<Combustion noise reduction control>
In the present embodiment, the combustion noise reduction control is performed in order to suppress the combustion noise below the upper limit value of the allowable range. When the combustion noise reduction control according to the present embodiment is executed, in the above equation (3) ′,
A ′ × log ₁₀ [(Psub) ⁿ¹ ′ + (Pmain) ⁿ¹ ′] + B ′ × log ₁₀ [(ΔPsub) ⁿ² ′ + (ΔPmain) ⁿ² ′] is a pressure component,
C ′ × log ₁₀ [(dΔP / dtsub) ⁿ³ ′ + (dΔP / dtmain) ⁿ³ ′] as a first-order time derivative component of the increase in the in-cylinder pressure,
D ′ × log ₁₀ [(d ² ΔP / dt ² sub) ⁿ⁴ ′ + (d ² ΔP / dt ² main) ⁿ⁴ ′] is a second-order time derivative component of the increase in the cylinder pressure,
E ′ × log ₁₀ (1 / Ne) as a time component,
The degree of correlation of each component with combustion noise is calculated.

  The degree of correlation of the above components with respect to combustion noise may vary depending on the internal combustion engine that is subject to combustion noise control. Therefore, in the combustion noise reduction control according to the present embodiment, the fuel injection pattern by the fuel injection valve 10 is controlled so as to preferentially reduce components having a higher degree of correlation with the combustion noise among the above components.

  For example, the correlation degree of the pressure component with respect to the combustion noise is 13.7%, the correlation degree with respect to the combustion noise of the first-order differential component of the increase in the in-cylinder pressure is 37%, and the combustion noise of the second-order time derivative component of the increase in the in-cylinder pressure. When the correlation degree with respect to is 21.8% and the correlation degree with respect to the combustion noise of the time component is 27.5%, the fuel injection valve 10 uses the fuel injection valve 10 to preferentially reduce the first-order time differential component of the increase in the in-cylinder pressure. Control the fuel injection pattern.

  In this embodiment, as the control of the fuel injection pattern for reducing the first-order time differential component of the increase amount of the in-cylinder pressure, the sub fuel injection timing is retarded, that is, the sub fuel injection and the main fuel injection are executed. Examples thereof include control for shortening the interval and control for reducing the sub fuel injection amount.

  FIG. 4 is a diagram showing the relationship between the auxiliary fuel injection timing and the first-order time differential value of the increase amount of the in-cylinder pressure. In FIG. 4, the vertical axis represents the first-order time differential value of the increase amount of the in-cylinder pressure, and the horizontal axis represents the crank angle. Also, among the curves (1) to (3) in FIG. 4, the curve (1) (solid line) shows the case where the sub fuel injection timing is the latest, and the curve (3) (dashed line) shows the fuel injection timing the most. It represents an early case. In each curve, the first peak shows the first-order time differential maximum value when the fuel injected by the sub fuel injection burns, and the next peak shows when the fuel injected by the main fuel injection burns The first-order time differential maximum is shown.

  As shown in FIG. 4, as the sub fuel injection timing is later, that is, the execution interval between the sub fuel injection and the main fuel injection is shorter, the first-order time differential maximum when the fuel injected by the sub fuel injection is combusted. The sum of the value and the first-order time differential maximum value when the fuel injected by the main fuel injection burns becomes small. That is, as the auxiliary fuel injection timing is retarded, the first-order time derivative component of the increase amount of the in-cylinder pressure is reduced.

FIG. 5 is a diagram showing the relationship between the auxiliary fuel injection amount and the first-order time differential value of the increase amount of the in-cylinder pressure. As in FIG. 4, in FIG. 5, the vertical axis represents the first-order time differential value of the increase amount of the in-cylinder pressure, and the horizontal axis represents the crank angle. Further, among the curves (1) to (3) in FIG. 5, the curve (1) (solid line) shows the case where the sub fuel injection amount is the smallest, and the curve (3) (dashed line) shows the fuel injection amount being the smallest. It represents a large number of cases. As in FIG. 4, in each curve, the first peak shows the first-order time differential maximum value when the fuel injected by the sub fuel injection burns, and the next peak is injected by the main fuel injection. The first-order time differential maximum value when the fuel burns is shown.

  As shown in FIG. 5, the smaller the sub fuel injection amount, the first time time differential maximum when the fuel injected by the sub fuel injection burns and the first floor when the fuel injected by the main fuel injection burns. The sum with the time differential maximum value becomes smaller. That is, as the sub fuel injection amount is decreased, the first-order time differential component of the increase amount of the in-cylinder pressure is reduced.

  As described above, the first-order time derivative component of the pressure component and the increase amount of the in-cylinder pressure, the second-order time derivative component of the increase amount of the in-cylinder pressure, and the component having a higher degree of correlation with the combustion noise are preferentially reduced. Thus, combustion noise can be reduced efficiently.

<Control routine for combustion noise reduction control>
Next, the control routine of the combustion noise reduction control according to this embodiment will be described based on the flowchart shown in FIG. This routine is stored in advance in the ECU 20 and is a routine that is repeated at predetermined intervals during the operation of the internal combustion engine 1.

  In this routine, first, in S101, the ECU 20 reads the engine speed Ne, the crank angle CA, the accelerator opening degree Da, and the coolant temperature Tw.

  Next, the ECU 20 proceeds to S102, and sets an upper limit value CNlimit of the combustion noise based on the engine speed Ne, the crank angle CA, the accelerator opening degree Da, and the cooling water temperature Tw. The relationship between the engine speed Ne, the crank angle CA, the accelerator opening degree Da, the coolant temperature Tw, and the upper limit value CNlimit of the combustion noise is stored in advance in the ECU 20 as a map.

  Next, the ECU 20 proceeds to S103 and reads the in-cylinder pressure Pc of the internal combustion engine 1.

Next, the ECU 20 proceeds to S104, and based on the in-cylinder pressure Pc, the maximum value Psub of the in-cylinder pressure when the fuel injected by the auxiliary fuel injection burns, and the fuel injected by the main fuel injection combusts. The maximum value Pmain of the in-cylinder pressure, the maximum value ΔPsub of the increase amount of the in-cylinder pressure due to the combustion of the fuel injected by the sub fuel injection, and the maximum value ΔPmain of the increase amount of the in-cylinder pressure due to the combustion of the fuel injected by the main fuel injection The first-order time differential maximum value dΔP / dtsub when the fuel injected by the auxiliary fuel injection burns, the first-order time differential maximum value dΔP / dtmain when the fuel injected by the main fuel injection burns, the auxiliary fuel injection The second-order time differential maximum value d ² ΔP / dt ² sub when the fuel injected by the fuel burns, the fuel injected by the main fuel injection burns The second-order time differential maximum value d ² ΔP / dt ² main when baked is derived.

  Next, the ECU 20 proceeds to S105 and calculates the combustion noise CN from the above equation (3) ′.

  Next, the ECU 20 proceeds to S106, and determines whether or not the combustion noise CN is larger than the upper limit value CNlimit. If an affirmative determination is made in S106, the ECU 20 proceeds to S107, and if a negative determination is made, the ECU 20 once ends the execution of this routine.

The ECU 20 having proceeded to S107 calculates the degree of correlation of the pressure component and the first-order time differential component of the increase amount of the in-cylinder pressure, the second-order time derivative component of the increase amount of the in-cylinder pressure, and the time component with respect to the combustion noise CN.

  Next, the ECU 20 proceeds to S108, and changes the fuel injection pattern by the fuel injection valve 10 so as to preferentially reduce the component having a higher degree of correlation with the combustion noise CN among the above components. Thereafter, the ECU 20 returns to S103.

  According to the control routine described above, the combustion noise CN can be efficiently reduced below the upper limit value CNlimit.

<Modification>
In addition, when the fuel injection in the internal combustion engine 1 is executed only by the main fuel injection, in the above formula (1) ′,
A ″ × log ₁₀ (Pmain) ^{n1 ″} + B ″ × log ₁₀ (ΔPmain) ^{n2 ″} as a pressure component,
C ″ × log ₁₀ (dP / dtmain) ^{n3 ″} is a first-order time differential component of the increase in the in-cylinder pressure,
D ″ × log ₁₀ [(dP ² / dt ² main) ^{n4 ″} is a second-order time differential component of the increase in the in-cylinder pressure,
Let E ″ × log ₁₀ (1 / Ne) be a time component,
The degree of correlation of each component with combustion noise is calculated.

  Also in this case, in the same manner as described above, in the combustion noise reduction control, the fuel injection pattern by the fuel injection valve 10 is controlled so as to preferentially reduce the component having a higher degree of correlation with the combustion noise. The

  In addition to the first-order time differential maximum value and the second-order time differential maximum value of the increase amount of the in-cylinder pressure, the maximum value of the third-order or higher higher-order time derivative of the increase amount of the in-cylinder pressure when the fuel burns is also used as an internal combustion parameter. When calculating the combustion noise in the engine 1, the degree of correlation of each component with respect to the combustion noise is calculated, including the higher-order time differential component of the amount of increase in the in-cylinder pressure.

For example, as described above, when the fuel injection is performed by the main fuel injection and one sub fuel injection, the third-order time differential maximum value of the increase amount of the in-cylinder pressure is also used as the parameter for calculating the combustion noise. In the case of the above formula (4),
G × log ₁₀ [(d ³ ΔP / dt ³ sub) ⁿ⁵ + (d ³ ΔP / dt ³ main) ⁿ⁵ ] is defined as the third-order time differential component of the increase in the in-cylinder pressure. And the correlation degree with respect to the combustion noise of each component including this third-order time differential component is calculated.

  In the combustion noise reduction control according to the present embodiment, when the time component is reduced, the engine speed Ne of the internal combustion engine 1 changes. This may affect the driving state of the vehicle on which the internal combustion engine 1 is mounted.

  Therefore, in the combustion noise reduction control, the time component may be removed from the above components, and the component having a higher degree of correlation with the combustion noise in the internal combustion engine 1 may be preferentially reduced. Thereby, combustion noise can be reduced efficiently while suppressing the influence on the driving | running state of the vehicle carrying the internal combustion engine 1. FIG.

The figure which shows schematic structure of the internal combustion engine which concerns on the Example of this invention, and its fuel system. (A) is a figure showing change of in-cylinder pressure. (B) is a figure which shows the change of the raise amount of the in-cylinder pressure by combustion of a fuel. (C) is a figure which shows the change of the first-order time differential value of the raise amount of in-cylinder pressure. (D) is a figure which shows the change of the 2nd-order time differential value of the raise amount of in-cylinder pressure. The figure which shows the relationship between the calculated value of the combustion noise calculated by Formula (3) 'which concerns on Example 1 of this invention, and the measured value of combustion noise. The figure which shows the relationship between sub fuel injection timing and the first-order time differential value of the raise amount of in-cylinder pressure. The figure which shows the relationship between the amount of sub fuel injections, and the first-order time differential value of the raise amount of cylinder pressure The flowchart which shows the control routine of the combustion noise reduction control which concerns on Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 10 ... Fuel injection valve 11 ... Fuel supply branch pipe 12 ... Common rail 13 ... Fuel supply pipe 14 ... Fuel tank 15 ... Fuel pump 20 ... ECU
21. ・ Pressure sensor 23 ・ ・ Crank position sensor

Claims (8)

In-cylinder pressure detecting means for detecting or estimating the in-cylinder pressure of the internal combustion engine,
at least,
The maximum value of the in-cylinder pressure during the compression stroke and the exhaust stroke;
The maximum amount of cylinder pressure rise due to fuel combustion,
The maximum value of the first-order time differential value of the amount of increase in the in-cylinder pressure when the fuel burns,
The maximum value of the second-order time differential value of the increase in the in-cylinder pressure when the fuel burns,
The time required for the compression and exhaust strokes;
A combustion noise calculation device for an internal combustion engine that calculates combustion noise in the internal combustion engine based on Let CN be the combustion noise in the internal combustion engine,
The maximum value of the in-cylinder pressure during the compression stroke and the exhaust stroke is Pmax,
ΔPmax is the maximum value of the cylinder pressure increase due to fuel combustion,
The maximum value of the first-order time differential value of the increase in the in-cylinder pressure when the fuel burns is defined as dΔP / dt,
D ² ΔP / dt ² is the maximum value of the second-order time differential value of the amount of increase in the in-cylinder pressure when the fuel burns,
When the engine speed of the internal combustion engine is Ne,
CN = A × log ₁₀ (Pmax) ⁿ¹ + B × log ₁₀ (ΔPmax) ⁿ² + C × log ₁₀ (dΔP / dt) ⁿ³ + D × log ₁₀ (d ² ΔP / dt ² ) ⁿ⁴ + E × log ₁₀ (1 / Ne) + F
(However, A and B, C, D, E, F, n1, n2, n3, and n4 are coefficients)
The combustion noise calculation apparatus for an internal combustion engine according to claim 1, wherein the combustion noise in the internal combustion engine is calculated from an expression expressed by:   When fuel injection is performed a plurality of times during one combustion cycle in the internal combustion engine, the maximum value of the first-order time differential value and the in-cylinder pressure when the fuel injected by each fuel injection burns The combustion noise calculation device for an internal combustion engine according to claim 1, wherein the combustion noise in the internal combustion engine is calculated based on each maximum value of the second-order time differential value of the amount of increase in the internal combustion engine. In the internal combustion engine, fuel injection is performed by main fuel injection and sub fuel injection that is executed at a time before the main fuel injection and the injected fuel is used for combustion,
Let CN be the combustion noise in the internal combustion engine,
Psub is the maximum value of the in-cylinder pressure when the fuel injected by the sub fuel injection burns,
Pmain is the maximum value of the in-cylinder pressure when the fuel injected by the main fuel injection burns,
ΔPsub is the maximum value of the increase in the in-cylinder pressure due to the combustion of the fuel injected by the auxiliary fuel injection,
ΔPmain is the maximum value of the cylinder pressure increase due to the combustion of the fuel injected by the main fuel injection,
DΔP / dtsub is the maximum value of the first-order time differential value of the amount of increase in the in-cylinder pressure when the fuel injected by the auxiliary fuel injection burns,
DΔP / dtmain is the maximum value of the first-order time differential value of the amount of increase in the in-cylinder pressure when the fuel injected by the main fuel injection burns,
D ² ΔP / dt ² sub is the maximum value of the second-order time differential value of the amount of increase in the in-cylinder pressure when the fuel injected by the auxiliary fuel injection burns,
D ² ΔP / dt ² main is the maximum second-order time differential value of the amount of increase in the in-cylinder pressure when the fuel injected by the main fuel injection burns,
When the engine speed of the internal combustion engine is Ne,
CN = A × log ₁₀ [(Psub) ⁿ¹ + (Pmain) ⁿ¹ ] + B × log ₁₀ [(ΔPsub)
^{n2 + (ΔPmain) n2] +} C × log 10 [(dΔP / dtsub) n3 + (dΔP / dt
main) ⁿ³ ] + D × log ₁₀ [(d ² ΔP / dt ² sub) ⁿ⁴ + (d ² ΔP / dt ² main) ⁿ⁴ ] + E × log ₁₀ (1 / Ne) + F
(However, A and B, C, D, E, F, n1, n2, n3, and n4 are coefficients)
4. The combustion noise calculation device for an internal combustion engine according to claim 3, wherein the combustion noise in the internal combustion engine is calculated from an expression expressed by:   4. The internal combustion engine according to claim 1, further comprising: calculating combustion noise in the internal combustion engine based on a maximum value of a third-order or higher order differential value of an increase in in-cylinder pressure when the fuel is combusted. Engine combustion noise calculation device. A combustion noise calculation device for an internal combustion engine according to claim 2,
A × log ₁₀ (Pmax) ⁿ¹ + B × log ₁₀ (ΔPmax) ⁿ² is a pressure component,
C × log ₁₀ (dΔP / dt) ⁿ³ is a first-order time derivative component of the increase in the in-cylinder pressure,
D × log ₁₀ (d ² ΔP / dt ² ) ⁿ⁴ is a second-order time derivative component of the increase in the in-cylinder pressure,
E × log ₁₀ (1 / Ne) is a time component,
Correlation degree calculating means for calculating a degree of correlation of each component with combustion noise in the internal combustion engine,
The first-order time derivative component of the pressure component and the increase amount of the in-cylinder pressure, the second-order time derivative component of the increase amount of the in-cylinder pressure, and the component having a higher degree of correlation with the combustion noise in the internal combustion engine are given priority. A combustion noise control system for an internal combustion engine, wherein the combustion noise calculated by the combustion noise detection device is controlled to a predetermined value or less by reducing the combustion noise to a predetermined value. A combustion noise calculation device for an internal combustion engine according to claim 4,
A × log ₁₀ [(Psub) ⁿ¹ + (Pmain) ⁿ¹ ] + B × log ₁₀ [(ΔPsub) ⁿ² + (ΔPmain) ⁿ² ] is a pressure component,
C × log ₁₀ [(dΔP / dtsub) ⁿ³ + (dΔP / dtmain) ⁿ³ ] as a first-order time derivative component of the increase in the in-cylinder pressure,
D × log ₁₀ [(d ² ΔP / dt ² sub) ⁿ⁴ + (d ² ΔP / dt ² main) ⁿ⁴ ] is a second-order time derivative component of the increase in the cylinder pressure,
E × log ₁₀ (1 / Ne) is a time component,
Correlation degree calculating means for calculating a correlation degree of each component with respect to combustion noise in the internal combustion engine,
The first-order time differential component of the pressure component and the increase amount of the in-cylinder pressure, the second-order time differential component of the increase amount of the in-cylinder pressure, and the component having a higher degree of correlation with the combustion noise in the internal combustion engine are given priority. A combustion noise control system for an internal combustion engine, wherein the combustion noise calculated by the combustion noise detection device is controlled to a predetermined value or less by reducing the noise to a minimum.   Combustion noise calculated by the combustion noise detection device is controlled to be equal to or less than the predetermined value by preferentially reducing, among the components excluding the time component, components having a higher degree of correlation with combustion noise in the internal combustion engine. 8. A combustion noise control system for an internal combustion engine according to claim 6 or 7, wherein:

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