JP2009013875A - Combustion noise control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform control which is not influenced by difference of devices, deterioration in an injection system, pressure pulsation, and the like so as to reduce combustion noise of an internal combustion engine. <P>SOLUTION: A representative value of the frequency of the combustion noise is obtained by computing the basic frequency of combustion noise of the current cylinder while taking a film vibration frequency of gas in a combustion chamber as basic frequency of combustion noise. The basic frequency of the combustion noise of a cylinder in a stable operating condition is computed as the target frequency of the combustion noise. One or more of pressure, density and specific heat of gas in a cylinder is changed so that the representative value of the frequency substantially agrees with the target value of the frequency. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a combustion noise control device for an internal combustion engine.

  When designing a control system, it is important to maintain the current system characteristics against uncertain fluctuations such as disturbances and design errors, that is, to ensure the robustness of the control system. .

  Conventionally, various means for reducing combustion noise of an internal combustion engine such as a diesel engine have been proposed. However, when controlling the fuel injection as in Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5, and Patent Document 6, because there are variations due to deterioration of the injection system and machine differences, It is difficult to perform stable control. Also, when controlling the ignition timing by changing the fuel injection interval, in the high-pressure injection system, the injection amount for the second and subsequent injections may deviate from the command due to the effect of pressure pulsation, and torque fluctuations may occur. There is. Therefore, highly robust control is required that is not affected by the deterioration of the injection system or variations due to machine differences, and that is not affected by pressure pulsation.

  In addition, the conventional combustion noise reduction means reduce the fuel injection pressure, increase the EGR rate, control the pilot injection, etc., control the ignition timing to reduce the combustion speed, and reduce the sound pressure level of the combustion noise Therefore, lowering the combustion speed inevitably deteriorates fuel consumption. However, it is possible to perform stable control by performing highly robust control, and to minimize deterioration in fuel consumption.

JP 2005-90280 A JP-A-9-22881 JP-A-8-334049 JP 2001-234800 A JP 2005-264814 A JP 2003-003883 A

  On the other hand, since the combustion sound of an internal combustion engine such as a diesel engine has a characteristic frequency component due to abrupt combustion, control of the combustion sound focusing on the frequency component has been proposed.

  In Patent Document 4, Patent Document 5, and Patent Document 6, control based on the frequency component of combustion sound is proposed, but the actual combustion sound of an internal combustion engine has a frequency shift for each cylinder. This frequency shift is considered to be caused by the above-described deterioration of the injection system, variation due to machine differences, pressure pulsation, and the like. Therefore, by controlling the frequency of the combustion sound of the internal combustion engine to approximately match the frequency of the combustion sound in a stable operating state obtained in advance through experiments or the like, variations in the injection system, variations due to machine differences, pressure pulsations It is considered that control with high robustness that is not affected by the above can be achieved, and combustion noise can be surely reduced.

  The combustion sound of an internal combustion engine includes various frequency components. By selecting a basic one frequency of the combustion sound and performing control to change the basic one frequency, various combustion sounds are generated. It is considered that the frequency component can also be changed.

  Therefore, the present invention considers the gas in the combustion chamber as a circular membrane, sets the frequency of the membrane vibration as the fundamental frequency of the combustion noise of the cylinder, and determines the membrane vibration in a stable operating state of the internal combustion engine obtained by experiments or the like. By making the frequency of the frequency the target value of the frequency, the frequency of the membrane vibration calculated from the current operating state of the cylinder is the representative value of the frequency of the combustion sound, and by matching the representative value of this frequency with the target value of the frequency, The purpose is to perform control with high robustness by making the various frequency components of the combustion sound substantially coincident and not being affected by the deterioration of the injection system, variations due to machine differences, pressure pulsation, and the like.

  According to the first aspect of the present invention, the frequency of the membrane vibration of the gas in the combustion chamber is set as the basic frequency of the combustion sound, the basic frequency of the combustion sound of the current cylinder is calculated, Calculate the basic frequency of the combustion sound of the cylinder in a stable operating state as the representative value of the frequency, and set it as the target value of the frequency of the combustion sound so that the representative value of the frequency substantially matches the target value of the frequency In addition, a combustion sound control device for an internal combustion engine is provided, wherein one or more of pressure, density, and specific heat of the gas in the cylinder are changed.

  That is, according to the first aspect of the present invention, the sound velocity of the gas is calculated from the pressure, density, and specific heat ratio of the gas in the cylinder, and the frequency of the gas membrane vibration is calculated from the sound velocity of the gas and the bore diameter of the cylinder. As a representative value of the frequency of combustion sound, on the other hand, the frequency of gas membrane vibration in a stable operating state is obtained in advance through experiments or the like, and this is used as the target value of frequency, and the representative value of frequency is used as the target value of frequency. Provided is a combustion sound control device having high robustness that is not affected by deterioration of an injection system, variation due to machine difference, pressure pulsation, or the like by performing control that substantially matches the value.

  According to the first aspect of the present invention, there is provided a combustion sound control device that is not affected by the deterioration of the injection system or variations due to machine differences, and that is not affected by pressure pulsation, and minimizes deterioration of fuel consumption. There is an effect that it can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a diagram illustrating a schematic configuration of an embodiment when the present invention is applied to a combustion noise control device for an internal combustion engine. In the present embodiment, the internal combustion engine 1 includes an intake throttle valve 41, a turbocharger 50. , A variable valve timing (VVT) mechanism 43, a fuel injection valve 44, an exhaust gas recirculation (EGR) valve 45, and the like. In the present embodiment, detection signals are taken into the combustion sound control device 10 from detection means such as the intake air temperature sensor 21, the intake pipe pressure sensor 22, the intake air amount sensor 23, and the internal combustion engine 1 is detected based on these detection signals. The pressure, density, and specific heat ratio of the gas in the cylinder are calculated, and the film vibration frequency of the gas in the cylinder is calculated from the pressure, density, and specific heat ratio to obtain a representative value of the frequency of combustion sound.

  The calculation of the representative value of the frequency of the combustion noise is performed at the timing at which the intake valve changes from open to closed for each cylinder (see FIG. 2). Therefore, the intake temperature sensor 21, the intake pipe pressure sensor 22, and the intake air amount sensor 23 are only installed one by one in the common mother pipe connected to the plurality of cylinders, and the representative values of the frequency of the combustion noise in each cylinder. Can be calculated.

  Further, the combustion sound control device 10 obtains the relationship between the frequency of the membrane vibration of the gas in the combustion chamber, the rotation speed, and the torque in a stable operation state where the combustion sound is small, and is provided as a map. Yes. Therefore, for each cylinder, a calculation for obtaining the target value of the frequency from the map is performed using the rotation speed and torque detection signal at the moment when the intake valve changes from open to closed.

  Next, the combustion sound control device 10 calculates an operation amount for changing one or more of the pressure, density, and specific heat of the gas so that the representative value of the frequency substantially matches the target value of the frequency. One or more of the intake throttle valve 41, the variable nozzle 42 of the exhaust turbine of the turbocharger 50, the variable valve timing (VVT) mechanism 43, the fuel injection valve 44, and the exhaust gas recirculation (EGR) valve 45 are operated based on the amount. Generate an operation signal.

  As described above, various frequency components of the combustion sound of the internal combustion engine can be changed by performing an operation to make the representative value of the frequency substantially coincide with the target value of the frequency. Control that is not affected by pulsation or the like can be performed, and a stable operation state with a low combustion noise obtained by experiments can be obtained.

ここで、
Ｆ：周波数の代表値（ｓ^-1）
ｃ：気体の音速（ｍ/ｓ）
Ｌ：代表長さ＝気筒のボア径（ｍ）
また、気体の音速は、以下の式で求める。

ここで、
ｐ（Ｎ/ｍ²）：気体の圧力
ρ（ｋｇ/ｍ³）：気体の密度
κ：気体の比熱比 FIG. 2 is a flowchart for explaining a schematic configuration of an embodiment of calculation in the control unit when the present invention is applied to a combustion sound control device for an internal combustion engine. The representative value of the frequency is obtained by the following equation, considering the vibration of the combustion gas in the combustion chamber as a circular membrane vibration.

here,
F: representative value of the frequency (s ^-1)
c: Gas sound velocity (m / s)
L: Representative length = bore diameter of cylinder (m)
Moreover, the sound speed of gas is calculated | required with the following formula | equation.

here,
p (N / m ² ): gas pressure ρ (kg / m ³ ): gas density κ: specific heat ratio of gas

  In the above, the specific heat ratio of the gas is obtained by calculating the specific heat from the EGR gas amount. Further, the EGR gas amount is calculated by calculating the EGR rate from the air amount sensor 23 and the intake pipe pressure sensor 22, and calculating the internal EGR amount based on the valve timing and lift of the VVT mechanism 43, and the EGR gas into the cylinder. It is obtained by calculating the quantity.

  The target value of the frequency is the frequency of the membrane vibration of the combustion chamber gas in a stable operating state, and is a target value for changing the representative value of the above-mentioned frequency to a stable operating state with low combustion noise. A map is created as a function of engine speed and torque by an engine operation test, and obtained from the current engine speed and torque.

  Next, the difference dF between the target frequency value and the representative frequency value is calculated.

  The operation amount that gives this difference dF is obtained in advance for an operation for changing the pressure of the gas, an operation for changing the density of the gas, and an operation for changing the specific heat ratio of the gas by an operation test of the engine. Each manipulated variable is calculated for dF obtained by the above calculation.

  That is, the gas pressure is changed by manipulating the amount of air when the intake pipe is closed. In order to change the gas pressure, the opening degree of the throttle valve 41 and the opening degree of the EGR valve 45 are manipulated. The operation of the residual gas amount (pressure) by the variable nozzle 42 of the turbocharger 50, the operation of the valve timing / lift amount of the VVT mechanism 43, and the like are performed.

  The gas density depends on the composition or temperature of the suction gas. In order to change the gas density, the operation of the EGR rate, that is, the operation of the opening of the EGR valve 45, the operation of the intercooler temperature, the EGR cooler temperature or the bypass is performed. The operation of the amount, the operation of the residual gas amount by the variable nozzle 42 of the turbocharger 50, the operation of the residual gas amount by the VVT mechanism 43, and the like are performed.

  The specific heat ratio of the gas depends on the composition of the suction gas. In order to change the specific heat ratio of the gas, the opening degree of the EGR valve 45, the operation of the residual gas amount by the variable nozzle 42 of the turbocharger 50, the VVT mechanism The operation of the residual gas amount by 43 is performed.

  In the illustration of FIG. 2, for example, when dF is negative, the representative value of the current frequency is larger than the target value of the frequency, so it is necessary to lower the sound speed in order to match the target value of the frequency. Therefore, in this case, the EGR valve 45 is opened to reduce the specific heat ratio.

It is a figure explaining schematic structure of an embodiment at the time of applying the present invention to a combustion sound control device of an internal-combustion engine. It is a flowchart explaining the schematic structure of embodiment of the calculation in a control unit at the time of applying this invention to the combustion sound control apparatus of an internal combustion engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Diesel engine 3 Intake pipe 10 Combustion sound control apparatus 21 Intake temperature sensor 22 Intake pipe pressure sensor 23 Air quantity sensor 24 VVT mechanism cam angle sensor 25 Accelerator opening sensor 26 Rotation speed sensor 31 Throttle valve operation signal 32 Variable nozzle operation signal 33 VVT mechanism operation signal 34 Fuel injection valve operation signal 35 EGR valve operation signal 41 Throttle valve 42 Variable nozzle of turbocharger exhaust turbine 43 VVT mechanism 44 Fuel injection valve 45 EGR valve 50 Turbocharger

Claims (1)

The frequency of the membrane vibration of the gas in the combustion chamber is the fundamental frequency of the combustion sound,
Calculate the basic frequency of the combustion noise of the current cylinder and use it as a representative value of the combustion noise frequency.
Calculate the basic frequency of the combustion noise of the cylinder in a stable operating state, and set it as the target value of the frequency of the combustion noise.
One or more of the pressure, density, and specific heat of the gas in the cylinder are changed so that the representative value of the frequency substantially coincides with the target value of the frequency. .

Images