JP2009264237A - Exhaust reflux rate measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust reflux rate measuring device capable of accurately obtaining a rate of reflux exhaust contained in mixed gas of fresh charge and the reflux exhaust sucked in by an internal combustion engine provided with an exhaust reflux passage, in other words, an exhaust reflux rate. <P>SOLUTION: A water vapor concentration MCW in the fresh charge is calculated based on a fresh charge humidity Ha1 to be detected and a fresh charge temperature Ta1 and a sonic speed Va2 of the fresh charge at a temperature Tin is calculated based on the water vapor concentration MCW and the temperature Tin of the mixed gas of the fresh air and the reflux exhaust (S12-S16). A sonic speed Vf of the reflux exhaust at the temperature Tin is calculated corresponding to the water vapor concentration MCW, a rate of gas component contained in the reflux exhaust and the temperature Tin (S17, S18). An exhaust reflux rate REGR is calculated by using a sonic speed Vin of the mixed gas detected by an ultrasonic sensor, a sonic speed Va2 of the fresh charge and the sonic speed Vf of the reflux exhaust (S19). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust gas recirculation rate measuring device that measures an exhaust gas recirculation rate in an internal combustion engine having an exhaust gas recirculation passage.

  Patent Document 1 discloses a gas concentration sensor that measures the concentration of a specific component in the intake air of an internal combustion engine. This gas concentration sensor detects the concentration of a specific component based on the propagation time required for ultrasonic waves to propagate a certain distance in the gas to be measured (measuring gas), in other words, based on the sound velocity of the gas to be measured. It is.

JP 2000-241399 A

  The gas sucked into the internal combustion engine contains other components (steam, exhaust gas to be recirculated) other than a specific component (evaporated fuel) whose concentration is to be measured. Also affected by other ingredients. Therefore, when the concentrations of other components change, the relationship between the sound velocity of the gas to be measured and the concentration of the specific component also changes, and the measurement accuracy of the specific component concentration decreases. The fresh air sucked into the internal combustion engine contains a lot of water vapor, and the recirculated exhaust gas recirculated from the exhaust system also contains water vapor generated by combustion.

  Patent Document 1 shows an example in which the gas concentration sensor is applied to the measurement of the concentration of the evaporated fuel supplied to the intake passage and the example of measuring the concentration of the water vapor. Focusing on the relationship (the ratio of both in the gas to be measured), no method for measuring the exact fuel vapor concentration is shown. Therefore, the gas concentration sensor disclosed in Patent Document 1 and the gas concentration measurement method using the sensor are directly applied to the measurement of the exhaust gas recirculation rate, which is the ratio of the recirculated exhaust gas in the mixed gas of fresh air and recirculated exhaust gas. It is not possible.

  The present invention has been made in consideration of the above-described points, and accurately determines the ratio of the recirculated exhaust gas contained in the mixed gas of fresh air and recirculated exhaust gas that is sucked into the internal combustion engine having the exhaust recirculation passage, that is, the exhaust gas recirculation rate. An object of the present invention is to provide an exhaust gas recirculation rate measuring device that can be obtained well.

  In order to achieve the above object, the invention according to claim 1 is an exhaust gas recirculation that is a ratio of the recirculated exhaust gas contained in a mixed gas of fresh air and recirculated exhaust gas that is sucked into an internal combustion engine having an exhaust gas recirculation passage (7). An exhaust gas recirculation rate measuring device for measuring a rate (REGR), a first sonic speed acquisition means for determining a sound speed (Va2) of the fresh air, a second sonic speed acquisition means for determining a sound speed (Vf) of the recirculated exhaust gas, The exhaust gas recirculation is based on a third acoustic velocity acquisition means for obtaining the acoustic velocity (Vin) of the mixed gas, the acoustic velocity (Va2) of the fresh air, the acoustic velocity (Vf) of the reflux exhaust, and the acoustic velocity (Vin) of the mixed gas. An exhaust gas recirculation rate calculating means for calculating a rate (REGR) is provided.

  The invention according to claim 2 is the exhaust gas recirculation rate measuring device according to claim 1, wherein the mixed gas temperature detecting means (14) for detecting the temperature (Tin) of the mixed gas, and the water vapor concentration in the fresh air Water vapor concentration acquisition means for acquiring (MCW), the first sonic speed acquisition means based on the temperature (Tin) of the mixed gas and the water vapor concentration (MCW) in the fresh air. The speed of sound (Va2) is calculated.

  According to a third aspect of the present invention, in the exhaust gas recirculation rate measuring device according to the first or second aspect, a mixed gas temperature detecting means (14) for detecting a temperature (Tin) of the mixed gas; Water vapor concentration acquisition means for acquiring water vapor concentration (MCW), and water vapor concentration estimation means for estimating the water vapor concentration (n (5) +0.944) in the recirculated exhaust based on the water vapor concentration (MCW) in the fresh air And the second sonic velocity acquisition means is configured to calculate the sonic velocity (Vf) of the recirculated exhaust gas based on the temperature (Tin) of the mixed gas and the water vapor concentration (n (5) +0.944) in the recirculated exhaust gas. Is calculated.

  According to a fourth aspect of the present invention, in the exhaust gas recirculation rate measuring apparatus according to the second or third aspect, the water vapor concentration acquisition means detects a fresh air temperature detection means (12) for detecting the fresh air temperature (Ta1). And fresh air humidity detecting means (11) for detecting the fresh air humidity (Ha1), and based on the detected fresh air temperature (Ta1) and fresh air humidity (Ha1), water vapor in the fresh air The concentration (MCW) is calculated.

  According to a fifth aspect of the present invention, in the exhaust gas recirculation rate measuring device according to any one of the first to fourth aspects, the third sonic velocity acquisition means includes an ultrasonic transmission means for transmitting ultrasonic waves, and the mixing Ultrasonic wave receiving means for receiving the ultrasonic wave via a gas, and obtaining a sound velocity (Vin) of the mixed gas based on a propagation time (TL) from the transmission time point to the reception time point of the ultrasonic wave It is characterized by.

  According to the first aspect of the present invention, the sound speed of the fresh air, the sound speed of the recirculated exhaust gas, and the sound speed of the mixed gas of the fresh air and the recirculated exhaust gas are obtained, and the exhaust gas recirculation rate is calculated based on these sound speeds. The speed of sound of the mixed gas sucked into the engine changes depending on the speed of sound of fresh air and recirculated exhaust, which are components of the mixed gas, and the ratio of fresh air and recirculated exhaust. Therefore, the exhaust gas recirculation rate, which is the ratio of the recirculated exhaust gas contained in the mixed gas, can be accurately calculated by using the sound speeds of the mixed gas, fresh air, and recirculated exhaust gas.

  According to the invention described in claim 2, the water vapor concentration in the fresh air is acquired, and the sound speed of the fresh air is calculated based on the temperature of the mixed gas and the water vapor concentration in the fresh air. Since the sound speed of fresh air varies depending on the water vapor concentration and temperature, calculating the sound speed of fresh air based on the temperature of the mixed gas and the water vapor concentration in the fresh air allows the new air in the state mixed with the recirculated exhaust gas. Qi sound speed can be calculated accurately. In addition, it is not necessary to use an ultrasonic sensor to obtain the fresh sound speed, and the cost can be reduced.

  According to the third aspect of the present invention, the water vapor concentration in the recirculated exhaust gas is estimated based on the water vapor concentration in the fresh air, and the sound velocity of the recirculated exhaust gas is determined based on the temperature of the mixed gas and the water vapor concentration in the recirculated exhaust gas. Is calculated. Of the components contained in the recirculated exhaust, the proportion of components other than water vapor can be calculated on the premise of complete combustion of standard fuel, but the water vapor proportion depends on the water vapor concentration in the fresh air. Change. Therefore, by using the water vapor concentration in the recirculated exhaust estimated based on the water vapor concentration in the fresh air and the temperature of the mixed gas, the sound velocity of the recirculated exhaust in a state mixed with the fresh air is accurately calculated. be able to. Further, it is not necessary to use an ultrasonic sensor for obtaining the sound velocity of the recirculated exhaust gas, and the cost can be reduced.

  According to the fourth aspect of the present invention, the water vapor concentration in the fresh air is calculated based on the detected fresh air temperature and fresh air humidity. Since the saturated water vapor pressure in the air can be calculated from the fresh air temperature by using the Tetens equation, an accurate water vapor concentration can be obtained from the saturated water vapor pressure and the detected humidity.

  According to the fifth aspect of the present invention, the sound velocity of the mixed gas can be calculated with high accuracy based on the propagation time from the transmission time point of ultrasonic waves to the reception time point.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an internal combustion engine and a control device thereof according to an embodiment of the present invention. An internal combustion engine (hereinafter simply referred to as “engine”) 1 has, for example, four cylinders, and a throttle valve 3 is disposed in the middle of an intake pipe 2 of the engine 1.

  A fuel injection valve 6 is provided for each cylinder slightly upstream of an intake valve (not shown). Each injection valve is connected to a fuel pump (not shown) and electrically connected to an electronic control unit (hereinafter referred to as “ECU”) 5. The valve opening time of the fuel injection valve 6 is controlled by a signal from the ECU 5.

  An exhaust gas recirculation passage 7 is provided between the exhaust pipe 4 of the engine 1 and the throttle valve downstream side of the intake pipe 2, and an exhaust gas recirculation control valve (hereinafter “ EGR valve ") 8 is provided. The EGR valve 8 is connected to the ECU 5, and the valve opening degree of the EGR valve 8 is controlled by the ECU 5.

  On the upstream side of the throttle valve 3 of the intake pipe 2, a humidity sensor 11 for detecting the fresh air humidity Ha1 sucked into the engine 1 and a fresh air temperature sensor 12 for detecting the fresh air temperature Ta1 are provided. Further, on the downstream side of the connection portion between the intake pipe 2 and the exhaust gas recirculation passage 7, an ultrasonic sensor 13 for detecting the sonic velocity Vin of the mixed gas of fresh air and the recirculated exhaust gas, and a mixed gas temperature for detecting the temperature Tin of the mixed gas A sensor 14 is provided. Detection signals from these sensors 11 to 14 are supplied to the ECU 5. Further, an atmospheric pressure sensor 15 for detecting the atmospheric pressure PA is connected to the ECU 5, and the detection signal is supplied to the ECU 5.

  The ECU 5 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, etc., and a central processing circuit (hereinafter “CPU”). A storage circuit for storing various calculation programs executed by the CPU and calculation results, an output circuit for supplying drive signals to the EGR valve 8 and the fuel injection valve 6, and the like. The ECU 5 controls the valve opening time of the fuel injection valve 6 and the opening degree control (EGR flow rate control) of the EGR valve 8 and calculates the exhaust gas recirculation rate REGR based on detection signals from various sensors.

  In the present embodiment, the exhaust gas recirculation rate measuring device is configured by the sensors 11 to 15 and the ECU 5.

  FIG. 2 is a diagram for explaining an outline of a method for calculating the exhaust gas recirculation rate REGR in the present embodiment. The fresh air GA is mixed with the recirculated exhaust gas GEGR to generate a mixed gas GMX. Fuel is injected into the mixed gas GMX by the fuel injection valve 6 and supplied to the combustion chamber 1a as a fuel-air mixture. That is, in this specification, the “mixed gas” is a gas in which fresh air and recirculated exhaust gas are mixed, and means a gas before fuel is injected (mixed).

  From the combustion chamber 1a, the gas (burned gas) after the fuel-air mixture burns is discharged as the feed gas GF. A part of the feed gas GF is recirculated to the intake pipe 2 through the exhaust gas recirculation passage 7 as recirculation exhaust gas GEGR.

  In the present embodiment, the sound speed of the fresh gas GA (sound propagation speed in fresh air) Va2, the sound speed Vf of the recirculated exhaust gas GEGR, and the sound speed Vin of the mixed gas GMX detected by the ultrasonic sensor 13 at the mixed gas temperature Tin. Using this, the exhaust gas recirculation rate REGR is calculated. The sonic speed Va2 of the fresh air is calculated according to the detected fresh air humidity Ha1, the fresh air temperature Ta1, and the mixed gas temperature Tin, and the sonic speed Vf of the recirculated exhaust gas is a ratio of components contained in the feed gas (recirculated exhaust gas). And is calculated according to the mixed gas temperature Tin.

FIG. 3 is a flowchart of a process for calculating the exhaust gas recirculation rate REGR, and this process is executed by the CPU of the ECU 5 every predetermined time.
In step S11, the fresh air temperature Ta1, the fresh air humidity Ha1, the mixed gas temperature Tin, the mixed gas sound velocity Vin, and the atmospheric pressure PA detected by the sensor are read. In step S12, the fresh air temperature Ta1 [° C.] is applied to the following equation (1) to calculate the saturated water vapor pressure Esat [hPa] in the air (standard atmospheric pressure) at the temperature Ta1. Equation (1) is well known as the Tetens equation.

In step S13, the saturated water vapor pressure Estat calculated in step S12 and the detected fresh air humidity Ha1 [%] are applied to the following equation (2) to calculate the fresh water vapor pressure PW.
PW = East × Ha1 / 100 (2)

In step S14, the water vapor pressure PW and the atmospheric pressure PA are applied to the following equation (3) to calculate the water vapor molar concentration MCW in fresh air, and the water vapor molar concentration MCW [%] is applied to the following equation (4). Then, the molar concentration MCA [%] of dry air (air with 0% humidity) in fresh air is calculated.
MCW = (PW / PA) × 100 (3)
MCA = 100-MCW (4)

In step S15, the mixed gas temperature Tin [° C.] is applied to the following formulas (5) and (6), the sound velocity VW [m / s] of the water vapor in the fresh air and the sound velocity of the dry air in the fresh air at the temperature Tin. VA [m / s] is calculated. ΚW and MW in formula (5) are the specific heat ratio and molecular weight of water vapor, respectively, and κA and MA in formula (6) are the specific heat ratio and equivalent molecular weight of dry air (molecular weight and components of dry air, respectively). Calculated from the molar ratio of Moreover, R of Formula (5) and (6) is a gas constant.

In step S16, the molar concentrations MCW and MCA calculated in step S14 and the sound speeds VW and VA calculated in step S15 are applied to the following equation (7) to calculate the fresh sound speed Va2 at the temperature Tin.
Va2 = (VW × MCW + VA × MCA) / 100 (7)

  In step S17, the component ratio of the feed gas, that is, the molar ratio of each component contained in the feed gas is calculated according to the molar concentrations MCW and MCA. Hereinafter, this calculation method will be described in detail.

First, at a temperature of 20 ° C. and a humidity of 30%, the fuel burned in air containing nitrogen (N ₂ ), oxygen (O ₂ ), argon (Ar), carbon dioxide (CO ₂ ), and water vapor (H ₂ O) as components. A standard gasoline composition formula that _sometimes gives a stoichiometric air-fuel ratio of 14.7 is CH _1.888 . The reaction formula of combustion of this gasoline CH _1.888 is given by the following formula (8).
CH _1.888 + 1.472 O ₂ → CO ₂ + 0.944H ₂ O (8)

The molar ratio parameters indicating the molar ratios of nitrogen, oxygen, argon, carbon dioxide, and water vapor constituting the air are n (1), n (2), n (3), n (4), and n (5), respectively. When the gasoline CH _1.888 is burned, the reaction formula is given by the following formula (9).

n (1) N ₂ + n (2) O ₂ + n (3) Ar + n (4) CO ₂ + n (5) H ₂ O + CH _1.888
→ n (1) N ₂ + n (3) Ar + (n (4) +1) CO ₂ + (n (5) +0.944) H ₂ O
(9)
Here, the molar ratio of the components constituting the dry air is approximately represented by the following formula (10).
N ₂ : O ₂ : Ar: CO ₂ = 78.06: 21: 0.9: 0.04 (10)

If the water vapor molar concentration CMW [%] in the air is known, the coefficient a indicating the dry air concentration CMA is calculated by the following equation (11), and the water vapor is determined using the relationship between the coefficient a and the equation (10). The molar ratio of the component which comprises the air to contain is given by following formula (12).
a = (100-MCW) / 100 = MCA / 100 (11)
N ₂ : O ₂ : Ar: CO ₂ : H ₂ O
= 78.06a: 21a: 0.9a: 0.04a: MCW (12)

Here, paying attention to the oxygen coefficient 1.472 of the equation (8) indicating the combustion reaction, and multiplying (1.472 / 21a) so that “21a” of the equation (12) becomes 1.472, Equation (13) is obtained.
N ₂ : O ₂ : Ar: CO ₂ : H ₂ O
= 5.472: 1.472: 0.063: 0.003: 7.01MCW / MCA (13)

Therefore, the molar ratio parameters n (1) to n (4) included in the equation (9) are as follows, and n (5) is given by the following equation (14).
n (1) = 5.472, n (2) = 1.472, n (3) = 0.063, n (4) = 0.003
n (5) = 7.01 × MCW / MCA (14)

  In step S18 of FIG. 3, using the mixed gas temperature Tin, the sound velocities V (1), V (3), and V (4) of nitrogen, argon, carbon dioxide, and water vapor, which are components of the feed gas (reflux exhaust). , And V (5). The sound velocity V (5) of water vapor is the sound velocity VW calculated in step S15. The sound velocities V (1), V (3), and V (4) are calculated by applying specific heat ratios κ and molecular weights M in Equation (5) corresponding to the respective components.

Then, the molar ratio parameters n (1), n (3) to n (5) and the sonic velocities V (1), V (3) to V (5) are applied to the following equation (15) to return the exhaust gas (feed gas). ) Is calculated.

In step S19, the sound speed Va2 of fresh air calculated in step S16, the sound speed Vf of the recirculated exhaust gas calculated in step S18, and the sound speed Vin of the detected mixed gas are applied to the following equation (16), and the exhaust gas recirculation rate REGR is calculated. calculate.

Equation (16) is derived as follows. Assuming that the molar ratio between the fresh air and the recirculated exhaust gas in the mixed gas is x: y, the sound velocity Vin of the mixed gas is given by the following equation (17), and the exhaust gas recirculation rate REGR is given by the following equation (18). From these equations (17) and (18), equation (16) is obtained.
Vin = (Va2 × x + Vf × y) / (x + y) (17)
REGR = y / (x + y) (18)

  In the present embodiment, the EGR valve 8 of the EGR valve 8 is adjusted so that the exhaust gas recirculation rate REGR calculated by the processing of FIG. 3 matches the target exhaust gas recirculation rate REGRT set according to the engine operating state (engine load and engine speed). Opening control is performed.

  Next, the configuration of the ultrasonic sensor 13 and the sound speed detection method will be described. FIG. 4 is a block diagram showing the configuration of the ultrasonic sensor 13. The ultrasonic sensor 13 includes a signal generator 21, a transmitter 22, a receiver 23, an amplifier 24, a rectifier 25, and a low pass. Filters (LPF) 26 and 29, a trigger signal generation unit 27, and an FV conversion unit 28 are provided. The transmitter 22 and the receiver 23 are attached to the inner wall of the intake pipe 2 at positions facing each other.

  The signal generator 21 generates burst-like transmission signals ST (ST1, ST2, ST3,...) Shown in FIG. 5A in response to the trigger signal STG shown in FIG. The transmission unit 22 converts the transmission signal ST into a sound wave and outputs it. The receiving unit 23 is provided at a distance L from the transmitting unit 22, and converts the transmitted sound wave into received signals SR (SR1, SR2, SR3,...) Shown in FIG. Reception signals SR1, SR2, and SR3 correspond to transmission signals ST1, ST2, and ST3, respectively. That is, the transmission signal ST is received by the receiving unit 23 with a delay of the propagation time TL required for the sound wave to propagate through the distance L.

  The amplification unit 24 amplifies the reception signal SR, and the rectification unit 25 performs full-wave rectification on the reception signal SR. The LPF 26 removes the high frequency component of the reception signal subjected to full-wave rectification, and outputs a detection signal SRF shown in FIG. The trigger signal generation unit 27 binarizes the detection signal SRF with the threshold value VTH to generate a trigger signal STG. This trigger signal STG is supplied to the signal generator 21 and also to the FV converter 28.

  The FV converter 28 converts the frequency FT of the trigger signal STG into a voltage proportional to the frequency FT and outputs the voltage. The LPF 29 removes the high frequency component of the signal output from the FV conversion unit 28 and outputs a frequency signal VFT indicating the frequency FT.

  The propagation time TL is obtained as the reciprocal of the frequency FT, and the sound velocity Vin of the mixed gas is (L / TL) and is proportional to the frequency signal VFT. Therefore, the sound speed Vin can be obtained by multiplying the frequency signal VFT by an appropriate coefficient. At this time, by correcting so that the propagation time TL does not include a delay time associated with signal processing, an accurate sound speed Vin can be obtained.

  As described above, in this embodiment, the sonic velocity Va2 of fresh air and the sonic velocity Vf of recirculated exhaust gas are calculated, and the sonic velocity Vin of the mixed gas of fresh air and recirculated exhaust gas is detected, and the exhaust gas recirculation rate is based on these sound velocities. REGR is calculated. The sonic speed Vin of the mixed gas changes depending on the sonic velocities Va2 and Vf of the fresh air and the recirculated exhaust, and the ratio of the fresh air and the recirculated exhaust (that is, the exhaust recirculation rate). Therefore, the exhaust gas recirculation ratio REGR, which is the ratio of the recirculated exhaust gas contained in the mixed gas, can be accurately calculated by using the sonic velocities Vin, Va2, Vf of the mixed gas, fresh air, and recirculated exhaust gas.

  Further, the water vapor concentration CMW in the fresh air is calculated according to the fresh air temperature Ta1 and the fresh air humidity Ha1, and the sound velocity Va2 of the fresh air is calculated based on the temperature Tin of the mixed gas and the water vapor concentration CMW in the fresh air. Is done. Since the sound speed of fresh air varies depending on the water vapor concentration and temperature, calculating the sound speed of fresh air based on the temperature of the mixed gas and the water vapor concentration in the fresh air allows the new air in the state mixed with the recirculated exhaust gas. Qi sound velocity Va2 can be accurately calculated. Further, it is not necessary to use an ultrasonic sensor to obtain the fresh sound speed Va2, and the cost can be reduced.

Further, a molar ratio parameter (n (5) +0.944) indicating the water vapor concentration in the recirculated exhaust gas is calculated based on the water vapor concentration CMW in the fresh air, and each component in the recirculated exhaust gas is determined according to the temperature Tin of the mixed gas. The sound speeds V (1) to V (5) are calculated. Then, using the sound speeds V (1) to V (5) and the molar ratio parameter (n (5) +0.944), the sound speed Vf of the recirculated exhaust gas is calculated by the equation (15). Among the components contained in the reflux exhaust, the molar ratio parameters n (1), n (3), and (n (4) +1) of components other than water vapor are the standard ratio of air components and standard fuel. Although it can be calculated by assuming a combustion formula (8) of a certain gasoline CH _1.888 , the ratio of water vapor changes depending on the water vapor concentration in fresh air. Therefore, by using the molar ratio parameter (n (5) +0.944) indicating the water vapor concentration in the recirculated exhaust estimated based on the water vapor concentration MCW in the fresh air and the mixed gas temperature Tin, The sound velocity Vf of the recirculated exhaust gas in the mixed state can be accurately calculated. Further, it is not necessary to use an ultrasonic sensor for obtaining the sound velocity Vf of the recirculated exhaust gas, and the cost can be reduced.

  Further, the water vapor concentration CMW in the fresh air is calculated from the saturated water vapor pressure Estat in the air and the detected fresh air humidity Ha1. The saturated water vapor pressure Esat can be calculated from the fresh air temperature Ta1 by using the Tetens equation (equation (1)), so that an accurate water vapor concentration can be obtained.

  Further, by using the ultrasonic sensor 13, the sound velocity Vin of the mixed gas can be accurately calculated based on the propagation time TL from the ultrasonic transmission time to the reception time.

  In the present embodiment, the humidity sensor 11 corresponds to fresh air humidity detection means, the fresh air temperature sensor 12 corresponds to fresh air temperature detection means, and the mixed gas temperature sensor 14 corresponds to mixed gas temperature detection means. Further, the humidity sensor 11, the fresh air temperature sensor 12, the mixed gas temperature sensor 14 and the ECU 5 constitute first sonic velocity acquisition means and second sonic velocity acquisition means, the ultrasonic sensor 13 constitutes third sonic velocity acquisition means, and the ECU 5 An exhaust gas recirculation rate calculating means and a water vapor concentration estimating means are configured. Further, the humidity sensor 11, the fresh air temperature sensor 12, and the ECU 5 constitute a water vapor concentration acquisition means. More specifically, steps S11 to S16 in FIG. 3 correspond to the first sound speed acquisition means, steps S11 to S14, S17, and S18 correspond to the second sound speed acquisition means, and step S19 corresponds to the exhaust gas recirculation rate calculation means. Steps S11 to S14 correspond to the water vapor concentration acquisition means, and step S17 corresponds to the water vapor concentration estimation means. Further, the signal generation unit 21 and the transmission unit 22 in FIG. 4 correspond to an ultrasonic transmission unit, and the reception unit 23 corresponds to an ultrasonic reception unit.

The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the process of FIG. 3, the fresh sound velocity Va2 at the temperature Tin is calculated by the calculation of steps S12 to S16. However, as shown in FIG. 6, the sound velocity Va1 is calculated from the air temperature Ta1 and the humidity Ha1. A map to be used is prepared in advance, and the sound velocity Va1 is calculated from the detected temperature Ta1 and humidity Ha1 using this map, and the sound velocity Va1 at the temperature Ta1 is converted to the sound velocity Va2 at the temperature Tin by the following equation (20). You may do it.

The calculation formula for the sound speed may be an approximate expression known for each component, such as the following expressions (21) to (24). The unit of the calculated sound speed is [m / s].
V (1) = 337 + 0.85Tin (21)
V (3) = 319 + 0.57Tin (22)
V (4) = 258 + 0.87Tin (23)
V (5) = 404.8 + 0.68Tin (24)

  Further, an ultrasonic sensor may be provided on the downstream side of the throttle valve 3 in the intake pipe 2 to detect the sonic speed Va1 at the fresh air temperature Ta1 and convert the sonic speed Va1 into the sonic speed Va2 at the temperature Tin. The sound velocity Vf of the recirculated exhaust gas can be obtained similarly. For example, an ultrasonic sensor and a temperature sensor may be provided in the exhaust gas recirculation passage 7 to detect the sonic velocity Vf1 and the recirculated exhaust gas temperature TEGR, and the detected sonic velocity Vf1 may be converted into the sonic velocity Vf at the temperature Tin.

  Further, as described in Patent Document 1, since the water vapor concentration in the gas to be measured can be detected using an ultrasonic sensor, an ultrasonic sensor provided on the downstream side of the throttle valve 3 of the intake pipe 2 is used. You may make it detect the water vapor | steam density | concentration in fresh air. Further, the water vapor concentration in the recirculated exhaust gas may be detected by an ultrasonic sensor provided in the exhaust recirculation passage 7.

  In the embodiment described above, the atmospheric pressure PA is detected and applied to the equation (3). However, the PA of the equation (3) may be set to an average atmospheric pressure, for example, “101.3 kPa”.

  The present invention is applicable not only to gasoline internal combustion engines but also to diesel internal combustion engines. Furthermore, the present invention can also be applied to the control of a marine vessel propulsion engine such as an outboard motor having a vertical crankshaft.

It is a figure which shows the structure of the internal combustion engine and its control apparatus concerning one Embodiment of this invention. It is a figure for demonstrating the calculation method of an exhaust gas recirculation rate. It is a flowchart of the process which calculates an exhaust gas recirculation rate. It is a block diagram which shows the structure of an ultrasonic sensor. It is a wave form diagram for demonstrating operation | movement of an ultrasonic sensor. It is a figure which shows the map for calculating a sound speed from humidity and temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Intake pipe 4 Exhaust pipe 5 Electronic control unit (1st sound speed acquisition means, 2nd sound speed acquisition means, exhaust gas recirculation rate calculation means, water vapor concentration acquisition means, water vapor concentration estimation means)
6 Exhaust gas recirculation passage 11 Humidity sensor (fresh air humidity detection means)
12 Fresh air temperature sensor (new air temperature detection means)
13 Ultrasonic sensor (third sound speed acquisition means)
14 Mixed gas temperature sensor (mixed gas temperature detection means)
21 Signal generator (ultrasonic transmission means)
22 Transmitter (Ultrasonic Transmitter)
23 Receiver (Ultrasonic Receiver)

Claims (5)

An exhaust gas recirculation rate measuring device that measures an exhaust gas recirculation rate that is a ratio of the recirculated exhaust gas contained in a mixed gas of fresh air and recirculated exhaust gas that is sucked into an internal combustion engine having an exhaust gas recirculation passage,
First sound speed obtaining means for obtaining the fresh sound speed;
Second sonic velocity acquisition means for determining the sonic velocity of the reflux exhaust;
Third sound speed acquisition means for determining the sound speed of the mixed gas;
An exhaust gas recirculation rate measuring device comprising exhaust gas recirculation rate calculating means for calculating the exhaust gas recirculation rate based on a sound speed of the fresh air, a sound speed of the recirculated exhaust gas, and a sound speed of the mixed gas. Mixed gas temperature detecting means for detecting the temperature of the mixed gas;
Water vapor concentration acquisition means for acquiring the water vapor concentration in the fresh air,
2. The exhaust gas recirculation rate measuring device according to claim 1, wherein the first sonic velocity acquisition unit calculates the sonic velocity of the fresh air based on a temperature of the mixed gas and a water vapor concentration in the fresh air. . Mixed gas temperature detecting means for detecting the temperature of the mixed gas;
Water vapor concentration acquisition means for acquiring the water vapor concentration in the fresh air;
Water vapor concentration estimating means for estimating the water vapor concentration in the recirculated exhaust gas based on the water vapor concentration in the fresh air,
3. The exhaust gas recirculation rate according to claim 1, wherein the second sonic speed acquisition unit calculates a sonic speed of the recirculated exhaust gas based on a temperature of the mixed gas and a water vapor concentration in the recirculated exhaust gas. Measuring device.   The water vapor concentration acquisition means includes fresh air temperature detection means for detecting the fresh air temperature and fresh air humidity detection means for detecting the fresh air humidity. The exhaust gas recirculation rate measuring apparatus according to claim 2 or 3, wherein a water vapor concentration in the fresh air is calculated based on the calculation result.   The third sound speed acquisition unit includes an ultrasonic transmission unit that transmits ultrasonic waves and an ultrasonic reception unit that receives the ultrasonic waves via the mixed gas, from the transmission time point to the reception time point of the ultrasonic waves. The exhaust gas recirculation rate measuring apparatus according to any one of claims 1 to 4, wherein a sound speed of the mixed gas is obtained based on a propagation time of the exhaust gas.

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