JP2006343136A - Partial pressure detector of steam, suction flow rate detector of engine and internal pressure detector of collector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a partial pressure detector of steam that is not affected by humidity (steam partial pressure), readily enhancing the detection accuracy of a sucked air flow rate, and then enhancing the control precision of a fuel jet amount in its turn. <P>SOLUTION: Atmospheric temperature Ta is detected, in a running state that a car speed VSP is a predetermined value VSP0 or higher, the saturated steam partial pressure Pwh(Ta) of the atmosphere is calculated, on the basis of the atmospheric temperature Ta and a predetermined ratio (e.g., 50%) of the saturated steam partial pressure Pwh(Ta) is calculated as the actual steam partial pressure Pw(Ta). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for detecting an estimated water vapor partial pressure (humidity) in the atmosphere and a technique for detecting an intake air flow rate of an engine or a pressure in a collector portion of an engine intake passage in consideration of the water vapor partial pressure.

  As a means of measuring the intake air flow rate of an engine (internal combustion engine), the amount of energization is maintained so that the temperature of the hot wire or heat film generated by energization tends to decrease due to heat being taken away by the intake air flow. There is known a thermal type flow meter that measures the intake air flow rate by utilizing the fact that this energization amount is proportional to the heat amount (heat flow rate) taken by the intake flow, and using the measured intake air flow rate The fuel injection amount and ignition timing are controlled.

  In the above flow rate measurement method, heat is taken not only by the air in the intake air but also by the water vapor, so that the required air flow rate cannot be accurately detected. In particular, the higher the humidity, the relatively lower the proportion of air, and the specific heat of water vapor is larger than that of air, so the amount of heat taken away by water vapor increases and the detection error of air flow rate increases. There is a problem that it ends up.

With respect to this problem, Patent Documents 1 and 2 disclose a technique for correcting the flow rate detection value using a mechanism for detecting humidity.
JP-A-5-346336 JP-A-5-52625

However, in Patent Documents 1 and 2, the manufacturing cost of the humidity detection mechanism is high, and the reliability is low.
In addition, when calculating the intake charge efficiency for calculating the fuel injection amount, the response of the collector may be modeled. However, conventionally, in addition to the deterioration of the calculation accuracy in the steady state due to the change of the water vapor partial pressure, Thus, the calculation accuracy deteriorated even in the transient state.

  The present invention has been made paying attention to such a conventional problem, and it is possible to easily estimate a partial pressure of water vapor (humidity) at low cost and to detect an engine detected by an air flow meter using the partial pressure of water vapor. An object of the present invention is to make it possible to accurately detect and correct the pressure in the collector used when calculating the intake air flow rate or modeling the intake air flow rate.

In order to solve the above-described problems, the present invention is configured as a first invention in which a partial pressure of water vapor in atmospheric pressure is detected by calculation based on an atmospheric temperature.
In addition, as a second invention, an intake flow rate detecting means for detecting an intake flow rate of the engine and a water vapor partial pressure detecting means for detecting a water vapor partial pressure in the intake air are provided, and the detected intake flow rate and the water vapor partial pressure are detected. Based on the above, the intake flow rate from which water vapor has been removed is calculated by the intake flow rate calculation means.

  Further, as a third invention, a molar inflow amount of intake air including water vapor flowing into the collector portion of the engine intake passage and a molar outflow amount of intake air including water vapor flowing out of the collector portion are calculated, and these molar inflow amounts are calculated. And the pressure in the collector portion is detected based on the molar outflow amount.

According to the first invention, based on the characteristic that the saturated water vapor partial pressure increases as the atmospheric temperature increases, the water vapor content suitable for practical use, such as the water vapor partial pressure in the engine intake air, is obtained by calculation without using a humidity sensor or the like. The pressure can be calculated.
According to the second aspect of the present invention, the flow rate of only the air from which the water vapor content has been removed is detected from the intake air flow rate including the water vapor detected by an air flow meter or the like, using the water vapor partial pressure determined by the above intake flow rate device. As a result, it is possible to calculate the fuel injection amount that accurately corresponds to the intake air amount without being affected by the humidity.

  According to the third invention, for example, when the intake system is modeled and the intake air flow rate is calculated using the collector internal pressure calculated by the balance calculation of the inflow amount and the outflow amount of the intake air from the collector, By using the collector internal pressure including the pressure, the intake flow rate can be calculated accurately, and the mass of the gas is constant regardless of the type of substance. By calculating using the molar flow rate, the pressure calculation can be performed easily and accurately.

FIG. 1 shows a configuration of an internal combustion engine according to an embodiment of the present invention.
An intake passage 2 that is connected to a combustion chamber of the engine 1 and sucks air is provided with an air cleaner 3 at an upstream end portion, and a collector portion 5 is provided via a throttle valve 4 interposed downstream of the air cleaner 3. The fuel injection valve 7 is attached to the intake port 6 of each cylinder connected to the collector unit 5, and the intake valve 8 that opens and closes the downstream end of the intake port is attached.

The air cleaner 3 is equipped with an atmospheric pressure sensor 9 for detecting atmospheric pressure, and a thermal flow meter such as a hot wire or a thermal film type incorporating an intake air temperature sensor 10 a is provided between the air cleaner 3 and the throttle valve 4. An air flow meter 10 is mounted, and the collector unit 5 is mounted with an intake pressure sensor 11 that detects the intake pressure in the collector unit 5 (collector internal pressure).
Further, an exhaust purification catalyst 14 is attached to an exhaust passage 13 connected to the combustion chamber of the engine 1 and exhausting combustion exhaust from the exhaust valve 12, and an air-fuel ratio sensor 15 is attached upstream of the catalyst 14. . In addition, a vehicle speed sensor 16 for detecting the speed of the vehicle on which the engine 1 is mounted is provided.

  Detection signals from the sensors are input to an engine control unit (hereinafter referred to as ECU) 20, which detects an intake air flow rate based on these detection signals and sets a fuel injection amount based on the intake air flow rate. Then, the fuel injection amount is controlled by driving the fuel injection valve 7. Here, in the present invention, the flow rate of the intake air containing water vapor is corrected based on the partial pressure of water vapor, and is accurately detected as the air flow rate from which water has been removed, thereby improving the control accuracy of the fuel injection amount.

FIG. 2 shows a control block diagram of the system for calculating the amount of air taken into the cylinder of the engine and setting the fuel injection amount corresponding to the cylinder intake air amount as described above.
In brief, the atmospheric temperature is detected, the water vapor partial pressure in the intake air is calculated based on parameters including the atmospheric temperature, the heat flow detected by the air flow meter, the atmospheric pressure detected by the atmospheric pressure sensor 9, and the water vapor content. Based on the pressure, a molar inflow amount of intake air to the collector unit 5 is calculated.

  On the other hand, the volume flow rate of the intake air to the cylinder is calculated based on the engine rotation speed, and the collector internal pressure is calculated based on the volume flow rate and the molar inflow amount of the intake air to the collector unit 5. Based on the amount of inflow, calculate the molar flow rate of the intake air that flows out from the collector and flows into the cylinder, and corrects the molar flow rate of the intake air to this cylinder by using the partial pressure of water vapor so that only air from which water vapor has been removed The flow rate is calculated. Based on the air flow rate and the engine speed, the intake air amount per cycle is calculated, and the fuel injection amount corresponding to the intake air amount is calculated.

Hereinafter, each block will be described.
FIG. 3 shows a flow for detecting the water vapor partial pressure in the atmosphere sucked into the engine 1 by estimation.
In step S1, it is determined whether or not the vehicle speed VSP detected by the vehicle speed sensor 16 is traveling above a predetermined value VSP0. If the vehicle speed VSP is less than the predetermined value VSP0, the routine ends and the water vapor content is detected without detecting the atmospheric temperature. Prohibit pressure detection.

  This is a state where the surrounding air such as hot air in the engine room is stagnant when the vehicle is stopped or is traveling at a low speed close to the stop, and the correct atmospheric temperature may not be measured. Therefore, by detecting under conditions where the vehicle speed is traveling at a predetermined speed or higher, it is possible to detect the temperature that does not rise abnormally without stagnating in the engine room, so the atmospheric temperature can be accurately obtained. As a result, the water vapor partial pressure can be obtained correctly.

If it is determined in step S1 that the vehicle speed is equal to or higher than the predetermined value, the process proceeds to step S2 to detect the atmospheric temperature Ta.
Specifically, the intake air temperature detected by the intake air temperature sensor 10a may be used. An intake air temperature sensor may be disposed in the collector unit 5 to use the temperature of the intake air in the collector unit 5.

Further, when an outside air temperature sensor is provided in an air conditioner or the like outside the engine 1, the outside air temperature may be used. However, when a plurality of sensors for detecting the atmospheric temperature are provided, detection values of these sensors are used. Of these, it is desirable to use the lowest detected value as the atmospheric temperature Ta.
This is because even if the detection temperature is high, there is a high possibility that the temperature has risen due to the influence of hot air in the engine room, and the actual water vapor partial pressure is unlikely to be abnormally high. Because it is good.

In step S3, a saturated water vapor partial pressure Pwh (Ta) is calculated based on the atmospheric temperature Ta detected in step S2. This may be obtained by referring to the conversion map shown in FIG. As is clear from FIG. 4 (logarithmic illustration), the higher the atmospheric temperature, the higher the saturated water vapor partial pressure.
In step S4, based on the saturated water vapor partial pressure Pwh (Ta) corresponding to the atmospheric temperature Ta, the atmospheric water vapor partial pressure Pw (Ta) is calculated by the following estimation.

First, since the water vapor partial pressure Pw (Ta) does not exceed the saturated water vapor partial pressure Pwh (Ta), the water vapor partial pressure Pwh (Ta) is limited to the saturated water vapor partial pressure Pwh (Ta) or less, and the saturated water vapor partial pressure Pwh (Ta) is reduced to the atmospheric temperature Ta. In accordance with the tendency to increase in accordance with the increase, the water vapor partial pressure is calculated to increase as the atmospheric temperature Ta increases.
Specifically, a value obtained by multiplying a saturated water vapor partial pressure Pwh (Ta) determined by the intake air temperature Ta by a coefficient k smaller than 1 as shown in the following equation is a water vapor pressure Pw (Ta) in the atmosphere (intake). Calculate as

Pw (Ta) = k × Pwh (Ta) (1)
Here, the coefficient k is set to a value smaller than 1, but 0.5 (50%) is selected as in the following equation, and the range of the water vapor partial pressure that can be taken at the intake air temperature Ta is 0 to Pwh (Ta ) Can be selected to minimize the average error (see FIG. 4).
Pw (Ta) = 0.5 × Pwh (Ta) (2)
The coefficient k may be set to a small value when the atmospheric pressure Pa detected by the atmospheric pressure sensor 9 is low. In this way, when the atmospheric pressure is low (the altitude is high) and the temperature is low, the air is often dry. In such a case, the partial pressure of the water vapor can be set to a small value. However, since it is originally a region where the absolute value of the partial pressure of water vapor is small, it does not cause a large error even if correction by atmospheric pressure is not performed.

The atmospheric pressure may be a value estimated according to the driving state, or altitude information from GPS obtained by car navigation may be used.
Further, as shown in FIG. 5, an upper limit value PwLMT may be set with respect to the water vapor partial pressure calculated as described above and limited to the upper limit value PwLMT or less.
In this way, even if the temperature is high, the possibility that the substantial water vapor partial pressure is abnormally high is low, so it is judged that it is the influence of engine hot air, etc., and over-correction is avoided by limiting with the upper limit value can do.

Here, the upper limit value PwLMT may be atmospheric pressure. This is because the water vapor partial pressure does not become higher than the atmospheric pressure. Here, the atmospheric pressure used may be simply the atmospheric pressure in the standard state (≈100 kPa).
The upper limit value PwLMT may be set to a predetermined ratio of atmospheric pressure (for example, about 10% of 10 kPa). Although the water vapor partial pressure estimated in this embodiment is used to accurately determine the intake air flow rate, the intake air flow rate is used for calculating the fuel injection amount, and the water vapor partial pressure is several tens of atmospheric pressure. %, Even if this is the case, setting the fuel injection amount according to the amount of air decreased according to the partial pressure of water vapor will increase the cooling effect by moisture and make the combustibility unstable. It would be an unfavorable result.

Therefore, the occurrence of the above situation can be avoided by limiting the water vapor partial pressure to a predetermined ratio or less of the atmospheric pressure.
FIG. 6 shows a flow for calculating the molar flow rate of the intake air flowing into the collector unit 5.
In step S11, a heat flow rate Q [J / K / mol] is calculated based on the output of the air flow meter 10. Here, as described above, the intake flow rate detected by the air flow meter 10 which is a thermal flow meter is detected as a value corresponding to the heat flow rate Q taken by air and water vapor.

In step S12, the water vapor partial pressure Pw (Ta) calculated in FIG. 2 is read.
In step S13, the constant pressure specific heat Cp of the intake air (air + water vapor) is calculated by the following equation (3).
Cp = Pw (Ta) × Cpw + {total pressure−Pw (Ta)} × Cpa (3)
Here, Cpw: constant pressure specific heat of water vapor = 2.04 [J / K / mol]
Cpa: constant pressure specific heat of air = 1.66 [J / K / mol]
Further, as the total pressure, the pressure upstream of the throttle, that is, the atmospheric pressure is used, or the collector internal pressure Pc (the detected value of the intake pressure sensor 11 or a calculated value described later) is used.

In step S14, a molar inflow amount nin flowing into the collector portion 5 is calculated by the following equation (4) using the heat flow rate Q and the constant pressure specific heat Cp.
nin = Q / Cp [mol / s] (4)
FIG. 7 shows a flow for calculating the volume flow rate of the air flowing out of the collector unit 5 and sucked into the cylinder.

In step S21, the engine rotational speed Ne and the collector internal pressure Pc (the detected value of the intake pressure sensor 11 or a calculated value described later) are read.
In step S22, the cylinder suction volume efficiency η is set with reference to the map shown in FIG. 8 based on the engine speed Ne. The cylinder suction volume efficiency η varies depending on the inertia of the intake air according to the engine rotational speed Ne, but data obtained through experiments in advance is assigned to the map.

In step S23, the volume flow rate Qcyl sucked into the cylinder is calculated by the following equation (5) based on the engine rotational speed Ne and the cylinder suction volume efficiency η.
Qcyl = V × Ne / 120 × η (5)
V: Engine Displacement FIG. 9 shows a flow for calculating and updating the collector internal pressure Pc that changes sequentially when the molar outflow amount nout of the intake air flowing out from the collector unit 5 is calculated and the intake pressure sensor 11 is not provided. Show.

In step S31, the temperature Tc in the collector part 5 and the molar inflow amount nin of the intake air to the collector part 5 calculated by the equation (5) are read. When the collector unit 5 does not have a temperature sensor, the temperature Tc may be substituted with the atmospheric temperature Ta.
In step S32, the molar outflow amount nout of the intake air flowing out from the collector unit 5 and sucked into the cylinder is calculated. This is because the volume flow rate Qcyl calculated by the above equation (2) is calculated using the previous calculated value Pc _(n-1) (initial value is the atmospheric pressure Pa) of the collector internal pressure Pc and the temperature Ta by the following equation (6): Convert as follows.

nout = Pc _(n-1) / (R · Ta) · Qcyl (6)
Where R: General gas constant (≈848 kgm / kmol · K)
In step S33, the collector internal pressure Pc that changes sequentially is calculated based on the molar inflow amount nin into the collector unit 5 and the molar outflow amount nout from the collector unit 5 as follows.

The equation of state of gas (air) in the collector is expressed by the following equation (7).
Pc · Vc = n · R · Tc (7)
Vc: collector section volume n: number of moles of intake air in the collector section When the collector section volume Vc and temperature Tc (≈Ta) are constant, the change amount ΔPc of the collector internal pressure Pc is expressed by the following equation (8): It is determined by the change amount Δn of the number of moles of intake air in the collector unit 5.

ΔPc = Δn · R · Tc / Vc (8)
The amount of change in the collector internal pressure for each calculation time interval is represented by Pc−Pc _(n−1) , and the amount of change Δn of the number of moles of intake air n in the collector unit 5 is represented by (nin−nout).
Therefore, the following equation (9) is established.
Pc-Pc _(n-1) = (nin-nout) .R.Tc / Vc
→ Pc = Pc _(n-1) + (nin-nout) .R.Tc / Vc (9)
Pc _(n-1) : Previously calculated value of the collector internal pressure Pc In this way, the collector internal pressure Pc is successively calculated and updated, and the molar outflow amount nout of the intake air from the collector unit 5 is expressed by the following equation (10). Calculation update is possible.

nout = nin- (Pc-Pc _(n-1) ). Vc / (R.Tc) (10)
It should be noted that the collector internal pressure Pc downstream of the throttle valve when starting operation from the engine stop state is equal to the atmospheric pressure Pa upstream of the throttle valve, and the initial value of the molar inflow amount nin into the collector portion 5 is zero. That is, there is no inflow of intake air to the collector portion at first, and the collector internal pressure Pc is reduced from the atmospheric pressure Pa by the molar outflow amount nout flowing out from the collector portion due to the negative pressure generated from the cylinder on the downstream side as a negative pressure source. The reduced pressure difference between the collector internal pressure Pc and the atmospheric pressure Pa causes a molar inflow amount nin to the collector portion 5 to start flowing into the collector portion.

When the detected value Pc of the intake pressure sensor 11 is used, the molar outflow amount nout may be calculated using the detected value Pc instead of Pc _{(n−1) in} the above equation (6).
FIG. 10 shows a flow of calculating the cylinder intake air amount from which water vapor has been removed and calculating the fuel injection amount corresponding to the air amount.
In step S41, the molar outflow amount nout of the intake air from the collector 5 and the engine speed Ne are read.

In step S42, since the molar outflow amount noout of the intake air is calculated as a molar flow rate that combines air and water vapor, the water vapor content is removed using the water vapor partial pressure Phw (Ta) as shown in the following equation. The molar outflow amount nota of only air is calculated as in the following equation (11).
nouta = nout · {1-Phw (Ta) / total pressure}
= {Nin- (Pc-Pc _(n-1) ). Vc / (R.Tc)}
・ {1-Phw (Ta) / Total pressure} (11)
Here, {1-Phw (Ta) / total pressure} represents the mole fraction of air in the intake air, and the total pressure uses atmospheric pressure Pa or collector internal pressure Pc. In step S43, as described above, Fuel set in synchronism with the cycle frequency based on the molar flow rate nouta flowing out from the collector portion 5 from which water vapor has been removed, that is, the molar flow rate ncyla (= nouta) of the air sucked into the cylinder, and the engine rotational speed Ne. The injection amount Ti is calculated as in the following equation (12).

Ti = k · ncyla / Ne, k is a constant (12)
In addition, it can convert into the mass flow rate m generally used by multiplying the molecular weight M of air to the molar flow rate ncyla.
In this way, the fuel injection amount corresponding to the air flow rate from which the water vapor component has been removed is set, and highly accurate air-fuel ratio control can be performed without being affected by the water vapor partial pressure (humidity).

In the above embodiment, the inflow amount nin of the intake air to the collector is obtained from the detected value of the air flow meter. However, the flow rate passing through the throttle valve 4 can be calculated as follows.
When the pressure ratio Pc / Pa before and after the throttle valve 4 is larger than the critical pressure ratio [= 2 / (κ + 1)} ^{κ / (κ-1)} ; κ is the specific heat ratio of the intake air], it is calculated by the following equation (13). The

Here, ATH is a throttle opening area corresponding to the opening degree of the throttle valve 4, a throttle sensor for detecting the throttle opening degree is provided, and a conversion map of throttle opening degree-throttle opening area as shown in FIG. 11 is set. Then, the calculation may be performed with reference to the map.
On the other hand, when the pressure ratio Pc / Pa is equal to or less than the critical pressure ratio, the front-rear pressure ratio in the vicinity of the throttle valve 4 is maintained constant regardless of the collector internal pressure Pc away from the throttle valve 4, and the throttle valve 4 becomes a sonic flow state in which the flow velocity of the intake air passing through 4 is constant in sound speed.

That is, in the equation (14), the value obtained by replacing Pc / Pa in the third term (√ portion) on the right side with the critical pressure ratio {2 / (κ + 1)} ^{κ / (κ-1)} ] is obtained. ).

In this way, the calculated intake air flow rate nin to the collector unit 5 is read in step S32 of FIG. 7, and thereafter, the collector internal pressure Pc and the intake air flow rate nout to the cylinder unit are the same as in the first embodiment. After the calculation is updated, the water vapor component is removed, and by multiplying by the molar fraction of air, the flow rate of only air can be detected, and the fuel injection amount control accuracy can be improved.
In the embodiment described above, since the intake system is modeled and the outflow amount from the collector is calculated as the intake flow rate to the cylinder, it is possible to cope with the delay in the intake flow rate detection value in the upstream portion in the transient state. it can.

On the other hand, in the simple intake flow rate detection, or when the steady state and the transient state are discriminated and the steady state is discriminated, the detected value of the air flow meter or the collector unit obtained by the above-described throttle unit flow rate calculation The fuel injection amount may be set using the inflow amount nin of the intake air to 5.
Also in this case, using the water vapor partial pressure Phw (Ta), the flow rate nina of only the air from which the water vapor has been removed can be calculated as in the following equation (15).

nina = nin · {1-Phw (Ta) / total pressure}
・ {1-Phw (Ta) / Total pressure} (15)
As the total pressure, the atmospheric pressure Pa or the collector internal pressure Pc is used. Further, the fuel injection amount Ti synchronized with the cycle frequency is calculated by the following equation (16) using the air flow rate nina.

Ti = k · nina / Ne, k is a constant (16)
Further, in the embodiment described above, the collector internal pressure Pc may be detected by providing a pressure sensor in the collector unit 5, and EGR or purged evaporated fuel is added as the flow rate of the intake air flowing into the collector unit 5. Can also be calculated.

The figure which shows the system configuration | structure of the engine (internal combustion engine) in embodiment which concerns on this invention. The control block diagram in embodiment same as the above. The flowchart which calculates the water vapor partial pressure in air | atmosphere (intake). The figure which showed the saturated water vapor partial pressure with respect to temperature, and the water vapor partial pressure computed (estimated) in embodiment by the logarithm. Similarly, the figure which showed the water vapor partial pressure restrict | limited by the upper limit. The flowchart which calculates the molar inflow amount of the intake air to a collector part. 6 is a flowchart for calculating a cylinder suction volume flow rate. The figure which shows the cylinder intake volume with respect to engine rotational speed. The flowchart which calculates a collector internal pressure. The flowchart which calculates the molar flow rate and fuel injection amount of cylinder intake air. Conversion map of throttle opening and throttle opening area.

Explanation of symbols

1 engine,
2 Intake passage 4 Throttle valve 5 Collector 7 Fuel injection valve 9 Atmospheric pressure sensor 10 Air flow meter 10a Intake temperature sensor 11 Intake pressure sensor 16 Engine control unit (ECU)

Claims (25)

  A water vapor partial pressure detecting device that detects a water vapor partial pressure in an atmospheric pressure by calculation based on a parameter including an atmospheric temperature.   The water vapor partial pressure detection apparatus according to claim 1, wherein the water vapor partial pressure is calculated to be higher as the saturated water vapor partial pressure determined by the atmospheric temperature is higher.   The water vapor partial pressure detection apparatus according to claim 2, wherein the water vapor partial pressure is calculated as a predetermined ratio of the saturated water vapor partial pressure.   The water vapor partial pressure detection apparatus according to claim 3, wherein the predetermined ratio is 50%.   The water vapor partial pressure detection apparatus according to claim 3, wherein the predetermined ratio is set to a smaller value as the atmospheric pressure is lower.   The water vapor partial pressure detection device according to any one of claims 1 to 5, wherein the water vapor partial pressure is calculated while being limited to an upper limit value or less.   The water vapor partial pressure detection apparatus according to claim 6, wherein the upper limit value is atmospheric pressure or a predetermined ratio of atmospheric pressure.   An apparatus for detecting a partial pressure of water vapor in an air sucked into an engine mounted on a vehicle uses an air temperature detected as an outside air temperature before inhaling the engine or an intake air temperature after inhaling the engine. The water vapor partial pressure detection device according to any one of claims 1 to 7.   A plurality of means for detecting the atmospheric temperature are provided, and the lowest temperature of the atmospheric temperature detected by these detecting means is used for calculating the water vapor partial pressure. The water vapor partial pressure detection device described. In a device for detecting a partial pressure of water vapor in air sucked into an engine mounted on a vehicle,
The water vapor partial pressure detection apparatus according to any one of claims 1 to 9, wherein the water vapor partial pressure is detected using an atmospheric temperature detected when the vehicle speed is equal to or higher than a low vehicle speed close to stopping. An intake flow rate detection means for detecting the intake flow rate of the engine;
A water vapor partial pressure calculating means for calculating a water vapor partial pressure during intake;
An intake air flow rate calculating means for calculating an intake air flow rate from which water vapor content is removed based on the detected intake air flow rate and the calculated water vapor partial pressure;
An intake air flow rate detection device for an engine characterized by comprising:   10. The engine intake air flow rate detection device according to claim 9, wherein the water vapor partial pressure calculation unit includes the water vapor partial pressure detection device according to claim 1.   The engine intake flow rate detection device according to claim 11 or 12, wherein the intake flow rate detection unit is a unit that detects a heat flow rate proportional to a product of a specific heat of the intake fluid and a molar flow rate.   The engine intake flow rate detection device according to claim 11, wherein the intake flow rate detection means is an air flow meter for detecting an intake air flow rate mounted in an intake passage of the engine. The engine according to any one of claims 11 to 13, wherein the intake flow rate detection means calculates a molar flow rate of air for each cycle sucked into a cylinder of the engine by the following equation. Intake flow rate detection device.
Heat flow rate [J / K / s] / Fixed pressure specific heat Cp [J / K / mol] × Mole fraction of air [%] × Cycle frequency [1 / s / cycle]
However, constant pressure specific heat Cp = {steam partial pressure × steam constant pressure specific heat Cpw + (total pressure−steam partial pressure) × air constant pressure specific heat Cpair} / total pressure   16. The engine intake flow rate detection device according to claim 15, wherein the total pressure and the partial pressure of water vapor use a pressure in the atmosphere or a pressure in a collector portion of an engine intake passage. The engine intake air flow rate detection device according to any one of claims 15 to 16, wherein the mole fraction [%] of the air is calculated by the following equation.
Molar fraction of air = 1-water vapor partial pressure / total pressure   The engine intake flow rate according to claim 11 or 12, wherein the intake flow rate detection means is a means for calculating an intake air flow rate based on a parameter including a pressure in a collector portion of an engine intake passage and an engine rotational speed. Detection device.   19. The intake air flow rate detection device for an engine according to claim 16, wherein the pressure in the collector part is detected by a sensor or is calculated using a model. The intake air flow of the engine according to claim 18 or 19, wherein the calculation of the intake air flow rate is calculated as a flow rate of air from which water vapor has been removed using a mole fraction of air represented by the following equation. Flow rate detection device.
Molar fraction of air = 1-water vapor partial pressure / total pressure   Calculate the molar inflow amount of the fluid containing water vapor flowing into the collector portion of the engine intake passage and the molar outflow amount of the fluid containing water vapor flowing out of the collector portion, and based on these molar inflow amount and molar outflow amount. A collector internal pressure detecting device that detects the internal pressure of the collector.   The collector internal pressure detection device according to claim 21, wherein the molar inflow amount is detected by the intake flow rate detection device according to any one of claims 11 to 20.   23. The collector internal pressure detection device according to claim 21, wherein the molar outflow amount is calculated using a parameter including an engine rotation speed.   The collector internal pressure detection device according to any one of claims 21 to 23, wherein the collector internal pressure is detected by using air or a temperature in the collector portion.   25. The collector internal pressure detection device according to claim 21, wherein the molar inflow amount includes EGR and evaporated fuel to be purged.