JP5233968B2 - EGR cooler cooling efficiency calculation device and internal combustion engine control device using the same - Google Patents

Description

  The present invention relates to a cooling efficiency calculation device for an EGR cooler and an internal combustion engine control device using the same.

  Conventionally, for example, as disclosed in Japanese Patent Application Laid-Open No. 2009-114871, in an internal combustion engine equipped with an external EGR system, a heat release amount (cooling efficiency) of an EGR cooler is obtained, and various controls are performed based on the value of the cooling efficiency. 2. Description of the Related Art A control device for an internal combustion engine that performs the above is known.

  In the above prior art, two temperature sensors are attached to the external EGR gas passage of the internal combustion engine. Of these two temperature sensors, one is provided upstream of the EGR cooler in the external EGR gas passage, and the other is provided downstream of the EGR cooler in the external EGR gas passage. According to this configuration, the EGR gas temperature before and after passing through the EGR cooler can be detected based on the outputs of the two temperature sensors. The cooling efficiency of the EGR cooler can be obtained based on the EGR gas temperatures before and after passing through the EGR cooler obtained based on the outputs of the two temperature sensors.

  The cooling efficiency of the EGR cooler affects the temperature of the EGR gas returned to the cylinder. Therefore, grasping the actual value of the cooling efficiency of the EGR cooler is an important matter in performing EGR control. In this regard, according to the above-described conventional technique, the EGR control can be accurately performed according to the temperature of the EGR gas by calculating the cooling efficiency of the EGR cooler based on the sensor output.

JP 2009-114871 A Japanese Patent Laid-Open No. 2004-21560

  The conventional EGR cooler cooling efficiency calculation technology relies on a method of directly measuring the EGR gas temperature using a temperature sensor.

  By the way, the cooling system of the internal combustion engine includes various devices such as a coolant passage through which the coolant flows, a radiator, and a thermostat interposed between the coolant passage and the radiator. The coolant passage extends inside the internal combustion engine body, and cools the internal combustion engine body by circulating the coolant.

  The external EGR system has an EGR cooler for cooling the EGR gas. The cooling of the EGR cooler is also performed in common with the cooling of the internal combustion engine body using the function of the cooling system of the internal combustion engine.

  The coolant flowing through the coolant passage receives heat from the internal combustion engine main body and the EGR cooler, and the heat is radiated in the radiator. That is, in the process of circulating the coolant in the cooling system, heat is transferred between the radiator side and the internal combustion engine and EGR cooler side with the thermostat as a boundary. Therefore, the inventors of the present application have found a method for calculating the EGR cooler cooling efficiency by a method different from the direct measurement of the EGR gas temperature by the temperature sensor according to the related art by solving the relationship of the heat balance of the coolant. .

  The present invention has been made to solve the above-described problems, and the cooling efficiency of the EGR cooler capable of calculating the cooling efficiency of the EGR cooler based on the heat balance of the coolant in the cooling system of the internal combustion engine. It is an object of the present invention to provide a calculation device and a control device for an internal combustion engine using the same.

In order to achieve the above object, a first invention provides a cooling efficiency calculation device for an EGR cooler,
An external EGR passage that recirculates EGR gas into a cylinder of the internal combustion engine, an EGR cooler that cools the EGR gas that flows through the external EGR passage, and a coolant that circulates inside the cylinder and is connected to a radiator. Cooling for calculating the cooling efficiency of the EGR cooler in an internal combustion engine comprising a coolant passage extending around the cylinder and connected to the EGR cooler, and a thermostat interposed between the coolant passage and the radiator An efficiency calculation device,
A total heat receiving amount calculating means for calculating a total heat receiving amount of the coolant in the coolant passage based on a valve opening rate of the thermostat;
Combustion heat receiving amount calculating means for calculating a combustion heat receiving amount that is a heat amount received from the internal combustion engine by the coolant in the coolant passage by combustion in the cylinder of the internal combustion engine;
A moving heat amount calculating means for calculating a moving heat amount that is a heat amount transferred from the EGR cooler to the cooling liquid in the cooling fluid passage from the total heat receiving amount and the combustion heat receiving amount;
Inlet coolant temperature acquisition means for acquiring the temperature of the coolant on the EGR cooler inlet side of the coolant passage;
Cooling efficiency calculating means for calculating the cooling efficiency of the EGR cooler based on the moving heat quantity calculated by the moving heat quantity calculating means and the temperature acquired by the inlet coolant temperature acquiring means;
It is characterized by providing.

The second invention is the above first invention, wherein
Actual heat in which the cooling efficiency calculating means calculates an actual heat transfer coefficient of the EGR cooler based on the transferred heat quantity calculated by the transferred heat quantity calculating means and the temperature acquired by the EGR cooler inlet coolant temperature acquiring means. Including a transmission rate calculation means,
further,
Inlet gas temperature acquisition means for acquiring the temperature of EGR gas flowing into the EGR cooler;
A temperature decrease amount calculating means for calculating a temperature decrease amount of the EGR gas due to passing through the EGR cooler based on the actual heat transfer coefficient calculated by the actual heat transfer coefficient calculating means;
EGR gas temperature calculation means for calculating the temperature of the EGR gas downstream of the EGR cooler based on the temperature calculated by the inlet gas temperature acquisition means and the temperature decrease amount calculated by the temperature decrease amount calculation means; ,
It is characterized by providing.

A third aspect of the invention is a control device for an internal combustion engine,
An external EGR system that recirculates EGR gas into the cylinder;
An EGR cooler for cooling EGR gas recirculated via the external EGR system;
A coolant passage in which the coolant flows, is connected to a radiator, extends around the cylinder of the internal combustion engine, and is connected to the EGR cooler;
A thermostat interposed between the coolant passage and the radiator;
A control device for controlling an internal combustion engine comprising:
The EGR cooler cooling efficiency calculation apparatus according to the first or second invention, which calculates the cooling efficiency of the EGR cooler or the temperature of the EGR gas downstream of the EGR cooler;
Control means for controlling the external EGR system based on the cooling efficiency of the EGR cooler calculated by the cooling efficiency calculation device of the EGR cooler or the temperature of the EGR gas downstream of the EGR cooler using the valve opening rate of the thermostat as input information When,
It is characterized by providing.

  According to the first invention, the cooling efficiency of the EGR cooler can be calculated based on the heat balance of the coolant in the cooling system of the internal combustion engine. That is, the thermostat changes the valve opening rate according to the coolant temperature for the purpose of adjusting the coolant temperature. The amount of heat transferred from the EGR cooler to the coolant can be calculated based on the total amount of heat received by the coolant calculated from the valve opening rate of the thermostat and the amount of heat received by the coolant due to combustion in the cylinder. If the temperature of the coolant on the EGR cooler inlet side and the amount of heat transferred from the EGR cooler to the coolant are known, the cooling efficiency of the EGR cooler can be calculated from these relationships.

  According to the second invention, the temperature of the EGR gas downstream of the EGR cooler can be calculated using the heat transfer coefficient obtained by solving the relationship of the heat balance of the coolant in the cooling system of the internal combustion engine.

  According to the third invention, the external EGR system can be controlled by using the EGR cooler cooling efficiency or the EGR gas temperature obtained in the first or second invention.

1 shows a configuration of an EGR cooler cooling efficiency calculation device and an internal combustion engine equipped with the same according to an embodiment of the present invention. It is a flowchart for demonstrating the cooling efficiency calculation method of the EGR cooler in embodiment of this invention. It is a flowchart of the routine which ECU performs in embodiment of this invention. 4 shows a flowchart of a routine for calculating the temperature of EGR gas at the inlet of the EGR cooler in the embodiment of the present invention. It is an example of the map used in embodiment of this invention. It is an example of the map used in embodiment of this invention. It is an example of the map used in embodiment of this invention.

Embodiment.
[Configuration of the embodiment]
FIG. 1 is a diagram illustrating a configuration of an EGR cooler cooling efficiency calculation apparatus and an internal combustion engine 2 including the same according to an embodiment of the present invention. The cooling efficiency calculation device for an EGR cooler and the internal combustion engine 2 according to the present embodiment can be suitably used as an internal combustion engine for a vehicle.

  The internal combustion engine 2 according to the present embodiment includes a cylinder 10 as shown in FIG. In this embodiment, for the sake of convenience, one cylinder is illustrated and described. However, the configuration of the internal combustion engine in which the present invention is mounted is not limited to that exemplified in the present embodiment, and the specific configuration of the internal combustion engine targeted by the present invention (number of cylinders and cylinder arrangement system, diesel, gasoline, There is no limitation for other.

  The cylinder 10 is provided with a piston 12. The piston 12 is connected to the crankshaft 14. The internal combustion engine 2 includes an intake valve 20 interposed between the cylinder 10 and the intake port, and an exhaust valve 22 interposed between the cylinder 10 and the exhaust port. The cylinder 10 includes a spark plug 16 and an in-cylinder pressure sensor 18 at the cylinder head so as to protrude into the combustion chamber. An intake passage including an intake port, a surge tank, and a throttle 24 is provided on the upstream side of the intake valve 20.

  The internal combustion engine 2 includes an external EGR system including an EGR gas passage 30, an EGR valve 34, and an EGR cooler 32. One end of the EGR gas passage 30 communicates with the exhaust port and the other end communicates with the intake port. The exhaust gas passes through the EGR gas passage 30 and is recirculated to the cylinder 10 at a flow rate corresponding to the opening degree of the EGR valve 34 while being lowered to a predetermined temperature by the EGR cooler 32.

  The internal combustion engine 2 includes a coolant passage 40. As shown in FIG. 1, the coolant passage 40 extends around the cylinder 10 and the EGR cooler 32, thereby cooling them with coolant (engine coolant, hereinafter simply referred to as “coolant”). be able to. An engine coolant temperature sensor 46 is provided on the downstream side of the cylinder 10 in the coolant passage 40. The engine coolant temperature sensor 46 detects the temperature of the coolant at the downstream position of the cylinder 10. In the middle of the coolant passage 40, a radiator 44, a thermostat 42, and a water pump (not shown) are provided.

The internal combustion engine 2 includes an ECU (Electronic Control Unit) 50. The ECU 50 is connected to the in-cylinder pressure sensor 18, the spark plug 16, the EGR valve 34, the thermostat 42, and the engine coolant temperature sensor 46. ECU50 is a cooling water temperature _{T W} based on the output of the engine coolant temperature sensor 46, the cylinder pressure _{P cyl} based on the output of the cylinder pressure sensor 18, it can be respectively acquired. Further, the ECU 50 gives a control signal to the thermostat 42 and can also acquire the current valve opening rate r of the thermostat 42.

  Although not shown, the ECU 50 is also connected to various sensors (for example, exhaust gas sensors such as an air flow meter, a crank position sensor, an air-fuel ratio sensor, and an oxygen sensor) attached to the internal combustion engine 2. Although not shown, the ECU 50 is also connected to various actuators (for example, an actuator for a fuel injection valve (not shown), an actuator for a drive mechanism for an intake / exhaust valve, etc.) related to the operation of the internal combustion engine 2.

[Calculation of EGR cooler cooling efficiency of embodiment]
Hereinafter, the content of the cooling efficiency calculation of the EGR cooler according to the embodiment of the present invention will be described.

  The cooling efficiency of an EGR cooler generally deteriorates with time due to deterioration of components, deposits and dirt. There is also a variation in cooling efficiency due to product variations. The cooling efficiency of the EGR cooler affects the temperature of the EGR gas at the outlet of the EGR cooler (that is, the temperature of the EGR gas returned to the cylinder). If EGR control is performed without accurately grasping the temperature of the EGR gas at the outlet of the EGR cooler, various problems (for example, deterioration of in-cylinder air amount estimation accuracy) are caused. Because of this background, grasping the actual value of the cooling efficiency of the EGR cooler is an important matter in performing EGR control.

  Therefore, in the present embodiment, the temperature of the EGR gas at the outlet of the EGR cooler 32 and the cooling efficiency of the EGR cooler 32 are reduced by solving the relationship of the heat balance of the cooling water according to the following policies (i) to (v). I decided to calculate.

(I) The temperature T _ex1 of the EGR gas at the inlet of the EGR cooler 32 is assumed to be equal to the exhaust gas temperature, and is obtained from the in-cylinder pressure. The in-cylinder pressure P _cyl can be obtained from the output of the in-cylinder pressure sensor 18. The temperature T _ex2 of the EGR gas at the outlet of the EGR cooler 32 can be obtained by subtracting the temperature drop of the EGR gas by the EGR cooler 32 from the temperature T _ex1 .

(Ii) The temperature drop of the EGR gas is calculated based on the cooling efficiency η _EGR of the EGR cooler 32. EGR cooler efficiency eta _EGR can be determined from Jitsunetsu transmissibility _{h EGR} of the EGR cooler 32.
(Iii) The actual heat transfer coefficient h _EGR is calculated from the amount of heat Q _EGR transferred from the EGR cooler 32 to the cooling water.
(Iv) The moving heat amount Q _EGR is calculated from the total heat receiving amount Q _W of the cooling water and the heat receiving amount Q _cyl which is the heat amount received by the cooling water from the cylinder 10.

(V) heat-receiving total amount _{Q W} is obtained from the valve opening rate r of the thermostat 42. The amount of heat received Q _cyl is obtained from the in-cylinder pressure.
In this embodiment, it obtains the heat amount Q _W from opening ratio r of the thermostat 42. The cooling water flowing through the coolant passage 40 receives heat from the cylinder 10, and the heat is radiated in the radiator 44. The thermostat 42 is provided for the purpose of adjusting the temperature of the cooling water, and changes the valve opening rate r to adjust the flow rate of the cooling water passing through the radiator 44 in accordance with the temperature of the cooling water. If the amount of heat received by the cooling water during operation of the internal combustion engine 2 is large, the temperature of the cooling water rises accordingly, and the valve opening rate r of the thermostat 42 also increases. Since such a relationship is established, it is possible to grasp the heat balance of the cooling water from the valve opening rate r of the thermostat 42.

  FIG. 2 is a flowchart for explaining a cooling efficiency calculation method of the EGR cooler in the embodiment of the present invention. In the flowchart of FIG. 2, steps S104 and S106 are the above step (v), step S108 is the above step (iv), step S112 is the above step (iii), steps S112 and S114 are Step S116 corresponds to step (ii) above, and step (i) above, respectively.

As described above, according to the present embodiment, the cooling efficiency η _EGR of the EGR cooler 32 can be calculated based on the heat balance of the cooling water in the cooling system of the internal combustion engine 2. That is, the thermostat 42 changes the valve opening rate r according to the cooling water temperature for the purpose of adjusting the temperature of the cooling water. A heat receiving amount Q _W of the cooling water obtained from the valve opening ratio r of the thermostat 42, based on the amount of heat received Q _cyl the cooling water received by the combustion in the cylinder 10, movement amount of heat transferred from the EGR cooler 32 to the cooling water Q _EGR can be calculated. If the temperature of the cooling water at the inlet side of the EGR cooler 32 and the amount of heat Q _EGR transferred from the EGR cooler 32 to the cooling water are known, the cooling efficiency η _EGR of the EGR cooler can be calculated from these relationships.

Further, according to the present embodiment, the cooling efficiency η _EGR of the EGR cooler 32 can be calculated by solving the relationship of the heat balance of the cooling water using the total amount of heat received from the valve opening rate r of the thermostat 42. it can. A thermostat is a component normally provided in a cooling system of an internal combustion engine. According to the present embodiment, the cooling efficiency of the EGR cooler can be calculated without requiring a dedicated component such as providing a temperature sensor near the entrance / exit of the EGR cooler.

[Specific processing of the embodiment]
FIG. 3 is a flowchart of a routine executed by the ECU 50 in the embodiment of the present invention. The routine of FIG. 3 embodies the contents of the flowchart of FIG. 2 described above.

  In the routine shown in FIG. 3, first, the in-cylinder pressure P and the in-cylinder volume V are detected (step S100). In this step, the in-cylinder pressure P and the in-cylinder volume V are calculated based on the output of the in-cylinder pressure sensor 18 and, for example, the output of a crank angle sensor (not shown).

ただし、上記の式において、ＳＡは点火時期、ＥＶＯは排気バルブの開弁時期、κは比熱比である。 Subsequently, an in-cylinder increased heat quantity Q _comb due to combustion is calculated (step S120). In this step, in-cylinder increased heat quantity Q _comb is calculated according to the following equation in accordance with the first law of thermodynamics and the state equation of gas.

In the above equation, SA is the ignition timing, EVO is the exhaust valve opening timing, and κ is the specific heat ratio.

Next, the lower heating value Q _{fuel of the fuel} is calculated (step S122). The lower heating value of the fuel can be uniquely obtained from the injected fuel type and the mass.

Next, the amount of heat received Q _cyl is calculated (step S102). The amount of heat received Q _cyl is the amount of heat received by the cooling water from the cylinder 10. In this step, the amount of heat received Q _cyl is calculated according to the following equation.

On the other hand, in the routine of FIG. 3, the valve opening rate r of the thermostat 42 is calculated in parallel with the processing of steps S100 to S102 (step S104). Based on the valve opening ratio r, the heat receiving amount _{Q w} of the cooling water is calculated (step S106).
The valve opening rate r can be calculated by obtaining the rate at which the thermostat 42 is opened per certain time based on the control signal to the thermostat 42. Specifically, for example, r = 48 (sec) / 60 (sec) = 80% can be obtained if it is opened for 48 seconds in the past 60 seconds. In addition to the time, the valve opening rate r may be obtained in consideration of the opening degree, that is, the flow sectional area.
The heat-receiving amount Q _w, in the present embodiment, prepared in advance a map as shown as an example in FIG. 5, allowed to store this map in ECU 50. For example in the case of the valve opening rate r = 80%, in FIG. 5, Q _w corresponding to the value of 0.8 on the horizontal axis is obtained. ECU50, by referring to this map, obtains a heat amount _{Q w} corresponding to the opening ratio r calculated in step S104. As a modification, it may be stored as a primary expression instead of a two-dimensional map.

Next, the amount of heat Q _EGR transferred from the EGR cooler 32 to the cooling water is calculated (step S108). In this step, the amount of heat transferred Q _EGR is calculated by subtracting the amount of heat received Q _cyl from the total amount of heat received Q _w according to the following equation.

上記の式において、Ｍ_ｗは、冷却水流量［ｇ／ｓ］である。本実施形態では、Ｍ_ｗとエンジン回転数とのマップ或いはそれらの一次式を予め作成してＥＣＵ５０に記憶しておくものとする。ｃ_ｐは、定圧比熱［Ｊ／（ｇ・Ｋ）］であり、定数或いはマップとして作成し、ＥＣＵ５０に記憶しておくものとする。 The cooling water temperature _{T W} at the inlet of the EGR cooler _32, the calculation of the _EGR is also performed (step S110). In this step, the coolant temperature _{TW, EGR} is produced according to the following equation.

In the above formula, M _w is the cooling water flow rate [g / s]. In the present embodiment, a map of _Mw and engine speed or a primary expression thereof is created in advance and stored in the ECU 50. c _p is the specific heat at constant pressure [J / (g · K) ], to create a constant or map, it is assumed to be stored in the ECU 50.

上記の式において、Ａ_ＥＧＲは、ＥＧＲクーラ３２とＥＧＲガス通路３０との接触面積を示す。図１の構成図でも模式的に示しているように、接触面積Ａ_ＥＧＲは、ＥＧＲガス通路３０を流れるＥＧＲガスがＥＧＲクーラ３２と接する面積に相当する。接触面積Ａ_ＥＧＲは、例えば設計値や実験値から求めて事前にＥＣＵ５０に記憶しておく。 Next, the actual heat transfer coefficient h _EGR of the EGR cooler 32 is calculated (step S112). In this step, the actual heat transfer coefficient h _EGR is calculated according to the following equation.

In the above formula, A _EGR indicates a contact area between the EGR cooler 32 and the EGR gas passage 30. As schematically shown in the configuration diagram of FIG. 1, the contact area A _EGR corresponds to an area where the EGR gas flowing through the EGR gas passage 30 contacts the EGR cooler 32. The contact area A _EGR is obtained from, for example, a design value or an experimental value and stored in the ECU 50 in advance.

上記の式において、筒内圧Ｐおよび容積Ｖのそれぞれの添え字のＩＶＣは、吸気バルブ２０の閉弁時の値を用いることを意味している。ＩＶＣ時（吸気バルブ閉弁時）の筒内温度は、エンジン水温に等しいと仮定し、エンジン冷却水温センサ４６から求める。Ｒは、気体定数である。 T _ex1 is the temperature of the EGR gas at the inlet of the EGR cooler 32 as described above, and is calculated according to the routine shown in FIG. FIG. 4 shows a flowchart of a routine for calculating the temperature T _ex1 of the EGR gas at the inlet of the EGR cooler 32 in the present embodiment. In the routine of FIG. 4, first, in-cylinder mass M _cyl is calculated according to the following equation (step S200).

In the above formula, the subscripts IVC of the in-cylinder pressure P and the volume V mean that the values when the intake valve 20 is closed are used. The in-cylinder temperature at the time of IVC (when the intake valve is closed) is obtained from the engine cooling water temperature sensor 46 on the assumption that it is equal to the engine water temperature. R is a gas constant.

上記の式において、筒内圧Ｐおよび容積Ｖのそれぞれの添え字のＥＶＯは、排気バルブ２２の開弁時の値を用いることを意味している。本実施形態では、ＥＧＲクーラ３２の入口におけるＥＧＲガスの温度Ｔ_ｅｘ１は、ＥＶＯ時（排気バルブ閉弁時）の筒内温度に等しいと仮定している。以上説明した図４のルーチン（サブルーチン）によって、ＥＧＲクーラ３２の入口におけるＥＧＲガスの温度Ｔ_ｅｘ１を算出することができる。 Next, using the in-cylinder mass M _cyl calculated in step S200, the temperature T _ex1 is calculated according to the following equation (step S202).

In the above formula, the subscripts EVO of the in-cylinder pressure P and the volume V mean that values at the time of opening of the exhaust valve 22 are used. In the present embodiment, it is assumed that the temperature T _ex1 of the EGR gas at the inlet of the EGR cooler 32 is equal to the in-cylinder temperature at the time of EVO (when the exhaust valve is closed). Or by-described FIG routines (subroutines), it is possible to calculate the temperature _{T ex1} of the EGR gas at the inlet of the EGR cooler 32.

After the actual heat transfer coefficient h _EGR is calculated in step S112 in FIG. 3, the EGR cooler cooling efficiency η _EGR is calculated by referring to the map in FIG. 6 (step S114). The map shown in FIG. 6 is shown as an example, and a map in which the relationship between h _EGR and η _EGR is determined in advance through experiments or the like is stored in the ECU 50. Instead of the two-dimensional map, it may be stored as a linear expression.

  With the above processing, the cooling efficiency of the EGR cooler 32 can be calculated.

In the routine of FIG. 3, subsequently, an EGR gas temperature count k is calculated (step S124). In this step, the EGR gas temperature count k corresponding to the value of the EGR cooler cooling efficiency η _EGR is calculated by referring to the map of FIG. The map shown in FIG. 7 is shown as an example, and a map in which the relationship between η _EGR and k is determined in advance by experiments or the like is stored in the ECU 50. Instead of the two-dimensional map, it may be stored as a linear expression.

Subsequently, the temperature T _ex2 of the EGR gas at the outlet of the EGR cooler 32 is calculated according to the following equation (step S116).

上記の式の右辺において、ＳはＥＧＲバルブ３４の開口面積に相当し、φ（Ｐ_ｉｎ／Ｐ_ｅｘ）は流速に、Ｐ_ｅｘ／（ＲＴ_ｅｘ２）^１／２は密度に相当している。φ（Ｐ_ｉｎ／Ｐ_ｅｘ）の値は、下記の式で求められる。

In the above formula, M _EGR is the mass flow rate of the EGR gas. Specifically, in the configuration diagram of FIG. 1, it is the mass flow rate of the EGR gas at the arrow position passing through the EGR valve 34. _MEGR is calculated according to the following equation. However, in the following equation, P _in is P _IVC, that is, the _in- cylinder pressure when the intake valve is closed, and P _ex is P _IVO, that is, the in-cylinder pressure when the intake valve is opened. T _ex2 uses the previous value.

In the right side of the above equation, S corresponds to the opening area of the EGR valve 34, φ (P _in / P _ex ) corresponds to the flow velocity, and P _ex / (RT _ex2 ) ^1/2 corresponds to the density. The value of φ (P _in / P _ex ) is obtained by the following equation.

With the above processing, the temperature T _ex2 of the EGR gas at the outlet of the EGR cooler 32 can be obtained.

  In the above-described embodiment, the ECU 50 executes the processes of steps S104 and S106 in the flowchart of FIG. 3 so that the “total heat receiving amount calculation means” in the first aspect of the invention is the steps S100 and S120. By executing the processing of S122 and S102, the “combustion heat receiving amount calculation means” in the first invention, and by executing the processing of step S108, the “moving heat amount calculation means” in the first invention By executing the process of step S110, the “inlet coolant temperature acquisition means” in the first invention, and by executing the process of step S114, the “cooling efficiency calculation means” in the first invention, Each is realized.

[Modification of Embodiment]
In the embodiment, the cooling efficiency η _EGR of the EGR cooler 32 was obtained, and the EGR cooler outlet temperature T _ex2 of EGR gas was calculated using this. Various control of the EGR system, such as correcting the control content of the EGR valve 34, may be performed using the temperature _Tex2 . Further, the calculated value of the cooling efficiency η _EGR may be used for controlling the internal combustion engine 2. As described in the section of calculating the EGR cooler cooling efficiency in the embodiment, the cooling efficiency of the EGR cooler has deterioration and variations with time. Since the cooling efficiency of the EGR cooler affects the temperature of the EGR gas, the change in the cooling efficiency of the EGR cooler affects various controls of the internal combustion engine including the deterioration of the cylinder air amount estimation accuracy. In this regard, the cooling efficiency η _EGR of the EGR cooler 32 obtained in the present embodiment may be utilized for various controls of the internal combustion engine 2 (for example, control related to in-cylinder air amount estimation). Alternatively, it may be used for abnormality diagnosis (abnormality determination) of the EGR cooler 32. Specifically, for example, the abnormality determination of the EGR cooler 32 is performed based on whether or not the current cooling efficiency η _EGR value is greatly deviated by a predetermined amount or more from a predetermined target value (reference value). Can do.

  In the present embodiment, a thermostat of a type that can be controlled by an electric signal from the ECU 50 is used as the thermostat 42. However, the present invention is not limited to this. The specific configuration of the thermostat is not particularly limited, and it is sufficient that a configuration for knowing the valve opening rate r of the thermostat is provided.

2 Internal combustion engine 10 Cylinder 12 Piston 14 Crankshaft 16 Spark plug 18 In-cylinder pressure sensor 20 Intake valve 22 Exhaust valve 24 Throttle 30 EGR gas passage 32 EGR cooler 34 EGR valve 40 Coolant passage 42 Thermostat 44 Radiator 46 Engine water temperature sensor

Claims (3)

An external EGR passage that recirculates EGR gas into a cylinder of the internal combustion engine, an EGR cooler that cools the EGR gas that flows through the external EGR passage, and a coolant that circulates inside the cylinder and is connected to a radiator. Cooling for calculating the cooling efficiency of the EGR cooler in an internal combustion engine comprising a coolant passage extending around the cylinder and connected to the EGR cooler, and a thermostat interposed between the coolant passage and the radiator An efficiency calculation device,
A total heat receiving amount calculating means for calculating a total heat receiving amount of the coolant in the coolant passage based on a valve opening rate of the thermostat;
Combustion heat receiving amount calculating means for calculating a combustion heat receiving amount that is a heat amount received from the internal combustion engine by the coolant in the coolant passage by combustion in the cylinder of the internal combustion engine;
A moving heat amount calculating means for calculating a moving heat amount that is a heat amount transferred from the EGR cooler to the cooling liquid in the cooling fluid passage from the total heat receiving amount and the combustion heat receiving amount;
Inlet coolant temperature acquisition means for acquiring the temperature of the coolant on the EGR cooler inlet side of the coolant passage;
Cooling efficiency calculating means for calculating the cooling efficiency of the EGR cooler based on the moving heat quantity calculated by the moving heat quantity calculating means and the temperature acquired by the inlet coolant temperature acquiring means;
A cooling efficiency calculating device for an EGR cooler, comprising: Actual heat in which the cooling efficiency calculating means calculates an actual heat transfer coefficient of the EGR cooler based on the transferred heat quantity calculated by the transferred heat quantity calculating means and the temperature acquired by the EGR cooler inlet coolant temperature acquiring means. Including a transmission rate calculation means,
further,
Inlet gas temperature acquisition means for acquiring the temperature of EGR gas flowing into the EGR cooler;
A temperature decrease amount calculating means for calculating a temperature decrease amount of the EGR gas by passing through the EGR cooler based on the actual heat transfer coefficient calculated by the actual heat transfer coefficient calculating means;
EGR gas temperature calculation means for calculating the temperature of the EGR gas downstream of the EGR cooler based on the temperature calculated by the inlet gas temperature acquisition means and the temperature decrease amount calculated by the temperature decrease amount calculation means; ,
The cooling efficiency calculating apparatus for an EGR cooler according to claim 1, comprising: An external EGR system that recirculates EGR gas into the cylinder;
An EGR cooler for cooling EGR gas recirculated via the external EGR system;
A coolant passage in which the coolant flows, is connected to a radiator, extends around the cylinder of the internal combustion engine, and is connected to the EGR cooler;
A thermostat interposed between the coolant passage and the radiator;
A control device for controlling an internal combustion engine comprising:
The cooling efficiency calculation device for an EGR cooler according to claim 1 or 2, which calculates the cooling efficiency of the EGR cooler or the temperature of EGR gas downstream of the EGR cooler,
Control means for controlling the external EGR system based on the cooling efficiency of the EGR cooler calculated by the cooling efficiency calculation device of the EGR cooler or the temperature of the EGR gas downstream of the EGR cooler using the valve opening rate of the thermostat as input information When,
A control device for an internal combustion engine, comprising:

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