JP4337686B2 - Intake valve temperature estimation device for internal combustion engine - Google Patents

Description

  The present invention relates to an intake valve temperature estimation device for an internal combustion engine, and more particularly to an intake valve temperature estimation device suitable for use in combination with a port injection type internal combustion engine.

  Conventionally, as disclosed in JP-A-8-61115, an apparatus for estimating the temperature of an intake valve of an internal combustion engine is known. The conventional apparatus detects the coolant temperature when starting the internal combustion engine, and sets the temperature as the initial value of the intake valve temperature. After a sufficient time has elapsed after the internal combustion engine is stopped, the temperature of the intake valve and the temperature of the cooling water can be considered equal. Therefore, according to the above method, the initial value of the intake valve temperature can be detected with high accuracy.

  In the above-described conventional device, after the internal combustion engine is started, the temperature rise of the intake valve is estimated according to the number of ignitions, and the intake valve temperature is estimated by adding the increase to the initial value. In an internal combustion engine, combustion of an air-fuel mixture occurs every time ignition is performed, and the intake valve is heated by the combustion. For this reason, a certain degree of correlation is recognized between the temperature rise of the intake valve and the number of ignitions. Therefore, according to the above-described conventional apparatus, the temperature of the intake valve can be estimated with a certain degree of accuracy after the internal combustion engine is started.

JP-A-8-61115 JP-A-8-49581 Japanese Patent Laid-Open No. 11-14507

  However, since the environment surrounding the intake valve is complicated, the temperature cannot be estimated with high accuracy based only on the number of ignitions. More specifically, in addition to transferring heat to and from the combustion gas, the intake valve transfers heat to and from a flowing gas (fresh air or blown-back gas) that flows around the intake valve when the valve is opened. I do.

  The amount of heat transferred between the intake valve and the flowing gas does not necessarily indicate a correlation with the number of ignitions after starting. For this reason, the temperature of the intake valve cannot be accurately estimated by the conventional method described above, as described above.

  The present invention has been made to solve the above-described problems, and accurately estimates the intake valve temperature after starting the internal combustion engine by independently considering the influence of the gas flowing around the intake valve. It is an object of the present invention to provide an intake valve temperature estimation device for an internal combustion engine that can be used.

In order to achieve the above object, a first invention is an intake valve temperature estimation device for an internal combustion engine,
A combustion gas heat receiving amount calculating means for calculating the amount of combustion gas received by the intake valve of the internal combustion engine from the combustion gas in the cylinder;
A flowing gas heat receiving amount calculating means for calculating a flowing gas heat receiving amount received from the flowing gas flowing around the intake valve;
A total heat receiving amount calculating means for calculating a total heat receiving amount received by the intake valve based on the combustion gas heat receiving amount and the flowing gas heat receiving amount;
A temperature change amount calculating means for calculating a temperature change amount of the intake valve based on the total heat receiving amount;
An initial temperature estimating means for estimating an initial temperature of the intake valve;
Intake valve temperature estimating means for estimating the temperature of the intake valve based on the initial temperature and the amount of temperature change;
It is characterized by providing.

The second invention is the first invention, wherein
When the fuel adhering to the intake valve is vaporized, it comprises vaporization heat amount calculating means for calculating the amount of vaporization carried away from the intake valve,
The total heat receiving amount calculation means is characterized in that a value obtained by subtracting the vaporization heat amount from a heat receiving amount calculated based on the combustion gas heat receiving amount and the flowing gas heat receiving amount is used as the total heat receiving amount.

The third invention is the first or second invention, wherein
The intake valve includes a contact surface heat receiving amount calculation means for calculating a contact surface heat receiving amount received by transmission from the valve seat,
The total heat receiving amount calculation means is characterized in that a value obtained by adding the contact surface heat receiving amount to a heat receiving amount calculated based on the combustion gas heat receiving amount and the flowing gas heat receiving amount is used as the total heat receiving amount.

Moreover, 4th invention is set in 3rd invention,
A variable valve mechanism that makes the working angle of the intake valve variable,
The contact surface heat receiving amount calculating means calculates the contact surface heat receiving amount based on the working angle.

The fifth invention is the first to fourth inventions,
The flowing gas heat receiving amount calculating means includes:
Intake gas heat receiving amount calculating means for calculating an intake gas heat receiving amount generated due to the intake gas flowing from the intake port into the cylinder;
Blow-back heat reception amount calculation means for calculating a blow-back heat reception amount generated due to the blow-back gas flowing backward from the cylinder to the intake port;
A final heat receiving amount calculating means for calculating the flowing gas heat receiving amount based on the intake gas heat receiving amount and the blow back heat receiving amount;
It is characterized by including.

The sixth invention is the fifth invention, wherein
A variable valve mechanism that makes the lift amount of the intake valve variable;
A lift amount determining means for determining whether or not the lift amount is below a determination value;
The final heat receiving amount calculation means takes into account the presence of the blow back heat receiving amount only when the lift amount is equal to or greater than the determination value.

The seventh invention is the first to fourth inventions,
The flowing gas heat receiving amount calculating means includes:
A normal heat receiving amount calculation means for calculating a normal heat receiving amount considering only the intake gas heat receiving amount caused by the intake gas flowing from the intake port into the cylinder;
In addition to the intake gas heat reception amount, the blowback heat reception amount calculation means for calculating the blowback heat reception amount in consideration of the blowback heat reception amount caused by the blowback gas flowing back from the cylinder to the intake port;
Blowback amount determination means for determining whether or not the flow rate of the blowback gas is greater than a determination value;
When the flow rate of the blowback gas is less than or equal to the determination value, the normal amount of heat received is the flowing gas heat reception amount. A final heat receiving amount setting means as a heat amount;
It is characterized by including.

The eighth invention is the seventh invention, wherein
A variable valve mechanism that makes the lift amount of the intake valve variable;
A lift amount determining means for determining whether or not the lift amount is below a determination value;
The final heat receiving amount setting means is characterized in that, when the lift amount is less than the determination value, the normal heat receiving amount is the flowing gas heat receiving amount.

The ninth invention relates to the first to eighth inventions,
A variable valve mechanism that makes the lift amount of the intake valve variable,
The flowing gas heat receiving amount calculating means calculates the flowing gas heat receiving amount based on the lift amount.

The tenth invention is the first to ninth inventions,
A fuel cut detecting means for detecting a fuel cut in the internal combustion engine;
The combustion gas heat receiving amount calculation means calculates the combustion gas heat receiving amount according to a rule set on the assumption that combustion does not occur in a cylinder during fuel cut.

The eleventh invention is the first to tenth invention,
Stop time counting means for counting the stop time of the internal combustion engine;
Cooling water temperature detecting means for detecting the cooling water temperature of the internal combustion engine;
An intake valve temperature resetting means for resetting the temperature of the intake valve to the coolant temperature at that time when the stop time exceeds a determination value;
It is characterized by providing.

  According to the first aspect of the present invention, the intake valve receives the combustion gas heat reception amount received from the combustion gas in the cylinder and the flowing gas heat reception amount received from the flowing gas flowing around the intake valve separately, and based on them. The total amount of heat received can be calculated. Therefore, according to the present invention, the influence of the flowing gas can be accurately reflected in the intake valve temperature, and the temperature can be estimated with high accuracy.

  According to the second aspect of the invention, the effect of the amount of heat generated when the fuel adhering to the intake valve is vaporized can be reflected in the temperature of the intake valve.

  According to the third aspect of the invention, the influence of the contact surface heat received by the intake valve from the valve seat can also be reflected in the temperature of the intake valve.

  According to the fourth aspect of the invention, the operating angle of the intake valve can be changed. By the way, when the working angle of the intake valve changes, the time during which the intake valve is in contact with the valve seat changes, and as a result, the amount of heat received by the contact surface also changes. According to the present invention, the change can be accurately captured and accurately reflected in the temperature of the intake valve.

  According to the fifth invention, the intake gas heat receiving amount caused by the intake gas flowing from the intake port into the cylinder and the blow back heat receiving amount caused by the blow back from the cylinder are separately calculated, A flowing gas heat receiving amount can be calculated. Therefore, according to the present invention, the amount of heat received by the flowing gas can be calculated with high accuracy, and as a result, the temperature of the intake valve can be estimated with high accuracy.

  According to the sixth aspect, the lift amount of the intake valve can be changed. By the way, when the lift amount of the intake valve is large, the flow rate of the intake air becomes relatively small, so that the blowback from the cylinder to the intake port is likely to occur. On the other hand, when the lift amount is small, the flow rate of the intake air is sufficiently high, so that the blow-back from the cylinder is unlikely to occur. According to the present invention, only when the lift amount is equal to or greater than the determination value, the presence of the blow back heat receiving amount is considered. For this reason, according to the present invention, the effect of blowback can be reflected efficiently and appropriately on the temperature of the intake valve.

  According to the seventh aspect, the normal amount of heat received considering only the influence of the intake gas flowing into the cylinder and the amount of heat received during reflow considering the effect of blowback in addition to the influence are calculated separately. Can do. Then, depending on whether or not the flow rate of the blown-back gas is higher than the determination value, any of them can be set as the flowing gas heat receiving amount. Therefore, according to the present invention, the amount of heat received by the flowing gas can be calculated with high accuracy, and as a result, the temperature of the intake valve can be estimated with high accuracy.

  According to the eighth aspect of the present invention, at the time of a small lift in which blow-back does not easily occur, it is not necessary to determine the amount of blow-back, and the normal-time heat reception amount can be made the flowing gas heat reception amount. For this reason, according to the present invention, the effect of blowback can be reflected efficiently and appropriately on the temperature of the intake valve.

  According to the ninth aspect, the lift amount of the intake valve can be changed. By the way, the flow velocity of the gas flowing around the intake valve varies depending on the amount of lift. And if the flow velocity of gas changes, a change will also arise in flowing gas heat receiving amount. According to the present invention, the change can be accurately reflected in the amount of heat received by the flowing gas, and as a result, the temperature of the intake valve can be estimated with sufficiently high accuracy.

  According to the tenth aspect, when the fuel is cut, the amount of heat received by the combustion gas can be calculated according to a rule set on the assumption that combustion does not occur in the cylinder. Therefore, according to the present invention, the temperature of the intake valve can always be accurately estimated without being affected by the presence or absence of fuel cut.

  According to the eleventh aspect of the invention, when the internal combustion engine has been stopped for a long time and the intake valve is sufficiently cooled, it is assumed that the temperature of the intake valve is equal to the cooling water temperature, and the temperature is Can be reset. Therefore, according to the present invention, the temperature of the intake valve can always be estimated with high accuracy even in a vehicle such as a hybrid vehicle in which the internal combustion engine frequently stops.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining the configuration of the first embodiment of the present invention. As shown in FIG. 1, the system according to the first embodiment of the present invention includes an internal combustion engine 10. An intake passage 12 and an exhaust passage 14 communicate with the internal combustion engine 10.

  An air flow meter 16 for detecting the intake air amount Ga is disposed in the intake passage 14. A throttle valve 18 is disposed downstream of the air flow meter 16. Further, an injector 20 for injecting fuel into the intake port is disposed further downstream of the throttle valve 18.

  The internal combustion engine 10 includes an intake valve 24 for controlling a conduction state between the intake passage 12 and the cylinder 22. A variable valve mechanism 26 is connected to the intake valve 24 as a drive source. The variable valve mechanism 26 can open and close the intake valve 24 while appropriately changing the valve opening timing, the operating angle, and the lift amount.

  An exhaust valve 28 is disposed between the cylinder 22 and the exhaust passage 14. A variable valve mechanism 30 is connected to the exhaust valve 28 as a drive source. The variable valve mechanism 30 can open and close the exhaust valve 28 while appropriately changing the valve opening timing, the operating angle, and the lift amount.

  In the system of this embodiment, as described above, the intake valve 24 and the exhaust valve 28 are each driven by the variable valve mechanism 30, but the mechanism for driving them is not limited to this. That is, in the system of the present embodiment, the intake valve 24 and the exhaust valve 28 may be driven by a normal cam mechanism.

  The internal combustion engine 10 is equipped with a rotation angle sensor 32 for detecting the engine speed Ne and a water temperature sensor 34 for detecting the cooling water temperature Tw. The system of this embodiment includes an ECU (Electronic Control Unit) 40. The ECU 40 is supplied with outputs from various sensors including the air flow meter 16 and the rotation angle sensor 32. The ECU 40 can control various actuators including the injector 20 and the variable valve mechanisms 26 and 30 based on the sensor outputs.

[Intake Valve Temperature Estimation Method in Embodiment 1]
During operation of the internal combustion engine 10, fuel is injected into the intake port by the injector 20. Part of the fuel injected into the intake port 20 adheres to the intake valve 24. When the internal combustion engine 10 is sufficiently warmed up and the intake valve 24 is at a high temperature, the adhering fuel is vaporized in a short time. Therefore, the influence of the adhering fuel amount is sucked into the cylinder. It does not extend greatly.

  However, under the situation where the temperature of the intake valve 24 has not risen sufficiently, a situation occurs in which the fuel attached thereto is not completely vaporized during the valve opening period. In this case, in order to accurately grasp the amount of fuel flowing into the cylinder, it is necessary to accurately estimate the proportion of fuel vaporized from the fuel adhering to the intake valve 24. In order to estimate the estimation with high accuracy, it is necessary to accurately estimate the temperature of the intake valve 24 during the warm-up process of the internal combustion engine 10. Therefore, in the system of the present embodiment, the temperature of the intake valve 24 is estimated by the method described below after the internal combustion engine 10 is started.

  2A and 2B are diagrams for explaining the principle by which the system of the present embodiment calculates the temperature Tv of the intake valve 24. FIG. More specifically, FIG. 2 (A) is a diagram for explaining the thermal environment of the intake valve 24 during valve closing. FIG. 2B is a view for explaining the thermal environment of the intake valve during valve opening.

  Symbols Qb, Qs, and Qf shown in FIG. 2A indicate the combustion gas heat reception amount, the contact surface heat reception amount, and the fuel vaporization heat amount, respectively. The combustion gas heat reception amount Qb is the amount of heat given from the combustion gas in the cylinder 22 to the intake valve 24. The contact surface heat receiving amount Qs is the amount of heat transferred to the intake valve 24 from the mechanical contact surface with the valve seat. Further, the fuel vaporization heat quantity Qf is a heat quantity taken away when the fuel adhering to the intake valve 24 is vaporized. As shown in FIG. 2A, during the closing of the intake valve 24, the above-described three types of heat are mainly transferred between the intake valve 24 and its surroundings.

  Symbols Qgin and Qgback shown in FIG. 2B indicate the intake gas heat reception amount and the blowback heat reception amount that are generated when the intake valve 24 is opened. The intake gas heat receiving amount Qgin is the amount of heat transferred between the fresh air flowing into the cylinder 22 from the intake port and the intake valve 24. On the other hand, the blowback heat reception amount Qgback is a heat reception amount generated due to the blowback gas flowing backward from the cylinder 22 to the intake port while the intake valve 24 is opened. As shown in FIG. 2B, during the opening of the intake valve 24, these two types of heat are mainly transferred between the intake valve 24 and its surroundings. Hereinafter, these heat reception amounts are collectively referred to as “fluid gas heat reception amount”.

  The temperature of the intake valve 24 rises by absorbing heat from the surrounding environment, and falls by releasing heat to the surrounding environment. For this reason, if the initial temperature of the intake valve 24 is known, it is possible to estimate the temperature of the intake valve 24 by detecting the total amount of heat received thereafter. And in order to perform the estimation with high accuracy, it is effective to detect the five types of heat amounts described above with high accuracy. In particular, since the flowing gas heat receiving amounts Qgin and Qgback shown in FIG. 2B vary greatly depending on the operating state of the internal combustion engine 10, the values are accurate to estimate the intake valve temperature Tv with high accuracy. It is important to ask for.

  Therefore, in the present embodiment, based on the operating state of the internal combustion engine 10, three types of heat receiving amounts Qb, Qs, Qf shown in FIG. 2A and flowing gas heat receiving amounts Qgin, Qgback shown in FIG. Are calculated separately, and the total amount of heat received by the intake valve 24 is accurately calculated by integrating them. Then, the intake valve temperature Tv is accurately estimated based on the total amount of heat received thus calculated.

[Specific Processing in Embodiment 1]
FIG. 3 is a flowchart of a routine executed in the present embodiment in order to realize the above function. The routine shown in FIG. 3 is started when the internal combustion engine 10 starts. Here, first, the coolant temperature Tw at that time is set as the initial value of the intake valve temperature Tv (step 101). When the internal combustion engine 10 is stopped for a sufficiently long time, the intake valve temperature Tv converges to the temperature of the internal combustion engine 10, that is, the cooling water temperature Tw. For this reason, when the internal combustion engine 10 is started, the process of step 101 can be performed to accurately estimate the intake valve temperature Tv.

  Next, various parameters representing the current state of the internal combustion engine 10 are measured (step 102). Specifically, in addition to the intake air amount Ga and the engine speed Ne, the state of the variable valve mechanism 26, that is, the valve opening timing VT of the intake valve 24, the lift amount VL, the operating angle Vθ, and the like. Detected.

  Next, it is determined whether or not the amount of blowback that occurs when the intake valve 24 is opened is greater than the determination value α (step 103). The blowback amount can be estimated based on the state of the internal combustion engine 10, specifically, for example, based on the load KL of the internal combustion engine 10, the valve overlap amount VOL, the engine speed NE, and the like.

  4 (A) to 4 (C) are diagrams showing the relationship between the blowback amount, the load KL, the valve overlap VOL, and the engine speed NE. In the present embodiment, the ECU 40 stores a map corresponding to these relationships. In step 103, by referring to the map, the amount of blowback predicted to occur under the current situation is estimated, and further, it is determined whether the estimated value is larger than a predetermined determination value α.

  The determination value α is a value for determining whether or not it is necessary to consider the blow back heat reception amount Qgback when obtaining the flowing gas heat reception amount. That is, it is a value for judging whether or not a large amount of blowback has occurred, and it is necessary to consider the blowback heat reception amount Qgback. Therefore, when it is recognized that the blowback amount> α is not satisfied, that is, when the blowback amount is equal to or less than the determination value α, it can be determined that it is not necessary to consider the influence of the blowback when estimating the flowing gas heat receiving amount. In this case, after calculating the intake gas heat receiving amount Qgin, the value is directly used as the flowing gas heat receiving amount (step 104). Hereinafter, the flowing gas heat receiving amount obtained here will be represented by the sign “Qg”.

  On the other hand, if it is determined in step 103 that the blowback amount> α is established, it can be determined that the influence of the blowback needs to be taken into account when obtaining the flowing gas heat receiving amount. In this case, the intake gas heat receiving amount Qgin and the blow back heat receiving amount Qgback are calculated, and the sum of them is set as the flowing gas heat receiving amount (step 105). Hereinafter, the flowing gas flow heat quantity obtained here will be denoted by the sign “Qg ′”.

(Example of calculation method for intake gas heat reception Qgin)
The intake gas heat receiving amount Qgin described above can be calculated by, for example, the following arithmetic expression.
Qgin = hgin ・ (Tin−Tv) ・ dtin
hgin = 0.0404 ・ (kg / Dv) ・ Revin ^0.868・ (Dv / liftv) ^0.275
Revin = (ρg ・ Ug ・ Dv) / μg (1)

  However, in the upper equation, hgin is a heat transfer coefficient and can be obtained by the intermediate equation. Further, Tin is the temperature of the intake gas, Tv is the intake valve temperature, and dtin is the time during which the intake gas is circulating around the intake valve 24. Tin can be substituted by the intake air temperature. As the Tv, an estimated value of the current intake valve temperature can be used. Dtin is determined based on the engine speed Ne.

  In the middle equation, kg is the heat transfer coefficient of the intake gas, and Dv is the diameter of the intake valve 24. These are all known values. Further, liftv is the lift amount of the intake valve 24 and can be detected from the state of the variable valve mechanism 26 in the present embodiment. Revin is a value defined by the lower equation.

  In the lower equation, ρg is the gas density of the intake port, and Ug is the gas flow rate of the intake port. ρg and Ug can be calculated by a known method based on the temperature of the intake port, the intake air amount Ga, the intake pipe pressure PM, and the like. Further, μg is a viscosity coefficient of inhaled gas, which is a known value. Therefore, the intake gas heat receiving amount Qgin can be obtained by calculation using the above equation (1).

(Example of calculation method for blowback heat reception Qgback)
The blow back heat receiving amount Qgback can be calculated by, for example, the following arithmetic expression.
Qgback = hgback ・ (Tback−Tv) ・ dtback
hgback = 1.2 · (kg / liftv) · Revback ^0.38 · (2 · liftv / Dv) ^0.62
Revback = (ρg ・ Ug ・ liftv) / μg (2)

  However, in the upper equation, hgback is a heat transfer coefficient and can be obtained by the intermediate equation. Tback is the temperature of the blowback gas, and dtback is the time during which blowback occurs around the intake valve 24. Tback can be substituted by the temperature of the in-cylinder gas that can be detected by a known method. Further, dt is obtained based on the engine speed Ne.

  In the middle equation, kg is the heat transfer coefficient of the blown-back gas, and Dv is the diameter of the intake valve 24. These are all known values. Further, liftv is the lift amount of the intake valve 24 and can be detected from the state of the variable valve mechanism 26 in the present embodiment. Revback is a value defined by the lower equation.

  In the lower equation, ρg is the gas density of the intake port, and Ug is the gas flow rate of the intake port. ρg and Ug can be calculated by a known method based on the temperature of the intake port, the intake air amount Ga, the intake pipe pressure PM, and the like. Further, μg is a viscosity coefficient of inhaled gas, which is a known value. For this reason, the blow back heat receiving amount Qgback can be obtained by calculation using the above equation (2).

  The flowing gas heat receiving amount Qg to be obtained in step 104 can be calculated by using the above equation (1). In addition, the flowing gas heat receiving amount Qg ′ to be obtained in the step 105 can be obtained by adding the calculation result of the equation (1) and the calculation result of the equation (2). In this way, the flowing gas heat receiving amount can be calculated by calculation both when the influence of blowback is not taken into account (Qg) and when the influence is taken into account (Qg ′).

(Examples of other calculation methods for fluid gas heat received Qg, Qg ')
However, the method for obtaining the flowing gas heat receiving amounts Qg and Qg ′ is not limited to the method using the arithmetic expression as described above. That is, the flowing gas heat receiving amount Qg that does not consider the influence of blowback can be mapped in advance using the engine speed Ne, the engine load KL, the valve opening timing VT of the intake valve 24, and the like as parameters. Similarly, it is possible to map the flowing gas heat receiving amount Qg ′ in consideration of the blowback effect in advance. For this reason, after these maps are stored in the ECU 40 in advance, in steps 104 and 105, the flow gas heat receiving amount Qg or Qg ′ may be obtained by referring to these maps.

(Calculation of contact surface heat reception Qs)
In the routine shown in FIG. 3, the contact surface heat receiving amount Qs is then calculated (step 106). The contact surface heat receiving amount Qs can be calculated by, for example, an arithmetic expression shown below.
Qs = hs ・ (Tvs−Tv) ・ dts
hs = 4130 · (Pm / 50000) ^0.6 (3)

  However, in the upper equation, hs is a heat transfer coefficient and can be obtained by the lower equation. Tvs is the temperature of the valve seat, and can be substituted by the cooling water temperature Tw. Dts is the time during which the intake valve 24 is seated on the valve seat, and can be calculated based on the engine speed Ne. Pm in the lower equation is the intake pipe pressure.

  The contact surface heat receiving amount Qs can be obtained by calculation using the state of the internal combustion engine 10 as a parameter by using the above equation (3). For this reason, in the said step 106, the contact surface heat-receiving amount Qs can be calculated | required correctly.

  However, the method for obtaining the contact surface heat receiving amount Qs is not limited to the method using the arithmetic expression as described above. That is, the amount of heat per unit time that the intake valve 24 receives from the valve seat is a value that is almost uniquely determined with respect to the difference ΔT between the valve seat temperature and the intake valve temperature Tv. The time during which the intake valve 24 is seated on the valve seat is a function of the engine speed Ne. Therefore, the contact surface heat receiving amount Qs can be mapped in advance using the temperature difference ΔT and the engine speed Ne as parameters. Therefore, in step 106, the contact surface heat receiving amount Qs may be obtained based on the map.

(Calculation of fuel vaporization heat quantity Qf)
Next, in the routine shown in FIG. 3, the fuel vaporization heat quantity Qf is calculated (step 107). The fuel vaporization heat quantity Qf can be calculated by, for example, an arithmetic expression shown below.
Qf = mf · {(Tv−Tf) · Cpf + Hf} · dtf (4)

  In the above equation (4), mf is the fuel evaporation amount. The fuel evaporation amount mf can be obtained based on the amount of fuel injected toward the intake valve 24, the intake valve temperature Tv, the intake pipe pressure Pm, and the like. Tf is the fuel temperature, and the value can be approximated by a fixed value corresponding to the cooling water temperature at the start, for example. Cpf is the specific heat of fuel, and Hf is the latent heat of fuel vaporization. Any of these can be treated as default values. Dtf is a time to be considered as the fuel vaporization period, and can be set here as a function of the engine speed Ne.

  The fuel vaporization heat quantity Qf can be obtained by calculation using the state of the internal combustion engine 10 as a parameter by using the above equation (4). Therefore, in step 107, the fuel vaporization heat quantity Qf can be accurately obtained.

  However, the method for obtaining the fuel vaporization heat quantity Qf is not limited to the method using the arithmetic expression as described above. That is, the fuel vaporization heat quantity Qf can be mapped in advance using the fuel injection quantity and the intake valve temperature Tv as parameters. Therefore, in step 107, the fuel vaporization heat quantity Qf may be obtained by referring to the map.

(Calculation of combustion gas heat received Qb)
In the routine shown in FIG. 3, next, the combustion gas heat receiving amount Qb is calculated (step 108). The combustion gas heat receiving amount Qb can be calculated by, for example, an arithmetic expression shown below.
Qb = hb ・ (Tc−Tv) ・ dtb
hb = 0.013 · Dc ^−0.2 · Pc ^0.8 · Uc ^0.8 · Tc ^−0.53 (5)

  However, in the upper equation, hb is a heat transfer coefficient and can be obtained by the lower equation. Tc is the gas temperature in the cylinder 22 and can be estimated by a known method based on the operating state of the internal combustion engine 10, for example. Further, dtb is a time during which the temperature of the combustion gas acts on the intake valve 24, and can be calculated based on the engine speed Ne here.

  In the lower equation, Dc is the cylinder diameter and can be treated as a predetermined value. Pc is the in-cylinder pressure, and can be measured by, for example, an in-cylinder pressure sensor. Uc and Tc are the gas flow velocity and gas temperature in the cylinder 22, respectively. These can be estimated by a known method based on the operating state of the internal combustion engine 10.

  The combustion gas heat receiving amount Qb can be obtained by calculation using the state of the internal combustion engine 10 as a parameter by using the above equation (5). Therefore, in step 108, the combustion gas heat receiving amount Qb can be accurately obtained.

  However, the method for obtaining the combustion gas heat receiving amount Qb is not limited to the method using the arithmetic expression as described above. That is, the combustion gas heat receiving amount Qb can be mapped in advance by using the engine speed Ne, the engine load KL, the opening timing of the intake valve 24, and the fuel injection amount as parameters. . Therefore, in step 108, the combustion gas heat receiving amount Qb may be obtained with reference to the map.

(Renewal of intake valve temperature Tv)
When the above process is completed, an update process for the intake valve temperature Tv is then performed (step 109). Specifically, first, the total heat receiving amount (Qg or Qg ′ + Qs−Qf + Qb) of the intake valve 24 is calculated based on all the heat receiving amounts obtained in the current processing cycle. Next, the total amount of heat received is divided by the specific heat of the intake valve 24 (assumed to be known), thereby calculating a temperature change ΔTv generated during the current processing cycle. Finally, by adding ΔTv to the current intake valve temperature Tv, the intake valve temperature Tv is updated to the latest value.

  As described above, according to the routine shown in FIG. 3, the amount of heat received that affects the intake valve temperature Tv includes the flow gas received amount Qg or Qg ′, the contact surface received heat amount Qs, the fuel vaporized heat amount Qf, and the combustion gas received amount. It can be divided into heat quantity Qb and estimated individually. In particular, the flowing gas heat receiving amount Qg or Qg ′ can be estimated by further distinguishing between the case where the influence of blowback should be considered and the case where it is necessary to consider it. Finally, the intake valve temperature Tv can be updated by integrating the amounts of heat received.

  According to such an updating method, various phenomena occurring in the internal combustion engine 10 can be finely reflected in the intake valve temperature Tv, and the estimation accuracy can be sufficiently increased. For this reason, according to the system of the present embodiment, the intake valve temperature Tv can be estimated with extremely high accuracy.

  By the way, in the first embodiment described above, in estimating the intake valve temperature Tv, in addition to the flowing gas heat reception amount Qg or Qg ′ and the combustion gas heat reception amount Qb, the contact surface heat reception amount Qs and the fuel vaporization heat amount Qf are calculated. However, the estimation method is not limited to this. That is, the influence of the contact surface heat reception amount Qs and the fuel vaporization heat amount Qf on the intake valve temperature Tv is smaller than the influence of the flowing gas heat reception amount Qg or Qg ′ and the combustion gas heat reception amount Qb. May be estimated without considering the contact surface heat reception amount Qs and the fuel vaporization heat amount Qf.

  In the first embodiment described above, the ECU 40 executes the process of step 108, so that the “combustion gas heat receiving amount calculation means” in the first invention executes the process of step 104 or 105. The “fluid gas heat receiving amount calculating means” in the first aspect of the invention executes the process of step 101, and the “initial temperature estimating means” of the first aspect of the invention executes the process of step 109. The “total heat reception amount calculation means”, “temperature change amount calculation means”, and “intake valve temperature estimation means” in the first invention are realized.

  Further, in the first embodiment described above, the “vaporization heat amount calculating means” in the second aspect of the present invention is realized by the ECU 40 executing the process of step 107. Further, here, the “contact surface heat receiving amount calculating means” in the third aspect of the present invention is realized by the ECU 40 executing the processing of step 106.

  In the first embodiment described above, the ECU 40 calculates the intake gas heat reception amount Qgin in step 104, whereby the “intake gas heat reception amount calculation means” in the fifth aspect of the invention is blown back in step 105. In step 104 or 105, the “blow-back heat receiving amount calculating means” in the fifth invention calculates the flowing gas heat receiving amount Qg or Qg ′ in step 104 or 105, thereby calculating the “final heat receiving amount calculation” in the fifth invention. Each means is realized.

  Further, in the first embodiment described above, the ECU 40 calculates the flowing gas heat receiving amount Qg, whereby the “normal heat receiving amount calculation means” in the seventh invention calculates the flowing gas heat receiving amount Qg ′. Thus, the “blow-back heat receiving amount calculation means” according to the seventh invention is realized, and the ECU 40 executes the processing of step 103, whereby the “blow-back amount determination means” according to the seventh invention is realized. By executing the processing of step 104 or 105 according to the determination of step 103, the “final heat receiving amount setting means” in the seventh aspect of the invention is realized.

Embodiment 2. FIG.
[Features of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIG. 5 and FIG. The system of the present embodiment can be realized by causing the ECU 40 to execute a routine shown in FIG. 6 described later in the system shown in FIG. However, in this embodiment, the variable valve mechanism 26 that is the drive source of the intake valve 24 is a mechanism that changes the lift amount VL and the operating angle Vθ simultaneously according to a predetermined rule, more specifically, the lift amount VL. It is assumed that this is a mechanism that increases or decreases the operating angle Vθ in accordance with the increase or decrease of.

  FIG. 5 is a diagram for explaining the relationship between the lift amount VL of the intake valve 24 and the intake flow velocity. More specifically, FIG. 5 (A) is a diagram for explaining a phenomenon that occurs under a situation where the lift amount VL is small, while FIG. 5 (B) occurs under a situation where the lift amount VL is large. It is a figure for demonstrating a phenomenon.

  When the lift amount VL of the intake valve 24 is small, the intake gas flowing into the cylinder 22 is concentrated in a narrow opening. As a result, when the lift amount VL is small, a faster flow velocity is generated around the intake valve 24 than when the lift amount VL is large. The amount of heat received from the intake gas by the intake valve 24 changes as the flow rate of the gas changes. For this reason, in order to calculate the total heat receiving amount of the intake valve 24 with high accuracy, the normal intake gas heat receiving amount Qgin (see FIG. 5B) generated under a situation where the lift amount VL is large and the lift amount VL are small. It is appropriate to distinguish from the intake gas heat reception amount QginS (see FIG. 5A) generated under the circumstances.

  In the present embodiment, as described above, the lift amount VL of the intake valve 24 and the operating angle Vθ change in conjunction with each other. As a result, under a situation where the lift amount VL is small, the operating angle Vθ is also small. Incidentally, the amount of heat received by the intake valve 24 from the valve seat, that is, the contact surface heat reception amount Qs is a function of the time dts during which the intake valve 24 is seated on the valve seat. The seating time dts is linearly related to the operating angle Vθ. For this reason, in order to accurately detect the total heat receiving amount of the intake valve 24, the contact surface heat receiving amount Qs is also a value Qs that occurs when the operating angle Vθ is large and a value that occurs when the operating angle Vθ is small. It is appropriate to distinguish it from QsS.

  Therefore, the system of the present embodiment distinguishes between the case where the lift amount VL (that is, the operating angle Vθ) of the intake valve 24 is small and the case where the lift amount VL is large, and in each situation, the intake gas heat receiving amount Qgin and The contact surface heat receiving amount Qs was calculated. Hereinafter, the processing content for realizing the function will be described in detail with reference to FIG.

[Specific Processing in Second Embodiment]
FIG. 6 is a flowchart of a routine executed by the ECU 40 in the present embodiment. The routine shown in FIG. 6 is the same as the routine shown in FIG. 3 except that steps 103 and 105 are replaced with steps 110 to 112. Hereinafter, of the steps shown in FIG. 6, the same steps as those shown in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 6, after various parameters are measured in step 102, it is determined whether or not the lift amount VL of the intake valve 24 is smaller than the determination value β (step 110). The determination value β is a lower limit value at which the lift amount VL can be regarded as a normal value. Therefore, if it is determined that the lift amount VL is not less than the determination value β, it can be determined that the lift amount VL can be handled as a normal value. In this case, the processes in steps 104 to 109 are sequentially executed thereafter, as in the case of the first embodiment.

  On the other hand, if it is determined in step 110 that the lift amount VL is lower than the determination value β, it can be determined that the lift amount VL is a small value that cannot be handled as a normal value. In this case, the flowing gas heat receiving amount Qg '' is calculated by a method on the assumption that the lift amount VL is small (step 111), and then the contact surface heat receiving amount Qs by a method on the assumption that the working angle Vθ is small. 'Is calculated (step 112). Thereafter, similarly to the case of the first embodiment, the processes of steps 107 to 109 are executed.

  According to the routine shown in FIG. 6, when the lift amount VL can be regarded as a normal value (when the lift amount VL is not less than the determination value β), the intake gas heat reception amount Qgin calculated according to the above equation (1) flows in step 104. The amount of gas heat received is Qg. In this case, in step 106, the contact surface heat receiving amount Qs is calculated according to the above equation (3).

  The above equation (1) accurately represents the relationship established between various parameters and the intake gas heat reception amount Qgin when the lift amount VL can be regarded as a normal value. Similarly, the above equation (3) accurately represents the relationship established between the various parameters and the contact surface heat receiving amount Qs when the operating angle Vθ is a normal value. For this reason, under conditions where a lift amount VL that can be regarded as a normal value is generated, the flowing gas heat receiving amount Qg and the contact surface heat receiving amount Qs can be calculated by using these arithmetic expressions.

  The above equation (1) includes the lift amount VL (liftv) of the intake valve 24 as one of the parameters. Therefore, as long as the lift amount VL fluctuates within a range that can be regarded as a normal value, the intake gas heat reception amount Qgin (that is, the flowing gas heat reception amount Qg in this case) can be calculated with high accuracy by the equation (1). However, in a region where the lift amount VL is sufficiently small, a non-negligible divergence may occur between the intake gas heat reception amount Qgin calculated by the equation (1) and the actual intake gas heat reception amount Qgin.

  The ECU 40 calculates an arithmetic expression (for example, a coefficient obtained by changing the coefficient of the expression (1)) that can calculate the intake gas heat receiving quantity Qgin in accordance with an actual value in an area where the lift amount VL is sufficiently small. Remember with. In step 111, the inflow gas heat receiving amount Qgin calculated according to the calculation formula is set as the flowing gas heat receiving amount Qg ''. For this reason, according to the processing of step 111, the flowing gas heat receiving amount Qg ″ in accordance with the actual value can be calculated under the condition that VL <β is satisfied.

  The above equation (3) includes the seating time dts of the intake valve 24 as a parameter. In step 106, the ECU 40 calculates the seating time dts based on the operating angle Vθ and the engine speed Ne, and substitutes the dts into equation (3). Therefore, as long as the lift amount VL (working angle Vθ) fluctuates within a range that can be regarded as a normal value, the contact surface heat receiving amount Qs can be accurately calculated by the processing of step 106. However, with respect to the contact surface heat receiving amount Qs as well, in a region where the lift amount VL is sufficiently small, that is, in a region where the working angle Vθ is sufficiently small, the calculated value by the equation (3) may deviate greatly from the actual value. .

  The ECU 40 calculates an arithmetic expression (for example, a formula obtained by changing the coefficient of the expression (3)) that can calculate the contact surface heat receiving quantity Qs in accordance with the actual value in an area where the lift amount VL is sufficiently small. Remember with. In step 112, the contact surface heat receiving amount Qs is calculated according to the calculation formula. For this reason, according to the process of step 112, under the situation where VL <β is established, the contact surface heat receiving amount Qs ′ in accordance with the actual value can be accurately calculated.

  As described above, according to the routine shown in FIG. 6, the calculation formula is switched between the case where the lift amount VL can be regarded as a normal value and the case where the lift amount VL does not reach the normal value. In addition, the flowing gas heat receiving amount Qg or Qg ″ and the contact surface heat receiving amount Qs or Qs ′ can be accurately calculated. Therefore, according to the system of the present embodiment, the intake valve temperature Tv can always be accurately estimated regardless of the lift amount VL.

  In the second embodiment described above, the flowing gas heat receiving amount Qg or Qg ″ and the contact surface heat receiving amount Qs or Qs ′ are calculated by calculation. They are calculated with reference to a map. It is good as well. In other words, a map to be applied when the lift amount VL is large and a map to be applied when the lift amount VL is small are prepared in advance, and the map to be referred to is switched according to the success or failure of VL <β. The gas heat receiving amount Qg or Qg ″ and the contact surface heat receiving amount Qs or Qs ′ may be calculated.

  Further, in the above-described second embodiment, it is assumed that Equations (1) and (3) do not match the actual situation in a region where the lift amount VL is sufficiently small. We are not caught by any premise. That is, the equations (1) and (3) may be capable of accurately calculating the flowing gas heat receiving amount Qg and the contact surface heat receiving amount Qs even in a region where the lift amount VL is sufficiently small. In this case, by substituting the actual liftv into equation (1) in step 104, it is possible to always obtain the accurate flowing gas heat receiving amount Qg. Further, in step 106, by substituting the seating time dts corresponding to the operating angle Vθ into the equation (3), it is possible to always obtain the accurate contact surface heat receiving amount Qs. Therefore, in this case, steps 110 to 112 can be deleted from the routine shown in FIG.

  Further, in the second embodiment described above, it is assumed that the lift amount VL of the intake valve 24 and the operating angle Vθ are linked, but the present invention is not limited to this, and the variable valve mechanism 26 is Alternatively, the lift amount VL and the operating angle Vθ of the intake valve 24 may be changed independently. In this case, whether or not the contact surface heat receiving amount Qs is calculated in step 106 or step 112 is determined by determining the magnitude of the operating angle Vθ separately from the determination of the magnitude of the lift amount VL. That's fine.

  In the second embodiment described above, the ECU 40 calculates the seating time dts based on the operating angle Vθ in steps 106 and 112, and calculates the contact surface heat receiving amount Qs or Qs ′ based on the dts. Thus, the “contact surface heat receiving amount calculating means” in the fourth invention is realized.

  In the second embodiment described above, the ECU 40 calculates the flowing gas heat receiving amount Qg or Qg ″ based on the lift amount liftv of the intake valve 24 in steps 104 and 111, whereby the ninth invention is described. The "fluid gas heat receiving amount calculating means" is realized.

Embodiment 3 FIG.
[Features of Embodiment 3]
Next, a third embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 40 to execute the routine shown in FIG. 7 in the system shown in FIG. However, in this embodiment, the variable valve mechanism 26 that is the drive source of the intake valve 24 is a mechanism that changes the lift amount VL and the operating angle Vθ in conjunction with each other as in the second embodiment. To do.

  In the system of the second embodiment described above, the flow gas heat receiving amount calculation method is switched according to the magnitude of VL in consideration of the fact that the flow velocity of the intake gas changes according to the lift amount VL. By the way, the flowing gas heat receiving amount is a physical quantity that varies greatly depending on the presence or absence of blow-back as described in the first embodiment. Therefore, in order to estimate the intake valve temperature Tv with high accuracy, it is appropriate to consider the effect of blowback as well as the effect of the lift amount VL when calculating the flowing gas heat receiving amount.

  In the internal combustion engine 10, the blowback from the cylinder 22 toward the intake port is more likely to occur as the pressure difference between the intake port and the cylinder increases, that is, as the pressure at the intake port decreases. Further, the blow-back tends to occur as the opening area connecting the intake port and the cylinder 22 increases. Under a situation where the intake valve 24 is largely lifted, a large amount of air in the intake port is sucked into the cylinder 22, so that the internal pressure of the intake port is likely to be negative. In this case, the area of the opening that communicates the in-cylinder 22 with the intake port also increases.

  For this reason, the blowback from the cylinder 22 to the intake port is likely to occur as the lift amount VL of the intake valve 24 increases. In other words, a region where the lift amount VL of the intake valve 24 is sufficiently small can be regarded as a region where no blowback occurs substantially. Therefore, in the system of the present embodiment, in the region where the lift amount VL of the intake valve 24 is sufficiently small, the intake gas heat reception amount Qgin is directly used as the flowing gas heat reception amount without considering the effect of blowback, and the lift amount VL is large. Only in the region, the flowing gas heat receiving amount was calculated in consideration of the effect of blowback.

[Specific Processing in Embodiment 3]
FIG. 7 is a flowchart of a routine executed by the ECU 40 in the present embodiment in order to realize the above function. The routine shown in FIG. 7 is the same as the routine shown in FIG. 3 except that steps 110 to 112 are added. This routine is the same as the routine shown in FIG. 6 except that the step following step 110 is changed from step 104 to steps 103 to 105.

  According to the routine shown in FIG. 7, after various parameters are measured in step 102, it is determined in step 110 whether or not the lift amount VL of the intake valve 24 is smaller than the determination value β. As a result, if it is determined that VL <β is satisfied, that is, if it is determined that the lift amount VL is less than the normal value, the intake gas heat receiving amount Qg is determined in step 111 as in the second embodiment. '' Is calculated, and then in step 112, the contact surface heat receiving amount Qs ′ is calculated.

  According to the processing of step 111, the intake gas heat receiving amount Qgin is calculated using an arithmetic expression (for example, an expression in which the coefficient is changed from the expression (1)) set on the assumption that the lift amount VL is small. The calculated value Qgin is directly used as the flowing gas heat receiving amount Qg ″. That is, here, the amount of heat received due to the suction gas generated in a state where the lift amount VL is small can be calculated as the flowing gas heat reception amount Qg ″ without considering the effect of blowback.

  According to the routine shown in FIG. 7, if it is determined in step 110 that VL <β is not satisfied, that is, if it is determined that the lift amount VL of the intake valve VL has reached the normal value, then step 103 is performed. Through this process, it is determined whether or not the occurrence of blow-back exceeding the determination value α is expected. As a result, when it is determined that the blowback amount> α is not established, it is determined that there is no need to consider the influence of the blowback, and the intake gas heat receiving amount Qg is calculated by the processing of step 104. On the other hand, when it is determined that the blowback amount> α is established, it is determined that the influence of the blowback needs to be taken into account, and the intake gas heat reception amount Qg ′ is calculated by the processing of step 105.

  According to the processing of step 104, the intake gas heat receiving amount Qgin calculated according to the above equation (1) is directly used as the flowing gas heat receiving amount Qg. Further, according to the processing of step 105, the sum of the intake gas heat reception amount Qgin calculated according to the above equation (1) and the blow back heat reception amount Qgback calculated according to the above equation (2) is set as the flowing gas heat reception amount Qg ′. . According to these processes, the flowing gas heat receiving amount Qg or Qg ′ can be appropriately calculated according to the actual blow-back occurrence state under a situation where the lift amount VL that can be regarded as a normal value is generated.

  As described above, according to the routine shown in FIG. 7, the flow gas heat receiving amounts Qg and Qg ′ are respectively determined by appropriate methods in consideration of both the lift amount VL of the intake valve 24 and the blowback amount. Or Qg '' can be calculated. For this reason, according to the system of the present embodiment, the estimation accuracy of the intake valve temperature Tv can be further increased as compared with the case of the first or second embodiment.

  In the above-described third embodiment, the ECU 40 executes the process of step 110 shown in FIG. 7 so that the “lift amount determining means” in the sixth or eighth invention is changed to step 104 shown in FIG. , 105 and 111, the “final heat receiving amount calculation means” in the sixth aspect of the invention executes the processing of step 111 shown in FIG. Each means is realized.

Embodiment 4 FIG.
[Features of Embodiment 4]
Next, a fourth embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 40 to execute the routine shown in FIG. 8 in the system shown in FIG.

  In the internal combustion engine 10, a fuel cut process may be performed when the accelerator pedal is released in a high rotation range. In the first to third embodiments described above, the fuel gas heat receiving amount Qb is calculated according to the above equation (5) on the premise that combustion of the air-fuel mixture occurs in the cylinder 22.

  However, during the fuel cut, only air blows from the intake passage 12 to the exhaust passage 14, and the air-fuel mixture does not burn in the cylinder 22. Since the above equation (5) is an arithmetic equation set on the assumption that combustion occurs in the cylinder 22, the calculated value of the equation (5), the in-cylinder gas, and the intake valve 24 are calculated during fuel cut. There may be a discrepancy between the amount of heat actually received and received. Therefore, in the system of the present embodiment, the case where the fuel is being injected and the case where the fuel cut is being performed are distinguished, and the combustion gas heat receiving amount Qb is calculated by different methods.

[Specific Processing in Embodiment 4]
FIG. 8 is a flowchart of a routine executed by the ECU 40 in the present embodiment in order to realize the above function. The routine shown in FIG. 8 is the same as the routine shown in FIG. 3 except that the step following step 107 is changed from step 108 to steps 113, 108 and 114.

  That is, in the routine shown in FIG. 8, when the processing of step 107 is completed, it is next determined whether or not a fuel cut (F / C) is being executed (step 113). As a result, when it is determined that the fuel cut has not been executed, the combustion gas heat receiving amount Qb is calculated in step 108 as in the case of the first embodiment. That is, here, the combustion gas heat receiving amount Qb is calculated according to the above equation (5).

  The above equation (5) is an arithmetic equation set on the assumption that combustion occurs in the cylinder 22. According to the routine shown in FIG. 8, step 107 is always executed only under a situation where combustion occurs in the cylinder 22. For this reason, according to the process of step 107, the combustion gas heat receiving amount Qb can be calculated with high accuracy while the fuel cut is not being executed.

  In the routine shown in FIG. 8, if it is determined in step 113 that the fuel cut is being performed, the combustion gas heat receiving amount Qb ′ is then calculated by a method on the premise that air blows through the cylinder 22. (Step 114). That is, here, during the fuel cut, the combustion gas heat receiving amount Qb ′ is calculated according to an arithmetic expression that can accurately calculate the amount of heat transferred between the in-cylinder gas and the intake valve 22.

  According to the process of step 114, a value corresponding to the amount of heat actually transferred between the in-cylinder gas and the intake valve 24 during execution of the fuel cut can be calculated as the combustion gas heat reception amount Qb ′. it can. Therefore, according to the routine shown in FIG. 8, the combustion gas heat receiving amount Qb or Qb ′ can always be accurately calculated without being affected by the execution state of the fuel cut. As a result, according to the system of the present embodiment, the estimation accuracy of the intake valve temperature Tv can be further increased as compared with the first to third embodiments.

  By the way, in Embodiment 4 described above, an arithmetic expression for calculating the combustion gas heat reception amount Qb ′ during fuel cut is obtained in advance, and in step 114, the combustion gas heat reception amount Qb ′ is calculated according to the calculation expression. However, the present invention is not limited to this. That is, during the fuel cut, the combustion gas heat reception amount Qb ′ may be set to zero or a fixed negative value without performing calculation.

  In the above-described fourth embodiment, the fuel vaporization heat quantity Qf is calculated by the process of step 107 even during the fuel cut, but the present invention is not limited to this. That is, according to the process of step 107, the fuel vaporization heat quantity Qf is calculated by the above equation (4). If mf is set to zero during the execution of the fuel cut, the fuel vaporization heat quantity Qf during the fuel cut can be appropriately calculated also by the equation (4). However, it is not necessary to perform such calculation, and the fuel vaporization heat quantity Qf may be set to zero during the fuel cut.

  In the fourth embodiment described above, the flowing gas heat receiving amount Qg ′ is calculated without distinguishing whether or not the fuel cut is being executed (see step 105), but the flowing gas heat receiving amount Qg is calculated. The calculation method of 'may be switched according to whether or not a fuel cut is being performed. That is, in step 105 executed in the fourth embodiment, the flowing gas heat receiving amount Qg ′ is calculated in consideration of the effect of blowback.

  Here, the blow back heat receiving amount Qgback which is the basis of the flowing gas heat receiving amount Qg ′ is calculated by the above equation (2). The equation (2) is an arithmetic expression set on the assumption that the air-fuel mixture burns in the cylinder 22. For this reason, during the fuel cut in which combustion does not occur in the cylinder 22, the calculated value by the equation (2) does not necessarily match the actual blow-back heat receiving amount Qgback with high accuracy.

  Therefore, in a situation where only air is sucked into the cylinder 22, an arithmetic expression that can calculate the blow-back heat receiving amount Qgback in accordance with the reality is set in advance, and the arithmetic expression is used during fuel cut execution. The flowing gas heat receiving amount Qg ′ may be calculated. If such a calculation method is used, it is possible to further increase the estimation accuracy of the intake valve temperature Tv as compared with the case of the fourth embodiment.

  In the fourth embodiment described above, the ECU 40 executes the process of step 113, so that the “fuel cut detecting means” in the tenth aspect of the invention executes the process of step 114. The “combustion gas heat receiving amount calculation means” in the present invention is realized.

Embodiment 5 FIG.
[Features of Embodiment 5]
Next, a fifth embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 40 to execute the routine shown in FIG. 9 in the system shown in FIG. In the present embodiment, the internal combustion engine 10 can realize a cylinder stop operation for maintaining a specific cylinder in a stopped state.

  During execution of the cylinder stop operation, the intake valve 24 and the exhaust valve 28 of the cylinder selected as the stop cylinder are maintained in the closed state, and the fuel injection to the cylinder is stopped. For this reason, in the stopped cylinder, when estimating the intake valve temperature Tv, the intake valve 24 does not open, combustion does not occur in the cylinder 22, and the intake valve 24 continuously receives heat from the valve seat. It is necessary to assume such as.

  In the first embodiment described above, the calculation method of the flowing gas heat receiving amount Qg or Qg ′ is set on the assumption that the suction gas or the blowback gas flows around the intake valve 24. For this reason, the flowing gas heat receiving amount Qg ′ ″ in the stopped cylinder cannot be accurately calculated depending on the method.

  In the first embodiment described above, the calculation method of the contact surface heat receiving amount Qs is set on the assumption that the intake valve 24 is intermittently seated on the valve seat. For this reason, a certain degree of divergence may occur between the calculated value obtained by this method and the actual value of the contact surface heat receiving amount Qs ′ in the stopped cylinder.

  Further, depending on the method used in the first embodiment described above, the combustion gas heat reception amount in the stopped cylinder is the same reason that the combustion gas heat reception amount Qb ′ during fuel cut cannot be accurately calculated (see the fourth embodiment). Qb '' cannot be calculated accurately. Therefore, the system of the present embodiment distinguishes between the operating cylinder and the stopped cylinder, and in the stopped cylinder, the flow gas heat receiving amount Qg ′ ″ is obtained by a special method on the premise that the intake valve 24 is stopped. And so on.

[Specific Processing in Embodiment 5]
FIG. 9 is a flowchart of a routine executed in the present embodiment in order to realize the above function. In the routine shown in FIG. 9, steps 101 to 102 and steps 104 to 109 are the same as the steps indicated by the same reference numerals in FIG. 3. In order to avoid duplication of explanation about these, detailed explanation thereof is omitted, and here, explanation will be given mainly on steps peculiar to the routine shown in FIG. Note that the routine shown in FIG. 9 is executed for each of a plurality of cylinders provided in the internal combustion engine 10.

  According to the routine shown in FIG. 9, after the process of step 102 is completed, it is determined whether the lift amount VL of the intake valve 24 is zero in the cylinder, that is, whether the cylinder is a stopped cylinder. (Step 122). As a result, when it is determined that VL = 0 is not established, the processes of step 104 and steps 106 to 109 are subsequently executed in the same manner as in the first embodiment.

  On the other hand, when it is determined that VL = 0 is established for the cylinder, the flowing gas heat receiving amount Qg ′ ″ is calculated on the assumption that the intake valve 24 is maintained in the closed state (step 123). In the present embodiment, the ECU 40 stores an arithmetic expression capable of calculating a flowing gas heat receiving amount Qg ′ ″ that is realistic under the above assumption (for example, an expression having a coefficient different from the expression (1)). . Here, the flowing gas heat receiving amount Qg ′ ″ is calculated according to the arithmetic expression.

  In the routine shown in FIG. 9, the contact surface heat receiving amount Qs ′ is then calculated on the assumption that the intake valve 24 is always seated on the valve seat (step 124). In the present embodiment, the ECU 40 stores an arithmetic expression that can calculate the actual contact surface heat receiving amount Qs ′ under the above assumption (for example, an expression having a coefficient different from the expression (3)). Here, the contact surface heat receiving amount Qs ′ is calculated according to the arithmetic expression.

  Next, the ECU 40 calculates a combustion gas heat receiving amount Qb ″ on the assumption that combustion does not occur in the cylinder 22 (step 125). The ECU 40 stores an arithmetic expression that can calculate the actual combustion gas heat receiving amount Qb ″ based on the above assumption (for example, an expression having a coefficient different from the expression (5)). Here, the combustion gas heat receiving amount Qb '' is calculated according to the arithmetic expression.

  As described above, according to the routine shown in FIG. 9, it is distinguished whether the cylinder is operating or stopped, and in each case, the flowing gas heat receiving amount and the contact surface heat receiving amount are appropriately determined by appropriate methods. , And the amount of heat received from the combustion gas can be calculated. Therefore, according to the system of the present embodiment, it is possible to accurately estimate the intake valve temperature Tv in all the cylinders even when the cylinder stop operation is being performed in the internal combustion engine 10.

  By the way, in the fifth embodiment described above, the flow gas heat reception amount Qg ′ ″, the contact surface heat reception amount Qs ′, and the combustion gas heat reception amount Qb ″ of the stopped cylinder are calculated using respective arithmetic expressions. However, the method of setting them is not limited to this. That is, in the stopped cylinder, the flowing gas heat reception amount Qg ′ ″, the contact surface heat reception amount Qs ′, and the combustion gas heat reception amount Qb ″ may be set to preset fixed values, respectively.

Embodiment 6 FIG.
[Features of Embodiment 6]
Next, a sixth embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 40 to execute the routine shown in FIG. 10 in the system shown in FIG.

  The system of this embodiment is a particularly effective system when used in combination with a hybrid vehicle or an eco-run vehicle. That is, in the hybrid vehicle and the eco-run vehicle, the internal combustion engine 10 is frequently required to stop and start during operation of the vehicle system. For this reason, in such a vehicle, the rise and fall of the intake valve temperature Tv are frequently repeated. Under such circumstances, it is difficult to accurately estimate the temperature Tv based on the total amount of heat received by the intake valve 24. Therefore, the system according to the present embodiment assumes that the intake valve temperature Tv becomes equal to the cooling water temperature Tw at the time when a sufficient time has elapsed after the stop of the internal combustion engine 10 is recognized. Therefore, it was decided to reset the estimation error.

[Specific Processing in Embodiment 6]
FIG. 10 is a flowchart of a routine executed by the ECU 40 in the present embodiment in order to realize the above function. The routine shown in FIG. 10 is the same as the routine shown in FIG. 3 except that steps 120 and 122 are added after step 109. Hereinafter, the steps unique to FIG. 10 will be mainly described.

  That is, according to the routine shown in FIG. 10, after the intake valve temperature Tv is updated in step 109, the stop time F / Ctime of the internal combustion engine 10 is updated (step 120). The stop time F / Ctime is a time incremented while the internal combustion engine 10 is stopped, and is reset to zero during the operation of the internal combustion engine 10.

  Next, it is determined whether or not the stop time F / Ctime of the internal combustion engine 10 exceeds the determination value t0 (step 121). The determination value t0 is the time required for the intake valve temperature Tv to converge to the cooling water temperature Tw after the internal combustion engine 10 is stopped. Therefore, if it is determined that F / Ctime> 0 is not established, it can be determined that the intake valve temperature Tv and the coolant temperature Tw are not equal. In this case, thereafter, the processing after step 102 is executed again to repeat the estimation of Tv by calculation.

  On the other hand, if the establishment of F / Ctime> t0 is recognized in step 121, it can be determined that the intake valve temperature Tv has converged to the coolant temperature Tw as a result of the internal combustion engine 10 being stopped for a long period of time. In this case, the ECU 40 executes the process of step 101 to reset the error superimposed on the intake valve temperature Tv, and sets the current intake valve temperature Tv to the current cooling water temperature Tw.

  According to the above process, every time the internal combustion engine 10 is stopped for a long time in a hybrid vehicle or an eco-run vehicle, the error of the intake valve temperature Tv can be reset. In addition, after the internal combustion engine 10 is stopped, the estimation can be continued by continuing to update Tv by calculation while the time has not passed. For this reason, according to the system of the present embodiment, the estimation of the intake valve temperature Tv can always be continued with high accuracy in a situation where the start and stop of the internal combustion engine 10 are repeated.

  In the sixth embodiment described above, the ECU 40 executes the process of step 101, so that the “cooling water temperature detecting means” in the eleventh invention executes the process of step 121. The “intake valve temperature resetting means” in the present invention is realized.

It is a figure for demonstrating the structure of Embodiment 1 of this invention. It is a figure for demonstrating the method in which the system of Embodiment 1 of this invention calculates intake valve temperature Tv. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is the figure which showed the relationship between the amount of blowbacks, load KL, valve overlap VOL, and engine speed NE. It is a figure for demonstrating the relationship between the lift amount VL of the intake valve of an internal combustion engine, and an intake air flow velocity. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a flowchart of the routine performed in Embodiment 4 of this invention. It is a flowchart of the routine performed in Embodiment 5 of this invention. It is a flowchart of the routine performed in Embodiment 6 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Intake passage 14 Exhaust passage 24 Intake valve 26, 30 Variable valve mechanism 28 Exhaust valve 40 ECU (Electronic Control Unit)

Claims (11)

A combustion gas heat receiving amount calculating means for calculating the amount of combustion gas received by the intake valve of the internal combustion engine from the combustion gas in the cylinder;
A flowing gas heat receiving amount calculating means for calculating a flowing gas heat receiving amount received from the flowing gas flowing around the intake valve;
A total heat receiving amount calculating means for calculating a total heat receiving amount received by the intake valve based on the combustion gas heat receiving amount and the flowing gas heat receiving amount;
A temperature change amount calculating means for calculating a temperature change amount of the intake valve based on the total heat receiving amount;
An initial temperature estimating means for estimating an initial temperature of the intake valve;
Intake valve temperature estimating means for estimating the temperature of the intake valve based on the initial temperature and the amount of temperature change;
An intake valve temperature estimation device for an internal combustion engine, comprising: When the fuel adhering to the intake valve is vaporized, it comprises vaporization heat amount calculating means for calculating the amount of vaporization carried away from the intake valve,
2. The total heat receiving amount calculating means, wherein the total heat receiving amount is a value obtained by subtracting the heat of vaporization from a heat receiving amount calculated based on the combustion gas heat receiving amount and the flowing gas heat receiving amount. Intake valve temperature estimation device for internal combustion engine. The intake valve includes a contact surface heat receiving amount calculation means for calculating a contact surface heat receiving amount received by transmission from the valve seat,
The total heat receiving amount calculation means uses the value obtained by adding the contact surface heat receiving amount to the heat receiving amount calculated based on the combustion gas heat receiving amount and the flowing gas heat receiving amount as the total heat receiving amount. 3. An intake valve temperature estimation device for an internal combustion engine according to 1 or 2. A variable valve mechanism that makes the working angle of the intake valve variable,
The intake valve temperature estimation device for an internal combustion engine according to claim 3, wherein the contact surface heat receiving amount calculation means calculates the contact surface heat receiving amount based on the operating angle. The flowing gas heat receiving amount calculating means includes:
Intake gas heat receiving amount calculating means for calculating an intake gas heat receiving amount generated due to the intake gas flowing from the intake port into the cylinder;
Blow-back heat reception amount calculation means for calculating a blow-back heat reception amount generated due to the blow-back gas flowing backward from the cylinder to the intake port;
A final heat receiving amount calculating means for calculating the flowing gas heat receiving amount based on the intake gas heat receiving amount and the blow back heat receiving amount;
The intake valve temperature estimation device for an internal combustion engine according to any one of claims 1 to 4, characterized by comprising: A variable valve mechanism that makes the lift amount of the intake valve variable;
A lift amount determining means for determining whether or not the lift amount is below a determination value;
6. The intake valve temperature estimation device for an internal combustion engine according to claim 5, wherein the final heat receiving amount calculation means considers the presence of the blow back heat receiving amount only when the lift amount is equal to or greater than the determination value. The flowing gas heat receiving amount calculating means includes:
A normal heat receiving amount calculation means for calculating a normal heat receiving amount considering only the intake gas heat receiving amount caused by the intake gas flowing from the intake port into the cylinder;
In addition to the intake gas heat reception amount, the blowback heat reception amount calculation means for calculating the blowback heat reception amount in consideration of the blowback heat reception amount caused by the blowback gas flowing back from the cylinder to the intake port;
Blowback amount determination means for determining whether or not the flow rate of the blowback gas is greater than a determination value;
When the flow rate of the blowback gas is less than or equal to the determination value, the normal amount of heat received is the flowing gas heat reception amount. A final heat receiving amount setting means as a heat amount;
The intake valve temperature estimation device for an internal combustion engine according to any one of claims 1 to 4, characterized by comprising: A variable valve mechanism that makes the lift amount of the intake valve variable;
A lift amount determining means for determining whether or not the lift amount is below a determination value;
8. The intake valve for an internal combustion engine according to claim 7, wherein the final heat reception amount setting means sets the normal-time heat reception amount as the flowing gas heat reception amount when the lift amount is less than the determination value. Temperature estimation device. A variable valve mechanism that makes the lift amount of the intake valve variable,
The intake valve temperature estimation device for an internal combustion engine according to any one of claims 1 to 8, wherein the flowing gas heat receiving amount calculation means calculates the flowing gas heat receiving amount based on the lift amount. A fuel cut detecting means for detecting a fuel cut in the internal combustion engine;
10. The combustion gas heat reception amount calculation means calculates the combustion gas heat reception amount according to a rule set on the assumption that combustion does not occur in a cylinder during fuel cut. The intake valve temperature estimation device for an internal combustion engine according to any one of the preceding claims. Stop time counting means for counting the stop time of the internal combustion engine;
Cooling water temperature detecting means for detecting the cooling water temperature of the internal combustion engine;
An intake valve temperature resetting means for resetting the temperature of the intake valve to the coolant temperature at that time when the stop time exceeds a determination value;
The intake valve temperature estimation device for an internal combustion engine according to any one of claims 1 to 10, further comprising:

Images