JP2007170283A - Fuel control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately calculate a fuel amount in each cylinder of an internal combustion engine and optimally control a fuel injection amount of the internal combustion engine, in a fuel control device for controlling the fuel injection amount of a port injection type internal combustion engine. <P>SOLUTION: The fuel control device for an internal combustion engine comprises: a fuel injection valve 28 injecting fuel to an intake port 26; a port wall surface temperature estimation means estimating a wall surface temperature of the intake port 26 for each cylinder; a port adhered fuel amount estimation means estimating, for each cylinder, a fuel amount adhered on the intake port, based on the port wall surface temperature; and a fuel injection amount calculation means calculating, for each cylinder, the fuel injection amount in the fuel injection valve 28, based on the fuel amount adhered to the port. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel control device for an internal combustion engine, and is particularly suitable for application to a fuel control device that controls the fuel injection amount of a port injection type internal combustion engine.

  In a port injection type internal combustion engine, fuel is injected into an intake port by a fuel injection valve disposed in an intake passage. The fuel injected in this way is sucked into the cylinder together with air by introducing the in-cylinder negative pressure to the intake port as the intake valve opens. Part of the fuel injected into the intake port adheres to the inner wall and the like. In the steady state, the fuel adhesion amount is constant, and the amount of fuel sucked into the cylinder is equal to the amount of fuel injected.

  However, during the transient operation of the internal combustion engine, the intake air amount and the fuel injection amount change, so that the fuel adhesion amount also increases or decreases. While this increase / decrease occurs, there is a difference between the amount of fuel sucked into the cylinder and the amount of fuel injected. Therefore, in order to suck a desired amount of fuel into the cylinder during the transient operation, it is necessary to correct the fuel injection amount so that the increase / decrease in the fuel adhesion amount is offset.

  Conventionally, for example, Japanese Patent Application Laid-Open No. 2005-48712 discloses a fuel injection device that corrects the fuel injection amount in a port injection type internal combustion engine. Specifically, this apparatus has a fuel behavior model in which the port attached fuel amount, the liquid inflow fuel amount, and the in-cylinder attached fuel amount are state variables. The parameters of the fuel behavior model are updated according to the operating state of the internal combustion engine. This device calculates the fuel adhesion amount according to the fuel behavior model updated according to the operating state of the internal combustion engine, and corrects the fuel injection amount based on the calculated amount.

JP-A-2005-48712 JP 2004-162588 A JP-A-9-303173 JP-A-7-54689

  By the way, as described in the above publication, parameters such as the adhesion rate and the residual rate of the fuel adhering to the intake port wall surface have a correlation with the temperature of the intake port wall surface. Then, assuming that the port wall surface temperature is the same as the cooling water temperature flowing in the vicinity of the port, the value detected by the water temperature sensor is used as the port wall surface temperature. However, the cooling water absorbs heat while circulating inside the engine. Therefore, strictly speaking, the coolant temperature is not constant inside the engine, and the port wall surface temperature of each cylinder has a different value. Therefore, the conventional method of uniformly estimating the wall surface temperature based on the output of the water temperature sensor cannot determine the amount of fuel in the cylinder in consideration of the port wall surface temperature of each cylinder. It was difficult to control.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to accurately determine the amount of fuel in each cylinder of an internal combustion engine and optimally control the fuel injection amount of the internal combustion engine. .

A first invention is a fuel control device for an internal combustion engine,
A fuel injection valve for injecting fuel into the intake port;
Port wall surface temperature estimating means for estimating intake port wall surface temperature for each cylinder;
Based on the port wall surface temperature, port attached fuel amount estimating means for estimating the amount of fuel attached to the intake port for each cylinder;
Fuel injection amount calculating means for calculating the fuel injection amount in the fuel injection valve for each cylinder based on the port attached fuel amount;
It is characterized by providing.

The second invention is the first invention, wherein
The port wall surface temperature estimating means estimates the port wall surface temperature for each cylinder based on a coolant temperature.

The third invention is the first or second invention, wherein
The port wall surface temperature estimation means estimates the port wall surface temperature for each cylinder based on a thermostat opening.

The fourth invention is the first to third inventions,
The port adhering fuel amount estimating means includes:
Port adhesion rate acquisition means for acquiring a port adhesion rate that represents a rate of adhesion to the intake port of the fuel injection amount by the fuel injection valve;
Port residual ratio acquisition means for acquiring a port residual ratio that represents a ratio of the fuel amount attached to the intake port remaining in the attached state,
The port attached fuel amount is estimated for each cylinder based on the port adhesion rate and the port residual rate.

The fifth invention is a fuel control device for an internal combustion engine,
A fuel injection valve for injecting fuel into the intake port;
Port wall surface temperature control means for controlling the port wall surface temperature for each cylinder so that the port wall surface temperature of each cylinder becomes equal;
Based on the port wall surface temperature, a port attached fuel amount estimating means for estimating a port attached fuel amount attached to the intake port;
Fuel injection amount calculation means for calculating a fuel injection amount in the fuel injection valve based on the port attached fuel amount;
It is characterized by providing.

The sixth invention is the fifth invention, wherein
The port wall surface temperature control means controls the port wall surface temperature for each cylinder based on a coolant temperature.

The seventh invention is the fifth or sixth invention, wherein
The port wall surface temperature control means controls the port wall surface temperature for each cylinder based on a thermostat opening degree.

The eighth invention is the fifth to seventh invention, wherein
The port adhering fuel amount estimating means includes:
Port adhesion rate acquisition means for acquiring a port adhesion rate that represents a rate of adhesion to the intake port of the fuel injection amount by the fuel injection valve;
Port residual ratio acquisition means for acquiring a port residual ratio that represents a ratio of the fuel amount attached to the intake port remaining in the attached state,
The port attached fuel amount is estimated for each cylinder based on the port adhesion rate and the port residual rate.

  According to the first invention, it is possible to estimate the port wall surface temperature of each cylinder according to the operating state of the internal combustion engine. Based on the estimated port wall temperature, the amount of fuel attached to the port can be estimated for each cylinder, and the amount of fuel to be injected can be calculated for each cylinder. Therefore, the fuel injection amount corresponding to the target air-fuel ratio can be calculated for each cylinder in consideration of the port wall surface temperature of each cylinder. Therefore, the air-fuel ratio in the cylinder can be controlled with high accuracy and optimally.

  According to the second invention, the port wall surface temperature of each cylinder can be estimated based on the coolant temperature. Therefore, the fuel injection amount corresponding to the target air-fuel ratio in the cylinder can be calculated in consideration of the port wall surface temperature of each cylinder.

  According to the third invention, the port wall surface temperature of each cylinder can be estimated based on the opening degree of the thermostat. Therefore, the fuel injection amount corresponding to the target air-fuel ratio in the cylinder can be calculated in consideration of the port wall surface temperature of each cylinder.

  According to the fourth aspect of the invention, the amount of fuel attached to the port can be estimated based on the port attachment rate and the port residual rate. Therefore, the fuel amount to be injected can be calculated using the estimated port attached fuel amount.

  According to the fifth aspect, the port wall surface temperature of each cylinder can be controlled for each cylinder so that the port wall surface temperature of each cylinder has the same value. Then, the amount of fuel attached to the port can be estimated based on the port wall surface temperature, and the amount of fuel to be injected can be calculated. Therefore, it is possible to calculate the fuel injection amount corresponding to the target air-fuel ratio in the cylinder while controlling the port wall surface temperature of each cylinder to the same value. Therefore, the air-fuel ratio in the cylinder can be controlled with high accuracy and optimally.

  According to the sixth aspect, the port wall surface temperature of each cylinder can be controlled based on the coolant temperature. Therefore, it is possible to calculate the fuel injection amount corresponding to the target air-fuel ratio in the cylinder while controlling the port wall surface temperature of each cylinder to the same value.

  According to the seventh aspect, the port wall surface temperature of each cylinder can be controlled based on the opening degree of the thermostat. Therefore, it is possible to calculate the fuel injection amount corresponding to the target air-fuel ratio in the cylinder while controlling the port wall surface temperature of each cylinder to the same value.

  According to the eighth aspect of the invention, the port attached fuel amount can be estimated based on the port attached rate and the port remaining rate. Therefore, the fuel amount to be injected can be calculated using the estimated port attached fuel amount.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining the configuration of the first embodiment of the present invention. The configuration shown in FIG. 1 includes an internal combustion engine 10. An intake passage 12 and an exhaust passage 14 communicate with the internal combustion engine 10. The intake passage 12 includes an air filter 16 at an upstream end.

  An air flow meter 18 is disposed downstream of the air filter 16. The air flow meter 18 is a sensor that detects an intake air amount Ga that flows through the intake passage 12. A throttle valve 20 is provided downstream of the air flow meter 18. A throttle sensor 22 that detects the throttle opening degree TA is disposed in the vicinity of the throttle valve 20.

  A surge tank 224 is provided downstream of the throttle valve 20. Further, a fuel injection valve 28 for injecting fuel into the intake port 26 of the internal combustion engine is disposed further downstream of the surge tank 24.

  The internal combustion engine 10 includes a variable valve timing (VVT) mechanism 32 that drives an intake valve 30 and a VVT mechanism 36 that drives an exhaust valve 34. Furthermore, the internal combustion engine 10 includes a water temperature sensor 38 that detects the coolant temperature THW, and a rotation speed sensor 40 that detects the engine speed NE.

  The system according to the present embodiment includes an ECU (Electronic Control Unit) 50. The ECU 50 can drive the fuel injection valve 28 to inject desired fuel, detect the state of the VVT mechanisms 32 and 36, and drive them appropriately.

  Next, the fuel behavior model according to the present embodiment will be described. FIG. 2 is an enlarged view of the vicinity of the intake port 26. Hereinafter, as shown in FIG. 2, the amount of fuel injected from the fuel injection valve 28 is “fuel injection amount fi”, and the amount of fuel adhering to the wall surface of the intake port 26 or the surface of the intake valve 30 is “fuel attachment”. “Amount fwp”, and the amount of fuel sucked into the cylinder is referred to as “cylinder inflow fuel amount fc”.

  FIG. 3 is a diagram for explaining a fuel behavior model used by the apparatus of the present embodiment. This fuel behavior model is a model representing the behavior of fuel after being injected from the fuel injection valve 28. The residual rate Rp, the adhesion rate Pp, and the fuel amounts fi, fwp, and fc shown in FIG. 3 are all parameters used in the fuel behavior model. Hereinafter, the relationship between the residual rate Rp, the adhesion rate Pp, and the fuel amounts fi, fwp, and fc will be described with reference to FIG.

  As described above, after the fuel injection amount fi is injected from the fuel injection valve 28, a part of the fuel injection amount fi adheres to the wall surface of the intake port 26 and the remaining part is sucked into the cylinder. At this time, if the ratio of the injection adhering to the inner wall of the intake port 26 or the like is defined as “port adhesion rate Rp”, the port wet is not sucked into the cylinder out of the fuel injection amount fi as shown in FIG. The fuel that becomes a part of is represented by “Rp × fi”, while the amount of fuel sucked into the cylinder is represented by “(1−Rp) × fi”.

  The in-cylinder inflow fuel amount fc flows into the cylinder out of the fuel amount of the amount expressed by the above equation fi × (1−Rp) and of the fuel adhering to the inner wall of the intake port 26 and the like. The amount of fuel used is included. Here, if the ratio of the port wet remaining on the wall surface or the like after the intake process is assumed to be “port residual ratio Pp”, the port that existed at the start of the intake process as shown in FIG. The amount of wall surface adhesion is reduced to the amount represented by “Pp × fwp” after the intake process, while “(1−Rp) × fwp” is applied during the intake process. The indicated amount of fuel has flowed into the cylinder due to the presence of port wet.

Accordingly, when the port wall surface adhering amount of the intake port 26 at the start of the injection stroke in the kth cycle is fwp (k) and the fuel injection amount in the kth cycle is fi (k), after the end of the kth cycle. The wall surface adhering amount of the intake port 30 (that is, the wall surface adhering amount in the (k + 1) th cycle) fwp (k + 1), and the in-cylinder inflow request amount fc (k) in the kth cycle are the port adhering rate Rp and the port residual amount. It can be expressed as the following equation using the rate Pp.
fwp (k + 1) = Pp × fwp (k) + Rp × fi (k) (1)
fc (k) = (1-Pp) * fwp (k) + (1-Rp) * fi (k) (2)

According to the above equation (2), the fuel injection amount fi (k) necessary for flowing the fuel of fc (k) into the cylinder can be expressed as follows.
fi (k) = {fc (k)-(1-Pp) × fwp (k)} / (1-Rp) (3)

  Therefore, in each cycle, if the fuel injection amount fi is corrected so that the above fc becomes the target value prior to fuel injection, the influence of the fuel adhesion amount fwp is eliminated and the desired air-fuel ratio A / F is always maintained. It is possible to obtain

  As described above, in the apparatus of the present embodiment, if the port adhesion rate Rp and the port residual rate Pp are known, the fuel adhesion amount fwp generated in each cycle can be accurately determined according to the above equation (1). Can be calculated. Then, by calculating the fuel injection amount fi according to the above equation (3), highly accurate fuel injection amount control can be realized.

  Here, the port adhesion rate Rp and the port residual rate Pp can be specified by, for example, preparing a conformity map determined in advance in relation to the operating state of the internal combustion engine 10 and referring to the maps. It is. More specifically, the engine load KL, the engine speed NE detected by the speed sensor 40, the valve opening timing (valve timing VT) of the intake valve 30, the wall surface temperature Tw of the intake port 26, and the like are used as parameters. The relationship between the state, the port adhesion rate Rp, and the port residual rate Pp is mapped, and in each cycle, values corresponding to KL, NE, VT, and Tw are read from the map, so that Rp and Pp Can be requested.

  Further, as described above, since the intake port wall surface temperature of each cylinder is not the same temperature, if the detected value of the water temperature sensor is uniformly estimated as the port wall surface temperature, a correct value cannot be estimated. Therefore, if the port wall surface temperature Tw of each cylinder can be estimated, Rp and Pp can be obtained more accurately.

Therefore, the port wall temperature Tw (n) of the nth cylinder is estimated using the following equation.
Tw (n) = THW + Twh (n) (n = 1, 2,...) (4)
Here, Twh (n) is the temperature correction amount of the nth cylinder, and can be obtained by reading a value corresponding to the operation state (KL, NE, VT, THW, etc.) from the map. Accordingly, the port adhesion rate Rp and the port residual rate Pp of each cylinder can be obtained from the port wall surface temperature Tw (n) of the nth cylinder, and highly accurate fuel injection amount control can be realized.

[Specific Processing in Embodiment 1]
FIG. 4 is a flowchart showing a routine executed by the ECU 50 in the present embodiment in order to realize the above-described function. The routine shown in FIG. 4 is a routine that is executed every time the internal combustion engine 10 operates for one cycle. Here, the routine in k cycles is shown. In this routine, first, the water temperature THW of the internal combustion engine 10 is acquired (step 100). Specifically, the output signal of the water temperature sensor 38 is supplied to the ECU 50 here.

  Next, various parameters representing the current state of the internal combustion engine 10 are acquired (step 102). Specifically, here, the intake air amount Ga detected by the air flow meter 18, the throttle opening degree TA detected by the throttle sensor 22, the engine speed NE detected by the speed sensor 40, the load factor KL, Output signals such as valve timing VT are supplied to the ECU 50.

  Next, the port wall temperature correction amount Twh (n) of each cylinder is specified (step 104). As described above, the port wall temperature correction amount Twh (n) is specified by the operation state (KL, NE, VT, THW, etc.). The ECU 50 stores a map that defines the relationship between the port wall temperature correction amount and these state quantities. Here, according to the map, the port wall temperature correction amounts corresponding to the various state quantities acquired in step 102 are specified for each cylinder.

  In the routine shown in FIG. 4, next, the port wall temperature Tw (n) of each cylinder is calculated (step 106). Specifically, here, the water temperature THW acquired in step 100 and the port wall temperature correction amount Twh (n) specified in step 104 are substituted into the above equation (4) to determine the cylinder temperature. The port wall temperature Tw (n) is calculated.

  Next, the ECU 50 calculates the port residual ratio Rp and the port adhesion ratio Pp, which are the in-port control parameters, for each cylinder (step 108). As described above, the port residual rate Rp and the port adhesion rate Pp are specified by the operation state (KL, NE, VT, THW, Tw, etc.). The ECU 50 stores a map that defines the relationship between Pp and Rp and these state quantities. Here, according to the map, Pp and Rp corresponding to the various state quantities acquired in steps 100 to 106 are specified for each cylinder.

  Next, in the routine shown in FIG. 4, the fuel adhesion amount fwp (k) in the k-th cycle is calculated for each cylinder (step 110). Specifically, in this step, the port residual ratio Rp and the port adhesion ratio Pp calculated in step 108 are substituted into the calculation of the equation (1) in the k−1th cycle, and the kth cycle. The fuel adhesion amount fwp (k) at is calculated.

Next, a transient increase / decrease amount Δfi (k) of the fuel injection amount is calculated for each cylinder (step 112). In this step, first, the basic injection amount fi ₀ (k) is calculated based on the intake air amount Ga and the like so that the air-fuel ratio A / F is close to the stoichiometric. Next, the fuel injection amount fi (k) in the k-th cycle is calculated. Specifically, first, the in-cylinder required fuel amount fc (k) in the k-th cycle is set to a predetermined value so that the air-fuel ratio A / F becomes stoichiometric. Then, fc (k), the port adhesion rate Rp and the port residual rate Pp calculated in step 108, and the fuel adhesion amount fwp (k) calculated in step 110 are substituted into the above equation (3). The fuel injection amount fi (k) is calculated. Next, a transient increase / decrease amount Δfi (k) is calculated by subtracting the basic injection amount fi ₀ (k) from the fuel injection amount fi (k). In this step, the above processing is performed for each cylinder.

As described above, in the first embodiment, the transient increase / decrease amount Δfi (k) in the k-th cycle is calculated, and this routine ends. Δfi (k) calculated for each cylinder is added to the basic injection amount fi ₀ (k) to determine the final fuel injection amount in each cylinder.

  As described above, according to the apparatus of the present embodiment, the port wall temperature of each cylinder is estimated. Based on the estimated port wall temperature, the fuel injection amount of each cylinder is calculated. Therefore, highly accurate fuel injection amount control that takes into account the temperature difference between the cylinders can be realized.

  Further, in the first embodiment described above, the port adhesion rate Rp and the port residual rate Pp are determined based on the engine load KL, the engine speed NE, the valve timing VT, the wall surface temperature Tw (n) of the intake port 26, and the like. Although the determination is made using a map storing the relationship with the state, the specifying method is not limited to the map. That is, it may be calculated in accordance with a well-known mathematical model calculation using in-port state quantities such as pressure, temperature, and flow velocity of the in-port gas as parameters.

  In the first embodiment described above, the ECU 50 executes the process of step 106, whereby the “port wall surface temperature estimating means” in the first invention executes the process of step 110. The “port injection fuel amount estimating means” in the first invention realizes the “fuel injection amount calculating means” in the first invention by executing the processing of step 112 described above.

  In the first embodiment described above, the ECU 50 realizes the “port adhesion rate acquisition unit” and the “port residual rate acquisition unit” in the fourth invention by executing the processing of step 108, respectively. Has been.

Embodiment 2. FIG.
[Configuration of Embodiment 2]
A second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a diagram illustrating a hardware configuration of the present embodiment. The configuration shown in FIG. 5 includes an internal combustion engine 10. Since the internal combustion engine 10 has the same configuration as that shown in FIG. 1, the description and description of the configuration are omitted. The internal combustion engine 10 further includes a thermostat 42 and a radiator 44. And as shown in FIG. 5, these are interposed in the cooling water passage 46a which the internal combustion engine 10 has. Further, a bypass passage 46 b is installed between the thermostat 42 and the internal combustion engine 10. Further, the present embodiment has an ECU 50. And it can implement | achieve by making ECU50 perform the routine shown in FIG. 6 mentioned later.

  Next, the operation of the thermostat will be described. The thermostat 42 shown in FIG. 5 has a control valve that opens and closes according to temperature, and can control the cooling water flow path. That is, when the cooling water temperature is low, the control valve is closed, and the cooling water that has passed through the internal combustion engine 10 circulates via the bypass passage 46b. On the other hand, when the cooling water temperature becomes high, the control valve is opened, and the cooling water circulates from the passage 46a through the radiator 44. Therefore, according to these devices, it is possible to realize early warm-up of the internal combustion engine and to control the temperature of the cooling water to a desired state.

[Features of Embodiment 2]
In the above-described first embodiment, the coolant temperature (THW) of the internal combustion engine and the operating state (KL, NE, VT, etc.) are correlated with the port wall temperature of each cylinder, and the port wall temperature specified according to the map. Based on the correction amount Twh (n), the port wall temperature Tw (n) of each cylinder is specified, and highly accurate fuel injection control considering the temperature difference of each cylinder is enabled. On the other hand, since the cooling water temperature changes depending on the operation of the thermostat, this operation also affects the port wall temperature of each cylinder. For this reason, by considering the thermostat opening, it is possible to improve the estimation accuracy of the port wall temperature Tw (n) for each cylinder and accurately calculate the fuel injection amount to be injected into each cylinder.

  That is, in a state where the control valve of the thermostat 42 is closed, the cooling water flowing out from the internal combustion engine 10 circulates in the engine through the bypass passage 46b without passing through the radiator 44. For this reason, the temperature difference of the cooling water inside the internal combustion engine 10 is small, and the port wall temperature difference of each cylinder is also small. On the other hand, when the control valve of the thermostat 42 starts to open, the cooling water (Cold) cooled by the radiator 44 is mixed into the cooling water circulating through the bypass passage 46b and circulates inside the internal combustion engine 10. . For this reason, the coolant temperature difference in the internal combustion engine 10 is large, and the port wall temperature difference of each cylinder is also large.

  The mixing amount of the cooling water (Cold) through the radiator changes according to the opening degree of the control valve. For this reason, the port wall temperature correction amount Twh (n) estimation accuracy can be increased by considering the operating state and the thermostat opening. Therefore, the port wall temperature correction amount Twh (n) can be specified from the map storing the relationship between the operating state, the thermostat opening and the port wall temperature correction amount, and the final port wall temperature of each cylinder can be calculated.

[Specific Processing in Embodiment 2]
FIG. 6 is a flowchart showing a routine executed by the ECU 50 in the present embodiment in order to realize the above-described function. The routine shown in FIG. 6 is a routine that is executed every time the internal combustion engine 10 operates for one cycle. Here, a routine in k cycles is shown. In this routine, first, the control valve opening Thang of the thermostat 42 is acquired (step 200). As described above, the thermostat is a valve that opens and closes according to temperature. For this reason, the valve opening degree is estimated here based on the output signal of the water temperature sensor 38.

  Next, various parameters representing the current state of the internal combustion engine 10 are acquired (step 202). Specifically, in this step, processing similar to that in step 102 shown in FIG. 4 is executed.

  Next, the port wall temperature correction amount Twh (n) for each cylinder is specified (step 204). As described above, the port wall temperature correction amount Twh (n) is specified by the operating state (KL, NE, VT, etc.) and the control valve opening Thang of the thermostat 42. The ECU 50 stores a map that defines the relationship between the port wall temperature correction amount, the operation state, and the valve opening. Here, the port wall temperature correction amount corresponding to the valve opening obtained in step 200 is specified for each cylinder according to the map.

  In the routine shown in FIG. 4, next, the port wall temperature Tw (n) of each cylinder is calculated (step 206). Next, the ECU 50 calculates the port residual ratio Rp and the port adhesion ratio Pp, which are the in-port control parameters, for each cylinder (step 208). Next, the fuel adhesion amount fwp (k) in the k-th cycle is calculated for each cylinder (step 210). Finally, a transient increase / decrease amount Δfi (k) of the fuel injection amount is calculated for each cylinder (step 212). In these steps 206 to 212, specifically, the same processing as in steps 106 to 112 shown in FIG. 4 is executed for each cylinder.

As described above, in the second embodiment, the transient increase / decrease amount Δfi (k) in the k-th cycle is calculated, and this routine ends. Δfi (k) calculated for each cylinder is added to the basic injection amount fi ₀ (k) to determine the final fuel injection amount in each cylinder.

  As described above, according to the apparatus of the present embodiment, the port wall temperature of each cylinder is estimated based on the thermostat opening. Based on the estimated port wall temperature, the fuel injection amount of each cylinder is calculated. Therefore, highly accurate fuel injection amount control that takes into account the temperature difference between the cylinders can be realized.

  Further, in the above-described second embodiment, the port adhesion rate Rp and the port residual rate Pp are determined based on the engine load KL, the engine speed NE, the valve timing VT, the wall surface temperature Tw (n) of the intake port 26, and the like. Although the determination is made using a map storing the relationship with the state, the specifying method is not limited to the map. That is, it may be calculated in accordance with a well-known mathematical model calculation using in-port state quantities such as pressure, temperature, and flow velocity of the in-port gas as parameters.

  In the second embodiment described above, the thermostat opening is estimated based on the output signal of the water temperature sensor 38, but means for acquiring the thermostat opening is not limited to this. That is, it is good also as detecting a direct opening degree by installing a sensor in a thermostat.

  In the above-described first embodiment, the ECU 50 executes the process of step 206, so that the “port wall surface temperature estimating means” in the first invention executes the process of step 210. The “port injection fuel amount estimating means” in the first invention implements the “fuel injection amount calculating means” in the first invention by executing the processing of step 212 described above.

  In the first embodiment described above, the ECU 50 realizes the “port adhesion rate acquisition unit” and the “port residual rate acquisition unit” in the fourth aspect of the invention by executing the processing of step 208 described above. Has been.

Embodiment 3 FIG.
[Configuration of Embodiment 3]
Next, Embodiment 3 of the present invention will be described with reference to FIGS. The hardware configuration of the present embodiment uses a port heater 48 shown in FIG. 7 in addition to the hardware configuration shown in FIG. And it is realizable by making ECU50 perform the routine shown in FIG. 8 mentioned later.

  In the first embodiment described above, the port wall temperature Tw of each cylinder is accurately estimated, and the fuel injection amount fi is calculated based on the estimated value. Fuel injection control is possible. On the other hand, if the port wall temperature of each cylinder is always controlled to be the same, the fuel injection amount fi common to all the cylinders can be calculated based on the port wall temperature.

  FIG. 7 is an enlarged view of the vicinity of the intake port 26 for explaining the configuration of the third embodiment of the present invention. As shown in FIG. 7, the port heater 48 is installed at a portion of the intake port wall where the fuel adheres. The ECU 50 is connected to the port heater 48 and appropriately drives the heater so that the cylinders have the same temperature.

[Specific Processing in Embodiment 3]
FIG. 8 is a flowchart showing a routine executed by the ECU 50 in the present embodiment in order to realize the above-described function. The routine shown in FIG. 6 is a routine that is executed every time the internal combustion engine 10 operates for one cycle. Here, a routine in k cycles is shown. In this routine, first, the water temperature THW of the internal combustion engine 10 is acquired (step 300). Specifically, the output signal of the water temperature sensor 38 is supplied to the ECU 50 here.

  Next, various parameters representing the current state of the internal combustion engine 10 are acquired (step 302). Specifically, here, output signals such as the intake air amount Ga, the throttle opening degree TA, the engine speed NE, the load factor KL, and the valve timing VT are supplied to the ECU 50.

  Next, in the routine shown in FIG. 8, the energization amount to the port heater 48 of each cylinder is calculated (step 304). Here, the energization amount is the operating condition (Ga, TA, KL, NE, VT, etc.) specified in step 302 so that the port wall temperature of each cylinder is the same as the coolant temperature detected in step 300. Specified based on. The ECU 50 stores a map that defines the relationship between the energization amount and these state amounts. Here, according to the map, the energization amounts corresponding to the various state amounts acquired in step 302 are specified for each cylinder.

  Next, the ECU 50 drives the port heater 48 of each cylinder based on the calculated energization amount (step 306). Thus, the port wall temperature of each cylinder is controlled so as to always have the same value as the water temperature THW.

  Next, the ECU 50 calculates a port residual rate Rp and a port adhesion rate Pp, which are in-port control parameters (step 308). Here, assuming that all the port wall temperatures (Tw) are the same values as the cooling water temperature THW, the port residual ratio Rp and the port adhesion ratio Pp are calculated. As described above, the port residual rate Rp and the port adhesion rate Pp are specified by the operation state (KL, NE, VT, THW, TW, etc.). The ECU 50 stores a map that defines the relationship between Pp and Rp and these state quantities. Here, according to the map, Pp and Rp corresponding to the various state quantities acquired in steps 300 to 302 are specified.

Next, in the routine shown in FIG. 8, the fuel adhesion amount fwp (k) in the k-th cycle is calculated (step 310). Then, a transient increase / decrease amount Δfi (k) of the fuel injection amount is calculated (step 312). In these steps 310 and 312, specifically, the same processing as in steps 110 and 112 shown in FIG. 4 is executed for each cylinder.
Is done.

As described above, the transient increase / decrease amount Δfi (k) in the k-th cycle is calculated, and this routine ends. The calculated Δfi (k) is added to the basic injection amount fi ₀ (k), and the final fuel injection amount is determined.

  As described above, according to the apparatus of the present embodiment, by driving the port heater 48, the port wall temperature of each cylinder is controlled to the same value as the coolant temperature THW. For this reason, the port wall temperature is estimated to be the same value (water temperature) in all the cylinders, and the fuel injection amount is calculated. Therefore, highly accurate fuel injection amount control can be realized without considering the temperature difference between the cylinders.

  In the third embodiment described above, the energization amount is specified in accordance with the map of the coolant temperature THW and the operation state (KL, NE, VT, etc.) and the port heater 48 is driven. The method is not limited to this. That is, in order to obtain the thermostat opening as in the second embodiment, and to use the map storing the relationship between the thermostat opening and the above operating state and the energization amount, the port wall temperature is set to the same value as the water temperature value. It is good also as specifying the amount of electricity supply.

  Further, in the above-described third embodiment, the port adhesion rate Rp and the port residual rate Pp are determined from the operating conditions such as the engine load KL, the engine speed NE, the valve timing VT, and the wall surface temperature Tw of the intake port 26. Although the identification is performed using the map storing the relationship, the identification method is not limited to the map. That is, it may be calculated in accordance with a well-known mathematical model calculation using in-port state quantities such as pressure, temperature, and flow velocity of the in-port gas as parameters.

  In the third embodiment described above, the port heater 48 is installed on each port wall surface and the heater is driven so that the port wall surface has the same value as the cooling water temperature THW. The temperature control method is not limited to the port heater. That is, instead of the port heater, a heat storage system that supplies heat storage by flowing hot water to each port wall surface is installed, and temperature control is performed by adjusting the amount of hot water flowing to each port wall surface by a control valve or the like. Good.

  In the third embodiment described above, the port heater 48 is installed on each port wall surface and the heater is driven so that the port wall surface has the same value as the cooling water temperature THW. The control temperature is not limited to the same value as the cooling water temperature. That is, if the port wall temperature of each cylinder is controlled to the same value, the fuel injection amount can be calculated based on the port wall temperature, even if the value is different from the cooling water temperature.

  In the above-described third embodiment, the ECU 50 executes the process of step 304, so that the “port wall surface temperature control means” in the fifth aspect of the invention executes the process of step 310. The “port injection fuel amount estimating means” in the fifth invention realizes the “fuel injection amount calculating means” in the fifth invention by executing the processing of step 312.

  In the above-described third embodiment, the ECU 50 implements the “port adhesion rate acquisition unit” and the “port residual rate acquisition unit” in the eighth invention by executing the processing of step 306, respectively. Has been.

It is a figure for demonstrating the structure of Embodiment 1 of this invention. It is the figure which expanded and represented the port vicinity of the internal combustion engine shown in FIG. It is a schematic diagram for demonstrating the fuel behavior model of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the structure of Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is the figure which expanded and represented the port vicinity in order to demonstrate the structure of Embodiment 3 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Intake passage 14 Exhaust passage 16 Air filter 18 Air flow meter 20 Throttle valve 22 Throttle sensor 24 Surge tank 26 Intake port 28 Fuel injection valve 38 Water temperature sensor 40 Revolution sensor 42 Thermostat 44 Radiator 46 Cooling water passage 48 Port heater 50 ECU (Electronic Control Unit)
fi Fuel injection amount fwp Fuel adhesion amount fc In-cylinder inflow fuel amount Rp Port adhesion rate Pp Port residual rate Tw Port wall temperature Twh Port wall temperature correction amount fi ₀ Basic injection amount Δfi Transient increase / decrease amount Tang Thermostat opening

Claims (8)

A fuel injection valve for injecting fuel into the intake port;
Port wall surface temperature estimating means for estimating intake port wall surface temperature for each cylinder;
Based on the port wall surface temperature, port attached fuel amount estimating means for estimating the amount of fuel attached to the intake port for each cylinder;
Fuel injection amount calculating means for calculating the fuel injection amount in the fuel injection valve for each cylinder based on the port attached fuel amount;
A fuel control apparatus for an internal combustion engine, comprising:   2. The fuel control apparatus for an internal combustion engine according to claim 1, wherein the port wall surface temperature estimating means estimates the port wall surface temperature for each cylinder based on a coolant temperature.   The fuel control apparatus for an internal combustion engine according to claim 1 or 2, wherein the port wall surface temperature estimating means estimates the port wall surface temperature for each cylinder based on a thermostat opening. The port adhering fuel amount estimating means includes:
Port adhesion rate acquisition means for acquiring a port adhesion rate that represents a rate of adhesion to the intake port of the fuel injection amount by the fuel injection valve;
Port residual ratio acquisition means for acquiring a port residual ratio that represents a ratio of the fuel amount attached to the intake port remaining in the attached state,
4. The fuel control device for an internal combustion engine according to claim 1, wherein the fuel amount adhering to the port is estimated for each cylinder based on the port adhesion rate and the port residual rate. A fuel injection valve for injecting fuel into the intake port;
Port wall surface temperature control means for controlling the port wall surface temperature for each cylinder so that the port wall surface temperature of each cylinder becomes equal;
Based on the port wall surface temperature, a port attached fuel amount estimating means for estimating a port attached fuel amount attached to the intake port;
Fuel injection amount calculation means for calculating a fuel injection amount in the fuel injection valve based on the port attached fuel amount;
A fuel control apparatus for an internal combustion engine, comprising:   6. The fuel control apparatus for an internal combustion engine according to claim 5, wherein the port wall surface temperature control means controls the port wall surface temperature for each cylinder based on a coolant temperature.   The fuel control device for an internal combustion engine according to claim 5 or 6, wherein the port wall surface temperature control means controls the port wall surface temperature for each cylinder based on a thermostat opening degree. The port adhering fuel amount estimating means includes:
Port adhesion rate acquisition means for acquiring a port adhesion rate that represents a rate of adhesion to the intake port of the fuel injection amount by the fuel injection valve;
Port residual ratio acquisition means for acquiring a port residual ratio that represents a ratio of the fuel amount attached to the intake port remaining in the attached state,
8. The fuel control apparatus for an internal combustion engine according to claim 5, wherein the amount of fuel adhering to the port is estimated for each cylinder based on the port adhering rate and the port remaining rate.

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