JP4872832B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device that controls the operating state of an internal combustion engine, and more particularly, to a control device for an internal combustion engine that can operate with a fuel in which gasoline and alcohol are mixed.

  2. Description of the Related Art Conventionally, as disclosed in, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2006-214415), an internal combustion engine capable of operating with a fuel in which gasoline and alcohol are mixed is known. The conventional internal combustion engine includes a port injection valve that injects fuel toward the intake port of the combustion chamber, and an in-cylinder injection valve that directly injects fuel into the combustion chamber.

  The control device for controlling the internal combustion engine injects fuel from one or both of the port injection valve and the in-cylinder injection valve in accordance with the operating state of the internal combustion engine. When fuel is injected from both injection valves, the fuel injection ratio from the in-cylinder injection valve is increased as the alcohol concentration in the fuel increases. In this case, in the prior art, it is assumed that a fuel with a high alcohol concentration can quickly vaporize the fuel and obtain a good mixture even when in-cylinder injection is performed with a short time from injection to combustion. Yes.

JP 2006-214415 A

  In the prior art described above, the injection ratio of the in-cylinder injection valve is set higher as the alcohol concentration in the fuel becomes higher. However, the fuel injected into the cylinder tends to form a heterogeneous mixture because the time until combustion is short. For this reason, as a method of fuel injection control, there is also an idea that among the entire operation regions of the internal combustion engine, the region in which the port injection valve operates is set as wide as possible to stabilize the operation performance.

  However, if the operating region of the port injection valve is simply set wide, the fuel injection amount of the in-cylinder injection valve is reduced accordingly. As a result, for example, in the region where the combustion temperature is high, the tip temperature of the in-cylinder injection valve rises, and deposits and the like are easily induced. Further, for example, in a region where it is desired to ensure the output of the internal combustion engine, if the fuel injection amount of the in-cylinder injection valve decreases, the intake air charging efficiency may decrease and the output may be insufficient. For this reason, in a prior art, there exists a problem that it is difficult to use properly a port injection valve and a cylinder injection valve properly.

  The present invention has been made to solve the above-described problems, and can properly use the port injection valve and the in-cylinder injection valve in accordance with the operating state of the internal combustion engine, satisfying the demand for output and the like. An object of the present invention is to provide a control device for an internal combustion engine that can improve driving performance such as fuel consumption and torque fluctuation.

A first invention is a port injection valve that injects fuel toward an intake port of an internal combustion engine;
An in-cylinder injection valve for injecting fuel into the cylinder of the internal combustion engine;
Target calculation means for calculating the total amount of fuel to be injected from the port injection valve and the in-cylinder injection valve as a target injection amount according to the operating state of the internal combustion engine;
Alcohol concentration detection means for detecting the alcohol concentration in the fuel;
When the alcohol concentration is higher than the determination value and the internal combustion engine is operated in a low rotation / high load state, an injection ratio of fuel injected from the port injection valve in the target injection amount is set as the alcohol Port injection ratio increasing means for increasing the injection ratio when the concentration is equal to or less than the determination value;
It is characterized by providing.

A second aspect of the present invention is a combustion state detection means for detecting a combustion pressure of an internal combustion engine and / or a variation state of the combustion pressure;
Combustion state determination means for determining whether or not the detection result of the combustion state detection means corresponds to a good combustion state of the internal combustion engine,
The port injection ratio increasing means determines the injection ratio of the port injection valve when the alcohol concentration is equal to or less than the determination value when the combustion state determination means determines that the combustion state of the internal combustion engine is good. It is configured to maintain the ratio.

A third invention comprises a rotation detecting means for detecting the engine speed of the internal combustion engine,
Combustion state determination means for determining whether or not the fluctuation state of the engine speed detected by the rotation detection means corresponds to a good combustion state of the internal combustion engine,
The port injection ratio increasing means determines the injection ratio of the port injection valve when the alcohol concentration is equal to or less than the determination value when the combustion state determination means determines that the combustion state of the internal combustion engine is good. It is configured to maintain the ratio.

  According to a fourth aspect of the present invention, when the fuel injection amount to be injected from any one of the port injection valve and the in-cylinder injection valve exceeds the maximum injection amount of the injection valve, the injection is performed from the other injection valve. The fuel injection amount supplementing means for increasing the fuel injection amount is provided.

  According to a fifth aspect of the present invention, there is provided a fuel pressurizing means for pressurizing fuel supplied to the port injection valve and the in-cylinder injection valve, and a maximum total injection summing up the maximum injection amounts of the port injection valve and the in-cylinder injection valve. Fuel pressure increasing means for increasing the pressure applied to the fuel by the fuel pressurizing means when the target injection amount becomes larger than the amount.

  According to the first aspect of the invention, in the operating region in the low rotation / high load state, the fluidity of the intake air is low because the engine speed is low. In addition, a relatively large amount of fuel is injected in response to high load conditions. Moreover, when the alcohol concentration in the fuel is high, a larger amount of fuel is injected in order to maintain the amount of heat generated during combustion. That is, since a large amount of fuel is injected into the intake air having low fluidity, it is difficult to form a homogeneous air-fuel mixture. In particular, when fuel is to be injected from the in-cylinder injection valve, since the time from injection to combustion is short, the air-fuel mixture tends to be heterogeneous.

  Thus, in a situation where the alcohol concentration in the fuel is high and the operation is performed in a low rotation / high load state, the port injection ratio increasing means can increase the injection ratio of the port injection valve. Thereby, the fuel injected from the port injection valve is mixed with the intake air before reaching the combustion chamber, so that a homogeneous air-fuel mixture can be formed as compared with the in-cylinder injection valve. As a result, the port injection ratio increasing means can stabilize the combustion state of the air-fuel mixture by the increase in the injection ratio of the port injection valve, and fuel injection that is disadvantageous for the formation of the air-fuel mixture is performed from the in-cylinder injection valve. Can be prevented.

  On the other hand, since the remaining fuel can be injected also from the cylinder injection valve, the output of the internal combustion engine can be ensured. Therefore, the port injection valve and the in-cylinder injection valve can be used at an appropriate injection ratio according to the operating state of the internal combustion engine, the alcohol concentration in the fuel, and the like. Then, it is possible to improve driving performance such as fuel consumption and torque fluctuation while satisfying the output demand of the internal combustion engine.

  According to the second invention, the combustion state determination means compares the combustion pressure of the internal combustion engine and / or the fluctuation state of the combustion pressure with the reference data in a good combustion state, for example, thereby comparing the combustion state of the internal combustion engine. It can be determined whether or not. And when it determines with a combustion state being favorable, even if the precondition which should increase the injection ratio of a port injection valve is satisfied, this injection ratio can be hold | maintained at the injection ratio when alcohol concentration is low. it can.

  As a result, when the operation is performed in a low rotation / high load state using a fuel having a high alcohol concentration, the injection ratio of the port injection valve can be increased only when the combustion state of the internal combustion engine is unstable. On the other hand, when the combustion state is good, in-cylinder injection can be sufficiently performed, and for example, the internal combustion engine can be operated with priority given to the output. Therefore, it is possible to avoid an increase in the injection ratio of the port injection valve at an unnecessary timing, and it is possible to appropriately control the injection ratio of each injection valve.

  According to the third aspect of the invention, the combustion state determination means determines whether the combustion state of the internal combustion engine is good, for example, by comparing the fluctuation state of the engine speed of the internal combustion engine with reference data in a good combustion state. Can be determined. And when it determines with a combustion state being favorable, even if the precondition which should increase the injection ratio of a port injection valve is satisfied, this injection ratio can be hold | maintained at the injection ratio when alcohol concentration is low. it can. As a result, as in the case of the second invention, it is possible to avoid an increase in the injection ratio of the port injection valve at an unnecessary timing.

  According to the fourth invention, the port injection valve and the in-cylinder injection valve can inject fuel that cannot be injected by one of the injection valves from the other injection valve, and complement each other's fuel injection. it can. Therefore, for example, even when the target injection amount is increased according to the alcohol concentration in the fuel, it is possible to reliably perform fuel injection in an amount corresponding to the target injection amount.

  According to the fifth invention, the fuel pressure increasing means increases the pressure of the fuel supplied to the injection valve by the fuel pressurizing means when the target injection amount of the fuel exceeds the maximum total injection amount of the two injection valves. Can be made. Thereby, the fuel injection quantity of the injection valve with respect to a fixed valve opening time can be increased. Therefore, for example, even when the target injection amount is increased in accordance with the alcohol concentration in the fuel, the maximum total injection amount of the injection valve can be increased correspondingly, and the amount of fuel injection corresponding to the target injection amount can be increased. Can be performed reliably.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
The first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram for explaining a system configuration according to the first embodiment. An internal combustion engine 10 shown in FIG. 1 is configured as a dual injection internal combustion engine for an FFV (Flexible Fuel Vehicle) operated by a fuel in which gasoline and alcohol are mixed at an arbitrary ratio.

  Here, the internal combustion engine 10 includes one or a plurality of cylinders 12 (in this embodiment, four cylinders are exemplified). An intake passage 14 including an intake manifold is connected to the intake port 12a of each cylinder 12. The intake passage 14 sucks air (intake air) into the individual cylinders 12. Further, an exhaust passage is connected to an exhaust port (not shown) of each cylinder 12.

  The intake passage 14 of each cylinder 12 is provided with a port injection valve 16 for injecting fuel toward the intake port 12a. Further, each cylinder 12 is provided with an in-cylinder injection valve 18 that directly injects fuel into the respective combustion chambers. In this case, the cylinder injection valve 18 often injects a relatively large amount of fuel when the internal combustion engine 10 is operated at a high rotation speed or a high load state. For this reason, the in-cylinder injection valve 18 is configured by using a large flow rate type injection valve, and the maximum fuel injection amount is set larger than that of the port injection valve 16.

  Next, a fuel supply system to each of the injection valves 16 and 18 will be described. First, the internal combustion engine 10 is provided with a fuel tank 20 in which gasoline and alcohol are supplied at an arbitrary mixing ratio. A low pressure fuel pipe 22 is connected between the fuel tank 20 and each port injection valve 16. A low pressure pump 24 is provided in the middle of the low pressure fuel pipe 22. Thereby, the low pressure pump 24 can suck the fuel stored in the fuel tank 20 and distribute it to the low pressure fuel pipe 22 and supply the pressurized fuel to the port injection valve 16.

  On the other hand, the low pressure fuel pipe 22 is provided with a high pressure fuel pipe 26 branched from the pipe 22 on the downstream side of the low pressure pump 24. The high-pressure fuel pipe 26 is connected to each in-cylinder injection valve 18 via a high-pressure pump 28 and another fuel pipe 30. As a result, the high pressure pump 28 can pressurize the fuel in two stages together with the low pressure pump 24 and distribute it to the high pressure fuel pipe 26 to supply high pressure fuel to the in-cylinder injection valve 18.

  Thus, the two pumps 24 and 28 constitute a fuel pressurizing unit that pressurizes the fuel supplied to the injection valves 16 and 18. The operating states of the pumps 24 and 28, the fuel discharge pressure, and the like are controlled by an ECU 42 described later.

  Next, a control system of the internal combustion engine 10 will be described. First, the internal combustion engine 10 includes various sensors including a rotation sensor 32, an air flow meter 34, a water temperature sensor 36, a combustion pressure sensor 38, and an alcohol concentration sensor 40. In this case, the rotation sensor 32 constitutes the rotation detection means of the present embodiment, and outputs a detection signal corresponding to the rotation speed of the output shaft of the internal combustion engine 10 (engine rotation speed Ne). The air flow meter 34 detects the flow rate of air flowing through the intake passage 14 as the intake air amount Ga.

  The water temperature sensor 36 detects the temperature of the cooling water of the internal combustion engine 10. The combustion pressure sensor 38 constitutes the combustion state detecting means of the present embodiment, and detects the pressure (combustion pressure P) generated during combustion in each cylinder 12 and its fluctuation state. Furthermore, the alcohol concentration sensor 40 constitutes the alcohol concentration detection means of the present embodiment, and detects the alcohol concentration Ma in the fuel stored in the fuel tank 20.

  Further, the system configuration of the present embodiment includes an ECU (Electronic Control Unit) 42 that controls the operating state of the internal combustion engine 10. The ECU 42 is constituted by a microcomputer or the like, and has a storage circuit 42a composed of a ROM, a RAM, and the like. In the storage circuit 42a, map data of an operation area shown in FIG. 2 described later, a program shown in FIGS. 3 and 4, and various data including determination values Mx, Kx, Nx and the like are stored in advance. Yes.

  Various sensors including the above-described sensors 32, 36, 38, 40 and the air flow meter 34 are connected to the input side of the ECU 42. Various actuators including the port injection valve 16 and the pumps 24 and 28 are connected to the output side of the ECU 42 and a drive circuit 44 for driving the in-cylinder injection valve 18 is connected.

  The ECU 42 detects the operation state of the internal combustion engine 10 and the operation operation of the operator by the sensors, and performs various controls including fuel injection control and ignition timing control according to the detection result. Here, the fuel injection control will be described. First, the ECU 42 calculates the target injection amount Q of the fuel according to the operating state of the internal combustion engine 10 and determines the fuel injection amount of the port injection valve 16 and the in-cylinder injection valve 18. Determine the ratio (injection ratio).

  This setting range of the injection ratio includes a case where the fuel injection amount of one of the injection valves 16 and 18 becomes zero (that is, a case where fuel injection is performed using only the other injection valve). Then, the ECU 42 sets the fuel injection amount shared by the injection valves 16 and 18 in the target injection amount Q according to the injection ratio, and causes the fuel to be injected from the individual injection valves 16 and 18. For example, when the injection ratio of the port injection valve 16 is 30%, 30% of the target injection amount Q is injected from the port injection valve 16 (port injection), and the remaining 70% of the fuel is injected. Is injected from the in-cylinder injection valve 18 (in-cylinder injection).

[Characteristics of Embodiment 1]
(Basic port injection ratio increase control)
FIG. 2 shows map data of the operation region stored in advance in the storage circuit 42 a of the ECU 42. As shown in FIG. 2, in the operating region of the internal combustion engine 10, a low rotation / high load region A that is a region for performing port injection ratio increase control is set in advance. Hereinafter, the port injection ratio increase control executed as necessary in the low rotation / high load region A will be described.

  First, in the example shown in the present embodiment, in the low rotation / high load region A, the engine speed Ne of the internal combustion engine 10 is lower than a preset rotation determination value Nx, and the load factor KL of the internal combustion engine 10 is It is set as an operation region higher than a preset load determination value Kx. In this case, the load factor KL is a numerical value representing the load state of the internal combustion engine 10, and is calculated using the engine speed Ne, the intake air amount Ga, and the like.

  Here, when the internal combustion engine 10 is in a high load state, there is basically a demand to improve the output (torque) of the internal combustion engine 10 by performing in-cylinder injection. That is, the fuel injected in the cylinder takes heat of vaporization from the surroundings when it is vaporized in the combustion chamber. For this reason, in-cylinder injection can lower the temperature of intake air as compared with port injection, and can improve the charging efficiency of intake air and improve the output.

  However, in the low rotation / high load region A, it is difficult to form a homogeneous mixture by in-cylinder injection. This is because, in the low rotation / high load region A, the fluidity of the intake air is low because the engine speed Ne is low. In addition, since a relatively large amount of fuel is injected in response to a high load state, the injected fuel is difficult to mix with the intake air. In particular, the fuel injected in the cylinder has a short time from injection to combustion, and thus tends to burn before it is mixed homogeneously with the intake air.

  For this reason, in this Embodiment, it is set as the structure which performs port injection and in-cylinder injection together in the low rotation and high load area | region A. FIG. Since the port-injected fuel is mixed with the intake air before reaching the combustion chamber, a homogeneous air-fuel mixture can be formed as compared with in-cylinder injection. Thereby, in the port injection, the combustion state of the air-fuel mixture can be stabilized, and fuel consumption and torque fluctuation can be improved.

  Therefore, in the low rotation / high load region A, the fuel consumption and torque fluctuation are improved by port injection while securing the output of the internal combustion engine 10 by in-cylinder injection. In this case, the ratio (injection ratio) of the fuel injection amount between the port injection valve 16 and the in-cylinder injection valve 18 is set to an appropriate value obtained through experiments or the like and stored in advance in the storage circuit 42a of the ECU 42.

  Thus, in the low rotation / high load region A, a relatively large amount of fuel is injected. However, when the alcohol concentration in the fuel is high, it is necessary to inject a larger amount of fuel. That is, when the alcohol concentration in the fuel is high, the fuel injection amount is set larger than in the case where the gasoline concentration is high in order to compensate for the decrease in the heat generation amount during combustion. For this reason, in the low rotation / high load region A, in a situation where it is difficult to homogenize the air-fuel mixture, a larger amount of fuel will be injected, making it even more difficult to homogenize the air-fuel mixture.

  Therefore, in the present embodiment, the port injection ratio increase control is performed when the alcohol concentration Ma in the fuel is higher than the concentration determination value Mx and the internal combustion engine 10 is operated in the low rotation / high load region A. It is configured to do. In this port injection ratio increase control, the injection ratio of fuel injected from the port injection valve 16 (hereinafter referred to as the port injection ratio) is increased from the normal injection ratio. In this case, the normal injection ratio is set, for example, as the injection ratio when the alcohol concentration Ma is equal to or less than the concentration determination value Mx.

  As a result, the port injection ratio increase control can form a homogeneous air-fuel mixture by the increased port injection ratio, and can stabilize the combustion state of the air-fuel mixture. Further, for example, fuel in the target injection amount Q that is disadvantageous for the formation of the air-fuel mixture in the in-cylinder injection can be injected from the port injection valve 16. As a result, it is possible to prevent excessive fuel injection from the in-cylinder injection valve 18 in a situation where homogenization of the air-fuel mixture is difficult. On the other hand, since the remaining fuel can be injected also from the cylinder injection valve 18, the output of the internal combustion engine 10 can be ensured.

  Therefore, the port injection valve 16 and the in-cylinder injection valve 18 can be used at an appropriate injection ratio in accordance with the operating state of the internal combustion engine 10, the alcohol concentration in the fuel, and the like. In addition, it is possible to improve driving performance such as fuel consumption and torque fluctuation while satisfying the output demand of the internal combustion engine 10. Note that the concentration determination value Mx used for this control is set as the minimum value of the alcohol concentration Ma that requires the port injection ratio to be increased.

  On the other hand, when the port injection ratio is increased, the injection ratio of the in-cylinder injection valve 18 (hereinafter referred to as the in-cylinder injection ratio) is decreased. However, when the alcohol concentration is high, as described above, the value of the target injection amount Q is set large in order to maintain the heat generation amount during combustion. For this reason, even if the in-cylinder injection ratio decreases, the fuel flow rate for cooling the tip of the in-cylinder injection valve 18 can be secured. Therefore, even if the port injection ratio increase control is executed, it is possible to prevent deposits and the like from accumulating due to the high temperature at the tip of the in-cylinder injection valve 18.

(Exception control when the combustion state is good)
As described above, in the basic port injection ratio increase control, the inhomogeneity of the air-fuel mixture can be promoted by distributing the fuel that is disadvantageous for the formation of the air-fuel mixture to the port injection when in-cylinder injection is performed. However, depending on the operating state of the internal combustion engine 10, even if the port injection ratio increase control is not performed, an air-fuel mixture that is more homogeneous than expected may be formed, and the combustion state may be good.

  For example, when the internal combustion engine 10 is sufficiently warmed up or when the gasoline in the fuel contains a lot of light components, a fuel with a high alcohol concentration is used in the low rotation / high load region A. Even when in-cylinder injection is performed, vaporization of the fuel is promoted more than expected, so that a homogeneous air-fuel mixture is easily formed in the combustion chamber.

  For this reason, in the present embodiment, for example, three parameters including the combustion pressure P of the internal combustion engine 10, the fluctuation amount of the combustion pressure P, and the fluctuation amount of the engine speed Ne are detected. In this case, as the fluctuation amount of the combustion pressure P and the engine speed Ne, a general index that can reflect the variation in data, such as a deviation from the average value, may be used.

  In the memory circuit 42a of the ECU 42, for example, the average value of the combustion pressure P in a good combustion state, the average fluctuation amount of the combustion pressure P, and the average fluctuation amount of the engine speed Ne are “good. It is stored in advance as “reference data corresponding to the combustion state”. Then, the ECU 42 compares all the above-described parameters with these reference data.

  When it is determined that all the parameters are equal to the reference data or within the allowable range with respect to the reference data, the combustion state of the internal combustion engine 10 is good because a homogeneous mixture is formed. Judge. In this case, even if the precondition for performing the port injection ratio increase control (the alcohol concentration in the fuel is high and the engine is operating in the low rotation / high load region A) is satisfied, Does not increase. That is, the port injection ratio is held at the above-described normal injection ratio (for example, the injection ratio when the alcohol concentration Ma is equal to or lower than the concentration determination value Mx).

  On the other hand, for example, when the combustion pressure P is lower than the reference data or the fluctuation amount of the combustion pressure P or the engine speed Ne is larger than the reference data, the combustion state is stable because the air-fuel mixture is inhomogeneous. It is not considered. Accordingly, in this case, as described above, the homogenization of the air-fuel mixture is promoted by increasing the port injection ratio.

  Thus, when the operation is performed in the low rotation / high load region A using the fuel having a high alcohol concentration, the port injection ratio can be increased only when the combustion state of the internal combustion engine 10 is unstable. When the combustion state is good, the in-cylinder injection can be sufficiently performed by maintaining the normal injection ratio. For example, the internal combustion engine 10 can be operated with priority given to the output.

  Therefore, it is possible to avoid the port injection ratio from being increased at an unnecessary timing, and the injection ratios of the injection valves 16 and 18 can be appropriately controlled. The above-described combustion state determination process using the combustion pressure P is executed individually for each cylinder 12. Then, only when it is determined that the combustion state is good in all the cylinders 12, the port injection ratio may be increased in accordance with the fluctuation amount of the engine speed Ne.

(Control when target injection amount is large)
When the alcohol concentration in the fuel is high, the target injection amount Q tends to increase as described above. In this case, even if the target injection amount Q is assigned to each of the injection valves 16 and 18 according to the set value of the injection ratio, the fuel injection amount assigned to each of the injection valves 16 and 18 is the maximum injection amount of the injection valve. May be exceeded.

  For this reason, in the present embodiment, when the fuel injection amount to be injected from either one of the injection valves 16 and 18 exceeds the maximum injection amount of the injection valve, only the amount that the injection amount has exceeded. The fuel injection amount of the other injection valve is increased. Thereby, the injection valves 16 and 18 can inject the fuel which cannot be injected with one injection valve from the other injection valve, and can complement each other's fuel injection. Therefore, for example, even when the target injection amount Q is increased in accordance with the alcohol concentration Ma in the fuel, it is possible to reliably perform fuel injection in an amount corresponding to the target injection amount Q.

  Further, when the value of the target injection amount Q further increases, the total maximum injection amount (hereinafter referred to as the maximum total injection amount) obtained by adding up the maximum injection amount of the port injection valve 16 and the maximum injection amount of the in-cylinder injection valve 18. The target injection amount Q may be larger than the target injection amount Q.

  For this reason, in the present embodiment, when the value of the target injection amount Q exceeds the maximum total injection amount of the injection valves 16, 18, the pressure of the fuel supplied to these injection valves 16, 18 is increased. Yes. That is, the ECU 42 increases the pressure of the fuel discharged from these pumps 24 and 28 by switching the operating state of the low-pressure pump 24 and the high-pressure pump 28, for example.

  In general, the fuel injection valve controls the fuel injection amount by changing the valve opening time in a state where pressurized fuel is supplied. Therefore, the ECU 42 can increase the fuel injection amount of the injection valves 16 and 18 for a certain valve opening time by increasing the pressure of the fuel supplied from the pumps 24 and 28 to the injection valves 16 and 18. Therefore, according to the present embodiment, even when the target injection amount Q increases due to, for example, the alcohol concentration in the fuel, the maximum total injection amount of the injection valves 16 and 18 can be increased correspondingly. Thus, fuel injection of an amount corresponding to the target injection amount Q can be reliably performed.

[Specific Processing for Realizing Embodiment 1]
FIG. 3 is a flowchart of a routine executed by the ECU 42 during the fuel injection control in order to realize the system operation of the present embodiment. Note that the routine shown in FIG. 3 is started when the internal combustion engine 10 is started, and is repeatedly executed at regular intervals.

  First, in step 100, the ECU 42 reads the detection signals from the sensors 32, 36, 38, 40 and the air flow meter 34 to thereby determine the engine speed Ne, the intake air amount Ga, the temperature, the alcohol concentration Ma, and the combustion pressure P. Is detected. In step 100, the fluctuation amount of the combustion pressure P and the engine speed Ne is also detected by performing an arithmetic process such as obtaining a deviation from the average value. In step 102, the load factor KL is calculated using the engine speed Ne, the intake air amount Ga, and the cylinder volume stored in advance.

  Next, in step 104, injection is performed from the injection valves 16 and 18 using the engine speed Ne, the intake air amount Ga, the alcohol concentration Ma, and the detection result of the operator's operation detected using other sensors. A target injection amount Q of the fuel to be calculated is calculated.

  Next, in step 106, it is determined whether or not the alcohol concentration Ma is higher than a preset concentration determination value Mx. Further, at step 108, for example, the current engine speed Ne and the load factor KL are compared with judgment values Nx and Kx stored in advance in the ECU 42, so that the current operation state belongs to the low rotation / high load region A. It is determined whether or not. Specifically, for example, when the engine speed Ne is lower than the rotation determination value Nx and the load factor KL is higher than the load determination value Kx, it is determined that the operation is performed in the low rotation / high load region A. To do.

  If “YES” is determined in both steps 106 and 108, the precondition for performing the port injection ratio increase control is established, and therefore the process proceeds to step 110. If it is determined as “NO” in at least one of steps 106 and 108, the process proceeds to step 114 described later, and the port injection ratio is set to the normal injection ratio.

  Next, in step 110, as the first combustion state determination means, whether or not the magnitude and the fluctuation amount of the combustion pressure P match the reference data stored in the ECU 42 (to be exact, it is equal to the reference data). Or whether it is within an allowable range with respect to the reference data). Further, in step 112, as a second combustion state determination means, it is determined whether or not the fluctuation amount of the engine speed Ne matches the reference data.

  If “YES” is determined in both steps 110 and 112, it is determined that the combustion state of the internal combustion engine 10 is stable, so the routine proceeds to step 114 and the port injection ratio is maintained at the normal injection ratio. To do. If it is determined as “NO” in at least one of steps 106 and 108, it is determined that the combustion state is not good, so the routine proceeds to step 116 where the port injection ratio is increased.

  Next, in step 118, an injection amount correction process, which will be described later, is executed. In step 120, fuel injection is performed according to the correction result by the injection amount correction process, the injection ratio set in steps 114 and 116, and the like.

  Next, the injection amount correction process will be described with reference to FIG. First, in step 130, it is determined whether or not the target injection amount Q is larger than the maximum total injection amount of the injection valves 16 and 18. Here, when it determines with "YES", the discharge pressure of the pumps 24 and 28 is raised at step 132, and it returns after that. If “NO” is determined in the step 130, the process proceeds to a step 134.

  In step 134, it is determined whether or not the fuel injection amount assigned to the port injection valve 16 exceeds the maximum injection amount of the injection valve 16. If "YES" is determined here, the fuel injection amount to be allocated to the in-cylinder injection valve 18 is increased in step 136, and then the process returns. This increase is performed, for example, by an amount corresponding to the difference between the fuel injection amount assigned to the port injection valve 16 and the maximum injection amount of the injection valve 16.

  If “NO” is determined in the step 134, the process proceeds to a step 138 to determine whether or not the fuel injection amount allocated to the in-cylinder injection valve 18 exceeds the maximum injection amount of the injection valve 18. Here, when it determines with "YES", the fuel injection amount allocated to the port injection valve 16 is increased in step 140, and it returns after that.

  As described above in detail, according to the present embodiment, the port injection valve 16 and the in-cylinder injection valve according to the operating state of the internal combustion engine 10, the alcohol concentration in the fuel, the fuel injection capacity of the injection valves 16 and 18, and the like. 18 can be used at an appropriate injection ratio. Thereby, it is possible to improve driving performance such as fuel consumption and torque fluctuation while satisfying the output demand of the internal combustion engine 10.

  In the first embodiment, step 104 in FIG. 3 shows a specific example of the target calculation means, and steps 106, 108, 114, and 116 show specific examples of the port injection ratio increasing means. Step 110 shows a specific example of the first combustion state detection means, and step 112 shows a specific example of the second combustion state detection means. Further, steps 134 to 140 in FIG. 4 show a specific example of the injection amount complementing means, and steps 130 and 132 show a specific example of the fuel pressure increasing means.

  Further, in the first embodiment, only the upper limit value (rotation determination value Nx) of the engine speed Ne and only the lower limit value (load determination value Kx) of the load factor KL are used as boundaries of the low rotation / high load region A. The configuration is set. That is, the lower limit value of the engine speed Ne is the lowest speed at which the internal combustion engine 10 can be operated, and the upper limit value of the load factor KL is the maximum load factor at which the internal combustion engine 10 can be operated. Set as being. However, the present invention is not limited to this, and both the upper limit value and the lower limit value may be set for each of the engine speed Ne and the load factor KL as the boundary of the low rotation / high load region A.

  Further, in the first embodiment, whether or not the combustion state of the internal combustion engine 10 is good using three parameters including the combustion pressure P of the internal combustion engine, the fluctuation amount of the combustion pressure P, and the fluctuation amount of the engine speed Ne. It was set as the structure which judges. However, the present invention is not limited to this, and the combustion state may be determined using any one or two of the three parameters.

  In the first embodiment, the discharge pressures of both the low pressure pump 24 and the high pressure pump 28 are increased when the target injection amount Q exceeds the maximum total injection amount of the injection valves 16 and 18. However, the present invention is not limited to this, and only the discharge pressure of one of the low-pressure pump 24 and the high-pressure pump 28 may be increased.

  Further, in the first embodiment, the load factor KL is used as a parameter representing the load state of the internal combustion engine 10. However, the present invention is not limited to this, and as an index indicating the load state, for example, parameters such as the target injection amount Q of fuel, the intake air amount Ga, the throttle opening, the accelerator operation amount of the operator, and the like are calculated. It is also possible to employ a configuration using parameters such as torque.

1 is an overall configuration diagram illustrating a control device for an internal combustion engine according to a first embodiment of the present invention. It is explanatory drawing which shows the low rotation and high load area | region in the driving | operation area | region of an internal combustion engine. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart which shows the injection quantity correction process routine in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Cylinder 12a Intake port 14 Intake passage 16 Port injection valve 18 In-cylinder injection valve 20 Fuel tank 22 Low pressure fuel piping 24 Low pressure pump (fuel pressurizing means)
26 High-pressure fuel pipe 28 High-pressure pump (fuel pressurizing means)
30 Fuel piping 32 Rotation sensor (Rotation detection means)
34 Air flow meter 36 Water temperature sensor 38 Combustion pressure sensor (combustion state detection means)
40 Alcohol concentration sensor (alcohol concentration detection means)
42 ECU
A Low rotation / High load area Ga Intake air volume
KL Load factor Kx Load judgment value Ne Engine speed Nx Rotation judgment value Ma Alcohol concentration Mx Concentration judgment value P Combustion pressure Q Target injection amount

Claims (5)

A port injection valve for injecting fuel toward the intake port of the internal combustion engine;
An in-cylinder injection valve for injecting fuel into the cylinder of the internal combustion engine;
Target calculation means for calculating the total amount of fuel to be injected from the port injection valve and the in-cylinder injection valve as a target injection amount according to the operating state of the internal combustion engine;
Alcohol concentration detection means for detecting the alcohol concentration in the fuel;
The higher than the alcohol concentration determination value, and when the internal combustion engine is prerequisite that Ru is operated at low speed and high load state is established, the injection of the fuel injected from the port injection valve of the target injection amount Port injection ratio increasing means for increasing the ratio more than the injection ratio when the alcohol concentration is equal to or less than the determination value;
If the combustion condition of the internal combustion engine is good even if the precondition is satisfied, the alcohol concentration of the port injection valve is equal to or less than the determination value without operating the port injection ratio increasing means. Means for maintaining the injection ratio when
A control device for an internal combustion engine, comprising: Combustion state detection means for detecting the combustion pressure of the internal combustion engine and / or the fluctuation state of the combustion pressure;
Detection result the control device for an internal combustion engine according to claim 1 comprising Ete Bei the combustion state determining means determines whether or not correspond to good combustion state of the internal combustion engine of the combustion state detection means. Rotation detection means for detecting the engine speed of the internal combustion engine;
Internal combustion engine according to claim 1 or 2 and determining the combustion state judging means Bei consisting Ete whether variation state of the engine rotational speed detected corresponds to a good combustion state of the internal combustion engine by said rotation detecting means Control device.   When the fuel injection amount to be injected from one of the port injection valve and the cylinder injection valve exceeds the maximum injection amount of the injection valve, the fuel injection amount injected from the other injection valve is 4. The control device for an internal combustion engine according to claim 1, further comprising an injection amount complementing means for increasing the amount.   A fuel pressurizing unit that pressurizes fuel supplied to the port injection valve and the in-cylinder injection valve, and the target injection more than a maximum total injection amount that is a sum of the maximum injection amounts of the port injection valve and the in-cylinder injection valve. The control apparatus for an internal combustion engine according to any one of claims 1 to 4, further comprising fuel pressure increasing means for increasing the pressure applied to the fuel by the fuel pressurizing means when the amount increases.

Images