JP2008298046A - Controller of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the fuel injection rate of the fuel injection valve provided in the air intake passage as the concentration of alcohol in the fuel increases, protects the cylinder fuel injection valve, and improve the operating performance of the dual injection type internal combustion engine for FFV. <P>SOLUTION: The internal combustion engine 10 is equipped with a port injection valve 16 to inject fuel into the air intake passage 14 and a cylinder injection valve 18 to inject fuel into the cylinder 12. The ECU 40 causes either or both of fuel injection valves 16 and 18 to inject fuel according to the operating status of the internal combustion engine 10. In this case, the ECU 40 increases the port injection rate α as the concentration of alcohol Ma in the fuel is higher. This can increase the fuel consumption of the port injection valve 16 to improve fuel consumptions and torque fluctuations, and adequately inject fuel into the cylinder injection valve 18 to prevent deposition of deposits and the like. <P>COPYRIGHT: (C)2009,JPO&INPIT

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. Here, the conventional internal combustion engine includes an intake passage injection valve that injects fuel into an intake passage (intake port) and an in-cylinder injection valve that directly injects fuel into the combustion chamber. The control device for the internal combustion engine changes the fuel injection amount ratio (injection ratio) between the intake passage injection valve and the in-cylinder injection valve as necessary, for example, depending on the alcohol concentration in the fuel. Fuel injection control is performed.

  Here, in general, when a fuel having a high alcohol concentration is used, the injected fuel is easily vaporized. For this reason, in the prior art, the higher the alcohol concentration in the fuel, the higher the injection ratio of the in-cylinder injection valve. That is, in the prior art, even in the case of in-cylinder injection in which the time from injection to combustion is short, it is assumed that if the fuel has a high alcohol concentration, the fuel is quickly vaporized and a good mixture can be obtained. .

JP 2006-214415 A

  In the prior art, if the fuel has a high alcohol concentration, it is considered that an air-fuel mixture is formed quickly, and the injection ratio of the in-cylinder injection valve is set high. However, since the fuel injected into the cylinder tends to form a heterogeneous mixture, there is a problem that the combustion state becomes unstable, resulting in deterioration of fuel consumption and fluctuation of output torque.

  In order to avoid such a problem, a method of increasing the injection ratio of the intake passage injection valve is also conceivable. However, in this case, since the fuel injection amount of the in-cylinder injection valve is relatively reduced, the temperature of the injection valve tends to increase. As a result, deposits are likely to accumulate at the injection port of the in-cylinder injection valve, and the operation and flow rate characteristics of the injection valve may become unstable.

  The present invention has been made to solve the above-described problems. When the injection ratio of the intake passage injection valve and the in-cylinder injection valve is controlled in accordance with the alcohol concentration in the fuel, the in-cylinder injection valve is It is an object of the present invention to provide a control device for an internal combustion engine capable of improving operating performance while protecting from foreign matters such as deposits.

A first invention is an intake passage injection valve that injects fuel into an intake passage 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 intake passage 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;
Intake side injection ratio increasing means for increasing the injection ratio of fuel injected from the intake passage injection valve in the target injection amount as the alcohol concentration is higher;
It is characterized by providing.

  In the second invention, the intake side injection ratio increasing means increases the injection ratio of the intake passage injection valve in a range where the temperature of the in-cylinder injection valve does not exceed an allowable limit.

  According to a third aspect of the invention, the intake side injection ratio increasing means sets the injection ratio of the intake passage injection valve and the in-cylinder injection valve variably according to the target injection amount and the alcohol concentration. Has map data.

  According to the first aspect of the invention, when the injection ratio between the intake passage injection valve and the in-cylinder injection valve is set, the injection ratio of the intake passage injection valve can be increased as the alcohol concentration in the fuel is higher. That is, when the alcohol concentration is high, the fuel injection amount is increased in order to ensure the amount of heat generated during combustion. For this reason, even if the injection ratio of the intake passage injection valve is increased, the in-cylinder injection valve can inject a sufficient amount of fuel to suppress the temperature on the tip side.

  Thereby, since the fuel injection amount of the intake passage injection valve can be increased, a homogeneous and good air-fuel mixture can be formed in the combustion chamber. As a result, the fuel consumption and torque fluctuation of the internal combustion engine can be improved. On the other hand, the in-cylinder injection valve can also keep the temperature on the tip side within an allowable range by injecting a sufficient amount of fuel. As a result, foreign matter such as deposits can be prevented from accumulating on the tip side of the in-cylinder injection valve. Accordingly, it is possible to improve the operation performance of the internal combustion engine while protecting the in-cylinder injection valve from foreign matters such as deposits.

  According to the second invention, when the alcohol concentration in the fuel is high, the fuel injection amount is increased in order to secure the heat generation amount during combustion. For this reason, the intake side injection ratio increasing means increases the fuel injection amount of the intake passage injection valve and also injects a sufficient amount of fuel to the in-cylinder injection valve to keep the tip temperature below the allowable limit. be able to.

  According to the third invention, by using the two-dimensional map data, the injection ratio of the intake passage injection valve can be freely changed according to the combination of the target injection amount and the alcohol concentration. Thereby, compared with the case where the injection ratio is corrected using a correction coefficient corresponding to the alcohol concentration, for example, the injection ratio can be changed with high accuracy. Further, the injection ratio can be variably set depending on the target injection amount. For this reason, even when a large amount of target injection amount is set, the injection performance (the range of applicable injection amount) of the intake passage injection valve and the in-cylinder injection valve is taken into consideration and appropriate for each injection valve. An amount of fuel can be dispensed.

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 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.

  Each cylinder 12 includes an intake passage injection valve (hereinafter referred to as a port injection valve) 16 that injects fuel into an intake passage 14 (or intake port), and a cylinder that directly injects fuel into the combustion chamber of each cylinder 12. And an internal injection valve 18. In this case, the in-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 using a large-flow-type injection valve, and the maximum amount of fuel that can be injected 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. The operating states of these pumps 24 and 28 are controlled by an ECU 40 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, and an alcohol concentration sensor 38. In this case, the rotation sensor 32 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. Further, the alcohol concentration sensor 38 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.

  In addition, the system configuration of the present embodiment includes an ECU (Electronic Control Unit) 40 that controls the operating state of the internal combustion engine 10. The ECU 40 is constituted by a microcomputer or the like, and has a storage circuit 40a composed of ROM, RAM, and the like. Various sensors including a rotation sensor 32, an air flow meter 34, and a water temperature sensor 36 are connected to the input side of the ECU 40. Various actuators including the port injection valve 16 and the pumps 24, 28 are connected to the output side of the ECU 40, and a drive circuit 42 that drives the in-cylinder injection valve 18 is connected.

  The ECU 40 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. In this case, in the fuel injection control, first, a target injection amount Q of fuel is calculated according to the detection result of each sensor, and an amount of fuel corresponding to the target injection amount Q is injected into each cylinder 12 from the injection valves 16 and 18. Let

  Further, at the time of fuel injection, fuel is injected from one or both of the injection valves 16 and 18 according to the operating state of the internal combustion engine 10 and the like. Specifically, the operating region of the internal combustion engine 10 is divided into three types of regions including a port injection region, an in-cylinder injection region, and an injection divided region, for example, according to the load state and the engine speed. In the port injection region, fuel of the target injection amount Q is injected using only the port injection valve 16. In the in-cylinder injection region, the target injection amount Q of fuel is injected using only the in-cylinder injection valve 18.

  Further, in the injection divided region, fuel is injected from both the injection valves 16 and 18. At this time, the ECU 40 refers to the two-dimensional map data E (Ma, Q) stored in advance in the storage circuit 40a using, for example, the target injection amount Q and the alcohol concentration Ma, thereby determining the port injection ratio α. Set. Here, the port injection ratio α is a ratio (%) that the fuel injection amount from the port injection valve 16 occupies in the entire target injection amount Q, and is set in a range of α = 0 to 100%. . Then, the ECU 40 injects fuel from each of the injection valves 16 and 18 based on the port injection ratio α.

[Characteristics of Embodiment 1]
FIG. 2 is a characteristic diagram showing two-dimensional map data E (Ma, Q) for setting the port injection ratio α. The two-dimensional map data E (Ma, Q) includes a plurality of types of injection ratio setting data En (n = 0 to 100) set in advance corresponding to different alcohol concentrations Ma. In this case, the subscript n attached to En is the alcohol concentration (%). The individual injection ratio setting data En is configured as one-dimensional map data for setting an optimal port injection ratio α according to the value of the target injection amount Q.

Accordingly, FIG. 2 shows the injection ratio setting data E ₀ and E ₂₅ for setting the port injection ratio α, respectively, when the alcohol concentration in the fuel is 0%, 25%, 50%, 75%, and 100%. , E ₅₀ , E ₇₅ , E ₁₀₀ . More specifically, for example, the injection ratio setting data E ₅₀ is data for setting the port injection ratio α according to the value of the target injection amount Q when the alcohol concentration is 50%.

  As can be seen from FIG. 2, in this embodiment, for example, when the target injection amount Q is considered as a constant value, the port injection ratio α is increased as the alcohol concentration Ma in the fuel increases. If comprised in this way, the operating performance of the internal combustion engine 10 can be improved, protecting the cylinder injection valve 18 from a deposit for the reason mentioned later. In the individual injection ratio setting data En, the port injection ratio α is set to increase as the fuel injection amount Q increases. Thereby, even when the fuel injection amount is large, the fuel can be stably injected into the two injection valves 16 and 18.

  Next, the reason why the port injection ratio α is increased when the alcohol concentration Ma is high will be described with reference to FIGS. 3 to 5. First, FIG. 3 shows a tendency of how the fuel consumption of the internal combustion engine 10, the torque fluctuation, and the tip temperature of the in-cylinder injection valve 18 change when the port injection ratio α changes. In this case, the tip temperature of the in-cylinder injection valve 18 is the temperature near the fuel injection port.

  As can be seen from FIG. 3, the fuel consumption and torque fluctuation tend to be improved as the port injection ratio α increases. That is, when fuel is injected from the port injection valve 16 into the intake passage 14, the fuel forms a relatively homogeneous and good mixture until it reaches the cylinder 12 while mixing with the intake air. Can do. As a result, since the combustion state of the air-fuel mixture can be stabilized, the state of fuel consumption and torque fluctuation can be improved.

  On the other hand, the tip temperature of the cylinder injection valve 18 tends to increase as the port injection ratio α increases. In this case, the front end side of the in-cylinder injection valve 18 that becomes high temperature in the combustion chamber is cooled by injecting fuel. However, when the target injection amount Q is considered as a constant value, if the port injection ratio α increases, the fuel injection amount of the in-cylinder injection valve 18 decreases accordingly, so that the cooling effect by fuel injection is reduced. become.

  For this reason, if the port injection ratio α becomes too large, the tip temperature of the in-cylinder injection valve 18 exceeds the allowable limit shown in FIG. 3 and reaches the NG region. This allowable limit is a temperature that serves as a guide for preventing deposits from being deposited, and is, for example, a temperature of about 150 ° C. That is, when the tip temperature of the in-cylinder injection valve 18 reaches the NG region, deposits are accumulated in the vicinity of the injection port, and the operation and flow rate characteristics of the injection valve tend to become unstable. Therefore, when increasing the port injection ratio α, it is necessary to pay attention to the tip temperature of the in-cylinder injection valve 18.

  Next, FIG. 4 shows a tendency of how the fuel injection amount under the same operating condition and the heat generation amount per unit amount of fuel change when the alcohol concentration Ma in the fuel changes. Yes. As can be seen from FIG. 4, the amount of heat generated by the fuel decreases as the alcohol concentration Ma increases.

  As a result, when the alcohol concentration Ma is high, the fuel injection amount is increased in order to ensure the amount of heat generated during combustion. Thus, in the state where the fuel injection amount is increased, the in-cylinder injection valve 18 can inject a sufficient amount of fuel to lower the tip temperature even if the port injection ratio α is set to be large. .

  Therefore, in consideration of the tendency shown in FIGS. 3 and 4, the present embodiment can obtain the effects shown in FIG. Here, FIG. 5 shows effects obtained with respect to fuel consumption, torque fluctuation, and tip temperature of the in-cylinder injection valve 18 when the port injection ratio α is increased in accordance with the alcohol concentration Ma in the fuel.

  As shown in FIG. 5, in this embodiment, the port injection ratio α is increased as the alcohol concentration Ma in the fuel increases. For this reason, the higher the alcohol concentration Ma is, the more the fuel injection amount of the port injection valve 16 can be increased, thereby improving the fuel consumption and torque fluctuation.

  The in-cylinder injection valve 18 can also keep the tip temperature within an allowable range by injecting a sufficient amount of fuel. As a result, it is possible to reliably prevent deposits from accumulating on the distal end side of the in-cylinder injection valve 18. Therefore, according to the present embodiment, it is possible to improve the operation performance of the internal combustion engine 10 while protecting the in-cylinder injection valve 18 from foreign matters such as deposits.

[Specific Processing for Realizing Embodiment 1]
FIG. 6 is a flowchart of a routine executed by the ECU 40 in order to realize the system operation of the present embodiment. The routine shown in FIG. 6 is started when the internal combustion engine 10 is started, and is repeatedly executed at regular intervals.

  In this fuel injection control, first, at step 100, detection signals from the rotation sensor 32, the air flow meter 34, and the alcohol concentration sensor 38 are used, whereby the engine speed Ne, the intake air amount Ga of the internal combustion engine 10 and the alcohol in the fuel are detected. The density Ma is detected.

  Next, in step 102, the load factor KL is calculated using the engine speed Ne, the intake air amount Ga, and parameters such as the cylinder volume. Here, the load factor KL corresponds to the charging efficiency of the intake air sucked into the cylinder 12 and represents the load state of the internal combustion engine 10. In step 104, the total fuel amount to be injected in the current operating state is calculated as the target injection amount Q by referring to map data for fuel injection using the load factor KL.

  Next, in step 106, the port injection ratio α is set by referring to the two-dimensional map data E (Ma, Q) in FIG. 2 using the target injection amount Q and the alcohol concentration Ma. At this setting, specific injection ratio setting data En is selected from a plurality of types of injection ratio setting data En in accordance with the value of the alcohol concentration Ma, and target injection is further selected from the selected injection ratio setting data En. A specific port injection ratio α is selected according to the quantity Q.

  In step 108, fuel injection is performed by driving the injection valves 16 and 18 according to the set value of the port injection ratio α. Specifically, the fuel corresponding to the port injection ratio α in the entire target injection amount Q is injected from the port injection valve 16 into the intake passage 14. Further, fuel corresponding to the remaining ratio (100−α) is directly injected into the cylinder 12 from the in-cylinder injection valve 18.

  In this case, in the present embodiment, the two-dimensional map data E (Ma, Q) is used to set the port injection ratio α. For this reason, the port injection ratio α can be freely changed in accordance with the combination of the target injection amount Q and the alcohol concentration Ma. As a result, for example, the port injection ratio α can be changed with higher accuracy than when the injection ratio is corrected using a correction coefficient corresponding to the alcohol concentration.

  Further, by using the two-dimensional map data E (Ma, Q), the port injection ratio α can be variably set also by the target injection amount Q. For this reason, even when a large amount of target injection amount Q is set, the injection performances of the port injection valve 16 and the in-cylinder injection valve 18 and the individual injection valves 16, An appropriate amount of fuel can be distributed to each of the 18.

  In the first embodiment described above, step 104 in FIG. 6 shows a specific example of the target calculation means. Further, the two-dimensional map data E (Ma, Q) in FIG. 2 and step 106 in FIG. 6 show a specific example of the intake side injection ratio increasing means.

  In the first embodiment, the alcohol concentration sensor 38 detects the alcohol concentration in the fuel. However, the present invention is not limited to this. For example, without using the alcohol concentration sensor 38, the alcohol concentration is estimated using the data of the refueling history for the fuel tank 20 (alcohol concentration and amount of fuel refueled in the past). It is good. Moreover, it is good also as a structure which mounts the sensor etc. which measure the emitted-heat amount when a fuel is burned, and estimates alcohol concentration from the measured value of emitted-heat amount. Further, for example, a liquid marker corresponding to the alcohol concentration may be mixed in the fuel to be supplied in advance, and the alcohol concentration may be grasped by detecting the liquid marker.

1 is an overall configuration diagram showing a system configuration of a control device for an internal combustion engine according to Embodiment 1 of the present invention. It is a characteristic diagram which shows the two-dimensional map data for setting a port injection ratio using the alcohol concentration in fuel and the target injection amount. It is a characteristic diagram which shows the tendency how the fuel consumption of an internal combustion engine, a torque fluctuation, and the front-end | tip temperature of a cylinder injection valve change when a port injection ratio changes. It is a characteristic diagram which shows the tendency how the emitted-heat amount and injection amount of a fuel change, when the alcohol concentration in a fuel changes. It is a characteristic diagram which shows the tendency how the fuel consumption of an internal combustion engine, a torque fluctuation, and the front-end | tip temperature of a cylinder injection valve change when a port injection ratio is increased according to the alcohol concentration in fuel. It is a flowchart of the routine performed in Embodiment 1 of the present invention.

Explanation of symbols

10 internal combustion engine 12 cylinder 14 intake passage 16 port injection valve (intake passage injection valve)
18 In-cylinder injection valve 20 Fuel tank 22 Low pressure fuel pipe 24 Low pressure pump 26 High pressure fuel pipe 28 High pressure pump 30 Fuel pipe 32 Rotation sensor 34 Air flow meter 36 Water temperature sensor 38 Alcohol concentration sensor (alcohol concentration detection means)
40 ECU
40a Storage circuit 42 Drive circuit Ne Engine speed Ga Intake air amount Ma Alcohol concentration Q Target injection amount α Port injection ratio E (Ma, Q) Two-dimensional map data (intake side injection ratio increasing means)
En injection ratio setting data

Claims (3)

An intake passage injection valve for injecting fuel into the intake passage 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 intake passage 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;
Intake side injection ratio increasing means for increasing the injection ratio of fuel injected from the intake passage injection valve in the target injection amount as the alcohol concentration is higher;
A control device for an internal combustion engine, comprising:   2. The control device for an internal combustion engine according to claim 1, wherein the intake side injection ratio increasing means increases the injection ratio of the intake passage injection valve in a range in which a temperature of the in-cylinder injection valve does not exceed an allowable limit.   The intake side injection ratio increasing means includes two-dimensional map data for variably setting an injection ratio between the intake passage injection valve and the in-cylinder injection valve in accordance with the target injection amount and the alcohol concentration. Item 3. The control device for an internal combustion engine according to Item 1 or 2.

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