Control device for internal combustion engine

Abstract

To enable appropriate fuel injection.SOLUTION: A control device for an internal combustion engine includes: a combustion chamber 3; an intake passage 4 leading to the combustion chamber 3; a fuel injection device 13 that injects fuel to the intake passage 4; an intake valve 6 that opens / closes a portion between the intake passage 4 and the combustion chamber 3; fuel adhesion amount acquisition means 23 for acquiring a fuel adhesion amount to the intake passage 4 and the intake valve 6; evaporation amount acquisition means 24 for acquiring a fuel evaporation amount from the fuel adhesion amount; and fuel injection amount acquisition means 22 for acquiring a fuel injection amount on the basis of the evaporation amount. An upper limit value of the fuel adhesion amount is set. The fuel adhesion amount acquisition means 23 calculates a fuel adhesion amount calculation value on the basis of the fuel injection amount. When the fuel adhesion amount calculation value exceeds the upper limit value, a value that does not exceed the upper limit value is set as the fuel adhesion amount.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for an internal combustion engine. [Background technology]

[0002] In a fuel-injected internal combustion engine, the required amount of fuel is injected according to the required torque, and an air-fuel mixture is formed in the combustion chamber. In an internal combustion engine equipped with a fuel injection valve in the intake port, some of the injected fuel adheres to the inner wall surface of the intake port and the intake valve. This adhered fuel (hereinafter referred to as "adhered fuel") then evaporates as appropriate depending on the temperature and pressure conditions inside the intake port, and the evaporated fuel is mixed into the air-fuel mixture.

[0003] Therefore, if a fuel injection amount corresponding to the required torque is set, the presence of evaporated fuel may result in an excess of fuel in the combustion chamber.To address this problem, for example, Patent Document 1 discloses a technology for setting the fuel injection amount from the fuel injection valve by taking into account the amount of evaporated fuel calculated from the amount of adhering fuel. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-173183 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technology of Patent Document 1 poses a problem in how to calculate the amount of evaporated fuel. Conventionally, a method has been adopted in which the evaporation rate relative to the amount of adhering fuel is determined based on the engine coolant temperature, and the amount of evaporated fuel is calculated based on that evaporation rate. However, conventional methods have not been able to accurately calculate the amount of adhering fuel, resulting in a discrepancy between the amount of evaporated fuel calculated based on the amount of adhering fuel and the actual amount of evaporated fuel. Specifically, because the amount of adhering fuel can increase without limit, the amount of evaporated fuel calculated based on the amount of adhering fuel can also increase without limit. However, there is an upper limit to the actual amount of adhering fuel, and therefore there is also an upper limit to the amount of evaporated fuel. Therefore, there is a need to more accurately calculate the amount of evaporated fuel to achieve appropriate fuel injection.

[0006] Therefore, an object of the present invention is to realize appropriate fuel injection by more accurately determining the amount of evaporated fuel. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a control device for an internal combustion engine comprising: a combustion chamber; an intake passage communicating with the combustion chamber; a fuel injection device that injects fuel into the intake passage; an intake valve that opens and closes between the intake passage and the combustion chamber; a fuel adhesion amount acquisition means that acquires the amount of fuel adhesion to the intake passage and the intake valve; an evaporation amount acquisition means that acquires the amount of fuel evaporation from the amount of fuel adhesion; and a fuel injection amount acquisition means that acquires the amount of fuel injection based on the amount of evaporation, wherein an upper limit value is set for the amount of fuel adhesion, the fuel adhesion amount acquisition means calculates a calculated value of the amount of fuel adhesion based on the amount of fuel injection, and, if the calculated value of the amount of fuel adhesion exceeds the upper limit value, sets the amount of fuel adhesion to a value that does not exceed the upper limit value (Configuration 1).

[0008] In the configuration 1, when the calculated value of the amount of adhered fuel exceeds the upper limit, a configuration can be adopted in which the fuel injection mode is changed to reduce the amount of fuel injected toward the head portion of the intake valve (configuration 2).

[0009] In the configuration 1 or 2, the upper limit value may be set based on the amount of deposits adhering to the intake passage and the intake valve (configuration 3).

[0010] In the configuration 3, an exhaust sensor may be provided in an exhaust passage extending from the combustion chamber, and the deposit amount may be calculated based on an exhaust air-fuel ratio acquired by the exhaust sensor (configuration 4).

[0011] In any one of the configurations 1 to 4, a configuration can be adopted in which a temperature acquisition means is provided for acquiring information on the temperature of the intake valve, and the upper limit value is set based on the temperature of the intake valve (configuration 5).

[0012] Furthermore, in any one of configurations 1 to 5, a configuration can be adopted in which a fuel information acquisition means for acquiring information on the quality of the fuel is provided, and the upper limit value is set based on the quality of the fuel (configuration 6). [Effects of the Invention]

[0013] According to the present invention, the amount of evaporated fuel can be determined more accurately, and appropriate fuel injection can be achieved. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a configuration diagram showing a control device for an internal combustion engine according to an embodiment of the present invention; [Figure 2] 3 is a flowchart showing the control of the present invention. [Figure 3] FIG. 4 is a graph showing the control of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a schematic diagram showing the configuration of an engine (internal combustion engine) E and a control device for the engine E according to this embodiment.

[0016] The engine E in this embodiment is a four-stroke gasoline engine with a supercharger for an automobile. A piston 2 is housed in a cylinder 1 of the engine E. A combustion chamber 3 is formed by the inner surface of the cylinder 1, the upper surface of the piston 2, etc.

[0017] The engine E is equipped with an intake passage 4 that sends intake air into the combustion chamber 3 of each cylinder, which houses a piston 2, and an exhaust passage 5 that leads out from the combustion chamber 3. The intake passage 4 is composed of an intake port 4a formed integrally with the cylinder head and an intake manifold connected to the intake port 4a, and is also a passage that extends upstream from the intake manifold to an air cleaner. The exhaust passage 5 is composed of an exhaust port formed integrally with the cylinder head and an exhaust manifold connected to the exhaust port, and is also a passage that extends downstream from the exhaust manifold to an opening to the outside. The intake valve hole and exhaust valve hole, which are the openings of the intake port and exhaust port to the combustion chamber 3, are opened and closed by intake valves 6 and exhaust valves 7, respectively.

[0018] The intake passage 4 is provided with a throttle valve 8 that adjusts the flow area of ​​the intake passage 4 to control the flow rate of intake air. Also provided within the intake passage 4 are various sensors (not shown), such as an air flow sensor (intake pressure sensor) that detects the amount of air passing through. Also provided within the exhaust passage 5 are an exhaust purification device 14 that removes harmful components contained in the exhaust, an exhaust sensor 15 that detects the components contained in the exhaust, and the like.

[0019] The engine E also includes a fuel injection device 13 that injects fuel into the intake port or the combustion chamber 3. In this embodiment, the fuel injection device 13 includes both a port injection valve 13a that injects fuel into the intake passage 4 (intake port 4a) and a direct injection valve 13b that injects fuel into the combustion chamber 3. The combustion chamber 3 includes an ignition device (spark plug) 12 that generates an ignition spark to combust the air-fuel mixture.

[0020] 1 mainly shows components and means directly related to the present invention, and other components are omitted. Also, although the drawing shows only one cylinder, the number of cylinders of engine E is not limited. Also, while FIG. 1 shows an embodiment equipped with an exhaust gas recirculation device 10 and a turbocharger 11, these devices are not essential, and the exhaust gas recirculation device 10 and turbocharger 11 may not be installed depending on the specifications of engine E and the vehicle.

[0021] A vehicle equipped with this engine E is equipped with an electronic control unit 20. The electronic control unit 20 acquires information from various sensors in the intake passage 4 and the exhaust passage 5, as well as from a rotation sensor that detects the rotation speed of the crankshaft of the engine E, a water temperature sensor 16 that detects the temperature of the coolant that cools the cylinder block, etc., a vehicle speed sensor that detects the speed of the vehicle, and other sensors that acquire information necessary for controlling the engine E, and utilizes this information for controlling the engine E. In addition, information on the operation of the ignition, accelerator, brake, and other various devices performed by the driver is input to the electronic control unit 20.

[0022] The control means 21 provided in the electronic control unit 20 controls the opening of the throttle valve 8 and the fuel injection device 13 based on the required torque determined according to the opening of the accelerator device and other driving conditions, and the target air filling efficiency determined according to the required torque. The control means 21 also controls the intake valve 6, the exhaust valve 7, the ignition means 12, and other devices necessary for the operation of the engine E.

[0023] The fuel injected from the port injection valve 13a is directed toward the back surface of the umbrella portion 6a of the intake valve 6 (the surface opposite the side facing the combustion chamber 3) while the intake valve 6 is in a position close to the closed state, and when the intake valve 6 is in an open state, it is directed toward the wall surface of the combustion chamber 3 through the gap between the intake valve hole and the umbrella portion 6a.

[0024] The electronic control unit 20 includes a fuel injection amount obtaining means 22. The fuel injection amount obtaining means 22 calculates the fuel injection amount based on the required torque.

[0025] The electronic control unit 20 also includes a fuel adhesion amount acquisition means 23 that acquires the amount of fuel adhesion to the inner wall surface of the intake port and the intake valve 6, and an evaporation amount acquisition means 24 that acquires the amount of fuel evaporation from the amount of fuel adhesion. When calculating the fuel injection amount, the fuel injection amount acquisition means 22 reflects the amount of evaporated fuel (hereinafter referred to as the evaporation amount) acquired by the evaporation amount acquisition means 24 in the fuel injection amount. Specifically, fuel is injected by subtracting the evaporation amount from the required amount of fuel injection calculated based on the required torque.

[0026] The fuel adhesion amount acquisition means 23 calculates a calculated fuel adhesion amount based on the fuel injection amount from the port injection valve 13a, etc. Specifically, the calculation is performed by multiplying the fuel injection amount from the port injection valve 13a by the fuel adhesion ratios set for the inner wall surface of the intake port 4a and the surface of the intake valve 6. The calculated fuel adhesion amount is calculated by subtracting the evaporation amount from the value calculated during the previous fuel injection, and then adding the currently calculated value to the result. The calculated fuel adhesion amount is calculated separately for each region of the inner wall surface of the intake port 4a and the surface of the intake valve 6. This calculation is more accurate when it is performed based on the fuel injection amount, the amount of deposits adhering to each region, the temperature of the inner wall surface of the intake port 4a, the temperature of the intake valve 6, the intake air amount (intake pressure), the engine speed, the charging efficiency, etc. This calculation may be performed using a map, for example. The reason for taking the amount of deposits into consideration here is that the larger the amount of deposits, the more likely it is that fuel injected from the port injection valve 13a will adhere to the deposits, making it more likely for the fuel to adhere to the inner wall surface of the intake port 4a and the intake valve 6. The reason for taking the temperature conditions of the components to which the fuel adheres into consideration is that the lower the temperature of the component to which the fuel adheres, the greater the viscosity of the fuel, which tends to increase the amount of fuel that adheres. Furthermore, the smaller the intake air volume, the more difficult it is for the fuel to be blown away by the intake air, which tends to increase the amount of fuel that adheres. Deposits are primarily products of incomplete combustion of fuel and engine oil.

[0027] The electronic control unit 20 is equipped with a temperature acquisition means 25 that acquires information on the temperature of the inner wall surface of the intake port 4a and the intake valve 6. The temperature acquisition means 25 estimates the temperature of the intake valve 6 based on the fuel injection amount, engine load, etc. The temperature of the inner wall surface of the intake port 4a is estimated based on the temperature of the coolant of the engine E. Note that a temperature sensor may be provided in the intake valve 6 to acquire the temperature, or a temperature sensor may be provided on the inner wall surface of the intake port 4a to acquire the temperature.

[0028] The deposit amount can be obtained from information obtained from the exhaust sensor 15. In this embodiment, an A / F sensor (LAFS sensor) 15 is used as the exhaust sensor 15. The LAFS sensor 15 detects the combustion air-fuel ratio (exhaust A / F) of the engine E from the oxygen concentration and unburned gas concentration in the exhaust gas. The larger the deposit amount, the more delayed the behavior of the exhaust A / F change. Therefore, by preparing a map showing the relationship between the amount of delay in this behavior and the deposit amount, the deposit amount can be obtained based on the amount of delay in the behavior. In this method, using the existing exhaust sensor 15 eliminates the need to install a new sensor to obtain the deposit amount, but the deposit amount may also be obtained using a separate sensor. The amount of deposits adhering to the inner wall surface of the intake port 4a and the amount of deposits adhering to the intake valve 6 are each obtained separately.

[0029] The amount of evaporated fuel is calculated by multiplying the calculated amount of adhered fuel by the evaporation rate. The evaporation rate is defined as the ratio of the amount of evaporated fuel to the amount of adhered fuel (fuel in a liquid state). For example, if all of the adhered fuel evaporates, the evaporation rate is 1, and if half of it evaporates, the evaporation rate is 0.5. The evaporation rate increases as the temperature increases. The amount of evaporated fuel from the inner wall surface of the intake port 4a is calculated by multiplying the amount of adhered fuel on the inner wall surface of the intake port 4a by the evaporation rate corresponding to the temperature of the inner wall surface of the intake port 4a. The amount of evaporated fuel from the surface of the intake valve 6 is calculated by multiplying the amount of adhered fuel on the surface of the intake valve 6 by the evaporation rate corresponding to the surface temperature of the intake valve 6. Conventionally, the evaporation rate from the intake valve 6 is calculated using the coolant temperature and the number of combustions. However, in this embodiment, the evaporation rate from the intake valve 6 is calculated using the intake air volume and the temperature of the intake valve 6. The larger the intake air volume, the more intake air comes into contact with the adhered fuel, making it more likely to evaporate.

[0030] However, the fuel adhesion amount acquisition means 23 sets an upper limit value when calculating the amount of adhered fuel. That is, if the calculated value of the amount of adhered fuel exceeds the upper limit value, a value not exceeding the upper limit value is determined as the amount of adhered fuel. In this embodiment, if the calculated value of the amount of adhered fuel exceeds the upper limit value, the upper limit value is determined as the amount of adhered fuel. Conventionally, the concept of an upper limit value for the amount of adhered fuel has not been set, but in this invention, an upper limit value is set for the amount of adhered fuel so that an amount of adhered fuel exceeding this limit is not set.

[0031] The upper limit of the amount of fuel adhesion is also calculated separately for each region of the inner wall surface of the intake port 4a and the surface of the intake valve 6. The upper limit for the intake valve 6 is set based on the temperature of the intake valve 6. This is because when the temperature of the intake valve 6 is high, the viscosity of the adhering fuel decreases, making it difficult for the fuel to adhere. The upper limit for the inner wall surface of the intake port 4a is also set based on the temperature of the inner wall surface of the intake port 4a.

[0032] In this embodiment, the upper limit value is calculated based on the temperature of the inner wall surface of the intake port 4a or the intake valve 6, the deposit amount in each region on the inner wall surface of the intake port 4a or the surface of the intake valve 6, and the intake air volume. This calculation can be performed, for example, by using a map that shows the relationship between the temperature of the inner wall surface of the intake port 4a or the intake valve 6, the deposit amount in each region, and the intake air volume. The larger the deposit amount, the more fuel that can adhere to the deposit, and therefore the higher the upper limit value. Furthermore, the smaller the intake air volume, the more difficult it is for the adhered fuel to be blown away, and therefore the higher the upper limit value.

[0033] When the amount of fuel adhesion reaches the upper limit, the adhered fuel turns into droplets and falls into the cylinder, causing the air-fuel ratio to become rich. This results in a deterioration of exhaust gas (EOE / Engine Out Emissions). However, this invention can detect whether the amount of fuel adhesion exceeds the upper limit, so various avoidance controls can be implemented to prevent the deterioration of exhaust gas.

[0034] One example of such avoidance control is to change the fuel injection mode when the amount of fuel adhesion (calculated value of the amount of fuel adhesion) exceeds an upper limit. Specifically, the fuel injection mode is changed to change part of the fuel injection amount from the port injection valve 13a to in-cylinder injection from the direct injection valve 13b, or the fuel injection amount while the intake valve 6 is closed is reduced and the fuel injection amount while the intake valve 6 is open (the fuel injection amount related to intake stroke injection) is increased. By doing so, the amount of fuel injected while the intake valve 6 is closed is reduced, that is, the amount of fuel injected toward the intake valve head 6a is reduced. This prevents fuel adhering to the intake valve 6 from turning into droplets and falling into the cylinder.

[0035] The electronic control unit 20 also includes a fuel information acquisition means 26 that acquires information about the quality of the fuel. The upper limit of the amount of fuel adhesion may be set based on the quality of the fuel. Specifically, the upper limit of the amount of fuel adhesion is determined taking into consideration the quality of the fuel in addition to the amount of deposits and the temperature of the components to which the fuel is attached.

[0036] Low-quality fuel, such as fuel with a low octane rating or fuel that has deteriorated over time or due to storage conditions, tends to become more viscous (sticky) than high-quality fuel due to the loss of volatile components. As a result, the amount of fuel adhering to the fuel tends to be greater. Therefore, taking octane rating information into account when calculating the upper limit for fuel adhering can improve accuracy. In other words, adding a new map showing the relationship between octane rating and the upper limit is recommended. Since octane rating is correlated with the knock learning value, the octane rating of a fuel can be obtained by obtaining the knock learning value. The knock learning value is the amount of retardation (delay) when the ignition timing is retarded to prevent knocking. The closer the knock learning value is to 1, the smaller the retard amount; the closer the knock learning value is to 0, the larger the retard amount. The larger the knock learning value or the smaller the retard amount, the higher the octane rating (see Figure 3).

[0037] The octane number information is also used to obtain the temperature of the part of the member to which the fuel adheres, because the latent heat of vaporization when the fuel evaporates varies depending on the octane number.

[0038] An example of control using the control device for the engine E will be described with reference to the flowchart of FIG.

[0039] Control is started in step S1, and the fuel injection amount corresponding to the required torque is obtained in step S2. Subsequently, the octane number of the fuel is obtained in step S3, and the temperatures of the parts to which the fuel adheres (the temperatures of the inner wall surface of the intake port 4a and the intake valve 6) are obtained in step S4.

[0040] In step S5, the deposit amount is acquired, in step S6, the amount of adhered fuel is acquired, and in step S7, the upper limit of the amount of adhered fuel is acquired.

[0041] In step S8, it is determined whether the amount of adhered fuel (calculated value of adhered fuel amount) exceeds an upper limit. If the amount of adhered fuel exceeds the upper limit, the process proceeds to step S9, where the upper limit is set as the amount of adhered fuel and stored. Thereafter, the process proceeds to step S10. If the amount of adhered fuel does not exceed the upper limit in step S8, the process proceeds to step S12, where the amount of adhered fuel is stored as is, and the process proceeds to step S13.

[0042] In step S10, the amount of fuel exceeding the upper limit of the amount of adhered fuel is stored, and in step S11, the fuel injection mode is changed, thereby preventing the adhered fuel from turning into droplets and falling into the cylinder.

[0043] In step S13, the amount of fuel evaporation is obtained based on the stored amount of fuel adhesion. Based on this, the amount of fuel injection is corrected in step S14, and the control ends in step S15. Thereafter, the same control is repeated.

[0044] By providing the above control device, the amount of fuel adhering to the intake port 4a and the intake valve 6 and the amount of fuel evaporating from the intake port 4a and the intake valve 6 can be determined more accurately, thereby realizing appropriate fuel injection.

[0045] In the above embodiment, the present invention has been described using an example of a configuration in which the fuel injection device 13 includes both a port injection valve 13a that injects fuel into the intake port 4a and a direct injection valve 13b that injects fuel into the combustion chamber 3. However, the present invention can also be applied to an engine E that includes only a port injection valve 13a as the fuel injection device 13.

[0046] In the above embodiments, a vehicle equipped with only the engine E as a driving source for traveling is assumed, but this may also be a hybrid vehicle equipped with both the engine E and a motor as a driving source for traveling. Furthermore, as the hybrid vehicle, in particular, a plug-in hybrid car may be adopted in which the battery 50 can be directly charged (external charging) using an attachment plug from a household outlet or the like, or the battery 50 can directly supply power to household electrical appliances or the like (external power supply) using an attachment plug.

[0047] In this embodiment, the upper limit of the amount of adhered fuel is described as the maximum amount of adhered fuel, but the upper limit is not limited to this value and may be set to, for example, a value obtained by subtracting a predetermined amount from the maximum amount of adhered fuel. Using such a value makes it easier to take action before the adhered fuel turns into droplets and falls into the cylinder, but the accuracy of calculating the evaporation amount is slightly lower than when the upper limit is set to the maximum amount of adhered fuel. [Explanation of symbols]

[0048] 3 Combustion chamber 4 Intake passage 4a intake port 5 Exhaust passage 6 intake valve 13 Fuel injection device 15 Exhaust sensor 16 Water temperature sensor 20 Electronic Control Unit 21 Control Means 22 Fuel injection amount acquisition means 23 Fuel adhesion amount acquisition means 24 Evaporation amount acquisition method 25 Temperature acquisition means 26 Fuel information acquisition means E. Internal combustion engine (engine)

Claims

1. a control device for an internal combustion engine comprising: a combustion chamber; an intake passage leading to the combustion chamber; a fuel injection device that injects fuel into the intake passage; an intake valve that opens and closes between the intake passage and the combustion chamber; a fuel adhesion amount acquisition means that acquires the amount of fuel adhesion to the intake passage and the intake valve; an evaporation amount acquisition means that acquires the amount of fuel evaporation from the amount of fuel adhesion; and a fuel injection amount acquisition means that acquires the amount of fuel injection based on the amount of evaporation, wherein an upper limit value is set for the amount of fuel adhesion, and the fuel adhesion amount acquisition means calculates a calculated value of the amount of fuel adhesion based on the amount of fuel injection, and when the calculated value of the amount of fuel adhesion exceeds the upper limit value, the fuel adhesion amount is set to a value that does not exceed the upper limit value.

2. 2. The control device for an internal combustion engine according to claim 1, wherein when the calculated value of the amount of adhered fuel exceeds the upper limit, the fuel injection mode is changed to reduce the amount of fuel injected toward the head portion of the intake valve.

3. 2. The control device for an internal combustion engine according to claim 1, wherein the upper limit value is set based on the amount of deposits adhering to the intake valve.

4. 4. The control device for an internal combustion engine according to claim 3, further comprising an exhaust sensor in an exhaust passage extending from the combustion chamber, and the deposit amount is calculated based on an exhaust air-fuel ratio obtained by the exhaust sensor.

5. temperature acquisition means for acquiring information on the temperature of the intake valve; 2. The control device for an internal combustion engine according to claim 1, wherein the upper limit value is set based on the temperature of the intake valve.

6. 2. The control device for an internal combustion engine according to claim 1, further comprising a fuel information acquisition means for acquiring information on the quality of the fuel, and the upper limit value is set based on the quality of the fuel.

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