Internal combustion engine system

Abstract

The present invention relates to an internal combustion engine system, comprising: an internal combustion engine having a cylinder, an intake valve and an exhaust valve, an in-cylinder injection valve, and a variable valve drive mechanism; and a control device that controls the in-cylinder injection valve and the variable valve drive mechanism, the control device including: a calculation unit that calculates a first crank angle range in which the temperature in the cylinder during the compression stroke is equal to or higher than the boiling point of the fuel and a second crank angle range in which the temperature in the cylinder during the closing period is equal to or higher than the boiling point of the fuel before the preheating of the internal combustion engine is completed; and an injection control unit that performs fuel injection by the in-cylinder injection valve in the first crank angle range and the second crank angle range.

Description

Technical Field

[0001] The present invention relates to an internal combustion engine system. Background Art

[0002] Internal combustion engines that can use fuels containing ethanol are known. Before the preheating of such an internal combustion engine is completed, the temperature in the cylinder is low, and it is possible that the vaporization property of the fuel injected into the cylinder decreases and combustion becomes unstable. Therefore, in order to promote the vaporization of the fuel injected into the cylinder, in-cylinder injection is performed in the latter half of the compression stroke in which the gas in the cylinder is adiabatically compressed and the in-cylinder temperature rises (for example, refer to Japanese Patent Laid-Open No. 2013-224623). Summary of the Invention

[0003] According to the required in-cylinder injection amount, in-cylinder injection needs to be performed in other strokes in addition to the latter half of the compression stroke described above. In this case, it is possible that the fuel injected into the cylinder cannot be sufficiently vaporized in other strokes and combustion becomes unstable.

[0004] Then, an object of the present invention is to provide an internal combustion engine system with stable combustion.

[0005] The above object can be achieved by the following internal combustion engine system. The internal combustion engine system includes: an internal combustion engine having a cylinder, an intake valve and an exhaust valve that open and close the cylinder, an in-cylinder injection valve that directly injects a fuel containing ethanol into the cylinder, and a variable valve drive mechanism that forms a closing period from the closing of the exhaust valve to the opening of the intake valve; and a control device that controls the in-cylinder injection valve and the variable valve drive mechanism. The control device includes: a calculation unit that calculates a first crank angle range in which the temperature in the cylinder is equal to or higher than the boiling point of the fuel in the compression stroke and a second crank angle range in which the temperature in the cylinder is equal to or higher than the boiling point of the fuel during the closing period before the preheating of the internal combustion engine is completed; and an injection control unit that performs fuel injection by the in-cylinder injection valve in the first crank angle range and the second crank angle range.

[0006] It may be that the control device includes a first determination unit that determines whether the in-cylinder injection valve can inject the required in-cylinder injection amount within the first crank angle range. The injection control unit, in the case of a positive determination by the first determination unit, performs fuel injection by the in-cylinder injection valve within the first crank angle range, and in the case of a negative determination by the first determination unit, performs fuel injection by the in-cylinder injection valve within the first crank angle range and the second crank angle range.

[0007] It is possible that the control device includes a second determination unit that determines whether the in-cylinder injection valve can inject the required in-cylinder injection amount in the first crank angle range and the second crank angle range, and an injection control unit that, when a negative determination is made by the first determination unit and a positive determination is made by the second determination unit, performs fuel injection by the in-cylinder injection valve in the first crank angle range and the second crank angle range, and when negative determinations are made by the first determination unit and the second determination unit, performs fuel injection by the in-cylinder injection valve in the first crank angle range, the second crank angle range, and the intake stroke.

[0008] It is possible that the control device includes an ethanol concentration acquisition unit that acquires the ethanol concentration in the fuel, and the higher the ethanol concentration, the more the calculation unit calculates the start crank angle of the first crank angle range to the delayed side.

[0009] It is possible that the higher the ethanol concentration, the more the calculation unit calculates the start crank angle of the second crank angle range to the delayed side.

[0010] It is possible that the control device includes a temperature acquisition unit that acquires the temperature of the internal combustion engine, and the lower the temperature, the shorter the calculation unit calculates the first crank angle range.

[0011] It is possible that the lower the temperature, the shorter the calculation unit calculates the second crank angle range.

[0012] It is possible that the control device includes a rotational speed acquisition unit that acquires the rotational speed of the internal combustion engine, and the lower the rotational speed, the shorter the calculation unit calculates the first crank angle range.

[0013] It is possible that the lower the rotational speed, the shorter the calculation unit calculates the second crank angle range.

[0014] It is possible that the closing period includes the intake top dead center.

[0015] It is possible that the calculation unit sets the end timing of the first crank angle range to the advanced side relative to the compression top dead center.

[0016] It is possible that the calculation unit sets the end timing of the second crank angle range to the advanced side relative to the intake top dead center.

[0017] According to the present invention, an internal combustion engine system with stable combustion can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The features, advantages, and technical and industrial significance of typical embodiments of the present invention will be described below with reference to the accompanying drawings, in which the same reference numerals denote the same elements, and in which:

[0019] Figure 1 is a schematic configuration diagram of an internal combustion engine system.

[0020] Figure 2 is an example of a timing chart of fuel injection control.

[0021] Figure 3 is an example of a timing chart of fuel injection control.

[0022] Figure 4 is an example of a timing chart of fuel injection control.

[0023] Figure 5 is an example of a flowchart showing fuel injection control executed by an ECU.

[0024] Figure 6 is an example of a map for determining the presence or absence of a compression stroke injection requirement based on ethanol concentration and coolant temperature.

[0025] Figure 7A is an example of a map for determining the start crank angle S1 set according to ethanol concentration, coolant temperature, and engine speed.

[0026] Figure 7B is an example of a map for determining the start crank angle S1 set according to ethanol concentration, coolant temperature, and engine speed.

[0027] Figure 8A is an explanatory diagram of the change in the start crank angle S1 in the case of a high ethanol concentration.

[0028] Figure 8B is an explanatory diagram of the change in the start crank angle S1 in the case of a low coolant temperature.

[0029] Figure 9A is an example of a map for determining the start crank angle S2 set according to ethanol concentration, coolant temperature, and engine speed.

[0030] Figure 9B is an example of a map for determining the start crank angle S2 set according to ethanol concentration, coolant temperature, and engine speed.

[0031] Figure 10A is an explanatory diagram of the change in the start crank angle S2 in the case of a high ethanol concentration.

[0032] Figure 10B is an explanatory diagram of the change in the start crank angle S2 in the case of a low coolant temperature. Detailed implementation mode

[0033] [Schematic configuration of internal combustion engine system]

[0034] Figure 1 It is a schematic configuration diagram of the internal combustion engine system 1. The internal combustion engine system 1 includes an engine 10 and an ECU (Electronic Control Unit) 30. The engine 10 is an internal combustion engine that can use a fuel mixture of ethanol fuel and gasoline fuel. The engine 10 is mounted on, for example, an engine vehicle, but is not limited thereto, and may also be mounted on a hybrid vehicle. In each cylinder 12 of the engine 10, a piston 13 is provided. The piston 13 is connected to a crankshaft 15, which is an output shaft of the engine 10, via a connecting rod 14. The reciprocating motion of the piston 13 is converted into the rotational motion of the crankshaft 15 by the connecting rod 14.

[0035] In each cylinder 12, a combustion chamber 16 is formed above the piston 13, and a spark plug 18 for igniting a mixture of fuel and air is installed in the combustion chamber 16. The ignition timing of the mixture ignited by the spark plug 18 is adjusted by an igniter 19 provided above the spark plug 18.

[0036] An intake valve 24 and an exhaust valve 25 for opening and closing the cylinder 12 are provided in the cylinder 12. By opening the intake valve 24, the combustion chamber 16 communicates with the intake passage 20, and by closing the intake valve 24, the communication between the combustion chamber 16 and the intake passage 20 is cut off. By opening the exhaust valve 25, the combustion chamber 16 communicates with the exhaust passage 21, and by closing the exhaust valve 25, the communication between the combustion chamber 16 and the exhaust passage 21 is cut off.

[0037] An intake-side variable valve drive mechanism (hereinafter referred to as intake VVT) 26 for changing the opening and closing timing of the intake valve 24 is provided on the intake valve 24. Similarly, an exhaust-side variable valve drive mechanism (hereinafter referred to as exhaust VVT) 27 for changing the opening and closing timing of the exhaust valve 25 is provided on the exhaust valve 25. The intake VVT 26 changes the opening and closing timing of the intake valve 24 to the advance side or the retard side by changing the phase of the intake-side drive cam that opens and closes the intake valve 24 provided on the intake-side camshaft relative to the intake-side camshaft. Similarly, the exhaust VVT 27 changes the opening and closing timing of the exhaust valve 25 to the advance side or the retard side by changing the phase of the exhaust-side drive cam that opens and closes the exhaust valve 25 provided on the exhaust-side camshaft relative to the exhaust-side camshaft. The phase of the drive cam relative to the camshaft is switched according to the hydraulic pressure adjusted by the oil control valve. In addition, an electric variable valve drive mechanism may be used instead of the hydraulic intake VVT 26 and exhaust VVT 27.

[0038] In the intake passage 20, a throttle valve 23 is provided for adjusting the amount of air introduced into the opposed combustion chamber 16. In the exhaust passage 21, a catalyst 50 is provided which exhibits maximum purification ability when the air-fuel ratio of the air-fuel mixture becomes the stoichiometric air-fuel ratio. The catalyst 50 is a three-way catalyst having an oxygen storage capacity of storing oxygen in the exhaust gas leaner than the stoichiometric air-fuel ratio and releasing the oxygen stored in the exhaust gas richer than the stoichiometric air-fuel ratio.

[0039] In each intake port 20a forming a part of the intake passage 20, an intake port injection valve 22 for injecting fuel into the intake port 20a is provided for each cylinder 12. In the engine 10, an in-cylinder injection valve 17 for directly injecting fuel into each combustion chamber 16 is provided.

[0040] The ECU 30 is an electronic control unit that performs control processing related to the engine 10. The ECU 30 is configured around a computer including volatile or non-volatile memories such as a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory). The ECU 30 realizes various control processes related to the engine 10 by executing a program installed in the memory on the CPU. As will be described later in detail, various sensors are connected to the ECU 30. The ECU 30 is an example of a control device and functionally realizes a calculation unit, a first determination unit, a second determination unit, a valve drive control unit, an injection control unit, an ethanol concentration acquisition unit, a temperature acquisition unit, and a rotational speed acquisition unit, which will be described later in detail.

[0041] An ignition switch 31, an accelerator opening sensor 32, an air flow meter 33, a crank angle sensor 34, a fuel pressure sensor 35, a water temperature sensor 36, and an ethanol concentration sensor 37 are connected to the ECU 30, and output signals from the various sensors are input thereto. The ignition switch 31 detects the on / off state of ignition. The accelerator opening sensor 32 detects the accelerator opening. The air flow meter 33 detects the intake air amount. The crank angle sensor 34 detects the rotational angle of the crankshaft 15. The fuel pressure sensor 35 detects the pressure of the fuel in the high-pressure delivery pipe that accumulates the fuel supplied to the in-cylinder injection valve 17. The water temperature sensor 36 detects the temperature of the cooling water that cools the engine 10. The ethanol concentration sensor 37 is provided, for example, in the fuel tank or the fuel delivery path and detects the ethanol concentration in the fuel.

[0042] The ECU 30 calculates the engine speed based on the detected value of the crankshaft angle sensor 34, and calculates the engine load based on the engine speed and the intake air amount. The ECU 30 calculates the target speed and the target load based on the accelerator opening degree, and controls the fuel injection amount, the intake air amount, and the ignition timing so that the engine speed and the load become the target speed and the target load, respectively. In addition, the ECU 30 controls the in-cylinder injection rate, which is the ratio of the injection amount from the in-cylinder injection valve 17 to the total fuel injection amount, and the port injection rate, which is the ratio of the injection amount from the port injection valve 22 to the total fuel injection amount, according to the driving state of the engine 10. In addition, the ECU 30 controls the intake VVT 26 and the exhaust VVT 27 according to the driving state of the engine 10, thereby controlling the opening and closing timing of the intake valve 24 and the exhaust valve 25.

[0043] As described above, the engine 10 uses a fuel containing ethanol. Regarding such a fuel, the higher the ethanol concentration, the higher its boiling point and the more difficult it is to vaporize. In particular, before the engine 10 is fully preheated, the temperature in the cylinder 12 (hereinafter referred to as the in-cylinder temperature) is also low. Therefore, the vaporization of the fuel injected from the in-cylinder injection valve 17 may be impaired and the combustion may be unstable. Therefore, in the ECU 30 of the present embodiment, when a predetermined condition is satisfied before the engine 10 is fully preheated, the following fuel injection control is executed.

[0044] [Fuel Injection Control]

[0045] Figures 2 - 4 is an example of a time chart of the fuel injection control. In Figures 2 - 4 the state of the in-cylinder injection, the fuel boiling point [°C], the in-cylinder temperature [°C], and the lift amounts [mm] of the intake valve 24 and the exhaust valve 25 are shown. Figures 2 - 4 The horizontal axis of Figures 2 - 4 represents the crankshaft angle [°CA]. In

[0046] First, Figure 2 will be described. In Figure 2 the opening timing of the intake valve 24 is set on the advance side with respect to the intake top dead center, and the closing timing of the exhaust valve 25 is set on the retard side with respect to the intake top dead center. That is, an overlap period during which both the intake valve 24 and the exhaust valve 25 are in the open state is ensured.

[0047] As Figure 2As shown, the in-cylinder temperature is lower than the fuel boiling point during the intake stroke and the first half of the compression stroke, and rises above the fuel boiling point during the second half of the compression stroke. This is because, during the intake stroke, the intake valve 24 is open and the piston 13 descends, so fresh air is introduced into the cylinder 12 while the volume of the combustion chamber 16 increases. Additionally, this is because, during the first half of the compression stroke, the volume of the combustion chamber 16 is relatively large, and during the second half of the compression stroke, the volume of the combustion chamber 16 decreases, and the gas in the cylinder 12 is adiabatically compressed as the piston 13 rises. In Figure 2 's example, during the second half of the compression stroke, the in-cylinder temperature becomes above the fuel boiling point up to the first crank angle interval C1 until the compression top dead center, and in-cylinder injection is performed. Thus, fuel vaporization can be promoted in the first crank angle interval C1. In addition, in Figures 2 - 4 , the start crank angle S1 and the end crank angle E1 of the in-cylinder injection during the second half of the compression stroke are shown.

[0048] In Figure 3 , the opening timing of the intake valve 24 is set to the retarded side relative to the intake top dead center, and the closing timing of the exhaust valve 25 is set to the advanced side relative to the intake top dead center. That is, a closing period during which both the intake valve 24 and the exhaust valve 25 are in the closed state is ensured. During the closing period, the in-cylinder temperature rises above the fuel boiling point. This is because the gas in the sealed cylinder 12 is adiabatically compressed as the piston 13 rises. In Figure 3 's example, similar to the Figure 2 's example, in-cylinder injection is performed in the first crank angle interval C1, and in-cylinder injection is also performed in the second crank angle interval C2 during the closing period when the in-cylinder temperature becomes above the fuel boiling point. Thus, fuel vaporization can be promoted in the second crank angle interval C2. In addition, in Figure 3 , the start crank angle S2 and the end crank angle E2 of the in-cylinder injection during the closing period are shown. Regarding Figure 3 , details will be described later, but it shows the in-cylinder injection timing in the case where the required in-cylinder injection amount is larger than that in the Figure 2 's example.

[0049] In Figure 4 , similar to Figure 3 , the closing period is ensured. In Figure 4 , similar to the Figure 3 's example, in-cylinder injection is performed in the first crank angle interval C1 and the second crank angle interval C2, and in-cylinder injection is also performed in the third crank angle interval C3 during the intake stroke. Since fresh air is being introduced into the cylinder 12 during the intake stroke when the intake valve 24 is open, the fuel is agitated by the fresh air introduced into the cylinder 12, and fuel adhesion to the wall surface in the combustion chamber 16 can be suppressed, promoting fuel vaporization. In addition, in Figure 4 , the start crank angle S3 and the end crank angle E3 of the in-cylinder injection during the intake stroke are shown. RegardingFigure 4 , which will be described later, shows the in-cylinder injection timing when the required in-cylinder injection amount ratio Figure 3 is larger than that in the example shown.

[0050] Figure 5 is an example of a flowchart showing the fuel injection control executed by the ECU 30. This control is repeatedly executed in the ignition-on state. First, the ECU 30 acquires the required in-cylinder injection amount, the ethanol concentration in the fuel, the temperature of the cooling water, and the engine speed (step S1). The required in-cylinder injection amount is calculated by multiplying the required total fuel injection amount by the in-cylinder injection rate. The ethanol concentration in the fuel is detected by the ethanol concentration sensor 37. The temperature of the cooling water is detected by the water temperature sensor 36. The engine speed is detected by the crank angle sensor 34. Step S1 is an example of the processing executed by the ethanol concentration acquisition unit, the temperature acquisition unit, and the speed acquisition unit.

[0051] Next, the ECU 30 determines, for example, whether the preheating of the engine 10 is before completion based on the temperature of the cooling water (step S2). If it is "No" in step S2, the ECU 30 performs fuel injection at a predetermined timing after the preheating is completed (step S3).

[0052] If it is "Yes" in step S2, the ECU 30 determines whether there is an in-cylinder injection request (step S4). Specifically, the ECU 30 determines that there is an in-cylinder injection request when the in-cylinder injection rate is other than 0%. If it is "No" in step S4, the ECU 30 performs fuel injection by the intake port injection valve 22 at a predetermined timing before the preheating is completed (step S3).

[0053] If it is "Yes" in step S4, the ECU 30 determines whether there is a compression stroke injection request (step S5). Specifically, the ECU 30 refers to the Figure 6 map to determine whether there is a compression stroke injection request. Figure 6This is an example of a map that determines the requirement for injection during the compression stroke based on the ethanol concentration and the cooling water temperature. The vertical axis represents the ethanol concentration [%], and the horizontal axis represents the cooling water temperature [°C]. When the cooling water temperature is low and the ethanol concentration is high, it is difficult for the fuel to vaporize, so injection during the compression stroke is required. When the cooling water temperature is high and the ethanol concentration is low, the fuel easily vaporizes, so injection during the compression stroke is not required. Additionally, when the ethanol concentration is constant, injection during the compression stroke is required when the cooling water temperature is low, and not required when the cooling water temperature is high. This is because when the cooling water temperature is low even with a constant ethanol concentration, it is difficult for the fuel to vaporize. Also, when the cooling water temperature is constant, injection during the compression stroke is required when the ethanol concentration is high, and not required when the ethanol concentration is low. This is because when the ethanol concentration is high even with a constant cooling water temperature, it is difficult for the fuel to vaporize. When the determination in step S5 is "No", step S3 is executed.

[0054] When the determination in step S5 is "Yes", the ECU 30 calculates the first crank angle interval C1 (step S6). The first crank angle interval C1 is the difference between the end crank angle E1 and the start crank angle S1. Here, the end crank angle E1 is a fixed value set on the advance side relative to the compression top dead center. Thereby, the amount of fuel adhering to the top surface of the piston 13 can be suppressed, ensuring a fuel amount contributing to combustion and stabilizing the combustion. The start crank angle S1 is a variable value set based on the ethanol concentration, the cooling water temperature, and the engine speed. Step S6 is an example of the processing executed by the calculation unit. Specifically, the ECU 30 refers to Figure 7A and Figure 7B to set the start crank angle S1 according to the map.

[0055] Figure 7A and Figure 7B are examples of maps that define the start crank angle S1 set according to the ethanol concentration, the cooling water temperature, and the engine speed. The vertical axis represents the ethanol concentration [%], and the horizontal axis represents the start crank angle S1 [°CA]. Figure 7A shows the cases of high and low cooling water temperatures, Figure 7B and Figure 7A shows the cases of high and low engine speeds. As shown in Figure 7B , the higher the ethanol concentration, the lower the cooling water temperature, and the lower the engine speed, the more the start crank angle S1 is set on the retard side.

[0056] Figure 8A is an explanatory diagram of the change in the start crank angle S1 in the case of a high ethanol concentration. The higher the ethanol concentration in the fuel, the higher the fuel boiling point. Therefore, as shown in Figure 8A , the timing at which the in-cylinder temperature exceeds the fuel boiling point shifts to the retard side. Additionally, Figure 8BIt is an explanatory diagram of the change in the starting crank angle S1 when the temperature of the cooling water is low. The lower the temperature of the cooling water, the lower the in-cylinder temperature. Therefore, as Figure 8B shown, the timing at which the in-cylinder temperature exceeds the fuel boiling point shifts toward the retard side. In addition, when the engine speed is low, the intake air amount introduced into the cylinder 12 also decreases, so the lower the engine speed, the lower the in-cylinder temperature. Also in this case, as Figure 8B shown, the timing at which the in-cylinder temperature exceeds the fuel boiling point shifts toward the retard side. From the above, the higher the ethanol concentration, the lower the cooling water temperature, and the lower the engine speed, the more the starting crank angle S1 is calculated toward the retard side. In addition, regarding the case where in-cylinder injection is performed only in the first crank angle range C1, the lower the ethanol concentration, the less the required in-cylinder injection amount. Therefore, it is not always the case that the higher the ethanol concentration, the shorter the first crank angle range C1 is calculated, but the lower the cooling water temperature and the lower the engine speed, the shorter the first crank angle range C1 is calculated.

[0057] In Figure 7A and Figure 7B 's map, the starting crank angle S1 changes curvilinearly with respect to the ethanol concentration, but it is not limited to this, and it may also change linearly or stepwise. In addition, in the above-described method for setting the starting crank angle S1, it is not limited to the above-described map, and the starting crank angle S1 may also be set based on an arithmetic expression that takes the ethanol concentration, the cooling water temperature, and the engine speed as independent variables.

[0058] Next, the ECU 30 determines whether the required in-cylinder injection range is smaller than the first crank angle range C1 (step S7). The required in-cylinder injection range is calculated based on the required in-cylinder injection amount and the fuel pressure detected by the fuel pressure sensor 35. The more the required in-cylinder injection amount and the lower the fuel pressure, the longer the required in-cylinder injection range. Step S7 is an example of the process performed by the first determination unit. When the result in step S7 is "Yes", the ECU 30 performs in-cylinder injection within the first crank angle range C1 (step S8). Step S8 is an example of the process performed by the injection control unit.

[0059] When the result in step S7 is "No", the ECU 30 controls the intake VVT 26 and the exhaust VVT 27 to advance the closing timing of the exhaust valve 25 and retard the opening timing of the intake valve 24 to form a predetermined closing period (step S9).

[0060] Next, the ECU 30 calculates the second crankshaft angle interval C2 (step S10). The second crankshaft angle interval C2 is the difference between the end crankshaft angle E2 and the start crankshaft angle S2. Here, the end crankshaft angle E2 is a fixed value set on the advance side relative to the intake top dead center. Thereby, it is possible to suppress the amount of fuel adhering to the top surface of the piston 13, ensure the amount of fuel contributing to combustion, and stabilize combustion. The start crankshaft angle S2, like the start crankshaft angle S1, is a variable value set based on the ethanol concentration, the coolant temperature, and the engine speed. Step S10 is an example of the processing performed by the calculation unit. Specifically, the ECU 30 refers to Figure 9A and Figure 9B to set the start crankshaft angle S2 by mapping.

[0061] Figure 9A and Figure 9B is an example of a map defining the start crankshaft angle S2 set according to the ethanol concentration, the coolant temperature, and the engine speed. The vertical axis represents the ethanol concentration [%], and the horizontal axis represents the start crankshaft angle S2 [°CA]. Figure 9A shows the case where the coolant temperature is high and the case where it is low, Figure 9B shows the case where the engine speed is high and the case where it is low. As shown in Figure 9A and Figure 9B the higher the ethanol concentration, the lower the coolant temperature, and the lower the engine speed, the more delayed the start crankshaft angle S2 is set.

[0062] Figure 10A is an explanatory diagram of the change in the start crankshaft angle S2 in the case of a high ethanol concentration. The higher the ethanol concentration in the fuel, the higher the fuel boiling point. Therefore, as shown in Figure 10A the timing at which the in-cylinder temperature exceeds the fuel boiling point shifts to the delayed side. In addition, Figure 10B is an explanatory diagram of the change in the start crankshaft angle S2 in the case of a low coolant temperature. The lower the coolant temperature, the lower the in-cylinder temperature. Therefore, as shown in Figure 10B the timing at which the in-cylinder temperature exceeds the fuel boiling point shifts to the delayed side. Further, in the case of a low engine speed, the intake air amount introduced into the cylinder 12 also decreases, so the lower the engine speed, the lower the in-cylinder temperature. Also in this case, as shown in Figure 10B the timing at which the in-cylinder temperature exceeds the fuel boiling point shifts to the delayed side. From the above, the higher the ethanol concentration, the lower the coolant temperature, and the lower the engine speed, the more delayed the start crankshaft angle S2 is calculated. In addition, regarding the case where in-cylinder injection is performed only in the first crankshaft angle interval C1 and the second crankshaft angle interval C2, the lower the ethanol concentration, the less the in-cylinder injection amount is required. Therefore, it is not the case that the higher the ethanol concentration, the shorter the second crankshaft angle interval C2 is necessarily calculated, but the lower the coolant temperature and the lower the engine speed, the shorter the second crankshaft angle interval C2 is calculated.

[0063] In Figure 9A and Figure 9B In the mapping of, the starting crank angle S2 changes curvilinearly with respect to the ethanol concentration, but is not limited thereto, and may also change linearly or stepwise. In addition, in the above-described method for setting the starting crank angle S2, it is not limited to the above mapping, and the starting crank angle S2 may also be set based on an arithmetic expression in which the ethanol concentration, the cooling water temperature, and the engine speed are independent variables.

[0064] Next, the ECU 30 determines whether the required in-cylinder injection period is less than the total period of the first crank angle period C1 and the second crank angle period C2 (step S11). Step S11 is an example of the process performed by the second determination unit. When the result in step S11 is "Yes", the ECU 30 performs in-cylinder injection in both the first crank angle period C1 and the second crank angle period C2 (step S12). Step S12 is an example of the process performed by the injection control unit.

[0065] When the result in step S11 is "No", the ECU 30 performs in-cylinder injection in the first crank angle period C1, the second crank angle period C2, and the third crank angle period C3, respectively (step S13). In addition, the third crank angle period C3 is determined in advance through experiments or the like, and is set to a crank angle period in which fuel is not likely to adhere to the top surface of the piston 13. Step S13 is an example of the process performed by the injection control unit.

[0066] As described above, according to the required in-cylinder injection amount, in-cylinder injection is preferably performed in the first crank angle period C1 and the second crank angle period C2 where the in-cylinder temperature exceeds the fuel boiling point, and in-cylinder injection is not performed in the third crank angle period C3 as much as possible. Thereby, fuel vaporization can be promoted and combustion can be stabilized.

[0067] In the above-described embodiment, in-cylinder injection may also be performed in a divided manner during at least one of the first crank angle period C1, the second crank angle period C2, and the third crank angle period C3.

[0068] In the above-described embodiment, the intake VVT 26 and the exhaust VVT 27 are used to ensure a closing period during which both the intake valve 24 and the exhaust valve 25 including the intake top dead center are closed, but it is not limited thereto. For example, when the intake VVT 26 is not provided and only the exhaust VVT 27 is provided, the exhaust VVT 27 is driven to ensure the closing period during the period when the piston 13 is rising. In addition, the closing period does not necessarily need to include the intake top dead center, but it is preferable when the closing period includes the intake top dead center because the in-cylinder temperature is the highest at the intake top dead center.

[0069] In the above-described embodiment, the temperatures of the cooling water are used to calculate the first crank angle range C1 and the second crank angle range C2. However, instead of the temperature of the cooling water, the temperature of the lubricating oil that lubricates the engine 10 may be used. This is because both the temperature of the cooling water and the temperature of the lubricating oil are temperatures related to the temperature of the engine 10.

[0070] In the above-described embodiment, both the in-cylinder injection valve 17 and the intake port injection valve 22 are provided in the engine 10. However, the present invention is not limited thereto, and it may be an engine provided with only the in-cylinder injection valve 17. In the above-described embodiment, the internal combustion engine system 1 mounted on a vehicle has been described. However, the present invention is not limited thereto. For example, the content of the above-described embodiment can also be applied to internal combustion engine systems other than vehicles, such as motorcycles, ships, and construction machinery.

[0071] As described above, embodiments of the present invention have been described in detail. However, the present invention is not limited to the above-described specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

Claims

1. An internal combustion engine system comprising: An internal combustion engine, the internal combustion engine having a cylinder, an intake valve and an exhaust valve for opening and closing the cylinder, an in-cylinder injection valve for directly injecting a fuel containing ethanol into the cylinder, and a variable valve drive mechanism for forming a closing period from the closing of the exhaust valve to the opening of the intake valve; and a control device that controls the in-cylinder injection valve and the variable valve drive mechanism, wherein the control device includes: a calculation unit that calculates a first crank angle range in which the temperature in the cylinder is equal to or higher than the boiling point of the fuel during the compression stroke and a second crank angle range in which the temperature in the cylinder is equal to or higher than the boiling point of the fuel during the closing period before the preheating of the internal combustion engine is completed; and an injection control unit that performs fuel injection by the in-cylinder injection valve in the first crank angle range and the second crank angle range.

2. The internal combustion engine system according to claim 1, wherein the control device includes a first determination unit that determines whether the in-cylinder injection valve can inject a required in-cylinder injection amount within the first crank angle range, and the injection control unit performs fuel injection by the in-cylinder injection valve within the first crank angle range when the first determination unit makes an affirmative determination, and performs fuel injection by the in-cylinder injection valve within the first crank angle range and the second crank angle range when the first determination unit makes a negative determination.

3. The internal combustion engine system according to claim 2, wherein the control device includes a second determination unit that determines whether the in-cylinder injection valve can inject the required in-cylinder injection amount within the first crank angle range and the second crank angle range, and the injection control unit performs fuel injection by the in-cylinder injection valve within the first crank angle range and the second crank angle range when the first determination unit makes a negative determination and the second determination unit makes an affirmative determination, and performs fuel injection by the in-cylinder injection valve within the first crank angle range, the second crank angle range, and the intake stroke when the first determination unit and the second determination unit make negative determinations.

4. The internal combustion engine system according to any one of claims 1 to 3, wherein the control device includes an ethanol concentration acquisition unit that acquires the ethanol concentration in the fuel, and the higher the ethanol concentration, the more the calculation unit calculates the start crank angle of the first crank angle range to the delay side.

5. The internal combustion engine system according to claim 4, and the higher the ethanol concentration, the more the calculation unit calculates the start crank angle of the second crank angle range to the delay side.

6. The internal combustion engine system according to any one of claims 1 to 5, wherein the control device includes a temperature acquisition unit that acquires the temperature of the internal combustion engine, and the lower the temperature, the shorter the calculation unit calculates the first crank angle range.

7. The internal combustion engine system according to claim 6, and the lower the temperature, the shorter the calculation unit calculates the second crank angle range.

8. The internal combustion engine system according to any one of claims 1 to 7, wherein the control device includes a rotational speed acquisition unit that acquires the rotational speed of the internal combustion engine, and the lower the rotational speed, the shorter the calculation unit calculates the first crank angle range.

9. The internal combustion engine system according to claim 8, The lower the rotational speed, the shorter the calculation unit calculates the second crank angle interval.

10. The internal combustion engine system according to any one of claims 1 to 9, The closing period includes the intake top dead center.

11. The internal combustion engine system according to any one of claims 1 to 10, The calculation unit sets the end timing of the first crank angle interval to be on the advance side with respect to the compression top dead center.

12. The internal combustion engine system according to any one of claims 1 to 11, The calculation unit sets the end timing of the second crank angle interval to be on the advance side with respect to the intake top dead center.

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