Control device

Abstract

To provide a control device capable of determining injection timing of fuel containing alcohol.SOLUTION: A control device calculates a second temperature in a combustion chamber at timing when a piston is located at a top dead center on the basis of first pressure detected by a cylinder inner pressure sensor at closing timing of an intake valve, a second pressure detected by the cylinder inner pressure sensor at timing when the piston is located at the top dead center and a first temperature detected by an intake temperature sensor. The control device corrects injection timing of fuel by an injector on the basis of the second temperature.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] As a conventional invention relating to a control device, for example, a control device for an internal combustion engine described in Patent Document 1 is known. The control device for an internal combustion engine described in Patent Document 1 controls the timing of fuel injection based on the engine temperature, alcohol concentration, and load of the internal combustion engine. As a result, the control device for an internal combustion engine described in Patent Document 1 can ensure a stable and good combustion state after cold start of an internal combustion engine using a fuel containing alcohol. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-180550 Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, when using a fuel containing alcohol, it is important to determine the fuel injection timing.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a control device that can determine the injection timing of a fuel containing alcohol. [Means for solving the problem]

[0006] A first aspect of the present invention is A control device for an internal combustion engine, the internal combustion engine includes a main body, a piston, an intake valve, an injector, an in-cylinder pressure sensor, and an intake temperature sensor; The main body is provided with a combustion chamber and a cylinder space, The piston reciprocates within the cylinder space, The intake valve opens and closes an intake port connected to the combustion chamber, The injector injects fuel containing alcohol into the combustion chamber, the cylinder pressure sensor detects pressure in the combustion chamber and the cylinder space; the intake air temperature sensor detects the temperature of the intake air flowing into the combustion chamber; the control device calculates a second temperature in the combustion chamber when the piston is at top dead center based on a first pressure detected by the in-cylinder pressure sensor when the intake valve closes, a second pressure detected by the in-cylinder pressure sensor when the piston is at top dead center, and a first temperature detected by the intake temperature sensor; The control device corrects the timing at which the injector injects the fuel based on the second temperature. It is a control device.

[0007] A second aspect of the present invention is When the second temperature increases, the control device advances the timing at which the injector injects the fuel. 1 is a control device according to a first aspect.

[0008] A third aspect of the present invention is the internal combustion engine further includes a camshaft and a cam angle sensor; The camshaft operates the intake valve, the cam angle sensor detects the phase of the camshaft; the control device detects the timing at which the intake valve closes based on the phase detected by the cam angle sensor; the control device calculates the second temperature based on a compression ratio obtained by dividing the sum of the volume of the combustion chamber and the volume of the cylinder space at the time when the intake valve is closed by the volume of the combustion chamber, the first pressure, the second pressure, and the first temperature. The control device according to either the first or second aspect.

[0009] A fourth aspect of the present invention is The timing at which the injector injects the fuel is between 90° before top dead center of the compression stroke and 0° before top dead center of the compression stroke. The control device is according to any one of the first to third aspects.

[0010] A fifth aspect of the present invention is A control device for an internal combustion engine, the internal combustion engine includes a main body, a piston, an intake valve, an injector, an in-cylinder pressure sensor, and an intake temperature sensor; The main body is provided with a combustion chamber and a cylinder space, The piston reciprocates within the cylinder space, The intake valve opens and closes an intake port connected to the combustion chamber, The injector injects fuel containing alcohol into the combustion chamber, the cylinder pressure sensor detects pressure in the combustion chamber and the cylinder space; the intake air temperature sensor detects the temperature of the intake air flowing into the combustion chamber; the control device advances the timing at which the injector injects the fuel when the first pressure detected by the in-cylinder pressure sensor increases at the timing at which the intake valve closes, the control device advances the timing at which the injector injects the fuel when the second pressure detected by the in-cylinder pressure sensor increases when the piston is positioned at top dead center, the control device advances the timing at which the injector injects the fuel when the first temperature detected by the intake air temperature sensor increases; It is a control device. [Effects of the Invention]

[0011] According to the present invention, the injection timing of the fuel containing alcohol can be determined. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of an internal combustion engine 10 . [Figure 2] FIG. 2 is a schematic diagram of an internal combustion engine 10. [Figure 3] FIG. 3 is a table showing the relationship between the water temperature, the number of injections, the injection timing, and the injection ratio. [Figure 4] FIG. 4 is a table showing the relationship between the water temperature, the number of injections, the injection timing, and the injection ratio. [Figure 5] FIG. 5 is a flowchart executed by the control device 100. DETAILED DESCRIPTION OF THE INVENTION

[0013] (Embodiment) [Structure of an internal combustion engine]

[0014] The structure of an internal combustion engine 10 according to one embodiment of the present invention will be described below with reference to the drawings. Figures 1 and 2 are schematic diagrams of the internal combustion engine 10. Figure 1 shows the internal combustion engine 10 when the piston 18 is at top dead center. Figure 2 shows the internal combustion engine 10 when the intake valve 20 is closed.

[0015] 1 and 2, the directions in which the piston 18 moves are defined as the upward and downward directions. However, the upward and downward directions in this specification are defined for the convenience of explanation and may not coincide with the upward and downward directions when the internal combustion engine 10 is actually used.

[0016] The internal combustion engine 10 is used, for example, as a power source for an automobile. The internal combustion engine 10 is, for example, a four-stroke engine. The fuel for the internal combustion engine 10 contains alcohol. The fuel for the internal combustion engine 10 is a mixture of gasoline and alcohol, or alcohol itself. Note that although the internal combustion engine 10 in FIG. 1 is an engine with one cylinder, it is generally an engine with multiple cylinders. When the internal combustion engine 10 is an engine with multiple cylinders, the multiple cylinders may be arranged in a single row, two rows, or four rows. The internal combustion engine 10 includes a main body 12, a crankshaft 14, a connecting rod 16, a piston 18, an intake valve 20, a camshaft 21, an exhaust valve 22, a camshaft 23, an ignition plug 24, and an injector 29.

[0017] The main body 12 is provided with a combustion chamber Sp and a cylinder space Sy. The main body 12 includes a cylinder block 12a, a cylinder head 12b, and a crankcase 12c. The cylinder block 12a is provided with the cylinder space Sy. The cylinder space Sy has a cylindrical shape with a central axis extending along the vertical axis.

[0018] The cylinder head 12b is located above the cylinder block 12a. The cylinder head 12b is fixed to the cylinder block 12a. The cylinder head 12b is provided with a combustion chamber Sp. The combustion chamber Sp is located above the cylinder space Sy. The combustion chamber Sp is connected to the cylinder space Sy.

[0019] The cylinder head 12b is provided with an intake port p1 and an exhaust port p2. The intake port p1 and the exhaust port p2 are connected to the combustion chamber Sp. The intake port p1 is a part of the intake path R1. The intake path R1 is a path through which air passes. The exhaust port p2 is a part of the exhaust path R2. The exhaust path R2 is a path through which exhaust gas passes. In this way, the internal combustion engine 10 is provided with the combustion chamber Sp, the intake path R1 connected to the combustion chamber Sp, and the exhaust path R2.

[0020] The injector 29 is fixed to the cylinder head 12b. The injector 29 injects fuel containing alcohol into the combustion chamber Sp. Therefore, the internal combustion engine 10 is a direct injection engine for a FFV (Flexible Fuel Vehicle).

[0021] The crankcase 12c is located below the cylinder block 12a and is fixed to the cylinder block 12a.

[0022] The crankshaft 14 is supported by the cylinder block 12a and the crankcase 12c. The crankshaft 14 can rotate about a rotation axis that is perpendicular to the vertical axis. The piston 18 is located in the cylinder space Sy. The piston 18 has a cylindrical shape.

[0023] The connecting rod 16 connects the crankshaft 14 and the piston 18. As a result, when the crankshaft 14 rotates, the piston 18 moves up and down. That is, the piston 18 reciprocates within the cylinder space Sy. The combustion chamber Sp described above is a space surrounded by the piston 18 and the cylinder head 12b when the piston 18 is at top dead center, as shown in FIG. 1.

[0024] The intake valve 20 is supported by the cylinder head 12b. The intake valve 20 opens and closes an intake port p1 connected to the combustion chamber Sp. When the intake valve 20 opens the intake port p1, air flows into the combustion chamber Sp from the intake path R1. The camshaft 21 is rotated by the crankshaft 14. The camshaft 21 operates the intake valve 20.

[0025] The exhaust valve 22 is supported by the cylinder head 12b. The exhaust valve 22 opens and closes an exhaust port p2 that connects to the combustion chamber Sp. When the exhaust valve 22 opens the exhaust port p2, exhaust gas flows from the combustion chamber Sp into the exhaust path R2. The camshaft 23 is rotated by the crankshaft 14. The camshaft 23 operates the exhaust valve 22.

[0026] The spark plug 24 is fixed to the cylinder head 12b. The spark plug 24 includes a center electrode and a ground electrode. The center electrode and the ground electrode are exposed to the combustion chamber Sp. A high voltage is applied between the center electrode and the ground electrode of the spark plug 24 by an ignition coil (not shown). This generates a spark between the center electrode and the ground electrode of the spark plug 24, igniting the fuel in the combustion chamber Sp.

[0027] The internal combustion engine 10 further includes a control device 100, an intake air temperature sensor 102, an in-cylinder pressure sensor 104, and a cam angle sensor .

[0028] The intake air temperature sensor 102 is provided in the intake path R1 and detects the temperature of the intake air flowing into the combustion chamber Sp.

[0029] The cylinder pressure sensor 104 is provided in the cylinder head 12b and detects the pressure in the combustion chamber Sp and the cylinder space Sy.

[0030] The cam angle sensor 106 is provided in the cylinder head 12b and detects the phase of the camshaft.

[0031] The control device 100 is an ECU (Engine Control Unit) and controls the timing at which the injector 29 injects fuel based on the temperature detected by an intake temperature sensor 102, the pressure detected by an in-cylinder pressure sensor 104, and the phase detected by a cam angle sensor 106.

[0032] [Operation of the control device 100] Next, the operation of the control device 100 will be described with reference to the drawings. Figures 3 and 4 are tables showing the relationship between water temperature, the number of injections, the injection timing, and the injection ratio. Figure 3 is a table when a fuel containing 100% ethanol is used. Figure 4 is a table when a fuel containing 22% ethanol and 78% gasoline is used.

[0033] The injection timing in Figures 3 and 4 means that fuel is injected at a time X degrees before top dead center during the compression stroke. The X degrees before top dead center during the compression stroke will be explained. The crank angle when the piston 18 is at top dead center during the compression stroke is defined as 0 degrees. X degrees before top dead center during the compression stroke is the time when the crank angle is X degrees earlier than the time when the crank angle is 0 degrees during the compression stroke.

[0034] Furthermore, the injection timings are listed in multiple numbers, such as 160 / 120 / 15-30, which means that the first injection is 160° before top dead center on the compression stroke, the second injection is 120° before top dead center on the compression stroke, and the third injection is 15°-30° before top dead center on the compression stroke.

[0035] The boiling point of alcohol is higher than that of gasoline. Therefore, when the temperature of the internal combustion engine 10 is low (hereinafter simply referred to as a low-temperature state), fuel containing alcohol is less likely to atomize. In FIGS. 3 and 4, the low-temperature state refers to a state in which the water temperature of the internal combustion engine 10 is 35°C or lower when the internal combustion engine 10 is started, and a state in which the water temperature of the internal combustion engine 10 is 30°C or lower when the internal combustion engine 10 is under normal control. The start-up state of the internal combustion engine 10 refers to a state in which the engine is operated with fixed values for each engine water temperature, including the fuel injection amount, throttle opening, and ignition timing, as combustion parameters. The normal control state of the internal combustion engine 10 refers to a state in which the engine is operated by feedback-controlling the fuel injection amount, throttle opening, and ignition timing, as combustion parameters, primarily to achieve a target rotation speed / stoichiometric air-fuel ratio. In contrast, the temperature of the combustion chamber Sp is high near 0° before top dead center during the compression stroke. Therefore, fuel containing alcohol is more likely to atomize.

[0036] Therefore, in a low-temperature state, the control device 100 causes the injector 29 to inject fuel into the combustion chamber Sp at a timing near 0° before top dead center of the compression stroke, as shown in Figures 3 and 4. This injection corresponds to the third injection in Figures 3 and 4. Thus, the timing at which the injector 29 injects fuel is between 90° before top dead center of the compression stroke and 0° before top dead center of the compression stroke. At this time, as shown in the graphs of Figures 3 and 4, the control device 100 changes the timing at which the injector 29 injects fuel based on the alcohol concentration of the fuel, the water temperature of the internal combustion engine 10, and whether the engine is starting or is under normal control.

[0037] As the alcohol concentration of fuel decreases, the fuel is more likely to atomize. Therefore, when the alcohol concentration of fuel decreases, the control device 100 advances the timing at which the injector 29 injects fuel for the third time. Specifically, the third injection timing in FIG. 4 is later than the third injection timing in FIG. 3. Furthermore, as the water temperature of the internal combustion engine increases, the fuel is more likely to atomize. Therefore, when the water temperature of the internal combustion engine 10 increases, the control device 100 advances the timing at which the injector 29 injects fuel for the third time. Specifically, the third injection timing when the water temperature is 5°C to 30°C in FIG. 4 is earlier than the third injection timing when the water temperature is -5°C to 0°C in FIG. 3. To achieve this control, the control device 100 performs the calculations described below.

[0038] The temperature inside the combustion chamber Sp when the piston 18 shown in FIG. 1 is located at top dead center is defined as a second temperature T2, the volume of the combustion chamber Sp is defined as a second volume V2, and the pressure inside the combustion chamber Sp is defined as a second pressure P2. The temperatures inside the combustion chamber Sp and the cylinder space Sy when the valve closes during the compression stroke shown in FIG. 2 are defined as a first temperature T1, the sum of the volumes of the combustion chamber Sp and the cylinder space Sy is defined as a first volume V1, and the pressure inside the combustion chamber Sp and the cylinder space Sy is defined as a first pressure P1. At this time, the change in the state of the gas from the state shown in FIG. 1 to the state shown in FIG. 2 is an adiabatic compression stroke. Therefore, the following equation (1) holds true. Here, k is the specific heat ratio, and ε is the compression ratio (V1 / V2).

[0039] T2 = T1 × (V1 / V2) k-1 =T1×(P2 / P1) ε-1 ···(1)

[0040] Here, the first temperature T1 is the temperature inside the combustion chamber Sp and the cylinder space Sy when the valves are closed during the compression stroke, and therefore corresponds to the temperature of the intake air flowing into the combustion chamber Sp. That is, the temperature detected by the intake air temperature sensor 102 corresponds to the first temperature T1. The control device 100 can also determine the time when the intake valve 20 is closed based on the phase detected by the cam angle sensor 106. Therefore, the control device 100 determines the pressure detected by the in-cylinder pressure sensor 104 when the intake valve 20 is closed as the first pressure P1. The control device 100 can also determine the time when the piston 18 is at top dead center based on the phase detected by the cam angle sensor 106. Therefore, the control device 100 determines the pressure detected by the in-cylinder pressure sensor 104 when the piston 18 is at top dead center as the second pressure P2.

[0041] The control device 100 can also detect the timing at which the intake valve 20 closes, based on the phase detected by the cam angle sensor 106. Therefore, the control device 100 can also determine the position of the piston 18 when the intake valve 20 closes. Therefore, the control device 100 can also determine the first volume V1 when the intake valve 20 closes. Furthermore, the second volume V2 of the combustion chamber Sp is a predetermined value. Therefore, the control device 100 can also determine the compression ratio ε.

[0042] As described above, the control device 100 can acquire the first temperature T1, the first pressure P1, the second pressure P2, and the compression ratio ε. The control device 100 calculates the second temperature T2 in the combustion chamber Sp when the piston 18 is at top dead center based on the first pressure P1 detected by the in-cylinder pressure sensor 104 when the intake valve 20 is closed, the second pressure P2 detected by the in-cylinder pressure sensor 104 when the piston 18 is at top dead center, the compression ratio ε, and the first temperature T1 detected by the intake temperature sensor 102.

[0043] Here, experiments have shown that if the temperatures of the combustion chamber Sp and the cylinder space Sy are around 230°C, fuel containing 100% ethanol can be ignited without any problems. In other words, if the control device 100 can calculate the second temperature T2 (compression end temperature), it can identify the time when the temperatures of the combustion chamber Sp and the cylinder space Sy will become higher than 230°C. Therefore, the control device 100 only needs to cause the injector 29 to inject fuel when the temperatures of the combustion chamber Sp and the cylinder space Sy become higher than 230°C. In this way, the control device 100 corrects the time when the injector 29 injects fuel based on the second temperature T2. Specifically, when the second temperature T2 increases, the control device 100 advances the time when the injector 29 injects fuel. When the second temperature T2 decreases, the control device 100 retards the time when the injector 29 injects fuel.

[0044] The above control performed by the control device 100 can be restated as follows. When the first pressure P1 detected by the in-cylinder pressure sensor 104 increases when the intake valve 20 closes, the second temperature T2 increases. Therefore, the timing at which the temperatures of the combustion chamber Sp and the cylinder space Sy become higher than 230°C becomes earlier. Therefore, when the first pressure P1 detected by the in-cylinder pressure sensor 104 increases when the intake valve 20 closes, the control device 100 advances the timing at which the injector 29 injects fuel. On the other hand, when the first pressure P1 detected by the in-cylinder pressure sensor 104 decreases when the intake valve 20 closes, the second temperature T2 decreases. Therefore, the timing at which the temperatures of the combustion chamber Sp and the cylinder space Sy become higher than 230°C becomes later. Therefore, when the first pressure P1 detected by the in-cylinder pressure sensor 104 drops when the intake valve 20 is closed, the control device 100 retards the timing at which the injector 29 injects fuel.

[0045] Furthermore, when the second pressure P2 detected by the in-cylinder pressure sensor 104 increases when the piston 18 is at top dead center, the second temperature T2 increases. Therefore, the timing at which the temperatures of the combustion chamber Sp and the cylinder space Sy become higher than 230°C becomes earlier. Therefore, when the second pressure P2 detected by the in-cylinder pressure sensor 104 increases when the piston 18 is at top dead center, the control device 100 advances the timing at which the injector 29 injects fuel. On the other hand, when the second pressure P2 detected by the in-cylinder pressure sensor 104 decreases when the piston 18 is at top dead center, the second temperature T2 decreases. Therefore, the timing at which the temperatures of the combustion chamber Sp and the cylinder space Sy become higher than 230°C becomes later. Therefore, when the second pressure P2 detected by the in-cylinder pressure sensor 104 decreases when the piston 18 is at top dead center, the control device 100 retards the timing at which the injector 29 injects fuel.

[0046] Furthermore, when the first temperature T1 detected by the intake air temperature sensor 102 increases, the second temperature T2 also increases. Therefore, the timing at which the temperatures of the combustion chamber Sp and the cylinder space Sy become higher than 230°C becomes earlier. Therefore, when the first temperature T1 detected by the intake air temperature sensor 102 increases, the control device 100 advances the timing at which the injector 29 injects fuel. On the other hand, when the first temperature T1 detected by the intake air temperature sensor 102 decreases, the second temperature T2 decreases. Therefore, the timing at which the temperatures of the combustion chamber Sp and the cylinder space Sy become higher than 230°C becomes later. Therefore, when the first temperature T1 detected by the intake air temperature sensor 102 decreases, the control device 100 retards the timing at which the injector 29 injects fuel.

[0047] Next, specific operations executed by the control device 100 will be described with reference to the drawings. Fig. 5 is a flowchart executed by the control device 100. The control device 100 executes the flowchart of Fig. 5 by reading a program stored in a storage device (not shown).

[0048] The control device 100 acquires first information (step S1). The first information is, for example, the rotation speed of the internal combustion engine 10 and the load applied to the internal combustion engine 10.

[0049] Next, the control device 100 determines whether the water temperature of the internal combustion engine 10 is equal to or lower than a predetermined temperature (step S2). Specifically, the control device 100 determines whether the water temperature detected by a water temperature sensor (not shown) is equal to or lower than a predetermined temperature. The predetermined temperature is 35°C at start-up and 30°C during normal control. In step S2, the control device 100 determines whether the internal combustion engine 10 is in a low-temperature state. If the water temperature is equal to or lower than the predetermined temperature, the process proceeds to step S3. If the water temperature is not equal to or lower than the predetermined temperature, the process proceeds to step S7.

[0050] Next, the control device 100 determines the timing at which the injector 29 injects fuel and the number of times the injector 29 injects fuel, based on the first information (step S3).

[0051] Next, the control device 100 acquires second information (step S4). The second information includes the first pressure P1, the second pressure P2, the first temperature T1, the first volume V1, and the second volume V2. The control device 100 detects the time when the intake valve 20 closes based on the phase detected by the cam angle sensor 106. The control device 100 then determines the sum of the volume of the combustion chamber Sp and the volume of the cylinder space Sy at this time as the second volume V2.

[0052] Next, the control device 100 calculates a second temperature T2 (compression end temperature) based on the first pressure P1, the second pressure P2, the first temperature T1, the first volume V1, and the second volume V2 (step S5). The control device 100 uses equation (1) to calculate the second temperature T2. However, the control device 100 may also calculate the second temperature T2 by referring to a table equivalent to equation (1).

[0053] Next, the control device 100 corrects the timing at which the injector 29 injects fuel, determined in step S3, based on the second temperature T2 (step S6). A storage unit (not shown) stores a table indicating the relationship between the second temperature T2 and the correction amount for the timing at which the injector 29 injects fuel. The correction amount is an advance or delay amount relative to the timing determined in step S3. The control device 100 corrects the timing at which the injector 29 injects fuel by referring to this table. After this, the process proceeds to step S8.

[0054] If the water temperature is not equal to or lower than the predetermined temperature, the control device 100 determines the timing at which the injector 29 injects fuel and the number of times the injector 29 injects fuel based on the first information (step S7). After this, the process proceeds to step S8. In other words, the injection timing is not corrected.

[0055] In step S8, the control device 100 determines whether or not to end this process (step S8). The control device 100 determines whether or not to end this process by determining whether or not to stop the internal combustion engine 10. If this process does not end, the process returns to step S2.

[0056] [effect] The control device 100 can determine the injection timing of the fuel containing alcohol. More specifically, the boiling point of alcohol is higher than that of gasoline. Therefore, when the temperature of the internal combustion engine 10 is low (hereinafter simply referred to as the low-temperature state), the fuel containing alcohol is less likely to atomize. In contrast, the temperature of the combustion chamber Sp is high near 0° before top dead center in the compression stroke. Therefore, the fuel containing alcohol is more likely to atomize.

[0057] Therefore, in a low-temperature state, the control device 100 causes the injector 29 to inject fuel into the combustion chamber Sp at a timing near 0° before top dead center of the compression stroke. At this time, in order to appropriately determine the injection timing, the control device 100 calculates a second temperature T2 in the combustion chamber Sp when the piston 18 is at top dead center based on a first pressure P1 detected by the in-cylinder pressure sensor 104 when the intake valve 20 closes, a second pressure P2 detected by the in-cylinder pressure sensor 104 when the piston 18 is at top dead center, and a first temperature T1 detected by the intake temperature sensor 102.

[0058] Here, experiments have shown that if the temperatures of the combustion chamber Sp and the cylinder space Sy are about 230°C, fuel containing 100% ethanol can be ignited without any problems. In other words, if the control device 100 can calculate the second temperature T2 (compression end temperature) as described above, it can identify the time when the temperatures of the combustion chamber Sp and the cylinder space Sy will become higher than 230°C. Therefore, the control device 100 only needs to cause the injector 29 to inject fuel when the temperatures of the combustion chamber Sp and the cylinder space Sy will become higher than 230°C. Therefore, the control device 100 corrects the time when the injector 29 injects fuel based on the second temperature T2. As a result, the control device 100 can determine the injection time of fuel containing alcohol.

[0059] However, as the second temperature T2 increases, the timing at which the temperatures of the combustion chamber Sp and the cylinder space Sy become higher than 230°C becomes earlier. Therefore, when the second temperature T2 increases, the control device 100 advances the timing at which the injector 29 injects fuel. In this way, the control device 100 can determine the injection timing of the alcohol-containing fuel.

[0060] The control device 100 can determine the injection timing of a fuel containing alcohol even in an internal combustion engine 10 that employs a variable valve timing mechanism. More specifically, in an internal combustion engine 10 that employs a variable valve timing mechanism, the timing at which the intake valve 20 closes changes. As a result, the second volume V2 changes. Therefore, the control device 100 detects the timing at which the intake valve 20 closes based on the phase detected by the cam angle sensor 106. This allows the control device 100 to calculate the second volume V2. As a result, the control device 100 can accurately calculate the second temperature T2 based on equation (1). Therefore, the control device 100 can determine the injection timing of a fuel containing alcohol even in an internal combustion engine 10 that employs a variable valve timing mechanism.

[0061] The control device 100 can also determine the injection timing of the alcohol-containing fuel for the following reason. More specifically, the control device 100 corrects the timing at which the injector 29 injects fuel based on the second temperature T2. The second temperature T2 is calculated based on the first pressure P1, the second pressure P2, and the first temperature T1. Therefore, when the first pressure P1, the second pressure P2, and the first temperature T1 change, the second temperature T2 also changes. Specifically, when the first pressure P1 increases, the second temperature T2 increases. When the second pressure P2 increases, the second temperature T2 increases. When the first temperature T1 increases, the second temperature T2 increases. In this way, when the first pressure P1, the second pressure P2, or the first temperature T1 increases, the timing at which the temperatures of the combustion chamber Sp and the cylinder space Sy become higher than 230°C becomes earlier.

[0062] Therefore, when the first pressure P1 detected by the in-cylinder pressure sensor 104 increases when the intake valve 20 is closed, the control device 100 advances the timing at which the injector 29 injects fuel. When the second pressure P2 detected by the in-cylinder pressure sensor 104 increases when the piston 18 is at top dead center, the control device 100 advances the timing at which the injector 29 injects fuel. When the first temperature T1 detected by the intake air temperature sensor 102 increases, the control device 100 advances the timing at which the injector 29 injects fuel. As described above, the control device 100 can determine the injection timing of fuel containing alcohol.

[0063] (Other embodiments) The control device according to the present invention is not limited to the control device 100, and can be modified within the scope of the gist thereof.

[0064] The automobile may be a four-wheeled automobile, a three-wheeled automobile, or a two-wheeled automobile. A two-wheeled automobile is a leaning vehicle in which the body leans in the same direction as the direction of travel around a corner. A three-wheeled automobile may be a leaning vehicle or a vehicle that rolls in the opposite direction to the direction of travel around a corner.

[0065] If the internal combustion engine 10 does not have a variable valve timing mechanism, the internal combustion engine 10 does not need to have the cam angle sensor 106. In this case, the second volume V2 is the sum of the volume of the combustion chamber Sp and the volume of the cylinder space Sy when the piston 18 is located at bottom dead center.

[0066] The internal combustion engine 10 may further include an alcohol concentration sensor. The alcohol concentration sensor detects the concentration of alcohol contained in the fuel (alcohol concentration). The control device 100 may acquire the alcohol concentration in step S4. In this case, when the alcohol concentration decreases, the control device 100 advances the timing at which the injector 29 injects fuel. When the alcohol concentration increases, the control device 100 retards the timing at which the injector 29 injects fuel.

[0067] Note that the injection timing in the table of Fig. 3 is listed as 15-30. This means that when the rotation speed of the internal combustion engine 10 is less than 400 rpm, fuel is injected 15 degrees before top dead center of the compression stroke, and when the rotation speed of the internal combustion engine 10 is 400 rpm or more, fuel is injected 30 degrees before top dead center of the compression stroke. When the rotation speed of the internal combustion engine 10 is less than 400 rpm, not much time has passed since the start of combustion, so fuel is injected at a timing when the temperature of the combustion chamber Sp is high. On the other hand, when the rotation speed of the internal combustion engine 10 is 400 rpm or more, the rotation speed is increasing, so fuel is injected at a timing when premixing is easily achieved. [Explanation of symbols]

[0068] 10: Internal combustion engine 12:Main body 18: Piston 20: Intake valve 21,23: Camshaft 22: Exhaust valve 29: Injector 100: Control device 102: Intake air temperature sensor 104: Cylinder pressure sensor 106: Cam angle sensor R1: Intake path R2: Exhaust route Sp: Combustion chamber Sy: Cylinder space p1: Intake port p2: Exhaust port

Claims

1. A control device for an internal combustion engine, the internal combustion engine includes a main body, a piston, an intake valve, an injector, an in-cylinder pressure sensor, and an intake temperature sensor; The main body is provided with a combustion chamber and a cylinder space, The piston reciprocates within the cylinder space, The intake valve opens and closes an intake port connected to the combustion chamber, The injector injects fuel containing alcohol into the combustion chamber, the cylinder pressure sensor detects pressure in the combustion chamber and the cylinder space; the intake air temperature sensor detects the temperature of the intake air flowing into the combustion chamber; the control device calculates a second temperature in the combustion chamber when the piston is at top dead center based on a first pressure detected by the in-cylinder pressure sensor when the intake valve closes, a second pressure detected by the in-cylinder pressure sensor when the piston is at top dead center, and a first temperature detected by the intake temperature sensor; The control device corrects the timing at which the injector injects the fuel based on the second temperature. Control device.

2. When the second temperature increases, the control device advances the timing at which the injector injects the fuel. The control device according to claim 1 .

3. the internal combustion engine further includes a camshaft and a cam angle sensor; The camshaft operates the intake valve, the cam angle sensor detects the phase of the camshaft; the control device detects the timing at which the intake valve closes based on the phase detected by the cam angle sensor; the control device calculates the second temperature based on a compression ratio obtained by dividing the sum of the volume of the combustion chamber and the volume of the cylinder space by the volume of the combustion chamber at the time when the intake valve is closed, the first pressure, the second pressure, and the first temperature. The control device according to claim 1 or 2.

4. The timing at which the injector injects the fuel is between 90° before top dead center of the compression stroke and 0° before top dead center of the compression stroke. The control device according to claim 1 or 2.

5. A control device for an internal combustion engine, the internal combustion engine includes a main body, a piston, an intake valve, an injector, an in-cylinder pressure sensor, and an intake temperature sensor; The main body is provided with a combustion chamber and a cylinder space, The piston reciprocates within the cylinder space, The intake valve opens and closes an intake port connected to the combustion chamber, The injector injects fuel containing alcohol into the combustion chamber, the cylinder pressure sensor detects pressure in the combustion chamber and the cylinder space; the intake air temperature sensor detects the temperature of the intake air flowing into the combustion chamber; the control device advances the timing at which the injector injects the fuel when the first pressure detected by the in-cylinder pressure sensor increases at the timing at which the intake valve closes, the control device advances the timing at which the injector injects the fuel when the second pressure detected by the in-cylinder pressure sensor increases when the piston is positioned at top dead center, the control device advances the timing at which the injector injects the fuel when the first temperature detected by the intake air temperature sensor increases; Control device.

Images