Control device for internal combustion engine

Abstract

To provide a control device for an internal combustion engine capable of obtaining good startability even when starting the spark ignition type internal combustion engine that directly injects fuel containing alcohol into a cylinder in a low temperature environment.SOLUTION: A control device for a spark ignition type internal combustion engine that directly injects fuel containing alcohol into a cylinder includes: control means 2 for controlling ignition timing of injecting the fuel from a fuel injection device 4 into the cylinder 3a and ignition timing of spark ignition of the fuel in the cylinder; and environment temperature detection means 20 for detecting an environment temperature. In the control device for the internal combustion engine, the control means performs spark ignition of the fuel within a fuel injection period in which the fuel is being injected into the cylinder in the case where the environment temperature is a predetermined value or smaller.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Traditionally, efforts have been made to mitigate or reduce the impact of climate change, and research and development into reducing carbon dioxide emissions has been carried out to achieve this. In recent years, attempts have been made to use alcohol-containing fuels as an alternative fuel to gasoline in spark-ignition internal combustion engines (SI engines).

[0003] For example, Patent Document 1 proposes a fuel control device for an internal combustion engine that uses a blended fuel of alcohol and gasoline and controls the amount of fuel to be increased at start-up. Patent Document 1 describes a fuel control device that includes an alcohol concentration detection means for detecting the alcohol concentration in the blended fuel, a low boiling point component content detection means for detecting the proportion of low boiling point components in the gasoline in the blended fuel, and an increase correction means for correcting the fuel injection amount to be increased more when the alcohol concentration is equal to or higher than a predetermined value and the proportion of the low boiling point components in the gasoline is lower.

[0004] Patent Document 2 also proposes a control device for an internal combustion engine that uses fuel containing alcohol and injects the fuel directly into a cylinder. Patent Document 2 describes a control device that includes: an engine temperature parameter acquisition means that acquires an engine temperature parameter that indicates the temperature of the internal combustion engine, an alcohol concentration acquisition means that acquires the alcohol concentration of the fuel, a load acquisition means that acquires the load of the internal combustion engine, and a control means that, after a cold start of the internal combustion engine, selects and executes one of intake stroke injection, in which fuel is injected in the intake stroke, and compression stroke injection, in which fuel is injected in the compression stroke, as a fuel injection mode, depending on the acquired engine temperature parameter, alcohol concentration, and load of the internal combustion engine. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 5-340286 [Patent Document 2] Japanese Patent Application Publication No. 2020-180550 Summary of the Invention [Problem to be solved by the invention]

[0006] Alcohols such as methanol and ethanol are difficult to vaporize at temperatures below their boiling points and have a larger latent heat of vaporization than gasoline. Therefore, in spark-ignition internal combustion engines that directly inject fuel into the cylinders, when fuel containing alcohol is used, starting problems are more likely to occur in low-temperature environments than when gasoline is used as the fuel. For this reason, there has been a demand for improved starting performance in low-temperature environments for spark-ignition internal combustion engines that directly inject fuel containing alcohol into the cylinders.

[0007] The present application has been made in view of the above-mentioned problems, and aims to provide a control device for an internal combustion engine that can achieve good startability even when starting a spark-ignition internal combustion engine that directly injects fuel containing alcohol into the cylinders in a low-temperature environment. [Means for solving the problem]

[0008] In order to solve the above problems, the following means are provided.

[0009] A first aspect of the present invention provides a control device for an internal combustion engine, which is a control device for a spark ignition internal combustion engine (3) that directly injects fuel containing alcohol into a cylinder (3 a), and includes a control means (2) that controls an injection timing for injecting the fuel from a fuel injection device (4) into the cylinder (3 a) and an ignition timing for spark igniting the fuel in the cylinder (3 a), and an environmental temperature detection means (20) that detects an environmental temperature, and when the environmental temperature is equal to or lower than a predetermined value, the control means (2) spark ignites the fuel within a fuel injection period during which the fuel is injected into the cylinder (3 a).

[0010] In the control device for an internal combustion engine of the first aspect, the control means spark-ignites the fuel during the fuel injection period in which the alcohol-containing fuel is injected into the cylinders when the ambient temperature is equal to or lower than a predetermined value. Therefore, good startability can be achieved even when a spark-ignition internal combustion engine in which the alcohol-containing fuel is directly injected into the cylinders is started in a low-temperature environment below the predetermined ambient temperature.

[0011] A second aspect of the present invention is a control device for an internal combustion engine in the first aspect, wherein the environmental temperature detection means (20) includes an outside air temperature detection means (22) for detecting the temperature of outside air taken into the cylinder (3 a) and an engine water temperature detection means (23) for detecting the temperature of engine water, and the environmental temperature is the temperature of the outside air and / or the temperature of the engine water.

[0012] In the internal combustion engine control device of the second aspect, the control means spark ignites the fuel within the fuel injection period when the ambient temperature (outside air temperature and / or engine water temperature) is equal to or lower than a predetermined value. Therefore, by spark igniting the fuel within the fuel injection period, the effect of improving the startability of the internal combustion engine can be more effectively obtained.

[0013] The control device for an internal combustion engine of a third aspect of the present invention is the control device of the first aspect, wherein the control means (2) spark-ignites the fuel within the fuel injection period when the environmental temperature is within a range of 5°C to -40°C.

[0014] When an internal combustion engine is started in a low-temperature environment where the ambient temperature, such as the temperature of outside air and / or the temperature of engine water, is 5°C or lower, starting problems of the internal combustion engine are more likely to occur. Also, when an internal combustion engine is started in a low-temperature environment where the ambient temperature is -40°C or higher, the effect of improving the startability of the internal combustion engine by spark igniting the fuel within the fuel injection period is more likely to be achieved. In the internal combustion engine control device of the third aspect, the control means spark ignites the fuel within the fuel injection period when the ambient temperature is within the range of 5°C to -40°C. Therefore, by spark igniting the fuel within the fuel injection period, the effect of improving the startability of the internal combustion engine is more pronounced.

[0015] The control device for an internal combustion engine of a fourth aspect of the present invention is the same as that of the first aspect, and further includes an alcohol concentration detection means (24) for detecting an alcohol content in the fuel, and the control means (2) spark-ignites the fuel within the fuel injection period when the alcohol concentration in the fuel is equal to or greater than a predetermined value.

[0016] The higher the alcohol concentration in the fuel, the more likely it is that poor starting will occur in low-temperature environments. Therefore, when the environmental temperature is below a predetermined value, the effect of improving the startability of the internal combustion engine by spark igniting the fuel within the fuel injection period becomes more pronounced as the alcohol concentration in the fuel increases. In the internal combustion engine control device of the fourth aspect, the control means spark ignites the fuel within the fuel injection period when the alcohol concentration in the fuel is equal to or higher than a predetermined value. Therefore, by spark igniting the fuel within the fuel injection period, the effect of improving the startability of the internal combustion engine can be more effectively achieved.

[0017] A fifth aspect of the present invention is the control device for an internal combustion engine of the fourth aspect, wherein the control means (2) spark-ignites the fuel within the fuel injection period when the alcohol concentration in the fuel is 90% by volume or more.

[0018] In the fifth aspect of the internal combustion engine control device, the control means spark ignites the fuel within the fuel injection period when the alcohol concentration in the fuel is 90% by volume or more. Therefore, by spark igniting the fuel within the fuel injection period, the effect of improving the startability of the internal combustion engine becomes more pronounced. Furthermore, fuel containing alcohol is preferable as an alternative fuel to gasoline when the alcohol concentration in the fuel is 90% by volume or more.

[0019] The control device for an internal combustion engine of a sixth aspect of the present invention is the same as that of the first aspect, and further includes crank angle detection means (21) that detects rotation of a crankshaft (3e) and outputs a crank angle signal and a top dead center signal, and the control means (2) injects the fuel from the fuel injection device (4) into the cylinder (3a) during the compression stroke.

[0020] In the sixth aspect of the control device for an internal combustion engine, the control means injects fuel into the cylinder from the fuel injector during the compression stroke. In this case, the fuel injection period is the compression stroke, the pressure inside the cylinder is high, the fuel is easily vaporized, and a decrease in mass-average temperature due to latent heat of vaporization is suppressed. By spark igniting the fuel during the fuel injection period, the effect of improving the startability of the internal combustion engine becomes more pronounced.

[0021] A seventh aspect of the present invention is the control device for an internal combustion engine of the first aspect, wherein the control means (2) spark-ignites the fuel within a period that is 1 / 3 of the retard angle of the fuel injection period. During the retarded 1 / 3 of the fuel injection period, the pressure inside the cylinder is higher, making it easier for the fuel to vaporize, and the decrease in mass-average temperature due to the latent heat of vaporization is suppressed. Therefore, by spark igniting the fuel during the retarded 1 / 3 of the fuel injection period, the startability of the internal combustion engine can be more effectively improved.

[0022] An eighth aspect of the present invention is an internal combustion engine control device in the first aspect, further comprising an in-cylinder pressure detection means for detecting the pressure in the cylinder (3 a), and the control means (2) determines whether the fuel has ignited based on a change in the pressure in the cylinder (3 a), and spark-ignites the fuel within the fuel injection period when the number of consecutive cycles in which the fuel has ignited is equal to or less than a predetermined value.

[0023] Spark ignition of fuel during the fuel injection period in which alcohol-containing fuel is injected into a cylinder has the effect of improving the startability of the internal combustion engine when the ambient temperature is below a predetermined value. However, in order to ensure a more stable combustion state after the internal combustion engine is started, it may be preferable to execute spark ignition of fuel at a timing other than the fuel injection period. In the internal combustion engine control device of the eighth aspect, the control means determines whether the fuel has ignited based on a change in pressure in the cylinder (3a), and spark ignites the fuel within the fuel injection period if the number of consecutive cycles in which the fuel has ignited (the number of ignitions) is below a predetermined value. Therefore, spark ignition of fuel during the fuel injection period sufficiently improves the startability of the internal combustion engine and makes it easier to ensure a more stable combustion state after the internal combustion engine is started.

[0024] The control device for an internal combustion engine of a ninth aspect of the present invention is the same as that of the first aspect, and further includes crank angle detection means (21) that detects rotation of a crankshaft (3e) and outputs a crank angle signal, and the control means (2) determines whether or not the fuel has ignited based on a change in the crank angle, and spark-ignites the fuel within the fuel injection period when the number of consecutive cycles in which the fuel has ignited is equal to or less than a predetermined value.

[0025] In the control device for an internal combustion engine of the ninth aspect, the control means determines whether or not the fuel has ignited based on a change in the crank angle, and if the number of consecutive cycles in which the fuel has ignited (the number of ignitions) is equal to or less than a predetermined value, spark ignition of the fuel within the fuel injection period. Therefore, by spark igniting the fuel within the fuel injection period, the effect of improving the startability of the internal combustion engine can be sufficiently obtained, and a more stable combustion state can be easily ensured after the internal combustion engine has been started. [Effects of the Invention]

[0026] In the control device of the present invention, the control means spark-ignites the fuel containing alcohol during the fuel injection period in which the fuel is injected into the cylinders when the ambient temperature is equal to or lower than a predetermined value. Therefore, good startability can be achieved even when starting a spark-ignition internal combustion engine in which fuel containing alcohol is directly injected into the cylinders in a low-temperature environment. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a schematic diagram for explaining an internal combustion engine controlled by a control device for an internal combustion engine according to this embodiment, and the control device. [Figure 2] FIG. 2 is a flowchart illustrating the control process of the engine 3 executed by the control device of this embodiment. [Figure 3] FIG. 3 is a graph showing the relationship between the crank angle and the pressure inside the cylinder when the engine is operated in a low-temperature environment. [Figure 4] FIG. 4 is a graph showing the relationship between the crank angle and the proportion of fuel vaporized in the cylinder when the engine is operated in a low-temperature environment. [Figure 5] FIG. 5 is a graph showing the relationship between the crank angle and the mass-average temperature in the cylinder when the engine is operated in a low-temperature environment. [Figure 6] FIG. 6 is a graph showing the relationship between the crank angle at which spark ignition occurs and the output when the engine is operated in a low-temperature environment. [Figure 7] FIG. 7 is a graph showing the relationship between the crank angle at which spark ignition occurs and the output when the engine is operated in a low-temperature environment. DETAILED DESCRIPTION OF THE INVENTION

[0028] In order to solve the above problems and improve the startability of an internal combustion engine in a low-temperature environment, the present inventors have conducted extensive research, focusing on the relationship between the characteristics of a fuel containing alcohol and the ignition timing for spark ignition of the fuel containing alcohol.

[0029] Generally, in spark-ignition internal combustion engines in which gasoline is injected directly into the cylinder, spark ignition is not performed during the fuel injection period in which the gasoline is injected into the cylinder. This is because the gasoline sprayed into the cylinder wets the spark plug, making it difficult to produce a spark, which is known as plug fouling, making it difficult for the gasoline to ignite and reducing startability.

[0030] However, the present inventors discovered that in a spark-ignition internal combustion engine in which fuel containing alcohol is directly injected into a cylinder, spark ignition of the fuel during the fuel injection period in which the fuel is injected into the cylinder improves startability in low-temperature environments compared to spark ignition of the fuel at a timing other than the fuel injection period, and thus arrived at the present invention.

[0031] The control device for an internal combustion engine according to this embodiment will be described in detail below with reference to the accompanying drawings. The drawings used in the following description may show characteristic portions enlarged for the sake of clarity. Therefore, the dimensional ratios of the components may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate modifications may be made within the scope of the present invention.

[0032] 1 is a schematic diagram for explaining an internal combustion engine controlled by an internal combustion engine control device according to this embodiment, and the control device. In this embodiment, the internal combustion engine control device according to this embodiment is described as an example in which the internal combustion engine control device is applied as a control device for controlling an engine 3 shown in FIG. 1, which is an example of an internal combustion engine. 1 is a spark-ignition internal combustion engine that directly injects fuel containing alcohol into cylinders 3a. The engine 3 may be mounted on a vehicle (not shown), for example.

[0033] Examples of the alcohol contained in the alcohol-containing fuel include one or more alcohols selected from methanol, ethanol, propanol, butanol, etc. Among the above, the alcohol contained in the alcohol-containing fuel is preferably methanol and / or ethanol. This is because controlling the engine 3 using the control device of this embodiment significantly improves the startability of the engine 3.

[0034] The alcohol-containing fuel may contain only alcohol, or may contain alcohol and compounds other than alcohol. Examples of compounds other than alcohol that may be contained in the alcohol-containing fuel include fuels other than alcohol, such as gasoline, impurities such as water, and additives. When the alcohol-containing fuel contains alcohol and compounds other than alcohol, the alcohol concentration in the fuel is preferably 90% by volume or more, and more preferably 95% by volume or more.

[0035] The engine 3 is, for example, a four-cylinder engine having four cylinders 3a (only one is shown in FIG. 1). A combustion chamber 3d is provided between the piston 3b of each cylinder 3a and a cylinder head 3c. A fuel injector 4 and an ignition plug 5 are provided in the cylinder head 3c for each cylinder 3a. In the engine 3 shown in FIG. 1, fuel is injected directly from the fuel injector 4 into the cylinder 3a.

[0036] 1, the fuel injector 4 and the spark plug 5 are electrically connected to the control means 2 of the control device of this embodiment. The injection timing and injection amount at which fuel is injected from the fuel injector 4 into the cylinder 3a, and the ignition timing at which the fuel in the cylinder 3a is spark-ignited are controlled by control signals from the control means 2.

[0037] As shown in FIG. 1, an intake passage 6 is connected to the cylinder head 3c of each cylinder 3a. A throttle valve 7 is provided in the intake passage 6. The throttle valve 7 has a butterfly-type valve element 7a and an actuator 7b that drives the valve element 7a. The actuator 7b is electrically connected to the control means 2 and is driven by a control signal from the control means 2. This controls the opening of the valve element 7a, and thereby the amount of air taken into the cylinder 3a.

[0038] The control device of this embodiment is provided with crank angle detection means 21, ambient temperature detection means 20 for detecting ambient temperature, alcohol concentration detection means 24, and in-cylinder pressure detection means (not shown). As shown in Fig. 1, these detection means (sensors) are each electrically connected to control means 2. Output signals output by these detection means are each input to control means 2.

[0039] In this embodiment, the environmental temperature detecting means 20 includes an outside air temperature detecting means 22 and an engine water temperature detecting means 23. The control device of this embodiment may include both the outside air temperature detecting means 22 and the engine water temperature detecting means 23 as the environmental temperature detecting means 20, or may include only one of them. Furthermore, in this embodiment, the case where the alcohol concentration detection means 24 is provided will be described as an example, but the alcohol concentration detection means 24 may not be provided.

[0040] The crank angle detection means 21 detects the rotation of the crankshaft 3e of the engine 3 and outputs a crank angle (CRK) signal and a top dead center (TDC) signal. The outside air temperature detection means 22 detects the temperature of the air flowing through the intake passage 6 as the temperature of the outside air taken into the cylinder 3a. The engine water temperature detection means 23 detects the temperature of the engine water, which is the temperature of the cooling water circulating inside the cylinder block of the engine 3.

[0041] The alcohol concentration detection means 24 detects the alcohol content in the fuel by a known method. The alcohol concentration detection means 24 is installed, for example, in a pipe connecting the fuel injection device 4 and a fuel tank (not shown). An in-cylinder pressure detection means (not shown) is installed in the cylinder 3a and detects the pressure in the cylinder 3a using a known pressure sensor or the like.

[0042] An ECU (electronic control unit), for example, can be used as the control means 2. The control means 2 is configured with a microcomputer including a CPU, RAM, ROM, EEPROM, an I / O interface, etc. The control means 2 executes various engine control processes in accordance with a control program stored in the ROM based on signals input from the above-mentioned detection means (sensors), etc. The control means 2 calculates the output obtained by burning fuel based on the change in pressure inside the cylinder 3a detected by an internal cylinder pressure detection means (not shown).

[0043] The control means 2 of the control device of this embodiment controls the injection timing at which fuel is injected into the cylinder 3a from the fuel injection device 4 and the ignition timing at which the fuel in the cylinder 3a is spark-ignited. In this embodiment, the control means 2 preferably spark-ignites the fuel only once per cycle. When the ambient temperature is equal to or lower than a predetermined value, the control means 2 spark-ignites the fuel during the fuel injection period in which the fuel is injected into the cylinder 3a. In this embodiment, the ambient temperature may be either the temperature of the outside air or the temperature of the engine water, or may be both the temperature of the outside air and the temperature of the engine water. In this embodiment, when the environmental temperature is both the temperature of the outside air and the temperature of the engine water, the predetermined value of the temperature of the outside air and the predetermined value of the temperature of the engine water may be the same or different.

[0044] The predetermined value of the environmental temperature in this embodiment can be determined appropriately depending on the application of the engine 3. The predetermined value of the environmental temperature in this embodiment is preferably 5°C or less, which is the temperature at which starting problems of the engine 3 are more likely to occur, and may be 0°C or less. The predetermined value of the environmental temperature can have a lower limit of, for example, -40°C or more.

[0045] Preferably, the control means 2 spark ignites the fuel within the fuel injection period when the ambient temperature is below a predetermined value and the alcohol concentration in the fuel is above a predetermined value. This is because spark ignition of the fuel within the fuel injection period more significantly improves the startability of the engine 3. The predetermined value of the alcohol concentration in the fuel in this embodiment can be determined appropriately depending on the application of the engine 3, etc. The predetermined value of the alcohol concentration in the fuel in this embodiment is preferably 90% by volume or more, more preferably 95% by volume or more, and the higher the alcohol concentration, the better.

[0046] When the environmental temperature is equal to or lower than a predetermined value, the control means 2 preferably injects fuel into the cylinder 3a from the fuel injector 4 during the compression stroke. In this case, the fuel injection period corresponds to the compression stroke. When the environmental temperature is equal to or lower than a predetermined value, the control means 2 preferably performs spark ignition within one-third of the retard angle of the fuel injection period.

[0047] Furthermore, the control means 2 determines whether or not the fuel has ignited based on a change in pressure inside the cylinder 3a detected by an in-cylinder pressure detection means (not shown), and if the number of consecutive cycles in which the fuel has ignited (cycles in which the fuel has ignited and combustion has been achieved) (number of ignitions) is equal to or less than a predetermined number, it is preferable that the control means 2 also spark-ignites the fuel within the fuel injection period in the next cycle. The predetermined number of consecutive cycles in which the fuel has ignited is preferably equal to or less than three, and may be equal to or less than two.

[0048] Furthermore, the control means 2 may determine whether or not the fuel has ignited based on a change in the crank angle detected by the crank angle detection means 21, and if the number of consecutive cycles (number of ignitions) in which the fuel has ignited (cycles in which the fuel has ignited and combustion has been achieved) is equal to or less than a predetermined number, the control means 2 may also spark ignite the fuel within the fuel injection period in the next cycle. The control means 2 may also determine whether or not the fuel has ignited based on a change in pressure inside the cylinder 3a and a change in the crank angle. In these cases, the predetermined value for the number of consecutive cycles in which fuel is ignited is preferably three or less, and may be two or less.

[0049] Next, the control process of the engine 3 performed by the control device of this embodiment will be described. FIG. 2 is a flowchart illustrating the control process of the engine 3 executed by the control device of this embodiment. In this embodiment, first, the control means 2 causes the engine water temperature detection means 23 to detect the temperature of the engine water (step S1). Next, the control means 2 causes the outside air temperature detection means 22 to detect the temperature of the outside air taken into the cylinder 3a (step S2). Next, the control means 2 causes the alcohol concentration detection means 24 to detect the alcohol content contained in the fuel (step S3).

[0050] Next, the control means 2 determines whether the temperature of the outside air, which is the environmental temperature, and the temperature of the engine water are each equal to or lower than a predetermined value, and also determines whether the alcohol concentration in the fuel is equal to or higher than a predetermined value (step S4). Then, if it is determined that both the outside air temperature and the engine water temperature are below a predetermined value and the alcohol concentration in the fuel is above a predetermined value, the control means 2 proceeds to step S5 as shown in FIG. 2, and spark ignites the fuel within the fuel injection period (step S5).

[0051] On the other hand, if one or more of the following conditions are met: the outside air temperature exceeds a predetermined value, the engine water temperature exceeds a predetermined value, or the alcohol concentration in the fuel is less than a predetermined value (in other words, if one or more of the conditions of the outside air temperature, the engine water temperature, and the alcohol concentration in the fuel are outside a predetermined numerical range), the control process by the control device of this embodiment is terminated.

[0052] In step S5, if the temperature of the outside air and / or engine water is within the range of 5°C to -40°C, the control means 2 preferably spark-ignites the fuel within the fuel injection period. In step S5, the control means 2 preferably spark-ignites the fuel within the fuel injection period if the alcohol concentration in the fuel is 90% by volume or more.

[0053] If the control means 2 determines in step S4 that both the outside air temperature and the engine water temperature are below a predetermined value and that the alcohol concentration in the fuel is above a predetermined value, it is preferable to inject fuel from the fuel injection device 4 into the cylinder 3a during the compression stroke in step S5. In addition, if the control means 2 determines in step S4 that both the outside air temperature and the engine water temperature are below a predetermined value and the alcohol concentration in the fuel is above a predetermined value, it is also preferable that in step S5 the fuel is spark-ignited within 1 / 3 of the retard period of the fuel injection period.

[0054] Here, we will explain the state inside the cylinder when an engine in which alcohol-containing fuel is directly injected into the cylinder is operated in a low-temperature environment. Figures 3 to 5 are graphs showing the state inside the cylinder when the engine is operated under the following operating conditions: engine speed: 1100 rpm, intake pipe pressure: full throttle opening, engine water temperature: 0°C, outside air temperature taken into the cylinder: 20°C, fuel pressure: 16 MPa, and fuel injection amount: three times the stoichiometric air-fuel ratio. Only methanol or only ethanol was used as the fuel. The fuel injection period for methanol was within the crank angle range of -70° ATDC to 0° ATDC. The fuel injection period for ethanol was within the crank angle range of -50° ATDC to 0° ATDC. In other words, whether the fuel was methanol or ethanol, fuel was injected into the cylinder from the fuel injector during the compression stroke.

[0055] Fig. 3 is a graph showing the relationship between crank angle and in-cylinder pressure (combustion chamber pressure) when the engine is operated in a low-temperature environment. Fig. 3 shows the in-cylinder pressure of air as well as the in-cylinder pressure of methanol and ethanol. The in-cylinder pressure (combustion chamber pressure) in Fig. 3 was measured by a pressure sensor, which is an in-cylinder pressure detection means. As shown in FIG. 3, whether the fuel is methanol or ethanol, the pressure inside the cylinder reaches its highest value near the compression top dead center (crank angle 0 deg. ATDC).

[0056] Figure 4 is a graph showing the relationship between the crank angle and the proportion of vaporized fuel in the cylinder (combustion chamber) when the engine is operated in a low-temperature environment. The proportion of vaporized fuel in Figure 4 (vaporized fuel / total fuel) was measured using the following method. That is, the amount of vaporized fuel was calculated by assuming that the difference in pressure between the cylinder pressure when the only gas in the cylinder was air (in other words, when no fuel was injected) and the cylinder pressure when fuel was injected was caused by the latent heat of vaporization of the fuel.The amount of vaporized fuel calculated in this way was then used to determine the ratio of the amount of vaporized fuel to the amount of fuel injected into the cylinder (total fuel).

[0057] As shown in Figure 4, whether the fuel is methanol or ethanol, the proportion of vaporized fuel (vaporized fuel / total fuel) increases as the crank angle approaches compression top dead center (0 deg. ATDC) after fuel injection begins, and around half of the total fuel in the cylinder is vaporized near compression top dead center.

[0058] When the fuel is ethanol, the vaporized fuel ratio (vaporized fuel / total fuel) continues to increase even after the end of fuel injection (crank angle 0 deg. ATDC), reaches its highest when the crank angle is around 10 deg. ATDC, and then gradually decreases. On the other hand, when the fuel is methanol, the proportion of vaporized fuel (vaporized fuel / total fuel) reaches its highest value when the crank angle is near the compression top dead center (0 deg. ATDC), and then gradually decreases.

[0059] Figure 5 is a graph showing the relationship between crank angle and mass-average temperature in the cylinder (combustion chamber) when the engine is operated in a low-temperature environment. Figure 5 shows the mass-average temperature in the cylinder for methanol and ethanol, as well as the mass-average temperature in the cylinder for air. The mass-average temperature in Figure 5 was calculated using measured values ​​of pressure in the cylinder.

[0060] As shown in Figure 5, whether the fuel is methanol or ethanol, the mass-average temperature gradually increases with the start of fuel injection, reaching its highest point when the crank angle is about -20 deg. ATDC, gradually decreasing as the crank angle approaches compression top dead center (0 deg. ATDC) from about -10 deg. ATDC, and then decreasing significantly after fuel injection ends. This change is due to the large latent heat of vaporization of methanol and ethanol.

[0061] As shown in Figure 5, when an engine is operated under the above-mentioned low-temperature conditions, the mass-average temperature in the cylinder is higher during the fuel injection period when methanol or ethanol is injected into the cylinder compared to timing other than the fuel injection period. The characteristics of the change in mass-average temperature that are specific to the use of fuel containing alcohol have a greater impact on the ignition ease of the fuel than the increase in the proportion of vaporized fuel after the end of fuel injection, as shown in Figure 4. Therefore, in this embodiment, it is estimated that better startability can be achieved by spark igniting the fuel during the fuel injection period compared to spark igniting the fuel at timing other than the fuel injection period.

[0062] Furthermore, when the fuel injection period is during the compression stroke, the pressure inside the cylinder during the fuel injection period is high as shown in Figure 3, the fuel is easily vaporized as shown in Figure 4, and the decrease in mass-average temperature due to the latent heat of vaporization is suppressed as shown in Figure 5. Therefore, by spark igniting the fuel during the fuel injection period, the effect of improving the startability of the engine can be more effectively achieved.

[0063] 3 to 5, during the retarded 1 / 3 of the fuel injection period, the pressure inside the cylinder is higher, the fuel is more likely to vaporize, and the decrease in mass-average temperature due to the latent heat of vaporization is suppressed, resulting in a higher mass-average temperature. Therefore, by spark-igniting the fuel during the retarded 1 / 3 of the fuel injection period, the effect of improving the startability of the engine becomes more pronounced.

[0064] Next, the relationship between the crank angle and the output when the engine is operated under the same operating conditions as in FIGS. 3 to 5 and spark ignition is performed at timings where the crank angle is varied by 5 degrees ATDC will be described. Figure 6 is a graph showing the relationship between the crank angle at which spark ignition occurs and the power output when the engine is operated in a low-temperature environment. The power output in Figure 6 was calculated based on the change in pressure inside the cylinder.

[0065] As shown in Figure 6, whether the fuel was methanol or ethanol, ignition was confirmed by spark ignition within the fuel injection period (methanol: -70 deg. ATDC to 0 deg. ATDC, ethanol: -50 deg. ATDC to 0 deg. ATDC), and good startability was obtained.

[0066] Figure 7 is a graph showing the relationship between the crank angle at which spark ignition occurred and the power output when the engine was operated in a low-temperature environment. Figure 7 shows an example under the same conditions as Figure 6, except that the fuel injection period for methanol was within the crank angle range of -80 deg. ATDC to -10 deg. ATDC, and the fuel injection period for ethanol was within the crank angle range of -60 deg. ATDC to -10 deg. ATDC. The power output in Figure 7 was measured using the same method as in Figure 6.

[0067] As shown in Figure 7, whether the fuel is methanol or ethanol, ignition was confirmed by spark ignition within the fuel injection period, even when fuel injection was terminated (10 deg. ATDC) before the crank angle reached compression top dead center (0 deg. ATDC), and good startability was achieved.

[0068] Returning to Fig. 2, after executing step S5, the control means 2 determines whether or not the fuel has ignited based on the change in pressure inside the cylinder 3a, calculates the number of consecutive cycles in which the fuel ignited (cycles in which the fuel ignited and combustion was achieved) (the number of ignitions), and determines whether or not the number of ignitions is equal to or less than a predetermined value (step S6). If the number of ignitions is equal to or less than the predetermined value, the process returns to step S5, and the control means 2 spark-ignites the fuel within the fuel injection period. On the other hand, if the number of ignitions exceeds the predetermined value, the control process by the control device of this embodiment ends.

[0069] In this embodiment, the control means 2 that executes step S5 determines whether or not the fuel has ignited based on the change in pressure inside the cylinder 3a, calculates the number of consecutive cycles in which the fuel has ignited (number of ignitions), and determines whether or not the number of ignitions is less than a predetermined value. However, the control means 2 may determine whether or not the fuel has ignited based on the change in the crank angle detected by the crank angle detection means 21, or may determine whether or not the fuel has ignited based on the change in pressure inside the cylinder 3a and the change in the crank angle.

[0070] In the control device of this embodiment, when the ambient temperature is equal to or lower than a predetermined value, the control means 2 spark-ignites the fuel during the fuel injection period in which the fuel containing alcohol is injected into the cylinder 3a. Therefore, even when the engine 3 in which the fuel containing alcohol is directly injected into the cylinder 3a is started in a low-temperature environment, good startability can be obtained.

[0071] In the above embodiment, as shown in FIG. 2, an example has been described in which steps S1 to S3 are executed in this order, but the order of steps S1 to S3 is not particularly limited. In the above-described embodiment, the control means 2 determines whether the ambient temperature, ie, the temperature of outside air and the temperature of engine water, are each equal to or lower than a predetermined value, and also determines whether the alcohol concentration in the fuel is equal to or higher than a predetermined value in step S4. However, the control means may determine whether the ambient temperature is equal to or higher than a predetermined value, and may determine, for example, whether either the ambient air temperature or the temperature of engine water is equal to or lower than a predetermined value. Therefore, as shown in Fig. 2, all of steps S1 to S3 may be executed, or it is sufficient to execute at least one of steps S1 and S2, and step S3 may not be executed.

[0072] In the above embodiment, the case where step S6 is executed is described as an example, as shown in Fig. 2, but the control process may be terminated without executing step S6. When the control process is terminated without executing step S6, the control process of the engine 3 shown in Fig. 2 may be repeatedly executed. [Explanation of symbols]

[0073] 2...control means, 3...engine, 3a...cylinder, 3b...piston, 3c...cylinder head, 3d...combustion chamber, 3e...crankshaft, 4...fuel injection device, 5...spark plug, 6...intake passage, 7...throttle valve, 7a...valve body, 7b...actuator, 20...ambient temperature detection means, 21...crank angle detection means, 22...outside air temperature detection means, 23...engine water temperature detection means, 24...alcohol concentration detection means.

Claims

1. A control device for a spark ignition internal combustion engine that directly injects fuel containing alcohol into a cylinder, comprising: a control means for controlling an injection timing at which the fuel is injected into the cylinder from a fuel injection device and an ignition timing at which the fuel in the cylinder is ignited by spark; an environmental temperature detection means for detecting an environmental temperature; The control device for an internal combustion engine, wherein the control means spark-ignites the fuel within a fuel injection period during which the fuel is injected into the cylinder when the environmental temperature is equal to or lower than a predetermined value.

2. the environmental temperature detecting means is an outside air temperature detecting means for detecting the temperature of outside air taken into the cylinder; an engine water temperature detecting means for detecting the temperature of engine water; The control device for an internal combustion engine according to claim 1 , wherein the environmental temperature is the temperature of the outside air and / or the temperature of the engine water.

3. 2. The control device for an internal combustion engine according to claim 1, wherein said control means spark-ignites said fuel within said fuel injection period when said environmental temperature is within a range of 5°C to -40°C.

4. an alcohol concentration detection means for detecting the alcohol content contained in the fuel; 2. The control device for an internal combustion engine according to claim 1, wherein the control means spark-ignites the fuel within the fuel injection period when the alcohol concentration in the fuel is equal to or greater than a predetermined value.

5. 5. The control device for an internal combustion engine according to claim 4, wherein the control means spark-ignites the fuel within the fuel injection period when the alcohol concentration in the fuel is 90% by volume or more.

6. a crank angle detecting means for detecting the rotation of the crankshaft and outputting a crank angle signal and a top dead center signal; 2. The control device for an internal combustion engine according to claim 1, wherein the control means injects the fuel from the fuel injection device into the cylinder during a compression stroke.

7. 2. The control device for an internal combustion engine according to claim 1, wherein said control means spark-ignites said fuel within a period that is one-third of the retard angle of said fuel injection period.

8. a cylinder pressure detecting means for detecting the pressure in the cylinder; 2. The control device for an internal combustion engine according to claim 1, wherein the control means determines whether the fuel has ignited based on a change in pressure inside the cylinder, and spark-ignites the fuel within the fuel injection period if the number of consecutive cycles in which the fuel has ignited is equal to or less than a predetermined value.

9. a crank angle detecting means for detecting the rotation of the crankshaft and outputting a crank angle signal; 2. The control device for an internal combustion engine according to claim 1, wherein the control means determines whether the fuel has ignited based on a change in crank angle, and spark-ignites the fuel within the fuel injection period when a number of consecutive cycles in which the fuel has ignited is equal to or less than a predetermined value.

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