JP2011132920A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accelerate vaporization of injected fuel even if a heater or the like is not used in an internal combustion engine using alcohol fuel. <P>SOLUTION: The internal combustion engine 10 includes an intake port injection valve 34 for injecting alcohol fuel toward a spray receiving wall 24a of an intake port 24. A hot water passage 44 supplied with hot water from a warmth keeping tank 46 is provided in the interior of the spray receiving wall 24a. At the starting of the internal combustion engine, the split injection control is performed to split and inject fuel of quantity to be burnt in one combustion stroke at two or more times separately. Thus, the split injection of fuel and the hot water passage 44 are combined to stably vaporize alcohol fuel in the intake port 24 even at the low-temperature starting. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that uses alcohol fuel.

  As a conventional technique, for example, as disclosed in Patent Document 1 (Japanese Utility Model Laid-Open No. 5-73255), fuel is injected toward the wall surface of the intake port by a fuel injection valve, and the injected fuel hits the inside of the wall surface. An internal combustion engine having a configuration in which an electric heater is installed is known. In the prior art, a space (or a recess) is provided inside the wall surface of the intake port, and a heater is disposed in this space. During cold operation or the like, while fuel injection is being performed, the heater is energized to heat the wall surface to promote vaporization of the injected fuel.

Japanese Utility Model Publication No. 5-73255

  In the prior art, a cooling water passage is provided in a cylinder block of the internal combustion engine so as to surround a cylinder bore (combustion chamber). The cooling water passage has a function of cooling the combustion chamber with the cooling water flowing through the passage and transferring heat generated in the combustion chamber to each part of the engine. However, in the conventional technology, since a space for heater placement is provided in the wall surface of the intake port, heat transfer from the cooling water passage to the intake port is hindered by this space, and the intake port is warmed during cold operation. The machine may be delayed. In addition, when a heater is used to avoid this problem, it is necessary to energize the heater even after the normal warm-up is completed, and there is a problem that the power consumption of the heater increases and the fuel consumption deteriorates. .

  The present invention has been made to solve the above-described problems, and an object of the present invention is to promote vaporization of injected fuel in an internal combustion engine using alcohol fuel without using a heater or the like. An object of the present invention is to provide a control device for an internal combustion engine that can perform the above-described operation.

A first aspect of the invention is an intake port injection valve that is provided in an intake port of an internal combustion engine and injects fuel containing an alcohol component toward a wall surface of the intake port.
A hot water passage which is provided inside the wall surface of the intake port at a position where fuel injected from the intake port injection valve hits, and hot water is supplied;
A split injection control means for splitting and injecting an amount of fuel to be burned in a single combustion stroke when the fuel is injected from the intake port injection valve;
It is characterized by providing.

  According to a second aspect of the present invention, there is provided a division number variable means for variably setting the number of times the fuel injection is divided by the divided injection control means based on the temperature of the internal combustion engine and the alcohol concentration in the fuel.

  The third invention is configured to include a spray range control means for narrowing the spray range of the fuel injected from the intake port injection valve as the alcohol concentration in the fuel is higher.

4th invention, the heat retention tank which can store warm water in a heat retention state,
Preheat control means for supplying hot water from the heat retaining tank to the hot water passage at least before starting the internal combustion engine;
It is set as the structure provided with.

5th invention, the water temperature adjustment means which can adjust the temperature of the cooling water of an internal combustion engine,
Water temperature control means for increasing the temperature of the cooling water by the water temperature adjusting means as the alcohol concentration in the fuel increases,
Cooling water whose temperature is controlled by the water temperature control means, hot water intake control means for taking in the heat retaining tank as warm water,
It is set as the structure provided with.

  6th invention is set as the structure provided with the warm water guide which concentrates the warm water which flows in the said warm water channel | path in the vicinity of the said intake port.

A seventh aspect of the invention is a cylinder injection valve that injects fuel into a cylinder of an internal combustion engine;
Injection ratio control means for increasing the ratio of the fuel injection amount of the intake port injection valve to the fuel injection amount of the in-cylinder injection valve as the alcohol concentration in the fuel is higher;
It is set as the structure provided with.

  According to the first invention, even before the internal combustion engine is warmed up, by supplying warm water to the warm water passage, it is possible to warm the portion of the wall surface of the intake port where the injected fuel hits, thereby promoting fuel vaporization. can do. Therefore, the wall surface of the intake port can be kept at a high temperature without using extra power by the heater, and fuel consumption can be improved. In the present invention, since a structure such as a heater is not disposed on the heat transfer path from the combustion chamber side to the intake port, the intake air is absorbed by the heat generated on the combustion chamber side after the internal combustion engine is warmed up. The port can be warmed up quickly. Moreover, according to the split injection control means, even when alcohol fuel that is hard to vaporize is used, the fuel that has already been injected can be gradually vaporized by the heat transmitted from the hot water passage while being injected little by little. Accordingly, by combining the fuel split injection and the hot water passage, the alcohol fuel can be stably vaporized in the intake port even at a low temperature start.

  According to the second aspect of the invention, the dividing number variable means increases the dividing number of the fuel injection as the injected fuel is less likely to vaporize, such as when the alcohol concentration in the fuel is high or at a low temperature. it can. Thereby, fuel can be injected little by little and vaporization of fuel can be promoted.

  According to the third aspect, the spray range control means can narrow the spray range of the fuel injected from the intake port injection valve, for example, by reducing the fuel injection pressure. Thereby, the fuel spray can be concentrated on the portion of the wall surface of the intake port where heat is more easily transmitted from the hot water passage as the fuel is more difficult to vaporize. Therefore, when the alcohol concentration in the fuel is high or at a low temperature, the spread of fuel spray can be suppressed and the injected fuel can be efficiently warmed right above the hot water passage.

  According to the fourth invention, the preheat control means can supply hot water from the heat retaining tank to the hot water passage at least before starting the internal combustion engine, and keeps the portion of the wall surface of the intake port where the injected fuel hits at a high temperature. can do. As a result, the alcohol fuel can be stably vaporized in the intake port even at a low temperature start.

  According to the fifth aspect of the invention, a fuel with a high alcohol concentration has a high octane number and thus has excellent knock resistance, and at the time of combustion, knocking hardly occurs even at a relatively high temperature. By utilizing this characteristic, when the alcohol concentration in the fuel is high, the control water temperature after warm-up can be increased without causing knocking. And since the cooling water which became high temperature by this temperature control can be stored in a heat retention tank, a high temperature warm water can be supplied to a warm water channel | path from a heat retention tank at the time of the next start. Thereby, sufficient hot water can be secured, and the intake port can be warmed up smoothly.

  According to the sixth aspect, the hot water guide can concentrate the hot water flowing in the hot water passage in the vicinity of the intake port. Thereby, the wall surface of an intake port can be warmed efficiently.

  According to the seventh invention, the injection ratio control means increases the ratio of the fuel injection amount of the intake port injection valve to the fuel injection amount of the in-cylinder injection valve (port injection ratio) in a situation where the injected fuel is difficult to vaporize. be able to. As a result, the amount of fuel injected into the cylinder, where the injected fuel is difficult to vaporize, can be relatively reduced. On the other hand, the fuel injection amount to the intake port can be increased, and this fuel can be quickly warmed by the heat transmitted from the hot water passage to the wall surface of the intake port. Therefore, vaporization of the injected fuel can be promoted even in a dual injection type internal combustion engine.

It is a whole block diagram for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is an enlarged view which expands and shows the cylinder head in FIG. It is explanatory drawing which looked at the cooling water path provided in the cylinder head from the upper side. FIG. 4 is a cross-sectional view of a hot water passage 44 broken along a cross section A in FIG. 3. In preheat control, it is a characteristic diagram for determining preheat time based on the water temperature at the time of starting, and the alcohol concentration in fuel. FIG. 6 is a characteristic diagram for determining the number of fuel split injections based on the water temperature at the start and the alcohol concentration in the fuel in the split injection control. In Embodiment 1 of this invention, it is a flowchart of the control performed by ECU. It is explanatory drawing which shows the relationship between the injection pressure of fuel, and the spray range. FIG. 5 is a characteristic diagram for determining the fuel injection pressure based on the water temperature at the start and the alcohol concentration in the fuel in spray range control. In Embodiment 2 of this invention, it is a flowchart of the control performed by ECU. It is a block diagram for demonstrating the system configuration | structure of Embodiment 3 of this invention. In hot water intake control, it is a characteristic diagram for determining control water temperature based on the alcohol concentration in fuel. In Embodiment 3 of this invention, it is a flowchart of the control performed by ECU. It is a whole block diagram for demonstrating the system configuration | structure of Embodiment 4 of this invention. In injection ratio control, it is a characteristic diagram for determining a port injection ratio based on the water temperature at the time of starting and the alcohol concentration in fuel. In Embodiment 4 of this invention, it is a flowchart of the control performed by ECU.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is an overall configuration diagram for explaining a system configuration according to the first embodiment of the present invention. The system of the present embodiment includes a multi-cylinder internal combustion engine 10 that uses alcohol fuel. The internal combustion engine 10 includes a cylinder block 12 in which a cylinder bore for each cylinder is formed, and a cylinder head 14 mounted on the cylinder block 12. Each cylinder of the internal combustion engine 10 is provided with a combustion chamber 18 that expands and contracts by the reciprocating motion of the piston 16, and the piston 16 is connected to the crankshaft 20.

  The internal combustion engine 10 also includes an intake passage 22 that sucks intake air into each cylinder. The intake passage 22 is connected to the combustion chamber 18 of each cylinder via an intake manifold constituting a part of the intake passage 22 and an intake port 24 provided in the cylinder head 14. The intake passage 22 is provided with an air flow meter 26 for detecting the intake air amount and an electronically controlled throttle valve 28 for increasing or decreasing the intake air amount. On the other hand, the internal combustion engine 10 includes an exhaust passage 30 through which exhaust gas flows, and the exhaust passage 30 is connected to the combustion chamber 18 of each cylinder via an exhaust port 32 and the like. Each cylinder has an intake port injection valve 34 for injecting fuel into the intake port 24, an ignition plug 36 for igniting an air-fuel mixture in the cylinder, and an intake air for opening and closing the intake port 24 with respect to the cylinder. A valve 38 and an exhaust valve 40 for opening and closing the exhaust port 32 with respect to the inside of the cylinder are provided.

  Further, the internal combustion engine 10 includes a cooling water passage 42 and a hot water passage 44. The cooling water passage 42 is provided inside the cylinder block 12 and the cylinder head 14, and circulates the cooling water between a radiator (not shown) attached to the internal combustion engine 10 and the like. On the other hand, the warm water passage 44 is provided inside the cylinder head 14 and circulates warm water between the warm water tank 46 (see FIG. 2) attached to the internal combustion engine 10. Details of the hot water passage 44 and the heat retaining tank 46 will be described later. The internal combustion engine 10 also includes a fuel pressure variable mechanism 48 that variably sets the pressure of the fuel supplied from the fuel tank (not shown) to the intake port injection valve 32. The variable fuel pressure mechanism 48 is configured by a generally known mechanism including a fuel pump, a pressure regulator, and the like. The variable fuel pressure mechanism 48 can change the injection pressure of the fuel injected from the intake port injection valve 34 to a desired value based on a control signal input from the ECU 60 described later.

  Furthermore, the system of the present embodiment includes a sensor system including a crank angle sensor 50, a water temperature sensor 52, an alcohol concentration sensor 54, and the like, and an ECU (Electronic Control Unit) 60 that controls the operating state of the internal combustion engine 10. Yes. The crank angle sensor 50 outputs a signal synchronized with the rotation of the crankshaft 20, and the ECU 60 can detect the engine speed and the crank angle based on this output. The water temperature sensor 52 detects the temperature of the cooling water, and the alcohol concentration sensor 54 detects the alcohol concentration in the fuel.

  In addition to the air flow meter 26 and the sensors 50 to 54, the sensor system includes various sensors necessary for control of the vehicle and the internal combustion engine (for example, an accelerator opening sensor for detecting an accelerator opening, an air sensor for detecting an exhaust air-fuel ratio). Fuel ratio sensors and the like), and these sensors are connected to the input side of the ECU 60. Various actuators including the throttle valve 28, the intake port injection valve 34, the spark plug 36, the fuel pressure variable mechanism 48, and the like are connected to the output side of the ECU 60. The ECU 60 drives each actuator while detecting the operating state of the internal combustion engine using a sensor system. Specifically, the fuel injection amount, the injection timing, and the ignition timing are set based on the output of the sensor system, and each actuator is driven according to these setting contents. The control of the ECU 60 includes preheat control and split injection control which will be described later.

[Features of Embodiment 1]
Next, a structure related to the hot water passage 44 will be described with reference to FIGS. 2 and 3. FIG. 2 is an enlarged view showing the cylinder head in FIG. 1 in an enlarged manner, and FIG. 3 is an explanatory view of a coolant passage provided in the cylinder head as viewed from the upper side. In FIG. 2, the valves 38 and 40 are not shown.

  First, in the present embodiment, as shown in FIG. 2, an intake port injection valve 34 that injects alcohol fuel is provided in the intake port 24, and the intake port injection valve 34 faces the wall surface of the intake port 24. And is configured to inject fuel. In the following description, a portion of the wall surface of the intake port 24 where the fuel injected from the intake port injection valve 34 hits is referred to as a spray receiving wall 24a. Inside the cylinder head 14, there is provided a hot water passage 44 that passes through the vicinity of the back surface side (lower side) of the spray receiving wall 24a. The hot water passage 44 is provided with an inlet 44 a that opens to the intake manifold side of the cylinder head 14, and the inlet 44 a is connected to the heat retaining tank 46. The hot water passage 44 is supplied with hot water from the heat retaining tank 46 through the inlet 44a. The warm water can efficiently warm the intake port 24 (spray receiving wall 24a) of each cylinder.

  Further, as shown in FIG. 3, the hot water passage 44 branches from the inlet 44 a and extends to the lower side of the intake port 24 (spray receiving wall 24 a) of each cylinder. FIG. 4 is a cross-sectional view of the hot water passage 44 broken along the cross-section A in FIG. 3. As shown in this figure, a plurality of hot water guides 44 b are provided in the hot water passage 44. These hot water guides 44b are formed as elongated plate-like ribs, and project from the peripheral wall of the hot water passage 44 toward the inside of the passage. In addition, at least a part of the hot water guide 44 b is provided upright on both sides of the intake port 24 of each cylinder and extends along the length direction of the intake port 24. Thereby, the hot water guide 44b concentrates the warm water flowing in the hot water passage 44 in the vicinity of the intake port 24, and can efficiently warm the spray receiving wall 24a.

  On the other hand, the heat retaining tank 46 is constituted by a heat retaining container capable of storing warm water in a heat retaining state, and includes a pump (not shown) that circulates warm water between the warm water passage 44 and the like. The water stored in the heat retaining tank 46 is heated by heat generated in the combustion chamber or the like during operation of the internal combustion engine, and becomes warm water. This warm water is kept warm by the heat retaining tank 46 even after the engine is stopped, and is supplied to the warm water passage 44 by preheating control described later when the engine is restarted.

  Next, preheat control and split injection control will be described. In the present embodiment, a fuel containing an alcohol component such as ethanol (alcohol fuel) is used as the fuel for the internal combustion engine 10. However, alcohol fuel is less likely to vaporize than gasoline, and therefore, particularly during cold start. It is difficult to form a good mixture. Therefore, in the present embodiment, preheat control and split injection control are executed to promote the vaporization of the injected fuel.

(Preheat control)
In the preheat control, warm water is supplied from the heat retaining tank 46 to the warm water passage 44 at least before the internal combustion engine is started (for example, a period from when the ignition switch is turned on to when the starter is started). The spray receiving wall 24a is heated. The fuel injected from the intake port injection valve 32 adheres to the spray receiving wall 24 a of the intake port 24. Therefore, vaporization of the injected fuel can be promoted by warming the spray receiving wall 24a.

  Further, the time (preheat time) Tp for continuing the preheat control is variably set based on the engine temperature at the start (for example, cooling water temperature) and the alcohol concentration in the fuel. FIG. 5 is a characteristic diagram for determining the preheating time based on the water temperature at the start and the alcohol concentration in the fuel in the preheating control. Note that “E100”, “E50”, and “E0” described in FIG. 5 exemplify cases where the alcohol concentration (ethanol concentration) in the fuel is 100%, 50%, and 0%, respectively. Since the injected fuel is difficult to vaporize when the alcohol concentration in the fuel is high, the preheat time Tp is set to a longer time as the alcohol concentration in the fuel is higher, as shown in FIG. Further, when the engine temperature at the start is high, the injected fuel is easily vaporized by that amount. Therefore, the preheat time Tp is set to a shorter time as the engine temperature (cooling water temperature) at the start is higher. According to this configuration, the preheat time Tp can be appropriately set according to the ease of vaporization of the injected fuel.

  Here, the effect of the preheat control using warm water will be described. First, in an internal combustion engine using alcohol fuel, it is difficult to achieve both startability and exhaust emission. This is because fuel with a high alcohol concentration has poor volatility at low temperatures, and in order to ensure startability, it is necessary to inject a large amount of fuel at the start, which tends to deteriorate exhaust emissions. Heating the fuel is effective to solve this problem, but if it is attempted to heat the fuel in a short time using a heater or the like, the heating equipment becomes large and difficult to mount on the vehicle, and the cost increases. . Further, when the intake port is heated by the heater as in the prior art, the wall surface of the intake port is cooled by the vaporization of the injected fuel when the heater is stopped. As a result, the amount of fuel adhering to the wall surface of the intake port increases even after the engine is warmed up, and the adhering fuel is vaporized, so that excessive fluctuation (roughness) of the air-fuel ratio is likely to occur. In order to avoid this, it is necessary to lengthen the heating time by the heater.

  On the other hand, in the preheat control, even when the spray receiving wall 24a is cooled by the vaporization of fuel, the spray receiving wall 24a can be continuously heated by the high thermal energy supplied from the hot water. Therefore, even before the internal combustion engine is warmed up, the spray receiving wall 24a can be kept at a high temperature without using extra power by the heater, and the air-fuel ratio can be stabilized by suppressing the amount of fuel wall surface adhesion. Can do. In addition, since heating equipment using a heater and power consumption thereof are not required, fuel consumption can be improved, and vehicle downsizing and cost reduction can be promoted.

  Furthermore, in the prior art, a structure such as a heater or a space in which the heater is disposed is provided at a position corresponding to the spray receiving wall 24a of the present embodiment. These structures become a factor that inhibits heat generated on the combustion chamber side after the internal combustion engine is warmed up from being transmitted to the intake port. In contrast, in the present embodiment, since it is not necessary to arrange these structures on the heat transfer path, the heat generated on the combustion chamber 18 side is efficiently transferred to the intake port 24 after the internal combustion engine is warmed up. Therefore, the intake port 24 can be warmed up quickly.

(Split injection control)
In the case of injecting alcohol fuel, if fuel injection is continuously performed under conditions such as low temperatures at which the injected fuel is difficult to vaporize, the liquid film of fuel attached to the spray receiving wall 24a tends to be thick. In the state where the liquid film of the fuel is thick, even if the spray receiving wall 24a is heated, it becomes difficult for heat to be transmitted to the surface layer side of the liquid film, and the vaporization of the fuel is delayed. On the other hand, when the adhesion area of the injected fuel is increased in order to avoid this state, the fuel adheres to a position away from the spray receiving wall 24a, which makes it difficult for the fuel to vaporize. These problems can be solved by split injection control.

  That is, in the split injection control, the amount of fuel burned in one combustion stroke is divided and injected into a plurality of times, so that the fuel injection amount by each injection operation can be reduced. Thus, while the fuel is injected little by little, the already injected fuel can be gradually vaporized by the heat transmitted from the hot water passage 44. Therefore, it is possible to avoid an increase in the liquid film of the fuel without increasing the adhesion area of the injected fuel, and to promote the vaporization of the fuel. As described above, by combining the hot water passage 44 and the divided fuel injection, the alcohol fuel can be stably vaporized in the intake port 24 even at a low temperature start.

  FIG. 6 is a characteristic diagram for determining the number of fuel split injections based on the water temperature at the start and the alcohol concentration in the fuel in the split injection control. 5 and 6 exemplify the ethanol concentration as the alcohol concentration in the fuel, the present invention is not limited to the ethanol fuel, but can be applied to other alcohol fuels including methanol and the like. The data described in FIGS. 5 and 6 is stored in advance in the ECU 60. In the divided injection control, as shown in FIG. 6, the number of times fns for dividing the fuel injection is variably set based on the engine temperature at the start and the alcohol concentration in the fuel. Specifically, the fuel injection division frequency fns is increased as the alcohol concentration in the fuel is higher and the engine temperature at the start is lower. According to this configuration, the more difficult the vaporization of the injected fuel is, the more the number of divisions fns can be increased, and the fuel can be injected little by little, and the vaporization of the fuel can be promoted.

[Specific Processing for Realizing Embodiment 1]
FIG. 7 is a flowchart of control executed by the ECU in the first embodiment of the present invention. The routine shown in this figure is repeatedly executed during operation of the internal combustion engine. In the routine shown in FIG. 7, it is first determined whether or not the ignition switch (start S / W) is turned on (step 100).

  When the above determination is made, as described above, the preheat time Tp is calculated based on the water temperature at the time of start detected by the water temperature sensor 52 and the alcohol concentration (ethanol concentration) in the fuel detected by the alcohol concentration sensor 54. In addition, the number of divisions fns of fuel injection at start-up is calculated (step 102). Then, preheat control is executed (step 104). Next, it is determined whether or not the preheat time Tp has elapsed by measuring the elapsed time since execution of the preheat control (step 106). When this determination is satisfied, the internal combustion engine is started (step 108). Then, the divided injection control is executed using the divided injection frequency fns obtained in step 102 (step 110).

  In the first embodiment described above, step 110 in FIG. 7 shows a specific example of the split injection control means. Step 102 shows a specific example of the division number variable means, and Step 104 shows a specific example of the preheat control means.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. Although the present embodiment employs the same system configuration (FIG. 1) as that of the first embodiment, the configuration described below differs from the first embodiment in the control described below. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 2]
In the present embodiment, the spray range control is performed to change the fuel spray range in accordance with the alcohol concentration in the fuel. FIG. 8 is an explanatory diagram showing the relationship between the fuel injection pressure and the spray range. As shown in this figure, the fuel spray range becomes narrower as the injection pressure is lower. Therefore, in the spray range control, as the alcohol concentration in the fuel is higher, the fuel injection pressure is lowered by the fuel pressure variable mechanism 48 to narrow the fuel spray range. Thereby, the fuel spray is more concentrated in the central portion of the spray receiving wall 24a (the central high-temperature portion where heat is easily transmitted from the hot water passage 44 in the spray receiving wall 24a) as the fuel is more difficult to vaporize. Can do. Therefore, when the alcohol concentration in the fuel is high or at a low temperature, the spread of the fuel spray can be suppressed, and the injected fuel can be efficiently warmed at the center of the spray receiving wall 24a (directly above the hot water passage 44). Vaporization can be promoted.

  FIG. 9 is a characteristic diagram for determining the fuel injection pressure based on the water temperature at the start and the alcohol concentration in the fuel in the spray range control. The data described in this figure is stored in the ECU 60 in advance. In the spray range control, as shown in FIG. 9, the fuel injection pressure fps is set higher as the alcohol concentration in the fuel is higher and as the engine temperature (water temperature) at the start is lower. Thus, in the spray range control, the spray range can be appropriately controlled by changing the fuel injection pressure based on the water temperature at the start and the alcohol concentration in the fuel.

[Specific Processing for Realizing Embodiment 2]
FIG. 10 is a flowchart of control executed by the ECU in the second embodiment of the present invention. The routine shown in FIG. 10 is repeatedly executed during operation of the internal combustion engine in parallel with the routine described in the first embodiment (FIG. 7).

  In the routine shown in FIG. 10, it is first determined whether or not the ignition switch is turned on (step 200). When this determination is established, the preheat time Tp is calculated based on the water temperature at the start and the alcohol concentration in the fuel as in the first embodiment. Further, based on these water temperature and alcohol concentration, the injection pressure fps for starting fuel injection is calculated (step 202). Then, preheat control is executed (step 204).

  Next, it is determined whether or not the preheat time Tp has elapsed (step 206). When this determination is established, the internal combustion engine is started while maintaining the injection pressure fps by the variable fuel pressure mechanism 48 (steps 208 and 210). . In the second embodiment described above, step 208 in FIG. 10 shows a specific example of the spray range control means.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIGS. In this embodiment, in addition to the system configuration (FIG. 1) similar to that of the first embodiment, a hot water intake mechanism is employed, and the configuration is different from that of the first embodiment in this respect. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 3]
FIG. 11 is a configuration diagram for explaining a system configuration according to the third embodiment of the present invention. As shown in this figure, the system of the present embodiment includes a variable thermo 70 and a hot water intake mechanism 72. The variable thermo 70 constitutes the water temperature adjusting means of the present embodiment, and adjusts the cooling water temperature of the internal combustion engine to a desired temperature in accordance with a control signal input from the ECU 60. The hot water intake mechanism 72 is a mechanism for taking cooling water from the cooling water passage 42 into the heat retaining tank 46, and this taking operation is controlled by the ECU 60. The hot water intake mechanism 72 includes a hot water intake passage connected between the cooling water passage 42 and the heat retaining tank 46, a passage opening / closing valve for opening and closing the hot water intake passage, and an opening of the passage opening / closing valve. A pump (none of which is shown) for supplying cooling water from the cooling water passage 42 to the heat retaining tank 46 at the time of the valve is provided.

  In the present embodiment, hot water intake control for taking the cooling water in the cooling water passage 42 into the heat retaining tank 46 as hot water is performed. More specifically, in the hot water intake control, the higher the alcohol concentration in the fuel, the higher the temperature of the cooling water is controlled by the variable thermo 70, and this hot cooling water is taken into the heat retaining tank 46 by the hot water intake mechanism 72. It is configured to include. FIG. 12 is a characteristic diagram for determining the control water temperature based on the alcohol concentration in the fuel in the hot water intake control. The data shown in this figure is stored in the ECU 60 in advance.

  The control water temperature thwe shown in FIG. 12 is the temperature of the cooling water maintained by the temperature adjustment function of the variable thermo 70. The control water temperature thwe is set to a higher temperature as the alcohol concentration in the fuel is higher. The ECU 60 controls the variable thermo 70 based on the output of the water temperature sensor 52 and performs feedback control so that the actual cooling water temperature matches the control water temperature thwe. When the cooling water temperature becomes equal to or higher than the control water temperature thwe, the cooling water is caused to flow into the heat retaining tank 46 by operating the hot water intake mechanism 72.

  According to the warm water uptake control described above, the following effects can be obtained. A fuel with a high alcohol concentration has a high octane number and is therefore excellent in knock resistance. During combustion, it is difficult for knocking to occur even at a relatively high temperature. By utilizing this characteristic, when the alcohol concentration in the fuel is high, the control water temperature after warm-up can be increased without causing knocking. And since the cooling water which became high temperature by this temperature control can be stored in the heat retention tank 46, high temperature warm water can be supplied from the heat retention tank 46 to the warm water passage 44 at the next start-up. Thereby, sufficient hot water can be secured, and the intake port 24 can be warmed up smoothly.

[Specific Processing for Realizing Embodiment 3]
FIG. 13 is a flowchart of the control executed by the ECU in the third embodiment of the present invention. The routine shown in FIG. 13 is repeatedly executed during the operation of the internal combustion engine in parallel with the routine described in the first embodiment (FIG. 7).

  In the routine shown in FIG. 13, first, the control water temperature thwe corresponding to the alcohol concentration is calculated by referring to the data of FIG. 12 based on the alcohol concentration in the fuel (step 300). Then, by operating the variable thermo 70, the water temperature is controlled so that the temperature of the cooling water becomes the control water temperature thwe (step 302).

  In the next process, it is determined whether or not the actual water temperature detected by the water temperature sensor 52 is equal to or higher than the control water temperature thwe (step 304). When this determination is established, the cooling water is taken into the heat retaining tank 46 by the hot water taking mechanism 72 (step 306). In the third embodiment described above, step 302 in FIG. 13 shows a specific example of the water temperature control means, and step 306 shows a specific example of the hot water intake control means.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIGS. In this embodiment, the present invention is applied to a dual injection type internal combustion engine having an intake port injection valve and an in-cylinder injection valve. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 4]
FIG. 14 is an overall configuration diagram for explaining a system configuration according to the fourth embodiment of the present invention. As shown in this figure, the internal combustion engine 80 includes an in-cylinder injection valve 82 that injects fuel into the cylinder in addition to the intake port injection valve 34. Then, the ECU 60 determines the total injection amount of fuel injected from both the injection valves 34 and 82 according to the intake air amount, the engine temperature, and the like. Further, the ECU 60 variably sets the ratio of the fuel injection amount of the intake port injection valve 34 to the fuel injection amount of the in-cylinder injection valve 82 (hereinafter referred to as a port injection ratio) in accordance with the operating state of the internal combustion engine. The injection valves 34 and 82 are driven based on the setting of the port injection ratio. Further, the ECU 60 is configured to perform the following injection ratio control.

  FIG. 15 is a characteristic diagram for determining the port injection ratio based on the water temperature at the start and the alcohol concentration in the fuel in the injection ratio control. The data shown in this figure is stored in advance in the ECU 60. As shown in FIG. 15, in the injection ratio control, the port injection ratio is increased as the alcohol concentration in the fuel is higher and as the engine temperature (water temperature) at the start is lower. This is due to the following reason. In the in-cylinder injection, the time from when the fuel is injected to when the mixture is ignited (that is, the time that can be spent for vaporizing the injected fuel) is shorter than that of the intake port injection. For this reason, when the alcohol concentration in the fuel is high or when the injected fuel is difficult to vaporize, such as at low temperatures, the fuel injection amount of the intake port injection valve 34 is increased and the fuel injection amount of the in-cylinder injection valve 82 is increased. It is preferable to reduce as much as possible.

  According to the injection ratio control, in a situation where the injected fuel is difficult to vaporize, the port injection ratio can be increased, and the amount of fuel injected into the cylinder where the injected fuel is difficult to vaporize can be relatively reduced. On the other hand, the amount of fuel injected into the intake port can be increased, and this fuel can be quickly warmed by the spray receiving wall 24a (hot water passage 44) of the intake port 24 as described above. Therefore, according to the present embodiment, vaporization of the injected fuel can be promoted even in the dual injection type internal combustion engine.

[Specific processing for realizing Embodiment 4]
FIG. 16 is a flowchart of control executed by the ECU in the fourth embodiment of the present invention. The routine shown in FIG. 16 is repeatedly executed during operation of the internal combustion engine in parallel with the routine described in the first embodiment (FIG. 7).

  In the routine shown in FIG. 16, it is first determined whether or not the ignition switch is turned on (step 400). When this determination is established, the preheat time Tp is calculated based on the water temperature at the start and the alcohol concentration in the fuel as in the first embodiment. Further, the port injection ratio (P / d4) at the start is calculated based on these water temperature and alcohol concentration (step 402). Then, preheat control is executed (step 404).

  Next, it is determined whether or not the preheat time Tp has passed (step 406). When this determination is satisfied, an amount of fuel corresponding to the port injection ratio is injected from the intake port injection valve 34 and the cylinder injection valve 82, respectively. At the same time, the internal combustion engine is started (steps 408 and 410). In the fourth embodiment described above, steps 402 and 410 in FIG. 16 show a specific example of the injection ratio control means. As described above, according to the fourth embodiment, even in a dual injection type internal combustion engine using alcohol fuel, both startability and exhaust emission can be achieved.

  In the second, third, and fourth embodiments, the case where the configurations of the second, third, and fourth embodiments are combined with the configuration of the first embodiment is illustrated. However, the present invention is not limited to this, and for example, any two configurations of the second, third, and fourth embodiments, or all three configurations may be combined with the first embodiment.

  In the embodiment, the case where the temperature of the cooling water detected by the water temperature sensor 52 is used as the engine temperature is exemplified. However, the present invention is not limited to this, and the engine temperature may be, for example, the temperature of the lubricating oil detected by an oil temperature sensor. In addition to the oil temperature, various temperatures reflecting the temperature state of the internal combustion engine can be used.

10, 80 Internal combustion engine 12 Cylinder block 14 Cylinder head 16 Piston 18 Combustion chamber 20 Crankshaft 22 Intake passage 24 Intake port 24a Spray receiving wall 26 Air flow meter 28 Throttle valve 30 Exhaust passage 32 Exhaust port 34 Intake port injection valve 36 Ignition plug 38 Intake valve 40 Exhaust valve 42 Cooling water passage 44 Hot water passage 44a Inlet 44b Hot water guide 46 Thermal insulation tank 48 Fuel pressure variable mechanism 50 Crank angle sensor 52 Water temperature sensor 54 Alcohol concentration sensor 60 ECU
70 Variable thermo (water temperature adjustment means)
72 Hot water intake mechanism 82 In-cylinder injection valve

Claims (7)

An intake port injection valve that is provided in an intake port of an internal combustion engine and injects fuel containing an alcohol component toward the wall surface of the intake port;
A hot water passage which is provided inside the wall surface of the intake port at a position where fuel injected from the intake port injection valve hits, and hot water is supplied;
A split injection control means for splitting and injecting an amount of fuel to be burned in a single combustion stroke when the fuel is injected from the intake port injection valve;
A control device for an internal combustion engine, comprising:   2. The internal combustion engine control according to claim 1, further comprising division number variable means for variably setting the number of times the fuel injection is divided by the divided injection control means based on the temperature of the internal combustion engine and the alcohol concentration in the fuel. apparatus.   3. The control apparatus for an internal combustion engine according to claim 1, further comprising spray range control means for narrowing a spray range of the fuel injected from the intake port injection valve as the alcohol concentration in the fuel is higher. A heat retaining tank capable of storing warm water in a heat retaining state;
Preheat control means for supplying hot water from the heat retaining tank to the hot water passage at least before starting the internal combustion engine;
The control apparatus for an internal combustion engine according to any one of claims 1 to 3, further comprising: Water temperature adjusting means capable of adjusting the temperature of the cooling water of the internal combustion engine;
Water temperature control means for increasing the temperature of the cooling water by the water temperature adjusting means as the alcohol concentration in the fuel increases,
Cooling water whose temperature is controlled by the water temperature control means, hot water intake control means for taking in the heat retaining tank as warm water,
The control apparatus for an internal combustion engine according to claim 4, comprising:   The control device for an internal combustion engine according to any one of claims 1 to 5, further comprising a hot water guide for concentrating hot water flowing in the hot water passage in the vicinity of the intake port. An in-cylinder injection valve for injecting fuel into the cylinder of the internal combustion engine;
Injection ratio control means for increasing the ratio of the fuel injection amount of the intake port injection valve to the fuel injection amount of the in-cylinder injection valve as the alcohol concentration in the fuel is higher;
The control device for an internal combustion engine according to any one of claims 1 to 6, further comprising:

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