JP2009137364A - Control device for internal combustion engine - Google Patents

Abstract

Provided is a control device for an internal combustion engine capable of suppressing the generation of deposits and the change of fuel into a gum-like state even when a fuel containing a large amount of high-boiling components and gum components is used.
SOLUTION: A fuel property determination device 50 for determining the property of fuel supplied to an engine 10 and a scavenging operation by forcibly rotating the engine 10 when the fuel supply to the engine 10 is stopped. The ECU 100 executes the intake air flow rate control that increases the flow velocity of the intake air flowing into the engine 10 during the scavenging operation according to the determination result of the fuel property determination device 50.
[Selection] Figure 4

Description

  The present invention relates to a control device for an internal combustion engine.

  Patent Document 1 is characterized in that after the internal combustion engine is stopped, the internal combustion engine is driven by power other than the internal combustion engine in a state where fuel injection is cut off, and the exhaust system is scavenged by the sucked external air. The technology is disclosed.

Japanese Patent Laid-Open No. 4-50415

  By the way, in an internal combustion engine, unburnt fuel adhering to an intake valve and an intake port is generally steamed by ambient temperature and easily deposited as a deposit. When such deposits accumulate on the intake valves, various adverse effects are exerted on the operation of the internal combustion engine. In the worst case, the unburned fuel adhering to the vicinity of the intake valve or the intake port is changed into a gum-like state, and the intake valve is fixed to the intake port. Such a situation is more likely to occur when a poor fuel containing a large amount of high-boiling components or gum components is used.

  Accordingly, an object of the present invention is to provide a control device for an internal combustion engine that can suppress the generation of deposits and the change of fuel into a gum-like state even when a fuel containing a large amount of high-boiling components and gum components is used. To do.

  The object is to perform a scavenging operation by forcibly rotating the internal combustion engine when fuel supply to the internal combustion engine is stopped, and fuel property determination means for determining the property of the fuel supplied to the internal combustion engine Scavenging means for executing the intake air flow rate control means for executing the intake air flow rate control for increasing the flow speed of the intake air flowing into the internal combustion engine during the scavenging operation according to the determination result of the fuel property determining means. This can be achieved by a control device for an internal combustion engine.

  With this configuration, the flow rate of the intake air can be increased during the scavenging operation, so that unburned fuel and deposits attached to the intake valve and the intake port can be blown away. In addition, when the fuel property determination result indicates that the fuel contains a large amount of high boiling point components, gum components, etc., by performing intake air flow rate control, deposit accumulation and intake air to the intake port are performed. It is possible to effectively prevent the valve from being fixed.

  In the above configuration, a variable valve mechanism capable of changing a valve opening characteristic of at least one of the intake valve and the exhaust valve is provided, and the intake flow rate control means executes the intake flow rate control by controlling the variable valve mechanism. The configuration can be adopted. Thereby, the intake flow velocity can be increased.

  In the above configuration, a supercharger that can be driven by a motor is provided, and the intake control unit can drive the supercharger during execution of the scavenging operation. By driving the supercharger during the scavenging operation, the intake flow velocity can be increased.

  In the above configuration, the port injection valve that injects fuel into the intake port of the internal combustion engine, the in-cylinder injection valve that injects fuel directly into the cylinder of the internal combustion engine, and the injection from the port injection valve and the in-cylinder injection valve, respectively. Fuel injection control means capable of controlling the amount of fuel injection to be performed, and when the fuel injection control means stops supplying fuel to the internal combustion engine, the in-cylinder injection is performed more than the port injection valve. It is possible to employ a configuration in which the fuel injection from both sides is stopped after controlling the fuel injection amount of the valve to be increased. When stopping fuel injection, the fuel injection from both sides is stopped after increasing the injection amount from the in-cylinder injection valve rather than the port injection valve, so that unburned fuel adheres to the intake port and intake valve. Can be prevented.

  The said structure WHEREIN: The said scavenging means can employ | adopt the structure which changes the execution period of the said scavenging driving | operation according to the determination result of the said fuel property determination means. For example, when the fuel contains a lot of high-boiling components and gum components, depositing and fixing of the intake valve to the intake port can be prevented by performing the scavenging operation for a long period of time.

  In the above configuration, the fuel property determination means determines the fuel properties of each of the plurality of fuels having different properties, and determines the fuel supplied to the internal combustion engine according to the determination result of the fuel property determination means. A configuration including a fuel selection means for selecting from the fuel can be employed. For example, it is possible to prevent deposit accumulation and fixing of the intake valve to the intake port by using a fuel having a lower proportion of the high boiling point component or the gum component contained in the fuel.

  In the above configuration, the intake flow rate control unit may control the variable valve mechanism so that the opening timing of the intake valve is retarded from the top dead center. If the opening timing of the intake valve is on the advance side from the top dead center, blowback from the inside of the cylinder to the intake port may occur and the intake flow rate may decrease. In the case of the retard angle side from the dead center, the blow-back can be suppressed, and the intake flow velocity is increased.

  The said structure WHEREIN: The said intake flow control means can employ | adopt the structure which controls the said variable valve mechanism so that the lift amount of the said intake valve may be changed. For example, by reducing the lift amount, the area between the intake valve and the intake port at the time of lift can be reduced, and thereby the intake flow velocity can be increased.

  In the above configuration, the intake air amount control unit may control the variable valve mechanism so that an overlap period in which both the intake valve and the exhaust valve are opened is changed. For example, the intake flow rate can be effectively increased by changing the overlap period in accordance with the period rotational speed of the internal combustion engine that is forcibly rotating by the scavenging operation.

  In the above configuration, the fuel property determination means includes a tank in which the fuel is stored, an evaporation means that evaporates at least a part of the fuel, and a specific gravity detection means that detects a change in the specific gravity of the fuel before and after evaporation. Can be adopted. With this configuration, it is possible to determine not only the ratio of the high boiling point component in the fuel but also the ratio of the gum component.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where the fuel containing many high boiling components and gum components is used, the control apparatus of the internal combustion engine which can suppress generation | occurrence | production of a deposit and the quality change of the fuel to the gum quality can be provided.

  A plurality of embodiments according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram of a hybrid system 1 according to the first embodiment. In FIG. 1, a hybrid system 1 includes an ECU 100, an engine system 200, a motor MG1, a motor MG2, a power split mechanism 300, an inverter 400, and a battery 500, and controls the hybrid vehicle 120.

  The ECU 100 is an electronic control unit that controls the overall operation of the hybrid system 1. The ECU 100 includes a ROM (Read Only Memory) and a RAM (Random Access Memory) (not shown), and is configured to execute a scavenging process to be described later according to a control program stored in the ROM. The RAM temporarily stores various data acquired in the course of the scavenging process, which will be described in detail later.

  Engine system 200 functions as a main power source of hybrid vehicle 120. The detailed configuration of the engine system 200 will be described later.

  The motor MG1 functions as a generator for charging the battery 500 or as an electric motor that assists the driving force of the engine system 200. The motor MG2 functions as an electric motor that assists the output of the engine system 200 or as a generator for charging the battery 500.

  Power split device 300 is composed of a plurality of gears (not shown). By the power distribution mechanism, the engine system 200 and the motor MG1 can be selectively switched as drive sources. Further, power split mechanism 300 is configured such that the drive of motor MG1 can be transmitted to the engine of engine system 200 via power split mechanism 300 even when engine system 200 is in a stopped state. Has been. Thereby, the engine can be forcibly rotated by the motor MG1. The power of engine system 200 or motor MG1 is transmitted to wheels 122 via transmission mechanism 121.

  Inverter 400 converts DC power extracted from battery 500 into AC power and supplies it to motors MG1 and MG2, and also converts AC power generated by motors MG1 and MG2 into DC power and supplies it to battery 500. Is configured to be possible.

  The battery 500 is a rechargeable storage battery that functions as a power source for driving the motors MG1 and MG2. The battery 500 is provided with an SOC sensor 510 that detects the remaining capacity of the battery 500. SOC sensor 510 outputs the detected value to ECU 100.

  Next, the engine system 200 will be described. FIG. 2 is a schematic diagram of the engine system 200. The engine 10 is a four-cylinder engine having four cylinders 2.

  A piston 4 is slidably provided in the cylinder 2. An intake port 6 and an exhaust port 7 are connected to the combustion chamber 5 in the upper part of the cylinder 2. The openings of the intake port 6 and the exhaust port 7 to the combustion chamber 5 are opened and closed by an intake valve 8a and an exhaust valve 8b, respectively. The intake valve 8a and the exhaust valve 8b are provided with an intake side variable valve mechanism 9a and an exhaust side variable valve mechanism 9b, respectively. The intake side variable valve mechanism 9a and the exhaust side variable valve mechanism 9b can change the operation characteristics (working angle, lift amount, opening / closing timing) of the intake valve 8a and the exhaust valve 8b, respectively. The cylinder 2 is provided with an in-cylinder injection valve 3 a that directly injects fuel into the cylinder 2 and an ignition plug 15 for igniting an air-fuel mixture in the combustion chamber 5. The intake port 6 is provided with a port injection valve 3 b that injects fuel toward the intake port 6.

  The intake port 6 and the exhaust port 7 are connected to an intake passage 12 and an exhaust passage 13, respectively. In the middle of the intake passage 12, a compressor 14a of the supercharger 14 is installed. On the other hand, a turbine 14 b of the supercharger 14 is installed in the middle of the exhaust passage 13. Further, an air flow meter 25 is provided in the intake passage 12 upstream of the compressor 14a, and an intercooler 41 for cooling intake air is controlled in the intake passage 12 downstream of the compressor 14a. There are provided a throttle valve 40 and an intake pressure sensor 24 for outputting an electric signal corresponding to the pressure in the intake passage 12.

  The exhaust passage 13 is provided with a bypass passage 13a that bypasses the turbine 14b, and the bypass passage 13a is provided with a waste gate valve 42. The wastegate valve 42 is formed so that the opening area of the bypass passage 13a can be adjusted by an actuator (not shown) driven by a command from the ECU 100.

  The supercharger 14 is provided with a drive motor 43 for assisting the operation of the supercharger 14. The drive motor 43 operates based on a command from the ECU 100. Thereby, the supercharger 14 can be driven forcibly.

  Further, the engine 10 includes an accelerator opening sensor 21 that outputs an electric signal corresponding to the accelerator opening, and an electric power corresponding to a rotation angle of a crankshaft (not shown) that rotates in conjunction with the reciprocating motion of the piston 4. A crank position sensor 22 that outputs a signal, a water temperature sensor 26 that detects the temperature of the engine coolant, and a throttle opening sensor 27 that detects the opening of the throttle valve 40 are provided.

  The ECU 100 is a unit that controls the operating state of the engine 10 in accordance with the operating conditions of the engine 10 and the driver's request. Detection signals from the air flow meter 25, the intake pressure sensor 24, the accelerator opening sensor 21, the crank position sensor 22, the water temperature sensor 26, and the throttle opening sensor 27 are output to the ECU 100.

  Further, the in-cylinder injection valve 3a, the port injection valve 3b, the spark plug 15, the intake side variable valve mechanism 9a, and the exhaust side variable valve mechanism 9b are electrically connected to the ECU 100. These are controlled by the ECU 100. For example, the ECU 100 controls the operation characteristics of the intake valve 8a and the exhaust valve 8b by controlling the intake side variable valve mechanism 9a and the exhaust side variable valve mechanism 9b, respectively. The intake-side variable valve mechanism 9a and the exhaust-side variable valve mechanism 9b may be driven by, for example, an electromagnetic valve, or include high-speed and low-speed cams having different lift amounts. Alternatively, the phase may be variable by hydraulic pressure, or a combination of these may be used.

  Further, an exhaust side displacement angle sensor 30a for detecting the displacement angle of the intake valve 8a by the intake side variable valve mechanism 9a, and an exhaust side displacement angle sensor for detecting the displacement angle of the exhaust valve 8b by the exhaust side variable valve mechanism 9b. 30b is provided. The output signals of the intake side displacement angle sensor 30a and the exhaust side displacement angle sensor 30b are also output to the ECU 100.

  Further, the ECU 100 controls the opening degree of the throttle valve 40 based on the output from the accelerator opening degree sensor 21. As a result, the intake air amount corresponding to the accelerator opening is introduced into the engine 10.

  The engine system 200 also includes a fuel property determination device 50 that determines the property of fuel supplied to the engine 10. The fuel property determination device 50 includes a small tank 51 having a smaller capacity than a fuel tank (not shown) that stores fuel supplied to the engine 10, and a heating device 52 that evaporates by heating the fuel stored in the small tank 51. And a specific gravity sensor 53 for detecting the specific gravity of the fuel by optically detecting the refractive index of the fuel.

  In order to supply fuel to the small tank 51, the user needs to supply fuel to the small tank 51 separately from the fuel tank when supplying fuel to the fuel tank. A part of the fuel supplied to the fuel tank may be supplied to the small tank 51.

  The heating device 52 is configured to generate heat, and evaporates at least a part of the fuel by heating the fuel in the small tank 51. The heating device 52 corresponds to an evaporation unit.

  The specific gravity sensor 53 can detect the specific gravity of the fuel indirectly by detecting the refractive index of the fuel in the small tank 51. The specific gravity sensor 53 corresponds to specific gravity detection means for detecting the amount of change in the specific gravity of the fuel before and after the fuel in the small tank 51 evaporates by the heating device 52. The specific gravity and refractive index of the fuel are related by a map stored in advance in the ROM. The operation of the heating device 52 and the specific gravity sensor 53 is controlled by the ECU 100.

  The fuel property determination device 50 can determine the ratio of the high boiling point component and the gum component in the fuel in the small tank 51. The high boiling point component means the octane number or olefin content in the fuel. The gum component is a substance that is usually dissolved in gasoline, but separates into a solid or tar form when fuel such as gasoline is evaporated. When the ratio of the high boiling point component in the fuel is large, the fuel is difficult to vaporize, and the fuel tends to adhere to the intake valve 8a and the intake port 6. Also, when the olefin content is high, the fuel is likely to be changed into a gum.

  Next, a method for determining the ratio of the high boiling point component and the gum component in the fuel by the fuel property determination device 50 will be described. When the fuel is supplied into the small tank 51, the ECU 100 operates the heating device 52 to heat the fuel in the small tank 51 and evaporates at least a part thereof. The ECU 100 detects a change in the specific gravity of the fuel before and after the evaporation by the specific gravity sensor 53. FIG. 3 is a graph showing changes in the specific gravity of fuel due to evaporation. In the graph shown in FIG. 3, the vertical axis indicates the specific gravity of the fuel in the small tank 51, and the horizontal axis indicates the elapsed time after the heating device 52 is activated.

  As shown in FIG. 3, when the ratio of the high boiling point component in the fuel is small, the specific gravity change amount is large, and when the high boiling point component rate is large, the specific gravity change amount is large. This is because the low-boiling component contained in the fuel evaporates first by the operation of the heating device 52, but the fuel having a large proportion of the high-boiling component has a small proportion of the low-boiling component, so the proportion of the high-boiling component is small. This is because it is harder to evaporate than a small fuel. Therefore, a fuel with a high proportion of high-boiling components has a smaller amount of evaporation per unit time than a small fuel.

  Further, FIG. 3 shows that when the ratio of the gum component in the fuel is large, even if the fuel evaporates, a large amount of residue remains, so that the specific gravity of the fuel is difficult to change. On the other hand, although not shown in FIG. 3, when the ratio of the gum component in the fuel is small, when the fuel evaporates, there is little residue, so the specific gravity of the fuel changes greatly. The ECU 100 can determine not only the ratio of the high boiling point component in the fuel but also the ratio of the gum component by detecting the amount of change in the specific gravity of the fuel before and after evaporation of the fuel.

  Next, the scavenging process executed by the ECU 100 will be described. FIG. 4 is a flowchart showing an example of the scavenging process executed by the ECU 100.

  First, the ECU 100 uses the fuel property determination device 50 to determine the property of the fuel supplied to the engine 10 (step S1). Next, the ECU 100 determines whether or not the amount of change in the specific gravity of the fuel per unit time is greater than a threshold value (step S2). This threshold value is a reference value for determining whether or not the scavenging process is executed.

  When the amount of change in specific gravity is greater than the threshold, ECU 100 ends this series of processes. That is, when the amount of change in specific gravity is larger than the threshold, it can be determined that the ratio of the high boiling point component or the gum component in the fuel is relatively small, and the ECU 100 ends the scavenging process. This is because, when the ratio of the high boiling point component in the fuel is small, the fuel is easily vaporized, so that the generation of deposits is small. Further, when the ratio of the gum component in the fuel is small, the fuel adhering to the intake valve 8a or the intake port 6 is unlikely to change into a gum quality.

  When the amount of change in specific gravity is smaller than the threshold value, that is, when it is determined that the ratio of the high boiling point component or the gum component in the fuel is relatively large, the ECU 100 determines whether or not the expected stop condition of the engine 10 is satisfied. Is determined (step 3). The predicted stop condition of the engine 10 is a condition that is established when, for example, the operation of the engine 10 is predicted to stop within a few minutes. For example, when the shift lever (not shown) is positioned at the parking position while the engine 10 is being driven, the ECU 100 predicts that the operation of the engine 10 will stop within a predetermined period. Further, when the rotational speed of the engine 10 approaches the rotational speed at which the drive source is switched from the engine 10 to the motor MG1, the operation of the engine 10 is expected to stop within a predetermined period.

  When the prediction condition is not satisfied, the series of processes is terminated. When the predicted condition is satisfied, the ECU 100 switches from the port injection valve 3b to the fuel injection by the in-cylinder injection valve 3a (step 4). By switching to the fuel injection by the in-cylinder injection valve 3a, the adhesion of unburned fuel to the intake valve 8a or the intake port 6 can be suppressed. Thereby, generation | occurrence | production of a deposit, etc. can be suppressed. Note that the ECU 100 may control the fuel injection amount by the in-cylinder injection valve 3a to be larger than the fuel injection amount by the port injection valve 3b. This is because the amount of unburned fuel adhering to the intake port 6 and the intake valve 8a can also be suppressed by such control. As will be described in detail later, after switching from the port injection valve 3b to the fuel injection by the in-cylinder injection valve 3a, the ECU 100 executes a fuel cut when the stop condition of the engine 10 is satisfied. As described above, when stopping the supply of fuel to the engine 10, the ECU 100 controls the fuel injection amount of the in-cylinder injection valve 3a to be larger than that of the port injection valve 3b, and then supplies fuel from both sides. This corresponds to fuel injection control means for stopping injection.

  Next, the ECU 100 determines whether or not a stop condition for the engine 10 is satisfied (step 5). If not established, the ECU 100 ends this series of processes. For example, ECU 100 determines that the engine stop condition is satisfied when the rotational speed of engine 10 is equal to or lower than the rotational speed at which the drive source is switched to motor MG1. When the stop condition is satisfied, the ECU 100 executes fuel cut (step S6). Thereby, the supply of fuel to the engine 10 is stopped.

  Next, the ECU 100 operates the motor MG1 to forcibly rotate the engine 10 via the power split mechanism 300, thereby executing a scavenging operation (step 7). As a result, intake air is introduced into the cylinder 2. Therefore, the ECU 100, the motor MG1, and the power split mechanism 300 correspond to scavenging means that executes the scavenging operation by forcibly rotating the engine 10.

  Next, the ECU 100 executes intake air flow velocity control for increasing the intake air flow velocity (step 8). FIG. 5 is an explanatory diagram of operation characteristics of the intake valve 8a and the exhaust valve 8b when the intake flow velocity control is executed. In FIG. 5, the vertical axis indicates the lift amount of the intake valve 8a and the exhaust valve 8b, and the horizontal axis indicates the crank angle. As shown in FIG. 5, the ECU 100 controls the intake side variable valve mechanism 9a so that the opening timing of the intake valve 8a is retarded from the top dead center. When the opening timing of the intake valve 8a is more advanced than the top dead center, the intake valve 8a is opened in the middle of the piston 4 toward the top dead center, so that the air in the cylinder 2 is inhaled. There is a possibility that the air will blow back to the port 6 side, and there is a possibility that the intake air flow rate will decrease due to this blow back. However, by controlling the valve opening timing of the intake valve 8a to be retarded from the top dead center, it is possible to prevent blow-back, and the intake valve 8a is inhaled more than when the valve opening timing is advanced from the top dead center. The flow rate can be increased.

  By increasing the intake flow velocity, unburned fuel or the like adhering to the intake valve 8a or the intake port 6 can be blown away, and deposits can be effectively prevented from being fixed to the intake port 6 or the like. Therefore, even when a fuel containing a large amount of high-boiling components and gum components is used, it is possible to suppress the generation of deposits and the deterioration of the fuel into a gum.

  Next, the ECU 100 determines whether or not the scavenging operation execution period has passed a predetermined period (step S9). The scavenging operation execution period is set based on the map shown in FIG. FIG. 6 is a map for setting the scavenging operation execution period. The vertical axis represents the scavenging operation execution period, and the horizontal axis represents the amount of change in the specific gravity of the fuel determined by the fuel property determination device 50. . It shows that the larger the amount of change in the specific gravity of the fuel, the smaller the ratio of the high boiling point component or the gum component in the fuel. Therefore, as shown in FIG. 5, the scavenging operation execution period is set to be shorter as the amount of change in the specific gravity of the fuel is larger. When the ratio of the high boiling point component or the gum component in the fuel is small, the amount of deposit generated in the intake port 6 and the intake valve 8a and the unburned fuel adhering to the gum quality are compared with the case where the ratio is high. Since deterioration is suppressed, even when the scavenging operation execution period is short, it is possible to prevent the occurrence of deposits and the like. Moreover, power consumption can be suppressed by setting the scavenging operation execution period to a short period. As described above, the ECU 100 sets the execution period of the scavenging operation according to the determination result of the fuel property. The map shown in FIG. 6 is stored in the ROM of the ECU 100.

  If the ECU 100 determines that the scavenging operation period has not elapsed, it executes the process of step S9 again. When it is determined that the scavenging operation period has elapsed, the ECU 100 stops the operation of the motor MG1, stops the scavenging operation (step S10), and ends this series of processes.

  Next, a modified example of the intake air flow rate control executed by the ECU 100 will be described. FIG. 7 is an explanatory diagram of a modified example of the intake air flow rate control executed by the ECU 100. FIG. 7A shows a first modification of the intake air flow rate control executed by the ECU 100. As shown in FIG. 7A, the ECU 100 controls the intake side variable valve mechanism 9a so that the operating angle of the intake valve 8a becomes small. Specifically, the ECU 100 controls the intake-side variable valve mechanism 9a so that the closing timing of the intake valve 8a is advanced from the bottom dead center. By controlling the closing timing of the intake valve 8a to the advance side with respect to the bottom dead center, the blowback from the cylinder 2 to the intake port 6 side can be suppressed. Thereby, it can suppress that unburned fuel blows back to the intake port 6 side.

  Next, a second modification of the intake air flow rate control executed by the ECU 100 will be described. FIG. 7B is an explanatory diagram of a second modification of the intake air flow rate control executed by the ECU 100. As shown in FIG. 7B, the ECU 100 controls the intake side variable valve mechanism 9a so that the lift amount of the intake valve 8a becomes small. By reducing the lift amount of the intake valve 8a, the area between the intake valve 8a and the intake port 6 at the time of valve opening becomes smaller than when the lift amount is large, so that the intake air flow velocity passing between the intake valve 8a and the intake port 6 can be reduced. Will increase.

  Next, a description will be given of a third modification of the intake air flow rate control executed by the ECU 100. FIG. FIG. 7C is an explanatory diagram of a third modification of the intake air flow rate control executed by the ECU 100. As shown in FIG. 7C, the ECU 100 controls the intake side variable valve mechanism 9a, the exhaust side variable valve so that the overlap period during which both the intake valve 8a and the exhaust valve 8b are opened is long. The mechanism 9b is controlled. In this way, by increasing the overlap period, it is possible to increase the intake air flow velocity as compared with the case where the overlap period is short. This is because by increasing the overlap period, intake air newly flows into the cylinder 2 from the intake valve 8a along with the inertial force of the intake air discharged from the exhaust valve 8b to the exhaust port 7. When the overlap period is set, it is necessary to rotate the engine 10 at a predetermined rotational speed so that the intake air flow rate increases. For example, it is necessary to rotate the engine 10 at a high speed so that the blowback to the intake port 6 does not increase by providing the overlap period.

  Next, a description will be given of a fourth modification of the intake air flow rate control executed by the ECU 100. FIG. The ECU 100 outputs a command to the drive motor 43 during the scavenging operation to force the supercharger 14 to operate. When the supercharger 14 is operated, the amount of intake air increases, so that the intake flow velocity can be increased. At this time, an overlap period in which both the intake valve 8a and the exhaust valve 8b are opened may be set, and the throttle valve 40 may be fully opened.

  Next, a hybrid system according to the second embodiment will be described. FIG. 8 is a schematic diagram of an engine system 200a employed in the hybrid system according to the second embodiment. In addition, about the same component as the engine system 200 employ | adopted as the hybrid system which concerns on Example 1, the description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  As shown in FIG. 8, the engine system 200a includes two fuel property determination devices 50 and 50a. The engine system 200a is configured to be operable with a plurality of different types of fuel. Specifically, the fuel supplied to the engine 10 can be selectively supplied from two types of fuel based on an instruction from the ECU 100, and the engine system 200a is a so-called bi-fuel engine system. The engine system 200a includes two tanks (not shown) in which two different fuels are stored individually. Specifically, the engine system 200a is configured to be operable with either gasoline fuel or ethanol fuel. For example, the user supplies gasoline fuel to the small tank 51 and ethanol fuel to the small tank 51a when supplying each fuel to the tank. Thereby, ECU100 can determine the property of each fuel by the output from the fuel property determination apparatuses 50 and 50a, respectively.

Next, the scavenging process executed by the ECU 100 will be described. FIG. 9 is a flowchart showing an example of the scavenging process executed by the ECU.
The ECU 100 determines the properties of the plurality of fuels (step S1a). Next, based on the outputs from the specific gravity sensors 53 and 53a, the amount of change in specific gravity per unit time of each fuel is compared (step S2a). By comparing the amount of change in the specific gravity of the fuel, it is possible to determine a fuel having a high proportion of high boiling point components or gum components.

  Next, when it is determined in step S3 that the predicted engine stop condition is satisfied, the ECU 100 switches the fuel supplied to the engine 10 to a fuel having a larger specific gravity change amount (step S4a). Since the fuel with the larger specific gravity change is a fuel with a small proportion of high boiling point components or gum components, switching to a fuel with a small proportion of high boiling point components or gum components causes the intake valve 8a or the intake port 6 to be switched. Deposits can be prevented from accumulating. As described above, the ECU 100 corresponds to a fuel selection unit that selects the fuel to be supplied to the engine 10 from a plurality of fuels based on the determination results of the fuel property determination devices 50 and 50a. Next, ECU100 performs the process after step S4.

  As described above, it is possible to suppress the occurrence of deposits in the intake valve 8a and the intake port 6 by determining the properties of the plurality of fuels and using the fuel having the smaller proportion of the high boiling point component or the gum component.

  The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.

  In the present embodiment, the fuel property determination device 50 is configured to be able to determine not only the high boiling point component but also the ratio of the gum component. For example, by detecting only the refractive index in the fuel, You may employ | adopt the sensor which determines only the ratio of a high boiling point component.

  In the above embodiment, various modified examples of the intake flow velocity control executed by the ECU 100 have been described. However, a plurality of these intake flow velocity controls may be combined.

It is a block diagram of the hybrid system which concerns on a present Example. It is a schematic diagram of an engine system. It is the graph which showed the change of the specific gravity of the fuel by evaporation. It is the flowchart which showed an example of the scavenging process which ECU performs. It is explanatory drawing of the operating characteristic of the intake valve 8a and the exhaust valve 8b at the time of execution of intake flow velocity control. It is a map for setting the scavenging operation execution period. It is explanatory drawing of the modification of intake flow velocity control. FIG. 6 is a schematic diagram of an engine system that is employed in a hybrid system according to a second embodiment. It is the flowchart which showed an example of the scavenging process which ECU performs.

Explanation of symbols

2 cylinder 3a cylinder injection valve 3b intake port injection valve 5 combustion chamber 6 intake port 8a intake valve 8b exhaust valve 9a intake side variable valve mechanism (variable valve mechanism)
9b Exhaust side variable valve mechanism (variable valve mechanism)
DESCRIPTION OF SYMBOLS 10 Engine 14 Supercharger 43 Drive motor 50, 50a Fuel property determination apparatus (fuel property determination means)
51, 51a Small tank 52, 52a Heating device 53, 53a Specific gravity sensor 100 ECU (scavenging means, intake flow rate control means, fuel injection control means, fuel selection means)
120 Hybrid vehicle 200 Engine system 300 Power split mechanism (scavenging means)
MG1, MG2 motor

Claims (10)

Fuel property determination means for determining the property of the fuel supplied to the internal combustion engine;
Scavenging means for performing a scavenging operation by forcibly rotating the internal combustion engine when the supply of fuel to the internal combustion engine is stopped;
Intake flow velocity control means for performing intake flow velocity control for increasing the flow velocity of intake air flowing into the internal combustion engine during execution of the scavenging operation according to the determination result of the fuel property determination means. Control device for internal combustion engine. A variable valve mechanism capable of changing a valve opening characteristic of at least one of the intake valve and the exhaust valve;
2. The control apparatus for an internal combustion engine according to claim 1, wherein the intake flow rate control means executes the intake flow rate control by controlling the variable valve mechanism. A turbocharger that can be driven by a motor
The control device for an internal combustion engine according to claim 1 or 2, wherein the intake control means drives the supercharger during execution of the scavenging operation. A port injection valve for injecting fuel into the intake port of the internal combustion engine;
An in-cylinder injection valve that directly injects fuel into the cylinder of the internal combustion engine;
Fuel injection control means capable of controlling the fuel injection amount respectively injected from the port injection valve and the cylinder injection valve,
When stopping the supply of fuel to the internal combustion engine, the fuel injection control means performs control so that the fuel injection amount of the in-cylinder injection valve is larger than that of the port injection valve, and then fuel from both sides The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the injection of the engine is stopped.   The control device for an internal combustion engine according to any one of claims 1 to 4, wherein the scavenging means changes an execution period of the scavenging operation in accordance with a determination result of the fuel property determination means. The fuel property determining means determines each fuel property of a plurality of fuels having different properties,
6. The fuel selection unit according to claim 1, further comprising: a fuel selection unit that selects a fuel to be supplied to the internal combustion engine from the plurality of fuels according to a determination result of the fuel property determination unit. Control device for internal combustion engine.   3. The control of the internal combustion engine according to claim 2, wherein the intake flow rate control unit controls the variable valve mechanism so that an opening timing of the intake valve is retarded from a top dead center. apparatus.   The control device for an internal combustion engine according to claim 2, wherein the intake flow rate control means controls the variable valve mechanism so that a lift amount of the intake valve is changed.   3. The variable valve mechanism according to claim 2, wherein the intake air amount control unit controls the variable valve mechanism so that an overlap period in which both the intake valve and the exhaust valve are opened is changed. Control device for internal combustion engine.   The fuel property determination means includes a tank in which the fuel is stored, an evaporation means for evaporating at least a part of the fuel, and a specific gravity detection means for detecting a change in the specific gravity of the fuel before and after evaporation. The control device for an internal combustion engine according to any one of claims 1 to 9.

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