JP6396635B2 - Control device for internal combustion engine - Google Patents

Description

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

  An internal combustion engine having an engine valve in which metallic sodium is sealed is known. Patent Document 1 discloses a method for suppressing solidification of metallic sodium during deceleration in order to prevent metallic sodium from solidifying during deceleration and being exposed to high-temperature exhaust during subsequent acceleration and damaging the engine valve. A heater is provided.

JP-A-4-339113

  Providing a heater increases the cost. Moreover, there is a possibility that fuel consumption may deteriorate due to energization of the heater. In addition, vibrations of the internal combustion engine may adversely affect the durability of the heater.

  Therefore, an object of the present invention is to provide a control device for an internal combustion engine that suppresses the breakage of the engine valve by a method different from the conventional one.

The above object includes an intake valve and an exhaust valve of an internal combustion engine, and a control unit that executes control for suppressing an increase in exhaust temperature during an acceleration period after the deceleration of the internal combustion engine. At least one of them contains a refrigerant that may solidify during operation of the internal combustion engine, and the control for suppressing the rise in the exhaust temperature is performed by retarding the ignition timing, setting the air-fuel ratio to the lean side. A process for setting and a process for increasing the compression ratio, and the control unit executes control for suppressing an increase in the exhaust temperature during an acceleration period after deceleration of the internal combustion engine, This can be achieved by a control device for an internal combustion engine that lowers the temperature of at least one of the intake valve and the exhaust valve as compared with the case where it is not executed. Rather than suppressing the solidification of the refrigerant during deceleration, the engine valve is prevented from being damaged by heat by suppressing an increase in the exhaust temperature during the acceleration period after deceleration.

When the period during which the internal combustion engine continues to decelerate is equal to or longer than a predetermined period, the control unit may execute control for suppressing an increase in the exhaust temperature.

When the degree of acceleration after deceleration of the internal combustion engine is equal to or greater than a predetermined value, the control unit performs the ignition timing retarding process, the process of setting the air-fuel ratio to the lean side, as control for suppressing an increase in the exhaust temperature , And at least two of the processes for increasing the compression ratio may be executed.

  It is possible to provide a control device for an internal combustion engine that suppresses damage to the engine valve by a method different from the conventional one.

FIG. 1 is an explanatory diagram of the engine system of this embodiment. FIG. 2 is an explanatory diagram of the exhaust valve. 3A and 3B are graphs showing the opening degree of the throttle valve and the temperature of the exhaust valve. FIG. 4 is a flowchart showing an example of control executed by the ECU. 5A to 5D are explanatory diagrams of processing for changing the operating characteristics of the engine valve.

  FIG. 1 is an explanatory diagram of an engine system 200 according to an embodiment. The engine system 200 includes an engine 10 and an ECU 100. The engine 10 is a four-cylinder engine having four cylinders 2, but is not limited to this. The ECU 100 is an electronic control unit that controls the overall operation of the engine system 200. The ECU 100 includes a ROM (Read Only Memory) and a RAM (Random Access Memory) (not shown), and is configured to be able to execute exhaust gas temperature suppression control, which will be described later, according to a control program stored in the ROM. . In addition, the RAM temporarily stores various data acquired in the control execution process, which will be described in detail later.

  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-side variable valve mechanism 9a and the exhaust-side variable valve mechanism 9b can change the operation characteristics (working angle, 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 according to 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 a hydraulic pressure or an electric motor, or a combination of these may be used.

  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.

  FIG. 2 is an explanatory diagram of the exhaust valve 8b. The exhaust valve 8b is sealed in the shaft portion 81, the umbrella portion 82, the neck portion 83 between the shaft portion 81 and the umbrella portion 82, the shaft portion 81, the hollow portion 85 formed inside the umbrella portion 82, and the hollow portion 85. Metal sodium N. Metal sodium N is an example of a refrigerant. As the refrigerant, any refrigerant other than metallic sodium may be used as long as it can be solidified while the engine 10 is in operation (including during fuel cut). The intake valve 8a is similarly filled with metallic sodium, but at least one of the intake valve 8a and the exhaust valve 8b only needs to be filled with metallic sodium.

  Next, the opening degree of the throttle valve 40 and the temperature of the exhaust valve 8b when accelerating after deceleration will be described. 3A and 3B are graphs showing the opening degree of the throttle valve 40 and the temperature of the exhaust valve 8b. In FIG. 3A, the vertical axis indicates the opening degree of the throttle valve 40, the horizontal axis indicates time, and in FIG. 3B, the vertical axis indicates the temperature of the outer surface of the exhaust valve 8b, and the horizontal axis indicates time. When the engine 10 decelerates and fuel cut is executed, the exhaust temperature decreases and the temperature of the exhaust valve 8b also decreases.

  During deceleration, the temperature of the exhaust valve 8b becomes lower than the melting point (98 ° C.) of the metallic sodium N, and the metallic sodium N may solidify. When the metal sodium N is accelerated after solidifying, it returns from the fuel cut and the exhaust valve 8b is exposed to high-temperature exhaust. As a result, before the metallic sodium N sealed in the exhaust valve 8b is melted, the exhaust valve 8b is rapidly heated to a high temperature, and the metallic sodium N may not take away the amount of heat of the exhaust valve 8b, for example, the neck 83 may be broken. is there. A curve X in FIG. 3B shows an example in which the exhaust temperature suddenly rises due to acceleration after deceleration and the exhaust valve 8b breaks. The ECU 100 according to the present embodiment executes control for suppressing the exhaust temperature during the acceleration period after deceleration, thereby suppressing heating of the exhaust valve 8b and suppressing breakage as described above. A curve A in FIG. 3B shows a case where the above control is executed.

  FIG. 4 is a flowchart illustrating an example of control executed by the ECU 100. ECU 100 determines whether or not engine 10 is decelerating (step S1). Specifically, the opening of the throttle valve 40 is less than a predetermined opening based on the output from the throttle opening sensor 27, and the engine speed is set to a predetermined rotational speed based on the output from the crank position sensor 22. If it is less than that, the ECU 100 determines that the engine 10 is decelerating. If the determination is negative, the process of step S1 is executed again.

  If the determination is affirmative, the ECU 100 determines whether or not the period during which deceleration is continued is equal to or longer than a predetermined period (step S2). For example, the ECU 100 measures time from when the affirmative determination is made in step S1. The “predetermined period” is set to a period during which the sodium metal N can be below the melting point during deceleration. If the determination is negative, the process of step S1 is executed again.

  In the case of an affirmative determination, the degree of acceleration after deceleration is detected, and it is determined whether or not the degree of acceleration is a predetermined value or more (step S3). The determination of the presence or absence of acceleration after deceleration may be performed based on the output from the throttle opening sensor 27 or based on the output from the crank position sensor 22. The degree of acceleration is, for example, the amount of change in the opening degree of the throttle valve 40 per unit time. When the degree of acceleration is less than the predetermined value, the ECU 100 executes any one of a plurality of processes included in the control for suppressing the exhaust gas temperature described later (step S4). When the degree of acceleration is greater than or equal to a predetermined value, ECU 100 executes at least two or more of a plurality of processes included in the control for suppressing the exhaust temperature (step S5).

  In any case, the ECU 100 executes control for suppressing the exhaust temperature during the acceleration period after deceleration, and suppresses the exhaust valve 8b from being rapidly heated to suppress damage to the exhaust valve 8b. As a result, the exhaust valve 8b can be prevented from being damaged without the provision of a heater that prevents the solidification of the metallic sodium N during deceleration. This increases the cost by providing the heater, deteriorates the fuel consumption by energizing the heater, It can solve the problem of durability. In addition, ECU100 stops control which suppresses exhaust temperature after progress for a predetermined period from the acceleration start.

  A plurality of processes included in the control for suppressing the exhaust temperature will be described. The exhaust gas temperature suppression control includes ignition timing retardation processing, processing for setting the air-fuel ratio to the lean side, processing for changing the operating characteristics of the engine valve, processing for lowering the boost pressure, and processing for increasing the compression ratio. The ECU 100 effectively suppresses the exhaust gas temperature by executing two or more of the above processes when the degree of acceleration is large.

  The ignition timing retarding process is a process for delaying the ignition timing of the fuel by the spark plug 15 from the timing predetermined according to the operating state of the engine 10 in advance. In the process of setting the air-fuel ratio to the lean side, the amount of intake air is adjusted by adjusting the fuel injection amount on at least one of the in-cylinder injection valve 3a and the port injection valve 3b, or by adjusting the opening of the throttle valve 40. This is a process of adjusting and setting a leaner side than the air-fuel ratio determined in advance according to the operating state of the engine 10. The process of changing the operating characteristics of the engine valve is performed by controlling the intake side variable valve mechanism 9a and the exhaust side variable valve mechanism 9b, and the intake valve 8a and exhaust valve 8b that are determined in advance according to the operating state of the engine 10. Is a process for changing the opening / closing timing of the valve or the operating angle of the intake valve 8a. The process of reducing the supercharging pressure is, for example, a process of suppressing the rotation of the supercharger 14 by stopping the drive motor 43 and suppressing the rotation of the supercharger 14 or increasing the opening of the wastegate bubble 42. is there. The process for increasing the compression ratio is a process for increasing the compression ratio in an engine (for example, Japanese Patent Application Laid-Open No. 2012-52483, etc.) that does not include the engine 10 of the present embodiment but can change the compression ratio.

  Processing for changing the operating characteristics of the engine valve will be described. 5A to 5D are explanatory diagrams of processing for changing the operating characteristics of the engine valve. In the process of changing the operating characteristic of the engine valve, the closing timing of the intake valve 8a is retarded as shown in FIG. 5A, and the opening timing of the intake valve 8a is advanced as shown in FIG. 5B. In this manner, the closing timing of the exhaust valve 8b is retarded, and the working angle of the intake valve 8a is expanded as shown in FIG. 5D. For example, if the operating angle of the intake valve 8a cannot be changed due to the structure of the intake side variable valve mechanism 9a, the process of any of FIGS. 5A to 5C is executed. When the intake side variable valve mechanism 9a is not provided and only the exhaust side variable valve mechanism 9b is provided, the process of FIG. 5C is executed. When the intake side variable valve mechanism 9a can change the lift amount of the intake valve 8a, a process for reducing the lift amount may be executed. This is because the exhaust temperature can also be suppressed by this treatment.

  Thus, the degree of suppression of the exhaust temperature can also be changed according to the degree of acceleration, the heating of the exhaust valve 8b can be effectively suppressed, and breakage can be suppressed.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

  The greater the acceleration degree, the greater the number of processes executed simultaneously.

3a In-cylinder injection valve 3b Port injection valve 8a Intake valve 8b Exhaust valve 81 Shaft part 82 Umbrella part 83 Neck part 85 Hollow part N Metal sodium (refrigerant)
9a Intake side variable valve mechanism 9b Exhaust side variable valve mechanism 10 Engine 14 Supercharger 15 Spark plug 100 ECU
200 engine system

Claims (3)

An intake valve and an exhaust valve of an internal combustion engine;
A control unit that executes control for suppressing an increase in exhaust temperature during an acceleration period after deceleration of the internal combustion engine,
At least one of the intake valve and the exhaust valve encloses therein a refrigerant that may solidify during operation of the internal combustion engine ,
The control for suppressing the rise in the exhaust temperature is at least one of ignition timing retarding processing, processing for setting the air-fuel ratio to the lean side, and processing for increasing the compression ratio,
The control unit executes a control that suppresses an increase in the exhaust temperature during an acceleration period after the deceleration of the internal combustion engine, so that the temperature of at least one of the intake valve and the exhaust valve is set to be lower than when the control unit is not executed. Control device for internal combustion engine to be lowered.   2. The control device for an internal combustion engine according to claim 1, wherein when the period during which the internal combustion engine continues to decelerate is equal to or longer than a predetermined period, the control unit executes control for suppressing an increase in the exhaust gas temperature.   When the degree of acceleration after deceleration of the internal combustion engine is equal to or greater than a predetermined value, the control unit performs the ignition timing retarding process, the process of setting the air-fuel ratio to the lean side, as control for suppressing an increase in the exhaust temperature, The control device for an internal combustion engine according to claim 1 or 2, wherein at least two of the processes for increasing the compression ratio are executed.

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