JP2008297930A - Internal combustion engine controlling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine controlling device reduced in accumulation of deposits in an intake port caused by a blowing-back phenomenon. <P>SOLUTION: An ECU 20 judges whether the engine is in an operation state of causing the exhaust pressure higher than the intake air pressure to control a waste gate valve 40 opening/closing a by-pass passage 13b by-passing a turbine 14b of a supercharger 14 to an open side, in the operation state with the exhaust pressure higher than the intake air pressure. The exhaust pressure can be reduced by controlling the waste gate valve 40 to the open side, by which the blowing-back phenomenon can be suppressed to reduce the accumulation of deposits in the intake port 6. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  In an internal combustion engine, the exhaust pressure may be higher than the intake pressure, which may cause a blow-back phenomenon. This blow-back phenomenon is a phenomenon that occurs remarkably during a so-called valve overlap period in which both the intake valve and the exhaust valve are simultaneously opened. When the blow-back phenomenon occurs, a large amount of burned gas remains in the combustion chamber, which may cause unstable combustion. Patent Document 2 discloses a technique for such a problem.

  Further, an internal combustion engine having a supercharger has been conventionally known. In Patent Document 1, a part of the air-fuel mixture is sufficiently vaporized and atomized by blowback generated by changing the valve closing timing of the intake valve to the retard side, and the opening degree of the wastegate valve of the supercharger is set. A technique is disclosed in which, by controlling, the decrease in the amount of PM (exhaust particulates) in the exhaust gas can be reduced and the output can be secured by complementing the decrease in the filling amount caused by the blow-back.

JP 2003-27977 A Japanese Patent Laid-Open No. 10-288055

  By the way, since the air-fuel mixture contains PM, there is a risk that the PM will adhere to the intake port or the like by blowing back. In particular, due to the influence of the blow-by gas reduction device, oil or the like may be deposited as a deposit on the intake port as a binder. Depending on the amount of deposit, the flow coefficient of the intake passage may fluctuate or the swirl flow (tumble flow or swirl flow) introduced into the combustion chamber may be affected. It is desirable to suppress as much as possible.

  The supercharger is intended to improve the output of the internal combustion engine. However, depending on the action of the turbine of the supercharger, there is a risk of promoting a state in which the exhaust pressure becomes higher than the intake pressure.

  Accordingly, an object of the present invention is to provide a control apparatus for an internal combustion engine in which deposit accumulation on an intake port caused by a blowback phenomenon is suppressed.

The above-described object is to bypass the turbocharger turbine in an operating state determining means for determining whether or not the exhaust pressure is higher than the intake pressure in an operating state in which the exhaust pressure is higher than the intake pressure. This can be achieved by an internal combustion engine control device comprising a wastegate valve control means for controlling the wastegate valve for opening and closing the bypass passage to the open side.
In an operating state in which the exhaust pressure is higher than the intake pressure, the possibility of a blow-back phenomenon increases, but the exhaust pressure can be lowered by controlling the wastegate valve to the open side. Thereby, the blow-back phenomenon can be suppressed, and deposit accumulation on the intake port can be suppressed.

The said structure WHEREIN: The said wastegate valve control means can employ | adopt the structure which controls the said wastegate valve to the open side according to the temperature of engine cooling water.
When the temperature of the engine cooling water is lower than the reference value, the temperature of the piston top surface and the like is low, so that the amount of PM generated increases, particularly in the case of the in-cylinder injection type. Therefore, when the temperature of the cooling water is lower than the reference value, deposit accumulation on the intake port can be effectively suppressed by controlling the wastegate valve to the open side.

In the above configuration, in an operating state in which the exhaust pressure is higher than the intake pressure, the opening and closing of at least one of the intake valve and the exhaust valve is suppressed so as to suppress the blowback phenomenon caused by the exhaust pressure becoming higher than the intake pressure. A configuration including a variable valve timing mechanism for controlling timing can be employed.
By controlling the opening / closing timing of at least one of the intake valve and the exhaust valve so as to suppress the blowback phenomenon, deposit accumulation on the intake port can be effectively suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the control apparatus of the internal combustion engine by which the accumulation of the deposit to the intake port resulting from the blowback phenomenon was suppressed can be provided.

Embodiments according to the present invention will be described below with reference to the drawings.
In the present embodiment, the case where the present invention is applied to a vehicle driving engine will be described. FIG. 1 is a diagram illustrating a schematic configuration of an engine and an intake / exhaust system thereof according to the present embodiment. The engine 1 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 8 and an exhaust valve 9, respectively. Further, the intake valve 8 and the exhaust valve 9 are respectively provided with an intake side valve timing mechanism (intake side VVT) 10 and an exhaust side valve timing mechanism (exhaust side VVT) 11, and the opening and closing timings thereof are variable. ing. The cylinder 2 is provided with a fuel injection valve 3 for injecting fuel into the combustion chamber 5 and a spark plug 15 for igniting the air-fuel mixture in the combustion chamber 5.

  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. An air flow meter 25 is provided in the intake passage 12 upstream of the compressor 14a, and an electric signal corresponding to the pressure in the intake passage 12 is output to the intake passage 12 downstream of the compressor 14a. An intake pressure sensor 24 is provided. The exhaust passage 13 upstream of the turbine 14b is referred to as an upstream exhaust passage 13a.

  Further, the exhaust passage 13 is provided with a bypass passage 13b that bypasses the turbine 14b, and the bypass passage 13b is provided with a waste gate valve 40. The wastegate valve 40 is formed so that the opening area of the bypass passage 13b can be adjusted by an actuator (not shown) that is driven by a command from the ECU 20.

  Further, the engine 1 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 for outputting a signal is provided. Further, a water temperature sensor 26 for detecting the water temperature of the engine cooling water is provided.

  The engine 1 configured as described above is provided with an ECU 20 for controlling the engine 1. The ECU 20 is a unit that controls the operating state of the engine 1 in accordance with the operating conditions of the engine 1 and the driver's request. An air flow meter 25, an intake pressure sensor 24, an accelerator opening sensor 21, a crank position sensor 22, and a water temperature sensor 26 are electrically connected to the ECU 20. These output signals are input to the ECU 20.

  Further, the fuel injection valve 3, the spark plug 15, the intake side valve timing mechanism 10, and the exhaust side valve timing mechanism 11 are electrically connected to the ECU 20. These are controlled by the ECU 20. For example, the ECU 20 controls the opening / closing timings of the intake valve 8 and the exhaust valve 9 by controlling the intake side valve timing mechanism 10 and the exhaust side valve timing mechanism 11, respectively. As a result, the valve overlap period during which both the intake valve 8 and the exhaust valve 9 are open is controlled. Further, an intake side displacement angle sensor 30 that detects the displacement angle of the intake valve 8 by the intake side valve timing mechanism 10 and an exhaust side displacement angle sensor 31 that detects the displacement angle of the exhaust valve 9 by the exhaust side valve timing mechanism 11 are provided. Is provided. The output signals of the intake side displacement angle sensor 30 and the exhaust side displacement angle sensor 31 are also output to the ECU 20.

  The ECU 20 includes a ROM (Read Only Memory) and a RAM (Random Access Memory) (not shown), and can execute VVT and wastegate valve control processing, which will be described later, according to a control program stored in the ROM. It is configured. Also, the RAM is configured to temporarily store various data acquired in the course of executing the VVT and wastegate valve control processing. Further, the ECU 20 determines, based on outputs from various sensors, whether or not the operation state is such that the exhaust pressure becomes higher than the intake pressure described later, that is, the operation state in which the blowback phenomenon can occur.

  Next, the VVT and waste gate valve control processing executed by the ECU 20 will be described. FIG. 2 is a flowchart showing an example of VVT and wastegate valve control processing executed by the ECU.

  Based on the output from the water temperature sensor 26, the ECU 20 determines whether the water temperature of the engine cooling water is lower than the reference value (step S1). This reference value refers to a reference value when the amount of combustion PM contained in the already burned gas exceeds a predetermined amount, and the engine when there is a possibility that PM may start to deposit as a deposit in the intake port 6 due to the blowback phenomenon. The temperature of cooling water.

  FIG. 3 is a graph showing the relationship between the amount of combustion PM and the water temperature. The vertical axis represents the combustion PM amount, and the horizontal axis represents the engine coolant temperature. As shown in FIG. 3, the amount of combustion PM increases as the water temperature decreases. Therefore, it can be said that the lower the water temperature, the higher the possibility of deposits being deposited on the intake port 6 due to the blow-back phenomenon.

  Therefore, when the engine coolant temperature is equal to or higher than the reference value, the ECU 20 executes normal processing on the intake side valve timing mechanism 10, the exhaust side valve timing mechanism 11, and the wastegate bubble 40 (step). S2). The normal process is a process for optimally controlling the intake side valve timing mechanism 10, the exhaust side valve timing mechanism 11, and the wastegate bubble 40 in accordance with the engine operating state.

  If the engine coolant temperature is lower than the reference value, the ECU 20 determines whether the required intake air amount is in the blow-back region (step S3). The blow-back region is a region where the intake pressure is higher than the exhaust pressure.

  Here, the blow-back area will be described. FIG. 4 is a map for determining whether or not the required air amount is in the blow-back area, and is stored in the ROM of the ECU 20. As shown in FIG. 4, the blow-back region where the exhaust pressure becomes higher than the intake pressure depends on the relationship between the engine speed and the crankshaft torque. In the low load region and the high load high rotation region, it becomes a blow-back region. On the other hand, in the high-load low-rotation region, it does not become a blow-back region but a blow-through region where the intake pressure is higher than the exhaust pressure. In this blow-by region, the intake pressure becomes higher than the exhaust pressure, so even if a valve overlap period is provided, there is little possibility that the already burned gas is blown back to the intake port 6.

  Based on this map, the ECU 20 determines whether or not the requested air amount is in the blow-back area. Here, the required air amount is an air amount necessary for realizing a predetermined engine speed and crankshaft torque, and the ECU 20 calculates based on outputs from various sensors such as the accelerator opening sensor 21. To do.

  When the required amount of air is in the blow-back region, the ECU 20 controls the operation of the exhaust-side valve timing mechanism 11 to open and close the exhaust valve 9 so that PM accumulation on the intake port 6 due to blow-back is minimized. Is controlled (step S4).

  Here, the amount of blowback to the intake port 6 that varies depending on the displacement angle of the intake side valve timing mechanism 10 and the exhaust side valve timing mechanism 11 will be briefly described.

  FIG. 5 is a graph showing the amount of blowback to the intake port 6 that varies depending on the displacement angle of the intake side valve timing mechanism 10 and the exhaust side valve timing mechanism 11. The abscissa indicates the displacement angle of the intake side valve timing mechanism 10, and advances toward the right side and retards toward the left side. The vertical axis indicates the displacement angle of the exhaust side valve timing mechanism 11, which is retarded toward the upper side and advanced toward the lower side. Therefore, the valve overlap period increases as it goes to the upper right of the graph. Moreover, the numbers from 0.8 to 0.1 shown on the graph indicate the degree of the blowback amount (the amount of the burned gas that blows back from the combustion chamber 5 to the intake port 6). It shows that the blowback amount to the intake port 6 is large. Further, the larger the blowback amount, the larger the PM amount adhering to the intake port 6.

  The low temperature control line is shown on the graph of FIG. This low-temperature control line shows the displacement angle of the exhaust side valve timing mechanism 11 with the smallest amount of blowback when the displacement angle of the intake side valve timing mechanism 10 is constant. In step S <b> 3, the ECU 20 controls the displacement angle of the exhaust side valve timing mechanism 11 to a displacement angle that minimizes the blowback amount regardless of the displacement angle of the intake side valve timing mechanism 10.

  Next, the ECU 20 controls the wastegate bubble 40 to the open side (step S5). Thereby, since exhaust gas bypasses the turbine 14b, the exhaust pressure is reduced. Therefore, the amount of burned gas blown back to the intake port 6 can be suppressed.

  In step S3, when the required air amount is not in the blow-back region, the ECU 20 sets the displacement angles of the intake side valve timing mechanism 10 and the exhaust side valve timing mechanism 11 so as to be optimal to the required air amount (step S6). When the required air amount is not in the blow-back region, the already burned gas can be discharged smoothly. For example, the valve can be overlapped to improve the volume efficiency and maintain a high torque. Next, the ECU 20 controls the waste gate bubble 40 to the closed side (step S7). Thereby, the output of the engine 1 is improved.

  Thus, drivability can be ensured by executing the processes of steps S6 and S7 when the required air amount is not in the blow-back region.

  As described above, since the ECU 20 executes the process for suppressing the blowback phenomenon based on the temperature of the engine cooling water, the blowback phenomenon is effectively prevented at a low temperature when the amount of PM contained in the burned gas increases. Can be suppressed. Thereby, deposit accumulation on the intake port 6 can be effectively 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.
In the above embodiment, when the required air amount is in the blowback region, the displacement angle of the exhaust side valve timing mechanism 11 is controlled to be the displacement angle of the exhaust side valve timing mechanism 11 that minimizes the blowback amount. Without being limited to such a configuration, for example, the displacement angle of both the intake side valve timing mechanism 10 and the exhaust side valve timing mechanism 11 is controlled to control the valve timing at which the blowback amount is suppressed. Also good. Further, only the displacement angle of the intake side valve timing mechanism 10 may be controlled.

It is a figure which shows schematic structure of the engine which concerns on a present Example, and its intake / exhaust system. It is the flowchart which showed an example of VVT and a waste gate valve control process which ECU performs. It is the graph which showed the relationship between combustion PM amount and water temperature. It is a map for determining whether a request | requirement air amount is a blow-back area | region. It is the graph which showed the return amount to the intake port which fluctuates with the displacement angle of the intake side valve timing mechanism and the exhaust side valve timing mechanism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Fuel injection valve 6 Intake port 7 Exhaust port 8 Intake valve 9 Exhaust valve 10 Intake side valve timing mechanism 11 Exhaust side valve timing mechanism 12 Intake passage 13 Exhaust passage 13b Bypass passage 14 Supercharger 14a Compressor 14b Turbine 20 ECU (operating state determination means, waste gate valve control means)
21 Accelerator opening sensor 22 Crank position sensor 24 Intake pressure sensor 25 Air flow meter 26 Water temperature sensor

Claims (3)

An operation state determining means for determining whether or not the exhaust gas pressure is higher than the intake pressure.
A wastegate valve control means for controlling a wastegate valve that opens and closes a bypass passage that bypasses the turbine of the turbocharger in an operating state in which the exhaust pressure is higher than the intake pressure. Control device for internal combustion engine.   2. The control device for an internal combustion engine according to claim 1, wherein the waste gate valve control means controls the waste gate valve to an open side in accordance with a temperature of engine cooling water.   A variable valve that controls the opening / closing timing of at least one of the intake valve and the exhaust valve so as to suppress the blow-back phenomenon caused by the exhaust pressure becoming higher than the intake pressure in an operating state in which the exhaust pressure becomes higher than the intake pressure. The control device for an internal combustion engine according to claim 1, further comprising a timing mechanism.

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