JP2017198110A - Variable valve control device of internal combustion engine - Google Patents

Abstract

A variable valve control apparatus for an internal combustion engine capable of improving fuel efficiency even when a difference between cylinders in distribution of external EGR is large. An intake side variable valve mechanism 13 capable of changing an opening / closing timing of an intake valve 12, an exhaust side variable valve mechanism 23 capable of changing an opening / closing timing of an exhaust valve 22, and a magnitude of knocking vibration of an engine 2. When it is determined that the difference between the cylinders of the external EGR is large based on the knock intensity for each cylinder calculated based on the knock signal output from the knock sensor 47 and the knock signal output from the knock sensor 47, the valve opening / closing timing ECU 3 for changing the map to a valve opening / closing timing map mainly composed of internal EGR so as to increase the amount of internal EGR gas. [Selection] Figure 1

Description

  The present invention relates to a variable valve control apparatus for an internal combustion engine.

  An internal combustion engine is known that has an EGR device that recirculates exhaust gas to the intake side as EGR (Exhaust Gas Recirculation) gas, thereby realizing NOx reduction of exhaust gas and improvement of fuel consumption.

  In Patent Document 1, when EGR is introduced, knock strength is detected for each cylinder from a knock signal from a knock sensor, and knocking is caused by variation in the air-fuel ratio between cylinders and variation in EGR distribution among cylinders. Discrimination from a cylinder is disclosed.

  In the thing of this patent document 1, when it is judged that it is knocking, the ignition timing is retarded uniformly for all cylinders or for each cylinder to avoid knocking.

JP 2013-11203 A

  However, the difference in EGR distribution between cylinders varies greatly depending on individual differences and environmental differences among internal combustion engines. In the case of an internal combustion engine in which the difference in EGR distribution between cylinders is large, if the ignition timing is uniformly retarded for all cylinders, even the cylinders in which knocking has not occurred are retarded, leading to deterioration in fuel consumption. Even if the retarding is performed for each cylinder, the fuel efficiency is deteriorated due to the decrease in the average torque of the cylinder, and the NVH (Noise, Vibration, Harshness) is deteriorated due to the increase in the torque difference among the cylinders.

  Accordingly, an object of the present invention is to provide a variable valve control apparatus for an internal combustion engine that can improve fuel efficiency even when the difference between cylinders in the distribution of external EGR is large.

  In order to solve the above problems, the present invention provides an exhaust gas recirculation pipe that recirculates a part of exhaust gas of an internal combustion engine to the intake side as external EGR gas, and adjusts the recirculation amount of the external EGR gas based on the operating state of the internal combustion engine. And an open / close timing of at least one of the intake valve and the exhaust valve of the internal combustion engine to control a part of the exhaust as internal EGR gas in the combustion chamber And a control unit that adjusts the amount of the internal EGR gas and detects the knock intensity of each cylinder of the internal combustion engine based on the detection result of the knock sensor. The amount of the internal EGR gas is changed based on the knock strength.

  Thus, according to the present invention, it is possible to provide a variable valve control apparatus for an internal combustion engine that can improve fuel efficiency even when the difference between cylinders in the distribution of the external EGR is large.

FIG. 1 is a schematic configuration diagram of a variable valve control apparatus for an internal combustion engine according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of a valve opening / closing timing map mainly for the external EGR of the variable valve control apparatus for an internal combustion engine according to the embodiment of the present invention. FIG. 3 is a diagram showing an example of a valve opening / closing timing map mainly for the internal EGR of the variable valve control apparatus for an internal combustion engine according to the embodiment of the present invention. FIG. 4 is a flowchart showing a variable valve control processing procedure of the variable valve control apparatus for an internal combustion engine according to the embodiment of the present invention.

  Hereinafter, a variable valve control apparatus for an internal combustion engine according to an embodiment of the present invention will be described in detail with reference to the drawings.

  In FIG. 1, a vehicle 1 equipped with an internal combustion engine variable valve control apparatus according to an embodiment of the present invention includes an internal combustion engine type engine 2 and an ECU (Engine Control Unit) 3 as a control unit. It is configured.

  The engine 2 is constituted by an in-line four cylinder having at least one, for example, four cylinders. The engine 2 is not limited to the in-line four cylinders, and may be, for example, a V-type engine, and the number of cylinders is not particularly limited to four.

  The engine 2 includes a piston, a cylinder, a connecting rod, and the like (not shown), and is a four-cycle engine that performs a series of four strokes including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke while the piston reciprocates the cylinder twice. It is configured.

  The piston housed in the cylinder is connected to the crankshaft via a connecting rod. The connecting rod converts the reciprocating motion of the piston into the rotational motion of the crankshaft.

  The cylinder head is provided with an ignition plug 4, an intake port 11, and an exhaust port 21. The spark plug 4 is disposed on the cylinder head with an electrode protruding into the combustion chamber, and its ignition timing is adjusted by the ECU 3.

  The intake port 11 is provided with an intake manifold 14 for introducing air into the combustion chamber. The intake manifold 14 is connected to an intake pipe 15 for sucking outside air. An intake passage 15 a communicating with the intake port 11 is formed in the intake pipe 15.

  The intake port 11 is provided with an intake valve 12. The intake valve 12 is opened and closed so as to communicate or block the intake passage 15a and the combustion chamber. The intake valve 12 is opened and closed by an intake side variable valve mechanism 13.

  As the intake side variable valve mechanism 13, for example, an electromagnetic variable valve mechanism that opens and closes the intake valve 12 by an electromagnetic actuator composed of an electromagnet and a spring can be used. Specifically, the intake side variable valve mechanism 13 opens the intake valve 12 that is normally urged in the valve closing direction by a spring by attracting a movable portion fixed to the intake valve 12 by excitation of an electromagnet. It is designed to move in the valve direction.

  The intake side variable valve mechanism 13 may be a hydraulic variable valve mechanism using a hydraulic actuator instead of the electromagnetic actuator. Further, as the intake side variable valve mechanism 13, a mechanical variable valve mechanism that can change the opening / closing timing of the intake valve 12 using cam members such as a main cam and a sub cam may be used.

  Further, the intake side variable valve mechanism 13 is configured such that, for example, the exciting current for the electromagnet is adjusted by the ECU 3 so that the lift amount of the intake valve 12 can be continuously changed with the opening / closing timing of the intake valve 12. It may be.

  The exhaust port 21 is provided with an exhaust manifold 24 for discharging exhaust gas generated by combustion of the air-fuel mixture in the combustion chamber to the outside of the vehicle. The exhaust manifold 24 is connected to the exhaust pipe 25. An exhaust passage 25 a communicating with the exhaust port 21 is formed inside the exhaust pipe 25.

  The exhaust port 21 is provided with an exhaust valve 22. The exhaust valve 22 is opened and closed so as to communicate or block the exhaust passage 25a and the combustion chamber. The exhaust valve 22 is opened and closed by an exhaust side variable valve mechanism 23.

  Since the exhaust side variable valve mechanism 23 has the same configuration as the intake side variable valve mechanism 13 described above, detailed description thereof is omitted, but the excitation and deexcitation of the electromagnet is controlled by the ECU 3 so that the exhaust The opening / closing timing of the valve 22 is arbitrarily changed. The exhaust side variable valve mechanism 23 may be a hydraulic variable valve mechanism using a hydraulic actuator instead of the electromagnetic actuator. Further, as the exhaust-side variable valve mechanism 23, a mechanical variable valve mechanism that can change the opening / closing timing of the exhaust valve 22 using cam members such as a main cam and a sub cam may be used. Therefore, the ECU 3 can easily adjust the valve opening period of the exhaust valve 22.

  A three-way catalyst 26 is provided in the exhaust pipe 25. The three-way catalyst 26 purifies the exhaust gas discharged from the combustion chamber of the engine 2, that is, burned gas.

  The engine 2 is provided with an exhaust recirculation pipe 41 that communicates the intake passage 15a and the exhaust passage 25a. The exhaust gas recirculation pipe 41 is configured to perform EGR to recirculate part of the exhaust gas to the intake side. The exhaust gas recirculation pipe 41 is provided with an EGR valve 42 as an exhaust gas recirculation control valve for adjusting the exhaust gas recirculation amount. EGR by the exhaust gas recirculation pipe 41 is referred to as external EGR.

  The EGR valve 42 is electrically connected to the ECU 3. The EGR valve 42 is configured to adjust the amount of exhaust gas recirculated to the intake side by controlling the valve opening degree according to a command signal from the ECU 3.

  The ECU 3 includes a computer unit that includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), a flash memory, an input port, and an output port.

  The ROM of the computer unit stores a program for causing the computer unit to function as the ECU 3 along with various control constants and various maps. That is, the computer unit functions as the ECU 3 when the CPU executes a program stored in the ROM.

  Various sensors such as a crank angle sensor 45, an accelerator opening sensor 46, and a knock sensor 47 are connected to the input port of the ECU 3.

  The crank angle sensor 45 outputs a rectangular crank angle signal for each predetermined crank angle as the engine 2 rotates. The ECU 3 calculates an engine speed that is the engine speed of the engine 2 based on the crank angle signal.

  The accelerator opening sensor 46 detects the amount of depression of an accelerator pedal (not shown) by the driver as the accelerator opening. Knock sensor 47 detects knocking vibration of engine 2 and outputs a knock signal corresponding to the magnitude of knocking vibration.

  On the other hand, various control objects such as the above-described ignition plug 4, intake side variable valve mechanism 13, exhaust side variable valve mechanism 23, EGR valve 42, and the like are connected to the output port of the ECU 3.

  The ECU 3 calculates the required load of the engine 2 based on the accelerator opening by the driver's operation, and calculates the intake air amount, fuel injection amount, and ignition timing of the engine 2 according to the required load. The ECU 3 controls the operating state of the engine 2 by controlling a throttle valve, an injector, and a spark plug 4 (not shown) so that the calculated intake air amount, fuel injection amount, and ignition timing are reached.

  The ECU 3 changes the opening / closing timing of the intake valve 12 and the exhaust valve 22 by controlling the intake side variable valve mechanism 13 and the exhaust side variable valve mechanism 23 described above, and opens the intake valve 12 and the exhaust valve 22. The valve period is adjusted. Here, changing the opening / closing timing of the intake valve 12 and the exhaust valve 22 means, for example, advancing or retarding the closing timing of the intake valve 12 and the exhaust valve 22.

  Further, the ECU 3 adjusts the length of the overlap period in which the valve opening period of the intake valve 12 and the valve opening period of the exhaust valve 22 overlap according to the engine speed and the magnitude of the engine load. ing. The ECU 3 controls the opening and closing timing of the intake valve 12 and the exhaust valve 22 to introduce a part of the exhaust gas discharged from the exhaust port 21 into the combustion chamber, the intake port 11 and the intake manifold 14 as internal EGR gas. EGR is performed.

  The total EGR gas amount of the external EGR gas and the internal EGR gas is experimentally obtained as a target amount according to the operating state of the engine 2, and based on this target amount, the amount of external EGR gas and the amount of internal EGR gas Is controlled.

  The ECU 3 is configured to switch whether the external EGR is executed (ON) or not (OFF) depending on the operating state of the engine 2. For example, the ECU 3 switches the external EGR on and off based on an external EGR map that is turned on or off depending on the engine speed and the engine load. The external EGR map is divided into an external EGR on area where the external EGR is turned on and an external EGR off area where the external EGR is turned off. Which area is entered depending on the engine speed and the engine load? It is decided. This external EGR map is experimentally obtained in advance and stored in the ROM of the ECU 3.

  For example, the ECU 3 obtains the engine load from a map in which the engine load is determined from the engine speed and the accelerator opening. The engine load map is experimentally obtained in advance and stored in the ROM of the ECU 3.

  The ECU 3 controls the amount of internal EGR gas in accordance with the operating state of the engine 2. For example, the ECU 3 controls the amount of internal EGR gas by controlling the opening / closing timing of the intake valve 12 and the exhaust valve 22 based on the valve opening / closing timing map in which the valve opening / closing timing is determined by the engine speed and the engine load. The ROM of the ECU 3 stores a valve opening / closing timing map obtained experimentally in advance.

  FIG. 2 is an example of a valve opening / closing timing map mainly composed of external EGR. The intake valve opening timing in FIG. 2 indicates which timing from the most retarded angle to the retarded angle or the advanced angle that the engine 2 can operate according to the engine speed and the engine load. The exhaust valve closing timing indicates which timing from the most advanced angle to the advanced angle or the retarded angle at which the engine 2 can be operated according to the engine speed and the engine load. In FIG. 2, the shaded portion indicates the external EGR on region.

  As shown in FIG. 2, this map shows that in the low load region, the opening amount of the intake valve 12 is retarded to increase the overlap amount and decrease the internal EGR amount, so that the external EGR gas is introduced. , Shaped to earn fuel economy. On the other hand, with respect to the exhaust valve 22, if the opening of the exhaust valve 22 is advanced, the exhaust valve 22 is quickly closed, and exhaust cannot be expelled and pump loss deteriorates.

  In the high load region, the throttle opening increases and the required torque increases, so the amount of intake air is large. Therefore, the amount of overlap is increased and the scavenging effect is enhanced. As a result, the introduction of the external EGR gas can be further promoted by discharging the internal EGR gas.

  When the external EGR is on, the ECU 3 determines that the difference between the external EGR cylinders is large on the basis of the knock strength for each cylinder, so that the internal EGR main valve opening / closing timing map is increased so as to increase the amount of internal EGR gas. Switch to.

  The ECU 3 calculates the knock intensity of each cylinder from the knock signal of the knock sensor 47 based on the combustion timing of each cylinder. For example, when the value obtained by subtracting the knock strength of the cylinder with the smallest knock strength from the knock strength of the cylinder with the largest knock strength continues for a predetermined time Y [s] or longer for a predetermined time Y [s], the ECU 3 It is determined that the difference is large. The predetermined value and the predetermined time are experimentally obtained in advance and stored in the ROM of the ECU 3.

  If the ECU 3 determines that the difference between the cylinders of the external EGR is large, the ECU 3 switches the valve opening / closing timing map from the valve opening / closing timing map mainly of the external EGR to the valve opening / closing timing map mainly of the internal EGR without performing ignition retard.

  FIG. 3 is an example of a valve opening / closing timing map mainly composed of internal EGR. Similar to FIG. 2, the intake valve opening timing indicates which timing from the most retarded angle to the retarded angle or the advanced angle at which the engine 2 can be operated. The exhaust valve closing timing indicates which timing from the most advanced angle at which the engine 2 can be operated to the advanced angle or the retarded angle is used. The hatched portion indicates the external EGR on region.

  As shown in FIG. 3, this map increases the internal EGR by increasing the overlap in the low load region. If the overlap is large, the intake pressure rises due to the internal EGR gas entering the intake pipe 15 during the exhaust stroke, so the external EGR also decreases.

  Further, in the high load region, if the intake valve opening timing is advanced, the internal EGR is reduced due to the scavenging effect contrary to the case of low load. When the exhaust valve closes in the high load region, the exhaust valve is closed early, the burned gas is trapped in the combustion chamber, and the internal EGR is increased.

  A variable valve control process performed by the variable valve control apparatus for an internal combustion engine according to the present embodiment configured as described above will be described with reference to FIG. Note that the variable valve control process described below is started when the ECU 3 starts operation and is executed at a preset time interval.

  In step S <b> 1, the ECU 3 calculates the knock intensity for each cylinder from the knock signal of the knock sensor 47.

  In step S2, the ECU 3 determines whether or not the operating state of the engine 2 is in the external EGR on region from the engine speed and the engine load. If it is determined that it is not the external EGR on region, the ECU 3 ends the process.

  If it is determined that the region is in the external EGR ON region, in step S3, the ECU 3 determines that the value obtained by subtracting the minimum knock strength from the maximum knock strength among the knock strengths for each cylinder exceeds a predetermined value for a predetermined time Y [ s] It is determined whether or not the process continues.

  When it is determined that the state in which the value obtained by subtracting the minimum knock strength from the maximum knock strength exceeds the predetermined value continues for a predetermined time Y [s] or longer, the ECU 3 in step S4, as shown in FIG. The intake valve 12 and the exhaust valve 22 are controlled using a valve opening / closing timing map mainly composed of internal EGR.

  On the other hand, when it is determined that the state in which the value obtained by subtracting the minimum knock intensity from the maximum knock intensity exceeds the predetermined value does not continue for the predetermined time Y [s] or longer, the ECU 3 in step S5, as shown in FIG. The intake valve 12 and the exhaust valve 22 are controlled using a valve opening / closing timing map mainly composed of external EGR.

  As described above, the above-described embodiment includes the ECU 3 that calculates the knock intensity for each cylinder based on the knock signal output from the knock sensor 47 and changes the amount of the internal EGR gas based on the knock intensity.

  Thus, when it is determined that the difference between the external EGR cylinders is large based on the knock strength, the amount of the internal EGR gas is changed. For this reason, even when the difference between the cylinders in the distribution of the external EGR is large, the fuel consumption can be improved.

  Further, when the value obtained by subtracting the knock strength of the cylinder with the smallest knock strength from the knock strength of the cylinder with the largest knock strength continues for a predetermined time Y [s] or longer for a predetermined time Y [s], the ECU 3 It is determined that the difference is large, and the amount of internal EGR gas is changed.

  As a result, when a state in which the value obtained by subtracting the knock strength of the cylinder having the smallest knock strength from the knock strength of the cylinder having the largest knock strength exceeds the predetermined value continues for a predetermined time Y [s] or longer, the difference between the cylinders of the external EGR Is determined to be large. For this reason, it is possible to reliably determine the case where the difference between the cylinders in the external EGR is large, and it is possible to improve the fuel efficiency even when the difference between the cylinders in the distribution of the external EGR is large.

  When the ECU 3 determines that the difference between the cylinders in the external EGR is large, the ECU 3 changes the valve opening / closing timing map to a valve opening / closing timing map mainly composed of the internal EGR so as to increase the amount of internal EGR gas.

  Thereby, when it is determined that the difference between the cylinders of the external EGR is large, the internal EGR gas is changed so as to increase the amount. For this reason, the amount of internal EGR gas can be increased when the difference between the cylinders of the external EGR is large, and the fuel efficiency can be improved even when the difference between the cylinders of the distribution of the external EGR is large.

  Furthermore, since the internal EGR has a larger heat capacity than the external EGR and does not easily rise in temperature when compressed, knocking can be prevented.

  In this embodiment, the valve opening / closing timing map is switched when the difference between the cylinders of the external EGR is large, but at the same time, the EGR valve 42 may be closed or the opening degree of the EGR valve 42 may be changed. Good.

  While embodiments of the invention have been disclosed, it will be apparent to those skilled in the art that changes may be made without departing from the scope of the invention. All such modifications and equivalents are intended to be included in the following claims.

1 vehicle 2 engine (internal combustion engine)
3 ECU (control unit)
12 Intake Valve 13 Intake Side Variable Valve Mechanism 22 Exhaust Valve 23 Exhaust Side Variable Valve Mechanism 41 Exhaust Recirculation Pipe 42 EGR Valve 45 Crank Angle Sensor 46 Acceleration Opening Sensor 47 Knock Sensor

Claims (3)

An exhaust gas recirculation pipe for recirculating a part of the exhaust gas of the internal combustion engine to the intake side as external EGR gas;
An EGR valve that adjusts a recirculation amount of the external EGR gas based on an operating state of the internal combustion engine;
A knock sensor for detecting knocking vibration of the internal combustion engine;
A control unit that controls the opening / closing timing of at least one of the intake valve and the exhaust valve of the internal combustion engine, introduces a part of the exhaust gas into the combustion chamber as an internal EGR gas, and adjusts the amount of the internal EGR gas. ,
The control unit detects a knock intensity for each cylinder of the internal combustion engine based on a detection result of the knock sensor, and changes the amount of the internal EGR gas based on the knock intensity for each cylinder. Valve control device.   2. The internal combustion engine according to claim 1, wherein the control unit changes the amount of the internal EGR gas when a state in which a difference value between a maximum value and a minimum value of knock strength for each cylinder exceeds a predetermined value continues for a predetermined time or longer. Variable valve controller for engine.   The variable valve control apparatus for an internal combustion engine according to claim 1, wherein the control unit is changed to increase the amount of the internal EGR gas.

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