JP2008274810A - Control device for variable valve train - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for a variable valve train implementing valve overlap in a suitable manner when acquiring internal EGR effect. <P>SOLUTION: An ECU 1 controls an InVVT 61 and an ExVVT 62 which can vary valve timing of intake and exhaust valves 54, 55 of an internal combustion engine 50. The ECU 1 comprises: a first specific valve timing changing means prioritizing change of the valve timing of the intake valve 54 to secure target overlap OL when the valve overlap is changed according to an operational status of the internal combustion engine 50, and when the internal combustion engine 50 is in the operational status where turbulence intensity in a cylinder should be focused; and a second specific valve timing changing means prioritizing change of the valve timing of the exhaust valve 55 to secure target overlap OL, when the internal combustion engine 50 is in the operational status where ignition property of air-fuel mixture should be focused. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for a variable valve mechanism, and more particularly, to a control device for a variable valve mechanism for controlling the variable valve mechanism so as to realize valve overlap in a preferred mode for obtaining an internal EGR effect.

  Conventionally, an internal combustion engine having a variable valve mechanism is known. In such an internal combustion engine, it is known that both reduction of NOx and high efficiency of the internal combustion engine can be achieved by an internal EGR effect obtained by controlling the valve timing of the intake and exhaust valves. In this regard, for example, Patent Documents 1 to 5 propose techniques that are considered to be related to the present invention as techniques that use the internal EGR effect.

JP 2003-148180 A JP-A-2005-315126 JP 2004-11620 A JP 2003-206789 A JP 2002-161770 A

  In obtaining an internal EGR effect in an internal combustion engine equipped with a variable valve mechanism, it has been considered that the valve overlap mode has not always been optimal. For this reason, in an internal combustion engine equipped with a variable valve mechanism, There is room for achieving a higher level of both NOx reduction and higher efficiency of the internal combustion engine. On the other hand, when the operation state of the internal combustion engine is an operation state in which it is difficult to ignite the air-fuel mixture (for example, at high rotation and low load), misfire due to blow-off occurs depending on the mode of valve overlap, As a result, there is a possibility that emission may increase or drivability may deteriorate, so that there is room for improvement in the aspect of valve overlap in this respect.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a control device for a variable valve mechanism capable of realizing valve overlap in a suitable manner for obtaining an internal EGR effect.

  In order to solve the above problems, the present invention provides a control device for a variable valve mechanism for controlling a variable valve mechanism that varies a valve timing of an intake / exhaust valve of an internal combustion engine. When changing the valve overlap according to the above, when the operating state of the internal combustion engine is in the first predetermined operating state, the required valve overlap has changed only the valve timing of the intake valve from the reference phase A first specific valve timing changing means for preserving a necessary valve overlap by preferentially changing the valve timing of the intake valve when the valve overlap has a size that can be ensured in the case; When the engine operating state is in the second predetermined operating state, the necessary valve overlap causes only the valve timing of the exhaust valve from the reference phase. A second specific valve timing changing means for ensuring a necessary valve overlap by preferentially changing the valve timing of the exhaust valve when the valve overlap has a size that can be secured in the case of a change. It is characterized by providing.

  Here, when the valve timing of the intake valve is changed, the turbulence intensity in the cylinder has a certain sensitivity to the change of the valve timing. FIG. 5 is a diagram showing the relationship between the turbulence intensity in the cylinder and the valve timing of the intake and exhaust valves. As a result of verifying the relationship between the in-cylinder turbulence intensity and the valve timing of the intake / exhaust valves with an engine simulator, the correlation as shown in FIG. 5 was obtained under all operating conditions. FIG. 5 shows the results of verification over the entire operating conditions generally assumed for a naturally aspirated SI (Spark Ignition) gasoline engine. Specifically, as an example of the entire operating conditions, engine rotation The number is in the range from 600 to 7,000 rpm, the charging efficiency is in the range from 15 to 90%, and the valve timing is from -3 to 37 deg. Within the range of btdc, the intake valve closing timing is 71 to 31 deg. Within the range of abdc, the exhaust valve opening timing is 60 to 25 deg. Within the range of bbdc, the exhaust valve closing timing is 4 to 39 deg. Verification was performed within the range of atdc.

  As shown in FIG. 5, it can be seen that when the valve timing of the intake valve is advanced, the turbulence intensity in the cylinder increases accordingly. This is thought to be due to changes in the inflow mode of the intake air. Specifically, the momentum of the intake air flowing into the cylinder and the movement speed of the piston at that time are major factors that affect the turbulence intensity in the cylinder. It can be considered that the more the intake valve valve timing is advanced, the more the intake air flows into the cylinder when the movement speed of the piston is faster. Therefore, when changing the valve overlap, if the valve timing of the intake valve is preferentially changed by the first specific valve timing changing means shown in the present invention to ensure the valve overlap, the same overlap amount is obtained. A larger internal EGR effect can be obtained, so that both reduction of NOx and high efficiency of the internal combustion engine can be realized at a higher level.

  On the other hand, as shown in FIG. 5, when the valve overlap is changed by changing the valve timing of the exhaust valve, the turbulence intensity in the cylinder hardly changes. As described above, it is considered that the strength of the flow of the intake air flowing into the cylinder and the moving speed of the piston at that time are the major factors affecting the turbulence intensity in the cylinder, as described above. It is considered that these factors are not affected by the valve timing of the exhaust valve. Therefore, when changing the valve overlap, if the valve timing of the exhaust valve is preferentially changed by the second specific valve timing changing means shown in the present invention to ensure the valve overlap, misfire due to blow-off will occur. In an operation state that is likely to occur, the occurrence of misfire can be suppressed while securing the internal EGR effect with the same overlap amount, thereby suppressing an increase in emission and deterioration in drivability due to misfire. Therefore, according to the present invention, by providing the first and second specific valve timing changing means, it is possible to realize the valve overlap in a suitable manner for obtaining the internal EGR effect.

  In the present invention, when the first specific valve timing changing means preferentially changes the valve timing of the intake valve, the valve timing of the intake valve is changed while keeping the valve timing of the exhaust valve at a reference phase. In addition, when the second specific valve timing changing means preferentially changes the valve timing of the exhaust valve, the valve timing of the exhaust valve is changed while keeping the valve timing of the intake valve at a reference phase. May be.

  Here, FIG. 5 specifically shows the result when the valve timing of the intake valve is changed while the valve timing of the exhaust valve is kept at the reference phase. If the expansion of the valve overlap from the state in which the valve timing is at the reference phase (hereinafter simply referred to as the reference state) is due to the change in only the valve timing of the intake valve, the turbulence intensity in the cylinder will be reduced. It can increase more suitably. FIG. 5 shows the result when the valve timing of the exhaust valve is changed while keeping the valve timing of the intake valve at the reference phase, and the valve overlap from the reference state is thus shown. If the expansion is made by changing only the valve timing of the exhaust valve, it is possible to more suitably suppress the occurrence of misfire due to blow-off while ensuring the internal EGR effect. Therefore, specifically, for example, it is preferable to change the valve timing as in the present invention.

  The invention according to claim 1 relates to the present invention, for example, when the first specific valve timing changing means is taken as an example, and the valve timing of the exhaust valve is in a phase very close to the reference phase. Even when the valve timing of the intake valve is changed, or when the valve timing of the exhaust valve is slightly changed from the reference state together with the valve timing of the intake valve, it is considered that the corresponding effect can be obtained. Yes. In this respect, the priority of the first aspect is that, for example, when the first specific valve timing changing means is taken as an example, the expansion of the valve overlap from the reference state mainly changes the valve timing of the intake valve. However, the higher the ratio is due to the change in the valve timing of the intake valve, the higher the effect will be obtained. It is preferable that the ratio is equivalent to a degree that can be regarded as a result of a change in only the valve timing, that is, a change in only a valve timing of the intake valve. The same applies to the second specific valve timing changing means.

  In the present invention, the first specific valve timing changing means may further be configured such that the required valve overlap is a valve overlap having a magnitude that cannot be secured when only the valve timing of the intake valve is changed from the reference phase. The valve timing of the intake valve is changed to the maximum in the direction of expanding the valve overlap, and the valve timing of the exhaust valve is changed to ensure the necessary valve overlap, and further When the second specific valve timing changing means has a valve overlap of a size that cannot be secured when the required valve overlap is changed only from the reference phase of the valve timing of the exhaust valve, the valve of the exhaust valve Change the timing to the maximum to increase the valve overlap. Together, by changing the valve timing of the intake valve may ensure the valve overlap required.

  If the necessary valve overlap cannot be obtained by simply changing the valve timing of the intake valve or the exhaust valve from the reference state, it is preferable to change the valve timing as in the present invention. According to the present invention, even in such a case, the first specific valve timing changing means can suitably obtain a larger internal EGR effect, and the second specific valve timing changing means is preferable. Moreover, the occurrence of misfire can be suppressed while ensuring the internal EGR effect.

  Further, in the present invention, the first predetermined operating state is an operating state in which the turbulence intensity in the cylinder of the internal combustion engine should be emphasized, and the second predetermined operating state emphasizes the ignitability of the air-fuel mixture. It may be the driving state to be performed. Further, from the nature of the first and second specific valve timing changing means, the first and second predetermined operating states are preferably operating states as in the present invention. More specifically, the first and second operating states include, for example, an operating state in which the turbulence intensity in the cylinder should be emphasized according to the operating state of the internal combustion engine by experiments and the like, and the ignitability of the air-fuel mixture It is possible to specify the operating state that should be emphasized by defining the operating state with map data corresponding to the operating state of the internal combustion engine.

  ADVANTAGE OF THE INVENTION According to this invention, the control apparatus of the variable valve mechanism which can implement | achieve a valve overlap in a suitable aspect in obtaining an internal EGR effect can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram schematically showing a control device for a variable valve mechanism according to the present embodiment realized by an ECU (Electronic Control Unit) 1 together with an internal combustion engine system 100. The internal combustion engine system 100 includes an intake system 10 and an internal combustion engine 50. The intake system 10 includes an air cleaner 11, an air flow meter 12, an electric throttle 13, an intake manifold 14, an intake port 52a, and intake pipes appropriately disposed between these components. Yes.

  The air cleaner 11 is configured to filter the intake air supplied to the internal combustion engine 50. The air flow meter 12 is configured to measure the intake air amount, and outputs a signal corresponding to the intake air amount. The electric throttle 13 is configured to adjust the intake flow rate supplied to the internal combustion engine 50 under the control of the ECU 1, and includes a throttle valve 13a, an electric motor (not shown), an idle SW, a throttle opening sensor, and the like. Has been. The intake manifold 14 is configured to distribute intake air to the cylinders of the internal combustion engine 50.

  The internal combustion engine 50 includes a cylinder block 51, a cylinder head 52, a piston 53, an intake valve 54, an exhaust valve 55, a spark plug 56, a connecting rod 57, a crankshaft 58, an intake side VVT (Variable Valve). Timing) 61 and an exhaust side VVT 62. The internal combustion engine 50 shown in the present embodiment is an in-line four-cylinder naturally aspirated SI gasoline engine. However, the cylinder arrangement structure and the number of cylinders are not limited to this, and the internal combustion engine 50 may be a so-called direct injection gasoline engine, a lean burn gasoline engine, or the like. It may be a naturally aspirated SI engine. In FIG. 1, the main part of the internal combustion engine 50 is shown with respect to the cylinder 51a as a representative of each cylinder, but the other cylinders have the same structure.

  The cylinder block 51 is formed with a substantially cylindrical cylinder 51a. A piston 53 is accommodated in the cylinder 51a. A cylinder head 52 is fixed to the upper surface of the cylinder block 51. The combustion chamber 59 is formed as a space surrounded by the cylinder block 51, the cylinder head 52 and the cylinder 53. The cylinder head 52 includes an intake port 52a for introducing intake air to the combustion chamber 59, and an exhaust port 52b for exhausting the combusted gas from the combustion chamber 59. The intake and exhaust ports 52a and 52b are opened and closed. An intake valve 54 and an exhaust valve 55 are provided.

  The spark plug 56 is disposed in the cylinder head 52 with an electrode protruding substantially at the center above the combustion chamber 59. The piston 53 is connected to the crankshaft 58 via a connecting rod 57, and the reciprocating motion of the piston 53 is converted into rotational motion by the crankshaft 58. The internal combustion engine 50 is provided with a crank angle sensor 60 that generates an output pulse proportional to the rotational speed NE, a water temperature sensor (not shown) for detecting the water temperature, and the like. In this embodiment, the fuel injection valve 31 is disposed in the intake manifold 14 with the injection hole projecting from the intake passage. However, the present invention is not limited to this, and the fuel injection valve 31 may be, for example, an intake port 52a or a cylinder. It may be arranged so that fuel can be injected into the inside.

  An intake side VVT (hereinafter simply referred to as InVVT) 61 is a configuration for changing the valve timing of the intake valve 54, and includes an intake side camshaft and a hydraulic device (not shown). Under the control of the ECU 1, the valve timing of the intake valve 54 is changed by changing the phase of the intake camshaft with respect to the phase of the crankshaft 59 by the hydraulic device. This hydraulic device employs a mechanism that can continuously change the phase of the intake camshaft.

  The exhaust side VVT (hereinafter simply referred to as ExVVT) 62 is a configuration for changing the valve timing of the exhaust valve 55, and includes an exhaust side camshaft and a hydraulic device (not shown). Under the control of the ECU 1, the ExVVT 62 can continuously change the valve timing of the exhaust valve 55 in the same manner as the InVVT 61. It should be noted that a mechanism capable of changing the valve lift amount, the operating angle (valve opening period) and the like together with the valve timing may be applied to the InVVT 61 and the ExVVT 62. In this embodiment, the variable valve mechanism is realized by the InVVT 61 and the ExVVT 62.

  The ECU 1 is a microcomputer (hereinafter simply referred to as a microcomputer) having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (not shown). And an input / output circuit and the like. The ECU 1 is mainly configured to control the internal combustion engine 50. In this embodiment, the ECU 1 also controls the fuel injection valve 31 and the ignition plug 56 (more specifically, an igniter not shown), InVVT 61, ExVVT 62, and the like. The ECU 1 includes an air flow meter 12, a throttle opening sensor and an idle switch built in the electric throttle 13, a crank angle sensor 60, and sensors 61 a for detecting the opening / closing timings of the intake and exhaust valves 54 and 55 included in the InVVT 61 and ExVVT 62, 62a, various sensors such as an ignition SW (not shown), and SWs are electrically connected. The ECU 1 is electrically connected to various control objects such as the electric throttle 13, the fuel injection valve 31, the spark plug 56, the InVVT 61, and the ExVVT 62. Note that these connections are omitted as appropriate in FIG. 1 for convenience of illustration.

  The ROM is configured to store a program describing various processes executed by the CPU, map data, and the like. In this embodiment, the ROM rotates based on the output of the crank angle sensor 60 in addition to the program for controlling the internal combustion engine 50. A program for detecting the rotational speed for detecting the number NE, a program for detecting the intake air amount for detecting the intake air amount GA based on the output of the air flow meter 12, and the detected rotational speed NE and the intake air amount A program for calculating the charging efficiency KL for calculating the charging efficiency KL based on the GA, a target overlap OL corresponding to the operating state of the internal combustion engine 50 to obtain the internal EGR effect (the required valve overlap described in the claims) The exhaust valve is based on a program for calculating a target overlap for calculating the output of the sensor 62a for detecting the opening / closing timing. 5 and the exhaust valve closing timing detecting program to detect closing timing are also stored programs for VVT control for controlling the InVVT61 and ExVVT62. These programs may be configured as a part of the program for controlling the internal combustion engine 50, for example.

  In the present embodiment, the VVT control program is configured to have the following first and second specific valve timing changing programs. The first specific valve timing changing program changes the valve overlap in accordance with the operation state of the internal combustion engine 50. When the operation state of the internal combustion engine 50 is in the first predetermined operation state, the target overlap is performed. When the OL is a valve overlap having a magnitude that can be secured when only the valve timing of the intake valve 54 is changed from the reference phase, the target overlap OL is changed by preferentially changing the valve timing of the intake valve 54. Has been created to ensure. The first predetermined operating state is set to an operating state in which the in-cylinder turbulence intensity of the internal combustion engine 50 should be emphasized, and more specifically, this operating state is a region corresponding to the operating state of the internal combustion engine 50. It is defined in the judgment map data. The area determination map data is stored in the ROM.

  In addition, when the first specific valve timing changing program preferentially changes the valve timing of the intake valve 54, in the present embodiment, specifically, the valve timing of the exhaust valve 55 is kept at the reference phase. It has been created to change the valve timing. Further, the first specific valve timing changing program, when the target overlap OL is a valve overlap of a size that cannot be secured when only the valve timing of the intake valve 54 is changed from the reference phase, The valve timing is set to a state in which the valve overlap is maximized in a direction in which the valve overlap is expanded, and the target overlap OL is secured by changing the valve timing of the exhaust valve 55.

  On the other hand, when changing the valve overlap according to the operating state of the internal combustion engine 50, the second specific valve timing changing program sets the target when the operating state of the internal combustion engine 50 is in the second predetermined operating state. When the overlap OL is a valve overlap having a magnitude that can be secured when only the valve timing of the exhaust valve 55 is changed from the reference phase, the valve timing of the exhaust valve 55 is changed preferentially, thereby It is created so as to secure the wrap OL. The second predetermined operation state is set to an operation state in which the ignitability of the air-fuel mixture should be emphasized, and more specifically, this operation state is defined by the above-described region determination map data.

  In addition, when the second specific valve timing changing program preferentially changes the valve timing of the exhaust valve 55, in the present embodiment, specifically, the valve timing of the intake valve 54 is kept at the reference phase. It has been created to change the valve timing. Further, the second specific valve timing changing program, when the target overlap OL is a valve overlap of a size that cannot be secured when only the valve timing of the exhaust valve 55 is changed from the reference phase, The valve timing is set to a state in which the valve overlap is maximized in the direction in which the valve overlap is expanded, and the valve timing of the intake valve 54 is changed to ensure the target overlap OL.

  In the present embodiment, various detection means, calculation means, determination means, control means, and the like are realized by the microcomputer and various programs described above, and in particular, the rotation speed detection means is realized by the microcomputer and the rotation speed detection program. The microcomputer and the program for detecting the intake air amount are the intake air amount detecting means, the microcomputer and the program for calculating the charging efficiency are the charging efficiency calculating means, and the microcomputer and the program for calculating the target overlap are the target overlap calculating means. However, the microcomputer and the exhaust valve closing timing detection program are the exhaust valve closing timing detection means, the microcomputer and the first valve timing change program are the first valve timing changing means, the microcomputer and the second valve timing are The second valve timing changing means is realized by the change program.

  Next, processing performed by the ECU 1 will be described in detail with reference to the flowchart shown in FIG. The ECU 1 controls the InVVT 61 and the ExVVT 62 by the CPU repeatedly executing the processing shown in the flowchart based on the above-described various programs stored in the ROM. The CPU executes a process of determining whether or not the ignition SW (IGSW) is ON (step S11). If the determination is negative, there is no need to execute special processing, and the process returns to step S11. On the other hand, if the determination is affirmative, the CPU executes processing for determining whether or not the idle SW is OFF (step S12). If it is idling, a negative determination is made in this step. In this case, since no special processing is required in this flowchart, the process returns to step S11.

  On the other hand, if an affirmative determination is made in step S12, the CPU executes a process of detecting the rotational speed NE based on the output of the crank angle sensor 60 (step S13). Subsequently, the CPU executes a process of detecting the intake air amount GA based on the output of the air flow meter 12 (step S14). Subsequently, the CPU executes a process for calculating the charging efficiency KL from the detected rotational speed NE and intake air amount GA (step S15). Further, the CPU executes a process for calculating the target overlap OL (step S16).

  FIG. 3 is a diagram schematically showing target overlap map data. The target overlap OL is target overlap map data and is set in advance according to the operating state of the internal combustion engine 50. More specifically, the target overlap OL in this map data is set in advance as the operating state of the internal combustion engine 50 in accordance with the rotational speed NE and the charging efficiency KL. Therefore, as shown in FIG. 3A, the target overlap map data has three-dimensional axes corresponding to the rotational speed NE, the charging efficiency KL, and the target overlap OL. On the other hand, FIG. 3B schematically shows a cross section of the target overlap map data at a certain filling efficiency KL, and FIG. 3C shows the target overlap map data at a certain rotational speed NE. Is schematically shown in cross section. The target overlap map data is stored in advance in the ROM.

  For this reason, the CPU refers to the target overlap map data described above based on the rotational speed NE specifically detected in step S16 and the calculated charging efficiency KL, and reads the corresponding target overlap OL by reading the corresponding target overlap OL. A process for calculating the overlap OL is executed. Subsequently, the CPU performs area determination (step S17). In this region determination, specifically, it is determined whether or not the operating state of the internal combustion engine 50 is in an operating state where importance should be given to the in-cylinder turbulence, or whether the ignitability of the air-fuel mixture should be emphasized. The

  FIG. 4 is a diagram schematically showing the area determination map data. In this area determination map data, an operating state in which the in-cylinder turbulence should be emphasized and an operating state in which the ignitability of the air-fuel mixture should be emphasized are set in advance according to the operating state of the internal combustion engine 50. In this map data, these operating states are more specifically set in advance as operating states of the internal combustion engine 50 according to the rotational speed NE and the charging efficiency KL. For this reason, the CPU refers to the region determination map data based on the rotational speed specifically detected in step S17 and the calculated charging efficiency KL, whereby the operating state of the internal combustion engine 50 determines the in-cylinder turbulence intensity. It is determined whether or not it is in an operating state that should be emphasized or whether or not it is in an operating state in which the ignitability of the air-fuel mixture should be emphasized.

If it is determined in step S17 that the operating state of the internal combustion engine 50 is in an operating state where the in-cylinder turbulence intensity should be emphasized, the CPU executes a process of calculating the target intake valve timing advance amount IVT ( Step S18). The target intake valve timing advance amount IVT is calculated by the following formula 1 or formula 2, with the advance limit value of InVVT 61 being IVTlim.
(Equation 1)
If OL ≦ IVTlim, IVT = OL
Here, OL ≦ IVTlim corresponds to a case where the target overlap OL is a valve overlap of a size that can be secured when only the valve timing of the intake valve 54 is changed from the reference phase.
(Equation 2)
If OL> IVTlim, IVT = IVTlim
Here, OL> IVTlim corresponds to a case where the target overlap OL is a valve overlap of a size that cannot be secured when only the valve timing of the intake valve 54 is changed from the reference phase.

Subsequently, the CPU executes a process of calculating the target exhaust valve timing retardation amount EVT (step S19). The target exhaust valve timing retardation amount EVT is calculated by the following equation (3).
(Equation 3)
EVT = OL-IVT
Here, when OL ≦ IVTlim, since IVT = OL, EVT = 0 (reference phase). Further, when OL> IVTlim, since IVT = IVTlim, EVT = OL-IVTlim.

  Thus, when changing the valve overlap according to the operating state of the internal combustion engine 50, when the operating state of the internal combustion engine 50 is in an operating state where emphasis is placed on the in-cylinder turbulence intensity, the IVT calculated in steps S18 and S19 is performed. Since the InVVT 61 and the ExVVT 62 can be controlled based on the EVT and the EVT, when the target overlap OL is a valve overlap of a size that can be secured when only the valve timing of the intake valve 54 is changed from the reference phase, the exhaust valve 55 The target overlap OL can be secured by changing the valve timing of the intake valve 54 while keeping the valve timing at the reference phase.

  If the target overlap OL is a valve overlap that cannot be secured when only the valve timing of the intake valve 54 is changed from the reference phase, the valve timing of the intake valve 54 is expanded to the valve overlap. The target overlap OL can be ensured by changing the valve timing of the exhaust valve 55 while changing to the maximum direction. Thereby, a larger internal EGR effect can be suitably obtained.

On the other hand, when it is determined in step S17 that the operating state of the internal combustion engine 50 is in an operating state where the ignitability of the air-fuel mixture should be emphasized, the CPU executes a process of calculating the target exhaust valve timing retardation amount EVT. (Step S21). That is, when it is determined that the operating state should place importance on the ignitability of the air-fuel mixture, first, processing for calculating the target exhaust valve timing retardation amount EVT is executed. The target exhaust valve timing retardation amount EVT is calculated by the following Equation 4 or Equation 5, with the ExVVT62 retardation limit value being EVTlim.
(Equation 4)
If OL ≦ EVTlim, EVT = OL
Here, OL ≦ EVTlim corresponds to a case where the target overlap OL is a valve overlap having a size that can be secured when only the valve timing of the exhaust valve 55 is changed from the reference phase.
(Equation 5)
If OL> EVTlim, EVT = EVTlim
Here, OL> EVTlim corresponds to a case where the target overlap OL is a valve overlap of a size that cannot be secured when only the valve timing of the exhaust valve 55 is changed from the reference phase.

Subsequently, the CPU executes a process of calculating the target intake valve timing advance amount IVT (step S22). The target intake valve timing advance amount IVT is calculated by the following equation 6.
(Equation 6)
IVT = OL-EVT
Here, when OL ≦ EVTlim, since EVT = OL, IVT = 0 (reference phase). Further, when OL> EVTlim, EVT = EVTlim, so IVT = OL-EVTlim.

  Thus, when changing the valve overlap according to the operating state of the internal combustion engine 50, when the operating state of the internal combustion engine 50 is in an operating state where importance should be placed on the ignitability of the air-fuel mixture, the IVT calculated in steps S21 and S22 and Since the InVVT 61 and the ExVVT 62 can be controlled based on the EVT, if the target overlap OL is a valve overlap having a size that can be secured when only the valve timing of the exhaust valve 55 is changed from the reference phase, the intake valve 54 The target overlap OL can be ensured by changing the valve timing of the exhaust valve 55 while keeping the valve timing at the reference phase.

  If the target overlap OL is a valve overlap that cannot be ensured when only the valve timing of the exhaust valve 55 is changed from the reference phase, the valve overlap of the exhaust valve 55 is increased. The target overlap OL can be ensured by changing the valve timing of the intake valve 54 while changing the direction to the maximum. Thereby, generation | occurrence | production of the misfire by blow-off can be suppressed suitably, ensuring the internal EGR effect. As described above, the ECU 1 capable of realizing the valve overlap in a preferable manner for obtaining the internal EGR effect can be realized.

  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.

1 is a diagram schematically showing an ECU 1 together with an internal combustion engine system 100. FIG. It is a figure which shows the process performed by ECU1 with a flowchart. It is a figure which shows the map data for target overlap typically. It is a figure which shows the map data for area | region determination typically. It is a figure which shows the relationship between the disturbance strength in a cylinder, and the valve timing of an intake / exhaust valve.

Explanation of symbols

1 ECU
10 Intake system 50 Internal combustion engine 61 InVVT
62 ExVVT
100 Internal combustion engine system

Claims (4)

A control device for a variable valve mechanism for controlling a variable valve mechanism that varies a valve timing of an intake / exhaust valve of an internal combustion engine,
In changing the valve overlap according to the operating state of the internal combustion engine, when the operating state of the internal combustion engine is in the first predetermined operating state, the necessary valve overlap is only the valve timing of the intake valve. The first specific valve timing for ensuring the necessary valve overlap by preferentially changing the valve timing of the intake valve when the valve overlap is large enough to be ensured when the valve is changed from the reference phase. Change means,
When the operating state of the internal combustion engine is the second predetermined operating state, the required valve overlap is a valve overlap having a magnitude that can be secured when only the valve timing of the exhaust valve is changed from the reference phase. In some cases, the control device for the variable valve mechanism includes second specific valve timing changing means for ensuring a necessary valve overlap by preferentially changing the valve timing of the exhaust valve. . When the first specific valve timing changing unit preferentially changes the valve timing of the intake valve, the valve timing of the intake valve is changed while keeping the valve timing of the exhaust valve at a reference phase,
The second specific valve timing changing means changes the valve timing of the exhaust valve while keeping the valve timing of the intake valve at a reference phase when changing the valve timing of the exhaust valve preferentially. The control device for a variable valve mechanism according to claim 1. Further, when the first specific valve timing changing means has a valve overlap of a size that cannot be secured when the required valve overlap is changed only from the reference phase of the valve timing of the intake valve, the intake valve In addition to ensuring the necessary valve overlap by changing the valve timing of the exhaust valve, the valve timing of
Further, when the second specific valve timing changing means has a valve overlap of a size that cannot be secured when the required valve overlap is changed only from the reference phase of the valve timing of the exhaust valve, the exhaust valve The valve timing is set to a state where the valve overlap is maximized in a direction in which the valve overlap is expanded, and the required valve overlap is secured by changing the valve timing of the intake valve. Or the control apparatus of the variable valve mechanism of 2. The first predetermined operating state is an operating state where importance is attached to the turbulence intensity in the cylinder of the internal combustion engine, and the second predetermined operating state is an operating state where importance is attached to the ignitability of the air-fuel mixture. The control device for a variable valve mechanism according to any one of claims 1 to 3, wherein the control device is a variable valve mechanism.

Images