JP2020007927A - Variable valve system of internal combustion engine and control device thereof - Google Patents

Abstract

To provide a variable valve system of an internal combustion engine which can favorably improve fuel economy even in a low-load region and a middle-load region which is larger in load than a low-load region, and its control device.SOLUTION: In a first load region, exhaust closing timing at which an exhaust valve 5 is closed is set at first exhaust closing timing (EVC1) before an exhaust top dead point, opening timing at which an intake valve is opened is set at first intake opening timing (IVO1) after the exhaust top dead point, and negative valve overlap zones (NVO) are formed at the exhaust valve and the intake valve. In a second load region exceeding the first load region, the exhaust closing timing is set at second exhaust closing timing (EVC2) after the exhaust top dead point, the intake opening timing is set at second intake opening timing (IVO2) before the exhaust top dead point, and positive valve overlap zones (PVO) are formed at the exhaust valve and the intake valve.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a variable valve operating system for an internal combustion engine, and more particularly, to a variable valve operating system for an internal combustion engine having a variable valve operating mechanism for controlling the valve timing of an exhaust valve and an intake valve, and a control device therefor.

  Regulations on automobile fuel consumption and exhaust gas harmful components have been tightened, and will continue to be more stringent in the future. In particular, with regard to fuel consumption (hereinafter referred to as fuel efficiency), further reduction in fuel efficiency is demanded because emitted carbon dioxide has a large effect on global warming.

  Against this background, recently, the exhaust-side variable valve mechanism that controls the valve timing (opening and closing timing) of the exhaust valve of the internal combustion engine, or the valve timing (opening and closing timing) of the intake valve is controlled. It has been proposed to mount a variable valve system including an intake-side variable valve mechanism on an internal combustion engine.

  As one method for achieving low fuel consumption, it is effective to reduce pump loss. For example, in the automotive engineering, September 1995, "Toyota VVT-i" (Non-Patent Document 1) Using the intake-side variable valve mechanism, the operating angle of the exhaust valve and the operating angle of the intake valve overlap each other to improve fuel efficiency in the medium load area (= partial load area). A variable valve operating system for setting a positive valve overlap (PVO: Positive Valve Overlap) section has been proposed.

  As described above, when the positive valve overlap section (PVO) is set in the medium load region, since both the intake valve and the exhaust valve are open, the pump loss caused when the piston descends is reduced, and the fuel consumption is reduced by that much. Can be improved.

Automotive Engineering September 1995 "Toyota VVT-i"

  As described above, when the positive valve overlap section (PVO) is set in the medium load region, fuel efficiency can be improved due to reasons such as a reduction in pump loss. However, if this positive valve overlap section (PVO) is set in the low load region, part of the exhaust gas is returned to the intake system, cooled there, and re-inhaled into the cylinder, so that the The temperature of the exhaust gas decreases accordingly, and in a low load region where the combustion quality is not good, a phenomenon occurs in which the combustion of the mixed gas deteriorates, and as a result, there is a new problem that improvement in fuel efficiency cannot be expected. appear.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide at least a variable operation of an internal combustion engine capable of satisfactorily improving fuel efficiency even in a low load region (first load region) and a medium load region (second load region) where the load is larger than this. It is to provide a valve system and its control device.

  A feature of the present invention is that, in a predetermined first load region, the exhaust closing timing (EVC) at which the exhaust valve is closed by the exhaust-side variable valve mechanism is the first exhaust closing timing (EVC1) before the exhaust top dead center (TDC). ), And the intake opening timing (IVO) at which the intake valve is opened by the intake-side variable valve mechanism is set to the first intake opening timing (IVO1) after the exhaust top dead center (TDC). A negative valve overlap section (NVO1) is formed between the valve and the intake valve, and in a predetermined second load area exceeding the first load area, the exhaust-side variable valve mechanism sets the exhaust closing timing (EVC) at the exhaust top dead center. (TDC) is set to the second exhaust closing timing (EVC2), and the intake opening timing (IVO) is set by the intake-side variable valve mechanism so that the intake opening timing (IVO) is earlier than the exhaust top dead center (TDC). IVO2), the exhaust valve and the intake valve The positive valve overlap period (PVO2) is formed, it is in place.

  According to the present invention, in the first load region, the combustion chamber is heated by the high temperature internal EGR gas by setting the negative valve overlap section (NVO1) to improve combustion, thereby improving fuel efficiency. In the second load range larger than the load range, the pump loss is reduced by switching to the positive valve overlap section (PVO2), and the internal temperature of the internal EGR gas is lower than the internal EGR gas in the negative overlap section (NVO1). By suppressing knocking as EGR gas, fuel efficiency can be improved, and as a result, fuel efficiency can be improved over a wide load range.

1 is an overall schematic view of a variable valve system for an internal combustion engine according to the present invention. FIG. 2 is a perspective view illustrating an external configuration of an intake-side variable valve mechanism and an exhaust-side variable valve mechanism. FIG. 4 is an explanatory diagram illustrating a relationship between a load region, valve characteristics of an intake valve and an exhaust valve, and an opening of an external EGR valve according to the first embodiment of the present invention. In the variable valve system for an internal combustion engine according to the first embodiment of the present invention, the relationship between the valve overlap between the exhaust valve and the intake valve from the start to the maximum load region and the valve timing between the intake valve and the exhaust valve will be described. FIG. In the variable valve operating system for an internal combustion engine according to the first embodiment of the present invention, changes in the valve overlap of an exhaust valve and an intake valve from idle to a maximum load region, gas temperature in a combustion chamber, and EGR rate in a combustion chamber FIG. 9 is an explanatory diagram illustrating a state. 4 is a flowchart illustrating a first half of a control flow for executing control from a start to a maximum load region in the variable valve system for an internal combustion engine according to the first embodiment of the present invention. 4 is a flowchart illustrating a latter half of a control flow for performing control from a start to a maximum load region in the variable operation system of the internal combustion engine according to the first embodiment of the present invention. 6 is a flowchart illustrating a control flow according to a modified example of the first embodiment of the present invention. FIG. 7 is an explanatory diagram illustrating a relationship between a valve overlap between an exhaust valve and an intake valve from a start to a maximum load region and a valve timing between the intake valve and the exhaust valve in a modified example of the first embodiment of the present invention. FIG. 7 is an explanatory diagram illustrating a relationship between a load region, valve characteristics of an intake valve and an exhaust valve, and an opening of an external EGR valve according to a second embodiment of the present invention. It is a flowchart which shows the control flow of the variable operation system of the internal combustion engine which becomes 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments, and various modifications and application examples are included in the technical concept of the present invention. Is included in the range.

  A variable valve operating system for an internal combustion engine according to a first embodiment of the present invention will be described. FIG. 1 shows the entire configuration of a variable valve operating system for an internal combustion engine to which the present invention is applied.

  First, the basic configuration of a variable valve system for an internal combustion engine will be described with reference to FIG. 1. A cylinder 01 formed in a cylinder block CB is slidable up and down by combustion pressure or the like. An intake port IP and an exhaust port EP respectively formed inside the cylinder head CH, and a pair of intakes per cylinder each slidably provided in the cylinder head CH to open and close the open ends of the intake and exhaust ports IP and EP. A valve 4 and an exhaust valve 5 are provided.

  The piston 01 is connected to the crankshaft via a connecting rod 02 and forms a combustion chamber 04 between the crown surface 03 and the lower surface of the cylinder head CH. An ignition plug 05 is provided substantially at the center of the cylinder head CH.

  The intake port IP is connected to an air cleaner 50, and the intake air is supplied via an electronically controlled throttle valve 51. The electronically controlled throttle valve 51 is controlled by a controller (= control means) 52, and its opening is basically controlled in accordance with the amount of depression of an accelerator pedal. Further, the exhaust port EP discharges exhaust gas from the tail pipe to the atmosphere via the exhaust gas purification catalyst 53.

  Next, the external EGR system will be described. The downstream of the exhaust gas purification catalyst 53 and the upstream of the electronically controlled throttle valve 51 are connected by an exhaust gas recirculation passage (hereinafter, referred to as an external EGR passage) 54. An EGR cooler 55 for cooling the external EGR gas and an external EGR valve 56 disposed downstream of the cooler 55 for controlling the flow rate of the external EGR gas are provided. The external EGR valve 56 is an electronically controlled valve driven by an electric motor, and adjusts the external EGR gas flow rate according to a control signal from the controller 52.

  As the external EGR valve 56, a butterfly valve or the like is used, and the external EGR valve 56 can be controlled from a minimum opening position where the flow rate of the external EGR gas is reduced to substantially “0” to a large opening position where a large amount of the external EGR gas flows. I have. The large opening position may be an opening position at which the maximum flow rate is obtained, but is not limited thereto, and may be an opening position set according to a required required flow rate. Further, the external EGR valve 56 has a fail-safe function in which when an abnormality or a failure occurs, the drive signal is cut off and the external EGR valve 56 is mechanically set to the minimum opening position.

  In the present embodiment, a so-called “LP-EGR system” (low-pressure EGR system) is provided in which the external EGR gas is extracted from a portion downstream of the exhaust gas purification catalyst 53 where the exhaust pressure and the exhaust temperature have decreased to some extent. In addition to the fact that the temperature of the external EGR gas is relatively low and the EGR cooler 55 is provided upstream of the external EGR valve 56, the temperature of the external EGR gas is further lowered to prevent knocking in a high load region. I try to improve the nature. That is, since the temperature of the exhaust gas supplied from the external EGR valve 56 is low, the temperature of the whole mixed gas supplied into the combustion chamber tends to be low.

  Further, the internal combustion engine is provided with an intake-side variable valve mechanism and an exhaust-side variable valve mechanism for controlling the opening characteristics of the intake valve 4 and the exhaust valve 5 as shown in FIG. On the intake side, an intake-side variable valve mechanism (hereinafter, referred to as an intake-side VTC mechanism) 1A that is a “phase angle variable mechanism” that controls the center phase angle of the valve lift of the intake valve 4 is provided. On the exhaust side, an exhaust-side variable valve mechanism (hereinafter, referred to as an exhaust-side VTC mechanism) 1B that is a “phase angle variable mechanism” that controls the central phase angle of a valve lift of the exhaust valve 5 is provided.

  The intake-side VTC mechanism 1A and the exhaust-side VTC mechanism 1B include hydraulic actuators 2A and 2B for phase control, and are configured to control the opening and closing timing of the intake valve 4 and the exhaust valve 5 by hydraulic pressure. The hydraulic pressure supply to the phase control hydraulic actuators 2A and 2B is controlled by a hydraulic control unit (not shown) based on a control signal from the controller 52. By controlling the hydraulic pressure to the phase control hydraulic actuators 2A and 2B, the central phase of the lift characteristic is controlled to the retard side or the advance side.

  In FIG. 2, the exhaust camshaft 10 is provided with two exhaust cams 11 per cylinder. The exhaust cam 11 opens and closes the exhaust valve 5. At one end of the exhaust camshaft 10, a sprocket mechanism 13 and an exhaust-side VTC mechanism 1B fixed to the sprocket mechanism 13 are attached, and the exhaust camshaft 10 is rotated relative to the sprocket mechanism 13 (phase conversion). Thus, the relative rotation position of the exhaust cam 11 is controlled.

  The sprocket mechanism 13 includes a timing sprocket 15, and is rotated by a timing belt (not shown) in synchronization with the crankshaft. The exhaust-side VTC mechanism 1B includes a housing 16 and a vane driven by hydraulic pressure in a space defined by a front cover 17 and a rear cover 18 fixed to both ends of the housing 16. The timing sprocket 15 and the rear cover 18 are fixed to each other, and the vane is fixed to the exhaust cam shaft 10.

  Therefore, by adjusting the rotation position of the vane by hydraulic pressure, the exhaust camshaft 10 adjusts the opening / closing phase of the exhaust valve correspondingly. The oil pressure in the housing 16 is controlled by an exhaust electromagnetic switching valve 29, and the exhaust electromagnetic switching valve 29 is driven by a controller 52.

  Similarly, the intake camshaft 20 is provided with two intake cams 21 per cylinder. The intake cam 21 opens and closes the intake valve 4. A sprocket mechanism 23 and an intake-side VTC mechanism 1A fixed to the sprocket mechanism 23 are attached to one end of the intake camshaft 20. The intake camshaft 20 is rotated relative to the sprocket mechanism 23 (phase conversion). Thus, the relative rotational position of the intake cam 21 is controlled.

  The sprocket mechanism 23 includes a timing sprocket 25, and is rotated by a crank shaft by a timing belt (not shown). The intake-side VTC mechanism 1A includes a housing 26 and a vane driven by hydraulic pressure in a space formed by a front cover 27 and a rear cover 28 fixed to both ends of the housing 26. The timing sprocket 25 and the rear cover 28 are fixed to each other, and the vane is fixed to the intake camshaft 20.

  Therefore, by adjusting the rotation position of the vane by hydraulic pressure, the intake camshaft 20 adjusts the opening / closing phase of the intake valve correspondingly. The hydraulic pressure in the housing 26 is controlled by the intake electromagnetic switching valve 30, and the intake electromagnetic switching valve 30 is driven by the controller 52.

  Here, in the intake-side VTC mechanism 1A of the present embodiment, the default position “the most retarded position” is used both when the hydraulic pressure is supplied from the hydraulic pump and when the control signal is interrupted and the hydraulic pressure is not supplied. ”. Here, the default position is a position that is mechanically stable (a mechanically stable position). In the phase control hydraulic actuator 2A, a bias spring that urges the vane to the most retarded side is used, and when the operating oil pressure does not act on the vane, it is stable near this “most retarded position”. It is supposed to. Then, when the rotational speed decreases in the state of the phase angle, the hydraulic pressure decreases, and the pin locks at a phase near the “most retarded position”.

  The “most retarded position” is the opening timing of the intake valve 4 (hereinafter, referred to as intake opening timing (IVO)) set in a “low load region” which is a “first load region” described later. A certain first intake opening timing (IVO1) is reached. This is shown as valve timing in the first load region in FIG.

  In addition, in the exhaust side VTC mechanism 1B, the default position (mechanically stable position), which is the "most advanced angle", is provided both when the hydraulic pressure is supplied from the hydraulic pump and when the control signal is cut off and the hydraulic pressure is not supplied. The position is controlled in the vicinity. In the phase control hydraulic actuator 2B, a bias spring that urges the vane to the advance side is used, and when the operating oil pressure does not act on the vane, the vane is stabilized near this "most advanced position". It has become. Then, when the rotational speed decreases in this phase, the hydraulic pressure decreases, and the pin locks at a phase near the “most advanced position”.

  The “most advanced angle position” is defined as a closing timing of the exhaust valve 5 (hereinafter referred to as an exhaust closing timing (EVC)) set in a “low load region” which is a “first load region” described later. Becomes the first exhaust closing timing (EVCl). This is also shown in FIG. 3 as the valve timing in the first load region.

  Returning to FIG. 1, the controller (= control means) 52 outputs an output signal from a crank angle sensor for detecting the current rotational speed Ne (rpm) of the internal combustion engine from the crank angle, an intake air amount from the air flow meter (load). ), An accelerator opening sensor, a vehicle speed sensor, a gear position sensor, an engine cooling water temperature sensor 31 for detecting the temperature of the engine body, and various information signals such as an output signal from an atmospheric humidity sensor. The state is being detected.

  The controller 52 outputs an intake VTC control signal to at least the intake VTC mechanism 1A, outputs an exhaust VTC control signal to the exhaust VTC mechanism 1B, and outputs an external EGR gas to the external EGR valve 56. It outputs a control signal. In the present embodiment, the intake-side VTC mechanism 1A and the exhaust-side VTC mechanism 1B are of a hydraulic type, but may be of an electric type. It can also be used.

  By the way, as described above, when the positive valve overlap section (PVO) is set in the middle load region, fuel efficiency can be improved due to reasons such as reduction of pump loss. However, if this positive valve overlap section (PVO) is set in the low load region, part of the exhaust gas is returned to the intake system, cooled there, and re-inhaled into the cylinder, so that the The temperature of the exhaust gas decreases accordingly, and at low loads where the combustion quality is not good, a phenomenon occurs in which the combustion of the mixed gas deteriorates. As a result, there is a new problem that improvement in fuel efficiency cannot be expected. I do.

  In the present embodiment, in order to solve such a problem, an internal combustion engine that forms a positive valve overlap section (PVO) by the intake-side VTC mechanism 1A and the exhaust-side VTC mechanism 1B when operating at a medium load is used. When the internal combustion engine is in a low-load region, the exhaust-side VTC mechanism 1B sets the exhaust closing timing (EVC) of the exhaust valve 5 to a predetermined angular position (EVC1) before the exhaust top dead center (TDC), and intakes the air. The side VTC mechanism 1A delays the intake opening timing (IVO) of the intake valve 4 to a predetermined angular position (IVO1) after the exhaust top dead center (TDC) to form a negative valve overlap section. According to this, by performing the internal EGR by confining the combustion gas into the combustion chamber, the temperature of the combustion chamber is increased, and the combustion of the air-fuel mixture can be stabilized.

  Next, a specific configuration of the present embodiment will be described with reference to FIGS. FIG. 3 shows the valve timing of the intake valve 4 and the exhaust valve 5 and the operating state of the external EGR valve by the variable valve mechanism corresponding to the load region. FIG. 4 shows the variable valve mechanism corresponding to the change of the load region. FIG. 5 shows the valve timing of the intake valve 4 and the exhaust valve 5 and the state of change of the valve overlap. FIG. 5 shows the valve overlap of the intake valve 4 and the exhaust valve 5 by a variable valve mechanism corresponding to the change of the load region. 3 shows a change state of the EGR rate in the combustion chamber and the gas temperature in the combustion chamber.

≪First load area (low load area including idle) ≫
3, in a predetermined first load region including the idle state, as shown in the lowermost part of FIG. 3, the exhaust closing timing (EVC) of the exhaust valve 5 is set to the exhaust top dead center (EVC) by the exhaust side VTC mechanism 1B. TDC) as a starting point, it is advanced by a predetermined angle (ED1) to the advanced side, here the most advanced position, and the exhaust opening timing (EVO) of the exhaust valve 5 is set to the first exhaust opening timing (EVO1). At the same time, the exhaust closing timing (EVC) of the exhaust valve 5 is set to the first exhaust closing timing (EVC1) before the exhaust top dead center (TDC).

  Similarly, the intake opening timing (IVO) of the intake valve 4 is delayed by a predetermined angle (ID1) from the exhaust top dead center (TDC) by the intake-side VTC mechanism 1A, starting from the exhaust top dead center (TDC). The intake opening timing (IVO) of the intake valve 5 is set to the first intake opening timing (IVO1) after the exhaust top dead center (TDC), and the intake closing timing (IVC) of the intake valve 5 is set. Is set to the first intake closing timing (IVC1). Note that the exhaust top dead center (TDC) is synonymous with the suction top dead center (TDC) in the next stroke.

  The first exhaust closing timing (EVC1) of the exhaust valve 5 is set to be advanced by a predetermined angle (ED1) before the exhaust top dead center (TDC), and the first intake opening timing (IVO1) of the intake valve 4 is set. ) Is set to the retard side by a predetermined angle (ID1) after the exhaust top dead center (TDC), and the operating angle of the exhaust valve 5 and the operating angle of the intake valve 4 do not overlap each other. NVO1) is formed. Note that the angle of the negative valve overlap section (NVO1) is represented by NVO1 = ED1 + ID1, and in this embodiment, ED1 ≒ ID1.

  Here, the predetermined angle (ID1) and the predetermined angle (ED1) are set to be substantially the same angle, but the substantially same angle means that the exhaust-side VTC mechanism 1B and the intake-side VTC mechanism 1A are mechanically assembled. This is a concept including errors and design tolerances, and does not necessarily mean the same angle.

  As described above, in the predetermined first load region including the idle state, as shown in FIG. 4, in the first load region including the engine stop and the cranking, and in the first load region including the idle, the first intake opening timing of the intake valve 4 ( IVO1) is delayed by a predetermined angle (ID1) starting from the exhaust top dead center (TDC), and the first exhaust closing timing (EVC1) of the exhaust valve 5 is started from the exhaust top dead center (TDC). The valve is advanced by a predetermined angle (ED1), and a negative valve overlap section (NVO1) is formed between the intake valve 4 and the exhaust valve 5.

  In the negative overlap section (NVO1), the exhaust valve 5 is closed at a predetermined advance angle (ED1) before the piston 01 reaches the exhaust top dead center (TDC), and the exhaust valve 5 reaches the exhaust top dead center (TDC). Since the intake valve 5 is opened at a predetermined angle (ID1) on the retard side after the combustion, the high-temperature combustion gas is contained as a high-temperature internal EGR gas in the combustion chamber without being cooled. In addition, the high-temperature internal EGR gas is compressed by the piston 01 until it reaches the exhaust top dead center (TDC), so that the internal EGR gas further becomes high pressure and high temperature and the combustion chamber is maintained at a high temperature.

  As described above, in the low load region which is the first load region, the high temperature combustion gas (internal EGR gas) is formed in the combustion chamber from the end of the exhaust stroke to the early stage of the intake stroke by forming the negative overlap section (NVO1). The temperature of the internal EGR gas in the combustion chamber remaining in the vicinity of the top dead center (TDC) of the exhaust gas can be further increased by the “contained internal EGR gas” obtained by pressurizing with the piston. As a result, the internal EGR gas remaining in the combustion chamber is sufficiently heated, the combustion in a low load region where unstable combustion is likely to occur can be improved, and the fuel efficiency can be improved.

  Next, after passing through the exhaust top dead center (TDC), the high pressure internal EGR gas in the combustion chamber pushes down the piston 01. Therefore, the high pressure internal EGR acting on the piston 01 before reaching the exhaust top dead center (TDC). The braking energy due to the gas is recovered when the piston 01 descends, and substantially no loss is caused in total.

  In particular, since the relationship between the predetermined angle (ED1) on the advance side of the exhaust valve 5 and the predetermined angle (ID1) on the retard side of the intake valve 4 is ID1 ≒ ED1, the first exhaust valve 5 is closed. The pressure in the combustion chamber at the closing timing (EVC1) and the pressure in the combustion chamber at the first intake opening timing (IVO1) when the intake valve 4 opens are almost the same, and the pump loss in the negative valve overlap section (NVO) Is suppressed as much as possible.

  Then, when the piston 01 further goes down, fresh air gas is introduced via the intake valve 4. The fresh air gas is originally introduced from the atmosphere through an air cleaner or an intake passage, and has a considerably lower temperature than the internal EGR. The low-temperature fresh gas is warmed by being mixed with the high-temperature internal EGR gas sealed in the combustion chamber.

  This trapped internal EGR gas is sufficiently hotter than the internal EGR gas in the normal positive valve overlap section (PVO), and consequently the gas temperature in the combustion chamber at the intake bottom dead center (BDC) is as shown in FIG. Since the temperature becomes high as shown by the gas temperature (T1), combustion is stable even at a low load, and fuel efficiency can be improved.

  FIG. 5 shows the EGR rate in the combustion chamber and the gas temperature (for example, the temperature at the intake bottom dead center (BDC)) in the combustion chamber with respect to the change in the load state. As described above, in the first load region (low load region including idle), the formation of the negative valve overlap section (NVO1) enables the “containment internal EGR” and the high-temperature combustion gas (internal EGR gas). ) In the combustion chamber and pressurized by the piston 01, the EGR rate (R1) in the combustion chamber can be maintained at, for example, about 20% only by the internal EGR gas, and the gas temperature can be maintained high. You.

  Here, considering the internal EGR due to a positive valve overlap section (PVO) in which the operating angles of the intake valve 4 and the exhaust valve 5 are simultaneously opened so as to overlap with each other, the internal EGR gas (burnt Since the exhaust gas is re-inhaled, the temperature of the internal EGR gas is lowered by the low-temperature intake system in the process, and the mixing of the internal EGR gas in the volume of the intake system is likely to be uneven. Therefore, the flow rate of the internal EGR gas re-introduced into each cylinder via the intake valve 4 varies between cylinders, and the combustion of the air-fuel mixture becomes more unstable as a whole.

  On the other hand, in the present embodiment, the negative valve overlap section (NVO1) is formed and the “containment internal EGR” is executed. Is maintained at a high temperature.

  Further, the EGR rate of the contained internal EGR gas is determined by the valve timings (EVCl, IVOl) of the intake valve 4 and the exhaust valve 5, and the variation in the internal EGR gas amount due to the intake system between cylinders does not occur in principle. . In other words, it is possible in principle to avoid inter-cylinder variation in the amount of EGR gas generated in the internal EGR due to the positive valve overlap section (PVO), thereby further stabilizing combustion and stabilizing engine rotation. , Fuel efficiency can be improved.

  Here, as shown in FIG. 3, since the external EGR valve 56 is controlled to be almost fully closed, the external EGR gas of a low temperature by the external EGR system is re-introduced, for example, only at a predetermined small flow rate or less. Or, desirably, it is not re-introduced, so that the above-described effect of the “containment inside EGR” can be sufficiently obtained.

  Here, the EGR gas is an inert gas. Regardless of the internal EGR and the external EGR, if the EGR rate is high, the engine torque decreases, and the throttle opening can be increased to obtain the same engine torque. Since pump loss in the intake stroke can be reduced, fuel efficiency can be improved.

  Further, since the combustion peak temperature is low, the cooling loss is small, and the specific heat ratio of the combustion gas can be improved. Therefore, there is room (potential) for improving the fuel efficiency by increasing the EGR rate.

  As is well known, the EGR gas is an inert gas containing almost no oxygen, and has a drawback that when the EGR rate is increased, the combustion deteriorates. Therefore, it is difficult to increase the EGR rate particularly in a low load region where combustion is not stable. On the other hand, in the present embodiment, the formation of the negative valve overlap section (NVO1) can increase the gas temperature in the combustion chamber as the high-temperature internal EGR gas to improve the combustion stability. Such a high EGR rate can be achieved, and the fuel efficiency can be improved from that aspect as well.

  Next, valve timing different from the viewpoint of valve overlap will be considered. In the first load region of FIG. 3, the first intake closing timing (IVC1) of the intake valve 4 is delayed from the intake bottom dead center (BDC), so that the so-called late closing Miller cycle (Atkinson cycle) effect. Fuel efficiency can be improved.

  Further, since the exhaust opening timing (EVO1) of the exhaust valve 5 is advanced from the bottom dead center (BDC) of the expansion, the pump loss at the end of the so-called expansion stroke can be reduced. In the low load range, the combustion peak pressure is low, so the pressure in the combustion chamber becomes negative before the piston 01 reaches the bottom dead center (BDC) in the expansion stroke, and the negative pressure causes the piston 01 to descend. Loss to be suppressed (pump loss at the end of the expansion stroke) is likely to occur. Therefore, before the negative pressure is generated in the combustion chamber, the exhaust valve 5 is opened earlier, so that the pump loss at the end of the expansion stroke can be reduced and the fuel efficiency can be improved.

  Returning to FIG. 4 again, the valve timing characteristics of the intake valve 4 and the exhaust valve 5 are the same in a low load region including cranking and idling from the stop state of the internal combustion engine. Therefore, before the internal combustion engine stops until the second load region is reached, the negative valve overlap section in the stop state, the negative valve overlap section in the cranking state, the negative valve overlap section in the idle state, and The same negative valve overlap section (NVO1) as the negative valve overlap section before reaching the second load region is formed.

  At the same time, from the stop state of the internal combustion engine to the second load region until it reaches the second load region, the stop state, the cranking state, the idle state, and the opening / closing timing (EVO) of the exhaust valve 5 until it reaches the second load region. , EVC) and the opening / closing timing (IVO, IVC) of the intake valve 4 are also set to be the same.

  Similarly, the opening degree of the external EGR valve 56 is the same minimum opening degree until the stop state, the cranking state, the idle state, and before the second load region is reached. The configuration is not re-introduced.

  As described above, by setting the valve timing characteristics of the intake valve 4 and the exhaust valve 5 and the opening characteristics of the external EGR valve 56 to be the same from the stop state of the internal combustion engine to before the second load region, the intake-side VTC Control of the mechanism 1A, the exhaust-side VTC mechanism 1B, and the external EGR valve 56 can be simplified. Further, in the present embodiment, when the electric control system of the intake-side VTC mechanism 1A, the exhaust-side VTC mechanism 1B, and the external EGR valve 56 fails, they are stabilized at their respective default positions, and fail-safe control is also performed. Simplified.

≪Second load area (medium load area) ≫
In the first load region including idling, the intake valve 4 is set on the retard side starting from the exhaust top dead center (TDC), and the exhaust valve 5 is set on the advance side starting from the exhaust top dead center (TDC). As a result, the negative valve overlap section (NVO1) is formed, and thus the effect of improving the fuel efficiency is high as described above. However, a new load is obtained in the medium load area where the load exceeds the first load area and further increases. Another challenge arises.

  That is, even in the second load region exceeding the first load region, when the negative valve overlap section (NVO1) is formed, the environment is shifted to an environment in which knocking easily occurs due to the high temperature internal EGR gas. For this reason, when knocking occurs, control is performed to retard the ignition timing to avoid knocking.However, if the ignition timing is retarded, the combustion efficiency is reduced, so that a large amount of fuel is required to compensate for this, and as a result, The fuel economy will deteriorate.

  In the medium load region, engine torque is required. However, when the negative valve overlap section (NVO1) is formed, when the piston 01 performs the descending operation, both the intake valve 4 and the exhaust valve 5 are closed. Therefore, it is difficult to increase the efficiency of charging the fresh air into the cylinder, and it is difficult to increase the engine torque, or the pump loss in the intake stroke increases, leading to deterioration of fuel efficiency.

  On the other hand, in the present embodiment, in the second load region, which is a medium load region where the load is larger than the first load region, as shown in the second load region of FIG. The closing timing (EVC) of the exhaust valve 5 is retarded by a predetermined angle (ED2) from the exhaust top dead center (TDC) to the retard side, here the most retarded position. EVO) is set to the second exhaust opening timing (EVO2), and the exhaust closing timing (EVC) of the exhaust valve 5 is set to the second exhaust closing timing (EVC2).

  Similarly, the opening timing (IVO) of the intake valve 4 is advanced by a predetermined angle (ID2) from the exhaust top dead center (TDC) to the advanced side, here the most advanced position, by the intake side VTC mechanism 1A. The intake opening timing (IVO) of the intake valve 5 is set to the second intake opening timing (IVO2), and the intake closing timing (IVC) of the intake valve 5 is set to the second intake closing timing (IVC2). You.

  Then, the second exhaust closing timing (EVC2) of the exhaust valve 5 is set to the retard side by a predetermined angle (ED2) after the exhaust top dead center (TDC), and the second intake opening timing (IVO2) of the intake valve 4 is set. ) Is set on the advance side by a predetermined angle (ID2) before the exhaust top dead center (TDC), and the operating angle of the exhaust valve 5 and the operating angle of the intake valve 4 overlap, and the positive valve overlap section (PVO2) Is formed. Here, the angle of the positive valve overlap section (PVO2) is represented by PVO1 = ED2 + ID2, and in the present embodiment, ED2 ≒ ID2.

  In this embodiment, the intake valve 4 is set to the most retarded position in the first load region, the exhaust valve 5 is set to the most advanced position, and the intake valve 4 is set to the most advanced position in the second load region. , And the exhaust valve 5 is set at the most retarded position, so that ED1ＥＤID1 ≒ ED2 ≒ ID2.

  In the second load region, as shown in FIG. 4, in the process of shifting from the first load region to the second load region, the second intake opening timing (IVO2) of the intake valve 4 is set at the exhaust top dead center (IVO2). TDC) as a starting point, it is switched and advanced by a predetermined angle (ID2), and the second exhaust closing timing (EVC2) of the exhaust valve 5 is set at a predetermined point starting from the exhaust top dead center (TDC). The valve is switched by the angle (ED2) like a switch and retarded, and a positive valve overlap section (PVO2) is formed between the intake valve 4 and the exhaust valve 5.

  As described above, since the switching from the negative valve overlapping section (NVO1) to the positive valve overlapping section (PVO2) is performed in a switch manner, the influence of pump loss and combustion deterioration during the switching can be reduced as much as possible. .

  In the positive overlap section (PVO2), the intake valve 4 is opened at a predetermined angle (ID2) on the advance side before the piston 01 reaches the exhaust top dead center (TDC), and the exhaust top dead center (TDC) Then, the exhaust valve 5 is closed at a predetermined angle (ED2) on the retard side after reaching. As described above, in the positive overlap section (PVO2), the combustion gas is returned to the intake system to be cooled, and then is introduced again into the combustion chamber.

  As shown in the EGR rate of FIG. 5, in this positive overlap section (PVO2), the combustion gas (internal EGR gas) is returned to the intake system once, and then sucked into the combustion chamber again to “re-intake internal EGR”. Gas ". In the process, the internal EGR gas returned to the intake system is cooled in the intake system and then introduced into the combustion chamber. Therefore, the gas temperature in the combustion chamber at the intake bottom dead center (BDC) becomes the temperature. The temperature falls from (T1) to the temperature (T2).

  As a result, since the temperature of the mixed gas in the combustion chamber becomes low, knocking is suppressed, and the frequency and the amount of retard of the ignition timing can be suppressed, so that the fuel efficiency can be improved and improved. On the other hand, in the positive overlap section (PVO2), the temperature of the internal EGR gas is higher than the temperature of the external EGR gas, so that the gas temperature in the combustion chamber can be maintained at a temperature (T2) sufficient for combustion. Therefore, deterioration of combustion can be suppressed while suppressing knocking, so that good fuel economy performance can be obtained.

  Here, as shown in FIG. 3, even in the second load region, the external EGR valve 56 is controlled to be almost fully closed, so that the low-temperature external EGR gas by the external EGR system is, for example, at a predetermined small flow rate or less. Is re-introduced, or desirably is not re-introduced, so that the above-described effect of the "re-intake internal EGR" can be sufficiently obtained.

  The opening degree of the external EGR valve 56 is set to the same minimum opening degree over almost the entire second load region, so that the external EGR gas at a low temperature by the external EGR system is not re-introduced. As shown in FIG. 5, in the second load range, the formation of the positive valve overlap section (PVO2) causes the “re-intake internal EGR gas” to be compared with the internal EGR gas in the negative valve overlap section (NVO1). Since the low-temperature internal EGR gas is introduced into the combustion chamber, the EGR rate (R2) in the combustion chamber can be maintained at, for example, about 20% by only the re-intake internal EGR gas, and the gas temperature is required. It can be maintained at a sufficient temperature (T2). Here, the EGR rate is determined by the total value of the internal EGR gas for the combustion chamber and the internal EGR gas re-inhaled.

  Here, if the absolute phase angle of the positive valve overlap section (PVO2) is equal to the absolute phase angle of the negative valve overlap section (NVO1) (PVO2 = NVO1), the negative valve overlap section (NVO1) The EGR rate (R1) due to the “contained internal EGR gas” and the EGR rate due to the “re-intake internal EGR gas” in the positive valve overlap section (PVO2) can be made substantially the same.

  That is, since the lift heights of the piston 01 before and after the valve overlap section are the same in both cases, the “containment internal EGR gas” in the negative valve overlap section (NVO1) and the “lift height in the positive valve overlap section (PVO2)”. This is because the amount of EGR gas (the volume of the combustion chamber above the piston) is considered to be the same, although there is a difference between the "reintake internal EGR gas". Thus, it is possible to suppress a decrease in the EGR rate in the combustion chamber before and after switching from the negative valve overlap period (NVO1) to the positive valve overlap period (PVO2).

  In addition, in the positive valve overlap section (PVO2), when "re-intake internal EGR gas" is sucked, fresh gas is also sucked together. Therefore, in the case of a multi-cylinder integrated intake system, the overlap section is set to (PVO2). )> (NVO1), the EGR rates of both can be made even closer. In the present embodiment, the overlap section is set to (PVO2) ≒ (NVO1), assuming that the intake ports of each cylinder are accurately separated and formed. As a result, as shown in the second load region of FIG. 5, for example, an EGR rate of about 20% is maintained even when the state shifts from the negative valve overlap section (NVO1) to the positive valve overlap section (PVO2). You.

  Here, strictly speaking, the positive valve overlap (PVO) and the negative valve overlap (NVO) are not formed between the first load region and the second load region, and the zero valve overlap (“0” VO) (Low EGR region), but since the load determination thresholds for separating the first load region and the second load region are almost the same, when FIG. The graph is drawn so that the EGR rate of about 20% continues, ignoring the low EGR region. However, during the transition from the first load region to the second load region, the low EGR region may become apparent, and this will be described with reference to the control flowchart of FIG.

  The “containment internal EGR gas” in the second load region shown in FIG. 5 is a gas amount corresponding to the volume of the combustion chamber at the lift position of the piston 01 when the exhaust top dead center (TDC) is reached. This gas amount exists even in the case of "re-intake internal EGR" or in the case of "external EGR" described later. The total gas amount obtained by adding the “contained internal EGR gas” and the “reintake internal EGR gas” of the combustion chamber volume corresponds to the EGR gas amount in the second load region in FIG.

  Next, valve timing different from the viewpoint of valve overlap will be considered. In the present embodiment, as shown in FIG. 4, by setting the second exhaust opening timing (EVO2) of the exhaust valve 5 close to the vicinity of the bottom dead center (BDC) of the expansion, here, by setting the bottom dead center (BDC) of the expansion, The expansion work can be increased, and as a result fuel efficiency can be improved.

  This is because the peak combustion pressure increases as the load increases, so that the pressure in the combustion chamber does not easily become lower than the atmospheric pressure (negative pressure) during the expansion stroke, so that pump loss at the end of the expansion stroke hardly occurs, and exhaust gas is exhausted. By delaying the second exhaust opening timing (EVO2) of the valve 5 to near the bottom dead center (BDC) of expansion, sufficient expansion work can be given to the piston 01, and as a result, expansion conversion efficiency is increased and fuel efficiency is improved. be able to.

  On the other hand, the second intake closing timing (IVC2) of the intake valve 4 conversely approaches the intake bottom dead center (BDC), in which the advance is advanced to just before the intake bottom dead center (BDC). The effect can further reduce pump loss and improve fuel efficiency.

≪Transition load area P to third load area (high load area) ≫
In the second load region, the intake valve 4 is set on the advance side from the exhaust top dead center (TDC), and the exhaust valve 5 is set on the retard side from the exhaust top dead center (TDC). The positive valve overlap section (PVO2) is formed, and as described above, the knock loss due to the reduction of the pump loss and the temperature of the internal EGR gas is suppressed, and the fuel efficiency is improved. Another problem arises in a high load region where the load is further increased beyond.

  That is, in the third load range exceeding the second load range, the temperature of the mixed gas in the combustion chamber becomes high even if the “re-suction internal EGR” is performed in the positive valve overlap section (PVO2), and knocking occurs. It will be easier. Therefore, control for increasing the concentration of the air-fuel mixture or delaying the ignition timing is performed, which results in deterioration of fuel efficiency.

  On the other hand, in the present embodiment, in the third load region where the load is higher than the second load region and the load is higher than the second load region, as shown in the third load region of FIG. The closing timing (EVC) of the exhaust valve 5 is advanced toward the exhaust top dead center (TDC) side as compared with the second load region, and the exhaust opening timing (EVO) of the exhaust valve 5 is set to the third exhaust opening timing (EVO3). And the exhaust closing timing (EVC) of the exhaust valve 5 is set to the third exhaust closing timing (EVC3).

  Similarly, the intake valve 4 is retarded by the intake side VTC mechanism 1A from the exhaust top dead center (TDC) side compared to the second load region, and the intake opening timing (IVO) of the intake valve 5 is set to the third position. The intake opening timing (IVO3) is set, and the intake closing timing (IVC) of the intake valve 5 is set to the third intake closing timing (IVC3).

  The third exhaust closing timing (EVC3) of the exhaust valve 5 is set to the exhaust top dead center (TDC), and the third intake opening timing (IVO3) of the intake valve 4 is also set to the exhaust top dead center (TDC). Therefore, the operating angle of the exhaust valve 5 and the operating angle of the intake valve 4 do not overlap, and the zero valve overlap (“0” VO) is formed in which the negative valve overlap section (NVO) is not formed. Accordingly, the operation of the “re-suction internal EGR” is stopped, but instead, the operation of the “external EGR” is executed as shown in the third load region of FIG.

  Accordingly, as shown in FIG. 4, in the transition region P, the exhaust closing timing (EVC) of the exhaust valve 5 is advanced from the second exhaust closing timing (EVC2) to the third exhaust closing timing (EVC3), The operation of the intake opening timing (IVO) of the valve 4 is delayed from the second intake opening timing (IVO2) to the third intake opening timing (IVO3).

  At the same time, by the operation of the external EGR valve 56, the external EGR gas amount by the “external EGR” is increased as shown in FIG. As described above, since the external EGR gas is cooled by the EGR cooler 55 and the like, the temperature of the external EGR gas is lower than that of the re-intake internal EGR gas in the second load region.

  In the transition load region P, when the load increases from the second load region to the third load region, the external EGR gas gradually increases, so that the gas temperature in the combustion chamber is sharply increased by the external EGR gas. , And the gas temperature in the combustion chamber is gradually reduced, so that the combustion state including the transient performance can be stabilized.

  As described above, in the transition load region P, since the state of the “re-intake internal EGR” in the second load region can be gently changed to the state of the “external EGR”, the gas temperature in the cylinder gradually decreases, In addition, since the transient variation in the EGR gas flow rate between the cylinders can be suppressed, it is possible to suppress instability of the transient performance, which is likely to occur in the process from the middle load region to the high load region. Further, the EGR rate (R3) in the combustion chamber of FIG. 5 indicates the sum of the gas amount in the “containment internal EGR” and the gas amount in the “external EGR”, and this value is maintained at about 20%. From this aspect, it is possible to stabilize the transient performance when the load shifts toward the high load region.

  As shown in FIG. 4, in the third load region, the intake opening timing (IVO) of the intake valve 4 is shifted to the exhaust side top dead center (TDC) on the retard side in the third load region as compared with the second load region. The opening timing (IVO3) is set, and the exhaust closing timing (EVC) of the exhaust valve 5 is advanced to the exhaust top dead center (TDC) to set the third exhaust closing timing (EVC3). Further, with the retardation of the intake opening timing (IVO) of the intake valve 4, the intake closing timing (IVC) of the intake valve 4 also changes from near the middle position between the intake bottom dead center (BDC) and the compression top dead center (TDC). It is shifted to the retard side until the third intake closing timing (IVC3) toward the intake bottom dead center (BDC). Further, with the advance of the exhaust closing timing (EVC) of the exhaust valve 5, the exhaust opening timing (EVO) of the exhaust valve 5 also moves toward the intake bottom dead center (BDC) side until the third exhaust opening timing (EVO3). It has been shifted to the advanced side.

  As a result, in the third load region, the third exhaust closing timing (EVC3) of the exhaust valve and the third intake opening timing (IVO3) of the intake valve are set close to each other near the exhaust top dead center (TDC). This forms a zero valve overlap valve (“0” VO3) in which the negative valve overlap section (NVO) and the positive valve overlap section (PVO) hardly exist.

  As described above, since the zero valve overlap valve (“0” VO3) is formed in the third load region, the “containment internal EGR” due to the high temperature combustion gas caused by the negative valve overlap section (NVO) is almost zero. Will not work. Further, the “re-suction internal EGR” caused by the positive valve overlap section (PVO) also hardly functions.

  Further, as shown in FIG. 4, in the third load region, the external EGR valve 56 is greatly opened to the maximum opening degree, so that a predetermined large amount of external EGR gas is introduced into the combustion chamber. The temperature of the external EGR gas is low, and the temperature is further lowered by the EGR cooler 55.

  For this reason, the gas temperature in the cylinder into which the external EGR gas has been introduced becomes low, and abnormal combustion such as knocking hardly occurs together with the low-temperature combustion effect based on the EGR gas. Therefore, the ignition timing can be advanced, so that the combustion efficiency can be increased, and the fuel consumption performance in the third load region can be improved.

  As shown in FIG. 5, in the third load region, both the “containment internal EGR” and the “re-suction internal EGR” hardly function due to the formation of the zero valve overlap valve (“0” VO3). Since the low-temperature external EGR gas is re-introduced instead, it is understood that the gas temperature can be lowered from the gas temperature (T2) to the gas temperature (T3) as shown in FIG.

  As described above, since the gas temperature can be suppressed low by the external EGR gas in the third load region, the ignition timing can be advanced while avoiding abnormal combustion such as knocking. As a result, the combustion efficiency can be increased, and the fuel efficiency in the third load region can be improved.

  Here, in the third load region, the “containment inside EGR gas” stops functioning, but as shown in FIG. 5, the “containment inside EGR gas” remains slightly. This is because at the exhaust top dead center (TDC), the combustion gas remains in the volume between the crown surface of the piston 01 and the upper wall of the combustion chamber, and in the next intake stroke, it is referred to as “contained internal EGR gas”. It is to remain.

  Further, by making the valve timing characteristics of the intake valve 4 and the exhaust valve 5 and the opening characteristics of the external EGR valve 56 substantially the same throughout the third load region, the intake-side VTC mechanism 1A and the exhaust-side VTC mechanism 1B , And the control of the external EGR valve 56 can be simplified, and since the EGR rate in the combustion chamber can be maintained at the same level, the transient performance can be stabilized even when the load changes suddenly. .

≪Transition load area H to fourth load area (maximum load area) ≫
In the third load region, both the “containment internal EGR” and the “re-suction internal EGR” hardly function due to the formation of the zero valve overlap valve (“0” VO3). Since the gas is reintroduced, the gas temperature can be reduced from the gas temperature (T2) to the gas temperature (T3) as shown in FIG. 5, and abnormal combustion such as knocking can be avoided.

  However, another new problem arises in the maximum load region where the load is further increased. That is, knocking is suppressed by lowering the temperature of the mixed gas in the third load region. However, in this control state, there is a possibility that a sufficient engine torque cannot be obtained in the maximum load region.

  Therefore, in the present embodiment, the external EGR valve 56 is set to the minimum opening degree (fully closed), the introduction of the external EGR gas is stopped, and the opening / closing timing of the intake valve 4 is kept the same as in the third load region. In this state, the exhaust valve closing timing (EVC) of the exhaust valve 5 is retarded to the fourth exhaust closing timing (EVC4), and similarly, the exhaust opening timing (EVO) is delayed to the fourth exhaust opening timing (EVO4). As shown, the valve is retarded to the bottom dead center (BDC) of the exhaust to form a positive valve overlap (PVO4). Thus, a so-called scavenging effect can be effectively obtained.

  As shown in FIGS. 3 and 4, in the fourth load region, which is the maximum load region where the load is larger than that in the third load region, the fourth intake opening timing (IVO4) of the intake valve 4 is set to the exhaust top dead center. (TDC), and the exhaust valve closing timing (EVC) of the exhaust valve 5 is shifted to the retard side after the exhaust top dead center (TDC) to be the fourth exhaust closing timing (EVC4).

  Further, the intake closing timing (IVC4) of the intake valve 4 is set to the intake bottom dead center (BDC), and the fourth exhaust opening timing (EVO4) of the exhaust valve 5 is set to the expansion bottom dead center (BDC). .

  As a result, in the transition load region H from the third load region to the maximum load, zero valve overlap (“4”) occurs due to the fourth exhaust closing timing (EVC4) of the exhaust valve and the fourth intake opening timing (IVO4) of the intake valve. A positive valve overlap section (PVO4) is formed for "0" VO3).

  In this case, as shown in FIG. 4, in the transition load region H from the third load region to the fourth load region, the phase angle of the positive valve overlap section (PVO) gradually increases in response to the increase in load. It is adjusted in the direction. Also, as shown in FIG. 5, the opening of the external EGR valve 56 is controlled correspondingly in the range of the minimum opening by decreasing the opening, and the external EGR gas amount becomes substantially “0” in the fourth load region. ".

  Further, the opening degree of the external EGR valve 56 is gradually reduced from the third load region to the fourth load region, and in addition, the positive valve overlap section (PVO) is also reduced to the zero valve overlap section (“0” VO3). To the positive valve overlap section (PVO4), the maximum torque is not suddenly generated even during rapid acceleration in this region, and smooth acceleration is possible.

  According to the above-described valve timing characteristics, it is possible to sufficiently increase the engine torque in the fourth load region. That is, as shown in FIGS. 3 and 4, since the exhaust closing timing (EVC) of the exhaust valve 5 is delayed from the exhaust top dead center (BDC), the timing at which the negative pressure wave of the exhaust pulsation arrives at the exhaust valve 5. Is delayed until near the positive valve overlap section (PVO4).

  For this reason, scavenging in which high-temperature combustion gas in the combustion chamber is sucked through the exhaust valve 5 in the open state by the negative pressure wave, and cool fresh gas is introduced into the combustion chamber through the intake valve 4 in the open state. The effect is obtained. As a result, not only the intake charging efficiency in the fourth load region is increased, but also the combustion chamber is cooled by fresh gas, so that knocking resistance is improved and the absolute value of the engine torque can be increased.

  That is, at the above-mentioned exhaust top dead center (TDC), the high-temperature combustion gas remaining in the volume between the piston crown surface and the upper wall of the combustion chamber is also sucked out, whereby the knocking resistance can be improved.

  Here, as shown in FIG. 5, the fact that the EGR rate decreases to almost “0” in the fourth maximum load region via the transition load region H is caused by the crown of the piston 01 at the exhaust top dead center (TDC). The combustion gas between the surface and the upper wall of the combustion chamber is taken into the combustion chamber as a confined internal EGR in the next intake stroke, and this combustion gas is also drawn out to the exhaust port side by the above-described scavenging effect. That's why.

  Then, as described above, a fresh gas having a lower temperature is introduced, and the fresh gas is lower in temperature than the external EGR gas. Therefore, as shown in FIG. The temperature can be lowered to the temperature (T4) to improve the knock resistance. Further, the introduction of the fresh gas means that the charging efficiency is increased, and the engine torque can also be increased.

  As described above, in the present embodiment, the positive valve overlap section (PVO) and the negative valve overlap section (NVO) are appropriately set in accordance with the load area, so that the good valve overlap section (NVO) is provided over a wide load area. As a result, excellent fuel efficiency can be obtained, and the engine torque can be increased.

  Further, the opening / closing timing of the intake valve 4 and the exhaust valve 5 in the first load region substantially coincides with the default positions of the intake-side VTC mechanism 1A and the exhaust-side VTC mechanism 1B. This default position is a mechanically stable position when the conversion power of the intake-side VTC mechanism 1A and the exhaust-side VTC mechanism 1B does not act.

  Therefore, the opening / closing timing of the intake valve 4 and the exhaust valve 5 in the first load region from the time of stopping and the time of cranking is set to this default position. Therefore, the above-described combustion improvement effect can be obtained immediately after the cranking is performed and the combustion is started by the engine start. In particular, at the time of cooling, the cold startability can be remarkably improved by the combustion improvement effect.

  By the way, as shown in FIG. 4, the load determination thresholds for determining the first load region and the second load region are drawn to be the same, but it is actually desirable to set the hysteresis (h).

  As shown in FIG. 8, it is necessary to make the load determination threshold different between the case where the load changes to a side where the load increases and the case where the load changes to a side where the load decreases. That is, the load determination threshold is set to “L (1 → 2)” when shifting from the first load area to the second load area, and the load determination threshold is set to “L (1 → 2)” when shifting from the second load area to the first load area. L (1 → 2) -h ”.

  As a result, frequent switching between the negative valve overlap section (NVO1) and the positive valve overlap section (PVO2) can be avoided, control hunting can be suppressed, and the durability of the variable VTC mechanisms 1A and 1B can be improved. Can be achieved.

  Next, a control flow for executing the valve timing characteristics according to the above-described embodiment will be described. This control flow is executed by the controller 52. A control flow when restarting the operation of the internal combustion engine will be described based on FIGS. 6A and 6B. Note that the opening and closing timings (EVO) and (EVC) of the exhaust valve 5 and the opening and closing timings (IVO) and (IVC) of the intake valve 4 are set to be the same from the stop of the internal combustion engine to the first load region. ing.

{Step S20}
First, in FIG. 6A, in step S20, engine start information for starting the internal combustion engine and operating condition information of the internal combustion engine are read. The engine start information for starting the internal combustion engine typically includes a key-on signal or a starter start signal, and there are many signals indicating operation condition information of the internal combustion engine. The information includes rotational speed information, intake air amount information, water temperature information, required load information (accelerator opening), and the like, and further includes actual position information of the exhaust-side VTC mechanism 1B and the intake-side VTC mechanism 1A. When various information is read in step S20, the process proceeds to step S21.

{Step S21}
In step S21, it is determined whether an engine start condition is satisfied. This determination can be made, for example, by monitoring the starter start signal. If the starter start signal is not input, the process returns to the start and waits for the next start timing. On the other hand, when the starter start signal is input, it is determined that the engine is started, and the process proceeds to step S22.

{Step S22}
In step S22, the cranking of the internal combustion engine by the starter motor is started in response to the starter start signal. Then, as soon as the cranking is started, the process proceeds to step S23.

{Step S23}
In step S23, a conversion control signal of at least the exhaust valve closing timing (EVC) and the intake valve opening timing (IVO) of the intake valve so that the exhaust-side VTC mechanism 1B and the intake-side VTC mechanism 1A shift to the default positions. Is output to the exhaust electromagnetic switching valve 29 of the exhaust-side VTC mechanism 1B and the intake electromagnetic switching valve 30 of the intake-side VTC mechanism 1A.

  This is because when the hydraulic pressure of the hydraulic oil of the hydraulic pump rises, even if the fastening pin is pulled out of the fastening hole for some reason and the fastening state is released, the exhaust-side VTC mechanism 1B and the intake-side VTC This is control for maintaining the vane of the mechanism 1A at the default position. This ensures that the negative valve overlap section (NVO1) is formed as the negative valve overlap section (NVO). Note that, as shown in FIG. 4, the negative valve overlap section (NVO1) in the stop state, the idle state, and the first load region aims at the same negative valve overlap section (NVO).

  When the conversion control signal is output to the exhaust electromagnetic switching valve 29 of the exhaust-side VTC mechanism 1B and the intake electromagnetic switching valve 30 of the intake-side VTC mechanism 1A, the process proceeds to step S24.

{Step S24}
In step 24, based on the actual position information of the exhaust-side VTC mechanism 1B and the intake-side VTC mechanism 1A, whether the exhaust-side VTC mechanism 1B and the intake-side VTC mechanism 1A have moved to the default positions, It is determined whether the closing timing (EVC) is set to the first exhaust closing timing (EVC1) and whether the intake opening timing (IVO) of the intake valve 4 is set to the first intake opening timing (IVO1).

  When it is determined that the exhaust valve 5 is not set to the first exhaust closing timing (EVC1) and that the intake valve 4 is not set to the first intake opening timing (IVO1), the process returns to step S23 again. When it is determined that the exhaust valve 5 is set to the first exhaust closing timing (EVC1) and the intake valve 4 is set to the first intake opening timing (IVO1), the process proceeds to step S25.

{Step S25}
In step S25, an output control signal is supplied to the fuel injection valve and the ignition device to start the internal combustion engine in accordance with the rotation of the starter motor. As a result, the rotation speed of the internal combustion engine increases, and accordingly, the hydraulic pressure of the hydraulic oil of the hydraulic pump increases. When the output control signal is supplied to the fuel injection valve and the ignition device, the process proceeds to step S26.

{Step S26}
In step S26, the engine temperature (cooling water temperature) of the internal combustion engine is detected to determine whether or not the temperature has exceeded a predetermined temperature. If the temperature does not exceed the predetermined temperature, it is determined that the engine is in the cold state, and the process returns to wait for the next start timing or executes another control flow. On the other hand, if the temperature exceeds the predetermined temperature, it is determined that the warm-up is completed from the cold state, and the operation condition information is read again and the process proceeds to step S27. It is to be noted that FIG.

{Step S27, Step S28, Step S29}
In step S27, the current load state is detected from the opening of the throttle valve or the opening of the accelerator pedal, and it is determined whether the current load is in the first load region, which is a low load region. If it is determined that the region is the first load region, the process proceeds to step S28, in which the opening of the external EGR valve 56 is converted and controlled to the minimum opening.

  Further, the process proceeds to step S29, in which the exhaust-side VTC mechanism 1B and the intake-side VTC mechanism 1A are driven to perform the first exhaust closing timing (EVC1) of the exhaust valve in the first load region and the first intake of the intake valve. Control is performed at the opening timing (IVO1) to form a negative valve overlap section (NVO1).

  Upon completion of the process in the step S29, the process returns to the control and waits for the next controller activation timing. On the other hand, if it is determined in step S27 that the current load is not in the first load region, the process proceeds to step S30.

{Step S30, Step S31, Step S32}
In step S30, the current load state is detected from the opening of the throttle valve or the opening of the accelerator pedal, and it is determined whether the current load is in the second load region. If it is determined that the load region is the second load region, the process proceeds to step S31, in which the opening of the external EGR valve 56 is controlled to be converted to the minimum opening.

  Further, the process proceeds to step S32, in which the exhaust-side VTC mechanism 1B and the intake-side VTC mechanism 1A are driven, and the second exhaust closing timing (EVC2) of the exhaust valve in the second load region and the second intake of the intake valve are performed. By controlling the opening timing (IVO2), a positive valve overlap section (PVO2) is formed.

  Upon completion of the process in the step S32, the process exits from the return and waits for the next controller activation timing. On the other hand, if it is determined in step S30 that the current load is not in the second load region, the process proceeds to step S33.

{Step S33, Step S34, Step S35}
In step S33, the current load state is detected from the opening of the throttle valve or the opening of the accelerator pedal, and it is determined whether the current load is in the third load region. The third load region is determined to include the transition load regions P and H shown in FIGS. Therefore, if it is determined that the load region is the third load region, the process proceeds to step S34. If it is determined that the load region is the transition load region P, the opening degree of the external EGR valve 56 is adjusted so that the EGR rate shown in FIG. Is converted to an opening corresponding to the detected load.

  Further, the process proceeds to step S35, in which the exhaust-side VTC mechanism 1B and the intake-side VTC mechanism 1A are driven according to the detected load, and the third exhaust closing timing (EVC3) of the exhaust valve in the third load region is determined. And the third intake opening timing (IVO3) of the intake valve to form a zero valve overlap (“0” VO3). When it is determined that the load range is the transition load region H, the opening of the external EGR valve 56 is converted and controlled to an opening corresponding to the detected load so that the EGR rate shown in FIG. 5 is obtained.

  When it is determined that the transition load region is the transition load region P or the transition load region H, as shown in FIG. 5, the positive valve from the positive valve overlap section (PVO2) to the zero valve overlap (“0” VO3). The intake valve 4 and the exhaust valve 5 are provided so that an overlap section (PVO) or a positive valve overlap section (PVO) from a zero valve overlap (“0” VO3) to a positive valve overlap section (PVO4) is obtained. The open / close timing is converted to the open / close timing corresponding to the detected load.

  Upon completion of the process in the step S35, the process exits from the return and waits for the next start timing. On the other hand, if it is determined in step S33 that the current load is not in the third load region, the process proceeds to step S36.

{Step S36, Step S37, Step S38}
In step S36, the current load state is detected from the opening of the throttle valve or the opening of the accelerator pedal, and it is determined whether the current load is in the fourth load region. When it is determined that the load region is the fourth load region, the process proceeds to step S37, in which the opening of the external EGR valve 56 is controlled to be converted to the minimum opening.

  Further, the processing shifts to step S38, where the exhaust-side VTC mechanism 1B and the intake-side VTC mechanism 1A correspond to the detected load and the fourth exhaust closing timing (EVC4) of the exhaust valve, and the fourth intake of the intake valve. Control is performed at the opening timing (IVO4). In this case, a positive valve overlap section (PVO4) is formed in which the PVO section increases from the zero valve overlap (“0” VO3).

  Upon completion of the process in the step S38, the process returns to the start and waits for the next start timing. On the other hand, if it is determined in step S36 that the current load is not in the fourth load area, the process returns to wait for the next start timing.

  As described above, according to the present embodiment, in the predetermined first load region, the exhaust closing timing at which the exhaust valve is closed by the exhaust-side variable valve mechanism is set to the first exhaust closing timing before the exhaust top dead center. At the same time, the intake opening timing at which the intake valve is opened by the intake-side variable valve mechanism is set to the first intake opening timing after the exhaust top dead center, and a negative valve overlap section is formed between the exhaust valve and the intake valve. In a predetermined second load region exceeding the first load region, the exhaust-side variable valve mechanism sets the exhaust closing timing to the second exhaust closing timing after the exhaust top dead center, and the intake-side variable valve mechanism sets intake air. The opening timing is set to the second intake opening timing before the exhaust top dead center, and a positive valve overlap section is formed between the exhaust valve and the intake valve.

  According to this, in the first load region, the combustion chamber is heated by the high temperature internal gas by the setting of the negative valve overlap section to improve combustion, thereby improving fuel efficiency. In the 2-load range, the pump loss is reduced by switching to the positive valve overlap section, and the fuel efficiency is improved by suppressing knock as internal gas that is lower in temperature than the internal gas in the negative overlap section. As a result, the fuel efficiency can be improved over a wide load range.

  Incidentally, in a transition state where the transition from the first load region where the negative valve overlap section (NVO1) is formed to the second load area where the positive valve overlap section (PVO2) is formed, it can be seen from FIGS. As described above, the intake closing timing (IVC) of the intake valve 4 is changed across the intake bottom dead center (BDC) as shown by the first intake closing timing (IVC1) and the second intake closing timing (IVC2). Will be.

  For this reason, the charging efficiency peaks in the course of this change, and a transient peak torque may be generated. In addition to this, although it is a short time in the transition process, a zero valve overlap (“0” VO) is also formed near the intake bottom dead center (BDC), so that the EGR rate sharply decreases and the transient peak torque decreases. To rise.

  As a countermeasure, it is advantageous to provide a transient peak torque suppressing means. At the time of transition from the negative valve overlap section (NVO1) to the positive valve overlap section (PVO2), the transient peak torque suppression means suppresses an increase in transient peak torque caused by a sudden decrease in the internal EGR amount. In addition, a sudden change in switching torque can be suppressed. As a method of suppressing the transient peak torque, a method of delaying the ignition timing, making the air-fuel ratio lean, and separating the intake closing timing (IVC) of the intake valve from the intake bottom dead center (BDC) may be adopted. it can.

  As one specific example, an example in which ignition timing retard control is combined will be described. In this specific example, control steps S39 to S42 shown in FIG. 7 are added to suppress the transient peak torque. Hereinafter, this will be briefly described with reference to FIG. The description of the same control steps as in FIG. 6B is omitted.

{Step S39}
In step S39, it is estimated whether or not to transition from the first load area to the second load area. For example, an actual intake opening timing (IVO) of the intake valve 4 is detected by an angle sensor provided in the intake-side VTC mechanism 1A, and the detected intake opening timing (IVO) of the intake valve 4 is determined as an exhaust top dead center (IVO). (TDC) or zero valve overlap (“0” VO) is determined to determine whether the transition from the first load region to the second load region is made. .

  The determination based on this history indicates that the intake closing timing (IVC) of the intake valve 4 is approaching the intake bottom dead center, and that the exhaust closing timing (EVC) of the exhaust valve 5 is approaching the exhaust top dead center (TDC). Can be detected.

  When the transition from the first load region to the second load region is not performed, the process returns to the return. When it is estimated that the transition from the first load region to the second load region is performed, the process proceeds to step S40.

{Step S40}
In step S40, control is performed to retard the ignition timing by a predetermined angle in order to suppress the generation of the transient peak torque. When the ignition timing is retarded, the generation of torque is quickly suppressed, so that transient peak torque can be efficiently suppressed. When the control for retarding the ignition timing is executed, the execution flag is set to “1”, and the process returns to the return.

{Step S41}
At the next start timing after executing the control of step S40, if it is determined in step S30 that the load state is in the second load region, in step S41, it is determined whether or not the ignition timing retard control is executed. judge. This determination can be made by monitoring the execution flag set in step S40. If “1” is not set in the execution flag, the process proceeds to step S31. If “1” is set in the execution flag, the process proceeds to step S42. Steps S31 and S32 have already been described, and will not be described.

{Step S42}
In step S42, the ignition timing retard control set in step S40 is released to return to normal ignition timing control. When this step S42 is completed, the procedure moves to step S31.

  As described above, the occurrence of the transient peak torque can be suppressed by retarding the ignition timing, and the sudden change phenomenon of the transient peak torque can be suppressed. This ignition timing retard control has very good control responsiveness and enables torque suppression with little delay.

  Further, during a transition from the negative valve overlap section (NVO1) to the positive valve overlap section (PVO2), the amount of fuel directly injected into the combustion chamber is reduced to reduce the air-fuel ratio of the air-fuel mixture in the combustion chamber. Then, the transient peak torque can be suppressed to suppress the sudden change phenomenon of the transient peak torque. In this case, the fuel consumption performance during the transition can be improved.

  Further, during a transition from the negative valve overlap section (NVO1) to the positive valve overlap section (PVO2), the intake closing timing (IVC) of the intake valve 4 is changed to the first intake closing timing (IVC1) in the first load region. ), It is set so as to be separated from the bottom dead center (BDC) in the direction of advance or retard to suppress the transient peak torque and suppress the sudden change phenomenon of the transient peak torque. In this case, as compared with the case where the ignition timing and the air-fuel ratio are controlled, it is possible to suppress the sudden change in the transient peak torque while maintaining the fuel consumption performance and the exhaust purification performance in the transient state.

  Here, in the present embodiment, for example, when the accelerator pedal is suddenly depressed and the transition from the first load region to the third load region is performed at once, the positive overlap section (PVO2) of the second load region elapses. Instead, the negative overlap section (NVO1) is converted to a zero valve overlap (“0” VO3).

  Accordingly, it is possible to avoid a conversion operation of a large phase angle by the intake-side VTC mechanism 1A and the exhaust-side VTC mechanism 1B caused by passing the positive overlap section (PVO2), and the intake-side VTC mechanism 1A, Not only can the control of the exhaust-side VTC mechanism 1B be simplified, but also the conversion time of the intake-side VTC mechanism 1A and the exhaust-side VTC mechanism 1B can be reduced, and the acceleration performance can be improved.

  Next, a second embodiment of the present invention will be described. In the first embodiment, an example is shown in which the intake-side VTC mechanism 1A and the exhaust-side VTC mechanism 1B are used in which the operating angle does not change as a variable valve operating mechanism. As the valve mechanism, an intake-side variable operating angle mechanism whose operating angle is changed (hereinafter, referred to as an intake-side VEL mechanism) is additionally used.

  Therefore, the operation angle and the phase angle of the intake valve 4 are simultaneously changed by the intake-side VEL mechanism, and the phase angle is also changed by the intake-side VTC mechanism 1A.

  The valve timings of the exhaust-side VTC mechanism 1B, the intake-side VTC mechanism 1A, and the intake-side VEL mechanism are as shown in FIG. Since the third and subsequent load regions are basically the same as those of the first embodiment, the description thereof is omitted. Therefore, hereinafter, the load region from the first load region to the second load region will be described.

  In the first load region, the operating angle (valve opening section) of the intake-side VEL mechanism is slightly enlarged, and the intake-side VTC mechanism 1A determines the intake closing timing (IVC) of the intake valve 4 to reduce the intake bottom dead center (BDC). And the intake closing timing (IVC1 ′) delayed to near the middle between the compression stroke and the compression top dead center (TDC). In this respect, although different from the first embodiment, with respect to the first load region, the opening timing (IVO1) of the intake valve 4, the first exhaust opening timing (EVO1) of the exhaust valve 5, and the first exhaust closing timing (EVC1). ) Are set the same.

  Further, in the second load region, the operating angle of the intake-side VEL mechanism is further enlarged, and the intake opening timing (IVO) of the intake valve 4 is set to the second angle by the intake-side VTC mechanism 1A, as in the first embodiment. The intake angle is advanced to the intake opening timing (IVO2), and the intake closing timing (IVC) is retarded to the intake closing timing (IVC2 ') which is almost the same as the intake closing timing (IVC1') in the first load region. . In this respect, although different from the first embodiment, with respect to the second load region, the second intake opening timing (IVO2) of the intake valve 4, the second exhaust opening timing (EVO2) of the exhaust valve 5, the second exhaust closing The timing (EVC2) is set the same.

  Here, preferably, if the intake closing timing (IVC1 ') in the first load region and the intake closing timing (IVC2') in the second load region are (IVC1 ') ≒ (IVC2'), the charging before and after the switching is performed. Efficiency is equal, and smooth load transfer is possible. That is, since both the first load region and the second load region are the mirror cycles on the late closing side of the intake closing timing (IVC), when the transition from the first load region to the second load region occurs, the intake closing timing is changed. Since the timing (IVC) does not straddle the intake bottom dead center (BDC) as in the first embodiment, transient torque fluctuation due to an increase in charging efficiency during transition is suppressed.

  Also, as shown in the transition region, when transitioning from the first load region to the second load region, the exhaust VTC mechanism 1B controls the exhaust closing timing (EVC) of the exhaust valve 5 to the retard side, The exhaust closing timing (EVC1 → EVC2) is set to coincide with the exhaust top dead center (TDC).

  Further, the operating angle of the intake valve 4 is enlarged by the intake side VEL mechanism, and the intake opening timing (IVO1 →) is set by the intake side VTC mechanism 1A such that the intake opening timing (IVO) coincides with the exhaust top dead center (TDC). Set to 2). At the same time, the intake closing timing (IVC1 ') is further retarded with respect to the intake closing timing (IVC1') in the first load region and the intake closing timing (IVC2 ') in the second load region. → Set to 2). Thereby, the fluctuation of the transient torque can be suppressed.

  Next, a control flow for executing the valve timing characteristics according to the above-described embodiment will be described. The control flow shown in FIG. 10 particularly shows control steps from the first load region to the second load region.

{Step S27, Step S28}
In step S27, the current load state is detected from the opening of the throttle valve or the opening of the accelerator pedal, and it is determined whether the current load is in the first load region, which is a low load region. If it is determined that the region is the first load region, the process proceeds to step S28, in which the opening of the external EGR valve 56 is converted and controlled to the minimum opening. When the setting of the opening degree of the external EGR valve 56 is completed, the process proceeds to step S43.

{Step S43}
In step S43, the exhaust-side VTC mechanism 1B, the intake-side VTC mechanism 1A, and the intake-side VEL mechanism are driven, and the first exhaust valve closing timing (EVO1) and the first exhaust closing timing (EVO1) of the exhaust valve in the first load region are driven. EVC1), the first intake opening timing (IVO1) of the intake valve, and the intake closing timing (IVC1 ′) to form a negative valve overlap section (NVO1). Upon completion of the process in the step S43, the process shifts to a step S44.

{Step S44}
In step S44, it is estimated whether or not to transition from the first load area to the second load area. For example, an actual intake opening timing (IVO) of the intake valve 4 is detected by an angle sensor provided in the intake-side VTC mechanism 1A, and the detected intake opening timing (IVO) of the intake valve 4 is determined as an exhaust top dead center (IVO). (TDC) or zero valve overlap (“0” VO) is determined to determine whether the transition from the first load region to the second load region is made. .

  The determination based on the history can be performed by detecting that the exhaust closing timing (EVC) of the exhaust valve 5 is approaching the exhaust top dead center (TDC).

  When the transition from the first load region to the second load region is not performed, the process returns to the return. When it is estimated that the transition from the first load region to the second load region is performed, the process proceeds to step S45.

{Step S45}
In step S45, the exhaust-side VTC mechanism 1B, the intake-side VTC mechanism 1A, and the intake-side VEL mechanism are driven, and the exhaust valve closing timing (EVO1 → 2) and the exhaust closing timing (EVC1 → 2) of the exhaust valve in the transition region are driven. , And the intake valve opening timing (IVO1 → 2) and the intake closing timing (IVC1 ′ → 2) to form a valve overlap (NVO1 → “0” VO2). Upon completion of the process in the step S45, the process returns to the step and waits for the next controller activation timing. On the other hand, if it is determined in step S27 that the current load is not in the first load region, the process proceeds to step S30.

{Step S30, Step S31}
In step S30, the current load state is detected from the opening of the throttle valve or the opening of the accelerator pedal, and it is determined whether the current load is in the second load region. If it is determined that the load region is the second load region, the process proceeds to step S31, in which the opening of the external EGR valve 56 is controlled to be converted to the minimum opening. When the setting of the opening degree of the external EGR valve 56 is completed, the process proceeds to step S46.

{Step S46}
In step S46, the exhaust-side VTC mechanism 1B, the intake-side VTC mechanism 1A, and the intake-side VEL mechanism are driven, and the second exhaust closing timing (EVO2) and the second exhaust closing timing (EVO2) of the exhaust valve in the second load region are driven. EVC2), the second intake opening timing (IVO2) of the intake valve, and the intake closing timing (IVC2 ') to form a positive valve overlap section (PVO2). Upon completion of the process in the step S46, the process goes to the return and waits for the next controller activation timing. On the other hand, if it is determined in step S30 that it is not the first load region, the process proceeds to step S33. Subsequent steps are the same as in the first embodiment, and a description thereof will be omitted.

  As described above, in the transition region where the first load region shifts to the second load region, the exhaust closing timing (EVC) of the exhaust valve 5 is set to the exhaust top dead center (TDC), and the exhaust closing timing (EVC1 → 2), the intake valve open timing (IVO) of the intake valve 4 is set to the exhaust top dead center (TDC), and the intake valve open timing (IVO1 ′ → 2), so that the valve overlap is zero valve overlap (NVO1 → It approaches "0" VO2). For this reason, the internal EGR rate temporarily decreases, so that the transient torque increases by that amount, causing torque fluctuation.

  Therefore, in the present embodiment, while maintaining the intake opening timing of the intake valve 4 (IVO1 → 2), the operating angle is expanded by the intake side VEL mechanism to achieve the intake closing timing of the intake valve 4 (IVC1 ′ → 2). Thus, the intake closing timing (IVC) is retarded.

  As a result, the fresh air charging efficiency can be reduced, so that an increase in transient torque due to a temporary decrease in the internal EGR rate can be suppressed. As described above, in the present embodiment, it is possible to suppress the fluctuation of the transient torque when transitioning from the first load region to the second load region.

  In the above-described embodiment, the hydraulic variable phase mechanism is described. However, the present invention is not limited to the hydraulic pressure, and an electric variable phase mechanism may be used, and a variable operating angle mechanism may be provided. . Further, although the butterfly valve is shown as the structure of the external EGR valve, it may be a poppet valve. The specific form and configuration of the specific variable valve mechanism and the external EGR valve are not limited as long as the gist of the present invention is satisfied.

  Note that the present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described above. In addition, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of one embodiment can be added to the configuration of another embodiment. Also, for a part of the configuration of each embodiment, it is possible to add, delete, or replace another configuration.

  01 ... piston, 02 ... crankshaft, 03 ... connecting rod, 04 ... combustion chamber, 05 ... spark plug, 1A ... intake side variable valve mechanism, 1B ... exhaust side variable valve mechanism, 2A, 2B ... phase control hydraulic actuator 4, an intake valve, 5: an exhaust valve, 51: an electrically controlled throttle valve, 52: a controller, 53: an exhaust gas purification catalyst, 54: an exhaust gas recirculation passage, 55: an EGR cooler, 56: an external EGR valve.

Claims (15)

At least an exhaust-side variable valve mechanism for adjusting a closing timing of an exhaust valve provided in the internal combustion engine (hereinafter referred to as “exhaust closing timing (EVC)”), and an opening of an intake valve provided in the internal combustion engine. An intake-side variable valve mechanism for adjusting the timing (hereinafter, referred to as “intake opening timing (IVO)”),
In a predetermined first load region, the exhaust side variable valve mechanism sets the exhaust closing timing (EVC) to a first exhaust closing timing (EVC1) before exhaust top dead center (TDC), The side variable valve mechanism sets the intake opening timing (IVO) to a first intake opening timing (IVO1) after the exhaust top dead center (TDC), so that the exhaust valve and the intake valve have a negative valve overflow. A lap section (NVO1) is formed,
In a predetermined second load region exceeding the first load region, the exhaust-side variable valve mechanism causes the exhaust closing timing (EVC) to be a second exhaust closing timing (EVC2) after the exhaust top dead center (TDC). And the intake side variable valve mechanism sets the intake opening timing (IVO) to a second intake opening timing (IVO2) prior to the exhaust top dead center (TDC), and the exhaust valve and the exhaust valve A variable valve operating system for an internal combustion engine, wherein a positive valve overlap section (PVO2) is formed in the intake valve. In the variable valve system of the internal combustion engine according to claim 1,
A variable valve operating system for an internal combustion engine, wherein a phase angle of the positive valve overlap section (PVO2) is equal to or larger than a phase angle of the negative valve overlap section (NVO1). In the variable valve system of the internal combustion engine according to claim 1,
In the first load region, the opening timing of the exhaust valve (hereinafter, referred to as “exhaust opening timing (EVO)”) by the exhaust-side variable valve mechanism is the first exhaust valve whose exhaust timing is before the exhaust bottom dead center (BDC). It is set at the opening time (EVO1),
In the second load region, the exhaust side variable valve mechanism delays the exhaust opening timing (EVO) of the exhaust valve to a second exhaust opening timing (EVO2) near the exhaust bottom dead center (BDC). A variable valve operating system for an internal combustion engine. In the variable valve system of the internal combustion engine according to claim 1,
In the transition from the negative valve overlap section (NVO1) to the positive valve overlap section (PVO2), occurrence of transient peak torque is suppressed by transient peak torque suppression means. Variable valve system. The variable valve system for an internal combustion engine according to claim 4,
The transient peak torque suppression means is the intake side variable valve mechanism,
By the intake side variable valve mechanism, the closing timing of the intake valve (hereinafter referred to as “intake closing timing (IVC)”) is advanced or retarded from the intake bottom dead center (BDC). A variable valve system for an internal combustion engine, which is set. In the variable valve system of the internal combustion engine according to claim 1,
The intake side variable valve mechanism causes the intake valve closing timing (hereinafter, referred to as “intake closing timing (IVC)”) of the intake valve in the first load region to exceed the intake bottom dead center (BDC). Is set to the first intake closing timing (IVC1), and the second intake closing timing (IVC2) in the second load region is also the second intake closing timing on the retard side beyond the intake bottom dead center (BDC). (IVC2), a variable valve operating system for an internal combustion engine. In the variable valve system of the internal combustion engine according to claim 1,
The intake side variable valve mechanism causes the intake valve closing timing (hereinafter, referred to as “intake closing timing (IVC)”) of the intake valve in the first load region to exceed the intake bottom dead center (BDC). The first intake closing timing (IVC1) is set at the first intake closing timing (IVC1), and the second intake closing timing (IVC2) in the second load region is a second advanced intake closing timing on the advance side before the intake bottom dead center (BDC). (IVC2), a variable valve operating system for an internal combustion engine. In the variable valve system of the internal combustion engine according to claim 1,
The first intake opening timing (IVO1) in the first load region substantially coincides with a default position (mechanical stable position) of the intake side variable valve mechanism, and the first exhaust in the first load region. A variable valve system for an internal combustion engine, wherein a closing timing (EVC1) substantially coincides with a default position (mechanical stable position) of the exhaust-side variable valve mechanism. In the variable valve system of the internal combustion engine according to claim 1,
When the load reaches a third load region that is larger than the second load region,
Compared to the second load region, the exhaust-side variable valve mechanism advances the exhaust closing timing (EVC) to the exhaust top dead center (TDC) and sets the third exhaust closing timing (EVC3). At the same time, the intake side variable valve mechanism delays the intake opening timing (IVO) to the exhaust top dead center (TDC) and sets it to a third intake opening timing (IVO3). (NVO1) and a zero valve overlap (“0” VO) where the positive valve overlap section (PVO2) does not exist, and further, the external EGR valve is opened to introduce the external EGR gas. Variable valve system for internal combustion engines. The variable valve system for an internal combustion engine according to claim 9,
When the load region changes greatly from the first load region to the third load region, the positive valve overlap section (PVO2) is passed by the exhaust side variable valve mechanism and the intake side variable valve mechanism. The variable valve operating system of the internal combustion engine, wherein a transition is made from the negative valve overlap section (NVO1) to the zero valve overlap (“0” VO). In the variable valve system for an internal combustion engine according to claim 9 or claim 10,
When the load reaches a fourth load region larger than the third load region,
Compared to the third load region, the exhaust-side variable valve mechanism sets the exhaust-closing timing (EVC) to a fourth exhaust-closing timing (EVC4) that is delayed from the exhaust top dead center (TDC). At the same time, the intake opening timing (IVO) is set as the fourth intake opening timing (IVO4) at the exhaust top dead center (TDC) by the intake side variable valve mechanism, and the positive valve overlap section (PVO4) is set. A variable valve system for an internal combustion engine, wherein the variable EEG valve is formed, and the introduction of the external EGR gas is interrupted by closing the external EGR valve. In the variable valve system of the internal combustion engine according to claim 1,
The load determination threshold value for determining the switching between the first load region and the second load region is determined when the transition from the first load region to the second load region and when the transition from the second load region to the first load region occurs. A variable valve system for an internal combustion engine, wherein a hysteresis is set at the time of transition. The exhaust-side variable valve mechanism used in an internal combustion engine having an exhaust-side variable valve mechanism that changes the exhaust closing timing of an exhaust valve and an intake-side variable valve mechanism that changes the intake opening timing of an intake valve, and A control device for a variable valve system for an internal combustion engine, comprising a control unit for controlling the intake side variable valve mechanism,
When the load region of the internal combustion engine is in a predetermined first load region, the control means causes the exhaust-side variable valve mechanism to set the exhaust valve closing timing (EVC) of the exhaust valve before the exhaust top dead center (TDC). , And the intake side variable valve mechanism sets the intake opening timing (IVO) of the intake valve after the first exhaust opening timing (TDC) after the exhaust top dead center (TDC). IVO1) to form a negative valve overlap section (NVO1) between the exhaust valve and the intake valve,
Further, in a state of the second load region where the load region of the internal combustion engine is larger than the first load region, the exhaust-side variable valve mechanism sets the exhaust closing timing (EVC) of the exhaust valve to the exhaust top dead center (EVC). TDC) is set to a second exhaust closing timing (EVC2), and the intake side variable valve mechanism sets the intake opening timing (IVO) of the intake valve to a second exhaust closing timing (TDC) before the exhaust top dead center (TDC). A control device for a variable valve system for an internal combustion engine, wherein a positive valve overlap section (PVO2) is formed between the exhaust valve and the intake valve by setting an intake opening timing (IVO2). A control device for a variable valve operating system for an internal combustion engine according to claim 13,
The control means moves the intake valve closing timing (IVC) of the intake valve in a direction to be retarded from the intake bottom dead center (BDC) during a transition from the first load region to the second load region. A control device for a variable valve system for an internal combustion engine, comprising: A control device for a variable valve operating system for an internal combustion engine according to claim 13,
The control device for a variable valve operating system for an internal combustion engine, wherein the control means executes a retard control for retarding an ignition timing during a transition from the first load region to the second load region. .

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