JP2018141403A - Variable valve system of internal combustion engine and control device of variable valve mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel variable valve system of an internal combustion engine which can reduce a harmful component of an exhaust gas by suppressing the deterioration of combustion at a cold start, and its controller.SOLUTION: At a cold start of an internal combustion engine, the opening timing (IVOc) of an intake valve is set at a retardant side by a prescribed angle (ITc) rather than an exhaust top dead point by an intake valve variable valve mechanism at an advance side rather than the most retardant opening timing (IVOrtd), and between the advance side and a retardant side rather than the most advance opening timing (IVOadv), and the close timing (EVCc) of an exhaust valve is set at an advance side by a prescribed angle (ETc) rather than the exhaust top dead point by the exhaust valve variable valve mechanism at a retardant side rather than the most advance close timing (EVCadv), and between the retardant side and an advance side rather than the most retardant close timing (EVCrtd), thus forming a "negative valve overlap" (NVOc) in which the opening timing (IVOc) of the intake valve and the close timing (EVCc) of the exhaust valve are not overlapped on each other.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a variable valve system for an internal combustion engine, and more particularly to a variable valve system for an internal combustion engine having a variable valve mechanism for controlling the opening and closing phases of an intake valve and an exhaust valve, and a control device for the variable valve mechanism. is there.

  As a conventional variable valve mechanism for controlling the opening / closing phase of an intake valve or an exhaust valve of an internal combustion engine, for example, one described in Non-Patent Document 1 below is known. In this non-patent document 1, a variable phase variable valve mechanism (hydraulic VTC) for controlling the opening / closing phase of the intake valve is provided on the intake side, and when the internal combustion engine is stopped, Reduces harmful exhaust components at the start of the internal combustion engine by controlling so that it is mechanically stable at a position that has a "positive valve overlap" (PVO: interval where the intake valve open timing and exhaust valve close timing overlap) A variable valve system is shown.

  In this non-patent document 1, high-temperature residual gas containing unburned HC is caused to flow back to the intake system during the period of “positive valve overlap” (PVO) at the beginning of startup, and unburned in the subsequent intake stroke thereafter. By reintroducing the residual gas containing HC gas into the cylinder and burning it, it is possible to reduce exhaust harmful components in the exhaust gas.

SAE Paper 2012-01-0416; Development of a Hydraulic Variable Valve Timing Control System with an Optimum Angular Position Locking Mechanism

  By the way, as described above in Non-Patent Document 1, high-temperature residual gas including unburned HC is caused to flow back to the intake system during the period of “positive valve overlap” (PVO) at the initial stage of starting, and the subsequent intake air thereafter. In the process, the unburned HC reintroduces the residual gas containing soot into the cylinder and re-combusts it, thereby reducing the emission of harmful exhaust components in the exhaust gas.

  However, in cold start where the internal combustion engine is cold, the residual gas containing unburned HC is allowed to flow back to the intake system during the period of “positive valve overlap” (PVO), so that the high temperature residual gas is It is cooled by returning to the intake system, and when it is re-inhaled into the cylinder, the temperature is lowered accordingly. Therefore, from the viewpoint of stabilizing the combustion in the cylinder, the effect of heating the air-fuel mixture by the high-temperature residual gas is reduced by that amount, which may cause deterioration of combustion at the time of cold start.

  SUMMARY OF THE INVENTION The main object of the present invention is to provide a novel variable valve system for an internal combustion engine and a variable valve control apparatus capable of reducing harmful exhaust components in exhaust gas by suppressing deterioration of combustion at the time of cold start. There is.

  The feature of the present invention is that when the internal combustion engine is cold-started, the intake valve opening timing (IVOc) is advanced from the most retarded angle opening timing (IVOrtd) by the intake valve variable valve mechanism, and the most advanced angle opening timing is set. Between (IVOadv) and the retarded angle side, a predetermined angle (ITc) is set to the retarded angle side with respect to the exhaust top dead center (TDC), and the exhaust valve variable valve mechanism sets the exhaust valve closing timing (EVCc). , More advanced than the exhaust top dead center (TDC) by a predetermined angle (ETc) on the retarded side from the most advanced angle closing timing (EVCadv) and between the most retarded timing (EVCrtd) It is set to form a “negative valve overlap” (NVOc) in which the intake valve opening timing (IVOc) and the exhaust valve closing timing (EVCc) do not overlap.

  According to the present invention, at the time of cold start of an internal combustion engine, a “negative valve overlap” (NVOc) is formed from the end of the exhaust stroke to the early stage of the intake stroke, whereby the high temperature combustion gas (high temperature EGR gas) is By confining inside and pressurizing with a piston, the remaining in-cylinder gas and the engine body are heated, and deterioration of combustion at the time of cold start can be suppressed to reduce exhaust harmful components in the exhaust gas. become able to.

It is a block diagram explaining the structure of the principal part of the variable valve system of an internal combustion engine. It is principal part sectional drawing which shows the principal part of an exhaust valve variable valve mechanism. It is a characteristic view which shows the valve timing characteristic explaining embodiment of this invention. It is a PV diagram which compared the valve timing characteristic at the time of the partial load after warming-up of the embodiment of the present invention, and the valve timing characteristic of the conventional form. It is a characteristic view which shows the relationship between the load and valve | bulb overlap of embodiment of this invention. It is a flowchart figure which shows the control flow at the time of the stop transition which controls the variable valve mechanism which becomes embodiment of this invention. It is a flowchart figure which shows the control flow at the time of the operation which controls the variable valve mechanism which becomes embodiment of this invention. It is a characteristic view which shows the valve timing characteristic which becomes other 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 also included in the range.

  FIG. 1 shows a configuration of a main part of a variable valve system of an internal combustion engine. An exhaust camshaft 10 is provided with two exhaust cams 11 per cylinder. The exhaust cam 11 opens and closes the exhaust valve 12. A sprocket mechanism 13 and an exhaust valve variable valve mechanism (hereinafter referred to as an exhaust VTC) 14 fixed to the sprocket mechanism 13 are attached to one end of the exhaust camshaft 10, and the exhaust camshaft 10 is connected to the sprocket mechanism. The relative rotational position of the exhaust cam 11 is controlled by making relative rotation (phase conversion) with respect to 13.

  The sprocket mechanism 13 includes a timing sprocket 15 and is rotated by a crankshaft by a timing belt (not shown). The exhaust VTC 14 includes a housing 16 and a vane that is hydraulically driven in a space formed by the front cover 17 and the 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 camshaft 10. Therefore, by adjusting the rotational position of the vane by hydraulic pressure, the exhaust camshaft 10 adjusts the opening / closing phase of the exhaust valve correspondingly.

  Similarly, the intake camshaft 20 is provided with two intake cams 21 per cylinder. The intake cam 21 opens and closes the intake valve 22. Further, a sprocket mechanism 23 and an intake valve variable valve mechanism (hereinafter referred to as intake VTC) 24 fixed to the sprocket mechanism 23 are attached to one end of the intake camshaft 20, and the intake camshaft 20 is connected to the sprocket mechanism. The relative rotational position of the intake cam 21 is controlled by relative rotation (phase conversion) with respect to 23.

  The sprocket mechanism 23 includes a timing sprocket 25 and is rotated by a crankshaft by a timing belt (not shown). The intake VTC 24 has a housing 26 and a vane that is hydraulically driven 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, the intake camshaft 20 adjusts the opening / closing phase of the intake valve correspondingly by adjusting the rotational position of the vane by hydraulic pressure.

  The control device 30 receives various operating state information of the internal combustion engine, an exhaust VTC actual position signal, an intake VTC actual position signal, and the like, supplies an exhaust phase control signal to the exhaust electromagnetic switching valve 31, and supplies an intake phase control signal. By supplying the intake electromagnetic switching valve 32, the exhaust phase control hydraulic pressure of the exhaust VTC 14 and the intake phase control hydraulic pressure of the intake VTC 24 are controlled.

  Next, the configurations of the exhaust VTC 14 and the intake VTC 24 will be briefly described. Since the configurations of the exhaust VTC 14 and the intake VTC 24 are substantially the same, the configuration of the exhaust VTC 14 will be described below.

  In the rear view sectional view shown in FIG. 2, the housing 35 (16) has a cylindrical housing body 35a whose front end opening is closed by a disc-shaped front cover 17 (see FIG. 1) and whose rear end opening is a disk. The rear cover 18 (see FIG. 1) is closed. Further, at a position of about 90 ° in the circumferential direction of the inner peripheral surface of the housing main body 35a, shoes 35b that are four partition walls project from the inner side.

  The rear cover 18 is integrally provided at the center position of the timing sprocket 13, and the outer peripheral portion thereof is fastened and fixed to the housing body 35 a and the front cover 17 by four bolts 39. In addition, a large-diameter bearing hole that is supported on the outer periphery of the cylindrical portion of the vane rotor 36 is formed in the center of the rear cover 18 in the axial direction.

  The vane rotor 36 includes a cylindrical rotor 37 having a bolt insertion hole in the center, and four vanes 38 and 38a provided integrally at a position approximately 90 ° in the circumferential direction of the outer peripheral surface of the rotor 37. The rotor 37 has a small diameter cylindrical portion on the front end side rotatably supported by the central support hole of the front cover 17, while a small diameter cylindrical portion on the rear end side is rotatably supported by the bearing hole of the rear cover 18. .

  The vane rotor 36 is fixed to the front end portion of the exhaust camshaft 10 from the axial direction by a fixing bolt 40 inserted through the bolt insertion hole of the rotor 37 from the axial direction. Each vane 38, 38a is disposed between each shoe 35b, and a seal member that slidably contacts the inner peripheral surface of the housing main body 35a in an elongated holding groove formed in the axial direction of each outer surface and the seal. A leaf spring that presses the member in the direction of the inner peripheral surface of the housing body is fitted and held.

  Further, four retard chambers 41 and advance chambers 42 are respectively defined between both sides of the vanes 38 and 38a and both sides of the shoes 35b. The vane 38a has an advance side stopper function and a retard side stopper function.

  Then, by switching the exhaust electromagnetic switching valve 31, the hydraulic oil is selectively supplied to the respective retard chambers 41 and the advance chambers 42, whereby the vane rotor 36 (the exhaust camshaft 10) is moved with respect to the crankshaft. The relative rotational phase is changed. Further, in each advance chamber 42, four coil springs 43 that constantly bias the vane rotor 36 in the advance direction are mounted.

  Similarly, the intake VTC 24 has the same configuration, but the advance chamber and the retard chamber have an opposite relationship, and the four coil springs that constantly urge the vane rotor 36 in the retard direction include the retard chamber. Are attached to each.

  In FIG. 2, in the state where the stopper surface 44 of the vane 38a coincides with the advance angle (Emax), the other side surface of the vane 38a and the side surface of the shoe 35b come into contact with each other to form the most advanced phase. Further, the phase of the most retarded angle is obtained by the contact of the stopper surface 44 in a state where the stopper surface 44 of the vane 38a coincides with the retard angle (Emin). Here, the coil spring 43 accommodated in the advance chamber 42 urges the vanes 38a and 38 toward the advance side as shown in FIG.

  Here, the intermediate angle timing (Emid) is between the most advanced angle timing (Emax) and the most retarded angle timing (Emin), and is slightly behind the most advanced angle timing (Emax). In the phase (default phase) that coincides with the intermediate angle timing (Emid), the fastening pin 45 built in the vane 38a and the fastening hole on the rear cover 18 side coincide with each other, and the vanes 38a and 38 are positioned at the default position. It is like that.

  The intake VTC 24 has a structure similar to that of the exhaust VTC 14 shown in FIG. 2, but the conversion phase angle formed between the most advanced angle timing (Imax) and the most retarded angle magnetism (Imin) is larger than that of the exhaust VTC 14. Is set.

  Similarly to the exhaust VTC 14, the intermediate angle timing (Imid) is set between the most advanced timing (Imax) and the most retarded timing (Imin), and the fastening pin in the vane matches the fastening hole on the rear cover side. The default position is set to the retard side that is larger than the most advanced timing (Imax), and is set to be slightly advanced from the most retarded timing (Imin).

  Therefore, at the phase where the stopper surface of the vane coincides with the intermediate angle timing (Imid), the fastening pin in the vane and the fastening hole on the rear cover 28 coincide with each other like the exhaust VTC 14 so that the vane is positioned at the default position. It has become.

Next, the valve timing characteristics of this embodiment will be described. In FIG. 3, “(A) cold start state”, “(B) partial load state after warm-up”, and “(C) post-warm state”. Each valve timing characteristic of “full load state” is shown. Here, “(A) the cold start state” is, for example, a state where the main body temperature of the internal combustion engine is 40 ° C. or less, and “(B) the partial load state after warming up” is, for example, the accelerator pedal being in the middle Further, “(C) full load state after warm-up” is a state where, for example, the accelerator pedal is depressed to the maximum extent. Hereinafter, each valve timing characteristic will be described.
≪Cooling start condition≫
At the time of cold start, the valve timing characteristics shown in “(A) cold start state” in FIG. 3 are obtained. Here, the exhaust VTC 14 is in the default position because the vane 38a is fastened to the rear cover 18 via the fastening pin 45 at the above-described intermediate angular timing (EVCc = Emid). Similarly, the vane of the intake VTC 24 is also in the default position because the vane is fastened to the rear cover via the fastening pin at the above-mentioned intermediate angular timing (IVOc = Imid).

  As a result, since both the exhaust VTC 14 and the intake VTC 24 are in the default positions, the valve timings of the exhaust valve and the intake valve are the valve timings shown in “(A) Cold machine start state” in FIG.

  That is, the exhaust top dead center is when the exhaust valve closing timing (EVC) is more retarded than the exhaust valve most advanced timing (EVCadv) and more advanced than the most retarded timing (EVCrtd). The exhaust valve closing timing (EVCc) on the advance side is set by a predetermined angle (ETc) from (TDC). Here, the most advanced angle closing time (EVCadv) is the same as the most advanced angle time (Emax) shown in FIG. 2, and the most retarded angle closing time (EVCrtd) is the same as the most retarded angle time (Emin) shown in FIG. It is.

  In addition, the intake valve opening timing (IVO) is an advance side of the most retarded angle opening timing (IVOrtd) of the intake valve, and is between the retarded side of the most advanced angle opening timing (IVOaddv) and the exhaust top dead center ( The intake valve opening timing (IVOc) is set at a delay angle side by a predetermined angle (ITc) from TDC). Here, the most advanced angle opening time (IVOadv) is the same as the most advanced angle time (Imax), and the most retarded angle opening time (IVOrtd) is the same as the most retarded angle time (Imin).

  As a result, at the time of cold start, “ITc + ETc” obtained by adding a predetermined angle (ITc) and a predetermined angle (ETc) between the closing timing (EVCc) of the exhaust valve and the opening timing (IVOc) of the intake valve. “Negative valve overlap” (NVOc) is set. Thus, high temperature combustion gas (high temperature EGR gas) is contained in the cylinder and pressurized by the piston from the end of the exhaust stroke to the initial stage of the intake stroke.

  Here, the predetermined angle (ITc) and the predetermined angle (ETc) are set to substantially the same angle. Note that substantially the same angle is a concept including mechanical errors after assembly of the exhaust VTC 14 and the intake VTC 24, design tolerances, and the like, and does not necessarily mean the same angle.

  Therefore, at the time of cold start, high temperature combustion gas (high temperature EGR gas) is sealed in the cylinder during the period of “negative valve overlap” (NVOc) (from the end of the exhaust stroke to the beginning of the intake stroke) By pressurizing, the temperature of the in-cylinder gas remaining at the compression top dead center can be raised, and the in-cylinder gas and the cylinder body are remarkably heated.

  For this reason, by increasing the temperature of the air-fuel mixture formed when fresh air is inhaled in the next intake stroke, it is possible to stabilize combustion at the time of cold start, to suppress fuel consumption improvement and generation of harmful exhaust components, Since the warm-up performance of the internal combustion engine (increase in the engine body temperature) can be improved, the friction resistance of the mechanical system can be reduced by reducing the oil viscosity, and the fuel efficiency can be improved, and the exhaust purification catalyst provided in the exhaust system can be improved. Since the effect of increasing the temperature quickly is also obtained, the effect of reducing exhaust harmful components can be further obtained.

  When the intake valve closing timing (IVCc) is set to be the same as the conventional closing timing (IVC), the intake valve opening timing (IVOc) is retarded in the present embodiment. The period (intake operating angle) can be set narrow, whereby the valve friction resistance of the intake valve can be reduced and the use of the driving force of the internal combustion engine can be suppressed.

  For the same reason, when the exhaust valve opening timing (EVOc) is set to be the same as the conventional opening timing (EVO), the exhaust valve closing timing (EVCc) is advanced in this embodiment. The valve opening period (exhaust operating angle) can be set narrow, whereby the valve frictional resistance of the exhaust valve can be reduced, and use of the driving force of the internal combustion engine can be suppressed.

  For this reason, it is possible to improve fuel efficiency. Furthermore, by opening the exhaust valve opening timing (EVO) as early as possible, the exhaust valve is opened before the combustion gas temperature decreases, and the exhaust gas having a high temperature is supplied to the exhaust gas purification catalyst. It is possible to increase the temperature of the exhaust gas purifying catalyst to reduce harmful components of exhaust gas at the time of cold start while suppressing an increase in valve frictional resistance.

  Here, the EGR gas can also be introduced into the cylinder by the conventional “positive valve overlap” (PVO). The temperature of the EGR gas is in principle the “negative valve overlap” according to the present embodiment. It is lower than (NVO), and the valve opening period (intake / exhaust operating angle) of the intake valve and the exhaust valve is set to be large, so there is a problem that the valve friction resistance of the intake valve and the exhaust valve increases. .

In addition, since the intake valve opening timing (IVOc) and the exhaust valve closing timing (EVCc) are between the respective most advanced timing timings (IVOaddv, EVCadv) and most retarded timing timings (IVOrtd, EVCrtd), warm-up operation is performed. During and after warm-up, the “Negative Valve Overlap” (NVO) can be increased or decreased, thereby improving various performances during and after warm-up. It can be realized.
≪Partial load after warm-up≫
Next, the valve timing in the partial load state after warm-up will be described. In the partial load (low load) after warm-up, the valve timing characteristics shown in “(B) Partial load state after warm-up” in FIG. 3 are obtained.

  That is, in the partial load (low load) state after warm-up, the intake valve opening timing (IVO) is further retarded than the intake valve opening timing (IVOc) in the cold start state, and the exhaust The timing is converted into the open timing (IVOp) on the retard side by a predetermined angle (ITp) from the dead point (TDC). Here, the opening timing (IVOp) is the same as the most retarded opening timing (IVOrtd).

  At the same time, the intake valve closing timing (IVC) is set to the intake valve closing timing (IVCp) retarded to near the middle position between the intake bottom dead center (BDC) and the compression top dead center (TDC). For example, the vane may be phase-converted by the intake VTC 24 until the aforementioned most retarded opening timing (Imin) of the intake valve.

  Further, in the partial load (low load) state after warm-up, the exhaust valve closing timing (EVC) is further advanced than the exhaust valve closing timing (EVCc) in the cold start state, and the exhaust The dead time (TDC) is converted into the closing timing (EVCp) on the advance side by a predetermined angle (ETp). Here, the closing time (EVCp) is the same as the most advanced angle closing time (EVCadv).

  At the same time, the exhaust valve opening timing (EVO) is advanced to a section between the exhaust bottom dead center (BDC) and the compression top dead center (TDC) to open the exhaust valve opening timing (EVOp). Set to. For example, the vanes 38a and 38 may be phase-converted by the exhaust VTC 14 up to the most advanced timing (Emax) of the exhaust valve.

  As a result, a “negative valve over” consisting of an angle of “ITp + ETp”, which is longer than the “negative valve overlap” (NVOc) in the cold start state and is a sum of the predetermined angle (ITp) and the predetermined angle (ETp). “Wrap” (NVOp) will be set. Therefore, high-temperature combustion gas (high-temperature EGR gas) can be contained in the cylinder and pressurized by the piston from the end of the exhaust stroke to the beginning of the intake stroke.

  For this reason, it becomes possible to sufficiently improve the fuel efficiency at the partial load (low load) after the internal combustion engine is warmed up. That is, at the partial load (low load) after warm-up, the frictional resistance of the internal combustion engine mechanism system may be lower than that in the cold state, and the intake air amount can be reduced compared to that in the cold state. In this case, if the throttle valve is closed to reduce the intake air amount, so-called pump loss may increase and fuel consumption performance may deteriorate.

  Therefore, the throttle valve opening time (IVC) is greatly retarded to near the middle position between the intake bottom dead center and the compression top dead center, so that a so-called "lately closed Atkinson cycle" is established, so that the throttle valve opening is greatly opened. It is conceivable to reduce the amount of intake air while maintaining the same.

  However, in this case, since the intake valve closing timing (IVC) is retarded, the effective compression ratio is lowered, the gas temperature at the compression top dead center is lowered, the combustion is deteriorated, and the desired fuel consumption is reduced. There is a risk that the effect will not be obtained.

  On the other hand, in this embodiment, the gas temperature at the compression top dead center can be increased by a large “negative valve overlap” (NVOp), so that the deterioration of combustion is avoided and the desired fuel consumption is reduced. An effect comes to be acquired.

  In addition, a large “negative valve overlap” (NVOp) reduces the amount of fresh air by relatively increasing the amount of high-temperature combustion gas in the cylinder, so that a predetermined partial load torque can be obtained. The required throttle opening can be further increased (throttle large opening θp range shown in FIG. 5), and thus pump loss can be further reduced and fuel efficiency can be improved.

  When the intake valve closing timing (IVCp) is set to be the same as the conventional closing timing (IVC), the intake valve opening timing (IVOp) is retarded in the present embodiment. The period (intake operating angle) can be set narrow, thereby reducing the valve frictional resistance of the intake valve and suppressing unnecessary use of the driving force of the internal combustion engine, resulting in improved fuel efficiency. It becomes possible to do.

  For the same reason, when the exhaust valve opening timing (EVOp) is set to be the same as the conventional opening timing (EVO), the exhaust valve closing timing (EVCp) is advanced in this embodiment. The valve opening period (exhaust operating angle) can be set narrow, thereby reducing the valve frictional resistance of the exhaust valve and suppressing the wasteful use of the driving force of the internal combustion engine. Can be improved.

  Here, in the present embodiment, the predetermined angle (ITp) and the predetermined angle (ETp) are set to be substantially the same angle. This makes it possible to reduce pump loss that occurs during “negative valve overlap” (NVOp). The reason will be described with reference to the PV diagram shown in FIG.

  Here, the predetermined angle (ITp) and the predetermined angle (ETp) are set to substantially the same angle. However, as described above, the substantially same angle is a mechanical error or design after assembling the exhaust VTC 14 and the intake VTC 24. It is a concept that includes the above tolerances, etc., and does not necessarily mean the same angle.

  4A shows a PV diagram of the present embodiment (the valve timing characteristics shown in FIG. 3B), and FIG. 4B shows Reference Example 1 (ETp≈0) as a comparison target. The PV diagram at <ITp) is shown, and FIG. 4C shows the PV diagram at Reference Example 2 (ETp> ITp≈0) as a comparison object.

  In the reference example 1 of FIG. 4B, in-cylinder negative pressure develops in the section (ITp) from the exhaust top dead center (TDC) to the intake valve opening timing (IVOp) in the process of lowering the piston. To do. This in-cylinder negative pressure acts so as to suppress the downward movement of the piston, so that a pump loss (downward triangular area) at the initial stage of suction occurs as shown in the PV diagram.

  Further, in Reference Example 2 in FIG. 5C, the piston rises toward the exhaust top dead center (TDC) from the closing timing (EVCp) when the exhaust valve before the exhaust top dead center (TDC) is closed. In the process, in-cylinder positive pressure develops in the section (ETp) to the exhaust top dead center (TDC). This in-cylinder positive pressure acts to suppress the upward movement of the piston. Here, since the intake valve opens when the exhaust top dead center (TDC) is exceeded, the positive pressure gas in the cylinder flows backward to the intake side and can be recovered as energy for promoting the downward movement of the piston. Can not. As a result, as shown in the PV diagram of (C), pump loss (upward triangular region) at the end of the exhaust stroke occurs.

  As described above, in both Reference Examples 1 and 2, the pump loss increases, so that the fuel consumption at the partial load is deteriorated.

  On the other hand, in the present embodiment, as shown in the PV diagram of FIG. 4A, both the pump loss at the initial stage of the intake stroke and the pump loss at the end stage of the exhaust stroke can be suppressed.

  That is, as in Reference Example 2, the exhaust valve closing timing (EVCp) is before the exhaust top dead center (TDC), and from the exhaust valve closing timing (EVCp) to the exhaust top dead center (TDC), the high-temperature combustion gas The (high temperature EGR gas) is compressed by a predetermined angle (ETp), and at that time, it acts to suppress the upward movement of the piston.

  On the other hand, since the opening timing (IVOp) of the intake valve is delayed from the exhaust top dead center (TDC) by the predetermined angle (ITp) at the same angle, the piston goes down after exceeding the exhaust top dead center (TDC). If it moves, the pressure of the hot combustion gas compressed previously will be open | released, and it will collect | recover as energy which promotes the downward movement of a piston. As a result, as shown in FIG. 4A, the generation of a triangular area is suppressed, and the pump loss before and after the exhaust top dead center (TDC) is suppressed.

Therefore, the relationship of predetermined angle (ETp) = predetermined angle (ITp) is most preferable. As shown in the PV diagram of FIG. 4A, the pump loss at the end of the exhaust stroke and the initial pump loss of the intake stroke Both can be removed. As described above, the valve timing characteristic in the partial load state of the present embodiment shown in FIG. 4A can further improve the fuel efficiency from the viewpoint of suppressing the pump loss before and after the exhaust top dead center (TDC). Is.
≪Full load condition after warm-up≫
Next, the valve timing in the full load state after warm-up will be described. At the full load after warm-up, the valve timing characteristics shown in “(C) Full-load state after warm-up” in FIG. 3 are obtained.

  That is, in the full load state after warming up, the maximum advance angle conversion is performed on the stopper surface of the intake VTC 24 until the most advanced angle timing (Imax). Therefore, the opening timing (IVO) of the intake air valve is advanced to a more advanced side than the opening timing (IVOc) of the intake valve in the cold start state, and is a predetermined angle from the exhaust top dead center (TDC). Only (ITh) is converted to the opening timing (IVOh) on the advance side. Here, the opening time (IVOh) is the same as the most advanced angle opening time (IVOadv).

  Further, in the full load state after warming up, the stopper surface 44 of the exhaust VTC 14 is subjected to maximum retardation conversion until the most retarded timing (Emin). The closing timing (EVC) of the exhaust valve is retarded to the far side of the closing timing (EVCc) of the exhaust valve in the cold start state, and a predetermined angle (ETh) from the exhaust top dead center (TDC). Is converted into the retard timing (EVCh). Here, the closing timing (EVCh) is the same as the most advanced angle closing timing (EVCrtd).

  Therefore, since the intake valve opening timing (IVOh) becomes the maximum advance opening timing (IVOadv) and the exhaust valve closing timing (EVCh) becomes the maximum retarded closing timing (EVCrtd), a large “positive valve overlap”. (PVOh) is set. Further, the intake valve closing timing (IVCh) is advanced to the vicinity of the intake bottom dead center, and the exhaust valve opening timing (EVOh) is delayed to the vicinity of the expansion bottom dead center. Here, the lead angle conversion angle of the intake VTC 24 is larger than the retard angle conversion angle of the exhaust VTC 14, and as a result, the section center of the above-mentioned “positive valve overlap” (PVOh) is shown in FIG. Thus, the advance is made from the exhaust top dead center (TDC).

  According to such valve timing characteristics, it is possible to sufficiently increase the engine torque in the full load state after warm-up. That is, since the opening timing (EVOh) of the exhaust valve is retarded to the vicinity of the expansion bottom dead center (BDC), the timing when the negative pressure wave of the exhaust pulsation arrives near the exhaust valve is “positive valve overlap” (PVOh). ) Will be delayed until near.

  For this reason, the so-called scavenging effect that the high-temperature combustion gas in the cylinder is sucked out by the negative pressure wave through the open exhaust valve, and cool fresh air is introduced into the cylinder through the open intake valve. can get. As a result, not only the intake charging efficiency in the full load state is increased, but also the inside of the cylinder is cooled by fresh air, so that the so-called knocking resistance is improved, and the absolute value of the engine torque can be increased by the effect of both. It becomes like this.

  Furthermore, since the section center of “positive valve overlap” (PVOh) is advanced from exhaust top dead center (TDC), the negative pressure wave of exhaust pulsation is synchronized with “positive valve overlap” (PVOh). The scavenging effect can be increased. That is, the timing at which the negative pressure wave of the exhaust pulsation arrives in the vicinity of the exhaust valve can be brought closer to the center of the section of “positive valve overlap” (PVOh).

  In the present embodiment, the air-fuel mixture burned in the cylinder of the internal combustion engine may be a lean air-fuel mixture in the partial load state after cold or warm-up. In this case, since the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, there are advantages such as less generation of harmful exhaust components from the engine body and further improvement in fuel efficiency, but there is a problem in combustion stability. However, in the present embodiment, the stability of combustion can be improved by the effect of the NVO described above, so that the advantage of using the lean air-fuel mixture can be fully exhibited.

  Next, a change in valve overlap and a change in the opening of the throttle valve when the operating condition (state) is changed will be described with reference to FIG.

  As described above, in the cold operation state (first idle after the cold start, etc.), a moderate “negative valve overlap” (NVOc) can stabilize the combustion and improve the warm-up performance during the cold operation. Improve fuel efficiency and reduce harmful components of exhaust gas through improvements. At this time, since the frictional resistance of the mechanical system of the internal combustion engine is large during cold operation, the opening degree θc of the throttle valve is increased to increase the engine torque in order to overcome this frictional resistance.

  In idle after warm-up, the valve timing during cold operation is maintained. That is, for example, the “negative valve overlap” (NVOi) of the idle after warm-up is matched with the “negative valve overlap” (NVOc) during the cold operation. Here, since the frictional resistance of the mechanical system of the internal combustion engine is small after warming up, the throttle valve opening is closed to a small opening θi in order to reduce the combustion torque.

  As a result, a large intake negative pressure is generated and the pump loss is increased. However, since the engine is idle after warm-up, combustion fluctuation and rotation fluctuation due to a small intake air amount (small combustion torque) are caused by this negative pressure. As a result of the fuel atomization improving effect, it is possible to improve the idling combustion stability, rotational stability, fuel efficiency, and the like.

  Here, if it is a normal “positive valve overlap” (PVO), the intake negative pressure increased by reducing the opening of the throttle valve causes the internal EGR in the cylinder to pass through the open intake valve. The exhaust gas is sucked into the intake system, and further, the intake negative pressure is re-inhaled into the cylinder from the exhaust port side through the exhaust valve opened in the positive valve overlap (PVO) section. End up. Then, the internal EGR sucked into the intake system is reintroduced into the cylinder in the next intake stroke, and the internal EGR introduced into the cylinder from the exhaust port side as described above is also added, and finally the cylinder EGR is added. There is a problem that the internal EGR introduced into the inside becomes excessive and the combustion stability deteriorates.

  On the other hand, in this embodiment, since it is “negative valve overlap” (NVOi), the intake valve and the exhaust valve are not opened at the same time, and both the intake valve and the exhaust valve are opened near the exhaust top dead center. Even in the idle after warm-up when the intake negative pressure has increased, excessive internal EGR is not introduced into the cylinder as in the case of PVO described above, so that a stable and good combustion state can be realized. Become.

  Therefore, for example, as shown in “Negative valve overlap” (NVOi ′) in FIG. 5, the valve overlap need not be set to “0”. It is possible to suppress the range of change from “lap” (NVOp) to “negative valve overlap” (NVOi) in the idle state after warm-up. As a result, it is possible to avoid the problem of delay in conversion response between the intake VTC 24 and the exhaust VTC 14 in an operating state in which the engine operating conditions cross both regions.

  In addition, in a partial load state after warm-up, in addition to being able to stabilize combustion with a high-temperature mixed gas with a large “negative valve overlap” (NVOp), fuel efficiency is improved by implementing the Atkinson cycle, reducing pump loss, etc. improves. In this case, a large “negative valve overlap” (NVOp) or an Atkinson cycle (slow closing of the intake valve) can reduce the charging efficiency (torque) without reducing the opening of the throttle valve. The degree is a large opening θp.

  Further, in the full load state after warming up, the engine torque in the full load state after warming up can be sufficiently increased. That is, since the opening timing (EVOh) of the exhaust valve is retarded to the vicinity of the expansion bottom dead center (BDC), the timing when the negative pressure wave of the exhaust pulsation arrives near the exhaust valve is “positive valve overlap” (PVOh). ) Therefore, the high-temperature combustion gas in the cylinder is sucked out by the negative pressure wave through the open exhaust valve, and cool fresh air is introduced into the cylinder through the open intake valve. As a result, the intake charge efficiency in the full load state is increased, and further, the inside of the cylinder is cooled by fresh air, so that the anti-knocking performance is also improved, and the absolute value of the engine torque can be sufficiently increased by the effects of both. Become.

  Next, a control flow for executing the valve timing characteristics according to the present embodiment described above will be described. This control flow is executed by the control device 30. FIG. 6 shows a control flow for mechanically stabilizing the exhaust VTC 14 and the intake VTC 24 at a default position where “negative valve overlap (NVOc)” occurs when the internal combustion engine is stopped.

<< Step S10 >>
First, in step S10, engine stop information for stopping the internal combustion engine and operating condition information for the internal combustion engine are read. As the engine stop information for stopping the internal combustion engine, there is typically a key-off signal, and there are many signals indicating the operating condition information of the internal combustion engine. In this embodiment, the engine speed information, the intake air There are quantity information, water temperature information, required load information (accelerator opening), and the like, and further, actual position information of the exhaust VTC 14 and the intake VTC 24, and the like. If various information is read in this step S10, it will transfer to step S11.

<< Step S11 >>
In step S11, it is determined whether the engine stop transition condition is satisfied. For this determination, for example, the key-off signal may be monitored, and if the key-off signal is not input, the process returns to return and waits for the next activation timing. On the other hand, when the key-off signal is input, the engine stop transition condition is determined and the process proceeds to step S12.

<< Step S12 >>
In step S12, the conversion control signal is output to the exhaust electromagnetic switching valve 31 of the exhaust VTC 14 and the intake electromagnetic switching valve 32 of the intake VTC 24 so that the exhaust VTC 14 and the intake VTC 24 are shifted to the default positions. That is, in order to respond to the next start, the hydraulic pressure is controlled so that the valve timing characteristics of “(A) cold start state” of FIG. 3 are obtained.

  Therefore, the exhaust valve closing timing (EVC) is set to the exhaust valve closing timing (EVCc = Emid: refer to FIG. 2) in “(A) Cold machine start state” in FIG. 3, and the intake valve opening timing (IVO) ) Is set at the opening timing of the intake valve (IVOc = Imid: see also FIG. 2). This sets a “negative valve overlap” (NVOc). When the conversion control signal is output to the exhaust electromagnetic switching valve 31 of the exhaust VTC 14 and the intake electromagnetic switching valve 32 of the intake VTC 24, the process proceeds to step S13.

<< Step S13 >>
In step 13, from the actual position information of the exhaust VTC 14 and the intake VTC 24, the exhaust VTC 14 and the intake VTC 24 are set to the default positions, that is, the exhaust valve closing timing (EVCc) is set, and the intake valve opening timing is set. It is determined whether or not (IVOc) is set. If it is determined that the exhaust valve closing timing (EVCc) and the intake valve opening timing (IVOc) are not set, the process returns to step S12 again, and the exhaust valve closing timing (EVCc) If it is determined that the opening time (IVOc) is set, the process proceeds to step S14.

<< Step S14 >>
In step S14, the output control signal to the fuel injection valve and the ignition device is stopped to stop the internal combustion engine. As a result, the rotational speed Ne of the internal combustion engine decreases, and the hydraulic pressure of the hydraulic oil of the hydraulic pump decreases accordingly. When the internal combustion engine is stopped, the exhaust VTC 14 and the intake VTC 24 execute the following operations based on the mechanism. This operation is not a control step in the flowchart, but will be described as a control step for convenience.

<< Step S15 to Step S17 >>
As the rotational speed Ne of the internal combustion engine decreases, the discharge pressure of the hydraulic oil from the hydraulic pump also decreases, so that the fastening pins 45 (see FIG. 2) held in the vanes of the exhaust VTC 14 and the intake VTC 24 are returned. It moves toward the rear cover by the spring. On the other hand, the advance chamber and the retard chamber of the exhaust VTC 14 and the intake VTC 24 are filled with hydraulic oil, and the vane position is maintained as it is even when the rotational speed Ne is decreased.

  The fastening pin is further moved toward the rear cover by the return spring and fastened to the fastening hole, so that the vane is fixed to the housing, the exhaust valve closing timing (EVCc), and the intake valve opening timing (IVOc). ) Is finally determined to the default position. Here, the tip of the fastening pin is formed in a taper shape, and the fastening pin can be engaged with the fastening hole even if the vane is slightly out of phase. The internal combustion engine stops at the engine speed Ne = 0.

  In this way, at the time of the stop transition to stop the internal combustion engine, the exhaust VTC 14 and the intake VTC 24 are expressed as “the negative valve overlap (NVOc) is obtained, the exhaust valve closing timing (EVCc) and the intake valve opening timing (IVOc). ) Can be mechanically stabilized at the default position.

  Next, a control flow for resuming the operation of the internal combustion engine from this state will be described with reference to FIG. This control flow is also executed by the control device 30.

<< Step S20 >>
First, in step S20, engine start information for starting the internal combustion engine and operating condition information for the internal combustion engine are read. The engine start information for starting the internal combustion engine is typically a key-on signal or a starter activation signal, and there are many signals indicating the operating condition information of the internal combustion engine. There are rotational speed information, intake air amount information, water temperature information, required load information (accelerator opening), and the like, and further, actual position information of the exhaust VTC 14 and the intake VTC 24, and the like. If various information is read in this step S20, it will transfer to step S21.

<< Step S21 >>
In step S21, it is determined whether the engine start condition is satisfied. For this determination, for example, the starter activation signal may be monitored. If the starter activation signal is not input, the process returns to return and waits for the next activation timing. On the other hand, when the starter activation signal is input, the engine start condition is determined and the process proceeds to step S22.

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

<< Step S23 >>
In step S23, the conversion control signal is output to the exhaust electromagnetic switching valve 31 of the exhaust VTC 14 and the intake electromagnetic switching valve 32 of the intake VTC 24 so that the exhaust VTC 14 and the intake VTC 24 are shifted to the default positions. This is because the vanes of the exhaust VTC 14 and the intake VTC 24 are maintained at the default positions even when the fastening pin is pulled out of the fastening hole for some reason and the fastening state is released when the hydraulic pressure of the hydraulic pump hydraulic oil rises. Control. When the conversion control signal is output to the exhaust electromagnetic switching valve 31 of the exhaust VTC 14 and the intake electromagnetic switching valve 32 of the intake VTC 24, the process proceeds to step S24.

<< Step S24 >>
In step 24, from the actual position information of the exhaust VTC 14 and the intake VTC 24, the exhaust VTC 14 and the intake VTC 24 are set to the default positions, that is, the exhaust valve closing timing (EVCc) is set, and the intake valve opening timing is set. It is determined whether or not (IVOc) is set. If it is determined that the exhaust valve closing timing (EVCc) and the intake valve opening timing (IVOc) are not set, the process returns to step S23 again, and the exhaust valve closing timing (EVCc) and the intake valve opening timing are set. If it is determined that the opening time (IVOc) is set, 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 in order to start the internal combustion engine in accordance with the rotation of the starter motor. As a result, the rotational speed Ne of the internal combustion engine increases, and the hydraulic pressure of the hydraulic oil of the hydraulic pump increases accordingly. 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 a predetermined temperature T0 has been exceeded. If the temperature does not exceed the predetermined temperature T0, it is determined that the engine is in a cold state, and the process returns to return and waits for the next start timing. This state is a cold start state. Therefore, the "negative valve overlap" (NVOc) is set by the exhaust valve closing timing (EVCc) and the intake valve opening timing (IVOc) in "(A) cold start state" in FIG. Will be.

  On the other hand, if the temperature exceeds the predetermined temperature T0, it is determined that the warm-up has been completed from the cold state, and the exhaust VTC 14 and the intake VTC 24 are controlled based on the control map according to the respective operation conditions. Therefore, if the warm-up is completed exceeding the predetermined temperature T0, the process proceeds to step S27.

<< Step S27, Step S28 >>
In step S27, it is determined whether the idle condition is satisfied from the opening of the throttle valve or the opening of the accelerator pedal. When the idle condition is determined, the process proceeds to step S28, and the exhaust VTC 14 and the intake VTC 24 cause the exhaust valve closing timing (EVCi) during idling and the intake valve opening timing (IVOi) to indicate "negative""ValveOverlap" (NVOi). On the other hand, if it is determined that the engine is not in the idle state, the process proceeds to step S29.

<< Step S29 to Step S30 >>
In step S29, it is determined whether the partial load condition is satisfied from the opening of the throttle valve or the opening of the accelerator pedal. If the partial load condition is determined, the process proceeds to step S30, where the exhaust VTC 14 and the intake VTC 24 cause the partial load depending on the exhaust valve closing timing (EVCp) at the partial load and the intake valve opening timing (IVOp). It controls to “negative valve overlap” (NVOp). The valve timing characteristic at this partial load is the valve timing shown in “(B) Partial load state after warm-up” in FIG. On the other hand, when it is determined that the partial load state is not established, the process proceeds to step S31.

<< Step S31 to Step S32 >>
In step S31, it is determined whether the full load condition is satisfied from the opening of the throttle valve or the opening of the accelerator pedal. When the full load condition is determined, the process proceeds to step S32, where the exhaust VTC 14 and the intake VTC 24 cause the exhaust valve closing timing (EVCh) at the full load and the intake valve opening timing (IVOh) to reach the full load. The time is controlled to “positive valve overlap” (PVOh). The valve timing characteristic at this full load is the valve timing shown in “(C) Full load state after warm-up” in FIG. On the other hand, if it is determined that the load is not fully loaded, the process returns to return and waits for the next activation timing.

  In this way, in the present embodiment, it is possible to obtain valve timing characteristics that can manage the combustion state in a stable state over a wide operation range, suppress the generation of harmful exhaust components, and improve the fuel efficiency. become able to.

  Next, a second embodiment of the present invention will be described with reference to FIG. In the first embodiment, the exhaust VTC 14 and the intake VTC 24 in which the operating angles of the exhaust valve and the intake valve are constant and the valve lift is unchanged are used. On the other hand, the second embodiment is different in that a variable valve lift valve mechanism that can continuously adjust the operating angle and the opening / closing timing is used on both the exhaust side and the intake side. .

  In this embodiment, the opening timing of each valve using an exhaust valve lift variable valve mechanism (hereinafter referred to as exhaust VEL) and an intake valve lift variable valve mechanism (hereinafter referred to as intake VEL). It adjusts the closing timing and the operating angle.

  In the cold start state, the operating angle is reduced by the intake air VEL, and the valve timing characteristic as shown in “(A) cold start state” in FIG. 8 is set. As can be seen by comparison as “(A) cold start state” in FIG. 3 of the first embodiment, the closing timing (IVC) of the intake valve advances to near the bottom dead center as the closing timing (IVCc ′). It is horned. As a result, the effective compression ratio is increased as compared with the first embodiment, so that the combustion state is improved and the exhaust harmful components in the exhaust gas can be further reduced.

  Further, in the partial load state after warm-up, the operating angle is expanded by the intake air VEL, and the valve timing characteristics such as “(B) partial load state after warm-up” in FIG. 8 are set. As can be seen from comparison with “(B) partial load state after warming-up” in FIG. 3 of the first embodiment, the closing timing (IVC) of the intake valve is dead as the closing timing (IVCp ′). It is retarded to the point side. As a result, the effect of the Atkinson cycle is enhanced as compared with the first embodiment, so that the fuel efficiency can be further improved.

  Further, in the full load state after warming up, the operating angle is reduced by the exhaust VEL, and the valve timing characteristics such as “(C) full load state after warming up” in FIG. 8 are set. As can be seen from comparison with “(C) full load state after warm-up” in FIG. 3 of the first embodiment, the exhaust valve closing timing (EVC) is dead as the closing timing (EVCh ′). It has been advanced to the point side. Compared with the first embodiment, this is a form in which a part on the retarded side in the “positive overlap” (PVO) is removed. In this vicinity, the exhaust pulsation starts to return from negative pressure to positive pressure, and if this part is removed, the reduction of the scavenging effect due to this return positive pressure can be suppressed, and the scavenging effect can be further enhanced. There is.

  As described above, the effects of the present invention can be further enhanced by adopting the exhaust VEL and the intake VEL.

  In the second embodiment described above, the variable valve lift valve mechanism capable of continuously adjusting the operating angle and the opening / closing timing is used on both the exhaust side and the intake side. It is also possible to use a variable valve mechanism and the other variable phase valve mechanism (the above-mentioned VTC) in which the operating angle is constant and the valve lift is unchanged.

  Furthermore, although a hydraulically driven phase variable mechanism (suction / exhaust VTC) has been shown as a form of the variable valve mechanism, it can be used not only with hydraulic drive but also with an electrically driven phase variable mechanism. Moreover, although the example of the intake / exhaust VEL in which the operating angle and the opening / closing timing are continuously changed is shown as the form of the variable valve mechanism, an intake / exhaust VVL that adjusts the operating angle stepwise should be used. Can do. In short, the specific form of the variable valve mechanism is not limited as long as the gist of the present invention is satisfied.

  As described above, according to the present invention, at the time of cold start of the internal combustion engine, the intake valve opening timing (IVOc) is advanced from the most retarded angle opening timing (IVOrtd) by the intake valve variable valve mechanism. Between the most advanced angle opening timing (IVOaddv) and the retarded angle side, a predetermined angle (ITc) is set to the retarded angle side from the exhaust top dead center (TDC), and the exhaust valve is closed by the exhaust valve variable valve mechanism. The timing (EVCc) is retarded from the most advanced angle closing timing (EVCadv), and more advanced than the most retarded timing (EVCrtd), and a predetermined angle (ETc) from the exhaust top dead center (TDC). Only the advance side is set to form a “negative valve overlap” (NVOc) in which the intake valve opening timing (IVOc) and the exhaust valve closing timing (EVCc) do not overlap.

  According to this, at the time of cold start of the internal combustion engine, a “negative valve overlap” (NVOc) is formed from the end of the exhaust stroke to the initial stage of the intake stroke, whereby high temperature combustion gas (high temperature EGR gas) is generated in the cylinder. The remaining in-cylinder gas and the engine main body are heated by pressurizing with a piston and suppressing deterioration of combustion at the time of cold start, and exhaust harmful components in the exhaust gas can be reduced. It becomes like this.

  In addition, this invention is not limited to above-described embodiment, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. Moreover, it is possible to add / delete / replace other configurations for a part of the configurations of the embodiments.

  DESCRIPTION OF SYMBOLS 10 ... Exhaust cam shaft, 11 ... Exhaust cam, 12 ... Exhaust valve, 13 ... Sprocket mechanism, 14 ... Exhaust valve variable valve mechanism (exhaust VTC), 15 ... Timing sprocket, 16 (35) ... Housing, 17 ... Front cover , 18 ... rear cover, 20 ... intake camshaft, 21 ... intake cam, 22 ... intake valve, 23 ... sprocket mechanism, 24 ... intake valve variable valve mechanism (intake VTC), 25 ... timing sprocket, 26 ... housing, 27 ... Front cover, 28 ... rear cover, 30 ... control device, 31 ... exhaust electromagnetic switching valve, 32 ... intake electromagnetic switching valve, IVOc ... opening timing of intake valve at cold start, EVCc ... exhaust valve closing at cold start Timing, IVOadv: Most advanced timing of intake valve, IVOrtd: Most retarded timing of intake valve, EVCadv: Exhaust valve Time the most advanced, EVCrtd ... the most retarded timing of the exhaust valve.

Claims (13)

At least an intake valve variable valve mechanism for adjusting the opening / closing timing of the intake valve, an exhaust valve variable valve mechanism for adjusting an opening / closing timing of the exhaust valve, the intake valve variable valve mechanism, and the exhaust valve variable valve mechanism A variable valve system for an internal combustion engine comprising a valve control system comprising control means for controlling
The valve control system is used at the time of cold start of the internal combustion engine.
By the intake valve variable valve mechanism, the opening timing (IVO) of the intake valve is advanced from the most retarded angle opening timing (IVOrtd), and between the most retarded angle opening timing (IVOaddv), Set the intake valve opening timing (IVOc) on the retard side by a predetermined angle (ITc) from the exhaust top dead center (TDC),
By the exhaust valve variable valve mechanism, the exhaust valve closing timing (EVC) is set to be retarded from the most advanced timing closing timing (EVCadv) and from the most retarded timing (EVCrtd) to the advanced timing side. Set the exhaust valve closing timing (EVCc) on the advance side by a predetermined angle (ETc) from the top dead center (TDC),
A variable valve system for an internal combustion engine, characterized in that a "negative valve overlap" (NVOc) is formed in which an opening timing (IVOc) of the intake valve and a closing timing (EVCc) of the exhaust valve do not overlap. The variable valve system for an internal combustion engine according to claim 1,
The variable valve operating system for an internal combustion engine, wherein the predetermined angle (ITc) and the predetermined angle (ETc) are substantially the same angle. In the variable valve system of the internal combustion engine according to claim 1,
At the time of partial load after warm-up of the internal combustion engine, the valve control system is
By the intake valve variable valve mechanism, the opening timing (IVO) of the intake valve is retarded from the closing timing (IVOc) of the intake valve by a predetermined angle (ITp) from the exhaust top dead center. The intake valve closing timing (IVOp) is set to the angle side intake valve opening timing (IVOp), and the intake valve closing timing (IVC) is set to close the intake valve close to the middle position between the intake bottom dead center (BDC) and compression top dead center (TDC). Set the time (IVCp)
By the exhaust valve variable valve mechanism, the exhaust valve closing timing (EVC) is advanced from the exhaust valve closing timing (EVCc) and at a predetermined angle (ETp) from the exhaust top dead center (TDC). ) Is set to the advance timing (EVCp) of the exhaust valve on the advance side. The variable valve system for an internal combustion engine according to claim 3,
The variable valve operating system for an internal combustion engine, wherein the predetermined angle (ITp) and the predetermined angle (ETp) are substantially the same angle. In the variable valve system of the internal combustion engine according to claim 1,
The valve control system is at full load after warming up the internal combustion engine.
The intake valve opening timing (IVO) is set to an intake valve opening timing (IVOh) that is more advanced than the intake valve opening timing (IVOp) by the intake valve variable valve mechanism.
By the exhaust valve variable valve mechanism, the exhaust valve closing timing (EVC) is set to the exhaust valve closing timing (EVCh) retarded from the exhaust valve closing timing (EVCp). Set the opening time (EVO) to the opening time (EVOh) of the exhaust valve near the expansion bottom dead center (BDC),
A variable valve operating system for an internal combustion engine, characterized in that a "positive valve overlap" (PVOh) is formed in which an opening timing (IVOh) of the intake valve and a closing timing (EVCh) of the exhaust valve overlap. The variable valve system for an internal combustion engine according to claim 5,
The variable valve operating system for an internal combustion engine, characterized in that a center of a period of the "positive valve overlap" (PVOh) is set to an advance side from the exhaust top dead center (TDC). In the variable valve system of the internal combustion engine according to claim 1,
The intake valve variable valve mechanism includes a mechanism for determining an intake side mechanical stable position, and an opening timing (IVOc) of the intake valve is determined by the intake side mechanical stable position.
The exhaust valve variable valve mechanism includes a mechanism for determining an exhaust side mechanical stable position, and the closing timing (EVCc) of the exhaust valve is determined by the exhaust side mechanical stable position. Variable valve system. In the variable valve system of the internal combustion engine according to claim 1,
The intake valve variable valve mechanism and the exhaust valve variable valve mechanism are phase variable type variable valve mechanisms in which the opening / closing timing changes with a constant operating angle. Valve system. In the variable valve system of the internal combustion engine according to claim 1,
At least one of the intake valve variable valve mechanism and the exhaust valve variable valve mechanism is a phase variable variable valve mechanism in which the opening / closing timing changes while the operating angle is constant, and the other is the operating angle A variable valve operating system for an internal combustion engine, characterized in that it is a variable valve lift variable valve operating mechanism in which both the opening and closing timings change. The variable valve system for an internal combustion engine according to claim 1,
The variable valve operating system for an internal combustion engine, wherein the air-fuel mixture supplied to the internal combustion engine is a lean air-fuel mixture. A control device for a variable valve mechanism comprising at least an intake valve variable valve mechanism for adjusting the opening / closing timing of the intake valve, and a control means for controlling the exhaust valve variable valve mechanism for adjusting the opening / closing timing of the exhaust valve. ,
The control means, at the time of cold start of the internal combustion engine,
The intake valve opening timing (IVO) is advanced from the most retarded opening timing (IVOrtd) and more retarded from the most advanced opening timing (IVOaddv) than the exhaust top dead center (TDC). A first function of controlling the intake valve variable valve mechanism so as to set the intake valve opening timing (IVOc) on the retard side by a predetermined angle (ITc);
The exhaust valve closing timing (EVC) is set to be more retarded than the most advanced angle closing timing (EVCadv) and more advanced than the most retarded timing (EVCrtd) than the exhaust top dead center (TDC). A second function of controlling the exhaust valve variable valve mechanism so as to set the exhaust valve closing timing (EVCc) on the advance side by an angle (ETc);
By executing the first function and the second function, the negative valve overlap (NVOc) in which the opening timing (IVOc) of the intake valve and the closing timing (EVCc) of the exhaust valve do not overlap each other. A control apparatus for a variable valve mechanism, characterized in that The control device for a variable valve mechanism according to claim 11,
At the time of partial load after warming up the internal combustion engine, the control means
The intake valve opening timing (IVO) is retarded from the intake valve closing timing (IVOc), and the intake valve opening timing (ITp) is retarded by a predetermined angle (ITp) from the exhaust top dead center. IVOp), and the intake valve closing timing (IVC) is set to the intake valve closing timing (IVCp) near the intermediate position between the intake bottom dead center (BDC) point and the compression top dead center (TDC). A third function for controlling the intake valve variable valve mechanism;
The exhaust valve closing timing (EVC) is advanced from the exhaust valve closing timing (EVCc), and the exhaust valve is closed by a predetermined angle (ETp) from the exhaust top dead center (TDC). Having a fourth function of controlling the exhaust valve variable valve mechanism so as to set the closing timing (EVCp);
A control device for a variable valve mechanism. The control device for a variable valve mechanism according to claim 11,
At the time of full load after warming up the internal combustion engine, the control means
A fifth control valve that controls the intake valve variable valve mechanism so that the intake valve opening timing (IVO) is set to the opening timing (IVOh) of the intake valve that is more advanced than the intake valve opening timing (IVOp); Functions and
The exhaust valve closing timing (EVC) is set to the exhaust valve closing timing (EVCh) retarded from the exhaust valve closing timing (EVCp), and the exhaust valve opening timing (EVO) A sixth function of controlling the exhaust valve variable valve mechanism so as to set the exhaust valve opening timing (EVOh) near the dead point (BDC);
By executing the fifth function and the sixth function, a “positive valve overlap” (PVOh) in which the opening timing (IVOh) of the intake valve and the closing timing (EVCh) of the exhaust valve overlap is overlapped. A control device for a variable valve mechanism characterized by forming.

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