WO2018211853A1 - Internal combustion engine variable operation system and control device therefor - Google Patents

Abstract

The present invention comprises: a variable compression ratio mechanism 3 that controls a mechanical compression ratio; and an intake variable valve mechanism 1A that controls the phase during opening/closing of an intake valve. During a cold start, the variable compression ratio mechanism 3 sets a piston position to a position at which a mechanical expansion ratio reaches substantially a minimum, and the intake variable valve mechanism 1A sets the closing timing of the intake valve 4 to near bottom dead center (BDC) and sets the opening timing (IVO) of the intake valve 4 to a position on an advance angle side beyond top dead center (TDC). Due to these configurations, the temperature of exhaust gas during a cold start of the internal combustion engine can be increased so as to promote the progress of warming-up of an exhaust gas purification catalyst.

Description

Variable operation system for internal combustion engine and control device therefor

The present invention relates to a variable operation system for an internal combustion engine, and in particular, includes a variable compression ratio mechanism for controlling a mechanical compression ratio (including an expansion ratio) in a four-cycle internal combustion engine, and a variable valve mechanism for controlling valve timing. The present invention relates to a variable operation system for an internal combustion engine and a control device therefor.

In a recent internal combustion engine, a geometric compression ratio and an expansion ratio of the internal combustion engine, that is, a variable compression ratio mechanism that variably controls the mechanical compression ratio and the mechanical expansion ratio, an intake valve and an exhaust that influence the actual compression ratio. It has been proposed to improve the operating performance of an internal combustion engine by combining with a variable valve mechanism that variably controls the valve timing (opening / closing timing) of the valve. Here, as the variable compression ratio mechanism, for example, one described in JP-A-2002-276446 (Patent Document 1) is known.

Further, in “CO2-potentialａof a two-stage VCR system in combination with future gasolinetrpowertrains" (Non-Patent Document 1), the mechanical compression ratio map is shown in Figs. The mechanical compression ratio increases as the load increases. This is because the problem of knocking is reduced as the load decreases, so that the mechanical compression ratio can be increased, and the mechanical expansion ratio (= mechanical compression ratio) can be increased accordingly, resulting in an internal combustion engine. The thermal efficiency of can be increased. For this reason, it is presumed that the mechanical compression ratio is close to the maximum mechanical compression ratio (= maximum mechanical expansion ratio) even at the start. Increasing the mechanical compression ratio at the time of starting increases the temperature at the compression top dead center, improving the combustion at the time of starting and leading to good startability.

JP 2002-276446 A

By the way, since the mechanical compression ratio is set to the maximum mechanical compression ratio in Non-Patent Document 1 at the time of cold start for starting the internal combustion engine, the exhaust gas discharged from the internal combustion engine is maximized. A phenomenon occurs in which the temperature decreases. For this reason, it is difficult to warm up the exhaust gas purification catalyst provided in the middle of the exhaust pipe, and the conversion rate of exhaust harmful components in the exhaust gas purification catalyst becomes low. As a result, there is a problem that the exhaust amount of exhaust harmful components in the exhaust gas discharged from the tail pipe after passing through the exhaust gas purifying catalyst increases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel variable internal combustion engine system and its control device that can increase the temperature of exhaust gas at the time of cold start of the internal combustion engine to promote the warm-up of the exhaust gas purification catalyst. Is to provide.

The features of the present invention include at least a variable compression ratio mechanism that controls a mechanical compression ratio and a mechanical expansion ratio in a four-cycle internal combustion engine, and an intake side variable valve mechanism that controls the phase of the opening and closing timing of the intake valve, At the time of cold start, the variable compression ratio mechanism sets the piston position to a position where the mechanical expansion ratio becomes substantially minimum, and the intake side variable valve mechanism closes the intake valve as compared with the low load after warm-up. The timing is set near the bottom dead center, and the opening timing of the intake valve is set at a position on the advance side before the top dead center.

According to the present invention, the temperature of the exhaust gas can be increased by reducing the mechanical expansion ratio at the time of cold start, and the exhaust gas purification catalyst can be warmed up early to improve the conversion efficiency of exhaust harmful components. The amount of exhaust harmful components in the exhaust gas can be reduced.

In addition to this, since the closing timing of the intake valve is close to bottom dead center, the effective compression ratio can be increased, and the combustion improvement effect can be enhanced. As a result, it is possible to reduce the amount of exhaust harmful components themselves from the engine body, improve the conversion rate of exhaust harmful components in the exhaust gas purification catalyst described above, and further reduce the exhaust harmful emissions in the exhaust gas discharged from the tailpipe. Components can be reduced.

1 is an overall schematic diagram of a variable operation system for an internal combustion engine according to the present invention. It is a block diagram which shows the structure of the variable compression ratio mechanism used for this invention, and shows the state currently controlled by the minimum mechanical compression ratio (minimum mechanical expansion ratio). It is a block diagram which shows the structure of the variable compression ratio mechanism used for this invention, and shows the state currently controlled by the maximum mechanical compression ratio (maximum mechanical expansion ratio). It is explanatory drawing explaining the control characteristic of the intake valve and exhaust valve of the variable operation system which becomes the 1st Embodiment of this invention. FIG. 3B is a lift characteristic diagram illustrating control characteristics of the intake valve and the exhaust valve shown in FIG. 3A with lift characteristic lines. It is a characteristic view explaining the control characteristic of the main parameters of the variable operation system of the internal combustion engine according to the first embodiment of the present invention. 3 is a control flowchart for executing control at the time of engine stop transition of the variable operation system for the internal combustion engine according to the first embodiment of the present invention. It is a control flowchart which performs control from the time of starting of the variable operation system of the internal combustion engine which becomes a 1st embodiment of the present invention. It is explanatory drawing which shows an example of the control value of the piston position by the variable compression ratio mechanism used for the 2nd Embodiment of this invention. It is a characteristic view explaining the control characteristic of the main parameter of the variable operation system of the internal combustion engine which becomes the 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 also included in the range.

The variable operation system for an internal combustion engine according to the first embodiment of the present invention will be described. FIG. 1 shows the overall configuration of the variable operation system for an internal combustion engine to which the present invention is applied.

First, a basic configuration of a variable operation system of an internal combustion engine will be described with reference to FIG. 1. A piston 01 provided inside a cylinder bore formed in a cylinder block SB so as to be slidable up and down by combustion pressure or the like, and a cylinder head An intake port IP and an exhaust port EP formed inside SH, respectively, and a pair of intake valves 4 per cylinder which are slidably provided on the cylinder head SH and open and close the open ends of the intake and exhaust ports IP and EP. And an exhaust valve 5.

The piston 01 is connected to the crankshaft 02 via a connecting rod 03 composed of a lower link 42 and an upper link 43 described later, and a combustion chamber 04 is formed between the crown surface and the lower surface of the cylinder head SH. Yes. In addition, a spark plug 05 is provided substantially at the center of the cylinder head SH.

The intake port IP is connected to an air cleaner (not shown), and intake air is supplied via the electric throttle valve 72. The electric throttle valve 72 is controlled by the controller 22 and basically its opening degree is controlled in accordance with the amount of depression of the accelerator pedal. The exhaust port EP discharges exhaust gas from the tail pipe to the atmosphere via the exhaust gas purification catalyst 74.

Further, in this internal combustion engine, as shown in FIG. 1, an intake side variable valve mechanism that controls the valve opening characteristics of the intake valve 4 and the exhaust valve 5, an exhaust side variable valve mechanism, and a variable that controls the piston position characteristics. And a compression ratio mechanism.

An intake side variable valve mechanism (hereinafter referred to as an intake side VTC mechanism) 1A, which is a “phase angle variable mechanism” for controlling the center phase angle of the valve lift of the intake valve 4, is provided on the intake side. On the exhaust side, there is provided an exhaust side variable valve mechanism (hereinafter referred to as an exhaust side VTC mechanism) 1B which is a “phase angle variable mechanism” that controls the central phase angle of the valve lift of the exhaust valve 5. Further, a variable compression ratio mechanism (hereinafter referred to as a VCR mechanism) 3 that is a “piston stroke variable mechanism” for controlling the mechanical compression ratio εC and the mechanical expansion ratio εE in the cylinder is provided. In the VCR mechanism 3, the mechanical compression ratio εC and the mechanical expansion ratio εE are both set to the same value.

The intake-side VTC mechanism 1A and the exhaust-side VTC mechanism 1B are equipped with phase control hydraulic actuators 2A and 2B, and are configured to control the opening / 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 2 </ b> A and 2 </ b> B is controlled by a hydraulic control unit (not shown) based on a control signal from the controller 22. The center phase θ of the lift characteristic is controlled to the retard side or the advance side by the hydraulic control to the phase control hydraulic actuators 2A and 2B.

That is, the whole curve of the lift characteristic itself is not changed, and the whole is moved to the advance side or the retard side. Moreover, this movement change can also be obtained continuously. The intake-side VTC mechanism 1A and the exhaust-side VTC mechanism 1B are not limited to hydraulic types, and various configurations such as those using an electric motor or an electromagnetic actuator are possible.

In the intake-side VTC mechanism 1A, both when there is a hydraulic supply from the hydraulic pump and when there is no hydraulic supply, the intake side VTC mechanism 1A is mechanically moved by a biasing spring or the like near the “most advanced position” that is the default position. It is controlled. Therefore, even when there is a disconnection failure or the like in the electrical system, the mechanical fail-safe effect is provided. Therefore, as will be described later, when the internal combustion engine is stopped, the intake valve is set near the “most advanced angle position”.

Similarly, in the exhaust-side VTC mechanism 1B, both when there is hydraulic supply from the hydraulic pump and when there is no hydraulic supply, a mechanical force is applied near the “most retarded position” that is the default position by an urging spring or the like. It is controlled by. Therefore, even when there is a disconnection failure or the like in the electrical system, the mechanical fail-safe effect is provided. Therefore, as will be described later, when the internal combustion engine is stopped, the exhaust valve is set near the “most retarded position”.

Since the intake side VTC mechanism 1A and the exhaust side VTC mechanism 1B are described in detail in Japanese Patent Application Laid-Open No. 2011-220349 filed by the present applicant, further explanation is omitted here. .

A controller (= control means) 22 outputs an output signal from a crank angle sensor that detects the current rotational speed Ne (rpm) of the internal combustion engine from a crank angle, an intake air amount (load) from an air flow meter, and the like. The present engine state is detected from various information signals such as an opening sensor, a vehicle speed sensor, a gear position sensor, an engine cooling water temperature sensor 31 that detects the temperature of the engine body, and humidity from the atmospheric humidity sensor. Then, the controller 22 outputs an intake VTC control signal to the intake side VTC mechanism 1A, and outputs an exhaust VTC control signal to the exhaust side VTC mechanism 1B.

Next, the VCR mechanism 3 will be described with reference to FIGS. 1, 2A, and 2B. 2A shows the piston position at the compression top dead center at the minimum mechanical compression ratio, and FIG. 2B shows the piston position at the compression top dead center at the maximum mechanical compression ratio. As for the position of the exhaust top dead center, the piston position at the exhaust top dead center coincides with the piston position at the compression top dead center shown in FIGS. 2A and 2B in both the minimum mechanical compression ratio and the maximum mechanical compression ratio. ing.

Since this VCR mechanism 3 is a mechanism that makes one cycle at a crank angle 360-, in principle, the piston position at the compression top dead center coincides with the piston position at the exhaust top dead center. For the same reason, the piston position at the intake bottom dead center and the piston position at the expansion bottom dead center also coincide. This means that the compression stroke between the piston position at the intake bottom dead center and the piston position at the compression top dead center coincides with the expansion stroke between the piston position at the compression top dead center and the piston position at the expansion bottom dead center. It means to do. Therefore, the mechanical compression ratio εC and the mechanical expansion ratio εE also coincide in principle (εC = εE).

The VCR mechanism 3 has the same configuration as that described in Patent Document 1 described above as the prior art. The crankshaft 02 includes a plurality of journal portions 40 and a crank pin portion 41, and the journal portion 40 is rotatably supported by the main bearing of the cylinder block SB. The crankpin portion 41 is eccentric from the journal portion 40 by a predetermined amount, and a lower link 42 serving as a second link is rotatably connected thereto. The lower link 42 is configured to be split into two left and right members, and the crankpin portion 41 is fitted in a substantially central connecting hole.

The upper link 43 serving as the first link has a lower end side rotatably connected to one end of the lower link 42 by a connecting pin 44, and an upper end side rotatably connected to the piston 01 by a piston pin 45. The control link 46 serving as the third link is pivotally connected at its upper end side to the other end of the lower link 42 by a connecting pin 47, and the lower end side of the lower part of the cylinder block SB that becomes part of the engine body via the control shaft 48. It is connected to the pivotable.

The control shaft 48 is rotatably supported by the engine body, and has an eccentric cam portion 48a that is eccentric from the center of rotation. The lower end portion of the control link 46 is rotatably fitted to the eccentric cam portion 48a. is doing. The rotation position of the control shaft 48 is controlled by a compression ratio control actuator 49 using an electric motor based on a control signal from the controller 22.

In the VCR mechanism 3 using such a multi-link type piston-crank mechanism, when the control shaft 48 is rotated by the compression ratio control actuator 49, the center position of the eccentric cam portion 48a, particularly the relative position with respect to the engine body. Changes. Thereby, the rocking | fluctuation support position of the lower end of the control link 46 changes. When the swing support position of the control link 46 changes, the stroke position and stroke amounts S1, S2 of the piston 01 change, and the position of the piston 01 at the piston top dead center becomes higher as shown in FIGS. 2A and 2B. It becomes lower or lower. Thereby, the mechanical compression ratio (εC) and the mechanical expansion ratio (εE) can be changed.

Supplementally, at the position of the minimum mechanical compression ratio (εCmin) shown in FIG. 2A, the eccentric cam portion 48a faces upward, thereby pushing up the control link 46 and rotating the lower link 42 counterclockwise. Accordingly, the position of the piston 01 is lowered by lowering the upper link 43. On the other hand, at the position of the maximum mechanical compression ratio (εCmax) shown in FIG. 2B, the eccentric cam portion 48a faces to the left side, whereby the control link 46 is relatively lowered and the lower link 42 is rotated clockwise. Thus, the position of the piston 01 is pushed up by pushing up the upper link 43.

This mechanical compression ratio (εC) is a geometric compression ratio determined only by the change in the volume of the combustion chamber due to the stroke of the piston 01, and the cylinder volume at the bottom dead center of the intake stroke of the piston 01 and the compression stroke of the piston 01. It is the ratio of the in-cylinder volume at the top dead center. 2A shows the state of the minimum mechanical compression ratio, and FIG. 2B shows the state of the maximum mechanical compression ratio, respectively, and the compression ratio can be continuously changed between these.

Here, when the cylinder volume at the piston compression top dead center is VO and the stroke volume is V, the cylinder volume at the piston bottom dead center is “VO + V”, so the mechanical compression ratio (εC) is “εC = (VO + V) / VO = V / VO + 1 ”. From this concept, the minimum mechanical compression ratio εCmin (= minimum mechanical expansion ratio εEmin) shown in FIG. 2A is “εCmin = V1 / VO1 + 1” (for example, εCmin = 9), and the maximum mechanical compression ratio εCmax (= The maximum mechanical expansion ratio εEmax is “εCmax = V2 / VO2 + 1” (for example, εCmax = 15).

By the way, as described above in “Problem to be Solved by the Invention”, at the time of cold start of the internal combustion engine, the mechanical compression ratio (εC) is set to the maximum mechanical compression ratio (εCmax) in Non-Patent Document 1. Therefore, the mechanical expansion ratio (εE) also becomes the maximum mechanical expansion ratio (εEmax), and the phenomenon that the temperature of the exhaust gas discharged from the internal combustion engine decreases occurs. For this reason, it is difficult to warm up the exhaust gas purification catalyst provided in the middle of the exhaust pipe, and the conversion rate of exhaust harmful components in the exhaust gas purification catalyst becomes low. As a result, there is a problem that the exhaust amount of exhaust harmful components in the exhaust gas discharged from the tail pipe after passing through the exhaust gas purifying catalyst increases.

In order to solve such a problem, in this embodiment, at the time of cold start, the VCR mechanism 3 sets the piston position to a position where the mechanical expansion ratio is substantially minimum, and the intake variable valve mechanism 1A Compared to the low load after warm-up, the closing timing of the intake valve 4 is set near the bottom dead center, and the opening timing of the intake valve 4 is set to a position on the advance side before the top dead center. It is what we propose.

Next, in the internal combustion engine having the intake side VTC mechanism 1A, the exhaust side VTC mechanism 1B, and the VCR mechanism 3 as described above, the control of the intake side VTC mechanism 1A, the exhaust side VTC mechanism 1B, and the VCR mechanism 3 at the time of cold start. The operation will be described.

FIG. 3A shows the control characteristics of the opening / closing timing of the intake valve 4 and the exhaust valve 5 by the intake side VTC mechanism 1A and the exhaust side VTC mechanism 1B according to this embodiment, and FIG. The lift characteristic line of the control characteristic of the exhaust valve 5 is shown. Hereinafter, referring to FIGS. 3A and 3B, “at the time of cold start”, “at the time of low load after warm-up” including “idle after warm-up”, “at the time of medium load after warm-up”, and “at the time of high load after warm-up” The opening / closing timing of the intake valve 4 and the exhaust valve 5 will be described.

[(A) During cold start] At the cold start, as described above, in the intake side VTC mechanism 1A, the intake valve 4 is controlled in the vicinity of the most advanced angle position which is the default position. Therefore, the opening timing (IVOc) and closing timing (IVCc) of the intake valve 4 are set near the most advanced position.

Similarly, in the exhaust side VTC mechanism 1B, the exhaust valve 5 is controlled in the vicinity of the most retarded angle position which is the default position. Therefore, the opening timing (EVOc) and closing timing (EVCc) of the exhaust valve 5 are set near the most retarded position.

In this state, the valve overlap between the intake valve 4 and the exhaust valve 5 is a positive valve overlap state in which both the intake valve 4 and the exhaust valve 5 are opened, and the phase angle of the positive valve overlap is The positive valve overlap (PVOLc) is set.

[(B) At low load after warming up] When the internal combustion engine is continuously warmed up and warmed up at low load, the intake valve 4 is controlled by the phase control hydraulic actuator 2A of the intake side VTC mechanism 1A. It is controlled to the retard side. Accordingly, the opening timing (IVOi) and closing timing (IVCi) of the intake valve 4 are set to the retarded position by a predetermined angle compared to the most advanced position.

Similarly, the exhaust valve 5 is controlled to the advance side by the phase control hydraulic actuator 2B of the exhaust side VTC mechanism 1B. Therefore, the opening timing (EVOi) and closing timing (EVCi) of the exhaust valve 5 are set to the advance position by a predetermined angle compared to the most retarded position.

In this state, the valve overlap between the intake valve 4 and the exhaust valve 5 is set to “substantially 0”. Here, the valve overlap is not completely “0”, and may include a valve overlap that does not cause a problem in control (positive valve overlap or negative valve overlap described later).

[(C) Medium Load after Warm-up] In the case of medium load after warm-up, when the intake valve 4 is “(B) at low load after warm-up” by the hydraulic actuator 2A for phase control of the intake side VTC mechanism 1A. It is further controlled to the retard side. Therefore, the opening timing (IVOm) and the closing timing (IVCm) of the intake valve 4 are set to a further retarded position by a predetermined angle as compared with “at the time of low load after warm-up”.

Similarly, the exhaust valve 5 is further controlled to be advanced by the phase control hydraulic actuator 2B of the exhaust side VTC mechanism 1B than in the case of “(B) low load after warming up”. Therefore, the opening timing (EVOm) and closing timing (EVCm) of the exhaust valve 5 are set to an advanced position by a predetermined angle as compared with “(B) Low load after warm-up”.

In this state, the valve overlap between the intake valve 4 and the exhaust valve 5 is a negative valve overlap state in which both the intake valve 4 and the exhaust valve 5 are closed, and the phase angle of the negative valve overlap is Negative valve overlap (NVOLm) is set.

[(D) High load after warm-up] When the load is high after warm-up, the intake valve 4 is "(C) medium load after warm-up" by the hydraulic actuator 2A for phase control of the intake-side VTC mechanism 1A. It is controlled to the advance side beyond the top dead center (TDC). Accordingly, the opening timing (IVOh) and closing timing (IVCh) of the intake valve are set by returning to the advance position by a predetermined angle compared to “(C) During middle load after warm-up”.

Similarly, the exhaust valve 5 is controlled by the phase control hydraulic actuator 2B of the exhaust side VTC mechanism 1B beyond the top dead center (TDC) to the retard side than in the case of “(C) middle load after warm-up”. The Accordingly, the opening timing (EVOh) and closing timing (EVCh) of the exhaust valve are set by returning to the retarded position by a predetermined angle as compared with “(C) During middle load after warm-up”.

In this state, the valve overlap between the intake valve and the exhaust valve is a positive valve overlap state in which both the intake valve 4 and the exhaust valve 5 are opened, and the phase angle of the positive valve overlap is positive. Valve overlap (PVOLh) is set.

The positive overlap (PVOLh) of “(D) at the time of high load after warm-up” is set to a smaller phase angle than the positive valve overlap (PVOLc) of “(A) at the time of cold start”, and “PVOLc> PVOLh ".

Thus, the intake valve opening timing (IVO) has a relationship of “IVOc> IVOh> IVOi> IVOm” with respect to the advance side. Similarly, since the operating angle is the same, the intake valve closing timing (IVC) also has a relationship of “IVCc> IVCh> IVCi> IVCm”.

On the other hand, the exhaust valve opening timing (EVO) has a relationship of “EVOc> EVOh> EVOi> EVOm” with respect to the retard side. Similarly, since the operating angle is the same, the exhaust valve closing timing (EVC) also has a relationship of “EVCc> EVCh> EVCi> EVCm”.

Next, the control operation of the intake side VTC mechanism 1A, the exhaust side VTC mechanism 1B, and the VCR mechanism 3 corresponding to the change in the operation region described above will be described for each operation region from when the internal combustion engine is stopped until it reaches full load. To do. FIG. 4 shows the main parameters of the variable operation system according to the first embodiment, which are the intake valve 4 opening timing (IVO), the exhaust valve 5 closing timing (EVC), the intake valve 4 closing timing (IVC), This shows the control characteristics of the mechanical expansion ratio εE (= mechanical compression ratio εC).

[(0) When stopped] When the internal combustion engine changes from an operating state to an engine stop condition, control such as fuel cut and ignition cut is performed and the driving combustion torque of the internal combustion engine is lost, and the rotational speed Ne of the internal combustion engine decreases. To go. At that time, when the internal combustion engine is stopped, the intake-side VTC mechanism 1A and the exhaust-side VTC mechanism 1B are stabilized at the above-described default positions, which are mechanically stable positions. Specifically, the intake valve 4 opening / closing timing (IVOc, IVCc) and the exhaust valve 5 opening / closing timing (EVOc, EVCc) shown in FIGS. 3A and 3B are stably shifted.

In this way, the intake side VTC mechanism 1A and the exhaust side VTC mechanism 1B are provided with an intake air that is suitable for cold start before the internal combustion engine is stopped and then left (cooling water temperature decreases) before the next start. The valve 4 is moved to near the opening / closing timing (IVOc, IVCc) and the exhaust valve 5 is opened / closed (EVOc, EVCc).

On the other hand, as shown in FIGS. 2A and 2B, the VCR mechanism 3 is a highly irreversible speed reduction mechanism such as a worm mechanism, and a return biasing spring is also particularly provided. However, a stable transition to a specific default position does not occur as the rotation speed of the internal combustion engine decreases. Then, the internal combustion engine is stopped near the position of the mechanical expansion ratio (εE = εC) immediately before reaching the stop condition, and according to the position of the mechanical expansion ratio εE (= mechanical compression ratio εC) immediately before the stop condition is reached, The mechanical expansion ratio εE (= mechanical compression ratio εC) when the internal combustion engine is stopped is generally determined. Therefore, the mechanical expansion ratio εE = (mechanical compression ratio εC) varies between “εEmax” and “εEmin” indicated by εE in FIG.

Here, when the internal combustion engine is stopped, the opening / closing timing (IVO, IVC) of the intake valve 4 and the opening / closing timing (EVO, EVC) of the exhaust valve 5 are the opening / closing timing (IVOc, IVCc) of the intake valve 4 and The default position substantially coincides with the opening / closing timing (EVOc, EVCc) of the exhaust valve 5. For this reason, since the amount of control conversion at the time of starting is small, the conversion response time can be extremely shortened, and the required energy (hydraulic energy) required for conversion can be suppressed.

In particular, as in the present embodiment, in the case of fixing with a fastening pin having a mechanical fixing function at the default position, the opening and closing timings of the intake valve 4 and the exhaust valve 5 when the engine is stopped, and the intake of the cold start Since the required opening / closing timings (IVOc, IVCc, EVOc, EVCc) of the valve 4 and the exhaust valve 5 can be made coincident with each other, it can be set to an appropriate valve opening / closing timing from the beginning of the start, and less driving energy is required. Therefore, even if it is a hydraulic actuator, start control without a problem is attained.

On the other hand, the VCR mechanism 3 has a large output in order to quickly convert it to the minimum mechanical expansion ratio (εEmin = εCmin) suitable for cold start since the position when the internal combustion engine is stopped varies as described above. Requires an electric actuator. As a result, the energy (electric power) necessary for the conversion becomes excessive, and the conversion response tends to deteriorate.

However, in the present embodiment, in the state of the cold start of the intake side VTC mechanism 1A and the exhaust side VTC mechanism 1B, almost no driving energy is consumed, so that only the VCR mechanism 3 has a large electric actuator. By using the data, it is possible to satisfy the conversion response function.

[(A) When the cold engine is started] Then, when the engine start condition (key-on) is reached and cranking is started and the cranking rotational speed reaches a predetermined rotational speed, the VCR mechanism 3 also has a target minimum mechanical expansion ratio ( Assuming that εEmin = εCmin), the start combustion control is started. Specifically, fuel injection control, ignition control, etc. are started and start combustion is started.

Here, (A) “εEmin” shown in FIG. 4 or the like when starting the cold machine indicates the mechanical expansion ratio at the time of starting combustion after finishing the cranking. That is, it is not the variation “εEmax” to “εEmin” at the beginning of cranking, but the mechanical expansion ratio at the time of completion of cranking and starting combustion.

And, in the case of this εEmin, it is possible to obtain good cold startability, particularly good performance for reducing harmful exhaust components in the exhaust gas. In other words, the piston position at which the mechanical expansion ratio (εE) is minimized is controlled by the VCR mechanism 3, and the closing timing (IVCc) of the intake valve 4 exceeds the bottom dead center (BDC) by the intake side VTC mechanism 1A. In addition to being controlled to the most advanced position on the bottom dead center (BDC) side, the opening timing (IVOc) of the intake valve 4 is controlled to the most advanced position beyond the top dead center (TDC). .

According to this, since the VCR mechanism 3 is controlled to a substantially minimum mechanical expansion ratio (εEmin), there is little expansion work, and the temperature of the exhaust gas is relatively increased accordingly. Thus, the exhaust gas purification catalyst 74 provided in the exhaust pipe can be warmed up early, and the conversion efficiency of the exhaust gas purification catalyst 74 can be improved.

Further, the intake side VTC mechanism 1A controls the closing timing (IVCc) of the intake valve 4 to a position close to the vicinity of the bottom dead center (BDC), so that the effective compression ratio is improved and the combustion improvement effect is enhanced. be able to. As a result, harmful exhaust components themselves in the exhaust gas of the internal combustion engine can be reduced. In addition to improving the conversion rate of exhaust harmful components in the exhaust gas purification catalyst described above, exhaust harmful components in the exhaust gas exhausted from the tail pipe are further reduced. Components can be reduced.

Further, the combustion gas containing a large amount of unburned HC and unburned PM (particulate matter) at the end of the exhaust stroke from the opening timing (IVOc) of the intake valve 4 to the top dead center (TDC) It is returned to the intake system by being pushed up, and the combustion improvement effect can be further enhanced by stirring the intake system. In addition to this, the combustion gas containing unburned HC and unburned PM is reintroduced into the cylinder in the next intake stroke. Exhaust harmful components in the gas can be further reduced.

In a general VCR mechanism, if the mechanical expansion ratio (εE) is set to be small, the mechanical compression ratio (εC) is also set to be small, which may cause deterioration of combustion. Therefore, in this embodiment, the closing timing (IVC) of the intake valve 4 is set to the most advanced angle position near the bottom dead center (BDC) that exceeds the bottom dead center (BDC) by the intake side VTC mechanism 1A. The effective compression ratio is improved, and the opening timing (IVOc) of the intake valve 4 is set to the position of the most advanced angle beyond the top dead center (TDC). It has a special supplementary effect of offsetting the deterioration of combustion.

Further, the closing timing (EVC) of the exhaust valve 5 is delayed by a predetermined angle from the most advanced angle phase within the variable range, and is controlled to the closing timing (EVCc) on the retarded side exceeding the top dead center (TDC). ing. In this embodiment, the most retarded position is set.

According to this, during the period from the top dead center (TDC) to the closing timing (EVCc), the high-temperature combustion gas on the exhaust port side can be sucked back into the cylinder by the piston lowering operation, and the in-cylinder heating effect thereby Thus, combustion can be improved and generation of harmful exhaust components from the internal combustion engine can be further reduced. In addition, high-concentration HC contained in the high-temperature combustion gas sucked back on the exhaust port side can be recombusted in the next combustion stroke, and from this aspect, the generation of harmful exhaust components from the internal combustion engine can be further reduced. Can do.

Next, another effect of the VCR mechanism 3 by a different mechanism is that, as described above, the mechanical expansion ratio εEmin (= εCmin) is controlled at the time of cold start. However, as shown in FIG. The compression top dead center position is the lowest position. As a result, the fuel spray injected from the in-cylinder fuel injection valve at the start of the cold engine is less likely to adhere to the piston crown surface, thereby suppressing the generation of unburned HC and unburned PM at the end of the exhaust stroke. Generation of harmful components can be further reduced. In particular, in a direct injection type internal combustion engine that is directly injected into a cylinder, this effect is increased when compression stroke injection is performed.

In this way, in this embodiment, exhaust gas harmful substances at the time of cold start can be sufficiently reduced by various effects.

[(B) At low load after warming up] Next, when the internal combustion engine warms up and the temperature of the cooling water reaches a predetermined temperature, the exhaust gas harmful component at the time of cold start is considered to be out of the region, and the fuel consumption Switch to a mode that emphasizes. When the load rises after warming up, the intake valve 4 opening / closing timing (IVO, IVC), exhaust gas by the intake side VTC mechanism 1A, the exhaust side VTC mechanism 1B, and the VCR mechanism 3 corresponding to this load. The opening / closing timing (EVO, EVC) of the valve 5 and the mechanical expansion ratio εE (= εC) are controlled as shown in FIG.

That is, the operation is performed at the maximum mechanical expansion ratio εEmax (= εCmax) with good fuel efficiency at a low load after warm-up including idling. This maximum mechanical expansion ratio εEmax (= εCmax) is the largest mechanical expansion ratio (εE) within a variable range.

Here, the reason why the fuel efficiency is improved is that when the mechanical expansion ratio (εE) is increased, the expansion work is increased even with the same fuel injection amount, so that the thermal efficiency is increased. Thus, since the engine torque increases at the same fuel injection amount, the closing timing (IVC) of the intake valve 4 is set by retarding the intake side VTC mechanism 1A in order to maintain the engine torque. Moving from the bottom dead center (BDC) to the retard side, the closing timing (IVCc) is changed to the closing timing (IVCi). Therefore, by reducing the charging efficiency of fresh air by this intake valve closing timing control, it becomes possible to reduce the combustion injection amount and improve the fuel efficiency.

Here, by moving the closing timing (IVC) of the intake valve 4 from the bottom dead center (BDC) to the retard side and changing the closing timing (IVCc) to the closing timing (IVCi) in this way, a so-called Atkinson cycle is performed. The effect (pump loss reduction effect) is also added, and fuel efficiency can be further improved.

In the present embodiment, the opening / closing timing (EVOi, EVCi) of the exhaust valve 5 is controlled to the advance side by the exhaust side VTC mechanism 1B. Since the mechanical expansion ratio (εE) is increased by the VCR mechanism 3 described above, a slight in-cylinder negative pressure tends to be generated in the cylinder slightly before the bottom dead center (BDC) at the end of the expansion stroke. . When negative pressure is generated in the cylinder, this negative pressure acts to hinder the downward movement of the piston, resulting in another pump loss (pump loss at the end of the expansion stroke).

Therefore, by opening the exhaust valve 5 opening timing (EVO) to the opening timing (EVOi) by the exhaust side VTC mechanism 1B, the exhaust valve 5 is opened before the in-cylinder negative pressure is generated, and the pump loss at the end of the expansion stroke is reduced. Suppresses and improves fuel efficiency.

By the way, the valve overlap between the closing timing (EVCi) of the exhaust valve 5 and the opening timing (IVOi) of the intake valve 4 is controlled to “substantially 0” by the intake side VTC mechanism 1A and the exhaust side VTC mechanism 1B. . Thereby, the amount of internal EGR gas, which is an inert gas, can be suppressed, and instability of combustion in a low load range that tends to occur during idling after warm-up can be sufficiently suppressed.

Also, assuming that lean burn combustion with good fuel efficiency is performed, it becomes possible to increase the amount of lean mixture as much as the internal EGR is reduced, and increase the limit torque in lean burn combustion. Since it can shift to the load side, the lean burn combustion region can be expanded, and the fuel efficiency can be reduced from that aspect.

[(C) Medium load after warm-up] When the load further increases from the low load after warm-up, the intake-side VTC mechanism 1A, the exhaust-side VTC mechanism 1B, and the VCR mechanism 3 correspond to this load increase. The opening / closing timing (IVO, IVC) of the intake valve 4, the opening / closing timing (EVO, EVC) of the exhaust valve 5, and the mechanical expansion ratio εE (= εC) are controlled as shown in FIG.

When the intermediate load is reached, the conversion of the piston position by the VCR mechanism 3 is suppressed, and the intake valve 4 is opened and closed by the intake side VTC mechanism 1A while maintaining a large mechanical expansion ratio εEmax (= εCmax). IVC) is retarded, and the exhaust side VTC mechanism 1B controls the opening / closing timing (IVO, IVC) of the exhaust valve 5 to advance.

As a result, as shown in FIGS. 3A, 3B, and 4, a large negative valve overlap (NVOLm) interval is generated between the closing timing (EVCm) of the exhaust valve 5 and the opening timing (IVOm) of the intake valve 5. It becomes like this. When negative valve overlap (NVOLm) occurs, high-temperature combustion gas is sealed in the cylinder.

This negative valve overlap (NVOLm) is different from the in-cylinder residual combustion gas by the positive valve overlap (PVOL) in which the combustion gas returned to the intake system is re-inhaled. The absolute temperature is high. For this reason, there is a volume expansion of the residual combustion gas in the cylinder, and the intake ratio (filling efficiency) of fresh air tends to decrease by that amount, so the throttle opening is opened more widely to obtain the predetermined engine torque. Therefore, the pump loss in the middle load range can be sufficiently reduced.

Furthermore, since the closing timing (IVC) of the intake valve 4 is further retarded from the closing timing (IVCi) to the closing timing (IVCm), the so-called Atkinson cycle effect (pump loss reduction effect) is further increased and fuel efficiency is further improved. Can be achieved.

Also, since the closing timing (IVCm) of the intake valve 4 is closed late, knock resistance can be improved by reducing the effective compression ratio. As a result, a large mechanical compression ratio εCmax (= εEmax) can be maintained in spite of an increase in load from a low load to a medium load, so that a high thermal efficiency can be obtained. Can be obtained.

[(D) High load after warm-up] When the load further increases from the middle load after warm-up, the intake side VTC mechanism 1A, the exhaust side VTC mechanism 1B, and the VCR mechanism 3 correspond to this load increase, The opening / closing timing (IVO, IVC) of the intake valve 4, the opening / closing timing (EVO, EVC) of the exhaust valve 5, and the mechanical expansion ratio εE (= εC) are controlled as shown in FIGS. .

When shifting from the middle load after warm-up to the high load after warm-up, the mechanical compression ratio εC (= εE) is controlled in a decreasing direction. This is because the knock resistance is abruptly deteriorated when the load is increased toward the high load side, so that the mechanical compression ratio εC (= εE) is rapidly decreased in accordance with the increase in the load. For example, when the engine torque (load) S further increases from the medium load state, the mechanical compression ratio εC (= εE) increases from the maximum mechanical compression ratio εCmax (= εEmax) to the substantially minimum mechanical compression ratio εCmin (= εEmin). It is controlled to decrease rapidly.

Here, as a technique for increasing the knock resistance, there is also a technique for retarding the ignition timing as in the prior art, but this is accompanied by a noticeable decrease in thermal efficiency due to a delay in the heat generation time due to combustion, and the temperature of the exhaust gas When the exhaust gas purification catalyst 74 is excessively increased, thermal deterioration of the exhaust gas purification catalyst 74 is caused to reduce the conversion efficiency of exhaust harmful components, that is, the durability of the exhaust gas purification catalyst 74 is deteriorated. Therefore, by reducing the mechanical compression ratio εCmin (= εEmin) to a substantially minimum mechanical compression ratio as the load increases, a desired engine torque can be generated while suppressing the retard of the ignition timing and suppressing the occurrence of knocking.

In the present embodiment, the intake valve 4 is controlled to be advanced by the intake side VTC mechanism 1A as the load increases, so that the closing timing (IVCh) of the intake valve 4 is slightly closer to the bottom dead center (BDC). Yes. This is because it is necessary to increase the charging efficiency as the required load increases, so that the closing timing (IVCh) of the intake valve 4 is made slightly closer to the bottom dead center (BDC) (slightly advanced). Yes. For further increases in load, the throttle opening is increased, and at full load (accelerator opening is fully open), the throttle opening is fully open.

Further, as the load from the medium load increases, the intake valve 4 opening timing (IVOh) is slightly advanced by the intake side VTC mechanism 1A, while the exhaust valve 5 closing timing (EVCh) by the exhaust side VTC mechanism 1B. ) Is slightly delayed. As a result, the negative valve overlap (NVOLm) described above suddenly changes to a positive valve overlap (PVOLh).

When set to negative valve overlap (NVOL), high-temperature combustion gas is sealed in the cylinder, so that the temperature of the air-fuel mixture becomes high and knocking is likely to occur at high loads. For this reason, by changing to positive valve overlap (PVOL), the combustion gas is returned to the intake system (relatively cold) and then sucked into the cylinder again, so that the temperature of the air-fuel mixture is negative valve overlap (NVOL). The occurrence of knocking can be suppressed in combination with the reduction in the mechanical compression ratio (εCmin).

On the other hand, if the load is further increased, the risk of knocking increases, but in the case of positive valve overlap (PVOL), the combustion gas is discharged from the cylinder as the load increases (intake pipe negative pressure decreases). Since it becomes difficult to suck back to the intake port side, as a result, the amount of burned gas sucked into the cylinder from the intake port side in the next stroke decreases, and the knock resistance is improved accordingly. As a result, even if the mechanical compression ratio (εCmin) is not further reduced in response to a further increase in load, in other words, even if the mechanical compression ratio (εCmin) is substantially constant, the requirement for knock resistance can be satisfied. become.

Next, a control flow for executing the control characteristics shown in FIG. 4 will be briefly described with reference to FIGS. 5A and 5B. This control flow is executed by a microcomputer built in the controller 22 at a start timing of every 10 ms, for example.

FIG. 5A shows a control flow for setting the stop positions of the intake side VTC mechanism 1A, the exhaust side VTC mechanism 1B, and the VCR mechanism 3 at the time of stop transition for stopping the internal combustion engine.

<< 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 intake side VTC mechanism 1A and the exhaust side VTC mechanism 1B. 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 ends 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, a fuel cut signal is sent to the fuel injection valve to stop the internal combustion engine, and an ignition cut signal is sent to the ignition device. As a result, the rotational speed Ne of the internal combustion engine decreases and the internal combustion engine is stopped.

<< Step S13 >> In step S13, the conversion control signal is transmitted to the intake side VTC mechanism 1A and the exhaust side VTC mechanism 1B to the default position, the phase control hydraulic actuator 2A of the intake side VTC mechanism 1A, and the exhaust side VTC mechanism. 1B is output to the hydraulic actuator 2B for phase control. That is, in order to respond to the next start, control is performed so that the opening / closing timing characteristics of “(O) When the engine is stopped” in FIG. 4 are obtained. Actually, it is configured to mechanically return to the default position when the conversion control signal is cut off.

Accordingly, the opening timing (IVO) of the intake valve 4 is set near the opening timing (IVOc), and the closing timing (IVC) of the intake valve 4 is set near the closing timing (IVCc), and the closing timing of the exhaust valve 5 is set. (EVC) is set near the closing timing (EVCc).

Further, the mechanical expansion ratio (εE) by the VCR mechanism 3 depends on the state of the internal combustion engine when it is stopped, and depends on the position of the mechanical expansion ratio (εE) immediately before reaching the stop condition of the internal combustion engine. The mechanical expansion ratio (εE) at the time of stoppage is almost determined. This is because the VCR mechanism 3 does not have a default position that is mechanically stable. Accordingly, the position is set to vary depending on the position at the start of the stop transition between “εEmax” and “εEmin”. In practice, the VCR mechanism 3 conversion control signal may be cut off. When the settings by the intake-side VTC mechanism 1A, the exhaust-side VTC mechanism 1B, and the VCR mechanism 3 are completed, the process goes to the end and waits for the start of the next internal combustion engine.

Next, a control flow when the operation of the internal combustion engine is resumed from this state will be described with reference to FIG. 5B. This control flow is also executed by a microcomputer built in the controller 22.

<< 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 volume information, water temperature information, required load information (accelerator opening), and the like, and further, actual position information of the exhaust side VTC mechanism 1B and the intake side VTC mechanism 1A. 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, a key-on signal or a starter activation signal may be monitored. If no starter activation signal is 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, the conversion control signal is transferred to the default position to the intake side VTC mechanism 1A and the exhaust side VTC mechanism 1B, and the phase control hydraulic actuator 2A and the exhaust side of the intake side VTC mechanism 1A. It is output to the phase control hydraulic actuator 2B of the VTC mechanism 1B. A conversion control signal is also output to the compression ratio control actuator 49 of the VCR mechanism 3. That is, in order to respond to the start, control is performed so that the valve opening / closing timing characteristics and the piston position characteristics shown in “(A) Cold start” in FIG. 4 are obtained.

Accordingly, the opening timing (IVO) of the intake valve 4 is set to the opening timing (IVOc), the closing timing (IVC) of the intake valve 4 is set to the closing timing (IVCc), and the closing timing (EVC) of the exhaust valve 5 is set. ) Is set to the closing timing (EVCc). Further, the mechanical expansion ratio (εE) is set to the mechanical compression ratio (εEmin). Then, the conversion control signal is output to the phase control hydraulic actuator 2A of the intake side VTC mechanism 1A and the phase control hydraulic actuator 2B of the exhaust side VTC mechanism 1B, and the conversion control is performed to the compression ratio control actuator 49 of the VCR mechanism 3. When the signal is output, the process proceeds to step S23 and step S24.

<< Step S23, Step S24 >> In step S23, cranking is started by the starter motor, and then it is determined in step 24 whether the rotational speed Ne has reached a predetermined cranking rotational speed. When the rotational speed Ne reaches the predetermined cranking rotation, it is determined that each mechanism has been converted to the target position, and the process proceeds to step S25.

<< Step S25 >> In step S25, a drive 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. When the engine is started by supplying a drive signal 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 To has been exceeded. If the temperature does not exceed the predetermined temperature To, it is determined that the engine is in the cold state, and the process returns to step S25 to execute again, and this loop is continued until the temperature exceeds the predetermined temperature To.

During the execution of steps S25 to S26 (until the predetermined temperature To is reached), the opening / closing timing of the intake valve 4 (IVO, IVC), the closing timing of the exhaust valve 5 (EVO, EVC), and With respect to the mechanical expansion ratio (εE), an operation as shown in FIG. 4 (A) is performed. That is, during this time, exhaust emission (exhaust harmful components) discharged from the tail pipe during the cold start operation is greatly suppressed. When the warm-up of the internal combustion engine proceeds and exceeds the predetermined temperature To, it is determined that the warm-up has been completed from the cold state, and the process proceeds to step S27.

<< Step S27 >> In step S27, the conversion control signal when the warm-up is completed is output to the phase control hydraulic actuator 2A of the intake side VTC mechanism 1A and the phase control hydraulic actuator 2B of the exhaust side VTC mechanism 1B. Is done. A conversion control signal is also output to the compression ratio control actuator 49 of the VCR mechanism 3. The example shown in FIG. 4B shows an idle state after warm-up as an example of “(B) low load after warm-up”.

Therefore, the opening timing (IVO) of the intake valve 4 is set to the opening timing (IVOi), the closing timing (IVC) of the intake valve 4 is set to the closing timing (IVCi), and the closing timing (EVC) of the exhaust valve 5 is set. ) Is set to the closing timing (EVCi). Further, the mechanical expansion ratio (εE) is set to the mechanical expansion ratio (εEmax).

Then, the conversion control signal is output to the phase control hydraulic actuator 2A of the intake side VTC mechanism 1A and the phase control hydraulic actuator 2B of the exhaust side VTC mechanism 1B, and the conversion control is performed to the compression ratio control actuator 49 of the VCR mechanism 3. When the signal is output, the process proceeds to step S28.

<< Step S28 >> In step S28, it is determined whether or not the load of the internal combustion engine has exceeded the low load range after warming up. When the load of the internal combustion engine does not exceed the low load region after warming up, the routine returns to return and waits for the next start timing. In this case, the program is created so as to execute the control step of step S27 without executing the control steps of step S20 to step 26 using the “execution flag” or the like. That is, when the “execution flag” is set after the process of step S27 and this “execution flag” is set at the next activation timing, the process proceeds to step S27.

On the other hand, when it is determined in step S28 that the load of the internal combustion engine exceeds the low load region after warming up, the process proceeds to step S29.

<< Step S29 >> In step S29, a conversion control signal corresponding to the load is output to the phase control hydraulic actuator 2A of the intake side VTC mechanism 1A and the phase control hydraulic actuator 2B of the exhaust side VTC mechanism 1B. A conversion control signal is also output to the compression ratio control actuator 49 of the VCR mechanism 3.

In the case of “(C) mid-load after warm-up”, the opening timing (IVO) of the intake valve 4 is set to the opening timing (IVOm), and the closing timing (IVC) of the intake valve 4 is set to the closing timing (IVCm). ) And the closing timing (EVC) of the exhaust valve 5 is set to the closing timing (EVCm). Further, the mechanical expansion ratio (εE) is set to the mechanical compression ratio (εEmax).

In the case of “(D) high load after warm-up”, the opening timing (IVO) of the intake valve 4 is set to the opening timing (IVOh), and the closing timing (IVC) of the intake valve 4 is the closing timing. (IVCh) is set, and the closing timing (EVC) of the exhaust valve 5 is set to the closing timing (EVCh). Further, the mechanical expansion ratio (εE) is set to the mechanical compression ratio (εEmin).

Then, the conversion control signal is output to the phase control hydraulic actuator 2A of the intake side VTC mechanism 1A and the phase control hydraulic actuator 2B of the exhaust side VTC mechanism 1B, and the conversion control is performed to the compression ratio control actuator 49 of the VCR mechanism 3. When the signal is output, the process ends and waits for the next activation timing.

As described above, according to the present embodiment, by setting a small mechanical expansion ratio by the VCR mechanism at the time of cold start, the exhaust gas purification catalyst is warmed up early by raising the temperature of the exhaust gas. In addition, the conversion efficiency of the exhaust gas purifying catalyst can be improved.

Further, by controlling the intake valve closing timing (IVC) near the bottom dead center (BDC) by the intake side VTC mechanism, the effective compression ratio can be increased and the combustion improvement effect can be enhanced. As a result, it is possible to reduce the amount of harmful exhaust components themselves in the exhaust gas, and in addition to improving the conversion efficiency of exhaust harmful components in the exhaust gas purification catalyst described above, the exhaust harmful components in the exhaust gas discharged from the tailpipe are further reduced. Components can be reduced.

Furthermore, the combustion gas containing a large amount of unburned HC and unburned PM (particulate matter) at the end of the exhaust stroke is pushed up to the piston from the opening timing (IVO) of the intake valve to the top dead center (TDC). By returning to the intake system, the combustion improvement effect can be further enhanced by stirring the intake system. In addition to this, the combustion gas containing unburned HC and unburned PM is reintroduced into the cylinder in the next intake stroke. Exhaust harmful components in the gas can be further reduced.

Next, a second embodiment of the present invention will be described. In the first embodiment, the mechanical compression ratio (εC) and the mechanical expansion ratio (εE) obtained by the VCR mechanism are equal, but in this embodiment, the mechanical compression ratio (εC) and the mechanical expansion ratio (εE) ) Is controlled using different values.

Hereinafter, this VCR mechanism is referred to as a “heterogeneous VCR mechanism” for convenience of explanation. The heterogeneous VCR mechanism is described in Japanese Patent Application Laid-Open No. 2016-17489 filed by the applicant of the present application, and therefore detailed description thereof is omitted here. In the present embodiment, the intake side VTC mechanism and the exhaust side VTC mechanism are the same as those in the first embodiment, and the same operation is performed. Therefore, when these explanations are not necessary, they are omitted.

FIG. 6 shows a variable range of the mechanical expansion ratio (εE) and the mechanical compression ratio (εC) by the heterogeneous VCR mechanism 3 according to the present embodiment, and the mechanical expansion ratio (εE) and the mechanical compression ratio ( The change characteristic of εC) is shown in FIG.

In FIG. 6, at the control position (A), the mechanical compression ratio is set to “10.5” of the maximum mechanical compression ratio (εCmax) with respect to “9.0” of the minimum mechanical expansion ratio (εEmin). In the control position (B), the mechanical compression ratio is set to the same value as “10.0” of the minimum mechanical compression ratio (εCmin) with respect to “10.0” of the maximum mechanical expansion ratio (εEmax). . Thus, the mechanical expansion ratio (εE) and the mechanical compression ratio (εC) can be set differently, and the minimum mechanical expansion ratio (εEmin) to the maximum mechanical expansion ratio (εEmax), and the minimum The configuration is such that it can be continuously changed within a variable range from the mechanical compression ratio (εCmin) to the maximum mechanical compression ratio (εCmax). This value is exemplary, and an appropriate value can be selected depending on the capacity of the internal combustion engine.

Therefore, as can be seen from FIG. 6, in the first embodiment, the mechanical expansion ratio (εE) and the mechanical compression ratio (εC) have a relationship of “εEmin = εCmin” and “εEmax = εCmax”. In the embodiment, the mechanical expansion ratio (εE) and the mechanical compression ratio (εC) have a relationship of “εEmin <εCmin” and “εEmax <εCmax”. Further, the relationship is “εEmax = εCmin”.

In this embodiment, at the time of cold start (control position (A)), the mechanical expansion ratio (εE) is set to the minimum mechanical expansion ratio (εEmin) as in the first embodiment. (εC) is set to the maximum mechanical compression ratio (εCmax). Thereby, the startability at the time of cold machine start-up and the reduction effect of exhaust harmful components can be improved as compared with the first embodiment.

That is, the closing timing (IVCc) of the intake valve 4 is controlled near the bottom dead center (BDC) by the intake side VTC mechanism 1A, and the effective compression ratio is increased. Since the mechanical compression ratio (εC) itself is set high, the overall effective compression ratio can be set even larger. Thereby, the combustion improvement effect at the time of cold start can be enhanced, and as a result, the stability of the start combustion and the purification of exhaust harmful components at the cold start can be further enhanced.

Of course, since the mechanical expansion ratio (εE) is the minimum mechanical expansion ratio (εEmin) as in the first embodiment, it is possible to increase the temperature of the exhaust gas and promote the warm-up of the exhaust gas purification catalyst. Is the same as in the first embodiment.

Next, control operations of the intake-side VTC mechanism 1A, the exhaust-side VTC mechanism 1B, and the heterogeneous VCR mechanism 3 will be described for each operation region from when the internal combustion engine is stopped until full load is reached. FIG. 7 shows the main parameters of the variable operation system according to the second embodiment, which are the intake valve 4 opening timing (IVO), the exhaust valve 5 closing timing (EVC), the intake valve 4 closing timing (IVC), The control characteristics of mechanical expansion ratio (εE) and mechanical compression ratio (εC) are shown. Parameters other than the mechanical expansion ratio (εE) and the mechanical compression ratio (εC) are the same as those in the first embodiment.

First, when “(0) is stopped”, the intake-side VTC mechanism 1A and the exhaust-side VTC mechanism 1B are stable at the above-described default positions, which are mechanically stable positions. Specifically, the intake valve opening / closing timing (IVOc, IVCc) and the exhaust valve opening / closing timing (EVOc, EVCc) are shifted to a position that substantially coincides with this, which is the same as in the first embodiment. .

Here, unlike the first embodiment, the heterogeneous VCR mechanism 3 also moves to the default position (the control position (A)). In the case of this embodiment, not only is the mechanical expansion ratio (εE) set to the minimum mechanical expansion ratio (εEmin), but also the mechanical compression ratio (εC) is set to the maximum mechanical compression ratio ( εCmax).

Next, in “(A) cold start”, the intake valve 4 is opened and closed (IVOc, IVCc) by the intake side VTC mechanism 1A, and the exhaust valve 5 is opened and closed (EVOc, EVCc) by the exhaust side VTC mechanism 1B. And controlled. This is the same as in the first embodiment.

On the other hand, the control position (A) of the heterogeneous VCR mechanism 3 is continued and controlled to the minimum mechanical expansion ratio (εEmin) and the maximum mechanical compression ratio (εCmax). Here, since the mechanical compression ratio (εC) is set to the maximum mechanical compression ratio (εCmax), the effective compression ratio can be set larger. Thereby, the combustion improvement effect at the time of cold start can be enhanced, and as a result, the stability of the start combustion and the purification of exhaust harmful components at the cold start can be further enhanced.

In addition, when the configuration in which the dissimilar VCR mechanism 3 of the present embodiment is fixed to the default position by a fastening pin having a fixing function, the mechanical expansion ratio (εE) and the mechanical compression ratio (εC) when the engine is stopped are set at the time of cold start. Therefore, it is possible to obtain appropriate mechanical expansion ratio (εE) and mechanical compression ratio (εC) from the beginning at the time of starting. As a result, although it is a secondary, the hydraulic energy required for the conversion of the heterogeneous VCR mechanism 3 can be reduced, and good start control can be performed even for the heterogeneous VCR mechanism 3 even if it is a hydraulic actuator. By the way, with respect to the VCR mechanism 3 of the first embodiment as well, the same effect can be obtained if a biasing spring is similarly provided for the return and is fixed to the default position by a fastening pin having a fixing function. Can do.

Next, in “(B) at the time of low load after warm-up” including the idle when the warm-up is completed, as shown in the control position (B) of FIG. 6, the mechanical expansion ratio (εE) is the minimum mechanical expansion. The ratio (εEmin) shifts to the maximum mechanical expansion ratio (εEmax), and the mechanical compression ratio (εC) shifts from the maximum mechanical compression ratio (εCmax) to the minimum mechanical compression ratio (εCmin). Here, in “(B) low load after warm-up” (in the present embodiment, when idling), the maximum mechanical expansion ratio (εEmax) and the minimum mechanical compression ratio (εCmin) are equal. For example, “ εEmax = εCmin = 10.0 ”.

Furthermore, even if the load increases from “(B) Low load after warm-up”, as shown in “(C) Medium load after warm-up” and “(D) High load after warm-up” The mechanical expansion ratio (εEmax) and the minimum mechanical compression ratio (εCmin) are maintained so as not to change. That is, after warm-up, the average (general) mechanical compression ratio (εC) and mechanical expansion ratio (εE) are maintained regardless of the magnitude of the load. As a result, even if there is a sudden change in load (torque), it is not necessary to convert the heterogeneous VCR mechanism 3 with high response following this, and it is not necessary to convert the heterogeneous VCR mechanism 3 that requires large drive energy. Therefore, instability of transient performance due to conversion delay can be avoided.

The conversion characteristics of the intake valve opening / closing timing (IVO, IVC) by the intake-side VTC mechanism 1A and the exhaust valve opening / closing timing (EVO, EIVC) by the exhaust-side VTC mechanism 1B from the low load to the high load after warm-up. Is the same as in the first embodiment. Accordingly, the valve overlap amount is set to “substantially 0” for “(B) low load after warm-up” including idle, and negative valve overlap (NVOLm) is set for “(C) medium load after warm-up”. In “(D) high load after warm-up”, the positive valve overlap (PVOLh) is set. Since the effects of these controls are the same as in the first embodiment, description thereof is omitted.

As can be seen from the above description, the VCR mechanism in the present invention may be a type in which the mechanical compression ratio and the mechanical expansion ratio are always controlled with the same value, or a type in which the mechanical compression ratio and the mechanical expansion ratio can be controlled to different values. It ’s good. The intake-side VTC mechanism and the exhaust-side VTC mechanism may be a hydraulic phase variable type or an electric variable phase type. Furthermore, a mechanism provided with a mechanism capable of controlling the lift may be used.

As described above, the present invention includes a variable compression ratio mechanism that controls the mechanical compression ratio and the mechanical expansion ratio in an at least four-cycle internal combustion engine, and an intake side variable valve mechanism that controls the phase of the opening / closing timing of the intake valve. At the time of cold start, the piston position is set to a position where the mechanical expansion ratio becomes substantially minimum by the variable compression ratio mechanism, and the intake valve is set by the intake side variable valve mechanism compared with the low load after warm-up. Is set near the bottom dead center, and the opening timing of the intake valve is set to a position before the top dead center.

According to this, the exhaust gas temperature can be increased by reducing the mechanical expansion ratio at the time of cold start, and the exhaust gas purification catalyst can be warmed up early to improve the exhaust gas harmful component conversion performance. It is possible to reduce emissions of harmful exhaust components in gas.

Also, since the closing timing of the intake valve is close to the bottom dead center, the effective compression ratio can be improved and the combustion improvement effect can be enhanced. As a result, the amount of harmful exhaust components themselves in the exhaust gas can be reduced. In addition to improving the conversion rate of harmful exhaust components in the exhaust gas purification catalyst described above, exhaust harmful components in the exhaust gas discharged from the tailpipe are further reduced. Components can be reduced.

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, and replace other configurations for a part of the configuration of each embodiment.

Claims (12)

1. A variable compression ratio mechanism that controls the mechanical compression ratio and the mechanical expansion ratio by changing the position of the piston of at least a four-cycle internal combustion engine; and an intake side variable valve mechanism that controls the phase of the opening and closing timing of the intake valve; Control means for controlling the variable compression ratio mechanism and the intake side variable valve mechanism, and at the time of cold start,
   By the variable compression ratio mechanism, the position of the piston is set to a position where the mechanical expansion ratio is substantially minimum,
   Further, the intake side variable valve mechanism sets the closing timing (IVC) of the intake valve near the bottom dead center (BDC) and the opening timing (IVO) of the intake valve as compared with the low load after warm-up. ) Is set to a position on the advance side before top dead center (TDC) (hereinafter referred to as an intake valve start position).
2. The internal combustion engine variable operation system according to claim 1,
   It has an exhaust side variable valve mechanism that controls the phase of the opening and closing timing of the exhaust valve, and the exhaust side variable valve mechanism is controlled by the control means, and at the time of cold start,
   By the exhaust side variable valve mechanism, the closing timing (EVC) of the exhaust valve is retarded by a predetermined angle from a predetermined most advanced angle position, and a position retarded beyond the top dead center (TDC) (hereafter, A variable operation system for an internal combustion engine that is controlled to an exhaust valve start position).
3. The variable operation system for an internal combustion engine according to claim 2,
   The position at which the mechanical expansion ratio of the variable compression ratio mechanism is substantially minimum is such that the position of the compression top dead center of the piston is lower than the highest position in the variable range of the variable compression ratio mechanism. Variable operating system for internal combustion engines.
4. The variable operation system for an internal combustion engine according to claim 3,
   The variable compression ratio mechanism is characterized in that the mechanical compression ratio and the mechanical expansion ratio at the time of cold start are set to the same value, or the mechanical compression ratio at the time of the cold start is set to a value larger than the mechanical expansion ratio. Variable operating system of the engine.
5. The variable operation system for an internal combustion engine according to claim 2,
   When stopping the internal combustion engine, the control means shuts off the conversion control signal to the variable compression ratio mechanism, the intake side variable valve mechanism, and the exhaust valve mechanism,
   When the conversion control signal is interrupted, the variable compression ratio mechanism sets the position of the piston so as to maintain the mechanical expansion ratio when stopped.
   When the conversion control signal is interrupted, the intake side variable valve mechanism sets the opening / closing timing of the intake valve in the vicinity of the intake valve start position,
   When the conversion control signal is cut off, the exhaust side variable valve mechanism sets the opening / closing timing of the exhaust valve in the vicinity of the exhaust valve starting position.
6. The variable operation system for an internal combustion engine according to claim 5,
   A variable operation system for an internal combustion engine, wherein the variable compression ratio mechanism, the intake side variable valve mechanism, and the exhaust side variable valve mechanism are fixed at positions by a mechanical fixing function.
7. The internal combustion engine variable operation system according to claim 1,
   When the temperature of the internal combustion engine rises to a predetermined temperature after the cold start,
   The variable compression ratio mechanism changes the position of the piston from a position where the mechanical expansion ratio is substantially minimum to a position where the mechanical expansion ratio is further increased,
   The intake-side variable valve mechanism moves the closing timing (IVC) of the intake valve to a retard side that is farther from the bottom dead center (BDC) than when the cold engine is started. .
8. A variable compression ratio mechanism that controls the mechanical compression ratio and the mechanical expansion ratio by changing the position of a piston of a four-cycle internal combustion engine, an intake side variable valve mechanism that controls the phase of the opening and closing timing of the intake valve, and the variable A control device for a variable operation system of an internal combustion engine comprising a compression ratio mechanism and a control means for controlling the intake side variable valve mechanism, and at the time of cold start,
   The control means includes
   Controlling the variable compression ratio mechanism to set the position of the piston to a position that is smaller than the maximum value of the variable range of the mechanical expansion ratio;
   Further, the intake valve closing timing (IVC) is set near the bottom dead center (BDC) and the intake valve opening timing (IVO) is set to the top dead center (TDC) compared to the low load state after warm-up. A control apparatus for a variable operation system of an internal combustion engine, wherein the intake side variable valve mechanism is controlled so as to be set to a position that is a front advance side.
9. The control device for a variable operation system for an internal combustion engine according to claim 8,
   In a low load state after warm-up after the temperature of the internal combustion engine rises to a predetermined temperature after cold start,
   The control means includes
   Controlling the variable compression ratio mechanism so as to change the position of the piston from a position that becomes a mechanical expansion ratio at the time of cold start to a position where the mechanical expansion ratio is further increased;
   Further, the intake side variable valve mechanism is controlled so as to move the closing timing (IVC) of the intake valve to a retarded side that is farther from the bottom dead center (BDC) than when the cold engine is started. Control device for variable operation system of engine.
10. The control device for a variable operation system for an internal combustion engine according to claim 9,
    In the full load state after warming up after the temperature of the internal combustion engine rises to a predetermined temperature,
    The control means includes
    Controlling the variable compression ratio mechanism so as to change the position of the piston from a position where the mechanical expansion ratio in the low load state after warm-up becomes a position where the mechanical expansion ratio becomes small;
    Further, the intake side variable valve mechanism is controlled so that the closing timing (IVC) of the intake valve is moved to the advance side closer to the bottom dead center (BDC) than in the low load state after warm-up. A control device for a variable operation system of an internal combustion engine.
11. The control device for a variable operation system for an internal combustion engine according to claim 8,
    The control apparatus for a variable operation system of an internal combustion engine, wherein the low load state after warm-up is an idle state after warm-up.
12. The control apparatus for a variable operation system for an internal combustion engine according to claim 10,
    The control apparatus for a variable operation system for an internal combustion engine, wherein the full load state after warm-up is an accelerator opening degree in a fully open state.

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