JP2002235567A - Combustion control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve exhaust emission control performance by delaying an ignition timing as much as possible, promoting a rise in an exhaust temperature and early activating a catalyst 3, in a cold state. SOLUTION: This device is provided with an operating angle changing mechanism 5 for changing an operating angle of an intake valve 4, a phase changing mechanism 6 for changing the center phase and an ignition timing changing device 14 for changing the ignition timing. In an exhaust passage 2, a catalyst 3 for exhaust emission control is disposed. An opening timing of the intake valve 4 is delayed as much as possible so that the ignition timing may be delayed as compared with an optimum ignition timing and a delay limit of the ignition timing may be expanded in the cold state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark ignition type internal combustion engine in which a catalyst is provided in an exhaust system, and more particularly to a technique for quickly raising a catalyst to an activation temperature in a cold state.

[0002]

2. Description of the Related Art In a spark ignition type internal combustion engine represented by a gasoline engine in recent years, a catalyst for purifying exhaust gas such as a three-way catalyst is generally provided in an exhaust system. However, even with today's advanced catalyst technology, in the engine cooling state where the engine cooling water temperature or catalyst temperature is low, such as immediately after engine startup, and the catalyst has not reached the predetermined activation temperature, the engine is not warmed up. At present, the effect of the catalyst on the exhaust gas is greatly limited as compared with the state described above.

[0003] This problem has been recognized for a long time, and in order to achieve early activation of the catalyst, a method of lowering the activation temperature itself of the catalyst or a method of introducing secondary air upstream of the catalyst to chemically activate the catalyst is used. There are known techniques for accelerating the time of formation. However, it is fundamentally important how quickly the catalyst temperature is raised to the activation temperature at which the catalyst starts to convert. Therefore, a method of raising the exhaust gas temperature and quickly raising the catalyst temperature by retarding the ignition timing from the optimum ignition timing at which the best efficiency can be obtained and retarding the combustion start timing is one of fuel consumption performance and the like. Despite the adverse effects, attempts have been made in the past.

[0004]

However, if the ignition timing is delayed from the optimum ignition timing, combustion becomes unstable, and in severe cases, a misfire may occur and a large amount of unburned HC may be released. is there. Therefore, when delaying the ignition timing in this way, it is essential to improve the combustion.
As a typical method for improving combustion, there is a method of providing a swirl control valve (SCV) at an intake port.

By the way, there are many inventions which have been known as mechanisms for changing the operating characteristics of the intake valve in order to improve combustion at low temperatures. Some of them are listed below.

First, Japanese Patent Laid-Open Publication No. Hei 11-036906 discloses an operating angle changing mechanism capable of continuously changing the operating angle of an intake valve. With this mechanism, the combustion performance can be improved and the fuel efficiency can be improved by optimizing the charging efficiency in a wide operating range from a low engine speed to a high engine speed. Further, by combining a phase changing mechanism for variably controlling the center phase of the operating angle of the intake valve with the above operating angle changing mechanism, the opening timing of the intake valve (hereinafter, IV
O) and closing timing of the intake valve (hereinafter referred to as I
VC (hereinafter referred to as VC) can be individually controlled.

Second, Japanese Utility Model Laid-Open Publication No. Sho 62-116106 discloses a switching mechanism for switching the valve lift and opening / closing timing of an intake valve between two stages. At the time of cranking (at the time of starting), the valve lift is reduced and the IVO is delayed to the vicinity of the bottom dead center of the intake to increase the temperature (fuel vaporization) due to the frictional heat of the intake throttle.
Startability is improved by increasing the speed during cranking due to the small lift. However, there is almost no description about the control of IVO and IVC after the engine is started, and nothing is described particularly about raising the exhaust gas temperature by delaying the ignition timing.

Third, Japanese Patent Application Laid-Open No. Hei 3-202640 discloses a switching mechanism capable of changing the valve timing of an intake valve in two stages. It is described that, in order to raise the pressure, the IVC is delayed, the EVO (opening timing of the exhaust valve) is advanced, and the exhaust gas during the expansion stroke is quickly discharged. However, this publication does not disclose that the ignition timing is delayed to increase the exhaust gas temperature.

According to the present invention, in a spark ignition type internal combustion engine provided with an exhaust gas purifying catalyst in an exhaust system, an intake characteristic changing means for changing an opening timing and a closing timing of an intake valve is effectively used to achieve a cold state. One of the objectives is to realize a large delay in the ignition timing at the, and to achieve early activation of the catalyst and a significant improvement in the exhaust purification performance by increasing the exhaust gas temperature with the retardation of the ignition timing. I have.

[0010] That is, in the cold state, in all operating states until the catalyst reaches the activation temperature (for example, a cold high idling state immediately after starting, a cold accelerating state, a cold steady operating state, etc.), the fuel efficiency is excessively deteriorated. It is an object of the present invention to early activate the catalyst with a rise in the exhaust gas temperature by retarding the ignition timing to a stability limit that does not cause a fire or misfire.

[0011]

SUMMARY OF THE INVENTION A combustion control apparatus for a spark ignition type internal combustion engine according to the present invention includes an intake characteristic changing means for changing an opening timing and a closing timing of an intake valve, and an ignition timing changing for changing an ignition timing. Means, and a cold detecting means for detecting a cold state of the engine, and a catalyst for purifying exhaust gas is provided in the exhaust system. Examples of the catalyst include an oxidation reduction catalyst such as an oxidation catalyst and a three-way catalyst, and a reduction catalyst.

In the above-mentioned cold state, the ignition timing is retarded from the optimal ignition timing at which the optimum combustion efficiency is obtained, and the opening timing of the intake valve is delayed so as to extend the retardation limit of the ignition timing. It is characterized by horns.

Typically, in the cold state, the opening timing (IVO) of the intake valve is retarded from the exhaust top dead center. In this case, even when the intake stroke is started, the intake air is not initially supplied, so that the negative pressure in the cylinder rapidly increases. Furthermore, since the piston speed is the largest at the center of the stroke and increases monotonically from the top dead center to the center of the stroke, if the IVO is delayed from the top dead center, the negative pressure in the cylinder becomes extremely large, The intake flow velocity when the intake valve is opened becomes very large. When the negative pressure in the cylinder increases, although the pump loss increases, the intake air temperature increases accordingly. In addition, due to the increase in the intake flow velocity, the atomization of the fuel injected into the intake port is sufficiently promoted, and the combustion state is improved. Further, the combustion speed itself increases in response to the increase in the degree of intake turbulence accompanying the increase in the intake air flow velocity. Thus, by retarding the opening timing of the intake valve, the combustion state is improved, and the retard limit (retard limit) of the ignition timing can be extended (retarded) accordingly.

As described above, by increasing the retardation limit of the ignition timing from the optimum ignition timing, a rise in the exhaust gas temperature is promoted, and a rise in the temperature of the catalyst provided in the exhaust system is promoted. It is activated at an early stage, and remarkable improvement in exhaust gas purification performance can be achieved.

Specifically, in the cold state, the opening timing of the intake valve is retarded more than in the warm-up state under substantially the same operating conditions.
In other words, in the cold state, although there is an adverse effect such as pump loss in order to maximize the retard limit of the ignition timing,
The opening timing of the intake valve is retarded as much as possible. On the other hand, in the warm-up state, in order to obtain optimal fuel efficiency,
The opening timing of the intake valve is set to be advanced compared to the above-described cold state.

More preferably, in the above-mentioned cold state, the closing timing of the intake valve is set near the intake bottom dead center. In this case, since the actual compression ratio increases and the suction negative pressure also increases,
The combustion speed is increased, and the ignition timing retard limit can be further expanded.

As described above, in the above-mentioned cold state, the IVO and the ignition timing are retarded as much as possible according to the engine operating state within a range that does not cause misfire or the like. For example, when the engine load increases in a cold state, it is necessary to increase the operating angle, so that the delay in the opening timing of the intake valve is reduced in accordance with the increase in the engine load, and accordingly, the ignition timing is retarded. The match will also be reduced.

According to the present invention, the ignition timing is
20 to 30 degrees crank angle than normal optimal ignition timing
For example, in a cold high idle state, it is possible to retard the pressure to near the compression top dead center.

The intake characteristic changing means typically includes an operating angle changing mechanism for changing the operating angle and the valve lift of the intake valve, and a phase changing mechanism for changing the central phase of the operating angle of the intake valve. Have. By individually controlling the driving of both mechanisms, the opening timing and the closing timing of the intake valve can be controlled to arbitrary values independently of each other. Specifically, in the cold state, the opening timing of the intake valve can be retarded to the stability limit while the closing timing of the intake valve is kept near the bottom dead center.

In the above-mentioned cold state, it is preferable that the valve lift of the intake valve be set equal to or less than that in the warm-up state under substantially the same operating conditions. When the valve lift amount is reduced in this way, the intake flow velocity increases as the opening area of the intake passage decreases. In particular, since the nozzle effect (minimum throttle portion) between the intake valve and the valve seat increases, atomization of the fuel injected into the intake port is effectively promoted. Therefore, it is possible to further retard the ignition timing by improving the combustion.

Furthermore, in the cold high idling state where the engine speed is higher than the warm idling state, it is necessary to retard both the opening timing and the closing timing of the intake valve compared to the warm idling state. What is necessary is just to retard the center phase of the operating angle of the intake valve.

The operating angle changing mechanism is typically mounted on a drive shaft that is rotated by rotational power transmitted from a crankshaft, and is swingably mounted on the drive shaft. An oscillating cam to be driven, an eccentric cam provided eccentrically to the drive shaft, a control shaft rotatively driven when the operating angle is changed, a control cam eccentrically provided to the control shaft, and a rotation A rocker arm that is mounted so as to be able to move, a first link that links one end of the rocker arm and the eccentric cam, and a second link that links the other end of the rocker arm and the swing cam. ing.

In this case, by rotating the control shaft in accordance with the operating state of the engine, the position of the control cam, which is the rocking center of the rocker arm, with respect to the engine body changes, and the initial position of each link, rocking cam and the like changes. Posture changes. As a result, the operating angle of the intake valve and the valve lift continuously change while the center phase of the operating angle of the intake valve with respect to the crank angle remains substantially constant. In the operating angle changing mechanism having such a configuration, since the swing cam for operating the intake valve is arranged coaxially with the drive shaft, there is no possibility that the swing cam and the drive shaft may be misaligned. In addition to being excellent in accuracy, the rocker arm and each link are integrated around the drive shaft, so that the mechanism can be made compact. In addition, since many of the connecting portions between the members are in surface contact, such as the bearing portion between the eccentric cam and the first link and the bearing portion between the control cam and the rocker arm, lubrication is easily performed and durability is improved. ， Excellent in reliability. Further, when the operating angle changing mechanism is applied to a general direct-acting valve train having a fixed cam and a camshaft, the swing cam and the drive shaft are arranged at the positions of the fixed cam and the camshaft. The layout can be changed very little, and the application is very easy.

The phase change mechanism is typically provided on a drive shaft that opens and closes an intake valve via the operation angle change mechanism, and is provided coaxially with the drive shaft.
A second gear provided on a sprocket or pulley that rotates in synchronization with the crankshaft, and a plunger including a helical gear meshing with the first gear and the second gear;
Drive means for driving the plunger in the axial direction of the drive shaft when the phase is changed.

[0025]

According to the present invention, when the engine is in a cold state,
The ignition timing is retarded from the optimal ignition timing, and the ignition timing in the cold state is greatly retarded by retarding the opening timing of the intake valve so as to extend the retardation limit of the ignition timing. As a result, the catalyst is activated early due to the increase in the exhaust gas temperature caused by the retardation of the ignition timing, and the exhaust gas purification performance can be greatly improved.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, the internal combustion engine 1 is a gasoline-fueled, spark-ignition type internal combustion engine for a vehicle, and has an exhaust passage 2 forming a part of an exhaust system for purifying exhaust gas. The catalyst 3 such as a three-way catalyst is provided. The internal combustion engine 1 has an operating angle changing mechanism 5 that can continuously change the operating angle and the valve lift amount of the intake valve 4 as an intake timing changing unit that changes the opening timing and the closing timing of the intake valve 4. ,
A phase changing mechanism 6 that can continuously change the center phase of the operating angle of the intake valve 4.

An ECU (engine control unit) 7 serving as an engine control unit includes an engine cooling speed detected by a water temperature sensor 8 in addition to an engine speed, an engine load, a suction negative pressure, and an exhaust temperature detected or estimated by various sensors. It is a known microcomputer including a memory and a CPU for storing and executing various engine control programs based on the water temperature, the catalyst temperature detected by the catalyst temperature sensor 9, and the like. That is, the ECU 7 outputs a control signal to various actuators and the like according to the engine operating state, and controls the operation of the engine 1 in an integrated manner.

More specifically, the ECU 7 outputs a control signal to the first hydraulic device 11 that switches the hydraulic pressure supplied to the operating angle control actuator 10 that hydraulically drives the operating angle changing mechanism 5, and controls the phase changing mechanism 6 Second hydraulic device 1 for switching hydraulic pressure supplied to driven phase control actuator 12
3 and outputs a control signal to an ignition timing control device (ignition timing changing means) 14 for changing the spark ignition timing of a spark plug (not shown) provided for each cylinder. By the ignition timing changing device 14, for example, the spark ignition timing by the ignition plug is corrected to be more retarded than the optimum ignition timing that gives the best efficiency.

Next, the operating angle changing mechanism 5 will be described with reference to FIGS. The operating angle changing mechanism 5 is attached to the driving shaft 21 which is rotatable around the axis by the rotational power transmitted from the crankshaft via the phase changing mechanism 6, and is swingably attached to the driving shaft 21. Swing cam 22 which comes into contact with and presses valve lifter 4a
An eccentric cam 23 eccentrically provided on the drive shaft 21 and an operating angle control actuator 10 for changing the operating angle.
, A control cam 25 eccentrically provided on the control shaft 24, and a rocker arm 2 rotatably mounted on the control cam 25.
6, a ring-shaped first link 27 that links one end of the rocker arm 26 and the eccentric cam 23, a rod-shaped second link 28 that links the other end of the rocker arm 26 and the swing cam 22, have.

Therefore, when the drive shaft 21 rotates in conjunction with the crankshaft, the first link 27 substantially translates around the eccentric cam 23 of the drive shaft 21 and the first link 27 moves.
The swing cam 22 swings through the rocker arm 26 and the second link 28 linked to the link 27, and the intake valve opens and closes.

Further, by rotating the control shaft 24 in accordance with the operating state of the engine, the position of the control cam 25, which is the rocking center of the rocker arm 26, with respect to the engine body changes.
The initial posture of each of the links 27 and 28 and the swing cam 22 changes. As a result, as shown in FIG. 3, while the center phase of the operating angle of the intake valve with respect to the crank angle remains substantially constant, the operating angle and the valve lift of the intake valve continuously change. In addition, the upper part of FIG. 4 shows a state of zero lift, and the lower part shows a state of full lift.

In the operating angle changing mechanism 5 having such a configuration, since the swing cam 22 for pushing down the valve lifter 4a of the intake valve 4 is arranged coaxially with the drive shaft 21, the swing cam 2
There is no possibility that the shaft 2 may be displaced from the drive shaft 21 and the control accuracy is excellent, and the rocker arm 26 and the links 27 and 28 are integrated around the drive shaft 21 to reduce the size of the mechanism. be able to. Eccentric cam 2
Many of the connecting portions between the members are in surface contact, such as the bearing portion between the third link 27 and the first link 27 and the bearing portion between the control cam 25 and the rocker arm 26. ， Excellent in reliability. Further, when the operating angle changing mechanism 5 is applied to a general direct-acting valve train having a fixed cam and a camshaft, the swing cam 22 and the drive shaft are located at the positions of the fixed cam and the camshaft. 21 can be arranged, and the layout change is very small, so that the application is very easy.

FIG. 5 shows the phase changing mechanism 6. The phase changing mechanism 6 includes an inner peripheral gear (first gear) 31 fixed or integrally attached to the outer periphery of one end of the drive shaft 21 (or camshaft), and a cam pulley (or sprocket).
An outer peripheral gear (second gear) 33 fixed or integrally attached to the inner periphery of the inner peripheral gear 32 and a helical gear 34 meshing with the inner peripheral gear 31 and the outer peripheral gear 33 are formed on the inner periphery and the outer periphery, respectively. Plunger 35.

The cam pulley 32 is disposed coaxially on the outer periphery of the drive shaft 21. To the cam pulley (or sprocket) 32, rotational power is transmitted from a crankshaft via a timing belt (or timing chain) (not shown) wound around the cam pulley, and the cam pulley (or sprocket) rotates in synchronization with the crankshaft.

The plunger 35 is a phase control actuator (driving means) 1 for changing the center phase of the operating angle of the intake valve.
2 drives the shaft 21 in the axial direction of the drive shaft 21. That is, in the initial state where the hydraulic pressure is not supplied to the hydraulic chamber 36, the plunger 35 is biased in the retard direction (leftward in FIG. 5) by the spring force of the return spring 37, and the center of the operating angle of the intake valve is set. The phase is held on the retard side in FIG. On the other hand, when the predetermined hydraulic pressure is supplied to the hydraulic chamber 36 by the second hydraulic device 13 (see FIGS. 1 and 2), the plunger 35 is advanced in the advance direction (rightward in FIG. 5) against the spring force of the return spring 37. Direction), and the center phase of the operating angle of the intake valve is changed to the advanced side in FIG. Then, by appropriately controlling the oil pressure in the oil pressure chamber 36, the plunger 35 is moved and held at an arbitrary position, and the center phase of the operating angle of the intake valve is changed and held at a substantially arbitrary value. Can be.

The operating angle changing mechanism 5 and the phase changing mechanism 6 can be used together without interfering with each other. By individually controlling the drive of the operating angle changing mechanism 5 and the phase changing mechanism 6, the opening timing (IVO) and closing timing (IVC) of the intake valve are controlled to substantially arbitrary values independently of each other. It is possible to

FIG. 6 shows the correlation between the operating characteristics (IVO, IVC, valve lift) of the intake valve and the effect of increasing the exhaust gas temperature in a cold state of the engine.

Here, as a feature of this embodiment, in a cold state, the ignition timing is retarded as much as possible (to a stability limit at which combustion becomes unstable) and the combustion start timing is retarded, so that the exhaust gas temperature is reduced. Is quickly raised to achieve early activation of the catalyst 3 provided in the exhaust passage 2. Therefore, the exhaust temperature increase effect in the figure can be replaced with the retard limit of the ignition timing, that is, the retard limit.

Retardation of IVO (when retarding from exhaust top dead center) If IVO is retarded from exhaust top dead center, intake air is not initially supplied even after entering the suction stroke. Negative pressure increases rapidly. In other words, the piston speed is the maximum at the stroke center and monotonically increases from the exhaust top dead center to the stroke center. Therefore, if the IVO is delayed from the top dead center, the negative pressure in the cylinder increases rapidly. At the same time, the intake flow velocity when the intake valve is opened becomes extremely large. When the negative pressure in the cylinder increases, the pump loss increases, but the intake air temperature increases accordingly. In addition, due to the increase in the intake flow velocity, the atomization of the fuel injected into the intake port is sufficiently promoted, and the combustion state is improved. Further, the combustion speed itself increases in response to the increase in the degree of intake turbulence accompanying the increase in the intake air flow velocity. As described above, if the IVO is delayed from the top dead center of the exhaust gas, the combustion state is improved, and accordingly, the retard limit of the ignition timing can be expanded (delayed), and the effect of increasing the exhaust temperature is improved. I do.

Reducing the Lift of the Intake Valve When the valve lift is reduced, the intake flow velocity increases as the opening area of the intake passage decreases. In particular, since the nozzle effect (minimum throttle portion) between the intake valve and the valve seat increases, atomization of the fuel injected into the intake port is effectively promoted, and the ignition timing retard limit (exhaust temperature rise effect). Can be expanded.

Retardation of IVC (when retarding from bottom dead center of intake) When IVC is retarded from bottom dead center of intake, the actual compression ratio decreases. This is because the air-fuel mixture sucked into the cylinder flows back into the intake port at the beginning of the compression stroke. Of course,
Since the charging efficiency also decreases as the actual compression ratio decreases, the suction negative pressure also decreases. Further, the temperature of the air-fuel mixture at the time of compression is reduced due to the reduction of the compression ratio, and the combustion speed is reduced. Furthermore,
Since the suction negative pressure is reduced, fuel vaporization is not so promoted, and the combustion speed is also reduced. As described above, when the IVC is retarded from the bottom dead center, the retard limit of the ignition timing tends to be reduced (advanced).

Advancement of IVC (when advanced from bottom dead center of intake) When the IVC is advanced beyond bottom dead center of intake, the actual compression ratio is similar to the case where it is retarded from bottom dead center. Causes a decrease in As a phenomenon, unlike the case where the IVC is retarded, the air-fuel mixture sucked into the cylinder adiabatically expands from the IVC to the bottom dead center.
The mixture temperature at the bottom dead center will decrease. As a matter of course, the charging efficiency is also reduced, so that the suction negative pressure is also reduced.
Therefore, when the IVC is advanced from the bottom dead center, the combustion speed tends to decrease, and the retard limit of the ignition timing tends to decrease.

In the case where the IVC is set in the vicinity of the intake bottom dead center. In this case, contrary to the case where the IVC is retarded or advanced, the intake negative pressure increases with the increase of the actual compression ratio. Speed increases. Therefore, the retard limit of the ignition timing can be expanded.

For this reason, as shown in FIGS. 7 and 8, in the cold state, the IVO is retarded more than the intake top dead center mainly for the purpose of expanding the retardation limit of the ignition timing. I have. Specifically, in a cold state, the IVO is greatly delayed compared to a warm-up state under substantially the same operating conditions (engine speed, engine load, acceleration, etc.).

Further, in the cold state, the closing timing (IVC) of the intake valve is mainly set to increase the retard limit of the ignition timing.
Is set near the bottom dead center, and the operating angle and valve lift are set to be equal to or less than the warm-up state under almost the same operating conditions (engine speed, engine load, acceleration, etc.). .

The individual operating states will be described in detail with reference to FIG. 7 and FIG.
In 1), in order to mainly improve the startability, an initial setting in which the IVO is set at the top dead center and the IVC is set near the bottom dead center is applied. That is, by retarding the IVO from the top dead center, the intake air flow rate is mainly increased to improve combustion, and the IVC is set near the bottom dead center mainly for the purpose of ensuring the actual compression ratio. In the warm-up idle state (H2), the same initial settings as in the cold start (C1) are applied. Therefore, when stopping the engine in the warm-up idle state,
There is no need to change the operating characteristics of the intake valve.

In the cold high idle state (C2), the valve lift and the operating angle are set equal to or less than the warm idle state (H2), and the center phase φ is mainly retarded. In other words, compared with the time of cold start (C1), IV
While keeping C near the bottom dead center of the intake, the IVO is greatly retarded. The reason is that the warm-up idle state (H
In the case of 2), the IVO is retarded from the top dead center. However, since the main purpose is to reduce the pump loss, the degree of the retard is set in the cold high idle state (C2).
Smaller than. On the other hand, in the cold high idle state (C2) where the rotational speed is relatively high, the in-cylinder negative pressure and the intake air flow rate are increased to improve combustion, and the retard limit of the ignition timing is expanded to increase the exhaust temperature increase effect. The main purpose is to obtain the maximum compression ratio, and therefore, the IVO is delayed as much as possible within a range where the actual compression ratio does not excessively decrease.

In the cold steady running state (C3), the amount of intake air is larger than in the cold high idling state (C2), so that the operating angle must be increased. As described above, the IVC is preferably near the bottom dead center. Accordingly, in the cold steady running state (C3), the cold high idling state (C3)
Compared to 2), the retard angle of the IVO is reduced by an amount corresponding to the increase in the operating angle. That is, in the cold state, the retard angle of the IVO is reduced in accordance with the increase in the engine load. In the cold running steady state (C3), the warm-up R
The center phase φ is set to be largely retarded compared to the / L state (H3).

In the cold acceleration state (C4), the amount of intake air is further increased as compared with the cold steady running state (C3). Therefore, it is necessary to increase the operating angle accordingly. In this case, since a large amount of the air-fuel mixture burns, there is a margin to slightly delay the IVC from the bottom dead center. Therefore, the increase in the operating angle is distributed to the relief of the retard angle of the IVO and the retardation of the IVC. Specifically, it is sufficient to make the center phase φ substantially constant and increase only the operating angle in the cold steady running state (C3). By the way, the warm-up acceleration state (H4
In a, H4b, H4c), the IVC is set to be significantly advanced compared to the cold acceleration state (C4).

FIG. 9 is a timing chart showing a specific control situation in a transitional period from the start of the cold (C1) to the high idle state of the cold (C2).

At the time of cranking, it is necessary to set the ignition timing to the optimum ignition timing before the compression top dead center, at which the ignition is most easily started. Further, the operating angle and the center phase of the intake valve are set so that IVC and IVO have the set values shown in FIG. 7 (C1). When shifting from this cranking to a cold state such as a cold high idle state, the ignition timing is retarded from the optimal ignition timing as much as possible in order to quickly raise the exhaust gas temperature and activate the catalyst early.

First, in the cold high idle state (C2),
The IVO is retarded more quickly than during cranking. Specifically, the central phase is greatly retarded while the operating angle is slightly reduced according to the rotation speed. Along with this,
The IVC shifts from before the bottom dead center to after the bottom dead center. However, the IVC is kept near the bottom dead center, and the adverse effect on the actual compression ratio is small. Then, the ignition timing is retarded from the optimum ignition timing toward the vicinity of the compression top dead center according to the combustion state. Specifically, the ignition timing is gradually retarded because the combustion state improves over time.

FIG. 10 is a timing chart showing a control state in a case where the state is shifted from the cold high idling (C2) to the cold steady running (C4) through the cold slow acceleration (C3) and then to the warm state. Although it looks like a complicated control, it basically follows the settings in FIG.

In a situation where the load increases, such as in the slow acceleration state (C3), as described above, I is increased with an increase in the operating angle.
Since the retard angle of VO is gradually reduced, the retard limit of the ignition timing is also gradually reduced. That is, the ignition timing gradually advances in accordance with the increase in the load. When the catalyst 3 reaches the activation temperature, that is, the conversion start temperature (T), the ignition retard is gradually released thereafter, and the IVO, I
VC is also gradually returned to the setting after warming up. Specifically, control is performed toward a target value after warm-up, at which driving performance such as fuel efficiency becomes the best. For reference, the ignition timing in the warm-up state (corresponding to the optimum ignition timing) is drawn by a broken line (a), and it can be seen that the ignition timing is significantly retarded in the cold state compared to the warm-up state. .

As shown in FIGS. 9 and 10, in the present embodiment, in order to improve the operation response and the like, the operation angle changing mechanism 5 suppresses the change width of the operation angle to a minimum, thereby reducing the phase. The change width of the center phase φ by the change mechanism 6 is set relatively large. And while keeping the IVC near the bottom dead center,
The IVO is finely controlled toward the retard limit.

Further, as shown in FIG. 7, in the initial setting (C1) when the engine is started and when the engine is stopped, the IVO is set to a position after the top dead center and the IVC is set to a position near the bottom dead center (before the bottom dead center). Therefore, mainly by slightly delaying the center phase, it is possible to quickly shift to the cold high idle state.
Therefore, as in the case of the cryogenic start, the hydraulic actuator 1
Even when the response of 0, 12, etc. is extremely slow, the retard limit of the ignition timing can be expanded relatively early.

FIG. 11 is a flowchart showing the flow of control executed by the ECU 7. In S10, it is determined (detected) whether the apparatus is in a warm-up state or a cold state. Specifically, it is determined whether the cooling water temperature or the catalyst temperature detected by the water temperature sensor 8 or the catalyst temperature sensor 9 is equal to or higher than a predetermined value. If YES, it is determined that the engine is warm, and if NO, it is determined that the engine is cold. Following S11
Alternatively, in S21, control maps of the ignition timing (IT), IVO, and IVC for the cold state or the warm-up state, which are individually prepared in advance, are read. In subsequent S12 or S22, various engine operating conditions such as the engine speed and the throttle opening are detected. By referring to the control map read in S11 or S21 in accordance with the engine operating conditions, the operation angle changing mechanism 5 and the phase changing mechanism 6 are drive-controlled so that IVO and IVC become target values ( In S13 and S14, or S23 and S24), the drive of the ignition timing changing device 14 is controlled so that IT becomes the target value (S15 and S16, or S25 and S26).

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a combustion control device for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a perspective view showing the operating angle changing mechanism of the embodiment.

FIG. 3 is a characteristic diagram showing a change characteristic of an operating angle and a valve lift of an intake valve by the operating angle changing mechanism.

FIG. 4 is an operation explanatory view showing a mode at the time of minimum or maximum swing of a zero lift and a full lift of the operating angle changing mechanism.

FIG. 5 is a sectional view and a characteristic diagram of the phase changing mechanism of the embodiment.

FIG. 6 is an explanatory diagram showing a relationship between an operation characteristic of an intake valve and an exhaust temperature increase effect.

FIG. 7 is an explanatory diagram showing operation characteristics of an intake valve in a cold state.

FIG. 8 is an explanatory diagram showing operating characteristics of an intake valve in a warm-up state.

FIG. 9 is a timing chart when shifting from a cold start to a cold high idle state.

FIG. 10 is a timing chart when shifting from a cold high idle state to a warm state through a cold acceleration state and a cold steady running state;

FIG. 11 is a flowchart showing a control flow according to the embodiment.

[Explanation of symbols]

 2. Exhaust passage (exhaust system) 3. Catalyst 4. Intake valve 5. Operating angle changing mechanism (intake characteristic changing means) 6. Phase changing mechanism (intake characteristic changing means) 8. Water temperature sensor (cooler detecting means) 9. Catalyst Temperature sensor (cooling device detecting means) 14 ... Ignition timing changing device (ignition timing changing means)

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F01N 3/24 ZAB F01N 3/24 ZABR 3G301 F02D 41/06 320 F02D 41/06 320 43/00 301 43/00 301B 301Z F02P 5/15 F02P 5/15 E (72) Inventor Tsuneyasu Nohara 2 Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Pref. Nissan Motor Co., Ltd. (72) Takanobu Sugiyama 2 Takara-cho 2 Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Automobile Stock In-house F-term (reference) 3G018 AB07 AB16 BA02 BA09 BA10 BA17 BA19 BA29 BA33 CA12 CA19 DA03 DA70 EA03 EA12 EA17 EA22 EA32 EA35 FA01 FA06 FA08 FA16 GA09 3G022 CA01 CA02 CA03 CA06 DA02 FA03 GA05 GA07 GA09 GA10 3G084 BA23 BA23 CA09 DA10 EC03 FA11 FA18 FA20 FA27 FA33 3G091 AA02 AA17 AB01 AB03 BA03 CB05 CB08 DA07 DB10 EA01 EA03 EA06 EA07 EA16 EA17 EA18 FA02 FA04 FA12 FA17 FA18 FB02 FC07 HA38 HA39 3G092 AA01 DA01 DA02 DA02 DA02 15 DF05 DG05 DG09 EA04 EA05 EA11 FA18 GA01 GA02 GA04 GA17 HA11Z HA13Z HC09Z HD02Z HE01Z HE08Z 3G301 HA01 HA19 JA26 KA01 KA05 KA07 KA24 LA07 LC01 LC08 LC10 NA08 NB18 NE12 PA07Z PA17Z PD12Z PE01Z PE08Z

Claims (11)

[Claims] An intake characteristic changing means for changing an opening timing and a closing timing of an intake valve, an ignition timing changing means for changing an ignition timing, and a cold detecting means for detecting a cold state of an engine, and In a combustion control apparatus for a spark ignition type internal combustion engine in which an exhaust purification catalyst is provided in an exhaust system, in the above-mentioned cold state, the ignition timing is retarded from the optimal ignition timing, and the ignition timing A combustion control device for an internal combustion engine, characterized in that the opening timing of an intake valve is retarded so as to increase the pressure. 2. The combustion control device for an internal combustion engine according to claim 1, wherein in the cold state, the opening timing of the intake valve is retarded from the exhaust top dead center. 3. The combustion control device for an internal combustion engine according to claim 1, wherein in the cold state, the opening timing of the intake valve is retarded more than in the warm-up state under substantially the same operating conditions. 4. The intake valve close timing is set near the intake bottom dead center in the cold state.
The combustion control device for an internal combustion engine according to any one of the above. 5. In the cold state, the retardation of the opening timing of the intake valve and the retardation of the ignition timing are reduced in accordance with an increase in the engine load. 5. The combustion control device for an internal combustion engine according to any one of 4. 6. At least in a cold high idle state,
The combustion control device for an internal combustion engine according to any one of claims 1 to 5, wherein the ignition timing is retarded to near the compression top dead center. 7. The intake characteristic changing means includes an operating angle changing mechanism for changing an operating angle and a valve lift of an intake valve, and a phase changing mechanism for changing a central phase of an operating angle of the intake valve. The combustion control device for an internal combustion engine according to any one of claims 1 to 6, wherein: 8. The combustion of an internal combustion engine according to claim 7, wherein the valve lift amount of the intake valve is set to be equal to or less than the warm state under substantially the same operating conditions in the cold state. Control device. 9. In a cold high idling state in which the engine speed is higher than in a warm idling state, the center phase of the operating angle of the intake valve is mainly retarded compared to the warm idling state. The combustion control device for an internal combustion engine according to claim 7 or 8, wherein: 10. A drive shaft which is rotated by a rotational power transmitted from a crankshaft;
A swing cam that is swingably mounted on the drive shaft and contacts the intake valve to operate the intake valve; an eccentric cam provided eccentrically to the drive shaft; and a control shaft that is driven to rotate when the operating angle is changed. A control cam provided eccentrically to the control shaft, a rocker arm rotatably mounted on the control cam, a first link for linking one end of the rocker arm and the eccentric cam, and the rocker arm The combustion control device for an internal combustion engine according to any one of claims 7 to 9, further comprising a second link that links the other end of the swing cam and the swing cam. 11. A first gear provided on a drive shaft for opening and closing an intake valve via the operation angle changing mechanism, a first gear provided coaxially with the drive shaft, and a phase change mechanism provided with a crankshaft. A second gear provided on a sprocket or pulley that rotates synchronously, a plunger having a helical gear meshing with the first gear and the second gear, and a drive for driving the plunger in the axial direction of the drive shaft when the phase is changed The combustion control device for an internal combustion engine according to any one of claims 7 to 10, comprising: