JP2000170556A - Exhaust valve operation controller for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly increase the temperature of a catalyst to an activation temperature without causing any reductions in the intake efficiency of an engine in the exhaust valve operation controller of an internal combustion engine. SOLUTION: When there is a request to increase the temperature of exhaust purifying catalyst, an exhaust valve operation varying means 60A is controlled by a control means 20, an exhaust valve is temporarily opened separately from the operation of the exhaust valve during an exhaust process after ignition and before the end of an expansion process, the exhaust gas of a temperature higher than that of exhaust gas during the exhaust process is discharged, and the temperature of the exhaust purifying catalyst is quickly increased to an activation temperature allowing a purifying function to be exhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust valve operation control device for an internal combustion engine, which is suitable for use in a vehicle having an exhaust purification catalyst.

[0002]

2. Description of the Related Art Unburned HC (hydrocarbon), CO contained in exhaust gas of an engine such as a gasoline engine has hitherto been used.
In order to purify harmful components such as (carbon monoxide) and NO _x (nitrogen oxide), an exhaust gas purifying catalyst (exhaust gas purifying catalytic converter) is provided in the exhaust passage.

[0003] Exhaust purification catalyst (hereinafter simply referred to as catalyst)
Generally cannot exhibit a sufficient exhaust gas purification function unless the temperature rises to a predetermined activation temperature range,
The problem was how to quickly raise the temperature of the catalyst to the active temperature range. Therefore, for example, Japanese Utility Model Laid-Open No. 5-96444 discloses that the phase of an exhaust cam is advanced from a normal position and an exhaust valve is opened at an early stage to discharge high-temperature combustion gas, and the exhaust gas is used as a catalyst. There has been proposed a technique for achieving early activation of the above.

[0004]

However, when the phase of the exhaust cam is advanced as described above, the exhaust valve is closed early, and the overlap (the exhaust valve and the intake valve are both open) is required. Therefore, when the intake efficiency is taken into consideration, the advance amount of the phase of the exhaust cam is naturally limited.

[0005] Therefore, in the above-mentioned technique, high-temperature exhaust gas cannot be sufficiently supplied to the catalyst, and there is a problem that it takes time for the catalyst to reach the activation temperature. Further, in the above-described technique, the phase change between the normal exhaust phase and the early exhaust phase can only be performed gradually in consideration of the drivability, so that the responsiveness of the exhaust valve operation switching control is poor. This also causes the catalyst not to be activated early.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above-described problems, and an internal combustion engine capable of rapidly increasing the temperature of a catalyst to an activation temperature without deteriorating the intake efficiency of the engine. It is an object of the present invention to provide an exhaust valve operation control device.

[0007]

Therefore, in the exhaust valve operation control apparatus for an internal combustion engine according to the first aspect of the present invention, when there is a request to raise the temperature of the exhaust purification catalyst, the control means controls the exhaust valve operation variable means. In addition to the operation of the exhaust valve during the exhaust stroke, the exhaust valve is temporarily opened after ignition and before the end of the expansion stroke, so that the exhaust gas having a higher temperature than the exhaust gas during the exhaust stroke is controlled. And the temperature of the exhaust gas purifying catalyst is quickly raised to an activation temperature at which the purifying function can be exhibited.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An exhaust valve operation control apparatus for an internal combustion engine according to one embodiment of the present invention will be described below with reference to FIGS. The engine according to the present embodiment is a four-stroke engine that performs each of the intake, compression, expansion, and exhaust strokes during one operation cycle. As shown in FIG. 2, fuel is directly injected into a cylinder and combustion is performed by spark ignition. The engine is configured as an in-cylinder injection internal combustion engine (in-cylinder injection gasoline engine), and in particular, is configured here as a V-type in-cylinder injection gasoline engine.

An intake passage 2 and an exhaust passage 3 are connected to the combustion chamber 1, and the intake passage 2 and the exhaust passage 3 are controlled to communicate with the combustion chamber 1 by an intake valve 4B and an exhaust valve 4A, respectively. ing. The intake passage 2 is provided with an air cleaner and a throttle valve (not shown), and the exhaust passage 3 is provided with an exhaust purification catalyst (hereinafter simply referred to as a catalyst) 6 for removing harmful components in exhaust gas and a muffler (not shown). (Silencer) is provided.

Reference numeral 8 denotes an injector (fuel injection valve) which is arranged so that its opening faces the combustion chamber 1 so as to directly inject fuel toward the combustion chamber 1 in the cylinder 32. Further, the operation of the injector 8 is controlled based on a signal from an electronic control unit (ECU) 20 as a control means. here,
The exhaust valve 4A is provided with a variable valve mechanism (VVT) 60A as an exhaust valve operation variable means capable of switching the operation state (valve opening timing and lift amount) of the exhaust valve 4A. On the other hand, the intake valve 4B is provided with a valve operating mechanism 60B that always drives the intake valve 4B to open at a constant timing.

By controlling the switching of the operating state of the variable valve mechanism 60A, in addition to the usual valve opening drive in the exhaust stroke, after the ignition and before the end of the expansion stroke (here, the expansion stroke). The exhaust valve 4A is driven to open during (middle), whereby exhaust gas having a higher temperature than during the exhaust stroke is discharged to the exhaust passage 3 to raise the temperature of the catalyst 6 so that early activation can be performed. It is. Hereinafter, exhaust during such an expansion stroke is referred to as sub-exhaust.

The mode for performing the sub exhaust is as follows.
As described later, a mode in which the sub exhaust is performed alone (first
Mode) and a mode in which sub-exhaust is performed together with additional fuel injection (second mode), and these modes can be switched according to the operating mode of the engine. In this embodiment, half of all cylinders provided in the engine are configured to be able to execute only the first mode, and the remaining half of the cylinders are executed only in the second mode. Has become available.

The timing suitable for performing the sub-exhaust is slightly different between the first mode and the second mode. In the present embodiment, the sub-exhaust is performed at an appropriate timing in each mode. The variable valve mechanism 60 of the cylinder capable of executing the first mode
A and the variable valve mechanism 60A that can execute the second mode are configured to have different characteristics.

Further, the first mode and the second mode include:
The configuration is such that only one of the modes is selectively executed. As a result, only half of the cylinders of the engine perform the sub-exhaust, so that a rapid decrease in engine torque is prevented. In other words, discharging the exhaust gas during the expansion stroke means that the combustion gas that generates the engine torque by pressing down the piston 31 in the cylinder is discharged at an early stage, which leads to a loss of the engine torque. Even when the temperature of the catalyst 6 is increased, the sub-exhaust is performed only in half of the cylinders of the engine so that a rapid decrease in engine torque does not occur.

The variable valve mechanism 60A and the valve mechanism 6
0B will be described later. By the way, as shown in FIGS. 1 and 2, this engine includes a catalyst temperature sensor 3A, a coolant temperature sensor 71, and an accelerator position sensor (AP).
S) 72, crank angle sensor 73, idle switch 7
4, various sensors such as a cam angle sensor 75 are provided, and a detection signal from each sensor is sent to the ECU 20.

The catalyst temperature sensor 3A is provided in the catalyst 6, and detects the temperature (catalyst temperature) T _WC in the catalyst 6. The cooling water temperature sensor 71 is inserted into a water jacket 30B provided in a cylinder block between the right bank and the left bank, and detects a cooling water temperature T _{W of the} engine. Furthermore, an accelerator position sensor 72 is for detecting the accelerator opening theta _A as an engine load. The crank angle sensor 73 is provided on the crankshaft 5 and detects the engine speed Ne. The idle switch 74 outputs an idle detection signal P during an idle state.

Further, in the present engine, as an operation mode, fuel is injected during the compression stroke, and the intake air flowing into the combustion chamber 1 is subjected to vertical vortex flow (counter tumbling) using the concave portion 31A on the top surface of the piston 31. A super-lean operation mode (compression lean operation mode) in which fuel spray is collected in the vicinity of the ignition plug 7 to operate in a stable stratified combustion state while utilizing the longitudinal vortex flow, and during the intake stroke. Inject fuel,
A lean operation mode (intake lean operation mode) in which the combustion chamber 1 is premixed and burned in a substantially uniform gaseous mixture state to operate in a lean state of fuel, and O ₂ so that the air-fuel ratio becomes close to the stoichiometric air-fuel ratio. A stoichiometric operation mode in which feedback control is performed based on sensor information or the like (stoichiometric feedback operation mode), and an enrichment operation mode in which operation is performed in a fuel rich state (that is, the air-fuel ratio is smaller than the stoichiometric air-fuel ratio) ( Open loop mode). Then, the ECU 20, based on detection information from each sensor is adapted to set the operating mode of the engine, during idling, in accordance with the coolant temperature T _W is lower, whereas, during the running of the vehicle As the engine speed Ne and the effective pressure Pe indicating the load state increase, the compression lean operation mode, the intake lean operation mode, the stoichiometric feedback operation mode, and the open loop mode are selected in this order. I have. Incidentally, effective pressure Pe is intended to be calculated from the information of the engine rotational speed Ne and the accelerator opening theta _A.

The operation in the super lean operation mode and the lean operation mode is referred to as lean operation, the operation in the stoichiometric operation mode is referred to as stoichiometric operation (stoichiometric air-fuel ratio operation), and the operation in the enrich operation mode is referred to as rich operation. . Next, the main functions of the present invention will be described with reference to FIG.
When the temperature of the catalyst 6 is requested (in the present embodiment, when the catalyst temperature T _WC detected by the catalyst temperature sensor 3A is lower than the predetermined temperature T _WC0 ), the operation state is changed. Accordingly, the operation of the variable valve mechanism (exhaust valve operation variable means) 60A of the exhaust valve 4A and the injector 8 is changed to E.
Controlled by the CU 20, the catalyst 6 is activated early.

That is, when the catalyst temperature T _WC is lower than the predetermined temperature T _WC0 , the catalyst 6 cannot exert a sufficient exhaust gas purifying function. Therefore, according to a control command from the ECU 20, during the rich operation or the stoichiometric operation, In the first mode, only the sub-exhaust is performed, and during the lean operation, additional fuel injection and sub-exhaust are performed in the second mode. As a result, the exhaust gas having a higher temperature than the exhaust gas discharged during the normal exhaust stroke is discharged, and the temperature of the catalyst 6 is quickly raised to an activation temperature or higher at which a sufficient exhaust purification function can be exhibited. It is.

It is desirable that the predetermined temperature T _WC0 be set higher than the activation temperature (the lower limit of the activation region of the catalyst 6) by a predetermined temperature α in consideration of control delay. Therefore, here, the predetermined temperature T _WC0 is obtained by adding the predetermined temperature α to the activation temperature (predetermined temperature T _WC0 = activation temperature + predetermined temperature α). Here, the additional fuel injection is a control command from the ECU 20 during the expansion stroke for the purpose of raising the temperature of the combustion gas in the cylinder, separately from the fuel injection (main injection) for the main combustion that generates the engine torque. The fuel is injected by the injector 8 in response to the fuel injection, and the additionally injected fuel (additional fuel) is ignited by the flame propagation of the main combustion. However, since air for additional fuel combustion (additional combustion) is required in addition to the air required for main combustion, additional fuel injection is performed during lean operation when there is an excess of air with respect to the main fuel. Can only do it.

Further, as described above, the sub-exhaust discharges a part of the combustion gas from the cylinder also in the expansion stroke, separately from the exhaust stroke. That is, the combustion gas which is ignited by the spark plug 7 immediately before the start of the expansion stroke and rapidly expands pushes down the piston 31 to generate engine torque, but the temperature of the combustion gas decreases in accordance with the expansion. Therefore, in order to supply the combustion gas having a lower degree of expansion (expansion ratio) than the combustion gas in the cylinder during the exhaust stroke and a higher temperature to the catalyst 6, exhaust (sub-exhaust) is performed during the expansion stroke. -ing

When the sub-exhaust is performed, the combustion gas which should normally push down the piston 31 to the bottom dead center is discharged from the cylinder at an early stage, and the engine torque is reduced. When the engine is idling, the effect of such a decrease in the engine torque is small, but the decrease in the engine torque is not negligible while the vehicle is running, so the amount of fuel added to compensate for the decrease in the engine torque is added. Is main injected in the next intake stroke or compression stroke.

Next, the control of the sub exhaust and the additional fuel injection will be described with reference to FIG. 3 and FIG. In the present embodiment, when the temperature of the catalyst 6 needs to be raised (early activation), as described above, the sub exhaust is performed during the rich operation or the stoichiometric operation, and the sub exhaust and the additional fuel injection are combined during the lean operation. To do it.

First, a description will be given of the sub-exhaust performed when the catalyst 6 needs to be activated early during the rich operation or the stoichiometric operation. During the rich operation or the stoichiometric operation, a fuel injection signal is input from the ECU 20 to the injector 8 during the intake stroke, and during this time, the injector 8
The fuel is injected into the combustion chamber 1. In addition,
This fuel injection is fuel injection for main combustion, that is, main injection.

On the other hand, during the compression stroke, the air-fuel mixture in the combustion chamber 1 is compressed by the rise of the piston 31 with the rotation of the crankshaft 5, and the temperature in the combustion chamber 1 (in-cylinder temperature) is reduced by the piston 31. It rises according to the compression ratio of the air-fuel mixture inside. Then, at the end of the compression stroke in which the fuel injection from the injector 8 is completed, an ignition signal is input from the ECU 20 to the ignition plug 7, and the ignition plug 7
To ignite the air-fuel mixture in the interior.

Due to the combustion of the air-fuel mixture, the temperature in the combustion chamber 1 rapidly rises with the pressure in the cylinder, and the position of the piston 31 reaches a maximum (TDC: Top Dead Center) at a point slightly after the top dead center (TDC). For example, 1000 ° C. or higher). Also,
The increase in the pressure in the combustion chamber 1 accompanying this combustion is output from the crankshaft 5 as engine torque. And
When the piston 31 exceeds the top dead center, a transition is made from the compression stroke to the expansion stroke, but as the in-cylinder pressure decreases in this expansion stroke, the temperature in the combustion chamber 1 decreases as shown in FIG. .

In order to activate the catalyst 6 early, the catalyst 6
Quickly increase the activation temperature (for example, about 570).
K). However, even if the temperature in the combustion chamber 1 reaches a high temperature due to the main combustion, the temperature of the combustion gas gradually decreases with the expansion of the volume in the subsequent expansion stroke. Exhaust gas cannot be supplied to the catalyst 6, and the catalyst 6 cannot be activated at an early stage.

Therefore, in the present engine, the catalyst temperature T _WC detected by the catalyst temperature sensor 3A is lower than the predetermined temperature T _WC0 (predetermined temperature T _WC0 = activation temperature + predetermined temperature α), and the engine is operated in a rich or stoichiometric state. During operation, the ECU 20
In response to the control command, the variable valve mechanism 60A of the exhaust valve 4A is operated, and the sub exhaust is performed at the timing and the cam profile shown in FIG.

That is, since the temperature of the combustion gas in the cylinder decreases as the expansion ratio increases, the exhaust valve 4A is opened in the expansion stroke earlier than the exhaust stroke, and the combustion gas is discharged into the exhaust passage 3 at a high temperature. It is to be discharged to. Next, sub-exhaust and additional fuel injection performed when early activation of the catalyst 6 is required during lean operation will be described.

At the time of the lean operation, the amount of air is excessive with respect to the main fuel, so that the fuel that is additionally injected during the expansion stroke can be burned by the excess air to raise the temperature of the combustion gas. It is. For this reason, in the present embodiment, during the lean operation, the catalyst 6 can be activated even earlier by performing the sub-exhaust together with the additional fuel injection.

That is, prior to the sub-exhaust executed according to the timing and cam profile shown in FIG. 3, additional fuel injection (expansion stroke injection) is performed by the injector 8 in the first half of the expansion stroke according to a control command of the ECU 20. Has become. Then, the additional fuel directly injected into the combustion chamber 1 is not ignited by the ignition plug 7 but is ignited by the flame propagation of the main combustion, and burns at a relatively low temperature as compared with the main combustion. As indicated by the inside, the temperature of the combustion gas rises. Then, the heated combustion gas is discharged into the exhaust passage 3 in the expansion stroke by the sub-exhaust performed thereafter, and high-temperature exhaust gas is also discharged in the exhaust stroke, so that the temperature of the catalyst 6 can be raised quickly. It is like that.

When the sub-exhaust is performed together with the additional fuel injection, the sub-exhaust is desirably performed after the additional fuel injection. The timing of starting the exhaust is late. Further, the energy generated by the combustion of the additional fuel is used exclusively for increasing the temperature in the combustion chamber 1 without being converted into an increase in the pressure in the combustion chamber 1.
Therefore, the engine torque does not fluctuate due to the additional fuel.

Next, the variable valve mechanism 60A and the valve mechanism 6
0B will be described. As described above, in the present embodiment, the exhaust valve 4A is provided with the variable valve mechanism 60A, and the intake valve 4B is provided with the variable valve mechanism 60B. The variable valve mechanism 60A is, for example, described later. Thus, the configuration is the same as that disclosed in JP-A-6-33719.

More specifically, as shown in FIGS. 4 and 5A, the variable valve mechanism 60A of the exhaust valve 4A rotates in accordance with the rotation of the crankshaft 5 of the engine (see FIG. 2). Cam 12A, 1 provided on camshaft 11A
3A and rocker arms 14A and 15A driven by these cams 12A and 13A.

Here, the cam 12A is a main cam for opening and driving the exhaust valve 4A to perform a normal exhaust stroke.
On the other hand, the cam 13A operates at the temperature T _WC in the catalyst 6 (see FIG. 2).
Is a sub-cam that can open and drive the exhaust valve 4A during the expansion stroke in order to activate the catalyst 6 early only when the temperature is lower than the predetermined temperature T _WC0 . The rocker arm 14A is a main rocker arm driven by the main cam 12A, and the rocker arm 15A is a sub rocker arm driven by the sub cam 13A.

On the other hand, as shown in FIG. 4, the valve operating mechanism 60B of the intake valve 4B is a mechanism having no sub-cam, sub-rocker arm and parts associated therewith with respect to the variable valve operating mechanism 60A. That is, the cam 12B includes a cam 12B for driving the opening of the intake valve 4B to perform the intake stroke and a rocker arm 14B driven by the cam 12B. The cam 12B rotates in conjunction with the rotation of the crankshaft 5 of the engine. 11B. Thereby, the intake valve 4B is pushed down via the rocker arm 14B at a predetermined rotation position by the cam 12B which rotates in conjunction with the crankshaft 5, that is, is driven to open.

Here, the exhaust valve 4A and the intake valve 4B of the present embodiment are set so as to have the cam profiles shown in FIG. 3, and the main cam 12A of the exhaust valve 4A and the cam 12B of the intake valve 4B are connected to each other. The phase difference is set to, for example, about 210 ° in the crank angle (about 105 ° in the cam angle), and the main cam 12A and the sub cam 13A of the exhaust valve 4A are set.
A is attached so as to have a predetermined phase difference Δθ (see FIG. 3) at the crank angle.

As described above, of the cylinders provided in the engine, half of the cylinders are sub-exhausted only during the rich operation or the stoichiometric operation, and the remaining half are additionally fueled only during the lean operation. The sub exhaust can be performed together with the injection. Therefore, as shown in FIG. 3, the timing at which the sub exhaust is performed differs for each half of the cylinders. Therefore, the above-described phase difference Δ between the sub cam 13A installed in the cylinder capable of performing the sub exhaust during the rich operation or the stoichiometric operation and the sub cam 13A installed in the cylinder capable of performing the sub exhaust together with the additional fuel injection during the lean operation.
θ is set slightly differently.

The maximum lift L _S of the sub cam 13A and the period during which the exhaust valve 4A is driven to open (valve opening period) θ _S are:
It is set to be slightly smaller than the maximum lift L _M and the valve opening period θ _M of the main cam 12A.
Even if the exhaust valve 4A is driven to open, that is, even if the sub exhaust is performed, only a part of the combustion gas in the cylinder is exhausted by the exhaust passage 3.
Is to be discharged.

In FIG. 3, the lift of the sub cam 13A is exaggerated, and is actually smaller than that shown. The variable valve mechanism 60A will be described in more detail with reference to FIGS. 5 (A), (B) and (C). The exhaust valve 4A is provided in two pairs as shown in FIG. 5A, and the variable valve mechanism 60A for driving the exhaust valves 4A, 4A is provided with the camshaft 11 as described above.
A and the cams 12A, 13A
Rocker arm 14A driven by 2A, 13A,
It has 15A.

Each of the rocker arms 14A and 15A is a rocker arm with a roller.
Are in contact with the exhaust valves 4A, 4A and
The rocker arm 15A is a sub rocker arm that is indirectly involved in opening and closing the exhaust valves 4A, 4A without contacting the exhaust valves 4A, 4A.

The main rocker arm 14A is shown in FIG.
As shown in (B) and (C), it is provided integrally with the rocker shaft 16. The rocker shaft 16 is pivotally supported by a bearing portion 30A provided on a cylinder head 30 (see FIG. 4) of the engine or the like.
A is configured to be able to turn around the rocker shaft 16.

At the intermediate portion of the main rocker arm 14A,
A main roller 18 that can contact the main cam 12A is provided. The main roller 18 is rotatably supported by a shaft 18A that is supported by an intermediate portion of the main rocker arm 14A so that the main roller 18 can smoothly rotate. With such a structure, the main cam 12A rotates with the camshaft 11A while rotating the main roller 1A at a predetermined rotation position.
8, the exhaust valves 4A, 4A are driven to open periodically via the main rocker arm 14A.

On the other hand, the sub rocker arm 15A is rotatably supported at its cylindrical base 62 so as to be rotatable with respect to the rocker shaft 16 (that is, the main rocker arm 14A). And a sub-roller 19 which can abut the roller. The sub-roller 19 is also pivotally supported by a shaft 19A supported by the swinging end 61 of the sub-rocker arm 15A, so that it can rotate smoothly.

Between the sub rocker arm 15A and the rocker shaft 16, a mode in which the sub rocker arm 15A is rotatable with respect to the rocker shaft 16 and does not operate in cooperation with the main rocker arm 14A (non-coupling mode).
A hydraulic piston mechanism 17 is provided as mode switching means for switching between a mode in which the sub rocker arm 15A rotates integrally with the rocker shaft 16 and operates in cooperation with the main rocker arm 14A (coupling mode).

As shown in FIGS. 5B and 5C, the hydraulic piston mechanism 17 as the mode switching means is movably disposed in the piston chamber formed in the rocker shaft 16 in the diameter direction of the rocker shaft 16. The installed piston 17A
Is provided. Then, when hydraulic oil is guided from an oil passage 16A formed in the axial center portion of the rocker shaft 16, the piston 17A is moved to the distal end side as shown in FIG. 5C [FIGS. 5B and 5C]. 5B, while the supply of the hydraulic oil is cut off, the piston 17A moves toward the base end side as shown in FIG. 5B [downward in FIGS. 5B and 5C]. To be driven.

That is, when the hydraulic oil is supplied, the sub-rocker arm 15 moves to the tip of the piston 17A.
A rotates integrally with the rocker shaft 16 to operate in cooperation with the main rocker arm 14A (cooperation mode) (see FIG. 5C). When the supply of the hydraulic oil is cut off, the piston 17A separates from the tip of the piston 17A. The sub rocker arm 15 is set to be in a mode in which the sub rocker arm 15 is rotatable with respect to the rocker shaft 16 and does not operate in cooperation with the main rocker arm 14A (non-coupling mode) (see FIG. 5B).

The hydraulic oil is supplied from the rocker shaft 1.
The operation is performed through a hydraulic oil supply system (not shown) via an oil passage 16 </ b> A in the inside 6. The supply state in which the hydraulic oil is supplied and the supply stop state in which the hydraulic oil is not supplied are switched by opening and closing the solenoid valve (hereinafter, referred to as a variable valve solenoid valve) provided in the hydraulic oil supply system by the ECU 20. It has become.

In this embodiment, the variable valve solenoid valve is controlled in accordance with the catalyst temperature T _WC from the catalyst temperature sensor 3A to switch the operation / non-operation of the exhaust valve 4A by the sub cam 13A. Thus, it is possible to switch whether or not to perform the sub exhaust for catalyst activation. Since the engine according to the embodiment of the present invention is configured as described above, control is periodically performed according to a flowchart as shown in FIG. 6, for example, and the operation mode is switched.

First, in step S10, it is determined whether cranking has been completed based on the engine speed Ne input from the crank angle sensor 73 or the cam angle sensor 75. If the engine speed Ne is higher than the predetermined speed, it is determined that combustion has already started in the engine and cranking has been completed, and step S2 is performed.
If the engine speed Ne is equal to or lower than the predetermined speed, it is determined that cranking has not been completed, and the process returns.

In step S20, it is determined whether or not the engine is idle by the idle switch 74. If the idle detection signal P is not detected, the engine is not in the idle state, that is, it is determined that the vehicle is running. Then, the process proceeds to step S150. On the other hand, if the idle detection signal P is detected, the engine is determined to be in the idle state, and the process proceeds to step S30.

Then, in step S30, the cooling water temperature
Cooling water temperature T input from the sensor 71 _WDriving mode according to
Is selected and the cooling water temperature T_WIs the cooling water reference temperature T_W0Than
Low, rich operation or stoichiometric operation is selected
The fuel injection (main injection) is controlled accordingly.
(Step S40), the process proceeds to Step S50. So
Then, in step S50, the catalyst 6 is activated.
Whether or not the catalyst temperature is inputted from the catalyst temperature sensor 3A.
T_WCAnd the catalyst temperature T_WCIs the predetermined temperature T_WC0that's all
At this time, the catalyst 6 is already activated,
It is determined that there is no
If this happens, the variable valve solenoid valve is closed and the sub exhaust is stopped.
(Step S310), and return. Meanwhile, the catalyst temperature
T_WCIs the predetermined temperature T_WC0When the temperature is lower than
If it is not possible to exhibit sufficient exhaust purification function
It is determined and compared with the exhaust gas discharged in the normal exhaust stroke
Variable to quickly raise the temperature of catalyst 6 with high temperature exhaust gas
Driving the valve-operating solenoid valve to open and drive half of the engine cylinders
In step S60, sub exhaust is performed.
The process proceeds to step S300.

Then, in step S300, it is determined whether or not the temperature of the catalyst 6 has been sufficiently raised. When the catalyst temperature T _WC is lower than the predetermined temperature T _WC0 , the catalyst 6 has not been activated yet. It is determined that the temperature needs to be raised, and the routine returns while continuing the sub exhaust. On the other hand, the catalyst temperature T
_{When the WC} is _{equal to} or higher than the predetermined temperature T _WC0 , the catalyst 6 is sufficiently activated and it is determined that there is no need to _{raise the} temperature further, and the process proceeds to step S310 to stop the sub exhaust.

Incidentally, at step S30, the cooling water temperature T
_{If W} is equal to or higher than the cooling water reference temperature T _W0 , step S7
If 0, lean operation is selected as the operation mode, and control of fuel injection (main injection) is performed in accordance with the selected operation.
Go to 80. Then, in step S80, the catalyst temperature T
_{When the WC} is _{equal to} or higher than the predetermined temperature T _WC0 , it is determined that the catalyst 6 has already been activated, and if the sub exhaust has been performed before that, the sub exhaust is stopped (step S310). On the other hand, when the catalyst temperature T _WC is lower than the predetermined temperature T _WC0, it is determined that the temperature of the catalyst 6 needs to be raised, and additional fuel injection is performed in the expansion stroke in step S90. The valve solenoid valve is driven to open to perform sub-exhaust in half of the cylinders of the engine, and the process proceeds to step S300.

On the other hand, in step S20, the engine is not in the idle state because the idle detection signal P is not detected.
That is, when it is determined that the vehicle is running, the engine speed Ne and the effective pressure Pe indicating the load state are determined according to the engine speed Ne.
The operation mode is selected (step S150), and the fuel injection (main injection) is controlled according to the selected operation mode (step S150).
160), and proceed to step S170.

In step S170, when the catalyst temperature T _WC is _{equal to} or higher than the predetermined temperature T _WC0 , it is determined that the temperature of the catalyst 6 does not need to be raised, and if the sub exhaust is being performed, the sub exhaust is stopped. On the other hand, if the catalyst temperature T _WC is lower than the predetermined temperature T _WC0, it is determined that the temperature of the catalyst 6 needs to be raised, and step S ₃₁₀ is performed.
Go to 180.

In step S180, for the cylinder performing the sub-exhaust, the fuel amount in the next main injection is corrected in order to compensate for the loss of engine torque due to the sub-exhaust. It is determined whether or not the mode is a lean operation. When it is determined in step S190 that the operation is not the lean operation, that is, the operation is the stoichiometric operation or the rich operation, the process proceeds to step S200, in which the sub exhaust is performed in half of the cylinders, and the process proceeds to step S300.
On the other hand, in the case of the lean operation, the additional fuel injection (step S210) and the sub exhaust (step
220) is performed, and thereafter, also in step S300
Proceed to.

As described above, according to the exhaust valve operation control apparatus for an internal combustion engine according to the present embodiment, the sub-exhaust is performed during the stoichiometric operation and the rich operation in which additional fuel injection cannot be performed, so that the high-temperature By exhausting the exhaust gas, the temperature of the catalyst 6 can be quickly raised and activated. Further, during the lean operation, by performing additional fuel injection simultaneously with the sub-exhaust, high-temperature exhaust gas can be discharged in the exhaust stroke in addition to the sub-exhaust, and the catalyst 6 can be more quickly activated. There is also an advantage.

Further, since the sub exhaust is performed independently of the exhaust stroke, it does not affect the opening timing of the exhaust valve 4A in the exhaust stroke. Therefore, the overlap (the state in which the exhaust valve 4A and the intake valve 4B are both open) is not reduced, and there is an advantage that the intake efficiency of the engine is not deteriorated. Further, by operating the exhaust valve 4A separately from the normal exhaust stroke, the operation timing (valve opening timing) and the operation amount (lift amount) of the exhaust valve 4A suitable for the early temperature rise of the catalyst 6 can be set. There is also an advantage that the catalyst 6 can be efficiently activated.

Switching between sub-exhaust and non-sub-exhaust can be instantaneously performed depending on whether hydraulic oil is supplied to the variable valve mechanism 60A, and there is also an advantage that such switching operation has good responsiveness. . Note that the exhaust valve operation control device for an internal combustion engine of the present invention is not limited to the above-described embodiment, and can be implemented with various modifications.

For example, in the above-described embodiment, in order to activate the catalyst 6 early, the sub exhaust is performed during the rich operation or the stoichiometric operation, and the additional fuel injection and the sub exhaust are performed during the lean operation. However, only the sub-exhaust may be performed as the early activation means of the catalyst 6 regardless of the operation mode of the engine. In this case, only a half of the cylinders of the engine have a structure in which the exhaust valve is provided with a variable valve operating mechanism to perform sub-exhaust, and the remaining half is a structure in which the exhaust valve is provided with a general valve operating mechanism. The exhaust may not be performed.

Further, instead of using the variable valve mechanism 60A, the exhaust valve 4A is constituted by an electromagnetic valve, and the exhaust valve 4A
May be opened and closed at an arbitrary timing, so that the sub exhaust can be performed. Also,
To prevent loss of engine torque when driving the vehicle,
The early activation of the catalyst 6 by the sub exhaust may be performed only at the time of idling.

The timing at which the sub-exhaust is started may not be in the middle of the expansion stroke but immediately after ignition by the spark plug 7 (end of the compression stroke). In this case, since the high-temperature gas during the combustion is discharged, the temperature of the catalyst can be raised earlier, and a small amount of gas is generated immediately before the piston 31 rises to the top dead center (the end of the compression stroke). Since the combustion gas is discharged and the pressure is released, the vertical vibration of the engine due to the movement of the piston 31 that switches from rising to falling at this timing is reduced, and noise due to this vibration is suppressed.

Further, in the above-described embodiment, the case where the direct injection type engine is applied has been described. However, the present invention may be applied to a general port injection type engine. However, in a general port injection type engine, the fuel injected into the intake passage is sucked into the combustion chamber 1 using the intake air flow. No injection can be performed. Therefore,
In this case, the means for raising the temperature of the catalyst 6 is only the sub exhaust.

[0065]

As described above in detail, according to the exhaust valve operation control device for an internal combustion engine of the present invention, during the stoichiometric operation or the rich operation, the exhaust valve is temporarily operated after ignition and before the end of the expansion stroke. By performing the exhaust (sub-exhaust) by performing the valve opening operation, a high-temperature combustion gas (exhaust gas) is discharged, and there is an advantage that the exhaust purification catalyst can be quickly activated.

Further, since the operation of the exhaust valve for the sub exhaust is performed separately from the operation of the exhaust valve during the exhaust stroke, it does not affect the opening timing of the exhaust valve in the exhaust stroke. Therefore, there is also an advantage that the intake efficiency of the internal combustion engine does not deteriorate. Also, by operating the exhaust valve separately from the normal exhaust stroke, it is possible to set the operation timing (valve opening timing) and the operation amount (lift amount) of the exhaust valve suitable for the early temperature rise of the exhaust purification catalyst. There is also an advantage that the exhaust gas purifying catalyst can be efficiently activated.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a configuration of a control system in an exhaust valve operation control device for an internal combustion engine as one embodiment of the present invention.

FIG. 2 is a schematic diagram showing an overall configuration of an internal combustion engine in an internal combustion engine exhaust valve operation control device as one embodiment of the present invention.

FIG. 3 is a diagram showing a cam profile, a timing of an ignition signal, and an in-cylinder temperature in relation to a piston position in an exhaust valve operation control device for an internal combustion engine as one embodiment of the present invention.

FIG. 4 is a configuration diagram schematically showing an exhaust valve operation variable means and a valve operating mechanism of an intake valve in an exhaust valve operation control device for an internal combustion engine as one embodiment of the present invention.

FIGS. 5A and 5B are schematic diagrams of an exhaust valve operation control unit in an exhaust valve operation control device for an internal combustion engine as one embodiment of the present invention, wherein FIG. 5A is a perspective view showing the entire configuration, and FIG. FIG. 3A is a cross-sectional view taken along the line AA, showing a state where the sub rocker arm does not operate in cooperation with the main rocker arm. FIG. 4C is a cross-sectional view taken along the line AA in FIG. FIG.

FIG. 6 is a flowchart showing control in an exhaust valve operation control device for an internal combustion engine as one embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 3 exhaust passage 4A exhaust valve 6 exhaust purification catalyst 20 ECU (control means) 60A variable valve mechanism (exhaust valve operation variable means)

Continued on the front page F term (reference) 3G092 AA01 AA06 AA09 AA10 AA11 AA15 BB06 BB13 DA02 DA04 DA12 DF04 DF09 DG05 EA05 EA06 EA07 EA08 EA11 EA26 EA27 EC01 FA15 HA09Z HD02X HD02Z HE01Z HE03Z HE08

Claims (1)

[Claims] 1. An internal combustion engine having an exhaust gas purification catalyst in an exhaust passage, an exhaust valve operation variable means capable of operating the exhaust valve separately from the operation of the exhaust valve during an exhaust stroke, and A control means for controlling the exhaust valve operation variable means to temporarily open the exhaust valve after ignition and before the end of the expansion stroke when there is a temperature increase request. An exhaust valve operation control device for an internal combustion engine.