JP2003074385A - Control device for internal combustion engine - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To suppress deterioration of a catalyst while improving fuel efficiency. A catalyst provided in an exhaust system of an internal combustion engine for purifying exhaust gas, an intake valve and an exhaust valve provided in each cylinder of the internal combustion engine, a catalyst temperature detecting means for detecting a temperature of the catalyst, And a control device for the internal combustion engine including fuel cut means for stopping supply of fuel to the internal combustion engine in response to the operating state of the internal combustion engine. When the supply of fuel is stopped, if the detected temperature of the catalyst is equal to or higher than a predetermined value, at least one of the intake valve and the exhaust valve is closed to introduce the exhaust gas to the catalyst. Ban. Since the introduction of the exhaust gas to the catalyst is prohibited, the catalyst is not exposed to an oxygen-rich atmosphere, and the deterioration of the catalyst can be suppressed.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust system for an internal combustion engine.
For controlling internal combustion engine that suppresses deterioration of catalyst provided in vehicle
About. 2. Description of the Related Art Normally, an exhaust system of an internal combustion engine is provided inside a vehicle.
A three-way catalyst is provided to purify the exhaust gas of the fuel engine.
ing. The three-way catalyst is used to empty the air-fuel mixture supplied to the internal combustion engine.
When the fuel ratio becomes lean, excess acid present in the exhaust gas
NOx is reduced by adsorbing and holding hydrogen, while the air-fuel ratio is reduced.
When the pressure rises, the adsorbed and held oxygen is released to release HC, CO
To reduce. [0003] On the other hand, the vehicle is decelerated without the need for fuel supply.
State (e.g., engine braking)
It is known how to stop the fuel supply when
You. Such a fuel supply stop is usually called a “fuel cut”.
Called. Improve fuel efficiency by cutting fuel
Is achieved. The fuel cut is, for example,
Fully closed for more than a fixed time and the engine speed
This is executed when the rotation speed is equal to or higher than the predetermined rotation speed. In fuel cut state
After entering, the engine speed falls below the specified speed
Or throttle valve after entering fuel cut state
Is opened, the fuel cut state is released and the fuel supply
Pay is resumed. As described above, fuel is supplied during the fuel cut.
The air supplied from the intake pipe is exhausted as it is
It flows to a tube and is supplied to a three-way catalyst. As a result, the three-way catalyst
Becomes an oxygen-rich atmosphere. When the temperature of the catalyst is high
In such an oxygen-rich atmosphere, noble metals in the catalyst
Oxidation and sintering of base metals and
Phenomenon of melting and agglomeration of particles and crystal growth)
Which is known to cause
This is a factor that degrades performance. FIG. 8 shows an oxygen-rich atmosphere with respect to the catalyst temperature.
It is a graph which shows NOx discharge amount in the presence / absence. From FIG.
As is evident, in a non-oxygen atmosphere, the catalyst
When the temperature is 800 ° C and the amount of NOx is 900 ° C
The amount of NOx at that time is almost the same. However,
In the case of oxygen-rich atmosphere (here, in the case of oxygen-rich atmosphere
This means that the hot catalyst is exposed to an oxygen-rich atmosphere for a long time.
Is a state where deterioration has progressed) is the temperature of the catalyst
Is 900 ° C compared to the amount of NOx when
In this case, the amount of NOx is remarkably large. This
As shown, when the temperature of the catalyst is high,
If it continues, purification performance will be enhanced by promoting catalyst degradation.
Is significantly reduced and is discharged without being purified by the catalyst
The amount of NOx increases. As a technique for preventing such catalyst deterioration,
JP-A-8-144814 discloses that the detected catalyst
Prohibit fuel cut when temperature is higher than the specified value
An apparatus is described. [0007] Japanese Patent Application Laid-Open No. 2001-132509
In order to keep the catalyst above the activation temperature,
The device that closes the intake and exhaust valves is described during
You. SUMMARY OF THE INVENTION [0008]
According to JP-A-8-144814, when the temperature of the catalyst is high,
Fuel cut is prohibited in the early stage, so that catalyst deterioration is suppressed.
But at the same time the execution of the fuel cut is restricted
I will. That is, during deceleration that does not require engine output
In such a case, a situation occurs in which fuel is supplied.
This has a negative effect on fuel economy. Further, Japanese Patent Application Laid-Open No. 2001-132509 is disclosed.
Closes intake or exhaust valves during fuel cut
To prevent unburned gas (air) from flowing out to the exhaust side,
Although it is described to prevent the temperature from dropping, the catalyst
It describes how to avoid the deterioration of
Absent. Therefore, the fuel cut is executed to reduce the fuel consumption.
Oxygen concentration in the exhaust pipe becomes excessive while improving
Technology is needed to prevent catalyst deterioration
I have. [0011] The present invention has been made to solve the above-mentioned problems.
The control device for an internal combustion engine according to one embodiment of the present invention
A catalyst provided in the exhaust system of the engine for purifying exhaust gas;
An intake valve and an exhaust valve provided in each cylinder of the internal combustion engine,
Catalyst temperature detecting means for detecting the temperature of the catalyst;
A fuel that stops supplying fuel to the internal combustion engine in response to a condition
Fuel supply by fuel cut means and fuel cut means
When stopped, detected by catalyst temperature detection means
If the temperature of the catalyst is equal to or higher than a predetermined value, at least
Close either the valve or the exhaust valve to exhaust the catalyst
A prohibition means for prohibiting the introduction of gas.
Take. According to the present invention, the supply of fuel is stopped.
At least if the temperature of the catalyst
Since either the intake valve or the exhaust valve is closed,
No fresh air is sent to the catalyst. Therefore, fuel economy deteriorates
Without exposing the catalyst to an oxygen-rich atmosphere.
Can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment will be described. FIG. 1 shows an embodiment of the present invention.
Internal combustion engine (hereinafter referred to as “engine”) and its control
FIG. 2 is an overall configuration diagram of a control device. An electronic control unit (hereinafter, referred to as "ECU")
5) receives data sent from each part of the vehicle.
The input circuit 5a to be input, a function for controlling each part of the vehicle.
CPU 5b that executes the calculation, read-only memory (RO
M) and a random access memory (RA) for temporary storage.
M), and a control signal is transmitted to each part of the vehicle.
An output circuit 5d for sending a signal is provided. R of the storage means 5c
The OM has programs and programs for controlling various parts of the vehicle.
And various data are stored. According to the invention,
A program for executing control to suppress catalyst deterioration
And data used when executing the program
And the table are stored in the ROM. reading
Read-only memory is rewritable like EEPROM
ROM may be used. The RAM is provided by the CPU 5a.
A work area for calculation is provided and sent from each part of the vehicle.
Data and control signals sent to various parts of the vehicle
Is memorized. The engine 1 is, for example, an engine having four cylinders.
And the intake pipe 2 is connected thereto. Above intake pipe 2
A throttle valve 3 is provided on the upstream side. throttle
Throttle valve opening sensor (θTH) 4 connected to valve 3
Outputs an electric signal corresponding to the opening of the throttle valve 3,
This is supplied to the ECU 5. In the intake pipe 2, a throttle valve 3 is bypassed.
A passage 18 is provided. In the bypass passage 18
Is an intake for controlling the amount of air supplied to the engine 1.
An air amount control valve 19 is provided. Intake air amount control valve
19 is an electromagnetic valve electrically controlled by the ECU 5
is there. The fuel injection valve 6 is connected to the engine 1 and a throttle.
Between the valves 3, the number of intake valves (not shown) of the intake pipe 2 is small.
An upstream side is provided for each cylinder. Fuel injection valve 6
Is connected to a fuel pump (not shown),
Via a fuel tank (not shown)
You. The fuel injection valve 6 is connected to the ECU 5,
The valve opening time is controlled by the control signal from the control unit 5. The intake pipe absolute pressure (PBA) sensor 7 and
The intake air temperature (TA) sensor 8 is connected to the throttle valve 3 of the intake pipe 2.
Of the intake pipe, the absolute pressure PBA and
And the intake air temperature TA are detected and converted into electric signals.
This is sent to the ECU 5. The engine water temperature (TW) sensor 10 has an engine
Cylinder block filled with cooling water in the cylinder block of gin 1
Mounted on a wall (not shown), the temperature of the engine cooling water
TW is detected and converted into an electric signal, which is sent to the ECU 5.
You. The cylinder discrimination (CYL) sensor 11 and the engine
The engine speed (NE) sensor 12 is a camshaft of the engine 1.
Or mounted around the crankshaft (both not shown)
You. The CYL sensor 11 detects a predetermined crank angle of each cylinder.
The cylinder discrimination signal CYL is output at the position. NE sensor 12
Is CRK every predetermined crank angle (for example, 1 °).
Outputs a signal pulse. These signals are sent to the ECU 5.
Can be The pulse of the CRK signal is counted by the ECU 5.
The engine speed NE is thus detected. An exhaust pipe 13 is connected to the downstream side of the engine 1.
The engine 1 emits exhaust gas to the exhaust pipe 13
I do. Exhaust gas purification device provided in the exhaust pipe 13
The three-way catalyst 14 is provided with HC, CO, NO in the exhaust gas.
Purify components such as x. Provided in the middle of the exhaust pipe 13
O ₂ The sensor 15 is an exhaust gas concentration sensor,
Detects the oxygen concentration of the air and converts it to an electric signal,
Send to 5. The ECU 5 is equipped with the engine 1.
The vehicle speed (V) for detecting the traveling speed (vehicle speed) VP of the vehicle
P) The sensor 17 is connected, and the VP sensor 17
The detected signal is sent to the ECU 5. An intake valve and an exhaust valve of each cylinder of the engine 1
Switches the valve timing variably according to the operating conditions
Variable valve timing mechanism 18
Driven. By the variable valve timing mechanism 18
The realized valve timing depends on the control signal from the ECU 5.
It is controlled according to the number. The signal sent to the ECU 5 is an input circuit.
5a. The input circuit 5a shapes the input signal waveform
To correct the voltage level to a predetermined level,
To a digital signal value. The CPU 5b converts
The digital signal processed is stored in the storage means 5c.
Calculation in accordance with the program
Produce control signals to send to the tutor. Output circuit 5d
Transmits these control signals to the fuel injection valve 6, the intake air amount control.
The control valve 19, the variable valve timing mechanism 18, and the
Send to other actuators. Variable valve timing provided in engine 1
The switching mechanism 18 responds to a control signal from the ECU 5 to
All cylinders operating state with all cylinders operating, and all cylinders operating state
The operation of all cylinders can be stopped freely.
It is configured to be interchangeable. Alternatively, one
So that only the cylinders in the
Is also good. Variable valve timing mechanism according to the present invention
18 is a fuel cut according to a control signal from the ECU 5
At least one of the intake and exhaust valves is closed
I will. By doing so, the exhaust gas is guided to the catalyst 14.
Entry is prohibited. That is, at least during fuel cut
When either the intake valve or the exhaust valve is closed, the catalyst
Is not supplied with new air (fresh air),
Excessive atmosphere is prevented and catalyst deterioration is prevented.
Can be suppressed. FIG. 2 shows an all-cylinder SOHC engine.
Can switch between operating state and all-cylinder deactivated state
One of the valve operating mechanisms to which the variable valve timing mechanism 18 is applied
Here is an example. Intake valve 50a provided in cylinder (not shown)
And the exhaust valve 50b are provided with valve springs 51a and 51b.
b, the intake port and exhaust port (both figures
(Not shown). The camshaft 53 has a lift cam 52 (see FIG.
3) is provided.
Rocker arms 54a and 54b for
Each is connected. Rocker arm for cam lift 54
a and 54b are rocker arm shafts 53a and
Each is rotatably supported via 53b. Rocker arm shafts 53a and 53
b includes rocker arms 55a and 55b for driving valves.
Are rotatably supported. Locker
The ends of the arms 55a and 55b are connected to the intake valves 50a and 50a.
And the upper end of the exhaust valve 50b, respectively, whereby
The intake valve 50a and the exhaust valve 50b open. Locker
Intake valve 50a and exhaust of arms 55a and 55b
The end opposite to the valve 50b is provided on the camshaft 53.
Connected to a circular rest cam 531 (see FIG. 3).
ing. FIGS. 3 (a) and 3 (b) show, by way of example, absorption.
3 shows a detailed structure of a valve operating mechanism of the air valve 50a. Of FIG.
As shown in (a) and (b), the hydraulic chamber 56
Rocker arm 54b for cam lift and locker for valve drive
It is formed to extend over the arm 55b. Inside the hydraulic chamber 56
Is provided with a pin 57 so as to be slidable.
You. The pin 57 is connected to the camry via a pin spring 58.
It is urged toward the rocker arm 54a for the lift. Inside the rocker arm shaft 53a
A hydraulic supply path 59 is formed. The hydraulic supply path 59 is
Opening 60 of hydraulic supply path 59 and locker for cam lift
Hydraulic pressure is provided through a communication passage 61 provided in the arm 54a.
It communicates with the chamber 56. Hydraulic control valve 63
When opened, the hydraulic oil flows from the oil pump 64 to the hydraulic supply path 59.
Is supplied. The hydraulic control valve 63 is
It is an electromagnetic valve formed of an id. Hydraulic control
The valve 63 is connected to the ECU 5,
Is driven to open and close in accordance with the control signal. FIG. 3A shows a hydraulic control valve.
63 is closed and no hydraulic oil is supplied to the hydraulic chamber 56.
It shows a bad state. In this state, the pin 57
The rocker lock for the cam lift is
Arm 54a and the valve drive rocker arm 55a.
It is positioned. Thus, locker for cam lift
The arm 54a and the valve driving rocker arm 55a are
57. The lift cam 52 operates
When the rocker arm 54a for cam lift is driven
At the same time, the valve drive rocker arm 55a is also driven.
As a result, it was connected to the valve drive rocker arm 55a.
The intake valve 50a is driven. FIG. 3B shows a control signal from the ECU 5.
The hydraulic control valve 63 is opened by the
The state in which hydraulic oil is supplied to the oil supply path 56 via the hydraulic supply path 59
Is shown. Due to the action of hydraulic pressure, the pin 57
Valve drive rocker arm 55a side against the pulling 58
Slide. As a result, rocker arm for cam lift
Connection between the valve 54a and the valve driving rocker arm 55a.
It is released. When the lift cam 52 operates in this state,
The cam lift rocker arm 54a is driven. Only
While the cam lift rocker arm 54a and the valve drive
The connection between the locker arm 55a and the locker arm 55a is released.
Therefore, the valve drive rocker arm 55a stops idling.
It is not driven only by the cam 531. Therefore,
Intake valve connected to valve drive rocker arm 55a
50a does not operate and is kept in the valve closed state. The exhaust valve 50b is also connected to the intake valve 5 shown in FIG.
It has the same structure as Oa. As described above, the present invention
According to one embodiment, the intake valve 50a and the exhaust valve 50b
Either one or the intake valve 50a and the exhaust valve 50b
By closing both in the manner described above.
Prohibit the introduction of fresh air into the catalyst. FIG. 4 shows an embodiment of the present invention, FIG.
Control of the hydraulic control valve 63 shown in FIG.
FIG. 2 is a functional block diagram of a control device according to the first embodiment. In each functional block
The function represented is typically the ECU 5 shown in FIG.
To the computer program stored in the storage means 5c
It is executed. Alternatively, each function block represents
Any hardware configured to perform the function
, Each functional block may be realized. As described above, the operating state detecting unit 31
Based on the CRK signal pulse received from the NE sensor 12
And detects the engine speed NE, and sets the throttle valve opening
Throttle valve opening based on the signal received from sensor 4
θTH is detected and the signal received from the VP sensor 17 is
The vehicle speed VP is detected based on the vehicle speed. Furthermore, the PBA sensor 7
And a signal from the TW sensor 10 to receive the intake pipe
Detects internal absolute pressure PBA and engine water temperature TW
I do. The condition satisfaction determination section 32 executes a fuel cut.
It is determined whether or not the condition for performing is satisfied. Concrete
Specifically, the condition satisfaction determination unit 32 determines that the engine speed NE is
The rotation speed is equal to or higher than a predetermined rotation speed (for example, 900 rpm),
Speed VP is equal to or higher than a predetermined value (for example, 15 km / h).
And the throttle valve opening θTH is a predetermined value close to fully closed.
(For example, 10 °) or less,
Set the fuel cut flag to execute. As conditions for executing the fuel cut,
Other conditions may be used. For example, if the throttle valve is
Fully closed for more than a fixed time (for example, 0.5 seconds)
And the engine speed NE is a predetermined speed (for example,
If it is more than 900rpm), execute fuel cut
It may be. Or, when the engine speed NE is
The vehicle speed VP is greater than or equal to a predetermined value, and
If the pipe absolute pressure PBA is lower than the predetermined pressure, the fuel
May be executed. The condition satisfaction determination section 32 sets the fuel cut state
After entering, the throttle valve opening θTH is equal to or greater than the predetermined value.
Is reached, the engine speed NE is equal to or less than the predetermined speed.
When the vehicle speed falls below, or when the vehicle speed VP is lower than the predetermined value.
When it runs out, cut fuel to resume fuel supply
Reset the flag. The fuel cut section 33 has a fuel cut flag
Signal to stop fuel supply, if set
To the fuel injection valve 6 (FIG. 1). Fuel cut release unit 34
If the fuel cut flag is reset,
A signal for performing the supply is sent to the fuel injection valve 6. The catalyst temperature estimating section 35 has a fuel cut flag
Is set, the engine water temperature TW and intake air
The catalyst temperature is calculated based on the in-pipe absolute pressure PBA. The hydraulic valve control unit 36 includes a catalyst temperature estimating unit
When the catalyst temperature calculated in step 35 is high,
Signal for opening the troll valve 63 (FIG. 3B)
To the hydraulic control valve 63. Meanwhile, fuel
When the cut flag is not set or when the catalyst temperature
When the temperature is not high, close the hydraulic control valve 63
To send to the hydraulic control valve 63
You. The hydraulic control valve 63 is opened
And the intake valve and / or exhaust valve
Shut off and the intake and / or exhaust valves close
You. On the other hand, the hydraulic control valve 63 is closed
And the intake and / or exhaust valves are activated,
It is driven to open and close. As described above, during the fuel cut, the intake valve and
(Or) the exhaust valve is closed. In other words, the engine
While no fuel is supplied, no fresh air is introduced into the catalyst.
As a result, the catalyst is prevented from being exposed to an oxygen-rich atmosphere.
The oxidation and oxidation of precious and base metals in the catalyst.
And sintering are suppressed. In addition, during fuel cut
Since the concentration of oxygen in the catalyst is prevented from increasing,
NOx purification performance decreases after charge cut is released
Phenomenon can be avoided. Thus, fuel economy
The deterioration of the catalyst can be suppressed while improving the performance. FIG. 5 shows a hydraulic system according to an embodiment of the present invention.
Float showing the process of controlling the control valve
It is a chart. This flowchart is performed, for example, at a predetermined time.
It is repeated every interval. In step 101, the fuel cut is executed.
It is determined whether or not the condition for executing is satisfied. Ingredient
Physically, as described above, the engine speed NE is a predetermined value.
More than the rotation speed, the vehicle speed VP is more than a predetermined value, and
If the throttle valve opening θTH is equal to or less than a predetermined value,
It is determined that the condition is satisfied. It is determined that the condition is satisfied
The delay timer to a predetermined time.
(102), and set the fuel cut flag (1).
03). As a result, a signal instructing the stop of the fuel supply is generated.
It is transmitted to the fuel injection valve 6 (FIG. 1), and the supply of fuel is stopped.
It is. Proceeding to step 106, the fuel cut is performed again.
It is determined whether the conditions for execution are satisfied.
The conditions determined here are the same as those in step 101
It is. This determination step 106 will be described later.
While the time set in the timer expires,
Intake air on condition that fuel cut condition is not satisfied
Valve and / or exhaust valve prior to refueling
This is in order to set the operation state. Y determined in step 101
If it is ES, the normal judgment step 106 is also YES,
Proceed to step 107. In step 107, according to the operation state
Temperature estimation routine (FIG. 6)
Execute Proceeding to step 108, the catalyst temperature estimation
When the catalyst temperature calculated by the tin reaches a predetermined value (the catalyst is activated
Temperature, for example, 500 ° C.)
This means that the catalyst is hot
You. Proceeding to step 109, the hydraulic control valve 6
3 ((b) in FIG. 3) is a signal for hydraulic control.
To the valve 63. Thus, the hydraulic control valve
3 is opened, and the state shown in FIG.
Become. As a result, the intake valve 50a and / or the exhaust valve
50b is closed. In step 108, the catalyst temperature estimation
Judgment that the catalyst temperature calculated by the routine is lower than the predetermined value
If so, the process proceeds to step 110 and the hydraulic control
The signal for closing the valve 63 is sent to the hydraulic control valve.
To the box 63. Thus, the hydraulic control valve 63
Is closed, and the state shown in FIG.
You. As a result, the intake valve 50a and / or the exhaust valve 5
0b is in the operating state. Thus, the supply of fuel is stopped.
Sometimes if the catalyst temperature is high, the intake valve and (also
) Since the exhaust valve is closed, fuel efficiency is not
In addition, catalyst deterioration can be suppressed. In step 101, the fuel cut is executed.
If it is determined that the condition to execute is not satisfied
If the time set in the delay timer has elapsed,
(104). If not, step
Proceed to 103 to continue fuel cut. Step 106
And the conditions for executing the fuel cut are satisfied again
Determine if you are. Step 101
If the answer is NO in the step
No, proceed to step 110. On the other hand, in step 104, the delay
After the time set in the timer has elapsed, the fuel
Reset the fuel flag and restart fuel supply (10
5). Thereafter, the process proceeds to step 110. Step 110
Then, as described above, the hydraulic control valve 63
A signal for closing is sent to the hydraulic control valve 63.
You. As shown in steps 104 and 105
The time set in the delay timer elapses.
The delay in releasing the fuel cut by the intake valve or exhaust
Fuel will be delivered when the valve is in a working state.
That's why. That is, the intake valve or exhaust valve
When transitioning from the resting state to the operating state,
It takes some time before the valve is driven. Accordingly
Without the above delay, fuel is injected but the mixture is
Phenomena such as not being supplied to the combustion chamber may occur. this
To avoid this, steps 104, 106 and 1 above
As shown in 10, the delay timer is set
Until the time has elapsed, the conditions for executing a fuel cut
Hydraulic control valve on condition that no
Close the valve and activate the intake and / or exhaust valves
Bring. This sets the delay timer
After the elapsed time, the intake valve and / or exhaust
Ensure that the air valve is operating. That
Later, as shown in steps 104, 105 and 110
When the time set in the delay timer elapses,
The fuel cut is released immediately when the air-fuel mixture is supplied to the combustion chamber.
The fuel supply is resumed in the state where it is done. FIG. 6 is executed in step 107 of FIG.
5 is a flowchart showing a catalyst temperature estimation routine.
You. In step 111, the vehicle is in the starting mode.
Judge whether it is a password. This is for example the engine
The rotation speed NE is less than a predetermined rotation speed (for example, 500 rpm).
If it is full, it is determined that the engine is in the start mode. Start mode
If it is determined that
Here, a predetermined initial value is added to the estimated catalyst temperature TCT.
Set. Specifically, in step 112, the engine
The water temperature TW is equal to a predetermined temperature #TWTCT (for example, 60 ° C.)
Determine if it is greater than. The judgment of step 112
If NO, the engine 1 is in a low temperature state,
Can also be estimated to be in a low temperature state. Step 1
Proceeding to step 13, the estimated catalyst temperature TCT is
The period value is set to #TCTO (for example, 200 ° C). On the other hand, if the determination in step 112 is YES
In this case, it can be estimated that the catalyst is in a high temperature state. S
Proceed to step 114 to determine the estimated catalyst temperature TCT in advance.
Set to the initial value # TCT1 (for example, 500 ° C.)
I do. Of course, the initial values used in step 114
# TCT1 is an initial value #T used in step 113
A temperature higher than CT0 is set. In step 111, it is not the start mode.
If it is determined that, in steps 115-119
Calculate the catalyst temperature. In step 115, the estimation
It is determined whether the value of the image TCATWOT is zero. Estimation
The timer is a down timer, and a predetermined time #T
MCATWOT (for example, 500 ms) is set
It is. If the value of the estimation timer TCATWOT is zero,
Time #TMCATWOT set in fixed timer elapses
Since it means that the user has performed
, The time #TMCATWOT is set in the estimation timer.
If the value of the estimation timer TCATWOT is not zero,
Leave this routine as is. Thus, step 117
The calculation of the estimated catalyst temperature TCT executed in
This is executed every fixed time #TMCATWOT. At step 117, the engine speed
Smoothing coefficient based on NE and intake pipe absolute pressure PBA
Search the calculation table to find the smoothing coefficient CTCTW
You. FIG. 7 shows an example of the smoothing coefficient calculation table. Figure
As shown in FIG. 7, the smoothing coefficient is a predetermined value #PBCT
High load set for CTH and predetermined value
#PBCTLCTL set for low load
Are prepared (graph 71 and graph 71, respectively).
72). In either case,
The coefficient CTCTW is calculated based on the absolute pressure PBA in the intake pipe and the engine.
The higher the engine speed NE, the larger the value
You. The magnitude of the detected intake pipe absolute pressure PBA
The averaging coefficient is searched according to. Specifically, detection
The magnitude of the determined intake pipe absolute pressure PBA is a predetermined value #PBC
When close to TCTL, the smoothing coefficient CTC is obtained from the graph 72.
Find TW. On the other hand, the detected intake pipe absolute pressure PBA
When the size of the graph is close to the predetermined value #PBCTCTH, the graph
Using 71, an averaging coefficient CTCTW is determined. Intake pipe
The internal absolute pressure PBA is equal to the predetermined values #PBCTLCTL and #PBC.
If it is between TCTH, the detected absolute pressure in the intake pipe
Shown in graphs 71 and 72, depending on the value of PBA
By interpolating the smoothing coefficient CTCTW,
Coefficient CTCT corresponding to the specified absolute PBA in the intake pipe
Calculate W. Proceeding to step 118, the engine speed N
Not shown based on E and intake pipe absolute pressure PBA
By searching the map, the basic estimated catalyst temperature TCT
Calculate M. This map shows the engine speed NE and
As the absolute pressure PBA in the intake pipe increases, the basic estimated catalyst temperature increases
Is set in advance to be higher. To step 119
Proceed to the smoother calculated in steps 117 and 118
Using several CTCTW and basic estimated catalyst temperature TCTM,
The estimated catalyst temperature TCT is calculated according to the following equation. This
Here, n is a number for identifying a cycle, and (n−
1) shows the previous cycle, and (n) shows the current cycle
Is shown. TCT (n) = TCT (n−1) + [TCTM−TCT
(n-1)] × CTCTW As described above, the smoothing coefficient CTCTW
The engine speed NE and the intake pipe absolute pressure PBA
The higher the value, the larger the value. Therefore, the engine
High rotation speed NE or intake pipe absolute pressure PBA is high.
When the catalyst temperature is more likely to rise,
Appropriate calculation of estimated catalyst temperature TCT in a state that reflects sound
can do. In this example, the catalyst temperature was
Calculated based on the rotation speed and the absolute pressure in the intake pipe. And
However, in another embodiment, the three-way catalyst 14 (FIG.
1) Attach a catalyst temperature sensor and signal from the sensor
May be received to detect the catalyst temperature. In the above embodiment, the SOHC type engine is used.
Although the gin was described as an example, other types (for example, DOHC
Type) engine. In the above embodiment,
Operates the intake and / or exhaust valves by hydraulic pressure
Valve timing mechanism for switching between idle and rest states
Was explained as an example. However, such a cut
It is not necessary to provide a replacement mechanism. In addition, intake valves and exhaust
The air valve is an electromagnetic valve mechanism that electromagnetically drives the valve, or
An electric valve mechanism that electrically drives the valve is applied.
Is also good. In this case, if the catalyst temperature is high during the fuel cut,
When the intake valve and / or exhaust valve
The valve is electromagnetically or electrically closed by a control signal. This
This prohibits the introduction of exhaust gas into the catalyst.
As a result, deterioration of the catalyst is suppressed. According to the present invention, the catalyst can be used during fuel cut.
If the temperature is high, the introduction of exhaust gas into the catalyst is prohibited.
Control of catalyst deterioration without deteriorating fuel economy
can do.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram schematically showing an internal combustion engine and a control device thereof according to one embodiment of the present invention. FIG. 2 is a diagram showing a structure of a valve train of the internal combustion engine according to one embodiment of the present invention. FIG. 3 is a diagram showing an operating state and a rest state of an intake valve according to one embodiment of the present invention. FIG. 4 is a functional block diagram of a control device for controlling a hydraulic control valve according to one embodiment of the present invention. FIG. 5 is a flowchart illustrating a process for controlling a hydraulic control valve according to an embodiment of the present invention. FIG. 6 is a flowchart illustrating a process for estimating a catalyst temperature according to an embodiment of the present invention. FIG. 7 shows an engine speed N according to one embodiment of the present invention.
E and smoothing coefficient C based on intake pipe absolute pressure PBA
The figure which shows an example of the smoothing coefficient calculation table for calculating | requiring TCTW. FIG. 8 shows NO in the presence or absence of an oxygen-rich atmosphere with respect to the catalyst temperature.
7 is a graph showing an example of the amount of x discharge. [Description of Signs] 1 engine 2 intake pipe 4 throttle valve 5 ECU 13 exhaust pipe 14 catalyst 50a intake valve 52 lift cam 531 rest cam 54a rocker arm for lift cam 55a rocker arm for intake valve drive 56 hydraulic chamber 59 hydraulic supply path 63 hydraulic control valve

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 41/04 320 F02D 41/04 330Z 330 B01D 53/36 B F-term (Reference) 3G091 AA02 AA17 AA23 AA28 AB03 BA04 BA08 BA10 BA14 BA15 BA19 CB02 DA01 DA02 DA03 DA07 DA08 DA10 DB01 DB06 DB10 EA00 EA01 EA05 EA06 EA07 EA15 EA16 EA18 EA30 EA31 EA34 EA39 FA05 FB03 FB10 FB11 FB12 FC04 FC08 GA06 HA36 HA39 3A09 A05 BB10 CB05 DA03 DA11 DC01 DC04 DC15 DE01Y DF01 DF06 DG05 DG07 EA06 EA08 EA11 EA17 EA21 EA28 EB01 FA17 FA18 FA20 FA24 FB07 GA13 GA16 GB06 GB08 HA04Z HA05Z HA06Z HA07Z HA08Z HA09Z HD02Z HD05Z HE01Z19 HE03Z01 KA16 KA26 KB07 LA01 LA08 LB02 MA01 MA11 MA13 MA18 NA01 NA06 NA07 NA08 NB12 NE01 NE06 NE14 NE23 PA04B PA04Z PA07B PA07Z PA10B PA10Z PA11B PA11Z PA13B PA13Z PB02B PB02Z PD12B PD12Z PE02B PE02Z PE03B PE03Z PE04B PE04Z PE05B PE05Z PE08B PE08Z PF01B PF01Z PF16A ADA14A04 DA03A04

Claims (1)

Claims: 1. A catalyst provided in an exhaust system of an internal combustion engine for purifying exhaust gas, an intake valve and an exhaust valve provided in each cylinder of the internal combustion engine, and a temperature of the catalyst. Catalyst temperature detecting means for detecting, fuel cut means for stopping supply of fuel to the internal combustion engine in response to a predetermined operating state, and when the supply of fuel is stopped by the fuel cut means, If the temperature of the catalyst detected by the catalyst temperature detecting means is equal to or higher than a predetermined value, at least one of the intake valve and the exhaust valve is closed to prohibit the introduction of exhaust gas into the catalyst. , Internal combustion engine control device.