JPH08291709A - Catalyst activation sensing device for internal combustion engine - Google Patents

Abstract

PURPOSE: To estimate an activated state of a catalyst with high accuracy by sensing an intake amount of an engine, and computing an integration value of heat quantity supplied to the catalyst based on the sensed intake amount. CONSTITUTION: In a control unit 12, a cooling water temperature Tw of an engine 1 is sensed by a water temperature sensor 15, and a reference quantity of heat Cϕ is set while corresponding the initial cooling water temperature Tw to an initial temperature of the catalyst 10. When the reference quantity of heat Cϕ is not zero, the catalyst is determined not to be activated. Warming-up control is started for early activation of the catalyst. When the engine 1 is not in a fuel cut state nor an idling state, quantity of heat A supplied to the catalyst 10 from exhaust is estimated and computed based on the intake air amount Q which is sensed by an air flow meter 13. The calculated quantity of heat A is added to the former integration value CHn-1 to obtain the present integration value CHn . When the quantity of heat integration value CHn exceeds the reference quantity of heat Cϕ, the catalyst 10 is determined to be activated, and warming-up control is completed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalytic activity detecting device for an internal combustion engine, and more particularly to a technique for indirectly detecting an active state of a catalyst provided in an exhaust passage for purifying exhaust gas of the internal combustion engine. .

[0002]

2. Description of the Related Art In an internal combustion engine for an automobile, it is general to remove harmful components such as NOx, HC and CO discharged from the engine by a three-way catalyst provided in an exhaust passage. Here, since the exhaust purification catalyst does not exhibit a sufficient purification rate in the inactive state, in the state immediately before the engine is activated and before the catalyst is activated, the emission amount of harmful components is larger than that in the activated state. There is a fear of becoming.

Therefore, secondary air is supplied to the upstream side of the catalyst, or the air-fuel ratio is made lean so that the upstream side of the catalyst becomes an excess air atmosphere, and the ignition timing is retarded to increase the exhaust temperature. For example, various catalyst warm-up controls for promptly activating the catalyst immediately after starting have been performed (Japanese Patent Laid-Open No. 6-129241 and Japanese Patent Laid-Open No. 5-1823).
No. 2).

By the way, the warm-up control for activating the above-mentioned catalyst is necessary for the non-activated state of the catalyst, and even though the catalyst has already been activated, the above-mentioned warm-up control is required. If the control is continuously executed, the exhaust property may be deteriorated rather, or the catalyst may be deteriorated by heat or melted. On the contrary, if the activation control is stopped even though the catalyst has not yet reached the activated state, the engine is operated with the purification rate of the catalyst being poor, and the exhaust property deteriorates.

Therefore, conventionally, the activation of the catalyst is estimated based on the elapsed time from the start and the temperature of the cooling water, and the activation control is canceled after the activation state of the catalyst is estimated. (See JP-A-6-129241).

[0006]

However, in the case of the configuration in which the catalyst activity is estimated based on the elapsed time from the start and the cooling water temperature, for example, when the catalyst is suddenly accelerated immediately after the start, FIG.
As shown in, the correlation between the cooling water temperature or the elapsed time from the start and the catalyst temperature shows a characteristic different from the normal time, and the activity is judged more than the cooling water temperature or the elapsed time from the start. The actual activation period may be earlier. In this case, since the activation determination is delayed, there is a fear that unnecessary activation control is executed during the period when the determination is delayed.

Further, in the case where the catalyst is left in the idle state after the start, as shown in FIG. 5, even if the catalyst activity is estimated from the cooling water temperature or the elapsed time from the start, the catalyst is not actually used. In some cases, it has not been activated.In this case, although the catalyst has not been activated, activation control may be stopped, and the catalyst may be left in a state where the purification rate of the catalyst is low, resulting in deterioration of exhaust properties. It was

The present invention has been made in view of the above problems, and provides a catalyst activity detecting device for an internal combustion engine capable of estimating the catalyst activation state with high accuracy, thereby appropriately controlling the catalyst warm-up control. The purpose is to be able to do.

[0009]

Therefore, a catalyst activity detecting device for an internal combustion engine according to the invention of claim 1 is a device for detecting an active state of an exhaust gas purifying catalyst provided in an exhaust passage of the internal combustion engine. And is configured as shown in FIG. FIG.
In, the intake air amount detecting means detects the intake air amount of the engine, and the heat amount estimating means estimates and calculates the integrated value of the heat amount given to the catalyst based on the intake air amount detected by the intake air amount detecting means. .

The catalyst activity determining means determines the activity of the catalyst when the integrated value of the heat quantity estimated and calculated by the heat quantity estimating means becomes equal to or larger than the reference heat quantity. In the catalyst activity detecting device for an internal combustion engine according to the invention of claim 2, the reference heat quantity compared with the integrated value of the heat quantity estimated and calculated by the heat quantity estimating means in the catalyst activity determining means is used as a cooling water temperature at engine startup. The reference calorific value setting means is set according to the above.

In the catalytic activity detecting apparatus for an internal combustion engine according to a third aspect of the present invention, there is provided fuel cut-off integration stopping means for stopping the integration of the heat quantity by the heat quantity estimating means while the fuel supply to the engine is stopped. It is configured to be provided. In the catalytic activity detecting apparatus for an internal combustion engine according to the invention of claim 4, the idling integration stopping means is provided for stopping the integration of the heat quantity by the heat quantity estimating means during the idle operation of the engine.

[0012]

According to the catalytic activity detecting device for an internal combustion engine of the first aspect of the present invention, since the exhaust gas temperature of the engine correlates with the intake air amount of the engine, the amount of heat given to the catalyst is estimated based on the intake air amount. Then, the catalyst activity is determined based on the fact that the integrated value of the amount of heat exceeds the reference amount of heat.

Therefore, if the intake air amount increases due to the acceleration operation or the like, the integrated value of the heat amount correspondingly increases, and it is possible to avoid delaying the activity determination with respect to the increase in the catalyst temperature due to the acceleration operation. According to the catalyst activity detecting device for the internal combustion engine of the second aspect of the present invention, by setting the reference value of the calorific value integrated value for determining the activity according to the cooling water temperature at the start, for example, the initial temperature of the catalyst is high. If the starting water temperature is estimated to be high, determine the catalyst activity with a lower heat quantity,
On the contrary, when the starting water temperature is estimated to be low at the initial temperature of the catalyst, it is possible to determine the catalyst activity with a higher amount of heat and avoid the deterioration of the activity determination accuracy due to the change in the initial temperature.

According to the catalyst activity detecting apparatus for an internal combustion engine of the third aspect of the present invention, since combustion is not performed while the fuel supply to the engine is stopped, the integration of the heat quantity based on the intake air quantity is stopped. It is possible to prevent the amount of heat from being accumulated in the state where the fuel supply is stopped as in the case of normal combustion to cause an error in the integrated value. According to the catalyst activity detecting device for an internal combustion engine of the fourth aspect of the present invention, during idle operation, the amount of heat given to the catalyst is small and there is a case where almost no increase in the catalyst temperature is obtained due to the balance with the amount of heat radiation. At this time, the integration of the heat quantity was stopped so that the integrated value corresponding to the actual temperature rise of the catalyst could be obtained.

[0015]

Embodiments of the present invention will be described below. FIG. 2 is a diagram showing a system configuration of the present embodiment. Air is sucked into an internal combustion engine 1 mounted on a vehicle (not shown) from an air cleaner 2 through an intake duct 3, a throttle valve 4 and an intake manifold 5. .

A fuel injection valve 6 is provided in the branch portion of the intake manifold 5 for each cylinder. The fuel injection valve 6 is an electromagnetic fuel injection valve that is energized by a solenoid to open the valve, is deenergized and is closed, and is energized by an injection pulse signal from a control unit 12 described later to open the valve. Fuel that is pressure-fed from a fuel pump (not shown) and adjusted to a predetermined pressure by a pressure regulator is injected and supplied into the intake manifold 5.

A spark plug 7 is provided in each combustion chamber of the engine 1 to spark-ignite and ignite and burn the air-fuel mixture. Exhaust gas is discharged from the engine 1 through the exhaust manifold 8, the exhaust duct 9, the exhaust purification three-way catalyst 10 (exhaust purification catalyst), and the muffler 11. The control unit 12 includes a CPU, ROM, RAM, A /
A microcomputer including a D converter and an input / output interface is provided, the fuel injection amount Ti is calculated based on detection signals input from various sensors, and the fuel injection valve 6 is calculated based on the fuel injection amount Ti. Is intermittently driven to open.

As the various sensors, an air flow meter 13 as an intake air amount detecting means for outputting a voltage signal according to the intake air amount Q of the engine 1, a crank angle sensor 14 for outputting a rotation signal of the engine 1, an engine A water temperature sensor 15 for detecting the cooling water temperature Tw in the water jacket 1 is provided. Further, an oxygen sensor 16 is provided at the collecting portion of the exhaust manifold 8 on the upstream side of the three-way catalyst 10.

The first oxygen sensor 16 is a known sensor whose output value changes in response to the oxygen concentration in the exhaust gas, and utilizes the fact that the oxygen concentration in the exhaust gas suddenly changes at the stoichiometric air-fuel ratio. It is a rich / lean sensor capable of detecting rich / lean of the exhaust air-fuel ratio with respect to the theoretical air-fuel ratio. Here, the CPU of the microcomputer incorporated in the control unit 12 controls the fuel injection amount in the direction in which the output of the oxygen sensor 16 approaches a value corresponding to the target air-fuel ratio when a predetermined feedback control condition is satisfied. Feedback control.

Further, the control unit 12 determines whether or not the three-way catalyst 10 has reached the activation temperature, and executes the catalyst warm-up control based on the determination result. The catalyst warm-up control is the supply of secondary air to the catalyst upstream side, leaning of the air-fuel ratio, or retard correction of the ignition timing, and the warm-up is performed from the start until the catalyst activity is determined. Control is performed to achieve early activation of the catalyst.

The flow chart of FIG. 3 shows the determination control of the catalyst activity by the control unit 12.
In the present embodiment, the functions of the heat quantity estimating means, the catalyst activity judging means, the reference heat quantity setting means, the fuel cut integration stopping means, and the idle integration stopping means are as shown in the flow chart of FIG. 12 have software.

In the flow chart of FIG. 3, first, in step 1 (denoted as S1 in the figure; the same applies hereinafter), it is determined whether the engine 1 has been started. If the engine has been started, the process proceeds to step 2, and the cooling water temperature Tws at the time of starting is read. In the next step 3, the reference heat quantity Cφ is set based on the cooling water temperature Tws at the time of starting.

Here, the cooling water temperature Tws at the time of the start
Can be regarded as corresponding to the initial temperature of the catalyst 10, and the higher the cooling water temperature Tws at the time of starting, the smaller the reference calorific value Cφ is set. That is, when the starting water temperature is estimated to be high when the catalyst has a high starting temperature, the catalyst activity is determined with a lower amount of heat, and conversely, when the starting water temperature is estimated to be low, the starting water temperature is low. In addition, the catalyst activity is determined with a higher amount of heat, and it is possible to avoid deterioration of the activity determination accuracy due to a change in the initial temperature.

In step 4, it is judged whether or not 0 is set as the reference heat quantity Cφ in step 3. Cooling water temperature T at the time of starting, when restarting immediately after the engine is stopped
When ws is equal to or higher than the predetermined temperature and it is considered that the catalyst activation state due to the previous operation is maintained, 0 is set as the reference heat quantity Cφ, so step 4 When it is determined that the reference heat quantity Cφ is 0, it is determined that the catalyst 10 is in the active state without the need for warm-up control, and the routine jumps to step 11,
The process ends without performing warm-up control.

On the other hand, when the reference heat quantity Cφ is not 0, it is judged that the catalyst 10 is not in the active state and needs to be warmed up, and the routine proceeds to step 5, where the secondary air for the upstream side of the catalyst is discharged. Warm-up control such as supply, lean air-fuel ratio, or ignition timing retard correction is started to promote early activation of the catalyst. In step 6, it is determined whether or not the fuel supply to the engine 1 is stopped (fuel cut state). The control of stopping the fuel supply is performed, for example, in a deceleration operation state in which the throttle opening is fully closed and the engine speed Ne is a predetermined value or more.

When it is judged in step 6 that the fuel is not cut, the routine proceeds to step 7, where it is judged whether the engine 1 is in the idle operation condition. If the fuel is not cut and the engine is not idle,
Proceeding to step 8, based on the intake air amount Q detected by the air flow meter 13, the heat amount A given to the catalyst 10 by the exhaust gas is estimated and calculated as A = Q ² × a (a is a proportional coefficient) .

In the next step 9, the heat quantity A obtained this time in step 8 is added to the integrated value C _Hn-1 up to the previous time, and the addition result is taken as the integrated value C _{Hn of} this time. The integrated value C _Hn is a value that is reset to zero by the initialization process when the key switch is turned on. On the other hand, when it is determined in step 6 that the fuel is cut, or when it is determined in step 7 that the engine is in the idling state, the process returns to step 6 without proceeding to steps 8 and 9. Then, the update of the integrated value C _Hn (integration of heat quantity) is stopped.

Since the combustion is not performed in the fuel cut state, the integration of the heat quantity based on the intake air quantity Q is stopped, and the heat quantity is integrated in the fuel supply stopped state as in the normal combustion to obtain the integrated value C _Hn . It is intended to prevent an error. In addition, since the amount of heat given to the catalyst is small during idle operation and the catalyst temperature hardly rises due to the balance with the amount of heat released, the integration of the amount of heat is stopped during idle operation, and the integration corresponding to the actual catalyst temperature rise is stopped. The value C _Hn is obtained.

In step 10, the integrated calorific value C _Hn and
The reference heat quantity Cφ set in step 3 is compared.
When the calorific value integrated value C _Hn is equal to or less than the reference calorific value Cφ, it is determined that the catalyst 10 has not reached the activation temperature,
The process returns to step 6 while the warm-up control state is continued.

On the other hand, when the calorific value integrated value C _Hn exceeds the reference calorific value Cφ, it is judged that the catalyst 10 has reached the activation temperature and is in the activated state, and the routine proceeds to step 11 to end the warm-up control. Let In the above embodiment, the detection result of the catalyst activity is used to determine the end of the catalyst warm-up control.
For example, an oxygen sensor is also provided on the downstream side of the catalyst 10, and in a system that feedback-controls the air-fuel ratio based on the air-fuel ratio detection results on the upstream and downstream sides of the catalyst, control using the oxygen sensor on the downstream side, It is performed after the catalytic activity is detected based on the integrated value C _Hn , or
In the catalyst deterioration diagnosis based on the air-fuel ratio reversal ratios on the upstream side and the downstream side during the air-fuel ratio feedback control, a state in which the catalyst activity is detected based on the integrated value C _Hn may be used as the diagnosis permission condition.

[0031]

As described above, according to the catalyst activity detecting device for an internal combustion engine according to the invention of claim 1, the amount of heat given to the catalyst is estimated based on the amount of intake air, and the integrated value of the amount of heat is equal to or greater than the reference amount of heat. Since the catalyst activity is determined based on that, the delay in activity determination with respect to the increase in the catalyst temperature due to the acceleration operation can be avoided, and the catalyst activity can be detected with high accuracy.

According to the catalyst activity detecting device for the internal combustion engine of the second aspect of the present invention, the initial value of the catalyst is set by setting the reference value of the calorific value integrated value for determining the activity of the catalyst according to the cooling water temperature at the time of starting. There is an effect that it is possible to avoid deterioration of the activity determination accuracy due to a change in temperature. According to the catalyst activity detecting device for an internal combustion engine of the third aspect of the present invention, in a state where fuel supply to the engine is stopped and combustion is not performed,
Since the integration of the amount of heat based on the intake air amount is stopped, there is an effect that it is possible to prevent an error in the integrated value due to the integration of the amount of heat as in normal combustion when the fuel supply is stopped.

According to the catalyst activity detecting device of the internal combustion engine of the invention of claim 4, the amount of heat given to the catalyst is small, and the amount of heat is integrated in the idling operation in which almost no increase in the catalyst temperature is obtained due to the balance with the amount of heat radiation. Since the configuration is stopped, the integrated value corresponding to the actual temperature rise of the catalyst can be obtained, and there is an effect that the activity detection can be performed with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of an apparatus according to the invention of claim 1.

FIG. 2 is a system configuration diagram of an embodiment.

FIG. 3 is a flowchart showing catalyst activity determination control according to the embodiment.

FIG. 4 is a time chart showing a conventional situation in which a delay occurs in activation determination due to acceleration operation.

FIG. 5 is a time chart showing a conventional state in which erroneous determination of activity occurs due to being left idle.

[Explanation of symbols]

 1 Internal combustion engine 10 Three-way catalyst (exhaust gas purification catalyst) 12 Control unit 13 Air flow meter 15 Water temperature sensor

Claims (4)

[Claims] 1. An apparatus for detecting an active state of an exhaust gas purification catalyst installed in an exhaust passage of an internal combustion engine, comprising: intake air amount detecting means for detecting an intake air amount of the engine; and the intake air amount. Based on the intake air amount detected by the detection means, a heat quantity estimating means for estimating and calculating the integrated value of the heat quantity given to the catalyst, and the integrated value of the heat quantity estimated and calculated by the heat quantity estimating means has become equal to or greater than the reference heat quantity. A catalytic activity detecting device for an internal combustion engine, comprising: a catalytic activity determining means for determining catalytic activity of the catalyst. 2. A reference heat quantity setting means for setting a reference heat quantity to be compared with an integrated value of the heat quantity estimated and calculated by the heat quantity estimating means in the catalyst activity judging means in accordance with a cooling water temperature at engine startup. The catalytic activity detecting device for an internal combustion engine according to claim 1, wherein 3. The fuel cut-off integration stopping means for stopping the integration of the heat quantity by the heat quantity estimating means while the fuel supply to the engine is stopped. Internal combustion engine catalytic activity detection device. 4. The internal combustion engine according to claim 1, further comprising idle-time integration stopping means for stopping the integration of the heat quantity by the heat quantity estimating means during idle operation of the engine. Engine catalytic activity detector.