JPH0835418A - Temperature controller of exhaust emission control device - Google Patents

Abstract

PURPOSE:To accurately control the temperature of a catalytic converter, so as to improve purifying efficiency, by judging the activating state of a catalyst through a process of estimating the temperature of the three-way catalytic converter by using the model constant and the model opposite to the model wherein the response delay of a three-way catalytic converter temperature detecting means is estimated, on the basis of the temperature of the three-way catalytic converter. CONSTITUTION:A control circuit 20 for controlling the fuel injection amount of a fuel injection valve 7 according to the operating state is provided with an exhaust gas temperature sensor 13 as a sensor for detecting the temperature of a three-way catalytic converter, and the output signal is inputted into a sensor model constant calculating unit 25. The model constant of the model wherein the detecting response delay of the temperature sensor 13 is estimated is calculated in real time. The temperature of the three-way catalytic converter is estimated by using the calculated model constant and the model opposite to the model wherein the response delay of the exhaust temperature sensor 13 is estimated on the basis of the temperature detected by the exhaust gas temperature sensor 13. When the estimated temperature is less than the target temperature, the control for raising the exhaust gas temperature to activate a catalyst is carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus (catalyst, oxygen concentration sensor, etc.) for an internal combustion engine, which is intended for locations where the temperature changes depending on the operating state of the internal combustion engine. The present invention relates to a temperature control device that detects temperature with high responsiveness and accuracy and controls the temperature of an exhaust gas purification device based on the detected temperature.

[0002]

2. Description of the Related Art As is well known, an internal combustion engine mounted on a vehicle is equipped with an exhaust gas purifying device for purifying harmful gas components in exhaust gas from the internal combustion engine into harmless components. Has been. As the exhaust gas purifying device, which uses a three-way catalyst, there is such as that using a lean NO _X catalyst, usually, the exhaust gas purification device air in order to improve the purification rate of the catalysts An oxygen sensor is provided to control the fuel ratio. Further, all of the above exhaust gas purifiers require accurate control over temperature.

For example, a three-way catalyst originally needs to be operated in a high temperature range to perform the above cleaning, but excessively high temperature not only lowers the purification rate, but also increases the durability of the catalyst itself. Also has a great impact and is not desirable. Therefore, conventionally, while the temperature of the exhaust gas is measured by an appropriate temperature sensor, as in the device disclosed in Japanese Patent Laid-Open No. 60-101241, the temperature is maintained within a certain target temperature range. As described above, the amount of fuel supplied to the internal combustion engine and the ignition timing of the internal combustion engine are operated. Incidentally, if the fuel supply amount is increased, the air-fuel ratio becomes rich and the temperature of the exhaust gas decreases. Further, with respect to the ignition timing, the temperature of the exhaust gas similarly decreases due to the large advance value.

[0004]

As described above, the temperature of the exhaust gas is measured using the temperature sensor, and the amount of fuel supplied to the internal combustion engine and the ignition timing of the internal combustion engine are controlled based on the measured value. In this way, the temperature of the exhaust gas is theoretically certainly maintained within a predetermined temperature range, and it seems that it can be avoided that the temperature is excessively high.

However, the above-mentioned temperature sensor is usually difficult to respond, and especially when it comes to a relatively inexpensive temperature sensor to be mounted on a mass-produced vehicle, its response is significantly delayed. For this reason, there is a large difference between the temperature measured by the temperature sensor and the actual temperature of the exhaust gas, and as a result, the temperature of the catalyst described above cannot be accurately controlled. there were.

The present invention has been made in view of the above circumstances, and the actual temperature of the target portion can be quickly captured regardless of the responsiveness of the temperature sensor itself, and based on the captured temperature information. An object of the present invention is to provide a temperature control device for an exhaust gas purification device, which can control the temperatures of the constituent elements of the exhaust gas purification device with high accuracy.

[0007]

In claim 1 of the present invention, as shown in FIG. 25, a three-way catalyst provided in an exhaust pipe for purifying exhaust gas and the temperature of the three-way catalyst are detected. Based on the temperature detected by the three-way catalyst temperature detecting means, the sensor model constant calculating means for calculating the model constant of the model in consideration of the detection response delay of the three-way catalyst temperature detecting means in real time, and the three-way catalyst temperature detecting means. A three-way catalyst temperature predicting means for predicting the actual temperature of the three-way catalyst by using the model constant calculated by the sensor model constant calculating means and an inverse model of a model in which the response delay of the three-way catalyst temperature detecting means is taken into consideration. When the predicted actual three-way catalyst temperature is lower than the target temperature, it is determined that the three-way catalyst is not activated, and the exhaust gas temperature is controlled to increase so that the actual three-way catalyst temperature is Provided is a temperature control device for an exhaust gas purification device, comprising: an exhaust gas temperature control means for deciding that the catalyst is activated when the temperature is equal to or higher than a reference temperature and stopping control of the exhaust gas temperature. .

Further, in the above apparatus, as described in claim 2, the exhaust gas temperature control means may be means for raising the exhaust gas temperature by retarding the ignition timing. In the above device, as described in claim 3,
The exhaust gas temperature control means may be a means for increasing the exhaust gas temperature by increasing the idle speed.

Further, in the above apparatus, as described in claim 4, the three-way catalyst temperature detecting means is an exhaust temperature sensor for detecting the temperature of exhaust gas, and the exhaust gas temperature predicting means is exhaust gas detected by the exhaust temperature sensor. It may be a means for predicting the temperature of the three-way catalyst based on the temperature of the gas. Further, in the above apparatus, as described in claim 5, the three-way catalyst temperature detecting means may be a three-way catalyst temperature sensor for detecting the temperature of the three-way catalyst.

Further, according to a sixth aspect of the present invention, there is provided a model of a model provided in the exhaust pipe for purifying exhaust gas, a catalyst temperature detecting means for detecting the temperature of the catalyst, and a response delay of the catalyst temperature detecting means. The model model constant calculating means for calculating constants in real time, and the model constant calculated by the sensor model constant calculating means based on the temperature detected by the catalyst temperature detecting means and the inverse of the model considering the response delay of the catalyst temperature detecting means. And a catalyst temperature predicting means for predicting an actual temperature of the catalyst by using the model, and controlling so that the exhaust gas temperature rises when the predicted actual catalyst temperature is lower than the first target temperature. An exhaust gas temperature control means for controlling the exhaust gas temperature to decrease when the actual catalyst temperature is equal to or higher than a second target temperature higher than the first target value. To provide a temperature control device of the exhaust gas purifying device, characterized in that.

Further, in the apparatus according to the sixth aspect, as described in the seventh aspect, the exhaust gas temperature control means controls the ignition timing to retard the exhaust gas temperature to increase the fuel injection amount. By doing so, a means for lowering the exhaust gas temperature may be provided. Further, as described in claim 8, the catalyst temperature detecting means is an exhaust temperature sensor for detecting the temperature of the exhaust gas, and the catalyst temperature predicting means predicts the temperature of the catalyst by the temperature of the exhaust gas detected by the exhaust temperature sensor. It may be used as a means.

The catalyst temperature detecting means may be a catalyst temperature sensor for detecting the temperature of the catalyst. Furthermore, as described in claim 10, the catalyst may be a three-way catalyst. Further, as described in claim 11, the catalyst may be a lean catalyst that mainly purifies nitrogen oxides in exhaust gas.

According to the twelfth aspect of the invention, an oxygen concentration sensor provided in the exhaust pipe for outputting a rich or lean signal in accordance with the oxygen concentration in the exhaust gas, and an oxygen concentration sensor temperature for detecting the temperature of the oxygen concentration sensor. Detecting means, heater for warming up the oxygen concentration sensor, sensor model constant calculating means for calculating the model constant of the model in consideration of the response delay of the oxygen concentration sensor temperature detecting means in real time, and detection by the oxygen concentration sensor temperature detecting means Based on the obtained temperature, the actual temperature of the oxygen concentration sensor is predicted using the model constant calculated by the sensor model constant calculation means and an inverse model of the model that allows for the response delay of the oxygen concentration sensor temperature detection means itself. Oxygen concentration sensor temperature prediction means,
When the predicted actual sensor temperature is lower than the target temperature, it is determined that the oxygen concentration sensor is not activated, and the heater is energized to control. When the actual sensor temperature is equal to or higher than the first target temperature, the oxygen concentration is There is provided a temperature control device for an exhaust gas purification device, comprising: a heater energization control means for determining that the sensor is activated and stopping energization of the heater.

Further, in the apparatus of claim 12, as described in claim 13, an exhaust temperature sensor for detecting the temperature of the exhaust gas flowing through the exhaust pipe is provided, and the oxygen concentration sensor temperature detecting means is used as the exhaust temperature sensor. The concentration sensor temperature predicting means may be a means for predicting the temperature of the oxygen concentration sensor using the exhaust gas temperature detected by the exhaust gas temperature sensor.

Further, in the apparatus according to the fourteenth aspect, a three-way catalyst provided in the exhaust pipe for purifying exhaust gas, three-way catalyst temperature detecting means for detecting the temperature of the three-way catalyst, and three-way catalyst Calculated by the sensor model constant calculation means based on the temperature detected by the sensor model constant calculation means and the three-way catalyst temperature detection means that calculates the model constant of the model in consideration of the detection response delay of the catalyst temperature detection means in real time A three-way catalyst temperature predicting means for predicting the actual temperature of the three-way catalyst by using a model constant and an inverse model of a model in which a response delay of the three-way catalyst temperature detecting means is used, and the predicted actual three-way catalyst When the catalyst temperature is higher than the target temperature, the exhaust gas temperature is controlled so as to decrease, and when the actual three-way catalyst temperature is lower than the target temperature, the exhaust gas temperature control is stopped. To provide a temperature control device of the exhaust gas purifying device, characterized in that it comprises a means.

Further, in each of the above-mentioned devices according to the fifteenth aspect of the present invention, there is provided a flow velocity detecting means for detecting the flow velocity of the exhaust gas, and the sensor model constant calculating means is a model constant based on the flow velocity detected by the flow velocity detecting means. May be calculated in real time. Further, as described in claim 16, a fuel cut detecting means for detecting whether or not the fuel cut is executed is provided, and the sensor model constant calculating means detects that the fuel cut is being performed by the fuel cut detecting means. At this time, a means for calculating the model constant based on the exhaust gas temperature estimated at the time of fuel cut may be used.

Further, as described in claim 17, the temperature predicting means sets the temperature detected by the temperature sensor at the current Texs.
(I), the previous temperature detected by the temperature sensor is Texs
(I-1), the temperature sensor model constants are a ₁ , b ₁ ,
Let b ₂ and c ₁ be the actual temperature Tex (i) of the target location predicted this time. May be used as a means for predicting.

[0018]

As described above, according to the device of the first aspect of the present invention, the three-way catalyst purifies the exhaust gas, and the three-way catalyst temperature detecting means detects the temperature of the three-way catalyst. The sensor model constant calculation means calculates the model constant of the model in consideration of the detection response delay of the three-way catalyst temperature detection means in real time.

The three-way catalyst temperature predicting means estimates the model constant calculated by the sensor model constant calculating means and the response delay of the three-way catalyst temperature detecting means based on the temperature detected by the three-way catalyst temperature detecting means. The inverse model of the model is used to predict the actual temperature of the three-way catalyst, and the exhaust gas temperature control means means that the catalyst is not activated when the predicted actual three-way catalyst temperature is less than the target temperature. When the actual three-way catalyst temperature is equal to or higher than the target temperature, it is determined that the catalyst is activated, and the control of the exhaust gas temperature is stopped.

In the second aspect, the exhaust gas temperature control means raises the exhaust gas temperature by retarding the ignition timing. Further, in claim 3, the exhaust gas temperature control means raises the exhaust gas temperature by raising the idle speed. Further, in claim 4, the three-way catalyst temperature detecting means detects the temperature of the exhaust gas, and the exhaust gas temperature predicting means predicts the temperature of the three-way catalyst based on the temperature of the exhaust gas detected by the exhaust temperature sensor.

Further, in claim 5, the three-way catalyst temperature detecting means detects the temperature of the three-way catalyst. According to the apparatus of claim 6, the catalyst purifies the exhaust gas, and the catalyst temperature detecting means detects the temperature of the catalyst. The sensor model constant calculation means calculates the model constant of the model in consideration of the response delay of the catalyst temperature detection means in real time.

The catalyst temperature predicting means calculates a model constant calculated by the sensor model constant calculating means and an inverse model of a model in which the response delay of the catalyst temperature detecting means is calculated based on the temperature detected by the catalyst temperature detecting means. make use of,
The actual temperature of the catalyst is predicted, and the exhaust gas temperature control means controls the exhaust gas temperature to increase when the predicted actual catalyst temperature is lower than the first target temperature. Is higher than the second target temperature higher than the first target value, the exhaust gas temperature is controlled to decrease.

Further, in claim 7, the exhaust gas temperature control means increases the exhaust gas temperature by retarding the ignition timing, and lowers the exhaust gas temperature by enriching the fuel injection amount. Further, in claim 8,
The catalyst temperature detecting means detects the temperature of the exhaust gas, and the catalyst temperature predicting means predicts the temperature of the catalyst based on the temperature of the exhaust gas detected by the exhaust temperature sensor.

Further, according to the apparatus of claim 12,
The oxygen concentration sensor outputs a rich or lean signal according to the oxygen concentration in the exhaust gas, and the oxygen concentration sensor temperature detecting means detects the temperature of the oxygen concentration sensor. Further, the heater warms up the oxygen concentration sensor. Further, the sensor model constant calculating means calculates the model constant of the model in consideration of the response delay of the oxygen concentration sensor temperature detecting means in real time, and the oxygen concentration sensor temperature predicting means is based on the temperature detected by the oxygen concentration sensor temperature detecting means. The actual temperature of the oxygen concentration sensor is predicted by using the model constant calculated by the sensor model constant calculating means and the inverse model of the model in which the response delay of the oxygen concentration sensor temperature detecting means itself is taken into consideration.

When the predicted actual sensor temperature is lower than the target temperature, the heater energization control means determines that the oxygen concentration sensor is not activated and energizes the heater to control the actual sensor temperature to the first value. When the temperature is equal to or higher than the target temperature of 1, it is determined that the oxygen concentration sensor is activated, and the energization of the heater is stopped. Further, in claim 13, the exhaust temperature sensor detects the temperature of the exhaust gas flowing through the exhaust pipe, and the oxygen concentration sensor temperature prediction means predicts the temperature of the oxygen concentration sensor using the exhaust gas temperature detected by the exhaust temperature sensor. To do.

In the apparatus according to the fourteenth aspect, the three-way catalyst purifies the exhaust gas, and the three-way catalyst temperature detecting means detects the temperature of the three-way catalyst. In addition, the sensor model constant calculating means calculates in real time the model constant of the model in consideration of the detection response delay of the three-way catalyst temperature detecting means, and the three-way catalyst temperature predicting means uses the temperature detected by the three-way catalyst temperature detecting means. Based on this, the actual temperature of the three-way catalyst is predicted by using the model constant calculated by the sensor model constant calculation means and the inverse model of the model that allows for the response delay of the three-way catalyst temperature detection means.

The exhaust gas temperature control means controls the exhaust gas temperature to decrease when the predicted actual three-way catalyst temperature is equal to or higher than the target temperature, and the actual three-way catalyst temperature is lower than the target temperature. At times, control of the exhaust gas temperature is stopped. Further, in claim 15, the flow velocity detection means detects the flow velocity of the exhaust gas, and the sensor model constant calculation means calculates the model constant in real time based on the flow velocity detected by the flow velocity detection means.

In the sixteenth aspect, the fuel cut detection means detects whether or not the fuel cut is executed,
The sensor model constant calculation means calculates the model constant based on the exhaust gas temperature estimated at the time of fuel cut when the fuel cut detection means detects that fuel cut is being performed. Further, in claim 17, the temperature predicting means sets the current temperature detected by the temperature sensor to Texs.
(I), the previous temperature detected by the temperature sensor is Texs
(I-1), the temperature sensor model constants are a ₁ , b ₁ ,
Let b ₂ and c ₁ be the actual temperature Tex (i) of the target location predicted this time. Predict as.

[0029]

1 shows a first embodiment of a temperature control device for an internal combustion engine according to the present invention. As shown in FIG. 1, this engine is provided with a throttle valve 3 on the downstream side of an air cleaner (not shown). The throttle valve 3 is provided with a throttle sensor 4 that detects the opening degree of the throttle valve 3.

A surge tank 5 is provided downstream of the throttle valve 3. The surge tank 5 is provided with a pressure sensor 1 that detects engine negative pressure.
In this embodiment, the pressure sensor 1 indirectly detects the amount of air taken in by the engine. The temperature of the intake air is detected by the intake air temperature sensor 2 arranged in the surge tank 5.

Further, an intake manifold 6 is connected to the surge tank 5, and the other end of the intake manifold 6 is further connected to a combustion chamber 8A of an engine body 8. The intake manifold 6 is provided with a fuel injection valve 7 for injecting fuel into the intake manifold 6, and the engine body 8 has a spark plug 9 and a cooling water temperature sensor for detecting the engine cooling water temperature. 10 are arranged respectively.

On the other hand, the combustion chamber 8A of the engine is connected via an exhaust manifold 11 to a catalytic converter (catalyst) 12 filled with a three-way catalyst. As described above, the catalytic converter (catalyst) 12 is a device for cleaning harmful gas components contained in the exhaust gas of the engine into harmless components. Here, an exhaust temperature sensor 13 is attached to the exhaust manifold 11, and the exhaust temperature sensor 13 detects the temperature of the gas exhausted through the exhaust manifold 11. A catalyst temperature sensor 14 is also attached to the catalytic converter (catalyst) 12, and the temperature of the catalytic converter (catalyst) 12 itself is detected through the catalyst temperature sensor 14. Further, an oxygen sensor 29 that outputs a signal according to the oxygen concentration in the exhaust gas is attached upstream of the catalytic converter (catalyst) 12.

The spark plug 9 provided in the engine body 8 is electrically connected to the distributor 15. The distributor 15 is also connected to the igniter 16, and the ignition plug 9, the distributor 15, and the igniter 16 constitute the ignition device of the engine illustrated in FIG. 1. Further, the distributor 15 is provided with a cylinder discrimination sensor 17 and an engine speed sensor 18, which are composed of a pickup and a signal rotor fixed to the distributor shaft. The cylinder discrimination sensor 17 outputs a cylinder discrimination signal to the control circuit 20 at every crank angle of 180 degrees if the engine is, for example, a four-cylinder engine. If the engine is, for example, a six-cylinder engine, the crank angle is The sensor outputs a cylinder discrimination signal to the control circuit 20 every 120 degrees. Further, the engine rotation speed sensor 18 is a sensor that outputs a crank angle signal proportional to the rotation speed of the engine to the control circuit 20, for example, every 30 degrees of the crank angle.

The control circuit 20 includes a well-known CPU, RAM,
It is composed of a microcomputer including a ROM, a backup RAM, an input / output port and the like. Figure 2
FIG. 3 is a block diagram showing a connection relationship of each part which constitutes the control circuit 20. Hereinafter, the function and operation of each of these parts constituting the control circuit 20 will be described in order.

Based on the application of the fuel cut signal indicating that the fuel cut is being performed, the sensor model constant calculating section 25 artificially sets a certain temperature T converged by the fuel cut with respect to the exhaust temperature. The temperature of the exhaust gas sensor 1
3 is a part for modeling the behavior of the temperature Texs detected through 3 until reaching the same temperature T. Note that fuel cut means that fuel injection is stopped when the engine speed is relatively high and the throttle valve is fully closed, that is, in the so-called engine braking state, or when the engine speed is above a set value. Control.
Then, if such fuel cut is performed during the operation of the engine, the exhaust temperature is lowered and eventually converges to a certain temperature.

The sensor model constant calculator 25 calculates a model constant (sensor model constant) for the model each time the modeling is performed. The calculation method is shown below. Here, the behavior (first-order lag) of the temperature Texs detected by the exhaust temperature sensor 13 is modeled. However, in order to improve its accuracy, the disturbance c ₁ is introduced, and this is set according to the following equation.

[0037]

[Number 2] Texs (i) = aTexs (i -1) + (1-a) Tex (i-1) + c 1 (2) It should be noted that the above (1-a), which for convenience, the constant b replace. Therefore, this model formula eventually becomes the following formula.

[0038]

Equation 3] Texs (i) = aTexs (i -1) + bTex (i-1) + c 1 (3) below, calculated based on the equation (3), the model constants a, b, and c ₁ To do. Here, since the model constants a, b, and c _{1 in the} equation (3) are all unknowns, these are rewritten as estimated values, and the equation is separated into a known signal and an unknown signal.

[0039]

[Equation 4]

It becomes Also in this case, the estimated values of the unknown values a, b, and c ₁ are obtained by the successive least squares method. That is, Θ is a parameter vector and W is a measurement value vector,

[0041]

(Equation 5)

In addition, here, the value T of the convergence temperature is put in Tex (i),

[0043]

(Equation 6)

When I say,

[0045]

(Equation 7)

Then, under the condition of i → ∞

[0047]

(Equation 8)

Will be guaranteed. Therefore, the model constants a, b, and c ₁ which are unknowns can be obtained by using the algorithm of the above formula (7). Therefore, here, we execute this equation (7) in real time,
For convenience, the obtained value is the model constant a,
Let b and c1. However, in this equation (7),
Γ is

[0049]

[Equation 9] And

[0050]

[Equation 10]

It is a 3 × 3 symmetric matrix having an initial value of
The exhaust temperature predicting unit 26 uses the exhaust temperature Texs detected by the exhaust temperature sensor 13 and the constant a of the sensor model constants calculated by the sensor model constant calculating unit 25 to determine the primary temperature of the sensor 13 itself. This is a part for predicting the actual temperature Tex of the exhaust gas in anticipation of a delay. The prediction method is shown below.

Letting i be a variable indicating the number of times of control and a be a model constant for the exhaust gas temperature sensor 13, the response delay of the exhaust gas temperature sensor 13 can be expressed by the following equation.

[0053]

Texs (i + 1) = aTexs (i) + (1-a) Tex (i) (11) This is calculated from the actual exhaust temperature Tex as (1-a) / (Z-
a) It shows that the sensor temperature Texs is detected with a first-order lag, which is shown in FIG.
become that way. However, here, since the actual exhaust gas temperature is estimated from the sensor temperature Texs, FIG.
Consider an inverse model as shown in (b). This inverse model is derived from the above equation (11).

[0054]

## EQU12 ## (ZA) Texs (i) = (1-a) Tex (i) (12). Therefore, the required exhaust temperature Tex is

[0055]

(Equation 13) Will be obtained as. However, future information such as (i + 1) cannot be used, so this is used here.

[0056]

[Equation 14] Is approximated as.

Thus, the actual exhaust temperature Tex (i) at that time is predicted by the model constant a, the current sensor temperature Texs (i) and the previous sensor temperature Texs (i-1). Become so. The exhaust temperature Tex predicted by the exhaust temperature predicting section 26 is given to the correction amount calculating section 22. The controlled object model constant calculation unit 24 calculates the model constant of the controlled object model in real time based on the temperature Texs detected by the exhaust gas temperature sensor 13 and the correction amount Fex calculated by the correction amount calculation unit 22 described later. This is the part to calculate. The calculation method is shown below.

The model constants of the controlled object model are α, β, and γ (wherein the constant α includes the time constant of the exhaust temperature sensor 13, and the constants β and γ include the mounting position of the exhaust temperature sensor 13 and various disturbances. When the variable indicating the number of times of control is i, the first-order lag of the temperature Texs detected by the exhaust gas temperature sensor 13 is expressed by the following equation.

[0059]

Texs (i + 1) = αTexs (i) + βFex (i-3) + γ (15) Here, since the model constants α, β, and γ in the equation (15) are all unknowns. If these are rewritten as estimated values and the same equation is separated into a known signal and an unknown signal,

[0060]

[Equation 16]

It becomes Then, here, the respective estimated values of α, β, and γ which are unknowns are obtained by the successive least squares method. That is, Θ is a parameter vector and W is a measurement value vector,

[0062]

[Equation 17]

When saying

[0064]

(Equation 18)

Then, under the condition of i → ∞

[0066]

[Formula 19]

Is guaranteed. Therefore, the model constants α, β, and γ that are unknowns can be obtained by using the algorithm of the equation (18). Therefore, here, the equation (18) is executed in real time, and the obtained value is the model constant α obtained here for convenience.
Let (i), β (i), and γ (i). However, in this equation (18), Γ is

[0068]

(Equation 20) And

[0069]

[Equation 21]

It is a 3 × 3 symmetric matrix having an initial value of
Further, the correction amount calculation unit 22 uses the model constant thus calculated and corrected in real time and the difference between the predicted actual exhaust gas temperature Tex and the target exhaust gas temperature TR, and the fuel injection valve 7 Correction amount Fex for the manipulated variable TAU
Is configured to calculate An example of the correction method is shown below.

In the apparatus of this embodiment, the difference between the actual exhaust gas temperature Tex and the target exhaust gas temperature TR is so-called proportional-plus-integral-derivative (PID) controlled to correct the manipulated variable TAU of the fuel injection valve 7. Let's ask for Fex. Here, in the correction amount calculation unit 22, the difference is

[0072]

[Mathematical formula-see original document] Assuming that e (i) = target catalyst temperature TR-predicted catalyst temperature Tex (22), the proportional term u ₁ (i) is

[0073]

## EQU23 ## This is obtained as u ₁ (i) = Kpe (i) (23), and the integral term u ₂ (i) is

[0074]

## EQU24 ## This is obtained as u ₂ (i) = u ₂ (i-1) + Kie (i) (24), and for the differential term u ₃ (i),

[0075]

Equation 25] _{u 3 (i) = Kd {} e (i) -e (i-1)} After determining this as (25), the correction amount Fex

[0076]

[Expression 26] Fex (i) = u ₁ (i) + u ₂ (i) + u ₃ (i) (26) It should be noted that both Ki and Kd are constants that are set in advance. Kp is a constant that can be replaced with the model constant calculated by the controlled object sensor model constant calculation unit 24. The replacement method is shown below.

First, when the term of the correction amount Fex is derived by modifying the model equation (15), the following equation is obtained.

[0078]

[Equation 27] Here, assuming that the temperature detected by the exhaust gas temperature sensor 13 when being corrected by the correction amount Fex0 is the temperature Texs0,
In this equation (27)

[0079]

[Equation 28] By substituting Texs (i + 1) = Texs (i) = Texs0 + e (i) (28) and rearranging,

[0080]

[Equation 29] Becomes Therefore, the proportional constant Kp of the proportional term is

[0081]

[Equation 30] As a result, the model constants α and β calculated and corrected in real time can be replaced. Further, by calculating the correction amount Fex using such model constants, the calculated correction amount Fex also becomes highly accurate information that is not affected by changes over time.

The correction amount Fex calculated by the correction amount calculation unit 22 is given to the multiplier 23. The multiplier 23 multiplies the calculated correction amount Fex by the operation amount TAU obtained in advance for the operation amount of the fuel injection valve 7 serving as an actuator to obtain the reference operation amount TAU '. Is the part to be corrected.
That is, the fuel injection valve operation amount (that is, the fuel injection amount) TAU ′ for controlling the temperature Tex of the exhaust gas to the target temperature TR in the device of this embodiment is calculated by the multiplier 23 as

[0083]

[Equation 31] TAU ′ = TAU × Fex (31) The reference operation amount T
AU is an operation amount (fuel supply amount) of the fuel injection valve 7 which is obtained as a suitable value for each time according to the operating state of the engine 8 through a well-known fuel injection control device or the like.

FIG. 4 to FIG. 9 show the processing procedure of the processing actually performed by the control circuit 20 of the apparatus of the first embodiment to control the exhaust gas temperature. 9 to 11, the operation of the entire apparatus of the first embodiment will be described in more detail. FIG. 4 shows a processing routine (timer interrupt routine 50) that is executed by a timer interrupt every 100 ms in order for the control circuit 20 to perform the temperature control in the apparatus according to the first embodiment.
0) is shown.

That is, the control circuit 20 which has entered the timer interrupt routine 500 based on the above timer interrupt.
First, the actual exhaust temperature predicting process is executed through the sensor model constant calculating unit 25 and the exhaust temperature predicting unit 26 (step 510). This actual exhaust temperature prediction routine 51
Details of 0 are shown in FIG. In the actual exhaust gas temperature prediction routine 510 shown in FIG. 5, the control circuit 20 first determines whether fuel is cut or not based on the fuel cut signal (510A). As a result, if the fuel is currently being cut, the above-mentioned pseudo exhaust gas temperature (pseudo exhaust gas temperature signal) T is determined through the sensor model constant calculation unit 25 (step 511), and based on the temperature T, the above (2)
The expression or the expression (3) is modeled (step 51).
2). Then, the control circuit 20 executes the correction process of the sensor model constant through the sensor model constant calculation unit 25 (step 513). The sensor model constant correction routine 513 is shown in detail in FIG.

In the sensor model constant correction routine 513 shown in FIG. 6, the control circuit 20 first initializes the object matrix Γ as shown in the above equation (10) (step 5).
131), the measurement value vector and the parameter vector are determined as in the above equations (5) and (6) (step 513).
2 and step 5133), the symmetric matrix Γ shown in equation (9) above is introduced (step 5134), and equation (7) above is executed (step 5135). Then, the model constants a, b, and c ₁ obtained as a result are stored in the RAM or the backup RAM in the control circuit 20 as modified values of the model constant (step 513).
6).

On the other hand, when it is determined in step 510A of the actual exhaust temperature prediction routine of FIG. 5 that the fuel cut is not currently being performed, the control circuit 20 causes the exhaust temperature sensor 1 to operate.
The current exhaust gas temperature Texs (i) output from No. 3 is taken in (step 514). Then, the model constant a held in the sensor model constant calculator 25 is read (step 515), and the previously detected exhaust temperature Texs (i- is held in the RAM or the backup RAM in the control circuit 20. The calculation of the above equation (14) is executed together with 1), and the actual temperature (estimated exhaust gas temperature) Tex (i) at that time for the exhaust gas temperature is calculated (step 516).

The control circuit 20 that has predicted the actual exhaust gas temperature Tex (i) in this manner then next predicts the predicted exhaust gas temperature Tex (i).
Is supplied to the correction amount calculation unit 22, and the correction amount (Fex) calculation process is executed through the correction amount calculation unit 22 (step 520 in FIG. 4). The details of the correction amount calculation routine 120 are shown in FIG. In the correction amount calculation routine 220 shown in FIG. 7, the control circuit 20 calculates the difference e (i) between the target temperature TR and the predicted exhaust temperature Tex based on the above equation (22). After first obtaining (step 221), regarding the proportional term u ₁ ,

[0089]

[Equation 32] As described above, the correction value is calculated using the model constant calculated and corrected in real time (step 22).
2). After that, the equations (24) and (25) are sequentially executed to obtain the correction values of the integral term u ₂ (i) and the differential term u ₃ (i) (step 223, step 224). The calculated correction values u ₁ (i), u ₂ (i), and u ₃ (i) are added based on the above equation (26) to determine the correction amount Fex (i) (step 225). As described above, the correction amount Fex (i) thus determined is highly accurate information that is not affected by changes over time. The determined correction amount Fex (i) is also stored in the RAM in the control circuit 20 or the backup RAM.

The control circuit 2 which determines the correction amount Fex in this way
0 is then the determined correction amount Fex (more accurately, RA
M or the correction amount Fex (i-3) three times before stored in the backup RAM and the current exhaust gas temperature Texs (i) fetched from the exhaust gas temperature sensor 13 through the controlled object model constant calculation unit 24. , Model constant correction processing is executed (step 530 in FIG. 4). Details of the model constant correction routine 530 are shown in FIG.

Model constant correction routine 2 shown in FIG.
In 30, the control circuit 20 first initializes the object matrix Γ as shown in equation (21) above (step 23).
1), the measurement value vector and the parameter vector are defined as in the above equation (17) (steps 232 and 233), and the symmetric matrix Γ shown in the above equation (20) is introduced (step 234). ) And the above equation (18) is executed (step 235). Then, the model constants α (i), β (i), and γ (i) obtained as a result are stored in the RAM or the backup RAM in the control circuit 20 as modified values of the model constant (step 236). .

FIG. 9 shows a main routine executed by the control circuit 20 in the apparatus of this embodiment for carrying out the temperature control. That is, the control circuit 20
In the main routine 1000,
Or the correction amount F stored in the backup RAM
ex (i) is read (step 1100), and the read correction amount Fex (i) is given to the multiplier 23. Then, the reference operation amount (reference injection amount of fuel) TAU of the fuel injection valve 7 is corrected based on the above equation (11) (step 12).
00).

As described above, in the first embodiment,
When the actual catalyst temperature is higher than the target catalyst temperature, the catalyst temperature can be lowered by reducing the fuel injection amount and lowering the exhaust gas temperature. Furthermore, since the catalyst temperature uses the temperature predicted in real time,
Since there is no delay in the response of the temperature sensor and the temperature can be lowered as soon as the catalyst temperature becomes high, it is possible to further suppress the thermal deterioration of the catalyst.

In the first embodiment, the catalyst temperature sensor 14 is not always necessary and may be omitted. Next, FIG. 10 shows a second embodiment of the temperature control device using the temperature predicting device for an internal combustion engine according to the present invention. The apparatus of this embodiment is intended for the above-mentioned catalyst that purifies harmful gas components contained in exhaust gas of an internal combustion engine (engine) mounted on a vehicle into harmless components, and the temperature of the catalyst is measured by a temperature sensor. It is a device that controls the temperature of the target catalyst to a target temperature by detecting and operating and correcting the amount of fuel supplied to the engine based on the detected temperature.

However, also in the device of the second embodiment, the basic configuration is the same as that shown in FIG. 1, and the control circuit 2 which is the characteristic part thereof is also here.
Only the 0 configuration is shown. Further, in FIG. 10, elements that are the same as or correspond to the elements shown in FIG. 1 above are denoted by the same reference numerals.

Now, in the device of the second embodiment,
The control circuit 20 calculates the time constant of the catalyst temperature sensor 14 in accordance with the operating state of the engine, and predicts the actual catalyst temperature using the model constant of the temperature prediction model obtained from this calculated time constant. Here, the flow velocity detector 28
The catalyst temperature sensor time constant calculation unit 27 is a part that detects the flow rate of exhaust gas, and is a part that calculates the time constant (sensor time constant) τ of the catalyst temperature sensor 14 according to the detected flow rate. The method of calculating the sensor time constant τ will be described below.

Generally, when measuring the temperature of a fluid, the sensor time constant τ is the density ρ of the sensor element, the specific heat c, the radius r,
And the heat transfer coefficient h between the sensor element and the fluid,

[0098]

[Expression 33] It is expressed as

Further, the heat transfer coefficient h is the representative dimension of the sensor,
Depends on the type of fluid and the flow velocity μ of the fluid. Therefore, if the types of the temperature sensor and the fluid are determined, the heat transfer coefficient h of the temperature sensor is expressed by the following equation.

[0100]

H = χ + ψμ ^1/2 (34) where χ and ψ are unknown constants that depend on the sensor element, diameter, fluid type, and the like. Thus, when measuring the catalyst temperature, the sensor time constant τ is the gas flow rate μ in the catalyst.
Varies by. Further, this means that if the gas flow rate μ in the catalyst is detected in real time and the time constant of the catalyst temperature sensor 14 is calculated according to the detected flow rate μ, it is always optimum in any engine operating state. This means that the sensor time constant τ can be obtained.

Therefore, for example, the engine speed sensor 18
And the gas flow velocity μ in the catalyst is calculated based on the information on the engine operating state detected by the pressure sensor 1, and the sensor time constant τ is calculated from this,

[0102]

[Equation 35] Becomes

Here, C ₁ and C ₂ are unknown constants depending on the element of the sensor, the kind of fluid, the heat transfer coefficient, and the like.
However, the optimum values of these constants C ₁ and C ₂ can be obtained in advance through experiments and the like. Here, for the sake of convenience, the gas flow velocity μ in the catalyst is calculated based on the information on the engine operating state detected by the engine speed sensor 18 and the pressure sensor 1, but in an engine equipped with an air flow meter, The gas flow rate μ in the catalyst can also be calculated based on the information detected by the air flow meter. Further, not only the gas flow rate μ in the catalyst but also an amount corresponding to this may be calculated.

The sensor model constant calculating section 25 is a section for calculating the model constant of the catalyst temperature model based on the time constant τ of the catalyst temperature sensor 14 calculated by the catalyst temperature sensor time constant calculating section 27 in this way. Here, the model constants of the model for predicting the actual temperature Tex of the catalyst temperature based on the catalyst temperature Texs detected by the catalyst temperature sensor 14 are a ₁ , b ₁ , b ₂ , and c ₁ , and the number of times of control is When the variable shown is i, the response delay for the temperature Texs detected by the catalyst temperature sensor 14 is expressed by the following equation.

[0105]

Texs (i + 1) = a ₁ Texs (i) + b ₁ Tex (i + 1) + b ₂ Tex (i) + c ₁ (36) This is calculated from the actual catalyst temperature Tex to (b ₁ Z + b ₂ ) /
This shows that the sensor temperature Texs is detected with a first-order lag of (Z−a ₁ ), and this is illustrated in FIG. 11A. Since the actual catalyst temperature Tex is estimated from the sensor temperature Texs,
Consider an inverse model as shown in FIG. This inverse model is derived from the equation (36) above.

[0106]

(37) (Z−a ₁ ) Texs (i) = (b ₁ Z + b ₂ ) Tex (i) (37). Therefore, the required catalyst temperature Tex is

[0107]

(38) Will be obtained as. However, future information such as (i + 1) cannot be used, so here

[0108]

[Formula 39] Is approximated as.

Thus, the model constants a ₁ , b ₁ ,
If b ₂ and c ₁ are given, the present sensor temperature Texs (i) and the previous sensor temperature Texs (i-1), and the previous catalyst predicted temperature Tex (i-1) by the catalyst temperature prediction unit 21 itself are used. , The actual catalyst temperature Tex (i) at that time can be predicted. However, these model constants a ₁ , b ₁ , b ₂ , c
₁ is an unknown constant depending on the time constant τ of the catalyst temperature sensor 14. Therefore, an example of a method of calculating the model constant a ₁ will be shown below.

That is, when the sampling period T of the sensor temperature Texs (i) is given, the sensor time constant τ calculated based on the equation (35) gives

[0111]

(Equation 40)

As a result, the unknown constant a ₁ depending on the sensor time constant τ is calculated in real time. Similarly, for other unknown constants b ₁ , b ₂ and c ₁ ,
By using the sensor time constant τ calculated based on the equation (35), it is possible to perform real-time calculation in a form according to the equation (40).

The catalyst temperature predicting section 21 uses the catalyst temperature Texs detected by the catalyst temperature sensor 14 and the model constant calculated by the sensor model constant calculating section 25 in the manner represented by the above equation (39). Estimate and predict the actual catalyst temperature. Both the correction amount calculation unit 22 and the multiplier 23 are the same as those of the apparatus according to the first embodiment described above, and redundant description of the details thereof will be omitted.

12 to 15 show the processing procedure of the processing actually performed by the control circuit 20 of the apparatus of the second embodiment to predict the catalyst temperature.
The operation of the entire apparatus of the second embodiment will be described in more detail with reference to FIGS. FIG. 12 shows this second
In the apparatus of the above embodiment, a processing routine (timer interrupt routine 700) is shown which is executed by the control circuit 20 with a timer interrupt every 120 ms in order to perform the temperature prediction.

That is, the control circuit 20 which has entered the timer interrupt routine 700 based on the above timer interrupt first takes in the present catalyst temperature Texs (i) output from the catalyst temperature sensor 14 (step 710). Next, the control circuit 20 detects the current operating state of the engine, and outputs the current engine speed information Ne (i) output from the engine speed sensor 18 and the pressure sensor 1.
The current intake pressure information Pm (i) output from is taken in (step 720).

The control circuit 20 which has thus taken in the engine speed information Ne (i) and the intake pressure information Pm (i),
Based on these pieces of information, the time constant τ of the catalyst temperature sensor 14 is calculated by the above equation (35) (step 730). The time constant calculation routine 730 of the catalyst temperature sensor is shown in detail in FIG. That is, the time constant calculation routine 7 of the catalyst temperature sensor shown in FIG.
At 30, the control circuit 20 first proceeds to the previous step 72.
The engine speed information Ne (i) and the intake pressure information Pm (i), which are fetched through 0 and temporarily stored in the RAM or the like, are read into the catalyst temperature sensor time constant calculation unit 27 (step 731). The control circuit unit 20 is also obtained in advance through experiments and the like, and this is also a backup RAM.
The constants C ₁ and C ₂ depending on the element of the sensor, the type of fluid, the heat transfer coefficient, etc., which are stored and held in the ROM or ROM are read into the catalyst temperature sensor time constant calculation unit 27 (step 732). Then, the control circuit calculates the time constant τ of the catalyst temperature sensor 14 corresponding to the read values through the catalyst temperature sensor time constant calculation unit 27 based on the above equation (31) (step 733).

The control circuit 20 which has obtained the time constant τ of the catalyst temperature sensor 14 in the above manner then calculates the model constants a ₁ , b ₁ , b ₂ and c ₁ based on the obtained sensor time constant τ. It is calculated (step 740 in FIG. 12). The model constant calculation routine 740 of this catalyst temperature prediction model is shown in detail in FIG. That is, in the model constant calculation routine 740 shown in FIG. 14, the control circuit 20 reads the sensor time constant τ obtained above into the sensor model constant calculation unit 25 (step 741) and sets a preset temperature detection cycle. Under T, for example, the model constant a ₁ is calculated based on the above equation (40) (step 742). Here, the sampling period T is provisionally set to 120 ms. In addition, in the example of FIG.
Only for the model constant a ₁ , the calculation of the equation (40) is executed based on the sensor time constant τ, and other model constants b ₁ ,
As for b ₂ and c ₁ , the values that match the optimum values are used through experiments and the like (steps 743 to 74).
5). Of course, with respect to these model constants b ₁ , b ₂ and c ₁ , it is also possible to calculate them in real time based on the sensor time constant τ to obtain them.

Thus, the model constants a ₁ , b ₁ , b ₂ , c
_The control circuit 20 that has obtained ₁ further determines the previous detected catalyst temperature Texs (i-1) and the previous predicted catalyst temperature Tex (i-) that are stored in the RAM or the backup RAM in the control circuit 20. 1) together with the obtained model constants, the actual catalyst temperature Tex (i) at that time is used.
Is calculated (estimated) (step 750 in FIG. 12). Regarding the calculation routine 750 of this estimated catalyst temperature Tex (i),
The details are shown in FIG.

That is, in the calculation routine 750 of the estimated catalyst temperature Tex (i) shown in FIG. 15, the control circuit 20 first (1) presents the catalyst temperature Texs (i output from the catalyst temperature sensor 14. ) Is read (step 751). (2) The previous detected catalyst temperature Texs (i-1) which is stored in the RAM or the backup RAM is read (step 752). (3) The previous predicted catalyst temperature Tex (i-1), which is also stored in the RAM or the backup RAM, is read (step 753). After performing such processing, the model constants a ₁ , b ₁ , b ₂ and c ₁ obtained through the processing of step 740 are also read in the same manner (step 754). Then, the control circuit 20 executes the calculation of the above equation (39) based on these read values through the catalyst temperature predicting unit 21 ″, and the actual temperature of the catalyst at that time (estimated catalyst temperature) Tex (i) is calculated (step 755).

The control circuit 20 that has predicted the actual catalyst temperature Tex (i) in this manner then next predicts the predicted catalyst temperature Tex (i).
(i) is given to the correction amount calculation unit 22, and the same correction amount (Fex) calculation process as described above is executed through the correction amount calculation unit 22 (see FIG. 7). Then, the main routine 1000 shown in FIG. 9 is similarly executed in the device of the second embodiment as well, and the reference operation amount (fuel reference injection amount) TAU based on the above equation (14) is calculated. Correction is performed.

As described above, in the apparatus of the second embodiment, the catalyst temperature sensor 14 is modeled as shown in the equation (39), and the gas flow velocity at that time is obtained from the equation (40). According to the above, the model constants of the modeled sensor model are calculated in real time. Therefore, no matter what the operating state of the engine, the catalyst temperature can be predicted as more reliable information, and thus the catalyst temperature can be controlled with higher accuracy.

In the second embodiment, the exhaust temperature sensor 13 is not always necessary, and may be omitted. In addition, in the device of the second embodiment, the case where the catalyst temperature is the control target is shown, but the temperature that is the control target of the device of the second embodiment is the same as in the device of the first embodiment. It may be the temperature of the exhaust gas to be controlled.

Further, the model of the assumed temperature sensor is not limited to the model exemplified by the equation (36), but may be any model, and the model of the first embodiment is also assumed (1
The model shown in the equation (1) can be appropriately adopted. Furthermore, the device of the second embodiment and the device of the first embodiment are combined, and at the time of fuel cut, the model constant of the model of the temperature sensor is based on the temperature of the control target estimated at that time. And a device that calculates the model constant of the sensor model in real time based on the detected fluid flow velocity at other times. As the above, the same temperature control device can be configured.

Next, a third embodiment will be described in which the exhaust temperature predicted in the first embodiment is used to execute the early warm-up control of the three-way catalyst of the exhaust gas purifying apparatus. In this embodiment, at the time of cold start, or when the three-way catalyst for purifying exhaust gas harmful substances does not reach the temperature at which exhaust gas harmful substances can be sufficiently purified, catalyst early warm-up means (for example, The catalyst temperature is raised to the catalyst activation temperature as quickly as possible by ignition timing retard processing, engine speed increase processing, etc.) to reduce the emission of exhaust gas harmful substances. Further, in order to prevent the exhaust temperature or the catalyst temperature from abnormally rising due to the catalyst early warm-up means and the exhaust system parts such as the three-way catalyst from being thermally deteriorated, the predicted exhaust temperature or the catalyst temperature is set to a predetermined temperature or higher. Then, the catalyst early warm-up means is stopped.

FIG. 16 is a flowchart showing the above processing.
Is. Hereinafter, description will be given according to this flowchart. 16 is a routine corresponding to the correction amount calculation routine of step 520 of FIG. 4 of the first embodiment. In the present embodiment, this processing is performed at predetermined time intervals (for example, 10
Every 0 ms). When this processing is executed, first, the deviation S (i) between the actual exhaust temperature Tex1 predicted by the exhaust temperature prediction processing described in the first embodiment and the target exhaust temperature TR1 is calculated (step 801). . Here, the target exhaust gas temperature TR1 is the exhaust gas temperature at which the three-way catalyst is activated to a predetermined temperature. Next, this deviation S (i) is 0
It is determined whether or not the following (step 802). Here, if the deviation S (i) is 0 or less, the present process is terminated without executing the following catalyst early warm-up process. At this time, it is determined whether the idle speed and the ignition timing controlled by the catalyst early warm-up process have been returned to the values before the catalyst early warm-up control (or the values according to the current operating state). (Step 807) If these values have not been returned, these values are returned (Steps 808 and 809) and this processing is terminated. If it has been returned, this processing is ended as it is.

When the deviation S (i) is greater than 0 in step 802, the idle engine speed is increased to a predetermined speed (for example, 1200 rpm) (step 803). Furthermore, fluctuations in engine speed (roughness)
Until the occurrence of a predetermined roughness or more, the ignition timing is retarded by a predetermined retard amount AR (step 804, step 8
05). When the predetermined roughness is reached, the retard control is stopped, and the ignition timing immediately before the roughness becomes equal to or higher than the predetermined roughness is held (step 806). Then, this processing is ended and the above processing is repeated.

A time chart when the above processing is executed is shown in FIG. 17 and will be described below with reference to this time chart. When the predicted exhaust gas temperature or catalyst temperature is equal to or lower than a predetermined value (for example, at the time of cold start), the catalyst early warm-up means performs warm-up of the three-way catalyst. Specifically, the idle engine speed (not shown) is set to 1200 rp.
The ignition timing is retarded at time t1 until the rotation fluctuation amount (roughness) reaches a predetermined value. Then, when the roughness exceeds a predetermined value, the ignition timing is fixed before the roughness exceeds the predetermined value. Furthermore, at time t2, when the exhaust gas temperature reaches or exceeds the predetermined temperature (850 ° C. in this embodiment), the idle engine speed increase is stopped, and
Advance the ignition timing.

By the above processing, the temperature of the three-way catalyst can be raised to the activation temperature in a shorter time. Furthermore, it is possible to prevent the exhaust temperature or the catalyst temperature from rising and the exhaust system parts such as the three-way catalyst from being thermally deteriorated. In the third embodiment, as shown in FIG. 18, the ignition timing retard amount during the early catalyst warm-up depends on the predicted deviation between the actual exhaust gas temperature and the target exhaust gas temperature. The ignition timing retardation amount may be increased by decreasing the ignition timing retardation amount and increasing the deviation. As a result, when the deviation is large, the ignition retard amount immediately increases, so that the exhaust temperature can be raised faster.

Further, in FIG. 16 of the third embodiment, the ignition timing is retarded until the catalyst early warm-up process reaches the predetermined roughness, but as shown in FIG. You may make it increase by predetermined value (alpha).
Further, the predetermined value α may be set to be larger as S (i) is larger, and by doing so, the three-way catalyst can be warmed up faster.

[0130] Next, using the predicted exhaust temperature in the first embodiment, an embodiment for performing the optimum catalyst temperature control of the lean NO _X catalyst as a fourth embodiment. In a lean burn system capable of lean combustion, in order to purify NO _X emitted in the lean air-fuel ratio range, a lean lean N zeolite system in which a transition metal or a noble metal is carried in the exhaust system.
It is disposed O _X catalyst. However, this lean NO _X
As shown in FIG. 20, the NO _x purification rate of the catalyst varies depending on the temperature of the exhaust gas flowing through this catalyst or the temperature of this catalyst bed, and the purification rate becomes maximum when this temperature is around 500 ° C. Then, the purification rate decreases at points other than this temperature.

Therefore, in the fourth embodiment, lean NO is set._Xcatalyst
In order to maintain a high purification rate of
Controls the catalyst bed temperature. FIG. 21 is a schematic diagram of the fourth embodiment.
It is a diagram. Lean NO installed in the exhaust system _Xcatalyst
An exhaust temperature sensor 13 is provided upstream of 19.
With this exhaust temperature sensor 13, lean NO_XFlow to catalyst 19
The temperature of incoming exhaust gas is detected. And this inspection
From the discharged exhaust gas temperature Texs, the explanation was made in the first embodiment.
The actual exhaust gas temperature is predicted by processing. Further this embodiment
Then, based on the predicted actual exhaust gas temperature, the actual exhaust gas
Control the temperature so that it falls within the target temperature range.

FIG. 22 is a flowchart showing the above processing.
Is. This FIG. 22 is step 5 of FIG. 4 of the first embodiment.
Equivalent to 20. Hereinafter, description will be given according to this flowchart. Note that this flowchart is executed every predetermined time (for example, every 100 ms). When this processing is executed, first, the actual exhaust temperature Tex predicted in the first embodiment is
Is read (step 821). Then, it is determined whether or not the read actual exhaust gas temperature Tex is the lower limit value T ₁ or more of the target temperature range (step 822). If the actual exhaust temperature Tex is less than the lower limit value T ₁ , the ignition retard amount is read, and the ignition timing is retarded to raise the exhaust temperature lower than the target temperature range (step 823, step 824), and this processing is executed. finish.

If an affirmative decision is made in step 822, the actual exhaust gas temperature Tex is the upper limit value T _{2 of the} target temperature range.
It is determined whether or not the following (step 825). here,
If an affirmative decision is made, in step 828, the ignition retard amount (AR) or the fuel injection amount correction amount (Fex) for exhaust gas temperature control is reset, and this processing ends. When a negative determination is made in step 825, the fuel injection amount correction amount is read (step 826), the fuel injection amount is increased and corrected (step 827), and this processing ends. In this way, by increasing the fuel injection amount, it is possible to reduce the exhaust gas temperature that has become higher than the target temperature range.

[0134] By executing the above processing, since the temperature Texs detected by the exhaust gas sensor 13 with a response delay, exhaust temperature to the temperature range obtained by high purification rate lean NO _X catalyst 19 using the temperature Texs Was difficult to adjust, but the exhaust gas temperature can be easily controlled by using the actual exhaust gas temperature Tex predicted by using the temperature Texs detected by the exhaust gas sensor 13. Therefore, it is possible to maintain a lean NO _X catalyst 19 is always high purification rate, it is possible to suppress deterioration of emission.

In the fourth embodiment, step 822 is used.
When T ₁ > Tex in Step 823, Step 82
In 4, the ignition timing is retarded to raise the actual exhaust temperature. However, in a normal operating state, there is no possibility that the actual exhaust gas temperature Tex becomes lower than or equal to the lower limit value T ₁ of the target temperature range. Good.

Although the exhaust gas temperature is controlled in the third and fourth embodiments, the catalyst bed temperature may be predicted and controlled by the method of the second embodiment instead. Next, using the exhaust gas temperature predicted in the first embodiment, the oxygen concentration detecting means (in this embodiment, the O ₂ sensor 2
The fifth embodiment will be described as an embodiment in which the optimum energization control of the heater for the early warm-up of 9) is executed.

The exhaust system of the internal combustion engine is provided with an oxygen (O ₂ ) sensor 29 as an oxygen concentration detecting means. Then, based on the oxygen concentration detected by the O ₂ sensor 29, feedback is given to the fuel control system or the ignition timing control system to adjust the fuel injection amount, the fuel injection timing or the ignition timing so that a preferable exhaust gas composition is obtained. Have control over. As a result, the purification rate of the exhaust purification catalyst is increased. The O ₂ sensor 29 measures the electromotive force or electric resistance generated therein by using an element such as zirconia to measure the oxygen concentration in the exhaust gas, but it must be heated to some extent (not activated). Do not output the correct signal according to the oxygen concentration.

Therefore, a heater for heating the O ₂ sensor 29 by embedding a resistance wire in the element of the O ₂ sensor 29 and flowing an electric current to warm up early is the O ₂ sensor 29 of this embodiment.
Is equipped with. However, since electric power is supplied to the heater of the O ₂ sensor 29 to raise the element temperature, the load on the power generator (alternator) is increased, and the load on the internal combustion engine is increased, which may deteriorate fuel efficiency. . When the exhaust gas temperature rises, the O ₂ sensor 29
Since the temperature also rises, there is no need for heating with a heater.

Therefore, in the fifth embodiment, in order to efficiently warm up the O ₂ sensor 29 early without supplying extra power, the energization of the heater of the O ₂ sensor 29 is controlled according to the exhaust temperature. are doing. FIG. 23 is a flowchart of this heater energization control process. Hereinafter, description will be given according to this flowchart. This FIG. 23 corresponds to step 520 of FIG. 4 of the first embodiment. Note that this flowchart is executed every predetermined time (for example, every 100 ms).

When this processing is executed, the actual exhaust gas temperature Tex predicted in the first embodiment is read (step 83).
1). Then, the actual exhaust temperature Tex is compared with the O ₂ sensor activation temperature T _O2 (step 832). If Tex <T _{O2, the} heater is energized to heat the O ₂ sensor 29 (step 832).
33), the present process is terminated. When Tex ≧ T _O2 in step 832, the integrated value S of the actual exhaust gas temperature Tex is calculated (step 834) and the integrated value S is compared with the predetermined value S _O2 (step 835). Where S <S
If _O2, heating the O ₂ sensor 29 by energizing the heater (step 833). If S ≧ S _O2, it is determined that the temperature of the O ₂ sensor 29 has risen sufficiently and a correct signal can be output, and the energization of the heater is stopped (step 836), and the integrated value S Is cleared (step 837), and this processing ends.

The above process is shown in the time chart.
FIG. 24. In FIG. 24, T _O2Is O₂Sensor 29
Is the temperature at which the_O2Below is O₂
Since the sensor 29 is not activated, oxygen in the exhaust gas
The correct signal corresponding to the concentration cannot be output.
Therefore, Tex <T_O2Energize the heater when
O₂The sensor 29 is heated (time t₀~Times of Day
t₁). Exhaust temperature rises to temperature T_O2When it is above,
The exhaust temperature Tex is integrated. Then, this integrated value S is predetermined
Value S_O2When the above is reached, the power supply to the heater is turned off (time t
₂). That is, the integrated value S is the predetermined value S_O2When
O₂The sensor 29 is fully activated by the exhaust gas and the heater.
And determine that the correct signal is being output according to the oxygen concentration
are doing.

Further, when the exhaust temperature Tex falls and becomes equal to or lower than the temperature T _O2 in the idle state or during deceleration, it is judged that the temperature of the O ₂ sensor 29 has fallen below the activation temperature, and the energization control to the heater is restarted. (Time t ₃ ). Then, the control described above is repeatedly executed.
In the fifth embodiment, since the actual exhaust gas temperature detected in real time is used, the timing for controlling the heater energization (stop) can be accurately grasped, so that the warm-up can be performed early and the heating control more than necessary. Can be prevented. Furthermore, the electric load on the internal combustion engine can be suppressed to the necessary minimum. Therefore, deterioration of fuel efficiency can be suppressed.

Further, in the above embodiment, the fuel injection amount is adopted as an element to be operated to control the catalyst temperature or the exhaust temperature, and the operation amount of the fuel injection valve which is the actuator is corrected or the ignition timing is adjusted. However, there are other factors that can be manipulated to control the temperature of the catalyst, such as exhaust gas circulation rate that is manipulated through EGR (exhaust gas recirculation system), This operating element can also be appropriately adopted as an operating element for controlling the temperature of the catalyst.

[0144]

As described above, according to the invention described in claim 1, when the catalyst temperature of the three-way catalyst is estimated in real time and the catalyst temperature is low, the exhaust gas temperature control means discharges the exhaust gas. The gas temperature is controlled to be high. As a result, the catalyst temperature can be raised and the three-way catalyst can be activated early. As a result, the purification efficiency of the exhaust gas purification device can be improved,
Emission deterioration due to exhaust gas can be suppressed.

Here, as means for increasing the exhaust gas temperature, for example, a means for retarding the ignition timing as described in claim 2 or an idle speed as described in claim 3 There is a means to raise. Further, as the means for detecting the temperature of the three-way catalyst, for example, a means for predicting from the exhaust gas temperature as described in claim 4 or the temperature of the three-way catalyst as described in claim 5 is used. There is a means of direct detection.

According to the apparatus of the sixth aspect, the temperature of the catalyst can be adjusted within the first target temperature and the second target temperature by using the temperature of the catalyst predicted in real time. Therefore, for example, when the three-way catalyst is used as the catalyst as described in claim 10, it is possible to perform early warm-up of the catalyst and control the catalyst temperature so that the catalyst does not become too hot and is not thermally deteriorated. it can. Also, for example,
When a lean catalyst is used as the catalyst according to the eleventh aspect, the temperature of the catalyst can be accurately controlled within a narrow temperature range where the purification rate is maximum.

At this time, as a means for raising or lowering the temperature of the catalyst, for example, by retarding the ignition timing as described in claim 7, the temperature is raised and the fuel injection amount is made rich. There is a means for lowering the temperature. Further, as a means for detecting the catalyst temperature, the method according to claim 8
The catalyst temperature may be predicted from the temperature of the exhaust gas, or the catalyst temperature may be directly detected as described in claim 9.

Further, in the apparatus according to the twelfth aspect, the temperature of the oxygen concentration sensor predicted in real time is used, and when it is determined that the oxygen concentration sensor is not warmed up, the heater is energized to warm it up. When it is determined that the heating has been finished, the heater energization is stopped, so that the oxygen concentration sensor can be warmed up early and the wasteful heater energization can be suppressed.

As means for predicting the temperature of the oxygen concentration sensor, there is, for example, means for predicting the temperature of the exhaust gas as described in claim 13. Further, according to the invention described in claim 14, when it is determined that the catalyst temperature is too high due to the catalyst temperature obtained in real time, for example, the fuel injection amount is increased and the catalyst temperature is controlled to be lowered. As a result, the response delay of the temperature sensor is eliminated, and the temperature is lowered as soon as the high temperature state of the catalyst is detected, so that thermal deterioration of the catalyst can be further suppressed.

According to the fifteenth aspect of the invention, the sensor model constant is calculated in real time from the flow velocity of the exhaust gas, so that the exhaust gas temperature or the catalyst temperature can be predicted more accurately. further,
According to the sixteenth aspect of the invention, the sensor model constant is calculated by utilizing the fact that the exhaust gas temperature becomes a known value when the fuel is cut, so the exhaust gas temperature or the catalyst temperature is predicted more accurately. can do.

According to the seventeenth aspect of the present invention, since the exhaust gas temperature or the catalyst temperature is predicted by the equation (1), the exhaust gas temperature or the catalyst temperature can be predicted more accurately.

[Brief description of drawings]

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

FIG. 2 is a block diagram mainly showing the functions of the control circuit part of the first embodiment of the temperature control apparatus for an internal combustion engine according to the present invention and the connection relationship between these functions.

3 is a block diagram exemplifying a discretized transfer function (digital amount) of a first-order lag used in configuring the catalyst temperature prediction unit shown in FIG.

FIG. 4 is a flowchart showing a processing procedure of a control circuit that is executed at a constant cycle as an operation example of the apparatus of the first embodiment.

5 is a flowchart showing the behavior of the sensor model constant calculation unit shown in FIG. 2 during fuel cut, and the processing procedure of the actual exhaust temperature prediction processing executed by the exhaust temperature prediction unit shown in FIG.

6 is a flowchart showing a procedure for correcting a sensor model constant, which is executed by a sensor model constant calculating section shown in FIG.

FIG. 7 is a flowchart showing a correction amount calculation procedure executed by a correction amount calculation unit shown in FIG.

8 is a flowchart showing a procedure of modifying a controlled object model constant executed by a controlled object model constant calculating unit shown in FIG.

FIG. 9 is a flowchart showing a processing procedure according to a main routine of the apparatus of the first embodiment.

FIG. 10 shows a temperature control device for an internal combustion engine according to a second embodiment of the present invention and a temperature predicting device used in the temperature control device, mainly regarding the functions of the control circuit part and the connection relationship between the functions. It is a block diagram shown.

11 is a block diagram exemplifying a discretized transfer function (digital amount) of a first-order lag used in configuring the catalyst temperature prediction unit shown in FIG.

FIG. 12 is a flowchart showing a processing procedure of a control circuit that is executed at a constant cycle as an operation example of the apparatus of the second embodiment.

13 is a flowchart showing a processing procedure of processing executed by a catalyst temperature sensor time constant calculation unit shown in FIG.

14 is a flowchart showing a processing procedure of processing executed by a sensor model constant calculating unit shown in FIG.

15 is a flowchart showing a processing procedure of processing executed by a catalyst temperature prediction unit shown in FIG.

FIG. 16 is a flowchart executed to warm up the three-way catalyst early in the third embodiment.

FIG. 17 is a time chart showing the behavior of the exhaust gas temperature, the catalyst temperature, the ignition timing, and the rotation fluctuation amount when the catalyst early warm-up control is executed.

FIG. 18 is a characteristic diagram showing the characteristics of a map used when the amount of retarding the ignition timing is variable according to the exhaust temperature in the catalyst early warm-up control.

FIG. 19 is a flowchart executed to warm up a three-way catalyst in an early stage in a modification of the third embodiment.

FIG. 20: NO of the lean NO _X catalyst used in the fourth embodiment
It is a characteristic view showing _X purification characteristics.

FIG. 21 is a configuration diagram showing a system configuration of a fourth embodiment.

FIG. 22 is a flowchart showing a control process of lean NO _x catalyst temperature in the fourth embodiment.

FIG. 23 is a flowchart showing an oxygen sensor early warm-up process executed in the fifth embodiment.

FIG. 24 is a diagram when an oxygen sensor early warm-up process is executed.
It is a time chart which shows the behavior of exhaust temperature and heater energization state.

FIG. 25 is a diagram corresponding to a complaint.

[Explanation of symbols]

1 Pressure Sensor 2 Intake Temperature Sensor 3 Throttle Valve 4 Throttle Sensor 5 Surge Tank 6 Intake Manifold 7 Fuel Injection Valve 8 Engine Body 9 Spark Plug 10 Cooling Water Temperature Sensor 11 Exhaust Manifold 12 Catalyst (Catalyst Converter) 13 Exhaust Temperature Sensor 14 Catalyst Temperature Sensor 15 Distributor 16 igniter 17 cylinder discriminating sensor 18 engine speed sensor 19 lean NO _X catalyst 20 ... control circuit 21, 21 ', 21 "catalyst temperature prediction unit 22, 22' correction amount calculation unit 23 the multiplier 24 controlled object model constants calculated Part 25, 25 ', 25 "Sensor model constant calculator 26, 26' Exhaust temperature predictor 27 Catalyst temperature sensor time constant calculator 28 Flow velocity detector 29 Oxygen sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F01N 3/28 301 C F02D 41/16 E 45/00 312 R F02P 5/15

Claims (17)

[Claims] 1. A three-way catalyst provided in an exhaust pipe for purifying exhaust gas, a three-way catalyst temperature detecting means for detecting the temperature of the three-way catalyst, and a detection response delay of the three-way catalyst temperature detecting means A sensor model constant calculating means for calculating the model constant of the expected model in real time, based on the temperature detected by the three-way catalyst temperature detecting means, the model constant calculated by the sensor model constant calculating means and the three-way catalyst A three-way catalyst temperature predicting means for predicting the actual temperature of the three-way catalyst by using an inverse model of a model in which the response delay of the temperature detecting means is used, and the predicted actual three-way catalyst temperature is the target temperature. When the temperature is less than the above, it is determined that the catalyst is not activated and the exhaust gas temperature is controlled to rise. When the actual three-way catalyst temperature is equal to or higher than the target temperature, the catalyst is activated. And it is determined that that the temperature control device of the exhaust gas purifying apparatus, comprising a discharge gas temperature control means to stop the control of the exhaust gas temperature. 2. The temperature control device for an exhaust gas purifying apparatus according to claim 1, wherein the exhaust gas temperature control means includes means for increasing the exhaust gas temperature by retarding the ignition timing. 3. The exhaust gas temperature control means includes means for increasing the exhaust gas temperature by increasing the idle speed.
The temperature control device for the exhaust gas purification device according to 1. 4. The three-way catalyst temperature detecting means is an exhaust gas temperature sensor for detecting the temperature of exhaust gas, and the exhaust gas temperature predicting means uses the exhaust gas temperature detected by the exhaust gas temperature sensor for detecting the temperature of the exhaust gas. The temperature control device for an exhaust gas purification device according to any one of claims 1 to 3, further comprising means for predicting a temperature of the original catalyst. 5. The exhaust gas according to claim 1, wherein the three-way catalyst temperature detecting means is a three-way catalyst temperature sensor that detects the temperature of the three-way catalyst. Purification device temperature control device. 6. A catalyst provided in an exhaust pipe for purifying exhaust gas, a catalyst temperature detecting means for detecting a temperature of the catalyst, and a model constant of a model in consideration of a response delay of the catalyst temperature detecting means in real time. Based on the temperature detected by the sensor model constant calculating means for calculating, and the catalyst temperature detecting means,
Catalyst temperature predicting means for predicting the actual temperature of the catalyst by using a model constant calculated by the sensor model constant calculating means and an inverse model of a model in which the response delay of the catalyst temperature detecting means is taken into account; When the actual catalyst temperature is lower than the first target temperature, the exhaust gas temperature is controlled to increase, and
An exhaust gas temperature control means for controlling the exhaust gas temperature to decrease when the actual catalyst temperature is equal to or higher than the second target temperature which is higher than the first target value. Temperature control device. 7. The exhaust gas temperature control means includes means for increasing the exhaust gas temperature by retarding the ignition timing and decreasing the exhaust gas temperature by enriching the fuel injection amount. The temperature control device for an exhaust gas purification device according to claim 6. 8. The catalyst temperature detecting means is an exhaust temperature sensor for detecting the temperature of exhaust gas, and the catalyst temperature predicting means determines the temperature of the catalyst according to the temperature of exhaust gas detected by the exhaust temperature sensor. The temperature control device for an exhaust gas purification device according to claim 6 or 7, further comprising a predicting unit. 9. The temperature control device for an exhaust gas purifying apparatus according to claim 6, wherein the catalyst temperature detecting means is a catalyst temperature sensor for detecting the temperature of the catalyst. . 10. The temperature control device for an exhaust gas purification device according to claim 6, wherein the catalyst is a three-way catalyst. 11. The temperature control device for an exhaust gas purification device according to claim 6, wherein the catalyst is a lean catalyst that mainly purifies nitrogen oxides in the exhaust gas. . 12. An oxygen concentration sensor which is provided in an exhaust pipe and outputs a rich or lean signal according to the oxygen concentration in exhaust gas, an oxygen concentration sensor temperature detecting means for detecting the temperature of the oxygen concentration sensor, A heater for warming up the oxygen concentration sensor, a sensor model constant calculation means for calculating a model constant of the model in consideration of a response delay of the oxygen concentration sensor temperature detection means in real time, and the oxygen concentration sensor temperature detection means Based on the temperature, the actual temperature of the oxygen concentration sensor is predicted by using a model constant calculated by the sensor model constant calculation means and an inverse model of a model that allows for a response delay of the oxygen concentration sensor temperature detection means itself. Oxygen concentration sensor temperature predicting means, and when the predicted actual sensor temperature is less than the target temperature, Temperature sensor is not activated, the heater is energized and controlled, and when the actual sensor temperature is equal to or higher than the first target temperature, it is determined that the oxygen concentration sensor is activated. A temperature control device for an exhaust gas purification device, comprising: heater energization control means for stopping energization. 13. An exhaust temperature sensor for detecting a temperature of exhaust gas flowing through the exhaust pipe, wherein the oxygen concentration sensor temperature detecting means is the exhaust temperature sensor, and the oxygen concentration sensor temperature predicting means is the exhaust gas. 13. The temperature control device for an exhaust gas purifying apparatus according to claim 12, further comprising means for predicting the temperature of the oxygen concentration sensor using the exhaust gas temperature detected by the temperature sensor. 14. A three-way catalyst provided in an exhaust pipe for purifying exhaust gas, a three-way catalyst temperature detecting means for detecting a temperature of the three-way catalyst, and a detection response delay of the three-way catalyst temperature detecting means. A sensor model constant calculating means for calculating the model constant of the expected model in real time, based on the temperature detected by the three-way catalyst temperature detecting means, the model constant calculated by the sensor model constant calculating means and the three-way catalyst A three-way catalyst temperature predicting means for predicting the actual temperature of the three-way catalyst by using an inverse model of a model in which the response delay of the temperature detecting means is used, and the predicted actual three-way catalyst temperature is the target temperature. In the above cases, the exhaust gas temperature is controlled so as to decrease, and when the actual three-way catalyst temperature is lower than the target temperature, the exhaust gas temperature control means for stopping the control of the exhaust gas temperature is provided. Temperature control of the exhaust gas purifying device according to claim Rukoto. 15. A flow velocity detecting means for detecting a flow velocity of exhaust gas is provided, and the sensor model constant calculating means includes a means for calculating the model constant in real time based on the flow velocity detected by the flow velocity detecting means. Claim 1 characterized by the above-mentioned.
15. The temperature control device for an exhaust gas purification device according to claim 14. 16. A fuel cut detecting means for detecting whether or not a fuel cut is being performed, wherein the sensor model constant calculating means detects that the fuel cut is being performed by the fuel cut detecting means. At this time, the temperature control device of the exhaust gas purifying apparatus according to any one of claims 1 to 15, further comprising means for calculating the model constant based on the exhaust gas temperature estimated at the time of fuel cut. 17. The temperature predicting means sets the current temperature detected by the temperature sensor to Texs (i), the previous temperature detected by the temperature sensor to Texs (i-1), and the temperature sensor model constants a ₁ and b. _{When 1} , b ₂ and c ₁ are used, the actual temperature Tex (i) of the target location predicted this time is expressed by 17. The temperature control device for an exhaust gas purification device according to claim 1, further comprising: