JPH01219340A - Temperature estimator of exhaust system parts for internal combustion engine - Google Patents

Abstract

PURPOSE:To estimate a temperature rise in an air-fuel ratio sensor in a highly accurate manner by compensating an increase time, when the integrating value of a compensation value conformed to an intake air quantity is increased up to the specified value, for prolongation according to an outside temperature drop, at time of estimating a temperature change in exhaust system parts. CONSTITUTION:A compensation value being set according to an intake air quantity of an internal combustion engine M1 detected by a detecting means M2 is integrated with time elapse by an integrating means M3, and when this integrated value is more than the specified value, it is so estimated that temperature in exhaust system parts (an air-fuel sensor or the like) M4 goes up, and when it is less than the specified value, the temperature goes down, respectively, by an estimating means M5. At this time, with the drop of outside temperature detected by a temperature detecting means M6, compensation of either decrease compensation of the integrated value or increase compensation of the specified value of the estimating means M5 is carried out by a compensating means M7. Thus, whether a temperature rise in the air-fuel ratio sensor, namely, it is in an active state or not is accurately detected without being affected by a variation in the outside temperature, and thus the promotion of high accuracy in air-fuel ratio feedback control is contrivable.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method for estimating the temperature of exhaust system components such as an oxygen concentration sensor, which is disposed in the exhaust system of an internal combustion engine. The present invention relates to a temperature estimating device for exhaust system parts for an internal combustion engine that is effective for.

[Conventional Technique W1] In a normal air-fuel ratio feedback control device, the so-called single oxygen concentration sensor system, an oxygen concentration sensor as an air-fuel ratio sensor for detecting oxygen concentration is arranged near the combustion chamber. It is installed on the side of the exhaust manifold. However, due to individual differences in the output characteristics of oxygen concentration sensors, there has been a limit to the improvement in air-fuel ratio control accuracy. Therefore, as a countermeasure against the decrease in control accuracy caused by individual differences in the output characteristics of the oxygen concentration sensor, individual differences in component parts such as fuel injection valves, changes over time, no changes over time, etc.
A downstream oxygen concentration sensor is disposed downstream of the catalytic converter, and in addition to air-fuel ratio feedback control using the downstream oxygen concentration sensor disposed upstream of the catalytic converter, the downstream oxygen) temperature sensor A so-called double oxygen concentration sensor system is known that executes air-fuel ratio feedback control using the . In the double oxygen concentration sensor system, although the responsiveness of the downstream oxygen concentration sensor is lower than that of the upstream oxygen concentration sensor, the output characteristics are relatively stable for the following reasons.

(a) Since the exhaust gas temperature on the downstream side of the catalytic converter is lower than that on the upstream side, there is relatively little adverse thermal effect on the downstream oxygen concentration sensor.

(b) Harmful substances in the exhaust gas that adversely affect the output characteristics of the oxygen concentration sensor are adsorbed inside the catalytic converter, so the oxygen concentration sensor is relatively unlikely to be adversely affected by the downstream exhaust gas.

(C) Since the exhaust gas on the downstream side of the catalytic converter is sufficiently mixed, the oxygen concentration in the exhaust gas is almost in an equilibrium state, so that it can be detected relatively accurately by the oxygen concentration sensor.

For this reason, air-fuel ratio feedback control based on the outputs of two oxygen concentration sensors (so-called double oxygen concentration sensor system) corrects the deterioration in the output characteristics of the upstream oxygen/temperature sensor using the detection signal of the downstream oxygen concentration sensor. can.

In other words, as shown in black in Fig. 23, in the double oxygen concentration sensor system, even if the output characteristics of the upstream oxygen concentration sensor deteriorate, the harmful components (HC, Co, NO
There was almost no increase in the emission amount of X), and no deterioration in exhaust characteristics was observed. On the other hand, as shown in white in the figure, in the single oxygen concentration sensor system when the output characteristics deteriorate, the harmful components in the exhaust gas increase considerably, and the deterioration of the exhaust characteristics becomes noticeable. In this way, in the double oxygen concentration sensor system, if the output of the downstream oxygen concentration sensor is stable, good exhaust characteristics are ensured.

In the double oxygen concentration sensor system as described above, during execution of air-fuel ratio feedback control based on the detection signal of the downstream oxygen concentration sensor, the control constant of the air-fuel ratio correction coefficient FAF is determined based on the detection signal of the upstream oxygen concentration sensor, for example,
A technique has been proposed in which the rich skip amount R3R, lean skip amount R5L, etc. are changed based on a detection signal from a downstream oxygen concentration sensor. For example, (1) Calculate the skip amount, which is an air-fuel ratio feedback control constant, according to the output of the downstream air-fuel ratio sensor, and use the skip amount to calculate the air-fuel ratio correction amount according to the output of the upstream air-fuel ratio sensor. "Air-fuel ratio control device for internal combustion engine" that adjusts the air-fuel ratio of the engine and prevents a decrease in response speed due to deterioration of the upstream air-fuel ratio sensor (Japanese Patent Application Laid-Open No. 61-234241)
Publication No.).

(2) ``Air-fuel ratio control device for internal combustion engine'' that prevents disturbances in air-fuel ratio control by stopping the calculation of air-fuel ratio feedback control constants by the downstream air-fuel ratio sensor when deterioration of the catalyst is detected. 61-286550).

Furthermore, when the output of the downstream oxygen concentration sensor becomes stable,
In other words, an improved technique is also known in which air-fuel ratio feedback control is started after a predetermined period of time has elapsed since the start of the engine, when the downstream oxygen concentration sensor has been sufficiently activated. Such improved technology requires a predetermined period of time (for example, 100
[sec]) After the passage of time, the count value of the counter is updated by a predetermined correction value determined according to the intake air amount, and when the count value of the counter increases to a predetermined judgment value or more, the downstream oxygen concentration sensor The air-fuel ratio feed pump control is started based on the detection signal.

Here, each value for determining activation of the downstream oxygen concentration sensor, such as the predetermined time, the predetermined correction value, and the predetermined judgment value, is set to a predetermined constant value regardless of the operating environment of the internal combustion engine. Ta.

[Problems to be Solved by the Invention] Generally, the temperature of exhaust system components of an internal combustion engine is affected by the outside temperature of the environment in which the internal combustion engine is operated.

For example, to explain the downstream oxygen concentration sensor, which is an exhaust system component, as an example, as shown in FIG. 24, the oxygen concentration sensor element temperature T.

increases according to the elapsed time after the internal combustion engine starting time TIG. Here, when the outside air temperature is high, the oxygen temperature sensor element temperature TO rises to a high temperature relatively quickly over time, as shown by the solid line in the figure, but when the outside air temperature is low, As shown by the red line in the figure, the oxygen concentration sensor element temperature TO increases only gradually over time, and furthermore, only increases to a lower temperature than when the outside air temperature is high. However, in the above-mentioned conventional technology, the time measurement prohibition time for estimating activation of the oxygen temperature sensor is always set to a constant time even if the outside air temperature changes. Therefore, when the outside air temperature changes, especially when it decreases, there is a problem in that the accuracy of estimating the temperature rise and temperature drop of exhaust system components such as the oxygen concentration sensor decreases.

This means, for example, that the temperature rise of an oxygen concentration sensor, which is an exhaust system component, is estimated without taking into account changes in outside air temperature, making it impossible to accurately determine whether or not the oxygen concentration sensor is active. There wasn't.

Therefore, even when the element temperature To of the oxygen concentration sensor is low due to a drop in outside air temperature and an accurate detection signal cannot be output yet, an early erroneous determination of activation of the oxygen concentration sensor may cause the oxygen moisture sensor to Air-fuel ratio feedback control based on the detection result ends up being started. For this reason, the control accuracy decreases and the air-fuel ratio becomes rich (Rich).
This tends to lead to over-correction of the internal combustion engine, resulting in problems such as deterioration of the exhaust characteristics of the internal combustion engine and generation of catalyst exhaust odor.

As described above, if the temperature estimation of exhaust system components is inaccurate, the high control accuracy of the double oxygen moisture sensor system may be insufficient, especially due to inaccurate detection signals due to insufficient activation of the downstream oxygen concentration sensor. There was also the problem that they were not able to demonstrate their full potential.

An object of the present invention is to provide a temperature estimating device for exhaust system components for an internal combustion engine that can estimate the temperature of exhaust system components with suitable accuracy even when the outside air temperature changes.

Structure of the Invention [Means for Solving the Problems] The present invention, which has been made to achieve the above object, as illustrated in FIG. and at least an integrating means M3 for calculating an integrated value by integrating over time a correction value determined according to the intake air amount detected by the intake air amount detecting means M2, and an exhaust system of the internal combustion engine M1. Estimating means M5 for estimating that the temperature of the component M4 has increased when the integrated value calculated by the integrating means M3 is equal to or higher than a predetermined value, and that it has decreased when the integrated value is less than a predetermined value. In the temperature estimating device for exhaust system components for an internal combustion engine, the temperature detecting means M6 detects the outside air temperature of the internal combustion engine M1, and as the outside air temperature detected by the air temperature detecting means M6 decreases, the integrating means M3 temperature estimation of an exhaust system component for an internal combustion engine, characterized in that: a compensating means M7 that performs at least one of a correction for decreasing the integrated value accumulated by, or an increasing correction for the predetermined value of the estimating means M5; The gist is the device.

The intake air amount detection means M2 is for detecting the intake air amount of the internal combustion engine M1. For example, it can be realized by various flow rate sensors such as well-known air flow meters, Karman vortex sensors, and hot wire sensors. Further, for example, the intake air amount can be configured to be detected based on the rain detection results of an intake pipe pressure sensor that measures the intake pipe pressure of the internal combustion engine M1 and a rotation speed sensor that detects the rotation speed.

The integrating means M3 means at least the intake air amount detecting means M
The correction value determined according to the detected intake air amount in step 2 is integrated over time to calculate the integrated value. For example, a correction value is determined based on the volumetric flow rate of intake air or the weight flow rate and the load of the internal combustion engine M1, and the correction value is added or subtracted from the integrated value every predetermined time period to obtain the integrated value. Can be configured to calculate In addition, the above cumulative amount is
For example, it may be configured to start after a predetermined prohibited time has elapsed from the start of the internal combustion engine M1.

The estimating means M5 determines that the temperature of the exhaust system component M4 of the internal combustion engine M1 has increased when the integrated value calculated by the integrating means M3 is equal to or higher than a predetermined value, and that it has decreased when the integrated value is less than a predetermined value. It is estimated that Here, the exhaust system components include, for example, a catalytic converter with a built-in three-way catalyst installed in the exhaust passage, a catalytic converter installed in the upstream side of the three-way catalyst, or a catalytic converter installed in the exhaust passage downstream of the three-way catalyst to remove oxygen in the exhaust gas. These are various gas sensors that detect the concentration of specific components such as - carbon oxide.

For example, the estimating means M5 estimates that the air-fuel ratio sensor, etc. has been activated when the integrated value is greater than or equal to a predetermined counting judgment value, and on the other hand, when the integrated value is less than the counting judgment value, the air-fuel ratio sensor, etc. can be configured to presume that it has not yet been activated.

The air temperature detection means M6 is for detecting the outside air temperature of the internal combustion engine M1. For example, it can be realized by an intake temperature sensor disposed in the intake system of the internal combustion engine M1. Also, for example,
It may also be configured with various temperature sensors made of a thermistor, semiconductor, etc., which are provided exclusively for measuring outside air temperature.

The compensating means M7 corrects at least one of a reduction in the integrated value accumulated by the integrating means M3 or an increase in a predetermined value of the estimating means M5 as the outside air temperature detected by the air temperature detecting means M6 decreases. It is something to do. For example, the integration prohibition time that delays the integration start time can be configured to be extended in accordance with a decrease in outside air temperature. Also, for example, the correction value that is determined according to the intake air amount and is integrated into the integrated value,
It may also be configured to decrease in response to a decrease in outside air temperature. Furthermore, for example, a configuration may be adopted in which a predetermined value that is compared with the integrated value at the time of determination is increased in accordance with a decrease in outside temperature.

The integrating means M3, the estimating means M5 and the compensating means M7 can be realized, for example, by independent discrete logic circuits. Further, for example, it may be configured as a logic operation circuit together with a well-known CPU, ROM, RAM, and other peripheral circuit elements, and implement the above-mentioned means according to a predetermined processing procedure.

[Operation] The temperature estimating device for exhaust system components for an internal combustion engine according to the present invention has a first
As illustrated in the figure, the correction value determined according to the intake air amount of the internal combustion engine M1 detected by the intake air amount detection means M2 is
When the integrated value calculated by the integrating means M3 that integrates over time is equal to or higher than a predetermined value, it is determined that the temperature of the exhaust system component M4 of the internal combustion engine M1 has increased. When the temperature is less than, when the estimating means M5 estimates that the temperature has decreased, the integrated value accumulated by the integrating means M3 is corrected to decrease in accordance with the decrease in the outside air temperature detected by the air temperature detecting means M6, or, Compensating means M7 performs at least one of the increase corrections of the predetermined value of the estimating means M5.
work as one would do.

That is, when estimating the temperature rise and temperature drop of the exhaust system component M4 of the internal combustion engine M1, when the integrated value obtained by integrating the correction value according to the intake air amount increases to a predetermined value or more set for the integrated value. The increase time is corrected to extend as the outside temperature decreases, and the time until it is estimated that the temperature of the exhaust system component M4 has increased is delayed in accordance with the decrease in the outside air temperature.

Therefore, the temperature estimating device for exhaust system components for an internal combustion engine of the present invention works to accurately estimate the temperature of the exhaust system component M4 even if the outside air temperature changes.

The technical problems of the present invention are solved by each component of the present invention acting as described above.

[Example] Next, a preferred example of the present invention will be described in detail based on the drawings. FIG. 2 shows a system configuration of an engine air-fuel ratio control device according to a first embodiment of the present invention.

As shown in the figure, the engine air-fuel ratio control device 1 includes an engine 2 and an electronic door opening device (hereinafter simply referred to as ECU) 3 that controls the engine 2.

The engine 2 includes a cylinder 4, a piston 5, and a cylinder head 6 to form a combustion chamber 7, and a spark plug 8 is disposed in the combustion chamber 7.

The intake system of the engine 2 includes the combustion chamber 7 and the intake valve 9.
It is comprised of an intake bow 10 that communicates with the engine through an intake pipe 11, a surge tank 12 that absorbs pulsation of intake air, a throttle valve 14 that adjusts the amount of intake air in conjunction with an accelerator pedal 13, and an air cleaner 15.

The exhaust system of the engine 2 includes an exhaust boat 17 communicating with the combustion chamber 7 via an exhaust valve 16, an exhaust manifold 18, a catalytic converter 19, and an exhaust pipe 20.

The ignition system of the engine 2 includes an igniter 21 equipped with an ignition coil that outputs a high voltage necessary for ignition, and an igniter 21 that is connected to a crankshaft (not shown).
It is composed of a distributor 22 that distributes and supplies the high voltage generated by the spark plug to the spark plug.

The fuel system of the engine 2 includes a fuel tank 23 for storing fuel, a fuel pump 24 for pumping the fuel, and an electromagnetic fuel injection valve 25 for injecting the pumped fuel into the vicinity of the intake boat 10. ing.

The engine air-fuel ratio control device 1 includes an air flow meter 31 which is installed upstream of the throttle valve 14 in the intake pipe 11 and measures the amount of intake air, and a detector which is installed inside the air flow meter 31 to measure the intake air temperature. An intake temperature sensor 32 for measuring, a throttle position sensor 33 for detecting the opening degree of the throttle valve 140 in conjunction with the throttle valve 14, an idle switch 34 for detecting the fully open state of the throttle valve 14, and a cooling system for the cylinder block 4a. A water temperature sensor 35 is installed to detect the cooling water temperature, and a heater 36a is installed in the exhaust manifold to promote activation, and the sensor 35 detects the concentration of residual oxygen in the exhaust gas before it flows into the catalytic converter 19. an upstream oxygen concentration sensor 36 that is installed in the exhaust pipe 20 and has a built-in activation promoting heater 37a, and a downstream acid S[degree sensor 37] that detects the residual oxygen concentration in the exhaust gas flowing out from the catalytic converter 19. , the above-mentioned distributor 2
The cylinder discrimination sensor 38 outputs a reference signal every 1 rotation of the camshaft of the distributor 22, that is, every 2 rotations of the crankshaft (not shown), and every 1/24 rotation of the camshaft of the distributor 22, that is, the crank angle is 0°. A rotation angle sensor 39 is provided which also serves as a rotation speed sensor and outputs a rotation angle signal every integer multiple of 306 to 306.

Detection signals from each of the sensors and switches described above are input to the ECU 3, and the ECU 3 controls the engine 2. ECU3
is configured as a logic operation circuit centered on the CPU 3a, ROM 3b, RAM 3c, backup RAM 3d, and timer 3e, and is connected to the human output boat 3 via the common bus 3f.
It is connected to g and performs human output with the outside. The CPU 3a inputs and outputs the detection signals of the idle switch 34 via the A/D converter 3h and the turnout capo 3g, and inputs and outputs the detection signals of the air flow meter 31, intake air temperature sensor 32, and throttle position sensor 33 mentioned above. 3g, the detection signals of the cylinder discrimination sensor 38 and rotation angle sensor 39 are transmitted to the waveform shaping circuit 31 and the turnout capo) 3g, to the water temperature sensor 35, upstream oxygen concentration sensor 36, and downstream oxygen concentration sensor 37. Detection signals are transmitted through the A/D converter 3J and the human output boat 3g, respectively. On the other hand, the CPU 3a controls the heater 36 via the human output section 3g and the drive circuit 3k.
a and 36b are driven and controlled. Further, the CPU 3a drives and controls the igniter 21 via the human output section 3g and the drive circuit 3m. Furthermore, the CPU 3a drives and controls the fuel injection valve 25 via the human output unit 3g, the down counter 3n, the flip-flop circuit 3p, and the drive circuit 3r. That is, the first shift corresponding to the fuel injection amount TAU calculated by the CPU 3a is entered into the down counter 3n, and the flip-flop circuit 3p is also set.

Therefore, the drive circuit 3r opens the fuel injection valve 25, and fuel injection is started. On the other hand, the down counter 3n counts the clock signal, and finally, when its carrier terminal becomes high level (1), the flip-flop circuit 3p is set and the drive circuit 3r closes the fuel injection valve 25, injecting the fuel. ends. In this way, the amount of fuel corresponding to the fuel injection amount TAU is supplied to the engine 2. In addition, the above E
The CU 3 operates by receiving power from the vehicle battery 41 via the ignition switch 40 .

Next, the timekeeping process executed by the ECU 3 is shown in FIG. 3, the activation estimation process is shown in FIG. 5, and the first air-fuel ratio feedback control process is shown in FIGS. The air-fuel ratio feedback control process will be explained based on the flowcharts in FIGS. 9(1) and (2), and the fuel injection control process in FIG. 10.

The timing process shown in FIG. 3 is started at predetermined time intervals after the ECU 3 is started. First, in step 100, a process of reading the detection results of each sensor described above is performed. In the following step 110, based on the idle switch signal, rotation angle signal, cooling water temperature THW, etc. read in the above step 100, it is determined whether the engine 2 is at the time of starting.
If the judgment is affirmative, the process proceeds to step 120, and if the judgment is negative, the process proceeds to step 150. In step 120, which is executed sometime during startup, the intake air temperature THA
The process of reading is performed. In the following step 130,
According to the map shown in FIG. 4, which is stored in advance in the ROM 3b, a process is performed to calculate the count-up prohibition time equivalent value A based on the intake air temperature THA. As shown in FIG. 4, the count-up prohibition time equivalent value A is specified to increase as the intake air temperature THA decreases. Next, the process proceeds to step 140, where the count start delay counter CTHACUT is reset to the value 0, and then the main time measurement process is ended. on the other hand,
In step 150, which is executed when it is determined in step 110 that it is not the start time, a process of adding a value of 1 to the count value of the count start delay counter CT HACUT is performed. In the following step 160, after performing a process to limit the count value of the count start delay counter CTHACUT added in the step 150 to within a predetermined range of a maximum value and a minimum value, -1, the main time measurement process is performed. end. Thereafter, in the main time counting process, steps 100 to 160 are repeated at predetermined intervals.

Next, the activation estimation process will be explained based on the flowchart shown in FIG. This activation estimation process is executed at predetermined time intervals after the ECU 3 is started. First, step 200
Now, the process of reading each of the data described above is performed. In the following step 210, the count start delay counter CTHACU, which is counted up in the above-mentioned time counting process, is
It is determined whether the count value of T is equal to or greater than the count-up prohibition time equivalent value A calculated in the above-mentioned time counting process, and if the determination is affirmative, the process proceeds to step 230, while if the determination is negative, the process proceeds to step 220. Each proceed. In step 220, which is executed when the count value of the count start delay counter CTHACUT is still less than the count up prohibition time equivalent value A, the downstream oxygen temperature sensor activation flag X5F is executed.
After performing the process of resetting to Bli:In, the activation estimation process ends on -1. On the other hand, step 210
In step 230, which is executed when it is determined that the count value of the count start delay counter CTHACUT is already equal to or greater than the count-up prohibition time equivalent value A, a process of reading the intake air amount Q is performed. In the following step 240, the following information is stored in the ROM 3b in advance.
According to the map shown in FIG. 6, the correction value Δ is calculated based on the intake air amount Q, engine load Q/Ne, and engine rotational speed Ne.
Processing to calculate csoxT is performed. Next step 2
The process proceeds to step 50, where processing is performed to update the count value of the activation estimation counter C90XT by adding the correction value ΔC3OXT calculated in step 240 above. In the following step 260, it is determined whether the count value of the activation estimation counter C5OXT added and updated in the step 250 is greater than or equal to the activation determination value B. If the determination is affirmative, step 270 is performed.
On the other hand, if a negative determination is made, step 220 described above is performed.
After that, the activation estimation process ends. In step 270, which is executed when it is determined in step 260 that the downstream oxygen concentration sensor 37 has been activated after a sufficient period of time has passed after startup, the downstream oxygen moisture sensor activation flag X5FBli is set to 1. After performing the setting process, the activation estimation process ends. Thereafter, in this activation estimation process, steps 200 to 270 are repeatedly executed at predetermined intervals.

Next, the first air-fuel ratio feedback control process is shown in FIG.
This will be explained based on the flowcharts shown in 1) and (2). The air-fuel ratio feedback control process for Hyouka 1 is based on EC
After starting U3, a predetermined period of time (for example, 4 [ms ec]
)H is executed. First, in step 302, a process of reading each data based on the detection signal of each sensor described above is performed. In the following step 306, it is determined whether or not the first air-fuel ratio feedback control execution condition is satisfied. If the determination is affirmative, the process proceeds to step 308. On the other hand, if the determination is negative, the value of the air-fuel ratio correction coefficient FAF is The value at the end of the previous control is set, and the air-fuel ratio feedback control process for frozen dessert 1 is ended on -1. Note that the value of the air-fuel ratio correction coefficient FAF may be set to a constant value, an average value up to the end of the previous control, a learned value stored in the backup RAM 3d, or the like. Here, for example, when the cooling water temperature THW is below a predetermined temperature (for example, 60 [' CF ), in the starting state, during increase in amount after starting, during increase in warm-up amount, during accelerated increase in amount (asynchronous injection),
During power increase, the output signal v of the upstream oxygen concentration sensor 36
1 has never crossed the first comparison voltage VRI, etc., the first air-fuel ratio feedback control execution condition is not satisfied. In step 308, which is executed when the first air-fuel ratio feedback control execution condition is satisfied, which does not correspond to each of the above conditions, the detection signal v of the upstream oxygen humidity sensor 36 is
1 is A/D converted and read. In the following step 310, the detection signal 1 of the upstream oxygen temperature sensor 36 is set to the first comparison voltage VRI (for example, 0°45 [V
] ') or less, and if an affirmative determination is made, it is determined that the air-fuel ratio is on the lean side (Lean) and step 31
2, on the other hand, if the judgment is negative, the air-fuel ratio is on the rich side (Ri
c h), and proceed to step 324, respectively. In step 312, which is executed when the air-fuel ratio is on the lean side (Lean), it is determined whether the count value of the delay counter Cr)LY is positive or negative, and if it is positive, the count value of the delay counter CDLY is set to 0 in step 314. After resetting, the process proceeds to step 316. On the other hand, if the value is negative, the process directly proceeds to step 316. In step 316, the count value of the day counter CDLY is subtracted by 1, and in the subsequent step 31
8. At 320, the count value of the delay counter CDLY is limited to the minimum value TDL, and the delay counter CDL, Y
When the value of TDL decreases to the minimum value TDL, step 32
After resetting the air-fuel ratio flag F1 to the value 0 (lean side) at step 2, the process proceeds to step 340. Note that the minimum value TDL is determined when the detection signal v1 of the upstream oxygen moisture sensor 36 changes from the rich side (Rich) to the lean side (L e a n).
This lean delay time is defined as a negative value to maintain the judgment that the condition is on the rich side (Rich) even if the condition changes. On the other hand, in step 324, which is executed when it is determined in step 310 that the air-fuel ratio is on the rich side (Rich), it is determined whether the count value of the delay counter CDLY is positive or negative, and if it is negative, the step At 326, the count value of the delay counter CDLY is reset to fiO, and then the process proceeds to step 328. On the other hand, if it is positive, the process directly proceeds to step 328. In step 328, the count value of the delay counter CDLY is incremented by the value 1, and in the following steps 330 and 332, the count value of the delay counter CDLY is limited to the maximum value TDR, and the count value of the delay counter CDLY is incremented by the value 1.
When the count value of Y increases to the maximum value TDR, the air-fuel ratio flag F1 is set to the value 1 (Rich side) in step 334.
)), the process proceeds to step 340. Note that the maximum value TDR is the detection signal of the upstream oxygen concentration sensor 36.
Even if 1 changes from the lean side (Lean) to the rich side (Rich), it is the Nori-Sochi delay time to maintain the judgment that it is on the lean side (L e a n), and it is a positive value. Defined.

In the subsequent step 340, it is determined whether the value of the air-fuel ratio flag F1 has been inverted, and if an affirmative determination is made, the process proceeds to step 34.
On the other hand, if the determination is negative, the process advances to step 348. In step 342, which is executed when the value of the air-fuel ratio flag F1 is inverted, 1M1ll! l (Ri c
h) to the lean side (Lean) or the lean side (L
ean) to the rich side (Rich). From the rich side (Rich) to the lean side (
In step 344 executed when reversing to the lean side (Lean), the rich skip amount R9R is added to the air-fuel ratio correction coefficient FAF to increase it in a skip manner.
) to the rich side (Rich), the lean skip amount R8Lli is calculated from the air-fuel ratio correction coefficient FAF and decreased in a skip manner, and the process proceeds to step 356. Further, in step 348, which is executed when the value of the air-fuel ratio flag F1 is not inverted in step 340, a process is performed to determine whether the air-fuel ratio is on the lean side (Le a n) or the rich side (Rich). It will be done.

Step 3 executed when on the lean side (Lean)
50, the rich integral constant KI is added to the air-fuel ratio correction coefficient FAF.
R is gradually increased by adding R, while on the rich side (Ri c
In step 352, which is executed when h), the lean integral constant KIL is subtracted from the air-fuel ratio correction coefficient FAF to gradually decrease it, and the process proceeds to step 356 in each case. Here, both integral constants KIR and KIL are both skip amounts R9R,
It is set sufficiently small compared to R9L. Therefore,
In steps 344 and 346, the fuel injection amount is quickly increased or decreased, while in steps 350 and 352, the fuel injection amount is gradually increased or decreased. Subsequent steps 356°358
Then, the value of the air-fuel ratio correction coefficient FAF is limited to, for example, a maximum value of 1.2 or less, and further, the following step 360,
362, the minimum value is 0.362. If the air-fuel ratio correction coefficient value FAF is excessive for some reason, or
Even if the air-fuel ratio becomes too low, the air-fuel ratio is prevented from shifting to an over-rich state or an over-lean state. Next, the process proceeds to step 364, and after storing the air-fuel ratio correction coefficient FAF calculated as described above in the RAM 3c,
The air-fuel ratio feedback control process ends. From then on, the air-fuel ratio feedback control process for frozen dessert 1 is performed at predetermined intervals.
The above steps 302 to 364 are repeatedly executed.

Next, an example of the above control will be explained according to the timing chart of FIG. 8. At time t1, the air-fuel ratio signal A/F based on the upstream oxygen humidity sensor detection signal is on the lean side (L
ean) to the rich side (Rich), the count value of the delay counter CDLY is reset, then counted up, and reaches the maximum value TDR at time t2 after the rich delay time TDR has elapsed. Then, the air-fuel ratio signal A/Fd (value of the air-fuel ratio flag F1) after the delay processing changes to the lean side (L
e a n) or to the filtration rich side (Rich).

Furthermore, at time t3, when the air-fuel ratio signal A/F based on the upstream oxygen concentration sensor detection signal changes from the rich side (Rich) to the lean side (Lean), the delay counter CD
After the count value of LY is reset, it is counted down and reaches the minimum [TD
Reach L. Then, the air-fuel ratio signal A/F after the delay processing
d (value of air-fuel ratio flag F1) is on the rich side (Rich
) to the lean side (Lean). However, for example, the air-fuel ratio signal A based on the upstream oxygen concentration sensor detection signal
/F at time t5. t6. When inverted with a tolerance shorter than the rich delay time TDR like t7, the delay counter C
The time for the count value of DLY to reach the maximum value TDR is extended, and at time t8, the air-fuel ratio signal A/Fd after the delay processing is
is reversed. In other words, the air-fuel ratio signal A/F after the delay processing
d (the slope of the air-fuel ratio flag F1) has a value that is more stable than the air-fuel ratio signal A/F based on the upstream oxygen concentration sensor detection signal.

In this way, the relatively stable air-fuel ratio signal A after the delay processing
/Fd, the air-fuel ratio correction coefficient FAF is determined.

Next, the second air-fuel ratio feedback control process will be explained. The second air-fuel ratio feedback control process
one that performs control to change the skimp amounts R9R, R9L, integral constants KIR, KIL, delay times TDR, TDL, and first comparison voltage VRI, which are control constants of the air-fuel ratio feedback control process; Fuel ratio correction coefficient FA
There is one that performs control to calculate F2.

Skip amounts R9R, R3L, which are control constants, integral constant K
In the control for changing IR, KIL, delay times TDR, TDL, and first comparison voltage VRI, for example, the air-fuel ratio is adjusted to the rich side (Ri) by increasing the rich skip amount R3R or decreasing the lean skip amount R5L. h h
), and on the other hand, the air-fuel ratio can be controlled to the lean side (I, ean) by decreasing the rich skip amount R5R or increasing the lean skip amount R5L. Therefore, depending on the detection signal of the downstream oxygen concentration sensor 37, the rich skip amount R9R1 or the lean skip amount R3L
By correcting at least one of the following, the air-fuel ratio can be controlled. Furthermore, for example, the air-fuel ratio can be controlled to the rich side (Rich) by increasing the rich integral constant KIR or decreasing the lean integral constant KIL, while decreasing the rich integral constant KIR or decreasing the lean integral constant KIL can control the air-fuel ratio to the rich side (Ri ch). Integral constant KIL
The air-fuel ratio can be controlled to the lean side (L e a ) by increasing the correction amount.

In this way, depending on the detection signal of the downstream oxygen concentration sensor 37, the rich integral constant KIR1 or the lean integral constant K I1. By correcting at least one of the following, the air-fuel ratio can be controlled. Further, for example, if the rich delay time TDR is set relatively larger than the lean delay time (-TDL), the air-fuel ratio can be controlled to the rich side (Rich), while the rich delay time TDR is set relatively larger than the lean delay time TDL. If the air-fuel ratio is set as low as possible, the air-fuel ratio will be on the lean side (L e a n
) can be controlled. That is, the downstream oxygen degree sensor 37
Rich delay time TDR5 or
The air-fuel ratio can be controlled by correcting at least one of the lean delay times TDL. Further, for example, the first comparison voltage VR
If I is corrected to decrease, the air-fuel ratio can be controlled to the lean side (Lean). Therefore, even if the first comparison voltage VRI is corrected according to the detection signal of the downstream oxygen temperature sensor 37, the air-fuel ratio can be controlled. By the way, the above skip amounts R9R, R9
L, integral constants KIR, KIL, delay times TDR, TDL
and the first comparison voltage VRI to the downstream oxygen concentration sensor 3.
For example, the delay time T
The correction of DR and TDL enables very delicate air-fuel ratio control, and the skip amounts R5R and R5L are the same as the above delay time TDR.
, TDL, it is possible to perform control that maintains high responsiveness without extending the air-fuel ratio feedback control period. Therefore, control that combines a plurality of the above control constants is effective.

Next, the second air-fuel ratio feedback control process is performed as shown in FIG.
This will be explained based on the flowcharts shown in 1) and (2). The air-fuel ratio feedback control process for Hyouka 2 is performed by the ECU 3.
After the start of , it is executed every predetermined time (for example, 512 m5ec) to correct the skip amounts R9R and R5L. First, in step 402, processing is performed to read each data based on the detection signal of each sensor described above. In the following step 7104, it is determined whether or not the second air-fuel ratio feedback control process execution condition is satisfied. If the determination is affirmative, the process proceeds to step 406. On the other hand, if the determination is negative, the values of the skip amounts R9R and R3L are determined. is set to the value at the end of the previous control, and the air-fuel ratio feedback control process for Hyouka 2A ends on -1. Note that the values of the skid/tsubu amounts R3R and R9L are the average values up to the end of the previous control, and the backup RAM.
It may also be set to a learned value stored in 3d. Here, for example, the cooling water temperature THW is set to a predetermined temperature (for example, 6
0 ['C]) or less, in the starting state, during fuel increase after startup, during warm-up fuel increase, during acceleration fuel increase (asynchronous injection), during power increase,
The detection signal v1 of the upstream oxygen moisture sensor 36 has never been the first
When the comparison voltage VRI is not crossed, the second air-fuel ratio feedback control processing execution condition is not satisfied. When the second air-fuel ratio feedback control processing execution condition is satisfied, which does not correspond to each of the above conditions, the process proceeds to steps 406 to 414, and the cooling water temperature THW is 70 [.

C] (step 406), whether the throttle valve is not fully closed (step 408), and whether the downstream oxygen concentration sensor activation flag X5FB is set to the value 1 (as described above). By executing the time measurement processing and activation estimation processing, after startup, the count-up prohibition time determined according to the intake air temperature THA and the time until the count value of the activation estimation counter reaches activation judgment [8 or more] are added. time has passed and it is determined that the downstream oxygen concentration sensor 37 has been activated (step 410), it is determined whether the downstream oxygen concentration sensor 37 is normal (i.e., the downstream oxygen moisture sensor 37 is determined to be activated) (step 410). (when the diagnosis signal indicates normal) (step 412), and whether the load of the engine 2 is equal to or higher than a predetermined load (step 414) are determined, and if all determinations are affirmative, the second air-fuel ratio feedback is performed. In order to execute the control, the process proceeds to step 420 and subsequent steps. On the other hand, if a negative determination is made in any step, the values of the skip amounts R5R and R5L are set to the values at the end of the previous control, and the empty bookcase 2 is The fuel ratio feedback control process ends.

In step 420, which is executed when the second air-fuel ratio feedback control process execution condition is satisfied, a process of A/D converting and reading the detection signal v2 of the downstream oxygen concentration sensor 37 is performed. In the following step 421, the skip amount R5R calculated last time is calculated.

Processing to read R9L is performed. Following step 422
Then, the detection signal v2 of the downstream oxygen humidity sensor 37 is
It is determined whether or not the comparison voltage VR2 (for example, 0.55 [V]) is lower than or not, and if an affirmative determination is made, the air-fuel ratio is determined to be on the lean side (Lean) and the process proceeds to step 424.
If a negative determination is made, it is determined that the air-fuel ratio is on the rich side (Rich), and the process proceeds to step 444. The air-fuel ratio is on the lean side (
In step 424, which is executed when the state is Lean), the value of the rich skip amount RS R is added by a constant value ΔR3, and in the following steps 426 and 428, the value of the rich skip amount R5R is limited to an amount equal to or less than the maximum value RMAX. Further, in step 430, the value of the lean skip amount R9L is subtracted by a constant value ΔR9, and in subsequent steps 432 and 43
4, the value of the lean skip amount R8L is limited to an amount greater than or equal to the minimum value LMIN. Here, for example, the maximum value is 7.5[
%], the minimum value is 2.5 [%]. Note that the maximum value is a value within a range in which drivability does not deteriorate due to fluctuations in the air-fuel ratio, and the minimum value is a value within a range in which transient followability does not deteriorate. In this way, the rich skip amount R5R is corrected to increase and the lean skip amount R5Ltl is corrected to decrease to make it easier to shift the air-fuel ratio to the rich side (Rich). Next, the process proceeds to step 436, and after storing the rich skip amount R9R and lean skip amount R3L corrected as described above in the RAM 3c and the backup RAM 3d, the air-fuel ratio feedback control process for the bookcase 2 is ended.

On the other hand, in step 422, the air-fuel ratio is set to the rich side (Ri
In step 444, which is executed when it is determined that c h), the rich skip amount R9R is set to a constant value ΔR
3 is subtracted, and in subsequent steps 446 and 448, the value of the rich skip amount R5R is limited to an amount equal to or greater than the minimum value RMIN, and then the process proceeds to step 450, where the lean skip amount R8
The value of L is added by a constant value ΔR9, followed by step 452
．． 454, the value of the lean skip amount R9L is set to the maximum value L.
Limit the amount to MAX or less. In this way, the rich skip amount RSRt- is corrected to decrease, and the lean skip amount R8L is corrected to increase to adjust the air-fuel ratio to the lean side (L e a n
). Thereafter, step 436 as described above.
After that, the air-fuel ratio feedback control process for the bookcase 2 is completed. Thereafter, the air-fuel ratio feedback control process for the bookcase 2 is executed by repeating steps 402 to 454 at predetermined intervals.

Next, the fuel injection control process will be explained based on the flowchart shown in FIG. This fuel injection control process is performed by the ECU
3, every predetermined crank angle (for example, 360 [
'CAI'). First, step 500
Now, the process of reading each of the data described above is performed. In the subsequent step 510, the basic fuel injection amount TAUO is calculated from the constant α, the intake air amount Q, and the rotational speed Ne using the following equation (1
) is calculated as follows.

TAUO=aXQ/Ne=-
(1) In the subsequent step 520, a process is performed to calculate the warm-up increase coefficient FWL according to the cooling water temperature THW by interpolation calculation according to the map shown in FIG. 11, which is stored in the ROM 3b. Next, proceed to step 530;
A process of calculating the actual fuel injection amount TAU as shown in the following equation (2) is performed. However, β and γ are correction coefficients determined according to other operating state parameters.

TAU = FAF during TAUO ◆ (FWL +β+ 1)
+γ... (2) In the following step 540, the actual fuel injection amount TAU calculated in the above step 530 is set in the down counter 3n, and a control signal is output to set the flip-flop circuit 3p to start fuel injection. After starting, the present fuel injection control process ends. Furthermore, as mentioned above,
When the time corresponding to the actual fuel injection amount TAU has elapsed, the flip-flop 3p is reset by the carrier signal of the down counter 3n, and the fuel injection ends.

Thereafter, this fuel injection control process repeats steps 500 to 540 at every predetermined crank angle.

Note that in the first embodiment, the engine 2 is an internal combustion engine M1.
, the air flow meter 31 is connected to the intake air amount detection means M2,
The ECU 3 and the processing executed by the ECU 3 (steps 230 to 250) function as the integrating means M3, and the downstream oxygen concentration sensor 37 functions as the exhaust system component M3.
4, the ECU3 and the processing executed by the ECU3 (
Steps 220, 260, and 270) function as estimation means M5. In addition, the intake air temperature sensor 32
corresponds to the temperature detection means M6, and the ECU3 and ECU3
The processing executed by (step 100 to step 160, step 210) functions as compensation means M7.

As explained above, according to the first embodiment, when the intake air temperature THA, which corresponds to the outside air temperature, decreases, the activation estimation counter C3OXT, which determines the activation of the downstream oxygen concentration sensor 37, starts counting. Since the count-up prohibition time (iA) which determines the count value of the count-start delay counter CTHACUT is increased and corrected, even if the outside temperature drops, the activation of the downstream oxygen temperature sensor 37 is controlled with high accuracy. It can be estimated by

That is, as shown in the timing chart of FIG. 12, the time t when the outside air temperature (intake air temperature THA) is at room temperature
When engine 2 is started at tll, the downstream oxygen concentration sensor activation flag X5FB is reset to 0, and the delay counter CTHA starts counting from the same time tll.
CUT counting is started. Eventually, at time t12 (after the count-up prohibition time ATlu has passed from the above-mentioned time tll) when the count value of the count start delay counter CTHACUT increases to a value A1 corresponding to the count-up prohibition time corresponding to the intake air temperature THA which is room temperature, the count-up delay counter CTHACUT is activated. Estimation counter C90XT starts counting. Thereafter, at time t13 when the count value of the activation estimation counter csoxT exceeds the activation determination value B, the downstream oxygen temperature sensor 37 is estimated to have been activated, and at the time t13, the activated oxygen concentration sensor activation flag X5FB is set to the value 1.

As shown in the figure, the downstream oxygen concentration sensor element temperature TO
starts to rise from the time of startup (time t11), and from the above time t1
3, the activation temperature TOA is reached. Therefore, the downstream oxygen concentration sensor 37 outputs an accurate detection signal from the same time t13. - side, outside air temperature (intake air temperature TH
When the engine 2 is started at time t14 when A) is at a low temperature, the downstream oxygen concentration sensor activation flag X5FB is reset to the value O, and the count start delay counter CTHACUT starts counting from the same time t14. Eventually, the count start delay counter CTHACUT
Time t16 when the count value increases to the count-up prohibition time equivalent value A2 corresponding to the low intake air temperature THA.
(Count-up prohibition time AT2u from the above time t14)
(after the activation period), the activation estimation counter C90XT starts counting, as shown by the solid line in the figure. Thereafter, at time t18 when the count value of the activation estimation counter C90XT exceeds the activation determination value B, the downstream oxygen concentration sensor 37 is estimated to have been activated, and at the time t18, the activated oxygen concentration sensor activation flag X5FB is set to clay 1. As shown in the figure, the downstream oxygen concentration sensor element temperature TO starts to rise from the time of startup (time t14) and reaches the activation temperature TOA at the time t18. Therefore, the downstream oxygen concentration sensor 37 outputs an accurate detection signal from the same time tlB. Incidentally, in the conventional technology, the count-up prohibition time is fixed regardless of the outside temperature, so when the temperature is low, the count value of the delay counter CTHACUT, which starts counting at time t15, is a constant value equivalent to the count-up prohibition time. After the count-up prohibition time AT1u has elapsed since the start time t14), the activation estimation counter C3OXT increases to A1, as shown by the broken line in the figure.
counting starts. Eventually, the activation estimation counter C
Time t17 when the count value of 90XT exceeds activation judgment value B
The downstream oxygen concentration sensor 37 was presumed to have been activated and was closed. However, as shown in the figure, the downstream oxygen concentration sensor element temperature TO has not yet reached the activation temperature TOA at the same time t17. Therefore, the downstream oxygen concentration sensor 37 could not output an accurate detection signal from the same time t17.

In this way, the activation of the downstream oxygen concentration sensor 37 can be accurately estimated without being affected by changes in the outside air temperature, so that the second air-fuel ratio feedback control process based on the downstream oxygen moisture sensor 37 can be Due to improved accuracy, the skip amount R9L, which is the control constant of the air-fuel ratio correction coefficient F A F,
Since R9R can be set to the optimal value, when the outside air temperature drops, the air-fuel ratio A/F will not be over-corrected to the rich side (Rich), reducing the amount of harmful components emitted in the engine 2 exhaust, and reducing the catalyst It can also prevent the generation of exhaust odor.

In the first embodiment, the count-up prohibition time equivalent value A is extended and corrected by the time measurement process in accordance with the decrease in the intake air temperature THA. However, for example, the activation judgment value B, which determines the count value of the activation estimation counter C3OXT in the activation estimation process, is set at two points in the timing chart of FIG. As shown by the chain line, the same effect as in the first embodiment can be obtained even if the intake air temperature THA is increased to the value B1 as the intake air temperature THA decreases. In addition to correcting the extension according to the decrease in the air temperature THA, the activation judgment value B is adjusted to the intake air temperature THA.
A higher level of temperature compensation can be achieved by configuring the structure so that the increase is compensated according to the decrease in temperature.

Further, although the correction value ΔC90XT was calculated from the load Q/Ne, the engine speed, and the intake air amount Q, for example, the intake pipe pressure PM or the throttle valve opening θ may also be used as the load.

Furthermore, in a so-called single oxygen concentration sensor system in which an oxygen concentration sensor is disposed only on the downstream side of the catalytic converter 19 to perform air-fuel ratio feedback control, the air-fuel ratio correction calculated in the first air-fuel ratio feedback control process is A configuration in which the air-fuel ratio feedback control is executed by using the rich skip amount R5R and the lean skip amount R3L calculated in the second air-fuel ratio feedback control process as the air-fuel ratio correction coefficient FAF instead of the coefficient FAF, or the second air-fuel ratio In addition to a configuration that performs air-fuel ratio feedback control based on an air-fuel ratio correction coefficient obtained by superimposing a square wave with a frequency corresponding to the operating state of the engine 2 on the downstream oxygen concentration sensor detection signal v2 detected in the feedback control process. Even if the time measurement process and activation estimation process are executed, the same effects as in the first embodiment can be obtained.

Also, if it is a so-called double oxygen concentration sensor system,
Other control constants used in the first air-fuel ratio feedback control process by the upstream oxygen moisture sensor 36, namely:
The delay time TDL, the TDR1 integral constants KIL, KIR, the first comparison voltage VRI, etc. are corrected by the detection signal V2 of the downstream oxygen concentration sensor 37, and
Similar effects can be achieved by adding the above-mentioned time measurement process and activation estimation process to a configuration in which the first air-fuel ratio feedback correction coefficient FAF and the second air-fuel ratio feedback correction coefficient FAF2 are used together.

Furthermore, skip amounts R5R, R3L, delay time TDL,
TDR1 integral constant KIL, KIR1 first comparison voltage VR
If the time measurement processing and activation estimation processing of the first embodiment are applied to the control constant configured to correct a plurality of control constants at the same time, control accuracy, responsiveness, and followability can be further improved. .

Also, skip amounts R9R, R9L, delay times TDL, T
DR, integral constant KIL, KIR5 first comparison voltage VRI
O, overtemperature side (Rich), or lean side (L
The timing processing and activation estimation processing of the first embodiment are applied to a configuration in which one of e a n) is set to a constant value and only the other is changed based on the detection signal v2 of the downstream oxygen concentration sensor 37. You can get similar benefits by doing this.

Furthermore, in the first embodiment described above, the oxygen moisture sensor 36.
Although 37 was used, for example, a gas sensor that detects -carbon oxide CO or a so-called lean mixture sensor may also be used.

Further, in the first embodiment described above, an air flow meter was used as the intake air amount sensor, but for example, a Karman vortex sensor, a heat wire sensor, etc. may be used.

Furthermore, in the first embodiment described above, the fuel injection amount is calculated based on the intake air amount and the engine rotation speed, but for example, the fuel injection amount is calculated based on the intake air pipe pressure and the engine rotation speed, or the throttle valve opening and the engine rotation speed. The fuel injection amount can be configured to be calculated according to the rotation speed.

Further, in the first embodiment described above, the engine air-fuel ratio control &III device 1 controls the fuel injection amount by the fuel injection valve 25.
explained. However, for example, in an engine equipped with a carburetor, the air control valve (EACV)
The bleed air control valve adjusts the amount of bleed air in the carburetor to control the air-fuel ratio by introducing atmospheric air into the main system passage and slow system passage.It is supplied to the exhaust system. 2
It can also be applied to engines that adjust the amount of air.

In this way, in an engine equipped with a carburetor, the basic fuel injection amount is determined from the characteristics of the carburetor, and the air-fuel ratio is controlled by calculating the amount of supplied air that achieves a desired air-fuel ratio.

(Hereinafter referred to as margins) Next, a second embodiment of the present invention will be described in detail based on the drawings. The differences between this second embodiment and the previously described first embodiment are as follows:
This is because the activation estimation process and the first air-fuel ratio feedback control process were changed in consideration of the relationship between the oxygen concentration sensor element temperature and the intake air weight, and the device configuration and other processes are exactly the same. Components are indicated by the same reference numerals, and description thereof will be omitted.

In general, the oxygen concentration sensor element temperature and intake air weight are:
The relationship is as shown in FIG. That is, the oxygen temperature sensor element temperature TO increases as the intake air weight Ga increases. Therefore, in the second embodiment, the intake air amount f
C90XT to the correction value of the activation estimation counter C3OXT used for determining the activity of the oxygen concentration sensor according to f1Ga
It was configured to calculate.

Next, the activation estimation process executed in the second embodiment is
FIG. 4 shows the first air-fuel ratio feedback control process in the 16th
This will be explained based on the flowcharts shown in FIGS. (1) and (2), respectively.

The activation estimation process shown in FIG. 14 is performed after the ECU 3 is started.
It is started every predetermined time. First, in step 600,
The process of reading each data described above is performed. In the subsequent step 610, the count start delay counter CTH, which is counted up in the time measurement process already described in the first embodiment, is
Determine whether or not the ACUT count value is equal to or greater than the count-up prohibition time equivalent value A calculated in the above timing process;
If the judgment is affirmative, the process proceeds to step 630, and if the judgment is negative, the process proceeds to step 620. In step 620, which is executed when the count value of the count start delay counter CTHACUT is still less than the count-up prohibition time equivalent value A, the downstream oxygen concentration sensor activation flag X5FB is reset to the value 0. ,-dan,
This activation estimation process ends. On the other hand, step 61
In step 630, which is executed when it is determined that the count value of the count start delay counter CTHACUT is already equal to or greater than the count-up prohibition time equivalent value A, the intake air volume flow rate Q is read. In the subsequent step 640, the intake air weight Ga is calculated from the intake air volumetric flow rate Q, the smoothed value FAFAVS obtained by rounding the average value of the air-fuel ratio feedback correction coefficient FAF at the time of air-fuel ratio reversal, and the high altitude learning value FGHAC using the following formula. The calculation process as shown in (3) is performed.

Ga = QX (FAFAVS + FGHAC)
(3) Next, the process proceeds to step 650, in which a correction value ΔC3OXT is calculated based on the intake air weight Ga according to the map shown in FIG. 15, which is stored in advance in the ROM 3b. Proceeding to step 660, a process is performed to update the count value of the activation estimation counter C90XT by adding C3OXT to the correction value calculated in step 650 above. Next, the process proceeds to step 670, in which it is determined whether the count value of the activation estimation counter C3OXT added and updated in the above step 660 is equal to or greater than the activation determination value B. If an affirmative determination is made, the process proceeds to step 680; If , a negative determination is made, the activation estimation process is terminated at step 620 described above. In step 680, which is executed when it is determined in step 670 that the downstream oxygen moisture sensor 37 has been activated after a sufficient period of time has passed after startup,
After performing the process of setting the downstream oxygen concentration sensor activation flag X5FB to 1, the activation estimation process is ended. Thereafter, this activation estimation process is performed in step 6 above.
Steps 00 to 680 are repeatedly executed at predetermined time intervals.

Next, the first air-fuel ratio feedback control process will be explained based on the flowcharts shown in FIGS. 16(1) and (2). The air-fuel ratio feedback control process in bookcase 1 is performed by the ECU
3 is started, it is executed every predetermined time (for example, 4 [m5ec]). First, in step 700, a process of reading each data based on the detection signal of each sensor described above is performed.

In the following step 705, it is determined whether or not the first air-fuel ratio feedback control execution condition is satisfied, and if the determination is affirmative, the process proceeds to step 710; on the other hand, if the determination is negative,
The process proceeds to step 707 where the value of the air-fuel ratio correction coefficient FAF is set to 1.0, and then the process proceeds to step 780.

Here, for example, when the cooling water temperature THW is below a predetermined temperature (e.g. 60 ['C]), in the starting state, during increase in amount after starting, during increase in warm-up, during increase in acceleration (asynchronous injection), during increase in power, When the output signal (1) of the upstream oxygen concentration sensor 36 never crosses the first comparison voltage VRI, etc., the first air-fuel ratio feedback control execution condition is not satisfied. Step 7 executed when the first air-fuel ratio feedback control execution condition is satisfied, which does not correspond to each of the above conditions.
At step 10, a process of A/D converting and reading the detection signal (1) of the upstream oxygen concentration sensor 36 is performed. In the following step 715, the detection signal ■1 of the upstream oxygen concentration sensor 36 is
is the first comparison voltage, which in this example is 0. 45 [V] or more, and if an affirmative determination is made, the air-fuel ratio is determined to be on the rich side (Rich) and the process proceeds to step 720. On the other hand, if a negative determination is made, the air-fuel ratio is on the lean side (Lean). Assuming that , the process proceeds to step 730. The air-fuel ratio is on the rich side (
In step 720, which is executed when the state of If the judgment is affirmative, it is determined that the air-fuel ratio continues to be on the rich side (Rich), and the process proceeds to step 725. On the other hand, if the judgment is negative, the air-fuel ratio is on the lean side (L e a n ).
) or the filtration is reversed to the rich side (Rich), step 7
40 respectively. The air-fuel ratio continues to be on the rich side (Rich)
In step 725, which is executed when the air-fuel ratio correction coefficient FAF is 0, the lean integral constant KILti is subtracted from the air-fuel ratio correction coefficient FAF to gradually decrease the lean integral constant KILti, and then the process proceeds to step 780. On the other hand, in step 715, the air-fuel ratio is set to the lean side (Le
Step 7 executed when it is determined that an)
30, the previous detection signal VIB of the upstream oxygen concentration sensor 36 is the first comparison voltage, which is 0.30 in this embodiment. 45 [
If the judgment is affirmative, the air-fuel ratio continues to be on the lean side (Lean) and the process goes to step 735; on the other hand, if the judgment is negative, the air-fuel ratio is on the excessive side (R
i ch h) to the lean side (Lean), and each proceeds to step 770. Step 7 executed when the air-fuel ratio continues to be on the lean side (L e a n)
35, the lean integral constant KI is added to the air-fuel ratio correction coefficient FAF.
After performing the process of adding and gradually increasing L, the process proceeds to step 780.

In step 740, which is executed when the air-fuel ratio is reversed from the lean side (Lean) to the rich side (Rich) in step 720, the air-fuel ratio correction coefficient FA at the previous reversal is
Average value F of FO and air-fuel ratio correction coefficient FAF at the time of current reversal
Processing to calculate AFAVE is performed. Next step 7
45, the average value FAF calculated in step 740 above is
The current annealing value FAFAv is calculated by weighted average calculation of AVE and the previously calculated annealing value FAFAVS.
Processing to calculate S is performed. Next, the process proceeds to step 750, where a process is performed in which a value of 1 is added to the count value of the reversal counter CGA that counts the number of reversals to the rich side (Rich). In the following step 752, it is determined whether the count value of the inversion counter CGA is equal to or greater than the value 4. If the judgment is affirmative, the process proceeds to step 756; on the other hand, if the judgment is negative, the process proceeds to step 75.
Proceed to step 4 individually. In step 754, which is executed when the number of reversals to the rich side (Rich) is still less than 4, the lean skip amount R9L is calculated from the air-fuel ratio correction coefficient FAF.
After subtracting 'C and decreasing it in a skipping manner, step 78
Go to 0. On the other hand, in step 752, the over-concentration side (Ri
In step 756, which is executed when the number of inversions to ch) is four or more, a process of resetting the inversion counter CGA to the value O is performed. In the following step 758, it is determined whether the average value FAFAVE is greater than or equal to 1.0+α1 (constant). If the determination is affirmative, the process proceeds to step 760, while if the determination is negative, the process proceeds to step 762.

In step 760, which is executed when the average value FAFAVE is greater than or equal to 1.0+α1 (constant), high altitude learning @FG
After performing an increase correction process by adding a constant γ1 to HAc, the process proceeds to step 780 via step 754 described above. On the other hand, in step 758 above, the average value FAFAVI
In step 762, which is executed when it is determined that IE is less than 1.0+α1 (constant), the average value FAFAV
Determine whether E is less than or equal to 1°0-β1 (constant),
If an affirmative determination is made, the process proceeds to step 764, whereas if a negative judgment is made, the process proceeds to step 780 via the above-mentioned step 754. Average value F A F A V E )! )'f 1
, 0-β1 (constant) or less, in step 764, the constant γ1 is calculated from the high altitude learning value FGHAC.
After performing the process of subtracting and correcting the decrease, the process proceeds to step 780 via step 754 described above.

Further, in step 730, the air-fuel ratio is set to the rich side (Ric
In step 770, which is executed when it is determined that the inversion has occurred from h) to the lean side (Lean), the air-fuel ratio correction coefficient FAFO at the previous inversion is changed to the air-fuel ratio correction coefficient FA at the current inversion.
Processing to update to F is performed. In the subsequent step 775, the rich skip amount R5R is added to the air-fuel ratio correction coefficient FAF to increase it in a skip manner, and then the process proceeds to step 780. In step 780, processing is performed to limit the value of the air-fuel ratio feedback correction coefficient FAF to within a predetermined range between a maximum value and a minimum value. In the following step 785, in preparation for the next process, a process is performed to update the previous detection signal VIB to the upstream oxygen concentration sensor detection signal 1 detected this time.

Next, the process proceeds to step 790, and the air-fuel ratio correction coefficient FAF calculated as described above is stored in the RAM3c and the backup RAM.
3d, the air-fuel ratio feedback control process for the bookcase 1 ends on -1. From then on, the air-fuel ratio feedback control process for the bookcase 1 is performed in step 700 at predetermined intervals.
- Repeat steps 790.

Note that in the second embodiment, the ECU 3 and the ECU 3
Among the processes executed by , steps (630 to 660) function as integration means M3, steps (670, 680) function as estimation means M5, and steps (610, 620) function as compensation means M7.

As explained above, according to the second embodiment, in addition to the effects of the first embodiment described above, the following effects are achieved.

That is, depending on the intake air weight Ga, the correction value ΔC3O
Since the configuration is configured to calculate XT, it is possible to accurately determine the activation of the downstream oxygen concentration sensor 37 even when the intake air density changes, so-called altitude compensation.

Next, a third embodiment of the present invention will be described in detail based on the drawings. The difference between this third embodiment and the previously described first embodiment is that the timing processing and activation estimation processing are different, but the device configuration and other processing are completely the same, so the same parts are denoted by the same reference numerals. The description will be omitted.

The activation estimation process executed in the third embodiment will be explained based on the flowchart shown in FIG. 17.

The activation estimation process shown in FIG. 17 is started at predetermined time intervals after the activation of EC (J3).

First, in step 800, the process of reading each of the previously described data is performed. In the subsequent step 805, processing for calculating the intake air volumetric flow rate Q is performed. Next step 81
[
A process is performed to calculate the intake air weight Ga from the F AF AV S and the high altitude learning value FGHAC as shown in the following equation (4).

Ga = Q
)... (4) Next, the process proceeds to step 815, where a process is performed to calculate a correction value ΔC3OXT based on the intake air weight Ga, according to the map shown in FIG. 18, which is stored in the 80M3b in advance. Proceed to the following step 820, and proceed to step 8 above.
It is determined whether or not the value of the correction value ΔC90XT calculated in step 15 is positive. If the determination is affirmative, the process proceeds to step 825, and if the determination is negative, the process proceeds to step 840. In step 825, which is executed when the value of C3OXT to the correction value is positive, the information stored in the 80M3b in advance,
According to the map shown in FIG. 19, a process is performed to calculate the correction coefficient f1 based on the intake air temperature THA. In the subsequent step 830, the correction value ΔcsoxT calculated in the step 815 is multiplied by the correction coefficient f1 to calculate CS OX 1' to the correction value that is increased for temperature compensation, and then the process proceeds to step 850. . On the other hand, in step 840, which is executed when the value of the correction value ΔC5OXT is negative in step 820, the intake air temperature THA is calculated according to the map shown in FIG. A process of calculating a correction coefficient f2 is performed. In the following step 845, the correction value calculated in step 815 is multiplied by C3OXT by the correction coefficient f2, and the correction value C90 is reduced for temperature compensation.
After performing the process of calculating XT, the process proceeds to step 850. In step 850, the activation estimation counter Cs o
A process of updating the counted value of x'r by adding the correction value ΔcsoxT corrected in step 830 or step 84δ is performed. Next, the process proceeds to step 855, and it is determined whether the count value of the activation estimation counter C3OXT, which has been added and updated in step 850, is equal to or greater than the activation determination f+1.If the determination is affirmative, the process proceeds to step 865; If a negative determination is made, each step proceeds to step 860. Finally, the count value of the activation estimation counter C90XT is
Activation determination [Step 860 executed when less than 8
Now, the downstream oxygen concentration sensor activation flag X5FBt-
[After performing the process of resetting to 0, -1, this activation estimation process ends. On the other hand, step 86 is executed when it is determined in step 855 that the downstream oxygen concentration sensor 37 has been activated after a sufficient period of time has passed after startup.
5, the downstream oxygen temperature sensor activation flag X5FI3
After performing the process of setting the value 1 to the value 1, the activation estimation process ends on -1. Thereafter, in this activation estimation process, steps 800 to 865 are repeatedly executed at predetermined intervals.

In addition, in this third embodiment, ECtJ3 and the ECU
Steps (800 to 815, 8
50) as the integrating means M3, steps (855 to 86)
5) as the estimation means M5, steps (820 to 845)
) respectively function as compensation means M7.

As explained above, according to the third embodiment, the correction coefficient f1.according to the intake air temperature THA is calculated based on the sign of the correction value ΔC8OXT calculated according to the intake air weight Ga. f
C9 to the correction value using the correction coefficients f1 and f2.
Since the count value of the activation estimation counter C3OXT is updated by increasing or decreasing 0XT, it is possible to realize activation estimation that takes into account the intake air temperature THA without performing timekeeping processing.

Note that the engine air-fuel ratio control device 1 of the third embodiment is as follows:
As shown in FIG. 21, the downstream oxygen humidity sensor 37 includes a heater 37a, and the drive circuit 3 of the ECU 3 includes a drive transistor 51 therein. Therefore, the heater 37a is driven and controlled based on the count value of the activation estimation counter C90XT of the downstream oxygen temperature sensor 37 updated in the activation estimation process, and the downstream oxygen concentration sensor 37 is heated. It is possible to promote the This promotion of activation is caused by E
This is realized by the CU 3 executing the heater control process shown in the flowchart of FIG. The heater control process is repeatedly executed at predetermined time intervals as the ECU 3 is activated.

First, in step 900, a process of reading each data is performed. In the following step 910, it is determined whether the count value of the activation estimation counter C3OXT updated in the activation estimation process described above exceeds the heating determination value Z. If the determination is affirmative, the process proceeds to step 930; Once determined, the process proceeds to step 920. In step 910 above,
The count value of the activation estimation counter C3OXT is the heating judgment value Z
Step 92 executed when it is determined that:
0, the downstream oxygen concentration sensor 37 has not yet been activated, so in order to promote activation by heating, a control signal is output to the driving transistor 51 described above, and a process is performed to energize the heater 37a. After that, the present heater control process ends. On the other hand, in the above-mentioned Stembu 910,
The count value of the activation estimation counter C3OXT is the heating judgment value Z
Step 930 is executed when it is determined that the
Now, since the downstream oxygen concentration sensor 37 has already been activated, it is assumed that there is no need to heat it, and a control signal is output to the drive transistor 51 described above, and the heater 37 is activated.
After performing the process of stopping the energization to a, the present heater control process ends on -1.

Thereafter, this heater control process repeats steps 900 to 930 at predetermined time intervals.

By executing the heater control process described above, the downstream oxygen temperature sensor 37 can be activated quickly, so high control accuracy can be achieved even when environmental conditions deteriorate, such as when the outside air temperature (intake air temperature THA) is low. There is also the advantage that air-fuel ratio feedback control using the double oxygen moisture sensor system can be started immediately.

Although several embodiments of the present invention have been described above, the present invention is not equally limited to these embodiments, and can be implemented in various forms without departing from the gist of the present invention. Of course.

Effects of the Invention As detailed above, the temperature estimating device for exhaust system parts for an internal combustion engine of the present invention integrates a correction value according to the amount of intake air when estimating the temperature rise and temperature drop of the exhaust system parts of an internal combustion engine. The increase time when the integrated value increases to a predetermined value or more set for the integrated value is extended and corrected as the outside temperature decreases until it is estimated that the temperature of the exhaust system components has increased. is configured to delay the time depending on the decrease in outside temperature. Therefore, even if the outside temperature changes,
This provides an excellent effect in that the temperature rise and temperature drop of exhaust system components can be estimated with high accuracy.

Therefore, for example, the temperature rise of the air-fuel ratio detector, which is an exhaust system component, can be estimated with high accuracy without being affected by changes in outside temperature, and it can be accurately determined whether the air-fuel ratio detector is in an active state. As a result, the accuracy of the air-fuel ratio feedback control based on the detection result of the air-fuel ratio detector is improved, and over-correction of the air-fuel ratio toward the rich side (Rich) is eliminated, which improves the exhaust characteristics of the internal combustion engine. The generation of catalyst exhaust odor can be more reliably prevented.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram conceptually illustrating the content of the present invention, Fig. 2 is a system configuration diagram of the first embodiment of the invention, Fig. 3 is a flowchart showing the control, and Fig. 4 is the same. A graph showing the map, Fig. 5 is a flow chart showing the control, Fig. 6 is a graph showing the map, Fig. 7 (1) and (2) are flow charts showing the control, and Fig. 8 is a flow chart showing the control. Timing charts also showing the state of the control, Fig. 9 (1), (2), 1st
Figure 0 is a flowchart showing the same control, Figure 11 is a graph showing the map, Figure 12 is a timing chart showing the control, and Figure 13 is a graph showing the relationship between the oxygen concentration sensor element temperature and the intake air weight. A graph showing the relationship, FIG. 14 is a flowchart showing the control of the second embodiment of the present invention, and FIG. 15 is a graph showing the map.
16(1) and (2) are flowcharts showing the same control, FIG. 17 is a flowchart showing the control of the third embodiment of the present invention, and FIGS. 18, 19, and 20 are the same maps. 21 is a schematic device configuration diagram of the main parts, FIG. 22 is a flowchart showing the control, FIG. 23 is a graph showing the exhaust characteristics of the conventional technology, and FIG. 24 is the oxygen concentration sensor element temperature. It is a graph showing the relationship between and time. Ml...Internal combustion engine M2...Intake air amount detection means M3...Integration means Ml...Exhaust system parts M5...Estimation means M6...Temperature detection means Ml...Compensation means 1... - Engine air-fuel ratio control device 2 ... Engine 3 ... Electronic door opening device (ECU) 3a ... CPU 31 ... Air flow meter 32 ... Intake temperature sensor 33 ... Throttle position sensor 34 -・
- Idle switch 36...Upstream oxygen concentration sensor 37...Downstream oxygen concentration sensor 37a...Heater 39...Rotation angle sensor

Claims (1)

[Scope of Claims] 1. An intake air amount detection means for detecting an intake air amount of an internal combustion engine; and at least a correction value determined according to the intake air amount detected by the intake air amount detection means as time passes. An integrating means for integrating and calculating an integrated value, and a temperature of the exhaust system components of the internal combustion engine are determined to have increased when the integrated value calculated by the integrating means is equal to or higher than a predetermined value; An apparatus for estimating the temperature of an exhaust system component for an internal combustion engine, further comprising: estimating means for estimating that the temperature has dropped when . Compensating means for performing at least one of a correction for decreasing the integrated value accumulated by the integrating means or an increasing correction for the predetermined value of the estimating means in accordance with a decrease in outside air temperature. Temperature estimation device for exhaust system parts for internal combustion engines.