JP2003138929A - Abnormality diagnosis device of catalyst early warm-up control system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine normality/abnormality of an exhaust gas temperature raising system and a secondary air introducing system, in a catalyst early warm-up control system which introduces a secondary air into an exhaust pipe while raising temperature of an exhaust gas during catalyst early warm-up control, to generate after burning. SOLUTION: During the catalyst early warm-up control, the temperature of the exhaust gas flowing in a periphery of an air-fuel ratio sensor and in a catalyst is changed depending on the normality/abnormality of the exhaust gas temperature raising system and the secondary air introducing system, and according to this change, a proceeding state of warm-up of the catalyst and a proceeding state of an activation of an air-fuel ratio sensor are changed. When the secondary air introducing system becomes abnormal and a secondary air introducing amount runs short or becomes excess, an air-fuel ratio of the exhaust gas in the periphery of the air-fuel ratio sensor is changed accordingly. By focusing attention on the relationship, the proceeding state of the activation of the air-fuel ratio sensor and an output (air-fuel ratio of the exhaust gas) of the air-fuel ratio sensor are determined, thereby respectively determining the normality/abnormality of the exhaust gas temperature raising system and the normality/abnormality of the secondary air introducing system.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an abnormality of a catalyst early warm-up control system of an internal combustion engine for diagnosing whether or not there is an abnormality of a catalyst early warm-up control system for promoting warm-up of a catalyst for purifying exhaust gas of an internal combustion engine. The present invention relates to a diagnostic device.

[0002]

2. Description of the Related Art Recent automobiles are equipped with a catalyst such as a three-way catalyst in order to purify exhaust gas.
Since the exhaust gas purification rate is low until the engine is warmed up to the activation temperature after starting, the catalyst early warm-up control is executed by ignition timing retard control, etc. until the catalyst is warmed up to the activation temperature after the engine is started. The exhaust heat is increased to warm up the catalyst in a short time. If the exhaust heat amount during the catalyst early warm-up control decreases due to the failure of the catalyst early warm-up control system and the amount of heat supplied to the catalyst becomes insufficient, the catalyst warm-up (activation) is delayed and the exhaust gas after engine start Since the emission deteriorates, it is necessary to detect an abnormality in the catalyst early warm-up control system at an early stage.

Therefore, as disclosed in Japanese Patent Laid-Open No. 2001-132438, a catalyst temperature sensor for detecting the temperature of the catalyst is provided, and based on the catalyst temperature detected by this catalyst temperature sensor and the cumulative intake air amount after starting. It has been proposed to compare the estimated estimated catalyst temperature to diagnose whether there is an abnormality in the catalyst early warm-up control system.

[0004]

By the way, in order to further improve the catalyst warm-up performance in response to the increasingly strict exhaust gas regulations, the exhaust gas temperature of the internal combustion engine is raised by the ignition timing retard control or the like. Introduce secondary air (oxygen) into the exhaust passage on the upstream side of the catalyst while raising the temperature of the exhaust gas at which the rich components (HC, CO, etc.) in the exhaust gas can burn in the exhaust passage on the upstream side. As a result, the rich components (HC, CO
Etc.) with secondary air (oxygen) to generate afterburn,
A catalyst early warm-up control system has been proposed which warms the catalyst efficiently and in a short time by further raising the temperature of exhaust gas flowing into the catalyst by the combustion heat.

The catalyst early warm-up control having the exhaust gas temperature raising system for raising the temperature of the exhaust gas capable of post-combustion in this way and the secondary air introduction system for introducing the secondary air for generating the after-combustion In the system, the exhaust gas temperature raising system and the secondary air introducing system are considered as the places where the abnormality occurs.

However, the above-mentioned conventional publication (Japanese Patent Application Laid-Open No. 2001-1)
In the abnormality diagnosis method of Japanese Patent No. 32438), it is possible to detect that an abnormality has occurred in the catalyst early warm-up control system, but it is specified whether it is an abnormality of the exhaust gas temperature raising system or an abnormality of the secondary air introduction system. Therefore, even if an abnormality of the catalyst early warm-up control system can be detected, it is not possible to quickly perform repair, replacement of parts, etc., in order to identify the abnormal portion. Moreover, in the configuration of the above-mentioned conventional publication, since it is necessary to newly provide a catalyst temperature sensor for detecting the catalyst temperature, the cost is increased accordingly, and cost reduction, which is an important technical problem in recent years, is reduced. Unable to meet demand.

The present invention has been made in consideration of such circumstances. A first object of the present invention is to reduce the cost of a function for diagnosing abnormalities in a catalyst early warm-up system of a secondary air introduction type. The second purpose is to realize whether an abnormality occurs in the exhaust gas temperature raising system or the secondary air introduction system when an abnormality occurs in the catalyst early warm-up system. An object of the present invention is to provide an abnormality diagnosis device for a catalyst early warm-up control system of an internal combustion engine that can be specified.

[0008]

In order to achieve the first object, an abnormality diagnostic device for a catalyst early warm-up control system for an internal combustion engine according to claim 1 of the present invention provides an exhaust gas temperature capable of post-combustion. In a catalyst early warm-up control system having an exhaust gas temperature raising system for raising temperature and a secondary air introducing system for introducing secondary air for generating afterburning, in the vicinity of a secondary air introducing portion or downstream thereof An exhaust gas sensor that detects the gas component concentration such as oxygen concentration of the exhaust gas, the air-fuel ratio, or rich / lean is installed in the exhaust passage on the side of the exhaust gas, and the progress of activation of the exhaust gas sensor is detected after the internal combustion engine is started. The determination is made by the activity determining means, and the presence / absence of abnormality of the catalyst early warm-up control system is determined by the abnormality diagnosing means based on the determination result.

In an electronically controlled internal combustion engine of recent years, a gas component concentration such as an oxygen concentration of exhaust gas, an air-fuel ratio, and the like are provided upstream of a catalyst (or both upstream and downstream of the catalyst) in an exhaust passage.
An exhaust gas sensor that detects either rich or lean is installed, and the air-fuel ratio is controlled to be near the stoichiometric air-fuel ratio based on the output of this exhaust gas sensor, thereby enhancing the exhaust gas purification efficiency of the catalyst. After the internal combustion engine is started, the exhaust gas sensor, like the catalyst, also rises in temperature due to exhaust heat (in the exhaust gas sensor with a built-in heater, the temperature rises due to both heat generated by the heater and exhaust heat),
As the activation of the exhaust gas sensor progresses, the output level of the exhaust gas sensor rises to the normal level.

For example, as shown in FIGS. 6 and 7, if both the exhaust gas temperature raising system and the secondary air introducing system of the catalyst early warm-up control system are functioning normally, the secondary air in the exhaust pipe is Afterburning occurs in the vicinity of the introduction part, and the temperature of the exhaust gas flowing around the exhaust gas sensor provided near the secondary air introduction part or on the downstream side and the temperature of the exhaust gas flowing through the catalyst become high. At the same time, the progress of activation of the exhaust gas sensor also becomes faster, but if an abnormality occurs in the exhaust gas temperature raising system or the secondary air introduction system, the temperature of the exhaust gas flowing around the exhaust gas sensor and the catalyst becomes low. Then, accordingly, the catalyst warm-up becomes slow, and at the same time, the progress of activation of the exhaust gas sensor becomes slow.

The present invention focuses on the correlation between the progress of catalyst warm-up and the progress of activation of the exhaust gas sensor, and determines the progress of activation of the exhaust gas sensor after starting the internal combustion engine. Thus, the progress of catalyst warm-up is indirectly determined, and the presence or absence of abnormality in the catalyst early warm-up control system is diagnosed. In this case, the exhaust gas sensor used for the abnormality diagnosis of the catalyst early warm-up control system may use the exhaust gas sensor installed for the air-fuel ratio control, so that it is necessary to provide a new sensor such as a catalyst temperature sensor. In addition, it is possible to realize the function of diagnosing the abnormality of the catalyst early warm-up system while satisfying the demand for cost reduction.

By the way, as shown in FIG. 7, when both the exhaust gas temperature raising system and the secondary air introducing system are functioning normally, a part of the oxygen in the secondary air introduced into the exhaust passage is formed. The exhaust gas air-fuel ratio becomes slightly lean (a little leaner than the target air-fuel ratio after completion of catalyst warm-up) as a result of remaining afterburning, but the exhaust gas temperature raising system is normal and the secondary air If the introduction system is abnormal and the amount of secondary air introduced is insufficient, the lean deviation of the air-fuel ratio of the exhaust gas due to the secondary air introduction is reduced, and the air-fuel ratio of the exhaust gas is near stoichiometry (the target air temperature after completion of catalyst warm-up). The fuel ratio is maintained). On the contrary, when the secondary air introduction system is normal and the exhaust gas temperature raising system is abnormal and the exhaust gas temperature is lower than normal, afterburning is incomplete and the oxygen content of the secondary air is reduced. Since most of them remain without post-combustion, the air-fuel ratio of the exhaust gas shifts to the lean side. Such a change in the air-fuel ratio of the exhaust gas appears as a change in the output of the exhaust gas sensor.

Focusing on such a relationship, when it is determined that there is an abnormality in the catalyst early warm-up control system as in claim 2, the progress of activation of the exhaust gas sensor and the output of the exhaust gas sensor or its output May be used to discriminate between the abnormality of the exhaust gas temperature raising system and the abnormality of the secondary air introduction system. For example, if the progress of activation of the exhaust gas sensor is slower than normal and it is determined that there is an abnormality in the catalyst early warm-up control system, by determining the air-fuel ratio of the exhaust gas from the output of the exhaust gas sensor, It is possible to accurately identify whether the gas temperature raising system is abnormal or the secondary air introducing system is abnormal, and when the abnormality occurs, repair, replacement of parts and the like are facilitated. In a system in which there are two types of abnormalities in the secondary air introduction system, that is, the secondary air introduction amount is insufficient and the secondary air introduction amount is excessive, as shown in FIG. The combination with the output of the gas sensor can also determine whether the amount of secondary air introduced is insufficient or excessive.

Further, as a method for judging the progress of activation of the exhaust gas sensor, as in claim 3, the time until activation of the exhaust gas sensor or a parameter correlated therewith may be used for the judgment. good. For example, if it takes a long time to activate the exhaust gas sensor, it can be determined that the progress of activation of the exhaust gas sensor is slow.

Further, in the case of an exhaust gas sensor having a built-in heater, the progress of activation of the exhaust gas sensor is correlated with the integrated value of power consumption of the heater until the exhaust gas sensor is activated, or the correlation thereof. You may make it determine using the parameter. As described above, since the exhaust gas sensor with a built-in heater is activated by both heat generation of the heater and exhaust heat, if the exhaust gas temperature around the exhaust gas sensor becomes low due to an abnormality in the catalyst early warm-up control system, Minutes, heater heat supplied until the exhaust gas sensor is activated (heater power consumption integrated value)
Need to increase. Therefore, if the integrated value of the power consumption of the heater until the exhaust gas sensor is activated increases, it can be determined that the progress of activation of the exhaust gas sensor due to exhaust heat is slow.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION << Embodiment (1) >> An embodiment (1) of the present invention will be described below with reference to FIGS. First, the schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner (not shown) is provided in the most upstream part of the intake pipe 12 of the engine 11 which is an internal combustion engine, and an air flow meter 13 for detecting the amount of intake air is provided downstream of the air cleaner. A throttle valve 14 and a throttle opening sensor 15 for detecting the throttle opening are provided downstream of the air flow meter 13.

Further, a fuel injection valve 17 for injecting fuel is attached near an intake port of an intake manifold 16 for introducing air into each cylinder of the engine 11. A spark plug 18 is attached to the cylinder head of the engine 11 for each cylinder, and a spark discharge of each spark plug 18 ignites an air-fuel mixture in the cylinder. Further, a cooling water temperature sensor 19 for detecting a cooling water temperature and a crank angle sensor 20 for detecting an engine rotation speed are attached to a cylinder block of the engine 11.

On the other hand, an exhaust pipe 21 (exhaust passage) of the engine 11 is provided with a catalyst 22 such as a three-way catalyst for reducing CO, HC, NOx, etc. in the exhaust gas, and the catalyst 22 is exhausted upstream of the catalyst 22. Air-fuel ratio sensor 23 for detecting the air-fuel ratio of gas
(Exhaust gas sensor) is provided. The sensor element 24 of the air-fuel ratio sensor 23 has a high activation temperature (about 6
It is difficult to activate the sensor element 24 early after the engine is started only by the heat of the exhaust gas. Therefore, the air-fuel ratio sensor 23 has a built-in heater 25, which activates the sensor element 24 early by the heat generated by the heater 25 and maintains the temperature of the sensor element 24 within the active temperature range during engine operation. Two
The energization to 5 is controlled. The impedance (hereinafter referred to as “element impedance”) Zdc of the sensor element 24 of the air-fuel ratio sensor 23 depends on the temperature of the sensor element 24, and the element impedance Zdc decreases as the temperature of the sensor element 24 increases. is there.

Next, the structure of the secondary air introducing device 34 for introducing the outside air into the exhaust pipe 21 as secondary air will be described. A secondary air introduction pipe 35 for introducing secondary air is connected to the exhaust pipe 21 upstream of the air-fuel ratio sensor 23. The position at which the secondary air is introduced into the exhaust pipe 21 from the secondary air introduction pipe 35 is such that the exhaust gas temperature in the exhaust pipe 21 is a temperature at which a rich component such as HC in the exhaust gas can burn (eg, 700 ° C.). It is set within the above range.

An air filter 36 is provided at the most upstream side of the secondary air introducing pipe 35, and an air pump 37 for sending the secondary air under pressure is provided downstream of the air filter 36. A combination valve 38 is provided downstream of the air pump 37. The combination valve 38 is configured by integrating a check valve 40 on the downstream side of a pressure-driven on-off valve 39 that opens and closes the secondary air introduction pipe 35. Open / close valve 3 of combination valve 38
Reference numeral 9 is connected to the intake pipe 12 via an intake pressure introducing pipe 41, and an electromagnetically driven switching valve 42 provided in the intake pressure introducing pipe 41 changes the drive pressure of the on-off valve 39 to atmospheric pressure and intake pressure. It is designed to switch between and.

When the secondary air is introduced, the switching valve 42 of electromagnetic drive type is turned on (intake pressure introduction position) and the intake pressure is introduced into the opening / closing valve 39 of pressure drive type to open / close the valve 3.
9 is opened. As a result, the secondary air discharged from the air pump 37 flows through the on-off valve 39 to the check valve 40 side, and the pressure causes the check valve 40 to open, so that the secondary air flows into the exhaust pipe 21. be introduced.

On the other hand, when the introduction of the secondary air is stopped,
The switching valve 42 is turned off (atmospheric pressure introduction position) and atmospheric pressure is introduced into the opening / closing valve 39 to close the opening / closing valve 39. As a result, the introduction of the secondary air into the exhaust pipe 21 is stopped, the pressure of the secondary air does not act on the check valve 40, and the pressure on the exhaust pipe 21 side rises.
The valve 0 is automatically closed to prevent the exhaust gas in the exhaust pipe 21 from flowing back to the air pump 37 side.

The air-fuel ratio sensor 23 described above is controlled by the sensor control circuit 26. The sensor control circuit 26 is provided with a sub-microcomputer (hereinafter abbreviated as “sub-microcomputer”) 27 that transmits and receives data to and from the engine control circuit 28. Engine control circuit 28
Is a microcomputer which plays a role of a host microcomputer for the sub-microcomputer 27 and is a main body for controlling the entire engine 11. Engine control circuit 28
Is composed of a CPU 29, a ROM 30, a RAM 31, a backup RAM 32, and the like, and executes various control routines stored in the ROM 30 to perform a fuel injection amount of the fuel injection valve 17 and the ignition plug 1 according to an engine operating state.
The ignition timing of No. 8 is controlled.

[Heater control] The sub-microcomputer 27 of the sensor control circuit 26 shown in FIG. 2 stored in the ROM (not shown).
By executing the heater control routine of the above, the current of the heater 25 of the air-fuel ratio sensor 23 (hereinafter referred to as "heater current")
To control. The processing contents of the heater control routine of FIG. 2 executed by the sub-microcomputer 27 will be described below.

The heater control routine shown in FIG. 2 is started by timer interrupt processing at a predetermined cycle (for example, 128 ms cycle). When this routine is started, first, at step 101, the sensor element 24 is brought into a semi-active state depending on whether or not the element impedance Zdc of the air-fuel ratio sensor 23 has fallen below a predetermined half-activity determination value (for example, 200Ω). It is determined whether or not it has been reached.

At this time, the element impedance Zdc is detected as follows. When the element impedance Zdc is detected, the voltage applied to the air-fuel ratio sensor 23 is temporarily changed in the positive direction and then changed in the negative direction. The element impedance Zdc is calculated from the voltage change amount ΔV and the current change amount ΔI when the applied voltage is changed in the positive direction (or the negative direction).
Is calculated by the following formula. Zdc = ΔV / ΔI

This detection method is an example, and the element impedance Zdc is detected based on the amount of change in the voltage and current on both the positive and negative sides, or the element impedance is calculated from the sensor current Ineg when the negative applied voltage Vneg is applied. Zd
c (= Vneg / Ineg) may be calculated.

If it is determined in step 101 that the element impedance Zdc has not dropped to the half-activity determination value (200Ω) or less, it is determined that the sensor element 24 has not reached the half-activity state, and step 102 is performed. Then, the energization of the heater 25 is controlled by "100% energization control". The 100% energization control is control for maintaining the energization rate (duty ratio) of the heater 25 at 100%, maintaining the maximum heat generation amount of the heater 25, and promoting the temperature rise of the sensor element 24. This 100% energization control is continuously performed during the period when the sensor element 24 has not reached the semi-active state.

Thereafter, the temperature of the sensor element 24 rises due to the heat generated by the heater 25, and when it is determined in step 101 that the element impedance Zdc has dropped to the half-activity determination value (200Ω) or less, the sensor element 24 is half-heated. When it is determined that the active state has been reached, the process proceeds to step 103, where the element impedance Zdc is equal to or less than a predetermined determination value for starting element impedance feedback control (hereinafter referred to as "element impedance F / B control"). Determine whether or not. Here, the determination value of the element impedance F / B control start determines whether or not the temperature of the sensor element 24 has risen to near the activation temperature (that is, whether or not the sensor element 24 has been activated). , A value larger than the target impedance ZdcTG stored and held in the backup RAM (not shown) of the sub-microcomputer 27 by about 10Ω. For example, the target impedance ZdcTG
When the initial value of (the value before sensor deterioration) is 30Ω, the judgment value of the element impedance F / B control start is 30 + 10.
= 40Ω is set.

If "No" is determined in this step 103, it is determined that the temperature of the sensor element 24 has not risen to the vicinity of the activation temperature (not activated), the process proceeds to step 104, and the heater 25 The energization of is controlled by "power control". At this time, a power command value is determined from a map or the like according to the element impedance Zdc, and the duty ratio Duty of the heater 25 is calculated according to the power command value. This power control is performed in the period when the sensor element 24 is in the semi-active state and before the activation is completed.

After that, the routine proceeds to step 108, where it is judged whether or not the power command value is equal to or larger than a predetermined power guard value WHGD calculated by a power guard value setting routine (not shown). If it is equal to or higher than the power guard value WHGD, the process proceeds to step 109, where the power command value is guarded with the power guard value WHGD (power command value = WH
GD), this routine ends. On the other hand, if the power command value is smaller than the power guard value WHGD, step 104
The power command value calculated in step 3 is adopted as it is, and this routine ends.

After that, when the temperature of the sensor element 24 is raised to near the activation temperature, when this routine is started,
In step 103, it is determined as “Yes”, and in step 10
5, the target impedance setting routine (not shown) is executed to set the temperature of the sensor element 24 to the optimum activation temperature (for example, 70
Target impedance Z so that it can be maintained near 0 ° C.
dcTG is set according to the degree of deterioration of the sensor element 24.

After that, the routine proceeds to step 106, where element impedance F / B control is carried out. In this element impedance F / B control, for example, the duty ratio Duty, which is the duty ratio of the heater 25, is calculated using PID control as follows.

First, the proportional term GP, the integral term GI, and the differential term GD are calculated by the following equations (1) to (3). GP = KP * (Zdc-ZdcTG) ... (1) GI = GI (i-1) + KI * (Zdc-ZdcTG) ... (2) GD = KD * {Zdc-Zdc (i-1)} ... (3) Here, KP is a proportional constant, KI is an integral constant, KD is a differential constant, and GI (i-1) and Zdc (i-1) are values at the time of the previous processing.

Then, the proportional term GP, the integral term GI, and the differential term GD are integrated to obtain the duty ratio Dut of the heater 25.
y is calculated (Duty = GP + GI + GD),
A power command value corresponding to the calculated duty ratio Duty is calculated. The duty ratio Duty is controlled by the above P
The control is not limited to the ID control, and PI control or P control may be used.

Then, in the next step 107, the element impedance F / B execution flag XFB is set to "1". This flag XFB indicates whether or not the element impedance F / B control is executed, and XFB =
1 means implementation of element impedance F / B control, and X
FB = 0 means that the element impedance F / B control is not executed. The flag XFB is reset to "0" when the ignition key is turned on.

Even during the element impedance F / B control period,
An electric power guard value WHGD is calculated by an electric power guard value setting routine (not shown), and the electric power command value is guarded (steps 108 and 109). At this time, if the power command value has reached the power guard value WHGD,
The duty ratio Duty calculated in step 106 is corrected according to the power guard value WHGD.

As described above, the temperature of the sensor element 24 is activated by executing the control of the heater 25 in the order of 100% energization control → power control according to the temperature rise of the sensor element 24 (the decrease of the element impedance Zdc). After the temperature is raised to near the temperature, the element impedance Zdc is controlled by the element impedance F / B control.
By maintaining the temperature at G, the temperature of the sensor element 24 is maintained at the activation temperature.

[Catalyst early warm-up control] Next, the catalyst early warm-up control will be described. The engine control circuit 28 is shown in FIG.
By executing the exhaust gas temperature raising control routine of (1), the ignition timing of the ignition plug 18 is retarded at the time of cold start, and rich components (HC, CO, etc.) in the exhaust gas can be burned in the exhaust pipe 21. By raising the temperature of the exhaust gas and executing the routine for secondary air introduction control of FIGS. 4 and 5,
The secondary air introducing device 34 is controlled to introduce the outside air for generating afterburn into the exhaust pipe 21 as secondary air. As a result, the rich component in the high-temperature exhaust gas discharged from the engine 11 is mixed with the oxygen of the secondary air introduced by the secondary air introducing device 34, and is mixed in the exhaust pipe 21 upstream of the catalyst 22. Burning is naturally generated, and the combustion heat thereof further raises the temperature of the exhaust gas flowing into the catalyst 22 to efficiently warm up the catalyst 22 in a short time.

In this case, the exhaust gas temperature raising system is constituted by the function of executing the exhaust gas temperature raising control routine of FIG. 3, the spark plug 18, the ignition device (not shown), etc., and the secondary gas temperature raising system of FIG. 4 and FIG. A secondary air introduction system is configured by the function of executing the routine for air introduction control, the secondary air introduction device 34, and the like.

Further, the engine control circuit 28 executes a fuel injection control routine (not shown) so that the air-fuel ratio of the exhaust gas flowing into the catalyst 22 during the catalyst early warm-up control is set to a weak lean (cylinder mixture). Is approximately stoichiometric air-fuel ratio or slightly rich) to reduce the amount of HC flowing into the catalyst 22. The processing contents of the exhaust gas temperature raising control routine of FIG. 3 and the routine for secondary air introduction control of FIGS. 4 and 5 executed by the engine control circuit 28 will be described below.

[Exhaust Gas Temperature Raising Control] The exhaust gas temperature raising control routine of FIG. 3 is executed, for example, each time fuel is injected into each cylinder. When this routine is started, first, step 201
At 203, whether or not the ignition timing retard control (exhaust gas temperature raising control) for the catalyst early warm-up control is executed is determined as follows. First, in step 201, it is determined whether or not a predetermined time (for example, 1 second) has elapsed from the completion of starting. Completion of the start is determined by, for example, whether or not the engine rotation speed Ne exceeds the start determination value. If the predetermined time has elapsed from the completion of the start, the routine proceeds to step 202, where it is determined whether the engine cooling water temperature Tw is lower than a predetermined temperature (for example, 60 ° C.), and if the engine cooling water temperature Tw is higher than the predetermined temperature. Then, it is determined that the engine 11 is not restarted at a high temperature in a high temperature restart state, and the process proceeds to step 203 to determine whether or not to continue the catalyst early warm-up control. Specifically, it is determined whether 20 seconds have passed since the starter was turned on (start of cranking), or whether the idle state was entered, and if 20 seconds have passed since the starter was turned on, If it is in the non-idle state, it is determined that the catalyst early warm-up control is not continued.

Any one of steps 201 to 203
If it is determined to be "No" at all, the routine proceeds to step 204, where it is determined that the catalyst early warm-up control is unnecessary, and the normal ignition timing control is executed. In this normal ignition timing control, the ignition timing is fixed at 5 ° C. before compression TDC (BTDC) at the beginning of engine start. Further, after the engine warm-up is completed, idle stabilization correction, knock advance correction, etc. are performed on the basic advance angle according to the engine operating state, and the ignition timing is controlled by the optimum advance value.

On the other hand, if all of the above steps 201 to 203 are determined to be "Yes", it is judged that the catalyst early warm-up control is necessary, and the routine proceeds to step 205, where the ignition timing retard control is executed and the ignition timing is controlled. The ignition timing of the plug 18 is retarded to, for example, 10 ° C. after compression TDC (ATDC). As a result, the combustion of the air-fuel mixture in the cylinder is delayed to raise the temperature of the exhaust gas discharged into the exhaust pipe 21.

[Secondary Air Introduction Control] The secondary air introduction control routine of FIG. 4 is executed at a predetermined cycle. When this routine is started, first, in step 301, FIG.
The secondary air introduction determination routine is executed and the secondary air introduction flag FAB is set to "ON", which means permission of secondary air introduction.
Or set to “OFF”, which means prohibition of secondary air introduction.

After that, the routine proceeds to step 302, where it is judged whether or not the secondary air introduction flag FAB is on. If the secondary air introduction flag FAB is on, then it proceeds to step 303.
After switching the switching valve 42 to ON (intake pressure introduction position) and opening the opening / closing valve 39, the routine proceeds to step 304, where the duty ratio Duty of the air pump 37 is set with the elapsed time from start (starter ON or start completion) as a parameter. Search the map of the air pump 3 according to the elapsed time from the start
The duty ratio Duty of 7 is calculated. The map characteristic of the duty ratio Duty is that the duty ratio Du depends on the elapsed time from the start until a predetermined time elapses from the start.
ty increases, and thereafter, the duty ratio Duty is set to a substantially constant value.

Thereafter, the routine proceeds to step 305, where the operating voltage Vp of the air pump 37 is obtained by multiplying the maximum operating voltage Vm of the air pump 37 by the duty ratio Duty (Vp = V
m × Duty), the air pump 37 is operated with this operating voltage Vp to introduce secondary air into the exhaust pipe 21.

On the other hand, if the secondary air introduction flag FAB is off, the switching valve 42 is switched off (atmospheric pressure introduction position) to close the on-off valve 39 and the air pump 37 is stopped (step 306, 307), the introduction of secondary air is stopped.

[Secondary Air Introduction Determination] Next, the processing contents of the secondary air introduction determination routine of FIG. 5 executed in step 301 will be described. When this routine is started, first, in step 401, it is determined whether or not the startup is completed, based on whether or not the engine speed Ne exceeds the startup determination value. Proceed to determine if the first explosion has occurred in the cylinder. yet,
If the first explosion has not occurred, the routine proceeds to step 404, the secondary air introduction flag FAB is set to OFF, and this routine ends. After that, when the first explosion occurs, the routine proceeds to step 405, where the secondary air introduction flag FA
B is set to ON, and this routine ends.

On the other hand, when it is determined in step 401 that the start is completed, the process proceeds to step 403, and it is determined whether or not the secondary air introduction condition is satisfied. The secondary air introduction conditions are, for example, the following items. Exhaust gas temperature is a temperature at which afterburning is possible (eg 700 ℃)
The above is true. The catalyst temperature is lower than a predetermined temperature. The engine 11 is in an operating state in which the HC emission amount is relatively large.

The above conditions are, for example, that the fluctuation amount of the engine speed Ne, the intake pipe pressure PM, the intake air amount Ga, etc. is a predetermined value or more, and the roughness value indicating the instability of combustion is a predetermined value or more. That is, the engine rotation speed Ne is equal to or higher than a predetermined value and the retard amount of the ignition timing is equal to or higher than a predetermined value. The point is that the combustion state in the cylinder is unstable to some extent. In such a case, the unburned H from the engine 11
Since C is discharged, HC necessary for afterburning is exhausted from the exhaust pipe 21.
The amount of HC flowing into the catalyst 22 due to afterburning (the amount of HC discharged into the atmosphere) can be reduced. Further, if the above conditions are satisfied, afterburning can be reliably generated immediately after the introduction of the secondary air.

The above-mentioned predetermined temperature is set, for example, near the lower limit of the activation temperature range of the catalyst 22 or a temperature slightly higher than it. Therefore, when the catalyst temperature is lower than the predetermined temperature, the catalyst 22 needs to be warmed up, so secondary air is introduced to promote warming up of the catalyst 22 by afterburning. On the other hand, when the catalyst temperature is equal to or higher than the predetermined temperature, the catalyst 22 is in an active state and it is not necessary to warm up the catalyst 22, so the introduction of secondary air is prohibited to prevent overheating of the catalyst 22 due to afterburning. To prevent.

When the conditions (1) and (2) described above are satisfied, or when the conditions (1) and (2) are satisfied, the secondary air introduction condition is satisfied, and the routine proceeds to step 405, where the secondary air introduction flag FAB is turned on. Set, permit the introduction of secondary air, and end this routine. On the other hand, when the secondary air introduction condition is not satisfied, the routine proceeds to step 404, the secondary air introduction flag FAB is set to OFF, the introduction of the secondary air is prohibited, and this routine is ended.

The method for determining the secondary air introduction condition can be changed in various ways. For example, when the condition (catalyst temperature <predetermined temperature) is satisfied, the secondary air introduction condition is satisfied. Alternatively, the secondary air introduction condition may be satisfied when the condition (increase in HC emission amount of the engine 11) is satisfied.

[Catalyst early warm-up control abnormality diagnosis] Further, the engine control circuit 28 executes the routines for catalyst early warm-up control abnormality diagnosis of FIGS. It plays a role of abnormality diagnosis means for determining the presence or absence of abnormality. Each routine for diagnosing the catalyst early warm-up control abnormality in FIGS. 8 to 11 may be executed by the sub-microcomputer 27.

Here, an abnormality diagnosis method for the catalyst early warm-up control system will be described. After the engine is started, the air-fuel ratio sensor 23 is heated by the heat of the exhaust gas flowing around the air-fuel ratio sensor 23 and the heat generated by the heater 25, and the temperature rises. The output level of the fuel ratio sensor 23 rises to the normal level.

As shown in FIGS. 6 and 7, if both the exhaust gas temperature raising system and the secondary air introduction system of the catalyst early warm-up control system are functioning normally, the secondary air in the exhaust pipe 21 Afterburning occurs near the introduction portion and the temperature of the exhaust gas flowing around the air-fuel ratio sensor 23 and the catalyst 22 becomes high,
As soon as the catalyst 22 warms up quickly, the air-fuel ratio sensor 23
However, if an abnormality occurs in the exhaust gas temperature raising system or the secondary air introducing system, the air-fuel ratio sensor 23
When the temperature of the exhaust gas flowing around and the catalyst 22 becomes low,
Accordingly, the warm-up of the catalyst 22 is delayed, and at the same time, the progress of activation of the air-fuel ratio sensor 23 is delayed. In this case, a combination of normality / abnormality of the exhaust gas temperature raising system and normality / abnormality of the secondary air introduction system (A) to
The temperature of the exhaust gas flowing around the air-fuel ratio sensor 23 changes according to (F), and the progress of activation of the air-fuel ratio sensor 23 also changes accordingly.

(A) When both the exhaust gas temperature raising system and the secondary air introducing system are normal, the high temperature exhaust gas exhausted from the engine 11 by the exhaust gas temperature raising control is after the secondary air is introduced. Since the temperature of the exhaust gas flowing around the air-fuel ratio sensor 23 becomes higher due to the further increase in temperature due to burning,
The progress of activation of the air-fuel ratio sensor 23 becomes very quick. During the catalyst early warm-up control, the air-fuel ratio of the exhaust gas flowing into the catalyst 22 (that is, the exhaust gas flowing around the air-fuel ratio sensor 23) is set to a weak lean, so both the exhaust gas temperature raising system and the secondary air introducing system are Is normal, the air-fuel ratio of the exhaust gas around the air-fuel ratio sensor 23 becomes weak lean.

(B) When the exhaust gas temperature raising system is normal and the secondary air introducing system is abnormal such that the secondary air is insufficiently introduced, the exhaust gas temperature increasing control causes the high temperature exhaust gas to be emitted from the engine 11. However, since the temperature rise effect due to afterburning is reduced by the shortage of the secondary air introduction amount and the temperature of the exhaust gas flowing around the air-fuel ratio sensor 23 becomes lower than that in the case of (A), the air-fuel ratio sensor The degree of activation of 23 is slower than in the case of (A). Further, in this case, the lean deviation of the air-fuel ratio of the exhaust gas due to the secondary air introduction is reduced, and the air-fuel ratio of the exhaust gas around the air-fuel ratio sensor 23 is near stoichiometric (around the target air-fuel ratio after completion of warming up of the catalyst 22). ) Is maintained.

(D) to (F) When the exhaust gas temperature raising system is abnormal, the temperature of the exhaust gas discharged from the engine 11 is not raised to a temperature at which afterburning is possible due to the abnormality of the exhaust gas temperature raising system. Therefore, even if the secondary air is introduced into the exhaust pipe 21, afterburning is not sufficiently generated, and on the contrary, the exhaust gas is cooled by the secondary air, so that the exhaust gas flowing around the air-fuel ratio sensor 23 is exhausted. The temperature is lower than that in the case of (B). In this case, (D) the abnormality that the secondary air introduction system is insufficient to introduce the secondary air, (E) the secondary air introduction system is normal,
(F) Since the secondary air introduction amount increases in the order of abnormalities in which the secondary air introduction system becomes excessive with the secondary air introduction, the air-fuel ratio sensor 23
The ambient exhaust gas temperature becomes lower in the order of (D), (E), and (F), and as a result, the progress of activation of the air-fuel ratio sensor 23 becomes slower in the order of (D), (E), and (F). Become.

When the exhaust gas temperature raising system is abnormal (D)
In (F), since afterburning does not occur sufficiently, the oxygen concentration in the exhaust gas flowing around the air-fuel ratio sensor 23 becomes higher as the secondary air introduction amount increases, and the lean deviation of the air-fuel ratio of the exhaust gas occurs. growing. Therefore, in the case of (F) the secondary air introduction system is in an abnormal state where the secondary air is excessively introduced, the lean deviation of the air-fuel ratio of the exhaust gas due to the secondary air introduction becomes maximum,
The air-fuel ratio of the exhaust gas around the air-fuel ratio sensor 23 becomes lean. On the other hand, when (D) the secondary air introduction system is abnormal such that the secondary air is insufficiently introduced, the lean deviation of the air-fuel ratio of the exhaust gas due to the secondary air introduction is reduced, and the exhaust gas around the air-fuel ratio sensor 23 is reduced. The air-fuel ratio is maintained near stoichiometry. Further, (E) when the secondary air introduction system is normal, the lean deviation of the air-fuel ratio becomes intermediate between (D) and (F), and the air-fuel ratio of the exhaust gas around the air-fuel ratio sensor 23 becomes weak lean. Become.

On the other hand, (C) When the exhaust gas temperature raising system is normal and the secondary air introducing system is abnormal such that the secondary air is excessively introduced, the exhaust gas temperature raising control causes the high temperature exhaust gas to be emitted from the engine 11. Although exhausted, the exhaust gas is cooled by the excess amount of the secondary air introduction amount, so that the temperature of the exhaust gas flowing around the air-fuel ratio sensor 23 decreases according to the excess amount of the secondary air introduction amount. Therefore, the temperature of the exhaust gas flowing around the air-fuel ratio sensor 23 is lower than that in the case of (A) and higher than that in the case of (E), and the progress of activation of the air-fuel ratio sensor 23 is The area is slower than in the case of (A) and earlier than in the case of (E). In the case of (C), since the amount of oxygen remaining in the exhaust gas without post-combustion increases, the air-fuel ratio of the exhaust gas around the air-fuel ratio sensor 23 becomes lean.

In the present embodiment (1), such normal / abnormal combinations (A) to (F) of the exhaust gas temperature raising system and the secondary air introducing system and the progress of activation of the air-fuel ratio sensor 23 ( Exhaust gas temperature), and the relationship between the secondary air introduction amount and the output of the air-fuel ratio sensor 23 (exhaust gas air-fuel ratio), the degree of activation of the air-fuel ratio sensor 23 and the air-fuel ratio sensor The output of 23 is determined to determine which of (A) to (F) the normal / abnormal combination of the exhaust gas temperature raising system and the secondary air introduction system corresponds to.

At this time, the progress of the activation of the air-fuel ratio sensor 23 is determined by the time from the engine start to the activation of the air-fuel ratio sensor 23 and the power consumption integrated value of the heater 25 (hereinafter referred to as "heater power integrated value"). Is called). That is, when the temperature of the exhaust gas flowing around the air-fuel ratio sensor 23 during the catalyst early warm-up control decreases due to an abnormality in the exhaust gas temperature raising system of the catalyst early warm-up control system or an abnormality in the secondary air introduction system, the air-fuel ratio sensor 23 As the time until activation becomes longer and the heater power integrated value increases, the time from engine start until the air-fuel ratio sensor 23 is activated and the heater power integrated value are respectively compared with the judgment value to compare the air-fuel ratio. The progress of activation of the sensor 23 is determined. This function corresponds to the sensor activity determining means in the claims.

The processing contents of each routine for the catalyst early warm-up control abnormality diagnosis of FIGS. 8 to 11 for performing the abnormality diagnosis of the catalyst early warm-up control system will be described below. The catalyst early warm-up control abnormality diagnosis routine of FIG. 8 is executed at a predetermined cycle. When this routine is started, first, step 501
Then, it is determined whether or not the sensor element 24 has not yet been activated, depending on whether or not the element impedance Zdc of the air-fuel ratio sensor 23 is larger than a predetermined activation determination value (for example, 40Ω). This activation determination value may be set to the same value as the element impedance F / B control start determination value used in step 103 of FIG.

In step 501, the element impedance Z
When it is determined that dc is larger than the predetermined activation determination value, it is determined that the sensor element 24 is not activated, and the process proceeds to step 502, where the heater power integrated value WHSM (i-1) from the start to the previous time. Is added to the current heater power WH to update the stored value of the heater power integrated value WHSM.

After that, the routine proceeds to step 503, where the post-start elapsed time counter CNT for measuring the elapsed time after the start is counted up, and at the next step 504, the intake air amount integrated value GASM ( i-1) This time intake air amount GA is added, intake air amount integrated value GASM
The stored value of is updated.

After that, the air-fuel ratio sensor 23 is activated and becomes empty.
The element impedance Zdc of the fuel ratio sensor 23 is set to a predetermined value.
When the value becomes less than the sex judgment value (for example, 40Ω), the step
If the answer is No in step 501, go to step 505.
A normal / abnormal combination of the exhaust gas temperature raising system and the secondary air introduction system
First determination value K1 for determining the matching_WHSM, K1
_CNTIs calculated by the following formula. K1_WHSM= B1_WHSM× C_WHSM K1_CNT= B1_CNT× C_CNT

Here, the first judgment value K1 _WHSM and K1
_{The CNT} is a heater electric power integrated value WHSM and an elapsed time C required from the start to the activation of the air-fuel ratio sensor 23 when both the exhaust gas temperature raising system and the secondary air introducing system are normal.
Equivalent to NT. Further, B1 _WHSM and B1 _CNT are the first base values and correspond to the first determination value set in advance in the standard engine operating condition, and C _WHSM and C _CNT are the first base value in accordance with the engine operating condition, respectively. Base value B1 _WHSM , B1
It is a correction coefficient for correcting _CNT .

In this routine, in consideration of the fact that the exhaust heat amount supplied to the air-fuel ratio sensor 23 changes depending on the intake air amount GA (exhaust gas flow rate), at step 504, from the start to the activation of the air-fuel ratio sensor 23. The intake air amount integrated value GASM is obtained, and after the air-fuel ratio sensor 23 is activated, the routine proceeds to step 505, where the correction coefficients C _WHSM , C are _calculated according to the intake air amount integrated value GASM from the maps of FIGS.
Calculate _CNT . At this time, in consideration of the fact that the intake air amount integrated value GASM increases, the exhaust heat amount supplied to the air-fuel ratio sensor 23 increases and the air-fuel ratio sensor 23 is activated faster. So that's it,
The correction factors C _WHSM and C _CNT are set to be small,
When the intake air amount integrated value GASM is the reference value, the correction coefficient C
_WHSM, C _{CN T} is 1.0. 1st base value B1 _WHSM ,
B1 _CNT is the first judgment value K set in the experiment or simulation when the intake air amount integrated value GASM is the reference value.
Equivalent to 1 _{WH SM} , K1 _CNT .

Instead of the intake air amount integrated value GASM,
Calculate the average value of intake air amount GA
Correction coefficient C according to the average value_WHSM, C_CNTTo calculate
You can Also, the exhaust gas temperature changes depending on the air-fuel ratio.
Change and the amount of exhaust heat supplied to the air-fuel ratio sensor 23 changes
Therefore, as shown in FIG. 14, the air-fuel ratio sensor 23
Depending on the air-fuel ratio integrated value (or average value) until the activation
Correction coefficient C_WHSM, C _CNTMay be set.

Alternatively, since the exhaust gas temperature changes in accordance with the exhaust pipe temperature at the initial stage of start and the exhaust heat quantity supplied to the air-fuel ratio sensor 23 changes, the exhaust pipe temperature at the initial stage of start is changed as shown in FIG. The correction coefficients C _WHSM and C _CNT may be set according to the correlated parameters (for example, cooling water temperature at starting, oil temperature, intake air temperature, engine stop time, etc.).

Further, in the engine equipped with the variable valve timing mechanism, the exhaust gas temperature changes according to the valve overlap amount and the exhaust heat amount supplied to the air-fuel ratio sensor 23 also changes, so that as shown in FIG. According to the valve overlap amount integrated value (or average value) from the start to the activation of the air-fuel ratio sensor 23, the correction coefficients C _WHSM , C
_You may set _CNT .

Further, as the vehicle speed increases, the exhaust pipe 21
1 increases because the amount of traveling air that cools the engine increases and the temperature of the exhaust pipe 21 does not rise so much that the exhaust gas temperature rises less and activation of the air-fuel ratio sensor 23 is delayed.
As shown in FIG. 7, the correction coefficient C depends on the vehicle speed integrated value (or average value) from the start to the activation of the air-fuel ratio sensor 23.
_WHSM and C _CNT may be set.

As described above, in step 505, the first
After calculating the judgment values K1 _WHSM and K1 _CNT , step 50
Proceeding to 6, it is determined whether or not both the exhaust gas temperature raising system and the secondary air introducing system are normal, depending on whether or not both the following conditions are satisfied. The heater power integrated value WHSM from the start to activation of the air-fuel ratio sensor 23 is less than or equal to the first determination value K1 _WHSM (WHSM ≦ K1 _WHSM ) The elapsed time CNT from start to activation of the air-fuel ratio sensor 23 is The first judgment value K1 _CNT or less (CNT
≤K1 _CNT )

If both of these two conditions are satisfied, it is judged that the activation of the air-fuel ratio sensor 23 and thus the early warm-up of the catalyst 22 have been normally performed, and the routine proceeds to step 507, where the exhaust gas temperature raising system is established. It is determined that both the secondary air introduction systems are normal [corresponding to (A) in FIG. 7], and this routine is ended.

On the other hand, if any of the above two conditions is not satisfied, it is determined that the activation of the air-fuel ratio sensor 23 and the early warm-up of the catalyst 22 were not normally performed. It is determined that at least one of the exhaust gas temperature raising system and the secondary air introducing system is abnormal, the process proceeds to step 508, the abnormality determination flag XCHECK is set to "1", and this routine is ended. In this case, according to the routines of FIGS. 9 to 11 described below,
Whether or not the exhaust gas temperature raising system or the secondary air introducing system is abnormal, that is, the normal / abnormal combination of the exhaust gas temperature raising system and the secondary air introducing system is shown in FIGS. Which of the above is applicable is determined.

[Abnormality determination preprocessing] The abnormality determination preprocessing routine of FIG. 9 is executed at a predetermined cycle, and the average air-fuel ratio MA
Whether or not F is leaner than stoichiometry is determined as follows. First, in step 601, it is determined whether or not the abnormality determination flag XCHECK is set to "1" which means an abnormality in the catalyst early warm-up control system. If it is determined that the abnormality determination flag XCHECK = 1,
After advancing to step 602 and counting up the counter CLEAN, advancing to step 603, the air-fuel ratio sensor 2
The current air-fuel ratio AF is added to the previous air-fuel ratio integrated value AFSM (i-1) of the exhaust gas air-fuel ratio detected in 3 to update the stored value of the air-fuel ratio integrated value AFSM.

After that, the routine proceeds to step 604, where it is judged whether or not the count value of the counter CLEAN exceeds the predetermined value KLEAN. If not, the present routine is terminated without performing the subsequent processing. As a result, when the abnormality determination flag XCHECK = 1, the counter CLEAN
The process of calculating the air-fuel ratio integrated value AFSM is repeated until the count value of exceeds the predetermined value KLEAN.

After that, when the count value of the counter CLEAN exceeds the predetermined value KLEAN, the routine proceeds to step 605, where the air-fuel ratio integrated value AFSM is divided by the count value of the counter CLEAN to obtain the average air-fuel ratio MAF. MAF = AFSM / CLEAN

After this, the routine proceeds to step 606, where it is judged if the average air-fuel ratio MAF is leaner than stoichiometric (14.6). If the average air-fuel ratio MAF is leaner than stoichiometric, the routine proceeds to step 607, where the air-fuel ratio lean flag XLEAN means that the average air-fuel ratio MAF of the exhaust gas flowing around the air-fuel ratio sensor 23 is lean "1. After setting to "0", the process proceeds to step 609, the abnormality determination flag XCHECK is reset to "0", and this routine is finished.

On the other hand, if "No" is determined in the step 606, the process proceeds to a step 608, the air-fuel ratio lean flag XLEAN is set and the average air-fuel ratio MAF of the exhaust gas flowing around the air-fuel ratio sensor 23 is stoichiometric or higher. After setting to "0" which means richer than that, the routine proceeds to step 609, where the abnormality determination flag XCHECK is reset to "0" and this routine is ended.

After resetting the abnormality determination flag XCHECK to "0", it is determined "No" at step 601 and the routine proceeds to step 610, where the counter CLEAN, the air-fuel ratio integrated value AFSM and the average air-fuel ratio MAF are all "0". Then, this routine is finished.

In the system in which the air-fuel ratio feedback control is performed even during the introduction of the secondary air, the average air-fuel ratio MAF
Instead of calculating, the average feedback correction amount or a parameter that correlates with the air-fuel ratio or the output of the air-fuel ratio sensor 23 may be calculated, and it may be determined whether leaner than stoichiometric.

[Abnormal Part Judgment] The abnormal part judgment routine shown in FIGS. 10 and 11 is executed at a predetermined cycle to determine whether the exhaust gas temperature raising system or the secondary air introducing system is abnormal, that is, the exhaust gas. Whether or not the normal / abnormal combination of the gas temperature raising system and the secondary air introducing system corresponds to any of (B) to (F) in FIG. 7 is determined as follows. First, in step 701, it is determined whether the abnormality determination flag XCHECK has been reset from "1" to "0". Step 607 or 6 of the abnormality determination preprocessing routine of FIG. 9 described above.
At step 08, the air-fuel ratio lean flag XLEAN is set to "1" or "0", and at step 609, the abnormality determination flag XCHECK is reset from "1" to "0". The second determination values K2 _WHSM and K2 _CNT for determining the normal / abnormal combination of the temperature system and the secondary air introduction system are calculated by the following formula. K2 _WHSM = B2 _WHSM x C _WHSM K2 _CNT = B2 _CNT x C _CNT

Here, the second judgment value K2 _WHSM and K2
_{In the CNT} , when the exhaust gas temperature raising system is abnormal and the secondary air introduction system is normal, that is, in the case of (E) of FIG. 7, the heater power integration required from the start to the activation of the air-fuel ratio sensor 23 is performed. It corresponds to the value WHSM and the elapsed time CNT. Also, B2
_WHSM and B2 _CNT are the second base values, which correspond to the second judgment value set in advance in the standard engine operating condition, and C
_WHSM and C _CNT are correction coefficients for correcting the second base values B2 _WHSM and B2 _CNT according to the engine operating conditions, respectively.

Thereafter, the routine proceeds to step 703, where the third judgment values K3 _WHSM and K3 _CNT for judging the combination of normal / abnormal of the exhaust gas temperature _raising system and the secondary air introducing system are calculated by the following equation. K3 _WHSM = B3 _WHSM x C _WHSM K3 _CNT = B3 _CNT x C _CNT

Here, the third judgment value K3 _WHSM and K3
_{In the case of CNT} , when the exhaust gas temperature raising system is abnormal and the secondary air introduction system is an abnormality in which the secondary air introduction is insufficient, that is, (D) in FIG.
In this case, it corresponds to the heater power integrated value WHSM and the elapsed time CN required from the start to the activation of the air-fuel ratio sensor 23. Further, B3 _WHSM and B3 _CNT are the third base values and correspond to the third determination value set in advance in the reference engine operating condition, and C _WHSM and C _CNT are respectively the third base value in accordance with the engine operating condition. It is a correction coefficient for correcting the base values B3 _WHSM and B3 _CNT .

After that, the routine proceeds to step 704, where the normal / abnormal combination of the exhaust gas temperature raising system and the secondary air introducing system is determined as shown in FIG. 7E or depending on whether or not both the following conditions are satisfied. It is determined whether or not (F). The heater power integrated value WHSM from the start to activation of the air-fuel ratio sensor 23 is not _less than the second determination value K2 _WHSM (WHSM ≧ K2 _WHSM ) The elapsed time CNT from start to activation of the air-fuel ratio sensor 23 is Second judgment value K2 _CNT or more (CNT
≧ K2 _CNT )

If both of these two conditions are satisfied, the activation of the air-fuel ratio sensor 23 and the warm-up of the catalyst 22 will be delayed most, which is the abnormal mode (E) or (F) in FIG.
Since it can be determined that the average air-fuel ratio MAF is leaner than a predetermined value (for example, 17), it is determined whether the average air-fuel ratio MAF is leaner than a predetermined value (for example, 17).

If the average air-fuel ratio MAF is leaner than the predetermined value (eg, 17), the routine proceeds to step 706.
The normal / abnormal combination of the exhaust gas temperature raising system and the secondary air introducing system is (F) in FIG. 7, that is, the exhaust gas temperature raising system is abnormal and the secondary air introducing system is an excessive secondary air introducing system. Then, this routine is ended.

On the other hand, if “No” is determined in step 705, the process proceeds to step 707, and the normal / abnormal combination of the exhaust gas temperature raising system and the secondary air introducing system is shown in FIG.
That is, it is determined that the exhaust gas temperature raising system is abnormal and the secondary air introducing system is normal, and this routine is ended.

If it is determined "No" in the above step 704, the normal / abnormal combination of the exhaust gas temperature raising system and the secondary air introducing system is any one of FIG. 7 (B) to (D). Because it can be judged that it is,
In step 708 of FIG. 11, the air-fuel ratio lean flag X is set.
Depending on whether LEAN is "1", it is determined whether the average air-fuel ratio MAF is lean due to stoichiometry.

If the air-fuel ratio lean flag XLEAN = 1
If so, the process proceeds to step 709, and the normal / abnormal combination of the exhaust gas temperature raising system and the secondary air introducing system is shown in FIG. 7C, that is, the exhaust gas temperature raising system is normal and the secondary air introducing system is When it is determined that the secondary air is excessively introduced, the routine is terminated.

On the other hand, the air-fuel ratio lean flag XLE
If AN = 0, it is determined that the normal / abnormal combination of the exhaust gas temperature raising system and the secondary air introducing system is (B) or (D) in FIG. 710
Proceed to and whether or not the following conditions are both satisfied,
It is determined whether or not the normal / abnormal combination of the exhaust gas temperature raising system and the secondary air introducing system is (D) in FIG. 7.

The heater electric power integrated value WHSM from the start to the activation of the air-fuel ratio sensor 23 is the third judgment value K3 _WHSM.
The above is (WHSM ≧ K3 _WHSM ) The elapsed time CNT from the start to the activation of the air-fuel ratio sensor 23 is the third determination value K3 _CNT or more (CNT
≧ K3 _CNT ) If both of these two conditions are satisfied, the routine proceeds to step 711, where the normal / abnormal combination of the exhaust gas temperature raising system and the secondary air introduction system is shown in FIG. It is determined that the temperature system is abnormal and the secondary air introduction system is an abnormality in which the secondary air introduction is insufficient, and this routine is ended.

On the other hand, if "No" is determined in step 710, the process proceeds to step 712, where the normal / abnormal combination of the exhaust gas temperature raising system and the secondary air introducing system is shown in FIG.
That is, it is determined that the exhaust gas temperature raising system is normal and the secondary air introduction system is an abnormality causing insufficient secondary air introduction, and this routine is ended.

The process of step 506 of FIG. 8 and the process of FIG.
The process of step 704 of FIG. 11 and the process of step 710 of FIG.
It is also possible to omit one of the calculations and the determination process and execute only one of the calculations and the determination process.

In the embodiment (1) described above, the normal / abnormal combinations (A) to (F) of the exhaust gas temperature raising system and the secondary air introduction system and the progress of activation of the air-fuel ratio sensor 23 ( Focusing on the relationship between the exhaust gas temperature around the air-fuel ratio sensor 23) and the relationship between the secondary air introduction amount and the output of the air-fuel ratio sensor 23 (exhaust gas air-fuel ratio around the air-fuel ratio sensor 23), the air-fuel ratio The progress of activation of the sensor 23 and the output of the air-fuel ratio sensor 23 are determined, and the normal / abnormal combination of the exhaust gas temperature raising system and the secondary air introducing system is shown in FIGS.
Since it was determined which of the above, it is of course possible to detect the abnormality of the catalyst early warm-up control system,
It is possible to accurately identify whether the abnormality of the catalyst early warm-up control system is the abnormality of the exhaust gas temperature raising system or the abnormality of the secondary air introduction system, and it becomes easy to repair or replace parts when the abnormality occurs. Moreover, by utilizing the output of the air-fuel ratio sensor 23, it is possible to determine whether the abnormality of the secondary air introduction system is the excess or the shortage of the secondary air introduction amount. Further, since the air-fuel ratio sensor 23 used for the abnormality diagnosis of the catalyst early warm-up control system may use the air-fuel ratio sensor 23 installed for the air-fuel ratio control, a new sensor such as a catalyst temperature sensor is used. It is not necessary to provide it, and the demand for cost reduction can be satisfied.

<< Embodiment (2) >> Next, in the embodiment (2) of the present invention, the catalyst early warm-up control abnormality diagnosis routine of FIGS. 18 and 19 is executed to detect the abnormality of the catalyst early warm-up control system. Determine the presence or absence. In this routine, first, in steps 801 to 804, the heater power integrated value WHSM from the start to the activation of the air-fuel ratio sensor 23, the elapsed time CNT, and the intake air amount integration are performed in the same manner as in the above embodiment (1). After calculating the value GASM, the routine proceeds to step 805, where the first judgment values K1 _WHSM and K1 _CNT are calculated, and at the next step 806, the second judgment values K2 _WHSM and K2 _CNT are calculated.

After that, the routine proceeds to step 807, where the heater power integrated value WHSM is _{equal to} or less than the first judgment value K1 _WHSM (WHS
M ≦ K1 _WHSM ), the elapsed time CNT is the first
It is determined whether the determination value is K1 _CNT or less (CNT ≦ K1 _CNT ). If both of these two conditions are satisfied, the routine proceeds to step 808, where both the exhaust gas temperature raising system and the secondary air introducing system are normal [normal / abnormal of the exhaust gas temperature raising system and the secondary air introducing system. The combination is (A) in FIG. 7], and this routine is ended.

On the other hand, in step 807, "N
If it is determined to be “o”, the process proceeds to step 809 in FIG. 19 and the heater power integrated value WHSM is the second determination value K2 _WHSM.
Whether or not (WHSM ≧ K2 _WHSM ) is satisfied, the elapsed time CNT is not less than the second determination value K1 _CNT (CNT ≧ K2 _CNT )
Or not. If both of these two conditions are satisfied, the routine proceeds to step 810, where at least the exhaust gas temperature raising system is abnormal [the normal / abnormal combination of the exhaust gas temperature raising system and the secondary air introducing system is shown in FIG. ) Or (F)], and this routine is ended.

On the other hand, if "No" is determined in the step 809, the process proceeds to a step 811, and at least the secondary air introducing system is abnormal [normal / abnormal of exhaust gas temperature raising system and secondary air introducing system]. The combinations of (B) to (D) in FIG.
This is the end of the routine.

In order to simplify the arithmetic processing, the processing of step 807 of FIG. 18 and the processing of step 809 of FIG. It is also possible to execute only the calculation and determination processing of.

In the catalyst early warm-up control abnormality diagnosis of the present embodiment (2) explained above, the catalyst early warm-up control abnormality diagnosis of the embodiment (1) is simplified while the operation process of the abnormality diagnosis is simplified. When an error occurs in the early warm-up control system,
It is possible to identify whether the exhaust gas temperature raising system is abnormal or the secondary air introducing system is abnormal.

In each of the above embodiments (1) and (2),
Only for one parameter (intake air amount integrated value GASM)
Based on each base value B1_WHSM~ B3_WHSM, B1_CNT~ B
Three_{CN T}To correct the judgment value K1_WHSM~ K3_WHSM, K1_CNT
~ K3_CNTI tried to find
Therefore, the base value B1_WHSM~ B3_WHSM, B1_CNT~ B3
_CNTTo correct the judgment value K1_WHSM~ K3_WHSM, K1_CNT~
K3_CNTMay be asked. In this case,
2 to multiply a plurality of correction coefficients calculated from the map of FIG.
Or a parameter that uses multiple parameters as variables.
Create a formula or formula and correct it from the map or formula
The coefficient may be calculated.

In each of the above embodiments (1) and (2),
Is each base value B1_WHSM~ B3_WHSM, B1_CNT~ B3
_CNTIs the correction coefficient C_WHSM, C_CNTCorrected with the judgment value K1
_WHSM~ K3 _WHSM, K1_CNT~ K3_CNTAsking for
However, from the start to the activation of the air-fuel ratio sensor 23,
Data accumulated power value WHSM and elapsed time counter CN after start
Correction value C for the count value of T_WHSM, C_CNTI will correct it with
You can do it. In this case, the base value B1_WHSM~ B3
_WHSM, B1_CNT~ B3_CNTIs the judgment value K1_WHSM~
K3_WHSM, K1_CNT~ K3_CNTIt can be used as

Further, in each of the above embodiments (1) and (2), the elapsed time CNT from the start to the activation of the air-fuel ratio sensor 23 and the heater power integrated value WHSM are measured.
After starting, the element impedance Zdc of the air-fuel ratio sensor 23
Elapsed time CNT from when the value falls below a predetermined value (for example, 100Ω) to when it drops to the activity determination value (for example, 40Ω)
And heater power integrated value WHSM are measured, and this elapsed time C
It is also possible to compare NT and the heater electric power integrated value WHSM with the respective judgment values to make an abnormality diagnosis of the catalyst early warm-up control system. In this way, even if the temperature (element impedance Zdc) of the air-fuel ratio sensor 23 at the beginning of starting is different, the time C required for activation of the air-fuel ratio sensor 23 is increased.
NT and the heater power integrated value WHSM can always be measured under the same conditions, and the abnormality diagnosis accuracy can be improved.

Further, considering that the catalyst early warm-up control such as the ignition timing retard control is started after waiting for a while until the engine operating condition is stabilized to some extent after the start, the ignition timing retard control after the start is performed. Elapsed time CN from when the catalyst early warm-up control is started until the element impedance Zdc of the air-fuel ratio sensor 23 decreases to the activation determination value (for example, 40Ω)
It is also possible to measure T and the heater power integrated value WHSM, and compare the elapsed time CNT and the heater power integrated value WHSM with the respective judgment values to make an abnormality diagnosis of the catalyst early warm-up control system. With this configuration, the air-fuel ratio sensor 23 based on the catalyst early warm-up control is not affected by the variation in the engine operating state before the catalyst early warm-up control is started.
It is possible to accurately determine the progress of the activation of, and it is possible to improve the accuracy of abnormality diagnosis.

Further, in each of the above embodiments (1) and (2), the progress of activation of the air-fuel ratio sensor 23 installed on the upstream side of the catalyst 22 is judged to determine the discharge of the catalyst early warm-up control system. Although the presence or absence of abnormality in the gas temperature raising system and the secondary air introducing system is diagnosed, any one of gas component concentration such as oxygen concentration of exhaust gas, air-fuel ratio, rich / lean is detected on the downstream side of the catalyst 22. In the system in which the exhaust gas sensor is installed, the progress of the activation of the exhaust gas sensor on the downstream side of the catalyst 22 is determined to determine whether the exhaust gas temperature raising system and the secondary air introducing system of the catalyst early warm-up control system are abnormal. The presence / absence may be diagnosed.

Further, in a system in which exhaust gas sensors are installed both upstream and downstream of the catalyst 22, the progress of activation of the exhaust gas sensor on the upstream side and the progress of activation of the exhaust gas sensor on the downstream side are determined. Then, the abnormality diagnosis of the exhaust gas temperature raising system and the secondary air introduction system of the catalyst early warm-up control system may be comprehensively performed based on the determination results of both of them. In this case, depending on the comparison or difference between the determination results of the progress of activation of the exhaust gas sensor on the upstream side and the progress of activation of the exhaust gas sensor on the downstream side (time required for activation of the exhaust gas sensor, heater power integrated value, etc.). Abnormality diagnosis of the exhaust gas temperature raising system and the secondary air introducing system of the catalyst early warm-up control system may be performed.

Further, during the power control period (200Ω ≧ element impedance Zdc> 40Ω), the average value of the change rate of the element impedance Zdc is calculated, and the average change rate of the element impedance Zdc is compared with the judgment value. Thus, abnormality diagnosis of the exhaust gas temperature raising system and the secondary air introducing system of the catalyst early warm-up control system may be performed.

The exhaust gas sensor arranged on the upstream side and / or the downstream side of the catalyst 22 is not limited to the air-fuel ratio sensor for detecting the air-fuel ratio, but may be a sensor for detecting the gas component concentration such as the oxygen concentration of the exhaust gas. The present invention can be applied to and implemented in a system equipped with an oxygen sensor that detects rich / lean of exhaust gas.

In each of the above embodiments (1) and (2), the activation of the exhaust gas sensor (air-fuel ratio sensor 23) is determined based on the element impedance Zdc, but the output of the exhaust gas sensor is equal to or greater than a predetermined value. The activity determination may be made based on whether or not Exhaust gas rich /
In the case of an oxygen sensor that detects lean, the activity determination may be performed depending on whether the output of the oxygen sensor changes from lean output to rich output.

Further, in each of the above embodiments (1) and (2), the air pump 37 of the secondary air introducing device 34 is duty-controlled during the catalyst early warm-up control so that the amount of secondary air introduced can be varied. However, the present invention can be applied to a system equipped with a simple secondary air introducing device that does not have a function of changing the amount of secondary air introduced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an entire engine control system showing an embodiment (1) of the present invention.

FIG. 2 is a flowchart showing a processing flow of a heater control routine.

FIG. 3 is a flowchart showing a processing flow of an exhaust gas temperature raising control routine.

FIG. 4 is a flowchart showing a processing flow of a secondary air introduction control routine.

FIG. 5 is a flowchart showing a processing flow of a secondary air introduction determination routine.

FIG. 6 is a diagram showing an exhaust gas temperature characteristic around an air-fuel ratio sensor.

FIG. 7 is a diagram for explaining a method of diagnosing an abnormality in the exhaust gas temperature raising system and the secondary air introduction system of the catalyst early warm-up control system.

FIG. 8 is a flowchart showing a processing flow of a catalyst early warm-up control abnormality diagnosis routine of the embodiment (1).

FIG. 9 is a flowchart showing a processing flow of an abnormality determination preprocessing routine.

FIG. 10 is a flowchart (part 1) showing a processing flow of an abnormal portion determination routine.

FIG. 11 is a flowchart showing a processing flow of an abnormal point determination routine (No. 2).

FIG. 12 Intake air amount integrated value GASM and correction coefficient C _WHSM
Figure that conceptually shows a map that defines the relationship with

FIG. 13: Intake air amount integrated value GASM and correction coefficient C _CNT
Figure that conceptually shows a map that defines the relationship with

FIG. 14 is a diagram conceptually showing a map that defines the relationship between the integrated value of air-fuel ratio and the correction coefficient C _WHSM (C _CNT ).

[Fig. 15] Cooling water temperature at start-up and correction coefficient C _WHSM (C _CNT )
Figure that conceptually shows a map that defines the relationship with

FIG. 16: Valve overlap amount integrated value and correction coefficient C
Figure that conceptually shows the map that defines the relationship with _WHSM (C _CNT ).

FIG. 17 is a diagram conceptually showing a map that defines the relationship between the vehicle speed integrated value and the correction coefficient C _WHSM (C _CNT ).

FIG. 18 is a flowchart showing a processing flow of a catalyst early warm-up control abnormality diagnosis routine of the embodiment (2) (No. 1).

FIG. 19 is a flowchart showing a processing flow of a catalyst early warm-up control abnormality diagnosis routine of the embodiment (2) (No. 2).

[Explanation of symbols]

11 ... Engine (internal combustion engine), 13 ... Air flow meter, 17 ... Fuel injection valve, 18 ... Spark plug, 21 ... Exhaust pipe (exhaust passage), 22 ... Catalyst, 23 ... Air-fuel ratio sensor (exhaust gas sensor), 24 ... Sensor Element, 25 ... heater, 2
6 ... Sensor control circuit, 27 ... Sub-microcomputer, 28 ... Engine control circuit (abnormality diagnosis means, sensor activity determination means),
34 ... Secondary air introducing device, 35 ... Secondary air introducing pipe.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshihiro Majima             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO (72) Inventor Tatsuya Oka             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO (72) Inventor Hideyuki Maechi             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO (72) Inventor Masayuki Tsutsumi             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO F-term (reference) 3G084 AA03 BA09 BA13 BA23 BA25                       CA02 DA10 DA31 DA33 EB11                       FA07 FA10 FA20 FA26 FA27                       FA29 FA33 FA38                 3G091 AB01 BA02 BA22 BA27 BA29                       CA22 CA23 CA24 DC01 EA01                       EA05 EA07 EA34 HA36

Claims (4)

[Claims] 1. An abnormality diagnosing device for a catalyst early warm-up control system for an internal combustion engine for diagnosing whether or not there is an abnormality in the catalyst early warm-up control system for promoting warm-up of a catalyst for purifying exhaust gas of an internal combustion engine, The catalyst early warm-up control system, an exhaust gas temperature raising system that raises the exhaust gas temperature of an internal combustion engine to an exhaust gas temperature at which a rich component in the exhaust gas can be post-combusted in the exhaust passage on the upstream side of the catalyst, And a secondary air introduction system for introducing secondary air for generating the afterburn into the exhaust passage on the catalyst upstream side, and an exhaust passage near the introduction portion of the secondary air or on the downstream side thereof. An exhaust gas sensor installed in the engine for detecting gas component concentration such as oxygen concentration of exhaust gas, air-fuel ratio, or rich / lean, and sensor activity for determining the progress of activation of the exhaust gas sensor after starting the internal combustion engine Judgment means And an abnormality diagnosis means for determining whether or not there is an abnormality in the catalyst early warm-up control system based on the progress of activation of the exhaust gas sensor determined by the sensor activity determination means. Abnormality diagnostic device for catalyst early warm-up control system of engine. 2. The abnormality diagnosis means, when determining that there is an abnormality in the catalyst early warm-up control system, the progress of activation of the exhaust gas sensor and the output of the exhaust gas sensor or a parameter correlated with the output. The abnormality diagnosis device for the catalyst early warm-up control system for an internal combustion engine according to claim 1, wherein an abnormality in the exhaust gas temperature raising system and an abnormality in the secondary air introduction system are discriminated using. 3. The sensor activity determining means determines the progress of activation of the exhaust gas sensor by using a time until the exhaust gas sensor is activated or a parameter correlated therewith. 3. An abnormality diagnostic device for a catalyst early warm-up control system for an internal combustion engine according to 1 or 2. 4. The exhaust gas sensor has a built-in heater that promotes activation, and the sensor activity determination means determines the progress of activation of the exhaust gas sensor until the exhaust gas sensor is activated. 4. The determination is performed by using an integrated power consumption value or a parameter correlated therewith.
An abnormality diagnostic device for a catalyst early warm-up control system for an internal combustion engine according to any one of 1.