JP4987354B2 - Catalyst early warm-up control device for internal combustion engine - Google Patents

Description

  The present invention relates to an early catalyst warm-up control device for an internal combustion engine that promotes warm-up of a catalytic converter disposed in an exhaust system of the internal combustion engine at the time of cold start, particularly by performing ignition retard and intake air increase.

Conventionally, it is known to provide a three-way catalyst in an exhaust pipe to purify HC, CO and NO _x in the exhaust. This catalyst becomes active at a certain warm-up temperature and can purify the exhaust gas. For this reason, after the cold start of the internal combustion engine, early warm-up control of the catalyst is performed to increase the exhaust gas temperature by retarding the ignition timing from the basic ignition timing.

  As one of such early catalyst warm-up control of an internal combustion engine, a technique disclosed in Patent Document 1 is known. In this Patent Document 1, when not only the catalyst early warm-up control but also the ignition timing is delayed from the basic ignition timing for early catalyst warm-up, the output torque decreases and the engine rotation speed becomes unstable. A technique for solving the problem of becoming is also disclosed.

Specifically, the amount of intake air is corrected to increase in accordance with the retard amount of the ignition timing, so that the output torque is kept constant, and uncomfortable operability and torque fluctuations are prevented. That is, when the ignition timing is retarded according to the cooling water temperature to promote warm-up after the complete explosion, the opening of the idle control valve provided in the passage bypassing the throttle valve is corrected, and the intake air amount is increased. The output torque is prevented from decreasing due to the ignition timing retardation correction. In order to prevent the ignition timing from changing stepwise at the end of the retard correction, the retard correction amount of the ignition timing is decreased with the passage of time and set to become the basic ignition timing after the correction is completed. Yes.
JP-A-6-101456

  By the way, although the catalyst can gradually purify the exhaust gas when the catalyst temperature reaches about 300 ° C., Patent Document 1 does not consider this.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an early catalyst warm-up control device for an internal combustion engine that takes into account the degree of catalyst activity in early catalyst warm-up control that performs ignition retard and intake air increase.

Accordingly, in the invention according to claim 1, basic ignition timing calculation means for calculating the basic ignition timing, and retard amount calculation for calculating the retard amount of the ignition timing in the early warm-up control of the catalyst for purifying the exhaust gas of the internal combustion engine. Means, ignition timing control means for performing ignition control with the ignition timing corrected based on the retard amount, and intake that is taken into the internal combustion engine based on the retard amount calculated by the retard amount calculating means In the catalyst early warm-up control device for an internal combustion engine having an air amount increasing means for increasing the air amount, the degree of activity of the catalyst is detected based on the temperature of the catalyst, and the temperature of the catalyst is from a state where the catalyst is not active. when a predetermined temperature is determined to be active and start state, and an active degree detecting means determines that the catalyst has begun to activity, the more catalyst is determined to have started to activity activatibility detecting means, flows through the catalyst In order to suppress the exhaust gas amount, the lower limit guard of the retard amount is calculated based on the catalyst temperature, the retard amount is compared with the lower limit guard, and the retard amount is set so that the ignition timing is set to the advance side. And the air amount limiting means for limiting the intake air amount taken into the internal combustion engine based on the ignition timing calculated based on the final retardation amount .

  When the catalyst reaches a predetermined temperature lower than the warm-up temperature, the exhaust gas is gradually purified. However, the exhaust gas cannot be sufficiently purified until the warm-up temperature is reached. Therefore, by limiting the amount of intake air according to the degree of activity of the catalyst, it is possible to reduce emissions until the catalyst reaches a warmed-up active state.

Moreover, activity degree detecting means is to detect the activity degree based on the temperature of the catalyst. Since the activity level of the catalyst depends on the catalyst temperature, the activity level of the catalyst can be detected more accurately based on the catalyst temperature.

Moreover, the activity degree detecting means and means for determining that a state in which the catalyst starts to activity from a state where no activity, the catalyst is determined to have begun to active by the activity degree detecting means air amount limitation means, It is to limit the amount of intake air sucked into the internal combustion engine. In this way, when it is determined that the catalyst has started to be activated, the amount of intake air can be reduced to reduce emissions until the catalyst reaches a warmed-up active state.

Further, the catalyst based on the temperature of the catalysts is to be judged and began to clean. Since the purification of the exhaust gas by the catalyst is started when the temperature of the catalyst reaches a predetermined temperature, it may be determined that the catalyst has started to be purified based on the temperature of the catalyst.

Further, in the invention according to claim 2, it may limit the intake air amount based on the beauty air Oyo ignition timing. In this way, by limiting the intake air amount based on the ignition timing and the air-fuel ratio, it becomes possible to suppress the deterioration of the drivability caused by the torque reduction.

Further, as in the invention according to claim 3 , the air-fuel ratio control means for controlling the air-fuel ratio upstream of the catalyst to the target air-fuel ratio is provided, and when the change amount of the catalyst temperature is smaller than a predetermined value, The air-fuel ratio may be forcibly changed with a predetermined period and amplitude. When the catalyst temperature is near the warm-up temperature, a reaction that purifies HC, CO, and NOx in the exhaust gas occurs in most of the catalyst, and thus a lot of heat of reaction is generated. For this reason, the oxidation / reduction reaction of the exhaust gas in the catalyst is promoted, and the catalyst is warmed up early by utilizing the reaction heat generated by the reaction.

Further, as in the invention according to claim 4 , the air-fuel ratio control means for controlling the air-fuel ratio upstream of the catalyst to the target air-fuel ratio and the exhaust gas temperature estimation means for estimating the exhaust gas temperature are provided, which are estimated by the exhaust gas temperature estimation means. When the temperature of the catalyst becomes higher than the exhaust gas temperature, the air-fuel ratio may be forcibly changed with a predetermined cycle and amplitude by the air-fuel ratio control means. As described above, when the catalyst temperature becomes higher than the estimated exhaust gas temperature, it is judged that the reaction for purifying HC, CO and NOx in the exhaust gas is carried out in the majority of the catalyst, and the oxidation of the exhaust gas in the catalyst is performed. -The reduction reaction may be promoted, and the catalyst may be warmed up early by utilizing the reaction heat generated by the reaction.

[First Embodiment]
Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic view of an engine control system that employs a catalyst early warm-up device for an internal combustion engine of the present invention. In FIG. 1, an electronic control unit (hereinafter referred to as “ECU”) 21 controls each part of an internal combustion engine (hereinafter referred to as “engine”) 11. As an intake system configuration of the engine 11, an intake pipe 12, a throttle valve 26, and an air flow meter 27 are provided. The intake air supplied to the engine 11 is controlled by adjusting the opening of the throttle valve based on a detection signal from an accelerator opening sensor provided in an accelerator pedal (not shown).

  Based on the detection signal of the accelerator opening sensor, the ECU 21 commands the motor to control duty for the throttle motor 22 in order to drive the throttle opening. An appropriate fuel injection amount is calculated based on the detection signal from the engine rotation speed sensor 23 that detects the engine rotation speed and the detection signal from the air flow meter 27, and a drive signal is sent to the injector 17 based on the calculated value. Is supplied. As a result, the optimal air-fuel mixture is supplied into the cylinder 19 of the engine 11, and the ignition is performed by the spark plug 18 at a desired timing, whereby the engine 11 is combusted. In addition, the idle determination sensor 25 outputs a detection signal to the ECU 21 as to whether or not the driving state is idle.

As an exhaust system configuration of the engine 11, an exhaust pipe 13, an air-fuel ratio sensor 20, and a three-way catalyst 16 are provided. The exhaust gas discharged from the engine 11 is purified by a three-way catalyst 16 installed in the exhaust pipe 13. More specifically, when the exhaust gas discharged by the engine 11 passes through the three-way catalyst 16, HC is a harmful substance in the exhaust gas, CO, oxidation-reduction reaction of the NO _x to occur, hydrogen, nitrogen, steam, dioxide Carbon is produced. Thereby, purification of harmful substances in the exhaust gas is performed. Further, in order to adjust the air-fuel ratio detected by the air-fuel ratio sensor 20 to the stoichiometric air-fuel ratio, control of the throttle valve 26 that adjusts the intake air amount and the injector 17 that adjusts the fuel injection amount is executed.

  FIG. 2 is a flowchart for adjusting the intake air amount by retarding the ignition timing in accordance with the degree of activity of the catalyst until the catalyst reaches the warm-up temperature in the embodiment of the present invention. This routine is repeatedly executed at predetermined time intervals.

  First, in step 100, it is determined whether or not the engine is in an idle operation state. When the engine is not in the idling state, the torque decreases when the ignition timing is retarded and the intake air amount is limited, so that a desired torque cannot be generated, resulting in a problem of acceleration failure. For this reason, when it is not in the idle operation state, the flowchart ends.

  If it is determined in step 100 that the engine is in the idling state, the process proceeds to step 101 where the catalyst temperature T is estimated. At this time, the estimated value of the catalyst temperature T can be obtained by the following equation.

T = k × ∫ (exhaust gas temperature × exhaust gas flow rate) dt + catalyst temperature at start-up The exhaust gas flow rate in this equation is an estimated value estimated from the intake air amount, the exhaust gas temperature is measured or estimated, and the catalyst temperature at start-up is the catalyst temperature at start-up Estimated from engine coolant temperature. Further, the catalyst temperature T may be directly detected by providing a catalyst temperature sensor.

  When the catalyst temperature T is detected in step 101, the process proceeds to step 102, and it is determined whether or not the catalyst temperature T is within the catalyst warm-up completion temperature T_end. If the catalyst temperature T has reached the catalyst warm-up temperature T_end, it is determined that the catalyst is sufficiently active, and this flowchart is ended.

  When the catalyst temperature T is equal to or lower than the catalyst warm-up temperature T_end in step 102, the process proceeds to step 103, and whether the catalyst temperature T is equal to or lower than a determination temperature T1 for determining whether or not the catalyst has started to purify the exhaust gas. Judging. This determination temperature T1 is set lower than the catalyst warm-up temperature T_end. In step 103, if the catalyst temperature T is equal to or lower than the determination temperature T1, the process proceeds to step 104, and an initial warm-up control flowchart for calculating the ignition timing sa1 and the target air-fuel ratio trgAF1 is executed. In the initial warm-up control, the exhaust gas cannot be purified by the catalyst. For this reason, priority is given to increasing the exhaust gas temperature, and the retard amount of the ignition timing is set large so as to warm up the catalyst early. Further, when the engine coolant temperature is low or when the elapsed time from the start of the engine is short, the fuel is difficult to atomize, so the air-fuel ratio is set to the rich side. When the calculation of the ignition timing and the air-fuel ratio in the initial warm-up control is completed in step 104, the process proceeds to step 108, and the throttle opening is calculated based on FIGS. A method for calculating the throttle opening will be described in detail later.

  In step 103, if the catalyst temperature T is higher than the determination temperature T1, the process proceeds to step 105, and it is determined whether or not the change amount ΔT of the catalyst temperature is equal to or greater than a predetermined change amount ΔTend. If the change in the catalyst temperature is larger than the predetermined change amount ΔTend in step 105, the process proceeds to step 106, and a flowchart of the intermediate warm-up control for calculating the ignition timing sa2 and the target air-fuel ratio trgAF2 is executed. In the middle of the warm-up control, the exhaust gas is not sufficiently purified by the catalyst. Therefore, the retard amount of the ignition timing and the air-fuel ratio are controlled in accordance with the degree of catalyst activity to limit the intake air amount.

  When the optimum ignition timing and air-fuel ratio according to the degree of catalyst activation in the medium-term warm-up control are calculated in step 106, the routine proceeds to step 108, where the throttle opening is calculated based on FIGS. A method for calculating the throttle opening will be described in detail later.

When the catalyst temperature change is smaller than the predetermined change amount ΔTend at step 105, the routine proceeds to step 107, where a flowchart of the late warm-up control for calculating the ignition timing sa3 and the target air-fuel ratio trgAF3 is executed. Here, when the change amount ΔT of the catalyst temperature is smaller than the predetermined change amount ΔTend, a reaction that purifies HC, CO, and NO _x in the exhaust gas occurs in most of the catalyst, and thus a lot of reaction heat is generated. For this reason, the reaction in the catalyst is promoted by forcibly amplifying the air-fuel ratio to rich / lean so as to warm up the catalyst early. When calculation of the ignition timing and air-fuel ratio in the late warm-up control is completed in step 107, the routine proceeds to step 108, where the throttle opening is calculated based on FIGS. Details of the processing for calculating the throttle opening will be described later.

  Next, a flowchart for calculating the ignition timing sa1 and the target air-fuel ratio trgAF1 in the initial warm-up control will be described with reference to FIG. In the initial warm-up control, the exhaust gas is not purified because the catalyst temperature is low. For this reason, the ignition timing is greatly retarded and the exhaust gas temperature is increased, so that the temperature of the exhaust gas is used to control the catalyst to warm up early.

  When this flowchart is executed, the routine proceeds to step 301, where the engine operating state necessary for calculating the ignition timing and the air-fuel ratio is calculated. The engine coolant temperature and the elapsed time after starting are detected as parameters of the engine operating state. In step 302, the retard amount ret1 is calculated based on the engine coolant temperature and the elapsed time from the start. As shown in FIG. 10, the retard amount is set small so that the ignition timing becomes the advance side as the engine coolant temperature rises. This is because the catalyst is warmed up early by setting the ignition timing to the retard side during cold start. Based on this retard amount ret1, in step 303, a sub-flowchart for calculating the ignition timing (sa1) is executed. A detailed description of the flowchart for calculating the ignition timing will be described later (see FIG. 6).

  Next, the routine proceeds to step 304, where the target air-fuel ratio trgAF1 is calculated. As shown in FIG. 11, the target air-fuel ratio trgAF1 is set to the lean side as the engine coolant temperature rises or as time elapses. When the engine coolant temperature is low at the cold start, fuel atomization is not promoted, so the air-fuel ratio is set to the rich side.

  When the target air-fuel ratio trgAF1 is calculated in step 304, the process returns to the main routine. In step 108, the throttle opening is calculated based on the ignition timing sa1 and the target air-fuel ratio trgAF1.

  A flowchart for calculating the ignition timing sa2 and the target air-fuel ratio trgAF2 in the medium-term warm-up control will be described with reference to FIG. In medium-term warm-up control, the catalyst is in a partially activated state, and the degree of activity of this catalyst increases as the catalyst temperature rises. Therefore, by controlling the amount of exhaust gas flowing through the catalyst according to the degree of catalyst activity, The emission until the catalyst reaches the warmed-up active state can be reduced.

  When this flowchart is executed, the routine proceeds to step 311 to calculate the engine operating state necessary for calculating the ignition timing and the air-fuel ratio. As engine operating parameters, the engine coolant temperature and the elapsed time after starting are detected when calculating the ignition timing and air-fuel ratio. In step 312, the retard amount ret1 is calculated based on the engine coolant temperature and the elapsed time from the start based on FIG.

In step 313, the lower limit guard ret2 of the retard amount is calculated based on the catalyst temperature (see FIG. 9). The lower limit guard ret2 is set to a large retard amount so that the ignition timing is retarded as the catalyst temperature rises. Thus, by setting the ignition timing according to the catalyst temperature, the amount of exhaust gas flowing through the catalyst can be controlled according to the degree of activity of the catalyst. Thereby, the purification efficiency of the exhaust gas until the warm-up temperature is reached can be improved.

  When the lower limit guard ret2 of the ignition timing is calculated in step 313, the process proceeds to step 314, the retard amount ret1 is compared with the lower limit guard ret2 of the retard amount, and the retard angle is set so that the ignition timing is set to the advance side. The smaller amount is calculated as the final retardation amount. Based on this retard amount, a sub-flowchart for calculating the ignition timing (sa2) is executed in step 315. A detailed description of the flowchart for calculating the ignition timing will be described later (see FIG. 6). Next, at step 315, the target air-fuel ratio trgAF2 is calculated based on FIG. When the air-fuel ratio is calculated in step 315, the process returns to the main routine. In step 108, the throttle opening is calculated based on the ignition timing sa2 and the target air-fuel ratio trgAF2.

  A flowchart for calculating the ignition timing sa3 and the target air-fuel ratio trgAF3 of the late warm-up control will be described with reference to FIG. In the late warm-up control, air-fuel ratio feedback control for forcibly switching to rich / lean based on the stoichiometric air-fuel ratio is performed, so that the catalyst reaches the warm-up temperature using reaction heat generated in the catalyst.

When this flowchart is executed, the process proceeds to step 321 to calculate an engine operating state necessary for calculating the ignition timing and the air-fuel ratio. As engine operating condition parameters, engine cooling temperature and elapsed time after start required for calculating the ignition timing and air-fuel ratio are detected. In step 322, the retard amount ret1 is calculated based on the engine coolant temperature and the elapsed time from the start as shown in FIG. Based on this retard amount, in step 323, a sub-flowchart for calculating the ignition timing (sa3) is executed. A detailed description of the flowchart for calculating the ignition timing will be given later (see FIG. 6).
In step 324, the reference air-fuel ratio AF is set. As a result, air-fuel ratio feedback control is executed, and control is performed so that the overall air-fuel ratio becomes the reference air-fuel ratio AF. Next, the routine proceeds to step 325, where it is determined whether or not the target air-fuel ratio trgAF3 of the previous cycle is rich. In step 325, if the target air-fuel ratio trgAF3 of the previous cycle is rich, the process proceeds to step 326, where the target air-fuel ratio trgAF3 is set to the lean side. The target air-fuel ratio trgAF3 at this time is set by increasing ΔK _AF with reference to the reference air-fuel ratio AF. If the target air-fuel ratio trgAF3 is not rich in step 325, the process proceeds to step 327 and the target air-fuel ratio trgAF3 is set to the rich side. The target air-fuel ratio trgAF3 at this time is set by reducing ΔK _AF with reference to the reference air-fuel ratio AF. In this way, by executing the control for forcibly rich / lean the air-fuel ratio around the reference air-fuel ratio AF, the oxidation / reduction reaction of the exhaust gas in the catalyst is promoted, and the reaction heat generated by the reaction Is used to warm up the catalyst early. Moreover, an oxygen concentration sensor may be used as a method for detecting the air-fuel ratio.

  When the air-fuel ratio is calculated, the process returns to the main routine, and in step 108, the throttle opening is calculated based on the ignition timing sa3 and the target air-fuel ratio trgAF3.

  Next, a flowchart for calculating the ignition timing will be described with reference to FIG. When this flowchart is executed, the routine proceeds to step 10 where the basic ignition timing is calculated from the engine speed and the intake air amount. The basic ignition timing is calculated from a map (not shown) of the engine speed and the intake air amount. When the basic ignition timing is calculated in step 10, the process proceeds to step 20 to calculate the retard amount of the ignition timing in the early catalyst warm-up. When the retard amount of the ignition timing in the catalyst early warm-up control is calculated in step 20, the process proceeds to step 30, and the final ignition timing is calculated based on the ignition timing calculated in the previous step. By executing this flowchart, the ignition timing can be calculated.

  Next, a method for calculating the throttle opening will be described with reference to FIGS. FIG. 8 is a block diagram for calculating the throttle opening. FIG. 7 is a flowchart for calculating the throttle opening. In the idle operation state, the final throttle opening is set by feedback of the engine coolant temperature, ignition timing, air-fuel ratio, difference between the target rotational speed and the actual rotational speed.

  In the idling operation state, in step 110, the base throttle opening degree Th1 is calculated based on the engine coolant temperature. As shown in FIG. 8, the base throttle opening degree Th1 is set to be smaller as the engine coolant temperature rises.

  When the base throttle opening degree Th1 is calculated based on the engine coolant temperature in step 110, the routine proceeds to step 111, where the correction amount Th2 of the throttle opening degree is calculated from the ignition retard amount. At the cold start, the ignition timing is set to the retard side in order to warm up the catalyst early. As described above, when the ignition timing is set to the retarded angle, the exhaust gas temperature becomes high, but since the optimum combustion is not performed in the cylinder, the generated torque becomes small and the engine rotation speed becomes unstable. Therefore, as shown in FIG. 8, the throttle opening correction amount Th2 is set to increase as the ignition timing becomes retarded.

  When the throttle opening is corrected based on the retard amount of the ignition timing in step 111, it is determined in step 112 whether or not the air-fuel ratio sensor is active. If the air-fuel ratio sensor is active, the routine proceeds to step 113, where the throttle opening correction amount Th3 is calculated based on the target air-fuel ratio as shown in FIG. The throttle opening correction amount Th3 is set to increase as the target air-fuel ratio becomes leaner. On the other hand, if the air-fuel ratio sensor is not active in step 112, the routine proceeds to step 114 where the throttle opening correction is set to zero and the throttle opening correction based on the target air-fuel ratio is not performed.

  In step 115, the throttle opening degree Th4 for performing feedback correction is calculated from the difference between the target idle speed and the actually measured actual engine speed. In step 116, the final throttle opening is calculated from the throttle opening calculated in steps 110 to 115.

  As described above, in the idling operation state, the throttle opening is set by feedback of the engine cooling water temperature, ignition timing, air-fuel ratio, difference between the target rotational speed and the actual rotational speed.

  According to the first embodiment described above, the activity in which the catalyst is warmed up by retarding the ignition timing and adjusting the intake air amount according to the degree of activity of the catalyst until the catalyst reaches the warm-up temperature. Emissions until reaching the state can be reduced. Further, catalyst warm-up is promoted by executing catalyst early warm-up control in accordance with the degree of catalyst activity.

[Second Embodiment]
In the first embodiment, when the amount of change in the catalyst temperature is smaller than a predetermined value, the catalyst warm-up control is switched from the middle stage to the latter stage. In the second embodiment, the catalyst temperature is estimated, and when the catalyst temperature is higher than the actually estimated or detected exhaust gas temperature, the catalyst warm-up control is switched from the middle stage to the latter stage. It is different from the form.

  A second embodiment will be described with reference to FIG. When this flowchart is executed, it is determined in step 200 whether or not the engine is in an idle operation state. In the case where the engine is not in the idling operation state, the flowchart is ended in order not to perform this control.

  If it is determined in step 200 that the engine is in the idling state, the process proceeds to step 201, where the catalyst temperature T and the exhaust gas temperature T_ex are detected. At this time, the estimated value of the catalyst temperature T can be obtained by the following equation.

T = k × ∫ (exhaust gas temperature × exhaust gas flow rate) dt + catalyst temperature at start-up The exhaust gas flow rate in this equation is an estimated value estimated from the intake air amount, the exhaust gas temperature is measured or estimated, and the catalyst temperature at start-up is the catalyst temperature at start-up Estimated from engine coolant temperature. Further, the catalyst temperature T may be directly detected by a catalyst temperature sensor. Further, the exhaust gas temperature T_ex may be estimated. The estimation of the exhaust gas temperature T_ex can be obtained by the following equation.

T_ex = starting water temperature + F (ignition timing, accumulated exhaust gas flow rate)
The start-up water temperature of this type is the engine coolant temperature. Further, F (ignition timing, integrated exhaust gas flow rate) is a value calculated using the ignition timing and the integrated exhaust gas amount from the starting time as parameters. The method for detecting the exhaust gas temperature is directly performed by an exhaust gas temperature sensor set in the exhaust pipe.

  When the catalyst temperature T and the exhaust gas temperature T_ex are estimated or detected in step 201, the process proceeds to step 202, and it is determined whether or not the catalyst temperature T is within the catalyst warm-up completion temperature T_end. If the catalyst temperature T has reached the catalyst warm-up temperature T_end, it is determined that the catalyst is sufficiently active, and this flowchart is ended.

  When it is determined in step 202 that the catalyst temperature T is equal to or lower than the catalyst warm-up completion temperature T_end, the process proceeds to step 203, and a determination temperature T1 for determining whether or not the catalyst temperature T has started to be purified. It is determined whether or not: When it is determined in step 203 that the catalyst temperature T is equal to or lower than the determination temperature T1, the process proceeds to step 204, and a flowchart for calculating the ignition timing sa1 and the target air-fuel ratio trgAF1 of the initial warm-up control as in the first embodiment. Execute. When the optimal ignition timing sa1 and the target air-fuel ratio trgAF1 for activating the catalyst early in the initial warm-up control are calculated, the routine proceeds to step 208, and the throttle opening is calculated based on FIGS.

  If it is determined in step 203 that the catalyst temperature T is higher than the determination temperature T1, the process proceeds to step 205, where the estimated or detected exhaust gas temperature T_ex is compared with the catalyst temperature T. When the catalyst temperature T is lower than the exhaust gas temperature T_ex, it is determined that the catalyst control is in the middle period, and the intake air amount is limited by setting the ignition timing and the air-fuel ratio according to the degree of catalyst activity.

  Further, when the catalyst temperature T is higher than the exhaust gas temperature T_ex, the reaction heat is generated in the catalyst by executing the control for promoting the oxidation / reduction reaction of the exhaust gas, and the generated reaction heat is used to generate the reaction heat of the catalyst. We are trying to warm up.

  If the catalyst temperature T is lower than the exhaust gas temperature T_ex in step 205, the process proceeds to step 206, and a flowchart for calculating the ignition timing sa2 and the target air-fuel ratio trgAF2 of the medium-term warm-up control is executed. In step 206, when calculation of the optimal ignition timing and air-fuel ratio corresponding to the degree of catalyst activity in the medium-term warm-up control is completed, the routine proceeds to step 208, where the throttle opening is calculated based on FIG. 8 and FIG.

  If the catalyst temperature T is higher than the exhaust gas temperature T_ex in step 205, the process proceeds to step 207, and the flowchart for calculating the ignition timing sa3 and the target air-fuel ratio trgAF3 for the late warm-up control is executed. In step 207, when calculation of the optimal ignition timing and air-fuel ratio in accordance with the purification of the catalyst in the late warm-up control is completed, the routine proceeds to step 208, where the throttle opening is calculated based on FIG. 8 and FIG.

  According to the second embodiment described above, the activity in which the catalyst is warmed up by retarding the ignition timing and adjusting the intake air amount in accordance with the degree of activity of the catalyst until the catalyst reaches the warming-up temperature. Emissions until reaching the state can be reduced. Further, catalyst warm-up is promoted by executing catalyst early warm-up control in accordance with the degree of catalyst activity.

  In the first and second embodiments, the intake air amount is limited when the catalyst temperature T reaches about 300 degrees, but the intake air amount is reduced before the catalyst temperature reaches about 300 degrees in consideration of delay in response. You may restrict.

It is a block diagram of this embodiment. 4 is a flowchart when performing catalyst early warming control in the first embodiment. 3 is a flowchart for calculating an ignition timing and an air-fuel ratio in initial warm-up control. 5 is a flowchart for calculating an ignition timing and an air-fuel ratio in medium-term warm-up control. 7 is a flowchart for calculating an ignition timing and an air-fuel ratio in late warm-up control. It is a flowchart which calculates ignition timing. It is a flowchart at the time of calculating a throttle opening. It is a block diagram at the time of calculating a throttle opening. It is a map showing the lower limit guard of the retard amount in the medium-term warm-up control. 3 is a map for calculating a retard amount. It is a map which calculates an air fuel ratio. 6 is a flowchart when performing catalyst early warming control in the second embodiment.

Explanation of symbols

11 Engine 16 Catalyst 17 Injector 18 Spark plug 20 Air-fuel ratio sensor 21 ECU
23 Engine rotation speed sensor 25 Idle sensor

Claims (4)

Basic ignition timing calculating means for calculating basic ignition timing;
A retard amount calculating means for calculating a retard amount of the ignition timing in the early warm-up control of the catalyst for purifying the exhaust gas of the internal combustion engine;
Ignition timing control means for correcting the basic ignition timing based on the retard amount and performing ignition control with the corrected ignition timing;
In the catalyst early warm-up control device for an internal combustion engine, comprising an air amount increasing means for increasing the intake air amount sucked into the internal combustion engine based on the retard amount calculated by the retard amount calculating means,
The degree of activity of the catalyst is detected based on the temperature of the catalyst. When the temperature of the catalyst reaches a predetermined temperature at which it is determined that the catalyst starts to be activated from the inactive state, the previous catalyst is activated. An activity level detection means for determining that it has started ,
More said catalyst is determined to have begun to active the active degree detecting means, in order to suppress the amount of exhaust gas flowing into the catalyst, calculates a lower limit guard of the retard amount based on the temperature of the catalyst, the Comparing the retard amount with the lower limit guard, the smaller retard amount is set as the final retard amount so that the ignition timing is set to the advance side, and based on the final retard amount An early catalyst warm-up control device for an internal combustion engine, comprising: an air amount restriction means for restricting an intake air amount sucked into the internal combustion engine based on a calculated ignition timing . The air amount limitation means, fast catalyst warm-up control device for an internal combustion engine according to claim 1, characterized in that to limit the intake air amount based on the beauty air Oyo ignition timing. Air-fuel ratio control means for controlling the air-fuel ratio upstream of the catalyst to a target air-fuel ratio,
3. The internal combustion engine according to claim 1, wherein when the amount of change in the catalyst temperature is smaller than a predetermined value, the air-fuel ratio is forcibly changed with a predetermined cycle and amplitude by the air-fuel ratio control means. Catalyst early warm-up control device. Air-fuel ratio control means for controlling the air-fuel ratio upstream of the catalyst to a target air-fuel ratio;
An exhaust gas temperature estimating means for estimating the exhaust gas temperature,
When the temperature of the catalyst becomes higher than the exhaust gas temperature estimated by the exhaust gas temperature estimating means, the air-fuel ratio is forcibly changed at a predetermined cycle and amplitude by the air-fuel ratio control means. The catalyst early warm-up control device for an internal combustion engine according to any one of claims 1 to 3 .

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