JP2011026999A - Catalyst warming-up control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst warming-up control device capable of preventing burnout of a catalyst while sufficiently promoting warming-up of the catalyst in the one having a secondary air supply means. <P>SOLUTION: It is assumed that the catalyst warming-up control device is applied to a catalyst warming-up system including a fuel injection valve for injecting fuel to an intake pipe or a combustion chamber of the internal combustion engine, and the secondary air supply means for supplying air (secondary air) to an exhaust pipe, and promoting warming-up of the catalyst attached to the exhaust pipe by oxidizing air supplied by the secondary air supply means and unburned gas. The catalyst warming-up control device includes an excessive oxidation reaction determination means for determining whether the oxidation reaction is excessive or not, and an injection amount correcting means for correcting the fuel injection amount to be reduced compared to the case where the oxidation reaction is not determined to be excessive when the oxidation reaction is determined to be excessive. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a catalyst warm-up control device applied to a catalyst warm-up system that promotes warm-up of a catalyst attached to an exhaust pipe of an internal combustion engine.

  Patent Document 1 discloses that a catalyst attached to an exhaust pipe of an internal combustion engine supplies air (secondary air) to an exhaust pipe using a secondary air pump in order to promote warm-up of the catalyst and achieve early activation. , 2 etc. According to this, the unburned components (HC, CO) flowing out from the combustion chamber to the exhaust pipe and the secondary air are oxidized (combusted), and the exhaust heat is instantaneously increased by the reaction heat to warm up the catalyst. Promotion can be aimed at.

  Here, the catalyst warm-up can be promoted as the oxidation reaction is promoted. However, if the oxidation reaction is excessive, the catalyst temperature exceeds an allowable limit and the catalyst is burned out. Therefore, it is required to control the heat of reaction so as to promote the oxidation reaction to the extent that the allowable limit is not reached. Therefore, in the conventional general control, a large amount of secondary air is supplied to be in a lean state, and the amount of unburned components (HC, CO) is adjusted by adjusting the fuel injection amount. The reaction heat is controlled.

JP-A-6-88519 JP-A-6-129241

  By the way, it is general to calculate the fuel injection amount based on the intake air amount detected by the airflow sensor or the intake air amount calculated from the intake air pressure detected by the intake pressure sensor. In some cases, an intake air amount that is larger than the actual intake air amount (actual intake air amount) may be calculated due to aging deterioration of the airflow sensor or the intake pressure sensor, foreign matter adhering to the sensing unit, or the like. For example, in the case of a hot wire type airflow sensor, a detection error occurs due to water adhering to the hot wire.

  When the intake air amount that is larger than the actual intake air amount is calculated in this way, an excessive fuel injection amount is injected with respect to the actual intake air amount, so that the unburned component becomes excessive. Then, in the above control, the amount of unburned components is adjusted in a lean state. Therefore, the excess unburned components are oxidized with the secondary air to cause an excessive oxidation reaction. There is concern about exceeding the allowable limit temperature.

  In response to the concern that the catalyst temperature exceeds the allowable limit temperature, if the countermeasure is taken to stop the supply of secondary air when the catalyst temperature is about to exceed the allowable limit temperature, It will not be possible to promote enough.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a catalyst warm-up that prevents the catalyst from burning out while sufficiently promoting the warm-up of the catalyst in the case where the secondary air supply means is provided. It is to provide a machine control device.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

  The invention according to claim 1 includes a fuel injection valve that injects fuel into an intake pipe or a combustion chamber of an internal combustion engine, and secondary air supply means that supplies air (secondary air) to an exhaust pipe. It is assumed that the present invention is applied to a catalyst warm-up system that promotes warm-up of the catalyst attached to the exhaust pipe by oxidizing the air supplied by the next air supply means and the unburned gas. And the over-oxidation determination means for determining whether or not the oxidation reaction is in an excessive oxidation state, and when the determination is affirmative that it is in the over-oxidation state, compared to the case where a negative determination is made And an injection amount correcting means for reducing the fuel injection amount.

  According to the above invention, when the excessive oxidation state is reached, the fuel injection amount is corrected to decrease, so that the oxidation reaction can be reduced before the catalyst temperature reaches the allowable limit, thereby preventing catalyst burnout. In addition, since the oxidation reaction is reduced by reducing the fuel injection amount without stopping the supply of the secondary air, it is possible to prevent catalyst burnout while sufficiently promoting warm-up of the catalyst.

  The invention according to claim 2 includes an airflow sensor that detects an intake air amount and a correlation sensor that detects a physical quantity correlated with the intake air amount. The fuel injection amount is controlled based on the intake air amount detected by the air flow sensor, and the excessive oxidation determination means is configured to estimate the intake air amount detected by the air flow sensor based on the physical amount detected by the correlation sensor. When the amount exceeds a predetermined amount, an affirmative determination is made that the state is an excessive oxidation state. Specific examples of the physical quantity include an opening degree of a throttle valve that adjusts the intake air amount, an accelerator pedal operation amount by a driver, an intake air pressure, and the like.

  For example, even if the airflow sensor is erroneously detected, according to the above-described invention, the intake air amount is estimated using a correlation sensor different from the airflow sensor, and the detected value of the airflow sensor is equal to the estimated value. Since it is determined that there is an excessive oxidation state when it exceeds a predetermined amount, it is easy to determine the excessive oxidation state that occurs due to the airflow sensor misdetecting a predetermined amount more than the actual intake air amount. be able to.

  In particular, when the intake air amount is estimated using detected values such as the throttle valve opening and the accelerator pedal operation amount, an existing sensor can be used as a correlation sensor, so compared with the case where a dedicated correlation sensor is used. Cost can be reduced.

  In normal times when the engine is not in an over-oxidized state, the intake air amount is directly detected by the airflow sensor, and the fuel injection amount is controlled based on the detected value, so that the throttle valve opening, accelerator pedal operation amount, and intake pressure are used. The injection amount can be controlled with higher accuracy than when the fuel injection amount is controlled based on the estimated intake amount.

  According to a third aspect of the present invention, there is provided an intake pressure sensor that detects an intake pressure, and a correlation sensor that detects a physical quantity that is correlated with the intake air quantity and that is different from the intake air pressure, and is not in the over-oxidized state. When the negative determination is made, the fuel injection amount is controlled based on the intake air amount calculated from the intake air pressure detected by the intake air pressure sensor, and the excessive oxidation determination means is detected by the intake air pressure sensor. When the intake air amount calculated from the intake air pressure is greater than a predetermined amount with respect to the intake air amount estimated from the physical amount detected by the correlation sensor, an affirmative determination is made that the state is an excessive oxidation state. And Specific examples of the physical quantity include an opening degree of a throttle valve that adjusts the intake air amount, an accelerator pedal operation amount by a driver, and the like.

  For example, even if the intake pressure sensor is erroneously detected, according to the above invention, the intake air amount is estimated using a correlation sensor different from the intake pressure sensor, and the intake pressure sensor Since it is determined that the state is an excessive oxidation state when the detected value is greater than a predetermined amount, the excessive oxidation state that is caused by the erroneous detection of the intake pressure sensor greater than the actual intake pressure by a predetermined amount or more, It can be easily determined.

  In particular, when the intake air amount is estimated using detected values such as the throttle valve opening and the accelerator pedal operation amount, an existing sensor can be used as a correlation sensor, so compared with the case where a dedicated correlation sensor is used. Cost can be reduced.

  Further, during normal times when the engine is not in an excessively oxidized state, the fuel injection amount is controlled based on the detected value of the intake pressure sensor, so the fuel injection amount is determined based on the intake amount estimated using the throttle valve opening and the accelerator pedal operation amount. Compared to the case of controlling, the injection amount can be controlled with high accuracy.

  According to a fourth aspect of the present invention, the fuel injection amount correction means controls the fuel injection amount in accordance with the physical amount detected by the correlation sensor when the positive determination is made that the state is the excessive oxidation state. The weight loss correction is performed.

  Here, when the fuel injection amount is reduced in the excessive oxidation state, when the fuel injection amount is reduced by a uniform amount, the amount of unburned gas to be oxidized is too small, and the effect of promoting catalyst warm-up is reduced. On the other hand, in the above invention, although the injection amount cannot be controlled with high accuracy compared to the normal time when it is not in an excessively oxidized state, the injection amount is controlled according to the detected value of the correlation sensor, so the intake amount is erroneously detected excessively. The effect of promoting the catalyst warm-up can be improved as compared with the case where the fuel injection amount is reduced (a reduction correction) as compared with the case where the fuel injection amount is controlled based on the sensor, and the fuel injection amount is reduced by a uniform amount.

  The invention according to claim 5 includes a temperature sensor that detects the temperature of the catalyst or the temperature of the exhaust gas that has risen in temperature due to the oxidation reaction, and the over-oxidation determination means sets the temperature detected by the temperature sensor in advance. When the set upper limit temperature is reached, an affirmative determination is made that the state is the excessive oxidation state.

  According to this, since the catalyst temperature or the exhaust gas temperature is directly detected by the temperature sensor and it is determined whether or not it is in the excessive oxidation state based on the detected temperature, the determination can be performed with high accuracy.

  The invention according to claim 6 is characterized in that the injection amount correction means performs the decrease correction by limiting the fuel injection amount when the upper limit temperature is reached. According to this, the avoidance certainty that the catalyst temperature or the exhaust gas temperature exceeds the upper limit temperature and reaches the allowable limit can be improved. Therefore, the certainty of avoiding catalyst burning can be improved.

1 is a diagram illustrating an overall schematic configuration of an engine control system in a first embodiment of the present invention. The flowchart which shows the main routine of the process by 1st Embodiment. The flowchart of the process which determines the operating state of a secondary air pump in 1st Embodiment. In 1st Embodiment, the flowchart of the process which determines whether the catalyst temperature has reached the allowable limit. The flowchart of the process which implements the fuel injection amount reduction correction control in the first embodiment. The flowchart of the process which determines whether the catalyst temperature has reached the allowable limit in 2nd Embodiment of this invention. In 2nd Embodiment, the flowchart of the process which implements reduction correction control of the fuel injection amount.

  Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals in the drawings, and the description of the same reference numerals is used.

(First embodiment)
In this embodiment, a spark ignition type multi-cylinder four-cycle gasoline engine (internal combustion engine) mounted on a vehicle is controlled, and electronic control of various actuators in the engine is performed. First, the overall schematic configuration of the engine control system will be described with reference to FIG.

  In the spark ignition engine (hereinafter referred to as the engine 10) shown in FIG. 1, an air cleaner 12a for filtering outside air (intake air) sucked into the intake pipe 11 is provided upstream of the intake pipe 11. An airflow sensor 12 for detecting the intake air amount (intake air amount Ga) is provided on the downstream side of the air cleaner 12a in the intake pipe 11. A throttle valve 13 whose opening degree is adjusted by an electric motor (not shown) such as a DC motor is provided on the downstream side of the airflow sensor 12, and the opening degree (throttle opening degree) of the throttle valve 13 is the throttle opening degree. It is detected by the degree sensor 14.

  An intake pressure sensor 15 that detects the intake pressure Pm is provided on the downstream side of the throttle valve 13 in the intake pipe 11. An electromagnetically driven injector 16 (fuel injection valve) is provided on the downstream side of the intake pressure sensor 15. ) Is provided. The example shown in FIG. 1 is a port injection type in which the fuel from the injector 16 is injected into the intake pipe 11. A direct injection type in which fuel is directly injected into the combustion chamber 17 may be used. The fuel injected from the injector 16 becomes an air-fuel mixture together with the amount of intake air adjusted by the throttle valve 13, and the air-fuel mixture is sucked into the combustion chamber 17 by the lowering of the piston 22.

  Further, an intake valve 18 and an exhaust valve 19 are respectively provided at the intake port and the exhaust port of the engine 10, and intake air is introduced into the combustion chamber 17 by opening operation of the intake valve 18, and opening operation of the exhaust valve 19 is performed. Thus, the exhaust gas after combustion is discharged to the exhaust pipe 20.

  An ignition device 21 having an ignition plug and an ignition coil is attached to each cylinder of the engine 10. Then, spark discharge is generated at a desired ignition timing, and the air-fuel mixture compressed in the combustion chamber 17 is ignited and burned.

  A cooling water temperature sensor 23 that detects the temperature of engine cooling water, a crank angle sensor 25 that detects the rotation angle of the crankshaft 24 of the engine, and the like are attached to the cylinder block of the engine 10.

  The exhaust pipe 20 is provided with a catalyst 26 for purifying exhaust gas. The catalyst 26 of the present embodiment employs a three-way catalyst, and has a function of oxidizing CO and HC in the exhaust gas component and a function of reducing NOx in the exhaust gas component. An oxygen concentration sensor 27 that detects the oxygen concentration in the exhaust gas is provided upstream of the catalyst 26 in the exhaust pipe 20. Instead of the oxygen concentration sensor 27, an air-fuel ratio that detects the air-fuel ratio may be adopted.

  A secondary air supply pipe 28 that supplies outside air as secondary air is connected to the upstream side of the catalyst 26 in the exhaust pipe 20. The secondary air supply pipe 28 includes a secondary air pump 29 (secondary air supply means) for supplying outside air to the exhaust pipe 20 through the secondary air supply pipe 28, and an opening / closing valve 30 for opening and closing the secondary air supply pipe 28. Is provided.

  The secondary air pump 29 is driven by an electric motor, and is a constant capacity pump with a constant discharge capacity. By supplying the secondary air to the exhaust pipe 20, the unburned gas (HC, CO) discharged from the combustion chamber 17 and the secondary air undergo an oxidation reaction, and the temperature of the catalyst 26 is raised by the reaction heat. Can do. In order to exert the purification function of the catalyst 26, it is necessary to raise the catalyst temperature to a predetermined activation temperature, but the catalyst warm-up time immediately after the engine 10 is started by generating the reaction heat by supplying the secondary air. And the warm-up of the catalyst can be promoted.

  An electronic control unit (hereinafter referred to as ECU 40) that controls the engine includes an airflow sensor 12, a throttle opening sensor 14, an intake pressure sensor 15, a cooling water temperature sensor 23, a crank angle sensor 25, an oxygen concentration sensor 27, an accelerator, and the like. Detection signals from various sensors such as the opening sensor 31 are input. The accelerator opening sensor 31 is a sensor that detects an operation amount of an accelerator pedal operated by a vehicle driver.

  The ECU 40 is mainly composed of a microcomputer comprising a CPU, a ROM, a RAM, and the like, and executes various control programs stored in the ROM, so that the injector 16 according to the detection signals from the various sensors and the like. The fuel injection amount, fuel injection timing, ignition timing by the ignition device 21, the opening degree of the throttle valve 13, and the like are controlled.

  For example, the microcomputer calculates the rotation speed (engine rotation speed Ne) of the crankshaft 24 based on the detection value of the crank angle sensor 25, and calculates the intake air amount Ga (corresponding to the engine load) based on the detection value of the airflow sensor 12. To do. Based on the engine speed Ne and the intake air amount Ga, the fuel injection amount, fuel injection timing, ignition timing, and throttle opening are controlled. Further, the fuel injection amount is feedback-controlled based on the detection value of the oxygen concentration sensor 27 so that the actual air-fuel ratio approaches the target air-fuel ratio.

  Further, the microcomputer controls the opening / closing operation of the on-off valve 30 and the driving of the secondary air pump 29 based on the cooling water temperature (starting water temperature) at the time of starting the engine. Specifically, if the starting water temperature is equal to or lower than the predetermined temperature, it is determined to supply the secondary air, and further, the secondary air supply time from the engine starting is set according to the starting water temperature. During the period of the set secondary air supply time, the on-off valve 30 is opened and the secondary air pump 29 is driven. When the secondary air supply time is reached, the on-off valve 30 is closed and 2 The drive of the next air pump 29 is stopped.

  When the secondary air supply is determined as described above, it is necessary to control the amount of unburned gas that undergoes an oxidation reaction with the secondary air. Therefore, in calculating the fuel required injection amount Qreq, the injection amount (secondary air increase amount Qair) corresponding to the unburned gas amount is increased. Specifically, in calculating the fuel required injection amount Qreq, the basic injection amount Qbse is calculated based on the engine speed Ne and the intake air amount Ga, and the starting increase Qwet and the secondary air increase Qair are calculated based on the starting water temperature. Is calculated. Then, the required injection amount Qreq is calculated by adding the starting increase amount Qwet and the secondary air increase amount Qair to the basic injection amount Qbse (Qreq = Qbse + Qwet + Qair).

  Here, during the secondary air supply time period, the constant capacity type secondary air pump 29 is only driven, and the secondary air supply amount is not variably controlled. Therefore, a large amount of secondary air is supplied so that the air-fuel mixture (exhaust gas mixture) in the exhaust pipe 20 is in a lean state, and the secondary air increase amount Qair is adjusted so that unburned components (HC, CO). The amount of reaction is adjusted to control the heat of reaction.

  Therefore, when an intake air amount greater than the actual intake air amount is calculated due to the detection error of the airflow sensor 12, the basic injection amount Qbse becomes excessive with respect to the actual intake air amount. Excess combustion gas. As a result, excess unburned gas is supplied to the lean exhaust gas mixture, so that the excess unburned components oxidize with the secondary air to cause an excessive oxidation reaction. As a result, there is a concern that the catalyst temperature exceeds the allowable limit temperature.

  Therefore, in this embodiment, the fuel injection amount is calculated as shown in FIGS. 3 to 5 show the subroutine processing of FIG. 2, which is repeatedly executed by the microcomputer at a predetermined cycle. The routine period (for example, 4 msec) in FIG. 2 is set shorter than the routine period (for example, 200 msec) in FIGS.

  First, the operation state of the secondary air pump 29 is determined in step S10 of FIG. If it is determined that the secondary air pump 29 is operating, whether or not the catalyst temperature has reached the allowable limit temperature in the subsequent step S20, or the upper limit temperature set lower than the allowable limit temperature by a predetermined value. It is determined whether it has been reached. If it is determined that the catalyst temperature has reached the allowable limit temperature (or the upper limit temperature), in the subsequent step S30, correction (decrease correction) is performed so as to decrease the required injection amount Qreq.

  Next, details of the operation determination process of the secondary air pump 29 in step S10 will be described. First, in step S11 of FIG. 3, it is determined whether or not the operating condition of the secondary air pump 29 is satisfied. In the present embodiment, the operation start condition of the secondary air pump 29 is that the water temperature at startup is lower than a preset threshold temperature. Instead of the starting water temperature, the start of operation may be determined based on a temperature correlated with the catalyst temperature (for example, exhaust gas temperature, in-cylinder temperature, outside air temperature, etc.). Then, the secondary air supply time from the start of the engine is set longer as the water temperature at the start is lower, and the secondary air pump 29 operation end condition is that the secondary air supply time has elapsed.

  Therefore, the operation condition of the secondary air pump 29 is that the water temperature at the time of start is lower than the threshold temperature and satisfies the operation start condition, and that the secondary air supply time has not elapsed and the operation end condition is not satisfied. . If it is determined in step S11 that the operating condition is satisfied (S11: YES), the secondary air pump operating flag is set (pumpon = 1) in the subsequent step S12, and the operating condition is not satisfied. If it is determined (S11: NO), in the subsequent step S13, the secondary air pump operating flag is reset (pumpon = 0).

  Next, details of the allowable limit determination process for the catalyst temperature in step S20 will be described. First, in step S21 in FIG. 4, the engine speed Ne, the intake air amount Ga, and the intake pressure Pm are read. In the subsequent step S22, whether or not the engine rotational speed Ne (actual Ne) read in step S21 matches the target rotational speed (target Ne), or a deviation between the actual Ne and the target Ne is set in advance. It is determined whether it is within the range. In short, it is determined whether the real Ne is in a stable state approaching the target Ne.

  If it is determined that the state is not stable (S22: NO), the processing of FIG. 4 is once ended. If it is determined that the state is stable (actual Ne≈target Ne) (S22: YES), the following steps are performed. In S23, an estimated intake amount Gaa is calculated based on the engine speed Ne (actual Ne) and the intake pressure Pm read in step S21. For example, the optimum value of the intake air amount estimated value Gaa with respect to the intake pressure Pm and the actual Ne is obtained by testing in advance, and is stored in the microcomputer as a map exemplified by the symbol M1 in FIG. Referring to the intake pressure Pm and the actual Ne, the intake amount estimated value Gaa may be calculated.

  In the subsequent step S24 (excess oxidation determination means), the intake air amount Ga read in step S21 and the value detected by the airflow sensor 12 (intake air amount detection value Ga) is greater than the intake air amount estimated value Gaa by a predetermined value or more. It is determined whether or not. In short, if Ga−Gaa ≧ predetermined value, there is a possibility that the detection value by the airflow sensor 12 is erroneously detected to the side larger than the actual intake air amount, and as a result, it is in an excessive oxidation state. judge.

  If it is determined that Ga−Gaa ≧ predetermined value (S24: YES), it is regarded as being in an excessive oxidation state, and a catalyst temperature allowable limit determination flag is set (catot = 1) in the subsequent step S25. If it is determined that Ga−Gaa ≧ predetermined value is not satisfied (S24: NO), it is considered that the state is not in an excessive oxidation state, and the catalyst temperature allowable limit determination flag is reset in subsequent step S26 (catot = 0).

  In the determination of FIG. 4, it may be determined whether the catalyst temperature has reached the allowable limit temperature, or it is determined whether the upper limit temperature set lower than the allowable limit temperature by a predetermined value has been reached. You may do it. Therefore, the predetermined value may be set as a threshold at the time when the excessive oxidation (allowable limit excessive oxidation state) reaches the allowable limit temperature, or the excessive oxidation (upper limit excessive oxidation) reaches the upper limit temperature. It may be set as a threshold value at the time of entering the state.

  Next, details of the control procedure for correcting the fuel injection amount in step S30 will be described. First, in step S31 in FIG. 5, the basic injection amount Qbse described above is calculated based on the intake air amount detection value Ga and the actual Ne. For example, the optimum value of the basic injection amount Qbse with respect to the intake air amount and the actual Ne is obtained by testing in advance, stored in the microcomputer as a map exemplified by the symbol M2 in FIG. 5, and the map M2 is referred to Thus, the basic injection amount Qbse may be calculated based on the intake air amount detection value Ga and the actual Ne. The map M2 is set so that the basic injection amount Qbse increases as the intake air amount increases, and the basic injection amount Qbse increases as the actual Ne increases.

  In subsequent steps S32 and S33, the state of the secondary air pump operating flag pumpon set in the process of FIG. 2 and the catalyst temperature allowable limit determination flag catot set in the process of FIG. 3 are determined, and pumpon = 1 and catot = 1. As a condition (decrease correction condition) (S32: YES, S33: YES), reduction correction is performed in steps S34 and S35 (injection amount correction means) described later. On the other hand, if at least one of both the flags pumpon and catot is reset, the process proceeds to step S36 without performing the reduction correction in steps S34 and S35.

  In step S34, the injection amount limit value Qcp is calculated based on the intake amount estimated value Gaa and the actual Ne. For example, the injection amount limit value Qcp may be calculated based on the intake amount estimated value Gaa and the actual Ne with reference to the same map as the map M2 used in step S31. In the subsequent step S35, the basic injection amount Qbse is replaced with the injection amount limit value Qcp.

  Here, since catot = 1 and determined to be in the excessive oxidation state is Ga−Gaa ≧ predetermined value, the injection amount limit value Qcp calculated in step S34 is the basic injection amount calculated in step S31. It should be less than Qbse. Therefore, replacing the basic injection amount Qbse with the injection amount limit value Qcp corresponds to correcting the decrease in the basic injection amount Qbse, and consequently reducing the required injection amount Qreq.

  Next, in step S36, the aforementioned start time increase Qwet is calculated based on the start time water temperature. For example, the optimum value of the starting increase Qwe with respect to the starting water temperature may be tested and acquired in advance and stored as a map, and the starting increase Qwet may be calculated based on the starting water temperature with reference to the map. The map is set so that the starting amount Qwet increases as the starting water temperature decreases.

  Next, in step S37, the secondary air increase amount Qair described above is calculated based on the water temperature at start-up. For example, the optimum value of the secondary air increment Qair relative to the starting water temperature is tested and acquired in advance and stored as a map, and the secondary air increment Qair is calculated based on the starting water temperature with reference to the map. do it. The map is set so that the secondary air increment Qair increases as the starting water temperature decreases. Incidentally, the secondary air increment Qair may be calculated based on at least one of the starting water temperature and the secondary air supply time.

  Further, when the secondary air pump 29 is not operating (pumpon = 0), the secondary air increment Qair is set to zero.

  In the subsequent step S38, the required injection amount Qreq described above is calculated by adding the starting increase Qwe calculated in step S36 and the secondary air increase Qair calculated in step S37 to the basic injection amount Qbse ( Qreq = Qbse + Qwet + Qair). As described above, when the reduction correction condition is not satisfied, the required injection amount Qreq is calculated using the basic injection amount Qbse calculated based on the intake amount detection value Ga. On the other hand, when the reduction correction condition is satisfied, the required injection amount Qreq is calculated using the injection amount limit value Qcp calculated based on the estimated intake air amount Gaa, thereby reducing the required injection amount Qreq.

  As described above, according to the present embodiment, if Ga−Gaa ≧ predetermined value is determined in step S24, it is considered that the state is in an excessive oxidation state, and the required injection amount Qreq is corrected to decrease by steps S34 and S35. The actual fuel injection amount is also corrected for reduction. Therefore, before the catalyst temperature reaches the allowable limit, the oxidation reaction between the secondary air and the unburned gas can be reduced, and burning of the catalyst 26 can be prevented.

  In addition, since the oxidation reaction is reduced by correcting the decrease in the fuel injection amount without stopping the supply of the secondary air, the effect of promoting the warm-up of the catalyst 26 can be achieved compared with the case where the supply of the secondary air is completely stopped. While improving, it is possible to prevent catalyst burnout by controlling the injection amount so that the catalyst temperature does not exceed the allowable limit.

  Further, since the estimated intake air amount Gaa used for determination of the excessive oxidation state is calculated using the existing intake pressure sensor 15, the cost can be reduced as compared with the case where a dedicated sensor used for determination is used.

  In normal times when the engine is not in an excessively oxidized state, the intake air amount is directly detected by the airflow sensor 12, and the required injection amount Qreq is calculated based on the detected value to perform injection control. Therefore, the intake pressure Pm, throttle opening degree, accelerator Compared with the case where the injection control is performed by calculating the required injection amount Qreq based on the intake air amount Gaa estimated using the operation amount or the like, the injection control can be performed with high accuracy so as to achieve a desired combustion state.

(Second Embodiment)
In the first embodiment, the excessive oxidation state is determined based on the comparison between the intake air amount detection value Ga and the intake air amount estimated value Gaa as shown in FIG. 4, whereas in this embodiment, the temperature at which the catalyst temperature is directly detected. A sensor 32 (see FIG. 1) is provided, and the excessive oxidation state is determined based on the temperature Tcat detected by the temperature sensor 32.

  This determination method will be described in detail below. First, in step S210 in FIG. 6, the temperature Tcat detected by the temperature sensor 32 is read. In subsequent step S220 (excess oxidation determination means), it is determined whether or not the detected temperature Tcat read in step S210 is equal to or higher than a preset upper limit temperature Tlim.

  If it is determined that Tcat ≧ Tlim (S220: YES), it is considered that the catalyst is in an excessive oxidation state, and a catalyst temperature allowable limit determination flag is set in the subsequent step S25 (catot = 1). If it is determined that Tcat ≧ Tlim is not satisfied (S220: NO), it is considered that the catalyst is not in an excessive oxidation state, and the catalyst temperature allowable limit determination flag is reset in the subsequent step S26 (catot = 0).

  FIG. 7 is a flowchart showing the control procedure of the weight loss correction according to this embodiment. In steps S31 to S33, the same processing as that of the first embodiment shown in FIG. 5 is performed. When the reduction correction condition that pumpon = 1 and catot = 1 is satisfied (S32: YES, S33: YES), the reduction correction is performed in step S350 (injection amount correction means) described later. On the other hand, if at least one of both the flags pumpon and catot has been reset, the process proceeds to step S36 without performing the reduction correction in step S350. In subsequent steps S36 to S38, processing similar to that of the first embodiment shown in FIG. 5 is performed.

  Here, when the catalyst temperature allowable limit determination flag is switched from the reset state to the set state by a routine process different from FIG. 7, that is, the catalyst detection temperature Tcat increases from the time of engine start, and the upper limit temperature Tlim The basic injection amount Qbse at the time of reaching is stored as the injection amount limit value Qlim.

  In step S350 in FIG. 7, the injection amount limit value Qlim stored as described above is replaced with the basic injection amount Qbse. As a result, even if the catalyst detection temperature Tcat rises to the upper limit temperature Tlim and then increases further, the basic injection amount Qbse is limited to the injection amount limit value Qlim, so that the increase in the catalyst detection temperature Tcat is suppressed. If such a restriction is not implemented, if the actual Ne or the engine load increases after the catalyst detection temperature Tcat rises to the upper limit temperature Tlim, the basic injection amount Qbse further increases and the catalyst detection temperature Tcat is allowed. There is concern about exceeding the limit.

  Therefore, according to this embodiment in which the basic injection amount Qbse is limited to the injection amount limit value Qlim when the reduction correction condition is satisfied, this corresponds to a reduction correction of the basic injection amount Qbse, and thus the required injection amount Qreq is reduced. It will be corrected.

  As described above, according to the present embodiment, the temperature sensor 32 that directly detects the catalyst temperature is provided, and if it is determined that the detected temperature Tcat is equal to or higher than the preset upper limit temperature Tlim, an over-oxidized state is established. Since the required injection amount Qreq is corrected to decrease in step S350, the actual fuel injection amount is also corrected to decrease. Therefore, before the catalyst temperature reaches the allowable limit, the oxidation reaction between the secondary air and the unburned gas can be reduced, and burning of the catalyst 26 can be prevented.

  In addition, since the oxidation reaction is reduced by correcting the decrease in the fuel injection amount without stopping the supply of the secondary air, the warming-up promotion effect of the catalyst 26 can be improved compared with the case where the supply of the secondary air is completely stopped. While improving, it is possible to prevent catalyst burnout by controlling the injection amount so that the catalyst temperature does not exceed the allowable limit.

  Further, since the catalyst temperature is directly detected and it is determined whether or not it is in an excessive oxidation state based on the detected temperature Tcat, the first embodiment is determined based on a comparison between the intake air amount estimated value Gaa and the intake air amount detected value Ga. The determination can be performed with higher accuracy than the form. Further, since the required injection amount Qreq is limited to the injection amount when the detected temperature Tcat reaches the upper limit temperature Tlim, the certainty of avoiding catalyst burning can be improved.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be modified as follows. Moreover, you may make it combine the characteristic structure of each embodiment arbitrarily, respectively.

  In the first embodiment, the required injection amount Qreq is calculated based on the intake amount detection value Ga during normal times when the reduction correction condition is not satisfied, and is estimated based on the intake pressure Pm when there is an abnormality when the decrease correction condition is satisfied. The required injection amount Qreq is calculated based on the intake air amount estimated value Gaa. In this case, the intake pressure sensor 15 corresponds to a correlation sensor. Instead, the required injection amount Qreq is calculated based on the intake amount estimated value Gaa estimated based on the intake pressure Pm at normal times, and other physical amounts (for example, throttle opening degree or accelerator pedal) correlated with the intake amount when abnormal. The required injection amount Qreq may be calculated based on the second intake amount estimated value Gab estimated based on the operation amount or the like. In this case, the throttle opening sensor 14 and the accelerator opening sensor 31 correspond to a correlation sensor.

  In this case, in step S24 of FIG. 4, it may be determined whether or not the intake air amount estimated value Gaa is larger than the second intake air amount estimated value Gab by a predetermined value or more. In short, if Gaa−Gab ≧ predetermined value, there is a possibility that the intake air amount estimated value Gaa by the intake pressure sensor 15 is erroneously detected to the side larger than the actual intake air amount. What is necessary is just to determine with becoming.

  In the first embodiment, the intake amount estimated value Gaa is calculated based on the actual Ne and the intake pressure Pm in step S23 of FIG. 4, but the present invention is not limited to this, and is a physical quantity related to the engine load. If it exists, it may not be the intake pressure Pm. For example, the estimated intake amount Gaa may be calculated based on the throttle opening and the actual Ne detected by the throttle opening sensor 14, or the intake air may be calculated based on the accelerator pedal operation amount and the actual Ne detected by the accelerator opening sensor 31. The quantity estimated value Gaa may be calculated.

  In the first embodiment, the required injection amount Qreq is calculated by the calculation formula of Qreq = Qbse + Qwet + Qair, and the basic injection amount Qbse is corrected to reduce the required injection amount Qreq. The injection amount Qreq may be directly corrected for reduction.

  When calculating the secondary air increase amount Qair in step S37 of FIG. 5, the secondary air increase amount Qair is calculated to be a constant amount during the period from when the engine is started until the secondary air supply time elapses. Alternatively, the secondary air increase amount Qair may be calculated to be gradually decreased.

  In the second embodiment, the temperature sensor 32 is disposed on the catalyst 26 to detect the catalyst temperature, but the temperature sensor is disposed on the downstream side of the secondary air supply pipe 28 in the exhaust pipe 20 to oxidize. You may make it detect the temperature of the waste gas which temperature rose by reaction. The temperature sensor in this case may be arranged on the upstream side of the catalyst 26 or may be arranged on the downstream side.

DESCRIPTION OF SYMBOLS 12 ... Air flow sensor, 14 ... Throttle opening sensor (correlation sensor), 15 ... Intake pressure sensor (correlation sensor), 16 ... Injector (fuel injection valve), 26 ... Catalyst, 29 ... Secondary air pump (secondary air supply means) ), 31 ... Accelerator opening sensor (correlation sensor), 32 ... Temperature sensor, S24, S220 ... Excess oxidation determination means, S34, S35, S350 ... Injection amount correction means.

Claims (6)

A fuel injection valve for injecting fuel into the intake pipe or combustion chamber of the internal combustion engine;
Secondary air supply means for supplying air to the exhaust pipe;
With
Applied to a catalyst warm-up system that promotes warm-up of the catalyst attached to the exhaust pipe by oxidizing the air supplied by the secondary air supply means and unburned gas;
Overoxidation determining means for determining whether or not the oxidation reaction is in an excessive oxidation state;
An injection amount correction means for correcting the fuel injection amount to be reduced when compared to a negative determination when an affirmative determination is made in the excessive oxidation state;
A catalyst warm-up control device comprising: An airflow sensor for detecting the intake air amount;
A correlation sensor that detects a physical quantity correlated with the intake air amount;
With
When a negative determination is made that the state is not the excessive oxidation state, the fuel injection amount is controlled based on the intake amount detected by the airflow sensor,
The over-oxidation determination unit is configured to detect the over-oxidation state when the intake air amount detected by the airflow sensor is greater than a predetermined amount with respect to the intake air amount estimated based on the physical amount detected by the correlation sensor. The catalyst warm-up control device according to claim 1, wherein an affirmative determination is made. An intake pressure sensor for detecting intake pressure;
A correlation sensor that detects a physical quantity that correlates with the intake air amount and is different from the intake air pressure;
With
When a negative determination is made that the state is not the excessive oxidation state, the fuel injection amount is controlled based on the intake amount calculated from the intake pressure detected by the intake pressure sensor,
The over-oxidation determination means is configured such that the intake air amount calculated from the intake air pressure detected by the intake air pressure sensor is greater than a predetermined amount with respect to the intake air amount estimated from the physical amount detected by the correlation sensor. The catalyst warm-up control device according to claim 1, wherein an affirmative determination is made that the state is an excessive oxidation state.   The injection amount correction means performs the decrease correction by controlling the fuel injection amount in accordance with the physical amount detected by the correlation sensor when an affirmative determination is made that the state is the excessive oxidation state. The catalyst warm-up control device according to claim 2 or 3. A temperature sensor that detects the temperature of the catalyst or the temperature of exhaust gas that has risen in temperature due to the oxidation reaction;
2. The catalyst according to claim 1, wherein the over-oxidation determination unit makes an affirmative determination that the over-oxidation state is present when the temperature detected by the temperature sensor reaches a preset upper limit temperature. Warm-up control device.   6. The catalyst warm-up control apparatus according to claim 5, wherein the injection amount correction means performs the decrease correction by limiting the fuel injection amount when the upper limit temperature is reached.

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