JP4049072B2 - Catalyst degradation degree judgment device - Google Patents

Description

  The present invention relates to a catalyst deterioration degree determining device (catalyst deterioration degree detecting device, catalyst deterioration determining device) for determining the deterioration degree of a catalyst disposed in an exhaust passage of an internal combustion engine.

  As this type of technology, a method is known in which the reaction rate distribution of the catalyst is predicted by desktop calculation, and the degree of deterioration (deterioration state) of the catalyst is predicted based on the predicted reaction rate distribution (or frequency factor distribution). (For example, see Patent Document 1).

  In this method, based on the catalyst noble metal particle size distribution (n) and the reaction rate distribution (n) at a certain time (deterioration stage n), the catalyst temperature distribution (n + 1) after a predetermined time tn (deterioration stage n + 1) and An oxygen concentration distribution (n + 1) is calculated, and a catalyst noble metal particle size distribution (n + 1) is calculated based on the calculated catalyst temperature distribution (n + 1) and the calculated oxygen concentration distribution (n + 1) and poisoning amount distribution (n + 1). The frequency factor distribution (n + 1) is calculated based on the calculated catalyst noble metal particle size distribution (n + 1) and poisoning amount distribution (n + 1), and the reaction rate distribution (n + 1) based on the calculated frequency factor distribution (n + 1). Is calculated.

  Therefore, if the catalyst noble metal particle size distribution (0), the reaction rate distribution (0), and the poisoning amount distribution (k) in each deterioration stage can be obtained in the deterioration stage (0), the deterioration in any deterioration stage (n) can be obtained. Since the frequency factor distribution (n) and the reaction rate distribution (n) of the catalyst can be obtained, the deterioration state of the catalyst can be estimated based on this.

The catalyst noble metal particle size distribution (0) in the deterioration stage (0) is a value determined according to the type of the catalyst noble metal and the supporting state on the carrier, and can be known in advance. Further, the reaction rate distribution (0) in the deterioration stage (0) can be obtained from actual measurements on a new catalyst. The poisoning amount distribution (k) is a distribution of the amount of poisoning substances adhering to the catalyst in the deterioration stage (k), and can be estimated from actual measurement in advance according to the deterioration stage (k). As a result, according to the above method, the deterioration state of the catalyst at an arbitrary deterioration stage can be estimated by desktop calculation without actually conducting a long-term deterioration durability test.
Japanese Patent Laid-Open No. 2001-12233 (FIG. 1)

  However, the above-mentioned conventional method gives the catalyst noble metal distribution (0) and reaction rate distribution (0) in the deterioration stage (0), that is, when the catalyst is new, so that the catalyst in any deterioration stage (n) can be obtained. Since the deterioration state is estimated, there is a problem that it is impossible to accurately determine the actual deterioration state of the catalyst that has complicatedly changed and has undergone a driving state that differs greatly from vehicle to vehicle.

  One of the objects of the present invention is to provide a catalyst deterioration degree determination device that can accurately determine the deterioration degree (deterioration state) of a catalyst mounted on a vehicle in real time.

The catalyst deterioration degree judging device according to the present invention is:
A catalyst deterioration degree determination device that is applied to a vehicle equipped with an internal combustion engine and determines a deterioration degree of a catalyst disposed in an exhaust passage of the internal combustion engine,
Inflow specific gas concentration acquisition means for acquiring the concentration of the specific gas contained in the gas flowing into the catalyst;
Outflow specific gas concentration acquisition means for acquiring the concentration of the specific gas flowing out from the catalyst;
Inflow reaction gas concentration acquisition means for acquiring the concentration of an inflow reaction gas that is a gas that reacts with the specific gas contained in the gas flowing into the catalyst;
Catalyst temperature acquisition means for acquiring the temperature of the catalyst;
A catalytic reaction model representing a purification reaction of the specific gas in the catalyst, a concentration of the specific gas flowing into the acquired catalyst, a concentration of the specific gas flowing out from the acquired catalyst, a concentration of the acquired inflowing reaction gas, and the A frequency factor calculating means for calculating a frequency factor of the purification reaction in the catalyst based on the obtained temperature of the catalyst;
Means for determining the degree of deterioration of the catalyst based on the calculated frequency factor;
Is provided.

  This catalyst deterioration degree determination device obtains a frequency factor in the reaction at the catalyst, and determines the catalyst deterioration degree based on the frequency factor. The frequency factor is a value used in a catalytic reaction model representing a purification reaction of a specific gas in the catalyst, and is a value indicating the ease of the reaction for purification. In this catalyst deterioration degree determination apparatus, the frequency factor includes the catalyst reaction model, the concentration of the specific gas flowing into the actually acquired catalyst, the concentration of the specific gas flowing out of the actually acquired catalyst, and the actually acquired inflowing reaction gas. And the temperature of the catalyst actually obtained (catalyst bed temperature). Therefore, the deterioration degree of the catalyst can be accurately determined in real time.

  In one aspect of the present invention, the catalyst deterioration degree determination device may be configured so that an air-fuel ratio of a gas flowing into the catalyst becomes an air-fuel ratio suitable for purifying the specific gas in the catalyst. It is preferable to provide air-fuel ratio control means for controlling the air-fuel ratio of the inflowing gas.

  According to this, the air-fuel ratio of the gas flowing into the catalyst is suitable for purifying the specific gas (for example, if the specific gas is NOx, the air-fuel ratio is richer than the theoretical air-fuel ratio, the specific gas is HC, If it is CO, the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, and the specific gas is controlled to an air-fuel ratio other than the stoichiometric air-fuel ratio that is purified with high efficiency by the catalyst. As a result, the catalytic reaction model and the reaction in the actual catalyst can be made to coincide with each other with high accuracy, so that the degree of deterioration of the catalyst can be determined with higher accuracy.

  In this case, the air-fuel ratio control means is configured to control the air-fuel ratio of the gas flowing into the catalyst to a constant air-fuel ratio that is richer or leaner than the stoichiometric air-fuel ratio, and the inflowing reaction gas concentration acquisition means includes It is preferable that the inflow reaction gas concentration is acquired based on an operating state of the internal combustion engine when the air-fuel ratio of the gas flowing into the catalyst is controlled by the air-fuel ratio control means. .

  According to this, since the concentration of the inflowing reaction gas flowing into the catalyst becomes substantially constant, the state of the purification reaction in the catalyst is stabilized. Therefore, the catalytic reaction model and the reaction in the actual catalyst are more accurately matched. In addition, since the inflowing reaction gas concentration is also stabilized, the inflowing reaction gas concentration can be accurately acquired based on the operating state of the internal combustion engine without providing an inflowing reaction gas concentration sensor to acquire the inflowing reaction gas concentration. can do.

  Further, the vehicle includes an auxiliary power source different from the internal combustion engine, and when the frequency factor is calculated by the frequency factor calculation means, the internal combustion engine is maintained in a steady operation state and is necessary for acceleration of the vehicle. It is also preferable that a simple power is generated by the auxiliary power source.

  According to this, since the amount of exhaust gas flowing into the catalyst becomes constant and the inflowing reaction gas concentration is stabilized, the inflowing reaction gas concentration can be obtained with higher accuracy. As a result, the frequency factor can be obtained with higher accuracy, and the degree of catalyst deterioration can be determined with higher accuracy.

  Hereinafter, embodiments of a catalyst deterioration degree determination apparatus according to the present invention will be described with reference to the drawings. The catalyst deterioration degree determination device is employed as part of a fuel injection amount control device for an internal combustion engine.

(First embodiment)
FIG. 1 shows a schematic configuration of a system in which a fuel injection amount control device including a catalyst deterioration degree determination device according to a first embodiment is applied to a four-cycle spark ignition type multi-cylinder internal combustion engine 10. FIG. 1 shows only a cross section of a specific cylinder, but the other cylinders have the same configuration.

  The internal combustion engine 10 includes a cylinder block portion 20 including a cylinder block, a cylinder block lower case, an oil pan, and the like, a cylinder head portion 30 fixed on the cylinder block portion 20, and a gasoline mixture to the cylinder block portion 20. An intake system 40 for supplying and an exhaust system 50 for releasing exhaust gas from the cylinder block 20 to the outside are included.

  The cylinder block unit 20 includes a cylinder 21, a piston 22, a connecting rod 23, and a crankshaft 24. The piston 22 reciprocates in the cylinder 21, and the reciprocating motion of the piston 22 is transmitted to the crankshaft 24 through the connecting rod 23, whereby the crankshaft 24 rotates. The heads of the cylinder 21 and the piston 22 form a combustion chamber 25 together with the cylinder head portion 30.

  The cylinder head portion 30 includes an intake port 31 communicating with the combustion chamber 25, an intake valve 32 that opens and closes the intake port 31, an intake camshaft that drives the intake valve 32, and a phase angle and lift amount of the intake camshaft are continuously provided. Variable intake timing device 33 to be changed, actuator 33a of variable intake timing device 33, exhaust port 34 communicating with combustion chamber 25, exhaust valve 35 for opening and closing exhaust port 34, exhaust camshaft 36 for driving exhaust valve 35, An ignition plug 37, an igniter 38 including an ignition coil that generates a high voltage to be applied to the ignition plug 37, and an injector (fuel injection means) 39 for injecting fuel into the intake port 31 are provided.

  The intake system 40 includes an intake pipe 41 including an intake manifold that communicates with the intake port 31 and forms an intake passage together with the intake port 31, an air filter 42 provided at an end of the intake pipe 41, a throttle valve 43, and a swirl control valve. (Hereinafter referred to as “SCV”) 44. The throttle valve 43 is rotationally driven in the intake pipe 41 by a throttle valve actuator 43a made of a DC motor so that the opening cross-sectional area of the intake passage is variable. The SCV 44 is a valve for generating a swirl in the combustion chamber 25, and is driven to rotate by an SCV actuator 44a composed of a DC motor.

  The exhaust system 50 includes an exhaust manifold 51 communicating with the exhaust port 34, an exhaust pipe 52 connected to the exhaust manifold 51, and an upstream catalyst (upstream three-way catalytic converter or start catalyst) interposed in the exhaust pipe 52. 53) and downstream catalyst (downstream three-way catalytic converter or disposed below the floor of the vehicle) disposed in (exposed to) the exhaust pipe 52 downstream of the upstream catalyst 53 and the upstream catalyst 53. Therefore, it is also called an under-floor catalytic converter.) 54. The exhaust port 34, the exhaust manifold 51, and the exhaust pipe 52 constitute an exhaust passage. In addition, this catalyst deterioration degree determination apparatus determines whether the upstream catalyst 53 has deteriorated.

  On the other hand, this system is disposed in an exhaust passage upstream of the hot-wire air flow meter 61, the intake air temperature sensor 62, the throttle position sensor 63, the cam position sensor 64, the crank position sensor 65, the water temperature sensor 66, and the upstream catalyst 53. Specific gas concentration sensor 67 (hereinafter referred to as “upstream specific gas concentration sensor 67”), a specific gas concentration sensor disposed in the exhaust passage downstream of the upstream catalyst 53 and upstream of the downstream catalyst 54 68 (hereinafter, referred to as “downstream specific gas concentration sensor 68”), a catalyst temperature sensor 69 and an accelerator opening sensor 70 disposed for the upstream catalyst 53 are provided.

  The air flow meter 61 outputs a signal corresponding to the mass flow rate Ga of the intake air flowing through the intake pipe 41. The intake air temperature sensor 62 detects the temperature of the intake air and outputs a signal representing the intake air temperature THA. The throttle position sensor 63 detects the opening (throttle valve opening) of the throttle valve 43 and outputs a signal representing the throttle valve opening TA.

  The cam position sensor 64 generates a signal (G2 signal) having one pulse every time the intake camshaft rotates 90 ° (that is, every time the crankshaft 24 rotates 180 °). The crank position sensor 65 outputs a signal having a narrow pulse every time the crankshaft 24 rotates 10 ° and a wide pulse every time the crankshaft 24 rotates 360 °. This signal represents the engine speed NE. The water temperature sensor 66 detects the temperature of the cooling water of the internal combustion engine 10 and outputs a signal representing the cooling water temperature THW.

  The upstream specific gas concentration sensor 67 constitutes inflow specific gas concentration acquisition means for detecting and acquiring the concentration of the specific gas contained in the gas flowing into the upstream catalyst 53. In this example, the specific gas is NO of NOx (nitrogen oxide). Accordingly, the upstream specific gas concentration sensor 67 outputs a signal representing the concentration [NO] in of NO flowing into the upstream catalyst 53.

  The downstream specific gas concentration sensor 68 constitutes outflow specific gas concentration acquisition means for detecting and acquiring the concentration of specific gas (NO) contained in the gas flowing out from the upstream catalyst 53, and flows out from the upstream catalyst 53. A signal representing the concentration [NO] out of NO to be output is output.

  The catalyst temperature sensor 69 constitutes catalyst temperature acquisition means for detecting and acquiring the catalyst temperature (catalyst bed temperature) of the upstream catalyst 53, and outputs a signal representing the catalyst temperature Tempccro. The accelerator opening sensor 70 outputs a signal representing the operation amount Accp of the accelerator pedal 71 operated by the driver.

  The electric control device 80 includes a CPU 81 connected to each other by a bus, a ROM 82 in which programs executed by the CPU 81, tables (maps, functions), constants, and the like are stored in advance, a RAM 83 in which the CPU 81 temporarily stores data as necessary, The microcomputer includes a backup RAM 84 that stores data while the power is turned on and holds the stored data even while the power is shut off, and an interface 85 including an AD converter.

  The interface 85 is connected to the sensors 61 to 70, supplies signals from the sensors 61 to 70 to the CPU 81, and in response to instructions from the CPU 81, the actuator 33a, the igniter 38, the injector 39, and the throttle of the variable intake timing device 33. Drive signals are sent to the valve actuator 43a and the SCV actuator 44a.

(Principle of catalyst deterioration degree judgment)
Next, the principle of the catalyst deterioration degree determination by this catalyst deterioration degree determination device will be described. Now, focus on NO (nitrogen monoxide), which is a kind of NOx, as a specific gas to be purified by the catalyst. Also, focus on CO (carbon monoxide) as a reactive gas that reacts with NO, which is a specific gas, to purify NO. At this time, NO and CO react as shown in the following formula (1). Such a reaction mainly occurs when the air-fuel ratio of the gas flowing into the catalyst is made richer than the stoichiometric air-fuel ratio.

From the equation (1), the following equation (2) is obtained. In the equation (2), k is a value indicating the reaction rate in the catalyst, and is called “reaction rate constant”.

On the other hand, the temporal change in the NO concentration in the catalyst, which is the term on the left side of the above equation (2), can be obtained based on the following equation (3).

この(4)式における頻度因子k0は、触媒における反応の起こり易さを示す指標である。従って、頻度因子k0は触媒の劣化度を表す。 On the other hand, the Arrhenius equation shown in the following (4) is widely known as an equation representing the purification reaction in the catalyst. Equation (4) represents a catalytic reaction model representing a purification reaction with a catalyst, and is an equation for obtaining a reaction rate constant.

The frequency factor k0 in the equation (4) is an index indicating the ease of reaction in the catalyst. Therefore, the frequency factor k0 represents the degree of deterioration of the catalyst.

Therefore, the catalyst deterioration degree determination apparatus obtains the frequency factor k0 and determines the catalyst deterioration degree based on the frequency factor k0. Specifically, first, the following equation (5) is obtained from the equations (2) and (3), and the reaction rate constant k is obtained based on the equation (5).

  In the equation (5), the concentration [NO] in of NO flowing into the catalyst is directly obtained from the upstream specific gas concentration sensor 67 (upstream NO concentration sensor) disposed upstream of the catalyst. The concentration [NO] out of NO flowing out from the catalyst is directly acquired from the downstream specific gas concentration sensor 68 (downstream NO concentration sensor) disposed downstream of the catalyst. The concentration of CO flowing into the catalyst [CO] in is a constant air-fuel ratio in which the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine (hereinafter referred to as “engine air-fuel ratio”) is richer than the stoichiometric air-fuel ratio. The air-fuel ratio of the air-fuel mixture is controlled so that the engine operating condition (Q, NE, THW) and the map MapCOin (Q, NE, THW) determined in advance are acquired. Note that a CO concentration sensor may be arranged upstream of the catalyst as an inflowing reaction gas concentration sensor, and the CO concentration [CO] in may be directly acquired from the CO concentration sensor. The exhaust gas flow rate Vg is set equal to the intake air flow rate Ga (or Q). The catalyst capacity X is known.

  Thus, the reaction rate constant k is obtained. The catalyst deterioration degree determination device applies the obtained reaction rate constant k to the equation (4) to obtain the frequency factor k0. In the formula (4), the activation energy E and the gas constant R are known. The catalyst bed temperature T (= Tempccro) is obtained directly from the catalyst temperature sensor 69. The catalyst deterioration degree determination device determines that the catalyst is normal if the frequency factor k0 is greater than a predetermined threshold k0th, and determines that the catalyst is deteriorated if the frequency factor k0 is equal to or less than the predetermined threshold k0th. .

The above is a case where attention is paid to NO as the specific gas, but it is also possible to pay attention to CO as the specific gas. In this case, since CO is purified when the air-fuel ratio of the engine is leaner than the stoichiometric air-fuel ratio, the catalyst deterioration degree determining device controls the engine air-fuel ratio to be leaner than the stoichiometric air-fuel ratio. Here, attention is focused on O ₂ (oxygen) as a reaction gas that reacts with CO to purify CO. At this time, CO and O ₂ react as shown in the following formula (6).

From this, as in the case of NO, the following equations (7) and (8) are obtained.

  The catalyst deterioration degree determination device obtains the reaction rate constant k from the equations (7) and (8), applies this to the equation (4) to obtain the frequency factor k0, and based on this frequency factor k0, the catalyst deterioration degree Determine. However, the catalyst deterioration degree determination device directly acquires the CO concentration [CO] in flowing into the catalyst from the upstream specific gas concentration sensor 67 (upstream CO concentration sensor) disposed upstream of the catalyst, and from the catalyst. The concentration [CO] out of the outflowing CO is directly acquired from the downstream specific gas concentration sensor 68 (downstream CO concentration sensor) disposed downstream of the catalyst.

Furthermore, the catalyst deterioration degree determination apparatus, the concentration [O _2] in the O ₂ flowing into the catalyst, the engine operating state at that time (Q, NE, THW) maps had previously been determined to MapO ₂ in (Q, NE, THW). Incidentally, the catalyst upstream disposed an O ₂ concentration sensor may acquire the O ₂ from the concentration sensor of the O ₂ concentration [O _2] in the direct.

  In this way, the catalyst deterioration degree determination device uses the model (for example, equation (4)) that represents the purification reaction in the catalyst to determine the concentration of the specific gas that is actually detected and acquired when flowing into the catalyst. The frequency factor k0 is calculated by applying the concentration of the gas flowing out from the catalyst, the concentration of the reaction gas flowing into the catalyst and reacting with the specific gas, and the temperature of the catalyst (catalyst bed temperature). The degree of catalyst deterioration is determined based on the above. Since this operation can be performed in real time on a computer mounted on the vehicle, the actual degree of deterioration of the catalyst can be accurately estimated. In the above-described example, attention is paid to NO or CO as the gas to be purified. However, the frequency factor k0 can be calculated by the same method when focusing on HC or the like.

(Operation)
Next, the actual operation of the fuel injection amount control device configured as described above will be described. The CPU 81 determines the target value of the opening degree of the throttle valve 43 based on the operation amount Accp of the accelerator pedal 71, and the throttle valve actuator 43a so that the actual opening degree of the throttle valve 43 becomes the determined target value. Is supposed to drive. The target value of the throttle valve opening is determined based on the actual operation amount Accp of the accelerator pedal 71 and the map MapTA. The map MapTA defines these relationships so that the target value of the throttle valve opening is substantially proportional to the operation amount Accp of the accelerator pedal 71.

  The CPU 81 determines that the crank angle of the engine 10 is a predetermined angle before the intake top dead center of the specific cylinder (here, the first cylinder) by a predetermined crank angle (for example, BTDC 90 ° and immediately before the intake stroke is reached). ), The fuel injection control routine of FIG. The CPU 81 executes the same routine as that shown in FIG. 2 for each of the other cylinders at the same timing.

Next, the CPU 81 proceeds to step 205 and uses the intake air flow rate Ga detected by the air flow meter 61 to determine the intake air flow rate Q sucked into the combustion chamber 25 of the first cylinder according to the following equation (9). Ask. In the following formula (9), α is an arbitrary coefficient from 0 to 1.
Q = α · Q + (1−α) · Ga (9)

  Next, the CPU 81 proceeds to step 210 and multiplies the value obtained by dividing the intake air flow rate Q by the engine rotational speed NE by a predetermined coefficient k1, and is sucked into the combustion chamber 25 of the first cylinder about to reach the intake stroke. Find the air volume KL.

  Next, in step 215, the CPU 81 determines whether or not the value of the catalyst deterioration degree determination execution flag Fhan is “0”. When the value of the catalyst deterioration degree determination execution flag Fhan is “1”, the catalyst deterioration degree (frequency factor k0) is obtained to determine whether or not the catalyst has deteriorated (that is, determination of the catalyst deterioration degree). This flag indicates that it should be performed, and indicates that the catalyst deterioration degree should not be determined when the value is “0”. The value of the catalyst deterioration degree determination execution flag Fhan is set to “0” by an initial routine (not shown) that is executed when an ignition key (not shown) is changed from OFF to ON. Further, the value of the catalyst deterioration degree determination execution flag Fhan is changed / set by a catalyst deterioration degree determination control routine shown in FIG.

  Now, assuming that the value of the catalyst deterioration degree determination execution flag Fhan is set to “0” immediately after the ignition key is changed from OFF to ON, the CPU 81 proceeds to “ The process proceeds to step 220 where the target air-fuel ratio Abyfref is set to a value stocih (for example, 14.7) corresponding to the theoretical air-fuel ratio.

  Next, the CPU 81 proceeds to step 225, determines the fuel injection amount fi by dividing the air amount KL by the target air-fuel ratio Abyfref, and supports the fuel corresponding to the fuel injection amount fi determined in the subsequent step 230 to the first cylinder. An instruction signal is sent to the injector 39 so as to inject from the injector 39. Thereafter, the CPU 81 once ends this routine at step 295.

  Thereafter, as long as the value of the catalyst deterioration degree determination execution flag Fhan is maintained at “0”, the CPU 81 repeatedly executes the above-described steps. As a result, the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine 10 is maintained at the stoichiometric air-fuel ratio.

  On the other hand, the CPU 81 repeatedly executes the catalyst deterioration degree determination control routine shown in FIG. 3 every elapse of a predetermined time. Therefore, when the predetermined timing comes, the CPU 81 starts the process from step 300 and proceeds to step 305 to determine whether or not the value of the catalyst deterioration degree determination completion flag Fdone is “0”.

  When the value of the catalyst deterioration degree determination completion flag Fdone is “1”, the catalyst deterioration degree is determined during the current traveling (that is, from the time when the ignition key is changed from OFF to ON until the present time). This flag indicates that the determination has been completed, and when the value is “0”, this flag indicates that the determination of the catalyst deterioration level has not been completed in the current travel. The value of the catalyst deterioration degree determination completion flag Fdone is set to “0” in an unillustrated initial routine that is executed when an unillustrated ignition key is changed from OFF to ON. Further, the value of the catalyst deterioration degree determination completion flag Fdone is set to “1” when the determination of the catalyst deterioration degree is completed by the catalyst deterioration degree determination routine shown in FIG. 4 described later.

  Now, since the ignition key is changed from off to on, the description of the catalyst deterioration degree is not completed (that is, the value of the catalyst deterioration degree determination completion flag Fdone is “0”). Then, the CPU 81 makes a “Yes” determination at step 305 to proceed to step 310.

  In step 310, the CPU 81 determines whether or not the catalyst bed temperature Tempccro detected by the catalyst temperature sensor 69 is higher than a predetermined threshold temperature Tempth. The threshold temperature Tempth is selected to be a value at which the upstream catalyst 53 exhibits sufficient purification performance when the catalyst bed temperature Tempccro is higher than the predetermined threshold temperature Tempth.

  At this point, if the catalyst bed temperature Tempccro is equal to or lower than the predetermined threshold temperature Tempth, the CPU 81 makes a “No” determination at step 310 and proceeds to step 315 to set the value of the catalyst deterioration degree determination execution flag Fhan to “0”. Set to. Next, the CPU 81 proceeds to step 320, stores the intake air flow rate Q at that time as the previous intake air flow rate Qold, and once ends this routine in step 395.

  Further, the CPU 81 repeatedly executes the catalyst deterioration determination routine shown by the flowchart in FIG. 4 every elapse of a predetermined time. Therefore, the CPU 81 starts processing from step 400 at a predetermined timing, and determines whether or not the value of the catalyst deterioration degree determination execution flag Fhan is “1” in step 405.

  As described above, when the catalyst bed temperature Tempccro is equal to or lower than the predetermined threshold temperature Tempth, the value of the catalyst deterioration degree determination execution flag Fhan is set to “0”. Accordingly, the CPU 81 makes a “No” determination at step 405 to immediately proceed to step 495 to end the present routine tentatively. As described above, when the catalyst bed temperature Tempccro is equal to or lower than the predetermined threshold temperature Tempth, the upstream catalyst 53 is not activated and the deterioration degree of the upstream catalyst 53 cannot be accurately determined. It is forbidden.

  Thereafter, when the operation is continued, the catalyst bed temperature Tempccro becomes higher than the threshold temperature Tempth. At this time, when the CPU 81 executes the routine shown in FIG. 3, the CPU 81 makes a “Yes” determination at step 310 to proceed to step 325, and the difference between the intake air flow rate Q at that time and the previous intake air flow rate Qold. Is obtained as an intake air flow rate change amount ΔQ. Next, in step 330, the CPU 81 determines whether or not the absolute value of the difference ΔQ is smaller than a predetermined positive threshold value ΔQth.

  Assuming that the operating state of the internal combustion engine 10 is an acceleration or deceleration state (transient operation state), the difference ΔQ is equal to or greater than the positive threshold value ΔQth, so the CPU 81 determines “No” in step 330. Proceeding to step 315, the value of the catalyst deterioration degree determination execution flag Fhan is set to “0”, and the routine proceeds to step 395 via step 320 to end the present routine tentatively. As described above, when the operation state of the internal combustion engine 10 is not a steady operation state (that is, when the temporal change amount of the gas flowing into the upstream side catalyst 53 is larger than a predetermined value), the deterioration degree of the upstream side catalyst 53 is accurately determined. Since the determination cannot be made well, the value of the catalyst deterioration degree determination execution flag Fhan is maintained at “0”, and the determination of the catalyst deterioration degree is prohibited.

  On the other hand, if the operation state of the internal combustion engine 10 is a steady operation state, the difference ΔQ is equal to or less than the positive threshold value ΔQth. Accordingly, when the CPU 81 proceeds to step 330, the CPU 81 determines “Yes” in step 330, proceeds to step 335, and sets the value of the catalyst deterioration degree determination execution flag Fhan to “1”. Thereafter, the CPU 81 proceeds to step 395 via step 320, and once ends this routine.

  As described above, the CPU 81 sets the value of the catalyst deterioration degree determination execution flag Fhan to “1” when the catalyst bed temperature Tempccro is larger than the threshold temperature Tempth and the difference ΔQ is smaller than the positive threshold ΔQth. The determination of the degree of catalyst deterioration is allowed.

  When the CPU 81 executes the fuel injection control routine shown in FIG. 2 in a state where the value of the catalyst deterioration degree determination execution flag Fhan is set to “1”, the CPU 81 proceeds to step 215 to “No” in step 215. The process proceeds to step 235 and sets the target air-fuel ratio Abyfref to a value Rich (for example, 12) corresponding to an air-fuel ratio richer than the stoichiometric air-fuel ratio. Thereby, when the fuel of the fuel injection amount fi obtained in step 225 is injected by executing step 230, the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine 10 is controlled to be richer than the stoichiometric air-fuel ratio. Is done. In step 620, the CPU 81 performs control for causing the electric motor M to generate necessary force for acceleration and deceleration according to the operation amount Accp of the accelerator pedal 71 and the like.

  At this time, when the CPU 81 executes the catalyst deterioration degree determination routine shown in FIG. 4, the value of the catalyst deterioration degree determination execution flag Fhan is set to “1”, so the CPU 81 determines “Yes” in step 405. And proceed to step 410.

  In step 410, the CPU 81 determines whether or not a predetermined time has elapsed since the value of the catalyst deterioration degree determination execution flag Fhan has changed from “0” to “1”. This step is provided so that the determination of the degree of catalyst deterioration is not performed until the catalyst is in a state where the catalyst is stably purifying NO. Since the present value is immediately after the value of the catalyst deterioration degree determination execution flag Fhan has changed from “0” to “1”, the CPU 81 makes a “No” determination at step 410 and proceeds to step 495 to end this routine once. To do.

  After that, when this state continues and a predetermined time has elapsed after the value of the catalyst deterioration degree determination execution flag Fhan has changed from “0” to “1”, the CPU 81 determines “Yes” in step 410. Proceeding to step 415, the CO concentration flowing into the upstream side catalyst 53 based on the actual engine operating state (Q, NE, THW) at that time and the predetermined map MapCOin (Q, NE, THW) [ Get CO] in.

  Next, in step 420, the CPU 81 calculates a reaction rate constant k based on the above-described equation (5). At this time, the value directly acquired from the upstream specific gas concentration sensor 67 is used as the concentration [NO] in of NO flowing into the upstream catalyst 53, and the downstream specification is performed as the concentration [NO] out of NO flowing out from the catalyst. A value obtained directly from the gas concentration sensor 68 is used. The exhaust gas flow rate Vg is set equal to the intake air flow rate Ga (or Q). The catalyst capacity X is known.

  Next, in step 425, the CPU 81 calculates the frequency factor k0 by the formula described in step 425 obtained based on the formula (4). At this time, the value obtained by the catalyst temperature sensor 69 is used as the catalyst bed temperature Tempccro, and the value obtained in step 420 is used as the reaction rate constant k. For gas constant R and activation energy E, values given in advance are used.

  Subsequently, the CPU 81 proceeds to step 430 and determines whether or not the frequency factor k0 calculated in step 425 is greater than a predetermined threshold value (catalyst deterioration determination value) k0th. If the frequency factor k0 is larger than the catalyst deterioration determination value k0th, the CPU 81 determines that the upstream catalyst 53 is normal (not deteriorated), and proceeds to step 435 to store that fact in the backup ram 84. . On the other hand, if the frequency factor k0 is equal to or less than the catalyst deterioration determination value k0th, the CPU 81 determines that the upstream catalyst 53 has deteriorated, proceeds from step 430 to step 440, and stores that fact in the backup ram 84. At this time, the CPU 81 lights a lamp or the like as necessary to inform the passenger that the upstream catalyst 53 should be replaced.

  Next, the CPU 81 proceeds to step 445, sets the value of the catalyst deterioration degree determination execution flag Fhan to “0”, and sets the value of the catalyst deterioration degree determination completion flag Fdone to “1” in the subsequent step 450, Proceeding to step 495, this routine is ended once.

  As a result, the value of the catalyst deterioration degree determination execution flag Fhan is set to “0”, so the CPU 81 determines “Yes” in step 215 of the fuel injection control routine of FIG. Become. As a result, the air / fuel ratio of the engine is controlled to be the stoichiometric air / fuel ratio. Further, since the value of the catalyst deterioration degree determination completion flag Fdone is set to “1”, the CPU 81 makes a “No” determination at step 305 in FIG. 3 and proceeds directly to step 395. Therefore, until the ignition key is changed from OFF to ON and the value of the catalyst deterioration degree determination completion flag Fdone is set to “0”, the CPU 81 executes step 335 to execute the catalyst deterioration degree determination execution flag Fhan. Since the value of is not set to “1”, the catalyst deterioration degree is not determined.

  As described above, the catalyst deterioration degree determination apparatus according to the first embodiment uses the frequency factor k0 representing the deterioration degree of the upstream catalyst 53 as the catalyst reaction model (formula (4)), the actually acquired upstream side. The concentration of the specific gas flowing into the catalyst 53 ([NO] in), the concentration of the specific gas flowing out of the actually acquired upstream catalyst 53 ([NO] out), the concentration of the actually acquired inflowing reaction gas ([CO] in) and the actually acquired temperature (catalyst bed temperature) of the upstream catalyst 53 (tempccro). Therefore, the deterioration degree of the upstream side catalyst 53 can be accurately determined in real time.

  Further, the catalyst deterioration degree determination device purifies the air-fuel ratio of the gas flowing into the upstream side catalyst 53 at the upstream side catalyst 53 when the catalyst deterioration degree is determined (when calculating the frequency factor k0). The air-fuel ratio of the engine so that the air-fuel ratio becomes a certain air-fuel ratio suitable for the air-fuel ratio. In other words, air-fuel ratio control means (step 235, step 225 and step 230) for forcibly controlling the air-fuel ratio of the gas flowing into the upstream catalyst 53 is provided.

  Therefore, since the catalyst reaction model of the equation (4) and the actual reaction in the upstream catalyst 53 can be made to coincide with each other with high accuracy, the degree of deterioration of the catalyst can be determined with higher accuracy. Furthermore, since the concentration [CO] in of the inflowing reaction gas flowing into the upstream side catalyst 53 becomes substantially constant, the state of the purification reaction in the upstream side catalyst 53 is stabilized, so the catalytic reaction model and the actual upstream side catalyst 53 The response matches with higher accuracy.

  Further, the inflowing reaction gas is based on the operating state (Q, NE, THW, etc.) of the internal combustion engine 10 when the air-fuel ratio of the gas flowing into the upstream catalyst 53 is controlled to a constant air-fuel ratio by the air-fuel ratio control means. The concentration [CO] in is acquired (step 415).

  Therefore, the inflowing reaction gas concentration [CO] in can be accurately obtained based on the operating state of the internal combustion engine without installing the inflowing reaction gas concentration sensor to obtain the inflowing reaction gas concentration [CO] in. Can do.

(Second Embodiment)
Next, a catalyst deterioration degree determination apparatus according to a second embodiment of the present invention will be described. FIG. 5 shows a schematic configuration of a power transmission system of a vehicle equipped with a spark ignition type multi-cylinder internal combustion engine 10 to which a fuel injection amount control device including the catalyst deterioration degree determination device is applied.

  This vehicle includes two types of power sources, that is, an internal combustion engine 10 and an electric motor M. The electric motor M functions as an auxiliary power source for the internal combustion engine 10. This vehicle is a front-wheel drive type vehicle that travels by driving front wheels with either one of the driving forces generated by the two power sources according to the driving state or the driving force optimally combining the two driving forces. This is a so-called hybrid vehicle.

  More specifically, the vehicle includes an internal combustion engine 10, an electric motor M, a power switching mechanism P that can switch a power transmission path (and direction) according to the state of the vehicle, and a power switching mechanism P. And a transmission TM for transmitting input power to a power transmission system on the front wheel side.

  The electric motor M is an AC synchronous motor. The electric motor M is driven and controlled by AC power supplied from the inverter I. The inverter I converts DC power supplied from the battery B into AC power.

  The power switching mechanism P includes a motor travel mode that transmits only the power of the electric motor M to the transmission TM, an engine travel mode that transmits only the power of the internal combustion engine 10 to the transmission TM, and the power of the internal combustion engine 10 and the power of the electric motor M. One of the three traveling modes of the motor-assisted traveling mode for transmitting both of them to the transmission TM is achieved.

  In the motor assist travel mode, a constant load is applied to the internal combustion engine 10. That is, in the motor-assisted travel mode, the vehicle is accelerated and / or decelerated by the driving force generated by the electric motor M, and during that time, the internal combustion engine 10 is operated in a steady operation state in which a constant intake air flow rate Q is sucked. It has become so. As a result, in the motor assist travel mode, exhaust gas having a constant gas flow rate flows into the upstream catalyst 53.

  In addition, this vehicle is equipped with an electric control device 90 that replaces the electric control device 80. The electric control device 90 has the same configuration as the electric control device 80 and is electrically connected to the electric motor M, the power switching mechanism P, the inverter I, and the battery B. In addition to the functions provided in the electric control device 80, the electric control device 90 has a function of inputting, for example, the voltage VB of the battery B and outputting a drive signal to the electric motor M, the power switching mechanism P, and the inverter I. To do.

(Operation)
Next, the operation of this catalyst deterioration degree determination device will be described. The CPU 81 of the electric control device 90 executes the routine shown in FIG. 4 and also executes the routine shown in FIG. 6 instead of FIG. 2 and FIG. 7 instead of FIG. 3 every elapse of a predetermined time. Yes. In addition, the same code | symbol is attached | subjected to the step same as the already demonstrated step, and detailed description is abbreviate | omitted.

  First, when the ignition key is changed from OFF to ON and the vehicle starts to operate, both the value of the catalyst deterioration degree determination execution flag Fhan and the value of the catalyst deterioration degree determination completion flag Fdone are both “0” by the above-described initial routine. Set to

  For this reason, when the CPU 81 starts the processing of the routine shown in FIG. 6 from step 600, the CPU 81 makes a “Yes” determination at step 215 to proceed to step 605, and sets the mode of the power switching mechanism P to the engine running mode. To do.

  Next, in step 610, the CPU 81 sets the throttle valve opening to a target value determined by a map MapTA that defines the relationship between the accelerator pedal operation amount Accp and the target throttle valve opening and the actual accelerator pedal operation amount Accp. To control. Next, the CPU 81 proceeds to step 220 and sets the target air-fuel ratio Abyfref to a value stoich corresponding to the stoichiometric air-fuel ratio. Thereafter, the CPU 81 performs the processing from step 205 to step 230, proceeds to step 695, and once ends this routine. As a result, the fuel injection amount fi is determined so that the air-fuel ratio of the engine becomes the stoichiometric air-fuel ratio, and the fuel of the fuel injection amount fi is injected.

  In such an operating state, when the CPU 81 starts the routine processing shown in FIG. 7 from step 700, the value of the catalyst deterioration degree determination completion flag Fdone is “0”, so the CPU 81 determines “Yes” in step 305. The process proceeds to step 705, where it is determined whether or not the battery voltage VB is greater than a predetermined threshold value VBth. As will be described later, this step is performed by determining whether or not the battery B has sufficient remaining power because the load on the battery B is increased when the catalyst deterioration determination control is executed and the load is applied to the battery B. It is provided to confirm whether or not the catalyst deterioration determination control can be entered.

  Now, assuming that the battery voltage VB is greater than the predetermined threshold value VBth, the CPU 81 makes a “Yes” determination at step 705 to execute the processing from step 310 to step 320 described above. The routine is temporarily terminated. Thus, if the catalyst bed temperature Tempccro is larger than the predetermined threshold temperature Tempth and the intake air flow rate change amount ΔQ is smaller than the threshold ΔQth, the value of the catalyst deterioration degree determination execution flag Fhan is set to “1”.

  When the CPU 81 executes the routine shown in FIG. 6 in this state, the CPU 81 makes a “No” determination at step 215 to proceed to step 615 to set the mode of the power switching mechanism P to the motor assist travel mode. Next, in step 620, the CPU 81 performs control to maintain the throttle valve opening at a constant value. As a result, a constant load is applied to the internal combustion engine 10, and the intake air flow rate sucked into the internal combustion engine 10 is constant. Therefore, the internal combustion engine 10 is in a state of generating a constant driving torque, and the acceleration and / or deceleration of the vehicle (that is, the change of the vehicle driving force) performed by the internal combustion engine 10 in the engine running mode described above is performed by the electric motor M. Is done by.

  Next, the CPU 81 sets the target air-fuel ratio Abyfref to a value Rich corresponding to the air-fuel ratio richer than the stoichiometric air-fuel ratio in step 235, executes step 205 to step 230, and then proceeds to step 695 to temporarily execute this routine. finish. As a result, the exhaust gas having a constant rich air-fuel ratio flows into the upstream catalyst 53 at a constant flow rate.

  On the other hand, since the CPU 81 executes the routine of FIG. 4 described above every elapse of a predetermined time, when the value of the catalyst deterioration degree determination execution flag Fhan is set to “1”, the CPU 81 is based on the frequency factor k0 described above. Judge the degree of catalyst deterioration. At this time, since the exhaust gas having a constant rich air-fuel ratio flows into the upstream catalyst 53 at a constant flow rate, the frequency factor k0 can be calculated with higher accuracy, and as a result, the deterioration of the catalyst with higher accuracy. Degree can be determined.

  When executing step 705 in FIG. 7, if the battery voltage VB is equal to or lower than the threshold value VBth, the CPU 81 determines “No” in step 705 and immediately proceeds to step 795. Therefore, when the battery voltage VB is decreasing, the catalyst deterioration determination control is executed and the motor assist travel mode is not entered.

  Thus, according to the catalyst deterioration degree determination device according to the second embodiment of the present invention, at the time of determination of the catalyst deterioration degree, the electric motor M, which is an auxiliary power source different from the internal combustion engine 10, is at least accelerated by the vehicle. The frequency factor k0 is calculated while generating the necessary power and maintaining the internal combustion engine 10 in a steady operation state (while maintaining the exhaust gas flow rate flowing into the upstream catalyst 53 constant). If the amount of exhaust gas flowing into the upstream catalyst 53 becomes constant, the inflowing reaction gas concentration (in this case, [CO] in) is also stabilized, so that the inflowing reaction gas concentration can be acquired with higher accuracy in step 415. As a result, since the frequency factor k0 is calculated with higher accuracy, the degree of catalyst deterioration can be determined with higher accuracy.

  As mentioned above, although each embodiment of the catalyst degradation degree determination apparatus by this invention has been described, this invention is not limited to each said embodiment, A various modification is employable within the scope of the present invention. it can. For example, as described above, the gas of interest for obtaining the frequency factor k0 is not limited to NO, and may be CO or HC. At this time, if the gas of interest is CO, the upstream specific gas concentration sensor 67 and the downstream specific gas concentration sensor 68 are respectively CO concentration sensors, and if the gas of interest is HC, the upstream specific gas concentration The sensor 67 and the downstream specific gas concentration sensor 68 may be HC concentration sensors, respectively.

1 is a schematic configuration diagram of a system in which a fuel injection amount control device including a catalyst deterioration degree determining device according to a first embodiment of the present invention is applied to an internal combustion engine. 2 is a flowchart showing a fuel injection control routine executed by a CPU shown in FIG. 2 is a flowchart showing a catalyst deterioration degree determination control routine executed by a CPU shown in FIG. 2 is a flowchart showing a catalyst deterioration degree determination routine executed by a CPU shown in FIG. It is a schematic block diagram about the power transmission system of the vehicle carrying the internal combustion engine to which the fuel injection amount control apparatus containing the catalyst deterioration degree determination apparatus which concerns on 2nd Embodiment of this invention is applied. It is the flowchart which showed the fuel-injection control routine which CPU of the catalyst degradation degree determination apparatus (fuel-injection-quantity control apparatus) which concerns on 2nd Embodiment of this invention performs. It is the flowchart which showed the fuel-injection control routine which CPU of the catalyst degradation degree determination apparatus (fuel-injection-quantity control apparatus) which concerns on 2nd Embodiment of this invention performs.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 25 ... Combustion chamber, 53 ... Upstream catalyst, 54 ... Downstream catalyst, 66 ... Water temperature sensor, 67 ... Upstream specific gas concentration sensor, 68 ... Downstream specific gas concentration sensor, 69 ... Catalyst temperature sensor 80 ... Electric control device.

Claims (4)

A catalyst deterioration degree determination device that is applied to a vehicle equipped with an internal combustion engine and determines a deterioration degree of a catalyst disposed in an exhaust passage of the internal combustion engine,
Inflow specific gas concentration acquisition means for acquiring the concentration of the specific gas contained in the gas flowing into the catalyst;
Outflow specific gas concentration acquisition means for acquiring the concentration of the specific gas flowing out from the catalyst;
Inflow reaction gas concentration acquisition means for acquiring the concentration of an inflow reaction gas that is a gas that reacts with the specific gas contained in the gas flowing into the catalyst;
Catalyst temperature acquisition means for acquiring the temperature of the catalyst;
A catalytic reaction model representing a purification reaction of the specific gas in the catalyst, a concentration of the specific gas flowing into the acquired catalyst, a concentration of the specific gas flowing out from the acquired catalyst, a concentration of the acquired inflowing reaction gas, and the A frequency factor calculating means for calculating a frequency factor of the purification reaction in the catalyst based on the obtained temperature of the catalyst;
Means for determining the degree of deterioration of the catalyst based on the calculated frequency factor;
A catalyst deterioration degree determination device. The catalyst deterioration degree determination device according to claim 1,
Air-fuel ratio control means for controlling the air-fuel ratio of the gas flowing into the catalyst so that the air-fuel ratio of the gas flowing into the catalyst becomes an air-fuel ratio suitable for purifying the specific gas in the catalyst; Catalyst degradation degree judging device. In the catalyst deterioration degree determination device according to claim 2,
The air-fuel ratio control means is configured to control the air-fuel ratio of the gas flowing into the catalyst to a constant air-fuel ratio richer or leaner than the stoichiometric air-fuel ratio,
The inflowing reaction gas concentration acquisition means acquires the inflowing reaction gas concentration based on the operating state of the internal combustion engine when the air-fuel ratio of the gas flowing into the catalyst is controlled by the air-fuel ratio control means. Constructed catalyst deterioration degree judging device. The catalyst deterioration degree determination device according to any one of claims 1 to 3,
The vehicle includes an auxiliary power source different from the internal combustion engine,
When the frequency factor is calculated by the frequency factor calculating means, the internal combustion engine is maintained in a steady operation state, and the power necessary for accelerating the vehicle is generated by the auxiliary power source. apparatus.

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