JP4949125B2 - Engine condition detection device - Google Patents

Description

  The present invention relates to an engine state detection device that can estimate an exhaust gas temperature using existing detection means without using a temperature sensor.

  Conventionally, deterioration diagnosis of an exhaust gas purification catalyst for an engine, which has been performed by an in-vehicle failure diagnosis system, is performed by comparing output values from air-fuel ratio sensors provided upstream and downstream of the catalyst, and based on the comparison value. Technology for determining the presence or absence of catalyst deterioration is known.

  Since the purification performance cannot be exhibited unless the temperature of the catalyst is raised to a certain temperature, it is necessary to monitor the catalyst temperature in order to prevent erroneous determination even in the deterioration diagnosis of the catalyst. As a technique for monitoring the catalyst temperature, a technique for directly detecting the temperature in the layer of the catalyst using a catalyst temperature sensor is also known. However, the special provision of the catalyst temperature sensor only increases the cost of the failure diagnosis system. In addition, since the inside of the catalyst layer largely fluctuates in the range of about 0 to 800 ° C., there is a problem in durability.

  Therefore, in general, the catalyst temperature is estimated based on signals from existing sensors used for engine control, and the active state of the catalyst is often determined based on the estimated catalyst temperature. .

  As a technique for determining whether or not the catalyst has reached the activation temperature based on the estimated catalyst temperature, for example, a count value is set based on the engine load and the intake air temperature, and this count value is integrated every calculation cycle. However, there is a technique for determining catalyst activity when the integrated value exceeds a preset determination value.

Further, for example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2006-291828), a first estimated exhaust gas temperature that is an exhaust gas temperature of an engine body using an annealing value set based on a fuel injection amount and an intake air amount. , And a second exhaust temperature estimated value that is an exhaust temperature upstream of the catalyst is calculated based on the first exhaust temperature estimated value, and the in-catalyst layer estimation is calculated based on the second exhaust temperature estimated value. A technique for estimating temperature is disclosed.
JP 2006-291828 A

  However, in the technology that determines the presence or absence of catalyst activity by setting a count value based on the engine load and intake air temperature and integrating this count value every calculation cycle, this integrated value correctly reflects the active state of the catalyst. Therefore, even a normal catalyst may be erroneously determined as deteriorated.

  Further, in the technique disclosed in Patent Document 1, the exhaust temperature is estimated based on the fuel injection amount and the intake air amount. However, the air-fuel ratio becomes richer in engine oil dilution and air-fuel ratio control. When this occurs, the intake air amount decreases, and it may be difficult to accurately estimate the exhaust temperature.

  In view of the above circumstances, the present invention is capable of accurately estimating the exhaust temperature, and without using a temperature sensor, an engine state in which the temperature in the catalyst layer can be estimated with high accuracy based on the estimated exhaust temperature. An object is to provide a detection device.

Rue engine state detecting device by the present invention for achieving the above object, an engine load detecting means for detecting an engine load based on the detected value of the intake pipe pressure sensor for detecting an intake pipe pressure downstream of the throttle valve, the Engine load smoothed value calculating means for calculating engine load smoothed value by smoothing engine load, and exhaust temperature estimated value calculating means for calculating engine exhaust temperature estimated value based on the engine load smoothed value; A catalyst layer estimated temperature calculating means for calculating an estimated temperature in the catalyst layer by adding a catalyst reaction temperature set based on an engine operating state to the estimated exhaust gas temperature, and the estimated temperature in the catalyst layer is set in advance. Compare with the catalyst activation temperature judgment value, and allow the deterioration diagnosis of the catalyst when the estimated temperature in the catalyst layer is higher than the catalyst activation temperature judgment value and this state continues for the set time Characterized in that it comprises a catalyst deterioration diagnosis start condition determining means that.

  According to the present invention, an engine exhaust temperature estimation value is calculated on the basis of the engine load smoothing value while paying attention to the fact that the engine load smoothing value and the exhaust temperature exhibit similar behavior. It is possible to accurately estimate the exhaust temperature without using.

  Further, since the estimated temperature in the catalyst layer is calculated based on this estimated exhaust gas temperature, the temperature in the catalyst layer can be estimated with high accuracy.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]
1 to 4 show a first embodiment of the present invention. FIG. 1 is an overall configuration diagram of the engine, and FIG. 2 is a circuit configuration diagram of an electronic control system.

  Reference numeral 1 in FIG. 1 denotes an engine body of a multi-cylinder engine mounted on a vehicle such as an automobile, and an intake port 2a and an exhaust port 2b are formed in a cylinder head 2 of the engine body 1 corresponding to each cylinder. ing. In the intake system of the engine body 1, an intake manifold 3 is communicated with each intake port 2a, and a throttle chamber 5 is communicated with the intake manifold 3 via an air chamber 4 in which intake passages of the respective cylinders are gathered. An air cleaner 7 is attached to the upstream side of the throttle chamber 5 via a suction pipe 6, and the air cleaner 7 is communicated with an air intake chamber 8.

  The throttle chamber 5 is provided with a throttle valve 5a that is linked to an accelerator pedal. A bypass passage 9 that bypasses the throttle valve 5a is connected to the suction pipe 6, and an idle speed that controls the idle speed by adjusting the amount of bypass air flowing through the bypass passage 9 based on the valve opening degree of the bypass passage 9 A rotational speed control (ISC) valve 10 is interposed. The ISC valve 10 is controlled by an electronic control unit (ECU) 40.

  As an exhaust system of the engine body 1, an exhaust pipe 12 is communicated with a collection portion of an exhaust manifold 11 communicating with each exhaust port 2b of the cylinder head 2, and a catalyst 13 is interposed in the exhaust pipe 12 so that the muffler 14.

  On the other hand, an injector 15 is exposed immediately upstream of each intake port 2 a of the intake manifold 3. Further, a spark plug 16 is attached to each cylinder of the cylinder head 2 to expose the discharge electrode at the tip to the combustion chamber. An ignition coil 18 of the spark plug 16 is connected to an igniter 19.

  When the ignition switch is turned on, the power relay 20 is turned on, the ECU 40 is activated, the ECU 40 calculates the ignition timing according to the engine operating state, and an ignition signal corresponding to the ignition timing is output from the ECU 40 to the igniter 19. Then, the primary side of the ignition coil 18 is turned on and off by the igniter 19, and the high voltage induced on the secondary side of the ignition coil 18 is distributed to the spark plug 16 and ignited.

  Furthermore, the engine body 1 is provided with various sensors for detecting the engine operating state. Explaining these sensors, a throttle opening sensor 21 is connected to the throttle valve 5a, and an intake pipe as an engine load detecting means for detecting an intake pipe pressure downstream of the throttle valve 5a with an absolute pressure in the air chamber 4. A pressure sensor 23 is communicated.

  Further, a cooling water temperature sensor 25 is faced in a cooling water passage 2c formed in the cylinder head 2 provided on the cylinder block 1a of the engine body 1, and an O2 sensor 26 is disposed upstream of the catalyst 13. Further, a crank rotor 27 is connected to the crankshaft of the engine body 1, and a cam rotor 28 is connected to a camshaft that rotates 1/2 with respect to the crankshaft. Further, a crank angle sensor 29 is provided on the outer periphery of the crank rotor 27, while a cam angle sensor 30 is provided on the cam rotor 28.

  A crank angle detection projection (or slit) is formed on the outer circumference of the crank rotor 27 for each set crank angle, and a cylinder discrimination projection (or slit) is formed on the outer circumference of the cam rotor 28. Yes.

  When the crank angle sensor 29 and the cam angle sensor 30 detect protrusions formed on the rotors 27 and 28, the crank angle sensor 29 and the cam angle sensor 30 output crank pulses and cam pulses to the ECU 40. The ECU 40 calculates the engine rotational speed Ne from the crank pulse interval time, and performs cylinder discrimination of the fuel injection target cylinder and the ignition target cylinder from the cam pulse.

  As shown in FIG. 2, the ECU 40 is configured around a microcomputer in which a CPU 41, a ROM 42, a RAM 43, a backup RAM 44, and an I / O interface 46 are connected to each other via a bus line. A peripheral circuit such as a constant voltage circuit 47 for supplying power, a drive circuit 48 connected to the I / O interface 46, and an A / D converter 49 are incorporated.

  The constant voltage circuit 47 is connected to the battery 50 via the first relay contact of the power relay 20 having two relay contacts. The relay coil of the power relay 20 is connected to the ignition switch 51 and the battery side. To the relay coil via a forward diode 52.

  The constant voltage circuit 47 is not only connected to the battery 50 via the first relay contact of the power relay 20, but is also directly connected to the battery 50, and the ignition switch 51 is turned on to turn on the power relay. When the 20 relay contacts are closed, power is supplied to each part in the ECU 40, while backup power is always supplied to the backup RAM 44 regardless of whether the ignition switch 51 is ON or OFF. A power line to each actuator is extended from the second relay contact of the power relay 20.

  A crank angle sensor 29 and a cam angle sensor 30 are connected to an input port of the I / O interface 46, and further, via an A / D converter 49, a throttle opening sensor 21, a suction pipe pressure sensor 23, The coolant temperature sensor 25 and the O2 sensor 26 are connected, and the battery voltage VB is input and monitored via the ignition switch 51 and the power supply relay 20.

  On the other hand, the ISC valve 10 and the injector 15 are connected to the output port of the I / O interface 46 via the drive circuit 48 and the igniter 19 is connected. Further, the relay coil of the power relay 20 (cathode side of the diode 52) is connected from the drive circuit 48 through the self-shut signal line, and the power relay 20 can be turned on as necessary even after the ignition switch 51 is turned off. The electric power is continuously supplied to the ECU 40 and the like during this period.

  In the CPU 41, according to the program stored in the ROM 42, based on the output signals from the sensors and switches, the fuel injection control for driving the injector 15, the ISC control for setting the valve opening of the ISC valve 10, and the igniter 19 In addition to executing various controls related to engine control such as ignition timing control for setting the ignition timing by, the deterioration diagnosis of the catalyst 13 is performed every predetermined cycle. At this time, since the catalyst deterioration diagnosis is performed when the catalyst 13 is in an active state, first, the in-layer temperature of the catalyst 13 is estimated.

The in-layer temperature of the catalyst 13 is estimated according to the estimated in-catalyst temperature setting routine shown in FIG. This routine is executed every predetermined calculation cycle after turning on the ignition switch 51. First, in step S1, the intake pipe pressure Pm as the engine load detected by the intake pipe pressure sensor 23 is read, and in step S2, the intake pipe is read. Based on the pressure Pm and the engine load smoothing value pm2smcatp calculated during the previous calculation (value obtained during the previous calculation of pm2smcat), the current engine load smoothing value pm2smcat is calculated from the following equation (1). Note that the processing in this step corresponds to engine load smoothing value calculation means.
pm2smcat ← pm2smcatp + (Pm−pm2smcatp) · kpm (1)
Here, kpm is a smoothing coefficient, and is a value obtained in advance by, for example.

  Next, the process proceeds to step S3, where the exhaust temperature estimated value ehaiki is set based on the engine load smoothed value pm2smcat calculated by the equation (1) with reference to the exhaust temperature estimated value setting table shown in FIG. 4 with interpolation calculation. The processing in this step corresponds to the exhaust gas temperature estimated value calculation means.

  According to experiments or simulations, it has been found that the value obtained by subjecting the intake pipe pressure Pm, which is employed as a representative of the engine load, to the exhaust gas temperature exhibits the same behavior (see FIG. 14).

  In the present embodiment, the exhaust temperature is estimated based on the engine load smoothing value pm2smcat using this characteristic. According to experiments or simulations, it was found that when the engine load smoothing value pm2smcat and the exhaust gas temperature estimation value ehaiki are plotted, both can be expressed by an approximate straight line or an approximate curve equation. Therefore, the exhaust gas temperature estimated value ehaiki can be obtained by multiplying the engine load smoothing value pm2smcat by the slope of the above-mentioned approximate straight line or approximate curve formula.

  Thereafter, the process proceeds to step S4, where the exhaust gas temperature estimated value ehaiki is compared with a preset exhaust gas temperature reference value ehaiki1. Then, it is checked whether or not the exhaust gas temperature estimated value ehaiki exceeds the exhaust gas temperature reference value ehaiki1 even once in one drive cycle (between turning on the ignition switch and turning it off). The exhaust temperature determination reference value ehaiki 1 is used to check the unstable state of the exhaust temperature in the warm-up operation from the cold start, and is set to an optimal value in advance through experiments or the like.

  When ehaiki <ehaiki1, the process proceeds to step S5 where the estimated catalyst temperature in the catalyst layer is set as the estimated exhaust gas temperature ehaiki calculated in step S13 (cat ← ehaiki), and the routine is exited.

  On the other hand, when ehaiki ≧ ehaiki1, the process proceeds to step S6 to calculate the catalyst reaction temperature hc-cocat. This catalytic reaction temperature hc-cocat is based on the engine speed Ne calculated based on the signal from the crank angle sensor 29 and the fuel injection pulse width (fuel injection amount) for driving the injector 15 calculated by the fuel injection control. Then, the reaction heat due to HC and CO in the catalyst 13 is obtained, and this is corrected by the suction pipe pressure Pm to obtain the catalyst reaction temperature hc-cocat.

Next, the process proceeds to step S7, and the value obtained by adding the catalyst reaction temperature hc-cocat to the exhaust gas temperature estimated value ehaki is subjected to a smoothing process based on the following equation (2) to calculate the estimated temperature cat in the catalyst layer, and the routine is executed. Exit. The processing in this step corresponds to the estimated temperature calculating means in the catalyst layer.
cat ← catp + [(ehaiki + hc−cocat) −catp] · kcat1 (2)
Here, catp is a value (hereinafter, referred to as “previous value”) obtained at the previous calculation of the estimated catalyst bed temperature cat, and kcat1 is an annealing coefficient.

  The catalyst layer estimated temperature cat is read, for example, when the deterioration diagnosis of the catalyst 13 is performed, and based on the catalyst layer estimated temperature cat, it is checked whether or not the catalyst layer temperature is in an active state. When it is determined that the 13 layers are in the active state, the deterioration diagnosis is started.

  As described above, in the present embodiment, the reaction temperature hc-cocat in the catalyst 13 is added to the estimated exhaust gas temperature ehaiki set based on the engine load smoothing value pm2smcat that exhibits the same behavior as the exhaust gas temperature. Since the estimated catalyst temperature in the catalyst layer is calculated, the temperature in the catalyst layer can be estimated with high accuracy without using the catalyst temperature sensor.

[Second Embodiment]
FIG. 5 shows an estimated temperature setting routine in the catalyst layer according to the second embodiment of the present invention. This embodiment is a modification of the first embodiment described above. In the first embodiment described above, the temperature increase due to the reaction heat in the catalyst layer is obtained from the catalyst reaction temperature hc-cocat. In this embodiment, the engine load smoothing value pm2smcat and the previously calculated catalyst layer in the catalyst layer are calculated. This is obtained based on the estimated temperature catp.

  First, in steps S11 to S13, processing similar to that in steps S1 to S3 of the first embodiment described above is executed. That is, the suction pipe pressure Pm is read in step S11, and in step S2, the current engine load smoothing value pm2smcatp is calculated as described above based on the suction pipe pressure Pm and the engine load smoothing value pm2smcatp calculated in the previous calculation ( In step S3, the exhaust temperature estimated value ehaki is set based on the engine load smoothed value pm2smcat, with reference to the exhaust temperature estimated value setting table shown in FIG. 4 with interpolation calculation.

  Next, the process proceeds to step S14, where the engine load smoothing value pm2smcat and the first engine load determination reference value pm1 are compared. Then, it is checked whether the engine load annealing value pm2smcat has exceeded the first engine load determination reference value pm1 even once in one drive cycle (between turning on the ignition switch and turning it off). The first engine load determination reference value pm1 is used to check whether or not the engine low load state is continued, and an optimal value is set in advance through experiments or the like.

  When pm2smcat <pm1, the process proceeds to step S15, the estimated catalyst temperature in the catalyst layer is set with the estimated exhaust gas temperature ehaiki (cat ← ehaiki), and the routine is exited. When pm2smcat ≧ pm1, the process proceeds to step S16, and based on the engine load smoothed value pm2smcat and the previous estimated catalyst layer temperature catp, the map is referred to with interpolation calculation to calculate the temperature correction added value tkasan. . Note that the processing in this step corresponds to temperature correction addition value calculation means.

  This temperature correction addition value tkasan corrects the temperature rise due to the heat of catalytic reaction generated in the catalyst 13 layer, and the map shows the engine load annealing value pm2smcat and the previous estimated catalyst layer temperature catp. Based on this, the optimum temperature correction addition value tkasan obtained from experiments or the like is stored.

Thereafter, the process proceeds to step S17, and the value obtained by adding the temperature correction addition value tkasan to the exhaust gas temperature estimation value ehaiki is annealed based on the following equation (3) to calculate the estimated temperature cat in the catalyst layer, and the routine is exited. . The processing in this step corresponds to the estimated temperature calculating means in the catalyst layer.
cat ← catp + [(ehaiki + tkasan) −catp] · kcat2 (2)
Note that kcat2 is an annealing coefficient, and in this embodiment, it is set to the same value as the annealing coefficient kcat1 of the first embodiment described above.

  The catalyst layer estimated temperature cat is read, for example, when the deterioration diagnosis of the catalyst 13 is performed, and based on the catalyst layer estimated temperature cat, it is checked whether or not the catalyst layer temperature is in an active state. When it is determined that the 13th layer is in the active state, the catalyst deterioration diagnosis is started.

  As described above, in this embodiment, the temperature correction addition value tkasan corresponding to the heat of reaction in the catalyst 13 is added to the exhaust temperature estimated value ehaiki set based on the engine load smoothing value pm2smcat that exhibits the same behavior as the exhaust temperature. Since the estimated catalyst temperature in the catalyst layer is calculated by adding, the catalyst layer temperature can be estimated with high accuracy without using a catalyst temperature sensor.

[Third Embodiment]
FIG. 6 shows an estimated temperature setting routine in the catalyst layer according to the third embodiment of the present invention. The present embodiment is a combination of the first embodiment and the second embodiment described above. That is, in this embodiment, the estimated catalyst temperature in the catalyst layer that is set when pm2smcat ≧ pm1 is experienced even once is further subdivided and set.

  First, in steps S21 to S24, processing similar to that in steps S11 to S14 of the second embodiment described above is executed.

  If it is determined in step S24 that pm2smcat <pm1, the process proceeds to step S25, and the estimated in-catalyst temperature cat is set to the estimated exhaust gas temperature ehaiki calculated in step S23 (cat ← ehaki), and the routine is performed. Exit. If it is determined that pm2smcat ≧ pm1, the process proceeds to step S26.

  In step S26, the engine load smoothing value pm2smcat and the second engine load determination reference value pm2 are compared, and the estimated in-catalyst temperature catp and the first in-catalyst layer estimated temperature determination reference value tcat1 calculated during the previous calculation are used. Compare. The second engine load determination reference value pm2 is a value higher than the first engine load determination reference value pm1, and an optimal value is set in advance through experiments or the like. The first catalyst layer estimated temperature determination reference value tcat1 is a value for determining whether or not the catalyst 13 has reached the activation temperature, and an optimal value is set in advance through experiments or the like.

  If it is determined that pm2smcat <pm2 and catp <tcat1, the process proceeds to step S27, and the same processes as in steps S16 and S17 shown in FIG. 5 described above are executed in steps S27 and S28. That is, in step S27, the temperature correction addition value tkasan is calculated by referring to the map with interpolation calculation based on the engine load smoothing value pm2smcat and the previous estimated catalyst layer temperature catp, and in the subsequent step S28, the exhaust gas temperature is calculated. A value obtained by adding the temperature correction addition value tkasan to the estimated value ehaiki is smoothed based on the above-described equation (3) to calculate the estimated temperature cat in the catalyst layer, and the routine is exited.

  On the other hand, if it is determined in step S26 that pm2smcat ≧ pm2 or catp ≧ tcat1, the process proceeds to step S29, and the same processes as in steps S6 and S7 shown in FIG. That is, in step S29, reaction heat due to HC and CO in the catalyst 13 is obtained based on the engine speed Ne and the fuel injection pulse width (fuel injection amount), and this is corrected by the intake pipe pressure Pm. The reaction temperature hc-cocat is calculated, and in the subsequent step S30, the value obtained by adding the catalyst reaction temperature hc-cocat to the exhaust temperature estimated value ehaiki is subjected to a smoothing process based on the above-described equation (2) to estimate within the catalyst layer. The temperature cat is calculated and the routine is exited.

  As described above, in this embodiment, the value to be added to the exhaust gas temperature estimated value ehaiki is added to the temperature correction addition according to the condition of the engine load smoothing value pm2smcat and the estimated temperature in the catalyst layer catp calculated at the previous routine execution. Since the value tkasan or the catalyst reaction temperature hc-cocat is selected, a more precise estimated temperature cat in the catalyst layer can be set.

[Fourth Embodiment]
7 to 12 show a fourth embodiment of the present invention. 7 is an estimated temperature setting routine in the catalyst layer, FIG. 8 is a routine for calculating the estimated temperature increase in the catalyst layer, FIG. 9 is an integrated value calculating routine for the estimated temperature increase in the catalyst layer, and FIG. FIG. 11 is an amount calculation routine, and FIG. 11 is an in-layer estimated temperature decrease change integrated value calculation routine.

  In this embodiment, as shown in FIG. 12, the amount of change in the estimated temperature cat / ΔT (ΔT: calculation cycle) in the catalyst layer per unit time subjected to the annealing process (the amount of change in the catalyst layer annealing value), Focusing on the fact that there is a strong correlation with the amount of change in engine load smoothing value pm2smcat / Δt per unit time, changes α and β are obtained from engine load smoothing value change amount pmtsm, and these are integrated values. The estimated in-catalyst temperature cat is obtained by adding the estimated in-catalyst temperature change amount Σcat.

  That is, first, in step S41, the engine load smoothed value pmsmm (where pmsmm = pm2smcat / ΔT) obtained at the time of the previous calculation is read, and then in step S42, the engine load per unit time of this time is read. An annealing value pmsm is calculated. The engine load smoothing value pm2smcat is obtained from the above-described equation (1).

In step S43, the engine load smoothing value change amount pmtsm per unit time is calculated from the following equation. The processing in this step corresponds to engine load smoothing value change amount calculation means.
pmtsm ← pmmsm−pmsmm (4)

  Next, the process proceeds to step S44, and it is determined whether the engine load smoothing value change amount pmtsm is increasing or decreasing. When pmtsm ≧ 0 is increased, the process proceeds to step S45, and when pmtsm <0 is decreased, the process proceeds to step S46.

When the process proceeds to step S45, the estimated temperature increase exhaust gas temperature change amount ehaikip is set from the following equation.
ehaikip <-pmtsm · ratep (5)
Here, ratep is the slope of the temperature rise. According to the experiment or simulation, when the engine load smoothing value change amount pmtsm and the temperature increase side exhaust temperature estimated value change amount ehaikip are plotted, it is found that both can be expressed by an approximate straight line or an approximate curve equation. Therefore, by multiplying the engine load annealing value change amount pmtsm by the above-described approximate straight line or approximate curve equation, the rising temperature rate change rate heikip can be set.

  Next, the process proceeds to step S47, where the estimated in-catalyst rise temperature change amount catpp is calculated. The catalyst layer rise estimated temperature change amount catpp is processed according to the catalyst layer rise estimated temperature change amount calculation routine shown in FIG.

In this routine, first, in step S61, the previous value catp of the estimated in-catalyst temperature cat is read and compared with the first in-layer estimated temperature determination reference value cat1. Then, when catp ≧ cat1, the process proceeds to step S62, and the catalyst layer rise estimated temperature change amount catpp is calculated from the following equation, and the process proceeds to step S48 in FIG.
catpp <-pmtsmp / ratep / A (6)
pmtsmp is the positive engine load smoothing value change amount pmtsm, and in this case, pmtsmp = pmtsm. A is a constant.

Further, when catp <cat1, the process proceeds to step S63, the catalyst layer rise estimated temperature change amount catpp is calculated from the following equation, and the process proceeds to step S48 in FIG.
catpp ← pmtsm · ratep · B (7)
Here, B is a constant.

  Then, when the process proceeds to step S48 in FIG. 7, the in-layer estimated temperature rise change integrated value Σcatp is calculated. This in-layer estimated temperature rise change amount integrated value Σcatp is processed according to the in-layer estimated temperature rise change amount integrated value calculation routine shown in FIG. In this routine, first, in step S71, the previous value catp of the estimated temperature in the catalyst layer is compared with the second estimated temperature temperature reference value 2, and the estimated increase in temperature in the catalyst layer catpp is compared with the first estimated temperature change amount catpp. The temperature increase criterion value catpp1 is compared.

  If catp ≧ cat2 and catpp ≧ catpp1, the process proceeds to step S72. If catp <cat2, or catpp <catpp1, the process proceeds to step S73.

  In step S72, the increase amount α is set with a constant C (α ← C), and the process proceeds to step S76. In step S73, the estimated in-catalyst temperature catp obtained in the previous calculation is compared with the third in-layer estimated temperature determination reference value cat3. If catp ≧ cat3, the process proceeds to step S74, the increase change amount α is set by the constant D (α ← D), and the process proceeds to step S76. On the other hand, if catp <cat3, the process branches to step S75, the rising change amount α is set by the estimated temperature change amount catpp in the catalyst layer (α ← catpp), and the process proceeds to step S76.

Then, when the process proceeds from any of steps S72, S74, and S75 to step S76, the in-layer estimated temperature increase change amount integrated value Σcatp is calculated from the following equation, and the process proceeds to step S49 in FIG.
Σcatp ← Σcatpp + α
Here, Σcatpp is the in-layer estimated temperature rise change integrated value calculated during the previous calculation.

  In step S49 in FIG. 7, the in-catalyst estimated temperature rise change amount integrated value Σcatp is set to the in-catalyst layer estimated temperature change amount Σcat (Σcat ← Σcatp), and the process proceeds to step S53. The processes in steps S45 and S47 to 49 and the processes in steps S46 and S50 to S52 described later correspond to the estimated temperature change amount calculation means in the catalyst layer.

On the other hand, when the process proceeds from step S44 to step S46, the temperature decrease side exhaust temperature estimated value change amount ehaikim is set from the following equation.
ehakim <-pmtsm / ratem (8)
Here, rate is an inclination on the temperature raising side. According to the experiment or simulation, when the engine load smoothing value change amount pmtsm and the temperature-decreasing-side exhaust temperature estimated value change amount ehaikim are plotted, it has been found that both can be expressed by an approximate straight line or an approximate curve equation. Therefore, by multiplying the engine load smoothing value change amount pmtsm by the above-described approximate straight line or approximate curve equation, the rising temperature-side slope ratem can set the descending exhaust temperature estimated value change amount ehaikim. .

Next, the process proceeds to step S50, and the in-catalyst layer drop estimated temperature change amount catmm is calculated. This in-catalyst layer descent estimated temperature change amount catmm is processed according to the in-catalyst layer descent estimated temperature change amount calculation routine shown in FIG. In this routine, first, in step S81, the previous value catp of the estimated in-catalyst temperature cat is read and compared with the fourth in-layer estimated temperature determination reference value cat4. When catp ≧ cat4, the process proceeds to step S82, the in-catalyst layer drop estimated temperature change amount catmm is calculated from the following equation, and the process proceeds to step S51 in FIG.
catmm ← pmtsmm ・ ratem ・ E ... (9)
Here, pmtsmm is a negative engine load smoothing value change amount pmtsm. Therefore, in this case, pmtsmm = pmtsm. E is a constant.

On the other hand, when catp <cat4, the process proceeds to step S83, the in-catalyst layer drop estimated temperature change amount catmm is calculated from the following equation, and the process proceeds to step S51 in FIG.
catmm ← pmtsm / ratem / F (10)
Here, F is a constant.

  Then, when the process proceeds to step S51 in FIG. 7, the in-layer estimated temperature decrease change integrated value Σcatm is calculated. This in-layer estimated temperature decrease change integrated value Σcatm is processed according to the in-layer estimated temperature decrease change integrated value calculation routine shown in FIG. In this routine, first, in step S91, the negative engine load smoothing value change amount pmtsmm is compared with the first engine load smoothing value change amount determination reference value pmts1, and the catalyst layer obtained in the previous calculation is calculated. The inward descent estimated temperature change amount catmm is compared with the first temperature drop determination reference value catmm1.

  If pmtsmm <pmts1 and catmm <catmm1, the process proceeds to step S92. If pmtsmm ≧ pmts1, or catmm ≧ catmm1, the process proceeds to step S93.

  When the process proceeds to step S92, the downward change amount β is set with the constant G (β ← G), and the process proceeds to step S100. In step S93, the estimated in-catalyst drop temperature change amount catmm is compared with the second temperature fall criterion value catmm2. If catmm <catmm2, the process proceeds to step S94, the lowering change amount β is set with a constant H (β ← H), and the process proceeds to step S100. If catmm ≧ catmm2, the process proceeds to step S95.

  In step S95, the fuel injection pulse width is read to determine whether or not the fuel is cut, and the estimated in-catalyst temperature catp obtained in the previous calculation is compared with the fifth in-layer estimated temperature determination reference value cat5. When the fuel cut is in progress and catp ≧ cat5, the process proceeds to step S96, the downward change amount β is set by the constant I (β ← I), and the process proceeds to step S100. If fuel injection is in progress or catp <cat5, the process proceeds to step S97.

  In step S97, it is checked whether or not the engine is idling based on the engine speed Ne, and the estimated in-catalyst temperature catp obtained in the previous calculation is compared with the sixth in-layer estimated temperature determination reference value cat5. When the idling operation is being performed and catp ≧ cat5, the process proceeds to step S98, the downward change amount β is set by the constant J (β ← J), and the process proceeds to step S100. Further, in the non-idle state or when catp <cat5, the process proceeds to step S99, the decrease change amount β is set by the estimated temperature change amount catmm in the catalyst layer (β ← catmm), and the process proceeds to step S100.

Then, when the process proceeds from any one of steps S92, S94, S96, S98, and S99 to step S100, the current estimated temperature drop change integrated value Σcatm is calculated from the following equation, and the process proceeds to step S49 in FIG.
Σcatm ← Σcatmm + β
Here, Σcatmm is the estimated temperature drop change amount in the catalyst layer calculated at the previous calculation.

  Then, in step S52 of FIG. 7, the in-catalyst layer estimated temperature decrease change integrated value Σcatm is set to the in-catalyst layer estimated temperature change amount Σcat (Σcat ← Σcatm), and the process proceeds to step S53. The estimated temperature change amount Σcat in the catalyst layer is a negative value or a zero value.

  Then, when the process proceeds from step S49 or step S52 to step S53, the estimated in-catalyst temperature change Σcat is added to the estimated in-catalyst temperature catp obtained at the previous calculation, and the present estimated in-catalyst temperature cat is calculated. (Cat ← catp + Σcat) and exit the routine. The processing in this step corresponds to the estimated temperature calculating means in the catalyst layer.

  As described above, in this embodiment, the temperature in the catalyst layer is estimated by adding the estimated temperature change amount Σcat in the catalyst layer, which is an integrated value of the change amounts α and β of the engine load smoothing value change amount pmtsm. Therefore, the change in the catalyst temperature per unit time and its transition can be estimated more precisely without using the catalyst temperature sensor.

  Further, since the rising change amount α and the falling change amount β are set according to the conditions of operation of the engine, the temperature in the catalyst layer can be estimated more accurately.

[Fifth Embodiment]
FIG. 13 shows a catalyst deterioration diagnosis start determination routine according to the fifth embodiment of the present invention. In the present embodiment, it is determined whether or not the catalyst deterioration diagnosis can be performed based on the estimated in-catalyst temperature cat obtained in the first to fourth embodiments. Since the catalyst 13 does not deteriorate rapidly, the routine is executed once or several times after turning on the ignition switch. The processing in this routine corresponds to the catalyst deterioration diagnosis start condition determining means.

  In this routine, first, in step S101, the fuel cut duration tcutinj and the fuel cut duration determination reference value tcut1 are compared, and the idle duration tid and the idle duration determination reference value tid1 are compared. That is, even if the estimated temperature in the catalyst layer is estimated to be equal to or higher than the predetermined temperature, immediately before that, the temperature in the catalyst layer is suddenly lowered due to fuel cut or long-term idle operation, etc. The in-layer state of the catalyst 13 may become unstable, and the air-fuel ratio control may diverge. If the deterioration diagnosis of the catalyst is executed in such a state, it is erroneously determined as deterioration despite being normal. The fuel cut continuation time determination reference value tcut1 and the idle continuation time determination reference value tid1 are set in advance by obtaining the continuation time during which the temperature of the catalyst 13 drops from an experiment.

  When a state of tcutinj ≧ tcut1 or tid ≧ tid1 is experienced, that is, when there is a possibility that the temperature in the catalyst layer is lowered, the process proceeds to step S102. If tcutinj <tcut1 and tid <tid1, the process proceeds to step S103.

  When the process proceeds to step S102, the estimated in-catalyst temperature cat described above is read, the estimated in-catalyst temperature cat is compared with the seventh in-layer estimated temperature determination reference value cat7 that is the catalyst activation temperature determination value, and cat ≧ cat7 If this state continues for a predetermined time or longer, it is determined that the catalyst 13 is active, and the process proceeds to step S104. Further, when the state of cat <cat7 or cat ≧ cat7 does not continue for the set time or longer, the catalyst 13 may not be active, and the process jumps to step S105.

  In step S103, the estimated in-catalyst temperature cat is compared with the eighth in-layer estimated temperature determination reference value cat8 to check whether the catalyst 13 has reached the activation temperature. If it is determined that the activation temperature of cat ≧ cat8 has been reached, the process proceeds to step S104. If cat <cat8, the process proceeds to step S105.

  In step S104, the catalyst deterioration diagnosis is permitted and the routine is exited. In step S105, the deterioration diagnosis of the catalyst is prohibited and the routine is exited.

  As described above, in the present embodiment, when the temperature in the catalyst layer suddenly falls due to fuel cut, long-term idle, or the like, the estimated temperature in the catalyst layer cat is the set temperature (the seventh in-layer estimated temperature determination reference value). Since the deterioration diagnosis of the catalyst 13 is permitted in the case of cat7) and the state continues for the set time, the diagnosis is not started when the catalyst 13 is in the inactive state, and a misdiagnosis is performed. Can be prevented in advance.

[Application example]
In FIG. 14, when the target engine speed is constant, the intake pipe pressure smoothing value (based on the actual engine speed, the actual exhaust temperature, and the intake pipe pressure Pm detected by the intake pipe pressure sensor 23) An engine load annealing value) pm2smcatp, and an estimated exhaust gas temperature ehaiki obtained based on the intake pipe pressure annealing value pm2smcatp are shown.

  As shown in the figure, the exhaust gas temperature estimated value ehaiki obtained based on the suction pipe pressure smoothing value pm2smcatp and the actual exhaust gas temperature show almost the same behavior. Further, as shown in FIG. 15, the exhaust temperature at the normal time, the exhaust temperature estimated value ehaiki at that time, the exhaust temperature at the time of abnormality, and the exhaust temperature estimated value at that time ehaiki are almost the same as the actual exhaust temperature. It is confirmed that correct behavior is shown.

  Therefore, using this, for example, the exhaust gas temperature estimated value ehaiki is performed during execution of the catalyst early warm-up control, and when the exhaust gas temperature estimated value ehaiki falls below a preset catalyst early warm-up determination value, the catalyst early warm-up is performed. It is possible to determine that the control is abnormal.

  In addition, since the exhaust temperature estimated value ehaiki and the actual exhaust temperature show almost the same behavior, naturally, the engine load smoothed value (suction pipe pressure smoothed value) pm2smcatp and the actual exhaust temperature have almost the same behavior. Will show.

  FIG. 16 shows the behavior of the engine load smoothing value (suction pipe pressure smoothing value) pm2smcatp at the normal exhaust temperature and the engine load at the abnormal exhaust temperature based on the suction pipe pressure Pm during idle operation. The annealing value (suction pipe pressure annealing value) pm2smcatp behavior is shown. As shown in the figure, if the behavior of the engine load smoothing value (suction pipe pressure smoothing value) at the exhaust temperature at the time of abnormality is stored in advance as a judgment reference value, When the catalyst early warm-up control is performed, the calculated engine load annealing value is compared with the determination reference value, and after a predetermined time has elapsed from the start of engine start, the engine load annealing value pm2smcatp obtained by calculation is the determination reference value. When it falls below, it can be determined that the catalyst early warm-up control is abnormal.

  The present invention is not limited to the above-described embodiments. For example, in the first to fourth embodiments, if the estimated catalyst temperature in the catalyst layer is corrected according to the engine warm-up state and the catalyst layer state, The temperature in the catalyst layer can be accurately estimated. In this case, the warm-up state of the engine is determined based on the cooling water temperature detected by the cooling water temperature sensor 25 as engine temperature detecting means for indirectly detecting the engine temperature, and the in-layer temperature state of the catalyst 13 is the catalyst temperature. The determination is made based on the previous value catp of the in-layer estimated temperature cat. Further, in the fifth embodiment, a catalyst deterioration diagnosis is performed by calculating a correction value by multiplying the engine water temperature by the previous value catp of the estimated catalyst temperature in the catalyst layer, and adding the corrected value to the estimated catalyst temperature in the catalyst layer. It may be possible to determine whether or not execution is possible.

Overall configuration diagram of an engine according to the first embodiment Same as above, circuit diagram of electronic control system Same as above, a flowchart showing an estimated temperature setting routine in the catalyst layer Explanatory drawing of exhaust temperature estimated value setting table The flowchart which shows the estimated temperature setting routine in a catalyst layer by 2nd Embodiment. The flowchart which shows the estimated temperature setting routine in a catalyst layer by 3rd Embodiment. The flowchart which shows the estimated temperature setting routine in a catalyst layer by 4th Embodiment of this invention. Same as above, a flowchart showing a routine for calculating an estimated temperature change amount in the catalyst layer Same as above, a flowchart showing an in-layer estimated temperature rise variation integrated value calculation routine Same as above, a flowchart showing a routine for calculating an estimated temperature change amount within the catalyst layer Same as above, a flow chart showing an in-layer estimated temperature decrease change integrated value calculation routine FIG. 5 is an explanatory diagram showing the correlation between the engine load annealing value change amount and the catalyst layer temperature annealing value change amount. The flowchart which shows the catalyst deterioration diagnosis start determination routine by 5th Embodiment. Explanatory diagram showing behavior of actual engine speed and actual exhaust temperature, intake pipe pressure smoothed value, and exhaust temperature estimated value according to application example Similarly, the exhaust temperature at normal time, the exhaust temperature estimated value at that time, the exhaust temperature at the time of abnormality, and the behavior of the exhaust temperature estimated value at that time Same as above, explanatory diagram showing behavior of engine load smoothing value at normal time during idling operation and behavior of engine load smoothing value at abnormal time

Explanation of symbols

1 ... Engine body,
13 ... Catalyst,
23 ... suction pipe pressure sensor,
A to J ... constants,
cat: Estimated temperature in the catalyst layer,
cat1 to cat8 ... In-layer estimated temperature determination reference value,
catmm: Estimated temperature change amount falling in the catalyst layer,
catmm1, catmm2 ... temperature drop criterion value,
catp ... Estimated temperature in catalyst layer (previous value),
catpp ... Estimated temperature change in catalyst layer rise,
catpp1 ... Temperature increase criterion value,
ehaiki ... exhaust temperature estimate,
ehaki1 ... exhaust temperature judgment reference value,
ehaikim, ehaikip ... exhaust temperature estimated value change amount,
hc-cocat: catalytic reaction temperature,
kcat1 ... annealing factor,
Pm ... suction pipe pressure,
pm1, pm2 ... engine load judgment reference value,
pm2smcatp ... engine load smoothing value (previous value),
pm2smcat… An engine load annealing value,
pmmsm: engine load smoothed value per unit time,
pmsmm: engine load smoothed value per unit time (previous value),
pmts1... first engine load smoothing value change criterion value,
pmtsm: engine load smoothing value change amount,
pmtsmm ... engine load smoothing value change (previous value),
rate, ratep ... inclination,
tcat1 ... Estimated temperature judgment reference value in the catalyst layer,
tcut1 ... fuel cut duration determination reference value,
tcutinj ... Fuel cut duration,
tid ... Idle duration,
tid1 ... idle duration determination reference value,
tkasan ... temperature correction addition value α ... increase change amount,
β: Descent change amount,
Σcat: Estimated temperature change in the catalyst layer,
Σcatm: In-layer estimated temperature decrease change integrated value,
Σcatp: In-layer estimated temperature rise change integrated value,

Claims (2)

Engine load detection means for detecting engine load based on a detection value of a suction pipe pressure sensor for detecting a suction pipe pressure downstream of the throttle valve ;
Engine load smoothed value calculating means for calculating the engine load smoothed value by smoothing the engine load;
An exhaust temperature estimated value calculating means for calculating an engine exhaust temperature estimated value based on the engine load annealing value ;
A catalyst layer estimated temperature calculation means for calculating a catalyst layer estimated temperature by adding a catalyst reaction temperature set based on an engine operating state to the exhaust gas temperature estimated value;
When the estimated temperature in the catalyst layer is compared with a preset catalyst activation temperature judgment value and the estimated temperature in the catalyst layer is equal to or higher than the catalyst activation temperature judgment value and this state continues for a set time, the catalyst deteriorates An engine state detection device comprising: catalyst deterioration diagnosis start condition determination means for permitting diagnosis . The engine state detection device according to claim 1 , wherein the estimated catalyst temperature calculation means calculates the estimated temperature in the catalyst layer by an annealing process.

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