JP5200865B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine.

  Conventionally, a catalyst having an oxidizing ability is disposed in the engine exhaust passage, and a secondary air supply device for supplying secondary air to a secondary air supply location in the exhaust passage upstream of the catalyst is provided, and the temperature of the catalyst should be increased. There is known an internal combustion engine in which secondary air is supplied while the in-cylinder air-fuel ratio is controlled to be rich so that unburned components (unburned HC, CO) in exhaust gas are oxidized on a catalyst. That is, in this internal combustion engine, by setting the in-cylinder air-fuel ratio to be rich, rich exhaust gas that is exhaust gas containing a large amount of unburned fuel is formed, and this rich exhaust gas is supplied from the engine body to the catalyst. On the other hand, secondary air, that is, oxygen is supplied to the catalyst from the secondary air supply device. As a result, unburned components in the rich exhaust gas are oxidized on the catalyst, and thus the temperature of the catalyst is increased.

  However, if the timing when the rich exhaust gas reaches the catalyst does not coincide with the timing when the secondary air reaches the catalyst, the fuel or the secondary air cannot be effectively used for raising the temperature of the catalyst.

Therefore, the start timing of combustion under the rich air-fuel ratio or the start timing of secondary air supply is set so that the timing at which the rich exhaust gas reaches the catalyst and the timing at which the secondary air reaches the catalyst substantially coincide with each other. An internal combustion engine to be controlled is known (see Patent Document 1). In this internal combustion engine, the secondary air is supplied by a constant amount or an amount corresponding to the catalyst temperature.
JP 2006-348801 A

  Considering the effective use of fuel or secondary air, it is preferable to make the air-fuel ratio of the exhaust gas at the secondary air supply point coincide with the target exhaust gas air-fuel ratio, for example, the stoichiometric air-fuel ratio. Therefore, a required secondary air amount, which is a secondary air amount required to make the air-fuel ratio of the exhaust gas at the secondary air supply location coincide with the target exhaust gas air-fuel ratio, is calculated, and the secondary air is calculated by the required secondary air amount. It is conceivable to control the secondary air supply device so that is supplied.

  However, it takes time for the exhaust gas generated by combustion in the cylinder to reach the secondary air supply location. Therefore, even if the current required secondary air amount is determined based on the current in-cylinder air-fuel ratio, the air-fuel ratio of the exhaust gas at the secondary air supply location cannot be made to exactly match the target exhaust gas air-fuel ratio. There is.

  In order to solve the above-mentioned problems, according to the present invention, a catalyst having an oxidizing ability disposed in an engine exhaust passage, a means for controlling the in-cylinder air-fuel ratio, and a secondary air supply in the exhaust passage upstream of the catalyst Secondary air supply means for supplying secondary air to the location, and when the temperature of the catalyst is to be raised, the secondary air is supplied while the in-cylinder air-fuel ratio is controlled to be rich, and the unburned portion in the exhaust gas In the exhaust gas purification apparatus for an internal combustion engine that oxidizes the exhaust gas on the catalyst, the means for repeatedly obtaining and storing the actual in-cylinder air-fuel ratio, and the air-fuel ratio of the exhaust gas at the secondary air supply location are determined as the target exhaust gas empty The required secondary air amount, which is the amount of secondary air required to match the fuel ratio, is changed to the actual in-cylinder air-fuel ratio that is the time required for the exhaust gas to reach the secondary air supply location from the inside of the cylinder. Based on the means to find based on the requested secondary air volume Secondary air is provided with a means for controlling the secondary air supply means to supply.

  The air-fuel ratio of the exhaust gas at the secondary air supply location can be made to exactly match the target air-fuel ratio.

  FIG. 1 shows a case where the present invention is applied to a spark ignition type internal combustion engine. However, the present invention can also be applied to a compression ignition type internal combustion engine.

  Referring to FIG. 1, for example, 1 is an engine body having four cylinders, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is an intake valve, 7 is an intake port, and 8 is an exhaust. A valve, 9 is an exhaust port, and 10 is a spark plug. The intake port 7 is connected to a surge tank 12 via a corresponding intake branch pipe 11, and the surge tank 12 is connected to an air cleaner 14 via an intake duct 13. An air flow meter 15 for detecting the amount of intake air and a throttle valve 17 driven by an actuator 16 are disposed in the intake duct 13. An electronically controlled fuel injection valve 18 is disposed in each combustion chamber 5. These fuel injection valves 18 are connected to a fuel pump 20 through a common rail 19, and the fuel pump 20 is connected to a fuel tank 21.

  On the other hand, the exhaust port 9 is connected to a catalytic converter 23 having a relatively small capacity via an exhaust manifold 22. The catalytic converter 23 is connected to a relatively large capacity catalytic converter 25 via an exhaust pipe 24, and the catalytic converter 25 is connected to an exhaust pipe 26. The catalytic converters 23 and 25 include catalysts having oxidation ability, for example, three-way catalysts 23a and 25a. In the first embodiment of the present invention, a secondary air supply device 27 for supplying secondary air into the exhaust passage upstream of the catalytic converter 23 is provided. The secondary air supply device 27 includes, for example, a secondary air supply pipe 28 connected to a collecting portion of the exhaust manifold 22 and a secondary air supply pump 29 capable of controlling the discharge amount. When the secondary air supply pump 29 is actuated, secondary air is supplied to the secondary air supply location 30 in the collecting portion of the exhaust manifold 22.

  The electronic control unit 40 is composed of a digital computer, and is connected to each other by a bidirectional bus 41. A ROM (read only memory) 42, a RAM (random access memory) 43, a CPU (microprocessor) 44, an input port 45 and an output port 46 are connected. It comprises. A water temperature sensor 31 for detecting the engine cooling water temperature is attached to the cylinder block 2. An oil temperature sensor 32 for detecting the engine oil temperature is attached to the engine body 1. Further, a load sensor 50 for detecting the depression amount of the accelerator pedal 49 is attached to the accelerator pedal 49. Output signals of the air flow meter 15, the water temperature sensor 31, the oil temperature sensor 32, and the load sensor 50 are input to the input port 45 via the corresponding AD converters 47. Further, the input port 45 is connected with a crank angle sensor 51 that generates an output pulse every time the crankshaft rotates by a certain angle, for example, 30 crank angles. The intake air flow rate detected by the air flow meter 15, the engine coolant temperature Tw detected by the water temperature sensor 31, the engine oil temperature To detected by the oil temperature sensor 32, and the crank angle θ detected by the crank angle sensor 51 are constant time. Each time as a function of time t. The CPU 44 calculates the engine speed based on the output pulse from the crank angle sensor 51. On the other hand, the output port 46 is connected to the spark plug 10, the actuator 16, the fuel injection valve 18, the fuel pump 20, and the secondary air supply pump 29 via corresponding drive circuits 48.

  In the first embodiment according to the present invention, the temperature raising process is performed to raise the temperature of the three-way catalyst 23a. That is, for example, the temperature raising process is started when the three-way catalyst 23a is not activated, and when the three-way catalyst 23a is activated, the temperature raising process is stopped. Specifically, the in-cylinder air-fuel ratio that is the air-fuel ratio of the air-fuel mixture burned in the cylinder is switched to rich, and secondary air is supplied from the secondary air supply device 27.

  In this case, the ratio of air and fuel (hydrocarbon) supplied into the exhaust passage upstream of a certain position in the intake passage, the combustion chamber, and the exhaust passage is referred to as the air-fuel ratio of the exhaust gas at that position. In the first embodiment according to the present invention, a target exhaust gas air-fuel ratio that is a target value of the air-fuel ratio of the exhaust gas at the secondary air supply location 30 is set, and the actual air-fuel ratio of the exhaust gas is set to this target exhaust gas air-fuel ratio. A required secondary air amount, which is a secondary air amount necessary for matching, is obtained. Next, secondary air is supplied from the secondary air supply device 27 by the required secondary air amount.

  The required secondary air amount is roughly determined as follows. That is, first, the actual in-cylinder air-fuel ratio is calculated. Next, the amount of fuel actually supplied into the cylinder is calculated from the actual in-cylinder air-fuel ratio and the intake air amount. Next, the required total amount that is the total amount of air required to make the air-fuel ratio of the exhaust gas at the secondary air supply point 30 coincide with the target exhaust gas air-fuel ratio from the actual in-cylinder supplied fuel amount and the target exhaust gas air-fuel ratio. The amount of air is calculated. Next, the required secondary air amount is calculated by subtracting the intake air amount from the required total air amount.

  In this case, it takes time for the exhaust gas to reach the secondary air supply point 30 from the combustion chamber 5 or the exhaust valve 8. Therefore, when this time is referred to as the required time, in the first embodiment according to the present invention, the in-cylinder air-fuel ratio, the in-cylinder supplied fuel amount, the intake air amount, and the target exhaust gas air-fuel ratio that are the required time before the present time are set. Based on this, the current required secondary air amount is calculated. As a result, the air-fuel ratio of the exhaust gas at the secondary air supply location can be made to exactly match the target exhaust gas air-fuel ratio.

  That is, if the required secondary air flow rate, the required total air flow rate, and the intake air flow rate at time t are mai2 (t), maT (t), ma (t) and the required time is Δt, the request at the current time t0. The secondary air flow rate mai2 (t0) is calculated using the following equation (1).

  Here, the intake air flow rate ma (t) is repeatedly detected by the air flow meter 15 and stored in the RAM 43 as described above. Therefore, if the time (t0−Δt) is known, the intake air flow rate ma (t0−Δt) can be obtained from the RAM 43.

  On the other hand, if the fuel flow rate in exhaust gas (described later) and the target exhaust gas air-fuel ratio at time t are mf (t) and rafet (t), respectively, the required total air flow rate maT (t0) at the current time t0 is: Calculated using (2).

  Here, the target exhaust gas air-fuel ratio rafet (t) is set to the stoichiometric air-fuel ratio or slightly lean and stored in the ROM 42, and therefore the target exhaust gas air-fuel ratio rafet (t0-Δt) at time (t0-Δt). Is also set to a stoichiometric air fuel ratio or slightly lean. The target exhaust gas air-fuel ratio rafet (t) may be repeatedly set according to, for example, the intake air amount or the engine load, and stored in the RAM 43.

  The exhaust gas fuel flow rate mf (t) is repeatedly calculated and stored in the RAM 43 as described later. Therefore, if the time (t0−Δt) is known, the exhaust gas fuel flow rate mf (t0−Δt) can be obtained from the RAM 43.

  That is, roughly speaking, mat (t0) at the current time t0 is calculated from mf (t0-Δt) and rafet (t0-Δt) for combustion at time (t0-Δt), and mat (t0 at current time t0). That is, mai2 (t0) at the current time t0 is calculated from ma (t0-Δt) regarding combustion at time t0) and time (t0−Δt).

The fuel supplied into the cylinder is in two parts: a burned part that will be burned and included in the exhaust gas in the form of CO, CO ₂ or HC (hydrocarbon), and a form such as soot and deposit Therefore, the exhaust gas fuel flow rate mf (t) represents the flow rate of the burned portion.

  Then, assuming that the actual in-cylinder air-fuel ratio at time t is rafc (t), the exhaust gas fuel flow rate mf (t0) at the current time t0 is calculated using the following equation (3).

  Here, the actual in-cylinder air-fuel ratio rafc (t0) is calculated based on the combustion time Tc. That is, there is a correlation shown in FIG. 2 between the in-cylinder air-fuel ratio rafc and the combustion time Tc. Therefore, when combustion is performed, a combustion time Tc that is the time required for this combustion is calculated, and then the in-cylinder air-fuel ratio rafc at this time is calculated as rafc (t0) from the map shown in FIG. The map shown in FIG. 2 is obtained in advance by experiments and is stored in the ROM 42.

  When the actual in-cylinder air-fuel ratio rafc (t0) is calculated, the fuel flow rate mf (t0) in the exhaust gas is calculated using equation (3).

  The combustion time Tc is calculated based on, for example, the combustion completion timing θT. That is, the combustion completion timing θT (crank angle) is calculated, and the difference (θSA−θT) between the ignition timing θSA (crank angle) representing the combustion start timing and the combustion completion timing θT is calculated, and the combustion time Tc is calculated from this difference. Calculated.

  The combustion completion timing θT is calculated based on, for example, the heat generation rate. That is, for example, when the heat generation rate dQ (θ) / dθ is calculated for each predetermined crank angle Δθ and the heat generation rate dQ (θ) / dθ is integrated from the ignition timing θSA to the combustion completion timing θT, for example, The value should substantially match the theoretical heat generation amount QT of the fuel amount Mf supplied into the cylinder. That is, the following expression (4) is established.

  In the first embodiment according to the present invention, the theoretical heat generation amount QT is calculated, the heat generation rate dQ (θ) / dθ is calculated, and then θT satisfying the equation (4) is calculated.

  In this case, the theoretical heat generation amount QT of the in-cylinder supplied fuel amount Mf is calculated using, for example, the following equation (5).

  Here, q represents the lower heating value of the fuel, and α represents a coefficient (for example, 0.7 to 0.8) taking into account the loss and unburned amount, both of which are stored in the ROM 42 in advance.

  Further, the in-cylinder supplied fuel amount Mf is calculated using the following equation (6).

  Here, Δtcyl represents a cycle time that is a time required for one combustion cycle, and Δt180 represents an elapsed time that is a time required for the crank angle to advance by 180 crank angles. That is, roughly speaking, the in-cylinder supply fuel amount Mf represents the amount of fuel supplied to one cylinder in the previous combustion cycle. The cycle time Δtcyl and the elapsed time Δt180 are calculated based on, for example, the crank angle θ (t). On the other hand, if the cycle time Δtcyl is known, mf (t0−Δtcyl) can be obtained from the RAM 43.

  On the other hand, the heat release rate dQ (θ) / dθ is calculated using, for example, the following equation (7).

  Here, γ represents the specific heat ratio of the cylinder gas, Pc (θ) represents the cylinder pressure at the crank angle θ, and V (θ) represents the cylinder volume at the crank angle θ.

  The specific heat ratio γ is a constant value. The specific heat ratio γ may be a function of temperature.

  The in-cylinder volume V (θ) is stored in advance in the ROM 42 in the form of a map shown in FIG. 3 as a function of the crank angle θ. Further, the change rate dV (θ) / dθ of the in-cylinder volume is calculated from the in-cylinder volume V (θ).

  The in-cylinder pressure Pc (θ) can be detected by, for example, an in-cylinder pressure sensor, but is calculated using the following equation (8) in the first embodiment according to the present invention.

  Here, TQp (θ) represents an in-cylinder pressure torque that is a torque generated by the force exerted on the piston 4 by the in-cylinder pressure Pc (θ).

  The in-cylinder pressure torque TQp (θ) is calculated using the following equation (9) derived from the equation of motion for the crankshaft.

  Here, J (θ) is the moment of inertia of the engine body 1, ω (θ) is the crank angular velocity as a function of the crank angle θ, and TQm (θ) is caused by the inertia of a moving member such as a piston of the engine body 1. Inertial mass torque that is torque, TQf (θ) represents mechanical loss torque that is torque generated by mechanical loss of the engine body 1.

  The inertia moment J (θ) and the inertia mass torque TQm (θ) are stored in advance in the ROM 42 in the form of maps shown in FIGS. 4 and 5 as a function of the crank angle θ.

  The crank angular velocity ω (θ) is calculated by converting the crank angular velocity ω (t) as a function of time t into a function of the crank angle θ. The crank angular velocity ω (t) is calculated from the crank angle θ (t) as a function of time t using the following equation (10).

  Mechanical loss torque TQf (θ) is a function of crank angular velocity ω (θ), engine load factor KL (θ) as a function of crank angle θ, and engine oil temperature To (θ) as a function of crank angle θ. It is stored in advance in the ROM 42 in the form of a map shown in FIG.

  The engine load factor KL (θ) represents the ratio of the engine load to the total load. In the first embodiment of the present invention, the engine load factor KL (t) as a function of time t is calculated and stored in advance based on the intake air flow rate ma (t), and this KL (t) is stored in the crank angle. KL (θ) is calculated by converting θ (t) into a function of the crank angle θ.

  The engine oil temperature To (θ) is calculated by converting the engine oil temperature To (t) as a function of time t into a function of the crank angle θ using the crank angle θ (t).

  That is, the crank angular speed ω (θ) is calculated from the crank angle θ (t), and the mechanical loss torque TQf (θ) is calculated from the crank angular speed ω (θ), the engine load factor KL (θ), and the engine oil temperature To (θ). Calculated. Next, the in-cylinder pressure torque TQp (θ) is calculated from the moment of inertia J (θ), the crank angular velocity ω (θ), the inertia mass torque TQm (θ), and the mechanical loss torque TQf (θ) using Equation (8). . Next, the in-cylinder pressure Pc (θ) is calculated from the in-cylinder pressure torque TQp (θ) and the in-cylinder volume V (θ) using Equation (7). Next, the heat release rate dQ (θ) / dθ is calculated from the in-cylinder pressure Pc (θ) and the in-cylinder volume V (θ) using Equation (6).

  In the first embodiment according to the present invention, the heat generation rate dQ (θ) / dθ is calculated from the ignition timing θSA to the exhaust valve opening timing θEVO at every predetermined set crank angle interval Δθ. However, the heat generation rate dQ (θ) / dθ may be calculated from, for example, the intake valve closing timing θIVC before the start of combustion. The other crank speed ω (θ), engine load factor KL (θ), etc. may be calculated as long as necessary for calculating the heat release rate dQ (θ) / dθ.

  When the heat generation rate dQ (θ) / dθ is calculated, the combustion completion timing θT that satisfies the equation (4) is calculated. That is, the calculated heat generation rate dQ (θ) / dθ is sequentially integrated from the ignition timing θSA, and the crank angle θ at which this integrated value is approximately equal to the theoretical heat generation rate QT is calculated as the combustion completion timing θT. When the combustion completion timing θT is calculated, the combustion time Tc is calculated, and when the combustion time Tc is calculated, the cylinder air-fuel ratio rafc (t0) is calculated.

  Therefore, in general terms, the in-cylinder pressure Pc (θ) is obtained, and the actual in-cylinder air-fuel ratio is calculated based on the obtained in-cylinder pressure Pc (θ).

  Now, the required time Δt or the time (t0−Δt) before the current time t0 by the required time Δt is calculated as follows, for example.

  As described above, it takes a required time Δt for the exhaust gas to reach the secondary air supply point 30 from the exhaust valve 8. Then, if the exhaust gas amount satisfying the exhaust passage portion EX (FIG. 1) from the exhaust valve 8 to the secondary air supply location 30 is referred to as a required gas amount, the required gas amount at the current time t0 is the time (t0−Δt). Is equal to the integrated value of the amount of exhaust gas discharged from the current time to the current time t0.

  That is, if the volume of the exhaust passage portion EX is Vex, and the density and required gas amount of the exhaust gas that fills the exhaust passage portion EX at time t are ρ (t) and Mex (t), respectively, the required gas mass at the current time t0. Mex (t0) is calculated using the following equation (11).

  On the other hand, the mass of the exhaust gas discharged to the exhaust passage portion EX per unit time can be expressed as the sum of the intake air flow rate ma (t) and the exhaust gas fuel flow rate mf (t) (ma (t) + mf (T)). Therefore, the required gas mass Mex (t0) at the current time t0 is also expressed by the following equation (12).

  Therefore, in the first embodiment according to the present invention, the exhaust gas density ρ (t0) at the current time t0 is calculated, and the required gas amount Mex (t0) is calculated using the equation (11). Next, a time (t0−Δt) that satisfies Expression (12) is calculated.

  In the first embodiment according to the present invention, the exhaust gas density ρ (t) at time t is stored in advance in the ROM 42 in the form of a map shown in FIG. 7 as a function of the intake air flow rate ma (t) at time t. . Therefore, the exhaust gas density ρ (t0) is calculated using the intake air flow rate ma (t0). Further, the volume Vex of the exhaust passage portion is obtained in advance by experiments and is stored in the ROM 42. On the other hand, the intake air flow rate ma (t) and the exhaust gas fuel flow rate mf (t) can be obtained from the RAM 43.

  In other words, the sum (ma (t) + mf (t)) is sequentially integrated retroactively from the current time t0, and this integrated value is approximately equal to the required gas amount Mex (t0) calculated using the equation (11). t is calculated as time (t0−Δt).

  Next, fuel injection control in the first embodiment according to the present invention will be described. If the fuel injection flow rate command value, basic fuel injection flow rate, and correction coefficient at time t are mfi (t), mfi0 (t), and Δmfi (t), respectively, the fuel injection flow rate command value mfi (t0) at the current time t0 is Calculated using equation (13).

  Here, the correction coefficient Δmfi (t) is for compensating the fuel remaining in the cylinder or the like in the form of soot or deposit, and Δmfi (t) = 1.0 when there is no need for correction. .

  The basic fuel injection flow rate mfi0 (t) is a fuel injection flow rate necessary to make the in-cylinder air-fuel ratio rich. The basic fuel injection flow rate mfi0 (t0) at the current time t0 is the engine load factor KL (t0) and the target exhaust gas. It is calculated from the gas air-fuel ratio rafet (t0) using the following equation (14).

  Here, f1 (x, y) represents a function of x and y.

  Fuel is injected from the fuel injection valve 18 so that the actual fuel injection flow rate becomes the fuel injection flow rate command value mfi (t0).

  Therefore, in summary, in the first embodiment according to the present invention, the target exhaust gas air-fuel ratio rafet (t0) and the fuel injection flow rate command value mfi (t0) are calculated in the combustion cycle to which the current time t0 belongs, that is, the current combustion cycle. The fuel is injected according to the fuel injection flow rate command value mfi (t0). Next, combustion in the current combustion cycle is performed, and the actual in-cylinder air-fuel ratio rafc (t0), fuel flow in exhaust gas mf (t0), time (t0-Δt), required total air flow rate maT ( t0) are sequentially calculated and stored. Then, the required secondary air flow rate mai2 (t0) is calculated.

  FIG. 8 shows the temperature raising control routine of the first embodiment according to the present invention. This routine is executed by interruption every predetermined time.

  Referring to FIG. 8, first, at step 100, it is judged if the temperature raising process should be performed. When the temperature raising process should not be performed, the processing cycle is terminated. That is, in this case, the temperature raising process is not performed and the normal operation is performed. In normal operation, the in-cylinder air-fuel ratio is controlled to be, for example, the stoichiometric air-fuel ratio or slightly lean.

  Next, when the temperature raising process is to be performed, the routine proceeds to step 110 where the target exhaust gas air-fuel ratio rafet (t0) at the current time t0 is calculated and set. In the following step 200, a fuel injection routine is executed. This routine is illustrated in FIG. In the subsequent step 300, a routine for calculating the actual in-cylinder air-fuel ratio rafc (t0) at the current time t0 is executed. This routine is illustrated in FIG. In the subsequent step 400, a routine for calculating the time (t0−Δt) is executed. This routine is illustrated in FIG. In the subsequent step 500, a routine for calculating the required secondary air flow rate mai2 (t0) at the current time t0 is executed. This routine is illustrated in FIG. In the subsequent step 600, secondary air is supplied from the secondary air supply device 27 so that the actual secondary air flow rate matches the required secondary air flow rate mai2 (t0).

  Referring to FIG. 9 showing the fuel injection routine, in step 201, the basic fuel injection flow rate mfi0 (t0) at the current time t0 is calculated using equation (14). In the following step 202, the correction coefficient Δmfi (t0) at the current time t0 is calculated. In the subsequent step 203, the fuel injection flow rate command value mfi (t0) at the current time t0 is calculated using equation (13). In the following step 204, fuel is injected from the fuel injection valve 18 so that the actual fuel injection flow rate becomes the fuel injection flow rate command value mfi (t0).

  Referring to FIG. 10 showing the actual calculation routine for in-cylinder air-fuel ratio rafc (t0), in step 310, the calculation routine for the heat generation rate dQ (θ) / dθ is executed. This routine is illustrated in FIG. In the subsequent step 330, a routine for calculating the theoretical heat generation amount QT is executed. This routine is illustrated in FIG. In the subsequent step 350, the combustion completion timing θT is calculated using equation (4). In the subsequent step 370, the difference (θSA−θT) between the ignition timing θSA and the combustion completion timing θT is calculated, and the combustion time Tc is calculated from this difference. In the following step 390, the actual in-cylinder air-fuel ratio rafc (t0) at the current time t0 is calculated using the map of FIG.

  Referring to FIG. 11 showing a routine for calculating the heat release rate dQ (θ) / dθ, in step 311, the moment of inertia J (θ) is calculated using the map of FIG. In the following step 312, the crank angular speed ω (t) is calculated using the equation (10). In the subsequent step 313, the crank angular speed ω (θ) is calculated from the crank angular speed ω (t). In the subsequent step 314, the change rate dω (θ) / dt of the crank angular velocity ω (θ) is calculated. In the subsequent step 315, the inertial mass torque TQm (θ) is calculated using the map of FIG. In the subsequent step 316, the engine load factor KL (θ) is calculated from the engine load factor KL (t) and the crank angle θ (t). In the subsequent step 317, the engine oil temperature To (θ) is calculated from the engine oil temperature To (t) and the crank angle θ (t). In the subsequent step 318, the mechanical loss torque TQf (θ) is calculated using the map of FIG. In the following step 319, in-cylinder pressure torque TQp (θ) is calculated using equation (9). In the following step 320, the in-cylinder volume V (θ) is calculated using the map of FIG. In the subsequent step 321, the rate of change dV (θ) / dθ of the in-cylinder volume V (θ) is calculated. In the subsequent step 322, the in-cylinder pressure Pc (θ) is calculated using the equation (8). In the subsequent step 323, the change rate dPc (θ) / dθ of the in-cylinder pressure Pc (θ) is calculated. In the subsequent step 324, the heat generation rate dQ (θ) / dθ is calculated using the equation (7).

  Referring to FIG. 12 showing the calculation routine of the theoretical heat generation amount QT, in step 331, the cycle time Δtcyl is calculated. In the subsequent step 332, the in-cylinder supplied fuel flow rate mf (t0−Δtcyl) in the previous combustion cycle is read from the RAM 43. In the subsequent step 333, the elapsed time Δt180 is calculated. In the following step 334, the in-cylinder supplied fuel amount Mf is calculated using the equation (6). In the following step 335, the theoretical heat generation amount QT is calculated using the equation (5).

  Referring to FIG. 13 showing the calculation routine of time (t0−Δt), in step 401, the exhaust gas fuel flow rate mf (t0) at the current time t0 is calculated using equation (3). In the subsequent step 402, the exhaust gas density ρ (t0) at the current time t0 is calculated using the map of FIG. In the subsequent step 403, the required gas amount Mex (t0) is calculated using the equation (11). In the subsequent step 404, the time (t0−Δt) is calculated using the equation (12).

  Referring to FIG. 14 showing a routine for calculating the required secondary air flow rate mai2 (t0), in step 501, the exhaust gas fuel flow rate mf (t0-Δt) at time (t0-Δt) is read from the RAM 43. In the subsequent step 502, the target exhaust gas air-fuel ratio rafet (t0-Δt) at the time (t0-Δt) is read from the ROM. In the subsequent step 503, the required total air flow rate maT (t0) at the current time t0 is calculated using the equation (2). In the subsequent step 504, the intake air flow rate ma (t0-Δt) at the time (t0-Δt) is read from the RAM 43. In the subsequent step 505, the required secondary air flow rate mai2 (t0) at the current time t0 is calculated using the equation (1).

  Next, a second embodiment according to the present invention will be described.

  In the first embodiment of the present invention described above, the basic fuel injection flow rate mfi0 (t0) is calculated from the engine load factor KL (t0) and the target exhaust gas air-fuel ratio rafet (t0), and this basic fuel injection flow rate mfi0 (t0). Is corrected with a correction coefficient Δmfi (t0), thereby calculating a fuel injection flow rate command value mfi (t0).

  As described above, the correction coefficient Δmfi (t0) is for compensating for the fuel remaining in the cylinder. However, during cold operation, a large amount of fuel may still adhere to the inner wall surface of the cylinder and the air-fuel ratio of the exhaust gas at the secondary air supply location 30 may become leaner than the target exhaust gas air-fuel ratio rafet (t0). . Further, when the fuel remains in the cylinder in this way, the fuel adhering to the inner wall surface of the cylinder at the time of the warm operation is vaporized all at once, and this time the exhaust gas in the secondary air supply location 30 is emptied. The fuel ratio may become richer than the target exhaust gas air-fuel ratio rafet (t0).

  Here, as described above, assuming that the fuel supplied into the cylinder can be divided into two parts, the burned portion and the remaining portion, in order to solve this problem, the fuel injection amount should be corrected to increase by the amount of the remaining portion. That's fine.

  On the other hand, when the ratio of the amount of the burned portion to the amount of fuel supplied into the cylinder is referred to as a combustion ratio, this combustion ratio reflects the remaining portion amount in a reflective manner.

  Therefore, in the second embodiment according to the present invention, the target exhaust gas fuel flow rate, which is the fuel flow rate in the exhaust gas necessary for making the air-fuel ratio of the exhaust gas at the secondary air supply point 30 coincide with the target exhaust gas air-fuel ratio, is set to this value. By correcting with the combustion ratio, the basic fuel injection flow rate in the next combustion cycle is obtained.

  That is, if the fuel flow rate and the combustion ratio in the target exhaust gas at time t are mft (t) and rcomb (t), respectively, the basic fuel injection flow rate mfi0 (t0 + Δtcyl) at the next combustion cycle, that is, time (t0 + Δtcyl) is 15).

  The target exhaust gas fuel flow rate mft (t0) at the current combustion cycle, that is, the current time t0 is calculated using the following equation (16).

  Here, f2 (x, y) represents a function of x and y.

  On the other hand, the amount of fuel supplied into the cylinder at the current time t0 is represented by the fuel injection flow rate command value mfi (t0), and the amount of burned part at the current time t0 is the fuel flow rate mf (t0) in the exhaust gas as described above. ). Therefore, the combustion ratio rcomb (t0) at the current time t0 is calculated using the following equation (17).

  The basic fuel injection flow rate mfi0 (t0 + Δtcyl) calculated using the equation (15) is stored in the RAM 43. Next, at the time (t0 + Δtcyl), the fuel injection flow rate command value mfi (t0 + Δtcyl) is calculated from the basic fuel injection flow rate mfi0 (t0 + Δtcyl) using the equation (13).

  FIG. 15 shows the temperature raising control routine of the second embodiment according to the present invention. This routine is executed by interruption every predetermined time.

  Referring to FIG. 15, first, at step 100, it is determined whether or not the temperature raising process should be performed. When the temperature raising process should not be performed, the processing cycle is terminated. Next, when the temperature raising process is to be performed, the routine proceeds to step 110 where the target exhaust gas air-fuel ratio rafet (t0) at the current time t0 is calculated and set. In the following step 200, a fuel injection routine is executed. This routine is illustrated in FIG. In the subsequent step 300, a routine for calculating the actual in-cylinder air-fuel ratio rafc (t0) at the current time t0 is executed. This routine is illustrated in FIG. In the subsequent step 400, a routine for calculating the time (t0−Δt) is executed. This routine is illustrated in FIG. In the subsequent step 500, a routine for calculating the required secondary air flow rate mai2 (t0) at the current time t0 is executed. This routine is illustrated in FIG. In the subsequent step 600, secondary air is supplied from the secondary air supply device 27 so that the actual secondary air flow rate matches the required secondary air flow rate mai2 (t0). In the subsequent step 700, a routine for calculating the basic fuel injection flow rate mfi0 (t0 + Δtcyl) in the next combustion cycle is executed. This routine is illustrated in FIG.

  Referring to FIG. 16 showing the fuel injection routine, in step 201a, the basic fuel injection flow rate mfi0 (t0) at time t0 is read from the RAM 43. This basic fuel injection flow rate mfi0 (t0) is calculated and stored in the previous cycle. In the following step 202, the correction coefficient Δmfi (t0) at the current time t0 is calculated. In the subsequent step 203, the fuel injection flow rate command value mfi (t0) at the current time t0 is calculated using equation (13). In the following step 204, fuel is injected from the fuel injection valve 18 so that the actual fuel injection flow rate becomes the fuel injection flow rate command value mfi (t0).

  Referring to FIG. 17 showing a routine for calculating the basic fuel injection flow rate mfi0 (t0 + Δtcyl) in the next combustion cycle, in step 701, the target exhaust gas fuel flow rate mft (t0) at the current time t0 is calculated using the equation (16). Calculated. In the subsequent step 702, the combustion ratio rcomb (t0) at the current time t0 is calculated using equation (17). In the subsequent step 703, the basic fuel injection flow rate mfi0 (t0 + Δtcyl) at time (t0 + Δtcyl) is calculated using equation (15).

  Note that the basic fuel injection flow rate mfi0 (t0) of the current combustion cycle may be calculated in the current combustion cycle. In this case, the basic fuel injection flow rate mfi0 (t0) uses, for example, the following equation (18). Is calculated.

  Since other configurations and operations of the second embodiment according to the present invention are the same as those of the first embodiment according to the present invention, the description thereof will be omitted.

  Next, a third embodiment according to the present invention will be described.

  In each of the embodiments described so far, the exhaust gas density ρ (t) is calculated based on the intake air flow rate ma (t).

  However, particularly during transient operation, the intake air flow rate ma (t) may not accurately correspond to the density ρ (t) of the exhaust gas, and as a result, the required gas mass Mex (t) cannot be accurately obtained. There is a possibility that the time (t0−Δt) cannot be obtained accurately.

  Therefore, in the third embodiment according to the present invention, the density of the exhaust gas is obtained using the one-dimensional compressible Euler equation for the exhaust passage portion EX.

  That is, as shown in FIG. 18, the position along the central axis of the exhaust passage portion EX is x, and the density, velocity, and pressure of the exhaust gas at the time t and the position x are ρ (t, x), u ( Assuming that t, x) and p (t, x), the following equation (19) is established for the current time t0.

  Here, Q and E are vectors. E (t, x) represents the energy per unit volume of the exhaust gas at time t and position x.

  In FIG. 18, xsta represents the inlet of the exhaust passage portion EX, and xend represents the outlet of the exhaust passage portion EX and represents the secondary air supply location 30. The exhaust gas pressure p (t, xsta) at the time t and the position xsta can be considered as the in-cylinder pressure Pc (θEVO) at the valve opening timing θEVO of the exhaust valve 8.

  Therefore, the density ρ (t0, x) of the exhaust gas from the position xsta to xend is obtained by solving the equation (19) as p (t, xsta) = Pc (θEVO).

  Then, the required gas amount Mex (t0) at the current time t0 is calculated using the following equation (20).

  That is, in general terms, the in-cylinder pressure when the exhaust valve is opened is calculated, the exhaust gas density that fills the exhaust passage portion is calculated based on this in-cylinder pressure, and the required gas amount is calculated based on this density. It will be that.

  Next, the time (t0−Δt) is calculated from the equations (12) and (20).

  In this way, the exhaust gas density ρ (t, x) can be obtained more accurately, and therefore the time (t0−Δt) can be obtained more accurately.

  In the third embodiment according to the present invention, the temperature raising control routine shown in FIG. 8 is also executed. However, in step 400, the routine for calculating the time (t0−Δt) shown in FIG. 19 is executed.

  Referring to FIG. 14, first, at step 401, the exhaust gas fuel flow rate mf (t0) at the current time t0 is calculated using equation (3). In the subsequent step 402b, the exhaust gas density ρ (t0, x) at the current time t0 and the position x is calculated using the equation (19). In the subsequent step 403b, the required gas amount Mex (t0) is calculated using the equation (20). In the subsequent step 404, the time (t0−Δt) is calculated using the equation (12).

  The remaining structure and operation of the third embodiment according to the present invention are the same as those of the first embodiment according to the present invention, so description thereof will be omitted. Further, the third embodiment according to the present invention can be combined with the second embodiment.

  Next, a fourth embodiment according to the present invention will be described.

  In each of the embodiments described so far, the required time Δt or the required secondary air flow rate mai2 (t) is calculated on the assumption that the configurations of the cylinders are the same.

  However, as shown in FIG. 20, when the exhaust passage portion from the exhaust valve 8 of the i-th cylinder (i = 1, 2, 3, 4) to the secondary air supply location 30 is represented by EX (i), these exhausts. The passage portion EX (i) is not necessarily the same configuration, and therefore the volumes Vex (i) of the exhaust passage portion EX (i) of the i-th cylinder are not necessarily equal to each other. Required time Δt (i) in the i-th cylinder, required gas amount Mex (i, t) in the exhaust passage portion EX (i) of the i-th cylinder at time t, and exhaust passage portion EX (i) of the i-th cylinder at time t The same applies to the density ρ (i, t) of the exhaust gas inside, and the intake air flow rate of the i-th cylinder.

  Therefore, in the fourth embodiment according to the present invention, the required secondary air flow rate mai2 (t) is calculated by calculating the required time Δt (i) and the like for each cylinder. As a result, the required secondary air flow rate (t) can be calculated more accurately.

  Specifically, assuming that the intake air flow rate of the i-th cylinder at time t is ma (i, t), the intake air flow rate ma (i, t0) of the i-th cylinder at the current time t0 uses the following equation (21). (I = 1, 2, 3, 4).

  Here, k (i) is a distribution coefficient of the i-th cylinder and satisfies the following equation (22).

  Therefore, assuming that the fuel flow rate in the exhaust gas of the i-th cylinder at time t is mf (i, t), the fuel flow rate mf (i, t0) in the exhaust gas of the i-th cylinder at the current time t0 is expressed by the following equation (23). Is used to calculate.

  The in-cylinder air-fuel ratio rafc (t) is calculated based on the combustion time Tc of the combustion performed in the i-th cylinder.

  Therefore, the required gas amount Mex (i, t0) of the i-th cylinder at the current time t0 is expressed by the following equation (24).

  On the other hand, from the volume Vex (i) of the exhaust passage portion EX (i) and the density of exhaust gas ρ (i, t), the required gas amount Mex (i, t0) of the i-th cylinder at the current time t0 is expressed by the following equation ( 25).

  Here, the density ρ (i, t) of the exhaust gas of the i-th cylinder is calculated from the intake air flow rate ma (i, t) of the i-th cylinder using the map of FIG.

  Next, a time (t0−Δt (i)) that satisfies Expression (24) is calculated.

  Next, the required total air flow rate maT (t0) at the current time t0 is calculated using the following equation (26).

  Next, the required secondary air flow rate mai2 (t0) at the current time t0 is calculated using the following equation (27).

  FIG. 21 shows the temperature raising control routine of the fourth embodiment according to the present invention. This routine is executed by interruption every predetermined time.

  Referring to FIG. 21, first, at step 100, it is judged if the temperature raising process should be performed. When the temperature raising process should not be performed, the processing cycle is terminated. Next, when the temperature raising process is to be performed, the routine proceeds to step 105, where the intake air flow rate ma (i, t0) of the i-th cylinder at the current time t0 is calculated using the equation (21). In the following step 110, the target exhaust gas air-fuel ratio rafet (t0) at the current time t0 is calculated and set. In the following step 200, a fuel injection routine is executed. This routine is illustrated in FIG. In the subsequent step 300, a routine for calculating the actual in-cylinder air-fuel ratio rafc (t0) at the current time t0 is executed. This routine is illustrated in FIG. In the subsequent step 400c, a routine for calculating the time (t0−Δt (i)) is executed. This routine is illustrated in FIG. In the subsequent step 500c, a routine for calculating the required secondary air flow rate mai2 (t0) at the current time t0 is executed. This routine is illustrated in FIG. In the subsequent step 600, secondary air is supplied from the secondary air supply device 27 so that the actual secondary air flow rate matches the required secondary air flow rate mai2 (t0).

  Referring to FIG. 22 showing a calculation routine of time (t0−Δt (i)), in step 401c, the fuel flow rate mf (i, t0) in the exhaust gas of the i-th cylinder at the current time t0 uses equation (23). Is calculated. In the subsequent step 402c, the exhaust gas density ρ (i, t0) of the i-th cylinder at the current time t0 is calculated using the map of FIG. In the subsequent step 403c, the required gas amount Mex (i, t0) of the i-th cylinder is calculated using equation (25). In the subsequent step 404c, the time (t0−Δt (i)) is calculated using the equation (24).

  Referring to FIG. 23 showing a calculation routine of the required secondary air flow rate mai2 (t0), in step 501c, the exhaust gas fuel flow rate mf (t0-Δt (i)) at the time (t0-Δt (i)) is stored in the RAM 43. Is read from. In the subsequent step 502c, the target exhaust gas air-fuel ratio rafet (t0-Δt (i)) at the time (t0-Δt (i)) is read from the ROM. In the subsequent step 503c, the required total air flow rate maT (t0) at the current time t0 is calculated using equation (26). In the subsequent step 504c, the intake air flow rate ma (t0-Δt (i)) at the time (t0-Δt (i)) is read from the RAM 43. In the subsequent step 505c, the required secondary air flow rate mai2 (t0) at the current time t0 is calculated using equation (27).

  The remaining structure and operation of the fourth embodiment according to the present invention are the same as those of the first embodiment according to the present invention, so description thereof will be omitted. Further, the fourth embodiment according to the present invention can be combined with the second or third embodiment.

1 is an overall view of an internal combustion engine. It is a figure which shows the map which shows the correlation of combustion time Tc and in-cylinder air fuel ratio rafc. It is a figure which shows the map of cylinder internal volume V ((theta)). It is a figure which shows the map of inertia moment J ((theta)). It is a figure which shows the map of inertia mass torque TQm ((theta)). It is a figure which shows the map of mechanical loss torque TQf ((theta)). It is a figure which shows the map of exhaust gas density (rho). It is a flowchart which shows a temperature rising control routine. It is a flowchart which shows a fuel-injection routine. It is a flowchart which shows the calculation routine of actual cylinder air-fuel ratio rafc (t0). It is a flowchart which shows the calculation routine of heat release rate dQ ((theta)) / d (theta). It is a flowchart which shows the calculation routine of the theoretical heat generation amount QT. It is a flowchart which shows the calculation routine of time (t0-Δt). It is a flowchart which shows the calculation routine of the request | requirement secondary air flow rate mai2 (t0). It is a flowchart which shows the temperature rising control routine of 2nd Example by this invention. It is a flowchart which shows the fuel-injection routine of 2nd Example by this invention. It is a flowchart which shows the calculation routine of the basic fuel injection flow volume mfi0 (t0 + (DELTA) tcyl) of 4th Example by this invention. It is the schematic for demonstrating 3rd Example by this invention. It is a flowchart which shows the calculation routine of the time (t0- (DELTA) t) of 3rd Example by this invention. It is the schematic for demonstrating 4th Example by this invention. It is a flowchart which shows the temperature rising control routine of 4th Example by this invention. It is a flowchart which shows the calculation routine of the time (t0- (DELTA) t (i)) of 4th Example by this invention. It is a flowchart which shows the calculation routine of the request | requirement secondary air flow rate mai2 (t0) of 4th Example by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine body 5 Combustion chamber 8 Exhaust valve 18 Fuel injection valve 22 Exhaust manifold 23a Three-way catalyst 27 Secondary air supply device

Claims (4)

A catalyst having an oxidizing ability disposed in the engine exhaust passage, means for controlling the in-cylinder air-fuel ratio, and secondary air supply means for supplying secondary air to a secondary air supply location in the exhaust passage upstream of the catalyst And when the temperature of the catalyst is to be raised, the exhaust of the internal combustion engine is configured such that secondary air is supplied while the in-cylinder air-fuel ratio is controlled to be rich so that unburned components in the exhaust gas are oxidized on the catalyst. In the purifying apparatus, the actual in-cylinder air-fuel ratio is repeatedly determined and stored, and the amount of secondary air required to make the air-fuel ratio of the exhaust gas at the secondary air supply point coincide with the target exhaust gas air-fuel ratio. Means for determining a required secondary air quantity based on an actual in-cylinder air-fuel ratio that is a time required for exhaust gas to reach the secondary air supply location from the inside of the cylinder; Secondary air supply so that secondary air is supplied by the amount of air Comprising means for controlling the stage, and calculates a combustion ratio is the ratio of the fuel amount to be included in the exhaust gas with respect to the amount of fuel supplied to the cylinder, the next combustion on the basis of the combustion ratio An exhaust emission control device for an internal combustion engine that calculates a fuel injection amount of a cycle .   The required gas amount that is the amount of gas that fills the exhaust passage from the exhaust valve to the secondary air supply point is calculated, the integrated amount of exhaust gas discharged from the cylinder is calculated, and the integrated amount is the required gas amount. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein a time required to substantially match is calculated as the required time.   The in-cylinder pressure when the exhaust valve is opened is calculated, the density of exhaust gas filling the exhaust passage portion is calculated based on the in-cylinder pressure, and the required gas amount is calculated based on the density. An exhaust purification device for an internal combustion engine. The exhaust purification device for an internal combustion engine according to any one of claims 1 to 3 , wherein an in-cylinder pressure is obtained and an actual in-cylinder air-fuel ratio is obtained based on the obtained in-cylinder pressure.

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