JP4622888B2 - Exhaust control device for internal combustion engine - Google Patents

Description

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

  Particulate matter (particulate, particulate matter (hereinafter referred to as “PM” in this application)), which is one of harmful substances discharged from the combustion chamber of an internal combustion engine (particularly, diesel engine), It is widely known that it is mainly composed of soot (soot) made of carbon or the like and SOF (Soluble Organic Fraction) made of unburned HC or oil.

  In this PM, the SOF is generally attached to the surface of the soot (a state surrounding the surface of the soot). Here, since SOF is a soluble organic component, it has a lower combustion temperature than Soot, which is an insoluble component. That is, SOF is more easily combusted by the oxidizing action of the catalyst disposed in the exhaust passage as compared with Soot.

  In addition, when an SOF that is easily combusted starts to combust due to the oxidizing action of the catalyst, the soot that is hardly combusted (enclosed in the SOF) surrounded by the SOF can be combusted. Therefore, when the ratio of SOF in PM is increased, the heat of combustion due to the combustion of SOF due to the oxidizing action of the catalyst increases, and soot can be effectively burned in addition to SOF.

From the above, the exhaust emission control device described in Patent Document 1 performs additional fuel injection in order to increase the SOF ratio in PM after the main fuel injection. Thereby, in addition to the SOF amount in the PM, the soot amount in the PM can also be effectively reduced, so that the total amount of PM (≈SOF + Soot) discharged from the catalyst can be effectively reduced.
JP 2003-269221 A

  By the way, increasing the SOF ratio in PM means increasing unburned HC. Therefore, if the SOF ratio in the PM is excessively increased, new problems such as deterioration in fuel consumption and reduction in output occur. That is, in order to reduce the total amount of PM discharged from the catalyst while suppressing deterioration of fuel consumption, output decrease, etc., the SOF ratio in PM is positively controlled to a certain appropriate value (range). It is considered necessary.

  However, in the apparatus described in the above document, there is no disclosure or suggestion about positively controlling the PM component ratio. As described above, the apparatus described in the above document has a problem that there is a possibility of increasing fuel efficiency deterioration, output reduction, etc. by increasing the SOF ratio in PM too much.

  The present invention has been made in order to deal with such problems, and its purpose is to positively control the PM component ratio and to discharge outside while suppressing deterioration in fuel consumption, reduction in output, and the like. An object of the present invention is to provide an exhaust control device for an internal combustion engine that can reduce the total amount of PM.

  The exhaust control device according to the present invention is applied to an internal combustion engine provided with PM collection means for collecting PM disposed in an exhaust passage of the internal combustion engine. The PM trapping means is a catalyst (oxidation catalyst, DPNR catalyst, three-way catalyst, etc.) that can exhibit at least an oxidizing action.

The exhaust control apparatus according to the present invention includes a component ratio acquisition means for acquiring a component ratio of PM generated by combustion of fuel in the combustion chamber of the internal combustion engine and discharged from the combustion chamber, and the acquired PM component It is determined whether or not the ratio is within a predetermined range, and when the acquired PM component ratio is outside the predetermined range, the acquired PM component ratio is acquired so as to be within the predetermined range. And a component ratio control means for controlling the control parameter of the internal combustion engine based on the PM component ratio.

More preferably, the component ratio acquisition means is configured to acquire a ratio of SOF in the PM, and the component ratio control means determines whether the ratio of SOF in the acquired PM is within a predetermined range. When the ratio of SOF in the acquired PM is out of the predetermined range, the ratio of SOF acquired so that the ratio of SOF in the acquired PM falls within the predetermined range. Based on the control parameter.

  Here, as the control parameter, for example, fuel injection pressure, fuel injection timing, EGR rate, and the like can be used. The soot amount can be reduced by increasing the fuel injection pressure or decreasing the EGR rate, and the amount of unburned HC can be increased and the SOF amount can be increased by delaying the fuel injection timing. Accordingly, the PM component ratio (particularly, the SOF ratio in the PM) can be adjusted by controlling these.

According to the above configuration, the PM component ratio (particularly, the SOF ratio in the PM) is positively controlled to be within a predetermined range by controlling the control parameters such as the fuel injection pressure. Therefore, if the predetermined value (predetermined range) is set to an appropriate value (range) that takes into account the suppression of deterioration of fuel consumption, reduction in output, etc., and the reduction of the total amount of PM discharged from the PM trapping means. Further, it is possible to reduce the total amount of PM discharged from the PM trapping means (thus, discharged to the outside) while suppressing deterioration of fuel consumption, decrease in output, and the like.

  In this case, the component ratio acquisition means includes a soot amount acquisition means for acquiring the amount of soot in the PM discharged from the combustion chamber, and an SOF amount for acquiring the amount of SOF in the PM discharged from the combustion chamber. An acquisition means, and on the assumption that the PM consists only of soot and SOF, so as to acquire the ratio of SOF in the PM based on the acquired soot amount and the acquired SOF amount It is suitable to be configured.

  According to this, the SOF ratio in PM (= Soot + SOF) can be acquired by simple calculation based on the acquired amount of soot (concentration, etc.) and the acquired amount of sof (concentration, etc.). it can.

  Note that the amount of soot (concentration, etc.) in the PM discharged from the combustion chamber is, for example, the soot generation rate (increase rate of soot concentration) in the combustion chamber between the fuel injection start timing and the exhaust valve opening time. For example, by time integration over a period of time. Similarly, the amount of SOF (concentration, etc.) in the PM discharged from the combustion chamber is, for example, the SOF generation rate (increase rate of SOF concentration) in the combustion chamber from the fuel injection start timing to the exhaust valve opening time. It can be obtained by time integration over time.

  The SOF amount acquisition means includes hydrocarbon amount acquisition means for acquiring the amount of hydrocarbon (HC) generated in the combustion chamber, and acquires the SOF amount based on the acquired amount of hydrocarbon. Preferably it is comprised. The amount of SOF (concentration, concentration increase rate, etc.) in the PM discharged from the combustion chamber largely depends on the amount of hydrocarbon (HC) generated in the combustion chamber (concentration, concentration increase rate, etc.). Therefore, according to the above configuration, the SOF amount in the PM discharged from the combustion chamber can be obtained with high accuracy.

  In this case, specifically, for example, the SOF generation speed (SOF concentration increase speed) is obtained from the hydrocarbon generation speed (HC concentration increase speed) in the combustion chamber, and this SOF generation speed is determined as the fuel. The amount of SOF (concentration, etc.) in the PM discharged from the combustion chamber can be determined by time integration from the injection start timing to the exhaust valve opening time.

The hydrocarbon amount acquisition means acquires the amount of the hydrocarbon based on the amount of fuel injected into the combustion chamber and at least one amount of CO, CO ₂ and Soot generated in the combustion chamber. constructed it is Ru preferred der.

The amount of HC generated in the combustion chamber (concentration, concentration increase rate, etc.) is generated in the combustion chamber and the amount of fuel injected into the combustion chamber (injection speed, injection rate, fuel concentration, fuel concentration increase rate, etc.) the amount of contained carbon atoms other than HC components (CO, CO _2, etc.) largely depends on (concentration, increased speed of concentration). Therefore, according to the above configuration, the amount of HC generated in the combustion chamber can be acquired with high accuracy, and as a result, the amount of SOF in PM discharged from the combustion chamber can also be acquired with high accuracy.

  Embodiments of an exhaust control device (exhaust gas purification device) for an internal combustion engine (diesel engine) according to the present invention will be described below with reference to the drawings.

  FIG. 1 shows a schematic configuration of an entire system in which an exhaust control device for an internal combustion engine according to an embodiment of the present invention is applied to a four-cylinder internal combustion engine (diesel engine) 10. This system includes an engine main body 20 including a fuel supply system, an intake system 30 for introducing gas into a combustion chamber (in a cylinder) of each cylinder of the engine main body 20, and an exhaust system for discharging exhaust gas from the engine main body 20. 40, an EGR device 50 for performing exhaust gas recirculation, and an electric control device 60.

  A fuel injection valve (injection valve, injector) 21 is disposed above each cylinder of the engine body 20. Each fuel injection valve 21 is connected to a fuel injection pump 22 connected to a fuel tank (not shown) via a fuel pipe 23. The fuel injection pump 22 is electrically connected to the electric control device 60, and the actual injection pressure of the fuel by a drive signal from the electric control device 60 (command signal corresponding to a command final fuel injection pressure Pcrfin described later). The fuel is boosted so that (discharge pressure) becomes the command final fuel injection pressure Pcrfin.

  Thereby, the fuel injection valve 21 is supplied with fuel whose pressure has been increased from the fuel injection pump 22 to the command final fuel injection pressure Pcrfin. Further, the fuel injection valve 21 is electrically connected to the electric control device 60, and the drive signals from the electric control device 60 (command pilot fuel injection amount (mass) Qp, command main fuel injection amount (mass) Qm). The valve is opened by a command signal corresponding to As a result, the fuel boosted to the command final fuel injection pressure Pcrfin is directly pilot-injected directly into the combustion chamber by the command pilot fuel injection amount Qp, and then main injection by the command main fuel injection amount Qm. It is like that.

  The intake system 30 includes an intake manifold 31 connected to a combustion chamber of each cylinder of the engine body 20, an intake pipe 32 connected to an upstream side assembly of the intake manifold 31 and constituting an intake passage together with the intake manifold 31, an intake pipe A throttle valve 33 rotatably held in the throttle 32, a throttle valve actuator 33a for rotating the throttle valve 33 in response to a drive signal from the electric control device 60, and an intake pipe 32 upstream of the throttle valve 33. The mounted intercooler 34, the compressor 35a of the supercharger 35, and the air cleaner 36 disposed at the tip of the intake pipe 32 are included.

  The exhaust system 40 includes an exhaust manifold 41 connected to each cylinder of the engine body 20, an exhaust pipe 42 connected to a downstream gathering portion of the exhaust manifold 41, and a turbine of the supercharger 35 disposed in the exhaust pipe 42. And a diesel particulate filter (hereinafter referred to as “DPNR”) 43 interposed in the exhaust pipe 42. The exhaust manifold 41 and the exhaust pipe 42 constitute an exhaust passage. DPNR43 corresponds to the PM collecting means.

  The EGR device 50 includes an exhaust recirculation pipe 51 that constitutes a passage for recirculating exhaust gas (EGR passage), an EGR control valve 52 interposed in the exhaust recirculation pipe 51, and an EGR cooler 53. The exhaust gas recirculation pipe 51 communicates the upstream exhaust passage (exhaust manifold 41) of the turbine 35b and the downstream intake passage (intake manifold 31) of the throttle valve 33. The EGR control valve 52 can change the amount of exhaust gas to be recirculated (exhaust gas recirculation amount, EGR gas flow rate) in response to a drive signal from the electric control device 60.

  The electrical control device 60 is connected to each other via a bus 61, a ROM 62 that stores programs executed by the CPU 61, tables (look-up tables, maps), constants, and the like, and the CPU 61 temporarily stores data as necessary. The microcomputer includes a RAM 63, a backup RAM 64 that stores data while the power is on, and holds the stored data while the power is shut off, an interface 65 including an AD converter, and the like.

  The interface 65 includes a hot-wire air flow meter 71 disposed in the intake pipe 32, an intake air temperature sensor 72 provided in an intake passage downstream of the throttle valve 33 and downstream of a portion to which the exhaust gas recirculation pipe 51 is connected. An intake pipe pressure sensor 73, a crank position sensor 74, an accelerator opening sensor 75, and a fuel injection pump 22 disposed in the intake passage downstream of the valve 33 and downstream of the portion where the exhaust gas recirculation pipe 51 is connected. A fuel temperature sensor 76 and a water temperature sensor 77 disposed in the fuel pipe 23 in the vicinity of the discharge port are connected to each other, and signals from these sensors are supplied to the CPU 61.

  The interface 65 is connected to the fuel injection valve 21, the fuel injection pump 22, the throttle valve actuator 33a, and the EGR control valve 52, and sends drive signals to these in accordance with instructions from the CPU 61. Yes.

  The hot-wire air flow meter 71 measures the mass flow rate of intake air (intake air amount per unit time, fresh air amount per unit time) passing through the intake passage and represents the same mass flow rate Ga (air flow rate Ga). A signal is generated. The intake air temperature sensor 72 detects the temperature of the gas drawn into the cylinder (ie, the combustion chamber, the cylinder) of the engine 10 (ie, the intake air temperature), and generates a signal representing the intake air temperature Tb. Yes. The intake pipe pressure sensor 73 detects the pressure of gas taken into the cylinder of the engine 10 (that is, the intake pipe pressure) and generates a signal representing the intake pipe pressure Pb.

  The crank position sensor 74 detects the absolute crank angle of each cylinder, and generates a signal that represents the actual crank angle CAact and also represents the engine rotational speed NE that is the rotational speed of the engine 10. The accelerator opening sensor 75 detects an operation amount of the accelerator pedal AP and generates a signal representing the accelerator operation amount Accp. The fuel temperature sensor 76 detects the temperature of the fuel passing through the fuel pipe 23 and generates a signal representing the fuel temperature Tcr. The water temperature sensor 77 detects the temperature of the cooling water and generates a signal indicating the cooling water temperature THW.

(Outline of gas flow around the combustion chamber)
FIG. 2 schematically shows a state in which gas is sucked from the intake manifold 31 into a cylinder of a certain cylinder (cylinder, combustion chamber), and the gas sucked into the combustion chamber is discharged to the exhaust manifold 41. It is a figure. As shown in FIG. 2, the gas sucked into the combustion chamber (accordingly, in-cylinder gas) includes fresh air sucked from the tip of the intake pipe 32 through the throttle valve 33, and exhaust gas recirculation pipe 51. EGR gas sucked through the EGR control valve 52 is included.

  The ratio of the amount of EGR gas to the sum of the amount of fresh air (mass) to be sucked and the amount of mass of EGR (mass) to be sucked (that is, the EGR rate) is appropriately controlled by the electric control device 60 (CPU 61) according to the operating state. It changes according to the opening of the throttle valve 33 and the opening of the EGR control valve 52.

  The fresh air and EGR gas are sucked into the combustion chamber as the piston descends via the intake valve Vin opened in the intake stroke, and become in-cylinder gas. The in-cylinder gas is sealed in the combustion chamber when the intake valve Vin closes near the time when the piston reaches compression bottom dead center, and is compressed as the piston rises in the subsequent compression stroke.

  At a predetermined time, pilot injection is first performed as described above. Pilot-injected (liquid) fuel immediately becomes fuel vapor due to heat received from the in-cylinder gas that has become hot due to compression. As the time elapses, the gas in the cylinder is taken in and becomes an air-fuel mixture that diffuses in a conical shape in the combustion chamber and diffuses and burns due to self-ignition at a predetermined timing.

  Thereafter, main injection is performed. As with the pilot-injected fuel, the main-injected fuel also becomes an air-fuel mixture and diffuses conically in the combustion chamber, and diffuses and burns due to self-ignition at a predetermined timing. The exhaust gas generated by the combustion is discharged into the exhaust passage as the piston moves up and down through the exhaust valve Vout that opens in the exhaust stroke.

(Hydrocarbon content estimation method)
An internal combustion engine exhaust control device (hereinafter referred to as “the present device”) according to an embodiment of the present invention configured as described above is provided from a combustion chamber as will be described in detail later with reference to a flowchart. The ratio (mass ratio) of SOF in the discharged PM (hereinafter referred to as “SOF / PM”) is calculated. In the SOF / PM calculation process, the increase rate d [HC] / dt of the concentration [HC] of hydrocarbons (hereinafter referred to as “HC”) generated in the combustion chamber is discharged from the pilot fuel injection start timing. It is necessary to obtain sequentially until the opening time of the valve Vout. Hereinafter, a method for obtaining the HC concentration increase rate d [HC] / dt by the present apparatus will be described. In this example, “concentration” means the average mass concentration in the gas in the combustion chamber.

When attention is paid to the number of carbon atoms in the gas in the combustion chamber, supply of fuel (in this example, C14H28) to the combustion chamber is considered as a factor that increases the increase rate of HC generated in the combustion chamber. As a factor for reducing the increase rate of HC generated in the combustion chamber, the generation of components containing carbon atoms C other than HC generated by the combustion of fuel in the combustion chamber can be considered. Here, as a representative example of “a component containing carbon atoms C other than HC generated in the combustion chamber”, carbon monoxide CO, carbon dioxide CO ₂ , and soot can be considered.

Considering the above, the following equation (1) is established. In equation (1), d [Fuel] / dt is the rate of increase in the fuel concentration [Fuel], d [CO] / dt is the rate of increase in the CO concentration [CO], and d [CO ₂ ] / dt is the CO ₂ concentration [ The increasing rate of CO ₂ ], d [Soot] / dt, is the increasing rate of the Soot concentration [Soot]. M _HCave is the average molecular weight of HC, M _C14H28 is the molecular weight of fuel (C14H28), M _CO is the molecular weight of CO, M _CO2 is the molecular weight of CO ₂ , and M _Soot is the molecular weight of Soot. N _HCave is the average number of carbon atoms in the HC molecule, and N _Soot is the average number of carbon atoms in the Soot molecule.

In the formula (1), the left side represents the number of moles of carbon atoms in HC that increase per unit mass of the gas in the combustion chamber and per unit time. Similarly, the first term on the right side is the number of moles of carbon atoms in the fuel increasing per unit mass and per unit time of the gas in the combustion chamber, and the second term on the right side is per unit mass and per unit time of the gas in the combustion chamber. The number of moles of carbon atoms in CO increasing, the third term on the right side is the number of moles of carbon atoms in CO ₂ increasing per unit mass and per unit time of the gas in the combustion chamber, and the fourth term on the right side is the gas in the combustion chamber Represents the number of moles of carbon atoms in the soot that increases per unit mass of the nuclei and per unit time.

Here, the fuel concentration increase rate d [Fuel] / dt, the CO concentration increase rate d [CO] / dt, the CO ₂ concentration increase rate d [CO ₂ ] / dt, and the Soot concentration increase rate d [Soot] / dt As will be described later with reference to the flowchart, each can be obtained sequentially while using a previously prepared table in correspondence with the crank angle.

  Therefore, the present apparatus converts the HC concentration increase rate d [HC] / dt to the pilot fuel injection start timing according to the following equation (2) obtained by solving the above (1) for the HC concentration increase rate d [HC] / dt. To the exhaust valve Vout until the valve opening timing.

As described above, this apparatus contains carbon atoms that are components other than the fuel injection amount (fuel concentration increase rate d [Fuel] / dt) into the combustion chamber and at least one hydrocarbon generated in the combustion chamber. The amount of hydrocarbon (d [HC] / dt) is acquired based on the amount of component (d [CO] / dt, d [CO ₂ ] / dt, d [Soot] / dt).

(Actual operation)
Next, the actual operation of the exhaust control device for the internal combustion engine configured as described above will be described. The CPU 61 is configured to repeatedly execute a routine for performing SOF / PM control shown in a series of flowcharts in FIGS. 3 to 5 for each cylinder every predetermined time. Accordingly, when the predetermined timing is reached, the CPU 61 starts processing from step 300 and proceeds to step 305 to determine whether or not the intake valve Vin has changed from the open state to the closed state (when the intake valve is closed (IVC)). If it is determined as “No”, the process immediately proceeds to step 395 to end the present routine tentatively.

  Assuming that the intake valve closing time has arrived, the CPU 61 makes a “Yes” determination when proceeding to step 305 and proceeds to step 310 where the IVC crank angle CAivc is acquired from the crank position sensor 74 at this time. Is set to the actual crank angle CAact value, the IVC in-cylinder gas pressure Pgivc is set to the current intake pipe pressure Pb value obtained from the intake pipe pressure sensor 73, and the IVC in-cylinder gas temperature Tgivc is set to the intake air temperature. The current intake air temperature Tb obtained from the sensor 72 is set, the IVC engine speed NEivc is set to the current engine speed NE obtained from the crank position sensor 74, and the IVC cooling water temperature THWivc is set. Is set to the value of the current cooling water temperature THW acquired from the water temperature sensor 77.

  Subsequently, the CPU 61 proceeds to step 315 to set the IVC hour cylinder gas pressure Pgivc, the IVC hour cylinder gas temperature Tgivc, the IVC hour cylinder volume Vg (CAivc), The total mass Mg of the in-cylinder gas is obtained based on the equation described in step 315 based on the state equation. The IVC in-cylinder volume Vg (CAivc) is a value when CA = CAivc in the in-cylinder volume Vg (CA) which is a function of the crank angle CA obtained from the design specifications. R is a gas constant (a constant in this example). According to this calculation, at the time of IVC, the pressure and temperature of the in-cylinder gas are close to the set IVC in-cylinder gas pressure Pgivc and the set IVC in-cylinder gas temperature Tgivc, respectively. Based on the facts.

  Next, the CPU 61 proceeds to step 320, where the current accelerator opening Accp obtained by the accelerator opening sensor 75, the current engine speed NE obtained from the crank position sensor 74, and the table (map) shown in FIG. ) The command fuel injection amount Qfin (= command pilot fuel injection amount Qp + command main fuel injection amount Qm) is obtained from MapQfin. The table MapQfin is a table that defines the relationship between the accelerator opening degree Accp, the engine speed NE, and the command fuel injection amount Qfin (= Qp + Qm), and is stored in the ROM 62.

  Next, the CPU 61 proceeds to step 325, where the pilot fuel injection start timing (crank angle) CAinjp and the main fuel injection start timing (crank angle) are determined from the command fuel injection amount Qfin, the engine speed NE, and the table MapCAinj shown in FIG. ) Determine CAinjm. The table MapCAinj is a table that defines the relationship between the command fuel injection amount Qfin and the engine rotational speed NE, the pilot fuel injection start timing CAinjp, and the main fuel injection start timing CAinjm, and is stored in the ROM 62.

  Subsequently, the CPU 61 proceeds to step 330 to determine the basic fuel injection pressure Pcrbase from the command fuel injection amount Qfin, the engine speed NE, and the table MapPcrbase shown in FIG. The table MapPcrbase is a table that defines the relationship between the command fuel injection amount Qfin and the engine rotational speed NE and the basic fuel injection pressure Pcrbase, and is stored in the ROM 62.

  Next, the CPU 61 proceeds to step 335 and sets both the concentration of SOF discharged from the combustion chamber [SOF] and the concentration of soot discharged from the combustion chamber [Soot] to an initial value “0”.

  Subsequently, the CPU 61 proceeds to step 340 and based on the IVC engine speed NEivc, the minute crank angle ΔCA (constant), and the function funcΔt for obtaining the minute time Δt using NE and ΔCA as arguments. A minute time Δt is obtained. The minute time Δt is a time corresponding to the minute crank angle ΔCA when the engine speed NE = NEivc (the time required for the crank angle to advance by the minute crank angle ΔCA).

  Next, the CPU 61 proceeds to step 345, sets the calculated crank angle CA to a value equal to the pilot fuel injection start time CAinjp obtained in the previous step 325, and proceeds to step 405 in FIG.

  When the CPU 61 proceeds to step 405, the engine rotational speed NEivc at IVC, the total mass Mg of the in-cylinder gas, the in-cylinder gas pressure Pgivc at the IVC, the in-cylinder gas temperature Tgivc at the IVC, and the command pilot fuel, which are obtained as described above Injection amount Qp, command main fuel injection amount Qm, pilot fuel injection start timing CAinjp, main fuel injection start timing CAinjm, basic fuel injection pressure Pcrbase, IVC cooling water temperature THWivc (hereinafter, these 10 values are referred to as “specific parameter values”. The fuel concentration increase rate d [Fuel] / dt at the crank angle CA is obtained from the calculated crank angle CA (currently equal to CAinjp by the processing of step 345) and the table MapdFuel. . The table MapdFuel is a table created in advance through experiments or the like that prescribes the relationship between the specific parameter value and the crank angle and the fuel concentration increase rate d [Fuel] / dt, and is stored in the ROM 62.

  Subsequently, the CPU 61 proceeds to step 410 to obtain the CO concentration increase rate d [CO] / dt at the crank angle CA from the specific parameter value, the calculated crank angle CA, and the table MapdCO. The table MapdCO is a table created through experiments and the like that prescribes the relationship between the specific parameter value and the crank angle and the CO concentration increase rate d [CO] / dt, and is stored in the ROM 62.

Next, the CPU 61 proceeds to step 415 to obtain the CO ₂ concentration increase rate d [CO ₂ ] / dt at the crank angle CA from the specific parameter value, the calculated crank angle CA, and the table MapdCO ₂ . The table MapdCO ₂ is a table created through experiments and the like that prescribes the relationship between the specific parameter value and the crank angle and the CO ₂ concentration increase rate d [CO ₂ ] / dt, and is stored in the ROM 62.

  Next, the CPU 61 proceeds to step 420, and obtains the soot concentration increase rate d [Soot] / dt at the crank angle CA from the specific parameter value, the calculated crank angle CA, and the table MapedSoot. The table MapedSoot is a table created through experiments and the like that prescribes the relationship between the specific parameter value and the crank angle and the soot concentration increase rate d [Soot] / dt, and is stored in the ROM 62.

Subsequently, the CPU 61 proceeds to step 425 to determine the fuel concentration increase rate d [Fuel] / dt, the CO concentration increase rate d [CO] / dt, the CO ₂ concentration increase rate d [CO ₂ ] / dt, and Based on the soot concentration increase rate d [Soot] / dt and the above equation (2), the calculated HC concentration increase rate d [HC] / dt at the crank angle CA is obtained.

  Next, the CPU 61 proceeds to step 430 to obtain the constant k, the IVC engine speed NEivc, the command fuel injection amount Qfin, the calculated HC concentration increase rate d [HC] / dt, and the function func. Based on this, the increasing speed d [SOF] / dt of the SOF concentration [SOF] at the calculated crank angle CA is obtained.

This function func is a function for obtaining the SOF concentration increase rate d [SOF] / dt with k, NE, Qfin (value corresponding to torque) and d [HC] / dt as arguments. Jiaotong University P-QTAN, Journal
of the Energy Institute, September 2004, 77, pp 68-75 ”. Thus, the amount of SOF (d [SOF] / dt) is acquired based on the amount of hydrocarbon (d [HC] / dt).

  Subsequently, the CPU 61 proceeds to step 435 and sets the SOF concentration increase rate d [SOF] / SOF to the value of the SOF concentration [SOF] at that time (currently “0” by the processing of the previous step 335). The value of SOF concentration [SOF] is updated by adding a value obtained by multiplying dt by the minute time Δt obtained in the previous step 340 (= increase amount of SOF concentration [SOF] during minute time Δt).

  Next, the CPU 61 proceeds to step 440 and sets the soot concentration [Sot] value at that time (currently “0” by the processing of the previous step 335) to the soot concentration increase rate obtained in the previous step 420. By adding a value obtained by multiplying d [Soot] / dt by the minute time Δt obtained in the previous step 340 (= an increase amount of the Soot concentration [Soot] during the minute time Δt), the Soot concentration [Soot] is increased. Update the value.

Next, the CPU 61 proceeds to step 505 in FIG. 5 and adds the minute crank angle ΔCA to the calculated crank angle CA at that time (currently equal to CAinjp by the processing of the previous step 345). The crank angle CA is updated, and in the subsequent step 510, it is determined whether or not the updated calculated crank angle CA exceeds the valve opening timing (crank angle) CA _EVO of the exhaust valve Vout.

At present, the calculated crank angle CA (= CAinjp + ΔCA) does not exceed the exhaust valve opening timing CA _EVO . Accordingly, the CPU 61 makes a “No” determination at step 510 to return to step 405 in FIG. 4, and again executes the series of processing in steps 405 to 440 in FIG. 4 and step 505 in FIG.

A series of processes in steps 405 to 440 in FIG. 4 and step 505 in FIG. 5 are repeatedly executed until the calculated crank angle CA updated by the repeated execution of step 505 exceeds the exhaust valve opening timing CA _EVO. Go. Thereby, in steps 435 and 440, the SOF concentration [SOF] and the Soot concentration [Soot] are updated.

When the calculated crank angle CA exceeds the exhaust valve opening timing CA _EVO , when the CPU 61 proceeds to step 505, it determines “Yes” and proceeds to step 515. It should be noted that the SOF concentration [SOF] and the Soot concentration [Soot] updated at Steps 435 and 440, respectively, at this point in time are the SOF amount in the PM discharged from the combustion chamber (the SOF in the exhaust gas). Concentration) and the amount of soot in the PM discharged from the combustion chamber (soot concentration in the exhaust gas).

  When the CPU 61 proceeds to step 515, the combustion is performed based on the respective values of the SOF concentration [SOF] and the soot concentration [Soot] updated in the previous steps 435 and 440 and the formula described in step 515, respectively. The value of SOF / PM, which is the SOF ratio in PM discharged from the chamber, is calculated. This calculation is based on the assumption that PM consists only of Soot and SOF.

  Subsequently, the CPU 61 proceeds to step 520 to determine whether or not the obtained value SOF / PM is not less than the first predetermined value α1 and not more than the second predetermined value α2 (> α1). The first predetermined value α1 is a lower limit value (a constant in this example) of the value SOF / PM determined from the viewpoint of reducing the total amount of PM discharged from the DPNR 43 (PM collecting means). The second predetermined value α2 is an upper limit value (constant in this example) of the value SOF / PM determined from the viewpoint of suppressing fuel consumption deterioration and output reduction.

  When the CPU 61 determines “Yes” in step 520 (α1 ≦ SOF / PM ≦ α2), the CPU 61 proceeds to step 525 and determines the basic fuel injection pressure Pcrbase obtained in the previous step 330 as the command final fuel injection pressure Pcrfin. Set to an equal value.

  On the other hand, if the CPU 61 determines “No” in step 520, it proceeds to step 530, determines whether the value SOF / PM is smaller than the first predetermined value α 1, and determines “Yes” (SOF In step 535, the command final fuel injection pressure Pcrfin is set to a value obtained by adding the adjustment value ΔPcr (positive constant) to the basic fuel injection pressure Pcrbase. This is based on the following reason.

  That is, it is known that the amount of soot discharged from the combustion chamber decreases as the fuel injection pressure increases. This is presumably because the fuel spray particle size decreases as the fuel injection pressure increases, and the reaction between fuel and oxygen is further promoted. On the other hand, a decrease in the amount of soot discharged from the combustion chamber means that the value SOF / PM increases (see the formula described in step 515). From the above, when the fuel injection pressure is increased, the value SOF / PM can be increased.

  On the other hand, when the CPU 61 makes a “No” determination at step 520 (SOF / PM> α2), the CPU 61 proceeds to step 540 to change the command final fuel injection pressure Pcrfin from the basic fuel injection pressure Pcrbase to the adjustment value ΔPcr (positive constant). ) Is subtracted. Contrary to the above, this is based on the fact that the value SOF / PM can be reduced by reducing the fuel injection pressure.

  Then, the CPU 61 proceeds to step 545 to instruct the fuel injection pump 22 so that the fuel injection pressure matches the command final fuel injection pressure Pcrfin obtained above, and then proceeds to step 395 to end the present routine temporarily. To do.

  Here, the time point at which the step 545 is executed is immediately after the time when the present intake valve closing time (IVC time) arrives (ie, when “Yes” is determined in the step 305) (that is, the current time) The actual pilot fuel injection start timing is sufficiently earlier than CAinjp). Therefore, by executing step 545, the fuel injection pressure can be adjusted to coincide with the determined final fuel injection pressure Pcrfin obtained before the actual actual pilot fuel injection start timing CAinjp.

  As a result, by adjusting the fuel injection pressure (control parameter) before the current fuel injection, the SOF ratio (SOF / PM) in the PM discharged from the combustion chamber after the combustion based on the current fuel injection is the first predetermined value. It can be positively controlled to be not less than the value α1 and not more than the second predetermined value α2 (predetermined value, predetermined range).

  Further, the CPU 61 repeatedly executes a routine for performing the fuel injection control shown in the flowchart of FIG. 9 for each cylinder every predetermined time. Therefore, when the predetermined timing is reached, the CPU 61 starts the process from step 900, proceeds to step 905, and determines whether or not the actual crank angle CAact coincides with the pilot fuel injection start timing CAinjp determined in the previous step 325. When the determination is “No”, the process proceeds to step 915 to determine whether or not the actual crank angle CAact coincides with the main fuel injection start timing CAinjm determined in the previous step 325. ”, The process immediately proceeds to step 995 to end the present routine tentatively.

  Assuming that the actual crank angle CAact coincides with the pilot fuel injection start timing CAinjp, the CPU 61 determines “Yes” when it proceeds to step 905, proceeds to step 910, and proceeds to the corresponding fuel injection valve 21. Then, an instruction to inject fuel of the command pilot fuel injection amount Qp determined in step 320 is issued, and in step 915, the determination is “No”. Then, the process proceeds to step 995, and this routine is temporarily ended. As a result, the fuel of the command pilot fuel injection amount Qp is injected at the command final fuel injection pressure Pcrfin described above.

  Thereafter, assuming that the actual crank angle CAact coincides with the main fuel injection start timing CAinjm, the CPU 61 makes a “No” determination at step 905 to determine “Yes” when the operation proceeds to step 915, and then proceeds to step 920. Then, after instructing the corresponding fuel injection valve 21 to inject the fuel of the command main fuel injection amount Qm determined in step 320, the routine proceeds to step 995 and this routine is once ended. Thereby, the fuel of the command main fuel injection amount Qm is injected at the command final fuel injection pressure Pcrfin described above.

  As described above, step 515 corresponds to the component ratio acquisition means, step 545 corresponds to the component ratio control means, step 435 corresponds to the SOF amount acquisition means, step 440 corresponds to the soot amount acquisition means, and step 425 corresponds to the carbonization. This corresponds to a hydrogen amount acquisition means.

  As described above, according to the embodiment of the exhaust control device of the present invention, the SOF in the PM discharged from the combustion chamber after combustion based on the current fuel injection is adjusted by adjusting the current fuel injection pressure. The ratio (SOF / PM) can be positively controlled to be not less than the first predetermined value α1 and not more than the second predetermined value α2. Thereby, it is possible to reduce the total amount of PM discharged from the DPNR 43 (thus, discharged to the outside) while suppressing deterioration of fuel consumption, output decrease, and the like.

  Further, the HC concentration increase rate d [HC] / dt used for calculating the value SOF / PM pays attention to the number of carbon atoms in the gas in the combustion chamber, so that the increase rate of HC generated in the combustion chamber "Supplying fuel to the combustion chamber", which causes the increase of the HC, and "carbon atoms other than HC generated by the combustion of the fuel in the combustion chamber, causing the increase rate of HC generated in the combustion chamber to decrease" It is calculated in consideration of the “generation of components containing”. Therefore, since the HC concentration increase rate d [HC] / dt can be calculated with high accuracy, the value SOF / PM can also be calculated with high accuracy.

  The present invention is not limited to the above embodiment, and various modifications can be employed within the scope of the present invention. For example, in the above embodiment, the value SOF / PM is not less than the first predetermined value α1 and not more than the second predetermined value α2 by adjusting the soot amount by adjusting the command final fuel injection pressure Pcrfin (and hence the fuel injection pressure). The value SOF / PM is controlled within the range between the first predetermined value α1 and the second predetermined value α2 by adjusting the soot amount by adjusting the EGR rate. It may be configured. Further, the value SOF / PM is controlled within the range between the first predetermined value α1 and the second predetermined value α2 by adjusting the fuel injection timing and adjusting the amount of unburned HC (that is, the amount of SOF). You may comprise.

  In the above embodiment, the value SOF / PM is controlled within the range of the first predetermined value α1 or more and the second predetermined value α2 or less, but the value SOF / PM is the first predetermined value α1 or more. Thus, the value may be controlled to a certain value equal to or less than the second predetermined value α2.

  In the above embodiment, the first predetermined value α1 and the second predetermined value α2 that are the upper limit value and the lower limit value of the value SOF / PM are constant. However, the first predetermined value α2 is constant depending on the operating state of the engine. The value α1 and the second predetermined value α2 may be variable.

In the above embodiment, the fuel concentration increase rate d [Fuel] / dt, the CO concentration increase rate d [CO] / dt, and the CO ₂ concentration increase rate d [CO ₂ , which are necessary for calculating the value SOF / PM. ] / Dt and Soot concentration increase rate d [Soot] / dt are obtained using corresponding tables, respectively, but these values may be obtained using a sensor.

  In addition, when the PM concentration [PM] in the exhaust gas is directly detected using a sensor that detects the PM concentration in the exhaust gas, the equation (SOF / PM = [SOF] / ([SOF] ] + [Soot])), the value SOF / PM may be calculated according to the equation (SOF / PM = [SOF] / [PM]). Further, the value SOF / PM may be calculated according to the equation (SOF / PM = ([PM] − [Soot]) / [PM]).

1 is a schematic configuration diagram of an entire system in which an exhaust control device for an internal combustion engine according to an embodiment of the present invention is applied to a four-cylinder internal combustion engine (diesel engine). It is the figure which showed typically a mode that the gas was suck | inhaled from the intake manifold in the cylinder (cylinder) of a certain cylinder, and the gas suck | inhaled in the cylinder was discharged | emitted to an exhaust manifold. 3 is a flowchart showing a first part of a routine for controlling an SOF ratio SOF / PM in PM executed by the CPU shown in FIG. 1. 3 is a flowchart showing a second part of a routine for controlling the SOF ratio SOF / PM in PM executed by the CPU shown in FIG. 1. 6 is a flowchart showing a third portion of a routine for controlling the SOF ratio SOF / PM in the PM executed by the CPU shown in FIG. 1. 4 is a table for determining a command fuel injection amount to be referred to when the CPU shown in FIG. 1 executes the routine shown in FIG. FIG. 4 is a table for determining a fuel injection timing that is referred to when the CPU shown in FIG. 1 executes the routine shown in FIG. 3. 4 is a table for determining a basic fuel injection pressure to be referred to when the CPU shown in FIG. 1 executes the routine shown in FIG. 2 is a flowchart showing a routine for performing fuel injection control executed by a CPU shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 ... Fuel injection valve, 43 ... DPNR, 60 ... Electric controller, 61 ... CPU, 72 ... Intake air temperature sensor, 73 ... Intake pipe pressure sensor, 74 ... Crank position sensor, 77 ... Water temperature sensor

Claims (6)

Applied to an internal combustion engine provided with PM collecting means for collecting PM disposed in an exhaust passage of the internal combustion engine;
Component ratio acquisition means for acquiring a component ratio of PM generated by combustion of fuel in the combustion chamber of the internal combustion engine and discharged from the combustion chamber;
It is determined whether or not the acquired PM component ratio is within a predetermined range. When the acquired PM component ratio is outside the predetermined range, the acquired PM component ratio is within the predetermined range. Component ratio control means for controlling the control parameter of the internal combustion engine based on the PM component ratio acquired so as to become,
An exhaust control device for an internal combustion engine comprising: The exhaust control device for an internal combustion engine according to claim 1,
The component ratio acquisition means acquires the ratio of SOF in the PM,
The component ratio control means determines whether or not the acquired SOF ratio in the PM is within a predetermined range, and when the acquired SOF ratio in the PM is outside the predetermined range, the acquisition An exhaust control device for an internal combustion engine configured to control the control parameter based on the acquired SOF ratio so that the SOF ratio in the PM is within the predetermined range . The exhaust control device for an internal combustion engine according to claim 2,
The component ratio acquisition means includes
Soot amount acquisition means for acquiring the amount of soot in the PM discharged from the combustion chamber;
SOF amount acquisition means for acquiring the amount of SOF in the PM discharged from the combustion chamber;
With
The component ratio acquisition means includes
An internal combustion engine configured to acquire a ratio of SOF in the PM based on the acquired amount of soot and the acquired amount of SOF, on the assumption that the PM consists of only soot and SOF Exhaust control device. The exhaust control device for an internal combustion engine according to claim 3,
The SOF amount acquisition means includes
An exhaust control device for an internal combustion engine, comprising a hydrocarbon amount acquisition means for acquiring the amount of hydrocarbon generated in the combustion chamber, and configured to acquire the amount of SOF based on the acquired amount of hydrocarbon . The exhaust control device for an internal combustion engine according to claim 4,
The hydrocarbon amount acquisition means includes
Exhaust control of the internal combustion engine configured to acquire the amount of the hydrocarbon based on the amount of fuel injected into the combustion chamber and at least one amount of CO, CO ₂ and Soot generated in the combustion chamber apparatus. The exhaust control device for an internal combustion engine according to any one of claims 1 to 5 ,
The component ratio control means includes
An exhaust control device for an internal combustion engine configured to use a fuel injection pressure as the control parameter.

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