JP4862735B2 - Fuel injection amount control device for internal combustion engine - Google Patents

Description

  The present invention injects fuel for premixed compression ignition combustion into the combustion chamber earlier than the vicinity of compression top dead center, and diffusion combustion in the combustion chamber near the compression top dead center separately from the fuel for premix compression ignition combustion A first fuel injection amount for premixed compression ignition combustion and a second fuel injection amount for diffusion combustion, which are applied to an internal combustion engine capable of adopting a two-stage injection mode for injecting fuel for fuel The present invention relates to a fuel injection amount control device for an internal combustion engine.

  In recent years, in order to reduce the amount of NOx, particulate matter, etc. generated in a direct injection internal combustion engine (particularly, a direct injection diesel engine) Combustion mode in which fuel is injected (in a low pressure state) and premixed gas that is substantially uniformly dispersed in the combustion chamber is self-ignited near the compression top dead center (hereinafter referred to as “premixed compression ignition combustion”) Or “HCCI (homogenerous charge compression ignition) combustion” has been proposed.

  In such HCCI combustion, generally, as the fuel injection amount for premixed compression ignition combustion increases, the noise generated by the combustion tends to increase, and this corresponds to the case where the noise becomes the upper limit of the range in which the noise does not increase excessively. There is a certain upper limit of the fuel injection amount for premixed compression ignition combustion.

  Therefore, for example, when the total required fuel injection amount per cycle of the internal combustion engine is larger than the upper limit amount, the noise is prevented from becoming excessively large, and as much fuel as possible is premixed. For the purpose of compression ignition combustion, the first fuel injection amount for premix compression ignition combustion is determined to be equal to the upper limit amount, and the fuel of the first fuel injection amount is set earlier than the compression top dead center (this cycle) And the second fuel injection amount for diffusion combustion is determined by subtracting the first fuel injection amount (the upper limit amount) from the total required fuel injection amount, and the fuel of the second fuel injection amount is compressed. It is conceivable to adopt a two-stage injection mode in which injection is performed near the top dead center (in the current cycle).

In the case of adopting this two-stage injection mode, in order to achieve the above object, it is necessary to accurately set the upper limit amount of the first fuel injection amount. For this reason, the control apparatus for an internal combustion engine described in Patent Document 1 below focuses on the fact that the upper limit of the first fuel injection amount is strongly influenced by the operation speed of the internal combustion engine, and based on the operation speed of the internal combustion engine. The upper limit amount is determined.
JP 2005-273513 A

  By the way, the noise due to the HCCI combustion described above tends to increase as the reaction rate of the combustion increases, with an increase in the increase gradient of the pressure of the gas in the combustion chamber due to the combustion. Further, the reaction rate of HCCI combustion increases as the temperature of the gas in the combustion chamber increases and as the fuel concentration in the premixed gas increases. That is, the upper limit amount of the first fuel injection amount is strongly influenced by the temperature of the gas in the combustion chamber and the fuel concentration in the premixed gas.

  However, in the apparatus described in the above document, the upper limit amount of the first fuel injection amount is determined based only on the operating speed, and the influence of parameters related to the reaction speed of HCCI combustion such as the temperature of the gas in the combustion chamber. Is not taken into account.

  Therefore, for example, when the operating speed is the same and the temperature of the gas in the combustion chamber rises, the upper limit amount of the first fuel injection amount is the same in the apparatus described in the above document regardless of the temperature of the gas. Determined by value. When the fuel of the first fuel injection amount equal to the upper limit amount in this case burns HCCI, the reaction speed of HCCI combustion increases as the temperature of the gas increases, and the noise caused by the combustion is excessively increased. There's a problem.

  The present invention has been made to cope with such a problem, and its purpose is to take into account parameters related to the reaction rate of HCCI combustion, such as the temperature of gas in the combustion chamber, and the noise caused by the combustion is excessively large. An object of the present invention is to provide a fuel injection amount control device capable of accurately determining an upper limit amount of a first fuel injection amount for premixed compression ignition combustion so as not to become a problem.

  A fuel injection amount control device for an internal combustion engine according to the present invention is applied to an internal combustion engine capable of adopting the above-described two-stage injection mode.

  The fuel injection amount control device for an internal combustion engine according to the present invention is characterized in that a total required fuel injection amount determination means for determining a total required fuel injection amount per cycle of the internal combustion engine based on an operating state of the internal combustion engine, Based on at least the temperature of the gas in the combustion chamber, the upper limit of the first fuel injection amount for premixed compression ignition combustion is set to an excessively large gradient of increase in the pressure of the gas due to combustion of the fuel of the first fuel injection amount. An upper limit amount determining means for determining an amount corresponding to an upper limit of a range, and an amount equal to the total required fuel injection amount when the total required fuel injection amount is equal to or less than the upper limit amount. And when the total required fuel injection amount is larger than the upper limit amount, the first fuel injection amount determination means for determining the first fuel injection amount equal to the upper limit amount, and the second fuel for diffusion combustion Injection amount Serial in that said first fuel injection amount from the total required amount of fuel injection and a second fuel injection quantity determining means for determining the amount reduced.

  Here, "when the increase gradient of the pressure of the gas is the upper limit of the range that is not excessively large" is, for example, a parameter that indicates the level of noise due to premixed compression ignition combustion should not exceed the level of the noise. For example, a predetermined value corresponding to a slightly smaller value may be used. The parameters indicating the degree of noise include, for example, an increasing gradient of the gas pressure due to the premixed compression ignition combustion with respect to the crank angle, an increasing rate of the gas pressure due to the premixed compression ignition combustion, and a premixed compression ignition combustion. Examples include, but are not limited to, sound pressure.

  As described above, the noise due to the premixed compression ignition combustion increases as the reaction rate of the premixed compression ignition combustion increases, with the increase in the pressure gradient of the gas in the combustion chamber due to the premixed compression ignition combustion. Further, the reaction rate of the premixed compression ignition combustion becomes larger as the temperature of the gas in the combustion chamber is higher and the fuel concentration in the premixed gas is higher. That is, the reaction rate of the premixed compression ignition combustion corresponds to the upper limit of the range in which the increase gradient of the gas pressure in the combustion chamber due to the premixed compression ignition combustion does not become excessively large (hereinafter referred to as the “upper reaction rate”). Over), noise from the combustion becomes excessively large.

  According to the above configuration, the upper limit amount can be determined to be smaller as the gas temperature is higher. Thereby, the higher the temperature of the gas in the combustion chamber, the lower the fuel concentration in the premixed gas when the first fuel injection amount determined by using the upper limit amount is injected. The reaction rate of the premixed compression ignition combustion can be suppressed from exceeding the upper limit reaction rate.

  Therefore, even when the temperature of the gas in the combustion chamber changes, it is possible to suppress the noise from becoming excessively large and to premix and burn as much fuel as possible. From the above, it is possible to accurately determine the upper limit amount of the first fuel injection amount so that noise due to premixed compression ignition combustion does not become excessively large.

Specifically, in the fuel injection amount control apparatus for an internal combustion engine according to the present invention, the upper limit amount determining means determines the operating speed of the internal combustion engine and the total required fuel injection amount that affect the temperature of the gas. used, the more the operating speed is high, or to determine said upper limit amount as the total required fuel injection amount is large to a smaller amount constituted.

  The greater the total required fuel injection amount per cycle (only the first fuel injection amount, the sum of the first and second fuel injection amounts, and any one of the second fuel injection amounts), the greater the one cycle. As the amount of heat generated by the combustion of the total fuel at the periphery increases, the temperature of the gas in the combustion chamber tends to become higher.

  On the other hand, even if the total required fuel injection amount per cycle is the same, the number of cycles in the same period (that is, the number of fuel injections of the total required fuel injection amount) increases as the operating speed of the internal combustion engine increases. By increasing, the total amount of heat generated by the combustion of fuel in the same period increases, and the temperature of the gas in the combustion chamber tends to become higher.

  From the above, the total required fuel injection amount and the operating speed of the internal combustion engine can be values indicating the temperature of the gas in the combustion chamber, which is one of the parameters relating to the reaction speed of the premixed compression ignition combustion. On the other hand, it is generally difficult to detect the temperature of the gas in the combustion chamber directly and accurately. Therefore, the total required fuel injection amount and the operating speed of the internal combustion engine may be used in order to determine the upper limit amount easily and accurately without directly detecting the gas temperature in the combustion chamber.

  The above configuration is based on such knowledge. According to this, as the total required fuel injection amount is larger or the operation speed is larger, it is determined that the temperature of the gas in the combustion chamber is higher, and the upper limit amount is determined to be smaller (that is, the first amount). 1 fuel injection amount is determined so that the fuel concentration in the premixed gas becomes smaller). Therefore, it can be suppressed that the reaction rate of the premixed compression ignition combustion exceeds the upper limit reaction rate. From the above, the upper limit amount of the first fuel injection amount can be determined accurately and easily.

As described above, by determining the first fuel injection amount using the total required fuel injection amount that can be a value indicating the temperature of the gas in the combustion chamber and the upper limit amount determined using the operation speed , Specifically, when the total required fuel injection amount is equal to or less than the upper limit amount , the first fuel injection amount determining means determines the first fuel injection amount to be larger as the total required fuel injection amount is larger. When the total required fuel injection amount is larger than the upper limit amount, the first fuel injection amount is determined to be smaller as the total required fuel injection amount is larger.

  Further, in the fuel injection amount control apparatus for an internal combustion engine according to the present invention, the upper limit amount determining means uses the temperature of the cooling water of the internal combustion engine that affects the temperature of the gas to control the temperature of the cooling water. The upper limit amount may be configured to be determined to be a smaller amount as the temperature is higher, or the upper limit amount may be determined to be a smaller amount as the temperature of the outside air is higher using a temperature of the outside air that affects the temperature of the gas. It may be configured to do.

  Here, “outside air” means air in the environment surrounding the internal combustion engine. According to these, even when the total required fuel injection amount and the operating speed of the internal combustion engine are the same, the upper limit amount is smaller as the temperature of the cooling water is higher and / or the temperature of the outside air is higher. Since it is determined, the fuel concentration in the premixed gas can be made smaller. Therefore, it can be more reliably suppressed that the reaction rate of the premixed compression ignition combustion exceeds the upper limit reaction rate.

  That is, the upper limit amount is determined in consideration of the influence of the temperature of the cooling water and / or the temperature of the outside air on the temperature of the gas in the combustion chamber (that is, the influence on the reaction rate of the premixed compression ignition combustion). Even when the temperature of the cooling water and / or the temperature of the outside air changes, the upper limit amount of the first fuel injection amount can be accurately determined.

  In the fuel injection amount control apparatus for an internal combustion engine according to the present invention, it is preferable that the upper limit amount determining means is configured to determine the upper limit amount to a smaller amount as the outside air pressure is smaller. .

  When the first fuel injection amount is the same, the smaller the outside air pressure is, the more the fuel concentration in the premixed gas is increased as the amount of air (mass) sucked into the combustion chamber decreases. Accordingly, in this case, the reaction rate of the premixed compression ignition combustion becomes larger as the pressure of the outside air becomes smaller. That is, regardless of the temperature of the gas in the combustion chamber, the reaction rate of premixed compression ignition combustion changes according to the pressure of the outside air.

  According to the above configuration, the upper limit amount is determined to be smaller as the outside air pressure is smaller. Thereby, even when the temperature of the gas in the combustion chamber is the same and the pressure of the outside air is reduced, it is possible to suppress an increase in the fuel concentration in the premixed gas. Therefore, it can be more reliably suppressed that the reaction rate of the premixed compression ignition combustion exceeds the upper limit reaction rate.

  That is, since the upper limit is determined in consideration of the influence of the pressure of the outside air on the fuel concentration in the premixed gas (that is, the influence on the reaction rate of the premixed compression ignition combustion), the pressure of the outside air changes. Even in this case, the upper limit amount of the first fuel injection amount can be accurately determined.

  Further, when the upper limit amount is determined using the total required fuel injection amount and the operating speed of the internal combustion engine, the change rate of the total required fuel injection amount is determined in the internal combustion engine fuel injection amount control device according to the present invention. Is greater than a predetermined speed, means for delaying the upper limit amount, and the first fuel injection amount determining means uses the value after the delay processing as the upper limit amount to determine the first fuel injection amount. It is preferred to be configured to determine.

  When the total required fuel injection amount changes, the temperature of the gas in the combustion chamber changes with a certain delay with respect to the change. According to the above configuration, when the total required fuel injection amount changes, the change in the value after delaying the upper limit amount can be brought close to the degree of change in the temperature of the gas in the combustion chamber. Therefore, when determining the first fuel injection amount, the value after delay processing of the upper limit amount is used instead of the upper limit amount, so that the reaction rate of premixed compression ignition combustion exceeds the upper limit reaction rate. Can be more reliably suppressed, and the opportunity to perform premixed compression ignition combustion can be increased.

  Hereinafter, one embodiment of a fuel injection amount control device for an internal combustion engine according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration of a whole system in which a fuel injection amount control device for an internal combustion engine according to 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 (command signal corresponding to a command fuel injection pressure Pcr described later) from the electric control device 60. The fuel is boosted so that (discharge pressure) becomes the command fuel injection pressure Pcr.

  As a result, the fuel injection valve 21 is supplied with fuel whose pressure has been increased from the fuel injection pump 22 to the command fuel injection pressure Pcr. Further, the fuel injection valve 21 is electrically connected to the electric control device 60, and a drive signal from the electric control device 60 (first fuel injection amount qhcci for premixed compression ignition combustion (and / or diffusion). Is opened for a predetermined time in response to a command signal corresponding to the second fuel injection amount qdiff) for combustion, and thereby the fuel boosted to the command fuel injection pressure Pcr in the combustion chamber of each cylinder is supplied to the first fuel injection amount. Only qhcci (and / or the second fuel injection amount qdiff) is directly injected. In this example, “˜fuel injection amount” means the volume of injected fuel.

  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 turbocharger 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 35 b of a turbocharger 35 disposed in the exhaust pipe 42. , A turbocharger throttle valve 35 c 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.

  The turbocharger throttle valve 35c is connected to the electric control device 60, and in response to a drive signal from the electric control device 60, the exhaust gas flowing into the turbine 35b so as to make the capacity of the turbocharger 35 substantially variable. This valve has a variable passage area. When the turbocharger throttle valve 35c is closed and the exhaust gas passage area flowing into the turbine 35b is reduced, the supercharging pressure is increased, and conversely, when the turbocharger throttle valve 35c is opened and the exhaust gas passage area flowing into the turbine 35b is increased. The supercharging pressure decreases.

  The DPNR 43 is a filter that includes a filter 43a formed of a porous material such as cordierite and collects particulates in exhaust gas that passes through the surface of the pores. DPNR43 includes alumina as a carrier, alkali metal such as potassium K, sodium Na, lithium Li, and cesium Cs, alkaline earth metal such as barium Ba and calcium Ca, and rare earth metal such as lanthanum La and yttrium Y. At least one selected from the above is supported together with platinum and functions as an NOx storage reduction catalyst that absorbs NOx and then releases and reduces the absorbed NOx.

  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 is an air flow rate (fresh air flow rate) measuring means, and is downstream of the hot-wire air flow meter 71 and the throttle valve 33 disposed in the intake pipe 32 and downstream of the portion to which the exhaust gas recirculation pipe 51 is connected. An intake air temperature sensor 72 provided in the intake passage, an intake pipe pressure sensor 73 disposed in the intake passage downstream of the throttle valve 33 and downstream of the portion to which the exhaust gas recirculation pipe 51 is connected, a crank position sensor 74, An accelerator opening sensor 75, a fuel temperature sensor 76 disposed in the fuel pipe 23 near the discharge port of the fuel injection pump 22, and a downstream of the throttle valve 33 and a portion where the exhaust gas recirculation pipe 51 is connected. The intake oxygen concentration sensor 77, the water temperature sensor 78, and the exhaust oxygen concentration sensor 8 provided in the downstream manifold of the exhaust manifold 41 are provided in the intake passage. The exhaust temperature sensor 82 provided at the downstream gathering portion of the exhaust manifold 41, the exhaust pressure sensor 83 provided at the downstream gathering portion of the exhaust manifold 41, and a predetermined position outside the internal combustion engine 10. It is connected to an outside air temperature sensor and an outside air pressure sensor (not shown), 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, the turbocharger throttle valve 35c, and the EGR control valve 52. In response to an instruction from the CPU 61, a drive signal is sent to these. It is supposed to be sent out.

  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 operating speed NE that is the rotational speed of the engine 10. The accelerator opening sensor 75 detects the operation amount (opening) of the accelerator pedal AP, and generates a signal representing the accelerator opening 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 intake oxygen concentration sensor 77 detects the oxygen concentration in the intake air and generates a signal representing the intake oxygen concentration RO2in. The water temperature sensor 78 detects the temperature of the cooling water for cooling the engine 10 and generates a signal representing the cooling water temperature THW. The exhaust oxygen concentration sensor 81 detects the oxygen concentration in the exhaust gas and generates a signal representing the exhaust oxygen concentration RO2ex. The exhaust gas temperature sensor 82 detects the temperature of the exhaust gas and generates a signal representing the exhaust gas temperature Tex. The exhaust pressure sensor 83 detects the pressure of the exhaust gas and generates a signal representing the exhaust pressure Pex. The outside air temperature sensor and the outside air pressure sensor detect the temperature and pressure of air in the environment surrounding the internal combustion engine 10 and generate signals representing the outside air temperature THatm and the outside air pressure Patm.

(Outline of two-stage injection mode)
Next, the outline of the two-stage injection mode adopted by the system configured as described above, and the premixed compression ignition by the fuel injection amount control device for the internal combustion engine (hereinafter also referred to as “this device”). An outline of a method for determining the first fuel injection amount qhcci for use and the second fuel injection amount qdiff for diffusion combustion will be described.

  FIG. 2 is a diagram schematically showing a state in which gas is sucked from the intake manifold 31 into a cylinder (cylinder) of one cylinder, and the gas sucked into the combustion chamber is discharged to the exhaust manifold 41. is there.

  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. The (external) 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 degree of the EGR control valve 52 to be performed.

  In this system, in the same cycle, the fuel of the first fuel injection amount qhcci is injected earlier than the vicinity of the compression top dead center, and the fuel of the second fuel injection amount qdiff is injected near the compression top dead center. It is like that. As will be described in detail later, this device determines the total required fuel injection amount qfin in the current operation cycle based on the operating state, and uses the first fuel injection amount qhcci in the total required fuel injection amount qfin as HCCI combustion. Decrease the volume as much as possible without causing excessive noise. Further, the second fuel injection amount qdiff is determined to be the amount of fuel not used for HCCI combustion out of the total required fuel injection amount qfin. That is, the present apparatus determines the first and second fuel injection amounts qhcci, qdiff according to the two-stage injection mode so that appropriate HCCI combustion is achieved.

  The fresh air and EGR gas are sucked into the combustion chamber as the piston descends via the intake valve Vin that is open in the intake stroke, and becomes in-cylinder gas. The in-cylinder gas is sealed in the cylinder by closing the intake valve Vin at a predetermined time during the compression stroke after the piston reaches compression bottom dead center, and after that time, the gas is compressed as the piston rises. It will be done. As a result, the temperature of the in-cylinder gas (hereinafter referred to as “in-cylinder temperature Tg”) increases.

  When a predetermined time earlier than the compression top dead center during the compression stroke arrives (specifically, when the crank angle CA matches a crank angle CAqhcci at the start of fuel injection for HCCI combustion described later), the first The fuel injection valve 21 is opened for a predetermined time corresponding to the fuel injection amount qhcci, so that the fuel is directly injected into the cylinder. In this case, the injected fuel (fuel spray, therefore, the premixed gas) does not immediately self-ignite but is sufficiently dispersed until it becomes substantially uniform in the combustion chamber. In this way, the premixed gas that is widely dispersed in the combustion chamber becomes high temperature and high pressure due to compression as the piston rises, and when the vicinity of the compression top dead center is reached, the entire premixed gas self-ignites almost simultaneously (therefore, HCCI combustion is achieved). Note that when the first fuel injection amount qhcci is determined to be “0”, HCCI combustion is not executed.

  Subsequently, when a predetermined time in the vicinity of the compression top dead center during the compression stroke arrives (specifically, when the crank angle CA coincides with the crank angle CAqdiff at the start of diffusion fuel injection described later), the second fuel The fuel injection valve 21 is opened for a predetermined time corresponding to the injection amount qdiff, so that fuel is directly injected into the cylinder. As a result, the injected (liquid) fuel immediately becomes fuel vapor due to the heat received from the in-cylinder gas that has already become high temperature due to compression, and is mixed while being mixed with the in-cylinder gas over time. Spontaneous self-ignition takes place (thus, diffusion combustion is achieved). When the second fuel injection amount qdiff is determined to be “0”, diffusion combustion is not executed. The above is the outline of the two-stage injection mode.

(Method for determining the upper limit of the first fuel injection amount and the first and second fuel injection amounts)
By the way, in the HCCI combustion in the above-described two-stage injection mode, as the reaction speed V of HCCI combustion increases, the increasing gradient (dPg / dCA. Cylinder in unit cylinder angle CA) As the gas pressure Pg increases, noise due to HCCI combustion tends to increase.

  Therefore, in order to suppress an excessive increase in noise due to HCCI combustion, the upper limit of the range in which the degree of noise due to HCCI combustion (for example, sound pressure) is not excessively large (that is, the pressure of in-cylinder gas due to HCCI combustion). It is necessary to suppress exceeding the upper limit reaction rate Vmax, which is the reaction rate corresponding to the case where the increase gradient dPg / dCA of Pg becomes an upper limit in a range where it is not excessively large.

  In this example, the upper limit qhccimax of the first fuel injection amount qhcci for premixed compression ignition combustion is set in order to suppress an excessive increase in noise due to HCCI combustion and to burn as much fuel as possible to HCCI. The amount corresponding to the case where the reaction rate V of HCCI combustion becomes a reaction rate equal to the upper limit reaction rate Vmax is determined.

  Further, the reaction rate V of HCCI combustion increases as the in-cylinder temperature Tg increases and as the fuel concentration [hcci] in the premixed gas increases. In view of this, the present apparatus determines the upper limit qhccimax in consideration of the in-cylinder temperature Tg and the fuel concentration [hcci], which are parameters related to the reaction rate V of HCCI combustion. Hereinafter, a method of determining the upper limit amount qhccimax of the first fuel injection amount qhcci by this device will be described.

  FIG. 3 is a graph showing the relationship between the total required fuel injection amount qfin and the operation speed NE and the in-cylinder temperature Tg that affects the reaction speed V of HCCI combustion when the internal combustion engine 10 is in a steady state. . Total required fuel injection amount qfin per cycle (that is, only the first fuel injection amount qhcci, the sum qhcci + qdiff of the first and second fuel injection amounts, and only the second fuel injection amount qdiff) As the injection amount) increases, the in-cylinder temperature Tg tends to increase as the amount of heat generated by the combustion of the total fuel per cycle increases.

  On the other hand, even if the total required fuel injection amount qfin per cycle is the same, the greater the operation speed NE, the more the number of cycles in the same period (that is, the number of fuel injections of the total required fuel injection amount qfin). By increasing, the in-cylinder temperature Tg tends to become higher as the total amount of heat generated by the combustion of the fuel in the same period increases. Therefore, the total required fuel injection amount qfin and the operation speed NE can be values representing the in-cylinder temperature Tg.

  Here, consider a case where it is assumed that the first fuel injection amount qhcci is determined to be equal to the total required fuel injection amount qfin. In this case, the larger the total required fuel injection amount qfin (that is, the first fuel injection amount qhcci), the higher the fuel concentration [hcci] in the premixed gas, and the more the in-cylinder temperature Tg as described above. Higher (see FIG. 3). Therefore, in this case, as the total required fuel injection amount qfin increases, the reaction speed V of HCCI combustion increases, and a situation may occur where the upper limit reaction speed Vmax is exceeded.

  In order to suppress the occurrence of the above situation, it is conceivable that the higher the in-cylinder temperature Tg, the smaller the fuel concentration [hcci] in the premixed gas. Therefore, the present apparatus uses the linear function funcqhccimax that defines the relationship between the total required fuel injection amount qfin and the upper limit amount qhccimax when the internal combustion engine 10 is in a steady state as shown in FIG. The limit qhccimax is determined.

  More specifically, in this example, the linear function funcqhccimax is assumed to be a temporary total required fuel injection amount qfin (hcci when it is assumed that the first fuel injection amount qhcci is determined to be equal to the total required fuel injection amount qfin. ) As an independent variable and the upper limit amount qhccimax as a dependent variable. The larger the provisional total required fuel injection amount qfin (hcci), the smaller the upper limit amount qhccimax is determined.

  Even if the provisional total required fuel injection amount qfin (hcci) is constant, the in-cylinder temperature Tg increases as the operating speed NE increases (see FIG. 3), so the upper limit amount qhccimax is smaller. The amount needs to be determined. That is, in this example, the slope −A (value A is a positive value) of the linear function funcqhccimax and the intercept B are values corresponding to the case where the reaction rate V of HCCI combustion is equal to the upper limit reaction rate Vmax. In particular, the intercept B is determined to be smaller as the operation speed NE is larger. The slope -A and intercept B of the linear function funcqhccimax are adapted when the cooling water temperature THW, the outside air temperature THatm, and the outside air pressure Patm are equal to the value THW1, the value THatm1, and the value Patm1, respectively. It has been done.

  FIG. 5 is a graph showing the relationship between the total required fuel injection amount qfin determined by the present apparatus and the first and second fuel injection amounts qhcci, qdiff when the internal combustion engine 10 is in a steady state. FIG. 6 shows the in-cylinder temperature Tg corresponding to the case where the fuel of the first and second fuel injection amounts qhcci, qdiff is injected at the respective injection timings when the internal combustion engine 10 is in a steady state. 6 is a graph corresponding to FIG. 5 showing the fuel concentration [hcci] in the premixed gas and the reaction rate V of HCCI combustion. The manner in which the first and second fuel injection amounts qhcci, qdiff are determined will be described with reference to FIGS. 5 and 6. In FIGS. 5 and 6, it is assumed that the operation speed NE is constant.

  First, the case where the total required fuel injection amount qfin is equal to or less than the upper limit amount qhccimax determined based on the linear function funcqhccimax will be described. In this case, the total required fuel injection amount qfin is at the intersection of the straight line indicated by the broken line indicating the relationship of qhcci = qfin and the straight line indicated by the one-dot chain line indicating the linear function funcqhccimax shown in FIG. This corresponds to the case where the corresponding total required fuel injection amount qfin1 or less.

  In this case, the first fuel injection amount qhcci is determined to be equal to the total required fuel injection amount qfin. Therefore, as shown by the solid line in FIG. 5A, the first fuel injection amount qhcci is larger as the total required fuel injection amount qfin is larger along the straight line shown by the broken line representing the relationship of qhcci = qfin. Determined in quantity. On the other hand, as shown by the solid line in FIG. 5B, the second fuel injection amount qdiff is determined to be “0”.

  Therefore, in this case, as shown by the solid lines in FIGS. 6A and 6B, the greater the total required fuel injection amount qfin, the higher the in-cylinder temperature Tg and the fuel concentration [hcci] in the premixed gas As the in-cylinder temperature Tg1 corresponding to the injection amount qfin1 and the fuel concentration [hcci] 1 increase, the reaction speed V of HCCI combustion becomes higher as shown by the solid line in FIG. It increases toward the upper limit reaction rate Vmax. That is, when the total required fuel injection amount qfin is equal to or less than the above injection amount qfin1, the reaction speed V of HCCI combustion becomes larger as the total required fuel injection quantity qfin is larger in a range smaller than the upper limit reaction speed Vmax.

  Next, the case where the total required fuel injection amount qfin is larger than the upper limit amount qhccimax determined based on the linear function funcqhccimax will be described. This case corresponds to the case where the total required fuel injection amount qfin is larger than the injection amount qfin1. In this case, the first fuel injection amount qhcci is determined as the upper limit amount qhccimax. Therefore, as shown by the solid line in FIG. 5A, the first fuel injection amount qhcci becomes larger as the total required fuel injection amount qfin increases along the straight line shown by the one-dot chain line representing the linear function funcqhccimax. Decide on a small amount. On the other hand, as shown by the solid line in FIG. 5B, the second fuel injection amount qdiff is determined to be an amount obtained by subtracting the first fuel injection amount qhcci (that is, the upper limit amount qhccimax) from the total required fuel injection amount qfin. Is done.

  Here, as a comparison object with the determination method of the upper limit amount qhccimax by the present apparatus, even when the total required fuel injection amount qfin is larger than the injection amount qfin1, as indicated by a two-dot chain line in FIG. Consider a case where the upper limit amount qhccimax is determined to be equal to the upper limit amount qhcci1 corresponding to the injection amount qfin1. In this case, paying attention to the state when the total required fuel injection amount qfin becomes the total required fuel injection amount qfin2 larger than the injection amount qfin1 by a predetermined amount from the injection amount qfin1, the first and second fuel injection amounts qhcci and qdiff are respectively determined as the upper limit amount qhcci1 and the injection amount (qfin2-qhcci1) (see the two-dot chain line in FIG. 5).

  For this reason, as shown by the two-dot chain line in FIG. 6A, the in-cylinder temperature Tg is changed from the temperature Tg1 corresponding to the injection amount qfin1 to the injection amount (qfin2-qhcci1 (= qifn2-qfin1)). The temperature Tg2 is higher by a corresponding amount. Further, as indicated by a two-dot chain line in FIG. 6B, the fuel concentration [hcci] is maintained at the above concentration [hcci] 1. Accordingly, as shown by the two-dot chain line in FIG. 6C, the reaction speed V of HCCI combustion becomes a reaction speed V2 that is larger than the upper limit reaction speed Vmax, and as a result, there is a situation in which noise due to HCCI combustion becomes excessively large. appear.

  On the other hand, according to the determination method of the upper limit amount qhccimax by the present apparatus, when the total required fuel injection amount qfin changes from the injection amount qfin1 to the injection amount qfin2, as shown by the solid line in FIG. Is determined to be an upper limit amount qhcci2 that is smaller than the upper limit amount qhcci1 by an amount dq obtained by a linear function funcqhccimax. Accordingly, the first and second fuel injection amounts qhcci, qdiff are respectively determined as an upper limit amount (qhcci1-dq) and an injection amount (qfin2-qhcci1 + dq) (see the solid line in FIG. 5).

  Therefore, as shown by the solid line in FIG. 6A, the in-cylinder temperature Tg is higher than the temperature Tg1 by an amount corresponding to the injection amount (qfin2-qfin1), as in the change in the two-dot chain line described above. Temperature Tg2. On the other hand, as shown by the solid line in FIG. 6B, the fuel concentration [hcci] becomes a concentration [hcci] 2 that is smaller than the concentration [hcci] 1 by an amount corresponding to the amount dq. Therefore, as shown by the solid line in FIG. 6C, the reaction rate V of HCCI combustion can be maintained at the upper limit reaction rate Vmax without exceeding the upper limit reaction rate Vmax. As a result, the noise due to HCCI combustion is excessively high. It can suppress that the situation which becomes large generate | occur | produces.

  As shown by the solid line in FIG. 5, when the total required fuel injection amount qfin is equal to or larger than the total required fuel injection amount qfin3 corresponding to the case where the upper limit amount qhccimax is “0”, the first fuel injection amount qhcci Is determined to be “0”, and the second fuel injection amount qdiff is determined to be equal to the total required fuel injection amount qfin. Therefore, the second fuel injection amount qdiff is determined to be larger as the total required fuel injection amount qfin is larger, along the straight line indicated by the broken line representing the relationship of qdiff = qfin. The above is the method for determining the upper limit amount qhccimax of the first fuel injection amount qhcci and the first and second fuel injection amounts qhcci, qdiff.

(Correction of the upper limit of the first fuel injection amount)
As described above, the linear function funcqhccimax is the fuel of the upper limit amount qhccimax when the cooling water temperature THW, the outside air temperature THatm, and the outside air pressure Patm are equal to the value THW1, the value THatm1, and the value Patm1, respectively. Is produced so that the reaction rate V of the combustion becomes equal to the upper limit reaction rate Vmax when HCCI combustion is performed (see FIG. 4).

  Therefore, even when the total required fuel injection amount qfin and the operation speed NE are the same, the cooling water temperature THW, the outside air temperature THatm, and / or the outside air pressure Patm are the value THW1, the value THatm1, and / or When the value is shifted from the value Patm1 (hereinafter, this case is simply referred to as “parameter is shifted from the reference value”), the fuel of the upper limit amount qhccimax itself determined from the linear function funcqhccimax is When HCCI combustion is performed, the reaction rate V of the combustion shifts from the upper limit reaction rate Vmax by an amount corresponding to the degree of shift.

  This is because when the total required fuel injection amount qfin and the operation speed NE are the same, the higher the coolant temperature THW and / or the outside air temperature THatm, the higher the in-cylinder temperature Tg (that is, the reaction of HCCI combustion). On the other hand, the smaller the outside air pressure Patm, the higher the fuel concentration [hcci] in the premixed gas (ie, HCCI combustion) as the oxygen concentration in the premixed gas decreases. The reaction rate V of the

  Therefore, when the parameter deviates from the reference value, the upper limit amount qhccimax determined from the linear function funcqhccimax is used to bring the reaction rate V when the fuel of the upper limit amount qhccimax burns HCCI closer to the upper limit reaction rate Vmax. Needs to be corrected in accordance with the degree of the shift of the cooling water temperature THW, the outside air temperature THatm, and / or the outside air pressure Patm.

  Specifically, in this example, a table MapK1 that defines the relationship between the cooling water temperature THW and the correction coefficient K1 multiplied by the upper limit amount qhccimax determined from the cooling water temperature THW and the linear function funcqhccimax shown in FIG. Based on this, the correction coefficient K1 is determined to be smaller as the cooling water temperature THW is higher. When the cooling water temperature THW is equal to the above value THW1, the correction coefficient K1 is determined to be “1.0”.

  Further, based on the outside air temperature THatm and the table MapK2 that defines the relationship between the outside air temperature THatm shown in FIG. 8 and the correction coefficient K2 multiplied by the upper limit amount qhccimax determined from the linear function funcqhccimax, The higher the temperature THatm, the smaller the correction coefficient K2 is determined. When the outside air temperature THatm is equal to the value THatm1, the correction coefficient K2 is determined to be “1.0”.

  In addition, based on the outside air pressure Patm and the table MapK3 that defines the relationship between the outside air pressure Patm and the correction coefficient K3 multiplied by the upper limit qhccimax determined from the linear function funcqhccimax shown in FIG. The smaller the pressure Patm is, the smaller the correction coefficient K3 is determined. When the outside air pressure Patm is equal to the value Patm1, the correction coefficient K3 is determined to be “1.0”.

  As described above, the correction coefficients K1, K2, and K3 determined based on the tables MapK1, MapK2, and MapK3 are respectively multiplied by the upper limit amount qhccimax determined from the linear function funcqhccimax. When the first fuel injection amount qhcci is determined, the corrected upper limit amount qhccimax is used, so that the reaction rate V of HCCI combustion is more accurately determined even when the parameter deviates from the reference value. Can be close to Vmax.

(Delay processing of the upper limit amount of the first fuel injection amount)
Now, consider a case where the total required fuel injection amount qfin increases (decreases) stepwise from a certain amount by a predetermined amount. Here, according to the linear function funcqhccimax, the upper limit amount qhccimax is determined to be smaller as the total required fuel injection amount qfin is larger (see FIG. 4). Therefore, in this case, the upper limit amount qhccimax is decreased (increased) stepwise by an amount corresponding to the predetermined amount at the same timing as when the total required fuel injection amount qfin changes.

  On the other hand, in this case, the in-cylinder temperature Tg rises (decreases) by an amount corresponding to the predetermined amount with a certain delay with respect to the change in the total required fuel injection amount qfin. That is, the degree of change in the in-cylinder temperature Tg is different from the degree of change in the upper limit amount qhccimax (that is, the degree of change in the total required fuel injection amount qfin). Therefore, in this case, when the fuel of the first fuel injection amount qhcci determined using the upper limit amount qhccimax itself is HCCI-combusted, the reaction rate V of HCCI combustion is increased by the amount corresponding to the difference in the change level. It becomes smaller (larger) than the speed Vmax.

  Accordingly, when the total required fuel injection amount qfin changes stepwise as described above, in order to bring the reaction rate V of HCCI combustion close to the upper limit reaction rate Vmax, In determining the single fuel injection amount qhcci, it is conceivable to use a value after delay processing of the upper limit amount qhccimax instead of using the upper limit amount qhccimax itself. That is, it can be considered that the change in the first fuel injection amount qhcci can simulate the change in the in-cylinder temperature Tg.

  From the above, in this apparatus, the upper limit amount qhccimax corrected using the correction coefficients K1, K2, and K3 is low-pass filtered to obtain the post-delay upper limit amount qhccimaxlow, and the upper limit amount qhcci itself is used. Instead, the first and second fuel injection amounts qhcci and qdiff are respectively determined using the post-delay upper limit amount qhccimaxlow.

(Actual operation)
Next, the actual operation of the fuel injection amount control device for an internal combustion engine configured as described above will be described.

  The CPU 61 is configured to repeatedly execute a routine for calculating the fuel injection amount and the like shown in the flowchart of FIG. 10 every elapse of a predetermined time and for each cylinder. Therefore, when the predetermined timing is reached, the CPU 61 starts processing from step 1000 and proceeds to step 1005 to arrive at the calculation time of the total required fuel injection amount qfin (specifically, near the compression bottom dead center). If it is determined as “No”, the process immediately proceeds to step 1095 to end the present routine tentatively.

  Assuming that the time for calculating the total required fuel injection amount qfin has arrived, the CPU 61 makes a “Yes” determination at step 1005 to proceed to step 1010, where the accelerator opening Accp, the operation speed NE, and the table Mapqfin are determined. To obtain the total required fuel injection amount qfin. The table Mapqfin is a table that defines the relationship between the accelerator opening degree Accp, the operation speed NE, and the total required fuel injection amount qfin, and is stored in the ROM 62. This step 1010 corresponds to a part of the total required fuel injection amount determining means.

  Next, the CPU 61 proceeds to step 1015 and determines the crank angle CAqhcci at the start of fuel injection for HCCI combustion from the total required fuel injection amount qfin, the operation speed NE, and the table MapCAqhcci. The table MapCAqhcci is a table that defines the relationship between the total required fuel injection amount qfin and the operation speed NE and the HCCI combustion fuel injection start crank angle CAqhcci, and is stored in the ROM 62.

  Subsequently, the CPU 61 proceeds to step 1020 to determine the crank angle CAqdiff at the start of diffusion combustion fuel injection from the total required fuel injection amount qfin, the operation speed NE, and the table MapCAqdiff. The table MapCAqdiff is a table that defines the relationship between the total required fuel injection amount qfin, the operation speed NE, and the diffusion combustion fuel injection start crank angle CAqdiff, and is stored in the ROM 62.

  Next, the CPU 61 proceeds to step 1025 to determine the intercept B of the linear function funcqhccimax from the operation speed NE and the table MapB (see FIG. 4). The table MapB is a table that defines the relationship between the operation speed NE and the intercept B of the linear function funcqhccimax, and is stored in the ROM 62.

  Next, the CPU 61 proceeds to step 1030 to determine the temporary total required fuel injection amount qfin (hcci) when the first fuel injection amount qhcci is determined to be equal to the total required fuel injection amount qfin, and the linear function shown in FIG. The upper limit amount qhccimax of the first fuel injection amount qhcci is determined from funcqhccimax. The linear function funcqhccimax is a linear function having the temporary total required fuel injection amount qfin (hcci) as an independent variable and the upper limit amount qhccimax as a dependent variable, and is stored in the ROM 62.

  Subsequently, the CPU 61 proceeds to step 1035 to determine the correction coefficient K1 from the cooling water temperature THW and the table MapK1 shown in FIG. The table MapK1 is a table that defines the relationship between the cooling water temperature THW and the correction coefficient K1, and is stored in the ROM 62.

  Next, the CPU 61 proceeds to step 1040 to determine the correction coefficient K2 from the outside air temperature THatm and the table MapK2 shown in FIG. The table MapK2 is a table that defines the relationship between the outside air temperature THatm and the correction coefficient K2, and is stored in the ROM 62.

  Next, the CPU 61 proceeds to step 1045 to determine the correction coefficient K3 from the outside air pressure Patm and the table MapK3 shown in FIG. The table MapK3 is a table that defines the relationship between the outside air pressure Patm and the correction coefficient K3, and is stored in the ROM 62.

  Subsequently, the CPU 61 proceeds to step 1050 and rewrites the upper limit amount qhccimax to a value obtained by multiplying the upper limit amount qhccimax obtained in step 1030 by the correction coefficients K1, K2, and K3. These steps 1025 to 1050 correspond to a part of the upper limit amount determining means.

  Next, the CPU 61 proceeds to step 1055 to obtain a post-delay upper limit qhccimaxlow by performing a low pass filter process on the upper limit qhccimax obtained in step 1050. In this example, the time constant of the low-pass filter processing is obtained in advance by experiments or the like, when the total required fuel injection amount qfin changes when the in-cylinder temperature Tg relates to the degree of delay relative to the change in the total required fuel injection amount qfin. The value is set equal to the constant. This step 1055 corresponds to a part of means for delaying the upper limit amount.

  Next, the CPU 61 proceeds to step 1060 to determine whether or not the total required fuel injection amount qfin is equal to or less than the post-delay processing upper limit amount qhccimaxlow. When determining “Yes”, the CPU 61 proceeds to step 1065 and performs premix compression ignition combustion The first fuel injection amount qhcci for use is set equal to the total required fuel injection amount qfin, and the second fuel injection amount qdiff for diffusion combustion is set to “0”, and then this routine is temporarily ended.

  On the other hand, if the CPU 61 makes a “No” determination at step 1060, it proceeds to step 1070 to set the first fuel injection amount qhcci for premixed compression ignition combustion to an amount equal to the post-delay processing upper limit amount qhccimaxlow. After the second fuel injection amount qdiff for diffusion combustion is set to a value obtained by subtracting the set first fuel injection amount qhcci (that is, the post-delay processing upper limit amount qhccimaxlow) from the total required fuel injection amount qfin, The routine is temporarily terminated. This prevents the first fuel injection amount qhcci from being set to a value larger than the post-delay processing upper limit amount qhccimaxlow. These steps 1060, 1065, and 1070 correspond to a part of the first fuel injection amount determining means and the second fuel injection amount determining means.

  Thereafter, the CPU 61 repeatedly executes the processes of steps 1000, 1005, and 1095 until the calculation time of the total required fuel injection amount qfin comes in the next operation cycle. In this way, the first fuel injection amount qhcci for premixed compression ignition combustion this time and the second fuel injection amount qdiff for diffusion combustion this time are determined near the compression bottom dead center.

  Then, in the routine for performing fuel injection control (not shown), the CPU 61 sets the actual crank angle CAact detected by the crank position sensor 74 to the HCCI combustion fuel injection start crank angle CAqhcci determined in step 1015. When it has been reached, an instruction to inject the fuel by the first fuel injection amount qhcci for premixed compression ignition combustion set in step 1065 or step 1070 is given to the corresponding fuel injection valve 21, and the actual crank When the angle CAact reaches the diffusion combustion fuel injection start crank angle CAqdiff determined in step 1020, only the second fuel injection amount qdiff for diffusion combustion set in step 1065 or step 1070 is reached. An instruction to inject fuel is given to the corresponding fuel injection valve 21.

  Note that when either the first or second fuel injection amount qhcci, qdiff is set to “0”, the fuel injection instruction corresponding to the combustion mode is not executed.

  As described above, the embodiment of the fuel injection amount control apparatus for an internal combustion engine according to the present invention is a two-stage injection that injects fuel for premixed compression ignition (HCCI) combustion and fuel for diffusion combustion in the same cycle. The present invention is applied to an internal combustion engine that can take a form. According to the above embodiment, the reaction rate V of HCCI combustion is equal to the upper limit reaction rate Vmax, which is the reaction rate corresponding to the case where the noise level due to the combustion is the upper limit of the range that is not excessively large. In addition, the upper limit amount qhccimax of the first fuel injection amount qhcci for premixed compression ignition combustion is determined. That is, the upper limit amount qhccimax is determined to be smaller as the total required fuel injection amount qfin is larger and / or as the operation speed NE is larger (thus, as the in-cylinder temperature Tg is higher).

  Further, when determining the first and second fuel injection amounts qhcci, qdiff, a post-delay upper limit amount qhccimaxlow obtained by low-pass filtering the corrected upper limit amount qhccimax is used. . When the total required fuel injection amount qfin is equal to or less than the delay-processed upper limit amount qhccimaxlow, the first fuel injection amount qhcci is determined to be equal to the total required fuel injection amount qfin, and the second fuel injection amount qdiff is determined to be “0”. Is done. On the other hand, when the total required fuel injection amount qfin is larger than the post-delay processing upper limit amount qhccimaxlow, the first fuel injection amount qhcci is determined to be equal to the post-delay processing upper limit amount qhccimaxlow, and the second fuel injection amount qdiff is set to the total required fuel injection amount The amount is determined by subtracting the first fuel injection amount qhcci (accordingly, the post-delay processing upper limit amount qhccimaxlow) from the amount qfin.

  That is, when the total required fuel injection amount qfin is equal to or less than the post-delay processing upper limit amount qhccimaxlow, the first fuel injection amount qhcci is determined to be larger as the total required fuel injection amount qfin is larger. In this case, the reaction rate V of HCCI combustion is smaller than the upper limit reaction rate Vmax (see the range of qfin ≦ qfin1 in FIGS. 5 and 6).

  On the other hand, when the total required fuel injection amount qfin is larger than the post-delay processing upper limit amount qhccimaxlow, the first fuel injection amount qhcci is determined to be smaller as the total required fuel injection amount qfin is larger. As a result, even if the in-cylinder temperature Tg increases due to an increase in the total required fuel injection amount qfin, the fuel concentration [hcci] in the premixed gas decreases so that the reaction rate V of HCCI combustion becomes the upper limit reaction rate. The reaction rate can be equal to Vmax (see the range of qfin> qfin1 in FIGS. 5 and 6). As described above, by determining the upper limit qhccimax of the first fuel injection amount qhcci while taking into account the in-cylinder temperature Tg and the fuel concentration [hcci], which are parameters related to the reaction rate V of HCCI combustion, The situation where noise becomes excessively large can be suppressed.

  Further, by using the post-delay upper limit amount qhccimaxlow as described above, even if the total required fuel injection amount qfin increases stepwise, the in-cylinder against the step increase of the total required fuel injection amount qfin While delaying the rise in temperature Tg is simulated, the upper limit amount qhccimaxlow after delay processing decreases. Thereby, compared with the case where delay processing is not performed, the opportunity to perform HCCI combustion can increase, and the generation amount of NOx etc. can be reduced more.

  On the other hand, even if the total required fuel injection amount qfin decreases stepwise, the delay amount upper limit amount is simulated while the delay in the in-cylinder temperature Tg is reduced with respect to the stepwise decrease in the total required fuel injection amount qfin. qhccimaxlow increases. Thereby, even in this case, the reaction rate V of HCCI combustion can be suppressed from exceeding the upper limit reaction rate Vmax, and the occurrence of a situation in which noise due to HCCI combustion becomes excessively large can be suppressed. .

  The present invention is not limited to the above-described embodiment, and various modifications can be employed within the scope of the present invention. For example, in the above embodiment, the higher the total required fuel injection amount qfin and / or the higher the operation speed NE, the smaller the upper limit amount qhccimax is determined using the linear function funcqhccimax, and the upper limit amount qhccimax However, instead of this, the upper limit amount qhccimaxlow after delay processing is obtained, but instead, the total required fuel injection amount qfin, the fuel temperature Tcr, and the state of the gas sucked into the combustion chamber are The in-cylinder temperature Tg is estimated based on parameters (for example, intake air temperature Tb, intake pipe pressure Pb, etc.), parameters indicating exhaust gas conditions (for example, exhaust gas temperature Tex, exhaust gas pressure Pex, etc.), etc. The higher the internal temperature Tg and the larger the provisional total required fuel injection amount qfin (hcci), the smaller the upper limit amount qhccimax is determined.Instead of using the post-delay upper limit amount qhccimaxlow, the above determination is made. Upper limit qhcci It may be configured such that max is used. In this case, instead of estimating the in-cylinder temperature Tg, the in-cylinder temperature Tg is directly detected by arranging a sensor for detecting the in-cylinder temperature Tg at a predetermined position in the combustion chamber. A temperature Tg may be used.

  In the above embodiment, the upper limit amount qhccimax is always subjected to low-pass filter processing to obtain the post-delay upper limit amount qhccimaxlow, so that the upper limit amount qhccimax is subjected to delay processing. Starting from the time when the change speed of the total required fuel injection amount qfin becomes larger than the predetermined change speed, the upper limit amount qhccimax for the predetermined period from the start time is determined to be equal to the upper limit amount qhccimax determined in the same start period. The delay processing may be performed.

  In this case, it is preferable to determine the predetermined period as a longer period as the change rate of the total required fuel injection amount qfin is larger. Further, after the end of the predetermined period, the upper limit amount qhccimax may be further subjected to low-pass filter processing.

  In the above embodiment, the upper limit amount qhccimax is always subjected to the low-pass filter process. Instead, the time when the change rate of the total required fuel injection amount qfin becomes larger than the predetermined change rate is started. Alternatively, the low pass filter process may be performed only for a predetermined period from the beginning. Also in this case, it is preferable to determine the predetermined period as a longer period as the change rate of the total required fuel injection amount qfin is larger.

  In the above embodiment, the first and second fuel injection amounts qhcci, qdiff are determined using the value after the delay processing of the upper limit amount qhccimax (that is, the upper limit amount qhccimaxlow after delay processing). However, instead of this, the first and second fuel injection amounts qhcci, qdiff may be determined using the upper limit amount qhccimax itself without performing delay processing.

  In addition, in the above-described embodiment, the upper limit amount qhccimax corrected using all the three correction coefficients K1, K2, and K3 is used. Instead, the correction coefficients K1, K2, and K3 are used. The upper limit amount qhccimax corrected using two or only one of K3 may be used, or the upper limit amount qhccimax not corrected by the correction coefficient may be used. Also good.

1 is a schematic configuration diagram of an entire system in which a fuel injection amount 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. 6 is a graph showing an example of the relationship between the total required fuel injection amount and the operating speed and the in-cylinder temperature when the engine is in a steady operation state. The temporary total required fuel injection amount when the total required fuel injection amount referred to by the CPU shown in FIG. 1 is equal to the first fuel injection amount for premixed compression ignition combustion is an independent variable, and the first fuel injection amount It is the graph which showed the linear function which uses the upper limit amount of as a dependent variable. 6 is a graph showing an example of a relationship between a total required fuel injection amount, a first fuel injection amount for premixed compression ignition combustion, and a second fuel injection amount for diffusion combustion when the engine is in a steady operation state. . 6 is a graph showing an example of the relationship between the total required fuel injection amount, the in-cylinder temperature, the fuel concentration in the premixed gas, and the reaction rate of HCCI combustion when the engine is in a steady operation state. 3 is a graph showing a table that defines a relationship between a coolant temperature and a correction coefficient for correcting an upper limit amount of a first fuel injection amount, which is referred to by a CPU shown in FIG. 1. 3 is a graph showing a table that defines a relationship between a temperature of outside air and a correction coefficient for correcting an upper limit amount of a first fuel injection amount referred to by a CPU shown in FIG. 1. 3 is a graph showing a table that defines a relationship between an external air pressure and a correction coefficient for correcting an upper limit amount of a first fuel injection amount, which is referred to by a CPU shown in FIG. 1. It is the flowchart which showed the program for determining the fuel injection quantity etc. which CPU shown in FIG. 1 performs.

Explanation of symbols

  21 ... Fuel injection valve, 60 ... Electric control device, 61 ... CPU, 74 ... Crank position sensor, 78 ... Water temperature sensor

Claims (5)

Means for injecting fuel for premixed compression ignition combustion into the combustion chamber earlier than the vicinity of compression top dead center;
Means for injecting fuel for diffusion combustion separately from the fuel for premixed compression ignition combustion into the combustion chamber in the vicinity of the compression top dead center;
Applied to an internal combustion engine with
Total required fuel injection amount determining means for determining a total required fuel injection amount per cycle of the internal combustion engine based on an operating state of the internal combustion engine;
Based on at least the temperature of the gas in the combustion chamber, the upper limit of the first fuel injection amount for the premixed compression ignition combustion is set to an excessive increase in the pressure of the gas due to the combustion of the fuel of the first fuel injection amount. An upper limit amount determining means for determining an amount corresponding to an upper limit of a range that is not large,
When the total required fuel injection amount is less than or equal to the upper limit amount, the first fuel injection amount is determined to be equal to the total required fuel injection amount, and when the total required fuel injection amount is greater than the upper limit amount, First fuel injection amount determining means for determining a first fuel injection amount equal to the upper limit amount;
Second fuel injection amount determining means for determining the second fuel injection amount for diffusion combustion to an amount obtained by subtracting the first fuel injection amount from the total required fuel injection amount;
In a fuel injection amount control device for an internal combustion engine comprising :
The upper limit amount determining means includes
Using the operation speed of the internal combustion engine that affects the temperature of the gas and the total required fuel injection amount, the higher the operation speed or the greater the total required fuel injection amount, the smaller the upper limit amount. Configured to determine the quantity,
The first fuel injection amount determining means includes
When the total required fuel injection amount is less than or equal to the upper limit amount, the larger the total required fuel injection amount, the larger the first fuel injection amount is determined, and the total required fuel injection amount is larger than the upper limit amount. A fuel injection amount control device for an internal combustion engine configured to determine the first fuel injection amount to be smaller as the total required fuel injection amount is larger . The fuel injection amount control apparatus for an internal combustion engine according to claim 1 ,
The upper limit amount determining means includes
Using the temperature of the cooling water of the internal combustion engine that affects the temperature of the gas,
A fuel injection amount control device for an internal combustion engine configured to determine the upper limit amount to a smaller amount as the temperature of the cooling water is higher. The fuel injection amount control device for an internal combustion engine according to claim 1 or 2 ,
The upper limit amount determining means includes
Using the temperature of the outside air that affects the temperature of the gas,
A fuel injection amount control device for an internal combustion engine configured to determine the upper limit amount to be smaller as the temperature of the outside air is higher. The fuel injection amount control device for an internal combustion engine according to any one of claims 1 to 3 ,
The upper limit amount determining means includes
A fuel injection amount control device for an internal combustion engine configured to determine the upper limit amount to be smaller as the pressure of the outside air is smaller. A fuel injection amount control device for an internal combustion engine according to any one of claims 1 to 4 ,
Means for delaying the upper limit when the rate of change in the total required fuel injection amount is greater than a predetermined rate;
The first fuel injection amount determining means has the upper limit amount as
A fuel injection amount control apparatus for an internal combustion engine configured to determine the first fuel injection amount using a value after the delay processing.

Images