JP2009209890A - Internal combustion engine and fuel supply control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain the air-fuel ratio from becoming excessively lean after starting an internal combustion engine. <P>SOLUTION: This internal combustion engine 1 has a port injection valve 32 for supplying furl to air A in an intake port 8i. When starting the internal combustion engine 1, after an engine speed of the internal combustion engine 1 becomes a peak value, a quantity of fuel F supplied to the intake port 8i from the port injection valve 32 is increased more than a reference fuel supply quantity set based on an operation condition of the internal combustion engine 1 when the engine speed reduces. Thus, after starting the internal combustion engine 1, the air-fuel ratio is restrained from becoming excessively lean. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to fuel supply to an internal combustion engine.

  A gasoline engine which is an internal combustion engine burns fuel in a combustion space inside the engine. If misfire occurs or the internal combustion engine stops after starting the internal combustion engine, unburned hydrocarbons (HC) increase. Therefore, there is a demand to avoid misfire and stop as much as possible after starting the internal combustion engine. . In Patent Document 1, in a fuel control method for reducing fuel increase with the passage of time when shifting from start-up control to post-startup control of an internal combustion engine, the rate of decrease in fuel increase is determined according to engine temperature. There has been disclosed a fuel control method that prevents the engine stall, which is likely to occur after a complete explosion, by preventing a problem that the air-fuel ratio becomes excessively lean at the time of return.

Japanese Utility Model Publication No. 7-34926 (0004, 0005)

  By the way, the change in the engine rotational speed at the time of starting the internal combustion engine usually increases with the starting operation, and after reaching the peak of the engine rotational speed, it decreases toward the target rotational speed at idling. As the engine speed decreases, the amount of air in the combustion space where the fuel / air mixture burns increases. That is, the efficiency of filling the air into the combustion space is increased.

  In the fuel control method disclosed in Patent Document 1, the amount of fuel increased at the time of start-up is only decreased according to the temperature of the internal combustion engine, and the engine speed decreases after the peak of the engine speed appears. However, it is not considered that the filling efficiency is increased. As a result, when the engine speed decreases, the air-fuel ratio becomes excessively lean, and there is a risk that the internal combustion engine may misfire or the internal combustion engine stops. The present invention has been made in view of the above, and an object of the present invention is to prevent the air-fuel ratio from becoming excessively lean after the internal combustion engine is started.

  In order to solve the above-described problems and achieve the object, an internal combustion engine according to the present invention supplies an intake port connected to a combustion space in which a mixture of fuel and air burns, and supplies the fuel to the intake port In addition, when the internal combustion engine starts, the amount of fuel supplied to the intake port when the engine rotational speed decreases after the engine rotational speed of the internal combustion engine reaches a peak value is determined. And a port injection valve that increases more than a reference fuel supply amount set based on the operating conditions.

  In the present invention, after the engine rotation speed reaches its peak value, the amount of fuel supplied to the intake port is increased in accordance with the decrease in the engine rotation speed and the increase in the charging efficiency of air into the combustion space. The reference fuel supply amount that is set based on the operating conditions of the internal combustion engine is increased. This increases the amount of air flowing into the combustion space due to an increase in the efficiency of filling the air into the combustion space, so that the air-fuel ratio becomes excessively lean after the internal combustion engine is started. Can be suppressed. As a result, deterioration of the combustion state of the internal combustion engine and misfire can be suppressed, and the internal combustion engine can be started and operated stably.

  As a preferred aspect of the present invention, in the internal combustion engine, it is desirable that the amount to be increased from the reference fuel supply amount becomes larger as the peak value of the engine speed increases.

  As a preferred aspect of the present invention, in the internal combustion engine, when the peak value of the engine rotation speed does not appear during a predetermined period after the start of the internal combustion engine, the port injection valve is It is desirable to supply fuel to the intake port with a reference fuel supply amount.

  As a preferred aspect of the present invention, in the internal combustion engine, when the peak value of the engine rotational speed is not more than a predetermined first threshold value or not less than a predetermined second threshold value, the port injection valve is Preferably, fuel is supplied to the intake port at the reference fuel supply amount.

  In order to solve the above-described problems and achieve the object, a fuel supply control device for an internal combustion engine according to the present invention supplies fuel to an intake port connected to a combustion space in which a mixture of fuel and air burns. In an internal combustion engine provided with a port injection valve, when starting the internal combustion engine, a peak value calculation unit that calculates a peak value of the engine rotation speed of the internal combustion engine, and the engine rotation speed decreases after the peak value appears A fuel supply amount calculation unit that increases the amount of fuel supplied by the port injection valve to the intake port from a reference fuel supply amount set based on an operating condition of the internal combustion engine. It is characterized by.

  In the present invention, after the engine rotation speed reaches its peak value, the amount of fuel supplied to the intake port is increased in accordance with the decrease in the engine rotation speed and the increase in the charging efficiency of air into the combustion space. The reference fuel supply amount that is set based on the operating conditions of the internal combustion engine is increased. This increases the amount of air flowing into the combustion space due to an increase in the efficiency of filling the air into the combustion space, so that the air-fuel ratio becomes excessively lean after the internal combustion engine is started. Can be suppressed. As a result, deterioration of the combustion state of the internal combustion engine and misfire can be suppressed, and the internal combustion engine can be started and operated stably.

  As a preferred aspect of the present invention, in the fuel supply control apparatus for an internal combustion engine, the fuel supply amount calculation unit increases an amount that is increased from the reference fuel supply amount as the peak value of the engine rotation speed increases. It is desirable to enlarge it.

  As a preferred aspect of the present invention, in the fuel supply control device for the internal combustion engine, when the peak value of the engine rotation speed does not appear during a predetermined period after the start of the internal combustion engine, the fuel supply is performed. It is preferable that the amount calculation unit sets the amount of fuel supplied from the port injection valve to the intake port as the reference fuel supply amount.

  As a preferred aspect of the present invention, in the fuel supply control device for an internal combustion engine, when the peak value of the engine rotation speed is not more than a predetermined first threshold value or not less than a predetermined second threshold value, Preferably, the fuel supply amount calculation unit sets the amount of fuel supplied to the intake port by the port injection valve as the reference fuel supply amount.

  The present invention can suppress the air-fuel ratio from becoming excessively lean after the internal combustion engine is started.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited by the best mode for carrying out the invention (hereinafter referred to as an embodiment). In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art, or those that are substantially the same, so-called equivalent ranges. The present invention can be applied regardless of cold start or start after completion of warm-up as long as the internal combustion engine is started.

  FIG. 1 is an apparatus configuration diagram showing an internal combustion engine and a fuel supply control apparatus for the internal combustion engine according to the present embodiment. In this embodiment, in an internal combustion engine including a port injection valve that supplies fuel to an intake port, when the engine rotational speed decreases after the engine rotational speed of the internal combustion engine reaches a peak value at the time of starting, port injection is performed. It is characterized in that the amount of fuel supplied from the valve to the intake port is increased from the reference fuel supply amount set based on the operating conditions of the internal combustion engine. Here, supplying the fuel from the port injection valve to the intake port of the internal combustion engine is synonymous with supplying the fuel to the internal combustion engine.

  The internal combustion engine 1 is a so-called reciprocating internal combustion engine in which a piston 5 reciprocates in a cylinder 3. The internal combustion engine 1 is controlled by an engine ECU (Electronic Control Unit) 50. The cylinder 3 of the internal combustion engine 1 is a cylindrical structure, and one end is attached to the cylinder head 2 and the other end is attached to the crankcase 4. A space 3B surrounded by the inner surface of the cylinder 3, the top surface of the piston 5, and the inner surface of the cylinder head 2 is a space in which the fuel F supplied to the internal combustion engine 1 burns. This space 3B is referred to as a combustion space 3B. The fuel F supplied to the internal combustion engine 1 is a fuel containing hydrocarbons, for example, gasoline.

  The cylinder 3 is formed with a water jacket 3W. Water (cooling water) for cooling the internal combustion engine 1 flows through the water jacket 3W to cool the internal combustion engine 1. The temperature of the cooling water is detected by the cooling water temperature sensor 40, taken into the engine ECU 50, and used for controlling the internal combustion engine 1.

  The cylinder head 2 includes an intake port 8i that is an intake passage for introducing air (combustion air) A for combustion of the fuel F into the combustion space 3B, and a combustion gas after the fuel F is burned in the combustion space 3B. (Exhaust gas) Exhaust port 8e which is an exhaust passage for discharging Ex to the outside of combustion space 3B is formed.

  The intake port 8i and the exhaust port 8e are connected to the combustion space 3B, respectively, and one end of each of the combustion spaces 3B opens to form an opening, and the other end of each other is formed in the cylinder head 2. Opens. An intake valve 9i is disposed at the opening of the intake port 8i that opens to the combustion space 3B, and an exhaust valve 9e is disposed at the opening of the exhaust port 8e that opens to the combustion space 3B. The intake valve 9i opens and closes the opening of the intake port 8i that opens to the combustion space 3B, and the exhaust valve 9e opens and closes the opening of the exhaust port 8e that opens to the combustion space 3B.

  The internal combustion engine 1 includes a port injection valve 32 as fuel supply means for injecting and supplying the fuel F into the intake port 8i. In the present embodiment, the port injection valve 32 is attached to the cylinder head 2. An ignition plug 30 is attached to the cylinder head 2 of the internal combustion engine 1 as ignition means for igniting an air-fuel mixture of fuel F and air A formed in the combustion space 3B. The air-fuel mixture in the combustion space 3B is ignited by the discharge from the spark plug 30 and burns. Thus, the internal combustion engine 1 is a so-called spark ignition type internal combustion engine.

  The port injection valve 32 provided in the internal combustion engine 1 is attached to the fuel distribution pipe 63 for the port injection valve, and its operation is controlled by the engine control unit 52 of the engine ECU 50. The port injection valve 32 is supplied with fuel from the port injection valve fuel distribution pipe 63 and injects fuel F into the air A in the intake port 8 i of the internal combustion engine 1. Thereby, an air-fuel mixture in which the fuel F and the air A are sufficiently mixed is formed.

  A throttle valve 10 is attached to the intake passage connected to the intake port 8i. The throttle valve 10 includes a valve body 10V and a throttle valve actuator 10A that is attached to and operates the valve body 10V. By adjusting the opening degree of the valve body 10V, the passage sectional area of the intake passage changes, and the amount of air A introduced into the combustion space 3B is adjusted. An air flow meter 43 is disposed upstream of the valve body 10V of the throttle valve in the flow direction of the air A, and the flow rate (mass flow rate) of the air A flowing through the intake passage, that is, the air flowing into the combustion space 3B. The flow rate of A is measured. The flow rate of the air A measured by the air flow meter 43 is taken into the engine ECU 50 and used for controlling the internal combustion engine 1.

  The fuel F supplied from the port injection valve 32 into the intake port 8 i is stored in the fuel tank 13. A feed pump 14 is disposed inside the fuel tank 13. The feed pump 14 and the port injector fuel distribution pipe 63 are connected by a fuel pipe 23, and the fuel F in the fuel tank 13 discharged from the feed pump 14 passes through the fuel pipe 23 and is a fuel for the port injector. It is sent to the distribution pipe 63. The operation of the feed pump 14 is controlled by the engine control unit 52 of the engine ECU 50.

  When the intake valve 9i opens and the piston 5 moves to the bottom dead center, the air A and the fuel F supplied from the port injection valve 32 to the intake port 8i are mixed from the opening of the intake port 8i to the combustion space 3B. Inflow of air (intake stroke). Note that the fuel F is supplied from the port injection valve 32 to the intake port 8i before the intake stroke. When the piston 5 passes through the bottom dead center and the piston 5 moves toward the top dead center (that is, in the direction of the cylinder head 2) with the intake valve 9i and the exhaust valve 9e closed, the fuel F formed in the combustion space 3B And air A are compressed (compression stroke).

  Before the piston 5 reaches top dead center, the spark plug 30 discharges and ignites the compressed air-fuel mixture. Thereby, the air-fuel mixture in the combustion space 3B burns. Here, the ignition timing of the spark plug 30 is controlled by the engine control unit 52 of the engine ECU 50.

  The piston 5 moves toward the bottom dead center by the combustion pressure when the air-fuel mixture burns (expansion stroke). The piston 5 that has passed through the bottom dead center moves again toward the top dead center. At this time, the exhaust valve 9e is opened, and the combustion gas (exhaust gas Ex) in the combustion space 3B is discharged to the exhaust port 8e (exhaust gas). Process). Thereby, one cycle of the internal combustion engine 1 is completed. For example, during the exhaust stroke, the fuel F of the next cycle is supplied from the port injection valve 32 into the intake port 8i.

  When the piston 5 comes close to top dead center, the intake valve 9i is opened, the exhaust valve 9e is closed, and the next cycle of the internal combustion engine 1 is started. Thus, the internal combustion engine 1 is a four-stroke one-cycle internal combustion engine in which one cycle is completed while the piston 5 reciprocates twice within the cylinder 3. The reciprocating motion of the piston 5 is transmitted to the crankshaft 7 in the crankcase 4 via the connecting rod 6 and converted into rotational motion. The rotation angle of the crankshaft 7 is detected by a crank angle sensor 41. The engine control unit 52 of the engine ECU 50 takes in the rotation angle of the crankshaft 7 detected by the crank angle sensor 41, and calculates the rotation speed (engine rotation speed) of the crankshaft 7 based on this. In this embodiment, the rotation speed (engine rotation speed) of the crankshaft 7 per unit time is used as the engine rotation speed. However, for example, the rotation angular speed of the crankshaft 7 may be used.

  The engine ECU 50 including the fuel supply control device 51 includes an input / output unit 54, a processing unit 50P, and a storage unit 53 that stores various maps used for controlling the internal combustion engine 1. A cooling water temperature sensor 40, a crank angle sensor 41, an ignition key 42, an air flow meter 43, a throttle valve actuator 10A, a port injection valve 32, a spark plug 30, and the feed pump 14 are connected to the input / output unit 54. The input / output unit 54 inputs / outputs input signals from the coolant temperature sensor 40, the crank angle sensor 41, and the like, and output signals to the port injection valve 32, the spark plug 30, and the like.

  The processing unit 50P includes, for example, a memory and a CPU (Central Processing Unit). The processing unit 50P includes a fuel supply control device (hereinafter referred to as a fuel supply control device) 51 for an internal combustion engine that executes fuel supply control according to the present embodiment and an engine control unit 52 that controls the internal combustion engine 1. Thus, in the present embodiment, the fuel supply control device 51 is realized as a function of the processing unit 50P.

  The fuel supply control device 51 includes a control condition determination unit 51A, a peak value calculation unit 51B, and a fuel supply amount calculation unit 51C. Among these, at least the peak value calculation unit 51B and the fuel supply amount calculation unit 51C realize the fuel supply control according to the present embodiment. That is, the function of the fuel supply control device 51 is realized by at least the peak value calculation unit 51B and the fuel supply amount calculation unit 51C.

  The storage unit 53 is a nonvolatile memory such as a flash memory, a memory that can only be read such as a ROM (Read Only Memory), a memory that can be read and written such as a RAM (Random Access Memory), or a combination thereof. Can be configured. The storage unit 53 stores a control program and a data map used when controlling the internal combustion engine 1, a control program and a data map used when executing the fuel supply control according to the present embodiment, and the like.

  FIG. 2 is an explanatory diagram showing a state of the internal combustion engine at the time of starting. FIG. 2 shows temporal changes in the engine speed Ne, the air-fuel ratio A / F, the intake pipe pressure Pi, and the fuel supply amount Qf. When the internal combustion engine 1 is started, time t = ts. When the internal combustion engine 1 is started, the crankshaft 7 starts to rotate and the engine rotational speed Ne increases. Then, the peak value Ne_p of the engine speed is taken at t = tp. Thereafter, the engine rotation speed gradually decreases to the idling target engine rotation speed Ne_t. The idling target engine speed Ne_t is an engine speed at idling that is targeted after the internal combustion engine 1 is warmed up.

  As the engine rotation speed Ne increases, the intake pipe pressure (pressure in the intake port 8i) Pi decreases, and after the peak value Ne_p of the engine rotation speed appears at t = tp, the intake pipe pressure Pi starts to increase. Thereby, since the charging efficiency of the air A to the combustion space 3B increases, the amount of air A flowing into the combustion space 3B of the internal combustion engine 1 shown in FIG. 1 increases. Further, when the intake pipe pressure Pi is lowered to a pressure lower than the atmospheric pressure, the fuel adhering to the wall surface of the intake port 8i evaporates and flows into the combustion space 3B. For this reason, the amount of the fuel F supplied from the port injection valve 32 adheres to the wall surface of the intake port 8i increases, and all the fuel F injected from the port injection valve 32 may not be introduced into the combustion space 3B. . By increasing the charging efficiency and decreasing the amount of fuel F introduced into the combustion space 3B, the air-fuel ratio A / F increases, and the internal combustion engine 1 is operated in a lean (excessive oxygen) state. Become.

  Further, the degree of increase in the charging efficiency varies depending on the difference (peak engine rotational speed difference) ΔNe between the peak value Ne_p of the engine rotational speed and the idling target engine rotational speed Ne_t, and the peak engine rotational speed difference ΔNe increases. Therefore, it becomes large. For this reason, the degree of lean air-fuel ratio A / F also changes as the peak engine speed difference ΔNe increases.

  In the conventional fuel supply control, since the fuel supply amount Qf is gradually decreased as indicated by the one-dot chain line in FIG. 2 from the time of starting the internal combustion engine 1 (t = ts), the peak engine speed difference ΔNe, that is, charging There was a case that it was not an appropriate value corresponding to the efficiency. Further, in the conventional fuel supply control, the amount of the fuel F introduced into the combustion space 3B may be decreased due to the evaporation of the fuel F adhering to the wall surface of the intake port 8i due to the decrease in the intake pipe pressure Pi. It was not considered. As a result, as shown in the one-dot chain line in FIG. 2, the air-fuel ratio A / F increases as the engine speed Ne decreases, and the internal combustion engine 1 may be operated in a lean state. . If the lean state becomes excessive, the combustion state deteriorates, and misfire or stop occurs in the internal combustion engine 1 to increase the amount of unburned HC or increase the vibration of the internal combustion engine. was there.

  In the fuel supply control according to the present embodiment, after the peak value Ne_p of the engine rotation speed appears, the engine rotation speed Ne decreases and the charging efficiency inside the combustion space 3B increases to the intake port 8i. The amount of fuel F to be supplied (fuel supply amount) Qf is increased from the reference fuel supply amount Qf_b set based on the operating conditions of the internal combustion engine 1. That is, at time t = ti, fuel F is supplied from the port injection valve 32 at an air-fuel ratio corrected fuel supply amount Qf_i obtained by adding the fuel increase amount ΔQf1 to the reference fuel supply amount Qf_b.

  As a result, as shown by the solid line in FIG. 2, the increase in the air-fuel ratio A / F is suppressed, so that the internal combustion engine 1 is avoided from being operated in an excessively lean state, and the deterioration of the combustion state is suppressed. Is done. As a result, the risk of misfire or stop occurring in the internal combustion engine 1 can be reduced, so that the risk of increasing the amount of unburned HC can be reduced, and vibration of the internal combustion engine 1 can be suppressed. As shown in FIG. 2, at the time when the supply of fuel F from the port injection valve 32 is started at the air-fuel ratio corrected fuel supply amount Qf_i (t = ti), after the peak value Ne_p of the engine speed appears, the engine speed While Ne is decreasing. Next, the procedure of fuel supply control according to this embodiment will be described.

  FIG. 3 is a flowchart showing a procedure of fuel supply control according to the present embodiment. 4 to 6 are diagrams for explaining the determination of the control condition of the fuel supply control according to the present embodiment. FIG. 7 is a fuel increase amount determination map describing the fuel increase amount in the fuel supply control according to the present embodiment. The fuel supply control according to the present embodiment can be realized by the fuel supply control device 51 shown in FIG.

  In executing the fuel supply control according to the present embodiment, in step S101, the control condition determination unit 51A of the fuel supply control device 51 determines whether or not the internal combustion engine 1 is in a starting state. For example, when the control condition determination unit 51A obtains a rotation command value of a starter motor for starting the internal combustion engine 1 from the ignition key 42, that is, when the starter motor starts rotating, the control condition determination unit 51A It is determined that the internal combustion engine 1 is being started.

  When it is determined No in step S101, that is, when the control condition determination unit 51A determines that the internal combustion engine 1 is not at the start time, the fuel supply control of the present embodiment ends. When it is determined Yes in step S101, that is, when the control condition determination unit 51A determines that the internal combustion engine 1 is at the time of starting, the process proceeds to step S102. Here, in FIGS. 2 and 4 to 6, the time t = ts corresponds to the start of the internal combustion engine 1.

  In step S102, the control condition determination unit 51A determines whether or not a predetermined period t1 shown in FIG. 4 has elapsed since the start of the internal combustion engine 1 (t = ts). For example, the control condition determination unit 51A obtains an elapsed time t from the start of the internal combustion engine 1 using a timer function provided in the processing unit 50P of the engine ECU 50, and compares it with a predetermined period t1. If the peak value Ne_p of the engine speed at the start of the internal combustion engine 1 does not appear between the start of the internal combustion engine 1 and the predetermined period t1, it is considered that the combustion of the internal combustion engine 1 is not normal. In such a case, the fuel supply control according to the present embodiment is terminated. The predetermined period t1 is a threshold value for determining the rising state of the internal combustion engine 1 at the start, and is determined by experiments, simulations, or the like based on the specifications of the internal combustion engine 1 or the allowable combustion state, for example. .

  When it is determined No in step S102, that is, when the control condition determination unit 51A determines that t ≧ t1, the fuel supply control according to the present embodiment is terminated. In this case, the time change of the engine rotational speed Ne is as indicated by a one-dot chain line B in FIG. When t ≧ t1, the fuel supply amount calculation unit 51C of the fuel supply control device 51 sets the amount of fuel F that the port injection valve 32 supplies to the intake port 8i based on the operating conditions of the internal combustion engine 1. The reference fuel supply amount Qf_b is set.

  The reference fuel supply amount Qf_b is the amount of fuel F supplied to the internal combustion engine 1 from the start of the internal combustion engine 1 to idling. For example, the reference fuel supply amount Qf_b is increased to the target fuel supply amount Qf_t that is the target fuel supply amount of the internal combustion engine 1 after the warm-up of the internal combustion engine 1 is increased (the internal combustion engine 1 is increased in the coolant temperature θw). It is obtained by adding a predetermined reference fuel increase ΔQf_b that becomes smaller with the increase in time t during which 1 is operated). The reference fuel increase amount ΔQf_b becomes 0 when the warm-up is completed. The target fuel supply amount Qf_t is, for example, an air-fuel ratio A / F that is a ratio of the intake air amount of the internal combustion engine 1 measured by the air flow meter 43 and the amount of fuel F supplied to the internal combustion engine 1. It is set to be the theoretical air fuel ratio. Since the intake air amount of the internal combustion engine 1 varies depending on the operating conditions (engine speed, intake air temperature, etc.) of the internal combustion engine 1, the reference fuel supply amount Qf_b obtained from the target fuel supply amount Qf_t and the target fuel supply amount Qf_t is: It is set based on the operating conditions of the internal combustion engine 1.

  When it is determined Yes in step S102, that is, when the control condition determination unit 51A determines that t <t1, the process proceeds to step S103. In step S103, the peak value calculation unit 51B of the fuel supply control device 51 calculates the peak value Ne_p of the engine speed of the internal combustion engine 1, and the control condition determination unit 51A determines whether or not the peak value Ne_p has appeared. . For example, when the value obtained by subtracting the engine rotational speed Ne_n−1 prior to the current time from the current engine rotational speed Ne_n becomes a negative value, the engine rotational speed Ne_n−1 prior to the current time is the peak value Ne_p. is there. Here, n is an integer.

  When it is determined No in step S103, that is, when the control condition determination unit 51A determines that the peak value Ne_p does not appear from the calculation result of the peak value calculation unit 51B, the process returns to step S102. That is, it is determined whether or not the peak value Ne_p appears until t ≧ t1. When it determines with Yes in step S103, ie, when the control condition determination part 51A determines from the calculation result of the peak value calculation part 51B that the peak value Ne_p has appeared, it progresses to step S104. In this case, the time change of the engine rotational speed Ne is, for example, as shown by a solid line A in FIG.

  In step S104, the control condition determination unit 51A determines whether or not the peak value Ne_p is larger than a predetermined first threshold value Ne_min and smaller than a predetermined second threshold value Ne_max. For example, as shown by a solid line C in FIG. 5, when the peak value Ne_p does not exceed the predetermined first threshold value Ne_min, the internal combustion engine 1 behaves unintentionally at the time of start, and therefore, in this embodiment. Such fuel supply control ends. In the present embodiment, the first threshold value Ne_min is smaller than the idling target engine speed Ne_t as shown in FIG. 5, but may be the idling target engine speed Ne_t. The first threshold value Ne_min is appropriately set according to the specifications of the internal combustion engine 1 and the like.

  As indicated by a solid line D in FIG. 6, when the peak value Ne_p is equal to or greater than a predetermined second threshold value Ne_max, sufficient air A and fuel F are supplied to the internal combustion engine 1. If the fuel F is further increased in this case, the engine rotational speed Ne becomes even larger than the peak value Ne_p, as shown by a one-dot chain line E in FIG. 6, giving the driver a sense of incongruity or increasing the exhaust gas Ex. To do. Therefore, when Ne_p ≧ Ne_max, the fuel supply control according to the present embodiment ends. In the present embodiment, the second threshold value Ne_max is set to a value larger than the idling target engine speed Ne_t, as shown in FIG. The second threshold value Ne_max is appropriately set according to the specifications of the internal combustion engine 1 and the like.

  When it is determined No in step S104, that is, when the control condition determination unit 51A determines that the peak value Ne_p is equal to or less than the first threshold value Ne_min or a predetermined second threshold value Ne_max, this embodiment The fuel supply control related to is terminated. In this case, the fuel supply amount calculation unit 51C sets the amount of fuel F that the port injection valve 32 supplies to the intake port 8i as the reference fuel supply amount Qf_b that is set based on the operating conditions of the internal combustion engine 1. When it is determined Yes in step S104, that is, when the control condition determination unit 51A determines that the peak value Ne_p is larger than the first threshold value Ne_min and smaller than the second threshold value Ne_max, the process proceeds to step S105. .

  In step S105, the fuel supply amount calculation unit 51C of the fuel supply control device 51 obtains a fuel increase amount ΔQf1 of the internal combustion engine 1 shown in FIG. The fuel increase amount ΔQf1 is an amount by which the amount of fuel F supplied to the internal combustion engine 1 is increased from the reference fuel supply amount Qf_b shown in FIG. Therefore, the air-fuel ratio corrected fuel supply amount Qf_i is Qf_b + ΔQf1 obtained by adding the fuel increase amount ΔQf1 to the reference fuel supply amount Qf_b shown in FIG.

  The fuel increase determination map 60 in FIG. 7 shows the initial value of the fuel increase ΔQf1, that is, the value at t = ti (the value at the start of fuel increase after the peak value appears). Thus, in the present embodiment, the fuel increase amount ΔQf1 is increased as the difference (peak engine rotational speed difference) ΔNe between the peak value Ne_p and the idling target engine rotational speed Ne_t increases. Here, since the idling target engine speed Ne_t is a constant value, the fuel increase amount ΔQf1 increases as the peak value Ne_p of the engine speed increases. Since the charging efficiency of the air into the combustion space 3B increases as the peak engine speed difference ΔNe increases, the charging efficiency change can be reflected in the fuel increase amount ΔQf1 in this way. As a result, the lean air-fuel ratio can be more reliably suppressed. The fuel increase amount determination map 60 is created in advance by experiments and experience values, and is stored in the storage unit 53 of the engine ECU 50 shown in FIG.

As shown in FIG. 2, the fuel increase amount ΔQf1 becomes smaller as time t passes, and becomes the target fuel supply amount Qf_t when the warm-up of the internal combustion engine 1 is completed. In the present embodiment, for example, to reduce the fuel increase amount DerutaQf1 over time t by ΔQf1 × ^{k t.} Here, k is an attenuation coefficient, and is arbitrarily set within a range of 0 <k <1. Further, ΔQf1 × k when reducing the fuel increase amount DerutaQf1 by ^t, the time to start the supply from the port injection valve 32 of the fuel F in the air-fuel ratio correction fuel supply amount Qf_i obtained by adding the fuel increase amount DerutaQf1 the reference fuel supply amount Qf_b The time point of t = ti that is is set to 0 (= t). That is, since t = 0 at t = ti, the fuel increase amount ΔQf1 is ΔQf1 × k ⁰ = ΔQf1 × 1 = ΔQf1. This ΔQf1 is an initial value of the fuel increase amount ΔQf1, and is determined by the fuel increase amount determination map 60. Note that the method of decreasing the fuel increase amount ΔQf1 is not limited to this.

  When the fuel supply amount calculation unit 51C calculates the fuel increase amount ΔQf1, the process proceeds to step S106. In step S106, the fuel supply amount calculation unit 51C obtains an air-fuel ratio corrected fuel supply amount Qf_i. As described above, the air-fuel ratio corrected fuel supply amount Qf_i is Qf_b + ΔQf1. When the air-fuel ratio corrected fuel supply amount Qf_i is obtained, the process proceeds to step S107, where the engine control unit 52 of the engine ECU 50 operates the port injection valve 32, and the fuel F of the air-fuel ratio corrected fuel supply amount Qf_i obtained in step S106. Is supplied from the port injection valve 32 to the intake port 8i.

  As described above, in the present embodiment, in an internal combustion engine having a port injection valve that supplies fuel to the intake port, at the time of start-up, after the peak value of the engine rotation speed of the internal combustion engine appears, the engine rotation speed decreases and the charging efficiency Is increased from the reference fuel supply amount set based on the operating condition of the internal combustion engine, to increase the amount of fuel injected and supplied from the port injection valve to the intake port. As a result, the amount of air flowing into the combustion space due to the increase in charging efficiency can be suppressed, so that the air-fuel ratio can be prevented from becoming excessively lean after the internal combustion engine is started. As a result, deterioration of the combustion state of the internal combustion engine and misfire can be suppressed, and the internal combustion engine can be started and operated stably. Further, even in an internal combustion engine having means capable of detecting the intake pipe pressure, when the means fails, the fuel supply control according to the present embodiment is applied so that the air-fuel ratio becomes excessively lean after the start of the internal combustion engine. The deterioration of the combustion state and misfire of the internal combustion engine can be suppressed.

  As described above, the internal combustion engine and the fuel supply control device for the internal combustion engine according to the present invention are useful for an internal combustion engine including a port injection valve that supplies fuel to an intake port. It is suitable for suppressing misfiring and stopping after starting the internal combustion engine by suppressing leaning.

It is an apparatus block diagram which shows the internal combustion engine which concerns on this embodiment, and the fuel supply control apparatus of an internal combustion engine. It is explanatory drawing which shows the state of the internal combustion engine at the time of starting. It is a flowchart which shows the procedure of the fuel supply control which concerns on this embodiment. It is a figure explaining judgment of the control conditions of fuel supply control concerning this embodiment. It is a figure explaining judgment of the control conditions of fuel supply control concerning this embodiment. It is a figure explaining judgment of the control conditions of fuel supply control concerning this embodiment. 6 is a fuel increase determination map describing a fuel increase in fuel supply control according to the present embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder head 3 Cylinder 3B Combustion space (space)
3W Water jacket 4 Crankcase 5 Piston 6 Connecting rod 7 Crankshaft 8i Intake port 8e Exhaust port 10 Throttle valve 13 Fuel tank 14 Feed pump 23 Fuel piping 30 Spark plug 32 Port injection valve 40 Coolant temperature sensor 41 Crank angle sensor 42 Ignition Key 43 Air flow meter 50 Engine ECU
50P processing unit 51 fuel supply control device 51A control condition determination unit 51B peak value calculation unit 51C fuel supply amount calculation unit 52 engine control unit 53 storage unit 54 input / output unit 60 fuel increase amount determination map

Claims (8)

In internal combustion engines,
An intake port connected to a combustion space in which a mixture of fuel and air burns;
The fuel is supplied to the intake port, and is supplied to the intake port when the engine rotation speed decreases after the engine rotation speed of the internal combustion engine reaches a peak value when the internal combustion engine is started. A port injector that increases the amount of fuel from a reference fuel supply amount set based on operating conditions of the internal combustion engine;
An internal combustion engine comprising:   2. The internal combustion engine according to claim 1, wherein an amount that is increased from the reference fuel supply amount increases as a peak value of the engine rotation speed increases.   When the peak value of the engine rotation speed does not appear during a predetermined period after the internal combustion engine is started, the port injection valve supplies fuel to the intake port at the reference fuel supply amount. The internal combustion engine according to claim 1 or 2.   When the peak value of the engine rotation speed is equal to or lower than a predetermined first threshold value or equal to or higher than a predetermined second threshold value, the port injector supplies fuel to the intake port at the reference fuel supply amount. The internal combustion engine according to any one of claims 1 to 3, wherein: In an internal combustion engine comprising a port injection valve that supplies fuel to an intake port connected to a combustion space in which a mixture of fuel and air burns,
At the time of starting the internal combustion engine, a peak value calculation unit that calculates a peak value of the engine rotation speed of the internal combustion engine;
When the engine speed decreases after the peak value appears, the amount of fuel that the port injector supplies to the intake port is set based on the operating condition of the internal combustion engine. A fuel supply amount calculation unit that increases more than,
A fuel supply control apparatus for an internal combustion engine, comprising:   6. The fuel supply for an internal combustion engine according to claim 5, wherein the fuel supply amount calculation unit increases the amount to be increased from the reference fuel supply amount as the peak value of the engine speed increases. Control device.   When the peak value of the engine rotation speed does not appear during a predetermined period after the start of the internal combustion engine, the fuel supply amount calculation unit determines the amount of fuel that the port injection valve supplies to the intake port. The fuel supply control device for an internal combustion engine according to claim 5 or 6, wherein an amount is the reference fuel supply amount.   When the peak value of the engine rotation speed is equal to or lower than a predetermined first threshold value or equal to or higher than a predetermined second threshold value, the fuel supply amount calculation unit supplies the port injection valve to the intake port. The fuel supply control device for an internal combustion engine according to any one of claims 5 to 7, wherein an amount of fuel is the reference fuel supply amount.

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