JP2010164010A - Fuel supply control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel supply control device for an internal combustion engine, avoiding poor combustion in restarting the internal combustion engine even when exhaust gas reversely flows into an intake passage with valve overlap produced between an intake valve and an exhaust valve when stopping it. <P>SOLUTION: The fuel supply control device for the internal combustion engine 3 is provided for controlling the amount of fuel to be supplied into a cylinder 3a. It includes a valve overlap determining means 2 for determining whether the valve overlap is produced or not at stopping the internal combustion engine 3, an exhaust gas reverse flow amount calculating means 2 for calculating an exhaust gas reverse flow amount QEX reversely flowing into the intake passage 4 depending on an intake air temperature Tin and an exhaust gas temperature Tex detected when the valve overlap is determined to be produced, an oxygen concentration estimating means 2 for estimating a first oxygen concentration ODI 1 in the intake passage 4 depending on the exhaust gas reverse flow amount QEX, and a fuel supply amount correcting means 2 for correcting a basic fuel injection amount QBASE depending on the first oxygen concentration ODI 1 at starting the internal combustion engine 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel supply control device for an internal combustion engine that controls the amount of fuel supplied to a cylinder in accordance with a valve overlap state between an intake valve and an exhaust valve.

  As a conventional fuel supply control device for an internal combustion engine, for example, one disclosed in Patent Document 1 is known. The internal combustion engine includes an exhaust passage for exhausting exhaust gas from the cylinder, and a catalyst is provided in the exhaust passage.

  In this fuel supply control device, when the internal combustion engine is stopped, the oxygen concentration on the upstream side and the oxygen concentration on the downstream side of the catalyst are detected, and the exhaust gas is exhausted in accordance with the detected upstream and downstream oxygen concentrations. It is determined whether the air is flowing backward. When it is determined that the exhaust gas is flowing backward in the exhaust passage, the fuel cut mode in which fuel injection is prohibited for a predetermined time from the start of cranking or the fuel injection amount when the internal combustion engine is started next time The fuel injection amount reduction mode for reducing the fuel consumption is executed. As a result, exhaust gas that has further flowed back into the cylinder from the exhaust passage is scavenged to avoid plug fogging and improve the startability of the internal combustion engine.

JP 2007-239570 A

  As described above, in this conventional fuel supply control device for an internal combustion engine, it is determined whether exhaust gas is flowing backward in the exhaust passage by using the upstream and downstream oxygen concentrations of the catalyst provided in the exhaust passage. Therefore, it cannot be determined whether or not the exhaust gas actually flows back into the intake passage. Such a backflow of exhaust gas to the intake passage is likely to occur, for example, when a valve overlap between the intake valve and the exhaust valve occurs. For this reason, when the internal combustion engine is restarted, the fuel cut mode or the fuel injection amount reduction mode may be executed even though the exhaust gas does not actually flow back into the intake passage. Delays the startability. On the contrary, although the exhaust gas actually flows back into the intake passage, the fuel cut mode or the fuel injection amount reduction mode is not executed, and the normal start mode may be executed. In that case, since the oxygen concentration in the intake passage is reduced by the exhaust gas flowing backward, the air-fuel ratio of the air-fuel mixture combusting in the cylinder becomes rich, thereby causing a combustion failure, resulting in a decrease in startability and It causes deterioration of exhaust gas characteristics.

  The present invention has been made to solve the above problems, and even when exhaust gas flows back into the intake passage due to valve overlap between the intake valve and the exhaust valve generated when the internal combustion engine is stopped, It is an object of the present invention to provide a fuel supply control device for an internal combustion engine that can avoid poor combustion at the time of restart and thereby improve startability and exhaust gas characteristics.

  In order to achieve the above object, according to the first aspect of the present invention, air is sucked from the intake passage 4 into the cylinder 3a via the intake valve 8, and the exhaust gas generated in the cylinder 3a is discharged via the exhaust valve 9. A fuel supply control device for the internal combustion engine 3 that discharges into the exhaust passage 5 and controls the amount of fuel supplied to the cylinder 3a. When the internal combustion engine 3 is stopped, the valve overflow between the intake valve 8 and the exhaust valve 9 occurs. Valve overlap determination means (ECU 2 in the embodiment (hereinafter the same in this section), step 2 in FIG. 4) for determining whether or not a lap has occurred, and an intake passage temperature parameter representing the temperature in the intake passage 4 Intake passage temperature parameter detecting means (intake air temperature sensor 25) for detecting (intake air temperature Tin) and an exhaust passage temperature parameter for detecting an exhaust passage temperature parameter (exhaust temperature Tex) representing the temperature in the exhaust passage 5. When it is determined by the meter detection means (exhaust temperature sensor 26) and the valve overlap determination means that the valve overlap has occurred, the exhaust is determined according to the detected intake passage temperature parameter and the exhaust passage temperature parameter. Exhaust gas reverse flow rate calculation means (ECU 2, step 5 in FIG. 4) for calculating the amount of exhaust gas flowing back from the passage 5 to the intake passage 4 via the cylinder 3a as the exhaust gas reverse flow rate QEX, and according to the calculated exhaust gas reverse flow rate The oxygen concentration estimating means (ECU 2, step 6 in FIG. 4) for estimating the oxygen concentration (first oxygen concentration ODI1) in the intake passage 4 and the fuel supply amount (basic fuel injection amount QBASE at the start of the internal combustion engine 3) The fuel supply amount setting means (ECU 2, step 40 in FIG. 7) and the set fuel supply amount are corrected according to the estimated oxygen concentration. Fuel supply quantity correcting means that is characterized in that it comprises, as (ECU 2, step 45 in FIG. 7).

  According to this fuel supply control apparatus for an internal combustion engine, when the internal combustion engine is stopped, it is determined by the valve overlap determination means whether or not a valve overlap between the intake valve and the exhaust valve has occurred. When it is determined that a valve overlap has occurred, the exhaust passage temperature parameter representing the detected temperature in the intake passage and the detected exhaust passage temperature parameter representing the detected temperature in the exhaust passage by the exhaust gas reverse flow rate calculation means. Accordingly, the amount of exhaust gas flowing backward from the exhaust passage to the intake passage through the cylinder is calculated as the exhaust gas reverse flow rate. Further, the oxygen concentration in the intake passage is estimated by the oxygen concentration estimating means in accordance with the calculated exhaust gas reverse flow rate. Then, at the time of starting the internal combustion engine, the fuel supply amount correction means corrects the set fuel supply amount according to the estimated oxygen concentration.

  If the valve overlap occurs between the intake valve and the exhaust valve when the internal combustion engine is stopped, the exhaust gas flows backward from the exhaust passage into the intake passage through the cylinder due to thermal convection due to a temperature difference between the intake passage and the exhaust passage. . Accordingly, the exhaust gas reverse flow rate that actually flows back into the intake passage from the exhaust passage through the cylinder is appropriately calculated according to the intake passage temperature parameter that represents the temperature of the intake passage and the exhaust passage temperature parameter that represents the temperature of the exhaust passage. be able to.

  Then, the oxygen concentration in the intake passage is estimated according to the exhaust gas reverse flow rate calculated as described above, and the set fuel supply amount is corrected according to the estimated oxygen concentration. An amount of fuel commensurate with the actual oxygen concentration can be supplied. As a result, the air-fuel ratio of the air-fuel mixture is properly controlled, and combustion failure at the time of restarting the internal combustion engine can be avoided, whereby startability and exhaust gas characteristics can be improved.

  According to a second aspect of the present invention, in the fuel supply control device for the internal combustion engine 3 according to the first aspect, the fuel supply amount correction means is configured to obtain a predetermined reference value (air oxygen concentration OATM) and the estimated oxygen concentration. As the difference (oxygen concentration decrease amount ΔODI) is larger, the fuel supply amount is corrected so as to decrease more.

  According to this configuration, the fuel supply amount correction means corrects the fuel supply amount so as to decrease more as the difference between the predetermined reference value and the estimated oxygen concentration is larger. For this reason, an amount of fuel commensurate with the degree of decrease in oxygen concentration in the intake passage can be supplied, and the air-fuel ratio of the air-fuel mixture can be controlled appropriately.

It is a figure showing roughly an internal-combustion engine to which a fuel supply control device by this embodiment is applied. It is a block diagram of a fuel supply control device. It is sectional drawing which shows schematic structure of the intake valve and exhaust valve, and the mechanism which drives them. It is a flowchart which shows the main flow of an oxygen concentration calculation process. It is a subroutine which shows exhaust gas reverse flow rate calculation processing. It is a subroutine which shows oxygen inflow amount calculation processing. It is a flowchart which shows a fuel control process at the time of starting. 6 is a map for setting a starting correction amount ΔQINJ.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically shows an internal combustion engine 3 to which a fuel supply control device 1 (see FIG. 2) according to the present embodiment is applied. The internal combustion engine (hereinafter referred to as “engine”) 3 is, for example, an in-line 4-cylinder type gasoline engine mounted on a vehicle (not shown).

  An intake passage 4 is connected to each cylinder 3a of the cylinder head 3c of the engine 3 via an intake manifold 4a, an exhaust passage 5 is connected via an exhaust manifold 5a, and a fuel injection valve 6 (see FIG. 2). However, it is attached so as to face the combustion chamber 3d (only one is shown). That is, the engine 3 is a direct injection type in which fuel is directly injected from the fuel injection valve 6 to the vicinity of a spark plug (not shown) in the combustion chamber 3d. The fuel injection amount QINJ injected from the fuel injection valve 6 is controlled by controlling the valve opening time by the ECU 2 (see FIG. 2).

  Each cylinder 3a is provided with a pair of intake valves 8, 8 (only one shown) and a pair of exhaust valves 9, 9 (only one shown).

  As shown in FIG. 3, in the cylinder head 3c, a rotatable intake camshaft 41, an intake cam 42 provided integrally with the intake camshaft 41, a rocker arm shaft 43, and a rocker arm shaft 43 are rotatable. And two rocker arms 44 and 44 (only one is shown) that respectively contact the upper ends of the intake valves 8 and 8.

  The intake camshaft 41 is connected to the crankshaft 3e (see FIG. 1) via an intake sprocket and a timing chain (both not shown), and rotates once every two rotations of the crankshaft 3e. When the intake camshaft 41 rotates, the rocker arms 44, 44 are pressed by the intake cam 42, and rotate about the rocker arm shaft 43, whereby the intake valves 8, 8 are opened and closed.

  Further, in the cylinder head 3c, a rotatable exhaust cam shaft 61, an exhaust cam 62 provided integrally with the exhaust cam shaft 61, a rocker arm shaft 63, and a rocker arm shaft 63 are rotatably supported. Two rocker arms 64 and 64 (only one is shown) that abut against the upper ends of the exhaust valves 9 and 9 are provided.

  The exhaust camshaft 61 is connected to the crankshaft 3e via an exhaust sprocket and a timing chain (both not shown), and rotates once every two rotations of the crankshaft 3e. When the exhaust camshaft 61 rotates, the rocker arms 64, 64 are pressed by the exhaust cam 62, and rotate about the rocker arm shaft 63, thereby opening and closing the exhaust valves 9, 9.

  The engine 3 is provided with a crank angle sensor 24. The crank angle sensor 24 includes a magnet rotor and an MRE pickup (both not shown), and outputs a CRK signal and a TDC signal, which are pulse signals, to the ECU 2 as the crankshaft 3e rotates.

  The CRK signal is output every predetermined crank angle (for example, 6 °). The ECU 2 calculates the engine speed (hereinafter referred to as “engine speed”) NE of the engine 3 based on the CRK signal. The TDC signal is a signal indicating that the piston 3b of the cylinder 3a is at a predetermined crank angle position near the TDC (top dead center) at the start of the intake stroke. In the case of the four-cylinder type as in the present embodiment, , Output at every 180 ° crank angle.

  The intake passage 4 is provided with a throttle valve mechanism 13 immediately upstream of the inlet of the intake manifold 4a. The throttle valve mechanism 13 has a throttle valve 13a rotatably provided in the intake passage 4 and a TH actuator 13b for driving the throttle valve 13a. The TH actuator 13b is a combination of a motor and a gear mechanism (both not shown), and is driven by a drive signal from the ECU 2. As a result, the amount of fresh air drawn into the cylinder 3a is controlled by changing the opening of the throttle valve 13a.

  An intake air temperature sensor 25 is provided in the intake manifold 4a. The intake air temperature sensor 25 detects the temperature in the intake passage 4 (hereinafter referred to as “intake air temperature”) Tin, and the detection signal is output to the ECU 2.

  The exhaust passage 5 is provided with a catalyst 7 made of a three-way catalyst for purifying the exhaust gas discharged from the cylinder 3a. An exhaust temperature sensor 26 is provided in the exhaust passage 5. The exhaust temperature sensor 26 detects the temperature (hereinafter referred to as “exhaust temperature”) Tex of the exhaust gas discharged from the cylinder 3 a to the exhaust passage 5, and outputs a detection signal to the ECU 2.

  Further, the ECU 2 outputs a detection signal representing an operation amount (hereinafter referred to as “accelerator opening”) AP of an accelerator pedal (not shown) from an accelerator opening sensor 27 (see FIG. 2).

  The ECU 2 is composed of a microcomputer including an I / O interface, a CPU, a RAM, and a ROM (all not shown). The detection signals from the various sensors 24 to 27 described above are input to the CPU after A / D conversion and shaping by the I / O interface. In accordance with these input signals, the ECU 2 determines the operating state of the engine 3 according to a control program stored in the ROM, and executes control of the engine 3 including fuel supply control according to the determined operating state.

  In the present embodiment, the ECU 2 corresponds to valve overlap determination means, exhaust gas reverse flow rate calculation means, oxygen concentration estimation means, fuel supply amount setting means, and fuel supply amount correction means. Hereinafter, various processes executed by the ECU 2 will be described with reference to the drawings.

  FIG. 4 shows an oxygen concentration calculation process. This process is executed at a predetermined cycle while the engine 3 is stopped. First, in step 1 (illustrated as “S1”, the same applies hereinafter), it is determined whether or not it is immediately after the ignition switch is turned off.

  If the determination result is YES and immediately after the ignition switch is turned off, it is determined whether or not a valve overlap between the intake valve 8 and the exhaust valve 9 has occurred (step 2). This determination is made based on whether or not the stop position of the piston 3b is included in a predetermined valve overlap section based on the TDC signal and the CRK signal. If the determination result is NO and no valve overlap has occurred, the valve overlap occurrence flag F_O / L is set to “0” (step 14), and this process is terminated.

  On the other hand, if the determination result in step 2 is YES and a valve overlap has occurred, the valve overlap occurrence flag F_O / L is set to “1” (step 3).

  Next, in step 4, it is determined whether or not the detected intake air temperature Tin and exhaust gas temperature Tex are substantially equal to each other. When the determination result is NO, the exhaust gas is flowing back from the exhaust passage 5 to the intake passage 4 through the valve overlapped cylinder 3a due to thermal convection due to the temperature difference between the intake air temperature Tin and the exhaust gas temperature Tex. In step 5, the exhaust gas reverse flow rate QEX is calculated. FIG. 5 shows the subroutine. First, in step 20, a pressure difference ΔP between the pressure in the intake passage 4 (hereinafter referred to as “intake pressure”) Pin and the pressure in the exhaust passage 5 (hereinafter referred to as “exhaust pressure”) Pex is calculated. The calculation of the pressure difference ΔP is performed as follows.

ここで、Ｐは気筒３ａ内の基準圧力、γｉｎは空気の比重、γｅｘは排ガスの比重である。Ｌｉｎは、吸気マニホルド４ａの入口（スロットル弁１３ａ）から吸気弁８までの距離（以下「算出対象通路部」という）を表す。また、Ｌｅｘは、排気弁９からの排気通路長さを表し、算出対象通路部の長さＬｉｎとほぼ等しい。 First, the intake pressure Pin and the exhaust pressure Pex are calculated according to the following equations (1) and (2), respectively.

Here, P is the reference pressure in the cylinder 3a, γin is the specific gravity of air, and γex is the specific gravity of the exhaust gas. Lin represents a distance from the inlet (throttle valve 13a) of the intake manifold 4a to the intake valve 8 (hereinafter referred to as “calculation target passage portion”). Lex represents the length of the exhaust passage from the exhaust valve 9 and is approximately equal to the length Lin of the calculation target passage portion.

Further, based on the gas equation of state, the exhaust gas specific gravity γex is expressed by the following equation (3).

Then, the pressure difference ΔP is calculated according to the following equation (4) using the relationships of the equations (1) to (3).

この式（５）は、ベルヌーイの式から導かれるものであり、ｇは重力加速度を表す。 Next, the flow velocity V of the exhaust gas flowing backward from the exhaust passage 5 to the intake passage 4 is calculated according to the following equation (5) (step 21).

This equation (5) is derived from Bernoulli's equation, and g represents the gravitational acceleration.

ここで、Ａは、吸・排気弁８、９によって開放された状態での吸気ポートおよび排気ポートの開口面積の平均値である。 Next, the exhaust gas reverse flow rate QEX is calculated according to the following equation (6) (step 22), and this process is terminated.

Here, A is an average value of the opening area of the intake port and the exhaust port in the state opened by the intake / exhaust valves 8 and 9.

ここで、Ｖｉｎは、算出対象通路部の容積であり、ＯＤＩ１（Ｎ−１）は、第１酸素濃度ＯＤＩ１の前回値である。したがって、右辺第１式のＶｉｎ×ＯＤＩ１（Ｎ−１）は、前回の処理サイクルにおける算出対象通路部内の酸素量を表す。なお、第１酸素濃度の前回値ＯＤＩ１（Ｎ−１）の初期値は、空気の酸素濃度ＯＡＴＭに設定される。 Returning to FIG. 4, in Step 6 following Step 5, the first oxygen concentration ODI1 (N) in the calculation target passage portion of the intake passage 4 is calculated according to the following equation (7).

Here, Vin is the volume of the calculation target passage portion, and ODI1 (N−1) is the previous value of the first oxygen concentration ODI1. Therefore, Vin × ODI1 (N−1) in the first expression on the right side represents the amount of oxygen in the calculation target passage portion in the previous processing cycle. Note that the initial value of the previous value ODI1 (N-1) of the first oxygen concentration is set to the oxygen concentration OATM of air.

  In addition, QEX × ODI1 (N−1) in the first expression on the right side of Expression (7) represents the amount of oxygen pushed out from the calculation target passage portion when the exhaust gas flows back to the calculation target passage portion.

  Therefore, the difference between Vin × ODI1 (N−1) and QEX × ODI1 (N−1) corresponds to the amount of oxygen in the current calculation target passage, and further, this amount of oxygen is divided by the volume Vin. The first oxygen concentration ODI1 (N) in the calculation target passage portion is calculated.

  Further, the second expression on the right side of Expression (7) is obtained by substituting the right side of Expression (6) as the exhaust gas reverse flow rate QEX.

  Next, the calculated first oxygen concentration ODI1 (N) is set as the oxygen concentration ODI (step 7) and is shifted to the previous value ODI1 (N-1) (step 8), and this process is terminated.

  On the other hand, when the determination result in step 4 is YES, there is almost no temperature difference between the intake air temperature Tin and the exhaust gas temperature Tex, and thermal convection of the exhaust gas due to the temperature difference from the exhaust passage 5 to the intake passage 4 and the resulting exhaust gas It is determined that the backflow has ended.

この式（８）は、フィックの法則に基づくものであり、Ｄは拡散定数、Ｌは、吸気通路４の上流端から吸気マニホルド４ａの入口（スロットル弁１３ａ）までの距離である。また、ＯＤＩ２（Ｎ−１）は、算出対象通路部内の第２酸素濃度ＯＤＩ２の前回値、ＯＡＴＭは、空気の酸素濃度である。したがって、−（ＯＤＩ２（Ｎ−１）−ＯＡＴＭ）／Ｌは、前回の処理サイクルにおける外部と算出対象通路部との間の酸素濃度の勾配を表し、この勾配に拡散定数Ｄを乗算することによって、単位面積あたりの酸素量Ｊが算出される。なお、第２酸素濃度ＯＤＩ２の初期値は、第１酸素濃度ＯＤＩ１の最終値に設定される。 Further, in this state, an oxygen concentration gradient occurs between the intake passage 4 and the outside, and diffusion due to this concentration gradient occurs. For this reason, in step 9 and subsequent steps, the second oxygen concentration ODI2 (N) in the calculation target passage portion that changes due to this diffusion is calculated. First, in step 9, the oxygen inflow amount QO2 is calculated. FIG. 6 shows the subroutine. In the first step 30, the oxygen amount J per unit area flowing into the intake passage 4 is calculated.

This equation (8) is based on Fick's law, D is the diffusion constant, and L is the distance from the upstream end of the intake passage 4 to the inlet (throttle valve 13a) of the intake manifold 4a. ODI2 (N-1) is the previous value of the second oxygen concentration ODI2 in the calculation target passage, and OATM is the oxygen concentration of air. Therefore,-(ODI2 (N-1) -OATM) / L represents the gradient of the oxygen concentration between the outside and the calculation target passage in the previous processing cycle, and this gradient is multiplied by the diffusion constant D. Then, the oxygen amount J per unit area is calculated. The initial value of the second oxygen concentration ODI2 is set to the final value of the first oxygen concentration ODI1.

ここで、Ａ２は吸気マニホルド４ａの入口面積である。したがって、式（９）によって求められる酸素流入量ＱＯ２は、前回と今回との処理サイクル間で、外部からの拡散により吸気マニホルド４ａを介して算出対象通路部に流入する酸素量に相当する。 Next, the oxygen inflow amount QO2 is calculated according to the following equation (9) (step 31).

Here, A2 is the inlet area of the intake manifold 4a. Therefore, the oxygen inflow amount QO2 obtained by the equation (9) corresponds to the oxygen amount flowing into the calculation target passage portion via the intake manifold 4a due to diffusion from the outside between the previous and current processing cycles.

ここで、右辺第１式のＶｉｎ×ＯＤＩ２（Ｎ−１）は、前回の処理サイクルにおける算出対象通路部内の酸素量を表し、したがって、この値と、前記式（９）によって算出された酸素流入量ＱＯ２との和は、今回の算出対象通路部内の酸素量に相当する。また、この酸素量を容積Ｖｉｎで除算することによって、算出対象通路部内の第２酸素濃度ＯＤＩ２（Ｎ）が得られる。 Returning to FIG. 4, in step 10 following step 9, the second oxygen concentration ODI2 (N) is calculated according to the following equation (10).

Here, Vin × ODI2 (N−1) in the first expression on the right side represents the amount of oxygen in the calculation target passage portion in the previous processing cycle, and therefore, this value and the oxygen inflow calculated by the expression (9). The sum with the amount QO2 corresponds to the amount of oxygen in the current calculation target passage. Further, the second oxygen concentration ODI2 (N) in the calculation target passage portion is obtained by dividing the oxygen amount by the volume Vin.

  Next, the calculated second oxygen concentration ODI2 (N) is set as the oxygen concentration ODI (step 11) and is shifted to the previous value ODI2 (N-1) (step 12), and this process is terminated.

  On the other hand, in the second and subsequent processing cycles in which the ignition switch is turned off, the determination result in step 1 is NO. At this time, it is determined whether or not the valve overlap occurrence flag F_O / L is “1”. A determination is made (step 13).

  When the determination result is YES, since valve overlap has occurred, the process proceeds to step 4 and thereafter, and this process is terminated.

  On the other hand, when the determination result in step 13 is NO, since no valve overlap has occurred, the exhaust gas does not flow back from the exhaust passage 5 to the intake passage 4, and thus this processing is terminated.

  FIG. 7 shows the start time fuel control process. First, in step 40, a basic fuel injection amount QBASE is calculated. The basic fuel injection amount QBASE is calculated by searching a predetermined map (not shown) based on the engine speed NE and the required torque PMCMD. Further, the required torque PMCMD is calculated based on the engine speed NE and the accelerator pedal opening AP.

  Next, it is determined whether or not the valve overlap occurrence flag F_O / L is “1” (step 41).

  When the determination result is NO, since the valve overlap does not occur while the engine 3 is stopped, the starting correction amount ΔQINJ is set to 0 (step 42).

  On the other hand, when the determination result in step 41 is YES, the difference (OATM−ODI) between the oxygen concentration OATM of air and the oxygen concentration ODI calculated in step 7 or 11 is calculated as the oxygen concentration decrease amount ΔODI (step 43).

  Next, at step 44, the correction amount ΔQINJ at the start is calculated by searching the map shown in FIG. 8 according to the oxygen concentration decrease amount ΔODI. In this map, the starting correction amount ΔQINJ is set to a larger value as the oxygen concentration decrease amount ΔODI is larger.

  Next, in step 45, the fuel injection amount QINJ is calculated by subtracting the starting correction amount ΔQINJ calculated in step 42 or 44 from the basic fuel injection amount QBASE calculated in step 40. The process ends.

  As described above, according to the present embodiment, when the valve overlap between the intake valve 8 and the exhaust valve 9 occurs when the engine 3 is stopped, the exhaust passage 5 depends on the intake temperature Tin and the exhaust temperature Tex. The exhaust gas reverse flow rate QEX flowing back to the calculation target passage portion of the intake passage 4 from the cylinder 3a is calculated, and the first oxygen concentration ODI1 in the calculation target passage portion is calculated according to the calculated exhaust gas reverse flow rate QEX.

  Further, when the temperature difference between the intake air temperature Tin and the exhaust gas temperature Tex almost disappears, it flows into the calculation target passage portion from the outside according to the gradient of the oxygen concentration generated between the outside and the calculation target passage portion of the intake passage 4. The oxygen inflow amount QO2 to be calculated is calculated, and the second oxygen concentration ODI2 in the calculation target passage portion is calculated according to the calculated oxygen inflow amount QO2.

  Then, the start time correction amount ΔQINJ is calculated according to the oxygen decrease amount ΔODI which is the difference between the oxygen concentration OATM of the air and the first oxygen concentration ODI1 or the second oxygen concentration ODI2, and the start time correction amount ΔQINJ is used as a basis. By subtracting from the fuel injection amount QBASE, the fuel injection amount QINJ is calculated. Thereby, an amount of fuel commensurate with the actual oxygen concentration in the intake passage 4 can be supplied. As a result, the air-fuel ratio of the air-fuel mixture is properly controlled, and combustion failure at the time of restarting the internal combustion engine can be avoided, so that startability and exhaust gas characteristics can be improved.

  Further, since the starting correction amount ΔQINJ is set to a larger value as the oxygen concentration decrease amount ΔODI is larger, the basic fuel injection amount QBASE is corrected so as to be further decreased. As a result, it is possible to supply an amount of fuel commensurate with the amount of decrease in oxygen concentration in the calculation target passage portion of the intake passage 4.

  In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. For example, in the embodiment, the exhaust temperature Tex is used as the exhaust passage temperature parameter, but the temperature of the catalyst 7 provided in the exhaust passage 5 may be used. Further, the exhaust temperature estimated from the engine speed NE and the intake negative pressure immediately before the engine 3 is stopped may be used.

  In the embodiment, the pressure difference ΔP is estimated according to the intake air temperature Tin and the exhaust gas temperature Tex. However, the pressure difference ΔP may be calculated using the actually detected pressures of the intake passage 4 and the exhaust passage 5.

  The embodiment is an example in which the present invention is applied to an in-line four-cylinder direct-injection gasoline engine mounted on a vehicle, but the present invention is not limited to this, and has an engine other than the four-cylinder engine or a V-type cylinder. You may apply to an engine and a port injection type engine. Moreover, the present invention may be applied to various engines other than gasoline engines, for example, diesel engines, and flexible fuel vehicles (FFV) engines, and engines other than vehicles, for example, crankshafts may be set vertically. It can also be applied to a marine vessel propulsion engine such as an outboard motor. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Fuel supply control apparatus 2 ECU (Valve overlap determination means, exhaust gas reverse flow rate calculation means, oxygen concentration estimation means, fuel supply amount setting means, fuel supply amount correction means)
3 Engine (Internal combustion engine)
4 Intake passage 5 Exhaust passage 8 Intake valve 9 Exhaust valve 25 Intake temperature sensor (intake passage temperature parameter detection means)
26 Exhaust temperature sensor (exhaust passage temperature parameter detection means)
Tin Intake air temperature (Intake passage temperature parameter)
Tex exhaust temperature (exhaust passage temperature parameter)
QEX Exhaust gas reverse flow rate ODI1 1st oxygen concentration (oxygen concentration)
OATM air oxygen concentration (reference value)
ΔODI Oxygen concentration decrease (difference between standard value and oxygen concentration)
QBASE Basic fuel injection amount (fuel supply amount)

Claims (2)

An internal combustion engine that sucks air from an intake passage into a cylinder through an intake valve, discharges exhaust gas generated in the cylinder to an exhaust passage through an exhaust valve, and controls the amount of fuel supplied to the cylinder The fuel supply control device of
Valve overlap determination means for determining whether or not valve overlap occurs between the intake valve and the exhaust valve when the internal combustion engine is stopped;
An intake passage temperature parameter detecting means for detecting an intake passage temperature parameter representing a temperature in the intake passage;
An exhaust passage temperature parameter detecting means for detecting an exhaust passage temperature parameter representing a temperature in the exhaust passage;
When it is determined by the valve overlap determining means that the valve overlap has occurred, the exhaust gas passage passes through the cylinder from the exhaust passage according to the detected intake passage temperature parameter and the exhaust passage temperature parameter. Exhaust gas reverse flow rate calculating means for calculating the amount of exhaust gas flowing back to the intake passage as an exhaust gas reverse flow rate,
Oxygen concentration estimating means for estimating the oxygen concentration in the intake passage according to the calculated exhaust gas reverse flow rate;
Fuel supply amount setting means for setting the fuel supply amount at the start of the internal combustion engine;
Fuel supply amount correction means for correcting the set fuel supply amount according to the estimated oxygen concentration;
A fuel supply control apparatus for an internal combustion engine, comprising:   2. The fuel supply amount correction unit according to claim 1, wherein the fuel supply amount correction unit corrects the fuel supply amount so as to decrease more as the difference between a predetermined reference value and the estimated oxygen concentration is larger. Fuel supply control device for internal combustion engine.

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