Fuel injection control device

Abstract

To sufficiently secure the opportunity of stratified combustion of a fuel in a combustion chamber by injecting the fuel from a cylinder injection valve three times or more in one cycle, while suppressing degradation of emission.SOLUTION: A combustion injection control device injects a fuel from a cylinder injection valve into a combustion chamber three times or more in one cycle to perform stratified combustion in the combustion chamber of an internal combustion engine when a predetermined execution condition is satisfied. A start timing of initial injection in one cycle is advanced on the basis of a start timing of last injection determining an air fuel ratio around an ignition plug of the combustion chamber, limiting the advance at the start timing of the initial injection by an advance guard value determined according to a temperature of the internal combustion engine, and adjusting a start timing of intermediate injection between the initial injection and the last injection so that it does not have influence on the initial injection and the last injection.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a fuel injection control device that injects fuel from a direct injection valve into a combustion chamber of an internal combustion engine. [Background technology]

[0002] Conventionally, there is known a control device for an internal combustion engine that splits fuel injection into a combustion chamber from an in-cylinder injection valve at multiple times during one intake stroke (see, for example, Patent Document 1). This control device acquires an advance limit, which is a crank angle at which the spray from the in-cylinder injection valve does not interfere with the piston top surface even when the piston forming the combustion chamber is near the intake top dead center, for the start timing of the first injection, and acquires a retard limit, which is a crank angle at which the spray from the in-cylinder injection valve does not interfere with the head portion of the intake valve that opens and closes the combustion chamber, for the end timing of the first injection. Furthermore, the control device sets the first injection period based on the acquired advance limit and retard limit, and prohibits split injection of fuel during one intake stroke if the first injection period is shorter than the minimum injection period at which linearity can be ensured for the injection from the in-cylinder injection valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-97652 A Summary of the Invention [Problem to be solved by the invention]

[0004] According to the conventional internal combustion engine control device, the start and end times of the first injection in split injection can be appropriately set to suppress the deterioration of emissions caused by the spray impinging on the piston top or the intake valve head. However, in the above internal combustion engine, if the first injection period set based on the advance limit and retard limit is shorter than the minimum injection period, split injection is prohibited, so that it is not possible to secure a sufficient opportunity to warm up the catalyst by performing stratified charge combustion of the fuel in the combustion chamber through split injection.

[0005] Therefore, a primary object of the present disclosure is to ensure sufficient opportunities for stratified charge combustion of fuel in the combustion chamber by injecting fuel from the direct injection valve three or more times per cycle while suppressing deterioration of emissions. [Means for solving the problem]

[0006] The fuel injection control device disclosed herein is a combustion injection control device that, when predetermined execution conditions are met, injects fuel from an in-cylinder injection valve into a combustion chamber of an internal combustion engine three or more times per cycle so that stratified combustion occurs in the combustion chamber, advances the start timing of an initial injection in one cycle based on the start timing of a final injection that determines the air-fuel ratio around the spark plug of the combustion chamber, and limits the advance of the start timing of the initial injection by an advance guard value that is set in accordance with the temperature of the internal combustion engine, and adjusts the start timing of an intermediate injection between the initial injection and the final injection so as not to affect the initial injection or the final injection.

[0007] The fuel injection control device of the present disclosure, when injecting fuel into a combustion chamber from an in-cylinder injection valve three or more times per cycle in response to the establishment of a predetermined execution condition, advances the start timing of a first injection in one cycle based on the start timing of a final injection that determines the air-fuel ratio around the spark plug of the combustion chamber, and limits the advance of the start timing of the first injection by an advance guard value that is set according to the temperature of the internal combustion engine. Furthermore, the fuel injection control device adjusts the start timing of an intermediate injection between the first injection and the final injection so as not to affect the first injection and the final injection. This makes it possible to set the start timings of the first injection and the intermediate injection so that the fuel injected into the combustion chamber by the first injection does not adhere to the piston or the like while ensuring the injection period and injection amount of the final injection as required. As a result, according to the fuel injection control device of the present disclosure, it is possible to inject fuel from the in-cylinder injection valve three or more times per cycle to ensure sufficient opportunities for stratified combustion of the fuel in the combustion chamber while suppressing deterioration of emissions.

[0008] The advance guard value may be set to a more retarded value as the temperature of the internal combustion engine decreases. This effectively prevents the fuel injected into the combustion chamber by the first injection from adhering to the piston, etc., when the temperature of the internal combustion engine is low and it is difficult to vaporize the fuel instantly, and prevents the advance of the start timing of the first injection from being unnecessarily limited when the temperature of the internal combustion engine is high and it is possible to vaporize the fuel instantly.

[0009] Furthermore, the fuel injection control device may set the injection amounts of the initial injection, the intermediate injection and the final injection, the tentative start timings of the initial injection and the intermediate injection, and the start timing of the final injection based on the rotation speed, load factor, temperature and target air-fuel ratio of the internal combustion engine, set the start timing of the initial injection by limiting the tentative start timing of the initial injection by the advance guard value, and set the start timing of the intermediate injection by limiting the tentative start timing of the intermediate injection by an end timing of the initial injection which is responsive to the start timing and injection amount of the initial injection and the pressure of the fuel supplied to the in-cylinder injection valve. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram showing an internal combustion engine to which a fuel injection control device according to the present disclosure is applied; [Diagram 2] 1 is a control block diagram showing a fuel injection control device according to the present disclosure. [Diagram 3] 4 is a flowchart showing an example of a routine executed by the fuel injection control device of the present disclosure. [Figure 4] FIG. 4 is an explanatory diagram showing an example of an advance guard value setting map used by the fuel injection control device of the present disclosure; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Next, an embodiment of the present disclosure will be described with reference to the drawings.

[0012] 1 is a schematic diagram showing an engine 10, which is an internal combustion engine to which the fuel injection control device of the present disclosure is applied. The engine 10 shown in the figure is a multi-cylinder gasoline engine (for example, an in-line 4-cylinder engine or a V-type 6-cylinder engine) that converts the reciprocating motion of pistons 13, which accompanies the combustion of a mixture of hydrocarbon fuel and air in a plurality of combustion chambers (cylinders) 12 formed in an engine block 11, into the rotational motion of a crankshaft (output shaft) 14. The engine 10 is mounted on a vehicle or a hybrid vehicle that uses the engine 10 as its only power source.

[0013] 1, the engine 10 includes an engine block 11, a plurality of combustion chambers 12, pistons 13, and a crankshaft 14, as well as an air cleaner 15, an intake pipe 16, an electronically controlled throttle valve 17, an intake manifold 18 having a surge tank and a plurality of intake ports, a plurality of intake valves 19i for opening and closing the corresponding intake ports, an exhaust valve 19e for opening and closing the corresponding exhaust ports, a plurality of port injection valves 20p for injecting fuel into the corresponding intake ports, a plurality of in-cylinder injection valves 20d for directly injecting fuel into the corresponding combustion chambers 12, a plurality of ignition plugs 21, and an exhaust pipe 22 forming an exhaust passage. In this embodiment, the in-cylinder injection valve 20d is an electromagnetic needle valve.

[0014] The engine 10 also includes an upstream purification device 23 and a downstream purification device 24, each of which is incorporated in the exhaust pipe 22, as exhaust gas purification devices. The upstream purification device 23 includes a NOx storage type exhaust gas purification catalyst (three-way catalyst) that purifies harmful components such as CO (carbon monoxide), HC, and NOx in the exhaust gas from each combustion chamber 12 of the engine 10. The downstream purification device 24 includes a particulate filter (GPF) that collects particulate matter (fine particles) in the exhaust gas, and is disposed downstream of the upstream purification device 23. In this embodiment, the particulate filter is a porous filter that supports a NOx storage type exhaust gas purification catalyst (three-way catalyst). That is, the downstream purification device 24 is configured as a four-way catalyst that has the purification function of a three-way catalyst and the collection function of particulate matter.

[0015] Furthermore, the engine 10 includes a coolant circulation passage 25 for cooling the engine block 11 etc., an electric pump 26, and a radiator 27. The electric pump 26 circulates coolant (LLC) through the coolant circulation passage 25. The radiator 27 cools the coolant that has absorbed heat from the engine block 11 etc. by heat exchange with air from traveling wind or an electric fan (not shown). A water temperature sensor 25t is also provided in the coolant circulation passage 25. The water temperature sensor 25t detects the water temperature Tw of the coolant that has absorbed heat from (flowed out of) the engine block 11.

[0016] In addition, the engine 10 includes a supercharger 28 that compresses intake air by utilizing the energy of exhaust gas, and a liquid-cooled intercooler 29 that cools the air compressed by the supercharger 28. The supercharger 28 is a turbocharger, and includes a turbine wheel 28t, a compressor wheel 28c, a turbine shaft 28s that integrally connects the turbine wheel 28t and the compressor wheel 28c, a wastegate valve 28w, and a blow-off valve 28b. The turbine wheel 28t is rotatably disposed in a turbine housing formed in the exhaust pipe 22 so as to be located upstream of the upstream purification device 23. The compressor wheel 28c is rotatably disposed in a compressor housing formed in the intake pipe 16 so as to be located between the air cleaner 15 and the throttle valve 17.

[0017] The engine 10 configured as described above is controlled by an engine electronic control unit (hereinafter referred to as "engine ECU") 100 including a microcomputer having a CPU, ROM, RAM, input / output interfaces, etc. (not shown), various drive circuits, various logic ICs, etc. As shown in Fig. 2, the engine ECU 100 obtains detection values ​​of the crank angle sensor 14a, the air flow meter 16a, the intake pressure sensor 16p, the boost pressure sensor 16c, the intake air temperature sensor 16t, the throttle opening sensor 17o, the surge pressure sensor 18p, the temperature sensor 18t, the fuel pressure sensor 20t, the upstream air-fuel ratio sensor 22f, the downstream air-fuel ratio sensor 22r, the exhaust gas temperature sensor 22t, the water temperature sensor 25t, etc., via an input port (not shown).

[0018] The crank angle sensor 14a detects the rotational position (crank position) of the crankshaft 14. The air flow meter 16a detects the intake air amount Qa upstream of the compressor wheel 28c of the intake pipe 16. The intake pressure sensor 16p detects the intake pressure Pin upstream of the compressor wheel 28c of the intake pipe 16. The boost pressure sensor 16c detects the boost pressure Pc, which is the pressure of air compressed by the compressor wheel 28c between the compressor housing of the intake pipe 16 and the intercooler 29. The intake air temperature sensor 16t detects the intake temperature Tin upstream of the compressor wheel 28c of the intake pipe 16. The throttle opening sensor 17o detects the opening TH of the throttle valve 17. The surge pressure sensor 18p detects the surge pressure Ps, which is the pressure of the air in the surge tank, and the temperature sensor 18t detects the surge temperature Ts, which is the temperature of the air in the surge tank. The fuel pressure sensor 20t detects the pressure Pf of fuel supplied to each in-cylinder injection valve 20d from a fuel pump (not shown). The upstream air-fuel ratio sensor 22f detects an upstream air-fuel ratio AFf, which is the air-fuel ratio of exhaust gas flowing into the upstream purification device 23, on the upstream side of the upstream purification device 23, and the downstream air-fuel ratio sensor 22r detects a downstream air-fuel ratio AFr, which is the air-fuel ratio of exhaust gas flowing into the downstream purification device 24, on the downstream side of the upstream purification device 23. The exhaust gas temperature sensor 22t detects the temperature Teg of exhaust gas flowing through a portion of the exhaust pipe 22 between the upstream purification device 23 and the downstream purification device 24.

[0019] The engine ECU 100 calculates the rotation speed Ne of the engine 10 (crankshaft 14) based on the crank position from the crank angle sensor 14a, and calculates a load factor KL based on the intake air amount Qa from the air flow meter 16a and the rotation speed Ne of the engine 10. The load factor KL is the ratio of the volume of air actually taken in during one cycle to the stroke volume per cycle of the engine 10. The engine ECU 100 controls the throttle valve 17, the multiple port injection valves 20p and the multiple in-cylinder injection valves 20d, the multiple ignition plugs 21, etc. based on the rotation speed Ne, the load factor KL, etc. Furthermore, the engine ECU 100 controls the electric pump 26 that pumps the cooling water, and the wastegate valve 28w and the blow-off valve 28b of the supercharger 28.

[0020] The engine ECU 100 also functions as a fuel injection control device that controls the multiple port injection valves 20p and the multiple in-cylinder injection valves 20d, and injects fuel from each in-cylinder injection valve 20d three or more times per cycle in order to perform stratified combustion in each combustion chamber 12 of the engine 10, depending on whether a predetermined stratified combustion execution condition is met. In this embodiment, the stratified combustion execution condition is met when the upstream purification device 23 and the downstream purification device 24 need to be warmed up. For example, the stratified combustion execution condition is met when the soak time of the engine 10 is equal to or longer than a predetermined time, when a fuel cut continues for a predetermined time, when the operation of the engine 10 is stopped for a predetermined time or longer in a hybrid vehicle, etc.

[0021] Next, a procedure for setting the fuel injection amount and fuel injection timing when fuel is injected from each in-cylinder injection valve 20d three times per cycle so as to perform stratified combustion in each combustion chamber 12 of the engine 10 in response to the establishment of the stratified combustion execution condition will be described. Fig. 3 is a flowchart showing an example of a routine executed by the engine ECU 100 for each cycle to set the fuel injection amount and fuel injection timing of each in-cylinder injection valve 20d when the stratified combustion execution condition is met.

[0022] 3, the engine ECU 100 acquires data necessary for setting the fuel injection amount and fuel injection timing of each in-cylinder injection valve 20d, such as the engine speed Ne, load factor KL, and target air-fuel ratio AFtag of the engine 10, which are calculated or set separately, the water temperature Tw detected by the water temperature sensor 25t, and the fuel pressure (fuel pressure) Pf detected by the fuel pressure sensor 20t (step S100). After the process of step S100, the engine ECU 100 derives the total injection amount Qt of fuel to be injected into the combustion chamber 12 from each in-cylinder injection valve 20d during one cycle, based on the engine speed Ne, load factor KL, and water temperature Tw acquired in step S100 (step S110). In step S110, the engine ECU 100 derives the total injection amount Qt for each combustion chamber 12 corresponding to the rotation speed Ne, load factor KL, and water temperature Tw obtained in step S100 from a total injection amount derivation map (not shown) that has been adapted in advance through experiments and analyses.

[0023] Next, the engine ECU 100 sets an injection amount Qf, which is the amount of fuel to be injected from each in-cylinder injection valve 20d into the combustion chamber 12 for the last time (here, the third time) in one cycle, based on the rotation speed Ne, load factor KL, and water temperature Tw obtained in step S100 (step S120). In step S120, the engine ECU 100 derives values ​​corresponding to the rotation speed Ne, load factor KL, and water temperature Tw obtained in step S100 from a final injection amount derivation map (not shown) that has been adapted in advance through experiments and analyses, and sets the injection amount Qf for the final injection in each combustion chamber 12.

[0024] Furthermore, the engine ECU 100 derives a distribution ratio k based on the rotation speed Ne, load factor KL, and water temperature Tw acquired in step S100 (step S130). The distribution ratio k indicates the ratio of the amount of fuel injected by the initial injection to the amount of fuel to be injected into each combustion chamber 12 by the initial injection and intermediate injection (second injection) in one cycle. In step S130, the engine ECU 100 derives the distribution ratio corresponding to the rotation speed Ne, load factor KL, and water temperature Tw acquired in step S100 from a distribution ratio setting map (not shown) that has been adapted in advance through experiments and analyses. After deriving the distribution ratio k, the engine ECU 100 calculates the injection amount Qi (= k·(Qt-Qf)) for the initial injection by multiplying the value obtained by subtracting the injection amount Qf for the final injection from the total injection amount Qt derived in step S110 by the distribution ratio k, and also calculates the injection amount Qm (= (1-k)·(Qt-Qf)) for the intermediate injection by multiplying the value obtained by subtracting the injection amount Qf for the final injection from the total injection amount Qt by the ratio (1-k) (step S140).

[0025] In addition, the engine ECU 100 determines tentative injection start timings τi for the initial injection, intermediate injection, and final injection in each combustion chamber 12 based on the rotation speed Ne, load factor KL, and water temperature Tw acquired in step S100. tmp , τm tmp , τf tmp In step S150, the engine ECU 100 derives the provisional injection start timing τi corresponding to the rotation speed Ne, the load factor KL, and the water temperature Tw obtained in step S100 from a provisional injection start timing derivation map (not shown) that has been adapted in advance through experiments and analyses. tmp , τm tmp , τf tmp The provisional injection start timing derivation map derives the provisional injection start timing τf tmp is set to the compression stroke before the top dead center of the compression stroke in one cycle (in the case of so-called center injection, the expansion stroke after the top dead center of the compression stroke), and the tentative injection start timing τi tmp , τm tmp The tentative injection start timing τf of the final injection tmpIn this embodiment, the engine ECU 100 advances the provisional injection start timing τf of the final injection based on the derived provisional injection start timing τf and sets it to the intake stroke in one cycle. tmp is set as the injection start timing τf of the final injection (step S160). As a result, by injecting fuel into the combustion chamber 12 by each in-cylinder injection valve 20d from the injection start timing τf by the injection amount Qf derived in step S110, the air-fuel ratio around the spark plug 21 at the time of ignition can be appropriately determined.

[0026] Furthermore, the engine ECU 100 sets an advance guard value τig for limiting the advance of the injection start timing τi of the first injection based on the water temperature Tw obtained in step S100 (step S170). In step S170, the engine ECU 100 derives a value corresponding to the water temperature Tw obtained in step S100 from an advance guard value setting map shown in FIG. 4, which has been adapted in advance through experiments and analysis, and sets the value as the advance guard value Tig. As shown in the figure, the advance guard value setting map is created so that the lower the water temperature Tw, the more the advance guard value Tig is set to a value on the retard side, and when the water temperature Tw is sufficiently high, the advance guard value Tig is set to a value (e.g., BTDC 450°) that does not substantially limit the advance of the injection start timing τi of the first injection. Next, the engine ECU 100 sets the tentative injection start timing τi of the first injection derived in step S150 as the advance guard value Tig. tmp The engine ECU 100 sets the retarded value of the advance guard value τig set in step S170 as the injection start timing τi of the first injection (step S180). Then, the engine ECU 100 sets (adjusts) the injection start timing τm of the intermediate injection based on the injection end timing of the first injection corresponding to the injection start timing τi of the first injection set in step S180 (step S190), and ends the routine of FIG.

[0027] In step S190, the engine ECU 100 derives the injection end timing of the first injection based on the injection start timing τi of the first injection set in step S180, the injection amount Qi of the first injection calculated in step S140, and the pressure Pf of the fuel supplied to each in-cylinder injection valve 20d. Furthermore, in step S190, the engine ECU 100 calculates the injection end timing by delaying the injection end timing by a predetermined minimum interval (precharge time of the in-cylinder injection valve 20d) and the tentative injection start timing τm derived in step S150. tmp The value on the retard side of the above is set as the injection start timing τi of the intermediate injection. As a result, the injection start timing τm of the intermediate injection is set (adjusted) so as not to affect the first injection and the final injection, that is, so as not to interfere with the injection end timing of the first injection and the injection start timing τf of the final injection.

[0028] As described above, when the engine ECU 100 as a fuel injection control device injects fuel into the combustion chamber 12 from each in-cylinder injection valve 20d three times in one cycle in response to the establishment of a predetermined stratified charge combustion execution condition, the engine ECU 100 advances the injection start timing τi of the first injection in that one cycle based on the injection start timing τf of the final injection that determines the air-fuel ratio around the spark plug 21 of the combustion chamber 12 (steps S150-S160), and limits the advance of the injection start timing τi of the first injection by an advance guard value that is set in response to the water temperature Tw that indicates the temperature of the engine 10 (steps S170-S180). Furthermore, the engine ECU 100 adjusts the injection start timing τm of the intermediate injection between the first injection and the final injection so as not to affect the first injection and the final injection (step S190).

[0029] More specifically, the engine ECU 100 determines the injection amounts Qi, Qm, Qf for the first injection, intermediate injection, and final injection, and the tentative injection start timings τi for the first injection and intermediate injection, based on the rotation speed Ne, load factor KL, water temperature Tw, and target air-fuel ratio AFtag of the engine 10. tmp , τm tmp The engine ECU 100 sets the tentative injection start timing τi of the initial injection and the injection start timing τf of the final injection (steps S100-S160).tmp The engine ECU 100 sets the injection start timing τi of the first injection by limiting the injection start timing τi of the intermediate injection with the advance guard value τig (steps S170-S180). tmp The injection start timing τm of the intermediate injection is set by limiting the injection start timing τi of the initial injection and the injection end timing of the initial injection according to the injection amount Qi and the pressure Pf of the fuel supplied to each in-cylinder injection valve 20d (step S190).

[0030] This makes it possible to set the injection start timings τi, τm of the initial and intermediate injections so that the fuel injected into the combustion chamber 12 by the initial injection does not adhere to the top of the piston 13, while ensuring the injection duration τf and injection amount Qf of the final injection as required. As a result, in the engine 10, it becomes possible to suppress deterioration of emissions such as an increase in PN (Particulate Number), while ensuring sufficient opportunities to inject fuel from each in-cylinder injection valve 20d three times per cycle to cause stratified charge combustion of the fuel in the combustion chamber 12, i.e., opportunities to warm up the catalyst.

[0031] Furthermore, in the engine 10, the advance guard value τig is set to a value on the retard side as the temperature of the engine 10, i.e., the water temperature Tw, decreases (step S170). This effectively prevents the fuel injected into each combustion chamber 1 by the first injection from adhering to the top of the piston 13 and the like when the temperature of the engine 10, i.e., the temperature in each combustion chamber 12, is low and it is difficult to vaporize the fuel instantly, and also prevents the advance of the start timing τi of the first injection from being unnecessarily limited when the temperature in each combustion chamber 12 is high and the fuel can be vaporized instantly.

[0032] In the above embodiment, the intermediate injection is performed only once, but the present invention is not limited to this. That is, the number of intermediate injections may be multiple, and fuel may be injected from each in-cylinder injection valve 20d into the combustion chamber 12, for example, four or five times in one cycle.

[0033] The present disclosure is not limited to the above embodiment, and various modifications can be made within the scope of the present disclosure. Furthermore, the above embodiment is merely a specific form of the invention described in the Summary of the Invention, and does not limit the elements of the invention described in the Summary of the Invention. [Industrial Applicability]

[0034] The invention of the present disclosure can be used in the internal combustion engine manufacturing industry and the like. [Explanation of symbols]

[0035] 10 engine, 12 combustion chamber, 13 piston, 20d in-cylinder injection valve, 20t fuel pressure sensor, 21 spark plug, 23 upstream purification device, 24 downstream purification device, 25 refrigerant circulation passage, 25t water temperature sensor, 100 engine electronic control unit (engine ECU).

Claims

[Claim 1] 1. A fuel injection control device for an internal combustion engine, comprising: a fuel injection valve for injecting fuel into a combustion chamber of an internal combustion engine three or more times in one cycle so that stratified charge combustion is performed in the combustion chamber when a predetermined execution condition is satisfied; a start timing of an initial injection in one cycle based on the start timing of a final injection which determines the air-fuel ratio around the spark plug of the combustion chamber, and limits the advance of the start timing of the initial injection by an advance guard value which is set in accordance with the temperature of the internal combustion engine, and adjusts the start timing of an intermediate injection between the initial injection and the final injection so as not to affect the initial injection or the final injection.

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