Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/02—Circuit arrangements for generating control signals
  • F02D41/04—Introducing corrections for particular operating conditions
  • F02D41/06—Introducing corrections for particular operating conditions for engine starting or warming up
  • F02D41/062—Introducing corrections for particular operating conditions for engine starting or warming up for starting
  • F02D41/065—Introducing corrections for particular operating conditions for engine starting or warming up for starting at hot start or restart
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/0002—Controlling intake air
  • F02D2041/001—Controlling intake air for engines with variable valve actuation

Definitions

• the invention relates to a startup control apparatus for an internal combustion engine installed in a vehicle or the like, and more particularly to control executed during startup on a variable valve timing mechanism capable of modifying an operation timing of an intake valve and an exhaust valve.
• variable valve timing mechanism also referred to as a VVT hereafter
• a VVT variable valve timing mechanism
• JP 2010-084587 A for example, a geometric compression ratio of a cylinder is increased to 1 3 or more, and in a normally used partial load operating region, a closing timing of an intake valve is retarded to at least a halfway point of a compression stroke by a VVT. As a result, pumping loss is reduced, and due to a reduction in an effective compression ratio, knocking is suppressed.
• idling stop control is performed to stop the engine automatically in a predetermined condition.
• the engine may be restarted immediately after being stopped automatically, and therefore the closing timing of the intake valve is retarded to a maximum extent by the VVT.
• the effective compression ratio becomes extremely low, and therefore, upon restarting of the engine, an air-fuel mixture is unlikely to self-ignite . (pre-ignite) even when high-temperature intake air flows into the cylinder from an intake system.
• the closing timing of the intake valve is advanced to a maximum extent by the VVT.
• the purpose of this is to increase the effective compression ratio of the cylinder in consideration of a startability of the engine in a cold weather region.
• the driver may restart the engine immediately after the stopping the engine normally, but during normal startup, fuel is supplied after purifying the high-temperature air by perfoiTning cranking a predetermined number of times, and therefore pre-ignition can be suppressed.
• pre-ignition may occur during the predetermined number of cranking operations even when a fuel supply is stopped, leaving room for improvement.
• the high-temperature air taken into the cylinder as a result of the cranking may intermix with fuel adhered to a wall surface of an intake port and fuel leaking from an injector to form an air-fuel mixture, and the air-fuel mixture may self-ignite during the cranking.
• the invention therefore provides a startup control apparatus for an internal combustion engine with which pre-ignition can be suppressed more reliably during startup while securing favorable startability in the internal combustion engine.
• a temperature condition of an internal combustion engine is detennined when the internal combustion engine is started rather than stopped, and a closing timing of an intake valve is modified in accordance with the temperature condition.
• a startup control apparatus for an internal combustion engine which starts an internal combustion engine by performing cranking thereon, includes: a variable valve timing mechanism capable of modifying at least a closing timing of an intake valve; and a control portion which determines a temperature condition at a startup time, and when a predetermined high temperature condition is established, retards the closing timing of the intake valve using the variable valve timing mechanism before the cranking is started.
• the closing timing of the intake valve is retarded by the variable valve timing mechanism before the cranking is started.
• an effective compression ratio of a cylinder can be reduced as required on the basis of an actual engine temperature condition at the time of startup, and therefore pre-ignition can be suppressed more reliably while securing favorable startability.
• control portion may further retard the closing timing of the intake valve as the temperature condition at the startup time is higher.
• the closing timing of the intake valve is retarded only slightly, and therefore the effective compression ratio does not decrease greatly, leading to an improvement in the startability.
• the likelihood of pre-ignition increases steadily as the temperature increases, but by retarding the closing timing of the intake valve in accordance with the temperature condition so that the effective compression ratio decreases, pre-ignition can be suppressed more reliably.
• control portion may delay the start of the cranking as the temperature condition at the startup time is higher. In so doing, time required for the variable valve timing mechanism to perform the operation for retarding the closing timing of the intake valve can be secured.
• variable valve timing mechanism Since the closing timing of the intake valve is modified at the time of engine startup, the variable valve timing mechanism may be driven by an electric motor.
• a hydrauhcally driven variable valve timing mechanism operates rather sluggishly while an oil pressure remains low immediately after engine startup.
• An electric variable valve timing mechanism on the other hand, can be operated not only immediately after engine startup but also before startup, and therefore the cranking does not have to be delayed greatly.
• control portion may operate the variable valve timing mechanism to retard the closing timing of the intake valve in response to a predetermined operation performed by a driver of the vehicle before a cranking start operation is performed by the driver. In so doing, the delay in the cranking can be minimized such that there is substantially no delay in the cranking.
• the startup control apparatus may further include a sensor for detecting a temperature of at least one of a coolant and an intake air of the internal combustion engine, and the control portion may determine the temperature condition at the engine startup time from a signal output by the sensor.
• the actual temperature condition of the internal combustion engine at the time of startup can be determined precisely, thereby ensuring that the effects of the invention can be secured.
• the control portion may be configured to determine the temperature condition at the engine startup time while taking into consideration not only the coolant temperature and the intake air temperature, but also at least one of an elapsed time following a preceding engine stoppage and an operation history up to the engine stoppage. As a result, the temperature condition of the engine at the time of startup can be determined even more precisely, enabling a further improvement in the effects of the invention.
• control portion may use the variable valve timing mechanism to control the closing timing of the intake valve to a predetermined timing at which an effective compression ratio enabling cold startup in a cold weather region is obtained. In so doing, startability in a cold weather region can be secured in the internal combustion engine even when the variable valve timing mechanism malfunctions so as to become inoperable.
• the temperature condition of the internal combustion engine is detennined when the internal combustion engine is started rather than stopped, and when the high temperature condition is detennined, the variable valve timing mechanism is operated before the cranking is started. Therefore, the closing timing of the intake valve of the internal combustion engine can be controlled favorably in accordance with the actual temperature condition at the time of startup, and as a result, pre-ignition can be suppressed more reliably while securing favorable startability in the internal combustion engine.
• FIG. 1 is a schematic view showing an example of an internal combustion engine (an engine) to which the invention is applied;
• FIG. 2 is a sectional view showing a configuration of a VVT
• FIG. 3 is a sectional view taken along a III-III line in FIG. 2;
• FIG. 4 is a block diagram showing a configuration of a control system of the engine
• FIG. 5 is a flowchart showing an example of engine startup control executed by an ECU, illustrating a VVT control routine
• FIG. 6 is a flowchart showing a starter motor control routine executed during the engine startup control
• FIG. 7A is a view illustrating a map used during the startup control on which a retardation amount of the VVT is set;
• FIG. 7B is a view illustrating a map used during the startup control on which a cranking delay is set.
• FIG. 8 is a timing chart showing an example of startup control, including the cranking delay and a VVT retardation operation implemented when a high temperature is determined.
• An engine 1 is a four-cylinder gasoline engine installed in a vehicle.
• a piston l c is housed to be capable of reciprocating vertically in each of four cylinders (only one cylinder is shown in FIG. 1 ) formed inside a cylinder block l a.
• a water jacket is formed on the cylinder block l a so as to surround the four cylinders, and a water temperature sensor 32 is disposed on the cylinder block l a to detect a temperature of engine cooling water (a coolant ).
• the reciprocating motion of the piston l c in each of the four cylinders is convened into a rotary motion of a crankshaft 15 via a connecting rod 16!
• the crankshaft 15 is coupled to a transmission (not shown) via a torque converter (or a clutch) and so on such that an output of the engine 1 can be transmitted to a drive wheel of the vehicle via the transmission.
• the transmission may be a multistage automatic transmission that uses frictional engagement elements such as a clutch and a brake and a planetary gear mechanism, or a belt type continuously variable transmission, for example.
• a starter motor 10 that is activated when the engine 1 is started can be coupled to the crankshaft 15, and the crankshaft 15 can be rotated forcibly (i.e. cranked) by the starter motor 10.
• a signal rotor 17 is attached to the crankshaft 15, and a plurality of teeth (projections) 17a are provided on an outer peripheral surface of the signal rotor 17 at equal angular intervals.
• the signal rotor 1 7 is also provided with a missing tooth portion 17b from which two of the teeth 17a are missing.
• a crank position sensor 3 1 that detects a crank angle is disposed near a side of the signal rotor 1 7.
• the crank position sensor 31 is an electromagnetic pickup, for example, that generates pulse-form signals corresponding to the teeth 17a of the signal rotor 17 while the crankshaft 15 rotates.
• An engine rotation speed ne can be calculated from an output signal of the crank position sensor 3 1 .
• an oil pan 18 for storing lubricating oil (engine oil) is provided in a lower portion of the cylinder block l a so as to cover the crankshaft 15.
• the lubricating oil stored in the oil pan 1 8 is pumped up by an oil pump (not shown) when the engine 1 is operated, supplied to respective parts of the engine such as the piston l c, the crankshaft 1 5, and the connecting rod 16, and used for lubrication, cooling, and so on of these parts.”
• a cylinder head l b is fastened to an upper end of the cylinder block l a, and a combustion chamber I d that is varied in volume by the reciprocating motion of the piston l c is formed in each of the cylinders, respective upper ends of which are closed by the cylinder head l b.
• a spark plug 3 is disposed in the cylinder head l b for each cylinder so as to oppose the combustion chamber I d, and an ignition timing of the spark plug 3 is regulated by an igniter 4.
• the igniter 4 is controlled by an electronic control unit (ECU) 200.
• An intake passage 1 1 and an exhaust passage 12 respectively communicate with the combustion chamber I d so that fresh air can be taken into the combustion chamber I d and combustion gas can be discharged therefrom.
• a downstream side of the intake passage 1 1 (a downstream side of an intake air flow) is constituted by an intake port 1 1 a and an intake manifold l i b, and a surge tank 1 1 c is disposed on an upstream side thereof.
• an air cleaner 7 that filters the intake air
• a hot wire air flow meter 33 a hot wire air flow meter 33.
• an intake air temperature sensor 34 built into the air flow meter 33, for example
• a throttle valve 5 for adjusting the intake air amount of the engine 1 , and so on are disposed in the intake passage 1 1 .
• the throttle valve 5 is provided on an upstream side of the surge tank 1 1 c and driven by a throttle motor 6. An opening of the throttle valve 5 is detected by a throttle opening sensor 35 and feedback-controlled by the ECU 200 so that an optimum intake air amount corresponding to an operating condition of the engine 1 is obtained.
• an injector (a fuel injection valve) 2 is disposed in the intake port 1 1 a for each cylinder.
• the respective injectors 2 are connected to a shared delivery pipe 101 , and fuel is supplied thereto from a fuel supply system 100.
• the fuel supply system 100 includes, for example, a fuel supply pipe 102 connected to the delivery pipe 101 , a fuel pump 103, a fuel tank 104, and so on.
• the injectors 2 are controlled by the ECU 200 to inject fuel into the respective cylinders at a predetermined timing.
• the fuel injected into the intake port 1 1 a from the injector 2 intermixes with the intake air, and a resulting air-fuel mixture is introduced into the combustion chamber I d of each cylinder when an intake valve 13 is opened.
• the air-fuel mixture is ignited by the spark plug 3 in a final phase of a compression stroke of the cylinder so as to burn and explode, thereby generating high-temperature high-pressure combustion gas that pushes the piston l c down and is then discharged into the exhaust passage 12 when an exhaust valve 14 is opened.
• An upstream side of the exhaust passage 12 (an upstream side of an exhaust gas flow) is constituted by an exhaust port 12a and an exhaust manifold, 12b, and a three-way catalyst 8 is disposed on a downstream side thereof.
• the three-way catalyst 8 purifies exhaust gas discharged into the exhaust passage 12 by performing oxidation of CO and HC contained in the exhaust gas and NOx reduction so as to turn the CO, HC and NOx into harmless CO2, H 2 0, and N 2 .
• a front air-fuel ratio sensor 37 having a linear characteristic with respect to an air-fuel ratio is disposed in the exhaust passage 12 on the upstream side of the three-way catalyst 8, and a rear 0 2 sensor 38 constituted by a lambda sensor, for example, is disposed in the exhaust passage 12 on the downstream side of the three-way catalyst 8.
• Output signals from the front air-fuel ratio sensor 37 and the rear O? sensor 38 are fed back to the ECU 200 and used to control the air-fuel ratio:
• Intake and discharge into and from the combustion chamber I d are performed by opening and closing the intake valve 13 and the exhaust valve 14.
• the intake valve 1 3 is provided between the intake port 1 1 a and the combustion chamber I d
• the exhaust valve 14 is provided between the exhaust port 12a and the combustion chamber I d.
• the intake valve 13 and the exhaust valve 14 are opened and closed at respective predetermined timings by intake and exhaust camshafts 21 , 22 that are rotated by the crankshaft 15 via a timing chain or the like.
• the intake and exhaust camshafts 21 , 22 are respectively rotated at 1 /2 the rotation speed of the crankshaft 1 5 so as to complete a single revolution in the time required for the piston l c to reciprocate twice.
• the respective camshafts 21 , 22 perform a single revolution in the time required for the crankshaft 1 5 to perform two revolutions (i.e. to rotate 720°) and the piston l c to perform an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke.
• the intake valve 13 opens during the intake stroke of each cylinder, while the exhaust valve 14 opens during the exhaust stroke.
• a cam position sensor 39 that generates a pulse-form signal when the piston l c of a specific cylinder (a first cylinder, for example) reaches compression top dead center (TDC) is provided in the vicinity of the intake camshaft 21 that rotates in the manner described above.
• the cam position sensor 39 is constituted by an electromagnetic pickup, similarly to the aforesaid crank position sensor 3 1 , which outputs a pulse-form signal when a single tooth (not shown) formed on a rotor outer periphery of the intake camshaft 21 passes by.
• an electric variable valve timing mechanism (abbreviated to VVT 40 hereafter) to be described below is attached to the intake camshaft 21 .
• VVT 40 an electric variable valve timing mechanism
• the engine 1 operates on a so-called Atkinson cycle (Miller cycle), in which a geometric compression ratio (a ratio between volumes of the combustion chamber I d when the piston l c is at TDC and bottom dead center) of each cylinder is set at a high value between 12 and 14, and in a frequently used partial load operating region, the closing timing of the intake valve 13 is retarded by the VVT 40 to at least a halfway point of the compression stroke.
• Atkinson cycle Friller cycle
• FIGS. 2 and 3 the VVT 40 (not shown in FIG. 1 ) is disposed on an end portion of the intake camshaft 21 .
• FIG. 2 is a sectional view showing an internal structure of the VVT 40.
• FIG. 3 is a sectional view taken along a III-III line in FIG. 2.
• a similar VVT may be disposed in the exhaust camshaft 22.
• the VVT 40 is driven by an electric motor 42 (referred to simply as a motor hereafter) that is controlled by the ECU 200.
• the electric motor 42 is a three-phase motor constituted by a motor shaft 44, bearings 46, a rotation speed sensor 47, a stator 50. and so on.
• the motor shaft 44 is supported by the two bearings 46 to be capable of rotating about an axis O.
• a disc-shaped rotor portion 45 that projects outward in a radial direction is fixed to the motor shaft 44, and a plurality of magnets 45a are embedded in an outer peripheral wall of the rotor portion 45.
• the stator 50 is disposed on an outer peripheral side of the motor shaft 44, and includes a plurality of coils arranged at equal intervals around the axis O of the motor shaft 44.
• Each coil is formed by winding a winding 52 around a core 51 , and when a current flows to the coil upon reception of a current supply from a drive circuit 108, the coil forms a rotating magnetic field on the outer peripheral side of the motor shaft 44, thereby generating rotary torque.
• the rotation speed sensor 47 is disposed in the vicinity of the rotor portion 45, and detects a rotation speed (to be referred to as a motor rotation speed hereafter) of the motor shaft 44 by sensing an intensity of a magnetic field formed by each magnet 45a.
• the VVT 40 further includes a phase variation mechanism 60.
• the phase variation mechanism 60 includes a sprocket 62. a ring gear 63, an eccentric shaft 64, a planetary gear 65. an output shaft 66, and so on.
• the sprocket 62 is disposed on an outer peripheral side of the output shaft 66 coaxially therewith so as to be capable of rotating relative to the output shaft 66 about the same axis O as the motor shaft 44.
• the sprocket 62 rotates about the axis O in a clockwise direction of FIG. 3 while maintaining a rotary phase relative to the crankshaft 15.
• the ring gear 63 is constituted by an internal gear and fixed to an inner peripheral wall of the sprocket 62 coaxially therewith so as to rotate integrally with the sprocket 62.
• the eccentric shaft 64 is coupled fixedly to the motor shaft 44 so as to be disposed eccentrically relative to the axis O, and rotates integrally with the motor shaft 44.
• the planetary gear 65 is an external gear capable of a planetary motion, which is disposed on an inner peripheral side of the ring gear 63 so as to mesh therewith.
• the planetary gear 65 is supported on an outer peripheral wall of the eccentric shaft 64 coaxially therewith, and is capable of rotating relative to the eccentric shaft 64 about an eccentric axis P.
• the output shaft 66 is fixed to the intake camshaft 21 coaxially therewith by a bolt, and rotates integrally with the intake camshaft 21 about the same axis O as the motor shaft 44.
• An annular plate-shaped engagement portion 67 centering on the axis O is formed on the output shaft 66. and a plurality of engagement holes 68 are provided in the engagement portion 67 at equal intervals around the axis O.
• a plurality of engagement projections 69 are provided in the planetary gear 65 at equal intervals about the eccentric axis P so as to oppose the engagement holes 68, and the respective engagement projections 69 project to the shaft 66 side so as to penetrate the corresponding engagement holes 68.
• the ECU 200 includes a central processing unit (CPU) 201 , a read only memory (ROM) 202, a random access memory (RAM) 203, a backup RAM 204, and so on.
• CPU central processing unit
• ROM read only memory
• RAM random access memory
• the ROM 202 stores various control programs, maps referred to when executing the various control programs, and so on.
• the CPU 201 executes various calculation processing on the basis of the various control programs and maps stored in the ROM 202.
• the RAM 203 is a memory for temporarily storing calculation results obtained by the CPU 201 , data input from respective sensors, and so on, while the backup RAM 204 is a non-volatile memory that stores data and the like to be saved when the engine 1 is stopped, for example.
• the CPU 201 , the ROM 202, the RAM 203, and the backup RAM 204 are connected to each other by a bus 207, and also connected to an input interface 205 and an output interface 206.
• Various sensors including the crank position sensor 31 , the water temperature sensor 32, the air flow meter 33, the intake air temperature sensor 34, the throttle opening sensor 35, an accelerator depression amount sensor 36 that outputs a detection signal coiTesponding to a depression amount of an accelerator pedal, the front air-fuel ratio sensor 37, the rear 0 2 sensor 38, and the cam position sensor 39 are connected to the input interface 205.
• An ignition switch 48 for switching a main power supply of the vehicle ON and OFF, and a starter switch 49 used by a driver of the vehicle to perform an operation relating to startup of the engine 1 are also connected to the input interface 205.
• the ignition switch 48 is switched ON. control of the engine 1 by the ECU 200 is started, and when the starter switch 49 is switched ON, cranking of the engine 1 by the starter motor 10 is started.
• the injectors 2 of the respective cylinders, the igniters 4 of the spark plugs 3 of the respective cylinders, the throttle motor 6 of the throttle valve 5, the starter motor 10, the VVT 40 of the intake camshaft 21 , and so on, for example, are connected to the output interface 206.
• the ECU 200 executes various types of control on the engine 1 , including drive control of the injector 2 (fuel injection amount and injection timing control), control of the ignition timing of the spark plug 3, drive control of the throttle motor 6 (throttle opening control), and operation control of the VVT 40 (phase control of the intake valve 1 3).
• the ECU 200 also executes engine startup control to be described below.
• the startup control apparatus for an internal combustion engine is realized by a program relating to the engine startup control to be described below, which is executed by the ECU 200.
• fuel injected by the injector 2 immediately before an operation is stopped may adhere to a wall surface of the intake port 1 1 a (including a rear surface of the intake valve 13), and after the engine 1 is stopped, fuel may leak from the injector 2. Therefore, even if fuel is not injected when the engine 1 is restarted, high-temperature air taken into the cylinder by the cranking may intermix with the fuel adhered to the wall surface and the leaked fuel, thereby forming an air-fuel mixture that may self-ignite (in other words, pre-ignition may occur).
• a temperature condition of the engine 1 is determined at the time of startup, and when a predetermined high temperature condition is established, the closing timing of the intake valve 13 is retarded by the VVT 40 before the cranking is started. In so doing, an effective compression ratio of the cylinder can be reduced, and as a result, pre-ignition can be prevented.
• An example of this engine startup control will be described below with reference to flowcharts shown in FIGS. 5 and 6.
• a startup VVT control routine shown in FIG. 5 is started (Start) when the ignition switch 48 is switched ON (IG-SW ON). Then, in step ST101 , the engine water temperature and the intake air temperature are detected from the respective output signals of the water temperature sensor 32 and the intake air temperature sensor 34, and mainly on the basis of these detection results, a determination is made as to whether or not a predetermined high temperature condition in which pre-ignition is likely to occur is established upon startup of the engine 1 .
• step ST101 a determination is made as to whether or not a pre-ignition condition constituted by four following conditions is established.
• the routine advances to step ST102, and when the determination is negative (NO), the routine advances to step ST 106, to be described below.
• the pre-ignition condition is established when: 1 ) the engine water temperature equals or exceeds a predetermined water temperature determination value; 2) the intake air temperature of the engine 1 equals or exceeds a predetermined intake air temperature determination value; 3) an elapsed time following a preceding stoppage of the engine 1 is less than a predetermined determination time; 4) at least a predetermined high load condition was reached between a preceding engine startup and the preceding engine stoppage, and so on.
• a temperature of the combustion chamber I d in the cylinder is higher as the engine water temperature increases, leading to an increase in the temperature of the intake air charged into the combustion chamber I d and a corresponding increase in the likelihood of pre-ignition occurring during the compression stroke.
• the temperature of the combustion chamber I d also is higher as the elapsed time following the preceding engine stoppage decreases, and when at least the predetermined high load condition is reached prior to the preceding engine stoppage, a site having a particularly high temperature (a heat spot) may exist in the combustion chamber I d.
• the determination as to whether or not the pre-ignition condition is established may be made by any one of the four conditions, or combining any of the four conditions in various combinations, or by adding further conditions.
• values of an engine water temperature, an intake air temperature, and an elapsed time following the preceding engine stoppage at which pre-ignition is likely to occur during startup may be obtained in advance by experiments, simulations, and so on, and a combination of values based on the obtained values may be set as the water temperature determination value, the intake air temperature determination value, and the determination time.
• step ST 102 When it is determined as a result of the determination that the pre-ignition condition is established (YES ), the routine advances to step ST 102, where a value of a pre-ignition flag F is set at 1 (F— 1 ). The routine then advances to step ST103, where the VVT 40 is operated to the retardation side in order to retard the closing timing of the intake valve 13.
• a VVT retardation amount An amount by which the VVT 40 is operated to the retardation side (a VVT retardation amount) is determined in accordance with the engine water temperature (a startup water temperature) and the intake air temperature by referring to a VVT retardation amount map shown in FIG. 7A, for example.
• the VVT retardation amount is increased as the engine water temperature and the intake air temperature increase.
• the closing timing of the intake valve 13 is retarded accordingly, leading to a reduction in the effective compression ratio of the cylinder, and as a result, a cylinder internal temperature does not reach a self-ignition temperature of the air-fuel mixture even at TDC.
• retardation amounts of the VVT 40 are set in accordance with the engine water temperature and the intake air temperature by experiments, calculations, and so on, whereupon resulting set values are mapped and stored thus in the ROM 202 of the ECU 200.
• the effective compression ratio at which the cylinder internal temperature does not reach the self-ignition temperature of the air-fuel mixture is set at an effective compression ratio at which a temperature increase caused by heat received from the cylinder wall and compression during the compression stroke does not cause the cylinder internal temperature to reach the self-ignition temperature, also taking into consideration effects of the intake air temperature at engine startup, a charging amount into the cylinder, latent heat generated by fuel evaporation, a specific heat ratio of the air-fuel mixture, and so on.
• This effective compression ratio may be set to have a predetermined margin.
• the VVT retardation amount is not limited to the map described above, and may be determined in accordance with only one of the engine water temperature and the intake air temperature, or set at a fixed value.
• step ST104 a determination is made as to whether or not the engine rotation speed ne calculated from the output signal of the crank position sensor 3 1 has reached a predetermined startup completion determination value Thne (500 rpm, for example; see FIG. 8).
• Thne 500 rpm, for example; see FIG. 8
• the routine enters standby, but when the engine rotation speed ne has reached the determination value Thne such that the determination is affirmative (YES), the value of the flag F is set at 0 (F ⁇ — 0) in step ST105, whereupon the startup VVT control routine is terminated.
• step ST101 when it is determined in step ST101 that the pre-ignition condition is not established (NO) such that the routine advances to step ST 106.
• the VVT 40 is not operated, and the startup VVT control routine is terminated (End) while maintaining the VVT position at the time of the preceding engine stoppage, or in other words keeping the closing timing of the intake valve 13 in a condition established at the time of the preceding engine stoppage.
• the VVT 40 when the engine 1 is stopped, the VVT 40 is normally controlled to control the closing timing of the intake valve 13 to a predetermined timing (approximately after top dead center (ATDC ) 60 to 70° CA, for example) so that an effective compression ratio enabling cold startup is obtained.
• ATDC top dead center
• step ST201 a determination is made as to whether or not the starter switch 49 has been switched ON (starter SW ON?). When the determination is negative (NO), the routine enters standby, and when the determination is affirmative (YES), the routine advances to step ST202.
• the routine advances to step ST203, where a starter relay is switched ON in order to start the cranking.
• the routine advances to step ST204, where a determination is made as to whether or not a cranking delay has elapsed.
• a counter an ignition ON counter
• the routine enters standby.
• the counter value reaches the set value, on the other hand, it is determined that the delay has elapsed (YES), whereupon the routine advances to step ST203 in order to switch the starter relay ON.
• the map shown in FIG. 7B is stored in the ROM 202 of the ECU 200 and set similarly to the VVT retardation amount map described above such that the cranking delay is increased steadily as the engine water temperature and the intake air temperature increase.
• an operation time of the VVT 40 required to reach a target VVT retardation amount is set by experiments, calculations, and so on and then mapped.
• the cranking may be started by feeding back an actual operating condition of the VVT 40 instead of using a map.
• the cranking is started, whereupon fuel injection by the injector 2 and ignition control by the spark plug 3 are performed in order to start the engine 1.
• the fuel injection amount and the ignition timing are determined on the basis of various conditions (the engine water temperature, the intake air temperature, and so on) at the time of engine startup using a startup injection amount map and a startup ignition timing map, for example.
• step ST205 of the flowchart shown in FIG. 6 a determination is made as to whether or not the engine rotation speed ne has reached the determination value Thne, and when the determination is negative (NO), the routine enters standby.
• the routine advances to step ST206, where the starter relay is switched OFF, thereby halting the cranking performed by the starter motor 10.
• the startup starter control routine is then terminated (End).
• FIG. 8 shows startup of the engine 1 (i.e. increasing of the engine rotation speed ne and so on) in a case where the high temperature condition is established such that the cranking is delayed and the closing timing of the intake valve 13 is retarded, in association with variation in the intake air temperature and the engine water temperature, an ON operation of the ignition switch 48 (an ignition ON counter), an ON operation of the starter switch 49 (a startup request flag), activation of the starter motor 10 (a starter relay ON flag), and the operation of the VVT 40 (the VVT retardation amount).
• the starter relay ON flag is not raised even when the starter switch 49 is subsequently switched ON such that the startup request flag is raised (time t l ), as shown in an intermediate section of the drawing, and as a result, the start of the cranking is delayed (the engine rotation speed does not increase).
• the ignition ON counter reaches a set value at substantially the same time as the VVT retardation amount reaches a target value (time t2), whereupon the starter relay ON flag is raised.
• the starter motor 10 when the starter motor 10 is activated such that cranking of the engine 1 is started, the engine rotation speed ne increases to a predetermined rotation speed (approximately 200 rpm, for example) at time t3, i.e. at a slight delay.
• a predetermined rotation speed approximately 200 rpm, for example
• fuel is supplied to the four cylinders and ignited in a predetermined order.
• the closing timing of the intake valve 13 is sufficiently retarded by retarding the VVT 40, leading to a considerable reduction in the effective compression ratio of the cylinder, and therefore pre-ignition is avoided.
• the VVT retardation amount is set precisely on the basis of the intake air temperature and the engine water temperature, and therefore the effective compression ratio does not decrease excessively, meaning that favorable startability is maintained.
• the air-fuel mixture is burned in the cylinder that is ignited first and the cylinder that is ignited second, for example, the rotation of the crankshaft 1 5 is accelerated, with the result that the engine rotation speed ne increases rapidly after starting to rise (time t4).
• the intake VVT 40 is positioned on the advancement side when the engine 1 is stopped, and when the high temperature condition is determined mainly on the basis of the intake air temperature and the engine water temperature at the time of startup thereafter, the VVT 40 is operated to retard the closing timing of the intake valve 13 before cranking is started. In so doing, the effective compression ratio of the cylinder can be reduced, and as a result, pre-ignition can be avoided.
• the effective compression ratio of the cylinder can be reduced as required on the basis of the actual temperature condition at the time of startup of the engine 1 , and therefore pre-ignition can be avoided more reliably while securing favorable startability.
• startability can be secured by increasing the effective compression ratio without greatly retarding the closing timing of the intake valve 13, and by steadily retarding the closing timing of the intake valve 13 so as to reduce the effective compression ratio as the temperature increases, pre-ignition can be avoided reliably.
• the VVT 40 is operated during startup and is therefore constituted by an electric mechanism. Moreover, the VVT 40 is operated in response to an operation (a predetermined operation) of the ignition switch 48 before the starter switch 49 is switched ON, or in other words before a cranking start operation is performed. Hence, the delay from the ON operation of the starter switch 49 to the start of cranking is small, and therefore a driver is unlikely to experience discomfort.
• VVT 40 As noted above, by positioning the VVT 40 on the advancement side when the engine 1 is stopped, startability is secured effectively in the engine 1 in a cold weather region. If the VVT 40 is controlled to the retardation side when the engine 1 is stopped and the engine 1 is subsequently restarted in extremely cold weather (approximately - 10°C, for example), the VVT 40 may malfunction so as to become inoperable, leading to a dramatic reduction in the startability of the engine 1 .
• extremely cold weather approximately - 10°C, for example
• the VVT 40 is operated to the retardation side in accordance with the intake air temperature and the engine water temperature when the pre-ignition condition is established at the time of startup of the engine 1 , whereby the closing timing of the intake valve 13 is retarded by a steadily greater retardation amount as the temperature increases.
• the invention is not limited thereto, and the VVT retardation amount may be varied in accordance with either one of the engine water temperature and the intake air temperature. Further, the VVT 40 may be retarded to a fixed value when the pre-ignition condition is established.
• the pre-ignition condition is determined immediately after the ignition switch 48 is switched ON, and when the condition is established, the VVT 40 is operated to the retardation side before the starter switch 49 is switched ON.
• the invention is not limited thereto, and the VVT 40 may be operated using a predetermined operation such as an operation of the starter switch 49, for example, as a trigger.
• the VVT 40 is controlled to the advancement side when the engine 1 is stopped, thereby advancing the closing timing of the ' intake valve 13 so that an effective compression ratio enabling cold startup in a cold weather region is obtained.
• the invention is not limited thereto, and the VVT 40 may be controlled to any position other than a maximum retardation position when the engine 1 is stopped.
• the invention is not limited thereto, and may be applied to startup control of an engine having another number of cylinders, such as a six-cylinder engine, for example.
• the invention may also be applied to startup control of an in-line multi-cylinder engine or a V type multi-cylinder engine.
• the invention can be applied as a startup control apparatus for an internal combustion engine (an engine), and is capable of suppressing pre-ignition during startup while securing favorable startability.
• the invention is therefore particularly effective when installed in a passenger vehicle or the like.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Output Control And Ontrol Of Special Type Engine (AREA)
• Control Of Vehicle Engines Or Engines For Specific Uses (AREA)
• Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
• Combined Controls Of Internal Combustion Engines (AREA)

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• 2012
  • 2012-08-01 JP JP2012170998A patent/JP5594332B2/ja not_active Expired - Fee Related
• 2013
  • 2013-07-30 WO PCT/IB2013/001649 patent/WO2014020404A1/en active Application Filing

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