JP5594332B2 - Start control device for internal combustion engine - Google Patents

Description

  The present invention relates to a start control device for an internal combustion engine mounted on a vehicle or the like, and more particularly to control at the start of a variable valve mechanism that can change the operation timing of an intake valve or an exhaust valve.

  2. Description of the Related Art Conventionally, in an internal combustion engine (hereinafter also referred to as an engine) mounted on a vehicle or the like, a variable valve timing (hereinafter also referred to as VVT) has been adopted in order to make the intake valve open / close timing variable. It is expanding. Also, the so-called Atkinson cycle and Miller cycle, in which the expansion stroke of the cylinder is longer than the compression stroke, are being put into practical use. If the expansion stroke is lengthened, the pressure of the combustion gas can be efficiently converted into the rotation of the crankshaft, and the engine efficiency is improved.

  For example, in the Miller cycle engine described in Patent Document 1, while the geometric compression ratio of the cylinder is increased to 13 or higher, the closing timing of the intake valve is caused by VVT in the operation region of the part load that is normally used. Is retarded until after the middle of the compression stroke to reduce pumping loss and to suppress knocking by lowering the effective compression ratio.

  In addition, the engine performs an idle stop control that automatically stops in a predetermined state. In this automatic stop, it is expected that the engine immediately restarts. Therefore, the closing timing of the intake valve is delayed to the maximum by VVT. I try to make it horn. In this way, the effective compression ratio becomes very low, and even if hot intake air flows from the intake system into the cylinder at the time of restart, it is difficult for self-ignition (pre-ignition) of the air-fuel mixture to occur.

  On the other hand, in the case of a normal stop in which the engine is stopped according to the driver's ignition operation or the like instead of an automatic stop such as an idle stop, the closing timing of the intake valve is advanced to the maximum by VVT. This is to increase the effective compression ratio of the cylinder in consideration of engine startability in a cold region.

  It should be noted that even after such a normal engine stop, the driver may immediately restart the engine, but at the normal start, after scavenging high-temperature air by a predetermined number of crankings, the fuel is discharged. Patent Document 1 describes that pre-ignition can be suppressed because it is supplied.

JP 2010-084587 A

  However, if the driver restarts the engine immediately after a normal stop as described above, there is a possibility that pre-ignition may occur even if the fuel supply is stopped for a predetermined number of crankings. There is room for. That is, the high-temperature air sucked into the cylinder by cranking and the fuel adhering to the intake port wall surface or the fuel leaking from the injector are mixed to form an air-fuel mixture, which self-ignites during cranking. Because there are things.

  Such a problem occurs because the technology of the conventional example (Patent Document 1) assumes a temperature state at the time of starting uniformly depending on whether the engine is stopped normally or automatically, and VVT is set accordingly. This is probably because the VVT control suitable for the actual temperature state at the time of start-up cannot be realized.

  Therefore, an object of the present invention is to more reliably suppress pre-ignition at the time of starting than before, while ensuring good startability of the internal combustion engine.

In order to solve the above-described problems, the present invention determines the temperature state at the time of starting the internal combustion engine rather than at the time of stopping, and changes the closing timing of the intake valve accordingly. Specifically, for a start control device that cranks and starts an internal combustion engine, a variable valve mechanism that can change at least the closing timing of an intake valve, a temperature state at the time of start, and a predetermined high temperature state Then, before starting the cranking, the variable valve mechanism is provided with a control means for changing the closing timing of the intake valve to the retard side, and this control means has a temperature state at the time of starting. The higher the value is, the more the start of cranking is delayed, and the closing timing of the intake valve is changed to the more retarded side .

  According to the present invention, when the internal combustion engine is in a high temperature state at the time of starting and there is a concern about the occurrence of pre-ignition, the closing timing of the intake valve is changed to the retarded side by the variable valve mechanism before the start of cranking. The That is, since the effective compression ratio of the cylinder can be reduced as necessary based on the actual engine temperature state at the time of starting, pre-ignition can be more reliably suppressed while ensuring good startability.

Further, the control means delays the start of cranking as the temperature state at the time of starting is higher, and changes the closing timing of the intake valve to the retard side, so when the temperature state is relatively low, Since the closing timing of the intake valve is not delayed so much and the effective compression ratio is not lowered so much, it is advantageous for improving the startability. And the higher the temperature, the higher the possibility of pre-ignition, but the intake valve closing timing is retarded accordingly, and the effective compression ratio is lowered, so that pre-ignition can be more reliably suppressed. it can.

  If the closing timing of the intake valve is changed when the engine is started, the variable valve mechanism is preferably driven by an electric motor. The hydraulically driven variable valve mechanism operates very slowly while the oil pressure immediately after engine startup is low, but the electric variable valve mechanism operates not only immediately after engine start but also before engine start. This is because it is not necessary to delay too much.

  In particular, when the internal combustion engine is mounted on a vehicle, the control means operates the variable valve mechanism according to a predetermined operation by the occupant before the cranking start operation is performed by the occupant of the vehicle, The closing timing of the intake valve may be changed to the retard side. In this way, the delay of cranking can be minimized, and it can be substantially prevented from delaying.

  Preferably, a sensor for detecting the temperature of at least one of the coolant and the intake air of the internal combustion engine is provided, and the control means may determine a temperature state at the time of engine start based on a signal from the sensor. . In this way, the actual temperature state of the internal combustion engine at the time of starting can be accurately determined, and the effectiveness of the above-described invention can be ensured.

  A more preferable configuration of the control means is that not only the coolant temperature and the intake air temperature, but also the temperature at the time of engine start taking into account at least one of the elapsed time since the previous engine stop and the operation history until this engine stop. The state is to be determined. In this way, the engine temperature state at the time of starting can be determined with higher accuracy, and the effects of the invention can be further enhanced.

  Furthermore, the control means may control the closing timing of the intake valve by the variable valve mechanism when the internal combustion engine is stopped at a predetermined timing so as to obtain an effective compression ratio that can be cold-started even in a cold region. In this way, even if the variable valve mechanism stops operating due to a failure, the startability of the internal combustion engine in a cold region can be ensured.

  According to the present invention, the temperature state is determined when starting the internal combustion engine instead of when it is stopped, and if it is in a high temperature state, the variable valve mechanism is operated prior to the start of cranking. The closing timing of the intake valve of the internal combustion engine can be suitably controlled in accordance with the actual temperature state at the time of starting, thereby ensuring good startability of the internal combustion engine and more reliably pre-ignition. Can be suppressed.

It is a schematic block diagram which shows an example of the internal combustion engine (engine) to which this invention is applied. It is sectional drawing which shows the structure of VVT. It is sectional drawing in the III-III line of FIG. It is a block diagram which shows the structure of the control system of an engine. It is a flowchart which shows an example of the engine starting control which ECU performs, and shows the control routine of VVT. It is a flowchart which shows the control routine of the starter motor in the engine starting control. It is explanatory drawing of the map used for starting control, Comprising: (a) shows what set the amount of retardation of VVT, (b) shows what set the delay time of cranking, respectively. It is a timing chart which shows an example of starting control, such as delay of cranking at the time of high temperature determination, retarding operation of VVT, etc.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

-Overall configuration of internal combustion engine-
First, an internal combustion engine (hereinafter also referred to as an engine) to which the present invention is applied will be described with reference to FIG. The engine 1 of this example is a four-cylinder gasoline engine mounted on a vehicle and reciprocates up and down in each of four cylinders (only one cylinder is shown in FIG. 1) formed in a cylinder block 1a. Thus, the piston 1c is accommodated. A water jacket is formed in the cylinder block 1a so as to surround these four cylinders, and a water temperature sensor 32 is arranged so as to detect the temperature of engine coolant (coolant).

  The reciprocating motion of the piston 1c in the four cylinders is converted into the rotational motion of the crankshaft 15 via the connecting rod 16, respectively. The crankshaft 15 is connected to a transmission (not shown) via a torque converter (or clutch) or the like, and can transmit the output of the engine 1 to the drive wheels of the vehicle via the transmission. As an example, this transmission may be a multi-stage automatic transmission using friction engagement elements such as clutches and brakes and a planetary gear mechanism, or a belt-type continuously variable transmission.

  A starter motor 10 that is started when the engine 1 is started can be connected to the crankshaft 15, and the crankshaft 15 can be forcibly rotated (cranking) by the starter motor 10. A signal rotor 17 is attached to the crankshaft 15, and a plurality of teeth (projections) 17 a are provided at equal angles on the outer peripheral surface, and a missing tooth portion 17 b in which two of the teeth 17 a are missing is also provided. Is provided.

  A crank position sensor 31 for detecting a crank angle is disposed near the side of the signal rotor 17. The crank position sensor 31 is, for example, an electromagnetic pickup, and generates a pulsed signal corresponding to the teeth 17a of the signal rotor 17 when the crankshaft 15 rotates. The engine speed ne can be calculated from the output signal of the crank position sensor 31.

  Further, an oil pan 18 for storing lubricating oil (engine oil) is provided below the cylinder block 1 a so as to cover the crankshaft 15. Lubricating oil stored in the oil pan 18 is pumped up by an oil pump (not shown) during operation of the engine 1 and supplied to various parts of the engine such as the piston 1c, the crankshaft 15, and the connecting rod 16 to lubricate / Used for cooling etc.

  On the other hand, a cylinder head 1b is fastened to the upper end of the cylinder block 1a, and a combustion chamber 1d whose volume is changed by the reciprocating motion of the piston 1c is formed for each cylinder whose upper end is closed by the cylinder head 1b. Yes. A spark plug 3 is arranged for each cylinder in the cylinder head 1b facing the combustion chamber 1d, and the ignition timing is adjusted by the igniter 4. The igniter 4 is controlled by an ECU (Electronic Control Unit) 200.

  An intake passage 11 and an exhaust passage 12 communicate with the combustion chamber 1d, respectively, for intake of fresh air and exhaust of combustion gas. A downstream side of the intake passage 11 (downstream side of the intake flow) is constituted by an intake port 11a and an intake manifold 11b, and a surge tank 11c is disposed upstream thereof. Further, in the intake passage 11, an air cleaner 7 that filters intake air, a hot-wire air flow meter 33, an intake air temperature sensor 34 (incorporated in the air flow meter 33), a throttle valve 5 for adjusting the intake air amount of the engine 1. Etc. are arranged.

  As an example, the throttle valve 5 is provided on the upstream side of the surge tank 11 c and is driven by the throttle motor 6. The opening degree of the throttle valve 5 is detected by a throttle opening degree sensor 35 and is feedback-controlled by the ECU 200 so as to obtain an optimum intake air amount corresponding to the operating state of the engine 1.

  An injector (fuel injection valve) 2 is disposed in the intake port 11a for each cylinder. These injectors 2 are connected to a common delivery pipe 101, and fuel is supplied from a fuel supply system 100. As an example, the fuel supply system 100 includes a fuel supply pipe 102 connected to a delivery pipe 101, a fuel pump 103, a fuel tank 104, and the like.

  The injector 2 is controlled by the ECU 200, and fuel injection is performed at a predetermined timing for each cylinder. The fuel injected from the injector 2 into the intake port 11a is mixed with intake air and introduced into the combustion chamber 1d in each cylinder when the intake valve 13 is opened. This air-fuel mixture is ignited by the spark plug 3 at the end of the compression stroke of the cylinder and burns and explodes. After the high-temperature and high-pressure combustion gas pushes down the piston 1c, it is discharged into the exhaust passage 12 when the exhaust valve 14 is opened. Is done.

An upstream side of the exhaust passage 12 (upstream side of the exhaust flow) is constituted by an exhaust port 12a and an exhaust manifold 12b, and a three-way catalyst 8 is disposed on the downstream side thereof. The three-way catalyst 8 purifies the exhaust gas by oxidizing CO and HC and reducing NOx in the exhaust gas exhausted to the exhaust passage 12 and converting them into harmless CO ₂ , H ₂ O, and N _2. To do.

For example, a front air-fuel ratio sensor 37 showing a linear characteristic with respect to the air-fuel ratio is disposed in the exhaust passage 12 upstream of the three-way catalyst 8, and the downstream exhaust passage 12 is composed of, for example, a lambda sensor. A rear O ₂ sensor 38 is arranged. The output signals of the front air-fuel ratio sensor 37 and the rear O ₂ sensor 38 are fed back to the ECU 200 and used for air-fuel ratio control.

  The intake and exhaust of the combustion chamber 1d as described above is performed by opening and closing operations of the intake valve 13 and the exhaust valve 14. That is, an intake valve 13 is provided between the intake port 11a and the combustion chamber 1d, and an exhaust valve 14 is provided between the exhaust port 12a and the combustion chamber 1d. The intake valve 13 and the exhaust valve 14 are opened and closed at predetermined timings by the intake and exhaust camshafts 21 and 22 rotated by the crankshaft 15 via a timing chain or the like.

  More specifically, each of the intake and exhaust camshafts 21 and 22 rotates at a half rotational speed of the crankshaft 15, and rotates once while the piston 1c reciprocates twice. In other words, while the crankshaft 15 rotates twice (720 °) and the piston 1c performs intake, compression, expansion, and exhaust strokes, the cam camshafts 21 and 22 rotate once, The intake valve 13 is opened during the intake stroke, and the exhaust valve 14 is opened during the exhaust stroke.

  In the vicinity of the intake camshaft 21 rotating in this way, a cam position sensor is arranged so that a pulse signal is generated when the piston 1c of a specific cylinder (for example, the first cylinder) reaches the compression top dead center (TDC). 39 is provided. The cam position sensor 39 is composed of an electromagnetic pickup like the crank position sensor 31 described above, and outputs a pulse signal when one tooth (not shown) on the outer periphery of the rotor of the intake camshaft 21 passes.

  In the present embodiment, the intake camshaft 21 is attached with an electric variable valve mechanism (hereinafter abbreviated as VVT 40) described below. Thereby, the rotation phase of the intake camshaft 21 based on the rotation of the crankshaft 15 is continuously changed, and the timing of opening and closing the intake valve 13 can be continuously changed to the advance side and the retard side. it can.

  The engine 1 of the present embodiment has a geometric compression ratio of each cylinder (volume ratio of the combustion chamber 1c when the piston 1c is at the top dead center and the bottom dead center) as 12 to 14. In the operation region of the partial load that is set high and frequently used, the operation of the so-called Atkinson cycle (Miller cycle) is performed by delaying the closing timing of the intake valve 13 by the VVT 40 until after the middle of the compression stroke. It is like that.

-VVT-
As shown in FIGS. 2 and 3, in this embodiment, a VVT 40 (not shown in FIG. 1) is disposed at the end of the intake camshaft 21. 2 is a cross-sectional view showing the internal structure of the VVT 40, and FIG. 3 is a cross-sectional view taken along the line III-III in FIG. A similar variable valve mechanism may be disposed on the exhaust camshaft 22 as well.

  In the illustrated example, the VVT 40 is driven by an electric motor 42 (hereinafter simply referred to as a motor) controlled by the ECU 200. The electric motor 42 includes a motor shaft 44, a bearing 46, and a rotation speed as shown in FIG. This is a three-phase motor including a sensor 47, a stator 50, and the like. The motor shaft 44 is supported by two bearings 46 and 46 and is rotatable around the axis O. A circular plate-like rotor portion 45 protruding outward in the radial direction is fixed to the motor shaft 44, and a plurality of magnets 45 a are embedded in the outer peripheral wall of the rotor portion 45.

  On the other hand, the stator 50 is provided on the 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. The coil is formed by winding a winding 52 around a core 51. When a current flows through supply from the drive circuit 108, a rotating magnetic field is formed on the outer peripheral side of the motor shaft 44 to generate a rotational torque. The rotation speed sensor 47 is disposed in the vicinity of the rotor portion 45, and detects the rotation speed of the motor shaft 44 (hereinafter referred to as motor rotation speed) by sensing the strength of the magnetic field formed by each magnet 45a.

  In addition to FIG. 2, the VVT 40 includes a phase change mechanism 60 as shown in FIG. 3. The phase change mechanism 60 includes a sprocket 62, a ring gear 63, an eccentric shaft 64, a planetary gear 65, an output shaft 66, and the like. The sprocket 62 is coaxially disposed on the outer peripheral side of the output shaft 66, and can rotate relative to the output shaft 66 around the same axis O as the motor shaft 44.

  When the rotation of the crankshaft 15 is transmitted to the sprocket 62 by a chain or the like, the sprocket 62 rotates around the axis O in the clockwise direction in FIG. 3 while maintaining the rotational phase with respect to the crankshaft 15. The ring gear 63 is composed of an internal gear, is coaxially fixed to the inner peripheral wall of the sprocket 62, and rotates integrally with the sprocket 62.

  The eccentric shaft 64 is eccentrically arranged with respect to the axis O by being connected and fixed to the motor shaft 44, and rotates integrally with the motor shaft 44. The planetary gear 65 is an external gear and is arranged on the inner peripheral side of the ring gear 63 so as to be capable of planetary movement so as to mesh with the ring gear 63. The planetary gear 65 supported coaxially on the outer peripheral wall of the eccentric shaft 64 is rotatable relative to the eccentric shaft 64 around the eccentric axis P.

  The output shaft 66 is bolted coaxially to the intake camshaft 21 and rotates integrally with the intake camshaft 21 about the same axis O as the motor shaft 44. The output shaft 66 is formed with an annular plate-like engagement portion 67 centering on the axis O, and the engagement portion 67 is provided with a plurality of engagement holes 68 around the axis O at equal intervals. ing. The planetary gear 65 is provided with a plurality of engagement projections 69 at equal intervals around the eccentric axis P so as to face the engagement holes 68, and each of the planetary gears 65 protrudes toward the shaft 66 and corresponds to the corresponding engagement projection. It rushes into the joint hole 68.

  In the VVT 40 having such a structure, when the motor shaft 44 does not rotate relative to the sprocket 62, the planetary gear 65 is integrated with the sprocket 62 while maintaining the meshing position with the ring gear 63 as the crankshaft 15 rotates. Rotate 3 clockwise. At this time, since the engaging protrusion 69 presses the inner peripheral wall of the engaging hole 68 in the rotation direction, the output shaft 66 rotates in the clockwise direction in FIG. 3 without rotating relative to the sprocket 62. Thereby, the rotation phase of the intake camshaft 21 with respect to the crankshaft 15 is maintained.

  On the other hand, when the motor shaft 44 rotates relative to the sprocket 62 in the counterclockwise direction in FIG. 3, the planetary gear 65 rotates relative to the eccentric shaft 64 in the clockwise direction in FIG. The meshing position with the gear 63 is changed. At this time, since the force with which the engagement protrusion 69 presses the engagement hole 68 in the rotation direction increases, the output shaft 66 advances with respect to the sprocket 62. Thereby, the rotation phase of the intake camshaft 21 changes to the advance side.

  On the other hand, when the motor shaft 44 rotates relative to the sprocket 62 in the clockwise direction of FIG. 3, the planetary gear 65 rotates relative to the eccentric shaft 64 in the counterclockwise direction of FIG. The meshing position with the gear 63 is changed. At this time, the engaging protrusion 69 presses the engaging hole 68 in the counter-rotating direction, so that the output shaft 66 is retarded with respect to the sprocket 62. As a result, the rotational phase of the intake camshaft 21 changes to the retard side.

-ECU-
The ECU 200 includes a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, a RAM (Random Access Memory) 203, a backup RAM 204, and the like, as shown in FIG.

  The ROM 202 stores various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU 201 executes various arithmetic processes based on various control programs and maps stored in the ROM 202. The RAM 203 is a memory that temporarily stores calculation results of the CPU 201, data input from each sensor, and the backup RAM 204 is a nonvolatile memory that stores data to be saved when the engine 1 is stopped, for example. Memory.

  The CPU 201, ROM 202, RAM 203, and backup RAM 204 are connected to each other via a bus 207, and are connected to an input interface 205 and an output interface 206.

The input interface 205 includes a crank position sensor 31, a water temperature sensor 32, an air flow meter 33, an intake air temperature sensor 34, a throttle opening sensor 35, an accelerator opening sensor 36 that outputs a detection signal corresponding to the depression amount of the accelerator pedal, a front Various sensors such as an air-fuel ratio sensor 37, a rear O ₂ sensor 38, and a cam position sensor 39 are connected.

  The input interface 205 is connected to an ignition switch 48 for turning on / off the main power source of the vehicle and a starter switch 49 that is operated by the vehicle occupant to start the engine 1. When the ignition switch 48 is turned on, control of the engine 1 by the ECU 200 is started, and when the starter switch 49 is turned on, cranking of the engine 1 by the starter motor 10 is started.

  On the other hand, for example, the output interface 206 includes an injector 2 for each cylinder, an igniter 4 for the ignition plug 3 for each cylinder, a throttle motor 6 for the throttle valve 5, a starter motor 10, and a VVT 40 for the intake camshaft 21. Etc. are connected.

  The ECU 200 controls the drive of the injector 2 (control of the fuel injection amount and injection timing), the control of the ignition timing by the spark plug 3, and the drive control of the throttle motor 6 based on the signals from the various sensors and switches described above. Various controls of the engine 1 including (control of throttle opening), operation control of the VVT 40 (phase control of the intake valve 13) and the like are executed, and further, engine start control described below is executed.

  In other words, the start control device for the internal combustion engine of the present invention is realized by the following program for engine start control executed by the ECU 200.

-Engine start control-
First, in the engine 1 of the present embodiment, the fuel injected from the injector 2 immediately before stopping the operation adheres to the wall surface of the intake port 11a (including the back surface of the intake valve 13), and after the engine 1 is stopped, the injector 2 From this, fuel may leak. For this reason, even if fuel injection is not performed at the time of restart, high-temperature air sucked into the cylinder by cranking is mixed with the wall-attached fuel or leaked fuel to form an air-fuel mixture and self-ignite ( That is, there is a possibility that pre-ignition occurs).

  Therefore, the temperature state of the engine 1 is determined at the start, and if the predetermined high temperature state is reached, the closing timing of the intake valve 13 is changed to the retarded side by the VVT 40 before cranking is started. . By doing so, the effective compression ratio of the cylinder can be reduced and pre-ignition can be prevented. Hereinafter, an example of such engine start control will be described with reference to the flowcharts of FIGS.

  First, the start-up VVT control routine shown in FIG. 5 is started (start) when the ignition switch 48 is turned on (IG-SW on). In step ST101, the engine water temperature and the intake air temperature are detected from the output signals of the water temperature sensor 32 and the intake air temperature sensor 34. Based on the detection results, the engine 1 is likely to generate pre-ignition when starting. It is determined whether or not the temperature is high.

  As an example, in step ST101, it is determined whether or not the pre-ignition generation condition including the following four conditions is satisfied. If the determination is affirmative (YES), the process proceeds to step ST102. . The pre-ignition generation conditions are: 1) the engine water temperature is equal to or higher than a predetermined water temperature determination value, 2) the intake air temperature of the engine 1 is equal to or higher than a predetermined intake air temperature determination value, and 3) the process since the previous stop of the engine 1 The time is less than a predetermined determination time, and 4) a high load state higher than a predetermined value has been obtained between the previous engine start and the stop.

  Regarding these four conditions, the higher the engine water temperature, the higher the temperature of the combustion chamber 1d in the cylinder, the higher the temperature of the intake air filled in the combustion chamber 1d, and preignition is likely to occur in the compression stroke. Of course, pre-ignition is likely to occur when the temperature of the intake air itself is high. Further, the shorter the elapsed time from the engine stop, the higher the temperature of the combustion chamber 1d. If the engine is in a high load state higher than a predetermined level before the previous engine stop, a particularly high temperature region (heat spot) is generated in the combustion chamber 1d. ) May exist.

  Therefore, when all four conditions are satisfied, for example, it can be determined that pre-ignition is likely to occur at the start. It should be noted that the establishment of the pre-ignition condition may be determined by various combinations such as one or two of the four conditions, or other conditions may be added. In addition, for the water temperature judgment value, intake air temperature judgment value, and judgment time, experiments and simulations, etc., are performed on the engine water temperature and intake air temperature at the start when there is a high possibility of pre-ignition, and the elapsed time since the previous engine stop. And a combination of values adapted based on these values may be set as the water temperature determination value, the intake air temperature determination value, and the determination time.

  As a result of the determination, if it is determined that the pre-ignition occurrence condition is satisfied (YES) and the process proceeds to step ST102, the value of the pre-flag flag F is set to 1 (F ← 1), and the VVT 40 is retarded in the subsequent step ST103. The closing timing of the intake valve 13 is changed to the retard side. The operation amount (VVT retardation amount) to the retard side of the VVT 40 is determined according to the engine water temperature (starting water temperature) and the intake air temperature with reference to the VVT retardation amount map shown in FIG. 7A as an example. To do.

  The map illustrated in the figure shows that the higher the engine water temperature and the higher the intake air temperature, the larger the VVT retard amount, and by reducing the effective compression ratio of the cylinder by slow closing of the intake valve 13, the TDC is also effective. The in-cylinder temperature is prevented from reaching the self-ignition temperature of the air-fuel mixture. For this purpose, the retard amount of the VVT 40 is adapted by associating it with the engine water temperature and the intake air temperature by experiments and calculations, etc., and the adaptation value is mapped and stored in the ROM 202 of the ECU 200.

  Note that the effective compression ratio at which the cylinder temperature does not reach the self-ignition temperature of the air-fuel mixture is the influence of the intake air temperature at the time of engine start, the amount of filling into the cylinder, the latent heat due to fuel evaporation, the specific heat ratio of the air-fuel mixture In consideration of the above, it is an effective compression ratio that does not reach the auto-ignition temperature due to heat received from the cylinder wall in the compression stroke or a temperature rise due to compression, and is preferably determined by adding a predetermined margin. In addition to the map as described above, the VVT retardation amount may be determined according to only the engine water temperature or the intake air temperature, or may be a constant value.

  Returning to the flow of FIG. 5, in step ST104, it is determined whether or not the engine speed ne calculated from the output signal of the crank position sensor 31 has reached a predetermined start completion determination value Thne (for example, 500 rpm: see FIG. 8). On the other hand, if the determination is negative (NO), the process waits. If the engine speed ne reaches the determination value Thne and the determination is affirmative (YES), the value of the flag F is set to 0 in step ST105 (F ← 0). The start-up VVT control routine is terminated.

  Further, when it is determined in step ST101 that the pre-ignition generation condition is not satisfied (NO) and the process proceeds to step ST106, the VVT 40 is not operated and is set as the VVT position at the previous engine stop, that is, the intake valve 13 The VVT control routine at the start is ended (end) while the closing timing is maintained in the state at the time of the previous engine stop. Here, in the present embodiment, when the engine 1 is stopped, the intake valve 13 is normally closed at a predetermined time (for example, about ATDC 60 to 70 ° CA) so that the effective compression ratio at which cold starting can be performed by controlling the VVT 40. I have control.

  Next, the start-time starter control routine will be described with reference to FIG. This routine is also started (start) when the ignition switch 48 is turned on (IG-SW on) as in the start-up VVT control routine. First, in step ST201, it is determined whether or not the starter switch 49 is turned on. (Starter SW on?) And if it is negative determination (NO), it will wait, and if it is affirmation determination (YES), it will progress to step ST202.

  In step ST202, it is determined whether or not the value of the pre-flag flag F is 0 (F = 0?). If the determination is affirmative (YES), the process proceeds to step ST203, the starter relay is turned on, and cranking is performed. Start. On the other hand, if the determination is negative (NO), the process proceeds to step ST204, where it is determined whether or not the cranking delay time has elapsed.

  That is, at the same time when the ignition switch 48 is turned on, the ECU 200 operates a counter (ignition ON counter), and it is determined that the delay time has not elapsed (NO) until the value of the counter reaches the set value. And wait. On the other hand, if the counter value reaches the set value, it is determined that the delay time has elapsed (YES), and the process proceeds to step ST203 to turn on the starter relay.

  That is, if the value of the pre-ignition flag F is 1 and the engine 1 is in a high temperature state where pre-ignition is likely to occur when the engine 1 is started, the operation of the starter motor 10 for a predetermined period of time even if the ignition switch 48 is turned on, Delay the start of cranking. This delay time is set in advance in, for example, a cranking delay time map shown in FIG. 7B in association with the end time of the operation of the VVT 40 by the start-up VVT control routine.

  The map illustrated in FIG. 7B is stored in the ROM 202 of the ECU 200, and the cranking delay time becomes longer as the engine water temperature is higher and the intake air temperature is higher as in the above-described VVT retardation amount map. ing. For example, the operation time of the VVT 40 until the target VVT retardation amount is reached is mapped by experiment and calculation. It is also possible to start cranking by feeding back the actual operating state of the VVT 40 without using a map.

  In this way, after the closing timing of the intake valve 13 is retarded, cranking is started, fuel injection by the injector 2 and ignition control by the spark plug 3 are performed, and the engine 1 is started. The fuel injection amount and the ignition timing are determined by a start injection amount map and an ignition timing map (not shown), for example, based on various conditions at the time of engine start (engine water temperature, intake air temperature, etc.).

  In step ST205 of the flow of FIG. 6, it is determined whether or not the engine speed ne has reached the determination value Thne. If the determination is negative (NO), the process waits. When the engine speed ne reaches the determination value Thne and the determination is affirmative (YES), the process proceeds to step ST206, the starter relay is turned off, the cranking by the starter motor 10 is stopped, and the starter starter control routine is executed. End (end).

-Suppression of pre-ignition by starting control-
FIG. 8 shows how the engine 1 is started when the cranking is delayed in the high temperature state as described above and the closing timing of the intake valve 13 is changed to the retard side (that is, the engine speed ne is increased, etc.). , Changes in intake air temperature and engine water temperature, ignition switch 48 on operation (ignition on counter), starter switch 49 on operation (start request flag), starter motor 10 operation (starter relay on flag) and VVT 40 operation (VVT) It is shown in relation to the retardation amount.

  When the ignition switch 48 is turned on when the intake air temperature or the engine water temperature is high as shown in the upper part of the figure (time t0), the ignition ON counter of the ECU 200 starts operation and the VVT 40 is shown in the lower part of the figure. Is operated to the retard side, and the VVT retard amount increases. That is, the opening / closing timing of the intake valve 13 is changed to the late closing side.

  In this case, when the starter switch 49 is subsequently turned on and the start request flag is raised (time t1) as shown in the middle of the figure (time t1), the starter relay ON flag is not raised and the start of cranking is delayed. (The engine speed does not increase.) Then, almost at the same time when the VVT retardation amount reaches the target value, the ignition ON counter reaches the set value (time t2), and the starter relay ON flag rises.

  As a result, when the starter motor 10 operates and cranking of the engine 1 is started, the engine speed ne rises to a predetermined speed (for example, about 200 rpm) at a time t3 with a slight delay. Although not shown, fuel is supplied and ignited in a predetermined order in the four cylinders. At this time, as described above, the closing timing of the intake valve 13 is retarded sufficiently large by the retardation of the VVT 40 and the effective compression ratio of the cylinder is considerably low, so that the occurrence of pre-ignition is avoided.

  In addition, since the VVT retardation amount is set based on the intake air temperature and the engine water temperature without being excessive or insufficient, the effective compression ratio is not unnecessarily lowered and good startability is ensured. Therefore, if the air-fuel mixture is combusted in the first ignition cylinder and the second ignition cylinder, the rotation of the crankshaft 15 is accelerated by this, and the engine speed ne rises (time t4), so that it quickly blows up.

  When engine speed ne that blows up in this way reaches determination value Thne (time t5), the start request flag and the starter relay ON flag are turned off, and the start control is completed. In addition, the intake air temperature rapidly decreases due to the inflow of outside air into the intake passage 11, and the engine water temperature also gradually decreases due to the flow of cooling water in the water jacket. Thereafter, the retard control of the VVT 40 is also immediately terminated, and the normal control corresponding to the operating state of the engine 1 is started.

  Therefore, according to the start control device for the engine 1 of the present embodiment, the intake VVT 40 is positioned on the advance side when the engine 1 is stopped, and it is determined that the engine is in a high temperature state mainly based on the intake air temperature and the engine water temperature at the subsequent start. Then, the VVT 40 is operated before the cranking starts, and the closing timing of the intake valve 13 is changed to the retard side. Thereby, the effective compression ratio of a cylinder can be reduced and the occurrence of preignition can be avoided.

  In other words, the effective compression ratio of the cylinder can be reduced as necessary based on the actual temperature state when the engine 1 is started, so that pre-ignition can be avoided more reliably while ensuring good startability. it can. If the temperature is relatively low, the intake valve 13 is not closed too late, and by increasing the effective compression ratio, startability can be ensured. On the other hand, the higher the temperature, the slower the closing timing of the intake valve 13 and the effective compression. The ratio can be reduced and pre-ignition can be avoided more reliably.

  Since the VVT 40 is operated at the time of starting as described above, the ignition switch 48 is operated (predetermined before the starter switch 49 is turned on, that is, before the cranking start operation is performed). The VVT 40 is operated according to the operation. For this reason, the delay time from the start operation of the starter switch 49 to the start of cranking is short, and there is little fear that the passenger feels uncomfortable.

  On the other hand, positioning the VVT 40 on the advance side when the engine 1 is stopped as described above is effective for ensuring the startability of the engine 1 in a cold region. If the VVT 40 is controlled to be retarded when the engine is stopped, if the VVT 40 does not operate due to an emergency failure when the subsequent restart of the engine 1 is extremely cold (for example, about minus 10 ° C.), the engine 1 This is because the startability of the battery may be significantly reduced.

-Other embodiments-
In the above-described embodiment, if the pre-ignition condition is satisfied when the engine 1 is started, the VVT 40 is retarded according to the intake air temperature or the engine water temperature, and the intake air is increased so that the retard amount increases as the temperature increases. Although the closing timing of the valve 13 is retarded, the present invention is not limited to this, and the VVT retardation amount may be changed according to either the engine water temperature or the intake air temperature .

  In the above-described embodiment, when the ignition switch 48 is turned on, the pre-ignition occurrence condition is immediately determined. If the condition is satisfied, the VVT 40 is retarded before the starter switch 49 is turned on. However, it is not limited to this. For example, the VVT 40 may be operated when a predetermined operation such as an operation of the starter switch 49 is performed.

  In the above-described embodiment, the VVT 40 is controlled to be advanced when the engine 1 is stopped, and the closing timing of the intake valve 13 is advanced so that the effective compression ratio can be cold-started even in a cold region. However, the present invention is not limited to this, and the VVT 40 may be controlled to a position other than the most retarded position when the engine is stopped.

  Furthermore, in the above-described embodiment, the example in which the present invention is applied to the start control of the port injection type engine 1 has been described. However, the present invention is not limited to this, and is also applied to the start control of an in-cylinder direct injection type engine. It is also possible to apply to start control of an engine provided with both port injection and in-cylinder fuel injection valves.

  In the above embodiment, the case where the present invention is applied to a four-cylinder engine has been described. However, the present invention is not limited to this, and the start control of an engine having any other number of cylinders such as a six-cylinder engine is possible. It is also applicable to. In addition to the in-line multi-cylinder engine, the present invention can be applied to start control of a V-type multi-cylinder engine.

  INDUSTRIAL APPLICABILITY The present invention can be applied as a start control device for an internal combustion engine (engine), and can suppress pre-ignition at the start while ensuring good startability, and is particularly effective when mounted on a passenger car or the like. is there.

1 engine (internal combustion engine)
10 Starter motor 13 Intake valve (intake valve)
15 Crankshaft 32 Water temperature sensor (sensor)
34 Intake air temperature sensor (sensor)
40 VVT (Variable valve mechanism)
48 Ignition switch 49 Starter switch 200 ECU (control means)

Claims (6)

A start control device for cranking and starting an internal combustion engine,
A variable valve mechanism that can change at least the closing timing of the intake valve;
Control means for determining a temperature state at the time of start and changing the closing timing of the intake valve to the retard side by the variable valve mechanism before starting cranking if the temperature is a predetermined high temperature state. ,
Wherein said control means delays the start of the more cranking temperature state is high at the start, start control system for an internal combustion engine, characterized in der Rukoto that changing the closing timing of the intake valve to a more retarded side . The start control device for an internal combustion engine according to claim 1,
An internal combustion engine start control device, wherein the variable valve mechanism is driven by an electric motor . The start control device for an internal combustion engine according to claim 1 or 2,
An internal combustion engine is mounted on the vehicle,
The control means operates the variable valve mechanism according to a predetermined operation by the occupant before the cranking start operation is performed by the occupant of the vehicle, and changes the closing timing of the intake valve to the retarded side. An internal combustion engine start control device. The start control device for an internal combustion engine according to any one of claims 1 to 3,
A sensor for detecting the temperature of at least one of the coolant and the intake air of the internal combustion engine ;
The internal combustion engine start control device , wherein the control means determines a temperature state at the time of engine start based on a signal from the sensor . The start control device for an internal combustion engine according to claim 4 ,
The control means determines the temperature state at the time of starting the engine by taking into account at least one of the elapsed time from the previous engine stop at the time of engine start and the operation history until the engine stop. . In the start control device for an internal combustion engine according to any one of claims 1 to 5 ,
The control means controls the start timing of the internal combustion engine at a predetermined timing by the variable valve mechanism when the internal combustion engine is stopped so that the effective compression ratio at which cold start is possible even in a cold region. .

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