JP2014098369A - Control device of internal combustion engine - Google Patents

Abstract

In an engine 1 equipped with a VVT 40 (variable valve mechanism) capable of changing an intake valve timing, a smooth start is realized while ensuring a good startability and suppressing a surging of engine rotation.
An intake valve timing is stored as a stop timing when the engine is stopped. When the intake valve timing cannot be calculated at the time of subsequent engine start, the start control is performed based on the stop timing (steps ST101 to ST104), and if the intake valve timing can be calculated, the start control is performed based on this. (Steps ST105 to 107).
[Selection] Figure 5

Description

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

  2. Description of the Related Art Conventionally, in an internal combustion engine mounted on a vehicle or the like, the adoption of a variable valve timing (hereinafter abbreviated as VVT) that makes the operation timing of an intake valve variable has been increasing. For example, in the device described in Patent Document 1, a VVT driven by a step motor is provided on the intake side, and the VVT is operated according to changes in the engine speed and the intake air amount.

  In the conventional example, when the internal combustion engine is in the middle rotation range, the basic advance amount of VVT is set to the advance side as compared with the low rotation range and the high rotation range. On the other hand, at the time of starting, the basic advance angle is set to 0, and the valve overlap between the intake valve and the exhaust valve is reduced, thereby reducing the internal EGR and improving the combustibility of the air-fuel mixture.

Japanese Patent Laid-Open No. 6-346664

  By the way, in an internal combustion engine equipped with VVT, normally, VVT is set to a predetermined target position in advance so that the operation timing of the intake valve is suitable for the next start when the engine is stopped (hereinafter also referred to simply as intake valve timing). However, VVT may not reach the target position for some reason, or VVT may move after that, and the intake valve timing may not be suitable when starting the engine. .

  Therefore, if the start control is performed assuming that the VVT is at the target position, a larger amount of fuel is injected, for example, where the charging efficiency of the cylinder is lower than the target value, and the startability is deteriorated. There is a fear. On the other hand, when the charging efficiency is high, the engine speed increases excessively, which may give the passenger an uncomfortable feeling.

  The actual intake valve timing can be calculated from the signals from the crank position sensor and cam position sensor, but when starting the engine, the pulse signal from the cam position sensor may not be obtained immediately after the cranking starts. Cannot calculate the intake valve timing.

  In consideration of such problems, the object of the present invention is to realize a smooth start with a suppressed start of engine rotation while ensuring a good startability of an internal combustion engine equipped with a VVT (variable valve mechanism). There is to do.

  In order to achieve the above-mentioned object, the present invention is directed to a control device for an internal combustion engine having a variable valve mechanism (hereinafter referred to as VVT) capable of changing the operation timing of the intake valve. Storage means for storing the operation time as the operation time at the time of stop, and if the operation time of the intake valve can be detected or calculated at the time of engine start, the start control is performed based on the operation time, but can be detected or calculated If not, start control means for performing start control based on the operation time at the time of stop is provided.

  If the operation timing of the intake valve cannot be detected or calculated at the time of starting the internal combustion engine due to the specific matter, the start control is performed based on the operation timing at the time of stop stored at the time of the previous engine stop. Therefore, even if the VVT does not return to the target position for some reason when the engine is stopped, it is possible to perform more accurate start control than in the past based on the stop operation timing close to the actual operation timing of the intake valve. it can.

  If the operation timing of the intake valve can be detected or calculated when the engine is started, the start control is performed based on this, so that the VVT is deviated from the target position between the stop and start of the internal combustion engine. However, this influence can be minimized and accurate start control can be performed.

  Specifically, the start control means starts the start control based on the operation position at the time of stop, and thereafter, signals are issued from the crank position sensor and the cam position sensor in accordance with cranking, and the operation timing of the intake valve is determined. If detection or calculation becomes possible, the start control based on the operation position may be switched.

  In this way, by performing start control promptly and as accurately as possible at the time of engine start, it is possible to realize a smooth start that suppresses the rising of engine rotation while ensuring good startability.

  The operation timing at the time of stop is calculated by signals from the crank position sensor and the cam position sensor until the crankshaft that rotates by inertia after the fuel injection and ignition ends when the engine is stopped. That's fine.

  More specifically, regarding the control at the time of engine start by the start control means, the charging to the cylinder is based on either the operation timing at the time of stop or the operation timing of the intake valve detected or calculated at the time of engine start. It is preferable to control the fuel injection amount so as to meet the efficiency. By injecting and supplying an appropriate amount of fuel commensurate with the actual charging efficiency in this way, the combustibility of the air-fuel mixture can be enhanced, which is advantageous for ensuring startability.

  Preferably, the start control means may control the ignition timing based on either the stop operation timing or the intake valve operation timing detected or calculated at the time of engine start. In this case, when the charging efficiency is lower than the target value, startability is ensured by the advance of the ignition timing, while when the charging efficiency is high, the engine rotation is suppressed by the retard of the ignition timing. it can.

  Further, the start control means may control the VVT based on either the operation timing at the time of stop or the operation timing of the intake valve detected or calculated at the time of engine start. For example, when the operation time at the time of stop and the actual operation time detected or calculated at the time of start deviate from a predetermined time suitable for engine start (corresponding to the target position of VVT), this deviation is reduced. VVT can be controlled.

  Furthermore, the start control means controls the VVT according to the temperature state of the internal combustion engine when starting the engine, and advances the operation timing of the intake valve on the low temperature side while delaying on the high temperature side. Also good. In this way, the charging efficiency into the cylinder can be increased on the low temperature side and the combustibility of the air-fuel mixture can be increased. On the other hand, the charging efficiency can be rather decreased on the high temperature side, and the engine speed can be suppressed.

  In other words, by changing the operation timing of the intake valve in accordance with the temperature state of the internal combustion engine at the time of starting, it is possible to achieve a charging efficiency suitable for starting, ensuring higher engine startability and smooth starting. Can be compatible in dimensions.

  In particular, when the internal combustion engine is mounted on the vehicle, the start control means performs the VVT according to a predetermined operation by the occupant before the cranking start operation is performed by the occupant of the vehicle when the engine is started. The control may be started. In this way, for example, the operation of the VVT can be started promptly in response to an ON operation of the ignition switch, and the charging efficiency can be controlled to a suitable filling efficiency sooner.

  Then, after starting VVT control in response to a predetermined operation such as an ignition switch, a signal is issued from the crank position sensor and cam position sensor in accordance with cranking, so that the operation timing of the intake valve can be detected or calculated. For example, the VVT may be controlled based on the operation position.

  The start control means is configured to delay the start of cranking and change the operation timing of the intake valve to the retard side by the control of VVT when the internal combustion engine is in a high temperature state higher than a predetermined value at the start. It is good.

  That is, when the temperature state of the internal combustion engine is considerably high, fuel remaining in the intake port or the like may be sucked into the cylinder by cranking and self-ignited, so that cranking is delayed at such a high temperature state. First, by retarding the operation timing of the intake valve, the charging efficiency and the effective compression ratio of the cylinder are lowered to suppress self-ignition.

  According to the present invention, in an internal combustion engine equipped with a VVT, when the operation timing of the intake valve cannot be detected or calculated at the time of starting, the intake valve If it is possible to detect or calculate the operation timing of the engine, the start control is performed based on the operation timing. Therefore, even if the VVT deviates from the target position, the engine speed can be increased while ensuring good engine startability. It is possible to realize a smooth start that is 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. It is explanatory drawing which shows an example of the characteristic diagram relevant to start control, Comprising: (a) shows the relationship between VVT position and filling efficiency, (b) (c) is fuel injection amount and ignition according to VVT position, respectively. The control map which set the target value of time is shown. It is a timing chart which shows an example of engine starting control. FIG. 6 is a view corresponding to FIG. 5 according to a modified example in which the VVT is operated at the time of starting. It is explanatory drawing which shows an example of the control map used for the VVT control of the modification. FIG. 8 is a view corresponding to FIG. 7 according to the same modification.

  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, a belt-type continuously variable transmission, or the like.

  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 pulse 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 the intake air and introduced into the combustion chamber 1d in each cylinder as 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 as the exhaust valve 14 opens. 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 (hereinafter also referred to as intake valve timing) is set to the advance side and the retard angle. Can be continuously changed to the side.

-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), control of VVT 40, that is, intake valve timing, and the like, and engine start control are executed as follows.

  That is, the control device for the internal combustion engine of the present embodiment is realized by the following program related to engine start control executed by the ECU 200. More specifically, the CPU 201, the ROM 202, the RAM 203, and the like of the ECU 200 correspond to the start control unit, and the backup RAM 204 corresponds to the storage unit.

-Engine start control-
In the engine 1 of the present embodiment, when the operation is stopped, the VVT 40 is operated to a predetermined target position in advance so that the intake valve timing suitable for the next start is reached. There is a possibility that the VVT 40 does not reach the position, or the VVT 40 moves before the engine is started and deviates from the target position.

  Therefore, if the start control is performed assuming that the VVT 40 is at the target position, for example, the charging efficiency to the cylinder corresponds to the target value even though the charging efficiency is lower than the target value (corresponding to the target position of the VVT 40). An amount of fuel is injected, and there is a possibility that startability may deteriorate due to a combination of a small amount of air in the cylinder and an excessive amount of fuel. On the other hand, when the charging efficiency is high, the engine speed rises, and there is a risk that the passenger will feel uncomfortable.

  As for the actual position of the VVT 40, that is, the intake valve timing, the absence of a pulse signal corresponding to the tooth missing portion 17b of the signal rotor 17 is detected from the signal of the crank position sensor 31, and the pulse signal from the cam position sensor 39 is input. If so, it can be calculated based on these.

  However, even if cranking is started when the engine is started, the pulse signal from the cam position sensor 39 may not be input immediately. In some cases, the intake valve timing is calculated until the crankshaft 15 rotates twice. Can not do it.

  Therefore, in the present embodiment, the intake valve timing is calculated in advance until the crankshaft 15 that rotates by inertia when the engine is stopped, and is stored in the backup RAM 204 as the stop timing (operation timing at the stop). Keep it. When starting the engine, first, start control is performed based on the stored stop timing, and if the actual intake valve timing can be calculated along with cranking, the start control is performed based on this. did.

  Hereinafter, an example of the engine start control as described above will be described with reference to the flowchart of FIG. The illustrated start control routine is started (started) when the ignition switch 48 is turned on (IG-SW is turned on). In step ST101, first, the intake valve timing (stop timing) stored at the previous engine stop is stored. ) To calculate the target value of the fuel injection amount and the ignition timing corresponding to the charging efficiency based on the intake valve timing.

  That is, in the present embodiment, the intake valve timing at the start of the engine is basically set so that the closing timing of the intake valve 13 is retarded, and an example is shown in the characteristic diagram of FIG. Thus, when the intake valve timing is advanced, the degree of slow closing of the intake valve 13 is reduced, and the charging efficiency of the cylinder is increased. On the contrary, when the intake valve timing is retarded, the charging efficiency gradually decreases.

  In consideration of this relationship, in this embodiment, as shown in the control map of FIG. 6B, the fuel injection amount increases as the intake valve timing is on the advance side, and changes to the retard side. It is set to decrease gradually as you go. That is, by injecting an appropriate amount of fuel commensurate with the amount of air filled in the cylinder, the air-fuel ratio of the air-fuel mixture is made suitable for starting and combustion stability is ensured.

  On the other hand, as shown in the control map of FIG. 6 (c) as an example of the ignition timing, the ignition timing is retarded as the intake valve timing is advanced, and the ignition timing is changed when the intake valve timing is changed to the retard side. The timing is gradually advanced. In this case, the ignition timing is retarded in order to suppress an excessive increase in engine speed when the charging efficiency of the cylinder is high.

  The control maps shown in FIGS. 6 (b) and 6 (c) are adapted to suitable fuel injection amounts and ignition timings corresponding to the charging efficiency of the cylinders through experiments, calculations, etc. It is stored in the ROM 202. The map is not limited to the above map, and the fuel injection amount and the ignition timing may be set in consideration of various conditions (engine water temperature, intake air temperature, etc.) when starting the engine.

  In step ST102 following step ST101, it is determined whether or not the starter switch 49 has been turned on (starter SW on?). If the determination is negative (NO), the process waits. If the determination is affirmative (YES), step ST103. Then, the starter motor 10 is operated and cranking of the engine 1 is started. Subsequently, in step ST104, fuel injection control by the injector 2 and ignition control by the spark plug 3 are started in order from a predetermined cylinder.

  Subsequently, in step ST105, it is determined whether or not the actual intake valve timing can be calculated from the signals of the crank position sensor 31 and the cam position sensor 39, and the process waits for a negative determination (NO). Proceed to ST106. If the calculated intake valve timing deviates from the target timing corresponding to the target position of the VVT 40, the VVT 40 is operated so as to be at this target timing (VVT operation is performed as necessary).

  Subsequently, in step ST107, based on the calculated intake valve timing, the target values of the fuel injection amount and the ignition timing are calculated with reference to the control maps of FIGS. 6 (b) and 6 (c). Thus, fuel injection control and ignition control are performed. That is, the start control is switched so that the fuel injection amount and the ignition timing correspond to the charging efficiency corresponding to the calculated actual intake valve timing.

  In step ST108, it is determined whether or not the engine speed ne calculated from the signal of the crank position sensor 31 has reached a predetermined start completion determination value Thne (for example, 500 rpm: see FIG. 7), and a negative determination (NO). If the engine speed ne reaches the determination value Thne and the determination is affirmative (YES), the operation of the starter motor 10 is stopped (starter off) and the start control routine is terminated (step ST109). End).

  FIG. 7 shows changes in the engine speed ne, the intake valve timing, and the like in the start control. In the example in the figure, when the engine 1 is stopped (engine speed ne = 0), the actual intake valve timing (actual timing: solid line) is shifted from the target timing (broken line) to the advance side as shown in the upper part of the figure. ing. That is, the degree of slow closing of the intake valve 13 is small, and the charging efficiency into the cylinder is larger than the target value.

  In this state, when the ignition switch 48 is turned on, the starter switch 49 is turned on for a while, and cranking of the engine 1 is started by the operation of the starter motor 10 (time t1), the engine speed ne is predetermined. The rotation speed is increased (for example, about 200 rpm). Although not shown, fuel is supplied and ignited in a predetermined order in the four cylinders.

  Along with the cranking, necessary signals are input from the crank position sensor 31 and the cam position sensor 39, and the actual intake valve timing can be calculated (time t2: timing determination flag OFF → ON). Since the actual intake valve timing (actual timing) is deviated from the target timing, the VVT 40 is operated in accordance with the deviation, and the actual intake valve timing is changed to the retard side.

  Further, since the actual intake valve timing is deviated from the target timing and the charging efficiency into the cylinder is higher than the target value, the fuel injection amount to each cylinder is corrected to increase, and the air-fuel ratio of the air-fuel mixture is good. It will be a value that can be obtained. On the other hand, since the ignition timing is retarded as shown in the drawing in accordance with the deviation of the target timing of the actual intake valve timing, excessive engine torque is suppressed even when the charging efficiency is high. .

  As a result, the engine speed ne that has risen at time t3 rises smoothly as shown by a solid line without excessively rising as shown by a virtual line in the figure. In addition, the actual intake valve timing is changed to the retard side by the operation of the VVT 40, and the fuel injection amount to each cylinder is reduced in response to the gradual decrease in the charging efficiency. At the same time, the ignition timing is gradually returned to the advance side.

  When the engine speed ne that smoothly blows up reaches the determination value Thne (time t4), the operation of the starter motor 10 is stopped, and the engine 1 starts to rotate independently. At this time, the intake valve timing is approximately the target timing, and the fuel injection amount and the ignition timing are also approximately the original target values. Thereafter, the start control is completed, and the routine shifts to normal control according to the operating state of the engine 1.

  Therefore, according to the control apparatus for the engine 1 according to the present embodiment, while the intake valve timing cannot be calculated at the time of engine start, the intake valve timing is set based on the stop timing stored when the engine is stopped and after cranking. If it can be calculated, start control is performed based on this, so that even if the VVT 40 is deviated from the target position, a good startability is ensured, and a smooth start that suppresses the engine speed increase is suppressed. realizable.

  That is, based on either the stop timing or the intake valve timing calculated at the start, a suitable amount of fuel is injected and supplied to meet the actual charging efficiency into the cylinder, and the actual charging efficiency from the target value is reached. For the deviation, the engine torque deviation caused by this is corrected by controlling the ignition timing, so that excessive engine speed increase can be suppressed while ensuring the necessary engine torque.

  Moreover, in this embodiment, if the intake valve timing calculated at the time of start is shifted from the target timing corresponding to the target position of the VVT 40, the VVT 40 is operated so as to reach this target timing. Also, it is possible to achieve a more suitable start control by bringing it closer to the target value.

-Modification of start control-
Next, a modification in which the VVT 40 is operated according to the temperature state when the engine 1 is started will be described. That is, for example, if the engine is cold, it is preferable to increase the filling efficiency into the cylinder and increase the combustibility of the air-fuel mixture. If the efficiency is not lowered, the engine speed cannot be controlled.

  Therefore, in this modified example, as shown in an example in FIG. 8, when the ignition switch 48 is turned on (start: IG-SW on), in step ST201, the output signals from the water temperature sensor 32 and the intake air temperature sensor 34 are used. Detect engine water temperature and intake air temperature. Based on the stop timing, the control of the VVT 40 is started according to the temperature state of the engine 1.

  That is, referring to a control map as shown in FIG. 9 as an example, the intake valve timing at which the charging efficiency is suitable according to the temperature state of the engine 1 is calculated. According to the illustrated control map, the lower the engine water temperature (the same for the intake air temperature), the higher the charging efficiency by advancing the intake valve timing, while the higher the engine water temperature (the same for the intake air temperature), The intake valve timing is retarded to reduce the charging efficiency.

  Such a control map is obtained by adapting suitable intake valve timings corresponding to the engine water temperature and intake air temperature through experiments, simulations, and the like, mapping the conformed values and storing them in the ROM 202 of the ECU 200. Then, the VVT 40 is operated to the advance side or the retard side in accordance with the deviation between the preferred intake valve timing and the stop timing calculated from the control map.

  Subsequently, in step ST202, as in step ST101 of the flow of FIG. 5 of the above-described embodiment, the fuel injection amount and the target value of the ignition timing are calculated based on the stop timing, and the starter switch 49 is turned on in step ST203. If so (YES), cranking by the starter motor 10 and control of fuel injection and ignition timing are started (steps ST204 and ST205).

  When the actual intake valve timing can be calculated in the same manner as in step ST105 in the flow of FIG. 5 (step ST206), the VVT control is executed based on the actual intake valve timing (step ST207). Then, the fuel injection and ignition timing are controlled (step ST208). That is, the start control based on the stop timing is switched to the start control based on the actual intake valve timing.

  Thereafter, similarly to steps ST108 and ST109 in the flow of FIG. 5, if the engine speed ne reaches the start completion determination value Thne (step ST209), the starter motor 10 is stopped (step ST210), and the start control is performed. End the routine (END).

-Effect of modification-
According to the start control of the modified example as described above, as shown in an example in FIG. 10, the VVT 40 is activated in response to the ON operation of the ignition switch 48 (time t1), and the actual intake valve is shown in the upper part of the figure. The timing (actual timing: solid line) approaches a suitable target timing (broken line) for the temperature state of the engine 1. Since this VVT control is performed based on the stop timing, even if the operation of the VVT 40 is stopped at time t2, a difference remains between the actual timing and the target timing.

  When the starter switch 49 is turned on in this state and cranking of the engine 1 is started by the operation of the starter motor 10 (time t3), the engine speed ne rises to a predetermined speed and fuel to the cylinders Injection and ignition control is started. When the actual intake valve timing can be calculated based on the signals from the crank position sensor 31 and the cam position sensor 39 (time t4), the actual intake valve timing deviates from the target timing (deviation). In response, the VVT 40 is activated again.

  At this time, as described above, the VVT control is already performed in response to the ON operation of the ignition switch 48, and the deviation of the air valve timing is reduced. It converges (time t5). Further, since the charging efficiency is only slightly higher than the target value, the increment of the fuel injection amount can be small, and the ignition timing retardation correction amount can be small.

  Then, if the engine speed ne that started up at time t6 rises smoothly without excessively rising and reaches the determination value Thne (time t7), the operation of the starter motor 10 is stopped and the engine 1 is operated according to the operating state of the engine 1. Move to normal control.

  According to this modification, in addition to the operational effects of the above-described embodiment, the VVT 40 is controlled according to the temperature state at the time of starting the engine 1. For example, the charging efficiency is increased on the low temperature side, and the combustibility of the air-fuel mixture is increased. On the other hand, on the high temperature side, the charging efficiency can be reduced, and the engine speed can be sufficiently suppressed. Therefore, ensuring startability of the engine 1 and smooth start can be achieved at a higher level while minimizing deterioration in fuel consumption due to an increase in the fuel injection amount and a delay in the ignition timing.

  In addition, in the modified example, before the cranking start operation is performed by the vehicle occupant, for example, the VVT 40 is operated in response to the ON operation of the ignition switch 48. Therefore, the control of the VVT 40 is as quick as possible. The intake valve timing can be converged to a target value, and can be controlled so as to obtain a charging efficiency suitable for starting.

-Other embodiments-
Note that the descriptions of the above-described embodiments and modifications are merely examples, and are not intended to limit the configuration and use of the present invention. For example, in the embodiment and the modification described above, the fuel injection amount, the ignition timing, and the VVT 40 are controlled as the start control of the engine 1 based on the stop timing in the initial stage of the start, and then the control based on the calculated intake valve timing However, it is not limited to this.

  For example, only the control of the fuel injection amount may be switched in the middle of the start control, and the ignition timing and VVT 40 may be controlled based on the stop timing, or the control of the fuel injection amount and the ignition timing may be switched. The control based on the stop timing may be maintained.

  Further, the start control method is not limited to the method of switching on the way, and if the intake valve timing cannot be calculated when the engine 1 is started, the start control is performed based on the stop timing, while the intake valve timing can be calculated. Based on this, start control may be performed. Moreover, the structure which detects an intake valve timing directly may be sufficient.

  In the above modification, the VVT 40 is operated before the cranking is started in response to the ON operation of the ignition switch 48. However, the present invention is not limited to this. For example, a predetermined operation such as an operation of the starter switch 49 is performed. The VVT 40 may be activated simultaneously with the start of cranking, triggered by the above.

  Further, for example, when the engine 1 is in a considerably high temperature during a warm restart after an idle stop and there is a possibility that abnormal combustion such as pre-ignition may occur, the start of cranking is delayed and the VVT 40 is delayed. May be operated. In this way, abnormal combustion can be suppressed by changing the intake valve timing to the retard side before cranking and sufficiently reducing the charging efficiency and effective compression ratio of the cylinder.

  Furthermore, in the above-described embodiment and modification, the example in which the present invention is applied to the port injection type engine 1 has been described. However, the present invention is not limited to this, and can be applied to an in-cylinder direct injection type engine. In addition, the present invention can be applied to an engine provided with fuel injection valves for both port injection and cylinder injection.

  In the above-described embodiment and modification, 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. For example, an engine having any other number of cylinders such as a six-cylinder engine. The present invention can also be applied to the starting control. 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.

  The present invention can be applied to an internal combustion engine (engine) equipped with a VVT (variable valve mechanism), and can achieve a smooth start with suppressed engine rotation while ensuring good startability. This is particularly effective when mounted on a passenger car or the like.

1 engine (internal combustion engine)
13 Intake valve 40 VVT (Variable valve mechanism)
200 ECU
201 CPU (starting control means)
202 ROM (starting control means)
203 RAM (starting control means)
204 Backup RAM (storage means)

Claims (8)

A control device for an internal combustion engine including a variable valve mechanism capable of changing an operation timing of an intake valve,
Storage means for storing the operation time of the intake valve as the operation time at the time of stop when the engine is stopped;
If the operation timing of the intake valve can be detected or calculated when the engine is started, the start control is performed based on the operation timing, whereas if it cannot be detected or calculated, the start control is performed based on the operation timing at the time of stop. An internal combustion engine control device. The control apparatus for an internal combustion engine according to claim 1,
The start control means starts the start control based on the operation position at the time of stop, and then switches to the start control based on the operation position when the operation timing of the intake valve can be detected or calculated with cranking. Control device for internal combustion engine. The control apparatus for an internal combustion engine according to claim 1 or 2,
The control device for an internal combustion engine, wherein the start control means controls a fuel injection amount based on either the operation timing at the time of stop or the operation timing of the intake valve detected or calculated at the time of engine start. The control device for an internal combustion engine according to any one of claims 1 to 3,
The control device for an internal combustion engine, wherein the start control means controls an ignition timing based on either the operation timing at the time of stop or the operation timing of the intake valve detected or calculated at the time of engine start. In the control device for an internal combustion engine according to any one of claims 1 to 4,
The control device for an internal combustion engine, wherein the start control means controls the variable valve mechanism based on either the operation timing at the time of stop or the operation timing of the intake valve detected or calculated at the time of engine start. The control apparatus for an internal combustion engine according to claim 5,
The start control means controls the variable valve mechanism according to the temperature state of the internal combustion engine when starting the engine, and advances the operation timing of the intake valve on the low temperature side while retarding on the high temperature side Control device. The control apparatus for an internal combustion engine according to claim 6,
An internal combustion engine is mounted on the vehicle,
The start control means starts the control of the variable valve mechanism according to a predetermined operation by the occupant before the start of cranking by the occupant of the vehicle at the time of engine start. apparatus. The control apparatus for an internal combustion engine according to claim 7,
The start control means starts control of the variable valve mechanism based on the stop operation position of the intake valve in response to a predetermined operation by the occupant, and then detects the operation timing of the intake valve along with cranking Alternatively, a control device for an internal combustion engine that controls the variable valve mechanism based on the operating position when calculation is possible.

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