JP2014043771A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability and reliability by preventing overheating of an electric motor 42 or a motor driving circuit 100 for actuating a variable valve mechanism (VVT 40) of an internal combustion engine (engine 1).SOLUTION: Control means (ECU 200) of an internal combustion engine has a stop period operation mode for driving a variable valve mechanism by an electric motor 42 during a stop period from stop to restart of the engine. Even when it is determined that there is a power source off request such as IG-OFF (in step S2, YES), a power source on state is continued (step S4), until temperature (estimated temperature T) of predetermined components (for example, a winding 52 of a coil and a switching element 108) of the electric motor 42 and the motor driving circuit 100 becomes not more than an allowable temperature Ta (in step S3, YES).

Description

  The present invention relates to a control device for an internal combustion engine mounted on a vehicle or the like, and more particularly to control of an electric variable valve mechanism.

  In recent years, a variable valve timing (hereinafter also referred to as VVT) that makes the operation timing of intake valves and exhaust valves variable in an internal combustion engine (hereinafter also referred to as an engine) mounted on a vehicle or the like has become widespread. Yes. As such VVT, a relatively inexpensive hydraulic operation type is mainstream, but an electric type is also increasing. The electric VVT can be operated even when the engine in which the hydraulic pump is stopped is stopped.

  For example, in the variable valve timing device described in Patent Document 1, after the fuel supply and ignition to the engine are stopped in response to a stop instruction, the rotation of the crankshaft due to inertia stops (complete stop). The VVT of the equation is operated, and the valve timing (valve timing) suitable for the subsequent engine start is changed. If the valve timing cannot be changed before the complete stop, the VVT is operated even at the start.

JP 2008-057351 A

  By the way, in the electric VVT as described above, for example, if foreign matter is mixed into a mechanism portion such as a gear meshing portion, the coil of the electric motor may be overheated due to an increase in load. Furthermore, in a lock energization state where only the energization is performed when the electric motor stops rotating (motor lock), there is a possibility that electronic components such as an IC of a drive circuit for driving and controlling the electric motor may be overheated.

  When the electric VVT is operated during the period from the engine stop to the subsequent start (engine stop period) as in the conventional example, the electric motor and electronic components are overheated during this operation. Durability reliability may be impaired. In other words, when the VVT is operated immediately after the main relay is turned off while the temperature of the electric motor or electronic component is relatively high when the engine is stopped, when the energization of the lock occurs, the overheated state occurs in a short time. Because it will be.

  In view of this point, an object of the present invention is to devise a control procedure at the time of stopping an internal combustion engine provided with an electric VVT (variable valve mechanism) as described above, and to provide electronic components for an electric motor and its drive circuit. It is to prevent the overheating and improve the durability reliability.

  In order to achieve this object, the present invention monitors the temperature state of the electric motor of the variable valve mechanism and its drive circuit when stopping the internal combustion engine, and turns off the power supply after the temperature drops below the allowable temperature. I did it.

  That is, the present invention is directed to a control device for an internal combustion engine that includes a variable valve mechanism that can change the operation timing of at least one of an intake valve and an exhaust valve, and the variable valve mechanism is driven by an electric motor. The control means for controlling the operation of the electric motor includes a stop period operation mode in which the variable valve mechanism is driven by the electric motor in a stop period from the stop of the internal combustion engine to the subsequent start. Shall be provided. And even if it determines with the said control means having a power-off request | requirement, it is set as the structure which continues a power-on state until the temperature of the predetermined components of the said electric motor and its drive circuit becomes below allowable temperature.

  For example, when the ignition means is operated and the internal combustion engine is stopped, the control means determines that there is a power-off request, for example, and the predetermined parts of the electric motor of the variable valve mechanism and the drive circuit thereof are determined. The power-on state is continued until the temperature of is lower than the allowable temperature. Then, after confirming that the temperature of the predetermined part has sufficiently decreased, the power is turned off.

  In this case, the variable valve mechanism is immediately operated immediately thereafter, and even if energization of the lock occurs at that time, the predetermined component that has fallen below the allowable temperature does not immediately fall into an overheated state. Therefore, it is possible to prevent overheating of predetermined parts of the electric motor and drive circuit of the variable valve operating apparatus, and to improve the durability reliability.

  Preferably, when the electric motor is controlled in the stop period operation mode, the control means limits an energization amount to the electric motor if the temperature of the predetermined component is equal to or higher than a first set temperature. Also good. In this way, the amount of heat generated by energization is reduced, so that the temperature rise of predetermined parts of the electric motor and the drive circuit can be suppressed, and overheating can be prevented.

  In particular, if the temperature of the predetermined part is equal to or higher than a second set temperature higher than the first set temperature, overheating of the predetermined part can be more reliably prevented by prohibiting energization of the electric motor. it can. At this time, if the failure diagnosis of the variable valve mechanism, the electric motor, and the drive circuit thereof is also prohibited, the erroneous diagnosis can be prevented.

  Further, the control unit may not determine whether or not the power-off request is present when the electric motor is controlled in the stop period operation mode. In this way, when the operation of the internal combustion engine is stopped as in the conventional example (Japanese Patent Laid-Open No. 2008-057351) described above, whether or not there is a power-off request is not determined while the variable valve mechanism is operating. Naturally, the power is kept on.

  Alternatively, the control means prohibits energization of the electric motor after, for example, an ignition-off operation is performed and it is determined that there is a power-off request until the temperature of the predetermined component falls below a set temperature. It may be. In this way, the temperature of the electric motor and its drive circuit components can be quickly lowered to turn off the power supply.

  Here, the temperature of the predetermined component can be detected by a temperature sensor. However, considering that overheating of the electric motor and electronic components is mainly caused by energization of the lock, at least the energization state of the electric motor and The temperature may be estimated based on the rotation state. That is, when the variable valve mechanism is operating during operation of the internal combustion engine and the electric motor is operating normally, the temperature of the electronic components (predetermined components) of the coil and control circuit is generally maintained at a constant design temperature. Therefore, if the lock energization occurs thereafter, the temperature of the predetermined component can be estimated on the assumption that the temperature rises according to the time and the energization amount. In addition, the temperature of the cooling water or lubricating oil of the internal combustion engine may be taken into account in the estimation.

  On the other hand, the temperature state when the internal combustion engine is stopped before the start of the internal combustion engine may affect the temperature of the predetermined component in addition to the outside air temperature and the temperature state of the engine. In consideration of this point, the control means sets the temperature of the predetermined component when the power is turned off, and a predetermined temperature state quantity that affects the temperature (that is, the cooling water temperature, the lubricating oil temperature, the intake air temperature). Etc.) is preferably stored.

  According to the present invention, when the internal combustion engine is stopped, the temperature state of the electric motor or drive circuit of the variable valve mechanism is monitored, and after confirming that the temperature has dropped below the allowable temperature, the power is turned off. As a result, even if the variable valve mechanism is operated in the stop period operation mode until the engine start after that, even if the lock energization state is assumed, the electric motor and the drive circuit do not immediately overheat, Their durability and reliability are improved.

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 electrically driven VVT. It is sectional drawing in the III-III line | wire of FIG. 2 which shows the structure of an electric motor. It is sectional drawing in the IV-IV line | wire of FIG. 2 which shows the structure of a phase change mechanism. It is a circuit diagram which shows the structure of the drive circuit of the electric motor of VVT. 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 control procedure of the stop period operation mode of VVT. It is a timing chart which shows an example of the operation state of the electric motor after IG-OFF, a temperature state, and a power supply ON / OFF state. FIG. 9 is a diagram corresponding to FIG. 8 when lock energization occurs before the engine is started.

  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 disposed so as to detect the temperature of the engine cooling water.

  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 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 is used for lubrication and cooling of various parts of the engine such as the piston 1c, the crankshaft 15, and the connecting rod 16. An oil temperature sensor 30 is disposed on the oil pan 18 so as to detect the temperature of the lubricating oil.

  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 so that fresh air is sucked and combustion gas is discharged. 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.

  In the present embodiment, 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.

  In addition, an injector 2 is disposed in the intake port 11 a for each cylinder, and these injectors 2 are connected to the fuel supply system 20 via a common delivery pipe 21. As an example, the fuel supply system 20 includes a fuel supply pipe 22 connected to a delivery pipe 21, a fuel pump 23, a fuel tank 24, 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 the intake stroke of each cylinder as the intake valve 13 opens. 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 25 and 26 rotated by the crankshaft 15 via a timing chain or the like.

  More specifically, each of the intake and exhaust camshafts 25 and 26 rotates at half the rotational speed of the crankshaft 15, and rotates once while the piston 1c reciprocates twice. In other words, the camshafts 25 and 26 rotate once while the crankshaft 15 rotates twice (720 °) and the piston 1c performs intake, compression, expansion, and exhaust strokes. 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 25 rotating in this manner, 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 25 passes.

  In the present embodiment, the intake camshaft 25 is attached with an electric variable valve mechanism (hereinafter abbreviated as VVT 40) described below. As a result, the rotational phase of the intake camshaft 25 based on the rotation of the crankshaft 15 is continuously changed, and the opening / closing timing of the intake valve 13 can be continuously changed from the advance side to the retard side. it can. For example, in the partial load operation region, the pumping loss can be reduced by retarding the closing timing of the intake valve 13 by the VVT 40.

-VVT structure-
As shown in FIGS. 2 to 4, in this embodiment, a VVT 40 (not shown in FIG. 1) is disposed at the end of the intake camshaft 25. 2 is a cross-sectional view showing the internal structure of the VVT 40, and FIGS. 3 and 4 are cross-sectional views taken along lines III-III and IV-IV in FIG. 2, respectively. A similar variable valve mechanism may be disposed on the exhaust camshaft 26 as well.

  In the illustrated example, the VVT 40 adjusts the operation timing of the intake valve 13 of the engine 1, that is, the intake valve timing, using the rotational torque of an electric motor 42 (hereinafter simply referred to as a motor) controlled by the ECU 200. Yes. That is, the variable valve timing mechanism 40 of this embodiment is configured as a so-called electric valve timing adjustment device (MD-VVT: Motor Drive-Variable Valve Timing).

  As shown in FIGS. 2 and 3, the motor 42 is a three-phase motor including a motor shaft 44, a bearing 46, a rotation speed 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.

  Further, in the vicinity of the rotor portion 45, for example, a Hall element is used, and by detecting the strength of the magnetic field formed by each magnet 45a, the rotation speed of the rotor portion 45, that is, the rotation speed of the motor shaft 44 (hereinafter referred to as the rotation speed). A rotation speed sensor 47 for detecting the motor rotation speed) is provided.

  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. As will be described later with reference to FIG. 5, the winding 52 is star-connected as a set of three, and a terminal on the non-connection side is a motor drive circuit 100. It is connected to the. When a current flows from the motor drive circuit 100 to the winding 52, a rotating magnetic field is formed on the outer peripheral side of the motor shaft 44, and rotational torque is generated.

  Under the control of the motor drive circuit 100, the plurality of coils of the stator 50 form a rotating magnetic field in the clockwise direction or the counterclockwise direction in FIG. When a clockwise rotating magnetic field is formed, each magnet 45 a of the rotor portion 45 receives an attractive force and a repulsive force in order, and this clockwise rotating torque is applied to the motor shaft 44. On the contrary, when the counterclockwise rotating magnetic field of FIG. 3 is formed, the counterclockwise rotating torque is applied to the motor shaft 44.

  Further, as shown in FIG. 4 in addition to FIG. 2, the VVT 40 includes a phase change mechanism 60. 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. 4 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 25 and rotates integrally with the intake camshaft 25 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 4 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. 4 without rotating relative to the sprocket 62. Thereby, the rotation phase of the intake camshaft 25 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 of FIG. 4, the planetary gear 65 rotates relative to the eccentric shaft 64 in the clockwise direction of 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. As a result, the rotational phase of the intake camshaft 25 changes to the advance side.

  On the other hand, when the motor shaft 44 rotates relative to the sprocket 62 in the clockwise direction in FIG. 4, the planetary gear 65 rotates relative to the eccentric shaft 64 in the counterclockwise direction in 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 25 changes to the retard side.

-Motor drive circuit-
FIG. 5 shows a configuration of a motor drive circuit 100 that performs drive control of the motor 42 of the VVT 40. The motor drive circuit 100 operates in response to a control signal from the ECU 200. In FIG. 5, the motor drive circuit 100 is shown to be located outside the motor 42, but in this embodiment, the motor drive circuit 100 is installed in the case of the motor 42 and the cylinder head 1 b of the engine 1 It is influenced by temperature, that is, engine water temperature and lubricating oil temperature.

  The illustrated motor drive circuit 100 includes an energization control unit 102 and a detection unit 104 as an example. The energization control unit 102 includes a bridge circuit 106 in which terminals on the non-connection side of the motor 42 are connected to three rows of arms 105. In the bridge circuit 106, one end of each arm 105 is connected to the power supply line 132 from the battery 120, and the other end of each arm 105 is grounded. In addition, a total of six switching elements 108 made of MOS transistors or the like are disposed on both sides of each arm 105 across the connection point 107 with the terminal of the motor 42.

  In response to the control signal from the ECU 200, the switching element 108 of the energization control unit 102 performs an on / off switching operation at a high speed, thereby controlling the energization state from the battery 120 to the motor 42. The rotation speed is controlled. That is, as will be described later, a control signal of the VVT 40 generated by the ECU 200 according to the operating state of the engine 1 is input to the energization control unit 102, and the energization control unit 102 controls the motor 42, for example, according to this control signal. It is supposed to be.

  In each arm 105 of the bridge circuit 106 shown in FIG. 5, a load resistance element 112 is disposed between the connection point 111 to which the power supply line 132 is connected and the switching element 108 closest thereto. The detection units 104 connected to both ends of the resistance element 112 detect the current value of each load resistance element 112 that represents the amount of current supplied to the motor 42. The detection unit 104 is connected to the ECU 200 and transmits a signal representing the current value, that is, the energization amount to the motor 42.

  In FIG. 5, reference numerals 130 and 140 denote main relays, which are arranged to conduct or cut off (on / off) the power supply from the battery 120 to the motor drive circuit 100 and the main control unit of the ECU 200, respectively. ing. Each of these main relays 130 and 140 receives a control signal from the power supply control unit of the ECU 200, and is switched to either an on or off state in conjunction with each other.

-ECU-
FIG. 6 shows the configuration of the ECU 200. FIG. 6 shows a main control unit that mainly controls the operation of the engine 1, and does not show a power supply control unit. As illustrated, 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.

  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 outputs an oil temperature sensor 30, 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, and an accelerator opening that outputs a detection signal corresponding to the depression amount of the accelerator pedal. Various sensors such as a degree sensor 36, a front air-fuel ratio sensor 37, a rear O ₂ sensor 38, and a cam position sensor 39 are connected.

  In addition, the input interface 205 is operated for starting the engine 1 by a rotation speed sensor 47 (VVT rotation speed sensor) of the VVT 40, an ignition switch 48 for turning on and off the main power supply of the vehicle, and a vehicle occupant. The starter switch 49 and the detection unit 104 of the motor drive circuit 100 of the VVT 40 are connected.

  On the other hand, in the output interface 206, for example, the injector 2 for each cylinder, the igniter 4 of the ignition plug 3 for each cylinder, the throttle motor 6 of the throttle valve 5, the starter motor 10, and the VVT 40 ( The motor drive circuit 100) and the like 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.

  For example, as an operation control of the VVT 40, the ECU 200 determines whether to maintain or change the valve timing based on signals from the crank position sensor 31 and the cam position sensor 39. This determination was calculated from the target rotational phase set from the engine operating state such as the throttle opening, the lubricating oil temperature, each detected value of the crank rotational speed or the cam rotational speed, the detected value of the crank rotational speed, and the cam rotational speed. This is done by comparing the actual rotational phase.

  That is, when maintaining the valve timing, the ECU 200 substantially represents the target change amount of the rotation speed of the motor 42 of the VVT 40 (corresponding to the phase change speed necessary to make the actual rotation phase coincide with the target rotation phase). 0. On the other hand, when changing the valve timing, the target rotational phase of the intake camshaft 25 is compared with the actual rotational phase to calculate the phase difference, and the target change amount of the motor rotational speed is set from the calculated phase difference. .

  As an example, a correlation (table) between the phase difference between the target rotational phase and the actual rotational phase and the target amount of change in the motor rotational speed is adapted to the ECU 200 through experiments or the like in advance according to the operating state of the engine 1. The target change amount can be obtained according to the correlation. A control signal corresponding to the set target change amount is transmitted from ECU 200 to motor drive circuit 100.

  The motor drive circuit 100 that has received this control signal controls the power supply to the motor 42 as described above, and the rotational torque and rotational speed of the motor 42 are controlled to change the rotational speed of the motor 42. The actual rotational phase approaches the target rotational phase. Thereby, the operation timing of the intake valve 13 (intake valve timing) is suitably controlled according to the operating state of the engine 1.

  In addition to such VVT control during operation of the engine 1, the ECU 200 of the present embodiment controls the operation of the VVT 40 during the period from the stop of the engine 1 to the subsequent start (engine stop period) as described below. , It has a stop period operation mode. Thus, the control device for an internal combustion engine of the present invention is realized by the following program related to VVT control executed by the ECU 200.

-Stop period operation mode-
In the stop period operation mode, for example, after the fuel supply to the engine 1 and the ignition are stopped in response to the turning-off operation of the ignition switch 48, the VVT 40 is operated to start the engine while the crankshaft 15 rotates 2-3 times by inertia. The intake valve timing may be changed to a suitable one. Further, the VVT 40 may be operated in response to the ON operation of the ignition switch 48.

  As described above, when the VVT 40 is operated in response to the ON operation of the ignition switch 48, the temperature of the motor 42 or the motor drive circuit 100 may already be high at the start of the operation. If this happens, the coil of the motor 42 and the switching element 108 of the drive circuit 100 may be overheated, which may impair durability reliability.

  That is, while the engine 1 is in operation, the VVT 40 is operated by the motor 42 so that the intake valve timing is suitable for the operation state, so the motor 42 is almost always energized, and its coil and drive circuit 100 switching elements 108 are kept at a constant design temperature (for example, about 100 to 120 ° C.).

  In this state, as described above, the operation of the engine 1 is stopped in response to the turning-off operation of the ignition switch 48, and when the main relays 130 and 140 are immediately turned off, the energization to the motor 42 is stopped, and the coil and the drive The temperature of the switching element 108 of the circuit 100 gradually decreases from the constant temperature. However, the ignition switch 48 once turned off may be immediately turned on.

  When the ignition switch 48 is immediately turned on in this way, the VVT 40 may also be operated. At this time, a large load is applied to the motor 42 due to foreign matter entering the phase change mechanism 60, and the coil (winding 52) When heat generation becomes large, it may fall into an overheating state in a short time. Also, the motor 42 may not rotate (motor lock), and the temperature of the two switching elements 108 that are energized in one phase may rapidly rise and fall into an overheated state.

  In order to prevent such overheating of the motor 42 and the switching element 108, in this embodiment, when the engine 1 is stopped, the temperature state of the motor 42 and the motor drive circuit 100 is estimated, and this estimated temperature is less than the allowable temperature. The main relays 130 and 140 are kept in the ON state until the voltage drops to. Further, when the VVT 40 is operated in the stop period operation mode, the energization to the motor 42 is limited according to the rise in the estimated temperature, and is prohibited as necessary.

  Hereinafter, the procedure of VVT control in the stop period operation mode will be specifically described with reference to the flowchart of FIG. This flow is repeatedly executed by the ECU 200 at regular time intervals when the ignition switch 48 is on.

  First, in step S1 after the start, the ECU 200 determines whether or not there is a VVT operation request. This is determined by the target change amount of the motor speed of the VVT 40. If the target change amount is not zero, an affirmative determination (YES) is made and the process proceeds to step S6 described later, whereas if the target change amount is zero, a negative determination ( NO), the process proceeds to step S2, and it is determined whether or not the ignition switch 48 has been turned off (IG-OFF requested?).

  In other words, since the determination of the presence or absence of the IG-OFF request is not performed when there is a VVT operation request, even if the ignition switch 48 is turned off during the operation of the VVT 40, this is not determined, and the main relay 130 and 140 are kept on.

  If a negative determination (NO) is made for the IG-OFF request, the process returns. On the other hand, if an affirmative determination is made that there is an IG-OFF request (YES), the process proceeds to step S3, and the coil (winding 52) of the electric motor 42 and the motor. It is determined whether or not the estimated temperature T of a predetermined component such as the switching element 108 of the drive circuit 100 is higher than the allowable temperature Ta. This allowable temperature Ta is set to a temperature (for example, about 30 to 40 ° C.) sufficiently lower than the designed constant temperature during the normal operation of the motor 42.

  In addition, regarding the estimation of the temperature of the predetermined component (winding 52, switching element 108, etc.), it is considered that the temperature is constant in the design during the normal operation of the motor 42. For example, it can be estimated that the temperature rises in proportion to the energization amount and the energization time when the motor 42 is not rotating in spite of the energized state.

  That is, when the energization to the motor 42 is stopped in response to the positive determination of IG-OFF as described above, the estimated temperature T of the predetermined component gradually decreases from the designed constant temperature with the passage of time. . Since the VVT 40 is disposed in the cylinder head 1d and the motor drive circuit 100 is installed in the case of the motor 42, it is preferable to consider the influence of the engine water temperature and the lubricating oil temperature on the estimated temperature T. .

  If the estimated temperature of the predetermined part (estimated temperature T) is higher than the allowable temperature Ta and the determination is affirmative (YES), a main relay ON request is issued in step S4, and the main relays 130 and 140 are turned on. Hold and return. That is, when the operation of the engine 1 is stopped in response to the request for IG-OFF, the power supply to the ECU 200 is continued until the estimated temperature T of the predetermined parts of the VVT 40 and the motor drive circuit 100 is sufficiently lowered.

  Thereafter, if the estimated temperature T decreases as the time elapses and becomes equal to or lower than the allowable temperature Ta as described above, a negative determination (NO) is made in step S3 and the process proceeds to step S5, and the estimated temperature T at this time point, In addition, the engine water temperature, the lubricating oil temperature, the outside air temperature and the like (temperature state quantity) that can affect the temperature of the predetermined part are stored in the backup RAM 204 of the ECU 200 and the process returns.

  The main relays 130 and 140 are turned on and off by the power supply control unit of the ECU 200 that is constantly supplied with power from the battery 120. The power supply control unit includes, for example, a throttle control routine or the like other than VVT control. A main relay ON request from the routine may also be input. Therefore, when the main relay ON request of the VVT control routine is not issued as in step S5, the main relays 130 and 140 are turned off unless the main relay ON request is issued from any other control routine.

  On the other hand, in step S6, which is affirmatively determined that there is a VVT operation request in step S1 described above (YES), it is determined whether or not the estimated temperature T of the predetermined component is equal to or lower than a first set temperature Tb. That is, for example, when the ignition switch 48 is turned on after the operation of the engine 1 is stopped as described above, the VVT 40 is operated in the stop period operation mode unless the target change amount of the motor speed of the VVT 40 is zero. Even at this time, the temperature states of the motor 42 and the motor drive circuit 100 are estimated.

  At this time, the estimated engine temperature T, the engine water temperature, the lubricating oil temperature, the outside air temperature, etc. stored in the backup RAM 204 in step S5, the oil temperature sensor 30, the water temperature sensor 32, the intake air temperature sensor 34, etc. The initial value of the temperature of the predetermined component (winding 52, switching element 108, etc.) is set based on the temperature data detected by, and the estimated temperature T is calculated based on the energization and operating state of the motor 42 thereafter. Can be sought.

  If the estimated temperature T is equal to or lower than the first set temperature Tb (YES), normal energization control for the motor 42 is performed (step S7), and the VVT 40 is advanced so that the target change amount approaches zero. Or operate at a retarded angle. That is, if the temperature of the predetermined component is lower than the first set temperature Tb, the VVT 40 can be operated in the stop period operation mode as usual.

  On the other hand, if the estimated temperature T is higher than the first set temperature Tb and a negative determination (NO) is made, the process proceeds to step S8, where the estimated temperature T is higher than the first set temperature Tb. It is determined whether or not the temperature is lower than the set temperature Tc. If this is an affirmative determination (YES), the VVT 40 is advanced or retarded while restricting the amount of current supplied to the motor 42 and suppressing its heat generation (step S9).

  On the other hand, if the estimated temperature T is higher than the second set temperature Tc (Yes in Step S8), the motor 42 is prohibited from being energized (Step S10). Prevent further temperature rise. Further, in order to prevent erroneous diagnosis due to the prohibition of energization of the motor 42 in this way, failure diagnosis of the VVT 40, the motor 42 and the motor control circuit 100 is prohibited (step S11), and the process returns.

-Functional effects of this embodiment-
By controlling the VVT 40 as described above, the motor 42 of the VVT 40 is operated when the operation of the engine 1 is stopped and when the engine 1 is started thereafter, and the coil (winding 52) and the motor control circuit 100 are controlled. How the temperature of a predetermined component such as the switching element 108 changes will be described with reference to FIGS.

  First, when the engine 1 shown in FIG. 8 is stopped, the ignition switch 48 (IG) is turned off (time t1), and even after the ECU 200 stops the fuel supply and ignition to the engine 1, the motor speed of the VVT 40 is reduced. Since the target change amount is not zero, the operation of the VVT 40 continues (stop period operation mode). Therefore, the determination of the IG-OFF request is not performed, the energization of the motor 42 is continued, and a pulse signal (motor pulse) from the rotation speed sensor 47 of the VVT 40 is input along with the rotation. In addition, the estimated temperature T is generally maintained at a constant design temperature.

  When the VVT 40 is thus operated to change the intake valve timing and the target change amount of the motor 42 becomes zero, the energization of the motor 42 is stopped (time t2), and the rotation of the motor 42 is also stopped. Then, the estimated temperature T gradually decreases from the stop of energization, but the main relays 130 and 140 are maintained in the ON state while the estimated temperature T is higher than the allowable temperature Ta.

  When the estimated temperature T becomes equal to or lower than the allowable temperature Ta at time t3, the main relays 130 and 140 are turned off in conjunction with each other, and power supply to the motor control circuit 100 and the ECU 200 (main control unit) is stopped. That is, after the temperatures of the motor 42 and the motor control circuit 100 of the VVT 40 are sufficiently lowered, the power source of the ECU 200 is turned off. In addition, temperature data such as the estimated temperature T is stored in the ECU 200 before the power is turned off.

  On the other hand, when the engine is started, as shown in FIG. 9, when the ignition switch 48 is turned on and the main relays 130 and 140 are turned on in conjunction with the power control unit of the ECU 200 (time t4), the ECU 200 (main control unit) ) And power supply to the motor control circuit 100 of the VVT 40 is started. At this time, if the target change amount of the motor 42 of the VVT 40 is not zero, the VVT control in the stop period operation mode is started, energization of the motor 42 is started, and the rotation speed sensor of the VVT 40 is accompanied with the rotation of the motor 42. 47 receives a pulse signal (motor pulse). Further, the estimated temperature T starts to increase with the start of energization of the motor 42.

  Thus, when the operation control of the VVT 40 is started, for example, if foreign matter is mixed in the phase change mechanism 60 and an excessive load is applied to the motor 42, the heat generation of the coil (winding 52) increases. When the rotation of the motor 42 stops (time t5), the temperatures of the two switching elements 108 that are energized in the motor control circuit 100 are rapidly increased.

  When the rotation of the motor 42 is stopped in this way, the estimated temperature T also rises suddenly due to the interruption of the motor pulse. When the estimated temperature T exceeds the first set temperature Tb (time t6), first, the energization amount to the motor 42 is limited. As a result, heat generation of the coil (winding 52) and the switching element 108 of the motor control circuit 100 is suppressed, and the temperature rise is slowed down. Therefore, overheating of these predetermined parts can be prevented.

  The example in the figure shows a situation where the temperature rise of the coil (winding 52) and the switching element 108 is not stopped even by the restriction of the energization amount as described above. In this case, the estimated temperature T further increases and the second temperature increases. Exceeds the preset temperature Tc (time t7). As the estimated temperature T rises, energization of the motor 42 is prohibited, and thereafter, the temperature of the coil (winding 52) and the switching element 108 starts to fall. That is, overheating of these predetermined parts can be prevented more reliably.

  Therefore, according to the engine control apparatus of the present embodiment, the temperature of a predetermined component such as the motor 42 of the electric VVT 40 or the switching element 108 of the motor drive circuit 100 is estimated, and the operation of the engine 1 is stopped. At this time, the power supply is turned off after confirming that the estimated temperature T has fallen below the allowable temperature Ta. Therefore, in the stop period operation mode in which the VVT 40 is operated until the subsequent engine start-up, the lock energization is temporarily performed. Even if it occurs, the motor 42 and the motor drive circuit 100 do not fall into an overheated state immediately, and their durability and reliability can be improved.

  Further, when the motor 42 of the VVT 40 is controlled in the stop period operation mode, if the estimated temperature T of the predetermined component is equal to or higher than the first set temperature Tb, the amount of current supplied to the motor 42 is limited, thereby The temperature rise of 42 and the motor control circuit 100 can be suppressed, and the overheating can be prevented.

  Further, when the estimated temperature T becomes equal to or higher than the second set temperature Tc higher than the first set temperature Tb, the motor 42 and the motor control circuit 100 are further overheated by prohibiting energization of the motor 42. It can be surely prevented. At this time, the fault diagnosis of the VVT 40, the motor 42, and the motor drive circuit 100 is also prohibited, thereby preventing the occurrence of erroneous diagnosis.

-Other embodiments-
In the above embodiment, as shown in the flowchart of FIG. 7, it is determined whether or not there is an IG-OFF request when there is no VVT operation request, and even if the ignition switch 48 is turned off during the operation of the VVT 40, Although it is not immediately determined that there is an IG-OFF request, the present invention is not limited to this, and the presence / absence of an IG-OFF request may be determined even during the operation of the VVT 40.

  Further, whether or not there is a power-off request to the ECU 200 may be determined based not only on the signal from the ignition switch 48 but also on signals from other switches and sensors.

  If it is determined that there is an IG-OFF request, the energization of the motor 42 of the VVT 40 may be stopped immediately. In this way, the temperature of predetermined components such as the coil (winding 52) of the motor 42 and the switching element 108 of the motor drive circuit 100 can be quickly lowered, and the main relays 130 and 140 can be turned off.

  Further, regarding the estimation of the temperatures of the predetermined parts of the motor 42 and the motor control circuit 100, the embodiment mainly focuses on the temperature rise caused by the motor lock, and estimates the temperature based on the energization amount of the motor 42 and the rotation state thereof. However, these temperatures may be detected by a temperature sensor or the like.

  In the above-described embodiment, the example in which the present invention is applied to the VVT 40 of 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. The present invention can also be applied to an engine having both port injection and in-cylinder fuel injection valves. The present invention is also applicable when the engine 1 is mounted on a so-called hybrid vehicle.

  INDUSTRIAL APPLICABILITY The present invention can prevent overheating of an electric motor that operates a variable valve mechanism of an internal combustion engine (engine) and its drive circuit, and can improve durability and reliability, and is a passenger vehicle that is relatively frequently operated and stopped. It is particularly effective when mounted on the like.

1 engine (internal combustion engine)
13 Intake valve (intake valve)
14 Exhaust valve (exhaust valve)
40 VVT (Variable valve mechanism)
42 Electric motor 52 Coil winding (predetermined parts)
100 Motor drive circuit (drive circuit for electric motor)
108 Switching elements (predetermined parts)
200 ECU (control means)

Claims (8)

A control device for an internal combustion engine comprising a variable valve mechanism capable of changing an operation timing of at least one of an intake valve and an exhaust valve,
The variable valve mechanism is driven by an electric motor;
A control means having a stop period operation mode for driving the variable valve mechanism by the electric motor in a stop period between the stop of the internal combustion engine and a subsequent start;
Even when it is determined that there is a power-off request, the control means is configured to continue the power-on state until the temperature of the predetermined parts of the electric motor and its drive circuit is below an allowable temperature. A control device for an internal combustion engine. The control apparatus for an internal combustion engine according to claim 1,
The control unit controls the internal combustion engine to limit an energization amount to the electric motor if the temperature of the predetermined component is equal to or higher than a first set temperature when the electric motor is controlled in the stop period operation mode. apparatus. The control apparatus for an internal combustion engine according to claim 2,
When the temperature of the predetermined component is equal to or higher than a second set temperature higher than the first set temperature when controlling the electric motor in the stop period operation mode, the control means energizes the electric motor. Control device for internal combustion engine prohibited. The control apparatus for an internal combustion engine according to claim 3,
When the temperature of the predetermined component is equal to or higher than a second set temperature and the energization of the electric motor is prohibited, the control means also performs fault diagnosis of the variable valve mechanism, the electric motor, and a drive circuit thereof. Control device for internal combustion engine prohibited. In the control device for an internal combustion engine according to any one of claims 1 to 4,
The control device of the internal combustion engine, wherein the control means does not determine the presence or absence of the power-off request when controlling the electric motor in the stop period operation mode. In the control device for an internal combustion engine according to any one of claims 1 to 5,
The control device of the internal combustion engine, which prohibits energization of the electric motor from when it is determined that the power-off request is made until the temperature of the predetermined part becomes equal to or lower than a set temperature. The control apparatus for an internal combustion engine according to any one of claims 1 to 6,
The control device of the internal combustion engine, wherein the control means estimates the temperature of the predetermined component based on at least an energization state and a rotation state of the electric motor. The control device for an internal combustion engine according to any one of claims 1 to 7,
The control means stores the temperature of the predetermined component and a predetermined temperature state quantity that affects the temperature when the temperature of the predetermined component is lower than an allowable temperature and the power is turned off. Control device.

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