JP2005180380A - ENGINE START CONTROL DEVICE, METHOD THEREOF, AND VEHICLE MOUNTING THE SAME - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine start control device for lessening the frequency of misfire in engine restart and increasing combustion energy in the engine restart. <P>SOLUTION: In a hybrid powered vehicle 20, an injector 32 injects fuel into a cylinder 31 which stops in an expansion stroke in engine stop, before stopping an engine 30. After that, when an engine restart condition is satisfied, a crankshaft 39 is reversely rotated so that a piston 38 of the cylinder 31 which stops in the expansion stroke is returned to an initial position or neighborhood of the position in the expansion stroke, and then air-fuel mixture in the cylinder 31 is ignited. Since the fuel is injected into the cylinder 31 before the engine stop, that is, when an engine temperature is relatively high, the fuel in the cylinder is sufficiently evaporated in the engine restart so that misfire is not susceptible to occurrence. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an engine start control device, a method thereof, and a vehicle equipped with the same.

Conventionally, as an engine start control device, for example, as disclosed in Patent Document 1, when the engine start condition is satisfied after the engine is stopped by the idle stop control, the fuel injection is commanded to the cylinder stopped in the expansion stroke In addition, it is known to ignite an air-fuel mixture in a cylinder after confirming that a predetermined time sufficient for the fuel to evaporate has elapsed after fuel injection. According to this engine start control device, after the fuel is injected into the cylinders that are stopped in the expansion stroke, the ignition is performed after the vaporization is sufficiently promoted.
JP2002-4929

  However, in the engine start control device described above, the cylinder stopped in the expansion stroke does not generate in-cylinder airflow and the temperature is not sufficiently increased. There was a fear. Also, since it is close to atmospheric pressure ignition, the thermal efficiency of the engine is small and combustion energy cannot be obtained sufficiently. Consequently, assistance from the starter motor at the time of engine restart is required, and the electric energy consumption of the starter motor is reduced to the starter motor. It was difficult to reduce compared to the case where the engine was restarted with the motor alone.

  The engine start control device of the present invention has one object of suppressing the misfire frequency at the time of engine restart. Another object is to increase the combustion energy when the engine is restarted.

  The present invention employs the following means in order to achieve at least a part of the above-described object.

The engine start control device of the present invention includes:
Rotational drive means for rotating the crankshaft of the engine;
Fuel injection means for injecting fuel into each cylinder of the engine;
Ignition means for igniting an air-fuel mixture in each cylinder of the engine;
Fuel injection control means for injecting fuel into the fuel injection means before the engine stops for a cylinder that stops in an expansion stroke when the engine stops;
Restart condition determining means for determining whether an engine restart condition is satisfied while the engine is stopped;
When it is determined by the restart condition determination means that the engine restart condition is satisfied, the crankshaft is connected to the rotational drive means so that the piston of the cylinder stopped in the expansion stroke returns to the initial position of the expansion stroke or the vicinity thereof. Rotational drive control means for rotating in reverse,
Ignition control means for controlling the ignition means to ignite an air-fuel mixture in a cylinder whose piston is returned to the initial position of the expansion stroke or in the vicinity thereof;
It is equipped with.

  In this engine start control device, fuel is injected into the cylinder that stops in the expansion stroke when the engine is stopped before the engine stops, and then the piston of the cylinder that stops in the expansion stroke when the engine restart condition is satisfied. After the crankshaft is rotated in the reverse direction so as to return to the initial position of the expansion stroke or the vicinity thereof, the air-fuel mixture in the cylinder is ignited. Since the fuel is injected before the engine is stopped, that is, when the engine temperature is relatively high, to the cylinder that stops in the expansion stroke when the engine is stopped, the fuel in the cylinder is sufficiently vaporized when the engine is restarted. There is little risk of misfire. Further, since the piston of the cylinder stopped in the expansion stroke is ignited after reverse rotation of the crankshaft so as to return to the initial stage of the expansion stroke or in the vicinity thereof, compression ignition can be realized, thereby reducing the risk of misfire. At the same time, the engine thermal efficiency increases and the combustion energy increases.

  In the engine start control device according to the present invention, the fuel injection control means injects fuel into the fuel injection means before the engine stops with respect to a cylinder that stops in an expansion stroke when the engine stops by idle stop control. The restart condition determining means may determine whether or not an engine restart condition is satisfied while the engine is stopped by the idle stop control. When the idle stop control is performed, the engine stop and restart are repeated many times during the traveling, so that it is significant to apply the present invention.

  In the engine start control device of the present invention, the fuel injection means may inject fuel into an intake port of each cylinder of the engine. In the present invention, a direct injection type can be employed, but a port type in which fuel is injected into the intake port is employed in order to inject fuel before the engine is stopped into a cylinder that stops in the expansion stroke when the engine is stopped. It is also possible.

  The engine start control device of the present invention may include exhaust valve control means for controlling to close an exhaust valve of a cylinder that stops in an expansion stroke when the engine stops. In this way, the exhaust valve of the cylinder that is stopped in the expansion stroke when the engine is stopped is closed, so that fuel in this cylinder does not flow out of the cylinder from the exhaust valve.

  The engine start control device according to the present invention controls the friction applied to the crankshaft by the friction applying means for applying friction to the crankshaft and the friction applying means so that a desired cylinder stops in an expansion stroke when the engine stops. And a friction control means. In this way, the desired cylinder can be stopped in the expansion stroke when the engine is stopped by the balance between the friction applied to the crankshaft and the rotational energy of the crankshaft, and fuel is put into the desired cylinder before the engine is stopped. be able to.

  The engine start control device of the present invention includes stop prediction means for predicting which cylinder stops in an expansion stroke if the engine is stopped as it is before the engine is stopped, and the fuel injection control means includes the fuel injection control means, Fuel may be injected into the fuel injection means before the engine stops for the cylinder predicted to stop in the expansion stroke by the stop prediction means. In this way, since the cylinder that stops in the expansion stroke when the engine is stopped is predicted before the engine is stopped, fuel can be put into the cylinder before the engine is stopped.

  In the engine start control device of the present invention, the fuel injection control means causes the fuel injection means to inject fuel before the engine stops even for a cylinder that stops in a compression stroke when the engine stops. The ignition control means may control the ignition means so that the air-fuel mixture in the cylinder is ignited before the cylinder, which has been stopped in the compression stroke when the engine is stopped, shifts to the expansion stroke. In this way, when the engine restart condition is satisfied, the piston of the cylinder stopped in the expansion stroke is first returned to the initial position of the expansion stroke or in the vicinity thereof, and then, the combustion gas is ignited by igniting the air-fuel mixture in the cylinder. After that, the cylinder that was stopped in the compression stroke when the engine was stopped moves to the expansion stroke, but the fuel is also contained in that cylinder, so that combustion energy can be obtained by ignition, and the engine can be restarted smoothly. Start is performed.

  In the engine start control device according to the present invention, the rotational drive control means may be configured such that the rotational speed of the crankshaft is previously set after the air-fuel mixture in the cylinder whose piston is returned to the initial position of the expansion stroke or in the vicinity thereof is ignited. The rotation driving means may be rotated forward until a predetermined number of rotations is reached. In this way, when it is difficult to restart the engine only with the combustion energy, the engine can be restarted reliably by assisting the rotation drive means.

  In the engine start control device of the present invention, the rotation driving means may be a starter motor of the engine. In this way, it is not necessary to provide a rotation driving means separately from the starter motor.

  In the engine start control device of the present invention, the rotation driving means has a function of converting rotational energy of the crankshaft into electrical energy and storing it in a battery, and a function of converting electrical energy of the battery into rotational energy of the crankshaft. The motor generator provided may be sufficient. In this way, for example, braking energy can be converted into electrical energy and stored in the battery, and the engine can be restarted using the electrical energy when the engine is restarted.

The engine starting method of the present invention includes:
(A) injecting fuel into the cylinder that stops in the expansion stroke when the engine stops before the engine stops;
(B) determining whether an engine restart condition is satisfied while the engine is stopped;
(C) the step of returning the piston of the cylinder stopped in the expansion stroke to the initial position of the expansion stroke or the vicinity thereof when it is determined in step (b) that the engine restart condition is satisfied;
(D) igniting the air-fuel mixture in the cylinder whose piston is returned to the initial position of the expansion stroke or in the vicinity thereof;
Is included.

  In this engine starting method, fuel is injected before the engine is stopped, that is, when the engine temperature is relatively high, to the cylinder that stops in the expansion stroke when the engine is stopped. There is little risk of misfire. Further, since the piston of the cylinder stopped in the expansion stroke is ignited after reverse rotation of the crankshaft so as to return to the initial stage of the expansion stroke or in the vicinity thereof, compression ignition can be realized, thereby reducing the risk of misfire. At the same time, the engine thermal efficiency increases and the combustion energy increases. In this engine starting method, steps for realizing the functions of various components included in the engine starting control device described above may be added.

  Since the vehicle equipped with the engine start control device of the present invention is equipped with the engine start control device of the present invention, the possibility of misfire at the time of engine restart can be reduced, and the engine thermal efficiency can be increased to increase the combustion energy. Can be increased.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing an outline of the configuration of a hybrid vehicle 20 according to an embodiment of the present invention. The hybrid vehicle 20 of this embodiment includes an engine 30 driven by gasoline, an injector 32 that injects fuel into each cylinder 31 of the engine 30, a spark plug 33 that ignites an air-fuel mixture in each cylinder of the engine 30, and an engine. A motor generator 40 for exchanging power with the crankshaft 39 of the engine 30; an engine electronic control unit (hereinafter referred to as engine ECU) 50 for controlling the engine 30; and starting and stopping of the engine 30 and driving of the motor generator 40 And a hybrid electronic control unit (hereinafter referred to as a hybrid ECU) 60 to be controlled.

  The engine 30 is a four-cylinder engine in the present embodiment, and each cylinder 31 is configured as a port type in which an injector 32 injects gasoline into an intake port 36 provided in front of the intake valve 34 in the intake passage 22. Yes. Here, the air sucked into the intake passage 22 through an air cleaner and a throttle valve (not shown) is mixed with gasoline injected from the injector 32 through the intake port 36 to become an air-fuel mixture. The air-fuel mixture is sucked into the combustion chamber 37 by opening the intake valve 34, ignited by the spark of the spark plug 33, and explosively burned. The piston 38 is reciprocated by the combustion energy, and the crankshaft 39 is rotated. Let The exhaust gas after combustion is discharged from the combustion chamber 37 when the exhaust valve 35 is opened. Further, each cylinder of the engine 30 sequentially repeats this cycle with an intake stroke, a compression stroke, an expansion stroke (also referred to as a combustion stroke), and an exhaust stroke as one cycle, and the crankshaft 39 rotates half a turn, that is, 180 °. Each time the stroke is switched, one cycle is advanced every time the crankshaft 39 rotates twice, that is, 720 °. In this embodiment, the ignition timings of the four cylinders are in the order of the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder. Therefore, for example, when the first cylinder is in the expansion stroke, the second cylinder is exhausted. The stroke, the third cylinder is the compression stroke, and the fourth cylinder is the intake stroke. FIG. 2 is an explanatory diagram showing the correspondence between the crank angle CA and the stroke of each cylinder.

  The crankshaft 39 of the engine 30 is connected to the automatic transmission 56. The automatic transmission 56 shifts the power output from the engine 30 to the crankshaft 39 and transmits it to the drive wheels 54 a and 54 b via the differential gear 52. A crank angle sensor 68 is attached to the crankshaft 39, and a cam angle sensor 69 is attached to a camshaft on which cams (not shown) that open and close the intake valve 34 and the exhaust valve 35 are arranged. Among these, the crank angle sensor 68 is an MRE rotation sensor in which a magnetoresistive element is disposed at a position facing a magnet rotor (not shown) attached to the crankshaft 39 in the present embodiment, and the crank angle sensor 68 is generated. The crank angle CA can be specified by using the pulse, or the engine speed Ne can be obtained. The cam angle sensor 69 is an electromagnetic induction pickup type sensor that outputs a pulse each time a tooth of a gear that rotates integrally with a camshaft (not shown) approaches the core of the coil. Each time the shaft 39 rotates twice), one pulse is generated.

  The motor generator 40 is configured as, for example, a synchronous AC motor generator that is driven as a motor and also as a generator, and the MG side pulley 26 attached to the rotating shaft is connected to a crankshaft 39 of the engine 30. The belt 28 is connected to the engine side pulley 24. For this reason, the motor generator 40 generates power using the power output from the engine 30 to the crankshaft 39 to charge the battery 44 via the inverter 42 or uses the electric power obtained from the battery 44 via the inverter 42. Power can be output to the crankshaft 39. The motor generator 40 also serves as a starter motor for the engine 30. For this reason, it is not necessary to provide a starter motor separately from the motor generator 40. The configuration shown in FIG. 1 is referred to as a hybrid vehicle because the rotational force of the motor generator 40 when the engine 30 is started is transmitted to the wheels via the automatic transmission 56 so that the motor generator 40 is used for driving the vehicle. It is because it can be utilized for.

  The engine ECU 50 controls the operation of the engine 30. Although not shown, the engine ECU 50 is constituted by a microprocessor centered on a CPU. In addition to the CPU, the ROM stores processing programs and data, and temporarily stores data. RAM, an input / output port, and a communication port. The engine ECU 50 includes various sensors that indicate the operating state of the engine 30, for example, the crank angle sensor 68 and the cam angle sensor 69 described above, an intake air temperature sensor that detects the temperature of intake air (not shown), and a throttle valve. A throttle valve position sensor for detecting the opening degree (position) of the engine 30 and a water temperature sensor for detecting the temperature (water temperature) of the cooling water of the engine 30 are connected, and detection signals from various sensors are input. Further, the engine ECU 50 supplies a drive signal to the injector 32, a control signal to the variable valve timing mechanism 72 that can change the opening / closing timing of the intake valve 34 and the exhaust valve 35, and an ignition coil 74 that applies a discharge voltage to the spark plug 33. A control signal is output. In order to output the required power based on the driver's operation from the engine 30, the engine ECU 50 has an accelerator that detects the shift position from the shift position sensor 63 that detects the position of the shift lever 62 and the position of the accelerator pedal 64. An accelerator pedal position from the pedal position sensor 65 and an on / off signal from the brake position sensor 67 for detecting whether or not the brake pedal 66 is depressed are also input.

  The hybrid ECU 60 includes a microprocessor centered on a CPU. Although not shown, the hybrid ECU 60 includes a ROM for storing processing programs and data, a RAM for temporarily storing data, an input / output port, and a communication port, in addition to the CPU. I have. The hybrid ECU 60 includes a rotation speed sensor and a motor temperature (not shown) attached to the motor generator 40, a motor rotation speed and a motor temperature from the rotation sensor, a phase current to the motor generator 40 from a current sensor (not shown) installed in the inverter 42, A battery temperature from a temperature sensor (not shown) attached to the battery 44, a voltage between terminals or a charge / discharge current from a voltage sensor or current sensor (not shown) attached in the vicinity of the output terminal of the battery 44 are input via the input port. The hybrid ECU 60 outputs a switching control signal to the inverter 42 for driving and controlling the motor generator 40 via an output port. Hybrid ECU 60 is connected to engine ECU 50 via a communication port, and receives data related to the state of engine 30 from engine ECU 50 and transmits a control signal to engine ECU 50 as necessary.

  Next, the operation of the hybrid vehicle 20 of the present embodiment, particularly the operation associated with the idle stop control will be described below. In this hybrid vehicle 20, the engine speed Ne is equal to or lower than a predetermined low speed when the accelerator pedal 64 is not depressed and the brake pedal 66 is depressed when the accelerator pedal 64 is depressed when the vehicle is idle. The engine 30 is automatically restarted by the motor generator 40 when a predetermined start condition is satisfied, such as when the predetermined stop condition is satisfied, the engine 30 is automatically stopped, and then the brake is turned off and the accelerator is turned on. Idle stop control is performed. Hereinafter, an automatic stop control routine and an automatic restart routine performed in the idle stop control will be described.

  First, the automatic stop control routine will be described. FIG. 3 is a flowchart of this routine. This routine is executed by the hybrid ECU 60 at every predetermined timing (for example, every several milliseconds) during engine operation. When this routine is started, the hybrid ECU 60 determines that the accelerator position from the accelerator pedal position sensor 65 is accelerator OFF, the brake pedal position from the brake position sensor 67 is brake ON, and the engine speed Ne is a predetermined low speed rotation. It is determined whether stop conditions equal to or less than a number have been met (step S100). Here, the engine speed Ne is calculated based on the time interval of pulses output from the crank angle sensor 68. Signals output from the accelerator pedal position sensor 65, the brake position sensor 67, and the crank angle sensor 68 are input to the hybrid ECU 60 via the engine ECU 50. Further, in the present embodiment, the predetermined low-speed rotational speed is set to a numerical value slightly exceeding the normal idling rotational speed.

  If the above stop condition is not met in step S100, this routine is terminated as it is. On the other hand, when the stop conditions are met in step S100, the engine ECU 50 is instructed to stop energizing the injectors 32 of the cylinders 31 of the engine 30 and stop energizing the spark plug 33 (step S110). As a result, since the ignition and fuel injection of each cylinder 31 of the engine 30 are stopped, the engine 30 does not generate torque that rotates the crankshaft 39. For this reason, the crankshaft 39 rotates only with an inertial force. Since this inertial force is attenuated by the gas compression force generated in the cylinder in the compression stroke, the rotation of the crankshaft 39 converges toward the stop.

  Subsequently, the hybrid ECU 60 determines whether or not the engine speed Ne is equal to or less than a predetermined threshold value Nth (step S120). If Ne is not equal to or less than Nth, the hybrid ECU 60 stands by and Ne is equal to or less than Nth. When it becomes, it is determined whether or not a predetermined specific cylinder (here, the third cylinder) has reached the timing immediately before the intake stroke (step S130). Here, the threshold value Nth is a value obtained by experimentally obtaining in advance an engine speed at which drivability does not deteriorate even if the crankshaft 39 rotating by inertial force is forcibly stopped. However, it is assumed that the crankshaft 39 rotates at least two to three cycles after Ne becomes equal to or less than the threshold value Nth. Whether or not the specific cylinder has reached the timing immediately before the intake stroke is determined based on the pulse output from the crank angle sensor 68 and the pulse output from the cam angle sensor 69. In this embodiment, the cam angle sensor 69 is set to output a pulse every time the first cylinder enters the expansion stroke, and the crank angle sensor 68 outputs a pulse every time the crankshaft 39 rotates by a predetermined angle. Is set to For this reason, the crank angle is reset to zero each time a pulse is output from the cam angle sensor 69, and the crank angle is advanced by a predetermined angle each time a pulse is output from the crank angle sensor 68. It can be calculated in a range of ˜720 °. Then, it is possible to determine which cylinder is in which stroke by comparing the calculated crank angle with the correspondence between the crank angle CA and the stroke of each cylinder shown in FIG. In this embodiment, since the specific cylinder is the third cylinder, as shown in FIG. 2, when the crank angle becomes 540 °, the intake stroke is entered, and the timing immediately before the intake stroke is 540 ° -α. Become. The signals output from the crank angle sensor 68 and the cam angle sensor 69 are input to the hybrid ECU 60 via the engine ECU 50.

  In step S130, when the specific cylinder has not reached the timing immediately before the intake stroke, the process waits as it is, and when the specific cylinder has reached the timing immediately before the intake stroke, the injector 32 of the specific cylinder is energized to inject fuel. Command to engine ECU 50 (step S140). As a result, the fuel injected from the injector 32 is mixed with the air in the intake port 36 to become an air-fuel mixture, and the air-fuel mixture is sucked into the combustion chamber 37 of the specific cylinder when the intake valve 34 is opened. Subsequently, it is determined based on the crank angle whether or not the specific cylinder has reached the expansion stroke (step S150). In this embodiment, since the specific cylinder is the third cylinder, the expansion stroke starts when the crank angle reaches 180 ° as shown in FIG. When the specific cylinder has not reached the expansion stroke in step S150, the process waits as it is, and when the specific cylinder has reached the expansion stroke, the motor generator 40 is operated as a generator to apply friction to the crankshaft 39 to force the crankshaft 39. (Step S160). Thereafter, the hybrid ECU 60 stores information for identifying the current specific cylinder in a backup RAM (not shown) (step S170), and ends this routine. Thus, in the idle stop control, the cylinder that stops in the expansion stroke when the engine 30 is stopped can be set as the specific cylinder, and the unburned air-fuel mixture can be sucked into the specific cylinder.

  Next, the automatic restart control routine will be described. FIG. 4 is a flowchart of this routine. This routine is executed by the hybrid ECU 60 every predetermined timing (for example, every several msec) after the automatic control routine ends. When this routine is started, the hybrid ECU 60 determines whether or not a restart condition is satisfied that the brake pedal position from the brake position sensor 67 is brake OFF and the accelerator position from the accelerator pedal position sensor 65 is accelerator ON (see FIG. Step S200).

  When the above restart conditions are not met in step S200, this routine is ended as it is. On the other hand, when the restart condition is met in step S200, the hybrid ECU 60 reads a specific cylinder from a backup RAM (not shown) (step S210), reverses the crankshaft 39 via the belt 28 by causing the motor generator 40 to act as a motor. Rotate (step S220). As a result, the piston 38 of the specific cylinder starts to move back to the top dead center TDC, which is the initial position of the expansion stroke. Subsequently, it is determined whether or not the crank angle has reached a predetermined crank angle (step S230). Here, the predetermined crank angle may be a crank angle when the piston 38 of the specific cylinder is at the top dead center TDC of the expansion stroke, or may be a crank angle slightly advanced from that. In this embodiment, since the specific cylinder is the third cylinder, the predetermined crank angle is set to 180 ° (see FIG. 2), which is the top dead center TDC of the expansion stroke, or a crank angle slightly advanced from that. When the crank angle has not reached the predetermined crank angle in step S230, it is determined based on the pulse output from the crank angle sensor 68 whether or not the crank angular velocity has become substantially zero (step S240). When the crank angular velocity is not substantially zero, the process returns to step S220 again. Here, it is determined whether or not the crank angular velocity has become substantially zero because the crankshaft 39 is further rotated in reverse by the resistance of the gas compression force or the like by the piston 38 before the crank angle reaches a predetermined crank angle. This is because it may stop and stop.

  When the crank angle reaches a predetermined crank angle at step S230 or when the crank angular speed becomes substantially zero at step S240, a discharge voltage is applied to the spark plug 33 of the specific cylinder to generate a spark (step S230). S250). Then, the air-fuel mixture in the combustion chamber 37 of the specific cylinder is compressed by rotating the crankshaft 39 in the reverse direction and returning it to the vicinity of the top dead center TDC of the expansion stroke. In addition, since relatively large combustion energy is generated by compression ignition, the piston 38 is urged toward the bottom dead center BDC, and the crankshaft 39 starts to rotate forward accordingly. Subsequently, engine restart is assisted by causing the motor generator 40 to act as a motor and causing the crankshaft 39 to rotate forward via the belt 28 (step S260), and the engine speed Ne reaches a predetermined start speed Nstart. (Step S270), when Ne has not reached Nstart, the process returns to Step S260 again. When Ne has reached Nstart, the forward rotation assist by the motor generator 40 is terminated (Step S280). Exit. In addition, after the completion of this routine, control during normal traveling is executed.

  Here, the correspondence between the components of the present embodiment and the components of the present invention will be clarified. The motor generator 40 of the present embodiment corresponds to the rotational drive means and the friction applying means of the present invention, the injector 32 corresponds to the fuel injection means, the spark plug 33 corresponds to the ignition means, and the hybrid ECU 60 corresponds to the restart condition determination means. The hybrid ECU 60 and the engine ECU 50 both correspond to the fuel injection control means and also correspond to the rotational drive control means. In the present embodiment, by explaining the operation of the hybrid vehicle 20, an example of the engine start control device of the present invention is clarified and an example of the engine start method of the present invention is also clarified.

  According to the hybrid vehicle 20 of the present embodiment described in detail above, the fuel is sucked before the engine is stopped, that is, when the engine temperature is relatively high, with respect to the specific cylinder that stops in the expansion stroke when the engine is stopped in the idle stop control. Therefore, when the engine is restarted, the fuel in the cylinder is sufficiently vaporized and there is little risk of misfire. In addition, compression ignition is performed in order to ignite after the crankshaft 39 is reversely rotated by the motor generator 40 so that the piston of the specific cylinder stopped in the expansion stroke returns to or near the top dead center TDC which is the initial position of the expansion stroke. Thus, the risk of misfire is further reduced, the engine thermal efficiency is increased, and the combustion energy is increased. In this way, a large amount of combustion energy can be obtained despite the reverse rotation of the crankshaft 39 by the motor generator 40, so that the total amount of electric energy used is reduced compared with the case where the motor generator 40 alone is restarted. Can be

  Further, in the idling stop control, the engine stop and restart are repeated many times during the running, which is advantageous because the accumulated value of the amount of electric energy to be reduced becomes large.

  Further, since the fuel is injected before the engine is stopped to the specific cylinder that stops in the expansion stroke when the engine is stopped, it is possible to adopt a port type in which fuel is injected into the suction port 36.

  Furthermore, the specific cylinder can be stopped in the expansion stroke when the engine is stopped by balancing the friction applied to the crankshaft 39 by the motor generator 40 and the rotational energy of the crankshaft 39 in step S160.

  When it is difficult to restart the engine 30 with only combustion energy, the engine 30 can be reliably restarted by assisting the motor generator 40 by rotating the crankshaft 39 in the forward direction. Since the motor generator 40 converts braking energy into electric energy and stores it in the battery 44, and assists restart of the engine 30 using the electric energy when the engine is restarted, the energy can be used effectively.

  It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

  For example, in the automatic stop control routine of the above-described embodiment, the timing of opening the exhaust valve 35 after stopping the ignition and fuel injection of each cylinder in step S110 as shown in FIG. 5 is set to the bottom dead center BDC of the expansion stroke. The engine ECU 50 may be instructed (step S115), and then the process may proceed to step S120 to determine whether or not the engine speed Ne has become equal to or less than a predetermined threshold value Nth. The engine ECU 50 having received the command in step S115 operates an actuator (not shown) of the variable valve timing mechanism 72 to change the opening timing of the exhaust valve 35. In this way, the exhaust valve 35 is normally opened before the bottom dead center BDC of the expansion stroke (see the solid line arrow in FIG. 6), but in step S115, the exhaust valve 35 is opened at the bottom dead center BDC of the expansion stroke ( In the expansion stroke, the exhaust valve 35 does not open, and the fuel sucked into the combustion chamber 37 of the specific cylinder does not go out of the cylinder from the exhaust valve 35. In this case, both the hybrid ECU 60 and the engine ECU 50 correspond to the exhaust valve control means of the present invention.

  In the idle stop control of the above-described embodiment, the automatic stop control routine of FIG. 3 and the automatic restart control routine of FIG. 4 are adopted, but the automatic stop control routine of FIG. 7 and the automatic restart control routine of FIG. 8 are adopted. May be. In the automatic stop control routine of FIG. 7, the hybrid ECU 60 performs the processing of steps S300 to S320 similar to steps S100 to S120, and then when the engine speed Ne becomes equal to or less than the threshold value Nth in step S320, the hybrid ECU 60 continues. If the engine 30 is stopped, it is predicted which cylinder stops in the expansion stroke, that is, which cylinder becomes the expansion stroke cylinder at the time of stop (step S330). An example of this prediction method is shown below. First, after the engine 30 is rotated only by inertial force, it is attenuated by gas compression force and the crank angle when the engine rotational speed Ne reaches the threshold value Nth, and further attenuated and the engine 30 is stopped. A map is prepared by experimentally obtaining the relationship with the crank angle at that time. Then, in step S320, the crank angle when the engine speed Ne becomes equal to or less than the threshold value Nth is obtained, the crank angle at the time of engine stop corresponding to the crank angle is read from the previous map, and the crank angle CA in FIG. The expansion stroke cylinder at the time of stop can be predicted from the correspondence relationship between the stroke and the stroke of each cylinder. Then, it is determined whether or not the predicted expansion stroke cylinder at the time of stop has reached the timing just before the intake stroke (step S340), and when that timing is reached, the engine 32 is energized to inject fuel. The ECU 50 is commanded (step S350). As a result, the fuel injected from the injector 32 mixes with the air in the intake port 36 to become an air-fuel mixture, and is sucked into the combustion chamber 37 of the specific cylinder when the intake valve 34 is opened. Subsequently, it is determined whether or not the engine speed Ne has become substantially zero (step S360), and when Ne becomes substantially zero, information for identifying a cylinder predicted as the expansion stroke cylinder at the time of stop this time is not shown. (Step S370), and this routine ends.

  On the other hand, in the automatic restart control routine of FIG. 8, after determining that the restart condition is satisfied in step S <b> 400 in step S <b> 400, the hybrid ECU 60 starts the stop-time expansion stroke cylinder from the backup RAM when the restart condition is satisfied. (Step S410), and thereafter, steps S420 to S480 similar to steps S220 to S280 are executed, and this routine is terminated. However, in steps 420 to S480, the specific cylinder in steps S220 to S280 is replaced with the stop-time expansion stroke cylinder to execute control. In this way, since the cylinder that stops in the expansion stroke when the engine is stopped is predicted before the engine is stopped, fuel can be injected into the cylinder before the engine is stopped, and the same effect as the above-described embodiment can be obtained. Can do. In this case, the hybrid ECU 60 corresponds to a stop prediction unit.

  Or you may employ | adopt the automatic stop control routine of FIG. 9, and the automatic restart control routine of FIG. In the automatic stop control routine of FIG. 9, after performing the processing of steps S500 to S520 similar to steps S100 to S120, when the engine speed Ne becomes equal to or less than the threshold value Nth in step S520, the first specific cylinder ( Here, it is determined whether or not the third cylinder) has reached the timing just before the intake stroke (step S530), and when that timing is reached, the engine ECU 50 is configured to energize the injector 32 of the first specific cylinder and inject fuel. (Step S540), and subsequently, it is determined whether or not the second specific cylinder (here, the fourth cylinder, the cylinder in the compression stroke when the first specific cylinder is in the expansion stroke) has reached the timing immediately before the intake stroke. (Step S550), when the timing is reached, the injector 32 of the second specific cylinder is energized to inject fuel. Yo instructs the engine ECU 50 (step S560). As a result, in each of the first and second specific cylinders, the fuel injected from the injector 32 mixes with the air in the intake port 36 to become an air-fuel mixture, and is sucked into the combustion chamber 37 when the intake valve 34 is opened. The Subsequently, it is determined whether or not the first specific cylinder has reached the expansion stroke (step S570), and when the first specific cylinder has reached the expansion stroke, the crankshaft 39 is forcibly stopped (step S580). Information for identifying the first and second specific cylinders is stored in a backup RAM (not shown) (step S590), and this routine ends. As a result, the cylinder that stops in the expansion stroke when the engine 30 is stopped can be the first specific cylinder, and the cylinder that stops in the compression stroke can be the second specific cylinder, and the uncombusted in the first and second specific cylinders. The air-fuel mixture can be inhaled.

  On the other hand, in the automatic restart control routine of FIG. 10, after determining that the restart condition is satisfied in step 600 as in step S200, the hybrid ECU 60 starts from the backup RAM when the restart condition is satisfied. The specific cylinder is read out (step S610), and then steps S620 to S670 similar to steps S220 to S270 are executed. However, in steps 620 to S670, the specific cylinders in steps S220 to S270 are replaced with the first specific cylinders, and control is executed. Then, when the engine speed Ne has not reached the predetermined start speed Nstart in step S670, it is determined whether or not it is the ignition timing of the second specific cylinder (step S672). Returning to step S660, when the ignition timing of the second specific cylinder is reached, a discharge voltage is applied to the spark plug 33 of the second specific cylinder to burn the air-fuel mixture in the cylinder (step S674), and then the process returns to step S660. On the other hand, when the engine speed Ne reaches the predetermined start speed Nstart in step S670, the forward rotation assist by the motor generator 40 is ended (step S680), and this routine is ended. In this way, when the engine restart condition is satisfied, the piston 38 of the first specific cylinder that is stopped in the expansion stroke is first returned to the top dead center TDC that is the initial position of the expansion stroke or the vicinity thereof, and After igniting the air-fuel mixture and obtaining combustion energy, the second specific cylinder, which was stopped in the compression stroke when the engine was stopped, moves to the expansion stroke, but fuel is also sucked into the cylinder, so the ignition Combustion energy is obtained, and the engine is restarted smoothly. Instead of determining the first and second specific cylinders in advance, the stop expansion stroke cylinder may be predicted as shown in the flowcharts of FIGS. In this case, the stop compression stroke cylinder is uniquely determined if the stop expansion stroke cylinder is determined (see FIG. 2).

  Further, in the above-described embodiment, energy transmission between the MG side pulley 26 of the motor generator 40 and the engine side pulley 24 connected to the crankshaft 39 of the engine 30 is performed via the belt 28. And energy transmission between the crankshaft 39 and the crankshaft 39 may be performed via a gear.

  Furthermore, in the above-described embodiment, the MRE rotation sensor is adopted as the crank angle sensor 68. However, a Hall element is arranged at a position facing the magnet rotor attached to the crankshaft 39 to convert the magnetic flux density change into a voltage change. A magnetoelectric conversion sensor may be employed, or a photoelectric sensor that detects a crank angle by rotating a disk with a light-emitting diode and a phototransistor facing each other and cutting a slit therebetween may be employed. You may employ | adopt the electromagnetic induction pick-up type sensor which outputs a pulse whenever the tooth | gear of the gear rotating integrally with the crankshaft 39 approaches the core of a coil. However, considering that a good output can be obtained even when the crankshaft 39 rotates at a low speed, an MRE rotation sensor, a magnetoelectric conversion sensor, or a photoelectric sensor is preferable. Note that the crank angle may be calculated based on the output from the rotation speed sensor attached to the motor generator 40 if no slippage occurs on the belt 28 spanned between the engine side pulley 24 and the MG side pulley 26. As the rotation speed sensor in this case, an MRE rotation sensor, a magnetoelectric conversion sensor, or a photoelectric sensor is preferable.

  In the above-described embodiment, the specific cylinder is described as the third cylinder, but the specific cylinder may be sequentially changed every time the idle stop control is executed. When a specific cylinder is fixed to a certain cylinder, the state of that cylinder may be different from that of other cylinders as the idle stop control is repeated. Few.

  In the above-described embodiment, a four-cylinder engine has been described as an example. However, the present invention can be similarly applied to other multi-cylinder engines. For example, in a 6-cylinder engine, two cylinders may enter an expansion stroke depending on the timing. In this case, the same processing as that of the above-described embodiment is performed on a cylinder that first enters the expansion stroke.

  Further, in the above-described embodiment, the forward rotation assist by the motor generator 40 is performed in the automatic restart control routine. However, such assist may be omitted or stopped in the expansion stroke when the engine is stopped. The engine may be assisted when the engine speed Ne does not reach the predetermined start speed Nstart even after a predetermined time has elapsed after compression and ignition of the cylinder air-fuel mixture.

  Furthermore, in the above-described embodiment, the case where the present invention is applied to the hybrid vehicle 20 is exemplified. However, the present invention is applied to a vehicle with a simple idle stop function in which the power of the motor generator 40 is not transmitted to the vehicle drive shaft. Needless to say.

It is explanatory drawing which shows the outline of a structure of a hybrid vehicle. It is explanatory drawing showing the correspondence of crank angle CA and the stroke of each cylinder. It is a flowchart of an automatic stop control routine. It is a flowchart of an automatic restart control routine. It is a flowchart of the modification of an automatic stop control routine. It is explanatory drawing showing the valve opening time of an exhaust valve. It is a flowchart of the automatic stop control routine of other embodiment. It is a flowchart of the automatic restart control routine of other embodiment. It is a flowchart of the automatic stop control routine of other embodiment. It is a flowchart of the automatic restart control routine of other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 ... Hybrid vehicle, 22 ... Intake passage, 24 ... Engine side pulley, 26 ... MG side pulley, 28 ... Belt, 30 ... Engine, 31 ... Cylinder, 32 ... Injector, 33 ... Spark plug, 34 ... Intake valve, 35 ... Exhaust valve, 36 ... intake port, 37 ... combustion chamber, 38 ... piston, 39 ... crankshaft, 40 ... motor generator, 42 ... inverter, 44 ... battery, 50 ... engine ECU, 52 ... differential gear, 54a, 54b ... drive Wheel, 56 ... Automatic transmission, 60 ... Hybrid ECU, 62 ... Shift lever, 63 ... Shift position sensor, 64 ... Accel pedal, 65 ... Accel pedal position sensor, 66 ... Brake pedal, 67 ... Brake position sensor, 68 ... Crank angle Sensor, 69 A cam angle sensor, 72 ... variable valve timing mechanism, 74 ... ignition coil.

Claims (12)

Rotational drive means for rotating the crankshaft of the engine;
Fuel injection means for injecting fuel into each cylinder of the engine;
Ignition means for igniting an air-fuel mixture in each cylinder of the engine;
Fuel injection control means for injecting fuel into the fuel injection means before the engine stops for a cylinder that stops in an expansion stroke when the engine stops;
Restart condition determination means for determining whether or not an engine restart condition is satisfied while the engine is stopped;
When it is determined by the restart condition determination means that the engine restart condition is satisfied, the crankshaft is connected to the rotational drive means so that the piston of the cylinder stopped in the expansion stroke returns to the initial position of the expansion stroke or the vicinity thereof. Rotational drive control means for rotating in reverse,
Ignition control means for controlling the ignition means to ignite an air-fuel mixture in a cylinder whose piston is returned to the initial position of the expansion stroke or in the vicinity thereof;
An engine start control device comprising: The fuel injection control means causes the fuel injection means to inject fuel before the engine stops with respect to a cylinder that stops in an expansion stroke when the engine is stopped by idle stop control.
The restart condition determining means determines whether or not an engine restart condition is satisfied while the engine is stopped by the idle stop control.
The engine start control device according to claim 1. The fuel injection means injects fuel into an intake port of each cylinder of the engine;
The engine start control device according to claim 1 or 2. The engine start control device according to any one of claims 1 to 3,
An exhaust valve control means for controlling to close an exhaust valve of a cylinder that stops in an expansion stroke when the engine is stopped;
An engine start control device comprising: The engine start control device according to any one of claims 1 to 4,
Friction applying means for applying friction to the crankshaft;
Friction control means for controlling the friction applied to the crankshaft by the friction applying means so that a desired cylinder stops in an expansion stroke when the engine is stopped;
An engine start control device comprising: The engine start control device according to any one of claims 1 to 4,
Stop prediction means for predicting which cylinder stops in the expansion stroke if the engine is stopped as it is before the engine is stopped,
With
The fuel injection control means causes the fuel injection means to inject fuel before the engine is stopped to a cylinder that is predicted to stop in an expansion stroke by the stop prediction means;
Engine start control device. The fuel injection control means causes the fuel injection means to inject fuel before the engine stops even for a cylinder that stops in a compression stroke when the engine stops.
The ignition control means controls the ignition means to ignite the air-fuel mixture in the cylinder before the cylinder stopped in the compression stroke shifts to the expansion stroke when the engine stops.
The engine start control device according to any one of claims 1 to 6. The rotation drive control means is configured to start the rotation of the crankshaft until a predetermined number of rotations of the crankshaft is reached after the air-fuel mixture in the cylinder whose piston is returned to the initial position of the expansion stroke or in the vicinity thereof is ignited. Rotating the rotation drive means forward,
The engine start control device according to any one of claims 1 to 7. The rotation driving means is a starter motor of the engine;
The engine start control device according to any one of claims 1 to 8. The rotational drive means is a motor generator having a function of converting rotational energy of the crankshaft into electrical energy and storing it in a battery and a function of converting electrical energy of the battery into rotational energy of the crankshaft.
The engine start control device according to any one of claims 1 to 9. (A) injecting fuel into the cylinder that stops in the expansion stroke when the engine stops before the engine stops;
(B) determining whether an engine restart condition is satisfied while the engine is stopped;
(C) the step of returning the piston of the cylinder stopped in the expansion stroke to the initial position of the expansion stroke or the vicinity thereof when it is determined in step (b) that the engine restart condition is satisfied;
(D) igniting an air-fuel mixture in a cylinder whose piston is returned to the initial position of the expansion stroke or in the vicinity thereof;
Engine starting method including.   A vehicle equipped with the engine start control device according to claim 1.

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