JP4291752B2 - Engine stop / restart control device and vehicle equipped with the same - Google Patents

Description

  The present invention relates to an engine stop / restart control device that automatically stops and restarts an engine and a vehicle equipped with the same.

Conventionally, as an engine stop / restart control device that automatically stops and restarts an engine, fuel is injected into a cylinder in an expansion stroke when the engine is stopped, and the cylinder is ignited when the engine is restarted. It is known that fuel is burned and cranking is performed using the combustion torque (see, for example, Patent Document 1). With this device, the starter motor can be deactivated if the engine restart by the combustion torque of the cylinder in the expansion stroke is successful, while the starter motor is assisted if the engine restart by the combustion torque of the cylinder fails. To complete the restart.
Japanese Patent Laid-Open No. 2002-4985

  However, in the engine stop / restart control apparatus described above, the engine stop position varies, so that when the cylinder stopped in the expansion stroke when the engine is stopped is stopped near the top dead center, the fuel is burned. Since a sufficient amount of air does not exist in the cylinder, the combustion torque at the time of ignition of the expansion stroke cylinder becomes insufficient and the engine restart may fail. For this reason, the number of times the engine is restarted by the starter motor is not so reduced, and there is a problem that the motor power consumption cannot be reduced much.

  The present invention has been made to solve such a problem, and provides an engine stop / restart control device capable of obtaining sufficient combustion torque at the time of ignition of an expansion stroke cylinder even if the stop position of the engine varies. One of the purposes is to do. Another object is to provide a vehicle equipped with this engine stop / restart control device.

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

That is, the engine stop / restart control device of the present invention is
Engine stop control means for performing engine stop control so that the piston of the cylinder that stops in the expansion stroke when the engine is stopped stops from the top dead center to the exhaust valve open position;
Cylinder processing execution means for putting an air-fuel mixture into a cylinder that stops in the expansion stroke when the engine is stopped;
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 determining means that the engine restart condition is satisfied, when the piston of the cylinder stopped in the expansion stroke stops beyond a predetermined angular position after the top dead center, When the piston of the cylinder stopped in the expansion stroke is stopped before the predetermined angular position after the top dead center, the engine is rotated in the reverse direction by rotating the engine in the expansion stroke. Restart control means for igniting the cylinder after compressing the stopped cylinder and causing the engine to rotate forward;
It is equipped with.

  In this engine stop / restart control device, engine stop control is performed so that the piston of the cylinder that stops in the expansion stroke when the engine is stopped stops between the top dead center and the exhaust valve open position. In addition, an air-fuel mixture is put in a cylinder that stops in the expansion stroke when the engine is stopped. After that, when the engine restart condition is satisfied, if the piston of the cylinder that is stopped in the expansion stroke when the engine is stopped is stopped beyond a predetermined angular position after top dead center, the cylinder is ignited and the engine is ignited. Rotate forward. At this time, the combustion chambers of the cylinders that are stopped in the expansion stroke when the engine is stopped have a relatively large volume and sufficient air, so that a large combustion torque can be obtained at the time of ignition. On the other hand, when the piston of the cylinder that is stopped in the expansion stroke when the engine is stopped is stopped before a predetermined angular position after top dead center, the cylinder is compressed after rotating the engine in the reverse direction to compress the inside of the cylinder Ignite the engine and rotate the engine forward. At this time, the cylinder stopped in the expansion stroke when the engine is stopped has a relatively small volume and it is difficult to obtain a large combustion torque as it is, but a large combustion torque can be obtained because it is ignited after being compressed once. Thus, even if the engine stop position varies, it is possible to sufficiently ensure the combustion torque at the time of ignition of the expansion stroke cylinder.

  The “predetermined angular position after top dead center” is empirically determined as a position where a combustion torque greater than a predetermined value can be obtained when a cylinder stopped in the expansion stroke is ignited when the engine is stopped. Specifically, it may be a position advanced by 90 ° or its vicinity (for example, 80 to 100 °) from the top dead center (the same applies hereinafter).

The engine stop / restart control device of the present invention comprises:
The piston of the cylinder that stops in the compression stroke when the engine is stopped stops at the top dead center side from the intake valve close position, and the piston of the cylinder that stops in the expansion stroke when the engine stops is stopped at the top dead center side from the exhaust valve open position Engine stop control means for performing engine stop control so as to
Cylinder processing execution means for putting an air-fuel mixture into a cylinder that stops in the expansion stroke and a cylinder that stops in the compression stroke when the engine is stopped;
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 determining means that the engine restart condition is satisfied, when the cylinder stopped in the expansion stroke stops beyond a predetermined angular position after top dead center, the cylinder is ignited. When the cylinder stopped in the expansion stroke is stopped before the predetermined angular position after the top dead center, the cylinder stopped in the compression stroke is ignited to ignite the engine. Restart control means for rotating the engine forward by igniting the cylinder after compressing the inside of the cylinder that has been rotated reversely and stopped in the expansion stroke;
It is good also as a thing provided.

  In this engine stop / restart control device, the piston of the cylinder that stops in the compression stroke when the engine is stopped stops at the top dead center side from the intake valve closing position, and the piston of the cylinder that stops in the expansion stroke when the engine is stopped opens the exhaust valve. The engine is controlled to stop at the top dead center side of the position. Further, an air-fuel mixture is put in a cylinder that stops in the expansion stroke and a cylinder that stops in the compression stroke when the engine is stopped. After that, when the engine restart condition is satisfied, if the piston of the cylinder that is stopped in the expansion stroke when the engine is stopped is stopped beyond a predetermined angular position after top dead center, the cylinder is ignited. Turn the engine forward. At this time, since the combustion chamber of the cylinder has a relatively large volume and sufficient air, a large combustion torque can be obtained at the time of ignition. On the other hand, if the piston of the cylinder that is stopped in the expansion stroke when the engine is stopped is stopped before a predetermined angular position after top dead center, the cylinder that is stopped in the compression stroke when the engine is stopped is ignited. Then, the engine is reversely rotated to compress the inside of the cylinder that has been stopped in the expansion stroke, and then the compressed cylinder is ignited to cause the engine to rotate forward. At this time, the cylinder that has been stopped in the expansion stroke when the engine is stopped has a relatively small volume, and it is difficult to obtain a large combustion torque as it is, but a large combustion torque is obtained because the cylinder is ignited after being compressed once. Thus, even if the engine stop position varies, it is possible to sufficiently ensure the combustion torque at the time of ignition of the expansion stroke cylinder.

  The engine stop / restart control device of the present invention can change the intake valve closing position when the air-fuel mixture is put into the cylinder stopped in the expansion stroke when the engine is stopped and the cylinder stopped in the compression stroke when the engine is stopped. The variable intake valve timing means, and before the cylinder stopped in the compression stroke when the engine is stopped is ignited by the restart control means, the intake valve closed position is set to the bottom dead center by the intake valve timing variable means. Alternatively, intake valve timing variable control means for executing an advance angle process for advancing to the position immediately before that may be provided. In this way, there is no possibility that the exhaust in the cylinder will flow backward from the intake valve when the engine rotates reversely due to ignition of the cylinder stopped in the compression stroke when the engine is stopped. Here, it is preferable that the intake valve timing variable control means executes the advance angle processing immediately after the engine is stopped. This makes it possible to reliably complete the advance processing before igniting the cylinders that are stopped in the compression stroke when the engine is stopped.

  The engine stop / restart control device of the present invention includes an exhaust valve timing variable means that can change the exhaust valve closing position, and before the cylinder that is stopped in the expansion stroke when the engine is stopped is ignited by the restart control means. The exhaust valve timing variable means may further include an exhaust valve timing variable control means for executing a retard process for delaying the exhaust valve opening position of the cylinder to the bottom dead center or immediately before it. In this way, when the engine is stopped, combustion torque is generated by ignition of the cylinder stopped in the expansion stroke, and after the engine starts to rotate forward, the combustion torque is applied to the piston until it reaches the bottom dead center or just before it. Can communicate. Here, it is preferable that the exhaust valve timing varying means executes the retardation processing immediately after the engine is stopped. In this way, it is possible to reliably complete the retarding process before igniting the cylinders that are stopped in the expansion stroke when the engine is stopped.

  In the engine stop / restart control apparatus according to the present invention, the engine stop control means controls the engine to stop when an engine stop condition in idle stop control is satisfied, and the restart condition determination means includes the idle stop control means. You may determine whether the engine restart conditions in control were satisfied. 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.

  The engine stop / restart control device of the present invention includes a motor capable of rotationally driving the engine, and the restart control means determines that the engine restart condition is satisfied by the restart condition determination means. The engine may be cranked based on the combustion torque of the cylinder that is stopped in the expansion stroke and the torque of the motor. By doing so, the cranking of the engine can be completed with a relatively small motor torque even if the cranking of the engine cannot be completely performed by the combustion torque at the time of ignition of the expansion stroke cylinder. Here, this motor may be a starter motor of the engine, or a function of converting the rotational energy of the crankshaft of the engine into electric energy and storing it in the battery, and the electric energy of the battery is converted into the rotational energy of the crankshaft. A motor generator having a function may be used. In the latter case, for example, braking energy can be converted into electric energy and stored in a battery, and the motor can assist the restart of the engine using the electric energy when the engine is restarted.

  Since the vehicle equipped with the engine stop / restart control device of the present invention is equipped with the engine stop / restart control device of the present invention, even if the engine stop position varies, the combustion torque at the time of ignition of the expansion stroke cylinder is reduced. Enough can be secured. For this reason, even when the motor is used for cranking the engine, the power consumption of the motor can be reduced.

  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 the present embodiment includes an engine 30 driven by gasoline, an injector 32 that injects fuel into an intake port 36 of each cylinder 31 of the engine 30, and an ignition plug that ignites an air-fuel mixture in each cylinder of the engine 30. 33, motor generator 44 for exchanging power with crankshaft 39 of engine 30, engine electronic control unit (hereinafter referred to as engine ECU) 70 for controlling engine 30, restart / stop of engine 30 and motor generator And a hybrid electronic control unit (hereinafter referred to as a hybrid ECU) 80 for controlling the drive of the motor 44.

  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 via 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 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 second cylinder, the fourth cylinder, and the third cylinder. Therefore, for example, when the first cylinder is in the expansion stroke, the second cylinder is compressed. The stroke, the third cylinder is the exhaust stroke, and the fourth cylinder is the intake stroke. FIG. 2 shows the correspondence between the crank angle CA and the stroke of each cylinder. In FIG. 2, TDC represents top dead center and BDC represents bottom dead center.

The upper end portions of the intake valve 34 and the exhaust valve 35 of each cylinder 31 of the engine 30 are in contact with the cam surface of the intake cam 40 and the cam surface of the exhaust cam 42 via springs, respectively. The intake cam 40 is fixed to the intake cam shaft 41 and rotates as the intake cam shaft 41 rotates. The intake valve 34 operates following the cam surface of the rotating intake cam 40. Specifically, when the cam surface of the intake cam 40 pushes down the intake valve 34, the intake valve 34 opens. When the cam surface of the intake cam 40 does not push down the intake valve 34, the intake valve 34 closes. On the other hand, the exhaust cam 42 is fixed to the exhaust cam shaft 43 and rotates as the exhaust cam shaft 43 rotates. The exhaust valve 35 operates following the cam surface of the rotating exhaust cam 42. Specifically, the exhaust valve 35 opens when the cam surface of the exhaust cam 42 pushes down the exhaust valve 35, and the exhaust valve 35 closes when the cam surface of the exhaust cam 42 does not push down the exhaust valve 35.

  Since the engine 30 has four cylinders, in principle, the intake valve 34 opens at the top dead center in the intake stroke and closes at the bottom dead center, and the exhaust valve 35 opens at the bottom dead center in the exhaust stroke. However, in actuality, since the valve operation is delayed or intake and exhaust are affected by inertia, the cams 40 and 42 and the camshafts 41 and 41 are closed so as to open earlier and close later. 43 is designed. Specifically, as shown in FIG. 3A, the intake valve 34 opens slightly before the top dead center in the intake stroke (α ° before the top dead center), and sets the bottom dead center in the intake stroke. Close after a while (β ° after bottom dead center). Further, as shown in FIG. 3B, the exhaust valve 35 opens slightly before the bottom dead center in the exhaust stroke (γ ° before the bottom dead center) and slightly exceeds the top dead center of the exhaust stroke. Close (δ ° after top dead center).

  An automatic transmission 50 is connected to the crankshaft 39 of the engine 30. The automatic transmission 50 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 56 is attached to the crankshaft 39. The crank angle sensor 56 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. The crank angle sensor 56 uses a pulse generated by the crank angle sensor 56 to The CA can be specified or the engine speed Ne can be obtained. On the other hand, a cam angle sensor 58 is attached to the intake camshaft 41. The cam angle sensor 58 is an electromagnetic induction pickup type sensor that outputs a pulse each time the gear teeth rotating integrally with the intake camshaft 41 approach the core of the coil, and the intake camshaft 41 rotates once ( Each time the crankshaft 39 rotates twice), one pulse is generated.

  An intake camshaft drive motor 60 that shifts the intake camshaft 41 to the advance side or retard side is attached to the intake camshaft 41, and the exhaust camshaft 43 is advanced to the advance side or to the exhaust camshaft 43. An exhaust camshaft drive motor 62 for shifting to the retard side is attached. By driving these drive motors 60 and 62, the open / close positions of the valves 34 and 35 can be changed.

  The motor generator 44 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. Therefore, the motor generator 44 generates power using the power output from the engine 30 to the crankshaft 39 and charges the battery 48 via the inverter 46, or uses the electric power obtained from the battery 48 via the inverter 46. Power can be output to the crankshaft 39. The motor generator 44 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 44. The configuration of FIG. 1 is referred to as a hybrid vehicle because the rotational force of the motor generator 44 when the engine 30 is restarted is transmitted to the wheels via the automatic transmission 50, so that the motor generator 44 is driven by the vehicle. It is because it can be utilized for.

  The engine ECU 70 controls the operation of the engine 30. Although not shown, the engine ECU 70 is composed of 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 70 includes various sensors that indicate the operating state of the engine 30, for example, the crank angle sensor 56 and the cam angle sensor 58 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. The engine ECU 70 applies a discharge signal to the injector 32, control signals to the camshaft drive motors 60 and 62 that can change the open / close positions of the intake valve 34 and the exhaust valve 35, and a spark plug 33. A control signal or the like to the ignition coil 64 is output. In order to output the required power based on the operation of the driver from the engine 30, the engine ECU 70 has an accelerator that detects the shift position from the shift position sensor 73 that detects the position of the shift lever 72 and the position of the accelerator pedal 74. An accelerator pedal position from the pedal position sensor 75 and an on / off signal from the brake position sensor 77 for detecting whether or not the brake pedal 76 is depressed are also input.

  The hybrid ECU 80 includes a microprocessor centered on a CPU. Although not shown, the hybrid ECU 80 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 80 includes a rotation speed sensor and a motor temperature (not shown) attached to the motor generator 44, a motor rotation speed and a motor temperature, a phase current from the current sensor (not shown) installed in the inverter 46 to the motor generator 44, A battery temperature from a temperature sensor (not shown) attached to the battery 48, 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 48 are input via the input port. The hybrid ECU 80 outputs a switching control signal to the inverter 46 for driving and controlling the motor generator 44 through the output port. The hybrid ECU 80 is connected to the engine ECU 70 via a communication port, and receives data related to the state of the engine 30 from the engine ECU 70 and transmits a control signal to the engine ECU 70 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 speed when the accelerator pedal 74 is not depressed when the vehicle is idle and the brake pedal 76 is depressed and the brake is ON. The engine 30 is automatically stopped when a predetermined stop condition is satisfied, and then the engine 30 is automatically restarted when a predetermined restart condition is satisfied such as when the brake is turned off and the accelerator is turned on. Control is performed. The engine speed Ne is calculated based on the time interval of pulses output from the crank angle sensor 56. The signals output from the accelerator pedal position sensor 75, the brake position sensor 77, and the crank angle sensor 56 are input to the hybrid ECU 80 via the engine ECU 70. 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. 4 is a flowchart of this routine. This routine is executed by the hybrid ECU 80 when the above-described predetermined stop condition of the idle stop control is satisfied during engine operation. When this routine is started, the hybrid ECU 80 instructs the engine ECU 70 to stop energizing the injectors 32 of the cylinders 31 of the engine 30 and to 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 regenerative torque of the motor generator 44, etc., the rotation of the crankshaft 39 converges toward the stop.

  Subsequently, the hybrid ECU 80 determines whether or not a predetermined engine state has been reached (step S120). Here, the predetermined engine state will be described. In the present embodiment, when the engine speed Ne reaches a predetermined predetermined speed when the fourth cylinder approaches the exhaust stroke by an experiment or the like in advance, the motor generator 44 is set to zero torque and the engine 30 is caused to friction by the friction of the engine 30. When the engine 30 is stopped, it is known that the engine 30 stops at the position of 90 ° (ATDC 90 °) after the top dead center of the expansion stroke after the No. 4 cylinder passes through the intake stroke and the compression stroke. . Here, before and after the position of the ATDC 90 ° in the expansion stroke of the fourth cylinder is from the closed position of the intake valve of the third cylinder to the open position of the exhaust valve of the fourth cylinder, as indicated by the white arrow in FIG. The stop position varies during this period. The intake valve closing position of the 3rd cylinder is the position of β ° after the bottom dead center of the 3rd cylinder, but the 3rd cylinder and the 4th cylinder are 180 ° out of phase. After the same position as β °. Further, the exhaust valve open position of the fourth cylinder is a position of γ ° before the bottom dead center of the fourth cylinder. In step S120, it is assumed that the engine speed Ne is the predetermined engine speed when the fourth cylinder approaches the exhaust stroke, and the torque control of the motor generator 44 is executed so that the predetermined engine condition is obtained. To do.

  Whether or not the fourth cylinder has reached the exhaust stroke is determined based on a pulse output from the crank angle sensor 56 and a pulse output from the cam angle sensor 58. In this embodiment, the cam angle sensor 58 is set to output a pulse every time the first cylinder enters the expansion stroke, and the crank angle sensor 56 outputs a pulse every time the crankshaft 39 rotates by a predetermined angle. Is set to Therefore, the crank angle is reset to zero each time a pulse is output from the cam angle sensor 58, and the crank angle is advanced by a predetermined angle each time a pulse is output from the crank angle sensor 56, thereby reducing the crank angle to zero. 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. Note that signals output from the crank angle sensor 56 and the cam angle sensor 58 are input to the hybrid ECU 80 via the engine ECU 70.

  When the predetermined engine state is not reached in step S120, the torque control of the motor generator 44 is continued as it is. On the other hand, when the predetermined engine state is reached in step S120, the torque of the motor generator 44 is made zero (step S130), and the engine 30 is stopped by the gas compression force generated in the compression stroke cylinder of the engine 30. Subsequently, it is determined whether or not the fourth cylinder has reached just before the intake valve open position (step S140). This determination is also made based on the pulse output from the crank angle sensor 56 and the pulse output from the cam angle sensor 58, as before.

  In step S140, when the fourth cylinder has not reached the position immediately before the intake valve open position, the engine waits as it is, and when it has reached the position immediately before the intake valve open position, the injector 32 of the fourth cylinder is energized to inject fuel. The ECU 70 is instructed (step S150). 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 fourth cylinder when the intake valve 34 is opened.

  Subsequently, whether or not the cylinder that performs the compression stroke when the No. 4 cylinder performs the expansion stroke, that is, the No. 3 cylinder, has reached just before the intake valve open position, and the pulse output from the crank angle sensor 56 as before. The determination is made based on the pulse output from the cam angle sensor 58 (step S160). In step S160, when the third cylinder does not reach the intake valve open position, the process waits. When the third cylinder reaches the intake valve open position, the injector 32 of the third cylinder is energized to inject fuel. The engine ECU 70 is instructed to do so (step S170). 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 third cylinder when the intake valve 34 is opened.

  Thereafter, it is determined whether or not the rotation of the engine 30 has stopped (step S180). If the rotation of the engine 30 has not stopped, the process waits as it is. If it has stopped, a valve timing change routine is executed (step S190). The automatic stop control routine is terminated. When this automatic stop control routine ends, as described above, the engine 30 stops within the range indicated by the white arrow in FIG. 6, that is, the piston 38 of the fourth cylinder is at a position around ATDC 90 ° in the expansion stroke. . Further, the air-fuel mixture is confined in the fourth cylinder stopped in the expansion stroke and the third cylinder stopped in the compression stroke.

Next, the valve timing change routine will be described with reference to FIG. First, in the fourth cylinder, it is determined whether or not the piston 38 is stopped between the position of ATDC 90 ° and the exhaust valve open position (step S192). Here, as is apparent from FIG. 2, the position of ATDC 90 ° in the fourth cylinder is synonymous with the crank angle of 450 ° CA, so that the crank angle is between 450 ° CA and (540−γ) ° CA after all. It is determined whether or not the vehicle is stopped.

  If an affirmative determination is made in step S192, the volume of the combustion chamber 37 of the fourth cylinder is relatively large, so that when the engine is restarted, the fourth cylinder in the expansion stroke is ignited to obtain sufficient combustion torque. . Therefore, in preparation for this, as shown in FIG. 7, the exhaust camshaft drive motor 62 is driven so that the exhaust valve open position of the fourth cylinder is at the bottom dead center, and the exhaust cam 42 is moved to the retard side ( Step S194), this routine is finished. That is, if the normal exhaust valve open position is maintained, even if combustion torque is generated when the fourth cylinder is ignited, the exhaust valve 35 opens immediately and the combustion torque decreases. Reducing the combustion torque is prevented by retarding to the bottom dead center.

  On the other hand, if a negative determination is made in step S192, the piston 38 of the third cylinder in the compression stroke is between the intake valve closed position and the ATDC 90 ° of the fourth stroke in the expansion stroke, that is, the crank angle is (360 + β) ° CA. It is stopped between ˜450 ° CA (see FIG. 2). In this case, since the volume of the combustion chamber 37 of the fourth cylinder is relatively small, it is difficult to obtain a sufficient combustion torque even if this fourth cylinder in the expansion stroke is ignited when the engine is restarted. Therefore, once the third cylinder in the compression stroke is ignited and the crankshaft 39 is rotated in the reverse direction, the combustion chamber 37 of the fourth cylinder is compressed, and then the fourth cylinder is ignited to provide sufficient combustion torque. To get. Therefore, in preparation for this, as shown in FIG. 8, the intake camshaft drive motor 60 is driven so that the intake valve closing position of the third cylinder is at the bottom dead center, and the intake cam 40 is moved to the advance side ( Step S196), this routine is finished. That is, if the normal intake valve closed position is maintained, when the third cylinder is ignited, the crankshaft 39 reversely rotates and immediately exceeds the intake valve closed position, the intake valve 34 opens, and the exhaust gas flows back into the intake passage 22. Therefore, the intake valve closing position is advanced to the bottom dead center to prevent the backflow of exhaust gas into the intake passage 22.

Next, the automatic restart control routine will be described. FIG. 9 is a flowchart of this routine. This routine is executed by the hybrid ECU 80 when the above-described predetermined restart condition for the idle stop control is satisfied after the automatic control routine is completed. When this routine is started, the hybrid ECU 80 determines that the piston 38 of the fourth cylinder of the engine 30 is in the expansion stroke from the ATDC 90 ° position to the exhaust valve open position, that is, the crank angle 450 ° CA˜ (540−γ). It is determined whether or not it has stopped between ° CA (step S305). When the piston 38 of the fourth cylinder is stopped in this range, a discharge voltage is applied to the spark plug 33 of the fourth cylinder that is the expansion stroke cylinder to generate a spark (step S310). Then, since the volume in the combustion chamber 37 of this expansion stroke cylinder is relatively large, a sufficient combustion torque is generated to cause the air-fuel mixture to combust by ignition and to cause the engine 30 to rotate normally. At this time, since the exhaust valve opening position is changed to the bottom dead center, the combustion torque acts on the piston 38 until the piston 38 of the fourth cylinder reaches the bottom dead center. Simultaneously with the ignition of the fourth cylinder, the motor generator 44 is also rotated using the power of the battery 48 to assist the cranking of the engine 30 (step S315).

  Thereafter, when the piston 38 of the cylinder that reaches the next compression stroke reaches near the top dead center, a spark is generated in the spark plug 33 of that cylinder (step S320). As a result, combustion torque that further rotates the engine 30 forward is obtained. Further, the exhaust camshaft drive motor 62 is driven in accordance with the blow-up of the engine 30 to advance the exhaust valve open position from the bottom dead center (step S325). As a result, the exhaust valve open position gradually returns from the bottom dead center to the normal position. Then, it is determined whether or not the engine speed Ne has reached a predetermined restart speed Nstart (step S330), and when the engine speed Ne has not reached the restart speed Nstart, the process returns to step S320 again. When the rotational speed Ne reaches the restart rotational speed Nstart, the forward rotation assist by the motor generator 44 is finished (step S370), and this automatic restart control routine is finished.

On the other hand, in step S305, the piston 38 of the fourth cylinder in the expansion stroke when the engine 30 is stopped is from the intake valve closed position of the third cylinder in the compression stroke to the ATDC 90 ° position , that is, the crank angle (360 + β) °. When it is stopped between CA and 450 ° CA (this is between the position of β ° and the position of 90 ° ATDC after top dead center in the fourth cylinder as shown in FIG. 6), it is a compression stroke cylinder 3 A discharge voltage is applied to the spark plug 33 of the numbered cylinder to generate a spark (step S335). Then, since the volume in the combustion chamber 37 of this compression stroke cylinder is relatively large, sufficient combustion torque is generated that causes the air-fuel mixture to burn by ignition and reversely rotate the engine 30. At this time, since the intake valve closing position is changed to the bottom dead center, the intake valve 34 is not opened until the piston 38 of the third cylinder reaches the bottom dead center, and the exhaust does not flow back into the intake passage 22.

  Subsequently, it is determined whether the piston 38 of the third cylinder, which is the compression stroke cylinder, has reached bottom dead center or the engine speed Ne has become zero (step S340), and the piston 38 of the third cylinder has reached bottom dead center. If the engine speed Ne is not zero and the engine speed Ne is not zero, the process returns to step S340. When the piston 38 of the third cylinder reaches the bottom dead center or the engine speed Ne becomes zero, the cylinder is the expansion stroke cylinder. A discharge voltage is applied to the spark plug 33 of the fourth cylinder to generate a spark (step S345). At this time, although the No. 4 cylinder is in the expansion stroke, the engine 30 is reversely rotated and the combustion chamber 37 is compressed. Therefore, when the air-fuel mixture in the compressed combustion chamber 37 is ignited, Sufficient combustion torque is generated for rotation. Simultaneously with the ignition of the fourth cylinder, the motor generator 44 is also driven to rotate using the electric power of the battery 48 to assist the cranking of the engine 30 (step S350). Further, the intake valve closed position that has been advanced to the bottom dead center is made the most retarded by driving the intake camshaft drive motor 60 (step S355). As a result, the intake valve closed position returns to the normal position.

  Thereafter, when the piston 38 of the cylinder that reaches the next compression stroke reaches near the top dead center, a spark is generated in the spark plug 33 of that cylinder (step S360). As a result, combustion torque that further rotates the engine 30 forward is obtained. Then, it is determined whether or not the engine speed Ne has reached a predetermined restart speed Nstart (step S365), and when the engine speed Ne has not reached the restart speed Nstart, the process returns to step S360 again, When the rotational speed Ne reaches the restart rotational speed Nstart, the forward rotation assist by the motor generator 44 is terminated (step S370), and this automatic restart control routine is terminated. 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 hybrid ECU 80 of this embodiment corresponds to restart condition determination means, and both the hybrid ECU 80 and the engine ECU 70 correspond to engine stop control means, cylinder processing execution means, restart control means, and variable valve timing control means. The generator 44 corresponds to the motor of the present invention. The intake camshaft drive motor 60 corresponds to intake valve timing variable means, and the exhaust camshaft drive motor 62 corresponds to exhaust valve timing variable means. In the present embodiment, by explaining the operation of the hybrid vehicle 20, an example of the engine stop / restart control device of the present invention is clarified and an example of the engine restart method of the present invention is also clarified.

  According to the hybrid vehicle 20 of the present embodiment described in detail above, when the engine restart condition in the idle stop control is satisfied, the piston 38 of the fourth cylinder, which is the expansion stroke cylinder, moves from the ATDC 90 ° position to the exhaust valve open position. When the engine is stopped during this period, the cylinder 30 is ignited to cause the engine 30 to rotate forward. At this time, since the expansion stroke cylinder has a relatively large volume of the combustion chamber 37 and sufficient air, a large combustion torque can be obtained when the expansion stroke cylinder is ignited. On the other hand, when the No. 4 cylinder, which is the expansion stroke cylinder, is stopped before the position of 90 ° ATDC, the No. 3 cylinder, which is the compression stroke cylinder, is ignited to reversely rotate the engine 30 and the combustion chamber 37 of the No. 4 cylinder. After compression, the cylinder 30 is ignited and the engine 30 is rotated forward. At this time, the combustion chamber 37 of the No. 4 cylinder at the time of the stop has a relatively small volume and it is difficult to obtain a large combustion torque as it is, but a large combustion torque can be obtained because it is ignited after being compressed once. As described above, even when the stop position of the engine 30 varies, it is possible to sufficiently ensure the combustion torque at the time of ignition of the expansion stroke cylinder that rotates the engine 30 in the forward direction.

  Further, when the engine is stopped, the exhaust valve opening position of the No. 4 cylinder is retarded to the bottom dead center. Therefore, when the engine is restarted, the combustion torque is generated by the ignition of the expansion stroke cylinder, and the piston 38 starts to rotate forward. The combustion torque can be transmitted to the piston 38 until the bottom dead center is reached. Since the exhaust valve opening position is retarded immediately after the engine 30 is stopped, the operation of retarding the exhaust valve opening position is reliably completed when the engine is restarted. Further, if the exhaust valve open position is switched by hydraulic pressure, the exhaust valve open position cannot be switched when the required hydraulic pressure cannot be obtained. However, in the present embodiment, since the switch is performed by electric power instead of hydraulic pressure, the exhaust valve open position can be switched reliably.

  Further, since the intake valve closing position is advanced to the bottom dead center before the third cylinder is ignited when the engine is stopped, there is no possibility that the exhaust generated by the ignition of the compression stroke cylinder flows backward from the intake valve 34 to the intake passage 22. . Since the intake valve closing position is advanced immediately after the engine 30 is stopped, the advance operation of the intake valve closing position is reliably completed when the engine is restarted. Also, if the intake valve closing position is switched by hydraulic pressure, the intake valve closing position cannot be switched when the required hydraulic pressure cannot be obtained. .

  Furthermore, when it is difficult to restart the engine 30 only with the combustion torque of the expansion stroke cylinder, the engine 30 can be reliably restarted by assisting the motor generator 44 by rotating the crankshaft 39 forward. Since the motor generator 44 converts braking energy into electric energy and stores it in the battery 48 and assists restart of the engine 30 using the electric energy when the engine is restarted, the energy can be used effectively.

  In the idle stop control, the engine stop and restart are repeated many times during the running, which is advantageous in that the cumulative amount of reduction in the electric energy of the motor generator 44 consumed at the time of engine restart becomes large.

  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, when a negative determination is made in step S305 in the automatic restart control routine of the above-described embodiment, the compression stroke cylinder is ignited and the crankshaft 39 is reversely rotated. However, instead of igniting the compression stroke cylinder, the motor generator 44 is ignited. Thus, the crankshaft 39 may be reversely rotated to return the piston 38 of the fourth cylinder, which is the expansion stroke cylinder when the engine is stopped, to near the top dead center. Also in this case, since the combustion chamber 37 of the 4th cylinder is compressed, if the 4th cylinder after compression is ignited, sufficient combustion torque for rotating the crankshaft 39 forward can be obtained.

  In the above-described embodiment, the port type that injects fuel into the intake port is adopted as the fuel injection method, but the direct injection type that directly injects fuel into the cylinder may be adopted.

  Furthermore, in the above-described embodiment, the engine 30 is cranked by the motor generator 44, but the engine 30 may be cranked by a starter motor that is used exclusively as an electric motor and not as a generator.

  Furthermore, in the above-described embodiment, the MRE rotation sensor is adopted as the crank angle sensor 56. However, the Hall element is arranged at a position facing the magnet rotor attached to the crankshaft 39 to convert the magnetic flux density change into the 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. It should be noted that the crank angle may be calculated based on the output from the rotation speed sensor attached to the motor generator 44 if no slip 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 expansion stroke cylinder when the engine is stopped is the fourth cylinder. However, the engine stop control is performed so that the cylinders other than the fourth cylinder become the expansion stroke cylinder when the engine is stopped. Also good. Alternatively, the expansion stroke cylinder when the engine is stopped may be sequentially changed every time the idle stop control is executed. When the expansion stroke cylinder when the engine is stopped is fixed to a specific cylinder, the state of the cylinder may be different from other cylinders as the idle stop control is repeated. Is less likely to do that.

  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.

  Further, in the above-described embodiment, the forward rotation assist by the motor generator 44 is performed in the automatic restart control routine, but such assist may be omitted.

  Furthermore, in the above-described embodiment, the case where the present invention is applied to the hybrid vehicle 20 is illustrated, but the present invention is applied to a vehicle with a simple idle stop function that does not transmit the power of the motor generator 44 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 valve timing diagram in each stroke, (a) is an intake / compression stroke, (b) is an expansion / exhaust stroke diagram. It is a flowchart of an automatic stop control routine. It is a flowchart of a valve timing change routine. It is a valve timing diagram of an expansion stroke cylinder and a compression stroke cylinder. It is a valve timing diagram of an expansion stroke cylinder and a compression stroke cylinder. It is a valve timing diagram of an expansion stroke cylinder and a compression stroke cylinder. It is a flowchart of an automatic restart control routine.

Explanation of symbols

20 hybrid vehicle, 22 intake passage, 24 engine pulley, 26 MG 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 intake cam, 41 intake camshaft, 42 exhaust cam, 43 exhaust camshaft, 44 motor generator, 46 inverter, 48 battery, 50 automatic transmission, 52 differential gear, 54a, 54b drive wheel, 56 Crank angle sensor, 58 cam angle sensor, 60 intake camshaft drive motor, 62 exhaust camshaft drive motor, 64 ignition coil, 70 engine ECU, 72 shift lever, 73 shift position sensor, 74 accelerator pedal, 75 accelerator pedal position sensor, 76 brake pedal, 77 brake position sensor, 80 hybrid ECU.

Claims (9)

The piston of the cylinder that stops in the compression stroke when the engine is stopped stops at the top dead center side from the intake valve close position, and the piston of the cylinder that stops in the expansion stroke when the engine stops is stopped at the top dead center side from the exhaust valve open position Engine stop control means for performing engine stop control so as to
Cylinder processing execution means for putting an air-fuel mixture into a cylinder that stops in the expansion stroke and a cylinder that stops in the compression stroke when the engine is stopped;
An intake valve timing variable means capable of changing the intake valve closing position;
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 determining means that the engine restart condition is satisfied, when the cylinder stopped in the expansion stroke stops beyond a predetermined angular position after top dead center, the cylinder is ignited. When the cylinder stopped in the expansion stroke is stopped before the predetermined angular position after the top dead center, the cylinder stopped in the compression stroke is ignited to ignite the engine. Restart control means for rotating the engine forward by igniting the cylinder after compressing the inside of the cylinder that has been rotated reversely and stopped in the expansion stroke;
Before the cylinder that is stopped in the compression stroke when the engine is stopped is ignited by the restart control means, the intake valve timing varying means advances the intake valve closed position of the cylinder to the bottom dead center or immediately before it. Intake valve timing variable control means for performing angle processing;
An engine stop / restart control device. The engine stop / restart control apparatus according to claim 1 , wherein the intake valve timing variable control means executes the advance angle processing immediately after the engine is stopped. 3. The engine stop / restart control apparatus according to claim 1, wherein the predetermined angular position after the top dead center is a position advanced by 90 ° or in the vicinity thereof from the top dead center. The engine stop / restart control device according to any one of claims 1 to 3 ,
Exhaust valve timing variable means that can change the exhaust valve opening position,
Before the cylinder stopped in the expansion stroke when the engine is stopped is ignited by the restart control means, the exhaust valve timing variable means delays the exhaust valve open position of the cylinder to the bottom dead center or immediately before it. Exhaust valve timing variable control means for performing angle processing;
An engine stop / restart control device. The engine stop / restart control device according to claim 4 , wherein the exhaust valve timing variable control means executes the retard processing immediately after the engine is stopped. The engine stop control means controls the engine to stop when an engine stop condition in the idle stop control is satisfied,
The restart condition determining means determines whether or not an engine restart condition in the idle stop control is satisfied;
The engine stop / restart control apparatus according to any one of claims 1 to 5 . The engine stop / restart control device according to any one of claims 1 to 6 ,
A motor capable of rotationally driving the engine;
With
When it is determined by the restart condition determination means that the engine restart condition is satisfied, the restart control means determines whether the engine is stopped by the combustion torque of the cylinder that is stopped in the expansion stroke when the engine is stopped and the torque of the motor. Ranking,
Engine stop / restart control device. The motor is a starter motor.
The engine stop / restart control apparatus according to claim 7 . A vehicle equipped with the engine stop / restart control device according to any one of claims 1 to 8 .

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