JP2019182301A - Engine start control device - Google Patents

Abstract

To make it possible to easily perform start control while suppressing consumption power of a motor with application of a technique for engine start and engine reverse rotation start by the motor.SOLUTION: An engine start control device comprises a motor 20 which can drive an engine 1, an engine control part 41 and a motor control part 42. The motor control part 42 sets a motor torque so that a piston 5a of a gas column 2a during a compression stroke at a stop time is stopped after moved to a prescribed reference position P0 that does not exceed a compression top dead point at a start time of the engine 1. The engine control part 41 operates the motor 20 by the motor torque when a piston stop position of the gas column 2a is on a bottom dead point side with respect to closing timing of an intake valve 11, and thereafter, causes the gas column 2a to burn and causes the engine 1 to temporarily reversely rotate, and then, causes to a gas column 2b during expansion stroke at a stop time to burn and causes the engine 1 to normally rotate. On the other hand, when the piston stop position is on the top dead point side with respect to closing timing of the intake valve 11, control for reverse rotation is not executed.SELECTED DRAWING: Figure 10

Description

  The present invention relates to an engine start control device for starting an engine having a plurality of cylinders and pistons using a motor.

  Generally, in a vehicle such as an automobile, an engine of an internal combustion engine is started by rotating a flywheel with a starter motor. On the other hand, in a hybrid electric vehicle (HEV) that combines an engine of an internal combustion engine and an electric drive motor as a vehicle drive source, it has been studied to abolish the starter motor and start the engine with the motor torque of the drive motor. Yes. In this case, it is necessary to leave surplus power in the power source battery of the drive motor in preparation for engine start, and this has pointed out a problem that the allowable cruising distance for electric travel is limited.

  On the other hand, for example, when starting an engine of an automobile equipped with an idling stop function, a technique for quickly starting the engine by temporarily rotating the engine reversely is known (see Patent Document 1). In this technique, when starting an engine, the compression stroke cylinder at the time of the stop which was in the state of the compression stroke when the engine is stopped is burned, and the piston is pushed down. That is, the engine is reversely rotated. Along with this, the piston in the expansion stroke cylinder at the time of stop is pushed up, and the cylinder pressure is increased. By burning such an expansion stroke cylinder, the engine can be started to rotate forward with high starting energy.

JP 2004-124753 A

  However, in the engine reverse rotation start described above, there is a problem that the degree of difficulty of piston position control for establishing the first combustion in the stop-time compression stroke cylinder is high. That is, the range of the piston position where combustion is established is narrow, and it is very difficult to perform stop position control for stopping the piston at the combustion establishment position when the engine is stopped. In addition, it is not always effective to start the reverse rotation using combustion in the compression stroke cylinder at the time of stop, and the combustion may become useless combustion.

  An object of the present invention is to reduce the power consumption of the motor while facilitating the start-up control while applying the engine start-up and engine reverse-rotation start-up techniques. It is another object of the present invention to provide an engine start control device that can be executed.

  An engine start control device according to one aspect of the present invention controls an engine having an intake valve and an exhaust valve and capable of driving an engine having a plurality of cylinders and pistons for burning fuel, and a combustion operation in the cylinders. A combustion control unit; a motor control unit that controls the operation of the motor; and a detection unit that detects a piston stop position when the engine is stopped, wherein the motor control unit includes the cylinder among the plurality of cylinders. When the engine is stopped so that the piston of the compression cylinder at the time of stop when the engine is stopped is stopped after moving to a predetermined reference position not exceeding the compression top dead center at the time of starting the engine. A first motor drive amount corresponding to the piston stop position of the compression stroke cylinder at the time of stop at, and the combustion control unit is detected by the detection unit, When the piston stop position of the compression stroke cylinder at the time of stop is in a first condition that is at the bottom dead center side with respect to the closing timing of the intake valve, the motor control unit operates the motor with the first motor driving amount. Later, the compression stroke cylinder at the time of stop is burned to temporarily reverse the engine, and then the expansion stroke cylinder at the time of stop when the engine is stopped is burned, and the engine is rotated forward. And when the second stop condition is detected by the detection unit and the piston stop position of the compression stroke cylinder at the time of stop is at the top dead center side with respect to the closing timing of the intake valve. The reverse rotation start control is not executed.

  According to this engine start control device, the motor control unit sets the first motor drive amount such that the piston of the stop compression stroke cylinder stops after moving to a predetermined reference position not exceeding the compression top dead center. To do. When the piston is moved, the timing for passing the compression top dead center at which the in-cylinder pressure becomes the highest is required to move the piston. For this reason, when starting the engine with a motor, if the motor drive amount is set such that the engine is rotated to the range where the piston passes the compression top dead center, the motor consumes a large amount of power. In the above configuration, only the motor drive amount necessary for moving the piston to the reference position is set, so that power consumption by the motor can be suppressed.

  In the first condition, the combustion control unit temporarily burns the engine during the stop-time compression stroke after the piston of the stop-time compression stroke cylinder moves to the reference position by the first motor drive amount. Reverse rotation. At this time, since the in-cylinder pressure is increased by the piston moved to the reference position, combustion easily occurs. Further, when the engine is stopped, the piston is moved to the reference position by the first motor driving amount regardless of the position (crank angle) of the piston of the compression stroke cylinder at the time of stop, so that the combustion is stably performed. Can be generated. Therefore, the combustion of the expansion stroke cylinder at the time of stop executed thereafter is also stable, and the engine can be reliably started to rotate forward.

  On the other hand, the combustion control unit does not execute the reverse rotation start control when the second condition is satisfied. When the piston stop position of the stop compression stroke cylinder is on the top dead center side with respect to the closing timing of the intake valve, the compression allowance of the combustion chamber in the stop compression stroke cylinder by the piston is small. That is, since the cylinder returns to atmospheric pressure when the engine is stopped, the degree of increase in the in-cylinder pressure decreases as the piston approaches the top dead center, even if the piston is moved to the reference position. For this reason, even if the compression stroke cylinder at the time of stop is burned in a situation where the second condition is satisfied, stable combustion may not be ensured or sufficient starting power may not be obtained. Therefore, useless combustion can be suppressed by not performing the reverse rotation start control in the second condition.

  In the engine start control device, when the combustion control unit does not execute the reverse rotation start control, the piston stop position of the stop-time expansion stroke cylinder detected by the detection unit is the opening of the exhaust valve. When the engine is on the top dead center side with respect to a predetermined position in the vicinity of the time, it is desirable that the expansion stroke cylinder at the time of stop is burned and the engine is rotated forward.

  According to this engine start control device, when the reverse start control is not executed, the stop-time expansion stroke cylinder is burned. Thereby, the engine can be rotated forward and the engine can be started.

  In the engine start control device, when the combustion control unit does not execute the reverse rotation start control, the piston stop position of the stop-time expansion stroke cylinder detected by the detection unit is the opening of the exhaust valve. It is desirable not to execute combustion in the stop-time compression stroke cylinder and the stop-time expansion stroke cylinder for starting the engine when it is at the bottom dead center side from a predetermined position near the time.

  If the piston stop position of the expansion stroke cylinder at the stop is at the bottom dead center side than the predetermined position near the opening timing of the exhaust valve, the sealing performance of the cylinder cannot be secured. The intended combustion cannot be performed. Therefore, in the above situation, useless combustion can be suppressed by not performing combustion not only in the stop-time compression stroke cylinder but also in the stop-time expansion stroke cylinder.

  In the engine start control device, the motor control unit is configured such that a piston of a stop-intake stroke cylinder that is in an intake stroke state when the engine is stopped does not exceed a compression top dead center when the engine is started. The second motor drive amount is set according to the piston stop position of the intake stroke cylinder at the time of stop so as to stop after moving to the reference position, and the combustion control unit is configured so that the motor control unit is driven by the second motor drive. After operating the motor by the amount, it is desirable to burn the stop-time intake stroke cylinder to temporarily reverse the engine.

  According to this engine start control device, when the stop-time compression and expansion stroke cylinders are not burned when the engine is started, the reverse start is executed using the stop-time intake stroke cylinder, and the engine is started. Is possible.

  In this case, following the temporary reverse rotation, the combustion control unit burns the cylinder at the stop compression stroke that has reached the expansion stroke due to the operation of the motor by the second motor drive amount. It is desirable to rotate the engine forward.

  According to this engine start control device, following the reverse rotation of the engine due to the combustion of the stop-time intake stroke cylinder, the engine is normally rotated by the combustion of the stop-time compression stroke cylinder that has advanced to the expansion stroke, thereby The engine can be started.

  In the engine start control device, when the engine is started, the motor control unit sets the motor drive amount, when an operator starts the engine or when a predetermined engine stop condition is satisfied. It is desirable to include a case where a predetermined engine restart condition is satisfied after the engine has stopped.

  According to this engine start control device, the power consumption of the motor can be suppressed and the start control can be facilitated both during the manual start of the engine and during the automatic start from an idling stop or the like.

  In the engine start control apparatus, the engine is mounted on the vehicle together with an electric drive motor as a drive source for running the vehicle, and the electric drive motor can drive the engine. It is desirable to also serve as a motor.

  According to this engine start control device, the use of a part called a starter motor can be omitted, and the electric power used by the electric drive motor can be suppressed. Therefore, the cruising distance of electric travel can be increased.

  ADVANTAGE OF THE INVENTION According to this invention, while applying the technique of the engine start by a motor and the reverse rotation start of an engine, the power consumption of a motor can be suppressed and start control can be made easy, and also the said reverse rotation start is effective. It is possible to provide a start control device for an engine that can be executed in the first place.

FIG. 1 is a system diagram of a hybrid vehicle to which an engine start control device according to the present invention is applied. FIG. 2 is a schematic cross-sectional view showing the configuration of the engine. FIG. 3 is a diagram for explaining the reverse rotation start control according to the comparative example. 4A to 4C are diagrams for explaining the operation by the reverse rotation start control according to the comparative example. 5A to 5C are diagrams for explaining the flow state of the fuel sprayed into the combustion chamber. FIG. 6 is a diagram for explaining the concept of the reverse rotation start control according to the present invention. 7A to 7D are diagrams for explaining the operation by the reverse rotation start control according to the present invention. FIG. 8 is a graph showing a setting example of the motor torque. FIG. 9 is a time chart showing the operation of the four cylinders when the engine is started. FIG. 10 is a diagram for explaining an embodiment in which the start mode is set according to the stop position of the piston. FIG. 11 is a flowchart showing an example of engine start control according to the present embodiment. FIG. 12 is a flowchart of the start mode I. FIG. 13 is a flowchart of the start mode II. FIGS. 14A to 14C are diagrams for explaining the operation in the start mode II. FIG. 15 is a flowchart of the start mode III. FIGS. 16A to 16D are diagrams for explaining the operation in the start mode III.

[Configuration of HEV]
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. First, the configuration of a hybrid vehicle HEV (vehicle) to which the engine start control device according to the present invention is applied will be described based on the system diagram of FIG. The hybrid vehicle HEV includes an engine 1 that is a drive source of the vehicle HEV, a motor 20 that is also a drive source of the vehicle HEV and is an electric drive, and a driving force generated by the engine 1 and the motor 20 at an appropriate speed ratio. A transmission 30 that transmits to the drive wheels W and a VCM (Vehicle Control Module) 40 that controls the overall operation of the automobile HEV are included.

  The engine 1 is a four-cycle internal combustion engine having a plurality of cylinders 2 for burning fuel such as gasoline. FIG. 1 shows an example in which four cylinders 2 are arranged in series. The combustion operation in the cylinder 2 is controlled by a PCM (Powertrain Control Module) 17 (a part of the combustion control unit). FIG. 2 is a schematic cross-sectional view showing the configuration of the engine 1, in which only one cylinder 2 is shown. The engine 1 can reciprocate in each cylinder 2, a cylinder block 3 in which the cylinder 2 is formed, a cylinder head 4 attached to the upper surface of the cylinder block 3 so as to close an upper opening of each cylinder 2, and the cylinder 2. And a plurality of pistons 5 inserted into.

  A pent roof type combustion chamber 6 is defined above the piston 5. In the combustion chamber 6, the mixture of fuel and air is combusted, and the piston 5 pushed down by the expansion force due to the combustion reciprocates in the vertical direction. A crankshaft 7 that is an output shaft of the engine 1 is provided below the piston 5. The crankshaft 7 is connected to the piston 5 via a connecting rod 8 and is driven to rotate according to the reciprocating motion of the piston 5.

  The cylinder head 4 includes an intake port 9 and an exhaust port 10 that open to the combustion chamber 6, an intake valve 11 that opens and closes the intake port 9, an exhaust valve 12 that opens and closes the exhaust port 10, and an intake valve 11 and an exhaust valve 12. Are assembled with valve operating mechanisms 13 and 14 that open and close in conjunction with the rotation of the crankshaft 7. Further, the cylinder head 4 is provided with an ignition plug 15 that forcibly ignites the air-fuel mixture in the combustion chamber 6 to generate combustion, and an injector 16 that injects fuel into the combustion chamber 6. The electrode portion of the spark plug 15 is disposed near the center of the ceiling surface of the combustion chamber 6, while the fuel injection valve of the injector 16 is disposed near the side wall of the combustion chamber 6. A cavity 5 </ b> A for receiving fuel injected from the injector 16 is formed on the crown surface of the piston 5.

  Returning to FIG. 1, an inverter 21 and a battery 22 are electrically connected to the motor 20. The motor 20 is a motor composed of, for example, an axial gap type synchronous motor. The motor 20 functions as an electric motor that generates driving force for propelling the automobile HEV by being driven by electric power supplied from the battery 22, while the generator is driven to rotate by regenerative power and charges the battery 22 with electric power. Also works. The inverter 21 converts the DC power of the battery 22 into AC power and supplies it to the motor 20. During regeneration, the inverter 21 converts AC power generated by the motor 20 into DC power and charges the battery 22.

  The transmission 30 is an automatic transmission that automatically shifts to a required speed ratio, and a plurality of power transmission paths and a plurality of power transmission paths having a specific speed ratio by selecting one of these paths. A transmission clutch 31 is provided. The transmission ratio of the transmission 30 is controlled by a TCM (Transmission Control Module) 32. The output of the transmission 30 is transmitted to the drive wheels W via the differential 33.

  A first clutch 34 is disposed in the power transmission path between the engine 1 and the motor 20. A second clutch 35 is disposed on the power transmission path between the motor 20 and the transmission 30. The first and second clutches 34 and 35 are used for connecting and disconnecting power transmission in the power transmission path, and include, for example, wet multi-plate clutches having a plurality of clutch plates immersed in oil. When the first and second clutches 34 and 35 are engaged, the drive wheels W are driven mainly by the engine 1 via the transmission 30 (engine running mode). In this state, driving assistance for engine running by the motor 20 is also possible. On the other hand, when the first clutch 34 is in the disengaged state and the second clutch 35 is in the engaged state, an electric travel mode in which the drive wheels W are driven via the transmission 30 only by the motor 20 is set. This state is also used during regenerative operation (during charging).

  Furthermore, in the present embodiment, the engine 1 can be driven by the motor 20. That is, no starter motor or the like is attached to the engine 1, and the electric drive motor 20 also serves as a motor that drives the engine 1 when the engine 1 is started. When the engine is started, the first clutch 34 is engaged and the second clutch 35 is disengaged, and the motor torque generated by the motor 20 is applied to the engine 1 (engine start mode).

  The VCM 40 controls the operation of the engine 1, the motor 20, the transmission 30, and the first and second clutches 34 and 35 based on sensors installed at various locations of the automobile HEV and operation information given from an operator. In FIG. 1, the engine oil temperature sensor SN1 that measures the temperature of the engine lubricating oil, the engine water temperature sensor SN2 that measures the temperature of the engine coolant, and the crankshaft 7 for detecting the engine speed and the position of the piston 5 are used as the sensors. The crank angle sensor SN3 for detecting the rotation angle of the vehicle and the atmospheric pressure sensor SN4 for measuring the atmospheric pressure of the traveling environment are shown. In addition, accelerator opening information, intake / exhaust pressure, temperature information, and the like are input to the VCM 40.

  The VCM 40 functionally includes an engine control unit 41 (a part of the combustion control unit), a motor control unit 42, a clutch control unit 43, and a transmission control unit 44. The engine control unit 41 controls various operations related to the engine 1, for example, ignition timing of the spark plug 15, timing of fuel injection by the injector 16, fuel injection amount, amount of air taken into the combustion chamber 6 and the like via the PCM 17. Control engine torque.

  The motor control unit 42 controls the operation of the motor 20 via the inverter 21. Specifically, the motor control unit 42 sets a required motor torque based on information from the various sensors described above, and controls the inverter 21 so that the motor 20 outputs the motor torque to control the motor from the battery 22. 20 is supplied with the required power. The motor control unit 42 controls the inverter 21 during the regenerative operation, and controls the charging operation to the battery 22. Further, in the present embodiment, the motor control unit 42 moves the piston 5 of the stop-time compression stroke cylinder 2 that is in the compression stroke state when the engine 1 is stopped to a predetermined position that does not exceed the compression top dead center when the engine 1 is started. The motor torque is set according to the stop position of the piston 5 and the motor 20 is operated so as to stop after moving to the position. This will be described in detail later.

  The clutch control unit 43 controls the engagement / release operation of the first and second clutches 34 and 35. Through the control of the engagement / release operation, the clutch control unit 43 executes control for switching at least the above-described engine travel mode (drive assist mode), electric travel mode, and engine start mode. The transmission control unit 44 controls the gear ratio of the transmission 30 via the TCM 32 according to the output torque, vehicle speed, and load set according to the driving scene.

[Reverse rotation start control according to comparative example]
In an automobile having an idling stop function, it is required to start the engine promptly when the engine is restarted after idling stop. In this case, a starting method that requires a considerable time to complete the start, such as starting the engine through cranking in which the engine output shaft is driven by the starter motor, is not desirable. Therefore, there is a case where reverse start control is employed in which the engine is started quickly by temporarily rotating the engine reversely when the engine is started. This reverse rotation start control is also adopted in this embodiment, but first, the conventional reverse rotation start control will be described as a comparative example.

  FIG. 3 is a diagram for explaining the reverse rotation start control according to the comparative example, and FIGS. 4A to 4C are diagrams for explaining the operation of the engine by the reverse rotation start control according to the comparative example. In these drawings, among the four cylinders 2 provided in the engine 1, a stop-time compression stroke cylinder 2a that was in a compression stroke state when the engine 1 was stopped, and a stop-time expansion stroke cylinder 2b that was in an expansion stroke state. Is schematically shown. In FIG. 3, “P1” indicates the stop position of the piston 5 when the engine 1 is stopped. In FIG. 4A, the positions of the pistons 5a and 5b in the respective cylinders 2a and 2b when the engine is stopped are simply shown.

  In the reverse rotation start control, the first ignition IG1 that is the first ignition is executed in the stop-time compression stroke cylinder 2a. Thereby, combustion occurs in the compression stroke cylinder 2a at the time of stop, and the piston 5a is pushed down as shown in FIG. 4 (B). That is, the engine 1 rotates in the reverse direction. Along with this, the piston 5b of the expansion stroke cylinder 2b at the time of stop is pushed up, and the in-cylinder pressure of the cylinder 2b is increased. Subsequently, the second ignition IG2 that is the second ignition is performed in the expansion stroke cylinder 2b at the time of stop. Thereby, combustion occurs in the expansion stroke cylinder 2b at the time of stop, and the piston 5b is pushed down as shown in FIG. That is, the engine 1 rotates forward. Since this combustion occurs in a state where the in-cylinder pressure of the cylinder 2b is increased, the engine can be started to rotate forward with high starting energy.

  However, in the above-described reverse rotation start, there is a problem that the difficulty of piston position control for establishing the first combustion in the stop-time compression stroke cylinder 2a is high. That is, as described in FIG. 3, the stop range PA of the piston 5a that can obtain a high ignition probability in the stop-time compression stroke cylinder 2a is limited to a narrow range (PA = BTDC 60 deg to 102 deg in FIG. 3). It has been. For example, when the engine 1 is temporarily stopped by idling stop control, it is difficult to stop the piston 5a in such a narrow stop range PA.

  The lower limit (BTDC 102 deg) of the stop range PA is the timing at which the intake valve 11 starts to close, and if it is on the further advance side than this, the sealing of the cylinder 2a cannot be ensured, and therefore combustion does not succeed. The upper limit (BTDC 60 deg) of the stop range PA allows the air-fuel mixture containing fuel sprayed from the injector 16 before the first ignition IG1 in the cylinder 2a to flow into the arrangement position of the electrode portion of the spark plug 15 satisfactorily. The maximum crank angle that can be achieved. This point will be described with reference to FIG.

  FIGS. 5A to 5C are views for explaining the flow state of the fuel sprayed from the injector 16 into the combustion chamber 6. FIG. 5A shows the flow state of the sprayed fuel when the piston 5 (5a) is stopped at the stop position P1 in FIG. A cavity 5 </ b> A is recessed in the crown surface of the piston 5. Around the cavity 5A, a squish area 5S is formed so as to be inclined downward toward the outer peripheral edge of the piston 5 along the pent roof type ceiling surface of the combustion chamber 6. The sprayed fuel discharged from one side wall position of the combustion chamber 6 is guided by the squish area 5S to the other side wall position of the combustion chamber 6 as indicated by an arrow A1, and moves upward along the other side wall. It turns up and goes to the electrode part of the spark plug 15 arranged in the center of the ceiling surface of the combustion chamber 6. Therefore, the probability that the sprayed fuel can be ignited by the first ignition IG1 becomes extremely high. The upper limit at which the flow of the spray fuel indicated by the arrow A1 can be obtained is the upper limit of the stop range PA.

  FIG. 5 (B) shows that when the piston 5 exceeds the upper limit of the stop range PA and approaches the compression top dead center (BTDC 54 deg) and stops, fuel is sprayed from the injector 16 into the combustion chamber 6. The flow state of the spray fuel in the case is shown. In this case, since the piston 5 is raised too much, as shown by the arrow A2, the sprayed fuel collides with the cavity 5A, the flow direction is changed, and it is not guided in the squish area 5S. For this reason, the return flow of the sprayed fuel as shown by the arrow A <b> 1 does not occur, and the sprayed fuel hardly reaches the electrode portion of the spark plug 15. For this reason, the ignition probability of the sprayed fuel by the first ignition IG1 is significantly reduced. Further, as shown in FIG. 5C, if the piston 5 is lowered too much, the squish area 5S cannot serve to guide the sprayed fuel upward. That is, as shown by the arrow A3, the sprayed fuel is folded downward at the other side wall position of the combustion chamber 6, and the sprayed fuel is difficult to reach the electrode portion of the spark plug 15.

  From the above, if the piston 5 does not stop within the stop range PA, for example, if the piston 5 does not stop at the stop position P1, the combustion condition for reverse rotation in the cylinder 2 is not satisfied. In other words, reverse start control cannot be performed, and there is no choice but to select another start control. However, when the engine is stopped, it is impossible to always naturally stop the piston 5 within a narrow stop range PA = BTDC 60 deg to 102 deg. Further, even if control is performed to stop the piston 5 within the stop range PA by, for example, applying a brake to the piston 5, it becomes complicated and difficult. In particular, in the hybrid vehicle HEV of the present embodiment, the motor 20 can rotate the engine 1, but the rotation cannot be forcibly stopped, so that the stop control of the piston 5 is inherently difficult. Therefore, the method of the comparative example has a problem that the reverse rotation start control cannot always be performed. Further, the range of BTDC 60 deg to 102 deg cannot be said to be a region where the in-cylinder pressure is large in the cylinder 2, and there is a problem that large reverse rotation energy cannot be obtained even if combustion is established.

[Reverse start control according to this embodiment]
In view of the above problem, in the present embodiment, the reverse rotation start control can be reliably performed regardless of the stop position of the piston 5 (5a) of the compression stroke cylinder 2 (2a) at the time of stop, and a large reverse rotation energy is obtained. Provided is reverse rotation start control capable of obtaining (reverse rotation driving force). FIG. 6 is a diagram for explaining the concept of the reverse rotation start control according to the present embodiment, and FIGS. 7A to 7D are diagrams for explaining the operation by the reverse rotation start control.

  The main difference from the comparative example described above is that, in the present embodiment, before the piston 5a of the stop-time compression stroke cylinder 2a is reversely combusted when the engine is started, the piston 5a exceeds the compression top dead center (TDC). This is a point to be moved to a predetermined reference position P0. For the reference position P0, a crank angle that can sufficiently increase the in-cylinder pressure of the compression stroke cylinder 2a at the time of stop is selected. For example, the reference position P0 can be set in the range of BTDC 50 deg to 15 deg, preferably in the range of BTDC 40 deg to 20 deg.

  When the engine 1 is started, the motor control unit 42 (FIG. 1) causes the piston 5a when the engine 1 is stopped to stop after the piston 5a stopped at the random crank angle position has moved to the reference position P0. The motor torque (motor drive amount) corresponding to the stop position is set. That is, as shown in FIG. 6, when the piston 5a is stopped at the stop position P11, the motor control unit 42 moves the piston 5a from the stop position P11 to the reference position P0 within a limited start time. The motor torque T1 that can be set is set.

  Similarly, when the piston 5a is stopped at a stop position P12 closer to the bottom dead center (BDC) than P11, a motor torque T2 is set that can move the piston 5a from the stop position P12 to the reference position P0. To do. Further, when stopping at the stop position P12 closer to the BDC than P12, the motor torque T3 that can move the piston 5a from the stop position P13 to the reference position P0 is set.

  Even if the piston 5a is stopped at any of the stop positions P11, P12, P13, it is necessary to move the piston 5a to the reference position P0 within a predetermined start time, so that the motor torque satisfies T1 <T2 <T3. It becomes a relationship. FIG. 8 is a graph schematically showing the relationship between the stop position of the piston 5a and the motor torque. As the stop position of the piston 5a approaches the BDC from the reference position P0, the set motor torque tends to increase. Actually, the set motor torque may not be linearly related to the crank angle as shown in FIG. The motor control unit 42 controls the inverter 21 so that the motor 20 outputs the set motor torque, and supplies required power from the battery 22 to the motor 20.

  Setting the reference position P0 within a range of, for example, BTDC 40 deg to 20 deg has the purpose of suppressing the power consumption of the motor 20 while increasing the in-cylinder pressure of the cylinder 2a to improve the ignitability. When moving piston 5a, the timing which requires the largest torque is a timing which passes TDC where cylinder pressure becomes the highest. For this reason, if it is going to rotate an engine to the range which piston 5a passes TDC, a big motor torque will be needed and the motor 20 will consume big electric power. However, the reference position P0 of the present embodiment is set to a crank angle that does not exceed TDC. For this reason, a relatively small motor torque for moving the piston 5a from the stop positions P11, P12, P13 to the reference position P0 is sufficient. Therefore, power consumption by the motor 20 can be suppressed.

  Further, as shown in FIG. 6, the reference position P0 is set to a position on the advance side with respect to TDC via a predetermined avoidance area Px. Since the avoidance region Px is close to TDC, when the piston 5a reaches the avoidance region Px, the in-cylinder pressure of the cylinder 2a is considerably increased. If the piston 5a is pushed up to such an avoidance region Px, a considerable motor torque is required although it is lower than when passing the TDC. However, in the present embodiment, since the reference position P0 is set by removing the avoidance region Px of the crank angle close to TDC, the motor torque can be suppressed.

  The motor control unit 42 corrects and sets the motor torque according to various conditions. The motor torque depends on the operating resistance of the piston. For example, when the piston 5a is moved with the motor torque from the stop position P13 in FIG. 6 to the reference position P0, the larger the operation resistance of the piston 5a, the larger the motor torque is required. Here, the operating resistance of the piston 5a varies depending on various factors. The variation factor is, for example, engine water temperature, engine oil temperature, atmospheric pressure, or the like. The sliding resistance of the piston 5a can change depending on the temperature of engine cooling water or lubricating oil. The altitude (atmospheric pressure) at which the automobile HEV travels also affects the sliding resistance. Therefore, when the engine 1 is started, the motor control unit 42 acquires current measurement data from the engine oil temperature sensor SN1, the engine water temperature sensor SN2, and the atmospheric pressure sensor SN4, and corrects the motor torque. As a result, even if a sliding resistance variation factor is present when the engine is started, the piston 5a can be accurately moved to the reference position P0.

  With reference to FIGS. 7A to 7D, the operation of the reverse rotation start control of the present embodiment will be described. FIG. 7A shows a stop-time compression stroke cylinder 2a (compression at stop) that is in a compression stroke state when the engine 1 is stopped and a stop-time expansion stroke cylinder 2b (expansion at stop) that is in an expansion stroke state. FIG. 5 is a diagram schematically showing stop positions of respective pistons 5a and 5b. It is assumed that the piston 5a of the compression stroke cylinder 2a at the time of stop is stopped at a stop position Ps at a certain crank angle.

  When the engine 1 is started from the state shown in FIG. 7A, the VCM 40 executes predetermined reverse rotation start control. Here, when the engine 1 is started, the engine is started when the operator performs a start operation of the engine 1 by pressing a start button provided in the hybrid vehicle HEV or when a predetermined engine stop condition is satisfied. When a predetermined engine restart condition is satisfied after stopping. In the latter case, in the case of idling stop, the engine stop condition is, for example, when the operator steps on the brake pedal and stops or when the select bar is in the “P” range, and the engine restart condition is, for example, the brake pedal When the operator lifts his / her foot. That is, in the present embodiment, the engine start includes both a manual start of the engine 1 and an automatic start from an idling stop or the like.

  When the engine is started, the motor control unit 42 calculates the motor torque T necessary to move the piston 5a from the stop position Ps to the reference position P0. At this time, the motor torque T is corrected with reference to the measurement data of the sensors SN1, SN2, and SN4. The clutch control unit 43 controls to release the second clutch 35 while engaging the first clutch 34. Then, the motor control unit 42 gives the calculated motor torque T to the motor 20. In other words, the motor control unit 42 controls the inverter 21 so that the motor 20 supplies electric power so that the motor 20 generates the required motor torque T.

  Accordingly, as shown in FIG. 7B, the motor 20 starts an operation of pushing up the piston 5a toward the reference position P0. Along with this, the piston 5b of the expansion stroke cylinder 2b at the time of stop is pushed down by reaction. At an appropriate timing while the piston 5a moves from the stop position Ps to the reference position P0, the engine control unit 41 controls the injector 16 of the stop-time compression stroke cylinder 2a to inject fuel into the cylinder 2a.

  When the piston 5a reaches the reference position P0, the engine control unit 41 controls the ignition plug 15 of the cylinder 2a, and the first ignition IG1 that is the first ignition after the start of the air-fuel mixture in the cylinder 2a. Execute. As a result, as shown in FIG. 7C, combustion occurs in the stop-time compression stroke cylinder 2a, and the piston 5a is pushed down by the combustion pressure. That is, the engine 1 temporarily reversely rotates. By the reaction, the piston 5b of the expansion stroke cylinder 2b at the time of stop is pushed up. Accordingly, the air in the cylinder 2b is compressed and the in-cylinder pressure rises.

  Next, the engine control unit 41 controls the injector 16 of the stop-time expansion stroke cylinder 2b to inject fuel into the cylinder 2b, and controls the spark plug 15 of the cylinder 2b for the second ignition. 2 ignition IG2 is performed. As a result, as shown in FIG. 7D, combustion occurs in the stop-time expansion stroke cylinder 2b, and the piston 5b is pushed down by the combustion pressure. That is, the engine 1 rotates forward. Thereafter, the same operation is executed in the other cylinders 2, so that the engine 1 enters an operating state.

  In the above description, the operation has been described focusing on the stop-time compression stroke cylinder 2a and the stop-time expansion stroke cylinder 2b. The operation of the four cylinders 2 at the time of engine start will be described with reference to the time chart of FIG. Reference numerals # 1 to # 4 in the figure represent four cylinders. In FIG. 9, the timing at which the engine is stopped is shown as “stop position Ps”. Here, the # 3 cylinder is the stop compression stroke cylinder, and the # 1 cylinder is the stop expansion stroke cylinder. The # 2 cylinder is a stop exhaust stroke cylinder, and the # 4 cylinder is a stop intake stroke cylinder. In addition, valve opening periods IV1 to IV4 of the intake valve 11 and valve opening periods EV1 to EV4 of the exhaust valve 12 are appended to the respective cycles of the cylinders # 1 to # 4.

  As described above, the piston 5 of the # 3 cylinder is moved by the motor 20 from the stop position Ps to the reference position P0. That is, the period during which the piston 5 is moved in the forward rotation direction from the stop position Ps to the reference position P0 is the drive period of the motor 20. Within this drive period, the first fuel injection F1 that is the first fuel injection after the start is executed in the # 3 cylinder, and then the first ignition IG1 that is the first ignition operation after the start is executed. As a result, combustion occurs in the # 3 cylinder, and the engine 1 temporarily reversely rotates.

  At an appropriate timing in the above reverse rotation period, the second fuel injection F2 is executed in the # 1 cylinder, and the second ignition IG2 is executed near the compression top of the # 1 cylinder. As a result, combustion occurs in the # 1 cylinder, and the engine 1 rotates forward. In a normal cycle, the next combustion is performed in the # 3 cylinder, but this # 3 cylinder cannot be used because it is already burned during the compression stroke in order to generate the reverse rotation. Therefore, the # 3 cylinder is skipped, and the third fuel injection F3 is executed during the compression stroke in the # 4 cylinder, and the third ignition IG3 is executed during the expansion stroke. Subsequently, in the # 2 cylinder, the fourth fuel injection F4 is executed during the compression stroke, and the fourth ignition is executed during the expansion stroke.

  According to the embodiment described above, the piston 20a of the stop-time compression stroke cylinder 2a is moved to the reference position P0 by driving the motor 20, and then the engine 2 is temporarily rotated reversely by burning the cylinder 2a. . For this reason, no matter what position (crank angle) the piston 5a of the cylinder 2a is stopped when the engine is stopped, the piston 5a is moved to the reference position P0 by the motor torque, so that combustion is stably generated in the cylinder 2a. be able to. Further, since the in-cylinder pressure of the cylinder 2a is increased by the piston 5a moved to the reference position P0, not only the ignitability to the air-fuel mixture is good, but also large reverse rotation energy (reverse rotation driving force) is generated. Can be made. Accordingly, the in-cylinder pressure of the stop-time expansion stroke cylinder 2b in which combustion is performed following the cylinder 2a can be increased, and the subsequent forward rotation of the engine 1 can be smoothly performed.

  Furthermore, since only the motor torque is used to move the piston to the reference position P0, the power consumption by the motor 20 can be suppressed. Therefore, in the hybrid vehicle HEV that eliminates the starter motor and starts the engine 1 with the motor torque of the motor 20, the amount of battery 22 used can be suppressed. Accordingly, it is possible to extend the allowable cruising distance for electric travel in a hybrid vehicle HEV that needs to leave surplus power in the battery in preparation for engine start.

[Starting control according to piston stop position]
In the above-described embodiment, the example in which the piston 5a of the stop-time compression stroke cylinder 2a is simply moved to the reference position P0 when the engine is started is shown. However, depending on the stop position of the piston 5a, it may be better to execute another start control. Here, an example in which the above-described reverse rotation start control and other start control are selectively used according to the piston stop position will be described.

  FIG. 10 is a diagram for explaining an embodiment in which the start mode is set according to the stop position of the piston. FIG. 10 shows the operation regions of the stop-time compression stroke cylinder 2a and the stop-time expansion stroke cylinder 2b in association with the crank angle. The stop-time compression stroke cylinder 2a is divided into three regions: region (1), region (2), and region (3). Region (1) is a region between BDC and BTDC 80 deg, region (2) is a region between BTDC 80 deg and BTDC 60 deg, and region (3) is a region between BTDC 60 deg and TDC. Here, BTDC 80 deg is a crank angle corresponding to the intake valve closing position P (IVC) in which the intake valve 11 is completely closed in the stop-time compression stroke cylinder 2a. Further, BTDC 60 deg is the upper limit crank angle at which the air-fuel mixture can be favorably guided to the spark plug 15 as described above with reference to FIG. These crank angles are examples.

  The expansion stroke cylinder 2b at the time of stop has a region (2A) substantially corresponding to the crank angle range of the region (2) and a region (3A) generally corresponding to the crank angle range of the region (3). Has been. The region (2A) is a region before and after the exhaust valve opening start position P (EVOS) at which the exhaust valve 12 starts to open in the stop-time expansion stroke cylinder 2b. Here, an example is shown in which the advance side end of the area (2A) is set to 90 deg and the retard side end is set to 138 deg. 138 deg is a crank angle corresponding to the exhaust valve open position P (EVOC) at which the exhaust valve 12 is fully open, and generally corresponds to the retard side end (BTDC 60 deg) of the region (2). The region (3A) is a region from the exhaust valve open position P (EVOC) to the BDC.

  In the VCM 40, when the engine 1 is stopped, the piston 5a of the stop-time compression stroke cylinder 2a is stopped in any of the regions (1) to (3), and the piston 5b of the stop-time expansion stroke cylinder 2b is Based on whether the region (2A) or (3A) is stopped, the start mode is selected and predetermined engine start control is executed. The stop positions of the pistons 5a and 5b when the engine is stopped are detected based on the measured values of the crank angle sensor SN3 (detection unit).

  When the piston 5a is stopped in the region (1) (first condition), the VCM 40 is set to the start mode I, and the piston 5a of the compression stroke cylinder 2a at the time of stop as described with reference to FIG. The engine 1 is moved to the reference position P0 by the first motor drive amount), and the cylinder 2a is combusted for the first time to perform the reverse rotation start control for temporarily rotating the engine 1 in the reverse direction. When the piston 5a is stopped in the region (2) (second condition), the VCM 40 does not execute the reverse rotation start control. In this case, in the start mode II, the VCM 40 performs start control for causing the engine 1 to rotate forward by burning the stop-time expansion stroke cylinder 2b in the first start (see FIG. 14). When the piston 5a is stopped in the region (3) (second condition), the VCM 40 does not perform the first start combustion in the stop-time compression stroke cylinder 2a and the stop-time expansion stroke cylinder 2b. In this case, the VCM 40 enters the start mode III by moving the piston 5c of the intake stroke cylinder 2c at the time of stop to the reference position P0 with the motor torque (second motor drive amount) and burning the cylinder 2c at the first start, Reverse rotation start control for temporarily rotating the engine 1 in reverse is executed. Hereinafter, these start modes I, II, and III will be described with reference to FIG.

  FIG. 11 is a flowchart showing an example of start control of the engine 1 by the VCM 40. The VCM 40 confirms that the engine 1 is stopped as a premise for executing the start control (step S1). Next, the VCM 40 checks whether or not there is an instruction to start the engine 1 (step S2). The start instruction here includes a predetermined engine restart condition after the engine 1 is stopped due to establishment of a predetermined engine stop condition, for example, when the engine 1 temporarily stopped by the idling stop operation is restarted. Includes a start instruction when the condition is established, and a start instruction when the operator of the hybrid vehicle HEV performs an engine start operation. If there is no engine 1 start instruction (NO in step S2), the VCM 40 suspends the start control.

  When the engine 1 is instructed to start (YES in step S2), the VCM 40 determines whether the stop position of the piston 5a of the stop-time compression stroke cylinder 2a is in the above regions (1) to (3). (Step S3). Specifically, the VCM 40 derives the crank angle at which the piston 5a is stopped based on the measured value (piston stop position information) of the crank angle sensor SN3. Then, the VCM 40 determines which of the crank angle ranges that are determined in advance as the crank angle dividing the regions (1) to (3).

  Subsequently, the motor control unit 42 of the VCM 40 sets a motor torque for operating the motor 20 when the engine 1 is started (step S4). When the start mode I is selected, the motor torque set in step S4 moves the piston 5a of the stop-time compression stroke cylinder 2a to the reference position P0 by the motor 20 within the predetermined start period as described above. This is the motor torque (first motor drive amount) required to make it. As will be described later, in the start mode II, when starting the engine 1 in the forward rotation, the motor torque necessary for starting the motor 20 is set. In the start mode III, the motor torque (second motor drive amount) necessary for moving the piston 5c of the intake stroke cylinder 2c at the time of stop to the reference position P0 by the motor 20 is set.

  Hereinafter, the VCM 40 sets one of the start modes I to III based on the determination result of step S3 (steps S5 and S6). In step S3, when it is determined that the stop position of the piston 5a of the stop-time compression stroke cylinder 2a is in the region (1) (YES in step S5; first condition), the start mode I is set (step S11; FIG. 12). If it is determined that the stop position of the piston 5a is not in the region (1) (NO in step S5; second condition) but in the region (2) (YES in step S6), the start mode II is set (step S6). S21; FIG. 13). When the stop position of the piston 5a is not in the region (2) (NO in step S6), the start mode III is set (step S31; FIG. 15).

<Starting mode I>
FIG. 12 is a flowchart showing the operation in the start mode I. The flow shown here is substantially the same as the operation described above with reference to FIG. In FIG. 12, the operations of the stop-time compression stroke cylinder 2a and the stop-time expansion stroke cylinder 2b are described in series, but the operations in both the cylinders 2a and 2b can be partially overlapped (the following flowchart). But the same).

  The motor control unit 42 controls the inverter 21 so that the motor 20 generates the motor torque set in step S3, and drives the motor 20 (step S101). After generating the motor torque, the motor 20 stops (step S102). In parallel with the operation of the motor 20, processing for the compression stroke cylinder 2a at the time of stop is executed. That is, the engine control unit 41 controls the injector 16 of the cylinder 2a to execute the fuel injection operation for the cylinder 2a (step S12). As the motor 20 stops (step S102), the piston 5a reaches the reference position P0 (step S13).

  Thereafter (or just before reaching), the engine control unit 41 controls the ignition plug 15 of the cylinder 2a to perform the first ignition for the first time in the cylinder 2a (step S14). As a result, combustion occurs in the cylinder 2a, and the piston 5a is pushed down from the reference position P0 toward the advance side. That is, the engine 1 temporarily reversely rotates (step S15).

  Along with the reverse rotation, the piston 5b of the expansion stroke cylinder 2b at the time of stopping starts to rise, and the air in the cylinder 2b is gradually compressed. In this state, the engine control unit 41 controls the injector 16 of the cylinder 2b to execute the fuel injection operation for the cylinder 2b (step S16). When the piston 5b reaches a predetermined crank angle in the cylinder 2b (step S17), the engine control unit 41 controls the ignition plug 15 of the cylinder 2b to perform the second ignition for the second start in the cylinder 2b. (Step S18). Thereby, combustion occurs in the cylinder 2b, and the piston 5b is pushed down to the retard side. That is, the engine 1 rotates forward (step S19). Thereafter, the third and subsequent ignitions are performed, and the engine 1 is started.

<Starting mode II>
In the region (2) in which the start mode II is selected, the piston 5a of the compression stroke cylinder 2a at the time of stop is stopped closer to the TDC than the intake valve closing position P (IVC) that is the closing timing of the intake valve 11. It is in a state. In this case, the engine control unit 41 does not execute reverse start control as in the start mode I. This is because when the stop position of the piston 5a is on the TDC side with respect to the closing timing of the intake valve 11, the compression allowance of the combustion chamber 6 in the cylinder 2a by the piston 5a is small. That is, since the cylinder 2a returns to atmospheric pressure when the engine is stopped, the degree of increase in the in-cylinder pressure decreases as the piston 5a approaches TDC, even if the piston 5a is moved to the reference position P0. For this reason, even if the cylinder 2a in which the piston 5a is stopped in the region (2) is burned, stable combustion may not be ensured or sufficient starting power may not be obtained. That is, useless combustion may be performed in the cylinder 2a.

  In this start mode II, the engine control unit 41 does not execute the combustion for reverse rotation in the stop-time compression stroke cylinder 2a, but burns the stop-time expansion stroke cylinder 2b in the first start to make the engine 1 normal. Start rotating. As shown in FIG. 10, when the piston 5a is present in the region (2) of the cylinder 2a, the piston 5b of the cylinder 2b is present in the region (2A). In this case, the stop position of the piston 5b is a position on the TDC side from the exhaust valve opening position P (EVOC = 138 deg).

  When the piston 5b is stopped on the BDC side from the exhaust valve open position P (EVOC), the airtightness of the cylinder 2b is not ensured. Therefore, the cylinder 2b cannot be used for the first start combustion. However, when the piston 5b is stopped on the TDC side from the exhaust valve opening position P (EVOC), the airtightness of the cylinder 2b can be ensured. The intake valve 11 starts to open at the exhaust valve opening start position P (EVOS = 116 deg), but since it is not completely opened, combustion can be generated. Actually, as noted in FIG. 10, the ignition rate in the region (2A) is high, and the average in-cylinder maximum pressure Pmax in the range of the crank angle of 116 deg to 138 deg is also high.

  As described above, in the start mode II, the stop-time expansion stroke cylinder 2b is used for the first start combustion. However, since the operation of pushing up the piston 5b as in the start mode I is omitted, the in-cylinder pressure of the cylinder 2b becomes insufficient. Therefore, it is assumed that in each cylinder 2 at the initial stage of the start, a sufficient torque that allows the piston 5 to pass TDC cannot be applied. For this reason, the driving force of the motor 20 is applied to the engine 1 in an assisting manner at the initial stage of the start to ensure a smooth start.

  FIG. 13 is a flowchart showing the operation in the start mode II, and FIGS. 14A to 14C are diagrams for explaining the operation in the start mode II. FIG. 14A schematically shows the stop positions of the pistons 5a and 5b of the stop-time compression stroke cylinder 2a and the stop-time expansion stroke cylinder 2b when the start mode II is selected. In this case, the piston 5a of the cylinder 2a is closer to the TDC than the intake valve closing position P (IVC), and the piston 5b of the cylinder 2b is closer to the TDC side than the exhaust valve opening position P (EVOC). Each is stopped.

  When executing the start mode II, the clutch control unit 43 controls to release the second clutch 35 while engaging the first clutch 34. This is for starting assistance by the motor 20. The motor control unit 42 sets a motor torque necessary for performing the start assist. Then, the motor control unit 42 controls the inverter 21 so that the motor 20 generates the set motor torque, starts driving the motor 20 (step S201), and applies the motor torque for starting assist to the engine 1.

  In parallel with the operation of the motor 20 as described above, processing for the stop-time expansion stroke cylinder 2b is executed. That is, the engine control unit 41 controls the injector 16 of the cylinder 2b to execute the fuel injection operation for the cylinder 2b (step S22). When the piston 5b reaches a predetermined crank angle in the cylinder 2b (step S23), the engine control unit 41 controls the spark plug 15 of the cylinder 2b to start 1 in the cylinder 2b as shown in FIG. First ignition IG21 is performed (step S24). As a result, combustion occurs in the cylinder 2b, and the piston 5b is pushed down to the retard side with the assistance of the driving force of the motor 20. That is, the engine 1 rotates forward (step S25).

  Subsequently, the engine control unit 41 controls the injector 16 of the stop-time compression stroke cylinder 2a to execute a fuel injection operation for the cylinder 2a (step S26). At this stage, the cylinder 2a has shifted to the expansion stroke. Then, when the piston 5a reaches a predetermined crank angle in the cylinder 2a (step S27), the engine control unit 41 controls the spark plug 15 of the cylinder 2a, and in the cylinder 2b as shown in FIG. 14 (C). A second ignition IG22 for the second start is performed (step S28). As a result, combustion occurs in the cylinder 2a, the piston 5a is pushed down to the retard side, and the engine 1 rotates forward (step S29). The start assist is continued until the stage of the second ignition IG22, and then the motor 20 is stopped (step S202). Thereafter, the third and subsequent ignitions are performed, and the engine 1 is started.

<Starting mode III>
The region (3) in which the start mode III is selected is a region in which the piston 5a of the stop-time compression stroke cylinder 2a is closer to the TDC than the intake valve closing position P (IVC) compared to the region (2). . As shown in FIG. 10, when the piston 5a exists in the region (3) of the cylinder 2a, the piston 5b of the cylinder 2b exists in the region (3A). In this case, the stop position of the piston 5b is a position on the BDC side with respect to the exhaust valve open position P (EVOC). Accordingly, since the airtightness cannot be secured, the cylinder 2b cannot be used for the first combustion of the start. Of course, the reverse rotation start using the cylinder 2a cannot be used because the compression allowance by moving the piston 5a by the motor 20 becomes smaller than that in the start mode II. For this reason, in the start mode III, the engine control unit 41 does not execute the first start combustion using the cylinder 2a and the cylinder 2b. Instead, in the start mode III, the engine control unit 41 performs the first start combustion using the stop-time intake stroke cylinder 2c (FIG. 16), and starts the engine 1 in the reverse rotation.

  FIG. 15 is a flowchart of the start mode III, and FIGS. 16A to 16D are diagrams for explaining the operation of the start mode III. FIG. 16A schematically shows the stop positions of the pistons 5a and 5b of the stop-time compression stroke cylinder 2a and the stop-time expansion stroke cylinder 2b when the start mode III is selected. In this case, the piston 5a of the cylinder 2a is closer to the TDC than the intake valve closed position P (IVC), and the piston 5b of the cylinder 2b is closer to the BDC side than the exhaust valve open position P (EVOC). Each is stopped. Referring to FIG. 10, the piston 5a of the cylinder 2a is stopped in the region (3) closest to the TDC. In this case, the piston 5c of the stop-time intake stroke cylinder 2c is located in a crank angle range corresponding to the region (3A) in FIG.

  In the start mode III, the piston 5c of the stop-time intake stroke cylinder 2c is moved to the reference position P0 by the driving force of the motor 20, and the first start combustion is performed in the cylinder 2c. With this combustion, the engine 1 is reversely rotated to increase the in-cylinder pressure of another cylinder (for example, the compression stroke cylinder 2a at the time of stop), and then the second combustion is performed to start the engine 1 in the normal rotation. When the start mode III is executed, the clutch control unit 43 controls to release the second clutch 35 while engaging the first clutch 34. As shown in FIG. 16B, the motor control unit 42 calculates the motor torque required to move the piston 5c of the cylinder 2c from its stop position Ps through the BDC to the reference position P0. At this time, the motor torque is corrected with reference to the measurement data of the sensors SN1, SN2, and SN4.

  Referring to FIG. 15, motor control unit 42 controls inverter 21 so that motor 20 generates the set motor torque, and drives motor 20 (step S301). After generating the motor torque, the motor 20 stops (step S302). As a result, as shown in FIG. 16C, the piston 5c of the stop-time intake stroke cylinder 2c is moved toward the reference position P0. In parallel with the operation of the motor 20 as described above, the process for the stop-time intake stroke cylinder 2c is executed. That is, the engine control unit 41 controls the injector 16 of the cylinder 2c to execute the fuel injection operation for the cylinder 2c (step S32). As the motor 20 is stopped (step S302), the piston 5c reaches the reference position P0 (step S33). At this time, the piston 5a of the stop-time compression stroke cylinder 2a is lowered, and the compression allowance is secured.

  Thereafter (or just before reaching), the engine control unit 41 controls the ignition plug 15 of the cylinder 2c to perform the first ignition IG31 for the first start in the cylinder 2c as shown in FIG. S34). Thereby, combustion occurs in the cylinder 2c, and the piston 5c is pushed down from the reference position P0 to the advance side. That is, the engine 1 temporarily reversely rotates (step S35).

  With this reverse rotation, the piston 5a of the stop-time compression stroke cylinder 2a starts to rise, and the air in the cylinder 2b is gradually compressed. Since the piston 5c of the cylinder 2c is moved forwardly beyond the BDC by the motor torque, the cylinder 2a is in the expansion stroke. In this state, the engine control unit 41 controls the injector 16 of the cylinder 2a to execute a fuel injection operation for the cylinder 2a (step S36). When the piston 5a reaches a predetermined crank angle in the cylinder 2a (step S37), the engine control unit 41 controls the ignition plug 15 of the cylinder 2a to perform the second start ignition in the cylinder 2a. (Step S38). Thereby, combustion occurs in the cylinder 2a, and the piston 5a is pushed down to the retard side. That is, the engine 1 rotates forward (step S39). Thereafter, the third and subsequent ignitions are performed, and the engine 1 is started.

[Modified Embodiment]
As mentioned above, although embodiment of this invention was described, this invention is not limited to this, The following modified embodiment can be taken.

  (1) In the above embodiment, the motor torque corresponding to the stop position of the piston 5a of the stop-time compression stroke cylinder 2a is set as the motor drive amount of the motor 20 set by the motor control unit 42. When there is a margin in the engine start period, the motor torque is fixed, and the drive time (motor drive amount) of the motor 20 is set according to the distance from the stop position of the piston 5a to the reference position P0. Also good.

  (2) In the above embodiment, the engine start control device according to the present invention is applied to the hybrid vehicle HEV. The present invention is not limited to the hybrid vehicle HEV, and can be applied to various vehicles and power equipment configured to be able to drive an internal combustion engine such as a gasoline engine or a diesel engine with a motor.

1 Engine 2, 2a, 2b, 2c Cylinder 5, 5a, 5b, 5c Piston 11 Intake valve 12 Exhaust valve 15 Spark plug 16 Injector 17 PCM (part of combustion control unit)
20 Motor (electric drive motor)
21 Inverter 22 Battery 40 VCM
41 Engine control part (part of combustion control part)
42 Motor control unit HEV hybrid vehicle SN3 Crank angle sensor (detection unit)
P0 Reference position Ps, P1, P11, P12, P13 Piston stop position

Claims (7)

A motor capable of driving an engine having a plurality of cylinders and pistons having an intake valve and an exhaust valve to burn fuel;
A combustion control unit for controlling a combustion operation in the cylinder;
A motor control unit for controlling the operation of the motor;
A detection unit for detecting a piston stop position when the engine is stopped,
The motor control unit is configured such that, among the plurality of cylinders, a piston in a compression stroke cylinder at a stop state that is in a compression stroke state when the engine is stopped does not exceed a compression top dead center when the engine is started. A first motor drive amount corresponding to the piston stop position of the stop-time compression stroke cylinder when the engine is stopped so as to stop after moving to a position;
The combustion control unit
When the piston stop position of the stop-time compression stroke cylinder detected by the detection unit is in a first condition that is at a bottom dead center side with respect to the closing timing of the intake valve, the motor control unit drives the first motor. After the motor is operated by the amount, the stop-time compression stroke cylinder is burned to temporarily reverse the engine, and then the stop-time expansion stroke cylinder that is in the expansion stroke state when the engine is stopped is burned. And performing reverse start control including a procedure for causing the engine to rotate forward,
The reverse rotation start control is not executed when the piston stop position of the compression stroke cylinder at the stop time detected by the detection unit is in a second condition that is at the top dead center side with respect to the closing timing of the intake valve. Start control device. The engine start control device according to claim 1,
The combustion control unit detects the piston stop position of the expansion stroke cylinder at the time of stop detected by the detection unit when the reverse rotation start control is not executed, and a top dead center from a predetermined position near the opening timing of the exhaust valve. When the engine is on the side, an engine start control device that combusts the expansion stroke cylinder when stopped and rotates the engine forward. The engine start control device according to claim 1,
The combustion control unit detects that the detection unit detects the piston stop position of the stop expansion stroke cylinder when the reverse rotation start control is not performed, and the bottom dead center is lower than a predetermined position near the exhaust valve opening timing. The engine start control device does not execute combustion in the stop-time compression stroke cylinder and the stop-time expansion stroke cylinder for starting the engine. The engine start control device according to claim 3,
The motor control unit stops after the piston of the stop-intake stroke cylinder, which is in the intake stroke state when the engine is stopped, moves to a predetermined reference position that does not exceed the compression top dead center at the start of the engine. And setting a second motor drive amount according to the piston stop position of the stop-time intake stroke cylinder,
The combustion control unit is configured to start the engine so that after the motor control unit operates the motor with the second motor driving amount, the engine is temporarily reverse-rotated by burning the intake stroke cylinder when stopped. apparatus. The engine start control device according to claim 4,
The combustion control unit burns a cylinder that has reached the expansion stroke by the operation of the motor by the second motor driving amount following the temporary reverse rotation and is the compression stroke cylinder at the time of stop. An engine start control device that rotates the engine forward. In the engine start control device according to any one of claims 1 to 5,
When starting the engine in which the motor control unit sets the motor drive amount,
When an operator starts the engine, or
An engine start control device, comprising: when a predetermined engine restart condition is satisfied after the engine has been stopped due to a predetermined engine stop condition being satisfied. In the engine start control device according to any one of claims 1 to 6,
The engine is mounted on the vehicle together with an electric drive motor as a drive source for running the vehicle,
An engine start control device, wherein the electric drive motor also serves as a motor capable of driving the engine.

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