JP2013087710A - Start control device of internal combustion engine for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a start control device of an internal combustion engine for a vehicle, configured to prevent an ignition failure to favorably start the internal combustion engine.SOLUTION: When an exhaust valve 108 corresponding to a cylinder 100 in process of expansion is opened during stopping a direct injection engine 12, in restarting the direct injection engine 12, fuel injection to the cylinder 100 in process of expansion is prohibited, so that when the stopped direct injection engine 12 is restarted, and when the ignition failure is likely to occur due to the shortage of oxygen quantity, no fuel is injected to the cylinder 100 in process of expansion, thereby preventing emission deterioration due to a misfire during restart.

Description

  The present invention relates to a start control device for an internal combustion engine for a vehicle, and more particularly, to an improvement for realizing a suitable start by suppressing ignition failure.

  An internal combustion engine of a type in which fuel is directly injected into a cylinder is widely used as a drive source for various vehicles. Such an internal combustion engine is preferably applied to a hybrid vehicle that selectively uses the internal combustion engine and an electric motor as a drive source. For example, in the eco-run mode (ECO mode), the internal combustion engine is stopped and the electric motor is used as a drive source. On the other hand, when the eco-run mode is released, the internal combustion engine is restarted, and travel using the internal combustion engine as a drive source is performed. As described above, a technique for starting the internal combustion engine by injecting and igniting fuel to the expansion stroke cylinder when the internal combustion engine is restarted after being stopped, that is, a direct connection start technique has been proposed. For example, this is the engine starting device described in Patent Document 1.

JP 2010-031834 A JP 2009-144643 A JP 2007-239570 A JP 2010-188905 A JP 2010-173381 A JP 2006-348862 A

  However, in the conventional technique, when the exhaust valve corresponding to the expansion stroke cylinder is opened in the stop process of the internal combustion engine, the exhaust gas flows into the expansion stroke cylinder, and the expansion is performed when the internal combustion engine is restarted. Even if fuel is injected into the stroke cylinder, ignition may fail (misfire) due to, for example, insufficient oxygen amount. Such a problem has been newly found by the present inventors in the process of continuing diligent research with the intention of improving start control of an internal combustion engine for a vehicle.

  The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a start control device for an internal combustion engine for a vehicle that realizes a suitable start by suppressing failure of ignition. is there.

  In order to achieve such an object, the gist of the first invention is that fuel injection and ignition are performed on an expansion stroke cylinder at the time of restart after an internal combustion engine of a type in which fuel is directly injected into the cylinder. When the exhaust valve corresponding to the expansion stroke cylinder is opened in the stop process of the internal combustion engine, the internal combustion engine start control device for starting the internal combustion engine is performed. The fuel injection to the expansion stroke cylinder is prohibited at the time of restart.

  As described above, according to the first aspect of the present invention, when the exhaust valve corresponding to the expansion stroke cylinder is opened while the internal combustion engine is stopped, the fuel injection to the expansion stroke cylinder is performed when the internal combustion engine is restarted. Therefore, when the internal combustion engine is restarted after being stopped, the fuel is not injected into the expansion stroke cylinder in a state where ignition failure is expected due to insufficient oxygen amount or the like. Emission deterioration due to misfire can be suitably prevented. That is, it is possible to provide a start control device for an internal combustion engine for a vehicle that realizes a preferable start by suppressing failure of ignition.

  The gist of the second invention subordinate to the first invention is that the internal combustion engine is connected to an electric motor that drives the internal combustion engine by electric energy supplied from a power storage device. When the amount of power stored in the power storage device has decreased to the minimum amount of power required to drive the internal combustion engine by the electric motor when the fuel injection to the cylinder is prohibited, the internal combustion engine is started by driving the electric motor at that time. Is to do. In this way, in the state where fuel injection to the expansion stroke cylinder is prohibited, it is possible to suitably suppress the occurrence of shock when starting the internal combustion engine.

1 is a schematic configuration diagram including a skeleton diagram of a drive system of a hybrid vehicle to which the present invention is preferably applied. It is sectional drawing explaining the direct-injection engine with which the hybrid vehicle of FIG. 1 was equipped. 2 is a chart for explaining the order of four-stroke strokes executed in each cylinder when the direct injection engine of FIG. 1 is a V-type eight cylinder. FIG. 2 is a cylinder phase diagram showing a correlation between phases of four cylinders involved in explosion within one rotation of a crankshaft in the V-type 8-cylinder engine of FIG. 1. FIG. 2 is a diagram illustrating a relationship stored in advance for determining one of a motor travel region and an engine travel region in hybrid travel control in the hybrid vehicle of FIG. 1. FIG. 2 is a cylinder phase diagram illustrating a behavior in a stopping process of the V-type 8-cylinder four-cycle direct injection engine of FIG. 1. It is a flowchart explaining the principal part of the engine stop / restart control of a present Example by the electronic controller of FIG.

  The present invention is preferably applied to a parallel type hybrid vehicle in which the internal combustion engine is connected to and disconnected from a power transmission path by a clutch. Preferably, the present invention is preferably applied to a hybrid vehicle that includes the clutch in a power transmission path between the internal combustion engine and the electric motor, and the electric motor is connected to a transmission via, for example, a torque converter. That is, the present invention is suitably applied to engine start control when starting (restarting) the internal combustion engine from the motor travel mode in which the travel is performed using only the electric motor as a driving force source. As the clutch, a single-plate or multi-plate friction engagement clutch such as a hydraulic friction clutch is preferably used.

  As the electric motor, a motor generator that can alternatively use the functions of both the electric motor and the generator is preferably used. As the internal combustion engine, a direct injection gasoline engine of a type in which gasoline as fuel is directly injected into a cylinder is preferably used, and a multi-cylinder engine of 3 or more cylinders, particularly direct injection of 6 cylinders, 8 cylinders, 12 cylinders or the like. It can also be applied to engines. That is, the present invention can be applied to any reciprocating internal combustion engine that can start ignition by injecting fuel into a cylinder in the expansion stroke when stopped.

  The stop process of the internal combustion engine preferably converges with the start point being the point at which the crankshaft repeats normal rotation and reverse rotation after the fuel injection and ignition to the internal combustion engine are stopped. The end point is when the crankshaft is stopped. That is, according to the present invention, preferably, with respect to the expansion stroke cylinder, after the fuel injection and ignition are stopped, the state of the crankshaft converges from the time when the crankshaft repeats normal rotation and reverse rotation, and the state converges. If the phase of the expansion stroke cylinder has advanced to a phase corresponding to opening of the exhaust valve even once until the crankshaft is stopped, when the internal combustion engine is restarted, the expansion stroke cylinder Prohibit fuel injection.

  The minimum storage amount may be determined in consideration of the starting assist force of the electric motor at the time of ignition failure (misfire) of the first explosion due to fuel injection and ignition to the expansion stroke cylinder. That is, in the system for determining whether or not the internal combustion engine can be started by the electric motor according to the amount of power stored in the power storage device, taking into account the starting assist force due to the misfire of the initial explosion due to fuel injection and ignition to the expansion stroke cylinder, The minimum power storage amount of the power storage device for restarting the internal combustion engine may be determined.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram including a skeleton diagram of a drive system of a hybrid vehicle 10 to which the present invention is preferably applied. A hybrid vehicle 10 shown in FIG. 1 includes a direct injection engine 12 that is an internal combustion engine that directly injects fuel into a cylinder, and an electric motor MG that functions as an electric motor and a generator as driving power sources for traveling. . The outputs of the direct injection engine 12 and the electric motor MG are transmitted from the torque converter 14 which is a fluid transmission device to the automatic transmission 20 via the turbine shaft 16 and the C1 clutch 18, and further, the output shaft 22 and the differential gear device. 24 to the left and right drive wheels 26. The torque converter 14 includes a lockup clutch (L / U clutch) 30 that directly connects the pump impeller and the turbine impeller, and an oil pump 32 is integrally connected to the pump impeller. It is rotationally driven mechanically by the direct injection engine 12 and the electric motor MG.

  In the present embodiment, the direct injection engine 12 is a V-type 8-cylinder four-cycle gasoline engine. Specifically, as shown in FIG. In addition, gasoline is directly injected in a high-pressure fine particle state. Preferably, gasoline is pressurized to a feed pressure by an electric feed pump, and further pressurized to a high pressure by a high-pressure pump, and then directly injected into the cylinder 100 by the fuel injection device 46. In the direct injection engine 12, air flows into the cylinder 100 from the intake passage 102 via the intake valve 104, and exhaust gas is discharged from the exhaust passage 106 via the exhaust valve 108. When the ignition device 47 is ignited at a predetermined timing, the air-fuel mixture in the cylinder 100 explodes and burns, and the piston 110 is pushed downward. The intake passage 102 is connected to an electronic throttle valve 45, which is an intake air amount adjusting valve, via a surge tank 103, and the intake passage 102 is in accordance with the opening (throttle valve opening) of the electronic throttle valve 45. Thus, the amount of intake air flowing into the cylinder 100, that is, the engine output is controlled. The piston 110 is fitted in the cylinder 100 so as to be slidable in the axial direction, and is connected to a crank pin 116 of the crankshaft 114 via a connecting rod 112 so as to be relatively rotatable. The crankshaft 114 is rotationally driven as indicated by an arrow R in accordance with the linear reciprocation of. The crankshaft 114 is rotatably supported by a bearing at a journal portion 118, and is integrally provided with a crank arm 120 that connects the journal portion 118 and the crankpin 116.

  In the direct injection engine 12 configured as described above, four strokes of an intake stroke, a compression stroke, an expansion (explosion) stroke, and an exhaust stroke are performed by two rotations (720 °) of the crankshaft 114 per cylinder. This is a so-called four-cycle engine in which the crankshaft 114 is continuously rotated by repeating this. The pistons 110 of the eight cylinders 100 provided in the direct injection engine 12 are configured such that the crank angles are shifted by 90 °. In other words, the position of the crank pin 116 of the crankshaft 114 protrudes in a direction shifted by 90 °, and each time the crankshaft 114 rotates 90 °, eight cylinders 100 are preliminarily shown in FIG. Explosive combustion is performed in the set ignition sequence, and rotational torque is continuously generated.

  In the direct injection engine 12, the expansion stroke in which the piston 110 is rotated by a predetermined angle from the top dead center (compression TDC) after the compression stroke, and the intake valve 104 and the exhaust valve 108 are both closed. When the fuel is stopped within a predetermined angle range θ, gasoline is injected into the cylinder 100 by the fuel injection device 46 and ignited by the ignition device 47 to explode the air-fuel mixture in the cylinder 100. It is possible to start ignition by burning and raising the engine rotation speed. For example, when the friction (friction) of each part of the direct injection engine 12 is small, there is a possibility that the direct injection engine 12 can be started only by ignition start, but the crankshaft 114 can be cranked even when the friction is large. Since the starting assist torque at the time of ranking and starting can be reduced, the maximum torque of the electric motor MG that generates the assist torque is reduced, so that the size and fuel consumption can be reduced. The angle range θ is a crank angle CA after top dead center. For example, a relatively large rotational energy can be obtained by starting ignition within a range of about 30 ° to 60 °, and the assist torque can be reduced. Rotational energy can be relatively obtained by starting ignition, and assist torque can be reduced.

  FIG. 3 is a diagram illustrating an operation stroke with respect to the crank angle CA for each of the cylinders No. 1 to No. 8 when the direct injection engine 12 is a V-type 8-cylinder engine that operates in four cycles. Each of the cylinders No. 1 to No. 8 indicates a mechanical arrangement position, but in the ignition order based on the crank angle CA of 0 °, the cylinder No. 2, the cylinder No. 4, the cylinder No. 5, The order is cylinder No. 6, cylinder No. 3, cylinder No. 7, cylinder No. 8, cylinder No. 1. For example, assuming that the cylinder No. 4 is the first cylinder K1 in the ignition order, the cylinder No. 5 is the second cylinder K2, the cylinder No. 6 is the third cylinder K3, and the cylinder No. 3 is the fourth cylinder K4. FIG. 4 is a cylinder phase diagram showing the interrelationship of the phases of the four cylinders involved in the explosion within one rotation of the crankshaft 114 in the V-type 8-cylinder engine, and shows the first cylinder K1 to the fourth cylinder K4. Are rotated clockwise while maintaining a 90 ° relationship with each other, and a compression stroke for compressing the intake air from the TDC to the TDC after the intake valve 104 is closed, and an explosion gas from the TDC until the exhaust valve 108 is opened. The expansion stroke in which the piston 110 is pushed down by the expansion is sequentially performed. The phase of the first cylinder K1 in FIG. 4 is located in the second half of the expansion stroke, the phase of the second cylinder K2 is located in the first half of the expansion stroke, the phase of the third cylinder K3 is located in the second half of the compression stroke, The phase of the cylinder K4 is located before the start of the compression stroke.

  Returning to FIG. 1, a K0 clutch 34 is provided between the direct injection engine 12 and the electric motor MG via the damper 38 to directly connect the direct injection engine 12 and the electric motor MG. The K0 clutch 34 is a hydraulic friction engagement device such as a single-plate or multi-plate friction clutch that is frictionally engaged by a hydraulic cylinder, for example, an electromagnetic linear control valve provided in the hydraulic control device 28, or the like. In this embodiment, the engagement / release control is performed in the oil chamber 40 of the torque converter 14 in an oil bath state. The K0 clutch 34 functions as a connecting / disconnecting device that connects or disconnects the direct injection engine 12 with respect to the power transmission path. The electric motor MG is connected to a battery 44 that is a power storage device via an inverter 42. The automatic transmission 20 is, for example, a stepped automatic transmission such as a planetary gear type in which a plurality of gear stages having different gear ratios are established depending on the disengagement state of a plurality of hydraulic friction engagement devices (clutch and brake). The shift control is performed by an electromagnetic hydraulic control valve, a switching valve or the like provided in the hydraulic control device 28. The C1 clutch 18 functions as an input clutch of the automatic transmission 20, and is similarly engaged and released by an electromagnetic linear control valve in the hydraulic control device 28.

  The hybrid vehicle 10 configured as described above is controlled by, for example, an electronic control device 70 provided in the hybrid vehicle 10. The electronic control unit 70 includes a so-called microcomputer having a CPU, a ROM, a RAM, an input / output interface, and the like, and performs signal processing in accordance with a program stored in the ROM in advance using the temporary storage function of the RAM. I do. The electronic control unit 70 is supplied with signals from various sensors provided in the hybrid vehicle 10. That is, the accelerator pedal operation amount (accelerator operation amount) from the accelerator operation amount sensor 48, the engine rotation speed sensor 50, the MG rotation speed sensor 52, the turbine rotation speed sensor 54, the vehicle speed sensor 56, the crank angle sensor 58, and the SOC sensor 60, respectively. A signal representing the amount) Acc, a signal representing the rotational speed (engine rotational speed) NE of the direct injection engine 12, a signal representing the rotational speed (MG rotational speed) NMG of the electric motor MG, and the rotational speed of the turbine shaft 16 (turbine) Rotation speed) Signal representing NT, rotation speed of output shaft 22 (output shaft rotation speed corresponding to vehicle speed V) NOUT, rotation angle from TDC (top dead center) for each of eight cylinders 100, that is, crank angle A pulse signal Φ representing CA and a signal representing the charge level (remaining charge amount) SOC of the battery 44 are The electronic control device 70 is supplied. In addition, various types of information necessary for various types of control are supplied. The accelerator operation amount Acc corresponds to the output request amount.

  Preferably, the crank angle sensor 58 detects the respective teeth in a crank position detecting gear provided so as to be rotated integrally with the crankshaft 114, whereby the crank angle CA of the crankshaft 114 is detected. Is detected. The crank angle detection gear (tooth) is generally provided every 10 ° with respect to the rotation direction of the crankshaft 114, and the crank angle sensor 58 sets the crank angle CA every 10 °, for example. It is configured so that it can be detected.

  As shown in FIG. 1, the electronic control unit 70 functionally includes a hybrid control unit 72, a shift control unit 74, an engine stop control unit 76, and an engine start control unit 78. This hybrid control unit 72 is a motor travel region that travels using only the electric motor MG as a driving force source based on the vehicle speed V and the required output amount (for example, the accelerator opening Acc) based on the prestored relationship shown in FIG. And determining the travel region of the direct injection engine 12 alone or the engine traveling region in which the direct injection engine 12 and the electric motor MG are used as a driving force source, and operating the direct injection engine 12 and the electric motor MG. By controlling the vehicle, hybrid drive control is performed for causing the hybrid vehicle 10 to travel in a plurality of predetermined travel modes such as an engine travel mode, a motor travel mode, and an engine + motor travel mode that travels using both. . The shift control unit 74 controls the automatic release of the plurality of hydraulic friction engagement devices by controlling electromagnetic hydraulic control valves, switching valves and the like provided in the hydraulic control device 28. The plurality of gear stages of the transmission 20 are switched in accordance with a predetermined relationship or a shift map using driving states such as the accelerator operation amount Acc and the vehicle speed V as parameters. This relationship or shift map is obtained in advance for the operating point of the direct injection engine 12 or the electric motor MG so as to satisfy the required driving force with the optimum fuel consumption or the optimum efficiency.

  The engine stop control unit 76 stops the direct injection engine 12 when a predetermined condition is satisfied in the hybrid vehicle 10. For example, when the accelerator operation amount Acc is zero (accelerator off), the vehicle speed is zero, the D range, the brake switch is on, or the like is satisfied in the hybrid vehicle 10 The fuel injection and ignition to the direct injection engine 12 are stopped and the direct injection engine is stopped based on the eco-run stop request issued to the engine, the engine stop request at the time of switching from the engine traveling region to the motor traveling region during traveling, etc. 12 is stopped and the K0 clutch 34 is released as necessary.

  The engine start control unit 78 includes an expansion stroke cylinder determination unit 80, an expansion stroke valve opening determination unit 82, an ignition start control unit 84, an engine operation determination unit 86, an electric motor cranking control unit 88, a restart control end determination unit 90, And the SOC determination unit 92, and when a predetermined condition is satisfied in the hybrid vehicle 10, the direct injection engine 12 is started. For example, in response to an engine restart request due to brake-off at idle stop, switching from the motor travel region to the engine travel region, etc., the direct injection engine 12 is started to ignite and, if necessary, the electric motor MG. And the direct injection engine 12 is restarted. For example, the restart control is terminated based on the fact that the rotational speed (engine rotational speed) NE of the direct injection engine 12 has reached a preset end determination value NE1. And the K0 clutch 34 is engaged.

  The expansion stroke cylinder determination unit 80 is based on the signal Φ from the crank angle sensor 58 that detects the crank angle CA from the TDC (top dead center) of the crankshaft 114 in the direct injection engine 12. Among the plurality of cylinders 100 included in the cylinder 100 is determined. For example, as in the second cylinder K2 shown in FIG. 4, the cylinder 100 in the expansion stroke in which the piston 110 is pushed down by the expansion of the explosion gas from the top dead center until the exhaust valve 108 is opened is determined. More preferably, with respect to the cylinder 100 determined to be in the expansion stroke, the direct injection engine 12 is started or directly connected by performing fuel injection and ignition on the cylinder 100 whose crankshaft angle CA is in the expansion stroke. It is determined whether or not the angle is suitable for starting. For example, in the cylinder 100 determined to be in the expansion stroke, whether the angle after the crankshaft angle CA passes the top dead center (TDC) of the cylinder 100 is within an angle range of, for example, 30 ° to 60 °. Determine whether or not.

  The expansion stroke valve opening determination unit 82 determines whether the exhaust valve 108 corresponding to the cylinder 100 is in the process of stopping the direct injection engine 12 with respect to the cylinder 100 that is determined to be in the expansion stroke by the expansion stroke cylinder determination unit 80. It is determined whether or not the valve has been opened. That is, it is determined whether or not the exhaust valve 108 corresponding to the expansion stroke cylinder 100 is opened and the exhaust backflow to the cylinder 100 is detected. FIG. 6 is a cylinder phase diagram for explaining the behavior in the stopping process of the V-type 8-cylinder 4-cycle direct injection engine 12. As shown in FIG. 6, in the stopping process of the direct injection engine 12, after the fuel injection by the fuel injection device 46 and the ignition by the ignition device 47 are stopped, the expansion stroke cylinder K2 and the compression stroke cylinder K4 are stopped. Due to the pressure balance, the crankshaft 114 repeats normal rotation and reverse rotation and stops. That is, even after the fuel injection by the fuel injection device 46 and the ignition by the ignition device 47 are stopped, the rotational force of the crankshaft 114 due to inertia remains, and as shown in FIG. And the compression stroke cylinder K4 is rotated in the compression direction within the cylinder. That is, the crankshaft 114 is rotated in the forward rotation direction. As a result, as shown in FIG. 6B, the pressure in the expansion stroke cylinder K2 is reduced, and the pressure in the compression stroke cylinder K4 is increased. Therefore, on the contrary, as shown in FIG. 6C, the expansion stroke cylinder K2 is rotated in the compression direction in the cylinder and the compression stroke cylinder K4 is rotated in the expansion direction in the cylinder. That is, the crankshaft 114 is rotated in the reverse direction. 6 again, the state shown in FIG. 6 (a), the state shown in (a), the state shown in (b), the state shown in (c), the state shown in (a), and the crankshaft 114 rotating forward. And reverse rotation are gradually converged, and the direct injection engine 12 is stopped.

  FIG. 6B illustrates a state in which the crank angle CA in the expansion stroke cylinder K2 overshoots and advances to a phase corresponding to opening of the exhaust valve. For example, the expansion stroke valve opening determination unit 82 may perform the crank operation in the stopping process of the direct injection engine 12 with respect to the cylinder 100 (expansion stroke cylinder K2) that is determined to be in the expansion stroke by the expansion stroke cylinder determination unit 80. Based on the crank angle CA continuously detected by the angle sensor 58, it is determined whether or not the phase of the expansion stroke cylinder K2 has advanced to the phase corresponding to the exhaust valve opening even once. Preferably, when the phase of the expansion stroke cylinder K2 has advanced even once to the phase corresponding to the opening of the exhaust valve, the reverse flow of the exhaust with respect to the expansion stroke cylinder K2 is determined. Here, as described above, the crank angle sensor 58 is configured to detect the crank angle CA every 10 °, for example, and therefore it is preferable to add an error corresponding to such an angle. . In the present embodiment, the stop process of the direct injection engine 12 preferably means that the crankshaft after the fuel injection by the fuel injection device 46 and the ignition by the ignition device 47 are stopped by the engine stop control unit 76. The time when 114 is in a state of repeating forward rotation and reverse rotation is set as a start point, and the time when the state is converged and the crankshaft 114 is stopped is set as an end point. That is, the expansion stroke valve opening determination unit 82 preferably performs forward rotation of the crankshaft 114 after the fuel injection by the fuel injection device 46 and the ignition by the ignition device 47 are stopped for the expansion stroke cylinder K2. And the phase of the expansion stroke cylinder K2 corresponds to the opening of the exhaust valve at least once from the time when the state is repeated until the time when the state is converged and the crankshaft 114 is stopped. Judgment is made as to whether or not the phase has been reached.

  Returning to FIG. 1, in response to the restart request of the direct injection engine 12 by the hybrid control unit 72, the ignition start control unit 84 is determined to be in the expansion stroke by the expansion stroke cylinder determination unit 80. The direct injection engine 12 is controlled to start by performing fuel injection by the fuel injection device 46 and ignition by the ignition device 47 on the cylinder 100 (expansion stroke cylinder K2). For example, in the example shown in FIG. 4, fuel is injected from the fuel injection device 46 into the second cylinder K <b> 2 determined to be in the expansion stroke by the expansion stroke cylinder determination unit 80 and ignited by the ignition device 47. As a result, the first explosion (first explosion) is generated and the engine speed NE is raised, and then the second explosion is similarly generated in the third cylinder K3, and the third explosion is further performed in the fourth cylinder K4. An explosion occurs to further increase the engine speed NE. That is, the ignition start control unit 84 generates an initial explosion in the cylinder 100 determined to be in the expansion stroke by the expansion stroke cylinder determination unit 80, and then sequentially generates an explosion in the remaining cylinders 100. The direct injection engine 12 is started.

  With respect to the cylinder 100 that is determined to be in the expansion stroke by the expansion stroke cylinder determination unit 80, the ignition start control unit 84 opens the exhaust valve 108 corresponding to the cylinder 100 by the expansion stroke valve opening determination unit 82. When it is determined that the fuel injection has been performed, the start control of the direct injection engine 12 by prohibiting the fuel injection by the fuel injection device 46 and the ignition by the ignition device 47 for the cylinder 100 is prohibited. That is, when it is determined that the exhaust valve 108 corresponding to the expansion stroke cylinder K2 has been opened during the stop process of the direct injection engine 12, at least the expansion stroke cylinder when the direct injection engine 12 is restarted after being stopped. The fuel injection by the fuel injection device 46 for K2 is prohibited. In other words, when it is determined that the exhaust gas flows backward to the expansion stroke cylinder K2 while the direct injection engine 12 is stopped, the fuel injection by the fuel injection device 46 and the ignition by the ignition device 47 are performed for the cylinder 100. The start control of the direct injection engine 12 is prohibited. As shown in FIG. 6B, when the phase of the expansion stroke cylinder K2 advances to the exhaust valve opening due to overshoot during the stop process of the direct injection engine 12, exhaust gas flows into the expansion stroke cylinder K2. As a result, the oxygen concentration decreases. In this case, even if fuel injection and ignition are performed on such an expansion stroke cylinder K2, there is a high risk of ignition failure (misfire) due to insufficient oxygen. Therefore, when it is determined that the exhaust valve 108 corresponding to the expansion stroke cylinder K2 is opened during the stop process of the direct injection engine 12, fuel injection and ignition are performed on the expansion stroke cylinder K2. By prohibiting the direct connection start by, it is possible to suitably prevent the emission deterioration due to misfire at the time of restarting the direct injection engine 12 after being stopped.

  Preferably, the ignition start control unit 84 injects fuel into the cylinder 100 whose crankshaft angle CA is in the expansion stroke with respect to the cylinder 100 determined to be in the expansion stroke by the expansion stroke cylinder determination unit 80. And when it is determined that the angle is suitable for starting the direct injection engine 12 by performing ignition, that is, a direct connection start, the direct connection start based on the determination result by the expansion stroke valve opening determination unit 82 Perform (permit) or prohibit. Preferably, the expansion stroke cylinder determination unit 80 determines that the angle is not suitable for starting the direct injection engine 12 by performing fuel injection and ignition to the cylinder 100 in the expansion stroke, that is, direct start. In this case, the direct injection engine 12 is prohibited from starting by performing fuel injection and ignition on the expansion stroke cylinder 100 regardless of the determination result by the expansion stroke valve opening determination unit 82. Alternatively, the direct injection engine 12 is allowed to start by performing fuel injection and ignition on the expansion stroke cylinder 100 while receiving torque assist from the electric motor MG via an electric motor cranking control unit 88 described later. On the other hand, the start of the direct injection engine 12 by only performing fuel injection and ignition to the expansion stroke cylinder 100 is prohibited.

  The engine operation determination unit 86 determines whether or not the rotation of the direct injection engine 12 is continued when the ignition start control unit 84 controls the start of the direct injection engine 12. For example, it is determined on the basis of the signal Φ from the crank angle sensor 58 whether or not the rotation of the direct injection engine 12 continues after the initial explosion of the expansion stroke cylinder K2 by the ignition start control unit 84. Since the signal Φ is in a pulse form, the determination is made based on whether the signal Φ is input within a predetermined time of, for example, about 50 (ms).

  The electric motor cranking control unit 88 controls the cranking of the direct injection engine 12 by the electric motor MG. That is, when the direct injection engine 12 is started, the engine rotational speed NE is raised by controlling the torque of the electric motor MG to rotationally drive the crankshaft 114. For example, due to misfire or the like of the direct injection engine 12, the engine operation determination unit 86 determines that the rotation of the direct injection engine 12 does not continue after the first ignition operation by the ignition start control unit 84. In this case, the K0 clutch 34 is immediately engaged, and torque assist is performed by the electric motor MG so that the engine rotational speed NE of the direct injection engine 12 is increased again to a predetermined or higher self-operable rotational speed. The injection engine 12 is restarted.

  Even when the electric motor cranking control unit 88 determines that the rotation of the direct injection engine 12 continues after the initial explosion by the ignition start control unit 84 by the engine operation determination unit 86, for example, When it is determined that the engine rotational speed NE is relatively small and torque assist by the electric motor MG is necessary, in order to restart the direct injection engine 12 with as little electric energy as possible, The K0 clutch 34 is engaged and the electric motor MG at a timing at which the engine rotational speed NE rises or at any timing within the rising section M where the rising from the rising time continues. Torque assist is performed.

  In the start control of the direct injection engine 12, the electric motor cranking control unit 88 opens the exhaust valve 108 corresponding to the expansion stroke cylinder K2 during the stop process of the direct injection engine 12 by the expansion stroke valve opening determination unit 82. If it is determined, for example, that the start control of the direct injection engine 12 by performing fuel injection and ignition on the cylinder 100 in the expansion stroke by the ignition start control unit 84 is prohibited, The K0 clutch 34 is engaged, and start control of the direct injection engine 12 by the electric motor MG is performed. That is, the engine rotational speed NE is raised by controlling the torque of the electric motor MG to rotationally drive the crankshaft 114, and until the engine rotational speed NE reaches a preset self-operable rotational speed NE1, Alternatively, electric cranking control is performed to increase the autonomous driving possible rising speed dNE1 / dt.

  The restart control end determination unit 90 determines the end of start control (restart control after stop) of the direct injection engine 12 by the engine start control unit 78. For example, the engine rotation speed NE raised by at least one of ignition start control of the ignition start control unit 84, engagement of the K0 clutch 34 by the electric motor cranking control unit 88, and torque control by the electric motor MG is determined in advance. Whether or not the self-driving speed NE1 of about 400 (rpm) has been reached, or the rate of change (increase rate, that is, the rising speed) dNE / dt of the engine rotational speed NE is set in advance. Based on whether or not dNE1 / dt has been reached, the end of restart control of the direct injection engine 12 (for example, the end of torque assist control by the electric motor MG) is determined.

  The SOC determination unit 92 reduces the charged amount SOC of the battery 44 detected by the SOC sensor 60 to a threshold value Sb that is a lower limit value for performing start control of the direct injection engine 12 by driving the electric motor MG. Determine whether or not. The threshold value Sb is, for example, that the direct-injection engine 12 is started by controlling the torque of the electric motor MG by the electric motor cranking control unit 88 (the engine rotational speed NE is raised up to an autonomous operation possible speed). This corresponds to the minimum amount of electricity that can be stored, and is predetermined according to the specifications of the direct injection engine 12.

  Preferably, the electric motor cranking control unit 88 is configured such that when the fuel injection to the expansion stroke cylinder K2 is prohibited by the ignition start control unit 84, the SOC determination unit 92 determines the charged amount SOC of the battery 44. When it is determined by the electric motor MG that the electric power storage MG has decreased to the minimum storage amount Sb for starting the direct injection engine 12, the electric motor cranking control unit 88 drives the electric motor MG at that time (torque control). The direct injection engine 12 is started. When the engine start is prohibited by fuel injection and ignition for the expansion stroke cylinder K2, EV running is performed until the storage amount SOC of the battery 44 becomes less than the minimum storage amount Sb for starting the direct injection engine 12 by the electric motor MG. If it continues, it becomes impossible to start the direct injection engine 12 due to cranking of the electric motor MG, but when the charged amount SOC of the battery 44 reaches the minimum charged amount Sb, the electric motor cranking control unit 88. Thus, the direct injection engine 12 can be restarted by starting the direct injection engine 12 by driving the electric motor MG.

  The threshold value Sb is preferably determined in consideration of the starting assist force of the electric motor MG when the ignition start control unit 84 fails to fire (misfire) of the first explosion due to fuel injection and ignition to the expansion stroke cylinder K2. It may be a thing. That is, the threshold value Sb is obtained by controlling the torque of the electric motor MG by the electric motor cranking control unit 88 when the ignition start control unit 84 fails to perform the initial explosion due to fuel injection and ignition to the expansion stroke cylinder K2. The direct injection engine 12 may be started up (corresponding to a minimum power storage amount capable of starting the engine rotation speed NE up to an autonomous operation possible speed).

  FIG. 7 is a flowchart for explaining a main part of the engine stop / restart control of this embodiment by the electronic control unit 70, which is repeatedly executed at a predetermined cycle.

  First, in step S1 (hereinafter, step is omitted), an eco-run stop request issued when an idle stop condition such as accelerator off, vehicle speed zero, D range, brake on, or the like is satisfied, or the motor from the engine running area during running It is determined whether or not there has been an engine stop request for stopping the driving (rotation) of the direct injection engine 12, such as an engine stop request at the time of switching to the travel region. If the determination in S1 is negative, the determination is made to wait by repeating the determination in S1, but if the determination in S1 is affirmative, fuel supply and ignition to the direct injection engine 12 are performed in S2. Is stopped, and the rotation of the direct injection engine 12 is stopped, and when the drag resistance of the direct injection engine 12 needs to be reduced, except when the engine brake is required, the K0 clutch 34 is Be released. In the stopping process of S2, the crank angle CA detected by the crank angle sensor 58 is continuously detected every very short predetermined time and stored in the RAM or the like.

  Next, in S <b> 3, based on the signal Φ from the crank angle sensor 58, the cylinder 100 in the expansion stroke among the plurality of cylinders 100 provided in the direct injection engine 12 is detected. Next, in S4, based on the transition of the crank angle CA in the stopping process of the direct injection engine 12 stored in the RAM or the like corresponding to the cylinder 100 in the expansion stroke detected in S3, the It is detected whether or not the exhaust valve 108 corresponding to the cylinder 100 in such an expansion stroke is opened in the stop process of the injection engine 12. Next, in S5, based on the detection result in S4, it is determined whether or not the exhaust valve 108 corresponding to the cylinder 100 in the expansion stroke is opened in the stopping process of the direct injection engine 12. When the determination of S5 is affirmed, the processes after S13 are executed. When the determination of S5 is negative, the processes after S6 are executed.

  In S6, it is determined whether or not an engine restart request has occurred due to brake-off at idle stop, switching from the motor travel region to the engine travel region, or the like. If the determination in S6 is negative, the determination is made to stand by by repeating the determination in S6. If the determination in S6 is affirmative, in S7, the cylinder in the expansion stroke detected in S3. 100 (for example, the second cylinder K2 shown in FIG. 4) is injected with fuel from the fuel injection device 46 and ignited by the ignition device 47, thereby generating an initial explosion (first explosion), and the engine speed NE. 4 is subsequently started, and similarly, a second explosion is caused in the third cylinder K3 shown in FIG. 4, and a third explosion is caused in the fourth cylinder K4 shown in FIG. Further launch.

  Next, in S8, for example, the crank angle CA detected by the crank angle sensor 58 is changed (increased) to determine whether or not the engine speed NE is maintained after the first explosion and the direct injection engine 12 is operating. Whether or not the pulse signal Φ is supplied from the crank angle sensor 58. If the determination in S8 is negative, the processing from S11 is executed, but if the determination in S8 is affirmative, in S9, the direct injection engine 12 is in a state where it can operate independently (autonomous). It is determined whether it has been reached. That is, whether or not the engine rotational speed NE detected by the engine rotational speed sensor 50 has reached the self-operable rotational speed NE1 set to about 400 rpm in advance, or the rate of change (increase speed) of the engine rotational speed NE. It is determined whether or not dNE / dt has reached a preset autonomous driving possible rising speed dNE1 / dt. If the determination in S9 is negative, the processing from S12 is executed, but if the determination in S9 is affirmative, torque assist (cranking) by the electric motor MG is terminated in S10. Thus, the torque assist when the direct injection engine 12 is restarted is terminated. That is, after the restart control of the direct injection engine 12 is terminated, this routine is terminated.

  In S11, for example, it is determined whether or not a certain standby time set in advance to about 50 (ms) has elapsed since the negative determination in S8. If the determination in S11 is negative, S8 and subsequent steps are repeatedly executed. If the determination in S11 is affirmative, the engagement of the K0 clutch 34 and the torque generated by the electric motor MG are immediately determined in S12. After the assist is executed and the engine rotational speed NE is raised by the torque assist of the electric motor MG, the processing from S9 is executed.

  In S13, starting of the direct injection engine 12 by fuel injection and ignition with respect to the cylinder 100 in the expansion stroke detected in S3 is prohibited. Next, in S14, the charged amount SOC of the battery 44 detected by the SOC sensor 60 is lowered to a threshold value Sb which is a lower limit value for performing start control of the direct injection engine 12 by driving the electric motor MG. It is determined whether or not. If the determination of S14 is negative, the determination is made to wait by repeating the determination of S14. However, if the determination of S14 is affirmative, the engagement of the K0 clutch 34 and the After the torque control by the electric motor MG is executed and the engine rotational speed NE is raised by the cranking by the torque of the electric motor MG, the processing from S9 is executed.

  In the above control, S1 and S6 are the operation of the hybrid control unit 72, S2 is the operation of the engine stop control unit 76, S3 to S15 are the operation of the engine start control unit 78, and S3 is the expansion stroke cylinder. In the operation of the determination unit 80, S4 and S5 are the operation of the expansion stroke valve opening determination unit 82, S7 and S13 are the operation of the ignition start control unit 84, S8 is the operation of the engine operation determination unit 86, S12 And S15 correspond to the operation of the electric motor cranking control unit 88, S9 and S10 correspond to the operation of the restart control end determination unit 90, and S14 correspond to the operation of the SOC determination unit 92, respectively.

  Thus, according to the present embodiment, when the exhaust valve 108 corresponding to the cylinder 100 in the expansion stroke is opened in the stop process of the direct injection engine 12 that is an internal combustion engine, the direct injection engine 12 is opened. Since the fuel injection to the cylinder 100 in the expansion stroke is prohibited at the time of restart of the engine, when the direct injection engine 12 is restarted after being stopped, the ignition is expected to fail due to insufficient oxygen amount or the like. Since the fuel injection to the cylinder 100 in the expansion stroke is not performed, it is possible to suitably prevent the deterioration of the emission due to the misfire at the time of restart. That is, it is possible to provide the electronic control device 70 as a start control device for the direct injection engine 12 that suppresses ignition failure and realizes a suitable start.

  The direct injection engine 12 is connected to an electric motor MG that drives the direct injection engine 12 by electric energy supplied from a battery 44 as a power storage device via a K0 clutch 34, and is a cylinder in the expansion stroke. When the fuel injection to the battery 100 is prohibited, if the storage amount SOC of the battery 44 is reduced to the minimum storage amount Sb for driving the direct injection engine 12 by the electric motor MG, the driving of the electric motor MG is performed at that time. Since the direct injection engine 12 is started by the above, in the state where the fuel injection to the cylinder 100 in the expansion stroke is prohibited, the occurrence of shock at the start of the direct injection engine 12 can be suitably suppressed. .

  The preferred embodiments of the present invention have been described in detail with reference to the drawings. However, the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the present invention. Is.

  12: direct injection engine (internal combustion engine), 44: battery (power storage device), 70: electronic control device (starting control device), 100: cylinder, 108: exhaust valve, MG: electric motor

Claims (2)

A start control device for an internal combustion engine for a vehicle that starts the internal combustion engine by injecting and igniting an expansion stroke cylinder when the internal combustion engine of the type in which fuel is directly injected into the cylinder is restarted after being stopped. And
When the exhaust valve corresponding to the expansion stroke cylinder is opened in the stop process of the internal combustion engine, fuel injection to the expansion stroke cylinder is prohibited when the internal combustion engine is restarted Start control device.   The internal combustion engine is connected to an electric motor that drives the internal combustion engine by electric energy supplied from the power storage device, and when the fuel injection to the expansion stroke cylinder is prohibited, the power storage amount of the power storage device is the motor. 2. The start control of the internal combustion engine for a vehicle according to claim 1, wherein the internal combustion engine is started by driving the electric motor at that time when the amount of charge is reduced to a minimum amount for driving the internal combustion engine. apparatus.

Images