WO2013030986A1

WO2013030986A1 - Engine stop control device for hybrid vehicle

Info

Publication number: WO2013030986A1
Application number: PCT/JP2011/069794
Authority: WO
Inventors: 小島　進; 直器仲西; 幸彦出塩
Original assignee: トヨタ自動車株式会社
Priority date: 2011-08-31
Filing date: 2011-08-31
Publication date: 2013-03-07

Abstract

A hybrid vehicle (10) comprises an eight-cylinder direct-injection engine (12) in which, if it is assumed that the piston (110) of one of the cylinders (100) has stopped at the compression TDC, the immediately preceding cylinder (100) is in the expansion stroke and the exhaust valve (108) thereof is in a closed state. In this hybrid vehicle, at the time of stopping the direct-injection engine (12) by disconnecting a K0 clutch (34) during vehicle drive, the piston (110) of one of the cylinders (100) is made to stop at a crank angle (Φ) near the compression TDC thereof by temporarily connecting the once-disconnected K0 clutch (34) and rotating the crankshaft (114). In this case, the crank angle (Φ) of the immediately preceding cylinder (100) will be around 90° greater than the compression TDC, and ignition startup can be performed suitably by injecting fuel into and igniting this cylinder (100). Because ignition startup can be performed even in cases where one of the cylinders (100) has been stopped at an intermediate position in the expansion stroke (around 45° greater than the compression TDC), the application range of ignition startup is widened and the degree of freedom in control is increased.

Description

Engine stop control device for hybrid vehicle

The present invention relates to an engine stop control device for a hybrid vehicle including a direct injection engine capable of starting ignition.

(a) A four-cycle direct injection engine that has multiple cylinders and directly injects fuel into the cylinder, and (b) a disconnect that connects (connects and disconnects) the direct injection engine to the power transmission path. And (c) a rotating machine that functions as at least an electric motor, and (d) a hybrid vehicle that can use the direct injection engine and the rotating machine as a driving force source for traveling. Yes. The hybrid vehicle described in Patent Document 1 is one example, and a friction clutch is connected (friction engagement) while a motor traveling using only a rotating machine as a driving force source to rotate a crankshaft of a direct injection engine, By adjusting so that the piston of the cylinder of the cylinder has a predetermined crank angle that is an intermediate position of the expansion stroke (explosion stroke), at the start of the engine, fuel is injected into the cylinder in the expansion stroke and ignition is started. The technology is described. In some cases, such as when the friction of a direct injection engine is small, the engine can be started on its own by just starting the ignition, but if necessary, it is possible to connect a connecting / disconnecting device when starting the engine and assist cranking with a rotating machine. Thus, the assist torque can be greatly reduced by starting ignition. As a result, the maximum torque of the rotating machine can be reduced, and the size and fuel consumption can be reduced.

Special table 2009-527411

By the way, such a conventional ignition start is performed at a crank angle at which the piston of any cylinder is at an intermediate position of the expansion stroke, and the compression TDC (Top Dead), which is the top dead center after the compression stroke, is performed. At the crank angle where the piston stops near the Center (top dead center), it was impossible to start ignition. Therefore, it is necessary to adjust the crank angle so that the piston of any cylinder is always in the middle of the expansion stroke. For example, when the piston of any cylinder stops near the compression TDC, It was necessary to rotate the crankshaft so as to advance to an intermediate position in the expansion stroke.

On the other hand, according to experiments and research conducted by the present inventors, it has been found that even when the piston of any cylinder stops near the compression TDC, ignition can be started under certain conditions. The present invention has been made on the basis of such knowledge, and its object is to expand the application range of ignition start and improve the degree of freedom of control.

In order to achieve this object, the first invention has (a) a four-cycle direct injection engine having a plurality of cylinders and directly injecting fuel into the cylinders, and (b) a power transmission to the direct injection engine. A connection / disconnection device that connects / disconnects to / from the path, and (c) a rotating machine that functions as at least an electric motor, and (d) uses the direct injection engine and the rotating machine as a driving force source for traveling. In a hybrid vehicle that can be used, (e) when stopping the direct-injection engine by stopping the connection / disconnection device during traveling, the connection / disconnection device once disconnected is temporarily connected to the crankshaft of the direct-injection engine. (F) The crank angle at which the crankshaft is stopped is that the piston of any cylinder has stopped at the compression TDC, which is the top dead center after the compression stroke. Assumed And exhaust valves of any other cylinder in the expansion stroke, characterized in that the determined at different angles depending on whether a closed state.

According to a second aspect of the present invention, in the engine stop control device for a hybrid vehicle according to the first aspect, the direct injection engine has six or more cylinders and the piston of any cylinder is assumed to have stopped at the compression TDC. When any cylinder is in the expansion stroke and the exhaust valve is closed, the crankshaft is stopped at a crank angle at which the piston of any cylinder is in the vicinity of its compression TDC.

According to a third aspect of the present invention, in the engine stop control device for a hybrid vehicle according to the first aspect, the direct injection engine has a number of cylinders of six cylinders or less, and when the piston of any cylinder is stopped at the compression TDC, When none of the cylinders is in the expansion stroke and does not satisfy the ignition start condition in which the exhaust valve is closed, the piston of any cylinder passes through the compression TDC and has a crank angle at which the intermediate position of the expansion stroke is reached. The crankshaft is stopped.

That is, even if the piston of any cylinder stops at the compression TDC, if any other cylinder is in the expansion stroke and the exhaust valve is closed, if fuel is injected into the cylinder and ignited, The engine can be started (ignition start) by pushing and moving the piston by explosion expansion. Therefore, when stopping the direct injection engine by shutting off the connecting / disconnecting device during traveling, temporarily connecting the disconnected / connecting device to rotate the crankshaft and stopping at a predetermined crank angle The crank angle at which the crankshaft is stopped is different depending on whether any other cylinder is in the expansion stroke and the exhaust valve is closed when it is assumed that the piston of any cylinder is stopped at the compression TDC. By setting the angle, it is possible to start ignition properly in any case. Thereby, the application range of ignition start is expanded and the degree of freedom of control is increased.

The second aspect of the invention is a case where a direct injection engine having 6 cylinders or more is provided. When it is assumed that the piston of any cylinder stops at the compression TDC, any other cylinder is in the expansion stroke and the exhaust valve is closed. In this case, since the crankshaft is stopped at a crank angle at which the piston of any cylinder is in the vicinity of its compression TDC, proper ignition start is performed by injecting fuel into the cylinder with the exhaust valve closed in the expansion process. It can be carried out. In that case, depending on conditions such as the timing of opening the exhaust valve and the number of cylinders, the amount of air in the cylinder increases compared to when stopping at an intermediate position of the expansion stroke that has passed through the compression TDC as in the third aspect of the invention. In some cases, a large rotational energy can be obtained at the first explosion, and the assist torque by the rotating machine at the time of starting can be further reduced.

The third invention is a case where a direct injection engine of 6 cylinders or less is provided, and when any of the other cylinders does not satisfy the ignition start condition when it is assumed that the piston of any cylinder stops at the compression TDC, Since the ignition start cannot be performed when the crankshaft is stopped at the compression TDC, the crankshaft is stopped at a crank angle at which the piston of any cylinder passes through the compression TDC and becomes an intermediate position in the expansion stroke. Thereby, ignition start can be performed similarly to the past.

It should be noted that both the second and third inventions include 6 cylinders. For example, in the case of 6 cylinders, if the cylinders are sequentially exploded at a uniform crank angle interval, the deviation of the crank angle of each cylinder is 720 °. ÷ 6 = 120 °, and assuming that the piston of any cylinder stops at compression TDC, the crank angle of the preceding cylinder is about compression TDC + 120 °, whereas the opening timing of the exhaust valve is compression TDC This is because both the second and third inventions can be applied depending on the opening timing angle of the exhaust valve.

It is the schematic block diagram which showed the principal part of the control system | strain in addition to the main point figure of the hybrid vehicle to which this invention is applied suitably. It is sectional drawing explaining the direct-injection engine of the hybrid vehicle of FIG. 2 is a flowchart for specifically explaining the operation of an engine stop control means functionally included in the electronic control device of FIG. 1. It is an example of the time chart which shows the change of the operation state of each part when engine stop control is performed according to the flowchart of FIG. FIG. 6 is a diagram for explaining the operation of a V-type 8-cylinder engine, in which (a) 程 is a stroke diagram showing the operating state of eight cylinders, and (b) is a diagram explaining the operating state of a cylinder in the vicinity of (a) 時 when TDC is stopped. (C) is a diagram for explaining the operating state of the cylinder in the vicinity of the 45 ATDC stop in a (a). 5 is a diagram for explaining ignition start from the time of TDC stop in FIG. 5, (a) is a diagram for explaining the state change of the cylinder near the compression TDC, (b) corresponds to the change in the operating state of each part with (a). It is an example of the time chart shown. FIG. 5 is a diagram for explaining ignition start from 45ATDC stop in FIG. 5, (a) is a diagram for explaining a change in the state of a cylinder in the vicinity of the compression TDC, (b) を is a diagram corresponding to (a) It is an example of the time chart shown. It is a figure explaining the piston position of the cylinder immediately before when it assumes that the piston of any cylinder of the direct-injection engine of various cylinder numbers stopped by compression TDC (0 degree). It is a figure which shows the result of having calculated | required the relationship between the crank angle (0 degree = compression TDC) in an expansion stroke, and the positional energy (pumping energy) by pumping in the direct-injection engine of various cylinder numbers. FIG. 5 is a diagram illustrating the operation of an in-line four-cylinder engine, where (a) is a stroke diagram illustrating the operating state of four cylinders, and (b) is a diagram illustrating the operating state of a cylinder in the vicinity of (a) when TDC stops. (C) is a diagram for explaining the operating state of the cylinder in the vicinity of the 90 ATDC stop in (a). It is a figure explaining the engine stop control at the time of applying this invention to the hybrid vehicle which has a 4-cylinder engine of FIG. 10, and is a flowchart used instead of FIG. It is an example of the time chart which shows the change of the operation state of each part when engine stop control is performed according to the flowchart of FIG.

The present invention is applied to various types of hybrid vehicles such as a parallel type, a series type, a split type, a one-motor type, and a two-motor type in which a direct injection engine is connected to a power transmission path by a connecting / disconnecting device. The present invention is applied to engine stop control when stopping a direct injection engine in a motor travel mode in which only a rotating machine is used as a driving force source or during vehicle deceleration. As the connecting / disconnecting device, a single-plate type or multi-plate type friction engagement clutch is preferably used, but the direct injection engine can be connected to a power transmission path to rotate or the power transmission can be cut off. Various means can be employed.

The hybrid vehicle of the present invention can use a direct-injection engine and a rotating machine as a driving power source for traveling, and the rotating machine can alternatively use the functions of both an electric motor and a generator. A motor generator is preferably used. As the direct injection engine, engines having various numbers of cylinders such as 2 cylinders, 3 cylinders, 4 cylinders, 5 cylinders, 6 cylinders, 7 cylinders, 8 cylinders, and 12 cylinders can be used.

When stopping the direct injection engine, a connecting / disconnecting device is temporarily connected to rotate the crankshaft, but immediately after the engine stops, a pumping action (a spring-like action due to compression of air in the cylinder) is generally obtained. As shown in FIG. 9, the pumping energy (positional energy) varies depending on the crank angle, and there are positions where it is easy to stop and positions where it is difficult to stop. That is, it is difficult to stop at the part where the pumping energy is changing, and it is easy to stop at the low and flat minimum region, so the connection of the connecting / disconnecting device to stop the crankshaft at a predetermined angle in consideration of the pumping energy It is desirable to determine timing, connection torque, and connection time. The connection timing of the connecting / disconnecting device may be before the crankshaft is completely stopped or after it is completely stopped. Although it is desirable to rotate the crankshaft by connecting the connecting / disconnecting device within the time when the pumping action can be obtained, it can be done after the pumping action is no longer obtained. The present invention can be applied even when it is not possible.

The crank angle at which the crankshaft is stopped satisfies the ignition start condition in which any of the cylinders is in the expansion stroke and the exhaust valve is closed when it is assumed that the piston of any of the cylinders stops at the compression TDC. Specifically, when any other cylinder satisfies the ignition start condition as in the second invention, the crank angle at which the piston of any cylinder is near its compression TDC is determined. When the shaft is stopped while none of the other cylinders satisfies the ignition start condition as in the third invention, the piston of any cylinder passes through the compression TDC at a crank angle at which the intermediate position of the expansion stroke is reached. Stop the crankshaft. If there is a variable valve timing device that changes the closing timing of the exhaust valve, and the above determination differs depending on the closing timing of the exhaust valve, for example, it is determined whether or not the ignition start condition is satisfied based on the earliest closing timing Although the stop position of the crankshaft may be determined, switching means for switching the crank angle for stopping the crankshaft according to the actual closing timing of the exhaust valve may be provided.

When any one of the other cylinders is in the expansion stroke and the exhaust valve is closed, that is, when the ignition start condition is satisfied as in the second aspect of the invention, the crank angle at which the piston of any cylinder is always near the compression TDC Although the crankshaft may be stopped, as in the case of the third invention, the ignition is started even when the piston of any cylinder passes through the compression TDC and stops at the crank angle at the intermediate position of the expansion stroke. It is possible to perform both of them depending on conditions. When the crankshaft is stopped in the vicinity of the compression TDC as in the second invention, there is a peak of pumping energy near the compression TDC (crank angle = 0 ° in FIG. 9) due to the pumping action, but for example ± 10 of the compression TDC. If it is within a range of about 0 °, the crankshaft can be stopped by the balance in the rotational direction and the friction of the engine. Further, since the crankshaft rotates reversely by the pumping action before the compression TDC, it is desirable to connect the connecting / disconnecting device and rotate the crankshaft to the vicinity of the compression TDC before starting the reverse rotation. The vicinity of the compression TDC means that the crankshaft stops in such a state that it rides on the peak of the pumping energy, and is usually within a range of about compression TDC ± 10 °.

In the third aspect of the invention, the crankshaft is stopped at a crank angle at which the piston of any cylinder passes through the compression TDC and becomes an intermediate position in the expansion stroke. The pumping energy shown in FIG. Therefore, it is desirable that the pumping energy is set within a flat and minimal region. Further, in order to start ignition, it is necessary that the intake valve is in the expansion stroke and the intake valve is closed. In order to obtain a large rotational energy by explosion, the intake valve is rotated by a predetermined angle from the compression TDC and from the opening timing angle (EVO) of the intake valve. The range up to several tens of degrees is desirable. That is, in the case of a two-cylinder engine to a four-cylinder engine, for example, a range of about 50 ° to 120 ° (or EVO-20 °) from the compression TDC (crank angle Φ = 0 ° in FIG. 9) is appropriate. A range of about 110 ° is desirable. In the case of a 6-cylinder engine, for example, a range of about 40 ° to 80 ° from the compression TDC is appropriate, and a range of about 60 ° to 80 ° is desirable. In the case of the 4-cylinder engine and the 6-cylinder engine, as apparent from FIG. 9, the pumping energy is automatically stopped at the valley portion where the pumping energy is low. It is also possible to simply disengage from the vicinity and stop at any intermediate position.

When it is assumed that the piston of any cylinder has stopped at the compression TDC, it is not always necessary to determine whether any other cylinder is in the expansion stroke and the ignition start condition is satisfied with the exhaust valve closed. It is not necessary to determine whether or not the ignition start condition is satisfied for the cylinder. That is, when the cylinder immediately preceding the cylinder stopped at the compression TDC is normally in the expansion stroke and the cylinder exceeds the expansion stroke, none of the cylinders satisfy the ignition start condition. It is only necessary to determine whether or not the immediately preceding cylinder satisfies the ignition start condition, and the immediately preceding cylinder is selected as the cylinder that is ignited by fuel injection when the engine is restarted. However, in the case of a multi-cylinder engine of 12 cylinders or more, there are cases where a plurality of cylinders are positioned in the expansion stroke and satisfy the ignition start condition, in which case, a cylinder that can obtain larger rotational energy at the start of ignition is selected, All cylinders that satisfy the ignition start condition may be ignited.

Hereinafter, 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. The hybrid vehicle 10 includes a direct injection engine 12 that directly injects fuel into a cylinder and a motor generator 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 motor generator 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 to the output shaft 22, the difference It is transmitted to the left and right drive wheels 26 via the dynamic gear device 24. 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 jet engine 12 and the motor generator MG. Motor generator MG corresponds to a rotating machine.

A K0 clutch 34 is provided between the direct injection engine 12 and the motor generator MG via a damper 38 to directly connect them. The K0 clutch 34 is a single-plate or multi-plate friction clutch that is frictionally engaged by a hydraulic cylinder, and is engaged and released by the hydraulic control device 28. In the present embodiment, the K0 clutch 34 is disposed in the oil chamber 40 of the torque converter 14. It is arranged in an oil bath state. The K0 clutch 34 is a hydraulic friction engagement device, and functions as a connection / disconnection device that connects or disconnects the direct injection engine 12 with respect to the power transmission path. Motor generator MG is connected to battery 44 via inverter 42. Further, the automatic transmission 20 is 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 subjected to engagement / release control by the hydraulic control device 28.

Here, the direct injection engine 12 has a plurality of cylinders that are sequentially exploded at a uniform crank angle interval. In this embodiment, a V-type 8-cylinder four-cycle gasoline engine is used. As specifically shown, gasoline (high-pressure fine particles) is directly injected into the cylinder (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 this 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 adjustment valve, via a surge tank 103. From the intake passage 102 to the cylinder according to the opening of the electronic throttle valve 45 (throttle valve opening). The amount of intake air flowing into 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 crankpin 116 of the crankshaft 114 via a connecting rod 112 so as to be relatively rotatable. Along with the reciprocation, the crankshaft 114 is rotationally driven as indicated by an arrow R. The crankshaft 114 is rotatably supported by a bearing in the journal portion 118, and integrally includes a crank arm 120 that connects the journal portion 118 and the crankpin 116.

In such a direct injection engine 12, the crankshaft 114 is rotated twice (720 °), and the intake stroke, the compression stroke, the expansion (explosion) stroke, and the exhaust stroke are performed. The shaft 114 is continuously rotated. The pistons 110 of the eight cylinders 100 are configured such that the crank angles are shifted by 90 °, and the eight cylinders 100 are sequentially exploded and rotated each time the crankshaft 114 rotates 90 °. Torque is generated. Further, the expansion stroke in which the crankshaft 114 rotates by a predetermined angle from the compression TDC in which the piston 110 of any cylinder 100 reaches the TDC (top dead center) after the compression stroke, and both the intake valve 104 and the exhaust valve 108 are closed. When the fuel is stopped within the predetermined angle range, gasoline is injected into the cylinder 100 by the fuel injection device 46 and ignited by the ignition device 47, whereby the mixture in the cylinder 100 is ignited to start combustion. Start is possible. When the friction (friction) of each part of the direct injection engine 12 is small, the direct injection engine 12 can be started only by ignition start. However, even when the friction is large, the start assist when cranking and starting the crankshaft 114 is started. Since the torque can be reduced, the maximum torque of the motor generator MG that generates the assist torque is reduced, and the size and fuel consumption can be reduced.

FIG. 5 is a diagram for explaining the operation of the direct injection engine 12 in more detail. FIG. 5A is a stroke diagram showing the operation state of the eight cylinders 100 in relation to the crank angle Φ. The lower cylinder 100 is operated in advance. That is, in the order of cylinder No 2 → No 4 → No 5 → No 6 → No 3 → No 7 → No 8 → No 1, every time the crank angle Φ rotates 90 °, the crankshaft 114 is continuously rotated. (b) indicates the operating state of the cylinder 100 near the compression TDC when the TDC is stopped in (a) 何れ, that is, when any cylinder 100 is stopped near the compression TDC, with compression TDC = 0 ° as a reference. In this figure, the No. 5 cylinder 100 is compression TDC, the crank angle Φ of the preceding No. 4 cylinder 100 is about 90 °, and the crank angle Φ of the No. 6 cylinder 100 immediately after is about −90 °. is there. In this case, the No. 4 cylinder 100 is in the expansion stroke, and the exhaust valve 108 is closed before the opening timing angle EVO (for example, 110 ° to 160 °) of the exhaust valve 108. Therefore, as shown in FIG. The fuel can be injected into the cylinder 100 and ignited to start (ignition start). “IVC” is a closing timing angle of the intake valve 104 in the compression process, and the intake valve 104 is closed in the expansion stroke.

FIG. 9 shows a result obtained by calculating approximately the relationship between the crank angle (0 ° = compression TDC) Φ in the expansion stroke and the positional energy (pumping energy) by pumping in the direct injection engine 12 having various numbers of cylinders. FIG. The pumping energy is potential energy generated by the action of an air spring generated when the air sucked into the cylinder 100 is compressed in the compression stroke. In any case, there is a mountain near the compression TDC. There is a high possibility that the crankshaft 114 stops in a low flat minimum region between them (see (c) in FIG. 5), but it stops in the vicinity of the compression TDC with a probability of about 10%. That is, since the rotational direction changes near the top of the pumping energy peak, the crankshaft 114 stops in a state where it rides on the pumping energy peak due to the balance of the rotational direction and the friction of the direct injection engine 12. In other words, even when the crankshaft 114 stops at the intermediate position shown in FIG. 5 (c), by applying rotational torque to the crankshaft 114, as shown in FIG. Therefore, the stop position of the crankshaft 114 can be positively adjusted so that it stops near the compression TDC. The graph of FIG. 9 is obtained approximately and is not necessarily accurate, and varies depending on the specifications of each part of the direct injection engine 12 and the opening / closing timing of the intake valve 104 and the exhaust valve 108. It can be considered as shown in FIG.

FIG. 6 shows a case where the ignition is started in a state where the piston 110 of the No. 4 cylinder 100 is stopped at a crank angle Φ of about 90 ° (more precisely, compression TDC + 90 °) as shown in FIG. (A) is a diagram for explaining the state change of the cylinder 100 in the vicinity of No4, (b) の一 is an example of a time chart showing the change in the operating state of each part, both parenthesized symbols correspond to each other. That is, when the direct injection engine 12 stopped in the state of (i) is started again at the time of transition to the engine running mode, at the time of accelerator operation, at the time of starting, etc., as shown in (ii) The fuel is injected into the No. 4 cylinder 100 and ignited to start (ignition start). When the piston 110 is pushed down by the explosion and expansion of the gas in the No. 4 cylinder 100, the crankshaft 114 starts to rotate as shown in (iii), and the subsequent No. 5 cylinder 100 becomes negative pressure by the expansion. On the other hand, the subsequent No. 6 cylinder 100 is pressurized by compression. The crank angle Φ at the beginning of ignition of the No. 4 cylinder 100 is about 90 °, and a relatively large amount of air is present in the cylinder 100. Therefore, a relatively large explosion energy is obtained, and the negative pressures of the No. 5 and No. 6 cylinders 100 are obtained. Regardless of the increase in pressure or the increase in pressure, the crankshaft 114 can be initially rotated only by this explosion energy. It should be noted that at the beginning of restart, all cylinders 100 are at substantially atmospheric pressure.

(iv) shows that the pressure in the No. 4 cylinder 100 decreases while the crankshaft 114 further rotates and reaches the EVO where the exhaust valve 108 opens, while the No. 5 and No. 6 cylinders 100 are further reduced in pressure and pressure. Therefore, the rotational resistance (load) of the direct injection engine 12 increases. Therefore, the rotation (cranking) of the crankshaft 114 is assisted by the motor generator MG slightly before the exhaust valve opening timing angle EVO. While the vehicle is running, the crankshaft 114 can be assisted by the kinetic energy of the vehicle, but the torque of the motor generator MG is increased and controlled as necessary to suppress fluctuations in the driving force. When the vehicle is stopped, the motor generator MG assists. A K0 clutch 34 is disposed between the direct injection engine 12 and the motor generator MG. When the K0 clutch 34 is disconnected, the direct injection engine 12 is disconnected from the power transmission path and stopped. . Further, by connecting the K0 clutch 34, it is possible to assist the motor generator MG and the kinetic energy of the vehicle.

After that, as shown in (v) IV, when the No. 6 cylinder 100 exceeds the compression TDC, the No. 6 cylinder 100 is ignited to explode, and the crankshaft 114 is driven with a large rotational torque by the explosion energy of the No. 6 cylinder 100. Can be rotated. As a result, as shown in (vi), the crankshaft 114 is appropriately rotated by the explosion energy of the No. 6 cylinder 100 regardless of whether the No. 5 or No. 3 cylinders 100 located at the front and rear are made negative or high in pressure. , The cylinder 100 is stably rotated by causing the subsequent cylinder 100 to explode every 90 °. That is, as shown in (v), if the crankshaft 114 rotates until the No. 6 cylinder 100 exceeds the compression TDC, then the crankshaft 114 can be rotated by itself, and the No. 6 cylinder 100 until the No. 6 cylinder 100 exceeds the compression TDC. The direct injection engine 12 can be appropriately started to start ignition simply by assisting cranking by the motor generator MG over an angle range of about 50 ° to 60 °.

Referring back to FIG. 5, (c) 作動 is the operating state of the cylinders 100 before and after 45ATDC in (a) 停止, that is, when any cylinder 100 is stopped at an intermediate position of about 45 ° from the compression TDC. Is shown on the basis of compression TDC = 0 °, in which the No. 7 cylinder 100 stops at about 45 °. Further, the crank angle Φ of the immediately preceding No. 3 cylinder 100 is about 135 °, and the crank angle Φ of the immediately following No. 8 cylinder 100 is about −45 °. In this case, the No. 7 cylinder 100 is in the expansion stroke, and the exhaust valve 108 is closed before the opening timing angle EVO (for example, 110 ° to 160 °) of the exhaust valve 108. Therefore, as shown in FIG. The fuel can be injected into the cylinder 100 and ignited to start (ignition start). In the immediately preceding No. 3 cylinder 100, the exhaust valve 108 is closed and ignition can be started. However, since the exhaust valve 108 opens with a slight rotation, sufficient rotational energy cannot be obtained. As is apparent from the characteristics of the pumping energy shown in FIG. 9, if nothing is done, the crank angle Φ at which any one of the cylinders 100 becomes an intermediate position in the vicinity of 45 ° as shown in FIG. As shown in FIG. 5B, when the crankshaft 114 is stopped in the vicinity of the compression TDC as shown in FIG. 5B, a rotational torque is applied to the crankshaft 114, as shown in FIG. The stop position of the crankshaft 114 can be positively adjusted so that any one of the cylinders 100 stops at the intermediate position.

FIG. 7 shows a case where ignition is started in a state where the piston 110 of the No. 7 cylinder 100 is positioned at a crank angle Φ of about 45 ° (more precisely, compression TDC + 45 °) as described above. The figure explaining the state change of the cylinder 100, (b) is an example of a time chart showing the change in the operating state of each part, and the reference numerals in parentheses correspond to each other. That is, when the direct injection engine 12 stopped in the state of (i) is started again at the time of transition to the engine running mode, at the time of accelerator operation, at the time of starting, etc., as shown in (ii) The fuel is injected into the No. 7 cylinder 100 and ignited to start (ignition start). Then, when the piston 110 is pushed down by the explosive expansion of the gas in the No. 7 cylinder 100 and the crankshaft 114 starts to rotate as shown in (iii), the subsequent No. 8 cylinder 100 is pressurized by compression. The crank angle Φ of the No. 7 cylinder 100 at the start of ignition is about 45 °, and the amount of air in the No. 7 cylinder 100 is smaller than that of the ignition cylinder No. 4 in FIG. From the beginning of the ignition start, the K0 clutch 34 is connected to assist the cranking by the motor generator MG.

(iv) is a state in which the subsequent No. 8 cylinder 100 reaches the compression TDC and is ignited. Since the air in the No. 8 cylinder 100 is set to substantially atmospheric pressure while the engine is stopped, the amount of air is It is relatively small and complete explosion energy cannot be obtained. For this reason, as shown in (v) IV, the motor generator MG still needs assistance even after an explosion and rotation. After that, when the third No. 1 cylinder 100 counting from No. 7 reaches the compression TDC as shown in (vi) and is ignited, complete explosion energy can be obtained for the first time. No assistance is required. Thereafter, the cylinder 100 is stably rotated by causing the subsequent cylinder 100 to explode every 90 ° rotation. That is, as shown in (vi), if the crankshaft 114 rotates until the No. 1 cylinder 100 exceeds the compression TDC, then the crankshaft 114 can be rotated by itself. By assisting cranking by the motor generator MG over an angle range of about 120 ° to 130 °, the direct injection engine 12 can be appropriately started to ignite. In this case, following the initial explosion of the No. 7 cylinder 100, the immediately following No. 8 cylinder 100 can also be ignited and exploded, so that the engine speed NE increases smoothly in combination with the assist by the motor generator MG. Compared to 6, the starting time is shortened.

In this way, in the 8-cylinder direct injection engine 12, even when the piston 110 of any cylinder 100 stops near the compression TDC as shown in FIG. 5B, it is shown in FIG. 5C. Thus, even when the compression TDC is stopped at an intermediate position exceeding about 45 °, the ignition can be appropriately started with the assistance of the motor generator MG. In that case, when stopped near the compression TDC as shown in FIG. 5 (b) 比較, compared to when stopping at an intermediate position that exceeds the compression TDC by about 45 ° as shown in FIG. 5 (c). Thus, the assist torque by the motor generator MG can be small. In other words, as shown in FIG. 5B, if the ignition start is performed with the piston 110 of any cylinder 100 stopped near the compression TDC, the assist torque for the ignition start is reduced. Further, the maximum torque of the motor generator MG can be further reduced, and further downsizing and fuel consumption can be achieved.

In that case, as shown in FIG. 5 (b), the condition that the ignition start can be performed when the piston 110 of any cylinder 100 stops at the compression TDC is that the preceding cylinder 100 is in the expansion stroke. In addition, the exhaust valve 108 needs to be closed. FIG. 8 is a diagram showing the piston position (crank angle Φa) of the immediately preceding cylinder 100 when the piston 110 of any cylinder 100 of the direct-injection engine 12 having various cylinder numbers stops at the compression TDC. ° is the compression TDC, and the crank angle Φ advances clockwise. In the case of 8 cylinders, since 720 ° ÷ 8 = 90 ° as described above, the crank angle Φa of the immediately preceding cylinder 100 is 90 °, and the crank angle Φa = 60 ° in the case of 12 cylinders, 7 Crank angle Φa = 103 ° in the case of cylinders and crank angle Φa = 120 ° in the case of 6 cylinders, both of which are expansion strokes. Further, when the exhaust valve opening timing angle EVO is about 140 °, the exhaust valve 108 is closed, and any of them can start ignition. In the case of a 12-cylinder engine, ignition can be started at the crank angle Φa = 120 ° for the two cylinders 100 before.

On the other hand, in the case of five cylinders, ignition start is impossible because the exhaust valve 108 is open although the crank angle Φa of the preceding cylinder 100 is 144 ° and the expansion stroke is in progress. Further, the crank angle Φa = 180 ° in the case of four cylinders and the crank angle Φa = 240 ° in the case of three cylinders, both of which exceed the expansion stroke, and the exhaust valve 108 is also open, so that ignition starts. Is not possible. The exhaust valve opening timing angle EVO is appropriately determined or made variable within a range of, for example, about 110 ° to 160 °. Therefore, if the exhaust valve opening timing angle EVO is set to 120 ° or less, the case of 6 cylinders Will not be able to start ignition. If the ignition start is impossible when the piston 110 of any cylinder 100 stops at the compression TDC in this way, the piston 110 of any cylinder 100 is compressed TDC as shown in FIG. It is possible to start ignition only when the engine passes through the valve and stops at an intermediate position in the expansion stroke.

Returning to FIG. 1, such a hybrid vehicle 10 is controlled by the electronic control unit 70. 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 according to a program stored in advance in the ROM while using a temporary storage function of the RAM. Do. A signal representing the accelerator pedal operation amount (accelerator operation amount) Acc is supplied from the accelerator operation amount sensor 48 to the electronic control unit 70. Further, from the engine rotation speed sensor 50, the MG rotation speed sensor 52, the turbine rotation speed sensor 54, the vehicle speed sensor 56, and the crank angle sensor 58, the rotation speed (engine rotation speed) NE of the direct injection engine 12 and the rotation of the motor generator MG, respectively. Speed (MG rotational speed) NMG, rotational speed of turbine shaft 16 (turbine rotational speed) NT, rotational speed of output shaft 22 (corresponding to vehicle speed V by output shaft rotational speed) NOUT, TDC for each of eight cylinders 100 (top dead) A signal relating to the rotation angle (crank angle) Φ from the point) 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.

The electronic control unit 70 is functionally provided with hybrid control means 72, shift control means 74, and engine stop control means 80. The hybrid control means 72 controls the operation of the direct injection engine 12 and the motor generator MG, for example, an engine travel mode in which only the direct injection engine 12 travels as a driving power source, or travels using only the motor generator MG as a driving power source. A plurality of predetermined driving modes such as an engine driving mode using both the motor driving mode and the motor driving mode are switched in accordance with the driving state such as the accelerator operation amount Acc and the vehicle speed V. The shift control means 74 controls an electromagnetic hydraulic control valve, a switching valve and the like provided in the hydraulic control device 28 to switch the engagement / disengagement state of the plurality of hydraulic friction engagement devices. These gear stages are switched in accordance with a predetermined shift map with the operating state such as the accelerator operation amount Acc and the vehicle speed V as parameters.

The engine stop control means 80 stops the direct injection engine 12 at the time of switching from the engine + motor running mode to the motor running mode, at the time of inertia running during the engine + motor running mode or the engine running mode, at the time of deceleration, at the time of stopping, etc. In this embodiment, as shown in FIG. 5B, the crankshaft 114 is stopped at a crank angle Φ at which the piston 110 of any one of the cylinders 100 is near the compression TDC. The engine stop control means 80 further includes an engine stop means 82, a crank angle determination means 84, and a clutch engagement means 86, and performs signal processing according to the flowchart of FIG. Steps S2 and S3 in FIG. 3 correspond to the engine stop means 82, steps S4 and S5 correspond to the crank angle determination means 84, and steps S6 and S7 correspond to the clutch engagement means 86. The clutch engaging means 86 functions as a connection control means for temporarily connecting the K0 clutch 34.

In step S1 of FIG. 3, it is determined whether or not an engine stop condition is satisfied. When the engine stop condition is satisfied when the engine stop condition is satisfied, such as when switching from the engine + motor drive mode to the motor drive mode or during deceleration in the engine drive mode, engine stop control in step S2 and subsequent steps is executed. As a precondition for the engine stop, the basic conditions for stop control such as intermittent operation conditions for turning on (running) and turning off (stopping) the direct injection engine 12 and the engine cooling water temperature being equal to or higher than a predetermined temperature are satisfied. Need to be. The time t1 in the time chart of FIG. 4 is the time when the determination in step S1 is YES (positive) and the engine stop control is started. FIG. 4 is a diagram showing changes in the operating state of each part when the engine stop control is performed due to inertial traveling with the accelerator off during traveling in the engine + motor traveling mode. The crank angle Φ is the compression TDC. FIG. 9 is a graph showing changes in the crank angle Φ from the intermediate position of the compression stroke 90 ° before the compression TDC to the compression TDC as 0 °, and the crank angles Φ of the eight cylinders 100 that reach the compression TDC at 90 ° intervals It is the figure which showed the change of and connected continuously. The K0 clutch pressure is the engagement hydraulic pressure of the K0 clutch 34, and is the maximum pressure (line pressure) at time t1 during running in the engine + motor running mode, and the K0 clutch 34 is fully engaged. The K0 clutch pressure corresponds to the engagement torque of the K0 clutch 34, that is, the connection torque that connects the direct injection engine 12 to the power transmission path.

In step S2, the K0 clutch 34 is disconnected to disconnect the direct injection engine 12 from the power transmission path. In the disconnection process of the K0 clutch 34, for example, the K0 clutch pressure is gradually reduced to zero. In step S3, stop processing of the direct injection engine 12 is executed. In this stop process, the fuel injection from the fuel injection device 46 is stopped (fuel cut), and the ignition control of the ignition device 47 is stopped. Thereby, coupled with the fact that the direct injection engine 12 is disconnected from the power transmission path in step S2, the engine rotational speed NE gradually decreases. The disconnection process of the K0 clutch 34 in step S2 and the fuel cut in step S3 may be performed after the fuel cut, but may be performed in parallel at the same time, or the fuel cut may be performed first. If the fuel has already been cut due to accelerator OFF or the like, the fuel cut may be continued.

In the next step S4, it is determined whether or not the rotation of the direct injection engine 12 has stopped substantially, specifically, whether or not the engine speed NE has become equal to or less than a predetermined value NE1 of about 100 rpm, for example. When the rotation of the cylinder is substantially stopped, step S5 is executed to determine whether or not the cylinder 100 in the latter half of the compression stroke exists based on the crank angle Φ. The latter half of the compression stroke is, for example, in the range from 90 ° before it to the compression TDC with reference to the compression TDC. In this embodiment having the eight-cylinder direct injection engine 12, any cylinder 100 is always in the latter half of the compression stroke. Yes, then step S6 is executed. In step S6, it is determined whether or not the engine rotational speed NE = 0. When NE = 0, the clutch engagement control in step S7 is executed. Whether or not NE = 0 can be determined, for example, based on whether or not the input of the pulse signal from the engine speed sensor 50 has not changed for a certain time (for example, several tens of milliseconds).

In the clutch engagement control in step S7, the crank angle of the cylinder 100 in which the piston 110 is positioned before the compression TDC is obtained by engaging the K0 clutch 34 with a predetermined engagement torque for a predetermined engagement time. The crankshaft 114 is rotated and stopped so that Φ is in the vicinity of the compression TDC (for example, compression TDC ± 10 ° or less). That is, the K0 clutch 34 is engaged so that the crankshaft 114 stops in a state where it rides on the peak of pumping energy shown in FIG. The engagement torque and engagement time of the K0 clutch 34 are determined according to a predetermined map, an arithmetic expression, or the like based on, for example, the crank angle Φstop when NE = 0 is determined. One of the engagement torque and the engagement time, for example, the engagement torque may be determined in advance, and only the other may be determined based on the crank angle Φstop. The engagement torque and the engagement time are determined based on pumping energy and the like as shown in FIG. 9 obtained by experiments and calculations, for example, from the crank angle Φstop when NE = 0 is determined to the compression TDC. The larger the angle, the longer the engagement time, but it is desirable to correct the learning so that it stops near the compression TDC. If one of the cylinders 100 is close to the compression TDC when NE = 0, it is not necessary to rotate the crankshaft 114 any further, and the engagement time is set to 0 and the clutch engagement control in step S7 is substantially performed. Is omitted. Note that the torque (MG torque) TMG of the motor generator MG is changed to the engagement torque of the K0 clutch 34 in order to prevent the drive torque from fluctuating due to the rotational resistance accompanying the rotation of the crankshaft 114 due to the engagement of the K0 clutch 34. Compensation control that increases correspondingly may be performed as necessary.

In step S8, it is determined whether or not the crankshaft 114 has stopped at a crank angle Φ at which the piston 110 of any one of the cylinders 100 is near the compression TDC. As a result, when the direct injection engine 12 is restarted, ignition can be started as shown in FIG. The time t2 in FIG. 4 is the time when the determination of step S6 is YES (affirmed) and the clutch engagement control of step S7 is started. The crankshaft 114 is rotated by the clutch engagement control, and the compression TDC It is a case where it is stopped in the vicinity.

If the determination in step S8 is NO (No), step S9 is executed to determine whether or not the compression TDC has been exceeded. That is, it is determined whether the crankshaft 114 has returned without being able to ride on the compression TDC regardless of the clutch engagement control in step S7 or whether the crankshaft 114 has passed over the compression TDC by the clutch engagement control. However, when it cannot return to the compression TDC and returns, the process from step S7 is executed again. In addition, when the vehicle has passed over the compression TDC, step S4 and the subsequent steps are executed, and the engagement control of the K0 clutch 34 is performed so that the next cylinder 100 before reaching the compression TDC stops near the compression TDC. The crankshaft 114 is rotated. In the second and subsequent engagement control of the K0 clutch 34, the engagement torque and the engagement time may be finely adjusted based on the result of the previous engagement control.

As described above, in the engine stop control device for the hybrid vehicle 10 of this embodiment, when it is assumed that the piston 110 of any cylinder 100 stops at the compression TDC, the preceding cylinder 100 is in the expansion stroke and the exhaust valve. An eight-cylinder direct injection engine 12 is provided in which 108 is closed. When the direct-injection engine 12 is stopped by disengaging the K0 clutch 34 while the vehicle is traveling, any cylinder can be obtained by temporarily connecting the once disengaged K0 clutch 34 and rotating the crankshaft 114. 100 pistons 110 are stopped at a crank angle Φ that is in the vicinity of the compression TDC. As a result, the crank angle Φ of the cylinder 100 immediately before the cylinder 100 stopped in the vicinity of the compression TDC becomes about compression TDC + 90 °, and fuel injection and ignition are performed on the cylinder 100. As shown, the ignition start can be performed appropriately.

That is, in the case of this 8-cylinder direct injection engine 12, even when the piston 110 of any one of the cylinders 100 is stopped at an intermediate position of the expansion stroke (for example, compression TDC + 45 °), ignition start is performed as shown in FIG. However, even if the crankshaft 114 is stopped at a crank angle Φ at which the piston 110 of any cylinder 100 is in the vicinity of the compression TDC, fuel injection and ignition are performed on the preceding cylinder 100. The ignition start can be performed appropriately, and the application range of the ignition start is expanded to increase the degree of freedom of control.

Further, since the immediately preceding cylinder 100 is stopped at around compression TDC + 90 °, as shown in FIG. 7, it is compared with an ignition start when stopping at an intermediate position (compression TDC + 45 °) where the pumping energy is low. Thus, the amount of air in the cylinder 100 at the time of the first explosion is large, and a large rotational energy can be obtained at the first explosion. For this reason, the assist torque by the motor generator MG at the time of starting can be further reduced, and the maximum torque of the motor generator MG can be further reduced to further reduce the size and fuel consumption.

Next, another embodiment of the present invention will be described. In the following embodiments, parts that are substantially the same as those in the above embodiments are denoted by the same reference numerals, and detailed description thereof is omitted.

FIGS. 10 to 12 show an embodiment in which an in-line four-cylinder four-cycle gasoline engine is used as the direct injection engine 12, and FIG. 10 is a view corresponding to FIG. In the stroke diagram showing the operating states of the four cylinders 100 in relation to the crank angle Φ, the cylinders 100 positioned in the upper part of the drawing are operated in advance. That is, in the order of cylinder No1 → No3 → No4 → No2, every time the crank angle Φ rotates 180 °, the combustion is caused by explosion, and the crankshaft 114 is continuously rotated. (b) shows the operating state of the cylinder 100 in the vicinity of the compression TDC when the TDC is stopped in (a) すなわち, that is, when any cylinder 100 is stopped at the compression TDC, based on the compression TDC = 0 °. In this figure, the No. 3 cylinder 100 is a compression TDC in this figure, and the crank angle Φ of the No. 1 cylinder 100 immediately before the preceding is about 180 ° (more precisely, the compression TDC + 180 °). Since the No. 1 cylinder 100 has passed the expansion stroke and the exhaust valve 108 is open, it is not possible to start ignition in this state. That is, in the case of the four-cylinder direct injection engine 12, when any one of the cylinders 100 is stopped at the compression TDC, any other cylinder 100 is in the expansion stroke and the exhaust valve 108 is closed. The starting condition is not satisfied.

Also in the above-described four-cylinder direct injection engine 12, as is apparent from the pumping energy graph shown in FIG. 9 (c) IV, there is a mountain near the compression TDC. The crankshaft 114 is likely to stop in a very small region (a range of about 50 ° to 120 °), but it stops in the vicinity of the compression TDC with a probability of about 10%. When the crankshaft 114 is stopped at a crank angle Φ at which any one of the cylinders 100 is in the vicinity of the compression TDC in this way, ignition start at the time of restart is impossible.

On the other hand, (c) in FIG. 10 shows the operation of the cylinder 100 in the vicinity thereof when 90ATDC is stopped in a, that is, when any cylinder 100 is stopped at an intermediate position rotated about 90 ° from the compression TDC. The state is shown with the compression TDC = 0 ° as a reference. In this drawing, the No. 4 cylinder 100 is stopped at around 90 °. The No. 4 cylinder 100 is in the expansion stroke, and the exhaust valve 108 is closed before the opening timing angle EVO of the exhaust valve 108. Therefore, fuel is injected into the No. 4 cylinder 100, and ignition is started (ignition). Start). As is clear from the pumping energy characteristics of FIG. 9 (c) 図, if nothing is done, there is a probability of about 90%, and as shown in FIG. 10 (c), any cylinder 100 is about 50 ° to 120 °. Although the crankshaft 114 is stopped at the crank angle Φ which is an intermediate position, even when the crankshaft 114 is stopped near the compression TDC as shown in FIG. (C) The stop position of the crankshaft 114 can be adjusted so that one of the cylinders 100 stops at the intermediate position, as shown in (c) IV.

Thus, in the four-cylinder direct injection engine 12, when the piston 110 of any cylinder 100 stops at the compression TDC as shown in FIG. 10B, the crank angle Φ of the cylinder 100 immediately before the preceding cylinder 100 Since the expansion stroke is over at about 180 ° and the exhaust valve 108 is open, none of the cylinders 100 satisfy the ignition start condition, and the ignition start is impossible. On the other hand, as shown in FIG. 10 (c) IV, when the compression TDC is stopped at an intermediate position exceeding about 90 °, ignition start can be performed. That is, as shown in FIG. 10B, when the piston 110 of any cylinder 100 stops near the compression TDC, rotational torque is applied to the crankshaft 114, as shown in FIG. 10C. The ignition start can be performed by rotating to the intermediate position.

FIG. 11 is a flowchart relating to engine stop control in the case of having the four-cylinder direct injection engine 12 as described above, and is executed by the engine stop control means 80 instead of the flowchart of FIG. In this embodiment, steps R2 and R3 in FIG. 11 correspond to the engine stop means 82, steps R4 and R5 correspond to the crank angle determination means 84, and step R6 corresponds to the clutch engagement means 86.

Steps R1 to R3 in FIG. 11 are the same as steps S1 to S3 in FIG. 3. In step R4, it is determined whether or not the engine speed NE = 0 has been reached in the same manner as in step S6. Then, when NE = 0, step R5 is executed, and whether or not the crankshaft 114 is stopped at the crank angle Φ at which the piston 110 of any cylinder 100 passes through the compression TDC and becomes the intermediate position of the expansion stroke. Judging. The intermediate position is, for example, in the range of about 50 ° to 120 ° from the compression TDC, and preferably in the range of about 70 ° to 110 °. Then, when the crankshaft 114 is stopped at a crank angle Φ at which any one of the cylinders 100 is at the intermediate position, the ignition start can be performed by fuel injection and ignition to the cylinder 100, and thus the process ends. To do.

On the other hand, if the determination in step R5 is NO, that is, if the crankshaft 114 is stopped at a crank angle Φ at which the piston 110 of any cylinder 100 is near the compression TDC, the clutch engagement control in step R6 is executed. To do. In this clutch engagement control, by engaging the K0 clutch 34 with a predetermined engagement torque for a predetermined engagement time, the piston 110 stopped in the vicinity of the compression TDC is released from the compression TDC, and the intermediate The crankshaft 114 is rotated and stopped so as to reach the position. That is, the crankshaft 114 stopped in a state where it rides on the pumping energy peak shown in FIG. 9 is detached from the pumping energy peak and stops in a low flat minimum region between the peaks. The K0 clutch 34 is engaged. In this embodiment, the crankshaft 114 automatically stops at an intermediate position of about 50 ° to 120 ° when separated from the peak of the pumping energy, so the engagement torque and engagement time of the K0 clutch 34 are constant in advance. The value may be determined, but may be determined according to a predetermined map, an arithmetic expression, or the like based on, for example, the crank angle Φstop when NE = 0 is determined. One of the engagement torque and the engagement time, for example, the engagement torque may be determined in advance, and only the other may be determined based on the crank angle Φstop. It is also possible to perform learning correction on these set values so as to stop at the intermediate position. In addition, even in the minimum region of 50 ° to 120 °, the engagement torque and the engagement time may be set so that the rotation is stopped in an angle range of about 70 ° to 110 ° where a relatively large rotational energy can be expected at the start of ignition. good. Note that the torque (MG torque) TMG of the motor generator MG is changed to the engagement torque of the K0 clutch 34 in order to prevent the drive torque from fluctuating due to the rotational resistance accompanying the rotation of the crankshaft 114 due to the engagement of the K0 clutch 34. Compensation control that increases correspondingly may be performed as necessary.

Thereafter, the steps after R4 are executed, and the crankshaft 114 is stopped at the crank angle Φ at which the piston 110 of any cylinder 100 is at the intermediate position of the expansion stroke. End engine stop control. FIG. 12 is a diagram showing changes in the operating states of the respective parts when the engine stop control is performed with the accelerator OFF coasting during the engine + motor running mode as in FIG. 6 is a time chart when the crankshaft 114 is stopped at a crank angle Φ at which the piston 110 of any cylinder 100 is at an intermediate position in the expansion stroke by performing the clutch engagement control once. The time t1 is the time when the determination of step R1 is YES and the engine stop control is started, and the time t2 is the time when the determination of step R5 is NO and the engagement control of the K0 clutch 34 is started. The crank angle Φ is a diagram showing a change in the crank angle Φ from the compression TDC to an angular position rotated by 180 ° with the compression TDC being 0 °. The crank angle Φ of the four cylinders 100 that reach the compression TDC at intervals of 180 ° is shown in FIG. It is the figure which showed the change of crank angle (PHI) continuously connected.

In this embodiment, when it is assumed that the piston 110 of any one of the cylinders 100 is stopped at the compression TDC, any of the other cylinders 100 is in the expansion stroke and does not satisfy the ignition start condition in which the exhaust valve 108 is closed. When the direct-injection engine 12 is provided and the direct-injection engine 12 is stopped by disengaging the direct-injection engine 12 while the vehicle is running, the once-disconnected K0 clutch 34 is temporarily connected to the crankshaft 114. , The piston 110 of any cylinder 100 passes through the compression TDC, and the crankshaft 114 is stopped at a crank angle Φ that is an intermediate position in the expansion stroke. Accordingly, it is possible to appropriately start ignition by performing fuel injection and ignition on the cylinder 100 stopped at an intermediate position in the expansion stroke.

As mentioned above, although the Example of this invention was described in detail based on drawing, these are one Embodiment to the last, This invention is implemented in the aspect which added the various change and improvement based on the knowledge of those skilled in the art. be able to.

10: Hybrid vehicle 12: Direct injection engine 34: K0 clutch (connection / disconnection device) 58: Crank angle sensor 70: Electronic control device 80: Engine stop control means 82: Engine stop means 84: Crank angle determination means 86: Clutch engagement Means 100: Cylinder 114: Crankshaft MG: Motor generator (rotary machine) Φ, Φa: Crank angle

Claims

A four-cycle direct injection engine having a plurality of cylinders and directly injecting fuel into the cylinders;
A connection / disconnection device for connecting / disconnecting the direct injection engine to a power transmission path;
A rotating machine that functions as at least an electric motor;
In a hybrid vehicle that can use the direct injection engine and the rotating machine as a driving power source for traveling,
When the direct-injection engine is stopped by shutting off the connection / disconnection device during traveling, the connection / disconnection device once disconnected is temporarily connected to rotate the crankshaft of the direct-injection engine. While stopping at the crank angle
The crank angle at which the crankshaft is stopped is that the piston of any cylinder is stopped at the compression TDC, which is the top dead center after the compression stroke, and any other cylinder is in the expansion stroke and the exhaust valve is closed. An engine stop control device for a hybrid vehicle, characterized in that the angle is determined depending on whether or not the vehicle is in a state.
The direct injection engine has 6 or more cylinders, and when any one of the cylinders is in the expansion stroke and the exhaust valve is closed when it is assumed that the piston of any cylinder stops at the compression TDC. 2. The engine stop control device for a hybrid vehicle according to claim 1, wherein the crankshaft is stopped at a crank angle at which a piston of any one of the cylinders is in the vicinity of the compression TDC.
The direct-injection engine has six or fewer cylinders, and when it is assumed that the piston of any cylinder has stopped at the compression TDC, any other cylinder is in an expansion stroke and the exhaust valve is closed. 2. The hybrid vehicle according to claim 1, wherein the piston of any one of the cylinders passes through the compression TDC and stops the crankshaft at a crank angle that is an intermediate position of an expansion stroke when the condition is not satisfied. Engine stop control device.