JP2005273630A - Engine starter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve startability of an engine by efficiently heightening the compression pressure of a cylinder in an expansion stroke in reverse rotating operation in the early stage of starting the engine. <P>SOLUTION: When predetermined restarting conditions are established, a piston of a cylinder in a compression stroke at the stop of the engine is operated in a reverse rotating direction to heighten pressure in the cylinder by the piston rise of the cylinder in the expansion stroke, and then the engine is rotated in a normal rotating direction by combustion in the cylinder in the expansion stroke to carry out restarting. A control means is provided for stopping the piston of the cylinder in the expansion stroke within a predetermined appropriate range at the stop of the engine and controlling the opening of a throttle valve based on the detection result of a piston position detecting means at the restart of the engine. The control means controls to increase the opening of the throttle valve in the reverse rotating direction operating period of the engine when the piston position of the cylinder in the expansion stroke is on the bottom dead center side rather than a predetermined reference position at the restart of the engine. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an engine starter that automatically starts an engine that has been stopped when idling or the like.

In recent years, to reduce fuel consumption and reduce CO ₂ emissions, the engine is automatically stopped when idling, and then restarted automatically when restart conditions such as start operation are established. Engine starters have been developed.

  When restarting automatically after stopping the engine in this way, it is required to start immediately according to the starting operation, etc., so the engine is started through cranking that drives the engine output shaft by the starting motor. The conventional general starting method that requires a considerable time to complete the starting operation is not preferable.

  Therefore, it is desirable to supply fuel to a specific cylinder of a stopped engine to cause ignition and combustion so that the engine can be started immediately with that energy. In this case, if the fuel is supplied to the cylinder in the expansion stroke while the engine is stopped to cause combustion, the energy of the combustion can be applied in the normal rotation direction of the engine. However, if the engine is in operation, combustion is performed after the combustion chamber is in a highly compressed state, so a large amount of energy is obtained. However, when the engine is stopped, air leaks from the cylinder in the expansion stroke, and the pressure in the combustion chamber is increased. Therefore, even if fuel is supplied into the combustion chamber at the low pressure and combustion is performed, energy necessary for starting is often not obtained sufficiently.

As a countermeasure for such a problem, in a multi-cylinder engine, the first combustion is performed on the compression stroke cylinder when the engine is stopped, and the piston of the compression stroke cylinder is pushed down. After increasing the in-cylinder pressure of the expansion stroke cylinder, the fuel is injected into the expansion stroke cylinder to ignite and burn, thus increasing the combustion energy acting in the forward direction of the engine. Have also been proposed (see, for example, Patent Document 1).
International Publication No. 01/38726 Pamphlet

  Here, in the case of the starting device as shown in Patent Document 1, a sufficient amount of air is secured in the expansion stroke cylinder at the time of stoppage to generate torque in the forward rotation direction, while compression at the time of engine stop at the start of the start. When combustion is performed in the stroke cylinder, it is desirable to increase the combustion pressure by securing the amount of air in the cylinder, thereby pushing down the piston of the cylinder to increase the compression pressure of the cylinder in the expansion stroke. It is difficult to reliably and continuously stop the pistons in the expansion stroke cylinder and the compression stroke cylinder within a predetermined appropriate range in order to ensure the air amount in each of the expansion stroke cylinder and the compression stroke cylinder when stopping. Even if the fuel injection and ignition timing when the engine is stopped are controlled with the aim of causing the engine to stop, there are cases where it falls outside this proper range. When the piston of the compression stroke cylinder is deviated to the top dead center side (the piston of the expansion stroke cylinder is the bottom dead center side), sufficient combustion energy cannot be obtained due to the lack of air amount in the compression stroke cylinder. There is a possibility that the compression pressure of the stroke cylinder cannot be sufficiently increased and the engine cannot be started normally. Therefore, in order to improve the practicality, it is desired to ensure a more reliable startability even when stopping within the appropriate range while expanding the appropriate range where the start can be properly performed in order to improve the startability.

  In view of the above circumstances, the present invention efficiently reduces the compression pressure of the expansion stroke cylinder by the combustion pressure acting on the piston when the piston of the cylinder is pushed down by combustion in the compression stroke cylinder at the start of the engine. It is possible to provide an engine starter that can be improved and thereby improve the startability of the engine.

  The engine starter according to the present invention automatically stops the engine when a predetermined engine stop condition is satisfied, and is applied to the compression stroke cylinder when the engine is stopped when the restart condition is satisfied after the engine is stopped. The fuel is supplied and ignited and burned to operate the engine in the reverse direction by a predetermined amount, and the cylinder pressure in the cylinder during the expansion stroke when the engine is stopped is raised to increase the in-cylinder pressure. In an engine starter that restarts by rotating the engine in the forward rotation direction by performing combustion, a throttle valve that adjusts the amount of intake air introduced into each cylinder from an intake passage, and an expansion stroke cylinder when the engine is stopped Piston position detecting means for detecting the piston position, and when the engine stop condition is satisfied, the expansion stroke at the stop Control means for controlling the piston of the cylinder to stop within a predetermined appropriate range, and for controlling the opening degree of the throttle valve when the engine is restarted based on the detection result by the piston position detection means. When the engine restart condition is satisfied and the piston position of the expansion stroke cylinder when the engine is stopped is at the bottom dead center side with respect to a predetermined reference position, at least the reverse rotation of the engine is performed. In the direction operation period, control is performed so that the opening degree of the throttle valve is increased as compared with the case where the piston position of the expansion stroke cylinder is on the top dead center side with respect to the reference position.

  According to the present invention, when the engine is restarted, the combustion is first performed in the cylinders in the compression stroke, so that the engine is reversed by a certain amount. After being increased, combustion is performed in the cylinder, whereby the combustion pressure due to the combustion effectively acts on the piston, and a driving force in the normal rotation direction of the engine is obtained. In such a start-up type, it is desired that the compression stroke cylinder in which the initial combustion is performed be stopped within an appropriate range suitable for the combustion. In the present invention, the piston of the expansion stroke cylinder when the engine is stopped is in a predetermined appropriate range. Since the control means for controlling to stop is provided, the probability that the piston of the compression stroke cylinder interlocked with the piston of the expansion stroke is stopped within a predetermined appropriate range capable of ensuring the amount of air necessary for proper combustion is increased. be able to.

  Here, the control means detects the piston position of the expansion stroke cylinder when the engine is stopped by the piston position detection means, and when the detection result is at the bottom dead center side with respect to the predetermined reference position, at least the reverse rotation of the engine. In the direction operation period, control is performed so that the opening of the throttle valve is increased compared to when the piston is at the top dead center side with respect to the reference position. Therefore, at least the reverse direction of the engine is increased by increasing the opening of the throttle valve. The pumping loss due to the piston resistance of the intake stroke cylinder can be reduced during the operation period. For this reason, energy loss due to depression of the piston of the compression stroke cylinder is suppressed to efficiently increase the compression pressure of the expansion stroke cylinder, and the appropriate range of the compression stroke cylinder is expanded to the top dead center side by suppressing the energy loss. (In other words, the appropriate range of the expansion stroke cylinder can be expanded to the bottom dead center side), thereby improving the startability of the engine. In addition, since the piston position is determined based on the predetermined reference position, even if the appropriate range of the piston position at which the reverse rotation operation of the engine can be executed is changed due to the deterioration of the engine over time or the change of the external environment, etc. Startability can be improved reliably.

  In the present invention, when the engine restart condition is satisfied and the piston position of the expansion stroke cylinder when the engine is stopped is on the top dead center side with respect to a predetermined reference position, the control means It is preferable to control the valve so as to be fully closed (claim 2).

  That is, when the piston position of the expansion stroke cylinder is on the top dead center side relative to the predetermined reference position, in other words, when the piston position of the compression stroke cylinder is on the bottom dead center side, combustion by the initial combustion in the compression stroke cylinder Since sufficient energy can be obtained, it is possible to effectively prevent the reverse rotation amount from becoming larger than necessary by increasing the piston resistance of the intake stroke cylinder by fully closing the throttle valve. Moreover, the pressure in the intake passage on the downstream side of the throttle valve increases due to the rise of the piston of the intake stroke cylinder during the reverse rotation operation of the engine, and by using this pressure, the piston resistance at the initial stage of the forward rotation operation of the engine is reduced. The engine can be started smoothly and reliably.

  The number of cylinders of the engine is not particularly limited. For example, when a four-cylinder engine is employed, the control means sets the piston of the expansion stroke cylinder when the engine is stopped when the engine stop condition is satisfied. It is preferable to control to stop within a predetermined range exceeding 90 ° after compression top dead center.

  If comprised in this way, air quantity of an expansion stroke cylinder can fully be ensured, the combustion at the time of the forward rotation operation | movement after reverse rotation operation of an engine can be performed appropriately, and desired torque can be obtained. it can.

  In this case, the reference position is not particularly limited. However, from the viewpoint of reliably performing the initial combustion for the reverse rotation operation of the engine and the next combustion for the forward rotation operation, the reference position is a compression top deadline. It is preferably set within the range of 100 ° to 125 ° after the point (claim 4).

  In the present invention, when the piston position detecting means detects that the expansion stroke cylinder at the time of stoppage is out of the predetermined appropriate range, the control means is a cylinder in the compression stroke. From the first restart mode in which combustion is performed in the cylinder in the expansion stroke after the engine is operated in the reverse rotation direction by a predetermined amount of combustion, the starter motor is driven to operate the engine in the normal rotation direction from the initial start. It is preferable to be configured to switch to the second restart mode (Claim 5).

  In other words, it is difficult to reliably and continuously stop the piston position within a predetermined appropriate range when the engine is stopped. Therefore, even if the piston stop position is controlled as described above, the environment Depending on various conditions such as these, the piston may not be stopped at this proper position. Therefore, in such a case, the engine can be started smoothly by operating with the starter motor in the same manner as the normal engine start, and the practicality can be improved.

  Further, when the opening of the throttle valve is increased during reverse rotation of the engine, the control means opens the throttle valve after the compression top dead center where the piston of the cylinder in the intake stroke first reaches when the engine is stopped. It is preferable to control to reduce the degree (Claim 6).

  That is, if the engine continues to operate in the forward rotation direction with the throttle valve opening being increased, the intake pressure becomes substantially the same as the atmospheric pressure, and there is a concern that excessive blowing will occur. Therefore, if constituted as described above, it is possible to effectively suppress a sudden increase in engine rotation speed and effectively suppress torque shock at the time of starting.

  According to the engine starting device of the present invention, the piston resistance of the intake stroke cylinder is adjusted by changing the opening degree of the throttle valve in accordance with the piston stop position of the expansion stroke cylinder, thereby ensuring the starting reliability. On the other hand, there is an advantage that a predetermined proper range in which the reverse operation of the engine can be executed while suppressing energy loss can be expanded. That is, when the piston of the cylinder is pushed down by combustion in the compression stroke cylinder at the start of the engine, the compression pressure of the expansion stroke cylinder can be efficiently increased by the combustion pressure acting on the piston. The startability of the can be improved.

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

  1 and 2 show a schematic configuration of a four-cycle spark ignition engine according to an embodiment of the present invention. In these drawings, the engine body is composed of a cylinder head 1 and a cylinder block 2, and has a plurality of cylinders, and in the illustrated embodiment, has four cylinders 3A to 3D. A piston 4 is fitted into each of the cylinders 3 </ b> A to 3 </ b> D, and a combustion chamber 5 is formed above the piston 4. The piston 4 is connected to a crankshaft 6 via a connecting rod.

  A spark plug 7 is provided at the top of the combustion chamber 5 of each cylinder 3 </ b> A to 3 </ b> D, and the tip of the plug faces the combustion chamber 5.

  Further, a fuel injection valve 8 that directly injects fuel into the combustion chamber 5 is provided at a side portion of the combustion chamber 5. The fuel injection valve 8 includes a needle valve and a solenoid (not shown). When a pulse signal is input, the fuel injection valve 8 is driven and opened for a time corresponding to the pulse width at the pulse input timing. It is comprised so that the quantity of fuel according to may be injected. The injection direction of the fuel injection valve 8 is set so as to inject fuel toward the vicinity of the spark plug 7. The fuel injection valve 8 is supplied with fuel via a fuel supply passage or the like by a fuel pump (not shown), and a fuel supply system so that a fuel pressure higher than the pressure in the combustion chamber during the compression stroke can be applied. Is configured.

  An intake port 9 and an exhaust port 10 are opened to the combustion chambers 5 of the respective cylinders 3A to 3D, and these ports 9 and 10 are equipped with an intake valve 11 and an exhaust valve 12, respectively. The intake valve 11 and the exhaust valve 12 are driven by a valve operating mechanism including a camshaft and the like (not shown). As described later in detail, the opening / closing timings of the intake and exhaust valves of each cylinder are set so that each cylinder performs a combustion cycle with a predetermined phase difference.

  An intake passage 15 and an exhaust passage 16 are connected to the intake port 9 and the exhaust port 10. A downstream side of the intake passage 15 close to the intake port 9 is an independent branch intake passage 15a corresponding to each of the cylinders 3A to 3D, and an upstream end of each branch intake passage 15a communicates with the surge tank 15b. Yes. A common intake passage 15c is provided on the upstream side of the surge tank 15b, and a throttle valve 17 is provided in the common intake passage 15c. The throttle valve 17 is driven by an actuator 18, and an air flow sensor 20 for detecting an intake flow rate and an intake pressure sensor 19 for detecting an intake pressure (negative pressure) are respectively provided upstream and downstream of the throttle valve 17. It is arranged.

  The engine is also provided with an alternator (generator) 26 connected to the crankshaft 6 by a timing belt or the like. The alternator 26 includes a regulator circuit 26a that adjusts the amount of power generated by controlling the current of a field coil (not shown) to adjust the output voltage, and a control signal from an ECU 30 (described later) that is input to the regulator circuit 26a. The control of the amount of power generation corresponding to the electrical load of the vehicle, the voltage of the vehicle-mounted battery, and the like is executed based on the above.

  Further, the engine is provided with a crank angle sensor for detecting the rotation angle of the crankshaft 6. In this embodiment, as described in detail later, cranks whose phases are shifted from each other by a certain amount are provided. Two crank angle sensors 21 and 22 for outputting angle signals are provided. Further, a cam angle sensor 23 that can give a cylinder identification signal by detecting the specific rotational position of the camshaft is provided. In addition to this, as a detection element necessary for engine control, a water temperature sensor 24 for detecting the temperature of the engine cooling water, an accelerator opening sensor 25 for detecting the accelerator opening (accelerator operation amount), and the like are provided. .

  30 is an ECU (engine control unit) as a control means, receives signals from the sensors 20 to 25, outputs a signal for controlling the fuel injection amount and the injection timing to the fuel injection valve 8, and An ignition timing control signal is output to the ignition device, a signal for controlling the throttle opening is output to the actuator 18 of the throttle valve 17, and the power generation amount is controlled to the regulator circuit 26a of the alternator 26. Output a signal. That is, the ECU 30 corresponds to the control means referred to in the present invention.

  When a predetermined engine stop condition is satisfied during idling, the engine is automatically stopped by stopping fuel supply or the like, and when the engine restart condition is subsequently satisfied, the engine is automatically restarted. When the stop position of the piston is within a specific range (appropriate range) when the engine is restarted, the first combustion is first performed on the compression stroke cylinder when the engine is stopped, the piston is pushed down, and the cylinder in the expansion stroke is After increasing the in-cylinder pressure by raising the piston, fuel is injected into the expansion stroke cylinder for ignition and combustion, and combustion air is injected into the combustion chamber after the initial combustion in the compression stroke cylinder. By supplying the fuel corresponding to the amount of air at an appropriate time after the initial combustion, when the cylinder turns to the piston rise and exceeds the compression top dead center, the cylinder is caused to re-combust. Control. That is, at the time of automatic engine restart, if the piston stop position is in an appropriate range, which will be described later, control is performed so that the engine is once reversely operated at the beginning of the start, and then the normal rotation operation is started.

  In the present embodiment, when the piston of the expansion stroke cylinder at the time of stop is within an appropriate range, the first restart control mode in which the initial combustion in the compression stroke cylinder and the combustion in the expansion stroke cylinder are performed as described above. On the other hand, when the piston is not within the proper range, the combustion in the expansion stroke cylinder and the next compression stroke cylinder are performed while assisting by the starter (starting motor) 31 without performing the initial combustion in the compression stroke cylinder. A second restart control mode for starting by combustion is performed.

  Specifically, in order to properly restart the engine in the first restart control mode, the combustion energy obtained by combusting the air-fuel mixture in the expansion stroke cylinder is sufficiently ensured. Therefore, a cylinder that reaches compression top dead center must overcome the compression reaction force and exceed compression top dead center. Therefore, in consideration of ensuring a sufficient amount of air in the expansion stroke cylinder, which is in the middle of the expansion stroke when the engine is automatically stopped, the piston is combusted in order to effectively increase the compression pressure of the cylinder. It is necessary to stop within a predetermined appropriate range suitable for the above.

  That is, as shown in FIGS. 3A and 3B, the cylinders that are in the expansion stroke cylinder and the compression stroke cylinder when the engine is stopped are out of phase by 180 ° CA. If the piston 4 of the expansion stroke cylinder is located on the bottom dead center side of the stroke center (90 ° CA after the top dead center), the amount of air in the cylinder increases and sufficient combustion energy is obtained. Is obtained. However, when the piston 13 of the expansion stroke cylinder is extremely positioned on the bottom dead center side, the amount of air in the compression stroke cylinder becomes too small and sufficient combustion energy for reversing the crankshaft 6 is obtained. Disappear.

  Therefore, as the predetermined appropriate range R, a predetermined range that slightly exceeds the center of the stroke of the expansion stroke cylinder, that is, the position where the crank angle after compression top dead center is 90 ° CA slightly toward the bottom dead center, for example, after compression top dead center. If the piston can be stopped within a range where the upper limit is 100 ° CA and the lower limit is 125 ° CA, preferably the upper limit is 105 ° CA and the lower limit is 120 ° CA, a predetermined amount is set in the compression stroke cylinder. Thus, sufficient combustion energy can be obtained by reversing the crankshaft 6 by the initial combustion. In addition, by increasing the compression pressure in the cylinder by reversing the crankshaft 6 and securing a large amount of air in the cylinder, the combustion energy for causing the crankshaft 6 to rotate forward is sufficiently generated to generate the engine. Can be reliably restarted. In this embodiment, since a means for suppressing the loss of combustion energy in the compression stroke cylinder is provided, the piston position suitable for the restart is more appropriate than the engine starter in which this means is not provided. The range has been slightly expanded.

  There are various specific methods for controlling the stop position of the piston when the engine is automatically stopped. Here, the compression of the expansion stroke cylinder and the compression stroke cylinder when the engine is stopped is controlled by controlling the opening degree of the throttle valve 17. A description will be given of a case where the reaction force is adjusted and the rotational speed of the engine is adjusted through the resistance of the crankshaft 6 by controlling the power generation amount of the alternator 26 in the process of automatically stopping the engine, thereby controlling the stop position of the piston 4. To do.

  As shown in FIG. 4, when the engine automatic stop condition is satisfied, a plurality of stages including a neutral state in which transmission of driving force to the wheel side is disconnected and a driving state in which transmission of driving force to the wheel side is possible The automatic transmission that can be switched to the drive state is switched from the drive state to the neutral state, and the target speed of the engine is higher than the normal idle speed when the engine is not automatically stopped (hereinafter referred to as “normal idle speed”). For example, in an engine in which a normal idle speed is set to 650 rpm (the automatic transmission is in a drive state), the target speed is set to about 850 rpm (the automatic transmission is in a neutral state) as an idle speed when the automatic stop condition is satisfied. By setting, control to stabilize at the engine speed N is executed, and the engine speed is There stopping fuel injection in a stable point at the target speed t1.

  Further, at the fuel injection stop timing t1, which is the initial stage of the control operation for automatically stopping the engine, the intake air amount during idling when the in-cylinder air-fuel ratio is set to λ = 1 (necessary for continuing the engine operation). The opening degree of the throttle valve 17 is set so that the intake flow rate is higher than the minimum intake flow rate), that is, the combustion state immediately before the time t1 is set so that the in-cylinder air-fuel ratio is set to λ = 1 or in the vicinity thereof. Therefore, the amount of intake air taken into the cylinders 3A to 3D of the engine is increased by increasing the opening of the throttle valve 17 (for example, opening the opening to about 30% of the fully opened state). By setting, the scavenging performance of the combustion gas is ensured, and the rotational resistance of the crankshaft 6 is reduced by reducing the power generation amount of the alternator 26 from the time t0 when the automatic stop condition is satisfied. Is configured to do.

  Further, by stopping the combustion injection at the time point t1, the throttle valve 17 is turned on at the time point t2 when it is confirmed that the engine rotational speed N has decreased and reached a preset reference speed, for example, about 760 rpm. The intake flow rate of the engine cylinders 3A to 3D is closed to reduce the intake flow rate, the power generation amount of the alternator 26 is increased, and the opening of the throttle valve 17 and the power generation amount of the alternator 26 are rotated as described later. By adjusting according to the degree of decrease in the speed N, control is performed to decrease the rotational speed N of the engine along a reference line set based on a result of an experiment performed in advance.

  When the engine is automatically stopped as described above, the kinetic energy of the crankshaft 6 or the flywheel is consumed due to mechanical loss due to friction or pump work of each cylinder 3A to 3D from the fuel injection stop time t1. As a result, the crankshaft 6 of the engine is rotated several times by inertia, and after reaching the compression top dead center (Abt: bt = ... 3, 2, 1 in FIG. 4) about 10 times in a 4-cylinder 4-cycle engine. Stop.

  Specifically, as shown in FIG. 4, after the engine speed N temporarily falls every time the cylinders 3 </ b> A to 3 </ b> D reach compression top dead center, they rise again when the compression top dead center is exceeded. The engine rotation speed N gradually decreases while repeating up and down.

  And in the cylinder which is going to reach the compression top dead center after the time t3 when the last compression top dead center is exceeded, the air pressure increases as the piston 4 rises due to the inertial force, and the piston 4 is pushed by the compression reaction force. Returned, the crankshaft 6 is reversed. Since the air pressure of the expansion stroke cylinder rises due to the reverse rotation of the crankshaft 6, the piston 4 of the expansion stroke cylinder is pushed back to the bottom dead center side according to the compression reaction force, and the crankshaft 6 starts to rotate forward again. The reverse rotation and forward rotation of the crankshaft 6 are repeated several times, and the piston 4 stops after reciprocating. The stop position of the piston 4 is substantially determined by the balance of the compression reaction forces in the compression stroke cylinder and the expansion stroke cylinder, and is affected by the friction of the engine and the like, and is t3 when the last compression top dead center is exceeded. This also changes depending on the rotational inertia of the engine, that is, the level of the engine rotational speed N.

  Accordingly, in order to stop the piston 4 of the cylinder in the expansion stroke within the predetermined appropriate range R suitable for restart when the engine automatically stops, first, the expansion stroke cylinder and the compression stroke cylinder in the compression stroke are used. It is necessary to adjust the intake air flow rates for both cylinders so that the compression reaction force of the cylinders becomes sufficiently large and the compression reaction force of the expansion stroke cylinder is larger than the compression reaction force of the compression stroke cylinder by a predetermined value or more. Therefore, in the present invention, the throttle valve 17 is opened at the fuel injection stop time t1, thereby allowing a predetermined amount of air to be sucked into both the expansion stroke cylinder and the compression stroke cylinder in the compression stroke, and then for a predetermined time. At the time t2 when the time elapses, the throttle valve 17 is closed and its opening degree is reduced to adjust the intake air amount.

  However, in an actual engine, since there are individual differences in the shapes of the throttle valve 17, the intake port 9, the branch intake passage 15a, and the like, the behavior of the air flowing through them changes, so that during the automatic engine stop period, Even if the intake flow rate sucked into the cylinders 3A to 3D is varied and the opening / closing control of the throttle valve 17 is performed as described above, the piston stop position of the cylinder in the expansion stroke and the cylinder in the compression stroke when the engine is stopped Is within the proper range R.

  With respect to this point, in the present embodiment, in the process in which the rotational speed of the engine decreases during the automatic engine stop period, as shown in an example in FIG. 5, when each cylinder 3A to 3D passes the compression top dead center. Paying attention to the fact that there is a clear correlation between the engine speed (top dead center speed) n and the piston stop position of the cylinder in the expansion stroke when the engine is stopped, the fuel injection is stopped at time t1. Later, in the process in which the engine rotational speed N decreases, the engine rotational speed when the piston 4 of each cylinder passes through the compression top dead center, that is, the top dead center rotational speed n is detected, and this top dead center rotational speed n is detected. By controlling the power generation amount of the alternator 26 according to the detected value, the rotational resistance of the crankshaft 6 is adjusted to adjust the degree of decrease in the engine rotational speed.

  That is, FIG. 5 shows the inertia by stopping the fuel injection at the time t1 when the engine speed N reaches the predetermined speed as described above, and maintaining the throttle valve 17 in the open state for a predetermined period thereafter. While measuring the top dead center rotational speed n when the piston 4 provided in each of the cylinders 3A to 3D of the rotating engine passes through the compression top dead center, the piston position of the expansion stroke cylinder when the engine is stopped is examined. The piston position is taken on the vertical axis, and the top dead center rotational speed n of the engine is taken on the horizontal axis, and the relationship between the two is graphed. By repeating this operation, a distribution diagram showing the correlation between the top dead center rotational speed n during the engine stop operation period and the piston stop position in the expansion stroke cylinder is obtained.

  From the above distribution diagram, a predetermined correlation is found between the top dead center rotational speed n during the engine stop operation period and the piston stop position in the expansion stroke cylinder. In the example shown in FIG. If the top dead center rotational speed n in the sixth to second before is within the range indicated by hatching (appropriate rotational speed range), the stop position of the piston 4 is within the range R (compression top dead center) suitable for restarting the engine. It turns out that it enters into 100 degrees-125 degrees CA) after a point. Therefore, after the time t2 when the throttle valve 17 is closed, the ECU 30 controls the power generation amount of the alternator 26 so that the predetermined top dead center rotational speed n is included in the appropriate rotational speed range. .

  The automatic engine stop control will be described based on the flowchart shown in FIG. The process shown in the flowchart of FIG. 6 starts from a state in which the engine is operated, and the ECU 30 first determines whether or not an idle stop condition is satisfied in step S1. This determination is performed based on the vehicle speed, the engine temperature (engine cooling water temperature), and the like. For example, a stopped state where the vehicle speed is 0 or an ultra-low speed state where the vehicle speed is 10 km / h or less continues for a predetermined time and the engine temperature. Is in a predetermined range, and when there is no particular inconvenience (for example, low battery level) in stopping the engine, the idle stop condition is established.

  When the idle stop condition is satisfied (YES in step S1), first, the automatic transmission is automatically switched to the neutral state, the engine speed is stabilized at a target speed higher than the normal idle speed, and EGR is further performed. After performing initial control such as closing an EGR valve (not shown) provided in the passage to stop exhaust gas recirculation, each engine is controlled based on predetermined conditions such as engine speed and boost pressure. The fuel supply to the cylinder is stopped (step S2), and then the throttle valve 17 is once opened to a predetermined opening degree (step S3), thereby ensuring the scavenging performance of the exhaust gas and the power generation amount of the alternator 26 under the automatic stop condition. It lowers from the establishment time (step S4), and thereby the rotational resistance of the crankshaft 6 is reduced. Then, this state is maintained until the engine speed becomes equal to or lower than a predetermined speed (in the example of FIG. 4, about 760 rpm) (step S5). When the engine speed becomes lower than the predetermined speed, the throttle valve 17 is closed (step S6). The intake flow rate sucked into each cylinder 3A to 3D is decreased.

  Next, the power generation amount of the alternator 28 is set to an initial value set to about 60 A in advance, and initial control of the power generation amount that operates the alternator 28 for a predetermined period (for example, about 300 ms) is executed (step S7).

  Subsequently, the top dead center rotational speed n which is the rotational speed of the engine when the piston 4 passes through the compression top dead center is detected (step S8), and the top dead center rotational speed n is within a predetermined range shown in FIG. It is determined whether it is within (appropriate rotation speed range) (step S9). If the result of this determination is that the top dead center rotational speed n is not within the predetermined appropriate rotational speed range, the alternator 26 is based on the rotational speed deviation between the top dead center rotational speed n and the appropriate rotational speed range. Is calculated (step S10). Thus, when the top dead center rotational speed n is not within the proper rotational speed range, for example, when the rotational speed is 470 rpm in FIG. 5, the proper rotational speed range (the high rotational side range and the low rotational speed) sandwiching this rotational speed. The deviation is calculated on the basis of the adjacent appropriate rotation speed range (low rotation side range in this example). Specifically, by determining whether the detected top dead center rotational speed is higher or lower than the intermediate value based on the intermediate value between the lower limit value of the high rotation side range and the upper limit value of the low rotation side range. Determine the appropriate rotational speed range that will serve as the basis for the deviation. Then, this power generation amount is read from a map set in advance based on the rotational speed deviation and the current power generation amount, and when the top dead center rotational speed n is higher than the reference appropriate rotational speed range, The power generation amount of the alternator 26 is increased. If the power generation amount is low, the power generation amount of the alternator 26 is decreased or stopped (step S11), and the process proceeds to step S12.

  If the top dead center rotational speed n is within the predetermined appropriate rotational speed range in step S9, the steps S10 and S11 are skipped, and the engine top dead center rotational speed n is less than or equal to a predetermined value. Is determined (step S12). This predetermined value is a value corresponding to the engine speed at the time when the top dead center is exceeded in the course of the engine speed decreasing along a preset reference line, and is set to about 260 rpm, for example. ing. When it is determined NO in step S12, the process returns to step S8 and the control operation is repeated. If it is determined as YES in step S8 and it is confirmed that the engine top dead center rotational speed n is equal to or lower than the predetermined value, it is determined in step S13 whether or not the engine has been stopped. Based on detection of the stop position of the piston by a stop position detection routine of FIG. 7 described later, the stop position is detected in step S14 and stored in a storage means (not shown) included in the ECU 30.

  FIG. 7 shows a stop position detection routine. When this routine starts, the ECU 30 examines the first crank angle signal CA1 (signal from the first crank angle sensor) and the second crank angle signal CA2 (signal from the second crank angle sensor), and the first crank angle signal. It is determined whether the second crank angle signal CA2 is low when CA1 rises or the second crank angle signal CA2 is high when the first crank angle signal CA1 falls. In short, by determining whether the phase relationship between these signals CA1 and CA2 is as shown in FIG. 8 (a) or FIG. 8 (b), it is determined whether the engine is rotating forward or reverse. Is determined (step S20).

  That is, at the time of forward rotation of the engine, as shown in FIG. 8A, the second crank angle signal CA2 is generated with a phase delay of about a half pulse width with respect to the first crank angle signal CA1, thereby the first crank angle signal. The second crank angle signal CA2 becomes Low when CA1 rises, and the second crank angle signal CA2 becomes High when the first crank angle signal CA1 falls. On the other hand, during reverse rotation of the engine, as shown in FIG. 8B, the second crank angle signal CA2 is generated with a phase advance of about a half pulse width with respect to the first crank angle signal CA1, so On the contrary, the second crank angle signal CA2 becomes High when the first crank angle signal CA1 rises, and the second crank angle signal CA2 becomes Low when the first crank angle signal CA1 falls. Accordingly, if the determination in step S20 is YES, the CA counter for measuring the crank angle change in the forward rotation direction of the engine is increased (step S21), and if the determination in step S20 is NO, the CA counter is decreased. (Step S22). Then, the stop position is obtained by checking the value of the CA counter when the engine is stopped (step S23).

  On the other hand, when the predetermined restart condition is satisfied for the engine that is in the automatic stop state as described above and the piston 4 of the expansion stroke cylinder is within the predetermined appropriate range, the ECU 30 The engine is controlled to automatically restart in the 1 restart control mode (direct start mode).

  As described above, the engine restart in the first restart control mode is performed by first injecting fuel into the compression stroke cylinder when the engine is stopped and igniting it, thereby executing the first combustion of the compression stroke cylinder. The piston is pushed down, and the movement of the piston is transmitted to the crankshaft 6 via the connecting rod of the cylinder. The rotational pressure of the crankshaft 6 raises the piston of the cylinder via the connecting rod of the expansion stroke cylinder, thereby increasing the in-cylinder pressure. After that, the fuel is injected into the expansion stroke cylinder for ignition and combustion so that the engine is restarted only by the torque generated by engine combustion without using the starter motor. It is a thing. In this way, if the engine is restarted only by the torque generated by the combustion of the engine, the engine can be restarted more quickly than when the starter motor is used, and the vehicle is not slack when starting. It can be suppressed as much as possible.

  By the way, in restarting the engine in the first restart control mode, the in-cylinder pressure of the expansion stroke cylinder is increased by using the combustion energy of the compression stroke cylinder when the engine is stopped. Not all of the combustion energy in the compression stroke cylinder contributes to an increase in the in-cylinder pressure of the expansion stroke cylinder, but the combustion energy in the compression stroke cylinder is partly due to the friction of the crankshaft 6 and the pump work of each cylinder 3A to 3D. Is consumed.

  Therefore, even when the piston of the expansion stroke cylinder is stopped at an appropriate position, if the piston is stopped at the bottom dead center side where the combustion energy of the compression stroke cylinder becomes relatively small, Compared with the case where the piston is stopped at the point side, the certainty of starting is lowered. Therefore, in the present invention, when the piston of the expansion stroke cylinder is stopped on the bottom dead center side, the certainty of this starting is ensured.

  In order to ensure the starting certainty, the inventor of the present application pays attention to the partial consumption of the combustion energy of the compression stroke cylinder, particularly the combustion energy consumed by the pump work during the reverse operation of the engine. As much as possible, the combustion energy of the compression stroke cylinder is efficiently contributed to the increase of the in-cylinder pressure of the expansion stroke cylinder.

  That is, the ECU 30 is when the engine restart condition is satisfied, and the piston position of the expansion stroke cylinder when the engine is stopped is on the bottom dead center side with respect to a predetermined reference position (115 ° CA in this embodiment). In this case, the piston position of the expansion stroke cylinder is higher than the reference position from the time of restart until the second combustion after the operation in the forward direction of the engine (before the first combustion in the intake stroke cylinder when the engine is stopped). Control is performed so that the opening of the throttle valve 17 is increased, for example, the throttle valve 17 is fully opened, compared to when it is on the dead side.

  Here, when the engine is stopped, the pressure in the intake passage 15 is at or near atmospheric pressure. Therefore, normally, when the engine is started, the intake pressure in the intake passage 15 is prevented in order to prevent excessive blow-up. The throttle valve 17 is in a fully closed state until becomes a predetermined negative pressure. However, if the reverse rotation operation of the engine is executed while the throttle valve 17 is fully closed, the air in the intake stroke cylinder when the engine is stopped is pushed back to the intake passage 15 along with the reverse rotation operation. Since the throttle valve 17 in the passage 15 is closed, the exhaust pressure of the intake stroke cylinder when the engine is stopped increases, and therefore the combustion energy consumed by the pump work increases. In addition, when the engine is rotating in reverse, the combustion energy of the compression stroke cylinder is low in the first place as compared with when rotating in the normal direction, so there is less need to consider excessive blow-up.

  Therefore, the exhaust pressure of the intake stroke cylinder in the reverse operation period can be reduced by fully opening the opening of the throttle valve 17 in the initial stage including the reverse operation period of the engine as described above. By reducing the piston resistance of the cylinder, the compression pressure of the expansion stroke cylinder can be efficiently increased. In addition, since the combustion energy of the compression stroke cylinder can be efficiently used as the compression pressure of the expansion stroke cylinder in this way, the appropriate range for the above-described appropriate range in the engine starter having no such means is provided. The range can be expanded to the bottom dead center side of the expansion stroke cylinder.

  On the other hand, the ECU 30 is when the engine restart condition is satisfied, and the piston position of the expansion stroke cylinder when the engine is stopped is on the top dead center side with respect to a predetermined reference position (115 ° CA in this embodiment). At this time, the throttle valve 17 is controlled to be fully closed from the restart.

  That is, when the piston position of the expansion stroke cylinder is on the top dead center side relative to the predetermined reference position, in other words, when the piston position of the compression stroke cylinder is on the bottom dead center side, combustion by the initial combustion in the compression stroke cylinder Since sufficient energy can be obtained, by fully closing the throttle valve 17, the piston resistance of the intake stroke cylinder when the engine is stopped is increased to effectively prevent the reverse rotation amount from becoming larger than necessary. Further, the pressure in the intake passage 15 on the downstream side of the throttle valve 17 is increased by the rise of the piston of the intake stroke cylinder during the reverse rotation operation of the engine, and the piston at the early stage of the forward rotation operation of the engine is utilized by using this pressure. The resistance can be reduced, and the engine can be started smoothly and reliably.

  The automatic engine restart control will be described based on the flowcharts shown in FIGS.

  When the control operation starts, it is determined whether or not the piston stop position of the expansion stroke cylinder when the engine is automatically stopped is within a predetermined appropriate range (100 ° to 125 ° CA in the present embodiment) (step S101). If it is not within the appropriate range, it is determined that starting in the first restart control mode is difficult, and control in the second restart control mode, that is, normal start control using the starter motor 31 is executed. (Step S102), the process proceeds to Step S123 described later.

  On the other hand, when the piston stop position of the expansion stroke cylinder is within the predetermined appropriate range (YES in step S101), this piston stop position is lower than the predetermined reference position (115 ° CA in this embodiment). It is determined whether it is on the side (step S103). When the stop position of the piston in the expansion stroke cylinder is 115 ° CA or more, the air in the compression stroke cylinder is short and the actuator 18 is driven from the viewpoint of suppressing the loss of combustion energy in the compression stroke cylinder. The throttle valve 17 is fully opened (step S104).

  On the other hand, when the stop position of the piston of the expansion stroke cylinder is less than 115 ° CA, sufficient air is sucked into the compression stroke cylinder and sufficient combustion energy can be secured. In order to prevent the blow-up, the throttle valve 17 is maintained in a fully closed state (step S104 is skipped).

  Then, when an engine restart condition is established (eg, when the determination in step S105 is YES) such as when an accelerator operation for starting is performed from a stopped state or when the battery voltage decreases, the piston is determined in step S106. The air amount of the compression stroke cylinder and the expansion stroke cylinder is calculated based on the stop position. That is, the combustion chamber volumes of the compression stroke cylinder and the expansion stroke cylinder are determined from the stop position, and when the engine is stopped, the engine is stopped after several revolutions after the fuel is cut, so the expansion stroke cylinder is also fresh. Since the in-cylinder pressure of the compression stroke cylinder and the expansion stroke cylinder is substantially atmospheric pressure while the engine is stopped and the engine is stopped, the amount of fresh air is obtained from the combustion chamber volume.

  The steps S101 to S104 may be executed after the determination of the restart establishment condition (step S105). However, by executing the steps S101 to S104 in advance, quick restart is possible. Is advantageous in that it becomes possible.

  Subsequently, in step S107, fuel is injected so that the predetermined compression stroke cylinder air-fuel ratio for the first compression stroke cylinder (A / F = 11 to 14) with respect to the calculated air amount of the compression stroke cylinder, and step S108. Thus, after the time set in consideration of the fuel vaporization time after fuel injection in the compression stroke cylinder, the cylinder is ignited. In this case, the air-fuel ratio for the first compression stroke cylinder is obtained from the map M1 according to the stop position of the piston. The map M1 is set in advance so that the first air-fuel ratio of the compression stroke cylinder is approximately the stoichiometric air-fuel ratio or an air-fuel ratio somewhat richer than the stoichiometric air-fuel ratio.

  Next, in step S109, it is determined whether or not the piston has moved, based on whether or not the edges of the crank angle sensors 21 and 22 (rise or fall of the crank angle signal) have been detected within a certain time after ignition. If the piston does not move due to misfire, re-ignition is repeatedly performed on the compression stroke cylinder (step S110).

  When the edges of the crank angle sensors 21 and 22 are detected (when the determination in step S109 is YES), the air-fuel ratio for the expansion stroke cylinder becomes a predetermined expansion stroke cylinder air-fuel ratio with respect to the air amount of the expansion stroke cylinder calculated in step S106. The fuel is injected into (step S111). In this case, the expansion stroke cylinder air-fuel ratio is obtained from the map M2 in accordance with the stop position of the piston. The map M2 is set in advance so that the air-fuel ratio for the expansion stroke cylinder becomes substantially the stoichiometric air-fuel ratio or a slightly richer air-fuel ratio than the stoichiometric air-fuel ratio, like the first air-fuel ratio for the compression stroke. Yes. Then, ignition is performed for the expansion stroke after a predetermined delay time has elapsed after edge detection (step SS112). The delay time is obtained from the map M3 according to the stop position of the piston.

  Further, in step S113, fuel is injected again into the compression stroke cylinder at a predetermined timing when the piston of the compression stroke cylinder approaches the vicinity of the top dead center. This fuel injection is not performed for recombustion in the compression stroke cylinder, but is performed to reduce the pressure in the compression stroke cylinder by latent heat of vaporization, and the compression stroke cylinder 2 is determined from the map M4 according to the stop position. The fuel injection amount for the second time is obtained, and the injection timing is set so that self-ignition does not occur due to the injected fuel.

  Here, the flow of air stops when the engine is stopped, and the fresh air temperature drawn into the intake stroke cylinder when the engine is stopped also rises. Therefore, in order to efficiently rotate the engine forward, after the engine is started, control is performed so that the engine efficiently rotates forward while preventing the self-ignition when the intake stroke cylinder starts the compression stroke for the first time. In this embodiment, the following control is executed.

  That is, moving to FIG. 10, the engine temperature is detected by the water temperature sensor 24, the engine stop time, the intake air temperature, and the like are detected based on a timer and a temperature sensor (not shown), and the in-cylinder temperature estimated from the detection result The initial intake air density after restarting the intake stroke cylinder when the engine is stopped is estimated based on the atmospheric pressure and the intake air amount of the intake stroke cylinder is calculated based on the estimated value (step S114).

  Subsequently, in step S115, in order to prevent self-ignition in the intake stroke cylinder, a correction value of the air-fuel ratio for the intake stroke cylinder is obtained based on the previously estimated in-cylinder temperature of the intake stroke cylinder. This correction value is calculated from a map M5 obtained in advance by experiments or the like based on the in-cylinder temperature.

  Then, the injection amount of fuel injected into the intake stroke cylinder is calculated from the correction value of the air-fuel ratio and the air amount calculated in step S114 (step S116), and the new temperature that has increased when the engine is stopped. Fuel is injected in the compression stroke with a delay from the normal injection timing (intake stroke) so as to suppress the rise in temperature by the latent heat of vaporization and reduce the compression pressure (step S117). The specific fuel injection timing is set in consideration of the engine water temperature, the engine stop time, the intake air temperature, and the like. For example, the fuel injection timing is set at the middle stage of the compression stroke or later.

  Further, when the throttle valve 17 is fully opened in step S104 (YES in step S118), the actuator 18 is driven to close the throttle valve 17 when the intake stroke cylinder exceeds the compression top dead center when the engine is stopped. Is fully closed (step S119).

  Note that the determination in step S118 is, specifically, for example, when the opening of the throttle valve 17 is increased in step S104, a flag is set to determine whether or not this flag is present.

  Thereafter, immediately after the piston 4 of the intake stroke cylinder at the time of stoppage exceeds the compression top dead center, the spark plug 7 ignites (step S120), and the engine is started by generation of reverse torque at a time when there is not sufficient inertial force at the initial stage of engine start It is made so as not to interfere.

  Next, the routine proceeds to step S121, where it is determined whether or not the intake pressure (intake pipe negative pressure) in the branch intake passage 15a downstream of the throttle valve 17 is higher than the intake pressure during normal idling operation of the engine. If the intake pressure is higher than that during idle operation (YES in step S121), the amount of air sucked into each of the cylinders 3A to 3D is secured, and from the viewpoint of preventing excessive blow-up, during idle operation. The throttle valve 17 is driven so that the opening (for example, 4 to 5% when fully opened) is smaller than the opening (for example, 8% when fully opened) (step S122). Then, the amount of air sucked into 3A to 3D is reduced until the intake pressure in the branch intake passage 15a is approximately the same as or lower than the intake pressure during idle operation. On the other hand, when it is determined that the intake pressure is the same or lower than that during the idling operation (NO in step S121), the routine shifts to normal engine control and is terminated.

  Although details of the routine of the second restart control mode (starter motor start mode) executed when the determination in step S101 in the flowchart of FIG. 9 is NO are omitted, normal engine start-up is performed. The same control is executed.

  The effect | action at the time of the restart in the apparatus of this embodiment as mentioned above is demonstrated.

  In a multi-cylinder four-cycle engine, each cylinder performs a cycle consisting of intake, compression, expansion, and exhaust strokes with a predetermined phase difference. When the cylinder 3A, the second cylinder 3B, the third cylinder 3C, and the fourth cylinder 3D are called, as shown in FIG. 11 and FIG. 12, the cycle is the first cylinder 3A, the third cylinder 3C, and the fourth cylinder 3D. The second cylinder 3B is performed in the order of 180 ° in crank angle in order of the second cylinder 3B.

  When a predetermined restart condition is satisfied after the engine is stopped, the engine is automatically restarted. At this time, the stop position of the piston is within a predetermined appropriate range in the vicinity of the stroke intermediate portion in the expansion stroke cylinder. If there is, the first restart control mode routine is executed. FIG. 11 shows the stroke of each cylinder of the engine in the first restart control mode and the combustion in each cylinder from the start of the start control (in accordance with the order of combustion in the figure (1), (2), (3). And the direction of operation of the engine by each combustion is indicated by an arrow, and FIG. 12 shows the engine rotation speed and the crank angle of the first cylinder in the case of the first restart control mode. 3 shows the temporal change in the cylinder pressure of the predetermined cylinder and the opening degree of the throttle valve 17.

  As shown in these drawings, in the case of the first restart control mode, first, the combustion air-fuel ratio in the compression stroke cylinder (the third cylinder in the illustrated example) is substantially the stoichiometric air-fuel ratio or a slightly richer air-fuel ratio than this. The first combustion ((1) in FIG. 11) is performed while the engine is turned on, and the piston of the compression stroke cylinder is pushed down to the bottom dead center side by the combustion pressure (part a in FIG. 12) due to this initial combustion, and the engine is reversed. Accordingly, when the piston of the expansion stroke cylinder (the first cylinder in the illustrated example) approaches top dead center, the air in the cylinder is compressed and the in-cylinder pressure rises (b in FIG. 12). portion). Then, when the piston of the expansion stroke cylinder is sufficiently close to the top dead center, the cylinder is ignited, and the fuel previously injected into the cylinder is burned ((2) in FIG. 11). The engine is driven in the forward rotation direction by the combustion pressure (c portion in FIG. 12). Further, the fuel is injected into the compression stroke cylinder at an appropriate timing in the latter half of the compression stroke, whereby the compression pressure near the top dead center of the compression stroke cylinder is reduced ((3) in FIG. 11). ). After that, the piston of the compression stroke cylinder overcomes this reduced compression pressure and exceeds the compression top dead center (part d in FIG. 12), and subsequently enters the stop intake stroke cylinder that reaches the compression stroke in the latter half of the compression stroke. Fuel is injected, and the piston of the cylinder is ignited at a predetermined timing exceeding the top dead center (portion e in FIG. 12), and combustion is performed in the intake stroke cylinder ((4) in FIG. 11). ). The combustion pressure (portion f in FIG. 12) increases the driving force of the engine, and a smooth start is executed.

  When the piston of the expansion stroke cylinder when the engine is stopped is at the bottom dead center side from the predetermined reference value, the piston of the intake stroke cylinder exceeds the top dead center from the start as shown in FIG. Until then, the throttle valve 12 is fully opened, and by reducing the exhaust pressure of the intake stroke cylinder during the reverse rotation operation of the engine, the piston resistance of the cylinder can be reduced, thereby reducing the piston resistance of the compression stroke cylinder. it can. Therefore, it is possible to efficiently increase the compression pressure of the expansion stroke cylinder by suppressing the energy loss caused by pushing down the piston of the compression stroke cylinder, and to set the appropriate range of the compression stroke cylinder to the top dead center side by suppressing the energy loss. (In other words, the appropriate range of the expansion stroke cylinder can be expanded to the bottom dead center side), thereby improving the startability of the engine. In addition, since the piston position is determined based on the predetermined reference position, even if the appropriate range of the piston position at which the reverse rotation operation of the engine can be executed is changed due to the deterioration of the engine over time or the change of the external environment, etc. Startability can be improved reliably.

  On the other hand, when the piston of the expansion stroke cylinder when the engine is stopped is at the top dead center side with respect to a predetermined reference value, it is fully closed until the intake negative pressure in the intake passage 15 reaches a predetermined negative pressure from the start. Thus, it is possible to effectively prevent the reverse rotation amount from becoming larger than necessary by increasing the piston resistance of the intake stroke cylinder during the reverse rotation operation of the engine. Moreover, the pressure in the intake passage 15 on the downstream side of the throttle valve 17 increases due to the rise of the piston of the intake stroke cylinder during the reverse rotation operation of the engine, and by using this pressure, the piston resistance at the initial stage of the forward rotation operation of the engine is reduced. The engine can be started smoothly and reliably (corresponding to the portion e in FIG. 12).

  The engine starting device described above is an embodiment of the device to which the starting device according to the present invention is applied, and the specific configuration of the device is appropriately changed without departing from the gist of the present invention. This is possible, and modifications will be described below.

  (1) In the above embodiment, when the first restart control mode is executed and the stop position of the piston of the expansion stroke cylinder is in the range closer to the bottom dead center than the predetermined reference position, the throttle Although the valve 17 is fully opened, if the opening degree is set larger than the case where the piston of the expansion stroke cylinder is in the range from the top dead center to the predetermined reference position, the throttle valve The opening degree of 17 is not particularly limited. Further, the period during which the throttle valve 17 is open is not limited to that of the above embodiment, and the throttle valve 17 may be closed after the reverse rotation of the engine is completed, for example.

  (2) In the above embodiment, combustion is not performed when the piston of the compression stroke cylinder at the time of automatic restart in the first restart control mode first reaches top dead center, and only fuel is injected. However, when the initial combustion for the reverse rotation operation of the engine in the cylinder is made the lean combustion with the lean air-fuel ratio rather than the stoichiometric air-fuel ratio, it can be burned even when the top dead center is first reached. . In addition, air may be replenished into the cylinder after the initial combustion. In this case, a valve timing variable mechanism that can change at least the intake valve closing timing is provided in the valve operating mechanism for the intake valve so that the engine is recombusted. Sometimes, the intake valve closing timing of the compression stroke cylinder may be delayed from the normal time so that the compression stroke cylinder enters the compression stroke by a predetermined crank angle from the bottom dead center.

  In this way, when the engine reverses to the advance side from the intake valve closing timing due to the initial combustion in the compression stroke cylinder, the intake valve is opened, so that a part of the in-cylinder gas and the fresh air are exchanged. Fresh air for the second combustion will be replenished. In addition to this effect, the pressure in the cylinder decreases when the intake valve is opened after the initial combustion, so that the resistance acting on the piston of the compression stroke cylinder during forward rotation of the engine due to combustion in the expansion stroke cylinder thereafter Reduced and advantageous for restart.

  Further, when the second combustion is performed in the compression stroke cylinder, the combustion may be controlled to be combustion by compression self-ignition.

  (3) In addition to the configuration of the above embodiment, the valve timing mechanism for the exhaust valve is provided with a valve timing variable mechanism that can change at least the exhaust valve opening timing. It is preferable to delay the opening timing of the exhaust valve at the time of the exhaust stroke for the first time from the normal time so that the exhaust valve opens at approximately bottom dead center.

  In this way, the energy from combustion in the expansion stroke effectively acts on the piston of the cylinder without escaping to the exhaust passage side until approximately the bottom dead center, so that the startability is improved.

  (4) In the example shown in FIG. 9, when the engine restart condition is satisfied, the initial combustion of the compression stroke cylinder fails by injecting the fuel for the expansion stroke cylinder after injecting the fuel for the initial combustion of the compression stroke cylinder. (If the ignition is not successful even after repeated reignitions), it is possible to avoid unnecessary fuel injection by stopping the fuel injection for the expansion stroke cylinder. The fuel for the expansion stroke may be injected substantially at the same time as the injection timing of the fuel for combustion. Thus, by advancing the fuel injection timing of the expansion stroke cylinder, it is possible to earn time for fuel vaporization from the fuel injection to the ignition of the expansion stroke cylinder. When the initial combustion of the compression stroke cylinder is unsuccessful, the restart control mode may be changed to start by motor assist in the starter motor 31.

  (5) In the above embodiment, the throttle valve 17 is provided in the common intake passage 15c. However, the arrangement location of the throttle valve 17 is not limited to this, and for example, each branch intake passage A multiple throttle valve may be provided at 15a.

  (6) The device of the present invention can also be applied to multi-cylinder engines other than four-cylinder engines.

1 is a schematic cross-sectional view of an engine provided with a starter according to the present invention. It is explanatory drawing which shows the structure of the intake system and exhaust system of an engine. It is explanatory drawing which shows the relationship between the piston stop position and air quantity of the cylinder which becomes an expansion stroke and a compression stroke at the time of an engine stop. It is a time chart which shows the change state etc. of the engine speed at the time of an engine stop. It is a distribution map which shows the correlation with the engine speed at the time of an engine stop, and a piston stop position. It is a flowchart which shows the automatic stop control operation | movement of an engine. It is a flowchart which shows detection control operation | movement of a piston stop position. It is explanatory drawing which shows an output signal in a crank angle signal. It is a flowchart which shows the first half of the control action at the time of engine restart. It is a flowchart which shows the latter half part of the control action at the time of engine restart. It is a time chart which shows the combustion operation etc. at the time of engine restart. It is a time chart which shows the change state etc. of the engine speed at the time of engine restart.

Explanation of symbols

3A to 3D Cylinder 4 Piston 6 Crankshaft 15 Intake passage 15b Surge tank 15c Common intake passage 17 Throttle valves 21, 22 Crank angle sensor (piston position detecting means)
26 Alternator 30 ECU (control means)
31 Starter motor R Appropriate range N Rotational speed n Top dead center rotational speed

Claims (6)

The engine is automatically stopped when a predetermined engine stop condition is satisfied, and when the restart condition is satisfied after the engine is stopped, fuel is supplied to the compression stroke cylinder when the engine is stopped, and ignition and combustion are performed. The engine is operated by a predetermined amount in the reverse rotation direction to increase the in-cylinder pressure by raising the piston of the cylinder in the expansion stroke when the engine is stopped, and then the combustion is performed in the expansion stroke cylinder to perform the normal rotation. In the engine starting device that is rotated in the direction and restarted,
A throttle valve for adjusting the amount of intake air introduced into each cylinder from the intake passage;
Piston position detecting means for detecting the piston position of the expansion stroke cylinder when the engine is stopped;
When the engine stop condition is satisfied, control is performed so that the piston of the expansion stroke cylinder at the time of stop is stopped within a predetermined appropriate range, and at the time of engine restart based on the detection result by the piston position detecting means. Control means for controlling the opening of the throttle valve in
When the engine restart condition is satisfied and the piston position of the expansion stroke cylinder when the engine is stopped is at the bottom dead center side with respect to a predetermined reference position, at least the reverse rotation direction of the engine An engine starter characterized in that, during an operation period, control is performed so as to increase the opening of the throttle valve as compared to when the piston position of the expansion stroke cylinder is on the top dead center side with respect to the reference position.   The control means fully closes the throttle valve when the engine restart condition is satisfied and the piston position of the expansion stroke cylinder when the engine is stopped is on the top dead center side with respect to a predetermined reference position. 2. The engine starting device according to claim 1, wherein the engine starting device is controlled to be in a state.   The engine is a four-cylinder engine in which the combustion cycle of each cylinder is performed with a predetermined phase difference, and the control means has an expansion stroke cylinder when the engine stop condition is satisfied when the engine stop condition is satisfied. The engine starter according to claim 1 or 2, wherein the piston is controlled to stop within a predetermined range exceeding 90 ° after compression top dead center.   The engine starting device according to claim 3, wherein the reference position is set within a range of 100 ° to 125 ° after compression top dead center.   The control means reversely rotates the engine by combustion in the cylinder in the compression stroke when the piston position detection means detects that the expansion stroke cylinder at the time of stoppage is stopped outside the predetermined appropriate range. From a first restart mode in which combustion is performed in a cylinder in an expansion stroke after a predetermined amount of operation in the direction is performed, a second restart mode in which the engine is operated in the normal rotation direction from the initial start by driving a starter motor. The engine starting device according to any one of claims 1 to 4, wherein switching is performed.   When the opening of the throttle valve is increased during the reverse rotation operation of the engine, the control means increases the opening of the throttle valve after the compression top dead center where the piston of the cylinder in the intake stroke first reaches when the engine is stopped. The engine starting device according to any one of claims 1 to 5, wherein the engine starting device is controlled to decrease.

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