JP2013113161A - Start control device of compression self-ignition type engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a start control device of a compression self-ignition type engine that increases the opportunity of a rapid engine restart by one compression starting, in an AT vehicle where the rotation decrease after fuel cut is relatively fast.SOLUTION: In a process of automatically stopping the engine, before a predetermined time passes from the point when an automatic stop condition is established, an ECU 50 makes the opening of an intake throttle valve 30 disposed in an intake passage 28 smaller than the opening before the automatic stop condition is established. The ECU 50 stops fuel injection from a fuel injection valve 15 after the predetermined time passes. After the fuel injection is stopped, the ECU 50 increases the opening of the intake throttle valve 15 near the top dead center next before the last top dead center of all cylinders before the engine stops.

Description

  The present invention is provided in a compression self-ignition engine that burns fuel injected from a fuel injection valve into a cylinder by self-ignition, and automatically stops the engine when a predetermined automatic stop condition is satisfied, When the restart condition is satisfied, if the stop position of the piston of the stop compression stroke cylinder that becomes the compression stroke when the engine is stopped is within a specific range set relatively near the bottom dead center, a starter motor is used. The present invention relates to a start-up control device for a compression self-ignition engine that restarts the engine by injecting fuel from a fuel injection valve into the stop-time compression stroke cylinder while applying a rotational force to the engine.

HCCI engine represented by a diesel engine, in general, better thermal efficiency than spark-ignition engines such as gasoline engines, since even small amounts of CO ₂ emitted, in recent years, widely spread as vehicle engine I am doing.

In the compression self-ignition engine as described above, in order to further reduce CO ₂ , the engine is automatically stopped during idle operation, and then the engine is restarted when the vehicle is started. It is effective to adopt a so-called idle stop control technique, and various studies have been conducted on this.

  For example, in Patent Document 1 below, when a predetermined automatic stop condition is satisfied, the diesel engine is stopped, and when a predetermined restart condition is satisfied, fuel injection is performed while the starter motor is driven to restart the diesel engine. In a control device for a diesel engine to be started, it is disclosed to variably set a cylinder for injecting fuel first based on a piston stop position of a cylinder stopped in a compression stroke (compression stroke cylinder at stop).

  Specifically, in this document, when the diesel engine is automatically stopped, the stop position of the piston of the stop-time compression stroke cylinder in the compression stroke at that time is obtained, and the piston stop position is relatively close to the bottom dead center. It is determined whether or not the engine is in the proper position set to the first position, and if it is in the proper position, the first compression top dead center of the engine as a whole is obtained by injecting the first fuel into the compression stroke cylinder at the time of stop. Combustion is started from the time of arrival (hereinafter referred to as “one compression start”).

  On the other hand, when the piston in the compression stroke at the time of stop is at the top dead center side from the appropriate position, the cylinder stopped in the intake stroke (intake stroke cylinder at the time of stop) shifts to the compression stroke and then the cylinder first By injecting this fuel, combustion is restarted from the time when the engine reaches the second compression top dead center (hereinafter referred to as “two-compression start”). As described above, the two-compression start in which fuel is injected into the stop intake stroke cylinder instead of the stop compression stroke cylinder is performed when the piston of the stop compression stroke cylinder is deviated from the appropriate position to the top dead center side. Because the compression allowance (stroke amount to top dead center) by the piston is small and the air in the cylinder does not sufficiently heat up, misfire may occur even if fuel is injected into the compression stroke cylinder at the time of stop. is there.

  Regarding the automatic engine stop, for example, in Patent Document 2, in the first half of the process of automatically stopping the engine, the intake valve is fully closed during the entire stroke of each cylinder, so There is disclosed a diesel engine that suppresses the introduction of air, suppresses a decrease in in-cylinder temperature, and suppresses energization of glow when the engine is restarted.

JP 2009-062960 (paragraph 0048) JP 2009-22002 A (paragraph 0047)

  In the technique of Patent Document 1 described above, when the piston of the compression stroke at the time of stoppage, which becomes the compression stroke when the engine is stopped, is in the proper position, the engine can be restarted quickly by one compression start, but the top dead center side from the appropriate position. If it is off, it is necessary to perform a two-compression start, and the time required for restarting becomes longer. That is, in the two-compression start, since the fuel is injected after waiting for the stop-intake cylinder to enter the compression stroke when the engine is stopped, until the engine reaches the second compression top dead center. The energy generated by combustion cannot be used, and the restart time is increased accordingly. For this reason, it is desirable to enable engine restart by one compression start as frequently as possible.

  Therefore, for example, in the process of automatically stopping the engine, by adjusting the absorption torque (power generation amount) of the alternator, the top dead center of each cylinder is set so that the piston stop position of the compression stroke cylinder at the time of stop is near the bottom dead center. It is proposed to control the point passing speed.

  However, since the compression self-ignition engine generally has a large inertia weight of the rotating system, it is difficult to stably converge the piston stop position to the target stop position even if the alternator is precisely controlled. In particular, in an MT vehicle equipped with a manual transmission, a flywheel having a large inertial mass for inputting smooth rotation is often incorporated into the transmission. For example, such a flywheel having a large inertial mass is incorporated. Compared to AT vehicles (vehicles equipped with automatic transmissions) that have nothing, the inertial mass of the rotating system becomes even larger, and it is more stable to converge the piston stop position to the target stop position by controlling the alternator. It becomes even more difficult.

  Therefore, in the process of automatically stopping the engine, during the intake stroke of the compression stroke cylinder at the time of stop (for example, the top dead center one before the last top dead center (referred to as “final TDC”) of all the cylinders before the engine automatically stops) The amount of air flowing into the stop-time compression stroke cylinder from the point (referred to as “2TDC”) to the final TDC during the intake stroke of the stop-time expansion stroke cylinder (for example, the final stroke) An intake throttle provided in the intake passage so as to be larger than the amount of air flowing into the stop expansion stroke cylinder at a top dead center (referred to as “3TDC”) two times before TDC to the 2TDC. It is proposed to control the valve.

  According to this, in the process of automatically stopping the engine, a larger amount of air flows into the stop compression stroke cylinder than in the stop expansion stroke cylinder. As a result, when the engine is automatically stopped, a compression reaction force (a force for expanding the compressed air) acts on the compression stroke cylinder when stopped, and an expansion reaction force (expanded air) acts on the expansion stroke cylinder when stopped. The force that tries to contract) works. Therefore, the piston of the compression stroke cylinder at the time of stoppage is lowered and the piston stop position is naturally close to the bottom dead center. The piston of the expansion stroke cylinder at the time of stop is naturally raised and the piston stop position is naturally close to the top dead center. As a result, the piston of the compression stroke cylinder at the time of stop can be stably stopped near the bottom dead center, and the compression self-ignition engine can be rapidly restarted with one compression start at a high frequency.

  However, there are the following problems. As described above, in the process of automatically stopping the engine, the intake throttle valve is controlled so that the amount of air flowing into the compression stroke cylinder at stop is larger than the amount of air flowing into the expansion stroke cylinder at stop. As an operation, for example, the intake throttle valve is closed (for example, opening degree 0%) during the intake stroke (3 TDC to 2 TDC) of the stop expansion stroke cylinder, and during the intake stroke (2 TDC to final TDC) of the stop compression stroke cylinder. ) Is considered to open the intake throttle valve (opening over 0%). By closing the intake throttle valve, the pressure in the intake passage on the downstream side of the intake throttle valve (hereinafter simply referred to as “downstream pressure”) decreases, and the amount of air flowing into the expansion stroke cylinder at the time of stop decreases. On the other hand, by opening the intake throttle valve, the downstream pressure increases, and the amount of air flowing into the compression stroke cylinder at the time of stop increases.

  Incidentally, the automatic stop of the engine is substantially achieved by stopping the fuel injection from the fuel injection valve into the cylinder (fuel cut). When the fuel cut is started, the combustion expansion disappears, the engine rotates by inertia, the engine rotation speed gradually decreases, and finally a complete stop (0 rpm) is reached. While the engine speed is gradually decreasing, the above-mentioned 3TDC (top dead center 2 before the last top dead center), 2TDC (top dead center 1 before the last top dead center), and The final TDC (last top dead center) comes in order.

  If the intake throttle valve is closed at the same time as the fuel cut, the air in the intake passage on the downstream side of the intake throttle valve is consumed every cycle and the downstream pressure decreases, and the engine speed gradually decreases. I will do it. Here, an AT vehicle equipped with an automatic transmission does not incorporate the above-described flywheel, and therefore the inertia weight of the rotating system is smaller than that of an MT vehicle that often incorporates it. The number of rotations due to inertia tends to be small (rotational decrease is fast). Then, in the AT vehicle, 3TDC arrives before the downstream pressure does not sufficiently decrease, and the amount of air flowing into the expansion stroke cylinder at the time of stop becomes small. Further, even if the intake throttle valve is opened at 2 TDC, the downstream pressure increases only slightly, and the increase in the amount of air flowing into the compression stroke cylinder at the time of stop is slight. Therefore, the difference between the amount of air flowing into the stop stroke cylinder and the amount of air flowing into the stop stroke cylinder becomes small, and the compression reaction force acting on the stop stroke cylinder when the engine automatically stops. In addition, the expansion reaction force acting on the expansion stroke cylinder at the time of stop is reduced, and as a result, it is difficult to stably stop the piston of the compression stroke cylinder at the time of stop near the bottom dead center.

  Such a problem becomes more prominent in an AT vehicle with a torque converter. This is because the resistance of the torque converter brakes the engine rotation, and the rotation decrease after the fuel cut becomes faster.

  The present invention has been made in view of the circumstances as described above, and in an AT vehicle in which a decrease in rotation after a fuel cut is relatively fast, the amount of air flowing into the stop compression stroke cylinder and the stop expansion stroke cylinder It is an object of the present invention to provide a start-up control device for a compression self-ignition engine that can sufficiently increase the deviation from the amount of air flowing into the interior and thereby increase the chance of quick engine restart by one compression start.

  In order to solve the above problems, the present invention is provided in a compression self-ignition engine that burns fuel injected from a fuel injection valve into a cylinder by self-ignition, and when a predetermined automatic stop condition is satisfied. The stop position of the piston of the stop-time compression stroke cylinder that is set to the compression stroke when the engine is stopped when the engine is automatically stopped and the predetermined restart condition is satisfied thereafter is set to be relatively close to the bottom dead center If it is within the range, a compression self-ignition that restarts the engine by injecting fuel from the fuel injection valve into the compression stroke cylinder at the stop while applying a rotational force to the engine using a starter motor. Type engine start control device, which is used in a vehicle equipped with an automatic transmission, in the process of automatically stopping the engine. The opening of the intake throttle valve provided in the intake passage is made smaller than the opening before the automatic stop condition is satisfied before the predetermined time elapses from the time when the automatic stop condition is satisfied, and the predetermined time is After a lapse of time, the fuel injection from the fuel injection valve is stopped, and after the fuel injection is stopped, the intake air in the vicinity of the top dead center before the last top dead center of all the cylinders before the engine stops. Control means for increasing the opening of the throttle valve is provided (claim 1).

  According to the present invention, in the process of automatically stopping the engine, the opening of the intake throttle valve is made smaller than the opening before the automatic stop condition is satisfied, and then the opening of the intake throttle valve is increased in the vicinity of 2TDC. As described above, the amount of air flowing into the stop-time expansion stroke cylinder in which the period from 3TDC to 2TDC is the intake stroke is larger than that in the stop-time compression stroke cylinder in which the period from 2TDC to the final TDC is the intake stroke. The amount of air flowing into the As a result, the piston of the compression stroke cylinder at the time of stop can be stably stopped near the bottom dead center, and the compression self-ignition engine can be quickly restarted with one compression start at a high frequency.

  In this case, since the opening of the intake throttle valve is reduced before the fuel cut, the pressure in the intake passage downstream of the intake throttle valve (downstream pressure) decreases before the engine speed decreases. Happens. Therefore, when 3TDC arrives, the downstream pressure sufficiently decreases, and the amount of air flowing into the expansion stroke cylinder at the time of stop is surely reduced. On the other hand, when the opening of the intake throttle valve is increased near 2TDC, the downstream pressure Significantly increases, and the amount of air flowing into the compression stroke cylinder at the time of stop increases.

  Therefore, even if the engine is used in an AT vehicle in which the rotation reduction after the fuel cut is relatively fast, the amount of air flowing into the stop compression stroke cylinder and the amount of air flowing into the stop expansion stroke cylinder The deviation is sufficiently widened, and the opportunity for quick engine restart by one compression start is increased.

  In the present invention, preferably, the control means reduces the opening of the intake throttle valve when the automatic stop condition is satisfied (claim 2).

  According to this configuration, in the process of automatically stopping the engine, the opening degree of the intake throttle valve is reduced at the earliest time, so that the downstream pressure drop starts earlier, and as a result, the compression stroke cylinder at the time of stop The deviation between the amount of air flowing in and the amount of air flowing into the expansion stroke cylinder at the time of stop is surely enlarged, and the opportunity for quick engine restart by one compression start is surely increased.

  In the present invention, preferably, the control means sets the opening degree of the intake throttle valve to a predetermined opening degree that is not fully closed before the predetermined time elapses, and closes the intake throttle valve simultaneously with the stop of the fuel injection. (Claim 3).

  According to this configuration, since the intake throttle valve is not fully closed before the predetermined time has elapsed, the downstream pressure (fresh air filling amount) sufficient to maintain idle rotation is maintained, and misfire occurs until the fuel cut is performed. The engine rotation can be continued without doing so. Since the intake throttle valve is fully closed simultaneously with the fuel cut, the deviation between the amount of air flowing into the stop-time compression stroke cylinder and the amount of air flowing into the stop-time expansion stroke cylinder can be reliably increased.

  In the present invention, preferably, the automatic transmission is an automatic transmission with a torque converter.

  According to this configuration, in the automatic transmission with a torque converter, the resistance of the torque converter brakes the engine rotation, and the rotation decrease after the fuel cut becomes faster, so the rotation decrease after the fuel cut is relatively fast. The effect of the present invention that the frequency of one compression start can be increased also in an AT vehicle is very large.

  In the present invention, preferably, the compression self-ignition engine is a diesel engine having a geometric compression ratio set to less than 16. (Claim 5)

  According to this configuration, a diesel engine having a geometric compression ratio of less than 16 has a lower compression ratio than a diesel engine that has been widely used so far, and the compression allowance of a piston that stops at an intermediate position in the compression stroke correspondingly. (Effective compression ratio from the stop position to the compression top dead center) is small, and the self-ignitability of the fuel is relatively low. Therefore, the piston of the compression stroke cylinder at the time of stop is stably stopped near the bottom dead center and compressed by 1 The effect of the present invention that the frequency of starting can be increased is very large.

  As described above, according to the present invention, the amount of air flowing into the compression stroke cylinder at the stop and the flow into the expansion stroke cylinder at the stop can be obtained even in an AT vehicle in which the rotation decrease after the fuel cut is relatively fast. Since the deviation from the air amount can be sufficiently increased, the opportunity for quick engine restart by one compression start can be increased.

It is a figure showing the whole diesel engine composition to which the starting control device concerning one embodiment of the present invention was applied. It is a time chart which shows the change of each state quantity at the time of the automatic stop control of the engine. It is explanatory drawing for showing the effect | action by the engine automatic stop control, (a) shows the piston position of each cylinder immediately before an engine stop, (b) has shown the piston position after completion | finish of an engine stop. . It is a flowchart which shows the specific operation example of the said engine automatic stop control. It is a flowchart which shows the specific operation example of the restart control of the said engine.

(1) Overall Configuration of Engine FIG. 1 is a diagram showing an overall configuration of a diesel engine to which a start control device according to an embodiment of the present invention is applied. The diesel engine shown in the figure is a four-cycle diesel engine used in an AT vehicle equipped with an automatic transmission with a torque converter as a driving power source. The engine body 1 of this engine is of a so-called in-line 4-cylinder type, and is provided on the upper surface of the cylinder block 3 having a cylinder block 3 having four cylinders 2A to 2D arranged in a line in a direction orthogonal to the paper surface. A cylinder head 4 and a piston 5 inserted in each of the cylinders 2A to 2D so as to be reciprocally slidable are provided.

  A combustion chamber 6 is formed above the piston 5, and light oil as fuel is supplied to the combustion chamber 6 by injection from a fuel injection valve 15 described later. The injected fuel (light oil) is self-ignited in the combustion chamber 6 that has been heated to a high temperature and pressure by the compression action of the piston 5 (compression self-ignition), and the piston 5 pushed down by the expansion force due to the combustion is moved vertically. It is designed to reciprocate.

  The piston 5 is connected to a crankshaft 7 via a connecting rod (not shown), and the crankshaft 7 rotates around the central axis in accordance with the reciprocating motion (vertical motion) of the piston 5. .

  Here, in the four-cycle four-cylinder diesel engine as shown in the figure, the piston 5 provided in each of the cylinders 2A to 2D moves up and down with a phase difference of 180 ° (180 ° CA) in crank angle. For this reason, the timing of combustion (fuel injection therefor) in each of the cylinders 2A to 2D is set to a timing shifted in phase by 180 ° CA. Specifically, if the cylinder numbers of the cylinders 2A, 2B, 2C, and 2D are 1, 2, 3, and 4, respectively, the first cylinder 2A → the third cylinder 2C → the fourth cylinder 2D → the second cylinder Combustion is performed in the order of 2B. Therefore, for example, if the first cylinder 2A is in the expansion stroke, the third cylinder 2C, the fourth cylinder 2D, and the second cylinder 2B are in the compression stroke, the intake stroke, and the exhaust stroke, respectively.

  The cylinder head 4 is provided with an intake port 9 and an exhaust port 10 that open to the combustion chambers 6 of the cylinders 2A to 2D, and an intake valve 11 and an exhaust valve 12 that open and close the ports 9 and 10, respectively. The intake valve 11 and the exhaust valve 12 are opened and closed in conjunction with the rotation of the crankshaft 7 by valve mechanisms 13 and 14 including a pair of camshafts and the like disposed in the cylinder head 4.

  The cylinder head 4 is provided with one fuel injection valve 15 for each of the cylinders 2A to 2D. Each fuel injection valve 15 is connected to a common rail 20 as a pressure accumulation chamber via a branch pipe 21. In the common rail 20, fuel (light oil) supplied from the fuel supply pump 23 through the fuel supply pipe 22 is stored in a high pressure state, and the fuel increased in pressure in the common rail 20 passes through the branch pipe 21 to each fuel injection valve. 15 respectively.

  The fuel injection valve 15 is of a multi-hole type having a plurality of injection holes at the tip, a fuel passage communicating with each of the injection holes, and an electromagnetic for opening and closing the fuel passage. And a needle-like valve body that is driven by the motor (not shown). The valve body is driven in the opening direction by electromagnetic force generated by energization, so that the fuel supplied from the common rail 20 is directly injected from the respective injection holes toward the combustion chamber 6. In addition, the fuel injection valve 15 in this embodiment has many injection holes called 8-12 pieces.

  A cavity 5a is formed in the center portion of the crown surface (upper surface) of the piston 5 facing the fuel injection valve 15 so as to be recessed below other portions (peripheral edge portions of the crown surface). For this reason, when the fuel is injected from the fuel injection valve 15 in a state where the piston 5 is near the top dead center, the fuel first enters the cavity 5a.

  Here, the engine body 1 of the present embodiment has a geometric compression ratio (ratio of the combustion chamber volume when the piston 5 is at bottom dead center and the combustion chamber volume when the piston 5 is at top dead center). Is set to 14. That is, the geometric compression ratio of a general on-board diesel engine is often set to 18 or more, whereas in this embodiment, the geometric compression ratio is set to a considerably low value of 14. Has been.

  A water jacket (not shown) through which cooling water flows is provided inside the cylinder block 3 and the cylinder head 4, and a water temperature sensor SW1 for detecting the temperature of the cooling water in the water jacket is provided in the cylinder. It is provided in the block 3.

  The cylinder block 3 is provided with a crank angle sensor SW2 for detecting the rotation angle and rotation speed of the crankshaft 7 (that is, the engine rotation speed). The crank angle sensor SW2 outputs a pulse signal according to the rotation of the crank plate 25 that rotates integrally with the crankshaft 7.

  Specifically, a large number of teeth lined up at a constant pitch are projected on the outer peripheral portion of the crank plate 25, and a tooth missing portion 25a (teeth) for specifying a reference position is provided in a predetermined range on the outer peripheral portion. A portion where no is present) is formed. Then, the crank plate 25 having the tooth missing portion 25a at the reference position rotates in this way, and a pulse signal based on the crank plate 25 is output from the crank angle sensor SW2, whereby the rotation angle (crank angle) of the crankshaft 7 and The rotational speed (engine rotational speed) is detected.

  On the other hand, the cylinder head 4 is provided with a cam angle sensor SW3 for detecting the angle of a camshaft (not shown) for valve actuation. The cam angle sensor SW3 outputs a pulse signal for cylinder discrimination according to the passage of the teeth of the signal plate that rotates together with the camshaft.

  That is, the pulse signal output from the crank angle sensor SW2 includes a no-signal portion generated every 360 ° CA corresponding to the above-mentioned tooth missing portion 25a. When the piston 5 is moving up, it is impossible to determine which cylinder corresponds to the compression stroke or the exhaust stroke. Therefore, a pulse signal is output from the cam angle sensor SW3 based on the rotation of the camshaft that rotates once every 720 ° CA, the timing at which the signal is output, and the timing of the non-signal portion of the crank angle sensor SW2 (tooth missing). The cylinder discrimination is performed on the basis of the passage timing of the section 25a.

  An intake passage 28 and an exhaust passage 29 are connected to the intake port 9 and the exhaust port 10, respectively. That is, intake air (fresh air) from the outside is supplied to the combustion chamber 6 through the intake passage 28 and exhaust gas (combustion gas) generated in the combustion chamber 6 is discharged to the outside through the exhaust passage 29. It is like that.

  Of the intake passage 28, a range from the engine body 1 to the upstream side by a predetermined distance is a branch passage portion 28a branched for each of the cylinders 2A to 2D, and the upstream end of each branch passage portion 28a is a surge tank 28b. It is connected to the. A common passage portion 28c including a single passage is provided on the upstream side of the surge tank 28b.

  The common passage portion 28c is provided with an intake throttle valve 30 for adjusting the amount of air (intake flow rate) flowing into the cylinders 2A to 2D. The intake throttle valve 30 is basically fully opened during operation of the engine or maintained at a high opening degree close thereto, and is configured to be closed only when necessary, such as when the engine is stopped, to block the intake passage 28. Has been.

  An air flow sensor SW4 for detecting the intake air flow rate is provided in the common passage portion 28c between the intake throttle valve 30 and the surge tank 28b. The surge tank 28b is provided with an intake manifold pressure sensor SW5 that detects the pressure in the surge tank 28b. Here, the pressure in the surge tank 28 b corresponds to the pressure in the intake passage 28 on the downstream side of the intake throttle valve 30, that is, the downstream pressure.

  An alternator 32 is connected to the crankshaft 7 via a timing belt or the like. This alternator 32 incorporates a regulator circuit that controls the current of a field coil (not shown) and adjusts the amount of power generation. The alternator 32 has a target value of power generation (target power generation determined from the electric load of the vehicle, the remaining battery capacity, etc.). Based on the current), the driving force is obtained from the crankshaft 7 to generate power.

  The cylinder block 3 is provided with a starter motor 34 for starting the engine. The starter motor 34 has a motor body 34a and a pinion gear 34b that is rotationally driven by the motor body 34a. The pinion gear 34b meshes with a ring gear 35 connected to one end of the crankshaft 7 so as to be detachable. When the engine is started using the starter motor 34, the pinion gear 34b moves to a predetermined meshing position and meshes with the ring gear 35, and the rotational force of the pinion gear 34b is transmitted to the ring gear 35. Thus, the crankshaft 7 is driven to rotate.

(2) Control system Each part of the engine configured as described above is centrally controlled by an ECU (engine control unit) 50. As is well known, the ECU 50 is a microprocessor including a CPU, a ROM, a RAM, and the like.

  Various information is input to the ECU 50 from various sensors. That is, the ECU 50 is electrically connected to the water temperature sensor SW1, the crank angle sensor SW2, the cam angle sensor SW3, the air flow sensor SW4, and the intake manifold pressure sensor SW5 provided in each part of the engine. Based on the input signal from SW5, various information such as engine coolant temperature, crank angle, engine rotation speed, cylinder discrimination information, intake air flow rate, intake air pressure (downstream pressure) and the like are acquired.

  The ECU 50 also receives information from various sensors (SW6 to SW9) provided in the vehicle. That is, the vehicle includes an accelerator opening sensor SW6 for detecting the opening degree of the accelerator pedal 36 that is depressed by the driver, and a brake sensor for detecting ON / OFF of the brake pedal 37 (presence of braking). SW7, a vehicle speed sensor SW8 for detecting the traveling speed (vehicle speed) of the vehicle, and a battery sensor SW9 for detecting the remaining capacity of the battery (not shown) are provided. The ECU 50 acquires information such as the accelerator opening, the presence / absence of the brake, the vehicle speed, and the remaining battery capacity based on the input signals from the sensors SW6 to SW9.

  The ECU 50 controls each part of the engine while executing various calculations based on input signals from the sensors SW1 to SW9. Specifically, the ECU 50 is electrically connected to the fuel injection valve 15, the intake throttle valve 30, the alternator 32, and the starter motor 34. The control signal is output.

  More specific functions of the ECU 50 will be described. For example, during normal operation of the engine, the ECU 50 causes the fuel injection valve 15 to inject a required amount of fuel that is determined based on operating conditions, and the required power generation amount that is determined based on the electric load of the vehicle, the remaining battery capacity, and the like. In addition to having a basic function such as power generation, a so-called idle stop function also has a function of automatically stopping or restarting the engine under a predetermined specific condition. For this reason, ECU50 has the automatic stop control part 51 and the restart control part 52 as a functional element regarding the automatic stop or restart control of an engine.

  The automatic stop control unit 51 determines whether or not a predetermined automatic engine stop condition is satisfied during engine operation, and whether the engine is in a state that does not hinder the operation (system). Whether or not the condition is satisfied) is determined, and when both are confirmed, control for automatically stopping the engine is executed.

  For example, it is confirmed that a plurality of requirements such as the vehicle is stopped (automatic stop condition is satisfied) and that there is no problem even if the engine is stopped (system condition is satisfied). In such a case, the engine is stopped, for example, by stopping fuel injection from the fuel injection valve 15 (fuel cut).

  The restart control unit 52 determines whether or not a predetermined restart condition is satisfied after the engine is automatically stopped, and executes control to restart the engine when the restart condition is satisfied.

  For example, when the driver needs to start the engine by depressing the accelerator pedal 36 to start the vehicle, it is determined that the restart condition is satisfied. Then, the engine is restarted by driving the starter motor 34 to apply rotational force to the crankshaft 7 and restarting fuel injection from the fuel injection valve 15.

(3) Automatic Stop Control Next, the details of the engine automatic stop control executed by the automatic stop control unit 51 of the ECU 50 will be described more specifically. FIG. 2 is a time chart showing changes in each state quantity during the automatic stop control of the engine. In this figure, the time when the automatic engine stop condition is satisfied is t1, and the time when the system condition is satisfied is t2. Also, t3, 2TDC (ii) (top dead center one before the last top dead center) arrives at the time when 3TDC (iii) (top dead center two before the last top dead center) arrives. The time point is t4, and the time point at which the final TDC (i) (last top dead center) arrives is t5. In the figure, “intake manifold pressure” refers to the pressure (downstream pressure) in the surge tank 28b detected by the intake manifold pressure sensor SW5.

  As shown in FIG. 2, at the time of engine automatic stop control, first, at the time t1 when the automatic stop condition is satisfied, the intake throttle valve 30 is driven in the closing direction, and the opening degree is determined according to the automatic stop condition. The opening is reduced to a non-fully closed opening (40% in the example) smaller than the opening during normal operation (80% in the example) set before the establishment. Then, control for stopping fuel injection from the fuel injection valve 15 at a time point t2 (a time point when the system condition is satisfied) after a predetermined time has elapsed from the time point t1 while keeping the opening of the intake throttle valve 30 small (fuel cut) ) Is executed. Simultaneously with the fuel cut, the opening of the intake throttle valve 30 is finally reduced to the fully closed position (0%).

  Here, the diesel engine of this embodiment is used in an AT vehicle equipped with an automatic transmission. For this reason, for example, the inertia weight of the rotating system is small compared to the case where the flywheel having a large inertial mass is often incorporated. Therefore, the number of revolutions that rotate by inertia after the fuel cut is reduced, and the fuel cut Later engine rotations tend to be relatively fast. Moreover, since the automatic transmission is an automatic transmission with a torque converter, the resistance of the torque converter brakes the engine rotation, and the decrease in the engine rotation after the fuel cut tends to become even faster.

  The predetermined time elapses from the time point t1 when the automatic stop condition is satisfied to the time point t2 when the system condition is satisfied, because the ECU 50 does not permit the engine to be automatically stopped by merely stopping the vehicle by the driver. In addition, it takes some time to determine whether or not the engine can be automatically stopped from the viewpoint of the vehicle system. Even if the automatic stop condition is satisfied, the engine is not automatically stopped unless the system condition is satisfied.

  Next, after the fuel cut is performed, the intake throttle valve 30 is opened again while the engine speed is decreasing. Specifically, when the last top dead center immediately before the engine stop in all the cylinders 2A to 2D is set as the final TDC, when the top dead center (2 TDC) immediately before this final TDC passes (time point t4). Further, the intake throttle valve 30 is driven in the opening direction, and the opening degree is increased to a predetermined opening degree (for example, about 10 to 30%, 20% in the illustrated example) exceeding 0%.

  Thereafter, after reaching the final TDC at time t5, the engine temporarily rotates backward due to the swinging back of the piston, but reaches the complete stop state at time t6 without exceeding the top dead center.

  Here, the control to open the intake throttle valve 30 as described above is executed at the time t4 because the cylinder in the compression stroke when the engine is completely stopped, that is, the compression stroke cylinder at the time of stop (the third cylinder 2C in FIG. 2). 3), as shown in FIG. 3B, the piston stop position is set within a specific range Rx set on the bottom dead center side with respect to the reference stop position X located between the top dead center and the bottom dead center. Because. The reference stop position X may vary depending on the shape of the engine (displacement, bore / stroke ratio, etc.), the degree of progress of warm-up, and the like. For example, the reference stop position X may be any value between 90 and 75 ° CA before top dead center (BTDC). Can be set to any position. For example, when the reference stop position X is BTDC 80 ° CA, the specific range Rx is a range of BTDC 80 to 180 ° CA.

  If the piston 5 of the stop-time compression stroke cylinder 2C is stopped within the specific range Rx, then when the engine restart condition is satisfied, the stop-time compression stroke cylinder 2C is first (the first engine as a whole). ) The engine can be restarted quickly by one compression start injecting fuel. On the other hand, if the piston stop position of the stop-time compression stroke cylinder 2C is out of the specific range Rx, after the start of restart, the cylinder that reaches the compression stroke next to the stop-time compression stroke cylinder 2C, that is, the intake stroke when the engine is stopped. It is necessary to restart the engine by the two-compression start in which fuel is injected into the intake stroke cylinder (4th cylinder 2D in FIG. 2) at a stop. Thus, the reason why the 1-compression start and the 2-compression start are properly used depending on the piston stop position is that the ignitability in the stop-time compression stroke cylinder 2C differs depending on the piston stop position.

  In the above-described two-compression start, the fuel cannot be combusted until the stop-time intake stroke cylinder 2D shifts to the compression stroke. Therefore, the one-compression start is more advantageous in terms of quick start. For this reason, in order to be able to execute one compression start with high frequency, it is necessary to keep the piston stop position of the stop-time compression stroke cylinder 2C within the specific range Rx as much as possible. Therefore, in the present embodiment, as shown in FIG. 2, the intake throttle valve 30 is opened at time t4. That is, according to the control of FIG. 2, until the top dead center (2 TDC) immediately before the final TDC (until time t4), the opening degree of the intake throttle valve 30 is 0%, and after 2 TDC ( After the time point t4), the opening degree of the intake throttle valve 30 is increased to a predetermined opening degree exceeding 0%. As a result, the intake stroke from 2TDC reaches the intake stroke (time t4 to time t5 becomes the intake stroke). The inflow air amount to the compression cylinder 2C at the time of stop changes the intake stroke from the top dead center (3TDC) immediately before the final TDC. More than the amount of inflow air for the cylinder that reaches (the time t3 to the time t4 is the intake stroke), in other words, the stop-time expansion stroke cylinder (first cylinder 2A in FIG. 2) that is in the expansion stroke when the engine is completely stopped Will do.

  This point will be described in more detail with reference to FIGS. As described above, when the intake throttle valve 30 is opened during the passage of 2TDC as described above, immediately before the engine is automatically stopped, the amount of air flowing into the stop-time compression stroke cylinder 2C (filling amount) is the stop-time expansion stroke. It becomes larger than the inflow air amount (filling amount) into the cylinder 2A. As a result, as shown in FIG. 3 (a), the pressing force by the compressed air acting on the piston 5 of the stop-time compression stroke cylinder 2C (the force by which the compressed air tends to expand) increases, while at the time of stop. The push-down force due to the compressed air acting on the piston 5 of the expansion stroke cylinder 2A becomes small (rather, the push-up force due to the expansion air acting on the piston 5 of the expansion stroke cylinder 2A when stopped) becomes large. For this reason, when the engine is completely stopped, as shown in FIG. 3B, the stop position of the piston 5 of the stop-time compression stroke cylinder 2C is naturally close to the bottom dead center (the piston 5 of the stop-time expansion stroke cylinder 2A As a result, the piston 5 of the compression stroke cylinder 2C at the time of stop can be stopped in the specific range Rx on the lower dead center side with respect to the reference stop position X with a relatively high frequency. become able to. If the piston 5 is stopped within the specific range Rx, when the engine is restarted, the engine can be quickly restarted by one compression start in which fuel is injected into the compression stroke cylinder 2C at the time of stop.

  Next, an example of a specific control operation of the automatic stop control unit 51 that controls the engine automatic stop control as described above will be described with reference to the flowchart of FIG.

  When the process shown in the flowchart of FIG. 4 is started, the automatic stop control unit 51 executes control for reading various sensor values (step S1). Specifically, detection is performed from the water temperature sensor SW1, the crank angle sensor SW2, the cam angle sensor SW3, the airflow sensor SW4, the intake manifold pressure sensor SW5, the accelerator opening sensor SW6, the brake sensor SW7, the vehicle speed sensor SW8, and the battery sensor SW9. Various signals such as engine coolant temperature, crank angle, engine rotation speed, cylinder discrimination information, intake air flow, intake manifold pressure, accelerator opening, presence / absence of brake, vehicle speed, remaining battery capacity, etc. are read based on these signals. Get information.

  Next, the automatic stop control unit 51 determines whether or not an automatic engine stop condition is satisfied based on the information acquired in Step S1 (Step S2). For example, when all the requirements such as the vehicle is stopped, the opening degree of the accelerator pedal 36 is zero (accelerator OFF), the brake pedal 37 is being operated (brake ON), etc. are all met. It is determined that the automatic stop condition is satisfied. The vehicle speed is not necessarily required to be a complete stop (vehicle speed = 0 km / h), and a condition of a predetermined low vehicle speed or lower (for example, 3 km / h or lower) may be set.

  When it is determined YES in step S2 and it is confirmed that the automatic stop condition is satisfied, the automatic stop control unit 51 sets the opening of the intake throttle valve 30 to the opening before the automatic stop condition is satisfied (for example, idle A control is executed to set the opening degree (40%) which is smaller than the opening degree corresponding to the rotation: 80% in FIG. 2 (step S3). That is, as shown in the time chart of FIG. 2, at the time t1 when the automatic stop condition is satisfied, the opening of the intake throttle valve 30 starts to be driven in the closing direction, and the opening is finally reduced to 40%. Let

  Next, the automatic stop control unit 51 determines whether or not there is no problem even if the engine is stopped, that is, whether or not the system condition is satisfied (step S4). For example, the engine cooling water temperature is a predetermined value or more, the remaining battery capacity is a predetermined value or more, and the difference between the set temperature of the air conditioner and the actual indoor temperature is a predetermined value or less. When all of the above are complete, it is determined that the system condition is satisfied.

  In addition, as described above, in order to determine whether or not the system condition is satisfied, it is necessary to investigate whether there is a problem when the engine is stopped based on the current state of the vehicle system. Therefore, it takes a certain amount of time. Therefore, after a predetermined time has elapsed from the time point t1 when the automatic stop condition is satisfied, the determination result of step S4 is obtained. Therefore, a predetermined time elapses from the time t1 when the automatic stop condition is satisfied to the time t2 when the system condition is satisfied.

  When it is determined as YES in Step S4 and it is confirmed that the system condition is satisfied, the automatic stop control unit 51 performs fuel cut for stopping the supply of fuel from the fuel injection valve 15 (Step S5). That is, after the time point t2 when the above system condition is satisfied, the drive signals for the fuel injection valves 15 of the cylinders 2A to 2D are all turned off and the valve bodies of the fuel injection valves 15 are maintained in the fully closed position, thereby Perform the cut.

  The automatic stop control unit 51 executes control for setting the opening of the intake throttle valve 30 to be fully closed (0%) simultaneously with the fuel cut (step S5). That is, as shown in the time chart of FIG. 2, at the time t2 when the above system condition is satisfied, the opening of the intake throttle valve 30 starts to be driven further in the closing direction, and the opening is finally reduced to 0%. Let

  Next, the automatic stop control unit 51 has a predetermined engine rotation speed (top dead center passing rotation speed) when the piston 5 of any of the four cylinders 2A to 2D reaches top dead center. It is determined whether it is within the range (step S6). As shown in FIG. 2, the engine rotational speed temporarily falls every time one of the four cylinders 2 </ b> A to 2 </ b> D reaches the compression top dead center (top dead center between the compression stroke and the expansion stroke). It gradually decreases while repeating the up-down that it rises again after exceeding the compression top dead center. Therefore, the top dead center passing rotation speed can be measured as the rotation speed at the timing of the up / down valley of the engine rotation speed.

  The determination regarding the top dead center passage rotation speed in the above step S6 is the timing of passing the top dead center (2TDC) immediately before the last top dead center (final TDC) immediately before the engine stop (time t4 in FIG. 2). ) Is done to identify. That is, in the process of automatically stopping the engine, there is a certain regularity in how the engine speed decreases, so if you check the rotation speed at that time (top dead center passing rotation speed) when passing through the top dead center, It can be estimated how many times before the final TDC it is the top dead center. Therefore, the top dead center passing rotation speed is always measured, and the rotation speed when passing through the predetermined range set in advance, that is, the top dead center (2 TDC) immediately before the final TDC, is obtained in advance through experiments or the like. By determining whether or not it falls within the predetermined range, the passing timing of the 2TDC is specified.

  When it is determined YES in step S6 and it is confirmed that the current time is the 2TDC passage timing (time t4 in FIG. 2), the automatic stop control unit 51 starts to drive the intake throttle valve 30 in the opening direction. Control is performed to increase the opening to a predetermined opening exceeding 0% (for example, about 10 to 30%, 20% in the figure) (step S7). As a result, the inflow air amount to the stop-time compression stroke cylinder 2C that reaches the intake stroke from the time point t4 is greater than the inflow air amount to the stop-time expansion stroke cylinder 2A that was the intake stroke one cycle before (time point t3 to time point t4). Also increases.

  Thereafter, the automatic stop control unit 51 determines whether or not the engine has completely stopped by determining whether or not the engine rotation speed is 0 rpm (step S8). If the engine is completely stopped (time t6), the automatic stop control unit 51 sets, for example, the opening of the intake throttle valve 30 to a predetermined opening (for example, 80%) set during normal operation. For example, the automatic stop control is terminated.

  As described above, in this automatic stop control, the intake stroke of the stop compression stroke cylinder 2C and the intake stroke of the stop expansion stroke cylinder 2A are controlled by the control in steps S6 to S7 that opens the intake throttle valve 30 when 2TDC passes at time t4. When the engine is completely stopped, when the engine is completely stopped, the intake manifold pressure deviation between the cylinder and the intake manifold pressure difference between the cylinder 2C and the expansion cylinder 2A during the stop is different. The piston 5 of the cylinder 2C is within the specific range Rx (FIG. 3B) near the bottom dead center with a relatively high frequency, and one compression start can be executed with a high frequency.

  When it is determined NO in step S4 and it is confirmed that the system condition is not satisfied, the automatic stop control unit 51 sets the opening of the intake throttle valve 30 to the opening before the automatic stop condition is satisfied. A control to return to (for example, an opening corresponding to idle rotation: 80% in FIG. 2) is executed (step S9). Thereafter, the automatic stop control is terminated.

(4) Restart Control Next, an example of a specific control operation of the engine restart control executed by the restart control unit 52 of the ECU 50 will be described with reference to the flowchart of FIG.

  When the process shown in the flowchart of FIG. 5 starts, the restart control unit 52 determines whether or not the engine restart condition is satisfied based on various sensor values (step S11). For example, the accelerator pedal 36 has been depressed to start the vehicle (accelerator ON), the engine coolant temperature has fallen below a predetermined value, the amount of decrease in the remaining battery capacity has exceeded an allowable value, When at least one of the requirements such as the stop time (elapsed time after automatic stop) exceeds a predetermined time is satisfied, it is determined that the restart condition is satisfied.

  If it is determined as YES in step S11 and it is confirmed that the restart condition is satisfied, the restart control unit 52 determines the stop-time compression stroke cylinder 2C that has stopped in the compression stroke in accordance with the automatic engine stop control described above. The piston stop position is specified based on the crank angle sensor SW2 and the cam angle sensor SW3, and the specified piston stop position is in the specified range Rx (see FIG. 3B) on the bottom dead center side from the reference stop position X. It is determined whether or not (step S12).

  When it is determined YES in step S12 and it is confirmed that the piston stop position of the stop-time compression stroke cylinder 2C is within the specific range Rx, the restart control unit 52 supplies the first fuel to the stop-time compression stroke cylinder 2C. Control is performed to restart the engine by one compression start for injection (step S13). That is, by driving the starter motor 34 and applying rotational force to the crankshaft 7, fuel is injected from the fuel injection valve 15 into the compression stroke cylinder 2 </ b> C at the time of stop and self-ignition is performed. The combustion is restarted from the time when the dead point is reached, and the engine is restarted.

  Here, the piston stop position of the stop-time compression stroke cylinder 2C is considered to be within the specific range Rx in a relatively large number of cases due to the effect of the automatic stop control (FIGS. 2 and 4) described above. However, in some cases, the piston stop position may deviate from the specific range Rx (the piston 5 stops at the top dead center side with respect to the reference stop position X). In such a case, NO is determined in step S12.

  When it is determined NO in step S12 (that is, when the piston 5 of the stop-time compression stroke cylinder 2C is stopped at the top dead center side from the specific range Rx), the restart control unit 52 stops in the intake stroke. The control for restarting the engine by the two-compression start that injects the first fuel into the stopped intake stroke cylinder 2D that has been performed is executed (step S14). That is, the engine is driven only by driving the starter motor 34 without injecting fuel until the piston 5 of the stop compression stroke cylinder 2C exceeds the top dead center and then the stop intake stroke cylinder 2D reaches the compression stroke. Force to rotate. Then, when the piston 5 of the stop-time intake stroke cylinder 2D approaches the compression top dead center, fuel is injected from the fuel injection valve 15 into the stop-time intake stroke cylinder 2D, and the injected fuel is self-ignited. The combustion is restarted from the time when the second compression top dead center is reached as a whole, and the engine is restarted.

  In the present embodiment, at least when one compression start is performed in step S13, the fuel injection valve 15 is caused to perform pre-injection. The pre-injection is a fuel injection that is preliminarily injected before the main injection when the fuel injection for diffusion combustion injected near the compression top dead center is used as the main injection. Combustion by pre-injection (pre-combustion) is used to reliably cause diffusion combustion (main combustion) near the compression top dead center based on main injection. That is, at a stage earlier than the main injection, a small amount of fuel is injected by pre-injection, and the injected fuel is burned (pre-combustion) after a predetermined ignition delay, thereby increasing the in-cylinder temperature and pressure, The subsequent main combustion is promoted.

  If the pre-injection as described above is performed on the compression stroke cylinder 2C at the time of stop, the in-cylinder temperature and pressure near the compression top dead center can be increased intentionally, so the piston of the compression stroke cylinder 2C at the time of stop is stopped. Even if the position slightly approaches the top dead center side, the engine can be reliably restarted by one compression start. The reference stop position X, which is the boundary of the specific range Rx shown in FIG. 3B, is set in consideration of the improvement in ignitability by such pre-injection. That is, when there is no pre-injection, the reference stop position X must be set to the bottom dead center side than the example of FIG. 3B, but by improving the ignitability by pre-injection. Thus, it is possible to set the reference stop position X closer to the top dead center, and as a result, the reference stop position X can be set to a position far away from the bottom dead center, for example, BTDC 90 to 75 ° CA. It becomes possible. As a result, the specific range Rx expands to the top dead center side, so that the piston 5 of the compression stroke cylinder 2C at the time of stoppage falls within the specific range Rx with a higher frequency, and an opportunity to perform a quick restart by one compression start Will increase.

  Here, the pre-injection in the present embodiment is executed a plurality of times (more specifically, 2 to 5 times) within a predetermined crank angle range before the compression top dead center. This is because if the same amount of fuel is used, it is richer in the cavity 5a provided on the crown surface of the piston 5 when the fuel is divided into a plurality of pre-injections than when the fuel is injected once. This is because a simple air-fuel mixture can be formed continuously and the ignition delay can be shortened.

(5) Operational effects and the like As described above, in the present embodiment, a diesel engine having a so-called idle stop function for automatically stopping or restarting the engine under a predetermined condition, particularly at the time of restarting. A diesel engine capable of one compression start employs the following characteristic configuration.

  In the process of automatically stopping the engine (automatic stop control), the ECU 50 sets the opening of the intake throttle valve 30 to the opening before the automatic stop condition is satisfied at the time t1 when the automatic stop condition is satisfied. (Opening is changed from 80% to 40%). Next, the ECU 50 starts from the fuel injection valve 15 from the time t1 when the automatic stop condition is satisfied to the time t2 when the system condition that requires a predetermined time to determine whether the engine can be automatically stopped is determined based on the current state of the vehicle system. Stop fuel injection and execute fuel cut. Further, the ECU 50 fully closes the opening of the intake throttle valve 30 simultaneously with the fuel cut (the opening is changed from 40% to 0%). Next, the ECU 50 increases the opening of the intake throttle valve 30 (changes the opening from 0% to 20%) at 2 TDC (time point t4) after execution of the fuel cut.

  With such a configuration, the opening of the intake throttle valve 30 is reduced from before the fuel cut is performed (time t1), and the intake throttle valve 30 is fully closed simultaneously with the fuel cut (time t2). Since the opening of the intake throttle valve 30 is increased at (time t4), the amount of air flowing into the stop expansion stroke cylinder 2A during the period from 3TDC to 2TDC (time t3 to t4) is the intake stroke is 2TDC. The amount of air flowing into the compression stroke cylinder 2C at the time of stop, in which the period from the time T4 to the final TDC (time t4 to t5) is the intake stroke, increases. As a result, the piston 5 of the stop-time compression stroke cylinder 2C can be stably stopped near the bottom dead center, and the compression self-ignition engine can be quickly restarted with one compression start frequently. .

  In this case, since the opening of the intake throttle valve 30 is reduced before the fuel cut, the pressure (intake manifold pressure) in the intake passage 28 on the downstream side of the intake throttle valve 30 is reduced as shown in FIG. The decrease occurs prior to the decrease in engine speed. Therefore, when 3TDC arrives (time point t3), the intake manifold pressure sufficiently decreases, and the amount of air flowing into the expansion stroke cylinder 2A at the time of stop reliably decreases. On the other hand, when the opening degree of the intake throttle valve 30 is increased at 2TDC (time t4), the intake manifold pressure is significantly increased, and the amount of air flowing into the compression stroke cylinder 2C at the time of stop is reliably increased.

  Therefore, even if the engine is used in an AT vehicle in which the rotation reduction after the fuel cut is relatively fast, the inflow air amount into the stop compression stroke cylinder 2C and the inflow air amount into the stop expansion stroke cylinder 2A And the chance of quick engine restart by one compression start is increased.

  For example, when the intake throttle valve 30 is not closed before the fuel cut and the intake throttle valve 30 is closed at the same time as the fuel cut, as shown by a chain line (a) in FIG. A shows a case where the first intake throttle valve 30 is closed and fuel cut is performed at time t2, and since the AT vehicle has a rapid decrease in rotation after the fuel cut, 3TDC (time t3) before the intake manifold pressure has sufficiently decreased. ) And 2TDC (time t4) have arrived, and the deviation of the amount of air flowing into the stop-time compression stroke cylinder 2C from the amount of air flowing into the stop-time expansion stroke cylinder 2A becomes small, so that the engine automatically stops. At this time, the compression reaction force acting on the compression stroke cylinder 2C at the stop time and the expansion reaction force acting on the expansion stroke cylinder 2A at the stop time become small, and as a result, the piston 5 of the compression stroke cylinder 2C at the stop time is stably stopped near the bottom dead center. Letting It's become difficult.

  In the present embodiment, a predetermined time is required from the time point t1 when the automatic stop condition is satisfied to the time point t2 when the system condition is satisfied. Even if the automatic stop condition is satisfied, the substantial engine stop is not performed until the system condition is not satisfied. Focusing on the fact that the fuel cut as a trigger is not executed, this time shift is used to perform the closing operation of the intake throttle valve 30 before the fuel cut is performed.

  In the present embodiment, in particular, since the opening degree of the intake throttle valve 30 is reduced at the time point t1 when the automatic stop condition is satisfied, the opening degree of the intake throttle valve 30 is reduced at the earliest time, and the intake manifold pressure is reduced. As a result, the deviation between the amount of air flowing into the stop-time compression stroke cylinder 2C and the amount of air flowing into the stop-time expansion stroke cylinder 2A is surely enlarged, and the rapid start by the one-compression start The opportunity for restarting the engine is definitely increased.

  In the present embodiment, in particular, since the opening degree of the intake throttle valve 30 is not fully closed before a predetermined time has elapsed from the time t1 when the automatic stop condition is satisfied, the intake manifold pressure and the cylinders 2A to 2D that can maintain the idle rotation are maintained. Thus, the engine speed can be maintained without misfire by time t2 when the fuel cut is performed.

  In the present embodiment, in particular, since the intake throttle valve 30 is fully closed simultaneously with the fuel injection cut at time t2, the amount of air flowing into the stop compression stroke cylinder 2C and the air flowing into the stop expansion stroke cylinder 2A Enlarging the deviation from the quantity is ensured.

  In this embodiment, in particular, an AT vehicle in which this diesel engine is used has an automatic transmission with a torque converter in which the resistance of the torque converter brakes the engine rotation and the decrease in rotation after fuel cut tends to be faster. Since this is an AT vehicle to be mounted, the effect of this embodiment that the frequency of one compression start can be increased even in an AT vehicle in which the rotation reduction after the fuel cut is relatively fast is very large.

  In the present embodiment, in particular, this diesel engine is a diesel engine whose geometric compression ratio is set to less than 16 (more specifically, 14).

  With such a configuration, the diesel engine having a geometric compression ratio of less than 16 has a lower compression ratio than that of a conventionally used diesel engine, and the compression of the piston 5 that stops at an intermediate position in the compression stroke correspondingly. The cost (effective compression ratio from the stop position to the compression top dead center) is small, and the self-ignitability of the fuel is relatively low. Therefore, the piston 5 of the compression stroke cylinder 2C at the time of stop is stably stopped near the bottom dead center. Thus, the effect of this embodiment that the frequency of one compression start can be increased is very large.

(6) Other Embodiments In the above embodiment, the first intake throttle valve 30 is closed at the time t1 when the automatic stop condition is satisfied, but the first intake throttle valve 30 is closed before the fuel cut. As long as it is performed, the present invention is not limited to this, and the first intake throttle valve 30 may be closed at any time after time t1 and before time t2. However, it is preferable that the closing operation of the intake throttle valve 30 and the execution of the fuel cut are separated in time.

  Further, in the above embodiment, the intake throttle valve 30 is closed in two stages at time t1 and time t2, but for example, if there is no problem such as misfire during idle rotation until fuel cut is performed, the situation Accordingly, the intake throttle valve 30 may be fully closed from the beginning.

  Further, in the above embodiment, the timing for switching the opening of the intake throttle valve 30 from 0% to over 0% (for example, about 10 to 30%, 20% in FIG. 2) is set to 2 TDC (time t4). However, the present invention is not limited to this, and as long as the amount of air flowing into the stop-time compression stroke cylinder 2C can be made larger than the amount of air flowing into the stop-time expansion stroke cylinder 2A, at a time before a predetermined time before 2TDC. The opening degree of the intake throttle valve 30 may be switched, or the opening degree of the intake throttle valve 30 may be switched at a time after a predetermined time from 2TDC. That is, the timing for switching the opening of the intake throttle valve 30 can be in the vicinity of 2TDC.

  Moreover, in the said embodiment, the diesel engine (engine which burns light oil by self-ignition) is used as an example of a compression self-ignition type engine, and the example which applied the automatic stop and restart control which concerns on this invention to the diesel engine was demonstrated. However, if it is a compression self-ignition engine, it is not limited to a diesel engine. For example, recently, an engine of a type that compresses fuel including gasoline at a high compression ratio and self-ignites (HCCI: Homogeneous-Charge Compression Ignition) type has been researched and developed. The automatic stop / restart control according to the present invention can also be suitably applied to a self-ignition gasoline engine.

DESCRIPTION OF SYMBOLS 1 Engine main body 2A Stop expansion stroke cylinder 2C Stop compression stroke cylinder 2D Stop intake stroke cylinder 5 Piston 15 Fuel injection valve 28 Intake passage 30 Intake throttle valve 34 Starter motor 50 Control means (ECU)
Rx Specific range X Reference stop position

Claims (5)

Provided in a compression self-ignition engine that burns fuel injected from a fuel injection valve into a cylinder by self-ignition, and automatically stops the engine when a predetermined automatic stop condition is satisfied, and then restarts with a predetermined restart condition. If the stop position of the piston of the stop compression stroke cylinder, which becomes the compression stroke when the engine is stopped, is within a specific range set relatively near the bottom dead center, the starter motor is used to A compression self-ignition engine start control device for restarting the engine by injecting fuel from the fuel injection valve into the stop-time compression stroke cylinder while applying a rotational force to the engine,
The engine is used for a vehicle equipped with an automatic transmission,
In the process of automatically stopping the engine,
The opening of the intake throttle valve provided in the intake passage before the predetermined time has elapsed from the time when the automatic stop condition is satisfied is made smaller than the opening before the automatic stop condition is satisfied,
Stop fuel injection from the fuel injection valve after the predetermined time has elapsed,
After stopping the fuel injection, it has control means for increasing the opening of the intake throttle valve in the vicinity of the top dead center one before the last top dead center of all the cylinders before the engine stops. A starting control device for a compression self-ignition engine. The start control device for a compression self-ignition engine according to claim 1,
A control device for starting a compression self-ignition engine, wherein the control means reduces the opening of the intake throttle valve when the automatic stop condition is satisfied. In the start control device for a compression self-ignition engine according to claim 1 or 2,
The control means sets the opening degree of the intake throttle valve to a predetermined opening degree that is not fully closed before the predetermined time elapses, and closes the intake throttle valve simultaneously with the stop of the fuel injection. Self-ignition engine start control device. The start-up control device for a compression self-ignition engine according to any one of claims 1 to 3,
A start control device for a compression self-ignition engine, wherein the automatic transmission is an automatic transmission with a torque converter. The start-up control device for a compression self-ignition engine according to any one of claims 1 to 4,
The compression self-ignition engine is a diesel engine having a geometric compression ratio set to less than 16 and a start-up control device for a compression self-ignition engine.

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