JP4259297B2 - Engine starter - Google Patents

Description

  The present invention relates to an engine starter that starts an engine that has been automatically stopped when idle in response to a restart request, and in particular, there is a restart request during a stop operation period from when the fuel supply is stopped until the engine stops. Belongs to the technical field of starting control.

Conventionally, in order to reduce fuel consumption and reduce CO ₂ emissions, the engine is automatically stopped when idling, and the engine is automatically restarted when there is a request for engine restart such as a start operation. An engine control system (idle stop system) is known.

  As described above, as a method of restarting the stopped engine, a method of starting the engine through cranking in which the engine output shaft is driven by an external power source such as a starter motor is generally used. In the above-described idle stop system that performs stop and restart, the number of times the engine is started is significantly higher than when the idle stop is not performed. There is a problem of increasing the cost.

  Therefore, in recent years, for example, as disclosed in Patent Documents 1 and 2, in a stopped engine, fuel is injected into a cylinder in an expansion stroke, and ignition and combustion are performed to give the engine a starting torque. As described above, the engine that restarts the engine without borrowing the power of the starting motor has been developed. In such a method of starting the engine without using a starter motor or the like, the starting torque at the time of engine restart varies depending on the piston stop position of the cylinder in the expansion stroke when the engine is stopped. As disclosed in FIG. 2, the piston is controlled to stop within a predetermined crank angle range when the engine is stopped by using a braking device or adjusting the opening of the valve.

Further, in order to obtain a larger starting torque than the starting method disclosed in Patent Documents 1 and 2, as disclosed in Patent Document 3, for example, fuel is injected into the cylinders in the compression stroke when the engine is stopped. By igniting and burning, the crankshaft is slightly rotated in the reverse direction. This compresses the air-fuel mixture in the cylinder in the expansion stroke when the engine is stopped, and then ignites the air-fuel mixture for combustion. There is also known a method for starting the engine.
Japanese Utility Model Publication No. 60-128975 Special table 2003-517134 gazette Special table 2003-515052 gazette

  By the way, in general, the engine rotates several times due to its inertia even after the fuel supply is stopped, and then stops, and if there is a restart request during that period (stop operation period), Similarly, it is considered that the engine can be restarted by injecting fuel into a cylinder in the intake or compression stroke to ignite and burn.

  However, in the state immediately before the stop where the engine speed is low and the cylinder in the compression stroke cannot exceed the next top dead center, the rotational inertia force of the engine at that time is very small. Even if it is ignited and burned, an effective starting torque cannot be obtained and the engine may fail to start.

  Therefore, in the engine control systems of Patent Documents 1 to 3, when there is an engine restart request within the engine stop operation period until the engine stop, the piston is within a predetermined crank angle range in order to reliably restart. Wait until the engine stops, and then restart the engine.

  Therefore, in the engine control system as described above, when an engine restart request is received from a driver or the like during the engine stop operation period, a certain amount of time is required until the engine stops. There was a problem that rattling occurred before the engine started.

  On the other hand, when the restart request is made, fuel is injected into the cylinder in the expansion stroke, and ignited and burned to give torque in the forward direction to the engine. If the top dead center is exceeded, it is considered that the engine can be restarted quickly even during the stop operation period.

  However, in such a method, a sufficient torque for restart can be obtained if the piston of the expansion stroke cylinder is relatively close to the top dead center immediately after the piston has exceeded the top dead center. However, if the piston moves away from the top dead center, the pressure in the cylinder will drop and the stroke due to combustion will be shortened. High nature.

  The present invention has been made in view of such a point, and an object of the present invention is to provide an engine starter that restarts an engine without using a starter motor in a state where the engine rotational speed immediately before the stop is low. It is intended to make it possible to restart the engine quickly and reliably even when a sufficient torque cannot be obtained by combustion of the expansion stroke cylinder, by devising a start control procedure when there is a restart request.

  In order to achieve the above object, in the engine starter according to the present invention, when a restart request is made at a low engine speed immediately before the engine is stopped, fuel is supplied to the expansion stroke cylinder at that time. In addition, a sufficient starting torque can be obtained by igniting and burning the expansion stroke cylinder by utilizing the fact that the expansion stroke cylinder is compressed by the reverse rotation operation of the engine (the rotation direction of the engine is the reverse rotation direction). To get.

  Specifically, according to the first aspect of the invention, an engine starter for starting an engine without using a starter motor by injecting fuel into at least an expansion stroke cylinder when the engine is stopped, and igniting and burning the fuel. Assuming Then, by stopping fuel injection to each cylinder of the engine during operation, engine stop means for stopping the engine, and restart condition determination means for determining that a predetermined restart condition of the engine is satisfied And an immediately before stop state detecting means for detecting that the engine rotational speed is lowered after the fuel injection is stopped by the engine stopping means and the cylinder in the compression stroke is in a state immediately before stopping so that the next top dead center cannot be exceeded. Engine rotation direction determination for determining the rotation direction of the engine when the engine rotation direction is reversed in the reverse rotation direction by the compression reaction force of the cylinder in the compression stroke and then the engine is stopped while repeating the reverse rotation. And when the restart condition is determined by the restart condition determining means, if the engine is in the state immediately before the stop, Fuel is injected into the cylinder in the stroke, and after the engine rotation direction determination means determines that the rotation direction of the engine has been reversed from the normal rotation direction to the reverse rotation direction, the expansion stroke cylinder is ignited. And engine restarting means for combustion.

  With this configuration, in the stop operation period in which the fuel injection to each cylinder of the engine is stopped and the engine rotation speed gradually decreases, the restart condition determining means determines that the engine restart condition is satisfied, If the detecting means detects that the cylinder in the compression stroke at that time is in a state immediately before stopping so that the next top dead center cannot be exceeded, the engine restarting means supplies fuel to the expansion stroke cylinder at that time. And after the engine rotation direction determination means determines that the engine rotation direction is the reverse rotation direction, that is, after the engine is reversely operated and the expansion stroke cylinder is compressed, the cylinder is ignited. And burn. That is, the expansion stroke cylinder burns in a state where the inside of the cylinder is compressed by the reverse rotation operation of the engine, so that sufficient torque can be obtained by combustion of the cylinder, and the engine is reliably restarted. be able to.

  Therefore, immediately before the engine is stopped, even when there is a restart request in a state where sufficient torque is not obtained even if the expansion stroke cylinder is combusted, the expansion stroke cylinder is compressed by the reverse rotation operation of the engine. Therefore, the engine can be restarted quickly and reliably without waiting for the engine to stop.

  According to a second aspect of the present invention, in the first aspect of the invention, the crank angle position detecting means for detecting the crank angle position of the engine, and the crank angle of the cylinder in the expansion stroke when the restart condition determining means determines that the restart condition is satisfied. Engine re-starting means comprising: a state immediately before reversal detection means for detecting that the rotation direction of the engine is in a state immediately before reversing in the reverse direction when the position is not within a predetermined range relatively close to top dead center. If the restart condition is satisfied and the state immediately before reversal is detected by the state detection means immediately before reversal, the engine rotation direction determination means has reversed the engine rotation direction from the normal rotation direction to the reverse rotation direction. It is assumed that after the determination is made, the expansion stroke cylinder is ignited and burned.

  As a result, the crank angle position of the expansion stroke cylinder when the restart condition is satisfied is not within the predetermined range, that is, the piston of the expansion stroke cylinder is separated from the TDC, and sufficient torque is generated even if the expansion stroke cylinder is burned. If it cannot be obtained and the engine rotation direction is reversed immediately thereafter, this is detected by the state detection means immediately before reversal. And in the case of such a state immediately before reversal, it waits for the rotation direction of the engine to reverse from the normal rotation direction to the reverse rotation direction, that is, the expansion stroke cylinder is compressed by the reverse rotation operation of the engine, A sufficiently large torque can be obtained by igniting and burning the cylinder.

  In the invention of claim 3, in any one of the inventions of claim 1 or 2, the engine restart means is determined by the engine rotation direction determination means that the rotation direction of the engine is reversed from the reverse rotation direction to the normal rotation direction. Thereafter, the expansion stroke cylinder is ignited and burned.

  Accordingly, the expansion stroke cylinder can be burned in the most compressed state by the reverse rotation operation of the engine, so that the starting torque generated by the combustion of the expansion stroke cylinder can be increased as much as possible.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the engine restarting means determines that the engine rotation direction is reversed from the normal rotation direction to the reverse rotation direction by the engine rotation direction determination means. Thereafter, fuel is injected into the expansion stroke cylinder.

  As a result, by injecting fuel into the cylinder in a state where the rotation direction of the engine is in the reverse rotation direction, that is, in a state where the expansion stroke cylinder is compressed, the temperature in the cylinder decreases due to the latent heat of vaporization, and the in-cylinder pressure Therefore, the piston of the cylinder can be moved to a position closer to the top dead center, and the stroke of the expansion stroke cylinder can be made longer. Therefore, the starting torque generated by the combustion of the expansion stroke cylinder can be further increased, and the engine can be started more reliably.

  According to the first aspect of the present invention, when a restart request is made immediately before the engine is stopped, the fuel is injected into the expansion stroke cylinder at that time, and the expansion stroke cylinder is compressed by the reverse operation of the engine. Since the combustion is performed in the generated state, a sufficient starting torque can be obtained, and the engine can be restarted quickly and reliably in response to the restart request.

  According to the invention of claim 2, when there is a restart request immediately before the rotation direction of the engine is reversed in the reverse direction, a sufficient starting torque can be obtained by burning after waiting for the reversal. In particular, according to the invention of claim 3, combustion is performed after the rotation direction of the engine is further reversed to the normal rotation direction, whereby the starting torque is maximized and the reliability of restarting the engine is improved. be able to.

  According to the invention of claim 4, by injecting fuel into the expansion stroke cylinder during engine reverse rotation, the piston can move to a position closer to the top dead center, and the starting torque due to combustion of the expansion stroke cylinder is further increased. Thus, the engine can be started more reliably.

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

-Schematic configuration of engine control system-
1 and 2 show a schematic configuration of an engine control system E using an engine starter according to an embodiment of the present invention. The engine system E includes an engine 1 having a cylinder head 10 and a cylinder block 11. And an ECU 2 (engine controller) for controlling the engine 1. As shown in FIG. 2, the engine 1 is provided with four cylinders 12A to 12D. Inside each of the cylinders 12A to 12D, pistons connected to the crankshaft 3 as shown in FIG. Thus, a combustion chamber 14 is formed above the piston 13 in each of the cylinders 12A to 12D.

  Here, in general, in a multi-cylinder four-cycle engine, each cylinder 12 performs a combustion cycle consisting of intake, compression, expansion, and exhaust strokes with a predetermined phase difference. In the case of a four-cylinder engine, when referred to as the first cylinder 12A, the second cylinder 12B, the third cylinder 12C, and the fourth cylinder 12D from one end in the cylinder row direction, as shown in FIG. 1) The combustion cycle is performed with a phase difference of 180 degrees in crank angle in order of the third cylinder (# 3), the fourth cylinder (# 4), and the second cylinder (# 2).

  A spark plug 15 for igniting and burning the air-fuel mixture in the combustion chamber 14 is provided at the top of each combustion chamber 14 of each of the cylinders 12A to 12D. An electrode is disposed so as to face the combustion chamber 14. A fuel injection valve 16 for directly injecting fuel into the combustion chamber 14 is provided on the side of the combustion chamber 14 (right direction in FIG. 1). The injection direction is adjusted so that fuel is injected toward the vicinity of the electrode of the plug 15. Here, the fuel injection valve 16 incorporates a needle valve and a solenoid (not shown) and is driven to open for a time corresponding to the pulse width in response to the input of a pulse signal from the ECU 2. A certain amount of fuel is injected into each cylinder 12. The fuel injection valve 16 is supplied with fuel through a fuel supply passage or the like by a fuel pump (not shown), and the fuel supply pressure of the engine system E is combusted in the compression stroke. The fuel supply system is configured to be higher than the pressure in the chamber 14.

  Further, an intake port 17 and an exhaust port 18 opening toward the combustion chamber 14 are provided at the upper part of the combustion chamber 14 of each of the cylinders 12A to 12D. Exhaust valves 20 are respectively provided. These intake valve 19 and exhaust valve 20 are driven by a valve operating mechanism including a camshaft (not shown), and as described above, each of the cylinders 12A to 12D performs a combustion cycle with a predetermined phase difference. The opening / closing timing of the intake / exhaust valve for each cylinder is set.

  The intake port 17 and the exhaust port 18 are provided so that an intake passage 21 and an exhaust passage 22 communicate with each other, and each cylinder of the intake passage 21 close to the intake port 17 as shown in FIG. Each of the twelve branch intake passages 21a is provided with a throttle valve 23 for reducing the area of the passage 21a. That is, the intake passage 21 has a branch intake passage 21a for each cylinder downstream of the surge tank 21b, and each lower end portion of the branch intake passage 21a communicates with the intake port 17 of each cylinder 12. . The throttle valve 23 disposed in the vicinity of the downstream end of each branch intake passage 21 a is a multiple rotary valve (multi-throttle) that simultaneously adjusts the throttle of each branch intake passage 21 a and is driven by an actuator 24. The Note that an aero flow sensor 25 for detecting the intake air amount is provided downstream of the throttle valve 23 of the intake passage 21 in a common intake passage 21c (shown only in FIG. 2) upstream of the surge tank 21b in the intake passage 21. Are each provided with an intake pressure sensor 26 for detecting the intake pressure.

  The engine system E is provided with two crank angle sensors 30 and 31 (crank angle position detecting means) for detecting the rotation angle of the crankshaft 3, and a signal from one crank angle sensor 30 is provided. While obtaining the engine rotation speed, as will be described in detail later, the rotation direction and the rotation angle of the crankshaft 3 are detected from the crank angle signals output from the two crank angle sensors 30, 31 that are out of phase with each other. Can be done. Further, the engine system E is provided with a cam angle sensor 32 that detects a specific rotational position of the camshaft and outputs it as a cylinder identification signal, and engine cooling as an essential component for controlling the engine 1. A water temperature sensor 33 that detects the temperature of the water (engine water temperature), an accelerator opening sensor 34 that detects the accelerator opening (accelerator operation amount), and the like are also provided.

  The ECU 2 receives signals from the sensors 25, 26, 30 to 34, outputs a signal for controlling the fuel injection amount and the injection timing to the fuel injection valve 16, and ignites the ignition plug 15. A signal for controlling the ignition timing is output to the device 27, and a signal for controlling the throttle opening is output to the actuator 24 of the throttle valve 23.

  As will be described in detail below, the ECU 2 automatically stops the engine 1 by stopping the fuel supply (fuel cut) when a predetermined engine stop condition is satisfied at the time of idling. The engine 1 is automatically restarted when a predetermined engine restart condition is established by the accelerator operation or the like of the person.

  That is, when the engine 1 is restarted, it is started by the power of the engine 1 itself without borrowing the power of the starting motor. In this embodiment, the piston 13 is first stopped in the middle of the compression stroke. The first combustion is performed in the cylinder 12 and the piston 13 is pushed down to slightly reverse the crankshaft 3. As a result, the piston 13 of the cylinder 12 in the expansion stroke is temporarily raised, Compress the mixture. Then, the engine 1 is started by applying a forward torque to the crankshaft 3 by igniting and burning the air-fuel mixture in the expansion stroke cylinder 12.

  In order to start the engine 1 only with its own power as such, the combustion in the expansion stroke cylinder 12 gives a torque in the forward rotation direction as large as possible to the crankshaft 3, and subsequently the compression top dead center. The cylinder 12 (hereinafter abbreviated as TDC) must overcome the compression reaction force and exceed TDC. Therefore, in order to reliably start the engine 1, it is necessary to ensure sufficient air for combustion in the cylinder 12 that is stopped in the middle of the expansion stroke. For this purpose, the engine 1 is stopped. Occasionally, fresh air is supplied in advance to scavenge burned gas, and the piston 13 of the cylinder 12 that stops in the expansion stroke (hereinafter also referred to as an expansion stroke cylinder during stoppage) is somewhat dead from the center of the stroke. It is preferable to stop within a predetermined range (for example, ATDC 100 to 120 ° CA) close to a point (hereinafter abbreviated as BDC).

  Therefore, when the engine 1 is automatically stopped at the time of idling, first, the fuel is cut at a predetermined rotational speed slightly higher than the idle rotational speed so that the scavenging of each cylinder 12 is sufficiently performed, and thereafter, the engine 1 rotates with inertia. A cylinder 12 that is in a compression stroke after the engine is stopped by opening the throttle valve 23 in a predetermined open state until the engine 1 is stopped (stop operation period) (hereinafter also referred to as a compression stroke cylinder when stopped). In addition, the amount of air sucked into the expansion stroke cylinder 12 at the time of stop is sufficiently large, particularly the amount of air in the cylinder 12 that is in the expansion stroke is increased, and the compression reaction force of the air becomes larger than that of the compression stroke cylinder 12. Like that. By doing so, the piston 13 of the expansion stroke cylinder 12 stops somewhat closer to the bottom dead center (BDC) from the center of the stroke due to the balance of the compression reaction forces acting in opposite directions in the two cylinders 12. Become.

  Furthermore, in this embodiment, the engine rotational speed that gradually decreases during the engine stop operation period is detected by signals from the crank angle sensors 30 and 31, and the opening degree of the throttle valve 23 is controlled based on the detected engine rotational speed. The amount of pump work of the engine 1 rotating at is changed to finely adjust the degree of decrease in engine rotation speed. In other words, the degree of decrease in the engine speed after the fuel cut is finely adjusted by controlling the throttle valve 23, thereby reliably stopping the piston 13 of the stop-time expansion stroke cylinder 12 within the range suitable for the restart described above. It is.

  However, when there is an engine restart request during the engine stop operation period, if the engine 1 is stopped by the start control after waiting for the engine 1 to stop by the stop control as described above, The time loss from when the engine 1 is restarted increases. Therefore, in this embodiment, if there is an engine restart request during the engine stop operation period, if the cylinder 12 in the compression stroke at that time exceeds the next TDC, fuel is injected into the cylinder 12. If the compression stroke cylinder 12 does not exceed the next TDC, the cylinder 12 in the expansion stroke is combusted at that time, and the engine 1 is rotated in the forward direction. The engine 1 is started by applying the following force.

  Thus, when the engine 1 is started by combustion of the expansion stroke cylinder 12, if the piston 13 of the cylinder 12 is in a position close to TDC, the cylinder 12 is immediately ignited and burned to obtain sufficient torque. However, when the piston 13 of the expansion stroke cylinder 12 is away from the TDC, the pressure in the cylinder is reduced and the combustion stroke is shortened. Even if the expansion stroke cylinder 12 is burned, a sufficient torque cannot be obtained, and the possibility that the restart of the engine 1 will fail increases.

  Therefore, although it is a characteristic part of the present invention, the compression stroke cylinder 12 is in a state immediately before the stop where it cannot exceed the next TDC, and the piston 13 of the expansion stroke cylinder 12 is relatively distant from the TDC and burns the cylinder 12. If a restart request is made when sufficient torque cannot be obtained even if the engine is rotated, the air-fuel mixture in the expansion stroke cylinder 12 is compressed by the reverse operation of the engine 1 (the rotational direction of the engine 1 is the reverse direction). By burning in this state, a sufficient starting torque is given to the engine 1 to start the engine 1 more reliably and quickly.

-Engine stop control-
Next, engine stop control by the ECU 2 will be described with reference to FIGS. FIG. 3 is a flowchart showing a stop control procedure, and FIG. 4 shows changes in engine rotation speed, crank angle, and stroke of each cylinder 12A to 12D during the engine stop operation period in association with each other. It is explanatory drawing which shows typically the control of the throttle opening performed, and the change of the intake pressure (intake pipe negative pressure) by this. FIG. 5 is a diagram showing a correlation between a decrease in TDC rotational speed (described later) during the engine stop operation period and a piston stop position in the stop-time expansion stroke cylinder 12.

  First, as shown in FIG. 4A, when a fuel cut is performed at a predetermined set rotational speed (800 rpm in the illustrated example) during operation of the engine 1 (time t0), the piston 13 and the crankshaft at that time The kinetic energy of the moving parts such as 3 and the flywheel is consumed by mechanical friction and pumping work of each cylinder 12, so that the engine rotation speed gradually decreases, and the engine 1 is stopped after several revolutions due to inertia. become. More specifically, while the engine 1 rotates by inertia (hereinafter referred to as an engine stop operation period), the engine rotation speed is microscopically every time each cylinder 12 reaches compression top dead center (TDC). In this way, the crank angle decreases again while repeating up / down every 180 ° CA. For example, when the fuel is cut at about 800 rpm as shown in the figure, the TDC is usually exceeded 8 or 9 times, and after the last TDC (time t3), the next TDC cannot be exceeded. To stop (time t4 to t6).

  That is, in the cylinder 12 (# 1 cylinder 12A in the illustrated example) that can not exceed TDC and remains in the compression stroke, the air pressure increases as the piston 13 rises due to the inertial force, and the piston 13 temporarily stops due to the compression reaction force. After the stop (time t4), it is pushed back toward the BDC. As a result, the crankshaft 3 is reversely rotated and the engine speed becomes a negative value as shown in FIG. 5A. Then, this time, the cylinder 12 in the expansion stroke (finally exceeds the TDC and shifts to the expansion stroke). In the illustrated example, the air pressure of the # 2 cylinder 12B) rises, and a compression reaction force to the BDC side acts on the piston 13. Then, the piston 13 of the expansion stroke cylinder 12 is temporarily stopped (time t5) by this compression reaction force and then pushed back toward the BDC, whereby the crankshaft 3 is rotated forward again and the engine speed is a positive value. Return to.

  As such, the piston 13 of each cylinder 12 is stopped after reciprocating several times by the compression reaction force acting in the opposite direction on the piston 13 of the compression stroke cylinder 12 and the expansion stroke cylinder 12 ( At time t6), the stop position is roughly determined by the balance of the compression reaction force of the compression and expansion stroke cylinders 12 and is affected by mechanical friction of the engine 1, so when the TDC is finally exceeded before the stop. It also changes depending on the rotational speed of the.

  Therefore, in order to stop the piston 13 of the stop expansion stroke cylinder 12 within a predetermined range suitable for restart, first, the compression reaction force of both the cylinder 12 and the stop compression stroke cylinder 12 becomes sufficiently large. In addition, it is necessary to adjust the intake air amount to both the cylinders 12 so that the compression reaction force of the expansion stroke cylinder 12 is larger than the compression stroke cylinder 12 by a predetermined amount and is in an appropriate balance. Therefore, in this embodiment, as shown in FIG. 4 (c), the throttle valve 23 is opened for a predetermined period after the fuel cut (time t1 to t2), and temporarily as shown in FIG. 4 (d). In addition, by reducing the intake pipe negative pressure (increase the intake air amount), the required amount of air is sucked into the compression and expansion stroke cylinders 12 at the time of stopping.

  However, in the actual engine 1, the shape of the throttle valve 23, the intake port 17, the branch intake passage 21 a, etc. has individual variations, and the behavior of the air flow that circulates there may change, so that the engine 1 is stopped. The amount of air that flows into each cylinder 12 during the operation period varies to some extent. Therefore, even if the opening / closing control of the throttle valve 23 is performed as described above, that alone causes the compression stroke and the expansion stroke when the engine is stopped. It is difficult to reliably keep the piston stop position of the cylinder 12 within the required range.

  In this embodiment, as shown in an example in FIG. 5, in this embodiment, the engine rotation speed during the stop operation period (in this embodiment, the rotation speed when the piston 13 is in compression TDC, hereinafter referred to as TDC rotation speed). Note that there is a clear correlation between the piston stop position of the cylinder 12 in the expansion stroke after the engine is stopped, and the engine speed is reduced as shown in FIG. The engine rotation speed for each TDC that appears every 180 ° CA in the process is detected, and the throttle valve 23 is controlled in accordance with the detected value to finely adjust the decrease in the engine rotation speed.

  Specifically, the distribution diagram of FIG. 5 shows that the fuel cut is performed when the engine speed is approximately 800 rpm as described above, and then each time each cylinder 12 of the engine 1 that rotates by inertia has exceeded TDC, The engine rotational speed (TDC rotational speed) is measured, and the piston position of the expansion stroke cylinder 12 after being stopped is examined. The piston stop position is plotted on the vertical axis, and the TDC rotational speed is plotted on the horizontal axis. It shows the relationship between the two. By repeating this operation a predetermined number of times, a distribution diagram showing the correlation between the TDC rotation speed during the stop operation period and the piston stop position of the stop-time expansion stroke cylinder 12 is obtained.

  In the example of the figure, the rotational speed when the last TDC before the engine stop is not shown, and the TDC rotational speed immediately after the fuel cut (the ninth thing counted from the last) is the last one before the TDC. Data up to the rotational speed (second one from the end) is shown. The 9th to 2nd TDC rotational speeds are distributed in a lump, and as clearly shown in the 6th to 2nd illustrated parts, the TDC rotational speed is within a predetermined rotational speed range (see FIG. It can be seen that the piston stop position is in a range suitable for restart (ATDC 100 to 120 ° CA in the example in the figure) when it is in the appropriate rotation speed range indicated by hatching. Note that the appropriate range of the TDC rotational speed varies depending on the structure and specifications of the engine 1 and is obtained experimentally as described above.

  In the engine stop control of this embodiment, the TDC rotation speed of the engine 1 is detected during the engine stop operation period after the fuel cut based on the correlation between the TDC rotation speed and the piston stop position as described above. When the TDC rotational speed is out of the proper rotational speed range, the opening degree of the throttle valve 23 is adjusted according to the rotational speed deviation, thereby increasing or decreasing the pump work of each cylinder 12. This ensures that the TDC rotational speed falls within the appropriate rotational speed range at least before the last TDC is exceeded. In this way, when the final TDC is exceeded, the kinetic energy possessed by the moving parts such as the crankshaft 3 and the flywheel of the engine 1, the potential energy of the high-temperature and high-pressure air in the compression stroke cylinder, etc. act thereafter. Therefore, the piston 13 of the expansion stroke cylinder 12 at the time of stop can be reliably stopped within the predetermined range suitable for restart.

  As a method for finely adjusting the engine rotational speed as described above, in addition to using the throttle valve 23 as described above, it is also conceivable to control the operating state of the auxiliary equipment of the engine 1 such as an alternator.

  Next, the specific procedure of the engine stop control described above will be described with reference to the flowchart of FIG. 3. This flow starts at a predetermined timing during engine operation (START), and in step SA1, the condition of the idle stop is determined. It is determined whether or not it is established. This determination is made based on the vehicle speed, the operating condition of the brake, the engine water temperature, etc. For example, the vehicle speed is smaller than a predetermined speed, the brake is operating, the engine water temperature is within a predetermined range, and the engine 1 is If there is no particular inconvenience for stopping, it is assumed that the idle stop condition is satisfied.

  When the idling stop condition is satisfied in the step SA1 (in the case of YES), any one cylinder 12 (the first cylinder 12A or the fourth cylinder 12D in the flow of FIG. 3) is specified in the subsequent step SA2. Then, it is determined whether or not a predetermined condition for stopping the engine 1 is satisfied. That is, it is determined whether or not the engine rotation speed is a fuel cut set rotation speed (approximately 800 rpm in this embodiment), whether or not the specified cylinder 12 is in a preset stroke (for example, an intake stroke). If all the conditions are satisfied and it is determined YES, the process proceeds to step SA3, and the fuel injection to each cylinder 12 is stopped.

  Subsequently, in step SA4, the throttle valve 23 is opened at a predetermined opening, and this state is maintained until it is determined in step SA5 that the engine rotational speed is equal to or lower than the predetermined rotational speed (engine rotational speed at time t2 in FIG. 4). If the rotation speed is lower than the predetermined rotation speed (in the case of YES in step SA5), the process proceeds to step SA6 and the throttle valve 23 is closed. By opening and closing the throttle valve 23 in accordance with the engine speed in this way, as shown in FIGS. 4C and 4D, the stop-time expansion stroke cylinder 12 (# 2 cylinder 12B in the illustrated example) and the stop-time compression are shown. Since the intake air amount to the stroke cylinder 12 (# 1 cylinder 12A in the figure) increases and the intake air amount to the stop expansion stroke cylinder 12 becomes larger than the stop compression stroke cylinder 12, the stop expansion stroke 12 The stop position of the piston 13 can be substantially within a predetermined range.

  Subsequently, in step SA7, it is determined whether or not the TDC rotational speed obtained from the signal from the crank angle sensor 30 is in the proper rotational speed range. If the determination is YES and the TDC rotational speed is in the proper rotational speed range, step SA8 is performed. Next, it is determined whether or not the TDC rotational speed is equal to or less than a predetermined value A. Although the predetermined value A will be described in detail later, it is experimentally set in advance in association with the last TDC rotational speed before the engine is stopped. If the TDC rotational speed obtained in step SA7 is equal to or smaller than the predetermined value A, If this is the case (if the determination is YES), the engine 1 cannot exceed the next TDC and stops, so the process proceeds to step SA11 described later, and if the TDC rotational speed is higher than the predetermined value A ( If the determination is NO), the engine 1 further exceeds the next TDC, so the process returns to step SA7.

  If it is determined in step SA7 that the TDC rotational speed is not in the appropriate rotational speed range (NO), the process proceeds to step SA9, where the rotational speed between the TDC rotational speed and the appropriate rotational speed range is set. Based on the deviation, the opening of the throttle valve 23 is calculated. Then, in step SA10, the actuator 24 of the throttle valve 23 is driven (throttle drive) so that the opening degree is reached, and the process proceeds to step SA8. That is, for example, when the TDC rotational speed is higher than the upper limit of the appropriate rotational speed range, the degree of decrease in engine rotational speed is increased by driving the throttle valve 23 toward the closing side to increase the pump work of each cylinder 12. To do. On the other hand, when the TDC rotational speed is lower than the lower limit of the appropriate rotational speed range, the degree of decrease in engine rotational speed is moderated by driving the throttle valve 23 to reduce the pump work of each cylinder 12. To do.

  By doing this, as shown in FIG. 4A, the engine rotational speed that gradually decreases while repeating up and down is shifted to the high speed side or the low speed side as a whole, and is appropriate when exceeding the last TDC at the latest. Thus, the piston 13 of the cylinder 12 in the expansion stroke can be surely stopped within a predetermined range suitable for restart when the engine 1 is stopped.

  Then, if the engine 1 exceeds the last TDC and the TDC rotational speed at that time becomes equal to or less than the predetermined value A, it is determined as YES in Step SA8 and proceeds to Step SA11. This time, the engine 1 is completely stopped. Determine if you did. That is, it is determined that the crankshaft 3 is stationary after repeating the forward rotation and the reverse rotation several times by the mutually opposite compression reaction forces of the cylinders 12 in the expansion stroke and the compression stroke at the time of stopping. If the determination is YES and it is confirmed that the engine 1 is stopped, the process proceeds to step SA12 to detect the piston stop position of the cylinder 12 in the expansion stroke by a stop position detection routine described later. The engine stop control is completed (END).

  Here, as described above, the crankshaft 3 rotates several times in both forward and reverse directions immediately before the engine 1 is completely stopped. Therefore, the piston stop position is determined only by counting the signal from the crank angle sensor 30. It cannot be detected. Therefore, in this embodiment, the rotation direction and the rotation angle of the crankshaft 3 are detected as follows based on the crank angle signals output from the two crank angle sensors 30 and 31 and shifted from each other. The piston stop position is detected.

  FIG. 6 is a flowchart showing a procedure for detecting the stop position of the piston 13. When this flow starts, in step SC1, the first crank angle signal CA1 (output signal from the first crank angle sensor 30) and the second Based on the crank angle signal CA2 (output signal from the second crank angle sensor 31), the ECU 2 determines whether the second crank angle signal CA2 is Low or High when the first crank angle signal CA1 rises, or When the first crank angle signal CA1 falls, it is determined whether the second crank angle signal CA2 is High or Low. That is, it is determined whether the phase relationship between these signals CA1 and CA2 is as shown in FIG. 7A or FIG. 7B, and the normal rotation and inversion of the engine 1 are thereby performed. Determine.

  More specifically, during forward rotation of the engine 1, as shown in FIG. 7A, the second crank angle signal CA2 has a phase delay of about a half pulse width with respect to the first crank angle signal CA1. When the first crank angle signal CA1 rises, the second crank angle signal CA2 becomes Low, and when the first crank angle signal CA1 falls, the second crank angle signal CA2 becomes High. On the other hand, at the time of reverse rotation of the engine 1, as shown in FIG. 7B, the second crank angle signal CA2 has a phase advance of about a half pulse width with respect to the first crank angle signal CA1. Contrary to the normal rotation of the engine, 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 signals CA1 fall. Because.

  When it is determined in step SC1 of the flow that the engine 1 is in the normal rotation state (in the case of YES), the count number of the CA counter for measuring the crank angle change in the normal rotation direction of the engine 1 is set. On the contrary, when it is determined that the reverse rotation state is established (in the case of NO), the count number of the CA counter is decreased. Here, the rise and fall of the first crank angle signal CA1 and the second crank angle signal CA2 are caused by rotation of the crankshaft 3 for each predetermined angle (in this embodiment, the interval between the rise and fall is approximately 10 °. Therefore, the forward / reverse rotation of the engine 1 is determined as described above according to the state of the second crank angle signal CA2 when the first crank angle signal CA1 rises and falls. In addition, the rotation angle of the crankshaft 3 can be obtained from the number of rising or falling times of the first crank angle signal CA1 and the second crank angle signal CA2. In this way, the piston stop position can be accurately obtained even if the crankshaft 3 rotates in the forward and reverse directions as described above when the engine is stopped.

  According to the engine stop control described above, when the engine 1 is automatically stopped during idling, the opening degree of the throttle valve 23 is controlled based on the detected value of the TDC rotational speed during the stop operation period after the fuel cut. The engine speed can be finely adjusted so that the TDC rotational speed falls within a predetermined appropriate rotational speed range. As a result, the piston 13 of the cylinder 12 in the expansion stroke after the engine is stopped can be adjusted to a predetermined value. It can be stopped at the stroke position. In addition, when the engine 1 rotates several times due to inertia during the engine stop operation period, almost all the burned gas in each cylinder 12 is scavenged out of the cylinder. After the engine 1 is stopped, the pressure in the expansion stroke cylinder 12 and the compression stroke cylinder 12 in which the intake / exhaust valves 19 and 20 are closed immediately decreases. There will be a state of fresh air (air).

-Engine start control-
Next, the control when the engine 1 is automatically restarted from the engine stop state during idling will be described with reference to FIGS. 8 and 9 are flowcharts showing the procedure of start control, and FIG. 10 is a flowchart showing the fuel injection and ignition timing for each of the cylinders 12A to 12D at the time of engine start, and the opening and closing operation of the intake and exhaust valves. FIG. FIG. 11 is a time chart showing changes in engine rotation speed, in-cylinder pressure of each cylinder 12A to 12D, and generated torque when the engine is started.

  First, the specific procedure of the start control will be described with reference to the flowcharts of FIGS. 8 and 9. This flow starts from the engine stop state after the stop control as described above is performed (START) and continues. In step SB1, it is determined whether or not a predetermined engine restart condition is satisfied. If the engine restart condition is not satisfied, the process waits until the restart condition is satisfied.

  Here, the engine restart condition determined in step SB1 is that the engine 1 is operated for the operation of the air conditioner or the like when the brake is released or the accelerator operation is performed in order to start from the stop state. When such a condition is satisfied (in the case of YES in step SB1), the process proceeds to the subsequent step SB2, and the stop position of the piston 13 obtained by counting the crank angle signal. Based on this, the air amounts of the compression stroke cylinder 12 (# 1 cylinder 12A in FIGS. 10 and 11) and the expansion stroke cylinder 12 (# 2 cylinder 12B in FIGS. 10 and 11) when the engine is stopped are calculated. In this step SB2, the volumes of the combustion chambers 14 of the stop compression stroke cylinder 12 and the stop expansion stroke cylinder 12 are obtained from the stop position of the piston 13, and as described above, the inside of the stop expansion stroke cylinder 12 is almost the same. The air amount of the stop-time compression stroke cylinder 12 and the stop-time expansion stroke cylinder 12 is determined in consideration of being in a state of being filled with fresh air and being substantially at atmospheric pressure.

  Subsequently, at step SB3, the compression stroke cylinder 12 is adjusted so as to have a predetermined air-fuel ratio (A / F for the first compression stroke cylinder) with respect to the air amount of the compression stroke cylinder 12 at the time of stop calculated at step SB2. Inject fuel into the tank. In this case, the air-fuel ratio is obtained from a map set in advance in association with the piston stop position or the like when the engine is stopped, whereby the air-fuel ratio of the compression stroke cylinder 12 is richer than the stoichiometric air-fuel ratio. (A / F ranges from approximately 11 to 14).

  Next, in step SB4, after elapse of a predetermined time set in consideration of fuel vaporization time from fuel injection to the stop compression stroke cylinder 12, the ignition plug 15 of the cylinder 12 is energized to ignite the air-fuel mixture. To do. Whether or not the piston 13 has moved in step SB5 depending on whether or not the edge of the signal from the crank angle sensors 30 and 31 (rise or fall of the crank angle signal) has been detected within a predetermined time from the ignition in step SB4. If the piston 13 does not move due to misfire or the like (in the case of NO), the process returns to step SB6 and the compression is performed. Re-ignition is repeatedly performed on the stroke cylinder 12.

  If the edge of the crank angle signal is detected in step SB5 (if the determination in step SB5 is YES) and it is determined that the piston 13 has moved, that is, the engine 1 has rotated in the reverse direction, in the subsequent step SB7 Then, fuel is injected into the expansion stroke cylinder 12 so as to be a predetermined air-fuel ratio (A / F for expansion stroke cylinder) with respect to the air amount of the expansion stroke cylinder 12 at the time of stop calculated at step SB2. Also in this case, the air-fuel ratio for the expansion stroke cylinder 12 is obtained from a map set in advance in association with the piston stop position or the like when the engine is stopped, as in step SB3. Or, a slightly richer value is set.

  In the following step SB8, the air-fuel mixture in the expansion stroke cylinder 12 at the time of stop is sufficiently compressed by the rise of the piston 13 accompanying the reverse rotation of the engine 1, and a predetermined time until the piston 13 is almost stopped by this compression reaction force. After the elapse of (ignition delay), the expansion stroke cylinder 12 is ignited. By igniting and burning the compressed air-fuel mixture in the expansion stroke cylinder 12 in this way, the engine 1 starts to rotate in the forward rotation direction. The ignition delay time is roughly the time until the piston 13 of the expansion stroke cylinder 12 reaches the vicinity of TDC after the engine 1 rotates in reverse, and is set in advance in association with the piston stop position when the engine is stopped. Is obtained from the generated map.

  In the following step SB9, the fuel is injected into the stop-time compression stroke cylinder 12 at a timing in consideration of the fuel vaporization time. As a result, the temperature in the compression stroke cylinder 12 is lowered due to the latent heat of vaporization of the injected fuel, and the in-cylinder pressure is lowered. Therefore, the compression reaction force of the cylinder 12 accompanying the forward rotation of the engine 1 is reduced, and the piston 13 can easily exceed TDC. Therefore, the rotation in the forward rotation direction of the engine 1 started by the combustion of the stop-time expansion stroke cylinder 12 in step SB8 is promoted, and each of the cylinders 12A to 12D advances to the next stroke.

  Subsequently, in step SB10 of FIG. 9, the intake stroke cylinder 12 at the time of stoppage by the forward rotation operation of the engine 1 based on the in-cylinder temperature and the atmospheric pressure estimated from the engine water temperature, the engine stop time, the intake air temperature, and the like. 10 and 11, the density of the air (cylinder air density) charged in the # 3 cylinder 12C) is estimated, and the air amount of the intake stroke cylinder 12 is calculated based on this estimated value. In step SB11, an air-fuel ratio correction value for preventing self-ignition is calculated mainly from the estimated value of the in-cylinder temperature of the intake stroke cylinder 12, and in step SB12, the air-fuel ratio considering the correction value is calculated. Based on the air amount in the intake stroke cylinder 12 calculated in step SB10, an appropriate fuel injection amount to the intake stroke cylinder 12 is calculated. That is, in these steps SB10 to SB12, the stop-time intake stroke cylinder 12 is prevented from self-igniting due to its compression pressure, in-cylinder temperature, and the like in the compression stroke first reached at the start of the engine, and the compression reaction force In order to make the air-fuel ratio as small as possible, the air-fuel ratio is set to a slightly rich state of A / F = 13.

  In step SB13, when the stop-time intake stroke cylinder 12 is in the compression stroke, fuel injection is performed in the middle of the compression stroke. That is, fuel is injected in the intake stroke at the time of starting by a normal starter motor, but in this embodiment, the engine stop time, intake air temperature, and so on are effectively reduced by the latent heat of vaporization of the fuel. In consideration of the cooling water temperature and the like, the fuel is injected in the middle of the compression stroke. As a result, the compression pressure of the stop-time intake stroke cylinder 12 is effectively reduced, and this also prevents self-ignition. Thereafter, the process proceeds to step SB14, where ignition is performed after the piston 13 of the intake stroke cylinder 12 at the time of stop exceeds TDC. This ignition timing is also before TDC if the engine is normally started. However, if the ignition is performed before TDC when the engine is not used, the reverse torque acting on the piston 13 may interfere with engine start. Therefore, the piston 13 is ignited after passing through TDC.

  In the following step SB15, it is determined whether or not the intake pressure (intake pipe negative pressure) in the branch intake passage 21a downstream of the throttle valve 23 is higher than that during idling. If it is determined in this determination that it is higher than when idling (in the case of YES), the process proceeds to step SB16, and the throttle valve 23 is driven so as to be smaller than the throttle opening during idling according to the intake pressure. Thus, the amount of air taken into the combustion chamber 14 of the cylinder 12 from the upstream side of the throttle valve 23 is reduced, and the process returns to step SB15. Then, the control of the throttle valve 23 is repeated until the intake pressure becomes equal to the intake pressure at the time of idling. On the other hand, if the intake pressure becomes lower than the intake pressure at the time of idling and it is determined NO in Step SB15, Proceed to SB17 and shift to normal engine control.

  In the above steps SB15 and SB16, when the air in the surge tank 21b and its downstream intake passage 21 that are close to the atmospheric pressure while the engine is stopped is sucked into the cylinder 12 at the time of start-up, In consideration of the problem that the engine speed increases rapidly and large vibrations occur, the amount of air taken into the cylinder 12 is limited by the throttle valve 23.

  According to the above-described flow, the engine 1 automatically stopped at the time of idling can be restarted without using a starting motor or the like in response to a restart request. That is, as shown in FIGS. 10 and 11, when an engine restart request is made when the engine is stopped when idling (time 0 in FIG. 11), first, the cylinder 12 in the compression stroke (# 1 cylinder 12A ) Is injected (indicated as a1 in both figures. The same applies to the following fuel injection and ignition), and the mixture is ignited (a2), whereby the engine 1 is rotated in the reverse direction (left direction in FIG. 10). ) To rotate. As a result, the compression pressure in the expansion stroke cylinder 12 (# 2 cylinder 12B) at the time of stop is increased, and fuel is injected (a3) into the expansion stroke cylinder 12 and ignited (a4). Rotate in the right direction (FIG. 10).

  Further, before the stop compression stroke cylinder 12 (# 1 cylinder 12A) exceeds TDC, fuel is again injected into the cylinder 12 (a5), thereby reducing the compression pressure of the cylinder 12 and the piston 13 It is easy to exceed TDC.

  In addition, for the intake stroke cylinder 12 at stop (# 3 cylinder 12C), the fuel is injected so as to be in a rich state, and the fuel injection timing is delayed from the normal (fuel injection in the intake stroke) and compressed. By setting the middle of the stroke (a6), self-ignition in the compression stroke of the cylinder 12 is prevented, and the ignition timing is retarded until after TDC (a7), so that no reverse torque is generated. The engine rotation speed is increased so that the engine is reliably started.

  Further, the throttle valve 23 is controlled to be closed when the engine is started, rather than during normal idle operation, thereby limiting the intake charge amount to the exhaust stroke cylinder 12 (# 4 cylinder 12D) at the time of stop, and at the time of the stop. By performing the same control (a8, a9) as the intake stroke cylinder 12 (# 3 cylinder), it is possible to prevent a sudden increase in engine rotation and the occurrence of vibrations.

-Restart control during engine stop operation-
Next, restart control when there is a restart request within the engine stop operation period after fuel cut, which is a characteristic part of the present invention, will be described with reference to FIGS. 12 and 13 are flowcharts showing the control procedure, and FIG. 14 is a time chart showing changes in the TDC rotational speed and crank angle during the engine stop operation period. FIG. 15 is a stroke diagram in which the fuel injection and ignition timing for each of the cylinders 12A to 12D during engine restart during the engine stop operation period is associated with the stroke.

  First, the restart procedure when there is a restart request during the stop operation period will be described with reference to the flowcharts of FIGS. 12 and 13. The flow of FIG. 12 starts from the state in which the engine 1 is operating. In step SD1, the counter 1 of the number of reverse rotations of the engine 1 is reset. This counter rotation number counter is used to determine the number of counter rotations of the engine 1 in step SD17 described later. In this embodiment, when the rotational inertia force of the engine 1 is small (details will be described later). , The TDC rotational speed is equal to or lower than a predetermined rotational speed), and the engine 1 is controlled to start according to the number of counter rotation counters.

  In subsequent step SD2, it is determined whether or not an idle stop condition is satisfied. If the idle stop condition is satisfied (in the case of YES), the process proceeds to step SD3, where the engine speed and the like satisfy the engine stop condition. Determine if it meets. If it is determined in this step SD3 that the engine stop condition is satisfied (in the case of YES), the fuel supply to the cylinders 12A to 12D of the engine 1 is stopped in the subsequent step SD4, and the throttle valve is determined in step SD5. 23 is controlled to open at a predetermined opening. The steps SD2 to SD5 are the same as steps SA1 to SA4 in the flow shown in FIG.

  Subsequently, at step SD6, it is determined whether or not a predetermined engine restart condition is satisfied. If an accelerator operation, brake release, or the like is performed, it is assumed that the engine restart condition is satisfied. In step SD7, the engine 1 is controlled to start according to the TDC rotational speed at that time, as will be described later. On the other hand, if it is determined in step SD6 that the engine restart condition is not satisfied (in the case of NO), the process proceeds to step SD8, and in the same manner as in step SA5 in FIG. Judge whether. If the engine rotational speed is equal to or lower than the predetermined rotational speed (in the case of YES), the throttle valve 23 is closed in step SD9, while if the engine rotational speed is higher than the predetermined rotational speed (in the case of NO). Returning to the step SD6, the process waits until the restart condition of the engine 1 is satisfied or the engine speed becomes equal to or lower than the predetermined speed.

  Then, in step SD10 following step SD9, it is determined whether or not the engine 1 has reversed from the forward rotation direction to the reverse rotation direction immediately before stopping. If YES, the counter counter is incremented by 1 in step SD11. On the other hand, the process proceeds to step SD12. On the other hand, in the case of NO (when the rotation direction of the engine 1 is not reversed from the normal rotation direction to the reverse rotation direction), the process proceeds to step SD12 as it is. That is, as described above, after exceeding the last TDC immediately before the stop (time t3 in FIG. 4), the engine 1 is prevented from rotating forward by the compression reaction force of the cylinder 12 in the expansion stroke and the cylinder 12 in the compression stroke. Reverse rotation, reverse rotation from reverse rotation to forward rotation several times, and the pistons 13 of the cylinders 12A to 12D reciprocate several times, and then stop, but in steps SD10 and SD11, the steps after SD17 to be described later In step, in order to perform start control of the engine 1 according to the number of reverse rotations of the engine 1, the number of times the engine 1 is reversed from normal rotation to reverse rotation is counted.

Next, in step SD12, it is determined again whether the engine restart condition is satisfied. If the restart condition is satisfied (in the case of YES), the throttle valve 23 is opened at a predetermined opening in the subsequent step SD13. Then, the process proceeds to step SD7. On the other hand, if the restart condition is not satisfied (in the case of NO), it is determined whether or not the engine 1 has stopped in step SD14 as in step SA11 in the flow of FIG. 3, and if the engine 1 has stopped. (In the case of YES) After storing the piston stop position, this flow ends (END), waits for the restart condition after the engine to stop, and the engine restart flowchart described above (FIGS. 8 and 9). Start control at. If the engine 1 is not stopped (NO in step SD14), the process returns to step SD10, and the number of inversions of the engine 1 is counted until the engine restart condition is satisfied or until the engine 1 stops. Further, although not shown in the flow of FIG. 12, after the throttle valve 23 is closed in step SD9, if the engine restart condition is not satisfied, the process from step SA7 of the flow of FIG. As in SA10, the correction control of the opening degree of the throttle valve 23 is performed according to the TDC rotational speed. Then, in step SD7 of FIG. 13 which proceeds when the engine restart condition is satisfied and YES is determined in steps SD6 and SD12, the engine speed at the last TDC that has exceeded the piston 13 before the restart condition is satisfied ( It is determined whether (TDC rotational speed) is higher than the same predetermined value A (predetermined rotational speed) as in step SA8 of the flow of FIG. As described above, the predetermined value A is used to determine whether or not the compression stroke cylinder 12 exceeds the next TDC. For example, at the next TDC, the rotational inertia force of the engine 1 and the compression stroke cylinder 12 are determined. The compression reaction force may be set to a value that is substantially equal.

  That is, in step SD7, based on the engine speed at the time of restart request (when the restart condition is satisfied), the engine 1 is in view of whether or not the cylinder 12 in the compression stroke at that time can exceed the next TDC. If the TDC rotational speed is higher than the predetermined value A and can exceed the next TDC (in the case of YES at step SD7), it is detected for the compression stroke cylinder 12 at that time. Then, the fuel is injected and the engine 1 is restarted by igniting after passing through the TDC, and thereafter, the routine proceeds to normal engine start control (step SD16).

  On the other hand, when it is estimated in step SD7 that the TDC rotational speed is equal to or lower than the predetermined value A and the compression stroke cylinder 12 at that time cannot exceed the next TDC (in the case of NO determination in step SD7). In step S17 and later described, optimal starting control is performed according to the rotational direction of the engine 1, the position of the piston 13 of the expansion stroke cylinder 12, and the like.

  The predetermined value A may be set so that the rotational inertia force of the engine 1 at the next TDC is larger than the compression reaction force of the compression stroke cylinder 12 by a predetermined amount. Here, the predetermined amount includes a subtle case in which the compression stroke cylinder 12 exceeds or cannot exceed the next TDC in consideration of aging deterioration and variation of the engine 1 in the range of the predetermined value A or less. Set as follows. In this way, when the TDC rotational speed is lower than the predetermined value A, the control of steps SD17 to SD27 described below is performed, so that the engine 1 is independent of the secular change of the engine 1 and the detection error of the TDC rotational speed. It is possible to reliably restart the engine by applying a sufficient starting torque.

  In step SD17 following step SD7, it is determined whether the number of reverse rotations of the engine 1 is zero based on the count number of the reverse rotation number counter. If the number of reverse rotations is 0 (in the case of YES), the following step SD18 is performed. In ~ SD27, the engine 1 is started by injecting fuel into the expansion stroke cylinder 12 to ignite and burn it. On the other hand, if the number of reverse rotations of the engine 1 is 1 or more (in the case of NO), detailed description is omitted, but the flow proceeds to a flow outside the figure (step SD29), The engine 1 is started by executing another start control according to the crank angle.

  If the determination in step SD17 is YES (the number of reverse rotations of the engine 1 is 0), then in step SD18, the position of the expansion stroke cylinder 12 (expansion stroke cylinder at stop) at that time is within a predetermined crank angle range from TDC ( From TDC to approximately 20-30 ° CA), that is, whether the piston 13 is located relatively close to the TDC. If YES (the position of the piston 13 is close to TDC), Proceeding to step SD19, fuel is injected into the expansion stroke cylinder 12 and ignited after a predetermined time considering the vaporization time of the fuel. In step SD20, fuel is injected also into the compression stroke cylinder 12 (compression stroke cylinder at the time of stop) at that time, and the compression pressure is reduced by lowering the in-cylinder pressure by lowering the temperature in the cylinder 12 by the latent heat of vaporization. While making it easy for the stroke cylinder 12 to exceed TDC, the process waits for the compression stroke cylinder 12 to exceed TDC (step SD21), and ignites when the expansion stroke is reached (step SD22). Then, the routine proceeds to normal engine start control (step SD23).

  That is, in steps SD18 to SD23, there is a restart request at the time of forward rotation before the rotation direction of the engine 1 is reversed in a state immediately before the stop in which the compression stroke cylinder 12 cannot exceed the next TDC. If the piston 13 of the expansion stroke cylinder 12 is close to TDC and sufficient torque can be obtained by burning the cylinder 12 in this state, the rotational inertia force of the engine 1 that rotates in the forward direction is used. The combustion in the expansion stroke cylinder 12 at that time gives the engine 1 a starting torque in the forward rotation direction, the fuel injection into the compression stroke cylinder 12 makes the piston 13 easily exceed TDC, and the piston 13 exceeds TDC. After that, by igniting the compression stroke cylinder 12, the engine 1 is further rotated in the normal rotation direction to restart the engine 1. .

  In this embodiment, the fuel is injected into the expansion stroke cylinder 12 in step SD19 and ignited, and then injected into the compression stroke cylinder 12 in step SD20. However, the present invention is not limited to this, and the step SD19 Thus, the fuel may be injected into the compression stroke cylinder 12 almost simultaneously with the injection into the expansion stroke cylinder 12.

  On the other hand, when it is determined in step SD18 that the expansion stroke cylinder 12 is not within the predetermined crank angle range after TDC (the position of the piston 13 is away from TDC) (in the case of NO), the state is maintained as it is. Thus, even if the expansion stroke cylinder 12 is combusted, sufficient torque cannot be obtained, and immediately after that, the rotation direction of the engine 1 is reversed in the reverse rotation direction. After the direction is once reversed and the expansion stroke cylinder 12 is compressed, the rotation direction of the engine 1 is reversed again, and the expansion stroke cylinder 12 is combusted after waiting for the rotation direction to return from the reverse rotation direction to the normal rotation direction. By doing so, the engine 1 is restarted.

  Specifically, after waiting for the rotation direction of the engine 1 to reverse from the normal rotation direction to the reverse rotation direction in step SD24, fuel is injected into the expansion stroke cylinder 12 in step SD25. Then, the expansion stroke cylinder 12 is compressed by the reverse operation of the engine 1, and after that, in step SD26, it waits for the rotation direction of the engine 1 to reverse from the reverse rotation direction to the normal rotation direction. The stroke cylinder 12 is ignited and burned to give the engine 1 a starting torque in the forward rotation direction. Further, after the fuel is injected into the compression stroke cylinder 12 in the subsequent step SD28, the process proceeds to the above-described steps SD21 to SD23 and waits for the piston 13 of the compression stroke cylinder 12 to exceed TDC. After ignition, the routine proceeds to normal engine start control.

  In other words, in steps SD24 to SD28 and SD21 to SD23, in the state immediately before reversal in which the position of the piston 13 of the expansion stroke cylinder 12 is away from the TDC in the state immediately before the stop when the compression stroke cylinder 12 cannot exceed the next TDC. When there is a restart request, even if the expansion stroke cylinder 12 is combusted in that state, an effective stroke is insufficient and sufficient torque cannot be obtained. The expansion stroke cylinder 12 is combusted after waiting for the inside of the expansion stroke cylinder 12 to be compressed.

  That is, the starting torque can be reliably applied to the engine 1 by burning the cylinder 12 in a state where the expansion stroke cylinder 12 is compressed using the reverse operation of the engine 1.

  Further, after detecting that the rotation direction of the engine 1 is reversed from the normal rotation direction to the reverse rotation direction in the step SD24, the fuel is injected into the expansion stroke cylinder 12 in the step SD25, so that the injected fuel Since the temperature in the expansion stroke cylinder 12 is lowered by the latent heat of vaporization and the pressure in the cylinder 12 is reduced, the piston 13 of the expansion stroke cylinder 12 moves to a position closer to TDC when the engine 1 rotates in reverse. become longer. Also by this, the starting torque generated by the combustion of the expansion stroke cylinder 12 can be increased. Although the above-described effects cannot be obtained, the timing of fuel injection to the expansion stroke cylinder 12 is not limited to the above timing, and the expansion stroke cylinder 12 is not rotated before the rotation direction of the engine 1 is reversed. You may make it inject a fuel.

  Further, after detecting that the rotation direction of the engine 1 is reversed from the reverse rotation direction to the normal rotation direction in the step SD26, fuel injection is performed on the compression stroke cylinder 12 in the step SD27, whereby the compression stroke cylinder 12 Since the fuel is injected in the middle of the compression stroke, self-ignition can be prevented by obtaining a vaporization latent heat effect. However, the timing at which the fuel is injected into the compression stroke cylinder 12 is not limited to this, and before the rotation direction of the engine 1 is reversed from the reverse rotation direction to the normal rotation direction, such as the same timing as the fuel injection to the expansion stroke cylinder 12. You may make it perform fuel injection.

  In the above-described flow, in order to burn the expansion stroke cylinder 12 in a sufficiently compressed state, it waits for the rotation direction of the engine 1 to reverse from the reverse rotation direction to the normal rotation direction in the step SD26. In step SD27, the expansion stroke cylinder 12 is ignited and combusted. However, the present invention is not limited to this, and the expansion stroke cylinder 12 may be ignited during the reverse rotation operation of the engine 1. In this way, the engine can be started more quickly.

  The engine stop means 2a for stopping the fuel supply to the cylinders 12A to 12D of the engine 1 is restarted by steps SD6 and SD12 of the flow in steps SD2 to SD4 of the restart flow shown in FIG. Restart condition determining means 2b for determining whether the condition is satisfied is configured.

  Further, in step SD7 of the flow shown in FIG. 13, the state immediately before stop detecting means 2c for detecting the state immediately before stop where the compression stroke cylinder 12 cannot exceed the next TDC is detected, and in step SD18 of the flow, the expansion stroke cylinder. When the crank angle of 12 is larger than a predetermined value, that is, when the piston 13 is away from the TDC, the immediately before reversal state detection means 2d for determining that the rotation direction of the engine 1 is just before reversing in the reverse rotation direction Each is composed. Further, the engine rotation direction determination means 2e for determining the rotation direction of the engine at steps SD24 and SD26 of the flow of FIG. 13 further supplies fuel to the expansion stroke cylinder 12 at steps SD25 to SD28 of the flow. The engine restart means 2f is configured to ignite and burn after the injection and the engine rotation direction is reversed from the reverse rotation direction to the normal rotation direction.

  By the above flow control, when there is a restart request during the stop operation period of the engine 1, optimal start control is performed according to the engine rotational speed (TDC rotational speed) and the piston position at that time. The engine 1 can be started reliably and quickly. That is, as shown in FIG. 14, when there is a restart request during the engine stop operation period from when the fuel supply to each cylinder 12A to 12D of the engine 1 is stopped (fuel cut) until the engine 1 is stopped, If the immediately preceding TDC rotational speed is higher than the predetermined value A, that is, if the rotational inertia force of the engine 1 is large and the compression stroke cylinder 12 exceeds the next TDC (FIG. 14 (a)). In FIG. 14 (a), R1 (broken line) is obtained by injecting fuel into the compression stroke cylinder 12 at that time, igniting (steps SD15 and SD16), and burning. Thus, the engine 1 can be restarted.

  On the other hand, when the TDC rotational speed becomes equal to or lower than the predetermined value A beyond the last TDC, the rotational inertia force of the engine 1 is small, and the compression stroke cylinder 12 cannot exceed the next TDC as it is. As shown in FIG. 14A, the piston 13 of the cylinder 12 in the expansion stroke at that time is relatively close to the TDC (in the example of the figure, 0 to 30 ° CA of the ATDC, If it is within the range, the fuel is immediately injected into the expansion stroke cylinder 12 (step SD19), ignited (step SD19), and burned. Give torque in forward direction.

  Subsequently, by injecting fuel also into the compression stroke cylinder 12 at the time of the restart request (step SD20), the temperature in the cylinder 12 is lowered by the latent heat of vaporization, thereby reducing the in-cylinder pressure, The cylinder 12 is made to easily exceed the next TDC. In the expansion stroke after the compression stroke cylinder 12 exceeds TDC, the cylinder 12 is ignited (step SD22) and burned, whereby the starting torque of the engine 1 can be further increased. The engine 1 can be reliably restarted as indicated by R2 (broken line) in FIG.

  Further, in the expansion stroke cylinder 12 at the time of the restart request, the piston 13 is separated from the TDC, and sufficient starting torque cannot be obtained even if combustion is performed in that state (range III in FIG. 14A). After that, as shown in FIG. 15, after the rotation direction of the engine 1 is reversed by the compression reaction force of the cylinder 12 in the compression stroke to become the reverse rotation direction (range IV in FIG. 14 (a)). Fuel is injected into the expansion stroke cylinder 12 (# 2 cylinder 12B) (step SD25, indicated by reference numeral b1 in FIG. 15; the same applies to fuel injection and ignition), and the expansion stroke cylinder 12 (# 2 cylinder 12B). ) Is moved to the TDC side and the inside of the cylinder is sufficiently compressed, and then the cylinder 12 is ignited when the rotational direction of the engine 1 is reversed in the normal rotation direction by the compression reaction force ( Step SD27, b2), by burning, it is possible to impart sufficient starting torque to the engine 1.

  Thereafter, similarly to the start control when the piston 13 is close to TDC, fuel injection (step SD28, b3) is performed on the compression stroke cylinder 12 (# 1 cylinder 12A), and the cylinder 12 performs TDC. By igniting (step SD22, b4) and burning after exceeding, the engine 1 can be reliably restarted as indicated by R3 (broken line) in FIG.

  Then, after restarting the engine 1 by the start control as described above, the routine proceeds to normal engine control (fuel injection in the intake stroke: b5 and b7, ignition in the latter half of the compression stroke: b6) (step SD23). 1 performs normal operation.

  Accordingly, during the stop operation period of the engine 1, by performing the start control as described above according to the engine rotation state when the start request is made, the engine 1 waits for the engine stop as shown by broken lines R1 to R3 in FIG. Compared to the case where the engine is restarted (shown by a solid line in FIG. 14), the time until the engine is started can be significantly reduced, and the engine 1 can be restarted quickly in response to the restart request. .

  In particular, when there is a restart request immediately before the rotation direction of the engine 1 is reversed, the cylinder 12 is sufficiently compressed after the inside of the expansion stroke cylinder 12 is sufficiently compressed using the reverse rotation operation of the engine 1 immediately after that. By burning, sufficient torque for starting can be reliably applied to the engine 1.

(Other embodiments)
The configuration of the present invention is not limited to the above embodiment, but includes various other configurations. That is, in the above embodiment, when a restart request is made, it is determined whether or not the compression stroke cylinder 12 can exceed the next TDC based on the TDC rotational speed immediately before the restart request (step of FIG. 13). SD7) is not limited to this, and the rotational speed at the piston bottom dead center (BDC) or other piston position is detected, and whether the compression stroke cylinder 12 can exceed the next TDC based on the rotational speed. May be determined.

  Further, in the above embodiment, the restart control when there is a restart request before the rotation direction of the engine 1 is reversed (range III in FIG. 14) in steps SD17 to SD28 of the flow of FIG. However, even when there is a restart request when the rotation direction of the engine 1 is the reverse rotation direction (range IV in FIG. 14), fuel is injected into the expansion stroke cylinder 12 so that the rotation direction of the engine 1 is It is only necessary to perform the restart control of steps SD25 to SD28 and SD21 to SD23 in which the cylinder 12 is ignited and combusted after waiting for reverse rotation in the forward direction.

  As described above, the engine starter according to the present invention can restart the engine quickly and reliably in response to a restart request immediately before the engine is stopped, and thus is particularly useful in, for example, an idling stop vehicle. .

It is a schematic structure figure of an engine system provided with an engine starting device concerning an embodiment of the present invention. It is the schematic diagram which showed the structure of the intake system and exhaust system of an engine. It is a flowchart which shows control of the engine automatic stop at the time of idling. It is explanatory drawing which shows the change of (a) engine rotational speed, (b) crank angle, (c) throttle opening degree, (d) intake pipe negative pressure, and (e) each cylinder of engine stop operation period. It is a figure which shows the relationship between the TDC rotational speed in an engine stop operation period, and the stop position of the piston at the time of an engine stop. It is a flowchart which shows the process for detecting the piston position at the time of an engine stop. It is explanatory drawing which shows the crank angle signal output from two crank angle sensors, (a) is an engine normal rotation, (b) is a crank angle signal at the time of engine reverse rotation. It is a flowchart which shows the control of the first half in the case of restarting an engine from the engine stop state at the time of idling. It is a flowchart which shows the latter half control in the case of restarting an engine from the engine stop state at the time of idling. It is explanatory drawing which shows the stroke and combustion operation | movement of each cylinder at the time of engine restart. It is a time chart which shows the change of (a) engine speed at the time of engine restart, (b)-(f) cylinder pressure of each cylinder, and torque. It is a flowchart which shows the control of the first half in the case of restarting an engine in an engine stop operation period. It is a flowchart which shows the latter half control in the case of restarting an engine in an engine stop operation period. It is a time chart which shows (a) engine rotational speed and (b) crank angle in an engine stop operation period. It is explanatory drawing which shows the stroke and combustion operation | movement of each cylinder in the case of restarting an engine in an engine stop operation period.

Explanation of symbols

E Engine system 1 Engine 2 ECU
2a Engine stop means 2b Restart condition determination means 2c State immediately before stop detection means 2d State immediately before reversal detection means 2e Engine rotation direction determination means 2f Engine restart means 3 Crankshafts 12A to 12D Cylinder 13 Piston 14 Combustion chamber 15 Spark plug 16 Fuel Injection valve 21 Intake passage 22 Exhaust passage 23 Throttle valve 30 First crank angle sensor (crank angle position detecting means)
31 Second crank angle sensor (crank angle position detecting means)
32 Cam angle sensor 33 Water temperature sensor 34 Accelerator opening sensor

Claims (4)

An engine starter that starts an engine without using a starter motor by injecting fuel into at least an expansion stroke cylinder when the engine is stopped, and igniting and burning the engine.
Engine stop means for stopping the engine by stopping fuel injection to each cylinder of the engine during operation;
Restart condition determining means for determining that a predetermined restart condition of the engine is satisfied;
An immediately before stop state detecting means for detecting that the engine rotational speed is reduced after the fuel injection is stopped by the engine stopping means and the cylinder in the compression stroke is in a state immediately before stopping so as not to exceed the next top dead center;
Engine rotation direction determination means for determining the rotation direction of the engine when the engine rotation direction is reversed in the reverse rotation direction by the compression reaction force of the cylinder in the compression stroke and then the engine is stopped while further reversing. ,
When it is determined by the restart condition determining means that the restart condition is satisfied, if the engine is in the state immediately before the stop, fuel is injected into the cylinder in the expansion stroke at that time, and the engine rotation direction is determined. Engine restarting means for igniting and burning the expansion stroke cylinder if it is determined by the means that the rotational direction of the engine has been reversed from the normal rotation direction to the reverse rotation direction. Starter. In claim 1,
Crank angle position detecting means for detecting the crank angle position of the engine;
Immediately before the rotation direction of the engine is reversed in the reverse rotation direction when the crank angle position of the cylinder in the expansion stroke is not within a predetermined range near the top dead center when the restart condition determination means determines that the restart condition is satisfied. And a state immediately before inversion state detecting means for detecting the state of
When the restart condition is established, the engine restarting means detects that the immediately preceding inversion state is detected by the immediately preceding inversion state detecting means. An engine starter characterized in that the expansion stroke cylinder is ignited and burned until it is determined that the engine has been reversed. In any one of Claim 1 or 2,
The engine restarting means is characterized in that after the engine rotation direction determining means determines that the engine rotation direction has been reversed from the reverse rotation direction to the normal rotation direction, the engine is ignited and combusted. apparatus. In any one of Claims 1-3,
The engine restarting means injects fuel into the expansion stroke cylinder after the engine rotation direction determining means determines that the engine rotation direction has been reversed from the normal rotation direction to the reverse rotation direction. apparatus.

Images