JP3966204B2 - Engine starter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an engine starter that automatically stops an engine temporarily when idling or the like and then automatically restarts the engine thereafter.
[0002]
[Prior art]
  In recent years, fuel consumption reduction and CO₂In order to reduce emissions, etc., the engine is automatically stopped when idling, and then automatically restarted when a restart condition such as a start operation is established (hereinafter referred to as idle stop or I / S). Such engine starting devices have been developed.
[0003]
  Since restart at idle stop is required to start immediately according to the start operation etc., start that starts the engine through cranking that drives the engine output shaft by a starter (starting motor) Conventional general start-up methods that require considerable time to complete are not preferred.
[0004]
  Therefore, it is desirable to supply fuel to specific cylinders (cylinders in the expansion stroke) of the stopped engine to cause ignition and combustion so that the engine can be started immediately with that energy. However, even if fuel is supplied to a cylinder in the expansion stroke and ignited, combustion does not always occur, and even if combustion occurs, sufficient torque for starting the engine is not always obtained. In order to perform a smooth restart, an ignitability that exceeds a certain level and a magnitude of generated torque are required.
[0005]
  As a countermeasure against such a problem, for example, as disclosed in Patent Document 1, after the IG OFF (ignition stop), the exhaust valve closing timing is controlled to make it easy to stop the engine with the piston in the proper position. Alternatively, as disclosed in Patent Document 2, a braking device is provided for the crankshaft of the engine, and the braking device is controlled such that the piston of the cylinder that is in the expansion stroke when the engine is stopped stops at an appropriate position during the stroke. Something has been proposed.
[0006]
  The proper stopping position of the piston for restarting is generally around 90 ° CA (crank angle) after top dead center, that is, near the middle of top dead center and bottom dead center, and the piston is stopped at this position. If it does, favorable combustion will be obtained with the cylinder air which exists moderately, and the fuel supplied at the time of restart, and it will be easy to generate sufficient torque for restart. That is, Patent Document 1 and Patent Document 2 attempt to regulate the stop position of the piston so that a sufficient restart torque can be obtained by combustion.
[0007]
[Patent Document 1]
          WO 01/44636 A2 publication
[Patent Document 2]
          Japanese Utility Model Publication No. 60-128975
[0008]
[Problems to be solved by the invention]
  The starting device disclosed in Patent Document 1 is an indirect method that utilizes a change in the in-cylinder gas pressure by controlling the exhaust valve, and thus tends to vary. Therefore, in order to perform the restart smoothly, a technique for stopping the piston at an appropriate position with higher probability has been demanded. Further, according to the starting device disclosed in Patent Document 2, a device capable of braking the crankshaft is required in addition to the vehicle braking device, and the braking device is accurately controlled so that the piston stops at an appropriate position. It was very difficult to do.
[0009]
  In view of the above circumstances, the present invention reduces the variation in piston stop position without providing a separate special braking device or the like, and can start the engine at an appropriate position with a higher probability, that is, a simple engine start device. By improving the restartability of the engine with the structure, further reduction of fuel consumption and CO₂It is an object of the present invention to provide an engine starter capable of suppressing the emission amount.
[0010]
[Means for Solving the Problems]
  The present inventionIn idle state,Predetermined engine stop conditionsAt a predetermined time after the establishment of In terms ofThe fuel supply is automatically stopped to stop the engine, and when the restart condition is established after the engine is stopped, the fuel is injected into the cylinder in the expansion stroke to perform ignition and combustion, and the engine is restarted. In the engine starter,During the idling operation, the idling engine speed feedback control is performed so that the actual engine speed falls within the target engine speed range of a predetermined width, and the idling engine speed feedback control is continued even after the engine stop condition is satisfied. The fuel supply stop allowable rotational speed range is set in a narrower range within the target rotational speed range of the idle rotational speed feedback control, and the idle rotational speed feedback control is executed at the predetermined time point when the fuel supply is stopped. It is the time when it is determined that the engine speed is within the fuel supply stop allowable speed rangeIt is characterized by that.
[0011]
  The inventor of the present invention has intensively studied that there is a strong correlation between the engine speed when the fuel supply is stopped and the piston position when the engine is stopped, and that the engine speed is easy to stop the piston at an appropriate position. We found that the range is narrower than the target speed range in feedback control of idling speed that is generally done.
[0012]
  According to the configuration of the present invention, when a predetermined engine stop condition is satisfied, it is determined whether or not the engine speed is within a predetermined fuel supply stop allowable speed (hereinafter also referred to as fuel cut allowable speed) (hereinafter referred to as fuel). (Referred to as cut determination). This fuel cut allowable rotation speed range is a rotation speed range in which the piston is likely to stop at an appropriate position when the engine is stopped. The rotational speed range is set to a narrower range within the target rotational speed range in feedback control of the idle rotational speed that is generally performed. For example, the idle rotation speed is set to 650 ± 50 rpm, and the fuel cut allowable rotation speed is set to 650 ± 10 rpm.
[0013]
  If YES in the fuel cut determination, the fuel supply is stopped (fuel cut). If NO, the fuel cut is suspended and waits. Since the engine speed constantly fluctuates within the target engine speed range of the idle engine speed, it will soon enter the fuel cut allowable engine speed range. That is, since the determination result is YES, fuel cut is performed at that time.
[0014]
  In this way, the fuel cut is always performed when the engine speed is within the fuel cut allowable speed range. Therefore, the probability that the piston can be stopped at an appropriate position when the engine is stopped can be further increased, and the restartability can be improved.
[0015]
  In the present invention, fuel is injected at least before the determination (fuel cut determination) and after the determination.Against that fuelIn the cylinder that reaches the ignition timing, the ignition timing is set so that the torque due to combustion after ignition decreases.With respect to the ignition timing after the engine stop condition is satisfied and before the determinationYou may make it retard (delay).
[0016]
  In this way, the torque generated by the cylinder in which combustion is performed after the fuel cut is reduced by the retard of the ignition timing, so that the engine speed can be reduced more smoothly and the engine can be stopped. Since the injected fuel is burned and discharged, adverse effects on emissions can be prevented.
[0017]
  By the way, even after the fuel cut determination is YES and the fuel supply is stopped, the fuel supplied before the fuel cut determination needs to be burned to prevent the emission from deteriorating. This hinders a rapid and smooth decrease in the engine speed and causes variation in the stop position of the piston when the engine is stopped.
[0018]
  Therefore, another aspect of the present invention is that the fuel supply is automatically stopped at a predetermined time after the predetermined engine stop condition is satisfied to stop the engine, and the expansion stroke is performed when the restart condition is satisfied after the engine is stopped. Fuel is injected into a cylinder to ignite and burn, and engine In the engine starter that restarts the engine, the predetermined time point at which the fuel supply is stopped is a time point when it is determined that the engine speed is within a predetermined fuel supply stop allowable engine speed range. The injection timing is set to the intake stroke before the engine stop condition is satisfied, and is set to the compression stroke after the engine stop condition is satisfied and until the determination time.
[0019]
  In this way, the fuel injection timingFrom intake stroke to compression strokeBy retarding, the probability that fuel cut determination is made before fuel injection is increased. If a YES determination is made before fuel injection, the fuel injection can be stopped immediately and not burned after the fuel cut, so that the engine speed can be reduced more quickly and smoothly and brought to a stop. The piston can be easily stopped at an appropriate position when the engine is stopped.
[0020]
  Also in the present invention, at least in the cylinder where the fuel is injected before the determination and the ignition timing is reached after the determination, the ignition timing is set so that the torque due to the combustion after the ignition is reduced, after the engine stop condition is satisfied and the above If the retard is performed with respect to the ignition timing before the determination, the torque generated by the cylinder in which combustion is performed after the fuel cut is reduced by the retard of the ignition timing, so that the engine speed can be reduced more smoothly and the engine can be stopped. it can.
[0021]
  Furthermore, the engine speed detection timing for performing the above determination (fuel cut determination) is set after the stroke intermediate time of each cylinder outside the combustion period, and the fuel injection timing after retarding the fuel injection is: It may be set after the detection time of the engine speed.
[0022]
  In this way, the detection of the engine speed for performing the fuel cut determination is performed after the stroke intermediate period where the rotation fluctuation is relatively small, avoiding the combustion period (the first half of the stroke) where the rotation fluctuation is large. Therefore, the engine speed can be detected more accurately. Further, since the fuel injection is performed after this detection, the determination result based on the detection of the engine speed can be reflected in the presence or absence of the fuel injection immediately after. That is, it is possible to shorten the time between the determination of YES and the subsequent fuel cut, and the number of combustions after the fuel cut can be reduced as much as possible. Therefore, the engine speed can be reduced more smoothly and the engine can be stopped.
[0023]
  Further, when detecting the engine speed for performing the above determination, the engine speed fluctuation can be further reduced by cutting the external load (such as an air conditioner) so as to reduce the rotational fluctuation width. If the external load is cut in synchronism with the establishment of the engine stop condition (the control is started as soon as possible after the condition is established), the influence of the time lag (before the external load is cut) In the fuel cut determination) can be effectively prevented.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0025]
  1 and 2 show a schematic configuration of an engine according to an embodiment of the present invention. In these drawings, the main body of the engine 1 is composed of a cylinder head 2 a and a cylinder block 2. In this embodiment, the engine 1 is a four-cylinder four-cycle engine and includes four cylinders 3 (specifically, the first cylinder 3A, the second cylinder 3B, the third cylinder 3C, the fourth cylinder in order from the left in the state shown in FIG. 2). 3D). A piston 4 is inserted into each cylinder 3, and a combustion chamber 5 is formed above the piston 4. The piston 4 is connected to a crankshaft 6 via a connecting rod.
[0026]
  A spark plug 7 is provided at the top of the combustion chamber 5 of each cylinder 3, and the tip of the plug faces the combustion chamber 5.
[0027]
  Further, a fuel injection valve 8 that directly injects fuel into the combustion chamber 5 is provided at a side portion of the combustion chamber 5. The fuel injection valve 8 includes a needle valve and a solenoid (not shown). When a pulse signal is input, the fuel injection valve 8 is driven and opened for a time corresponding to the pulse width at the pulse input timing. It is comprised so that the quantity of fuel according to may be injected. The injection direction of the fuel injection valve 8 is set so as to inject fuel toward the vicinity of the spark plug 7. The fuel injection valve 8 is supplied with fuel via a fuel supply passage or the like by a fuel pump (not shown), and a fuel supply system so that a fuel pressure higher than the pressure in the combustion chamber during the compression stroke can be applied. Is configured.
[0028]
  An intake port 9 and an exhaust port 10 are opened to the combustion chamber 5 of each cylinder 3, and an intake valve 11 and an exhaust valve 12 are provided in these ports 9 and 10. The intake valve 11 and the exhaust valve 12 are driven by a valve operating mechanism including camshafts 26, 27 and the like. As described later in detail, the intake / exhaust valve opening / closing timing of each cylinder 3 is set so that each cylinder 3 performs a combustion cycle with a predetermined phase difference.
[0029]
  The opening / closing timing of the intake valve 11 and the exhaust valve 12 is variable by cam phase variable mechanisms 26a and 27a. The cam phase variable mechanisms 26a and 27a are conventionally known mechanisms that vary the rotational phase of the camshafts 26 and 27 with respect to the rotational phase of the crankshaft. 2, the camshaft 26 on the intake valve 11 side is provided with a cam phase variable mechanism 26a, and the camshaft 27 on the exhaust valve 12 side is provided with a cam phase variable mechanism 27a, which are controlled independently. ing. Therefore, the opening / closing timings of the intake valve 11 and the exhaust valve 12 can be varied back and forth generally independently by the cam phase variable mechanisms 26a and 27a.
[0030]
  An intake passage 15 and an exhaust passage 16 are connected to the intake port 9 and the exhaust port 10. The intake passage 15 has a branch intake passage 15a for each cylinder downstream of the surge tank 15b, and the downstream end of each branch intake passage 15a communicates with the intake port 9 of each cylinder, but the downstream of each branch intake passage 15a. In the vicinity of the end, there is disposed a throttle valve 17 composed of a multiple rotary valve that simultaneously throttles the branch intake passages 15a. The throttle valve 17 is driven by a throttle valve actuator 18.
[0031]
  An air flow sensor 20 for detecting the intake air amount is provided in the common intake passage 15c upstream of the surge tank 15b in the intake passage 15. The crankshaft 6 is provided with a crank angle sensor that detects its rotation angle. In this embodiment, as will be described in detail later, crank angle signals that are out of phase with each other by a certain amount are output. Two crank angle sensors 21 and 22 are provided. Further, a cam angle sensor 23 is provided that can give a cylinder identification signal to the camshafts 26 and 27 by detecting their specific rotational positions. Further, a starter 28 that is a motor for starting the engine 1 is provided, and the driving force of the starter 28 is directly transmitted to the crankshaft 6 through a starter gear (not shown), whereby the engine 1 is started. It is configured as follows.
[0032]
  In addition, as other detection elements necessary for controlling the engine 1, a water temperature sensor 24 for detecting the temperature of the engine cooling water, and an accelerator opening sensor 25 for detecting the accelerator opening (accelerator operation amount) (see FIG. 3). Etc. are equipped.
[0033]
  FIG. 3 is a control block diagram of the engine 1, and shows a switch and a sensor for inputting a signal, a device and an actuator for outputting, etc., with an ECU (engine control unit) 30 as a center. Since this block diagram relates to idle stop control, other control-related parts are omitted.
[0034]
  On the input side of the ECU 30, in addition to the air flow sensor 20, the crank angle sensors 21 and 22, the cam angle sensor 23, the water temperature sensor 24 and the accelerator opening sensor 25, sensors for performing I / S (idle stop) are provided. , A brake sensor 62 for detecting a brake depression depth, a vehicle speed sensor 63 for detecting a vehicle speed, an inhibitor switch 64 for detecting a shift lever position of an AT (automatic transmission), and a parking brake switch for detecting ON / OFF of a parking brake. 65, a turn signal switch 66 for detecting ON / OFF of the turn signal, an air conditioner switch 67 for detecting ON / OFF of an air conditioner, and a brake negative pressure sensor 68 for detecting brake negative pressure are connected, and each detection signal is inputted.
[0035]
  On the output side of the ECU 30, in addition to the spark plug 7, the fuel injection valve 8, the throttle valve actuator 18, the cam phase variable mechanisms 26a and 27a, and the starter 28, an idle stop display lamp 71, an electric oil pump 72, an ATF switching valve. 73 and a hill holder solenoid valve 74 are connected to output drive signals to the devices.
[0036]
  The idle stop display lamp 71 is a lamp for indicating to the driver the implementation status of the I / S. As will be described in detail later, the engine is stopped by the I / S or the I / S is prohibited. This is a general term for lamps that indicate that the engine is restarted.
[0037]
  The electric oil pump 72 is an electric oil pump that supplies hydraulic pressure to the AT while the engine is stopped by I / S. During normal operation, the clutch inside the AT operates with a mechanical oil pump (not shown) driven directly connected to the crankshaft 6 as a hydraulic pressure supply source. Therefore, when the engine is stopped by I / S, the hydraulic pressure is reduced and the clutch is released. This causes a time loss for re-engaging the clutch after restarting the engine, and the startability deteriorates. In order to prevent this, hydraulic pressure is separately supplied to the AT by the electric oil pump 72 while the engine is stopped.
[0038]
  The ATF switching valve 73 is a switching valve that switches a passage of ATF (automatic transmission fluid) from the hydraulic supply source to the AT. During normal operation, the ATF is guided from the mechanical oil pump to the AT, and is switched from the electric oil pump 72 while the engine is stopped by I / S.
[0039]
  The hill holder solenoid valve 74 is a solenoid valve for driving an unillustrated hill holder that blocks the brake oil supply passage. During normal operation, a booster linked to the engine operates to increase the brake hydraulic pressure. However, since the booster does not operate while the engine is stopped, the brake hydraulic pressure decreases and the braking force decreases. Therefore, for example, when idle stop is performed on a slope, the vehicle may move due to insufficient braking force. In order to prevent this, the hill holder is configured to maintain the brake hydraulic pressure in a high state by blocking the brake oil supply passage by the hill holder solenoid valve 74.
[0040]
  The ECU 30 includes a throttle valve control means 31, a fuel injection valve control means 32, an ignition control means 33, an idle stop control means 34, a cam phase control means 35, a display control means 36, an AT control means 37, and a hill holder control means 38. Including.
[0041]
  The throttle valve control means 31 calculates the required opening of the throttle valve 17 from the engine opening speed based on the accelerator opening information from the accelerator opening sensor 25 and the crank angular speed information from the crank angle sensors 21 and 22. The throttle valve actuator 18 is controlled.
[0042]
  The fuel injection valve control means 32 and the ignition control means 33 determine the required fuel injection amount based on the intake air amount information from the air flow sensor 20 and the cooling water temperature information from the water temperature sensor 24 in addition to the accelerator opening information and engine speed information. And the injection timing and appropriate ignition timing are calculated and a control signal is output to the fuel injection valve 8 and the spark plug 7.
[0043]
  Feedback control is performed by the throttle valve control means 31 and the fuel injection valve control means 32 so that the engine speed becomes a predetermined target speed during idling (for example, 650 ± 50 rpm when warm) (bypassing the throttle valve 17). An ISC (idle speed control) valve that forms an intake path may be provided to control the idling speed).
[0044]
  Further, the throttle valve control means 31, the fuel injection valve control means 32, and the ignition control means 33 are controlled by an idle stop control means 34 described below in addition to the above control when I / S is performed.
[0045]
  The idle stop control unit 34 determines an execution condition of the I / S and provides information necessary for executing the I / S to each unit in the ECU 30.
[0046]
  I / S execution conditions are classified into basic stop conditions, basic restart conditions, and I / S prohibition conditions. Each condition may be set as appropriate. For example, the brake depression depth obtained from the brake sensor 62 is not less than a predetermined value, the vehicle speed obtained from the vehicle speed sensor 63 is zero, and the AT shift lever position obtained from the inhibitor switch 64 Is the non-traveling range, the parking brake switch 65 signal is ON, the blinker switch 66 signal is OFF, and the air conditioner switch 67 is OFF, the basic stop condition is established.
[0047]
  Further, for example, the brake depression depth is a predetermined value or less, the vehicle speed is a predetermined value or more, the shift lever position of the AT is the travel range, the signal of the turn signal switch 66 is ON, the air conditioner switch 67 is ON, or the brake negative pressure The basic restart condition is established when the brake negative pressure obtained from the sensor 68 (negative pressure in the booster constituting the booster that supplements the braking force) is a predetermined value or less.
[0048]
  For example, when the engine coolant temperature Tc is not more than a predetermined value (for example, Tc <60 ° C.), the monitor voltage of the battery is not more than a predetermined value, or the elapsed time since the previous restart is not more than a predetermined value, I / S prohibition The condition is met.
[0049]
  When the basic stop condition is satisfied and the I / S prohibition condition is not satisfied, the engine stop condition is finally satisfied (in this specification, this is referred to as the satisfaction of the engine stop condition). The engine is automatically stopped. That is, the fuel injection from the fuel injection valve 8 is stopped and the ignition of the spark plug 7 is stopped.
[0050]
  As control when the engine is stopped, a cylinder that is in the compression stroke when the engine is stopped (for convenience of explanation, this cylinder is assumed to be the third cylinder 3C, and hereinafter referred to as the compression stroke cylinder 3C) and a cylinder that is in the expansion stroke. (In the same way, assuming that the cylinder is the first cylinder 3A, hereinafter referred to as the expansion stroke cylinder 3A), in order to increase the resistance to the movement in the piston top dead center direction, at least the intake amount for these cylinders is increased, and in particular the expansion stroke In order to supply more intake air to the cylinder 3A, the throttle valve 17 is opened for a predetermined period during the engine stop operation period. Other injection timing retards, ignition timing retards, etc., will be described later.
[0051]
  After the engine 1 is automatically stopped in this way, when the basic restart condition or the I / S prohibition condition is satisfied, the restart condition is finally satisfied (in this specification, this is called the satisfaction of the restart condition), A restart is made. That is, the fuel injection from the fuel injection valve 8 and the ignition of the spark plug 7 are returned.
[0052]
  As the control at the time of restarting, first, the first combustion is performed on the compression stroke cylinder 3C and the engine is slightly reversed to increase the in-cylinder pressure by raising the piston of the expansion stroke cylinder 3A. Combustion is performed in the expansion stroke cylinder 3A.
[0053]
  In the present embodiment, as described above, the initial combustion in the compression stroke cylinder 3C and the combustion in the expansion stroke cylinder 3A are performed, and the combustion air remains in the cylinder of the compression stroke cylinder 3C after the initial combustion to perform compression. The first restart control mode in which re-combustion is performed when the piston 4 of the stroke cylinder 3C starts to rise and the vicinity of the top dead center is reached, and the initial combustion in the compression stroke cylinder 3C and the combustion in the expansion stroke cylinder 3A And the second restart control mode in which recombustion in the compression stroke cylinder 3C is not performed, and combustion in the expansion stroke cylinder 3A while assisting with the starter 28 without performing initial combustion in the compression stroke cylinder 3C and The third restart control mode in which the engine is started by combustion in the next compression stroke cylinder 3C is selectively executed according to the stop position of the piston 4.
[0054]
  The cam phase control means 35 outputs the phase fluctuation signals of the cam shafts 26 and 27 with respect to the crankshaft 6 to the cam phase variable mechanisms 26a and 27a, and controls the opening / closing timings of the intake valve 11 and the exhaust valve 12. During normal operation, an optimal intake / exhaust valve opening / closing timing is set according to the engine speed, and control for obtaining a high output over a wide rotation range is performed. In addition, as will be described later, during engine stop control for idling stop, control is performed to delay the closing timing of the intake valve 11 in order to suppress fluctuations in output torque.
[0055]
  The display control means 36 performs ON / OFF control of the idle stop display lamp 71 according to the execution status of the I / S. The idle stop display lamp 71 is composed of an automatic stop lamp, an idle stop prohibition lamp, and a restart lamp that are not shown. During the automatic stop of the engine due to I / S, the automatic stop lamp is turned on. When the I / S prohibition condition is satisfied, the idle stop prohibited lamp is turned on. When the engine is restarted, the restart lamp is turned on. In this way, the driver can recognize the idle stop control status.
[0056]
  The AT control means 37 outputs a switching command signal to the ATF switching valve 73 when the pressure of the hydraulic oil supplied to the automatic transmission decreases due to execution of the idle stop, and supplies the hydraulic oil supply path. Is switched from the mechanical oil pump side (not shown) driven by the engine 1 to the electric oil pump 72 side, and an operation command signal for operating the electric oil pump 72 is output from the electric oil pump 72 to the automatic transmission. The hydraulic fluid is configured to supply a predetermined pressure.
[0057]
  The hill holder control means 38 controls the hill holder by the hill holder solenoid valve 74 while the engine is stopped by the I / S.
[0058]
  Next, the operation of the apparatus of the present embodiment as described above will be described.
[0059]
  In the engine 1 which is a four-cylinder four-cycle engine, each cylinder 3 performs a cycle composed of intake, compression, expansion, and exhaust strokes with a predetermined phase difference. As shown in FIG. However, the first cylinder 3A, the third cylinder 3C, the fourth cylinder 3D, and the second cylinder 3B are sequentially performed with a phase difference of 180 ° (180 ° CA) in crank angle.
[0060]
  When a predetermined idling state that does not require the output of the engine 1 is achieved while the engine 1 is in operation, an idle stop is executed based on whether or not the engine stop condition is met.
[0061]
  When the engine stop condition is satisfied at time t1, a series of control for engine stop by idle stop is performed. In order to stop the engine, fuel supply is first stopped (fuel cut). When performing fuel cut, a fuel cut allowable rotation speed (fuel supply stop allowable rotation speed) area is provided, and the fuel cut is performed when the engine rotation speed is within the fuel cut allowable rotation speed area. ing.
[0062]
  FIG. 5 is an enlarged view of the engine speed shown in FIG. 4 from the engine stop condition satisfaction time point t1 to the fuel cut time point t2. The target rotational speed range 81 of the idle rotational speed that is feedback-controlled is set to 650 ± 50 rpm, while the fuel cut allowable rotational speed range 83 is set to 650 ± 10 rpm. That is, when the engine is idling, the engine speed fluctuates in the range of 650 ± 50 rpm, and the fuel cut is performed aiming at the moment of entering the range of 650 ± 10 rpm. As shown in FIG. 5, when the engine speed is not within the fuel cut allowable speed range 83 at the time t1 when the engine stop condition is satisfied, the fuel cut is suspended and waits. Then, fuel cut is performed at time t2 when the fuel cut allowable rotation speed region 83 is entered.
[0063]
  This is done to stop the piston 4 within a preferable range for restarting (range A in FIG. 6). When the fuel is cut in the fuel cut allowable rotation speed region 83, the piston 4 is in the preferable range. It has been confirmed that there is a high probability of stopping within. If the engine speed when the engine stop condition is satisfied is within the fuel cut allowable speed range 83, the fuel is cut immediately.
[0064]
  The description will be continued with reference to FIG. After the engine stop condition satisfaction time t1, the fuel injection timing is retarded (delayed). The injection 101 of the first cylinder 3A, the injection 105 of the fourth cylinder 3D, and the injection 111 of the second cylinder 3B (all indicated by white circles) are virtual fuel injection timings when the fuel injection timing is not retarded. Indicates. As shown, these injections are made during the intake stroke.
[0065]
  On the other hand, the injection 107 of the fourth cylinder 3D and the injection 113 of the second cylinder 3B (both indicated by black circles) indicate the fuel injection timing of the present embodiment in which the fuel injection timing is retarded. The injection 107 corresponds to the injection 105, and the injection 113 corresponds to the injection 111. As shown, these injections are made late in the compression stroke.
[0066]
  By the way, the injection timing of this embodiment corresponding to the virtual injection 101 of the first cylinder 3A is not shown. This is because the fuel injection time t2 comes immediately after the virtual injection 101 and before the retarded injection timing, so that the injection is stopped. If the fuel is actually injected at the time of the virtual injection 101, the fuel needs to be burned in the next expansion stroke (after the fuel cut) (discharging without burning will adversely affect the emission). This hinders a rapid and smooth decrease in the engine speed and causes variations in the stop position of the piston 4 when the engine is stopped. However, in this embodiment, by retarding the fuel injection timing, fuel injection corresponding to the virtual injection 101 is not performed, and the number of times of combustion after the fuel cut is reduced correspondingly.
[0067]
  By retarding the fuel injection timing in this way, the probability that the fuel cut time t2 will be before fuel injection is increased, the engine speed is decreased quickly and smoothly, and the piston 4 is stopped when the engine is stopped. It is easy to stop at the proper position.
[0068]
  In addition, after the engine stop condition is satisfied, the ignition timing is retarded in advance to reduce the generated torque in preparation for the engine stop. In this embodiment, this retard is applied to the ignition 103 of the third cylinder 3C and the ignition 109 of the fourth cylinder 3D. The retard at this time is a relatively small retard amount that does not excessively reduce the engine speed. In addition to the retard of the ignition timing, the closing timing of the intake valve 11 may be delayed or the air-fuel ratio may be increased (to the lean side) by the cam phase variable mechanism 26a. Then, the throttle valve 17 is opened by a predetermined amount as shown so that the engine speed does not decrease more than necessary.
[0069]
  When the engine speed enters the fuel cut allowable speed range 83 (see FIG. 5), the fuel is cut. The detection time of the engine speed for performing the determination (hereinafter referred to as fuel cut determination) is outside the combustion period. It is set after the stroke intermediate time of each cylinder 3. That is, the engine speed is detected after the stroke intermediate period with a relatively small rotation fluctuation, avoiding the combustion period (the first half of the stroke) where the rotation fluctuation is large. This more accurately detects the engine speed and improves the accuracy of fuel cut determination.
[0070]
  The detection time is set before the fuel injection time after retarding. Then, the fuel cut determination result based on the detection of the engine speed is reflected in the presence or absence of fuel injection immediately after. Therefore, the time from when the fuel cut determination is YES until the subsequent fuel cut is shortened. That is, the number of combustions after the fuel cut is reduced as much as possible.
[0071]
  Further, after the engine stop condition is satisfied, the rotational fluctuation range is reduced by cutting off an external load such as an air conditioner. Thereby, the detection accuracy of the engine speed for performing the fuel cut determination is further improved.
[0072]
  In the example shown in FIG. 4, the engine speed is detected with high accuracy as described above, and the fuel cut determination result is YES when the engine speed is N2 (time point t2). Therefore, the fuel supply after the fuel cut time t2 is stopped. The ignition timing is retarded in the cylinders in which combustion is performed after the fuel cut time t2. In the present embodiment, the second cylinder 3B corresponds to this. In the second cylinder 3B, the virtual fuel injection 111 is retarded, and the fuel injection 113 is performed in the latter half of the compression stroke. However, since it is slightly earlier than the fuel cut time t2, the combustion is performed after the fuel cut. The ignition 115 for the combustion is retarded relatively large so that the generation of torque due to the combustion becomes sufficiently small. In this way, the injected fuel is burned to prevent an adverse effect on the emission, and the engine speed is smoothly reduced to bring the engine to a stop.
[0073]
  Then, the fuel is cut at the fuel cut time t2, the throttle valve 17 is opened to a predetermined opening, and then the time t3 when the engine speed is reduced to a predetermined speed N3 (N3 = 500 rpm in the present embodiment) set in advance. Thus, the throttle valve 17 is controlled to be closed. Thereby, the probability that the engine stop position is within a preferable range is increased by using the pressure of air in the cylinder 3.
[0074]
  That is, during the period from the time point t2 to the time point t3, the throttle valve 17 is opened to a predetermined opening, so that the intake negative pressure temporarily decreases (intake amount increases) with some time delay, and then the intake pressure negative Although the pressure increases (intake amount decreases), the predetermined rotation speed and the like are set in advance so that the period in which the intake negative pressure temporarily decreases substantially corresponds to the period of the intake stroke of the expansion stroke cylinder 3A. . Thereby, compared with the case where the throttle valve 17 is not opened, the amount of air sucked into each cylinder 3 before the engine is stopped increases, and among them, the amount of intake air that flows into the expansion stroke cylinder 3A in particular increases.
[0075]
  When the engine is stopped, in the compression stroke cylinder 3C, as the piston 4 approaches top dead center, the air in the cylinder 3C is compressed and pressure is applied in a direction to push the piston 4 back, thereby causing the engine 1 to reverse. When the piston 4 of the compression stroke cylinder 3C is pushed back to the bottom dead center side, the piston 4 of the expansion stroke cylinder 3A moves to the top dead center side, and accordingly, the air in the cylinder 3A is compressed, The piston 4 of the expansion stroke cylinder 3A is pushed back toward the bottom dead center. In this way, the piston 4 is stopped after being vibrated to some extent. At this time, in the compression stroke and the expansion stroke, the force to push the piston 4 closer to the top dead center is larger, so the stop position of the piston 4 is the middle of the stroke. In many cases, the position is close to the portion (range A in FIG. 6).
[0076]
  Since the intake air amount is increased before the engine is stopped as described above, the force to push back the piston 4 when approaching the top dead center is increased, so that the probability that the piston 4 stops within the range A is increased. Further, if the intake amount of the expansion stroke cylinder 3A is made larger than that of the compression stroke cylinder 3C by the control of the throttle valve 17 as described above, the piston 4 in the expansion stroke cylinder 3A is within the range close to the stroke intermediate portion. However, it often stops near the bottom dead center (range A2 in FIG. 6).
[0077]
  Then, as described above, the engine speed N2 at the fuel cut time t2 is within the fuel cut allowable speed range 83, and the generated torque after the fuel cut is suppressed, so that the piston 4 can be generated with higher probability. Is easily stopped in the range A2.
[0078]
  In addition, since the engine 1 is rotated several times by inertia from the fuel cut until the engine 1 is completely stopped, the burned gas is discharged, and the inside of the cylinder becomes almost fresh even in the expansion stroke. Further, when the engine 1 is stopped, the pressure leaks immediately even in the compression stroke cylinder 3C. Therefore, after the engine is stopped, all cylinders are in a state where fresh air at substantially atmospheric pressure exists in the cylinder.
[0079]
  The throttle valve 17 may not be closed until the engine is stopped. However, since the intake amount continues to be large until the engine is stopped, the push-down force of the piston 4 due to the compression of the intake is difficult to attenuate. In some cases, the number of vibrations increases and the swing back increases when the engine stops. Therefore, it is desirable to close the throttle valve 17 at a suitable time t3 as shown in the present embodiment.
[0080]
  The stop position of the piston 4 is detected by signals from the crank angle sensors 21 and 22 as follows. FIG. 7 is a pulse signal obtained by rotating the crankshaft 6, and shows a first crank angle signal CA 1 from the crank angle sensor 21 and a second crank angle signal CA 2 from the crank angle sensor 22. FIG. 7A shows the case of normal rotation (clockwise in the state of FIG. 1), and FIG. 7B shows the case of reverse rotation. At the time of forward rotation of the engine, as shown in FIG. 7A, the second crank angle signal CA2 is generated with a phase delay of about a half pulse width with respect to the first crank angle signal CA1, so that the first crank angle signal CA1 The second crank angle signal CA2 is Low when rising, and the second crank angle signal CA2 is High when the first crank angle signal CA1 is falling. On the other hand, during reverse rotation of the engine, as shown in FIG. 7B, the second crank angle signal CA2 is generated with a phase advance of about a half pulse width with respect to the first crank angle signal CA1, so On the contrary, the second crank angle signal CA2 becomes High when the first crank angle signal CA1 rises, and the second crank angle signal CA2 becomes Low when the first crank angle signal CA1 falls. The ECU 30 detects this difference and counts the pulse signal while determining whether the crankshaft 6 is rotating forward or rotating backward. The counted value is stored as a CA counter value and is constantly updated while the engine 1 is operating. The state in which the increase or decrease in the CA counter value is lost is the stop of the engine 1, and the stop position of the piston 4 is detected based on the CA counter value at that time.
[0081]
  FIG. 8 is an accumulation flowchart of CA counter values. After the start, in step S51, the second crank angle signal CA2 is Low when the first crank angle signal CA1 rises, or the second crank angle signal CA2 becomes High when the first crank angle signal CA1 falls. If it is YES, it indicates that the engine 1 is rotating forward, so that the process proceeds to step S52 and the measured pulse number is added to the CA counter value (CA counter up). If “NO” in the step S51, it indicates that the engine 1 is reversely rotated, so that the process proceeds to the step S53 and the number of pulses measured is subtracted from the CA counter value (CA counter down).
[0082]
  FIG. 9 shows a schematic control flowchart of the ECU 30 until the engine stops in the idle stop. After the start, signals from various sensors (see FIG. 3) are read (step S1). Next, based on the signal, it is determined whether or not the engine stop condition is satisfied (step S2). If NO, the process returns. If YES, a series of control for automatic engine stop is subsequently performed. . First, an external load such as an air conditioner is cut (step S3), and the fuel injection timing is retarded (step S4). In the next step S5, the ignition timing is retarded (relatively small) in order to suppress fluctuations in the output torque (the closing timing of the intake valve 11 may be delayed or the air-fuel ratio may be set to the lean side). At the same time, the opening of the throttle valve 17 is slightly increased so that the idling speed can be maintained. Steps S3, S4 and S5 are executed (as soon as possible) in synchronization with the YES determination in step S2.
[0083]
  Subsequently, fuel cut determination is performed in step S6. That is, it is determined whether or not the engine speed is within the fuel cut allowable speed range 83 (650 ± 10 rpm). If “NO” in the step S6, the process waits until “YES”. When YES is determined in step S6, the engine speed is such that the piston 4 is easily stopped at a position suitable for restart, and the fuel supply from the fuel injection valve 8 is stopped (fuel cut) (step S7). . Further, the ignition timing is retarded (relatively large), and the fuel injected before the fuel cut is burned (step S8). Thereafter, ignition is stopped in step S9.
[0084]
  In the subsequent step S11, the throttle valve 17 is opened to reduce the intake negative pressure. Thereafter, the throttle valve 17 is closed when the engine speed becomes lower than 500 rpm (steps S13 and S15). Next, the CA counter value (see FIG. 8) during constant counting is read (step S16). In the next step S17, it is determined whether or not the engine 1 has completely stopped from the degree of change of the CA counter value. If YES, the stop position of the piston 4 determined from the CA counter value is stored (step S19). And return.
[0085]
  Next, engine restart will be described. When the basic restart condition or the I / S prohibition condition is satisfied after the engine is stopped, it is determined that the restart condition is satisfied, and control for automatically restarting the engine 1 is performed. At this time, if the stop position of the piston 4 is within a predetermined range near the middle of the stroke in the expansion stroke cylinder 3A and within the range A1 (FIG. 6) near the top dead center, the first restart control mode is executed. Is done.
[0086]
  FIG. 10 shows the stroke of each cylinder of the engine in the case of the first restart control mode and the combustion in each cylinder from the starting control start time (in accordance with the order of combustion in the figure).Circles "1", "2", "3" ...And the operation direction of the engine by each combustion is indicated by an arrow, and FIG. 11 shows the engine rotation speed, crank angle, and cylinder of the square cylinder in the case of the first restart control mode. The time change of the internal pressure and the indicated torque is shown.
[0087]
  As shown in these figures, in the case of the first restart control mode, first combustion is performed in the compression stroke cylinder 3C while the combustion air-fuel ratio is leaner than the stoichiometric air-fuel ratio (in FIG. 9)."1") Is performed, and the piston 4 of the compression stroke cylinder is pushed down to the bottom dead center side by the combustion pressure by the initial combustion (a portion in FIG. 11), and the engine 1 is driven in the reverse rotation direction. When the 3A piston 4 approaches top dead center, the air in the cylinder 3A is compressed and the in-cylinder pressure rises (portion b in FIG. 11). When the piston 4 of the expansion stroke cylinder 3A is sufficiently close to top dead center, the cylinder 3A is ignited, and the fuel previously injected into the cylinder 3A is combusted (in FIG. 10).“2”), The engine 1 is driven in the forward rotation direction by the combustion pressure (c portion in FIG. 11). Further, by injecting fuel into the compression stroke cylinder 3C at an appropriate timing, the second combustion in the cylinder 3C is performed near the top dead center of the compression stroke cylinder 3C (in FIG. 10).“3”). The engine driving force is increased by the combustion pressure (d portion in FIG. 11).
[0088]
  In this case, in the initial combustion of the compression stroke cylinder 3C, since the air-fuel ratio is lean, air remains in the cylinder 3C even after the initial combustion, so that the second combustion is possible. Since the fuel is injected and the compression is performed while the temperature in the compression stroke cylinder 3C is high due to the initial combustion, the second combustion in the cylinder 3C is performed by compression self-ignition.
[0089]
  After the second combustion is performed in this way, after reaching the compression top dead center of the cylinder (fourth cylinder 3D) that reaches the compression stroke next to the cylinder 3C, each cylinder is sequentially controlled by normal control. Combustion is performed and restart is completed.
[0090]
  At the time of restart when the stop position of the piston 4 is within a predetermined range near the middle of the stroke in the expansion stroke cylinder 3A and within the range A2 near the bottom dead center (see FIG. 6), the second restart control mode is used. Control is performed.
[0091]
  As the control in the second restart control mode, first, in the compression stroke cylinder 3C, the initial combustion (in FIG. 10) while the combustion air-fuel ratio is substantially stoichiometric or richer than that."1"(Combustion equivalent to) is performed. Then, the piston 4 of the compression stroke cylinder 3C is pushed down by the initial combustion and the engine 1 is driven in the reverse direction, and as a result, the piston 4 of the expansion stroke cylinder 3A approaches the top dead center, so that the air in the cylinder 3A is compressed. Thus, when the in-cylinder pressure rises and the piston of the expansion stroke cylinder 3A is sufficiently close to the top dead center, the cylinder 3A is ignited and the fuel previously injected into the cylinder 3A is combusted ( In FIG.“2”Is equivalent to the control in the first restart control mode. However, in the second restart control mode, after the combustion of the expansion stroke cylinder 3A, combustion occurs when the compression stroke cylinder 3C passes the top dead center (in FIG. 10).“3”Combustion is not performed, and the rotation of the engine is maintained at the inertia until the compression top dead center of the cylinder (fourth cylinder 3D) that reaches the next compression stroke is reached, and then the normal control is shifted to complete the restart. .
[0092]
  As described above, the first restart control mode and the second restart control mode are selectively used depending on the stop position of the piston 4, whereby the engine 1 is effectively restarted. This point will be described with reference to FIG.
[0093]
  FIG. 12 shows the relationship between the piston position when the engine is stopped and the required air-fuel ratio in the first combustion (for reverse rotation) of the compression stroke cylinder 3C, the air amount of the compression stroke cylinder 3C, the air amount of the expansion stroke cylinder 3A, and the generation frequency. As shown in this figure, when the engine is stopped, the piston 4 of the expansion stroke cylinder 3A approaches the top dead center (the piston 4 of the compression stroke cylinder 3C approaches the bottom dead center). As the air amount in the stroke cylinder 3C increases, the air amount in the expansion stroke cylinder 3A increases as the piston 4 in the expansion stroke cylinder 3A approaches the bottom dead center (the piston 4 in the compression stroke cylinder 3C approaches the top dead center). The amount of air in the compression stroke cylinder 3C is reduced.
[0094]
  In the initial combustion in the compression stroke cylinder 3C, the engine is reversely rotated to a predetermined position where the piston 4 of the compression stroke cylinder 3C is slightly before the bottom dead center (the piston 4 of the expansion stroke cylinder 3A is slightly before the top dead center). However, if the piston 4 of the compression stroke cylinder 3C is close to the top dead center, the amount of air in the compression stroke cylinder 3C is small and the reverse rotation to the predetermined position is performed. Since the required torque is relatively large, the required air-fuel ratio becomes rich. On the other hand, if the piston 4 of the compression stroke cylinder 3C is close to the bottom dead center, the amount of air in the compression stroke cylinder 3C is large, and the predetermined position Since the torque required for reverse rotation up to is relatively small, the required air-fuel ratio becomes lean.
[0095]
  In the expansion stroke cylinder 3A, since the amount of air increases as the piston 4 is closer to the bottom dead center, more fuel can be burned.
[0096]
  Accordingly, when the piston position of the expansion stroke cylinder 3A is within a predetermined range A2 near the bottom dead center from the middle portion (the piston position of the compression stroke cylinder 3C is near the top dead center) when the engine is stopped, the compression stroke cylinder 3C is in the initial combustion. The air-fuel ratio of the engine is made rich so as to meet the above requirements, and no combustion air remains after the first combustion, so the second combustion near the compression top dead center is not performed. A relatively large amount of fuel is injected, and after being compressed and then ignited and combusted, a relatively large torque is obtained, and further after the compression top dead center of the compression stroke cylinder 3C. The engine can be rotated until the compression top dead center of the next cylinder is exceeded, and restart can be achieved.
[0097]
  On the other hand, when the engine is stopped, the piston position of the expansion stroke cylinder 3A is in the predetermined range A1 closer to the top dead center than the intermediate portion (the piston position of the compression stroke cylinder 3C is closer to the bottom dead center), compared to the case where the piston is in the range A2. Since the amount of air in the expansion stroke cylinder 3A is small, the torque obtained by the combustion in the expansion stroke is small. However, in the compression stroke cylinder 3C, the air-fuel ratio at the time of the first combustion is made lean corresponding to the above requirement, thereby Since the surplus air remaining after the first combustion is used and the second combustion near the compression top dead center is performed, the torque for driving in the engine forward direction is supplemented, and the combustion in the expansion stroke cylinder 3A Torque sufficient to achieve restart is obtained by both of the second combustion in the compression stroke cylinder 3C.
[0098]
  By the way, in the present embodiment, when the engine is stopped as described above, the throttle valve 17 is kept in a predetermined open state for a predetermined period after the fuel supply is stopped, and the intake air amount is increased to increase the compression stroke cylinder 3C and the expansion stroke cylinder 3A. In FIG. 12, since the resistance to movement in the direction of the top dead center of the piston 4 is increased and the intake air amount of the expansion stroke cylinder 3A is increased, as shown in FIG. In most cases, the piston position at 3A is within a predetermined range A near the middle of the stroke, and within that range, it is often within the range A2 that is slightly closer to the bottom dead center. Effective restart is performed.
[0099]
  That is, when the piston stop position is too close to the top dead center side of the expansion stroke cylinder 3A (the bottom dead center side of the compression stroke cylinder 3C) with respect to the range A, a sufficient amount of movement in the engine reverse rotation direction is taken. Since the amount of air in the expansion stroke cylinder 3A is reduced, the torque obtained by the combustion in the expansion stroke cylinder 3A is reduced, and the bottom dead center side of the expansion stroke cylinder 3A (the compression stroke cylinder) If it is too close to 3C (top dead center side), the amount of air in the compression stroke cylinder 3C decreases, so that sufficient torque for engine reverse rotation cannot be obtained. On the other hand, if the piston stop position is within the above range A, the reverse rotation drive by the initial combustion in the compression stroke cylinder 3C is possible, and the combustion in the expansion stroke cylinder 3A is favorably performed and the combustion energy is reduced. In particular, if the piston stop position is in the range A2 near the bottom dead center of the expansion stroke cylinder 3A, a sufficiently large amount of air can be secured in the expansion stroke cylinder 3A. Combustion energy can be increased and startability can be improved.
[0100]
  In the rare case where the piston position when the engine is stopped is out of the above range A, or when the in-cylinder temperature decreases while the engine is stopped and the cooling water temperature Tc becomes Tc <60 ° C., the third restart The start control mode is executed and the starter 28 assists the start.
[0101]
  The specific configuration of the apparatus of the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims. For example, specific values of the target engine speed range 81 and the fuel cut allowable engine speed range 83 for the idle speed may be set as appropriate according to the engine characteristics. Further, when idling up (control for increasing the target engine speed range 81 of the idling engine speed when the engine temperature is relatively low) is performed, the fuel cut allowable engine speed area 83 is also changed accordingly. May be.
[0102]
  Only one of the fuel injection retard and the ignition timing retard after the fuel cut may be performed. However, by implementing both, it becomes easy to stop the piston 4 in an appropriate range (range A in FIG. 6, preferably range A2) with higher probability.
[0103]
  Since the external load may be cut at the fuel cut time t2, it is not always necessary to synchronize with the engine stop condition satisfaction time t1. However, by performing in synchronization with the engine stop condition establishment time t1, it is possible to effectively prevent the influence of the time lag (YES in the fuel cut determination before cutting of the external load) while performing relatively simple control. Can do.
[0104]
  In the above embodiment, when starting the engine when the piston position when the engine is stopped is within a predetermined range, the combustion is performed in the expansion stroke cylinder 3A after the initial combustion is performed in the compression stroke cylinder 3C and the engine is slightly reversed. However, the engine is not reversed due to the initial combustion in the compression stroke cylinder 3C, but the fuel is suddenly supplied to the expansion stroke cylinder 3A in the engine stopped state, and ignited after a predetermined time, thereby expanding the expansion stroke cylinder 3A. You may make it carry out combustion by first.
[0105]
【The invention's effect】
  As described above, according to the engine starting device of the present invention,In idle state,Predetermined engine stop conditionsAt a predetermined time after the establishment ofThe fuel supply is automatically stopped to stop the engine, and when the restart condition is established after the engine is stopped, the fuel is injected into the cylinder in the expansion stroke to perform ignition and combustion, and the engine is restarted. In the engine starter,During the idling operation, the idling engine speed feedback control is performed so that the actual engine speed falls within the target engine speed range of a predetermined width, and the idling engine speed feedback control is continued even after the engine stop condition is satisfied. The fuel supply stop allowable rotational speed range is set in a narrower range within the target rotational speed range of the idle rotational speed feedback control, and the idle rotational speed feedback control is executed at the predetermined time point when the fuel supply is stopped. It is the time when it is determined that the engine speed is within the fuel supply stop allowable speed rangeTherefore, without providing a special braking device or the like, it is possible to reduce variations in the stop position of the piston and to stop at an appropriate position with a higher probability. That is, by improving the restartability of the engine with a simple structure, further reduction of fuel consumption and CO₂Emissions can be suppressed.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an engine provided with a starting device according to an embodiment of the present invention.
FIG. 2 is a schematic plan view of the engine.
FIG. 3 is a schematic control block diagram of the engine.
FIG. 4 is an explanatory diagram showing a change in engine speed, throttle opening, intake pipe negative pressure, and cycle of each cylinder when the engine is stopped.
FIG. 5 is an enlarged view of the engine speed shown in FIG. 4 in the vicinity of a fuel cut.
FIG. 6 is an explanatory diagram showing setting of a range for selecting a restart control mode according to a piston position when the engine is stopped.
FIGS. 7A and 7B show crank angle signals from two crank angle sensors, where FIG. 7A shows a signal at the time of normal engine rotation, and FIG. 7B shows a signal at the time of engine reverse rotation.
FIG. 8 is a flowchart showing a process for detecting a piston position when the engine is stopped.
FIG. 9 is a flowchart showing a process for detecting a piston position when the engine is stopped.
FIG. 10 is an explanatory diagram showing the cycle and combustion operation of each cylinder when the engine is restarted.
FIG. 11 is an explanatory diagram showing changes in engine speed, crank angle, in-cylinder pressure of each cylinder, and indicated torque when the engine is restarted.
FIG. 12 is an explanatory diagram showing the relationship between the piston position when the engine is stopped and the required air-fuel ratio of the compression stroke cylinder, the air amount of the compression stroke cylinder, the air amount of the expansion stroke cylinder, and the generation frequency.
[Explanation of symbols]
    1,1a engine
    3 (3A, 3B, 3C, 3D) cylinder (1st cylinder, ..., 4th cylinder)
    4 Piston
    7 Spark plug
    8 Fuel injection valve
    11 Intake valve
    12 Exhaust valve
    15 Intake passage
    16 Exhaust passage
    17, 17a Throttle valve
    21, 22 Crank angle sensor
    26a, 27a Cam phase variable mechanism
    28 Starter
    30, 30a ECU
    31 Throttle valve control means
    32 Fuel injection valve control means
    33 Ignition control means
    81 Target speed range for idle speed
    83 Allowable speed range for fuel cut

Claims (7)

A cylinder that is in an idle operation state and automatically stops fuel supply at a predetermined time after the predetermined engine stop condition is satisfied to stop the engine, and is in an expansion stroke when the restart condition is satisfied after the engine is stopped. In an engine starting device for injecting fuel to cause ignition, combustion, and restarting the engine,
During the idling operation, the idling engine speed feedback control is performed so that the actual engine speed falls within the target engine speed range of a predetermined width, and the idling engine speed feedback control is continued even after the engine stop condition is satisfied. ,
The fuel supply stop allowable rotational speed range is set in a narrower range within the target rotational speed range of the idle rotational speed feedback control,
The predetermined time point at which the fuel supply is stopped is a time point when it is determined that the engine speed during execution of the idle speed feedback control is within the fuel supply stop allowable speed range. Starting device. At least in the cylinder where the fuel is injected before the determination and the ignition timing for the fuel reaches after the determination, the ignition timing is set so that the torque due to the combustion after ignition is reduced, after the engine stop condition is satisfied and before the determination. The engine starter according to claim 1 , wherein retarding is performed with respect to the ignition timing of the engine. The fuel supply is automatically stopped at a predetermined time after the predetermined engine stop condition is satisfied to stop the engine, and fuel is injected into the cylinder in the expansion stroke when the restart condition is satisfied after the engine is stopped. In an engine starter that ignites and burns and restarts the engine,
The predetermined time point at which the fuel supply is stopped is a time point when it is determined that the engine speed is within a predetermined fuel supply stop allowable engine speed range,
The engine fuel injection timing is set to an intake stroke before the engine stop condition is satisfied, and is set to a compression stroke after the engine stop condition is satisfied and until the determination time. . At least in the cylinder where fuel is injected before the determination and the ignition timing is reached after the determination, the ignition timing is set so that the torque due to combustion after ignition decreases, and the ignition timing after the engine stop condition is satisfied and before the determination. The engine starter according to claim 3 , wherein the starter is retarded .   The engine speed detection timing for making the above determination is set after the stroke intermediate time of each cylinder outside the combustion period, and the fuel injection timing after the retarded fuel injection is the engine speed detection timing. The engine starting device according to any one of claims 1 to 4, wherein the engine starting device is set later.   6. The apparatus according to claim 1, wherein an external load is cut so that a rotational fluctuation range is reduced when detecting the engine speed for performing the determination. 7. Engine starter.   7. The engine starting device according to claim 6, wherein the cutting of the external load is performed in synchronization with the establishment of the engine stop condition.

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