JP2007270792A - Engine starter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance responsiveness and accuracy of adjustment of the intake air amount of each cylinder by control of a throttle valve during an automatic stop operation period of an engine, and to effectively make control to enable a stop in an appropriate stop position. <P>SOLUTION: The engine starter is provided with: the throttle valve 23 arranged on an intake passage and adjusting the intake air flowing amount; an intake passage capacity variable means for changing the capacity of the intake passage in the downstream side from the throttle valve 23; and an ECU 2 including an automatic stop control means for controlling automatic stop of the engine. The ECU 2 operates the intake passage capacity variable means so as to reduce the volume of the intake passage during the automatic stop operation period after an engine automatic stop condition is achieved. Then, the ECU 2 closes the throttle valve 23 and makes control such that intake air amount in a cylinder in a compression stroke at stop of the engine becomes smaller than that in a cylinder in an expansion stroke at stop of the engine. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention automatically stops the engine when a preset engine automatic stop condition is satisfied in an idle operation state of the engine or the like, and automatically restarts the engine when the restart condition is satisfied in this state. The present invention relates to an engine starter configured to be restarted.

Recently, in order to reduce fuel consumption, reduce CO2 emissions, etc., when a restart condition is established such that the engine is automatically stopped once during idle operation, etc., and then the vehicle is started. Thus, a technology for automatic engine stop control (so-called idle stop control) that automatically restarts the engine has been developed. The restart at the time of the idle stop control requires a quickness to immediately start the engine in accordance with the start operation of the vehicle or the like, but the engine output by the starter motor is generally performed conventionally. According to the method of restarting the engine through cranking that drives the shaft, there are problems that the starter motor is frequently operated and power is consumed, and that the life of the starter motor is shortened.

  Therefore, it is desirable to immediately start the engine with the combustion energy by injecting fuel into a cylinder that is in a stopped state in the expansion stroke to ignite and burn the cylinder. However, when the piston stop position of a cylinder that is in a stopped state in the expansion stroke is inappropriate, for example, when the piston is stopped at a position very close to top dead center or bottom dead center, the amount of air in the cylinder There is a possibility that the engine cannot be started normally due to the fact that the combustion energy is not sufficiently obtained due to remarkably reduced or the stroke of the combustion energy acting on the piston is too short.

  As a countermeasure against such a problem, for example, an engine starting device as shown in Patent Document 1 below is known. This device stops the fuel supply when the automatic engine stop condition is satisfied, and controls the intake flow rate adjusting means during the automatic stop operation period, for example, controls the throttle valve provided in the intake passage, The intake flow rate is increased by opening the throttle valve at a predetermined time of 1, and the intake air flow rate is decreased by closing the throttle valve at a subsequent second predetermined time.

According to this device, the scavenging performance for discharging unburned gas from the cylinder is increased by increasing the intake air flow rate at the initial stage of the automatic stop operation period, and the compression stroke when the engine is stopped from the cylinder that is in the expansion stroke when the engine is stopped Since the intake air amount of the cylinder becomes smaller, the piston of the cylinder that becomes the expansion stroke when the engine is stopped can be stopped at an appropriate position suitable for restart, slightly closer to the bottom dead center than the stroke center position. .
JP-A-2005-282418

  Incidentally, the intake air amount is generally adjusted by controlling a throttle valve provided in the intake passage. Usually, the throttle valve is provided upstream of the surge tank in the intake passage and downstream of the throttle valve. Since the intake passage has a considerable volume, if the intake flow rate is controlled by the throttle valve during the automatic stop operation period of the engine as described above, even after the throttle valve is closed at the second predetermined time, The intake pressure in the intake passage downstream of the throttle valve does not rapidly decrease but gradually decreases as the intake is repeated. For this reason, it is difficult to sufficiently improve the response and accuracy of adjusting the intake air amount of each cylinder by controlling the throttle valve during the automatic stop operation period, and should be improved in control for stopping at an appropriate stop position, etc. The point was left.

  In view of the above circumstances, the present invention provides control for increasing the responsiveness and accuracy of adjusting the intake air amount of each cylinder by controlling the throttle valve during the automatic stop operation period of the engine, and stopping the engine at an appropriate stop position. It is an object of the present invention to provide an engine starter that can be effectively performed.

  In order to solve the above-described problems, the present invention is to restart the engine in an automatic stop state while stopping the fuel supply and stopping the engine automatically when a preset automatic engine stop condition is satisfied. An engine starter configured to automatically restart an engine by causing combustion in at least a cylinder that has been automatically stopped in an expansion stroke when a condition is satisfied, and is provided in an intake passage to A throttle valve for adjusting a flow rate; an intake passage volume varying means for changing an intake passage volume downstream of the throttle valve; and an automatic stop control means for controlling an automatic stop of the engine. And means for operating the intake passage volume varying means so that the intake passage volume decreases during the automatic stop operation period after the automatic stop condition is satisfied. It is intended.

  According to this device, the volume of the intake passage downstream of the throttle valve is reduced during the automatic stop operation period, so that the followability of the change in the intake pressure downstream of the throttle valve is enhanced with respect to the subsequent change in the opening of the throttle valve. . Thereby, the responsiveness and accuracy when adjusting the intake air amount of each cylinder by controlling the throttle valve for adjusting the stop position and the like are improved.

  In the engine starter of the present invention, the automatic stop control means performs an automatic stop operation so that the intake air amount of the cylinder that becomes the compression stroke when the engine is stopped is smaller than the intake air amount of the cylinder that becomes the expansion stroke when the engine is stopped. It is preferable that the throttle valve is closed at a predetermined timing in the middle of the period, and the intake passage volume varying means is operated so that the intake passage volume decreases before the closing timing of the throttle valve.

  In this case, the intake air amount of the compression stroke cylinder at the time of stoppage is smaller than the intake air amount of the expansion stroke cylinder at the time of stoppage, so that the piston of the expansion stroke cylinder at stop time is slightly closer to the bottom dead center than the center position of the stroke. Stop in the proper range suitable for restart. In particular, when the throttle valve is closed in a state where the intake passage volume is small, the gradient of the accompanying decrease in the intake pressure increases, so that the intake air amount of the stop expansion stroke cylinder and the stop compression stroke cylinder is moderate. A disparity is given and the probability of stopping in the appropriate range is increased.

  In this case, the automatic stop control means is configured to change the intake passage volume changing means to reduce the intake passage volume within a predetermined period until the timing near the third top dead center of the piston before stopping the engine. It is preferable to perform the operation.

  In this way, a state is realized in which the intake pressure is reduced with good responsiveness due to the closing of the throttle valve by the intake stroke of the stop-time compression stroke cylinder.

  Further, the automatic stop control means opens the throttle valve for scavenging after the automatic stop condition is satisfied, and the intake passage volume variable means for reducing the intake passage volume after the opening of the throttle valve. It is preferable to perform the operation.

  In this way, the intake air amount is increased by opening the throttle valve, and sufficient scavenging is performed until the throttle valve is closed thereafter.

  Preferably, the automatic stop control means opens the throttle valve for scavenging after the automatic stop condition is established before the fuel supply is stopped.

  In this way, the intake air amount increases from the earliest possible time, and the scavenging performance is improved.

  The automatic stop control means controls the automatic stop of the engine while maintaining the drive state of the automatic transmission when the automatic transmission connected to the engine is in the drive state when the automatic stop condition is satisfied. Is preferred.

  If the automatic transmission is kept in the drive state in this way, if there is a reacceleration request (accelerator on) during the automatic stop operation period, the vehicle is reaccelerated smoothly and quickly simply by returning the combustion of the engine. be able to.

  However, the engine's rotational resistance (load) increases compared to when the engine is switched to the neutral state (the state in which the transmission of the driving force from the engine side to the drive wheel side is disconnected) and automatically stopped. The period until complete stop is shortened. This tends to cause a decrease in scavenging performance, which is a disadvantageous condition for restart. However, according to the present invention, the scavenging performance is improved, so that a good restart can be performed even in such a case.

  As described above, according to the starter of the present invention, the volume of the intake passage downstream of the throttle valve is reduced during the automatic stop operation period. Therefore, the throttle valve opening is changed to adjust the stop position, etc. When the intake air amount is adjusted, the responsiveness and accuracy can be improved. Therefore, stop control can be performed properly and restartability can be improved.

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

  1 and 2 show a schematic configuration of a four-cycle spark ignition engine having an engine starter according to the present invention. The engine includes an engine main body 1 having a cylinder head 10 and a cylinder block 11 and an ECU 2 for engine control. The engine body 1 is provided with a plurality of cylinders, for example, four cylinders 12A to 12D, and a piston 13 connected to the crankshaft 3 is fitted into each cylinder 12A to 12D and burns above it. A chamber 14 is formed.

  An ignition plug 15 is installed at the top of the combustion chamber 14 of each of the cylinders 12 </ b> A to 12 </ b> D so that the plug tip faces the combustion chamber 14, and the ignition plug 15 is connected to an ignition device 27. A fuel injection valve 16 that directly injects fuel into the combustion chamber 14 is provided on the side of the combustion chamber 14. This fuel injection valve 16 incorporates a needle valve and a solenoid (not shown), and is driven and opened for a time corresponding to the pulse width of the pulse signal input from the ECU 2, and has an amount corresponding to the valve opening time. The fuel is injected toward the vicinity of the electrode of the spark plug 15.

  In addition, an intake port 17 and an exhaust port 18 that open toward the combustion chamber 14 are provided above the combustion chamber 14 of each of the cylinders 12A to 12D, and an intake valve 19 and an exhaust gas are connected to these ports 17 and 18, respectively. Each valve 20 is equipped. The intake valve 19 and the exhaust valve 20 are driven by a valve mechanism having a camshaft or the like (not shown), whereby each cylinder 12A to 12D performs a combustion cycle with a predetermined phase difference. 12D intake / exhaust ports 17 and 18 are opened and closed.

  An intake passage 21 and an exhaust passage 22 are connected to the intake port 17 and the exhaust port 18. The intake manifold 50 on the downstream side of the intake passage 21 has a surge tank 51 and a branched intake passage 53 that is independent for each cylinder downstream of the surge tank 51. A common intake passage 21a is provided upstream of the surge tank 50, and a throttle valve 23 driven by an actuator 24 is disposed in the common intake passage 21a. An air flow sensor 25 for detecting the intake flow rate and an intake pressure sensor 26 for detecting the intake pressure (negative pressure) are disposed on the upstream side and the downstream side of the throttle valve 23, respectively.

  The intake manifold 50 is provided with an intake passage volume varying means that can change the intake passage volume downstream from the throttle valve 23. The intake passage volume varying means is, for example, as shown in FIGS. It is configured.

  That is, the intake passage volume varying means is for each cylinder having a relatively large capacity surge tank 51, a surge tank upstream passage 52 formed integrally with the surge tank 51, a low speed passage 53a, and a high speed passage 53b. Branch passage 53, switching valve 54, and shutter valve 55. The surge tank upstream side passage 52 communicates with the surge tank 51 via the communication portion 51 a and the upstream end portion is connected to the throttle body 58. The throttle body 58 forms part of the common intake passage 21a (see FIG. 1), and the throttle valve 23 is built in the throttle body 58.

  The low-speed passage 53a is constituted by a relatively long passage that leads to the surge tank 51 and passes around the surge tank 51, and the high-speed passage 53b is constituted by a short passage that leads to the surge tank upstream side passage 52. The branch passage 53 downstream of the joining portion 53c of these passages 53a and 53b extends to the engine body side and is connected to the intake port 17.

  The switching valve 54 opens the communication portion 51a between the surge tank 51 and the surge tank upstream passage 52 and closes the high-speed passage 53b (the state shown in FIG. 2), and the communication portion 51a. It is possible to switch to the second state (the two-dot chain line in FIG. 2A and the state shown in FIG. 3) that shields and opens the high-speed passage 53b with respect to the surge tank upstream passage 52.

  The shutter valve 55 is located in the low speed passage 53a immediately upstream of the junction 53c, and the low speed passage 53a is opened (state shown in FIG. 2) and closed (state shown in FIG. 3) at this position. Can be switched to.

  The switching valve 54 and the shutter valve 55 are driven by actuators 56 and 57 such as motors, respectively.

  Returning to FIG. 1, the engine body 1 is provided with an alternator (generator) 28 connected to the crankshaft 3 by a timing belt or the like. The alternator 28 includes a regulator circuit 28a that adjusts the target generated current by controlling the current of a field coil (not shown) and adjusting the output voltage, and the control from the ECU 2 that is input to the regulator circuit 28a. Based on the signal, the control of the target generated current corresponding to the electric load of the vehicle and the voltage of the vehicle-mounted battery is executed at normal times.

Further, the engine is provided with two crank angle sensors 30 and 31 for detecting the rotation angle of the crankshaft 3, and the rotation speed of the engine is detected based on a detection signal output from one crank angle sensor 30. In addition, as will be described later, the rotation direction and the rotation angle of the crankshaft 3 are detected based on detection signals out of phase output from the crank angle sensors 30 and 31.

  Further, an automatic transmission (hereinafter also abbreviated as AT) 40 is connected to the engine body 1. The AT 40 is a mechanism that automatically converts the engine output into an optimum rotational speed and driving torque and transmits it to the axle according to the traveling state of the vehicle and the operation of the driver. The AT 40 is configured to be switchable between a neutral state in which transmission of driving force to the wheel side is disconnected and a driving state in which transmission of driving force to the wheel side is possible.

  Note that the drive state or neutral state of the AT 40 refers to its power transmission form and does not necessarily coincide with the position of the shift lever or the like operated by the driver. For example, even if the position of the shift lever is in the “D” range, the AT 40 can be brought into the neutral state by releasing the power transmission system (such as a hydraulic clutch) inside the AT 40.

  The ECU 2 is a control unit that comprehensively controls the operation of the engine. The ECU 2 includes the air flow sensor 25, the intake pressure sensor 26, the crank angle sensors 30, 31, a cam angle sensor 32 for detecting a specific rotational position for cylinder identification provided on the camshaft, and engine cooling water. A water temperature sensor 33 that detects the temperature, an accelerator sensor 34 that detects the accelerator opening corresponding to the accelerator operation amount of the driver, and a brake sensor 35 that detects that the driver has operated the brake, respectively. A detection signal is input.

  The ECU 2 receives the detection signals from the sensors 25, 26, 30 to 35, and outputs a control signal for controlling the fuel injection amount and the injection timing to the fuel injection valve 16. 15 outputs a control signal for controlling the ignition timing to the ignition device 27 attached to 15, and outputs a control signal for controlling the throttle opening degree to the actuator 24 of the throttle valve 23; Signals for controlling these valves are also output to the actuators 56 and 57 of the switching valve 54 and the shutter valve 55 of the intake passage volume varying means. Further, a control signal is input / output to / from the AT 40, and comprehensive control of the engine and the AT 40 is performed.

  The ECU 2 functionally includes an automatic stop control means. When the automatic engine stop condition is satisfied, the ECU 2 performs control to stop the fuel supply and automatically stop the engine, and after the automatic stop condition is satisfied. During the automatic stop operation period, the switching valve 54 and the shutter valve 55 of the intake passage volume varying means are controlled so that the intake passage volume downstream of the throttle valve decreases. In addition, after the automatic stop, the engine is automatically restarted when a restart condition is satisfied, for example, when the driver performs an accelerator operation.

  Specifically, when the engine is automatically stopped, the first combustion is performed in a cylinder in which the piston 13 is stopped in the middle of the compression stroke (compression stroke cylinder at the time of stop), so that the piston 13 is pushed down and the crankshaft 3 is slightly moved. Reverse. As a result, when the engine is automatically stopped, the piston 13 of the cylinder in which the piston 13 is stopped in the middle of the expansion stroke (expansion stroke cylinder at the time of stop) is temporarily raised, and the mixture is ignited in a compressed state. Then, the engine is restarted by applying a driving torque in the forward rotation direction to the crankshaft 3 by burning.

  In order to restart the engine properly only by igniting the fuel injected into a specific cylinder without using a restart motor or the like in principle as described above, the mixture of the expansion stroke cylinder at the time of stop is used. Combustion energy obtained by burning the fuel must be sufficiently secured, and the cylinder that reaches the compression top dead center must overcome the compression reaction force and exceed the compression top dead center. Therefore, it is necessary to ensure a sufficient amount of air in the expansion stroke cylinder at the time of stop.

  That is, as shown in FIGS. 4A and 4B, the phases of the stop expansion stroke cylinder and the stop compression stroke cylinder are shifted by 180 ° CA, so that the pistons 13 operate in opposite directions. If the piston 13 of the expansion stroke cylinder at the time of stop is located on the bottom dead center side with respect to the stroke center, the amount of air in the cylinder increases and sufficient combustion energy is obtained. However, when the piston 13 of the expansion stroke cylinder at the time of stop is in an extremely positioned state at the bottom dead center side, the amount of air in the compression stroke cylinder at the time of stop becomes too small, and the combustion energy for reversing the crankshaft 3 is sufficient. Can not be obtained.

  On the other hand, a predetermined range R slightly lower than the position where the crank angle after the compression top dead center is 90 ° CA, that is, the crank angle after the compression top dead center, for example, the crank angle after the compression top dead center. If the piston 13 can be stopped within an appropriate range of 100 ° to 120 ° CA, a predetermined amount of air is secured in the compression stroke cylinder when stopped, and the crankshaft 3 is slightly reversed by the initial combustion. A sufficient amount of combustion energy can be obtained. In addition, by securing a large amount of air in the expansion stroke cylinder, it is possible to generate sufficient combustion energy for normal rotation of the crankshaft 3 and reliably restart the engine.

  Therefore, control as shown in FIG. 5 is performed by the automatic stop control means included in the ECU 2. That is, first, at a time point t0 when the engine automatic stop condition is satisfied, the engine target rotational speed is set to a value higher than the normal idle rotational speed when the engine is not automatically stopped, and control is performed to be stabilized. For example, in an engine in which the normal idle rotation speed is set to 650 rpm, the target rotation speed (idle rotation speed when the automatic stop condition is satisfied) is set to about 860 rpm, and the target intake pressure is set to a predetermined negative pressure (for example, − 400 mmHg), and the control to achieve the target rotational speed and the target intake pressure is executed, the intake pressure is stabilized at the target intake pressure, and the engine rotational speed Ne is stabilized at the target rotational speed. Fuel injection is stopped at time t2. Further, the throttle valve is controlled to open at a time t1 before the stop of the fuel injection, that is, the opening K of the throttle valve 23 is set so as to increase the intake flow rate, thereby reducing the intake throttle amount. The intake flow rate sucked into the cylinders 12A to 12D of the engine is sufficiently secured to enhance the scavenging performance.

  Further, during the automatic stop operation period, the intake passage volume varying means is controlled so that the intake passage volume downstream of the throttle valve decreases, that is, the switching valve 54 is set in the second state and the shutter valve 55 is closed (FIG. 3 state). The operation of the switching valve 54 and the shutter valve 55 so as to reduce the intake passage volume is performed in a period up to the timing near the third piston top dead center before stopping the engine, and preferably an automatic stop operation. This is performed in the vicinity of the fuel injection stop time t2, which is the initial stage.

  By stopping the combustion injection at the time point t2, the target generated current Ge of the alternator 28 is detected at the time point t3 when it is confirmed that the rotational speed Ne of the engine has decreased to a preset reference speed (for example, 760 rpm) or less. , And the target generated current Ge of the alternator 28 is a value corresponding to the reduced state of the engine rotational speed Ne at the time t4 when the engine top dead center rotational speed ne is within a predetermined range as will be described later. Thus, the control is executed to reduce the rotational speed Ne of the engine along the reference line set based on the results of experiments performed in advance.

  When the engine is automatically stopped as described above, the kinetic energy of the crankshaft 3, the flywheel, etc. from the fuel injection stop time t1 is caused by mechanical loss due to frictional resistance or pump work of each cylinder 12A to 12D. When consumed, the crankshaft 3 of the engine is rotated several times by inertia. Specifically, as shown in FIGS. 4 and 5, each time the cylinders 12A to 12D reach compression top dead center, the engine After the rotational speed Ne has temporarily dropped, the engine rotational speed Ne gradually decreases while repeating an up-down that rises again when the compression top dead center is exceeded.

  Then, in the cylinder 12C that reaches the compression stroke after the time t6 when the last top dead center is exceeded before the engine is stopped, the air pressure increases as the piston 13 rises due to the inertial force, and the piston 13 is pushed by the compression reaction force. Returned, the crankshaft 3 reverses. Due to the reverse rotation of the crankshaft 3, the air pressure of the stop expansion stroke cylinder 12 </ b> A increases, so that the piston 13 of the stop expansion stroke cylinder 12 </ b> A is pushed back to the bottom dead center side according to the compression reaction force, and the crankshaft 3 is The forward rotation starts again, and the reverse rotation and forward rotation of the crankshaft 3 are repeated several times to stop the piston 13 after reciprocating.

  In order for the engine to stop the piston 13 of the stop expansion stroke cylinder 12A within the appropriate range R suitable for restart, first, the compression reaction forces of the stop expansion stroke cylinder 12A and the stop compression stroke cylinder 12C are respectively determined. It is necessary to adjust the intake air flow rates for both cylinders 12A and 12C so that the compression reaction force of the stop expansion stroke cylinder 12A is sufficiently larger than the compression reaction force of the stop compression stroke cylinder 12C by a predetermined value or more. is there. For this reason, in this embodiment, by setting the opening K of the throttle valve 23 to a large value at the time t1 before the stop of fuel injection, a predetermined amount is applied to both the expansion stroke cylinder 12A and the compression stroke cylinder 12C. The throttle valve 23 is closed when a predetermined time has elapsed after the air is inhaled, and the opening K is reduced to adjust the intake air amount.

  Further, the switching valve 54 and the shutter valve 55 are operated so that the intake passage volume decreases before the closing timing of the throttle valve 23.

  Note that, if the automatic transmission 40 is in the drive state when the automatic stop condition is satisfied, the drive state is maintained during the automatic stop operation period. In this way, if there is a reacceleration request (accelerator on) during the automatic stop operation period, the vehicle can be reaccelerated smoothly and quickly simply by returning the combustion of the engine.

  A control operation when the engine is automatically stopped by the automatic stop control means of the ECU 2 will be described based on the flowcharts shown in FIGS. When this control operation starts, it is determined whether or not an automatic stop permission flag F for determining whether or not the engine is in an operating state capable of executing the automatic stop control is ON (step S1). This automatic stop permission flag F is satisfied when the vehicle speed is a predetermined value (for example, 10 km / h) or more, the steering angle is not more than a predetermined value, the battery voltage is not less than a reference value, and the air conditioner is in an OFF state. In addition, it is determined that the engine can be automatically stopped and is turned on.

  If YES is determined in step S1, it is determined whether the accelerator sensor 34 is in an OFF state and the brake sensor 35 is in an ON state (step S2). When it is confirmed that the engine is in a state, it is determined whether or not the engine speed Ne is larger than a reference value F / C · ON for fuel cut during deceleration that is set in advance to about 1100 rpm (step S1). S3) If NO is determined, the process proceeds to the following step S7.

  If it is determined YES in step S3 and it is confirmed that the engine speed Ne is larger than the determination reference value F / C · ON for fuel cut during deceleration, the fuel cut (FC) during deceleration is determined. Execute (step S4). Next, it is determined whether or not the engine rotational speed Ne has dropped below a fuel return determination reference value F / C · OFF that is set to about 900 rpm in advance (step S5). When it is determined YES, The fuel cut (FC) at the time of deceleration is terminated and the normal fuel injection state is restored (step S6).

  Next, the target rotational speed of the engine is set to a value higher than the normal idle rotational speed (about 650 rpm) by a predetermined amount, for example, about 800 rpm (step S8).

  Then, it is determined whether or not the accelerator sensor 34 is in the ON state or the brake sensor 35 is in the OFF state, that is, whether or not the deceleration state is released (step S10). Returning to step S1, the above control operation is repeated. If it is determined NO in step S10 and it is confirmed that the deceleration state is not released, it is determined whether or not the vehicle speed is 0, that is, whether or not the vehicle is stopped and the automatic stop condition is satisfied. Determination is made (step S11).

  When it is determined YES in step S11 and the vehicle is stopped, the engine target rotational speed N1 is set to a value higher than the normal idle rotational speed (650 rpm) by a predetermined amount, for example, about 860 rpm. (Step S15), the throttle valve 23 is operated in the valve opening direction, and the opening degree K of the throttle valve 23 is feedback-controlled so that the boost pressure Bt becomes the target pressure P1 set to, for example, about −400 mmHg. .

  Subsequently, the process waits until the boost pressure Bt is stabilized at the target pressure (−400 mmHg) (step S17), and then opens the throttle valve 23 and sets its opening degree K to, for example, about 30% (step S22).

  Next, whether or not the fuel injection stop condition (FC condition) is satisfied, specifically, the boost pressure Bt becomes the target pressure P1 and the engine rotational speed Ne becomes the target rotational speed N1 is stable. It is determined whether or not (step S19). If the accelerator sensor 34 is turned off or the brake sensor 35 is turned on during the determination operation, the process returns without stopping the fuel injection. Thereby, it is possible to prevent an inappropriate automatic stop of the engine from being performed in a case where the vehicle speed is shifted to 0 immediately after the vehicle speed becomes zero.

  Then, when it is determined YES in step S19 and it is confirmed that the engine speed Ne and the boost pressure Bt are in a stable state (time t2 in FIG. 5), fuel injection is stopped (step S20). At the same time, the switching valve 54 in the intake passage volume variable mechanism is set to the second state (step S21), and the shutter valve 55 is closed (step S22).

  Thereafter, whether or not a predetermined time has elapsed from the time t1 when the fuel injection is stopped in the above step S20, that is, the combustion of the fuel injected before reaching the compression top dead center several times after the fuel injection is stopped is performed. It is determined whether or not the process has been completed (step S23), and when it is determined YES, the ignition by the ignition device 27 is stopped (step S24). Next, by determining whether or not the engine rotation speed Ne is equal to or lower than a reference speed set in advance to about 760 rpm (step S25), the engine rotation speed after the fuel injection stop time t2 shown in FIG. 4 is determined. It is determined whether or not Ne starts to decrease, and at time t3 when it is determined YES, the power generation control for operating the alternator 28 by setting the target power generation current Ge of the alternator 28 to an initial value set to about 60 A in advance. Start (step S26).

  Next, it is determined whether or not the engine top dead center rotational speed ne is within a first predetermined range (step S27). This first predetermined range is a time point t4 when the engine passes through the fourth compression top dead center before the engine is stopped, for example, in the process in which the engine rotational speed Ne decreases along the preset reference line. Is a value set based on the top dead center rotational speed ne, and specifically, is set within the range of 480 rpm to 540 rpm.

  When it is determined YES in step S27 and it is confirmed that the engine top dead center rotational speed ne is within the predetermined range (480 rpm to 540 rpm), it corresponds to the top dead center rotational speed ne at that time t4. The target generated current Ge of the generated alternator 28 is set (step S28). In this case, the higher the top dead center rotational speed ne of the engine is, the larger the value of the target generated current Ge is read from the map in which the target generated current Ge corresponding to the top dead center rotational speed ne is read, and the alternator is based on this value. The control for reducing the 28 target power generation current Ge is executed.

  Further, the throttle valve 23 is closed (K = 0%) (step S28).

  Next, the engine top dead center rotational speed ne is within a second predetermined range set based on the top dead center rotational speed ne at the time t5 when the engine passes the second compression top dead center before the engine stops, for example, 260 rpm to It is determined whether it is within the range of 400 rpm (step S30). The fuel injection amount increases as the engine top dead center rotational speed ne increases at time t5 when it is determined YES in step S30 and it has been confirmed that the second compression top dead center before the engine stop has passed. From the map (not shown) set to (2), the fuel injection amount for the cylinder 12C that is in the compression stroke when the engine is stopped is set, and fuel is injected in the latter half of the compression stroke of the cylinder 12C (step S31). When the fuel injected into the cylinder 12C is vaporized, the temperature in the cylinder is lowered, and the increase in the internal pressure is suppressed.

  Then, it is determined whether or not the engine top dead center rotational speed ne is equal to or lower than a predetermined value (step S32). This predetermined value is a value corresponding to the top dead center rotational speed ne when exceeding the last compression top dead center in the process in which the engine rotational speed Ne is decreasing along a preset reference line. It is set to about 260 rpm. Further, the boost pressure Bt at each time when each of the cylinders 12A to 12C sequentially passes the compression top dead center is detected and stored.

  If it is determined YES in step S32 and it is confirmed that the engine top dead center rotational speed ne is equal to or lower than the predetermined value, that is, the engine has passed the last compression top dead center, this time At t6, the boost pressure Bt at the time of passing the previous compression top dead center is read, and this value is set as the boost pressure Bt2 at the second compression top dead center (TDC) before engine stop (step S33). ).

  The top dead center rotational speed ne at the time t6 when the engine reaches the final compression top dead center (hereinafter referred to as the final top dead center rotational speed ne1) and the boost pressure Bt2 at the second compression top dead center before the engine is stopped. Based on the above, it is determined whether or not the piston 13 tends to stop at a later position in each stroke (a position closer to the bottom dead center in the expansion stroke cylinder 12A) (step S34). Specifically, when the final top dead center rotational speed ne1 is equal to or higher than a predetermined rotational speed N4 (for example, N4 = 200 rpm) and the boost pressure Bt2 is equal to or lower than a predetermined pressure P2 (for example, P2 = −200 mmHg) (vacuum side) ), The piston stop position in the expansion stroke cylinder 12A during the stop is within an appropriate range R in the range of 100 ° to 120 ° CA after compression top dead center. On the other hand, since the tendency to stop at a position close to 120 ° CA is large, YES is determined in step S34.

  If it is determined NO in step S34, the engine does not tend to stop at a position near the latter stage of the stroke as described above, but the position at a relatively earlier stage of the stroke, that is, the expansion stroke cylinder at the time of stop. There is a possibility that the piston stop position at 12A stops at a position close to 100 ° CA or 100 ° CA or less with respect to an appropriate range R that becomes 100 ° to 120 ° CA after compression top dead center. Therefore, in order to stop the piston 13 within the proper range R more reliably, the throttle valve 23 is opened. For example, the throttle valve 23 is opened so that the opening degree K of the throttle valve 23 is set to the first opening degree K1 set to about 40% of full opening (step S35), and the intake air flow rate is increased to thereby increase the intake stroke. The intake resistance of the cylinder 12D is reduced. As a result, the engine is likely to stop at a later position in the stroke, and as a result, the stop position of the piston 13 in the stop-time expansion stroke cylinder 12A is prevented from exceeding the lower limit (100 ° CA) within the appropriate range R. Will be.

  On the other hand, if it is determined as YES in step S34, the rotational inertia of the engine is large, the intake air flow rate in the final intake stroke to the stop-time compression stroke cylinder 12C is small, and the compression reaction force is small. The conditions that the piston 13 is likely to stop at a position near the later stage of the stroke have already been prepared. Therefore, the throttle valve 23 is operated so that the opening degree K of the throttle valve 23 becomes the second opening degree K2 set to, for example, about 5% (step S36). The second opening K2 may be a smaller opening or a closed state according to engine characteristics and the like. In this way, an appropriate intake resistance is generated in the stop-time intake stroke cylinder 12D, and the occurrence of a situation in which the stop position of the piston 13 exceeds the appropriate range R and becomes further late is effectively prevented.

  Next, it is determined whether or not the engine is stopped (step S37). When it is determined YES, the automatic stop permission flag F is turned OFF (step S38), and the control operation is terminated.

  A control operation when the engine that has been automatically stopped as described above is restarted will be described based on the flowcharts shown in FIGS. First, it is determined whether or not a predetermined engine restart condition is satisfied (step S101). If YES is determined, for example, if an accelerator operation for starting from a stopped state is performed, the battery voltage is When the air temperature decreases or when the air conditioner is activated, the in-cylinder temperature is estimated based on the engine water temperature, the elapsed time since the automatic stop, the intake air temperature, and the like (step S102).

  Based on the stop position of the piston 13 detected when the engine is automatically stopped, the amount of air in the stop compression stroke cylinder 12C and the stop expansion stroke cylinder 12A is calculated (step S103). That is, the combustion chamber volumes of the stop compression stroke cylinder 12C and the stop expansion stroke cylinder 12A are obtained from the stop position of the piston 13, and the fresh air amount is obtained from the combustion chamber volumes.

  Next, the piston stop position detected according to the output signals of the crank angle sensors 30, 31 is below the appropriate stop range R (BTDC 60 to 80 ° CA before top dead center) in the stop-time compression stroke cylinder 12C. It is determined whether or not the vehicle is near the dead center BDC (step S104). If it is determined as YES in step S104 and it is confirmed that the air amount in the stop-time compression stroke cylinder 12C is relatively large, the air amount in the stop-time compression stroke cylinder 12C calculated in step S103 is compared with the air amount in the stop-time compression stroke cylinder 12C. , Λ (excess air ratio)> 1 (for example, air-fuel ratio = about 20), the first fuel injection is performed (step S105). This air-fuel ratio is obtained from the first air-fuel ratio map M1 for the first time of the stop-time compression stroke cylinder 12C set in advance according to the stop position of the piston 13, and is set to a lean air-fuel ratio of λ> 1. This prevents excessive combustion energy for reverse rotation even when the amount of air in the stop-time compression stroke cylinder 12C is relatively large.

  On the other hand, when it is determined as NO in step S104 and the air amount in the stop compression stroke cylinder 12C is relatively small, λ ≦≦ the air amount in the stop compression stroke cylinder 12C calculated in step S103. The first fuel injection is performed so that the air-fuel ratio becomes 1 (step S106). This air-fuel ratio is obtained from the first-time second air-fuel ratio map M2 of the stop-time compression stroke cylinder 12C set in advance according to the stop position of the piston 13, and λ ≦ 1 (the stoichiometric air-fuel ratio or richer air-fuel ratio than that) ), Sufficient combustion energy for reverse rotation can be obtained even when the amount of air in the stop-time compression stroke cylinder 12C is small.

  Next, the cylinder 12C is ignited after the elapse of a predetermined time set in consideration of the vaporization time from the first fuel injection into the stop-time compression stroke cylinder 12C (step S107). Then, it is determined whether or not the piston 13 has moved based on whether or not the edges of the crank angle sensors 30 and 31, that is, the rising or falling edge of the crank angle signal are detected within a certain time after ignition (step S 108). When it is determined NO and it is confirmed that the piston 13 has not moved due to misfire, the ignition cylinder 12C at the time of stop is re-ignited (step S109).

  If it is determined YES in step S108 and it is confirmed that the piston 13 has moved, the split fuel injection split for the stop-time expansion stroke cylinder 12A based on the piston stop position and the in-cylinder temperature estimated in step S102. The ratio (the ratio between the first pre-injection and the second post-injection) is calculated (step S121). The latter injection ratio is set to a larger value as the piston stop position in the stop-time expansion stroke cylinder 12A is closer to the bottom dead center and as the in-cylinder temperature is higher.

  Next, the fuel injection amount is calculated so that a predetermined air-fuel ratio (λ ≦ 1) is obtained with respect to the air amount in the stop-time expansion stroke cylinder 12A calculated in step S103 (step S122). The air-fuel ratio at this time is obtained from the air-fuel ratio map M3 for the stop-time expansion stroke cylinder 12A set in advance according to the stop position of the piston 13. Further, the first-stage fuel injection amount for the stop expansion stroke cylinder 12A is calculated from the fuel injection amount to the stop expansion stroke cylinder 12A calculated in step S122 and the split ratio calculated in step S121. Are injected (step S123).

  Next, based on the in-cylinder temperature estimated in step S102, the subsequent (second) fuel injection timing for the stop-time expansion stroke cylinder 12A is calculated (step S124). The second injection timing is a timing when the air in the cylinder is compressed after the piston 13 starts moving toward the top dead center (reverse rotation of the engine), and the vaporization latent heat of the injected fuel is reduced to the compression pressure. Is set so that the piston 13 approaches the top dead center, and the time for the second injected fuel to evaporate by the ignition timing is set as long as possible. .

  Next, the subsequent (second) fuel injection amount for the stop expansion stroke cylinder 12A is calculated from the fuel injection amount to the stop expansion stroke cylinder 12A calculated in step S122 and the split ratio calculated in step S121. (Step S125), and the injection is performed at the second injection timing calculated in Step S124 (Step S126).

  After the second fuel injection into the stop expansion stroke cylinder 12A, ignition is performed when a predetermined delay time has elapsed (step S127). This delay time is obtained from the ignition map M4 for the stop-time expansion stroke cylinder 12A set in advance according to the stop position of the piston 13. Due to the initial combustion in the expansion stroke cylinder 12A at the time of stop by the ignition, the engine turns from reverse rotation to normal rotation.

  Next, taking the fuel vaporization time into consideration, the second-time fuel is injected into the stop-time compression stroke cylinder 12C (step S128). The fuel injection amount at this time is such that the entire air-fuel ratio based on the total injection amount with the first injection amount becomes richer (for example, about 6) than the combustible air-fuel ratio (lower limit is 7 to 8). It is obtained from the second air-fuel ratio map M5 for the stop-time compression stroke cylinder 12C set in advance according to the stop position of the piston 13. The compression top dead center is easily reduced by reducing the compression pressure near the compression top dead center of the stop compression stroke cylinder 12C in accordance with the latent heat of vaporization by the second injection fuel in the stop compression stroke cylinder 12C. It is possible to exceed.

  It should be noted that the second fuel injection into the stop-time compression stroke cylinder 12C is performed exclusively to reduce the compression pressure in the cylinder, and ignition and combustion are not performed on this, and it is richer than the combustible air-fuel ratio. Therefore, self-ignition does not occur, and this non-combustible fuel is made harmless by subsequently reacting with oxygen stored in the exhaust gas purification catalyst in the exhaust passage 22.

  Next, after calculating the air amount of the intake stroke cylinder 12D when stopped (step S140), an air-fuel ratio correction value for preventing self-ignition is calculated based on the in-cylinder temperature estimated at step S102 (step S102). S141).

  Next, based on the air amount of the stop-time intake stroke cylinder 12D calculated in step S140 and the air-fuel ratio considering the air-fuel ratio correction value calculated in step S141, the fuel injection amount to the stop-time intake stroke cylinder 12D Is calculated (step S142). Then, fuel injection is performed for the intake stroke cylinder 12D at the time of stop, and this fuel injection is performed so that the compression pressure is reduced by the latent heat of vaporization, that is, the energy required for exceeding the compression top dead center is reduced. The delay is delayed until the later stage of the compression stroke (step S143), and the delay amount is calculated based on the automatic engine stop period, the intake air temperature, the engine water temperature, and the like.

  Further, in order to suppress the occurrence of reverse torque due to self-ignition, the ignition timing is delayed after top dead center and ignited (step S144). By executing the control described above, in the stop-time intake stroke cylinder 12D, the compression pressure is reduced to the compression top dead center and easily exceeds the top dead center. A torque in the forward direction is generated.

  After the step S144, as control for suppressing the engine speed increase (the engine speed increasing more than necessary), first, the target current value of the alternator 28 is set higher than normal (step S1). S145), the rotational resistance of the crankshaft 3 (external load of the engine) is increased by the power generation of the alternator 28. Next, it is determined whether or not the intake pressure detected by the intake pressure sensor 26 is higher than the intake pressure during normal idling when the engine is not automatically stopped (step S150). Since the engine rotation speed is likely to increase, the opening of the throttle valve 23 is made smaller than the throttle opening during normal idle operation (step S151).

  Then, it is determined whether or not the temperature of the exhaust gas purification catalyst provided in the exhaust passage 22 is equal to or lower than the activation temperature (step S152). If YES is determined, the target air-fuel ratio in the cylinder is set to λ ≦ The rich air-fuel ratio is set to 1 (step S153), and the ignition timing is delayed after top dead center (step S154). Thereby, the temperature rise of the catalyst is promoted, and the amount of combustion energy generated is suppressed by the delay of the ignition timing.

  On the other hand, if it is determined NO in step S152 and it is confirmed that the temperature of the exhaust gas purification catalyst is higher than the activation temperature, the target air-fuel ratio in the cylinder is set to a lean air-fuel ratio with λ> 1. A stratified lean combustion state is set (step S158). This lean combustion suppresses fuel consumption and suppresses the amount of combustion energy generated.

  The process returns to step S150 through step S154 or step S158, and it is determined that the intake pressure has decreased even during normal idling when it is determined NO in step S150 and the engine is not automatically stopped. The control operation is repeated. If it is determined NO in step S150, there is no possibility that the engine speed will increase any more, so that the normal control state including the generated current of the alternator 28 is entered (step S160).

  During this normal control, the switching valve 54 and the shutter valve 55 of the intake passage volume varying means are controlled based on a map corresponding to the engine load and the engine speed. Specifically, at least in the high load region, the switching valve 54 is in the first state (the state indicated by the solid line in FIG. 2A) in the low speed region where the engine rotational speed is lower than a specific rotational speed (for example, 4500 rpm). 55 is in an open state, and the switching valve 54 is in a second state (a state indicated by a two-dot chain line in FIG. 2A) in a high speed range higher than the specific rotation speed.

  According to the apparatus of the present embodiment as described above, when the automatic engine stop condition is satisfied, the fuel injection for continuing the engine operation is stopped and the engine is automatically stopped. In addition, the scavenging performance is improved by opening the throttle valve 23 before the fuel supply is stopped.

  Further, at an appropriate time during the automatic stop period, for example, substantially simultaneously with the stop of the fuel supply, the switching valve 54 of the intake passage volume varying means is operated to the second state and the shutter valve 55 is closed to cause the surge. The tank 51 and the low speed passage 53a are blocked, and the intake passage volume (the intake passage volume downstream of the throttle valve) of the portion of the intake manifold 50 that communicates with the intake port 28 is reduced.

  Thereafter, the throttle valve 23 is closed at a predetermined time until the last intake stroke of the stop-time compression stroke cylinder 12C, so that the intake air amount in the stop-time compression stroke cylinder 12C is larger than that in the stop-time expansion stroke cylinder 12A. That is, the compression reaction force of the stop expansion stroke cylinder 12A becomes larger than the compression half force of the stop compression stroke cylinder 12C, so that the piston of the stop expansion stroke cylinder 12A is slightly closer to the bottom dead center than the stroke center position. Stops within the proper range R.

  At this time, since the intake passage volume has already been reduced as described above, the probability of stopping at the appropriate position is increased.

  That is, when the intake passage volume downstream of the throttle valve is large as in the conventional device having no intake passage volume varying means, the intake pressure Bt is changed after the throttle valve is closed, as indicated by a two-dot chain line in FIG. Although the pressure gradually decreases, the decrease is relatively slow. Therefore, the difference in intake air amount between the stop expansion stroke cylinder 12A and the stop compression stroke cylinder 12C is small, and the stop can be surely stopped within the appropriate range R. difficult.

  On the other hand, when the intake passage volume is small, as shown by the solid line in FIG. 5, the gradient of the decrease in the intake pressure Bt after the throttle valve is closed becomes large, and the stop expansion stroke cylinder 12A and Since the amount of intake air in the compression stroke cylinder 12C at the time of stop can have an appropriate difference, the probability of stopping within the appropriate range R can be increased.

  Further, when the intake passage volume downstream of the throttle valve is large, it is expected that the decrease in the intake pressure Bt after the throttle valve 23 is closed will be slow, so that it is considerably greater than the last intake stroke of the stop-time compression stroke cylinder 12C. Although it is necessary to close the throttle valve 23 at an early stage (two-dot chain line in FIG. 5), if the intake passage volume is small, the timing at which the throttle valve 23 is closed is the last of the compression stroke cylinder 12C at the time of stop. Since the intake stroke can be approached, that is, the period during which the throttle valve 23 is open can be lengthened, scavenging performance can also be improved.

  In particular, in this embodiment, the automatic transmission 40 is in the drive state during the automatic stop operation period, and the automatic stop operation period until the engine stops is relatively short due to the rotational resistance caused by this. Even under such conditions, the period during which the throttle valve 23 is open is ensured as long as possible during the automatic stop operation period, and the scavenging performance is improved.

  By these actions, the startability at the time of engine restart is improved.

  Control at the time of engine restart is performed according to the flowcharts shown in FIGS. 9 to 11, and after the restart is achieved, the control shifts to normal control.

  Further, during normal control, the intake passage volume varying means is controlled in accordance with the operating state, thereby contributing to improvement in engine output and the like.

  That is, when the engine speed is lower than a specific speed (for example, 4500 rpm), the switching valve 54 is in the first state (the state indicated by the solid line in FIG. 2A) and the shutter valve 55 is in the open state. The high-speed passage 53b is closed and the low-speed passage 53a is opened, and the length of the intake passage from the surge tank 51 to the intake port 17 is increased (the intake passage volume is increased). Is obtained. On the other hand, in the high speed range higher than the specific rotation speed, the switching valve 54 is set to the second state (the state indicated by the two-dot chain line in FIG. 2A), thereby opening the high speed passage 53b and The intake passage length to the intake port 17 is shortened, and a resonance tuning state is obtained in a high speed range. Thus, as shown in FIG. 12, the engine torque is increased by resonance supercharging in the low speed range and the high speed range.

  In the engine starter according to the above-described embodiment, when restarting the engine in the automatic stop state, the crankshaft 3 is slightly started first by causing the stop-time compression stroke cylinder 12C to perform the first combustion. However, the engine starter according to the present invention is not limited to this, and the stop-time expansion stroke cylinder 12A is not limited thereto. However, the engine may be restarted by first performing ignition.

  Although omitted in the above embodiment, when the engine is restarted, when the predetermined condition is satisfied, for example, when the piston stop position is not within the proper stop range R, or when the engine rotation speed is increased by the predetermined time after the start. You may make it perform control accompanied by the assist by a starter motor, when it does not reach a predetermined value.

1 is a schematic cross-sectional view of an engine provided with a starter according to the present invention. 1 schematically shows an intake manifold provided with an intake passage volume varying means, wherein (A) is a longitudinal sectional view, (B) is a sectional view taken along line 2B-2B, and (C) is a sectional view taken along line 2C-2C. is there. FIG. 2 schematically shows an intake manifold provided with intake passage volume varying means in a case where the switching valve and the shutter valve are in a state different from that in FIG. 2, wherein (A) is a longitudinal sectional view and (B) is 3B. -3B sectional view, (C) is a 3C-3C sectional view. It is explanatory drawing which shows the relationship between the piston stop position and air quantity of the cylinder which becomes an expansion stroke and a compression stroke at the time of an engine stop. It is a time chart which shows the change state etc. of various control amounts at the time of an engine stop. It is a flowchart which shows the first half of the engine automatic stop control operation. It is a flowchart which shows the middle part of an engine automatic stop control operation | movement. It is a flowchart which shows the second half part of the engine automatic stop control operation. It is a flowchart which shows the first half part of the control action at the time of engine restart. It is a flowchart which shows the middle part of control action at the time of engine restart. It is a flowchart which shows the latter half part of the control action at the time of engine restart. It is a graph which shows an engine torque at the time of switching an intake passage volume according to an engine speed.

Explanation of symbols

1 Engine body 2 ECU (automatic stop control means)
13 Piston 16 Fuel Injection Valve 23 Throttle Valve 54 Switching Valve 55 Shutter Valve

Claims (6)

When the preset engine automatic stop condition is satisfied, the fuel supply is stopped to automatically stop the engine, and when the engine restart condition in the automatic stop state is satisfied, at least in the expansion stroke An engine starter configured to automatically restart an engine by causing combustion in an automatically stopped cylinder,
A throttle valve that is provided in the intake passage and adjusts the intake flow amount;
An intake passage volume variable means for changing the intake passage volume downstream of the throttle valve;
Automatic stop control means for controlling the automatic stop of the engine,
The engine start device according to claim 1, wherein the automatic stop control means operates the intake passage volume varying means in a state where the intake passage volume decreases during an automatic stop operation period after the automatic stop condition is satisfied. The engine starting device according to claim 1, wherein
The automatic stop control means has a throttle valve at a predetermined time during the automatic stop operation period so that the intake air amount of the cylinder that becomes the compression stroke when the engine is stopped is smaller than the intake air amount of the cylinder that becomes the expansion stroke when the engine is stopped. And starting the intake passage volume variable means so as to reduce the intake passage volume before the closing timing of the throttle valve. The engine starting device according to claim 2,
The automatic stop control means operates the intake passage volume variable means to a state where the intake passage volume decreases within a predetermined period until a time near the third piston top dead center before the engine stops. The engine starter. The engine starting device according to claim 2 or 3,
The automatic stop control means opens the throttle valve for scavenging after the automatic stop condition is satisfied, and operates the intake passage volume varying means to a state where the intake passage volume decreases after the throttle valve is opened. An engine starter characterized in that The engine starter according to claim 4, wherein
The engine start device according to claim 1, wherein the automatic stop control means opens the throttle valve for scavenging after the automatic stop condition is established before the fuel supply is stopped. The engine starting device according to any one of claims 1 to 5,
The automatic stop control means controls the automatic stop of the engine while maintaining the drive state of the automatic transmission when the automatic transmission connected to the engine is in the drive state when the automatic stop condition is satisfied. The engine starting device.

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