JP2005337185A - Engine starter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stop a piston at a proper position when an engine stops automatically while increasing reacceleration performance to restart the engine securely. <P>SOLUTION: This engine starter is constituted to stop the engine automatically when automatic stop conditions set in advance of the engine are satisfied and restart the engine automatically when restart conditions of the engine are satisfied. This engine starter is provided with an automatic stop control means 43 for detecting a speed ratio being a ratio of rotation speed of the engine to rotation speed of a turbine and a power generation current control means 46 and a gear shift means 47 for receiving output from the automatic stop control means 43 and adjusting load acting on the engine large or small. This automatic stop control means 43 and the power generation current control means 47 adjust engine load to a smaller value relatively when the speed ratio detected by the automatic stop control means 43 is less than 1 when compared with a case where the speed ratio is 1 or more. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an engine starting device, and when an engine automatic stop condition set in advance in an engine idling state or the like is satisfied, the engine is automatically stopped and a restart condition is satisfied in this state. The present invention relates to an engine starter configured to automatically restart the engine.

In recent years, in order to reduce fuel consumption and reduce CO ₂ emissions, a restart condition has been established such that the engine is automatically stopped temporarily during idling and the vehicle is then started by the driver. At the time, 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 idling stop control requires a quickness to start the engine immediately in accordance with the start operation of the vehicle, etc., but the output of the engine by a starter motor which has been 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 the cylinder that is in the stopped state in the expansion stroke as described above is inappropriate, for example, when the piston is stopped at a position very close to top dead center or bottom dead center, There is a possibility that the engine cannot be started normally due to the fact that the amount of air is so small that combustion energy cannot be obtained sufficiently or the stroke of the combustion energy acting on the piston is too short.

As a countermeasure against such a problem, for example, as shown in Patent Document 1 below, a braking device is provided for the crankshaft of the engine, and the piston of the cylinder that is stopped in the expansion stroke stops at an appropriate position during the stroke. If it is determined that the engine automatic stop condition is satisfied, as shown in Patent Document 2 below, the lean air-fuel ratio injection mode is selected and the intake pressure is increased as shown in Patent Document 2 below. The compression pressure is increased so that the piston of the cylinder that is stopped in the expansion stroke can be stopped at a predetermined position.
Japanese Utility Model Publication No. 60-128975 JP 2001-173473 A

  By the way, the vehicle includes an automatic transmission mechanism that can be switched to a plurality of ranges including a neutral state in which transmission of driving force to the wheel side is disconnected and a driving state in which driving force can be transmitted to the wheel side. In addition, there is a so-called automatic vehicle, and in such an automatic vehicle, as in Patent Document 1 and Patent Document 2 described above, the rotational speed of the engine is adjusted only by the crank angle sensor so that the piston stop position is within an appropriate range. When the automatic transmission mechanism is in the drive state, when the vehicle decelerates or stops, force such as driving force or resistance force is transmitted from the wheel side to the crankshaft when the vehicle is decelerated, and the degree of decrease in engine speed is not stable. Therefore, it is desirable that the automatic transmission control is performed by setting the automatic transmission mechanism to the neutral state. However, there are cases where the vehicle is reaccelerated at the time of deceleration or immediately after stopping depending on the road conditions or the like. In such a case, if the automatic transmission mechanism is in the neutral state, it is difficult to quickly reaccelerate.

  In view of the above circumstances, the present invention provides an engine starter capable of reliably restarting an engine by stopping a piston at an appropriate position when the engine is automatically stopped with a simple configuration while improving reacceleration performance. Is.

  The engine starter according to the present invention stops the fuel supply to the engine automatically when the preset automatic engine stop condition is satisfied, and automatically stops the engine in the automatic stop state. An automatic transmission having a torque converter that is configured to automatically restart the engine by injecting fuel into a cylinder that has been automatically stopped at least during the expansion stroke to cause ignition and combustion when the restart condition is satisfied. A starter for an engine mounted on a vehicle with a mechanism, wherein a speed ratio detecting means for detecting a speed ratio that is a ratio of a turbine speed of a torque converter to a speed of the engine, and a load acting on the engine are adjusted in magnitude Load adjusting means, and this load adjusting means is in the automatic stop operation period of the engine after the fuel supply is stopped. When the speed ratio detected by the speed ratio detecting means is smaller than a predetermined reference value, the piston is suitable for restarting the engine by adjusting the engine load relatively smaller than when it is large. Control is performed so as to stop within an appropriate range.

  According to the present invention, instead of executing the automatic engine stop based only on the engine rotation speed in order to stop the piston in an appropriate range, the turbine rotation speed with respect to the engine rotation speed detected by the speed ratio detection means. Since the engine is automatically stopped based on the speed ratio (turbine rotational speed / engine rotational speed), the automatic transmission mechanism is set in a drive state in which the driving force can be transmitted to the wheels, for example. Even in this case, it is possible to take into account the degree of change in the engine rotation speed due to the resistance force or the like corresponding to the speed ratio. In addition, when the engine is automatically stopped, when the speed ratio detected by the speed ratio detecting means is smaller than a predetermined reference value, the engine load is adjusted relatively smaller than when the speed ratio is large. The engine speed can be adjusted by adjusting the load on the engine in consideration of the degree of decrease in the engine speed, not only in the neutral state but also in the drive state, and the piston can be adjusted within a proper range with a high probability. Can be stopped within. In addition, if the automatic transmission mechanism is set to the drive state during the automatic stop operation period of the engine, the responsiveness to the reacceleration request of the vehicle can be improved.

  The specific configuration of the load adjusting means is not particularly limited. For example, the load adjusting means is switched between a neutral state where transmission of driving force to the wheel side is disconnected and a driving state where transmission of driving force to the wheel side is possible. When the speed ratio detected by the speed ratio detection means is greater than or equal to the reference value, the automatic speed change mechanism is set to the drive state and the speed ratio is less than the reference value. Is configured to set the automatic transmission mechanism to a neutral state, and it is preferable that 1 or a value close to 1 is set as the predetermined reference value.

  According to this configuration, it is possible to selectively adjust the engine load using an automatic transmission mechanism mounted on a so-called automatic vehicle, and to stop the piston within an appropriate range with a simple configuration. it can. When the speed ratio is greater than or equal to the reference value (1 or a value close to 1), the automatic transmission mechanism is set to the drive state, and when the speed ratio is less than the reference value, the automatic transmission mechanism is set to neutral. The automatic transmission mechanism is set to the drive state as much as possible to improve the reacceleration performance. On the other hand, when the engine load is large and the degree of decrease in the rotational speed is large, the automatic transmission mechanism is neutral. The load acting as a state is reduced, and the degree of decrease is reduced to prevent a decrease in the number of strokes of the piston until the engine is stopped, whereby the piston can be stopped within an appropriate range. In addition, since the automatic transmission mechanism is in the neutral state to prevent the number of strokes of the piston from being reduced, scavenging performance can be improved, and thereby the fresh air can be taken in and the engine can be restarted reliably. .

  Here, the predetermined reference value is set to 1 or a value close to 1 when the speed ratio is 1 or more, because the turbine rotational speed is equal to or higher than the engine rotational speed, the load acting on the engine. On the contrary, when the speed ratio is less than 1, the turbine rotational speed is smaller than the engine rotational speed, so the load acting on the engine is considered to be large. This is because the acting load is adjusted by the load by the load adjusting means to stop the piston within an appropriate range.

  On the other hand, the load adjusting means includes an alternator driven by the engine instead of or in addition to the above specific configuration, and when the speed ratio detected by the speed ratio detecting means is smaller than the predetermined reference value It is preferable that the target generated current by the alternator is made lower than that when it is high (Claim 3). In this case, the predetermined reference value may be a predetermined value (for example, a value close to 1 to 1), or the speed ratio is detected at least twice by the speed ratio detecting means during the automatic stop operation period. It is good also as a value detected at the time of this last detection by constituting so that it may detect.

  If comprised in this way, an engine load can be finely adjusted using an alternator, and a piston can be stopped within an appropriate range with a simple construction. Further, when the speed ratio detected by the speed ratio detecting means is smaller than the predetermined reference value, the target power generation current by the alternator is reduced, so that the automatic transmission mechanism remains in the drive state. When the load acting on the engine is large and the degree of decrease in the rotation speed is large, the target generator current of the alternator is lowered to reduce the load and the degree of decrease described above. Is reduced to prevent the number of strokes of the piston from being reduced until the engine is stopped, whereby the piston can be stopped within an appropriate range. Moreover, since the target power generation current of the alternator is reduced to prevent the number of strokes of the piston from being reduced, scavenging performance can be improved, and the engine can be reliably restarted.

  In this case, the load adjusting unit sets the target generated current of the alternator according to the speed ratio detected by the speed ratio detecting unit after setting the target generated current by the alternator to a predetermined value after the fuel supply is stopped. It is preferable to adjust (claim 4).

  According to this configuration, the target generated current of the alternator is once set to a predetermined value (for example, a relatively high value) by the load adjusting means. Therefore, the load adjustment by the load adjustment means can be executed reliably, and the engine rotation speed can be adjusted quickly and accurately by the load adjustment means.

  On the other hand, another engine starter according to the present invention stops the fuel supply to the engine and automatically stops the engine when a preset engine automatic stop condition is satisfied. The engine is automatically restarted by injecting fuel into at least a cylinder that has been automatically stopped during the expansion stroke to cause ignition and combustion when the engine restart condition is satisfied. An engine starter mounted on a vehicle with an automatic transmission mechanism having an automatic shift mechanism for automatically setting the engine rotation speed when stopping fuel injection when the engine is stopped to a value higher than a normal idle rotation speed A speed ratio for detecting a speed ratio, which is a ratio of the turbine speed of the torque converter to the engine speed and the stop control means. And an automatic stop control means for controlling the fuel supply with respect to the case where the speed ratio detected by the speed ratio detection means before the stop of the fuel supply is smaller than a predetermined reference value. The engine rotation speed before the stop is set to a higher value (claim 5).

  In this case, the automatic stop control means is preferably set to 1 or a value close to 1 as the predetermined reference value.

  According to this invention, in order to stop the piston within an appropriate range, the engine is not automatically stopped based only on the engine rotation speed, but the ratio of the turbine rotation speed to the engine rotation speed is determined by the speed ratio detection means. Since the engine is automatically stopped based on a certain speed ratio (turbine rotational speed / engine rotational speed), for example, even when the automatic transmission mechanism is set in a drive state in which the driving force can be transmitted to the wheels. The degree of change in the engine speed due to the resistance force according to the speed ratio can be taken into account, and the engine speed can be adjusted by adjusting the load on the engine in consideration of the degree of decrease. In addition, when the engine is automatically stopped, the automatic stop control means performs the above operation when the speed ratio detected by the speed ratio detection means before the fuel supply is stopped is smaller than a predetermined reference value. Since the engine speed before stopping fuel supply is set to a higher value, the automatic transmission mechanism is in the neutral state by adjusting the number of piston strokes during the automatic stop operation period when the fuel supply is stopped. The piston can be stopped within an appropriate range with high probability not only in the case of being in the drive state but also in the drive state. In addition, if the automatic transmission mechanism is set to the drive state during the automatic stop operation period of the engine, the responsiveness to the reacceleration request of the vehicle can be improved.

  According to this invention, not only the engine speed but also the degree of decrease thereof is taken into account, and the engine speed is adjusted by the load adjusting means to execute the automatic engine stop. Even when the drive state is set so that the rotational speed tends to become unstable, the rotational speed of the engine can be adjusted in consideration of the degree of decrease, and the piston can be stopped at a position suitable for restart with high probability. There is an advantage that you can.

  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 four cylinders 12A to 12D, and a piston 13 connected to the crankshaft 3 is fitted into each of the cylinders 12A to 12D so that a combustion chamber 14 is provided above the cylinder 13. Is formed.

  A spark 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. 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 operating mechanism having a camshaft (not shown), so that each cylinder 12A to 12D performs a combustion cycle with a predetermined phase difference. The opening / closing timings of the 12D intake / exhaust valves 19, 20 are set.

  An intake passage 21 and an exhaust passage 22 are connected to the intake port 17 and the exhaust port 18. As shown in FIG. 2, the downstream side of the intake passage 21 close to the intake port 17 is an independent branch intake passage 21a corresponding to each of the cylinders 12A to 12D. The upstream ends of the branch intake passages 21a are respectively It communicates with the surge tank 21b. A common intake passage 21c is provided upstream of the surge tank 21b, and an intake flow rate adjusting means including a throttle valve 23 driven by an actuator 24 is disposed in the common intake passage 21c. 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.

  Further, an exhaust gas purification catalyst 37 is disposed downstream of the collection portion of the exhaust passage 22 where exhaust from each of the cylinders 12A to 12D collects. The exhaust gas purification catalyst 37 is formed of, for example, a so-called three-way catalyst in which the purification rate of HC, CO and NOx is extremely high when the air-fuel ratio of the exhaust is in the vicinity of the theoretical air-fuel ratio, and the oxygen concentration in the exhaust gas Has an oxygen storage capacity for storing it in a relatively high oxygen-excess atmosphere, and releases the stored oxygen to react with HC, CO, etc. when the oxygen concentration is relatively low. The exhaust gas purification catalyst 37 is not limited to a three-way catalyst, and may be any catalyst that has the above-described oxygen storage capability. For example, the exhaust gas purification catalyst 37 is a so-called lean NOx catalyst that can purify NOx even in an oxygen-excess atmosphere. Also good.

  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.

  Also, a cam angle sensor 32 for detecting a specific rotational position for cylinder identification provided on the camshaft, a water temperature sensor 33 for detecting the coolant temperature of the engine, and an accelerator opening corresponding to the accelerator operation amount of the driver. Each detection signal output from the accelerator sensor 34 to be detected and the brake sensor 35 to detect that the driver has performed a brake operation is input to the ECU 2.

  Further, as shown in FIG. 3, the engine is connected to an automatic transmission mechanism 50 through a crankshaft 3 as an output shaft thereof. The automatic transmission mechanism 50 includes a torque converter 51 connected to the crankshaft 3 and a multi-stage transmission mechanism 52 connected to a turbine shaft 59 that is an output shaft of the torque converter 51. By switching between a plurality of included frictional engagement elements, it is possible to switch to a plurality of ranges including a neutral state where transmission of driving force to the wheel side is cut off and a driving state where transmission of driving force to the wheel side is possible, In addition, it is configured to be capable of multi-stage shifting in the drive state.

  The torque converter 51 includes a pump cover 53 connected to the crankshaft 3, a pump impeller 54 (torque converter input side) formed integrally with the pump cover 53, and a turbine runner installed so as to face the pump impeller 54. 55 (torque converter output side), and a stator 58 attached to a case 57 via a one-way clutch 56 therebetween. A turbine shaft 59 serving as an output shaft of the torque converter 51 is connected to the turbine runner 55. The space in the pump cover 53 is filled with oil as a working fluid, and the driving force of the pump impeller 54 is transmitted to the turbine runner 55 via the working oil. A turbine runner rotation sensor 36 is provided in the vicinity of the turbine runner 55, and the rotation sensor 36 is configured to transmit the rotational speed of the turbine runner 55 to the ECU 2.

  The torque converter 51 is further provided with a lock-up clutch 64 interposed between the pump cover 53 and the turbine runner 55 and directly connecting the crankshaft 3 and the turbine runner 55 via the cover 53. . This lock-up clutch 64 is connected to an oil pump or the like (not shown) via a hydraulic control circuit (not shown). The oil passage is switched to switch between a lock-up state and an unlock-up state.

  On the other hand, the multi-stage transmission mechanism 52 includes first and second planetary gear mechanisms 65 and 66 and a plurality of frictional engagement elements 67 to 72 such as clutches and brakes for switching a power transmission path including the planetary gear mechanisms 65 and 66. In addition, the frictional engagement elements 67 to 72 are appropriately connected and switched to a drive state of a plurality of stages such as a neutral state, a reverse speed, and a plurality of stages of forward speed.

  The frictional engagement element includes a forward clutch 67 interposed between the turbine shaft 59 and the sun gear of the first planetary gear mechanism 65, and a river interposed between the turbine shaft 59 and the sun gear of the second planetary gear mechanism 66. The scratch 68, the 3-4 clutch 69 interposed between the turbine shaft 59 and the carrier of the second planetary gear mechanism 66, the 2-4 brake 70 for fixing the sun gear of the second planetary gear mechanism 66, and these planets A power transmission path including a low reverse brake 71 and a one-way clutch 72 that are interposed in parallel between the gear mechanisms 65 and 66 and the case 57, and these frictional engagement elements 67 to 72 are intermittently connected to the output gear 73. Has been changed or cut off. As the output gear 73 rotates, the driving force is transmitted to the left and right axles 78 and 79 via the wheels, that is, through the transmission gears 74, 75 and 76 and the differential mechanism 77.

  In principle, the automatic transmission mechanism 50 switches between a neutral state, a drive state, and the like based on a shift lever provided in a driver's seat (not shown). In this embodiment, the shift lever is in the drive state range. Even in some cases, the ECU 2 can automatically switch to the neutral state during a predetermined period of the automatic engine stop or automatic restart period. Here, the neutral state means a state in which the transmission of the driving force to the wheel side is disconnected, and in this state, at least both the forward clutch 67 and the reverse clutch 68 are disconnected. The drive state refers to a state in which the driving force can be transmitted to the wheel side. In this state, at least one of the forward clutch 67 and the reverse clutch 68 is engaged. In the present embodiment, when the automatic transmission mechanism 50 is in the neutral state, all the frictional engagement elements 67 to 72 including the lockup clutch 64 are set in a disconnected state and act on the crankshaft 3. The rotational resistance is reduced.

  On the other hand, the ECU 2 receives detection signals from the sensors 25, 26, 30 to 36, outputs a control signal for controlling the fuel injection amount and injection timing to the fuel injection valve 16, and performs ignition. By controlling the ignition timing with respect to the ignition device 27 attached to the plug 15, the combustion control means 41 for executing the combustion control corresponding to the operating state of the engine and the actuator 24 of the throttle valve 23 to open the throttle. An intake flow rate control means 42 for controlling the intake flow rate by outputting a control signal for controlling the degree of fuel, and predetermined fuel injection to each cylinder 12A to 12D when a predetermined automatic engine stop condition is satisfied Stops at the timing (fuel cut), automatically stops the engine, and then restarts when the driver performs an accelerator operation, etc. The automatic stop control means 43 for executing control for automatically restarting the engine when the dynamic condition is satisfied, the generated current control means 46 for setting the target generated current of the alternator 28, and the multi-stage transmission mechanism 52 in the neutral state. Shift control means 47 having a function of switching between drive states is provided. The generated current control means 46 and the shift control means 47 receive the output from the automatic stop control means 43 and change the target generated current by the alternator 28 or switch the multi-stage transmission mechanism 52 between the neutral state and the drive state. To adjust the load on the engine. That is, the automatic stop control means 43, the generated current control means 46, and the shift control means 47 correspond to the load adjustment means in the claims of this application.

  The automatic stop control means 43 automatically stops the engine by stopping fuel supply or the like when the predetermined engine stop condition is satisfied at the time of deceleration for stopping or idling when the vehicle is stopped. When established, the engine is automatically restarted. When the engine is restarted, the automatic stop control means 43 of the present embodiment first executes the initial combustion on the compression stroke cylinder when the engine is stopped to push down the piston, and the cylinder pressure is increased by raising the piston of the cylinder in the expansion stroke. The fuel is injected into the expansion stroke cylinder to perform ignition and combustion, and combustion air is present in the combustion chamber after the initial combustion in the compression stroke cylinder. Is supplied at an appropriate time after the initial combustion, so that the cylinder is controlled to re-combust when the piston goes up and the compression top dead center is exceeded. ing. That is, at the time of automatic restart of the engine, if the piston stop position is in an appropriate range, which will be described later, control is performed so that the engine is temporarily reversely operated at the initial stage of the start, and thereafter, the normal rotation is started.

  In order to properly restart the engine by igniting the fuel injected into a specific cylinder without using a restart motor in principle as described above, the air-fuel mixture in the expansion stroke cylinder is combusted. Thus, it is necessary to ensure sufficient combustion energy and to make the cylinder that reaches the compression top dead center 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 where the piston 13 is in the middle of the expansion stroke when the engine is automatically stopped.

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

  In contrast, the center of the stroke of the expansion stroke cylinder, that is, a predetermined range slightly lower than the position where the crank angle after compression top dead center is 90 ° CA, for example, the crank angle after compression top dead center is 100 If the piston 13 can be stopped within an appropriate range R of ° to 120 ° CA, a predetermined amount of air is secured in the compression stroke cylinder, and the crankshaft 3 can be slightly reversed by the initial combustion. 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, the automatic stop control means 43 provided in the ECU 2 controls the intake flow rate control means 42, the generated current control means 46 and the shift control means 47 to stop the piston 13 within the appropriate range R. .

  That is, as shown in FIG. 5, the automatic stop control means 43 has a target engine speed higher than the normal idle speed when the engine is not automatically stopped at the time t0 when the engine automatic stop condition is satisfied. Executes control to stabilize by setting to a value. For example, in an engine in which the normal idle rotation speed is set to 650 rpm (the multi-stage transmission mechanism 52 is in the drive state), when the multi-stage transmission mechanism 52 is switched to the neutral state and the engine is automatically stopped (shown by a solid line in FIG. 5). ), By setting the target rotational speed to about 810 rpm (the multi-stage transmission mechanism 52 is in the neutral state), the engine rotational speed Ne is controlled at a rotational speed slightly higher than the normal idle rotational speed, and the engine is executed. The fuel injection is stopped at the time t1 when the rotational speed Ne of the engine is stabilized at the target rotational speed, and the rotational speed Ne of the engine is decreased.

  When the multi-stage speed change mechanism 52 is in the neutral state when the engine is automatically stopped as described above, the engine rotation speed is stabilized, and therefore the intake flow rate control means 42 and the generated current control means are based only on the engine rotation speed. By controlling 46, the rotational speed of the engine can be adjusted and the piston 13 can be stopped in the appropriate range R with high probability.

  Here, when the multi-stage transmission mechanism 52 is in the neutral state, the external load acting on the engine is smaller than in the drive state, so the engine speed is relatively stable as described above. When the vehicle is reaccelerated, etc., the multi-stage transmission mechanism 52 must be switched from the neutral state to the driving state, which is inferior in responsiveness to the accelerator pedal operation by the occupant, and there is room for improvement in this respect.

  Therefore, in the apparatus of the present embodiment, the multi-stage speed change mechanism 52 is maintained in the drive state when the fuel stop at the time of deceleration is executed in which the fuel supply is stopped when the vehicle is decelerated in order to prevent the generation of the rich mixture. The engine is automatically stopped using this fuel injection stop during deceleration (FC during deceleration), that is, without returning fuel injection from the FC during deceleration. In this case, since the multi-stage transmission mechanism 52 is in the drive state and the drive transmission path is connected to the crankshaft 3 from the axles 78 and 79 side, the rotational speed of the engine is unstable, that is, the degree of engine decrease is the multi-stage transmission mechanism 52. However, in this apparatus, the automatic stop control means 43 includes the crank angle sensors 30 and 31, and the turbine runner rotation sensor 36. , The speed ratio α (= Te / Ne), which is the ratio of the rotational speed Te of the turbine runner 55 to the engine rotational speed Ne (the rotational speed of the crankshaft 3), is detected, and this detected speed ratio is detected. The generated current control means 46 and the shift control means 47 are controlled depending on whether α is greater than or less than a predetermined reference value (1 in the present embodiment). Thus, the load on the engine is adjusted, so that the influence of the external load acting from the axles 78, 79, etc. is absorbed, and the piston 13 is configured to stop in the appropriate range R with high probability. That is, the automatic stop control means 43 includes the speed ratio detection means described in the claims. In FIG. 5, a time chart showing a change state of the engine speed when the multi-stage transmission mechanism 52 is set to the neutral state is shown by a solid line, the multi-stage transmission mechanism 52 is set to the drive state, and the speed A time chart showing a change state of the rotational speed of the engine when the ratio α is less than 1 is indicated by a dotted line. Therefore, the degree of decrease in the engine rotation speed is larger than that in the neutral state.

  This automatic engine stop control will be specifically described first when the multi-stage transmission mechanism 52 is set to the neutral state, and then specifically described when the multi-stage transmission mechanism 52 is set to the drive state. .

  That is, as shown in FIG. 6, the opening K of the throttle valve 23 is increased to, for example, about 30% of full opening at the fuel injection stop time t1, which is the initial stage of the control operation for automatically stopping the engine. By increasing the boost pressure (intake pressure) Bt, the intake air flow sucked into each of the engine cylinders 12A to 12D is set to a state larger by a predetermined amount than the minimum intake air flow required for continuing the engine operation. Then, control for ensuring the scavenging performance of each of the cylinders 12A to 12D is executed in the intake flow rate control means 42, and the target power generation current Ge of the alternator 28 is set at the time when the automatic stop condition is satisfied at the fuel injection stop time t1. The rotational resistance of the crankshaft 3 is reduced by lowering than t0 (indicated by a dotted line in FIG. 6), and preferably by reducing the generated current to 0 (indicated by a solid line in FIG. 6). Control is configured to run in the power generation current control means 46 that.

  Further, when the combustion injection is stopped at the time point t1, the throttle valve 23 is turned off at the time point t2 when it is confirmed that the engine rotational speed Ne has decreased to a preset reference speed N2 (for example, 790 rpm) or less. Close. From the time t2 when the throttle valve 23 is closed, the boost pressure Bt starts to decrease, and the intake flow rate introduced into the cylinders 12A to 12D of the engine decreases, and from the opening time t1 to the closing time t2 of the throttle valve 23. The air introduced into the common intake passage 21c passes through the surge tank 21b and the branch intake passage 21a, and thereby reaches the intake stroke of the fourth cylinder 12D, the second cylinder 12B, the first cylinder 12A, and the third cylinder 12C. Introduced in sequence with a predetermined transport delay. By setting the opening time t1 and the closing time t2 of the throttle valve 23 at appropriate times in consideration of the transport delay of the intake air, the expansion stroke is made more than the third cylinder 12C that is in the compression stroke when the engine is stopped. More air is introduced into the first cylinder 12A.

  Next, the target power generation current Ge of the alternator 28 is temporarily increased at the time t2, and the target power generation of the alternator 28 is performed at the time t3 when the engine top dead center rotational speed ne is within a predetermined range as described later. By adjusting the current Ge to a value corresponding only to the engine rotational speed Ne, control is performed to decrease the engine rotational speed Ne along a reference line set based on the results of experiments performed in advance. Has been.

  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, and in a 4-cylinder 4-cycle engine, it stops after reaching the compression top dead center of about 10 times. Specifically, as shown in FIG. 6, after the engine rotational speed Ne has temporarily dropped each time the cylinders 12 </ b> A to 12 </ b> D reach compression top dead center, they are again displayed when the compression top dead center is exceeded. The engine rotation speed Ne gradually decreases while repeating up and down.

  In the cylinder 12C that reaches the compression top dead center after the time t5 when the last compression 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 compression reaction force causes the piston to 13 is pushed back, and the crankshaft 3 is reversely rotated. Due to the reverse rotation of the crankshaft 3, the air pressure of the expansion stroke cylinder 12 </ b> A that becomes the expansion stroke when the engine is stopped increases, so that the piston 13 of the expansion stroke cylinder 12 </ b> A is pushed back toward the bottom dead center according to the compression reaction force. Thus, the crankshaft 3 starts to rotate forward again, and the reverse rotation and forward rotation of the crankshaft 3 are repeated several times to stop the piston 13 after reciprocating. The stop position of the piston 13 is substantially determined by the balance of the compression reaction force in the compression stroke cylinder 12C and the expansion stroke cylinder 12A, and is influenced by the frictional resistance of the engine and exceeds the last compression top dead center. It also changes depending on the rotational inertia of the engine at the time t5, that is, the level of the engine rotational speed Ne.

  As described above, in order to stop the piston 13 of the expansion stroke cylinder 12A in the expansion stroke within the appropriate range R suitable for restart when the engine automatically stops, first, the expansion stroke cylinder 12A and the compression stroke cylinder The intake flow rates for both cylinders 12A and 12C are adjusted so that the compression reaction force of 12C is sufficiently large and the compression reaction force of the expansion stroke cylinder 12A is larger than the compression reaction force of the compression stroke cylinder 12C by a predetermined value or more. There is a need to. For this reason, in this embodiment, the opening K of the throttle valve 23 is set to a large value at the time t1 when the fuel injection is stopped, and the throttle valve 23 is closed to reduce the opening K at the subsequent time t2. Thus, the intake air amount is adjusted.

  Here, in an actual engine, there are individual differences in the intake passage, such as the throttle valve 23 and the intake port 17, and the behavior of the air flowing through the passage changes, so that the intake flow rate varies, as described above. Even if the opening / closing control of the throttle valve 23 is performed, the piston stop position may deviate from the appropriate range R. In this regard, in the present embodiment, when the rotational speed of the engine decreases during the automatic engine stop operation period, as shown in an example in FIG. 7, each cylinder 12A to 12D passes the compression top dead center. Note that there is a clear correlation between the engine rotation speed (top dead center rotation speed) ne and the piston stop position of the cylinder in the expansion stroke at the time of engine stop, and the time t1 when the fuel injection is stopped After that, in the process in which the engine rotational speed Ne decreases, the engine rotational speed when the piston 13 of each cylinder passes through the compression top dead center, that is, the top dead center rotational speed ne is detected, and this top dead center rotational speed is detected. By controlling the target generated current of the alternator 28 according to the detected value of ne, the rotational resistance of the crankshaft 3 is adjusted to adjust the degree of decrease in the engine rotational speed Ne. So that fit with high probability the down stop position within the proper range R.

  That is, FIG. 7 shows that when the multi-stage speed change mechanism 52 is in the neutral state, the fuel injection is stopped at the time t1 when the engine rotational speed Ne becomes a predetermined speed as described above, and the throttle valve is continuously operated for a predetermined period thereafter. 23, the top dead center rotational speed ne when the piston 13 provided in each cylinder 12A to 12D of the engine rotating due to inertia passes through the compression top dead center so as to maintain the valve open state, The piston position of the expansion stroke cylinder 12A at the time when the engine is stopped is examined, the piston position is taken on the vertical axis, and the top dead center rotational speed ne is taken on the horizontal axis, and the relationship between the two is graphed. is there. By repeating this operation, a distribution map showing the correlation between the top dead center rotational speed ne during the engine stop operation period and the piston stop position in the expansion stroke cylinder 12A is obtained.

  From the above distribution diagram, a predetermined correlation is found between the top dead center rotational speed ne during the engine stop operation period and the piston stop position in the expansion stroke cylinder 12A. In the example shown in FIG. 7, the engine is stopped. If the top dead center rotational speed ne at the sixth to second before the state is within the range indicated by hatching, the stop position of the piston 13 is within a range R suitable for restarting the engine (after the compression top dead center). 100 ° to 120 ° CA). Particularly, regarding the second top dead center rotational speed ne before the engine is stopped, the top dead center rotational speed ne is within the range of about 280 rpm to 380 rpm as shown in FIG. On the low rotation side below 320 rpm, the piston stop position gradually changes closer to the top dead center as the top dead center rotation speed ne decreases. On the other hand, on the high rotation side where the top dead center rotational speed ne is 320 rpm or higher, the stop position of the piston 13 becomes substantially constant and falls within the substantially appropriate range R regardless of the top dead center rotational speed ne. I understand. Therefore, the automatic stop control means 43 adjusts the target generated current by the generated current control means 46 so that the top dead center rotational speed ne is within the hatching in the figure, and the top dead center until the engine is stopped as necessary. The number of point passes is thinned so that the piston 13 falls within the appropriate range R with a high probability.

  On the other hand, the automatic stop control of the engine by the automatic stop control means 43 when the multi-stage transmission mechanism 52 is set to the drive state is basically the same as when the neutral state is set, but the turbine rotational speed is set. The influence of the external load is detected by detecting the speed ratio α taking into account Te, and the load of the engine is adjusted by the generated current control means 46 and the shift control means 47 based on the speed ratio α. It is configured to offset the effects of. The adjustment of the opening degree K of the throttle valve 23 is the same as that in the neutral state, and the description thereof is omitted here.

  That is, as shown in FIGS. 8A and 8B, the target generated current Ge of the alternator 28 is lowered from the time t0 when the automatic stop condition is satisfied at the fuel injection stop time t1 (shown by a dotted line in FIG. 8). ) Preferably, the generated current is set to 0 (indicated by a solid line in FIG. 8) so that the generated current control means 46 performs control for reducing the rotational resistance of the crankshaft 3.

  Also, from the fuel injection stop time t1 to the time t2 when it is confirmed that the engine rotational speed Ne has dropped below a preset reference speed N2 (for example, 790 rpm) due to the stop of the combustion injection. In addition, the automatic stop control means 43 detects the speed ratio α, and the automatic stop control means 43 is configured to control the shift control means 47 based on the speed ratio α. That is, the automatic stop control means 43 detects the engine rotational speed Ne and the turbine rotational speed Te from the crank angle sensors 30 and 31 and the turbine runner rotation sensor 36, and the automatic stop control means 43 detects the speed from the rotational speeds Ne and Te. It is configured to detect the ratio α. When the speed ratio α detected by the automatic stop control unit 43 is equal to or greater than a predetermined reference value, here, 1 or greater, the shift control unit 47 is set so as to maintain the multi-stage transmission mechanism 52 in the drive state. On the other hand, when the speed ratio α is less than 1, the shift control means 47 is controlled to switch the multi-stage transmission mechanism 52 from the drive state to the neutral state.

  That is, when the speed ratio α is less than 1, the rotational speed Te of the turbine runner 55 is slower than the rotational speed of the crankshaft 3 (engine rotational speed Ne), so that an external load is generated on the engine. Accordingly, the external load acting on the engine is reduced by setting the multi-stage transmission mechanism 52 to the neutral state. On the other hand, when the speed ratio is 1 or more, the rotational speed Te of the turbine runner 55 is faster than the rotational speed of the crankshaft 3, so that when the low reverse brake 71 is ON, the rotation of the turbine runner 55 is reversed. When the crankshaft 3 is in a state of being rotated by the engine, or an external load is hardly applied to the engine, and therefore when the re-acceleration request is made by setting the multi-stage transmission mechanism 52 to the drive state, It is configured to be able to accelerate.

  Next, by stopping the combustion injection at the time point t1, the generation current control means 46 at the time point t2 when it is confirmed that the rotational speed Ne of the engine has decreased below a preset reference speed N2 (for example, 790 rpm). Thus, the target generated current Ge of the alternator 28 is temporarily increased. At this time, the value after the increase of the target generated current Ge of the alternator 28 is determined by the automatic stop control means 43.

  That is, the automatic stop control means 43 sets the target generated current Ge to a predetermined value G01 (80A in the present embodiment) when the detected speed ratio α is equal to or greater than a predetermined reference value, here 1 or more. On the other hand, when the speed ratio α is less than 1, the target generated current Ge is set to a value G02 (60A in this embodiment) smaller than a predetermined value G01. In this embodiment, when the speed ratio α is less than 1 from the fuel injection stop time t1 to the confirmation time t2, the neutral state is set, and therefore the multi-stage transmission mechanism 52 is in the drive state. In addition, the target generated current Ge by the alternator 28 is set to a predetermined value G01, and the target generated current Ge is set to a value G02 lower than the predetermined value G01 when in the neutral state.

  Here, in FIG. 9, the horizontal axis indicates the number of times of passing through the compression top dead center until the piston stops, the vertical axis indicates the top dead center rotational speed ne, and the piston 13 is stopped within the appropriate range R with high probability. The appropriate range r of the top dead center rotation speed ne that can be generated is shown for each of the cases where the speed ratio α is larger and smaller than a predetermined reference value (1 in the present embodiment). In this figure, the range indicated by diagonal lines indicates the appropriate range of the top dead center rotational speed ne when the speed ratio α is small, and the range indicated by dots indicates the appropriate range of the top dead center rotational speed ne when the speed ratio α is large. Show. As described above, the engine is stopped after the fuel supply is stopped by making the target generated current Ge between time t2 and time t3 different between the large and small values G01 and G02 in accordance with the speed ratio α. Before reaching the fourth compression top dead center, the opening of the appropriate range r of the top dead center rotation speed ne due to the speed ratio α can be gradually reduced. When the second compression top dead center is passed, the two appropriate ranges can be smoothly merged, and the subsequent control of the engine rotational speed Ne can be easily performed.

  When the multi-stage transmission mechanism 52 is set to the drive state, the target power generation current Ge of the alternator 28 is set according to the speed ratio α at the time t3 when the engine top dead center rotational speed ne is within the predetermined range. By adjusting to values G11 to G14 corresponding to the degree of decrease in the engine rotation speed Ne, control for decreasing the engine rotation speed Ne is executed along the reference line shown in FIG. It is configured to reduce the influence of an external load acting on the engine as much as possible based on being in a state where transmission is possible.

  Adjustment of the target generated current after time t3 is set such that the larger the speed ratio α is, the larger the target generated current is set. Therefore, from the time t3 shown in FIG. The values of the target generated current up to are set to values G11, G12, G13, and G14 in order from the side with the larger speed ratio α. If a plurality of values are set as the set values, the value of the target generated current corresponding to the speed ratio α is set by an experiment or the like performed in advance regardless of the number of the set values.

  On the other hand, when the multi-stage transmission mechanism 52 is switched to the neutral state in accordance with the speed ratio α, the target generated current Ge of the alternator 28 is set at the time t3 when the engine top dead center rotational speed ne is within the predetermined range. By adjusting to a value corresponding only to the engine speed Ne, control is performed to reduce the engine speed Ne along a reference line set based on the results of experiments performed in advance shown in FIG. It is configured.

  Then, after the time t5 when the last compression top dead center is exceeded before the engine is stopped, the reverse rotation and the normal rotation of the crankshaft 3 are repeated several times, and the piston 13 stops after reciprocating. The stop position of the piston 13 is substantially determined by the balance of the compression reaction force in the compression stroke cylinder 12C and the expansion stroke cylinder 12A, and is influenced by the frictional resistance of the engine. It also changes depending on the rotational inertia of the engine at the time t5 when the last compression top dead center is exceeded, that is, the level of the engine rotational speed Ne, and the multi-stage speed change mechanism is realized by the speed change control means 47 and the generated current control means 46 by the automatic stop control means 43. Even when 52 is set to the drive state, it can be within the appropriate range R with high probability.

  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 satisfies all the conditions such as 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 such a case, it is determined that the engine can be automatically stopped and is turned on.

  If it is determined YES in step S1, it is determined whether or not the accelerator sensor 34 is in an OFF state (step S2). If YES is determined and it is confirmed that the vehicle is in a predetermined deceleration state. Determines whether the engine rotational speed Ne is larger than a reference value FC • ON for deceleration fuel injection stop (fuel cut during deceleration) set in advance to about 1100 rpm (step S3). When it determines, it transfers to the following step S17.

  When it is determined YES in step S3 and it is confirmed that the engine speed Ne is larger than the determination reference value FC • ON for stopping fuel injection during deceleration, fuel cut (FC) during deceleration is executed. (Step S4).

  Next, the automatic stop control means 43 confirms whether or not the lockup clutch 64 is in the engaged state, and if the lockup clutch 64 is in the engaged state, has the engine speed Ne become the lockup release rotational speed Nlu or less? It is determined whether or not (step S5), and if it is equal to or lower than the lockup release rotational speed Nlu (YES in step S5), the lockup clutch 64 is released to release the lockup (step S6). The relationship between the turbine runner 55 and the crankshaft 3 that has been rotating due to the release of the lockup clutch 64 is broken, and the ratio between the rotational speed Te of the turbine runner 55 and the rotational speed of the crankshaft 3 (engine rotational speed Ne) is different. Come on. Normally, when the vehicle is decelerated, the rotational speed of the crankshaft 3 rapidly decreases due to the release of the lockup clutch 64, and the rotational speed of the turbine runner 55 becomes higher than the rotational speed of the crankshaft 3. If the lockup clutch 64 is not in the engaged state in step S5, this step S6 is skipped although not shown.

  Then, it is determined whether or not the engine rotational speed Ne has decreased below the fuel return determination reference value FC · OFF set in advance to about 900 rpm (step S7), and when the determination is NO, the accelerator is in the ON state. Is determined (step S8), and if the accelerator is in the OFF state, the process returns to step S7.

  On the other hand, if YES is determined in step S7, it is determined whether or not the brake sensor 35 is in an ON state (step S10). If NO is determined in step S10 and YES is determined in step S8, Then, it is recognized that there is a request for reacceleration by the occupant, the fuel injection stop (FC) is terminated, the normal fuel injection state is restored (step S9), and the process returns.

  It is determined whether or not the multi-speed transmission mechanism 52 determined as YES in step S10 is set to a high speed, that is, for example, whether or not the 3-4 clutch 69 is engaged (step S11), and is set to a high speed. If it is, the rotation speed Te of the turbine runner 55 is increased by shifting down (step S12), thereby increasing the speed ratio α.

  Then, by setting the target generated current Ge of the alternator 28 to 0 and stopping the power generation (step S13), the load by the alternator 28 is temporarily set to the no-load state and the subsequent load state is prepared, and the throttle valve 23 is turned on. The valve is opened and the opening degree K is set to, for example, about 30% (step S14) to ensure sufficient scavenging performance.

  Subsequently, when the vehicle speed reaches a predetermined value, for example, 20 km / h, the automatic stop control means 43 receives the detection results from the crank angle sensors 30 and 31 and the detection results from the turbine runner rotation sensor 36 to obtain a speed ratio. α is detected, and it is determined whether or not the speed ratio α is equal to or greater than a predetermined reference value (1 in the present embodiment) (step S15). If the speed ratio α is 1 or more (YES in step S15), the process proceeds to step S27 as it is. On the other hand, if the speed ratio α is less than 1 (NO in step S15), the multi-stage transmission mechanism 52 is set to neutral. After switching to a state (shift range is neutral) (step S16), the process proceeds to step S27.

  That is, when the degree of engine decrease is small, it is easier to control the engine rotational speed Ne than when it is large. Therefore, when the speed ratio α is 1 or more, the load acting on the engine is in a small state, so the degree of decrease in the engine speed is also small. In this case, the multi-stage transmission mechanism 52 is maintained in the drive state. By doing so, when the driver's accelerator operation is performed during deceleration, that is, when there is a request for re-acceleration of the vehicle, automatic stop control of the engine is prohibited and re-acceleration responsiveness is improved. On the other hand, when the speed ratio α is less than 1, since the load acting on the engine is in a large state, the degree of decrease in the engine speed is also large. In this case, the multi-stage transmission mechanism 52 is switched to the neutral state. As a result, the piston 13 can be within the appropriate range R with high probability.

  On the other hand, if NO is determined in step S3, it is determined whether or not the brake sensor 35 is in an ON state (step S17). If the brake sensor 35 is not in an ON state, step S1 is determined. When the process returns to the ON state, the process proceeds to step S18 to determine whether or not the engine speed is equal to or higher than a predetermined speed N1, for example, about 860 rpm + 50 to 100 rpm. If the engine speed Ne is less than N1 as a result of this determination, the engine speed Ne is once increased to an extent exceeding the predetermined value N1, and the engine is in a drive state when the engine speed Ne becomes equal to or higher than the predetermined value N1. The transmission mechanism 52 is switched to the neutral state (step S20).

  Next, it is determined whether or not a predetermined time set in advance in about 1 sec (seconds) has elapsed after time t0 when it is determined that the engine automatic stop condition is satisfied by determining YES in step S17. (Step S21) When it is determined NO, it is determined whether or not the accelerator sensor 34 is turned on, that is, whether or not the driver has performed a start operation (Step S22). If YES is determined in step S22, the process proceeds to step S1 without automatically stopping the engine. As a result, immediately after the vehicle speed becomes zero, or when the driver's accelerator operation is performed during deceleration, that is, when there is a request for re-acceleration of the vehicle, the automatic engine stop control is prohibited and the re-acceleration response Will be secured.

  Then, when it is determined YES in step S21, whether or not the fuel injection stop condition (FC condition) is satisfied, specifically, the engine rotational speed Ne becomes the target rotational speed and the boost pressure Bt is It is determined whether or not the target pressure P1 has been stabilized (step S23). After determining YES in step S23 and confirming that the engine speed Ne and the boost pressure Bt are stable (time t1 in FIG. 6), after stopping the fuel injection (step S24) Then, the target power generation current Ge of the alternator 28 is set to 0 to stop power generation (step S25), the throttle valve 23 is opened, and the opening degree K is set to about 30%, for example (step S26). Control goes to step S27.

  As a premise of this step S27, whether or not a predetermined time has elapsed from the time t1 when the fuel injection is stopped, that is, the combustion of the fuel injected before reaching the two compression top dead centers after the fuel injection is stopped is performed. It is determined whether or not it has been completed, and the ignition by the ignition device 27 is stopped when it is determined that it has ended. Then, in this step S27, it is determined whether or not the engine rotational speed Ne has become equal to or lower than the reference speed N2 set to about 790 rpm in advance, so that after the fuel injection stop time t1 shown in FIGS. Then, it is determined whether or not the engine rotational speed Ne has started to decrease, and at the time t2 when it is determined YES, the throttle valve 23 is closed and its opening degree K is set to 0% (step S28). As a result, the boost pressure Bt that has risen so as to approach the atmospheric pressure when the throttle valve 23 is opened in steps S14 and S26 starts to decrease with a predetermined time difference in accordance with the closing operation of the throttle valve 23. . Note that the engine top dead center is replaced with the above embodiment in which the throttle valve 23 is closed at time t2 when it is determined in step S28 that the engine rotational speed Ne has become equal to or lower than the reference speed N2. For example, the throttle valve 23 may be closed when it is determined that the rotational speed ne is equal to or lower than the reference speed N2 set to about 790 rpm, for example.

  Next, it is determined whether or not the multi-stage speed change mechanism 52 is set to the neutral state (step S29). If the multi-speed transmission mechanism 52 is set to the neutral state, the alternator 28 performs the steps S30 to 32 based on only the engine speed Ne. When the value of the target generated current is set, and when the drive state is set, the alternator 28 based on the speed ratio α in consideration of not only the engine speed Ne but also the turbine speed Te in steps S33 to S35. Set the target generated current value by.

  That is, when the multi-stage transmission mechanism 52 is in the neutral state (when the shift range is in the N range), the alternator 28 is set by setting the target generated current Ge of the alternator 28 to an initial value set in advance to about 60A. The power generation control for actuating is started (step S30).

  Then, it is determined whether or not the engine top dead center rotational speed ne is within the first predetermined range (step S31). This first predetermined range is a time point t3 when the engine passes through the fourth compression top dead center before the engine is stopped, for example, in the process in which the rotational speed Ne of the engine decreases along a 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 S31 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 t3. The target generated current Ge of the generated alternator 28 is set (step S32). That is, as the engine top dead center rotational speed ne is higher, the target generated current Ge corresponding to the top dead center rotational speed ne is read from the map in which the target generated current Ge is set to a larger value, and the alternator 28 is based on this value. The target generated current Ge is controlled from the initial value (60A) to the value read from the map.

  On the other hand, when the multi-stage speed change mechanism 52 is in the drive state (when the shift range is in the D range), the alternator 28 is set by setting the target generated current Ge of the alternator 28 to the corresponding initial value G0 corresponding to the speed ratio α. The power generation control for actuating 28 is started (step S33). That is, the speed ratio α at this time is detected by the automatic stop control means 43, and when the speed ratio α is less than 1, the corresponding initial value G0 is set to a predetermined value G01 (80A in this embodiment). When the speed ratio α is 1 or more, the corresponding initial value G0 is set to a predetermined value G02 (60A in the present embodiment).

  Then, it is determined whether or not the engine top dead center rotational speed ne is within the second predetermined range (step S34). As shown in FIG. 9, the first predetermined range is a fourth compression top dead before the engine is stopped, for example, in the process in which the engine rotational speed Ne decreases along a preset reference line. The value is set based on the top dead center rotational speed ne at the time point t3 when the point is passed, and is specifically set within a range of 480 rpm to 510 rpm.

  When it is determined YES in step S34 and it is confirmed that the engine top dead center rotational speed ne is within the predetermined second range (480 rpm to 510 rpm), the speed ratio α at that time t3 is detected. The target generated current Ge of the alternator 28 corresponding to the speed ratio α is set to the corresponding value G1 (step S35). That is, as the speed ratio α is larger, the target generated current Ge is set to a larger value G11, G12. Based on this value, the target generated current Ge of the alternator 28 is reduced from the corresponding initial value G0 to the corresponding value G1. Execute control.

  That is, when the speed ratio α is 1 or more, since the load acting on the engine is in a small state, the degree of decrease in the engine speed is also small. Therefore, the degree of decrease in the engine rotational speed Ne is increased by setting the initial value of the target generated current Ge to a value G01 that is larger than that when the multi-stage transmission mechanism 52 is in the neutral state. On the other hand, when the speed ratio α is less than 1, since the load acting on the engine is in a large state, the degree of decrease in the engine speed is also large. Therefore, the degree of decrease in the engine rotation speed Ne is reduced by setting the initial value of the target generated current Ge to a value G02 (60A in the present embodiment) that is smaller than the corresponding initial value G01. As a result, the appropriate range r of the top dead center rotation speed ne when passing through the compression top dead center after a predetermined period of time gradually matches, and at a predetermined time when the appropriate range matches (in this embodiment, the engine The configuration is such that the piston 13 is stopped within the appropriate range R regardless of the speed ratio α by adjusting the value of the target generated current in accordance with the speed ratio α from the fourth compression top dead center before the stop state). Has been.

  Therefore, for example, even when the automatic transmission mechanism 50 is set in a drive state in which the driving force can be transmitted to the wheel side, the driving force transmitted from the wheel side to the engine side through the rotational speed of the turbine runner 55 The degree of change in the engine rotational speed Ne can be taken into account, and the engine rotational speed Ne can be adjusted by adjusting the load on the engine in consideration of the degree of decrease. Moreover, when the engine is automatically stopped, the value of the target generated current is made smaller when the speed ratio detected by the automatic stop control means 43 is smaller than a predetermined reference value (1 in the present embodiment) compared to when it is larger. Since the load acting on the engine is adjusted to be relatively small, the piston 13 can be stopped within the appropriate range R with high probability not only when the automatic transmission mechanism 50 is in the neutral state but also in the drive state. .

  Next, the engine top dead center rotational speed ne is within a third predetermined range set based on the top dead center rotational speed ne at time t4 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 S36). The fuel injection amount increases as the engine top dead center rotational speed ne increases at time t4 when it is determined YES in step S36 and it has been confirmed that the second compression top dead center before the engine stop has passed. From the set map M0, 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 S37). 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 less than a predetermined value N3 (step S38). This predetermined value N3 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, For example, it is set to about 260 rpm. Further, the boost pressure Bt at each time when each of the cylinders 12A to 12D sequentially passes the compression top dead center is detected, and the value is stored.

  If it is determined YES in step S38 and the engine top dead center rotational speed ne is equal to or lower than the predetermined value N3, that is, if it is confirmed that the engine has passed the last compression top dead center, At time t5, the boost pressure Bt at the time of passing through the previous compression top dead center is read, and this value is set as the boost pressure Bt at the second compression top dead center (TDC) before engine stop (step). S39).

  The top dead center rotational speed ne at the time t5 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 Bt at the second compression top dead center before the engine stops. Based on (hereinafter referred to as boost pressure Bt2), it is determined whether or not the piston 13 tends to stop at a later position in each stroke (a position near the bottom dead center in the expansion stroke cylinder 12A) (step S41). . 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 is 100 ° to 120 ° CA after the compression top dead center with respect to the appropriate range R. 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 S40, the engine does not tend to stop at a position near the latter stage of the stroke as described above, and the position at a relatively earlier stage of the stroke, that is, in the expansion stroke cylinder 12A. There is a possibility that the piston stop position may stop at a position close to 100 ° CA or 100 ° CA or less with respect to an appropriate range R of 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 that is set to about 40% of full opening (step S41), and the intake air flow is increased to thereby increase the intake stroke. The intake resistance of the cylinder 12D is decreased. 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 expansion stroke cylinder 12A is prevented from exceeding the lower limit (100 ° CA) within the appropriate range R. become.

  On the other hand, if YES is determined in step S40, the rotational inertia of the engine is large, the intake air flow rate in the final intake stroke to the compression stroke cylinder 12C is small, and the compression reaction force is small. There is already a condition where 13 is likely to stop at a later stage of the stroke. 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 about 5%, for example (step S42). 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 intake stroke cylinder 12D, and the occurrence of a situation where the stop position of the piston 13 exceeds the appropriate range R and is further on the late stage is effectively prevented.

  Next, it is determined whether or not the engine is stopped (step S43). When it is determined YES, it is determined whether or not the multi-stage transmission mechanism 52 is in the neutral state (step S44), and the neutral state is present. In this case, the drive state (D range) is restored (step S45), the automatic stop permission flag F is turned off (step S46), and the control operation is terminated.

  A control operation for restarting the engine that has been automatically stopped as described above will be described based on the flowcharts shown in FIGS. 13 to 15 and the time charts shown in FIGS. 16 and 17. 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 compression stroke cylinder 12C and the expansion stroke cylinder 12A is calculated (step S103). That is, the combustion chamber volumes of the compression stroke cylinder 12C and the expansion stroke cylinder 12A are obtained from the stop position of the piston 13. When the engine is automatically stopped, the engine is stopped after several revolutions after the fuel injection is stopped. Therefore, the expansion stroke cylinder 12A is also filled with fresh air, and the compression stroke cylinder 12C and the expansion cylinder 12C are expanded while the engine is stopped. Since the inside of the stroke cylinder 12A is at substantially atmospheric pressure, the amount of fresh air is obtained from the combustion chamber volume.

  Next, the stop position of the piston 13 detected according to the output signals of the crank angle sensors 30 and 31 is within the proper stop range R (before BTDC 60 ° CA to 80 ° CA) in the compression stroke cylinder 12C. Then, it is determined whether or not it is close to the bottom dead center BDC (step S104). When it is determined YES in step S104 and it is confirmed that the air amount in the compression stroke cylinder 12C is relatively large, the air amount in the compression stroke cylinder 12C calculated in step S103 is λ ( The first fuel injection is performed such that the air / fuel ratio (excess air ratio)> 1 (for example, air / fuel ratio = about 20) (step S105). This air-fuel ratio is obtained from the first air-fuel ratio map M1 for the first time of the 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 compression stroke cylinder 12C is relatively large.

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

  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 to the 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, have been detected within a certain time after ignition (step S108). If it is determined NO and it is confirmed that misfire has occurred and the piston 13 has not moved, the compression stroke cylinder 12C 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 expansion stroke cylinder 12A is based on the stop position of the piston 13 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 expansion stroke cylinder 12A is closer to the bottom dead center or 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 of the expansion stroke cylinder 12A calculated in step S103 (step S122). The air-fuel ratio at this time is obtained from an air-fuel ratio map M3 for the expansion stroke cylinder 12A set in advance according to the stop position of the piston 13. Further, based on the fuel injection amount to the expansion stroke cylinder 12A calculated in step S122 and the division ratio calculated in step S121, the first stage fuel injection amount for the expansion stroke cylinder 12A is calculated, and the fuel is Injecting (step S123).

  Next, based on the in-cylinder temperature estimated in step S102, the subsequent (second) fuel injection timing for the expansion stroke cylinder 12A is calculated (step S124). This 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 latent heat of vaporization of the injected fuel is compressed. The pressure is set to be reduced effectively, that is, the piston 13 is set to approach the top dead center, and the time for the second injected fuel to evaporate by the ignition timing is set to be as long as possible. The

  Next, the subsequent (second) fuel injection amount for the expansion stroke cylinder 12A is calculated based on the fuel injection amount for the expansion stroke cylinder 12A calculated in step S122 and the split ratio calculated in step S121 (step S125). ), And is injected at the second injection timing calculated in step S124 (step S126).

  After the second fuel injection into the 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 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 by the ignition, the engine turns from reverse rotation to normal rotation. Therefore, the piston 13 of the compression stroke cylinder 12C moves to the top dead center side, and the gas in the cylinder (burned gas combusted by the ignition in step S107) starts to be compressed.

  Next, taking into account the fuel vaporization time, the second time fuel is injected into the 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 compression stroke cylinder 12C set in advance according to the stop position of the piston 13. The compression top dead center can be easily exceeded by reducing the compression pressure in the vicinity of the compression top dead center of the compression stroke cylinder 12C according to the latent heat of vaporization caused by the second injection fuel in the compression stroke cylinder 12C. It becomes.

  Note that the second fuel injection into the 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 the non-combustible fuel is made harmless by reacting with oxygen stored in the exhaust gas purification catalyst 37 in the exhaust passage 22 thereafter.

  Since the fuel injected for the second time in the compression stroke cylinder 12C does not burn as described above, the next combustion following the first combustion in the expansion stroke cylinder 12A is the intake stroke cylinder 12D, that is, as shown in FIG. This is the first combustion in the fourth cylinder that was in the intake stroke when stopped. As energy for the piston 13 of the intake stroke cylinder 12D to exceed the compression top dead center, a part of the initial combustion energy in the expansion stroke cylinder 12A is used, and the initial combustion energy in the expansion stroke cylinder 12A is compressed. The stroke cylinder 12C is used both for overcoming the compression top dead center and for the intake stroke cylinder 12D for exceeding the compression top dead center.

  Therefore, for smooth start-up, it is desirable that the energy required for the intake stroke cylinder 12D to exceed the compression top dead center is small. For this purpose, the air density in the intake stroke cylinder 12D is estimated, and the intake air is estimated from the estimated value. After calculating the air amount of the stroke cylinder 12D (step S140), an air-fuel ratio correction value for preventing self-ignition is calculated based on the in-cylinder temperature estimated in step S102 (step S141). That is, when self-ignition occurs, a force (reverse torque) that pushes the piston 13 back to the bottom dead center side is generated before reaching the compression top dead center due to the combustion, and much energy is required to exceed the compression top dead center. Since it is consumed, it is not desirable. Therefore, in order to suppress the reverse torque, the air-fuel ratio is corrected to the lean side so that compression self-ignition does not occur.

  Next, the fuel injection amount to the intake stroke cylinder 12D is calculated based on the air amount of the intake stroke cylinder 12D calculated in step S140 and the air-fuel ratio in consideration of the air-fuel ratio correction value calculated in step S141 ( Step S142). Then, fuel is injected into the intake stroke cylinder 12D. In this fuel injection, the compression pressure is reduced by the latent heat of vaporization, that is, the energy required to exceed the compression top dead center is reduced. The process 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 the reverse torque, ignition is performed with a delay after the top dead center (step S144). By executing the control described above, in the intake stroke cylinder 12D, the compression pressure is reduced to the compression top dead center and easily exceeds the top dead center. Directional torque will be generated.

  After step S144, the control state may be shifted to a normal control state. However, in this embodiment, control for further suppressing the increase in engine speed is performed. This increase in engine rotation speed means that the engine rotation speed suddenly increases more than necessary after the initial combustion in the intake stroke cylinder 12D, and causes an acceleration shock or a feeling of strangeness to the driver. This is not desirable. The increase in the engine rotation speed is immediately after starting (after the first combustion in the intake stroke cylinder 12D) because the intake pressure (pressure downstream of the throttle valve 23) during the automatic stop period is substantially atmospheric pressure. It is generated when the combustion energy in each of the cylinders 12A to 12D temporarily becomes larger than the combustion energy during normal idle operation. For this purpose, in steps S145 to S158 described below, control for suppressing the engine speed from rising is performed.

  First, power generation is started by setting the target current value of the alternator 28 higher than usual (step S145), and the rotational resistance (external load of the engine) of the crankshaft 3 is increased by the power generation of the alternator 28 to increase the engine speed. Suppresses the rising of. 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 speed is likely to rise, the amount of combustion energy generated is reduced by making the opening of the throttle valve 23 smaller than the throttle opening during normal idle operation (step S151). Suppress.

  Then, it is determined whether or not the temperature of the exhaust gas purification catalyst 37 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 37 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. The 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).

  By executing the restart control, as shown in FIGS. 16 and 17, first, the first fuel injection J3 is performed in the compression stroke cylinder 12C (third cylinder), and combustion is performed by the ignition (FIG. 16). (1)) is performed. With the combustion pressure (part a in FIG. 17) due to this combustion (1), the piston 13 of the compression stroke cylinder 12C is pushed down to the bottom dead center side, and the engine is driven in the reverse direction. Here, the first fuel injection J3 of the compression stroke cylinder 12C becomes a lean air-fuel ratio (λ> 1) when the air amount is relatively large, and a stoichiometric air-fuel ratio or a rich air-fuel ratio (λ ≦ 1) when it is small. Therefore, an appropriate combustion energy for reversing the engine, that is, a combustion energy that does not excessively reverse the compression top dead center while sufficiently compressing the air in the expansion stroke cylinder 12A. Can be obtained.

  As the engine starts reverse rotation, the piston 13 of the expansion stroke cylinder 12A (first cylinder) starts to move in the direction of the top dead center. Immediately thereafter, the first fuel injection J1 in the expansion stroke cylinder 12A is performed and vaporization starts. Then, when the piston 13 of the expansion stroke cylinder 12A moves to the top dead center side (preferably closer to the top dead center from the stroke center) and the air in the cylinder 12A is compressed, the second (rear stage) fuel injection J2 is performed. Is done. The compression pressure is reduced by the latent heat of vaporization of the injected fuel, and the piston 13 comes closer to the top dead center, so that the density of the compressed air (air mixture) increases (part b in FIG. 17).

  When the piston 13 of the expansion stroke cylinder 12A is sufficiently close to top dead center, the cylinder 12A is ignited, and the first injected fuel (J1) and the second injected fuel (J2) whose vaporization is promoted are promoted. ) Are combusted ((2) in FIG. 16), and the engine is driven in the forward rotation direction by the combustion pressure (c portion in FIG. 17).

  Further, fuel (J4) richer than the combustible air-fuel ratio is injected into the compression stroke cylinder 12C at an appropriate timing ((3) in FIG. 16). The compression pressure of the compression stroke cylinder 12C is reduced by the latent heat of vaporization caused by fuel injection (part d in FIG. 17), and accordingly, the compression top dead center (the first compression top dead center from the start of starting) is exceeded. The initial combustion energy of the expansion stroke cylinder 12A that is consumed is reduced.

  Furthermore, the timing of fuel injection (J5) in the intake stroke cylinder 12D, which is the next combustion cylinder, is set to an appropriate timing ((4) in FIG. 16) for reducing the temperature in the cylinder and the compression pressure by the latent heat of vaporization of the fuel. As shown in the figure, since, for example, the middle stage of the compression stroke is set, self-ignition before the compression top dead center is prevented in the compression stroke of the intake stroke cylinder 12D. Further, in combination with the ignition timing of the intake stroke cylinder 12D being set after the compression top dead center, combustion before the compression top dead center is prevented (part e in FIG. 17). That is, by reducing the compression pressure by the fuel injection (J5) and not performing the combustion before the compression top dead center, the energy of the first combustion in the expansion stroke cylinder 12A becomes the compression top dead center (the second compression from the engine start start time). It is possible to suppress consumption to exceed the top dead center.

  Thus, the first compression top dead center ((3) in FIG. 16) after the start of restart and the second compression by the energy of the first combustion ((2) in FIG. 16) in the expansion stroke cylinder 12A. The top dead center ((4) in FIG. 16) can be exceeded, and smooth and reliable startability can be ensured, and thereafter ((5), (6) in FIG. ) Makes the air-fuel ratio lean (λ> 1) according to the temperature of the catalyst, or delays the ignition timing, thereby shifting to the normal operation while preventing the engine speed from rising.

  When the engine automatic stop condition set in advance as described above is satisfied, the fuel injection for continuing the operation of the engine is stopped to automatically stop the engine, and the engine restart condition in the automatic stop state. In the engine starter configured to restart the engine by injecting fuel into the cylinder 12A that is stopped in at least the expansion stroke to cause ignition and combustion when 43 detects the speed ratio α, which is the ratio of the turbine rotational speed Te to the engine rotational speed Ne, and controls the generated current control means 46 and the shift control means 47 according to the speed ratio α. When the speed ratio α is smaller than a predetermined reference value, the target generated current by the alternator 28 is set lower than when the speed ratio α is large. Alternatively, by switching the multi-stage transmission mechanism 52 to the neutral state, the piston 13 is controlled so as to be stopped in an appropriate range R suitable for restarting the engine, so that from the wheel side to the engine side through the rotational speed Te of the turbine runner. The degree of change in the engine rotational speed Ne due to the transmitted force such as the driving force can be taken into account, and the engine rotational speed can be adjusted by adjusting the load on the engine in consideration of the degree of decrease.

  In addition, when the engine is automatically stopped, the load acting on the engine is adjusted to be relatively small when the speed ratio α is smaller than a predetermined reference value compared to when the speed ratio α is large. The re-acceleration performance can be improved and, on the other hand, when the load acting on the engine is large and the degree of decrease in the rotational speed Ne is large, the load is reduced by reducing the target generated current Ge of the alternator 28 or the like. In addition, the degree of decrease is reduced and the number of strokes of the piston 13 before the engine is stopped is prevented from being reduced, whereby the piston can be stopped within the appropriate range R. Since the reduction in the number of strokes of the piston 13 is prevented, the scavenging performance can be improved, and the engine can be reliably restarted.

  In addition, since the engine is automatically stopped without using the fuel injection stop at the time of deceleration to restore the stop of the fuel injection at the time of deceleration when the engine is automatically stopped, the engine is automatically stopped. Can be executed smoothly.

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

  (1) In the above embodiment, when the engine is automatically stopped without stopping the fuel injection at the time of deceleration and returning to the stop of the injection, the engine load adjustment control is performed by the speed ratio α. Even when the injection is not stopped or cannot be performed, the engine load adjustment control based on the speed ratio α can be executed.

  In this case, the engine rotation speed is kept constant and stabilized, and then the fuel injection is stopped. However, the stabilized rotation speed may be changed according to the speed ratio α. Good. That is, the automatic stop control means 43 stops the fuel supply when the speed ratio α detected before the fuel supply is stopped is smaller than a predetermined reference value (for example, 1 or approximately 1). The previous engine rotation speed may be set to a higher value.

  Even with this configuration, the engine 13 is not automatically stopped based on only the engine speed Ne in order to stop the piston 13 within the appropriate range R, but is automatically stopped based on the speed ratio α. For example, even when the automatic transmission mechanism is set in a drive state in which the driving force can be transmitted to the wheel side, the force such as the driving force transmitted from the wheel side to the engine side through the rotational speed of the turbine runner 55 is executed. Therefore, the engine rotation speed Ne can be taken into consideration, and the engine rotation speed can be adjusted by adjusting the load on the engine in consideration of the decrease degree. In addition, when the engine is automatically stopped, the automatic stop control means 43 stops the fuel supply with respect to when the speed ratio α detected before the fuel supply is stopped is larger than a predetermined reference value. Since the previous engine speed Ne is set to a higher value, when the speed ratio α is less than 1, that is, when the engine load is large and the degree of decrease in the engine speed Ne is large, the engine speed when the fuel supply is stopped The speed Ne is set to be large and the decrease in the number of strokes of the piston 13 until the engine is stopped compared to when the speed ratio α is 1 or more is suppressed, and the piston 13 is stopped within the appropriate range R with high probability. Can do.

  (2) In the above embodiment, the generated current control means 46 once increases the target generated current Ge of the alternator 28 and then adjusts the load acting on the engine by decreasing the amount of generated power. Further, the rotational resistance of the crankshaft 3 can be accurately adjusted over a wide range by adjusting the target generated current Ge to an arbitrary value from about 0 A to about 80 A, for example.

  However, it is known that when the target power generation current Ge is set to a large current value of about 60 A from a small current value of about 10 A, for example, it takes about 0.1 sec. On the other hand, when the target generated current Ge of the alternator 28 is set to a small current value of about 10 A from a large current value of about 60 A, for example, the generated current can be instantaneously changed. . Therefore, when the target generated current Ge is once increased and then decreased as in the above embodiment, the generated current can be changed quickly, and the piston 13 can be stopped within the appropriate range R more reliably. Can do.

  (3) In the above-described embodiment, an example in which the intake flow rate to each of the cylinders 12A to 12D is adjusted by the intake flow rate adjusting means including the throttle valve 23 disposed on the upstream side of the surge tank 21b will be described. However, the present invention is not limited thereto, and the intake flow rate to each of the cylinders 12A to 12D is adjusted by providing a known variable valve mechanism that changes the lift amount of the intake valve 19 provided in each of the cylinders 12A to 12D. Alternatively, the flow rate of intake air to each of the cylinders 12A to 12D using a multiple throttle valve in which a valve body is individually disposed in the branch intake passage 21a connected to each of the cylinders 12A to 12D. You may comprise so that it may adjust.

  (4) In the engine starter in the above embodiment, when the engine in the automatic stop state is restarted, the compression stroke cylinder 12C is caused to perform the first combustion, so that the crankshaft 3 is slightly changed at first. The ignition is performed after the air-fuel mixture in the expansion stroke cylinder 12A is compressed by rotating in the reverse direction. However, the engine starter according to the present invention is not limited to this, and the expansion stroke cylinder 12A is first applied to the expansion stroke cylinder 12A. You may comprise so that an engine may be restarted by performing ignition.

  (5) In the above embodiment, when the engine is restarted, the fuel injection for the initial combustion in the expansion stroke cylinder 12A is divided injection (J1 + J2). A timing (predetermined fuel injection timing) at which ensuring can be achieved as much as possible may be determined by experiments or the like, and one fuel injection at the predetermined fuel injection timing may be performed. Further, the divided fuel injection performed for the first combustion in the expansion stroke cylinder 12A when the engine is restarted may be divided into three or more as required.

  (6) Although omitted in the above embodiment, when the engine is restarted, when a 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 reached by a predetermined time after the start. When the value does not reach a predetermined value, control with assist by a starter motor may be performed.

1 is a schematic cross-sectional view of an engine provided with a starter according to the present invention. It is explanatory drawing which shows the structure of the intake system and exhaust system of an engine. It is the schematic which shows an example as an automatic transmission mechanism in the starter which concerns on this invention. 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 of the engine speed at the time of an engine stop when the automatic transmission mechanism is set to the drive state and the neutral state. It is a time chart which shows the change state of an accelerator opening, a target electric power generation current, etc. at the time of engine stop in a neutral state. It is a distribution map which shows the correlation with the engine speed at the time of an engine stop, and a piston stop position. It is a time chart which shows the change state of an accelerator opening degree, a target electric power generation current, etc. at the time of engine stop in a drive state. It is explanatory drawing which shows the appropriate range of the top dead center rotational speed at the time of the engine stop based on the magnitude of speed ratio. 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 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 restart of an engine. It is a flowchart which shows the latter half part of the control action at the time of engine restart. It is a time chart which shows the combustion operation etc. at the time of engine restart. It is a time chart which shows the change state etc. of the engine speed at the time of engine restart.

Explanation of symbols

1 Engine body 2 ECU
3 Crankshafts 12A to D Cylinder 13 Piston 28 Alternator 30, 31 Crank angle sensor (engine rotation speed detection sensor)
36 Rotation sensor for turbine runner 43 Automatic stop control means 46 Generated current control means 47 Shift control means 50 Automatic transmission mechanism 51 Torque converter 52 Multistage transmission mechanism 55 Turbine runner R Appropriate range α Speed ratio Ne Engine rotation speed Te Turbine rotation speed

Claims (6)

When the preset engine automatic stop condition is satisfied, the fuel supply to the engine is stopped to automatically stop the engine, and when the restart condition of the engine in the automatic stop state is satisfied, at least An engine mounted on a vehicle equipped with an automatic transmission mechanism having a torque converter is configured to automatically restart the engine by injecting fuel into a cylinder automatically stopped in the expansion stroke to cause ignition and combustion. A starting device,
A speed ratio detecting means for detecting a speed ratio, which is a ratio of a turbine speed of the torque converter to the engine speed, and a load adjusting means for adjusting a load acting on the engine; By adjusting the engine load to be relatively small when the speed ratio detected by the speed ratio detecting means is smaller than a predetermined reference value during the automatic stop operation period of the engine after the supply stop compared to when it is large. The engine starter is controlled to stop the piston in an appropriate range suitable for restarting the engine.   The load adjusting means includes an automatic transmission mechanism capable of switching between a neutral state in which transmission of driving force to the wheel side is disconnected and a driving state in which driving force can be transmitted to the wheel side, and is detected by the speed ratio detecting means. The automatic transmission mechanism is set to the drive state when the speed ratio is greater than or equal to the reference value, and the automatic transmission mechanism is set to the neutral state when the speed ratio is less than the reference value. 2. The engine starting device according to claim 1, wherein the predetermined reference value is set to 1 or a value close to 1.   The load adjusting means includes an alternator driven by an engine, and the target generated current by the alternator is higher than the case where the speed ratio detected by the speed ratio detecting means is higher when the speed ratio is smaller than the predetermined reference value. 3. The engine starting device according to claim 1, wherein the engine starting device is configured to be lowered.   The load adjusting means adjusts the target generated current of the alternator according to the speed ratio detected by the speed ratio detecting means after setting the target generated current by the alternator to a predetermined value after the fuel supply is stopped. The engine starting device according to claim 3. When the preset engine automatic stop condition is satisfied, the fuel supply to the engine is stopped to automatically stop the engine, and when the restart condition of the engine in the automatic stop state is satisfied, at least An engine mounted on a vehicle equipped with an automatic transmission mechanism having a torque converter is configured to automatically restart the engine by injecting fuel into a cylinder automatically stopped in the expansion stroke to cause ignition and combustion. A starting device,
This is the ratio of the turbine rotation speed of the torque converter to the engine rotation speed, and the automatic stop control means for setting the engine rotation speed when stopping fuel injection at the time of automatic engine stop to a value higher than the normal idle rotation speed. A speed ratio detecting means for detecting a speed ratio, wherein the automatic stop control means is large when the speed ratio detected by the speed ratio detecting means before the fuel supply is stopped is smaller than a predetermined reference value. On the other hand, the engine starter before stopping the fuel supply is set to a higher value.   6. The engine starting device according to claim 5, wherein the automatic stop control means is set to 1 or a value close to 1 as the predetermined reference value.

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