JP4581949B2 - Powertrain engine starter - Google Patents

Description

  The present invention provides a powertrain including an engine and an automatic transmission that transmits the driving force of the engine while performing a predetermined shift. The present invention relates to an engine starter for a power train that stops and then automatically starts the stopped engine.

In recent years, in order to reduce fuel consumption, reduce CO ₂ emissions, etc., the engine is automatically stopped once at idle, and then the engine is automatically restarted when a restart condition such as a start operation is established. Such engine starting devices have been developed.

  This restart of the engine is required to start immediately according to the establishment of the restart condition, so that the engine is started through cranking that drives the engine output shaft by a starter (starting motor), The conventional general starting method which requires a considerable time to complete the starting is not preferable.

  Therefore, fuel is supplied to a specific cylinder of a stopped engine (a cylinder in an expansion stroke; hereinafter, a cylinder in an expansion stroke when the engine is stopped is referred to as an expansion stroke cylinder for convenience) to perform combustion, and the engine uses the energy. It is desirable to ensure that is started immediately. However, a sufficient torque for starting the engine is not always obtained by simply supplying fuel to the expansion stroke cylinder for combustion. In order to restart smoothly, it is necessary to generate sufficient torque by combustion.

  For this purpose, it is desirable that the piston of the expansion stroke cylinder is stopped within an appropriate range when restarting. This appropriate range is generally around 90 ° CA (crank angle) after top dead center, that is, near the middle of top dead center and bottom dead center, or a slightly deviated range. When the piston is stopped at this point, good combustion can be obtained with moderately present in-cylinder air and fuel supplied at the time of restart, and torque sufficient for restart can be generated.

As an engine stop control for stopping the piston within the proper range as described above, for example, Patent Document 1 discloses that the in-cylinder air amount is optimized by adjusting the intake air flow rate during the engine stop operation, and the piston is within the proper range. The technique which made it easy to stop is disclosed. According to the engine starting device described in Patent Document 1, since the piston is accurately stopped within the appropriate range, restartability can be improved.
JP 2004-124754 A

  However, the restart request after starting the engine automatic stop control does not always occur after the engine is completely stopped. There may be a case where a restart request is generated during the automatic engine stop operation period. In such a case, it is conceivable that the engine is restarted after the engine is completely stopped. This is because, for example, when the restart request places importance on quickness, for example, when the accelerator is on. There is a possibility of giving the person a feeling of delay in starting.

  Therefore, when a restart request occurs during the automatic engine stop operation period, it is desirable to continue the engine operation by restarting the fuel supply as much as possible even before the engine is completely stopped ( Engine return).

  However, although a good restart can be performed in an environment near the standard atmospheric pressure, the restartability may be reduced in an environment with a low atmospheric pressure such as a high altitude. This is because if the atmospheric pressure is low, the amount of intake air in the intake stroke is reduced, the combustion energy for restarting will be reduced.

  The present invention has been made in view of the above circumstances, and is capable of restarting with high speed in an environment in the vicinity of standard atmospheric pressure with relatively good restartability, and has a concern about restartability. An object of the present invention is to provide a powertrain engine starter that can perform restart as good as possible even in a low environment.

According to a first aspect of the present invention for solving the above-described problem, the vehicle is stopped or is in a state where the vehicle is stopped with respect to the power train of the vehicle including the engine and an automatic transmission that transmits the driving force of the engine while performing a predetermined shift. When the engine automatic stop condition including at least the condition that the vehicle speed is below a predetermined low vehicle speed is satisfied, the engine automatic stop control is performed to automatically stop the engine by stopping the fuel supply for continuing the engine operation. And a stop / restart control means for automatically restarting the engine by causing combustion in the cylinder in the expansion stroke at least when the engine is stopped when the restart condition of the engine in the automatic stop state is satisfied. a engine starting apparatus of the power train, comprising a detecting means that detect the atmospheric pressure, the automatic transmission is driving from the engine side A drive state capable of transmitting the driving force to the wheel side, the transmission of the driving force is configured to be switched between a neutral state of being disconnected, the stop restart control means is in the automatic engine stop control, the at atmospheric pressure is equal to or larger than a predetermined value, when the standard air 圧近 near the said automatic transmission immediately after the time at least the fuel supply stop and the drive state, when the atmospheric pressure is less than the predetermined value, at least the fuel supply The automatic transmission is set to the neutral state immediately after the stop point.

Note that this includes a case where the automatic transmission is once in a neutral state before the fuel supply is stopped when the atmospheric pressure is equal to or higher than a predetermined value .

  According to a second aspect of the present invention, in the engine starting device for a powertrain according to the first aspect, the stop / restart control means is in a state where the engine rotational speed is reduced during the engine stop operation period during the engine automatic stop control. Accordingly, an external load amount for the engine is adjusted, and control is performed so that the piston stops within a predetermined appropriate range.

  According to a third aspect of the present invention, in the engine starter for a powertrain according to the first or second aspect, the stop / restart control means determines the engine rotational speed at the time of the fuel supply stop in the engine automatic stop control as a warm. It is characterized in that it is set to a value higher than the engine speed during idling.

According to a fourth aspect of the present invention, in the engine starter for a powertrain according to the third aspect, the stop / restart control means is configured to have a predetermined value or more when the atmospheric pressure is less than a predetermined value in the engine automatic stop control. The engine rotational speed at the time of stopping the fuel supply is set to a higher value than in the case of.

  According to the first aspect of the invention, as will be described below, the pressure at which the restartability is a concern is low while the restart is highly rapid in an environment near the standard atmospheric pressure with relatively good restartability. It is possible to perform restart as good as possible even in an environment.

  According to the configuration of the present invention, the automatic transmission after the fuel supply stop point is in the drive state under the environment near the standard atmospheric pressure with relatively good restartability. Therefore, even if a restart request that emphasizes quickness, such as accelerator-on, occurs during the engine automatic stop operation period, the engine can be restarted immediately to quickly respond to start and reacceleration.

  On the other hand, in an environment where the atmospheric pressure is low and there is concern about restartability, the automatic transmission after the fuel supply stop point is in a neutral state. When the automatic transmission is set to the neutral state, the rotational resistance of the engine (crankshaft) is reduced, so that the reduction speed of the engine rotational speed in the engine automatic stop control is reduced. Therefore, more strokes (intake, compression, expansion, exhaust) are repeated in the process until the engine is completely stopped. As a result, scavenging is promoted, and the fresh air ratio at the time of restart increases. Therefore, the reduction of combustion energy due to the low atmospheric pressure can be effectively compensated.

  According to the invention of claim 2, by adjusting the external load amount, even when the engine rotation speed reduction speed (pattern) varies in the engine automatic stop control due to the influence of the operating environment or the like, the variation is reduced (corrected) )can do. That is, it becomes easy to reduce the engine speed in a constant pattern at all times. Therefore, an engine rotation speed decrease pattern with a high probability that the piston will stop within a predetermined appropriate range is obtained in advance through experiments or the like, stored in the stop / restart control means, and the engine rotation speed decreases along the pattern. If the external load amount is adjusted in such a manner, the piston can be stopped within a predetermined appropriate range with a high probability.

  According to the invention of claim 3, in the engine automatic stop control, the engine is stopped at a high rotational speed. As a result, scavenging is promoted because more strokes are repeated in the process of the engine being completely stopped. That is, restartability can be improved.

  According to the invention of claim 4, scavenging is further promoted in an environment with a low atmospheric pressure where there is a concern about restartability, which is advantageous in performing good restart.

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

  1 and 2 show a schematic configuration of a four-cycle spark ignition engine according to an embodiment of 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 (see FIG. 5) for engine control. The engine main body 1 includes a plurality of cylinders (four in the illustrated embodiment). Cylinders) 12A to 12D. A piston 13 connected to the crankshaft 3 via a connecting rod is fitted into each cylinder 12A to 12D, and a combustion chamber 14 is formed above the piston 13.

  A spark plug 15 is provided at the top of the combustion chamber 14 of each cylinder 12 </ b> A to 12 </ b> D, and the tip of the plug faces the combustion chamber 14. Further, a fuel injection valve 16 that directly injects fuel into the combustion chamber 14 is provided at a side portion of the combustion chamber 14. The fuel injection valve 16 includes a needle valve and a solenoid (not shown). When a pulse signal is input, the fuel injection valve 16 is driven and opened for a time corresponding to the pulse width at the pulse input timing. It is comprised so that the quantity of fuel according to may be injected. The injection direction of the fuel injection valve 16 is set so that fuel is injected toward the vicinity of the spark plug 15. The fuel injection valve 16 is supplied with fuel via a fuel supply passage or the like by a fuel pump (not shown), and can supply a fuel pressure higher than the pressure in the combustion chamber during the compression stroke. Is configured.

  An intake port 17 and an exhaust port 18 are opened to the combustion chambers 14 of the cylinders 12A to 12D, and an intake valve 19 and an exhaust valve 20 are provided in these ports 17 and 18. The intake valve 19 and the exhaust valve 20 are driven by a valve operating mechanism including a camshaft and the like (not shown). As described later in detail, the opening / closing timings of the intake / exhaust valves 19 and 20 of the cylinders 12A to 12D are set so that the cylinders 12A to 12D perform a combustion cycle with a predetermined phase difference.

  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 (boost pressure) are disposed on the upstream side and the downstream side of the throttle valve 23, respectively.

  The engine body 1 is also provided with an alternator (generator) 28 connected to the crankshaft 3 by a timing belt or the like. The alternator 28 is configured so that the output voltage can be adjusted by controlling the current of a field coil (not shown) by a regulator circuit 28a. Based on the control signal from the ECU 2, the electric load of the vehicle, the voltage of the vehicle battery, etc. The control of the target generated current corresponding to is performed.

  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, the rotation direction and the rotation angle of the crankshaft 3 are detected based on the detection signals out of phase output from the crank angle sensors 30 and 31.

  Further, the engine is provided with a cam angle sensor 32 that detects a specific rotational position of the camshaft and outputs it as a cylinder identification signal, and a water temperature sensor 33 that detects the cooling water temperature of the engine, as shown in FIG. Are provided with an accelerator sensor 34 for detecting the accelerator opening corresponding to the accelerator operation amount of the driver, a brake sensor 35 for detecting that the driver has operated the brake, and a vehicle speed sensor 38 for detecting the vehicle speed. Yes.

Further, as the detecting means that detect the atmospheric pressure, that are is provided an atmospheric pressure sensor 39.

  Each detection signal output from each of these various sensors is input to the ECU 2.

  FIG. 3 is a schematic diagram of the power train (drive system from the engine body 1 to the axles 78 and 79) of the present embodiment. The engine body 1 is connected to an automatic transmission 50 through a crankshaft 3 that is an output shaft thereof. The automatic transmission 50 includes a torque converter 51 coupled to the crankshaft 3 and a multi-stage transmission mechanism 52 coupled to a turbine shaft 59 that is an output shaft of the torque converter 51, and includes a plurality of frictions included therein. By switching the elements 67 to 71 intermittently, it is possible to switch between a neutral state in which the transmission of the driving force to the wheel side is cut off and a drive state in which the driving force can be transmitted to the wheel side.

  The torque converter 51 includes a pump cover 53 connected to the crankshaft 3, a pump impeller 54 formed integrally with the pump cover 53, and a turbine (turbine liner) 55 installed so as to face the pump impeller 54. In the meantime, a stator 58 attached to a case 57 via a one-way clutch 56 is provided. The space in the pump cover 53 is filled with oil (working oil, also called ATF) as working fluid, and the driving force of the pump impeller 54 is transmitted to the turbine 55 through this working oil. Yes. The driving force is transmitted to and from the multi-stage transmission mechanism 52 via the turbine shaft 59 connected to the turbine 55.

  The case 57 is provided with a turbine rotation sensor 36 that detects the rotation speed of the turbine 55 in a state of facing the outer peripheral surface of the forward clutch 67 that rotates integrally with the turbine shaft 59. Specifically, the turbine rotation sensor 36 has a tip portion disposed opposite to the outer peripheral surface of the drum of the forward clutch 67, and a spline-like unevenness provided on the outer peripheral surface of the drum is displaced by the rotation of the drum. The rotational speed of the turbine 55 is detected through the rotational speed of the turbine shaft 59 by detecting a periodic change in the induced voltage generated.

  A hollow rotary shaft 60 is connected to the pump impeller 54, and an oil pump 61 is attached to the rear end portion (the end portion opposite to the engine body 1 side) of the shaft 60. An electric oil pump 62 (see FIG. 5) is provided in the case 57 in addition to the oil pump 61, and these oil pumps 61 and 62 are connected to the hydraulic control mechanism 63 (see FIG. 5) via a switching valve 91. It is connected. The switching valve 91 performs switching control between the oil pump 61 and the electric oil pump 62 based on a switching signal from the ECU 2. In addition, the ECU 2 changes the oil passage (fluid passage) of the hydraulic control mechanism 63, sets the line pressure (hydraulic pressure during engagement of the friction elements 67 to 71), and performs transient transitions when the friction elements 67 to 71 are engaged and released. The friction elements 67 to 71 are configured to be intermittent (fastened or released) by performing hydraulic control or the like.

  The reason why the electric oil pump 62 is provided separately from the oil pump 61 is that it is difficult to supply a desired line pressure depending on the oil pump 61 because the engine rotation speed is not sufficient when the engine is stopped or at the start of the engine. In this case, the line pressure is ensured, and the timing for switching between the oil pump 61 and the electric oil pump 62 is set from this viewpoint.

  The torque converter 51 is further provided with a lock-up clutch 64 that is interposed between the pump cover 53 and the turbine 55 and directly connects the crankshaft 3 and the turbine 55 via the cover 53. The lockup clutch 64 is connected to the oil pump 61 and the electric oil pump 62 via a hydraulic control mechanism 63, and on / off control of various solenoid valves provided in the hydraulic control mechanism 63 according to the vehicle speed. By doing so, the oil passage is switched, and the lockup clutch 64 is engaged / disengaged.

  On the other hand, the multi-stage transmission mechanism 52 includes first and second planetary gear mechanisms 65 and 66 and a fastening element (a plurality of friction elements 67 such as a clutch plate and a band brake) for switching a power transmission path including the planetary gear mechanisms 65 and 66. -71 and one-way clutch 72), and according to the shift range (D range, N range, R range, etc.), these fastening elements 67-72 are intermittently switched so as to switch forward speed, neutral state, and reverse speed. It is configured.

  The “drive state” and “neutral state” used in this specification do not necessarily indicate the shift operation position (D or N) by the shift lever or the like, but substantially automatic based on the transmission state of the driving force. The state of the transmission 50 is said. Accordingly, the neutral state includes a state in which the transmission operation of the automatic transmission 50 is disconnected by the control of each solenoid valve while the shift operation position by the shift lever or the like remains in the D range position.

  The first and second planetary gear mechanisms 65, 66 are arranged around the sun gear 65a, the sun gear 66a, and the sun gears 65a, 66a, respectively, and a plurality of (for example, three) planetary gears 65b that mesh with them. , 66b, carriers 65c, 66c that support these planetary gears 65b, 66b, and ring gears 65d, 66d that are arranged so as to surround the planetary gears 65b, 66b and mesh therewith, and are configured as a first planetary gear. The ring gear 65d of the mechanism 65 and the carrier 66c of the second planetary gear mechanism 66 are coupled, and the carrier 65c of the first planetary gear mechanism 65 and the ring gear 66d of the second planetary gear mechanism 66 are coupled to each planetary gear. The mechanisms 65 and 66 can be interlocked.

  The friction element includes a forward clutch 67 interposed between the turbine shaft 59 and the sun gear 65a of the first planetary gear mechanism 65, and a reverse clutch 68 interposed between the turbine shaft 59 and the sun gear 66a of the second planetary gear mechanism 66. A 3-4 clutch 69 interposed between the turbine shaft 59 and the carrier 66c of the second planetary gear mechanism 66, a 2-4 brake 70 for fixing the sun gear 66a of the second planetary gear mechanism 66, and the first planetary gear. A ring gear 65d of the gear mechanism 65 and a low reverse brake 71 for fixing the carrier 66c of the second planetary gear mechanism 66. Further, the one-way clutch 72 allows only rotation in one direction (the driving direction of the crankshaft 3) of the ring gear 65d and the carrier 66c (unlocking), and locks it so as not to rotate in the reverse direction. These fastening elements 67 to 72 are intermittently connected, and the power transmission path connected to the output gear 73 is changed or disconnected.

  As the output gear 73 rotates, the driving force is transmitted to the left and right axles 78 and 79 via the driving wheel side, that is, the transmission gears 74, 75 and 76 and the differential mechanism 77. . The axles 78 and 79 are configured to rotate integrally with a wheel (drive wheel) (not shown).

  In addition, fixing here means integrating with the fixed member (case 57 or what was integrated with this).

  FIG. 4 is a diagram illustrating the relationship between the intermittent state of the fastening elements 67 to 72 and the gear position. In FIG. 4, a circle indicates a state in which the friction elements 67 to 71 are fastened, and a circle indicates that the one-way clutch 72 is locked when driving (when the driving force from the engine is directed toward the driving wheel). The driving force can be transmitted, and indicates that the reverse driving force is not transmitted when unlocked (in the case where the reverse driving force from the driving wheel is directed to the engine side). No mark indicates a state in which each fastening element 67 to 72 is released or unlocked. Accordingly, in the N range, all the engaging elements 67 to 72 are released / unlocked, and in the first speed of the D range, the forward clutch 67 is engaged and the one-way clutch 72 is in the driving side locked state and the reverse driving side unlocked. The forward clutch 67 and the 2-4 brake 70 are engaged at the second speed, the forward clutch 67 and the 3-4 clutch 69 are engaged at the third speed, and the 3-4 clutch 69 is established at the fourth speed. And the 2-4 brake 70 is fastened.

  In the present embodiment, a specific mode M is provided. Although the specific mode M is different from the N range, when the specific mode M is selected, the automatic transmission 50 is in a neutral state. In the specific mode M, the 2-4 brake 70 is engaged, and the one-way clutch 72 is locked as necessary (indicated by (●)). That is, the carrier 65c or the ring gear 66d is locked when trying to operate in the locking direction, and is unlocked otherwise.

  Note that FIG. 4 does not cover all shift ranges and gear positions, and omits portions not directly related to the description of the present embodiment.

  FIG. 5 is a block diagram of the engine starting device of the present embodiment. The ECU 2 includes a computer having a CPU, ROM, RAM, and the like. Specifically, various operations of the vehicle are controlled by the CPU executing a program stored in advance in the ROM (or RAM). Is done. The ECU 2 receives signals from the sensors 25, 26, 30 to 36, 38, 39 and outputs a signal for controlling the fuel injection amount and the injection timing to the fuel injection valve 16, and to the spark plug 15. In contrast, an ignition timing control signal is output, a control signal for controlling the throttle opening is output to the actuator 24 of the throttle valve 23, and the power generation amount is controlled to the regulator circuit 28a of the alternator 28. Output a signal.

  The ECU 2 receives a signal from each of the sensors 25, 26, 30 to 36, 38, 39 and switches the source of the original pressure of the hydraulic control mechanism 63 between the oil pump 61 and the electric oil pump 62. A signal is output to the switching valve 91, and a signal for adjusting the operating pressure of each friction element 67 to 71 is output to the hydraulic control mechanism 63 (specifically, a solenoid valve included therein).

  Then, the ECU 2 automatically stops the fuel supply by stopping the fuel supply when a predetermined engine automatic stop condition is satisfied, and also during the automatic stop operation period of the engine or after the automatic stop of the engine, There is provided stop / restart control means 2a for automatically restarting the engine by energy generated by combustion of the engine when a predetermined engine restart condition is satisfied by operating an accelerator or a brake.

  Next, the operation of the engine starter of this embodiment will be described. First, the operation of the automatic transmission 50 will be described.

  FIG. 6 is a schematic diagram showing the driving force transmission path of the automatic transmission 50 and the rotation direction of each part in the D range first speed. In this figure, when viewed from the left front side, the left rotation is the forward rotation direction, and the right rotation is the reverse rotation direction. When the engine is in a normal operating state, the turbine shaft 59 rotates in the forward direction. Further, when the vehicle is in the forward traveling state, the transmission gear 76 rotates in the forward rotation direction together with the axles 78 and 79.

  At the first speed shown in FIG. 6, the turbine shaft 59 rotates in the forward rotation direction, and the rotation and driving force are transmitted to the sun gear 65 a via the forward clutch 67. Further, it is transmitted to the planetary gear 65b, and this planetary gear 65b rotates in the reverse direction. Here, since the one-way clutch 72 is locked (indicated by a path β), the rotation of the ring gear 65d in the reverse rotation direction is restricted, so that the planetary gear 65b rotates in the reverse rotation direction around the support shaft (carrier 65c). While rotating, the periphery of the sun gear 65a is rotated in the forward rotation direction integrally with the carrier 65c. That is, the carrier 65c rotates in the forward rotation direction. The rotation and driving force of the carrier 65c in the forward rotation direction are transmitted to the output gear 73 and the transmission gears 74, 75, and 76. 3 is transmitted to the axles 78 and 79 through the differential mechanism 77 as shown in FIG.

  Since the carrier 65c is connected to the ring gear 66d, the ring gear 66d rotates in the forward rotation direction. The carrier 66c is connected to the ring gear 65d. Since the ring gear 65d is stopped by locking the one-way clutch 72 or engaging the low reverse brake 71, the carrier 66c is also stopped. Therefore, the planetary gear 66b rotates in the forward rotation direction. The sun gear 66a meshing with the planetary gear 66b rotates in the reverse direction.

  FIG. 7 is a velocity diagram of the first and second planetary gear mechanisms 65 and 66. The velocity diagram is a schematic diagram showing the rotation speed of each element of the first and second planetary gear mechanisms 65 and 66 with respect to the rotation speed of the input shaft (turbine shaft 59). In this figure, four lines arranged in the vertical order are the sun gear 65a (first rotating element), the carrier 65c (the ring gear 66d and the output gear 73 also rotate together), and the ring gear 65d (the carrier 66c also integrated from the left). Rotating) and the sun gear 66a (second rotating element). The distance between each other is uniquely determined by the number of teeth of each planetary gear. The vertical axis represents the speed ratio with respect to the rotational speed of the turbine shaft 59 (turbine rotational speed Nt). When the rotational speed is the same as the turbine rotational speed Nt, the speed ratio = 1. In the stop state, the speed ratio = 0.

  In this speed diagram, the first speed stage shown in FIG. 6 is indicated by a first speed line 111. At the first speed, the sun gear 65a rotates integrally with the turbine shaft 59 when the forward clutch 67 (clutch means) is engaged, so the speed ratio of the sun gear 65a becomes 1 at the input point 116. Further, since the ring gear 65d is locked by the one-way clutch 72, the speed ratio = 0 at the fixed point 117. At this time, 0 <speed ratio <1 (for example, speed ratio≈0.36) at the output point 121 (output gear 73).

  FIG. 8 is a schematic diagram showing the driving force transmission path of the automatic transmission 50 and the rotation direction of each part in the D range second speed. The definition of the rotation direction conforms to FIG.

  As shown in FIG. 4, the D range second speed is obtained by further engaging the 2-4 brake 70 from the D range first speed in which the forward clutch 67 is engaged. As described above, in the D range first speed, the sun gear 66a rotates in the reverse direction. When the 2-4 brake 70 is engaged from this state, the sun gear 66a stops. For this reason, the planetary gear 66b rotates around the sun gear 66a in the forward direction integrally with the carrier 66c while rotating in the forward direction around the support shaft (carrier 66c). That is, at the first speed in the D range, the one-way clutch 72 restricts the rotation in the reverse direction, and the stopped carrier 66c rotates in the normal direction.

  At this time, the planetary gear 65b rotates around the sun gear 65a in the forward rotation direction integrally with the carrier 65c while rotating in the reverse rotation direction around the carrier 65c as in the first speed. In this case, unlike the first speed, since the ring gear 65d rotates in the forward direction, the rotational speed of the carrier 65c is relatively higher than that in the first speed. However, it is decelerated from the rotational speed of the turbine shaft 59. Thereafter, as in the first speed, the rotation and driving force of the carrier 65c in the forward rotation direction are transmitted to the output gear 73 and the transmission gears 74, 75, and 76.

  The state of the second speed stage is indicated by the second speed line 112 in the speed diagram of FIG. At the second speed, the sun gear 65a rotates integrally with the turbine shaft 59 by the engagement of the forward clutch 67, so that the speed ratio of the sun gear 65a becomes 1 at the input point 116. Further, since the sun gear 66a is fixed by the 2-4 brake 70 (brake means), the speed ratio = 0 at the fixing point 118. At this time, the output point 122 (output gear 73) has a speed ratio (for example, speed ratio≈0.67) larger than that of the first gear.

  FIG. 9 is a schematic diagram showing the driving force transmission path of the automatic transmission 50 and the rotation direction of each part in the third range of the D range. The definition of the rotation direction conforms to FIG.

  This D range second speed is a state where the forward clutch 67 and the 3-4 clutch 69 are engaged, as shown in FIG.

  At the third speed shown in FIG. 9, the turbine shaft 59 rotates in the forward rotation direction, and the rotation and driving force thereof are the first path via the forward clutch 67 and the second path via the 3-4 clutch 69. Distributed to the path. In the first path, the driving force is transmitted to the sun gear 65 a through the forward clutch 67. Further, it is transmitted to the ring gear 65d through the planetary gear 65b. That is, the sun gear 65 a, the carrier 65 c, and the ring gear 65 d rotate together at the same rotational speed as the turbine shaft 59. On the other hand, in the second path, the driving force is transmitted to the carrier 66c through the 3-4 clutch 69 at a constant speed.

  That is, the driving forces dispersed in the first path and the second path are merged by the ring gear 65d and output from the carrier 65c to the output gear 73. Eventually, a driving force equal to the driving force input from the turbine shaft 59 is output to the output gear 73 at the same speed as the rotational speed of the turbine shaft 59 (directly connected state). Thereafter, it is transmitted to the transmission gears 74, 75 and 76, and then transmitted to the axles 78 and 79 via the differential mechanism 77 as shown in FIG.

  The state of the third speed stage is indicated by the third speed line 113 in the speed diagram of FIG. At the third speed, the sun gear 65a rotates integrally with the turbine shaft 59 when the forward clutch 67 is engaged, and the carrier 66c rotates integrally with the turbine shaft 59 when the 3-4 clutch 69 is engaged. At 119, the speed ratio = 1. At this time, the speed ratio = 1 at the output point 123 (output gear 73) (directly connected state).

  Although description of the operation of each part of the automatic transmission 50 in the D range fourth speed is omitted, the 3-4 clutch 69 and the 2-4 brake 70 are engaged and input from the turbine shaft 59 as shown in FIG. The driving force is increased from the rotational speed of the turbine shaft 59 and transmitted to the carrier 65c. In the same manner, it is transmitted to the axles 78 and 79 through the output gear 73, the transmission gears 74, 75 and 76 and the differential mechanism 77.

  The state of the fourth speed stage is indicated by a fourth speed line 114 in the speed diagram of FIG. At the fourth speed, the carrier 66c rotates integrally with the turbine shaft 59 by engaging the 3-4 clutch 69, so that the speed ratio of the carrier 66c becomes 1 at the input point 119. Further, since the sun gear 66a is fixed by the 2-4 brake 70, the speed ratio = 0 at the fixed point 118. At this time, the speed ratio> 1 (for example, speed ratio≈1.38) at the output point 124 (output gear 73).

  FIG. 10 is a velocity diagram in the neutral state when the vehicle is stopped. The way of reading the figure is based on FIG. In the present embodiment, the neutral state includes a normal neutral state (corresponding to the N range) and a specific mode M (see FIG. 4).

  First, the speed line 131 in the specific mode will be described. The speed line 131 in the specific mode is specified by a fixed point 135 when the 2-4 brake 70 is engaged and a fixed point 137 when the vehicle is stopped, that is, when the output gear 73 is stopped. That is, the speed ratio = 0 over the entire area.

  On the other hand, in the normal neutral state, only the fixed point 137 is specified. Accordingly, there is a possibility that the speed ratio = 0 in the entire area as in the case of the speed line 131 in the specific mode. However, in reality, this is not the case, and in general, the normal time N is slightly inclined around the fixed point 137. Speed line 132. Normally, the speed line 132 at N hours is not uniquely determined, but is shown as an example. The reason why the speed line 132 is normally inclined in this way is that some elements of the first and second planetary gear mechanisms 65 and 66 are rotated together. In the illustrated example, the carrier 66c rotates along with the turbine shaft 59, and the input point 141 satisfies 0 <speed ratio <1. At this time, the sun gear 65a has a negative speed ratio and rotates in the opposite direction to the turbine shaft 59 (point 143).

  Here, consider the case where the forward clutch 67 is engaged from each of the above neutral states. As is apparent from FIG. 4, when the forward clutch 67 is engaged from the specific mode M, the second speed is established, and when the forward clutch 67 is engaged from the normal neutral state, the first speed is established. In any case, since the speed ratio = 0 in the output gear 73, the speed ratio = 0 in the sun gear 65a. As a result, the speed ratio = 0 also in the turbine shaft 59. That is, the turbine shaft 59 stops (turbine rotational speed Nt = 0).

  In the case of the specific mode M, since the sun gear 65a is stopped from the beginning (point 139), it is only necessary to stop the rotation of the turbine shaft 59 and its integrally rotating object by fastening the forward clutch 67. Energy is relatively small. On the other hand, when the forward clutch 67 is fastened from the normal neutral state, not only the rotation of the turbine shaft 59 and its integral rotating object is stopped, but also the sun gears 65a and 66a, the ring gear 65d, the carrier 66c, and these integral rotating objects. The rotation must be stopped. If it corresponds to a velocity diagram, it can be said that the absorbed energy for moving the inclined normal N-hour velocity line 132 horizontally is required. Therefore, the energy absorbed by the forward clutch 67 is relatively large.

  If the absorbed energy is large, the clutch engagement time becomes long, and vibration (ND shock) when switching from the neutral state to the drive state also increases. From the above, it can be understood that the engagement time can be shortened and the ND shock can be reduced when the forward clutch 67 is engaged from the specific mode M, rather than when the forward clutch 67 is engaged from the normal neutral state.

  Next, engine automatic stop control will be described. FIG. 11 is a diagram showing the relationship between the compression stroke cylinder and the expansion stroke cylinder when the engine is automatically stopped. The compression stroke cylinder does not indicate a specific cylinder, but is any one of the cylinders 12A to 12D, and is a cylinder that is in a compression stroke when the engine is stopped or a cylinder that is in a compression stroke. That's it. Similarly, the expansion stroke cylinder is a cylinder that is in an expansion stroke when the engine is stopped or a cylinder that is to be in an expansion stroke. FIG. 11A is a diagram showing the positional relationship of the piston 13 of the compression stroke cylinder and the expansion stroke cylinder, and FIG. 11B is a diagram showing the relationship between the stop position of the piston 13 and the air amount in each cylinder. is there.

  Since the engine of the present embodiment is a four-cylinder four-cycle engine, as shown in FIG. 11A, the compression stroke cylinder and the expansion stroke cylinder are shifted in phase by 180 ° CA. The direction is out of phase. That is, as indicated by the white arrow, when the piston 13 moves in the TDC (top dead center) direction in the compression stroke cylinder, the piston 13 moves in the BDC (bottom dead center) direction in the expansion stroke cylinder.

  By utilizing this operation, in this embodiment, when the engine that has been automatically stopped is restarted after a complete stop, the piston 13 is burned in the compression stroke cylinder prior to the combustion in the expansion stroke cylinder. Is once pushed in the reverse direction so as not to exceed the BDC (the crankshaft 3 temporarily rotates in the reverse direction). As a result, the piston 13 of the expansion stroke cylinder also moves once in the reverse direction, that is, in the TDC direction. Then, the air in the expansion stroke cylinder (which becomes an air-fuel mixture after fuel injection) is compressed. Therefore, the compressed air-fuel mixture is ignited and burned, so that the piston 13 is reversed with a strong force and pushed down in the BDC direction. That is, the rotation direction of the crankshaft 3 is changed from reverse rotation to normal rotation. Thus, by rotating the engine once and then burning it in the expansion stroke cylinder, a driving torque in the forward rotation direction stronger than simply burning in the expansion stroke cylinder is obtained, and the restartability of the engine is improved.

  As described above, the engine is restarted properly only by igniting the fuel injected into a specific cylinder without using a restart motor or the like. The combustion energy obtained by burning is not all output from the crankshaft 3, but a cylinder that reaches compression top dead center after the expansion stroke cylinder (in this embodiment, the compression stroke cylinder and the intake stroke cylinder). Is also consumed to overcome the compression reaction force and exceed the compression top dead center. Therefore, even if the consumed amount is subtracted, the driving force in the forward rotation direction must remain on the crankshaft 3. Therefore, it is necessary to ensure a sufficient amount of air in the expansion stroke cylinder in the initial state (engine stop state). On the other hand, in the compression stroke cylinder, it is necessary to secure an amount of air sufficient to first reverse the crankshaft 3 to compress the air in the expansion stroke cylinder.

  In FIG. 11B, the horizontal axis indicates the piston stop position (ATDC ° CA: crank angle after top dead center) of the expansion stroke cylinder, and the vertical axis indicates the in-cylinder air amount of the expansion stroke cylinder and the compression stroke cylinder. A certain amount of time has elapsed after each cylinder has stopped, and the air amount is in a state where the cylinder is at substantially atmospheric pressure. As described above, since the piston 13 of the expansion stroke cylinder and the piston 13 of the compression stroke cylinder are in opposite phases, when one air amount increases (the piston 13 moves in the BDC direction), the other air amount decreases ( The piston 13 moves in the TDC direction).

  Therefore, in order to obtain a large amount of combustion energy in the expansion stroke cylinder while ensuring a certain amount of combustion energy in the compression stroke cylinder, the piston 13 of the expansion stroke cylinder is slightly closer to the BDC than the center of the stroke, for example, 100 to 120 ATDC °. It is preferable to stop within the range of CA (within the range R shown in FIG. 11B). Hereinafter, this range is referred to as an appropriate range R.

  Although there are various specific methods for controlling the piston 13 of the expansion stroke cylinder within the appropriate range R, the stop / restart control means 2a of the present embodiment mainly adjusts the opening of the throttle valve 23 as will be described later. By doing so, control is performed to increase or decrease the intake flow rate.

  FIG. 12 is a time chart showing in detail the engine automatic stop control. The horizontal axis represents time t (s), the vertical axis represents engine speed Ne (rpm), throttle opening K (%), boost pressure (intake pressure) Bt (mmHg), and transition of stroke in each cylinder 12A to 12D. Show. Regarding the engine rotation speed Ne, a characteristic 148 indicated by a solid line is a characteristic when the atmospheric pressure measured by the atmospheric pressure sensor 39 is close to the standard atmospheric pressure (equivalent to a flat ground). A characteristic 149 is a characteristic indicating an example in which the engine is restored in the middle of the characteristic 148. The characteristic 150 is a characteristic when the atmospheric pressure is lower than the standard atmospheric pressure by a predetermined value or more (equivalent to a highland or a mountainous area).

  In FIG. 12, the cylinder in the expansion stroke when the engine is completely stopped (time t10) is the cylinder 12A. Hereinafter, for convenience, the description will be made assuming that the cylinder 12A is the expansion stroke cylinder 12A. The other cylinders are similarly referred to as a compression stroke cylinder 12C, an intake stroke cylinder 12D, and an exhaust stroke cylinder 12B.

  First, the characteristic 148 (in the case of near the standard atmospheric pressure) will be described. In this case, the following control is performed with the automatic transmission 50 in the drive state. That is, one of the first speed to the third speed is selected according to the vehicle speed.

  When the idle stop condition is satisfied at time t0, the stop / restart control means 2a performs pre-F / C control. In the pre-F / C control, a pre-operation of F / C (fuel stop) is performed. That is, the target rotational speed of the engine rotational speed Ne is set to N1 (for example, N1 = 860 rpm). Next, the throttle opening degree K is adjusted to guide the boost pressure Bt to a predetermined target value (for example, −400 to −600 mmHg). At the same time, the ignition timing is retarded so that the engine speed Ne does not increase too much. The retard amount is feedback-controlled so that the engine rotational speed Ne converges to the target rotational speed N1.

  The target rotational speed N1 is set higher than the engine rotational speed (about 650 rpm) during warm idle operation. In this way, by performing F / C from a high rotational speed, the number of strokes (intake, compression, expansion, exhaust) until complete stop can be increased, and scavenging can be promoted. Further, various controls (increase / decrease in throttle opening K, alternator control, etc.) are easily incorporated before the complete stop, so that the piston 13 can be easily stopped within the appropriate range R.

  When the engine rotational speed Ne converges to the target rotational speed N1 and the boost pressure Bt converges to the target value, the F / C condition is established, and the throttle opening K is increased to, for example, about 30% and fuel injection is performed. Is stopped (F / C) (time t3).

  When the fuel injection is stopped at time t3, the kinetic energy of the crankshaft 3 or the like is consumed by mechanical loss due to frictional resistance or pump work of each cylinder 12A to 12D, so that the crankshaft 3 of the engine With inertia, it rotates several times, and in a 4-cylinder 4-cycle engine, it stops after reaching the compression top dead center of about 10 times.

  The stop position of the piston 13 is substantially determined by the balance between the amount of air in the expansion stroke cylinder 12A immediately before the engine is completely stopped and the amount of air in the compression stroke cylinder 12C, and is affected by the frictional resistance of the engine. It also changes depending on the rotational inertia of the engine at the time t6 when the last compression top dead center is exceeded, that is, the level of the engine rotational speed N6.

  Therefore, in order to stop the piston 13 of the expansion stroke cylinder 12A within the appropriate range R, first, sufficient air is supplied to the expansion stroke cylinder 12A and the compression stroke cylinder 12C, and the amount of air in the expansion stroke cylinder 12A is reduced to the compression stroke. It is necessary to adjust the intake air flow rates for both cylinders 12A and 12C so as to be larger than the air amount of the cylinder 12C.

  For this reason, in the present embodiment, the boost pressure Bt is increased by setting the throttle opening K to a large value (for example, about 30% of the opening when fully opened) at the fuel supply stop time t3, and the expansion stroke cylinder 12A and After inhaling a predetermined amount of air into both compression stroke cylinders 12C, at time t5 when it has been confirmed that the engine speed Ne has dropped below a preset reference speed N2 (for example, about 790 rpm), the throttle is opened. The intake air amount is adjusted by reducing the degree K.

  By the way, the fuel injection is stopped at the time point t3 when the engine rotational speed Ne becomes the target rotational speed N1, and the throttle valve 23 is kept open for a predetermined period thereafter. When the piston 13 provided in each of the cylinders 12A to 12D measures the top dead center rotational speed ne when the piston 13 passes through the compression top dead center and examines the piston position of the expansion stroke cylinder 12A when the engine is stopped, the engine is When the top dead center rotational speed ne at the sixth to second before the stop state is within a predetermined range as shown by hatching in FIG. 13, the stop position of the piston 13 is within the appropriate range R. Has been confirmed experimentally.

  Therefore, in order to finally stop the piston 13 of the expansion stroke cylinder 12A within the appropriate range R, the respective top dead center rotational speeds ne before the engine is stopped are shown in FIG. What is necessary is just to reduce the engine rotational speed Ne so that it may enter sequentially within the predetermined range as shown by hatching.

  Therefore, in this embodiment, when the engine rotational speed Ne is in a range where N4> Ne> N5, the crankshaft is set so that each top dead center rotational speed ne sequentially enters a predetermined range as shown by hatching in FIG. The external load acting on the shaft 3 is appropriately adjusted. For example, N4 = 650 rpm and N5 = 400 rpm are set. An alternator 28 is used as an external load. That is, the external load acting on the crankshaft 3 is adjusted (alternator control) by appropriately increasing or decreasing the power generation amount Ge of the alternator 28 (characteristic 140). By such control, the piston stop position accuracy in the engine automatic stop control can be increased, and the restartability can be improved.

  After the fuel injection stop time t3, the stop / restart control means 2a reads each top dead center rotational speed ne as the engine rotational speed Ne decreases. Then, at the time t6 when the top dead center rotational speed ne becomes lower than a predetermined final TDC determination threshold N6 (for example, N6 = 260 rpm), it is the last compression top dead center (final TDC. In this embodiment, expansion) The compression top dead center in the stroke cylinder 12A is determined. After time t6, the piston 13 moves in each of the cylinders 12A to 12D, but does not move to the next stroke beyond the top dead center TDC or the bottom dead center BDC.

  Although omitted in the flowchart described later, after time t6, the throttle opening K may be increased again as illustrated. By so doing, the boost pressure Bt increases, so that the intake resistance in the intake stroke cylinder 12D is reduced, and the load on the crankshaft 3 is reduced. Therefore, the operation of the piston 13 in the expansion stroke cylinder 12A and the compression stroke cylinder 12C becomes smoother and can be easily stopped within the target appropriate range R. As described above, since the stroke does not change in each of the cylinders 12A to 12D after the time point t6, the intake valve 19 does not open in the expansion stroke cylinder 12A or the compression stroke cylinder 12C. Therefore, even if the boost pressure Bt increases, there is no change in the amount of air already distributed in a well-balanced manner to the expansion stroke cylinder 12A and the compression stroke cylinder 12C.

  After time t6, the piston 13 vibrates several times within the same stroke, and then stops completely at time t10. The stop / restart control means 2a detects the stop position of the piston 13 by detecting the operation of the piston 13 from immediately before the stop to the stop by the crank angle sensors 30 and 31.

  FIG. 14 is a flowchart showing the detection control operation of the piston stop position. When this detection control is started, based on the first crank angle signal CA1 (signal from the crank angle sensor 30) and the second crank angle signal CA2 (signal from the crank angle sensor 31), when the first crank angle signal CA1 rises. It is determined whether or not the second crank angle signal CA2 is low, or whether or not the second crank angle signal CA2 is high when the first crank angle signal CA1 falls (step S1). As a result, it is determined whether the phase relationship between the signals CA1 and CA2 during the engine stop operation is as shown in FIG. 15A or FIG. Whether it is in a state or a reverse state is determined.

  That is, at the time of forward rotation of the engine, as shown in FIG. 15A, the second crank angle signal CA2 is generated with a phase delay of about a half pulse width with respect to the first crank angle signal CA1, thereby the first crank angle signal. The second crank angle signal CA2 becomes Low when CA1 rises, and the second crank angle signal CA2 becomes High when the first crank angle signal CA1 falls. On the other hand, during reverse rotation of the engine, as shown in FIG. 15B, the second crank angle signal CA2 is generated with a phase advance of about a half pulse width with respect to the first crank angle signal CA1, so On the contrary, the second crank angle signal CA2 becomes High when the first crank angle signal CA1 rises, and the second crank angle signal CA2 becomes Low when the first crank angle signal CA1 falls.

  Therefore, if the determination in step S1 is YES, the CA counter for measuring the crank angle change in the forward rotation direction of the engine is increased (step S2). If the determination in step S1 is NO, the CA counter is increased. Down (step S3). Then, after stopping the engine, the piston stop position is obtained by examining the measured value of the CA counter (step S4).

  Returning to FIG. 12, when there is a restart request such as accelerator on during the engine automatic stop control, the engine is returned as soon as possible (characteristic 149). At this time, since the automatic transmission 50 is in the drive state, the driving force can be immediately transmitted to the drive wheels by restarting the engine. Therefore, quick start or reacceleration can be performed.

  Next, the characteristic 150 (when the atmospheric pressure is low) will be described. In this case, the following control is performed with the automatic transmission 50 in the neutral state in most regions. In particular, in this embodiment, the neutral state according to the specific mode M described above is applied.

  As shown in FIG. 12, the characteristic 150 has a slower decrease rate of the engine rotation speed Ne than the characteristic 148. This is because the rotational resistance of the engine (crankshaft 3) is reduced by setting the automatic transmission 50 to the neutral state. Accordingly, scavenging is promoted. Further, since the disturbance from the drive wheel side to the engine is substantially cut off, it is advantageous in that the piston 13 is stopped within the appropriate range R.

  Further, in the characteristic 150, the target rotational speed after the idle stop condition is established is set higher by ΔN1 (= about 50 rpm) than N1 in the characteristic 148. This also facilitates further scavenging.

  FIG. 16 is a time chart showing an enlarged characteristic 150 of the engine rotation speed Ne. In the same figure, a characteristic 151 of the turbine rotational speed Nt is also shown. The horizontal axis represents time t (s), and the vertical axis represents engine rotational speed Ne (rpm) and turbine rotational speed Nt (rpm). The outline of the engine stop / restart control by the stop / restart control means 2a will be described in more detail with reference to the characteristics 150 and 151 shown in FIG.

  The main purpose of the engine stop / restart control is to first stop the fuel supply (F / C) at the time t3 after the time t0 when the idle stop condition (engine automatic stop condition) is satisfied, and the expansion stroke at the time t10 when the engine is completely stopped. The purpose is to guide the piston stop position of the cylinder within an appropriate range R (automatic stop control). Then, there is a restart request such as accelerator-on, and when the restart condition is satisfied (time t11), combustion is performed at least in the expansion stroke cylinder, and the engine is restarted quickly and smoothly ( Engine speed characteristics 156). Further, when there is a restart request between time t0 and time t10, the engine is restarted as soon as possible (for example, engine speed characteristic 155). Details of this control will be described later with reference to a flowchart.

  FIG. 17 is a schematic main flowchart including engine stop / restart control by the stop / restart control means 2a.

  When this control operation starts, it is determined whether or not an engine idle stop condition (automatic stop condition) is satisfied based on detection signals output from various sensors during execution of normal control (step S6). Specifically, the accelerator is OFF, the brake is ON, the vehicle speed is 19 km / h or less (including the stop state), the steering angle is less than a predetermined value, the blinker is not operated, the battery voltage is more than a predetermined value, and the engine room (near the battery) The idle stop condition is satisfied when all of the conditions such as the temperature of 10 ° C. or higher and the ATF (hydraulic oil of the automatic transmission 50) temperature of 40 ° C. or higher are satisfied.

  If YES is determined in the step S6, the process proceeds to a step S7 so as to determine whether or not the atmospheric pressure is smaller than the predetermined value Pm. The predetermined value Pm is a value lower by a predetermined amount than the standard atmospheric pressure (= 1013 hPa), and is a threshold value for determining whether the automatic transmission 50 is in the drive state or the neutral state in the engine automatic stop control.

  If it is determined NO in step S7, engine stop / restart control (A) is executed (step S8). If YES is determined in step S7, engine stop / restart control (B) is executed (step S9). After execution of step S8 or step S9 (after restart), the control returns to normal control (step S10).

  FIGS. 18 to 19 are subroutines for engine stop / restart control (A) corresponding to step S8 in the flowchart shown in FIG. 17 when the atmospheric pressure is at or close to the standard atmospheric pressure. In the following description, portions overlapping with the description of the engine automatic stop control are omitted as appropriate. The time points such as time point t0 and time point t3 correspond to the respective time points shown in FIG.

  When the idle stop condition is satisfied and this subroutine is started (time t0), the stop / restart control means 2a first executes the pre-F / C control (step S121). In the pre-F / C control, the above-described pre-operation of F / C (fuel stop) is performed. That is, the target rotational speed of the engine rotational speed Ne is set to N1. Next, the throttle opening K is adjusted to guide the boost pressure Bt to a predetermined target value. At the same time, the ignition timing is retarded.

  Next, it is determined whether or not there is a restart request (step S122). Specifically, it is determined that there is a restart request when a predetermined restart condition (for example, at least one of accelerator ON, brake OFF, battery voltage is equal to or lower than a predetermined value, etc.) is satisfied. If YES is determined here, the pre-F / C control is immediately stopped and the process returns (return to normal control).

  If NO in step S122, it is determined whether the F / C condition is satisfied (step S123). When the engine rotational speed Ne converges to the target rotational speed N1 and the boost pressure Bt converges to the target value, it is determined that the F / C condition is satisfied (time point t3). When the F / C condition is satisfied, the throttle opening K is increased as described above (step S125) and the fuel injection is stopped (F / C) (step S127).

  Next, in step S129, it is determined whether there is a restart request as in step S122. In the case of YES here, since the rotational speed has hardly decreased, the engine is immediately restored (step S131) and the process returns. In the case of NO in step S129, it is determined whether or not the engine rotational speed Ne is equal to or lower than a reference speed N2 that is set in advance to about 790 rpm (step S133). When it is determined YES in step S133 (time t5), the opening degree of the throttle valve 23 is reduced (step S135).

  Next, it is determined whether or not predetermined rotational speed N4> engine rotational speed Ne> predetermined rotational speed N5 (steps S141 and S143). For example, the predetermined rotational speed N4 = 650 rpm and the predetermined rotational speed N5 = 400 rpm are set. When the predetermined rotational speed N4> the engine rotational speed Ne> the predetermined rotational speed N5 (YES in step S141 and NO in step S143), the stop / restart control means 2a executes the above-described alternator control (step S145). If YES in step S143, that is, if engine rotational speed Ne <predetermined rotational speed N5, the alternator control is terminated.

  Next, in step S147, it is determined whether or not the state of the engine including the engine speed Ne is a recoverable state. If it determines with YES, step S129 to step S147 will be repeated. If NO in step S147, the system waits for the engine to stop completely (YES in step S157), waits until there is a restart request, and after the complete stop at the time when there is a restart request (YES in step S159) The restart control is executed, and the process returns to the normal control.

  Here, the restart control after a complete stop will be described based on the time charts of FIGS. The engine restart control is not limited to this, and may be other known restart control.

  As shown in FIGS. 23 and 24, first, the first fuel injection J2 is performed in the compression stroke cylinder 12C (third cylinder), and combustion ((1) in FIG. 23) is performed by the ignition. With the combustion pressure (part a in FIG. 24) 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.

  With the reverse rotation of the engine, the piston 13 of the stop expansion stroke cylinder 12A (first cylinder) starts to move in the direction of top dead center. The fuel injection J1 is performed 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 expansion stroke cylinder 12A is compressed. 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 the density of the compressed air (air mixture) increases (part b in FIG. 24).

  When the piston 13 of the expansion stroke cylinder 12A is sufficiently close to top dead center, the expansion stroke cylinder 12A is ignited, and the injected fuel (J1) is combusted ((2) in FIG. 23). The engine is driven in the forward rotation direction by the combustion pressure (c portion in FIG. 24).

  Further, fuel (J3) richer than the combustible air-fuel ratio is injected into the compression stroke cylinder 12C at an appropriate timing ((3) in FIG. 23). The compression pressure of the compression stroke cylinder 12C is reduced by the latent heat of vaporization caused by the fuel injection (part d in FIG. 24) and accordingly exceeds the compression top dead center (the first compression top dead center from the start of the start). The initial combustion energy of the consumed expansion stroke cylinder 12A is reduced.

  Furthermore, the timing of fuel injection (J4) in the intake stroke cylinder 12D, which is the next combustion cylinder, is set to an appropriate timing ((4) in FIG. 23) for reducing the temperature in the cylinder and the compression pressure by the latent heat of vaporization of the fuel. As shown, for example, after the middle stage of the compression stroke), 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. 24). That is, by reducing the compression pressure by the fuel injection (J4) 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 start of the engine start). It is possible to suppress consumption to exceed the top dead center.

  Thus, the first compression top dead center ((3) in FIG. 23) after the start of restart and the second compression by the energy of the first combustion ((2) in FIG. 23) in the expansion stroke cylinder 12A. It is possible to exceed the top dead center ((4) in FIG. 23), it is possible to ensure a smooth and reliable startability, and thereafter, shift to normal operation.

  20 to 22 show a subroutine of engine stop / restart control (B) corresponding to step S9 in FIG. 17 when the atmospheric pressure is lower than the predetermined value Pm. In the following description, portions overlapping with the descriptions of the engine automatic stop control and the engine stop / restart control (A) are omitted as appropriate. The time points such as the time point t0 and the time point t1 correspond to the respective time points shown in FIGS.

  For the sake of brevity, it is assumed that the automatic transmission 50 is in the first speed when the idle stop condition is satisfied.

  When the idle stop condition is satisfied and this subroutine starts (time t0), the stop / restart control means 2a first shifts the automatic transmission 50 to the specific mode M. That is, first, a 2-4 brake engagement command is issued and the timer tm1 is reset (step S11).

  Thereafter, it is determined whether or not there is a restart request (step S13). If NO is determined here and there is no restart request, it is determined in step S15 whether or not the timer tm1 has exceeded a predetermined period t50 (for example, set to t50 = 0.3 s). If NO in step S15, the process returns to step S13. If YES, that is, if a predetermined period t50 has elapsed from the 2-4 brake engagement command, the stop / restart control means 2a issues a forward clutch release command to the automatic transmission 50. (Time t1). In response to this, the forward clutch 67 is released (time t2). When the forward clutch 67 is released, the turbine rotational speed Nt increases (approaches the engine rotational speed Ne) as indicated by the characteristic 151 in FIG. The predetermined value t50 is a time difference set as appropriate so that the forward clutch 67 is completely released after the 2-4 brake 70 is completely engaged.

  Thus, the automatic transmission 50 is in the specific mode M in which the forward clutch 67 is released and the 2-4 brake 70 is engaged. As described above, since the automatic transmission 50 is in the neutral state in the specific mode M, the rate of decrease in the engine rotation speed Ne becomes slower after time t2 than when the automatic transmission 50 is in the drive state. Become. Accordingly, scavenging of the engine is promoted and it is easy to perform a good restart, so that a reduction in combustion energy due to a low atmospheric pressure can be compensated. Further, disturbance from the drive wheel side to the engine is substantially cut off. Therefore, stable automatic engine stop control can be performed.

  Returning to the flowchart, it is then determined in step S19 whether or not there is a restart request. If NO, the process proceeds to pre-F / C control (step S21). This pre-F / C control is basically the same as step S121 in FIG. 18, except that the target rotational speed is set to N1 + ΔN1 (= about 910 rpm) as described above. When the engine rotational speed Ne converges to the target rotational speed N1 and the boost pressure Bt converges to the target value, it is determined that the F / C condition is satisfied (YES in step S23, time point t3). When the F / C condition is satisfied, the throttle opening K is increased as described above (step S25) and the fuel injection is stopped (F / C) (step S27).

  Next, in step S29, it is determined whether or not there is a restart request. If YES here, 1 is input to the natural reverse rotation return flag F1 (the default value of the natural reverse rotation return flag F1 is 0). The natural reverse rotation is an operation that makes use of the fact that the engine reverses immediately before stopping as described above, and performs a smooth restart using the momentum (inertia) that changes from the reverse rotation to the normal rotation (FIG. 16). Engine speed characteristics 155). When 1 is input to the natural reverse rotation return flag F1, natural reverse rotation return is performed at a later restart with some exceptions.

  Next to step S29 or step S31, it is determined whether or not the engine rotational speed Ne has become equal to or lower than a reference speed N2 set in advance to about 790 rpm (step S33). Then, when the determination is YES in step S33 (time t5), the opening of the throttle valve 23 is reduced (step S35).

  Next, it is determined whether or not the engine rotational speed Ne has become equal to or lower than the N → D rotational speed N3 set in advance to about 750 rpm (step S37). When it is determined as YES in step S37 (time t4), the stop / restart control means 2a executes specific clutch engagement control. That is, a forward clutch engagement command is issued to the automatic transmission 50 that is in the specific mode M (step S39), and the forward clutch 67 is engaged.

  Thus, the specific clutch engagement control is executed, and the engagement operation of the forward clutch 67 is started. In the specific clutch engagement control, the substantial engagement start timing of the forward clutch 67 (actually when the transmission torque is generated; time t7) is set to the time after the final TDC passage time t6, and the time when the engagement is completed is during the first reverse rotation ( The target time is between t8 and t9. The N → D rotational speed N3 is a set value that is obtained in advance by experiments or the like so that the engagement of the forward clutch 67 matches the target. Since the time required for engaging the forward clutch 67 varies somewhat depending on the ATF temperature, the ATF temperature may be detected by an oil temperature sensor or the like, and the N → D rotation speed N3 may be adjusted appropriately according to the temperature. .

  When the forward clutch 67 is engaged by the specific clutch engagement control, the automatic transmission 50 changes from the neutral state to the drive state (in the present embodiment, the second speed state). However, this is different from normal N → D switching in that the forward clutch 67 is engaged while the automatic transmission 50 is in the specific mode M. As described above, when the forward clutch 67 is engaged while the automatic transmission 50 is in the specific mode M, the energy to be absorbed by the forward clutch 67 is reduced. This is advantageous for starting. Further, torque fluctuation (ND shock) at the time of N → D switching is also suppressed.

  If the substantial engagement start timing of the forward clutch 67 is after the final TDC passage time t6, the automatic transmission 50 is brought into the neutral state in a region where it is particularly desirable to interrupt the disturbance in the automatic engine stop control (before time t6). Therefore, more stable engine automatic stop control can be performed.

  Returning to the flowchart, after step S39, it is determined whether or not the predetermined rotational speed N4> the engine rotational speed Ne> the predetermined rotational speed N5 (steps S41 and S43). When YES in step S41 and NO in step S43, the stop / restart control means 2a executes the above-described alternator control (step S45). If YES in step S43, that is, if engine rotational speed Ne <predetermined rotational speed N5, the alternator control is terminated.

  Next, in step S47, it is determined whether or not it is before the natural reverse rotation return timing. The natural reverse rotation return timing is a timing for determining whether or not the natural reverse rotation return described above is possible, and when it is possible, the natural reverse rotation return is performed. In the present embodiment, the natural reverse rotation return timing is set to the time when the engine completes the first reverse rotation immediately before the stop, that is, the initial reverse rotation end time t9 to immediately before.

  If “YES” in the step S47, that is, if it is before the natural reverse rotation return timing, the process returns to the step S29, and the processes from the step S29 to the step S47 are repeated. Similarly, in the case of NO in step S33, in the case of NO in step S37, in the case of NO in step S41 and in the case of NO in step S43 (during alternator control execution), the process returns to step S29 and the processes are repeated. If there is a restart request during that time, 1 is input to the natural reverse rotation return flag F1 in step S31.

  When NO is determined in step S47, that is, when the natural reverse rotation return timing t9 is reached, the natural reverse rotation return flag F1 is determined in step S51. If the natural reverse return flag F1 ≠ 1 (NO in step S51), there is no restart request yet at this point, so the natural reverse return is not performed.

  In step S53, it is determined whether or not the forward clutch 67 is completely engaged. Specifically, when the turbine rotation speed Nt is a value corresponding to the vehicle speed and the shift speed, it is determined that the engagement of the forward clutch 67 is completed. As described above, when the forward clutch 67 is engaged by the specific clutch engagement control, the automatic transmission 50 enters the second speed state. The turbine rotation speed Nt is proportional to the vehicle speed, and the proportionality constant is uniquely determined from the tire radius, the gear ratio of the second speed, and the like. Therefore, the stop / restart control means 2a can determine that the engagement of the forward clutch 67 is completed when the turbine rotational speed Nt reaches a value corresponding to the vehicle speed. In this embodiment, it is determined that the engagement of the forward clutch 67 is completed when the turbine rotational speed Nt = 0 rpm at a vehicle speed of 0 km / h (stopped state) and the turbine rotational speed Nt≈560 rpm at a vehicle speed of 10 km / h.

  If such a determination is difficult, for example, the forward clutch 67 may be engaged after a predetermined period (eg, 0.4 s) has elapsed since the forward clutch engagement command was issued. You may determine with having completed.

  This method for determining the completion of engagement of the forward clutch 67 is also common to other steps (steps S73, S85, S87) to be described later.

  If the engagement of the forward clutch 67 is complete (YES in step S53), immediately, if it is not complete (NO in step S53), wait for completion, issue a 2-4 brake release command, and 2-4 brake 70 Is released (step S55). When the release of the 2-4 brake 70 is completed, the automatic transmission 50 enters the first speed state in which only the forward clutch 67 is engaged.

  After step S55, it waits for the engine to stop completely (YES in step S57), waits until there is a restart request, and after the above-mentioned complete stop at the time when the restart request is made (YES in step S59) (See the engine speed characteristic 156 in FIG. 16).

  In the above flow, there is no restart request until the engine is completely stopped, and the engine is restarted based on the restart request after the complete stop. Next, the engine is restarted before the engine is completely stopped. The control when there is a start request will be described.

  First, the case where it is determined in step S13 that there is a restart request will be described. This corresponds to a case where there is a restart request in the section 161 in FIG. In this case, as a specific operation, since the engagement of the 2-4 brake 70 has just been started, this is immediately stopped and the normal control is resumed.

  That is, first, the stop / restart control means 2a issues a 2-4 brake release command and resets the timer tm2 (step S75). After confirming the elapse of a predetermined period t55 (for example, the predetermined period t55 = 0.2 s) by the timer tm2 (YES in step S77), the engine stop / restart control is ended (step S79) and the process returns. . That is, the control shifts to normal control. Note that the predetermined period t55 is a time sufficient for the 2-4 brake 70 to be released, and is a value that is obtained and set as appropriate by an experiment or the like in advance.

  Next, the case where it is determined in step S19 that there is a restart request will be described. This corresponds to the case where there is a restart request in the section 162 of FIG. In this case, as a specific operation, since the engagement of the 2-4 brake 70 is started and the release of the forward clutch 67 is just started, these are immediately stopped and returned to the normal control.

  That is, the stop / restart control means 2a issues a forward clutch engagement command (step S71), and the forward clutch 67 is engaged. Then, after the forward clutch 67 is engaged (YES in step S73), the process proceeds to step S75. Step S75 and subsequent steps are the same as when it is determined in step S13 that there is a restart request.

  Next, the case where it is determined in step S29 that there is a restart request will be described. This corresponds to a case where there is a restart request in the section 163 in FIG. In this case, the process does not immediately shift to the restart operation but waits until at least the natural reverse rotation return timing t9. In step S85, it is determined whether or not the forward clutch 67 is completely engaged. As described above, the stop / restart control means 2a issues the forward clutch engagement command at such a timing that the forward clutch 67 completes the engagement between the time point t8 and the time point t9 (step S39). Therefore, in most cases, YES is determined in the step S85.

  If YES is determined in step S85, the stop / restart control means 2a issues a 2-4 brake release command (step S95. In the automatic transmission 50, 2-1 shift starts), and executes natural reverse rotation return control. (Step S97). The natural reverse return control is a control for performing the natural reverse return described above. Between the time point t8 and the time point t9, that is, while the engine is rotating in reverse, the piston 13 of the expansion stroke cylinder 12A rises and the in-cylinder air is compressed. At time t9, the engine changes from reverse rotation to normal rotation. That is, the piston 13 starts to descend in the expansion stroke cylinder 12A. By capturing the timing, fuel is injected from the fuel injection valve 16 (or may be injected in advance and vaporization and atomization may be promoted in advance) and ignited by the spark plug 15. By causing combustion in the expansion stroke cylinder 12A in this way, the combustion pressure is added to the momentum (inertia) for turning from reverse to forward, and the piston 13 drops vigorously with a large force. Thus, an easy and stable restart is performed.

  Thus, by performing the natural reverse rotation return at time t9, it is possible to perform a quicker restart than when restarting after waiting for the complete stop of the engine (time t10).

  The inventor of the present application indicates that the longest case from the fuel stop time t3 to the restart and the completion of the 2 → 1 shift of the automatic transmission 50 was 0.85 s when the natural reverse rotation is performed in this embodiment. I have confirmed. Considering that this is a sufficiently short time for practical use and a relatively simple control that does not involve precharge control, this natural reverse recovery control is remarkably highly practical.

  Note that it is assumed that the forward clutch 67 is not completely engaged at time t9 (NO in step S85) due to variations and other factors. In such a case, without spontaneously returning to the reverse rotation, the completion of the forward clutch 67 is awaited (YES in step S87), and a 2-4 brake release command is issued (step S89). Then, waiting for the complete stop of the engine (YES in step S91), the restart control after the complete stop is executed (step S61). By doing so, it is possible to effectively prevent the driver from feeling uncomfortable or damaging the forward clutch 67 by starting and accelerating the fastening of the forward clutch 67 in an incomplete state.

  The engine stop / restart control when the automatic transmission 50 is in the first speed state when the idle stop condition is satisfied has been described above. However, when the automatic transmission 50 is in the second speed state when the idle stop condition is satisfied, This is basically the same as the engine stop / restart control described above. However, since the 2-4 brake 70 is already engaged in the second speed, the engagement of the 2-4 brake 70 is omitted when shifting to the specific mode M immediately after the idle stop condition is established. That is, steps S11 to S15 are omitted. Therefore, the transition to the specific mode M can be achieved easily and quickly.

  Further, when the automatic transmission 50 is in the third speed state when the idle stop condition is satisfied or is predicted to be satisfied, first, a shift from the third speed to the second speed is performed. By doing so, it is possible to smoothly shift to the specific mode M only by continuing the engaged state of the 2-4 brake 70 and releasing the forward clutch 67 thereafter.

  As mentioned above, although embodiment of this invention was described, this embodiment can be suitably changed in the range which does not deviate from the summary of this invention. The modification will be described below.

  (1) In the restart control after a complete stop in the above embodiment, the engine is temporarily reversely operated after the engine is restarted, and then the normal rotation operation is performed. However, the restart control is performed only by the normal rotation operation. May be. However, once the engine is reversely operated, the combustion energy of the stop-stroke expansion stroke cylinder 12A increases, so that the engine can be restarted more reliably.

  (2) In the above embodiment, when restarting the engine, the fuel is supplied to the expansion stroke cylinder 12A and the compression stroke cylinder 12C after at least the restart condition is satisfied, but before the restart condition is satisfied. Fuel may be supplied in advance. For example, fuel may be injected during the intake stroke immediately before stopping during the automatic engine stop operation. In this way, vaporization atomization is promoted by the time of restart. At the time of restart, quick and good combustion can be performed only by igniting the spark plug 15 in the air-fuel mixture.

  (3) In the above embodiment, the automatic transmission 50 is a four-speed automatic transmission. However, the automatic transmission may be an automatic transmission having three or more stages. Further, the combination of the input element, the fixed element, and the output element of the planetary gear mechanism is not limited to the above embodiment.

  (4) Although omitted in the above embodiment, even when the engine is restarted and a predetermined condition is satisfied, for example, when the piston stop position is not within the predetermined proper range or within the proper range, the stop is performed. When the position is close to the boundary of the appropriate range, or when the engine rotation speed does not reach the predetermined value by the predetermined time after the start, and when the initial combustion of the engine is performed in the stop expansion stroke without further reverse rotation of the engine In addition, control with assist by a starter motor or the like (including a motor (ISG: Integrated Starter Generator) integrated with a starter and an alternator) may be performed. Even in this case, the burden on the starter motor can be reduced by the energy generated by the combustion of the engine. However, in this case, the fuel injection valve 16 may inject the fuel in the intake stroke so that vaporization and atomization of the injected fuel and mixing with the air proceed sufficiently directly into each cylinder. preferable.

  (5) In the above embodiment, the in-cylinder injection type is used as the fuel injection valve 16, but the present invention can also be applied to the case where a port injection type fuel injection valve is used.

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 of the power train which concerns on this invention. It is a relationship figure which shows the example of a relationship between the intermittent state of the fastening element in the automatic transmission mechanism, and a gear stage. It is a block diagram in the starting device concerning the present invention. It is a schematic diagram which shows the driving force transmission path | route in the D range 1st speed of the automatic transmission, and the rotation direction of each part. It is a speed diagram corresponding to the 1st speed stage-the 4th speed stage of the automatic transmission. It is a schematic diagram which shows the driving force transmission path | route in the D range 2nd speed of the automatic transmission, and the rotation direction of each part. It is a schematic diagram which shows the driving force transmission path | route in the D range 3rd speed of the automatic transmission, and the rotation direction of each part. It is a speed diagram of the neutral state in the vehicle stop state of the automatic transmission. It is a figure which shows the relationship between the compression stroke cylinder at the time of making an engine stop automatically, and an expansion stroke cylinder. (A) is a figure which shows the positional relationship of the piston of a compression stroke cylinder and an expansion stroke cylinder, (b) is a figure which shows the relationship between the stop position of a piston, and the air quantity in each cylinder. It is a time chart at the time of stopping an engine automatically, and is a figure which shows each time change of an engine speed, throttle opening, boost pressure, and the stroke in each cylinder. 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 flowchart which shows detection control operation | movement of a piston stop position. It is explanatory drawing which shows the output signal of a crank angle signal, (a) shows the pattern at the time of forward rotation, (b) shows the pattern at the time of reverse rotation. It is a time chart at the time of stopping an engine automatically, and shows an engine rotational speed and a turbine rotational speed. It is a general | schematic main flowchart including the engine stop / restart control by a stop restart control means. FIG. 18 is a previous stage of a subroutine showing engine stop / restart control (A) in step S8 of the flowchart shown in FIG. This is the latter stage of the subroutine shown in FIG. FIG. 18 is a previous stage of a subroutine showing engine stop / restart control (B) in step S9 of the flowchart shown in FIG. This is the middle stage of the subroutine shown in FIG. FIG. 22 is a subsequent stage of the subroutine shown in FIG. 21. FIG. It is a time chart which shows the combustion operation etc. at the time of engine restart. It is a time chart which shows temporal changes, such as engine speed at the time of engine restart.

Explanation of symbols

1 Engine body 2a Stop / restart control means 13 Piston 28 Alternator (external load)
39 atmospheric pressure sensor (detection means)
50 Automatic transmission M Specific mode (neutral state)
Ne Engine speed t3 Fuel supply stop point

Claims (4)

An engine automatic including at least a condition that the vehicle is in a stopped state or below a predetermined low vehicle speed with respect to a power train of the vehicle including the engine and an automatic transmission that transmits the driving force of the engine while performing a predetermined shift. When the stop condition is satisfied, the engine automatic stop control for automatically stopping the engine by stopping the fuel supply for continuing the engine operation is performed, and the restart condition of the engine in the automatic stop state is satisfied. Sometimes, an engine starter for a power train is provided with stop / restart control means for automatically restarting the engine by performing combustion in a cylinder in an expansion stroke at least when the engine is stopped,
Equipped with a detection means that detecting the atmospheric pressure,
The automatic transmission includes a drive state capable of transmitting the driving force from the engine side to the drive wheel side, the transmission of the driving force is configured to be switched between a neutral state of being disconnected,
The stop restart control means is in the automatic engine stop control, in the atmospheric pressure is equal to or higher than a predetermined value, when the standard air 圧近 near the the automatic transmission and the drive state immediately after the time point at least the fuel supply stop When the atmospheric pressure is less than a predetermined value, the automatic transmission is set to the neutral state at least immediately after the fuel supply is stopped.   The stop / restart control means adjusts the external load amount to the engine according to the reduced state of the engine speed during the engine stop operation period during the engine automatic stop control, and the piston stops within a predetermined appropriate range. The engine starter for a powertrain according to claim 1, wherein the engine starter is controlled so as to   The stop / restart control means sets the engine rotation speed at the time of stopping the fuel supply in the engine automatic stop control to a value higher than the engine rotation speed during warm idle operation. 2. An engine starter for a powertrain according to 2. In the engine automatic stop control, when the atmospheric pressure is less than a predetermined value , the stop / restart control means sets the engine rotation speed at the time of stopping the fuel supply to a higher value than when the atmospheric pressure is greater than or equal to a predetermined value. 4. The engine starting device for a power train according to claim 3, wherein

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