JP2007100550A - Engine starter of power train - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure quick startability or accelerability of a vehicle after restarting by improving restartability of an engine. <P>SOLUTION: A stopping restarting control means 2a is arranged for performing control for automatically stopping or restarting the engine, and performing control for restoring an automatic transmission 50 to a drive state in a specific period A in an engine stopping operation period, by outputting a engaging command to a clutch means 67 of the automatic transmission 50 in the predetermined timing T4 after stopping fuel supply, by displacing the automatic transmission 50 to a neutral state until a supply stopping point T2 of fuel, at the latest. The timing T4 for outputting the engaging command to the clutch means 67 by the stopping restarting control means 2a, is set to become an earlier timing than when in a high temperature state when a hydraulic fluid ATF of the clutch means is in a low temperature state. <P>COPYRIGHT: (C)2007,JPO&INPIT

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 and reduce CO ₂ emissions in automobiles, etc., the engine is automatically stopped once when it is stopped or decelerated, and then restart conditions such as start operation or acceleration operation are established. Engine starters have been developed that automatically restart the engine when the engine is started.

  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. Therefore, 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.

  In order to further improve the accuracy of the engine stop control as disclosed in Patent Document 1, it is desirable that the disturbance acting on the engine (crankshaft) during the stop operation is small. Therefore, recently, it has been studied to disengage the starting clutch of the automatic transmission (that is, switch from the drive state to the neutral state) when the engine is automatically stopped.

However, in this case, when the engine is requested to restart, the engine must be restarted and the automatic transmission must be promptly returned from the neutral state to the drive state. In order to suppress the return delay, for example, in Patent Document 2, after the engine is automatically stopped, the shift position of the automatic transmission is changed from the non-drive position (corresponding to the neutral state in the present specification) to the drive position (the drive in the present specification). The engine is restarted when it is changed to a state equivalent to the state), and rapid pressure increase control is performed to increase the hydraulic pressure temporarily and rapidly at the initial stage of oil supply to the clutch to be engaged when starting. In this way, the engagement of the clutch can be speeded up to some extent.
JP 2004-124754 A JP-A-11-351371

  However, in the engine starting device described in Patent Document 2, the rapid hydraulic pressure increase control is executed for the first time after the engine is restarted. A certain amount of time lag was unavoidable.

  The present invention has been made in view of the above circumstances, and when the engine is automatically stopped, the automatic transmission is switched from the drive state to the neutral state to improve the restartability of the engine and to automatically stop the engine. It is an object of the present invention to provide an engine starter for a powertrain that can ensure quick startability or acceleration of a vehicle after restart by returning the automatic transmission to a driving state before completion.

  In order to solve the above-mentioned problems, the present invention is such that an automatic stop condition for the engine is established for a power train including an engine and an automatic transmission that transmits a driving force of the engine while performing a predetermined shift. When the engine automatic stop control is performed to stop the fuel supply for continuing the engine operation and automatically stop the engine, and when the restart condition of the engine in the automatic stop state is satisfied, at least An engine starter for a powertrain having stop / restart control means for automatically restarting the engine by causing combustion in a cylinder in an expansion stroke when the engine is stopped, wherein the automatic transmission includes a planetary gear mechanism A hydraulically driven clutch means capable of intermittently connecting the first rotating element of the planetary gear mechanism and its input shaft; Oil temperature detecting means for detecting the oil temperature of the moving oil, and releasing or engaging the clutch means based on a command from the stop / restart control means, whereby transmission of the driving force of the engine is disconnected. The stop / restart control means sets the automatic transmission in the neutral state at the latest from the time when the fuel supply is stopped. And at the predetermined timing after the fuel supply is stopped, the engagement command is output to the clutch means, so that the engine returns to the normal rotation from the vicinity where the engine starts reverse rotation for the first time during the automatic stop operation period. The automatic transmission is controlled to return to the driving state within a specific period until the vicinity of the vehicle. The timing for outputting the engagement command to the clutch means is determined based on the oil temperature detected by the oil temperature detecting means, and when the hydraulic oil of the clutch means is in a low temperature state, compared to when it is in a high temperature state. It is characterized in that it is set so as to be in an early period (claim 1).

  According to this power train engine starting device, when the engine is automatically stopped, the influence transmitted from the wheel side to the engine is substantially reduced by displacing the automatic transmission to the neutral state at the latest from the time of stopping the fuel supply. Since it can be shut off, the stop position of the piston when the engine completes automatic stop can be accurately set within a range suitable for engine restart, and the restartability of the engine can be improved. . Moreover, the engine automatically stops by returning the automatic transmission to the drive state within a specific period from the vicinity where the engine starts reverse rotation for the first time during the automatic stop operation period to the vicinity where the engine returns to normal rotation. It is possible to return to the drive state with little influence on the piston position at the completion. At this time, if the temperature of the hydraulic oil of the hydraulically driven clutch means, which is a fastening element for returning the automatic transmission to the drive state, is low, the viscosity of the hydraulic oil increases and the resistance in the oil passage increases. Therefore, the time required from when the engagement command is issued to the clutch means until the engagement is actually completed becomes longer. In the present invention, the hydraulic oil for the clutch means (that is, the hydraulic oil for the automatic transmission) ) Is in a low temperature state, the output timing of the engagement command to the clutch means is advanced compared to when it is in a high temperature state, so that the clutch means is always at an appropriate time even if the temperature of the hydraulic oil fluctuates. Can be completed. According to the engine starter of the present invention that can reliably return the automatic transmission to the drive state before the completion of the automatic engine stop as described above, the engine restart condition is satisfied after that. When the vehicle restarts, it is possible to quickly restart or reaccelerate the vehicle simultaneously with the restart of the engine.

  Depending on the situation, the period from when the engine automatic stop condition is satisfied to when the restart condition is satisfied may be extremely short. An engine restart condition may be satisfied. Even in such a case, in order to restart the engine quickly and reliably, the stop / restart control means reverses the engine once during the automatic stop operation period when the restart condition is satisfied during the automatic stop operation period of the engine. It is preferable to perform natural reverse rotation return control in which the engine is restarted by burning in the cylinder in the expansion stroke when rotating and returning to normal rotation again (Claim 2).

  In this way, when the engine is reversely rotated once and returns to normal rotation again, the cylinder in the expansion stroke, that is, the piston approaches the top dead center due to the reverse rotation of the engine, the density of the compressed air (air mixture) becomes higher. By allowing combustion in the expanded stroke cylinder, which is in an increased state, it is possible to ensure a high combustion pressure and reliably restart the engine, and without waiting for the engine to stop completely automatically By causing the combustion, the engine can be restarted quickly.

  Preferably, the stop / restart control means maintains the rotational speed of the engine at a rotational speed higher than the rotational speed during warm idling before the automatic engine stop condition is satisfied and fuel supply is stopped. (Claim 3).

  Thus, by maintaining the rotational speed of the engine before stopping the fuel supply at a rotational speed higher than the rotational speed at the time of warm idling, the fuel supply is stopped until the engine is completely automatically stopped. Since the period can be made relatively long, the time required from when the engagement command is output to the clutch means to when the engagement is actually completed is somewhat longer due to the low temperature of the hydraulic oil in the automatic transmission. Even in such a case, the clutch means can be securely engaged within a specific period immediately before the completion of the automatic stop of the engine.

  The stop / restart control means judges from the detection result of the oil temperature detection means, and outputs a fastening command to the clutch means after the fuel supply is stopped, but still within a specific period during the engine stop operation period. If it is predicted that the engagement of the clutch means cannot be completed, it is preferable to stop the fuel supply stoppage (Claim 4).

  As a result, the engagement of the clutch means (return time to return to the drive state of the automatic transmission) is likely to be delayed later than the specific period during the engine stop operation period, and the engine is automatically stopped. Can be avoided.

  As described above, according to the engine starter for a powertrain of the present invention, when the engine is automatically stopped, the automatic transmission is switched from the drive state to the neutral state, thereby improving the restartability of the engine. By returning the automatic transmission to the drive state before completion of the automatic stop of the vehicle, it is possible to ensure quick startability or acceleration of the vehicle after 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. This engine includes an engine main body 1 having a cylinder head 10 and a cylinder block 11 and an ECU 2 (see FIG. 9) 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 for a time corresponding to the pulse width at the pulse input timing to open the valve. 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 (negative pressure) are disposed on the upstream side and the downstream side of the throttle valve 23, respectively.

  As shown in FIG. 1, the engine body 1 is provided with two crank angle sensors 30 and 31 for detecting the rotation angle of the crankshaft 3, and based on a detection signal output from one crank angle sensor 30. The rotational speed of the engine is detected, and the rotational direction and rotational angle of the crankshaft 3 are detected based on detection signals out of phase output from the crank angle sensors 30 and 31. The engine body 1 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 body 1. . The detection signals output from the sensors 25, 26, 30 to 33 are input to the ECU 2 as shown in FIG.

  Various detection signals are input to the ECU 2 from sensors provided in each device other than the engine. Specifically, the ECU 2 includes an accelerator sensor 34 that detects an accelerator opening corresponding to the accelerator operation amount of the driver, a brake sensor 35 that detects that the driver has performed a brake operation, and an automatic transmission described later. An oil temperature sensor 37 that detects the oil temperature of 50, a turbine rotation sensor 36 that detects the rotation speed of the turbine 55 of the automatic transmission 50 (details will be described later), and a vehicle speed sensor 38 that detects the vehicle speed. Detection signals are input respectively.

  Returning to FIG. 1 again, the engine body 1 is provided with an alternator (generator) 28 connected to the crankshaft 3 by a timing belt or the like. The alternator 28 is configured to be able to adjust the output voltage by controlling the current of the field coil (not shown), and based on the control signal from the ECU 2, the target corresponding to the electric load of the vehicle, the voltage of the vehicle battery, etc. The control of the generated current is executed.

  As shown in FIG. 3, the engine configured as described above is connected to an automatic transmission 50 through a crankshaft 3 as an output shaft thereof. The automatic transmission 50 includes a torque converter 51 connected to the crankshaft 3, and a multi-stage transmission mechanism 52 connected to a turbine shaft 59 (corresponding to an input shaft according to the present invention) that is an output shaft of the torque converter 51. Between the neutral state in which the transmission of the driving force to the wheel side is disconnected and the driving state in which the driving force can be transmitted to the wheel side. It is configured to be displaceable.

  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 referred to as ATF) as a working fluid, and the driving force of the pump impeller 54 is transmitted to the turbine 55 through the ATF. . The driving force transmitted to the turbine 55 is transmitted to the multi-stage transmission mechanism 52 via the turbine shaft 59 connected to the turbine 55.

  The case 57 includes a forward clutch 67 (corresponding to clutch means according to the present invention, which will be described later in detail) in which a turbine rotation sensor 36 that detects the rotational speed of the turbine 55 rotates integrally with the turbine shaft 59. It is provided in a state facing the outer peripheral surface. 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 spline-like irregularities provided on the outer peripheral surface of the drum are displaced by the rotation of the drum. By detecting a periodic change in the induced voltage, the rotational speed of the turbine 55 is detected through the rotational speed of the turbine shaft 59.

  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. In addition to the oil pump 61, an electric oil pump 62 (see FIG. 7) is provided in the case 57, and these oil pumps 61 and 62 are connected to a hydraulic control mechanism 63 described later. Then, the ECU 2 performs switching control between the oil pump 61 and the electric oil pump 62 and performs control such as switching of the oil path (fluid path) of the hydraulic control mechanism 63 and setting of the line pressure. Friction elements 67 to 71, which will be described later, are intermittently (fastened or released) by hydraulic control (pressure control of the working fluid).

  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 lockup clutch 64 interposed between the pump cover 53 and the turbine 55 and directly connecting 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 shown in FIG. The various solenoid valves provided in the hydraulic control mechanism 63 are on / off controlled based on a signal output from the ECU 2 (see FIG. 9) according to the vehicle speed, so that the oil passage is switched and locked. The up clutch 64 is disengaged.

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

  The N range, D range, and the like referred to here do not necessarily indicate the shift operation position by the shift lever, but the substantial transmission state in which each solenoid valve is controlled. For example, even if the shift operation position by the speed change lever remains in the D range position, if the automatic transmission 50 is in the N range (neutral) state by the control of each solenoid valve, the substantial shift range is the N range.

  The first and second planetary gear mechanisms 65 and 66 are arranged around the sun gear 65a (corresponding to the first rotating element according to the present invention), the sun gear 66a, and the sun gears 65a and 66a, respectively. A plurality (for example, three) of planetary gears 65b and 66b, carriers 65c and 66c that support these planetary gears 65b and 66b, and ring gears 65d that are arranged so as to surround the planetary gears 65b and 66b and mesh with each other. , 66d, the ring gear 65d of the first planetary gear 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 second planetary gear mechanism 66 are coupled. The planetary gear mechanisms 65 and 66 can be interlocked by being connected to the ring gear 66d.

  Each friction element of the multi-stage transmission mechanism 52 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 sun gear 66a of the turbine shaft 59 and the second planetary gear mechanism 66. The reverse clutch 68 interposed therebetween, the 3-4 clutch 69 interposed between the turbine shaft 59 and the carrier 66c of the second planetary gear mechanism 66, and the sun gear 66a of the second planetary gear mechanism 66 are fixed 2-4. The brake 70 is constituted by a low reverse brake 71 and the like interposed in parallel between the planetary gear mechanisms 65 and 66 and the case 57. The one-way clutch 72 is configured to permit (unlock) only rotation in one direction (drive direction of the crankshaft 3) of the carrier 65c and the ring gear 65d, and restrict (lock) rotation in the reverse direction. Has been. These fastening elements 67 to 72 are configured to be able to be interrupted, whereby 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 wheels, that is, via 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).

  The relationship between the intermittent state of these fastening elements 67-72 and a gear stage is shown in FIG. In FIG. 4, ◯ indicates a state in which the fastening elements 67 to 72 are fastened or locked, and no mark indicates a state in which they are released or unlocked. Accordingly, in the R range, the reverse clutch 68 and the low reverse brake 71 are engaged, and in the N range (neutral range), all the engagement elements 67 to 72 are released / unlocked. Further, at the first speed of the D range (drive range), the forward clutch 67 is engaged and the one-way clutch 72 is locked, and at the second speed, the forward clutch 67 and the 2-4 brake 70 are engaged. The forward clutch 67 and the 3-4 clutch 69 are engaged at the third speed, and the 3-4 clutch 69 and the 2-4 brake 70 are engaged at the fourth speed.

  FIG. 5 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, the left rotation is the forward rotation direction and the right rotation is the reverse rotation direction as viewed from the left front side. 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 in the D range shown in FIG. 5, the turbine shaft 59 rotates in the forward rotation direction, and the rotation and driving force are transmitted to the sun gear 65 a through 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 rotation of the ring gear 65d in the reverse rotation direction is restricted when the one-way clutch 72 is locked, the planetary gear 65b rotates in the reverse rotation direction around the support shaft (carrier 65c), and the carrier 65c. It integrally rotates around the sun gear 65a in the forward rotation direction. 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.

  On the other hand, since the carrier 65c is connected to the ring gear 66d, the ring gear 66d rotates in the forward rotation direction. Further, since the carrier 66c is connected to the ring gear 65d, and the ring gear 65d is stopped by the locking of the one-way clutch 72, 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. 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 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, the carrier 66c, which has been stopped because the rotation in the reverse direction is restricted by the one-way clutch 72, is moved in the forward direction at the second speed as the 2-4 brake 70 is engaged. The one-way clutch 72 is unlocked for rotation in the forward 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. However, unlike the first speed, the ring gear 65d rotates in the forward rotation direction, so that the rotation speed of the carrier 65c is relatively higher than that in the first speed. 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 description of the operation of each part of the automatic transmission 50 in the third and fourth speeds of the D range is omitted, but the friction elements 67 to 71 are fastened sequentially by fastening and releasing in a combination as shown in FIG. (The rotational speed of the transmission gear 76 is relatively greater than the input rotational speed of the turbine shaft 59).

  The friction elements 67 to 71 are connected to the oil pump 61 and the electric oil pump 62 through a hydraulic control mechanism 63 (see FIG. 7), similarly to the lock-up clutch 64. The first and second shift solenoid valves 83 and 84 and the first to third duty solenoid valves 85 to 87 (details will be described later) provided in the hydraulic control mechanism are in response to commands from the ECU 2 (see FIG. 9). By being driven based on this, the oil passage, hydraulic pressure, and the like are switched and changed, and the friction elements 67 to 71 are intermittently connected.

  Specifically, the hydraulic control mechanism 63 includes a hydraulic control circuit as shown in FIG. 7, and this hydraulic control circuit is connected to the oil pump 61 and the electric oil pump 62 to supply the original pressure from the pumps 61 and 62. Is done. The hydraulic control mechanism 63 is arranged in the vicinity of the downstream side of the pumps 61 and 62 in the line 81 and the line 81 (oil passage) connected from the pumps 61 and 62 to the hydraulic chambers (not shown) of the friction elements 67 to 71. The first and second shift solenoid valves 83 and 84 (hereinafter simply referred to as “first and second SV”) for turning ON / OFF the regulator valve 82 provided for regulating the line pressure and the various valves for switching the lines communicating with the pumps 61 and 62. And first to third duty solenoid valves 85 to 87 (hereinafter simply referred to as “first to third DSVs”) for adjusting the operating pressure based on the duty value output from the ECU 2. The first and second SVs 83 and 84 and the first to third DSVs 85 to 87 are configured as three-way valves. Further, a switching valve 91 for switching the oil supply source between the oil pump 61 and the electric oil pump 62 is provided on the oil passage connecting the pumps 61 and 62 and the line 81.

  Then, according to the position of the shift lever or automatically, the ECU 2 performs control to switch the automatic transmission 50 between a plurality of stages by operating the various valves to intermittently connect the friction elements 67 to 71. It is configured. FIG. 8 shows combinations of operating states for the respective speeds of the solenoid valves 83 to 87. In FIG. 8, the circles are ON for the first and second SVs 83 and 84, and are OFF for the first to third DSVs 85 to 87, both of which connect the upstream line to the downstream line. A state in which the original pressure is supplied as it is or as a working pressure is supplied to the downstream side, and the X mark is OFF for the first and second SVs 83 and 84, and is ON for the first to third DSVs 85 to 87. Also shows a state in which the upstream line is blocked and the downstream line is drained.

  For example, the operation of the hydraulic control mechanism 63 when the automatic transmission 50 is switched from the N range to the D range first speed will be described. In this case, as shown in FIG. 8, only the third DSV 87 is operated to generate an operating pressure using the upstream line pressure as a source pressure, and this operating pressure is supplied to the lockup control valve 88 via the line 81b. Is done. At this point, the spool of the lock-up control valve 88 is positioned on the right side, so that the forward clutch pressure (operating pressure) is further supplied to the hydraulic chamber of the forward clutch 67 via the forward clutch line 81c. The forward clutch 67 is engaged.

  In this way, the third DSV 87 is operated to generate an operating pressure, and the operating pressure is supplied to the forward clutch 67 through a predetermined oil passage so that the forward clutch 67 is fastened. A certain amount of time is required from when the signal is output from the ECU 2 until the forward clutch 67 is actually engaged. The time required for engaging the forward clutch 67 has a property of fluctuating depending on the operating oil (that is, ATF) temperature in the oil passage. The relationship between the ATF temperature and the engaging time of the forward clutch 67 is shown in FIG. Show. As shown in FIG. 18, the time required to engage the forward clutch 67 is short when the ATF temperature is high, and becomes longer as the ATF temperature is lower. This is because if the temperature of the ATF is low, the viscosity of the ATF increases, the resistance in the oil passage increases, and it takes time to transmit the operating pressure.

  FIG. 9 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 38 and outputs a signal for controlling the fuel injection amount and the injection timing to the fuel injection valve 16, and the ignition timing to the spark plug 15. A control signal is output, a control signal for controlling the throttle opening is output to the actuator 24 of the throttle valve 23, and a signal for controlling the power generation amount is output to the regulator circuit 28a of the alternator 28. To do.

  The ECU 2 receives a signal from each of the sensors 25, 26, 30 to 38, and switches a switching signal for switching 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 for adjusting the operating pressure of each of the friction elements 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. In this embodiment, a plurality of the above automatic stop conditions are set, and the engine is automatically stopped when all these conditions are satisfied. On the other hand, a plurality of restart conditions are set, and the engine is automatically restarted when one or more conditions are satisfied according to the contents of the conditions.

  Next, the operation at the time of automatic stop and restart of the engine by the stop / restart control means 2a will be described.

  First, engine automatic stop control will be described. FIG. 10 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 referred to here 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 compression stroke. It is the cylinder that will be. 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. 10A is a diagram showing the positional relationship between the pistons 13 of the compression stroke cylinder and the expansion stroke cylinder. Since the engine of the present embodiment is a four-cylinder four-cycle engine, in the drawing, the phases of the compression stroke cylinder and the expansion stroke cylinder are shifted by 180 ° CA, respectively, and the position and moving direction of the piston 13 are in opposite phases. ing. 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, so that the rotation direction of the crankshaft 3 is changed from reverse to normal. 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.

  FIG. 10B is a diagram showing the relationship between the stop position of the piston 13 and the amount of air in each cylinder. In this figure, the horizontal axis represents the piston stop position (ATDC ° CA: crank angle after top dead center) of the expansion stroke cylinder, and the vertical axis represents 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 securing 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 (in the range R shown in FIG. 10B). Hereinafter, this range is referred to as an appropriate range R.

  There are various specific methods for controlling the piston 13 of the expansion stroke cylinder within the appropriate range R. In this embodiment, as will be described later, by controlling the opening of the throttle valve 23, the expansion stroke cylinder 12A and The stop position of the piston 13 is controlled by adjusting the compression reaction force caused by the air in the compression stroke cylinder 12C and by controlling the power generation amount of the alternator 28 and adjusting the external load of the engine.

  FIG. 11 is a time chart when the engine is automatically stopped. The horizontal axis represents time t (s), and the vertical axis represents engine rotational speed Ne (rpm). The outline of the engine stop / restart control by the stop / restart control means 2a will be described with reference to the engine rotation speed characteristic 150 shown in FIG. The general operation of the engine stop / restart control is as follows. First, after the time T0 when the idle stop condition (engine automatic stop condition) is satisfied, the fuel supply is stopped (F / C) at the time T2, and the expansion stroke at the engine complete stop time T10. The piston stop position of the cylinder is guided into the appropriate range R (see FIG. 10B) (automatic stop control). After that, when there is a restart request such as accelerator-on, and when the restart condition is satisfied (time point T11), at least combustion is performed in the expansion stroke cylinder, and the engine is restarted promptly and smoothly (after complete stop) The engine rotation speed characteristic 156). On the other hand, when there is a restart request between time T0 and time T9, the engine is restarted as soon as possible without waiting for the engine to completely stop (natural reverse recovery control. Engine speed characteristics). 155). Details of these controls will be described later.

  FIG. 12 is a time chart for explaining the details of the automatic engine stop control in more detail. 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. 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.

  When the idle stop condition is satisfied at the time T0, the stop / restart control means 2a at least forwards the friction elements 67 to 71 in order to switch the automatic transmission 50 from the D range (drive state) to the N range (neutral state). A command for releasing the clutch 67 is output. Here, “at least the forward clutch 67” means that only the forward clutch 67 needs to be released when switching from the D range first speed to the N range, but for example, switching from the D range second speed to the N range is also possible. In such a case, it is necessary to release not only the forward clutch 67 but also the 2-4 brake 70 (see FIG. 4). Then, the release of the forward clutch 67 is completed after a predetermined time difference, and the automatic transmission 50 is substantially switched to the N range at time T1.

  Further, the stop / restart control means 2a performs pre-control (pre-F / C control) before stopping the fuel supply at time T0, in addition to the control for releasing the forward clutch 67. In the pre-F / C control, the throttle opening K is adjusted to set the engine speed Ne to the target speed N1 (for example, N1 = 860 rpm), and the ignition timing is set so that the engine speed Ne does not increase too much. Perform retard. The retard amount is feedback-controlled so that the engine rotational speed Ne converges to the target rotational speed N1. This target rotation speed N1 is set to a value larger than the engine rotation speed during warm idling (for example, 640 rpm). By stopping the fuel supply at the relatively high target rotational speed N1, the time from the fuel supply stop time T2 to the engine complete stop time T10 can be made relatively long. It is possible to sufficiently secure the time necessary for returning the automatic transmission 50 that has been switched to the D range at an appropriate timing (details will be described later). There is also an advantage that the burned gas in the engine can be sufficiently scavenged.

  Then, at a time T2 when the engine speed Ne converges to the target rotational speed N1 after a predetermined time has elapsed and the boost pressure Bt converges to a predetermined target value (for example, −400 to −600 mmHg), the F / C condition is satisfied. As it is established, the throttle opening K is increased to about 30%, for example, and the fuel supply is stopped (F / C).

  When the fuel supply is stopped at the time T2 as described above, the kinetic energy of the crankshaft 3 and the like is consumed by mechanical loss due to frictional resistance and pump work of each cylinder 12A to 12D, thereby The crankshaft 3 is rotated several times by inertia, and in a four-cylinder four-cycle engine, it stops after reaching a 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 point T6 when the final compression top dead center is exceeded, that is, 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 T2, and the expansion stroke cylinder 12A and After inhaling a predetermined amount of air into both the compression stroke cylinders 12C, at the time T3 when it is confirmed that the engine rotational 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 supply is stopped at the time point T2 when the rotational speed Ne of the engine becomes a predetermined speed, and the cylinders of the engine rotating by inertia are maintained so as to keep the throttle valve 23 open for a predetermined period thereafter. When the top dead center rotational speed ne when the piston 13 provided in 12A to 12D passes through the compression top dead center is measured and the piston position of the expansion stroke cylinder 12A at the time of engine stop is examined, the engine is stopped. If the top dead center rotational speed ne at the sixth to second before 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 (FIG. 10 (b It has been experimentally confirmed that it is within the scope of)).

  Therefore, in order to finally stop the piston 13 of the expansion stroke cylinder 12A within the appropriate range R, the top dead center rotational speed ne in the sixth to second before the engine is stopped is within the predetermined range. What is necessary is just to reduce the engine rotational speed Ne so that it may enter sequentially. In order to perform such precise control, it is desirable to eliminate the effect of acting on the crankshaft 3 from the drive wheel side.

Therefore, in the present embodiment, prior to the fuel supply stop time T2, the automatic transmission 50 is switched from the drive state (D range) to the neutral state (N range) as described above, so that from the drive wheel side during engine stop control. The effect of this is substantially cut off. By doing so, the piston stop position accuracy by the engine stop control can be improved, and the restartability can be improved. In addition, since the piston can be accurately stopped within the appropriate range even while the vehicle is running, the opportunity to automatically stop the engine is expanded, and fuel consumption reduction and CO ₂ emission reduction are promoted. The

  Similarly, in order to increase the accuracy of the piston stop position by the engine stop control, in this embodiment, the rotation resistance of the crankshaft 3 (external load of the engine) is further adjusted by adjusting the target generated current Ge of the alternator 28. I am doing so. Specifically, the target generated current Ge of the alternator 28 is set to, for example, 0 at the fuel supply stop time T2, and the target generated current Ge of the alternator 28 is set at the time T3 when the engine speed Ne is decreased to the reference speed N2 or less. After the control for increasing the engine speed to the preset initial value, at the time T5 when the engine top dead center rotational speed ne is within the predetermined range, the target generated current Ge of the alternator 28 is decreased to the engine rotational speed Ne. The external load of the engine is optimally adjusted by reducing it to a value corresponding to the situation, and thereby the engine rotational speed Ne is set to a target reduction pattern (upper sixth to second before the engine is stopped). The dead center rotation speed ne is decreased along a decreasing pattern (sequentially entering the predetermined range shown by hatching in FIG. 13). That.

  The stop / restart control means 2a reads each top dead center rotational speed ne as the engine rotational speed Ne decreases after the fuel supply stop time T2. 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 this time T6, the piston 13 moves (vibrates) in each of the cylinders 12A to 12D, but does not shift to the next stroke beyond the top dead center TDC or the bottom dead center BDC.

  Although omitted in the flowchart described later, after the time T6, the throttle opening K may be increased again as shown in the figure. 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 the piston 13 can be easily stopped within the appropriate range R. Further, since there is no transition of the stroke in each of the cylinders 12A to 12D after the time 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.

  The detection of the stop position of the piston 13 is performed based on the detection results of 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, the stop / restart control means 2a is operated 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). It is determined whether or not the second crank angle signal CA2 is low when the first crank angle signal CA1 rises, 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 (Step S3). Then, after stopping the engine, the piston stop position is obtained by examining the measured value of the CA counter (step S4).

  On the other hand, in parallel with the control as described above, the stop / restart control means 2a returns the automatic transmission 50 that has been in the neutral state (N range) after the time T1 to the drive state (D range). Control. The contents of the control will be specifically described with reference to FIG. The stop / restart control means 2a first calculates an engine rotation speed (N → D rotation speed) N3 when an engagement command should be output to the forward clutch 67 of the automatic transmission 50 based on the ATF temperature, and the calculation is performed. An engagement command is output to the forward clutch 67 at time T4 when it is confirmed that the engine speed Ne has decreased below the engine speed N3. The N → D rotation speed N3 is set to a larger value as the ATF temperature is lower. That is, the timing at which the engagement command is output to the forward clutch 67 is advanced as the time required to engage the forward clutch 67 becomes longer because the ATF temperature is lower. The reason is that the forward rotation of the forward clutch 67 (that is, the return timing of the automatic transmission 50 to the drive state) T8 does not depend on the ATF temperature, and the engine starts reverse rotation for the first time during the automatic stop operation period. This is because the time is within an appropriate period A (FIG. 11) from time T7 to time T9 when the engine returns to normal rotation. If the fastening of the forward clutch 67 is completed during such a period, the automatic transmission 50 can be maintained in the neutral state in a region where it is particularly desirable to interrupt the disturbance in the engine automatic stop control (before time T6). The automatic transmission 50 can be reliably returned to the drive state before the engine is completely stopped.

  Next, control during engine restart will be described. As described above, the engine restart control includes a restart control after a complete stop after waiting for a complete stop of the engine and a restart of the engine without waiting for a complete stop of the engine. There are two types of natural reverse return control. First, restart control after complete stop will be described.

  16 and 17 are time charts when the engine is restarted. As shown in these drawings, first, the first fuel injection J2 is performed in the compression stroke cylinder 12C (third cylinder), and combustion ((1) in FIG. 16) is performed by the ignition. With the combustion pressure (part a in FIG. 17) due to this combustion (1), the piston 13 of the compression stroke cylinder 12C is pushed down to the bottom dead center side, and the engine is driven in the reverse direction.

  With the reverse rotation of the engine, the piston 13 of the expansion stroke cylinder 12A (first cylinder) starts to move in the direction of top dead center. Then, when the piston 13 of the expansion stroke cylinder 12A moves to the top dead center side (preferably closer to the top dead center than the center of the stroke) and the air in the expansion stroke cylinder 12A is compressed, the fuel injection J1 (in this embodiment). Twice). The compression pressure is reduced by the latent heat of vaporization of the injected fuel, and the piston 13 comes closer to the top dead center, so that the density of the compressed air (air mixture) increases (part b in FIG. 16).

  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. 16). The engine is driven in the forward direction by the combustion pressure (c portion in FIG. 17).

  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. 16), but the compression stroke cylinder 12C is not combusted. The compression pressure of the compression stroke cylinder 12C is reduced by the latent heat of vaporization caused by fuel injection (part d in FIG. 17), and accordingly, the compression top dead center (the first compression top dead center from the start of the start) is exceeded. 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. 16) 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. 17). 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. 16) after the start of restart and the second compression by the energy of the first combustion ((2) in FIG. 16) in the expansion stroke cylinder 12A. It is possible to exceed the top dead center ((4) in FIG. 16), and a smooth and reliable startability can be ensured.

  Next, the natural reverse rotation return control for restarting the engine without waiting for the complete stop of the engine will be described with reference to FIG. This natural reverse rotation return control is a control for promptly responding to a request for restart during the automatic engine stop operation period (between times T0 and T9 in this embodiment). This is a control that uses a reverse rotation just before a complete stop and uses a momentum (inertia) that changes from the reverse rotation to the normal rotation to perform a quick restart. That is, while the engine is reversely rotated immediately before the complete stop (between time points T7 and T9), the piston 13 of the expansion stroke cylinder 12A is raised and the in-cylinder air is compressed. Since the forward rotation is started (that is, the piston 13 starts to descend in the expansion stroke cylinder 12A), the fuel is injected from the fuel injection valve 16 and is ignited by the ignition 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. In this way, it is possible to perform a more rapid restart than when restarting after waiting for a complete stop of the engine (time T10).

  FIG. 19 is a schematic main flowchart relating to 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 the conditions such as the temperature of 10 ° C. or higher and the ATF temperature of 40 ° C. or higher are satisfied.

  If YES is determined in the step S6, the process proceeds to a step S7 to execute the engine stop / restart control as described above. That is, the fuel supply for continuing the engine operation is stopped and the engine is automatically stopped (engine automatic stop control). When the restart condition of the engine in the automatic stop state is satisfied, at least the expansion stroke cylinder 12A In this control, combustion is performed and restarted automatically. Then, after the engine stop / restart control is executed, the process proceeds to step S8 and returns to the normal control. When it is determined NO in step S6, the process returns to continue normal control.

  Here, in the idle stop condition, the condition that the ATF temperature is 40 ° C. or higher is provided. If the ATF temperature is lower than 40 ° C., the time required for engaging the forward clutch 67 of the automatic transmission 50 is greatly increased. This is because it becomes longer (see FIG. 18), and there is a higher possibility that the shift control to be performed on the automatic transmission 50 cannot be appropriately performed as the engine is stopped / restarted. In other words, during the engine stop / restart control, as described above, it is necessary to perform control for switching the automatic transmission 50 from the drive state to the neutral state and then returning to the drive state again, but the ATF temperature is low. After that, for example, even if an engagement command is output to the forward clutch 67 at an early time such as immediately after the fuel supply stop time T2 (FIG. 12), the timing for completing the engagement of the forward clutch 67 is determined as described above. There is a high possibility that it will not be possible to fall within the appropriate period A (FIG. 11) immediately before completion of the automatic stop (that is, the return time to the drive state will be after time T9). Therefore, in such a case, it is highly possible that the automatic transmission 50 cannot be returned to the drive state at an appropriate time by not performing the engine automatic stop control (not stopping the fuel supply). The situation where the engine is automatically stopped is avoided.

  20 to 22 are subroutines showing the engine stop / restart control in step S7 of FIG. In the following description, time points such as time point T0 and 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 state when the idle stop condition is satisfied. That is, as shown in FIG. 4, only the forward clutch 67 is engaged among the friction elements 67 to 71.

  When this subroutine starts, that is, when the idle stop condition is satisfied (time T0), the stop / restart control means 2a first outputs a forward clutch release command to the automatic transmission 50. When the release of the forward clutch 67 is completed after a lapse of a predetermined time (time point T1), the automatic transmission 50 enters a neutral state, and disturbance from the drive wheel side to the engine is cut off after this time point T1. Accordingly, stable automatic engine stop control can be performed thereafter.

  Next, in step S13, it is determined whether or not there is a restart request. 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 NO in step S13, the control proceeds to pre-F / C control (pre-fuel stop control) (step S15). In this pre-F / C control, the engine rotational speed Ne is set to a target rotational speed N1 (for example, N1 = 860 rpm) as pre-control before stopping fuel supply. Then, the throttle opening degree K is adjusted to guide the boost pressure Bt to a predetermined target value (for example, −400 to −600 mmHg). In parallel with these, 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.

  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 (execution condition for stopping fuel supply) is satisfied (in step S17). YES) When this F / C condition is satisfied (time point T2), the throttle opening K is increased to, for example, about 30% (step S19), and the fuel supply is stopped (step S21).

  Next, in step S23, it is determined whether or not there is a restart request as in step S13. If YES here, “1” is input to the natural reverse rotation return flag F1 (its default value is 0) (step S25). When “1” is input to this natural reverse rotation return flag F1, at the time of subsequent engine restart, with the exception of some exceptions, natural reverse rotation return control, that is, control that restarts the engine without waiting for a complete stop of the engine. Is done.

  After step S23 or step S25, it is determined whether or not the engine rotational speed Ne is equal to or lower than a reference speed N2 (for example, N2 = 790 rpm) (step S27). The throttle valve 23 is closed at the time T3 when YES is determined in step S27, and the opening degree K is reduced (step S29). As a result, the boost pressure Bt that has approached the atmospheric pressure by increasing the throttle opening K in step S19 starts to decrease with a predetermined time difference according to the throttle opening reduction operation.

  Next, control is performed to return the automatic transmission 50 that has been switched to the neutral state after the time T1 as described above to the drive state again. First, as the preliminary control, the timing for outputting the engagement command to the forward clutch 67 is adjusted and set. Specifically, first, based on the ATF temperature detected by the oil temperature sensor 37, an N → D rotational speed N3 that is an engine rotational speed when an engagement command is to be output to the forward clutch 67 is determined (step S31). ). As described above, the N → D rotational speed N3 is determined so that the engagement completion timing of the forward clutch 67 (that is, the return timing of the automatic transmission 50 to the drive state) does not depend on the ATF temperature, and the appropriate period A (time T7). (Between T9 and T9), the larger the ATF temperature is, the larger the value is set. Then, it is determined whether or not the engine rotational speed Ne is equal to or lower than the N → D rotational speed N3 (step S33). If YES is determined in this step S33, an engagement command is output to the forward clutch 67 (step S35), the engagement of the forward clutch 67 is completed at a time T8 when a predetermined time has elapsed, and the automatic transmission 50 enters the drive state. Return.

  Then, after the step S35, it is determined whether or not the predetermined rotational speed N4> the engine rotational speed Ne> the predetermined rotational speed N5 (steps S37 and S39). For example, the predetermined rotational speed N4 = 650 rpm and the predetermined rotational speed N5 = 400 rpm are set. As described above, when it is determined that N4> Ne> N5 (YES in step S37 and NO in step S39) (time point T5), the stop / restart control means 2a executes alternator control (step S41).

  The alternator control referred to here is to reduce the initial value of the target generated current Ge of the alternator 28 (target generated current Ge between time points T3 and T5 in FIG. 12) to a value corresponding to the decrease state of the engine speed Ne. is there. Thus, the external load of the engine is adjusted so that the engine rotation speed Ne decreases along the target decrease pattern, and the piston 13 is surely stopped within the appropriate range R (see FIG. 10B). To. In this flowchart, the control of the alternator 28 before time T5 is omitted.

  If YES in step S39, that is, if engine rotational speed Ne <predetermined rotational speed N5, the alternator control is terminated, and it is determined in step S43 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 the natural reverse rotation return control is executed if earlier than this timing. In this embodiment, the natural reverse rotation return timing is set to a time point when the engine changes from normal rotation to reverse rotation, that is, time T9 in FIGS.

  If YES in step S43, that is, if it is before the natural reverse rotation return timing, the process returns to step S23, and the processing from step S23 to step S43 is repeated. Similarly, in the case of NO in step S37 and in the case of NO in step S39 (during alternator control execution), the process returns to step S23 and each process is repeated. If there is a restart request during that time, “1” is input to the natural reverse rotation return flag F1 in step S25.

  When it is determined NO in Step S43, 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 rotational speed of the turbine shaft 59 in the automatic transmission 50 is a value corresponding to the vehicle speed and the gear position, it is determined that the engagement of the forward clutch 67 has been completed. The turbine rotation speed is proportional to the vehicle speed, and the proportional constant is uniquely determined from the tire radius, the gear ratio of the automatic transmission 50, and the like. Therefore, the stop / restart control means 2a can determine that the engagement of the forward clutch 67 has been completed when the turbine rotational speed reaches a value corresponding to the vehicle speed. When such a determination is difficult, even if it is determined that the forward clutch 67 is completely engaged due to another method, for example, a predetermined period after the forward clutch engagement command is issued. good.

  This complete engagement determination method for the forward clutch 67 is common to other steps (steps S73, S85, and S87) described later.

  When it is confirmed in the determination in step S53 that the engagement of the forward clutch 67 is completed (YES), the stop / restart control means 2a indicates that the engine has completely stopped (YES) in step S55. Confirm. And it waits until there exists a restart request | requirement, and the restart control after a complete stop is performed at the time of a restart request | requirement (it is YES at step S57).

  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. 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 is when there is a restart request from when the idle stop condition is satisfied and the engagement command is issued to the forward clutch 67 until the fuel supply is stopped (F / C) (section 161 shown in FIG. 11). It corresponds to. In this case, since the release of the forward clutch 67 has just been started, this is immediately stopped and the normal control is resumed. That is, the stop / restart control means 2a outputs an engagement command to the forward clutch 67 (step S71), waits for the forward clutch 67 to be engaged (YES in step S73), and ends the engine stop / restart control ( Step S75) and return. That is, the control shifts to normal control.

  Next, the case where it is determined in step S23 that there is a restart request will be described. This corresponds to a case where there is a restart request from the time when the fuel supply is stopped (F / C) to the natural reverse rotation return timing T9 (section 162 shown in FIG. 11). 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. At this time, since the natural reverse rotation return flag F1 = 1, it is determined YES in step S51, the process proceeds to step S85, and it is determined whether or not the engagement of the forward clutch 67 is completed. Here, the stop / restart control means 2a outputs an engagement command to the forward clutch 67 at a timing such that the engagement completion timing of the forward clutch 67 falls within the appropriate period A (between time points T7 and T9) as described above. (Step S35), in most cases, YES is determined in Step S85.

  Thus, if it determines with YES by step S85, the stop restart control means 2a will perform natural reverse rotation return control (step S95).

  As described above, the natural reverse rotation return control is a control that causes the engine to perform a quick restart using momentum (inertia) at which the engine turns from reverse rotation to normal rotation at time T9. However, due to variations and other factors, It is assumed that the forward clutch 67 is not fully engaged at time T9 (NO in step S85). In such a case, the natural reverse rotation is not forcedly returned, and the restart control after the complete stop is executed after completion of the engagement of the forward clutch 67 and the complete stop of the engine (YES in Step S87 and Step S89) (Step S59). ). By so doing, it is possible to effectively prevent the driver from feeling uncomfortable or damaging the forward clutch 67 when the forward clutch 67 is not fully engaged.

  As described above, according to the engine starter of the present embodiment, when the engine is automatically stopped, the automatic transmission 50 is displaced to the neutral state from the time T1 before the stop of fuel supply (F / C). By doing so, the influence transmitted from the wheel side to the engine can be substantially cut off, so that the stop position of the piston 13 at the time when the engine completes the automatic stop is accurately within a range suitable for restarting the engine. The engine restartability can be improved. In addition, by returning the automatic transmission 50 to the drive state within a proper period A between the time T7 when the engine starts reverse rotation for the first time during the automatic stop operation period and the time T9 when the engine returns to normal rotation, It is possible to return to the drive state with almost no influence on the position of the piston 13 when the automatic engine stop is completed. At this time, if the temperature of the hydraulic oil (ie, ATF) of the forward clutch 67, which is an engaging element for returning the automatic transmission 50 to the drive state, is low, the viscosity of the ATF increases and the resistance in the oil passage increases. For this reason, the time required from when the engagement command is issued to the forward clutch 67 to when the engagement is actually completed becomes longer. In this embodiment, when the ATF is in a low temperature state, it is in a high temperature state. Since the output timing of the engagement command to the forward clutch 67 is advanced compared to the above, the engagement of the forward clutch 67 can always be completed at an appropriate time even if the temperature of the ATF fluctuates. As described above, according to the engine starter of the present invention that can reliably return the automatic transmission 50 to the drive state within the appropriate period A before the completion of the automatic stop of the engine, the engine restart thereafter When the condition is satisfied and the engine is restarted, the vehicle can be rapidly restarted or reaccelerated simultaneously with the restart of the engine.

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

  (1) In the 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 automatic transmission in the starting device which concerns on this invention. FIG. 6 is a relationship diagram illustrating an example of a relationship between an operating state of a friction element and a gear position in the automatic transmission. 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 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 the schematic which shows an example of the hydraulic control circuit of the automatic transmission. It is a relationship figure which shows the example of a relationship between the operating state of the solenoid valve in the automatic transmission, and a gear stage. It is a block diagram in the starting device concerning the present invention. It is a figure which shows the relationship between the compression stroke cylinder at the time of stopping an engine 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 stop of a piston. It is a figure which shows the relationship between a position and the air quantity in each cylinder. It is a time chart which shows the change state of the engine speed at the time of an engine automatic stop. It is a time chart which shows the change state of an engine speed at the time of an engine automatic stop, change states, such as a throttle opening and a target electric power generation current. It is a distribution map which shows the correlation with the engine rotational speed at the time of an engine automatic 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 which shows the combustion operation etc. at the time of engine restart. It is a time chart which shows the change state etc. of the engine speed at the time of engine restart. It is a figure which shows the relationship between ATF temperature and clutch fastening time. It is a general | schematic main flowchart including the engine stop / restart control by a stop restart control means. FIG. 20 is a previous stage of a subroutine showing engine stop / restart control in the flowchart shown in FIG. 19. This is the middle stage of the subroutine shown in FIG. This is the latter stage of the subroutine shown in FIG.

Explanation of symbols

1 Engine body 2a Stop / restart control means 37 Oil temperature sensor (oil temperature detection means)
50 Automatic transmission 59 Turbine shaft (input shaft for planetary gear mechanism)
65 Planetary gear mechanism 65a Sun gear (first rotating element)
67 Forward clutch (clutch means)
D Drive state N Neutral state A Appropriate period (specific period during engine stop operation period)

Claims (4)

Fuel supply for continuing engine operation when the engine automatic stop condition is satisfied for a power train including an engine and an automatic transmission that transmits the driving force of the engine while performing a predetermined shift. In addition to performing engine automatic stop control to stop and automatically stop the engine, when the restart condition of the engine in the automatic stop state is satisfied, combustion is performed at least in the cylinder in the expansion stroke when the engine is stopped. An engine starter for a powertrain provided with stop / restart control means for automatically restarting the engine,
The automatic transmission detects a planetary gear mechanism, a hydraulically driven clutch means capable of intermittently connecting the first rotating element of the planetary gear mechanism and its input shaft, and an oil temperature of hydraulic oil of the clutch means. A neutral state in which transmission of the driving force of the engine is disconnected by releasing or engaging the clutch unit based on a command from the stop / restart control unit, and the driving force It is configured to be displaceable between drive states that can transmit
The stop / restart control means displaces the automatic transmission to a neutral state at the latest by the fuel supply stop time, and outputs a fastening command to the clutch means at a predetermined timing after the fuel supply stop. Performing control to return the automatic transmission to the drive state within a specific period from the vicinity where the engine starts reverse rotation for the first time during the automatic stop operation period to the vicinity where the engine returns to normal rotation,
The timing at which the stop / restart control means outputs an engagement command to the clutch means is determined based on the oil temperature detected by the oil temperature detecting means, and when the hydraulic oil of the clutch means is in a low temperature state, the temperature is high. An engine starter for a powertrain that is set to be earlier than when it is in a state. The engine starting device for a powertrain according to claim 1,
When the restart condition is satisfied during the automatic stop operation period of the engine, the stop / restart control means is in an expansion stroke when the engine once reversely rotates and returns to normal rotation during the automatic stop operation period. An engine starter for a powertrain that performs natural reverse rotation control to perform combustion in a cylinder and restart the engine. The engine starter for a powertrain according to claim 1 or 2,
The stop / restart control means maintains the rotational speed of the engine at a rotational speed higher than the rotational speed during warm idling before the engine automatic stop condition is satisfied and the fuel supply is stopped. Powertrain engine starter. In the engine starting device of the power train according to any one of claims 1 to 3,
The stop / restart control means judges from the detection result of the oil temperature detection means, and outputs a fastening command to the clutch means after the fuel supply is stopped, but still within a specific period during the engine stop operation period. When it is predicted that the engagement of the clutch means cannot be completed, execution of the fuel supply stop is stopped.

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