JP2006144970A - Starter of engine of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a starter of an engine capable of securely re-starting the engine when the engine is automatically stopped while a vehicle is running. <P>SOLUTION: An ECU 2 mounted on the vehicle automatically stops the engine even while the vehicle is running and re-starts the engine in an automatic stop state. The ECU changes over an automatic transmission mechanism from a drive state to a neutral state when the requirements for the automatic stop of the engine are satisfied. Also, when the requirements for the re-start of the engine are satisfied and the vehicle is determined to be running based on the detected results of a vehicle speed sensor, the ECU controls the automatic transmission mechanism from the neutral state to the drive state at a prescribed timing in a prescribed re-start instability period between a time when a piston rotates in a normal direction when the engine is re-started and a time when the piston of a cylinder in an intake stroke is passed through a compression stroke top dead point coming first when the engine is stopped. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an engine starting device that automatically stops an engine once at the time of deceleration of a vehicle and automatically starts the stopped engine.

In recent years, in order to reduce fuel consumption and reduce CO ₂ emissions, the engine is automatically stopped once during idling, 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.

  In this type of engine starting device, in a multi-cylinder engine, the first combustion is performed on the compression stroke cylinder when the engine is stopped, and the piston of the compression stroke cylinder is pushed down. To increase the in-cylinder pressure of the expansion stroke cylinder, and then inject fuel into the expansion stroke cylinder to perform ignition and combustion, thus increasing the combustion energy acting in the forward rotation direction of the engine. There has been proposed a system in which the engine is instantly started only by torque generated by engine combustion (see, for example, Patent Document 1).

In addition, in this type of engine starter, there is also known an engine starter that automatically stops the engine by cutting fuel injection when the vehicle is decelerated in order to reduce fuel consumption (see Patent Document 2).
International Publication No. 01/38726 Pamphlet JP-A-7-266932

  By the way, when a starter as shown in Patent Document 1 is applied to a four-cycle engine and the engine is started only by torque generated by the combustion of the engine by this device, the change with time in the engine speed is shown in FIG. It was experimentally confirmed that there was a characteristic as represented.

  That is, after the engine restart is started, first, the engine is operated in the reverse rotation direction by the initial combustion in the cylinder in the compression stroke when the engine is stopped, and the cylinder pressure is increased by the piston rise of the cylinder in the expansion stroke when the engine is stopped. When the engine is operated in the forward direction by burning in the expansion stroke cylinder, the piston of the compression stroke cylinder overcomes the compression pressure and first exceeds the compression top dead center (first TDC), and then the intake stroke cylinder at the time of stop, The piston of the exhaust stroke cylinder will sequentially exceed the compression top dead center (second and third TDC), but after restart, when the piston of the intake stroke cylinder at the stop exceeds the first compression top dead center (second TDC) It can be seen that the engine rotational speed decreases extremely, and the combustion energy due to the above combustion in the expansion stroke cylinder is small, or this combustion energy When the loss of over is large or can not the piston exceeds the said first 2TDC losing out to the compression pressure, it was found that there may not be able to properly start the engine.

  By the way, in the engine starting device described in Patent Document 1, in order to obtain a further fuel efficiency improvement effect, the engine is shifted to the automatic stop state from the traveling (deceleration) of the vehicle as in the device described in Patent Document 2. It is preferable to be configured to be able to be made. However, after the engine is shifted to the automatic stop state while the vehicle is traveling as described above, for example, when the restart condition is satisfied by restarting the engine by depressing the accelerator pedal before stopping, as described above, If the piston of the stop stroke intake stroke cylinder cannot exceed the compression top dead center and the engine cannot be restarted properly, the response to the operation of the accelerator pedal is deteriorated.

  SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides an engine starter that can improve responsiveness such as a reacceleration request by reliably restarting the engine when the engine is automatically stopped during vehicle travel. Is.

  The engine starter for a vehicle according to the present invention automatically stops the fuel supply by stopping the fuel supply to the engine when the engine automatic stop condition set so as to be established even when the vehicle is running is satisfied. At the same time, when the restart condition is satisfied after the engine is stopped, the engine is operated in a reverse direction by causing combustion in the cylinder in the compression stroke when the engine is stopped, and the cylinder that is in the expansion stroke when the engine is stopped. An engine starter having stop / restart control means for rotating the engine in the forward rotation direction and restarting the engine by causing combustion in a cylinder in the expansion stroke after increasing the in-cylinder pressure. The vehicle speed detection means for detecting the vehicle, the drive state in which the driving force can be transmitted to the wheel side, and the neutral in which the transmission of the driving force to the wheel side is separated An automatic transmission mechanism that is switchable between states, and the stop / restart control means switches the automatic transmission mechanism from the drive state to the neutral state when the engine automatic stop condition is satisfied, When the restart condition is satisfied and it is determined that the vehicle is running based on the detection result of the vehicle speed detecting means, the intake air is taken when the engine is stopped from when the piston is rotating forward when the engine is restarted. The automatic transmission mechanism is controlled so that the switching from the neutral state to the drive state is completed at a predetermined timing of the restart instability period until the piston of the cylinder in the stroke first passes through the compression top dead center. It is a feature. Here, “switching is completed” means that the automatic transmission mechanism is switched to a drive state that can actually transmit the driving force, and the stop / restart control means switches to the automatic transmission mechanism. It does not matter when the signal is output. Therefore, the timing when the switching signal is output may be during the reverse rotation operation of the engine.

  According to the present invention, the stop / restart control means is configured to perform the automatic operation when the engine restart condition is satisfied and when it is determined that the vehicle is running based on the detection result of the vehicle speed detection means. Since the transmission mechanism is controlled so as to be switched from the neutral state to the drive state, the engine can be restarted using the reverse driving force from the wheel side. Therefore, coupled with restarting the engine after reverse operation, the reverse driving force can suppress the decrease in the engine rotation speed during the unstable restart period, thereby reliably restarting the engine. Can be started. In addition, the stop / restart control means is operated at a predetermined time in a restart instability period from when the engine normally rotates until when the piston of the cylinder in the intake stroke passes through the compression top dead center when the engine first stops. Since the switching of the automatic transmission mechanism is controlled to be completed, the reverse driving force does not affect the reverse rotation operation of the engine, and the effect of the restart accompanying the reverse rotation operation can be maximized. it can.

  The automatic transmission mechanism may include, for example, an electromagnetic clutch. However, an automatic transmission mechanism including a torque converter is preferable from the viewpoint of versatility, and in this case, the automatic transmission mechanism is in a drive state when the automatic transmission mechanism is in a neutral state. Turbine rotation speed prediction means for predicting the turbine rotation speed of the torque converter when switched is further provided, and the stop / restart control means determines the predicted rotation speed of the turbine based on the detection result of the turbine rotation speed prediction means. When it is determined that the rotational speed of the engine crankshaft is greater than or equal to the predetermined influence rotational speed by the reverse driving force from the wheel side, the switching completion timing of the automatic transmission mechanism from the neutral state to the drive state is set to It is preferable to set to a predetermined time in the unstable starting period (claim 2).

  In other words, the automatic transmission mechanism including the torque converter has a characteristic that the crankshaft of the engine is not rotated by the reverse driving force from the wheels unless the turbine speed reaches a certain level. Therefore, in order to reliably use the turbine rotation of the torque converter for restarting the engine, it is preferable to switch the automatic transmission mechanism when it is determined that the rotational speed is higher than the affected rotational speed as described above.

  Note that the influence rotational speed varies depending on the type of the engine, the automatic transmission mechanism, and the like, and therefore, it is preferably determined in advance through experiments or the like. Further, when it is determined that the predicted rotational speed of the turbine is lower than the affected rotational speed, the switching completion time may be during the reverse rotation operation of the engine.

  In this case, the stop / restart control means reliably sets the output timing of the switching signal to the automatic transmission mechanism at a predetermined timing after the initial combustion in the cylinder in the expansion stroke when the engine is stopped, during the forward rotation operation of the engine. The automatic transmission mechanism may be switched to the drive state at the same time, but the output timing of the switching signal to the automatic transmission mechanism in the unstable restart period is the same as that before combustion in the cylinder in the expansion stroke when the engine is stopped. It is preferable to set at a predetermined time (claim 3).

  With this configuration, the automatic transmission mechanism can be switched after the reverse rotation of the engine in consideration of the time lag from when the switching signal is output until it is actually switched, thereby ensuring the desired configuration with a simple configuration. The automatic transmission mechanism can be switched at the time of.

  The automatic transmission mechanism includes a plurality of friction elements that are interrupted by fluid pressure control, and is configured to switch between the neutral state and the drive state by intermittently connecting these friction elements, and the stop Preferably, the restart control means is in a precharge state in which a predetermined fluid path connected to the friction element is filled with a working fluid until a predetermined fluid pressure is reached as the neutral state.

  With this configuration, even in the automatic stop operation period in which the automatic transmission mechanism is switched to the neutral state, the automatic transmission mechanism can be quickly switched from the neutral state to the drive state in response to the establishment of the restart condition. The automatic transmission mechanism can be switched to the drive state at a more appropriate time, thereby further improving the restartability of the engine.

  According to the vehicle engine starter of the present invention, the engine can be restarted by using the reverse driving force from the wheel side, which is coupled with the forward rotation operation after the engine is reversely operated. Thus, the reverse driving force can suppress the decrease in the engine speed during the unstable restart period, and there is an advantage that the engine can be reliably restarted. In addition, by setting the switching timing of the automatic transmission mechanism by the stop / restart control means to an appropriate timing, the reverse drive force does not hinder the reverse rotation of the engine, and the effect of the reverse rotation start of the engine is maximized. It can be pulled out.

  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 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 (negative 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 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.

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

  Further, 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 coolant temperature of the engine. Each detection signal output from these sensors 32 and 33 is input to the ECU 2. Further, as shown in FIG. 9, the ECU 2 includes an accelerator sensor 34 that detects an accelerator opening corresponding to the accelerator operation amount of the driver, and a brake sensor 35 that detects that the driver has operated the brake. An oil temperature sensor 37 for detecting the oil temperature of the automatic transmission mechanism 50, which will be described later, a vehicle speed sensor 38 for detecting the vehicle speed, and an operating pressure sensor 39 for detecting an operating pressure corresponding to each friction element in the automatic transmission mechanism 50. Each detection signal output is input to the ECU 2. That is, the vehicle speed sensor 38 corresponds to the vehicle speed detecting means referred to in the present invention.

  Further, as shown in FIG. 3, the engine is connected to an automatic transmission mechanism 50 through a crankshaft 3 as an output shaft thereof. The automatic transmission mechanism 50 includes a torque converter 51 connected to the crankshaft 3 and a multi-stage transmission mechanism 52 connected to a turbine shaft 59 that is an output shaft of the torque converter 51, and includes a plurality of frictions included therein. By switching the elements 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 driving state in which the driving force can be transmitted to the wheel side.

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

  The case 57 is provided with a turbine rotation sensor 36 that detects the rotation speed of the turbine runner 55 in a state of facing an outer peripheral surface of a forward clutch 67 (described later) that rotates integrally with the turbine shaft 59. ing. Specifically, the turbine rotation sensor 36 has a tip portion arranged to face 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 as the drum rotates. The rotational speed of the turbine runner 55 is detected through the rotational speed of the turbine shaft 59 by detecting the periodic change of the induced voltage caused by the above.

  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, the torque converter 51 is provided with an electric oil pump 62 (see FIG. 5), 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 that is interposed between the pump cover 53 and the turbine runner 55 and directly connects the crankshaft 3 and the turbine runner 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 speed change mechanism 52 includes first and second planetary gear mechanisms 65 and 66 and fastening elements (a plurality of friction elements 67 to 71 such as clutches and brakes) for switching a power transmission path including the planetary gear mechanisms 65 and 66. And a one-way clutch 72), and is configured to switch the forward speed, the neutral state, and the reverse speed by intermittently connecting these fastening elements 67 to 72 according to the shift range (D range, N range, R range, etc.). ing.

  The first and second planetary gear mechanisms 65 and 66 are respectively provided with sun gears 65a and 66a, and a plurality of (for example, three) planetary gears 65b and 66b that are disposed around and mesh with the sun gears 65a and 66a. A ring gear of the first planetary gear mechanism 65, which includes carriers 65c and 66c for supporting the planetary gears 65b and 66b, and ring gears 65d and 66d that are arranged so as to surround the planetary gears 65b and 66b. 65d 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 mechanism 65, 66. Can be linked.

  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 these planets. A low reverse brake 71 or the like interposed in parallel between the gear mechanisms 65 and 66 and the case 57 is provided. The one-way clutch 72 only allows rotation in one direction (the driving direction of the crankshaft 3) of the carrier 65c and the ring gear 66d. Therefore, the one-way clutch 72 is unlocked with respect to the rotation in the one direction. It is locked against rotation 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 wheels, that is, through the transmission gears 74, 75 and 76 and the differential mechanism 77.

  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. Therefore, 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 and 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.

  Similar to the lock-up clutch 64, these friction elements 67 to 71 are connected to the oil pump 61 and the electric oil pump 62 via the hydraulic control mechanism 63 (see FIG. 5). In addition, the second shift solenoid valves 83 and 84 and the first to third duty solenoid valves 85 to 87 are driven to switch and change the oil passages, hydraulic pressures, and the like.

  Specifically, the hydraulic control mechanism 63 includes a hydraulic control circuit as shown in FIG. 5, and this hydraulic control circuit is connected to the oil pump 61 and the electric oil pump 62 so that the original pressure is supplied from the pumps 61 and 62. Supplied. 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. In addition, 1st and 2SV83,84 and 1st-3rd DSV85-87 are comprised as a three-way valve. A switching valve 91 that is controlled by the ECU 2 and switches the oil supply source between the oil pump 61 and the electric oil pump 62 is provided on an oil passage connecting the pumps 61 and 62 and the line 81.

  Then, by operating various valves based on the vehicle speed, the throttle opening, the engine speed, the turbine speed, and the like to intermittently connect the friction elements 67 to 71, the automatic transmission mechanism 50 is switched between a plurality of stages to correspond to the vehicle speed and the like. The ECU 2 is configured to perform control for automatically selecting the selected gear according to the position of the shift lever. FIG. 6 shows a switching map of the automatic transmission mechanism 50 according to the vehicle speed and the throttle opening. FIG. 7 shows combinations of operating states for the respective gear positions of the solenoid valves 82 to 87. In FIG. 7, the circles indicate ON for the first and second SVs 82 and 83, and OFF for the first to third DSVs 84 to 86. In both cases, the upstream line communicates with the downstream line. The state where the pressure is supplied to the downstream side as it is is shown. The crosses are OFF for the first and second SVs 83 and 84, and are ON for the first to third DSVs 85 to 87, both of which shut off the upstream line. The state where the downstream line is drained is shown.

  For example, the operation of the hydraulic control mechanism 63 when the first speed is selected for the multi-stage transmission mechanism 52 will be described. As shown in FIGS. 5 and 7, only the third DSV 87 is operated, and the upstream line An operating pressure is generated using the pressure as an original pressure, and this operating pressure is supplied to the lock-up control valve 88 via the line 81b. At this time, the spool of the lock-up control valve 88 is positioned on the right side, so that it is further supplied as a forward clutch pressure (operating pressure) to the hydraulic chamber of the forward clutch via the forward clutch line 81c. The forward clutch 67 is engaged.

  The time change of the operating pressure of the forward clutch 67 will be described with reference to FIGS. 5 and 8. When only the third DSV 87 is operated, the operating oil is supplied to the downstream line 81b and the forward clutch line 81c of the third DSV 87. . At the time t1 when the lines 81b and 81c are filled with the hydraulic oil, the hydraulic pressures of the lines 81b and 81c, that is, the operating pressure of the forward clutch 67 increases. At the time t2 when the operating pressure reaches the predetermined value P1, the piston (not shown) of the forward clutch 67 in the released position starts to move in the fastening direction against the return spring (not shown). Then, when the operating pressure reaches the predetermined value P2 and the forward clutch 67 moves to the contact position and the clearance becomes zero (time t3 in FIG. 8), the movement pressure is restricted, and the rate of increase of the operating pressure is increased. As a result, the forward clutch 67 slips from one another and gradually shifts to a state where the transmission driving force is large. Then, at time t4 when the operating pressure reaches the predetermined operating pressure P3, the accumulator 90 is operated, whereby the rate of increase of the operating pressure is reduced, and the fastening proceeds while suppressing rapid torque fluctuation (shock). . The forward clutch 67 is completely engaged until time t5 when the capacity of the accumulator 90 is full. Further, by increasing the operating pressure, a sufficiently large fastening force that can cope with a change in the transmission driving force accompanying a sudden torque change is obtained. Even when a gear other than the first gear is selected, the operation is the same as that of the conventional automatic transmission mechanism.

  Further, when the automatic transmission mechanism 50 is in a neutral state in which the hydraulic control mechanism 63 is controlled by the ECU 2 and the transmission of the driving force to the wheels is cut off, the friction elements 67 to 71 are immediately before the fastening as necessary. The state can be set to a so-called precharge state. That is, in general, in this type of automatic transmission mechanism, gear shifting or the like is performed by supplying the operating pressure generated by the hydraulic control circuit to the hydraulic chamber of the friction element at the time of shifting or engagement operation. Even when the operating pressure is generated and supplied to the hydraulic chamber of the friction element immediately after the start of the shifting operation, the hydraulic oil is drained from the hydraulic chambers of the hydraulic control circuit or the hydraulic chamber of the friction element, or the operating pressure decreases. In order to fill them with hydraulic oil during the shifting operation and move the friction element from the release position to the contact position, a time lag occurs for a predetermined time, and the fastening operation of the friction element is delayed. There was a problem.

  Therefore, in this embodiment, the ECU 2 is operated by the electric oil pump 62 when the automatic transmission mechanism 50 is in the neutral state and the friction elements 67 to 71 are in the released state at least during the automatic stop operation period of the engine. By supplying the pressure, at least one of the friction elements 67 to 71 is moved from the predetermined release position in the fastening direction, and a slip state in which the driving force is not transmitted in the friction elements 67 to 71 (completely Thus, the automatic transmission mechanism 50 can be set to a precharged state in which the startup time of the operating pressure and the movement time of the friction elements 67 to 71 are omitted.

  For example, the precharge state of the forward clutch 67 will be described with reference to FIGS. When the forward clutch 67 is in the precharge state, the ECU 2 controls the third DSV 87 to adjust the operating pressure to the precharge pressure Pp. In the present embodiment, the precharge pressure Pp is slightly displaced in the release direction from the contact position P2 or the forward clutch 67 when the forward clutch 67 is moved to the substantially contact position and is in the slip state. In this case, the operating pressure is set to a value slightly lower than the operating pressure P2. Since the precharge pressure Pp changes depending on the oil temperature or the like, the precharge pressure Pp is set to a value slightly lower than the operating pressure P2 from the viewpoint of more reliably preventing the movement of the piston 13. preferable.

  Here, the precharge state is an initial precharge stage in which the line 81 connected to the friction elements 67 to 71 is filled with hydraulic oil, that is, an example of the forward clutch 67, and the hydraulic oil is supplied to the line 81b at a predetermined operating pressure P1. A stage of charging until it becomes (period t0 to t2 in FIG. 8), and a late precharge in which the friction elements 67 to 71 are moved from the release position in the fastening direction via the initial precharge stage to be in a state immediately before fastening. In the above example, the step includes the step of filling the line 81b with hydraulic oil and increasing the operating pressure to P2 (period t2 to t3 in FIG. 8). In the present embodiment, at least one of the friction elements 67 to 71 is in a precharge state in the late precharge stage.

  The ECU 2 includes a computer having a CPU, a ROM, a RAM, and the like. Specifically, various operations of the vehicle are performed by executing a program stored in the ROM (or RAM) in advance by the CPU. Be controlled. As shown in FIG. 9, the ECU 2 receives signals from the sensors 25, 26, 30 to 34 and outputs a signal for controlling the fuel injection amount and the injection timing to the fuel injection valve 16. An ignition timing control signal is output to the spark plug 15, a control signal for controlling the throttle opening is output to the actuator 24 of the throttle valve 23, and further to the regulator circuit 28 a of the alternator 28. A signal for controlling the amount of power generation is output. Further, the ECU 2 receives a signal from each of the sensors 25, 26, 30 to 39 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 working pressure of each of the friction elements 67 to 71 is output to the hydraulic control mechanism 50 (specifically, a solenoid valve included therein).

  The ECU 2 sets the predetermined engine stop condition so that it can be satisfied not only when the vehicle is idling but also when the vehicle is running. When the automatic engine stop condition is satisfied, the ECU 2 stops the fuel supply. The engine is automatically stopped and automatically during the automatic stop operation period of the engine or after the engine is automatically stopped, when a predetermined engine restart condition is established by an accelerator operation or the like by the occupant. The engine is automatically restarted. 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. That is, the ECU 2 corresponds to the stop / restart control means in the claims.

  Specifically, the restart of the engine is first performed by a cylinder 12 in the compression stroke when the engine is stopped (hereinafter referred to as a compression stroke cylinder when stopped. When other cylinders need to be distinguished from each other, the engine is stopped. The first combustion is performed to push down the piston 13 to increase the in-cylinder pressure by the reverse operation of raising the piston 13 of the stop expansion stroke cylinder 12. By injecting fuel into the expansion stroke cylinder 12 to cause ignition and combustion, the combustion energy in the expansion stroke cylinder 12 at the time of stop is increased and the stroke of the cylinder 12 is ensured to restart the engine. The ECU 2 is configured as described above.

  Thus, in order to restart the engine only with the combustion energy, it becomes a problem how to maximize the combustion energy in the expansion stroke cylinder 12 at the time of stop. For this purpose, the piston 13 is used when the engine is stopped. Must be stopped within a predetermined range, and the amount of air for combustion in the stop-time compression stroke cylinder 12 and the stop-time expansion stroke cylinder 12 must be ensured appropriately. Therefore, with reference to the expansion stroke cylinder 12 at the time of stop, a predetermined range slightly beyond the center of the stroke, that is, a position where the crank angle after compression top dead center is 90 ° CA slightly toward the bottom dead center side, for example, after compression top dead center. If the piston 13 can be stopped in a range where the crank angle is 100 ° to 120 ° CA, a predetermined amount of air is secured in the compression stroke cylinder at the time of stop, and the engine is slightly reversed by the initial combustion. In addition, sufficient energy can be secured by combustion in the expansion stroke cylinder 12 at the time of stopping.

  There are various specific methods for controlling the stop position of the piston 13 when the engine is automatically stopped. Here, the opening of the throttle valve 23 is controlled to control the air depending on the air in the expansion stroke cylinder and the compression stroke cylinder when the engine is stopped. While adjusting the compression reaction force and controlling the amount of power generated by the alternator 28 during the automatic engine stop process, the engine rotation speed is finely adjusted through the resistance of the crankshaft 3. Ne is lowered along a reference line determined in advance by experiments or the like to control the stop position of the piston 13.

  Specifically, as shown in FIGS. 10 and 11, the ECU 2 releases the friction elements 67 to 71 at a time T0 when the engine automatic stop condition is satisfied, so that the automatic transmission mechanism 50 is driven ( Here, it is configured to switch from the D range to the neutral state (N range here). In the neutral state in the automatic stop operation period of the engine (the period from when the automatic stop condition is satisfied until the restart condition is satisfied), the operating pressure is set to the precharge pressure Pp. 71 is in a precharge state immediately before fastening. By switching the automatic transmission mechanism 50 to the neutral state in this manner, the influence of the reverse driving force from the wheel side can be eliminated, and since the precharged neutral state is achieved, the automatic transmission mechanism 50 is restarted during the engine stop process. Even when the start condition is satisfied, the period from the time point t0 to the time point t3 in FIG. 8 can be omitted and the restart response can be improved.

  Then, the ECU 2 stabilizes the opening degree K of the throttle valve 23 at 15%, and then the engine speed Ne and the boost pressure Bt stop the piston 13 within a predetermined appropriate range at a time T1 when a predetermined time has elapsed. Therefore, the fuel injection to each cylinder 12 is stopped when it is within a predetermined control appropriate range in which the control for this can be properly executed. When the fuel injection is stopped at this time T1, the kinetic energy of the crankshaft 3 or the like is consumed due to mechanical loss due to frictional resistance or pumping work of each cylinder 12A to 12D, thereby causing the crankshaft 3 of the engine. The inertia is several revolutions, and in a 4-cylinder 4-cycle engine, it stops after reaching the compression top dead center of about 10 times.

  As described above, the stop position of the piston 13 is substantially determined by the balance of the compression reaction force in the stop-time compression stroke cylinder 12C and the stop-time expansion stroke cylinder 12A, and is influenced by the frictional resistance of the engine. It also changes depending on the rotational inertia of the engine at the time T4 when the compression top dead center is exceeded, that is, the level of the engine rotational speed Ne. Therefore, in order to stop the piston 13 of the expansion stroke cylinder 12A in the expansion stroke within the appropriate range suitable for restart when the engine is automatically stopped, first, the compression reaction of the expansion stroke cylinder 12A and the compression stroke cylinder 12C. It is necessary to adjust the intake air flow rates for both cylinders 12A and 12C so that the force becomes sufficiently large and the compression reaction force of the expansion stroke cylinder 12A is larger than the compression reaction force of the compression stroke cylinder 12C by a predetermined value or more. .

  Therefore, in this embodiment, the expansion stroke cylinder 12A and the opening stroke cylinder 12A and the throttle opening 23 are set to a large value (for example, about 30% of the opening degree when fully opened) at the fuel injection stop time T1. After a predetermined amount of air is sucked into both the compression stroke cylinders 12C, at the time T2 when it is confirmed that the engine rotational speed Ne has dropped below a preset reference speed N1 (for example, about 790 rpm), the throttle The intake air amount is adjusted by closing the valve 23 and reducing the opening K thereof.

  By the way, the fuel injection is stopped at the time T1 when the rotational speed Ne of the engine reaches a predetermined speed, and the cylinders of the engine that rotate due to 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 in the sixth to second before is within a predetermined range as shown by hatching in FIG. 14, the stop position of the piston 13 is in a range suitable for engine restart ( It was experimentally confirmed that it entered 100 ° to 120 ° CA after compression top dead center.

  Therefore, the ECU 2 sets the target generated current Ge of the alternator 28 at the fuel injection stop time T1 in order to maintain the engine rotational speed Ne at a speed at which the control for stopping the piston 13 within the appropriate range is possible. The engine is set to 0, and at the time T2 when the engine speed Ne drops below the reference speed N1, the control is performed to increase the target generated current Ge of the alternator 28 to a preset initial value, and then the engine is rotated at the top dead center. At the time T3 when the speed ne falls within the predetermined range, the target power generation current Ge of the alternator 28 is decreased to a value corresponding to the decreased state of the engine rotational speed Ne to adjust the rotational resistance of the crankshaft 3, and the outside of the engine By changing the load according to the degree of decrease in the engine speed Ne, the load is changed to the reference line set based on experiments conducted in advance. It is configured to perform control to reduce the engine rotational speed Ne me.

  Summarizing the control of the ECU 2 at the time of the automatic engine stop, the ECU 2 controls the opening of the throttle valve 23 when the engine is automatically stopped, and the air in the expansion stroke cylinder 12A and the compression stroke cylinder 12C when the engine is stopped. While adjusting the compression reaction force and controlling the amount of power generated by the alternator 28 during the automatic engine stop process, the engine rotation speed is finely adjusted through the resistance of the crankshaft 3. Ne is decreased along a reference line determined in advance by experiments or the like, and control is performed to stop the piston 13 within a predetermined appropriate range.

  By the way, in this type of engine starter, when a predetermined restart condition is satisfied, it is desired to quickly restart the engine and shift the vehicle to a state where it can be re-accelerated at an early stage. After the automatic stop, it is preferable to prepare for the establishment of the restart condition by switching the automatic transmission mechanism 50 from the neutral state to the drive state regardless of whether the restart condition is satisfied. However, when the automatic transmission mechanism 50 is switched to the drive state, a reverse driving force is transmitted from the axles 78 and 79 to the turbine 55 via the multi-stage transmission mechanism 52 when the vehicle is running, and this reverse driving force is By acting on the pump impeller 54 via the hydraulic oil, it acts on the crankshaft 3, which may cause the piston 13 that has been stopped within a predetermined appropriate range of the folding angle to move.

  Therefore, in this starting device, in the automatic transmission mechanism 50 including the torque converter 51, if the rotational speed of the turbine 55 does not reach a certain rotational speed Tri (hereinafter referred to as an influence rotational speed), a reverse driving force from the wheel side is used. When the restart response is improved by effectively utilizing the characteristic that the crankshaft 3 of the engine is not rotated, and the rotational speed of the turbine 55 exceeds the affected rotational speed Tri when the automatic transmission mechanism 50 is switched to the drive state. However, when the engine restart condition is satisfied, the reverse driving force is effectively used.

  That is, the ECU 2 calculates a predicted value of the rotational speed of the turbine 55 of the torque converter 51 (hereinafter referred to as a predicted turbine rotational speed Tre) when the automatic transmission mechanism 50 is switched to the drive state when in the neutral state. Specifically, when the ECU 2 determines the engine stop based on the detection results of the crank angle sensors 30 and 31, the vehicle speed sensor 38 is provided at predetermined intervals from the engine stop time T5 until the restart condition is satisfied. By detecting the vehicle speed. For example, if the automatic transmission mechanism 50 outputs a switching signal from the neutral state to the driving state at time T6, this switching is finally completed, and the predetermined friction elements 67 to 71 can transmit the driving force. At the time point T7 when the state is shifted to the fastened state, the predicted turbine rotational speed Tre rotated by the reverse driving force transmitted from the axles 78 and 79 is predicted. More specifically, the predicted turbine rotation speed Tre is determined in the ECU 2 based on the vehicle speed detected by the vehicle speed sensor 38, and the gear speed corresponding to the vehicle speed is selected based on the map shown in FIG. Then, it is calculated by applying a predetermined mathematical formula based on these vehicle speed, deceleration, gear ratio of the selected gear, the tire diameter inputted in advance, the gear ratio of the differential mechanism 77, and the like. Therefore, this ECU 2 corresponds to the turbine rotation speed predicting means in the claims.

  The affected rotational speed Tri differs depending on the configuration of the automatic transmission mechanism 50 and is obtained in advance through experiments and stored in the ECU 2. In the present embodiment, the affected rotational speed Tri is 1200 rpm which is higher than the idle rotational speed (650 rpm in the D range).

  Then, as shown in FIG. 11, after the time T5 when the automatic stop of the engine is determined based on the detection results of the crank angle sensors 30 and 31, it is determined that the predicted turbine rotational speed Tre is lower than the influence rotational speed Tri. At T7, the ECU 2 controls the automatic transmission mechanism 50 to be switched from the neutral state to the drive state. As described above, since the automatic transmission mechanism 50 is switched to the drive state after the predicted turbine rotational speed Tre becomes lower than the influence rotational speed Tri, the piston 13 is unexpectedly moved by the reverse driving force and deviates from the predetermined appropriate range. This can be effectively prevented, so that the restartability of the engine can be kept good.

  On the other hand, as shown in FIG. 12, when a predetermined engine restart condition is satisfied after the engine is automatically stopped, and when it is determined that the predicted turbine rotational speed Tre is equal to or higher than the affected rotational speed Tri (time in FIG. 12). At time T10), the ECU 2 executes the combustion of the stop-time compression stroke cylinder 12C and the stop-time expansion stroke cylinder 12A, and the stop-time intake stroke cylinder 12D reaches compression top dead center first after restarting. By the time, the automatic transmission mechanism 50 is controlled so as to be switched from the neutral state to the drive state.

  Specifically, for the automatic transmission mechanism 50 at a time T11 after a predetermined time (for example, 0.05 seconds) has elapsed since the initial combustion in the stop-time compression stroke cylinder 12C for the reverse rotation operation of the engine is executed. The ECU 2 is configured to output a switching signal for switching to the drive state. Then, based on this switching signal, the automatic transmission mechanism 50 increases the operating pressure of the corresponding friction elements 67 to 71 so as to select the gear position corresponding to the vehicle speed, and after the reverse rotation operation of the engine is finished, Until the intake stroke cylinder 12D reaches compression top dead center for the first time (for example, time T12), the corresponding friction elements 67 to 71 are completely engaged and the switching to the drive state is completed. The predetermined time from the execution of the initial combustion to the output of the switching signal is appropriately set from this viewpoint.

  As described above, when the predicted turbine rotational speed Tre exceeds the influence rotational speed Tri at the time T10 when the engine restart condition is satisfied, the combustion is automatically performed after the combustion associated with the restart is executed in the stop expansion stroke cylinder 12A. When the transmission mechanism 50 is switched to the drive state, reverse driving force is applied to the crankshaft 3. Before the reverse driving force is applied, the stop compression stroke cylinder 12C and the stop expansion stroke cylinder 12A are applied. Therefore, the deterioration of restartability due to the movement of the piston 13 can be prevented by the reverse driving force accompanying the switching of the automatic transmission mechanism 50. In addition, since the automatic transmission mechanism 50 is switched during an unstable restart period until the piston 13 of the intake stroke cylinder 12D at the time of stop reaches the first compression top dead center after the restart, the reverse driving force is applied to the crankshaft 3. This reverse drive force acts in the forward direction, and this reverse drive force can be used as an assist when restarting the engine. As shown by a two-dot chain line in FIG. Compared to the case where the engine is not in operation, a drop in the engine rotation speed when the intake stroke cylinder 12D at the time of stopping first reaches the compression top dead center can be suppressed, whereby the engine can be reliably restarted. Further, since the restart assist by the reverse driving force is applied after the reverse rotation of the engine, the reverse rotation of the engine is not hindered, and the in-cylinder pressure of the stop expansion cylinder 12A is effectively increased during the stop. The combustion energy of the expansion stroke cylinder 12A can be sufficiently obtained.

  As described above, when the engine restart condition is satisfied and it is determined that the predicted turbine rotational speed Tre is lower than the affected rotational speed Tri, the ECU 2 does not wait for the elapse of a predetermined time and immediately The automatic transmission mechanism 50 is controlled to be switched. That is, when the predicted turbine rotational speed Tre is lower than the influence rotational speed Tri, the reverse driving force does not act on the crankshaft 3 and does not hinder the reverse rotation operation of the engine. Sometimes, a switching signal is output to the automatic transmission mechanism 50.

  Then, the ECU 2 is in the case where a predetermined restart condition is satisfied for the engine that is in the automatic stop state as described above, and the piston 13 of the stop-time expansion stroke cylinder 12A is within a predetermined appropriate range. Performs the initial combustion in the stop-time compression stroke cylinder 12C and reversely operates the engine, thereby increasing the in-cylinder pressure of the stop-time expansion stroke cylinder 12A. Control is performed so that the engine is automatically restarted by injecting fuel into the expansion stroke cylinder 12A to cause ignition and combustion.

  Specifically, when a predetermined restart condition is established after the engine is stopped, the ECU 2 automatically controls to restart the engine. At this time, the stop position of the piston is set at the middle of the stroke in the expansion stroke cylinder. If it is within a predetermined appropriate range in the vicinity, the engine is once reversely operated and then restarted.

  This engine restart control will be described based on the time charts of FIGS. 15 and 16. The engine restart control is not limited to this, and may be other known restart control.

  As shown in FIGS. 15 and 16, first, the first fuel injection J2 is performed in the compression stroke cylinder 12C (third cylinder), and combustion ((1) in FIG. 15) is performed by the ignition. With the combustion pressure (part a in FIG. 16) 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. Then, when the piston 13 of the expansion stroke cylinder 12A moves to the top dead center side (preferably closer to the top dead center from the stroke center), the fuel injection J1 is performed when the air in the 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. 15).

  When the piston 13 of the expansion stroke cylinder 12A is sufficiently close to top dead center, the cylinder 12A is ignited, and the injected fuel (J1) is combusted ((2) in FIG. 14). The engine is driven in the forward direction by the pressure (c portion in FIG. 15).

  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. 14). 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. 14), and accordingly, the compression top dead center (the first compression top dead center from the start of starting) is exceeded. The initial combustion energy of the consumed expansion stroke cylinder 12A is reduced.

  Further, 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. 14) for reducing the temperature in the cylinder and the compression pressure by the vaporization latent heat 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. 15). 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 (second from the start of engine start). It is possible to suppress consumption to exceed the compression top dead center).

  Thus, the first compression top dead center ((3) in FIG. 14) after the start of restart and the second compression by the energy of the first combustion ((2) in FIG. 14) in the expansion stroke cylinder 12A. It is possible to exceed the top dead center ((4) in FIG. 14), it is possible to ensure a smooth and reliable startability, and thereafter, shift to normal operation.

  The control operation when the ECU 2 automatically stops and restarts the engine will be described based on the flowcharts shown in FIGS.

  FIG. 16 shows a main flowchart of the automatic stop / restart control of the engine. When this control operation starts, it is first determined whether or not a fuel injection stop condition (hereinafter referred to as FC condition) is satisfied (step S1). This FC condition is a condition included in the engine automatic stop condition. In this embodiment, the FC condition is also used as a fuel injection stop condition during deceleration executed for a predetermined period during vehicle deceleration. Specifically, as the FC condition, it is determined whether or not the engine rotational speed Ne is larger than a predetermined reference value Nfc for stopping fuel injection set to about 1200 rpm that is set in advance, and the vehicle speed is set to a predetermined value ( For example, it is determined whether it is 10 km / h) or more and the accelerator sensor 34 is in an OFF state.

  If it is determined as YES in step S1, it is determined based on the vehicle speed detected by the vehicle speed sensor 38 whether or not the lockup clutch 64 of the torque converter 51 is in a non-lockup region. (Step S2). That is, the lock-up clutch 64 of the torque converter 51 is configured to be engaged / disengaged based on a signal output from the ECU 2 in accordance with the vehicle speed, and the vehicle is decelerated while the lock-up clutch 64 is engaged. Since the fuel consumption reduction effect can be obtained by stopping the fuel injection at the time of deceleration performed normally, the stop of the fuel injection at the time of deceleration is first used. Therefore, the stop of the fuel injection for the automatic engine stop is executed when the vehicle is stopped or when the vehicle is decelerating and the vehicle is out of the traveling state in which the fuel injection stop control at the time of deceleration can be controlled. When the fuel injection is stopped, when the vehicle goes out of the lockup region, the fuel injection stop at the time of deceleration is used as the fuel injection stop for the automatic stop. Therefore, the condition that the running state of the vehicle is in the non-lockup region is also included in the automatic stop condition.

  If the determination in step S2 is YES, the engine automatic stop and restart control shown in FIG. 17 is executed (step S3). Then, when the engine is restarted, the routine proceeds to normal engine control (step S3). S4) Returned. The engine automatic stop and restart control will be described later.

  On the other hand, if it is determined NO in step S2 and it is determined that the lockup clutch 64 is in the engaged state, the fuel injection stop during deceleration that is normally performed over a predetermined period during vehicle deceleration (Fuel Cut during deceleration). ) Is stopped (step S5), and the process returns. Even when the deceleration fuel injection stop is executed and the return is performed, if the FC condition is satisfied and the lockup clutch 64 is released (YES in both steps S1 and S2). ) Using the stop of fuel injection at the time of deceleration, the engine automatic stop and restart control which will be described later is executed as it is, and the fuel efficiency improvement effect can be improved.

  Next, returning to step S1, if it is determined NO in step 1, that is, if the FC condition is not satisfied, it is determined whether or not the fuel injection stop (FC) is executed (step S6). If it is determined NO in step S6, the process is returned as it is. On the other hand, if it is determined that the fuel injection is stopped (YES in step S6), the routine proceeds to normal control of the engine. Thus, the fuel injection to each cylinder 12 is restored (step S4).

  Here, the engine automatic stop and restart control executed in step S3 of the flowchart shown in FIG. 16 will be described based on the flowchart of FIG.

  When it is determined in steps S1 and S2 of the flowchart shown in FIG. 16 that a part of the automatic stop condition is satisfied, the engine automatic stop / restart control is started, and a time point T0 at which this automatic stop condition is partially satisfied. Thus, the automatic transmission mechanism 50 is switched from the drive state to the neutral state (step S51). The neutral state in this automatic stop operation period is the above-described late-stage precharge state. Specifically, the oil pump is a pump that outputs signals from the ECU 2 to the switching valve 91, the electric oil pump 62, the solenoid valves 82 to 87 of the hydraulic control mechanism 63, and the like to supply the original pressure to the hydraulic control mechanism 63. In addition to switching from 61 to the electric oil pump 62, the solenoid valves 82 to 87 are adjusted and the friction elements 67 to 71 in the released state and the friction elements 67 to 71 in the engaged state capable of transmitting the driving force are both used as the clutch clearance. Although there is no contact position, the slipping state immediately before the fastening state in which the driving force can be transmitted is shifted. That is, the friction elements 67 to 71 are shifted to the precharged neutral state. Therefore, in the neutral state of this precharge, the transmission of the driving force including the reverse driving force is disconnected between the crankshaft 3 and the axles 78 and 79 while ensuring a quick transition to the engaged state. Thus, it is possible to stop the piston 13 within a predetermined appropriate range without being influenced by the reverse driving force while improving the response to the establishment of the restart condition.

  Next, after adjusting the opening degree K of the throttle valve 23 to 15% (step S52) and stabilizing the boost pressure Bt, is the stop appropriate condition established to check whether the automatic stop can be properly performed? A determination of whether or not is made (step S53). The appropriate stop condition is a condition for finally confirming whether or not the automatic stop control of the engine for stopping the piston of the stop-time expansion stroke cylinder 12A within a predetermined appropriate range is possible. One of them. Specifically, it is determined whether or not the engine rotation speed Ne detected by the crank angle sensors 30 and 31 is within a predetermined range (for example, a range of 790 to 1200 rpm) where the engine can be automatically stopped. It is determined whether or not the boost pressure Bt detected by the atmospheric pressure sensor 26 is within a predetermined range (for example, −450 to −300 mmHg) in which the engine can be automatically stopped. In this embodiment, in order to improve the accuracy of stopping the piston 13 within a predetermined appropriate range, the engine stop speed Ne and the boost pressure Bt are both within a predetermined range. However, either one, preferably only the engine speed Ne may be within a predetermined range. Even in this case, a certain degree of accuracy can be ensured.

  If it is determined as NO in step S53, it is difficult to stop the piston 13 of the expansion stroke cylinder 12A at the stop in a predetermined appropriate range. The mechanism 50 is switched from the neutral state to the drive state (step S54). In some cases, the process proceeds to step S54 in the next routine from the state where the deceleration-time fuel injection is stopped in step S5 of the flowchart shown in FIG. 16. In this case, in step S54, the process proceeds to step S54. After the automatic transmission mechanism 50 is switched to the drive state, the process returns to step S4, and fuel injection is restored by the normal engine control in step S4.

  On the other hand, if it is determined as YES in step S53, it is determined whether or not the fuel injection during deceleration executed when the vehicle is decelerated has already been performed in step S5 of the flowchart shown in FIG. S55) If the fuel injection is not stopped, the fuel injection for each cylinder 12 is stopped at a time T1 when a predetermined time has elapsed since the opening K of the throttle valve 23 is set to 15%. (Step S56), and if it is determined YES in step S55, step S56 is skipped. If the fuel injection is stopped including step S5, ignition by the ignition device 27 is stopped when a preset predetermined time has passed.

  Then, based on the engine rotational speed Ne, the engine top dead center rotational speed ne, etc., the opening K of the throttle valve 23 is controlled (step S57), and the expansion stroke cylinder 12A and the compression stroke cylinder 12C when the engine is stopped are controlled. While adjusting the compression reaction force by air and controlling the power generation amount of the alternator 28 during the engine automatic stop operation period (step S58), the engine rotational speed is finely adjusted through the resistance of the crankshaft 3, thereby the fuel injection. After the stop time T1, the engine rotational speed Ne is decreased along a reference line determined in advance through experiments or the like, and control is performed to stop the piston 13 within a predetermined appropriate range.

  An example of control of the opening degree K of the throttle valve 23 and control of the target generated current Ge of the alternator 28 will be specifically described. First, regarding the opening degree control of the throttle valve 23, at the fuel injection stop time T1, the throttle valve 23 is opened, and the opening degree K is larger than the adjusted opening degree (15% in the above example) (for example, 30%). Thereafter, it is determined whether or not the engine rotational speed Ne has become equal to or lower than a reference speed N1 set in advance to about 790 rpm, so that after the fuel injection stop time T1 shown in FIG. 10 and FIG. It is determined whether or not the speed Ne has started to decrease. At a time T2 when it is determined that the speed Ne has started to decrease, the throttle valve 23 is closed and its opening degree K is set to 0%. As a result, the boost pressure Bt that has risen so as to approach the atmospheric pressure when the throttle valve 23 is opened starts to decrease with a predetermined time difference accompanying the movement from the throttle valve 23 to the cylinder 12 in accordance with the closing operation of the throttle valve 23. become.

  Next, regarding the target generated current control of the alternator 28, the power generation is stopped by setting the target generated current Ge of the alternator 28 to 0 at the fuel injection stop time T1. Then, at the time T2 when the engine speed Ne drops below the reference speed N1 set to about 790 rpm in advance, the target generated current Ge of the alternator 28 is set to the initial value set to about 60 A in advance and the alternator 28 is operated. The power generation control to be started is started. As a result, a predetermined rotational resistance acts on the crankshaft 3 of the engine. Subsequently, when the engine top dead center rotational speed ne falls within a predetermined control appropriate range, the target power generation current Ge of the alternator 28 corresponding to the top dead center rotational speed ne at that time T3 is set. This appropriate control range is the fourth compression level before the engine is stopped, for example, in the process of decreasing the engine speed Ne along the reference line indicating the time change of the engine speed set in advance. The value is set based on the top dead center rotational speed ne at the time T3 when passing through the dead center, and specifically, is set within a range of 480 to 540 rpm. The target generated current Ge of the alternator 28 corresponding to the top dead center rotational speed ne is stored in advance in the ECU 2 and is determined based on a map showing the relationship between the top dead center rotational speed ne and the target generated current Ge. .

  In parallel with the opening degree control of the throttle valve 23 and the target generated current control of the alternator 28 being executed in accordance with the engine speed Ne or the like, for example, a return condition for fuel injection such as the accelerator sensor 34 being turned on. Whether or not is established is determined (step S59). If YES is determined in this step S59, the fuel injection for each cylinder 12 is restored and returned, and the routine proceeds to normal engine control shown in step S4.

  On the other hand, if NO is determined in step S59, it is determined whether or not the engine is stopped (step S61), and steps S57 to S59 are repeatedly executed until the engine is stopped. . Then, when it is determined YES in step S61, engine restart control is executed (step S62), and the process returns to the flowchart shown in FIG.

  Next, engine restart control executed in step S62 of the flowchart shown in FIG. 17 will be described based on the flowchart of FIG.

  When it is confirmed in step S61 in FIG. 17 that the engine has completely stopped, the predicted turbine rotational speed Tre is calculated by the ECU 2 prior to the switching of the automatic transmission mechanism 50, and this predicted turbine rotational speed Tre is influenced by the affected rotation. It is determined whether or not the speed is lower than the speed Tri (step S101). If it is determined YES, the reverse driving force is applied from the turbine 55 of the torque converter 51 to the pump impeller 54 even when the friction elements 67 to 71 are in the engaged state. Since the crankshaft 3 is not rotationally driven by the reverse driving force because it is not transmitted, the automatic transmission mechanism 50 is switched from the neutral state to the driving state (step S102) to prepare for the later establishment of the restart condition. In this drive state, the friction elements 67 to 71 to be fastened are determined based on the map of FIG. 6 based on the vehicle speed detected by the vehicle speed sensor 38. When the automatic transmission mechanism 50 is switched, the movement of the piston 13 may be detected based on the crank angle sensors 30 and 31. If it is determined that the piston 13 is moving, the engine is operated by a starter motor described later. It may be one that assists restarting.

  Next, it is determined whether or not a predetermined engine restart condition is satisfied (step S103). If it is determined NO, the process waits until the restart condition is satisfied. On the other hand, when it is determined YES in step S103, for example, when an accelerator operation for acceleration is performed, when the battery voltage is reduced, or when the air conditioner is activated, the engine is restarted. Start (step S104).

  Although the specific control for this restart is not specifically limited, For example, it can comprise as follows. That is, the amount of air in the stop-time compression stroke cylinder 12C is calculated, fuel injection is performed so that the air-fuel ratio becomes rich, and after a time set in consideration of the vaporization time of the injected fuel, Ignition is performed on the cylinder 12C. The ignition to the compression stroke cylinder 12C at the time of stop is repeatedly performed until the engine is rotated by detecting the rising or falling of the crank angle sensors 30, 31. As a result, the engine is operated in reverse to increase the in-cylinder pressure of the compression stroke cylinder 12C when stopped.

  Next, a predetermined air-fuel ratio with respect to the air amount in the stop expansion stroke cylinder 12A is determined by a predetermined map, fuel is injected so as to be the air-fuel ratio, and the in-cylinder pressure is increased by the reverse operation of the engine. The cylinder 12A is ignited. As a result, the engine starts to operate in the forward rotation direction.

  Then, an amount of fuel obtained from a map determined in advance for the compression stroke cylinder 12C is injected into the latter half of the compression stroke cylinder 12C, and the compression top dead center of the cylinder 12C is caused by the latent heat of vaporization of the injected fuel. By reducing the compression reaction force in the vicinity, the compression top dead center can be easily exceeded. After the second combustion of the stop-time compression stroke cylinder 12C, fuel injection is performed to the stop-time intake stroke cylinder 12D that reaches the compression top dead center so that, for example, the air-fuel ratio is in a lean state, and the reverse torque In order to suppress the occurrence of this, the ignition timing is delayed after the top dead center and ignited before the normal engine control shown in step S4 is performed.

  On the other hand, returning to step S101, if it is determined that the predicted turbine rotational speed Tre is greater than or equal to the affected rotational speed Tri (NO in step S101), the turbine of the torque converter 51 is assumed to be in the engaged state. Since the reverse drive force acts on the pump impeller 54 from 55 and the piston 13 moves, it is determined that the predetermined engine restart condition is satisfied (step S105), and the restart condition is satisfied. It will be in a standby state except in some cases.

  Next, when it is determined in step S105 that the engine restart condition is satisfied, the restart of the engine described in step S104 is started and the count of the timer built in the ECU 2 is started. (Step S106).

  The time measured by this timer waits for the elapse of a predetermined time (for example, 0.05 seconds) after executing the initial combustion in the stop-time compression stroke cylinder 12C for the reverse rotation operation of the engine (step S107), and the automatic shift By outputting a switching signal for switching from the neutral state to the driving state to the mechanism 50, the switching of the automatic transmission mechanism 50 is completed after the forward rotation of the engine (step S108), and the process returns. That is, the predetermined time is set in consideration of a time lag from when the automatic transmission mechanism 50 receives the switching signal until the driving state where the driving force is actually transmitted is completed. The timing is set so that it is after the forward rotation of the engine and until the compression top dead center at which the intake stroke cylinder 12D at the time of stop comes first after the restart. Therefore, the above-mentioned timer built in the ECU 2 restarts the piston 13 of the stop-time intake stroke cylinder 12D from the time when the piston 13 of the stop-time intake stroke cylinder 12D first passes through the compression top dead center when the engine is restarted. The automatic transmission mechanism 50 is switched within the unstable period. Thus, since the automatic transmission mechanism 50 is switched to the drive state after the reverse rotation operation of the engine is completed, the reverse rotation force of the axles 78 and 79 does not impede the reverse rotation operation of the engine, and the stop expansion stroke cylinder. The in-cylinder pressure of 12A can be sufficiently increased. In addition, the reverse driving force acts during forward rotation of the engine, thereby assisting the restart of the engine in the unstable restart period in which the stop-time intake stroke cylinder 12D first reaches the compression top dead center after the restart. Can be restarted more reliably.

  As described above, the ECU 2 sets the predicted turbine rotational speed Tre when the engine restart condition is satisfied and when it is determined that the vehicle is traveling based on the detection result of the vehicle speed sensor 38. When the calculated turbine rotational speed Tre is determined to be equal to or greater than the influence rotational speed Tri, the automatic transmission mechanism 50 is controlled so as to be switched from the neutral state to the driving state, so that the reverse driving force from the wheel side is used. Then, the engine can be restarted. Therefore, coupled with restarting the engine after reverse operation, the reverse driving force can suppress the decrease in the engine rotation speed during the unstable restart period, thereby reliably restarting the engine. Can be started. Moreover, the ECU 2 operates the automatic transmission mechanism 50 at a predetermined time in the restart instability period from when the engine rotates forward until the piston 13 of the intake stroke cylinder 12D at the stop passes through the compression top dead center. Since the control is performed so that the switching is completed, the reverse driving force does not affect the reverse rotation operation of the engine, and the effect by the restart accompanying the reverse rotation operation can be maximized.

  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) 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 a predetermined value by a predetermined time after the start, control with assistance by the start motor 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.

  (2) In the above embodiment, when assisting restart using reverse driving force, the automatic transmission mechanism 50 switches to the drive state by performing initial combustion in the stop-time compression stroke cylinder 12C. Is set to a predetermined time after a predetermined period (0.05 seconds in the above embodiment) has elapsed, but this switching time is not limited to this. For example, for this switching timing, the start of the period may be set to the combustion timing in the stop-time expansion stroke cylinder 12A, or the period may be set according to the stop position of the piston 13 of the stop-time compression stroke cylinder 12C. It may be changed. Further, even after the forward rotation operation of the engine is detected by the crank angle sensors 30 and 31, the piston 13 of the intake stroke cylinder 12D at the time of stop is set to a predetermined time before exceeding the first compression top dead center. Good.

  (3) In the above embodiment, the automatic transmission mechanism 50 is switched from the neutral state to the drive state when the predicted turbine rotational speed Tre falls below the influence rotational speed Tri. The monitoring may be performed by the crank angle sensors 30, 31 and the like. When the piston 13 moves, it may be determined again whether or not the piston 13 is stopped within an appropriate range, and the starter motor may assist as necessary.

  (4) In the above embodiment, the automatic transmission mechanism 50 is in the late-stage precharge state during the engine automatic stop operation period, but it may be in the early-stage precharge state. Responsiveness after establishment of the engine restart condition can be improved as compared with the case where the charging state is not established.

  (5) In the above embodiment, in-cylinder injection is performed when the engine is restarted, but port injection may be employed.

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 mechanism in the starter which concerns on this invention. It is a relationship figure which shows the example of a relationship between the operating state of the friction element in the automatic transmission mechanism, and a gear stage. It is the schematic which shows an example of the hydraulic control circuit of the hydraulic control mechanism in the starting device which concerns on this invention. It is a switching map of the automatic transmission mechanism according to the vehicle speed and the throttle opening in the starting device. It is a relationship figure which shows the example of a relationship between the operating state of the solenoid valve in the automatic transmission mechanism, and a gear stage. It is explanatory drawing which shows the time change of the working pressure in the hydraulic control circuit of the automatic transmission mechanism. It is a block diagram in the starting device concerning the present invention. It is a time chart which shows the change state of the engine speed at the time of an engine stop, change states, such as a throttle opening and a target electric power generation current. It is a time chart which shows the selection gear at the time of an engine stop and restart, a turbine rotational speed, a vehicle speed, etc. It is a time chart which shows the selection gear at the time of an engine stop and restart, a turbine rotational speed, a vehicle speed, etc. It is a distribution map which shows the correlation with the engine speed at the time of an engine stop, and a piston stop position. It is a time chart which shows the 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 flowchart which shows the control operation of an engine. It is a flowchart which shows the control action at the time of an automatic stop and restart of an engine. It is a flowchart which shows the control action at the time of engine restart. It is a time chart which shows the time-dependent change of the rotation speed of the engine at the time of restart in the conventional engine starting device.

Explanation of symbols

1 Engine body 2 ECU (stop / restart control means, turbine rotation speed prediction means)
3 Crankshaft 12 Cylinder 13 Piston 30, 31 Crank angle sensor (engine speed detection means)
34 Vehicle speed sensor (vehicle speed detection means)
36 Turbine Rotation Sensor 50 Automatic Transmission Mechanism 51 Torque Converter 63 Hydraulic Control Mechanism 67-72 Friction Element Tre Rotation Speed Tri Influenced Rotation Speed

Claims (4)

When the engine automatic stop condition that can be satisfied even when the vehicle is running is satisfied, the fuel supply to the engine is stopped and the engine is automatically stopped, and the restart condition is satisfied after the engine is stopped. Sometimes, when the engine is stopped, combustion is performed in the cylinder in the compression stroke, the engine is operated in a predetermined amount in the reverse direction, and the cylinder pressure of the cylinder that becomes the expansion stroke when the engine is stopped is increased. An engine starter having stop / restart control means for rotating the engine in the forward rotation direction and restarting the engine by performing combustion in a cylinder,
Vehicle speed detecting means for detecting the vehicle speed, and an automatic transmission mechanism capable of switching between a driving state in which driving force can be transmitted to the wheel side and a neutral state in which transmission of driving force to the wheel side is disconnected. ,
The stop / restart control means is configured to switch the automatic transmission mechanism from the drive state to the neutral state when the engine automatic stop condition is satisfied, and to detect the vehicle speed detecting means when the engine restart condition is satisfied. When it is determined that the vehicle is running based on the detection result, the compression top dead center at which the piston of the cylinder in the intake stroke first hits when the engine is stopped from the forward rotation of the piston when the engine is restarted. An engine starter for a vehicle, wherein the automatic transmission mechanism is controlled to be switched from a neutral state to a drive state at a predetermined time in an unstable restart period until passing. Turbine rotation speed prediction means for predicting the turbine rotation speed of the torque converter when the automatic transmission mechanism including the torque converter is switched to the drive state when the automatic transmission mechanism is in the neutral state;
Based on the detection result of the turbine rotational speed predicting means, the stop / restart control means has a predicted rotational speed of the turbine equal to or higher than a predetermined influence rotational speed at which the crankshaft of the engine is rotated by the reverse driving force from the wheel side. 2. The vehicle according to claim 1, wherein when it is determined that the automatic transmission mechanism is switched, a timing for completing the switching from the neutral state to the drive state of the automatic transmission mechanism is set to be a predetermined time of the restart unstable period. Engine starter.   The stop / restart control means sets the output timing of the switching signal to the automatic transmission mechanism during the restart unstable period to a predetermined timing before the first combustion in the cylinder in the expansion stroke when the engine is stopped. The engine starting device for a vehicle according to claim 2.   The automatic speed change mechanism has a plurality of friction elements that are interrupted by fluid pressure control, and is configured to switch between the neutral state and the drive state by intermittently connecting these friction elements, and the stop and restart 3. The control means according to claim 2, wherein the neutral state is a precharge state in which a predetermined fluid path connected to the friction element is filled with a working fluid until a predetermined fluid pressure is reached. 3. A starter for a vehicle engine according to 3.

Images