JP2012136980A - Engine rotation stop control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy of engine rotation stop control executed when an idle stop request is generated, in a system including a constant engagement type starter with an inverse rotation prevention function.SOLUTION: When stopping engine rotation in response to an idle stop request, a target track of engine rotation behavior is calculated so that the engine rotation stops at a target stop crank angle, and engine rotation stop control for controlling load torque of an alternator 33 is executed to adjust actual engine rotation behavior to the target track. By executing in-cylinder pressure variation reduction control for controlling a variable valve lift mechanism 31 to reduce in-cylinder pressure variation of the engine 11 during execution of the engine rotation stop control, variation of composite torque acting on the engine 11 is reduced, and engine rotation is prevented from being easily stopped in a specific crank angle region. Thereby, an engine rotation stop position can be easily controlled to a target stop crank angle by the engine rotation stop control.

Description

  The present invention relates to an engine rotation stop control device having a function of controlling an engine rotation stop position (stop crank angle).

  In recent years, for example, as described in Patent Document 1 (Japanese Patent Laid-Open No. 2010-43532), in a vehicle equipped with an engine automatic stop / start system (idle stop system), the engine restartability is improved. In addition, when the engine is stopped (during idle stop), the engine rotation is set to the target stop crank angle (crank angle suitable for starting) for the purpose of controlling the engine rotation stop position (stop crank angle) to a crank angle range suitable for starting. The target trajectory of engine rotation behavior is calculated so that it stops at a crank angle within the range), and the load torque of the generator (alternator) is controlled so that the actual engine rotation behavior matches the target trajectory when stopping the engine rotation. There is one that performs engine rotation stop control. Further, in a vehicle equipped with an idle stop system, for the purpose of improving the restartability of the engine, etc., a constant mesh starter with a reverse rotation prevention function (a constant mesh starter having a function to prevent reverse rotation of the engine) Some have adopted this.

JP 2010-43532 A

  As shown in FIG. 2, generally, in the process of stopping the rotation of the engine, the in-cylinder pressure is increased / decreased by the compression / expansion of the in-cylinder air due to the rotation of the engine, and the combined torque acting on the engine is increased / decreased.

  At that time, in a system including a general starter (a starter that allows reverse rotation of the engine), the combined torque is in the reverse rotation region (the crank angle at which the combined torque acts in the reverse rotation direction) immediately before the engine stops rotating. When entering (region), the engine rotates in the reverse direction, so the engine rotation is likely to stop in the crank angle region (see A in FIG. 2) where the combined torque is near zero. In this case, since the crank angle range (see A in FIG. 2) in which the engine rotation is likely to stop is included in the crank angle range suitable for starting, if the engine rotation stop control is executed, the crank angle range suitable for starting The probability that the engine rotation stops in a range other than is reduced.

  On the other hand, in a system equipped with a constantly meshing starter with a reverse rotation prevention function, the reverse rotation of the engine is prevented even if the combined torque enters the reverse rotation region just before the rotation of the engine stops. The engine rotation is likely to stop in the range from the crank angle region where the combined torque is near 0 to the reverse rotation region (see B in FIG. 2). In this case, the range other than the crank angle range suitable for starting (that is, the crank angle range not suitable for starting) is included in the crank angle region where the engine rotation is likely to stop (see B in FIG. 2), but is suitable for starting. Since the crank angle range is only partially included in the crank angle region where engine rotation is likely to stop (see B in FIG. 2), even if engine rotation stop control is executed, the crank angle range other than the crank angle range suitable for starting There is a possibility that the engine rotation is likely to stop within the range (see FIG. 3).

  Therefore, the problem to be solved by the present invention is to make it easy to control the engine rotation stop position to the target stop crank angle in a system including a constantly meshing starter with a reverse rotation prevention function. An engine rotation stop control device capable of improving the accuracy of the engine is provided.

  In order to solve the above-mentioned problems, the invention according to claim 1 controls the engine rotation behavior with the torque of the electric motor so that the engine rotation stops at the target stop crank angle when the engine rotation is stopped in response to the engine stop request. Control means for executing engine rotation stop control, a mechanism for preventing reverse rotation of the engine, and a variable valve mechanism for changing a valve opening / closing characteristic of at least one of an intake valve and an exhaust valve of the engine. In-cylinder pressure change reduction control for controlling the variable valve mechanism so as to reduce the in-cylinder pressure change of the engine during execution of the engine rotation stop control is executed.

  The present invention reduces the change in the resultant torque acting on the engine by executing the in-cylinder pressure change reduction control for controlling the variable valve mechanism so as to reduce the in-cylinder pressure change of the engine during the engine rotation stop control. It is possible to suppress the engine rotation from being easily stopped (or difficult to stop) in a specific crank angle region. Thereby, the engine rotation stop position can be easily controlled to the target stop crank angle by the engine rotation stop control, and the accuracy of the engine rotation stop control can be improved.

  In this case, it is preferable that the engine rotation stop control and the in-cylinder pressure change reduction control are not executed when the engine stop request is generated by the driver's operation of turning off the ignition switch. In this way, when an engine stop request (manual stop request) is generated due to the driver turning off the ignition switch, the fuel cut is immediately performed without executing the engine rotation stop control and the in-cylinder pressure change reduction control. It can be executed to stop the engine operation.

  By the way, the appropriate control amount (control amount necessary to sufficiently reduce the in-cylinder pressure change) due to individual differences in the system and changes over time (for example, changes in intake characteristics and exhaust characteristics due to deposit accumulation), etc. ) Will change.

  Accordingly, as in claim 3, the in-cylinder pressure determining means for detecting or estimating the in-cylinder pressure of the engine is provided, and the in-cylinder pressure is determined based on the in-cylinder pressure detected or estimated by the in-cylinder pressure determining means during execution of the in-cylinder pressure change reduction control. A correction value for correcting the control amount of the change reduction control may be learned, and then the control amount of the in-cylinder pressure change reduction control may be corrected using the correction value when executing the in-cylinder pressure change reduction control. . In this way, even if the appropriate control amount for in-cylinder pressure change reduction control changes due to system differences or changes over time, the in-cylinder pressure change reduction control control amount is corrected accordingly and the in-cylinder pressure change reduction control is corrected. The control amount of the change reduction control can be set to an appropriate value.

  In addition, the atmospheric pressure changes due to changes in altitude due to vehicle travel, etc., but the appropriate control amount for reducing the change in in-cylinder pressure (to reduce the change in in-cylinder pressure sufficiently) is also affected by the change in intake pressure due to the change in atmospheric pressure. Necessary control amount) changes.

  In view of this, as in the fourth aspect of the present invention, the intake pressure detection means for detecting the intake pressure of the engine is provided, and the control amount of the in-cylinder pressure change reduction control is changed according to the intake pressure detected by the intake pressure detection means. good. In this way, even if the appropriate control amount of the in-cylinder pressure change reduction control changes due to the change of the intake pressure due to the change of the atmospheric pressure, the control amount of the in-cylinder pressure change reduction control is changed accordingly, The control amount of the internal pressure change reduction control can be set to an appropriate value.

FIG. 1 is a diagram showing a schematic configuration of an engine control system in Embodiment 1 of the present invention. FIG. 2 is a diagram for explaining a crank angle region in which engine rotation is likely to stop. FIG. 3 is a diagram showing a distribution of engine rotation stop positions when conventional engine rotation stop control is executed. FIG. 4 is a diagram showing the behavior of the combined torque when the in-cylinder pressure change reduction control is executed. FIG. 5 is a diagram for explaining in-cylinder pressure change reduction control using the variable valve lift mechanism of the first embodiment. FIG. 6 is a flowchart showing the flow of processing of the engine stop control routine of the first embodiment. FIG. 7 is a flowchart illustrating an execution example of engine rotation stop control according to the first embodiment. FIG. 8 is a diagram for explaining in-cylinder pressure change reduction control using the electromagnetically driven valve mechanism of the second embodiment. FIG. 9 is a flowchart showing the flow of processing of the engine stop control routine of the second embodiment. FIG. 10 is a diagram illustrating a schematic configuration of the variable valve mechanism of the third embodiment. FIG. 11 is a diagram for explaining in-cylinder pressure change reduction control using the variable valve mechanism of the third embodiment.

  Hereinafter, some embodiments embodying the mode for carrying out the present invention will be described.

A first embodiment of the present invention will be described with reference to FIGS.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.
An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. A throttle valve 16 whose opening is adjusted by a motor 15 and a throttle opening sensor 17 for detecting the opening (throttle opening) of the throttle valve 16 are provided on the downstream side of the air flow meter 14.

  Further, a surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 (intake pressure detecting means) for detecting the intake pipe pressure (intake pressure) is provided in the surge tank 18. . The surge tank 18 is provided with an intake manifold 20 that introduces air into each cylinder of the engine 11, and a fuel injection valve that injects fuel toward the intake port in the vicinity of the intake port of the intake manifold 20 of each cylinder. 21 is attached. An ignition plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of the ignition plug 22 of each cylinder.

  On the other hand, the exhaust pipe 23 of the engine 11 is provided with an exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting the air-fuel ratio or rich / lean of the exhaust gas. A catalyst 25 such as a three-way catalyst for purifying gas is provided.

  A cooling water temperature sensor 26 that detects the cooling water temperature is attached to the cylinder block of the engine 11. A crank angle sensor 28 that outputs a pulse signal each time the crankshaft 27 rotates by a predetermined crank angle is attached to the outer peripheral side of the crankshaft 27 of the engine 11. The engine speed is detected.

  Further, the engine 11 is provided with a variable valve lift mechanism 31 (variable valve mechanism) that changes the lift amount and operating angle of the intake valve 29. The variable valve lift mechanism 31 is configured to switch the lift amount and operating angle of the intake valve 29 in a plurality of stages by switching the cam profile of the cam that drives the intake valve 29 in a plurality of stages. The variable valve lift mechanism 31 may be configured to continuously change the lift amount and operating angle of the intake valve 29.

  Further, the engine 11 is provided with a starter 32 for rotationally driving (cranking) the crankshaft 27 at the start. The starter 32 is a constantly meshing starter having a reverse rotation preventing function having a clutch that always meshes a pinion with a ring gear connected to the crankshaft 27 of the engine 11 and prevents the engine 11 from rotating backward.

  The rotation of the crankshaft 27 is transmitted to the alternator 33 (generator) via a belt transmission mechanism (not shown). Thereby, the alternator 33 is rotationally driven by the power of the engine 11 to generate power. The load torque of the alternator 33 can be controlled by duty-controlling the power generation control current (field current) of the alternator 33. In this embodiment, the alternator 33 is used as an electric motor referred to in the claims.

  Outputs of the various sensors described above are input to an electronic control unit (hereinafter referred to as “ECU”) 34. The ECU 34 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount and the ignition timing according to the engine operating state. The throttle opening (intake air amount) and the like are controlled.

  Further, the ECU 34 executes engine automatic stop / start control (so-called idle stop control) by executing an engine automatic stop / start control routine (not shown). In this automatic engine stop / start control, when the driver performs a deceleration operation (accelerator fully closed, brake operation, etc.) while the vehicle is running, the vehicle enters a predetermined deceleration state that may cause the vehicle to stop, or the vehicle is stopped. When the brake operation is continued, it is determined that an automatic stop request (idle stop request) has occurred, combustion of the engine 11 (fuel injection and / or ignition) is stopped, and the engine 11 is automatically started. Stop. After that, it is determined that a restart request has occurred when the driver performs a preparation operation for starting the vehicle (brake release, operation of the shift lever to the drive range, etc.) or a start operation (depressing the accelerator, etc.). Then, the starter 32 is energized, the engine 11 is cranked, the fuel injection is restarted and restarted. In addition, the engine 11 may be restarted when a restart request is generated from a control system of an in-vehicle device such as a battery charge control system or an air conditioner.

  Further, the ECU 34 executes an engine stop control routine shown in FIG. 6 described later to stop the engine rotation in response to an automatic stop request (idle stop request). The engine rotation behavior target trajectory is calculated so as to stop at a crank angle within the crank angle range), and engine rotation stop control is performed to control the load torque of the alternator 33 so that the actual engine rotation behavior matches the target trajectory. . Note that the target trajectory of the engine rotation behavior may be calculated in advance before the automatic stop request is generated.

  As shown in FIG. 2, generally, in the process of stopping the rotation of the engine, the in-cylinder pressure is increased / decreased by the compression / expansion of the in-cylinder air due to the rotation of the engine, and the combined torque acting on the engine is increased / decreased.

  At that time, in a system including a general starter (a starter that allows reverse rotation of the engine), the combined torque is in the reverse rotation region (the crank angle at which the combined torque acts in the reverse rotation direction) immediately before the engine stops rotating. When entering (region), the engine rotates in the reverse direction, so the engine rotation is likely to stop in the crank angle region (see A in FIG. 2) where the combined torque is near zero. In this case, since the crank angle range (see A in FIG. 2) in which the engine rotation is likely to stop is included in the crank angle range suitable for starting, if the engine rotation stop control is executed, the crank angle range suitable for starting The probability that the engine rotation stops in a range other than is reduced.

  On the other hand, in a system equipped with a constantly meshing starter with a reverse rotation prevention function, the reverse rotation of the engine is prevented even if the combined torque enters the reverse rotation region just before the rotation of the engine stops. The engine rotation is likely to stop in the range from the crank angle region where the combined torque is near 0 to the reverse rotation region (see B in FIG. 2). In this case, the range other than the crank angle range suitable for starting (that is, the crank angle range not suitable for starting) is included in the crank angle region where the engine rotation is likely to stop (see B in FIG. 2), but is suitable for starting. Since the crank angle range is only partially included in the crank angle region where engine rotation is likely to stop (see B in FIG. 2), even if engine rotation stop control is executed, the crank angle range other than the crank angle range suitable for starting There is a possibility that the engine rotation is likely to stop within the range (see FIG. 3).

  As a countermeasure, the ECU 34 executes in-cylinder pressure change reduction control for controlling the variable valve lift mechanism 31 so as to reduce the in-cylinder pressure change of the engine 11 during execution of the engine rotation stop control. As a result, as shown in FIG. 4, it is possible to reduce the change in the combined torque acting on the engine 11 and to suppress the engine rotation from being easily stopped (or difficult to stop) in a specific crank angle region. be able to.

  In the first embodiment, as shown in FIG. 5, the variable valve lift mechanism 31 makes the lift amount of the intake valve 29 smaller than that during engine operation, and the operating angle (valve opening period) of the intake valve 29 is during engine operation. The variable valve lift is configured to be able to switch to a working angle expansion mode in which at least one of the intake valve 29 and the exhaust valve 30 is opened in the entire crank angle region. By switching the mechanism 31 to the operating angle expansion mode, the in-cylinder pressure change of the engine 11 is reduced.

Hereinafter, the processing content of the engine stop control routine of FIG. 6 executed by the ECU 34 in the first embodiment will be described.
The engine stop control routine shown in FIG. 6 is repeatedly executed at a predetermined cycle during the power-on period of the ECU 34 (while the ignition switch 35 is on), and serves as a control means in the claims.

  When this routine is started, first, at step 101, it is determined whether or not an automatic or manual engine stop request has been generated. If neither engine stop request has been generated, this routine is immediately terminated. .

  On the other hand, if it is determined in step 101 that an automatic or manual engine stop request has been generated, the process proceeds to step 102 to determine whether or not the generated engine stop request is an automatic stop request (idle stop request). If it is determined that the request is not an automatic stop request, it is determined that a manual stop request has been generated by the driver's turning-off operation of the ignition switch 35, and the routine proceeds to step 107 where normal stop processing is executed. In the normal stop process, the fuel cut is performed immediately and the operation of the engine 11 is stopped without executing the engine rotation stop control and the in-cylinder pressure change reduction control.

  On the other hand, if it is determined in step 102 that the generated engine stop request is an automatic stop request, the process proceeds to step 103 to determine whether or not an execution condition for engine rotation stop control is satisfied. The determination is made based on whether or not the engine rotation speed when the stop request is generated is equal to or higher than a predetermined value, whether or not the air conditioner is off, and the like.

  If it is determined in step 103 that the engine rotation stop control execution condition is not satisfied, it is determined that it is difficult to ensure the accuracy of the engine rotation stop control. Execute time processing.

  On the other hand, if it is determined in step 103 that the conditions for executing the engine rotation stop control are satisfied, the process proceeds to step 104, the fuel cut is started, and then the process proceeds to step 105 to execute the engine rotation stop control. To do. In this engine rotation stop control, the target trajectory of engine rotation behavior is calculated so that the engine rotation stops at the target stop crank angle (crank angle within the crank angle range suitable for starting), and the actual engine rotation behavior is set to the target trajectory. The load torque of the alternator 33 is controlled to match. Note that the target trajectory of the engine rotation behavior may be calculated in advance before the automatic stop request is generated.

  Thereafter, the process proceeds to step 106, and in-cylinder pressure change reduction control is executed. In this in-cylinder pressure change reduction control, the variable valve lift mechanism 31 is operated in the operating angle expansion mode (the lift amount of the intake valve 29 is made smaller than that during engine operation, and the operating angle of the intake valve 29 is expanded more than that during engine operation). By switching to the state in which at least one of the intake valve 29 and the exhaust valve 30 is opened in the crank angle region, the in-cylinder pressure change of the engine 11 is reduced.

  An execution example of the engine stop control of the first embodiment described above will be described with reference to the time chart of FIG. At the time t1 when the automatic stop request (idle stop request) is generated during engine operation and the automatic stop request flag is turned ON, it is determined whether or not the engine rotation stop control execution condition is satisfied. At the time t2 when it is determined that the execution condition of the rotation stop control is satisfied and the execution condition flag is turned on, the fuel cut flag is turned on and the fuel cut is executed to stop the combustion of the engine 11, and The engine rotation stop control flag is turned on to execute engine rotation stop control for controlling the load torque of the alternator 33 so that the actual engine rotation behavior matches the target trajectory, and the in-cylinder pressure changes during execution of this engine rotation stop control. The decrease control flag is turned on to control the variable valve lift mechanism 31 so as to decrease the in-cylinder pressure change of the engine 11. Perform small control.

  In the first embodiment described above, during the execution of the engine rotation stop control, the in-cylinder pressure change reduction control for controlling the variable valve lift mechanism 31 so as to reduce the in-cylinder pressure change of the engine 11 is executed. It is possible to reduce the change in the composite torque acting on the engine 11 and to suppress the engine rotation from being easily stopped (or difficult to stop) in a specific crank angle region. As a result, the engine rotation stop position can be easily controlled to the target stop crank angle by the engine rotation stop control, the accuracy of the engine rotation stop control can be improved, and the range other than the crank angle range suitable for starting Thus, the probability of engine rotation stopping can be reduced.

  Next, Embodiment 2 of the present invention will be described with reference to FIGS. However, description of substantially the same parts as those in the first embodiment will be omitted or simplified, and different parts from the first embodiment will be mainly described.

  In the second embodiment, an electromagnetically driven valve mechanism (not shown) that drives the intake valve 29 to open and close with an electromagnetic actuator is provided as a variable valve mechanism. By this electromagnetically driven valve mechanism, the valve opening and closing characteristics (opening and closing timing, Lift amount, working angle, etc.) can be freely changed.

  As shown in FIG. 8, in the electromagnetically driven valve mechanism, the lift amount of the intake valve 29 is set to a required lift amount smaller than that during engine operation in a predetermined crank angle region (at least the crank angle region where the exhaust valve 30 is closed). It is possible to control to a lift amount holding mode that holds and opens at least one of the intake valve 29 and the exhaust valve 30 in the entire crank angle region. Therefore, in the second embodiment, the in-cylinder pressure change of the engine 11 is reduced by controlling the electromagnetically driven valve mechanism to the lift amount holding mode during the in-cylinder pressure change reduction control.

  The cylinder head of the engine 11 is provided with an in-cylinder pressure sensor 36 (see FIG. 1) for detecting the in-cylinder pressure for each cylinder (or only a specific cylinder) as in-cylinder pressure determining means. The in-cylinder pressure sensor 36 may be of a type integrated with the spark plug 22 or may be of a type that is attached so that a sensor part separate from the spark plug 22 faces the combustion chamber. good.

  By the way, the appropriate control amount (control amount necessary to sufficiently reduce the in-cylinder pressure change) due to individual differences in the system and changes over time (for example, changes in intake characteristics and exhaust characteristics due to deposit accumulation), etc. ) Will change. Further, the atmospheric pressure changes due to altitude change or the like due to running of the vehicle, but the appropriate control amount of the in-cylinder pressure change reduction control also changes due to the change in intake pressure due to the change in atmospheric pressure.

  In consideration of these circumstances, in the second embodiment, the in-cylinder pressure changes according to the intake pressure (intake pipe pressure) detected by the intake pipe pressure sensor 19 by executing an engine stop control routine of FIG. 9 described later. A lift amount correction value for correcting the required lift amount of the in-cylinder pressure change reduction control based on the in-cylinder pressure detected by the in-cylinder pressure sensor 36 during the execution of the in-cylinder pressure change reduction control while changing the required lift amount of the reduction control. After that, when the in-cylinder pressure change reduction control is executed, the required lift amount of the in-cylinder pressure change reduction control is corrected using the lift amount correction value.

  In the engine stop control routine shown in FIG. 9, first, in step 201, it is determined whether an automatic or manual engine stop request has been generated, and it is determined that an automatic or manual engine stop request has been generated. For example, the routine proceeds to step 202, where it is determined whether the generated engine stop request is an automatic stop request (idle stop request). If it is determined that the request is not an automatic stop request, the driver's ignition switch 35 is turned on. It is determined that a manual stop request has been generated by the off operation, and the process proceeds to step 211 to execute a normal stop process.

  On the other hand, if it is determined in step 202 that the generated engine stop request is an automatic stop request, the process proceeds to step 203 to determine whether or not an execution condition for engine rotation stop control is satisfied, and the engine If it is determined that the execution condition of the rotation stop control is not established, it is determined that it is difficult to ensure the accuracy of the engine rotation stop control, and the process proceeds to step 211 to execute the normal stop process.

  On the other hand, if it is determined in step 203 that the engine rotation stop control execution condition is satisfied, the process proceeds to step 204, fuel cut is started, and then the process proceeds to step 205 to execute the engine rotation stop control. To do.

  Thereafter, the process proceeds to step 206, and after the intake pressure detected by the intake pipe pressure sensor 19 is read, a basic lift amount corresponding to the intake pressure is calculated with reference to a basic lift amount map (not shown). Here, the basic lift amount map is set such that, for example, the basic lift amount decreases as the intake pressure decreases. This basic lift amount map is created in advance based on test data and design data, and is stored in the ROM of the ECU 34.

  Thereafter, the process proceeds to step 207, and the learned value of the lift amount correction value is read. The learned value of the lift amount correction value is stored in a rewritable nonvolatile memory (a rewritable memory that holds stored data even when the ECU 34 is powered off) such as a backup RAM (not shown) of the ECU 34.

Thereafter, the process proceeds to step 208, and the required lift amount is obtained by the following equation using the basic lift amount and the lift amount correction value (learned value).
Required lift amount = Basic lift amount + Lift amount correction value

  As described above, the required lift amount is calculated according to the intake pressure by calculating the required lift amount using the basic lift amount according to the intake pressure, and the required lift amount is calculated using the lift amount correction value. Correct the required lift amount with.

  Thereafter, the process proceeds to step 209, and in-cylinder pressure change reduction control is executed. In this in-cylinder pressure change reduction control, the electromagnetically driven valve mechanism is operated in a lift amount holding mode (the lift amount of the intake valve 29 is maintained at a required lift amount smaller than that during engine operation in a predetermined crank angle region, and the intake valve is maintained in all crank angle regions. 29 is a state in which at least one of the exhaust valve 30 and the exhaust valve 30 is opened), the in-cylinder pressure change of the engine 11 is reduced.

  Thereafter, the process proceeds to step 210, and after reading the in-cylinder pressure detected by the in-cylinder pressure sensor 36 during execution of the in-cylinder pressure change reduction control (for example, the maximum value of the in-cylinder pressure during the compression stroke), a map of lift amount correction values ( Referring to (not shown), a lift amount correction value corresponding to the in-cylinder pressure is calculated. Here, the lift amount correction value map is set, for example, such that the lift amount correction value increases as the in-cylinder pressure increases. The lift amount correction value map is created in advance based on test data and design data, and is stored in the ROM of the ECU 34. Then, the lift amount correction value is learned by updating the learned data of the lift amount correction value stored in the rewritable nonvolatile memory such as the backup RAM of the ECU 34 with the currently calculated lift amount correction value. To do.

  In the second embodiment described above, the basic lift amount is calculated according to the intake pressure detected by the intake pipe pressure sensor 19, and the required lift amount is calculated using this basic lift amount, so that the required lift amount is calculated according to the intake pressure. Since the required lift amount is changed, even if the appropriate required lift amount for in-cylinder pressure change reduction control changes due to a change in intake pressure due to a change in atmospheric pressure, the required lift for in-cylinder pressure change reduction control correspondingly changes. By changing the amount, the required lift amount for the in-cylinder pressure change reduction control can be set to an appropriate value.

  Further, in the second embodiment, the lift amount correction value is learned based on the in-cylinder pressure detected by the in-cylinder pressure sensor 36 during the execution of the in-cylinder pressure change reduction control, and then the lift is performed when the in-cylinder pressure change reduction control is executed. Because the required lift amount for in-cylinder pressure change reduction control is corrected using the amount correction value, even if the appropriate required lift amount for in-cylinder pressure change reduction control changes due to individual differences in the system or changes over time, etc. Correspondingly, the required lift amount of the in-cylinder pressure change reduction control can be corrected, and the required lift amount of the in-cylinder pressure change reduction control can be set to an appropriate value.

  In the second embodiment, the in-cylinder pressure is detected by the in-cylinder pressure sensor 36. However, the present invention is not limited to this. For example, the in-cylinder pressure may be estimated based on engine rotation behavior, intake pressure, or the like. good.

  In the second embodiment, the lift amount correction value is calculated according to the in-cylinder pressure. However, the present invention is not limited to this. For example, the amount of change in the in-cylinder pressure (for example, the difference between the peak value and the bottom value) is calculated. Accordingly, the lift amount correction value may be calculated. Alternatively, the lift amount correction value may be increased when the in-cylinder pressure or the change amount of the in-cylinder pressure is a predetermined value or more.

  Next, Embodiment 3 of the present invention will be described with reference to FIGS. However, description of substantially the same parts as those in the first embodiment will be omitted or simplified, and different parts from the first embodiment will be mainly described.

  In the third embodiment, as shown in FIG. 10, a variable valve mechanism 37 that controls the lift amount of the intake valve 29 via hydraulic pressure is provided. The variable valve mechanism 37 reciprocates when the cam side piston 40 is driven by a cam 39 provided on the cam shaft 38 of the engine 11, and the cam side hydraulic chamber 41 and the valve side hydraulic pressure are reciprocated by the reciprocating motion of the cam side piston 40. The hydraulic oil moves between the chamber 42 and the valve side piston 43 is driven by the hydraulic pressure of the valve side hydraulic chamber 42 to reciprocate. The reciprocating motion of the valve side piston 43 drives the intake valve 29 to open and close. Operate. A check valve 45 and an accumulator 46 are provided in the middle of an oil passage 44 that guides hydraulic oil discharged from an oil pump (not shown) to the cam-side hydraulic chamber 41. The accumulator 46, the cam-side hydraulic chamber 41, In between, the hydraulic release valve 47 and the check valve 48 are arranged in parallel.

  When the hydraulic release valve 47 is opened during the opening operation of the intake valve 29, the hydraulic pressure in the cam side hydraulic chamber 41 is released to the accumulator 46 and the intake valve 29 is closed. Thus, the lift timing of the intake valve 29 can be adjusted by changing the valve closing timing of the intake valve 29.

  As shown in FIG. 11, the variable valve mechanism 37 is set so that the intake valve 29 is completely closed and the valve clearance amount = 0 when the intake valve 29 returns to the minimum lift position during engine operation. However, by increasing the hydraulic pressure supplied to the variable valve mechanism 37 and offsetting the minimum lift position of the intake valve 29 in the valve opening direction, the valve clearance amount of the intake valve 29 is made larger than 0 and the entire crank angle region is set. It is possible to control to the valve clearance expansion mode in which the intake valve 29 is opened. Therefore, in the third embodiment, the in-cylinder pressure change of the engine 11 is reduced by controlling the variable valve mechanism 37 to the valve clearance expansion mode during the in-cylinder pressure change reduction control.

  In the third embodiment as well, the required valve clearance amount for the in-cylinder pressure change reduction control may be changed according to the intake pressure. Further, a correction value for correcting the required valve clearance amount for in-cylinder pressure change reduction control is learned based on the in-cylinder pressure during execution of in-cylinder pressure change reduction control, and then corrected when executing in-cylinder pressure change reduction control. The required valve clearance amount for in-cylinder pressure change reduction control may be corrected using the value.

  In the first to third embodiments, the variable valve mechanism of the intake valve is controlled to execute the in-cylinder pressure change reduction control. However, the present invention is not limited to this. For example, the variable valve mechanism of the exhaust valve is controlled. Then, the in-cylinder pressure change reduction control may be executed, or the in-cylinder pressure change reduction control may be executed by controlling both the variable valve mechanism of the intake valve and the variable valve mechanism of the exhaust valve.

  Further, in each of the first to third embodiments, at the time of in-cylinder pressure change reduction control, control is performed so that at least one of the intake valve and the exhaust valve is opened in the entire crank angle region. There is no need to control at least one of the intake valve and the exhaust valve in the region, and if the change in the cylinder pressure can be sufficiently reduced, there is a period during which both the intake valve and the exhaust valve are closed. May be.

  Further, in each of the first to third embodiments, the torque of the alternator is controlled during the engine rotation stop control. However, the present invention is not limited to this, and an electric motor other than the alternator (for example, a generator motor of a hybrid vehicle). The torque may be controlled.

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 16 ... Throttle valve, 19 ... Intake pipe pressure sensor (intake pressure detection means), 21 ... Fuel injection valve, 22 ... Spark plug, 23 ... Exhaust pipe, 29 ... Intake Valves, 30 ... exhaust valves, 31 ... variable valve lift mechanism (variable valve mechanism), 32 ... starter, 33 ... alternator (electric motor), 34 ... ECU (control means), 36 ... in-cylinder pressure sensor (in-cylinder pressure determination means), 37 ... Variable valve mechanism

Claims (4)

Control means for executing engine rotation stop control for controlling the engine rotation behavior with the torque of the electric motor so that the engine rotation stops at the target stop crank angle when stopping the engine rotation in response to the engine stop request;
A mechanism for preventing reverse rotation of the engine;
A variable valve mechanism for changing a valve opening / closing characteristic of at least one of the intake valve and the exhaust valve of the engine,
The engine rotation stop control device, wherein the control means executes in-cylinder pressure change reduction control for controlling the variable valve mechanism so as to reduce an in-cylinder pressure change of the engine during execution of the engine rotation stop control. .   The said control means does not perform the said engine rotation stop control and the said in-cylinder pressure change reduction control, when the said engine stop request | requirement generate | occur | produces by the driver's ignition switch OFF operation. Engine rotation stop control device. In-cylinder pressure determining means for detecting or estimating the in-cylinder pressure of the engine,
The control means learns a correction value for correcting the control amount of the in-cylinder pressure change reduction control based on the in-cylinder pressure detected or estimated by the in-cylinder pressure determination means during execution of the in-cylinder pressure change reduction control, 3. The engine rotation stop control device according to claim 1, wherein when the in-cylinder pressure change reduction control is executed, a control amount of the in-cylinder pressure change reduction control is corrected using the correction value. 4. Intake pressure detection means for detecting the intake pressure of the engine,
The engine rotation stop control according to any one of claims 1 to 3, wherein the control means changes a control amount of the in-cylinder pressure change reduction control according to the intake pressure detected by the intake pressure detection means. apparatus.

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