JP2010216350A - Engine rotation stop control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent drop of engine rotation stop control accuracy due to change over of target locus of engine rotation stop control. <P>SOLUTION: When engine rotation is stopped by controlling load of an alternator 33 so as to match actual engine rotation behavior to a target locus, command delay time until the alternator actually responds from power generation command value of the alternator is calculated is calculated, engine rotation speed change quantity during the command delay time is estimated, it is determined that influence of command delay time is large and target locus of engine rotation stop control is fixed to a target locus selected at the beginning if the command delay time until the alternator 33 actually responds after power generation command value of the alternator 33 is calculated is not shorter than a prescribed value, and it is prohibited after that to select target locus at every prescribed timing until engine rotation stops. Consequently, the target locus is prevented from being changed over during execution of engine rotation stop control and hunting phenomenon in which fluctuation of power generation command of the alternator 33 and response delay of actual engine rotation behavior due to change-over of the target locus are repeated is prevented. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  In recent years, as described in Patent Document 1 (Japanese Patent Laid-Open No. 2008-215182) and Patent Document 2 (Japanese Patent Laid-Open No. 2008-215230), a vehicle equipped with an engine automatic stop / start system (idle stop system) Then, in order to improve restartability, engine rotation stops at the target stop crank angle for the purpose of controlling the engine rotation stop crank angle to a crank angle range suitable for starting when the engine is stopped (idle stop). Rotational behavior until the engine rotation is calculated as the target trajectory, and engine rotation stop control is performed to control the load torque of the generator (alternator) so that the actual engine rotational behavior matches the target trajectory when stopping the engine rotation There is something. Specifically, a target engine rotational speed (engine rotational speed on the target trajectory) is set based on target trajectory data at predetermined timings, and the deviation between the target engine rotational speed and the actual engine rotational speed is reduced. Calculate the required load torque of the generator, and use the load torque characteristics of the generator (the relationship between the power generation command value, the engine speed and the load torque) to generate a power generation command according to the current engine speed and the required load torque. The value is calculated, and the power generation control current (field current) of the generator is controlled by this power generation command value to control the load torque of the generator.

JP 2008-215182 A JP 2008-215230 A

  By the way, as shown in FIG. 9, when the target engine speed is set based on the target trajectory data at predetermined timing (for example, every TDC) during execution of the engine rotation stop control, the current actual engine speed is set. The target engine speed on the lower rotation side or the target engine speed on the higher rotation side can be selected. At this time, if the target engine speed on the low rotation side is selected, the target trajectory on the advance side passing through the target engine speed on the low rotation side at the current crank angle is selected, while the target engine speed on the high rotation side is selected. If the target engine speed is selected, the target angle on the retard side that passes the target engine speed on the high speed side at the current crank angle (the target trajectory delayed by a predetermined crank angle interval from the target angle on the advance side) ) Will be selected.

  Therefore, in order to improve the controllability of the engine rotation stop control, the inventor sets the target engine rotation speed on the low rotation side when setting the target engine rotation speed based on the target trajectory data for each predetermined timing. By selecting the target engine speed that has a smaller deviation from the actual engine speed among the target engine speeds on the high speed side, the actual engine speed is selected from the target trajectory on the advance side and the target trajectory on the retard side. We are studying a system that selects the target trajectory with the smaller deviation from the above, but the following new problems were found in this research process.

  Depending on the communication specifications of the control system, when the engine rotation stop control is performed, the power generation command value of the generator is calculated by the control circuit and then the power generation command value is transmitted and the generator actually responds (power generation command value A delay time (hereinafter referred to as “command delay time”) may occur.

  As shown in FIG. 10, when the target trajectory is switched during execution of the engine rotation stop control, the required load torque (required generated current) of the generator changes greatly, and the generated command value changes greatly. It is easy to be affected by the command delay time from when the generator is calculated until the generator actually responds. If the command delay time is long, the response delay of the actual load torque to the required load torque of the generator (actual The response delay of the actual engine rotation behavior with respect to the target trajectory increases, and the deviation between the target trajectory and the actual engine rotation behavior (deviation between the target engine rotation speed and the actual engine rotation speed) quickly increases. Therefore, the accuracy of the engine rotation stop control may be reduced.

  Furthermore, there is a possibility that the target trajectory of the engine rotation stop control frequently switches between the target trajectory on the advance side and the target trajectory on the retard side due to a delay in response of the actual engine rotational behavior, and accordingly the generator A hunting phenomenon in which the power generation command value repeatedly increases and decreases may occur, and the accuracy of engine rotation stop control may further decrease.

  Therefore, the problem to be solved by the present invention is to provide an engine rotation stop control device that can prevent a decrease in engine rotation stop control accuracy due to switching of a target trajectory for engine rotation stop control.

  In order to solve the above-described problem, an invention according to claim 1 is an engine rotation stop control device that stops combustion by stopping combustion when an engine stop request is generated, and a generator driven by the engine; Target trajectory calculating means for calculating rotational behavior (hereinafter referred to as “target trajectory”) until the engine rotation stops at the target stop crank angle, and adjusting the actual engine rotational behavior to the target trajectory when stopping the engine rotation. Stop control means for executing engine rotation stop control for controlling the load of the generator, and the stop control means is a target engine at a lower speed side than the actual engine speed based on the data of the target trajectory at every predetermined timing. By selecting one of the rotational speed and the target engine rotational speed higher than the actual engine rotational speed, the target engine on the low rotational speed side is selected. A selection means for selecting one of the advance side target trajectory corresponding to the gin rotation speed and the retard side target trajectory corresponding to the high rotation side target engine rotation speed, and the target engine selected by the selection means A power generation command value calculation means for calculating a power generation command value of the generator so as to reduce a deviation between the rotation speed and the actual engine rotation speed, and from when the power generation command value of the generator is calculated until the generator responds Prohibiting means for fixing the target trajectory for engine rotation stop control to the target trajectory initially selected by the selecting means and prohibiting the selecting means from selecting the target trajectory at every predetermined timing when the command delay time is equal to or greater than a predetermined value It is set as the structure provided with.

  In this configuration, when the command delay time is shorter than the predetermined value, it is determined that the effect of the command delay time is small or almost absent, and the target engine speed on the low speed side and the high speed side are determined at each predetermined timing. By selecting one of the target engine rotation speeds, one of the advance side target trajectory and the retard side target trajectory can be selected, and the controllability of the engine rotation control can be improved.

  On the other hand, if the command delay time is greater than or equal to a predetermined value, it is determined that the effect of the command delay time is large, and the target trajectory for engine rotation stop control is fixed to the first selected target trajectory, and the target trajectory is set at every predetermined timing. Can be prohibited. As a result, when the command delay time is greater than or equal to a predetermined value, it is possible to prevent the target track from being switched during execution of the engine rotation stop control. Hunting phenomenon in which the power generation command value repeatedly increases and decreases can be prevented in advance, the deterioration of the engine rotation stop control accuracy can be prevented, and the engine stop crank angle is accurately controlled within the target crank angle range. be able to.

  In this case, as in the second aspect, the selection means is configured such that, for each predetermined timing, the deviation between the target engine speed on the low speed side and the target engine speed on the high speed side from the actual engine speed or the engine By selecting the target engine rotational speed with the smaller parameter deviation obtained by converting the rotational speed into the energy amount, the deviation between the actual engine rotational speed of the advance side target trajectory and the retarded side target trajectory is small. The target trajectory may be selected. In this way, when the command delay time is shorter than the predetermined value, the target engine speed with the smaller deviation from the actual engine speed is always selected, and the actual engine speed is quickly set to the target engine speed. The speed can be controlled, and the controllability of the engine rotation stop control can be improved.

  According to a third aspect of the present invention, the prohibiting means sets the target trajectory for engine rotation stop control to the target trajectory selected by the selecting means at the timing when the cylinder whose combustion has been stopped in response to the engine stop request first enters the expansion stroke. Then, it is preferable to prohibit the selection of the target trajectory at every predetermined timing by the selection means until the engine rotation stops. In this way, it is possible to reliably prevent the target track from being switched during the execution of the engine rotation stop control.

FIG. 1 is a schematic configuration diagram of an entire engine control system according to an embodiment of the present invention. FIG. 2 is a diagram for explaining a method for calculating a target trajectory. FIG. 3 is a diagram for explaining alternator load characteristics. FIG. 4 is a diagram for explaining an apparent alternator load characteristic during engine rotation stop control. FIG. 5A is a time chart for explaining a comparative example in which the engine rotation stop control is performed by setting the reference load torque Tref (Ne (i)) = 0, and FIG. 5B is a reference load torque Tref ( 6 is a time chart illustrating an embodiment in which engine rotation stop control is performed with Ne (i)) set to half of the maximum load. FIG. 6 is a block diagram illustrating an engine rotation stop control function of the engine ECU. FIG. 7 is a block diagram illustrating the configuration of the alternator load characteristic model. FIG. 8 is a diagram schematically showing an example of a map of load torque characteristics. FIG. 9 is a diagram illustrating a method for setting the target engine speed. FIG. 10 is a time chart for explaining a problem caused by switching the target trajectory when the command delay time is long. FIG. 11 is a flowchart for explaining the flow of processing of the target trajectory calculation routine. FIG. 12 is a flowchart for explaining the flow of processing of the command delay time calculation routine. FIG. 13 is a flowchart (part 1) for explaining the flow of processing of the engine rotation stop control routine. FIG. 14 is a flowchart (part 2) for explaining the flow of processing of the engine rotation stop control routine. FIG. 15 is a flowchart for explaining the processing flow of the target engine speed setting routine.

Hereinafter, an embodiment embodying a mode for carrying out the present invention will be described.
First, the overall configuration of the engine control system will be schematically described with reference to FIG.
A throttle valve 14 is provided in the middle of the intake pipe 13 connected to the intake port 12 of the engine 11, and the opening (throttle opening) of the throttle valve 14 is detected by a throttle opening sensor 15. Further, an intake pipe pressure sensor 18 for detecting an intake pipe pressure is provided on the downstream side of the throttle valve 14, and fuel injection for injecting fuel toward the intake port 12 in the vicinity of the intake port 12 of each cylinder. A valve 19 is attached.

  On the other hand, an exhaust gas purifying catalyst 22 is installed in the middle of the exhaust pipe 21 connected to the exhaust port 20 of the engine 11. The cylinder block of the engine 11 is provided with a cooling water temperature sensor 23 that detects the cooling water temperature. A crank angle sensor 26 is installed facing the outer periphery of the signal rotor 25 attached to the crankshaft 24 of the engine 11. The crank angle sensor 26 synchronizes with the rotation of the signal rotor 25 from the crank angle sensor 26 at every predetermined crank angle (for example, 30 ° C.). A crank pulse signal is output every A). A cam angle sensor 29 is installed opposite to the outer periphery of the signal rotor 28 attached to the cam shaft 27 of the engine 11, and the cam pulse is generated at a predetermined cam angle in synchronization with the rotation of the signal rotor 28 from the cam angle sensor 29. A signal is output.

  The rotation of the crank pulley 34 connected to the crankshaft 24 is transmitted to the alternator 33 (generator) via the belt 35. As a result, the alternator 33 is rotationally driven by the power of the engine 11 to generate power. The load on the alternator 33 can be controlled by duty-controlling the power generation control current (field current) of the alternator 33.

  Outputs of the various sensors described above are input to an engine control circuit (hereinafter referred to as “engine ECU”) 30. The engine ECU 30 is mainly composed of a microcomputer, and controls the fuel injection amount and fuel injection timing of the fuel injection valve 19 and the ignition timing of the spark plug 31 according to the engine operating state detected by various sensors, and the engine ECU 30. Stop combustion (ignition and / or fuel injection) when an engine stop request is generated when a predetermined automatic stop condition (for example, accelerator fully closed, brake operation, idle operation, etc.) is satisfied during operation. An idle stop that stops the engine rotation is executed, and during the engine stop due to this idle stop (during idle stop), the driver prepares for starting the vehicle (brake release, operation of the shift lever to the drive range, etc.) When a start operation (accelerator depression, etc.) is performed, or from the control system of the in-vehicle device When the dynamic request occurs, by energizing a predetermined automatic start condition is satisfied in the starter (not shown) to restart the engine 11 by cranking.

  Further, the engine ECU 30 executes a routine shown in FIGS. 11 to 15 to be described later, thereby calculating a target trajectory calculation for calculating a rotational behavior (hereinafter referred to as “target trajectory”) until the engine rotation stops at a target stop crank angle. In addition to functioning as a means, it also functions as a stop control means for executing engine rotation stop control for controlling the load of the alternator 33 so that the actual engine rotation behavior matches the target trajectory when the engine rotation is stopped.

  Here, the target trajectory is obtained by calculating the relationship between the crank angle up to the target stop crank angle and the target engine speed at predetermined crank angle intervals and assigning it to a table (not shown). This target trajectory is calculated, for example, in the direction of turning the crank angle with the target stop crank angle as an initial value using a relational expression of an energy conservation law that takes loss torque into account (see FIG. 2).

The relational expression of the energy conservation law is expressed by the following expression.
Ne (i + 1) ² = Ne (i) ² −2 / J × {Tloss (θ (i)) − Tref (Ne (i))}
Here, Ne (i + 1) is the engine speed at the time (i + 1) before the current crank angle (i), Ne (i) is the engine speed at the current time (i), and J is the engine speed. 11 moment of inertia. Tloss (θ (i)) is a loss torque obtained by adding the pumping loss and the friction loss at the crank angle θ (i) at the current time (i), and the crank angle θ at the current time (i) using a preset map or the like. The loss torque Tloss (θ (i)) corresponding to (i) is calculated. Tref (Ne (i)) is the reference load torque of the alternator 33 at the current engine speed Ne (i). In the relational expression of the above energy conservation law, “Tloss (θ (i)) − Tref (Ne (i))” is the sum of the pumping loss, the friction loss, and the reference load torque Tref (Ne (i)) of the alternator 33. Corresponds to loss torque.

  In this embodiment, the reference load torque Tref (Ne (i)) of the alternator 33 is set to half (1/2) of the maximum load that can be controlled by the alternator 33 as shown in FIG. In this way, unlike the motor generator, the alternator 33 can virtually control the load torque of the alternator 33 in both the positive and negative directions even if there is a situation where the assist torque cannot be output (reference load Tref). It is possible to control the load torque of the alternator 33 using the following load torque as a virtually negative load torque and a load torque greater than the reference load Tref as a positive load torque), and following the engine rotation behavior to the target track Can be improved.

Note that the reference load torque Tref (Ne (i)) of the alternator 33 is not limited to half (1/2) of the maximum load, for example, 1/3, 1/4, 2/3, 3 / of the maximum load. 4 or the like may be used. In short, an appropriate load smaller than the maximum controllable load of the alternator 33 and larger than 0 may be set as the reference load torque Tref (Ne (i)).
0 <Tref (Ne (i)) <maximum load

  FIG. 5A shows a comparative example in which the engine rotation stop control is performed by setting the reference load torque Tref (Ne (i)) = 0. In this comparative example, since the load torque of the alternator 33 can be controlled only in the positive direction, when the actual engine rotation behavior overshoots, the actual engine rotation behavior cannot be matched with the target trajectory.

  On the other hand, if the reference load torque Tref (Ne (i)) of the alternator 33 is set to an appropriate load smaller than the maximum load as in this embodiment, the alternator is virtually set as shown in FIG. Since the load torque 33 can be controlled in both positive and negative directions, as shown in FIG. 5B, even when the actual rotational behavior overshoots, the actual rotational behavior can be matched with the target trajectory.

  Furthermore, in this embodiment, as shown in FIG. 6, when calculating the target trajectory, the target trajectory corresponding to the reference load torque Tref (Ne (i)) of the alternator 33 is calculated, and during engine rotation stop control, The reference load torque Tref (Ne (i)) corresponding to the engine speed Ne (i) is calculated, and the deviation between the target engine speed and the actual engine speed at the crank angle θ (i) at the current time (i) is calculated. The base load torque is calculated so as to reduce the required load torque Talt by adding the reference load torque Tref (Ne (i)) to the base load torque (in practice, the required load torque Talt is set to the pulley). The ratio Ratio is multiplied to convert to the required shaft torque Talt.final).

  Thereafter, as shown in FIG. 7, the power generation command value calculation unit 38 (power generation command value calculation means) uses the load torque characteristic of the alternator 33 (see FIG. 8) to request the required load torque Talt (request shaft) of the alternator 33. The power generation command value (duty duty) according to the torque Talt.final) and the engine rotational speed Ne (or the rotational speed Nalt of the alternator 33 obtained by multiplying the engine rotational speed Ne by the pulley ratio Ratio) is calculated.

  The load torque characteristics shown in FIG. 8 are characteristics when the output voltage of the alternator 33 is constant at 13.5 V, and the same characteristics are set for each output voltage. Based on this power generation command value (duty duty), the power generation control current (field current) of the alternator 33 is controlled to control the load torque of the alternator 33.

  Such control of the load torque of the alternator 33 is periodically executed at a predetermined crank interval until the engine rotational speed decreases below the power generation limit rotational speed Nelow (see FIG. 3) of the alternator 33, thereby realizing the actual engine rotational behavior. The engine rotation stop control is performed so that the load torque of the alternator 33 is feedback controlled so as to match the target track.

  During engine rotation stop control, the engine ECU 30 calculates a power generation command value at a predetermined crank angle cycle, and the power generation command value is transmitted to the power supply system ECU 36 (see FIG. 1) at a predetermined time cycle by CAN (Controller Area Network) communication. Send. Further, the power supply system ECU 36 transmits the received power generation command value to the alternator 33 at a predetermined time period by LIN (Local Interconnect Network) communication.

  Due to the difference between the calculation cycle of these power generation command values and the transmission cycle of CAN communication, or the difference between the transmission cycle of CAN communication and the transmission cycle of LIN communication, the engine ECU 30 causes the alternator 33 to There is a delay time from when the power generation command value is calculated to when the power generation command value is transmitted and when the alternator 33 actually responds (operates according to the power generation command value). May decrease.

  Therefore, in this embodiment, during the engine rotation stop control, a command delay time from when the power generation command value of the alternator 33 is calculated until the alternator 33 actually responds is calculated, and the engine during the command delay time is calculated. Estimate the amount of change in the rotation speed, subtract the amount of change in the engine rotation speed during the command delay time from the current engine rotation speed to obtain the engine rotation speed after the command delay time elapses. A power generation command value is calculated according to the speed and the required load torque.

  Specifically, as shown in FIG. 7, first, the command delay time calculation unit 39 sets the required load torque Talt of the alternator 33 to the initial value when the engine rotation stop control is started when the engine stop request is generated. When (for example, the reference load torque Tref (Ne)) is set, the time when the alternator 33 actually responds (for example, to the change of the power generation command value) from the time when the power generation command value corresponding to the required load torque Talt is calculated. Accordingly, the command delay time dt is obtained by counting the time until the generation current starts to change).

Then, the engine speed change amount estimation unit 40 estimates the engine speed change amount dNe during the command delay time during the engine rotation stop control. At this time, for example, the target trajectory slope Kt calculated according to the reference load torque Tref (Ne) of the alternator 33 (for example, the amount of change in the engine speed per unit time near the current engine speed in the target trajectory). Is calculated by multiplying the inclination Kt of the target trajectory by the command delay time dt to determine the engine speed change amount dNe during the command delay time.
dNe = Kt × dt

Alternatively, a slope Kr of the actual engine rotational behavior (for example, a change amount of the engine rotational speed per unit time in the vicinity of the current engine rotational speed in the actual engine rotational behavior) is calculated, and a command is given to the slope Kr of the actual engine rotational behavior. The engine speed change amount dNe during the command delay time may be obtained by multiplying the delay time dt.
dNe = Kr × dt

Thereafter, the engine rotational speed Ne.hosei after the command delay time elapses is obtained by subtracting the engine speed change amount dNe during the command delay time from the current engine speed Ne.
Ne.hosei = Ne-dNe

Further, the engine rotational speed Ne.hosei after the command delay time has elapsed may be multiplied by the pulley ratio Ratio to convert the rotation speed Nalt.hosei of the alternator 33 after the command delay time has elapsed.
Nalt.hosei = Ne.hosei × Ratio

  Thereafter, the power generation command value calculation unit 38 uses the load torque characteristics (see FIG. 8) of the alternator 33 to request the required load torque Talt (requested shaft torque Talt.final) of the alternator 33 and the engine after the command delay time has elapsed. A power generation command value (duty duty) corresponding to the rotational speed Ne.hosei (or the rotational speed Nalt.hosei of the alternator 33 after the command delay time has elapsed) is calculated.

  At this time, the power generation command value (duty duty) may be directly calculated from the required load torque Talt and the engine rotational speed Ne.hosei (or the rotational speed Nalt.hosei of the alternator 33). The required field current (required excitation current) may be calculated from the rotational speed Ne.hosei (or the rotational speed Nalt.hosei of the alternator 33), and the power generation command value (duty duty) may be calculated from the required field current.

  By the way, as shown in FIG. 9, when setting the target engine speed based on the target trajectory table (target trajectory data) at every predetermined timing (for example, every TDC) during the execution of the engine rotation stop control, It is possible to select a target engine speed that is lower than the current actual engine speed or a target engine speed that is higher. At this time, if the target engine speed on the low rotation side is selected, the target trajectory on the advance side passing through the target engine speed on the low rotation side at the current crank angle is selected, while the target engine speed on the high rotation side is selected. If the target engine speed is selected, the target angle on the retard side that passes the target engine speed on the high speed side at the current crank angle (the target trajectory delayed by a predetermined crank angle interval from the target angle on the advance side) ) Will be selected.

  Therefore, in this embodiment, in order to improve the controllability of the engine rotation stop control, when setting the target engine speed based on the target trajectory table for each predetermined timing, By selecting the target engine speed that has a smaller deviation from the actual engine speed among the target engine speeds on the high speed side, the actual engine speed is selected from the target trajectory on the advance side and the target trajectory on the retard side. The target trajectory with the smaller deviation is selected.

  However, as shown in FIG. 10, when the target trajectory is switched during the execution of the engine rotation stop control, the required load torque (required power generation current) of the alternator 33 is greatly changed and the power generation command value is greatly changed. It is easily affected by the command delay time from when the command value is calculated until the alternator 33 actually responds. If the command delay time is long, the response delay of the actual load torque with respect to the required load torque of the alternator 33 (with respect to the required generated current) Response delay of actual power generation current) increases, response delay of actual engine rotation behavior with respect to target trajectory increases, and deviation between target trajectory and actual engine rotation behavior (deviation between target engine rotation speed and actual engine rotation speed) May not be reduced quickly, and the accuracy of engine rotation stop control may be reduced. Furthermore, there is a possibility that the target trajectory for the engine rotation stop control frequently switches between the advance target trajectory and the retard target trajectory due to the response delay of the actual engine rotation behavior. A hunting phenomenon in which the power generation command value repeatedly increases and decreases may occur, and the accuracy of engine rotation stop control may further decrease.

As a countermeasure, in this embodiment, when the command delay time is a predetermined value or more, it is determined that the effect of the command delay time is large, and the first selected target trajectory (combustion is stopped in response to the engine stop request). The target trajectory of the engine rotation stop control is fixed to the target trajectory selected at the timing when the cylinder is first in the expansion stroke, and then the target trajectory is selected at every predetermined timing (for example, every TDC) until the engine rotation stops. By prohibiting this, the target trajectory is prevented from being switched during execution of the engine rotation stop control.
The engine rotation stop control described above is executed by the engine ECU 30 according to the routines shown in FIGS. The processing contents of these routines will be described below.

[Target trajectory calculation routine]
The target trajectory calculation routine shown in FIG. 11 is repeatedly executed at a predetermined cycle (predetermined crank angle cycle) while the engine ECU 30 is powered on. When this routine is started, first, in step 101, it is determined whether or not the target trajectory calculation completion flag is set to “0”, which means that the target trajectory is not calculated. If it is set to “1” indicating completion of trajectory calculation, this routine is terminated without performing the subsequent processing.

On the other hand, if it is determined in step 101 that the target trajectory calculation completion flag = 0 (before the target trajectory is calculated), the process proceeds to step 102 where the loss torque Tloss (θ (i)) and the reference load torque Tref (Ne) of the alternator 33 are obtained. (i)) is used to calculate the square of the target engine speed Ne (i + 1) at the next time point (i + 1) using the relational expression of the energy conservation law expressed by the following formula.
Ne (i + 1) ² = Ne (i) ² −2 / J × {Tloss (θ (i)) − Tref (Ne (i))}

  Here, J is the moment of inertia of the engine 11, and Tloss (θ (i)) is a loss torque obtained by adding the pumping loss and the friction loss, and the crank angle θ at the present time (i) is determined using a preset map or the like. The loss torque Tloss (θ (i)) corresponding to (i) is calculated.

  In the relational expression of the above energy conservation law, “Tloss (θ (i)) − Tref (Ne (i))” is the sum of pumping loss, friction loss, and reference load torque Tref (Ne (i)) of the alternator 33. Corresponds to loss torque.

  Initial values are i = 0, θ (0) = target stop crank angle, and Ne (0) = 0 rpm (engine speed at stop). The target trajectory is calculated every predetermined crank angle (for example, every TDC) in the direction of turning the crank angle with the target stop crank angle θ (0) as an initial value.

  After this, the routine proceeds to step 103, where it is determined whether or not the square of the target engine speed Ne (i + 1) exceeds the square of the maximum engine speed Nemax at which the engine rotation stop control can be executed. If it does not exceed the square of Nemax, the process proceeds to step 104, and the target trajectory calculation completion flag is maintained at “0” (reset).

  Thereafter, the routine proceeds to step 106, where the square root of the square of the target engine speed Ne (i + 1) is calculated to obtain the target engine speed Ne (i + 1), which is obtained as a target trajectory table (not shown). To complete this routine. In order to reduce the calculation load on the engine ECU 30, the square of the engine speed may be assigned to the table as it is. The target trajectory table is stored in the memory of the engine ECU 30.

  The above processing is repeated, and the square of the target engine speed Ne (i + 1) is calculated for each predetermined crank angle (for example, every TDC) in the direction of turning the crank angle with the target stop crank angle θ (0) as an initial value. The process of calculating and assigning the target engine speed Ne (i + 1) to the target trajectory table is repeated. When it is determined in step 103 that the square of the target engine rotational speed Ne (i + 1) exceeds the square of the maximum engine rotational speed Nemax that can execute the engine rotational stop control, the process proceeds to step 105, and the target The trajectory calculation completion flag is set to “1” which means the completion of the target trajectory calculation, and the routine proceeds to step 106 where the square root of the last target engine speed Ne (i + 1) is calculated to calculate the target engine speed Ne. (i + 1) is obtained, assigned to the target trajectory table, and this routine is terminated.

[Command delay time calculation routine]
The command delay time calculation routine shown in FIG. 12 is repeatedly executed at a predetermined cycle (predetermined crank angle cycle) while the engine ECU 30 is powered on. When this routine is started, first, in step 201, it is determined whether or not an engine stop request (idle stop signal) has been generated. If no engine stop request has been generated, the subsequent processing is not performed. This routine ends.

  Thereafter, when it is determined in step 201 that an engine stop request has been generated, the routine proceeds to step 202, where the requested load torque Talt of the alternator 33 is set when the engine rotation stop control is started with the generation of the engine stop request. When the initial value (for example, the reference load torque Tref (Ne)) is set, the time when the alternator 33 actually responds (for example, the power generation command value of the power generation command value from the time when the power generation command value corresponding to the required load torque Talt is calculated). The command delay time dt is obtained by counting the time until the generated current starts to change according to the change.

[Engine rotation stop control routine]
The engine rotation stop control routine shown in FIGS. 13 and 14 is repeatedly executed at a predetermined cycle (predetermined crank angle cycle) while the engine ECU 30 is powered on. When this routine is started, first, at step 301, it is determined whether or not an engine stop request (idle stop signal) has been generated. If no engine stop request has been generated, the subsequent processing is not performed. This routine is ended, and engine operation (fuel injection control and ignition control) is continued.

  Thereafter, when it is determined in step 301 that an engine stop request has been generated, the routine proceeds to step 302, where the current crank angle θ and engine rotational speed Ne are calculated. Thereafter, the process proceeds to step 303, where it is determined whether or not the current crank angle θ is the load torque control timing (for example, TDC) of the alternator 33. This routine is terminated without performing.

  If it is determined in step 303 that the current crank angle θ is the control timing of the load torque of the alternator 33, the process proceeds to step 304, and the maximum engine speed at which the current engine speed Ne can execute the engine rotation stop control. It is determined whether the speed is lower than the speed Nemax. If the current engine speed Ne is equal to or higher than the maximum engine speed Nemax, this routine is terminated without performing the subsequent processing.

On the other hand, if it is determined in step 304 that the current engine speed Ne is lower than the maximum engine speed Nemax, the process proceeds to step 305 to determine whether or not the engine 11 is in combustion. If it is determined in step 305 that the engine 11 is still in combustion immediately after the engine stop request is generated, the process proceeds to step 306, and the required load torque Talt of the alternator 33 when starting engine rotation stop control. Is set to an initial value (eg, reference load torque Tref (Ne)).
Talt = Tref (Ne)

  Thereafter, when it is determined in step 305 that the combustion of the engine 11 has stopped, the routine proceeds to step 307, where a target engine speed setting routine shown in FIG. ) To obtain the target engine speed Netg corresponding to the current control timing. Here, when the vehicle is an MT vehicle (manual transmission vehicle), it may be determined whether or not the clutch is in an open state, and a target track corresponding to the clutch open / engaged state may be selected.

  Thereafter, the routine proceeds to step 308, where the required load torque Talt is calculated by the following equation using the current engine rotational speed Ne, the target engine rotational speed Netg, and the reference load torque Tref (Ne) of the alternator 33.

Here, J is the moment of inertia of the engine 11, K is the feedback gain, and Δθ is the crank angle change amount.
Thereafter, the process proceeds to step 309, where the required load torque Talt is multiplied by the pulley ratio Ratio to convert it to the required shaft torque Talt.final of the alternator 33.

Thereafter, the process proceeds to step 310 in FIG. 14, and after reading the command delay time dt calculated when the engine rotation stop control is started by the above-described command delay time calculation routine in FIG. 12, the process proceeds to step 311 where the alternator The target trajectory slope Kt calculated according to the reference load torque Tref (Ne) 33 (for example, the amount of change in the engine speed per unit time near the current engine speed in the target trajectory) is calculated. The trajectory gradient Kt is multiplied by the command delay time dt to determine the engine speed change amount dNe during the command delay time.
dNe = Kt × dt

Alternatively, a slope Kr of the actual engine rotational behavior (for example, a change amount of the engine rotational speed per unit time in the vicinity of the current engine rotational speed in the actual engine rotational behavior) is calculated, and a command is given to the slope Kr of the actual engine rotational behavior. The engine speed change amount dNe during the command delay time may be obtained by multiplying the delay time dt.
dNe = Kr × dt

Thereafter, the process proceeds to step 312, where the engine rotational speed Ne.hosei after the lapse of the command delay time is obtained by subtracting the engine speed change amount dNe during the command delay time from the current engine speed Ne.
Ne.hosei = Ne-dNe

In the next step 313, the engine speed Ne.hosei after the command delay time elapses is multiplied by the pulley ratio Ratio to convert it to the rotation speed Nalt.hosei of the alternator 33 after the command delay time elapses.
Nalt.hosei = Ne.hosei × Ratio

  Thereafter, the process proceeds to step 314, and after detecting the battery voltage, the process proceeds to step 315, and the load corresponding to the current battery voltage is selected from a plurality of load torque characteristic maps (see FIG. 8) created for each battery voltage. A torque characteristic map is selected, and the current required load torque Talt (required shaft torque Talt.final) and the engine speed Ne.hosei after the command delay time has elapsed (or the rotation speed Nalt of the alternator 33 after the command delay time has elapsed) .hosei) to calculate a power generation command value (duty duty).

[Target engine speed setting routine]
The target engine speed setting routine shown in FIG. 15 is a subroutine executed in step 307 of the engine rotation stop control routine of FIG. 13, and plays a role as selection means in the claims. When this routine is started, first, at step 501, it is determined whether or not the command delay time dt is equal to or greater than a predetermined value.

  If it is determined in step 501 that the command delay time dt is equal to or greater than the predetermined value, it is determined that the effect of the command delay time dt is large, the process proceeds to step 502, and the target track switching prohibition flag is set to the target track switching prohibition flag. Set to “1” which means switching prohibition.

  On the other hand, if it is determined in step 501 that the command delay time dt is shorter than the predetermined value, it is determined that the effect of the command delay time dt is small or almost absent, and the process proceeds to step 503 to switch the target trajectory. The prohibition flag is maintained (or reset) at “0”, which means that the target track switching is permitted.

  Thereafter, the process proceeds to step 504, and the i-th target engine speed Ne (i) and (i + 1) -th target engine speed Ne (i +) from the target stop crank angle are referred to with reference to the target trajectory table. By reading 1), the target engine speed Ne (i) on the low speed side and the target engine speed Ne (i + 1) on the high speed side are obtained. The initial values are i = 0 and Ne (0) = 0 rpm (engine speed when stopped).

  In this embodiment, the target engine rotation speed is calculated using the relational expression of the energy conservation law in the target trajectory calculation routine of FIG. 11 described above and assigned to the target trajectory table, but the target trajectory of FIG. The calculation routine may be omitted, and the target engine rotation speed may be calculated in this step 504 using the energy conservation law relational expression.

  Thereafter, the process proceeds to step 505, where it is determined whether the target trajectory switching prohibition flag = 1 (target trajectory switching prohibition) or not. In this step 505, the target trajectory switching prohibition flag = 0 (target trajectory switching permission). If it is determined, the routine proceeds to step 507, where it is determined whether or not the current actual engine speed Ne is lower than the high target engine speed Ne (i + 1).

  If it is determined in step 507 that the current actual engine speed Ne is equal to or higher than the target engine speed Ne (i + 1) on the high speed side, the process proceeds to step 508, and then the target read from the target trajectory table. After increasing the number i of the engine speed Ne (i), Ne (i + 1) by “1”, the process returns to step 504.

  Thereafter, when it is determined in step 507 that the current actual engine speed Ne is lower than the target engine speed Ne (i + 1) on the high speed side, the process proceeds to step 509 and the target engine on the high speed side is determined. The deviation (Ne (i + 1) -Ne) between the rotational speed Ne (i + 1) and the actual engine rotational speed Ne is the deviation between the actual engine rotational speed Ne and the target engine rotational speed Ne (i) on the low speed side. It is determined whether or not (Ne−Ne (i)).

  In this step 509, the deviation (Ne (i + 1) -Ne) between the target engine speed Ne (i + 1) on the high speed side and the actual engine speed Ne becomes the difference between the actual engine speed Ne and the low engine speed side. When it is determined that the deviation (Ne−Ne (i)) from the target engine speed Ne (i) is larger, the target engine speed Ne (i) on the low speed side is the actual engine speed Ne. Therefore, the process proceeds to step 510, and the target engine speed Ne (i) on the low speed side is selected as the target engine speed Netg corresponding to the current control timing, so that the target engine speed on the low speed side is selected. A target trajectory on the advance side corresponding to the speed Ne (i) is selected. Thereafter, the process proceeds to step 511, where the number i of the target engine speed Ne (i), Ne (i + 1) read from the target trajectory table at the next control timing is decreased by “1”, and then the process proceeds to step 514. The target trajectory selection completion flag is set to “1”.

  On the other hand, in step 509, the deviation (Ne (i + 1) -Ne) between the target engine speed Ne (i + 1) on the high speed side and the actual engine speed Ne is the actual engine speed Ne. And the target engine speed Ne (i + 1) on the high speed side is determined to be equal to or less than the deviation (Ne−Ne (i)) between the target engine speed Ne (i) on the low speed side and the target engine speed Ne (i) on the low speed side. Since the deviation from the actual engine speed Ne is smaller, the process proceeds to step 512, and the target engine speed Ne (i + 1) on the high speed side is selected as the target engine speed Netg corresponding to the current control timing. Then, the target trajectory on the retard side corresponding to the target engine speed Ne (i + 1) on the high speed side is selected. Thereafter, the process proceeds to step 513, and the process proceeds to step 514 while maintaining the current number i of the target engine speed Ne (i), Ne (i + 1) read from the target track table at the next control timing, and the target track. The selection completion flag is set to “1”.

  As described above, when the command delay time dt is shorter than the predetermined value (when the target trajectory switching prohibition flag = 0), it is determined that the effect of the command delay time is small or almost not, and at each predetermined timing. The target engine speed Netg corresponding to the current control timing is set to the smaller difference between the target engine speed on the low speed side and the target engine speed on the high speed side (for example, every TDC). By selecting, the target trajectory having the smaller deviation from the actual engine speed among the target trajectory on the advance side and the target trajectory on the retard side is selected.

  On the other hand, if it is determined in step 505 that the target trajectory switching prohibition flag = 1 (target trajectory switching prohibition), first, in step 506, it is determined whether the target trajectory selection completion flag = 1. If it is determined that the target trajectory selection completion flag = 0, the processing of steps 507 to 514 is executed, and the actual engine speed among the low-speed side target engine speed and the high-speed side target engine speed is determined. By selecting the smaller deviation from the engine rotational speed as the target engine rotational speed Netg corresponding to the current control timing, the actual engine rotational speed of the advanced target trajectory and the retarded target trajectory The target trajectory with the smaller deviation is selected, and the target trajectory selection completion flag is set to “1”.

  After the target trajectory is selected for the first time, it is determined in step 506 that the target trajectory selection completion flag = 1, the process proceeds to step 515, and the target engine speed Ne () read from the target trajectory table at the current control timing. After setting i) as the target engine speed Netg corresponding to the current control timing, the process proceeds to step 516, and the target engine speed Ne (i), Ne (i +) read from the target trajectory table at the next control timing. The process of reducing the number i of 1) by “1” is repeated to fix the target trajectory for engine rotation stop control to the first selected target trajectory.

  As described above, when the command delay time dt is equal to or greater than a predetermined value (when the target track switching prohibition flag = 1), it is determined that the command delay time has a large influence, and the first selected target track (engine The target trajectory of the engine rotation stop control is fixed to the target trajectory selected at the timing when the cylinder whose combustion has been stopped in response to the stop request is first in the expansion stroke), and thereafter at predetermined timings until the engine rotation stops ( For example, it is prohibited to select a target trajectory every TDC. This function serves as a prohibition means in the claims.

  In the present embodiment described above, when the command delay time dt is shorter than a predetermined value, it is determined that the effect of the command delay time is small or almost absent, and the low rotation side is determined at every predetermined timing (for example, every TDC). By selecting the target engine speed that has a smaller deviation from the actual engine speed among the target engine speed of the high speed side and the target engine speed of the high speed side, the target trajectory on the advance side and the target trajectory on the retard side Since the target trajectory with the smaller deviation from the actual engine rotation speed is selected, the target engine rotation speed with the smaller deviation from the actual engine rotation speed is always selected to quickly increase the actual engine rotation speed. Therefore, the target engine speed can be controlled, and the controllability of the engine rotation stop control can be improved.

  In addition, it is configured to select a target engine rotation speed with a smaller deviation from the actual engine rotation speed among the target engine rotation speed on the low rotation side and the target engine rotation speed on the high rotation side at every predetermined timing (for example, every TDC). Without being limited, for example, among the target engine speed on the low speed side and the target engine speed on the high speed side at every predetermined timing (for example, every TDC), the target engine speed on the low speed side / high speed side and the actual engine You may make it select the target engine rotational speed with the smaller deviation of the parameter which each converted rotational speed into energy amount.

  On the other hand, if the command delay time dt is equal to or greater than the predetermined value, it is determined that the command delay time has a large influence, the target trajectory for engine rotation stop control is fixed to the initially selected target trajectory, and then the engine rotation Since the selection of the target trajectory at every predetermined timing (for example, every TDC) is prohibited until the engine stops, if the command delay time is greater than or equal to the predetermined value, the target trajectory will be detected during execution of the engine rotation stop control. Switching can be prevented, response delay of actual engine rotation behavior caused by switching of the target trajectory, and hunting phenomenon in which the power generation command value of the alternator 33 repeatedly increases and decreases can be prevented in advance, and the engine rotation stop control accuracy decreases. Therefore, the engine stop crank angle can be accurately controlled within the target crank angle range.

  In the above embodiment, the target trajectory is obtained in the direction of turning the crank angle with the target stop crank angle as an initial value. For example, the engine rotation speed immediately before the stop so that the engine rotation stops at the target stop crank angle. And the crank angle (for example, TDC) may be set as an initial value, and the target trajectory calculation method may be appropriately changed.

  In addition, the scope of application of the present invention is not limited to a general vehicle having only an engine as a power source of the vehicle, and the present invention may be applied to a hybrid vehicle having an engine and a motor as the power source of the vehicle. .

  DESCRIPTION OF SYMBOLS 11 ... Engine, 13 ... Intake pipe, 14 ... Throttle valve, 19 ... Fuel injection valve, 21 ... Exhaust pipe, 26 ... Crank angle sensor, 29 ... Cam angle sensor, 30 ... Engine ECU (target trajectory calculation means, stop control means) , Selection means, prohibition means), 33 ... alternator (generator), 36 ... power supply system ECU, 38 ... power generation command value calculation unit (power generation command value calculation means)

Claims (3)

In an engine rotation stop control device for stopping combustion by stopping combustion when an engine stop request is generated,
A generator driven by an engine;
Target trajectory calculating means for calculating rotational behavior (hereinafter referred to as “target trajectory”) until engine rotation stops at the target stop crank angle;
Stop control means for executing engine rotation stop control for controlling the load of the generator so that the actual engine rotation behavior matches the target trajectory when stopping engine rotation;
The stop control means includes
By selecting one of a target engine rotational speed lower than the actual engine rotational speed and a target engine rotational speed higher than the actual engine rotational speed based on the target trajectory data at each predetermined timing. Selecting means for selecting one of an advance side target trajectory corresponding to the low rotation side target engine rotation speed and a retard side target trajectory corresponding to the high rotation side target engine rotation speed;
Power generation command value calculation means for calculating a power generation command value of the generator so as to reduce a deviation between the target engine speed selected by the selection means and the actual engine speed;
The target trajectory that is first selected by the selection means as the target trajectory for the engine rotation stop control when the command delay time from when the power generation command value of the generator is calculated until the generator responds is a predetermined value or more The engine rotation stop control device, further comprising: a prohibiting unit that prohibits selection of a target trajectory at each predetermined timing by the selection unit.   The selection means is a parameter obtained by converting a deviation between the target engine speed at the low speed side and the target engine speed at the high speed side from the actual engine speed at every predetermined timing or converting the engine speed to an energy amount. Means for selecting a target trajectory having a smaller deviation between the target trajectory on the advance side and the target trajectory on the retard side and the actual engine speed among the target trajectories on the retard side by selecting the target engine speed having the smaller deviation; The engine rotation stop control device according to claim 1.   The prohibiting means fixes the target trajectory of the engine rotation stop control to the target trajectory selected by the selecting means at the timing when the cylinder whose combustion has been stopped in response to the engine stop request first enters the expansion stroke, and thereafter 3. The engine rotation stop control device according to claim 1, further comprising means for prohibiting the selection means from selecting a target trajectory at each predetermined timing until the engine rotation is stopped.

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