JP6046542B2 - Stop control device for internal combustion engine - Google Patents

Description

  The present invention relates to a stop control device applied to an internal combustion engine in which an electric motor is connected to a crankshaft so that power can be transmitted.

  There is known a control device that applies a torque from an electric motor to the crankshaft to brake the crankshaft when the internal combustion engine is stopped so that the crankshaft stops at a predetermined rotational position (crank angle). As is well known, the rotational resistance in an internal combustion engine changes due to manufacturing errors of the internal combustion engine, so-called machine differences and aging. Therefore, a control device is known that learns and corrects the torque output from the electric motor based on the amount of change in the crank angle when the internal combustion engine is stopped (see Patent Document 1). In addition, there is Patent Document 2 as a prior art document related to the present invention.

JP 2009-143377 A JP 2005-016505 A

  In the device of Patent Document 1, in order to stop the crankshaft at a predetermined crank angle, torque output from the electric motor based on the rotational position of the crankshaft when the rotational speed of the internal combustion engine reaches the first predetermined rotational speed Is changing. When the rotational speed of the internal combustion engine reaches less than the second predetermined rotational speed, the torque of the electric motor is reduced. At this time, if the torque reduction amount is made constant even though the torque output from the electric motor is different, the rotational speed of the internal combustion engine when the electric motor torque becomes zero varies. In this case, the crankshaft may rotate in the forward rotation direction or the reverse rotation direction from the time when the torque of the electric motor becomes zero to the time when the crankshaft is stopped, and the vibration may be deteriorated. In addition, there may be variations in the rotational position of the crankshaft at the time of stopping.

  Therefore, an object of the present invention is to provide a stop control device for an internal combustion engine that can suppress vibrations when the internal combustion engine is stopped.

  The stop control device of the present invention is applied to an internal combustion engine in which an electric motor is connected to a crankshaft so that power can be transmitted, and after the predetermined engine stop condition is satisfied and combustion of the internal combustion engine is stopped, the crankshaft In the stop control device for executing the rotation speed reduction control for outputting the torque from the electric motor and reducing the rotation speed of the crankshaft until the rotation speed reaches a predetermined first target rotation speed, the crankshaft Control means for executing torque change control for setting the torque of the motor to zero from the torque at the end of the rotation speed reduction control after the rotation speed reaches the first target rotation speed, As the torque at the end of the rotation speed reduction control is larger, the unit time of the motor torque when the torque of the motor is reduced from the torque at the end of the rotation speed reduction control to zero. Torque change amount which is the amount of change of the Ri changes the torque change amount based on the end of the torque of the rotation speed reduction control so as to be larger (claim 1).

  In the stop control device of the present invention, the torque change amount is increased as the torque at the end of the rotation speed reduction control is increased. Therefore, the torque of the electric motor becomes zero after the rotation speed of the crankshaft reaches the first target rotation speed. The length of the period up to can be made substantially the same. Thereby, the rotation speed of the crankshaft when the torque of the electric motor becomes zero can be made substantially the same. Therefore, it is possible to suppress vibration when the internal combustion engine is stopped. In addition, by making the rotation speed of the crankshaft substantially the same as described above, the behavior of the crankshaft from the end of the torque change control to the stop of the internal combustion engine can be made substantially constant. Therefore, the crank angle when the crankshaft is stopped can be made substantially the same.

  In one mode of the stop control device of the present invention, the control means executes the torque change control and the torque of the electric motor becomes zero, and then the forward rotation direction in which the crankshaft rotates during operation of the internal combustion engine. Reverse rotation prevention control is performed to output a predetermined reverse rotation prevention torque from the electric motor so that the crankshaft stops at a predetermined target crank angle without rotating in the reverse rotation direction opposite to the reverse rotation direction, and the rotation speed decreases When the torque change amount set based on the torque at the end of the control is greater than or equal to a predetermined allowable value set in advance, the allowable value is set as the torque change amount, and a predetermined second target rotational speed and The reverse rotation prevention torque may be changed so that the reverse rotation prevention torque increases as the absolute value of the difference from the rotational speed of the internal combustion engine when the torque of the electric motor becomes zero increases. Claim 2). As is well known, when the torque of the electric motor is suddenly reduced to zero, the torque applied to the crankshaft changes suddenly, and vibration is generated in the internal combustion engine. In this configuration, when the torque change amount is greater than or equal to the allowable value, the allowable value is set for the torque change amount. Therefore, by setting an appropriate value for the allowable value, vibration when the torque of the motor is made zero is suppressed. it can. Further, since the reverse rotation prevention torque is increased as the difference between the rotation speed of the internal combustion engine when the torque of the motor becomes zero and the second target rotation speed is larger, the crank angle when the crankshaft is stopped is substantially the same. Can be.

  In this embodiment, the control means, when the torque change amount set based on the torque at the end of the rotation speed reduction control is equal to or greater than a predetermined allowable value set in advance, the torque change amount to the allowable value. And the larger the absolute value of the difference between the second target rotational speed and the rotational speed of the internal combustion engine when the torque of the electric motor becomes zero, and the predetermined reference crank angle and the The reverse rotation prevention torque may be changed so that the reverse rotation prevention torque becomes larger as the difference from the crank angle of the internal combustion engine when the torque of the electric motor becomes zero becomes larger. In this embodiment, since the reverse rotation prevention torque is changed based on the crank angle in addition to the rotational speed of the internal combustion engine when the torque of the electric motor becomes zero, the crankshaft can be accurately stopped at the target crank angle. it can.

  In one mode of the stop control device of the present invention, the control means executes the torque change control and the torque of the electric motor becomes zero, and then the forward rotation direction in which the crankshaft rotates during operation of the internal combustion engine. Reverse rotation prevention control is performed to output a predetermined reverse rotation prevention torque from the electric motor so that the crankshaft stops at a predetermined target crank angle without rotating in the reverse rotation direction opposite to the reverse rotation direction, and the rotation speed decreases When the torque change amount set based on the torque at the end of the control is equal to or greater than a preset predetermined allowable value, the allowable value is set for the torque change amount, and the torque change amount and the allowable value are set. The reverse rotation prevention torque may be changed so that the reverse rotation prevention torque increases as the difference between the reverse rotation prevention torque and the reverse rotation prevention torque increases. Even if the reverse rotation prevention torque is set in this way, it is possible to suppress variation in crank angle when the crankshaft is stopped.

  In one form of the stop control device of the present invention, the internal combustion engine is mounted on a hybrid vehicle, and the hybrid vehicle includes a first motor / generator and an output unit for transmitting power to the drive wheels. A first rotating element of the three rotating elements is connected to the internal combustion engine, a second rotating element is connected to the first motor / generator; A differential mechanism in which a rotating element is connected to the output unit and a second motor / generator capable of outputting power to the output unit are provided, and the electric motor may be the first motor / generator. (Claim 5). In such a hybrid vehicle, the torque of the first motor / generator can be transmitted to the crankshaft of the internal combustion engine. Therefore, there is no need to provide another electric motor for outputting torque to the crankshaft of the internal combustion engine.

  As described above, according to the stop control device of the present invention, the torque change amount is increased as the torque at the end of the rotation speed reduction control is increased. Therefore, the rotation of the crankshaft when the motor torque becomes zero. The numbers can be approximately the same. Therefore, it is possible to suppress vibration when the internal combustion engine is stopped.

The figure which shows schematically the hybrid vehicle carrying the internal combustion engine to which the stop control apparatus which concerns on the 1st form of this invention is applied. The flowchart which shows the engine stop control routine which a vehicle control apparatus performs. The flowchart following FIG. The figure which shows an example of the relationship between the engine speed at the time of a combustion stop, and rotation speed reduction torque. The figure which shows an example of the relationship between the absolute value of a control final value, and a torque release rate. The figure which shows an example of the time change of the rotation speed of an engine, the torque of 1st MG, and a crank angle when an engine stop control routine is performed and an engine is stopped. The figure which shows a part of engine stop control routine which a vehicle control apparatus performs in the stop control apparatus which concerns on the 2nd form of this invention. The absolute value of the difference between the engine speed when the first MG torque becomes zero and the predetermined target speed, and the difference between the crank angle and the second reference crank angle when the first MG torque becomes zero FIG. 6 is a diagram illustrating an example of a relationship between the reverse rotation prevention torque and the reverse rotation prevention torque. The figure which shows an example of the time change of an engine speed, the torque of 1st MG, and a crank angle when the engine stop control routine of a 2nd form is performed and an engine is stopped.

(First form)
Hereinafter, an embodiment in which the stop control device of the present invention is applied to an internal combustion engine mounted on a hybrid vehicle will be described. FIG. 1 schematically shows a hybrid vehicle 1. The vehicle 1 includes an internal combustion engine (hereinafter may be referred to as an engine) 11, a first motor / generator (hereinafter also referred to as a first MG) 12, and a second motor / generator (hereinafter referred to as a first motor / generator). 2MG) .13). The engine 11 includes three cylinders 11a arranged in a row. That is, the engine 11 is configured as an in-line three-cylinder internal combustion engine. Since this engine 11 is a well-known internal combustion engine mounted on a hybrid vehicle, detailed description thereof is omitted. The first MG 12 and the second MG 13 are well-known motor generators that function as an electric motor and a generator. The first MG 12 includes a rotor 12b that rotates integrally with the output shaft 12a, and a stator 12c that is coaxially disposed on the outer periphery of the rotor 12b and fixed to a case (not shown). Similarly, the second MG 13 includes a rotor 13b that rotates integrally with the output shaft 13a, and a stator 13c that is coaxially disposed on the outer periphery of the rotor 13b and fixed to the case.

  The crankshaft 11 b of the engine 11 and the output shaft 12 a of the first MG 12 are connected to the power split mechanism 14. An output unit 15 for transmitting power to the drive wheels 2 of the vehicle 1 is also connected to the power split mechanism 14. The output unit 15 includes a first drive gear 16, a counter gear 18 that meshes with the first drive gear 16 and is fixed to the counter shaft 17, and an output gear 19 that is fixed to the counter shaft 17. The output gear 19 meshes with a ring gear 20 a provided in the case of the differential mechanism 20. The differential mechanism 20 is a well-known mechanism that distributes the power transmitted to the ring gear 20 a to the left and right drive wheels 2. In FIG. 1, only one of the left and right drive wheels 2 is shown.

  The power split mechanism 14 includes a planetary gear mechanism 21 as a differential mechanism. The planetary gear mechanism 21 is a single-pinion type planetary gear mechanism, and includes a sun gear Su that is an external gear, a ring gear Ri that is an internal gear coaxially disposed with respect to the sun gear Su, and these gears Su. , And a carrier Ca that holds the pinion gear Pi meshing with Ri so as to be capable of rotating and revolving around the sun gear Su. The sun gear Su is connected to the output shaft 12a of the first MG 12. The carrier Ca is connected to the crankshaft 11b of the engine 11. The ring gear Ri is connected to the first drive gear 16. Therefore, the sun gear Su corresponds to the second rotating element of the present invention, the carrier Ca corresponds to the first rotating element of the present invention, and the ring gear Ri corresponds to the third rotating element of the present invention.

  As shown in this figure, a second drive gear 22 is provided on the output shaft 13 a of the second MG 13. The second drive gear 22 meshes with the counter gear 18. The first MG 12 and the second MG 13 are electrically connected to the battery 23 via an inverter and a boost converter (not shown).

  Operations of the engine 11, the first MG 12, and the second MG 13 are controlled by the vehicle control device 30. The vehicle control device 30 is configured as a computer unit including a microprocessor and peripheral devices such as RAM and ROM necessary for its operation. The vehicle control device 30 holds various control programs for causing the vehicle 1 to travel appropriately. The vehicle control device 30 executes control of the control target such as the engine 11 and the MGs 12 and 13 by executing these programs. Various sensors for acquiring information related to the vehicle 1 are connected to the vehicle control device 30. For example, a vehicle speed sensor 31 and a crank angle sensor 32 are connected to the vehicle control device 30. The vehicle speed sensor 31 outputs a signal corresponding to the speed (vehicle speed) of the vehicle 1. The crank angle sensor 32 outputs a signal corresponding to the crank angle of the engine 11. In addition to this, various sensors, switches, and the like are connected to the vehicle control device 30, but these are not shown.

  When a predetermined engine stop condition is satisfied, the vehicle control device 30 stops the fuel supply to each cylinder 11a to stop the combustion, and thereby stops the engine 11. In the vehicle 1, the vehicle 1 is driven only by the second MG 13 when the vehicle speed is equal to or lower than a predetermined determination speed set in advance. Therefore, it is determined that the engine stop condition is satisfied, for example, when the vehicle speed is equal to or lower than the determination speed.

  In addition, vehicle control device 30 controls first MG 12 so that the number of revolutions of engine 11 decreases when engine 11 is stopped. At this time, the vehicle control device 30 changes the control of the first MG 12 according to the rotational speed of the engine 11. As the control of the first MG 12, rotation speed reduction control, alignment control, torque release control, and reverse rotation prevention control are provided. These controls are executed in the order of rotational speed reduction control, alignment control, torque release control, and reverse rotation prevention control.

  The rotational speed reduction control is executed until the rotational speed of the engine 11 becomes equal to or lower than a predetermined alignment determination rotational speed N1. The alignment determination rotation speed N1 is a rotation speed at which alignment control is started. When the rotational speed of the engine 11 is equal to or lower than the alignment determination rotational speed N1, the alignment control is started. In this alignment control, torque is output from the first MG 12 so that the crankshaft 11b has a predetermined target crank angle set in advance when the engine 11 is stopped. The target crank angle is set to a crank angle at which vibration can be most suppressed when the engine 11 is started, for example. Specifically, for example, the crank angle at which one of the cylinders 11a becomes the top dead center of the compression stroke is set as the target crank angle.

  The alignment control is executed until the rotation speed of the engine 11 becomes equal to or less than a predetermined torque removal rotation speed N2. This torque release rotational speed N2 is the rotational speed at which torque release control is started. When the rotation speed of the engine 11 becomes equal to or less than the torque release speed N2, torque release control is started. In this torque release control, the torque of the first MG 12 is reduced to zero. The torque release control is executed until the rotation speed of the engine 11 becomes equal to or lower than the reverse rotation prevention determination rotation speed N3. The reverse rotation prevention determination rotation speed N3 is a rotation speed at which reverse rotation prevention control is started. The magnitude relationship among the alignment determination rotation speed N1, the torque release rotation speed N2, and the reverse rotation prevention determination rotation speed N3 is N3 <N2 <N1 <idle rotation speed.

  When the rotation speed of the engine 11 becomes equal to or lower than the reverse rotation prevention determination rotation speed N3, the reverse rotation prevention control is executed. In this reverse rotation prevention control, torque is applied from the first MG 12 so that the crankshaft 11b does not rotate in the reverse rotation direction opposite to the normal rotation direction that rotates when the engine 11 is operated, and the crankshaft 11b stops at the target crank angle. Output. This reverse rotation prevention control is executed until the engine 11 is stopped. When the engine 11 stops, the first MG 12 is also stopped.

  2 and 3 show an engine stop control routine executed by the vehicle control device 30 to control the first MG 11 in this way. FIG. 3 is a control routine following FIG. This control routine is repeatedly executed at a predetermined cycle while the engine 11 is operating. In addition, this control routine is executed in parallel with other control routines executed by the vehicle control device 30. By executing this control routine, the vehicle control device 30 functions as the control means of the present invention.

  In this control routine, the vehicle control device 30 first acquires the state of the vehicle 1 in step S11. As the state of the vehicle 1, the vehicle speed and the crank angle are acquired. In this process, the rotational speed of the engine 11 is also acquired based on the output signal of the crank angle sensor 32. In the next step S12, the vehicle control device 30 determines whether or not the engine stop condition described above is satisfied. If it is determined that the engine stop condition is not satisfied, the current control routine is terminated.

  On the other hand, if it is determined that the engine stop condition is satisfied, the process proceeds to step S13, and the vehicle control device 30 executes combustion stop control. In this combustion stop control, the fuel supply to the engine 11 is stopped, and the combustion of the engine 11 is stopped. In the next step S14, the vehicle control device 30 sets the rotation speed reduction torque based on the rotation speed of the engine 11 when the combustion is stopped. This rotational speed reduction torque is a torque output from the first MG 12 in order to rapidly reduce the rotational speed of the engine 11. The higher the rotation speed of the engine 11 when combustion is stopped, the greater the torque required to reduce the rotation speed of the engine 11. FIG. 4 shows an example of the relationship between the rotational speed of the engine 11 and the rotational speed reduction torque when the combustion is stopped. As shown in this figure, the rotational speed reduction torque is set to a larger value as the rotational speed of the engine 11 when the combustion of the engine 11 is stopped is larger. The relationship shown in this figure may be obtained in advance by experiments, numerical calculations, etc., and stored in the ROM of the vehicle control device 30 as a map. Then, the rotational speed reduction torque may be set based on this map and the rotational speed of the engine 11.

  In the next step S <b> 15, the vehicle control device 30 executes the rotational speed reduction control. In this rotational speed reduction control, the set rotational speed reduction torque is output from the first MG 12 to reduce the rotational speed of the engine 11. In the next step S16, the vehicle control device 30 determines whether or not the rotational speed of the engine 11 has become equal to or lower than the alignment determination rotational speed N1. If it is determined that the rotation speed of the engine 11 is higher than the alignment determination rotation speed N1, the process returns to step S15, and the vehicle control device 30 performs steps S15 and S16 until the rotation speed of the engine 11 becomes equal to or less than the alignment determination rotation speed N1. Run repeatedly.

  On the other hand, if it is determined that the rotational speed of the engine 11 is equal to or lower than the alignment determination rotational speed N1, the process proceeds to step S17, and the vehicle control device 30 determines that the rotational speed of the engine 11 is equal to or lower than the alignment determination rotational speed N1. The alignment torque is set based on the crank angle at the time (hereinafter, sometimes referred to as the alignment control start crank angle). This alignment torque is a torque that is output from the first MG 12 so that the crankshaft 11b has the above-described target crank angle when the engine 11 becomes a predetermined rotational speed N1 or less. It is assumed that the rotational speed reduction torque is continuously output from the first MG 12 until the rotational speed of the engine 11 changes from the alignment determination rotational speed N1 to the torque release rotational speed N2. In this case, the crank angle at the start of the alignment control in which the crank angle when the engine 11 is stopped becomes the target crank angle is determined according to the target crank angle and the specifications of the engine 11. Hereinafter, such a crank angle at the start of alignment control may be referred to as a first reference crank angle. In order to set the crank angle when the engine 11 is stopped to the target crank angle, it is necessary to increase the torque output from the first MG 12 as the difference between the crank angle at the start of the alignment control and the first reference crank angle increases. is there. Therefore, a larger value is set for the alignment torque as the difference between the crank angle at the start of alignment control and the first reference crank angle increases. The relationship between the difference between the crank angle at the start of the alignment control and the first reference crank angle and the alignment torque may be obtained in advance by experiments, numerical calculations, etc., and stored in the ROM of the vehicle control device 30 as a map. . Then, the alignment torque may be set based on this map and the crank angle at the start of alignment control.

  In the next step S18, the vehicle control device 30 performs alignment control. In this alignment control, a torque obtained by adding the rotation speed reduction torque and the alignment torque is output from the first MG 12. In subsequent step S19, the vehicle control device 30 determines whether or not the rotational speed of the engine 11 has become equal to or less than the rotational speed N2 for torque removal. If it is determined that the rotational speed of the engine 11 is higher than the torque release rotational speed N2, the process returns to step S18, and the vehicle control device 30 repeatedly executes steps S18 and S19 until the rotational speed of the engine 11 becomes equal to or lower than the torque release rotational speed N2. To do.

  On the other hand, if it is determined that the rotational speed of the engine 11 has become equal to or lower than the torque-removed rotational speed N2, the process proceeds to step S20 in FIG. The torque release rate is set based on the torque of the first MG 12 at the time of determination, that is, the torque of the first MG 12 at the end of the alignment control (hereinafter sometimes referred to as a control final value). This torque release rate is the amount of change in torque per unit time when the torque of the first MG 12 is made zero from the final control value in torque release control. FIG. 5 shows an example of the relationship between the absolute value of the final control value and the torque release rate. As shown in this figure, the torque release rate is set to a larger value as the absolute value of the final control value is larger. Further, this relationship is set so that the rotational speed of the engine 11 becomes the same rotational speed when the torque of the first MG 12 is made zero by the torque removal control even if the final control values are different. The relationship shown in this figure may be obtained in advance by experiments, numerical calculations, etc., and stored in the ROM of the vehicle control device 30 as a map. Then, the torque release rate may be set based on this map and the final control value.

  In the next step S21, the vehicle control device 30 executes torque release control. In this torque release control, the first MG 12 is controlled so that the torque of the first MG 12 decreases at the set torque release rate. In subsequent step S22, the vehicle control device 30 determines whether or not the rotational speed of the engine 11 is equal to or lower than the reverse rotation prevention determination rotational speed N3. If it is determined that the rotational speed of the engine 11 is higher than the reverse rotation prevention determination rotational speed N3, the process returns to step S21, and the vehicle control device 30 performs steps S21 and S21 until the rotational speed of the engine 11 becomes equal to or lower than the reverse rotation prevention determination rotational speed N3. S22 is repeatedly executed.

  On the other hand, when it is determined that the rotation speed of the engine 11 is equal to or less than the reverse rotation prevention determination rotation speed N3, the process proceeds to step S23, and the vehicle control device 30 determines the crank angle when the torque of the first MG 12 becomes zero (hereinafter, reverse). The reverse rotation prevention torque is set based on the crank angle at the start of the rotation prevention control. The reverse rotation prevention torque is a torque output from the first MG 12 in order to stop the crankshaft 11b at the target crank angle while preventing the crankshaft 11b from rotating in the reverse direction. It is assumed that the output torque of the first MG 12 is made zero until the rotational speed of the engine 11 becomes zero from the reverse rotation prevention determination rotational speed N3. In this case, the crank angle at the start of reverse rotation prevention control in which the crank angle when the engine 11 is stopped becomes the target crank angle is determined according to the target crank angle and the specifications of the engine 11. Hereinafter, the crank angle at the start of the reverse rotation prevention control may be referred to as a second reference crank angle. In order to set the crank angle when the engine 11 is stopped to the target crank angle, it is necessary to increase the torque output from the first MG 12 as the difference between the crank angle at the start of reverse rotation prevention control and the second reference crank angle increases. There is. Therefore, the reverse rotation prevention torque is set to a larger value as the difference between the reverse rotation prevention control start crank angle and the second reference crank angle is larger. The relationship between the difference between the crank angle at the start of the reverse rotation prevention control and the second reference crank angle and the reverse rotation prevention torque can be obtained in advance by experiments or numerical calculations and stored in the ROM of the vehicle control device 30 as a map. That's fine. Then, the reverse rotation prevention torque may be set based on this map and the reverse rotation prevention control start crank angle.

  In the next step S24, the vehicle control device 30 performs reverse rotation prevention control. In this reverse rotation prevention control, the set reverse rotation prevention torque is output from the first MG 12. In subsequent step S25, the vehicle control device 30 determines whether or not the engine 11 has stopped, that is, whether or not the rotational speed of the engine 11 has become zero. When it determines with the engine 11 not having stopped, it returns to step S24, and the vehicle control apparatus 30 repeatedly performs step S24 and S25 until the engine 11 stops.

  On the other hand, when it determines with the engine 11 having stopped, it progresses to step S26 and the vehicle control apparatus 30 performs 1st MG stop control. In the first MG stop control, the output torque of the first MG 12 is set to zero and the first MG 12 is stopped. Thereafter, the current control routine is terminated.

  FIG. 6 shows an example of changes over time in the rotational speed of the engine 11, the torque of the first MG 12, and the crank angle when the engine 11 is stopped by executing the engine stop control routine. In addition, the part shown with the broken line among the torques of 1st MG12 has shown the case where the maximum value is set to the alignment torque. In this figure, the torque output from the first MG 12 when the first MG 12 is rotated in the forward direction is shown as a positive torque, and the torque output from the first MG 12 when the first MG 12 is rotated in the reverse direction. Is shown as a negative torque.

  In the example shown in this figure, the engine stop condition is satisfied at time t1, and the engine speed reduction control is executed. Thereby, the rotational speed reduction torque is output from the first MG 12, and the rotational speed of the engine 11 is reduced. Then, when the rotational speed of the engine 11 decreases to the alignment determination rotational speed N1 at time t2, alignment control is executed. When the minimum value, that is, zero is set for the alignment torque, the rotational speed reduction torque is output from the first MG 12 in the alignment control as shown by the solid line in FIG. On the other hand, when the maximum value is set for the alignment torque, a lower torque, that is, a larger torque on the negative side, is output from the first MG 12 as shown by the broken line in FIG.

  When the rotational speed of the engine 11 decreases to the torque release rotational speed N2 at time t3, torque release control is executed. At this time, as shown by the broken line, the torque release rate is changed according to the final control value. Therefore, as shown in this figure, the rotational speed of the engine 11 when the torque of the first MG 12 becomes zero can be made substantially the same. Thereafter, when the rotational speed of the engine 11 decreases to the reverse rotation prevention determination rotational speed N3 at time t4, the reverse rotation prevention control is executed. When engine 11 stops at time t5, first MG stop control is executed and first MG 12 stops.

  As described above, according to the first embodiment, since the torque release rate is changed according to the final control value, the torque of the first MG 12 is zero after the rotational speed of the engine 11 reaches the torque release rotational speed N2. The length of the period until it becomes can be made substantially the same. Therefore, the rotational speed of the engine 11 when the torque of the first MG 12 becomes zero can be made substantially the same regardless of the final control value. Therefore, vibration when stopping the engine 11 can be suppressed. In addition, by making the rotation speed of the engine 11 when the torque of the first MG 12 becomes zero in this way, the behavior of the crankshaft 11b from the end of the torque release control to the stop of the engine 11 is almost the same. Can be constant. Therefore, the crank angle when the crankshaft 11b is stopped can be made substantially the same. Therefore, the crankshaft 11b can be accurately stopped at the target crank angle.

  The present invention is particularly suitably applied to a two-cylinder or three-cylinder small-cylinder internal combustion engine. In such a small cylinder internal combustion engine, there is a possibility that the variation in the rotational position of the crankshaft at the time of stoppage becomes large. As is well known, in a two-cylinder or three-cylinder small-cylinder internal combustion engine, the interval of the top dead center of the compression stroke is wide compared to an internal combustion engine having four or more cylinders. For example, in a three-cylinder internal combustion engine, the interval is 240 ° in crank angle. In this case, the torque output from the electric motor when the internal combustion engine is stopped is set based on the crank angle in the range of 240 °. On the other hand, in a four-cylinder internal combustion engine, the interval of the top dead center of the compression stroke is 180 ° in crank angle, so the output torque of the motor is set based on a crank angle in the range of 180 °. Therefore, when stopping at the same predetermined crank angle in the same stop processing time, it is necessary to move the crank angle larger as the number of cylinders decreases. Therefore, the smaller the number of cylinders, the larger the maximum value of torque output from the electric motor when stopping the internal combustion engine. Therefore, if the amount of torque decrease is made constant, the variation in the rotational speed of the internal combustion engine when the torque of the electric motor becomes zero increases. As a result, vibration may be deteriorated. In addition, there may be variations in the rotational position of the crankshaft at the time of stopping. In the present invention, since the torque release rate is changed according to the final control value, the crankshaft can be stopped at the target crank angle while suppressing vibration.

  In this embodiment, the first MG 12 corresponds to the electric motor of the present invention. The torque removal rotational speed N2 corresponds to the first target rotational speed of the present invention. The rotational speed reduction control and the alignment control correspond to the rotational speed reduction control of the present invention. Torque release control corresponds to torque change control of the present invention. The torque release rate corresponds to the torque change amount of the present invention. The final control value corresponds to the torque at the end of the rotational speed reduction control of the present invention.

(Second form)
Next, a stop control device according to a second embodiment of the present invention will be described with reference to FIGS. In this embodiment as well, FIG. 1 is referred to for the vehicle 1. Therefore, parts common to the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  FIG. 7 shows a part of an engine stop control routine executed by the vehicle control device 30 in this embodiment. 7 is used in place of the portion of FIG. 3 of the first embodiment. Therefore, even in the engine stop control routine of this embodiment, the part before FIG. 7, that is, the part of FIG. 2 is the same.

  Even in this form of the engine stop control routine, the processing proceeds in the same manner as in the first form until step S19. In the next step S30 shown in FIG. 7, the vehicle control device 30 sets a torque release rate. In this process, the torque release rate is set based on the final control value as in step S20. However, when the set torque release rate is equal to or higher than a predetermined allowable value set in advance, the allowable value is set as the torque release rate. As is well known, when the torque of the first MG 12 is suddenly reduced to zero, the torque applied to the crankshaft 11b suddenly changes, so that vibration occurs in the engine 11. Therefore, as the allowable value, an upper limit value of the range of the torque release rate at which no vibration is generated when the torque of the first MG 12 is changed to zero is set.

  After the torque release rate is set, steps S21 and S22 are executed. If it is determined in step S22 that the rotation speed of the engine 11 has become equal to or less than the reverse rotation prevention determination rotation speed N3, the process proceeds to step S31, and the vehicle control device 30 sets the reverse rotation prevention torque. However, in this embodiment, the reverse rotation prevention torque is set based on the rotation speed and crank angle of the engine 11 when the torque of the first MG 12 becomes zero (the reverse rotation prevention control start crank angle). FIG. 8 shows the absolute value of the difference between the rotational speed of the engine 11 when the torque of the first MG 12 becomes zero and a predetermined target rotational speed (hereinafter sometimes referred to as a rotational speed difference), and the inverse value. An example of the relationship between the difference between the crank angle at the start of rotation prevention control and the second reference crank angle (hereinafter sometimes referred to as a crank angle difference) and the reverse rotation prevention torque is shown. The target rotational speed is set as follows. First, it is assumed that the torque release rate is set based on the final control value when the alignment torque is zero, and the torque release control is executed at this torque release rate. As the target rotational speed, the rotational speed of the engine 11 when the torque removal control is executed and the torque of the first MG 12 is set to zero is set. That is, the target rotational speed is the rotational speed that the engine 11 should be when the torque of the first MG 12 becomes zero. This target rotational speed corresponds to the second target rotational speed of the present invention. As shown in this figure, the reverse rotation prevention torque is set to a larger value as the absolute value of the rotational speed difference is larger and as the crank angle difference is larger. The relationship shown in this figure may be obtained in advance by experiments, numerical calculations, etc., and stored in the ROM of the vehicle control device 30 as a map. The reverse rotation prevention torque may be set based on this map and the rotation speed and crank angle of the engine 11 when the torque of the first MG 12 becomes zero.

  After setting the reverse rotation prevention torque, the process proceeds to step S24, and thereafter the process proceeds in the same manner as in FIG. Thereafter, the current control routine is terminated.

  FIG. 9 shows an example of changes over time in the rotational speed of the engine 11, the torque of the first MG 12, and the crank angle when the engine 11 is stopped by executing the engine stop control routine of this embodiment. In this figure, the same parts as those in FIG. Also in this figure, the torque of the first MG 12 when the maximum value is set as the alignment torque is indicated by a broken line.

  As indicated by broken lines in this figure, in this embodiment, the upper limit of the torque release rate is limited to an allowable value. Therefore, the torque gradually increases when the torque of the first MG 12 is reduced from the final control value to zero as compared with the first embodiment. However, in this case, since the rotational speed difference when the torque of the first MG 12 becomes zero becomes large, the reverse rotation prevention torque is large.

  As described above, according to the second embodiment, when the torque release rate is larger than the allowable value, the allowable value is set as the torque release rate. Therefore, when the torque of the first MG 12 is changed to zero, the engine 11 Can suppress the occurrence of vibration. Further, in this embodiment, the reverse rotation prevention torque is set based on the rotation speed and crank angle of the engine 11 when the torque of the first MG 12 becomes zero, so that the crankshaft 11b is accurately stopped at the target crank angle. Can do.

  Note that the reverse rotation prevention torque may be set based only on the rotational speed difference. The reverse rotation prevention torque may be set based on the difference between the torque removal rate and the allowable value so that the reverse rotation prevention torque increases as the difference between the torque removal rate and the allowable value increases. Thus, even if the reverse rotation prevention torque is set, the crankshaft 11b can be accurately stopped at the target crank angle.

  The present invention is not limited to the above-described form and can be implemented in various forms. For example, the internal combustion engine to which the present invention is applied is not limited to a three-cylinder internal combustion engine. The present invention may be applied to a two-cylinder internal combustion engine or an internal combustion engine having four or more cylinders. Further, the internal combustion engine to which the present invention is applied is not limited to the internal combustion engine mounted on the hybrid vehicle. The present invention may be applied to an internal combustion engine of a vehicle in which only the internal combustion engine is mounted as a power source.

  An electric motor may be connected to the crankshaft of the internal combustion engine so that power can be transmitted. At this time, the electric motor may be directly connected to the crankshaft.

DESCRIPTION OF SYMBOLS 1 Hybrid vehicle 2 Drive wheel 11 Internal combustion engine 11b Crankshaft 12 1st motor generator (electric motor)
13 Second motor / generator 15 Output unit 21 Planetary gear mechanism (differential mechanism)
30 Vehicle control device (control means)
Su sun gear (second rotating element)
Ri ring gear (third rotating element)
Ca carrier (first rotating element)

Claims (5)

Applied to an internal combustion engine in which an electric motor is connected to the crankshaft to transmit power,
After a predetermined engine stop condition is satisfied and combustion of the internal combustion engine is stopped, torque is output from the electric motor until the rotation speed of the crankshaft reaches a predetermined first target rotation speed. In a stop control device that executes rotation speed reduction control for reducing the rotation speed of the crankshaft,
Control means for executing torque change control for setting the torque of the electric motor to zero from the torque at the end of the rotation speed reduction control after the rotation speed of the crankshaft reaches the first target rotation speed;
The control means changes the torque of the motor per unit time when the torque of the motor is reduced from the torque at the end of the rotation speed reduction control to zero as the torque at the end of the rotation speed reduction control is larger. A stop control device that changes the torque change amount based on a torque at the end of the rotation speed reduction control so that a torque change amount that is a quantity becomes large. The control means includes
After the torque change control is executed and the torque of the electric motor becomes zero, the crankshaft does not rotate in the reverse rotation direction opposite to the normal rotation direction that rotates during operation of the internal combustion engine, and the crankshaft is Performing reverse rotation prevention control for outputting a predetermined reverse rotation prevention torque from the electric motor so as to stop at a predetermined target crank angle;
When the torque change amount set based on the torque at the end of the rotation speed reduction control is greater than or equal to a predetermined allowable value set in advance, the allowable value is set as the torque change amount and a predetermined second The reverse rotation prevention torque is changed so that the reverse rotation prevention torque increases as the absolute value of the difference between the target rotation speed and the rotation speed of the internal combustion engine when the torque of the electric motor becomes zero is larger. The stop control device according to 1.   The control means sets the allowable value to the torque change amount when the torque change amount set based on the torque at the end of the rotation speed reduction control is equal to or larger than a predetermined predetermined allowable value. The larger the absolute value of the difference between the second target rotational speed and the rotational speed of the internal combustion engine when the torque of the electric motor becomes zero, and the predetermined reference crank angle and the torque of the electric motor 3. The stop control device according to claim 2, wherein the reverse rotation prevention torque is changed so that the reverse rotation prevention torque increases as the difference from the crank angle of the internal combustion engine when it becomes zero increases. The control means includes
After the torque change control is executed and the torque of the electric motor becomes zero, the crankshaft does not rotate in the reverse rotation direction opposite to the normal rotation direction that rotates during operation of the internal combustion engine, and the crankshaft is Performing reverse rotation prevention control for outputting a predetermined reverse rotation prevention torque from the electric motor so as to stop at a predetermined target crank angle;
When the torque change amount set based on the torque at the end of the rotation speed reduction control is equal to or greater than a predetermined allowable value set in advance, the allowable value is set as the torque change amount, and the torque change amount 2. The stop control device according to claim 1, wherein the reverse rotation prevention torque is changed so that the reverse rotation prevention torque increases as a difference between the first rotation amount and the allowable value increases. The internal combustion engine is mounted on a hybrid vehicle,
The hybrid vehicle includes
A first motor generator;
An output for transmitting power to the drive wheels;
Three rotational elements capable of differentially rotating with each other, a first rotational element of the three rotational elements is connected to the internal combustion engine, and a second rotational element is connected to the first motor / generator; A differential mechanism in which a third rotating element is connected to the output unit;
A second motor / generator capable of outputting power to the output unit;
The stop control device according to any one of claims 1 to 4, wherein the electric motor is the first motor / generator.

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