Hybrid vehicle control device

Abstract

To provide a control device of a hybrid vehicle capable of suppressing fluctuation in a number of rotations of a rear stage shaft during execution of catalyst warming-up processing.SOLUTION: A vehicle 100 to which a control device 90 is applied, is equipped with an internal combustion engine 10, a first motor generator 61, and a torsional damper 21. The control device 90 executes: a catalyst warming-up processing for controlling the operation of the internal combustion engine 10 so as to raise a temperature of a catalyst 15 of the internal combustion engine 10, a processing for obtaining a vibration damping torque reference valve by feedback control inputting a number of rotations of a rear stage shaft 22 or the first motor generator 61 and a target value of the number of rotations; a processing for obtaining a compensation torque by performing a filter processing according to the magnitude of a resonance frequency of the torsional damper 21 to the number of rotations; a processing for obtaining a damping torque by subtracting the compensation torque from the damping torque reference value; and a processing for outputting the damping torque from the first motor generator 61 during the execution of the catalyst warming-up processing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for a hybrid vehicle. [Background technology]

[0002] Patent Document 1 describes an example of a hybrid vehicle equipped with an internal combustion engine and an electric motor as power sources. In this hybrid vehicle, a torsional damper is provided in a torque transmission path between the internal combustion engine and the electric motor. In addition, a catalyst is provided in an exhaust passage of the internal combustion engine.

[0003] Immediately after starting the internal combustion engine, the catalyst temperature is low and the catalyst may not function properly. Therefore, if it is determined that the catalyst temperature is low, a catalyst warm-up process is executed to raise the catalyst temperature.

[0004] However, when catalyst warm-up processing is being performed, the output of the internal combustion engine may become unstable. When the output of the internal combustion engine is unstable, the engine torque, which is the output torque of the internal combustion engine, is likely to fluctuate. When the engine torque fluctuates, the rotation speed of the rear shaft connected to the crankshaft of the internal combustion engine via a torsional damper may fluctuate. A control device for a hybrid vehicle executes a resonance suppression processing to suppress such fluctuations in the rotation speed of the rear shaft. In the resonance suppression processing, the deviation between the rotation speed of the rear shaft or the electric motor and a target value for that rotation speed is derived as a damping torque. Then, the electric motor is controlled so that the damping torque is output from the electric motor. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-79890 Summary of the Invention [Problem to be solved by the invention]

[0006] When a catalyst warm-up process is performed while the internal combustion engine is running, a resonance may occur in the torsional damper due to a fluctuation in engine torque. If a resonance occurs in the torsional damper, there is a risk that fluctuations in the rotation speed of the rear shaft cannot be suppressed even if the damping torque calculated as described above is output from the electric motor. [Means for solving the problem]

[0007] A control device for a hybrid vehicle that solves the above-mentioned problems is applied to a hybrid vehicle that includes an internal combustion engine, an electric motor, and a torsional damper located in a torque transmission path between the internal combustion engine and the electric motor, and that is provided with a catalyst in an exhaust passage of the internal combustion engine. The control device executes the following processes: a catalyst warm-up process that controls operation of the internal combustion engine to increase the temperature of the catalyst; a torque reference value acquisition process that acquires, as a damping torque reference value, a torque derived by feedback control that inputs a rotation speed of the electric motor or a rear shaft connected to a crankshaft of the internal combustion engine via the torsional damper and a target value for the rotation speed; a compensation torque acquisition process that acquires, as a compensation torque, a value obtained by subtracting the compensation torque from the damping torque reference value; and a resonance suppression process that causes the electric motor to output the damping torque when the catalyst warm-up process is being executed.

[0008] According to the above configuration, a value that takes into account the resonance frequency of the torsional damper is acquired as the damping torque. Then, when the catalyst warm-up process is being executed, the electric motor is controlled by executing the resonance suppression process so that the output torque of the electric motor becomes the damping torque. This allows the damping torque to offset the engine torque fluctuations, even if the torsional damper resonates due to fluctuations in the engine torque, i.e., the output torque of the internal combustion engine. As a result, it becomes possible to suppress fluctuations in the rotation speed of the rear shaft during the catalyst warm-up process. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a configuration diagram showing a control device according to an embodiment and a vehicle to which the control device is applied; [Figure 2] 4 is a flowchart illustrating a processing routine executed by the control device. [Figure 3] FIG. 3 is a block diagram illustrating the flow of processing executed by the control device. [Figure 4] 10 is a flowchart illustrating a compensation torque obtaining process. [Figure 5] 4 is a graph showing the relationship between the frequency of fluctuations in output torque of an internal combustion engine provided in a vehicle and damping gain. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of a control device for a hybrid vehicle will be described below with reference to FIGS. <Configuration of vehicle 100> FIG. 1 shows a vehicle 100 to which a control device 90 of this embodiment is applied.

[0011] The vehicle 100 is a hybrid vehicle and includes an internal combustion engine 10, a first motor generator 61, and a second motor generator 62. The internal combustion engine 10 includes a crankshaft 11 and a plurality of cylinders 12. Each cylinder 12 is connected to an intake passage 13 and an exhaust passage 14. Air is introduced into each cylinder 12 from the intake passage 13. An oxygen storage catalyst 15 is provided in the exhaust passage 14.

[0012] The internal combustion engine 10 is provided with a fuel injection valve 18 and a spark plug 19 for each cylinder 12. In each cylinder 12, an air-fuel mixture containing fuel injected by the fuel injection valve 18 and air is generated. The air-fuel mixture is then combusted in each cylinder 12 by the spark plug 19. This causes the crankshaft 11 to rotate. In addition, exhaust gas generated in each cylinder 12 by the combustion of the air-fuel mixture is discharged into the exhaust passage 14.

[0013] The vehicle 100 is equipped with a power split device 40. A torsional damper 21 is provided in a torque transmission path between the internal combustion engine 10 and the power split device 40. The power split device 40 is connected to the torsional damper 21 via a rear shaft 22.

[0014] The power split mechanism 40 includes a planetary gear mechanism. That is, the power split mechanism 40 has a sun gear 41, a ring gear 42, a plurality of pinion gears 43, and a carrier 44. The sun gear 41 is connected to the ring gear 42 via the plurality of pinion gears 43. The carrier 44 supports the pinion gear 43 in a state in which it can rotate. The carrier 44 supports the pinion gear 43 in a state in which it can revolve. That is, the pinion gear 43 revolves in accordance with the rotation of the carrier 44. The rear shaft 22 is connected to the carrier 44. The rotating shaft of the first motor generator 61 is connected to the sun gear 41. That is, the first motor generator 61 corresponds to the "electric motor."

[0015] When engine torque, which is the output torque of the internal combustion engine 10, is input to the carrier 44, the engine torque is distributed to the sun gear 41 side and the ring gear 42 side. Then, when the engine torque transmitted via the sun gear 41 is input to the first motor generator 61 via the torsional damper 21, the first motor generator 61 functions as a generator.

[0016] On the other hand, when the first motor generator 61 is made to function as an electric motor, the first motor torque, which is the torque of the first motor generator 61, is input to the sun gear 41. Then, the first motor torque input to the sun gear 41 is distributed to the carrier 44 side and the ring gear 42 side. Then, when the first motor torque transmitted via the carrier 44 is input to the crankshaft 11 via the torsional damper 21, the crankshaft 11 of the internal combustion engine 10 rotates.

[0017] The vehicle 100 includes a ring gear shaft 45. The ring gear 42 is connected to the ring gear shaft 45. The ring gear shaft 45 rotates integrally with the ring gear 42. The vehicle 100 includes a transmission mechanism 66, a differential 67, and a plurality of drive wheels 68. A ring gear shaft 45 is connected to the transmission mechanism 66. Torque output from the transmission mechanism 66 is input to each drive wheel 68 via the differential 67.

[0018] The vehicle 100 is equipped with a reduction mechanism 50. A ring gear shaft 45 is connected to the reduction mechanism 50. The reduction mechanism 50 includes a planetary gear mechanism. That is, the reduction mechanism 50 has a sun gear 51, a carrier 52, a plurality of pinion gears 53, and a ring gear 54. The sun gear 51 is connected to the ring gear 54 via the plurality of pinion gears 53. The carrier 52 supports the pinion gear 53 in a rotatable state. The carrier 52 is fixed to a case 55 of the reduction mechanism 50. Therefore, the carrier 52 cannot rotate. The pinion gear 53 is prevented from revolving by the carrier 52. The ring gear 54 is connected to the ring gear shaft 45. A rotating shaft of a second motor generator 62 is connected to the sun gear 51.

[0019] The vehicle 100 is equipped with a parking mechanism 70. The parking mechanism 70 is a mechanism for preventing the rotation of each of the drive wheels 68. By placing the parking mechanism 70 in a locked state, it is possible to prevent the rotation of each of the drive wheels 68. On the other hand, by placing the parking mechanism 70 in a released state, it is possible to allow the rotation of each of the drive wheels 68.

[0020] <Detection system for vehicle 100> The vehicle 100 is equipped with various sensors. Examples of the sensors include a catalyst temperature sensor 81, a crank angle sensor 82, and a motor angle sensor 83. The catalyst temperature sensor 81 detects the catalyst temperature TMP, which is the temperature of the catalyst 15, and outputs a detection signal corresponding to the detection result to the control device 90. The crank angle sensor 82 outputs a signal corresponding to the rotational speed of the crankshaft 11 as a detection signal to the control device 90. The motor angle sensor 83 outputs a signal corresponding to the rotational speed of the rotating shaft of the first motor generator 61 as a detection signal to the control device 90. The rotational angular speed of the crankshaft 11 is referred to as the "engine rotational speed Ne." The rotational speed of the rotating shaft of the first motor generator 61 is referred to as the "first motor rotational speed Ng1."

[0021] <Control device 90> The control device 90 includes a CPU 91, a ROM 92, and a storage device 93. The ROM 92 stores various control programs executed by the CPU 91. That is, since the CPU 91 executes the control programs stored in the ROM 92, the CPU 91 can also be called an "execution device." The storage device 93 is configured, for example, by a non-volatile memory. The storage device 93 stores the results of calculations performed by the CPU 91.

[0022] <Processing flow when warming up the catalyst 15> 2 shows a processing routine executed by the CPU 91 of the control device 90 to warm up the catalyst 15. The CPU 91 repeatedly executes this processing routine while the internal combustion engine 10 is operating.

[0023] In this processing routine, first in step S11, the CPU 91 determines whether a first execution flag FLG1 is set to ON. The first execution flag FLG1 is a flag that is set to ON when a catalyst warm-up process, which will be described later, is being executed, and is set to OFF when the catalyst warm-up process is not being executed. If the first execution flag FLG1 is set to OFF (S11: NO), the CPU 91 proceeds to step S13.

[0024] In step S13, the CPU 91 determines whether or not the conditions for executing the catalyst warm-up process are met. For example, the CPU 91 determines that the conditions for executing the catalyst warm-up process are met if both the catalyst temperature TMP is equal to or lower than a start temperature determination value and the internal combustion engine 10 is not operating under high load. The CPU 91 does not determine that the conditions for executing the process are met if the catalyst temperature TMP is higher than the start temperature determination value. The CPU 91 does not determine that the conditions for executing the process are met if the internal combustion engine 10 is operating under high load. The start temperature determination value is set to, for example, the lower limit of the temperature range in which the catalyst 15 is activated, or a temperature slightly higher than the lower limit.

[0025] If it is determined that the execution condition is met (S13: YES), the CPU 91 proceeds to step S15. On the other hand, if it is not determined that the execution condition is met (S13: NO), the CPU 91 temporarily ends this processing routine.

[0026] In step S15, the CPU 91 starts catalyst warm-up processing. The catalyst warm-up processing is processing for warming up the catalyst 15. For example, in the catalyst warm-up processing, the CPU 91 retards the ignition timing of the internal combustion engine 10. By retarding the ignition timing in this manner, the temperature of the exhaust gas discharged from each cylinder 12 into the exhaust passage 14 increases. As a result, the catalyst 15 is exposed to higher temperature exhaust gas, which promotes an increase in the catalyst temperature TMP. After starting the catalyst warm-up processing, the CPU 91 proceeds to step S17.

[0027] In step S17, the CPU 91 sets the first execution flag FLG1 to ON, and then the CPU 91 temporarily ends this processing routine. On the other hand, if the first execution flag FLG1 is set to ON in step S11 (YES), the CPU 91 proceeds to step S19. In step S19, the CPU 91 determines whether or not a termination condition for the catalyst warm-up process is met. For example, the CPU 91 determines that the termination condition is met when the catalyst temperature TMP is equal to or higher than an termination temperature determination value. Also, for example, the CPU 91 determines that the termination condition is met when the internal combustion engine 10 is operating under high load. The termination temperature determination value is a criterion for determining whether or not the catalyst 15 is activated. For example, a temperature higher than the start temperature determination value is set as the termination temperature determination value.

[0028] If it is determined that the termination condition is met (S19: YES), the CPU 91 proceeds to step S21. On the other hand, if it is determined that the termination condition is not met (S19: NO), the CPU 91 temporarily terminates this processing routine. In this case, the CPU 91 continues the catalyst warm-up processing.

[0029] In step S21, the CPU 91 ends the catalyst warm-up process. For example, if the catalyst warm-up process is a process for retarding the ignition timing, the CPU 91 returns the ignition timing to the pre-warm-up timing. The pre-warm-up timing is the ignition timing before the catalyst warm-up process is executed. Then, after ending the catalyst warm-up process, the CPU 91 proceeds to step S23. In step S23, the CPU 91 sets the first execution flag FLG1 to OFF. Thereafter, the CPU 91 temporarily ends this processing routine.

[0030] <Processing flow for suppressing vehicle body vibration> When catalyst warm-up processing is being performed, the output of the internal combustion engine 10 may become unstable. When the output of the internal combustion engine 10 becomes unstable, the engine torque of the internal combustion engine 10 fluctuates. This causes torsional vibration in the torsional damper 21. When torsional vibration occurs, resonance may occur in the torsional damper 21. When resonance occurs in the torsional damper 21, fluctuations in the rotation speed of the rear shaft 22 become large. When fluctuations in the rotation speed of the rear shaft 22 are large, vibrations caused by these fluctuations may be transmitted to the case 55, causing the vehicle body to vibrate. In particular, when the parking mechanism 70 is in a locked state, fluctuations in the rotation speed of the rear shaft 22 are likely to be transmitted to the vehicle body via the case 55.

[0031] FIG. 3 shows a series of processes when the first motor generator 61 is controlled to suppress the occurrence of vehicle body vibrations during the catalyst warm-up process. The CPU 91 executes a torque reference value acquisition process M11 to acquire a vibration-damping torque reference value Tg1B. In the torque reference value acquisition process M11, the CPU 91 performs feedback control using as inputs the first motor rotation speed Ng1, which is a detection value of the motor angle sensor 83, and a first motor rotation speed target value Ng1Tr. The first motor rotation speed target value Ng1Tr is a target value (command value) for the first motor rotation speed Ng1. The CPU 91 then acquires the torque derived by the feedback control as the vibration-damping torque reference value Tg1B.

[0032] The feedback control performed here includes at least proportional control among proportional control, integral control, and differential control. For example, the CPU 91 performs proportional control and integral control as feedback control. In this case, the CPU 91 may also perform differential control.

[0033] When torsional vibration occurs in the torsional damper 21, the first motor rotation speed Ng1 also vibrates. A vibration-damping torque reference value Tg1B is acquired as the first motor torque for suppressing such vibration of the first motor rotation speed Ng1.

[0034] The CPU 91 executes a compensation torque acquisition process M13 to acquire a compensation torque Tc. The compensation torque Tc is a torque component corresponding to the influence of resonance of the torsional damper 21. In the compensation torque acquisition process M13, the CPU 91 acquires, as the compensation torque Tc, a torque based on the first motor rotation speed Ng1 and the magnitude of the resonance frequency of the torsional damper 21. That is, the CPU 91 acquires, as the compensation torque Tc, a torque derived by performing a filter process on the first motor rotation speed Ng1 according to the magnitude of the resonance frequency of the torsional damper 21. The specific contents of the compensation torque acquisition process M13 will be described later.

[0035] The CPU 91 executes oscillation-damping torque acquisition process M15 to acquire oscillation-damping torque Tg1. In oscillation-damping torque acquisition process M15, the CPU 91 acquires, as oscillation-damping torque Tg1, a value obtained by subtracting compensation torque Tc from oscillation-damping torque reference value Tg1B.

[0036] The CPU 91 executes a resonance suppression process M17 that causes the first motor generator 61 to output the vibration damping torque Tg1. In this embodiment, the CPU 91 executes the resonance suppression process M17 when the catalyst warm-up process is being executed.

[0037] The compensation torque acquisition process M13 will be specifically described with reference to FIG. In the compensation torque acquisition process M13, first, in step S41, the CPU 91 determines whether or not catalyst warm-up process is being executed. If catalyst warm-up process is being executed (S41: YES), the CPU 91 proceeds to step S43. In step S43, the CPU 91 sets a second execution flag FLG2 to ON. The second execution flag FLG2 is a flag that is set to ON when it is necessary to derive the compensation torque Tc, and is set to OFF when it is not necessary to derive the compensation torque Tc.

[0038] Next, in step S45, the CPU 91 acquires the ignition retard amount X. For example, the ignition retard amount X is a retard amount from a reference ignition timing. At this time, it is preferable to set the ignition timing before the start of the catalyst warm-up process as the reference ignition timing. In the next step S47, the CPU 91 derives a value corresponding to the ignition retard amount X as the control gain K. The control gain K is a coefficient used when deriving the compensation torque Tc. In this embodiment, the CPU 91 derives a larger value as the ignition retard amount X increases. Therefore, if the ignition retard amount X increases during the execution of the catalyst warm-up process, the control gain K also increases as the ignition retard amount X increases.

[0039] Then, in step S49, the CPU 91 derives the compensation torque Tc. For example, the CPU 91 can derive the compensation torque Tc using the following relational expressions (Equation 1), (Equation 2), and (Equation 3). In the following relational expressions, "HP" is a high-pass filter according to the magnitude of the resonance frequency of the torsional damper 21. "LP" is a low-pass filter according to the magnitude of the resonance frequency of the torsional damper 21. "T1" and "T2" are each set to values according to the magnitude of the resonance frequency of the torsional damper 21. That is, "T2" is set to a length of time according to the resonance frequency. When a cutoff frequency higher than the resonance frequency is set, "T2" is set to a length of time according to a cutoff frequency even higher than the cutoff frequency. Furthermore, "s" is a variable for the Laplace transform.

[0040]

number

[0041] After deriving the compensation torque Tc, the CPU 91 proceeds to step S51. In step S51, the CPU 91 determines whether the derived compensation torque Tc is greater than the sum of the previous compensation torque value Tc1 and a first guard value α. The previous compensation torque value Tc1 is the compensation torque Tc acquired the previous time the compensation torque acquisition process M13 was executed. The first guard value α is a guard value that prevents the difference between the latest value of the compensation torque Tc and the previous compensation torque value Tc1 from becoming too large.

[0042] If the compensation torque Tc is greater than the sum of the previous compensation torque value Tc1 and the first guard value α (S51: YES), the CPU 91 proceeds to step S53. On the other hand, if the compensation torque Tc is equal to or less than the sum of the previous compensation torque value Tc1 and the first guard value α (S51: NO), the CPU 91 proceeds to step S55.

[0043] In step S53, the CPU 91 derives the compensation torque Tc as the sum of the previous compensation torque value Tc1 and the first guard value α, and then the CPU 91 proceeds to step S55.

[0044] In step S55, the CPU 91 acquires the smaller of the compensation torque Tc and the compensation torque upper limit value TcL as the compensation torque Tc. In other words, in this embodiment, a value greater than the compensation torque upper limit value TcL is not acquired as the compensation torque Tc. Subsequently, in step S57, the CPU 91 assigns the compensation torque Tc to the previous compensation torque value Tc1. Thereafter, the CPU 91 temporarily ends the compensation torque acquisition process M13.

[0045] The reason for setting the compensation torque upper limit value TcL will now be explained. The control device 90 executes a misfire determination process to determine whether a misfire has occurred in some of the cylinders 12 among the multiple cylinders 12 of the internal combustion engine 10. The misfire determination process determines whether any of the cylinders 12 has misfired based on fluctuations in the engine speed Ne, etc. Therefore, if the compensation torque Tc is allowed to be greater than the compensation torque upper limit value TcL, there is a risk that the fluctuations in the engine speed Ne will not be large even if a misfire occurs in some of the cylinders 12. In other words, the accuracy of determining whether a misfire has occurred in some of the cylinders 12 will be reduced. Therefore, in this embodiment, the compensation torque upper limit value TcL is set so that the accuracy of the misfire determination process can be sufficiently maintained.

[0046] On the other hand, if the catalyst warm-up process is not being executed in step S41 (NO), the CPU 91 proceeds to step S61. In step S61, the CPU 91 determines whether the second execution flag FLG2 is set to ON. If the second execution flag FLG2 is still set to ON, it can be assumed that the catalyst warm-up process has just ended. Therefore, if the second execution flag FLG2 is set to ON (S61: YES), the CPU 91 proceeds to step S63. On the other hand, if the second execution flag FLG2 is not set to ON (S61: NO), the CPU 91 temporarily terminates the compensation torque acquisition process M13.

[0047] In step S63, the CPU 91 derives the compensation torque Tc by subtracting the second guard value β from the previous compensation torque value Tc1. The second guard value β is a guard value for gradually reducing the compensation torque Tc. The second guard value β may be equal to the first guard value α or may be a value different from the first guard value α.

[0048] Subsequently, in step S65, the CPU 91 acquires the larger of the compensation torque Tc and 0 (zero) as the compensation torque Tc. In the next step S67, the CPU 91 determines whether the compensation torque Tc is equal to 0 (zero). If the compensation torque Tc is greater than 0 (zero) (S67: NO), the CPU 91 proceeds to step S57. On the other hand, if the compensation torque Tc is equal to 0 (zero) (S67: YES), the CPU 91 proceeds to step S69.

[0049] In step S69, the CPU 91 sets the second execution flag FLG2 to OFF. Subsequently, in step S71, the CPU 91 resets the previous compensation torque value Tc1 to 0 (zero). Thereafter, the CPU 91 temporarily ends the compensation torque acquisition process M13.

[0050] <Actions and Effects of the Present Embodiment> Fig. 5 shows the relationship between the frequency of engine torque fluctuations of the internal combustion engine 10 and the damping gain. The predetermined frequency range HP in Fig. 5 includes, for example, the frequencies of the inter-cylinder fluctuation components of the engine torque fluctuation components. Specifically, the predetermined frequency range HP is the range of frequencies at which inter-cylinder torque fluctuations occur during catalyst warm-up processing. The damping gain is a parameter that indicates the damping characteristics of fluctuations in the rotation speed of the rear shaft 22. The smaller the damping gain, the more quickly the fluctuations in the rotation speed of the rear shaft 22 can be converged.

[0051] The characteristic line L1 shown by the two-dot chain line in Fig. 5 is a line showing the relationship between frequency and damping gain in the first conventional example. The characteristic line L2 shown by the dashed line in Fig. 5 is a line showing the relationship between frequency and damping gain in the second conventional example. The characteristic line L3 shown by the solid line in Fig. 5 is a line showing the relationship between frequency and damping gain in this embodiment.

[0052] In the first conventional example, when engine torque fluctuates due to the execution of catalyst warm-up processing, damping torque is not output from the first motor generator 61. In the second conventional example, when engine torque fluctuates due to the execution of catalyst warm-up processing, damping torque is output from the first motor generator 61, but the damping torque is equal to the damping torque reference value Tg1B.

[0053] In the first conventional system, even if the fluctuations in engine torque caused by the catalyst warm-up process cause resonance in the torsional damper 21, no vibration-damping torque is output from the first motor-generator 61. As a result, as shown by the two-dot chain line in FIG. 5, the damping gain becomes large in the predetermined frequency range HP. In other words, the fluctuations in the rotation speed of the rear shaft 22 do not converge easily. As a result, the fluctuations in the rotation speed of the rear shaft 22 are transmitted to the case 55, causing the vehicle body to vibrate significantly.

[0054] In the second conventional system, when the fluctuations in engine torque caused by the catalyst warm-up process cause resonance in the torsional damper 21, a damping torque is output from the first motor-generator 61. However, the damping torque does not take into account the resonance frequency of the torsional damper 21. As a result, as shown by the two-dot chain line and the dashed line in FIG. 5 , although the damping gain is smaller in the predetermined frequency range HP than in the first conventional system, a delay occurs in the convergence of fluctuations in the rotation speed of the rear shaft 22. In other words, the damping torque cannot completely offset fluctuations in engine torque. As a result, the fluctuations in the rotation speed of the rear shaft 22 cannot be prevented from being transmitted to the case 55, causing vehicle body vibration.

[0055] In contrast, in this embodiment, when resonance occurs in the torsional damper 21 due to fluctuations in engine torque accompanying the execution of the catalyst warm-up process, a damping torque Tg1 is output from the first motor-generator 61. The damping torque Tg1 takes into account the resonance frequency of the torsional damper 21. As a result, as shown by the solid line in FIG. 5 , the damping gain can be made smaller than in the second conventional case in the predetermined frequency range HP. In other words, even if resonance occurs in the torsional damper 21, the fluctuations in engine torque can be offset by the damping torque. This increases the effect of suppressing fluctuations in the rotation speed of the rear shaft 22. This makes it possible to suppress transmission of fluctuations in the rotation speed of the rear shaft 22 to the case 55. Therefore, it is possible to suppress the occurrence of vehicle body vibrations when the catalyst warm-up process is being executed.

[0056] In this embodiment, the following effects can be further obtained. (1) In this embodiment, when the catalyst warm-up process is started, acquisition of the compensation torque Tc is started, and the damping torque Tg1 is derived using the compensation torque Tc. Once acquisition of the compensation torque Tc is started, the compensation torque Tc is gradually increased. This suppresses a sudden increase in the first motor torque compared to when the compensation torque Tc suddenly increases. The first motor torque is the output torque of the first motor generator 61. Therefore, it is possible to suppress the occurrence of vibrations caused by a sudden increase in the first motor torque.

[0057] Furthermore, when the catalyst warm-up process is completed, the compensation torque Tc is gradually reduced toward 0 (zero). This prevents a sudden decrease in the first motor torque compared to when the compensation torque Tc is suddenly reduced. Therefore, it is possible to suppress the occurrence of vibrations caused by a sudden decrease in the first motor torque.

[0058] (2) The greater the ignition retard amount X associated with the execution of the catalyst warm-up process, the greater the amplitude of engine torque fluctuations, which tends to increase vehicle body vibration. Therefore, in this embodiment, the greater the ignition retard amount X associated with the execution of the catalyst warm-up process, the greater the value set as control gain K. As a result, the greater the amplitude of engine torque fluctuations, the greater the amplitude of vibration damping torque Tg1 fluctuations. Therefore, even if the ignition retard amount X is large, fluctuations in the rotation speed of rear shaft 22 can be suppressed, and ultimately vehicle body vibration can be suppressed.

[0059] (3) In this embodiment, the compensation torque upper limit value TcL is set. Therefore, the process for suppressing the occurrence of vehicle body vibration during the catalyst warm-up process and the process for determining whether a misfire has occurred in cylinder 12 can coexist.

[0060] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0061] It is not essential to set the compensation torque upper limit TcL. For example, if the cylinder misfire determination process is not executed, the compensation torque Tc may be allowed to be greater than the compensation torque upper limit TcL.

[0062] The control gain K may be varied according to the engine load factor. The engine load factor can be calculated based on the engine speed Ne and the amount of intake air into the internal combustion engine 10. In this case, the control gain K should be set to a larger value as the engine load factor increases. This makes it possible to suppress the occurrence of rattle noise in the power split device 40 and the reduction mechanism 50 when the engine load factor is low.

[0063] When the control gain K is varied in accordance with the engine load factor as described above, it is not necessary to vary the control gain K in accordance with the ignition retard amount X. The control gain K does not have to be variable. For example, the control gain K may be fixed at a predetermined value.

[0064] When the catalyst warm-up process is started, the process of gradually increasing the compensation torque Tc does not have to be executed. When the catalyst warm-up process is completed, the process of gradually decreasing the compensation torque Tc does not have to be executed.

[0065] In torque reference value acquisition process M11, the rotation speed of rear shaft 22 may be used instead of first motor rotation speed Ng1. That is, in torque reference value acquisition process M11, a torque derived by feedback control using the rotation speed of rear shaft 22 and a target value for that rotation speed as input may be acquired as vibration damping torque reference value Tg1B.

[0066] The catalyst warm-up process does not have to be a process of retarding the ignition timing as long as it can promote an increase in the catalyst temperature TMP. For example, the catalyst warm-up process may be a process of stopping combustion in some of the cylinders 12 and continuing combustion in the remaining cylinders 12. In this process, fuel supply to the cylinders 12 where combustion is stopped is stopped.

[0067] The hybrid vehicle to which the control device 90 is applied may have a configuration different from that of the vehicle 100 shown in FIG. 1, as long as it includes the internal combustion engine 10, the first motor generator 61, and the torsional damper 21.

[0068] The control device 90 is not limited to a device that includes a CPU 91 and a ROM 92 and executes software processing. That is, the control device 90 may have any one of the following configurations (a) to (c). (a) The control device 90 includes one or more processors that execute various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions that cause the CPU to execute processes. Memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or special-purpose computer. (b) The control device 90 includes one or more dedicated hardware circuits that perform various processes. Examples of dedicated hardware circuits include application specific integrated circuits (ASICs) or FPGAs. ASIC stands for "Application Specific Integrated Circuit," and FPGA stands for "Field Programmable Gate Array." (c) The control device 90 includes a processor that executes some of the various processes in accordance with a computer program, and a dedicated hardware circuit that executes the remaining processes of the various processes. [Explanation of symbols]

[0069] 10...Internal combustion engine 11...Crankshaft 14...Exhaust passage 15...Catalyst 21...Torsion damper 22...Rear shaft 61...First motor generator 90...Control device 100...Vehicle

Claims

[Claim 1] The present invention is applied to a hybrid vehicle including an internal combustion engine, an electric motor, and a torsional damper located in a torque transmission path between the internal combustion engine and the electric motor, and in which a catalyst is provided in an exhaust passage of the internal combustion engine, a catalyst warm-up process for controlling the operation of the internal combustion engine to increase the temperature of the catalyst; a torque reference value acquisition process that acquires, as a vibration damping torque reference value, a torque derived by feedback control using as input a rotation speed of the electric motor or a rear-stage shaft that is connected to the crankshaft of the internal combustion engine via the torsional damper and a target value of the rotation speed; a compensation torque acquisition process for acquiring, as a compensation torque, a torque derived by performing a filter process on the rotation speed in accordance with the magnitude of a resonance frequency of the torsional damper; a vibration-damping torque acquisition process for acquiring a value obtained by subtracting the compensation torque from the vibration-damping torque reference value as the vibration-damping torque; a resonance suppression process for outputting the damping torque from the electric motor when the catalyst warm-up process is being performed; During the catalyst warm-up process, the compensation torque acquisition process derives a larger compensation torque as the ignition retard amount, which is the amount of retard from a reference ignition timing in the internal combustion engine, increases. A control device for a hybrid vehicle.

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