Control device for internal combustion engine

Abstract

To suppress rotation fluctuation of an internal combustion engine generated when a starting engagement element is engaged.SOLUTION: The control device 100 is configured to, when one of a condition that an amount of change in the oil pressure of the hydraulic fluid supplied to the starting engagement elements 52s included in the transmission mechanism 50 is equal to or greater than a predetermined value after the gearshift lever 300 is shifted from the non-driving position to the driving position and a condition that a target time from when the gearshift lever 300 is shifted from the non-driving position to the driving position to when the starting engagement elements 52s start to engage has elapsed, engine torque of an internal combustion engine 10 is feedback-controlled so that an engine rotation speed of the internal combustion engine 10 becomes a target rotation speed, and torque control for increasing a correction amount to an increase side of the engine torque is started when a load torque increase speed of a torque converter 40 is high as compared with when it is low.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for an internal combustion engine. [Background technology]

[0002] The vehicle described in Patent Document 1 has an automatic transmission equipped with a transmission mechanism having multiple friction engagement elements and a torque converter. The torque converter has a pump impeller connected to the output shaft of the internal combustion engine and a turbine impeller connected to the input shaft of the transmission mechanism. The vehicle also has a shift lever that can be switched between a non-driving position and a driving position.

[0003] The friction engagement elements of the transmission mechanism have a starting engagement element whose operating state is switched from a released state to an engaged state when the shift lever is switched from a non-driving position to a driving position. The non-driving position is a position where the vehicle is not driving, such as a parking position (P position) or a neutral position (N position). The driving position is a position where the vehicle is driving, such as a drive position (D position) or a reverse position (R position). The starting engagement element is an engagement element that forms a first gear for forward driving, or an engagement element that forms a gear for reverse driving. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-167611 Summary of the Invention [Problem to be solved by the invention]

[0005] In such vehicles, when the shift lever is shifted from a non-driving position to a driving position, the operating state of the launch engagement element is switched from a disengaged state to an engaged state. When the launch engagement element begins to engage during this shift, the torque converter load torque begins to increase. The torque converter load torque is the load torque of the turbine impeller that resists the rotation of the pump impeller. If the torque generated by the internal combustion engine is insufficient or excessive relative to the increase in the torque converter load torque, rotational fluctuations in the internal combustion engine occur.

[0006] Therefore, it is conceivable to perform feedback control of engine torque so that the engine rotation speed becomes the target rotation speed, and to implement torque control that increases the amount of correction to increase the engine torque when the torque converter load torque increases quickly compared to when it increases slowly. However, if the start timing of such torque control does not coincide with the start timing of engagement of the starting engagement element of the launch, the engine torque may be excessive or insufficient relative to the increase in the torque converter load torque. As a result, it may be impossible to suppress the rotation fluctuation of the internal combustion engine that occurs when the starting engagement element of the launch is engaged. [Means for solving the problem]

[0007] A control device for an internal combustion engine for solving the above problem is provided with an automatic transmission having a transmission mechanism with multiple friction engagement elements and a torque converter having a pump impeller connected to the output shaft of the internal combustion engine and a turbine impeller connected to the input shaft of the transmission mechanism, and a shift lever that can be switched between a non-driving position and a driving position, and the friction engagement elements are applied to an internal combustion engine mounted on a vehicle having a starting engagement element whose operating state is switched from a released state to an engaged state when the shift lever is switched from the non-driving position to the driving position. When the load torque of the turbine impeller resisting the rotation of the pump impeller is defined as the torque converter load torque, and the increase rate of the torque converter load torque is defined as the load torque increase rate, this control device feedback controls the engine torque generated in the internal combustion engine so that the engine rotation speed of the internal combustion engine becomes a target rotation speed, and when the load torque increase rate is fast, performs torque control that increases the amount of correction to increase the engine torque compared to when the load torque increase rate is slow, and also executes a process of obtaining a target time from when the shift lever is switched from a non-driving position to a driving position until the start of engagement of the launch engagement element, and a process of starting the torque control when either of the following conditions is met: the amount of change in oil pressure of the hydraulic oil supplied to the launch engagement element is equal to or greater than a predetermined value after the shift lever is switched from the non-driving position to the driving position; or the target time has elapsed since the shift lever was switched from the non-driving position to the driving position.

[0008] In addition, a control device for an internal combustion engine to solve the above problem is applied to an internal combustion engine mounted on a vehicle that includes an automatic transmission having a transmission mechanism with multiple friction engagement elements and a torque converter having a pump impeller connected to the output shaft of the internal combustion engine and a turbine impeller connected to the input shaft of the transmission mechanism, and a shift lever that can be switched between a non-driving position and a driving position, wherein the friction engagement elements are starting engagement elements whose operating state is switched from a released state to an engaged state when the shift lever is switched from the non-driving position to the driving position. When the load torque of the turbine impeller resisting the rotation of the pump impeller is defined as a torque converter load torque and the increase rate of the torque converter load torque is defined as a load torque increase rate, this control device feedback controls the engine torque generated by the internal combustion engine so that the engine rotation speed of the internal combustion engine becomes a target rotation speed, and when the load torque increase rate is fast, performs torque control that increases the amount of correction to increase the engine torque compared to when the load torque increase rate is slow, and also executes a process of obtaining a target time from when the shift lever is switched from a non-driving position to a driving position until the start of engagement of the launch engagement element, and a process of starting the torque control when either of the following conditions is met: the amount of change in the rotation speed of the turbine impeller is equal to or greater than a predetermined value after the shift lever is switched from the non-driving position to the driving position; or the target time has elapsed since the shift lever was switched from the non-driving position to the driving position. [Effects of the Invention]

[0009] According to this invention, it is possible to suppress fluctuations in rotation of the internal combustion engine that occur when the starting engagement element is engaged. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a vehicle equipped with a control device according to one embodiment. [Figure 2] FIG. 2 is a flowchart showing the procedure of processing executed by the control device of the embodiment. [Figure 3] FIG. 3 is a flowchart showing the procedure of processing executed by the control device of the embodiment. [Figure 4] FIG. 4 is a flowchart showing the procedure of the process executed by the control device of the embodiment. [Figure 5] FIG. 5 is a timing chart showing the transition of each value when the operating state of the launch engagement element switches from a disengaged state to an engaged state. FIG. 5(a) shows the transition of the FB correction amount. FIG. 5(b) shows the transition of the engine rotation speed, target rotation speed, and turbine rotation speed. FIG. 5(c) shows the transition of the control start flag. FIG. 5(d) shows the transition of the shift position. FIG. 5(e) shows the transition of the torque converter load torque. [Figure 6] FIG. 6 is a flowchart showing the procedure of a process executed by the control device in the modification of the embodiment. [Figure 7] FIG. 7 is a flowchart showing the procedure of a process executed by the control device in the modification of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of a control device for an internal combustion engine will be described below with reference to FIGS. <Vehicle configuration> 1, an internal combustion engine 10 provided in a vehicle 500 includes an intake passage 11, a throttle valve 12 provided in the intake passage 11, and a fuel injection valve 13 that supplies fuel to a cylinder. In a combustion chamber of the internal combustion engine 10, a mixture of intake air and fuel injected from the fuel injection valve 13 is combusted, thereby generating engine output.

[0012] The crankshaft 18 of the internal combustion engine 10 is connected to a multi-stage automatic transmission 200 that includes a torque converter 40 and a speed change mechanism 50 . The torque converter 40 includes a pump impeller 42P connected to the crankshaft 18 and a turbine impeller 42T connected to an input shaft 49 of the transmission mechanism 50. In this torque converter 40, torque is transmitted between the pump impeller 42P and the turbine impeller 42T via an automatic transmission fluid (ATF). The torque converter 40 also includes a lock-up clutch 45 whose operating state changes between an engaged state in which the pump impeller 42P and the turbine impeller 42T are directly connected, and a disengaged state in which the engaged state is released.

[0013] The transmission mechanism 50 is a planetary gear type multi-speed transmission having a well-known structure, and includes multiple planetary gear mechanisms and multiple hydraulically operated friction engagement elements 52, which are clutches and brakes. Various gear stages are formed by changing which of the friction engagement elements 52 are engaged and which are released. In this embodiment, the engaged state of the friction engagement elements 52 refers to a state in which power transmission is possible. Therefore, a state in which the friction engagement elements 52 are not fully engaged and are slipping is also included in the engaged state.

[0014] The friction engagement element 52 has a starting engagement element 52s whose operating state is switched from a released state to an engaged state when a shift lever 300 (described later) is switched from a non-driving position to a driving position. The starting engagement element 52s is an engagement element that forms a first gear for forward travel or an engagement element that forms a reverse gear.

[0015] The output shaft of the transmission mechanism 50 is connected to drive wheels 65 of the vehicle 500 via a differential gear 60 . Operations of the automatic transmission 200, such as operation of the clutches and brakes of the speed change mechanism 50 and operation of the lock-up clutch 45, are performed by controlling a hydraulic circuit 90 that supplies hydraulic oil to each of these mechanisms.

[0016] The control device 100 controls the internal combustion engine 10, and operates various operating parts of the internal combustion engine 10, such as the throttle valve 12 and the fuel injection valve 13, to control the torque, exhaust component ratio, and other control variables. The control device 100 also controls the lock-up clutch 45 and the automatic transmission 200, and operates the hydraulic circuit 90 to control the hydraulic pressure, which is the control variable.

[0017] Various controls of the internal combustion engine 10, the automatic transmission 200, etc. are executed by a control device 100 mounted on a vehicle 500. The control device 100 includes a CPU 110 and a memory 120 that stores control programs and data. The CPU 110 executes the programs stored in the memory 120 to perform various controls and various processes described below. Although not shown, the control device 100 is made up of multiple control units, such as a control unit for an internal combustion engine and a control unit for an automatic transmission.

[0018] When controlling the above-mentioned controlled variables, the control device 100 refers to an output signal Scr from a crank angle sensor 70 that detects the rotation angle of the crankshaft 18, and a coolant temperature THW of the internal combustion engine 10 that is detected by a water temperature sensor 71. The control device 100 also refers to an intake air amount GA of the internal combustion engine 10 that is detected by an air flow meter 72, and an accelerator operation amount ACCP that is the depression amount of the accelerator pedal that is detected by an accelerator position sensor 73. The control device 100 also refers to a vehicle speed SP of the vehicle 500 that is detected by a vehicle speed sensor 74, and a turbine rotation speed Nt that is the rotation speed of the turbine impeller 42T that is detected by a rotation speed sensor 75. The control device 100 also refers to an oil pressure Pat of the hydraulic oil supplied to the friction engagement element 52 that is a value detected by an oil pressure sensor 76, and an oil temperature Toil that is the temperature of the hydraulic oil that is detected by an oil temperature sensor 77.

[0019] The control device 100 calculates the engine speed NE based on the output signal Scr of the crank angle sensor 70. The control device 100 also calculates the engine load factor KL based on the engine speed NE and the intake air amount GA.

[0020] The vehicle 500 is provided with a shift lever 300 that is switched between a non-driving position and a driving position by the vehicle driver. The non-driving position is a position where the vehicle 500 is not driving, such as a parking position (P position) or a neutral position (N position). When the shift lever 300 is in the non-driving position, a gear for non-driving is established in the transmission mechanism 50. The driving position is a position where the vehicle 500 is driving, such as a drive position (D position) or a reverse position (R position). When the shift lever 300 is in the driving position, a gear for driving is established in the transmission mechanism 50. A shift position sensor 310 that detects the shift position SFT, which is the operating position of the shift lever 300, is connected to the control device 100.

[0021] <Torque control of internal combustion engines> When the shift lever 300 is switched from the non-travel position to the travel position, the operating state of the launch engagement element 52s is switched from the disengaged state to the engaged state. When the launch engagement element 52s begins to engage during this switching, the torque converter load torque begins to increase.

[0022] This torque converter load torque has the following value. That is, when the start engaging element 52s begins to engage, the transmission torque capacity of the transmission mechanism 50 gradually increases. Therefore, in the torque converter 40, the load torque of the turbine impeller 42T that resists the rotation of the pump impeller 42P increases. This load torque of the turbine impeller 42T that resists the rotation of the pump impeller 42P is the torque converter load torque. This torque converter load torque is a value that represents the magnitude of the load acting on the internal combustion engine 10 from the driveline of the vehicle 500.

[0023] If the torque generated by the internal combustion engine 10 is excessive or insufficient relative to an increase in the torque converter load torque, the engine rotation speed of the internal combustion engine 10 will fluctuate, resulting in rotation fluctuations. Therefore, when the shift lever 300 is switched from the non-driving position to the driving position, the control device 100 performs, for example, the following torque control.

[0024] In this torque control, engine torque, which is the torque generated by the internal combustion engine 10, is feedback-controlled so that the engine speed NE of the internal combustion engine 10 becomes a target speed NEt. The target speed NEt is a target value of the engine speed NE when the internal combustion engine 10 is idling. The target value NEn, which is the value of the target speed NEt when the shift lever 300 is in the non-driving position, is higher than the target value NEd, which is the value of the target speed NEt when the shift lever 300 is in the driving position. When a control start flag F, which will be described later, is turned ON, a gradual change value obtained by gradually changing the target value NEn toward the target value NEd is set as the target speed NEt. The control device 100 calculates a basic torque Tb as a feedforward term based on the target speed NEt thus set. The control device 100 also calculates an FB correction amount Tfb, which is a torque value as a feedback term, based on the deviation between the target speed NEt and the actual engine speed NE, a feedback gain (hereinafter referred to as FB gain) M, and the like. The control device 100 then assigns the value obtained by adding the FB correction amount Tfb to the basic torque Tb to the required torque Td. The control device 100 then controls the intake air amount, fuel injection amount, etc. of the internal combustion engine 10 so that the required torque Td is obtained. Note that when the FB correction amount Tfb is a positive value, the basic torque Tb is corrected to increase. On the other hand, when the FB correction amount Tfb is a negative value, the basic torque Tb is corrected to decrease.

[0025] Furthermore, in this torque control, when the load torque increase rate LTS, which is the increase rate of the torque converter load torque, is fast, the control device 100 executes processing to increase the correction amount to increase the engine torque generated in the internal combustion engine 10 compared to when it is slow. By executing this processing, a decrease in engine rotation speed due to an increase in the torque converter load torque is suppressed, thereby suppressing the occurrence of, for example, engine stall. Note that this processing can be executed as appropriate. For example, when the increase rate of the load torque increase rate LTS is fast, the value of the basic torque Tb may be set to a larger value compared to when it is slow. Furthermore, when the load torque increase rate LTS is fast, the gain may be changed so that the FB correction amount Tfb is larger on the side of increasing the engine torque compared to when it is slow.

[0026] If the timing at which the torque control starts and the timing at which the starting engagement of the launch engagement element 52s are not synchronized, the engine torque may be either excessive or insufficient relative to the increase in torque converter load torque, which may make it impossible to suppress the rotational fluctuations of the internal combustion engine 10 that occur when the launch engagement element is engaged.

[0027] Therefore, the control device 100 executes the processes described below to prevent such inconveniences from occurring. <Control start flag setting process> 2 shows the procedure of the process executed by the control device 100 at predetermined intervals to set the control start flag F. In the following, the step number of each process is represented by a number preceded by "S."

[0028] When this process starts, the control device 100 determines whether the vehicle 500 is stopped (S100). In the process of S100, the control device 100 determines that the vehicle 500 is stopped, for example, when the vehicle speed SP is equal to or less than a predetermined threshold value.

[0029] If it is determined that vehicle 500 is stopped (S100: YES), control device 100 determines whether shift position SFT is the drive position (S110). If it is determined that the shift position SFT is the drive position (S110: YES), the control device 100 determines whether the shift position SFT was the non-drive position when this process was last executed (S120). If the determination in S120 is affirmative, this means that the shift lever 300 has been switched from the non-drive position to the drive position between the last time this process was executed and the current time this process is executed.

[0030] If the determination in the processing of S120 is affirmative, the control device 100 determines whether the control start flag F is OFF or not (S130). The initial value of the control start flag F is OFF. Then, when the control start flag F is ON, the above-mentioned torque control is performed, whereas when the control start flag F is OFF, the above-mentioned torque control is stopped.

[0031] If it is determined in the processing of S130 that the control start flag F is OFF (S130: YES), the control device 100 counts up the counter DC (S140). The counter DC is a value that indicates the elapsed time since the shift lever 300 was switched from the non-driving position to the driving position.

[0032] On the other hand, if a negative determination is made in the process of S120, the control device 100 executes initialization to set the value of the counter DC to "0" (S150). After executing the process of S150, the control device 100 next acquires the target time TCLt (S160). The target time TCLt is the target time from when the shift lever 300 is switched from the non-driving position to the driving position until the start engagement of the launch engagement element 52s. The automatic transmission control unit sets the target time TCLt based on the oil temperature Toil, etc. Then, the automatic transmission control unit controls the oil pressure Pat, etc. so as to obtain the target time TCLt. In the process of S160, the internal combustion engine control unit acquires the target time TCLt calculated by the automatic transmission control unit.

[0033] After executing the process of S140 or the process of S160, the control device 100 then acquires the oil pressure Pat of the hydraulic oil supplied to the starting engagement element 52s (S170). Next, the control device 100 calculates the hydraulic pressure change amount PatH (S180). The hydraulic pressure change amount PatH is a value obtained by subtracting the hydraulic pressure Pat obtained in the process of S170 in the previous execution cycle from the hydraulic pressure Pat obtained in the process of S170 in the current execution cycle. Note that the hydraulic pressure Pat used to calculate the hydraulic pressure change amount PatH is preferably a value obtained by smoothing the detection value of the hydraulic pressure sensor 76.

[0034] Next, the control device 100 determines whether or not either of the following conditions (A) and (B) is satisfied (S190). Condition A: The current value of the counter DC is equal to or greater than the target time TCLt.

[0035] Condition B: The hydraulic pressure change amount PatH is equal to or greater than a predetermined value PatHref. The predetermined value PatHref is the hydraulic pressure change amount PatH when the starting engagement element 52s begins to engage, and is a preset optimum value.

[0036] If it is determined in the processing of S190 that either the condition (A) or the condition (B) is satisfied, the control device 100 changes the control start flag F from OFF to ON (S200). When the control start flag F is set ON by the processing of S200, the torque control is started.

[0037] On the other hand, if a negative determination is made in the process of S100 or S110, the control device 100 sets the control start flag F to OFF (S220). Then, when the control device 100 executes the processing of S200, or when the control device 100 executes the processing of S220, or when the control device 100 makes a negative judgment in the processing of S130, or when the control device 100 makes a negative judgment in the processing of S190, the control device 100 temporarily terminates this processing.

[0038] <Load torque increase speed calculation process> FIG. 3 shows a procedure of processing that the control device 100 executes at predetermined intervals to calculate the load torque increasing speed of the torque converter used when carrying out the torque control.

[0039] When this process starts, the control device 100 determines whether or not the control start flag F is ON (S300). If it is determined that the control start flag F is ON (S300: YES), the control device 100 acquires the target turbine change rate NtHt and the above-described hydraulic pressure change amount PatH (S310). The target turbine change rate NtHt is a target rate of change of the rotational speed of the turbine impeller 42T. In other words, it is a target amount of change of the turbine rotational speed Nt per unit time. The automatic transmission control unit sets the target turbine change rate NtHt so that the rate of change of the turbine rotational speed Nt becomes an appropriate value as the engagement of the launch engaging element 52s progresses. Then, the automatic transmission control unit controls the hydraulic pressure Pat and the like so as to obtain the target turbine change rate NtHt. In the processing of S310, the internal combustion engine control unit acquires the target turbine change rate NtHt calculated by the automatic transmission control unit.

[0040] Next, the control device 100 calculates a first torque increase speed LTS1 based on the turbine target change speed NtHt (S320). The first torque increase speed LTS1 is an increase speed of the torque converter load torque obtained by converting the turbine target change speed NtHt using an appropriate model formula or the like.

[0041] Next, the control device 100 calculates a second torque increase speed LTS2 based on the acquired hydraulic pressure change amount PatH (S330). The second torque increase speed LTS2 is the increase speed of the torque converter load torque obtained by converting the hydraulic pressure change amount PatH using an appropriate model formula or the like.

[0042] Next, the control device 100 determines whether the first torque increase acceleration LTS1 is greater than or equal to the second torque increase acceleration LTS2 (S340). And when it is determined that the first torque increase acceleration LTS1 is greater than or equal to the second torque increase acceleration LTS2 (S340: YES), the control device 100 substitutes the first torque increase acceleration LTS1 for the load torque increase acceleration LTS (S350).

[0043] On the other hand, when it is determined that the first torque increase acceleration LTS1 is not greater than or equal to the first torque increase acceleration LTS1 (S340: NO), the control device 100 substitutes the second torque increase acceleration LTS2 for the load torque increase acceleration LTS (S360). By executing each of these processes of S340, S350, and S360, when the first torque increase acceleration LTS1 and the second torque increase acceleration LTS2 are different, the larger value is substituted for the load torque increase acceleration LTS.

[0044] And when the control device 100 executes the process of S350, or executes the process of S360, or makes a negative determination in the process of S300, this process is temporarily terminated. [[ID=ll]]

[0045] <FB gain correction process> FIG. 4 shows the procedure of the process that the control device 100 executes every predetermined period. This process includes a process for correcting the FB gain M used in the implementation of the torque control. Incidentally, when the value of the FB gain M is greater than "1", the larger the value of the FB gain M, the larger the correction amount for increasing the engine torque to the increasing side. On the other hand, when the value of the FB gain M is less than "1", the smaller the value of the FB gain M, the larger the correction amount for decreasing the engine torque to the decreasing side.

[0046] When starting this process, the control device 100 calculates the current FB gain M (S400). In the process of S400, the control device 100 calculates the value obtained by dividing the currently set target rotational speed NEt by the current engine rotational speed NE. And substitutes the calculated value for the current FB gain M.

[0047] Next, the control device 100 determines whether or not the control start flag F is ON (S410). If it is determined that the control start flag F is ON (S410: YES), the control device 100 determines whether or not the current engine rotation speed NE is equal to or higher than the target rotation speed NEt (S420).

[0048] If it is determined that the current engine rotation speed NE is equal to or greater than the target rotation speed NEt (S420: YES), the control device 100 calculates a first coefficient K1 based on the rotation speed difference ΔNE (S430). The rotation speed difference ΔNE is a value obtained by subtracting the current engine rotation speed NE from the target rotation speed NEt. The first coefficient K1 is a value equal to or greater than 1, and is variably set so that the value of the first coefficient K1 increases as the absolute value of the rotation speed difference ΔNE increases.

[0049] After executing the process of S430, the control device 100 then calculates a second coefficient K2 based on the elapsed time TE (S440). The elapsed time TE is the time that the control device 100 starts measuring when the process of S200 is executed and the control start flag F is set to ON, and is a value corresponding to the elapsed time since the torque control started to be executed. The second coefficient K2 is a value equal to or greater than 1, and is variably set so that the shorter the elapsed time TE is and the less progress there is in converging the engine rotation speed NE to the target rotation speed NEt, the larger the value of the second coefficient K2 becomes.

[0050] Next, the control device 100 determines whether the first coefficient K1 is equal to or greater than the second coefficient K2 (S450). If it is determined that the first coefficient K1 is equal to or greater than the second coefficient K2 (S450: YES), the control device 100 assigns the first coefficient K1 to the reflection coefficient K (S460).

[0051] On the other hand, if it is determined that the first coefficient K1 is not greater than or equal to the second coefficient K2 (S450: NO), the control device 100 assigns the second coefficient K2 to the reflection coefficient K (S470). By executing the processes of S450, S460, and S470, if the values ​​of the first coefficient K1 and the second coefficient K2 are different, the larger value is assigned to the reflection coefficient K.

[0052] Next, the control device 100 corrects the FB gain M by multiplying the FB gain M calculated in the process of S400 by the reflection coefficient K (S480). The control device 100 performs the torque control using the FB gain M corrected in the process of S480.

[0053] If the determination in the processing of S420 above is affirmative, the current engine rotation speed NE is equal to or greater than the target rotation speed NEt, and therefore the value of the FB gain M calculated in the processing of S400 will be a value of 1 or less, which basically corrects the engine torque to a decreasing side.

[0054] Here, the first coefficient K1 is a value equal to or greater than "1," and is variably set so that the value of the first coefficient K1 increases as the absolute value of the rotational speed difference ΔNE increases. Therefore, when the first coefficient K1 is substituted for the reflection coefficient K, the value of the corrected FB gain M increases as the absolute value of the rotational speed difference ΔNE increases. Therefore, the amount of correction by which the engine torque is corrected to decrease decreases, and the correction to decrease the engine torque is suppressed.

[0055] On the other hand, the second coefficient K2 is also a value equal to or greater than "1," and is variably set so that the shorter the elapsed time TE, the larger the value of the second coefficient K2. Therefore, when the second coefficient K2 is substituted for the reflection coefficient K, the shorter the elapsed time TE, the larger the value of the corrected FB gain M. Therefore, the amount of correction by which the engine torque is corrected to decrease becomes smaller, and the correction to decrease the engine torque is suppressed.

[0056] If the determination in the processing of S420 is negative (S420: NO), that is, if the current engine rotation speed NE is lower than the target rotation speed NEt, the control device 100 determines whether the absolute value of the rotation speed difference ΔNE exceeds a predetermined value ΔNEref (S490). The predetermined value ΔNEref is the absolute value of the rotation speed difference ΔNE at which the engine may stall, and is a preset adaptive value.

[0057] If it is determined that the absolute value of the rotational speed difference ΔNE exceeds the predetermined value ΔNEref (S490: YES), the control device 100 determines whether the current coolant temperature THW is less than the predetermined value THWref (S500). The predetermined value THWref is the coolant temperature THW at which the engine stall may occur, and is a preset adaptive value.

[0058] If it is determined that the current coolant temperature THW is lower than the preset value THWref (S500: YES), the control device 100 sets the shift change stop request flag FS to ON (S510). When the shift change stop request flag FS is set to ON, the engagement operation of the start engagement element 52s is prohibited and the start engagement element 52s is temporarily set to a disengaged state, thereby suppressing the occurrence of an engine stall.

[0059] Then, when the control device 100 has executed the process of S480 or the process of S510, it temporarily ends this process. Also, when the control device 100 makes a negative determination in the process of S410, when the control device 100 makes a negative determination in the process of S490, or when the control device 100 makes a negative determination in the process of S500, it temporarily ends this process.

[0060] <Operation of this embodiment> Figure 5 shows the transition of each value when the operating state of the start engaging element 52s switches from a disengaged state to an engaged state. Figure 5(a) shows the transition of the FB correction amount Tfb. Figure 5(b) shows the transition of the engine rotation speed NE, the target rotation speed NEt, and the turbine rotation speed Nt. Figure 5(c) shows the transition of the control start flag F. Figure 5(d) shows the transition of the shift position SFT. Figure 5(e) shows the transition of the torque converter load torque.

[0061] When the shift position is switched from a non-driving position (e.g., N position) to a driving position (e.g., D position) at time t1, hydraulic pressure supply to the starting engagement element 52s begins, and the operating state of the starting engagement element 52s changes from a released state to an engaged state.

[0062] When the starting engaging element 52s begins to engage at time t2, the turbine rotation speed Nt decreases and the torque converter load torque begins to increase. Also, at time t2, either the condition (A) or the condition (B) is satisfied, and the control start flag F is changed from OFF to ON. Therefore, the torque control described above begins at time t2.

[0063] When torque control is initiated, the target rotation speed NEt gradually changes from the target value NEn toward the target value NEd. Then, the engine torque is feedback-controlled so that the actual engine rotation speed NE matches the target rotation speed NEt. Furthermore, when torque control is performed, a load torque increase speed LTS, which is the increase speed of the torque converter load torque, is calculated. Then, the engine torque is corrected in accordance with the calculated load torque increase speed LTS. That is, when the load torque increase speed LTS is fast, a process is executed to increase the amount of correction to the increasing side of the engine torque compared to when the load torque increase speed LTS is slow, thereby suppressing fluctuations in the engine rotation speed NE caused by the torque converter load torque.

[0064] Furthermore, after time t2, when the engine speed NE is equal to or higher than the target engine speed NEt, the FB gain M is corrected using the reflection coefficient K, thereby preventing the value of the FB correction amount Tfb from increasing in a way that reduces the engine torque. Therefore, when the engine speed NE decreases toward the target engine speed NEt, the decrease in the engine speed NE is gradual. This makes it possible to prevent the engine from stalling when the start engaging element 52s enters the engaged state.

[0065] Then, at time t3, when the engagement of the start engaging element 52s is completed, the decrease in turbine rotation speed Nt stops and the increase in torque converter load torque also stops. Then, after time t3, the engine rotation speed NE converges to the target rotation speed NEt set as the target value NEd.

[0066] <Effects of this embodiment> (1) When the hydraulic pressure of the hydraulic oil supplied to the starting engagement element 52s increases, the operating state of the starting engagement element 52s switches from a disengaged state to an engaged state. Therefore, after the shift lever 300 is switched from the non-driving position to the driving position, when the change in the hydraulic pressure of the hydraulic oil supplied to the starting engagement element 52s reaches or exceeds a predetermined value, it can be assumed that the operating state of the starting engagement element 52s has changed from a disengaged state to an engaged state.

[0067] In this embodiment, a target time TCLt is set from when the shift lever 300 is switched from the non-travel position to the travel position until the start of engagement of the launch engagement element 52s. In this case, it can be estimated that the actuation state of the launch engagement element 52s will have changed from the released state to the engaged state when the target time TCLt has elapsed.

[0068] Therefore, when either the above condition (A) or the above condition (B) is satisfied after the shift lever 300 is switched from the non-driving position to the driving position, the control device 100 sets the control start flag F to ON and starts the execution of the torque control described above. Therefore, the torque control of the internal combustion engine 10, which takes into account the increasing speed of the torque converter load torque, is started in accordance with the timing when the start engaging element 52s starts to engage. Therefore, it is possible to suppress the rotation fluctuation of the internal combustion engine 10 that occurs when the start engaging element 52s engages.

[0069] (2) When a target rate of change of the turbine rotation speed Nt is set when switching the operating state of the launch engaging element 52s from a disengaged state to an engaged state, the target rate of change and the rate of increase of the torque converter load torque are correlated. Furthermore, the amount of change in hydraulic pressure supplied to the launch engaging element 52s are correlated with the rate of increase of the torque converter load torque. Therefore, the control device 100 acquires the target turbine rate of change NtHt, which is the target rate of change of the turbine rotation speed Nt, and calculates a first torque increase rate LTS1, which is the rate of increase of the torque converter load torque, based on the target turbine rate of change NtHt. The control device 100 also calculates a second torque increase rate LTS2, which is the rate of increase of the torque converter load torque, based on the hydraulic pressure change rate PatH, which is the amount of change in hydraulic pressure supplied to the launch engaging element 52s. The control device 100 then assigns the larger of the first torque increase rate LTS1 and the second torque increase rate LTS2 to the load torque increase rate LTS. Therefore, compared to when the smaller of the first torque increase speed LTS1 and the second torque increase speed LTS2 is substituted for the load torque increase speed LTS, the amount of correction to the increasing side of the engine torque through the torque control of the internal combustion engine 10 is increased. Therefore, it is possible to suppress the occurrence of engine stall due to insufficient torque of the internal combustion engine 10 relative to the load torque increase speed LTS.

[0070] (3) When the engine rotation speed NE is equal to or higher than the target rotation speed NEt, the engine torque is corrected to decrease by the torque control. Here, if such torque correction to decrease is performed excessively, there is a risk of the engine stalling when the starting engaging element 52s is engaged. In this regard, when the engine rotation speed NE is equal to or higher than the target rotation speed NEt, the control device 100 executes a process to suppress the correction of the engine torque to decrease by the torque control by correcting the FB gain M as described above. Therefore, it is possible to suppress the occurrence of an engine stall when the starting engaging element 52s is engaged.

[0071] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0072] When the operating state of the launch engaging element 52s switches from a released state to an engaged state, the rotational speed of the turbine impeller 42T connected to the input shaft of the transmission mechanism 50 increases. Therefore, after the shift lever 300 is switched from the non-driving position to the driving position, if the change in the rotational speed of the turbine impeller 42T reaches or exceeds a predetermined value, it can be assumed that the operating state of the launch engaging element 52s has changed from a released state to an engaged state.

[0073] Therefore, in the above embodiment, the determination as to whether or not to turn on the control start flag F is made based on the hydraulic pressure change amount PatH, but the same determination may also be made based on the change amount of the turbine rotation speed Nt.

[0074] This modified example omits the processes of S170, S180, and S190 from the series of processes shown in Fig. 2. Then, instead of the omitted processes, the modified example can be realized by executing the processes of S600, S610, and S620 shown in Fig. 6.

[0075] As shown in FIG. 6, the control device 100 executes either the process of S140 or the process of S160, and then executes the process of S600. In the process of S600, the control device 100 acquires the turbine rotation speed Nt.

[0076] Next, the control device 100 calculates a speed change amount NtH (S610). The speed change amount NtH is a value obtained by subtracting the turbine rotation speed Nt obtained in the process of S600 in the previous execution cycle from the turbine rotation speed Nt obtained in the process of S600 in the current execution cycle. Note that the turbine rotation speed Nt used to calculate the speed change amount NtH is preferably a value obtained by smoothing the detection value of the rotation speed sensor 75.

[0077] Next, the control device 100 determines whether or not the above-mentioned condition (A) and any one of the following conditions (C) are met (S620). Condition A: The current value of the counter DC is equal to or greater than the target time TCLt.

[0078] Condition C: The speed change amount NtH is equal to or greater than a predetermined value NtHref. The predetermined value NtHref is the speed change amount NtH when the starting engagement element 52s starts to engage, and is a preset suitable value.

[0079] If it is determined in the processing of S620 that either the condition (A) or the condition (C) is satisfied, the control device 100 changes the control start flag F from OFF to ON (S200). When the control start flag F is set ON by the processing of S200, the torque control is started.

[0080] On the other hand, if a negative determination is made in the process of S620, the control device 100 temporarily ends the series of processes shown in FIG. In this modified example, torque control of the internal combustion engine 10, which takes into account the increasing speed of the torque converter load torque, is initiated in accordance with the timing at which the starting engagement element 52s begins to engage, thereby suppressing rotation fluctuations of the internal combustion engine 10 that occur when the starting engagement element 52s engages.

[0081] The amount of change in the rotational speed of the turbine impeller 42T and the rate of increase in the torque converter load torque are correlated. Therefore, in the above embodiment, the second torque increase rate LTS2 is calculated based on the amount of change in the hydraulic pressure PatH, but the second torque increase rate LTS2 may also be calculated based on the amount of change in the turbine rotational speed Nt.

[0082] This modified example omits the processes of S310 and S330 from the series of processes shown in Fig. 3. Then, instead of the omitted processes, the process of S700 and S710 shown in Fig. 7 is executed, thereby realizing the modification example.

[0083] As shown in FIG. 7, when the determination in the process of S300 is affirmative, the control device 100 acquires the turbine target change speed NtHt and the speed change amount NtH (S700).

[0084] Next, the control device 100 executes the process of S320 described above to calculate the first torque increase speed LTS1 based on the turbine target rate of change NtHt. Next, the control device 100 calculates a second torque increase speed LTS2 based on the acquired speed change amount NtH (S710). The second torque increase speed LTS2 here is the increase speed of the torque converter load torque obtained by converting the speed change amount NtH using an appropriate model formula or the like.

[0085] When the processing of S710 is executed, the control device 100 executes the processing from S340 onwards described above, thereby substituting the larger of the first torque increase speed LTS1 and the second torque increase speed LTS2 as the load torque increase speed LTS.

[0086] Therefore, compared to the case where the smaller of the first torque increase speed LTS1 and the second torque increase speed LTS2 is substituted for the load torque increase speed LTS, in this modified example, the amount of correction to the increasing side of the engine torque through the torque control of the internal combustion engine 10 is increased. Therefore, it is possible to suppress the occurrence of engine stall due to insufficient torque of the internal combustion engine 10 relative to the load torque increase speed LTS.

[0087] When at least one of the above conditions (A), (B), and (C) is satisfied, the control start flag F may be set to ON. The first torque increase speed LTS1, which is the increase speed of the torque converter load torque, is calculated based on the turbine target rate of change NtHt. The increase speed of the torque converter load torque is also calculated based on the hydraulic pressure change amount PatH. The increase speed of the torque converter load torque is also calculated based on the speed change amount NtH. The maximum value of the three calculated increase speeds of the torque converter load torque may then be substituted for the load torque increase speed LTS.

[0088] Although the load torque increase speed LTS is calculated based on the turbine target change speed NtHt, the oil pressure change amount PatH, and the speed change amount NtH, the load torque increase speed LTS may be calculated based on other parameters.

[0089] The process for correcting the FB gain M shown in Fig. 4 may be omitted. Even in this case, effects other than the above (3) can be obtained. The process of setting the shift stop request flag FS to ON shown in FIG. 4 may be omitted. [Explanation of symbols]

[0090] 10...internal combustion engine 40...torque converter 42P...pump impeller 42T...turbine impeller 45...lock-up clutch 50...transmission mechanism 52...friction engagement element 52s...starting engagement element 100...control device 200...automatic transmission 300...shift lever 500...vehicle

Claims

1. A control device for an internal combustion engine mounted on a vehicle, the control device comprising: an automatic transmission including a transmission mechanism having a plurality of friction engagement elements; and a torque converter including a pump impeller connected to an output shaft of an internal combustion engine and a turbine impeller connected to an input shaft of the transmission mechanism; and a shift lever that is operated to switch between a non-driving position and a driving position, the friction engagement elements having a launch engagement element whose operating state is switched from a released state to an engaged state when the shift lever is switched from the non-driving position to the driving position, When the load torque of the turbine impeller resisting the rotation of the pump impeller is defined as a torque converter load torque and the increasing rate of the torque converter load torque is defined as a load torque increasing rate, feedback control is performed on the engine torque generated in the internal combustion engine so that the engine rotation speed of the internal combustion engine becomes a target rotation speed, and when the increasing rate of the load torque is fast, torque control is performed to increase the amount of correction to the increasing side of the engine torque compared to when the increasing rate of the load torque is slow, and A process of acquiring a target time from when the shift lever is switched from a non-driving position to a driving position until when the starting engagement element starts to be engaged; and executing a process for starting the torque control when either one of the following conditions is met: after the shift lever is switched from the non-driving position to the driving position, a change in hydraulic pressure of the hydraulic oil supplied to the starting engagement element is equal to or greater than a predetermined value; and, after the shift lever is switched from the non-driving position to the driving position, the target time has elapsed. Control device for internal combustion engines.

2. A control device for an internal combustion engine mounted on a vehicle, the control device comprising: an automatic transmission including a transmission mechanism having a plurality of friction engagement elements; and a torque converter including a pump impeller connected to an output shaft of an internal combustion engine and a turbine impeller connected to an input shaft of the transmission mechanism; and a shift lever that is operated to switch between a non-driving position and a driving position, the friction engagement elements having a launch engagement element whose operating state is switched from a released state to an engaged state when the shift lever is switched from the non-driving position to the driving position, When the load torque of the turbine impeller resisting the rotation of the pump impeller is defined as a torque converter load torque and the increasing rate of the torque converter load torque is defined as a load torque increasing rate, feedback control is performed on the engine torque generated in the internal combustion engine so that the engine rotation speed of the internal combustion engine becomes a target rotation speed, and when the increasing rate of the load torque is fast, torque control is performed to increase the amount of correction to the increasing side of the engine torque compared to when the increasing rate of the load torque is slow, and A process of acquiring a target time from when the shift lever is switched from a non-driving position to a driving position until when the starting engagement element starts to be engaged; and executing a process of starting the torque control when either one of the following conditions is met: after the shift lever is switched from the non-driving position to the driving position, a change in the rotation speed of the turbine impeller is equal to or greater than a predetermined value; and, after the shift lever is switched from the non-driving position to the driving position, the target time has elapsed. Control device for internal combustion engines.

3. a process of acquiring a target rate of change of the rotational speed of the turbine impeller, and calculating a first torque increase rate, which is an increase rate of the torque converter load torque, based on the target rate of change; a process of calculating a second torque increase rate, which is an increase rate of the torque converter load torque, based on an amount of change in hydraulic pressure supplied to the starting engagement element; and performing a process of setting the load torque increase speed to the increase speed that is larger than the first torque increase speed or the second torque increase speed. The control device for an internal combustion engine according to claim 1 or 2.

4. a process of acquiring a target rate of change of the rotational speed of the turbine impeller, and calculating a first torque increase rate, which is an increase rate of the torque converter load torque, based on the target rate of change; calculating a second torque increase rate, which is an increase rate of the torque converter load torque, based on an amount of change in the rotational speed of the turbine impeller; and performing a process of setting the load torque increase speed to the increase speed that is larger than the first torque increase speed or the second torque increase speed. The control device for an internal combustion engine according to claim 1 or 2.

5. When the rotation speed of the internal combustion engine is equal to or higher than the target rotation speed, a process is executed to suppress the correction of the engine torque to the decreasing side by the torque control. The control device for an internal combustion engine according to claim 1 or 2.

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