JP2008025376A - Control device and control method for power train, program executing the control method, and recording medium recording the program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress engine stall, by setting a recovery rotation speed for halting fuel cut before releasing a lock-up clutch. <P>SOLUTION: In a control device for a power train, an ECU executes a program comprising: a step S102 setting a recovery rotation speed nrtlu in lock-up of a rotation speed recovered from the fuel cut; a step S104 setting a finishing rotation speed ntdced of a threshold value for releasing the lock-up clutch, based on an oil temperature of an automatic transmission; a step S106 setting a coefficient α; a step S110 setting the sum of the finishing rotation speed ntdced and the coefficient α as a final recovery rotation speed nrtluf in lock-up, when the recovery rotation speed nrtlu in lock-up is less than the sum of the finishing rotation speed ntdced and the coefficient α (YES in S108); and a step S116 setting the final recovery rotation speed nrtluf in lock-up as a recovery rotation speed nrt used for the threshold value halting the fuel cut. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power train control device, a control method, a program for executing the control method, and a recording medium on which the program is recorded. In particular, the lockup clutch is engaged and half-engaged during fuel cut. The present invention relates to a technique for controlling a power train in at least one of the states.

  Conventionally, at the time of deceleration of a vehicle using an internal combustion engine as a power source, fuel efficiency is improved by executing fuel cut to stop fuel injection. When the output shaft speed of the internal combustion engine is reduced by executing the fuel cut, the internal combustion engine may stall. Therefore, in a vehicle provided with a torque converter having a lock-up clutch between the internal combustion engine and the transmission, the output shaft of the internal combustion engine is changed to the engaged state or the partially engaged state. It is suppressing that it falls.

  Therefore, it is desirable that the return rotational speed at which the fuel cut is stopped is determined according to the control state of the lockup clutch. In view of this, a technique has been proposed in which the return rotational speed from the fuel cut is set according to the control state of the lockup clutch.

  Japanese Patent Laid-Open No. 2000-320374 (Patent Document 1) discloses that when the engine speed becomes equal to or higher than the fuel cut speed during deceleration operation, the fuel supply to the engine is stopped by fuel cut (fuel cut). After the execution of the above, a fuel injection control device for the engine that releases the fuel cut when the engine speed decreases below the fuel recovery speed (return speed) is disclosed. The fuel injection control device described in Patent Document 1 is a control state of a lockup clutch capable of mechanically directly connecting the input side and the output side of a speed change drive system connected to an output shaft of an engine with a fuel cut speed. A fuel cut rotational speed setting unit that variably sets the fuel recovery rotational speed according to the control state of the lockup clutch. The fuel cut rotation speed and the fuel recovery rotation speed when the lockup clutch is in the slip control state (half-engaged state) are set to the lowest.

According to the fuel injection control device described in this publication, during the deceleration operation, the control state of the lockup clutch that can mechanically directly connect the input side and the output side of the speed change drive system connected to the output shaft of the engine is set. Accordingly, the fuel cut speed is variably set, and when the engine speed exceeds the fuel cut speed, the fuel supply to the engine is stopped by the fuel cut. It is possible to achieve stable convergence of engine rotation by avoiding the above. In addition to the fuel cut speed, the fuel recovery speed is also variably set according to the control state of the lockup clutch, and the fuel cut is released at the fuel recovery speed according to the control state of the lockup clutch. It is possible to promote the optimization and expansion of the fuel cut region while preventing the above.
JP 2000-320374 A

  By the way, when the lockup clutch is engaged or half-engaged during the fuel cut, and the vehicle decelerates rapidly, the output shaft speed of the internal combustion engine can be reduced and the internal combustion engine can stall. . In order to suppress such a stall, when the vehicle speed decreases, the lock-up clutch is released. At this time, in order to suppress the stall, it is desirable that the fuel cut is stopped when the lockup clutch is released. However, in the fuel injection control device described in Japanese Patent Application Laid-Open No. 2000-320374, the return rotational speed from the fuel cut is merely set according to the control state of the lockup clutch. Therefore, when the vehicle suddenly decelerates when the lock-up clutch is engaged or semi-engaged, the output shaft speed of the internal combustion engine is restored to the return speed after the lock-up clutch is released due to the vehicle speed decreasing. It is possible that the fuel cut will be stopped. In such a case, even if the fuel cut is stopped, the output shaft speed of the internal combustion engine may not be increased and the internal combustion engine may stall.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to control a power train capable of suppressing a stall of an internal combustion engine, a control method, and a program and program for executing the control method. Is provided.

  A power train control device according to a first aspect of the present invention controls a power train having a lockup clutch capable of connecting an internal combustion engine and a transmission. The control device includes: means for controlling the internal combustion engine to perform fuel cut while the vehicle is decelerating; and at least one of the engagement state and the semi-engagement state of the lockup clutch during the fuel cut. Means for controlling the lockup clutch so as to be in one of the states, and the internal combustion engine is controlled so as to stop the fuel cut when the output shaft rotational speed of the internal combustion engine is equal to or lower than a predetermined return rotational speed Means for controlling the lockup clutch so that the lockup clutch is released when a predetermined condition is satisfied, and for setting the condition according to the state of the power train First setting means and second setting means for setting the return rotational speed based on the conditions.

  According to the first invention, the internal combustion engine is controlled so that the fuel cut is executed during deceleration of the vehicle. During the fuel cut, the lockup clutch is controlled to be in at least one of an engaged state and a semi-engaged state. The fuel cut is stopped when the output shaft rotational speed of the internal combustion engine is equal to or lower than a predetermined return rotational speed. The lockup clutch is controlled so as to be released when a predetermined condition is satisfied. A condition that must be satisfied to release the lockup clutch is set according to the state of the power train. Based on this condition, a return rotational speed at which the fuel cut is stopped is set. As a result, for example, it is possible to set a return rotational speed such that the fuel cut is stopped before the lockup clutch is released. Therefore, when releasing the lockup clutch, the fuel cut can be stopped. As a result, it is possible to provide a power train control device capable of suppressing the stall of the internal combustion engine.

  In the power train control device according to the second invention, in addition to the configuration of the first invention, the second setting means includes means for resetting the return rotational speed when the conditions change.

  According to the second invention, when the condition for releasing the lockup clutch changes, the return rotational speed is reset. Accordingly, the return rotational speed can be updated in accordance with the condition for bringing the lockup clutch into the released state.

  In the power train control device according to the third invention, in addition to the configuration of the first or second invention, the first setting means includes means for setting conditions according to the oil temperature of the transmission.

  According to the third invention, the condition for releasing the lockup clutch is set according to the oil temperature of the transmission. Thereby, the conditions according to the viscosity of the oil supplied to a transmission can be set. Therefore, a condition for releasing the lockup clutch can be set so that the lockup clutch is released earlier when the viscosity is low than when the viscosity is high. As a result, the release delay of the lockup clutch can be suppressed, and the stall of the internal combustion engine can be suppressed.

  In the power train control device according to the fourth aspect of the invention, in addition to the configuration of the third aspect of the invention, the lockup clutch is provided in the torque converter. The condition is that the turbine speed of the torque converter is lower than a predetermined threshold value. The first setting means includes means for setting a condition by setting a threshold value so as to be higher as the oil temperature of the transmission is lower. The second setting means includes means for setting a value higher than the threshold value as the return rotational speed.

  According to the fourth invention, when the vehicle speed is lower than the threshold value, the lockup clutch is released. As a result, it is possible to suppress the output shaft speed of the internal combustion engine from being lowered and the internal combustion engine from stalling. The threshold value is set to be higher as the oil temperature of the transmission is lower. Thereby, when the viscosity of the oil supplied to the transmission is high and the operation of the lockup clutch is slow, the lockup clutch can be released early. Therefore, it can suppress that the timing released by operation delay is delayed. A value higher than the threshold value is set as the return rotational speed. Thereby, when releasing a lockup clutch, a fuel cut can be stopped. Therefore, stall of the internal combustion engine can be suppressed.

  A power train control method according to a fifth aspect of the invention is a method of controlling a power train having a lockup clutch capable of connecting an internal combustion engine and a transmission. The control method includes a step of controlling the internal combustion engine so as to execute fuel cut during deceleration of the vehicle, and at least one of an engaged state and a semi-engaged state when the lockup clutch is engaged during the fuel cut. A step of controlling the lockup clutch so as to be in a state of, and a step of controlling the internal combustion engine to stop the fuel cut when the output shaft rotational speed of the internal combustion engine is equal to or lower than a predetermined return rotational speed, Controlling the lock-up clutch so that the lock-up clutch is released when a predetermined condition is satisfied, setting a condition according to the state of the power train, and returning based on the condition Setting the number of revolutions.

  According to the fifth aspect of the invention, the internal combustion engine is controlled so that the fuel cut is executed during deceleration of the vehicle. During the fuel cut, the lockup clutch is controlled to be in at least one of an engaged state and a semi-engaged state. The fuel cut is stopped when the output shaft rotational speed of the internal combustion engine is equal to or lower than a predetermined return rotational speed. The lockup clutch is controlled so as to be released when a predetermined condition is satisfied. A condition that must be satisfied to release the lockup clutch is set according to the state of the power train. Based on this condition, a return rotational speed at which the fuel cut is stopped is set. As a result, for example, it is possible to set a return rotational speed such that the fuel cut is stopped before the lockup clutch is released. Therefore, when releasing the lockup clutch, the fuel cut can be stopped. As a result, it is possible to provide a power train control method capable of suppressing the stall of the internal combustion engine.

  In the power train control method according to the sixth invention, in addition to the configuration of the fifth invention, the step of setting the return rotational speed includes the step of resetting the return rotational speed when the condition changes.

  According to the sixth aspect of the invention, when the condition for bringing the lockup clutch into the released state changes, the return rotational speed is reset. Accordingly, the return rotational speed can be updated in accordance with the condition for bringing the lockup clutch into the released state.

  In the power train control method according to the seventh invention, in addition to the configuration of the fifth or sixth invention, the step of setting the condition includes a step of setting the condition according to the oil temperature of the transmission.

  According to the seventh invention, the condition for releasing the lockup clutch is set according to the oil temperature of the transmission. Thereby, the conditions according to the viscosity of the oil supplied to a transmission can be set. Therefore, a condition for releasing the lockup clutch can be set so that the lockup clutch is released earlier when the viscosity is low than when the viscosity is high. As a result, the release delay of the lockup clutch can be suppressed, and the stall of the internal combustion engine can be suppressed.

  In the power train control method according to the eighth aspect of the invention, in addition to the configuration of the seventh aspect of the invention, the lockup clutch is provided in the torque converter. The condition is that the turbine speed of the torque converter is lower than a predetermined threshold value. The step of setting the condition includes the step of setting the condition by setting a threshold value so that the temperature becomes higher as the oil temperature of the transmission is lower. The step of setting the return rotation speed includes the step of setting a value higher than the threshold value as the return rotation speed.

  According to the eighth invention, when the vehicle speed is lower than the threshold value, the lockup clutch is released. As a result, it is possible to suppress the output shaft speed of the internal combustion engine from being lowered and the internal combustion engine from stalling. The threshold value is set to be higher as the oil temperature of the transmission is lower. Thereby, when the viscosity of the oil supplied to the transmission is high and the operation of the lockup clutch is slow, the lockup clutch can be released early. Therefore, it can suppress that the timing released by operation delay is delayed. A value higher than the threshold value is set as the return rotational speed. Thereby, when releasing a lockup clutch, a fuel cut can be stopped. Therefore, stall of the internal combustion engine can be suppressed.

  A program according to a ninth invention is a program for causing a power train control means to execute the control method according to any of the fifth to eighth inventions.

  According to the ninth aspect of the invention, it is possible to provide a program capable of causing a power train control means to execute a power train control method capable of suppressing a stall of an internal combustion engine.

  A recording medium according to a tenth invention is a computer-readable recording medium on which the program of the ninth invention is recorded.

  According to the tenth aspect of the present invention, it is possible to provide a recording medium on which a program capable of causing the power train control means to execute the power train control method capable of suppressing the stall of the internal combustion engine is provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  With reference to FIG. 1, the power train of the vehicle carrying the control apparatus which concerns on embodiment of this invention is demonstrated. The control device according to the present embodiment is realized, for example, by a program stored in a ROM (Read Only Memory) of an ECU (Electronic Control Unit) 1000 shown in FIG.

  As shown in FIG. 1, the power train of this vehicle includes an engine 100, a torque converter 200, an automatic transmission 300, and an ECU 1000.

  The output shaft of engine 100 is connected to the input shaft of torque converter 200. Engine 100 and torque converter 200 are connected by a rotating shaft. Therefore, engine 100 output shaft rotational speed NE (engine rotational speed NE) detected by engine rotational speed sensor 400 and torque converter 200 input shaft rotational speed (pump rotational speed) are the same.

  An auxiliary machine 102 such as an air conditioner compressor, alternator, or oil pump is connected to the output shaft of the engine 100 via a belt or the like. The auxiliary machine 102 is driven by the engine 100.

  The torque converter 200 includes a lockup clutch 210 that directly connects the input shaft and the output shaft, a pump impeller 220 on the input shaft side, a turbine runner 230 on the output shaft side, and a one-way clutch 250, and has a torque amplification function. And a stator 240 that expresses.

  Torque converter 200 and automatic transmission 300 are connected by a rotating shaft. An output shaft rotational speed NT (turbine rotational speed NT) of the torque converter 200 is detected by a turbine rotational speed sensor 410. The output shaft rotational speed NOUT of the automatic transmission 300 is detected by the output shaft rotational speed sensor 420.

  The automatic transmission 300 may be a stepped transmission including a planetary gear unit, or may be a CVT (Continuously Variable Transmission) that changes the gear ratio steplessly.

  The ECU 1000 that controls these power trains has a signal representing the engine speed NE from the engine speed sensor 400, a signal representing the turbine speed NT from the turbine speed sensor 410, and an output shaft from the output shaft speed sensor 420 to the output shaft. A signal representing the rotational speed NOUT is a signal representing the temperature of the cooling water of the engine 100 from the water temperature sensor 430 (hereinafter also referred to as water temperature), and a signal representing the opening of the accelerator pedal 1200 from the accelerator opening sensor 440 A signal representing the temperature of an automatic transmission fluid (ATF) of the automatic transmission (hereinafter also referred to as oil temperature) is input from the temperature sensor 450.

  ECU 1000 detects the vehicle speed based on output shaft speed NOUT. ECU 1000 controls engine 100, lockup clutch 210, automatic transmission 300, and the like based on these signals.

  In the present embodiment, ECU 1000 includes an engine ECU 2000 that controls engine 100 and an ECT (Electronic Controlled Automatic Transmission) _ECU 3000 that controls automatic transmission 300. Engine ECU 2000 and ECT_ECU 3000 are provided so that signals can be transmitted to and received from each other.

  A hydraulic circuit 500 that regulates the hydraulic pressure supplied to the torque converter 200 to control the state of the lockup clutch 210 will be described with reference to FIG. FIG. 2 shows only a part of the hydraulic circuit 500 related to the present invention.

  Hydraulic circuit 500 includes an oil pump 510, a primary regulator valve 520, a secondary regulator valve 530, a solenoid modulator valve 540, and a lockup control valve 550.

  Oil pump 510 is connected to the crankshaft of engine 100. As the crankshaft rotates, the oil pump 510 is driven to suck in ATF stored in the oil pan 512 and generate hydraulic pressure. The hydraulic pressure generated by the oil pump 510 is adjusted by the primary regulator valve 520 to generate a line pressure.

  Excess hydraulic fluid that has flowed out (discharged) from the primary regulator valve 520 flows into the secondary regulator valve 530. Secondary pressure is generated by the secondary regulator valve 530.

  The solenoid modulator valve 540 generates a solenoid modulator pressure using the line pressure as a source pressure. The solenoid modulator pressure is supplied to duty solenoid 560.

  The lock-up control valve 550 supplies the secondary pressure to the engagement side oil chamber (pump impeller 220 side) and the release side oil chamber (a space defined by the lock-up clutch 210 and the converter cover 260) of the torque converter 200. Selectively switch between.

  Lock-up control valve 550 operates using the hydraulic pressure supplied from duty solenoid 560 as a pilot pressure. When the hydraulic pressure is not supplied from the duty solenoid 560 to the lock-up control valve 550, the spool of the lock-up control valve 550 is in the state shown in FIG.

  In this case, the secondary pressure is supplied to the release side oil chamber of the torque converter 200, and the oil pressure of the torque converter 200 engagement side oil chamber is supplied to the oil cooler (not shown). Therefore, lockup clutch 210 is pulled away from converter cover 260, and lockup clutch 210 is released.

  When the hydraulic pressure is supplied from the duty solenoid 560 to the lock-up control valve 550, the spool of the lock-up control valve 550 is in the state shown in (2) in FIG.

  In this case, the secondary pressure is supplied to the engagement side oil chamber of the torque converter 200, and the hydraulic pressure is drained from the release side oil chamber of the torque converter 200. Therefore, lock-up clutch 210 is pressed against converter cover 260 and lock-up clutch 210 is engaged.

  The engagement force of the lockup clutch 210 (the force acting to engage the lockup clutch 210) is a value corresponding to the differential pressure between the hydraulic pressure of the engagement side oil chamber and the release side oil chamber of the torque converter 200. become.

  The differential pressure between the oil pressure in the engagement side oil chamber and the oil pressure in the release side oil chamber of the torque converter 200 becomes a value corresponding to the oil pressure supplied from the duty solenoid 560 to the lockup control valve 550.

  Duty solenoid 560 outputs a pressure corresponding to the indicated duty value transmitted from ECU 1000. The instruction duty value is output so that the differential pressure between the oil pressure in the engagement side oil chamber and the oil pressure in the release side oil chamber of torque converter 200 matches the oil pressure command value set in ECU 1000.

  With reference to FIG. 3, functions of engine ECU 2000 and ECT_ECU 3000 will be described. It should be noted that the functions of engine ECU 2000 and ECT_ECU 3000 described below may be realized by software or hardware.

  Engine ECU 2000 includes a fuel cut execution unit 2002, a fuel cut cancellation unit 2004, and a return rotation speed setting unit 2006. The fuel cut execution unit 2002 determines that the vehicle speed is equal to or higher than a predetermined vehicle speed and the fuel cut execution condition including the condition that the accelerator opening (the opening of the accelerator pedal 1200) is “0” is satisfied. The engine 100 is controlled so as to execute a fuel cut that stops fuel injection from an injector (not shown) at the time of deceleration.

  The fuel cut canceling unit 2004 controls the engine 100 so as to cancel the fuel cut when the engine speed NE decreases to the return speed nrt or less. The return rotation speed setting unit 2006 sets the return rotation speed nrt. A method for setting the return rotation speed nrt will be described later.

  ECT_ECU 3000 includes a flex lockup execution unit 3002, a flex lockup end unit 3004, and an end rotation speed setting unit 3006. The flex lockup execution unit 3002 locks up so as to execute flex lockup (also referred to as slip control) that causes the lockup clutch 210 to be half-engaged and slip when fuel cut is executed during deceleration of the vehicle. The clutch 210 is controlled. The lockup clutch 210 may be engaged.

  The flex lockup execution unit 3002 executes flex lockup when conditions relating to water temperature, oil temperature, vehicle speed, gear ratio, turbine rotation speed, and the like are satisfied. It should be noted that a well-known general condition may be used as a condition to be satisfied in order to execute flex lockup, and therefore further detailed description will not be repeated here.

  The flex lockup end unit 3004 releases the lockup clutch 210 when a predetermined time has elapsed since the fuel cut was stopped, and when the turbine speed NT has dropped below the end speed ntdced. In other words, the lockup clutch 210 is controlled so as to end the flex lockup. End rotation speed setting unit 3006 sets end rotation speed ntdced according to the oil temperature of automatic transmission 300. The end rotation speed ntdced is set based on a map using the oil temperature as a parameter.

  Instead of or in addition to the oil temperature, end rotation speed ntdced may be set according to the load acting on engine 100 by auxiliary machine 102 or the deceleration of the vehicle. End rotation speed ntdced is a threshold value for bringing lockup clutch 210 into a released state.

  With reference to FIG. 4, a control structure of a program executed by ECU 1000 which is the control apparatus according to the present embodiment will be described. The program described below is repeatedly executed at a predetermined cycle.

  In step (hereinafter, step is abbreviated as S) 100, ECU 1000 sets base return rotation speed nrtb, which is the return rotation speed when flex lockup is not being executed. The base return rotation speed nrtb is set to be a value as indicated by a solid line and a broken line in FIG. 5 with the water temperature and the operating state of the auxiliary machine 102 as parameters.

  Returning to FIG. 4, in S102, ECU 1000 sets a lockup return rotation speed nrtlu, which is a return rotation speed when flex lockup is being executed. The return rotation speed nrtlu at the time of lock-up is set to a value as indicated by a solid line and a broken line in FIG. 6 with parameters such as the correction amount of the intake air amount during idle by ISC (Idle Speed Control) and the operation state of the auxiliary machine 102 as parameters. Set to

  Returning to FIG. 4, in S <b> 104, ECU 1000 sets end rotation speed ntdced based on the oil temperature detected using oil temperature sensor 450. The end rotational speed ntdced is set to be higher as the oil temperature is lower. As shown in FIG. 7, if the oil temperature has been warmed up, the end rotational speed ntdced is set to a value lower than the lock-up return rotational speed nrtlu. On the other hand, when the oil temperature is low, the end rotation speed ntdced may be set to a value higher than the lockup return rotation speed nrtlu.

  Returning to FIG. 4, in S <b> 106, ECU 1000 sets coefficient α (α> 0) based on end rotation speed ntdced. The coefficient α is set by a map using the end rotation speed ntdced as a parameter. As shown in FIG. 8, the coefficient α is set to be larger as the end rotational speed ntdced is higher.

  Returning to FIG. 4, in S108, ECU 1000 determines whether or not lock-up return rotation speed nrtlu is smaller than the sum of end rotation speed ntdced and coefficient α. If lockup return rotation speed nrtlu is smaller than the sum of end rotation speed ntdced and coefficient α (YES in S108), the process proceeds to S110. If not (NO in S108), the process proceeds to S112.

  In S110, ECU 1000 sets the final rotation speed ntdced, the coefficient α, and the sum to the final return rotation speed nrtluff upon lockup. In S112, ECU 1000 sets lockup return rotation speed nrtlu to lockup final return rotation speed nrtluf.

  In S114, ECU 1000 determines whether or not flex lockup is being executed. If flex lockup is being executed (YES in S114), the process proceeds to S116. If not (NO in S114), the process proceeds to S118.

  In S116, ECU 1000 sets lock-up-time final return rotational speed nrtluf to return rotational speed nrt used as a threshold value for stopping fuel cut. Thereafter, this process ends. In S118, ECU 1000 sets base return rotational speed nrtb to return rotational speed nrt used as a threshold value for stopping fuel cut. Thereafter, this process ends.

  An operation of ECU 1000 that is the control device according to the present embodiment based on the above-described structure and flowchart will be described.

  While the vehicle is running, a base return speed nrtb, which is a return speed when flex lockup is not executed, is set (S100). Further, the lockup return rotation speed nrtlu, which is the return rotation speed when flex lockup is being executed, is set (S102).

  Further, based on the oil temperature of automatic transmission 300, end rotation speed ntdced, which is a threshold value for releasing lockup clutch 210, is set (S104). A coefficient α is set based on the end rotational speed ntdced (S106).

  Here, it is assumed that return rotation speed nrtlu at the time of lockup is larger than the sum of end rotation speed ntdced and coefficient α (NO in S108). In this case, the lock-up return rotation speed nrtlu is set to the lock-up final return rotation speed nrtluf (S112). If flex lockup is being executed (YES in S114), the final return rotational speed nrtluf at the time of lockup is set to the return rotational speed nrt used as a threshold value for stopping the fuel cut (S116).

  In this state, as shown in FIG. 9, if the vehicle is slowly decelerating, the fuel cut is stopped when the engine speed NE becomes equal to or lower than the return speed at time T (1). When a predetermined time ΔT elapses after the fuel cut is stopped, the lockup clutch 210 is released at time T (2).

  As shown in FIG. 10, if the vehicle is decelerating rapidly, the fuel cut is stopped when the engine speed NE decreases to the return speed at time T (3). If the turbine rotation speed NT becomes equal to or lower than the end rotation speed ntdced at time T (4) before a predetermined time ΔT has elapsed since the fuel cut is stopped, the lockup clutch 210 is released. Thereby, when releasing the lockup clutch 210, the fuel cut can be stopped.

  However, since the oil temperature is low, the lock-up clutch 210 may be released before the fuel cut is canceled in a state where the end rotational speed ntdced is set high. In this case, the engine 100 can stall.

  Therefore, if lock-up return rotation speed nrtlu is smaller than the sum of end rotation speed ntdced and coefficient α (YES in S108), end rotation speed ntdced and coefficient α and the sum are the final return rotation speed nrtluf at lockup. (S110).

  If flex lockup is being executed (YES in S114), the final return rotational speed nrtluff at the time of lockup is set to the return rotational speed nrt used as a threshold value for stopping the fuel cut (S116).

  As a result, when flex lockup is being executed, the return rotational speed from the fuel cut can be made higher than the end rotational speed ntdced as shown in FIG. Therefore, when releasing the lock-up clutch 210, the fuel cut can be stopped in advance. As a result, stall of engine 100 can be suppressed.

  These processes are repeatedly executed at a predetermined cycle. Therefore, if the oil temperature changes and the end rotation speed ntdced changes, the lockup final return rotation speed nrtluff is reset. Thereby, the return rotation speed nrt can be changed in accordance with the change in the end rotation speed ntdced.

  As described above, according to the ECU that is the control device according to the present embodiment, the end rotational speed ntdced for releasing the lockup clutch is set based on the oil temperature of the automatic transmission. A coefficient α is set based on the end rotational speed ntdced. When the lockup return rotation speed nrtlu used when executing the flex lockup is larger than the sum of the end rotation speed ntdced and the coefficient α, the lockup return rotation speed nrtlu is set to the lockup final return rotation speed nrtluf. The When the lockup return rotation speed nrtlu used during the flex lockup is smaller than the sum of the end rotation speed ntdced and the coefficient α, the sum of the end rotation speed ntdced and the coefficient α is the lockup final return rotation speed nrtluf. Set to If the flex lockup is being executed, the final return rotational speed nrtluff at the time of lockup is set to the return rotational speed nrt used as a threshold value for stopping the fuel cut. As a result, when flex lockup is being executed, the return rotation speed nrt from the fuel cut can be made higher than the end rotation speed ntdced for releasing the lockup clutch. Therefore, when releasing the lockup clutch, the fuel cut can be stopped in advance. As a result, engine stall can be suppressed.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic block diagram which shows the power train of the vehicle carrying the control apparatus which concerns on this Embodiment. It is a figure which shows the hydraulic circuit which adjusts the hydraulic pressure supplied to a torque converter in order to control the state of a lockup clutch. It is a functional block diagram of ECU of FIG. It is a flowchart which shows the control structure of the program which ECU which is a control apparatus which concerns on this Embodiment performs. It is a figure which shows base return rotation speed nrtb. It is a figure which shows return rotation speed nrtlu at the time of lockup. It is a figure which shows the relationship between return rotation speed nrtlu at the time of lockup, and completion | finish rotation speed ntdced. It is a figure which shows the relationship between coefficient (alpha) and end rotation speed ntdced. It is a timing chart (the 1) which shows transition of engine speed NE and turbine speed NT. It is a timing chart (the 2) which shows transition of engine speed NE and turbine speed NT. It is a figure which shows return rotation speed nrt and completion | finish rotation speed ntdced.

Explanation of symbols

  100 Engine, 102 Auxiliary machine, 200 Torque converter, 210 Lock-up clutch, 220 Pump impeller, 230 Turbine runner, 240 Stator, 250 one-way clutch, 260 Converter cover, 300 Automatic transmission, 400 Engine speed sensor, 410 Turbine speed Sensor, 420 Output shaft rotational speed sensor, 430 Water temperature sensor, 440 Accelerator opening sensor, 450 Oil temperature sensor, 500 Hydraulic circuit, 510 Oil pump, 512 Oil pan, 520 Primary regulator valve, 530 Secondary regulator valve, 540 Solenoid modulator valve 550 Lock-up control valve, 560 duty solenoid, 1000 ECU, 1200 accelerator pedal, 2000 Engine ECU, 2002 fuel cut execution unit, 2004 the fuel cut suspension part, 2006 return rotational speed setting unit, 3000 ECT_ECU, 3002 flex lock-up execution unit, 3004 flex lock-up end portion, 3006 end rotation number setting unit.

Claims (10)

A control device for a power train having a lock-up clutch capable of connecting an internal combustion engine and a transmission,
Means for controlling the internal combustion engine to perform a fuel cut during deceleration of the vehicle;
Means for controlling the lockup clutch so that the lockup clutch is in at least one of an engaged state and a semi-engaged state during execution of the fuel cut;
Means for controlling the internal combustion engine to stop the fuel cut when the output shaft rotational speed of the internal combustion engine is equal to or lower than a predetermined return rotational speed;
Means for controlling the lock-up clutch such that the lock-up clutch is released when a predetermined condition is satisfied;
First setting means for setting the condition according to the state of the power train;
And a second setting unit configured to set the return rotational speed based on the condition.   2. The power train control device according to claim 1, wherein the second setting unit includes a unit for resetting the return rotation speed when the condition is changed. 3.   The power train control device according to claim 1 or 2, wherein the first setting means includes means for setting the condition in accordance with an oil temperature of the transmission. The lock-up clutch is provided in a torque converter,
The condition is that the turbine speed of the torque converter is lower than a predetermined threshold value,
The first setting means includes means for setting the condition by setting the threshold value so as to become higher as the oil temperature of the transmission is lower,
The power train control device according to claim 3, wherein the second setting means includes means for setting a value higher than the threshold value to the return rotational speed. A control method of a power train having a lockup clutch capable of connecting an internal combustion engine and a transmission,
Controlling the internal combustion engine to perform a fuel cut during deceleration of the vehicle;
Controlling the lockup clutch so that the lockup clutch is in at least one of an engaged state and a semi-engaged state during execution of the fuel cut;
Controlling the internal combustion engine to stop the fuel cut when the output shaft rotational speed of the internal combustion engine is equal to or lower than a predetermined return rotational speed;
Controlling the lock-up clutch so that the lock-up clutch is released when a predetermined condition is satisfied;
Setting the condition according to the state of the power train;
And a step of setting the return rotation speed based on the condition.   The power train control method according to claim 5, wherein the step of setting the return rotational speed includes a step of resetting the return rotational speed when the condition changes.   The power train control method according to claim 5 or 6, wherein the step of setting the condition includes a step of setting the condition according to an oil temperature of the transmission. The lock-up clutch is provided in a torque converter,
The condition is that the turbine speed of the torque converter is lower than a predetermined threshold value,
The step of setting the condition includes the step of setting the condition by setting the threshold value so as to be higher as the oil temperature of the transmission is lower,
The power train control method according to claim 7, wherein the step of setting the return rotational speed includes the step of setting a value higher than the threshold value for the return rotational speed.   The program for making the control means of the said power train perform the control method in any one of Claims 5-8.   A computer-readable recording medium on which the program according to claim 9 is recorded.

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