JP2008045570A - Control device for vehicle having automatic transmission with lockup clutch, control method thereof, program for carrying out this method and recording medium in which the program is recorded - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control a lockup clutch so as to avoid a degradation in drivability and an increase in fuel consumption while preventing a deterioration in clarification of a catalyst. <P>SOLUTION: An ECU executes a program including the step of: (S300) estimating a catalyst temperature THC from an engine cooling water temperature THW and a suction air quantity Q that have been detected by the ECU (S100, S200); (S400) detecting a degree of opening of an accelerator, and (S1000) prohibiting fuel cut when the THC is equal to or above a THC threshold value as well as the accelerator is OFF (YES in S500), and when a gear stage is the highest (YES in S900) so as to prohibit disengagement of the lockup clutch that is ordinarily performed during deceleration. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to control of a vehicle equipped with an automatic transmission equipped with a lock-up clutch, and more particularly to a vehicle that achieves improved fuel efficiency by avoiding deterioration of drivability while avoiding deterioration of an exhaust purification device that purifies exhaust. Regarding control.

In general, an exhaust system of an engine is provided with an exhaust purification device (exhaust purification catalyst, catalytic converter) for purifying a specific component in exhaust gas. As this catalytic converter, a three-way catalytic converter is widely used, which oxidizes carbon monoxide (CO) and unburned hydrocarbons (HC), which are specific three components in the exhaust gas, and nitrogen oxide ( NOx) is reduced and converted into carbon dioxide (CO ₂ ), water vapor (H ₂ O), and nitrogen (N ₂ ).

  The purification characteristics of the three-way catalytic converter depend on the air-fuel ratio of the air-fuel mixture formed in the combustion chamber, and the three-way catalytic converter functions most effectively when it is close to the stoichiometric air-fuel ratio. This is because if the air-fuel ratio is lean and the amount of oxygen in the exhaust gas is large, the oxidizing action becomes active but the reducing action becomes inactive, and if the air-fuel ratio is rich and the amount of oxygen in the exhaust gas is small, On the contrary, the reduction action becomes active, but the oxidation action becomes inactive, and all the above three components cannot be purified well. Therefore, an engine having a three-way catalytic converter is provided with an output linear oxygen sensor in its exhaust passage, and the air-fuel mixture in the combustion chamber is feedback controlled to the stoichiometric air-fuel ratio using the oxygen concentration measured thereby. Yes. Here, when the air-fuel ratio is lean and the amount of oxygen in the exhaust gas is large, the reducing action becomes inactive, the action of reducing nitrogen oxide (NOx) is lowered, and the NOx purification function is lowered.

  In addition, control for stopping the supply of fuel during deceleration, so-called fuel cut control, is applied to the vehicle in order to improve fuel efficiency. This fuel cut control is a control that improves fuel efficiency by reducing the supply of fuel to the engine as much as possible within a range that does not impair driving performance and riding comfort. In general, the supply of fuel is stopped when the engine speed falls within a predetermined range (more than the fuel cut speed) during deceleration while the engine is idling. Specifically, the fuel supply is stopped when the throttle valve is closed during traveling (decelerated traveling) and the engine speed is equal to or higher than the fuel cut speed. Further, when the engine speed decreases and reaches the return speed (fuel cut return speed) that defines the lower limit of the range, the fuel supply is resumed.

  During fuel cut control, fuel injection is stopped, so the air-fuel ratio becomes lean and the NOx purification function is degraded. If fuel is injected after returning from the fuel cut in this state, the NOx purification action in the three-way catalytic converter is reduced, so that NOx cannot be sufficiently purified. Also, if fuel cut control is executed when the temperature of the three-way catalytic converter is high, the catalyst is likely to cause sintering if exposed to an atmosphere with a high temperature and a lean air-fuel ratio and excessive oxygen, thereby The exhaust purification catalyst has a characteristic that the purification capability is easily deteriorated.

  For this reason, if fuel cut is performed under conditions where the temperature of the three-way catalytic converter is high, the catalyst will be exposed to a high-temperature and oxygen-excess atmosphere for a long period of time, which accelerates the deterioration of the purification capability of the three-way catalytic converter. There is a possibility that.

  Japanese Patent Laying-Open No. 2004-116657 (Patent Document 1) discloses an apparatus for suppressing deterioration of an exhaust purification catalyst in a vehicle equipped with an automatic transmission having a lock-up clutch. The catalyst deterioration suppressing device includes an internal combustion engine having a fuel injection valve, an automatic transmission having a lockup clutch, and a lockup clutch when a rotational speed of the internal combustion engine exceeds a predetermined lockup rotational speed. A lockup clutch control unit to be engaged, and a fuel injection stop unit that stops the operation of the fuel injection valve when the internal combustion engine is in a decelerating operation state and the rotational speed of the internal combustion engine is equal to or higher than a predetermined fuel cut execution rotational speed; An exhaust purification catalyst provided in the exhaust system of the internal combustion engine, and a correction unit that increases the lockup rotational speed by a predetermined amount when the internal combustion engine is in a decelerating operation state and the temperature of the exhaust purification catalyst is equal to or higher than a predetermined temperature; Is provided.

  According to this catalyst deterioration suppressing device, when the internal combustion engine is in a decelerating operation state and the temperature of the exhaust purification catalyst is equal to or higher than a predetermined temperature, the lockup rotation speed is increased by a predetermined amount. In this case, since the lockup clutch is released early during the deceleration operation of the internal combustion engine, the speed of decrease in the rotational speed of the internal combustion engine increases (the rotational speed of the internal combustion engine decreases quickly). As described above, when the speed of decrease in the rotational speed of the internal combustion engine is increased, the time required until the rotational speed of the internal combustion engine is decreased to a rotational speed lower than the fuel cut execution rotational speed is shortened. As a result, since the fuel cut execution period is shortened, the period during which the exhaust purification catalyst is exposed to a high-temperature and oxygen-excess atmosphere is shortened, so that deterioration of the exhaust purification catalyst is suppressed.

  Japanese Patent Application Laid-Open No. 2003-207043 (Patent Document 2) discloses a vehicle control system that can suppress deterioration of a catalyst device and that does not complicate control of a transmission due to prohibition of cut-off of fuel supply. An apparatus is disclosed. This vehicle control device is a vehicle provided with an engine and a transmission, a catalyst device for purifying exhaust gas from the engine, and a fuel cut control device that shuts off fuel supplied to the engine during predetermined traveling. A control device for a vehicle that controls the transmission according to the state of the engine, and a catalyst temperature determination unit that determines whether or not the temperature of the catalyst device is higher than a preset determination reference value; When the catalyst temperature determination unit determines that the temperature of the catalyst device is higher than a preset determination reference value, the transmission is controlled so that the fuel cut-off operation by the fuel cut control device is suppressed. And a transmission control unit. This transmission is an automatic transmission to which engine output torque is input via a fluid transmission device with a lock-up clutch, and the transmission control unit changes the engagement or slip engagement region of the lock-up clutch.

According to this vehicle control device, when the catalyst temperature determination unit determines that the temperature of the catalyst device is higher than the predetermined value, the transmission control unit suppresses the fuel cutoff operation by the fuel cut control device. Since the transmission is controlled in such a manner, deterioration of the catalyst device is suppressed, and at the same time, the catalyst device has a higher temperature than that of a conventional control device that uniformly prohibits the fuel cutoff operation when the catalyst device becomes hot. Since the transmission is controlled so that the fuel cut-off operation is sometimes avoided, the execution of the fuel cut-off is reduced or is not executed, so that the control of the transmission is complicated due to the prohibition of the fuel supply cut-off The possibility to do is greatly reduced. At this time, the transmission control unit changes the engagement region or slip engagement region of the lockup clutch. For example, the engagement region or slip engagement region of these lock-up clutches is shifted to the high vehicle speed side, or the engagement or slip engagement is stopped. When the catalyst device is at a high temperature, the engagement region or slip engagement region of the lockup clutch is shifted to the higher vehicle speed side (easily released), or the engagement or slip engagement is stopped (released). By doing so, the engine speed is reduced early, and the fuel cutoff operation by the fuel cut control device is suppressed (fuel injection).
JP 2004-116657 A JP 2003-207043 A

  Any of the above-mentioned patent documents discloses that when the catalyst temperature is high, if the catalyst is exposed to a lean atmosphere by performing fuel cut, the catalyst deterioration may be accelerated. ing. In other words, as a catalyst deterioration suppression control, the lockup clutch is released (the engine is not driven from the drive wheels), and the engine speed is reduced earlier than the fuel cut execution speed, so that the fuel cut is performed. To prevent the fuel cut from being executed.

  Even when the vehicle is decelerating with a high engine load, such as during high-speed driving, the catalyst deterioration suppression control is executed if the catalyst temperature is high, but it is prohibited to engage the lockup clutch depending on the catalyst temperature. (Release) or allow (engagement or slip), fuel cut may or may not be performed. For this reason, the state of the lock-up clutch changes depending on the catalyst temperature, so that the same degree of deceleration is not obtained when the catalyst deterioration suppression control is executed and when it is not executed, the drivability during deceleration is improved. Getting worse. That is, since the driver does not know whether or not the catalyst deterioration suppression control is being executed and the state of the lockup clutch is changed, the vehicle is decelerating in the same way under the same road condition (gradient). In some cases, the feeling of deceleration felt by the driver is different. Furthermore, if engagement of the lock-up clutch is prohibited (released), the engine speed greatly fluctuates after returning from fuel cut (during reacceleration), and drivability during reacceleration deteriorates. At the same time, since the lock-up clutch is released, there is a problem that the efficiency of power transmission from the engine to the automatic transmission is reduced and the fuel consumption is also deteriorated. However, none of the patent documents can solve such a problem.

  The present invention has been made in order to solve the above-described problems, and its object is to provide a lockup clutch that can prevent deterioration of drivability and fuel consumption while preventing deterioration of the catalyst purification action. To provide a control device for a vehicle equipped with an automatic transmission, a control method, a program for realizing the method, and a recording medium on which the program is recorded.

  According to a first aspect of the present invention, a vehicle control apparatus controls a vehicle equipped with an automatic transmission having a lock-up clutch. The control device is configured to detect temperature of a catalyst device for purifying exhaust gas from an internal combustion engine mounted on a vehicle, and supply fuel to the internal combustion engine when a vehicle condition satisfies a predetermined condition. The fuel cut execution means for stopping the engine, the detection means for detecting the gear ratio of the automatic transmission, and the temperature of the catalyst device is equal to or higher than a predetermined temperature and the gear ratio is equal to or lower than the predetermined ratio. And a control means for controlling the fuel cut execution means so as to execute the fuel cut avoidance control for suppressing or prohibiting the fuel cut by the fuel cut execution means even when the vehicle is decelerating. When the fuel cut avoidance control is being executed, the lockup clutch is engaged or slipped, and the As the lock-up clutch is released if the Erukatto avoidance control is not executed, and a lock-up clutch control means for controlling the lock-up clutch. The control method according to the fourth invention has the same requirements as the control device according to the first invention.

  According to the first or fourth invention, when the temperature of the catalyst device is high and the gear ratio is the high speed gear ratio (the gear ratio is small), even if the vehicle is in a decelerating state, fuel cut is suppressed. The fuel cut avoidance control in which fuel is supplied is prohibited. For this reason, it can avoid that a catalyst apparatus is exposed to high temperature and lean atmosphere, and can suppress degradation of a catalytic action. At this time, since the lockup clutch has been released conventionally, when the vehicle is reaccelerated, a delay occurs in the power transmission, and the drivability during the reacceleration deteriorates and the efficiency of the power transmission decreases. And the fuel economy was getting worse. In the present invention, when the fuel cut avoidance control at the high speed side gear ratio is being executed, the lockup clutch is brought into the engaged state or the slip state even during deceleration. For this reason, it is possible to avoid deterioration in drivability and fuel consumption during reacceleration. Further, the fuel cut avoidance control in which such a lockup clutch is engaged or slipped is performed only in the case of a specific high speed side gear ratio (for example, in the case of a 7-speed automatic transmission only at the highest speed gear stage, 7-speed Only), in other cases (in the case of 1-6 speed other than the highest gear), the fuel cut control and the lock-up clutch control are executed in the same manner, so there is a difference in the feeling of deceleration. Can be avoided. As a result, it is possible to provide a vehicle control device equipped with an automatic transmission equipped with a lock-up clutch that can prevent deterioration of drivability and fuel consumption while preventing deterioration of the catalyst purification action.

  In the vehicle control apparatus according to the second aspect of the invention, in addition to the configuration of the first aspect, the lockup clutch control means includes a lockup clutch until the vehicle is reaccelerated when fuel cut avoidance control is being executed. Means for controlling the lock-up clutch to be in either engaged or slipped state. The control method according to the fifth invention has the same requirements as those of the control device according to the second invention.

  According to the second or fifth invention, since the lockup clutch is in an engaged state or a slip state until it is re-accelerated, the power is directly transmitted from the internal combustion engine to the speed change mechanism without a fluid coupling. Therefore, the vehicle can be accelerated quickly at the time of re-acceleration, deterioration of drivability can be avoided, and power transmission efficiency is improved, so that deterioration of fuel consumption can be avoided.

  In the vehicle control apparatus according to the third invention, in addition to the configuration of the first or second invention, the fuel cut execution means has a rotational speed of the internal combustion engine within a predetermined range, and Means are included for stopping fuel supply to the internal combustion engine upon satisfying the condition that the accelerator is off. The control method according to the sixth invention has the same requirements as those of the control device according to the third invention.

  According to the third or sixth aspect of the invention, when the gear ratio is not the high speed side gear ratio (the gear ratio is small), the fuel cut avoidance control is not executed, so the lockup clutch is released and the engine speed is reduced. The time required for the internal combustion engine to decrease to a lower rotational speed than the fuel cut execution rotational speed is shortened by rapidly decreasing (the speed of decrease increases (the rotational speed of the internal combustion engine decreases quickly)). As a result, since the fuel cut execution period is shortened, the period during which the exhaust purification catalyst is exposed to a high-temperature and oxygen-excess atmosphere is shortened, so that deterioration of the exhaust purification catalyst is suppressed.

  A program according to a seventh invention is a program for realizing a control method according to any one of the fourth to sixth inventions by a computer, and the recording medium according to the eighth invention is any one of the fourth to sixth inventions. This is a medium recording a program for realizing the control method according to the invention by a computer.

  According to the seventh or eighth invention, the control method according to any of the fourth to sixth inventions can be realized using a computer (which may be general purpose or dedicated).

  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.

  As shown in FIG. 1, a vehicle equipped with a control device according to the present embodiment includes an engine 150, an intake system 152, an exhaust system 154, an engine ECU (Electronic Control Unit) 100, and an ECT (Electronically Controlled Automatic). Transmission) -ECU 200. The engine 150 transmits power to the drive theory through a stepped 7-speed automatic transmission equipped with a torque converter with a lock-up clutch. Note that the present invention is not limited to a seven-speed automatic transmission. For example, in the case of a stepped transmission, it may be a fifth speed, a sixth speed, an eighth speed, or a continuously variable transmission.

  Intake system 152 includes an intake passage 110, an air cleaner 118, an air flow meter 104, a throttle motor 114, a throttle valve 112, and a throttle position sensor 116.

  The air taken in from the air cleaner 118 passes through the intake passage 110 and flows to the engine 150. A throttle valve 112 is provided in the middle of the intake passage 110. The throttle valve 112 is opened and closed when the throttle motor 114 is operated. At this time, the opening degree of the throttle valve 112 can be detected by the throttle position sensor 116. An air flow meter 104 is provided in the intake passage between the air cleaner 118 and the throttle valve 112, and detects the amount of intake air. The air flow meter 104 transmits an intake air amount signal representing the intake air amount Q to the engine ECU 100.

  Engine 150 includes a cooling water passage 122, a cylinder block 124, an injector 126, a piston 128, a crankshaft 130, a water temperature sensor 106, and a crank position sensor 132.

  The cylinder block 124 is provided with a cylinder corresponding to a specific number (the specific number corresponds to the number of cylinders), and each cylinder is provided with a piston 128. An air-fuel mixture of the fuel injected from the injector 126 and the sucked air is introduced into the combustion chamber above the piston 128 through the intake passage 110 and burned by ignition of a spark plug (not shown). When combustion occurs, the piston 128 is pushed down. At this time, the vertical motion of the piston 128 is converted into a rotational motion of the crankshaft 130 via the crank mechanism. Note that engine speed of engine 150 is detected by engine ECU 100 based on a signal detected by crank position sensor 132.

  A cooling water passage 122 is provided in the cylinder block 124, and the cooling water circulates by the operation of a water pump (not shown). The cooling water in the cooling water passage 122 flows to a radiator (not shown) connected to the cooling water passage 122 and is radiated by a cooling fan (not shown). A water temperature sensor 106 is provided on the cooling water passage 122 and detects the temperature (engine cooling water temperature) THW of the cooling water in the cooling water passage 122. Water temperature sensor 106 transmits a signal indicating detected engine cooling water temperature THW to engine ECU 100.

  Exhaust system 154 includes an exhaust passage 108, a first air-fuel ratio sensor 102A, a second air-fuel ratio sensor 102B, a first three-way catalytic converter 120A, and a second three-way catalytic converter 120B. A first air-fuel ratio sensor 102A is provided on the upstream side of the first three-way catalytic converter 120A, and the second is provided on the downstream side of the first three-way catalytic converter 120A (upstream side of the second three-way catalytic converter 120B). The air-fuel ratio sensor 102B is provided. One three-way catalytic converter may be used.

  The exhaust passage 108 connected to the exhaust side of the engine 150 is connected to the first three-way catalytic converter 120A and the second three-way catalytic converter 120B. That is, the exhaust gas generated by the combustion of the air-fuel mixture in the combustion chamber in the engine 150 first flows into the first three-way catalytic converter 120A. HC and CO contained in the exhaust gas flowing into the first three-way catalytic converter 120A are oxidized in the first three-way catalytic converter 120A. Further, NOx contained in the exhaust gas flowing into the first three-way catalytic converter 120A is reduced in the first three-way catalytic converter 120A. The first three-way catalytic converter 120A is installed in the vicinity of the engine 150, and even when the engine 150 is cold-started, the temperature is quickly raised to exhibit a catalytic function.

  Further, the exhaust gas is sent from the first three-way catalytic converter 120A to the second three-way catalytic converter 120B for the purpose of purifying NOx. The first three-way catalytic converter 120A and the second three-way catalytic converter 120B basically have the same structure and function.

  First air-fuel ratio sensor 102A provided upstream of first three-way catalytic converter 120A, provided downstream of first three-way catalytic converter 120A and upstream of second three-way catalytic converter 120B The second air-fuel ratio sensor 102B thus detected detects the concentration of oxygen contained in the exhaust gas that has passed through the first three-way catalytic converter 120A or the second three-way catalytic converter 120B. By detecting the oxygen concentration, it is possible to detect the so-called air-fuel ratio of the fuel and air contained in the exhaust gas.

  The first air-fuel ratio sensor 102A and the second air-fuel ratio sensor 102B generate a current corresponding to the oxygen concentration in the exhaust gas. This current is converted into a voltage, for example, and input to engine ECU 100. Therefore, the air-fuel ratio of the exhaust gas upstream of the first three-way catalytic converter 120A can be detected from the output signal of the first air-fuel ratio sensor 102A, and the second output signal from the second air-fuel ratio sensor 102B can be detected. The air-fuel ratio of the exhaust gas upstream of the three-way catalytic converter 120B can be detected. The first air-fuel ratio sensor 102A and the second air-fuel ratio sensor 102B generate, for example, a voltage of about 0.1 V when the air-fuel ratio is lean, and a voltage of about 0.9 V when the air-fuel ratio is rich. It is what happens. A value converted into an air-fuel ratio based on these values is compared with an air-fuel ratio threshold value, and air-fuel ratio control by engine ECU 100 is performed.

  The first three-way catalytic converter 120A and the second three-way catalytic converter 120B function to reduce NOx while oxidizing HC and CO when the air-fuel ratio is substantially the stoichiometric air-fuel ratio, that is, simultaneously perform HC, CO, and NOx. Has the function of purifying. In these first three-way catalytic converter 120A and second three-way catalytic converter 120B, if the air-fuel ratio is lean and the amount of oxygen in the exhaust gas is large, the oxidizing action becomes active but the reducing action becomes inactive. If the air-fuel ratio is rich and the amount of oxygen in the exhaust gas is small, the reduction action becomes active, but the oxidation action becomes inactive, and all the above three components cannot be purified well.

  The engine ECU 100 is connected to an accelerator pedal opening sensor that detects an accelerator pedal opening (accelerator pedal opening ACC) operated by the driver.

  As described above, the output from the engine 150 is transmitted to the drive wheels via the 7-speed automatic transmission provided with a torque converter with a lock-up clutch. Engine ECU 100 is communicably connected to ECT-ECU 200 that controls the automatic transmission. Connected to the ECT-ECU 200 are an AT output shaft rotational speed sensor 210 that detects the output shaft rotational speed (AT output shaft rotational speed NOUT) of the automatic transmission, and a lockup clutch hydraulic circuit 220 that controls the lockup clutch. ing. The ECT-ECU 200 controls a hydraulic circuit that controls the engagement state of friction engagement elements (clutch and brake) of an automatic transmission (not shown), and is based on a map defined by the vehicle speed and the throttle opening. Thus, a desired transmission gear stage is realized.

  The lock-up clutch hydraulic circuit 220 increases the engagement pressure of the lock-up clutch so that the lock-up clutch is in an engaged state, a released state, or a slip state intermediate between the engaged state and the released state. Control.

  In the following, engine ECU 100 and ECT-ECU 200 will be described as a single ECU.

  The ECU executes fuel cut control when the accelerator pedal is not depressed and the engine speed NE is higher than a predetermined fuel cut return speed. As a result, fuel injection from the injector 126 is stopped, and fuel consumption and emissions can be improved. When the fuel supply is stopped, the speed of the vehicle decreases, and when the engine speed is lower than the fuel cut return speed, the fuel cut control is stopped to prevent engine stall and fuel injection by the injector 126 is performed. Is resumed. Further, when the driver steps on the accelerator pedal, there is an acceleration request, so the fuel cut control is stopped and fuel injection by the injector 126 is resumed. At this time, the throttle valve 112 is opened according to the opening of the accelerator pedal, and the intake air amount Q increases.

  Further, this ECU injects fuel from the injector 126 to avoid OT (Over Temperature) when the temperature of the first three-way catalytic converter 120A and / or the second three-way catalytic converter 120B is high. Execute. Conventionally, the relationship between the OT control and the fuel cut control is that when the temperature of the first three-way catalytic converter 120A and / or the second three-way catalytic converter 120B is high, the lock-up clutch is released and the engine rotation is performed. The fuel cut control is stopped by making the number lower than the fuel cut return rotational speed at an early stage so that the fuel injection by the injector 126 is resumed. Therefore, the lockup clutch was released. In the control device according to the present embodiment, it is necessary to execute OT control at a specific gear position (the temperature of first three-way catalytic converter 120A and / or second three-way catalytic converter 120B is When the fuel cut control execution condition is satisfied (the engine speed NE is sufficiently high and the accelerator is off), the fuel cut is suppressed or prohibited (fuel cut avoidance control is executed) and the lockup clutch is Engaged or slipped.

  With reference to FIG. 2, a functional block diagram of the control device according to the present embodiment will be described. As shown in FIG. 2, this control device is connected to a catalyst device temperature THC detection unit 10000, a transmission gear stage (gear ratio) detection unit 20000, and an accelerator pedal opening ACC detection unit 30000, and performs fuel control for OT control. A fuel cut avoidance control execution determination unit 40000 that determines whether or not to execute control to avoid the cut, a fuel cut control unit 50000 that is connected to the fuel cut avoidance control execution determination unit 40000 and executes fuel cut, and a lock-up And a lock-up clutch control unit 60000 that controls the state of the clutch (engaged state, slip state, released state).

  The catalyst device temperature THC detection unit 10000 is connected to the engine cooling water temperature THW detection unit 10100 and the intake air amount Q detection unit 10200, and based on the engine cooling water temperature THW and the intake air amount Q, the catalyst device (first three The temperature THC of the original catalytic converter 120A and / or the second three-way catalytic converter 120B) is detected. The temperature of the first three-way catalytic converter 120A and / or the second three-way catalytic converter 120B may be detected by a temperature sensor.

  The transmission gear stage (gear ratio) detecting unit 20000 is connected to the engine speed NE detecting unit 20100 and the AT output shaft speed NOUT detecting unit 20200, and based on the engine speed NE and the AT output shaft speed NOUT, Detect the gear position of the automatic transmission. Note that the shift gear may be detected by a neutral switch provided in the automatic transmission.

  The fuel cut control unit 50000 is connected to the fuel injection mechanism 50100 (control unit of the injector 126), and performs fuel cut so as not to inject fuel from the injector 126. The lock-up clutch control unit 60000 controls the lock-up clutch hydraulic circuit 60100 so that the lock-up clutch is in an engaged state, a slip state, or a released state.

  The control device according to the present embodiment having such a functional block is read from a CPU (Central Processing Unit) and a memory and a memory included in the ECU even in hardware mainly composed of a digital circuit or an analog circuit. It can also be realized by software mainly composed of programs executed by the CPU. In general, it is said that it is advantageous in terms of operation speed when realized by hardware, and advantageous in terms of design change when realized by software. Below, the case where a control apparatus is implement | achieved as software is demonstrated. Note that a recording medium on which such a program is recorded is also an embodiment of the present invention.

  With reference to FIG. 3, a control structure of a program executed by ECU (engine ECU 100 or ECT-ECU 200) will be described. Note that this program is repeatedly executed at a predetermined cycle time.

  In step (hereinafter, step is referred to as S) 100, the ECU detects the engine coolant temperature THW. At this time, the ECU detects the engine cooling water temperature THW based on the signal input from the water temperature sensor 106.

  In S200, the ECU detects an intake air amount Q. At this time, the ECU detects the intake air amount Q based on the intake air amount signal input from the air flow meter 104.

  In S300, the ECU detects catalyst temperature THC. At this time, the ECU estimates the catalyst temperature based on the engine speed NE and the intake air amount Q, thereby obtaining the catalyst temperature THC of the first three-way catalytic converter 120A and / or the second three-way catalytic converter 120B. To detect.

  In S400, the ECU detects the accelerator pedal opening ACC. In S500, the ECU determines whether or not the condition that the catalyst temperature THC is equal to or higher than a THC threshold value (for example, 800 ° C. to 900 ° C.) and the accelerator pedal opening degree ACC is 0% is satisfied. to decide. If catalyst temperature THC is equal to or higher than the THC threshold value and accelerator pedal opening degree ACC is 0% (YES in S500), the process proceeds to S600. If not (NO in S500), the process proceeds to S1200.

  In S600, the ECU detects an engine speed NE. At this time, the ECU detects the rotational speed NE of the engine 150 based on the signal input from the crank position sensor 132.

  In S700, the ECU detects AT output shaft rotation speed NOUT. In S800, the ECU calculates the AT gear stage (gear ratio) based on engine speed NE and AT output shaft speed NOUT. Assuming that the turbine speed NT of the torque converter is the engine speed NE, the gear ratio is calculated as NE / NOUT. The gear stage is calculated based on this gear ratio.

  In S900, the ECU determines whether or not the gear stage is the highest 7th speed. This determination can also be made based on whether or not the gear ratio is equal to or less than the gear ratio threshold corresponding to the highest gear. If the gear stage is the highest 7th speed (YES in S900), the process proceeds to S1000. If not (NO in S900), the process proceeds to S1100.

  In S1000, the ECU prohibits (suppresses or prohibits) fuel cut and prohibits deceleration lockup release. The prohibition of deceleration lock-up release refers to prohibiting the lock-up clutch from being released during traveling with the accelerator off and entering an engaged state or a slip state. Thereafter, this process ends.

  In S1100, the ECU cancels the inhibition (suppression or prohibition) of the fuel cut and releases the deceleration lockup. Deceleration lockup release is to release the lockup clutch while the vehicle is traveling with the accelerator off. Thereafter, this process ends.

  In S1200, the ECU executes the fuel cut when the fuel cut execution condition is satisfied, and performs the deceleration lockup engagement when the engagement condition is satisfied. The deceleration lock-up engagement is to bring the lock-up clutch into an engaged state or a slip state during traveling with the accelerator off. Thereafter, this process ends.

  The operation of the vehicle controlled by the control device according to the present embodiment based on the above structure and flowchart will be described with reference to FIGS.

[When the catalyst temperature is low or the accelerator is not off]
The engine coolant temperature THW is detected (S100), the intake air amount Q is detected (S200), and the accelerator opening ACC is detected (S300). If catalyst temperature THC estimated and detected based on engine coolant temperature THW and intake air amount Q is less than the THC threshold value, or the accelerator opening is not 0% (the accelerator is not off) (in S500) NO), fuel cut is executed based on the fuel cut execution condition, and deceleration lockup control (engagement control or slip control) is executed (S1200).

  In such a case, since the catalyst temperature is not high, it is not necessary to execute control in consideration of deterioration of the catalyst purification action, so that conventional fuel cut control and deceleration lockup control are performed.

[When the catalyst temperature is high and the accelerator is off and not the fastest gear stage]
The catalyst temperature THC estimated and detected based on the engine coolant temperature THW and the intake air amount Q is equal to or higher than the THC threshold value, and the accelerator opening is 0% (accelerator is off) (S500). At YES, the AT gear stage is calculated (S800).

  If the gear stage is not the seventh speed, which is the highest stage (NO in S900), the prohibition of fuel cut is canceled and the lockup clutch is released (S1100).

  In this way, since the same control is performed at the 1st to 6th speeds, a difference in drivability felt by the driver is unlikely to occur. Further, as shown in FIG. 4, although the catalyst temperature is high, the lock-up clutch is released, so even if the fuel cut is executed because the engine speed NE is lowered early, the fuel cut is started early. After returning, fuel is injected from the injector 126. For this reason, the time during which the first three-way catalytic converter 120A and / or the second three-way catalytic converter 120B is exposed to a high temperature and lean atmosphere is shortened, and deterioration of the catalytic action can be avoided.

[When the catalyst temperature is high and the accelerator is off and the gear is at the highest speed]
The catalyst temperature THC estimated and detected based on the engine coolant temperature THW and the intake air amount Q is equal to or higher than the THC threshold value, and the accelerator opening is 0% (accelerator is off) (S500). At YES, the AT gear stage is calculated (S800).

  If the gear is the highest gear (7th gear) (YES in S900), the fuel cut is prohibited (suppressed or prohibited), the release of the lockup clutch is prohibited, and the lockup clutch is engaged or slipped. A state is set (S1000).

  In this way, at the seventh speed, fuel cut is prohibited and fuel is injected from the injector 126. For this reason, the time during which the first three-way catalytic converter 120A and / or the second three-way catalytic converter 120B is exposed to a high temperature and lean atmosphere is shortened, and deterioration of the catalytic action can be avoided. Further, at this time (during fuel cut), the lockup clutch is in an engaged state or a slip state until at least reacceleration. For this reason, the efficiency of power transmission from the engine 150 to the drive wheels at the time of reacceleration is good. For this reason, since the vehicle accelerates quickly, drivability at the time of reacceleration is good. Further, since the power transmission efficiency is good, fuel efficiency is improved.

  FIG. 5 shows changes over time in engine speed NE, vehicle speed, fuel consumption, catalyst temperature, and accelerator opening when such control is performed (fuel cut prohibited and lock-up clutch engaged). Further, for comparison with FIG. 5, changes with time in engine speed NE, vehicle speed, fuel consumption, catalyst temperature, and accelerator opening of the comparative technique (prohibition of fuel cut and release of lockup clutch) are shown.

  5 and 6 are compared, even in the case of the same accelerator opening (C (1) in FIG. 5 and C (2) in FIG. 6), in the case of the present invention shown in FIG. In the case of the comparison technique shown in FIG. 6, the lock-up clutch is released and the efficiency of power transmission is not good, whereas the engagement and the power transmission efficiency are good. For this reason, the fluctuation of the engine speed NE is smaller in A (1) in FIG. 5 than in A (2) in FIG.

  Furthermore, the fuel consumption is less shown in B (1) in FIG. 5 than in B (2) in FIG. Since the lock-up clutch is in the engaged state, the power transmission efficiency is good and the fuel consumption is improved.

  As described above, according to the control device according to the present embodiment, when the catalyst temperature is high and the gear ratio is the highest gear, the fuel cut is suppressed or prohibited even when the vehicle is decelerating. Thus, fuel is supplied and fuel cut is avoided. For this reason, it can avoid that a catalyst apparatus is exposed to high temperature and lean atmosphere, and can suppress degradation of a catalytic action. At this time, even if the vehicle is decelerating, the lockup clutch is not released and is in an engaged state or a slipped state. For this reason, it is possible to avoid deterioration in drivability and fuel consumption during reacceleration.

  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.

1 is a control block diagram of a vehicle on which a control device according to an embodiment of the present invention is mounted. It is a functional block diagram of a control device concerning an embodiment of the invention. It is a flowchart which shows the control structure of the program performed with ECU which is a control apparatus which concerns on embodiment of this invention. It is a figure which shows the content of the process of S1000 of a flowchart, and S1100. It is a timing chart which shows the state of a vehicle at the time of being controlled by ECU which is a control device concerning an embodiment of the invention. It is a timing chart which shows the comparison technique contrasted with FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 Engine ECU, 102A 1st air fuel ratio sensor, 102B 2nd air fuel ratio sensor, 104 Air flow meter, 106 Water temperature sensor, 108 Exhaust passage, 110 Intake passage, 112 Throttle valve, 114 Throttle motor, 116 Throttle position sensor, 118 air cleaner, 120A first three-way catalytic converter, 120B second three-way catalytic converter, 122 cooling water passage, 124 cylinder block, 126 injector, 128 piston, 130 crankshaft, 150 engine, 152 intake system, 154 exhaust system 160 Accelerator pedal opening sensor, 200 ECT-ECU, 210 AT output shaft rotational speed sensor, 220 Lock-up clutch hydraulic circuit.

Claims (8)

A vehicle control device equipped with an automatic transmission with a lock-up clutch,
Temperature detecting means for detecting the temperature of a catalyst device for purifying exhaust gas of an internal combustion engine mounted on the vehicle;
A fuel cut execution means for stopping fuel supply to the internal combustion engine when the vehicle condition satisfies a predetermined condition;
Detecting means for detecting a gear ratio of the automatic transmission;
When the temperature of the catalyst device is equal to or higher than a predetermined temperature and the gear ratio is equal to or lower than a predetermined ratio, fuel cut by the fuel cut execution means is suppressed and prohibited even when the vehicle is in a deceleration state. Control means for controlling the fuel cut execution means so as to execute the fuel cut avoidance control in any of the states,
When the fuel cut avoidance control is being executed, the lockup clutch is engaged or slipped, and when the fuel cut avoidance control is not being executed, the lockup is performed. And a lockup clutch control means for controlling the lockup clutch so that the clutch is released.   When the fuel cut avoidance control is being executed, the lockup clutch control means engages the lockup clutch until it is accelerated again until the lockup clutch is engaged or slipped. The vehicle control device according to claim 1, comprising means for controlling.   The fuel cut execution means includes means for stopping fuel supply to the internal combustion engine when a condition that the rotational speed of the internal combustion engine is within a predetermined range and the accelerator is off is satisfied. The vehicle control device according to claim 1, further comprising: A method for controlling a vehicle equipped with an automatic transmission with a lock-up clutch,
A temperature detecting step for detecting a temperature of a catalyst device for purifying exhaust gas of an internal combustion engine mounted on the vehicle;
A fuel cut execution step for stopping fuel supply to the internal combustion engine when the vehicle condition satisfies a predetermined condition;
A detecting step for detecting a gear ratio of the automatic transmission;
When the temperature of the catalyst device is equal to or higher than a predetermined temperature and the gear ratio is equal to or lower than a predetermined ratio, the fuel cut in the fuel cut execution step is suppressed and prohibited even when the vehicle is in a deceleration state. A control step of controlling the fuel cut execution step so as to execute the fuel cut avoidance control to be in any one of the states,
When the fuel cut avoidance control is being executed, the lockup clutch is engaged or slipped, and when the fuel cut avoidance control is not being executed, the lockup is performed. And a lockup clutch control step of controlling the lockup clutch so that the clutch is released.   In the lockup clutch control step, when the fuel cut avoidance control is being executed, the lockup clutch is engaged so that the lockup clutch is engaged or slipped until it is accelerated again. The vehicle control method according to claim 4, comprising a controlling step.   The fuel cut execution step includes a step of stopping fuel supply to the internal combustion engine when a condition that the rotational speed of the internal combustion engine is within a predetermined range and the accelerator is off is satisfied. The vehicle control method according to claim 4 or 5.   The program which makes a computer implement | achieve the control method in any one of Claims 4-6.   A recording medium recording a program for causing a computer to implement the control method according to claim 4.

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