Vehicle control device

Abstract

To suppress deterioration of drivability when returning from deceleration-time fuel cut control with a large load of accessories.SOLUTION: When returning from deceleration-time fuel cut control at a high load time with a large accessory load, an engine is started by restart of fuel supply and the like while deceleration-time flex control is continued and a lockup clutch is kept in a slip engagement state, and at the same time, torque down control is performed (step S6). Thereby, deceleration G can be maintained appropriately, and when an accelerator is subsequently operated, driving force can be generated quickly with the engine suppressed from racing. Thus, deterioration of drivability at the time when returning from fuel cut control can be suppressed.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a vehicle control device, and more particularly to control when returning from fuel cut control during deceleration. [Background technology]

[0002] Vehicles having an engine that generates power by burning fuel and a disconnecting device that is provided in a power transmission path between the engine and drive wheels and that connects and disconnects the power transmission are widely known. The vehicle described in Patent Document 1 is one example, and for example, a lock-up clutch of a torque converter functions as the disconnecting device. Patent Document 2 describes a vehicle control device that performs fuel cut control during deceleration, in which the disconnecting device stops the fuel supply to the engine while keeping the power transmission path connected when the vehicle decelerates. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-125900 A [Patent Document 2] JP 2010-281347 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the load of the auxiliary equipment driven by the engine power, such as the compressor and alternator of the air conditioner, is large, the load (resistance) of the engine's rotation during fuel cut becomes large, and the deceleration G (acceleration) of the vehicle may become too strong. In this case, for example, it is possible to open the disconnecting device to disconnect the engine from the power transmission path, or to return from the fuel cut control during deceleration and resume the fuel supply to the engine, but this may cause a sense of discomfort due to a sudden decrease in deceleration G and a feeling of free running, or there may be a delay in the response to the generation of driving force when the accelerator is operated afterwards, or the engine speed may increase, which may deteriorate the drivability.

[0005] The present invention has been made against the background of the above circumstances, and its purpose is to suppress the deterioration of drivability when returning from fuel cut control during deceleration when the load on the accessories is large. [Means for solving the problem]

[0006] In order to achieve the above object, the first invention relates to a vehicle having (a) an engine that generates power by burning fuel, accessories driven by the power of the engine, and a disconnecting device that is provided in a power transmission path between the engine and drive wheels and that connects and disconnects the power transmission, (b) a vehicle control device that performs a fuel cut control during deceleration that stops the supply of fuel to the engine while maintaining the power transmission path in a connected state using the disconnecting device when the vehicle is decelerating, and (c) a recovery control unit that determines whether or not a predetermined high load is being applied to the accessories, and when returning from the fuel cut control during deceleration under the high load, resumes the supply of fuel while maintaining the power transmission path in a connected state using the disconnecting device, starts the engine, and performs torque reduction control of the engine. (d) the torque down control is a control for retarding the ignition timing of the engine so as to obtain a torque down amount for obtaining a vehicle deceleration obtained based on an actual vehicle speed from a predetermined relationship between the vehicle deceleration and the vehicle speed under the high load. It is characterized by:

[0007] The second invention is characterized in that, in the vehicle control device of the first invention, when returning from the deceleration fuel cut control during a low load other than the high load, the return control unit cuts off the power transmission path using the disconnecting device and resumes the fuel supply without performing the torque down control to start the engine, and the return control during the low load is performed at a lower vehicle speed than the return control during the high load.

[0008] A third invention is characterized in that, in the vehicle control device of the first or second invention, (a) the disconnecting device is a lock-up clutch of a fluid transmission device provided in the power transmission path, and (b) when the deceleration fuel cut control is performed during deceleration of the vehicle, deceleration flex control is performed to slip-engage the lock-up clutch in order to maintain the power transmission path in a connected state. Effect of the Invention

[0009] In such a vehicle control device, when returning from fuel cut control during deceleration under high load conditions due to heavy load from accessories, the fuel supply is resumed while the power transmission path is kept connected, the engine is started, and torque down control is implemented, so that the deceleration G can be appropriately maintained and, when the accelerator is subsequently operated, driving force can be quickly generated while suppressing engine revs, thereby preventing a deterioration in drivability when fuel cut is returned. In addition, the torque down control retards the ignition timing of the engine so as to obtain a torque down amount for obtaining a vehicle deceleration based on the actual vehicle speed from the predetermined relationship between the vehicle deceleration and vehicle speed under high load, so that when returning from the fuel cut control during deceleration under high load, a front-rear G that provides a moderate sense of deceleration can be obtained.

[0010] In the second invention, when returning from fuel cut control during deceleration when the load is low rather than high, the power transmission path is cut off to isolate the engine as in the conventional case, and fuel supply is resumed to start the engine without performing torque reduction control. Since this return control during low load is performed at a lower vehicle speed than the return control during high load, the same fuel efficiency improvement effect as in the conventional case can be obtained.

[0011] The third invention is a case in which deceleration flex control is performed to slip-engage the lock-up clutch, which is the disconnection device, when the vehicle decelerates, and deceleration fuel cut control is also performed, and by applying the present invention, the effect of suppressing deterioration of drivability when fuel cut is resumed under high load can be appropriately obtained. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram illustrating an example of a vehicle drive device to which the present invention is applied, showing main parts of a control system. [Diagram 2] FIG. 2 is a cross-sectional view illustrating an example of an intake and exhaust system of the engine of FIG. [Diagram 3] 4 is a flowchart illustrating the operation of a return control unit that is functionally provided in the electronic control device of FIG. [Figure 4] 13 is an example of a data map illustrating a relationship between an allowable rotation speed Nefcon and a return rotation speed Nefcoff of the fuel cut control during deceleration and an engine water temperature Tw. [Diagram 5] 1 is an example of a data map illustrating the relationship between the permissible rotation speed Nefcon and the return rotation speed Nefcoff of the fuel cut control during deceleration when the lockup clutch is engaged, and the vehicle speed V. [Figure 6] 4 is an example of a time chart showing changes in vehicle speed V, vehicle longitudinal G, etc. when returning from fuel cut control during deceleration according to the flowchart of FIG. 3 under a high load condition where the load on the auxiliary equipment is large. [Figure 7] 7 is an example of a time chart showing changes in vehicle speed V, engine speed Ne, and vehicle longitudinal G when an accelerator pedal is operated during the return control of FIG. 6. [Figure 8] 4 is a diagram illustrating an example of a change in vehicle longitudinal G with a decrease in vehicle speed V when the return control is performed according to the flowchart of FIG. 3 under high load conditions where the load on the auxiliary devices is large. FIG. [Figure 9]4 is a diagram illustrating an example of a change in vehicle longitudinal G with a decrease in vehicle speed V when the return control is performed according to the flowchart of FIG. 3 at a low load when the load on the auxiliary devices is small. FIG. [Figure 10] FIG. 2 is a diagram illustrating an example of the relationship between vehicle longitudinal G and vehicle speed V that provides an appropriate feeling of deceleration. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention is preferably applied to an engine-driven vehicle equipped with only an engine that generates power by burning fuel as a driving force source for traveling, but may also be applied to a hybrid vehicle equipped with another power source such as an electric motor in addition to the engine. The engine is an internal combustion engine such as a gasoline engine or a diesel engine, and is configured with a fuel injection device that can automatically stop fuel supply by deceleration fuel cut control. The deceleration fuel cut control is performed, for example, on the condition that the engine speed is equal to or higher than a predetermined fuel cut permission speed, and is performed to return from the fuel cut and resume fuel supply when the engine speed falls to or below a predetermined fuel cut return speed that is lower than the permission speed. The fuel cut return speed is a speed at which the engine can be started (rotated under its own power) immediately by resuming fuel supply, and is determined using vehicle conditions such as engine water temperature, vehicle speed, deceleration, load of auxiliary equipment, and operating state of the lock-up clutch as parameters. For engine torque reduction control during return control, retarding of ignition timing is appropriate, but other means such as limiting the amount of intake air can also be adopted.

[0014] The disconnecting device for connecting and disconnecting the power transmission of the power transmission path is suitably a lock-up clutch (direct clutch) provided in a fluid-type power transmission device such as a torque converter, but may be a clutch or brake of a friction engagement type or a synchromesh type provided independently of the fluid-type power transmission device. The lock-up clutch is brought into a slip engagement state in order to suppress a decrease in engine speed and expand the fuel cut region (vehicle speed range) when the vehicle is decelerating during deceleration fuel cut control. The deceleration flex control for bringing the clutch into this slip engagement state is feedback-controlled, for example, by controlling the engagement torque, for example, the differential pressure between the engagement side and the release side, so as to achieve a target slip amount (differential rotation). The deceleration fuel cut control may be performed with the lock-up clutch fully engaged.

[0015] A stepped or continuously variable transmission that changes the gear ratio (= input rotation speed / output rotation speed) stepwise or continuously is provided in the power transmission path as necessary, but if the load on the auxiliary equipment is large when fuel cut control during deceleration is executed, the resistance (engine brake) caused by the entrainment of the engine is large, so that the deceleration G may become too strong when a low-speed gear stage (or gear ratio) with a large gear ratio is selected. For this reason, when the load is high, it is desirable to perform return control accompanied by engine torque reduction control while keeping the disconnecting device connected, when predetermined implementation conditions are met, including the gear stage (or gear ratio) being a specified high-speed gear stage with a smaller gear ratio than the gear stage at which return control is performed at low load. EXAMPLES

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the following embodiments, the drawings are appropriately simplified or modified for the purpose of explanation, and the dimensional ratios, shapes, angles, etc. of each part are not necessarily drawn accurately.

[0017] FIG. 1 is a schematic diagram for explaining an example of a drive device of a vehicle 10 to which the present invention is applied, and is also a diagram showing the main parts of a control system. The drive device of the vehicle 10 includes an engine 12 as a driving force source for running, and the output of the engine 12 is transmitted to left and right drive wheels (rear wheels in this embodiment) 20 via a power transmission path including a torque converter (T / C) 14, an automatic transmission 16, a differential gear device 18, etc. The engine 12 is an internal combustion engine such as a gasoline engine that generates power by burning fuel, and includes a fuel injection device 22 that controls the fuel injection amount, an electronic throttle valve 24 that controls the intake air amount Q, and an ignition timing control device 26 that controls the ignition timing. The fuel injection device 22 controls the fuel injection amount according to a fuel injection control signal Se1 supplied from an electronic control device 70. The electronic throttle valve 24 controls a throttle valve opening θth according to a throttle control signal Se2 supplied from the electronic control device 70, and the intake air amount Q is controlled according to this throttle valve opening θth. The ignition timing control device 26 controls the ignition timing of an ignition device 28 (see FIG. 2) in accordance with an ignition timing control signal Se3 supplied from the electronic control device 70. Auxiliary devices driven by the power of the engine 12, such as an air conditioner compressor 40 and an alternator 42, are mechanically connected to the engine 12 at all times via belts, chains, etc.

[0018] 2 is a cross-sectional view for explaining an example of an intake and exhaust system of the engine 12. In the intake passage 100, in addition to the fuel injection device 22 and the electronic throttle valve 24, an intake air amount sensor 54 for detecting the intake air amount Q, an air cleaner 102, a vacuum sensor 106, etc. are provided. The electronic throttle valve 24 has a valve body 108, a throttle motor 110, etc., and is equipped with a throttle valve opening sensor 56 for detecting the opening degree (throttle valve opening degree) θth of the valve body 108. The exhaust passage 120 is provided with catalysts 122, 124, an air-fuel ratio sensor 126, an oxygen sensor 128, etc., and an EGR (Exhaust-Gas Recirculation) passage 130 is provided between the exhaust passage 120 and the intake passage 100. The EGR passage 130 is for returning a part of the exhaust gas to the intake passage 100 for re-burning, and an EGR cooler 132 and an EGR valve 134 are provided in the EGR passage 130. In addition, the cylinder section 140 of the engine 12 is provided with an engine speed sensor 58 which detects the rotation of the crankshaft 142, i.e., the engine speed Ne, an engine water temperature sensor 64 which detects the engine water temperature Tw, which is the temperature of the engine cooling water, and a knock sensor 144. The cylinder head section is provided with an igniter 28 together with intake and exhaust valves.

[0019] Returning to Fig. 1, the torque converter 14 includes a pump wheel connected to the crankshaft 142 of the engine 12, a turbine wheel connected to the input shaft of the automatic transmission 16, and a stator, and transmits power between the pump wheel and the turbine wheel via a fluid, and also includes a lock-up (L / U) clutch 30 that directly connects the pump wheel and the turbine wheel. The lock-up clutch 30 is a hydraulic friction clutch that is frictionally engaged in response to a lock-up differential pressure ΔPlu, which is the hydraulic pressure difference between the hydraulic pressure in an engagement-side oil chamber and the hydraulic pressure in a release-side oil chamber. When the lock-up clutch 30 is fully engaged so as to prevent relative rotation, the pump wheel and the turbine wheel rotate together, and the rotation of the crankshaft 142 is directly transmitted to the automatic transmission 16. When the hydraulic pressure in the release-side oil chamber is increased, the pump wheel and the turbine wheel are allowed to rotate relative to each other, and power is transmitted exclusively via a fluid. In addition, by feedback-controlling the lock-up differential pressure ΔPlu so as to engage in a predetermined slip state, it is possible to perform flex control to rotate the turbine wheel and the pump wheel at a predetermined slip amount (differential rotation) ΔNlu, such as 50 rpm. The lock-up differential pressure ΔPlu is adjusted by controlling the electromagnetic pressure regulating valve and the electromagnetic switching valve of the hydraulic control circuit 32 according to the lock-up control signal Slu output from the electronic control device 70, and the lock-up clutch 30 is switched to any one of a fully engaged state, a slip engaged state, and an open state. The fully engaged state and the slip engaged state are collectively called lock-up ON (L / UON), and the power transmission path is in a connected state, and the open state is called lock-up OFF (L / UOFF), and the power transmission path is in a disconnected state. The torque converter 14 is a fluid-type power transmission device, and the lock-up clutch 30 is a disconnecting device that connects and disconnects the power transmission.

[0020] The automatic transmission 16 is a planetary gear type stepped transmission capable of establishing multiple gears with different gear ratios (=input rotation speed / output rotation speed), and for example, five forward gears and one reverse gear are established according to the engagement states of multiple clutches and brakes. The engagement and release states of the multiple clutches and brakes are switched by switching the manual valves of the hydraulic control circuit 32 according to a selection range such as PRND using a shift lever or the like, and by controlling the electromagnetic pressure regulating valves, electromagnetic switching valves, etc. of the hydraulic control circuit 32 according to a shift control signal Sat output from the electronic control device 70.

[0021] The vehicle 10 is provided with an electronic control device 70 as a control device for controlling the engine 12, the automatic transmission 16, etc. The electronic control device 70 is configured to include a so-called microcomputer equipped with a CPU, RAM, ROM, an input / output interface, etc., and the CPU performs signal processing according to a program previously stored in the ROM while utilizing the temporary storage function of the RAM, thereby executing output control of the engine 12, shift control of the automatic transmission 16, engagement / disengagement control of the lock-up clutch 30, etc. The electronic control device 70 functionally includes an engine control unit 72, a shift control unit 80, and a lock-up clutch (L / U clutch) control unit 90. The electronic control device 70 may be provided separately for engine control, shift control, lock-up clutch control, etc., as necessary.

[0022] The electronic control device 70 receives signals representing various information required for control, such as the accelerator pedal 50 operation amount (accelerator operation amount) Acc, the intake air amount Q of the engine 12, the opening degree (throttle valve opening degree) θth of the electronic throttle valve 24, the engine speed Ne which is the rotation speed of the crankshaft 142, the turbine speed Nt which is the output speed of the torque converter 14, the vehicle speed V, and the engine water temperature Tw which is the temperature of the engine coolant, from, for example, the accelerator operation amount sensor 52, the intake air amount sensor 54, the throttle valve opening sensor 56, the engine speed sensor 58, the turbine speed sensor 60, the vehicle speed sensor 62, and the engine water temperature sensor 64. The accelerator operation amount Acc corresponds to the output required by the driver. The turbine speed Nt corresponds to the rotation speed (input speed) Nin of the input shaft of the automatic transmission 16. The vehicle speed V corresponds to the rotation speed (output speed) Nout of the output shaft of the automatic transmission 16. The electronic control device 70 is also supplied with signals indicating the presence or absence of operation and the operating state (load) of the auxiliary devices, the compressor 40 and the alternator 42. The vacuum sensor 106, the air-fuel ratio sensor 126, the oxygen sensor 128, and the knock sensor 144 shown in Fig. 2 also supply their respective detection signals to the electronic control device 70. On the other hand, the electronic control device 70 outputs a fuel injection control signal Se1, a throttle control signal Se2, and an ignition timing control signal Se3 as engine control signals for controlling the operation of the engine 12, as well as a shift control signal Sat for hydraulic control related to shifting and the like of the automatic transmission 16, a lock-up control signal Slu for switching the engaged / disengaged state of the lock-up clutch 30, and the like.

[0023] The engine control unit 72 basically controls the output of the engine 12 by outputting a fuel injection control signal Se1, a throttle control signal Se2, and an ignition timing control signal Se3 based on the accelerator operation amount Acc, the vehicle speed V, etc. The engine control unit 72 also functionally includes a deceleration fuel cut (F / C) control unit 74, which performs deceleration fuel cut control to stop the fuel supply to the engine 12 during coast deceleration in forward running where the accelerator operation amount Acc is approximately 0 and the vehicle is coasting with the accelerator OFF, thereby stopping the engine 12 from rotating under its own power and improving fuel efficiency. This deceleration fuel cut control is performed based on the engine speed Ne, the vehicle speed V, etc., and is started when the engine speed Ne is equal to or higher than a predetermined fuel cut permission speed Nefcon, and when the engine speed Ne becomes equal to or lower than a predetermined fuel cut return speed Nefcoff, the return control unit 76 resumes the fuel supply to the engine 12 and starts the engine 12.

[0024] The fuel cut permission speed Nefcon and the fuel cut return speed Nefcoff may be the same, but it is desirable to provide a predetermined hysteresis so that Nefcon > Nefcoff. For example, as shown in FIG. 4, the engine water temperature Tw is set as a parameter depending on whether the lockup clutch 30 is ON (fully engaged, slipping engaged) or OFF (disengaged). In FIG. 4, when the lockup clutch 30 is OFF (L / UOFF), the fuel cut permission speed Nefcon is variably set in the range of about 2000 rpm to 3500 rpm depending on the engine water temperature Tw, and the fuel cut return speed Nefcoff is variably set in the range of about 1000 rpm to 2500 rpm depending on the engine water temperature Tw. Also, when the lockup clutch 30 is ON (L / UON), the fuel cut permission speed Nefcon is set to about 1000 rpm regardless of the engine water temperature Tw, and the fuel cut return speed Nefcoff is set to about 900 rpm regardless of the engine water temperature Tw.

[0025] Also, when the lock-up clutch 30 is ON, the vehicle speed V is used as a parameter to switch, as shown in Fig. 5, for example, and the fuel cutoff permission speed Nefcoff is set to about 1000 rpm at vehicle speeds higher than a predetermined switching vehicle speed Vfcon (about 30 km / h in Fig. 5), and is set to about 2500 rpm when the vehicle speed falls below the switching vehicle speed Vfcon. The fuel cutoff return speed Nefcoff is changed according to the magnitude of the auxiliary load Faux. That is, when the auxiliary load Faux is large, the vehicle speed is switched at the switching vehicle speed Vfcoff ≒ 30 km / h as shown by the solid line in Fig. 5, and is set to about 900 rpm at vehicle speeds higher than the switching vehicle speed Vfcoff, and is set to about 1400 rpm when the vehicle speed falls below the switching vehicle speed Vfcoff. Also, when the auxiliary load Faux is small, as shown by the dashed line in Fig. 5, the switching speed is set at a switching speed Vfcoff ≈ 20km / h, and at a vehicle speed higher than the switching speed Vfcoff, the switching speed is set to about 900rpm, and at a vehicle speed lower than the switching speed Vfcoff, the switching speed is set to about 1400rpm. The auxiliary load Faux is the load on the compressor 40 and the alternator 42, which are auxiliary devices, and when the air conditioner is ON and the compressor 40 is in operation, or when the electrical load of the alternator 42 is equal to or greater than a predetermined judgment value, the auxiliary load Faux is set to be large. In Fig. 5, the switching speed Vfcoff is changed in two stages depending on the magnitude of the auxiliary load Faux, but the switching speed Vfcoff may be changed in multiple stages of three or more stages or continuously depending on the magnitude of the auxiliary load Faux. The switching speed Vfcon of the fuel cut permission rotation speed Nefcon may also be changed depending on the auxiliary load Faux. It is also possible to change the fuel cut permission speed Nefcon and the fuel cut return speed Nefcoff up or down depending on the auxiliary load Faux.

[0026] Returning to FIG. 1, the shift control unit 80 performs a shift decision according to a shift map (shift conditions) that is determined in advance using vehicle conditions such as the vehicle speed V and accelerator operation amount Acc as parameters, and automatically changes the gear of the automatic transmission 16 by outputting a shift control signal Sat as necessary. Specifically, the multiple forward gears are shifted to a lower gear with a larger gear ratio as the vehicle speed V decreases, and even during coast deceleration with the accelerator OFF and the accelerator operation amount Acc being approximately 0, the gears are sequentially shifted from a higher gear to a lower gear as the vehicle speed V decreases. In addition, the shift control signal Sat is output in accordance with a shift request by the driver using a shift lever or the like, thereby performing a manual shift that switches the gear of the automatic transmission 16. During the shift, a torque down command or the like for the engine 12 is output to the engine control unit 72 as necessary to temporarily reduce the engine torque by retarding the ignition timing or the like.

[0027] The lockup clutch control unit 90 controls the switching of the operating state of the lockup clutch 30, and switches the lockup clutch 30 to one of a fully engaged state, a slipping engaged state, and an open state by controlling the lockup differential pressure ΔPlu according to the lockup control signal Slu. For example, the lockup clutch control unit 90 uses a predetermined relationship (lockup region diagram) having a lockup fully engaged region, a slipping engaged region, and a lockup off region as parameters, such as the vehicle speed V and the throttle valve opening θth, to determine whether the lockup clutch 30 is in the lockup fully engaged region, the slipping engaged region, or the lockup off region according to the actual vehicle speed V and the throttle valve opening θth, etc. Then, the lockup clutch control unit 90 outputs a lockup control signal Slu for controlling the lockup differential pressure ΔPlu to the hydraulic control circuit 32 so that the lockup clutch 30 is in an operating state corresponding to the determined region. That is, the lockup clutch 30 is in a fully engaged state in the lockup fully engaged region, in a slipping engaged region, and in an open state in the lockup off region.

[0028] The lockup clutch control unit 90 is functionally equipped with a deceleration flex control unit 92, and executes deceleration flex control that outputs a lockup control signal Slu for placing the lockup clutch 30 in a predetermined slip engagement state during coasting deceleration in forward travel in which the accelerator operation amount Acc is approximately 0. When the lockup clutch 30 is slip-engaged during coasting deceleration in this manner, a reverse input from the drive wheel side is transmitted to the engine 12 side, and the engine speed Ne is raised to the vicinity of the turbine speed Nt, so that the application range (vehicle speed range) of the deceleration fuel cut control by the deceleration fuel cut control unit 74 is expanded, improving fuel economy. This deceleration flex control is executed in cooperation with the deceleration fuel cut control by the deceleration fuel cut control unit 74, and when the engine speed Ne reaches the vicinity of the fuel cut return speed Nefcoff or when a sudden stop of the vehicle is determined, the deceleration flex control is stopped to avoid engine stall, and the lockup clutch 30 is placed in a released state.

[0029] Next, a specific description will be given of the return control by the return control unit 76 provided in the engine control unit 72. The return control by the return control unit 76 is executed in accordance with steps S1 to S11 (hereinafter, steps will be omitted and simply referred to as S1 to S11) in the flowchart of Fig. 3. In this flowchart, YES in the decision steps indicated by diamonds means affirmative, and NO means negative.

[0030] 3, it is determined whether or not a predetermined return control execution condition is satisfied, and if the return control execution condition is satisfied, the return control from S2 onwards is executed, but if the return control execution condition is not satisfied, the process ends. The return control execution condition is, for example, when all of the following conditions are satisfied: the accelerator operation amount Acc is approximately 0, i.e., the accelerator is OFF, the deceleration flex control unit 92 is executing deceleration flex control, and the deceleration fuel cut control unit 74 is executing deceleration fuel cut control.

[0031] In S2, it is determined whether the engine speed Ne is equal to or lower than the fuel cut return speed Nefcoff, and if Ne ≦ Nefcoff, S3 and subsequent steps are executed, but if Ne > Nefcoff, S11 is executed and the deceleration fuel cut control accompanied by the deceleration flex control is continued. The fuel cut return speed Nefcoff is variably set according to the data maps in Figures 4 and 5 based on the vehicle speed V, engine water temperature Tw, lock-up conditions, etc., and here, the fuel cut return speed Nefcoff when the auxiliary load Faux is large as shown by the solid line in Figure 5 is used.

[0032] In S3, which is executed when the determination in S2 is YES, it is determined whether the auxiliary load Faux is large or not, and if the auxiliary load Faux is large or not, that is, the air conditioner is ON and the compressor 40 is in operation, or the electrical load of the alternator 42 is equal to or greater than a predetermined determination value, S4 and subsequent steps are executed. If the auxiliary load Faux is small or not, that is, the air conditioner is OFF and the compressor 40 is not in operation, and the electrical load of the alternator 42 is lower than a predetermined determination value, S9 is executed to determine whether the vehicle speed V is equal to or less than a predetermined lock-up slip lower limit vehicle speed Vlu1. The lockup slip lower limit vehicle speed Vlu1 at this time is set to a vehicle speed equivalent to the switching vehicle speed Vfcoff (approximately 20km / h in FIG. 5) of the fuel cut return speed Nefcoff when the auxiliary load Faux is small, and if the determination in S9 is NO, i.e., V>Vlu1, the above-mentioned S11 is executed to continue the fuel cut control during deceleration. If the determination in S9 is YES, i.e., V≦Vlu1, S10 is executed to perform return control to restart fuel supply and start the engine 12, and the lockup clutch 30 is released to prevent engine stall. The lockup slip lower limit vehicle speed Vlu1 corresponds to a return judgment vehicle speed at which the deceleration fuel cut control is returned to when the load is low, and when the load is low, the return control in S10 is performed when the automatic transmission 16 is in a low gear such as second gear. The release of the lock-up clutch 30 is executed by the lock-up clutch control section 90 by outputting a command to the lock-up clutch control section 90 to stop the deceleration flex control by the deceleration flex control section 92, or the like.

[0033] In S4, which is executed when the determination in S3 is YES, it is determined whether the vehicle speed V is equal to or lower than a predetermined lock-up slip lower limit vehicle speed Vlu2. The lock-up slip lower limit vehicle speed Vlu2 at this time is set to a vehicle speed equivalent to the switching vehicle speed Vfcoff (approximately 30 km / h in FIG. 5) of the fuel cut return speed Nefcoff when the auxiliary load Faux is large, for example. If the determination in S4 is NO, i.e., V>Vlu2, the above-mentioned S11 is executed to continue the fuel cut control during deceleration. If the determination in S4 is YES, i.e., V≦Vlu2, S5 is executed to determine whether the implementation condition of the "flex control + torque down control during deceleration" is satisfied. The implementation condition is, for example, when all of the following conditions (1) to (5) are satisfied, S6 is executed when the implementation condition of S5 is satisfied, but if the implementation condition of S5 is not satisfied, the above-mentioned S10 is executed to perform the return control to start the engine 12 and release the lock-up clutch 30. (1) Vehicle speed V is within the torque down range (for example, 20km / h to 40km / h). (2) The engine speed Ne is equal to or higher than a predetermined speed (e.g., the target idle speed + 50 rpm). (3) The gear stage of the automatic transmission 16 is a predetermined gear stage (for example, the fourth gear stage or the third gear stage). (4) The engine speed Ne is not dropping rapidly (for example, below -20 rpm / 8 ms). (5) The engine water temperature Tw is equal to or higher than a predetermined water temperature (e.g., 70°C).

[0034] In S6, which is executed when the implementation condition of S5 is satisfied, a return control is performed to start the engine 12 by restarting the fuel supply while continuing the deceleration flex control of the lock-up clutch 30, and the engine torque is reduced from the normal level by retarding the ignition timing, thereby performing "deceleration flex control + torque down control". The amount of torque down at this time is determined based on the vehicle speed V and the ISC (Idle Speed ​​Control) required torque for each gear, so that an appropriate deceleration feeling can be obtained by the entrainment of the engine 12, for example, as shown in Fig. 10. Specifically, the vehicle longitudinal G is set to -0.2 m / s when the vehicle speed V is in the range of about 20 km / h to 30 km / h, so that an appropriate deceleration feeling can be obtained based on a predetermined relationship between the vehicle longitudinal G and the vehicle speed V. 2 ~-0.3m / s 2 The lock-up slip lower limit vehicle speed Vlu2 in S4 corresponds to the return judgment vehicle speed at which the deceleration fuel cut control is returned to under high load conditions, and is set to a higher vehicle speed than the lock-up slip lower limit vehicle speed Vlu1 under low load conditions in S9. As a result, under high load conditions, the return control in S6 is performed in a higher gear position with a smaller gear ratio than under low load conditions, such as fourth gear position or third gear position.

[0035] In the next S7, it is determined whether the conditions for performing "flex control during deceleration + torque down control" are not satisfied. For example, the conditions for performing S5 can be used as they are as they are, but different conditions can also be set. If the conditions for performing the control are satisfied, that is, if the determination in S7 is NO, the control in S6 is repeatedly executed, whereas if the conditions for performing the control are not satisfied, for example, if the vehicle speed V drops below 20 km / h and the determination in S7 is YES, S8 is executed. In S8, the torque down control of the engine 12 is prohibited, the ignition timing is returned to normal, and the lockup clutch 30 is released to prevent engine stall. The release of the lockup clutch 30 is executed by the lockup clutch control unit 90 by outputting a command to the lockup clutch control unit 90 to stop the flex control during deceleration by the deceleration flex control unit 92.

[0036] FIG. 6 is an example of a time chart showing changes in vehicle speed V and vehicle longitudinal G when returning from fuel cut control during deceleration under high load conditions where the auxiliary load Faux is large. The solid line indicates the case of this embodiment in which return control is performed according to the flowchart of FIG. 3. In FIG. 6, time t1 is the time when the determinations of S3, S4, and S5 are all YES, and return control by "flex control during deceleration + torque down control" of S6 is started, and the fuel cut instruction flag becomes OFF, indicating return from fuel cut control during deceleration. As a result, the engine 12 is started by fuel supply while continuing the flex control during deceleration of the lock-up clutch 30, and the torque of the engine 12 is reduced below normal by torque down control by retarding the ignition timing, and the vehicle longitudinal G becomes -0.2 m / s. 2 ~-0.3m / s 2 In Fig. 6, the vehicle longitudinal G momentarily increases when the engine 12 is started (immediately after time t1), but this can be suppressed by adding vibration damping control.

[0037] In contrast, the dashed line in the vehicle longitudinal G column in Fig. 6 represents the case of a conventional device in which return control is executed according to S9 to S11 in Fig. 3 regardless of the magnitude of the auxiliary load Faux, and the normal deceleration fuel cut control and deceleration flex control in S11 are continued until the vehicle speed V falls below the lock-up slip lower limit vehicle speed Vlu1 (for example, about 20 km / h). In this case, the auxiliary load Faux is large, so the load (resistance) caused by the co-rotation of the engine 12 is large, and coupled with the downshift, the vehicle longitudinal G becomes -0.6 m / s 2 If the acceleration / deceleration force becomes too strong, the driver may feel uncomfortable.

[0038] On the other hand, the dashed lines in the vehicle speed V and vehicle longitudinal G columns in FIG. 6 indicate a case where, in order to prevent the deceleration G from becoming too strong, it is determined in S3 whether or not the load is high, and if the result is YES, S4 is executed, and when the vehicle speed V falls below the lock-up slip lower limit vehicle speed Vlu2 (for example, about 30 km / h), the return control in S10 is executed. In this case, the lock-up clutch 30 is released and the engine 12 is separated from the power transmission path, so that resistance (engine brake) due to the entrainment of the engine 12 is not obtained, and the vehicle longitudinal G increases (deceleration G decreases), and there is a possibility that the driver feels uncomfortable due to a sudden decrease in deceleration G and a feeling of free running. In this embodiment, in order to suppress this change in the vehicle longitudinal G, the return control by the "flex control during deceleration + torque down control" in S6 is executed, and when the vehicle longitudinal G decreases to the value indicated by the arrow α (for example, 0.2 m / s 2 The speed is reduced by only a small amount, resulting in a moderate feeling of deceleration.

[0039] Fig. 7 is an example of a time chart showing changes in vehicle speed V, engine speed Ne, and vehicle longitudinal G when the accelerator is operated during return control after time t1 in Fig. 6, i.e., during execution of "flex control during deceleration + torque down control" in S6 of the flowchart in Fig. 3, under high load conditions where the auxiliary load Faux is large. The solid line in Fig. 7 represents the case of this embodiment in which return control is performed using "flex control during deceleration + torque down control" in S6, and the dashed line represents the case in which normal return control in S10 is performed when the vehicle speed V falls below the lock-up slip lower limit vehicle speed Vlu2 (for example, about 30 km / h) under high load conditions, similar to the dashed line in Fig. 6.

[0040] At time t2 in Fig. 7, the accelerator pedal 50 is depressed, and in this embodiment shown by the solid line, the lock-up clutch 30 is slip-engaged by the deceleration flex control, so that the engine 12 is prevented from racing and the vehicle longitudinal G increases quickly, resulting in excellent driving force response. In contrast, in the case of normal return control shown by the dashed line, the lock-up clutch 30 is released, so the engine 12 revs up and the increase in the vehicle longitudinal G is delayed, resulting in poor driving force response. In other words, according to this embodiment, the rise in the engine speed Ne is prevented as shown by the arrow β, and the rise in the vehicle longitudinal G is accelerated by about 200 ms as shown by the arrow γ.

[0041] Fig. 8 is a diagram showing an example of the change in vehicle longitudinal G with a decrease in vehicle speed V when returning from fuel cut control during deceleration under high load conditions where the auxiliary load Faux is large, and the solid line shows the case of this embodiment in which return control is performed according to the flowchart of Fig. 3. In this case, by performing return control by "flex control during deceleration + torque down control" in S6 in Fig. 3, the vehicle longitudinal G is -0.2 m / s as shown in the "F / C return + L / U flex + torque down" region in Fig. 8. 2 ~-0.3m / s 2The broken line in Fig. 8 indicates the case where normal return control of S10 is performed when the vehicle speed V becomes equal to or lower than the lock-up slip lower limit vehicle speed Vlu2, as in the broken line in Fig. 6, and the vehicle longitudinal G suddenly increases (deceleration G suddenly decreases), causing a feeling of free running. Note that the "F / C+L / U flex" region in Fig. 8 is the region where the fuel cut control during deceleration of S11 in Fig. 3 is performed, and the "L / U release+torque down prohibited" region is the region where S8 in Fig. 3 is performed.

[0042] Fig. 9 is a diagram illustrating the change in vehicle longitudinal G with a decrease in vehicle speed V when the return control is performed according to the flowchart of Fig. 3 at a low load when the auxiliary load Faux is small, and the same return control as in the past is performed. That is, when the vehicle speed V becomes equal to or lower than the lock-up slip lower limit vehicle speed Vlu1 and the determination in S9 becomes YES, the normal return control in S10 is performed, so that the fuel cut control during deceleration is performed to a lower vehicle speed compared to when the load is high, and the same fuel efficiency improvement effect as in the past is obtained. Note that the "F / C+L / U flex" region in Fig. 9 is the region where the fuel cut control during deceleration in S11 in Fig. 3 is performed, and the "F / C return+L / U release" region is the region where the normal return control in S10 in Fig. 3 is performed.

[0043] In this manner, in the electronic control device 70 of the vehicle 10 of this embodiment, when returning from the fuel cut control during deceleration under high load conditions where the auxiliary load Faux is large, the flex control during deceleration is continued to hold the lock-up clutch 30 in the slipping engagement state, fuel supply and the like are resumed to start the engine 12, and torque down control is also implemented (S6). This makes it possible to appropriately maintain the deceleration G, and during the subsequent accelerator operation, it is possible to quickly generate driving force while suppressing the increase in the engine speed Ne, thereby suppressing deterioration of drivability when returning from the fuel cut.

[0044] When returning from the fuel cut control during deceleration under a low load other than the high load, the lock-up clutch 30 is released to separate the engine 12 from the power transmission path as in the conventional method, and the fuel supply is resumed without performing the torque reduction control to start the engine 12 (S10). In this case, the return control under the low load is performed at a lower vehicle speed than the return control under the high load, so that the same fuel economy improvement effect as in the conventional method can be obtained.

[0045] Although the embodiment of the present invention has been described in detail above with reference to the drawings, this is merely one embodiment, and the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0046] 10: Vehicle 12: Engine 14: Torque converter (fluid transmission device) 20: Drive wheels 30: Lock-up clutch (disconnecting device) 40: Compressor (auxiliary device) 42: Alternator (auxiliary device) 70: Electronic control device (control device) 74: Fuel cut control unit during deceleration 76: Recovery control unit 92: Flex control unit during deceleration

Claims

1. A vehicle having an engine that generates power by burning fuel, accessories that are driven by the power of the engine, and a disconnecting device that is provided in a power transmission path between the engine and drive wheels and that connects and disconnects the power transmission, A control device for a vehicle that performs a fuel cut control during deceleration in which the power transmission path is maintained in a connected state by the disconnecting device while fuel supply to the engine is stopped during deceleration of the vehicle, a recovery control unit that determines whether a load caused by the auxiliary devices is large as determined in advance, and when the deceleration fuel cut control is resumed under the high load, restarts the fuel supply while keeping the power transmission path connected by the disconnecting device, starts the engine, and performs a torque reduction control of the engine, The torque down control is a control for retarding the ignition timing of the engine so as to obtain a torque down amount for obtaining a vehicle deceleration obtained based on an actual vehicle speed from a predetermined relationship between the vehicle deceleration and the vehicle speed under the high load. A vehicle control device comprising:

2. When returning from the deceleration fuel cut control during a low load other than the high load, the return control unit cuts off the power transmission path using the disconnecting device, restarts the fuel supply without performing the torque down control, and starts the engine, and the return control during the low load is performed at a lower vehicle speed than the return control during the high load.

2. The vehicle control device according to claim 1.

3. The disconnecting device is a lock-up clutch of a hydrodynamic power transmission device provided in the power transmission path, When the fuel cut control during deceleration is performed during the deceleration of the vehicle, a flex control during deceleration is performed to slip-engage the lock-up clutch in order to maintain the power transmission path in a connected state.

3. The vehicle control device according to claim 1 or 2.

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