Controller of vehicle

Abstract

To provide a controller of a vehicle which can avoid, when performing deceleration by a cruise control, fuel cut hunting and prevent deterioration of drivability due to loss of deceleration at the beginning of deceleration.SOLUTION: A controller of a vehicle is given in which: when decelerating a vehicle during execution of a cruise control, when a requested deceleration ratio is a prescribed ratio or more even if requested engine torque is within a prescribed range, and when a lapsed time after the requested engine torque is within the prescribed range is a prescribed time or less, fuel cut is executed. Thereby, when the requested deceleration ratio is the prescribed ratio or more, the fuel cut is temporarily executed at an initial stage of deceleration so that deterioration of deceleration is avoided at the initial stage of deceleration. Thereafter, the fuel cut is prohibited so that fuel cut hunting is avoided.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device that performs cruise control. [Background technology]

[0002] Vehicle control devices are well known that include a cruise control unit that controls an engine connected to drive wheels in a power-transmittable manner and a brake device that applies braking force to the wheels, including the drive wheels, to perform cruise control to adjust vehicle speed. Patent Document 1 discloses an example of such a vehicle control device. Patent Document 1 discloses that, when decelerating a vehicle while cruise control is in operation, a fuel cut is prohibited if the required engine torque is within a predetermined range that is smaller than the minimum engine torque when a fuel cut that stops fuel supply to the engine is not in operation and larger than the engine torque when a fuel cut is in operation. Patent Document 1 also discloses that prohibiting fuel cut avoids fuel cut hunting, which is a state in which the engine is stopped due to fuel cut and then operates at a minimum engine torque, repeatedly in a short period of time, thereby preventing deterioration of drivability associated with fuel cut hunting. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-157932 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the technology described in Patent Document 1, when the required deceleration rate is equal to or greater than a predetermined level, fuel cut is prohibited, which impairs deceleration at the initial stage of deceleration. Furthermore, if deceleration at the initial stage of deceleration is impaired, a large braking force is applied by the brake device in the latter stage of deceleration, which may result in a deterioration in drivability due to strong deceleration.

[0005] The present invention was made against the background of the above circumstances, and its purpose is to provide a vehicle control device that can avoid fuel cut hunting when decelerating in cruise control, while preventing a deterioration in drivability due to a loss of deceleration at the beginning of deceleration. [Means for solving the problem]

[0006] The gist of the first invention is (a) a vehicle control device including a driving control unit that performs cruise control to adjust vehicle speed by controlling an engine connected to drive wheels in a power-transmittable manner and a brake device that applies braking force to wheels including the drive wheels, wherein (b) when decelerating the vehicle while the cruise control is being performed, the driving control unit prohibits fuel cut if the required engine torque required of the engine is within a predetermined range that is smaller than the minimum output engine torque when a fuel cut that stops fuel supply to the engine is not being performed and larger than the engine torque when the fuel cut is being performed, while (c) even if the required engine torque is within the predetermined range, the required deceleration is greater than or equal to a predetermined degree and the elapsed time since the required engine torque entered the predetermined range is less than or equal to a predetermined time. [Effects of the Invention]

[0007] According to the first aspect of the present invention, when decelerating a vehicle while cruise control is being executed, fuel cut is prohibited if the required engine torque is within a predetermined range that is smaller than the minimum output engine torque when fuel cut is not being executed and larger than the engine torque when fuel cut is being executed. On the other hand, when decelerating a vehicle while cruise control is being executed, fuel cut is executed even if the required engine torque is within the predetermined range, if the required deceleration rate is equal to or greater than a predetermined rate and the elapsed time since the required engine torque entered the predetermined range is less than a predetermined time. As a result, when the required deceleration rate is equal to or greater than the predetermined rate, fuel cut is temporarily executed at the beginning of deceleration, preventing loss of deceleration at the beginning of deceleration. Since fuel cut is then prohibited, fuel cut hunting is avoided. Therefore, when decelerating under cruise control, fuel cut hunting can be avoided while preventing deterioration of drivability due to loss of deceleration at the beginning of deceleration. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of a vehicle to which the present invention is applied, and is also a diagram illustrating main parts of control functions and control systems for various controls in the vehicle. [Figure 2] This is a flowchart explaining the main parts of the control operation of the electronic control device, and is a flowchart explaining the control operation to prevent deterioration of drivability due to loss of deceleration at the initial stage of deceleration while avoiding fuel cut hunting during deceleration in cruise control. [Figure 3] FIG. 3 is a diagram illustrating an example of an implementation of S30 in the flowchart of FIG. 2. [Figure 4] 3 is a diagram showing an example of a time chart when the control operation shown in the flowchart of FIG. 2 is executed. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0010] Fig. 1 is a diagram illustrating the schematic configuration of a vehicle 10 to which the present invention is applied, and also illustrates the main parts of the control functions and control systems for various controls in the vehicle 10. In Fig. 1, the vehicle 10 is equipped with an engine 12 that functions as a power source, drive wheels 14, and a power transmission device 16 provided in a power transmission path between the engine 12 and the drive wheels 14.

[0011] The engine 12 is a known internal combustion engine. The engine 12 has an engine control device 50, which is provided in the vehicle 10 and includes an electronic throttle valve, a fuel injection device, an ignition device, etc., and is controlled by an electronic control device 80, which will be described later, to control the engine torque Te of the engine 12.

[0012] The power transmission device 16 includes a torque converter 20 connected to the engine 12, an automatic transmission 22 connected to the torque converter 20, and the like, housed within a case 18, which is a non-rotating member attached to the vehicle body. The power transmission device 16 also includes a propeller shaft 26 connected to a transmission output shaft 24, a differential gear 28 connected to the propeller shaft 26, and a pair of drive shafts 30 connected to the differential gear 28. The transmission output shaft 24 is an output rotating member of the automatic transmission 22. The power transmission device 16 also includes an engine connecting shaft 32 that connects the engine 12 and the torque converter 20. The power transmission device 16 transmits power from the engine 12 to the drive wheels 14 via the torque converter 20, the automatic transmission 22, and the like. The engine 12 is connected to the drive wheels 14 so as to be capable of transmitting power.

[0013] The torque converter 20 is a known fluid-type power transmission device. The torque converter 20 includes a pump wheel 20p connected to an engine connecting shaft 32 and a turbine wheel 20t connected to a transmission input shaft 34. The transmission input shaft 34 is an input rotating member of the automatic transmission 22.

[0014] The automatic transmission 22 is, for example, a known planetary gear type automatic transmission. The automatic transmission 22 is configured to have one of a plurality of gear stages (also synonymous with gear stages) with different gear ratios (also synonymous with gear ratios) γ (= transmission input rotation speed Ni / transmission output rotation speed No). The transmission input rotation speed Ni is the rotation speed of the transmission input shaft 34, and is the input rotation speed of the automatic transmission 22. The transmission output rotation speed No is the rotation speed of the transmission output shaft 24, and is the output rotation speed of the automatic transmission 22.

[0015] The vehicle 10 is equipped with a mechanical oil pump 52 connected to the pump impeller 20p. The oil pump 52 is driven to rotate by the engine 12 and discharges oil FLD, which serves as the source pressure for various hydraulic pressures. The oil FLD discharged by the oil pump 52 is supplied to a hydraulic control circuit 54 provided in the vehicle 10. The hydraulic pressure is the hydraulic pressure of the oil FLD, which is adjusted by the hydraulic control circuit 54 and is used to establish gear stages of the automatic transmission 22.

[0016] The vehicle 10 is equipped with a wheel brake device 56. The wheel brake device 56 includes a brake master cylinder and a cylinder actuator (not shown) that generate brake hydraulic pressure. Each of the wheels WH, including the drive wheels 14 and the driven wheels 15, is equipped with a wheel brake 58. If the vehicle 10 is an all-wheel drive vehicle, the driven wheels are drive wheels. The wheel brake device 56 is a brake device that applies wheel braking force, which is braking force exerted by the wheel brakes 58, to the wheels WH in accordance with a command from an electronic control device 80 (described later). The wheel brake device 56 supplies brake hydraulic pressure to wheel cylinders (not shown) provided in each wheel brake 58 in response to, for example, the driver's depression of the brake pedal. In the wheel brake device 56, under normal conditions, a master cylinder hydraulic pressure corresponding to the brake operation amount Bra generated by the brake master cylinder is supplied to the wheel cylinder as brake hydraulic pressure. On the other hand, in the wheel brake device 56, for example, when the ABS function is activated, constant speed cruise control is performed, follow cruise control is performed, automatic brake control is performed, etc., in order to generate wheel braking force, brake hydraulic pressure of a magnitude corresponding to the wheel braking force required for each control is supplied to the wheel cylinder. The brake operation amount Bra is a signal that corresponds to the brake pedal depression force and indicates the magnitude of the brake pedal depression operation by the driver, i.e., the magnitude of the brake operation.

[0017] The vehicle 10 further includes an electronic control device 80 as a controller including control devices for the vehicle 10 related to the control of the engine 12 and the automatic transmission 22. The electronic control device 80 includes a so-called microcomputer equipped with, for example, a CPU, RAM, ROM, an input / output interface, etc. The CPU executes various controls of the vehicle 10 by performing signal processing in accordance with a program stored in advance in the ROM while utilizing, for example, the temporary storage function of the RAM.

[0018] The electronic control device 80 receives various signals based on detection values from various sensors provided in the vehicle 10. The various sensors include, for example, an engine rotation speed sensor 60, an input rotation speed sensor 62, an output rotation speed sensor 64, an accelerator pedal position sensor 66, a throttle valve position sensor 68, a brake sensor 70, a vehicle surroundings information sensor 72, and a cruise control setting device 74. The various signals include, for example, an engine rotation speed Ne, a transmission input rotation speed Ni, a transmission output rotation speed No, an accelerator pedal position θacc, a throttle valve position θth, a brake-on signal Bon, a brake operation amount Bra, vehicle surroundings information Iard, and cruise control setting information Icru. The engine rotation speed Ne is the rotation speed of the engine 12. The transmission output rotation speed No is the rotation speed corresponding to the vehicle speed V. The accelerator pedal position θacc is the accelerator operation amount by the driver, which indicates the magnitude of the driver's acceleration operation. The throttle valve position θth is the opening of the electronic throttle valve. The brake-on signal Bon is a signal that indicates a state in which the brake pedal for actuating the wheel brake 58 is being operated by the driver.

[0019] The vehicle surroundings information sensor 72 includes at least one of, for example, a lidar, a radar, and an on-board camera, and directly acquires information about the road on which the vehicle is traveling and information about objects present around the vehicle. For example, the vehicle surroundings information sensor 72 detects objects in front of, on the sides of, and behind the vehicle 10, and outputs object information about the detected objects as vehicle surroundings information Iard. The object information includes the distance and direction of the detected object from the vehicle 10. The vehicle surroundings information Iard includes, for example, the inter-vehicle distance D to a vehicle ahead, i.e., a leading vehicle, traveling immediately in front of the vehicle 10.

[0020] The cruise control setting device 74 is a device for selecting cruise control that controls the engine 12 and the wheel brake device 56 to adjust the vehicle speed V so that the vehicle travels at a predetermined target travel state without the need for acceleration or deceleration operations by the driver. Cruise control includes, for example, constant speed travel control and follow-up travel control. Constant speed travel control is travel control that causes the vehicle 10 to travel at a constant target vehicle speed Vt, for example, when there is no preceding vehicle. Follow-up travel control is travel control that causes the vehicle 10 to follow the preceding vehicle at a target inter-vehicle distance Dt, for example. Follow-up travel control is also executed when the preceding vehicle is traveling at a speed less than the target vehicle speed Vt while constant speed travel control is being executed. The target inter-vehicle distance Dt during follow-up travel control is variably set, for example, depending on the vehicle speed V. The cruise control setting device 74 is a device that not only selects cruise control but also sets the target vehicle speed Vt, increases or decreases the target vehicle speed Vt, etc. The cruise control setting device 74 outputs information input by the driver, such as cruise control selection and target vehicle speed Vt, as cruise control setting information Icru.

[0021] The electronic control device 80 outputs various command signals to each device provided in the vehicle 10. The devices include, for example, the engine 12, the hydraulic control circuit 54, and the wheel brake device 56. The various command signals include, for example, an engine control command signal Se, a transmission control command signal Sat, and a brake control command signal Sbra. The engine control command signal Se is a command signal for controlling the engine 12. The transmission control command signal Sat is a command signal for controlling the shifting of the automatic transmission 22, etc. The brake control command signal Sbra is a command signal for controlling the wheel braking force.

[0022] The electronic control unit 80 includes a driving control unit 82 and a transmission control unit 84 in order to realize various controls in the vehicle 10.

[0023] The travel control unit 82 includes an engine control unit 82 a that controls the engine 12 and a brake control unit 82 b that controls the wheel brake device 56 .

[0024] The engine control unit 82a calculates a drive demand amount from the driver for the vehicle 10 by applying the accelerator opening θacc and the vehicle speed V to a drive demand amount map that is determined in advance, for example, experimentally or by design, i.e., a predetermined drive demand amount map. The engine control unit 82a outputs an engine control command signal Se to the engine control device 50 to control the engine 12 so as to obtain a required engine torque Tedem for realizing the drive demand amount, which has been calculated in consideration of transmission loss, auxiliary load, gear ratio γ, etc. During constant speed cruise control, follow-up cruise control, etc., the engine control unit 82a outputs an engine control command signal Se to the engine control device 50 to control the engine 12 so as to obtain a required engine torque Tedem for realizing the drive demand amount required for each control. The required engine torque Tedem is the torque required for the engine 12.

[0025] The brake control unit 82b outputs a brake control command signal Sbra to the wheel brake device 56 to generate a wheel braking force corresponding to the brake operation amount Bra. When the ABS function is activated, constant speed cruise control is performed, follow-up cruise control is performed, the automatic brake function is activated, or the like, the brake control unit 82b outputs a brake control command signal Sbra to the wheel brake device 56 to generate a wheel braking force required for each control.

[0026] The transmission control unit 84 determines whether the automatic transmission 22 should be shifted, for example, using a predetermined shift map, and outputs a transmission control command signal Sat to the hydraulic control circuit 54 to execute shift control of the automatic transmission 22 based on the results of the shift determination.

[0027] The cruise control unit 82 executes cruise control, such as constant speed cruise control and follow-up cruise control.

[0028] In constant speed cruise control, the cruise control unit 82 calculates a drive demand required to make the current vehicle speed Vp follow the target vehicle speed Vt set by the driver. The current vehicle speed Vp is the current vehicle speed V and is synonymous with the vehicle speed V unless otherwise specified. In follow-up cruise control, the cruise control unit 82 calculates a drive demand required for the vehicle 10 to follow the preceding vehicle when the current inter-vehicle distance Dp is the target inter-vehicle distance Dt. The current inter-vehicle distance Dp is the current inter-vehicle distance D and is synonymous with the inter-vehicle distance D unless otherwise specified. The cruise control unit 82 outputs a command to the engine control unit 82a to obtain a required engine torque Tedem that realizes the calculated drive demand. The drive demand in constant speed cruise control is calculated, for example, by feedback control, feedforward control, or the like based on the difference between the current vehicle speed Vp and the target vehicle speed Vt. The drive demand in follow-up cruise control is calculated, for example, by feedback control, feedforward control, or the like based on the difference between the current inter-vehicle distance Dp and the target inter-vehicle distance Dt. In addition, when decelerating the vehicle 10 in cruise control, the driving control unit 82 generates engine braking or generates wheel braking force by the wheel brake device 56 through automatic brake control, thereby realizing a negative driving demand amount.

[0029] The engine control unit 82a generates engine braking by outputting an engine control command signal Se to the engine control device 50 to execute a fuel cut that stops the supply of fuel to the engine 12. When a fuel cut is executed, a negative engine torque Te corresponding to the engine rotation speed Ne is generated by the engine braking. The fuel cut is synonymous with a fuel cut (FC).

[0030] Here, when decelerating the vehicle 10 under cruise control, the required engine torque Tedem may be set within a predetermined range RNGte that is smaller than the minimum output engine torque Tmin and larger than the fuel-cut engine torque Tfc. The minimum output engine torque Tmin is the minimum value within the range of engine torque Te that the engine 12 can output when fuel cut is not being performed, that is, the minimum output engine torque Te when fuel cut is not being performed. The fuel-cut engine torque Tfc is the engine torque Te when fuel cut is being performed. Due to its characteristics, the engine 12 cannot be controlled to an engine torque Te within the predetermined range RNGte. Therefore, when attempting to achieve the required engine torque Tedem within the predetermined range RNGte, the engine 12 is controlled to alternately generate the minimum output engine torque Tmin and the fuel-cut engine torque Tfc, that is, fuel cut hunting occurs, which may deteriorate drivability.

[0031] In response to this, when decelerating the vehicle 10 while cruise control is being executed, the traveling control unit 82 prohibits the engine control unit 82a from cutting fuel if the requested engine torque Tedem is within the predetermined range RNGte.

[0032] Incidentally, when decelerating the vehicle 10 while cruise control is being executed, if fuel cutoff is prohibited when the required engine torque Tedem is within the predetermined range RNGte, the deceleration at the initial stage of deceleration will be insufficient, i.e., the deceleration will be impaired. As a result, the deceleration timing will be delayed, and a large wheel braking force will be applied in the rear by automatic brake control, resulting in strong deceleration, which may result in deterioration of drivability. Note that, in order to suppress shocks associated with fuel cutoff, the engine control unit 82a may gradually reduce the engine torque Te by retarding the ignition timing of the engine 12 when fuel cutoff is initiated. In this case, deceleration occurs due to torque attenuation caused by the ignition timing retard and fuel cutoff. However, if fuel cutoff is prohibited, ignition timing will not be retarded, which may further impair the deceleration at the initial stage of deceleration, further deteriorating drivability.

[0033] Therefore, in order to prevent deterioration of drivability while avoiding fuel cut hunting, the cruise control unit 82 temporarily cuts fuel when a required engine torque Tedem within a predetermined range RNGte occurs while cruise control is being executed. Then, after realizing initial deceleration by engine braking through fuel cut, the cruise control unit 82 prohibits fuel cut. Furthermore, deterioration of drivability due to loss of deceleration at the initial stage of deceleration is more likely to occur the larger the required deceleration ratio EXrsdem. Therefore, the cruise control unit 82 temporarily cuts fuel when the required deceleration ratio EXrsdem is relatively large. The required deceleration ratio EXrsdem is the deceleration ratio EXrs required when decelerating the vehicle 10 while cruise control is being executed. The deceleration ratio EXrs indicates the degree of deceleration of the vehicle 10, i.e., the extent of deceleration of the vehicle 10.

[0034] In other words, when decelerating the vehicle 10 during cruise control, the traveling control unit 82 executes fuel cut if the required deceleration rate EXrsdem is equal to or greater than the predetermined rate EXrsf, even if the required engine torque Tedem is within the predetermined range RNGte, and the elapsed time PS since the required engine torque Tedem entered the predetermined range RNGte is equal to or less than the predetermined time PSf. The predetermined rate EXrsf is a predetermined threshold value for determining, for example, that the required deceleration rate EXrsdem is at a level at which drivability is likely to deteriorate due to a loss of deceleration at the initial stage of deceleration. The predetermined time PSf is a predetermined threshold value for determining, for example, that the vehicle is at the initial stage of deceleration when insufficient deceleration is desired to prevent deterioration of drivability.

[0035] When the vehicle 10 is decelerating during cruise control, the current vehicle speed Vp is made to follow a target vehicle speed Vt, which is lower than the current vehicle speed Vp. Therefore, the vehicle speed difference ΔV (=Vp-Vt) between the current vehicle speed Vp and the target vehicle speed Vt corresponds to the required deceleration rate EXrsdem, and the larger the vehicle speed difference ΔV, the larger the required deceleration rate EXrsdem. The vehicle speed difference ΔV corresponds to the vehicle speed required to reduce the current vehicle speed Vp to the target vehicle speed Vt in cruise control. The cruise control unit 82 determines whether the required deceleration rate EXrsdem is equal to or greater than a predetermined rate EXrsf based on whether the vehicle speed difference ΔV is equal to or greater than a predetermined vehicle speed ΔVf. The predetermined vehicle speed ΔVf is a predetermined threshold value for determining whether the vehicle speed difference ΔV is at a level at which drivability is likely to deteriorate due to a loss of deceleration at the initial stage of deceleration, for example.

[0036] The state in which the vehicle 10 is decelerating during cruise control is a state in which, in follow-up cruise control, the current inter-vehicle distance Dp is made to follow a target inter-vehicle distance Dt, which is longer than the current inter-vehicle distance Dp. Therefore, the inter-vehicle distance difference ΔD (= Dt - Dp) between the target inter-vehicle distance Dt and the current inter-vehicle distance Dp corresponds to the required deceleration rate EXrsdem, and the larger the inter-vehicle distance difference ΔD, the larger the required deceleration rate EXrsdem. The inter-vehicle distance difference ΔD corresponds to the distance by which the current inter-vehicle distance Dp from the preceding vehicle is increased to the target inter-vehicle distance Dt in cruise control. The cruise control unit 82 determines whether the required deceleration rate EXrsdem is equal to or greater than a predetermined degree EXrsf based on whether the inter-vehicle distance difference ΔD is equal to or greater than a predetermined distance ΔDf. The predetermined distance ΔDf is a predetermined threshold value for determining whether the inter-vehicle distance difference ΔD is such that drivability is likely to deteriorate due to a loss of deceleration at the initial stage of deceleration, for example.

[0037] FIG. 2 is a flowchart explaining the main parts of the control operation of the electronic control device 80, which is a flowchart explaining the control operation for preventing deterioration of drivability due to loss of deceleration at the initial stage of deceleration while avoiding fuel cut hunting during deceleration in cruise control, and is executed repeatedly, for example.

[0038] In FIG. 2, each step of the flowchart corresponds to a function of the traveling control unit 82. In step (hereinafter, "step" will be omitted) S10, it is determined whether the required engine torque Tedem is within a predetermined range RNGte that is smaller than the minimum output engine torque Tmin and larger than the fuel cut-off engine torque Tfc. If the determination in S10 is positive, the process proceeds to S20, where the elapsed time PS since the required engine torque Tedem fell within the predetermined range RNGte is counted up. Next, in S30, it is determined whether the required deceleration rate EXrsdem is less than a predetermined rate EXrsf. If the determination in S30 is negative, it is determined in S40 whether the elapsed time PS exceeds a predetermined time PSf. If the determination in S40 is negative, the process proceeds to S50, where fuel cut is executed. On the other hand, if the determination in either S30 or S40 is positive, the fuel cut prohibition flag is set on in S60, whereby fuel cut is prohibited. On the other hand, if the determination in S10 is negative, the process in S70 for when the required engine torque Tedem is within the predetermined range RNGte is not performed. For example, if a fuel cut is being performed, the fuel cut is canceled, and if a fuel cut is prohibited, the fuel cut prohibition flag is turned off.

[0039] Figure 3 is a diagram illustrating an example of an embodiment of S30 in the flowchart of Figure 2. In Figure 3(a), in S30a corresponding to S30 in Figure 2, it is determined whether the required deceleration rate EXrsdem is less than a predetermined rate EXrsf based on whether the vehicle speed difference ΔV (=Vp-Vt) is less than a predetermined vehicle speed ΔVf. In Figure 3(b), in S30b corresponding to S30 in Figure 2, it is determined whether the required deceleration rate EXrsdem is less than a predetermined rate EXrsf based on whether the inter-vehicle distance difference ΔD (=Dt-Dp) is less than a predetermined distance ΔDf.

[0040] FIG. 4 is a diagram showing an example of a time chart when the control operation shown in the flowchart of FIG. 2 is executed. FIG. 4 illustrates an example in which the vehicle 10 is decelerated toward the target vehicle speed Vt while cruise control is being executed. In FIG. 4, time t1 indicates the time when the required engine torque Tedem, which is gradually reduced during deceleration of the vehicle 10, is made smaller than the minimum output engine torque Tmin and is within a predetermined range RNGte. In the comparative example shown by the dashed line, the fuel cut prohibition flag is turned on at time t1, and fuel cut is prohibited. As a result, the deceleration at the initial stage of deceleration is impaired, and the vehicle speed tracking ability to the target vehicle speed Vt is impaired. In addition, in the latter half of deceleration, a large wheel braking force is applied by automatic brake control, resulting in strong deceleration. In contrast, in the present embodiment shown by the solid line, the fuel cut prohibition flag is not turned on and fuel cut is executed from time t1 until the vehicle speed difference ΔV becomes less than the predetermined vehicle speed ΔVf or the elapsed time PS exceeds the predetermined time PSf (see time t1-t2). This prevents the deceleration rate from being impaired in the initial stage of deceleration, improving the vehicle speed's ability to follow the target vehicle speed Vt. Additionally, in the latter stage of deceleration, the peak of the wheel braking force due to the automatic brake control is reduced, resulting in gentle deceleration. When the vehicle speed difference ΔV is less than the predetermined vehicle speed ΔVf or the elapsed time PS exceeds the predetermined time PSf, the fuel cut prohibition flag is turned on, and fuel cut is prohibited (see time t2). This prevents fuel cut hunting.

[0041] As described above, according to this embodiment, when decelerating the vehicle 10 while cruise control is being executed, fuel cut is prohibited if the required engine torque Tedem is within the predetermined range RNGte. On the other hand, when decelerating the vehicle 10 while cruise control is being executed, even if the required engine torque Tedem is within the predetermined range RNGte, fuel cut is executed if the required deceleration rate EXrsdem is equal to or greater than the predetermined rate EXrsf and the elapsed time PS since the required engine torque Tedem entered the predetermined range RNGte is equal to or less than the predetermined time PSf. As a result, when the required deceleration rate EXrsdem is equal to or greater than the predetermined rate EXrsf, fuel cut is temporarily executed at the beginning of deceleration, preventing the loss of deceleration at the beginning of deceleration. Since fuel cut is then prohibited, fuel cut hunting is avoided. Therefore, when deceleration is executed under cruise control, fuel cut hunting can be avoided while preventing deterioration of drivability due to the loss of deceleration at the beginning of deceleration.

[0042] Furthermore, according to this embodiment, it is determined whether the required deceleration rate EXrsdem is equal to or greater than a predetermined rate EXrsf based on whether the vehicle speed difference ΔV is equal to or greater than a predetermined vehicle speed ΔVf. This allows for an appropriate determination of whether the required deceleration rate EXrsdem is equal to or greater than the predetermined rate EXrsf. Furthermore, when the vehicle speed difference ΔV is equal to or greater than the predetermined vehicle speed ΔVf, a temporary fuel cut is executed at the beginning of deceleration, thereby preventing a loss of deceleration at the beginning of deceleration.

[0043] Furthermore, according to this embodiment, it is determined whether the required deceleration rate EXrsdem is equal to or greater than a predetermined rate EXrsf based on whether the inter-vehicle distance difference ΔD is equal to or greater than a predetermined distance ΔDf. This allows for an appropriate determination of whether the required deceleration rate EXrsdem is equal to or greater than the predetermined rate EXrsf. Furthermore, when the inter-vehicle distance difference ΔD is equal to or greater than the predetermined distance ΔDf, a temporary fuel cut is executed at the beginning of deceleration, thereby preventing a loss of deceleration at the beginning of deceleration.

[0044] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the present invention can also be applied to other embodiments.

[0045] For example, in the above-described embodiment, a planetary gear type automatic transmission was exemplified as the automatic transmission 22, but this is not limiting. For example, the automatic transmission 22 may be a known belt type continuously variable transmission or the like. Note that the automatic transmission 22 does not necessarily have to be provided. In short, the present invention can be applied to any control device that performs cruise control that adjusts the vehicle speed V by controlling the engine 12 and the wheel brake device 56.

[0046] It should be noted that the above is merely one embodiment, and the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0047] 10: Vehicle 12: Engine 14: Drive wheel 56: Wheel brake device (brake device) 80: Electronic control device (control device) 82: Travel control unit WH: Wheel

Claims

1. A vehicle control device including a travel control unit that performs cruise control to adjust vehicle speed by controlling an engine coupled to drive wheels in a power-transmittable manner and a brake device that applies braking force to wheels including the drive wheels, The traveling control unit When decelerating the vehicle while the cruise control is being performed, When a required engine torque required of the engine is within a predetermined range that is smaller than the minimum output engine torque when a fuel cut that stops fuel supply to the engine is not executed and is larger than the engine torque when the fuel cut is executed, the fuel cut is prohibited, A vehicle control device characterized in that, even if the required engine torque is within the predetermined range, if the required deceleration is equal to or greater than a predetermined degree and the elapsed time since the required engine torque entered the predetermined range is less than a predetermined time, the fuel cut is executed.

2. 2. The vehicle control device according to claim 1, wherein the driving control unit determines whether the required deceleration is equal to or greater than the predetermined degree based on whether the vehicle speed required to reduce the current vehicle speed to the target vehicle speed in the cruise control is equal to or greater than a predetermined vehicle speed.

3. The vehicle control device according to claim 1 or 2, characterized in that the driving control unit determines whether the required deceleration is equal to or greater than a predetermined degree based on whether the distance by which the current inter-vehicle distance from the preceding vehicle is increased to the target inter-vehicle distance in the cruise control is equal to or greater than a predetermined distance.

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