JP2020157894A - Vehicle control device - Google Patents

Abstract

To provide a vehicle control device which can easily perform sharp turn faithful to intention of a driver.SOLUTION: A vehicle control device comprises: a rear wheel brake control part which can control a rear wheel brake force independently from a front wheel brake force of a vehicle; a sharp turn request detection part which detects a driver's sharp turn request; and a behavior control part which generates a brake power difference between the left and right front wheels of the vehicle to give a yaw moment to a vehicle body. According to this vehicle control device, the rear wheel brake control part increases the rear wheel brake force so as to generate wheel lock according to detection of the sharp turn request, and the behavior control part performs sharp turn control for giving a yaw moment in a direction of increasing a yaw rate of the vehicle body.SELECTED DRAWING: Figure 6

Description

The present invention relates to a vehicle control device provided in an automobile such as a passenger car and controlling the behavior of the vehicle when turning.

When driving on a curved road (tight corner) with a small radius of curvature in sports driving or competition driving by automobile, the manual brake (side brake / parking brake) is used at the same time as the vehicle body yaw is generated by the steering operation. A technique (side brake turn) is known in which the wheels are locked and the vehicle is intentionally put into spin mode to generate a sudden yaw behavior of the vehicle body and make a sharp turn.
As a conventional technique relating to control on the vehicle side when performing such a side brake turn, for example, Patent Document 1 states that when a spin turn using a parking brake is performed, the slip of the front wheels, which are the driving wheels, becomes excessive. It is stated that the slip control to prevent this is stopped.

Further, in recent vehicles, a behavior control device is provided which controls the braking force of the brakes of each wheel individually to generate a difference in braking force between the inner and outer wheels of turning and gives an arbitrary yaw rate to the vehicle body. ..
As a conventional technique relating to such a behavior control device, for example, Patent Document 2 describes a behavior in which the turning performance of a vehicle is improved when the additional steering operation performed by the driver during turning braking of the vehicle is active steering. It is described that control is performed.

Japanese Unexamined Patent Publication No. 63-192644 Japanese Unexamined Patent Publication No. 2015-182516

Conventionally, in order to perform a spin turn using a parking brake, the rear wheels are locked in a short time after the yaw behavior of the vehicle body is sufficiently generated by the steering operation by the driver and the operation of the foot brake (service brake). It was necessary to operate with a strong force to make it work.
That is, if the rear wheels are locked when sufficient yaw behavior is not obtained, or if the side brakes are not sufficiently operated even if the yaw behavior is sufficient and the rear wheels cannot be locked, the vehicle Did not enter spin mode, and as a result of not being able to make the sharp turn intended by the driver, it was sometimes impossible to trace the line intended by the driver.
For this reason, in order to properly perform a spin turn using a parking brake, a high degree of skill and physical strength have been required in the past.

On the other hand, if a behavior control device as described in Patent Document 2 is used, it becomes easy to increase the yaw rate at the initial stage of turning to generate sufficient yaw behavior, but after that, the rear wheels are locked to lock the vehicle. When trying to enter the spin mode, the existing behavior control recognizes that it is an abnormal oversteer behavior and generates a yaw moment in the recovery direction (yaw rate reduction direction), so it is still faithful to the driver's intention. There was a problem that it was not possible to make a sharp turn.
In view of the above-mentioned problems, an object of the present invention is to provide a vehicle control device capable of easily performing a sharp turn faithful to the intention of the driver.

The present invention solves the above-mentioned problems by the following solutions.
The invention according to claim 1 is a rear wheel braking control unit that can control the braking force of the rear wheels of the vehicle independently of the braking force of the front wheels by an actuator, and a sharp turning request detecting unit that detects a sharp turning request of the driver. A vehicle control device including a behavior control unit that generates a controlling driving force difference between the left and right front wheels of the vehicle and gives a yaw moment to the vehicle body, and the rear wheel braking control in response to the detection of the sharp turning request. The unit is characterized in that the braking force of the rear wheels is increased so that the wheels are locked, and the behavior control unit performs a sharp turning control that gives the difference in the controlling driving force in the direction of increasing the yaw rate of the vehicle body. It is a vehicle control device.
According to this, the vehicle is put into spin mode by locking the rear wheels in response to a sharp turn request, the yaw rate is rapidly increased, and the yaw moment in the direction of increasing the yaw rate of the vehicle body is generated by the behavior control. As a result, when the driver intends to make a sharp turn, a high yaw rate sharp turn (so-called spin turn) accompanied by the behavior of the spin mode can be easily performed.

The invention according to claim 2 is the vehicle control device according to claim 1, wherein the sharp turn request detection unit detects the sharp turn request in response to a sharp turn request operation by a driver.
According to this, by starting the sharp turn control according to the operation of the driver, it is possible to perform the sharp turn faithfully to the intention of the driver.

According to the third aspect of the present invention, the sharp turn request detection unit detects the sharp turn request when at least one of the steering angle, steering speed, yaw rate, and turning centripetal acceleration at the initial stage of turning of the vehicle exceeds a predetermined threshold value. The vehicle control device according to claim 1, wherein the vehicle control device is characterized by the above.
According to this, the sharp turn control is automatically started in response to the driving operation recognized that the driver intends to make a sharp turn, so that the driver can make a sharp turn faithfully to the driver's intention with the minimum operation. It can be carried out.

The invention according to claim 4 includes a selection operation unit in which the user can select a first traveling mode in which the sharp turning control is permitted and a second traveling mode in which the sharp turning control is prohibited. The vehicle control device according to any one of claims 1 to 3, which is characteristic.
According to this, when the second traveling mode is selected, the sharp turning control is prohibited, so that it is possible to prevent an unintended sharp turning due to an erroneous operation of the driver or the like.

The invention according to claim 5 is the invention according to claim 1, wherein the end operation detection unit for detecting the end operation of the turning state by the driver is provided, and the sharp turning control is terminated in response to the detection of the end operation. Item 5. The vehicle control device according to any one of items up to item 4.
The vehicle control device according to claim 6, wherein the end operation detection unit detects the end operation based on a decrease in the steering angle.
6. The invention according to claim 6 is characterized in that the behavior control unit increases the reduction speed of the control driving force difference in response to an increase in steering speed when the steering angle decreases. The vehicle control device described.
The vehicle control device according to claim 8, wherein the end operation detection unit detects the end operation in response to an increase in the accelerator operation amount by the driver.
The vehicle control device according to claim 8, wherein the behavior control unit increases the rate of decrease of the control driving force difference according to the rate of increase of the accelerator operation amount. Is.
According to each of these inventions, the sharp turn control can be appropriately and automatically terminated by simple control, and the vehicle state can be shifted to the state of escaping the sharp curve portion.
Further, according to the inventions according to claims 7 and 9, a decrease in the driving force difference that generates an oversteer-prone yaw moment in response to an increase in the operation speed of the end operation that is a factor for determining the end of the turning state. By increasing the speed, it is possible to recover from a sharp turning state that is faithful to the driver's intention (whether the recovery from the sharp turning state is performed rapidly or slowly).

The invention according to claim 10 includes a clutch control unit for controlling the connection and disconnection of a clutch provided between the engine and a power transmission mechanism, and the clutch control unit responds to the start of the sharp turning control. The vehicle control device according to any one of claims 1 to 9, wherein the clutch is engaged in response to the termination of the sharp turning control.
According to this, in the sharp turning control, the clutch is disengaged when the rear wheels are locked, and a series of operations for connecting the clutch according to the end of the sharp turning control can be automated, and the burden on the driver can be reduced.
According to an eleventh aspect of the present invention, the clutch control unit increases the engagement force when connecting the clutch at the end of the sharp turning control, and the reduction speed of the control driving force difference increases. The vehicle control device according to claim 10, wherein the speed is increased.
According to this, the clutch connection operation can be automatically performed according to the recovery speed from the sudden turning state intended by the driver.

According to a twelfth aspect of the present invention, the behavior control unit controls the rear wheels when at least one of the accelerator operation amount, the accelerator operation speed, and the steering angle at the end of the sharp turning control is equal to or more than a predetermined threshold value. The vehicle control device according to any one of claims 1 to 11, wherein the suppression control of the oversteer behavior of the vehicle after the power is reduced is limited.
According to this, when the driver intends to maintain the turning state by, for example, power oversteer (for example, transition to steady circular turning) even after the end of the sharp turning control, it is possible to perform appropriate vehicle attitude control.

The invention according to claim 13 includes a transfer clutch control unit that controls a transfer clutch that restrains a difference in rotational speed between the front wheel drive force transmission mechanism and the rear wheel drive force transmission mechanism of the vehicle, and the transfer clutch control unit is the said. The vehicle control device according to any one of claims 1 to 12, wherein the transfer clutch is maintained in an released state during execution of the sharp turn control.
According to this, by releasing the transfer clutch when locking the rear wheels in the sharp turning control, the torque input from the front wheels to the rear wheels prevents the rear wheels from locking, and the four wheels are simultaneously locked. Locking It is possible to prevent falling into a cascade lock state.

As described above, according to the present invention, it is possible to provide a vehicle control device capable of easily performing a sharp turn faithful to the intention of the driver.

It is a block diagram which shows typically the structure of the vehicle which has 1st Embodiment of the vehicle control device to which this invention is applied. It is a flowchart which shows the operation at the time of a sharp turn in the vehicle control device of 1st Embodiment. It is a figure which shows an example of the vehicle state transition at the time of a sharp turn in the vehicle which has the vehicle control device of the comparative example of this invention. It is a figure which shows an example of the vehicle behavior transition at the time of a sharp turn in the vehicle which has the vehicle control device of the comparative example. It is a figure which shows an example of the vehicle state transition at the time of a sharp turn in the vehicle which has the vehicle control device of 1st Embodiment. It is a figure which shows an example of the vehicle behavior transition at the time of a sharp turn in the vehicle which has the vehicle control device of 1st Embodiment. It is a block diagram which shows typically the structure of the vehicle which has the 2nd Embodiment of the vehicle control device to which this invention is applied. It is a figure which shows an example of the vehicle state transition at the time of a sharp turn in the vehicle which has the vehicle control device of 2nd Embodiment. It is a flowchart which shows the operation at the time of a sharp turn in the 3rd Embodiment of the vehicle control device to which this invention is applied.

<First Embodiment>
Hereinafter, the first embodiment of the vehicle control device to which the present invention is applied will be described.
The vehicle control device of the first embodiment is provided in, for example, a four-wheeled automobile such as a passenger car having wheels on the front, rear, left and right.
In addition, the vehicle is provided with a four-wheel drive (AWD) driving force transmission mechanism in which the output of the engine is transmitted to the front wheels and the rear wheels.
In the first embodiment, the vehicle is equipped with a manual transmission in which the transmission is changed and the clutch is operated by the operation of the driver.
FIG. 1 is a block diagram schematically showing a configuration of a vehicle having the vehicle control device of the first embodiment.
The vehicle includes an engine control unit 10, an AWD control unit 20, an electric power steering control unit 30, a behavior control unit 40, a master cylinder 50, a hydraulic unit 60, and the like.

The engine control unit 10 is a device that comprehensively controls the engine, which is a power source for traveling the vehicle, and its accessories.
An accelerator pedal sensor 11 is connected to the engine control unit 10.
The accelerator pedal sensor 11 detects an operation amount (accelerator opening degree) of an accelerator pedal (not shown) for which the driver inputs an accelerator operation (acceleration request operation).
The engine control unit 10 sets the driver required torque based on the accelerator opening degree, and performs output control so that the actual output torque of the engine 10 matches the driver required torque.
The output of the engine is transmitted to each wheel via a manual transmission and an AWD transfer (not shown).
A clutch (not shown) that is disengaged in response to a disengagement operation by the driver is provided between the engine and the manual transmission.

The AWD control unit 20 controls a transfer clutch 21 provided on the AWD transfer that transmits the output of the transmission mechanism to the drive systems of the front wheels and the rear wheels.
The transfer clutch 21 has a restrained state that constrains the rotational speed difference between the power transmission mechanism on the front wheel side and the power transmission mechanism on the rear wheel side, and an open state that allows the rotational speed difference, for example, a hydraulic or electromagnetic wet type. It can be switched using a multi-plate clutch or the like.

The electric power steering control unit 30 is provided in the steering device of the vehicle and comprehensively controls the electric power steering (EPS) device and its accessories that assist the steering operation by the driver.
A steering angle sensor 31 is connected to the electric power steering control unit 30.
The steering angle sensor 31 detects the steering angle (steering angle) of the current vehicle by detecting, for example, the rotation angle position of the steering shaft.

The behavior control unit 40 performs, for example, behavior stabilization control, anti-lock brake control, dynamic parking brake control, and the like.
The behavior stabilization control generates a yaw moment in the direction of suppressing (recovering) the behavior by generating a difference in braking force between the inner and outer wheels of the vehicle when oversteer behavior or understeer behavior occurs in the vehicle.
The anti-lock brake control is intended to recover the rotation by periodically reducing the wheel cylinder hydraulic pressure of the wheel when the wheel lock (stopping the rotation of the wheel) occurs due to the braking force.
In the dynamic parking brake control, when the parking brake switch 42 is operated while the vehicle is running, hydraulic pressure is applied to the wheel cylinders of each wheel to generate a braking force.

A mode selection switch 41, a parking brake switch 42, a yaw rate sensor 43, a lateral G sensor 44, a vehicle speed sensor 45, and the like are connected to the behavior control unit 40.
The mode selection switch 41 inputs an operation for selecting a control mode for vehicle body behavior control (behavior stabilization control, etc.) in the behavior control switch from a plurality of control modes prepared in advance.
As the control mode, for example, a normal mode for normal driving, a sports mode suitable for sports driving, and the like are prepared.
In the sport mode, the intervention threshold value of the behavior stabilization control is set so that it is difficult to intervene in the normal mode, and the execution of the sharp turning control described later is permitted.
This point will be described in detail later.
When the sharp turn control is executed, the behavior control unit 40 functions as a rear wheel braking control unit that can control the braking force of the rear wheels of the vehicle independently of the braking force of the front wheels.

The parking brake switch 42 inputs a parking brake operation operation that brakes only the rear two wheels of the vehicle to prevent the vehicle from starting to move when the vehicle is stopped, a parking brake release operation that releases the braking of the rear two wheels, and the like. It is an operation unit.
Further, the parking brake switch 42 can also perform a dynamic braking start operation for braking the front wheels and the rear wheels while the vehicle is traveling.
Further, the parking brake switch 42 brakes and locks only the rear wheels when the above-mentioned sports mode is selected and satisfies a predetermined turning condition, puts the vehicle in the spin mode, and suddenly. It is possible to input a start request for a sharp turn control to turn.
The parking brake switch 42 functions as a sharp turn request detection unit according to the present invention.
The parking brake switch 42 can be provided as various switches such as a pull type and a push type on the center console, instrument panel, steering wheel, etc. of the vehicle, for example.

The yaw rate sensor 43 detects the yaw rate (rotation speed around the vertical axis) of the vehicle body.
The lateral G-sensor 44 detects the acceleration of the vehicle body in the vehicle width direction.
The vehicle speed sensor 45 is provided on each of the front, rear, left, and right wheels, and detects the rotational speed of the corresponding wheel.
When the wheels are not in a slipped state, it is possible to detect the traveling speed (vehicle speed) of the vehicle based on the rotational speed of the wheels.

Each of the above-mentioned units is configured to include, for example, an information processing unit such as a CPU, a storage unit such as a RAM or ROM, an input / output interface, and a bus connecting them.
Further, each unit is communicably connected via, for example, an in-vehicle LAN system or directly.

The master cylinder 50 pressurizes the brake fluid hydraulic pressure of the hydraulic service brake according to the operation amount of a brake pedal (not shown) in which the driver operates the brake.
The hydraulic service brake includes a rotor that rotates with each wheel and a caliper that holds the rotor by pressurizing a brake pad having a friction material with the rotor.
The calipers provided on the front, rear, left, and right wheels are provided with a left front wheel cylinder 61, a right front wheel cylinder 62, a left rear wheel cylinder 63, and a right rear wheel cylinder 64, respectively.
In each of the wheel cylinders 61 to 64, the friction material is brought into pressure contact with the rotor by the brake fluid hydraulic pressure transmitted from the hydraulic unit 60 to generate a braking force.

The hydraulic unit 60 is a hydraulic pressure control device (brake actuator) that independently pressurizes and depressurizes the hydraulic pressure of the brake fluid pressurized by the master cylinder 50 for each wheel in response to a command from the behavior control unit 40. ).
The hydraulic unit 60 includes a pressurizing pump driven by an electric actuator such as a motor, and a solenoid valve such as a pressurizing valve, a pressure reducing valve, and a holding valve.
The hydraulic unit 60 has a function of individually controlling the brake fluid hydraulic pressure of the left front wheel cylinder 61, the right front wheel cylinder 62, the left rear wheel cylinder 63, and the right rear wheel cylinder 64 provided on the front, rear, left, and right wheels, respectively.

Next, the operation of the vehicle control device of the first embodiment will be described.
FIG. 2 is a flowchart showing an operation at the time of a sharp turn in the vehicle control device of the first embodiment.
Hereinafter, each step will be described step by step.

<Step S01: Behavior control mode determination>
The behavior control unit 40 determines whether or not the sport mode is selected by the mode selection switch 41.
If the sport mode is selected, the process proceeds to step S02, and in other cases, a series of processes is completed (returned).

<Step S02: Turn start determination>
Based on the information from the steering angle sensor 31, the yaw rate sensor 43, the lateral G-force sensor 44, the vehicle speed sensor 45, etc., the behavior control unit 40 has started a predetermined turning state in which the sharp turning control can intervene in the future. To determine.
For example, the vehicle speed is equal to or less than a predetermined threshold value (for example, 20 km / h), the steering angle detected by the steering angle sensor 31 is equal to or more than a predetermined threshold value, and the steering speed obtained by differentiating the steering angle is a predetermined threshold value (for example). For example, if the yaw rate is 200 deg / sec or more, the yaw rate is 10 deg / sec or more, and the lateral G is the predetermined threshold value or more, the process proceeds to step S03, and in other cases, the process proceeds to step S03. End (return) a series of processing.

<Step S03: Parking brake switch operation judgment>
The behavior control unit 40 determines whether or not the driver has operated the parking brake switch 42 within a predetermined time after detecting the start of turning in step S02.
When the parking brake switch 42 is operated, the process proceeds to step S04 in order to start the sharp turn control that puts the vehicle in the spin turn state, and in other cases, a series of processes is ended.

<Step S04: Start of sharp turn control>
The behavior control unit 40 gives a command to the hydraulic unit 60 to increase the brake fluid hydraulic pressure of the left rear wheel cylinder 63 and the right rear wheel cylinder 64 to lock (stop rotation) the left and right rear wheels and lock (stop rotation) the left and right rear wheels. Brake fluid hydraulic pressure that does not reach the lock is applied to the front wheels to generate braking force, and a sharp turn control is started to generate a yaw moment in the direction of increasing the yaw rate of the vehicle (improving turning performance).
At this time, the AWD control unit 20 releases (disengages) the transfer clutch 21 to allow the rear wheels to lock while the front wheels are rotated.
After that, the process proceeds to step S05.

<Step S05: Detection of the end of sharp turn>
The behavior control unit 40 determines whether or not the driver has performed an operation to end the sharp turn state (spin turn state) of the vehicle.
For example, when the rudder angle detected by the rudder angle sensor 31 decreases to a predetermined value or less (the rudder is returned), or the accelerator opening degree (accelerator pedal depression amount) detected by the accelerator pedal sensor 11 becomes a predetermined value or more. When the number increases, it can be determined that there was an operation to end the sharp turning state.
The behavior control unit 40 functions as an end operation detection unit that detects the end operation of the turning state by the driver.
If there is an operation to end the sharp turning state, the process proceeds to step S06, and in other cases, step S05 is repeated at predetermined time intervals.

<Step S06: Judgment of presence / absence of oversteer maintenance request (1)>
The behavior control unit 40 determines whether or not the driver intends to maintain the oversteer behavior of the vehicle even after the rear wheel lock is restored by the sharp turn control.
For example, when the steering angle detected by the steering angle sensor 31 is cut in the turning inner direction by a predetermined value or more and the accelerator opening degree detected by the accelerator pedal sensor 11 is a predetermined value or more (for example, fully open), the driver Can be determined to be intended to maintain oversteer behavior due to power oversteer.
If the request for maintaining such oversteer behavior is recognized, the process proceeds to step S08, and in other cases, the process proceeds to step S07.

<Step S07: End of sharp turn control / return to normal sports mode>
The behavior control unit 40 gives a command to the hydraulic unit 60 to reduce the brake fluid hydraulic pressure of the left rear wheel cylinder 63 and the right rear wheel cylinder 64 to put the rear wheels in an unlocked state (rotating state) and stabilize the behavior. Return control to normal control in sport mode.
That is, when oversteer behavior is occurring in the vehicle at this point, the behavior control unit 40 gives a command to the hydraulic unit 60 to apply a braking force to the front wheels on the turning outer wheel side to suppress the oversteer behavior. Generates a yaw moment in the direction of
At this time, the speed at which the brake fluid hydraulic pressure of the front wheel cylinder on the turning inner wheel side is reduced (the speed at which the difference in braking force between the left and right front wheels is reduced) is the steering speed (return speed) when the steering angle is reduced. It is controlled to increase in response to an increase in at least one of the speeds of increase in the accelerator opening when the accelerator is depressed.
After that, a series of processing is completed (returned).

<Step S08: Oversteer maintenance control>
The behavior control unit 40 gives a command to the hydraulic unit 60 to reduce the brake fluid hydraulic pressure of the left rear wheel cylinder 63 and the right rear wheel cylinder 64 to unlock the rear wheels.
Further, the behavior control unit 40 performs oversteer maintenance control that controls the yaw moment of the vehicle body so that the current oversteer behavior is maintained. That is, when the yaw rate further increases and is in a divergent tendency (spin mode), the yaw rate is suppressed, while when there is a sign that the yaw rate suddenly decreases and becomes an understeer tendency, the yaw rate is increased and oversteered. Controls to maintain steer behavior.
After that, the process proceeds to step S09.

<Step S09: Judgment of presence / absence of oversteer maintenance request (2)>
The behavior control unit 40 determines whether or not the driver intends to maintain the oversteer behavior of the vehicle, as in step S06.
If the request for maintaining the oversteer behavior is not recognized, the process proceeds to step S07, and in other cases, step S09 is repeated at predetermined time intervals.

Hereinafter, the effects of the first embodiment described above will be described in comparison with the vehicle control device of the comparative example of the present invention described below.
In addition, in the comparative example and each embodiment described later, the same reference numerals are given to the parts common to the first embodiment described above, the description thereof will be omitted, and the differences will be mainly described.

The vehicle control device of the comparative example has a normal behavior of generating a yaw moment in a direction to suppress the oversteer behavior even when the rear wheels are locked by operating the parking brake switch 42. It controls stabilization.

FIG. 3 is a diagram showing an example of a vehicle state transition at the time of a sharp turn in a vehicle having a vehicle control device of a comparative example.
In FIG. 3, the horizontal axis represents time, and the vertical axis represents vehicle speed, steering angle, yaw rate, parking brake state, front / rear / left / right wheel cylinder brake fluid hydraulic pressure, foot brake braking force, clutch state, accelerator opening, and engine torque. Shown. (The same applies to FIGS. 5 and 8 described later)
FIG. 4 is a diagram showing an example of vehicle behavior transition during a sharp turn in a vehicle having a vehicle control device of a comparative example.
In FIG. 4, the wheels painted in black indicate that they are in the locked state, and the shaded wheels indicate that braking force that does not reach the lock is applied. In FIG. 4, the increase in the subscripts (numbers) attached to the vehicle V indicates the transition of the state in the time series. (Same in FIG. 6)
3 and 4 show a state in which the vehicle V enters a tight corner turning left from a straight road. (Same in FIGS. 5 and 6)
First, the driver returns the accelerator from the fully open state to the fully closed state, then decelerates with the foot brake, then steers to the left, and immediately after that, disengages the clutch with the intention of a spin turn, and presses the parking brake switch 42. I'm operating.

As in the vehicle V1 shown in FIG. 4, the left front wheel Wfl and the right front wheel Wfr are first steered to the left, so that the vehicle generates a yaw rate in the counterclockwise direction and the vehicle starts turning left.
After that, when the left rear wheel Wrl and the right rear wheel Wrr are locked like the vehicle V2, these rear wheels lose directional stability and are lowered to the outside of the turn (in this case, the right side) by inertial force, and the vehicle V Attempts to enter spin mode with strong oversteer behavior.
However, in the comparative example, the braking force F is applied to the right front wheel Wfr by the intervention of the behavior stabilization control of the behavior control unit 40, and a yaw moment in which the oversteer behavior is suppressed is generated.
As a result, like the vehicle V3, the vehicle travels in a direction deviating from the lane with an understeer tendency, and as a result, as shown in FIG. 3, for example, the rear wheels cannot be re-accelerated while the rear wheels are locked, and the clutch is disengaged. It will be cut and stopped with the rear wheels locked.

FIG. 5 is a diagram showing an example of a vehicle state transition at the time of a sharp turn in the vehicle having the vehicle control device of the first embodiment.
FIG. 6 is a diagram showing an example of vehicle behavior transition during a sharp turn in a vehicle having the vehicle control device of the first embodiment.
Also in the first embodiment, as in the comparative example, as in the vehicle V1 shown in FIG. 6, the left front wheel Wfl and the right front wheel Wfr are first steered to the left, so that the vehicle is in the counterclockwise direction. A yaw rate occurs and the vehicle begins to turn left.
After that, when the left rear wheel Wrl and the right rear wheel Wrr are locked as in the vehicle V2, these rear wheels lose directional stability and are ejected to the outside of the turn (in this case, the right side) by inertial force, and the vehicle is released. Attempts to enter spin mode with strong oversteer behavior.
At this time, in the first embodiment, the behavior control unit 40 applies a braking force F to the left front wheel Wfl on the turning inner wheel side to generate a yaw moment in the direction of promoting oversteer behavior, and the vehicle V2 spins. Shows sharp turning behavior with mode.

After that, when the driver engages the clutch at the position of the vehicle V3 and starts to return the steering angle while depressing the accelerator, the behavior control unit 40 ends the sharp turning control and the rear wheels recover from the locked state.
In this state, the vehicle V3 is turning in the direction of the exit of the corner, and as shown in the vehicle V4, the vehicle can quickly escape from the corner while accelerating at a small steering angle.

As described above, according to the first embodiment, the following effects can be obtained.
(1) By locking the left and right rear wheels Wrl and Wrr in response to the operation of the parking brake switch 42 at the start of turning, the vehicle V is put into spin mode, the yaw rate is rapidly raised, and the turning inner wheel side By applying the braking force F to the front wheels to generate a yaw moment in the direction of increasing the yaw rate of the vehicle body, it is possible to easily perform a spin turn which is a sharp turn with a high yaw rate when the driver intends to make a sharp turn.
Further, by starting the sharp turn control in response to the operation of the parking brake switch 42 by the driver, the spin turn can be performed faithfully to the driver's intention.
(2) By permitting the sharp turn control only when the sport mode is selected by the mode selection switch 41, it is possible to prevent an unintended sharp turn from being performed due to an erroneous operation of the driver when traveling in the normal mode.
(3) By terminating the sharp turn control in response to the decrease in the steering angle or the increase in the accelerator opening, the sharp turn control is appropriately and automatically terminated by simple control, and the vehicle state is changed to the state of escaping the tight corner. Can be migrated.
In addition, the driver's intention to shift from the sharp turn state to the corner escape state by increasing the decrease speed of the braking force of the front wheels on the turning inner wheel side in accordance with the speed increase of the steering angle decrease or the accelerator opening increase ( It is possible to recover from the spin-turn state according to (whether it recovers gently or rapidly).
(4) If the driver determines the intention to maintain the oversteer behavior at the end of the sharp turn control, the behavior control that maintains the oversteer behavior due to the difference in braking force between the left and right front wheels even after the rear wheels are locked back is performed. By doing so, it is possible to perform appropriate vehicle attitude control when the driver intends to maintain the turning state (for example, transition to a steady circular turning) by, for example, power oversteer even after the end of the sharp turning control.
(5) When the rear wheels are locked in the sharp turning control, the transfer clutch 21 that restrains the front wheel side power transmission mechanism and the rear wheel side power transmission mechanism is released, so that the transfer clutch 21 is input from the front wheel side to the rear wheels. It is possible to prevent the rear wheels from being locked by the torque and the cascade lock state in which the four wheels are locked at the same time.

<Second Embodiment>
Next, a second embodiment of the vehicle control device to which the present invention is applied will be described.
FIG. 7 is a block diagram schematically showing the configuration of a vehicle having the vehicle control device of the second embodiment.
The vehicle of the second embodiment is provided with an automated manual transmission (AMT) as a transmission, instead of the manual transmission of the first embodiment, in which a transmission mechanism similar to that of the manual transmission and a clutch are driven by an actuator. ..

As shown in FIG. 7, in the second embodiment, the transmission control unit 20A is provided instead of the AWD control unit 20 of the first embodiment.
In addition to the transfer clutch 21, which is controlled in the same manner as in the first embodiment, the transmission control unit 20A is connected to the transmission actuator 22 and the clutch actuator 23.
The transmission control unit 20 gives a command to the speed change actuator 22 according to the traveling state of the vehicle to perform a speed change operation.
Further, the transmission control unit 20 gives a command to the clutch actuator 23 to release (disengage) the clutch when shifting gears, stopping the vehicle, or the like.

In the second embodiment, the clutch is automatically released when the sharp turning control is started, and the clutch is automatically engaged (connected) when the sharp turning control is completed.
The speed at which the fastening force is increased when the clutch is engaged is set so as to increase as the braking force decreasing speed of the front wheels on the turning inner ring side increases.
FIG. 8 is a diagram showing an example of a vehicle state transition at the time of a sharp turn in the vehicle having the vehicle control device of the second embodiment.
As shown in FIG. 8, in the second embodiment, after the sharp turning control is completed, the clutch is automatically engaged and then the accelerator on operation is permitted, so that the clutch is engaged immediately after the rear wheel lock is restored. Start assist control that prevents the vehicle behavior from becoming unstable due to a sudden change in driving force due to the connection, and smoothes a series of behavior from recovery from spin mode in sharp turn control to re-acceleration of the vehicle. Is running.

According to the second embodiment described above, the clutch is disengaged when the rear wheel is locked in the sharp turning control, and a series of operations for connecting the clutch are automated according to the end of the sharp turning control, thereby burdening the driver. It can be mitigated.
Further, by increasing the speed of increase of the fastening force when the sharp turning control is completed and the clutch is engaged, the braking force lowering speed of the front wheels on the turning inner ring side becomes faster, so that the sharp turning intended by the driver is increased. The clutch connection operation can be automatically performed according to the speed of recovery from the state.

<Third Embodiment>
Next, a third embodiment of the vehicle control device to which the present invention is applied will be described.
The vehicle control device of the third embodiment operates the parking brake switch 42 when it is determined by the steering angle, steering speed, yaw rate, lateral G, etc. at the initial stage of turning that the driver intends to make a sharp turn. The feature is that the sharp turn control is automatically started.
In the third embodiment, the behavior control unit 40 itself functions as a sharp turn request detection unit that detects a sharp turn request of the driver.
FIG. 9 is a flowchart showing an operation at the time of a sharp turn in the vehicle control device of the third embodiment.
Hereinafter, each step will be described step by step.

<Step S11: Behavior control mode determination>
The behavior control unit 40 determines whether or not the sport mode is selected by the mode selection switch 41.
If the sport mode is selected, the process proceeds to step S12, and in other cases, a series of processes is completed (returned).

<Step S12: Judgment of detection of sudden turn start>
The behavior control unit 40 determines whether or not the driver has performed a driving operation intended for a sharp turn (spin turn) based on information from the steering angle sensor 31, yaw rate sensor 43, lateral G sensor 44, vehicle speed sensor 45, and the like. Determine.
For example, when the vehicle speed is below a predetermined threshold, the steering angle is at least a predetermined threshold, the steering speed is at least a predetermined threshold, the yaw rate is at least a predetermined threshold, and the lateral G is at least a predetermined threshold, the driver makes a sharp turn. It is determined that the intention is to start, the process proceeds to step S13, and in other cases, a series of processes is terminated (returned).

<Step S13: Start of sharp turn control>
Similar to step S04 described above, the behavior control unit 40 locks (stops rotation) the left and right rear wheels and starts sharp turning control for generating braking force on the front wheels on the turning inner ring side.
At this time, the AWD control unit 20 releases the transfer clutch 21.
After that, the process proceeds to step S14.

<Step S14: Detection of the end of sharp turn>
Similar to step S05 described above, the behavior control unit 40 determines whether or not the driver has performed an operation to end the sharp turn state (spin turn state) of the vehicle.
If there is an operation to end the sharp turning state, the process proceeds to step S15, and in other cases, step S14 is repeated at predetermined time intervals.

<Step S15: Judgment of presence / absence of oversteer maintenance request (1)>
The behavior control unit 40 determines whether or not the driver intends to maintain the oversteer behavior of the vehicle, as in step S06 described above.
If the request for maintaining the oversteer behavior is recognized, the process proceeds to step S17, and in other cases, the process proceeds to step S16.

<Step S16: End of sharp turn control / return to normal sports mode>
Similar to step S07 described above, the behavior control unit 40 ends the sharp turn control and returns to the control of the normal sport mode.
After that, a series of processing is completed (returned).

<Step S17: Oversteer maintenance control>
The behavior control unit 40 performs oversteer maintenance control in the same manner as in step S08 described above.
After that, the process proceeds to step S18.

<Step S18: Judgment of presence / absence of oversteer maintenance request (2)>
The behavior control unit 40 determines whether or not the driver intends to maintain the oversteer behavior of the vehicle, as in step S15.
If the request for maintaining the oversteer behavior is not recognized, the process proceeds to step S16, and in other cases, step S18 is repeated at predetermined time intervals.

According to the third embodiment described above, the driver's intention is performed by the minimum operation by automatically starting the sharp turn control in response to the driving operation recognized that the driver intends to make a sharp turn. It is possible to make a sharp turn faithfully.

(Modification example)
The present invention is not limited to the embodiments described above, and various modifications and modifications can be made, and these are also within the technical scope of the present invention.
(1) The configuration of the vehicle control device and the vehicle controlled by the vehicle control device is not limited to each of the above-described embodiments, and can be appropriately changed.
For example, in each embodiment, the vehicle is a four-wheel drive (AWD) vehicle using an engine as a driving power source, but the present invention also applies to an electric vehicle such as an engine-electric hybrid vehicle or an electric vehicle. It is possible, and the drive system is not particularly limited.
(2) In each embodiment, the rear wheels are locked by a hydraulic brake at the time of a sharp turn, but for example, an electric brake that generates a braking force by an electric actuator may be used.
(3) In each embodiment, the transmission of the vehicle is a manual transmission or an AMT, but the transmission is not limited to these, and may be another type. For example, it may be a continuously variable transmission (CVT), a step AT using a planetary gear set, a DCT, or the like.
(4) In each embodiment, the behavior control unit generates a yaw moment in the direction of improving the turning performance by applying a braking force larger than that on the outer ring side to the turning inner ring side, but the turning is not limited to this. A larger driving force may be applied to the outer ring side than to the inner ring side. Further, control using both braking force and driving force may be performed.
(5) In each embodiment, the sudden turning control is automatically terminated based on the steering angle, the accelerator opening, and the like, but the present invention is not limited to this, and suddenly responds to an operation from the driver. It may be configured to end the turning control.
(6) In the first embodiment, sharp turning control is permitted only when all of the vehicle speed, steering angle, steering speed, yaw rate, and lateral G satisfy the predetermined conditions, but some of these are permitted. It may be configured to allow sharp turning control when only the conditions are satisfied. Further, the structure may be configured to allow sharp turning control based on conditions other than these. Similarly, the condition for automatically starting the sharp turning control in the third embodiment is not limited to the configuration of the third embodiment.
(7) In the first embodiment, control for suppressing oversteer behavior is restricted when both the steering angle and the accelerator opening at the end of the sharp turning state are equal to or higher than a predetermined value. Is not limited to this, and can be changed as appropriate.
For example, when at least one of the steering angle, the accelerator opening degree, and the accelerator operating speed is at least a predetermined value, the suppression control of the oversteer behavior may be restricted.

10 Engine control unit 11 Accelerator pedal sensor 20 AWD control unit 20A Transmission control unit 21 Transfer clutch 22 Speed change actuator 23 Clutch actuator 30 Electric power steering control unit 31 Steering angle sensor 40 Behavior control unit 41 Mode selection switch 42 Parking brake switch 43 Yaw rate sensor 44 Lateral G sensor 45 Vehicle speed sensor 50 Master cylinder 60 Hydraulic unit 61 Left front wheel cylinder 62 Right front wheel cylinder 63 Left rear wheel cylinder 64 Right rear wheel cylinder V Vehicle F Braking force Wfl Left front wheel Wfr Right front wheel Wrr Left rear wheel Wrr Right Rear wheel

Claims (13)

A rear wheel braking control unit that can control the braking force of the rear wheels of the vehicle by an actuator independently of the braking force of the front wheels.
A sharp turn request detection unit that detects a sharp turn request of the driver,
A vehicle control device including a behavior control unit that gives a yaw moment to the vehicle body by generating a control driving force difference between the left and right front wheels of the vehicle.
In response to the detection of the sharp turning request, the rear wheel braking control unit increases the braking force of the rear wheels so that wheel lock occurs, and the behavior control unit increases the yaw rate of the vehicle body. A vehicle control device characterized by performing sharp turn control that gives a difference in driving force. The vehicle control device according to claim 1, wherein the sharp turn request detection unit detects the sharp turn request in response to a sharp turn request operation by the driver. The claim is characterized in that the sharp turn request detection unit detects the sharp turn request when at least one of a steering angle, a steering speed, a yaw rate, and a turning centripetal acceleration at the initial stage of turning of a vehicle exceeds a predetermined threshold value. The vehicle control device according to 1. The first aspect of claim 1 is characterized in that the user can select a first traveling mode in which the sharp turning control is permitted and a second traveling mode in which the sharp turning control is prohibited. Item 3. The vehicle control device according to any one of items up to item 3. Equipped with an end operation detection unit that detects the end operation of the turning state by the driver
The vehicle control device according to any one of claims 1 to 4, wherein the sharp turn control is terminated in response to the detection of the termination operation. The vehicle control device according to claim 5, wherein the end operation detection unit detects the end operation based on a decrease in the steering angle. The vehicle control device according to claim 6, wherein the behavior control unit increases the reduction speed of the control driving force difference in response to an increase in the steering speed when the steering angle decreases. The vehicle control device according to claim 5, wherein the end operation detection unit detects the end operation in response to an increase in the accelerator operation amount by the driver. The vehicle control device according to claim 8, wherein the behavior control unit increases the reduction speed of the control driving force difference according to the increase speed of the accelerator operation amount. It is equipped with a clutch control unit that controls the connection and disconnection of the clutch provided between the engine and the power transmission mechanism.
The first to ninth aspects of the invention, wherein the clutch control unit disengages the clutch in response to the start of the sharp turn control and connects the clutch in response to the end of the sharp turn control. The vehicle control device according to any one of the following items. The clutch control unit is characterized in that, at the end of the sharp turning control, the increasing speed of the engaging force when connecting the clutch is increased as the decreasing speed of the controlling driving force difference increases. Item 10. The vehicle control device according to item 10. When at least one of the accelerator operating amount, the accelerator operating speed, and the steering angle at the end of the sharp turning control is equal to or greater than a predetermined threshold value, the behavior control unit reduces the braking force of the rear wheels of the vehicle. The vehicle control device according to any one of claims 1 to 11, wherein the suppression control of the oversteer behavior is limited. It is equipped with a transfer clutch control unit that controls the transfer clutch that restrains the difference in rotational speed between the front wheel drive force transmission mechanism and the rear wheel drive force transmission mechanism of the vehicle.
The vehicle control device according to any one of claims 1 to 12, wherein the transfer clutch control unit maintains the transfer clutch in an released state during execution of the sharp turning control.

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