JP2010064720A - Motion control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motion control device for the vehicle, which can predict a generation of rapid yawing behavior based on the steering operation to enhance the responsiveness of a braking liquid pressure in vehicle stability control only when necessary. <P>SOLUTION: In the vehicle motion control device for executing the vehicle stability control for suppressing the over-steering of the vehicle, the rapid yawing behavior of the vehicle is predicted based on the steering angle and a control starting threshold value relative to a braking means provided on an appropriate wheel is adjusted. The steering angle is detected with a steering angle sensor and a steering angular speed is operated based on the detected steering angle. The turn-back state of steering is determined when the steering angle is increased, and when the steering angular speed at the turn-back steering state is large, the control starting threshold value relative to the braking means is adjusted to become small. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle motion control device that maintains the stability of a vehicle by controlling the brake fluid pressure in the brake device.

As a conventional vehicle motion control device, for example, there is one disclosed in Patent Document 1. This motion control device improves the response of the brake fluid pressure when performing vehicle stability control, and eliminates the need for the frequency of operation of the pressure source (pump, motor) and pressure regulating valve means used for vehicle stability control. In order to suppress the increase, it is highly likely that the brake control is executed next in the combination of the current braking control execution wheel and the change (increase / decrease) tendency of the yaw rate deviation during the control of the vehicle stability control. It is described that a wheel is predicted and preload control is performed using the wheel as a target wheel.
JP 11-227586 A

  However, in the vehicle motion control device described in Patent Document 1 described above, the preload of the brake fluid pressure is the difference between the yaw rate deviation (the calculated target yaw rate and the detected actual yaw rate) during the control of the vehicle stability control. Deviation). That is, the preload control of the brake fluid pressure is executed after the yawing behavior to the extent that the vehicle stability control is started occurs in the vehicle. In order to further improve the responsiveness of the brake fluid pressure, even if a yawing behavior that does not start the vehicle stability control is identified, the start of the vehicle stability control is predicted and the preload control is performed. Is required.

  On the other hand, if the preload control is started even when the vehicle stability control is not started, only the preload control may be performed even though the vehicle stability control is not started. In order to execute the preload control, it is necessary to drive the brake fluid pressure control device (brake actuator), but when this is driven, a slight noise is generated, which makes the driver feel uncomfortable. Therefore, it is necessary to perform preload control only when necessary.

  By the way, the scene where the response of the brake fluid pressure is required in the vehicle stability control will be described. A highly responsive braking fluid pressure is required when a fast (rapid) yawing behavior occurs (for example, when the yaw rate or the vehicle skid angular velocity is very high). Normally, the steering characteristic of a vehicle is set to weak understeer according to vehicle specifications, suspension settings, and the like. Therefore, in a steering operation that gradually turns the steering wheel (a steering operation that generates a steady turning state of the vehicle), the vehicle becomes understeer and reaches the turning limit. Therefore, a highly responsive braking fluid pressure characteristic is not required.

  On the other hand, in a steering operation that urgently avoids an obstacle or the like, a fast yawing behavior occurs, so that a high response of braking fluid pressure is required. Here, the emergency avoidance steering operation refers to a steering operation (e.g., moving the vehicle laterally from the currently traveling line to avoid an obstacle, and then returning the vehicle to the original traveling line ( Steering operation for generating a transient turning state of the vehicle), and is called, for example, a double lane change.

  The emergency avoidance steering operation will be described with reference to FIG. In FIG. 10, as the turning direction, the positive sign (+) is the left turning direction, and the negative sign (−) is the right turning direction. In the following, when explaining the magnitude relation (size comparison, increase / decrease) of the state quantity such as the steering angle and the turning state quantity, it is expressed by the magnitude relation of the absolute value of the state quantity in order to avoid complicated explanation. . FIG. 10 shows the steering operation when moving leftward to avoid an obstacle, return to the original travel line, and then move rightward to avoid the next obstacle. ing.

  First, in order to turn the vehicle in the left direction, the driver cuts the steering wheel in the left turning direction (counterclockwise direction when viewed from the driver). Accordingly, the steering angle Sa increases from the steering neutral position “0 (represents straight traveling of the vehicle)” to the left turning direction (positive sign direction) (the steering operation from the point a1 to the point a2 in the figure, (Also referred to as 1 steering cut). Then, the steering wheel is turned back so that the vehicle can pass while avoiding obstacles, and the steering angle Sa decreases accordingly toward the steering neutral position “0” (the steering operation from the point a2 to the point a3 in the figure, Also referred to as a one-steering turning-back state). Further, in order to return to the original travel line (in order to move the vehicle to the right), the driver cuts the steering wheel in the right turn direction (clockwise as viewed from the driver), and accordingly the steering angle Sa Increases from the steering neutral position “0 (means straight traveling of the vehicle)” to the right turning direction (the direction of the negative sign) (the steering operation from the point a3 to the point a4 in the figure, and the second steering cut) Also called state). Then, in order to make the vehicle travel in a straight line stably in the original travel line, the steering wheel is turned back and the third steering is performed.

  In the steering operation in which the turning direction changes from one direction to the other as described above, the steering operation in one direction is the first steering, the steering operation in the other direction different from the one direction is the second steering, and the subsequent operation. A steering operation in which the steering direction changes is referred to as third steering. A state in which the steering angle Sa (absolute value) increases is referred to as turning steering (steering turning state), and a state in which the steering angle Sa (absolute value) decreases is referred to as turning steering (steering turning state).

  The vehicle stability when the above steering operation is performed will be described. In a vehicle using steering wheels as front wheels, first, a slip angle is generated in the front wheels by the steering wheel operation, thereby generating a lateral force in the front wheel tires. By this front wheel lateral force, a yawing moment acts on the vehicle, and the turning motion of the vehicle is started. As a result of this turning motion, a slip angle is also generated for the rear wheel, and the rear tire begins to generate lateral force. The lateral force of the rear wheel reduces the yawing moment, and finally the front wheel lateral force and the rear wheel lateral force are balanced, and the vehicle performs a steady turning motion.

  However, when the steering operation in which the turning direction is reversed (change from one direction to the other direction) as described above is repeated, the time delay (phase difference) in the generation of the rear wheel lateral force with respect to the front wheel lateral force is generated. Increases, and an excessive yawing moment is generated with respect to the vehicle. Furthermore, since the rear tire reaches the lateral force limit (the state where the lateral force is already saturated and does not increase even if the slip angle increases), a rapid yawing behavior may occur.

  In view of the above points, the present invention can predict the occurrence of a sudden yawing behavior based on a steering operation, and can improve the response of braking hydraulic pressure in vehicle stability control only when necessary. An object of the present invention is to provide a vehicle motion control device.

  The vehicle motion control apparatus according to the present invention includes a braking means provided on a vehicle wheel, an actual turning amount acquisition means for acquiring an actual turning state amount of the vehicle, and the actual turning state amount based on the actual turning state amount. Oversteer identifying means for identifying the degree of oversteer of the vehicle, and stability control for executing stability control for starting application of braking fluid pressure to the braking means when the identification result of the oversteer identifying means exceeds a threshold value Means, steering angle acquisition means for acquiring a steering angle by a driver of the vehicle, steering angular speed calculation means for calculating a steering angular speed based on the steering angle, and a magnitude of the steering angular speed when the steering angle decreases. Threshold adjustment means for adjusting the threshold based on the threshold

  The threshold value of the vehicle stability control is adjusted instead of the preload application control that is separate from the vehicle stability control, so that the response of the brake fluid pressure of the vehicle stability control can be improved reliably. Further, when the steering angle decreases, that is, based on the magnitude of the steering angular velocity when the turn-back steering is performed, threshold adjustment for applying a preload is performed. Therefore, it is possible to predict a yawing behavior (oversteer behavior) that occurs suddenly and perform threshold adjustment in an appropriate situation.

  In the vehicle motion control apparatus according to the present invention, the threshold value adjusting means can adjust the threshold value when the magnitude of the steering angular velocity is a predetermined value or more. A rapid yawing behavior occurs when fast turnback steering is performed, and an appropriate threshold value can be adjusted for this behavior.

  In the vehicle motion control apparatus according to the present invention, the threshold value adjusting means can adjust the threshold value even when oversteer of the vehicle is not identified. Even when oversteer is not identified in the first steering, a sudden yawing behavior may occur in the second steering, and an appropriate threshold value can be adjusted for this behavior.

  The vehicle motion control apparatus according to the present invention further includes a turning direction identifying unit that identifies the turning direction of the vehicle based on the steering angle, and the threshold value adjusting unit is configured to reduce the steering angle when the steering angle decreases. The threshold value can be adjusted with respect to the wheel located outside in the turning direction opposite to the turning direction and in front of the vehicle. The threshold adjustment effect can be improved by adjusting the threshold value for the braking means for the front outer wheel that is most effective in suppressing oversteer.

  The vehicle motion control apparatus according to the present invention includes a braking operation acquisition unit that acquires an operation of the braking member of the driver, and the threshold adjustment unit is based on an acquisition result of the braking operation acquisition unit. It can be determined that the braking member is being operated, and when the determination is affirmative, the adjustment of the threshold value can be prohibited. When threshold adjustment is unnecessary, the adjustment is prohibited, and unnecessary threshold adjustment can be avoided.

  In the vehicle motion control apparatus according to the present invention, the threshold adjustment means prohibits the adjustment of the threshold when the magnitude of the steering angular velocity when the steering angle increases is less than a predetermined value. can do. A rapid yawing behavior occurs when fast cutting steering is performed, but a rapid yawing behavior hardly occurs during slow cutting steering. Therefore, when the steering angle is increased, that is, when the steering angular velocity is less than a predetermined value when the steering steering is performed, threshold adjustment is prohibited, and unnecessary threshold adjustment is performed. Can be avoided.

  In the vehicle motion control apparatus according to the present invention, the threshold value adjusting means is configured such that the magnitude of the steering angle when the steering angle shifts from the increasing state to the decreasing state is less than a predetermined value. Adjustment of the threshold value can be prohibited. When the steering operation state changes from the turning steering to the turning steering, the steering angle is small, so that a rapid yawing behavior is unlikely to occur. Therefore, when the magnitude of the steering angle when the steering operation shifts from the turning state to the turning-back state is less than a predetermined value, threshold adjustment is prohibited, and unnecessary threshold adjustment can be avoided.

  In the vehicle motion control apparatus according to the present invention, the threshold adjustment means is configured such that the magnitude of the actual turning state amount corresponding to the shift of the steering angle from the increasing state to the decreasing state is less than a predetermined value. The threshold value can be prohibited from being adjusted. If the magnitude of the actual turning state amount that occurs when the steering operation state transitions from turning steering to turning steering is small, a rapid yawing behavior is unlikely to occur. Therefore, when the actual turning state amount corresponding to the steering operation transitioning from the turning state to the turning-back state is less than a predetermined value, threshold adjustment is prohibited, and unnecessary threshold adjustment is avoided. Can do.

  In the vehicle motion control apparatus according to the present invention, the threshold value adjusting means ends the adjustment of the threshold value when a predetermined time elapses after starting the adjustment of the threshold value, The threshold can be returned to the initial value. By terminating the threshold adjustment when a predetermined time has elapsed since the threshold adjustment was started, the threshold adjustment can be appropriately terminated.

  In the vehicle motion control apparatus according to the present invention, the threshold value adjusting means ends the adjustment of the threshold value when the stability control is completed, and returns the threshold value to the initial value. Can do. By terminating the threshold adjustment when the vehicle stability control is terminated, the threshold can be adjusted appropriately.

  In the vehicle motion control apparatus according to the present invention, the stability control means may determine the result of the identification of the oversteer identification means when the magnitude of the steering angular velocity when the steering angle decreases is greater than or equal to a predetermined value. The brake fluid pressure can be controlled so that the increase gradient of the brake fluid pressure with respect to the increase increases with the increase of the identification result. By appropriately controlling the brake fluid pressure, the response of the brake fluid pressure can be improved and unnecessary operation of the fluid pressure control device can be prevented.

  Embodiments of a vehicle motion control device according to the present invention will be described below with reference to the drawings. The subscript “zz” attached to the end of various symbols, etc. indicates that the various symbols are related to any of the four wheels, “fl” is the left front wheel, “fr” is the right front wheel, “Rl” indicates the left rear wheel, and “rr” indicates the right rear wheel. Further, there are a “left turn direction” and a “right turn direction” in the turning direction of the vehicle. The left turning direction is a positive sign (+) of a state quantity (Sa, etc.), and the right turning direction is a state. It is expressed by a minus sign (-) of the quantity (Sa etc.). In order to avoid complication, when expressing the magnitude relationship (size comparison, increase / decrease) of the value, the magnitude relationship is expressed using the absolute value (size) of the value. Moreover, since what is attached | subjected with the same symbol is the same, the overlapping description is abbreviate | omitted.

  FIG. 1 shows a schematic configuration of a vehicle equipped with a vehicle motion control device (hereinafter referred to as “the present device”) according to an embodiment of the present invention.

  The apparatus includes a wheel speed sensor WSzz that detects a wheel speed Vwzz, a steering wheel rotation angle sensor SA that detects a rotation angle θsw of the steering wheel SW (from a neutral position “0” corresponding to straight traveling of the vehicle), A steering angle sensor SB that detects the steering angle δfa of the steered wheel (front wheel), a steering torque sensor ST that detects torque Tsw when the driver operates the steering wheel SW, and a yaw rate sensor that detects the yaw rate Yr of the vehicle body YR, longitudinal acceleration sensor GX that detects longitudinal acceleration Gx in the longitudinal direction of the vehicle body, lateral acceleration sensor GY that detects lateral acceleration Gy in the lateral direction of the vehicle body, and wheel cylinder pressure sensor that detects braking hydraulic pressure Pwzz of the wheel cylinder WCzz An engine that detects PWzz and the rotational speed Ne of the engine EG A rotational speed sensor NE, an acceleration operation amount sensor AS that detects an operation amount As of the driver's acceleration operation member AP, a braking operation amount sensor BS that detects an operation amount Bs of the driver's braking operation member BP, A shift position sensor HS for detecting the shift position Hs of the operating member SG and a throttle position sensor TS for detecting the opening Ts of the throttle valve of the engine are provided.

  The apparatus also includes a brake actuator BRK for controlling the brake fluid pressure, a throttle actuator TH for controlling the throttle valve, a fuel injection actuator GI for controlling fuel injection, and an automatic transmission AT for controlling the shift. ing.

  In addition, the apparatus includes an electronic control unit ECU. The electronic control unit ECU is a microcomputer composed of a plurality of independent electronic control units ECU (ECUb, ECUs, ECUe, ECUa) connected to each other via a communication bus CB. The electronic control unit ECU is electrically connected to the above-described various actuators (such as BRK) and the above-described various sensors (such as WSzz). Each system electronic control unit (ECUb, etc.) in the electronic control unit ECU executes a dedicated control program. Various sensor signals and signals calculated in the electronic control units of each system are shared via the communication bus CB.

  Specifically, the brake system electronic control unit ECUb is a known anti-skid control (ABS control), traction control (TCS control) based on signals from the wheel speed sensor WSzz, the yaw rate sensor YR, the lateral acceleration sensor GY, and the like. Slip suppression control (braking / driving force control) is executed. Further, based on the wheel speed Vwzz of each wheel detected by the wheel speed sensor WSzz, the vehicle speed Vx is calculated by a known method. The steering system electronic control unit ECUs executes well-known electric power steering control based on a signal from the steering torque sensor ST and the like. The engine system electronic control unit ECUe executes control of the throttle actuator TH and the fuel injection actuator GI based on signals from the acceleration operation amount sensor AS and the like. The transmission system electronic control unit ECUa controls the gear ratio of the automatic transmission AT.

  The brake actuator BRK has a known configuration including a plurality of electromagnetic valves (hydraulic pressure regulating valves), a hydraulic pump, an electric motor, and the like. At the time of non-control, the brake actuator BRK supplies the brake hydraulic pressure corresponding to the operation of the brake operation member BP by the driver to the wheel cylinder WCzz of each wheel, and the brake operation member (brake pedal) BP for each wheel. A braking torque corresponding to each operation is given. During braking control such as anti-skid control (ABS control), traction control (TCS control), or vehicle stability control (ESC control) that suppresses vehicle understeer or oversteer, the brake actuator BRK operates the brake pedal BP. Independently, the braking hydraulic pressure in the wheel cylinder WCzz is controlled for each wheel WHzz, and the braking torque can be adjusted for each wheel.

  As the braking means, each wheel is provided with a known wheel cylinder WCzz, brake caliper BCzz, brake pad PDzz, and brake rotor RTzz. When brake fluid pressure is applied to the wheel cylinder WCzz provided in the brake caliper BCzz, the brake pad PDzz is pressed against the brake rotor RTzz, and braking torque is applied by the friction force. Here, when the gap (also referred to as a pad gap) between the brake pad PDzz and the brake rotor RTzz is reduced, the response of the brake fluid pressure is improved.

  The brake actuator BRK will be described with reference to FIG. When the driver depresses the brake pedal (braking operation member) BP, the pedaling force is boosted by the booster VB and presses the master piston disposed in the master cylinder MC. As a result, the same master cylinder pressure Pmc is generated in the first chamber and the second chamber defined by these master pistons. Master cylinder pressure Pmc is applied to wheel cylinder WCzz of each wheel WHzz through brake actuator BRK.

  The configuration shown in FIG. 2 is a configuration called diagonal piping. The brake actuator BRK has a first piping system HP1 connected to the first chamber of the master cylinder MC and a second piping system HP2 connected to the second chamber of the master cylinder MC. The first piping system HP1 controls the braking fluid pressure applied to the left front wheel WHfl and the right rear wheel WHrr, and the second piping system HP2 controls the braking fluid pressure Pwzz applied to the right front wheel WHfr and the left rear wheel WHrl. . Since the first piping system HP1 and the second piping system HP2 have the same configuration, the first piping system HP1 will be described below, and the description of the second piping system HP2 will be omitted. The brake piping configuration may be front and rear piping.

  The first piping system HP1 includes a pipeline A (main pipeline) that generates wheel cylinder pressures Pwfl and Pwrr. The pipe A is provided with a first differential pressure control valve SS1 that can be controlled to a communication state and a differential pressure state, and a master cylinder pressure Pmc is provided to the wheel cylinder WCfl provided to the left front wheel WHfl and the right rear wheel WHrr. Is transmitted to the wheel cylinder WCrr. During normal braking in which the driver operates the brake pedal BP (when braking fluid pressure control is not being executed), the valve position is opened so that the first differential pressure control valve SS1 is in a communicating state. Adjusted. When a current flows through the solenoid coil provided in the first differential pressure control valve SS1, the valve position is adjusted to the closed state, and the first differential pressure control valve SS1 enters the differential pressure state.

  The pipeline A branches into two pipelines Afl and Arr on the side of the wheel cylinders WCfl and WCrr with respect to the first differential pressure control valve SS1. The pipe line Afl is provided with a first pressure-increasing control valve SZfl that controls the increase of the brake hydraulic pressure to the wheel cylinder WCfl, and the pipe line Arr is a first controller that controls the increase of the brake hydraulic pressure to the wheel cylinder WCrr. A two pressure increase control valve SZrr is provided.

  The first and second pressure increase control valves SZfl and SZrr are constituted by two-position electromagnetic valves that can control the communication / blocking state. The first and second pressure-increasing control valves SZfl and SZrr are used when the control current to the solenoid coil provided in the first and second pressure-increasing control valves SZfl and SZrr is “0” (when not energized). The communication state (open state) is established, and the control state is controlled to the cutoff state (closed state) when a control current is supplied to the solenoid coil (when energized). The first and second pressure increase control valves SZfl and SZrr are so-called normally open types.

  The pipe B is a pressure reducing pipe that connects the first and second pressure increase control valves SZfl and SZrr and the wheel cylinders WCfl and WCrr to the pressure regulating reservoir R1. The pipe B is provided with a first pressure reduction control valve SGfl and a second pressure reduction control valve SGrr configured by two-position electromagnetic valves capable of controlling the communication / blocking state. The first and second pressure reduction control valves SGfl and SGrr are so-called normally closed types that are closed when not energized and open when energized.

  Between the pressure regulation reservoir R1 and the pipeline A (main pipeline), a pipeline C (reflux pipeline) is disposed. The pipe C is provided with a hydraulic pump OP1. The hydraulic pump OP1 sucks brake fluid from the pressure adjusting reservoir R1 and discharges the brake fluid toward the master cylinder MC or the wheel cylinders WCfl and WCrr. The hydraulic pump OP1 is driven by an electric motor MT. The drive control of the electric motor MT is performed by controlling the supply voltage by turning on / off a semiconductor switch provided in the motor relay MR.

  A conduit D is provided between the pressure regulating reservoir R1 and the master cylinder MC. At the time of motion control that requires automatic pressurization such as vehicle stability control and traction control, the hydraulic pump OP1 draws brake fluid from the master cylinder MC through the pipe D and discharges it to the pipes Afl and Arr. Brake fluid is supplied to the wheel cylinders WCfl and WCrr, and the wheel cylinder of the target wheel is pressurized.

  The brake system electronic control unit ECUb is composed of a well-known microcomputer having a CPU, ROM, RAM, IO (input / output interface), etc., and executes various arithmetic processes according to a program stored in the ROM, etc. Drives and controls solenoid valves (hydraulic pressure regulating valves), electric motors, etc. Signals and the like used for various arithmetic processes are obtained from various sensors and communication buses via the input / output interface IO.

  Next, vehicle motion control by this apparatus will be described with reference to the functional block diagram of FIG.

  In the target turning state amount calculation block B100, a target turning state amount (target turning state amount Jrt) of the vehicle is calculated using a known method. Here, the turning state quantity is at least one of yaw rate, vehicle body side slip angle, and vehicle body side slip angular velocity. Moreover, it is a value calculated using at least one of these state quantities. For example, the target turning state amount calculation block B100 calculates the target yaw rate Yrt as the target turning state amount Jrt based on the vehicle speed Vx and the steering wheel rotation angle θsw (or the front wheel steering angle δfa). The target turning state quantity Jrt can be calculated not as a single turning state quantity but as a relationship combining a plurality of turning state quantities. For example, as the target turning state quantity Jrt, the relationship between the target vehicle body side slip angle βt and the target vehicle body side slip angular velocity dβt is calculated.

  The actual turning state quantity acquisition unit B110 acquires the actual turning state quantity Jra corresponding to the target turning state quantity Jrt. For example, when the target turning state amount Jrt is the target yaw rate, the actual yaw rate Yr detected by the yaw rate sensor YR is acquired as the actual turning state amount Jra. Further, when the target turning state quantity Jrt is calculated based on the relationship between the target vehicle body side slip angle βt and the target vehicle body side slip angular velocity dβt, the actual vehicle body side slip occurs based on the vehicle speed Vx, the actual yaw rate Yr, and the actual lateral acceleration Gy. The relationship between the angle βa and the actual vehicle side skid angular velocity dβa is calculated.

  The oversteer identification calculation block B115 identifies the degree of oversteer of the vehicle based on the outputs from the target turning state quantity calculation block B100 and the actual turning state quantity acquisition means B110. That is, in the calculation block B115, the oversteer state quantity Jos representing the degree of oversteer is calculated based on the actual turning state quantity Jra (output of the acquisition unit B110) and the target turning state quantity Jrt (output of the calculation block B100). . For example, the deviation ΔJr (= Jra−Jrt) between the actual turning state quantity Jra and the target turning state quantity Jrt is calculated as the oversteer state quantity Jos. Further, when the turning state quantity is a vehicle body side slip angle or a vehicle body side slip angular velocity, those target values can be set to constants (for example, the target value is “0”). Therefore, the target turning state quantity Jrt can be omitted in oversteer identification.

  In a vehicle stability control calculation (oversteer suppression control calculation) block B120, a target braking amount, which is a target of braking hydraulic pressure control that suppresses oversteer of the vehicle, is calculated based on the oversteer state amount Jos. As the target braking amount, the wheel cylinder WCzz (the suffix “zz” at the end of the symbol is “fl” for the left front wheel, “fr” for the right front wheel, “rl” for the left rear wheel, and “rr” for the right rear wheel, The target braking hydraulic pressure Pot of the same applies to other symbols) or the target slip Spt which is a target value in the front-rear slip of the wheel is calculated. Then, a target braking amount (target braking hydraulic pressure Pot or target slip Spt) is calculated based on the oversteer state amount Jos using a preset target braking amount calculation map. In this calculation map (displayed by the characteristic Pch1), when the oversteer state quantity Jos indicating the degree of oversteer is less than the threshold value Tho (a predetermined value set as an initial value), the target braking amounts Pot and Spt are set to “ When the oversteer state amount Jos is equal to or greater than the threshold value Th, the target braking amounts Pot and Spt are increased from “0” as the oversteer state amount Jos increases.

  Further, the calculation map (characteristic Pch1) is adjusted based on an output (adjustment threshold Th) from a threshold adjustment calculation block B180 described later. The calculation map is changed to the characteristic Pch2 based on the adjustment threshold Th that is smaller than the threshold Th set as the initial value. In the changed calculation map (characteristic Pch2), when the oversteer state amount Jos indicating the degree of oversteer is less than the adjustment threshold Th, the target braking amounts Pot and Spt are set to “0”, and the oversteer state amount Jos is adjusted. When the threshold value Th is equal to or greater than the threshold value Th, the target braking amounts Pot and Spt are increased from “0” as the oversteer state amount Jos increases.

  In the calculation block B120, when oversteer is identified (when the oversteer state quantity Jos exceeds a threshold value Tho (initial value) or Th (adjustment value)), the target braking amounts Pot and Spt for suppressing oversteer are “ It is calculated based on the oversteer state quantity Jos representing the identified degree of oversteer so as to rise from “0”. Since the adjustment threshold Th is a value smaller than the initial threshold Th, the start threshold for vehicle stability control is adjusted to a smaller value by the adjustment threshold Th. Therefore, the target braking amounts Pot and Spt are increased from “0” when the degree of oversteering (oversteer state amount Jos) is small. That is, the vehicle stability control can be started earlier. The response of the brake fluid pressure is improved, and it is possible to effectively cope with a rapid yawing behavior (excessive oversteer state).

  In the steering angle acquisition means B130, the steering angle Sa is acquired via the steering angle sensor (the steering wheel operation angle sensor SA, the front wheel steering angle sensor SB) or the communication bus CB. As the steering angle Sa, the steering wheel angle θsw or the front wheel steering angle δfa is acquired.

  In the steering angular velocity calculation block B140, the steering angular velocity dSa is calculated based on the steering angle Sa. The steering angular velocity dSa is a change amount of the steering angle Sa per time, and is calculated by differentiating the steering angle Sa with time. When the steering angle Sa is the steering wheel operating angle θsw, the steering angular velocity dSa is the steering wheel operating angular velocity dθsw, and when the steering angle Sa is the front wheel steering angle δfa, the steering wheel angular velocity dδfa.

  In the threshold adjustment calculation block B180, a start threshold Th (simply referred to as a threshold) for starting vehicle stability control (oversteer suppression control) is calculated. The calculation block B180 includes a start / end calculation block B181 for determining start / end of threshold adjustment, an adjustment threshold determination calculation block B182 for calculating the adjusted threshold, and threshold adjustment. It is comprised by adjustment object wheel calculation block B183 which determines the object wheel to perform. Details of these will be described later.

  The braking fluid pressure control unit B160 gives the braking fluid pressure Pwzz to the braking unit B170 (WCzz or the like) based on the target braking amount Pot (or Spt) calculated in the calculation block B120. The brake fluid pressure control means B160 is composed of a brake actuator BRK, its drive means (for example, an electric motor for a hydraulic pump, a drive means for an electromagnetic valve), and a brake system electronic control unit ECUb. The actual wheel cylinder pressure Pwzz is controlled based on Spt. When the target braking amount is the target braking hydraulic pressure Pot, the electric motor MT, the hydraulic pressure adjusting valve (electromagnetic) is used so that Pwzz matches the target braking hydraulic pressure using the detection result Pwzz of the wheel cylinder pressure sensor PWzz. Valves) SS1, SS2, SZzz, and SGzz are so-called feedback controlled. Further, the braking pressure sensor PWzz of the wheel cylinder can be omitted. In this case, the operating states of the hydraulic pump, the electric motor, the electromagnetic valve, and the like constituting the brake actuator BRK are controlled based on a preset control map. When the target braking amount is the target slip Spt, the electric motor MT, the hydraulic pressure adjusting valve, etc. so that the actual wheel slip calculated based on the detection result of the wheel speed sensor WSzz matches the target slip Spt. Is controlled.

  The braking means B170 includes a wheel cylinder WCzz, a brake caliper BCzz, a brake pad PDzz, and a brake rotor RTzz. The brake pad PDzz and the brake rotor RTzz are brought into contact with each other by the braking hydraulic pressure, and braking torque is applied by the frictional force, thereby generating a braking force on the wheel WHzz. A known drum brake can be used as the braking means B170.

  The calculation map in the vehicle stability control calculation (oversteer suppression control calculation) block B120 can be a characteristic Pch3 shown in FIG. Based on the adjustment threshold Th, the initial characteristic Pch1 is adjusted to the characteristic Pch3. In the characteristic Pch3, when the oversteer state amount Jos indicating the degree of oversteer is less than the adjustment threshold Th, the target braking amounts Pot and Spt are set to “0”, and the oversteer state amount Jos is equal to or larger than the adjustment threshold Th. In this case, the target braking amounts Pot and Spt are increased from “0” as the oversteer state amount Jos increases. In addition, the increase gradient of the target braking amounts Pot and Spt with respect to the increase of the oversteer state amount Jos is set so as to increase as the oversteer state amount Jos increases. When the oversteer state quantity Jos coincides with the adjustment threshold Th, the target braking quantity Pot, Spt rises from “0”, and the oversteer state quantity Jos increases until the oversteer state quantity Jos corresponds to the point s1. The increase gradient of the target braking amounts Pot and Spt with respect to is set so as to be gentler (the increase gradient is smaller) than the initial characteristic Pch1. After the oversteer state quantity Jos exceeds the oversteer state quantity Jos corresponding to the point s1, the increase gradient is set to be equal to the initial characteristic Pch1.

  Even if the threshold value is unnecessarily adjusted for some reason, the increase gradient of the target braking amounts Pot and Spt with respect to the increase of the oversteer state amount Jos is small, so that the driver does not feel uncomfortable. The range of the oversteer state amount Jos that has a gentle increase gradient can be associated with the brake fluid pressure that can close the pad gap. The pad gap is eliminated (the brake pad and the brake rotor are brought into contact) by the oversteer state amount Jos corresponding to the point s1, and the braking hydraulic pressure is increased in a range larger than the oversteer state amount Jos corresponding to the point s1. It should be noted that the characteristic that the increase gradient of the target braking amounts Pot and Spt with respect to the increase of the oversteer state amount Jos increases as the oversteer state amount Jos increases can be set by a curve or a characteristic composed of a plurality of straight lines. it can.

  The threshold value adjustment calculation block B180 in FIG. 3 will be described with reference to FIG. In step G100, the vehicle speed Vx and the braking operation amount Bs are read. In step G105, the steering angle Sa (steering wheel operation angle θsw, front wheel steering angle δfa), steering angular velocity dSa (steering wheel operation angular velocity dθsw, front wheel steering angular velocity dδfa), and actual turning state amount Jra (for example, yaw rate Yr). , Lateral acceleration Gy) is read. Further, in step G110, the control state of the vehicle stability control (whether or not the vehicle stability control has already been started, and if so, what brake fluid pressure is applied to which wheel) Is read).

  In step G112, the turning direction of the vehicle is identified based on the sign of the steering angle Sa. When the sign of the steering angle Sa is a positive sign (+), the left turn direction (counterclockwise turn direction when viewing the vehicle from above) is identified. When the sign of the steering angle Sa is a negative sign (-), the right turning direction (the clockwise turning direction when viewing the vehicle from above) is identified.

  In step G115, a steering angular velocity (also referred to as a cutting steering angular velocity) dSak for the cutting steering is calculated based on the steering angle Sa and the steering angular velocity dSa. A case where the absolute value of the steering angle Sa increases is determined as a steering operation cut-in state. The previous steering angle Sa [n−1] and the current steering angle Sa [n] in the calculation cycle are compared, and the current steering angle Sa [n] is compared with the absolute value of the previous steering angle Sa [n−1]. If the absolute value has increased, it is determined that the steering operation has been cut. Here, [n-1] at the end of the symbol represents the previous value, [n] represents the current value, and so on. Then, the absolute value of the steering angular velocity dSa when the cutting state is determined is calculated as the cutting steering angular velocity dSak. That is, the steering angular velocity dSak in the cutting state is a value representing the magnitude of the steering angular velocity dSa when the driver performs the cutting steering operation.

  In step G120, a steering angular velocity (also referred to as a switching steering angular velocity) dSam for the return steering is calculated based on the steering angle Sa and the steering angular velocity dSa. When the absolute value of the steering angle Sa decreases, it is determined that the steering operation is switched back. The previous steering angle Sa [n−1] and the current steering angle Sa [n] in the calculation cycle are compared, and the current steering angle Sa [n] is compared with the absolute value of the previous steering angle Sa [n−1]. If the absolute value has decreased, it is determined that the steering operation has been switched back. Then, the absolute value of the steering angular velocity dSa when the turning-back state is determined is calculated as the turning-back steering angular velocity dSam. That is, the steering angular velocity dSam in the turning-back state is a value representing the magnitude of the steering angular velocity dSa when the driver performs the turning-back steering operation.

  In step G125, a turning state amount (also referred to as a turning state amount at the time of transition) Jrm or a steering angle (also referred to as a steering angle at the time of transition) Sam corresponding to the steering transition is calculated. Here, the steering shift means that the steering operation state shifts from the cutting state to the switching state. When it is continuously determined that the cutting state is described above, the steering shift is determined when the switching state is determined. Then, the absolute value of the steering angle Sa at the time of steering transition is calculated as the steering angle Sam corresponding to the steering transition. Further, the actual turning state amount Jra when the steering is shifted is calculated as the turning state amount Jrm corresponding to the steering shift. Since there is a time delay in the actual turning state amount with respect to the steering operation, the maximum value of the actual turning state amount Jra immediately after the steering shift is determined can be calculated as the turning state amount Jrm corresponding to the steering shift. Since the time delay can be predicted in advance, the actual turning state amount Jra after the elapse of the predetermined time t3 after the determination of the steering shift can be calculated as the turning state amount Jrm corresponding to the steering shift.

  Next, based on the determination steps G130, G135, and G140, the start / end of threshold adjustment is determined. In step G130, it is determined whether threshold adjustment is currently being executed. If the threshold adjustment is not executed and a negative determination is made in step G130, the arithmetic processing proceeds to step G135. In step G135, it is determined whether the threshold adjustment start condition is satisfied. The threshold adjustment start conditions will be described later. In step G135, when the determination to start threshold adjustment is affirmed, the calculation process proceeds to step G145, and threshold adjustment is started. On the other hand, if the start of threshold adjustment is denied in step G135, the threshold adjustment is not started.

  If threshold adjustment is being executed and an affirmative determination is made in step G130, the arithmetic processing proceeds to step G140. In step G140, it is determined whether the threshold adjustment end condition is satisfied. The threshold adjustment end condition will be described later. In step G140, the threshold adjustment is ended when the determination of completion of the threshold adjustment is affirmed. On the other hand, if the end of the threshold adjustment is denied in step G140, the calculation process proceeds to step G145, and the threshold adjustment is continued.

  The threshold adjustment start determination calculation will be described with reference to FIG. The threshold adjustment start determination is performed for each wheel.

  In step G200, based on the vehicle speed Vx read in step G100, it is determined that the vehicle speed Vx is equal to or higher than a predetermined value V3. If vehicle speed Vx is less than predetermined value V3 and a negative determination is made in step G200, the start of threshold adjustment is denied and execution is prohibited. When the vehicle is low, a sudden yawing behavior that requires a highly responsive braking fluid pressure does not occur. If the vehicle speed Vx is equal to or greater than the predetermined value V3 and an affirmative determination is made in step G200, the arithmetic processing proceeds to step G205.

  In step G205, it is determined that the driver is not performing a braking operation based on the braking operation amount Bs read in step G100. If the braking operation is being performed (the braking operation member BP is being operated) and a negative determination is made in step G205, the start of threshold adjustment is denied and execution is prohibited. This is because the brake fluid pressure is already generated in the wheel cylinder WCzz during the braking operation, and the effect of the threshold adjustment is not expected. If no braking operation is performed by the driver and an affirmative determination is made in step G205, the calculation process proceeds to step G210.

  In step G210, it is determined that the determination target wheel is not the current vehicle stability control target wheel based on the control state of the vehicle stability control read in step G110. If it is the current vehicle stability control target wheel and a negative determination is made in step G210, the start of threshold adjustment is denied and execution is prohibited. This is because the brake fluid pressure is already generated in the wheel cylinder WCzz on the current target wheel of the vehicle stability control, and the effect of the threshold adjustment is not expected. If an affirmative determination is made in step G210 instead of the current vehicle stability control wheel, the calculation process proceeds to step G215.

  In step G215, based on the turning direction identified in step G112, it is determined whether or not the wheel (determination target wheel) for which threshold value adjustment is to be started is the turning outer front wheel. If the wheel for which threshold adjustment is to be started is not a turning outer front wheel and a negative determination is made in step G215, the start of threshold adjustment is denied for that wheel and execution is prohibited. A sudden yawing behavior that requires a highly responsive braking fluid pressure occurs during oversteering. To suppress this oversteering, it is effective to apply braking fluid pressure to the front wheels outside the turn. If the target wheel for threshold adjustment start determination is the front outer wheel, and if an affirmative determination is made in step G215, the arithmetic processing proceeds to step G220. Steps G210 and G215 correspond to the preload target wheel calculation block B153 in FIG.

  In step G220, based on the steering angular velocity dSak at the time of turning steering calculated in step G115, it is determined that the turning steering angular velocity dSak is equal to or greater than a predetermined value Tk2. If the turning steering angular velocity dSak is less than the predetermined value Tk2 and a negative determination is made in step G220, the start of threshold adjustment is denied and execution is prohibited. When the steering angular velocity dSak at the time of turning steering is small, a temporal phase difference between the front wheel lateral force and the rear wheel lateral force is difficult to occur, so that a rapid yawing behavior that requires a highly responsive braking fluid pressure does not occur. . When the steering angular velocity dSak at the time of turning steering is equal to or greater than the predetermined value Tk2 and an affirmative determination is made in step G220, the arithmetic processing proceeds to step G225.

  In step G225, based on the steering angular velocity dSam at the time of reverse steering calculated in step G120, it is determined that the reverse steering angular velocity dSam is equal to or greater than a predetermined value Tm2. If the turning steering angular velocity dSam is less than the predetermined value Tm2, and a negative determination is made in step G225, the start of threshold adjustment is denied and execution is prohibited. When the steering angular velocity dSam at the time of the turn-back steering is small, a temporal phase difference between the front wheel lateral force and the rear wheel lateral force is unlikely to occur, and thus a rapid yawing behavior that requires a highly responsive braking fluid pressure does not occur. . When the steering angular velocity dSam during the turn-back steering is equal to or greater than the predetermined value Tm2 and an affirmative determination is made in step G225, the calculation process proceeds to step G230.

  In step G230, it is determined that the turning state amount Jrm is equal to or greater than the predetermined value Tj2 based on the turning state amount Jrm corresponding to the steering shift calculated in step G125. If the turning state amount Jrm is less than the predetermined value Tj2 and a negative determination is made in step G230, the start of threshold adjustment is denied and execution is prohibited. When the turning state amount Jrm corresponding to the steering transition is small, the rear wheel lateral force does not reach the limit, and a rapid yawing behavior that requires a highly responsive braking fluid pressure does not occur. If the turning state amount Jrm corresponding to the steering shift is equal to or greater than the predetermined value Tj2, and an affirmative determination is made in step G230, the calculation process proceeds to step G235, and threshold value adjustment is started.

  In the determination in step G230, the steering angle Sam corresponding to the steering shift calculated in step G125 can be used instead of the turning state amount Jrm corresponding to the steering shift. That is, in step G230, it is determined that the steering angle Sam corresponding to the steering shift calculated in step G125 is equal to or greater than the predetermined value Ts2. If the steering angle Sam is less than the predetermined value Ts2 and a negative determination is made in step G230, the start of threshold adjustment is denied and execution is prohibited. When the steering angle Sam corresponding to the steering shift is small, the rear wheel lateral force does not reach the limit, and a rapid yawing behavior that requires a highly responsive braking fluid pressure does not occur. If the steering angle Sam corresponding to the steering shift is equal to or greater than the predetermined value Ts2 and an affirmative determination is made in step G230, the calculation process proceeds to step G235, and threshold value adjustment is started.

  In step G230, a determination is made based on one of the transitional turning state amount Jrm and the transitional steering angle Sam. When both of these two determination conditions are satisfied, threshold adjustment is performed. You can also start. The threshold adjustment is prohibited when either one of the determination condition of the turning state quantity Jrm at the time of transition and the determination condition of the steering angle Sam at the time of the transition is denied, so that the reliability of the start determination is improved.

  In step G235, threshold value adjustment is started. Details of the threshold adjustment will be described later. The determination blocks from Step G200 to Step G230 do not have to include all of them, and any one or more of them can be omitted.

  FIG. 7 is a control flow diagram of the threshold adjustment end determination calculation. The threshold adjustment end determination is performed for each wheel.

  In step G400, the time during which the threshold adjustment is continued (duration Tcs) is counted and calculated. In step G410, based on the calculated threshold adjustment duration Tcs, it is determined that duration Tcs is equal to or greater than predetermined time Tc2. If the duration time Tcs is equal to or longer than the predetermined time Tc2 and an affirmative determination is made in step G410, the arithmetic process proceeds to step G430, the threshold value adjustment is terminated, and the threshold value is returned to Tho (initial value). Since the vehicle stability control is not started after a predetermined time has elapsed since the sudden turn-back steering is performed, it is not necessary to adjust the threshold value. On the other hand, if the duration Tcs is less than the predetermined time Tc2 and a negative determination is made in step G410, the calculation process proceeds to step G420, and the threshold adjustment is continued.

  In step G420, it is determined whether the vehicle stability control has been completed based on the control state of the vehicle stability control read in step G110. If the vehicle stability control has been completed and an affirmative determination is made in step G420, the calculation process proceeds to step G430, the threshold value adjustment is terminated, and the threshold value is returned to Tho (initial value). When the vehicle stability control is finished, it is not necessary to adjust the threshold value. On the other hand, if the vehicle stability control is not finished and a negative determination is made in step G420, the threshold adjustment is continued. At least one of steps G410 and G420 can be omitted.

  The threshold value adjustment calculation block B180 in FIG. 3 will be described with reference to FIG. In particular, an adjustment value for threshold adjustment (also referred to as adjustment threshold Th) calculated in the adjustment threshold determination calculation block B182 will be described. The adjustment threshold value Th is calculated for each wheel.

  Based on the turning steering angular velocity dSam calculated in step G120, an adjustment threshold value Th for adjusting the vehicle stability control start threshold value is calculated in the adjustment threshold value calculation block B300. In the range where the turning steering angular velocity dSam is “0” or more and less than the predetermined value Tm2 (corresponding to the predetermined value Tm2 in Step G225), the adjustment threshold value Th is calculated as an initial value Tho (predetermined value). In the range where the turning steering angular velocity dSam is equal to or greater than the predetermined value Tm2, the adjustment threshold value Th is calculated as a characteristic (characteristic Tch1) that decreases from the predetermined value Tho as the switching steering angular velocity dSam increases.

  Further, in the range where the turning steering angular velocity dSam is “0” or more and less than the predetermined value Tm2, the adjustment threshold Th is calculated as an initial value Tho (predetermined value), and in the range where the turning steering angular velocity dSam is the predetermined value Tm2 or more. The adjustment threshold value Th can be calculated as a characteristic (characteristic Tch2) having a predetermined value Thn (a value smaller than the initial value Tho). In this case, instead of the input of the turning steering angular velocity dSam, a signal (control flag) indicating that the determination condition in step G225 is satisfied (positive determination) can be input to the calculation block B300.

  The adjustment threshold value Th calculated in the calculation block B300 can be adjusted based on the turning steering angular velocity dSak. Based on the cutting steering angular velocity dSak calculated in step G115, the adjustment coefficient Ktk is calculated in the adjustment calculating block B310 based on the cutting steering angular velocity. In the range where the turning steering angular velocity dSak is “0” or more and less than the predetermined value Tk2 (corresponding to the predetermined value Tk2 in Step G220), the coefficient Ktk is calculated as “1”. In the range where the turning steering angular velocity dSak is equal to or greater than the predetermined value Tk2, the coefficient Ktk is calculated as a characteristic (characteristic Chk1) that decreases from “1” as the turning steering angular velocity dSak increases.

  Further, the coefficient Ktk is calculated as “1” when the turning steering angular velocity dSak is equal to or greater than “0” and less than the predetermined value Tk2, and the coefficient Ktk is equal to the predetermined value Kk2 ( It can be calculated as a characteristic (characteristic Chk2) having a value smaller than “1”. In this case, instead of the input of the turning steering angular velocity dSak, a signal (control flag) indicating that the determination condition of Step G220 is satisfied (positive determination) can be input to the calculation block B310.

  The multiplication means B340 multiplies the adjustment threshold value Th output from the calculation block B300 by the coefficient Ktk output from the calculation block B310, so that the adjustment threshold value Th is adjusted based on the turning steering angular velocity dSak. The The adjustment threshold Th calculated based on the turning-back steering angular velocity dSam is adjusted based on the magnitude of the turning steering angular velocity dSak by the calculation block B310 and the multiplying unit B340. That is, as the turning steering angular velocity dSak increases, the adjustment threshold value Th is decreased and adjusted, and the vehicle stability control can be activated early.

  The adjustment threshold value Th calculated in the calculation block B300 can be adjusted based on the turning state quantity Jrm during transition (or the steering angle Sam during transition). Based on the transition-time turning state quantity Jrm (or transition-time steering angle Sam) calculated in step G125, the adjustment coefficient Ktm is calculated in the calculation block B320. Transition turning state quantity Jrm (or transition steering angle Sam) is “0” or more, and predetermined value Tj2 (corresponding to predetermined value Tj2 in step G230) (or predetermined value Ts2 (corresponding to predetermined value Ts2 in step G230)) ), The coefficient Ktm is calculated as “1”. When the transition turning state amount Jrm (or transition steering angle Sam) is in the range of the predetermined value Tj2 (or predetermined value Ts2) or more, the transition turning state amount Jrm (or transition steering angle Sam) increases. The coefficient Ktm is calculated as a characteristic (characteristic Chm1) that decreases from “1”.

  Also, in the range where the turning state quantity Jrm at transition (or the steering angle Sam at transition) is “0” or more and less than the predetermined value Tj2 (or the predetermined value Ts2), the coefficient Ktm is calculated as “1”, and at the time of transition A characteristic (characteristic Chm2) in which the coefficient Ktm becomes a predetermined value Km2 (a value smaller than “1”) in a range where the turning state amount Jrm (or the transition steering angle Sam) is equal to or larger than the predetermined value Tj2 (or the predetermined value Ts2). Can be computed as In this case, a signal (control flag) indicating that the determination condition of step G230 is satisfied (affirmation determination) is input to the calculation block B320 instead of the input of the transition state amount Jrm at transition (or the steering angle Sam at transition). Can be entered.

  The predetermined value Tj2 (or the predetermined value Ts2) can be adjusted based on the road surface friction coefficient μmax acquired by the road surface friction coefficient acquisition unit B330. The road surface friction coefficient μmax is obtained by a known method. When the road surface friction coefficient μmax is small, the predetermined value Tj2 (or predetermined value Ts2) is adjusted to a smaller predetermined value Tj4 (<predetermined value Tj2) (or predetermined value Ts4 (<predetermined value Ts2)). At this time, the above-mentioned characteristic Chm1 is changed to the characteristic Chm3, and in the range where the transitional turning state amount Jrm (or the transitional steering angle Sam) is “0” or more and less than the predetermined value Tj4 (or the predetermined value Ts4), The coefficient Ktm is calculated as “1”, and when the transition turning state amount Jrm (or the transition steering angle Sam) is equal to or larger than the predetermined value Tj4 (or the predetermined value Ts4), the transition turning state amount Jrm (or The coefficient Ktm can be calculated to decrease from “1” as the transition steering angle Sam) increases.

  Further, the characteristic Chm2 is changed to Chm4, and the coefficient Ktm is set in a range where the turning state amount Jrm (or the steering angle Sam at the time of transition) is “0” or more and less than the predetermined value Tj4 (or the predetermined value Ts4). Is calculated as “1”, and the coefficient Ktm is greater than the predetermined value Km2 (from “1”) in the range where the turning state amount Jrm (or the steering angle Sam at the time of transition) is equal to or greater than the predetermined value Tj4 (or the predetermined value Ts4). (Small value) can be calculated. By considering the road surface friction coefficient μmax, the degree to which the vehicle behavior reaches the turning limit in the first steering is evaluated, the sudden yawing behavior in the second steering is predicted, and the vehicle stability control is started early. The start threshold is adjusted so that it is possible.

  The multiplication means B340 multiplies the adjustment threshold value Th output from the calculation block B300 by the adjustment coefficient Ktm output from the calculation block B320, so that the adjustment threshold value Th changes to the turning-time turning state quantity Jrm (or , The shift steering angle Sam). The adjustment threshold Th calculated based on the turning steering angular velocity dSam by the calculation block B320 and the multiplication unit B340 is adjusted based on the magnitude of the transition state Jrm (or the transition steering angle Sam). Is done. That is, the adjustment threshold value Th is decreased and adjusted in accordance with an increase in the transitional turning state amount Jrm (or the transitional steering angle Sam). Note that at least one of the operation blocks B310 and B320 may be omitted.

  The operation and effect of threshold adjustment will be described with reference to FIG.

  As shown by the characteristic Chb, in the first steering, when the turning steering is performed from the origin 0 to the point b1, and then the turning steering is performed from the point b1 to the point b2, the magnitude (absolute value) of the steering angular velocity dSam at the turning steering. ) Is equal to or greater than the predetermined value Tm2, execution of threshold adjustment for the second steering is started. At this time, the threshold adjustment start condition can be that the magnitude (absolute value) of the steering angular velocity dSa in the cut state in the first steering is equal to or greater than the predetermined value Tk2. Furthermore, the threshold adjustment start condition can be that the magnitude (absolute value) of the steering angle Sam at the time of transition from the turning state to the turning-back state in the first steering is equal to or greater than the predetermined value Ts2. Also, the magnitude (absolute value) of the actual turning state amount Jrm corresponding to the transition from the turning state to the turning back state in the first steering (the actual turning state amount at the point e1 at the time of steering transition, the actual turning state amount after the steering transition) The maximum value (actual turning state quantity at point e2) and the magnitude of any of the actual turning state quantities at point e3 after elapse of the predetermined time t3 from the time of steering shift are equal to or greater than the predetermined value Tj2. Can be used as a threshold adjustment start condition. By evaluating the steering state of the first steering according to the magnitude of the infeed steering angular velocity, the steering angle at the time of steering transition, or the actual turning state quantity, a sudden yawing behavior is predicted, and the threshold Value adjustment can be performed appropriately.

  The threshold value adjustment is performed on a wheel to which no brake fluid pressure is applied by vehicle stability control (oversteer suppression control). Further, the turning direction of the vehicle is identified based on the steering angle, outside in the turning direction (the turning direction of the first steering) opposite to the turning direction when the steering angle decreases (the turning direction of the second steering), and The threshold value can be adjusted for the front wheel braking means. The threshold adjustment is performed on the turning outer front wheel. In FIG. 9, the threshold value is adjusted for the left front wheel that is the outer front wheel in the second steering (right turn). Compared with the case where the threshold adjustment is not performed, the response of the brake fluid pressure is improved.

  In FIG. 9, the brake fluid pressure control by the vehicle stability control (oversteer suppression control) is executed in the first steering, but the oversteer state is not so large that the oversteer suppression control is started in the first steering. However, a sudden yawing behavior may occur in the second steering. Therefore, even when the vehicle oversteer state is not detected (identified), the threshold value adjustment is started when the threshold adjustment start condition is satisfied.

  When the vehicle stability control (oversteer suppression control) is finished, there is no need for threshold adjustment. Therefore, when the vehicle stability control is terminated, the threshold adjustment is also terminated, and the adjustment threshold Th is returned to the initial value Tho. Further, even when threshold adjustment is performed, vehicle stability control (oversteer suppression control) may not be performed. Therefore, the duration Tcs after the threshold adjustment is started is counted, and when the duration Tcs exceeds the predetermined time Tc2, the threshold adjustment is terminated and the adjustment threshold Th is returned to the initial value Tho. .

  As shown in the characteristic Chc, when the turning steering angular velocity of the first steering (steering angular velocity from the origin 0 to the point c1) is less than the predetermined value Tk2, since the rapid yawing behavior does not occur, the threshold value adjustment is performed. It is forbidden. Further, as indicated by the characteristic Chd, the magnitude (absolute value) of the steering angle Sam at the time of transition from the turning state of the first steering to the turning-back state (steering angle Sa2 at the point d1), a predetermined value Ts2 (threshold value). If it is less than the threshold value, threshold adjustment is prohibited because no rapid yawing behavior occurs. Also, the magnitude (absolute value) of the actual turning state amount Jrm corresponding to the transition from the turning state of the first steering to the turning back state (the absolute value of the actual turning state amount at the time of steering transition, the maximum value of the actual turning state amount immediately after the steering transition) If the magnitude of any of the actual turning state values after a predetermined time has elapsed from the time of steering shift is less than the predetermined value Tj2 (threshold value), rapid yawing behavior does not occur. Threshold adjustment is prohibited.

  The determination of whether or not the steering operation has been turned in steps G115 and G120 can be made based on the sign of the steering angle Sa and the sign of the steering angular velocity dSa. If the sign of the steering angle Sa and the sign of the steering angular speed dSa match, the turning steering state is determined. If the sign of the steering angle Sa and the sign of the steering angular speed dSa are different, the reverse steering state is determined. The For example, in a left turn, if the steering angle Sa is a positive sign (+) and the steering angular velocity dSa is a positive sign (+), the cutting state is determined. On the other hand, if the steering angle Sa is a positive sign (+) and the steering angular velocity dSa is a negative sign (−) in the left turn, the turning-back state is determined.

  The determination of the transition from the turning state of the steering operation to the turning-back state in Step G125 can be made based on the sign of the steering angle Sa and the sign of the steering angular velocity dSa. When the sign of the steering angle Sa and the sign of the steering angular velocity dSa coincide with each other (cut-in steering state), the sign of the steering angle Sa and the sign of the steering angular velocity dSa become different (turn-back steering state). Next, the steering shift is determined.

  In the above-described threshold adjustment target wheel determination, the threshold adjustment is performed on the wheel that is the front outer wheel in the turning direction of the second steering. However, threshold adjustment can be made for all wheels. The threshold adjustment can be performed on the front two wheels regardless of the turning direction of the vehicle.

1 is a schematic configuration diagram of a vehicle equipped with a vehicle motion control device according to an embodiment of the present invention. It is a figure which shows the whole structure of a brake actuator. FIG. 2 is a functional block diagram when vehicle stability control is performed by the vehicle motion control device shown in FIG. 1. Fig. 4 is a second calculation map related to the vehicle stability control calculation shown in Fig. 3. FIG. 4 is a control flow diagram related to the entire processing of threshold adjustment calculation shown in FIG. 3. It is a control flowchart regarding the start determination of threshold value adjustment. It is a control flow figure regarding the end judgment of threshold adjustment. It is a functional block diagram regarding the determination method of the adjustment threshold value in threshold value adjustment. It is a figure for demonstrating the effect | action and effect of embodiment. It is a figure for demonstrating steering operation which avoids an obstacle etc.

Explanation of symbols

BRK ... brake actuator, ECU ... electronic control unit, YR ... yaw rate sensor, GY ... lateral acceleration sensor, WSzz ... wheel speed sensor, SA ... steering wheel operation angle sensor, SB ... front wheel steering angle sensor, WCzz ... wheel cylinder for each wheel

Claims (11)

Braking means provided on the wheels of the vehicle;
An actual turning amount acquisition means for acquiring an actual turning state amount of the vehicle;
Oversteer identifying means for identifying the degree of oversteer of the vehicle based on the actual turning state quantity;
Stability control means for executing stability control for starting application of braking fluid pressure to the braking means when the identification result of the oversteer identification means exceeds a threshold value;
Steering angle acquisition means for acquiring a steering angle by a driver of the vehicle;
Steering angular velocity calculating means for calculating a steering angular velocity based on the steering angle;
Threshold adjustment means for adjusting the threshold based on the magnitude of the steering angular velocity when the steering angle decreases;
A vehicle motion control apparatus comprising: 2. The vehicle motion control apparatus according to claim 1, wherein the threshold value adjusting means adjusts the threshold value to a small value when the magnitude of the steering angular velocity is equal to or greater than a predetermined value. 3. The vehicle according to claim 1, wherein the threshold adjustment unit adjusts the threshold even when the oversteer identification unit does not identify oversteer of the vehicle. Motion control device. A turning direction identifying means for identifying a turning direction of the vehicle based on the steering angle;
The threshold value adjusting means adjusts the threshold value for a wheel located outside and in front of the vehicle in a turning direction opposite to the turning direction when the steering angle decreases. The vehicle motion control device according to any one of claims 1 to 3, wherein the vehicle motion control device is characterized in that: A braking operation acquisition means for acquiring an operation of the braking member of the driver;
The threshold adjustment means determines that the operation of the braking member is performed based on the acquisition result of the braking operation acquisition means, and prohibits the adjustment of the threshold when the determination is affirmed. The vehicle motion control device according to any one of claims 1 to 4, wherein the vehicle motion control device is characterized in that: 6. The threshold value adjusting means prohibits adjustment of the threshold value when the magnitude of the steering angular velocity when the steering angle increases is less than a predetermined value. The vehicle motion control apparatus described in any one of these. The threshold adjustment means prohibits adjustment of the threshold when the steering angle is less than a predetermined value when the steering angle shifts from an increasing state to a decreasing state. The vehicle motion control apparatus according to any one of claims 1 to 6. The threshold adjustment means prohibits the adjustment of the threshold when the actual turning state amount corresponding to the shift of the steering angle from the increasing state to the decreasing state is less than a predetermined value. The vehicle motion control apparatus according to any one of claims 1 to 7, wherein 9. The threshold value adjusting unit according to claim 1, wherein the threshold value adjusting unit ends the adjustment of the threshold value when a predetermined time elapses after the adjustment of the threshold value is started. A vehicle motion control apparatus according to one of the above. The vehicle motion according to any one of claims 1 to 9, wherein the threshold value adjusting unit ends the adjustment of the threshold value when the stability control is completed. Control device. When the magnitude of the steering angular velocity when the steering angle decreases is greater than or equal to a predetermined value, the stability control means indicates that the increase gradient of the brake hydraulic pressure with respect to the increase in the identification result of the oversteer identification means is the identification result. The vehicle motion control device according to any one of claims 1 to 10, wherein the brake fluid pressure is controlled so as to increase with an increase in the braking force.