JP2011073605A - Motion control device of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle motion control device capable of restraining an under-steer condition by controlling the action of a vehicle prior to the under-steer condition accompanying rapid steering. <P>SOLUTION: This motion control device for a vehicle provides a braking force to a wheel to restrain an under-steer condition. The device comprises a steering speed calculation means (106) for calculating a steering speed, and a braking force providing means (110) for providing a braking force to an outer turning wheel when the steering speed calculated by the steering speed calculation means is larger than a reference threshold value. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a vehicle motion control device that can control the motion of a vehicle and suppress the occurrence of an understeer state prior to the occurrence of an understeer state accompanying sudden steering.

  As one device for controlling the behavior of a vehicle such as an automobile when turning, for example, as described in Patent Document 1, the steer state is estimated from the deviation between the actual yaw rate of the vehicle body and the target yaw rate when the vehicle turns. A behavior control apparatus configured to control the difference in braking force between the left and right wheels in accordance with the steering state and thereby improve the stability of the vehicle during a turn is conventionally known.

  According to such a behavior control device, it is possible to prevent the steering state from being excessively oversteered or excessively understeering at the time of turning, thereby causing undesired turning such as spin or drift out of the vehicle. The behavior can be reduced.

Japanese Patent Laid-Open No. 2-70561

  However, in the conventional behavior control device described in Patent Document 1, since the yaw rate deviation becomes large and the control is started when understeer is actually generated, the occurrence of understeer cannot be suppressed. There is a problem that the control for eliminating understeer becomes complicated.

  The present invention was made to solve the above-described conventional problems, and prior to the occurrence of an understeer state accompanying sudden steering, the vehicle is controlled so that the occurrence of an understeer state can be suppressed. An object of the present invention is to provide a motion control device.

  According to a first aspect of the present invention, there is provided a vehicle motion control device that applies a braking force to a wheel to suppress the occurrence of an understeer state, a steering speed calculating means that calculates a steering speed, and the steering speed And a braking force applying unit that applies a braking force to the outer turning wheel when the steering speed calculated by the calculating unit exceeds a reference threshold value.

  The invention according to claim 2 is characterized in that, in claim 1, the braking force applying means controls the turning outer wheel when a predetermined time has elapsed after starting to apply the braking force to the turning outer wheel. This is to end the application of power.

  According to a third aspect of the present invention, in the first aspect, the braking force application unit starts to apply the braking force to the turning outer wheel, and then the steering speed calculated by the steering speed calculation unit is a reference. When it becomes smaller than the threshold value, the application of the braking force to the turning outer wheel is terminated.

  According to a fourth aspect of the present invention, there is provided a vehicle motion control device that applies braking force to wheels and suppresses the occurrence of an understeer state, a steering speed calculating means that calculates a steering speed, and the steering speed When the steering speed calculated by the calculating means becomes larger than a reference threshold value, a first braking force applying means for applying a braking force to the turning inner wheel, and a braking force applied by the first braking force applying means. Subsequent to the application, second braking force applying means for applying a braking force to the turning outer wheel is provided.

  According to a fifth aspect of the present invention, in the fourth aspect, the second braking force applying unit is configured to perform the steering after the braking force is applied to the turning inner wheel by the first braking force applying unit. The application of braking force to the turning outer wheel is started after the passage of time according to the speed.

  According to the first aspect of the present invention, the steering speed calculation means for calculating the steering speed, and when the steering speed calculated by the steering speed calculation means exceeds a reference threshold value, the braking force is applied to the turning outer wheel. The braking force is applied to the vehicle so that the turning outer wheel is applied with a braking force prior to the occurrence of an understeer state due to sudden steering, thereby increasing the turning ability of the vehicle. be able to. Therefore, the occurrence of the understeer state can be easily suppressed by simple control that only applies the braking force to the turning outer wheel.

  According to the second aspect of the present invention, the braking force application means ends the application of the braking force to the turning outer wheel when a predetermined time has elapsed after starting to apply the braking force to the turning outer wheel. Therefore, before the deterioration of the understeer state due to the generation of the outward turning moment due to the application of the braking force to the turning outer wheel exceeds the suppression effect of the understeer state due to the improvement of the turning performance, the braking force is applied to the turning outer wheel. Therefore, the occurrence of an understeer state can be further suppressed.

  According to the invention of claim 3, when the braking force applying means starts applying the braking force to the turning outer wheel, the steering speed calculated by the steering speed calculating means becomes smaller than the reference threshold value. In addition, since the application of the braking force to the turning outer wheel is finished, the same effect as that of the invention according to claim 2 can be obtained.

  According to the invention of claim 4, when the steering speed calculated by the steering speed calculating means and the steering speed calculated by the steering speed calculating means become larger than the reference threshold value, the braking force is applied to the turning inner wheel. Since the first braking force applying means to be applied and the second braking force applying means for applying the braking force to the turning outer wheel following the application of the braking force by the first braking force applying means, the turning inner wheel is provided. By applying a braking force to the vehicle, a bending moment in the steering direction can be generated, and the front wheel load can be increased to improve the turning ability of the vehicle. After that, the vehicle starts turning, and the load on the turning outer wheel increases, but by applying the braking force to the turning outer wheel following the application of the braking force to the turning inner wheel, the load is effectively moved to the front side of the vehicle. Further, the turning ability can be improved. Thereby, the occurrence of understeer can be further suppressed.

  The speed of load transfer to the turning outer wheel accompanying the turning of the vehicle increases as the steering speed increases. Therefore, in the invention according to claim 5, the second braking force applying means, after the time corresponding to the steering speed has elapsed since the start of applying the braking force to the turning inner wheel by the first braking force applying means, Added braking force to the turning outer wheel. Therefore, the load can be moved more effectively to the front side of the vehicle.

1 is a schematic diagram showing an embodiment of a vehicle to which a vehicle motion control device according to the present invention is applied. It is a figure which shows the oil path | route containing the brake hydraulic pressure generator shown in FIG. It is a block diagram which shows the input / output relationship of the signal of brake ECU. It is a flowchart of the control program which concerns on 1st Embodiment performed by brake control ECU shown in FIG. It is a figure which shows the time chart which concerns on 1st Embodiment. It is a figure which shows the control map which memorize | stored the relationship of the controlled variable with respect to the steering speed in 1st Embodiment. It is a flowchart which shows the modification of 1st Embodiment. It is a time chart which shows the modification of 1st Embodiment. It is a flowchart of the control program which concerns on 2nd Embodiment performed by brake control ECU shown in FIG. It is a figure which shows the time chart which concerns on 2nd Embodiment. It is a figure which shows the control map which memorize | stored the relationship of the controlled variable with respect to the steering speed in 2nd Embodiment. It is a figure which shows the modification of 2nd Embodiment.

  Hereinafter, an embodiment of a vehicle to which a vehicle motion control device according to the present invention is applied will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the overall configuration of the vehicle. This vehicle is a front-wheel drive vehicle and is of a type in which the driving force of the engine 11 that is a drive source mounted on the front portion of the vehicle body is transmitted to the front wheels.

  The vehicle includes a drive system 10 that drives the vehicle and a braking system 20 that brakes the vehicle. The drive system 10 includes an engine 11, a transmission 12, a differential 13, left and right drive shafts 14a and 14b, an accelerator pedal 15, and an engine control ECU 16. The driving force of the engine 11 is transmitted through the differential 13 and the left and right drive shafts 14a and 14b to the left and right front wheels Wfl and Wfr, which are drive wheels, after being shifted by the transmission 12.

  The braking system 20 includes a hydraulic brake device that supplies hydraulic pressure to the left and right front wheels Wfl, Wfr and the left and right rear wheels Wrl, Wrr to brake the vehicle. The hydraulic brake device (braking system) 20 causes the diaphragm to act on each diaphragm by the wheel cylinders WCfl, WCfr, WCrl, WCrr for restricting the rotation of each wheel Wfl, Wfr, Wrl, Wrr and the intake pressure of the engine 11. The booster 22 is a booster that boosts (increases) the brake operation force generated by the depression of the brake pedal 21, and the base fluid according to the brake operation force boosted by the negative pressure booster 22 A master cylinder 23 that generates a hydraulic pressure (hydraulic pressure) that is a pressure and supplies it to each wheel cylinder WCfl, WCfr, WCrl, WCrr; a reservoir tank 24 that stores the brake fluid and replenishes the master cylinder 23 with the brake fluid; , Master cylinder 23 and each wheel cylinder WCfl, WCfr, WCrl, WCr The brake fluid pressure generating device 25 that generates the control fluid pressure and applies it to the wheel to be controlled regardless of the depression state of the brake pedal 21, and the brake control ECU 26 that controls the brake fluid pressure generating device 25. And.

  Each wheel cylinder WCfl, WCfr, WCrl, WCrr is provided in each caliper CLfl, CLfr, CLrl, CLrr, and houses a piston (not shown) that slides in a liquid-tight manner. When basic hydraulic pressure or control hydraulic pressure is supplied to each wheel cylinder WCfl, WCfr, WCrl, WCrr, each piston presses a pair of brake pads BPfl, BPfr, BPrl, BPrr, and each wheel Wfl, Wfr, Wrl , Wrr and the disk rotor DRfl, DRfr, DRrl, DRrr that rotate integrally with each other are sandwiched from both sides to restrict the rotation.

  Next, the configuration of the brake fluid pressure generator 25 will be described in detail with reference to FIG. The brake fluid pressure generating device 25 is generally well known, and fluid pressure control valves 41 and 51 that are master cylinder cut valves, and pressure increase valves 42 and 43 that are electromagnetic valves constituting an ABS control valve. , 52, 53 and pressure reducing valves 45, 46, 55, 56, pressure regulating reservoirs 44, 54, pumps 47, 57, motor 33, and the like.

  As shown in FIG. 2, the brake fluid pressure generator 25 includes first and second oil paths Lr and Lf connected to the first and second fluid pressure chambers 23 a and 23 b of the master cylinder 23. The first oil path Lr communicates the first hydraulic pressure chamber 23a with the left rear wheel Wrl and the wheel cylinders WCrl and WCfr of the right front wheel Wfr, and the second oil path Lf is the second hydraulic pressure chamber 23b. Are communicated with the wheel cylinders WCfl and WCrr of the left front wheel Wfl and the right rear wheel Wrr, respectively.

  The first oil path Lr of the brake fluid pressure generating device 25 is provided with a linear control type fluid pressure control valve 41 composed of a differential pressure control valve. The hydraulic pressure control valve 41 is controlled to be switched between a communication state and a differential pressure state by the brake control ECU 26. The hydraulic pressure control valve 41 is normally de-energized and is in a normal communication state. However, by energizing to a differential pressure state (closed side), the oil path Lr2 on the wheel cylinders WCrl, WCfr side is connected to the master cylinder 23 side. It can be maintained at a pressure higher than the oil path Lr1 by a predetermined control differential pressure. This control differential pressure is regulated by the brake control ECU 26 according to the control current.

  The first oil path Lr2 is branched into two. One is provided with a pressure increasing valve 42 for controlling the increase of the brake fluid pressure to the wheel cylinder WCrl in the ABS control pressure mode, and the other is provided with the other. Is provided with a pressure increasing valve 43 for controlling an increase in the brake fluid pressure to the wheel cylinder WCfr in the ABS control pressure mode. These pressure increasing valves 42 and 43 are configured as two-position valves that can control the communication / blocking state by the brake control ECU 26. The booster valves 42 and 43 are normally open type open / close solenoid valves that are in a communication state when not energized, and are energized and shut off. When the pressure increasing valves 42 and 43 are controlled to be in communication, the basic hydraulic pressure of the master cylinder 23 or / and the control hydraulic pressure generated by the drive of the pump 47 and the control of the hydraulic pressure control valve 41 are changed. It can be added to the wheel cylinders WCrl, WCfr. The pressure increasing valves 42 and 43 can execute ABS control together with the pressure reducing valves 45 and 46 and the pump 47.

  Note that, during the normal brake in which the ABS control is not executed, the pressure increasing valves 42 and 43 are always controlled to communicate. Further, the pressure increasing valves 42 and 43 are respectively provided with safety valves 42a and 43a in parallel. When the driver lifts his / her foot from the brake pedal 21 during the ABS control, the safety cylinders WCrl and WCfr are associated with it. The brake fluid is returned to the reservoir tank 24.

  The oil path Lr2 between the pressure increasing valves 42 and 43 and the wheel cylinders WCrl and WCfr is communicated with the pressure regulating reservoir 44 via the oil path Lr3. The oil path Lr3 is provided with pressure reducing valves 45 and 46 that can control the communication / blocking state by the brake control ECU 26, respectively. The pressure reducing valves 45 and 46 are normally closed on-off solenoid valves that are in a cut-off state when not energized and are in a communication state when energized. These pressure reducing valves 45 and 46 are always cut off in the normal brake state (when the ABS is not operating), and are appropriately connected to allow the brake fluid to escape to the pressure regulating reservoir 44 through the oil path Lf3, so that the wheel cylinders WCrl, The brake fluid pressure in the WCfr is controlled to prevent the wheels from becoming locked.

  Further, a pump 47 is disposed together with a safety valve 47a in an oil path Lr4 connecting the oil path Lr2 and the pressure regulating reservoir 44 between the hydraulic pressure control valve 41 and the pressure increasing valves 42 and 43. An oil path Lr5 is provided so as to connect the pressure regulating reservoir 44 to the master cylinder 23 via the oil path Lr1. The pump 47 is driven by the motor 33 according to a command from the brake control ECU 26. In the ABS control pressure-reduction mode, the pump 47 sucks brake fluid in the wheel cylinders WCrl and WCfr or brake fluid stored in the pressure-regulating reservoir 44, and passes through the fluid pressure control valve 41 which is in communication. It returns to the master cylinder 23.

  In addition, when the pump 47 executes control for automatically applying hydraulic pressure to any of the wheel cylinders WCfl to WCrr, such as vehicle motion control and brake assist, the liquid that has been switched to the differential pressure state. In order to generate a control differential pressure in the pressure control valve 41, the brake fluid in the master cylinder 23 is sucked in through the oil paths Lr1, Lr5 and the pressure regulating reservoir 44, and the pressure increase valve 42 in communication with the oil paths Lr4, Lr2. , 43 to discharge to each wheel cylinder WCrl, WCfr to apply a control hydraulic pressure. In order to alleviate the pulsation of the brake fluid discharged from the pump 47, a damper 48 is disposed on the upstream side of the pump 47 in the oil path Lr4.

  The oil path Lr1 is provided with a pressure sensor P for detecting a master cylinder pressure that is a brake fluid pressure in the master cylinder 23, and this detection signal is transmitted to the brake control ECU 26. Note that the pressure sensor P may be provided in the oil path Lf1.

  Further, the second oil path Lf of the brake fluid pressure generating device 25 is composed of oil paths Lf1 to Lf5 in the same manner as the first oil path Lr. The second oil path Lf includes a fluid pressure control valve 51 similar to the fluid pressure control valve 41 and a pressure regulating reservoir 54 similar to the pressure regulating reservoir 44. The branched oil paths Lf2, Lf2 communicating with the wheel cylinders WCfl, WCrr are provided with pressure increasing valves 52, 53 similar to the pressure increasing valves 42, 43, and the pressure reducing valves similar to the pressure reducing valves 45, 46 are provided in the oil path Lf3. 55 and 56 are provided. The oil path Lf4 includes a pump 57, a safety valve 57a, and a damper 58 similar to the pump 47, the safety valve 47a, and the damper 48. The pressure increasing valves 52 and 53 are provided with safety valves 52a and 53a in parallel with the safety valves 42a and 43a, respectively.

  Thus, the brake fluid pressure generator 25 can directly apply the basic fluid pressure from the master cylinder 23 to the wheel cylinders WCfl, WCfr, WCrl, WCrr. Further, the brake fluid pressure generator 25 generates the control fluid pressure generated by driving the pumps 47 and 57 and controlling the fluid pressure control valves 41 and 51, and the wheel cylinders WCfl and WCfr of each wheel Wfl, Wfr, Wrl and Wrr. , WCrl, WCrr. In other words, the brake fluid pressure generating device 25 can also apply a fluid pressure to the wheel cylinders WCfl, WCfr, WCrl, WCrr according to the operation state (depression state) of the brake pedal 21 of the driver, or the driver's brakes. Regardless of the operation state of the pedal 21, the hydraulic pressure to the wheel cylinders WCfl, WCfr, WCrl, WCrr can be controlled.

  The brake control ECU 26 controls the vehicle motion control device of the present invention that controls the control system of the hydraulic brake device 20, and is constituted by a known microcomputer including a CPU, a ROM, a RAM, an I / O, and the like. Various calculations and the like are executed in accordance with a program stored in the ROM. FIG. 3 is a block diagram showing the input / output relationship of signals of the brake control ECU 26.

  As shown in FIGS. 1 and 3, the brake control ECU 26 includes wheel speed sensors Sfl, Sfr, Srl, Srr, steering angle sensor 27, yaw rate sensor 28, lateral acceleration provided in each wheel Wfl, Wfr, Wrl, Wrr. (Horizontal G) The detection signal from the sensor 29 is received, and the obtained various physical quantities are stored in the RAM of the microcomputer. For example, the brake control ECU 26 actually controls the wheel speed and vehicle speed (estimated vehicle body speed) of each wheel Wfl, Wfr, Wrl, Wrr, the steering angle according to the operation amount of the steering wheel 27a by the driver, and the vehicle based on each detection signal. The yaw rate and lateral G generated in Further, based on these, it is determined whether or not the vehicle motion control is to be executed, and the control target wheel when the vehicle motion control is executed is determined, or the control amount, that is, the wheel cylinder WCfl, The hydraulic pressure generated in WCfr, WCrl, WCrr is obtained. Based on the result, the brake control ECU 26 controls the hydraulic pressure control valves 41 and 51 and also controls the motor 33 for driving the pumps 47 and 57.

  As described above, the vehicle motion control apparatus according to the present embodiment includes the ABS control pressure increasing valves 42, 43, 52, 53 and the pressure reducing valves 45, 46, 55, 56 that constitute the brake fluid pressure generating device 25. Linear control type fluid that controls the fluid pressure supplied to the wheel cylinders WCfl, WCfr, WCrl, WCrr to the brake fluid pressure generator 25 while diverting the pressure regulating reservoirs 44, 54, the pumps 47, 57 and the motor 33. The pressure control valves 41 and 51 are provided, and the brake control ECU 26 is configured to control the brake hydraulic pressure generator 25 based on outputs from the steering angle sensor 27, the yaw rate sensor 28, the lateral G sensor 29, and the like.

  The wheel speed sensors Sfl, Sfr, Srl, Srr are provided in the vicinity of the wheels Wfl, Wfr, Wrl, Wrr, respectively, and the frequency according to the rotation speed (wheel speed) of each wheel Wfl, Wfr, Wrl, Wrr. Are output to the brake control ECU 26. The steering angle sensor 27 detects a rotation angle (steering angle) from a neutral position of steering and outputs a steering angle signal to the brake control ECU 26. The yaw rate sensor 28 detects the yaw rate of the vehicle and outputs a detection signal to the brake control ECU 26. The lateral acceleration sensor 29 detects the acceleration in the left-right direction of the vehicle and outputs a detection signal to the brake control ECU 26.

  Next, the motion control of the vehicle according to the first embodiment will be described with reference to the flowchart shown in FIG. 4 and the time chart shown in FIG. The control according to the flowchart shown in FIG. 4 is started when an ignition switch (not shown) is turned on, and is repeatedly executed every predetermined time (for example, 5 msec). In the following description, it is assumed that the steering wheel 27a is steered rightward, for example, with the steering amount shown in FIG. That is, the turning outer wheel as the wheel to be controlled in this case is the left front wheel Wfl.

  First, at step 100, the steering angle detected by the steering angle sensor 27 is read. In step 102, the steering speed is calculated based on the amount of change in the steering angle detected by the steering angle sensor 27, and in step 104, the calculated steering speed is a predetermined reference threshold value THwv (FIG. 5). It is determined whether it is larger than (see). If the steering speed is less than the threshold value THwv, the program is returned. Step 102 constitutes a steering speed calculation means in the claims.

  If the steering speed is greater than the threshold value THwv, in step 106, the braking force to be applied to the turning outer wheel (left front wheel) Wfl is set. That is, the hydraulic pressure generated in the wheel cylinder WCfl of the turning outer wheel Wfl is set. The wheel cylinder pressure (braking force) is calculated as a control amount corresponding to the steering speed based on a control map M1 (see FIG. 6) stored in the ROM of the microcomputer. In step 108, a braking time T1 to be given to the turning outer wheel Wfl is set. The braking time T1 is set based on a set value (for example, 200 msec) similarly stored in the ROM. Subsequently, in step 110, the brake fluid pressure generating device 25 is controlled to apply a braking force to the turning outer wheel Wfl, and the turning outer wheel is operated with the braking force set in step 106 and the braking time T1 set in step 108. A braking force is applied to Wfl. Step 110 described above constitutes the braking force applying means in the claims.

  That is, in order to generate the hydraulic pressure set in the wheel cylinder WCfl using the left front wheel Wfl as a control target wheel, the hydraulic pressure control valve 51 is set in a differential pressure state, and the pumps 47 and 57 are driven by the motor 33. The brake fluid pressure on the downstream side (wheel cylinder side) of the fluid pressure control valve 51 is increased by the differential pressure generated by the fluid pressure control valve 51. At this time, by increasing the pressure-increasing valve 53 corresponding to the right rear wheel Wrr that is the non-control target wheel, the wheel cylinder WCrr is not pressurized, and the pressure increase valve corresponding to the left front wheel Wfl that is the control target wheel is set. The pressure valve 52 is prevented from flowing current. In this state, a desired hydraulic pressure can be generated in the wheel cylinder WCfl by adjusting the amount of current flowing through the linear control type hydraulic pressure control valve 51.

  In step 110 described above, when a braking force corresponding to the steering speed is applied to the turning outer wheel (left front wheel) Wfl for a predetermined braking time T1, the brake fluid pressure generating device 25 is controlled, as shown in FIG. The supply of hydraulic pressure to the wheel cylinder WCfl of the turning outer wheel Wfl is stopped.

  Thus, according to the flowchart shown in FIG. 4, when the steering speed is larger than the reference threshold value THwv, the wheel cylinder pressure (braking force) having a magnitude corresponding to the steering speed is applied to the turning outer wheel Wfl for a predetermined time T1. As a result, a forward load is generated on the vehicle, the gripping force of the turning outer wheel Wfl is increased, and the turning ability of the vehicle is improved. This makes it possible to easily suppress the occurrence of understeer by simple control that only applies a braking force to the turning outer wheel Wfl.

  Moreover, by setting the braking time for applying the braking force to the turning outer wheel Wfl to the predetermined time T1, the generation of the yaw force for turning the vehicle in the direction opposite to the turning direction by applying the braking force to the turning outer wheel Wfl for a long time is generated. Before the deterioration of the understeer state due to the generation of an outward turning moment due to the application of the braking force to the turning outer wheel Wfl exceeds the effect of suppressing the understeering state due to the improvement of the turning ability as described above. The application of power can be terminated, and the occurrence of an understeer state can be further suppressed.

  FIGS. 7 and 8 are flowcharts and time charts showing modifications of FIGS. 4 and 5, in which the braking force applied to the turning outer wheel Wfl is based on the condition that the steering speed is smaller than the reference threshold value THwv. It is made to end as.

  That is, in FIG. 7, until the braking force to be applied to the turning outer wheel (front left wheel) Wfl is set according to the steering speed TH (steps 100 to 106), the flow chart is the same as the flowchart of FIG. When the braking force to be applied to the turning outer wheel (front left wheel) Wfl is set, the brake fluid pressure generator 25 is controlled (control mode) to apply the braking force to the turning outer wheel Wfl in the next step 110 (step S100). The braking force is applied to the turning outer wheel Wfl with the braking force set in 106. Thereafter, the program returns. Then, such a program is repeatedly executed every predetermined time (for example, 5 msec), and when it is determined in step 104 that the steering speed is lower than the threshold value THwv, the process proceeds to step 107 and the mode is set to the non-control mode. The hydraulic pressure control by the brake hydraulic pressure generator 25 is terminated (see FIG. 8).

  Next, the motion control of the vehicle according to the second embodiment will be described with reference to the flowchart shown in FIG. 9 and the time chart shown in FIG. In the second embodiment, when the steering speed becomes greater than a predetermined reference threshold value THwv, the turning outer wheel (for example, the left front wheel) Wfl described in the first embodiment is controlled. Prior to applying power, braking force is applied to the turning inner wheel (for example, the right front wheel) Wfr.

  In FIG. 9, at step 200, the steering angle detected by the steering angle sensor 27 is read. In step 202, a steering speed is calculated based on the amount of change in the steering angle detected by the steering angle sensor 27. In step 204, whether the calculated steering speed is greater than a predetermined reference threshold value THwv. It is determined whether or not. If the steering speed is lower than the threshold value THwv, the program is returned. If the steering speed is higher than the threshold value THwv, the process proceeds to step 206.

  In step 206, the braking force to be applied to the turning inner wheel (right front wheel) Wfr is set. That is, the hydraulic pressure generated in the wheel cylinder WCfr of the turning inner wheel Wfr is set. The wheel cylinder pressure (braking force) is calculated as a control amount corresponding to the steering speed based on a control map M2A (see FIG. 11) stored in the ROM of the microcomputer. Next, at step 208, a braking time T1 (for example, 200 msec) to be applied to the turning inner wheel Wfr is set. In step 210, the braking force to be applied to the turning outer wheel (front left wheel) Wfl, that is, the hydraulic pressure generated in the wheel cylinder WCfl of the turning outer wheel Wfl is set. The wheel cylinder pressure (braking force) is calculated as a control amount corresponding to the steering speed based on a control map M2B (see FIG. 11) stored in the ROM. In step 212, a braking time T2 to be given to the turning outer wheel Wfl is set. The braking time T2 to be given to the turning outer wheel Wfl may be the same as or different from the braking time T1 to be given to the turning inner wheel Wfr.

  In step 214, a delay time ΔT (see FIG. 10) for applying a braking force to the turning outer wheel Wfl with respect to the turning inner wheel Wfr is set. The delay time ΔT is about 100 msec, for example, and is set according to the steering speed. Subsequently, in step 216, the brake fluid pressure generating device 25 is controlled to apply a braking force to the turning inner wheel Wfr, and the brake fluid pressure is continuously applied to the turning outer wheel Wfl with a time difference by a delay time ΔT. The generator 25 is controlled (step 218).

  Thus, as shown in FIG. 10, first, the braking force is applied to the turning inner wheel Wfr with the braking force set in step 206 and for the braking time T1 set in step 208, and the predetermined delay time ΔT is reduced. Then, the braking force is applied to the turning outer wheel Wfl for the braking time T2 set in step 210 with the braking force set in step 208.

  The above-described step 202 constitutes the steering speed calculation means in the claims, the step 216 constitutes the first braking force application means in the claims, and the step 218 constitutes the second braking force application means in the claims. It is composed.

  As described above, in the second embodiment, as shown in the time chart of FIG. 10, when the steering speed becomes greater than a predetermined reference threshold value THwv, first, the turning inner wheel Wfr is set to the steering speed. A braking force is applied for a predetermined time T1 (for example, 200 msec) at a corresponding wheel cylinder pressure (braking force), and after a predetermined delay time ΔT has elapsed, the turning outer wheel Wfl has a predetermined wheel cylinder pressure (braking force) for a predetermined time T2. The braking force is applied only (for example, 200 msec), and the program is returned. Note that the application of the braking force to the turning outer wheel Wfl may be continued until it is possible to prevent the occurrence of understeer, in addition to the time management.

  According to the second embodiment described above, the braking force is applied to the turning inner wheel Wfr by the first braking applying means, thereby generating a bending moment in the steering direction and increasing the front wheel load. Can improve the turning ability. Thereafter, when the vehicle starts to turn, the load on the turning outer wheel Wfl increases, but following the application of the braking force to the turning inner wheel Wfr, by applying the braking force to the turning outer wheel Wfl by the second braking applying means, The load can be effectively moved to the front side of the vehicle to further improve the turnability. Thereby, the occurrence of understeer can be further suppressed. In this case, the speed of load movement to the turning outer wheel Wfl accompanying turning of the vehicle increases as the steering speed increases. Therefore, the second braking application means applies the braking force to the turning outer wheel Wfl after the elapse of time ΔT according to the steering speed after the braking force application to the turning inner wheel Wfr by the first braking force application means is started. Since the application is started, the load can be moved to the front side of the vehicle more effectively.

  Note that the timing at which the braking force to the turning outer wheel Wfl is started with respect to the turning inner wheel Wfr can be the timing at which understeer occurs (steering yaw rate> actual yaw rate), or the braking force is applied to the turning inner wheel Wfr. May be the timing at which the load moves to the turning outer wheel Wfl.

  FIG. 12 is a time chart showing a modification of the second embodiment. The end of applying the braking force to the turning inner wheel Wfr is made on the condition that the steering speed becomes smaller than the threshold value THwv. Is. In this case, as shown in FIG. 12, the application of the braking force to the turning outer wheel Wfl is terminated under the condition that the steering speed is lower than 0, that is, when the steering holding state or the switchback steering state is entered. Is preferred.

  In the above-described embodiment, the example in which the braking force is applied by the hydraulic brake device has been described. However, the present invention can also be applied to a brake system that applies the braking force by an electric actuator.

  Further, in the above-described embodiment, the example has been described in which the outer turning wheel or the inner turning wheel to which the braking force is applied is the front wheel. However, even if the braking force is applied to the rear wheel side, the same effect can be obtained. . In this case, when the braking force is applied to the turning outer wheel following the application of the braking force to the turning inner wheel, for example, the braking force is applied to the outer front wheel after the braking force is applied to the inner rear wheel. Also good. The vehicle to which the present invention can be applied is not limited to a front wheel drive vehicle, but can be applied to a rear wheel drive vehicle.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited to the configurations described in the embodiments, and can take various forms within the scope described in the claims. Is.

  The vehicle motion control apparatus according to the present invention is suitable for use in a vehicle motion control prior to the occurrence of an understeer state accompanying sudden steering.

DESCRIPTION OF SYMBOLS 20 ... Hydraulic brake device, Wfl, Wfr, Wrl, Wrr ... Wheel, WCfl, WCfr, WCrl, WCrr ... Wheel cylinder, 21 ... Brake pedal, 23 ... Master cylinder, 25 ... Brake hydraulic pressure generator, 26 ... Brake control ECU, 27 ... steering angle sensor, 33 ... motor, 41, 51 ... hydraulic pressure control valve, 42, 43, 52, 53 ... pressure increasing valve, 45,46,55,56 ... pressure reducing valve, 47,57 ... pump, Sfl , Sfr, Srl, Srr ... wheel speed sensors, 106, 206 ... steering speed calculation means, 110 ... braking force application means, 216 ... first braking force application means, 218 ... second braking force application means.

Claims (5)

A vehicle motion control device that applies braking force to the wheels and suppresses the occurrence of an understeer state,
Steering speed calculating means for calculating a steering speed, and braking force applying means for applying a braking force to the outer turning wheel when the steering speed calculated by the steering speed calculating means exceeds a reference threshold value. A vehicle motion control apparatus comprising the vehicle.   2. The braking force applying means according to claim 1, wherein the braking force applying means finishes applying the braking force to the turning outer wheel when a predetermined time has elapsed after starting to apply the braking force to the turning outer wheel. A vehicle motion control device.   In Claim 1, the braking force application means starts applying the braking force to the turning outer wheel, and when the steering speed calculated by the steering speed calculation means becomes smaller than a reference threshold value, A vehicle motion control device characterized in that the application of braking force to the turning outer wheel is terminated. A vehicle motion control device that applies braking force to the wheels and suppresses the occurrence of an understeer state,
Steering speed calculating means for calculating the steering speed, and first braking force applying means for applying a braking force to the turning inner wheel when the steering speed calculated by the steering speed calculating means exceeds a reference threshold value. And a second braking force applying means for applying a braking force to the turning outer wheel following the application of the braking force by the first braking force applying means.   5. The method according to claim 4, wherein the second braking force application unit is configured to perform the operation after a lapse of time according to the steering speed from the start of applying the braking force to the turning inner wheel by the first braking force application unit. A vehicle motion control apparatus, characterized in that the application of braking force to a turning outer wheel is started.

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