JP5333119B2 - Vehicle motion control device - Google Patents

Description

  The present invention relates to an apparatus for controlling movement when a vehicle turns and travels.

Conventionally, a device for controlling motion to stabilize vehicle travel is known, and according to Patent Document 1 as such a control device, a departure determination means for determining that a vehicle is likely to depart from a traveling lane, It is described that it has braking / driving force control means for generating a yaw moment in a direction to avoid the departure by a difference in braking force between the left and right wheels when it is determined that the vehicle is likely to deviate. This is to generate a yaw moment in a direction that avoids deviation from the traveling lane by applying a brake with a difference in braking force between the left and right wheels. For example, the left direction is a direction that avoids deviation from the lane. If so, a left yaw moment is generated by applying more braking force to the left front wheel and rear wheel than to the right front wheel and rear wheel.

JP 2001-310719 A

However, considering the case where the vehicle is in a turning state, for example, in Patent Document 1, when the vehicle is about to deviate from the traveling lane due to an understeer state, a large amount of brake is applied to the front and rear wheels on the inner wheel side of the turning. By doing so, it is planned to generate an inward yaw moment of turning that avoids deviation from the driving lane. In this case, the front and rear wheels on the inner ring cause the brakes to act more, but the load on the front and rear wheels on the outer ring is greater than the front and rear wheels on the inner ring due to the centrifugal force during turning. The load acting on the front and rear wheels on the inner ring side is reduced. For this reason, the planned braking force does not act on the front and rear wheels on the inner ring side, and the generation of the inward yaw moment may be delayed, and the elimination of understeer may be delayed.

The present invention has been made in view of the above-described conventional problems, and provides a vehicle motion control device that eliminates understeer with high responsiveness even when the vehicle is understeered during turning.

In order to solve the above-described problem, the structural feature of the invention according to claim 1 is that an understeer detecting unit that detects an understeer state of the vehicle, and the vehicle when the understeer state is detected by the understeer detecting unit. Outer wheel braking force application starting means for starting the application of the braking force to the turning outer wheel of the vehicle, and an outward direction for detecting an increase in the moment of turning outward after the outer wheel braking force application starting means starts to apply the braking force to the turning outer wheel. An outer ring that stops applying the braking force to the outer turning wheel started by the outer wheel braking force application starting means when an increase in turning outward moment is detected by the moment increase detecting means and the outward moment increase detecting means. And a braking force application stopping means.

According to a second aspect of the present invention, there is provided a structural feature according to the first aspect, further comprising a lateral acceleration detecting means for detecting a lateral acceleration of the vehicle, wherein the outer ring brake applying start means and the outer ring brake force applying stop means The magnitude of the applied braking force is to increase as the lateral acceleration detected by the lateral acceleration detecting means increases.

The structural feature of the invention according to claim 3 is detected by the understeer detection means in claim 1 or 2 after the outer wheel brake force application starting means starts applying the braking force to the turning outer wheel. The vehicle is provided with an inner wheel brake force application start means for starting to apply a brake force to the turning inner wheel of the vehicle according to the understeer state.

According to a fourth aspect of the present invention, in the third aspect, the inner ring brake force application start means is applied to the turning outer wheel by the outer ring brake force application start means and the outer ring brake force application stop means. The application of the braking force to the turning inner wheel is started while the braking force remains.

According to a fifth aspect of the present invention, there is provided a structural feature of any one of the second to fourth aspects, further comprising friction coefficient estimating means for estimating a friction coefficient between a wheel and a road surface. The larger the estimated friction coefficient is, the smaller the magnitude of the braking force applied to the turning outer wheel by the outer wheel braking force application starting means and the outer wheel braking force stopping means.

The structural feature of the invention according to claim 6 is that, in any one of claims 1 to 5, comprising slip ratio calculation means for calculating the slip ratio of the turning outer wheel, wherein the outward moment increase detection means is the slip When the slip rate calculated by the rate calculating means is 0 or a value in the vicinity thereof, an increase in the moment of turning outward is detected.

The structural feature of the invention according to claim 7 is that in any one of claims 1 to 6, the braking force by the outer wheel braking force application starting means and the outer wheel braking force application stopping means is
It is to be given to the turning outer front wheel.

According to the first aspect of the present invention, the understeer state is detected by the understeer detection means in the vehicle that runs while turning. When the understeer state is detected, braking force is applied to the turning outer wheel by the outer wheel braking force application starting means. When the vehicle is turning, the load on the turning outer wheel is large. Therefore, the load acting on the outer ring is increased by causing the vehicle to generate a forward leaning load that assumes a forward leaning posture by the braking force based on the braking force applied to the outer ring. As a result, the grip force of the outer ring is increased and the grip force of the outer ring exceeds the centrifugal force acting on the vehicle based on turning, thereby promptly eliminating the understeer state. If a braking force is continuously applied to the turning outer wheel in this way, a turning outward moment may be generated, but when an increase in the turning outward moment is detected by the outward moment increase detecting means, the outer wheel braking force is stopped. The application of the braking force to the turning outer wheel is stopped by the means. As a result, it is possible to prevent an understeer state from being caused by the moment of turning outward.

According to the second aspect of the present invention, the magnitude of the lateral force generated by the centrifugal force of the vehicle during turning travel increases as the lateral acceleration of the vehicle increases, so that the turning increases as the lateral acceleration detected by the lateral acceleration sensor increases. By increasing the braking force on the outer ring and increasing the forward leaning load that brings the vehicle to the forward turning posture, the grip force of the outer ring can be increased and the understeer state can be efficiently eliminated.

According to the invention of claim 3, by applying a braking force to the outer wheel, the understeer state is suppressed. However, when the vehicle is still in the understeer state, the inner wheel braking force application starting means applies the braking force to the turning inner wheel of the vehicle. By applying, an inward turning moment can be generated and the understeer state can be eliminated.

According to the invention of claim 4, by applying a braking force to the outer wheel, the understeer state is suppressed, but when the understeer state occurs, the vehicle continuously turns while the braking force remains on the outer wheel. By applying a braking force to the inner ring, an inward turning moment is generated, so the understeer state can be reliably eliminated.

According to the fifth aspect of the present invention, when the vehicle is traveling at a constant speed, the braking force applied to the outer ring is reduced as the friction coefficient between the wheel and the road surface estimated by the friction coefficient estimating means increases. Therefore, it is possible to prevent the occurrence of an outward turning moment and prevent an understeer state.

According to the invention of claim 6, and when the slip ratio of the outer ring is calculated to be 0 or a value close thereto, the outward moment increase detecting means detects an increase in the outward moment and The application of the braking force is stopped.

For example, even when a front wheel drive vehicle is turning, the vehicle travels with a predetermined slip ratio between the front wheel and the road surface. When the slip ratio is positive, the driving force acts on the left and right front wheels. To do.
However, when the slip ratio becomes negative, the braking force from the road surface acts on the outer front wheel, the turning outward moment increases, and the understeer state further increases. Therefore, the slip rate is 0
Alternatively, when it becomes a value close to it, the outward moment increase detecting means detects an increase in the outward moment, and the outer wheel braking force application stopping means stops applying the braking force to the outer front wheel.

According to the invention of claim 7, by applying the braking force by the outer wheel braking force application starting means and the outer wheel braking force application stopping means to the turning outer front wheel, the forward leaning load that makes the vehicle lean forward is more effectively applied. Can be generated. As a result, the load acting on the turning outer front wheel is increased, the grip force of the outer front wheel is increased, and the understeer state can be quickly and reliably eliminated.

The top view of the vehicle of the embodiment concerning the present invention. Hydraulic brake circuit diagram. The flowchart of exercise | movement control. The figure which shows the relationship between the braking force provided to an outer front wheel, and the lateral acceleration of a vehicle. The figure which shows the brake force provided to an outer front wheel, and the timing which provides the brake force by ESC control. The figure which shows the turn of the turning direction of the vehicle M, and the order of the wheel to which a braking force is provided.

Embodiments of a vehicle using a vehicle motion control device according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of the vehicle. The vehicle M 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 M includes a drive system 10 that drives the vehicle M and a braking system 20 that brakes the vehicle M.
The drive system 10 includes an engine 11, a transmission 12, a differential 13, and a left and right drive shaft 14.
a, 14b, an accelerator pedal 15 and an engine control ECU 16 are provided. The driving force of the engine 11 is changed by the transmission 12, and the differential 13 and the left and right drive shafts 14a.
, 14b and transmitted to the left and right front wheels Wfl, Wfr, which are drive wheels, respectively. The engine 11 is provided with an intake pipe (not shown) through which air flows into the combustion chamber of the engine 11, and the amount of air passing through the intake pipe is adjusted in the intake pipe by adjusting the opening / closing amount of the intake pipe. A throttle valve (not shown) is provided.

When the amount of depression of the accelerator pedal 15 increases, the throttle valve increases its opening and the output of the engine 11 increases, thereby increasing the driving force of the vehicle M and accelerating, and when the amount of depression decreases, the throttle valve And the output of the engine 11 decreases, thereby reducing the driving force of the vehicle M and decreasing the acceleration.

The braking system 20 includes a hydraulic brake device that applies a hydraulic braking force to the wheels Wfl, Wfr, Wrl, Wrr to brake the vehicle. The hydraulic brake device 20 includes a wheel cylinder WCfl that regulates the rotation of the wheels Wfl, Wfr, Wrl, Wrr.
, WCfr, WCrl, WCrr, and a negative pressure booster 22 that is a booster that boosts (increases) the brake operating force generated by depressing the brake pedal 21 by applying the intake negative pressure of the engine 11 to the diaphragm. And a brake fluid (oil) of a hydraulic pressure (hydraulic pressure) that is a basic hydraulic pressure corresponding to a brake operating force (that is, an operating state of the brake pedal 21) boosted by the negative pressure booster 22 to generate each wheel cylinder WCfl. , WCfr, WCrl,
A master cylinder 23 that supplies WCrr, a reservoir tank 24 that stores brake fluid and replenishes the brake fluid to the master cylinder 23, and is provided between the master cylinder 23 and each wheel cylinder WCfl, WCfr, WCrl, WCrr. A brake hydraulic pressure control device 25 that can form a control hydraulic pressure regardless of the depression state of the brake pedal 21 and can be applied to the wheel to be controlled, and a brake control ECU 26 that controls the brake hydraulic pressure control device 25. Yes.

Each wheel cylinder WCfl, WCfr, WCrl, WCrr is connected to each caliper CLfl.
, CLfr, CLrl, CLrr, and accommodates a fluid-tightly sliding piston (not shown). 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, which are friction members, and each wheel Wfl, Wfr, Wrl, W
Disc rotors DRfl, DRfr, DRrl, DR which are rotating members that rotate integrally with rr
The rotation is regulated by sandwiching rr from both sides. Brake pad BPfl,
BPfr, BPrl, BPrr and disc rotors DRfl, DRfr, DRrl, DRr
A friction brake is composed of r.

Brake control ECU 26, wheel speed sensors Srl, Srr, yaw rate sensor (described later)
27 and a steering sensor (described later) 29a constitute an understeer detecting means.

In this embodiment, the disc type brake is adopted, but a drum type brake may be adopted. In this case, each wheel cylinder WCfl, WCf
When basic fluid pressure or control fluid pressure is supplied to r, WCrl, WCrr, each piston presses (expands) a pair of brake shoes, and the brake drum rotates integrally with each wheel Wfl, Wfr, Wrl, Wrr. The rotation is restricted by contacting the peripheral surface.

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

The brake piping system of the hydraulic brake device 20 according to the present embodiment is configured by an X piping system, and the brake hydraulic pressure control device 25 has first and second hydraulic chambers 23a of the master cylinder 23 as shown in FIG. , 23b, and first and second oil paths Lr and Lf. 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 control device 25 is provided with a 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. Although the hydraulic pressure control valve 41 is not energized and is normally connected, the wheel cylinder W is activated by energizing it to a differential pressure state (closed side).
The oil path Lr2 on the Crl, WCfr side can be maintained at a pressure higher than the oil path Lr1 on the master cylinder 23 side 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 of which 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 the ABS. There is provided a pressure increasing valve 43 that controls an increase in the brake fluid pressure to the wheel cylinder WCfr in the control pressurization 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. Booster valve 4
Reference numerals 2 and 43 are normally open on-off solenoid valves which 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 formed by driving the pump 47 and controlling the hydraulic pressure control valve 41 are set. 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.

In the case of a normal brake in which the ABS control is not executed, these pressure increasing valves 42,
43 is always controlled in a communication state. Further, each of the pressure increasing valves 42 and 43 includes a safety valve 4.
2a and 43a are provided in parallel, and the driver can use the brake pedal 2 during ABS control.
When the foot is released from 1, the brake fluid from the wheel cylinders WCrl and WCfr is returned to the reservoir tank 24 accordingly.

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 in a normal brake state (
When the ABS is not operated), the wheel cylinders WCrl, W are always cut off, and the brake fluid is released to the pressure regulating reservoir 44 through the oil path Lf3 in an appropriate communication state.
The brake fluid pressure at Cfr is controlled to prevent the wheels from becoming locked.

Further, a pump 47 is provided 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 in the brake fluid in the wheel cylinders WCrl and WCfr or the brake fluid stored in the pressure-regulating reservoir 44, and is connected to the master via the fluid pressure control valve 41 that is in communication. It is returned to the cylinder 23.

Further, the pump 47 controls the hydraulic control valve 41 that is switched to the differential pressure state when executing control for automatically applying hydraulic pressure to any of the wheel cylinders WCfl to WCrr, such as ESC control. In order to generate a differential pressure, the brake fluid in the master cylinder 23 is sucked in through the oil paths Lr1, Lr5 and the pressure regulating reservoir 44, and each wheel is connected through the oil paths Lr4, Lr2 and the pressure increasing valves 42, 43 in communication. A control hydraulic pressure is applied by discharging to the cylinders WCrl and WCfr. 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 control device 25 is composed of oil paths Lf1 to Lf5 in the same manner as the first oil path Lr. 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 are provided in the second oil path Lf. A pressure increasing valve 42 is provided in the branched oil paths Lf2 and Lf2 communicating with the wheel cylinders WCfl and WCrr.
, 43 are provided with pressure increase valves 52, 53, and the oil path Lf3 is provided with pressure reduction valves 55, 56 similar to the pressure reduction valves 45, 46. 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 include safety valves 52a and 5 similar to the safety valves 42a and 43a, respectively.
3a is provided in parallel.

In this way, the brake hydraulic pressure control device 25 can directly apply the basic hydraulic pressure from the master cylinder 23 to the wheel cylinders WCfl, WCfr, WCrl, WCrr. Further, the brake fluid pressure control device 25 applies the control fluid pressure formed by driving the pumps 47 and 57 and controlling the fluid pressure control valves 41 and 51 to the wheel cylinders WCfl, WCfr, Wrr of each wheel Wfl, Wfr, Wrl, Wrr. It can be given to WCrl, WCrr. That is, the brake fluid pressure control device 25 can also apply a fluid pressure corresponding to the operation state (depressed state) of the brake pedal 21 of the driver to the wheel cylinders WCfl, WCfr, WCrl, WCrr, and the driver's brake. It is also possible to control the hydraulic pressure to the wheel cylinders WCfl, WCfr, WCrl, WCrr regardless of the operation state (depressed state) of the pedal 21. The vehicle motion control device in this embodiment includes a brake fluid pressure control device 25 and a brake control ECU 2.
6, the brake fluid pressure control device 25 applies the braking force independently to the left and right front and rear wheels of the vehicle M.

As shown in FIG. 1, the brake control ECU 26 detects wheel speed sensors Sfl, Sfr, Srl, Srr that detect the wheel speeds of the left and right front and rear wheels, a yaw rate sensor 27 that detects the actual yaw rate, and a vehicle longitudinal acceleration. Acceleration sensor 28, steering sensor 29a
A temperature sensor 30 that detects the temperature outside the vehicle, and a camera sensor 31 that detects the condition of the road surface outside the vehicle.
And it is connected with the lateral acceleration sensor 34 which detects the lateral acceleration concerning a vehicle. The lateral acceleration sensor 34 corresponds to a lateral acceleration detection unit.

The wheel speed sensors Sfl, Sfr, Srl, Srr are connected to the wheels Wfl, Wfr, Wrl,
Each is provided in the vicinity of Wrr, and a pulse signal having a frequency corresponding to the rotational speed (wheel speed) of each wheel Wfl, Wfr, Wrl, Wrr is output to the brake control ECU 26. The yaw rate sensor 27 detects the yaw rate of the vehicle M, and uses the detection signal as a brake control EC.
It is output to U26. The acceleration sensor 28 detects the acceleration in the front-rear direction and the left-right direction of the vehicle M and outputs a detection signal to the brake control ECU 26. The steering sensor 29a detects the rotation angle from the neutral position of the steering 29, and outputs a signal indicating the actual steering angle θ (actual steering angle corresponding value) to the brake control ECU 26.

The brake control ECU 26 has a microcomputer (not shown). The microcomputer has an input / output interface, a CPU,
RAM and ROM (both not shown) are provided. The CPU executes a program corresponding to the flowchart of FIG. 3 and performs vehicle motion control according to the embodiment of the present invention.
The RAM temporarily stores variables necessary for executing the program, and the ROM stores the program.

Next, the vehicle motion control device configured as described above will be described below with reference to the drawings. When an ignition switch (not shown) of the vehicle M is turned on, the brake control ECU 26 executes a program corresponding to the flowchart of FIG.

The brake control ECU 26 determines that the actual steering angle (steering wheel angle) θ is a threshold value RA from the signal indicating the actual steering angle (steering wheel angle) θ input from the steering sensor 29a.
It is determined whether or not this is the case (step 102). In the present embodiment, as shown in FIG. 6, the vehicle M is in a state of turning counterclockwise. The brake control ECU 26
When it is determined in step 102 that the steering wheel angle is smaller than the threshold value RA, the program proceeds to step 138 and ends once (step 138).

When it is determined that the actual steering angle θ is equal to or greater than the threshold value RA, the turning state is calculated. The calculation of the turning state is performed by obtaining the yaw rate deviation Δω (step 104).
).

Therefore, the brake control ECU 26 sets the wheel speed sensors Sfl, Sfr, Srl, S
Based on the wheel speed signal from rr, the wheel speed V of each wheel Wfl, Wfr, Wrl, Wrr
Wfl to VWrr are calculated. The brake control ECU 26 calculates the calculated wheel speed VW.
Of the fl to VWrr, for example, since the rear wheels Wrr and Wrl are driven wheels, the vehicle speed VB is calculated by obtaining an average value of the outer rear wheel speed VWrr and the inner rear wheel speed VWrl. Also,
The brake control ECU 26 acquires a signal representing the direction and magnitude of the yaw rate from the yaw rate sensor 27 as an actual yaw rate Rω that is an actual yaw rate generated in the vehicle M.

The brake control ECU 26 calculates a target yaw rate Tω. Specifically, brake E
The CU 26 calculates the steering angle θ of the vehicle M from the signal indicating the actual steering angle θ input from the steering sensor 29a. Then, from the calculated steering angle θ, the turning angle ξ (steering angle of the vehicle) of the steering wheel is calculated by the following equation (1).

(Equation 1)
Steering wheel turning angle ξ = C × steering angle θ

Further, the brake control ECU 26 determines the vehicle speed VB and the vehicle steering angle ξ
Based on the stability factor A, the target yaw rate Tω is calculated.

C is a proportional constant (for example, steering gear ratio) of the steering wheel turning angle ξ with respect to the steering angle θ. Further, the steering wheel turning angle ξ refers to an angle of the steering direction of the steering wheel with respect to the direction in which the vehicle M travels straight. L is a wheel base of the vehicle M.

The brake ECU 26 calculates the yaw rate deviation Δω (Δω = Tω−Rω) by subtracting the actual yaw rate Rω acquired previously and the calculated target yaw rate Tω.

Then, the brake control ECU 26 compares, for example, a preset threshold value Tus with the calculated yaw rate deviation Δω to determine whether or not an understeer state is set (step 106).
. When the yaw rate deviation Δω is larger than the threshold value Tus, the vehicle M is in an understeer state, and when it is smaller than the threshold value Tus, it is not in an understeer state. Brake control ECU
If it is determined at step 106 that the program is not understeered, the program proceeds to step 138 and ends once. If it is determined that the vehicle is understeered, it is determined whether the vehicle M is accelerating (step 108). Whether the vehicle M is accelerating is calculated by differential calculation of the vehicle speed VB.

If dVB / dt is positive, the vehicle M is accelerating, and in this case the brake control ECU
26 causes the brake fluid pressure control device 25 to apply a braking force A to the outer front wheel (right front wheel) Wfr (step 110). In this case, the pump 47 is driven by the electric motor 33 to cause a brake fluid of a predetermined flow rate to flow out to the master cylinder 23 and the wheel cylinder WCfr side, thereby applying a hydraulic pressure to the wheel cylinder WCfr.

Specifically, the hydraulic pressure control valves 41 and 51 are excited to be in a differential pressure state. The pressure increasing valve 43 and the pressure reducing valve 46 corresponding to the right front wheel Wfr are de-energized to be in an open state and a closed state, respectively.
As a result, the brake fluid at a predetermined flow rate is caused to flow out to apply a hydraulic pressure to the wheel cylinder WCfr, and a braking force A is applied to the outer front wheel (right front wheel) Wfr. The magnitude of applying the braking force A increases as the lateral acceleration increases, and is executed by changing the current applied by the linear solenoid 41 a provided in the hydraulic control valve 41. The size is determined based on a map A prepared in advance (see FIG. 4). In order not to apply hydraulic pressure to the right rear wheel Wrr, the pressure increasing valve 53 corresponding to the wheel is excited and closed, and the pressure reducing valve 56 is excited and opened, so that the wheel cylinder WCrr is stored in the reservoir 54. Communicated with Similarly, the pressure increasing valves 52 and 42 corresponding to the respective wheels are excited and closed, and the pressure reducing valves 55 and 45 are excited so that the hydraulic pressure is not applied to the left front wheel Wfl and the right rear wheel Wrl as well. Opened.

Next, the brake control ECU 26 calculates the slip ratio of the outer front wheel (right front wheel) Wfr (step 112). The slip ratio Sfo of the right front wheel Wfr is calculated by the following equation 3 based on the wheel speed VWfr and the vehicle speed VB of the right front wheel Wfr.

Next, the brake control ECU 26 determines whether or not the calculated slip ratio Sfo is 0 or a value close thereto (step 114). This step 114 constitutes an outward moment increase detecting means. When it is determined that the slip ratio Sfo is 0 or a value close to it, the brake control ECU 26 stops the brake force A applied to the right front wheel Wfr by the brake hydraulic pressure control device 25 in order to stop the fluid in the wheel cylinder WCfr. An operation for lowering the pressure is performed (step 116).

Subsequently, the brake control ECU 26 applies an ESC (Electrometer) that applies a braking force to the inner ring.
The process proceeds to ronic stability control, and control by the skid prevention device is started (step 118). Specifically, for example, when the understeer state occurs, the brake control ECU 26 causes the brake hydraulic pressure control device 25 to have an inner rear wheel (left rear wheel).
A braking force is applied to Wrl to generate an inward turning moment in the vehicle. In this case, as shown in FIG. 5, the braking force is applied to the inner rear wheel (left rear wheel) Wrl before the effect of causing the forward tilting load on the vehicle M by the braking force A disappears. Even when the braking force A is applied to the right front wheel Wfr, ESC control is performed to continuously apply the braking force to the inner wheel Wrl while the braking force A to the outer front wheel Wfr remains in the understeer state. Then, an inward turning moment is generated in the vehicle M to cancel the understeer state.

Then, under the control of the ESC, the program is advanced to step 120 and terminated once (step 120).

When the brake control ECU 26 determines in step 108 that the vehicle is not accelerating, the brake control ECU 26 proceeds to step 122 and determines whether or not the vehicle is decelerating. If dVB / dt is negative, the vehicle M is decelerating, and if dVB / dt is 0, the vehicle M is turning at a constant speed. If it is determined that the vehicle M is decelerating, the program proceeds to step 138 and ends once.

When dVB / dt is 0, that is, when turning at a constant speed, the brake control E
The CU 26 estimates whether or not the friction coefficient μ between the wheel and the road surface is low (step 124). In this case, the friction coefficient μ between the road surface and the wheel is estimated by the temperature sensor 30, the camera sensor 31, and the like. For example, the temperature sensor 30 detects that the temperature is 0 ° C. or less, and the camera sensor 3
When it is determined that the road surface is frozen according to 1, the friction coefficient μ is estimated to be small. On the contrary, the temperature sensor 30 determines that the air temperature is 20 ° C. and the camera sensor 31 determines that the road surface is also dry. Therefore, it is estimated that the friction coefficient μ is large. This step 124 constitutes a friction coefficient estimating means. If the friction coefficient μ is estimated to be large, the brake control ECU
26 causes the brake fluid pressure control device 25 to apply the braking force B to the outer front wheel (right front wheel) Wfr (step 126). The application of the braking force B is performed according to the above-described application of the braking force A shown in FIG. 5. Since the friction coefficient μ is large, the braking force B is controlled to prevent the understeer state from increasing. A relatively small value of braking force is applied.
Note that the operation of the pump 47, the pressure increasing valve 43, and the like that apply the braking force B is the same as when the braking force A is applied, and thus the description thereof is omitted.

If it is determined that the friction coefficient μ is low, the routine proceeds to step 134 where control by the skid prevention device (ESC) is performed.

Next, the brake control ECU 26 calculates the slip ratio of the outer front wheel (right front wheel) Wfr (step 128). The slip ratio Sfo of the right front wheel Wfr is calculated in the same manner as step 112 based on the wheel speed VWfr and the vehicle speed VB of the right front wheel Wfr.

Next, the brake control ECU 26 determines whether or not the slip ratio Sfo is 0 or a value close thereto (step 130). When it is determined that the slip ratio Sfo is 0 or a value close to it, the brake control ECU 26 stops the brake force B applied to the right front wheel Wfr by the brake hydraulic pressure control device 25 in order to stop the fluid in the wheel cylinder WCfr. An operation for reducing the pressure is performed (step 132).

Subsequently, the brake control ECU 26 shifts to ESC and starts control by the skid prevention device (step 134). Specifically, the braking force is applied to the inner rear wheel (left rear wheel) Wrl before the effect of causing the forward lean load on the vehicle by the braking force B is lost. In this way, control by the ESC that continuously applies the braking force to the inner wheel Wrl is performed while the action of the braking force applied to the right front wheel (outer front wheel) Wfr remains, so that the inward moment of turning is applied to the vehicle. To eliminate the understeer condition.

Then, under the control of the ESC, the program is advanced to step 136 and terminated once (step 136).

In step 110 of the program, the brake control ECU 26 constitutes outer wheel brake application start means for applying a braking force to the brake hydraulic pressure control device 25 to the outer wheel Wrr of the vehicle M (for example, in the case of a left turn). Thus, an outer wheel brake force application stopping means for stopping the application of the brake force of the outer front wheel Wrr by the brake hydraulic pressure control device 25 is configured.

The brake control ECU 26 and the wheel speed sensors Sfr, Srl, Srr constitute a slip ratio calculating means for determining the slip ratio of the outer front wheel Wrr in step 112 and step 128 of the program. The brake control ECU 26 constitutes an inner wheel brake force application starting means in steps 118 and 134 of the program.

According to the vehicle motion control device described above, an understeer state is detected by the understeer detection means (wheel speed sensors Srr, Srl, brake control ECU 26, steering sensor 29a, yaw rate sensor 27) in the vehicle M that turns and travels. When the understeer state is detected, the brake control ECU 26 applies a braking force to the outer front wheel Wfr for turning. The braking force based on the braking force applied to the outer front wheel Wrr causes the vehicle M to generate a forward tilt load that assumes a forward leaning posture, the load acting on the outer front wheel Wfr increases, the grip force of the outer front wheel Wfr increases, and the vehicle turns. Based on this, the grip force exceeds the centrifugal force acting on the vehicle, so that the understeer state can be quickly eliminated.

Then, when it is determined that the slip ratio of the outer front wheel Wfl is 0 or a value in the vicinity thereof, applying the braking force to the outer front wheel Wfr is stopped.

Even when the front wheel drive vehicle turns, the vehicle M travels with a predetermined slip ratio between the front wheel and the road surface, and when the slip ratio is positive, the driving force acts on the left and right front wheels. . However, when the slip ratio becomes negative, the braking force from the road surface acts on the outer front wheel Wfr, the moment of turning outward increases, and the understeer state increases more and more. Therefore, the slip rate is 0
When approaching, stopping applying the braking force to the outer front wheel Wfr is stopped.

Further, since the magnitude of the lateral force generated by the centrifugal force of the vehicle M during turning is increased as the lateral acceleration of the vehicle M is increased, the braking force is increased as the lateral acceleration is increased, so that the vehicle M is in a forward posture. By increasing the forward tilting load, the grip force of the outer front wheel Wfr can be increased, and the understeer state can be efficiently eliminated.

Also, the brake control ECU 26 causes the brake fluid pressure control device 25 to apply a braking force to the outer front wheel Wfr, thereby suppressing the understeer state. Nevertheless, the understeer state can be eliminated by operating the ESC control while still in the understeer state.

The brake control ECU 26 applies the brake fluid pressure control device 25 to the outer front wheel Wfr and applies the brake force A
By imparting, the understeer state is suppressed. However, when the understeer state occurs, the inner wheel Wrl continues while the braking force A to the outer front wheel Wfr remains.
Since the ESC control for starting the application of the braking force is performed, the understeer state can be reliably eliminated.

When the vehicle M is traveling at a constant speed, the brake control ECU 26 and the temperature sensor 3
When the friction coefficient between the wheel and the road surface estimated by 0 and the camera sensor 31 is large, the braking force applied to the outer front wheel Wfr is reduced, so that the generation of an outward moment of turning is suppressed and an understeer state occurs. Can be prevented.

In the above embodiment, the lateral acceleration is detected by the lateral acceleration sensor 34. However, the present invention is not limited to this. For example, the vehicle travels based on the vehicle speed obtained from the wheel speed sensor, the steering angle obtained from the steering sensor, or the like. The lateral acceleration may be obtained by calculating a centrifugal force.

Further, while the vehicle is accelerating and decelerating is calculated by the differential value dVB / dt of the vehicle speed VB, the present invention is not limited to this, and may be determined based on, for example, detection of an acceleration sensor.

In addition, by applying a braking force to the turning outer front wheel, the vehicle was set as a front wheel load, but by applying a braking force to the rear wheel outside the turning, or applying a braking force to the front and rear wheels outside the turning, The vehicle may be a front wheel load.

Further, although the increase in the outward moment after the start of the application of the braking force to the outer turning wheel is detected based on the slip ratio, the method for detecting the increase in the outward moment is not limited to this. For example, equipped with a load sensor that detects the load applied to the left and right wheels of the vehicle,
After the start of the application of the braking force to the outer turning wheel, when the load of the inner turning wheel detected by the load sensor increases, an increase in the outward turning moment may be detected. Also,
A height sensor is provided for detecting the distance between the sprung and unsprung wheels of the left and right wheels of the vehicle. When the distance decreases, an increase in the outward turning moment may be detected.

Thus, the specific configuration described in the above-described embodiment is merely an example of the present invention, and the present invention is not limited to such a specific configuration. Various embodiments can be adopted without departing from the scope.

26 ... outer wheel brake force application start means, slip ratio calculation means, outer wheel brake force application stop means, inner ring brake force application start means, friction coefficient estimation means (brake control ECU), 27 ... understeer detection means (yaw rate sensor), 29a ... Understeer detection means (steering sensor), 30 ... friction coefficient estimation means (temperature sensor), 31 ... friction coefficient estimation means (camera sensor), 34 ... lateral acceleration detection means (lateral acceleration sensor), Sfl, Sfr, Srl,
Srr: Understeer detection means / slip rate calculation means (wheel speed sensor).

Claims (7)

Understeer detecting means for detecting an understeer state of the vehicle;
When an understeer state is detected by the understeer detection means,
Outer wheel braking force application starting means for starting application of braking force to the turning outer wheel of the vehicle;
An outward moment increase detecting means for detecting an increase in an outward turning moment after the start of the application of the braking force to the turning outer wheel by the outer wheel braking force application starting means;
Outer wheel braking force application stopping means for stopping the application of braking force to the turning outer wheel started by the outer wheel braking force application starting means when an increase in the moment of turning outward is detected by the outward moment increase detecting means; ,
A vehicle motion control device comprising: In Claim 1, it comprises a lateral acceleration detection means for detecting the lateral acceleration of the vehicle,
The magnitude of the braking force applied to the turning outer wheel by the outer wheel brake application start means and the outer wheel brake force application stop means increases as the lateral acceleration detected by the lateral acceleration detection means increases. Vehicle motion control device. 3. The turning inner wheel of the vehicle according to claim 1, wherein after the outer wheel braking force application starting means starts applying the braking force to the turning outer wheel, the under steering state detected by the under steer detecting means is applied to the turning inner wheel of the vehicle. A vehicle motion control device comprising an inner wheel brake force application start means for starting application of a brake force. 4. The inner ring brake force application start means according to claim 3, wherein the inner ring brake force application start means is applied to the turning inner wheel while the brake force applied to the turning outer wheel by the outer ring brake force application start means and the outer wheel brake force application stop means remains. A vehicle motion control device characterized by starting to apply a braking force. In any one of Claims 2 thru | or 4, The friction coefficient estimation means which estimates the friction coefficient between a wheel and a road surface is provided,
The larger the friction coefficient estimated by the friction coefficient estimating means, the smaller the magnitude of the braking force applied to the turning outer wheel by the outer wheel braking force application starting means and the outer wheel brake force stopping means. Vehicle motion control device. The slip ratio calculating means for calculating the slip ratio of the turning outer wheel according to any one of claims 1 to 5, wherein the outward moment increase detecting means has a slip ratio calculated by the slip ratio calculating means of 0 or A vehicle motion control device that detects an increase in an outward turning moment when the value is a neighborhood value. The vehicle motion control device according to any one of claims 1 to 6, wherein the braking force applied by the outer wheel braking force application starting means and the outer wheel braking force application stopping means is applied to the turning outer front wheel.

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