JP2009035217A - Control device of vehicle in turning - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of a vehicle in turning which can reduce the turning radius of the vehicle, the suppressing feeling of drag which a driver of the vehicle feels from increasing by applying a braking force to an inside wheel in the turning direction when the vehicle is turned. <P>SOLUTION: An ECU performs brake control in turning to apply the braking force to the inside rear wheel in the turning direction (step S17) when all conditions that a steering angle A of a steering wheel is not smaller than a steering angle threshold KA (yes determination in a step S11), brake operation is not performed (yes determination in a step S12), an accelerator pedal is operated (yes determination in a step 13), and the vehicle travels at a low speed (yes determination in a step S16) are established. Furthermore, the ECU also performs friction force reduction control to reduce a μ value of a road surface when a friction coefficient μ of the road surface on which the vehicle travels is high (yes determination in a step S 20). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vehicle turning control device for reducing a turning radius during turning of a vehicle.

  2. Description of the Related Art Conventionally, as a vehicle turning control device of this type, for example, a vehicle turning control device (hereinafter referred to as “conventional turning control device”) described in Patent Document 1 has been proposed. This conventional turning control device detects the steering angle of the steering wheel and, based on the detection result, determines that the steering wheel has been steered to the maximum, the rear wheel inside the turning direction of the vehicle (when turning right) , A braking control during turning (also referred to as “small turning control”) is performed to apply a braking force to the right rear wheel) such that the rear wheel does not lock. “Maximum steering” refers to a state in which the steering wheel is steered to the maximum in a certain direction (right or left in the rotational direction).

Thus, in a vehicle that turns in a state in which the braking control during turning is executed, the turning radius is smaller than that of a vehicle that does not execute the braking control during turning, so that a small turn is effective. For this reason, when the driver of a general passenger vehicle (hereinafter referred to as “vehicle”) equipped with this conventional turning control device performs maximum braking control by turning the steering wheel, the vehicle travels. Even if the road width is narrow, the vehicle can be reversed.
Japanese Patent No. 3465394 (Claim 1)

  By the way, when the vehicle is reversed (turned) on a narrower road, it is desirable to make the turning radius of the vehicle smaller by executing the braking control during turning. Therefore, as a method of achieving such desire, a method of turning the vehicle with the rear wheel locked by applying a strong braking force to the rear wheel inside the turning direction is conceivable. In this case, since the vehicle turns while the rear wheel inside the turning direction slides sideways, the turning radius of the vehicle can be further reduced. However, when the vehicle is turned with the rear wheel on the inner side in the turning direction locked as described above, a braking force large enough not to lock the rear wheel is applied to the rear wheel on the inner side in the turning direction. As compared with the case where the vehicle is turned in a state, there is a problem that the feeling of drag that is felt by the driver of the vehicle is increased by applying the braking force to the rear wheel inside the turning direction.

  The present invention has been made in view of such circumstances, and an object of the present invention is to suppress an increase in the drag feeling felt by the driver of the vehicle by applying braking force to the wheels on the inner side in the turning direction when the vehicle turns. However, an object of the present invention is to provide a vehicle turning control device that can make the turning radius of the vehicle smaller.

  In order to achieve the above object, the invention according to claim 1 according to the turning control device for a vehicle includes wheels (FR, FL, RR) on both the front and rear sides in the traveling direction of the vehicle (C) and on both the left and right sides with respect to the traveling direction. , RL) mounted on the vehicle (C), and the vehicle turning control device (15) for applying braking force to the wheels (FR, RR) on the inner side in the turning direction when the vehicle (C) turns. The vehicle (C) includes a braking force applying mechanism (13) for individually applying a braking force to the wheels (FR, FL, RR, RL), and the wheels (FR, FL, (FR, RL) and a friction force reduction mechanism (14) for reducing the friction force between the road surface and a steering angle calculation for calculating the steering angle (A) of the steering (16) of the vehicle (C). Means (S10) and the steering angle calculation means (S10) When the absolute value of the calculated steering angle (A) is equal to or greater than a preset steering angle threshold (KA), braking force is applied to the wheels (FR, RR) on the inner side in the turning direction of the vehicle (C). In order to achieve this, the turning braking control for controlling the driving of the braking force applying mechanism (13) is executed, and the frictional force between the wheels (RR, RL) on the rear side in the traveling direction of the vehicle (C) and the road surface is reduced. Therefore, the gist is provided with control means (S17, S21) for controlling the driving of the frictional force lowering mechanism (14).

  In the above configuration, when the steering angle of the steering is equal to or greater than the steering angle threshold value, the braking control during turning is performed to apply braking force to the wheels inside the turning direction of the vehicle, and the rear side in the traveling direction of the vehicle In order to reduce the frictional force between the wheels and the road surface, the frictional force reducing mechanism is driven. Therefore, when the vehicle turns, the frictional force between the wheels on the rear side in the traveling direction of the vehicle and the road surface decreases, so that the frictional force reduction mechanism is not driven and the frictional force reduction mechanism is not mounted on the vehicle. As a result, the rear wheels in the traveling direction are liable to skid. As a result, the turning radius of the vehicle can be reduced as compared with the conventional case without applying a strong braking force to the wheels that locks the wheels inside the turning direction. Therefore, the turning radius of the vehicle can be made smaller while suppressing an increase in the drag feeling felt by the driver of the vehicle by applying braking force to the wheels on the inner side in the turning direction when the vehicle is turning.

  According to a second aspect of the present invention, in the vehicle turning control device according to the first aspect, the frictional force lowering mechanism (14) stores at least one of a liquid and a granular material (41). ) And at least one of the liquid and the granular material supplied from the reservoir (41) toward the at least one of the wheels (FR, FL, RR, RL) and the road surface ( 42, 43).

  In the above configuration, when the absolute value of the steering angle of the steering is greater than or equal to the steering angle threshold value, at least one of the liquid and the granular material stored in the storage portion is the wheel and road surface on the rear side in the traveling direction of the vehicle. It flows out toward at least one of them, and the μ value of the road surface with respect to the wheel on the rear side in the traveling direction decreases. Therefore, it is possible to easily create a situation in which the wheels on the rear side in the traveling direction are easily slid.

  According to a third aspect of the present invention, in the vehicle turning control device according to the first or second aspect, the road surface μ value estimating means (S19) for estimating the μ value of the road surface on which the vehicle (C) travels. And the control means (S17, S21) determines that the road surface is a low μ road based on the estimation result by the road surface μ value estimating means (S19). The gist is to regulate the driving of

  When the road surface on which the vehicle travels is a low μ road (for example, a frozen road surface), the frictional force between the wheels on the rear side in the traveling direction of the vehicle and the road surface is increased by driving the frictional force reduction mechanism. (For example, the μ value of the road surface may increase). In such a case, the turning radius of the vehicle may be larger than when the frictional force reduction mechanism is not driven. In this regard, in the present invention, when the road surface on which the vehicle travels is a low μ road even if the absolute value of the steering angle of the steering is equal to or greater than the steering angle threshold, the braking control during turning is executed while the frictional force is applied. Drive of the lowering mechanism is restricted. Therefore, when the vehicle turns on a low μ road, it is avoided that the turning radius of the vehicle becomes large, unlike the case where the frictional force reduction mechanism is driven.

  According to a fourth aspect of the present invention, in the vehicle turning control device according to any one of the first to third aspects, the control means (S17, S21) includes the wheels (FR, FL). , RR, RL), when it is detected that the driver is operating a brake to apply a braking force, the gist is to restrict the execution of the braking control during turning.

  When the driver performs a braking operation during turning of the vehicle, a braking force is applied to each wheel of the vehicle, so that the turning radius of the vehicle can be reduced without executing the braking control during turning. Is possible. Therefore, in the present invention, when the driver performs a braking operation during turning of the vehicle, execution of the braking control during turning is restricted even if the absolute value of the steering angle of the steering is greater than or equal to the steering angle threshold. The increase in the control load of the control means is suppressed.

  According to a fifth aspect of the present invention, in the vehicle turning control device according to any one of the first to fourth aspects, the vehicle body speed calculating means for calculating the vehicle body speed (VS) of the vehicle (C). (S14, S15), and the control means (S17, S21) is such that the vehicle speed (VS) calculated by the vehicle speed calculation means (S14, S15) is low and the vehicle (C) travels at a low speed. If the vehicle body speed threshold value (KVS) is not less than a preset vehicle body speed threshold value (KVS) as a criterion for determining whether or not the vehicle is turning, the execution of the braking control during turning is restricted and the drive of the friction force reduction mechanism (14) is restricted. The gist.

  If the friction force reduction mechanism is driven to reduce the frictional force between the wheels on the rear side of the traveling direction and the road surface when the vehicle is turning at a high speed, the lateral acceleration applied to the vehicle becomes too large, The behavior of the vehicle may become unstable. In this regard, in the present invention, when it is determined that the vehicle is turning at a high speed, the execution of the braking control during turning is restricted even if the absolute value of the steering angle of the steering is greater than or equal to the steering angle threshold. Driving of the frictional force lowering mechanism is restricted. Therefore, when the vehicle is turning at high speed, it is possible to suppress the behavior of the vehicle from becoming unstable due to the execution of braking control during turning and the driving of the frictional force reduction mechanism.

  Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS. In the following description of the present specification, the traveling direction (forward direction) of the vehicle is assumed to be the front (front of the vehicle). Unless otherwise specified, the left-right direction in the following description is the same as the left-right direction in the vehicle traveling direction.

  As shown in FIG. 1, the vehicle in the present embodiment is an automatic four-wheel vehicle having a right front wheel FR, a left front wheel FL, a right rear wheel RR, and a left rear wheel RL, and the driver depresses the accelerator pedal 11. A driving force based on the above is transmitted to driving wheels (for example, rear wheels RR, RL) to travel. In this vehicle, a steering mechanism 12 for turning the front wheels FR and FL as steered wheels (steering wheels) and a braking force applying mechanism 13 for applying a braking force to the wheels FL, FR, RL, and RR. And are provided. Further, the vehicle is provided with a frictional force reducing mechanism 14 for injecting (outflowing) water as liquid toward the road surface on which the rear wheels RR and RL, which are wheels on the rear side in the traveling direction of the vehicle, pass. Yes. Further, the vehicle is provided with an electronic control device (hereinafter referred to as “ECU”) 15 as a turning control device for appropriately controlling each of the mechanisms 12, 13, and 14 according to the traveling state of the vehicle. ing.

  The steering mechanism 12 is provided with a steering wheel 16, a steering shaft 17 to which the steering wheel 16 is fixed, and a steering actuator 18 connected to the steering shaft 17. Further, the steering mechanism 12 is provided with a link mechanism unit 19 including a tie rod that is movable in the left-right direction of the vehicle by a steering actuator 18 and a link that steers the front wheels FL and FR by the movement of the tie rod. ing. Further, the steering mechanism 12 is provided with a steering angle sensor SE1 for detecting the steering angle of the steering wheel 16, and a signal corresponding to the steering state of the steering wheel 16 is output from the steering angle sensor SE1 to the ECU 15. It has become so.

Next, the braking force application mechanism 13 will be described below with reference to FIGS.
As shown in FIGS. 1 and 2, the braking force applying mechanism 13 of the present embodiment includes a hydraulic pressure generating device 22 having a master cylinder 20 and a booster 21, and a hydraulic pressure control device having two hydraulic pressure circuits 23 and 24. (Indicated by a two-dot chain line in FIG. 2). The first hydraulic circuit 23 is connected to a wheel cylinder 26b for applying a braking force to the left front wheel FL and a wheel cylinder 26c for applying a braking force to the right rear wheel RR. The second hydraulic circuit 24 is connected to a wheel cylinder 26a for applying a braking force to the right front wheel FR and a wheel cylinder 26d for applying a braking force to the left rear wheel RL.

  The hydraulic pressure generating device 22 is provided with a brake pedal 27, and the master cylinder 20 and the booster 21 of the hydraulic pressure generating device 22 are driven based on a depression operation (ie, a brake operation) of the brake pedal 27 by a vehicle driver. It is like that. Further, each hydraulic circuit 23, 24 is connected to the master cylinder 20. Further, the hydraulic pressure generating device 22 is provided with a brake switch SW1 electrically connected to the ECU 15, and a signal corresponding to the operation state of the brake pedal 27 is output from the brake switch SW1 to the ECU 15.

  In the hydraulic pressure control device 25, on the first hydraulic pressure circuit 23, a reservoir 28 for temporarily storing brake fluid flowing out from the wheel cylinders 26b, 26c, and a pump 29 driven based on the rotation of the motor M, Is provided. The pump 29 increases the brake fluid pressure in the wheel cylinders 26b and 26c when the brake fluid in the reservoir 28 is discharged to the master cylinder 20 side in the first hydraulic circuit 23 and regardless of the brake operation by the driver. It is designed to be driven when making it happen. The first hydraulic circuit 23 includes a left front wheel path 30 connected to the wheel cylinder 26b and a right rear wheel path 31 connected to the wheel cylinder 26c. On these paths 30, 31, normally open solenoid valves 32, 33 are provided closer to the master cylinder 20 than the wheel cylinders 26b, 26c, and normally closed closer to the reservoir 28 than the wheel cylinders 26b, 26c. Molded solenoid valves 34 and 35 are provided.

  In addition, a normally open proportional solenoid valve 36 and a relief valve that is in parallel with the proportional solenoid valve 36 are located on the master cylinder 20 side of the first hydraulic circuit 23 from the portion branched into the paths 30 and 31. 37, and the proportional differential pressure valve 38 is constituted by the proportional solenoid valve 36 and the relief valve 37. The proportional differential pressure valve 38 is driven when a hydraulic pressure difference (brake hydraulic pressure difference) is generated between the master cylinder 20 and the wheel cylinders 26b and 26c than the proportional differential pressure valve 38 is. The maximum value of the hydraulic pressure difference is a value based on the urging force of the spring 37a constituting the relief valve 37. The first hydraulic pressure circuit 23 is formed with a branch hydraulic pressure passage 39 that branches from the reservoir 28 and the pump 29 toward the master cylinder 20, and is normally closed on the branch hydraulic pressure passage 39. A type solenoid valve 40 is connected.

  Of the electromagnetic valves 32 to 36, 40 described above, the normally open type electromagnetic valves 32, 33, 36 are closed when the solenoid coils are energized. On the other hand, the normally closed solenoid valves 34, 35, 40 are configured to open when their solenoid coils are energized. The brake hydraulic pressure in each wheel cylinder 26b, 26c is increased by individually controlling the opening / closing operation of each of the solenoid valves 32 to 36, 40 and the driving of the pump 29 (that is, the rotation of the motor M). To be held, held, or lowered. Since the configuration on the second hydraulic circuit 24 is the same as that of the first hydraulic circuit 23, the description is omitted in this specification and the drawings.

Next, the frictional force lowering mechanism 14 will be described with reference to FIG.
As shown in FIG. 1, the frictional force reduction mechanism 14 includes a tank 41 as a storage unit for storing water, a right rear wheel nozzle unit 42 disposed in front of the right rear wheel RR, and a left rear wheel. The nozzle part 43 for left rear wheels arrange | positioned ahead of RL is provided, and these each nozzle parts 42 and 43 are each connected with the tank 41 via the water supply path 44, respectively. Further, a water supply pump 45 is disposed on the water supply path 44, and the water supplied from the tank 41 into the nozzle portions 42 and 43 is jetted by driving the water supply pump 45. It has become so.

Next, the ECU 15 of this embodiment will be described below with reference to FIG.
The ECU 15 is mainly configured by an input side interface (not shown), an output side interface (not shown), a digital computer including a CPU 50, a ROM 51, a RAM 52, and the like, and a drive circuit for driving each device. Yes. The brake switch SW1, the steering angle sensor SE1, and the accelerator opening sensor SE2 for detecting the opening of the accelerator pedal 11 are electrically connected to the input side interface of the ECU 15. The input side interface includes wheel speed sensors SE3, SE4, SE5, SE6 for detecting the wheel speed of each wheel FR, FL, RR, RL, and lateral acceleration in the lateral direction (left-right direction) of the vehicle. A lateral acceleration sensor SE7 (also referred to as “lateral G sensor”) for detection is electrically connected.

  The steering angle sensor SE1 outputs a signal indicating that the ECU 15 indicates a positive value when the steering wheel 16 is steered to the right in the rotational direction, while the ECU 15 is negative when the steering wheel 16 is steered to the left in the rotational direction. It is set to output a signal indicating the value of. The lateral acceleration sensor SE7 outputs a signal indicating that the ECU 15 indicates a positive value when acceleration to the right of the vehicle in the vehicle traveling direction is detected, while the acceleration to the left of the vehicle in the vehicle traveling direction is detected. If detected, the ECU 15 is set to output a signal indicating a negative value.

  On the other hand, the motor M for driving the pump 29, the electromagnetic valves 32 to 36 and 40, and the water supply pump 45 are electrically connected to the output side interface of the ECU 15. The ECU 15 individually controls the driving of the pump 29 (motor M), the electromagnetic valves 32 to 36, 40, and the water supply pump 45 based on various input signals from the brake switch SW1 and the various sensors SE1 to SE7. It is supposed to be.

  In the digital computer, the ROM 51 has various control programs for individually controlling the motor M, each of the solenoid valves 32 to 36, 40, and the water supply pump 45 (braking control control execution determination process described later), and Various threshold values (a steering angle threshold value, a vehicle body speed threshold value, a lateral acceleration threshold value, etc., which will be described later) are stored. The RAM 52 stores various information (such as steering angles of steering wheels, wheel speeds of wheels FR, FL, RR, and RL, estimated vehicle body speed, lateral acceleration, etc.) that can be rewritten as appropriate during driving of the vehicle. It has come to be remembered.

  Next, among the control processes executed by the ECU 15 of the present embodiment, the turning-time braking control execution determination process routine will be described based on the flowchart shown in FIG. 3 and the timing charts shown in FIGS. 4 (a), 4 (b), and 4 (c). To do.

  The ECU 15 executes a turning-time braking control execution determination processing routine at predetermined intervals (for example, every “0.01 seconds”). In the turning braking control execution determination processing routine, the ECU 15 calculates the steering angle A of the steering wheel 16 based on the input signal from the steering angle sensor SE1 (step S10). In this regard, in this embodiment, the ECU 15 also functions as a steering angle calculation unit. Then, the ECU 15 determines whether or not the steering angle A calculated in step S10 is greater than or equal to a preset steering angle threshold KA (step S11). The steering angle threshold KA is a value (for example, “360 °”) for determining whether or not the steering wheel 16 has been steered to the maximum, and is set in advance through experiments, simulations, or the like. “Maximum steering” refers to a state in which the steering wheel 16 is steered to the maximum in a certain direction (right or left in the rotational direction).

  If the determination result in step S11 is negative (A absolute value <KA), the ECU 15 proceeds to step S18 to be described later. On the other hand, if the determination result in step S11 is affirmative (A absolute value ≧ KA), the ECU 15 determines whether or not the brake switch SW1 is “off” (step S12). If this determination result is a negative determination (SW1 = “ON”), the ECU 15 determines that the brake is being operated, and proceeds to step S18 described later. On the other hand, if the determination result in step S12 is affirmative (SW1 = “off”), the ECU 15 determines that a non-brake operation is being performed, and the accelerator pedal 11 is operated based on an input signal from the accelerator opening sensor SE2. It is determined whether or not it is performed (step S13).

  When this determination result is a negative determination, the ECU 15 proceeds to step S18 to be described later. On the other hand, if the determination result in step S13 is affirmative, the ECU 15 determines the wheel speeds VWfr, VWfl, VWrr, VWrl of the wheels FR, FL, RR, RL based on the input signals from the wheel speed sensors SE3 to SE6. Are respectively calculated (step S14). Then, the ECU 15 calculates the estimated vehicle body speed VS of the vehicle based on the wheel speeds VWfr, VWfl, VWrr, VWrl calculated in step S14 (step S15). In this regard, in the present embodiment, the ECU 15 also functions as a vehicle body speed calculation unit.

  Subsequently, the ECU 15 determines whether or not the estimated vehicle speed VS calculated in step S15 is less than a preset vehicle speed threshold KVS (step S16). The vehicle body speed threshold value KVS is a value for determining whether or not the vehicle is traveling at a low speed that can ensure the behavior stability of the vehicle even if the braking control during turning and the frictional force lowering control described later are executed ( For example, “10 km / h” (10 kilometers per hour)), which is set in advance by experiments or simulations. If the determination result in step S16 is negative (VS ≧ KVS), the ECU 15 proceeds to step S18 described later. On the other hand, if the determination result of step S16 is affirmative (VS <KVS), the ECU 15 executes turning-time braking control (also referred to as “small turning control”) (step S17), and the process is described later in step S19. Migrate to

Here, as an example of the braking control during turning, the braking control during turning when the vehicle turns rightward will be described below.
As shown in FIGS. 4A, 4B, and 4C, the ECU 15 indicates that the absolute value of the steering angle A of the steering wheel 16 is equal to or greater than the steering angle threshold KA, and the brake switch SW1 is “off”. That is, when the accelerator pedal 11 is depressed and the estimated vehicle body speed VS of the vehicle is all less than the vehicle body speed threshold value KVS, the right rear wheel RR that is the rear wheel inside the turning direction is established. The driving of the braking force applying mechanism 13 is controlled to increase the brake hydraulic pressure BP in the wheel cylinder 26c to a predetermined hydraulic pressure BP1. Specifically, on the first hydraulic circuit 23 side, the ECU 15 closes the proportional solenoid valve 36, opens the solenoid valve 40 on the branch hydraulic pressure path 39, and further opens the left front wheel path 30. The upper normally open solenoid valve 32 is closed. Further, the ECU 15 closes the proportional solenoid valve corresponding to the proportional solenoid valve 36 of the first hydraulic circuit 23 on the second hydraulic circuit 24 side, and the electromagnetic valves 32 and 33 of the first hydraulic circuit 23. Each solenoid valve corresponding to is closed.

  In this state, the ECU 15 drives the pump 29 by rotating the motor M. Then, the brake fluid flows into the wheel cylinder 26c for the right rear wheel RR from the master cylinder 20 side via the branch hydraulic pressure passage 39, and the brake hydraulic pressure BP in the wheel cylinder 26c increases. On the other hand, the brake fluid pressure BP in the wheel cylinders 26a, 26b, and 26d for the wheels (the right front wheel FR, the left front wheel FL, and the left rear wheel RL) other than the right rear wheel RR is maintained. When the ECU 15 determines that the brake hydraulic pressure BP in the wheel cylinder 26c has reached the predetermined hydraulic pressure BP1 based on the driving of the pump 29, the ECU 15 stops the driving of the motor M and closes the electromagnetic valve 33. Then, the brake hydraulic pressure BP in the wheel cylinder 26c is held at the predetermined hydraulic pressure BP1. The predetermined hydraulic pressure BP1 is set in advance to such a level that a wheel (for example, the right rear wheel RR) is not locked by applying a braking force based on the predetermined hydraulic pressure BP1.

  Returning to the flowchart shown in FIG. 3, in step S <b> 18, the ECU 15 stops execution of the above-described braking control during turning, and cancels the application of braking force to the rear wheel (for example, the right rear wheel RR) inside the turning direction. That is, the ECU 15 performs steps S11, S12, S13. When at least one of the determination results in the determination process of S16 is a negative determination, the driving of the electromagnetic valves 32 to 36.40 of the braking force applying mechanism 13 and the pump 29 (motor M) is stopped. Then, the brake fluid flows back to the master cylinder 20 from the inside of the wheel cylinder (for example, the wheel cylinder 26c) corresponding to the rear wheel (for example, the right rear wheel RR) in the turning direction, and the brake fluid pressure in the wheel cylinder is reduced. Will descend. As a result, the braking force for the rear wheel inside the turning direction is eliminated. Thereafter, the ECU 15 proceeds to step S22 described later.

  In step S19, the ECU 15 calculates the lateral acceleration GY of the vehicle based on the input signal from the lateral acceleration sensor SE7. During turning control during turning when the vehicle is traveling at a substantially constant speed (low speed in the present embodiment), the lateral acceleration GY of the vehicle increases as the μ value (friction coefficient) of the road surface on which the vehicle is traveling increases. The absolute value of becomes larger. Therefore, the ECU 15 can estimate the μ value of the road surface from the magnitude of the lateral acceleration GY of the vehicle. In this regard, in the present embodiment, the ECU 15 also functions as a road surface μ value estimation unit.

  Then, the ECU 15 determines whether or not the absolute value of the lateral acceleration GY calculated in step S19 is larger than a preset lateral acceleration threshold value KGY (step S20). This lateral acceleration threshold value KGY is a value for determining whether or not the vehicle is traveling on a high μ road where the μ value of the road surface can be lowered by injecting water onto the road surface. It is preset by experiment or simulation. If the determination result in step S20 is negative (GY absolute value ≦ KGY), the ECU 15 determines that the vehicle is traveling on a low μ road (for example, a frozen road surface or a snowy road surface). The process proceeds to step S22 described later. When water is jetted from the nozzle portions 42 and 43 to such a low μ road, the μ value of the road surface may be increased. For example, when water is injected on a frozen road surface, the μ value of the road surface becomes high, and when water is injected on a road surface wet with rain, the μ value of the road surface changes substantially. Absent.

  On the other hand, if the determination result in step S20 is affirmative (GY absolute value> KGY), the ECU 15 determines that the vehicle is traveling on a high μ road, and executes frictional force reduction control (step S21). . Specifically, the ECU 15 drives the water supply pump 45 of the friction force reducing mechanism 14 to inject water from the nozzle portions 42 and 43, respectively. Therefore, in this embodiment, the ECU 15 also functions as a control unit that executes the braking control during turning and the frictional force reduction control. Thereafter, the ECU 15 once terminates the turning braking control execution determination processing routine.

  In step S22, the ECU 15 stops the friction force reduction control by restricting the drive of the water supply pump 45. Thereafter, the ECU 15 once terminates the turning braking control execution determination processing routine.

  Next, the operation when the vehicle of this embodiment turns in the right direction will be described with reference to FIG. It is assumed that the determination processes in steps S11, S12, S13, S16, and S20 described above are all positive determinations.

  Now, when both the turning braking control and the frictional force lowering control are executed, the brake hydraulic pressure BP in the wheel cylinder 26c is applied to the right rear wheel RR, which is the rear wheel in the turning direction, as shown in FIG. While the braking force based on (= BP1) is applied, the μ value of the road surface on which the right rear wheel RR travels is lowered by water being injected from the right rear wheel nozzle portion 42. As a result, the right rear wheel RR is more likely to skid sideways (leftward) than in the conventional case where the friction force reduction control is not executed. In the present embodiment, since the μ value of the road surface on which the left rear wheel RL travels is lowered by the water injection from the left rear wheel nozzle portion 43, the left rear wheel RL that is the rear wheel on the outer side in the turning direction is also As compared with the conventional case where the friction force lowering control is not executed, it becomes easier to skid sideways (leftward).

  Therefore, the turning radius of the vehicle C when the friction force reduction control is executed is smaller than the turning radius of the conventional vehicle (hereinafter referred to as “conventional vehicle”) C1 where the friction force reduction control is not executed. In addition, since the right rear wheel RR is not applied with a strong braking force that locks the right rear wheel RR, the right rear wheel RR is applied with a strong braking force that locks the right rear wheel RR. Compared to the case where the vehicle is driven, an increase in the drag feeling felt by the driver is suppressed by executing the braking control during turning.

Therefore, in this embodiment, the following effects can be obtained.
(1) When the absolute value of the steering angle A of the steering wheel 16 is equal to or greater than the steering angle threshold KA, the vehicle C turns to apply a braking force to the rear wheel (for example, the right rear wheel RR) inside the turning direction. Brake control and frictional force reduction control are executed. Therefore, when the vehicle C turns, the frictional force between the rear wheels RR and RL and the road surface is reduced, so that the rear wheels RR and RL are more likely to skid compared to the conventional vehicle C1 in which the frictional force reduction control is not performed. As a result, the turning radius of the vehicle C can be made smaller than that of the conventional vehicle C1 without applying a strong braking force that locks the rear wheel to the rear wheel inside the turning direction. Accordingly, the turning radius of the vehicle C can be further reduced while suppressing an increase in the drag feeling felt by the driver of the vehicle C by applying braking force to the wheels on the inner side in the turning direction when the vehicle C is turning.

  (2) When the absolute value of the steering angle A of the steering wheel 16 is greater than or equal to the steering angle threshold KA, water is injected from the nozzle portions 42 and 43 of the friction force reduction mechanism 14, resulting in the rear wheels RR and RL. The μ value of the road surface with respect to decreases. For this reason, it is possible to easily create a situation in which the rear wheel can easily skid without increasing the braking force on the rear wheel (for example, the right rear wheel RR) inside the turning direction of the vehicle C.

  (3) When the road surface of the vehicle C is a low μ road, the μ value of the road surface with respect to the rear wheels RR and RL is increased by injecting water from the frictional force reducing mechanism 14 onto the road surface. There is. When the frictional force reduction control is executed during the turning of the vehicle C on such a low μ road, the turning radius of the vehicle C may be larger than the turning radius of the conventional vehicle C1. In this respect, in the present embodiment, when the road surface on which the vehicle C travels is a low μ road even if the absolute value of the steering angle A of the steering wheel 16 is equal to or greater than the steering angle threshold KA, the braking control during turning is executed. On the other hand, the execution of the friction force reduction control is restricted. Therefore, when the vehicle C turns on a low μ road, it is possible to avoid an increase in the turning radius of the vehicle C, unlike when the frictional force reduction control is executed.

  (4) When the driver performs a braking operation when turning the vehicle, the braking force is applied to each wheel FR, FL, RR, RL of the vehicle C. Even without this, the turning radius of the vehicle C can be reduced. Therefore, in the present embodiment, when the driver is performing a brake operation when the vehicle C is turning, the braking control during turning is performed even if the absolute value of the steering angle A of the steering wheel 16 is equal to or greater than the steering angle threshold KA. Execution is regulated. Accordingly, an increase in the control load of the ECU 15 can be suppressed, and unnecessary driving of the motor M (pump 29) of the braking force applying mechanism 13 and the electromagnetic valves 32 to 36, 40 can be suppressed.

  (5) When water is injected from the friction force reduction mechanism 14 onto the road surface when the vehicle C is turning at a high speed, the lateral acceleration GY applied to the vehicle C becomes too large, and the behavior of the vehicle C is increased. May become unstable. In this regard, in this embodiment, when it is determined that the vehicle C is turning at a high speed, even when the absolute value of the steering angle A of the steering wheel 16 is greater than or equal to the steering angle threshold KA, Since the execution of the frictional force lowering control is restricted, the behavioral stability of the turning vehicle C can be ensured.

The embodiment may be changed to another embodiment as described below.
In the embodiment, when the vehicle braking control is executed when the vehicle C turns to the left, the brake fluid pressure in the wheel cylinder 26d corresponding to the left rear wheel RL is set to the predetermined fluid pressure BP1. The braking force applying mechanism 13 is driven.

  In the embodiment, when the vehicle C is turning at a high speed, the execution of the braking control during turning may be restricted while the frictional force reduction control is executed. However, when it is detected that the driver is operating the brake during the turn, it is desirable to stop the execution of the frictional force reduction control in order to ensure the behavior stability of the vehicle.

  In the embodiment, even when the brake is operated while the vehicle C is turning, the absolute value of the steering angle A of the steering wheel 16 is not less than the steering angle threshold KA, and the accelerator pedal 11 is operated. When it is established that the estimated vehicle body speed VS of the vehicle C is less than the vehicle body speed threshold value KVS and that the absolute value of the lateral acceleration GY of the vehicle is larger than the lateral acceleration threshold value KGY, the friction force reduction control is performed. You may make it perform.

  -In embodiment, it is not necessary to perform the determination process of step S12. In this case, even when the driver performs a brake operation, the braking control during turning and the frictional force reduction control can be executed. However, in the turning braking control during the brake operation, the braking force applied to the rear wheel (for example, the right rear wheel RR) inside the turning direction of the vehicle C is applied to other wheels (for example, the right front wheel FR, the left front wheel FL, the left rear wheel). It is desirable that the braking force is greater than RL). In such a configuration, even when a braking force is applied to each of the wheels FR, FL, RR, and RL by a brake operation by the driver, the braking during turning is performed by executing the braking control during turning. The turning radius of the vehicle C can be made smaller than when control is not executed.

  When the vehicle body speed of the vehicle C (estimated vehicle body speed VS) is constant and the absolute value of the steering angle A of the steering wheel 16 is constant, the higher the μ value of the road surface, the higher the yaw rate ( Yaw Rate) is lowered. Therefore, a yaw rate sensor for detecting the yaw rate of the vehicle C may be provided in the vehicle C, and the μ value of the road surface on which the vehicle C is traveling may be estimated based on the yaw rate of the vehicle C.

  -In embodiment, it is not necessary to perform the determination process of said step S20. That is, when all the conditions for executing the turning braking control are satisfied, the friction force reduction control may be executed together with the turning braking control.

  In the embodiment, the frictional force reduction mechanism 14 may have a configuration in which nozzle portions corresponding to the front wheels FR and FL are individually provided. And when performing frictional force reduction | decrease control when the vehicle C reverses, you may make it inject water to the front-wheel FR, FL side.

  In the embodiment, in the frictional force reduction control, water may be injected only to the rear wheel (for example, the left rear wheel RL) side in the turning direction, or the rear wheel (for example, the right rear wheel RR) inside the turning direction. Water may be jetted only on the side.

  In the embodiment, water may be jetted from the nozzle portions 42 and 43 of the frictional force reduction mechanism 14 toward the portion of the rear wheels RR and RL that contacts the road surface (for example, the outer surface of the tire). Good. Even in this case, the frictional force between the rear wheels RR and RL and the road surface can be reduced by reducing the μ value of the rear wheels RR and RL by executing the friction force reduction control.

  Further, water may be jetted from the nozzle portions 42 and 43 of the frictional force reduction mechanism 14 toward the road surface through which the rear wheels RR and RL pass and the portions of the rear wheels RR and RL that are in contact with the road surface. Good.

  In the embodiment, the frictional force lowering mechanism 14 does not include a drive source such as the water supply pump 45, arranges the tank 41 above the nozzle portions 42 and 43, and determines the weight of the water in the tank 41. Thus, the water may flow down from the nozzle portions 42 and 43 toward the road surface.

  In the embodiment, the frictional force reduction mechanism 14 is a liquid other than water (a liquid such as a lubricating oil, a liquid obtained by dispersing or mixing functional material particles in a liquid, or a fluid such as a gel). Or the structure which can inject the granular material (solid which can be flowed and injected) from each nozzle part 42 and 43 may be sufficient. For example, the frictional force lowering mechanism 14 includes a liquid material in which particles (sand, etc.) are dispersed or mixed in a liquid, a flow material such as a gel (eg, physical gel), and a powder (powder material) such as sand. A solid material as an example may be ejected from the nozzle portions 42 and 43. Moreover, the frictional force lowering mechanism 14 may inject both the liquid and the granular material described above.

In the embodiment, the steering angle threshold KA may be a value (for example, “300 °”) smaller than the maximum steering angle.
-In embodiment, when performing braking control at the time of turning, you may make it provide braking force also to the front wheel inside the turning direction of the vehicle C. FIG. Alternatively, the braking force may be applied only to the front wheel inside the turning direction without applying the braking force to the rear wheel inside the turning direction of the vehicle C.

  In the embodiment, in the braking control during turning, the brake fluid pressure in the wheel cylinder corresponding to the rear wheel inside the turning direction may be changed according to the absolute value of the steering angle A of the steering wheel 16. Good.

  In the embodiment, even when the vehicle C moves backward, the turning braking control and the friction force reduction control may be executed. For example, when the vehicle C turns to the left, the braking force application mechanism 13 is driven so that the braking force is applied to the left front wheel FL, and water is injected toward the road surface through which the front wheels FR and FL pass. Will be.

The block diagram of the vehicle by which the control apparatus at the time of turning of this embodiment is mounted. The block diagram which shows a part of braking force provision mechanism in this embodiment. The flowchart which shows the braking control execution determination processing routine at the time of turning. (A) is a timing chart showing the change in the steering angle of the steering wheel, (b) is a timing chart showing the change in the estimated vehicle body speed, and (c) is the brake hydraulic pressure in the wheel cylinder corresponding to the wheel inside the turning direction. The timing chart which shows a change. Schematic diagram showing a comparison between a state in which the vehicle is turning with both the braking control during turning and the frictional force reduction control being executed, and a state in which the vehicle is turning with only the braking control during turning being executed. .

Explanation of symbols

  DESCRIPTION OF SYMBOLS 13 ... Braking force provision mechanism, 14 ... Friction force reduction mechanism, 15 ... Turning time control apparatus, Steering angle calculation means, Control means, Road surface μ value estimation means, ECU as vehicle body speed calculation means, 16 ... Steering wheel, 41 ... Tank as a storage part, 42, 43 ... Nozzle part, A ... Steering angle, C ... Vehicle, FR, FL, RR, RL ... Wheel, KA ... Steering angle threshold, KVS ... Body speed threshold, VS ... Estimated body speed.

Claims (5)

The vehicle (C) is mounted on a vehicle (C) in which wheels (FR, FL, RR, RL) are respectively arranged on both the front and rear sides in the traveling direction and on the left and right sides with respect to the traveling direction. A vehicle turning control device (15) for applying braking force to inner wheels (FR, RR),
The vehicle (C) includes a braking force applying mechanism (13) for individually applying a braking force to the wheels (FR, FL, RR, RL), and the wheels (FR, FL, RR, RL). And a friction force reducing mechanism (14) for reducing the frictional force between the road surface and the road surface,
Steering angle calculation means (S10) for calculating the steering angle (A) of the steering (16) of the vehicle (C);
When the absolute value of the steering angle (A) calculated by the steering angle calculation means (S10) is greater than or equal to a preset steering angle threshold (KA), the wheel (FR, In order to apply a braking force to RR), braking control during turning that controls driving of the braking force applying mechanism (13) is executed, and wheels (RR, RL) on the rear side in the traveling direction of the vehicle (C) and the road surface And a control means (S17, S21) for controlling the driving of the frictional force reducing mechanism (14) in order to reduce the frictional force with the vehicle. The frictional force lowering mechanism (14) includes a storage unit (41) that stores at least one of liquid and powder, and at least one of the liquid and powder supplied from the storage unit (41). The vehicle turning control device according to claim 1, further comprising a nozzle portion (42, 43) for flowing out toward at least one of the wheels (FR, FL, RR, RL) and a road surface. Road surface μ value estimation means (S19) for estimating the μ value of the road surface on which the vehicle (C) travels is further provided,
The control means (S17, S21) regulates driving of the frictional force reduction mechanism (14) when it is determined that the road surface is a low μ road based on the estimation result by the road surface μ value estimation means (S19). The vehicle turning control device according to claim 1 or 2. When the control means (S17, S21) detects that the driver is operating a brake to apply a braking force to each wheel (FR, FL, RR, RL), the braking during turning is performed. The vehicle turning control device according to any one of claims 1 to 3, wherein execution of control is restricted. Vehicle speed calculation means (S14, S15) for calculating the vehicle speed (VS) of the vehicle (C) is further provided;
In the control means (S17, S21), the vehicle body speed (VS) calculated by the vehicle body speed calculating means (S14, S15) is set in advance as a criterion for determining whether or not the vehicle (C) is traveling at a low speed. Any one of claims 1 to 4, wherein when the vehicle body speed threshold value (KVS) is exceeded, the execution of the turning braking control is restricted and the driving of the frictional force reduction mechanism (14) is restricted. The vehicle turning control device according to one item.

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