JPH08142716A - Stable control device for vehicle - Google Patents

Abstract

PURPOSE: To provide a stable control device for a vehicle having a driving force control means, a braking force control means, and a rear wheel steering angle control means and capable of quickly securing the driving stability of the vehicle. CONSTITUTION: The deviation between the actual yaw rate and the target yaw rate is calculated by a yaw rate deviation calculating means DY, a rear wheel steering angle control means RC is controlled in response to the calculated result, and the first slip ratio is calculated by the first slip ratio calculating means SY based on the calculated result. The steering angle of the wheels RL, RR is detected by a rear wheel steering angle detecting means DA, and the second slip ratio is calculated by the second slip ratio calculating means SR based on the detected steering angle. The target slip ratio is set by a target slip ratio setting means TS based on the first and second slip ratios, and the driving force control means DC and braking force control means BC are controlled based on the target slip ratio so that the yaw rate deviation becomes a prescribed level or below.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving force control means for controlling a driving force applied to a vehicle rear wheel by an engine mounted on a vehicle and a braking force control for controlling a braking force of a brake device mounted on each wheel of the vehicle. In addition to the means, a rear wheel steering angle control means for controlling a steering angle of a wheel behind the vehicle, and relates to a vehicle stability control device for maintaining steering stability.

[0002]

2. Description of the Related Art Recent vehicles are provided with a driving force control means and a braking force control means, and have various control functions such as anti-skid control, traction control, and front / rear braking force distribution control. . Further, it is equipped with a rear wheel steering angle control means, which enables the steering angle control of the wheels behind the vehicle in addition to the conventional front wheel steering function, and has a four-wheel steering function. For example, Japanese Patent Laid-Open No. 4-317863 discloses a vehicle having a steering function for driving wheels. As described as the prior art in the publication, in the traction control device, the presence or absence of slippage of the drive wheel is detected from the rotational speed difference between the drive wheel and the driven wheel, and when the slippage occurs, the output torque of the engine, The intake air amount control and the ignition timing control are used to suppress and prevent the slip, and the drive wheel is also controlled to prevent the slip. In this publication, in order to stabilize the drivability even if the friction coefficient of the road surface is different between the left and right drive wheels, the shaft torques of the left and right drive wheels are detected, and when a difference between those shaft torques occurs, the shaft torque is detected. It is described that it is determined that slip has occurred in the drive wheel with the smaller torque, and the drive wheel is steered so that the drive wheel with the smaller axial torque is on the outside of the turn.

Further, in the anti-skid control device disclosed in Japanese Patent Laid-Open No. 63-315355, regarding a vehicle having an anti-skid control function and a four-wheel steering function, the motion that appears around the vertical axis of the vehicle at the time of braking is applied. A device for controlling the steering angle of the rear wheels in a canceling direction has been proposed.

[0004]

However, the device disclosed in Japanese Patent Laid-Open No. 4-317863 mentioned above is designed to improve the acceleration drivability on a so-called split road surface in which the friction coefficient is different between the left and right driving wheels, and the driving is performed. The steering torque for the driving wheels is detected by detecting the axial torque of the wheels and is not directly related to the braking force control means. The device is also unrelated to the driving force control means for controlling the driving force by the engine to perform traction control and the like, and the rear wheel steering angle control means for controlling the steering angle of the vehicle rear wheels including the driven wheels.
On the other hand, the device described in Japanese Patent Laid-Open No. 63-315355 does not include a driving force control means, and its necessity is not suggested.

Therefore, an object of the present invention is to provide a vehicle stability control device which is provided with a driving force control means, a braking force control means, and a rear wheel steering angle control means, and which can quickly secure the steering stability of the vehicle. To do.

[0006]

In order to achieve the above object, the present invention has wheels RL, R on the rear side of the vehicle by an engine EG mounted on the vehicle, as shown in the outline of the configuration in FIG.
Driving force control means DC for controlling the driving force for R and brake device B mounted on each wheel FL, FR, RL, RR
Braking force control means BC for controlling the braking force of R and rear wheel steering angle control means RC for controlling the steering angles of the wheels RL, RR behind the vehicle at least in accordance with the steering amounts of the wheels FL, FR in front of the vehicle.
And a driving state detection means DS for detecting the driving state of the vehicle
And a target yaw rate setting means TY for setting a target yaw rate according to the detection result of the operating state detection means DS,
Actual yaw rate detection means A for detecting the actual yaw rate of the vehicle
A vehicle stability control device that includes Y and yaw rate deviation calculation means DY that calculates the deviation of the actual yaw rate from the target yaw rate, and controls the rear wheel steering angle control means RC according to the calculation result of the yaw rate deviation calculation means DY. A first slip ratio calculating means SY for calculating a first slip ratio based on the calculation result of the yaw rate deviation calculating means DY;
Wheels RL, RR behind the vehicle by the rear wheel steering angle control means RC
A rear wheel steering angle detection means DA for detecting the steering angle of the vehicle, and a second slip ratio calculation means SR for calculating a second slip ratio based on the detected steering angle of the rear wheel steering angle detection means DA; The target slip ratio setting means TS for setting the target slip ratio based on the second slip ratio is provided, and the driving force control means DC and the braking force control means BC are controlled based on the target slip ratio set by the target slip rate setting means TS. It is something that is done.

In the above-described vehicle stability control device, the driving force control means DC includes a throttle control device for controlling the throttle opening degree of the engine EG, and based on the target slip ratio set by the target slip ratio setting means TS, the throttle The control unit may be configured to perform throttle opening control and braking force control means BC to perform braking force control.

Further, in the above-described vehicle stability control device, wheel speed detecting means for detecting the wheel speed of each wheel,
The vehicle body speed estimating means for estimating the vehicle body speed based on the detection output of the wheel speed detecting means is provided, and the driving state detecting means DS is a front wheel steering angle sensor for detecting the steering angle of the wheels FL, FR in front of the vehicle. In addition, the driving state of the vehicle can be detected based on the steering angle detected by the front wheel steering angle sensor and the vehicle body speed estimated by the vehicle body speed estimation means.

Further, the actual yaw rate detecting means may be configured to calculate the actual yaw rate based on the difference between the wheel speeds on the driven wheel side of the wheel speeds detected by the wheel speed detecting means.

[0010]

In the vehicle stability control system shown in FIG. 1 having the above-described structure, the wheels R located behind the vehicle from the engine EG.
The driving force transmitted to L, RR is controlled by the driving force control means DC, and the wheels FL, FR, RL, RR are also controlled.
The braking force of the brake device BR applied to the vehicle is controlled by the braking force control means BC. Further, the rear wheel steering angle control means R
C controls the steering angles of the wheels RL, RR on the rear side of the vehicle at least according to the steering amounts of the wheels FL, FR on the front side of the vehicle. Further, the target yaw rate setting means TY sets the target yaw rate according to the detection result of the driving state detection means DS, and the actual yaw rate detection means AY detects the actual yaw rate of the vehicle. Then, the yaw rate deviation calculation means DY calculates the deviation of the actual yaw rate from the target yaw rate, and the rear wheel steering angle control means RC is controlled according to the calculation result. Further, based on the calculation result of the yaw rate deviation calculation means DY, the first slip ratio calculation means SY calculates the first slip ratio, and the wheels RL and RR controlled by the rear wheel steering angle control means RC are calculated. The steering angle is detected by the rear wheel steering angle detection means DA, and the second slip ratio calculation means SR calculates the second slip ratio based on the detected steering angle of the rear wheel steering angle detection means DA. The target slip ratio setting unit TS sets the target slip ratio based on the first and second slip ratios, and the driving force control unit DC and the braking force control unit B are set based on the target slip ratio.
C is controlled so that the yaw rate deviation becomes equal to or lower than a predetermined level.

In the vehicle stability control device according to the second aspect of the invention, the throttle opening of the engine EG is controlled by the throttle control device based on the target slip ratio set by the target slip ratio setting means TS, and the braking force is increased. Braking force control is performed by the control means BC.

In the vehicle stability control device according to the third aspect, the vehicle body speed is estimated by the vehicle body speed estimating means based on the detection output of the wheel speed detecting means, and the front wheel rudder constituting the operating state detecting means DS is also provided. The steering angle of the wheel in front of the vehicle is detected by the angle sensor, and the driving state of the vehicle is detected based on the steering angle and the vehicle speed estimated by the vehicle speed estimation means. Further, in the vehicle stability control device according to the fourth aspect, the actual yaw rate is calculated based on the difference between the left and right wheel speeds of the driven wheels detected by the wheel speed detecting means.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows an embodiment of the stability control device of the present invention. Driving force control means for controlling the driving force for the rear wheels by an engine mounted on the vehicle, braking force control means for controlling the braking force of each wheel. , And rear wheel steering angle control means for controlling the steering angle of the rear wheels. First, the drive system will be described. The engine EG of the present embodiment is a throttle control device T.
In an internal combustion engine equipped with H, the throttle control device TH is configured to control the throttle opening amount according to the operation of the accelerator pedal AP and to control the throttle opening amount according to the output of the electronic control device ECU. ing. The engine EG is connected to the wheels RL and RR on the rear side of the vehicle via a well-known differential gear DF, and constitutes a so-called rear wheel drive system.

Next, regarding the braking system, the wheels FL, F
Wheel cylinders Wfl and Wf for R, RL and RR respectively
r, Wrl, Wrr are mounted, and a hydraulic pressure control device FV is interposed in a hydraulic pressure path connecting these wheel cylinders Wfl and the like and the master cylinder MC. Note that the wheel FL indicates the wheel on the front left side as viewed from the driver's seat, hereinafter the wheel FR indicates the front right side, the wheel RL indicates the rear left side, and the wheel RR indicates the rear right side. In the present embodiment, the hydraulic control of the front wheel is performed. Although the front and rear pipes are divided into the system and the hydraulic control system for the rear wheels, so-called X pipes may be used.

The master cylinder MC is a brake pedal BP.
Hydraulic control device F driven according to the operation of the master cylinder MC and interposed between the master cylinder MC and the wheel cylinder Wfl, etc.
V is configured as shown as a control part of the wheel RL in FIG. 3, and includes a normally open solenoid valve EV1 and a normally open solenoid valve EV1 in a fluid pressure passage connecting one output port of the master cylinder MC and the wheel cylinder Wrl. A closed solenoid valve EV2 is interposed as shown in FIG. 3, and the discharge side of the pump HP is connected between these and the master cylinder MC. The other wheels have the same structure. Pump HP is motor F
The brake fluid, which is driven by M and is pressurized to a predetermined pressure, is supplied to the hydraulic passage. The discharge side hydraulic pressure passage of the normally closed electromagnetic valve EV2 is connected to the pump HP via the reservoir RV, and the reservoir RV is provided with a piston and a spring, respectively, and is recirculated from the electromagnetic valve EV2 via the discharge side hydraulic pressure passage. The brake fluid is stored and is supplied to the pump HP when the pump HP is activated.

The solenoid valves EV1 and EV2 are 2-port 2-position solenoid directional control valves, each of which is in the first position shown in FIG. 3 when the solenoid coil is not energized, and the wheel cylinder Wrl communicates with the master cylinder MC and the pump HP. There is. When the solenoid coil is energized, it is in the second position, and the wheel cylinder Wrl is disconnected from the master cylinder MC and the pump HP and communicates with the reservoir RV. These solenoid valves E
V1 and EV2 are connected to the electronic control unit ECU of FIG. 2. The electronic control unit ECU controls energization and de-energization of the solenoid coil according to the braking state of the vehicle, and the brake fluid pressure in the wheel cylinder Wrl is controlled. Boosting,
Reduced pressure or maintained. That is, when the solenoid coils of the solenoid valves EV1 and EV2 are not energized, the wheel cylinder Wrl
The brake fluid pressure is supplied from the master cylinder MC and the pump HP to increase the pressure, and when energized, the brake fluid pressure is communicated with the reservoir RV side to reduce the pressure. If the solenoid coil of the solenoid valve EV1 is energized and the solenoid coil of the solenoid valve EV2 is non-energized, the brake fluid pressure in the wheel cylinder Wrl is maintained. Therefore, so-called pulse pressure increase (step pressure increase) or pulse pressure decrease can be performed by adjusting the time interval of energization / de-energization, and control can be performed so as to gradually increase or decrease the pressure. Although a pair of 2-port 2-position solenoid operated directional control valves are used in this embodiment, a 3-port 3-position solenoid operated directional control valve may be used. Further, the motor FM that drives the pump HP is also connected to the electronic control unit ECU, and the drive is controlled thereby.

As shown in FIG. 2, wheels FL, FR, R
Wheel speed sensors WS1 to WS4 are arranged in L and RR, and these are connected to an electronic control unit ECU, and a pulse signal of a pulse number proportional to the rotation speed of each wheel, that is, the wheel speed is sent to the electronic control unit ECU. Is configured to be input to. Further, a brake switch BS that is turned on when the brake pedal BP is depressed, a yaw rate sensor YS that detects the yaw rate of the vehicle, and the like are connected to the electronic control unit ECU. The yaw rate sensor YS detects a change speed of the vehicle rotation angle (yaw angle) around the vertical axis passing through the center of gravity of the vehicle, that is, a yaw angular speed (yaw rate) γ, and outputs it to the electronic control unit ECU. The yaw rate γ can be calculated based on the wheel speed difference between the driven wheels (front wheels FL and FR), and the yaw rate sensor YS can be calculated.
Can be omitted.

As for the rear wheel steering angle control means, as shown in FIG. 2, the steering angle control device SC is provided between the wheels RL, RR behind the vehicle.
D is provided, and the steering angles of the wheels RL and RR are controlled by the motor SM according to the output of the electronic control unit ECU. A rear wheel steering angle sensor SSr is attached to the steering angle control device SCD to detect the actual steering angles of the wheels RL and RR. The motor SM is a yaw rate sensor Y.
Drive control is performed based on the amount of rotation set by the electronic control unit ECU according to the outputs of S, the wheel speed sensors WS1 to WS4, the front wheel steering angle sensor SSf, and the rear wheel steering angle sensor SSr.

The rudder angle control device SCD of this embodiment has a structure in which a rack shaft 60 is provided at right angles to the traveling direction of the vehicle as shown in FIG. Is connected to a rear knuckle arm 63 via a ball joint 62. The rack 61 formed on the rack shaft 60 is configured to mesh with a pinion 64 extending in the front-rear direction of the vehicle. A pinion 65 is provided at the tip of the motor shaft of the motor SM, and a gear 66 meshes with the pinion 65 to form a hypoid gear. The hypoid gear transmits the rotation of the motor shaft of the motor SM as the rotation of the gear 66.
The motor SM is configured not to rotate when a rotational force is applied to the gear 66 from the 0 side.

As shown in FIG. 2, the electronic control unit ECU is a microcomputer C including a processing unit CPU, a memory ROM, a RAM, an input port IPT, an output port OPT and the like which are connected to each other via a bus.
Equipped with MP. The wheel speed sensors WS1 to WS
4. Output signals from the brake switch BS, the yaw rate sensor YS, etc. are input through the amplifier circuit AMP to the input port IP respectively.
The processing unit CPU is configured to be input from T. Further, the output port OPT is configured to output a control signal to the throttle control device TH, the hydraulic pressure control device FV, and the steering angle control device SCD via the drive circuit ACT. In the microcomputer CMP, the memory ROM stores a program corresponding to the flowchart shown in FIG. 5, the processing unit CPU executes the program while an ignition switch (not shown) is closed, and the memory RAM stores the program. Temporarily stores variable data required for execution.

In the present embodiment configured as described above, the electronic control unit ECU performs a series of processes relating to the various controls described above, and when the ignition switch (not shown) is closed, the flow chart shown in FIG. Execution of the corresponding program starts. In FIG. 5, first, at step 101, the microcomputer CMP is initialized and various calculated values are cleared. Next step 102
, The detection signals of the wheel speed sensors WS1 to WS4 are read, and the detection signals of the yaw rate sensor YS (actual yaw rate) and the actual steering angles of the rear wheels RL, RR detected by the rear wheel steering angle sensor SSr are detected. Is read. Then, in step 103, the front wheel steering angle sensor S
The target yaw rate γ _o is set based on the steering angle θf of the front wheels FL and FR detected in Sf and the estimated vehicle body speed Vso calculated based on the outputs of the wheel speed sensors WS1 to WS4. That is, the target yaw rate γ _o is {1 / (1 + S · T)} · {Vso / Ks (1 + Kh ·
Vso ² )} · θf. Here, S is a Laplace converter, T is a target yaw rate first-order lag time constant, and K is
s represents a steering gear ratio, and Kh represents a target stability factor (target stability coefficient).

Next, at step 104, the deviation Δγ (= γ _o −γ) between the actual yaw rate γ detected by the yaw rate sensor YS and the target yaw rate γ _o is calculated, and the routine proceeds to step 105. In step 105, the absolute value | Δγ | of the deviation Δγ is compared with a predetermined value K0, and if it is less than this value, the process ends as it is, but if it exceeds the predetermined value K0, rear wheel steering angle control is performed in step 106. Step 1
In 06, the steering angle control device SCD is based on the deviation Δγ.
Of the motor SM is controlled so that the deviation Δγ falls below a predetermined level, that is, the absolute value | Δγ |
The steering angles of the wheels RL and RR are drive-controlled so as to be 0 or less. Therefore, the steering angle control device SCD operates so as to cancel the yaw moment that may occur while the vehicle is traveling, and the compensation operation is performed.

Next, at step 107, the rear wheel steering angle sensor SSr detects the rear wheel steering angle θr. Next, in step 108, according to the map shown in FIG.
Based on the value of the yaw rate deviation Δγ calculated in step 104, the first slip ratio SyR * (R * is the rear wheel RL,
Represents either one of RR). Further, in step 109, the second slip ratio SrR * is obtained based on the value of the rear wheel steering angle θr detected in step 107 according to the map shown in FIG. 7. And step 11
0, the first and second slip ratios SyR *, S
The minimum value of rR * is set as the target slip ratio SR * o (MIN shown in FIG. 5 represents a function for obtaining the minimum value). Note that K1 and K2 in FIG. 6 and K3 and K4 in FIG.
Is a constant for setting the map.

Then, throttle control is performed in step 111 and braking force control is performed in step 112 so that the target slip ratio SR * o is obtained. That is, the engine E is controlled by the throttle control device TH.
The output of G is limited, and the braking force is applied to the wheels RL and RR. As a result, as shown in FIG.
With respect to the driving force Fx, the lateral force Fy is increased as indicated by arrow RF by the rear wheel steering angle control performed at step 106, and is increased by the throttle control performed at step 111 as indicated by arrow SF. Step 11
By the braking force control performed in step 2, the braking force is increased as indicated by the arrow BF and is controlled to approximate the ideal friction circle. As shown on the left side of FIG. 8, the same control is performed when Fx is the braking force. Since the lateral force Fy is increased with respect to the driving force Fx in FIG. 8 as indicated by arrows SF and BF, the driving force Fx is reduced from point A to point B in FIG. 9, and lateral force Fy is reduced. It increases from point C to point D. Therefore,
According to the present embodiment, the steering stability can be quickly ensured and reliably maintained regardless of whether the vehicle is going straight or turning.

Incidentally, the driving force control means of the present invention, in particular, the means for limiting the driving force is not limited to the means for limiting the driving force by controlling the throttle control device TH as described above. Alternatively, a means for limiting the driving force by fuel cut may be used.

[0026]

Since the present invention is configured as described above, it has the following effects. That is, in the vehicle stability control device of the present invention, as described in claim 1, the driving force control means and the braking force control means are controlled based on the target slip ratio set by the target slip ratio setting means. Therefore, the steering stability of the vehicle can be quickly secured and reliably maintained.

In the vehicle stability control device according to the second aspect, the throttle opening control by the throttle control device and the braking force control by the braking force control device are performed based on the target slip ratio set by the target slip ratio setting device. Since it is configured as described above, it is possible to reliably maintain the steering stability of the vehicle with a simple means.

In the vehicle stability control device according to the present invention, the driving condition detecting means detects the driving condition of the vehicle based on the steering angle detected by the front wheel steering angle sensor and the vehicle speed estimated by the vehicle speed estimating means. Therefore, the driving state of the vehicle can be easily detected.

Further, in the vehicle stability control device according to the fourth aspect, since the actual yaw rate detecting means is configured to calculate the actual yaw rate based on the difference between the left and right wheel speeds of the driven wheels. The actual yaw rate can be obtained by simple means.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a vehicle stability control device of the present invention.

FIG. 2 is an overall configuration diagram of an embodiment of a vehicle stability control device of the present invention.

FIG. 3 is a configuration diagram showing a part of an example of a hydraulic control device according to an embodiment of the present invention.

FIG. 4 is a sectional view showing a part of an example of a steering angle control device according to an embodiment of the present invention.

FIG. 5 is a flowchart showing a process for vehicle stability control in one embodiment of the present invention.

FIG. 6 is a graph showing an example of a map for obtaining the first slip ratio in step 108 of FIG.

FIG. 7 is a graph showing an example of a map for obtaining a second slip ratio in step 109 of FIG.

FIG. 8 is a graph showing a relationship between a driving force and a braking force and a lateral force in a vehicle according to an embodiment of the present invention.

FIG. 9 is a graph showing slip ratio-friction characteristics regarding a driving force, a braking force, and a lateral force in a vehicle according to an embodiment of the present invention.

[Explanation of symbols]

 BP brake pedal BS brake switch EG engine AP accelerator pedal YS yaw rate sensor SSf front wheel steering angle sensor SSr rear wheel steering angle sensor SCD steering angle control device MC master cylinder HP pump Wfr, Wfl, Wrr, Wrl wheel cylinder WS1 to WS4 wheel speed sensor FR, FL, RR, RL wheels

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B62D 105: 00 113: 00 (72) Inventor Yoshiyuki Yasui 2-1-1 Asahi-cho, Kariya city, Aichi prefecture Aisin Seiki Co., Ltd.

Claims (4)

[Claims] 1. A driving force control means for controlling a driving force applied to a wheel behind the vehicle by an engine mounted on the vehicle, and a braking force control means for controlling a braking force of a brake device mounted on each wheel of the vehicle. Rear wheel steering angle control means for controlling the steering angle of the wheels behind the vehicle according to at least the steering amount of the wheels in front of the vehicle, operation state detection means for detecting the operation state of the vehicle, and the operation state detection Target yaw rate setting means for setting a target yaw rate according to the detection result of the means, actual yaw rate detection means for detecting the actual yaw rate of the vehicle, and yaw rate deviation calculation means for calculating the deviation of the actual yaw rate from the target yaw rate. A yaw rate deviation control means for controlling the rear wheel steering angle control means according to a calculation result of the yaw rate deviation calculation means. First slip ratio calculation means for calculating a first slip ratio based on the calculation result of the difference calculation means, and rear wheel steering angle detection means for detecting the steering angle of the wheel behind the vehicle by the rear wheel steering angle control means. And a second slip ratio that is calculated based on the steering angle detected by the rear wheel steering angle detecting means.
And a target slip ratio setting means for setting a target slip ratio based on the first and second slip ratios, and the drive force control based on the target slip ratio set by the target slip ratio setting means. Means for controlling the braking force control means and the braking force control means. 2. The driving force control means includes a throttle control device for controlling a throttle opening degree of the engine,
The throttle opening control by the throttle control device and the braking force control by the braking force control means are performed based on the target slip rate set by the target slip rate setting means. Vehicle stability control device. 3. A wheel speed detecting means for detecting a wheel speed of each wheel of the vehicle, and a vehicle body speed estimating means for estimating a vehicle body speed based on a detection output of the wheel speed detecting means. A front wheel steering angle sensor that detects a steering angle of a wheel in front of the vehicle, and detects a driving state of the vehicle based on a steering angle detected by the front wheel steering angle sensor and a vehicle body speed estimated by the vehicle body speed estimating means. The vehicle stability control device according to claim 1, wherein the stability control device is configured as described above. 4. The actual yaw rate detecting means is configured to calculate the actual yaw rate based on a difference between left and right wheel speeds on the driven wheel side of the vehicle among the wheel speeds detected by the wheel speed detecting means. The stability control device for a vehicle according to claim 3, wherein: