JPH0345452A - Turning behavior controller of vehicle - Google Patents

Abstract

PURPOSE:To prevent unwanted turning behavior of a vehicle by braking wheels to reduce detected vehicle speed to predetermined limit vehicle speed when any slip of the wheel is judged on the basis of a rate of a change in the steering amount of the wheel to a change in the turning behavior of the vehicle. CONSTITUTION:In a vehicle turned by the steering of a wheel W, the behaviors of the vehicle accompanying the steering amount of the wheel W, vehicle speed and turn are detected respectively by means A-C. When the rate of change in the steering amount to change in the behavior is less than a set value, the lateral slip of tire of the wheel W is judged by a means D. Tire grip limit vehicle speed corresponding to the steering amount is detected by a means E. In the judgement of the wheel slip, the wheel W is braked by a means F so that the detected vehicle speed is reduced up to the limit vehicle speed. Thus, the superfluous vehicle speed in the slip of the wheel W is restrained by braking the wheel W to prevent the vehicle from the unwanted turning behavior.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device for suppressing undesirable behavior of a vehicle during turning by automatic braking.

(Prior Art) As a turning behavior control device for this type of vehicle, that is, an automatic braking technology, there is a device that applies braking force only to the inner wheel in the turning direction during turning, and assists the generation of the vehicle's yaw rate. This is proposed in Japanese Patent Publication No. 63-279976.

(Problems to be Solved by the Invention) However, this device is intended to promote the generation of a yaw rate of the vehicle during cornering, and is not effective in suppressing lateral slip of the wheels. In other words, when the vehicle enters a corner at high speed and turns the steering wheel, or when the steering wheel is turned further while turning, a centrifugal force that exceeds the grip limit of the wheels is generated in the vehicle, causing the wheels to turn. It is not possible to prevent the vehicle from slipping laterally, spinning, or drifting out to the outside in the turning direction.

The present invention is advantageous in that such undesirable turning behavior can be determined from the rate of change in vehicle behavior with respect to changes in steering amount, and since undesirable turning behavior is based on excessive vehicle speed, An object of the present invention is to provide a device that prevents undesirable turning behavior from occurring by suppressing the amount of movement caused by automatic braking.

(Means for Solving the Problems) For this purpose, the turning behavior control device of the present invention, as conceptually shown in FIG. means, vehicle speed detection means for detecting vehicle speed; turning behavior detection means for detecting behavior accompanying turning of the vehicle; a wheel slip determining means for determining the condition, a limit vehicle speed detecting means for determining a tire grip limit vehicle speed corresponding to the steering amount, and a brake for braking the wheels so that the detected vehicle speed decreases to the limit vehicle speed when determining the lateral slip condition. It is configured by providing means.

(Operation) When the vehicle is turning with its wheels steered, the steering amount detection means detects the steering amount of the wheels, and the limit vehicle speed detection means determines the tire grip limit vehicle speed from this steering amount. The turning behavior detecting means detects the behavior of the vehicle as it turns, and the wheel slip determining means determines that the wheel tires are in a lateral slip state when the rate of change in the turning behavior with respect to a change in the steering amount is less than a set value. . The brake means automatically brakes the wheels so that the vehicle speed detected by the vehicle speed detection means decreases to the tire grip limit vehicle speed when such a lateral slip state is determined.

This reduces the vehicle speed, and the wheels and tires are free from lateral slip under any steering conditions, allowing the vehicle to always run in the grip range, preventing the vehicle from spinning or drifting out when turning. can do.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows an embodiment of the device of the present invention, in which IL and IR indicate left and right front wheels, 2L and 2R indicate left and right rear wheels, 3L and 3R indicate front wheel cylinders, and 4L and 4R indicate rear wheel cylinders, respectively. 5 is a brake pedal, and 6 is a master cylinder that simultaneously outputs the same hydraulic pressure to two systems 7 and 8 when the brake pedal is depressed.The master cylinder hydraulic pressure of system 7 is routed through branched systems 7L and 7R to wheel cylinder 3L. ,
When reaching 3R, the front wheels IL and IR are braked, and the master cylinder hydraulic pressure of system 8 is routed through the branched systems 8L and 8R.
Wheel cylinders 4L and 4R lead to rear wheel 2L.

Brake 2R.

In contrast to such a normal front and rear sprint type two-system hydraulic brake system, in this example, cut valves 11L are provided in systems 7L, 7R, 8L, and 8R, respectively, to open these systems in the normal state.

III? , 12L, 12R. And an accumulator 1 that functions as a hydraulic pressure source for automatic braking.
3, to which the pump 14 supplies brake fluid from a reservoir 65 to accumulate hydraulic pressure for automatic braking. The drive motor 15 of the pump 14 is the pressure switch 1
6 to a power source 17, and this pressure switch opens when the internal pressure of the accumulator 13 reaches a specified value, turning off the motor 15 (pump 14). In this way, the above specified pressure is always stored in the accumulator 13.

The internal pressure of the accumulator 13 is controlled by the cut valve 1 by the circuit 18.
1L, IIR, 12L, and 12R, and these cut valves respond to the accumulator internal pressure to open the corresponding system 7.

7R, 8L, and 8R shall be cut off. The output chambers of cylinders 19L, 19R, 20L, and 20R are connected to these systems, respectively, and a solenoid proportional valve 21L is connected to the input chamber of the cylinder.
, 21R.

Connect the output ports of 22L and 22R. These electromagnetic proportional valves connect their output ports to the accumulator pressure circuit 18 and the drain circuit 23 according to the solenoid drive currents i, xi, and supply hydraulic pressure proportional to the corresponding solenoid drive current to the cylinders 19L, 19R, 2OL, 2OR. do.

The solenoid drive currents i, ~i, are controlled by a controller 31, which includes hydraulic pressure PF of systems 7 and 8,
Pressure sensor 32 for detecting PR. 'Signal from 33,
A signal from the steering angle sensor 34 that detects the turning angle θ of the steering wheel (not shown), and the left front wheel rotation speed ω1,
Right front wheel rotation speed ω2, left rear wheel rotation speed ω3, right rear wheel rotation speed ω
Signals from wheel rotation sensors 35 to 38 that detect 4, respectively, and a yaw rate sensor 39 that detects the yaw rate Y of the vehicle.
Or a lateral G sensor 4 that detects lateral acceleration G acting on the vehicle.
The signal from 0 is manually generated. Note that the yaw rate Y and the lateral acceleration G are examples of the behavior of the vehicle as it turns, and only one of them needs to be detected.

Based on this input information, the controller 31 repeatedly executes the control program shown in FIG. 3 for a certain period of time at intervals of 6 to perform normal wheel braking and wheel braking for turning behavior control, which will be described below. That is, first, in steps 41 to 43, system 7.
8 hydraulic pressure PFIPR1 wheel rotational speed ω, ~ω4, yaw 1-Y or lateral acceleration G, and steering angle θ are read. pressure P
Of course, F and PR are O unless the brake pedal 5 is depressed.

In the next step 44, the current turning behavior read value Y (or G) and steering angle θ and the turning behavior Y(OLD) (or G(OLD)) and θ(
AY (or AG) and 2θ are calculated.

Next, in step 45, the ratio of the turning behavior change JY (or JG) to the steering amount change Aθ! IY/Jθ (or lG
/lθ). In the next step 46, the vehicle speed V is calculated from the wheel rotational speeds ω1 to ω4. In this calculation, during non-braking when the brake pedal 5 is not depressed, the rotation speed of the front wheel, which is a non-driving wheel, is ω8. Since ω2 almost matches the vehicle speed, when the front wheel radius is R3, V=L (ω1+ω2
)/2. During braking, a pseudo vehicle speed is determined from all the wheel rotational speeds ω1 to ω by a method commonly used in anti-skid control, and this is set as the vehicle speed V.

In step 47, the vehicle speed ■ is determined from the table data in FIG.
The turning behavior change rate with respect to the steering amount change, d
Look up the setting value β of Y#lθCIG/13θ). Figure 4 shows the boundary between whether the wheel tires are gripping the road surface or slipping laterally, expressed as the rate of change in turning behavior relative to changes in the amount of steering.
It can be determined in advance through experiments as a function of . Therefore, the area above the boundary line in Fig. 4 indicates the grip area, and the area below indicates the slip area.For example, if the vehicle is running at point A (in the slip area) with the vehicle speed set to Vo, the centrifugal This indicates that the tires are unable to resist the force and slip laterally, causing the vehicle to spin or drift out. The above set value β is the turning behavior ratio on the boundary line corresponding to the current vehicle speed in Figure 4 (β in Figure 4 is the vehicle speed V0
) and the vehicle speed■. If the turning behavior ratio, dY/Jθ (or JG#θ), is greater than or equal to the set value β, it indicates that the wheels and tires are gripping the road surface; however, if it is less than the set value β, the wheels and tires are horizontally Indicates a slip.

In step 48, based on this, it is determined whether lY#Iθ≧β (or aG#θ≧β) and whether or not the grip region is in the grip region (slip region). If the grip is in the grip range, undesirable turning behavior such as vehicle spin or drift-out will not occur, so the control proceeds to steps 49 to 51 and normal wheel braking is performed depending on the brake pedal depression force as described below. . That is, in step 49, the target brake fluid pressures P+ and Pz for the front wheel cylinders 3L and 3R are changed to the fluid pressure P of the corresponding system 7.
Set the same to v, rear wheel cylinder 4L, 4
The target brake hydraulic pressures P, , P4 for R are set to be the same as the hydraulic pressure PR of the corresponding system 8. Then, in step 50, the electromagnetic proportional valves 21L, 21R, 22 are determined from the table data corresponding to FIG. 6 in order to obtain these target brake fluid pressures.
The drive currents 11 to i4 of L22R are looked up, and in step 51 these are output to the corresponding electromagnetic proportional valves.

By the way, if the automatic brake fluid pressure sources 13 to 17 are normal and pressure is stored in the accumulator 13, the cut valves 11L, 111? , 12L, 12R
is blocking the corresponding systems 7L, 7R, 8L, and 8R. For this reason, the electromagnetic proportional valves 21L, 21R, 22L,
22R is supplied with drive currents 11 to i4, and pressures proportional to these are applied to the corresponding cylinders 19L, 19R, 20.
L, 20R, these cylinders can supply brake main hydraulic pressure to the corresponding wheel cylinders. By the way, in order to determine the electromagnetic proportional valve drive currents 11 to i4 as described above so that these brake fluid pressures are the same as the fluid pressures Pr and P* from the master cylinder 6, each wheel operates normally according to the brake pedal depression force. is braked.

In addition, in the final step 52, the current read value Y (or G)
and θ as Y (OLD) (or G (OLD) )
and θ(OLD) in preparation for the next step 44.

If the slip area is determined in step 48, step 5
The control proceeds to step 3, and the automatic brake for turning behavior control is applied as follows. That is, in step 53, the tire grip limit vehicle speed ■ corresponding to the current steering angle θ is determined from the table data corresponding to FIG.

Look up. In FIG. 5, α indicates the tire grip limit vehicle speed, which varies depending on the steering angle θ, but if the vehicle speed V is less than the limit vehicle speed, it is in the grip region, and if it exceeds the limit vehicle speed, it is in the slip region. In the slip region, as described above with reference to FIG. 4, the tires cannot resist the centrifugal force that accompanies cornering and slip in the lateral direction, causing the vehicle to spin or drift out. For example, while driving at point B (vehicle speed VO + steering angle θ) in Fig. 5,
By increasing the steering angle θ to θ1, point A (fourth
To explain the case where the vehicle shifts to running at point A (same as point A in the figure), at this time the vehicle enters the slip region from the grip region, causing the vehicle to spin or drift out. In this case, if the vehicle speed is equal to or less than the limit vehicle speed V on the line α, the above-mentioned undesirable turning behavior will not occur.

From this point of view, in the next step 54, the deviation E between the detected vehicle speed V and the limit vehicle speed V is calculated, and in step 55, the deviation E between the detected vehicle speed V and the limit vehicle speed V is calculated, and in order to reduce this deviation, that is, the vehicle speed V is changed to the limit vehicle speed
Set the target brake fluid pressure P, ~P4 to P, - to bring it closer to
Then, calculate by E (where i=1 to 4). Here, (K, ~4) is a proportionality constant, which is a factor that determines the speed at which the deviation E becomes O.

Next, the control proceeds to step 50.51, where the electromagnetic proportional valve drive currents i, to i are used to obtain the target brake fluid pressures P1 to P4.
4 is determined and outputted to the corresponding electromagnetic proportional valve to bring the vehicle speed to the limit vehicle speed by automatic braking without having to press the brake pedal. Therefore, when the vehicle enters the slip region, the vehicle speed is reduced to the limit vehicle speed and returned to the grip region, thereby preventing the vehicle from spinning or drifting out.

In addition, if the above-mentioned braking operation becomes impossible due to a failure of the hydraulic pressure sources 13 to 17, the pressure in the accumulator pressure circuit 18 disappears, so the cut valves 11L, IIR, 12L, 12R
opens the corresponding systems 7L, 7R, 8L, and 8R.

Therefore, when the brake pedal 5 is depressed, the master cylinder hydraulic pressure output from the master cylinder 6 to the system 7.8 is directly applied to the wheel cylinders 3L, 3R, and 4L.

Heading to 4R, you can brake each wheel directly without becoming unable to brake.

In addition, the target brake fluid pressure P, calculated in step 55 in Fig. 3, is calculated by P,=,・E+L,・−Et (where L is a differential constant) instead of the above, and the change in deviation E is calculated as follows. The deviation E may be set to 0 more quickly as the difference E becomes larger. Also, wheels IL, IR2L,
Detect the supporting load L ''L of 2R, and set P,=,・
The target brake fluid pressure P may be determined by Wl·E or Pi=W1(Kl-E + Li-E)t.

In this case, the target brake fluid pressure takes into consideration the load distribution between the wheels, and it is possible to prevent the braking force from becoming unbalanced between the wheels.

(Effects of the Invention) Thus, the device of the present invention detects the tire slip region where undesirable turning behavior of the vehicle occurs by adjusting the ratio of turning behavior change (yaw rate change AY or lateral acceleration change, dG, etc.) to steering amount change 2θ as described above. Since the vehicle is configured to use automatic braking to suppress excess vehicle speed that causes undesirable turning behavior at the time of this determination, the vehicle can be driven in the grip range at all times, thereby preventing problems such as vehicle spin or drift-out. Desired turning behavior can be prevented, greatly contributing to safety.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram of the turning behavior control device of the present invention, Fig. 2 is a system diagram showing an embodiment of the device of the present invention, Fig. 3 is a flowchart showing the control program of the controller on the same side, and Fig. 4 is the main A slip area-grip area determination diagram used in the invention, FIG. 5 is a diagram illustrating tire grip limit vehicle speed, and FIG. 6 is a relationship diagram between electromagnetic proportional valve drive current and target brake fluid pressure. IL, IR...Front wheel 2L, 2R...Rear wheel 3L, 3R, 4L, 4R...Wheel cylinder 5
...Brake pedal 6...Master cylinder ILL, 111? , 12L, 12R...Cut valve 13...Accumulator 14...Pump

Claims (1)

[Scope of Claims] 1. In a vehicle that is turned by wheel steering, a steering amount detection means for detecting the amount of wheel steering, a vehicle speed detection means for detecting vehicle speed, and a turning means for detecting behavior accompanying the turning of the vehicle. behavior detection means; wheel slip determination means for determining that a wheel tire is in a lateral slip state when a change rate of the behavior with respect to a change in steering amount is less than a set value; and a limit for determining a tire grip limit vehicle speed corresponding to the steering amount. A turning behavior control device for a vehicle, comprising: a vehicle speed detecting means; and a braking means for braking a wheel so that the vehicle speed detected at the time of determining the lateral slip condition is reduced to the limit vehicle speed.