JPH0717134B2 - Suspension control device in vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention controls the suspension device to change the roll rigidity of the front and rear of the vehicle at the time of turning, thereby achieving agile turning performance and stable running performance. The present invention relates to a suspension control device for a vehicle that can achieve both of the above.

[Conventional technology]

As a suspension control device in a conventional vehicle,
For example, there is one described in JP-A-60-82424.

In this conventional example, a torsional rigidity variable stabilizer capable of changing roll rigidity by a control signal is applied as a suspension device, and a steering state detector for detecting a rotation angle of a steering wheel and a vehicle speed detector for detecting a vehicle speed are provided. Based on the detection signal, during steering (that is, during turning), the control signal from the control means is output to the variable torsional rigidity stabilizer to increase the total roll rigidity of the vehicle to make the steering characteristics neutral steering or oversteering. Therefore, the turning performance is improved.

[Problems to be solved by the invention]

However, in the above-described conventional suspension control device for a vehicle, when the steering state is determined to be controlled so as to oversteer the steer characteristic of the vehicle, the turning operation becomes agile. The turning performance at the beginning of turning is improved, but the convergence after that is not sufficient, and there is an unsolved problem that the vehicle body is difficult to stabilize.

Therefore, the present invention has been made by paying attention to the problems of the above-mentioned conventional example, and an object of the present invention is that the steering characteristic during turning is oversteer or neutral steering during turning of the vehicle body. To provide a suspension control device for a vehicle that independently controls roll rigidity of front and rear wheels so as to have an understeer characteristic when the turning motion converges, thereby achieving both agile turning motion and stable running. Has an aim.

[Means for solving problems]

In order to achieve the above object, the present invention provides a turning state detecting means for detecting a turning state of a vehicle body due to steering in a vehicle including a suspension device capable of changing a steer characteristic of the vehicle by inputting a control signal, When the turning state determining means determines whether the turning state is actually turning or converging the vehicle body based on the detection signal of the turning state detecting means, and the result of the turning movement determining means is the vehicle body turning operation. And a control means for outputting to the suspension device a control signal for oversteering or neutral steering the vehicle steer characteristic, and a control signal for understeering the steer characteristic of the vehicle at the time of convergence, respectively. To do.

[Action]

According to the present invention, in a vehicle equipped with a suspension device capable of changing the roll rigidity of the vehicle by a control signal to select the steer characteristic, the initial or turning of the vehicle body turning motion is performed based on the detection signal of the turning motion detection means. When the vehicle is turning, the suspension is controlled by the control means so as to improve the turning performance by oversteering or neutral steering during the operation, and understeering during the convergence period of the turning movement to improve the steering stability. Achieving both improved driving performance and stable running performance.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 are views showing an embodiment of the present invention.

In FIG. 1, 1FL, 1FR, 1RL and 1RR are vehicle body side members 2 respectively.
And an active-type suspension device interposed between wheel-side members 4 that individually support the wheels 3FL, 3FR, 3RL, 3RR, each including a hydraulic cylinder 5 as an actuator, a coil spring 6, a stroke sensor 7, and And a direction switching valve 8 that controls the supply of the working fluid to the hydraulic cylinder 5.

Here, in the hydraulic cylinder 5, its cylinder tube 5a is attached to the vehicle body side member 2, and the piston rod 5b is attached to the wheel side member 4. Also, the coil spring 6
Is mounted between the vehicle body side member 2 and the wheel side member 4 to support the vehicle body load. In normal times, the amount of fluctuation from the neutral point due to wheel load movement during vibration or turning is the hydraulic pressure. It is adjusted by adjusting the stroke of the cylinder 5. Further, the stroke sensor 7 is composed of, for example, a potentiometer, detects a stroke from the neutral position between the vehicle body side member 2 and the wheel side member 4, and detects positive when the stroke sensor 7 is displaced upward from the neutral position accordingly. A negative detection signal is output when the signal is displaced downward. Furthermore, the directional switching valve 8 has its input ports connected to a hydraulic unit 10 having a built-in hydraulic pump and its return port connected to a tank 11, respectively, and the viscous resistance of hydraulic oil passing through these directional switching valves 8 To generate a damping force, to exert the same function as a conventional shock absorber, and high-pressure side pipes and low-pressure side pipes are connected to high-pressure accumulators 12f and 12r and low-pressure accumulators 13f and 13r, respectively, by which the directional control valve 8 Responsiveness is improved.

Then, the detection signal of the stroke sensor 7 of each of the suspension devices 1FL to 1RR and the detection signal of the yaw rate sensor 14 that detects the angular velocity around the vertical axis of the vehicle body as the turning state detection means of the vehicle, that is, the yaw rate are supplied to the control device 15. The control device 15 outputs a control signal for controlling the direction switching valve 8 of each suspension device 1FL to 1RR based on the detection signal of the yaw rate sensor 14 and the detection signal of the stroke sensor 7.

In an example of the controller 15, as shown in the block diagram of FIG. 2, the yaw rate detection signal of the yaw rate sensor 14 is supplied to the turning motion determination circuit 16.

An example of this turning motion determination circuit 16 is a yaw rate sensor 14
Of the yaw rate detection signal output from the differentiator 18, which has a front wheel side amplifier 17f, a rear wheel side amplifier 17r and a rear wheel side amplifier 17r with adjustable gain, and a differential value || The differential output d, which is d || / dt, is the discriminator
When the value of the differential output d exceeds the predetermined set value A, the yaw rate is increased by the angular acceleration exceeding the set value A. It means that the absolute value || is increasing, and it is judged that it is the turning operation, and the judgment signal of logical value "1"
Da is set to the gain setter 20a, and when the value of the differential output dφ is equal to or smaller than the predetermined set value A, the absolute value || of the yaw rate slightly increases or decreases at the angular acceleration of the set value A or less. It is determined that it is time, and the determination signal Db having the logical value "1" is output to the gain setter 20b.

The gain setter 20a sets the gain constant Kf of the front wheel side amplifier 17f to a predetermined set value B when the control signal Da is supplied, and sets the gain constant Kr of the rear wheel side amplifier 17r to a predetermined set value C equal to or larger than the set value B. The gain setting unit 20b sets the control signal D
When b is supplied, the gain adjustment output for setting the gain constant Kf of the front wheel side amplifier 17f to the predetermined set value D and the gain constant Kr of the rear wheel side amplifier 17r to the predetermined set value E less than the set value D, respectively. It outputs to front wheel side amplifier 17f and rear wheel side amplifier 17r, and controls the gains of these amplifiers 17f and 17r.

Then, the amplified output of the front wheel side amplifier 17f is the stroke target value T for controlling the front wheel suspension devices 1FL and 1FR, respectively.
It is supplied to the comparison units 21FL and 21FR as f, and the amplified output of the rear wheel side amplifier 17r is supplied to the rear wheel suspension device 1 respectively.
Comparing unit 21R as the stroke target value Tr that controls RL, 1RR
Supplied to L, 21RR. Here, the comparison units 22FL, 22RL and 22FR,
22RR is compared with the stroke detection signal of the stroke sensor 7 in the relationship that the target values Tf and Tr have opposite signs.

The output deviation signals from the comparison units 21FL to 21RR are supplied to controllers 22FL to 22RR that output control signals for controlling the directional control valve 8 based on them.

Here, the gain adjustment output is obtained from the gain setter 20a, assuming that the wheel loads before and after the vehicle and the characteristics of the hydraulic cylinder 5, the hydraulic system loop gain, the coil spring 6 of the suspension devices 1FL to 1RR are equal. Then, the gain constant Kf of the front wheel side amplifier 17f is controlled to be equal to or lower than the gain constant Kr of the rear wheel side amplifier 17r, so that the steering characteristic of the vehicle is neutral steered or oversteered. Conversely, if a gain adjustment output is obtained from the gain setter 20b, the gain constant Kf of the front wheel side amplifier 17f is controlled to be larger than the gain constant Kr of the rear wheel side amplifier 17r, so that the steering characteristic of the vehicle is improved. Understeered.

Thus, the gain constants Kf, K on the front and rear wheels are
The reason why the steer characteristic can be changed by changing the value of r is as described below.

That is, depending on the magnitudes of the gain constants Kf and Kr, when the vehicle turns, the reverse roll moment for opposing the centrifugal force can be made different between the front wheel side and the rear wheel side. Corresponding to different share rates. Therefore, when Kf> Kr is selected, the amount of left and right wheel load movement on the front wheels increases during turning, and the total left and right tire cornering power decreases compared to that on the rear wheels, which results in stability. The factor Ks increases and the steering characteristic of the vehicle becomes an understeer characteristic. Similarly, if Kf <Kr is selected, the left and right wheel load movement amount on the rear wheel side is increased contrary to the above, and the total left and right tire cornering power is reduced compared to that on the front wheel side. Stability factor Ks is reduced and the steering characteristics of the vehicle become oversteering characteristics.
If Kf = Kr is selected, neutral steer characteristics can be obtained.

Next, the operation of the above embodiment will be described with reference to FIGS. 3 (a) to 3 (c) showing the behavior of the vehicle when traveling on an S-shaped road.

Assuming that the vehicle is traveling straight ahead as shown in FIG. 3 between times t ₀ and t ₁ , in this state, yawing does not occur in the vehicle, so the yaw rate detection signal of the yaw rate sensor 14 is As shown in the figure, it is maintained at approximately zero. Therefore, the differential value d output from the differentiator 18 also shows substantially zero, and the determiner 19 outputs the determination signal Db having the logical value "1" to the gain setting circuit 20b. For this reason, gain constants Kf = D and Kr for making the vehicle an understeer characteristic by the gain setter 20b.
= E (D> E) are selected, and these are front-wheel amplifiers, respectively.
It is supplied to 17f and the rear wheel side amplifier 17r to control their amplification gains. At this time, since the yaw rate detection signal from the yaw rate sensor 14 is zero, the front wheel side and rear wheel side amplifiers 17f, 17r output zero, that is, the target value Tf, Tr that sets the vehicle height to the neutral state, and this and each The deviation from the stroke detection signal of the wheel stroke sensor 7 is the controller 22FL.
Supplied to ~ 22RR. As a result, the controller 22FL ~
A predetermined switching signal is output from 22RR to the directional control valve 8 to control the stroke of the hydraulic cylinder 5 to the neutral position. In this state, the steering characteristic of the vehicle is controlled to understeer, which improves straight running stability.

Then, when the steering wheel is turned to the right by turning the steering wheel at the time t ₁ from the straight traveling state, the yaw rate detection signal from the yaw rate sensor 14 according to the turning state is shown in FIG. 3 (b). As described above, it gradually increases in the positive direction, and the differential output d of its absolute value also increases as shown in FIG. 3 (c). Then, at time t ₂ , the differentiator 18
If the value of the differential output d from is greater than the set value A,
Instead of the determination signal Db of 19, the determination signal Da becomes the logical value "1", and this is supplied to the gain setter 20a. For this reason,
Gain constants Kf = B and Kr = C for making the vehicle an oversteer or neutral steer characteristic by the gain setter 20a.
(B ≦ C) are selected, and these are front wheel side amplifiers 17r, respectively.
Also, the amplification gains are supplied to the rear wheel side amplifier 17r to control their amplification gains.

Therefore, the target value Tf output from the front wheel side amplifier 17f according to the magnitude of the yaw rate detection signal output from the yaw rate sensor 14 becomes equal to or smaller than the target value Tr output from the rear wheel side amplifier 17r. The amount of load movement of the left and right wheels on the rear wheel side becomes equal to or larger than that on the front wheel side to provide neutral steering or oversteering characteristics, and a swift turning operation can be performed.

In this right turning state, the left side of the vehicle sinks from the neutral position due to the lateral acceleration generated by the turning motion, the output of the stroke sensor 7 becomes negative, and conversely, the right side rises from the neutral position and the stroke sensor 7 The output will be positive, but front and rear wheel amplifiers 17f,
Since the target values Tf, Tr from 17r are supplied to the comparison units 21FL, 21RL, 21FR, 21RR as positive for the left wheel and negative for the right wheel, the hydraulic cylinder 5 is extended with respect to the suspension device on the left wheel side. The anti-roll effect can be exhibited by controlling so that the hydraulic cylinder 5 is contracted for the suspension device on the right wheel side.

Then, at a time point t ₃ , it approaches the vicinity of the central portion of the S-shaped road, and the turning operation state in the right turn changes to the convergence state, and the differentiator
When the differential output d of 18 becomes equal to or less than the predetermined set value A, the judging device
The determination signal Db of 19 becomes the logical value "1", and the gain setter 20
Since the front wheel side and rear wheel amplifiers 17f and 16r are set to the gain constants Kf and Kr set in b, the vehicle is changed to the understeer characteristic, and it is possible to easily perform the return steering to the neutral position of the steering wheel. it can.

Then, at time t ₄ , turn the steering wheel to the left and shift to the left turning state.
The yaw rate detection signal 14 increases in the negative direction as shown in FIG. 3 (b), and the differential output d output from the differentiator 18 again increases in the positive direction as shown in FIG. 3 (c). Therefore, the determination signal Da is output from the determiner 19, the vehicle is again changed to the oversteer characteristic, and quick turning ability can be obtained. Then, at this time, since the yaw rate detection signal output from the yaw rate sensor 14 is a negative value, the target value Tf, Tr output from the front wheel side and rear wheel side amplifiers 17f, 17r becomes a negative value, and the right side Contrary to the turning state, the left wheel side suspension device is controlled to contract the hydraulic cylinder 5, and the right wheel side suspension device is controlled to extend the hydraulic cylinder 5. And can exert an anti-roll effect.

Next, when the end of the S-shaped road is reached at time t ₅ , the value of the yaw rate detection signal of the yaw rate sensor 14 becomes a peak value in the negative direction, and when the differential output d of the differentiator 18 becomes the predetermined set value A or less, as in the case convergence right turn, the vehicle is changed to understeer characteristic, the return steering to the neutral position of the steering wheel can be easily performed, then shifting to the straight running state at time T _6, a yaw rate sensor 14 The value of the yaw rate detection signal becomes zero, the understeer characteristic is maintained, and the normal straight traveling state in which the anti-roll effect is not generated is restored.

In the above embodiment, the case where the yaw rate sensor 14 is applied as the vehicle turning state detecting means has been described, but the present invention is not limited to this, and the steering angle, the lateral acceleration, the steering force, the hydraulic pressure of the power steering, or the like. The turning state may be detected by detecting a physical quantity capable of detecting the turning state of the vehicle.

Further, in the above embodiment, the case where the active suspension device is applied when controlling the steering characteristic of the vehicle has been described. However, the present invention is not limited to this, and a vehicle having a damping force variable shock absorber as the suspension device may be used. Is to increase the damping force of the damping force variable shock absorber on the rear wheel side at the time of turning operation and reduce the damping force of the damping force shock absorber on the front wheel side to achieve neutral steering or oversteer characteristics, and at the time of turning convergence, The damping force of the variable damping shock absorber may be increased, and the damping force of the variable damping shock absorber on the rear wheel side may be reduced to control the understeer characteristics. For vehicles equipped with a variable spring constant air spring, Torsional stiffness of, by controlling the spring constant, the neutral steering to over steering characteristic during turning operation, it is possible to respectively control the understeer characteristic when turning round convergence.

〔The invention's effect〕

As described above, according to the present invention, the turning state of the vehicle body due to the steering of the steering wheel is detected, and the turning motion determination means determines whether the turning state is the turning operation or the turning convergence based on the detected value. If there is a turning operation, the steering system is controlled so that the steering characteristics are changed to neutral steering or oversteering during turning operation, and understeering is performed when turning is converged. It is possible to obtain an effect that both swift turning performance during traveling and stable traveling performance can be achieved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a suspension control device showing an embodiment of the present invention, FIG. 2 is a block diagram showing an example of the control device, and FIG. 3 is an explanatory diagram for explaining the operation of the present invention. . In the figure, 1FL, 1FR, 1RL, 1RR are suspension devices, 5 are hydraulic cylinders, 7 is a stroke sensor, 8 is a directional valve,
14 is a yaw rate sensor, 15 is a control device, 16 is a turning motion determination circuit, 17f is a front wheel side amplifier, 17f is a rear wheel side amplifier, 18 is a differentiator, 19 is a determiner, 20a, 20b is a gain setter, 21 is The comparison unit, 22 is a controller.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Hamino 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (56) References JP-A-60-113712 (JP, A) JP-A-62-39945 (JP, A) JP 62-198511 (JP, A)

Claims (1)

[Claims] 1. A vehicle provided with a suspension device capable of changing a steer characteristic of the vehicle by inputting a control signal,
A turning state detecting means for detecting a turning state of the vehicle body due to steering, and a turning motion determining means for determining whether the turning state is actually the vehicle body turning operation or the convergence state based on a detection signal of the turning state detecting means. A control signal for making the steering characteristic of the vehicle oversteer or neutral steering when the judgment result of the turning movement judging means is a turning operation of the vehicle body, and a control signal for making the steering characteristic of the vehicle understeer at the convergence time. A suspension control device for a vehicle, comprising: a control unit that outputs the suspension device.