JPH0829655B2 - Active suspension - Google Patents

Description

TECHNICAL FIELD The present invention relates to an active suspension for a vehicle,
In particular, the present invention relates to an active suspension configured to generate an anti-roll moment against a roll of a vehicle body according to an acceleration generated in a lateral (left-right) direction of the vehicle.

[Conventional technology]

A conventional active suspension is disclosed in
Some are described in Japanese Patent No. 61-181715.

An example of the active suspension according to this conventional example is an actuator composed of a cylinder / piston device or the like arranged between various types of vehicles and a vehicle body, and a vehicle width direction for detecting acceleration in the vehicle body width direction (that is, left-right direction). Acceleration detection means, roll angular acceleration detection means for detecting the roll angular acceleration of the vehicle body, and each actuator controlled based on the detection values of these two acceleration detection means, and between the wheels and the vehicle body via the actuators. An arithmetic and control unit that increases or decreases the force acting on the.

That is, the arithmetic and control unit determines, based on both input acceleration detection signals, that the direction of acceleration (centripetal acceleration) in the vehicle width direction and the direction of roll angular acceleration are relative to the center of gravity of any portion above the center of gravity of the vehicle body. In view of the vehicle width direction acceleration detection value, it is determined that the vehicle is turning and if the determination means determines that the directions are different from each other. And the means for calculating the amount of load movement between the wheels and the determining means determine that they are in the same direction,
Assuming that the vehicle receives a crosswind, a means for calculating the load movement amount between the vehicle body and each wheel based on the detected roll angular acceleration value, and a control for controlling each actuator according to the calculation result by each calculation means. And means.

[Problems to be Solved by the Invention]

However, such a conventional active suspension adopts a complicated configuration using many sensors including a vehicle-width direction acceleration sensor and a roll angular acceleration sensor for roll control of the vehicle body, and is resistant to lateral wind disturbance. Although the roll control is performed using the roll angular acceleration of the roll angular acceleration sensor, the response delay of the control is mainly due to the delay due to the process from the cross wind to the generation of the roll that can be actually detected. Therefore, there is a problem that the control becomes extremely unstable, such as oscillation due to the relationship between the gain and the phase of the control loop.

Further, basically, assuming that the roll flat control by the vehicle width direction acceleration is almost completely performed, the roll angular acceleration by the cross wind is a small amount around zero (and the direction is positive due to the control deviation). However, it is actually very difficult to distinguish between the inertial force and the cross wind by using the roll angular acceleration, and as a result, the vehicle width direction acceleration detection means The control during turning based on the detected value is always given priority. That is, even when a lateral wind disturbance causes a vehicle width direction acceleration, the vehicle width direction acceleration is considered to be caused by turning.

This will be described with reference to FIG. In the figure, a vehicle that is in a straight-ahead state without a crosswind (state indicated by a dotted line) receives a crosswind (force F) on the right side of the vehicle (as viewed from the rear of the vehicle), is displaced to the left by wind pressure, and is displaced by y (solid line). State). At this time, the vehicle width direction acceleration detector 1 based on the pendulum principle detects the acceleration by the movement of the mass 1a,
Since the mass 1a has inertia, the pendulum is sensed as an acceleration in the same direction as when it is steered to the left (the roll state in which the vehicle body is falling to the right).

For this reason, the arithmetic and control unit erroneously controls the vehicle attitude in a direction of raising the right (windward) vehicle body and lowering the left (leeward) vehicle body in an attempt to prevent the vehicle body from rolling to the right. As a result, the side wind disturbance will encourage the vehicle body to try to roll to the left.If this acceleration occurs, the pressure receiving surface for aerodynamic force increases and the aerodynamic center becomes higher, so that the roll is not suppressed. As a result, the vehicle was in an unstable state with respect to cross wind disturbances, such as overshooting.

The present invention has been made in view of such a conventional problem and further simplifies the overall configuration for roll control of a vehicle body, and can perform accurate roll attitude control at the time of turning, and also has a side wind disturbance. However, the problem to be solved is to make it difficult to be affected by the above and to ensure the traveling stability of the vehicle.

[Means for solving the problem]

In order to solve the above-mentioned problems, claim (1) of the present invention
The described active suspension has actuators respectively interposed between the vehicle body and each wheel, lateral acceleration detecting means for detecting the lateral acceleration of the vehicle body, and the detection value of the lateral acceleration detecting means can be changed. Based on the value multiplied by the gain,
In an active suspension equipped with roll control means for driving each of the actuators in a direction of suppressing roll of the vehicle body, a steering angle sensor for detecting a steering angle of the vehicle, and a detection value of the steering angle sensor and a preset reference. A straightness detecting means for calculating a straightness by calculating a steering angle ratio representing a ratio with the steering angle, and a constant value regardless of the steering angle ratio when the steering angle ratio of the straightness detecting means exceeds 1. Gain control means for setting a large gain and for setting a gain that decreases in accordance with a decrease in the steering angle ratio when the steering angle ratio is 1 or less.

Further, the active suspension according to claim (2),
The reference steering angle is a function of vehicle speed.

[Action]

According to the present invention, the gain for multiplying the lateral acceleration detection value is obtained when the steering angle ratio between the steering angle detection value and the reference steering angle exceeds 1 in the straightness detection means, which is outside the range regarded as straight traveling, that is, when the vehicle is turning or meandering. By setting a large fixed value, a large anti-roll moment is used to accurately prevent rolls associated with turning. On the other hand, when the steering angle ratio is 1 or less, it is determined that the vehicle is traveling in the range considered to be straight ahead, and the roll control means is made less sensitive by setting the value to decrease in accordance with the decrease in the steering angle ratio. To do. In other words, even when a vehicle receives a crosswind when it is straight or almost straight, the gain for the lateral acceleration generated by the crosswind is reduced, and the anti-roll moment of each actuator is also small. As a result, the roll caused by the crosswind is reduced. Will not be encouraged.

Further, the straightness detecting means of the present invention is configured by a steering angle sensor and a calculator for calculating the steering angle ratio, and the degree of straight traveling can be detected by the steering angle ratio. Therefore, since the roll angular acceleration or the like is not used, the configuration can be simplified. Further, if the reference steering angle related to the computing unit is a function of the vehicle speed, for example, the higher the speed, the narrower the range considered to be straight ahead, and the more precise the control becomes.

〔Example〕

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

(First Embodiment) FIGS. 1 to 6 are views showing a first embodiment of the present invention.

In FIG. 1, 10FL and 10FR are front wheels, 10RL and 10RR are rear wheels, 12 is a wheel side member, 14 is a vehicle body side member, and 16 is an active suspension.

Of these, the active suspension 16 has wheels 10FL to 10FL.
Hydraulic cylinders 18FL to 18RR (actuators) and coil springs 19FL to 19RR inserted between the wheel side member 12 and the vehicle body side member 14 at the RR position, and the hydraulic cylinders 18FL to
Pressure control valves for individually controlling 18RR operating pressure 20FL to 20RR
And a hydraulic cylinder 22 and a tank 24 of this hydraulic system, and a lateral acceleration sensor 268 (lateral acceleration detecting means), a steering angle sensor 28, and a controller 32.

Each of the hydraulic cylinders 18FL to 18RR has a cylinder tube 18a attached to the vehicle body side member 14 and a piston rod 18b attached to the wheel side member 12, respectively.
A pressure chamber L separated from the piston 18c is formed therein. The pressure chamber L communicates with a hydraulic vibration absorbing accumulator 36 via a throttle valve 34. The coil springs 19FL to 19RR have a relatively low spring constant and support the static load of the vehicle body.

Further, each of the pressure control valves 20FL to 20RR is composed of an electromagnetic spool valve, the supply port of which is a hydraulic unit 22 having a built-in hydraulic pump, the return port is a tank 24, and the output ports are hydraulic cylinders 18FL to 18RR. Each of the pressure chambers L is connected to the controller 32, and the controller 32 supplies a command signal I, which is an exciting current, to the electromagnetic solenoid. Each pressure control valve 20FL to 20RR supplies a pressure P proportional to the change of the command signal I from its output port to the hydraulic cylinders 18FL to 18RR, as shown in FIG. That is, when the command signal I (= If, Ir) is zero, the predetermined offset pressure P ₀ is output, and from this state, the command signal I
Increases in the positive or negative direction, the pressure P that increases or decreases is output with the proportional gain K ₁ . In addition, in FIG.
P _MAX is the line pressure.

Further, the lateral acceleration sensor 26 is provided in the vicinity of the center of gravity of the vehicle, detects a lateral acceleration of the vehicle body which acts on the vehicle, and outputs a signal corresponding to the acceleration (corresponding to a right turn of the vehicle in this embodiment). Signal to turn positive, signal corresponding to left turn negative)
Is supplied to the controller 32. Further, the steering angle sensor 28 is
A detector, which is fixed to a predetermined position on the vehicle body and includes a slider and a linear displacement gauge, outputs a signal θ _H according to the steering angle to the controller 32. That is, the oscillator of the steering angle sensor 28 is fixed to the steering rack 42 via the hook 40, and when the steering wheel 44 is steered, the steering device
Since the steering rack 42 makes a stroke in the cylinder 46 in accordance with the steering angle, a signal θ _H corresponding to this stroke is obtained.

On the other hand, as shown in FIG. 3, the controller 32 serves as a roll control command section 48 for controlling the anti-roll moment based on the lateral acceleration detection signal and a straightness degree detecting means for calculating the magnitude of the steering angle detection signal θ _H. It has an arithmetic unit 49 and a function generator (gain control means) 50 having the output signal α of the arithmetic unit 49 as a variable. Here, the steering angle sensor 28
The calculator 49 constitutes a straight traveling state detecting means.

As shown in FIG. 3, the roll control command unit 48 commands the gain adjusters 52f and 52r, which are variable gain amplifiers capable of individually adjusting the gain constants Kf and Kr, and the opposite-phase exciting currents between the left and right wheels. And inverters 54f and 54r for doing so.

Then, in the roll control command unit 48, the lateral acceleration signal is input to the gain adjusters 52f, 52r, the output side of the gain adjusters 52f, 52r is directly the pressure control valve 20FL,
20RL, while on the other hand, the inverter 54f,
It reaches pressure control valves 20FR and 20RR via 54r. Therefore, the input lateral acceleration detection signal is multiplied individually by the gain constants Kf, Kr set at that time by the gain adjusters 52f, 52r to become the command signals If, Ir, to the front right and rear right. On the other hand, the reverse phase command signal −If,
-Ir is formed.

Further, the gain adjusters 52f and 52r can change their gain constants Kf and Kr, respectively, by a gain setting signal Zy described later, as shown in FIG. That is, when the gain setting signal Zy is increased, it is possible to set the gain constants Kf and Kr that increase with the predetermined proportional gain K ₂ .

Here, in the present embodiment, the roll control command unit 48, the pressure control valves 20FL to 20RR, the hydraulic unit 22, and the tank 24 constitute roll control means.

On the other hand, the calculator 49 receives the input steering angle detection signal θ _H
And a ratio of an absolute value to a reference steering angle θ ₀ (θ ₀ > 0) set in advance to a value that can be regarded as a straight traveling range, and the result is used as a signal α (≧ 0) to generate a function generator. Output to 50.
That is, it indicates that the degree of straight traveling is higher as α (= | θ _H / θ ₀ |) is closer to zero.

Therefore, if the relationship of | θ _H | <θ ₀ (α <1) is satisfied, the function generator 50 determines that the vehicle is traveling straight or in a straight traveling range close to this, while | θ _H | ≧ θ If there is a relationship of ₀ (α ≧ 1), it is determined that the vehicle is not traveling in such a straight traveling range, and a gain setting signal Zy that changes as shown in FIG. It is designed to be supplied to 52f and 52r. That is, when α <1, a predetermined value Z _y0 (> 0) is taken at α = 0, and the signal Zy is increased with a proportional gain K ₃ as α increases from this state, while α ≧ 1. For example, a signal with a constant coefficient Z _y1 (> Z _y0 ) is output. The above-mentioned signal value Z _y1 is set to a value that can sufficiently secure the anti-roll moment by each hydraulic cylinder 18FL to 18RR, and the signal value Z _y0 is set to a value that can sufficiently reduce the anti-roll moment.

By the way, in the first embodiment, since the vehicle speed is not involved in the above-described configuration for detecting traveling in the straight traveling range, the range considered as straight traveling is shown by the relationship between the vehicle speed V and the steering angle θ _H. It becomes like the figure. That is, the straight traveling area (hatched area) in the figure has a constant steering width regardless of the vehicle speed V.

 Next, the operation of the above embodiment will be described.

Now, it is assumed that the vehicle is traveling straight on a good road at a constant speed and almost completely. In this running state, since there is no lateral acceleration generated in the vehicle body, the lateral acceleration detection signal is zero, and since steering is not performed, the steering angle detection signal θ _H is also zero.

Therefore, the calculator 49 of the controller 32 determines that the steering angle ratio α =
Since | θ _H / θ ₀ | = 0 is calculated, the function generator 50 calculates Zy =
A gain setting signal Zy that is Z _y0 is given to the gain adjusters 52f and 52r (see FIG. 6). This allows the gain adjuster 52
The f, 52r sets its gain constants Kf, Kr to the corresponding value Kf, Kr = K ₀ for the signal Z _y0 (see FIG. 4).

Therefore, the gain adjusters 52f and 52r multiply the input lateral acceleration signal by the set gain constants Kf and Kr to calculate the command signals If and Ir, respectively. Command signal If, Ir = supplied to valves 20FL to 20RR
It becomes 0. As a result, the operating pressure P supplied from each pressure control valve 20FL to 20RR to the corresponding hydraulic cylinder 18FL to 18RR is
From the characteristics shown in FIG. 2, the offset pressure becomes P ₀ . For this reason,
The stroke amount of each of the hydraulic cylinders 18FL to 18RR is set to a value corresponding to the offset pressure P ₀ , and a flat vehicle body posture with a predetermined vehicle height value is obtained.

In this straight traveling state, the vehicle receives a lateral wind and the vehicle body is swept in the lateral direction to change, whereby the lateral acceleration sensor 26 detects the lateral acceleration in the direction opposite to the roll at the time of turning as described above, and responds accordingly. It is assumed that the detection signal is output. In other words, the gain adjusters 52f and 52r have If = · Kf and I
Outputs command signals If and Ir for r ＝ ・ Kr, and pressure control valve 20FL ～
20RR gives the pressure P according to the command signals If and Ir to the hydraulic cylinders 18FL to 18RR in opposite phases of the left and right wheels.

However, since the gain constants Kf and Kr in such a straight traveling state are set to a very small value K ₀ , the sensitivity thereof is very low, and the roll force caused by the crosswind is promoted by the operating force of the hydraulic cylinders 18FL to 18RR. The anti-roll moment generated in the direction is suppressed to a very small value.
In other words, the lateral acceleration generated due to the lateral wind disturbance is mistaken for that during turning, and the roll caused by the lateral wind is not promoted. Therefore, the pressure receiving surface is not increased and the aerodynamic center is not increased, resulting in rollover. The conventional unintentional roll moment can be reliably prevented from occurring, and a stable vehicle body state can be secured.

Further, it is assumed that the vehicle travels from the above-mentioned almost complete straight traveling state while slightly steering. However, also in the case, since the steering angle detection signal θ _H is relatively small and is within the range of the steering angle ratio α <1, the function generator 50 considers that the straight traveling state falls within the range of the straight traveling state. The corresponding gain setting signal Zy is output. In other words, even if Zy <Z _y1 is maintained, it is necessary to increase the anti-roll moment as α = 1 approaches, and a larger signal Zy is output,
A relatively small gain constant Kf, Kr corresponding to the signal value Zy is set.

Therefore, for example, if a positive lateral acceleration signal corresponding to this is detected by a small right-turn steering, the pressure control valves 20FL to 20RR are connected to the front left and rear left hydraulic cylinders 18FL and 18RL as described above. the slightly higher pressure P than the offset pressure P _0, the front right, rear right hydraulic cylinders 18FR, the 18RR outputs a somewhat lower pressure P than the offset pressure P _0. Therefore, on the left side of the vehicle body, a force against the subsidence acts, and on the right side of the vehicle body, its lifting is not promoted,
A weak anti-roll moment acts against the vehicle body that rolls to the left when viewed from the rear side, an anti-roll effect is obtained, and changes in the vehicle body are accurately suppressed. The same applies to turning left.

In a running state where the vehicle can be regarded as going straight while slightly meandering, if a cross wind is received, the control gain
Since Kf and Kr are kept relatively low as described above, in this case as well, the situation in which the roll motion is promoted due to the crosswind can be almost avoided, and the stability of the vehicle is ensured.

On the other hand, it is assumed that the steering wheel is largely steered by hard cornering or the like and deviates from the preset straight-ahead driving range. In this case, since the steering angle ratio α ≧ 1, the gain setting signal Zy =
Z _y1 and gain constants Kf and Kr = K _1, and the control gain is set to a sufficiently large value, and the roll control sensitivity is enhanced.
Therefore, a large lateral acceleration detection signal and gain constant K
Based on f and Kr, a large anti-roll moment can be obtained in the same manner as described above. Therefore, the roll of the vehicle body due to the turning is accurately suppressed, and a substantially constant vehicle body posture is obtained.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. Here, the same reference numerals are used for the same or equivalent components as in the first embodiment, and the description thereof will be omitted or simplified.

In the second embodiment, the reference steering angle θ ₀ in the first embodiment is changed according to the vehicle speed V. That is, the lateral acceleration generated by the steering angle θ _H is the vehicle speed V
Since there is a relation of = kθ _H V ² (k: constant) in proportion to the square of, the roll due to steering increases as the vehicle speed V increases even with the same steering angle. This is because it is necessary to accelerate the return timing of the control sensitivity.

As shown in FIG. 7, the structure is such that a vehicle speed sensor 60 is added to the structure of the first embodiment, and a vehicle speed signal V from this vehicle speed sensor 60 is input to a calculator 62 in a controller 32. In this embodiment, the vehicle speed sensor 60 magnetically or optically detects the rotation speed of the transmission on the output side and outputs a vehicle speed signal V corresponding to the rotation speed. Also, the arithmetic unit
As shown in FIG. 8, reference numeral 62 changes the reference steering angle θ ₀ in inverse proportion to the vehicle speed V, and obtains the ratio α between the variable reference steering angle θ ₀ and the input detected value θ _H. ing. That is, the shaded area in FIG. 8 is a range considered to be the straight ahead area, and when the vehicle speed V is low, the lateral acceleration generated by steering is small, and therefore a large straight ahead area is set. Then, from this state, as the vehicle speed V increases, the straight traveling region is gradually narrowed, so that the timing of returning the gain constants Kf, Kr to the predetermined value K ₁ with high control sensitivity is advanced.

In the second embodiment, the calculator 62 and the vehicle speed sensor are used.
60 constitutes a straightness detecting means.

 Other configurations are the same as those in the first embodiment.

Therefore, according to the second embodiment as well, the same operational effect as that of the first embodiment can be obtained, and as the vehicle speed V becomes higher, the timing of returning the roll control sensitivity is automatically advanced, and the turning is performed regardless of the vehicle speed V. There is an advantage that the roll associated with is reliably prevented and the reliability of control is significantly improved.

In each of the above embodiments, when the steering angle ratio α <1, the gain setting signal Zy is linearly reduced in proportion to the steering angle ratio α. It may be divided into stages according to α and may be reduced stepwise.

Further, the controller 32 in each of the above-described embodiments may be configured by a microcomputer equipped with a program having the same function as the controller 32. Furthermore, in each of the above-described embodiments, the case where the lateral acceleration is detected by the sensor has been described, but the present invention is not limited to this. For example, the lateral acceleration is detected by an estimation calculation based on the steering angle and the vehicle speed (special feature). (See Kasho No. 62-293167). Further, the actuator in the present invention may be a flow control type cylinder or a pneumatic cylinder in addition to the actuators described above.

[Advantages of the Invention] As described above, in the suspension according to claim (1) of the present invention, the anti-roll moment given by the operation of each actuator is determined when the vehicle is in a straight traveling range. The gain for commanding is set smaller according to the decrease in the straightness, that is, the steering angle ratio, and the control sensitivity is suppressed as the steering angle ratio becomes smaller. Therefore, the gain is simplified as compared with the conventional example. Despite the composition
Even when a vehicle receives a crosswind while traveling in a straight ahead area, it is possible to accurately prevent a situation in which a slight downwind roll caused by the crosswind is inadvertently promoted, which increases the projected area for the crosswind. Since the wind pressure due to the crosswind is minimized, the instability of the vehicle due to the crosswind can be sufficiently suppressed, and if the vehicle makes a large turn outside the straight ahead range, a sufficiently large gain will provide adequate anti-roll. When the effect is obtained, there is an excellent effect.

Further, since the straightness detecting means can also serve as a steering angle sensor mounted on a normal vehicle, the structure thereof is further simplified. Further, in the suspension described in claim (3), the control timing can be adjusted according to the vehicle speed, so that the reliability of control can be improved.

[Brief description of drawings]

1 is a configuration diagram showing a first embodiment of the present invention, FIG. 2 is a graph showing a relationship between a command signal and an output pressure in a pressure control valve, FIG. 3 is a block diagram showing a controller of the first embodiment, FIG. 4 is a graph showing a change in the gain constant with respect to a change in the gain setting signal, FIG. 5 is a graph showing a relationship between the steering angle ratio and the gain setting signal, and FIG. 6 is a straight traveling range with respect to the vehicle speed V in the first embodiment. FIG. 7 is a block diagram showing the controller in the second embodiment of the present invention, FIG. 8 is a graph showing the straight running range with respect to the vehicle speed V in the second embodiment, and FIG. 9 is a change in the vehicle body posture due to cross wind. FIG. 3 is an explanatory diagram showing a detection situation of a vehicle width direction acceleration sensor. In the figure, 10FL to 10RR are wheels, 12 is a wheel side member, 14 is a vehicle body side member, 16 is an active suspension, 18FL to 18RR are hydraulic cylinders as actuators, 20FL to 20RR are pressure control valves, and 26 is lateral acceleration detection. Lateral acceleration sensor as a means, 28
Is a steering angle sensor, 32 is a controller, 48 is a roll control command unit, 49 is a calculator, 50 and 62 are function generators as gain control means, and 60 is a vehicle speed sensor.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Toshi Fujimura, 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Masaharu Sato, 2 Takaracho, Kanagawa-ku, Yokohama, Nissan Nissan Motor Co., Ltd. ( 56) References JP-A-63-106133 (JP, A) JP-A-61-181715 (JP, A)

Claims (2)

[Claims] 1. An actuator inserted between a vehicle body and each wheel, a lateral acceleration detecting means for detecting a lateral acceleration of the vehicle body, and a gain changeable to a detected value of the lateral acceleration detecting means. A steering angle sensor for detecting a steering angle of a vehicle, and a detection of the steering angle sensor, in an active suspension including roll control means for driving each of the actuators in a direction of suppressing a roll of a vehicle body based on a multiplied value. A straightness detecting means for calculating a straightness by calculating a steering angle ratio representing a ratio of a value and a preset reference steering angle, and a steering angle ratio when the steering angle ratio of the straightness detecting means exceeds 1. Regardless of whether the steering angle ratio is 1 or less, a large gain is set, and when the steering angle ratio is 1 or less, gain control means for setting a gain that decreases in accordance with a decrease in the steering angle ratio is provided. . 2. The active suspension according to claim 1, wherein the reference steering angle is a function of vehicle speed.