Honda Giken Kogyo Kabushiki Kaisha

Hideaki Shibue

Nobuharu Kuriki

Yoshiki Noro

Kei Oshida

Masaki Izawa

Seiji Ohsaki

Seiji Osaki

Yasuo Shimizu

Hiromi Inagaki

Toshiharu Yoshioka

Yoshiaki Noro

Hideki Mizutani

An active actuator is interposed between the unsprung mass and the sprung mass of a vehicle, and a controller selectively extends and retracts the actuator at a prescribed acceleration so as to selectively apply an additional contact load to the wheel by making use of the inertial force of the sprung mass and/or the unsprung mass of the vehicle. A particularly advantageous result can be achieved by increasing the tire contact load when the wheel is about to lock up when braking. The present invention can thus reduce the braking distance for the given road condition.

Tire contact load control system

An active actuator is interposed between the unsprung mass and the sprung mass of a vehicle, and a controller selectively extends and retracts the actuator at a prescribed acceleration so as to selectively apply an additional contact load to the wheel by making use of the inertial force of the sprung mass and/or the unsprung mass of the vehicle. Thus, the tire contact load of each wheel can be increased at will and independently from the other wheels so that the gripping force available to each wheel can be increased as required by appropriately operating the corresponding actuator. Therefore, the braking performance and the accelerating performance for the given road condition can be improved. Additionally, even when a frictional coefficients for the right and left wheels differ from each other, by appropriately applying an additional contact load to the wheel travelling over the more slippery part of the road surface, the stability of the vehicle can be also substantially increased.

An active actuator is interposed between the unsprung mass and the sprung mass of a vehicle, and extended and retracted in a cyclic manner so as to apply a prescribed reaction to the unsprung mass during an extending stroke of the actuator. Thus, the additional contact load is applied to the tire in a cyclic manner over a desired period of time so that the gripping force of the tire can be increased over a desired period of time. Although the increase in the tire contact load and the reduction in the tire contact load occurs in an alternating, cyclic manner, it is possible to achieve an overall advantage for instance in reducing the braking distance by intermittently increasing the tire contact load of the rear wheels by detecting the braking action of the vehicle with a suitable acceleration sensor or the like. In particular, by setting a retracting stroke of the actuator substantially longer in time duration than an extending stroke of the actuator, it is possible to reduce the degree of the contact load reduction between each consecutive phase of contact load increase, and to achieve an even better overall result.

A left hydraulic pump 3L connected to a left wheel and a right hydraulic pump 3R connected to a right wheel are interconnected by a first oil passage 21 and a second oil passage 22 to constitute a closed circuit. First and second variable throttle valves 8L and 8R are mounted between the first and second oil passages 21 and 22 and a tank 6. A first on-off valve 11L is disposed between two working chambers 9L.sub.2 and 9L.sub.3 of the left hydraulic pump 3L and the second oil passage 22, and a second on-off valve 11R is disposed between two working chambers 9R.sub.2 and 9R.sub.3 of the right hydraulic pump 3R and the first oil passage 21. For example, if the first variable throttle valve 8L is throttled, the pressure in the first oil passage 21 is risen to open the first on-off valve 11L, thereby increasing the amount of oil discharged from the first hydraulic pump 3L. As a result, the first and second hydraulic pumps 3L and 3R generate a braking force and a driving force respectively to generate a yaw moment in a rightward turning direction.

Yaw moment control system in vehicle

In a suspension system, a trailing arm and a knuckle are interconnected by a first rubber bush joint located in front of and below an axle, a second rubber bush joint located above the axle, and a third rubber bush joint located in back of and below the axle. Each of the rubber bush joints has a characteristic such that it is soft in a direction of an axis thereof and hard in a direction perpendicular to the axis in order to ensure a longitudinal compliance. The rigidity of the first rubber bush joint in the direction perpendicular to its axis is set lower than that of the third rubber bush joint in the direction perpendicular to its axis in order to produce inward towing of the outer wheel as viewed in the turning direction. Rear sides of the axes of the second and third rubber bush joints are inclined outwardly of the vehicle body in order to generate inward towing during braking. Thus, it is possible to insure a high longitudinal compliance to provide an excellent stability during turning and during braking of the vehicle.

Vehicle suspension having bushings with different rigidities

In a vehicle suspension system including a hydraulic actuator between a sprung mass consisting substantially of a vehicle body and an unsprung mass consisting substantially of a wheel, a force proportional to but opposite in phase to an inertia force acting on the unsprung mass is applied by the actuator to the unsprung mass so that the ability of the tire to maintain contact with the road surface may be improved. This produces very little effect on the behavior of the sprung mass, but the vehicle handling is significantly improved. Better contact with the road surface not only improves the vehicle handling but also reduces the consumption of energy by the hydraulic actuator. A particularly favorable result can be obtained when the hydraulic actuator further applies a damping force proportional to the absolute velocity of the sprung mass to the sprung mass.

Active suspension system

In an active vehicle suspension system employing a spring and a hydraulic actuator for supporting a wheel relative to a vehicle body, a control unit actuates the actuator so as to cancel the force applied by the spring force of the spring and a damping force applied by the hydraulic actuator. This damping force is typically produced by the flow resistance which the hydraulic oil encounters in the hydraulic circuit. This control action is carried out according to a signal obtained by processing an output of a displacement sensor between the wheel and the vehicle body with a first-order lead filter circuit. Thus, the control action is based on a readily available and highly responsive detection signal, an accurate and stable vibration control of the sprung mass of the vehicle or the vehicle body is made possible. This control action may be combined with a conventional feedback control based on the acceleration of the sprung mass or the load acting between the suspension system and the vehicle body, and a low-pass filter which ensures the stability of the system even when the first-order lead filter circuit is used.

Active vehicle suspension system and a control method therefor

In an active vehicle suspension system employing a double acting type single rod hydraulic linear actuator in which a piston is provided with two pressure receiving surfaces facing two different piston chambers defined by the piston received in a cylinder and having different areas, even when the line pressure of the hydraulic oil passage is lost, the height of the vehicle body can be maintained at a fixed level and a sudden change of the height of the vehicle body can be avoided by providing a hydraulic control device which appropriately controls the pressures of the upper and lower chambers so as to be inversely proportional to the areas of the corresponding pressure receiving surfaces as the pressure supplied to the hydraulic actuator is reduced.

Hydraulic control device for active suspension system

In an hydraulic active vehicle suspension system using a linear hydraulic cylinder as a primary actuator, controlled hydraulic pressure is supplied to an upper chamber of the hydraulic cylinder defined by a smaller pressure receiving surface of the piston and the cylinder while a reduced and fixed pressure is supplied to a lower chamber of the hydraulic cylinder defined by a larger pressure receiving surface of the piston and the cylinder, and an accumulator is connected to the lower chamber so that a desired hydraulic actuation can be accomplished by the controlled hydraulic pressure while sudden forces or inputs containing high frequency components applied to the lower chamber are absorbed by the accumulator. Thus, the accumulator offers a favorable response to the wheel riding over a bump or otherwise experiencing sudden movements and the absence of any accumulator connected to the upper chamber ensures a high speed response property of the system without requiring a large power capacity of the pump serving as the pressure source for the system.

Active vehicle suspension system

A hydraulic control device for an active suspension system employing a linear hydraulic cylinder including a piston connected in parallel with a spring between a wheel and a vehicle body, the piston having two pressure receiving surfaces of different areas facing two chambers separated by the piston in the cylinder, comprising a balancing valve for reducing the pressures of the two chambers to a level near the atmospheric pressure, a switch valve provided in a bypass passage between the two chambers for selectively communicating the two chambers with each other, a flow restricting orifice provided in the bypass passage; and an accumulator connected to the bypass passage capable of accommodating a change in the capacity of one of the chambers due to a piston rod extending from the piston out of the cylinder when the pressures of the two chambers are at the level near the atmospheric pressure. Alternatively, the accumulator could be replaced with a storage container connected to the bypass passage capable of accommodating an amount of actuating oil corresponding to a capacity of the cylinder. Thus, the active suspension system can serve as a workable passive suspension system when the supply of hydraulic oil is interrupted for any reason, and the reliability of the system can be improved.

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Saitama, Japan

Hideaki Shibue